EPITHELIAL CELL PENETRATION AS AN ESSENTIAL STEP IN THE PATHOGENESIS OF BACILLARY DYSENTERY.

LaBrec, Eugene H., Herman Schneider, Thomas J. Magnani, and Samuel B. Formal. Epithelial cell penetration as an essential step in the pathogenesis of bacillary dysentery. J. Bacteriol. 88:1503-1518. 1964.-A parent strain of Shigella flexneri 2a and a colonial mutant derived from it were studied in three animal models. Both strains were equally virulent for mice when living cells suspended in hog gastric mucin were injected by the intraperitoneal route. Feeding the parent strain to starved guinea pigs, followed by the intraperitoneal injection of opium, resulted in the formation of ulcerative lesions in the intestinal tract and in the death of these animals. When the colonial variant was fed to similarly prepared animals, the animals survived and the intestinal tract remained normal. The parent produced diarrheal symptoms and intestinal lesions after its oral administration to rhesus monkeys; the variant caused neither symptoms nor pathology in this species. Studies were carried out to define the characteristics present in the parent strain and absent in the colonial mutant, which would enable the parent to produce ulcerative lesions of the bowel and death in the guinea pig model or intestinal lesions and diarrheal symptoms in the monkey. Neither serological studies nor growth studies conducted both in vitro and in vivo offered a clue to explain this difference. The virulent parent strain was shown to penetrate the bowel epithelium and enter the lamina propria; the avirulent mutant did not do this. Entrance to the lamina propria was by way of the epithelial cell of the mucosa. The avirulent mutant did not possess the capacity to penetrate this cell. This observation was extended to show that the virulent parent possesses the ability to infect and multiply within HeLa cells; furthermore, the organisms are able to penetrate epithelial cells of the guinea pig cornea, causing ulcerative lesions. The avirulent variant possesses neither of these capacities. It is suggested that epithelial cell penetration is a major factor in determining the pathogenicity of dysentery bacilli.     

Ein Beitrag zur Bekämpfung der Fritfliege in der Roggenzüchtung

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Phi SC623, a temperate actinophage of Streptomyces coelicolor Müller, and its relatives phi SC347 and phi SC681

Three species-specific, temperate actinophages of Streptomyces coelicolor Müller, phi SC623, phi SC347 and phi SC681, were compared with respect to host range, virion structure, antiserum cross-inactivation, DNA-restriction pattern, DNA hybridization, and DNA base composition. The restriction map of phi SC623 (57 kb) was established with eight restriction enzymes; the homologies of this phage with phi SC347 and phi SC681 suggested that it might be a hybrid phage composed of approximately equal parts homologous to one of the other two phages. No homology was detected between phi SC623 and R4, a temperate, wide-host-range phage which can also lysogenize S. coelicolor Müller.     

Crystals of the NC1 domain of human type IV collagen

Crystals of the non-collagenous C-terminal region (NC1) of type IV collagen have been obtained from human placenta. These crystals diffract to 2.0 A, and belong to space group P22(1)2(1), with cell dimensions a = 81 A, b = 158 A, c = 138 A, alpha = beta = gamma = 90 degrees. The crystals contain one hexamer in the asymmetric unit; they are very stable with respect to X-rays.     

3-Diazirine-derivatives of bile salts for photoaffinity labeling

New carbene-generating photolabile bile salt derivatives, 3,3-azo-7 alpha,12 alpha-dihydroxy-5 beta [7 beta-3H]cholan-24-oic acid and (3,3-azo-7 alpha,12 alpha-dihydroxy-5 beta [7 beta-3H]cholan-24-oyl)-2- aminoethanesulfonic acid were synthesized with high specific radioactivity. These 3-diazirine-derivatives could be activated to the corresponding carbenes by irradiation with ultraviolet light at 350 nm with a half-life time of 2 min. The 3-diazirine derivatives behaved in enterohepatic circulation like the natural bile salts. The uptake of [3H]taurocholate into isolated hepatocytes was competitively inhibited by (3,3-azo-7 alpha,12 alpha-dihydroxy-5 beta-cholan-24-oyl)-2- aminoethanesulfonic acid indicating that the 3,3-azo-derivative of taurocholate shares the hepatic transport systems for natural bile salts. It was demonstrated that the radioactively labeled 3-diazirine bile salt derivatives are useful probes for photoaffinity labeling of bile salt binding proteins especially in intact cells and tissues.     

Excess information at bacteriophage T7 genomic promoters detected by a random cloning technique.

In our previous analysis of the information at binding sites on nucleic acids, we found that most of the sites examined contain the amount of information expected from their frequency in the genome. The sequences at bacteriophage T7 promoters are an exception, because they are far more conserved (35 bits of information content) than should be necessary to distinguish them from the background of the Escherichia coli genome (17 bits). To determine the information actually used by the T7 RNA polymerase, promoters were chemically synthesized with many variations and those that function well in an in vivo assay were sequenced. Our analysis shows that the polymerase uses 18 bits of information, so the sequences at phage genomic promoters have significantly more information than the polymerase needs. The excess may represent the binding site of another protein.