共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
C D Fitch 《Life sciences》1977,20(7):1281-1284
Studies of infective potency were done to determine why chloroquine-resistant is an obligate parasite of immature erythrocytes. Infective potency was estimated from the length of time required for mice to develop parasitemia of 2% (delay in parasitemia). The delay in parasitemia was an inverse linear function of the logarithm of the number of parasites inoculated. A single regression line fitted the data both for susceptible and for resistant parasites, indicating identical infective potencies which, in turn, indicates that chloroquine-resistant selects and preferentially infects immature erythrocytes whereas it rejects mature erythrocytes. 相似文献
3.
Joseph Schrèvel François Bernard Christèle Maintier Roger Mayer Michel Monsigny 《Biochemical and biophysical research communications》1984,124(3):703-710
By using fluorogenic peptidyl-3-amino-9-ethyl-carbazole a highly selective endopeptidase for the Val-Leu-Gly-Arg sequence was demonstrated in endoerythrocytic stages of . Val-Leu-Gly-Arg-endopeptidase showed a maximum activity in pH range 7.0–8.0; it was completely inhibited by 1 mM leupeptin and 1 mM antipain. A complete inhibition was also obtained by 15 mM chloroquine. This trypsin-like activity was negligible in uninfected red blood cells. The high sensitive fluorogenic procedure could be performed on cell fractions, cell lysates as well as supernatants. 相似文献
4.
An electron cytochemical study of 6-phosphogluconate dehydrogenase activity in infected erythrocytes during malaria 总被引:1,自引:0,他引:1
The distribution of 6-phosphogluconate dehydrogenase (6-PGD) was examined by an electron microscopic technique in erythrocytes of rodents infected with , chickens with and rhesus monkeys with . Unlike glucose-6-phosphate dehydrogenase, which is restricted to the host erythrocyte, 6-PGD was found to be present in the parasite as well as the host erythrocyte in all infections studied. The implications of these findings are discussed in relation to the metabolism of malaria parasites. 相似文献
5.
Dibucaine at 0.1 and 0.25 mM markedly inhibited epinephrine-stimulated lipolysis in rat epididymal fat cells but did not inhibit protein kinase activity. At 1.0 mM, dibucaine half-maximally stimulated protein kinase of fat cells under basal conditions but did not stimulate lipolysis. It is concluded that dibucaine inhibits lipolysis by a mechanism not involving inhibition of protein kinase. 相似文献
6.
Wilfredo Mellado Neal F. Magri David G.I. Kingston Renee Garcia-Arenas George A. Orr Susan Band Horwitz 《Biochemical and biophysical research communications》1984,124(2):329-336
Synthesis and biological activity of 2′-acetyltaxol and 7-acetyltaxol are reported. Activity is measured by cytotoxicity toward the macrophage-like cell line J774.2, and by promotion of microtubule assembly in the absence of exogenous GTP. Addition of an acetyl moiety at C-2′ results in loss of activity but not cytotoxicity. The properties of 7-acetyltaxol are similar to those of taxol in its effects on cell replication and on microtubule polymerization. Therefore a free hydroxyl group at C-7 is not required for activity and this position is available for structural modifications. 相似文献
7.
J A Villarreal W Vale M Brown M Butcher P Brazeau C Rivier R Burgus 《Biochemical and biophysical research communications》1976,70(2):551-558
A protein has been isolated from ovine hypothalamus on the basis of its ability to stimulate release of growth hormone by cultures of dispersed pituitary cells. This protein has been identified as being myelin basic protein. With no similar biological activity , myelin basic protein is thus to be recognized as a potentially interfering substance in any search for the physiological growth hormone releasing factor using assay systems. 相似文献
8.
