Biochemistry of normal and irradiated strains of Hymenolepis diminuta

Procedures are described for obtaining uniform infections of Hymenolepis diminuta in rats, and for preparing random samples of this parasite for analysis or in vitro metabolic studies. Best results were obtained when rats were caged individually, both before and after infection. In H. diminuta obtained from pre-patent (14 or 15 days) infections, carbohydrate (glycogen) accounted for 40 to 50% of the tissue solids. Parasites in fasting rats lost 60% of this carbohydrate within 24 hours. Lipids, mainly triglycerides, were also abundant, but unlike carbohydrates were not metabolized during starvation, and may even increase. Cholesterol was the major unsaponifiable substance, and all the phospholipids normally found in higher animals were present, except sphingomyelin. Cerebrosides were also present. Lipids tended to be relatively more abundant in the more posterior proglottids, whereas total nitrogen decreased and carbohydrates were equally distributed throughout the length of the worm. Infective eggs obtained from the terminal proglottids contained relatively little carbohydrate or fats, which were, however, extremely abundant in the parenchyma of these proglottids. Anaerobic in vitro incubation of H. diminuta in bicarbonate buffer confirmed the conclusion that lipids were not catabolized in detectable amounts, and suggested the presence of a significant nitrogen catabolism. Ammonia, urea, and α-amino nitrogen were excreted. Fermentation of exogenous glucose was greater in carbohydrate-depleted worms, but even in undepleted worms endogenous carbohydrate continued to be synthesized. Succinic acid was the major product of fermentation; acetic acid was also excreted in considerable amounts, and lactic and other 3- to 6-carbon acids in small amounts. Fermentation and glycogen synthesis were effectively inhibited when phosphate was substituted for bicarbonate buffer, thus suggesting that carbon dioxide may be an essential nutrient for H. diminuta. Using the procedures and techniques described above, no evidence was found for biochemical differences between normal and irradiated strains of this species.