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At least 847 records · Page 47Linked to original sources
PubMed1985

Developmental physiology of cestodes: cyclic nucleotides and the identity of putative crowding factors in Hymenolepis diminuta.

Worm-conditioned saline (WCS) was prepared by incubating Hymenolepis diminuta from crowded infections for 12 hr in a balanced salt solution. The effect of the WCS on the incorporation of [3H] thymidine into DNA in the anterior regions of fresh H. diminuta was compared to effects produced by the cyclic nucleotides in the WCS. Cyclic AMP and cGMP were found in the WCS, and cGMP but not cAMP (at the concentration in WCS) caused some inhibition of DNA synthesis. For further study of the effects of cyclic nucleotides, worms were incubated with theophylline, caffeine, 3-isobutyl-1-methyl xanthine, 2-deoxy cGMP, and L-ascorbic acid, all of which produced some inhibition of [3H] thymidine incorporation. Treatment of WCS with 3',5' cyclic nucleotide phosphodiesterase abolished part of its inhibitory activity, i.e., that part presumed to be due to cGMP. When worms were incubated in the presence of succinate, acetate, D-glucosaminic acid, and cGMP simultaneously and in the concentrations each was found in the WCS, DNA synthesis was inhibited to a degree equal to that found in the WCS. Thus these substances apparently represent the putative crowding factors in the WCS. WCS prepared with worms from different population densities contained the same levels of cAMP but varied in content of cGMP, which decreased as the worm density increased. WCS prepared with patent worms contained high levels of cAMP, but the same amounts of cGMP as WCS prepared with 10-day-old worms. At least some inhibitors of cyclic nucleotide phosphodiesterase inhibited the secretion of cGMP by the worms. Levels of cGMP in the host intestine varied with the presence or absence of worms, number of worms, and area of the intestine.

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PubMed1988

Adoptive transfer of immunity with peritoneal exudate cells to the cestode Hymenolepis nana.

Under certain conditions, peritoneal exudate cells (PEC) removed from Hymenolepis nana-eggs infected mice, transferred to normal recipients severely inhibited the establishment of worms from a challenge infection, as expected in an immune state. A close relationship was observed between numbers of challenge worms and immune response. A significant effect was clearly demonstrable when the highest dose of eggs (150) was used, but the effect was less and not significant different when a smaller doses (30) was administered.

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PubMedDate not supplied

[The ability of cestodes to synthesize serotonin].

The ability of the parasitic flat worms Hymenolepis diminuta and Mesocestoides corti to synthetize serotonin (5-HT) has been investigated by means of incubation the worms in metabolic precursor of 5-HT, L-tryptophan, and monoamineoxidase inhibitor, indopan, followed by spectrofluorimetric determination of the tissue level of 5-HT. To avoid possible inhibition of 5-HT synthesis by exogenous 5-HT of the host, experiments were carried out on worms in which the level of 5-HT was previously decreased by reserpine. The increase in the level of 5-HT in tissues after incubation of the worms in L-tryptophan and indopan was observed, indicating their ability to synthetize serotonin from tryptophan.

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PubMed1985

Thymus dependency of induced immune responses against Hymenolepis nana (cestode) using congenitally athymic nude mice.

Anti-parasite antibody responses were compared among several strains of mice experimentally infected with the dwarf tapeworm, Hymenolepis nana. The antibody titres were highly variable among the mouse strains in addition to variation in worm fecundity and longevity. The influence of the thymus on both infection and anti-parasite antibody production (especially of IgE isotype) was studied by the use of congenitally athymic (nu/nu) nude and their phenotypically normal (nu/+) CD-1(ICR) mice infected with H. nana. All nude (nu/nu) mice harboured fully mature 70 day old adult tapeworms of the first generation derived from eggs initially given on day 0. In addition, they contained (a) younger second generation adults derived from autoinfection and present in the intestinal lumen, (b) a number of abnormally large (about 1-2 mm in diameter) balloon like, fluid filled cysticercoids in not only the intestinal tissue but also parenteral tissues such as the mesenteric lymph nodes, liver and lung, and (c) normal cysticercoids derived from challenging eggs in the intestinal tissue. Infected nude mice produced no antibodies detectable by PCA (IgE) and double diffusion (IgG) tests. In contrast, normal (nu/+) mice and nude mice reconstituted with thymocytes expelled almost all luminal adults of the primary infection by day 70 and produced antibodies to extracts of adult H. nana. Neither autoinfection nor reinfection following egg challenge occurred in any of these normal (nu/+) and reconstituted nude mice. Therefore, acquired immune responses against H. nana (as assessed by resistance not only to the tissue phase measured by the failure of tissue cysticercoid recovery from egg challenge, but also to the lumen phase assessed by the failure of autoinfection adult recovery and 'worm expulsion' of the initially established adults) are all thymus-dependent in mice. The antibody responses examined are also thymus-dependent.

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