Inhibitory Effect of Autoclaving Whey-Based Medium on Propionic Acid Production by Propionibacterium shermanii

Propionic acid production by Propionibacterium shermanii was compared in pasteurized and autoclaved whey-based media. Propionic acid production decreased with increasing whey concentration in autoclaved media but not in pasteurized media. Increasing the yeast extract concentration from 5 to 10 g/liter greatly reduced the inhibitory effect of autoclaving.     

Production of High-Viscosity Whey-Glucose Broths by a Xanthomonas campestris Strain

Acclimation of a sandy soil to an air-natural gas mixture stimulated the biological oxidation of chloroform to carbon dioxide. Acetylene and methane inhibited chloroform oxidation. Chloroform oxidation continued up to 31 days in the absence of methane. Chloroform oxidation rates increased at chloroform concentrations up to 5 μg g of soil^-1.     

The kinetics of the first wave of spermatogenesis in the newborn male mouse

A combination of autoradiography and air-dried techniques was used to calculate the duration of the major meiotic stages in the first wave of spermatogenesis in the newborn mouse. The data indicated that the entry into meiosis occurred asynchronously over 2 days, and the time required for each stage and the total cycle was constant. These time intervals were nearly identical with those estimated for adult animals in the present study and by other authors.     

Studies of myofibrillar ATPase in ragweed-sensitized canine pulmonary smooth muscle

The maximal shortening velocities of tracheal and pulmonary vascular smooth muscle from ragweed-sensitized dogs were significantly higher than those of muscles from their littermate controls. Myofibrils of tracheal and pulmonary vascular smooth muscle from ragweed-sensitized and control dogs were obtained with use of Triton X-100 homogenizing solution. The myofibrillar adenosinetriphosphatase (ATPase) activities of the sensitized tissues were significantly higher (P less than 0.05) than those of their respective controls.     

Evidence for [D-Ala2,D-Leu5]Enkephalin-Induced Supersensitivity to 5-Hydroxytryptamine in a Neurotumor × Brain Hybrid Cell Line (NCB-20)

A neuroblastoma X Chinese hamster embryonic brain explant hybrid cell line (NCB-20) expressed 5-hydroxytryptamine (5-HT1) receptors, linked to adenylate cyclase, which closely resembled 5-HT1 receptors previously characterized in central nervous tissue. However, the affinity of the receptors for 5-HT was only 150 nM compared to 5 nM in membranes prepared from cerebral cortex. The elevation of cyclic AMP levels in NCB-20 cells produced by 5-HT was found additive to that produced by cholera toxin but synergistic with that produced by either prostaglandin E1 (PGE1) or forskolin, suggesting that these latter two agents elevate cyclic AMP levels by a different mechanism than 5-HT. The elevation of cyclic AMP levels by either 5-HT or PGE1 was reversed by [D-Ala2,D-Leu5]enkephalin (DADLE), morphine, clonidine, and 3,4-dihydroxyphenylethylamine (dopamine) on a short (30 min) time scale. However, continued exposure to DADLE resulted in loss of the initial inhibitory effects of DADLE after 6 h and return of cyclic AMP levels to that seen with either 5-HT or PGE1 alone. When the DADLE exposure time was increased to 48 h, 5-HT produced a further twofold increase in cyclic AMP levels, but there was no increase in the responsiveness of the cells to PGE1 unless naloxone was added 1 h prior to treatment with PGE1. Scatchard analysis showed that the increased potency of 5-HT resulted from an increase in receptor affinity for 5-HT (from a KD of 150 +/- 20 nM to one of 20 +/- 7 nM), with a reduction in the number of apparent binding sites. The 5-HT supersensitivity observed in NCB-20 cells may be a good model for neurotransmitter interactions that produce desensitization or facilitation in the intact nervous system.     

