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90386f9e-70b5-450a-9309-0724390de5ff
| 4 |
These results indicate that the major role of the methionine-80 in cytochrome c is to preserve a closed hydrophobic heme crevice which is essential for the maintainance of the necessary redox potential.
|
6b330d56-8c12-4277-8675-aa3c7da48a14
| 0 |
A kinetic study of protein-protein interactions. Kinetic studies have been carried out of the monomer-dimer interaction of insulin, beta-lactoglobulin, and alpha-chymotrypsin using stopped-flow and temperature-jump techniques. The pH indicators bromothymol blue, bromophenol blue, and phenol red were used to monitor pH changes associated with the monomer-dimer interaction.
|
6b330d56-8c12-4277-8675-aa3c7da48a14
| 1 |
In all three cases a kinetic process was observed which could be attributed to a simple monomer-dimer equilibrium, and association (k1) and dissociation (k-1) rate constants were determined. The results obtained are as follows: for insulin at 23 degrees C, pH 6.8, 0.125 M KNO3, k1 = 1.14
|
6b330d56-8c12-4277-8675-aa3c7da48a14
| 2 |
X 10(8) M-1 s-1, k-1 - 1.48 X 10(4)s(-1); for beta-lactoglobulin AB at 35 degrees C, pH 3.7, 0.025 M KNO3, d1 = 4.7 X 10(4) M-1 s-1, k-1 = 2.1 s-1;
|
6b330d56-8c12-4277-8675-aa3c7da48a14
| 3 |
for alpha-chymotrypsin at 25 degreesC, pH 4.3, 0.05 M KNO3 k1 - 3.7 X 10(3) M-1 s-1, k-1 - 0.68 s-1. The kinetic behavior of the separated beta-lactoglobulin A and B was similar to that of the mixture. In the case of chymotrypsin, bromophenol blue was found to activate the enzyme catalyzed hydrolysis of p-nitrophenyl acetate, and a rate process was observed with the temperature jump which could be attributed to a conformational change of the indicator-protein complex.
|
6b330d56-8c12-4277-8675-aa3c7da48a14
| 4 |
The association rate constant for dimer formation of insulin approaches the value expected for a diffusion-controlled process, while the values obtained for the other two proteins are below those expected for a diffusion-controlled reaction unless unusally large steric and electrostatic effects are present.
|
5d4ee966-c5fa-4c72-9a94-6da63b71fe60
| 0 |
Ionophore A23187: the effect of H+ concentration on complex formation with divalent and monovalent cations and the demonstration of K+ transport in mitochondria mediated by A23187. The two-phase extraction technique has been used to study the equilibrium between A23187, metal cations, and H+. Under these conditions the ionophore forms charge neutral isostoichiometric complexes with divalent cations in which both carboxylate groups of the 2:
|
5d4ee966-c5fa-4c72-9a94-6da63b71fe60
| 1 |
1 A23187:M2+ complexes are deprotonated. In ethanol, however, the methyl ester of A23187 also binds divalent cations indicating that protonated complexes between A23187 and cations should also exist. With monovalent cations, A23187 forms two charge-neutral complexes of stoichiometries and relative stabilities: A2HM greater than AM.
|
5d4ee966-c5fa-4c72-9a94-6da63b71fe60
| 2 |
Examination of energy utilization K+ and H+ movements, and light scattering capacity of mitochondria in the presence of divalent cation chelators, A23187, and valinomycin demonstrates that A23187 can act as a nigericin type K+ ionophore under appropriate conditions. Formation constants for the A2HM complexes with monovalent cations indicate that with appropriate conditions transport of Li+ and Na+ mediated by A23187 would also be expected.
|
5d4ee966-c5fa-4c72-9a94-6da63b71fe60
| 3 |
The binding constant data and associated free energies of complex formation are compared as a function of ionic radius and of cation charge. The data indicate that lack of conformational mobility in A23187 is responsible for the high cation size selectivity of this compound. To explain the transport selectivity of A23187 for divalent cations, it is proposed that this ionophore forms a family of five complexes, isostoichiometric between cations of different valence but of which only charge-neutral species are permeant to membranes.
|
5d4ee966-c5fa-4c72-9a94-6da63b71fe60
| 4 |
The charge of a given complex is in turn determined by that of the cation. The concept is consistent with the divalent cation transport specificity of A23187, explains the observed monovalent cation transport, and is useful in rationalizing the differences in charge selectivity between A23187 and X-537A.
|
5f371c8a-6d4d-4342-83e1-c69b1fde6cfc
| 0 |
Properties of the tetrodotoxin binding component in plasma membranes isolated from Electrophorus electricus. The biochemical properties of the electrically excitable sodium channels in the electroplaque of Electrophorus electricus were investigated using tritiated tetrodotoxin (TTX) as a specific membrane probe. Membrane fragments from the electroplaque were isolated essentially by differential centrifugation and characterized with respect to the plasma membrane markers acetylcholine receptors, acetylcholinesterase, (Na+ + K+)ATPase, and [3H]TTX binding.
