Christian Rémy

Vertebrate neuropeptide-like substances in the suboesophageal ganglion of two insects: Locusta migratoria R. and F. (Orthoptera) and Bombyx mori L. (Lepidoptera) immunocytological investigation

Abstract A comparative immunocytological investigation carried out through the use of various antisera to vertebrate neuropeptides permitted to show, in one orthopteran and one lepidopteran cells that are neurophysin-vasopressin-like in their antigenicity. In locust suboesophageal ganglion, two paraldehyde fuchsin positive cells (type A cells) have a positive immunofluorescent reaction in presence of anti-neurophysin II and anti-vasopressin antisera. The neurosecretory product of such cells would thus have a dual constitution as in vertebrates: a hormonal peptide (vasopressin-like) linked to a carrier protein (neurophysin-like). In silkworm suboesophageal ganglion, two groups of paraldehyde fuchsin negative cells (three and four cells respectively) contain an α-endorphin-like secretion. This confirms results that we had obtained in another type of lepidopteran and in an oligochete annelid. Thus, there seems to be in the central nervous system of some invertebrates, peptides that have similar immunoreactive groups to the morphinomimetic peptides recently discovered in the vertebrate hypophysis or encephalon.

Anatomical organization of two vasopressin - neurophysin-like neurosecretory cells throughout the central nervous system of the migratory locust.

Abstract In the entire central nervous system of Locusta migratoria , only two neurosecretory cells give a positive immunoreaction with antineurophysin and antivasopressin antisera. The perikaria of both of these cells are located in the ventromedial zone of the suboesophageal ganglion. The cell processes are found in the entire central nervous system from the forebrain and especially the optic lobes to the last abdominal ganglion. They penetrate every nerve originating in the suboesophageal ganglion and in each segmental nerve of the thoracic and abdominal ganglia, although limited to the proximal dorsal zone. Sections of connectives show that the neurosecretory product elaborated by the two perikarya proceeds from the suboesophageal ganglion forward towards the brain and backwards towards the thoracic and abdominal cord. In locusts submitted to hygrometric variations, it was not possible to record significant changes in the amount of neurosecretory material of these two vasopressin-like neurosecretory cells.

Immunohistological evidence of methionine enkephalin-like material in the brain of the migratory locust

SummaryFour neurons in the brain of the migratory locust were immunohistologically identified with an anti-met-enkephalin antiserum. The perikarya of two of these cells are located in the center of each of the two groups of lateral protocerebral neurosecretory cells. The fibres coming from these perikarya terminate in numerous immunoreactive ramifications visible at the periphery of both tractus I to the corpora cardiaca, through which pass the neurosecretory products of the pars intercerebralis. The other two cell bodies are located at the bases of the two optic lobes; their fibres enter the posterior part of the protocerebrum and ramify around the root of the nervus corporis cardiaci II, another area through which neurosecretory products pass. The topographic distribution of these met-enkephalin arborizations suggests that these four neurons may act as neuromodulators of the acitivity of the major neurosecretory cells in the brain of this insect.

Immunohistological demonstration of a substance related to neuropeptide Y and FMRFamide in the cephalic and thoracic nervous systems of the locust Locusta migratoria

SummaryA neuropeptide related to the mammalian neuropeptide Y (NPY) is present in various neurosecretory cells (NSC) of the cephalic and thoracic nervous systems of the insect Locusta migratoria. Immunoreactive perikarya are detected in the protocerebrum, tritocerebrum, optic lobes and the suboesophageal and thoracic ganglia. They give rise to many immunoreactive processes that ramify extensively throughout the neuropiles. In the brain, prominent axon bundles tightly surround the tractus I to the corpora cardiaca. This fiber pattern suggests that the NPY-like substance may have a neuromodulator and/or neurotransmitter function. This substance may also have a neurohormonal role, since some immunoreactive tracts penetrate into neurohaemal organs via the nervi corporis cardiaci II and the thoracic median nerves. NCS containing NPY-like neuropeptide also display an FMRFamide-like immunore-activity (except for the abdominal part of the metathoracic ganglion). NPY or FMRFamide antisera are not inactivated after preabsorption with FMRFamide or NPY, respectively. It might therefore be inferred that in locust NSC these two antisera recognize two distinct antigenic sites belonging either to a large polypeptide, or to two distinct neuropeptides.

Immunofluorescence of somatostatin-producing sites in the hypothalamus of the tadpole, Alytes obstetricans Laur.

SummaryThree sites of somatostatin-synthesizing perikarya, or a related antigen, were determined by immunofluorescence in the hypothalamus of the tadpole, Alytes obstetricans (Amphibia, Anura). Two sites of neurosecretory perikarya were localized in the preoptic nuclei of the anterior hypothalamus; the axons extended either to the anterior diencephalon or to the median eminence and the pituitary. The third site was found in the posterior hypothalamus. These neurosecretory cells showed a strong immunofluorescent reaction; their axons all terminated at the level of the median eminence. Somatostatin cells were only found in intact or hypophysectomized tadpoles given somatotropin (STH). The strong reaction observed in hypophysectomized tadpoles was possibly due to the loss of the terminal portion of the neurosecretory pathway (median eminence and pituitary) by which the agent is transported to the site of discharge.