Bovine serum albumin and preparations of cell sap from malaria parasites and normal erythrocytes were tested for ability to protect cellular membranes against the toxicity of ferriprotoporphyrin IX (FP) and a chloroquine-FP complex. Suspensions of (approximately 7 × 106 parasites per ml, isolated from saponin-lysed, infected erythrocytes) were used as a test system. Toxicity was monitored by measuring changes in turbidity of these suspensions at 700 nm. Parasite cell sap (0.56 mg protein per ml) and albumin (1 mg per ml) completely prevented the toxicity of 40 μM FP. Erythrocyte cell sap (8.6 mg of hemoglobin per ml) provided only partial protection from 40 μM FP. Neither the cell sap preparations nor albumin eliminated the toxicity of a chloroquine-FP complex formed from 20 μM chloroquine and 40 μM FP. These observations suggest that the cell sap preparations contain FP binding substances and that the mode of action of chloroquine may be to shunt FP away from a nontoxic complex with these substances and into a toxic chloroquine-FP complex. 相似文献
9.
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
10.
The antiinflammatory activity of a homologous series of α-alkyl substituted [4-(1-oxo-2-iso-indolinyl)-phenyl]-acetic acid has been assayed by some and tests.These compounds were shown to be particularly active in inhibiting prostaglandin biosynthesis from bovine seminal vesicles, and their potency was seen to increase as the size of the substituents in the side chain increased.The antiinflammatory activity is not correlated with inhibition of PG-synthetase. Discussion of the data takes into account the plasma protein binding and pharmacokinetics of these compounds. 相似文献
11.
Effect of carbamyl phosphate on the regulation of nitrogenase in Clostridium pasteurianum 总被引:5,自引:0,他引:5
One mM carbamyl phosphate inhibited the acetylene reduction activity of nitrogenase 30% whereas at high concentrations a maximum inhibition of 50% was observed. When 1 mM carbamyl phosphate was added to a culture growing of N2 1) nitrogenase synthesis was completely repressed and 2) after a period of 2.5 hrs in the absence of growth, the specific activity decreased to less than 50% of its activity just before the addition of the inhibitor. 相似文献
12.
Heavy concentrations of viable P. berghei in the natural milieu [20% () parasitized red blood cells, or 20% () homogenate of splenic tissue in which malarial cells sequestered wer suspended in a serum-free, protective medium. Various rates of cooling are designated as low (1.3 °C/min) and intermediate (4 °C/ min) on exposure in cold gas evolving from liquid nitrogen refrigerant to ?70 °C, and this followed by direct immersion in the low temperature refrigerant (?196 °C). Cooling designated high was accomplished by abrupt immersion of the sealed vials with the live malaria-bearing tissue in the liquid nitrogen refrigerant. Rates of warming and thawing were designated low (after slow rewarming of frozen tissue in air at 25.5 °C) and high (after rapid rewarming and thawing in a water bath at 40 °C). Strip chart recordings were made of the complete cooling and freezing wave patterns of the suspending medium to ?70 ° C. The functional survivals of the freeze-thaw P. berghei malaria were measured by a special infectivity titration method.None of the cooling and freezing treatments adversely influenced the parasite survivals. Our data showed the optimum cooling velocity that maximally protected this highly lethal P. berghei strain within the host erythrocyte matrix was 1.3 ° C/min to ?70 to ?196 ° C. The functional survivals of two RBC stabilates with P. berghei, after retrieval from 25 days storage in the liquid nitrogen refrigerant, excelled by more than 100-fold the infectivity titer found by viability assay in the pool of the 0-days nonfrozen infected RBC.The precise factors favoring the maximal survivals of the freeze-thaw P. berghei are unclear. Several factors, singly or in combination, may have played key roles in protecting the living P. berghei from the freeze-thaw damage. These factors are: The composition of the suspending medium fortified by additions of bicarbonate, glucose, lactalbumin hydrolysate and yeastolate; the presence of naturally occurring peptide-containing materials surrounding the parasites in the host red cell milieu; and the protective glycerol agent. Any of these constituents singly or combined possess potential for reducing freeze-thaw injury to the parasites to produce maximal survivals. 相似文献
13.
14.