|
5f371c8a-6d4d-4342-83e1-c69b1fde6cfc
| 1 |
Equilibrium binding studies showed that [3H]TTX bound to a single population of noninteracting receptor sites with an apparent dissociation constant of 6 +/- 1 X 10(-9) M. The toxin-membrane complex dissociated with a first-order rate constant of 0.012 sec-1. Studies on the pH dependence of complex formation demonstrated the requirement for an ionizable, functional group with a pK of 5.3
|
5f371c8a-6d4d-4342-83e1-c69b1fde6cfc
| 2 |
and this group has been shown to be a carboxyl. Treatment of the membranes with trimethyloxonium tetrafluoroborate, a carboxyl group modifying reagent, resulted in an irreversible loss in the binding of [3H]TTX, which could be prevented by low concentrations of TTX or saxitoxin. This decrease was due to a reduction in the total number of binding sites and not to a decrease in toxin binding affinities.
|
5f371c8a-6d4d-4342-83e1-c69b1fde6cfc
| 3 |
The relative binding affinities of various monovalent alkali metal and polyatomic cations for the TTX-receptor site showed that this site displayed cation discrimination properties which were similar to those reported previously for the electrically excitable sodium channel in intact nerve fibers. A possible role for this site in the ion selectivity of the sodium channel is proposed.
|
14311d83-6918-48d3-b37a-a79ef0d095f5
| 0 |
The arrangement of subunits in cholera toxin. Cholera toxin consists of five similar B subunits of apparent molecular weight about 10 600 and one A subunit (29 000) consisting of two peptides (A1 23 000-24 000 and A2 about 5500) linked by a single disulfide bond. Each B subunit also contains one internal disulfide bond which is readily reduced but is protected from carboxymethylation unless the reduced subunits are heated in urea.
|
14311d83-6918-48d3-b37a-a79ef0d095f5
| 1 |
Tyrosine residues in A1 and in B subunits are readily iodinated, but the intact B assembly does not react with iodine. Upon reaction with the cross-linking reagent dimethyl suberimidate, B subunits may be covalently connected to each other, to A1 and to A2. A1 and A2 may also be cross-linked.
|
14311d83-6918-48d3-b37a-a79ef0d095f5
| 2 |
The B subunits are probably arranged in a ring with A on the axis. A2 is required for the re-assembly of toxin from its subunits and may serve to hold A1 on the B ring. The maximum activity of cholera toxin in vitro is obtained only when the active peptide, A1, is separated from the rest of the molecule.
|
14311d83-6918-48d3-b37a-a79ef0d095f5
| 3 |
Such separation, and the insertion of A1 into the cytosol, must follow the binding of the complete toxin, through component B, to the exterior of intact cells. This binding increases the effective concentration of the toxin in the vicinity of the plasma membrane. Possible ways in which A1 then crosses the membrane are considered in the Discussion.
|
2eae417b-bf58-427a-b792-f0b1f046283e
| 0 |
Kinetics of reaction of anions with methemerythrin derivatives. The kinetics of anation of methemerythrin over a wide range of pH and concentration of anions have been studied at 25 degrees C. The azide and thiocyanate ions have been most intensively investigated but experiments with fluoride and chloride are also reported.
|
2eae417b-bf58-427a-b792-f0b1f046283e
| 1 |
The replacement of anion in methemerythrin-anionic adducts by other anions has also been studied. Except for replacement of met-fluoride by azide, all replacements can be explained by a dissociative mechanism via the aquated species. Anations are second-order and an associative mechanism is preferred. The second-order rate constant decreases with increasing anion concentrations (from 20 muM to 20 mM).
|
2eae417b-bf58-427a-b792-f0b1f046283e
| 2 |
This is attributed to the effect of a secondary anion binding site. The behavior of octameric and monomeric forms of the protein toward thiocyanate is identical. A comparison of results with simple Fe(III) complexes and certain metalloproteins is made.
|
9aa59bce-d91b-4baf-b97e-1997ca7f24ba
| 0 |
Comparative studies on the structure and aggregative properties of the myosin molecule. III. The in vitro aggregative properties of the lobster myosin molecule. The solubility of rabbit skeletal and lobster abdominal muscle myosin has been studied in monovalent salt solutions as a function of pH (over the range 4.75
|
9aa59bce-d91b-4baf-b97e-1997ca7f24ba
| 1 |
to 8.5) and ionic strength (50-500 mM). Rabbit skeletal muscle myosin was found to precipitate over a narrower pH range than the lobster abdominal muscle myosin but at equivalent pH values and ionic strengths the former exhibited greater solubility. Comparison of the solubility of rabbit myosin, per se with that of light meromyosin and lobster myosin with its equivalent proteolytically produced fragment (fraction B1) showed that both rod fragments were more soluble than their parent molecules.
|
9aa59bce-d91b-4baf-b97e-1997ca7f24ba
| 2 |
Under conditions of low solubility (low ionic strength and pH) the quantitiy of protein in solution remained essentially constant with increasing total protein, thus suggesting that the aggregation phenomenon is of a phase transition type. Examination of the aggregates by electron microscopy revealed that rabbit myosin formed classical, elongate, spindle-shaped filaments similar to those previously observed by others.
