In the course of studying molluscicidal effects of microorganisms, a microorganism belonging to Streptomycetaceae, Streptomyces griseolus (Strain 230) was isolated from soil and a certain microbial ingredient proved to have a molluscicidal activity. The effective substance was named antibiotic 230. As a result of several investigations on the antibiotic, the following chemical features were made clear. The chemical substance was an indol-carbazole-heterocyclic compound, the molecular weight 446 and the molecular formula C₂₈H₂₆N₄O₃. The antibiotic demonstrated a molluscicidal effect against Oncomelania snails and their eggs both in the laboratory and in the field. The compound had a wide bacteriostasis spectrum and a slight toxicity to fish in addition to the above, but it was non-toxic to plants.

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Sera collected from 2, 564 inhabitants of different areas in Hyogo Prefecture, Japan, were examined for antibody to Toxoplasma gondii by enzymelinked immunosorbent assay. The overall prevalence rates of male (11.6%) and female populations (7.6%) were significantly different (P<0.001) . The prevalence also depended on age of the population. Of 11 districts three, being far from the sea and occupied mainly by mountains with relatively high altitudes (95-195m), showed a significantly lower average prevalence (5.0%) than the other districts with altitudes of 3-58 m, a part of which was adjacent to the sea (10.6%; P<0.001) . The average prevalence obtained in two districts with annual rainfall of 1, 862-2, 062 mm (16.8%) was significantly higher than that obtained in six districts with annual rainfall of 1, 026-1, 204 mm (8.6%; P<0.001) .

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The present study revealed that the total fluoride level in human whole blood is closely related to the renal function. For the undialyzed patients who had not undergone hemodialysis, the total fluoride level in whole blood linearly increased with the increase of creatinine (Cr) value. The increased fluoride was found to be nonionic in the other blood part than serum, while the nonionic fluoride level in serum was almost constant. That is, the hemodialysis treatment finally reduced the nonionic fluoride level in the other blood part than serum. On the other hand, one hemodialysis treatment could excrete ionic fluoride, but not nonionic fluoride. These results suggest that the ionic fluoride is transformed to nonionic fluoride to be accumulated in other blood part than serum and the nonionic fluoride is transformed to the ionic fluoride to be excreted. Thus the accumulation of nonionic fluoride in other blood part than serum plays a role of the buffer in preventing a too high serum fluoride level.

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