Sensitivity of Escherichia coli to cephaloridine at different growth rates.

Steady-state populations of Escherichia coli B/r were treated with cephaloridine at minimal inhibitory concentrations. The antibiotic sensitivity of the cells and the localization of spheroplast emergence along the cell surface were examined as a function of cell length and growth rate. In fast-growing populations (greater than 1 division per h) the sites of cephaloridine interaction occurred preferentially at the cell pole in the smaller cells and at the cell center in dividing cells. At decreasing growth rates the cells became more resistant to cephaloridine, and a gradual shift from the cell pole toward the cell center was observed for the sphere position. A similar growth rate-dependent change in localization was found for sucrose-induced plasmolysis vacuoles.     

中国西北沙漠夜间活动的东鳖甲属昆虫二新种(鞘翅目:拟步甲科:漠甲亚科)

记述中国西北地区东鳖甲属2新种:巴丹东鳖甲A.badainica Ba,Ren&Liu sp.nov.和古尔班东鳖甲A.gurbantunggutica Ba&Ren sp.nov.,提供了主要鉴别特征和形态图,并简要讨论了其昼夜活动规律.     

Haemosporidian Parasites of Antelopes and Other Vertebrates from Gabon,Central Africa

Re-examination, using molecular tools, of the diversity of haemosporidian parasites (among which the agents of human malaria are the best known) has generally led to rearrangements of traditional classifications. In this study, we explored the diversity of haemosporidian parasites infecting vertebrate species (particularly mammals, birds and reptiles) living in the forests of Gabon (Central Africa), by analyzing a collection of 492 bushmeat samples. We found that samples from five mammalian species (four duiker and one pangolin species), one bird and one turtle species were infected by haemosporidian parasites. In duikers (from which most of the infected specimens were obtained), we demonstrated the existence of at least two distinct parasite lineages related to Polychromophilus species (i.e., bat haemosporidian parasites) and to sauropsid Plasmodium (from birds and lizards). Molecular screening of sylvatic mosquitoes captured during a longitudinal survey revealed the presence of these haemosporidian parasite lineages also in several Anopheles species, suggesting a potential role in their transmission. Our results show that, differently from what was previously thought, several independent clades of haemosporidian parasites (family Plasmodiidae) infect mammals and are transmitted by anopheline mosquitoes.     

Molecular basis of ion permeability in a voltage‐gated sodium channel

Voltage‐gated sodium channels are essential for electrical signalling across cell membranes. They exhibit strong selectivities for sodium ions over other cations, enabling the finely tuned cascade of events associated with action potentials. This paper describes the ion permeability characteristics and the crystal structure of a prokaryotic sodium channel, showing for the first time the detailed locations of sodium ions in the selectivity filter of a sodium channel. Electrostatic calculations based on the structure are consistent with the relative cation permeability ratios (Na⁺ ≈ Li⁺ ≫ K⁺, Ca²⁺, Mg²⁺) measured for these channels. In an E178D selectivity filter mutant constructed to have altered ion selectivities, the sodium ion binding site nearest the extracellular side is missing. Unlike potassium ions in potassium channels, the sodium ions in these channels appear to be hydrated and are associated with side chains of the selectivity filter residues, rather than polypeptide backbones.     

Genetic evidence of an essential role for cytomegalovirus small capsid protein in viral growth

Many steps in the replication cycle of cytomegalovirus (CMV), like cell entry, capsid assembly, and egress of newly synthesized virions, have not been completely analyzed yet. In order to facilitate these studies, we decided to construct a recombinant CMV that incorporates the green fluorescent protein (GFP) into the nucleocapsid. A comparable herpes simplex virus type 1 (HSV-1) mutant has recently been generated by fusion of the GFP open reading frame (ORF) with the HSV-1 ORF encoding small capsid protein (SCP) VP26 (P. Desai and S. Person, J. Virol. 72:7563-7568, 1998). Recombinant CMV genomes expressing a fusion protein consisting of GFP and the SCP were constructed by the recently established bacterial artificial chromosome mutagenesis procedure. In transfected cells, the SCP-GFP fusion protein localized to distinct foci in the nucleus that may represent sites for capsid assembly (assemblons). However, no viable progeny was reconstituted from these mutant CMV genomes. CMV genomes with deletion of the SCP ORF also did not give rise to infectious virus. Rescue of the mutation by insertion of the SCP gene at an ectopic position in an SCP knockout genome indicates that, in contrast to the HSV-1 SCP, the CMV SCP is essential for viral growth. Expression of the SCP-GFP fusion protein together with the authentic SCP blocked the CMV infection cycle, suggesting that the SCP-GFP fusion protein exerts a dominant-negative effect on the assembly of new virions. The results of this study are discussed with regard to recently published data about the structure of the CMV virion and its differences from the HSV-1 virion.     

Efficacy of hyaluronic acid binding assay in selecting motile spermatozoa with normal morphology at high magnification

Background  

The present study aimed to evaluate the efficacy of the hyaluronic acid (HA) binding assay in the selection of motile spermatozoa with normal morphology at high magnification (8400x).     

基于ISSR标记的辽宁4个东北林蛙种群遗传多样性分析

辽宁是东北林蛙Rana dybowskii主要分布地之一,种群数量巨大,其群体遗传多样性有待评估.本研究应用ISSR标记技术对东北林蛙4个种群105个样本进行研究,5个引物共获得44条清晰谱带,4个种群的多态位点率均大于75%,Nei's基因多样性为0.2851,Shannon信息指数为0.4476,显示了较高的遗传多样性.对遗传分化系数、Nei's遗传距离、AMOVA分子变异巢式方差分析和F-统计量等遗传参数的统计结果表明,辽宁东北林蛙种群间已经出现一定程度的遗传分化,分析认为,自然屏障(高山和平原等)以及栖息地片段化是其遗传分化形成的主要因素.