| Abstract: | The temporal development of Dictyostelium discoideum is altered by the disruption of pyrimidine metabolism in amoeba during mitotic cell division or following nutritional starvation. The well-defined differentiation process is accelerated by exposure to specific biosynthetic intermediates, degradative products, uridine analogues, and drugs affecting pyrimidine biosynthesis or nucleotide interconversion. These perturbations appear to be stage specific and are induced by specific effectors. Artifical elevation of orotate and dihydroorotate pools or uridine pools by medium supplement (50 mg!ml) causes the abrupt cessation of amoeboid growth for 14-18 hours followed by a resumption of normal growth rates. Folate analogues, allopurinol, and barbiturates induce similar changes. A variety of pyrimidine analogues independent of nitrogenous base cause multifarious effects. However, enhanced differentiation resulting from exposure to naturally occurring pyrimidine metabolites is not observed with cytidine and thymidine derivatives. |
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