Isolation of stem cells from the mid gut epithelium of culex pipiens mosquitoes [diptera: culicidae]

Stem cells are undifferentiated cells that remarkable ability to self-renew and produce differentiated cells that support normal development and tissue homeostasis. The authors isolated spherical stem cells from the midgut epithelium of the late third larval instars of Culex pipiens mosquitoes. In vitro, cultivated epithelial stem cells were able to proliferate and differentiate in fresh culture for 48 hr in absence of 20- hydroxyecdysone [20-E]. The stem cells were the most common cells in the initial culture. One hundred of epithelial stem cells had been cultured. After 24 hr became 132 cells, 78% was undifferentiated stem cells and 8.3% and 13.7% was enterocytes and goblet cells respectively. This ratio slightly decreased after de 48 hr to be 74% undifferentiated stem cells, 4.5% enterocytes and 5.6% goblet cells. After 72 hr the undifferentiated stem cells were not able to proliferate .The most differentiated goblet and enterocytes survived few days then died

Psorophora columbiae and Psorophora toltecum (Diptera: Culicidae) Colombian populations cannot be differentiated by isoenzymes

Two populations of the mosquito Psorophora columbiae from the central Andean area of Colombia and one population of Ps. toltecum from the Atlantic coast of Colombia were analyzed for 11 isoenzyme markers. Psorophora columbiae and Ps. toltecum are two of the main vectors of Venezuelan equine encephalitis. We found no conspicuous genetic differences between the two species. The relatively high gene flow levels among these populations indicate that these are not two different species or that there has been recent divergence between these taxa. In addition, no global differential selection among the loci was detected, although the alpha-GDH locus showed significantly less genetic heterogeneity than the remaining loci, which could mean that homogenizing natural selection acts at this locus. No isolation by distance was detected among the populations, and a spatial population analysis showed opposite spatial trends among the 31 alleles analyzed. Multiregression analyses showed that both expected heterozygosity and the average number of alleles per locus were totally determined by three variables: altitude, temperature and size of the human population at the locality. Individually, the expected heterozygosity is more related to these three variables than to the average number of alleles

Involvement of mono-oxygenases as a major mechanism of deltamethrin-resistance in larvae of three species of mosquitoes.

Role of mono-oxygenases as a mechanism of resistance to the synthetic pyrethroid, deltamethrin in the larvae of Culex quinquefasciatus Say, Aedes aegypti L. and Anopheles stephensi Liston developed by laboratory selections with deltamethrin, DDT or deltamethrin and the synergist, piperonyl butoxide (PBO) in the ratio of 1:5, was investigated. There was a significant correlation with mono-oxygenase activity and larval LC50 to deltamethrin in various strains of all the three species. In addition, the activity of glucose-6-phosphate dehydrogenase (G6PD), the main NADPH generating enzyme for mono-oxygenases, also showed enhanced activity in deltamethrin and DDT-selected strains. The present data, therefore, clearly suggest that deltamethrin resistance in the larvae of Cx. quinquefasciatus, Ae. aegypti and An. stephensi is mainly due to the detoxification of deltamethrin by microsomal mono-oxygenases. High activity of G6PD observed in DDT-selected strains seems to be related to its role as a rate-limiting enzyme in GSH-dependent dehydrochlorination of DDT.