Proton nuclear magnetic resonance (NMR) spectra of liver extracts from mice infected with cysticerci of Taenia crassiceps for 84 or 200 days showed differences in the concentrations of liver metabolites as compared with those of normal liver. The livers of mice infected for 84 days contained less glycogen and β-hydroxybutyrate but more glycine, taurine, betaine, phosphocholine (PC), choline, alanine and lactate. At 200 days post-infection (p.i.) the levels of hepatic glycogen and β-hydroxybutyrate remained lower and those of taurine, PC, choline, alanine and lactate were still elevated, but the concentration of glycine fell below that seen in the 84-day group and that of betaine assumed a value not statistically different from that of either the controls or the 84-day group. The concentrations of glucose, glycerophosphocholine, acylcarnitine, succinate and acetate stayed unchanged throughout the experiment.& b d y : During their existence in the mammalian host, cysticerci of Taenia crassiceps successfully resist the immunological responses of the host and induce various histopathological manifestations (Freeman 1964;Chernin and McLaren 1983;Bojail et al. 1993). As they proliferate in the peritoneal cavity, their demand for nutrients increases, which results in a pronounced loss of the host's net body weight (Crompton et al. 1985) and its eventual death. To explore further the consequences of nutrient competition in this host-parasite system we examined, utilizing nuclear magnetic resonance (NMR) spectroscopy, the influence of cysticerci on liver metabolism in the mouse host.A total of 20 Swiss-Webster female mice aged 3 months were inoculated intraperitoneally with 0.5 ml of packed T. crassiceps metacestodes each. Ten uninfected mice served as controls. Half of the infected mice were dissected on day 84 of the infection and the other half were killed at 200 days post-infection (p.i.). At the time of dissection the mice were anaesthetized intramuscularly with pentobarbital (60 mg/kg), after which their abdomens were opened and their livers, excised. The organs and the cysticerci collected from the peritoneal cavity of infected mice were rinsed in saline, weighed and immediately frozen in liquid N 2 . All samples were kept at -70°C until extracted and prepared for NMR analysis according to the method described by Blackburn et al. (1993) except that each sample was resuspended in 1.3 ml D 2 O. A known amount of sodium [2, 2, 3, 3-2 H 4 ]-3-trimethylsilylpropionate (TSP) was added as a chemical shift and intensity standard. The 1 H-NMR spectra of extracts were obtained with a Bruker AMX-500 NMR spectrometer using the acquisition parameters previously described by Novak et al. (1992); peak assignments and the method of quantitative measurement are also discussed therein. Data were analyzed statistically using analysis of variance (ANOVA). An α value of ≤0.05 was deemed significant.The livers of mice infected for 84 days contained less glycogen (the values indicate the concentration in micromoles of glucose units havin...