A salmonella protein antagonizes Rac-1 and Cdc42 to mediate host-cell recovery after bacterial invasion.

An essential feature of the bacterial pathogen Salmonella spp. is its ability to enter cells that are normally non-phagocytic, such as those of the intestinal epithelium. The bacterium achieves entry by delivering effector proteins into the host-cell cytosol by means of a specialized protein-secretion system (termed type III), which causes reorganization of the cell's actin cytoskeleton and ruffling of its membrane. One of the bacterial effectors that stimulates these cellular responses is SopE, which acts as a guanyl-nucleotide-exchange factor on Rho GTPase proteins such as Cdc42 and Rac. As the actin-cytoskeleton reorganization induced by Salmonella is reversible and short-lived, infected cells regain their normal architecture after bacterial internalization. We show here that the S. Typhimurium effector protein SptP, which is delivered to the host-cell cytosol by the type-III secretion system, is directly responsible for the reversal of the actin cytoskeletal changes induced by the bacterium. SptP exerts this function by acting as a GTPase-activating protein (GAP) for Rac-1 and Cdc42.     

鸡油菌,喇叭菌和钉菇的25SrDNA部分序列及其系统学关系

从分子系统学角度出发,对鸡油菌属（Ｃａｎｔｈａｒｅｌｕｓ）、喇叭菌属（Ｃｒａｔｅｒｅｌｕｓ）和钉菇属（Ｇｏｍｐｈｕｓ）的模式种的２５ＳｒＤＮＡ部分序列进行了测定,并与另外１０目的１３个担子菌和１个接合菌的２５ＳｒＤＮＡ序列进行比较分析,以接合菌总状毛霉（Ｍｕｃｏｒｒａｃｅｍｏｓｕｓ）为外类群构建出这些担子菌的部分２５ＳｒＤＮＡ序列的系统树图,探讨它们３属之间及它们与其他担子菌的关系及其系统学上的意义．认为鸡油菌与同科的喇叭菌关系最为亲近,而钉菇属看来也应该归入鸡油菌目Ｃａｎｔｈａｒｅｌａｌｅｓ中,这与传统方法的分析结果较为一致;虽然鸡油菌类真菌又与各肉质的伞菌类群的关系相对较密切,但它应该有其相对独立的进化路线,将这一类真菌上升至目一级的分类阶元是比较恰当的;但钉菇目Ｇｏｍｐｈａｌｅｓ上升到目的水平是否恰当则有待更多的数据去证明．     

昆虫精子获能与顶体反应的研究

综述了近年来国内外在昆虫精子获能与顶体反应方面的研究概况,并系统地简述了昆虫精子顶体复合体基本结构,以及目前用于动物精子获能与顶体反应方面先进的方法和技术,同时对昆虫受精机理的研究进行了展望     

鼻咽癌细胞核DNA倍体和颈淋巴结转移与预？…

目的：为加深对影响鼻咽癌（ＮＰＣ）预后因素的认识。方法：采用流式细胞仪（ＦＣＭ）对４４例ＮＰＣ癌细胞核ＤＮＡ进行检测,发现二倍本肿瘤（ＤＴ）１０例,近二倍体肿瘤（ｎＤＴ）１７例,非整倍体肿瘤（ＡＴ）１７例;４４例中,颈淋巴转移３５例,经放疗后３年追踪观察,鼻咽局部复发和（或）远处转移２４例。将不同ＤＮＡ倍体的ＮＰＣ、颈淋巴结转移和预后进行相关性分析。结果：ＮＰＣ ＤＮＡ倍体与转移之颈淋巴结及其大小     

Two kinds of Carlin-type gold deposite in southwestern Guizhou, China

Based on the organic geochemical studies on two typical Carlin-type deposits in southwestern Guizhou, as well as the comparison between the two deposits in terms of geological background, igneous rock, paleo-oilfield, lithofacies and paleogeographical and geochemical features, two kinds of Carlin-type deposit were proposed: Lannigou Type and Getang Type. The former includes Lannigou, Banqi and Yata gold deposits. These deposits are hosted by turbidite, geographically situated in the southwest of the mineralized district, and related genetically to paleo-oilfields. The latter includes Getang, Zimudang and Dachang gold (mercury and thallium) deposits, situated geographically in the northwest of the mineralized district where Emeishan basalt commonly occurs. These deposits are associated with reduction of coaly organic matter.     

