Esterification of arylhydroxylamines: Evidence for a specific gene product in mutagenesis

Characterization of a $\text{Salmonella}\text{typhmurium}$ mutant strain (TA98/1,8-DNP₆) resistant to the mutagenicity of nitrated polycyclic aromatic hydrocarbons (nitroarenes) revealed that it was also non-responsive to the mutagenic action of nitroso- and N-hydroxylaminoarenes. The mutant strain was fully sensitive to the mutagenic action of the corresponding hydroxamic acid ester. These results suggest that TA98/1,8-DNP₆ is deficient in a specific esterifying enzyme and that esterification of the penultimate mutagenic metabolites of nitro- and aminoarenes ($\text{e.g.}$, arylhydroxylamines) to form potent electrophiles is controlled by a specific gene.     

The role of trehalose in the osmoadaptation of Escherichia coli NCIB 9484: interaction of trehalose, K+ and glutamate during osmoadaptation in continuous culture.

Natural abundance 13C nuclear magnetic resonance spectroscopy identified the disaccharide trehalose as the major organic osmolyte synthesized by Escherichia coli grown in continuous culture under nitrogen limitation in the presence of 0.5 M-NaCl. Trehalose accumulation was dependent on both the growth phase of the culture and the osmolality of the growth medium, but independent of the solute used to increase the osmolality as long as the solute was non-penetrant. The penetrant solute glycerol did not induce trehalose synthesis indicating that the loss of cell turgor rather than increasing medium osmolality per se was the mechanism stimulating trehalose synthesis. Under conditions of either carbon or nitrogen limitation osmoadaptation was distinctly biphasic. The initial response consisted of a rapid (within 30 min) accumulation of K+ and a concurrent synthesis of the amino acid glutamate; trehalose synthesis occurred during the second slower phase of osmoadaption. Chloramphenicol severely inhibited trehalose accumulation indicating that the enzyme(s) involved in trehalose synthesis were inducible.     

Induction of vascular smooth muscle cell growth by selective activation of the thrombin receptor. Effect of heparin.

The synthetic peptide, SFLLRNPNDKYEPF, has been recently described as a peptide mimicking the new amino-terminus created by cleavage of the thrombin receptor, therefore acting as an agonist of the thrombin receptor. This peptide was a potent mitogen for rabbit arterial smooth muscle cells (SMC) and exhibited the same activity as that of native alpha-thrombin. Both compounds stimulated the proliferation of growth-arrested SMCs with half-maximum mitogenic responses at 1 nM. NAPAP, a synthetic inhibitor of the enzymatic activity of thrombin, specifically inhibited thrombin-induced SMC growth (IC50 = 0.35 +/- 0.04 microM) but was without effect on the mitogenic effect of the agonist peptide. These results therefore demonstrate that the mitogenic effect of alpha-thrombin for SMCs is intimately linked to its esterolytic activity. Heparin, which inhibited fetal calf serum-induced SMC growth, was without effect on thrombin-induced SMC growth but strongly reduced the mitogenic effect of the agonist peptide (IC50 = 32 +/- 5 micrograms/ml). This effect was not related to the anti-coagulant activity of heparin but was highly dependent on molecular mass and on the global charge of the molecule and was also observed for other sulphated polysaccharides such as pentosan polysulphate.     

Construction of Bordetella pertussis strains that overproduce genetically inactivated pertussis toxin.

Nontoxic analogs of pertussis toxin (PT), produced by in vitro mutagenesis of the tox operon, are immunogenic and protective against infection by Bordetella pertussis. The moderate levels of PT production by B. pertussis, however, make it the limiting antigen in the formulation of multicomponent, acellular, recombinant whooping cough vaccines. To increase production of the highly detoxified Lys9Gly129 PT analog by B. pertussis, additional copies of the mutated tox operon were integrated into the bacterial chromosome at the tox or fha locus by unmarked allelic exchange. Recombinant strains produced in this way secreted elevated levels of the PT analog proportional to gene dosage. The strains were stable during 10-liter fermentations, and yields of up to 80 mg of PT analog per liter were obtained under production-scale conditions. The nontoxic analog was purified and shown to be indistinguishable from material obtained from a B. pertussis strain that contained only a single copy of the toxLys9Gly129 operon. Such strains are therefore suitable for large-scale, industrial production of an acellular whooping cough vaccine containing a genetically detoxified PT analog.     

