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string | predicted_class
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|---|---|---|
Calculation result images in one case of pancreatic cancer. (a) DR. (b) DRR at the position of calculation result. (c) DRR at reference position. The red box indicates one vertebra on the DR; the red line indicates the diaphragm position. The blue boxes indicate the position of the same vertebra, and the blue lines indicate the position of the diaphragm. The ZNCC for the calculation position shown in (b) is 0.953; the ZNCC for the reference position shown in (c) is 0.757.
|
study
| 84.75 |
Regarding the relationship between evaluation values and calculation errors ΔD shown in Fig. 6, no correlation was found in prostate, lung, or H&N cancer cases, which had relatively small errors. However, in the liver and pancreas cases, which had large errors, a correlation was found. We assume that in cases where the errors were large, the reproducibility of patient conditions (diaphragm position, gas position, and gas volume, for example) between treatment planning and actual treatment was low. Consequently, it is unlikely that the DR and DRR will accurately match on the bony structure for our system, even if the f(di)was minimized (ZNCCdiwas maximized). Radiological technologists expertly adjust their images on the bony structure by omitting the above‐described low‐reproducibility regions on the basis of their knowledge and experience. It is currently impossible to automatically perform such calculations with our system. To address this problem, it is necessary to add a technique for omitting low‐reproducibility regions from the calculation, as technologists do.
|
study
| 100.0 |
To illustrate the dependence of accuracy on ROI size at each site (Table 2), Fig. 8 shows DRR examples of calculation results in a prostate cancer case with a large ROI, a lung cancer case with a small ROI, and a pancreatic cancer case with a small ROI. First, we consider the size dependence of prostate, lung, and H&N cancer cases, which all were acceptable under the optimal ROI size condition. The errors were smallest with the small ROI in the prostate cancer case. This finding can be attributed to the fact that the small ROI did not contain joints such as the hips, whose reproducibility is low. If the center of a small ROI moves the accuracy would be changed; however, the ROI center would not move significantly because the patient positioning is performed using the isocenter (center of the PTV), and therefore the accuracy may be little changed. With a large ROI, as shown in Fig. 8(a), the calculation errors increased because the large ROI often included low‐reproducibility areas such as joints and the bones just below the joints. However, the errors with the small ROI were largest in the case of lung cancer [Fig. 8(b)]. In these cases, the small ROI contained only low‐density regions such as ribs, but not high‐density regions such as vertebrae and shoulder blades. We found that the errors were large if the reproducibility of the shoulder blades was low. In contrast, calculation accuracy was not dependent on ROI size in H&N cancer cases.
|
study
| 100.0 |
In liver cancer cases, the error was smallest with a small ROI. As shown in Fig. 7, if the ROI was large, the diaphragm, whose reproducibility is low, was often included within the ROI. This inclusion caused increased errors because the calculation was affected by different positions of the diaphragm. In contrast, in pancreatic cancer cases, the error was smallest with a large ROI. Kumagai et al. and Houweling et al. reported that the reproducibility of the volume or position of gas in the bowel surrounding the pancreas was very low.22, 23 Therefore, as shown in Fig. 8(c), when the ROI was small, the relative size of the low‐reproducibility regions within the ROI increased, consequently increasing the error.
|
study
| 100.0 |
In cases of liver and pancreatic cancer with low calculation accuracy, the following two methods can be used to increase calculation accuracy: enlarging the ROI to include the bony structures necessary for calculation or excluding low‐reproducibility regions such as the diaphragm, gas regions, and joints for the calculation.
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other
| 99.9 |
The average calculation times for each ROI size showed little difference. There are two possible reasons for this difference. One is that the calculation did not converge in cases with large error such as the liver or pancreas. Another is that the calculation system involves extra processing other than the displacement calculation, such as outputting of the log for the verification. As manual matching by the radiological technologist took approximately 30–60 s, the current calculation time (approximately 25 s) may be less than the manual matching time. However, we think this is still too long for introduction to clinical sites, and we expect that the calculation time could be reduced to within 10 s by inclusion of preliminary processing and exclusion of the extra processing.
|
study
| 99.94 |
In this study, the calculation accuracy was evaluated under several initial positional conditions (2 mm, 0.2°; 5 mm, 0.5°; 10 mm, 1°; and 20 mm, 2°). In our previous study, the average of the absolute value of the initial deviation before positioning in prostate cancer cases was 3.0 ± 3.4 mm (maximum value, 14.8 mm).1 17 In the case of patient positioning at our facility, because laser alignment is performed before x‐ray image acquisition, there is no large error. Therefore, from the results in Fig. 5, we assume that the calculation in almost all cases of prostate, lung, and H&N cancer might be acceptable. However, the calculation results for three H&N cases were unacceptable when the initial value was 20 mm and 2°. If the initial positional error is greater than 10 mm, it is necessary to devise a calculation.
|
study
| 100.0 |
The limitations of this study include the low number of cases included. Only 10 cases were analyzed per site. Different cases might have had different results. Thus, further analyses including a greater number of cases are necessary in the future. Additionally, evaluation of special cases, such as patients with metal implants, is necessary.24
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study
| 99.94 |
The verifications performed in this study tested only one image with some errors. To introduce this system to clinical sites, it is necessary to verify its effectiveness in actual positioning with testing involving repeating the calculating errors and moving a couch based on the calculated results.
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other
| 99.75 |
The calculation system was evaluated on the basis of bony structures. The tumor matching method can improve the target delivered dose for liver or lung cancer cases.20, 25, 26, 27 Either the automatic marker or soft tissue alignment method28, 29 should be included in the calculation system to realize the tumor matching method for patient positioning.
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other
| 99.06 |
In this study, we developed a system for calculating patient positional displacement between DRs and DRRs, evaluated its practicality for patient data at five lesion sites, and assessed its ROI size dependency at these five sites. We found that almost all prostate, lung, and H&N cancer cases were acceptable for our setup tolerance in clinical practice. Additionally, our comparison of calculation errors for each ROI size suggested the causes of decreased calculation accuracy. In the future, it is necessary to determine how to exclude low‐reproducibility regions from the calculation to improve accuracy in tumors of the liver and pancreas.
|
study
| 100.0 |
Substance use disorders (SUD) belong to the most frequent behavioural consequences of childhood abuse and neglect (CAN). Of all patients seeking treatment for SUD, 16.3–60.9% report sexual abuse and 28.6–46.2% report physical abuse during their childhood (Simpson & Miller, 2002). Conversely, a lifetime diagnosis of SUD is found in 14–35% of adult survivors of CAN in community samples and in 30–35% of individuals who seek treatment for the consequences of CAN (Levitt & Cloitre, 2005; Mullen, Martin, Anderson, Romans, & Herbison, 1993).
|
review
| 98.6 |
Both psychological and biological factors seem to play a role for the development of SUD after experiences of CAN, but many aspects of this relationship remain poorly understood. Among the most important mediators are comorbid mental disorders, namely posttraumatic stress disorder (PTSD). Their important role for the development of SUD was initially suggested by proponents of the ‘self-medication hypothesis’ (Khantzian, 1985), and has been confirmed in many studies with different methodological approaches over the past two decades (Coffey, Stasiewicz, Hughes, & Brimo, 2006; Gielen, Krumeich, Tekelenburg, Nederkoorn, & Havermans, 2016; Kaysen, Stappenbeck, Rhew, & Simpson, 2014; Stewart, Conrod, Samoluk, Pihl, & Dongier, 2000). More recently, psychological consequences of CAN that could be important for different diagnostic entities have received increasing attention. This refers, for instance, to emotion regulation (ER) difficulties as a consequence of trauma (Ehring & Quack, 2010), which are also a potential predictor for SUD (Aldao, Nolen-Hoeksema, & Schweizer, 2010). Only few studies exist, however, on the interaction between ER deficits and subsequent craving and relapse in patients with SUD (Fox, Hong, & Sinha, 2008), and the impact of childhood trauma in this context (Banducci, Hoffman, Lejuez, & Koenen, 2014; Mandavia, Robinson, Bradley, Ressler, & Powers, 2016). Another promising perspective concerns alterations of the neuroendocrine responses to stress in victims of CAN (Tyrka, Burgers, Philip, Price, & Carpenter, 2013) that could also play an important role in the development of SUD (Enoch, 2011). Again, little empirical evidence exists regarding potential interactions between CAN and the neuroendocrine response to stress in patients with SUD (Moran-Santa Maria et al., 2010; Schäfer et al., 2010).
|
review
| 99.9 |
On a clinical level, PTSD is a frequent consequence of CAN in patients with SUD. Among patients treated for SUD, 26–52% have a lifetime diagnosis of PTSD and 15–41% currently meet criteria for the disorder (Schäfer & Najavits, 2007). In European studies, the rate of current PTSD is slightly lower, but still substantial (e.g. 15–36%; Driessen et al., 2008). However, PTSD is only one of the most obvious consequences of CAN and many SUD patients with a history of CAN suffer from more complex psychological consequences. They typically include pervasive disturbances in ER, a diminished and defeated sense of self, and difficulties in interpersonal relationships (Hien, Cohen, & Campbell, 2005). Such complex symptom presentations can dominate the clinical picture, or they can exist in addition to PTSD, which led the International Classification of Diseases (ICD) task force on stress-related disorders to propose a new diagnosis of ‘Complex PTSD’ for ICD-11 (Maercker et al., 2013).
|
review
| 99.9 |
SUD patients with a history of CAN present significant challenges to clinicians and the consequences of CAN have been related to poorer outcomes, lower treatment engagement and retention in this group (Bartholomew, Courtney, Rowan-Szal, & Simpson, 2005; Greenfield et al., 2002). With regard to specialized therapies for SUD patients with comorbidities related to CAN, preference is given to integrated treatments that conceptualize both disorders as related and plan treatment accordingly. While it is unclear if integrated treatments have a superior efficacy compared to one efficacious treatment alone (Torchalla, Nosen, Rostam, & Allen, 2012), the clinical needs of patients with SUD and PTSD often make such an integrated approach necessary. The most studied integrated treatment thus far is ‘Seeking Safety’ (SS; Najavits, 2002). This present-focused programme covers 25 topics that address the diverse consequences of CAN in four domains (cognitive, behavioural, interpersonal and case management) and has been shown to be effective in many SUD samples in the USA. The literature indicates, overall, positive outcomes on SUD and PTSD symptoms, as well as other consequences of CAN, in various populations (Najavits & Hien, 2013). A pilot study in Germany yielded positive results (Kaiser et al., 2015), suggesting that the programme could be a promising option also for European SUD settings, but no controlled studies on the efficacy of this treatment have been published in Europe so far.
