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Biomedical subjects

J Hemingway

Publications and source records attributed to J Hemingway.

96 records · Page 6Linked to original sources
PubMed1983

Biochemical studies on malathion resistance in Anopheles arabiensis from Sudan.

The change from larval to adult mosquito control in the Gezira area of Sudan resulted in a decrease in the prevalence of malaria in this region. House spraying with malathion began in 1975 and resistance to this compound was first detected in 1978. Laboratory tests showed that adult Anopheles arabiensis Patton were resistant to malathion and phenthoate but susceptible to all other organophosphates tested. The larvae of this strain were susceptible to malathion. The malathion resistance in the adults was synergized by triphenyl phosphate, but not by piperonyl butoxide. This suggests that a carboxylesterase enzyme may be the basis of malathion resistance in this strain. Analysis of general esterase levels to alpha- and beta-naphthyl acetate showed that there was no quantitative change in the amount of carboxylesterase enzyme present in the resistant strain as compared to the susceptible. The absence of larval resistance suggests that house spraying rather than agricultural spraying is the major source of selection pressure. The presence of a high level of adult malathion resistance in A. arabiensis may decrease the efficacy of malathion for malaria control in Sudan. The lack of cross-resistance to organophosphates which do not contain a carboxylester bond means that insecticides such as fenitrothion are still practical alternatives.

Animals↗
PubMed1983

Resistance to organophosphate and carbamate insecticides in Anopheles atroparvus.

Adult Anopheles atroparvus, from Cadiz, Spain (strain AT SPA) were resistant to several organophosphorus and carbamate insecticides. Separate lines of the AT SPA strain selected with propoxur, fenitrothion, fenthion and malathion were cross-resistant to these insecticides as well as chlorphoxim and bendiocarb. Lack of synergism between malathion and triphenyl phosphate (TPP), a carboxylesterase inhibitor and between fenitrothion and piperonyl butoxide (PB), a multi-function oxidase inhibitor, against the selected lines suggests that resistance to these insecticides may be non-metabolic. Lack of synergism of propoxur after 2 h exposure with PB, sensamex and SV1 (which all inhibit multi-function oxidases), may suggest that the same mechanism is involved here. However, all three synergists were effective in conjunction with 6 h exposure to propoxur. The postulated mechanisms are: a non-metabolic resistance, possibly an altered site of action, responsible for the non-synergizable resistance to organophosphorus insecticides and to a lesser extent the carbamates and a multi-function oxidase inhibitor-suppressed mechanism conferring resistance to propoxur.

Anopheles↗
PubMedDate not supplied

Natural swarming behaviour of the molecular M form of Anopheles gambiae.

In Anopheles gambiae, as in most species of mosquitoes, mating is initiated in flight. The males aggregate in aerial swarms and conspecific females individually fly to these swarms where they mate with males. In this study, we investigated the swarming behaviour of A. gambiae and conducted 2 surveys in the rice field area of the Vallée du Kou in Burkina Faso in 1999 and 2002. A high number of anopheline mosquitoes were observed in this area and both molecular M and S forms of A. gambiae were found in sympatry. Swarms formed a few minutes after sunset in different places and no obvious markers were associated with their occurrence. However, swarms occurred close to cow herds generally in open flat areas, 2-3 m above the ground. Overall, 2829 anopheline mosquitoes were collected from 21 swarms composed primarily of males. A few specimens of Culex quinquefasciatus were collected from 3 swarms. Although both molecular M and S forms were found in sympatry in the village, swarms were composed almost exclusively of the molecular M form. This suggests that there are alternative swarming habits for both molecular M and S forms of A. gambiae in nature.

Africa, Western↗
PubMedDate not supplied

Cloning, expression and characterization of an insect class I glutathione S-transferase from Anopheles dirus species B.

Insect class I glutathione S-transferases (GSTs) were expressed from cDNA obtained from larvae of the Thai malaria vector. Anopheles dirus in a PCR RACE (rapid amplification of cDNA ends) reaction using a primer to the conserved N-terminal region of An. gambiae class I GSTs and a synthetic oligo d(T)-adaptor primer. Seven different plasmids, resulting from sub-cloning of an original single 0.7 Kb PCR band, were picked at random and sequenced. Four of these were clearly GSTs on the basis of putative amino acid sequence conservation. All the sequences had a conserved N-terminal region, but were highly divergent at the C-terminus. The variability in the PCR products suggests that there is a high level of GST class I isoenzyme variability in larval An. dirus. One of the subclones from the PCR reaction contained a full coding region of the cDNA for GST. This had a putative amino acid sequence which was 76 and 91% identity to the An. gambiae GST class I, agGST 1-5 and agGST 1-6 respectively, but only 48% identity to agGST 1-2. The catalytically active enzyme, expressed in Escherichia coli, was strongly immuno-cross reactive with antisera raised against the two An. gambiae class I GSTs. The expressed enzyme was purified to homogeneity from an E. coli cell lysate by S-hexylglutathione agarose affinity chromatography. The enzyme had a high specific activity with CDNB, and also used DCNB and ethacrynic acid as substrates. In addition, it had peroxidase and DDTase activity and its activity with CDNB, was strongly inhibited by a range of organophosphorus and pyrethroid insecticides. This is consistent with the predicted role of this GST class in insecticide resistance.

Amino Acid Sequence↗