Frans Vandesande

Coexistence of corticotropin-releasing factor-like immunoreactivity and vasotocin in perikarya of the preoptic nucleus in the eel

A corticotropin-releasing factor (CRF)-like system has been identified in eels (Anguilla anguilla, A. rostrata, and A. japonica) with immunocytochemical techniques. Immunoreactive perikarya were located in the preoptic area, in magno- and parvocellular regions of the preoptic nucleus. Fine fibers reached the pituitary and terminated in the neurohypophysis close to the corticotropic cells of the rostral pars distalis and caudally close to the melanocorticotropic cells of the intermediate lobe. Double immunostainings revealed the presence of three subpopulations of perikarya: one population containing only CRF, a second containing only arginine vasotocin (VT), and a third one containing both CRF and VT. This coexistence of CRF and VT was also demonstrated by comparing adjacent sections stained with anti-CRF and anti-VT, respectively. Because antisera used in the present work were carefully absorbed, these data strongly suggest that CRF and VT coexist in some perikarya, at least in the animals studied.

Autoradiographic localization of binding sites for vasotocin in the brain and pituitary of the sea bass (Dicentrarchus labrax).

Specific binding sites for vasotocin (VT) were detected in brain and pituitary of a teleost fish, the sea bass, after in vitro incubation of tissue sections with [3H]arginine-vasopressin (AVP) and light microscopic autoradiography. Conditions for the binding assay were optimized and as a result the binding was saturable and specific. In the brain [3H]AVP binding was found to occur in the pars lateralis and the pars ventralis of the ventral telencephalon, in the pars centralis of the dorsal telencephalon, in the hypothalamic region (especially in the nucleus preopticus, in the tuberal hypothalamus and around the posterior recess), in the tectum opticum and in the noncellular layer of the corpus cerebelli. In the pituitary a high density of [3H]AVP binding was observed in the areas of the pars distalis (PD) occupied by ACTH-, TSH- and GH-cells and also in the pars intermedia (PI). The present study presents the first anatomical evidence for the presence of VT specific binding sites in teleost brain and pituitary.

Immunocytochemical identification and localization of the different cell types in the pituitary of the seabass (Dicentrarchus labrax).

Antisera raised against chum salmon prolactin (PRL), trout growth hormone (GH), mammalian adrenocorticotropic hormone (ACTH), thyroid-stimulating hormone (TSH), luteinizing hormone (LH), and alpha-melanophore-stimulating hormone (alpha-MSH) were used to localize PRL, GH, ACTH, gonadotropic, TSH, and MSH cells in the hypophysis of the teleost Dicentrarchus labrax using the unlabeled peroxidase anti-peroxidase method. In the rostral pars distalis, ACTH cells stained very intensively with anti-ACTH; so did the MSH cells in the pars intermedia. The prolactin cells stained very specifically with anti-prolactin without staining the growth hormone cells. In the proximal pars distalis anti-GH, anti-TSH beta, and anti-LH stained selectively the corresponding cells; with these antisera no cross-reaction with any other cell type was observed. Anti-alpha-MSH only stained cells in the pars intermedia. Some cells in the pars intermedia did not react at all; these could correspond to the PAS-positive cells. A characteristic feature was positive staining with anti-LH in some cell groups encircling the pars intermedia, indicating the fact that in the seabass some cells of the proximal pars distalis surround the pars intermedia.

Sequence and distribution of pro‐opiomelanocortin in the pituitary and the brain of the chicken (Gallus gallus)

Although pro‐opiomelanocortin (POMC) is a well‐known hormone precursor in many species, molecular information about avian POMCs is still relatively scarce. In a former study Berghman et al., [ 1998 ] Mol Cell Endocrinol. 142:119–130) the nucleotide and amino acid sequence of N‐terminal POMC in the chicken were reported. To complete the nucleotide sequence of the precursor, rapid amplification of 3` and 5` cDNA end reactions were performed and the polymerase chain reaction (PCR) products were cloned and sequenced. The chicken POMC coding region appears to consist of 678 base pairs in the pituitary and also in the hypothalamus, as assessed by reverse transcriptase PCR. Overall nucleotide sequence homology with other species ranges from 41% (in bovine) to 57% (in rat). The distribution of the POMC mRNA in pituitary and brain was analyzed by in situ hybridization by using 33P‐labelled oligonucleotides. Expression of POMC mRNA in the pituitary was restricted to the cephalic lobe, whereas in the brain, the signal was limited to the hypothalamic region. As assessed by Northern blot analysis, the length of the POMC mRNA in both the pituitary and the hypothalamus was approximately 1,200 nucleotides. By using antisera to N‐terminal POMC, α‐melanotropin and β‐endorphin, POMC‐containing cells were observed in the cephalic lobe of the pituitary and immunopositive perikarya were localized in the infundibular nucleus and median eminence of the hypothalamus. Immunoreactive fibers were found in the preoptic area and in the medial basal hypothalamus surrounding the third ventricle and more dorsally in the thalamus. Double‐staining experiments in the pituitary clearly indicated a complete overlap of the signals generated by these antisera. J. Comp. Neurol. 417:250–262, 2000. ©2000 Wiley‐Liss, Inc.

