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Y S Chow

Publications and source records attributed to Y S Chow.

6 recordsLinked to original sources
PubMed1997

Involvement of juvenile hormone in regulation of prothoracicotropic hormone transduction during the early last larval instar of Bombyx mori.

We previously reported that a deficiency in prothoracicotropic hormone (PTTH) transduction during the early last larval instar of Bombyx mori plays a role in leading to very low ecdysteroid levels in the hemolymph, inactivation of corpora allata, as well as larval-pupal transformation. In the present study, the role of juvenile hormone (JH) in the regulation of PTTH transduction was clarified. When JH analog (hydroprene) was applied to early last instar larvae, the development of larvae was greatly inhibited. It was found that it was not PTTH release, but prothoracic gland competency in both cAMP generation and ecdysteroidogenesis to the stimulation of PTTH which was developmentally inhibited by hydroprene application. Glands in hydroprene-treated larvae showed no response in ecdysteroidogenesis to either PTTH or 1-methyl-3-isobutylxanthine (MIX) until day 7, 4 days later than those of control larvae. JH-I application showed the same effects as those of hydroprene. By contrast, allatectomy on day 0 of the last instar accelerated development, and glands showed the activation response to either PTTH or MIX in both cAMP generation and ecdysteroidogenesis 1 day after allatectomy. From these results, we conclude that the absence of JH is a prerequisite for successful PTTH transduction and for acquisition of the cAMP generating system of gland cells.

Animals↗
PubMed1996

A deficiency in prothoracicotropic hormone transduction pathway during the early last larval instar of Bombyx mori.

The prothoracicotropic hormone (PTTH) is an insect cerebral peptide that stimulates the prothoracic glands to produce ecdysteroids that initiate moulting and metamorphosis. During the last larval instar of holometabolous insects, a reduction in the hemolymph juvenile hormone (JH) levels is a necessary step in initiating larval-pupal transformation. Recently we have demonstrated that very low ecdysteroid levels in the early last larval instar of Bombyx mori initiate the complete inactivation of corpora allata (CA). Results presented here further indicate that PTTH signal transduction pathways undergo specific developmental changes, with a deficiency in transduction in prothoracic gland cells occurring during the early last instar. Glands from the early last instar showed no increase in either cAMP levels or steroidogenesis to the stimulation of PTTH, indicating the absence of the PTTH receptors in gland cells. We propose that this absence of PTTH receptors plays a critical role in directing larval-pupal transformation.

Animals↗
PubMed1990

[The application of sex pheromones and juvenile hormone analogs on cockroaches].

The sex pheromone of cockroaches is the chemical which transmits the copulation signal between female and male roaches of the same species. It is produced by virgin females in most roaches, and the chemical structures have been identified for the American, German and Japanese cockroaches. Periplanone-B (PB) and periplanone-A (PA) have been synthesized in the laboratory and tested both in lab and field, showing good biological responses. The sex pheromones of the German cockroach are 3,11-dimethyl-2-nonacosanone, 29-hydroxy-3,11-dimethyl-2-nonacosanone and 29-oxo-3,11-dimethyl-2-nonacosanone, and because of their low volatile nature, they would not be used up in a short time. Periplanone-J (PJ) is produced by the Japanese cockroach. The juvenile hormone analogs (JHA) are chemicals which mimic the juvenile hormones (JH). They have the physiological actions of JH which are maintaining the larvae and nymphs in their immature stages or making the reproductive organs differentiate incompletely, and thereby interfering with their reproduction. The JHA which have been commercialized to control roaches are hydroprene, pyriproxyfen and fenoxycarb. The first two have been proved to reduce the roach population in field tests in the USA and Japan. For some reason, if the sex pheromone and the JHA are used together, the net effect will be more than if they are used alone. In the presence of the sex pheromone, the cockroaches' movements increase, so the chance for a roach to contact the sprayed JHA is also increased. This might be the possible reason for the above observation.

Animals↗
PubMed1985

Templeting and self-assembly.

Templeting and self-assembly represent the two extremes of the spectrum of determinate pattern-assembly processes. A templeted pattern can be defined as one that requires a prepattern or templet explicitly specifying the final topology of the pattern. Conversely, a self-assembling pattern can be defined as one for which the inherent constraints of the precursor elements alone are sufficient to specify the final pattern. Both concepts can be directly expressed in matrix notation, and a simple matrix measure, the templeting index, characterizes the relative amount of templeting or of self-assembly in any particular system. With this language, a fundamental principle of pattern-assembly becomes evident: in the determinate realm, some patterns can only be assembled using the same-sized templets--templets that are at least as large as the final pattern.

Mathematics↗