共查询到20条相似文献,搜索用时 15 毫秒
1.
M Mori S Chiba S Suzuki K Kosaka Y Miura 《Biochemical and biophysical research communications》1974,60(1):281-287
Bone marrow cells from methenolone acetate injected normal or hypertransfused polycythemic rats were cultured with erythropoietin. Heme synthesis rate in these cells was apparently increased as compared to control bone marrow cells similarly cultured. Plasma erythropoietin activity of methenolone treated rats was not detectable either by nor by assay methods. It was suggested that methenolone stimulates erythropoiesis by increasing the number and/or sensitivity of erythropoietin responsive cells. 相似文献
2.
1--Hexadecanoyl [U-14C]ethanediol can serve as substrate in the formation of 1--hexadecanoyl ethanediol 2-phosphorylcholine by particulate cell-free preparations from rat liver. Catalytic activity is largely associated with the microsomal fraction. The reaction requires CDPcholine and Mg++. Phosphatidylcholine cannot substitute for CDPcholine, but Mn++ is almost as effective as Mg++. Ca++ inhibits the reaction. The acyl ethanediol phosphorylcholine produced was identified by repeated cochromotography with authentic diol phospholipid to constant specific radioactivity, and by enzymatic and chemical degradations. 相似文献
3.
A nucleosidediphosphate kinase activity (EC 2.7.4.6) which phosphorylates GDP to GTP is present in bovine brain microtubule protein prepared by cycles of assembly-disassembly. This activity persists through 5 cycles of assembly-disassembly and sediments with microtubules in sucrose density gradients, but is not associated with the tubulin dimer. It is proposed that the kinase is an integral part of the microtubule and is therefore a microtubule associated protein (MAP). Several isozymes of nucleosidediphosphate kinase exist in our preparations with a pI 7.6 form predominant. It may be speculated that this enzyme affects tubulin assembly by modulating the ratio in the microtubule environment. 相似文献
4.
Membrane vesicles from Escherichia coli wild type and an otherwise isogenic mutant were used to immunize rabbits. In addition, a membrane protein fraction, containing the material found deficient in A mutants, was purified by preparative polyacrylamide gel electrophoresis in sodium dodecylsulfate, and used for immunization. The antisera produced were analyzed by immunoelectrophoresis and immunofluorescence microscopy. The antisera obtained by immunization with membrane vesicles from either wild type or mutant membrane preparations were qualitatively similar in the precipitin bands seen after immunoelectrophoresis. The antisera obtained by immunization with the purified protein fraction contained a subset of the antibodies seen when whole vesicles were used for immunization. In a semiquantitative precipitin assay, the antisera prepared against whole membrane vesicles or the isolated protein fraction both caused the precipitation of more protein from sodium dodecylsulfate-solubilized membranes of wild type than of mutants. No difference was seen by immunoelectrophoresis between the protein composition of wild type or membrane preparations. Thus, the mutant appears to differ from the wild type in the quantitative composition of its membrane proteins, whereas no qualitative differences were detected.Fluorescein-conjugated antiserum preparations were employed to assess the reactivity of intact cells, spheroplasts and membrane vesicles with the antisera studied above. Wild type cells of E. coli have a barrier to reaction with the antisera; this barrier is removed when the cells are converted to spheroplasts or to membrane vesicle. Similarly, a highly permeable mutant of E. coli permits reaction of the antisera with unaltered cells. Antisera to both whole membrane vesicles and to the isolated protein fraction react identically with the cellular and subcellular preparations. Thus, antisera prepared from membrane proteins isolated after sodium dodecylsulfate-polyacrylamide gel electrophoresis can still recognize some antigens present in membrane vesicle preparations. 相似文献
5.
The functional role of a chlorophyll complex associated with Photosystem I (PS I) has been studied. The rate constant for P-700 photooxidation, KP-700, which under light-limiting conditions is directly proportional to the size of the functional light-harvesting antenna, has been measured in two PS I preparations, one of which contains the chlorophyll complex and the other lacking the complex. KP-700 for the former preparation is half of that of the preparation which has the chlorophyll complex present. This difference reflects a decrease in the functional light-harvesting antenna in the PS I complex devoid of the chlorophyll complex. Experiments involving reconstitution of the chlorophyll complex with the antenna-depleted PS I preparation indicate a substantial recovery of the KP-700 rate. These results demonstrate that the chlorophyll complex functions as a light-harvesting antenna in PS I. 相似文献
6.
P J Lad J W Brown W T Shier 《Biochemical and biophysical research communications》1978,85(4):1472-1479
Of seven marine sponges tested only two, and , yielded preparations that activated rat heart microsomal guanylate cyclase and exhibited direct hemolytic activity. These two preparations also inhibited basal and fluoride-activated adenylate cyclase in rat heart microsomes and glucagon-stimulated adenylate cyclase in rat liver plasma membranes. Hemolytic activity co-purified with nucleotide cyclase-modulating activity during a standard lipid fractionation procedure. This fraction was cytotoxic to 3T3-4a Swiss mouse fibroblasts. 相似文献
7.
