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C Bugnon

Publications and source records attributed to C Bugnon.

At least 19 recordsLinked to original sources
PubMed1994

Induction of Fos-like immunoreactivity in rat oxytocin neurons following insulin injections.

Double immunostaining for oxytocin (OT) and Fos was used to study the oxytocinergic system of the rat hypothalamic paraventricular nucleus (PVN) following intraperitoneal insulin injections. The expression of c-fos in the PVN appeared about 3 h after insulin treatment and was very high after 5 h while no labelling was observed in isotonic saline-injected animals. Twelve to 18% of OT neurons expressed Fos-like immunoreactivity and these activated neurons were found in both the magno- and the parvocellular compartments of the PVN suggesting that the OT neuron responses to insulin induced disturbances are complex and involve hormonal as well as autonomic pathways.

Animals↗
PubMed1994

Induction of Fos-immunoreactivity in prolactin-like containing neurons of the rat lateral hypothalamus after insulin treatment.

The role of the lateral hypothalamus (LHT) in the regulation of feeding behavior has long been established. The major contribution of LHT glucose-sensitive neurons, activated by low glucose concentration, is well accepted. Two peptidergic neuron populations, whose perikarya are exclusively located within this area, have been recently described. They respectively produce peptides derived from the melanin-concentrating hormone (MCH) precursor and prolactin-like immunoreactive peptide (PLI). In the present study, hypoglycemia-induced neuron stimulation was assessed in the rat LHT, by using Fos immunocytochemistry 1 to 5 h after a single insulin injection. In control animals, very scarce Fos-like immunoreactivity (FLI)-containing nuclei were observed in LHT. Insulin treatment induced an important and progressive increase in the number and staining intensity of neuron nuclei detected by Fos antiserum. Five hours after injection, few MCH neurons exhibited FLI, but about 80% of PLI-containing neurons expressed FLI and more than 50% of the FLI-containing nuclei belonged to PLI neurons. It was thus concluded that PLI-expressing neurons, which dramatically responded to insulin treatment, might correspond to a subpopulation of the glucose-sensitive LHT neurons.

Animals↗
PubMed1994

Prolactin immunoreactive neurons of the rat lateral hypothalamus: immunocytochemical and ultrastructural studies.

A population of neurons immunoreactive to an antiserum (AS) raised against ovine prolactin (LHPLI neurons) was previously described in the rat perifornical areas and lateral hypothalamus. In the present paper, we demonstrate by complementary immunocytochemical studies using AS to various biologically active peptides or neurotransmitters that these neurons are also detected by AS to bradykinin and to dynorphin B. Electron microscope examination shows that the LHPLI neurons are peptidergic neurons synthesizing apparently only one type of secretory granules. Numerous synapses on their perikarya and processes reflect the complexity of their relationships with other neuron populations, which have yet to be mapped and elucidated.

Animals↗
PubMed1994

Evidence for the expression of dynorphin gene in the prolactin-immunoreactive neurons of the rat lateral hypothalamus.

Dynorphin B (DYN B) immunoreactivity was recently reported in a population of prolactin (PRL)-immunoreactive neurons of the rat lateral hypothalamus (LH). By coupling immunocytochemistry and in situ hybridization using two synthetic oligonucleotide probes complementary to DYN mRNA, a hybridization signal was observed over the neurons of the LH exhibiting both DYN- and PRL-like immunoreactivities. Our results clearly demonstrate that these neurons contain the mRNA encoding preproDYN and are able to synthesize authentic DYN B in colocalization with a peptide related to PRL.

Animals↗
PubMed1994

Melanin-concentrating hormone-producing neurons in reptiles.

Melanin-concentrating hormone (MCH)-like producing neurons were mapped in the brains of several reptiles using antisera (AS) prepared against salmon MCH (sMCH) and peptides derived from the rat MCH precursor (rMCH, NGE, NEI) or cross-reacting with these peptides (anti-GRF37 and anti-alpha-MSH). MCH neurons were detected in the periventricular and lateral hypothalamic nuclei. The coexpression of MCH-, GRF37- and NEI-like immunoreactivities suggests that the reptile precursor presents large sequence homologies with the rat/human precursor. MCH neurons project to many brain areas, but fibers are very scarce in the median eminence, and the neurohypophysis is devoid of immunoreactive processes. Thus the MCH produced by these neurons would not be a neurohormone as in fish. The great quantity of processes observed in the optic lobes and in the olfactive encephalic areas (particularly in the septum) is most probably related to behavioral and adaptive regulations controlled by the hypothalamus.

Animals↗
PubMed1994

Insulin treatment stimulates the rat melanin-concentrating hormone-producing neurons.

