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1.
Respiratory control and mitochondrial monovalent cation permeability of isolated liver cells 总被引:1,自引:0,他引:1
Uncoupling agent releases the respiratory control of rat hepatocytes to approximately the same degree as in isolated mitochondria indicating that mitochondria possess a low H+ conductance as . Mitochondria also have no detectable natural K+ conductance since the ionophore, valinomycin, is required for K+ ions to uncouple. Na+ but not K+ or choline inhibits the uncoupled respiration of liver cells. This is consistent with operation of neutral mitochondrial Na+ for H+ exchange . These results indicate a considerable similarity between certain functional and permeability properties of mitochondria and . These similarities form the basis for discussion of the role of mitochondrial ion transport in metabolic regulation. 相似文献
2.
Inability of detect cyclic AMP in vegetative or sporulating cells or dormant spores of Bacillus megaterium 总被引:23,自引:0,他引:23
P Setlow 《Biochemical and biophysical research communications》1973,52(2):365-372
Cyclic AMP was not found in vegetative cells or sporulating cells or dormant spores of using an assay which would have detected an concentration of 1 – 2 × 10?9 M. Adenyl cyclase and cyclic AMP phosphodiesterase were also not detected in sonicates of vegetative or sporulating cells. 相似文献
3.
Michael H. Gelb Pentti Malkonen Stephen G. Sligar 《Biochemical and biophysical research communications》1982,104(3):853-858
In addition to the normal 5--hydroxylation of camphor, bacterial cytochrome P450 is shown to carry out the facile epoxidation of dehydrocamphor to give -5,6-epoxycamphor. A detailed kinetic study of the reaction demonstrates that epoxidation and hydroxylation reactions occur with nearly identical rates both in the reconstituted system containing flavoprotein dehydrogenase, iron-sulfur protein, and NADH as well as in the single turnover reaction beginning with ferrous, oxygenated cytochrome P450. Dehydrocamphor is not a suicide substrate for the enzyme since competent enzyme remains after several thousand reaction cycles per P450 molecule. 相似文献
4.
F Ulrich 《Biochemical and biophysical research communications》1974,60(4):1453-1459
Macrophages, lymphocytes, and HeLa cells when incubated at 37° in Krebs-Ringer phosphate buffer release a dialyzable, heat-stable, ninhydrin-reacting factor which inhibits protein synthesis by intact cells and isolated ribosomes. Release of the inhibitor appears to be dependent on metabolism. Partial purification of the inhibitor by Sephadex G-10 chromatography suggests it has a molecular weight of 400–600. 相似文献
5.
The tricyclic antidepressant imipramine and its metabolites desipramine, 2-hydroxyimipramine and 2-hydroxydesipramine are all pharmacologically active in the central nervous system as determined by inhibition of biogenic amine uptake by rat brain synaptosomes and their effect on spontaneous and forced motor activity. Since hydroxylation of both imipramine and desipramine produced compounds of similar pharmacological activity as the parent compounds, these results suggest that clinical studies relating plasma levels of tricyclic antidepressants to efficacy should also take into consideration the levels of hydroxylated metabolites. 相似文献
6.
Jayalakshmi Kumpati 《Biochemical and biophysical research communications》1982,105(2):482-487
To investigate the role of phenylalanine and tryptophane as potential antisickling agents in intact human SS-red blood cells a liposomal transport system was employed to transfer phenyl-alanine or tryptophane into intact SS-red blood cells. Aromatic amino acids and short peptides containing phenylalanine have been demonstrated to increase the minimum gelling concentration and solubility of deoxy-hemoglobin S in aqueous solution. However, these compounds do not cross the red blood cell membrane under usual incubation conditions. Incorporation of phenylalanine or tryptophane into intact SS-red blood cells liposomal transport system markedly inhibited the sickling of deoxy-hemoglobin S. These findings raise the possibility that a nontoxic liposomal transport system which facilitates incorporation of antisickling agents into intact SS-RBC may have significant therapeutic implications in the treatment of sickle cell disease. 相似文献
7.
8.
Cycloheximide at 0.1 to 0.2 m increases cAMP concentration up to five-fold in epididymal fat tissue . This increase in cAMP concentration is accompanied by a 40% activation of glycogen phosphorylase. Propranolol, a specific β-adrenergic antagonist, blocks the cycloheximide-mediated cAMP increase. Epinephrine stimulates cAMP formation up to 25-fold under the same condition. This increase is also blocked by propranolol. Cycloheximide also partially blocks the epinephrine stimulated cAMP increase, suggesting that both compounds act at the same site. 相似文献
9.
