The possibility of invasion of the extra-intestinal organs of cats by the merozoites and zoites of Isospora rivolta were examined. Four cats (donor) given the organs of mice that had been inoculated with 2.3×10^5 oocysts were necropsied 3 days thereafter. Numerous merozoites in their small intestines and a few zoites in the mesenteric lymph nodes were found. Their intestinal mucosa and extraintestinal organs (liver, mesenteric lymph nodes and spleen) were separated and fed to 2 recipient cats (the 1 st recipient), respectively. The 1 st recipient cats were sacrificed on day 9 and the extra-intestinal organs of each group were fed to other cats (the 2 nd recipient). Both of 2 nd recipients began to shed oocysts from 7 or 9 days after feeding. A greate number of merozoites in donor cats were inoculated into 1 st recipients, whereas the 2 nd recipient shed few oocysts. This result indicate that a few merozoites and zoites may invade the extra-intestinal organs of the 1 st recipient cats.
The mechanism of the development of serotonin-induced gastric mucosal lesions was experimentally studied by administration of exogenous serotonin in rats. The factors considered to affect the microcirculation, such as gastric mucosal blood flow and platelet aggregation, were investigated. Biogenic amines (histamine, serotonin) were also investigated as regulating factors of gastric mucosal blood flow. Furthermore distribution of serotonin in the gastric mucosa was investigated immunohistochemically. Serotonin-induced gastric mucosal lesions were histopathologically observed as hemorrhagic erosion with congestion and necrosis. Gastric mucosal blood flow was significantly decreased soon after the administration of serotonin. Platelet aggregation was also accelerated. As to the distribution of serotonin in the gastric mucosa, cells with positive immunoreaction were found in the deep layer adjacent to the submucosa as well as in the submucosa. These cells were supposed to be mast cells or enterochromaffin cells. The incidence of gastric mucosal lesions closely corresponded with the decrease of mucosal blood flow. These circulatory disturbances seemed to play an important role on the development of the gastric mucosal lesions after administration of serotonin.