The majority of cells infected with the defective murine AIDS virus belong to the B-cell lineage.

Murine AIDS (MAIDS) is caused by a defective retrovirus which encodes a gag fusion protein (Pr60gag). We previously reported that this virus induced an oligoclonal proliferation of infected cells and suggested that this cell expansion was an important event in the pathogenesis of MAIDS. To identify these target cells, we constructed novel defective viruses whose genomes could be detected with specific probes. Helper-free stocks of these viruses induced MAIDS. Using in situ hybridization and immunocytochemistry and Southern analysis, we found that most infected cells belong to the B-cell lineage. Transformation of these B cells appears to be the primary event responsible for the development of immunodeficiency. This animal model may be relevant to our understanding of AIDS, of the immunodeficiencies associated with B-cell lymphoproliferative disorders, and of the role of B-cell proliferation and transformation in the effects of superantigens, since Pr60gag appears to be a superantigen.     

Splenocyte subsets in normal and protein malnourished mice after long-term exposure to cocaine or morphine

An experimental model which resembles human drug addiction was developed to study the effect of chronic drug (cocaine or morphine) administration on the immune system. As malnutrition has been associated with drug use, a low protein diet has been evaluated for its contribution to the impairment of the immune system during cocaine/morphine addiction. Female C57BL/6 mice that received a 20% or 4% casein diet were studied. Both drugs were administered intraperitoneally daily for 11 weeks and drugs were administered in increasing daily doses, beginning after 3 weeks of diet consumption. Doses of cocaine began with 5 mg/kg body weight and reached the maximum dose of 40 mg/kg/day at the fourth week. Doses of morphine gradually increased from 10 mg/kg to 75 mg/kg body weight with the maximum dose reached after 5 weeks of treatment. Cocaine administration reduced body weight, particularly in the low protein diet group, and spleen weight in protein malnourished mice. Cocaine as well as saline injected mice showed a decrease in the percentage of CD4+ CD8+ and Mac-1+ cells and an increase in B cells in the spleens of well nourished mice. Morphine-treated mice showed similar results to those observed in cocaine or saline treated mice. These results suggest that cocaine, morphine or saline injection can alter the percentage of cells that express a defined phenotype independently of the nutritional status of the subject. Moreover, the effect appears dependent on a stress mediated process.     

Detection and activity of a bacteriocin produced by Leuconostoc mesenteroides.

Leuconostoc mesenteroides UL5 was found to produce a bacteriocin, referred as mesenterocin 5, active against Listeria monocytogenes strains but with no effect on several useful lactic acid bacteria. The antimicrobial substance is a protein, since its activity was completely destroyed following protease (pronase) treatment. However, it was relatively heat stable (100 degrees C for 30 min) and partially denaturated by chloroform. The inhibitory effect of the bacteriocin on sensitive bacterial strains was determined by a critical-dilution micromethod. Mutants of L. mesenteroides UL5 which had lost the capacity to produce the bacteriocin were obtained. The mutant strain was stable and phenotypically identical to parental cells and remained resistant to the bacteriocin. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis was used to detect bacteriocin activity corresponding to an apparent molecular mass of about 4.5 kDa.     

Changes in pulmonary Cu−Zn contents in superior mesenteric artery occlusion shock of rabbit

Contents of Cu and Zn of into-pulmonary blood (IPB), out-pulmonary blood (OPB), Lung tissue, and supernatant and macrophages of Lung Lavage were determined in superior mesenteric artery occlusion (SMAO) shock of rabbits. Zn of pulmonary tissue was 11.42 +/- 0.60 and 14.52 +/- 1.78 (micrograms/g wet wt) in SMAO shock and control groups, respectively. Content of Zn was found to be lower, Cu was not changed, and Cu/Zn ratio increased in lung tissue in SMAO shock. Contents of Cu and Zn in other samples were not changed. The results suggest that lower Zn in lung tissue related to acute lung injury.     

Crystal structure of the Y52F/Y73F double mutant of phospholipase A2: increased hydrophobic interactions of the phenyl groups compensate for the disrupted hydrogen bonds of the tyrosines.

