The fumigant and repellent activity of aliphatic lactones against Pediculus humanus capitis (Anoplura: Pediculidae)

New alternative insecticides are necessary for the chemical control of head lice. In this study the fumigant knockdown time 50 percent (KT50) and repellency index (RI) of three aliphatic lactones was compared with two essential oils and DDVP, against permethrin-resistance Pediculus humanus capitis from Argentina. In the fumigant assay, none of the lactones were effective compared to the highest activity of eucalyptus (KT50 15.53 m). In the repellency test, the three lactones were equally or more effective (RI ranging from 60.50 to 76.68) than the positive control (piperonal). These lactones are promising as head lice repellents.

Validation of an electrometric blood cholinesterase measurement in goats

A modified electrometric method was described and validated for measurement of plasma and erythrocyte cholinesterase activities in 6~18 months old goats. The enzymatic reaction mixture contained 3 ml distilled water, 3 ml barbital-phosphate buffer (pH 8.1), 0.2 ml plasma or erythrocytes and 0.1 ml acetylthiocholine iodide (7.5%) as a substrate. The mixture was incubated at 37 degrees C for 40 minutes. The pH of the reaction mixture was determined by a pH meter before and after the incubation. The initial pH was measured before the substrate addition. The enzyme activity was expressed as deltapH/40 min. The coefficients of variation of the described method in measuring plasma and erythrocyte cholinesterase activities were 4 and 2%, respectively. Preliminary reference values (n = 14) of the mean cholinesterase activity (deltapH/40 min) and 95% confidence interval in the plasma were 0.194 and 0.184~ 0.204, respectively, and those of the erythrocytes were 0.416 and 0.396~0.436, respectively. The pseudocholinesterase activity of the plasma cholinesterase was 63.5% as determined by quinidine sulfate inhibition. The organophosphorus insecticides dichlorvos and diazinon at 0.5~4 micrometer and the carbamate insecticide carbaryl at 5~20 micrometer in the reaction mixture significantly inhibited plasma (13.7~85.5%) and erythrocyte (16.4~71.9%) cholinesterases in vitro in a concentration-dependent manner. The results suggest that the described electrometric method is simple, precise and efficient in measuring blood cholinesterase activity in goats.

Change in nucleic acids [RNA and DNA] contents, of Musca Domestica, under the effects of neem compounds and DDVP

Nucleic acids [RNA and DNA] contents were estimated in Musca domestica [PCSIR strain] after LD50 treatment of nem compounds [i. e. Margosan [OTM], H - 34, N6 - b] and an organophosphate [DDVP]. RNA and DNA contents were inhibited by all the undertest compounds. Treatment with Margosan - [OTM], H -34 and N6 - b resulted in the inhibition of RNA content upto 23.37%, 23.55% and 33.32% respectively. Whereas the organophosphate, DDVP decreased the RNA content upto 9.67% The effectiveness of the compounds for inhibiting RNA contents may be summarized as follows DDVP < Margosan - O[TM] < H -34 < N6-b. DNA contents also decreased by all the compounds. Inhibition was 19.49% by Margosan - OTM 35.52% by H - 34; 25.02% by N - 6 - b, and 28.82% by DDVP. The effectiveness of the compounds for inhibiting DNA contents may be summarized as follows. Margosan- O[TM]