Structure of the L1 protuberance in the ribosome

The L1 protuberance of the 50S ribosomal subunit is implicated in the release/disposal of deacylated tRNA from the E site. The apparent mobility of this ribosomal region has thus far prevented an accurate determination of its three-dimensional structure within either the 50S subunit or the 70S ribosome. Here we report the crystal structure at 2.65 A resolution of ribosomal protein L1 from Sulfolobus acidocaldarius in complex with a specific 55-nucleotide fragment of 23S rRNA from Thermus thermophilus. This structure fills a major gap in current models of the 50S ribosomal subunit. The conformations of L1 and of the rRNA fragment differ dramatically from those within the crystallographic model of the T. thermophilus 70S ribosome. Incorporation of the L1-rRNA complex into the structural models of the T. thermophilus 70S ribosome and the Deinococcus radiodurans 50S subunit gives a reliable representation of most of the L1 protuberance within the ribosome.     

Rous sarcoma virus mutant dlPA105 induces different transformed phenotypes in quail embryonic fibroblasts and neuroretina cells.

dlPA105 is a spontaneous variant of Rous sarcoma virus, subgroup E, which carries a deletion in the N-terminal portion of the v-src gene coding sequence. This virus was isolated on the basis of its ability to induce proliferation of quiescent quail neuroretina cells. The altered v-src gene encodes a phosphoprotein of 45,000 daltons which possesses tyrosine kinase activity. DNA sequencing of the mutant v-src gene has shown that deletion extends from amino acid 33 to 126 of wild-type p60v-src. We investigated the tumorigenic and transforming properties of this mutant virus. dlPA105 induced fibrosarcomas in quails with an incidence identical to that induced by wild-type virus. Quail neuroretina cells infected with the mutant virus were morphologically transformed and formed colonies in soft agar. In contrast, dlPA105 induced only limited morphological alterations in quail fibroblasts and was defective in promoting anchorage-independent growth of these cells. Synthesis and tyrosine kinase activity of the mutant p45v-src were similar in both cell types. These data indicate that the portion of the v-src protein deleted in p45v-src is dispensable for the mitogenic and tumorigenic properties of wild-type p60v-src, whereas it is required for in vitro transformation of fibroblasts. The ability of dlPA105 to induce different transformation phenotypes in quail fibroblasts and quail neuroretina cells is a property unique to this Rous sarcoma virus mutant and provides evidence for the existence of cell-type-specific response to v-src proteins.     

长爪沙鼠肝细胞体外分离培养体系的建立

目的建立长爪沙鼠原代肝细胞分离培养体系。方法以雄性长爪沙鼠为供体,采用组织消化法和Seglen两步灌流法分离肝细胞,以台盼蓝染色检测细胞得率和活率,过碘酸-希夫氏反应(PAS)鉴定肝细胞,倒置显微镜观察肝细胞形态变化,并使用含有多种细胞因子的培养基维持培养。结果组织消化法和Seglen两步灌流法平均每只长爪沙鼠可分别获得肝细胞(1.33±0.34)×107个、(3.97±1.15)×107个,细胞活率分别为(29.4±6.05)%、(80.3±4.56)%,这两种方法在细胞得率及活率方面存在显著差异。肝细胞内因有大量的糖原颗粒,经PAS染色后被染成红色。结果表明肝细胞在贴壁后72 h内,肝细胞形态发生显著变化。结论采用胶原酶经肝门静脉灌流分离肝细胞是一种高效获得肝细胞的方法。各种细胞因子有利于维持肝细胞在体外的生长分化,长爪沙鼠原代肝细胞分离培养体系的建立将为肝脏相关疾病研究和防治药物的开发提供技术支持。     

中国三种常见蒿属植物潜在地理分布及其主导气候因子

裂叶蒿(Artemisia tanacetifolia)、大籽蒿(Artemisia sieversiana)和艾(Artemisia argyi)是我国常见的蒿属(Artemisia)植物,其分布区域遍布全国.本文利用MaxEnt模型预测3种蒿属植物在当前气候条件以及未来两种气候情景下的潜在分布区.采用受试者工作特征...     

The early life history of two sympatric New Zealand octopuses: eggs and paralarvae of Octopus huttoni and Pinnoctopus cordiformis

This study combined morphological and morphometric information on egg clutches, egg capsules and paralarvae of two sympatric coastal octopuses from New Zealand waters, Octopus huttoni and Pinnoctopus cordiformis, to provide species-specific traits to identify their early life stages obtained from field surveys. Eggs of O. huttoni (2.5 mm length; 1 mm width) were entwined with one another forming strings that ranged from 11 to 25.8 mm in length. Eggs of P. cordiformis (6.4 mm length; 1.5 mm width) were significantly bigger than those of O. huttoni and were grouped in small clusters of about seven eggs. Paralarvae O. huttoni and P. cordiformis differed in hatching size (1.4 mm versus 3.1 mm mantle length), number of suckers per arm (four versus eight), number of lamellae per outer demibranch (five versus ten) and arrangements of chromatophores in the body surface (29 to 59 versus 91 to 179), respectively. The morphological traits described in hatchlings from the laboratory allowed comparisons with field-collected paralarvae, suggesting that such characters were reliable species-specific patterns to enable a consistent differentiation between the early life stages of these two sympatric species, even in the absence of the brooding female.