A Pierré M Robert-Géro C Tempête J Polonsky 《Biochemical and biophysical research communications》1980,93(3):675-686
The effects of eleven quassinoids on Rous sarcoma virus induced cell transformation and on growth of normal cells were examined. At concentrations of 0.15-1 μg/ml they inhibited foci formation (76–99 %) without toxic effects on normal cells. The most active compounds also affected virus production by transformed cells. In intact normal and transformed cells, protein and DNA synthesis was equally affected after 3 hours of exposure to quassinoids of both cell types. RNA synthesis was not inhibited. This study has shown that the structural requirement of a C-15 ester in the quassinoids for antileukemic activity and is not essential for their antitransforming activity. 相似文献
10.
Evidence is presented which shows that 1-(2-chloroethyl) -3-cyclohexyl-1-nitrosourea (CCNU) upon degradation provides a 2-chloroethyl alkylating intermediate, possibly 2-chloroethyl carbonium ion, and 2-chloroethanol. Thiol alkylation occurs and a major urinary metabolite of CCNU is thiodiacetic acid. A rapid microsomal hydroxylation of the cyclohexyl ring occurs which yields varying ratios of at least five metabolites: cis or trans 2-hydroxy, trans- 3-hydroxy, cis-3-hydroxy, cis-4-hydroxy and trans-4- hydroxy-CCNU. carbamoylation appears to not be due to cyclohexylisocyanate but to the various hydroxy-cyclohexylisocyanates which are formed from hydroxy CCNU metabolites. 相似文献
11.
W K Kaufmann D G Kaufman J W Grisham 《Biochemical and biophysical research communications》1979,91(1):297-302
Administration of the carcinogenic methylating agent, methylnitrosourea, to rats caused a significant increase in endogenous DNA synthesis assayed subsequently in isolated hepatic nuclei . DNA synthesis was related directly to the dose of carcinogen and inversely to the interval between treatment and isolation of nuclei. This synthesis appears to represent the continuation of unscheduled, reparative DNA synthesis initiated in damaged cells . 相似文献
12.
A particulate factor of rat liver is described which interconverts three forms of rat liver cytosolic tyrosine aminotransferase with no alteration of enzyme activity. The factor appears to be a heat- and pH-sensitive lysosomal protein. The interconversion process is stimulated by 2.5 mM MgCl2 and 2.5 mM ATP. Asparate aminotransferase multiple forms are also susceptible to interconversion by the lysosomal factor. The properties of the factor explain several anomalous effects of manipulation on the tyrosine aminotransferase forms which have been reported in the literature and implicate the form interconversion in the degradation of tyrosine aminotransferase. 相似文献
13.
Guinea pig ileum tissue preparations contain enzymes which degrade both leucine and methionine enkephalin by cleavage of the N-terminal tyrosine residue. Similar enkephalin degrading activity is also found in the fluid bath surrounding ileum tissue preparations and appears to arise from serum and broken cell enzymes. Chelating agents such as 1,10-phenanthroline and 8-OH quinoline are effective inhibitors of enkephalin destruction by these enzymes but in the concentrations necessary to inhibit all enzyme activity, they disturb the contractility of the ileum during bioassays. The presence of enkephalin degrading enzymes and the lack of appropriate peptidase inhibitors may hinder the determination and quantification of enkephalin release in this tissue. 相似文献
14.
R.M. Sharpe D.G. Doogan I. Cooper 《Biochemical and biophysical research communications》1982,106(4):1210-1217
Injection of a luteinizing hormone-releasing hormone (LHRH) agonist into 55-day-old male rats which had been hypophysectomized 3 days earlier resulted in a 10- to 30-fold increase in the levels of testosterone in serum and testicular interstitial fluid (IF) in the 4h following injection. The levels achieved were within or above the normal range for intact untreated rats of this age. In similar animals, injection of LHRH agonist also enhanced the serum testosterone response to injected hCG at , but not at later times after injection, and by 24h reduced IF levels of testosterone suggested that LHRH agonist had begun to inhibit stimulation by hCG. , dispersed Leydig cells from untreated hypophysectomized rats showed a 2-fold increase in testosterone responsiveness to LHRH agonist when compared to cells from intact rats, and this change was associated with an 80% increase in the number of Leydig cell LHRH-receptors. 相似文献
15.
