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Biomedical subjects

D N Medearis

Publications and source records attributed to D N Medearis.

29 records · Page 2Linked to original sources
PubMed1968

Cell wall composition and virulence in Escherichia coli.

Uridine diphosphate galactose 4-epimerase and phosphomannose isomerase-deficient mutants of Escherichia coli O111:B4 were studied to test the hypothesis that in E. coli a specific relationship exists between O antigenicity, virulence, and capacity to resist phagocytosis. The first mutant, designated J-5, produces a cell wall lipopolysaccharide, the side chains of which do not contain galactose, glucose, N-acetylglucosamine, or colitose. The second mutant produces a cell wall lipopolysaccharide which lacks only colitose. The capacity of these various organisms to kill mice was strikingly different. E. coli O111 was 1000 times as virulent as J-5, and 100 times as virulent as L-2. The capacity of the organisms to kill mice was correlated with their ability to resist phagocytosis and to persist in the peritoneal cavity. The parent strain of O111 resisted phagocytosis by macrophages in vivo and polymorphonuclear leukocytes in vitro. The mutants did not, and the organism most deficient in the saccharide component of its LPS was most susceptible to phagocytosis and least virulent. These results were corroborated by growing the mutants in appropriately supplemented media which permitted the synthesis of complete LPS, reversed the susceptibility to phagocytosis, and restored virulence. Finally, serological reactivity was consistent with previous observations which had demonstrated that the O antigenicity of E. coli is determined by the saccharide composition of its cell wall lipopolysaccharide. Despite the difference in the capacity of the various log-phase organisms to kill mice when injected intraperitoneally, purified lipopolysaccharides extracted from them did not differ significantly in their capacity to kill or produce fever. Thus virulence was shown to be independent of endotoxin activity which in turn seemed to be unrelated to the saccharide composition of the cell wall LPS. Collectively, these data provide at least a partial molecular definition of virulence in E. coli by demonstrating that the presence or absence of specific sugars in its cell wall lipopolysaccharide is a determinant of its antiphagocytic capacity and its virulence.

Agglutination Tests↗
PubMedDate not supplied

Cell-mediated immunity in experimental cytomegalovirus infections: a perspective.

Treatment of cytomegalovirus (CMV) infections has assumed increasing importance in the care of immunocompromised patients, particularly allograft recipients and patients with symptomatic infection with the human immunodeficiency virus. The crucial role of T cells in the host defense against CMV may be inferred by the expression of life-threatening CMV disease in these restricted patient subpopulations. However, detailed understanding of the pathogenesis of CMV disease in the compromised host is lacking, and the mechanisms by which T cells confer protection are unknown. Insight into the pathogenesis of CMV in these patients is crucial for the development of rational therapeutic strategies. A considerable body of data has been generated to explore the role of T cell-mediated immunity in a number of model viral infections as well as in experimental CMV infections in both normal and immunocompromised mice. This experience will be critically reviewed to clarify the often conflicting observations regarding a protective or, conversely, a pathogenic role for T cells in producing CMV disease.

Animals↗