共查询到20条相似文献,搜索用时 31 毫秒
1.
Kern von Hungen Claude F. Baxter 《Biochemical and biophysical research communications》1982,106(3):1078-1082
Rats were fed ethanol (Lieber-DeCarli diet) for three weeks. Stimulation of cerebellar adenylate cyclase by calcium was measured in control (pair-fed), chronic-alcohol and alcohol-withdrawn animals. No differences in the sensitivity or maximal stimulation of this enzyme were observed among these groups. Ethanol , (1%) stimulated brain adenylate cyclase approximately 50% in the presence or absence of calcium. Chronic alcohol exposure , did not alter the sensitivity of adenylate cyclase to stimulation by alcohol ,. 相似文献
2.
An ATPase is demonstrated in plasma membrane fractions of goldfish gills. This enzyme is stimulated by Cl? and HCO3?, inhibited by SCN?.Biochemical characterization shows that HCO3? stimulation () is specifically inhibited in a competitive fashion by SCN? (). The residual Mg2+-dependent activity is weakly is weakly affected by SCN?.In the microsomal fraction chloride stimulation of the enzyme occurs in the presence of HCO3? (); no stimulation is observed in the absence of HCO3?. Thiocyanate exhibits a mixed type of inhibition () towards the Cl? stimulation of the enzyme.Bicarbonate-dependent ATPase from the mitochondrial fraction is stimulated by Cl?, but this enzyme has a relatively weak affinity for this substrate (). 相似文献
3.
Effect of prostaglandin E2 on vascular responses of the rabbit kidney to nerve stimulation and noradrenaline, in vitro and in situ 总被引:2,自引:0,他引:2
The effect of prostaglandin E2 on vascular responses of the rabbit kidney to renal nerve stimulation and noradrenaline was examined and as a test of the hypthesis that prostaglandins of the E series may be involved in the regulation of adrenergic neuroeffector transmission. Intraarterial administration of prostaglandin E2 to the kidney caused marked inhibition of vascular responses to nerve stimulation whereas the responses to noradrenaline were not significantly altered. In the preparation, vascular responses to both nerve stimulation and noradrenaline were inhibited by prostaglandin E2 infusion, although its effect on responses to nerve stimulation was approximately twice that observed on responses to noradrenaline.It is concluded that prostaglandin E2 acts primarily at a prejunctional level of adrenergic neuroeffector transmission in the kidney, although a postjunctional effect has also been observed. 相似文献
4.
Charles D. Boyer Jack Preiss 《Biochemical and biophysical research communications》1978,80(1):169-175
Purification of starch branching enzymes from kernels of two nonlinked mutants of maize, and , showed the basis of the two mutations to be associated with branching enzymes I and IIb, respectively. Branching enzyme I from kernels purified as nonmutant branching enzyme I, but had an altered pattern of activity when amylose was used as a substrate. In addition to the typical fall in absorbance at high wavelengths (550–700 nm) of the amylose-iodine complex, branching of amylose by branching enzyme I caused an increase in absorbance at low wavelengths (400–550 nm). Branching enzyme IIb was undetected in extracts of kernels, while branching enzymes I and IIa appeared unaltered. Low umprimed starch synthase activity was also observed in DEAE-cellulose fractions of maize, but this activity was regenerated by the addition of any branching enzyme. 相似文献
5.
The cytochrome oxidase (EC 1.9.3.1) of HB8 was isolated from the membrane fraction, and was highly purified. The oxidase contained heme and heme as the prosthetic groups. The purified preparation showed a single band in polyacrylamide gel electrophoresis, and three major polypeptides with apparent molecular weights of 52,000, 37,000 and 29,000 were observed in the presence of sodium dodecyl sulfate. The enzyme reacted rapidly with cytochrome c-552. The oxidation of cytochrome -555,549 by the enzyme was very slow, and was stimulated by the addition of cytochrome -552. The enzyme was highly stable to heat. 相似文献
6.