The enzyme phospholipase A2 (PLA2) catalyzes the hydrolysis of the sn-2 ester bond of membrane phospholipids. The highly conserved Tyr residues 52 and 73 in the enzyme form hydrogen bonds to the carboxylate group of the catalytic Asp-99. These hydrogen bonds were initially regarded as essential for the interfacial recognition and the stability of the overall catalytic network. The elimination of the hydrogen bonds involving the phenolic hydroxyl groups of the Tyr-52 and -73 by changing them to Phe lowered the stability but did not significantly affect the catalytic activity of the enzyme. The X-ray crystal structure of the double mutant Y52F/Y73F has been determined at 1.93 A resolution to study the effect of the mutation on the structure. The crystals are trigonal, space group P3(1)21, with cell parameters a = b = 46.3 A and c = 102.95 A. Intensity data were collected on a Siemens area detector, 8,024 reflections were unique with an R(sym) of 4.5% out of a total of 27,203. The structure was refined using all the unique reflections by XPLOR to a final R-factor of 18.6% for 955 protein atoms, 91 water molecules, and 1 calcium ion. The root mean square deviation for the alpha-carbon atoms between the double mutant and wild type was 0.56 A. The crystal structure revealed that four hydrogen bonds were lost in the catalytic network; three involving the tyrosines and one involving Pro-68. However, the hydrogen bonds of the catalytic triad, His-48, Asp-99, and the catalytic water, are retained. There is no additional solvent molecule at the active site to replace the missing hydroxyl groups; instead, the replacement of the phenolic OH groups by H atoms draws the Phe residues closer to the neighboring residues compared to wild type; Phe-52 moves toward His-48 and Asp-99 of the catalytic diad, and Phe-73 moves toward Met-8, both by about 0.5 A. The closing of the voids left by the OH groups increases the hydrophobic interactions compensating for the lost hydrogen bonds. The conservation of the triad hydrogen bonds and the stabilization of the active site by the increased hydrophobic interactions could explain why the double mutant has activity similar to wild type. The results indicate that the aspartyl carboxylate group of the catalytic triad can function alone without additional support from the hydrogen bonds of the two Tyr residues.     

A general approach toward the design of inhibitors of serine proteinases: inhibition of human leukocyte elastase by substituted dihydrouracils

A general approach toward the rational design of potential inhibitors of serine proteinases is described. The approach is exemplified and validated through the use of appropriate heterocyclic systems in inhibiting human leukocytes elastase (HLE).     

羊蹄甲属植物种子的裂解色谱鉴定法研究

本文探索了裂解气相色谱法作为植物种子分类表征方法的可能性。对豆科植物中不同属、不同亚属及相同亚属的共10种种子的裂解色谱图,用分区编码法进行区别,分析结果表明,不同种子最少有一个编码不同,方法简易快速,可为高等植物种子的区分提供一种佐证手段。     

广西南宁、柳州、桂林城市园林植物的调查与分析

于1988年春,对广西南宁、柳州、桂林市区的园林植物作了全面调查。结果如下:1)三市区园林植物较丰富,其中南宁市351种隶属245属108科;柳州76科152属198种;桂林76科144属172种。2)园林植物的性状组成中,乔木占50—60％;灌木占20—30％,草本和藤本分别占15%和5%。3)园林植物的主要科是桑科、大戟科、棕榈科、木兰科、桃金娘科、苏木科、蔷薇科、樟科等;优势种是扁桃、人面子、柠檬桉、羊蹄甲、芒果、阴香、樟树、榕树、桂花、银桦、大红花、夹竹桃、九里香、正木等。4)园林植物的区系成分以热带—亚热带为主。5)园林植物的分布以公园最为丰富,其种数占总种数的67—87％,街道和阳台分别为43％和30％。6)不同市区园林植物的优势科、优势种、区系成分、生态外貌有明显差异,反映出各自的特点。与当地自然景观相一致。最后,在调查分析的基础上,对城市园林绿化的发展问题讨论。