Biomedical subjects
Publications and source records attributed to A Fournier.
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Lungfishes, which share similarities with both fishes and amphibians, represent an interesting group in which to investigate the evolutionary transition from fishes to tetrapods. In the present study, we have investigated the localization and biochemical characteristics of neuropeptide Y (NPY)-immunoreactive material in the central nervous system of the African lungfish, Protopterus annectens. NPY-immunoreactive cell bodies were found in various regions of the brain, most notably in the telencephalon (septal area, ventral striatum, and nucleus accumbens), in the diencephalon (preoptic nucleus, periventricular region of the hypothalamus, and ventral thalamus), and in the tegmentum of the mesencephalon. A strong immunoreaction was also detected in cell bodies of the nervus terminalis. Immunoreactive nerve fibers were particularly abundant in the ventral striatum, the nucleus accumbens, the diagonal band of Broca, the hypothalamus, and the mesencephalic tegmentum. Positive fibers were also seen in the median eminence and in the neural lobe of the pituitary. The NPY-immunoreactive material localized in the brain and pituitary was characterized by combining high-performance liquid chromatography (HPLC) analysis and radioimmunological quantitation. The displacement curves obtained with synthetic porcine and frog NPY and serial dilutions of brain and pituitary extracts were parallel. Reversed-phase HPLC analysis of telencephalon, diencephalon, and pituitary extracts resolved a major NPY-immunoreactive peak that coeluted with frog NPY. The similarity between the distribution of NPY-containing neurons and the biochemical characteristics of the immunoreactive peptide in the brain of lungfish and frog strongly favors a close phylogenetic relationship between dipnoans and amphibians.
In order to determine the influence of neuropeptide Y (NPY) on the biosynthesis of prolactin (PRL), we have studied the effects of NPY and some NPY analogs on PRL gene expression in the male rat anterior pituitary gland. The following peptides (4 micrograms/100 g body wt): NPY, peptide YY (PYY), NPY13-36 (a Y2 receptor agonist) and [Leu31,Pro34]NPY (a Y1 receptor agonist) were injected into the left lateral ventricle of adult male rats. Control animals received only the vehicle (0.9% NaCl). All the animals were perfused with 4% paraformaldehyde 4 h after injection and processed for in situ hybridization. The intracerebroventricular injection of NPY, PYY, and NPY13-36 induced a significant increase in the hybridization signal (22-40% over control). On the other hand, the Y1 receptor agonist [Leu31,Pro34]NPY did not influence PRL mRNA levels. These data then suggest that activation of the Y2 NPY receptor subtype at the central level can positively regulate PRL gene expression.
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In the arcuate nucleus which is richly innervated by both proopiomelanocortin (POMC) and neuropeptide Y (NPY) neurons, it has been shown that NPY fibers are in synaptic contact with POMC cell bodies. In order to determine whether NPY could influence POMC neuronal activity, we have studied the effects of NPY and some NPY analogs on POMC gene expression using quantitative in situ hybridization. The following peptides NPY, [Leu31,Pro34]-NPY (a Y1 receptor agonist), and NPY13-36 (a Y2 receptor agonist) were injected into the left lateral cerebral ventricle of adult male rats 4 h before being perfused for histological procedures. The intracerebroventricular injection of NPY and NPY13-36 induced a significant decrease in the number of grains overlying the labelled neurons. On the other hand, the Y1 receptor agonist [Leu31,Pro34]-NPY did not modify POMC mRNA levels. These data then strongly suggest that NPY negatively regulates the genetic expression of POMC neurons via the Y2 NPY receptor subtype.
