Impact of Cymbopogon Flexuosus (Poaceae) Essential Oil and Primary Components on the Eclosion and Larval Development of Aedes Aegypti

The current study describes the effects of sub-lethal concentrations and constituent compounds (citral and geranyl acetate) of Cymbopogon flexuosus essential oil (EO) on the development of Aedes aegypti. We treated eggs with 6, 18, and 30 mg.L-1 and larvae with 3 and 6 mg.L-1 EO concentrations. Citral and geranyl acetate were evaluated at 18, 30, and 42 mg.L-1 and compared to the commercial growth inhibitors (diflubenzuron and methoprene). We measured larval head diameter, siphon length, and body length. Finally, we examined concentrations of moult hormone (MH) and juvenile hormone III (JH III) using high-performance liquid chromatography coupled to mass spectrometry. The EO decreased egg hatching at all concentrations and altered molting among larval instars and between larvae and pupae, with an increase in the length (3 mg.L-1: 6 ± 0.0 mm; 6 mg.L-1: 6 ± 0.7 mm) and head width (3 mg.L-1: 0.8 ± 0 mm; 6 mg.L-1: 0.8 ± 0.0 mm) compared with the control group. We did not detect chromatographic signals of MH and JH III in larvae treated with C. flexuosus EO or their major compounds. The sub-lethal concentrations C. flexuosus EO caused a similar effect to diflubenzuron, decreasing hormone concentration, extending the larval period, and death.

The influensing of the tick-borne encephalitis virus to the process of metamorphosis of engorged larvaes and nimphs of the tick Ixodes ricinus

In laboratory experience the conditions for development engorged larvaes (n = 2 500) and nymphs (n = 800) of Ixodes ricinus with diapause (6 h of light) are simulated. In contrast to control (diapause), the ticks with tick-borne encephalitis virus (strain EK- 328), developed under three variants; namely with diapause, with acceleration metamorphosis, and without diapause. The distinc- tions are caused by a season of the year and influence of the virus. The realization of variants carries out by stimulation or blocking of moult hormone.

Effects of nutrition on hormone profiles and patterns of deiodinase activity in the skin and associated patterns of hair follicle activity and moult in cashmere goats

The effects of nutrition on patterns of live-weight change, hair follicle activity, moult, hormone profiles and associated activities of monodeiodinase enzyme types II and III (MDII and MDIII) in cashmere goats were investigated. From 1 week before the winter solstice (mid December), one group of 15 animals was given a ration designed to provide 2·0 × live weight maintenance requirements (high; H) while a second, similar, group was given 0·8 × live weight maintenance requirements (low; L). After approximately 3 months, L animals had significantly lower mean live weights (P<0·01) than H animals. This was associated with lower (P<0·05) overall mean hair follicle activity in L than H animals during the March to May period and a lower overall mean moult score during March and April in L animals (P<0·01) but a similar mean date of moult onset. Mean concentrations of all of the hormones measured exhibited significant changes (P<0·01) with date of sampling. Overall mean concentrations of insulin, tri-iodothyronine and thyroxine did not differ with treatment but, compared with L animals, H animals exhibited higher mean concentrations of prolactin in April and May (P<0·05) and of insulin-like growth factor-1 in December and January (P<0·001). Rates of activity of MDII and MDIII in skin differed with date (P<0·001) but were not significantly affected by nutritional treatment. The MDIII/MDII ratio differed (P=0·05) with month but was significantly higher (P<0·05) in L than H animals in January, only. It is concluded that the reduction in hair follicle activity and the slower onset of moult associated with reduced nutrition were unlikely to be controlled, directly, by differences in activities of MDII or MDIII in skin tissue.