Variation in the susceptibility to cold injury in Indians

The peripheral vascular responses during local cold stress, (heat output from the hands and cold induced vasodilatation-CIVD response) were studied on 4 groups (10 each) of Indian population, viz., South-Indians, North-Indians, Gurkhas and High Altitude Natives (HAN) of 3,500m. The parameters were recorded at Delhi, and at 3,500 m in thermoneutral laboratory (25–28°C). The sea level readings of HAN were taken after 3 weeks of their stay at Delhi; and that of lowlanders at 3,500 m were taken after 3 weeks of their sojourn. The results show that the heat output and CIVD were highest in HAN, and lowest in the South-Indians. The responses of the other two groups were similar in nature and were better than that of South-Indians. Based on an earlier study which has shown that individuals with higher heat output and CIVD are better protected against the occurrence of cold injuries, it can be suggested that HAN are most resistant and the South-Indians are highly susceptible to the occurrence of cold injuries.     

Microplate assay of elevated esterase activity in individual pyrethroid-resistant mosquitoes

Involvement of esterase-mediated hydrolysis as a mechanism of pyrethroidresistance in three species of mosquitoes,viz., Aedes aegypti, Culex quinquefasciatus andAnopheles Stephensi was investigated by microplate assay of Β-esterases in individual larva and adult female and male mosquitoes. Assuming an absorbance value of 0.4 and above at 555 nm as the threshold level of elevated esterase activity which confers resistance, frequency distributions of such individual test mosquitoes were constructed in resistant and susceptible populations. The results indicate the involvement of ester hydrolysis of Pyrethroids as a predominant mechanism of pyrethroid-resistance in the larvae ofCulex quinquefasciatus but not inAedes aegypti. However, a marginal role of esterases is indicated in the larvae ofAnopheles stephensi.