scholarly journals Nutritional sensitivity of fifth instar prothoracic glands in the tobacco hornworm, Manduca sexta

2009 ◽  
Author(s):  
Amy L. Walsh
Keyword(s):  
Manduca Sexta ◽  
Tobacco Hornworm ◽  
Prothoracic Glands

scholarly journals Developmental endocrinology of larval moulting in the tobacco hornworm, Manduca sexta

1987 ◽  
Vol 128 (1) ◽  
pp. 175-192
Author(s):  
W. E. Bollenbacher ◽  
N. A. Granger ◽  
E. J. Katahira ◽  
M. A. O'Brien
Keyword(s):  
Manduca Sexta ◽  
Cumulative Effect ◽  
Peptide Hormone ◽  
Tobacco Hornworm ◽  
Corpora Allata ◽  
Indirect Measure ◽  
Prothoracic Glands ◽  
Single Burst ◽  
Larval Moult

A larval moult in the tobacco hornworm, Manduca sexta, involves an endocrine cascade that begins with the release of a cerebral peptide hormone, the prothoracicotropic hormone (PTTH). The release of PTTH is gated, occurs during the scotophase and appears to be developmentally cued. In fourth instar Manduca larvae, PTTH release into the haemolymph occurs as a single burst over a few hours during the head critical period, i.e. the time during which the head (brain) is needed for the initiation of the moult to the fifth (last) instar. Released PTTH activates the prothoracic glands (PGs), and within a few hours the cumulative effect of this event results in a dramatic increase in the haemolymph ecdysteroid titre, which then elicits the moult. An assessment of the capacity of the corpora allata (CA) to synthesize juvenile hormone (JH) in vitro indicates that the above sequence of endocrine events begins only when JH synthesis has reached a nadir for the instar. Since CA activity is an indirect measure of the haemolymph titre of the hormone, it is conceivable that the developmentally cued release of PTTH is permissively controlled by a decreasing haemolymph titre of JH. With the increase in the ecdysteroid titre which marks the end of this endocrine cascade, the CA again become active, presumably to cause the increase in the JH haemolymph titre which directs the larval moult. This investigation has thus established the temporal and quantitative dynamics of the PTTH-PG axis that drive larval moulting and provides insight into the interendocrine regulatory relationships that may exist between the ecdysteroids and JHs. These possible relationships and the role of the brain in their regulation are discussed.

scholarly journals Regulation of ecdysone biosynthesis in the tobacco hornworm, Manduca sexta: titre of the haemolymph stimulatory factor during the last larval instar

1987 ◽  
Vol 128 (1) ◽  
pp. 159-173
Author(s):  
R. D. Watson ◽  
T. K. Williams ◽  
W. E. Bollenbacher
Keyword(s):  
Manduca Sexta ◽  
Dose Response ◽  
Larval Instar ◽  
Critical Role ◽  
Tobacco Hornworm ◽  
Pupal Development ◽  
Prothoracic Glands ◽  
Important Regulator ◽  
Titration Protocol ◽  
Stimulatory Factor

A recently isolated haemolymph protein appears to be an important regulator of ecdysone biosynthesis by prothoracic glands in Manduca sexta. Using a dose-response titration protocol, the haemolymph titre of this stimulatory factor was determined during the last larval instar. The titre was high (greater than 2.0 U ml-1) on days 0 and 1, then dropped significantly to 0.55 U ml-1 on day 2, and remained depressed until day 4. The titre of the stimulatory factor then increased to a peak of 1.62 U ml-1 on day 7, and remained elevated (approx. 1.1 U ml-1) until the end of the instar. A set of physical and biochemical criteria was used to confirm that the stimulatory activity present in haemolymph on different days of the instar represented the presence of the factor. The data are consistent with the hypothesis that fluctuations in the titre of the haemolymph stimulatory factor play a critical role in regulating ecdysone biosynthesis during larval-pupal development.

In vitro metabolism of possible ecdysone precursors by the prothoracic glands of the tobacco hornworm, manduca sexta

Steroids ◽  
1979 ◽  
Vol 34 (5) ◽  
pp. 509-526 ◽  
Author(s):  
W.E. Bollenbacher ◽  
A.F. Faux ◽  
M.N. Galbraith ◽  
L.I. Gilbert ◽  
D.H.S. Horn ◽  
...  
Keyword(s):  
Manduca Sexta ◽  
Tobacco Hornworm ◽  
In Vitro Metabolism ◽  
Prothoracic Glands
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