Lethal effects of synthetic juvenile hormone on the human body louse.

Abstract

Synthetic juvenile hormone (SJH) was prepared as described by Law et al.2 by bubbling hydrogen chloride gas through an ice-cold solution of farnesenic acid (Frinton Laboratories, South Vineland, New Jersey) dissolved in 100 volumes of absolute ethanol. The flow of gas was continued for five minutes to give a 9.4 per cent increase in weight. The flask was stoppered and stored in an ice bath in the dark for four hours. It was then warmed to room temperature and stored in the dark for an additional 19 hours. The reaction mixture was rinsed with petroleum ether into a separatory funnel and washed three times with an excess of water. The ethereal phase was collected and the solvent removed on a rotary evaporator at room temperature. The resultant golden oil was rinsed with 95 per cent ethanol into a separatory funnel and water added to incipient cloudiness. The solution was neutralized with 0.1 M sodium hydroxide to a phenolphthalein end-point and the ethereal phase collected and reduced to dryness on a rotary evaporator. The resultant golden oil, which was used without any further purification, is known to contain six materials with high juvenile hormone activity. For convenience of expression in the present report, this mixture of materials is called synthetic juvenile hormone. Exposure of lice and lice eggs to SJH: Adult lice were placed on 3- X 3-cm woolen pads impregnated with known concentrations of SJH and eggs were deposited on the pads. In control experiments lice were- placed and eggs were laid on pads impregnated with a corresponding amount of peanut oil. Each pad was impregnated with 1 ml of a solution of SJH or peanut oil in absolute methanol; the solvent was evaporated before use. The number of eggs on each pad was counted with the aid of a dissecting microscope. Empty or collapsed eggs were discarded. To facilitate counting, a piece of glass marked into a grid with a diamond pencil was placed over the pad. The grid was rinsed in acetone and in 95 per cent ethanol to prevent contamination of subsequent pads. Experimental and control lice were fed in separate compartments of an arena on the shaved belly of a rabbit. The shaved skin was washed with 70 per cent ethanol before and after feeding and the arena with acetone after each use.