Identification of the cellular target for eclosion hormone in the abdominal transverse nerves of the tobacco hornworm,Manduca sexta (original) (raw)
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Peripheral Neurosecretory Cells of Insects Contain a Neuropeptide with Bursicon-Like Activity
The Journal of Experimental Biology, 1989
In insects, neurosecretory cells have been found not only within ganglia of the central and stomatogastric nervous system, but also in the peripheral nerves (Fifield & Finlayson, 1978; Wasserman, 1985; Baudry-Partiaoglou, 1987). These peripheral neurones and their processes along peripheral nerves contain electrondense granules and stain with various dyes for neurosecretory cells, suggesting that they produce, store and probably release neurosecretory material. The nature of this material, however, is unknown. Only the results of Raabe (1986), showing that some abdominal peripheral neurosecretory cells of three insects are glucagonimmunoreactive, have suggested that such cells are peptidergic. We demonstrate in this study that a group of peripheral neurosecretory cells in crickets contains such a peptide. Moreover, we are able to suggest a function for this peptide and thus for an identified set of peripheral neurosecretory neurones. We have discovered a group of three, hitherto undescribed, peripheral neurosecretory cells (PNC) in the neck region of crickets (Gryllus bimaculatus) with the aid of cobalt chloride backfills (Tyrer & Altman, 1974) of prothoracic and suboesophageal nerves, followed by silver intensification (Bacon & Altman, 1977) (Fig. 1). In addition, a network of fibres with superficial varicosities is revealed on all anterior nerves of the prothoracic ganglion and one nerve of the suboesophageal ganglion when PNC are labelled anterogradely (Figs 1, 2A,B). Electron micrographs of the PNC (Fig. 2C) reveal a cytoplasm containing electron-dense vesicles, mitochondria, Golgi complexes and rough-surfaced endoplasmic reticulum, indicating that these cells are in an active metabolic phase. Sections of the nerves covered with PNC projections show processes embedded in the neural sheath of the nerve, filled with electron-dense vesicles of the same type as those in the PNC cytoplasm (Fig. 2D). Many PNC fibres enter the median nerve, an unpaired nerve between the neck connectives, via its branches, the transverse nerves (Fig. 1). In insects, median and transverse nerves are neurohaemal organs (NHO) where neurosecretory material is stored and released into the haemolymph (Gupta, 1983).
Journal of Experimental Biology
In insects, neurosecretory cells have been found not only within ganglia of the central and stomatogastric nervous system, but also in the peripheral nerves (Fifield & Finlayson, 1978; Wasserman, 1985; Baudry-Partiaoglou, 1987). These peripheral neurones and their processes along peripheral nerves contain electrondense granules and stain with various dyes for neurosecretory cells, suggesting that they produce, store and probably release neurosecretory material. The nature of this material, however, is unknown. Only the results of Raabe (1986), showing that some abdominal peripheral neurosecretory cells of three insects are glucagonimmunoreactive, have suggested that such cells are peptidergic. We demonstrate in this study that a group of peripheral neurosecretory cells in crickets contains such a peptide. Moreover, we are able to suggest a function for this peptide and thus for an identified set of peripheral neurosecretory neurones. We have discovered a group of three, hitherto undescribed, peripheral neurosecretory cells (PNC) in the neck region of crickets (Gryllus bimaculatus) with the aid of cobalt chloride backfills (Tyrer & Altman, 1974) of prothoracic and suboesophageal nerves, followed by silver intensification (Bacon & Altman, 1977) (Fig. 1). In addition, a network of fibres with superficial varicosities is revealed on all anterior nerves of the prothoracic ganglion and one nerve of the suboesophageal ganglion when PNC are labelled anterogradely (Figs 1, 2A,B). Electron micrographs of the PNC (Fig. 2C) reveal a cytoplasm containing electron-dense vesicles, mitochondria, Golgi complexes and rough-surfaced endoplasmic reticulum, indicating that these cells are in an active metabolic phase. Sections of the nerves covered with PNC projections show processes embedded in the neural sheath of the nerve, filled with electron-dense vesicles of the same type as those in the PNC cytoplasm (Fig. 2D). Many PNC fibres enter the median nerve, an unpaired nerve between the neck connectives, via its branches, the transverse nerves (Fig. 1). In insects, median and transverse nerves are neurohaemal organs (NHO) where neurosecretory material is stored and released into the haemolymph (Gupta, 1983).