The conformational properties of atrial natriuretic factor (ANF), brain natriuretic peptide (BNP), and various analogs and homologs were studied by circular dichroism (CD) spectroscopy in solvent mixtures inducing secondary structures. The CD spectra obtained for rat ANF(99-126), porcine BNP32, and their related analogs indicated that these peptides exhibited mainly a random-coil conformation in pure water. However, the addition of increasing concentrations of 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) gave rise for all peptides to a more ordered secondary structure. The analysis of the far-ultraviolet CD spectra suggested that the peptides exist under two conformational states, beta-turn and beta-sheet, in the presence of 20-60% HFIP/water solutions. Moreover, the characterizations of rANF(99-126) and the analog pBNP1, which combines the cyclic core of bBNP32 with the carboxy- and amino-terminal segments of rANF-(99-126), have been carried out by Fourier transform infrared spectroscopy (FTIR) in 40% HFIP/D2O. The FTIR results indicated that these peptides exist predominantly under a beta-turn and beta-sheet mixed conformation. In addition, the amount of organized secondary structure obtained for human BNP32, bovine aldosterone secretion inhibitory factor, also known as ASIF(69-103) and beta-rANF(92-126), in the presence of a 40% HFIP/phosphate buffer mixture, was similar to that of porcine BNP32, whereas rat BNP32 was found to be more structured. In the same solvent mixture, the CD spectra of Met(O)110-human ANF(99-126) and chicken ANF(99-126) indicated that these peptides possess conformational features different to those of rANF(99-126) and hANF(99-126). Porcine CNP22, C-type natriuretic peptide, and the fragment C-ANF exhibited undefined secondary structure in the presence of 40% HFIP/phosphate buffer. These results suggest that the amino acid residues, not common to the various natriuretic peptides, would be involved in the stabilization of either beta-turn and/or beta-sheet conformations. Moreover, these secondary structures appear as particularly important for the recognition of the ANF-R1A receptor subtype found in bovine adrenal cortex.
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Because thermoregulation and food consumption are interrelated, and because thermoregulation processes are influenced by ambient temperature, we examined the effects of neuropeptide Y (NPY) on both body temperature and food intake in various thermal environments after intracerebroventricular administration of 20 micrograms. Results reveal that the prominent effects of NPY on body temperature and food intake in relatively thermoneutral environments are drastically altered at more extreme ambient temperatures. NPY produced hypothermia in animals placed at 4, 12, and 21 degrees C, and actually increased body temperature in animals subjected to 30 and 38 degrees C temperature. On the other hand, in comparison with ambient temperatures of 12 and 21 degrees C, ambient temperatures of 4 and 30 degrees C significantly reduced the stimulatory effect of NPY on food consumption. Moreover, at 38 degrees C the effect of NPY on food intake was totally abolished. These data demonstrate that ambient temperature has a critical influence on central actions of NPY.
In a previous study, we have shown that neuropeptide Y inhibits the release of alpha-melanocyte-stimulating hormone from the rat hypothalamus in vitro. The aim of the present study was to investigate the possible effect of neuropeptide Y on the regulation of proopiomelanocortin-derived peptides in vivo. Rats received acute or chronic administration of neuropeptide Y in the lateral ventricle and the amount of alpha-melanocyte-stimulating hormone was measured in the hypothalamus and in the neurointermediate lobe of the pituitary. In the same experiments, the amounts of corticotropin-releasing factor and corticotropin were quantified in the hypothalamus and anterior pituitary, respectively. Acute treatment with synthetic neuropeptide Y (0.1 to 10 micrograms/rat) did not modify the amount of alpha-melanocyte-stimulating hormone in the hypothalamus. In contrast, chronic infusion of neuropeptide Y (1.25 micrograms/h) over a seven day period significantly decreased the hypothalamic content of alpha-melanocyte-stimulating hormone, suggesting that neuropeptide Y regulates the synthesis and/or the processing of proopiomelanocortin. Concurrently, we found that both acute and chronic infusion of neuropeptide Y induced a significant reduction in corticotropin-releasing factor in the hypothalamus as well as a significant decrease in alpha-melanocyte-stimulating hormone and corticotropin in the neurointermediate and anterior lobes, respectively. Quantitative in situ hybridization histochemistry showed that chronic administration of neuropeptide Y also caused a reduction of proopiomelanocortin messenger RNA levels both in the intermediate and anterior lobes of the pituitary. Administration of neuropeptide Y (10(-6) M) on perifused rat hypothalamic slices caused a significant increase in corticotropin-releasing factor release.(ABSTRACT TRUNCATED AT 250 WORDS)
The purpose of the present study was to examine structure-activity relationships for three known motor effects of neuropeptide Y (NPY): decreased spontaneous activity, enhancement of muscle tone, and catalepsy. Various NPY fragments and structural analogues were synthesized and administered intracerebroventricularly in several doses (2.5-160 micrograms); their effects on these three motor variables were evaluated and compared. Globally, results indicate that the C-terminal portion of the peptide is responsible for the three motor effects of NPY. However, the distributions of potencies of the various fragments and analogues for each effect were clearly different, suggesting that the putative receptors mediating each motor effect are pharmacologically different. The findings of the present work are discussed in relation to those obtained in previous structure-activity studies.
