安全的霍乱活菌苗?

<正> 当前使用的霍乱菌苗有两大类,一是由全菌体加或不加毒素B亚单位组成的死菌苗,给苗途径可肠道外或口服;二是口服活菌苗,由霍乱弧菌基因工程减毒株或由表达霍乱抗原的异源载体菌(即伤寒Tyzla)组成。前一类费钱效果不理想,后一类有反应原性、变异性和稳定性方面的问题。 最近,我们鉴别出了菌毛定居因子(协同调节的毒素菌毛( toxin coregulated pil-usTCP),它可能是审定菌苗可否应用的一种重要的新免疫原。本文介绍TCP菌毛应用于霍乱菌苗研究中的一些初步结果。     

Sex differences in the electrocommunication signals of the electric fish Apteronotus bonapartii

The South American weakly-electric knifefish (Apteronotidae) produce highly diverse and readily quantifiable electrocommunication signals. The electric organ discharge frequency (EODf), and EOD modulations (chirps and gradual frequency rises (GFRs)), vary dramatically across sexes and species, presenting an ideal opportunity to examine the proximate and ultimate bases of sexually dimorphic behavior. We complemented previous studies on the sexual dimorphism of apteronotid communication signals by investigating electric signal features and their hormonal correlates in Apteronotus bonapartii, a species which exhibits strong sexual dimorphism in snout morphology. Electrocommunication signals were evoked and recorded using a playback paradigm, and were analyzed for signal features including EOD frequency and the structure of EOD modulations. To investigate the androgenic correlates of sexually dimorphic EOD signals, we measured plasma concentrations of testosterone and 11-ketotestosterone. A. bonapartii responded robustly to stimulus playbacks. EODf was sexually monomorphic, and males and females produced chirps with similar durations and amounts of frequency modulation. However, males were more likely than females to produce chirps with multiple frequency peaks. Sexual dimorphism in apteronotid electrocommunication signals appears to be highly evolutionarily labile. Extensive interspecific variation in the magnitude and direction of sex differences in EODf and in different aspects of chirp structure suggest that chirp signals may be an important locus of evolutionary change within the clade. The weakly-electric fish represent a rich source of data for understanding the selective pressures that shape, and the neuroendocrine mechanisms that underlie, diversity in the sexual dimorphism of behavior.     

德国科隆市Stammheim污水处理厂简介

介绍德国科隆市Stammheim污水处理厂各构筑物和生产运行情况。     

pSV—2neo和HPV—Ⅱ DNA共同转染NIH3T3细胞的结果

本实验将neo及HPV-11两种DNA共同转染NIH 3T3细胞,以G418抗生素作为选择剂,对诱导的转化灶进行筛选。同时还就G418对NIH 3T3细胞的毒性进行了观察。neo单独使用诱导的转化灶数为44.00/1×10~5;neo与HPV-11合用诱导的转化灶数为162.66/1×10~5。由neo转化的细胞含有neo基因,由neo和HPV-11转化的细胞内含有该两种基因。     

Mathematical analysis of two-phase mass transfer in a batch reactor for the chemical transformation of a steroid

A reactor is described for the conversion of the slightly water-soluble steroid testosterone (T) to 4-androstene-3, 17-dione (4-AD) by enzyme in the presence of excess cofactor. Since the enzyme is subject to substrate inhibition, reaction rates are strong functions of aqueous substrate concentration. High concentrations of the substrate, testosterone, per unit reactor volume are maintained within poly(dimethylsiloxane) beads that are suspended in the aqueous enzyme solution. Mass transfer (controlled by bead size, polymer to water volume ratio, enzyme loading) is used to control the degree and rate of conversion. The reactor dynamics are predicted over a wide range of reaction conditions. The product steroid is recovered in the polymeric beads from the enzyme solution.