Showing papers by "University of Rouen published in 1989"
TL;DR: Etude axee sur les poly(α-hydroxacides) and poly(β-hydroxyacides), fonctionnels derives d'hydroxy acides naturels (lactique, glycolique et maleique) as mentioned in this paper.
Abstract: Etude axee sur les poly(α-hydroxyacides) et poly(β-hydroxyacides) fonctionnels derives d'hydroxyacides naturels (lactique, glycolique et maleique). Proprietes des polymeres et copolymeres
127 citations
TL;DR: The observation of NPY-immunoreactive fibers in the pituitary gland suggests that, among its other functions, NPY may play a role in the neuroendocrine regulation of pituitARY function.
Abstract: The distribution of neuropeptide Y (NPY) immunoreactivity has been studied by means of immunocytochemistry and radioimmunoassay in the brain of the goldfish. It was found that NPY had a widespread distribution in the entire brain in particular in the telencephalon, diencephalon, optic tectum and rhombencephalon. In the pituitary gland, positive type-B fibers were observed in the various lobes frequently in direct contact with secretory cells, in particular the gonadotrophs, somatotrophs and MSH (melanocyte-stimulating hormone) secreting cells. When measured by radioimmunoassay, the highest NPY concentrations were found in the pituitary and telencephalon, confirming the results of immunocytochemistry. The displacement curves obtained with serial dilutions of brain extracts were parallel to that of synthetic porcine NPY. Following high performance liquid chromatography, the NPY-like material extracted from goldfish brain co-eluted as a single peak with synthetic porcine NPY. These data demonstrate the presence of an NPY-like substance widely distributed in the goldfish brain. The observation of NPY-immunoreactive fibers in the pituitary gland suggests that, among its other functions, NPY may play a role in the neuroendocrine regulation of pituitary function.
110 citations
TL;DR: The data indicate for the first time in teleosts that NPY is present and widely distributed in the brain and pituitary, and that among other putative functions, could be implicated in the multihormonal release of GTH from the pituitsary.
Abstract: The presence of a peptide closely related to porcine NPY has been demonstrated in the goldfish brain and pituitary by means of radioimmunoassay (RIA) and high performance liquid chromatography (HPLC). The RIA data demonstrate that displacement curves of brain extracts are parallel to a porcine NPY standard and that in HPLC a compound present in brain extracts is co-eluted with porcine NPY. The distribution of this NPY-like factor within the central nervous system was studied by radioimmunoassay and immunohistochemistry. The results indicated that NPY has a widespread distribution with the highest concentrations being found in the telencephalon and diencephalon. In the pituitary gland, NPY immunoreactive terminals characterized at the electron microscope level were found in the different lobes and, in particular, in close association with the gonadotrophin (GTH) secreting cells. Using anin vitro perifusion system, it was shown that NPY causes a dose dependent increase of GTH release from anterior lobe fragments.These data indicate for the first time in teleosts that NPY is present and widely distributed in the brain and pituitary, and that among other putative functions, could be implicated in the multihormonal release of GTH from the pituitary.
83 citations
TL;DR: The high density of somatostatin receptors observed in proliferative or pre-migratory areas suggests that som atostatin may be an important factor involved in the organization of the central nervous system.
80 citations
TL;DR: The biochemical characterization and anatomical distribution of somatostatin binding sites were examined in the brain of the frog Rana ridibunda, and the distribution of the receptors was compared with the location of som atostatin immunoreactive neurons.
Abstract: The biochemical characterization and anatomical distribution of somatostatin binding sites were examined in the brain of the frog Rana ridibunda, and the distribution of the receptors was compared with the location of somatostatin immunoreactive neurons. The pharmacological profile of somatostatin receptors was determined in the frog brain by means of an iodinated superagonist of somatostatin, [125I-Tyr0,DTrp8]S-14. Membrane-enriched preparations from frog brain homogenates were shown to contain high-affinity receptors (KD = 0.78 ± 0.34 nM; Bmax = 103 + 12.7 fmoles /mg protein) with pharmacological specificity for [DTrp] substituted S14 and S28 analogs. The distribution of somatostatin-binding sites was studied by autoradiography on coronal sections of frog brain. Various densities of somatostatin receptors were detected in discrete areas of the brain. The highest concentration of binding sites was observed in the olfactory bulb, in the pallium, and in the superficial tectum. Moderate binding was observed in the striatum, amygdaloid complex, preoptic area, and cerebellum.
