Ruth Kaplan

The Capacitation Rate of Rat Sperm in Vitro

In the rat, as in many rodents where semen is deposited directly into the uterus, it is believed that the principal site for capacitation is the oviduct. In vivo, there is a temporal correlation between the migration of fertilizing sperm into the ampulla and the appearance of oocyte-cumulus complexes there. It has been suggested (Gwatkin 77) that in some rodents cumulus cells play an important part in capacitation while in others (Hoppe & Whitten 74, Niwa & Chang 74) their importance was not shown.

The resolution of pyrimidine bases, nucleosides, and nucleotides by thin-layer chromatography

Abstract Nucleic acid research frequently necessitates the analytical resolution of nucleic acid derivatives. Thin-layer chromatography (tlc), for its simplicity, short development time, and superior resolving power, is often preferable to other methods (1–3). Although the literature contains a large number of methods that have been devised for the separation of purine and pyrimidine derivatives (4,5) no tlc technique has hitherto been described for the concomitant separation of bases, nucleosides, nucleoside 5′-monophosphates, nucleoside 3′-monophosphates, nucleoside diphosphates, and nucleoside triphosphates. The present communication deals with methods devised for the simultaneous separation of the above-mentioned pyrimidine derivatives. They enable the resolution of either the six uracil derivatives or the six cytosine derivatives, on commercial cellulose tlc sheets. Alternatively, the six pyrimidine derivatives can be separated on cellulose layers 0.75 mm thick. Since formic acid extracts of bacterial cells do not interfere with the separation, these methods can be used for the direct estimation of extracts of biological materials.

Purine-pyrimidine requirement for ribonucleic acid synthesis in an Escherichia coli mutant defective in potassium accumulation

Abstract The effect of base supplementation on RNA synthesis in potassium-deprived Escherichia coli B-207 was investigated. In unsupplemented minimal medium, potassium deprivation inhibits the net accumulation of RNA. Supplementation of the minimal-sodium medium with one purine and one pyrimidine restores net RNA accumulation. In the presence of the base supplement, the rate of RNA synthesis in the potassium-depleted cell is identical to the rate observed in potassium-grown cells. Potassium deprivation decreases by 40 % the amount of pyrimidine triphosphates in the pool but does not affect the amount of purine triphosphates. The rate of labelling of purine and pyrimidine nucleoside triphosphates in the pool is decreased by 85–90 % during potassium starvation. The addition of one purine and one pyrimidine to the sodium medium increases by 70 % and by 140 % the respective amounts of CTP and of UTP in the pool. The short-term labelling of all four nucleoside triphosphates is increased up to 10-fold by base supplementation.