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  • Title: Effect of host feeding and available glucose on glycogen synthase and phosphorylase activities in Hymenolepis diminuta and Vampirolepis microstoma.
    Author: Wages SE, Roberts LS.
    Journal: J Parasitol; 1990 Dec; 76(6):796-804. PubMed ID: 2123923.
    Abstract:
    The influences of host feeding and the availability of glucose in vitro on the activities of glycogen synthase and glycogen phosphorylase in Hymenolepis diminuta and in Vampirolepis microstoma were studied. The worms were recovered from hosts that had been fed ad libitum, starved for 24 hr, or starved 24 hr and then refed for 1 hr immediately prior to worm recovery. The ratios of active to inactive glycogen synthase and phosphorylase were correlated with the host feeding regimen prior to recovery. Glycogen synthase in H. diminuta was predominately in the inactive D form in worms from both fed and fasted hosts. One hour after refeeding, up to 80% of the synthase was in the active I form. Phosphorylase in H. diminuta was predominantly in the active a form in worms from fed and fasted hosts, but activity of this enzyme was suppressed in worms from refed hosts. When H. diminuta from fasted hosts was incubated in a balanced salt solution containing 40 mM glucose, glycogen synthase I increased, and phosphorylase a decreased. Glycogen synthase in V. microstoma was predominantly in the inactive D form in worms from both the fed and fasted hosts, but the proportion in the active I form increased to over half the total synthase by 1 hr of host refeeding. The proportion of glycogen phosphorylase a was high in worms from fed hosts and decreased, but not dramatically, in worms from fasted hosts. The results suggested that the worms had access to another source of glucose, probably from the host bile, and we measured a low but significant concentration of carbohydrate in the gall bladder bile of mice.(ABSTRACT TRUNCATED AT 250 WORDS)
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