Ana María Fernández Presas

The key steroidogenic enzyme 3β-hydroxysteroid dehydrogenase in Taenia solium and Taenia crassiceps (WFU)

Larval and adult stages of Taenia solium and Taenia crassiceps WFU strain were analyzed by histochemical and biochemical methods to determine the existence of steroid pathways. The presence of the key enzyme 3β-hydroxisteroid-dehydrogenase (3β-HSD) was examined in frozen sections of cysticerci obtained from mice and segments of tapeworms obtained from the intestine of hamsters. 3β-HSD activity was detected by nitroblue-tetrazolium products after incubation with dehydroepiandrosterone, androstendiol, or pregnenolone. Tapeworm tissues exhibited 3β-HSD activity in the subtegumentary areas of the neck and immature proglottids following incubation with androstendiol, as well as surrounding the testes in mature proglottids. T. solium cysticerci exhibited 3β-HSD activity in the subtegumentary tissues. The synthesis of steroid hormones involving the activity of 3β-HSD was studied in cysticerci or tapeworms incubated in the presence of tritiated steroid precursors. The culture media were analyzed by thin layer chromatography and showed synthesis of androstendiol, testosterone, and 17β-estradiol by cysticerci, androstendiol, and 17β-estradiol by tapeworms. The results strongly suggest the activity of 3β-HSD in taeniid parasites that have at least a part of the enzymatic chain required for androgen and estrogen synthesis and that the enzymes are present in the larval stage and from the early strobilar stages to the mature proglottids.

Apoptosis patterns in experimental Taenia solium and Taenia crassiceps strobilae from golden hamsters

Apoptosis or programmed cell death (PCD) patterns of two taeniid species, Taenia solium and Taenia crassiceps, were explored in adult tapeworms grown in golden hamsters. Animals were fed either ten viable T. solium cysticerci from naturally infected pigs or from T. crassiceps WFU strain maintained in Balb/c mice. Adult strobilae were recovered from the intestine at different times after infection and either frozen at −70°C or fixed in paraformaldehyde–glutaraldehyde. Frozen sections were processed using the DNA fragmentation fluorescent TUNEL reagents and examined in an epifluorescent microscope. Fixed tissues were processed for light and electron microscopy. Typical apoptotic cells were found in the central core of scolex and strobilar tissues, mainly in the germinal tissue and subtegumentary areas. By the TUNEL technique, cells exhibited the characteristic fluorescent images of condensed nuclear chromatin. By light microscopy of thick sections stained with toluidine blue, we found a number of small rounded cells which had lost their cytoplasmic bridges and had shrunken nuclei with aggregated chromatin, cells which were found interspersed with normal syncytial cells. Similar cell morphology was confirmed by electron microscopy. Stunted viable worms, recovered with longer mature specimens, had very short strobilae and exhibited a large number of apoptotic cells in the germinal neck tissues. The results are consistent with the syncytial nature of these parasites, and strongly suggest that cell proliferation and PCD in these adult cestodes are continuous processes of the germinal tissue and tegumentary cytons.