The objective of the present study was to identify hypothalamic sites that might be implicated in the effects of neuropeptide Y (NPY) on both body temperature and food intake. For this purpose, the effects of direct microinjections of NPY in several doses (0.156-20 micrograms) into discrete hypothalamic nuclei on body temperature were examined in rats. To examine specificity of effects, food consumption of animals following injections was also measured. Results indicate that the influence of NPY on body temperature varies with the hypothalamic region where the peptide is administered. NPY had no effect on temperature after administration into the ventromedial (VMH) and the perifornical hypothalamus (PeF). However, a significant hypothermia was seen following administration into the preoptic (POA) and arcuate nucleus (Arc), and hyperthermia was seen after injection into the paraventricular nucleus (PVN). Finally, a biphasic effect was observed after injection into the lateral hypothalamus (LH): hyperthermia with relatively small doses and hypothermia with higher doses. Similar effects were obtained when administered into the third ventricle (3V) but in an inverted dose-related fashion: hypothermia at low and hyperthermia at higher doses. For feeding, NPY consistently increased food intake in all regions examined, with the strongest effect obtained after administration into the PeF. The present results clearly dissociate the effects of NPY on food intake and body temperature, and demonstrate that these effects are related to specific hypothalamic nuclei.
Our previous in vivo structure-activity studies suggested that the putative receptors mediating the effects of NPY and NPY2-36 on food intake and body temperature are pharmacologically different [17]. In the present study, we examined and compared dose-related effects of NPY and NPY2-36 on ad lib food intake and rectal temperature after administration into discrete hypothalamic nuclei of the rat. Results indicate that NPY and NPY2-36 have opposite effects on body temperature to those of NPY when injected in the preoptic area (POA): hypothermia and hyperthermia, respectively. When administered in the paraventricular nucleus (PVN), both increased body temperature. When injected into the third ventricle (3V), NPY produced a biphasic effect: hypothermia at low doses and hyperthermia at high doses. Similar effects were obtained with NPY2-36, but in an inverted dose-related fashion: hyperthermia at low and hypothermia at higher doses. In the arcuate nucleus (Arc), NPY induced a significant hypothermia whereas NPY2-36 had no effect. Finally, neither peptide affected body temperature when injected into the ventromedial (VMH) and perifornical (PeF) nuclei. Both NPY and NPY2-36 increased food intake after injection in all regions examined. In general, NPY was more potent and efficacious than NPY2-36. The present results clearly dissociate the effects of NPY on food intake and body temperature. Furthermore, the data support the hypothesis that the putative receptors underlying the effects of NPY and NPY2-36 on food intake are similar, whereas those mediating the effects on body temperature are pharmacologically different.
Our aim was to develop a recombinant replication-defective adenovirus suitable for the vaccination of cats against feline immunodeficiency virus. We first demonstrated that this vector was able to transfer a marker gene (E. coli beta-galactosidase) in feline cells in vitro. We then constructed an adenovirus type 5 expressing the Feline Immunodeficiency Virus (FIV) envelope (ENV) gene of the Wo isolate in the absence of the rev gene (Ad-ENV-Wo). Ad-ENV-Wo was then tested in four cats in a 3 injections scheme (at day 0, day 30 and day 210). Four other control cats received Ad-gp50, a similar recombinant adenovirus expressing gp50 (Ad-gp50) of pseudorabies virus (PRV). Viruses were formulated in two different kind of oil adjuvants (water/oil and water/oil/water), a protocol previously shown to enhance the immune response against the virus-induced protein. The control cats developed neutralizing antibodies against PRV, demonstrating the potency of recombinant human adenovirus 5 (Ad5) as a vector in cats. Antibody responses appeared after the first injection and were higher with the water/oil/water formulation than with the water/oil controls. However, none of the four cats vaccinated with Ad-ENV-Wo developed antibodies against two peptides of the envelope protein. Animals were challenged with 20 infectious doses 50% of the strain Wo. All of them developed antibodies against FIV within 4 to 5 weeks, and FIV virus could be isolated from all.