The Biology of the Prothoracicotropic Hormone Peptidergic Neurons in an Insect
Integrative and Comparative Biology, 1993
SYNOPSIS. The prothoracicotropic hormone and the cerebral peptidergic neurons that produce it have traditionally been thought to have the singular function of acting as a primary effector of insect postembryonic development. Recent investigations of this neuroendocrine axis in the tobacco hornworm, Manduca sexta, are leading to a new view that these peptidergic neurons and their peptide phenotypes may be multifunctional. They may act in different ways depending upon the animal's developmental stage and site of phenotype release. The possibility for this functional diversity of the prothoracicotropic hormone is possibly even greater due to multiple neuronal sites of peptide expression within the central nervous system. Similarly, the L-NSC III may have more functions due to the expression of multiple peptide phenotypes. The data, thus far, have not enabled us to identify additional physiological roles for the peptide, but they have provided insight into the experimental approaches that might be effective in resolving these functions.
Cell and Tissue Research, 2006
Morphology and metamorphosis of the peptidergic Va neurons and the median nerve system of the fruit fly, Drosophila melanogaster Abstract Metamorphosis is a fundamental developmental process and has been intensively studied for various neuron types of Drosophila melanogaster. However, detailed accounts of the fate of identified peptidergic neurons are rare. We have performed a detailed study of the larval morphology and pupal remodelling of identified peptidergic neurons, the CAPA-expressing Va neurons of D. melanogaster. In the larva, Va neurons innervate abdominal median and transverse nerves that are typically associated with perisympathetic organs (PSOs), major neurohaemal release sites in insects. Since median and transverse nerves are lacking in the adult, Va neurites have to undergo substantial remodelling during metamorphosis. We have examined the hitherto uncharacterised gross morphology of the thoracic PSOs and the abdominal median and transverse nerves by scanning electron microscopy and found that the complete reduction of these structures during metamorphosis starts around pupal stage P7 and is completed at P9. Concomitantly, neurite pruning of the Va neurons begins at P6 and is preceded by the high expression of the ecdysone receptor (EcR) subtype B1 in late L3 larvae and the first pupal stages. New neuritic outgrowth mainly occurs from P7-P9 and coincides with the expression of EcR-A, indicating that the remodelling of the Va neurons is under ecdysteroid control. Immunogoldlabelling has located the CAPA peptides to large translucent vesicles, which are released from the transverse nerves, as suggested by fusion profiles. Hence, the transverse nerves may serve a neurohaemal function in D. melanogaster.
