共查询到20条相似文献,搜索用时 31 毫秒
1.
Robert A. Schatz Timothy E. Wilens Otto Z. Sellinger 《Biochemical and biophysical research communications》1981,98(4):1097-1107
The administration of adenosine together with homocysteine resulted in a dose-related elevation of cerebral S-adenosyl-L-homocysteine without concomitant perturbation of S-adenosyl-L-methionine levels. The adenosine + homocysteine treatment also decreased the incorporation of labile and stable methyl groups into brain proteins. Brain [3H]-phosphatidyl N,N-dimethylethanolamine and [3H]-phosphatidylcholine were also significantly decreased while [3H]-phosphatidyl-N-monomethylethanolamine remained unchanged. The data indicate that elevated brain S-adenosylhomocysteine can markedly and selectively inhibit the methylation of brain proteins and phospholipids. 相似文献
2.
Metabolic sequestration of putrescine in Neurospora crassa 总被引:3,自引:0,他引:3
The metabolic fate of putrescine labelled was investigated after administration of a trace (10?7 M) of L-[14C]ornithine to exponentially growing mycelia of , followed by a large chase (2 mM) of L-[12C]ornithine. The specific radioactivities of putrescine and spermidine were determined during the chase period by reaction with [3H]dansyl chloride of known specific radioactivity and isolation of the dansyl-derivatives by thin-layer chromatography. Radioactivity remained in the putrescine pool for over 2 h during the chase period. This suggests that putrescine is largely sequestered (80% or more) . The metabolic sequestration of polyamines may be a significant factor in the regulation of polyamine synthesis. 相似文献
3.
A proteinase (called Proteinase I) present in myxamoebae of the cellular slime mold, , was labeled with [32P] by growth of cells on media containing [32P] orthophosphate. The labeled proteinase was purified to apparent homogeneity and characterized by dissociation chromatography and quantitative immune-precipitin analysis. Based upon the results of these studies it was concluded that phosphoryl moieties were tightly associated (presumably covalently bonded) with the polypeptide subunits of Proteinase I. 相似文献
4.
C Hedgcoth K Thomas K Scheets S Allen 《Biochemical and biophysical research communications》1980,95(2):880-886
When murine sarcoma virus-transformed cells are labeled with [3H]lysine for various periods, 5 of 6 isoaccepting lysine tRNAs separable by RPC-5 chromatography are aminoacylated in 1 hr to the same extent that they are aminoacylated . The sixth isoacceptor, tRNA6Lys, is not aminoacylated to a measurable extent in 1 hr, although it is present in the tRNA prepared from the cells. All six isoacceptors are aminoacylated with [3H]lysine when the labeling period is 2 or 3 hr. These results further show that correlations of the amount of tRNA4Lys with cell division accurately reflect the situation . Results of differential centrifugation indicate that tRNA6Lys occurs in mitochondria. 相似文献
5.
Benzodiazepine receptors were labeled with [3H] diazepam following intravenous injection in rats. Binding of [3H] diazepam to rat forebrain membranes was displaceable by co-injection of clonazepam or the pharmacologically active enantiomers of two benzodiazepines, B9 and B10, but was not displaced by equal doses of the pharmacologically in-active enantiomers. Binding of [3H] diazepam was bserved in kidney, liver, and abdominal muscle, but was not stereospecifically diplaced in any peripheral tissue studied. The regional distribution of benzodiazepine receptors in brain was uneven, with specific [3H] diazepam binding being highest in the cerebral cortex and lowest in the ponsmedulla. Preliminary studies of the subcellular distribution of [3H] diazepam binding demonstrated highest specific binding to synaptosomal membranes. These data demonstrate the feasibility of labeling benzodiazepine receptors in rat brain . 相似文献
6.
Deborah A. Eppstein Charles E. Samuel 《Biochemical and biophysical research communications》1977,79(1):145-153
A low-molecular-weight interferon-mediated ribosome-associated inhibitor of reovirus mRNA translation was purified from the 0.5 KCl ribosomal salt-wash fraction of mouse L929 cells. The inhibitor possessed nucleolytic activity with reovirus [3H]mRNA as a substrate. Loss of translational inhibitory activity correlated with the thermal inactivation of the nuclease. A low-molecular-weight (10K) component present in the Bio-Gel P150 chromatography fractions which contained the interferon-mediated nucleolytic activity was labeled in vivo with [14C]valine; a smaller component present in the same fractions was phosphorylated in vitro with [γ-32P]ATP. The 10K components were resolved from ~50K, ~30K and ~20K phosphorylatable proteins associated with ribosomes that possess the interferon-mediated inhibitor(s) of viral mRNA translation. 相似文献
7.