|
9aa59bce-d91b-4baf-b97e-1997ca7f24ba
| 3 |
In contrast lobster myosin only formed short, dumbbell-shaped filaments 0.2-0.3 mum long. Consideration of the pH ranges over which aggregation occurred suggests that protonation of histidine residues may be involved in rabbit myosin filament formation while for lobster myosin, aggregation may involve protonation of epsilon-amino or guanidino groups.
|
9aa59bce-d91b-4baf-b97e-1997ca7f24ba
| 4 |
The possible relationship between the distribution of these groups along the rod portion of the myosin molecule and the formation of elongate filaments has been explored.
|
1ab309f5-184c-41db-987c-a451ba277f2b
| 0 |
Properties of cholera toxin- and NaF-stimulated adenylate cyclase from mouse thymocytes. Kinetic parameters of mouse thymocyte adenylate cyclase activity were determined. NaF and cholera toxin stimulated adenylate cyclase. Stimulation by either agent did not change the pH or Mg2+ optima relative to control (unstimulated cyclase). The Km value for ATP of adenylate cyclase stimulated by NaF was significantly reduced from control.
|
1ab309f5-184c-41db-987c-a451ba277f2b
| 1 |
By contrast, cholera toxin treatment did not change the Km relative to control. Adenylate cyclase, when stimulated by NaF, had an optimum for Mn2+ alone, or Mn2+ in combination with Mg2+, at least twice that of control. In contrast, cyclase activity prepared from cells treated with cholera toxin remained unchanged with regard to these divalent cations when compared to control.
|
1ab309f5-184c-41db-987c-a451ba277f2b
| 2 |
Addition of NaF to adenylate cyclase prepared from cells treated with cholera toxin resulted in a significant reduction (30%) in activity suggesting that both NaF and cholera toxin were acting on the same cyclase. NaF inhibition of cholera toxin-stimulated activity was shown to be a direct interaction of fluoride on the stimulated cyclase enzyme.
|
1ab309f5-184c-41db-987c-a451ba277f2b
| 3 |
This inhibition appeared to be immediate and independent on pH, Mg2+ or ATP concentrations. Although NaF inhibition was lost when Mn2+ was present in the reaction mixture, the activity expressed by addition of NaF to cyclase prepared from cholera toxin-treated cells was much less than by addition of NaF to control.
|
1ab309f5-184c-41db-987c-a451ba277f2b
| 4 |
As observed with cholera toxin stimulation alone, activity expressed by the inhibited enzyme (cholera toxin treated + NaF) exhibited a Km for ATP and an optimum for Mn2+ alone or in combination with Mg2+ similar to control.
|
1f05550a-9330-4fa1-b4dd-04ad45f84bfc
| 0 |
Regulation of the NADH and NADPH-ferredoxin oxidoreductases in clostridia of the butyric group. NADH and NADPH-ferredoxin oxidoreductases have been studied in Clostridium acetobutylicum, Cl. tyrobutyricum and Cl. pasteurianum. The study of the distribution and regulation of these enzymatic activities in well-defined culture conditions, reveals that the essential function of NADPH-ferredoxin oxidoreductase is to produce NADPH, while NADH-ferredoxin oxidoreductase can, depending on cellular conditions, produce or oxidize NADH.
|
1f05550a-9330-4fa1-b4dd-04ad45f84bfc
| 1 |
When these Clostridia use glycolysis, regulation of the NADH-ferredoxin oxidoreductase by acetyl-CoA (obligatory activator of NADH-ferroxin reductase activity) and by NADH (competitive inhibitor of ferredoxin-NAD+ reductase activity) allow the enzymes to function correlatively with glyceraldehyde-3-phosphate dehydrogenase and thus control the levels of NAD+ and NADH in the cell.
|
1f05550a-9330-4fa1-b4dd-04ad45f84bfc
| 2 |
In Cl. tyrobutyricum and Cl. pasteurianum, the ferredoxin-NADP+ reductase activities are regulated by NAD+ and NADH in accordance with the intracellular concentrations of these coenzymes. In Cl. tyrobutyricum growing on pyruvate/acetate, NADH and NADPH-ferredoxin reductase activities cannot be detected; only the ferredoxin-NAD+ and ferredoxin-NADP+ reductase activities are found.
|
1f05550a-9330-4fa1-b4dd-04ad45f84bfc
| 3 |
In this Clostridium, regulation of the ferredoxin-NADP+ reductase activity is the same whether it is grown on glucose or pyruvate. Contrary to this, the ferredoxin-NAD+ reductase activity undergoes a drastic change, since NADH no longer controls the enzymatic activity. In this case regulation is no longer necessary, since glyceraldehyde-3-phosphate dehydrogenase does not function.
|
d21f05b1-53c6-4d5d-bdc1-57cedd62618a
| 0 |
Lysophospholipase activity in cell-wall fragments contaminating mitochondrial fractions of Neurospora crassa. Crude mitochondrial preparations from Neurospora crassa contain high levels of lysophospholipase (EC 3.1.1.5) activity when assayed with lysophosphatidylcholine as a substrate. In mitochondria purified by centrifugation on a sucrose-density gradient this activity is virtually absent.