Immunocytochemical studies of the distribution of somatostatin-28 (S28) related peptides were also conducted in the frog brain. Two antisera that recognize distinct epitopes of the somatostatin molecule have been used for immunohistochemical mapping of the peptide. Antiserum SS9 recognizes both S28 and somatostatin-14 (S14) and allowed the labelling of perikarya. Antiserum S320 recognizes the N-terminal fragment (1–12) resulting from enzymatic cleavage of S28. This latter antiserum, which does not cross-react with S28, stained mainly neuronal processes. At the infundibular level, however, both antisera stained cell bodies and fibers. Immunoreactive somatostatin-related peptides were detected in many areas of the frog brain. In the diencephalon, a heavy accumulation of perikarya and fibers was seen in the preoptic nucleus, the dorsal and ventral infundibular nuclei, and the median eminence. Immunoreactive perikarya were also observed in the telencephalon, especially in the pallium and in thalamic nuclei. Immunostained processes were detected in many telencephalic areas and in the tectum.
There was good correlation between the distribution of somatostatin-immunoreactive elements and the location of somatostatin-binding sites in several areas of the brain, in particular in the median pallium, the tectum, and the interpeduncular nucleus. In contrast, mismatching was observed in the olfactory bulb, lateral pallium, and the cerebellum (which contained moderate to high levels of binding sites but virtually no somatostatin-immunoreactive fibers) and the hypothalamic areas (preoptic area and infundibular nuclei), in which a low concentration of binding sites but a high density of immunoreactive perikarya and fibers were detected.
The present data provide the first pharmacological characterization and anatomical distribution of somatostatin-binding sites in the brain of a non-mammalian vertebrate species. The present results suggest that many of the major features of somatostatinergic systems described in mammals (e.g., the wide distribution of somatostatinergic neurons and somatostatin-binding sites; pharmacological characteristics of somatostatin receptors) had already arisen in tetrapod ancestors. Such findings suggest that both neuroendocrine and extrahypothalamic somatostatinergic systems have important functions throughout the vertebrate phylum.
80 citations
TL;DR: Results are consistent with the interpretation that the glycans of beta-fructosidase are necessary for its stability, and that in these suspension-cultured cells, the unglycosylated enzyme is degraded during the last stage(s) of secretion, or immediately after its arrival in the wall.
Abstract: Suspension-cultured carrot (Daucus carota) cells synthesize and secrete β-fructosidase, a glycoprotein with asparagine-linked glycans. Treatment of the cells with tunicamycin completely inhibits the apparent secretion of β-fructosidase as measured by the accumulation of the radioactive protein in the cell wall or the culture medium. In the past, such a result has been interpreted as an inhibition of secretion by tunicamycin, but we suggest another explanation based on the following results. In the presence of tunicamycin, unglycosylated β-fructosidase is synthesized and is associated with an endoplasmic-reticulum-rich microsomal fraction. Pulse-chase experiments show that the unglycosylated β-fructosidase does not remain in the cells and appears to be secreted in the same way as glycosylated β-fructosidase; however, no radioactive, unglycosylated β-fructosidase accumulates extracellularly (cell wall or medium). Protoplasts obtained from carrot cells secrete β-fructosidase protein and activity, and treatment of the protoplasts with tunicamycin results in the synthesis of unglycosylated β-fructosidase. In the presence of tunicamycin, there is no accumulation of β-fructosidase activity or unglycosylated β-fructosidase polypeptide in the protoplast incubation medium. These results are consistent with the interpretation that the glycans of β-fructosidase are necessary for its stability, and that in these suspension-cultured cells, the unglycosylated enzyme is degraded during the last stage(s) of secretion, or immediately after its arrival in the wall.