|
review
| 99.9 |
It has been proposed that a trauma-informed organizational culture, that takes into account the role and impact of trauma in the patient’s lives, should be the basis for the implementation of trauma-specific services in health care settings (Brown, Harris, & Fallot, 2013). In current practice, however, this rarely seems to be realized. There is a wealth of evidence that health professionals often do not even ask about their clients’ experiences of CAN (Havig, 2008). The most important reason for this failure is an obvious lack of training for adequate inquiry and response to patients’ histories of abuse. For instance, in a large study among clinicians in community support centres, personal confidence and competence were positively related to the percentage of clients with whom trauma and PTSD had been discussed, documented, and addressed in treatment (Salyers, Evans, Bond, & Meyer, 2004). Other reasons seem to be a general underestimation of the prevalence of posttraumatic disorders in SUD patients and concerns to do harm when assessing trauma and PTSD (Gielen, Krumeich, Havermans, Smeets, & Jansen, 2014). Strategies to train practitioners regarding the consequences of trauma in their clients and regarding skills to assess CAN and other traumatic experiences therefor are a prerequisite for the dissemination of trauma-specific treatments in SUD settings.
|
review
| 99.9 |
Finally, SUD are not only a frequent consequence of CAN, but also belong to the most important risk factors for the perpetration of CAN. Studies of court registers indicate that about 40–60% of all significant CAN cases involve parents with substance use problems. A variety of factors seem to enhance the risk for CAN in families with SUD. Findings include dysfunctional internal and external boundaries, poor communication skills, high family conflict levels, and low levels of family competence (Vernig, 2011). One of the best-established hypotheses focuses on ‘disinhibition’ caused by active use of substances. Though under-studied so far, ER is emerging as another predictor for CAN among individuals with SUD. ER deficits can be linked to both addictive and aggressive behaviours (Simons & Carey, 2002) and they exceeded other diagnostic and demographic variables in predicting CAN among individuals with SUD (Hien, Cohen, Caldeira, Flom, & Wasserman, 2010). A prerequisite for efforts to prevent CAN by parents with SUD is effective screening of individuals at risk. The existing attempts to develop specific instruments for SUD populations, however, share some methodological shortcomings.
|
review
| 99.9 |
Some of the questions outlined above are currently addressed by the research network ‘CANSAS’, 1 which is funded by the German Ministry for Education and Research. In a multi-disciplinary approach, the CANSAS network brings together experts in the fields of trauma treatment for patients with SUD, epidemiology and risk factor research, biological and psychological moderators, as well as health services research. The aims of the network are (1) to gain a better understanding of the relationships between the two important public health problems CAN and SUD; (2) to promote evidence-based treatments for survivors of CAN with SUD; and (3) to provide services with trainings to improve the assessment of CAN among clients with SUD and to assess risk factors for the perpetration of CAN in this population. The following sections give an overview of the six different projects of the CANSAS network.
|
review
| 99.75 |
The first cluster of the CANSAS network consists of projects with a focus on potential mediators between CAN and SUD in adult life. The project ‘Trauma, ER and substance-use disorder: does emotion dysregulation moderate the association between trauma and substance use/relapse?’ (PI Sven Barnow, Heidelberg) examines the mediating role of ER in the relationship between CAN and SUD. To this aim, N = 80 male and female healthy individuals with a history of CAN are compared with N = 160 SUD patients of both genders with such a history using different methodological approaches. This also includes ecological momentary assessment (EMA) to collect real-time data about subjects’ emotional status and ER strategies as they go about their lives within their normal environments. It is expected that traumatized SUD patients show ER deficits (e.g. more often use rumination, avoidance and less often reappraisal, show inflexibility) compared to traumatized healthy controls. Moreover, it is expected that ER deficits are related to characteristics of substance use as well as craving/relapse in currently abstinent traumatized SUD patients.
|
study
| 99.94 |
A second project (‘Relationship between CAN and neuroendocrine response to stress in individuals with SUD’; PI: Ingo Schäfer, Hamburg) examines relationships between CAN and neuroendocrine reactions to social stress in patients with alcohol dependence (AD). To this aim, N = 72 male and female AD patients (with and without childhood trauma) will be compared to N = 72 healthy controls (with and without childhood trauma) regarding their reactions to a social stress task (‘Trier Social Stress Test’; TSST). Other markers (e.g. hair cortisol levels) will be used to get a more holistic view of potential relationships between CAN and stress reactivity in AD patients and to identify their potential predictive value. It is expected that individuals with AD and CAN show decreased cortisol responses to the TSST as compared to AD individuals without CAN, the latter being comparable to healthy controls with CAN.
|
study
| 99.94 |
In the project ‘Cognitive-behavioural treatment for female patients with PTSD and SUD’ (PI Ingo Schäfer, Hamburg) N = 342 female patients with PTSD and SUD are included in a multi-centric study in Hamburg, Cologne, Essen, Bielefeld, and Hannover to compare the effects of SS (Najavits, 2002) to another standardized CBT intervention (relapse prevention training; RP), and treatment as usual (TAU). SS is suitable for patients of both genders, but this study will focus on female patients. While single-sex studies are clearly limited with regard to the generalizability of their findings (Kristman-Valente & Wells, 2013), this decision was made because of the higher prevalence of the comorbidity of SUD and PTSD in females (e.g. Driessen et al., 2008; Schäfer & Najavits, 2007), and the suggestion of some authors that trauma treatment should preferably be offered in gender-specific groups (e.g. Greenfield et al., 2007). Patients in the SS group receive 14 weekly sessions (90 min each) in groups of four to eight patients. The intervention is offered in addition to TAU. The same number and duration of sessions is offered to patients in the ‘RP + TAU’ group. Patients in the TAU group are offered individual SUD treatment on a weekly basis and may obtain any treatment they normally would (detoxification, rehabilitation, individual psychotherapy, self-help groups, etc.). While the primary outcomes are PTSD symptoms as measured by the PTSD Symptom Scale Interview (PSSI), the secondary outcomes include substance use and other domains of psychopathology. The primary hypothesis consists of three two-group comparisons: (1) Enhanced treatment (SS + TAU) is more effective with regard to reduction of PTSD symptoms at six-month follow-up than TAU alone; (2) the same is expected for relapse prevention training (RP) + TAU as compared to TAU alone; and (3) SS + TAU will be at least as effective as RP + TAU.
|
study
| 96.3 |
The second study of the cluster (‘Cognitive-behavioural treatment for adolescents with PTSD and SUD’; PI: Rainer Thomasius, Hamburg) examines the feasibility and efficacy of the adolescent version of SS in N = 74 adolescent girls diagnosed with PTSD related to CAN and substance use disorders. As in the first study of the cluster, the decision to focus on girls was made because of the higher prevalence of the comorbidity of SUD and PTSD in females, and the advantages related to offering trauma treatment in gender-specific groups. In this uncontrolled pilot study, it is expected that participants attending at least eight of 14 SS sessions (‘completers’) will show a significant reduction of posttraumatic symptoms at three-month follow-up as compared to baseline, as well as significant reductions of substance use.
|
study
| 99.94 |
The project ‘Learning how to ask – evaluation of a training programme for practitioners in SUD services’ (PI: Martin Härter, Hamburg) aims at (1) adapting a standardized training programme for CAN inquiry and response (‘Learning how to ask’; Read, Hammersley, & Rudegeair, 2007) to the requirements of the German health care system; and (2) evaluating the effects of the programme on acceptance, knowledge about abuse in SUD clients, competence of abuse inquiry and the rate of abuse inquiry by practitioners in SUD services. The programme consists of one-day workshops and has been successfully used in New Zealand and in the UK (Read et al., 2007). The participants are provided with background information about forms and consequences of abuse, legal issues, and local possibilities for referral as well as guidelines for abuse inquiry and response. The effects of the training will be examined in a randomized-controlled trial among N = 120 practitioners of both gender in outpatient SUD counselling services in Hamburg. It is expected that the number of documented CAN inquiries is significantly higher in the six months post training in the intervention group as compared to the control group.
|
study
| 99.1 |
Another project of the cluster (‘Assessing the risk of CAN in parents with SUD: development of an evidence-based instrument’; PI: Ulrike Ravens-Sieberer, Hamburg) finally aims at the development and psychometric testing of a short risk inventory to identify the risk of CAN among parents with SUD. The instrument will be based on a meta-analysis of specific risk factors of families with parental SUD, a systematic assessment in 392 SUD counselling services representative for 1399 such services in Germany, as well as on qualitative interviews with different groups of SUD practitioners. The short risk inventory will be tested regarding acceptance and practicability in N = 40 SUD services in Hamburg.
|
study
| 99.94 |
Substance use disorders are not only one of the most significant consequences of violence and neglect in childhood, but, if parents are concerned, they are also one of the most important risk factors for maltreatment against children. Interdisciplinary research activities are necessary to identify the relationships between early adversity and substance use disorders, to provide effective treatments for patients with comorbid posttraumatic disorders and to inform preventive approaches. To our knowledge, the CANSAS network is the largest European research initiative in this field so far. It is expected that the findings of the network will lead to more sophisticated models regarding the role of early adversity for substance use disorders. First results confirmed the important role of emotions and their regulation and brought new insights into the details of this relationship (Wolff et al., 2016). The findings of CANSAS could thus provide a basis for early intervention approaches in children and adolescents with a history of CAN, and for specific ER trainings adapted to the needs of patients with SUD. The results of the studies on a treatment model for SUD patients with PTSD will bring forward the discussion about promising treatments for this group in European SUD settings. This includes the question of which patients can benefit from present-focused models like SS and which patients might need (additional) trauma-focused approaches. Finally, the findings on trainings of practitioners and screening tools will contribute to both, improving the assessment of CAN in patients with SUD and breaking the transgenerational cycles of adversity through a better assessment of CAN by parents with SUD. There are manifold relationships between CAN and SUD, and the network will only be able to make a limited contribution to this rapidly developing field of research. Nevertheless, it can be expected that the broad perspective of CANSAS and its interdisciplinary approach, that brings together experts in the fields of childhood abuse and neglect, substance use disorders, as well as health services research, will contribute to a better understanding of some relevant questions that might help to bring forward the idea of ‘trauma-informed care’ (Brown et al., 2013) in European addiction services.
|
review
| 99.9 |
Staphylococcus aureus is nearly unrivaled among bacterial pathogens, both in the diversity of clinical syndromes it causes (from skin abscesses and food-borne illness to endocarditis and sepsis) and in its complex array of virulence mechanisms. In addition, antimicrobial resistance rates continue to increase, both in methicillin-susceptible (MSSA) and methicillin-resistant (MRSA) isolates . S. aureus harbors numerous gene regulatory and quorum sensing systems, and features substantial genomic plasticity and frequent redundancy among specific virulence factors. For these reasons, this pathogen represents a daunting target for the development of novel therapeutic and preventive measures, dating back to the first published attempt at a S. aureus vaccine in 1902 .
