Influence of Methanogenic Populations in Holocene Lacustrine Sediments Revealed by Clone Libraries and Fatty Acid Biogeochemistry

Methanogenic populations were investigated in subsaline Laguna Potrok Aike sediments, southern Argentina. Microbial density and activity were assessed via cell count and in situ ATP detection for the last ～11K years. Methanogen phylogenetics highlighted species stratification throughout depth, whereas CO₂ reduction was the major pathway leading to methane production. Organic substrates, characterized using pore water analysis, bulk organic fractions and saturated fatty acids, showed a clear link between sediment colonization and initial organic sources. Concentrations and δ¹³C compositions of methane and fatty acids provided final evidence of a microbial imprint on Holocene organic proxies in the most colonized intervals.     

Interaction between the Effects of Inside and Outside Na and K on Bullfrog Skin Potential

The composition of the solution bathing one border of the isolated frog skin affects the response of the potential across the skin to changes in the composition of the solution bathing the opposite border. Increasing the K concentration of the inside (corium) bathing solution decreased the sensitivity of the potential to a change in outside Na concentration. Decreasing the outside Na concentration decreased the sensitivity of the potential to a change in inside K concentration. Increasing the total ionic strength of the outside bathing solution or of both bathing solutions decreased the sensitivity of the potential to a change in outside Na concentration.     

Isolation of heparin-binding growth factors from bovine, porcine and canine hearts

Fresh bovine, porcine and canine hearts were homogenized and mitogens for mesoderm-derived cells were purified in three different steps. Extraction by two different ammonium sulfate precipitations was followed by cation-exchange chromatography and by heparin-Sepharose affinity chromatography. A heparin-Sepharose fraction from heart (eluted at 1.1 M NaCl) increased mitotic activity in serum-deprived cultures of porcine aortic endothelial and smooth muscle cells, and in human fibroblasts. This mitogenic activity is potentiated by heparin and inhibited by gamma-interferon. The heart mitogenic fraction showed one double peak on HPLC at A215 and one polypeptide band on SDS/PAGE. These peaks and bands were identical to those obtained from bovine brain. The heart acidic fibroblast growth factor (aFGF) showed a positive signal in Western blots using antibodies raised against brain aFGF. Gas-phase amino acid sequencing established that the mitogens were identical to aFGF and the N-terminally truncated aFGF. Extraction in the presence of a protease inhibitor (pepstatin A) produced a higher-molecular mass form of aFGF with a blocked amino terminus. Another mitogen, eluted at 1.6 M NaCl from heparin-Sepharose, reacted with polyclonal antiserum against human recombinant basic fibroblast growth factor (bFGF) and showed a 66% (12 from 18 amino acids determined by gas-phase sequencing) similarity with bFGF. This polypeptide increased the mitotic activity of the same cell lines but was more potent than aFGF.     

Chlorierte Kohlenwasserstoffe in Brutv?geln aus dem Binnenland Niedersachsens

Zusammenfassung Rückstände chlorierter Kohlenwasserstoffe in Eiern und Lebern von im Binnenland Niedersachsens brütenden Vogelarten — Feldsperling, Mehlschwalbe, Weißstorch, Graureiher, Saatkrähe, Stockente und andere Arten — werden angegeben und deren Abhängigkeit von Brutort, Nahrung und Zugverhalten diskutiert.

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Chlorinated hydrocarbons of some bird species breeding in the inland of Lower Saxony (FRG)

Summary Residues of chlorinated hydrocarbons in eggs and livers of some bird species — Tree Sparrow, House Martin, White Stork, Heron, Rook, Mallard, and further species — are presented. The dependence on place of breeding, food web, and migration is discussed.

     

自发性高血压大鼠血管α1肾上腺素受体亚型的改变

本工作在离体与整体条件下比较易卒中型自发性高血压(SHRSP)大鼠与WKY大鼠血管中α_1受体的两种亚型。在离体灌流的主动脉、肾动脉与肠系膜动脉,50μmol/L氯甲基可乐定(CEC)预温育30min可使α_1受体激动时引起的最大收缩张力在SHRSP与WKY大鼠分别降为对照时的31.4±8.3％与35.2±2.9％,68.4±8.2％与80.1±7.3％,68.4±6.3％与55.4±7.0％,两者间均无显著性差别。但10μmol/L硝苯吡啶对α_1受体收缩效应的阻断作用则在SHRSP大鼠大大超过WKY大鼠,最大收缩张力分别降为对照时的3.1±1.5％与56.5±4.8％(P<0.01),9.0±4.1％与23.6±3.5％(P<0.05),5.9±2.5％与28.0±0.8％(P<0.01)。整体动物实验也显示硝苯吡啶的降血压作用及对苯肾上腺素升血压效应的阻断作用在SHRSP大鼠都较WKY大鼠显著增强。离体主动脉a_1受体激动时的快速相与持续相收缩均主要由α_(1B)亚型激动引起,硝苯吡啶对快速相收缩的阻断作用在SHRSP与WKY大鼠无显著性差别,但对持续相收缩的阻断作用则在SHRSP大鼠显著强于WKY大鼠。上述结果提示SHRSP大鼠血管α_1受体两种亚型的分布没有显著改变,但α_(1B)受体激动时继发性细胞外Ca~(2+)进入的途径由非双氢吡啶敏感性钙通道转变为双氢吡啶敏感性钙通道。