H E Sheerin 《Life sciences》1979,24(17):1609-1615
Serotonin has previously been implicated as the cause of the diarrhea associated with carcinoid syndrome and the amine has been shown by others to be an intestinal secretagogue in preparations of intestinal loops . In the present paper the action of serotonin on isolated segments of rabbit ileal mucosa stripped of muscle layers was studied . Serotonin (10?4M) caused an abrupt significant rise in short-circuit current (Isc) across the mucosal epithelial cell layer but this effect was transient. No change was observed in tissue conductance. In this preparation, serotonin did not alter 22Na, 36Cl or residual ion fluxes across the mucosa. High blood serotonin levels for a period of several days also did not alter ion fluxes or Isc in isolated rabbit ileum. Therefore, it is concluded that serotonin must cause its secretory activity observed by some mechanism other than a direct action on epithelial cell transport mechanisms. 相似文献
8.
Y Gopalakrishna T K Narayanan G R Rao 《Biochemical and biophysical research communications》1976,69(2):417-422
produced β-phenethyl alcohol and β-phenyllactic acid when grown in a synthetic medium containing L-phenylalanine as sole source of nitrogen. The cell-free preparations from these cells showed the following enzymes: phenylalanine aminotransferase, phenylpyruvate decarboxylase, phenylpyruvate reductase and phenylacetaldehyde reductase. The cell-free preparations of grown in medium with ammonium sulfate, lacked these enzyme activities, indicating the inducible nature of these enzymes. The results indicate the role of β-phenylpyruvate as a key intermediate in the pathway of biosynthesis of β-phenethyl alcohol and β-phenyllactic acid from L-phenylalanine. 相似文献
9.
Renal basal-lateral and brush border membrane preparations were phosphorylated in the presence of [γ-32P]ATP. The 32P-labeled membrane proteins were analysed on SDS-polyacrylamide gels. The phosphorylated intermediates formed in different conditions are compared with the intermediates formed in well defined membrane preparations such as erythrocyte plasma membranes and sarcoplasmic reticulum from skeletal muscle, and with the intermediates of purified renal enzymes such as and alkaline phosphatase. Two Ca2+-induced, hydroxylamine-sensitive phosphoproteins are formed in the basal-lateral membrane preparations. They migrate with a molecular radius of about 130 000 and 100 000. The phosphorylation of the 130 kDa protein was stimulated by La3+-ions (20 μM) in a similar way as the from erythrocytes. The 130 kDa phosphoprotein also comigrated with the erythrocyte . In addition in the same preparation, another hydroxylamine-sensitive 100 kDa phosphoprotein was formed in the presence of Na+. This phosphoprotein comigrates with a preparation of renal . In brush border membrane preparations the Ca2+-induced and the Na+-induced phosphorylation bands are absent. This is consistent with the basal-lateral localization of the renal Ca2+-pump and Na+-pump. The predominant phosphoprotein in brush border membrane preparations is a 85 kDa protein that could be identified as the phosphorylated intermediate of renal alkaline phosphatase. This phosphoprotein is also present in basal-lateral membrane preparations, but it can be accounted for by contamination of those membranes with brush border membranes. 相似文献
10.
Beverly A. Teicher Mikio Shikita Paul Talalay 《Biochemical and biophysical research communications》1978,83(4):1436-1441
A heat-stable protein activator from bovine adrenal cortex mitochondria stimulates the conversion of cholesterol to pregnenolone in crude extracts of adrenal mitochondria, and resembles in some of its properties, the sterol carrier protein of liver (Kan . . . . . , 423–429, 1972). We have shown that activator preparations also stimulate highly purified adrenal enzyme preparations comprising four components: cytochrome P-450 specific for side chain cleavage, adrenodoxin, adrenodoxin reductase, and an NADPH-generating system. Furthermore, this activator stimulates the conversion not only of cholesterol, but also of (20S)-20-hydroxycholesterol, (22)-22-hydroxycholesterol, and (20, 22)-20,22-dihydroxycholesterol to pregnenolone. Our findings provide additional evidence that the steroid-activator complexes are the substrates for the side chain cleavage enzyme and that the monohydroxy and dihydroxycholesterols are true intermediates in the conversion of cholesterol to pregnenolone by bovine adrenal cortex mitochondria. 相似文献
11.