|
review
| 99.8 |
Since the onset of the community-associated MRSA epidemic, a family of toxins produced by S. aureus, the leukocidins, have gained increasing attention as important virulence determinants and potential targets of intervention against this pathogen. The leukocidins known to be produced by clinical isolates of S. aureus include Panton-Valentine leukocidin (PVL), LukAB (also known as LukGH), LukED, and the γ-hemolysins HlgAB and HlgCB . Each of these two-component toxins is secreted as a pair of monomers that oligomerize to form a pore on the surface of phagocytes, lymphocytes, and natural killer cells, and they are important mediators of staphylococcal evasion of innate host defenses. The neutrophil represents the primary innate defense against S. aureus infection in humans, as evidenced in part by the clear predilection toward invasive S. aureus disease in patients with neutrophil defects . The leukocidins exert their effect at the level of the neutrophil and other phagocytes, binding receptors in the chemokine and complement receptor families [5–8], forming a pore, and potently lysing these cells, thereby facilitating infection in a variety of in vivo models [9–13]. S. aureus elaborates a number of additional pore-forming toxins outside the leukocidin family, prominently including alpha-hemolysin (Hla), which primarily targets erythrocytes, epithelial and endothelial cells, and lymphocytes. While the role of Hla has been carefully elucidated in numerous animal models , most of the leukocidins exhibit a markedly increased tropism for human leukocytes in comparison to murine cells , likely resulting in a previous underappreciation of the importance of the leukocidins when extrapolating from murine data.
|
review
| 99.8 |
Since its discovery by two independent groups in 2010 , LukAB/LukGH has garnered attention as an important S. aureus virulence factor based on its clear role in both ex vivo and in vivo models of disease . Infection of human neutrophils with diverse S. aureus strains indicates that LukAB/LukGH is the dominant toxin responsible for neutrophil targeting and killing . This toxin is also highly conserved, being present in the genome of all known clinical isolates tested to date . Finally, LukAB/LukGH is clearly produced during human infection, as evidenced by its recognition by the humoral response following invasive human disease .
|
study
| 99.94 |
In this issue of Virulence, Rouha et al have thoroughly evaluated the capacity of a pair of human monoclonal antibodies to inhibit the cytotoxicity of the leukocidins and Hla . These antibodies, termed ASN-1 and ASN-2, were isolated by screening a human IgG1 antibody library using a yeast selection system; ASN-1 exhibits cross-reactive neutralizing activity against Hla and four of the leukocidins (PVL, LukED, and the γ-hemolysins), while ASN-2 neutralizes LukAB/LukGH. The authors have previously reported the cross-reactive capacity of ASN-1 , itself an important discovery given the redundant nature of S. aureus virulence factor expression. In this report, Rouha and colleagues characterize the individual and combined effects of the mAbs in a variety of in vitro models using human leukocytes, an important distinction given leukocidin tropism.
|
review
| 61.56 |
Several notable findings emerge from this work. First, the authors observed marked differences in toxin production in the presence of different culture media, particularly for the leukocidins. This speaks to the difficulty of interpreting the importance of staphylococcal toxins (and many other virulence factors) from different in vitro models, as protein expression by S. aureus may vary dramatically based on factors such as pH, oxygen tension, and nutrient availability . Of note, the authors found that LukAB/LukGH was the dominant toxin in the media that may best recapitulate the host environment in the setting of human infection, RPMI + Casamino acids. Second, the authors observed that toxin production also varied widely across S. aureus strains. As the pore-forming toxins are evaluated as putative targets of intervention against S. aureus, it will be important to define the critical toxin(s) in the setting of human infection and produced by widely circulating clinical isolates. The authors also found that both antibodies were required to fully prevent toxin-mediated lysis of human neutrophils in most in vitro conditions, emphasizing the apparent redundancy in this pathway, though caution must be used when extrapolating these in vitro findings to what occurs in the human host during natural infection.
|
review
| 96.3 |
Many fascinating questions remain unanswered regarding pore-forming toxin biology and the interaction between these important S. aureus virulence factors and the human host. Despite the robust in vitro characterization of antibody-mediated pore-forming toxin inhibition reported by Rouha and colleagues, gaps remain in our understanding of antibody-toxin interactions in the setting of serious human infections, the setting in which a putative therapeutic would be deployed. For example, our group recently reported that different human antibodies (purified from B-cells obtained from children with invasive S. aureus disease) neutralize LukAB/LukGH-mediated cytotoxicity by distinct mechanisms . It remains unclear whether certain of these mechanisms are more biologically relevant or important in the setting of invasive human infection. Further, evidence of antibody-enhanced disease has been reported in a murine model for at least one of the leukocidins (PVL) , and the relevance of this in humans (both for PVL and the other leukocidins) remains largely unexplored. The authors note that the antibody combination reported in this manuscript is under investigation in a Phase II clinical trial involving mechanically ventilated patients heavily colonized with S. aureus. The findings of this and other future work will hopefully provide further insights into the potential roles of antibody-mediated neutralization of pore-forming toxins in the setting of human disease.
|
review
| 99.0 |
As people get older, they tend to perform many activities more slowly and less accurately. We walk to the shops more slowly; we become more forgetful; we do not hit a golf ball as far in our 60s as we did in our 20s. Executive function is responsible for high-level cognitive operations, including planning, task management, working memory (WM), and inhibitory control (IC). A large body of behavioral research has focused on the effect of natural aging on executive function and has observed age-related deteriorations across a range of cognitive domains including WM and IC (e.g., Anderson et al., 2012; Heilbronner and Münte, 2013). It has been claimed that the natural aging process adversely affects saccadic eye movement functioning (Dowiasch et al., 2015), with the voluntary control over saccadic eye movements showing less resilience to aging (Peltsch et al., 2011). The natural process of aging, however, does not inevitably lead to cognitive decline, and the extent of this cognitive decline varies across tasks and individuals (Friedman et al., 2008; Park and Reuter-Lorenz, 2009; Crawford et al., 2013). Numerous studies have described the effects of aging on saccadic eye movement performance, but with clear inconsistencies; saccade parameters such as reaction times and error rates have been correlated with aging (Abel and Douglas, 2007; Peltsch et al., 2011), whereas, others have shown no difference between older and younger participants (Eenshuistra et al., 2004; Pratt et al., 2006). Clearly, further research is required in order to fully understand the neurocognitive changes involved in human aging. There have been several attempts to locate the decline of specific cognitive operations in aging. However, previous research has often relied on complex tasks with multiple interacting cognitive elements (Rabbit, 2005); therefore in this study we have turned to the well characterized antisaccade task (AST). The current experiment is an attempt to clarify whether, during the aging process, IC, WM, or both processes are associated with the decline in AST performance, which has been previously observed across the literature.
|
study
| 99.9 |
Cognitive inhibition can be operationalized as the rejection of a prepotent or highly practiced response, in favor of a more contextually appropriate or desirable response (Butler and Zacks, 2006). The AST presents participants with a central fixation stimulus on a screen, which is then followed (after a brief temporal gap in the commonly employed AST gap task) by a suddenly appearing visual peripheral stimulus. The correct task response requires participants to avoid the instinctive compulsion to look towards the target, and instead to execute a saccadic eye movement to a position on the screen, equidistant from the center of the screen, but in the opposite horizontal direction to the target (an antisaccade). The AST is thought to comprise several critical components: remembering the rule of the task; inhibiting the prepotent response to look towards the target; translating the spatial location of the target across to its mirror image location; and executing the oculomotor saccade to what is essentially a blank, undefined location. The composite processes necessary for successful AST responses can be fractionated into sub processes reliant predominantly upon WM or IC (Crawford et al., 2011). While these two cognitive mechanisms may be interrelated, the active suppression of the prepotent saccade to the target, and the active fixation upon the spatial location of the end point of the AST (while self-prohibiting further eye or head movements) rely primarily upon the inhibition system. However, the implementation of the rules of the AST, the translation of the spatial location of the target, and subsequent execution of the antisaccade movement rely more heavily upon WM processes.
|
study
| 99.9 |
In young controls, the AST elicits longer latencies and a higher incidence of directional errors than the prosaccade task (PST). In older adults, these differences are inflated (e.g., Eenshuistra et al., 2004; Crawford et al., 2005; Butler and Zacks, 2006; Peltsch et al., 2011). Despite the prevalence of AST impairments in older adults, the source of these impairments remains unclear. An increased AST latency and the higher error rate found in older adults have been interpreted as a typical age-related decline of inhibitory function (Klein et al., 2000; Sweeney et al., 2001; Peltsch et al., 2011). In agreement with research on the decline of IC with age (Raemaekers et al., 2006; Peltsch et al., 2011), Alichniewicz et al. (2013) demonstrated the reduced ability of older adults to voluntarily inhibits saccadic responses compared to young adults. Additionally, the onset latencies of both prosaccades and antisaccades were significantly longer in healthy older adults, compared to their young counterparts. WM capacity is also suggested to account for the difference between younger and older adults in the AST (Eenshuistra et al., 2004; Crawford et al., 2013). For example, the observed age-related AST impairments could be influenced by declining WM capacity (Baltes et al., 1999), declining levels of activation of task goals, and/or rates of refreshment of crucial task information in WM (e.g., Duncan et al., 1996; Nieuwenhuis et al., 2004), or declining inhibitory efficiency in controlling the amount of task-irrelevant information entering, remaining in, and being filtered out of, WM (e.g., Hasher and Zacks, 1988; Hasher et al., 1999). The accounts differ in the extent to WM (or IC) decline is considered to be a direct source of AST impairments, rather than an indirect, emergent property of cognitive impairment.
|
review
| 98.4 |
Roberts et al. (1994) and Mitchell et al. (2002) presented healthy young adults with a WM task concurrent with an AST, and reported that prolonged latencies and higher directional error rates were observed for young participants that were comparable to that found among much older adults in other studies (Olincy et al., 1997; Sweeney et al., 2001; Eenshuistra et al., 2004). This was interpreted as evidence suggesting that a reduction in WM capacity is the likely source of poor AST performance. In contrast, it has been argued that the failure to inhibit the prepotent response may account for the poorer performance across the older samples in the AST (Butler and Zacks, 2006; Ryan et al., 2006). This is because it is essential to inhibit this response towards a visual stimulus (e.g., Godijn and Kramer, 2006). Butler and Zacks (2006) investigated the extent to which IC could explain age-related AST impairments. Antisaccades that are triggered by the onset of a peripheral stimulus require IC to suppress the prepotent prosaccade response to that stimulus (Theeuwes et al., 1999), while antisaccades signaled by a central directional arrow require endogenous planning, but clearly have reduced inhibitory requirement, as there is no peripheral stimulus to capture visual attention. Thus, a marked increase in AST errors or latencies with age, in a peripheral onset condition, in comparison with a central cue, would suggest support for a specific IC deficit with age. In the Butler and Zacks (2006) study, the older adults generated longer reaction times when the inhibitory load of the AST was increased using the onset of the peripheral stimulus, which is compatible with the hypothesis of an age-related decline in IC. However, the peripheral vs. central cue manipulation yielded no group effect on AST errors between the young and older participants.