The Journal of Comparative Neurology, 2000
Allatotropin (AT) was isolated from the moth Manduca sexta as a peptide stimulating biosynthesis of juvenile hormone in the corpora allata, but has also been shown to be cardioactive in the same species. Here, we have investigated the presence and biological activity of AT-like peptide in the cockroaches Leucophaea maderae and Periplaneta americana with focus on abdominal ganglia and their target tissues. An antiserum to M. sexta AT was used for immunocytochemical mapping of neurons in the abdominal ganglia. A small number of interneurons and efferent neurons were found AT-like immunoreactive (AT-LI) in each of the abdominal ganglia. A prominent sexual dimorphism was detected in the terminal abdominal ganglion: in L. maderae the male ganglion there are approximately 18 AT-LI neurons with cell bodies posteriorly and efferent axons in the genital nerves; in the female ganglion 4-5 AT-LI cell bodies (with efferent axons) were found in the same region. Correlated with the extra efferents in males, the male accessory glands are richly supplied by AT-LI fibers and in females a less prominent innervation was seen in oviduct muscle. A similar dimorphism was seen in abdominal ganglia of P. americana. A sexual dimorphism was also detected in the abdominal ganglia A4-A6 of L. maderae. In each of these ganglia, approximately 8-10 large AT-LI neuronal cell bodies were found along the midline; in females these neurons have significantly larger cell bodies than in males. In both sexes, and both cockroach species, two large dorsal midline neurons were detected in A-5 and 6, which seem to send axons to the hindgut: the rectal pads of the hindgut are supplied by arborizing AT-LI axons. In males and females of both species, efferent AT-LI axons from midline neurons in A3-A6 supply the lateral heart nerves and other neurohemal release sites with arborizations. The efferent midline neurons of females contain colocalized serotonin-immunoreactivity. We tested the in vitro actions of M. sexta AT on muscle contractions in the L. maderae hindgut and the abdominal heart of both species. The frequency of contractions in the hindgut increased dose dependently when applying AT at 5 ϫ 10 Ϫ8 to 5 ϫ 10 Ϫ6 M (maximal response at 5 ϫ 10 Ϫ7 M). Also the frequency of contractions of the heart increased by application of AT (threshold response at 5 ϫ 10 Ϫ9 M). This effect was more prominent in males of both species (maximal response was a 35-40% increase in males and 10-20% in females). In conclusion, an AT-like peptide is present in neurons and neurosecretory cells of cockroach abdominal ganglia and seems to play a role in control of contractions in the hindgut and heart and also to have some function in male accessory glands and oviduct.
Cell and Tissue Research, 1981
Retrograde cobalt filling followed by silver intensification revealed new features of the anatomy of neurons which project from the brain to the corpus cardiacum (CC) of the fifth instar larva ofManduca sexta. Filling via the fused nervi corporis cardiaci (NCC) I+ II demonstrated four groups of cell bodies (Ia, Ib, II, and III) previously described by Nijhout (1975), plus three major axonal tracts (A, B, and C), and four previously unobserved areas of dendritic branching, dendritic fields (DF) 1, 2, 3, and 4. Tract C is unusual in that it originates from cell bodies on the side contralateral to the filled nerve, travels ventrally and crosses over to the ipsilateral side where it turns dorsally, forming a hook in the center of the brain. It then turns ventrally again to join with tract A. DF 1 and 2 are located ventrally on the ipsilateral and contralateral sides of the brain respectively. DF 3 and 4 are situated in the dorsal protocerebrum, on the ipsilateral and contralateral sides respectively. Fills via the NCC III revealed one cell group (IV) and a fifth dendritic field (DF 5). Simultaneous fills of both the fused NCC I+ II and the NCC III showed an overlapping of DF 1 and 5, indicating the possibility of synaptic connections between these two fields.
Regeneration of the neurohemal terminals for identified cerebral neurosecretory cells in an insect
Journal of Comparative Neurology, 1989
The axons of specific neurosecretory cells, L-NSC III, in the brain of the tobacco hornworm, Manduca sexta, were transected during larval-pupal development to study the effects of this type of lesion on these peptidergic neurons and to begin to identify factors that may regulate their regeneration and growth. The two somata of these bilaterally paired neurons produce the prothoracicotropic hormone and are located in the pars intercerebralis. Their axons exit from the contralateral brain lobe via a retrocerebral nerve and pass through the corpus cardiacum before terminating at the glandular corpus allatum. At the corpus allatum, the L-NSC III axons arborize to form the terminal neurohemal organ for prothoracicotropic hormone release. The retrocerebral nerve was severed either in vitro followed by brain transplantation or in situ; in either protocol, the distal axon segments and corpus allatum were removed. The ability of the injured L-NSC III axons to regenerate was assessed immunocytologically by using a monoclonal antibody against the prothoracicotropic hormone. In both treatments, the proximal axon stumps exhibited regenerative growth as early as 1 day after axotomy, and, by the third day, neurites had extended. By the fifth day, the regenerating axons had branched to form terminal varicosities similar to those of a normal neurohemal organ. The regenerated neurohemal structure appeared to be functional, because larvae that had been bilaterally axotomized were able to metamorphose to pupae, a process requiring temporally precise periods of prothoracicotropic hormone release. In addition to the regeneration of the terminal axon structures, several other responses to axotomy and retrocerebral organ excision occurred. These included an apparent accumulation of prothoracicotropic hormone in the axons and regenerating neurohemal-like structures, sprouting of ectopic neurites from the axotomized somata, and a change in shape of the cell bodies from spherical to ovoid.