Involvement of protein kinase C in the mitogenic and chemotaxis effects of basic fibroblast growth factor on bovine cerebral cortex capillary endothelial cells

Basic fibroblast growth factor is increasingly implicated in cellular growth, differentiation, angiogenesis and oncogenesis. In culture, basic fibroblast growth factor greatly improved the growth rate of bovine brain cortex capillary endothelial cells. Down-regulation of protein kinase C by prolonged treatment with phorbol esters prevented the mitogenic effect of basic fibroblast growth factor on capillary endothelial cells. Furthermore, staurosporine, a potent protein kinase inhibitor, showed strong antiproliferative activity against basic fibroblast growth factor-induced endothelial cell growth. Similarly, the chemotaxis effect of basic fibroblast growth factor on capillary endothelial cells was abolished by down-regulation of protein kinase C or by staurosporine treatment. Therefore, it is suggested that protein kinase C could account for part of the angiogenic effect of basic fibroblast growth factor.     

Glycosphingolipids in insects. Chemical structures of two variants of a glucuronic-acid-containing ceramide hexasaccharide from a pupae of Calliphora vicina (Insecta: Diptera), distinguished by a N-acetylglucosamine-bound phosphoethanolamine sidechain

The two major components of the acidic glycolipid fraction from the pupae of Calliphora vicina were isolated using high-performance liquid chromatography. The acidic moiety was identified as glucuronic acid by beta-glucuronidase cleavage and gas chromatographic analysis as the pentafluoropropionyl derivative. The structures of the carbohydrate moiety were elucidated by peracetylation, methylation, exoglycosidase cleavage, fast-atom-bombardment mass spectrometric and 1H-nuclear magnetic resonance spectroscopic analysis. The only difference between the two hexasaccharide variants was the presence, in one of them, of a between the two hexasaccharide variants was the presence, in one of them, of a phosphoethanolamine (AeP) sidechain on the third sugar of the sequence, i.e. N-acetylglucosamine. The composition of the ceramide moiety was dominated by a C20:0 fatty acid (arachidic acid) and a C14:1 sphingoid base (tetradecasphing-4-enine). The chemical structures of the two insect acidic glycosphingolipids were determined to be: GlcA(beta 1-3)Gal-(beta 1-3)GalNAc(beta 1-4)GlcNAc(beta 1-3)Man (beta 1-4)Glc(beta 1-1)Cer; GlcA(beta 1-3)Gal(beta 1-3)GalNAc(beta 1-4)[2AeP-6]-GlcNAc(beta 1-3) Man(beta 1-4)Glc(beta 1-1)Cer. Such glucuronic-acid-containing insect glycosphingolipids have been given the generic name arthrosides, with the implied synonymity to the gangliosides.     

Cytofluorometric Determination of Nuclear DNA in Living and Preserved Algae

Three DNA-localizing fluorochromes used in conjunction with epi (incident) UV illumination were examined for sensitivity and selectivity for the cytofluorometric determination of nuclear DNA in ten species of six algal genera: Mougeotia, Oedogonium, Sirogonium, Spirogyra and Zygnema among the green algae, and the marine red alga Polysiphonia boldii. In comparison with absorption photometry for the determination of nuclear DNA, the cytofluorometric procedure proved to be simpler and considerably more sensitive. Following staining with 4',6-diamidino-2-phenylindole (DAPI), nuclei fluoresce blue-white, the fluorescence intensity of the DNA-DAPI complex being considerably greater than that of the unbound dye molecule. Algal strains stained with 2,5-bis[4'-aminopheny](1')]-1,3,4-oxadiazole (BAO) also showed brilliant blue-white nuclear fluorescence. Although the BAO schedule requires the use of freshly prepared dye and sulfite water, and careful control of hydrolysis, nuclear fluorescence of the stained specimens does not fade under irradiation of the UV beam as rapidly as it does with certain other fluorochrome procedures. A more useful fluorochrome was the fungal antibiotic mithramycin. Its staining schedule is simple and the bright orange-yellow fluorescence of the nuclei is associated with an exceptional degree of sensitivity and specificity for DNA. Forty-eight-year-old preserved filaments of Spirogyra jatobae, stained with either BAO or mithramycin, exhibited a fluorescence brilliance of nuclear and chloroplast DNA equal to that of fresh specimens of this species. The three schedules, but particularly the one with mithramycin, have proven useful in providing indirect evidence for variation in ploidy level in several of the above algal genera, and in verifying the assumed ploidy level of the gametophyte (haploid) and tetrasporophyte (diploid) of Polysiphonia boldii