Innervation and control of the adenohypophysis by hypothalamic peptidergic neurons in teleost fishes: EM immunohistochemical evidence

Previous light microscopic studies have revealed neuropeptide‐immunoreactive neurosecretory fibers in the teleostean neurohypophysis, and ultrastructural work has reported direct innervation of endocrine cells by the terminals of fibers penetrating the adenohypophysis. This paper reviews our recent data from ultrastructural, immunohistochemical, receptor localization, and superfusion studies, which suggest a role for neuropeptides in the control of teleost pituitary secretion. We have used a combination of pre‐ and post‐embedding electron microscopic immunolabeling methods to determine which neuropeptides are present in fibers innervating the pituitaries of three species: Poecilia latipinna, Dicentrarchus labrax, and Clarias gariepinus. Numerous axon profiles with immunoreactivity for the neurosecretory peptides vasotocin and isotocin formed large Herring bodies and terminal‐like boutons in contact with corticotropic, growth hormone, thyrotropic, and pars intermedia cells. Numerous melanin‐concentrating hormone‐immunoreactive fibers and scarcer neurotensin and corticotropin‐releasing factor‐immunoreactive fibers showed similar distributions, terminating close to pars intermedia and corticotropic cells. Somatostatin, cholecystokinin, galanin, substance P, neuropeptide Y, growth hormone‐releasing factor, thyrotropin‐releasing hormone, and gonadotropin‐releasing hormone‐immunoreactivities were found in small calibre fibers penetrating among growth hormone, thyrotropic, and gonadotropic cells. These morphological findings have been supplemented by autoradiographic studies, which showed the distribution of binding sites for vasotocin, isotocin, galanin, and neuropeptide Y ligands over specific groups of pituitary cells, and superfusion studies that showed growth hormone release was stimulated by growth hormone‐releasing factor and thyrotropin‐releasing hormone, but inhibited by somatostatin. The implications of these results for neuropeptidergic control of teleostean pituitary secretions are discussed. Microsc. Res. Tech. 44:19–35, 1999.

Immunohistochemical localization of corticotropin-releasing factor (CRF)-like immunoreactivity in the hypothalamus of the newt, Triturus cristatus

The distribution of corticotropin-releasing factor (CRF) immunoreactivity was investigated in the hypothalamus and preoptic area of the newt by single and double immunocytochemical procedures. CRF immunopositive cell bodies were seen in the preoptic area (from the anterior wall of the preoptic recess to the dorsal parts of the preoptic nucleus) and in the tuberal portions of the posterior hypothalamus. Abundant nerve fibres are seen in the outer zone of the median eminence, while the pars nervosa lacks CRF-immunoreactivity. CRF immunoreactive material is seemingly separated from neurophysins- and somatostatin immunoreactive cell bodies and fibres.

Autoradiographic distribution of galanin binding sites in the brain and pituitary of the sea bass (Dicentrarchus labrax)

Specific binding sites for galanin (GAL) were detected in brain and pituitary of a marine teleost fish, the sea bass, after in vitro incubation of tissue sections with [125I]GAL and light microscopic autoradiography. Binding conditions were optimized and as a result the binding was saturable and specific. In the brain, [125I]GAL binding was found to occur in all parts of the dorsal and ventral telencephalon, in the anterior, tuberal and posterior hypothalamus, in the thalamus and in the tectum opticum, in the inferior lobe and in the ventral medulla oblongata. In the pituitary dense [125I]GAL binding was confined to the area occupied by the prolactin cells in the rostral part of the adenohypophysis. These findings provide the first anatomical evidence for the presence of GAL specific binding sites in the teleost brain and pituitary.

Characterization of Vertebrate Peptide Hormone-Like Materials in the American Cockroach: Different Methods Employed to Investigate these Substances and Their Results

During the last few years many investigations have reported the occurrence of substances in insects that resemble vertebrate (neuro)peptide hormones. Our particular contribution to this study concerns the exploration of Periplaneta americana L. (Blattidae) for suchlike products. This paper will critically comment three complementary approaches which, in our opinion, may lead to the ultimate characterization of these substances.