|
d21f05b1-53c6-4d5d-bdc1-57cedd62618a
| 1 |
The enzyme was shown to be linked to a contaminating cell fraction which mainly consists of cell-wall material as was demonstrated by electron microscopy and chemical analysis. The enzyme has no absolute Ca2+ requirement but it is slightly stimulated by 10 mM CaCl2. The pH optimum is 5.8
|
d21f05b1-53c6-4d5d-bdc1-57cedd62618a
| 2 |
in presence of CaCl2 and is shifted to 4.2 when EDTA is present. In contrast to other lysophospholipases this enzyme is only slightly inhibited by deoxycholate. This detergent is able to release part of the lysophospholipase activity from the wall fragments without producing an increase in specific activity. The enzyme is possibly secreted by the cells as high lysophospholipase activities were also found in the culture medium.
|
070b66f2-0622-46b7-93d9-fa1e1b7434ec
| 0 |
Purification and properties of cholesterol ester hydrolase from human aortic intima and media. 1. Cholesterol ester hydrolase of human aortic intima and media was isolated and purified about 650-fold with 10-15% recovery of the original activity by sequential precipitation with 35% acetone, gel filtration on Sephadex G-75 and DEAE-cellulose column chromatography.
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070b66f2-0622-46b7-93d9-fa1e1b7434ec
| 1 |
2. Two pH optima of 4.5-5.0 and 7.0-7.5 were consistently observed for the partially purified cholesterol ester hydrolase of human aortic intima and media. 3. In the system used in the present study, the increasing concentration of emulsifiers, sodium taurocholate and phosphatidylcholine, inhibited the activity of the neutral enzymes but not on the acid enzymes.
|
070b66f2-0622-46b7-93d9-fa1e1b7434ec
| 2 |
On the contrary, reaction products, cholesterol and oleic acid, were much more inhibitory on the acid enzymes than on the neutral ones. 4. Results of studies on the effect of presentation of substrate on the enzyme activity and on the difference between acid and neutral enzymes are also discussed.
|
6437af1f-e84e-4265-be2a-ba31ebe93198
| 0 |
Effect of maternal diet on fetal hepatic lipogenesis. The effects of: a, maternal diet; b, cyclic-3',5'-adenosinemonophosphate (cyclic AMP) and c, clofibrate on hepatic lipogenesis in fetal rats were studied. The experimental diets contained 22% protein, 40--50% carbohydrate, adequate vitamins, and minerals.
|
6437af1f-e84e-4265-be2a-ba31ebe93198
| 1 |
In addition, the fat-containing diets were supplemented with either 15% corn oil, 25% corn oil, or 5% cholesterol + 10% oleic acid. In the clofibrate feeding studies, 0.3% (w/v) of the ethyl ester was added to a stock ration or to fat-free diet.
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6437af1f-e84e-4265-be2a-ba31ebe93198
| 2 |
Lipogenesis was measured in liver slices incubated with [2-14C]pyruvate, [1-14C]acetate, or 3H2O. In addition, activities of lipogenic enzymes were measured in cytosol fractions from liver homogenates. The effec-s of the experimental diets on liver composition were also examined. Lipogenic activity was higher in fetal than in maternal liver.
|
6437af1f-e84e-4265-be2a-ba31ebe93198
| 3 |
When 15% corn oil was added to the maternal diet, fatty acid synthesis in fetal liver did not decrease as it did in maternal liver. Maternal fasting decreased fetal fatty acid synthesys by 50% when measured with 14C and less than 10% when measured with 3H2O. Although the addition of cholesterol to the maternal diet decreased cholesterol synthesis in maternal liver, no such decrease was observed in fetal liver.
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6437af1f-e84e-4265-be2a-ba31ebe93198
| 4 |
Changes in enzyme activities paralleled alterations in lipogenesis in maternal but not in fetal liver. Corn oil feeding or fasting increased the rate of transfer of linoleate from the dam to the fetus. However, accumulation of linoleate in fetal liver did not correlate with a decreased rate of fatty acid synthesis as it did in maternal liver.
|
6437af1f-e84e-4265-be2a-ba31ebe93198
| 5 |
Maternal hepatic glycogen stores were depleted by fasting, but glycogen levels in fetal liver remained high under these conditions.
|
fd40b3f4-8c4e-49e9-bb57-c1b034bc75e7
| 0 |
Translational control of protein synthesis in stimulated WI-38 fibroblasts. A cell-free protein synthesis system employing ribosomes from WI-38 human diploid fibroblasts was developed and its optimum MgC12 and KC1 levels and pH value found. The rate at which ribosomes are able to incorporate radioactive leucine into proteins ([14C]leucine incorporation/10 min/100 mug rRNA) and the number of growing peptide chains [3H]puromycinpeptides formed/100 mug rRNA) was determined.