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study
| 99.8 |
Currently, we have various findings, with no consensus. However, no study so far has manipulated WM and IC within the same task domain. Here we present, for the first time, a set of novel ASTs that attempt to manipulate the IC and WM processes independently within the AST. This was achieved by two simple manipulations: First, using a memory-guided condition, the memory-load was increased, while removing the usual inhibition of a saccade towards the prepotent target. Memory load was increased by introducing five “to-be-remembered” possible target locations that were embedded within an array of distracters; critically the inhibitory element was simultaneously minimized by the requirement to fixate the target immediately at presentation, before then returning back to the central fixation point ready for the subsequent AST away from the remembered target. By allowing the observer to fixate the target at the time of presentation, the typical requirement to inhibit the saccade to the prepotent target was removed (Figure 1). In a second condition (go/no-go), inhibition was increased while simultaneously minimizing the memory load. In the go/no-go task, participants were presented with an initial fixation stimulus, followed by either a ‘go’ cue (green light) or a ‘no-go’ cue (red cross), before the onset of a target stimulus. On trials where a ‘go’ cue is presented, participants must make a saccadic eye movement to the target (prosaccade) or away from the target (antisaccade). In trials where a ‘no-go’ cue is presented, participants must maintain fixation on the fixation stimulus (i.e., must refrain from making a saccadic eye movement towards or away from the target). Go/no-go paradigms are known to increase inhibition errors, even beyond the standard AST (see Crawford et al., 2005). Critically, the WM load was minimized by presenting a clear visual arrow marker that pointed towards to the correct direction on the “Go” trials, thus eliminating the need to keep this location in mind (Figure 1). We employed variants of the AST to selectively load IC or WM, to compare performance on these tasks with performance on the standard AST, across two age groups. Performance was assessed in terms of latencies of correct saccades, spatial accuracy, and the proportion of directionally erroneous saccades on the ASTs (i.e., saccades towards the target, rather than away from the target). The aim was to clarify the extent to which the previously documented age-related impairments on the AST are affected by spatial WM deficits, in contrast to the inhibition of a prepotent response. The AST-go/no-go was designed to assess the effect of an inhibitory load (specifically the ability to successfully inhibit the “urge to go” in the no-go condition), while the memory-guided AST conditions assessed the effect of an increased load on WM. A standard version of the AST (AST-s) acted as a baseline assessment of saccadic performance. The gap paradigm (i.e., where the fixation point is removed 200 ms before the target is presented) was employed in all tasks so as to reduce the possibility of floor effects, whereby the tasks are insufficiently taxing as to elicit any errors from the participants. Including such a temporal gap in eye movement studies increases the distraction error probability in AST trials (Saslow, 1967; Fischer and Weber, 1992; Dorris and Munoz, 1995; Eenshuistra et al., 2004). Kimberg and Farah (2000) proposed in their model that IC was simply an expression or by-product of WM; in other words IC is not a distinct cognitive operation. However, using a single case study methodology, Crawford and Higham (2016) recently discovered evidence for independence and modularity. In this study, we assess IC and WM as part of the cognitive operations underpinning antisaccades in both young and older participants. Saccade latencies and error rates of saccades of older participants were compared to the same measures in healthy young controls.
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study
| 100.0 |
Left panel: Example sequence of screens in the standard prosaccade task (PST) and standard antisaccade task (AST-s). Although visually identical, the difference between the PST and the AST, in terms of the requisite eye movement response towards or away from the target, was made clear in the instructions given to participants before each task. Middle panel: Example sequence of screens in the memory-guided AST task (AST-mem). Right panel: Example sequence of screens in the AST-go/no-go task shows the orders in which screen were presented to participants in the AST-go/no-go task.
|
study
| 93.2 |
A total of 16 younger adults (age range = 18–30) and 15 older adults (age range = 50–77) each participated in four conditions. The young group were recruited in person through their attendance at an undergraduate- and masters-level Psychology course at Lancaster University and were reimbursed at a remuneration rate of £6 per hour (with most sessions lasting approximately 90 min). The remaining younger participants were undergraduate-level Psychology students, recruited via an online system and reimbursed in course credits. Approximately half of the older participants were recruited from the Lancaster University Veteran’s Society via advertisements and consequently had all previously studied and/or worked at Lancaster University. The remaining older participants were recruited in person through their attendance at local interest group meetings. All participants were free from psychiatric disorder, as determined by self-report and were free from psychoactive medication. All older participants lived independently in their own homes, and were classified as having no early signs of dementia, or general cognitive impairments according to the Mini Mental State Examination (Molloy et al., 1991). Participants were screened for color blindness using the Ishihara Test (Ishihara, 1973), and for normal or corrected to normal visual acuity using a standardized Snellen chart. The study received ethical approval from Lancaster University ethics committee.
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study
| 99.94 |
Prior to the eye-tracking phase of the experiment, all participants were assessed using a cognitive battery comprising a standardized digit span from the Wechsler Adult Intelligence Scale III (WAIS III; Wechsler, 1997a); Corsi blocks of the spatial span (Wechsler Memory Scale III; Wechsler, 1997b); and the National Adult Reading Test (Nelson, 1982). The older group of participants was additionally screened using the Mini Mental State Examination (Molloy et al., 1991), a brief screening instrument for dementia in order that any participants exhibiting signs of dementia or mild cognitive impairment could be excluded from the experiment.
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study
| 100.0 |
Stimuli were displayed against a white background on a 19-inch computer monitor, controlled by a Dell PC, which also recorded the experimental data. Participants were seated at a distance of 57 cm from the screen, with their chins placed on a specially adapted, adjustable chin rest to reduce head movements. Testing was conducted in a quiet, darkened room, to which participants were acclimatized before testing commenced. Eye movements were recorded using an EyeLink II high-speed camera eye tracking system (500 Hz, < 0.5° accuracy) running on a Dell PC. A hand-held computer controller was also connected to the host computer. This permitted participants to control the pace of the presentation of the stimuli for each trial. Participants were required to wear a non-invasive headband supporting three small cameras throughout the experiment. Two cameras recorded eye movements using infra-red technology whereby differential absorbencies of the infra-red energy by the pupil and the sclera permitted the tracking of micro-movements of the pupil. The third tracking camera maintained optimal alignment by monitoring the positioning of four infra-red markers on the computer screen.
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study
| 99.94 |
The presentation order of the resulting three conditions was controlled so as to balance any potential effects resulting from asymmetric transfer of experience from one task to the next. Since a PST (where the desired response was for participants to orient their eyes towards the visual target) by definition required less deliberation than the AST (in which participants were required to avert their eyes from the visual target), a PST was always presented before the three ASTs to prevent the additional cognitive processing inherent within the AST impacting on the PST. The two standard tasks (standard PST and AST-s) each comprised 60 trials, split into three blocks of 20, with the location of the visual target (4° to the left or to the right of the central fixation cross) randomized across each block, with the constraint that no more than five consecutive runs of each target location was to be deployed, in order to prevent participants anticipating the target location, or displaying practice effects to that particular target location. The memory-guided task comprised 48 trials, organized into two blocks of 24 trials. The location of the target (1, 3, or 5° to the left or to the right of the central fixation cross) was randomized, with the constraint that no more than five consecutive runs of each target location would be deployed. The go/no-go task comprised 48 trials organized into two blocks of 24. In these conditions, both the target location (4° to the left or to the right of the central fixation cross) and the type of central cue presented (a red cross denoting a no-go trial, or a green arrow denoting a go trial) were randomized, subject to a maximum of five consecutive runs of any one target location and central cue combination. In every condition, participants were offered a brief period of respite after each block of trials, if desired, in addition to a break after each of the three experimental conditions. Performance was assessed in terms of saccade latencies (mean response times after presentation of the target stimulus), spatial accuracy (mean deviation of final eye position from the centre of the intended target location), and error rates (the proportion of trials in which participants moved their eyes in a direction contrary to the task requirements).
|
study
| 100.0 |
A nine-point calibration and validation was conducted prior to each condition to obtain a high degree of tracking accuracy. Participants were presented with standardized on-screen instructions before commencing each condition, and after each block of trials within each condition. Additional verbal clarification was provided where necessary, and participants were permitted to ask for help should they require further explanation. The appearance of a centrally located stimulus consisting of two concentric monochrome circles signaled the start of the trial, and pending initiation from the participants in the form of a button press on the console controller, a central black fixation cross was presented for 200 ms, followed by the experimental stimuli. For each condition, 12 initial practice trials were conducted, and participants were permitted to proceed to the experimental trials subject to satisfactory completion of these practice trials. All tasks incorporated a 200 ms gap between the extinguishing of the central fixation stimulus and the onset of the target stimulus in order to increase the potential for erroneous trials, since these trials were to form part of the basis of the analysis.
|
study
| 100.0 |
In a standard PST trial, after the task instructions had been presented on screen, the initial central fixation cross was superseded by the target stimulus (a 0.7° diameter, red filled circle) that remained on the screen for 2 s, before disappearing. A 200 ms gap then elapsed, while the screen was completely blank, before the target stimulus reappeared at a location of 4° to the left or right of the screen center, where it remained for 2 s. The 4° target eccentricity has been used in previous saccadic eye movement studies (e.g., Nieuwenhuis et al., 2004) and thus allows for comparisons with the present research. Similarly, the standard timings utilized in the gap paradigm are of 200 ms (cf. Crawford et al., 2002; Eenshuistra et al., 2004; Evdokimidis et al., 2006). After a further 700 ms, the target stimulus was extinguished, and the next trial commenced with the appearance of the two concentric circles for drift correction. After 30 consecutive trials, the instruction screen reappeared to remind participants of the requirements of the task at hand and also to allow for short recess in testing should participants so wish. The presentation order of the composite screens in the standard PST (and standard AST-s) condition is shown in Figure 1 (left panel).
|
study
| 100.0 |
The AST-s condition was visually identical to the PST condition, with the exception of the instructions given to participants. The initial instruction screen requested that participants look to a point in space that they considered being the horizontal mirror-image location of the target stimulus. Further verbal clarification was given to ensure that participants knew that they were required to look to a point equally distant from the center, but in the opposite direction to, the target stimulus. The presentation order of the composite screens in the AST-s condition (and standard PST condition) is represented in Figure 1 (left panel).
