GI双突变体GIK253RA198C的构建及其性质分析

以双引物法对葡萄糖异构酶（GI）基因进行定点突变,将突变体基因于大肠杆菌中表达,获得了GI双点突变体GIK253RA198C.研究K253R和A198C双点突变对GI的结构和性质的作用,结果表明GIK253RA198C的热稳定性明显下降,最适反应温度降低5℃.文章从结构和机制上解释了为何同是K253R突变,对SM33 GI和密苏里游动放线菌GI的热稳定性产生不同的影响,认为这是由于Lys253在两种GI结构的位置上存在微小差异,从而使引入的Arg对亚基间的相互作用产生了相反效应所引起.     

Matching models of left ventricle and systemic artery

To reveal how the matching models of the left ventricle and its afterload affect the pressure and flow in the aortic root, the differences between the measured pressure and flow waveforms and those determined by three kinds of matching model were compared. The results showed that, compared with the results by both matching models 1 and 2, the pressure and flow waveforms determined by matching model 3 established in this work were in the closest agreement with the corresponding experimental waveforms, therefore indicating that matching model 3 was a matching model that closely and rationally characterized the match between the left ventricle and the systemic artery.     

Construction of a trivalent candidate Shigella vaccine strain with host-vector balanced-lethal system

A trivalent liveShigella vaccine candidate FSD01 against S.flexneri 2a, S.sonnei and S.dysenteriae I was constructed. This candidate strain was based on the S.flexneri 2a vaccine T32. By homologous recombination exchange, the chromosomalasd gene of T32 was site-specifically inactivated, resulting in the strain unable to grow normally in LB broth, while anotherasd gene of S.mutans was employed to construct an Asd⁺ complementary vector. This combination ofasd ^- host/Asd⁺ vector formed a balanced-lethal expression system in T32 strain. By use of this system, two important protective antigen genes coding for S.sonnei Form I antigen and Shiga toxin B subunit were cloned and expressed in T32, which led to the construction of trivalent candidate vaccine FSD01. Experimental results showed that this strain was genetically stable, but its recombinant plasmid was non-resistant. Moreover, it was able to effectively express trivalent antigens in one host and induce protective responses in mice against the challenges of the above threeShigella strains.     

Sequence analysis of lacZ- mutations induced by ion beam irradiation in double-stranded M13mp18DNA

While M13mp18 double-stranded DNA was irradiated with ion beam, and transfected intoE. coli JM103, a decrease of transfecting activity was discovered. The lacZ^- mutation frequency at 20% survival could reach (3.6–16.8) × 10⁴, about 2, 3–10 times that of unirradiated M13DNA. Altogether, 27 IacZ^-mutants were selected, 10 of which were used for sequencing. 7 of the sequenced mutants show base changes in 250-bp region examined (the remaining 3 mutants probably have base changes outside the regions sequenced). 5 of the base-changed mutants contain more than one mutational base sites (some of them even have 5–6 mutational base sites in 250-bp region examined); this dense distribution of base changes in polysites has seldom been seen in X-rays, Y-rays or UV induced DNA mutations. Our experiments also showed that the types of base changes include transitions(50%), transversions (45%) and deletion (5%); no addition or duplication was observed. The transitions were mainly C→T and A→G; the transversions were mainly C→A and C→G. The mutations involving cytosine residue (in the template strand) constitute about 60% of all the base changes observed. In comparison with the surrounding sequences of mutational base sites, the base located between TG and CT is found to be easily substituted.     

猫纹状皮层神经元整合野的形状和范围

用正弦调制的移动光栅测量了１２０个猫纹状皮层神经元在长度和宽度方向上的空间整合特性。结果表明：（１）大多数细胞的传统感受野具有长宽相近的结构,然而它们的整合野多数是宽而短或者窄而长的长条形。（２）整合野大小为传统感受野的２—７倍,平均为３．７倍。简单细胞与复杂细胞整合野的大小没有显著差别。（３）随着感受野的视网膜偏心度的增加,整合野大小有逐渐增大的趋势。（４）感受野靠近视网膜垂直中线的细胞,其整合野可以跨越中线进入同侧视野;在两半视野中整合野的范围没有显著差异,但是同侧视野整合野的作用强度明显弱于对侧视野。以上结果提示,初级视皮层神经元能够对大范围内的图形特征进行整合,这种整合作用来自两侧视野。     

