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。     

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。     

Culture of one- and two-cell bovine embryos to the blastocyst stage in the ovine oviduct

The ovine oviduct was evaluated as a culture system for early bovine embryos. One- to two-cell embryos were collected from superovulated heifers killed 36 or 48 h after the onset of estrus, embedded in agar cylinders, and transferred to oviducts ligated at the uterotubal junction. After 5 d (6.5 to 7.0 d after donor estrus), embryos were recovered and evaluated for development to the late morula or blastocyst stage. In Experiment 1, 86 embryos were cultured in 10 ewes in which the onset of estrus was synchronized with that of the donors. Fifty-eight embryos (68%) were recovered; of these, 31 (53%) had continued normal development. In Experiment 2, development in ovariectomized versus intact cyclic ewes was compared. Recovery from ovariectomized ewes (26/39, 67%) did not differ from intact cyclic ewes (26/35, 74%) and the proportion developing normally also did not differ (ovariectomized: 7/26, 27%; intact cyclic: 11/26, 42%). In Experiment 3, embryo development was compared in anestrous versus ovariectomized ewes. Recovery rate (anestrous: 22/43, 51%; ovariectomized: 20/51, 39%) and the proportion developing normally (anestrous: 8/22, 37%; ovariectomized: 9/20, 45%) did not differ between treatments. Developmental competence of oviduct-cultured embryos was tested by transfer to 16 synchronous heifers, of which eight (50%) became pregnant; five delivered calves. Results indicate that the ovine oviduct provides an adequate site for the culture of early bovine embryos.     

Induction of Medicarpin Biosynthesis in Ladino Clover Callus by p-Chloromercuribenzoic Acid Is Reversed by Dithiothreitol

Treatment of Ladino clover (Trifolium repens L.) callus with 1 millimolar p-chloromercuribenzoic acid (PCMBA) stimulated the biosynthesis of the phytoalexin medicarpin. Increased medicarpin concentration was detected at 6 hours, and maximum level was achieved by 36 hours. Dithiothreitol (DTT), added to callus at 2, 6, 10, and 18 hours following addition of PCMBA, partially counteracted the effect of PCMBA in the cells. The greatest effect on reversal of medicarpin accumulation was found at the earlier times for DTT addition. Compared to a 24-hour PCMBA control, final medicarpin concentrations were 9 to 19%, 37 to 45%, and 92 to 105% of the control value when DTT was added at 0.5, 1 or 2 hours, 3 or 4 hours, and 6, 8, 10, or 12 hours, respectively, after PCMBA addition. The results indicate that stimulation of medicarpin biosynthesis is reversible, but once activated, the pathway is not shut down by removal of elicitor.