Modulation of the epidermal growth factor receptor by brain-derived growth factor in Swiss mouse 3T3 cells

Incubation of Swiss mouse 3T3 cells at 37 degrees C with bovine brain-derived growth factor (BDGF) decrease the cell surface 125I-EGF binding activity of these cells by 70-80%. This down-modulation of the EGF receptor by BDGF was time, temperature, and dose dependent. Scatchard plot analysis indicated that BDGF binding led to a selective decrease in the number of high-affinity EGF receptors. The BDGF-induced down-modulation of the EGF receptor was completely blocked by protamine, a potent inhibitor of receptor binding and mitogenic activities of BDGF. BDGF down-modulated the EGF receptor in phorbol myristic acetate (PMA)-pretreated cells, as well as in control cells. Furthermore, PMA-pretreated cells responded mitogenically to BDGF, whereas PMA itself failed to stimulate the mitogenic response of PMA-pretreated cells. This BDGF-induced down-modulation of the EGF receptor in PMA-desensitized cells suggests that BDGF down-regulates the EGF receptor by a mechanism distinct from that of PMA. Incubation of cells with compounds which are known to inhibit pinocytosis blocked the down-modulation induced either by BDGF or by platelet-derived growth factor (PDGF) but had no effect on the PMA-induced down-modulation. Incubation of cells with inhibitors of receptor recycling enhanced the BDGF-induced down-modulation of the EGF receptor. These results suggest that BDGF and PDGF induce down-modulation of the EGF receptor by increasing the internalization of cell surface high-affinity receptors and that the internalization process may not be required for down-modulation induced by PMA.     

国产姜科植物的染色体计数(5)

<正> 本文继续对7属15种国产姜科植物作染色体计数观察,其中10种是染色体计数的新纪录(表、图)。通过对黄花大苞姜(Caulokaempferia coenobialis)和大苞姜(C.yunnanensis)以及凹唇姜(Bosenbevgia rotunda)和心叶凹唇姜(B.fallax)的染色体观察,确定了大苞姜属(Caulokaempferia)和凹唇姜属(Bosenbergia)的染色体基数分别为12和9。     

中药马蓝叶及其混乱品的比较鉴别

马蓝叶是加工传统中药青黛的主要原料。为了确保药材质量,作者对中药马蓝叶及其混乱品种球花马蓝、疏花马蓝、广西马蓝的原植物、药材性状、叶组织显微特征和薄层层析鉴别等进行了研究。指出其混乱品种虽与马蓝叶是同属植物,但不含马蓝叶的有效成分靛玉红,应仔细鉴别,不宜混用。     

修剪强度对乌桕产量的影响

对乌桕Sapium sebiferum(L.)Roxb.林进行四种不同强度的修剪试验,结果表明,以中度修剪产量最高,结实性状最好。     

图论在中国慈姑属数量分类研究中的应用

慈姑属(Sagittaria L.)是水生单子叶植物泽泻科(Alismataceae)的一个重要属。近年来,陈家宽等对中国慈姑属进行了系统研究。作者应用聚类分析和主成分分析进行了中国慈姑属的数量分类,取得了良好的效果。由于慈姑属分类性状数目较大,因而在压缩后的三维空间中描述分类群间的距离,     

不同季节银木叶精油化学成分的研究

用毛细管气相色谱-质谱-计算机联用技术、毛细管气相色谱双柱保留指数法和双柱标准品叠加法分析了不同季节银木叶精油化学成分。从分离出来的207—250个色谱峰中,初步鉴定出59个成分,被鉴定成分的总量占精油总组成的94.45—98.92%,其主要成分随采油季节不同而有所不同。     

樗蚕丝腺5SrRNA的核苷酸顺序

本文用凝胶直读法、末端鉴定法等相配合,测定了樗蚕(Philosamia cynthia)絲腺5SrRNA的核苷酸顺序:AGACAACGUCCAUACCACGUUGAAAACACCGGUUCUCGUCCGAUCACCGAAGUCAAGCAACGUCGGGCGCGGUCAGUACUUGGAUGGGUGACCGCCUGGGAACACCGCGUGCUGUUGGCUU比较了樗蚕、蓖麻蚕、柞蚕、家蚕、果蝇等5SrRNA结构差异,在分子水平上探讨了昆虫的分化。     

猪肺炎支原体膜上ATP酶生化性质的研究

猪肺炎支原体膜上ATP酶为Mg~(2+)激活,乌巴因不抑制。DCCD和寡霉素对该酶也无抑制作用,只有NBD与Quercetin才有一定的抑制效果。用梯度凝胶电泳可获均一的具有活性的酶蛋白带。     

Improved media for normal human muscle satellite cells: Serum-free clonal growth and enhanced growth with low serum

Summary We have developed a serum-free medium for clonal growth of normal human muscle satellite cells (HMSC). It consists of an optimized nutrient medium MCDB 120, plus a serum-free supplement, designated SF, that contains epidermal growth factor (EGF), insulin, dexamethasone, bovine serum albumin, and fetuin. Fibroblast growth factor was needed with dialyzed fetal bovine serum (dFBS) as the only other supplement, but in media containing SF, it was only slightly beneficial, and was omitted from the final medium without significant loss. Clonal growth of HMSC in MCDB 120 plus SF is as good as with 15% serum and 0.5% chicken embryo or bovine pituitary extract. However, growth is further improved by use of a doubly-supplemented (DS) medium containing both SF and 5% dFBS. Clonal growth of HMSC in the DS medium far exceeds that in previous media with any amount of serum, and monolayer growth is at least equal to that in conventional media with higher levels of serum. Cells grown in these media exhibit little differentiation, even when grown to high densities. However, they retain the capacity for extensive fusion and synthesis of increased creatine kinase when transferred to a serum-free differentiation-promoting medium, such as Dulbecco's modified Eagle's medium plus insulin. All experiments were done with clonal cultures of HMSC to insure that observed growth responses were always those of muscle cells. This research was supported by a grant from the Muscular, Dystrophy Association. Editor's statement This article describes the optimization of both the basal nutrient medium and growth factor requirements for human muscle cells in vitro. This system is critical for studies of normal muscle cell and molecular biology, as well as for understanding diseases of muscle such as Duchenne, Muscular Dystrophy.     

Conversion of cyanide to formate and ammonia by a pseudomonad obtained from industrial wastewater

Summary A cyanide-degrading pseudomonad was isolated by selective enrichment in a chemostat inoculated with coke-plant activated sludge and maintained at a dilution rate of 0.042/h for 60 days with a feed of 10 mg/l cyanide. The isolate, a facultative methylotroph capable of growth on methanol and methylamine, degraded cyanide to formate and ammonia; it could utilize the released ammonia as a nitrogen source but did not further metabolize formate under the experimental conditions employed. Both cyanide-degrading enzyme activity and respiratory resistance to cyanide were inducible and were enhanced by repeated exposure to the compound. Cell-free extracts stoichiometrically converted cyanide to formate and ammonia in a reaction that did not require oxygen. Enzyme activity, lost upon dialysis, was restored by less than equimolar ratios of NAD(P)H or ascorbate to cyanide, indicating that the reductants did not function directly as co-enzymes.