By chromatography on diethylaminoethyl Sephadex, three enzyme fractions with pyrimidine nucleoside phosphorylase activity have been separated from extracts of normal or regenerating liver of rats. Two of these probably represent isoenzymes of uridine phosphorylase. Both are phosphate-dependent and both exhibit maximal activities toward uridine, deoxyuridine, and thymidine at pH values of 7.9 to...

Development of the cellular slime mold Dictyostelium discoideum is initiated by the removal of nutrients, and results in formation of a mature fruiting body composed of two cell types, the stalk and spore cells. A considerable body of evidence supports the hypothesis that cytoplasmic pH may be an essential regulator of the choice to differentiate in either the prestalk or prespore pathway. We h...

Tumor cell survival relies upon adaptation to the acidic conditions of the tumor microenvironment. To investigate potential acidosis survival mechanisms, we examined the effect of low pH (6.7) on human breast carcinoma cells. Acute low pH exposure reduced proliferation rate, induced a G1 cell cycle arrest, and increased cytoplasmic vacuolization. Gene expression analysis revealed elevated level...