几种变温脊椎动物的血细胞比较

脊椎动物血细胞在体内执行着气体运输、机体免疫和凝血等重要的生理功能。目前关于变温脊椎动物血细胞的研究多集中于形态分类和亚显微结构方面(Savage,1983;冯怀亮等,1991),其形态变化和生理功能的比较研究报道较少(Pica et al.,1990;Pellizzon et al.,2002),对于小淋巴细胞参     

Metabolism of poly(A)(+)RNA in toad bladder epithelial cells

Summary Previous studies have characterized the induction of poly(A)(+)RNA synthesis by aldosterone during the latent period, preceding the increased active transepithelial sodium transport (measured as short-circuit current, SCC). To assess the role of aldosterone in the maintenance of the response in general and the metabolism of this RNA in particular, the decay of the increased SCC and of the newly synthesized poly(A)(+)RNA was monitored. On removal of the hormone, the SCC decayed with a half-life of 6.5 hr after a lag period of 2–3 hr. Studies on the disappearance from the cytoplasm of poly(A) (+)RNA synthesized in the first two hours after addition of aldosterone revealed a number of RNA species with diverse size decaying at a relatively slow rate after removal of aldosterone, and RNA sedimenting in the 10–14 S region decaying at a faster rate closely related to the decay in SCC. Maintenance of aldosterone in the media resulted in a much slower rate of decay of this 10–14 S. It is concluded that the decay of the 10–14 S poly(A)(+)RNA is closely related to the decay in SCC and the stability of this RNA is influenced by the retention of aldosterone in the medium.     

Mechanisms of hormonal modulation of ion transport in the toad's urinary bladder: Subcellular localization of aldosterone-induced proteins

A dual-label isotope technique was used to study the effects of aldosterone upon the incorporation of amino acids into proteins of the in vitro toad urinary bladder. Following labeling, the mucosal cells were disaggregated and the mitochondria-rich and granual cells were separated. Proteins with an elevated isotope ratio were found in a plasma membrane fraction (170 000, 110 000 and 85 000 daltons) and in the cytosol (36 000 and 6 000 daltons) of the preparations enriched in mitochondria-rich cells. These effects of aldosterone were blocked by cycloheximide. There was no evidence that aldosterone had induced the incorporation of labeled amino acids into carbonic anhydrase isolated from the soluble fraction by affinity chromatography. The results suggests that the physiologic response of the toad bladder to aldosterone is related to the synthesis of both soluble and plasma membrane proteins.     

华南地区黒眶蟾蜍的遗传变异和地理分化

黒眶蟾蜍Bufo melanostictus(Anura,Bufonidae)是亚洲常见的蟾蜍,广泛分布于中国华南地区。由于华南地区分布着众多的大陆架岛屿及其地貌的复杂性与多样性,因而不同地区的黑眶蟾蜍种群可能存在地理上的遗传变异。本文首次采用DNA序列分析方法,检测了采自我国华南6个省市地区(福建、广东、广西、海南、香港、台湾),包括4个主要大陆架岛屿(海南岛、大屿山、南澳岛、台湾岛)的12个黑眶蟾蜍种群共84个个体,获得mtDNA控制区序列长956bp的片段,共有75个变异位点(26.3%为单个多态位点,73.7%为简约信息位点),12个插入/缺失。所获得的44个单倍型中有5个为种群间共享的单倍型。华南地区黒眶蟾蜍较高的的遗传多样性(单倍型多样性h=0.977)不但表现为海岛种群内普遍具有较高的遗传变异,而且遗传分化指数(FST)、基因流(Nm)、Amova和Samova等分析均表明种群之间已经发生了明显的遗传分化。从Amova分析和分子系统发育分析结果来看,华南地区分布于大陆与分布于海岛的种群之间并未发生明显的遗传分化,说明由陆缘浅海造成的阻隔作用(isolation by barrier)并不能很好地解释华南地区黑眶蟾蜍种群之间遗传分化的原因。遗传距离与地理距离的低度相关(Mantel测试R=0.192,P<0.001)说明华南地区黑眶蟾蜍的种群分化並不完全符合距离决定分化(isolation by distance)的假说。Samova的结果表明华南沿海大陆东部的3个种群(广东汕头、福建莆田和东山)与其它地区9个种群之间的变异最大(FCT=0.35097),因此,推测黑眶蟾蜍这2个地理区域组之间应该存在着其它地理隔离屏障,对两地黑眶蟾蜍的迁移有一定的阻隔作用,产生此隔离效应的天然地理屏障可能为莲花山脉。黑眶蟾蜍种群在历史上曾发生多次局部扩张,时间大约在距今0.025MYA左右,这与最后一次冰期结束的时间相吻合,而位于我国华南大陆周边的4个主要大陆架岛屿(海南岛、大屿山、南澳岛、台湾岛)可能是华南地区黒眶蟾蜍在第四纪冰期的"避难所"。南澳岛种群所存在的特殊单倍型验证了这一岛屿避难所的存在。本研究揭示的地理种群之间的遗传变异和分化,对进一步了解华南地区乃至亚洲的黒眶蟾蜍的生物地理关系有重要意义。     

