Specific Activity Tritium Research Articles

Missing hydrogen transfer from estradiol to androstenedione in the diethylnitrosamine-induced rat hepatoma

In liver-tissue of female rats estradiol-17 α-T is oxydized by NAD or NADP, yielding the tritiumlabelled coenzymes NAD-T or NADP-T which can transfer the tritium to androstendione. So tritium-labelled androstandiol is obtained. Of the added activity 10–30% is oxydized to water. In diethylnitrosamine-induced hepatomas estradiol-17 α-T is oxydized to tritium-water in a comparatively small amount and no transport of the tritium to reduction-products of androstendions occurs. Testing the in-vivo-oxydation of estradiol in normal female rats and in females with hepatoma with the aid of the ‘Stoffwechsel-labil’ labelling (measuring the specific activity of tritium in body-water after injecting estradiol-17 α-T) a lower oxydation-rate was also found in rats with hepatoma than in normal rats.

BEGRENZT DIE KAPAZITÄT DER 17β-STEROID-DEHYDROGENASE DEN IN VIVO UMSATZ VON OESTRADIOL ZU OESTRON?

ABSTRACT By injecting oestradiol-17α-T and testosterone-17α-T to animals or men and measuring the specific activity of tritium in the body water, it is possible to determine the oxydation of these steroids to the corresponding ketones in the whole organism. Using this method combined with a simple arrangement for collecting breathing water it can be shown that the capacity of the 17β-steroid-dehydrogenase does not limit the oxydation of oestradiol and testosterone in intact rats and that no significant difference in the oxydation of both steroids can be found between 0.2 μmol/kg – 200 μmol/kg of injection dosis.

Tritium and deuterium content of atmospheric hydrogen

A substantial increase of man-made tritium in atmospheric hydrogen was first reported by Gonsior in 1959. Begemann and Friedman, also in 1959, pointed out that admixture of industrial hydrogen causes large fluctuations in specific tritium activity. In further measurements Gonsior was able to show that in at least a few cases large activity peaks were directly due to test explosions, thus suggesting that unburned tritium leaves the fire ball. A series of new measurements on the hydrogen extracted directly from raw neon samples shows quantitatively that admixture of industrial hydrogen has indeed a serious effect. In many cases, however, a correction by means of a deuterium assay as suggested by Begemann and Friedman seems practicable. The corrected values show a steady and relatively steep rise in tritium up to 106 TU in 1962. As there was an extended gap in the test series between 1958 and 1961, this behavior points to an additional source of tritium, presumably the nuclear industry, as is the case with Kr83.

Transfer of water across the perfused umbilical cord.

Summary1. Fresh human umbilical cords 20 cm in length were perfused with heparinized Group O blood while immersed in a solution the composition of which was similar to amniotic fluid. 2. Tritiated water was added to the perfusion fluid (blood) or the surrounding bath and the change in specific tritium activity determined as a function of time. 3. Rate of exchange of water between the 2 compartments was calculated to be 40.5 and 50.5 ml of water per hour. 4. Evidence is presented that the umbilical vessels and Wharton's jelly play a significant role in the water exchange of the amniotic fluid.

Observations on the suitability of tritium-labeled cholesterol for the study of cholesterol metabolism

Following the feeding of cholesterol doubly labeled with radioactive hydrogen and carbon, the ratio of tritium specific activity to C 14 specific activity in the serum cholesterol over a 10-day period was found to correspond to the ratio of tritium specific activity to C 14 specific activity in the material fed. These results show that tritium-labeled cholesterol is a suitable tracer compound for biological investigations of many aspects of cholesterol absorption and turnover.