Ecdysteroid titer during larval-pupal-adult development of the tobacco hornworm, Manduca sexta

Bollenbacher, Walter E.; Smith, Stan L.; Goodman, Walter G.; Gilbert, Lawrence I.

doi:10.1016/0016-6480(81)90005-8

Cited by 303 publications

(125 citation statements)

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“…PTTH is synthesized in the brain and released from the corpora allata. PTTH stimulates the synthesis and secretion of ecdysone (Bollenbacher et al, 1979;Bollenbacher et al, 1981). The release of PTTH is dependent upon the time of day (Truman, 1972;Truman and Riddiford, 1974).…”

Section: Hormonal Regulation Of Molting and Metamorphosismentioning

confidence: 99%

“…Upon ecdysis into the fifth instar there is a high level of JH that inhibits prothoracic glands and prevents the release of PTTH (Nijhout and Williams, 1974b;Bollenbacher et al, 1981). By the second day of the fifth larval stage there is a decline in JH (Wolfgang and Riddiford, 1986;Baker et al, 1987).…”

Section: Hormonal Regulation Of Molting and Metamorphosismentioning

confidence: 99%

“…Once secreted, PTTH stimulates the prothoracic glands to secrete the first peak of ecdysone (Bollenbacher et al, 1981). The first peak of ecdysone occurs on the fourth day of the fifth instar.…”

Section: Hormonal Regulation Of Molting and Metamorphosismentioning

confidence: 99%

“…In normally feeding larvae, JH levels drop by the second day of the fifth instar (Wolfgang and Riddiford, 1986;Baker et al, 1987). This is permissive of the release of PTTH from the brain and allows the prothoracic glands to respond to PTTH (Nijhout and Williams, 1974b;Bollenbacher et al, 1981). It has been shown that when larvae are starved, levels of JH remain high until feeding was resumed (Cymborowski et al, 1982;MacWhinnie et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

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

Walsh

Smith

2011

Journal of Insect Physiology

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The tobacco hornworm, Manduca sexta, has been a useful model for studying insect endocrinology. In M. sexta the majority of growth occurs during the fifth (final) larval stage. This growth is concurrent with endocrine changes that lead to a metamorphic molt. Past research has focused on the interplay of three growth hormones: juvenile hormone (JH), prothoracicotropic hormone (PTTH) and ecdysone, in regulating metamorphosis. The prothoracic glands, source of ecdysteroid molting hormones in insects, play a crucial role in coordinating growth. Insulin/insulin-like growth factor (IGF) signaling has been shown to regulate growth and secretion of steroidogenic tissues in both vertebrates and invertebrates, but it had yet to be well-characterized in M. sexta.In this dissertation I examined the role of insulin-directed growth in prothoracic glands during both normal larval development and in response to nutrient deprivation. In particular, I predicted that in response to a reduction in nutrients, the prothoracic glands would stop growing and ecdysone secretion would be reduced. Changes were assessed in actin abundance and in two nutritionally sensitive transcripts, insulin receptor and 4EBP.Actin abundance in prothoracic glands increased in the first four days of this stage, demo nstrating significant growth. Actin decreased in glands from starved larvae, indicating a cessation of growth. Both insulin receptor and 4EBP transcript were present during normal larval development. As expected, both insulin receptor and 4EBP transcript increased in response to starvation. This research was the first demonstration of insulin signaling in prothoracic glands of fifth instar M. sexta larvae, and revealed nutritional sensitivity of the prothoracic glands. 5Finally, ecdysone assays were conducted to determine the impact of nutrition on glandular secretory capacity. Starved larvae were unable to secrete as much ecdysone as fed controls. Injections of insulin were unable to rescue the ability of the glands to secrete high levels of ecdysone. This demonstrated that although insulin signaling was correlated with normal growth of the glands, insulin is not sufficient to impact the ability of the glands to secrete ecdysone in the absence of nutrie nts. 6 This thesis is dedicated to my parents,Robert and Angela Walsh, whose love and support made this dissertation possible.

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Section: Hormonal Regulation Of Molting and Metamorphosismentioning

confidence: 99%

Section: Hormonal Regulation Of Molting and Metamorphosismentioning

confidence: 99%

Section: Hormonal Regulation Of Molting and Metamorphosismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Walsh

Smith

2011

Journal of Insect Physiology

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“…[129][130][131] Later on, the changes of the concentration of the molting hormone were determined in the hemolymph. 132 The so-called "commitment peak" of 20E appears just at the beginning of the wandering period when the first autophagic structures are formed in the fat body cells. The physiological or developmental autophagy in the course of the normal postembryonic development is induced by this hormonal stimulus.…”

Section: Pcd Of Nurse Cells and Follicle Cells Is Absolutely Requiredmentioning

confidence: 99%

Autophagy and its physiological relevance in arthropods: Current knowledge and perspectives

Malagoli¹,

Abdalla²,

Cao³

et al. 2010

Autophagy

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Remodeling of the peripheral processes and presynaptic terminals of leg motoneurons during metamorphosis of the hawkmoth,Manduca sexta

1996

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During metamorphosis of the hawkmoth, Manduca sexta, the muscles, cuticular structures, and most sensory neurons of the larval thoracic legs are replaced by new elements in the adult legs. The thoracic leg motoneurons, however, survive the loss of the larval muscles and persist to innervate new targets in the imaginal legs. Here we have used biocytin staining, immunocytochemistry, and confocal microscopy to follow the fates of the peripheral processes and presynaptic terminals of the leg motoneurons. Although the most distal processes of the motor nerves retract following the degeneration of larval leg muscles, the axon terminals always retain close association with the muscle remnants and the anlagen of the new adult muscles. As the imaginal muscles differentiate and enlarge, the motor terminals expand to form adult presynaptic terminals. An antibody to the presynaptic protein, synaptotagmin, revealed its localization to the terminal varicosities in both larval and adult stages but distribution within pre-terminal branches during adult development. Electrophysiological methods revealed that functional neuromuscular transmission first occurs quite early during metamorphosis, before the differentiation of contractile elements in the muscle fibers.

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Ecdysteroid titer during larval-pupal-adult development of the tobacco hornworm, Manduca sexta

Cited by 303 publications

References 10 publications

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

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

Autophagy and its physiological relevance in arthropods: Current knowledge and perspectives

Remodeling of the peripheral processes and presynaptic terminals of leg motoneurons during metamorphosis of the hawkmoth,Manduca sexta

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