Effect of the Lower Kihansi Hydropower Project and post-project mitigation measures on wetland vegetation in Kihansi Gorge,Tanzania

Reduction in flow of the Lower Kihansi River, Tanzania, caused by implementation of a hydropower project in May 2000 has the potential to lead to changes in vegetation composition of spray maintained wetlands. These wetlands are the only known habitat for the Kihansi Spray Toad, Nectophrynoides asperginis. In this paper, change over time is assessed by comparing samples taken in 1998 before reduction in flow, with those taken in 2000 after reduction in flow, in 2001 following installation of a sprinkler system built to maintain the wetlands and in 2002 eighteen months after sprinkler installation. The vegetation was found to change markedly following initiation of the project, with marsh and stream side species dying back and weedy species entering the wetland. The wetland continued to change following installation of the sprinkler system and has not appeared to have reverted back towards the pre-project condition, although diversity and the proportion of marsh and stream side species are greater in 2002 than in 1998.     

蟾蜍冬眠期和排卵前后垂体中精氨酸催产素含量的变化

利用高效液相色谱结合荧光检测的技术,在pmol(10~(12)M)水平上,测定了不同时期单个蟾蜍脑垂体中精氨酸催产素(Arginine Vasotocin,AVT)的含量,发现排卵前期AVT含量最高,而排卵后则迅速下降;冬眠期AVT含量略高于排卵后期。AVT在蟾蜍动情、排卵的过程中可能起着重要的作用。     

蟾蜍血清梭曼水解酶的酶学性质研究

蟾蜍血清梭曼水解酶已被纯化。该酶有两个温度作用高峰,最适为ｐＨ１０,其次为ｐＨ７。最适温度为３０℃。以梭曼为底物,在ｐＨ７．７３条件下测定其米氏常数为５．８６４ｍｍｏｌ／Ｌ,最大反应速度为６９２μｍｏｌ／Ｌ。过高的底物浓度对酶活性有抑制作用。Ｍｇ＋＋、Ｃａ＋＋对酶有激活作用,而Ｎｉ＋＋、Ｃｕ＋＋、Ｆｅ＋＋、Ｎａ＋、Ｋ＋对酶活性无明显影响。     

Regulation of Epithelial Na+ Permeability by Protein Kinase C is Tissue Specific

Protein kinase C (PKC) is a major regulator of a broad range of cellular functions. Activation of PKC has been reported to stimulate Na⁺ transport across frog skin epithelium by increasing the apical Na⁺ permeability. This positive natriferic response has not been observed with other epithelial preparations, and could reflect the specific experimental conditions of different laboratories, or species or organ specificity of the response to PKC. In the present study, measurements were conducted with skins and urinary bladders from the same animals of two different species. The PKC activator TPA uniformly increased the transepithelial Na⁺ transport (measured as amiloride-sensitive short-circuit current, I _SC, across skins from Rana temporaria and Bufo marinus, and inhibited I _SC across bladders from the same animals. Inhibitors of PKC (staurosporine, H-7 and chelerythrine) partially blocked the TPA-induced stimulation of I _SC across frog skin. The specificity of the PKC response by amphibian skin could have reflected an induction of moulting, similar to that observed with aldosterone. However, light micrographs of paired areas of frog skin revealed no evidence of the putative moulting. Separation of stratum corneum from the underlying stratum granulosum could be detected following application of aldosterone. We conclude that the effect of PKC on epithelial Na⁺ channels is organ, and not species specific. The stimulation of Na⁺ permeability in amphibian skin does not arise from sloughing of the stratum corneum. These observations are consistent with the hypothesis that the natriferic action arises from the calcium-independent isozyme of PKC previously detected in frog skin. Received: 19 January 1996/Revised: 10 April 1996