Temporary Character of "Fastness" of Staphylococci to Penicillin

Lung Cancer: An Evolutionary Approach

“…Of normal adult tissues, fibroblasts and endothelium replicate best in tissue culture (Paul, 1960;White and Parshley, 1951). Harris (1956) has shown that fibroblasts proliferate in the complete absence of oxygen and he concluded that they were facultatively anaerobic.…”

“…This concentration of CO is 4 • 2 per cent. Carbon monoxide is a direct cytochrome inhibitor (Castor and Chance, 1955) and as little as 0-05 per cenit will depress the overall metabolism of rats (Walters, 1927), Hydrogen cyanide is present in cigarette smoke in a concentration of 1600 ppm (10-* M) or 160 times tlie "safe level" (Smoking and Health, 1964), Hydrogen cyanide has long been used as a specific poison of respiratory enzymes, being active at concentrations of 10~" M or even less (Andrejew, 1949;Robbie, 1949;Burrin and Beechey, 1963), This means that both of these constituents of cigaiette smoke can be diluted ait least a hundredfold and still produce significant depression of respiration by ciliated epithelium in the lung. It is amazing how little attention these well-known respiratory poisons have received in discussions on lung cancer.…”

“…However, there are two pieces of evidence which indicate that fibroblasts will not proliferate if the oxygen tension is high. Trowell (1959) attempted to grow a large number of adult rat tissues in vitro using a system which supplied much more oxygen to the cells than conventional tissue culture techniques supply. Despite the fact that fibroblasts are usually quiite easy to grow in vitro, Trowell observed that rat fibroblasts and endothelium did not prohferate.…”

Penicillin-Resistant Staphylococci: Mechanisms Involved in the Development of Resistance

“…In an attempt to define the nature of the resistance of staphylococci to penicillin, the results of several studies have appeared in which sensitive strains have acquired a high degree of resistance by in vitro methods (4, 11, 13, 18, 20 to 24). Todd and Turner (25) succeeded in adapting 2 strains of staphylococcus resistant to penicillin by making repeated subcultures of the cocci in increasing quantities of penicillin. When the strains had acquired resistance, they subcultured the organisms daily in broth without penicillin and observed that there was a rapid decline in resistance.…”

Selection of Penicillin-sensitive Mutants of Escherichia coli following Ultraviolet Irradiation

“…Many people have shown that strains of bacteria with an induced resistance to penicillin will sometimes become more sensitive simply by repeated subculture in the absence of the drug (Todd, Turner & Drew, 1945;Chain & Duthie, 1945). Very little work has been done on these lines with organisms which are naturally resistant to penicillin, even before contact with the drug.…”