P. McGing B. Reed D.G. Weir J.M. Scott 《Biochemical and biophysical research communications》1978,82(2):540-546
Using 5-[14C] methyltetrahydropteroylglutamate and [3H] pteroylglutamate it was found that vitamin B12 dependent methyltransferase can be inhibited in mice by nitrous oxide. Examination of the liver [3H] folates showed as expected that both controls and nitrous oxide treated mice had synthesised the reduced 5-methyl form. However, the controls had converted [3H] almost exclusively into a polyglutamate with virtually no monoglutamate present, while nitrous oxide treated mice had failed to add glutamates to over half of the incorporated folate. Thus demethylation may be necessary prior to polyglutamate biosynthesis and act as a method of controlling folate accumulation, or be used to create a concentration gradient with the circulating folate. 相似文献
8.
[3H]Flunitrazepam was used to characterize benzodiazepine binding sites in human brain. The benzodiazepine binding sites exhibited high affinity, pharmacological specificity and saturability in their binding of [3H]flunitrazepam. The dissociation constant (KD) of [3H]flunitrazepam binding was determined by three different methods and found to be in the range of 2–3 nM. The potency of several benzodiazepine analogs to inhibit specific [3H]-flunitrazepam binding correlated well with their potency in several human and animal tests. The density of [3H]-flunitrazepam binding sites was highest in the cerebrocortical and rhinencephalic areas, intermediate in the cerebellum, and lowest in the brain stem and commissural tracts. 相似文献
9.
Chester Meyers Akira Arimura Ariel Gordin R. Fernandez-Durango David H. Coy Andrew V. Schally Jacques Drouin Louise Ferland Michele Beaulieu Fernand Labrie 《Biochemical and biophysical research communications》1977,74(2):630-636
Three analogs of somatostatin, [-Cys14] -, [Ala2, -Cys14] - and [-Trp8, -Cys14] - somatostatin, were synthesized by the solid phase method, characterized by several means, and tested for their effects on the release of insulin, glucagon, and growth hormone. The peptides sharply suppressed the release of growth hormone and glucagon , but had less effect on insulin secretion . These analogs, particularly [-Trp8, -Cys14] - somatostatin, could possibly be useful for the treatment of diabetes mellitus. 相似文献
10.
Phosphorylation of high mobility group proteins 14 and 17 by nuclear protein kinase NII in rat O6 glioma cells 总被引:1,自引:0,他引:1
J J Harrison R A Jungmann 《Biochemical and biophysical research communications》1982,108(3):1204-1209
High mobility group (HMG) proteins 14 and 17 of rat C6 glioma cells are phosphorylated on both serine and threonine. In HMG 14 about 60% of the total [32P]phosphate was identified as phosphoserine and 40% as phosphothreonine. In HMG 17, there was 88% phosphoserine and 12% phosphothreonine. Glioma cell nuclear protein kinase NII phosphorylates HMG 14 and 17 on serine as well as threonine and the relative percentages of [32P]phosphoamino acid are similar to those seen . Nuclear protein kinase NI and the type I and II cAMP-dependent protein kinases exhibit only minor phosphorylating activity towards HMG 14 and 17. We conclude that nuclear protein kinase NII is responsible for the phosphorylation of HMG 14 and 17 . 相似文献
11.
