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Biomedical subjects

H S Carr

Publications and source records attributed to H S Carr.

34 records · Page 2Linked to original sources
PubMed1970

Synergism between cysteine and alkylating agents.

Contrary to expectation, l-cysteine did not protect Escherichia coli from the lethal action of two monofunctional alkylating agents (nitrosomethylurethane and methylmethane sulfonate). The antibacterial action of these compounds was actually greatly enhanced by l-cysteine. This synergistic effect was also exhibited, to some extent, by d-cysteine but not by homocysteine, S-methylcysteine, or serine. The synergistic action between methylating agents and l-cysteine was not due to the formation of S-methylcysteine. l-Cysteine had no effect on the bacteriostatic action of ethylmethane sulfonate.

Alkanes↗
PubMed1967

Electron microscopy of chloramphenicol-treated Escherichia coli.

Thin sections of Escherichia coli were examined by electron microscopy at sequential intervals after addition and then removal of chloramphenicol. The first changes, occurring at 1 hr after exposure to the drug, were disappearance of the ribosomes and aggregation of the nuclear material toward the center of the bacteria. At 2 hr, aggregates of abnormal cytoplasmic granules first appeared and subsequently increased in size. By 23 hr, amorphous, electron-dense material had accumulated within, and at the periphery of, the nuclear matrix. With the removal of chloramphenicol, the bacteria became normal in appearance, passing through a series of stages that were sequential but not synchronous. At 145 min after removal of chloramphenicol, bacteria were encountered in the process of abnormal division. The influence of deoxyribonucleic acid and ribonucleic acid synthesis, and of energy metabolism, upon the changes seen electron microscopically in chloramphenicol-treated cells, was investigated by selectively inhibiting these functions with hydroxyurea, azauracil, and sodium azide, respectively.

Azides↗
PubMed1967

Studies with hydroxyurea. VII. Hydroxyurea and the synthesis of functional proteins.

Hydroxyurea affected neither the synthesis nor the degradation of bacterial messenger-ribonucleic acid. The proteins made by hydroxyurea-treated cells were structurally intact and fully functional. Since the expression of the lethal action of hydroxyurea requires active protein production, the data indicate that treated cells do not die as the result of the synthesis of abnormal proteins.

Alkaline Phosphatase↗
PubMed1966

Studies with hydroxyurea. II. Prolonged exposure of Escherichia coli to hydroxyurea.

Rosenkranz, Herbert S. (Columbia University, New York, N.Y.), and Howard S. Carr. Studies with hydroxyurea. II. Prolonged exposure of Escherichia coli to hydroxyurea. J. Bacteriol. 92:178-185. 1966.-Concurrent with an inhibition of the synthesis of deoxyribonucleic acid, hydroxyurea devitalized Escherichia coli when exposure to the drug was prolonged to more than 3 hr. Active protein synthesis, but not ribonucleic acid (RNA) production, was a prerequisite for this lethal action. These findings are contrasted to thymineless death, which requires RNA synthesis.

Antimetabolites↗
PubMedDate not supplied

Diagnosis of gastritis caused by Helicobacter pylori in children by means of an ELISA.

In this study, the systemic immune response to bacterial cell sonicates of Helicobacter pylori was characterized in children with symptomatic gastroduodenal disease. Isotype-specific antibodies to H. pylori in samples of serum from 16 children with culture-proven disease caused by H. pylori and from 19 controls with negative cultures were measured by ELISA with bacterial cell lysates. The levels in serum of IgA antibody to cell sonicates of H. pylori were significantly higher in the patients with positive cultures than in the controls. Only 45% of patients were infected when the established optical density cutoff was used to discriminate between patients infected and not infected with H. pylori. Levels of IgM antibody in serum were not significantly higher in patients who were infected with H. pylori. On the basis of this survey and of previous work conducted in our laboratory, we conclude that at a serum dilution of 1:800, IgG but not IgA or IgM antibody to H. pylori is useful in the rapid screening of symptomatic children for the presence of H. pylori.

Adolescent↗