共查询到20条相似文献,搜索用时 31 毫秒
1.
M S Balakrishnan T R Sharp J J Villafranca 《Biochemical and biophysical research communications》1978,85(3):991-998
Oxygen-18 exchange out of [18O]Pi catalyzed by Mg2+-activated unadenylated glutamine synthetase from was followed by 31P-NMR in the presence of the other substrates, ADP and L-glutamine. The pattern of the in the species P18O4, P18O316O1, P18O216O2, P18O116O3, P16O4 during the exchange followed a binomial distribution consistent with indiscriminate removal of any of the four oxygens of Pi. The rate constant for exchange was 410±40 min?1 while the rate constant for net reaction (ATP formation) was 62±4 min?1. Thus exchange proceeds ~7 times faster than net reaction, a finding in accord with that of Stokes and Boyer ( (1976) , 5558) for the Mn2+-activated adenylylated glutamine synthetase. A model for the overall catalytic events first derived from rapid kinetic fluorescence experiments (Rhee and Chock, Proc. Natl. Acad. Sci. USA, (1976) , 476) was successfully used to fit the oxygen exchange data in this paper. 相似文献
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R.L. Horst B.C. Pramanik T.A. Reinhardt S.-J. Shiuey J.J. Partridge M.R. Uskokovic J.L. Napoli 《Biochemical and biophysical research communications》1982,106(3):1006-1011
23,25-Dihydroxyvitamin D3 was isolated from the plasma of vitamin D3-toxic pigs. An ultraviolet absorbance spectrum confirmed its purity. The configuration of the 23-hydroxyl group was determined to be S by comparison of the natural product with synthetic 23,25- and 23,25-dihydroxyvitamin D3 by high-pressure liquid chromatography. The affinity of both 23,25- and 23,25-dihydroxyvitamin D3 for the plasma vitamin D binding protein was similar to vitamin D3. Thus, with respect to the plasma vitamin D binding protein, 23,25-dihydroxyvitamin D3 is the least potent, naturally-occurring, dihydroxylated vitamin D3 metabolite known. 相似文献
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A radioimmunoassay method for the measurement of plasma levels of 18-hydroxy-11-deoxycorticosterone (18-OH-DOC) has been developed. The antiserum against 18-OH-DOC was produced in rabbits immunized against 18-OH-DOC-3-oxime-bovine serum albumin. Plasma (1–2 ml) was extracted with dichloromethane and chromatographed on paper. The purified extracts were incubated with antiserum at a dilution for hour at 37°C and for 2 hours at 4°C. Saturated ammonium sulfate was used to separate free from bound 18-OH-DOC. 1, 2-3H-18-OH-DOC was added to all samples to correct for losses and to determine the percent free. Pyridine (0.1%) was added to solvents to maintain the stability of 18-OH-DOC. Recovery after extraction was 58 ± 8 (S.D.)%. The accuracy and precision of the method were acceptable, and a sensitivity of 2 pg per sample enabled the measurement of very low levels of 18-OH-DOC. High specificity was demonstrated by a low blank value (0 ± 0.2 pg) and by demonstrating that alternative paper chromatography separation systems gave results not differing significantly from those obtained by the present method. The mean 8AM plasma 18-OH-DOC level was 8.5 ± 1.2 ng per 100 ml in 18 normotensive control subjects. There was a marked response of plasma 18-OH-DOC to ACTH stimulation and dexamethasone suppression and a significant increase after 3 hours upright posture. 相似文献
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Using enthalphy data from differential scanning calorimetry experiments and 13C-NMR linewidths of specifically ( lipids, the miscibility properties of phosphatidylcholines and lysophosphatidylcholines in liposomal dispersions have been investigated. It was found that 16 : 0 lysophosphatidylcholine mixes homogeneously in 16 : 0/16 : 0 phosphatidylcholine bilayers. Mixtures of 16 : 0 lysophosphatidylcholine with 18 : 1c/18 : 1c phosphatidylcholine, of 18 : 1c lysophosphatidylcholine with 16 : 0/16 : 0 phosphatidylcholine and of 18 : 1c lysophosphatidylcholine with 18 : 1c/18 : 1c phosphatidylcholine exhibited immiscibility in the phosphatidylcholine gel state. 相似文献
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Drug-induced changes in lipid composition of E. coli and of mammalian cells in culture: ethanol, pentobarbital, and chlorpromazine. 总被引:1,自引:0,他引:1
Both Chinese hamster ovary cells in culture and cells change their lipid composition when grown in the presence of ethanol, pentobarbital, and chlorpromazine. The effects of ethanol and the cross-tolerant drug, pentobarbital, are similar. Both cause a shift from 18:0 fatty acid to 16:0 fatty acids in CHO cells and a decrease in the proportion of saturated fatty acids in . Chlorpromazine, a non-cross-tolerant drug, causes the opposite effect in , a decrease in the proportion of unsaturated fatty acids. Chlorpromazine has little effect on the fatty acid composition of CHO cells. These changes in lipid composition are proposed as an adaptive response and a part of the mechanism for the development of drug tolerance. 相似文献
6.
