A candidate spermatogenesis gene on the mouse Y chromosome is homologous to ubiquitin-activating enzyme E1.

The human X-linked gene A1S9 complements a temperature-sensitive cell-cycle mutation in mouse L cells, and encodes the ubiquitin-activating enzyme E1. The gene has been reported to escape X-chromosome inactivation, but there is some conflicting evidence. We have isolated part of the mouse A1s9 gene, mapped it to the proximal portion of the X chromosome and shown that it undergoes normal X-inactivation. We also detected two copies of the gene on the short arm of the mouse Y chromosome (A1s9Y-1 and A1s9Y-2). The functional A1s9Y gene (A1s9Y-1) is expressed in testis and is lost in the deletion mutant Sxrb. Therefore A1s9Y-1 is a candidate for the spermatogenesis gene, Spy, which maps to this region. A1s9X is similar to the Zfx gene in undergoing X-inactivation, yet having homologous sequences on the short arm of the Y chromosome, which are expressed in the testis. These Y-linked genes may form part of a coregulated group of genes which function during spermatogenesis.     

Homology of a candidate spermatogenic gene from the mouse Y chromosome to the ubiquitin-activating enzyme E1.

The Sxr (sex-reversed) region, a fragment of the Y chromosome short arm, can cause chromosomally female XXSxr or XSxrO mice to develop as sterile males. The original Sxr region, termed Sxra, encodes: Tdy, the primary sex-determining gene; Hya, the controlling or structural locus for the minor transplantation antigen H-Y; gene(s) controlling the expression of the serologically detected male antigen (SDMA); Spy, a gene(s) required for the survival and proliferation of A spermatogonia during spermatogenesis; Zfy-1/Zfy-2, zinc-finger-containing genes of unknown function; and Sry, which is probably identical to Tdy. A deletion variant of Sxra, termed Sxrb, which lacks Hya, SDMA expression, Spy and some Zfy-2 sequences, makes positional cloning of these genes possible. We report here the isolation of a new testis-specific gene, Sby, mapping to the DNA deleted from the Sxrb region (the delta Sxrb interval). Sby has extensive homology to the X-linked human ubiquitin-activating enzyme E1. The critical role of this enzyme in nuclear DNA replication together with the testis-specific expression of Sby suggests Sby as a candidate for the spermatogenic gene Spy.     

贵州省藓类植物新记录种——无肋树平藓(Homaliodendron pulchrum)

无肋树平藓(Homaliodendron pulchrum L.Y.Pei&Y.Jia)是2011年报道的新种,先前记载于中国四川、湖南和广西.发现了该种在中国贵州的新记录,并详细描述了采自贵州茂兰国家自然保护区该种的形态特征,绘制了墨线图,编制了贵州省境内树平藓属的分种检索表.     

植物细胞膜H -ATPase对必需矿质养分的适应性

植物细胞膜H -ATPase是初级转运蛋白,在各种离子和代谢产物的跨膜运输中起着重要的作用;介绍了植物细胞H -ATPase的结构、生化特性、生理功能与调控机制;重点综述了细胞膜H -ATPase的活性及其蛋白数量与基因表达对植物必需矿质养分的适应性.     

植物细胞膜H+ -ATPase对必需矿质养分的适应性

植物细胞膜H -ATPase是初级转运蛋白,在各种离子和代谢产物的跨膜运输中起着重要的作用;介绍了植物细胞H -ATPase的结构、生化特性、生理功能与调控机制;重点综述了细胞膜H -ATPase的活性及其蛋白数量与基因表达对植物必需矿质养分的适应性。     

植物细胞膜H+-ATPase对环境因子和逆境胁迫的适应

植物细胞膜H -ATPase是初级转运蛋白,它在养分离子跨膜运输、胞内pH调节、细胞伸长生长、气孔开闭,以及植物适应所处的环境与发育过程等生命活动中起着重要的作用.综述了植物细胞膜H -ATPase在酶活性、基因表达水平以及蛋白水平等方面对不同环境因子及逆境胁迫的适应性;指出分离鉴定、信号传导H -ATPase等将是进一步的研究方向.     

Subtractive and divisive adaptation in the human visual system.

Sensory systems can adapt to the conditions imposed on them. In the visual system, adapting to a pattern increases the threshold of the ability to see that pattern, and reduces the perceived contrast of the pattern above threshold. Most neurons of the striate cortex reduce their responsiveness after being stimulated for some time by a high-contrast pattern. Such an effect may lie behind these psychophysical adaptation phenomena. These adaptation effects have been reported to be confined to patterns of similar orientation, which is understandable in that the visual neurons that adapt are only excited by a small range of orientations. Neurophysiological evidence suggests that neurons with different orientation preferences have inhibitory interconnections. It is therefore of interest to explore the possible effects of these connections on perception. Here we show that adapting to a horizontal pattern can reduce the perceived contrast of a vertical test pattern more than a horizontal test pattern. These 'cross-orientation' effects are modelled by a division-like process, whereas the more normal 'similar-orientation' effects are modelled by a subtractive process.     

Protein deprivation causes reversible impariment of mucosal immune response to cholera toxoid/toxin in rat gut

Scretory antibodies may be the major defence against mucosal infections, especially those due to viruses and non-invasive pathogens such as Vibrio cholerae and toxinogenic Escherichia coli. The high incidence of mucosal infections in malnourished protein-deficient children may result from defective antibody production, but evidence for this is conflicting. We report here that protein deficiency markedly impairs the mucosal immune reponse to cholera toxiod/toxin (CT), a protein antigen, in rats and that this impairment is rapidly reversed by refeeding.