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Biomedical subjects

O Washington

Publications and source records attributed to O Washington.

8 recordsLinked to original sources
PubMed1992

Immunological signals which control T cell responses.

A number of identifiable immunological parameters can influence the elicitation and regulation of antigen-specific inflammatory responses to immunogenic epitopes. Injection of antigen in vivo can lead to the activation of type IV hypersensitivity responses, or to the induction of immunological tolerance to that antigen. We have used the hapten trinitrophenol as a model system for studying the factors which influence the generation and regulation of hypersensitivity responses to immunogenic epitopes in vivo. The generation of hypersensitivity or tolerance to trinitrophenyl depends on a number of immunological factors, including the form of the antigen, the route of immunization, and the presence of immune complexes of antibody and antigen on the surface of the antigen-presenting cell. Immunization with trinitrophenyl resulting in unresponsiveness can be the result of either the inability to prime inflammatory cells in vivo or the induction of suppressor T cells.

Animals↗
PubMed1986

Effect of guinea pig or monkey colonic mucus on Shigella aggregation and invasion of HeLa cells by Shigella flexneri 1b and 2a.

The effects of guinea pig and rhesus monkey colonic mucus preparations on Shigella aggregation and invasion of HeLa cell monolayers by Shigella flexneri serotype 1b, 2a, and 5 strains were investigated. Guinea pig mucus caused agglutination of S. flexneri serotype 1b but not of S. flexneri serotype 2a or 5. Guinea pig mucus also inhibited HeLa cell invasion by S. flexneri serotypes 1b and 2a. Monkey mucus neither agglutinated any Shigella strain nor inhibited HeLa cell invasion.

Adhesiveness↗
PubMed1981

Construction of a potential bivalent vaccine strain: introduction of Shigella sonnei form I antigen genes into the galE Salmonella typhi Ty21a typhoid vaccine strain.

Shigella sonnei, an intestinal pathogen, produces a characteristic form I cell surface antigen now known to be plasmid encoded. We considered that the GalE Salmonella typhi Ty21a oral vaccine strain, highly effective against typhoid, might be modified so as to be protective also against shigellosis due to S. sonnei. The plasmid responsible for form I antigen synthesis was therefore conjugally transferred to the galE S. typhi strain. Serological studies revealed that the derivative strain produces the form I antigen in addition to the normal S. typhi somatic antigens. Testing in mice demonstrated that the derivative form I galE S. typhi strain is protective against both S. sonnei and S. typhi challenges. These data suggest that the galE S. Ty21a oral vaccine strain, which presumably stimulates the local immune system in the intestine, may also serve as a useful carrier for other antigenic determinants to protect against different intestinal infections.

Animals↗
PubMed1980

Genetic and physical evidence for plasmid control of Shigella sonnei form I cell surface antigen.

Virulent Shigella sonnei synthesize a surface antigen (form I) which appears to be one of several requirements needed for this host to invade epithelial cells. Upon restreaking on agar media, form I cells readily and irreversibly generate form II cells that lack the form I antigen. All form II cells are avirulent. Plasmid deoxyribonucleic acid of form I and II cells of four different S. sonnei isolates, obtained from different areas of the world, was analyzed by agarose gel electrophoresis. A large plasmid (approximately 120 megadaltons in three of the strains) that is present in form I cells was always absent from form II derivatives. Attempts to transfer conjugally only this large plasmid from form I to genetically marked form II cells were unsuccessful. However, a composite molecule, apparently formed by recombination between the large form I plasmid and a self-transmissible plasmid, was found to transfer the form I trait. Transconjugant S. sonnei strains acquiring the form I antigen could retransfer this trait to S. sonnei, Shigella flexneri, or Salmonella typhi. These preliminary findings demonstrate that S. sonnei form I antigen synthesis is mediated by a large plasmid which is lost spontaneously at a relatively high frequency from S. sonnei strains.

Antigens, Bacterial↗
PubMed1972

Virulence of Shigella flexneri hybrids expressing Escherichia coli somatic antigens.

The genes controlling either Escherichia coli somatic antigen 8 or 25 were conjugally transferred to virulent Shigella flexneri 2a recipients to determine whether the aquisition of these antigens would affect the virulence of the resulting hybrid. A high proportion of such hybrids were found to be rough and hence were avirulent. Some smooth S. flexneri hybrids which replaced their native group antigens with E. coli factor 25 were still virulent in the animal models employed. All S. flexneri O-8 hybrids were uniformly avirulent. Our finding, that S. flexneri hybrids with the chemically divergent E. coli O-8 repeat unit are avirulent whereas some hybrids with the chemically related O-25 repeat unit retain virulence, suggests that the chemical composition and structure of the O side chain of somatic antigens may represent one determining factor for bacterial penetration of mucosal epithelial cells, the primary step in the pathogenesis of bacillary dysentery.

Animals↗
PubMedDate not supplied

Effects of cognitive and experiential group therapy on self-efficacy and perceptions of employability of chemically dependent women.

This quasi-experimental study assessed effects of cognitive and experiential group therapy on self-efficacy and perceptions of employability for 52 chemically dependent adult women. The sample was 98% African American. Therapy consisted of six 90-min group sessions held twice weekly. The participants were pre- and posttested with the Self-Efficacy Scale (M. Sherer et al., 1982) and the Ghiselli Self-Description Inventory (E. E. Ghiselli, 1975). After the intervention, the cognitive group had significantly higher levels than the experiential group of social self-efficacy and need for self-actualization, an indicator of aspiration for employment. General self-efficacy and decisiveness, indicators of employability, significantly increased over time for both groups. Interventions to enhance people's belief in their ability to successfully perform tasks and control outcomes, promote personal growth, teach responsibility, and enhance self-awareness could be used to develop employability skills that reduce recidivism.

Adult↗