中国主要五针松群落学特征及其生物量的研究

本文根据现有的文献资料,系统地分析了中国五针松的分布．群落学特征,按不同分布区、不同群落类型探讨了中国五针松的群落生物量和年净生产量及在群落的不同层次上的分布．比较分析了不同分布区五针松的年干物质累积速度（ＮＰ／Ｂ）．结果表明：１１５─１３５ａ生的阔叶红松林群落生物量在９７．０９─１２０．５１ｔ／ｈｍ￣２之间,年净生产量在８．６９８─１０．３４ｔ／ｈｍ￣２．ａ之间,年净生产量长白山山脉沙松、鹅耳枥红松林＞小兴安岭南坡枫桦、水曲柳红松林＞小兴安岭北坡云杉、冷杉红松林;３０─３６ａ生的华山松林群落生物量在７８．７５─９４．７３ｔ／ｈｍ￣２之间,年净生产量在４．９９３─５．５３７ｔ／ｈｍ￣２．ａ之间,年净生产量贵州山地常绿阔叶华山松林＞秦岭中山地阔叶华山松林＞甘肃小陇山针阔叶华山松林．ＮＰ／Ｂ值：长白山山脉的阔叶红松林＞小兴安岭山脉的阔叶红松林;秦岭中山地阔叶华山松林＞甘肃小陇山针阔华山松林＞贵州中山地常绿阔叶华山松林．     

昆虫神经毒素的研究:各种神经毒剂引起毒素的产生

用五类(七种)神经毒性的杀虫药剂,对美洲(虫非)蠊测定了它们能否引起血淋巴中毒素的产生。DDT、溴氰菊酯及六六六均能引起血淋巴中毒素的产生,而E605、西维因、巴丹及杀虫脒均无此效果。纸层析及薄层层析,用标准样品(酪氨酸、酪胺、苯乙胺、L-亮氨酸及异戊胺)作比较,测定了这一产生的血淋巴中的毒素乃是酪胺,或主要是酪胺。增效试验,证明了杀虫脒与DDT或溴氰菊酯合用时,能增加酪胺的产量。讨论了这一毒素产生的条件,以及这一毒素有可能不是单一成分,而是几种单胺及氨基酸的复合物,但酪胺为其主要成分。     

我国西部地区蚤目四种未知雌性的记述

本文系青海省蚤目研究的第四报。首次记述蚤目的四种未知雌性。雄性根据我国西藏采获的标本已先后有人记述:近缘纤蚤Rhadinopsylla accola Wagner,1930;端圆盖蚤Callopsylla kozlovi(Wagner.1929);卷带倍蚤Amphalius sptrataenius Liu,Wu ＆ Wu,1966;短突角叶蚤Ceratophyllus breviprolectus Liu,Wu ＆ Wu,1966。     

Mycotoxin Producing Potential of Fungi Associated with Dry Shrimps

Among 114 fungi isolated from 20 dry shrimp samples, 27 isolates were capable of producing mycotoxins. Aspergillus and Penicillium were-the-predominant fungi. Two of 3 Aspergillus flavus could produce aflatoxin B₁ and G₁ on yeast extract sucrose medium and on surface sterilized dry shrimps. For other toxigenic species, toxicity was found mostly in the chloroform extracts of cultures. Visibly mouldy dry shrimps had significantly higher moisture content than the non-mouldy ones. Most of the fungi were isolated from mouldy samples.     

性信息素对红铃虫雄蛾近距离性行为的抑制效应

鳞翅目昆虫雄蛾在交配之前的性行为可以分为远距离对雌蛾的定向和包括着陆、搜索、交配等直接导致雌、雄蛾交配成功的近距离行为。这两类不同的行为可由复合性信息素中的不同化学成分引起(Roelofs et al.,1977)或者由同种物质不同浓度所诱发,即雄蛾接受较低浓度刺激时出现远距离定向飞行;而高浓度诱发雄蛾近距离的交配性行为反应(Bartell et al.,1969)。从棉花红铃虫[Pectinophora gossypiella(Saund.)]雌蛾体内已经鉴定得到两种化学成份,顺-7,顺-11-十六碳二烯醇醋酸酯和顺-7,反-11-十六碳二烯醇醋酸酯。这两种成份的1:1混合物称为红铃虫性诱素(Gossyplure)(Hummel et al.,1973),它具有在田间引诱红铃虫雄蛾和诱发雄蛾近距离行为反应的作用。 在田间释放性信息化合物来扰乱雌、雄蛾之间的性信息联系,从而抑制其交配和繁殖是一种有希望的害虫防治方法。用红铃虫性诱素扰乱红铃虫交配的田间试验已取得一定成效(Gaston et al.,1977)。但是我们在田间试验中发现,性诱素抑制红铃虫雄蛾远距离定向后,田间还有相当比例的雌蛾发生了交配,这个现象表明,性诱素还未能完全抑制红铃虫雄蛾的近距离行为。为此我们进行了本项试验,用以阐明环境中红铃虫性诱素的存在对雄蛾近距离性行为的影响。