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.     

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.     

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。     

鲥鱼的驯养与生物学研究Ⅰ.O~+龄幼鱼的生长与食性

本文主要描述池塘养殖条件下鲥鱼幼鱼的生长与食性。1)1987—1989年8月至11月幼鱼生长迅速,快于同期珠江天然个体的生长速度;2)体长26.6—94.9mm的幼鱼主要摄食浮游动物,轮虫和浮游植物出现率随个体增大而减少。食物共有18个属种,摄食频度为100％;3)幼鱼的平均饱满指数为75.70‰。各类食物重量百分比的顺序为:桡足类>枝角类>无节幼体>虾类溞状幼体>轮虫>藻类。     

Further investigation on nuclear transplantation in different orders of teleost: the combination of the nucleus of Tilapia (Oreochromis nilotica) and the cytoplasm of Loach (Paramisgurnus dabryanus).

The nucleus of a blastula cell from Tilapia (Oreochromis nilotica, family Cichlidae, order Perciformes) was transplanted into an enucleated egg of Loach (Paramisgurnus dabryanus, family Cobitidae, order Cypriniformes). From among 3747 nucleo-cytoplasmic hybrid (NCH) eggs two NCH larval fish (0.05%) were obtained; one died on the 6th day and the other died on the 12th day after the operation. Morphological examinations showed that both NCH larval fish had developed normally with an opened mouth except they could not take food after complete utilization of their egg yolk on the 5th day of development. The possible mechanisms for obtaining such inter-order NCH larval fish are discussed. This is the first report indicating that inter-order NCH larval fish can be obtained in spite of their evolutionary divergence.     

Electrostatic destabilization of the cytochrome b6f complex in the thylakoid membrane.

Three of the membrane-spanning polypeptides of the chloroplast cytochrome (cyt) b6f complex were sequentially released from the thylakoid membrane, in the order cyt b6, suIV and Rieske iron-sulfur protein, as the pH was increased from 10 to 12, a protocol usually employed to remove peripheral proteins from membranes. The fourth polypeptide of the cyt b6f complex, cyt f, which spans the membrane once, was apparently not released. The pH values for half-release at low ionic strength were approximately 10.7, 11.1 and 11.3 respectively. The separation of the polypeptides of the complex and the sequential release is readily seen at pH 11, where the loss from the membrane of cyt b6, suIV and Fe iron-sulfur center is approximately 90%, 50% and 20%, respectively. the release of cyt b6 from the membrane was reflected by the absence of its characteristic reduced minus oxidized absorbance signal. The pH values at which the release occurred increased as the ionic strength was raised, implying that the release of the b6f polypeptides arises from extrusion due to repulsive electrostatic interactions probably caused by deprotonation of tyrosine and lysine residues. The lipid content of the released polypeptides was very low, consistent with the observation of a non-membranous state. It is proposed that the pH-dependent extrusion requires two electrostatic effects at alkaline pH higher than approximately 10.5: (i) increased electrostatic repulsion between neighbouring polypeptides of the complex, arising from increased net negative charge in the peripheral segments of these polypeptides, which can cause separation of the polypeptides from the complex; and (ii) ionization of residues such as tyrosine in the membrane-spanning alpha-helices, and neutralization of residues such as lysine which can bind to the negative membrane surface.(ABSTRACT TRUNCATED AT 250 WORDS)