Salt glands inGlycine soja L. China

A scanning electron microscope observation is carried out on Glycine soja L., which grows around the estuary of the Yellow River, in Kenli County, Shandong Province. It is first discovered that there are salt glands, in the shape of balls, on the surface of the stems and leaves of G. soja L., and distributed at the intercellular layer. With a handle at the base, the salt glands are not equal in size, and show a layer-upon-layer structure. They have a diameter of 21.6 μm, a handle length of 1.2 μm, their secretory pore's diameter is 5.6 μm. There are two ways to secrete salt ions: younger glands secrete salt ions through the secretory pore, and mature glands by breaking themselves.     

Synchrotron radiation photoemission study on growth of gadolinium film over Ni(110) surface

The growth of Gd film on Ni (110) surface was studied by synchrotron radiation photoemission spectroscopy and XPS techniques. It is revealed that in the coverage range of 0–0.22 nm Gd4f core level showed a single-peak structure, therefore Gd film grows over Ni(110) in the layer-by-layer mode. However, when Gd coverage was larger than 0.22 nm the Gd4f peak turned gradually into double-peak and a double-peak structure with 2.3 eV separation was formed at 1.51 nm, meanwhile similar phenomenon was observed in the Gd4d XPS spectra. It is suggested that the double-peak structure of Gd4f was derived from the growth of Gd film in cluster mode and the Gd atomic clusters may exhibit different electronic states from Gd metal owing to their special structures. The Gd4f double-peak e-volved into a single-peak on annealing at 600 K, implying that Gd clusters are thermodynamically unstable.     

二阶非线性微分系统解的振动比较定理

利用３个微分恒等式及线性泛函ｔｒ建立了二阶非线性微分系统（Ｐ（ｔ）Ｙ′（ｔ））′＋Ｑ（ｔ）Ｙ（ｔ）＋Ｆ（ｔ,Ｙ（ｔ）,Ｙ′（ｔ））＝０解的振动比较定理．     

Bid-deficient mice are resistant to Fas-induced hepatocellular apoptosis.

The protein Bid is a participant in the pathway that leads to cell death (apoptosis), mediating the release of cytochrome c from mitochondria in response to signals from 'death' receptors known as TNFR1/Fas on the cell surface. It is a member of the proapoptotic Bcd-2 family and is activated as a result of its cleavage by caspase 8, one of a family of proteolytic cell-death proteins. To investigate the role of Bid in vivo, we have generated mice deficient for Bid. We find that when these mice are injected with an antibody directed against Fas, they nearly all survive, whereas wild-type mice die from hepatocellular apoptosis and haemorrhagic necrosis. About half of the Bid-deficient animals had no apparent liver injury and showed no evidence of activation of the effector caspases 3 and 7, although the initiator caspase 8 had been activated. Other Bid-deficient mice survived with only moderate damage: all three caspases (8 and 37) were activated but their cell nuclei were intact and no mitochondrial cytochrome c was released. We also investigated the effects of Bid deficiency in cultured cells treated with anti-Fas antibody (hepatocytes and thymocytes) or with TNFalpha. (fibroblasts). In these Bid-/- cells, mitochondrial dysfunction was delayed, cytochrome c was not released, effector caspase activity was reduced and the cleavage of apoptosis substrates was altered. This loss-of-function model indicates that Bid is a critical substrate in vivo for signalling by death-receptor agonists, which mediates a mitochondrial amplification loop that is essential for the apoptosis of selected cells.     

Dynamic measurement of myosin light-chain-domain tilt and twist in muscle contraction.

A new method is described for measuring motions of protein domains in their native environment on the physiological timescale. Pairs of cysteines are introduced into the domain at sites chosen from its static structure and are crosslinked by a bifunctional rhodamine. Domain orientation in a reconstituted macromolecular complex is determined by combining fluorescence polarization data from a small number of such labelled cysteine pairs. This approach bridges the gap between in vitro studies of protein structure and cellular studies of protein function and is used here to measure the tilt and twist of the myosin light-chain domain with respect to actin filaments in single muscle cells. The results reveal the structural basis for the lever-arm action of the light-chain domain of the myosin motor during force generation in muscle.