Purification of human plasma retinol-binding protein by hydrophobic interaction chromatography

Human plasma retinol-binding protein has been purified to homogeneity by a simple method that requires an ammonium sulfate fractionation, a hydrophobic interaction chromatography on phenyl-Sepharose, which dissociates the complex between retinol-binding protein and its carrier, transthyretin, and a gel filtration on Sephadex G-50. The yield of pure protein is comparable or higher than that obtained with the more complex procedures previously reported.     

A mechanism for rich-medium inhibition of the repair of daughter-strand gaps in the deoxyribonucleic acid of UV-irradiated Escherichia coli K12 uvrA

Ultraviolet-irradiated Escherichia coli K12 uvrA(B,C) cells show higher survival if plated on minimal growth medium (MM) rather than on rich growth medium (RM). This phenomenon has been referred to as 'minimal medium recovery' (MMR). UV-irradiated (4 J/m2) uvrA cells showed a similar rate of protein synthesis, whether incubated in MM or RM, however, they showed a severe depression in DNA synthesis when incubated in MM that lasted for about 30 min, and the normal rate of DNA synthesis was not reestablished until about 60 min after irradiation. When a sample of these same cells was switched to RM immediately after UV-irradiation, there was only a slight slowing of DNA synthesis, and the normal rate of synthesis was reestablished by 60 min. An additional mmrA mutation or growth retardation by valine blocked both this extra DNA synthesis in RM, and the inhibitory effect of RM on survival. These findings suggest that the absence of a marked delay in DNA synthesis observed in RM may be responsible for the inhibitory effect of RM on the survival of UV-irradiated excision-deficient cells. Two hypotheses, which are not mutually exclusive, are proposed and supported by data to explain why a fast rate of DNA synthesis after UV-irradiation partially inhibits postreplication repair and enhances cell lethality.     

Changes in synthetic activity of cell walls during the cell cycle in a synchronous culture of Catharanthus roseus

The incorporation rates of [¹⁴C] glucose into various fractions of the cell walls and into the sugar constituent of each fraction were investigated in a synchronous culture of Catharanthus roseus (L.) G. Don in order to elucidate the synthetic aspects of the cell walls during the cell cycle. Changes in the incorporation of radioactivity were closely correlated with changes in the amount of each cell wall fraction as well as with those in sugar composition as reported previously (S. Amino et al. Physiol. Plant. 60: 326–332, 1984). The specific activity of galactose was higher than that of other sugars throughout the cell cycle, and a temporary increase in the incorporation of radioactivity into all cell wall fractions except cellulose was observed just before the increase in cell numbers. The synthetic activities may play key roles in the regulation of cell wall polysaccharide dynamics during the cell cycle.     

Uptake of free amino acids by the diatom,Melosira mediocris

Individual ¹⁴C-labelled amino acids are rapidly removed from dilute solution in artificial sea water (0.2 mol 1^–1) by suspensions of Meliosira medocris. The rate of disappearance of radioactivity corresponds closely to removal of primary amines as determined by measurement of the rate of decrease of fluorescamine-positive material. Net removal of naturally occurring free amino acids from the sea water habitat from which the alga was isolated is demonstrated using high performance liquid chromatography. Removal of amino acids from natural sources makes a significant contribution to the carbon requirements of the alga as well as supplying significant amounts of amino nitrogen.     

Diversity in the immune system: “Preconceived ideas” or ideas preconceived?

Two concepts of the evolution and regulation of expression of the combining site repertoire of the immune system, are compared. One view is based on the Associative Recognition Theory as formulated by the author and the other is based on the Idiotype Network Idea as conceived by Jerne. The two concepts are analyzed from the point of view of their logic, internal consistency and factual support.     

Stereospecific formation of 1,2-epoxypropane, 1,2-epoxybutane and 1-chloro-2,3-epoxypropane by alkene-utilizing bacteria

Resting cells of ethene grown Mycobacterium 2W produced 1,2-epoxypropane stereospecifically from propene as revealed by optical rotation, ¹H n.m.r. using a chiral shift reagent, and also by complexation gas chromatography involving a glass capillary column coated with an optically active metal chelate. The gas-liquid chromatography method allowed the rapid screening of 11 strains with regard to stereospecific formation of 1,2-epoxypropane, 1,2-epoxybutane and 1-chloro-2,3-epoxypropane. Bacteria grown on either ethene, propene or butadiene all predominantly produced the R form of 1,2-epoxypropane from propene and 1,2-epoxybutane from 1-butene while the strains tested for 1-chloro-2,3-epoxypropane production from 3-chloro-1-propene predominantly accumulated the S enantiomer.     

