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21.
Yan Yongshan Qian Jin Xi Xiahui 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1985,70(5):529-535
Summary Two 30 g/ml BrdU-resistant sublines and two 60 g/ml BrdU-resistant sublines are induced from a Chinese hamster cell line Wg3h (HGPRT–) by one-step and two-step selections, respectively. By inoculating the cells into BrdU-free medium or by adding more BrdU into the culture medium for 26–27 h, it was found that the two BrdU-resistant sublines analysed have very clear sister chromatid differential (SCD) staining patterns. This indicates that some of the nuclear DNA of the BrdU-resistant cells incorporate with BrdU to reach a kinetic balance. Frequencies of sister chromatid exchange (SCE) of the resistant cells are twice to four times as high as those of the Wg3h cells, depending on which BrdU-resistant subline is analysed. The SCE frequencies of the resistant cells also increase with the BrdU concentration in the medium. Analysis of silver-stained nucleolar organizer regions (NORs) indicates that the NOR activity of three out of the four BrdU-resistant sublines is significantly suppressed, i.e., averages of the Ag-NOR number and number of the chromosomes bearing Ag-NORs per cell decrease significantly. The degree of suppression for different BrdU-resistant sublines may be quite different. The suppressed NOR activity of the resistant cells can gradually be restored when the cells are inoculated into BrdU-free medium, but the recovery speed is far lower than that of the Wg3h cells. The suppression of the NOR activity of the BrdU-resistant sublines should be due to BrdU toxicity. 相似文献
22.
Rats were treated with highly purified gossypol acetic acid at doses of 15 or 30 mg/kg day-1 for 6 weeks to produce an effect on spermatogenesis as shown by reduced sperm motility and increased sperm malformation rates. The treated rats did not differ from the controls in the body weight growth curves and reproductive organ weights. When stimulated with hCG, testicular blood flow was increased in the low dose group; the testosterone concentrations in peripheral and testicular venous blood were also increased to a greater extent than those of the control group. No difference was found between the high dose and control groups in testicular blood flow or testosterone concentrations. The morphology of the Leydig cells was apparently normal, although some degenerative changes in the germinal epithelium were observed in the high dose group. Therefore, there is no evidence in our experiment to show any anti-androgenic effect following 6-week treatment of gossypol in rats, even at the dose of 30 mg/kg day-1. 相似文献
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The crystal structure of plakalbumin, a proteolytically nicked form of ovalbumin, has been determined to a resolution of 2.8 A by the isomorphous replacement method and preliminary refinement. The structure closely resembles that of the cleaved form of alpha-1-proteinase inhibitor, with some important exceptions. The disposition of the new carboxyl chain terminus liberated by proteolysis is different with respect to the central beta-sheet A in the structures of these two molecules. In alpha-1-proteinase inhibitor, the new chain terminus inserts in beta-sheet A to add a middle strand to the sheet. In plakalbumin, this strand remains free near the site at which the cleavage occurs. A structural basis for this difference in behavior is proposed from the structures and sequences of these two molecules and other members of the serpin family. The structures and positions of the putative signal peptide of ovalbumin, the several post-translational modifications, and the relationship of the intron-exon patterns of plakalbumin and alpha-1-proteinase inhibitor to their protein structures are also described. 相似文献
26.
用组胺H_2受体拮抗剂(甲氰咪胍或呋喃硝胺)处理正常和亚致死量γ-射线照射小鼠,探讨正常体内造血和再生骨髓中造血重建与组胺受体的关系。发现非毒性剂量的甲氰咪胍对正常小鼠骨髓多能造血干细胞(CFU-s)无抑制作用,但可抑制小鼠体内粒单系祖细胞(CFU-GM)的生长和亚致死量照射后CFU-s产率的恢复。组胺可能与骨髓的再生有关,组胺H_2受体拮抗剂可抑制骨髓的造血重建。 相似文献
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Muscarinic acetylcholine receptor regulates phosphatidylcholine phospholipase D in canine brain 总被引:10,自引:0,他引:10
The hydrolytic activity of phosphatidylcholine phospholipase D in the synaptosomes from canine brain was examined using a radiochemical assay with 1,2-dipalmitoyl-sn-glycerol-3-phosphoryl[3H]choline as the exogenous substrate. The involvement of G protein(s) in regulation of this enzyme was demonstrated by a 2- to 3-fold stimulation of the basal activity (4.81 +/- 0.44 nmol choline released/mg protein/h) with guanosine 5'-(3-O-thiol)triphosphate (GTP gamma S), guanyl-5'-yl-(beta, gamma-methylene)diphosphonate, aluminum fluoride, or cholera toxin. The stimulation of phospholipase D hydrolytic activity by GTP gamma S was inhibited by 2 mM guanosine 5'-(2-O-thiol)diphosphate. GTP gamma S at the maximum stimulatory concentration (10 microM) had an additive effect on the maximum cholera toxin stimulation of phospholipase D activity. However, the reverse was not true, thus indicating the possibility that more than one G protein may be involved. Furthermore, cholinergic agonists, including acetylcholine, carbachol, and muscarine, were able to increase the phospholipase D hydrolytic activity at low but not maximally stimulatory concentrations of guanine nucleotide. These cholinergic stimulations were antagonized by atropine, a muscarinic blocker. In addition, O-tetradecanoylphorbol 13-acetate, a protein kinase C activator, was able to stimulate the hydrolytic activity of phospholipase D more than 300% in the presence of 0.2 microM GTP gamma S. However, in the absence of GTP gamma S, stimulation was less than 60%. Our results not only indicate that the receptor-G protein-regulated phospholipase D may be directly responsible for the rapid accumulation of choline and phosphatidic acid in the central nervous system but also reveal that muscarinic acetylcholine receptor-G protein-regulated phospholipase D is a novel signal transduction process coupling the neuronal muscarinic receptor to cellular responses. 相似文献
30.
The effect of attachment of a dimethylaminoethoxy or a dimethylaminopropoxy group at the 11 beta-position of estradiol (E2) on its relative binding affinity (RBA) to estrogen receptor (ER) and intrinsic biologic activity is described. The binding of 11 beta-[2-(N,N-dimethylamino) ethoxy]estra-1,3,5(10)-triene-3,17 beta-diol (4) and 11 beta-[3-(N,N- dimethylamino)propoxy]estra-1,3,5(10)-triene-3,17 beta-diol (5) to the ER from immature rat uterine tissue was measured relative to that of [3H]E2 by a competitive binding assay. It was found that the 11 beta-substituted E2 analogs have considerably lower RBA to ER than the corresponding parent compound. The intrinsic activity of compounds 4 and 5 were studied in terms of uterotrophic and antiuterotrophic activity. It was found that the uterotrophic activity of these compounds was drastically reduced compared with E2. However, no antiuterotrophic activity was observed in these compounds at dosages ranging from 1 to 100 micrograms/rat/d. 相似文献