ADAPTATIONS TO A TERRESTRIAL EXISTENCE BY THE ROBBER CRAB, BIRGUS LATRO L.: III. NITROGENOUS EXCRETION

Nitrogenous excretion by the terrestrial anomuran crab Birgus latro L. was examined. The main excretory product was uric acid, representing 79.5 % of total excretory nitrogen. It was eliminated as white faeces separate from undigested food material and made up 82.6% of excretory faecal nitrogen. The faeces were the principal route of nitrogenous excretion, accounting for 96.2% of total excretion. Loss of nitrogen in the urine and as gaseous ammonia was negligible. The midgut gland had substantial activity of xanthine oxidase and was considered to be the site of production of uric acid and its point of entry into the gut

Arginine synthesis and nitrogen excretion in the myxomycete Physarum polycephalum

The nitrogen excretory metabolism of the myxomycete Physarum polycephalum was studied. When cultured in partially defined broth medium or on agar, the principal excretory product was ammonia nitrogen. A small, variable quantity of urea was excreted in liquid culture. No uric acid or other purines were detected in the cultures. When microplasmodia were incubated with sodium [14C]bicarbonate, radioisotope was incorporated into citrulline, arginine, and urea. Incubation with L-[carbamoyl-14C]citrulline yielded labelled arginine, urea, and CO2. Substantial urease activity was found in extracts of the microplasmodia. These results, in conjunction with the lack of an absolute nutritional requirement for arginine, provide evidence that Physarum has a functional arginine biosynthetic pathway, an arginase, and a urease.

Metabolism of Intravenously Administered 17α-[6,7-3H]Estradiol-17-Glucoside in Normal Women

17α-[6,7-3H]estradiol-17-glucoside was injected intravenously into two normal young women. Within 72 h, 60 and 46% of the 3H dose was excreted in the urine in the two experiments. In the first 6 h, 4 and 1.4% of the dose was excreted as the unchanged glucoside, together with 14 and 5% in the form of a double conjugate, identified as 17α-estradiol-3-glucuronide-17-glucoside. Over the periods 6–24 h and 24–48 h none of the injected glucoside and only minor amounts of the double conjugate were present in the urine. The main excretory product after 6 h was 17 α-estradiol-17-glucuronide. This latter result contrasts with that obtained in previous experiments in which 17β-estradiol-6,7-3H-17-glucoside was injected, and in which the main monoconjugates excreted were the 3-glucuronides of 17β-estradiol and estrone.