The araBAD operon of Salmonella typhimurium LT2. I. Nucleotide sequence of araB and primary structure of its product, ribulokinase

Hybrid plasmids containing the araBAD operon of Salmonella typhimurium LT2 were characterized by Southern blot and genetic analyses. The nucleotide sequence of araB was determined. The araB gene product, ribulokinase (EC 2.7.1.16), was purified and the results of amino acid composition analysis and partial amino acid sequence are in agreement with predictions from the DNA sequence. Ribulokinase is 569 amino acid residues long and has a calculated Mr of 61 793. Ribulokinase shares significant homology with xylulose kinase from Escherichia coli. Codon usage in the araB gene does not favor those codons which have intermediate codon-anticodon binding energy.     

肿瘤坏死因子受体超家族成员在免疫系统和疾病中的研究

肿瘤坏死因子受体超家族 (tumor necrosis factor receptor superfamily, TNFRSF) 是细胞因子受体的一个蛋白质超家族,其显著特征是通过细胞外富含半胱氨酸结构域结合肿瘤坏死因子(tumor necrosis factor,TNF)。肿瘤坏死因子受体(tumor necrosis factor receptors,TNFRs)是古老的细胞因子,TNFRs同源基因最早可追溯到节肢动物果蝇中。TNFRs在炎症反应、细胞凋亡、淋巴细胞稳态和组织发育中发挥重要的作用,TNFRs最主要的功能是与免疫系统相关。鉴于其在免疫系统中发挥重要的作用,肿瘤坏死因子受体家族成员已成为治疗糖尿病、动脉粥样硬化、骨质疏松、自身免疫性疾病、移植排斥反应和癌症等人类疾病的靶点。随着科学技术发展,关于TNFRs的功能有了新的进展,在无脊椎动物和低等脊椎动物中已经有大量报道。在本篇综述中,主要总结了在高等哺乳动物中发现的29种TNFR成员的相关报道,包括8种死亡受体和21种非死亡受体,主要涉及在免疫系统以及与疾病相关领域的研究。大多数研究处于基础实验阶段,少数走向临床研究的案例取得的临床效果并不理想,靶向设计针对自身免疫性疾病、炎症和肿瘤疾病的治疗方案需要更深入的理解TNFRs功能。本文旨在对TNFRs成员发挥的功能有进一步的认识。     

七鳃鳗p38α和β参与LPS介导的VLRB类淋巴细胞亚群的免疫应答反应

p38MAPK是丝裂原活化蛋白激酶（mitogen activated protein kinases,MAPK）家族的一个亚类,在高等脊椎动物免疫应答的信号转导过程中扮演着非常重要的角色。在日本七鳃鳗（Lampetra japonica）中发现,p38MAPK以两种异构体的形式存在。通过克隆它们的开放阅读框并进行同源序列比对和系统发育分析,鉴定它们分别为p38α（Lja-mapk14）和p38β（Lja-mapk11）。用混合菌刺激七鳃鳗,利用免疫印迹方法,检测Lja-mapk14在外周血类淋巴细胞、鳃组织和髓样小体中,分别在加强免疫36 h、24 h和24 h后,表达量达到峰值,分别为对照组的2.9、2.1和2.6倍;而Lja-mapk11在以上组织中,都在加强免疫36 h后达到表达量峰值,分别为对照组的2.2、2.5和6.3倍。实时荧光定量PCR检测发现,Lja-mapk14的mRNA表达水平在混合菌加强免疫36 h后,分别在类淋巴细胞、鳃组织和髓样小体中,上调2.3、1.5和3.4倍;而Lja-mapk11的则分别在类淋巴细胞、鳃组织和心肌中,上调1.3、2.6和1.6倍。以上结果在mRNA和蛋白质水平证明,Lja-mapk14和Lja-mapk11均参与七鳃鳗的免疫应答反应。采用B细胞和T细胞丝裂原LPS和PHA分别对七鳃鳗进行刺激,免疫印迹结果显示,Lja-mapk14和Lja-mapk11蛋白质表达量经LPS加强免疫36 h后,在类淋巴细胞、鳃组织和髓样小体中,上调表达1.3 ～ 4.1倍;而经PHA加强免疫36 h后,Lja-mapk14和Lja-mapk11在上述组织中表达量均不存在显著变化。以上结果说明,Lja-mapk14和Lja-mapk11可能参与了B细胞丝裂原LPS介导的VLRB类淋巴细胞亚群的免疫应答反应。