下丘脑外侧区注射TRH对大鼠胃酸分泌的影响

本文采用连续收集胃腔灌流法,观察下丘脑外侧区(LHA)注射促甲状腺激素释放激素(TRH)对大鼠胃酸分泌的影响,并分析TRH在LHA促进胃酸分泌的作用机制。结果表明:(1)LHA注射TRH(1μg)明显地刺激胃酸分泌;(2)预先向LHA注射酚妥拉明(10μg)、美多心安(5μg)及胃泌素抗体1μl(1:640)并不影响TRH的泌酸作用,如预先向LHA注射阿托品(5μg)则可消除TRH的泌酸效应;(3)垂体摘除及肾上腺切除均不影响TRH的泌酸作用;(4)隔下迷走神经切断后,LHA注入TRH的泌酸效应仍然出现,但持续时间显著缩短;腹腔交感神经节摘除后,TRH仍能促进胃酸分泌,但分泌量少而平稳。以上结果提示:LHA是TRH中枢泌酸效应的有关结构之一,其中枢机制是通过胆碱能M受体中介的,腹腔交感神经节和膈下迷走神经是TRH泌酸效应的传出途径。前者引起的泌酸反应出现较早且引起泌酸高峰,但持续时间短;后者则引起低平的持续分泌。     

Derived amino acid sequence and identification of active site residues of Escherichia coli beta-hydroxydecanoyl thioester dehydrase

The nucleotide sequence of the fabA gene encoding beta-hydroxydecanoyl thioester dehydrase, a key enzyme of the unsaturated fatty acid synthesis pathway of Escherichia coli, has been determined by the dideoxynucleotide sequencing technique. Most of the sequence was obtained by sequencing intragenic insertions of the transposon, Tn1000, isolated in vivo. A synthetic primer complementary to a portion of the inverted repeat sequences at the ends of the transposon was used to prime DNA synthesis into the flanking fabA sequences. The gene is composed of 516 nucleotides (171 amino acid residues) encoding a protein with a molecular weight of 18,800. Approximately half of the derived amino acid sequence was confirmed by automated Edman sequencing of peptides obtained by cyanogen bromide cleavage. The active site histidine residue (His-70) has been identified by analysis of the peptides labeled by reaction with 14C-labeled 3-decynoyl-N-acetylcysteamine, a specific mechanism-activated inhibitor. A cysteine residue (Cys-69) adjacent to the active site histidine may play the role in catalysis previously assigned to a tyrosine residue. We also report a simplified purification process for the dehydrase beginning with extracts of a brain which greatly overproduces the enzyme.     

立枯丝核菌蛋白质电泳图谱研究 Ⅰ.融合群与图谱的相关性

用来自日本和美国的立枯丝核菌8个融合群11个类群代表菌株进行可溶性蛋白质电泳,其结果表明,各融合群及亚群之间电泳图谱有显著差异,而同一类群菌株的电泳图谱则相似。分析来源于华东等地已鉴定的融合类群117个菌株的电泳图谱显示,同一融合群内菌株,虽然采集地区、寄主植物或致病力不同,其蛋白质图谱仍十分相似;而不同融合类群的菌株,即使在同一田块中同一种寄主植物上引起相似病害,其图谱也显示出明显差异。本文就上述可溶性蛋白质图谱显示的结果与其它研究者在血清学、DNA同源性.酯酶等生化水平上对融合群的研究结果进行了比较和探讨。     

中华白蛉的自育性研究

现场及实验室结果表明,我国黄土高原的大多数中华白蛉(Phlebotomus chinensis)应属自育性品系,它通常在羽化后、吸血前经交配能依靠腹节内脂肪体发育卵泡,一般在产卵后始行吸血。其生理性状是:胃内无血、腹节内有大量块状或条状脂肪体。羽化24小时后,附腺内有暗色颗粒,卵巢内有发育的卵泡。在25℃士1℃下它的生活史分快、慢两型。快型从卵至成虫仅需44—50夭,慢型需要以四龄幼虫滞育,其长短随滞育期而定,最长的滞育期达301天。观察了白蛉幼虫在饥饿状态下对自育性的影响。此外,还比较了吸血白蛉与自育性白蛉的妊卵数。吸血白蛉的妊卵数约较自育性的高出1/5。这种自育性品系的中华白蛉在自然居群约内占92%、主要栖于洞穴内为野栖种类。本文对自育性中华白蛉的生态及其防制策略作了分析和讨论。     

