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Biomedical subjects

W W Kilgore

Publications and source records attributed to W W Kilgore.

At least 55 records · Page 3Linked to original sources
PubMed1967

Effects of mitomycin C on macromolecular synthesis in Escherichia coli.

When cells of Escherichia coli B growing in a glucose-synthetic medium were treated with mitomycin C, the effects produced by the antibiotic varied, depending on the concentration. When the concentration was reduced to less than 0.1 mug/ml, the action of the antibiotic was bacteriostatic; cell elongation resulted, but no effect on the synthesis of cellular macromolecules was apparent. At higher levels (more than 5 mug/ml), mitomycin C was highly bactericidal and inhibited deoxyribonucleic acid synthesis almost completely. The exposure of growing cells to a bactericidal level of mitomycin C resulted also in a delayed inhibition of the synthesis of ribonucleic acid (RNA) and protein. The capacity of the treated cells to synthesize beta-galactosidase inducibly in a medium free from a carbon source remained constant for the first 30 min and then was destroyed progressively with time. Prolonged incubation with the bactericidal level of mitomycin C caused a degradation of cellular nucleic acids, particularly RNA. The degraded nucleic acid components were eventually released into the medium.

Bacterial Proteins↗
PubMed1967

Filamentous cells of Escherichia coli formed in the presence of mitomycin.

The effects of mitomycin C on cell elongation of Escherichia coli B were studied. Filament formation was most marked in cultures treated with a moderate level (1 mug/ml) of the antibiotic, becoming less obvious at higher levels (10 mug/ml). Cells treated with a bacteriostatic concentration (0.1 mug/ml or less) of mitomycin C were also significantly elongated. The filamentous or elongated cells appeared to lack septa, since their spheroplasts were considerably larger than those formed from normal cells. The appearance of empty spheres also indicated some defects in the surfaces of the filamentous cells. Electron micrographs of the filaments revealed a characteristic difference in the arrangement of the nuclei in the filaments formed in the presence of low (0.1 mug/ml) and high (5 mug/ml) concentrations of mitomycin C. The filaments formed by the low level of mitomycin C had normal well-defined nuclear bodies distributed along the long axis, whereas those formed by the elevated level of the antibiotic contained smaller nuclei. The latter were characteristically confined to the center of the cells and did not extend out to the tips of the filaments.

Cell Nucleus↗
PubMed1967

Decomposition of ribosomal particles in Escherichia coli treated with mitomycin C.

Exposure of cells of Escherichia coli to mitomycin C (5 mug/ml) resulted in a marked change in the sedimentation profiles of the cell-free extracts, indicating a specific decomposition of ribosomal particles. When the extracts were prepared in the presence of 0.01 m Mg(++) and analyzed by sucrose density gradient centrifugations, the 100S fraction disappeared rapidly from the treated cells. The 70S ribosomes were also degraded, but more slowly, with a concomitant accumulation of a fraction having a sedimentation coefficient of about 50S. However, decomposition of the 70S ribosomes was preceded by an almost complete loss of the 50S ribosomal subunits, as revealed by sedimentation analyses in the presence of 10(-4)m Mg(++). Synthesis of the ribosomes in the treated cells was also suppressed, being demonstrated by a lower incorporation of uracil-2-(14)C into the ribosomal fractions. However, the change in the ribosomal profile in the treated cells apparently resulted from the decomposition of pre-existing ribosomes, rather than from the inhibition of the net synthesis of ribosomes. Sedimentation analyses and chromatography of the nucleic acids extracted from the treated cells indicated extensive but delayed degradation of the ribosomal ribonucleic acid (RNA), but not of the soluble RNA or deoxyribonucleic acid fractions. Altered structure of the ribosomes in the treated cells was also indicated by their lower melting temperature, broadened thermal profile, higher electrophoretic mobility, and extreme sensitivity to ribonuclease treatment, compared with normal ribosomes. The synthesis of messenger RNA was inhibited progressively with time in the treated cells.

Carbon Isotopes↗
PubMedDate not supplied

Learning impairment in mice following acute exposure to dichloromethane and carbon tetrachloride.

Mice were exposed via inhalation to high concentrations of either dichloromethane (168 mg/l) or carbon tetrachloride (134.3 mg/l). The mice were tested for learning ability using a passive-avoidance conditioning task. Exposed animals were found to have a significantly decreased ability to learn when compared with controls. The 3-wk-old mice were more affected than the 5-wk-old and the 8-wk-old mice. The exposed animals were indistinguishable from controls in terms of motor activity, weight gain, and absence of analgesia.

Age Factors↗