The effect of morphine sulfate (MS) on adenylate cyclase (AC) and phosphodiesterase (PDE) activities in the rat striatum was investigated. MS produced a dose-dependent increase in basal AC activity and did not alter sodium fluoride-induced stimulation both (7.5–30 mg/kg, 1 hr pretreatment, i.p.) and (1–100μM). , when submaximal effective concentrations of dopamine and MS were combined, there was an additive effect. However, administration of MS did not alter dopamine-induced stimulation of AC activity. MS, and inhibited PDE activity in a dose-dependent manner only with the high substrate concentration (3.3 × 10−3M cyclic AMP). Preliminary results from this study indicate that morphine affects the cyclic AMP system. 相似文献
15.
Cytoplasmic free and bound polysomes were isolated from bovine adrenal cortex, and used to program protein synthesis in rat liver cell sap and wheat germ lysate systems. Synthesis of adrenodoxin(Ad) and adrenodoxin reductase(AdR) in the cell-free systems was determined by immunoprecipitation using monospecific antibodies, and the sizes of the products were analyzed by SDS-polyacrylamide gel electrophoresis. Ad was synthesized by both free and bound polysomes as a putative large precursor having molecular weight of approximately 20,000 daltons, which was processed to mature size Ad (MW 12,000 daltons) by incubation with adrenal cortex mitochondria. On the other hand, AdR was synthesized only by free polysomes apparently as the mature size product. 相似文献
16.
The ability of a number of phospholipids to stimulate undecaprenyl pyrophosphate synthetase was investigated. The detergent Triton X-100, which is added to stabilize the enzyme during purification and is required for activity, was removed with the non-ionic resin XAD-2. The effects of cardiolipin, phosphatidyl ethanolamine, phosphatidyl choline, and phosphatidyl glycerol on the activity of XAD-2 treated undecaprenyl pyrophosphate synthetase were determined. Of the phospholipids studied only cardiolipin stimulated enzymic activity as effectively as Triton X-100. 相似文献
17.
The isolated myenteric plexus-longitudinal muscle of the guinea-pig ilem (GPI) was used as testsystem to study the influence of chronic morphine treatment on the levels of enkephalins, β-endorphin and some of its fragments. The peptides were assayed by means of a combination of high pressure liquid chromatography and radioimmunoassays. It was found that the levels of methionine- and leucine-enkephalin and β-endorphin were not altered by chronic morphine treatment of guinea-pigs nor in GPI exposed to morphine . However, the levels of some β-endorphin fragments i.c. γ-endorphin and des-tyrosine-γ-endorphin were elevated after morphine treatment and respectively. It is suggested that β-endorphin and its fragments are involved in homeostatic processes during development of opiate tolerance. 相似文献
18.
The zymosan particles induced a time-dependent release of the chloride-dependent arginine aminopeptidase from rat peritoneal macrophages during incubations. Intraperitoneal injections of zymosan, a streptococcal cell preparation and a -suspension caused the release of the chloride-activated arginine aminopeptidase into the peritoneal fluid. The arginine aminopeptidases obtained both from the cell cultivation media and the peritoneal washes were partly purified. The enzymes were similar with regard to the following properties: chloride activation with an optimum at physiological concentrations; strong inhibition by 10?6M -chloromercuribenzoate; similar elution properties and preferential hydrolysis of mainly the -L-aminoacyl-2-naphthylamines of arginine and lysine. The chloride-activated arginine aminopeptidase released into the media in conditions was inactivated in contrast to the enzyme released into the peritoneal fluid as a result of the intraperitoneal injections. The timing of the release of the chloride-activated arginine aminopeptidase both and suggests that the enzyme plays a role in the initial phases of inflammation. 相似文献
19.
Altered restriction of nuclear RNA during incubation in vitro 总被引:1,自引:0,他引:1
Nuclei were isolated from rat liver and incubated in two commonly employed RNA transport assays. Released [14C] RNA was isolated and hybridized with filter-bound DNA in the presence of competing cytoplasmic RNA. A significant portion of RNA which was transported to either medium was not represented in cytoplasmic RNA. These results indicate that the restriction of some sequences to the nucleus is not maintained . 相似文献
20.
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