Effect of hexavalent chromium on eukaryotic plasma membrane studied by EPR spectroscopy

The effect of Cr(VI) anion on an ergosterol-producing strain of eukaryotic yeast Candida albicans and its mutant with ergosterol-less membrane was studied with EPR spectroscopy. 5- and 14-doxyl stearic acid spin probes were used to label the protoplast membrane after removal of the cell wall. In control experiments, the mutant strain exhibited larger rigidity in the membrane than its parental strain. Addition of Cr(VI), at a minimum inhibitory concentration of 0.6 mM, increased the rotational mobility of the spin labels significantly and decreased the temperature of the structural changes in both strains, in the temperature range between 0 and 30 degrees C. The ergosterol-less mutant, having a membrane composition with increased polyunsaturated fatty acid content, exhibited higher Cr(VI) sensitivity. Treatment of the membrane with Cr(VI) for 10 min already resulted in an increase in membrane fluidity. An EPR signal of Cr(V) was detected which reached maximum amplitude after 120 min of treatment with Cr(VI). Further chemical reduction of Cr(V) in the absence of extracellular Cr(VI) led to a lack of detectable paramagnetic chromium intermediates within 200 min.     

斯氏黄河猴(哺乳动物纲,灵长目)较完整下颌骨的发现

新发现的下颌骨说明斯氏黄河猴下齿式为 ２？, １,３, ３。 ｐ２为双根齿,其前后有短的齿隙;ｐ３具有低小的后跟;ｐ４未臼齿化,无下前尖,有初始的下后尖,在较大的跟盆上,有明显的下次尖和很小的下内尖？; ｍ１下前尖小,有些前后收缩（与Ｒｅｎｃｕｎｉｕｓ ｚｈｏｗｉ比较）,ｍ３下次小尖不如正模发育。下颌骨联合部倾斜,不愈合。黄河猴的下臼齿在形态上与西瓦兔猴亚科和原始类人猿──渐新猿亚科有许多共同点,但上臼齿形态差异显著。黄河猴类可能出自亚洲的ｃｅｒｃａｍｏｎｉｉｎｅ形的兔猴形灵长类。     

金小蜂科一新属(膜翅目:小蜂总科)

本文记述了我国金小蜂科、寡金小蜂亚科的１新属和１新种。模式标本存于中国科学院动物研究所动物标本馆。     

Mosaic evolution of ruminant stomach lysozyme genes

The genomes of ruminant artiodactyls, such as cow and sheep, have approximately 10 lysozyme genes, 4 of which are expressed in the stomach. Most of the duplications of the lysozyme genes occurred 40-50 million years ago, before the divergence of cow and sheep. Despite this, the coding regions of stomach lysozyme genes within a species (e.g., cow, sheep, or deer) are more similar to each other than to lysozyme genes in other ruminants. This observation suggests that the coding regions of the stomach lysozyme genes have evolved in a concerted fashion. Our previous characterization of 3 cow stomach lysozyme genes suggested that it was only the coding exons that had participated in concerted evolution. To determine whether the introns and flanking regions of ruminant stomach lysozyme genes are evolving in a concerted or a divergent fashion, we have isolated and characterized 2 sheep stomach lysozyme genes. Comparison of the sequences of the sheep and cow stomach lysozyme genes clearly shows that the introns and flanking regions have evolved, like the 3' untranslated region of the mRNAs, in a divergent manner. Thus, if the four coding exons are evolving by concerted evolution, then a mosaic pattern of concerted and divergent evolution is occurring in these genes. The independent concerted evolution of coding exons of the ruminant stomach lysozyme gene may have assisted in the accelerated adaptive evolution of the lysozyme to new function in the early ruminant.     

氚—烟酰苯胺在钉螺体内分布示踪的研究

本文应用氚－烟酰苯胺标记湖北钉螺，示踪观察不同时间烟酰苯胺进入螺体组织和脏器内的分布和进入途径。结果显示，钉螺接触药物从２２分钟开始检测出组织、脏器内氚含量，以后逐渐增高，至１４４０分钟达最高峰；合计不同时间各组织和脏器中药物含量由高至低排列次序为外套膜、胃肠、肝脏、肠内粪梗、睾丸、卵巢、鳃、神经节、心脏；转换氚含量为烟酰苯胺剂量，证实了烟酰苯胺杀螺的低用量与高效性；由单位重量组织和脏器中药物含量排位，反映出药物在螺体分布动态变化，以及药物通过消化系统、呼吸系统、外套膜表皮三条途径进入。     

Effect of oxygen transfer on lipase production by Acinetobacter radioresistens

The influence of oxygen on alkaline lipase production by Acinetobacter radioresistens was studied under two operating modes: controlled dissolved oxygen (DO) concentration and controlled aeration rate. Compared with cell growth, the lipase production depended more extensively on oxygen. The intrinsic factor determining cell growth and lipase production was oxygen transfer rate (OTR) rather than DO concentration. Improvements in OTR, either by aeration or agitation, resulted in an increase in lipase yield and/or a reduction in fermentation time. The formation of A. radioresistens lipase could be described by a mixed-growth-associated model, and the enzyme was mainly a growth-associated product. The overall productivity for the lipase, which depended more strongly on agitation than aeration, could be related with kLa. DO concentration could not be employed in this correlation, though it has been useful as a criterion for ensuring no oxygen limitation in an aerobic fermentation.     

Induced fit activation mechanism of the exceptionally specific serine protease, complement factor D

We have investigated the mechanism by which the complement protease, Factor D, achieves its high specificity for the cleavage of Factor B in complex with C3(H2O). Kinetic experiments showed that Factor B and C3(H2O) associate with a KD of >/=2.5 microM and that Factor D acts on this complex with a second-order rate constant of kcat/KM >/= 2 x 10(6) M-1 s-1, close to the rate of a diffusion-controlled reaction for proteins of this size. In contrast, Factor D, which is a member of the trypsin family of serine proteases, was 10(3)-10(4)-fold less active than trypsin toward both thioester and p-nitroanilide substrates containing an arginine at P1. Furthermore, peptides spanning the Factor B cleavage site were not detectably cleaved by Factor D (kcat/KM /=9 kcal/mol of binding energy to stabilize the transition state for reaction. In support of this, we demonstrate that chemical modification of Factor D at a single lysine residue that is distant from the active site abolishes the activity of the enzyme toward Factor B while not affecting activity toward small synthetic substrates. We propose that Factor D may exemplify a special case of the induced fit mechanism in which the requirement for conformational activation of the enzyme results in a substantial increase in substrate specificity.     

猫基底前脑胆碱能皮质投射神经元区的P物质样免疫反应神经元

应用免疫组织化学和邻位切片法,研究了猫基底前脑胆碱能皮质投射神经元区的Ｐ物质样免疫反应神经元的分布特征,及其与胆碱乙酰化酶样免疫反应神经元的分布关系,从内侧隔核至Ｍｅｙｎｅｒｔ基底核,２种神经元分布范围相近,且形态,大小相似。但在邻位切片,未见分别呈此二免疫反应的同一神经元的对应剖面。Ｐ物质样免疫反应神经元在内侧隔核和斜角带核数量较多,但在基底核明显减少,在Ｃｈ４间质部及腹侧苍白球连合下部仅为偶见