George M. Stancel Judy S. Ireland Venkat R. Mukku Alice K. Robison 《Life sciences》1980,27(12):1111-1117
The pesticide o,p'-DDT stimulates the production of a specific uterine protein, the so-called induced protein or IP, normally associated with an estrogenic response of the uterus. stimulation of IP production is observed 1 hour after the administration of 250 mg/kg of o,p'-DDT to immature rats. stimulation of IP production is observed after a 1 hour incubation of uteri with 100 μM o,p'-DDT. This response is blocked by Actinomycin D. In contrast to o,p'-DDT, which binds to the cytoplasmic estrogen receptor and stimulates IP production, p,p'-DDT which does not bind well to the estrogen receptor does not stimulate IP production . These findings represent the first report of an estrogenic effect of o,p'-DDT in a completely system. 相似文献
7.
K Okazaki 《Biochemical and biophysical research communications》1975,64(1):20-27
Thiamine pyrophosphokinase (E.C. 2.7.6.2.) from was found to require the presence of a non-protein, non-metal compound for its activity. -Inositol was found capable of stimulating the kinase activity in the presumably resolved but otherwise crude sample of the enzyme. The hexytol was also found capable of inducing the enzyme in growing yeast cells. The cultured yeast cells, in which the kinase had been induced, were used as source of the enzyme for its purification. The compound that had been left adsorbed to the final column of DEAE-Sephadex was proved to have a coenzyme activity towards the enzyme and tentatively identified with -inositol 1-pyrophosphate. A sample of synthetic -inositol 1-pyrophosphate was made and its coenzyme activity was observed. 相似文献
8.
One-way mixed lymphocyte cultures were established between related cell donors A (haplotype designated ) and B (). The cells from A, proliferating in response to stimulation by mitomycin treated cells from B, were eliminated from the culture by a hot pulse of 3H-thymidine. A marginal response was observed when the remaining cells from A reencountered additional stimulating cells from B, or cells from an HL-A identical sibling to B. In addition, the remaining responding cells were virtually incapable of responding to secondary stimulation by family member C (), who shared one haplotype (b) with individual A and the other haplotype (c) with the individual stimulating cell donor B. The MLC secondary stimulation response to family member D (), who differed from A by both haplotypes, but shared one haplotype with B, was reduced to approximately 50% of control values. In other experiments it was found possible to completely eliminate the response of A () to D () by using a combination of stimulating cells from related donors B () and C () in the initial hot pulse MLC.Separate populations of responding cells reactive to antigenic products of each major histocompatibility system haplotype is a likely explanation of these observations. 相似文献
9.
M K Thakur R Das M S Kanungo 《Biochemical and biophysical research communications》1978,81(3):828-831
During purification of branched chain ketoacid dehydrogenase from , large losses in enzyme activity occurred. Much of the activity was restored by the addition of a heat-treated, soluble fraction. The factor had a molecular weight less than 1000 and, of several potential effectors tested, the branched chain amino acids were the only compounds which stimulated enzyme activity, with valine being the most effective. The concentration of valine in the heat-treated fraction was found to be sufficient to account for all of the stimulation produced by this fraction. Valine had no effect on either pyruvate or 2-ketoglutarate dehydrogenases. 相似文献
10.
The role of the synaptic vesicles in transmission at the insect nerve-muscle junction 总被引:1,自引:0,他引:1
The ultrastructure of nerve-muscle synapses on red and white fibres of locust () retractor unguis muscle fibres was examined before and after stimulation. At a stimulation frequency of 15Hz, the synapses on the white fibres fatigued completely; those on the red fibres also fatigued, but during prolonged stimulation they showed intermittent periods of recovery. Synaptic vesicles at both types of fatigued synapses were reduced in volume compared with controls and at fatigued synapses on white fibres the vesicles had irregular outlines. Aggregation of vesicles were observed at fatigued synapses on red fibres and the synaptic cleft width at these synapses was less than at control synapses on red fibres. These results are discussed in the light of the vesicle hypothesis for synaptic transmission. 相似文献
11.
M S Kilberg H N Christensen M E Handlogten 《Biochemical and biophysical research communications》1979,88(2):744-751
The rapid transport of -cysteine into isolated rat hepatocytes escapes detectable inhibition by 2-(methylamino)-isobutyric acid at levels up to 50 mM. The system transporting cysteine instead is convincingly similar to the system described for the Ehrlich cell in structural and steric specificity and in pH sensitivity. The Na+-dependent uptake of 2-aminoisobutyric acid is almost evenly divided between Systems and , showing better accommodation of its two α-methyl groups by than in the Ehrlich cell. The hepatocyte system tolerates Li+-for-Na+ substitution better than does System , although the tolerance depends on amino acid structure. Adaptive regulation and insulin and glucagon stimulation were not seen under conditions producing these effects for System . 相似文献
12.
