Synergistic growth promoting action of L-cysteine and nitrogen upon Hymenolepis diminuta cysticercoids in vitro.

Development in vitro of cysticercoids of the cestode Hymenolepis diminuta in the presence of L-cysteine proceeded twice as rapidly under 100% nitrogen as it did with air as the gas phase. No growth was obtained with the following: D-cysteine, L-cysteine methyl ester, S-aminoethyl cysteine, L-cystine, glutathione (reduced), L-methionine, D-pantothenic acid, taurine, or thioglycolic acid; limited growth only was obtained with ascorbic acid and dithiothreitol. Homocysteine or coenzyme A was as effective as L-cysteine in stimulating the complete development of oncospheres to cysticercoids. Experiments with 14C-L-cysteine indicated that L-cysteine was perhaps incorporated into the organisms.