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Studies on the in vitro exsheathment of Brugia pahangi—I. The effects of abdomen and midgut homogenates of susceptible Aedes aegypti compared with refractory Anopheles stephensi and Culex quinquefasciatus on endopeptidase induced in vitro exsheathment of B. pahangi

Published online by Cambridge University Press:  19 September 2011

Lucy W. Irungu
Affiliation:
The International Centre of Insect Physiology and Ecology (ICIPE), P.O. Box 30772, Nairobi, Kenya
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Abstract

Abdomen homogenates of refractory C. quinquefasciatus and Anopheles stephensi prepared from equal and varying wet weights of abdomen, were shown to inhibit endopeptidase induced in vitro exsheathment of Brugia pahangi microfilariae. This inhibitory effect was removed by heat treatment and centrifugation of the homogenates. Abdomen homogenate from susceptible Aedes aegypti did not inhibit exsheathment. This suggested the presence of some inhibitory factor in the abdomens of the two insusceptible species of C. quinquefasciatus and An. stephensi. There was no evidence of this inhibitory effect in the midgut homogenates of the three mosquito species. Foetal calf serum and bovine serum albumin also inhibited endopeptidase induced exsheathment of B. pahangi microfllariae, suggesting that the protein concentration of the proteinaceous substances also determined the extent of inhibition. In the absence of endopeptidase, incubation in midgut homogenate of the 3 species of mosquito did not initiate exsheathment, suggesting that the conditions present in vitro did not simulate those persisting in the mosquito midgut in vivo.

Résumé

Il a été montré que des homogenats de l'abdomen du Culex quinquefasciatus refractoire et du Anopheles stephensi préparés à partir des poids humides de l'abdomen inhibent le dégagement in vitro sous l'effet de l'endopeptidase, des microfilaires du B. pahangi. Cet effet inhibiteur était écarté pour un traitement à la chaleur et par la centrifugation des homogénats. L'homogénat abdominal des Ae. aegypti susceptibles n'a pas empêché le dégagement—ceci suggère la présence d'un facteur inhibiteur dans les abdomens des deux espèces non susceptible (C. quinquefasciatus et An. stephensi). Aucune évidence de cet effet inhibiteur ne fut tracée dans les homogénats des mi-intestins des 3 espèces de moustiques. Le sérum d'un faetus d'un agneau et l'albumine du sérum bovin empêchent aussi le dégagement, sous l'effet de l'endopeptidase, des microfilaires du B. pahangi, suggerant ainsi que la concentration en protéine des substances à protéine determinent aussi le niveau d'inhibition.

En l'absence d'endopeptidase, l'incubation dans les homogénats des mi-intestins des 3 espèces de moustiques n'a pas déclenché le dégagement, suggérant ains que les conditions prevalent in vitro n'ont pas simulé cells qui persistent dans les mi-intestins de la moustique in vivo.

Type
Research Articles
Copyright
Copyright © ICIPE 1987

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References

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