Association between GRB2/Sos and insulin receptor substrate 1 is not sufficient for activation of extracellular signal-regulated kinases by interleukin-4: implications for Ras activation by insulin.

Insulin receptor substrate 1 (IRS-1) mediates the activation of a variety of signaling pathways by the insulin and insulin-like growth factor 1 receptors by serving as a docking protein for signaling molecules with SH2 domains. We and others have shown that in response to insulin stimulation IRS-1 binds GRB2/Sos and have proposed that this interaction is important in mediating Ras activation by the insulin receptor. Recently, it has been shown that the interleukin (IL)-4 receptor also phosphorylates IRS-1 and an IRS-1-related molecule, 4PS. Unlike insulin, however, IL-4 fails to activate Ras, extracellular signal-regulated kinases (ERKs), or mitogen-activated protein kinases. We have reconstituted the IL-4 receptor into an insulin-responsive L6 myoblast cell line and have shown that IRS-1 is tyrosine phosphorylated to similar degrees in response to insulin and IL-4 stimulation in this cell line. In agreement with previous findings, IL-4 failed to activate the ERKs in this cell line or to stimulate DNA synthesis, whereas the same responses were activated by insulin. Surprisingly, IL-4's failure to activate ERKs was not due to a failure to stimulate the association of tyrosine-phosphorylated IRS-1 with GRB2/Sos; the amounts of GRB2/Sos associated with IRS-1 were similar in insulin- and IL-4-stimulated cells. Moreover, the amounts of phosphatidylinositol 3-kinase activity associated with IRS-1 were similar in insulin- and IL-4-stimulated cells. In contrast to insulin, however, IL-4 failed to induce tyrosine phosphorylation of Shc or association of Shc with GRB2. Thus, ERK activation correlates with Shc tyrosine phosphorylation and formation of an Shc/GRB2 complex. Thus, ERK activation correlates with Shc tyrosine phosphorylation and formation of an Shc/GRB2 complex. Previous studies have indicated that activation of ERks in this cell line is dependent upon Ras since a dominant-negative Ras (Asn-17) blocks ERK activation by insulin. Our findings, taken in the context of previous work, suggest that binding of GRB2/Sos to Shc may be the predominant mechanism whereby insulin as well as cytokine receptors activate Ras.     

Yeast mRNA cap methyltransferase is a 50-kilodalton protein encoded by an essential gene.

RNA (guanine-7-)methyltransferase, the enzyme responsible for methylating the 5' cap structure of eukaryotic mRNA, was isolated from extracts of Saccharomyces cerevisiae. The yeast enzyme catalyzed methyl group transfer from S-adenosyl-L-methionine to the guanosine base of capped, unmethylated poly(A). Cap methylation was stimulated by low concentrations of salt and was inhibited by S-adenosyl-L-homocysteine, a presumptive product of the reaction, but not by S-adenosyl-D-homocysteine. The methyltransferase sedimented in a glycerol gradient as a single discrete component of 3.2S. A likely candidate for the gene encoding yeast cap methyltransferase was singled out on phylogenetic grounds. The ABD1 gene, located on yeast chromosome II, encodes a 436-amino-acid (50-kDa) polypeptide that displays regional similarity to the catalytic domain of the vaccinia virus cap methyltransferase. That the ABD1 gene product is indeed RNA (guanine-7-)methyltransferase was established by expressing the ABD1 protein in bacteria, purifying the protein to homogeneity, and characterizing the cap methyltransferase activity intrinsic to recombinant ABD1. The physical and biochemical properties of recombinant ABD1 methyltransferase were indistinguishable from those of the cap methyltransferase isolated and partially purified from whole-cell yeast extracts. Our finding that the ABD1 gene is required for yeast growth provides the first genetic evidence that a cap methyltransferase (and, by inference, the cap methyl group) plays an essential role in cellular function in vivo.     