|
fd40b3f4-8c4e-49e9-bb57-c1b034bc75e7
| 1 |
When confluent monolayers of WI-38 cells were stimulated to proliferate by serum, a transient increase in the rate of peptide elongation by ribosomes was observed at 60 min after stimulation. This increase was not affected by the presence of actinomycin D (10 mug/ml) in the stimulating medium.
|
fd40b3f4-8c4e-49e9-bb57-c1b034bc75e7
| 2 |
A change in the relative amount of certain ribosome-associated proteins accompanied the increased elongation rate of peptide growth. The alteration in associated proteins could not be accounted for by an increased synthesis of protein. Finally, the early activation of ribosomes in stimulated WI-38 cells appears to result from the removal of an inhibitor(s) of ribosome function.
|
82731076-6251-4b01-b341-4b043daafd58
| 0 |
A non-equilibrium thermodynamics analysis of active transport within the framework of the chemiosotic theory. The proton circuit devised by Mitchell in the chemiosmotic theory was subjected to analysis using the formalism of irreversible thermodynamics. The phenomenological coefficients and the degree of coupling relating co-permeant flows were derived from anion/H+, substrate/H+, cation/H+ and anion/anion biporter models.
|
82731076-6251-4b01-b341-4b043daafd58
| 1 |
Linearity and equality of the cross-coefficients in Onsager relations were always satisfied. Macroscopic flows leading to charges splitting, such as oxido-reduction, hydro-dehydratation and transhydrogenase, are driven by a composite thermodynamic force which includes the proton-motive component. Multiple coupling occurs in the circuit when it is assumed that the net inward flux of protons becomes zero, i.
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82731076-6251-4b01-b341-4b043daafd58
| 2 |
e. when the circulation of protons reaches a stationary state. Under these conditions, oxidative phosphorylation, ATPase- or respiration-linked transhydrogenase and uptake of anion or cation against their electrochemical gradient may be predicted, in agreement with known experimental evidence.
|
5d9ca07e-3ff0-4b3c-b3a5-002473bf6716
| 0 |
Kinetics of the slow variation of peak sodium current in the membrane of myelinated nerve following changes of holding potential or extracellular pH. (1) Changes of the holding potential applied to the membrane of myelinated nerve fibres induced slow variations of the peak sodium current, which are super-imposed on the effect of sodium inactivation.
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5d9ca07e-3ff0-4b3c-b3a5-002473bf6716
| 1 |
(2) These slow variations are transitions between various steady levels of available sodium conductance. Their time course can be described by the function erfc (square root t/tau) where tau is the time and erfc the error function complement. The characteristic time tau lies in the range 2-4 min and depends on the membrane potential.
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5d9ca07e-3ff0-4b3c-b3a5-002473bf6716
| 2 |
(3) Changes of extracellular pH cause a rapid change of the peak sodium current followed by a slow variation as observed after changes of the holding potential. This slow variation can be prevented by applying simultaneously an appropriate change of the holding potential, e.g. the effect of changing pH from 7.3
|
5d9ca07e-3ff0-4b3c-b3a5-002473bf6716
| 3 |
to 5.3 is balanced by changing the potential from --70 to --55 mV. (4) The results are interpreted by postulating charged components diffusion slowly within the nodal membrane. Their transverse distribution controls the number of sodium channels available at a given membrane potential. The equivalence between change of pH and voltage is explained by assuming negative fixed charges at the outer surface of the membrane, which are protonated at low pH and thus affect the intrinsic membrane potential.
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5d9ca07e-3ff0-4b3c-b3a5-002473bf6716
| 4 |
(5) It is concluded that effects which are ascribed to the action of agents on individual sodium channels have to be corrected for variations in the number of available channels if these agents influence the intrinsic membrane potential, e.g. changes of extracellular pH.
|
e2ffe850-d549-4ba8-b77f-e601e6fbf9d8
| 0 |
Effects of pH during recombination of human erythrocyte membrane apoprotein and lipid. The recombinates from human red cell membrane proteins and lipids resulting from dialysis of the components in 2-chloroethanol against aqueous buffers from pH2-12 have been studied by density gradient centrifugation, polyacrylamide gel electrophoresis and freeze-fracture electron microscopy.
|
e2ffe850-d549-4ba8-b77f-e601e6fbf9d8
| 1 |
Between pH 4 and 10 most of the proteins were found in the recombinates whereas below pH 4 and above pH 10 only part of them were recovered in the lipoprotein band after density gradient centrifugation. At low pH, increasing incorporation of the "major glycoprotein" into the recombinates was detected by gel electrophoresis and in parallel increasing amounts of particles were found in the freeze-fracture membrane faces.
|
e2ffe850-d549-4ba8-b77f-e601e6fbf9d8
| 2 |
The necessity of working at low pH values from pH 2-4, however, and a critical evaluation of all the data presently available leads to the conclusion that the 2-choloroethanol technique is not adequate for recombination studies tending to membrane reconsitution.
|
5bbcbdf7-0580-463e-9d5f-c6ec5a5e210e
| 0 |
[pH dependence and EPR spectra of Fe-NO complexes with purines and pyrimidines]. Equilibria between different types of Fe(I)-dinitrosyl complexes with nucleobases in solution were studied by means of EPR spectroscopy. Computer simulation and 15NO isotopic substitution were used in order to make easier the interpretation of complicated EPR patterns.