67 citations
TL;DR: The indirect immunofluorescence technique shows that an AVT-like peptide is stored in chromaffin granules of frog adrenal gland, and indicates that synthetic AVT is a potent stimulator of corticosteroid secretion by frog interrenal cells.
Abstract: The presence of neurohypophyseal nonapeptides in the adrenal gland of nonmammalian vertebrates and the possible action of these regulatory peptides on corticosteroid secretion have never been investigated. We have applied the indirect immunofluorescence technique to examine whether vasotocin (AVT) and/or mesotocin (MT) are located in frog adrenal (interrenal) tissue. Using antisera against AVT and tyrosine hydroxylase, we found that all chromaffin cells contain an AVT-like peptide. Labeling of consecutive sections with phenylethanolamine-N-methyltransferase or AVT antibodies showed that both noradrenaline- and adrenaline-storing cells contain AVT-like immunoreactivity. In contrast no labeling of frog adrenal slices was observed using a MT antiserum. At the ultrastructural level, the immunogold technique revealed that the AVT-immunoreactive peptide is sequestered in chromaffin granules with varying electron densities. Filtration of frog adrenal tissue extracts on Sep-Pak C-18 cartridges showed that the elution profile of the AVT-like peptide was similar to that of synthetic AVT. The apparent concentration of AVT in the adrenal was 2.7 ng/g tissue. Since chromaffin cells represent approximately one third of all interrenal cells, the actual concentration of AVT in chromaffin tissue was about 8 ng/g tissue. The role of AVT in the regulation of frog adrenal steroidogenesis was studied in vitro using perifused frog interrenal slices. Graded doses of AVT (10(-10)-10(-7) M) induced a dose-dependent stimulation of both corticosterone and aldosterone secretion. The other neurohypophyseal peptides (vasopressin, oxytocin, and MT) were also able to enhance corticosteroid secretion, but AVT was by far the most potent stimulator of steroidogenesis. Prolonged administration (4 h) of AVT induced a rapid increase in corticosterone and aldosterone output, followed by a gradual decline of corticosteroid secretion. These results show that an AVT-like peptide is stored in chromaffin granules of frog adrenal gland. Our data also indicate that synthetic AVT is a potent stimulator of corticosteroid secretion by frog interrenal cells. Since in amphibians adrenocortical and chromaffin cells are intimately intermingled, these results suggest that AVT produced by chromaffin cells may regulate corticosteroid release locally, through a cell to cell mode of communication.
55 citations
TL;DR: In this article, the authors studied the asymptotic behavior of the hydrodynamical limit at the shock in a semi-infinite one-dimensional initial distribution with respect to the position of the leftmost particle.
Abstract: We study for a semi-infinite one dimensional initial distribution the asymptotic behaviour in the hydrodynamical limit at the shock. In this case the location of the shock is naturally identified by the position of the leftmost particle of the system for which we prove a central limit theorem. From this we deduce that at the shock local equilibrium does not hold
54 citations
TL;DR: The localization of thyrotropin-releasing hormone-immunoreactive structures was investigated in the hypothalamo-hypophyseal complex of the frog, Rana ridibunda, by light and electron microscopy and the immuno-gold technique.
51 citations
TL;DR: The results support the conclusion that N-linked glycan processing is not necessary for sorting, but glycosylation is required for accumulation of secreted proteins in the extracellular compartment.
Abstract: Suspension-cultured cells of sycamore (Acer pseudoplatanus L.) secrete a number of acid hydrolases and other proteins that have both highmannose and complex asparagine-linked glycans. We used affinity chromatography with concanavalin A and an antiserum specific for complex glycans in conjunction with in vivo-labeling studies to show that all of the secreted proteins carry glycans. The presence of complex glycans on secretory proteins indicates that they are passing through the Golgi complex on the way to the extracellular compartment. The sodium ionophore, monensin, did not block the transport of proteins to the extracellular medium, even though monensin efficiently inhibited the Golgi-mediated processing of complex glycans. The inhibition of N-glycosylation by tunicamycin reduced by 76% to 84% the accumulation of newly synthesized (i.e. radioactively labeled) protein that was secreted by the sycamore cells, while cytoplasmic protein biosynthesis was not affected by this antibiotic. However, in the presence of glycoprotein-processing inhibitors, such as castanospermine and deoxymannojirimycin, the formation of complex glycans was prevented but glycoprotein secretion was unchanged. These results support the conclusion that N-linked glycan processing is not necessary for sorting, but glycosylation is required for accumulation of secreted proteins in the extracellular compartment.