Melanin-concentrating hormone (MCH) is involved in the regulation of body colour in teleost fish. A peptide highly homologous to salmon MCH has been found in the rat brain, but its physiological functions have not yet been precisely defined. The location of MCH neurons in the lateral hypothalamus (LHT) of the rat suggests possible implication in feeding behaviour. In the present study, immunohistochemical and in situ hybridization methods were used to investigate MCH gene expression following insulin injections. Five hours after insulin injection, a significant increase in the abundance and staining intensity of MCH immunoreactive perikarya and fibres was observed. Concurrently the level of MCH mRNA significantly increased (50%). Insulin-treatment also induced a marked and progressive increase in the number and staining intensity of nuclei detected by a Fos antiserum in LHT and other brain areas. Double labelling technique demonstrated that very few if any MCH neurons exhibited Fos-like immunoreactivity. These results demonstrate that an insulin-treatment stimulates MCH neuron activity without the mediation of the proto-oncogene c-fos. The mechanisms triggering this activation remain to be elucidated.

Analysis of Variance↗
PubMed1994

Activation of the rat melanin-concentrating hormone neurons by ventromedial hypothalamic lesions.

The occurrence of a melanin-concentrating hormone-like peptide (MCH) was previously reported in the lateral hypothalamus of the rat. The sequence of this peptide was determined but its role as well as its regulation remain unclear. In the present study, we examined the effects of minor electrolytic lesions of the ventromedial nuclei (VMN) on MCH neurons by using immunocytochemical and in situ hybridization procedures. We report that VMN lesions resulted in (1) a clear elevation in the number and staining intensity of MCH immunoreactive perikarya and fibres, (2) a significant increase in the level of hybridocytochemical signal obtained with an oligonucleotide probe complementary to rMCH mRNA. These data provide evidence for a role of VMN in modulating the MCH gene a peptide expression.

Animals↗
PubMed1993

Diffusible factors from rat arcuate nucleus and Broca's diagonal band nucleus increase size and neurite outgrowth, respectively, of cultured melanin-concentrating hormone containing neurons.

Using a co-culture model, we showed that diffusible factors from arcuate nucleus (AN) specifically increased the number and the size of hypothalamic neurons producing melanin-concentrating hormone (MCH). In this model neurite outgrowth and contacts between MCH neurons and dopaminergic neurons were also prominently increased, as compared to control lateral areas of the posterior hypothalamus (LH) primary cultures. These effects were mediated in part by AN glia but also by neurons of both fetal and adult AN. AN glia produced diffusible factor(s) mainly responsible for an important MCH neurite outgrowth and expressed inhibiting factors, preventing the adhesion of LH cells on AN glial cells. Furthermore, we report here a nerve growth factor-like effect from Broca's diagonal band on MCH hypothalamic neurons.

Animals↗
PubMed1993

Colocalization of prolactin- and dynorphin-like substances in a neuronal population of the rat lateral hypothalamus.

Using an antiserum (AS) raised against dynorphin B (DYN B), we revealed immunoreactive neurons in different nuclei of the rat hypothalamus as well as a population of neurons scattered in the lateral areas of the posterior hypothalamus. This population corresponds to that previously shown to be specifically recognized by an ovine prolactin (PRL) AS. Our results suggest that in these neurons, DYN B and PRL AS reacted with different epitopes and that these epitopes could be carried by distinct unidentified peptides.

Animals↗
PubMed1992

Immunoreactivities for antisera to three putative neuropeptides of the rat melanin-concentrating hormone precursor are coexpressed in neurons of the rat lateral dorsal hypothalamus.

Antisera (AS) raised against rat melanin-concentrating hormone (rMCH) and against two additional peptides sequences derived from the rat MCH precursor (neuropeptide glutamic acid-isoleucineamide (NEI), and neuropeptide glycine-glutamic acid (NGE)) exclusively stained the hypothalamic neurons previously described using AS to salmon MCH, human somatocrinin 1-37 (GRF37) and alpha-MSH. Liquid phase and dot-blot controls for specificity indicated that rMCH-, NEI- and NGE-AS bound epitopes recognized by sMCH-, alpha-MSH- and GRF-37-AS, respectively. The distinct intracellular patterns of immunoreactivity obtained in control animals with rMCH-, NGE- and NEI-AS, as well as the changes observed after intracerebroventricular injection of colchicine matched previous findings using sMCH-, GRF37- and alpha-MSH-AS.

Animals↗
PubMed1991

Expression of peptides derived from the melanin-concentrating hormone precursor in serum-free culture of rat fetal hypothalamic neurons: role of attachment factors.

A serum-free medium culture was developed in order to study the secretory behavior of neurons producing the melanin-concentrating hormone (MCH) precursor. The present results show that our culture conditions (supplemented RPMI 1640, poly-D-lysine substrate) are efficient in promoting attachment and growth of MCH neurons dissociated from rat fetal hypothalamus. These neurons acquire a differentiation stage in which neuropeptides of interest to us are expressed in a pattern similar to that observed on tissue sections: (1) coexpression of salmon MCH, growth-hormone-releasing factor (GRF37), alpha-melanocyte-stimulating hormone and acetylcholinesterase immunoreactivities, and (2) different intracellular distribution of salmon MCH and 1-37 sequence of GRF37 staining. Neurite growth was rapid and interneuronal connections were observed early. These observations suggest that our model of defined medium culture is suitable for functional investigations on MCH neurons.