, the initial membrane enzyme in the biosynthesis of peptidoglycan, requires a lipid microenvironment for function. was reversibly intercalated into membranes to perturb the hydrophobic interactions in this microenvironment in order to define further the role of lipid. In the concentration range for maximal stimulation of enzymic activity (0.12–0.18 M), causes a 40% decrease in the fluorescence emission of the dansylated product, undecaprenyl . Since no change in emission maximum occurs below 22°C in the presence of 0.12 M , it is concluded that intercalation of this alkanol causes an increase in fluidity. Above 22°C this concentration of causes both a decrease in the fluorescence emission and a red shift in the emission maximum. It is concluded that a polarity change as well as fluidity change occurs above 22°C. also causes a significant change in the phase transition experienced by the dansylated lipid product. Thus, it is possible with , e.g. , to perturb lipid-translocase interactions resulting in an increase in fluidity in the microenvironment of the enzyme. This change in fluidity correlates with a stimulation of enzymic activity. 相似文献
13.
Substrate specificity of glycogen synthase phosphatase from bovine heart: action on phosphorylase a and histone 总被引:3,自引:0,他引:3
Glycogen synthase phosphatase has been purified from bovine heart. This preparation catalyzes conversion of synthase D into I and phosphorylase into and is able to dephosphorylate synthase D, phosphorylase , active phosphorylase kinase, and phosphorylated histone and casein. The activity of phosphatase was assayed with synthase D, phosphorylase , and histone as substrates after chromatography on Sephadex G-100, after sucrose gradient centrifugation, and after isoelectric focusing in a sucrose gradient. In all cases no separation of enzyme activity was observed with the above substrates. The phosphatase activity on all substrates was lost at the same rate by heat denaturation. These results indicate that this enzyme preparation contains a single phosphoprotein phosphatase which is responsible for the activity observed on the above substrates. 相似文献
14.
S.G. Laychock 《Cell calcium》1982,3(1):43-54
Phospholipase A2 activity in islet cell homogenates and dispersed islet cells of the rat was determined using an exogenous radiolabeled phospholipid substrate from membranes. Phospholipase A2 activity in islet homogenates was found to have two pH optima in acid or neutral/alkaline pH ranges. The enzyme activity at pH 7.5 was calcium dependent and responded to increasing calcium concentrations with graded increases in phospholipid hydrolysis. Preincubation of islets with a concentration of glucose known to elicit maximum rates of insulin secretion resulted in a stable activation of phospholipase A2 activity which was assayable in islet homogenates. Glucose stimulated phospholipase A2 in these preparations by as much as 220% above control. 2-Deoxy-D-glucose, a nonsecretory analogue of glucose, did not elicit a significant increase in islet phospholipase A2 activity. The glucose sensitive enzyme was associated with a membrane-enriched subcellular fraction in which the glucose-stimulated activity was greater than 2-fold higher than control activity. Glucose stimulation potentiated the phospholipase A2 activity measured in the presence of high calcium concentrations. Phospholipase A2 activity was also found in dispersed islet cell preparations where glucose stimulation of what may be a partly externalized membrane enzyme was most apparent at low calcium concentrations. These data indicate that islet cells possess phospholipase A2 activity which may be in part localized to the plasma membrane as well as other membrane systems, and which exhibits the characteristic properties of pH and calcium dependency, and sensitivity to secretagogue stimulation reported for the enzyme in other secretory systems. 相似文献
15.
In homogenates of (Rhesus) or amygdaloid nuclear complex, adenylate cyclase activity was approximately doubled by either 10μ dopamine or 8m NaF. In the presence of morphine, the stimulation by dopamine was reduced. A 90–100% inhibition of the dopamine stimulation was obtained with 20μ, and a 50% inhibition, with 5μ morphine. The effects of 10μ morphine on dopamine stimulation were reversed by 10μ naloxone. Morphine itself did not significantly affect the basal adenylate cyclase activity, but in the presence of 10μ morphine the stimulation by 8m NaF was reduced approxiamtely 50%. The data suggest an action of morphine at a receptor site which is distinct from the dopamine receptor, but which inhibits the dopamine-stimulated adenylate cyclase. In addition, the cyclic GMP content of amygdala slices was reduced by 50–75% during incubation for 5–20 minutes with morphine. Maximum effects on cyclic GMP were obtained with 10μ, and half-maximum effects, with 0.1μ morphine. The effect of morphine on amygdala cyclic GMP was not reversed by naloxone. Thus, this action of morphine may not be receptor mediated, or may involve the interaction of morphine with receptors other than the opiate receptor. 相似文献
16.