OBJECTIVES: The purpose of this study was to characterize peripheral flow kinetics in response to progressive discontinuous maximal exercise in 10 patients who underwent repair of coarctation of the aorta and 11 age-matched healthy adolescents. BACKGROUND: An impairment of leg blood flow has been suggested on the basis of exaggerated femoral muscle lactate accumulation in patients with successful repair of coarctation. Few data are available describing blood flow kinetics of the exercising leg in such patients. METHODS: Duplex ultrasound provided transcutaneous measurements of peak systolic and end-diastolic flow velocities of the femoral, humeral and renal arteries at rest and immediately after mild, moderate and maximal exercise intensities for computation of mean velocity, resistance index and femoral blood flow. RESULTS: Femoral mean velocity and femoral blood flow increased linearly with exercise intensity in both groups, but the slope of this increase was significantly lower in patients. Similarly, humeral mean velocity increased significantly less in patients than in control subjects. Femoral resistance index sharply decreased from that at rest (patients [mean +/- SE] 1.4 +/- 0.04; control subjects 1.4 +/- 0.03) to mild exercise intensity in both groups (patients 0.69 +/- 0.03; control subjects 0.72 +/- 0.03). A further decrease was observed at maximal exercise in patients (0.60 +/- 0.04, p = 0.08) but not in control subjects (0.69 +/- 0.02). CONCLUSIONS: These observations suggest that despite a greater exercise-induced femoral vasodilation, patients with successful correction of coarctation of the aorta demonstrate an impaired lower limb blood flow in response to strenuous dynamic exercise. In the absence of stenosis at rest, this alteration could result from exaggerated flow turbulence in the descending aorta distal to the site of correction because of loss of elasticity at the site of the resection of the coarcted segment.
The presence of receptors for the novel neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) has been recently demonstrated in the external granule cell layer of the cerebellum, a germinative matrix that generates the majority of cerebellar interneurons. In the present study, we have taken advantage of the possibility of obtaining a culture preparation that is greatly enriched in immature cerebellar granule cells to investigate the effect of PACAP on the adenylyl cyclase and phospholipase C transduction pathways. The two molecular forms of PACAP, i.e., 27-(PACAP27) and 38-(PACAP38) amino-acid forms of PACAP, induced a dose-dependent stimulation of cyclic AMP production in granule cells. The potencies of PACAP27 and PACAP38 were similar (ED50 = 0.12 +/- 0.01 and 0.23 +/- 0.07 nM, respectively), whereas vasoactive intestinal polypeptide (VIP) was approximately 100 times less potent. PACAP27 and PACAP38 also induced a dose-dependent stimulation of polyphosphoinositide breakdown (ED50 = 19.1 +/- 6.3 and 13.4 +/- 6.0 nM, respectively), whereas VIP had no effect on polyphosphoinositide metabolism. The effect of PACAP38 on inositol phosphate formation was significantly reduced by U-73122 and by pertussis toxin, indicating that activation of PACAP receptors causes stimulation of a phospholipase C through a pertussis toxin-sensitive G protein. In contrast, forskolin and dibutyryl cyclic AMP did not affect PACAP-induced stimulation of inositol phosphates. Taken together, the present results demonstrate that PACAP stimulates independently the adenylyl cyclase and the phospholipase C transduction pathways in immature cerebellar granule cells. These data favor the concept that PACAP may play important roles in the control of proliferation and/or differentiation of cerebellar neuroblasts.
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The structures of human NPY and of its centrally truncated agonist analog [Ahx5-17]NPY have been investigated in DMSO-d6 by two-dimensional NMR and by molecular modeling. For both peptides, a complete resonance assignment was achieved and a large number (more than 200) of inter-residue NOE connectivities were observed, including long-range connectivities between the N- and C-terminal ends of the chain. Molecular models were calculated using NOE constraints by distance geometry, simulated annealing and conjugate gradient energy minimization. The results indicate that both peptides are folded in the center of their chain, NPY adopting the hairpin shape, whereas the central portion of [Ahx5-17]NPY is characterized by relatively large loops. In contrast to previous models, practically no alpha-helical structure exists for these peptides under our conditions, but two beta-turns are found in NPY and one in [Ahx5-17]NPY. The proximity of the terminal ends could be the determinant factor for their activity.