|
study
| 100.0 |
The memory-guided condition consisted of two parts: participants were initially presented with an instruction screen then a central fixation cross, which was accompanied after 700 ms by a red, circular target stimulus identical to that used in the standard PST and AST-s conditions, to the left or right. However, this target was adjacent to four distracter stimuli, spaced 1° apart, occupying locations from 1 to 5° of visual angle from the central fixation point. Hence, participants were required to distinguish the target from the distracters and subsequently remember the target location using spatial WM. The distracter stimuli were identical in size and shape to the target stimulus (that is, filled circles of 0.7° diameter), but filled green instead of red. The location of the red target was randomized across possible locations of 1, 3, or 5° from the screen center (i.e., distracters always occupied the locations 2 and 4° from the center). The remaining viable stimulus locations were occupied by the four green distracters, which remained on the screen for 1 s.
|
study
| 100.0 |
The first component of the AST-mem required participants to look directly at the red target stimulus as quickly and accurately as possible, ignoring the green distracters, and then back to the center. In this way, the AST-mem condition eliminated the need for participants to actively inhibit the target, as required in the standard AST-s and in the AST-go/no-go task. In the second part of the task, however, the voluntary saccade was to be executed to the mirror-image location of the previous target location within a blank screen. This variant, the AST-mem condition, thus taxed spatial WM while minimizing the extent to which IC was to be exercised. To reduce the likelihood of older participants neglecting to respond at all, after the delay period (as might be expected according to advocates of the goal neglect hypothesis of aging, e.g., Duncan et al., 1996), a double cross-modality cue was presented to prompt participants to initiate the saccade: the visual offset of the central fixation stimulus, was presented simultaneously with an auditory beep. At the time of the subsequent voluntary saccade, the screen was completely blank, thus creating a situation likely to load more heavily onto WM, since no markers were present to aid the recollection of the previous target location, and the eye movement was programmed according to the spatial representation of the target location in memory. The presentation order of the composite screens in the AST memory-guided (AST-mem) condition is represented in Figure 1 (middle panel).
|
study
| 100.0 |
In this condition, the target was a black filled circle of 0.7° diameter, which appeared at 4° to the left or right of the screen center. The two possible locations of the target were highlighted at all times throughout the trial with faint circular markers, 0.7° in diameter, to reduce the need for participants to maintain location-based representations of the target in WM. Upon extinction of the central cross after 200 ms, one of two stimuli appeared in the same central location: either a red cross or a green arrow, matched in size (approximately 0.7° diameter), and approximate pixel density. A 200 ms gap then elapsed, followed by the appearance of the stimulus to either the left or right as displayed in Figure 1 (right panel).
|
study
| 100.0 |
Participants were instructed that a central red cross denoted a no-go trial, and consequently participants should remain fixated on this stimulus, making no voluntary eye movements. Participants were instructed that they were required to saccade in the direction indicated by the central green arrow, which would always point in the opposite direction to the location of the target stimulus. The central cue (green arrow or red cross) and the black target remained simultaneously visible for 1 s, before they were extinguished and the trial ended. In this way, the central arrow cues further reduced the WM load, by aiding the orienting of attention, and subsequently, eye movements.
|
study
| 99.9 |
The use of the color red to denote stop and the color green to denote go was considered to be a pairing that was ecologically valid; participants are likely to have experienced this pairing on many occasions previously (for example at traffic lights or pedestrian crossings). Furthermore, the arrow was considered to be easily comprehensible encouragement to look in the direction indicated by arrowhead, and the cross, an obvious reminder that no eye movements were permitted. Previous research has demonstrated that arrow cues rapidly direct attention towards the direction in which the arrowhead is pointing (Hommel et al., 2001; Tipples, 2002; Butler and Zacks, 2006). Thus, the arrowhead cue pointing towards the opposite visual hemifield to the target location should reduce WM load relative to the standard AST condition, and greatly reduce WM load relative to the memory-guided AST condition. Importantly, the AST-go/no-go still posed an inhibitory load, since participants were required to inhibit the reflexively programmed prosaccade to the sudden-onset of the red distractor. The presentation order of screens in the AST-go/no-go condition is displayed in Figure 1 (right panel). The mean latencies and mean accuracy deviations of correct saccades, and mean proportion of directional errors were collated for each condition, per participant. Saccades were identified using algorithms applied by DataViewer (SR Research Ltd.,) and then visually inspected by the experimenter to ensure that all saccades were executed at least 80 ms after the appearance of the target stimuli in each condition, and exceeding 1° in amplitude. Latencies of less than 80 ms were deemed anticipatory errors, and such trials were excluded from the analysis. Latencies greater than 800 ms were discounted from the analysis on the grounds that they represented a lapse in concentration and not representative of saccadic performance in general. Visual inspection of the data files enabled trials in which the eye sample visibility was lost by the eye tracker (for example, trials in which the participant may have moved their head, or closed their eyes) to be identified and omitted from data analysis.
|
study
| 100.0 |
The amplitudes of correctly executed saccades were collated, in order that the spatial accuracy of saccades between the conditions, as well as between the two age groups could be assessed. Accuracy was calculated as the absolute error of the eye landing position in relation to the target. Trials in which participants looked in a direction contrary to the task requirements (i.e., where participants look towards the target in AST conditions; where participants looked towards the target in no-go trials of the AST-go/no-go conditions; or where participants failed to look at the target in PST) were classed as errors, and were analyzed separately to valid trials. The number of such directional errors was recorded, and the proportional error rate was calculated as the absolute number of errors divided by the number of valid trials recorded for that participant in that condition. Repeated-measures analyses of variance using SPSS (v22) were conducted in order to distinguish the effects of WM and IC on the different tasks. Mauchly’s test was used to examine any violations of sphericity in the repeated-measures analyses. Where Mauchly’s failed to reject the null hypothesis of sphericity, the Greenhouse-Geisser, Huyn-Feldt, and Lower-Bound corrections were examined using the corrected degrees of freedom. As all the effects remained statistically significant (p < 0.01), for both the sphericity assumed and sphericity corrected, we only report the F- and p-values for the sphericity unassumed analyses. The Levene’s test was used to examine the assumption of homogeneity of variance. Where this assumption was not satisfied, we re-examined the analyses using square-root transformation. As the pattern of results was unchanged and remained significant at p < 0.01, we report the statistics for the untransformed data.
|
study
| 100.0 |
First, we conducted a one-way ANOVA on the PST data to determine whether the groups were comparable in the baseline, control task, where there was no IC or WM load. The mean latencies and spatial accuracy for the PST baseline task were comparable in the older group (mean latency = 171 ms, SD = 43; mean spatial accuracy = 0.66°, SD = 0.27) and younger group (mean latency = 154 ms, SD = 25.1; mean spatial accuracy = 0.57°, SD = 0.14). The ANOVA revealed that there was no effect of age group on prosaccade latencies [F(1,30) = 1.76, p = 0.195] or spatial accuracy [F(1,30) = 1.324, p = 0.259]. This confirms that there was no general decline in motor processing speed or spatial accuracy with age.
|
study
| 100.0 |
The WM hypothesis predicts an interaction between age group and the tasks; according to this hypothesis, the older group should reveal disproportionate slowing on the AST-mem task, due to the fact that the AST-mem places a high load on spatial memory (together with a low inhibition load – eye-movements were permitted to the prepotent target). The IC hypothesis also predicts an interaction between age group and task. However, according to the IC hypothesis, the older group should show a greater slowing in the AST-go/no-go, due to the fact that this task demands a higher level of IC than the AST-s (together with a low load on WM). Therefore, we submitted the latency data to a 2 (age group) × 4 (task) mixed ANOVA. This analysis revealed that there was an overall increase in mean reaction times for the older adults [Group effect: F(1,29) = 12.716, p = 0.001, η2 = 0.305]. Critically, there was a significant task × group interaction [F(3,87) = 8.008, p = 0.001, η2 = 0.216]. In support of the IC hypothesis, Figures 2 and 4 reveal that the saccade latencies of the older groups were disproportionately slowed in the AST-go/no-go task. To determine the source of this interaction, we conducted a series of t-tests to evaluate the effect of age group in each of the three AST tasks. The t-tests revealed that there was a significant effect of age group in the AST-go/no-go task [t(29) = -3.282, p = 0.003], but there was no age group effect for the AST-s [t(29) = -1.419, p = 0.167], or AST-mem tasks [t(29) = -0.128, p = 0.899].
|
study
| 100.0 |
It shows the means of saccade latencies for the younger and older participants in the prosaccade (PST), the standard antisaccade (AST-s), memory-guided antisaccade (AST-mem), and go/no-go antisaccade tasks (AST-go/no-go). Older participants have substantially longer latencies in the AST-go/no-go in comparison with the younger participants. Error bars represent standard errors.
|
study
| 100.0 |
Compared to the young group, the older group committed more errors across all the AST conditions [F(1,29) = 8.122, p = 0.008, η2 = 0.219]. Unsurprisingly, there was a significant task effect [F(2,58) = 7.391, p = 0.001, η2 = 0.203], with the AST-mem yielding the smallest proportion of errors (recall that participants were permitted to look immediately towards the prepotent target at its target onset). The AST-s yielded the most errors, presumably because this task did not facilitate either memory (cf. AST-go/no-go) or the release from inhibition (cf. AST-mem). This analysis revealed that there was no significant interaction of the task with age group (Figures 3, 4).
|
study
| 100.0 |
It shows that older participants make a higher proportion of errors than younger participants in all, the standard antisaccade (AST-s), memory-guided antisaccade (AST-mem), and go/no-go antisaccade tasks (AST-go/no-go). Error bars represent standard errors.
|
study
| 99.94 |
There was no effect of age group on the accuracy of saccades across the three ASTs [F(1,29) = 0.901, p = 0.258, η2 = 0.044]. Older groups show no deterioration in accuracy in any of the three variants of the AST (AST-s: Old = 1.49°, SD = 0.93; Young = 1.66°, SD = 0.82; AST-mem: Old = 0.66°, SD = 0.13, Young = 0.56°, SD = 0.25; AST-go/no-go: Old = 1.17°, SD = 1.18, Young = 0.71°, SD = 0.32). There was a significant main effect of AST task, in a similar fashion to the errors data reported above: the least spatially accurate saccades were generated in AST-s, and the highest spatial accuracy was found in the AST-mem [F(3,87) = 15.246, p = 0.000, η2 = 0.34].
