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排序方式: 共有898条查询结果,搜索用时 15 毫秒
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PM Visscher 《遗传、选种与进化》1995,27(4):335-345
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R. J. Hutz G. S. Krueger P. A. Meller S. A. Sholl D. J. Dierschke Ph.D. 《Cell and tissue research》1987,250(1):101-104
Summary We have shown previously that estradiol-17 (E2) reduces number of ovulations in cyclic rats, induces atresia of the dominant preovulatory follicle in monkeys, and that the initial effects of this treatment include reduced viability and estrogen accumulation in vitro by aspirated granulosa cells (GC) from monkeys and hamsters. The present experiment was designed to determine whether the reduction in estrogen accumulation can be ascribed to a direct action of E2 on the aromatization of androgen to estrogen in vitro. Female hamsters were injected with 30 I.U. pregnant-mare serum gonadotropin i.p. and sacrificed 3 days later. GC were aspirated from the largest follicles and incubated for 48 h (initial incubation period) in the presence of human pituitary follicle-stimulating hormone (hFSH, 100 ng/ml). Following initial incubation, GC were further incubated for up to 24 h (secondary incubation period). During this subsequent incubation, medium was supplemented with 100nM 3H-1-androstenedione (3H-A4). Initial incubation with E2 at doses of 10 ng/ml, 100 ng/ml and 1 m E2/ml induced variability in GC response, and a maximal depression of 70%. The inhibition by E2 of hamster GC function in vitro parallels that shown in vivo for both hamsters and monkeys, but contrasts with that shown for rats. Thus, hamsters may represent an appropriate model in which to study the atretogenic effects of E2 directly on antral follicle development. 相似文献
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R Fathi-Afshar T M Allen C A Krueger D A Cook A S Clanachan R Vriend H P Baer C E Cass 《Canadian journal of physiology and pharmacology》1989,67(4):276-281
Agelasimine A and agelasimine B, two novel compounds related to adenine, have been isolated from the orange sponge, Agelas mauritiana, and have been tested for a variety of biological activities. Both compounds inhibited proliferation of cultured L1210 leukemia cells at nanomolar concentrations with accumulation in the G1 stage of the cell cycle. However, no prolongation of life was observed in mice bearing P388 leukemia treated with these compounds. In the rat isolated aorta, micromolar concentrations of agelasimines were very effective in inhibiting contractions elicited by potassium chloride but had little or no effect on responses for prostaglandin F2 alpha and had modest effects on the responses to noradrenaline and significant effects on 5-hydroxytryptamine. Agelsamines A and B appeared to be equipotent in causing relaxation in rabbit jejunum and bovine coronary artery, and they also inhibited nucleoside transport into rabbit erythrocytes in micromolar concentrations. 相似文献
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Preparation and use of N-iodoacetyltyramine in generation of 125I-labeled compounds is described. The kinetics of alkylation of N-acetylcysteine by N-iodoacetyltyramine (k2 = 3.0 M-1 s-1) and N-chloroacetyltyramine (k2 = 0.12 M-1 s-1) indicate that N-iodoacetyltyramine is more useful for labeling sulfhydryl-containing compounds to high specific activity with 125I. Conditions for preparation of carrier-free 125I-labeled N-iodoacetyl-3-monoiodotyramine in 50% yield based on starting iodide are described. The high degree of group specificity of N-iodoacetyl-3-monoiodotyramine reaction with sulfhydryl groups is demonstrated by the high reactivity toward sulfhydryl-containing bovine serum albumin and low reactivity toward N-ethylmaleimide-blocked bovine serum albumin and IgG. 125I-labeled N-iodoacetyl-3-monoiodotyramine was also used to prepare an 125I-labeled ACTH derivative that retains full biological activity, further demonstrating the selectivity toward reactions with sulfhydryl groups. 相似文献
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A micropropagation system was developed to test concepts for automation and microenvironment alteration. Amelanchier x grandiflora Rehd. Princess Diana (serviceberry) shoot cultures were grown in seven-liter polycarbonate containers. Through computer control, the apparatus intermittently applied culture medium to the plant material according to a selected schedule. Shoot growth in the programmable system was compared with four micropropagation treatments: gelled and liquid medium in baby food jars and gelled and non-cycling liquid medium in a seven-liter vessel. Plants cultured in continuous contact with liquid medium became increasingly vitrified. Significantly greater shoot number, shoot length, shoot weight, and culture weight occurred in the programmable system than in jars with gelled medium. The combination of liquid medium, 7-liter vessel, and intermittent contact with medium caused a significantly higher proliferation rate than any combination of jar/vessel and gelled/liquid medium tested. 相似文献
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Purification and characterization of a protein associated with peripheral-type benzodiazepine binding sites 总被引:4,自引:0,他引:4
L Antkiewicz-Michaluk A G Mukhin A Guidotti K E Krueger 《The Journal of biological chemistry》1988,263(33):17317-17321
The photoaffinity ligand [3H]PK 14105 was utilized to modify covalently peripheral-type benzodiazepine binding sites in rat adrenal mitochondrial preparations. The photolabeled membrane preparations were then solubilized in 1% digitonin and the detergent-soluble extracts subjected to fractionation by ion-exchange chromatography and reversed-phase high performance liquid chromatography. This scheme resulted in the purification of the putative binding site protein for PK 14105 which we have entitled PKBS. Purified preparations of PKBS exhibited a single band with a Mr of approximately 17,000 when analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by silver-staining or autoradiographic detection. Additional criteria examining the purity of PKBS preparations were provided by radioiodination with Bolton-Hunter reagent, amino acid analysis, gas-phase sequencing, and reversed-phase chromatography suggesting that this protein was purified to apparent homogeneity. These results demonstrate that a protein associated with peripheral-type benzodiazepine recognition sites has been isolated thus facilitating more direct studies on the structure of this receptor and on the role of these binding sites in mediating responses elicited by benzodiazepines acting at these sites. 相似文献