SYNOPSIS The present report describes a simple and useful method for synchronizing mass cultures of the ciliate Tetrahymena pyriformis. The method employs a nutritional approach which involves starvation of the cells in a non‐nutrient phosphate buffer followed by refeeding with an enriched nutritional growth medium. It takes 240 minutes after refeeding before the first cells start to divide. Radioautographic and DNA determinations taken together show that starved cells are stalled in the GI nuclear DNA condition and that essentially all of the cells replicate their DNA prior to their first cell division.
Adult mice were pulse labeled with tritiated thymidine [3H]TdR and killed 9 hr later. A low level incorporation of [3H]TdR into the nuclear DNA of Purkinje neurons was found in autoradiographs. Enzymatic digestions with DNase and with RNase in combination with autoradiographic grain counts indicate that a portion of nuclear DNA is not stable in the Purkinje nucleus. These results are discussed in light of reports of the stable nature of DNA in Purkinje neurons of adult mice.
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