Acetylcholinesterase↗
PubMed1991

A simple method for coupling in situ hybridization and immunocytochemistry: application to the study of peptidergic neurons.

We have devised a simple procedure for immunostaining of sections that have previously undergone autoradiographic visualization of mRNAs by in situ hybridization. Classical hybridocytochemistry techniques were performed first on cryostat sections of formaldehyde-fixed tissue. Standard methods were used for slide coating by emulsion dipping and for revelation, fixation, and coverslipping steps. The key to this method is the emulsion removal, or permeabilization, by a short trypsin incubation (0.2% for 20-30 sec) which facilitates the good access of antibodies used in a subsequent immunocytochemical technique to section epitopes. Usual immunofluorescence and immunoperoxidase procedures were successfully performed after this treatment. The immunoreactivity of several neuropeptides was well preserved after this procedure. In addition to its usefulness in our studies, this general method should be applicable to many other situations in which autoradiographic and immunocytochemical detections must be coupled.

Animals↗
PubMed1991

[Effect of colchicine on vasopressin and melanin-concentrating hormone neurons of rat hypothalamus: hybridocytochemistry and immunocytochemistry studies].

48 hrs. after an intra-cerebroventricular injection of colchicine (100 micrograms), antisera to three putative peptides included in the rat melanin-concentrating hormone (MCH) precursor, strongly stained the secretory granules accumulated in perikarya. In control rats, these antisera stained endoplasmic reticulum, Golgi apparatus, or neurosecretory granules respectively. Colchicine also induced a dramatic decrease in hybridization signal obtained with a probe complementary to the prepro-MCH-mRNA. Similarly, colchicine induced a strong increase in vasopressin immunoreactivity in neurons of the paraventricular and supraoptic nuclei, and a strong decrease of the vasopressin precursor mRNA. These results demonstrated that, in two peptidergic neuron populations of the rat hypothalamus, colchicine lowers mRNAs and impairs neuropeptide protein synthesis, consecutively to the accumulation of neurosecretory granules in perikarya.

Animals↗
PubMed1991

[Organotypic culture of human corneal epithelium. Preliminary results].

The authors compared the growth of limbal and central explants removed from human cornea. Epithelial growth began on the third day, was greater during the first week and was subsequently slightly invaded by fibroblasts. This study demonstrated that peripheral corneal epithelial cells growth better than central cells. In this study, the cytologic and histologic features of the cells were examined. However, epithelial immunofluorescence staining by anti-cytokeratin antibodies was rather poor. This in vitro system may provide a suitable model for epithelial human corneal cell culture, allowing further biocompatibility studies.

Cell Division↗
PubMed1989

Cloning of cDNAs encoding a rat neuropeptide immunologically related to salmon melanin-concentrating hormone.

In order to identify the neuropeptide related to melanin-concentrating hormone (MCH) synthetized by neurons of the posterior hypothalamus in the mammals, we have screened rat hypothalamus and rat brain cDNA expression libraries using MCH antiserum. We isolated 5 distinct immunopositive recombinants with cross-hybridizing cDNA inserts. One of them hybridized to RNAs exclusively located in neurons stained by the same antiserum, as seen by successively performing in situ hybridization and then an immunocytochemical technique on the same section. Sequencing of this MCH-like cDNA is in progress.

Animals↗
PubMed1989

Human hypothalamic neuronal system revealed with a salmon melanin-concentrating hormone (MCH) antiserum.

An antiserum raised against synthetic salmon melanin-concentrating hormone (MCH) reveals an extensive neuronal system in the posterior lateral areas of the human hypothalamus. These neurons correspond to those previously described in the rat, which are characterized by expression of MCH-like, alpha-melanotropin-like and human growth hormone-releasing factor (1-37)-like immunoreactivities.

Adult↗
PubMed1989

Coexistence of acetylcholinesterase-, human growth hormone-releasing factor(1-37)-, alpha-melanotropin- and melanin-concentrating hormone-like immunoreactivities in neurons of the rat hypothalamus: a light and electron microscope study.

Using an antiserum (AS) raised against rat cerebral acetylcholinesterase (AChE), we revealed a neuron population in lateral and dorsal areas of the posterior rat hypothalamus. These neurons were previously described using antibodies to human growth hormone-releasing factor(1-37) (GRF-37), alpha-melanotropin (alpha-MSH) and melanin-concentrating hormone (MCH). Different intracytoplasmic distributions of the immunodeposits were observed depending on the used serum. Ultrastructural investigations demonstrated that AChE-AS labeled rough endoplasmic reticulum and nuclear envelope in control rats. MCH-AS stained Golgi apparatus in control animals and secretory granules in colchicine-injected rats. GRF-37-AS always revealed secretory granules, and alpha-MSH-AS gave the same staining only after colchicine injection.

Acetylcholinesterase↗