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用蛙胫前肌小束为材料,研究了提高胞外钾[K+]O对咖啡因挛缩的作用。[K+]O从2mmol/L提高到10或25mmol/L,由3mmol/L咖啡因引起的挛缩明显增强。以PKC/PC(PKC和PC分别为在高钾和正常钾条件下的咖啡因挛缩)表示的咖啡因挛缩增强,依赖[K+]O和高钾作用时间。随着10mmol/L[K+]O作用时间延长,直至10min,增强逐渐增加。但是,25mmol/L[K+]O作用1min时增强达到最大,然后下降到对照。PKC/PC变化时程不能用高钾引起的去极化解释,而与由相似[K+]O引起的胞浆自由钙变化时程相符。提示,至少在蛙骨骼肌,高钾引起的咖啡因挛缩增强主要是由胞浆自由钙升高引起的。 相似文献
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红腹锦鸡肺的组织结构与微血管构筑 总被引:2,自引:0,他引:2
为了了解红腹锦鸡(Chroysolophus pictus)肺的微细结构和微血管构筑特征,为呼吸生物学研究提供形态学依据,用组织学方法和微血管铸型技术在光镜和扫描电镜下观察研究了红腹锦鸡肺的组织结构与微血管构筑情况。结果表明,红腹锦鸡肺主要由各级支气管构成,从三级支气管上呈辅射状分出许多呼吸毛细管(微气管),并相互吻合成网状,呼吸毛细管外面包围有丰富的毛细血管;红腹锦鸡肺毛细血管垂直围绕在各微气管外,并相互吻合成密集的立体微血管网;毛细血管管径4.5~7.0μm,微气管直径11~50μm。并对肺微血管构筑情况与呼吸效率的关系作了探讨。 相似文献
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Samuel EI Jones Andrew J Bladon Nigel J Collar Galgalo Dadacha Jarso Denge Paul F Donald 《Ostrich》2018,89(1):41-46
The Ethiopian Bush-crow Zavattariornis stresemanni is an endangered, co-operatively breeding southern Ethiopian endemic with a remarkably restricted range (c. 6 000 km2). The species’ range was recently found to be almost perfectly predicted by an envelope of cooler, drier and more seasonal climate than surrounding areas, but the proximate determinants of this range restriction remain unclear. We assessed whether specialisation in diet or foraging may restrict the range of the species by conducting foraging watches to determine prey composition, augmented by observations of opportunistic foraging techniques, and by comparing our results to previously published information on diet. Prey composition comprised a range of arthropods, such as insect larvae (62.7%), beetles (Coleoptera) (15.6%), and grasshoppers and crickets (Orthoptera) (11.8%). Prey was primarily obtained by pecks above ground (74.2%) but also frequently dug up (23.8%). Prey capture was most successful during pecks and we also found chicks were preferentially fed larger prey items over smaller ones by adults. We documented opportunistic behaviours such as nest-raiding and ox-pecking. Diet and foraging are varied and unspecialised, and therefore do not appear to explain the restricted range of the Ethiopian Bush-crow. 相似文献
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The interaction between legumes and rhizobia has been well studied in the context of a mutualistic, nitrogen‐fixing symbiosis. The fitness of legumes, including important agricultural crops, is enhanced by the plants’ ability to develop symbiotic associations with certain soil bacteria that fix atmospheric nitrogen into a utilizable form, namely, ammonia, via a chemical reaction that only bacteria and archaea can perform. Of the bacteria, members of the alpha subclass of the protebacteria are the best‐known nitrogen‐fixing symbionts of legumes. Recently, members of the beta subclass of the proteobacteria that induce nitrogen‐fixing nodules on legume roots in a species‐specific manner have been identified. In this issue, Bontemps et al. reveal that not only are these newly identified rhizobia novel in shifting the paradigm of our understanding of legume symbiosis, but also, based on symbiotic gene phylogenies, have a history that is both ancient and stable. Expanding our understanding of novel plant growth promoting rhizobia will be a valuable resource for incorporating alternative strategies of nitrogen fixation for enhancing plant growth. 相似文献
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Developmental biology of legume nodulation 总被引:28,自引:1,他引:28
ANN M. HIRSCH 《The New phytologist》1992,122(2):211-237
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