Survival of stressed rats following experimental cardiac necrosis

Résumé Une nécrose myocardique a été produite chez. le rat mâle adulte avec de l'isoprotérénol. Aucune différence de survie significative n'a été constatée entre les individus traités et les non traités lorsque les uns et les autres ont été soumis à l'hypoxémie, la nage forcée dans l'eau froide, ou la restriction par attache.

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This work was conducted in the Department of Chemical Pharmacology. We wish to thank Dr.D. A. Buyske for his interest and suggestions.     

A structural model for the retroviral proteases

In many retroviruses the 5' end of the pol gene codes for a protease vital for the processing of the gag polyprotein into the separate core proteins. In some viruses this protease is encoded at the 3' end of the gag gene, or between the gag and pol genes in a different reading frame to either. A sequence, Asp-Thr-Gly, which is conserved in retroviral proteases is also conserved in the active sites of aspartic proteases, an observation which has led to the suggestion that the retroviral proteases could belong to this family. We have examined the sequences of the aspartic and retroviral protease families, using pattern-recognition, structure prediction and molecular modelling techniques, and conclude that the viral protease sequences probably correspond to a single domain of an aspartic protease and may function in a dimeric form. We have constructed a model of the pol-protease of human immunodeficiency virus 1 (HIV-1) to test this hypothesis.     

A primitive Y chromosome in papaya marks incipient sex chromosome evolution

Many diverse systems for sex determination have evolved in plants and animals. One involves physically distinct (heteromorphic) sex chromosomes (X and Y, or Z and W) that are homozygous in one sex (usually female) and heterozygous in the other (usually male). Sex chromosome evolution is thought to involve suppression of recombination around the sex determination genes, rendering permanently heterozygous a chromosomal region that may then accumulate deleterious recessive mutations by Muller's ratchet, and fix deleterious mutations by hitchhiking as nearby favourable mutations are selected on the Y chromosome. Over time, these processes may cause the Y chromosome to degenerate and to diverge from the X chromosome over much of its length; for example, only 5% of the human Y chromosome still shows X-Y recombination. Here we show that papaya contains a primitive Y chromosome, with a male-specific region that accounts for only about 10% of the chromosome but has undergone severe recombination suppression and DNA sequence degeneration. This finding provides direct evidence for the origin of sex chromosomes from autosomes.     

High resolution X-ray analyses of renin inhibitor-aspartic proteinase complexes

Inhibitors of the conversion of angiotensinogen to the vasoconstrictor angiotensin II have considerable value as antihypertensive agents. For example, captopril and enalapril are clinically useful as inhibitors of angiotensin-converting enzyme. This has encouraged intense activity in the development of inhibitors of kidney renin, which is a very specific aspartic proteinase catalysing the first and rate limiting step in the conversion of angiotensinogen to angiotensin II. The most effective inhibitors such as H-142 and L-363,564 have used non-hydrolysable analogues of the proposed transition state, and partial sequences of angiotensinogen (Table 1). H-142 is effective in lowering blood pressure in humans but has no significant effect on other aspartic proteinases such as pepsin in the human body (Table 1). At present there are no crystal structures available for human or mouse renins although three-dimensional models demonstrate close structural similarity to other spartic proteinases. We have therefore determined by X-ray analysis the three-dimensional structures of H-142 and L-363,564 complexed with the aspartic proteinase endothiapepsin, which binds these inhibitors with affinities not greatly different from those measured against human renin (Table 1). The structures of these complexes and of that between endothiapepsin and the general aspartic proteinase inhibitor, H-256 (Table 1) define the common hydrogen bonding schemes that allow subtle differences in side-chain orientations and in the positions of the transition state analogues with respect to the active-site aspartates.     

人工配合饵料饲养剑尾鱼的初步研究

本文探讨了用人工配合饵料代替天然后饵饲养剑尾鱼的可行性。试验表明：人工配合饵料组仅在生长速度上稍差于天然活饵组，在成活率、性腺发育及鱼体生化组成等方面两组间无多大差异。这为今后制订剑尾鱼的营养标准打下了基础。     

围油栏前压力垂直结构对油水界面稳定性的影响

油水界面不稳定是围油栏失效的主要原因.该文采用油水二维湍流模型,基于PLIC-VOF(Piecewise Linear Interface Construction-Volume of Fluid)方法模拟油水界面运动,以油水密度比值、水流流速、围油栏吃水深度和油的运动黏度为参数,研究了围油栏前压力梯度的变化及其对油水界面稳定性影响的规律.研究结果表明围油栏前压力垂直结构直接决定了油水界面稳定性;临界压力梯度作为判断油水界面稳定性的标准在多数情况下都是很有效的,但是由于没有考虑运动黏度的影响,当运动黏度小于0.15cm2s-1时,不能再运用临界压力梯度标准判断油水界面稳定性.     

尼罗罗非鱼RAPD标记及其遗传多样性分析

采用 4 18个引物对尼罗罗非鱼进行了RAPD分析 ,筛选出 4 6个重复性好、可用于尼罗罗非鱼RAPD标记的引物 .另用 12个引物对尼罗罗非鱼群体 (2 3尾 )进行了遗传多样性分析 :共检出 5 8个位点 ,其中 18个位点表现出多态性 ,多态位点比例达 31.0 3% ,其群体的Nei&Li氏遗传相似率为 90 .2 3% ,申农信息指数为0 .10 0 5bit.上述三项指标表明 ,该尼罗罗非鱼群体保持着较高水平的遗传变异 .     

An intense stratospheric jet on Jupiter

The Earth's equatorial stratosphere shows oscillations in which the east-west winds reverse direction and the temperatures change cyclically with a period of about two years. This phenomenon, called the quasi-biennial oscillation, also affects the dynamics of the mid- and high-latitude stratosphere and weather in the lower atmosphere. Ground-based observations have suggested that similar temperature oscillations (with a 4-5-yr cycle) occur on Jupiter, but these data suffer from poor vertical resolution and Jupiter's stratospheric wind velocities have not yet been determined. Here we report maps of temperatures and winds with high spatial resolution, obtained from spacecraft measurements of infrared spectra of Jupiter's stratosphere. We find an intense, high-altitude equatorial jet with a speed of approximately 140 m s(-1), whose spatial structure resembles that of a quasi-quadrennial oscillation. Wave activity in the stratosphere also appears analogous to that occurring on Earth. A strong interaction between Jupiter and its plasma environment produces hot spots in its upper atmosphere and stratosphere near its poles, and the temperature maps define the penetration of the hot spots into the stratosphere.     

Simulation of Transport Channel in China’s Middle Route South-to-North Water Transfer Project

The unsteady flow in the Middle Route South-to-North Water Transfer Channel was simulated numerically using an implicit solution procedure for the Saint Venant equations. An equivalent roughness was used to simulate the effect of many transfer structures on the water levels in the main channel. Various gate operating and control methods were analyzed to study the response to disturbances produced by varying the flow rates through the Tianjin outlet. The results show that when the inflow at the head changes ...