|
study
| 100.0 |
There were no significant effects of age group on any of the standard psychometric measures. For both age groups combined, there was a significant correlation between digit and verbal span (Pearson’s r = 0.707, p < 0.01); spatial span was also significantly correlated with NART scores (r = 0.463, p < 0.01). The saccade latencies in the AST-s (r = -0.468, p < 0.01) and AST-go/no-go (r = -0.477, p < 0.01) were both significantly, negatively correlated with spatial span. There were no significant correlations between AST error rates and the psychometric measures for the young or old groups. However, for the young group, there was an unexpected correlation (r = 0.69, p = 0.003) between error rates in the AST-go/no-go task and the NART. This suggests that this demanding inhibition task yields fewer errors in those young people with greatest amount of cognitive reserve, and yields more errors in those with lower cognitive reserve as reflected in the NART premorbid IQ measure.
|
study
| 100.0 |
Theories about the cause of the age-related differences on the AST have largely centered around two sources of cognitive dysfunction: IC and WM. According to Hasher et al. (1999), Hasher and Zacks (1988), and Crawford et al. (2011) a reduction in IC with advancing age could affect performance on cognitive tasks in various ways: an age-related deterioration of an inhibitory filter, acting as a gateway into WM, could lead to a decline in the efficiency in which task-irrelevant information is prevented from entering WM; a reduction in the ability to suppress irrelevant information that has entered WM could prevent distracting information from being inhibited, and thus increase the interference effects of this irrelevant information on the current cognitive task. Therefore, the IC hypothesis claims that the age-related impairments in tasks involving WM are causally related to inhibitory cognitive mechanisms deteriorating with age, and not the other way round. The alternative WM-led approaches claim that this should be reversed; it is primarily a deterioration of WM that is responsible for age-related AST impairments.
|
review
| 99.7 |
Before turning to the aging effects on AST cognitive control, it is worth noting several features of the prosaccadic eye movements that were preserved in the older population. The PST data allows for a baseline comparison against the three ASTs across the age groups. The reaction times of prosaccades were relatively well preserved in the older group (mean = 175 ms vs. young group mean = 154 ms), showing that processing speed was preserved in the older group. It is important to note that there was no evidence that these fast reaction times were achieved at the expense of accuracy. The older group (mean = 0.64°) was not significantly different to the prosaccade spatial accuracy of the young group (mean = 0.58°). The frequency of prosaccade errors was negligible for both age groups. This confirms that prosaccades are fast, automatic responses that are relatively well preserved in healthy aging. As expected, prosaccade latencies were significantly faster than AST latencies for both the young and older adults, reflecting the additional processing component required for motor programming in the AST (Hallett, 1978).
|
study
| 100.0 |
According to previous research, older people generate increased latencies and/or an increase in the proportion of directional errors in the AST (e.g., Fischer et al., 1997; Eenshuistra et al., 2004). The aim of the present research was to determine whether WM or IC was the source of this effect. The key findings revealed the following: First, the older adults were substantially slower in the AST-go/no-go task. Clearly, the additional inhibitory load had a disproportionate effect on the saccade slowing for the older group. Saccade latencies in AST-go/no-go task were markedly slower than AST-mem latencies. This slowing was probably due to the element of response uncertainty in the AST-go/no-go task. This appears to have resulted in a general response hesitancy presumably due to the 50% chance that any given trial will require an eye movement away from the target, or complete inhibition of the saccade. Participants did not know whether they would be required to execute an antisaccade, or to maintain fixation on the central cross.
|
study
| 100.0 |
Second, the older group generated more errors in each of three ASTs compared to the young group. In contrast to response latencies, this age group effect was of a similar magnitude across the ASTs. The proportion of errors differed between the AST-mem and the AST-go/no-go. As expected, higher error rates were generated in AST-s due to the absence of any cues to facilitate either WM or IC. This implies that both WM and IC contributed to the increased error rates of the older group. In contrast, the spatial accuracy of the saccades was similar in the two groups.
|
study
| 100.0 |
No significant differences were observed in the psychometric measures, between the two age groups. Since some of these measures purportedly reflected WM efficiency (the digit span forward; digit span backward; spatial span forward; and spatial span backward), this suggests these psychometric measures are relatively insensitive to the AST effects on aging. This result has been found previously. Surprisingly in the Eenshuistra et al. (2004) experiment reported earlier, conclusions were drawn in favor of a deterioration of WM as the key source of age-related AST impairments, under the assumption that WM deficits among older participants may only noticeably affect cognitive task performance under conditions of competing task responses (e.g., Roberts et al., 1994). Thus, the WM measures derived from the AST conditions of the various tasks may be more sensitive to subtle age-related cognitive changes in healthy adults.
|
study
| 100.0 |
The primary question this research addressed was whether it was possible to detect independent influences of IC and WM processes on the decline in the age-related executive control of eye gaze. A significant interaction was observed between age group and the AST-go/no-go latencies. The AST-go/no-go demands a greater IC than the standard AST; the substantive effects in the older cohort provide strong evidence that it is the increased inhibitory load (rather than WM) that was problematic for this older group. This finding supports the Hasher and Zacks (1988) Inhibition Hypothesis. However, AST errors were increased in all of the ASTs. This suggests that, for the older group, neither the selective facilitation of WM nor IC was sufficient to eliminate AST errors. Apparently, both of these operations contribute to the errors that older people experience in the ASTs. The error data demonstrates that healthy aging is associated with changes in both IC and WM. Reduced IC was related to the slowing in the speed of reaction times in the older groups, while reduced WM and IC both contribute to the increased errors.
|
study
| 100.0 |
An understanding of the specific mental operations that underlie the changes in aging and dementia is of theoretical and practical importance. Clearly, valid cognitive models of aging require a clearer understanding of the core cognitive processes and their interrelationships (Crawford et al., 2011). This will also help to develop effective and preventative strategies for maintaining cognitive health in old age.
|
review
| 99.56 |
This study was carried out in accordance with the recommendations of Lancaster University Psychology Ethics Committee with written informed consent from all subjects. All subjects gave written informed consent in accordance with the Declaration of Helsinki and ethical guidelines of the British Psychology Society. The protocol was approved by the Lancaster University Psychology Ethics Committee.
|
other
| 99.94 |
In the last decade, the importance of both whole-brain radiation therapy (WBRT) and stereotactic radiosurgery (SRS) in the management of brain metastasis (BM) has been highlighted again with the latest improvement in prognostic stratification. Sperduto et al. published the results of a secondary analysis of the Radiation Therapy Oncology Group (RTOG) 9508 trial comparing WBRT + SRS with WBRT alone in the management of 1–3 BMs . In that analysis, non-small cell lung cancer (NSCLC) was the dominant primary tumor. The patients with favorable prognoses showed improved survival when treated with WBRT + SRS compared to those treated with WBRT alone (p = 0.05). In their secondary analysis of the JROSG 99-1 trial, Aoyama et al. post-stratified the NSCLC patients. They reported that the patients with BM from NSCLC in the favorable-prognosis group had longer survival when treated with WBRT + SRS compared to those treated with SRS alone (p = 0.04) . The difference in overall survival was not observed in the worse-prognosis group (p = 0.86). For the patients with a good systemic condition and a small number of systemic metastases, improved intracranial tumor control could lead to prolonged survival.
|
review
| 99.9 |
Although both WBRT and SRS are indispensable in the management of BM, two trials demonstrated a negative impact of WBRT on the patients’ neurocognitive function (NCF) at 3–4 months after the treatment, and these results set the trend toward the SRS-alone strategy . It is of note that the Hopkins Verbal Learning Test-Revised (HVLT-R) was used in both of those studies, and this test is considered to have adequate properties to assess the NCF after brain irradiation; the English version of the HVLT-R has been increasingly used in trials dealing with brain metastasis and other brain tumors .
|
review
| 99.8 |
The objectives of the present study were to (1) investigate the feasibility of the use of the Japanese version of the HVLT-R; (2) identify the clinical factors influencing the HVLT-R (Japanese version) scores of patients who have undergone WBRT; and (3) compare the patients’ NCF after WBRT in different dose fractionation schedules.
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study
| 100.0 |
The characteristics of the 45 patients are listed in Table 1. The 25-Gy group was comprised of only the LD-SCLC patients who were assigned to prophylactic WBRT (n = 11), and they had no intracranial metastases at the beginning of the WBRT. Sixteen patients (36%) underwent HVLT-R at four months after WBRT but did not undergo the eight-month examination. The remaining 29 patients (64%) underwent the eight-month examination. The most common reason for the discontinuation of HVLT-R was death from cancer (n = 8). The proportion of patients who did not undergo the eight-month examination was significantly higher in the Karnofsky Performance Status (KPS) ≤ 70 group compared to the KPS ≥ 80 group (Table 2, p = 0.014 by Fisher’s exact test).
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study
| 99.94 |
Table 3 shows the association between the baseline scores of the subdomains TR, DR, DRecog of the HVLT-R, and the clinical factors. The patients with KPS ≥ 80 had significantly higher TR scores (p = 0.0053 by Mann-Whitney U-test), higher DR scores (p = 0.012), and higher DRecog scores (p = 0.0078) compared to the patients with KPS ≤ 70. The patients aged ≤65 years also had significantly higher TR scores (p = 0.030) and higher DRecog scores (p = 0.031) compared to the patients aged ≥66 years, and they tended to have higher DR scores (p = 0.080). There were no significant differences in any HVLT-R subdomain scores among the WBRT dose groups, or among the different types of the cranial lesion.
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study
| 100.0 |
Figure 1 summarizes the HVLT-R subdomain scores in the patients who did not undergo the eight-month examination. The DR scores were significantly decreased four months after WBRT compared to the baseline (p = 0.0073 by Wilcoxon signed rank test). The TR scores tended to decline four months after WBRT (p = 0.057), but this change was not observed in the DRecog scores (p = 0.15).
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study
| 100.0 |
Table 4 shows the HVLT-R scores of the patients whose total number of examinations was three (baseline, four, and eight months) by WBRT dose fractionation. In the 25-Gy group, the four-month TR scores were significantly higher than the baseline scores (Bonferroni-adjusted p = 0.045). To test the hypothesis that the patients who underwent 25-Gy WBRT and three examinations had worse baseline TR scores compared to the other WBRT dose groups, we compared the baseline TR scores of each WBRT dose group by Kruskal-Wallis test. There were no significant differences in the baseline TR scores among the WBRT dose groups (p = 0.40). The eight-month HVLT-R scores were not significantly declined in any subdomain regardless of the WBRT dose fractionation.
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study
| 100.0 |
Table 5 shows the proportion of significant decline in four-month individual HVLT-R scores and clinical factors. The patients with KPS ≤ 70 were significantly more likely to have declined TR scores at four months compared to the patients with KPS ≥ 80 (Fisher’s exact test, p = 0.013). Similarly, the patients who underwent two examinations (worse-prognosis group; baseline and four months) were significantly more likely to have declined TR scores (p = 0.0017) and DR scores (p = 0.035) compared to the patients who underwent three examinations (better-prognosis group; baseline, four, and eight months).
