Ecdysteroids in Helminths. In: Hoffmann J, Porchet M, editors. Biosynthesis, Metabolism and Mode of Action of Invertebrate Hormones. Berlin: Springer Berlin Heidelberg; 1984. pp. 323-30. [DOI: 10.1007/978-3-642-69922-1_30]

Levels of ecdysteroid-like material in adults of Nippostrongylus brasiliensis during the intestinal phase

Total ecdysteroid-like immunoreactive material was assayed and quantified in adults of the parasitic nematode N. brasiliensis during the intestinal phase in the rat in order to detect possible physiological fluctuations in titre. Worms of the same sex isolated from one rat were pooled in order to quantify ecdysteroids using enzyme immunoassay (EIA). The concentration of ecdysteroids fluctuated during adult life according to the sex and the age of the parasite. Important differences of levels of ecdysteroid-like compounds between the two sexes of parasites were noted particularly at 128 and 168 h post-infection. The peak at 128 h, present in female, but not in male worms, corresponds to the time of egg-laying. Following HPLC-EIA analysis, the presence of ecdysone, 20-hydroxyecdysone and apolar ecdysteroid-like material was ascertained during this peak. The physiological role and the possible origin of ecdysteroids in this nematode are discussed.

The effect of invertebrate hormones and potential hormone inhibitors on the third larval moult of the filarial nematode, Dirofilaria immitis, in vitro

The effects of the insect hormones, ecdysone and 20-hydroxyecdysone, certain non-steroidal ecdysteroid agonists (RH compounds) and the inhibitor, azadirachtin, on the timing of the 3rd-stage moult of Dirofilaria immitis were investigated. 20-Hydroxyecdysone and RH 5849 when used at a concentration of 10(-5) M, resulted in a premature timing of this moult. Azadiracthin, at a similar concentration, prevented moulting of most of the larvae to the 4th stage. The results are discussed in relation to the possibility of a hormonal role for ecdysteroids and neuropeptide-like compounds in the control of ecdysis in filarial nematodes, that maybe somewhat comparable to the system which is found in insects.

Effects of potential inhibitors on Brugia pahangi in vitro: macrofilaricidal action and inhibition of microfilarial production

A series of compounds that apparently disrupt hormonally regulated processes in insects have been examined for effects on the viability and microfilarial production of adult Brugia pahangi cultured in vitro. The azasteroids, 25-azacoprostane and 25-azacholestane, inhibited the production of microfilariae at 5 ppm, the former also exhibiting macrofilaricidal activity at this concentration. The brassinosteroids examined inhibited microfilarial production at 5 ppm but did not affect worm viability. Azadirachtin also proved to be a significant inhibitor of microfilarial release without effect on worm motility or viability. Of all the compounds tested, the non-steroidal amines appeared to be the most promising as potential filaricides, several of them proving to be macrofilaricidal at 1 ppm and affecting microfilarial production at even lower concentrations.