P P Hipps M R Eveland M H Laird W R Sherman 《Biochemical and biophysical research communications》1976,68(4):1133-1138
-Inositol:NAD(P)+ oxidoreductase (-inositol oxidoreductase) has been identified in bovine brain. This enzyme elutes from DEAE cellulose with 0.3 M KCl in 50 mM Tris buffer, pH 7.5. Using NADH as cofactor -inosose-2 is reduced selectively to -inositol. With NADPH the enzyme forms both -inositol and -inositol, however, at a lower rate. The enzyme was chromatographed on G-100 Sephadex and found to have an apparent molecular weight of 74,000. This enzyme differs in DEAE binding, molecular weight and cofactor specificity from the previously described -inositol oxidoreductase which utilizes NADPH exclusively to produce 3 fold more -inositol than -inositol. 相似文献
17.
George Boguslawski William S. Oetting Dean A. Stetler 《Biochemical and biophysical research communications》1977,78(2):684-689
An enzyme, ribonucleotide polymerase, isolated from the yeast phase of a fungus, has been found to stimulate the incorporation of dTMP in the reaction catalysed by DNA polymerase from and . The stimulation is dependent on the amount of ribonucleotide polymerase added. The data indicate that protein-protein interaction is responsible for the increase in DNA synthesis. It is suggested that ribonucleotide polymerase may be involved in supplying short RNA primers for DNA polymerase. 相似文献
18.
T Lloyd P Montgomery G Guroff 《Biochemical and biophysical research communications》1979,86(4):1058-1062
Tyrosine hydroxylation, measured in superior cervical ganglia from neonatal rats, is increased two-fold by the addition of carbachol. This increase occurs within one hour and is not due to the synthesis of new enzyme protein, nor to a direct effect of carbachol on the enzyme. The stimulation is blocked by atropine, but not by hexamethonium. This stimulation represents the first report of a receptor-mediated short-term action on this rate-limiting enzyme. 相似文献
19.
Phagocytosis in adherent P388D1 (D1) cells was monitored utilizing formalin treated () previously labeled with 125iododeoxyuridine. The dependence of this phagocytic process on calcium was studied by using several agents which alter calcium metabolism. The calcium antagonist ruthenium red (RR) produced a dose and time dependent stimulation (60–70%) of phagocytosis by D1 cells. Utilizing another calcium antagonist, D-600, a prolonged inhibition (4 hours) of phagocytosis (40%) was observed. The addition of the cation ionophore A23187 produced a transient stimulatory increase (38% at 2 hours) in the phagocytic response. The concomitant addition of RR and D-600 did not alter the phagocytosis of by D1 cells as compared to control cells. However, this complete drug/drug antagonism was not seen with the combinations of A23187 and D-600 or RR and A23187. The addition of A23187 and D-600 resulted in a time dependent inhibition of phagocytosis which did not become maximal until 3 to 4 hours. A23187 and RR produced a time independent stimulation of phagocytosis which was significantly less than that which was observed for RR alone, but was of longer duration than the response produced by A23187 alone. The use of these calcium probes in the P388D1 macrophage model suggests a role for calcium in the phagocytic process. 相似文献
20.
Klaus Schneider Hans G. Schlegel 《Biochemical and biophysical research communications》1978,84(3):564-571
The flavin component of soluble hydrogenase (hydrogen: NAD+ oxidoreductase, EC 1.12.1.2) from was identified as FMN by thin layer chromatography in two solvent systems and by binding studies with apoflavodoxin from . The flavin of hydrogenase reacted rapidly with apoflavodoxin with almost complete quenching of the fluorescence at 525 nm. Quantitative determination of FMN was performed by fluorimetric titration with a standardized solution of apoflavodoxin. From the determined FMN content of different enzyme preparations and from the percentage of stimulation of hydrogenase activity by exogenous FMN it is concluded that hydrogenase contains 2 FMN per molecule. 相似文献