Carlos E. Argaraña Carlos A. Arce Hector S. Barra Ranwel Caputto 《Archives of biochemistry and biophysics》1977,180(2):264-268
In vitro incorporation of [14C]tyrosine into the C-terminal position of the α subunit of tubulin was not affected by 4 mm cycloheximide. This inhibitor of protein synthesis was used for in vivo experiments. The in vivo incorporation of [14C]tyrosine into soluble brain protein of cycloheximide-treated rats was 10% of that of untreated rats. Treatment with vinblastine sulfate of the soluble brain protein showed that the incorporation of [14C]tyrosine into tubulin was higher in cycloheximide-treated than in untreated rats with respect to the incorporation into the total soluble protein. In the case of cycloheximide-treated rats, about 60% of the radioactivity incorporated into protein was released by the action of carboxypeptidase A, whereas 10% was liberated from the protein of untreated rats. The radioactive compound released by the action of carboxypeptidase A was identified as [14C]tyrosine. The α and β subunits of tubulin from animals that received [14C]tyrosine were separated by polyacrylamide gel electrophoresis. The radiosactivity ratio of subunits of tubulin from cycloheximide-treated rats was threefold higher than that of untreated rats. When a mixture of [14C]amino acids was injected, the radioactivity ratio of subunits of tubulin was similar for cycloheximide-treated and untreated rats. The results reported are consistent with the assumption that the α subunit of tubulin can be tyrosinated in vivo. 相似文献
12.
Phospholipid methylation by hepatic microsomes was measured following glucagon or epinephrine administration either to intact rats or to the isolated perfused liver. Both hormones stimulated the methylation measured as the incorporation of S-adenosyl-L-[methyl-3H]methionine into phospholipids. The labeled products were identified by thin layer chromatography and most of the counts were found to be incorporated into phosphatidylcholine. The stimulatory effects of the hormones were evident already 5 minutes following hormone administration both in and in . The observed stimulation of the methylation process by glucagon and epinephrine might be related to the previously reported stimulatory effect of these hormones on the microsomal Ca2+-ATPase, and indicate that methylation process(es) might mediate some of the effects of these hormones. 相似文献
13.
Transfer of phospholipids between the endoplasmic reticulum and mitochondria in rat hepatocytes in vivo 总被引:1,自引:0,他引:1
I Eggens C Valtersson G Dallner L Ernster 《Biochemical and biophysical research communications》1979,91(3):709-714
The transfer of phospholipids from the endoplasmic reticulum to the inner mitochondrial membrane was investigated by pulse labeling . With [3H]glycerol microsomal phosphatidylethanolamine and phosphatidylcholine were rapidly labeled during the first 30 min; while maximum incorporation into the inner mitochondrial membrane occurred only after about 5 hours. It appears that the transfer of these phospholipids between the two membrane compartments is a relatively slow process. 相似文献
14.
Acetylcholine stimulates hydrolysis of 32 P-labeled phosphatidic acid in guinea pig synaptosomes 总被引:3,自引:0,他引:3
[3H]-inositol or [3H]-arachidonate was injected intracerebrally into guinea pigs. Labeled nerve endings were incubated with Ach1 or CCh, both of which stimulate labeling of PhA and PhI from 32Pi by > 100% and 70% respectively. Their addition did not affect the labeled phosphatidyl-[3H]-inositol or [3H]-arachidonyl-diglyceride and -PhI. Enhanced hydrolysis of [3H]-inositol-PhiP and -PhIP2 in the presence of ACh, CCh or choline was not reversed by atropine. In a two-step experiment, PhA was labeled with 32Pi, and DNP was added to block further formation. Addition of ACh stimulated an atropine-sensitive in [32P]-PhA. 相似文献
15.
A study was made of the phosphorylation of chromatographically purified histone H1 subfractions from the liver of premetamorphic tadpoles (). Two H1 subfractions were obtained which differed in terms of net incorporation of [32P]phosphate . Analysis of N-bromosuccinimide cleavage products further revealed that the two subfractions also differed in the relative distribution of [32P]phosphate in N- and C-terminal regions of the molecule. Incorporation of [32P]phosphate into both regions of the molecule occurred virtually exclusively in serine residues. 相似文献
16.
The ability of a series of tetrahydroisoquinoline (THIQ) alkaloids to inhibit the binding of radioligands to catecholamine receptors in the CNS has been examined. THP was the most potent inhibitor of [3H] dihydroalprenolol binding to β-adrenergic receptors and of [3H] haloperidol to dopaminergic receptors and was the least potent inhibitor of [3H] WB-4101 binding to α-adrenergic receptors. Other THIQ alkaloids examined such as salsoline, salsolinol, and reticuline were less potent than THP in inhibiting radioligand binding to β-adrenergic and dopaminergic receptors, and more potent than THP in inhibiting radioligand to α-adrenergic receptors. The marked potency of THP in inhibiting radioligand binding to β-adrenergic receptors (IC50 ~ 10?7 M) was confirmed by the potency of this compound in inhibiting (?) isoproternol elicited accumulations of cyclic AMP in brain slice preparations. These data indicate that, if formed during alcohol consumption, THIQ derivatives such as THP may affect catecholamine neurons in the CNS. 相似文献
17.