Role for fadR in unsaturated fatty acid biosynthesis in Escherichia coli

Escherichia coli K-12 mutants constitutive for the synthesis of the enzymes of fatty acid degradation (fad) synthesize significantly less unsaturated fatty acid (UFA) than do wild-type (fadR+) strains. The constitutive fadR mutants synthesize less UFA than do fadR+) strains both in vivo and in vitro. The inability of fadR strains to synthesize UFAs at rates comparable to those of fadR+ strains is phenotypically asymptomatic unless the fadR strain also carries a lesion in fabA, the structural gene for beta-hydroxydecanoyl-thioester dehydrase. Unlike fadR+ fabA(Ts) mutants, fadR fabA(Ts) strains synthesize insufficient UFA to support their growth even at low temperatures and, therefore, must be supplemented with UFA at both low and high temperatures. The low levels of UFA in fadR strains are not due to the constitutive level of fatty acid-degrading enzymes in these strains. These results suggest that a functional fadR gene is required for the maximal expression of UFA biosynthesis in E. coli.     

中国拟盘多毛孢属真菌的七个新组合

作者按照Steyaert(1949)和Sutton(1980)的分类观点,对1987—1988年从我国广西、江西、浙江等地采集的Pestalotiopsis属真菌进行了研究,确认了拟盘多毛孢属真菌的7个新组合种,即Pestalotiopsis carveri(Guba)comb nov.,Pestalotiopsis elasticae(Koord.)comb.nov.,Pestalotiopsis langloisii(Guba)comb.nov.,Pestalotiopsis oleandri(Guba)comb.nov.,Pestalotiopsis sinensis(shen)comb.nov.,Pestalotiopsis sydowiana(Bres.)comb.nov.和Pestalotiopsis zahlbruckneriana(Bres.)comb.nov.     

Acetoacetyl-acyl carrier protein synthase. A target for the antibiotic thiolactomycin

The biochemical basis for the inhibition of fatty acid biosynthesis in Escherichia coli by the antibiotic thiolactomycin was investigated. A biochemical assay was developed to measure acetoacetyl-acyl carrier protein (ACP) synthase activity, a recently discovered third condensing enzyme from E. coli (Jackowski, S., and Rock, C.O. (1987) J. Biol. Chem. 262, 7927-7931). In contrast to the other two condensing enzymes in E. coli, acetoacetyl-ACP synthase (synthase III) condensed malonyl-ACP with acetyl-CoA, rather than with acetyl-ACP. The concentration dependence of thiolactomycin inhibition of fatty acid biosynthesis in vivo was the same as the inhibition of acetoacetyl-ACP synthase activity in vitro indicating that the two phenomena were related. A thiolactomycin-resistant mutant (strain CDM5) was isolated. The specific activity of acetoacetyl-ACP synthase in extracts from this mutant was 10-fold lower than in extracts from its thiolactomycin-sensitive parent resulting in a marked defect in the ability of strain CDM5 to incorporate acetyl-CoA into fatty acids in vitro. The residual acetoacetyl-ACP synthase activity in the resistant strain was refractory to thiolactomycin inhibition. In addition, acetyl-CoA:ACP transacylase activity in strain CDM5 was resistant to inactivation by thiolactomycin suggesting that the acetoacetyl-ACP synthase also catalyzes this transacylation reaction. These data point to acetoacetyl-ACP synthase as a target for thiolactomycin inhibition of bacterial fatty acid biosynthesis.     

斜胸叶蝉属一新种（同翅目：叶蝉总科：耳叶蝉科）

本文记述耳叶蝉科斜胸叶蝉属一新种:黄缘斜胸叶蝉Epiclinata flavomarinata sp.nov.。标本采自我国西藏。文中描述了新种的外部形态及雄性外生殖器构造特征,并与近似种进行比较,附有主要特征图。模式标本保存于中国科学院动物研究所。     

豚鼠主动脉前庭组织的自律性研究和形态学观察

用细胞内微电极技术,对８２只豚鼠主动脉自发电活动进行观察和分析,表明,１６例（１９．５％）出现自律性电活动;６１例（７４．４％）在电刺激诱导下也可出现自律性电活动。进一步观察发现,在主动脉瓣右瓣与后瓣交界以下的局部区域,可记录到有明显４相自动增极化的慢反应自律细胞样的动作电位,并可被钙通道阻滞剂Ｍｎ＾２＋,硝苯吡啶阻断。这一部位之外的其它大部分区域均表现为快反应动作电位,经光镜和电镜观察（ｎ＝１３