Aggression and preputial gland of male mice affected by the presence of other males

The level of aggressiveness and the weight of preputial gland and testis in male mice (Mus musculus) were influenced by housing condition, especially by the presence of cohabitant males. In this study, the relation between aggressiveness and the preputial gland and testis weight was studied for various housing conditions. The mouse individually housed in a cage that was linked to another cage containing another male separated by wire net was more aggressive than isolated or paired mice. The preputial gland weight also showed the same tendency, suggesting that the odor from other males promotes pituitary-gonadal activity in males, and that long-term cohabitance inhibits it.     

短盖巨脂鲤卵巢发育组织学研究

通过对短盖巨脂鲤各个生长时期卵巢组织学研究以及成熟卵超微结构观察,获得短盖巨脂鲤生长发育过程中卵巢发育规律;同时对卵母细胞核仁排出物与核质关系及在卵黄形成中的作用等问题作了初步探讨;并根据卵巢的卵母细胞组成确定了其产卵类型。     

In vitro propagation of Clerodendrum colebrookianum Walp., a potential natural anti-hypertension medicinal plant

A rapid clonal propagation system for Clerodendrum colebrookianum Walp. (Verbenaceae), a anti-hypertension folk medicinal shrub has been developed. A range of cytokinins has been investigated for multiple shoot induction with shoot apex, axillary shoot, leaf, petiole and root explants. Optimum shoot induction occurred with axillary buds using 6-benzyladenine where an average of 21 shoots were produced per explant in 6 weeks. Subculturing the newly produced shoots, by separating into groups of five shoots, produced an average of 43 new shoots per culture within 4 weeks. In vitro rooting and weaning of over 200 plantlets was completely successful. Cytological studies revealed no visible abnormalities in chromosome number.Abbreviations 2iP 2-isopentenyladenine - BA 6-benzyladenine - LSD Least Significant Difference - NAA 1-naphthaleneacetic acid - TDZ thidiazuron - WPM Woody Plant Medium (Lloyd & McCown 1980) basal medium     

Alcohol and aldehyde dehydrogenase genotypes and drinking behavior of Chinese living in Shanghai

Alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH), the principal enzymes responsible for oxidative metabolism of ethanol, exist in multiple, genetically determined molecular forms. Widely different kinetic properties in some of these isozymes account for the individual differences in alcohol sensitivity. In this study we used the polymerase chain reaction/restriction fragment length polymorphism method to determine the genotypes of the ADH2 and ALDH2 loci of alcoholic and nonalcoholic Chinese living in Shanghai. We also investigated the subjects' drinking patterns by means of semistructured interviews. The alcoholics had significantly lower frequencies of the ADH2² and ALDH2² alleles than did the nonalcoholics, suggesting the inhibitory effects of these alleles for the development of alcoholism. In the nonalcoholic subjects, ADH2² had little, if any, effect, despite the significant effect of the ALDH2² allele in decreasing the alcohol consumption of the individual. Taken together, these results fit the proposed hypothesis for the development of alcoholism, i.e., drinking behavior is greatly influenced by the individual's gentoypes of alcohol-metabolizing enzymes, and the risk of becoming alcoholic is proportionate with the ethanol consumption of the individual.     

甾体激素受体超家族的基因调控机制

甾体激素受体超家族是一类基因反式作用因子,对RNA聚合酶Ⅱ转录的某些蛋白质基因和RNA聚合酶Ⅰ转录的核糖体RNA基因均有正或负的转录调节作用.超家族对RNA polⅡ转录的基因调控的机理包括受体激活,相关蛋白解离,磷酸化,同源/异源二聚化,核转位,与正/负激素应答元件及相应转录蛋白作用,最终激活或抑制特异靶基因的转录.甾体激素对RNA polⅠ转录的基因的调节作用以及超家族中的经典受体和孤儿受体非配合的激活机制是目前研究的热点.     

Formation of bioorganic compounds in aqueous solution induced by flames

Flames of flammable gases, when blown against a surface of an aqueous solution of organic compounds, were found to induce oxidation as well as other reactions in the solution. This reaction would be regarded as a new model for formation of bioorganic molecules in the primitive hydrosphere exposed to some radical-containing atmosphere.