Plasma membranes were isolated from HM7 melanoma cells grown in the presence of [3H]glucosamine and Na235SO4 or [3H]mannose and [14C]glucosamine. The labelled glucoconjugates were solubilized with 0.6 M lithium diiodosalicylate/0.5% Triton X-100. Fractionation of glycoconjugates by repeated chromatography on columns of Sepharose CL-6B and DEAE-Sepharose and by affinity chromatography on WGA-Sepharose yielded three radiochemically homogenous glycoproteins. One of these having an apparent molecular weight of 100 000 was found to contain clusters of (AcNeu)1 or in2 å [Gal å GalNAc] linked to the protein. One other glycoprotein contained both and oligosaccharides, and the third contained only carbohydrates. Preliminary results indicate that the 100 000 molecular weight mucin-type glycoprotein is present in significantly reduced quantities in cultured human fetal uveal melanocytes. Further, the bulk of the glycoproteins from the melanocytes were of lower molecular size compared to those from the melanoma cells. 相似文献
18.
Up to now the only drugs known to be able to inhibit the binding of benzodiazepines to rodent brain receptors are members of this chemical family.Zopiclone (RP 27 267), a new drug with a pharmacological profile similar to that of chlordiazepoxide and nitrazepam but entirely different chemically from benzodiazepines, has been tested for its ability to inhibit benzodiazepine binding. and studies have shown that zopiclone is able to inhibit the binding of [3H] diazepam and [3H] flunitrazepam to brain receptors. The potency of zopiclone is quite comparable to that of diazepam and nitrazepam and to that of chlordiazepoxide .These results confirm the pharmacological similarities existing between zopiclone and the benzodiazepines. 相似文献
19.
[3 H] Estradiol-17β-succinyl bovine serum albumin conjugate ([3H]-E2-BSA) was synthesized with a specific activity of 1.92 × 107 cts/min/mg. The conjugate was administered iv to ovariectomized rats and the quantity of free [3H] steroid in the uterus was determined. Radioactive material was detected in all of the subcellular fractions of the uterus and identified as estradlol-17β. Similar subcellular distribution of the radioactivity was observed when [3H]E2-BSA was added to uterine homogenate. Free estradlo1-17β was released when the conjugate was Incubated with rat uterine homogenate or with serum. The results of the present study suggest that E2-BSA is hydrolyzed and under conditions. It is recommended that the stability of a hormone-protein conjugate be established before use. 相似文献
20.
A E Pegg A Corti H G Williams-Ashman 《Biochemical and biophysical research communications》1973,52(2):696-701
Treatment of rats with large but sublethal doses of methyl glyoxal bis(guanylhydrazone), a potent inhibitor of animal S-adenosylmethionine decarboxylases, causes marked increases in the enzyme activity of extracts of kidney, ventral prostate, and testis which had been extensively dialyzed to remove any remaining drug. One day after administration of the inhibitor to female rats, the renal S-adenosylmethionine decarboxylase activity was 12 times the normal level and remained greatly enhanced for a further 24 hr. As indicated by decline in decarboxylase activity following depression of protein biosynthesis by injection of cycloheximide, the apparent half-life of the kidney enzyme in normal female rats is roughly 2 hr; in contrast, the apparent half-life of the enzyme is elevated to a value of more than 20 hr in animals that were previously treated with methyl glyoxal bis(guanylhydrazone). The increased renal S-adenosylmethionine decarboxylase activity following administration of the specific enzyme inhibitor may thus be due, at least in part, to stabilization of the enzyme against intracellular inactivation as a result either of direct combination of the enzyme protein with the inhibitor, or with substance(s) in the tissue whose levels are influenced by treatment with methyl glyoxal bis(guanylhydrazone). 相似文献