Kiyoshi Satouchi R.Neal Pinckard Donald J. Hanahan 《Archives of biochemistry and biophysics》1981,211(2):683-688
The preparation of the potent new lipid chemical mediator, 1-O-alkyl-2-acetyl-sn-glyceryl-3-phosphorylcholine (AGEPC), through a facile semisynthetic procedure utilizing the vinyl ether-containing lecithins (plasmalogens) of bovine heart muscle as the starting material results in a derivative with mixed chain alkyl residues. In order to focus more closely on the importance of the various components of AGEPC relative to its biological activity, it was of importance to develop a method for isolation of molecules rich in a specific chain length of the alkyl residue. In the current study it was found that a simple thin-layer chromatographic technique, using a solvent system of methanol water (2:1, ), afforded an excellent separation of semisynthetic AGEPC into two species, one containing over 95 mol% 16:0 and the other 95 mol% 18:0 alkyl chain species. The same procedure allowed a comparable separation of the species of 1-O-alkyl-2-acetyl-sn-glyceryl-3-phosphorylethanolamine (AGEPE) prepared from AGEPC by phospholipase D action. On the basis of their effectiveness in releasing serotonin from washed rabbit platelets, the 16:0-rich derivatives of AGEPC and AGEPE exhibited significantly higher specific activities, from three to six-fold, on a molar basis, respectively, than the corresponding 18:0-rich derivatives. These findings are discussed in relation to the importance of the chain length of the alkyl ether group in expression of the biological activity of AGEPC. 相似文献
7.
In five experiments, fertilization, early (18–19-day) pregnancy, and lambing were examined after insemination with semen stored at 5°C in tris-fructose-egg yolk diluent.After deposition into uterine horns by surgical insemination of semen stored for 0 (control), 2, 4, 6, 8, 9 or 10 days, fertilized eggs were recovered in , and ewes; the 18–19-day pregnancy rates determined by progesterone assay were , and for the respective storage periods. There was a linear decrease in fertilization rates beyond 4 days of storage and in early pregnancy rates after 6 days of storage (P<0.001). The decline with time of storage in the fertilization rate was not associated with an increase in early embryonic loss. Surgical insemination with semen stored for 0, 4, 6, 8, 9 and 10 days resulted in 53, 35, 40, 25, 5, and 0% lambing.Single cervical (normal) insemination of a total of 281 ewes with 0, 1, 2 or 3-day-old semen, using within each semen treatment 90 × 106 and 180 × 106 spermatozoa, yielded mean lambing rates of 60.0, 34.3, 33.8, and 17.1%; and after using 150 × 106 and 300 × 106 spermatozoa in a total of 393 ewes the mean lambing rates for the above semen treatments were 69.0, 46.4, 36.1, and 24.2% (linear, P < 0.001). In both tests the lambing results were better after insemination of the higher number of spermatozoa, but the slope of decline in fertility with age of semen was not affected by the sperm dose.When single and double cervical inseminations were performed in a total of 411 ewes, with 150 × 106 and 300 × 106 spermatozoa per inseminate, the lambing rates for semen stored for 0, 1, 2 and 3 days were 57.7, 30.4, 26.8, and 4.7% after single insemination, and 66.7, 56.8, 46.4, and 41.5% after double inseminations. The sperm dose within method of insemination and semen treatment had no effect. The lambing rate was better after double than single insemination (P<0.001), but the slope of decline in fertility with age of semen was not significantly affected by number of inseminations.In the final experiment, involving 408 ewes, 300 μg of prostaglandin F2α added to the inseminate did not improve the fertility of fresh semen or semen stored for 1 day. 相似文献