50 citations
TL;DR: In vitellogenic females treated with 1-4-6 androstadien 3–7 dione, an inhibitor of aromatase activity, the pituitary response to NPY was similar to that obtained in ovulated females, suggesting thein vitro action of NPY might depend on thein vivo steroidogenic environment.
Abstract: This work investigated the action of neuropeptide Y (NPY) on thein vitro pituitary release of the maturing gonadotropic hormone (GtH) of the rainbow trout using a perifusion system employing trout balanced salt solution (pH 7.5) at 15°C and a 12.5 ml/h flow rate. In vitellogenic females a 20 minutes NPY application (10−7 M) induced a 20–30% decrease in GtH secretion. Removal of NPY was followed by a rebound in GTH secretion. On the contrary, in ovulated females, NPY (15 minutes, 10−7 M) directly stimulated GTH secretion. The greatest stimulation was obtained the day of ovulation where the stimulatory effect of NPY was similar to those induced by s.GnRH in the same conditions, reaching 400% of the basal GTH level. In vitellogenic females treated with 1-4-6 androstadien 3–7 dione, an inhibitor of aromatase activity, the pituitary response to NPY was similar to that obtained in ovulated females. Thus thein vitro action of NPY might depend on thein vivo steroidogenic environment.
TL;DR: The involvement of the GABA-benzodiazepine receptor complex in the regulation of melanotropin secretion has been investigated using perfused frog neurointermediate lobes and it appears that the GABAergic control of alpha-melanocyte-stimulating hormone release is mainly achieved through activation of GABAA receptors.
TL;DR: The distribution of melanin-concentrating hormone (MCH) in the central nervous system of the dogfish Scyliorhinus canicula was determined by indirect immunofluorescence and peroxidase-anti-peroxid enzyme techniques, using an antiserum raised against synthetic salmon MCH.
TL;DR: The perifusion system was found useful in order to follow the characteristics of melatonin release from pineal glands and should allow investigations of neuronal or hormonal control of pineal gland activities.
Abstract: In previous studies, noradrenaline was found to elicit a rise of melatonin secretion through activation of typical beta-adrenergic receptors. In the present study, a perifusion system was developed to characterize the kinetics of melatonin release from rat pineal glands. Isolated pineal glands from adult male rats were continuously perifused for 15 h in a Krebs-Ringer solution, and the concentration of melatonin in the effluent perifusate was monitored using a specific radioimmunoassay. The rate of release of melatonin declined during the first 3-4 h of perifusion and then remained fairly stable for at least 11 h. The spontaneous release of melatonin was around 20 pg per min and per gland. When pineal glands were stimulated with isoproterenol, melatonin release output linearly increased for at least 2 h after the stimulation. The increase in melatonin release depended on the isoproterenol concentration and on the duration of the stimulation. The analysis of the pattern of melatonin secretion by a single rat pineal gland showed that the secretion was irregular but did not present a clear feature of pulsatile or oscillatory release over a 11 h-long study. The perifusion system was found useful in order to follow the characteristics of melatonin release from pineal glands and should allow investigations of neuronal or hormonal control of pineal gland activities.
TL;DR: It is suggested that TRH stimulates the release of peptide hormones from teleost melanotropes and that the goldfish neurointermediate lobe in vitro releases numerous peptides derived from POMC.
TL;DR: The composite structures, however, suffered from high diffusion limitations which increased with the population of immobilized bacteria and could be maintained over several months by periodically incubating the biocatalytic structures in a rich nutrient broth.