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study
| 100.0 |
This is the first clinical study in which the Japanese version of the HVLT-R was used to investigate the serial changes in NCF after brain irradiation. By applying this test, we were able to assess subtle differences or changes before and after brain irradiation, which might not be detected by the Mini-Mental State Examination (MMSE).
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study
| 99.9 |
At the baseline, the patients with either older age or lower KPS exhibited lower HVLT-R scores. A similar association was observed with the MMSE. Aoyama et al. reported that BM patients aged ≥66 years or those with KPS ≤ 80 had lower baseline MMSE scores than their counterparts . Kurita et al. used the MMSE to analyze the NCF of 1915 cancer patients who underwent treatment with opioids , and they reported that older age and lower KPS were independently associated with MMSE scores <27.
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study
| 99.94 |
Although it has been used widely, a weak point of the MMSE is that it is designed to evaluate global cognitive function rather than learning and memory. It also has a ceiling effect . Sun et al. published the results of their secondary analysis of the RTOG 0214 trial evaluating the effect of prophylactic WBRT for advanced NSCLC : the rate of decline in individual TR scores of the HVLT was significantly higher in the prophylactic WBRT arm at 3, 6, and 12 months, whereas the rate of decline in individual MMSE scores was higher in the intervention arm only at three months. The ability of the HVLT-R to detect subtle changes in learning and memory supports its routine use in trials evaluating cranial radiation therapy for BM.
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study
| 98.75 |
One of the interesting findings of the present study is that a significant decline in the score at four months was observed only in the patients who underwent the examination twice (worse-prognosis group; baseline and four months) but not in the patients who underwent the examination three times (better-prognosis group; baseline, four, and eight months). Sixteen (36%) of our patients underwent the four-month HVLT-R but dropped out before the eight-month examination. Their DR scores declined significantly compared to the baseline, and they were also significantly more likely to have declined individual TR and DR scores at four months compared to the patients who completed the four-month examination. The reason for dropping out by eight months was mostly death from cancer or worsened general condition. The KPS ≤ 70 at the baseline was a risk factor for discontinuation of the HVLT-R and declined individual TR scores at four months. The KPS is regarded as a prognostic factor of several primary cancer sites, and it is reasonable that the patients with a low KPS have worse survival and cannot undergo repeated HVLT-R examinations.
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study
| 99.94 |
Cognitive deterioration determined by the HVLT-R at three or four months was employed as a primary endpoint in two randomized clinical trials (RCTs) comparing SRS alone and SRS + WBRT for patients with one to three brain metastases . In a recent publication from North America, Brown et al. reported that there was less cognitive deterioration at three months after SRS alone (40/63, 63.5%) than when SRS was combined with WBRT (44/48, 91.7%). In a smaller RCT from the MD Anderson Cancer Center, Chang et al. reported that patients who were randomly assigned to receive SRS + WBRT were significantly more likely to show a decline in learning and memory function (mean posterior probability of decline 52%) at four months than patients assigned to receive SRS alone (mean posterior probability of decline 24%). It should be noted that the former (Brown et al.) study recruited 213 patients (SRS alone, n = 111, SRS + WBRT, n = 102); however, only 57% (63/111) of the patients in the SRS-alone group and 47% (48/102) of the patients in the SRS + WBRT group underwent HVLT-R at three months. Similarly, in the Chang et al. study, only 67% (20/30) of the patients in the SRS-alone group and 39% (11/28) of the patients in the SRS + WBRT group underwent the HVLT-R at four months. The results of the present study suggest that the four-month decline in NCF is characteristic of the lower-KPS group, and this early decline must be distinguished from the true long-term toxicities that affect the favorable-prognosis group. This finding is supported by the RTOG 0933 trial evaluating hippocampus-avoiding WBRT; Gondi et al. reported that the HVLT-R DR scores of the patients who had died by six months declined significantly over time . This decline was not observed in the patients who were alive at six months.
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study
| 99.9 |
Regarding the association between the schedule of WBRT and the HVLT-R score among the 29 patients who underwent both the four- and eight-month tests in the present study, neither the total dose nor the fractionation of WBRT affected the four- and eight-month HVLT-R scores. Wolfson et al. conducted the RTOG 0212 trial comparing three different prophylactic WBRT dose fractionations in LD-SCLC . They used the HVLT, the Controlled Oral Word Association Test (COWAT), and the Trail Making Test (TMT) parts A and B. Chronic neurotoxicity was defined as deterioration in at least one test without the development of brain metastases at 12 months. In a logistic regression analysis, chronic neurotoxicity was associated with the WBRT dose fractionation of 36 Gy in 18 fractions and older age. It seems difficult to assess the relationship between the WBRT dose fractionation and the incidence of 12-month decline in the NCF of BM patients, because the median survival time for all BM patients is approximately eight months . The late adverse effects of therapeutic WBRT for BM will be of clinical importance for long-term survivors.
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study
| 99.94 |
Our study has several limitations. First, the study population was heterogeneous because we compared the NCF of patients who had undergone different WBRT fractionation schedules; Second, the small sample size made it difficult to elucidate possible confounders with a multivariate analysis; Finally, the degree of radiation-induced NCF deterioration might be overestimated, because it was difficult to eliminate the effect of the regrowth of intracranial tumors.
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study
| 100.0 |
We enrolled the patients who were assigned to therapeutic WBRT for the treatment of BM, skull metastasis, dural metastasis, leptomeningeal dissemination of cancer, or central nervous system (CNS) involvement of non-Hodgkin lymphoma (NHL) from April 2012 to May 2014 at Niigata University Hospital and Niigata Cancer Center Hospital. We also included patients with limited-disease small cell lung cancer (LD-SCLC) who were assigned to prophylactic WBRT. Patients with a neurological deficit, such as a consciousness disorder, hemiparesis, visual defect, or aphasia, that could disturb the neuropsychological examinations were excluded. The dose fractionation of therapeutic WBRT was 35 Gy in 14 fractions over 3 weeks at Niigata University Hospital, and 30 Gy in 10 fractions over 2 weeks at Niigata Cancer Center Hospital. The fractionation of prophylactic WBRT was 25 Gy in 10 fractions over 2 weeks at both institutions. After WBRT, a follow-up neuroradiological examination was performed with contrast-enhanced x-ray computed tomography (CT) or magnetic resonance imaging (MRI) every 2–6 months. Written consent was obtained from all patients or their relative before WBRT. This study was approved by the Institutional Review Board of Niigata University Hospital (Study #1449).
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study
| 99.94 |
Each patient’s NCF was assessed with the HVLT-R (Japanese version), consisting of the total recall (TR), delayed recall (DR), and delayed recognition (DRecog) subdomains. The HVLT-R was performed before (baseline) and at 4 months and 8 months after the completion of WBRT. The HVLT-R test battery contains six different question forms so that the participant cannot memorize the answers. The interval between the day exactly 4 or 8 months after WBRT and the actual date of the follow-up HVLT-R was <1 month. The HVLT-R scores were analyzed in two different ways. One way was an inter-group or intra-group (the baseline, 4, and 8 months) comparison of raw scores with nonparametric tests, and the other way was to judge whether the 4- or 8-month score of a participant was significantly declined compared to the baseline beyond a specific cutoff value. Significant deterioration in an individual’s NCF was defined as a drop from the baseline score by ≥5 points for TR, ≥3 points for DR, and ≥2 points for DRecog . For example, if the baseline TR score was 15 and the 8-month TR score was 9, the 8-month TR score was judged as declined compared to the baseline.
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study
| 100.0 |
The association between the patient characteristics and the baseline HVLT-R scores in each subdomain was evaluated with the Mann-Whitney U-test and the Kruskal-Wallis test. Among the patients who underwent the 4-month examination and did not undergo the 8-month examination, the HVLT-R scores at the baseline and 4 months after WBRT were compared using the Wilcoxon signed rank test. Among the patients who completed the 8-month examination, we used the Friedman test to compare the baseline, 4-month, and 8-month scores. A univariate Fisher’s exact test was performed to determine the factors associated with a significant decline from the baseline score in each HVLT-R subdomain. A p-value <0.05 was considered significant.
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study
| 100.0 |
The results of this study demonstrated the feasibility of the HVLT-R Japanese version for evaluating the patients’ NCF after brain irradiation. We found that the patients with either older age or lower KPS had impaired NCF as assessed with the HVLT-R at the baseline. The four-month NCF deterioration was associated with both the KPS and poor outcome. The WBRT dose fractionation did not have an impact on the incidence of the decline in the NCF at four or eight months. The early decline in the NCF is characteristic of the worse-prognosis group, and thus the NCF of favorable-prognosis patients might better be evaluated later (i.e., at six months or later) after irradiation.
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study
| 100.0 |
Recently in Scientific Reports, Skoufias and co-workers published a paper entitled “Self protein-protein interactions are involved in TPPP/p25 mediated microtubule bundling” in which a number of data are presented on the interaction of Tubulin Polymerization Promoting Protein (TPPP/p25) forms with tubulin and microtubule (MT)1. In our previous studies following the discovery of TPPP/p25 as a microtubule associated protein (MAP) our data support a model for TPPP/p25-induced MT bundling2345. Our reported findings in relation to the structure and function of TPPP/p25 - relevant to the Skoufias’s paper1 - are as follows: i) it is a disordered protein with unstructured N- and C-termini straddling a flexible CORE region as detected by multinuclear magnetic resonance spectroscopy6; ii) its dimers display higher tubulin assembly activity than the monomers4; ii) it induces MT assembly coupled with bundling activity resulting in resistance against anti-MT agents7. These findings indirectly support a mechanism for the stabilization of the MT network by dimeric TPPP/p25.
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study
| 100.0 |
The objective of this Comment paper is to highlight a critical point leading the authors to the suggestion as follows: “the central folded domain of TPPP/p25 following binding to microtubules can drive homotypic protein-protein interactions leading to bundled microtubules” (cf. Abstract)1. In fact, this hypothesis is based upon the observation that: “Our biophysical analysis of all the fragments though did not support the formation of TPPP/p25 dimers in solution” (page 11). Our biochemical, biophysical and immunological Please change analysis to analyses. have provided evidence for concentration-dependent dimerization of TPPP/p25 in the absence of MTs4, however, it is promoted by the presence of ligands such as GTP4 and the bivalent zinc ion8. We have also established the role of intermolecular disulphide bridges in the stabilization of the dimers4, and that in the presence of dithioerythritol (DTE) (its epimer, DTT was used in the commented paper) the detection of the dimer forms is ambiguous48. In the experiments presented in Skoufias’s paper1, DTT (1 mM) is present in the TPPP/p25 solutions including the stored stock solutions and the solutions used for the binding and polymerization assays. This condition favours neither the detection of the dimeric form nor the dimer-enhanced tubulin polymerization activity resulting in low polymerization potency (cf. Fig. 1C of ref. 1 versus Fig. 3B of ref. 5). In order to enhance the relative amount of the disulphide-stabilized dimers, in selected experiments the stock solutions of TPPP/p25 (200 μM) were pre-incubated at room temperature, and the dimers could be detected even by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) (cf. Fig. 1) as demonstrated earlier4.