Pharmacological properties of canine intrapulmonary blood vessels

The contractile response of ring segments of large, medium, and small pulmonary arteries and veins of the dog to histamine, norepinephrine, and serotonin have been studied. The maximum contractile response to these drugs was normalized with respect to the maximal response obtained in stimulation with 127 mM K+. The small pulmonary artery was more reactive to histamine, norepinephrine, and serotonin when compared with large and medium pulmonary arteries. The medium and large pulmonary artery showed no difference in reactivity to histamine. However, the mean effective dose (ED50) values for these agonists among the different segments of pulmonary arteries showed no significant difference. The small and medium pulmonary veins demonstrated increased reactivity to histamine, but not norepinephrine and serotonin. The ED50 values also indicated that both small and medium veins were more sensitive to histamine when compared with the large pulmonary vein. The log concentration percent response curves for both small and medium pulmonary veins were displaced leftward (increased sensitivity) with respect to that for the large pulmonary vein. However, the reactivity and sensitivity to histamine between medium and small pulmonary veins were no different. The reactivity and sensitivity of different segments of pulmonary veins to norepinephrine and serotonin showed no significant differences among them. We conclude that histamine and other vasoactive substances, which are directly or indirectly related to mast cell degranulation, exert pharmacological effects on the pulmonary vasculature which possesses differential responsiveness at various levels of the vascular tree.     

油菜细胞质雄性不育系叶绿体DNA特异片段的分子克隆

采用高离子浓度缓冲液法分别提取油菜不育系及保持系的叶绿体DNA。经Sepharcse 4B柱层析纯化后,得到具有较高纯度的叶绿体DNA样品。将其分别用Eco RI、Bam HI、HimdHI、PstI和XhoI 5种限制性内切酶酶解,得到5种限制性内切酶图谱。其中除PstI图谱外,其它4种酶谱均显示出明显的两系间叶绿体DNA结构差异。以pBR 322为载体,分别克隆了不育系Bam HI图谱上的3个特异片段。得到的3个克隆,经克隆杂交及电泳分析后,证实分别带有上述3个目的片段。这些特异片段的特性及其与花粉育性的关系尚在研究中。     

Structural analysis of a maize gene coding for glutathione-S-transferase involved in herbicide detoxification

Summary We have used the cDNA clone encoding maize glutathione-S-transferase (GST I) to isolate a genomic DNA clone containing the complete GST I gene. Nucleotide sequence analysis of the cDNA and genomic clones has yielded a complete amino acid sequence for maize GST I and provided the exon-intron map of its gene. The mRNA homologous sequences in the maize GST I gene consist of a 107 bp 5 untranslated region, a 642 bp coding region and 340 bp of the 3 untranslated region. They are divided into three exons by two introns which interrupt the coding region. The 5 untranslated spacer contains an unusual sequence of pentamer AGAGG repeated seven times. The inbred maize line (Missouri 17) contains a single gene for GST I, whereas the hybrid line (3780A) contains two genes. Nucleotide sequence analysis of the primer extended cDNA products reveals that the 5 untranslated regions of the two genes in the hybrid 3780A are identical except for a 6 bp internal deletion (or insertion). The amino acid sequence of maize GST I shares no apparent sequence homology with the published sequences of animal GST's and represents the first published sequence of a plant GST. re]19850813 ac]19851126     

Synthesis and maturation of cross-reactive glycoprotein in fibroblasts deficient in arylsulfatase a activity

The biosynthesis of arylsulfatase A was studied in cultured fibroblasts by pulse-chase labeling with [2-³H]mannose; the enzyme was isolated by immunoprecipitation and denaturing polyacrylamide gel electrophoresis. In normal fibroblasts, and in fibroblasts from a patient with multiple sulfatase deficiency, the enzyme was synthesized as a glycoprotein of apparent molecular weight of 59,000; half of it was processed over a period of 4 days to M_r= 57,000. The precursor chain of M_r= 59,000 was secreted in the presence of 10 mM NH₄Cl. An immunoprecipitable glycoprotein of normal size was synthesized by fibroblasts from two unrelated patients with metachromatic leukodystrophy, but this material disappeared within twenty hours. In fibroblasts from an individual with pseudodeficiency of arylsulfatase A, the immunoprecipitable precursor glycoprotein was smaller (M_r= 56,000). The synthesis of cross-reactive proteins with altered properties supports the concept of allelic mutations as the genetic basis of metachromatic leukodystrophy and of arylsulfatase A pseudodeficiency.