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anterior pituitaries removed on days 5 through 19 of , were incubated for 3 h in the presence of 3H-leucine. Incorporation of radioactivity into electrophoretically separated in medium and pituitary homogenate was used to determine patterns of prolactin synthesis, release, per cent release and storage. Prolactin synthesis, release and per cent release were high on days 5 through 7, low on days 8 through 16, and intermediate to high on days 18 and 19. Prolactin storage did not change significantly throughout pregnancy. 相似文献
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H.R. Bosshard M. Zürrer H. Schägger G. von Jagow 《Biochemical and biophysical research communications》1979,89(1):250-258
Cytochrome 1, the electron donor for cytochrome , is a subunit of the mitochondrial cytochrome 1 complex (complex III, cytochrome reductase). To test if cytochrome 1 is the cytochrome -binding subunit of the 1 complex, binding of cytochrome to the complex and to isolated cytochrome 1 was compared by a gel-filtration method under non-equilibrium conditions (a 1 complex lacking the Rieske ironsulfur protein was used; von Jagow et al. (1977) Biochim. Biophys. Acta , 549–558). The approximate stoichiometries and binding affinities were found to be very similar. Binding of cytochrome to isolated cytochrome which is another subunit of the reductase was not detectable by the gel-filtration method. Further, the same lysine residues of cytochrome were shielded towards chemical acetylation in the complexes 1 and 1. From this we conclude that the same surface area of cytochrome is in direct contact with cytochrome 1 and with cytochrome 1 in the respective complexes and that therefore cytochrome is most probably the structural ligand for cytochrome in mitochondrial cytochrome reductase. 相似文献
10.
Controlled alkaline hydrolysis of 16α-bromo-17-keto steroids , and with potassium carbonate and tetra-n-butylammonium hydroxide (n-Bu4NOH) and synthesis of 2α-hydroxy-3-ones , and by the controlled hydrolysis of the corresponding 2α-bromo-3-ones , and are described. Treatm carbonate in aqueous acetone or with n-Bu4NOH in aqueous dimethylformamide (DMF) gave 16α-hydroxy-17-ones , and in 85–90% yield, respectively. 2α-Hydroxy-3-ones , and were obtained by hydrolysis of the corresponding bromoketones , and in high yields using the above conditions or sodium hydroxide in pyridine or DMF, respectively. Deuterium labeling experiments suggested that equilibration between the 2α-bromoketone and the 2β-bromo isomer precedes the formation of the ketol in which the true intermediate might be the 2β-isomer . However, rearranged androstane derivatives, 3β-hydroxy-2-ones and , were stereoselectively obtained by treatment of the bromoketones and with an excess amount of sodium hydroxide. 相似文献
11.
(1) The polymorphic phase behaviour of aqueous dispersions of various synthetic phosphatidylethanolamines, both singly and in mixtures, has been investigated by 31P-NMR. (2) PE remains in the lamellar phase up to 90°C. PE exhibits a lamellar to hexagonal (HII) transition between 60°C and 63°C. For PE, the lamellar to hexagonal (HII) transition occurs between 7 and 12°C, whereas for PE, the hexagonal (HII) phase is the preferred structure above ?15°C. (3) Mixtures of PE and PE exhibit near-ideal miscibility behaviour. For mixtures of PE and PE there is evidence of fluid-solid immiscibility at temperatures below the gel-liquid crystalline transition temperature of the PE component. Mixtures of PE and PE exhibit complex phase behaviour involving limited fluid-solid immiscibility at low temperatures and formation of a phase allowing isotropic motional averaging at higher temperatures. (4) 31P-NMR provides a graphic method for investigating the miscibility properties of mixed PE systems. 相似文献
12.
