用马来酰亚胺自旋标记研究库存血红细胞膜蛋白质构象

用两种马来酰亚胺自旋标记物—马来酰亚胺Ⅰ和马来酰亚胺Ⅴ研究了红细胞膜蛋白质构象及巯基结合位点性质在ACD-B方库存血保存期间的动态变化。结果发现,在35天的血液保存期间,马来酰亚胺Ⅰ所标记红细胞膜的S/w值很快下降到一低水平,而马来酰亚胺Ⅴ所标记红细胞膜的旋转相关时间则呈现迅速下降后缓慢升高的双相性变化。作者结合膜蛋白构象及其周围微观环境进行了讨论。     

人酸性成纤维细胞生长因子神经营养作用的初步研究

本实验研究了人酸性成纤维细胞生长因子(haFGF)的体外神经营养作用。结果表明,haFGF在体外能明显促进鸡胚(E-8)脊髓组织神经突起的生长,并能明显改变新生大鼠脑星形胶质细胞的形态,使扁平、多角形紧密联接的细胞转化为具有纤维样突起的胶质细胞,同时对胶质细胞DNA合成也有一定促进作用。实验还证明,haFGF可增加体外培养新生大鼠海马神经元的存活,且大大增加神经元胞体体积及突起长度。     

Catalytic properties of chloroplast F1-ATPase modified at catalytic or noncatalytic sites by 2-azido adenine nucleotides

When heat-activated F1-ATPase from chloroplasts was repeatedly exposed to Mg2+ and 2-azido-ATP, followed by separation from medium nucleotides and photolysis, a total of two sites per enzyme, both catalytic and noncatalytic, were labeled. In a coupled assay with pyruvate kinase about half the activity was lost when one site per enzyme was modified. However, increased modification resulted in no further loss of activity. In contrast, methanol-sulfite activation of the enzyme showed a loss of most of the catalytic capacity when one site per enzyme was modified. Predominant labeling of either one catalytic or one noncatalytic site caused a loss of most of the activity in either assay. An indication that the enzyme modified at one site retained some catalytic activity was verified by measurement of the [18O]Pi species formed when [gamma-18O]ATP was hydrolyzed by partially derivatized enzyme. With either catalytic or noncatalytic site modification, the distributions of [18O]Pi species formed showed that the modified enzyme had different catalytic characteristics. An interpretation is that with modification by azido nucleotides at either catalytic or noncatalytic sites, capacity for rapid catalysis is largely lost but the remaining sites retain weak modified catalytic properties.     

Cross-reactive cellular and humoral immunity to carcinogen-induced chicken fibrosarcomas. I. Protective cross-immunity between transplantable tumor lines

Dimethylbenz[a]anthracene (DMBA)-induced transplantable fibrosarcomas in B2 homozygous chickens (SC line) grow progressively in normal chickens, but are rejected by chickens immunized previously with irradiated tumor cells and Corynebacterium parvum. Tumor-immune chickens resist challenge by the immunizing tumor lines as well as by some, but not all, fibrosarcoma lines. The pattern of cross-reactivity between four DMBA-induced transplantable tumor lines was examined in detail. Ability to reject a tumor challenge correlated very well (p less than 0.001) with the presence of delayed-type hypersensitivity (DTH) to that tumor. Immunization with one of two of the DMBA-induced lines tested also caused rejection of transplantable tumors developed from methylcholanthrene-induced and benzo(a)pyrene-induced primary fibrosarcomas. Although immunization with tumor caused DTH to chicken embryo fibroblasts (CEF), immunization with CEF failed to cause protective immunity or DTH to tumors. Presence of protective immunity, where tested, also correlated with the ability of spleen cells from immune donors to inhibit tumor growth in Winn tests. Humoral immunity exhibited even greater cross-reactivity than did cellular immunity. Distinct patterns of cross-reactivity were nevertheless observed with respect to the serum antibodies as detected in ELISA. Two of these patterns were also observed in several sera from primary tumor-bearing chickens, both including reactivity with CEF. Such reactivity was absent from normal chicken sera.     

In vivo and in vitro studies on the segregation of autonomic and sensory cell lineages

Analysis of interspecific quail/chick chimaeras (made by grafting neural primordium from one species to the other) has demonstrated that the neural crest cell population, which gives rises to a large number of derivatives, including the great majority of peripheral ganglion cells, is pluripotential. When peripheral ganglia themselves are transplanted, it can be shown that many of the developmental potentialities of the parent structure are retained, their ultimate expression depending on the microenvironment in which they become located. One of the conclusions obtained from these in vivo studies, that sensory ganglia contain dormant precursors with autonomic potentialities, has been confirmed and extended by the results of in vitro investigations with dissociated 9- to 15-day embryonic quail dorsal root ganglia. Undetectable during normal embryonic development, adrenergic properties (tyrosine hydroxylase immunoreactivity, radio- and cytochemically demonstrable catecholamine production) develop in a population of small, multipolar cells after four days in culture. This differentiation is strongly dependent on the presence of chick embryo extract in the medium. Unlike the postmitotic primary sensory neurons of the ganglia, many of the adrenergic cells were found to incorporate 3H-thymidine during the culture period. These results support the contention that the latent autonomic percursors belong to the non-neuronal compartment of sensory ganglia.     

Regulation of methyl group metabolism in lactating ewes

The effect of lactation on a number of enzymes involved in transmethylation reactions and the secretion of major methyl compounds into milk have been examined in sheep. The activities of hepatic phospholipid methyltransferase and 5-methyltetrahydrofolate-homocysteine methyltransferase were significantly higher in lactating ewes, compared with those in non-lactating ewes, while the activity of both hepatic and pancreatic glycine methyltransferase was significantly lower in the lactating state. No differences were observed in the activities of hepatic guanidoacetate methyltransferase, betaine-homocysteine methyltransferase and cystathionine beta-synthase on lactation. These results suggest that the extra demand for methyl groups for the secretion of methyl compounds in the milk is facilitated by enhancing the rate of de novo methyl group synthesis and lowering the rate of physiologically nonessential methylation.     

沙田柚染色体组型及Giemsa带型分析

本文以沙田柚为材料,对其染色体组型及带型进行了观察分析。组型分析:染色体数目2n=18,根据染色体的相对长度分成大小染色体两种类型,前者包括1、2、3、4和5对,后者为6、7、8和9对,根据臂比,9对染色体能够被分成中部着丝点和近中着丝点染色体两种类型。即第5、7,9对为亚中部着丝点,其余为中部着丝点,第6对染色体上有随体;Giemsa带型:除第二对染色体只显中间带外,其余都显着丝点带,并在3、4、8对染色体短臂上和2、3、1对染色体长臂上均显端带,第2、3,6对同源染色体之间的C带显示杂合性。