Filamentous vibriophage fs2 encoding the rstC gene integrates into the same chromosomal region as the CTX phage [corrected]

The genome of the filamentous phage of Vibrio cholerae fs2 was found to contain rstC and rstB1 (truncated) genes downstream of ORF500. att-fs2-dir and att-fs2-rev sequences homologous to that of att-CTXphi were found between orf500 and rstC of the fs2 genome. This prompted us to search for the integration site of fs2 in the genomes of V. cholerae O1 and O139. The genome of fs2 was found to integrate downstream of attRS of the CTXphi phage, which integrated into chromosome I of V. cholerae O1 and O139. When infected with fs2, a fimbriate strain of V. cholerae O1 appeared to reduce fimbrial production in an adult rabbit ileal loop assay.     

对郭德栋主编的《遗传学》中若干问题的商榷

本文参阅有关文献及十多年遗传学教学中所使用的不同版本的教材 ,对郭德栋主编的《遗传学》教材中的若干问题进行了商榷。     

Gαo is a major determinant of cAMP signaling in the pathophysiology of movement disorders

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A rapid, two-step method for high-yield purification of recombinant rat acidic and basic fibroblast growth factors

We describe the preparation of vectors for T7 polymerase-driven, high-level expression of rat acidic (aFGF) or basic (bFGF) fibroblast growth factors in Escherichia coli. Following isopropyl-beta-D-thiogalactoside induction of T7 polymerase, rat aFGF or bFGF represented a major portion of the proteins synthesized by vector-transformed E. coli. Passage of cell extracts through an Amicon YM-100 membrane provided ultrafiltrates containing either aFGF or bFGF as the principal component. A single heparin-Sepharose chromatography of the ultrafiltrates yielded essentially homogenous, biologically active, recombinant rat aFGF or bFGF. By silanizing vessels and using buffers containing 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonic acid, we could store homogenous aFGF or bFGF preparations without significant loss during repeated freezing and thawing. Previous methods for purifying aFGF or bFGF utilized salt fractionation followed by sequential ion exchange and heparin-Sepharose chromatography. These purified aFGF or bFGF preparations routinely were stored in buffered carrier protein to minimize mitogen loss resulting from adsorption to glass or plastic surfaces. In contrast, the methods that we detail are rapid, require minimal manipulation of preparations, and permit storage of carrier-free, homogenous preparations without loss resulting from surface adsorption. The protocols can be used for preparation of homogenous aFGF or bFGF of other species and may be readily applied to the isolation and characterization of FGF-like mitogens present in cultured cell extracts, conditioned medium, or tissue preparations.     

Two different mechanisms of ampicillin resistance operating in strains of Vibrio cholerae O1 independent of resistance genes

Autoagglutinable strains of Vibrio cholerae O1 (seven nonfimbriate strains and one fimbriate strain) were transformed to obtain resistance to ampicillin. Two distinct mechanisms were found in these strains. One was operating in nonfimbriate strains by reducing OmpU protein production and the other was operating in a fimbriate strain (Bgd17) by newly overproducing cpxP protein. The twitching motility in the fimbriate Bgd17 strain disappeared depending on the production of cpxP protein, suggesting that fimbriation of V. cholerae O1 is controlled by a two-component signal transduction system.     

Synthesis and secretion of an estrus stage-specific protein by rat uterus.

A specific protein with an estimated molecular weight of 260 kDa was found to be synthesized and secreted into the incubation medium by rat uterus only during the estrus stage of the cycle. This secreted uterine protein was designated as estrus stage-specific protein (ESP). ESP was not produced by pregnant, lactating or immature pup rat uteri. Estradiol administered to ovariectomized rats induced production of ESP which was blocked by the antiestrogen, ICI 182, 780. The present results show that the synthesis and secretion of ESP is regulated by estradiol and this protein maybe involved in blastocyst implantation.