Mutagenicity of the reaction products of carbazole in the presence of nitrogen dioxide and nitrocarbazole

The mutagenicity of the photochemical reaction products of carbazole in the presence of nitrogen dioxide (NO2) and nitrocarbazole was investigated using a high-pressure mercury lamp (100 W). Samples extracted from the photochemical reaction products of carbazole with NO2 were more mutagenic than those of acridine and phenazine with NO2 for Salmonella typhimurium strain TA98 in the absence of S9 mix with a trend toward detoxification in the presence of the metabolic system. The mutagenicity of the photochemical reaction products of carbazole with NO2 were higher than those of the reaction products of carbazole with a mixture of NO2 and sulfur dioxide (SO2) and no irradiation. Mononitro- and dinitro-carbazole in the samples extracted from the reaction products were analyzed by mass spectrometry. It was suggested that mononitrocarbazole, which seemed to be weakly mutagenic, and dinitrocarbazole were readily formed by the reaction of carbazole with NO2, and that the other high-potency mutagens were formed by the photochemical reaction of carbazole with NO2 with irradiation by light.     

EnterohemorrhagicEscherichia coli O157:H7 possesses somatic (O) antigen identical with that ofSalmonella O301

The O antigen of enterohemorrhagicEscherichia coli O157:H7 is identical with that ofSalmonella O30₁ and is also related toSalmonella O30₁30₂ in an a-a, b type of relationship.     

Increased expression in vivo and in vitro of foreign genes directed by A-type inclusion body hybrid promoters in recombinant vaccinia viruses.

We constructed A-type inclusion body (ATI) hybrid promoters, that is, late ATI promoters followed by tandemly repeated early regions of the promoter for the 7.5-kDa protein (the 7.5-kDa promoter). The repetition of the whole early promoter sequence of the 7.5-kDa gene, including the upstream consensus sequence and initiation region, efficiently increased the early expression of the bacterial chloramphenicol acetyltransferase gene in recombinant vaccinia virus. Recombinant vaccinia virus could express influenza virus hemagglutinin via the hybrid promoter more efficiently, induced higher levels of neutralizing antibody and cytotoxic T lymphocytes, and consequently protected mice more efficiently against challenge with influenza virus than did recombinant vaccinia virus containing the widely used 7.5-kDa promoter.     

Absolute configurations of pittosporatobiraside A and B from Pittosporum tobira

The absolute configuration at C-12 of pittosporatobiraside A and B isolated from the leaves of Pittosporum tobira was determined to be S on the basis of the exciton chirality of their dibenzoate derivative. The structures of the two glycosides were thus established to be (1S,9S,10S,11S,12S,14R,16R)-12-[(Z)-2-methyl-1-oxo-2-butenyl]-6,14-dimethyl-2-methylene-9-(1-methylethyl)-15,17-dioxatricyclo[8.7.0.0^11,16]heptadec-5-en-13-one and (1S,9S,10S,11S,12S,14R,16R)-12-(3-methyl-1-oxo-2-butenyl)-6,14-dimethyl-2-methylene-9-(1-methylethyl)-15,17-dioxatricyclo [8.7.0.0^11,16]heptadec-5-en-13-one, respectively.     

Comparison of beta-glucan structures in a cell wall mutant of Saccharomyces cerevisiae and the wild type

A mutant of Saccharomyces cerevisiae defective in the cell wall beta-glucan structure was obtained. The mutant cells are extremely sensitive to (beta 1-3)-glucanase digestion and mild alkali treatment. Structural analysis revealed that the alkali-insoluble, skeletal glucan from wild type cells contains two components, a (beta 1-3) linked glucan with a laminated structure, and a highly branched glucan containing predominantly (beta 1-6) linkages. The mutant cells lack the latter component.     

Raman diagnosis of nucleic acid structure: sugar-puckering and glycosidic conformation in the guanosine moiety.

Observations of Raman spectra of various nucleic acids indicate that the guanine ring breathing frequency is sensitive to the internal rotation angle around the glycosidic bond and to the conformation of the five-membered ring of the ribose residue that is directly connected with the guanine residue in question. It is found that 682 cm-1 for C2'-endo-anti, at 665 cm-1 for C3'-endo-anti, and at 625 cm-1 for C3'-endo-syn. A DNA octamer d(GpGpApApTpTpCpC) shows, in its aqueous solution, a broad Raman band at 680 cm-1 with a tail at 670 cm-1. This fact suggests that the guanosine residues in this oligomer take primarily C2'-endo-anti conformation but an appreciable amount of fluctuation of the ribose ring structure towards C3'-endo is involved.     

