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71.
本文用放射免疫测定法(RIA),测定了200~290例中国四川成都市郊30~73岁的正常成年男性血清睾酮(T)促黄体激素(LH).卵泡刺激素(FSH)及泌乳激素(PRL)的水平及其分布,进行了不同年龄水平差异显著性的观察,见到睾酮与泌乳激素水平无显著差异,促黄体激素及卵泡刺激素水平,随年龄之增加而升高,差异有显著性,并测得它们在血清中水平的分布:LH、FSH及PRL均为对数正态公布,T既非正态又非对数正态,但其频率分布较对称,接近正态分布。 相似文献
72.
Direct evidence for the existence of nominal antigen binding sites on T cell surface Ti alpha-beta heterodimers of MHC-restricted T cell clones 总被引:15,自引:0,他引:15
R F Siliciano T J Hemesath J C Pratt R Z Dintzis H M Dintzis O Acuto H S Shin E L Reinherz 《Cell》1986,47(2):161-171
The binding of nominal antigen to Ti alpha-beta heterodimers on MHC-restricted human T cell clones specific for fluorescein-5-isothiocyanate (FL) was detected by flow cytometry and affinity chromatography. The FL-Ti interaction is of physiologic significance, since T cell activation is induced by cross-linked arrays of FL in the absence of the specific MHC recognition. High antigen valence is required to achieve stable binding to cells and subsequent activation, which is consistent with estimated Ti-FL association constants of less than 3 X 10(5) l/mol. In addition to providing direct evidence that the Ti alpha-beta heterodimer is the receptor for antigen, these data suggest that nominal antigen binding sites exist on the Ti molecules of at least some MHC-restricted clones. 相似文献
73.
74.
A possible phagocytic role for folliculo-stellate cells of anterior pituitary following estrogen withdrawal from primed male rats 总被引:3,自引:0,他引:3
Summary Ultrastructural changes suggesting a phagocytic role for the nongranular folliculo-stellate cells of the anterior pituitary are investigated in estrogen-primed male rats after withdrawal of estrogen. Morphological changes in mammotropes following the removal of a subcutaneous estradiol-containing Silastic implant include the formation of intracellular lipid bodies. These lipid bodies appear to be associated with enhanced estrogen-dependent prolactin secretion in mammotropes. Seven and 24 h after estrogen withdrawal intracellular lipid within mammotropes seems to be released into the intercellular space. Seventy-two h after estrogen withdrawal, lipid droplets are almost entirely cleared from mammotropes while folliculo-stellate cells become packed with lipid globules. Folliculo-stellate cells also undergo dramatic hypertrophy 7 and 24 h after the removal of E2-containing implants. Extensive intercellular junctions including zonulae adhaerentes, desmosomes, and putative gap junctions are formed. Intercellular junctions delineate extravascular channels into which numerous microvilli project. Folliculo-stellate cells appear capable of accumulating many lipid droplets, presumably related to mammotrope metabolism. What appear to be large secondary lysosomes as well as the lipid droplets are observed within folliculostellate cells; lipid, therefore, may be degraded through a lysosomal pathway in folliculo-stellate cells. 相似文献
75.
宁夏同心中新世铲齿象化石 总被引:8,自引:6,他引:2
本文记述了宁夏同心地区中中新世哺乳动物群中铲齿象化石——同心铲齿象 (Platybelodon tongxinensis) (原定为同心嵌齿象 (Gomphotherium tongxinensis). 通过与国内外已现的有关铲齿象对比,确认其与国内已发现的葛氏种关系最近,可能属同一枝系.同心种与葛氏种相比,是性质相对原始分布层位较低的我国第二个铲齿象种.文章初步讨论了其 M_3 的某些变异性状.并结合现有的其它标本初步阐述了铲齿象类下门齿的两种结构类型,原始型的同心层状结构和衍生型的齿质柱状结构.建议根据这两种结构仍将铲齿象类划分为 Platybelodontinae 和 Amebelodontinae. 相似文献
76.
S S Lee J H Ye D P Jones D B McCormick 《Biochemical and biophysical research communications》1983,117(3):788-793
A substantial decrease in liver peroxisomal catalase was found during riboflavin deficiency in rats. This decrease is greater than that found among other hemoproteins and seems to follow decrease in flavin-dependent peroxisomal oxidases. This is not due to a general depression of peroxisomal enzymes, since Cu-dependent urate oxidase activity was not changed. Furthermore, the level of catalase activity as well as flavin-dependent oxidases was restored by riboflavin repletion. These results suggest that hydrogen peroxide, the substrate for catalase produced by several flavoprotein oxidases, induces catalase in mammals as has been indicated for certain bacteria. 相似文献
77.
Recessive lethal mutations in the T/t-complex of the mouse characteristically show defective genetic complementation, even when they affect very different stages of embryogenesis and are known to be nonallelic. To address the question of their genetic or functional relationship, we have applied the cis-trans test, using several well defined recombinant t-chromosomes that carry two or more lethal mutations, and others that are devoid of specific lethals. We show here that the defective complementation that occurs between different t-lethals is a specific result of the trans configuration; thus these genes, which may map as much as 15 cM apart, constitute a functional unit. Some speculations are presented to interpret this enigma in terms of DNA plasticity. 相似文献
78.
Structural correlates of cellular tumorigenicity and anchorage independence in transformed fibroblasts 总被引:1,自引:0,他引:1
The ability on nonhematopoietic cells to proliferate in vitro without attachment to a solid surface (anchorage independence) is known to be highly correlated with their ability to form tumors in nude mice. Transformed cells in vitro frequently also show less organization of the intracellular actin-containing microfilament bundles and less cell-surface fibronectin compared to normal cells. We have examined whether the loss of the anchorage requirement for growth is related to either of these structural changes in the cellular cytoskeleton. Our approach was to select a series of subclones from a nontransformed Syrian hamster fibroblast line, NIL8, for the acquisition of either anchorage independence in vitro or tumorigenicity in nude mice. These subclones were then examined for concomitant changes in the cytoskeletal structures. We found that anchorage independence, decreased actin cable organization, and tumorigenicity in nude mice were coordinately induced in both the in vitro- and in vivo-selected subclones, whereas the loss of fibronectin was not consistently coinduced with these three markers. These results suggest that the transformation-associated decrease in actin cable organization in this type of cell enhances the ability to grow without anchorage in vitro and to form tumors in vivo. 相似文献
79.
80.
Y A Shin 《Biopolymers》1973,12(11):2459-2475
Changes in the conformation of poly(G), poly(C), poly(U), and poly(I) in the presence of divalent metal ions Mg2+, Ca2+, Mn2+, Co2+, Ni2+, Cu2+, Cd2+, and Zn2+ have been measured by means of ORD and u.v. spectra. Mg2+ and Ca2+ ions stabilize helical structures of all the polynucleotides very effectively at concentrations several orders of magnitude lower than the effective concentration of Na+ion. Cu2+ and Cd2+ destabilize the helical structure of polynucleotides to form random coils. Zn2+, Ni2+, Co2+, and Mn2+ions do not behave in such a clear-cut manner: they selectively stabilize some ordered structures, while destabilizing others, depending on the ligand strength of the nucleotide base as well as the preferred conformation of that polynucleotide. 相似文献