Evidence Of Refractoriness Research Articles

Effect of mating on sex attraction in Bactericera cockerelli with evidence of refractoriness

AbstractWe investigated the effect of mating on female attractiveness and male responsiveness in the potato psyllid, Bactericera (= Paratrioza) cockerelli (Šulc) (Hemiptera: Triozidae), a major pest of potato. Assays were designed to examine response by mated or virgin males to volatile odors produced by virgin or mated females. Mating induced a behavioral refractory period during which males were not attracted to females. The refractory period was shown to include a mating‐induced lowering of male response to females, as well as a mating‐induced lowering of female attractiveness. The refractory period was longer in females (at least 48 h) than in males (less than 24 h). Following a post‐copulatory refractory period of 96 h, females were as attractive to males as virgin females. We also explored how rapidly spermatophores became depleted in females as a function of the amount of time following mating. The percent of females carrying spermatophores and the number of spermatophores per female decreased with the length of the female post‐mating period, possibly due to the absorption by females of the spermatophores and their content. By 96 h following mating, spermatophores were not visible in the majority of females, thus the absence of spermatophores in females of this species should not be used as evidence of mating status.

Refractoriness of TSH- and PGE2-stimulated iodine metabolism in cultured porcine thyroid cells, evidence for refractoriness at the level of cAMP action.

In an attempt to study intrinsic regulatory mechanism involved in iodine metabolism, chronic and acute effects of TSH, PGE2 and DBC on iodine uptake, iodide discharge and organic binding of iodine were examined using cultured porcine thyroid cells. Culture in the presence of TSH, PGE2 and DBC for 6 days maintained the ability to thyroid cells to take up iodine and organify it, but culture in the absence of these substances failed to do so. When incubated with NaI in the presence of 1 mM methylmercaptoimidazole (MMI), the cells took up iodide and this accumulated iodide was discharged by TSH, pGE2 and DBC. TSH-, PGE2, and DBC-stimulated iodide discharge was depressed greatly after chronic exposure to TSH, PGE2 or DBC. This refractoriness of TSH-, PGE2- or DBC-stimulated iodide discharge was not specific for each thyroid stimulating substance; previous exposure to TSH, PGE2 or DBC induced refractoriness of TSH-, PGE2- and DBC-stimulated iodide discharge, providing evidence for the existence of refractoriness at the level of cyclic AMP action on iodide discharge. When incubated with NaI in the absence of MMI, the cells took up iodide and organified it. After 30 min incubation with NaI, TSH, PGE2 and DBC were added and they stimulated iodide organification further. This TSH- and PGE2-stimulated iodide organification was also depressed after exposure to TSH or PGE2. These data indicate that, as an intrinsic regulatory mechanism, refractoriness is operating at the level of cAMP action on iodine discharge and organification.