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5bbcbdf7-0580-463e-9d5f-c6ec5a5e210e
| 1 |
The pH dependence of the purine and pyrimidine complexes was investigated. Several EPR signals, under slow exchange conditions, were present in the range of pH values of biological significance. Four types of complexes were identified on the basis of the nuclear hyperfine structure: B' = where two purine molecules were bound to iron via N-7 in the imidazole ring;
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5bbcbdf7-0580-463e-9d5f-c6ec5a5e210e
| 2 |
B'' = where two mercapto-base molecules were bound to iron via S-; B''' = where one mercapto-base molecule was bound to iron via S- and another via pyrimidine-nitrogen; B* = where two pyrimidine molecules were bound to iron via pyrimidine-nitrogen.
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48c0fa65-e9dc-4253-816f-41a8ec98bd94
| 0 |
Maximization of steady-state bacterial production in a chemostat with pH and substrate control. This analytical study deals with the steady-state behavior and control of microbial growth in continuous cultures. A second order Haldane-Monod model of continuous cultures is used as a basis for study of the effects of the adjustment of pH by the addition of acidic (or basic) materials.
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48c0fa65-e9dc-4253-816f-41a8ec98bd94
| 1 |
The treatment of a hydrogen ion concentration, in addition to substrate and microbial concentrations as state variables, results in a third order system of equations describing the process. The analysis of the system in equilibrium yields several admissible steady states, that is, steady states which satisfy all constraints.
|
48c0fa65-e9dc-4253-816f-41a8ec98bd94
| 2 |
An optimal control problem is formulated and subsequently solved to maximize steady-state microbial production.
|
497650c7-6113-4159-ad46-11e85c9988a9
| 0 |
Preparation and properties of soluble-insoluble nicotinamide coenzymes. A soluble-insoluble form of nicotinamide adenine dinucleotide (NAD+), which can be rendered either soluble or insoluble by simply adjusting the pH, has been prepared by covalently coupling NAD to alginic acid using 1,2,7,8-diepoxyoctane. The NAD bound to the alginic acid showed the coenzymic function in the soluble state and could be collected for further use as precipitate by lowering the pH to below 3. Coupling soluble-insoluble coenzymes with insolubilized apoenzymes is possible in fluidized and fixed-bed reactors.
|
fb60c730-7244-4f3e-8bf7-537e397fe7a1
| 0 |
Studies on some lipogenic enzymes of cultured myeloid leukemic cells. The microsomal fraction of M1 cells (an established cell line of myeloid leukemia) was capable of catalyzing acylation of sn-glycerol 3-phosphate by long-chain fatty acyl-CoA thioesters. The principal lipid product formed was identified as phosphatidic acid.
|
fb60c730-7244-4f3e-8bf7-537e397fe7a1
| 1 |
Palmityl-CoA, stearyl-CoA, and oleyl-CoA were more effective acyl donors than linoleyl-CoA and arachidonyl-CoA. M1 cells and macrophages differentiated from them exhibited similar levels of sn-glycerol 3-phosphate-acylating activity, which were approximately one-half that in mouse liver and approximately four times that in peritoneal macrophages.
|
fb60c730-7244-4f3e-8bf7-537e397fe7a1
| 2 |
The levels of acetyl-CoA carboxylase activity in M1 cells and macrophages differentiated from them were not significantly different from each other and were comparable to those in mouse liver, whereas no activity was detected in peritoneal macrophages. These results indicated that differentiation of the myeloid leukemic cells, which results in loss of leukemogenicity and mitotic activity, is not associated with changes in the activities of these lipogenic enzymes, although the cultured cells exhibited remarkably higher activities than freshly harvested peritoneal macrophages.
|
fb60c730-7244-4f3e-8bf7-537e397fe7a1
| 3 |
Furthermore, the present study supports the view that the glycerophosphate pathway makes an essential contribution to the de novo synthesis of phospholipids in M1 cells, as well as in both types of macrophages.
|
c0d05d7f-dc56-4f63-9397-a40700bd4eb4
| 0 |
Impairment in the hepatic clearance of (35S)-bromosulphophthalein in paracetamol-intoxicated rats. 1 The overall functional capacity of the liver was evaluated using [35S]-bromosulphophthalein (BSP, 100 mg/kg, i.v.) in biliary fistulated adult rats pretreated orally with different doses of paracetamol (APAP) for varying time intervals.