Functional comparison of transactivation by human retrovirus rev and rex genes.

The effect of rev-responsive element deletion on human immunodeficiency virus type 1 (HIV-1) and type 2 (HIV-2) gene expression was examined. The phenotypes of HIV-1 and HIV-2 provirus DNAs lacking the rev-responsive element, as determined by transfection experiments, were indistinguishable from those of virus DNAs carrying rev gene mutations. By using rev-response elements derived from these two viruses, we developed two monitoring systems to evaluate the functionality of HIV-1 rev, HIV-2 rev, and human T-lymphotropic virus type I rex. In both systems, HIV-1 rev and human T-lymphotropic virus type I rex transactivated HIV-2 very efficiently. On the contrary, HIV-2 rev and human T-lymphotropic virus type I rex were poor activators of HIV-1. No functional replacement of rex by HIV-2 rev was observed.     

Lipopolysaccharides of Escherichia coli K12 Strains That Express Cloned Genes for the Ogawa and Inaba Antigens of Vibrio cholerae O1: Identification of O-Antigenic Factors

Structural and serological studies were performed with the lipopolysaccharide (LPS) expressed by Escherichia coli K12 strains No. 30 and No. 64, into which cosmid clones derived from Vibrio cholerae O1 NIH 41 (Ogawa) and NIH 35A3 (Inaba) had been introduced, respectively. The two recombinant strains, No. 30 (Ogawa) and No. 64 (Inaba), produced LPS that included, in common, the O-polysaccharide chain composed of an α(1 → 2)-linked N-(3-deoxy-L -glycero-tetronyl)-D -perosamine (4-amino-4,6-dideoxy-D -manno-pyranose) homopolymer attached to the core oligosaccharide of the LPS of E. coli K12. Structural analysis revealed the presence of N-(3-deoxy-L -glycero-tetronyl)-2-O-methyl-D -perosamine at the non-reducing terminus of the O-polysaccharide chain of LPS from No. 30 (Ogawa) but not from No. 64 (Inaba). Serological analysis revealed that No. 30 (Ogawa) and No. 64 (Inaba) LPS were found to share the group antigen factor A of V. cholerae O1. They were distinguished by presence of the Ogawa antigen factor B [co-existing with relatively small amounts of the Inaba antigen factor (c)] in the former LPS and the Inaba antigen factor C in the latter LPS. It appears, therefore, that No. 30 (Ogawa) and No. 64 (Inaba) have O-antigenic structures that are fully consistent with the AB(c) structure for the Ogawa and the AC structure for the Inaba O-forms of V. cholerae O1, respectively. Thus, the present study clearly confirmed our previous finding that the Ogawa antigenic factor B is substantially related to the 2-O-methyl group at the non-reducing terminus of the α(1 → 2)-linked N-(3-deoxy-L -glycero-tetronyl)-D -perosamine homopolymer that forms the O-polysaccharide chain of LPS of V. cholerae O1 (Ogawa).     

Nitric Oxide Induces Phytoalexin Accumulation in Potato Tuber Tissues

We investigated whether nitric oxide (NO) radical could inducephytoalexin production. Treatment of potato tuber tissues with1-hydroxy-2-oxo-3,3-bis(2-aminoethyl)-1-triazene (NOC-18), anNO-releasing compound, induced the accumulation of the potatophytoalexin rishitin. This induction was inhibited by carboxy-2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide(carboxy-PTIO), an NO-specific scavenger, or by Tiron, a radicalscavenger, suggesting a phytoalexin inducing activity for NO. (Received December 7, 1995; Accepted January 4, 1996)     

Cloning and Characterization of the Murine GPI Anchor Synthesis GenePigf,a Homologue of the HumanPIGFGene

Many eukaryotic proteins are bound to the plasma membrane via a glycosylphosphatidylinositol (GPI) anchor. Its core backbone, which is conserved in different organisms, is synthesized in the endoplasmic reticulum by the sequential addition of glycan components to phosphatidylinositol. One of the human GPI synthesis genes,PIGF(phosphatidylinositol glycan complementation class F), which is involved late in the synthesis pathway, has been cloned. In this study, we isolated complementary and genomic clones ofPigf,a murine counterpart ofPIGF. Pigfencodes a 219 amino acid protein that complements a class F mutation. ThePigfgene consists of six exons spanning 30 kb and was mapped to chromosome 17 at 17E4–E5. These features are very similar toPIGF,thus demonstrating the interspecies conservation of structure, function, gene organization, and genetic locus between these GPI synthesis genes. The results also extend a region in murine distal chromosome 17 that is syntenic to human chromosome 2p16–p22.