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H Townson

Publications and source records attributed to H Townson.

35 records · Page 2Linked to original sources
PubMed1990

Purification and properties of an esterase from organophosphate-resistant strain of the mosquito Culex quinquefasciatus.

Organophosphate-resistant and -susceptible strains of Culex quinquefasciatus (mosquito) have been compared on the basis of their esterase activities. The homozygous resistant strain (Dar) shows two highly active esterases after starch-gel electrophoresis, of Rm 0.2 and 0.4, which are absent from susceptible strains (Apo, Mon), and which previous selection studies have shown to be inseparable from organophosphate resistance. After SDS/polyacrylamide-gel electrophoresis and silver staining of total C. quinquefasciatus proteins, a 62 kDa band is observed in strain Dar at high concentrations, and in susceptible strains in trace amounts. After Western blotting, this 62 kDa protein is recognized by antisera raised against the two esterases eluted from starch gels. After chromatofocusing of Dar proteins, the 62 kDa protein is seen to be associated with esterase activity, and of a similar pI to that observed for esterases after isoelectric focusing. Post-translational modification is not required for recognition of the 62 kDa putative esterase, since the protein is immunoprecipitated by the anti-esterase serum from products of translation of Dar mRNA in vitro.

Animals↗
PubMed1981

Enzymes for species identification in the Simulium damnosum complex form West Africa.

An electrophoretic survey of 44 enzyme systems of the Simulium damnosum complex has revealed only two that are of value in species diagnosis, namely PGM and trehalase. S. yahense has a unique PGM variant, and S. yahense and S. squamosum have a different trehalase variant from S. sirbanum, S. damnosum s.s., S. sanctipauli and S. soubrense. Examination of S. damnosum s.l. from Mali, Ivory Coast and Ghana has shown that PGM and trehalase can be used to distinguish accurately adult S. yahense from S. squamosum and these two from S. sirbanum, S. damnosm s.s., S. sanctipauli and S. soubrense.

Africa, Western↗
PubMedDate not supplied

Morphometric differentiation of Onchocerca volvulus and O. ochengi infective larvae.

By microinjection of cryopreserved microfilariae (mf) into nulliparous flies, a comparison of the lengths of the infective larvae (L3) of Onchocerca volvulus and O. ochengi from the head of Simulium damnosum s.l. (presumed S. sirbanum) has been made. The suitability of S. sirbanum as a host was similar for both Onchocerca spp. The mean length +/- standard deviation of O. ochengi infective larvae measured in aqueous medium after storage of infected flies in liquid nitrogen was 762 +/- 63 microns (n = 39), significantly longer (P much less than 0.0001) than those of a savanna isolate of O. volvulus (676 +/- 56 microns, n = 26). Although the frequency distributions of the lengths of larvae of the 2 species overlapped, a critical value for discrimination of 719 microns applied to normally distributed populations with means and standard deviations of these samples would result in correct classification of 78% of true O. volvulus and 75% of true O. ochengi. A discriminant function analysis incorporating width measurements did not usefully improve the level of accuracy of discrimination. Larvae from flies stored in 70% ethanol and stained with acid haemalum were about 10% shorter, but O. ochengi infective larvae were still proportionately longer than those of O. volvulus (693 +/- 40 microns, n = 45 compared to 580 +/- 38 microns, n = 6, respectively). These data show that the infective L3 of O. volvulus and O. ochengi differ morphologically. Although the population length distributions overlap, by classifying larvae greater than 719 microns long as O. ochengi and those less than 719 microns long as O. volvulus a more accurate estimation of true O. volvulus infection rates in S. damnosum s.l. can be derived than is currently possible.

Animals↗