Early immunohistochemical detection of somatostatin-like and methionine-enkephablin-like neuropeptides in the brain of the migratory locust embryo

SummaryThe two groups of neurosecretory cells producing neuropeptides related to somatostatin (SRIF) and methionine-enkephalin (met-enkephalin), previously high-lighted in the brain of adult migratory locusts, were detected by immunofluorescent techniques during the embryonic development of these insects. The earliest detection of these neurosecretory products occurred firstly in the terminal arborizations, then in the fibres, and finally in the perikarya.SRIF-like material is present in the corpora cardiaca already four days before hatching, i.e. at two-thirds of embryonic life, whereas immunoreactivity can be detected only after hatching in the perikarya located in the pars intercerebralis. The synthesis of met-enkephalin-like neuropeptide starts in the four cells of this system at least two days before hatching as shown by the immunofluorescence in the terminal arborizations along the tractus I to the corpora cardiaca.SRIF-like and met-enkephalin-like neurosecretory products are synthesized and carried to their release areas whilst the formation of brain structures and of the corpora cardiaca has not yet been completed.

Immunohistological demonstration of a CRF-like material in the central nervous system of the annelid Dendrobaena

SummaryCSF is the most recently isolated and synthetized hypothalamic releasing factor in vertebrates. The use of an antiserum raised against CRF made it possible to reveal, in an oligochaetous annelid, immunoreactive cells in the suboesophageal ganglion and in all ganglia of the ventral nerve cord. Ten cells were numbered in each ganglion and each presents a pattern which is identical from one somite to the next. It thus appears that in the case of CRF as well as other vertebrate neuropeptides, there exist immunologically related neurosecretory products in the central nervous systems of some invertebrates.

Immunohistological evidence of dopamine cells in the cephalic nervous system of the silkworm Bombyx mori. Coexistence of dopamine and α endorphin-like substance in neurosecretory cells of the suboesophageal ganglion

SummaryEvidence of dopamine cells in the brain and the suboesophageal ganglion of the silkworm Bombyx mori was obtained immunohistologically in larvae and pupae. From six to eight and eight (two symmetrical groups of four) immunoreactive cells are present respectively in median and lateral protocerebral areas of the brain. In the suboesophageal ganglion, two cell clusters with dopamine immunoreactivity were observed. There was no clear difference in the nature of the immunohistochemical reaction and the number of cells between diapause- and non-diapause-egg producers, in both brains and suboesophageal ganglia. By examination of adjacent sections, it was possible to show that dopamine-immunoreactive cells in larval suboesophageal ganglia also contain an α endorphin-like substance.

Identification of immunoreactive neurophysin-like proteins in the central nervous system of an insect; Locusta Migratoria

Abstract Proteins exhibiting the immunoreactivity of vertebrate neurophysin were detected in acido-ethanolic extracts of suboesophagial ganglia of the locust. These components possess an apparent molecular weight approximating 10,000, acidic isoelectric points (4.5 and 4.75) and bind to antibovine neurophysin antibodies immobilized on CH-Sepharose 4B. These results suggest that the immunoreactive material observed in the Locusta Migratoria is composed of proteins structurally related to vertebrate neurophysin.

Development of an enzyme immunoassay for arginine-vasopressin (AVP)-like insect diuretic hormone

1. The AVP-like insect diuretic hormone is a biologically active antiparallel dimer present, along with its non-active monomeric form (Cys-Leu-Ile-Thr-Asn-Cys-Pro-Arg-GlyNH2), in the African locust. 2. It exhibits diuretic activity by increasing fluid excretion at the level of the Malpighian tubules. 3. To date, both monomer and dimer have been assayed using a radioimmunoassay originally prepared for mammalian AVP. 4. We have developed here an original enzyme immunoassay based on the use of antibodies to insect AVP-like raised in rabbits against synthetic monomers and dimers, using acetylcholinesterase conjugate as an enzymatic tracer. 5. This enzyme immunoassay enables measurement of the dimer to be made with adequate sensitivity (0.3 nmol/l, i.e. 21 pg/well) and reproducibility while sensitivity of the monomer is somewhat lower (14 nmol/l, i.e. 480 pg/well). 6. The assay was validated by assaying native dimer and monomer throughout the different steps of purification (from a crude extract to reversed-phase liquid chromatographic fractions). 7. A good correlation was observed between radioimmunoassays and enzyme immunoassays. 8. The enzyme immunoassay was also used to measure the level of AVP-like peptides in several insect tissues not explored to date.