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SHORT COMMIUNICATIONS 27c pronounced change in the ratio of the trans to the cw forms, with the concentration of the former always being several times greater than that of the latter. There was little evidence of double-bond migration under normal conditions. The conjugated linoleic acid and linolenic acid have retention volumes greater than those ofthe normal compounds and could be separated by gas-liquid chromatography (Daniels & Richmond, 1960). No conjugated linoleic acid and linolenic acid could be detected either during control periods or during periods in which oleic acid was infused. Conjugates accounted for 5-10% of the polyenoic acids during infusion of small amounts of nonconjugated linoleic acid and linolenic acid and 15-25% during infusion of larger amounts. The conjugated polyenoic acids are hydrogenated with difficulty (Garton, 1959) and would be expected to accumulate to a much greater extent than the non-conjugated acids. The above results offer no support for the hypothesis that the process of hydrogenation involves appreciable bond migration and accumulation of conjugated acids (Shorland et al. 1957; Kepler et al. 1965), but they are consistent with the hypothesis that elaidic acid, and not oleic acid, is an intermediate in the hydrogenation of the polyenoic acids in the rumen. We are grateful to Miss G. H. McG. Breckenridge for her assistance with the analyses.

SUMMARYMethods for the assay of sporidesmin and the sporidesmolides were worked out and used in the study of the production of these metabolites by Pithomyces chartarum (Commonwealth Mycological Institute, Kew, England, Herbarium no. 74873) growing on an enriched potato carrot medium. High yields of sporidesmin and the sporidesmolides were associated with high utilization of medium constituents. No increase in the quantity of sporidesmin isolated from unit volume of medium was observed after the third day of incubation, despite further rapid growth of the fungus; by contrast good correlation was observed between the weight of sporidesmolides produced and fungal growth. These results were successfully applied to the production of experimental quantities of these materials.

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