Calf thymocytes were isolated and incubated with concanavalin A. The effect of the mitogen on the enzyme activity of membrane-bound lysolecithin acyltransferase (acyl-CoA: , EC 2.3.1.23) was determined as also the binding of 125I-labelled concanavalin A to intact cells and isolated membranes.The lysolecithin acyltransferase was found to be activated three times in microsomal membranes. The activation occurred directly after binding of concanavalin A and was temperature independent, since similar activities were found in cells treated with concanavalin A at 0 and 37 °C.The acyltransferase activation using increasing concentrations of concanavalin A revealed a different behaviour, as compared to the binding of concanavalin A. While the binding of concanavalin A to intact cells expressed a normal hyperbolic saturation function the activation process of the acyltransferase described a sigmoidal relationship. Corespondingly, the interaction coefficients for both functions were different (Sips coefficient for binding = 1.0 and Hill coefficient of the enzyme activation = 1.8).These results indicate that the acyltransferase activation is due to a cooperative interaction between the ligand-receptor complex and the enzyme. 相似文献
16.
CS7BL/6 mice were sensitized with an ip injection of allogeneic P-815 mastocytoma cells. Fifteen days later the spleen cells of the tumor allosensitized mice were cultured and tested for their responsiveness to mitogens and alloantigens, and for their ability to generate cytotoxic cells in vitro. The results indicate that 15 day tumor-sensitized spleen cells are hypo-responsive in mixed lymphocyte culture (MLC) with DBA/2 or AKR as stimulating spleen cells. The cells which are hypo-responsive in MLC can proliferate in response to mitogens and they also can generate cytotoxic cells in vitro. MLC reactivity recovers in about 2–3 months which is months after the mice have rejected their tumors. The mechanism of MLC hypo-responsiveness was investigated. The results suggest the presence of a suppressor cell which does not appear to be a macrophage or a B-cell. The suppressor cell can be separated from the cytotoxic cell and therefore appears to be a noncytotoxic T-cell. 相似文献
17.
Two populations of L5178Y murine leukemic cells, maintained by different methods, were studied for their implantation ability in BDF1 mice. Implantation ability was measured by number of tumor nodules formed, liver weight, and day of death of the animal. 1) Cells from a population grown for 10 years had no implantation ability; i.e., no tumor nodules were formed when injected into the tail vein. After 30 days of growth in the peritoneal cavity of BDF1 mice, these same cells were injected into the tail vein and 10 days later had produced over 200 liver tumor nodules. When cells taken from these tumors were recultured for 60 days , they lost the acquired implantation ability, but regained it after another single peritoneal passage. 2) L5178Y murine leukemic cells grown for six years in ascites tumor cells were extremely tumorigenic; over 200 tumor nodules appeared in the liver after tail vein injection. These cells were not rendered less tumorigenic and did not lose their implantation ability by culturing for 60 days. The results suggest that implantation ability is a property of the cell's growth environment; furthermore, they have strong implications for the and manipulation of this property. 相似文献
18.
Incorporation of C14 Leucine was determined or in isolated mitochondria and microsomes of rat brain and liver after acute or chronic ethanol administration .The protein synthesis in mitochondrial and microsomal preparation was inhibited respectively by chloramphenicol and cycloeximide, specific inhibitors for the two systems tested. The experimental data demonstrate that the protein synthesis in both systems, mitochondrial and microsomal, is strongly affected only after chronic treatment which produces significant activation at the mitochondrial and microsomal level in the liver and an inhibition on the same systems of the brain.The data for protein synthesis instead show strong inhibition after acute administration, except for brain mitochondria, which are practically unaffected, while after chronic treatment no significant alterations are observed. 相似文献
19.
Dennis A. Carson Kwang-Poo Chang 《Biochemical and biophysical research communications》1981,100(3):1377-1383
The inosine analog formycin B (1–10 μM) inhibited the growth of promastigotes and amastigotes. When administered to Syrian hamsters infected with , formycin B (10 mg qd × 5) decreased by greater than 90% the number of liver amastigotes, with a concomitant reduction in hepatosplenomegaly. Both extracts and intact cells of , unlike mammalian cells, effectively phosphorylated formycin B. The resulting formycin B monophosphate inhibited dose dependently the conversion of IMP to adenylosuccinate in parasite extracts. This effect may be related to the potent anti-leishmanial activity of formycin B. 相似文献
20.
E Ambellan 《Biochemical and biophysical research communications》1974,57(2):520-525
Glucocorticoid binding to certain cell particles of rat liver and thymus following treatments and consists in part of a very “tight binding” that resists hot and cold perchloric acid extractions. This binding is found in thymus nuclei and in liver cytoplasmic particles, but not in liver nuclei nor in thymus mitochondria or microsomes. The existence of “tight binding” coincides with the ability of the same particles to bind free corticoid directly in incubations . The difference in the cellular location of this binding suggests that different methods of glucocorticoid activation exist in the anabolic target tissue, liver, and the catabolic target tissue, rat thymus. 相似文献