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Biomedical subjects

G Medoff

Publications and source records attributed to G Medoff.

At least 145 records · Page 8Linked to original sources
PubMed1974

Ribonucleic acid polymerases of the yeast phase of Histoplasma capsulatum.

Ribonucleic acid (RNA) polymerases of Histoplasma capsulatum (yeast phase) were fractionated by phosphocellulose chromatography and partially characterized. Three distinct, active fractions were seen. The major RNA polymerase species was inhibited strongly by alpha-amanitin, whereas the other two were resistant. When either slightly purified (HSE) extract or the major active component was assayed at 37 C, the incorporation of tritiated uridine monophosphate into RNA stopped after 10 to 15 min. In contrast, the synthesis continued for at least 1 h at 23 C. The other two RNA polymerase species exhibited higher rates of incorporation when tested at 37 C, and continued to synthesize RNA even after 60 min. However, by that time the levels of incorporation at 23 C were higher than at 37 C for all three enzymes. The temperature sensitivity was not affected by changing substrate concentration or employing either native or denatured calf thymus deoxyribonucleic acid as a template. These results are compared with the data obtained with RNA polymerases from different fungi and other organisms. A possible involvement of RNA polymerase(s) in morphological differentiation of H. capsulatum is discussed.

Ammonium Sulfate↗
PubMed1972

Antibiotic synergism against Listeria monocytogenes.

The effectiveness of ampicillin, penicillin, streptomycin, and gentamicin against 20 strains of Listeria monocytogenes was studied in vitro. For all strains, the minimal bactericidal concentration (MBC) of both ampicillin and penicillin was much higher than the minimal inhibitory concentration (MIC). The MBC of both streptomycin and gentamicin was close to the MIC, but relatively high concentrations of these antibiotics were necessary to inhibit the growth of most of the strains of Listeria. The combination of penicillin plus streptomycin was synergistic against 19 of 20 strains and in the remaining strain produced enhanced killing (but of less magnitude than our criterion for synergism). Combinations of penicillin plus gentamicin, ampicillin plus streptomycin, and ampicillin plus gentamicin produced enhanced killing against all strains tested. No antagonism was observed when ampicillin or penicillin was combined with streptomycin or gentamicin.

Ampicillin↗
PubMed1972

Antifungal properties of polymyxin B and its potentiation of tetracycline as an antifungal agent.

High concentrations of polymyxin B inhibited the growth of Candida albicans and Saccharomyces cerevisiae. When these yeasts were incubated with concentrations of polymyxin B too low to affect growth, and were then exposed to tetracycline, protein synthesis was inhibited and at least 99% of the organisms were killed. Neither inhibition of protein synthesis nor cell death occurred in cultures treated with high concentrations of tetracycline alone. We conclude that polymyxin B at high concentrations affects the cell membrane of yeasts, which results in inhibition of growth. At low concentrations, it increases the permeability of the yeast cell membrane to tetracycline, which then inhibits protein synthesis and leads to cell death.

Antifungal Agents↗
PubMed1972

Potentiation of the antifungal effects of antibiotics by amphotericin B.

Amphotericin B was found to potentiate the antifungal effects of mycophenolic acid glucuronide, tetracycline, and actinomycin D by increasing the penetration of these antibiotics through the fungal cytoplasmic membrane. Because the fungi were over 100 times more susceptible than animal cells to these effects of amphotericin B, these observations might have clinical application.

Amphotericin B↗