ABSTRACT
Although estrogen is well known as a vertebrate sex steroid, its presence in insects, including Bombyx mori, raises questions about its precise role in the physiology of insects. It was reported earlier that estradiol-17beta (E(2)) exerts a specific effect on silk-gland function in B. mori and that it may act in a nuclear-mediated way. To evaluate further the effect of E(2) on cocoon characters, larval growth and development, 1µg/g of E(2) was applied topically to the first and second day of fifth instar larvae. This resulted in a significant enhancement of cocoon characters, such as cocoon shell weight, silk filament length per cocoon, denier per filament and reelability of the cocoons, without any adverse effect on fecundity and hatchability. In the present study, E(2) levels in the haemolymph were quantified on different days of the fifth instar larvae and age-dependent changes in the endogenous E(2) titre have been demonstrated. These age-dependent variations in E(2) content coincide with physiological events occurring during the fifth instar. Such observations exclude the possibility of a dietary origin for E(2), as a sudden and sharp rise of the E(2) level in the haemolymph was observed on the 10th day of the fifth instar, preceded by a small increase on the ninth day after an eight-day feeding period. The increased level of estradiol in the haemolymph of larvae treated topically with E(2) indicates effective penetration of this hormone through the larval cuticle. Moreover, similar patterns of alteration of E(2) levels on different days of the fifth instar in both control and treated groups suggests the existence of some internal metabolic pathway in the silkworm body to regulate the hormone titre. Thus, the present investigation offers a system for investigating the unique function of E(2) in B. mori and offers potential for improvement of silk production.
ABSTRACT
An experimental technique based on a modified vibrating orifice aerosol generator has been employed to study unsteady evaporation of linear streams of highly monodisperse binary microdroplets of volatile constituents over short time periods (i.e., <1 ms), such that the droplet composition remains nearly constant. The droplet size and temperature (i.e., refractive index) have been determined with high temporal resolution from the resonances observed in the simultaneous elastic and Raman light scattering spectra obtained by varying the droplet size through modulation of droplet generation frequency. By using this technique we show that thermodynamic parameters of binary systems, such as activity coefficients as well as vapor pressures of the constituents as functions of temperature, can be determined. We have applied the procedure to study unsteady evaporation rates of pure ethanol and methanol droplets as well as binary droplets containing various ratios of ethanol and methanol. We have obtained vapor pressures of ethanol and methanol as functions of temperature as well as activity coefficients of ethanol and methanol as functions of composition, and the results show excellent agreements with the values reported in the literature. The technique presented in this paper is applicable to any binary system containing at least one volatile constituent. Copyright 2000 Academic Press.
