Activity of the prothoracic gland and its sensitivity to prothoracicotropic hormone in the penultimate and last-larval instar of Bombyx mori

Okuda, Miho; Sakurai, Shigeki; Ohtaki, Tetsuya

doi:10.1016/0022-1910(85)90092-7

Cited by 90 publications

(32 citation statements)

References 25 publications

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“…For example, a surge of basal activity of isolated PG during the feeding period has been reported in Bombyx and Manduca, which is not reflected by the increased hemolymph ecdysteroid titer in intact animals (29,30). This discrepancy is presumably due to the removal of active neural inhibition from isolated PGs.…”

Section: Ementioning

confidence: 89%

Regulation of insect steroid hormone biosynthesis by innervating peptidergic neurons

Yamanaka

Žitňan

Kim

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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In insects, steroid hormones named ecdysteroids elicit molting and metamorphosis. The prothoracic gland (PG) is a predominant source of ecdysteroids, where their biosynthesis (ecdysteroidogenesis) is regulated by several neuropeptides. Here, we report that FMRFamide-related peptides (FaRPs) regulate ecdysteroidogenesis through direct innervation of the PG in the silkworm Bombyx mori. We purified a previously uncharacterized Bombyx FaRP, DPSFIRFamide, and identified the corresponding Bombyx FMRFamide gene (Bommo-FMRFamide, BRFa), which encodes three additional FaRPs. All BRFa peptides suppressed ecdysteroidogenesis in the PG by reducing cAMP production by means of the receptor for Bommomyosuppressin, another FaRP we have previously shown to act as a prothoracicostatic factor. BRFa is predominantly expressed in neurosecretory cells of thoracic ganglia, and the neurons in the prothoracic ganglion innervate the PG to supply all four peptides to the gland surface. Electrophysiological recordings during development confirmed the increased firing activity of BRFa neurons in stages with low PG activity and decreased ecdysteroid levels in the hemolymph. To our knowledge, this study provides the first report of peptides controlling ecdysteroidogenesis by direct innervation.ecdysteroid ͉ FMRFamide-related peptides ͉ metamorphosis ͉ molting ͉ prothoracic gland

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Section: Ementioning

confidence: 89%

Regulation of insect steroid hormone biosynthesis by innervating peptidergic neurons

Yamanaka

Žitňan

Kim

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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“…It is also reported that the PTG in the early stage of the fifth instar is not even responsive to PTTH due to a deficiency in PTTH signaling . Although PTTH does not induce steroidogenesis in isolated PTGs during the early stages of the last larval instar (Okuda et al, 1985;Gu & Chow, 1993;Gu et al, , 1997, in intact larvae, however, a detectable level of ecdysteroid in the haemolymph is reported Sakurai et al, 1998;this study). Thus, we hypothesize that although the PTG is a likely candidate for insulin-mediated increased ecdysteroidogenesis in 1 day old Bombyx larvae provided with food, the involvement of other tissues cannot be ruled out, as in the present study an increase in ecdysteroid level was recorded in both neckand thorax-ligated day 4 larvae injected with insulin.…”

Section: Discussionmentioning

confidence: 73%

A comprehensive study of the changes in ecdysteroid levels during the feeding phase of fifth instar larvae of the silkworm, Bombyx mori (Lepidoptera: Bombycidae)

Keshan¹,

Thounaojam²,

Kh.³

2015

Eur. J. Entomol.

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Abstract. The present study describes changes in haemolymph ecdysteroid levels during the feeding phase of fifth instar larvae of Bombyx mori. A small and sharp peak in ecdysteroid level was recorded on day 4 when larvae had already reached the critical weight (2.76 ± 0.11 g) for metamorphosis. Food deprivation of larvae from day 4 resulted in an increase in the ecdysteroid level. Injection of insulin in both 1 day (before reaching critical weight) and 4 day (after reaching critical weight) old fed larvae resulted in an increase in the ecdysteroid level. However, when deprived of food only the haemolymph ecdysteroid levels of 4 day old larvae respond to an injection of insulin. The hormone level was also increased by treating 1day old larvae with a juvenile hormone analogue, but again, like insulin, only the fed larvae were affected by this treatment. Neck-and thorax-ligated 4 day old larvae had decreased ecdysteroid levels compared to both fed and food deprived larvae. However, a significant increase in ecdysteroid level was recorded in both neck-and thorax-ligated larvae injected with insulin. The injection of 20-hydroxyecdysone into 4 day old larvae resulted in an increase in the level of this substance in the haemolymph of fed and food deprived larvae, but the level was significantly higher in neck-and thoraxligated la rvae. The data, thus, indicates that ecdysteroid levels vary both in relation to the critical weight of the larvae and its nutritional status, and insulin might also play an important role in regulating the level of ecdysteroid.

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“…The present results agree with the report by . Okuda et al (1985) reported that the responsiveness of the PG to PTTH in the penultimate larval instar was higher than that of the last larval instar of Bombyx mori. supported this finding by following the change of the signal transduction pathway in the PG to PTTH.…”

Section: Discussionmentioning

confidence: 99%

Ecdysteroid Titer, Responsiveness of Prothoracic Gland to Prothoracicotropic Hormone (PTTH), and PTTH Release of the Recessive Trimolter Strain of Bombyx mori in Extra-ecdysed Larvae by JHA and 20E Application

et al. 2001

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Activity of the prothoracic gland and its sensitivity to prothoracicotropic hormone in the penultimate and last-larval instar of Bombyx mori

Cited by 90 publications

References 25 publications

Regulation of insect steroid hormone biosynthesis by innervating peptidergic neurons

Regulation of insect steroid hormone biosynthesis by innervating peptidergic neurons

A comprehensive study of the changes in ecdysteroid levels during the feeding phase of fifth instar larvae of the silkworm, Bombyx mori (Lepidoptera: Bombycidae)

Ecdysteroid Titer, Responsiveness of Prothoracic Gland to Prothoracicotropic Hormone (PTTH), and PTTH Release of the Recessive Trimolter Strain of Bombyx mori in Extra-ecdysed Larvae by JHA and 20E Application

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