Bernard J.R. Philogène 《Journal of insect physiology》1975,21(7):1415-1417
Subjecting larvae of Hypocrita jacobaeae to temperatures of 21 and 28°C and photoperiods of , , , and does not interfere with the phenomenon of diapause. The last larval instar is particularly affected by the higher temperature. Effects include numerous deaths, a high proportion of ill-formed pupae, and failure of adults to emerge properly from the pupal case. The significance of these findings is discussed. 相似文献
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A method is described for the measurement of prednisone and prednisolone in human plasma by high-performance liquid chromatography (hplc). An ether/dichloromethane extract (60:40, ) of plasma is evaporated to dryness and chromatographed on a 250 × 4.5-mm Whatman Partisil column with uv detection at 239 nm. Prednisone, prednisolone cortisol, and the internal standard dexamethasone are satisfactorily resolved with the elution system of water-saturated dichloromethane/ethanol (95:4, ). The hplc method can be used for plasma prednisolone concentrations as low as 25 ng/ml. The values correlate well with those obtained by a radioimmunoassay procedure for prednisolone. 相似文献
15.
After a series of preliminary tests on inert substances and on saliva drawn from donors of know MN blood group, 31 right femura from Pisa cemetery buried for 25–30 years and 37 eneolithic femura from Gaudo necropolis near Paestum (2500 – 2000 B.C.) were submitted to 140 assays for the MN system using the standard technique already devised in our Laboratory for ABO blood group determination.Positive and reproducible results were obtained in 18:31 recent femura (58%) and in 24:37 eneolithic bones (65%). The following phenotype and gene frequencies were obtained: When the ABO and the MN blood group determinations are performed in parallel, a significant positive connection between the two diagnosabilities is observable: P = 0·0387 in the case of the eneolithic bones, in the case of the total sample of 59 eneolithic and recent bones tested in parallel. This fact could be reasonably explained considering the similarity of the chemical structure of MN and ABO glycoproteins, which would account for a similar behaviour in preservation.The absence or the very low concentration of M and N substances in tissues and body fluids would on the other hand agree with the percentage of diagnosability: lower in the MN system (60–65%) than in the ABO system (75–80%). The more problematical character of MN blood group typing of bones could be better approached if further research were done. 相似文献
16.
Penile intromissions have been thought to be the primary stimulus for reflex ovulation in light-induced persistent estrus (LLPE) rats, even though other stimuli also trigger reflex ovulation. To clarify the nature of these noncoital stimuli, intact (nonadrenalectomized) LLPE rats were briefly exposed to a variety of environmental stimuli, other than intromissions, and checked for ova 19–22 hr later. Summary of results (number of rats ovulating/number of rats tested): (A1) home cage (); (B1) home cage + vaginal taping (); (C1) home cage + male-soiled bedding (); (D1) novel cage (); (E1) novel cage + vaginal taping (); (F1) novel cage + vaginal taping + male-soiled bedding (); (G1) novel cage + vaginal taping + male-soiled bedding + male mounts without intromissions (). The percentage of LLPE rats that ovulated in the last-mentioned test condition was related to the degree of proceptivity/receptivity of the LLPE females. Eight of eight proceptive LLPE females ovulated, but only nonproceptive females ovulated. To account for reflex ovulation in the absence of intromission it has been suggested that adrenal progesterone (P) stimulates release of an ovulatory quota of luteinizing hormone. This study demonstrates no significant differences in percentage of LLPE females ovulating in corresponding groups of adrenalectomized (ADX) and adrenal-intact females. Summary of results: A2 = , B2 = , C2 = , D2 = , E2 = , F2 = , G2 = . Conclusion: (a) Exposure to a factor in male-soiled bedding induces reflex ovulation in a significant proportion of adrenal-intact LLPE animals while exposure to a novel cage and/or vaginal taping does not, (b) penile intromissions are not the primary stimulus for reflex ovulation in intact proceptive LLPE rats, and (c) adrenal P is not required for reflex ovulation after tests with noncoital stimuli. 相似文献
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