The Journal of Comparative Neurology, 1996
Abdominal Ganglion (TAG) of the adult male cockroach Periplaneta americana were described based on wholemount preparations and paraffin sections and by using anterograde and retrograde cobalt mapping, octopamine-like immunohistochemistry, and double immunofluorescence technique with both conjugated gamma-aminobutyric acid (GABA) and octopamine antisera. Among 60 ? 6 neurones with large somata (diameter 40 to 60 km) on the dorsal midline surface of the TAG that were stained with toluidine blue, about 36 efferent DUM neurones exhibited octopamine-like immunoreactivity. The DUM neurones were arranged in three clusters (anterior, median and posterior) corresponding to the 7th-1 l t h abdominal ganglia of the fused TAG. Anterior efferent DUM neurones with one, two, and four pairs of lateral neurites entered segmental nerves VIIB; VIIB and phallic nerves; IXB and phallic nerves; VIIIA, IXA, X, and IX, respectively. Three octopamine-like immunoreactive DUM neurones innervating heart chambers via segmental nerves (VIIA, VIIIA, and I=) in the last abdominal segments occurred within abdominal ganglia 7,8, and 9. Together with octopaminelike immunoreactive efferent DUM neurones, GAJ3A-like immunoreactive dorsal midline neurones with small somata (10 to 20 km) also occurred within the median group. The spatial distribution of DUM neurones in the TAG suggested that they had their origins in the median neuroblast, as for DUM neurones in the grasshopper. G 1996 Wiley-Liss, Inc.
Nerves in the antennae of pupalManduca sexta Johanssen (Lepidoptera: Sphingidae)
Wilhelm Roux's Archives of Developmental Biology, 1975
Summa~'y. The antennal rudiment of pupal Manduca sexta contains two small nerves in its lumen. Each nerve is made up of about 160 axons that run from neurons near the tip of the pupal antenna to "Ghe brain. These neurons are also present in antennae of pharate pupae, diapausing pupae, and developing adults, and are distinct from the primary sensory neurons that are associated with the cuticular sensilia of larval and adult antennae. The antennae of the sphinx moth, Manduca sexta, bear cuticular hairs that enclose dendrites of associated primary sensory neurons. These neurons arise from epidermal ceils early in the pnp~l-adult metamorphosis. As part of a study of neurogenesis in antennae, we have examined pupal antennae immediately before and after the initiation of adult development. We have found that, prior to the 'birth' of the adult sensory neurons, small bundles of axons are present in the lumen of the pupal antenna. Later, the developing adult sensory neurons send out axons, which join the fibers in the small nerves and grow along them to enter the brain (Sanes and Hildebrand, in preparation). This communication describes the pupal nerves and their cells of origin.
Journal of Neurobiology, 1984
Cobalt backfilling, Lucifer yellow injection and neurophysiological recordings have been used to identify the neurons, in particular dorsal unpaired median neurons, which contribute axons to the oviducal muscles of the locust Locustu rnigrutoriu. A total of eight neurons within the VIIth abdominal ganglion have axons passing to the oviducts. Three pairs of bilaterally symmetrical neurons have ventrally located cell bodies. One neuron from each pair projects to the left side of the oviducts and the other the right side of the oviducts. These cells lie ipsilateral to the nerve root through which they exit. The neuropilar branches are intraganglionic and lie mainly in the ipsilateral neuropile, however one of the neurons from each side possesses a giant process, reaching 10 km in diameter, which passes dorsally to the contralateral side of the ganglion.