W T Shier 《Biochemical and biophysical research communications》1977,75(1):186-193
Acyl coenzyme A:lysolecithin acyltransferase plays a major role in regulating the amount of lysolecithin in cell membranes. The acyltransferase activity in microsomal preparations from rat liver, rat heart and rabbit gastric mucosa is inhibited by a series of tertiary amine local anesthetics, detergents, and some inhibitors of cyclic nucleotide phosphodiesterases. Aspirin and indomethacin cause elevated lysolecithin/lecithin ratios in the stomachs of mice after oral administration. Inhibition of acyltransferase activity in microsomal preparations by local anesthetics correlates with reported anesthetic potencies at approximately reported therapeutic dosages. In BHK-13 cells acyltransferase activity is inhibited at to the concentrations that have been reported to cause alterations in the mobility and topography of cell surface receptors. 相似文献
12.
S C Chang D Sikkema E Goldwasser 《Biochemical and biophysical research communications》1974,57(2):399-405
Rat bone marrow cells, , respond to erythropoietin by increased RNA synthesis even in the absence of protein synthesis. Trypsin treated cells lose their ability to respond to the hormone if protein synthesis is inhibited, but retain responsiveness if protein synthesis is permitted during the incubation. The data suggest that a protein receptor on the external surface of the responsive cells is required for the action of erythropoietin on marrow cells. 相似文献
13.
Cecilia P.C. Soh W.T.J. Morgan Winifred M. Watkins A.S.R. Donald 《Biochemical and biophysical research communications》1980,93(4):1132-1139
Substances with the human blood group Sda character occur on red cells and are also present in secretions. In urine Sda activity is associated with the Tamm and Horsfall (T-H) glycoprotein. About 4% of Caucasian individuals, whose red cells are Sda negative, have a T-H glycoprotein that is without Sda activity. The two immunologically distinct forms of T-H glycoprotein have almost identical qualitative and quantitative amino acid and carbohydrate compositions. The only exception is the -acetylgalactosamine content which falls in the range of 1–2% for preparations from Sd(a+) individuals whereas the level is negligible in the Sda inactive preparations. These results strongly indicate that -acetylgalactosamine makes an important contribution to the Sda determinant structure in the T-H glycoprotein. 相似文献
14.
P. Fonlupt C. Rey H. Pacheco 《Biochemical and biophysical research communications》1981,100(4):1720-1726
In acellular membrane preparations from rat brain, two phosphatidylethanolamine-N-methylase activities were found: a first with a Km ranging near 10?6M, a second with a Km higher than 10?3M. Methylase I accepted exogenous phospholipids as substrate. Both enzymes were strongly inhibited by S-adenosylhomocysteine. Our results are compared to those obtained by Crews with synaptosomal preparations and paralleled with binding to rat brain membranes. 相似文献
15.
José Remacle 《生物化学与生物物理学报:生物膜》1980,597(3):564-576
The in vitro incorporation of cytochrome into purified plasma membranes was investigated by biochemical and immunological methods. Plasma membrane preparations incorporated three times less cytochrome than did microsomal preparations; 60% of this cytochrome could not be reduced by the NADH-cytochrome reductase and was considered as being bound to the plasma membrane. The morphological observations made after the immunochemical labeling of cytochrome clearly showed a good but asymmetrical distribution of the ferritin labeling: only the inner face of the plasma membrane incorporated cytochrome . These results are discussed with respect to theories which concern the subcellular membrane relationships in the cell. 相似文献
16.
C Y Chiou 《Life sciences》1975,17(6):907-913
The pharmacology of a possible false cholinergic transmitter, (2-hydroxyethyl) methyldiethylammonium (diethylcholine, DEC) was studied with various preparations. It was found to inhibit the neuromuscular transmission of frog sciatic nerve-gastrocnemius muscle with ED50 of 1.93 (0.66 - 5.79) × 10−4 M. DEC was also found to inhibit dog chorda tympani-Wharton's duct (postganglionic parasympathetic neuro-effector junction) and cat superior cervical ganglionnictitating membrane (sympathetic ganglion) preparations with ED50's of 6.2 (1.8 – 21.1) mg/kg and 12.0 (5.7 - 25.2) mg/kg, respectively. After blockade of these preparations with DEC, the former was still responsive to intravenous injection of pilocarpine (1 mg/kg) and choline (10 mg/kg) and the latter to close arterial injection of acetylcholine (100 μg/injection) and choline (3 mg/min infusion). These results support the idea that DEC paralyzes cholinergic neurons possibly through false cholinergic transmission without blocking the cholinergic receptor at the post-junctional membrane. 相似文献
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18.
High blood concentrations of the naturally occurring polyamines have been reported in leukemia, psoriasis, cystic fibrosis and polycythemia rubra vera. Spermidine and spermine inhibit plate-let aggregation of platelet rich plasma preparations in which ADP and Ristocetin are the agglutinating agents. The proposal is made that these organic cations may modulate platelet agglutinability. 相似文献
19.
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