We have recently shown that 5% CO2/95% O2 in the serosal bathing solution, with 100% O2 in the mucosal solution, results in CO2-diffusion limitation of acid secretion in bullfrog gastric mucosa. Changing to 10% CO2/90% 02 on both surfaces doubles the acid secretory rate. We calculate that, were the rate of oxygen consumption to increase significantly as a result of secretory stimulation, the tissue would now be oxygen limited. This prediction is tested by raising the P02 by increasing the total pressure in a hyperbaric chamber. Since no change in acid secretory rate or potential difference was observed upon changing from PO2 = 0.9 to PO2 = 1.9 atm, we conclude that the tissue is not O2 limited at normal pressure. Decreasing PO2 below 0.9 atm, by contrast, decreases the acid secretory rate and raises both PD and resistance. We infer that the rate of oxygen consumption did not rise significantly when acid secretion was increased by supplying sufficient CO2.
A light and electron microscopic study of Sarcocystis orientalis sp. n. was made. The life cycle of this parasite is in two hosts. Gametogony is in the intestinal epithelial cells of a predator, Python reticulatus. Isospora-like oocysts developed. Sporocysts average 9.1 by 7.7 mum. Rats (Rattus norvegicus) were infected with sporocysts and asexual stages developed. Ten days after infection large zoites (average 7.85 by 2.48 mum) were observed free in peripheral blood and within white blood cells. Small schizonts producing merozoites 2-3 mum long were seen in lung tissue. Tissue cysts developed in skeletal muscle and produced numerous cystozoites (average 5.53 by 1.38 mum). Fine structure was similar to previously described Sarcocystis spp.