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c0d05d7f-dc56-4f63-9397-a40700bd4eb4
| 1 |
2 The maximal hepatic damage occurred between 12-18 h after single doses of APAP (0.5 or 1 g/kg); hepatic excretory function returned to control levels by 48-72 hours. 3 Administration of either 0.5 or 1 g/kg APAP 18 h before BSP caused a dose-dependent inhibition of the choleretic effect of BSP and of the 60 min cumulative excretion of the dye, but conversely, produced a significant increase in the liver and plasma concentrations of 35S.
|
c0d05d7f-dc56-4f63-9397-a40700bd4eb4
| 2 |
4 Following acute (0.25 g/kg), or subacute (0.5 g/kg, twice daily for 7 days) treatment with APAP, the total excretion of 35S in bile and the retention of 35S in the liver or plasma remained essentially the same as that for the controls. 5 In rats given single doses of 1 g/kg APAP, the hepatic uptake of the dye was significantly increased during the early stages of intoxication, while the opposite effect was observed at late periods.
|
c0d05d7f-dc56-4f63-9397-a40700bd4eb4
| 3 |
6 The bile flow appeared to be inversely related to the excretion of unchanged BSP, and directly related to the excretion of the major BSP conjugate in bile. 7 The hepatic clearance of BSP was more rapid in rats treated subacutely with 0.5 or 1 g/kg APAP, than in those treated acutely with equal doses, suggesting that the intensity of APAP-induced hepatotoxicity became less severe after the repeated administration of this drug.
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c0d05d7f-dc56-4f63-9397-a40700bd4eb4
| 4 |
8 It is concluded that the hepatic uptake, metabolism and excretion of BSP are reversibly impaired following APAP-induced liver injury.
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ef6a27f9-6ecb-4a7a-aa56-2ea3e1504404
| 0 |
Dual effect of alpha-adrenoceptor antagonists in rat isolated vas deferens. 1 In rat isolated vas deferens, the isotonic contractile responses to low doses of noradrenaline or adrenaline were antagonized, and those to high doses were potentiated, by yohimbine, piperoxan, phentolamine and tolazoline. Effects due to intermediate doses were not affected, or were potentiated within about 30 min, following an initial inhibition.
|
ef6a27f9-6ecb-4a7a-aa56-2ea3e1504404
| 1 |
2 The alpha-adrenoceptor blockers thus caused a shift to the right and an increase of the maximum height of log dose-response curves of alpha-adrenoceptor stimulants. For a given dose of antagonist, the onset was slower for the potentiating than for the blocking effect. 3 The shift to the right induced by piperoxan and yohimbine on dose-response curves of noradrenaline and adrenaline was analysed with the Schild plot, and the slopes obtained, around 0.3
|
ef6a27f9-6ecb-4a7a-aa56-2ea3e1504404
| 2 |
, were lower than expected from receptor theory. When cocaine was used to block neuronal uptake, the slopes were close to 1.0. 4 The increase in maximum response to noradrenaline and adrenaline induced by alpha-adrenoceptor blockers was dependent on the time of incubation, on the dose of antagonist, and on the initial height of responses to the agonist.
|
ef6a27f9-6ecb-4a7a-aa56-2ea3e1504404
| 3 |
A less pronounced potentiation was also obtained when acetylcholine was used as agonist. 5 The findings are explained in terms of receptor theory as being due to a dual effect of alpha-adrenoceptor antagonists; competitive antagonism proper, which may be disclosed after blockade of neuronal uptake, and an interaction at a different locus, which results in potentiation of the effects of noradrenaline and adrenaline.
|
90ff08f9-3ec0-4e99-b25a-8c66ff09a2e7
| 0 |
[Isotopic study of fluid and electrolyte disturbances in decompensated chronic respiratory insufficiency (author's transl)]. The study of fluid and electrolyte disturbances by isotope radiodilution method is carried out in 22 patients with chronic respiratory insufficiency and cardiac failure. The simultaneous measurements of hydro-ionic compartments have been carried out with tritiated water (HTO), labelled sodium (22Na), labelled potassium (42K) and labelled bromine (82Br).
|
90ff08f9-3ec0-4e99-b25a-8c66ff09a2e7
| 1 |
From these measurements, the various water spaces are calculated: total water (ET) and extracellular fluids (LEC), also exchangeable electrolytes: sodium (NaE), potassium (KE), chlorine (ClE) and derived values. Results are compared to corresponding values in controls with the same obesity index. Patients with respiratory insufficiency show a fluid and sodium rise, similar to that found in cardiac failure and denutrition.
|
90ff08f9-3ec0-4e99-b25a-8c66ff09a2e7
| 2 |
The (NaE + KE)/ET ratio is not significantly decreased and the natremia is only slightly lower. There is no real potassium depletion in most patients.
|
11329ea1-b1f1-422d-b112-120213bc8b11
| 0 |
[Role of P50 in resuscitation (author's transl)]. The amount of oxygen made available to the tissues of the body depends essentially upon pulmonary gas exchanges, cardiac output and its regional distribution, haemoglobin concentration and also upon the oxygen affinity of the haemoglobin molecule. That a standard oxyhaemoglobin dissociation curve faithfully describes oxygen loading and unloading both in healthy subjects and in those suffering from pathological process has come under attack.
|
11329ea1-b1f1-422d-b112-120213bc8b11
| 1 |
Beside the effect of pH, PCO2 and temperature, the oxyhaemoglobin dissociation curve can be modified by alterations of other factors (concentration of 2,3-diphosphoglycerate, hormones, drugs). Although the shifts of the oxyhaemoglobin dissociation curve, expressed by variations of P50 may seem minute, the effect of these shifts, expressed in terms of the "functional value of haemoglobin" are very large.
