autoradiography). With maturation of the marrow elements, the tritiated thymidine indices fell below pretreatment values. Serial serum samples obtained from these patients affected the incorporation of tritiated thymidine into DNA in primary cultures of normal bone marrows. In relation to pretreatment sera, samples obtained during the proliferative phase caused a twofold increase in tritiated t...

Barnacle embryos were reared in Millipore cytology monitors containing approximate tritiated water (HTO) concentrations of background plus 0, 10, 10, 10, 10, 10, and 10 μCi/ml. After 32 days the cultures were fixed and the numbers of larvae counted. A “molting index,” the percentage of larvae that molted at least once, was used to evaluate the effects of HTO on normal development. Effects were ...

Tritiated digoxin turnover studies were performed in nine children aged 4 days to 7 years. Mean serum turnover time was 32.5 (range 18-48) hours, and the 3-day urine and stool excretion was 55% of the total dose administered. These findings are quite similar to those observed in adults and indicate that the larger doses of digoxin required for digitalization in infants are not accompanied by in...

The effects of an intraruminal load of 3 litres of water on body water movements was compared in Sardi sheep during the last month of pregnancy, lactation and a non-pregnant, non-lactating control period. Before the water load, rumen fluid volume, estimated by polyethylene glycol was similar in pregnant, compared to control, animals and 27% higher in lactating sheep. After the water load, rumen...

A rapid and sensitive radiometric assay for assessing the potential of drugs to inhibit cytochrome P450 (P450) 3A4/5 in human liver microsomes is described. In contrast to the conventional testosterone 6beta-hydroxylation assay, the new method does not require high-performance liquid chromatography (HPLC) separation and mass spectrometry. The assay is based on the release of tritium as tritiate...

Rats were fed a semi-purified diet containing 0.5% cholesterol; cholesterogenesis was measured in vivo 70 min after [1-14C]-acetate or tritiated water was incorporated into the gastrointestinal tract sterols. The results were qualitatively similar with the two precursors. Cholesterol synthesis was preponderant in the small intestine and mainly occurred in its mucosa with a decreasing biosynthet...