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study
| 99.94 |
In addition, we detected the dimeric form by other approaches as well such as sandwich enzyme-linked immunosorbent assay (ELISA)8, size exclusion gel chromatography4 and isothermal titration calorimetry4. Now we have performed sandwich ELISA experiment with the N- and/or C-terminal free forms as earlier with the full length protein to establish the role of the unstructured terminal segments in the dimerization of the TPPP/p25. To validate the in vitro data obtained with isolated protein variants, we have performed in vivo experiments as well using bimolecular fluorescence complementation assay (mVenus BiFC), similarly as described in the commented paper1.
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study
| 100.0 |
Figure 1a shows a typical dissociation curve of the full length (FL) TPPP/p25 in the absence and presence of the reducing agent DTE. The finding is that the amount of the dimeric forms without reducing agent is much higher than with added DTE. Obviously, a fraction of the dimers stabilized by disulphide bridges in the stock solution does not dissociate into monomers.
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study
| 100.0 |
To obtain information about the ratio of the stabilized dimers and monomers, aliquots from the stock solutions (200 μM) were loaded directly into SDS-PAGE. As shown in Fig. 1b, substantial fraction of all TPPP/p25 solutions contains disulphide-stabilized dimers. The stock solutions of the FL and the different truncated forms diluted to 1 μM were applied for sandwich ELISA experiments according to the following experimental design as illustrated schematically, the result are presented in Fig. 1c,d:
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study
| 100.0 |
In one set of sandwich ELISA experiments the FL TPPP/p25 and its truncated forms were added to the immobilized mAb, and the dimer forms were quantified by biotinylated mAb (Fig. 1c). In the second set of experiments reduced FL or CORE form were added to the immobilized mAb, then the associations of the different TPPP/p25 forms with the monomeric FL or CORE forms were tested by the biotinylated mAb (Fig. 1d).
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study
| 100.0 |
The sandwich ELISA data presented in Fig. 1c,d demonstrate the dimerization/oligomerization potency of all TPPP/p25 forms including the double truncated (CORE) one; in addition, the capability of both the reduced (monomer) FL and CORE forms to interact with the various TPPP/p25 forms, even if to different extents, is validated. This issue occurred in the absence of tubulin/MTs.
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study
| 100.0 |
As shown in Fig. 2, the polymerization potency of the FL TPPP/p25 to both tubulin and MT is affected by the nature of the truncation. According to the Skoufias’s paper the order of the binding constants are published for the interaction of the MT with FL, N- or C-terminal free forms (cf. Fig. 4 in ref. 1)1. However, it needs to emphasise that there is a difference between the length of the CORE segments 50–157 vs 44–174, used in the two labs, consequently the lengths of the termini are shorter in our case. Nevertheless, the data presented in Fig. 2 qualitatively do not differ from that presented in the commented paper. According to our studies, the following qualitative order could be established for the binding and polymerization potencies of the TPPP/p25 forms:
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study
| 100.0 |
As we revealed earlier TPPP/p25 co-localizes with the MT network and displays extensive bundling activity in different cell lines expressed by transfection (HeLa) or doxycycline induction (CHO10) or endogenously (CG-4), and it regulates the dynamics and organization of the MT network via its tubulin polymerization promoting and MT bundling activity as well as tubulin acetylation enhancing activity5710. We have also shown with immunofluorescence microscopy that in contrast to the FL TPPP/p25 the CORE segment (double truncated form) distributed homogeneously within the cytoplasm5. Most importantly, we suggested that “The finding that the double truncated TPPP/p25 cannot associate with the MT network underlines the role of the unstructured termini in the physiological function of TPPP/p25” 5.
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study
| 100.0 |
We have performed a similar set of experiments using BiFC assay (mVenus 1–173 and 155–238 constructs) as described in the commented paper1 using mVenus vectors (cf. Fig. 3. legend) to test the associations of the FL-FL and CORE-CORE pairs at cellular level as well. As shown in Fig. 3a,b, the assembly of the mVenus pair (green fluorescence signal) is visible in both cases that correspond to the in vitro data (cf. Fig. 1). We have performed control experiments with the empty mVenus pair (Fig. 3c) in order to distinguish the BiFC signal produced by the TPPP/p25 forms from the non-specific BiFC signal generated by the intrinsic tendency of the two fluorescent protein domains to complement each other. In this control experiment low fluorescent signal could be detected as compared to that performed with the FL or CORE pairs. However, the intracellular localization of the BiFC signals was very distinct: in the case of FL protein it is aligned along the bundled MT network (Fig. 3d–f); while, the CORE segment-derived signal distributes predominantly homogeneously within the intracellular space of HeLa cells (Fig. 3g–i). These in vivo data suggest the involvement of the unstructured termini of TPPP/p25 in the cross-linking of the MT network. Periodical cross-linking of isolated MTs by recombinant TPPP/p25 were visualized by electron microscopy as well11. The electron microscopic images showed that the majority of MTs, 25–26 nm in diameter, formed bundles consisting of dozens of MTs decorated by rows of tiny projections and dense particles with a periodicity of about 16 nm. Similar electron microscopic analysis provided evidence for the periodic crosslinking of MTs by the tetrameric phosphofructokinase derived by the MT-bound dimeric enzymes1213.
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| 100.0 |
Both the monomeric and dimeric TPPP/p25 bind to tubulin and MT inducing MT assembly, however, the polymerization potency of dimers seems to be higher; MT bundling activity is displayed by the dimers as illustrated in the tentative model. On the basis of our previous and present data, we have established a molecular model for the maturation of the bundled MT structure stabilized by TPPP/p25 dimers (Fig. 4).
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study
| 100.0 |
TPPP/p25 has been recognized as a MAP that displays two crucial features: i) it does not have a 3D structure, namely it is disordered2614; ii) it is enriched in inclusions of the neurons and oligodendrocytes in the cases of Parkinson’s disease and multiple system atrophy, respectively15; although in normal brain it is expressed primarily in oligodendrocytes1617. The mechanism by which TPPP/p25 contributes to toxicity in Parkinson’s disease is related to its interaction with α-synuclein; their pathological complex has been considered as a potential drug target515. The physiological role of TPPP/p25 manifests itself in the differentiation of the progenitor oligodendrocytes as demonstrated by siRNA technique and specific microRNA (mir206)17. The differentiated oligodendrocytes are the major constituents of the myelin sheath.
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study
| 99.94 |
The commented and critique papers, however, focus exclusively on the nature of the association of TPPP/p25 with the MT system. It has been well-documented earlier that TPPP/p25 promotes tubulin polymerization and the simultaneous bundling of the polymerized tubulin forms2 that stabilizes the intracellular MT ultrastructures such as perinuclear cage or aggresome10, and it makes them resistant against anti-microtubular agents such as nocodazole or vinblastine710. At cellular level bundling of the MT network by ectopically expressed TPPP/p25 in HeLa cells was demonstrated by both confocal and electron microscopies as well10, which revealed the existence of cross-linked MTs: the perinuclear cage consists of bundles of densely packed, parallel-aligned MTs running at different angles in close proximity to the nuclear membrane (cf. electron microscopic image).
|
review
| 99.44 |
Our experiments performed by immunofluorescent microscopy were reproduced by the Skoufias’ lab and presented in the DeBonis’ paper1 with references to our reported data. The single experiment that was not reproduced is the in vitro dimerization of the human recombinant TPPP/p25 in the absence of tubulin/MTs1. By studying carefully the differences of the experimental conditions used in the two labs we recognized a critical point causing the discrepancy, namely that all experiments performed in relation to the dimerization of TPPP/p25 by Skoufias and co-workers were carried out at reducing conditions (in the presence of DTT) that counteracted the stabilization of the dimers by disulphide bridges4. The spontaneous formation of the intermolecular covalent bridges at room temperature above 10 μM TPPP/p25 concentration can ensure the detection of dimers even by SDS/PAGE4. However, it is important to emphasize that TPPP/p25 dimers were detected in our lab, but not in Skoufias’s lab, by sandwich ELISA, isothermal titration calorimetry and size exclusion gel chromatography as well48.
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study
| 100.0 |
In this paper we refer to a couple of data reported previously458; in addition, new sets of experiments have also been performed that allowed us to suggest a plausible mechanism for the role of the unstructured N- and C-termini of TPPP/p25 in the dimer-derived MT bundling. Our previous electron microscopic studies underlined that the MTs are cross-linked by TPPP/p25, formed bundles of 25–26 nm in diameter consisting of dozens of MTs decorated by rows of tiny projections and dense particles with a periodicity of about 16 nm were observed211. In fact, the particles, likely dimers, express significant stabilization effect, similar to one as detected in the case of tau protein18. The tau protein, a key MAP of the brain MT system occurs in soluble form in normal neuronal cells, and the soluble tau-tau interactions display stabilizing effect as well on the MT structures1920. The formation of the pathological tau filaments has been reported, the development of which are promoted by the presence of MTs19. No TPPP/p25 filament formations have been detected as indicated in a recent paper as well to our knowledge; however, the formation of α-synuclein filaments has been established at substoichiometric TPPP/p25 concentration21.
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study
| 100.0 |
In conclusion, our previous and the new data presented in this comment paper support the role of TPPP/p25 in the MT bundling in agreement with the title’s message of the Skoufias’s paper1 that focuses on the dimerization potency of this disordered, brain-specific MAP24. This issue does not seem to be affected by differences manifesting in the truncation sites: the Skoufias’s group chose shorter CORE segment based on bioinformatics analysis1 than we had published originally on the basis of multinuclear magnetic resonance study6. Based upon our previous and present in vitro and in vivo data obtained with the FL and truncated TPPP/p25 forms, we have established a molecular model for the maturation of the bundled MT structure stabilized by TPPP/p25 dimers (Fig. 4). We do not exclude other possible mechanisms such as the binding of the N- and C- termini to separate MTs. Nevertheless, the key issue is the crucial role of the unstructured termini, not in the dimerization but in the cross-linking of MTs, in which all segments (CORE, N- and C-termini) are involved with distinct binding affinity in a cooperative manner. The TPPP/p25-derived stabilization of the MT network seems to be of physiological importance in the development of projections in the course of the differentiation of oligodendrocytes17.
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study
| 99.9 |
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