|
11329ea1-b1f1-422d-b112-120213bc8b11
| 2 |
Assessment of the intensive care patient must take into account the effect of alterations of the oxyhaemoglobin dissociation curve which can either increase or diminish tissue oxygenation.
|
539b8b20-d985-404b-95f6-3d68161ca0b5
| 0 |
[Acid-base disorders in status asthmaticus (author's transl)]. In 85 patinets withstatus asthmaticus, the authors have studied the acid-base balance, the blood gas tensions and various humoral parameters. The values were classified into two groups according to the PaCO2 level: below or equal to 44 torr (Group I), higher than 44 torr (Group II).
|
539b8b20-d985-404b-95f6-3d68161ca0b5
| 1 |
In the 58 cases of Group II, there was a very close positive correlation between PaCO2 and H + ions, practically the same as that established by BRACKETT et al. [3] in experimental acute hypercapnia in man. On the contrary, the correlation derived from cases of status asthmaticus in the literature showed, in some cases, a metabolic component in acidosis.
|
539b8b20-d985-404b-95f6-3d68161ca0b5
| 2 |
In the present work, the mean value of lactates was close to normal; there was a slow increase in protein content and hematocrit, in the two groups. The prognosis of the status asthmaticus depends on the degrees of hypercapnia: when it reaches 70 torr, mechanical ventilation is urgently needed and is the main part of the treatment;
|
539b8b20-d985-404b-95f6-3d68161ca0b5
| 3 |
the use of additional drugs remains a matter of specific case.
|
2e1e8c78-e00d-4d6d-89ae-ef02d497d39f
| 0 |
The evaluation of the novel pressor activity of gamma-piperidinobutyramide (WY 20051, DF480). 1 gamma-Piperidinobutyramide (Wy 20051, DF480) injected intravenously evoked pressor responses in the anaesthetized ganglion blocked rat preparation over the dose range 2.4 x 10(-6)-3.0 x 10(-4) mol/kg. 2 High doses (greater than 3.8
|
2e1e8c78-e00d-4d6d-89ae-ef02d497d39f
| 1 |
x 10(-5) mol/kg) or even repeated submaximal doses (1.9 x 10(-5) mol/kg) of Wy 20051 caused tachyphylaxis of this pressor response. 3 The noradrenaline pressor-response curve was shifted significantly to the right of the control curve following a dose of Wy 20051 (1.5
|
2e1e8c78-e00d-4d6d-89ae-ef02d497d39f
| 2 |
x 10(-4) mol/kg cumulative). 4 The dose-response curve for the pressor action of Wy 20051 was potentiated in reserpine-treated anaesthetized rats. In contrast, tyramine-induced pressor responses were abolished. 5 Wy 20051 contracted the guinea-pig isolated aortic spiral preparation (3.8 x 10(-5)-6.0
|
2e1e8c78-e00d-4d6d-89ae-ef02d497d39f
| 3 |
x 10(-4) mol) and evoked constrictor responses in the perfused mesenteric vasculature preparation of the rat (5.9 x 10(-7)-1.2 x 10(-5) mol). At higher doses the responses were reduced. 6 Wy 20051-induced constrictor responses of the perfused mesentery were unaffected by blockade of alpha-adrenoceptors or by tachyphylaxis of 5-hydroxytryptamine receptors.
|
2e1e8c78-e00d-4d6d-89ae-ef02d497d39f
| 4 |
7 The time for abolition of Wy 20051-induced constrictor responses of the mesentery in a calcium-free medium was not significantly different from that required for noradrenaline, but was significantly greater than that for KCl (P less than 0.001). 8 Wy 20051 and noradrenaline, but not KCl, evoked constrictor responses in the depolarized rat mesenteric vasculature.
|
2e1e8c78-e00d-4d6d-89ae-ef02d497d39f
| 5 |
9 The results indicate that Wy 20051 evokes pressor responses which have some of the characteristics of those of noradrenaline. However, the responses are not elicited by an alpha-adrenoceptor mechanism.
|
99db939c-b5e4-4b7a-b153-5ca3caf69018
| 0 |
Electroconvulsive shock increases the behavioural responses of rats to brain 5-hydroxytryptamine accumulation and central nervous system stimulant drugs. 1 A single electroconvulsive shock (ECS) of 150 V for 1 s increased the concentration of rat brain 5-hydroxyindoleacetic acid (5-HIAA) but did not alter brain 5-hydroxytryptamine (5-HT) or tryptophan concentrations 3 h later.
|
99db939c-b5e4-4b7a-b153-5ca3caf69018
| 1 |
2 A single ECS decreased 5-HT synthesis 3 h and 6 h later. Synthesis was back to normal after 24 hours. The ECS-treated rats did not show greater hyperactivity produced by the increased brain 5-HT accumulation following administration of L-tryptophan and tranylcypromine at any time up to 24 h later.
|
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