Abstract: Viable cells of Rhodospirillum rubrum were immobilized by entrapment in a planar agar matrix bounded by a microporous membrane filter and were tested for H2 photoproduction in synthetic waste water provided with malate and glutamate. Optimum H2 production was obtained at 15 klx for a C/N ratio of 7–8. Production rates as high as 565 mm3 H2 · h-1 per cubic centimetre of agar were recorded. The composite structures, however, suffered from high diffusion limitations which increased with the population of immobilized bacteria. The H2-evolving activity could be maintained over several months by periodically incubating the biocatalytic structures in a rich nutrient broth. No contamination of the nutrient broth due to leakage of photosynthetic organisms from the gel appeared during incubation of the structures.
TL;DR: The involvement of a low-affinity dopamine/neuroleptic receptor in dopamine inhibition of GtH and alpha-MSH release from the pituitary of the goldfish is suggested.
TL;DR: The data show that ACh stimulates in vitro alpha MSH secretion by frog NIL, and indicates that amphibian pars intermedia cells possess two types of cholinergic receptors, an M1-muscarinic receptor sensitive to pirenzepine and nicotinic receptors sensitive to hexamethonium and alpha-bungarotoxin.
Abstract: The release of alpha MSH from the pars intermedia of amphibians is regulated by multiple factors, including classical neurotransmitters and neuropeptides. In this study we have examined the possible involvement of acetylcholine (ACh) in the regulation of alpha MSH secretion from the pars intermedia of the frog (Rana ridibunda) using the perifusion technique. When intact neurointermediate lobes (NIL) were exposed to graded doses of ACh (3 X 10(-7) to 3 X 10(-4) M), a dose-dependent stimulation of alpha MSH release was observed. Repeated administration of ACh (10(-4) M) induced reproducible responses of NIL without any desensitization phenomenon. ACh was also capable of stimulating alpha MSH release from dispersed intermediate lobe cells, indicating that the neurotransmitter exerts its effect by acting directly on frog melanotrophs. Using the monoclonal antibody M-35 against calf muscarinic receptors we have visualized, by the immunofluorescence technique, the presence of muscarinic receptor-like immunoreactivity in the frog pars intermedia. The stimulatory action of ACh was mimicked by both nicotine and muscarine (10(-5) M each). Nicotine-induced stimulation of alpha MSH release was partially abolished by alpha-bungarotoxin (10(-6) M) and hexamethonium (10(-4) M). The stimulatory effect of muscarine was suppressed by atropine and the M1-muscarinic antagonist pirenzepine (10(-5) M), but not by the M2-muscarinic antagonist gallamine. We have investigated the effect of ACh during administration of specific nicotinic and muscarinic antagonists. While hexomethonium or atropine could block only part of the stimulatory effect of ACh, concomitant administration of these antagonists totally abolished the response of NIL to ACh. Finally, the stimulatory effect of ACh was not impaired during prolonged administration of the beta-adrenergic antagonist propranolol. These data show that ACh stimulates in vitro alpha MSH secretion by frog NIL. Our results also indicate that amphibian pars intermedia cells possess two types of cholinergic receptors, an M1-muscarinic receptor sensitive to pirenzepine and nicotinic receptors sensitive to hexamethonium and alpha-bungarotoxin.
TL;DR: The European Mechanics Colloquium number 237 was held at the Institut de Mecanique Statistique de la Turbulence (Universite d'Aix-Marseille II) from 18 to 21 July 1988 as mentioned in this paper.
Abstract: The European Mechanics Colloquium number 237 was held at the Institut de Mecanique Statistique de la Turbulence (Universite d'Aix-Marseille II) from 18 to 21 July 1988. This was the first meeting to consider the influence of density variations on turbulent flows for both non-reacting and reacting flows in a variety of configurations. Several new experiments, computational models and theoretical analyses were presented for non-reacting flows. All these approaches showed the marked effects of density variations on coherent structures in turbulent shear flows. It was found that the approximate models used for turbulent Reynolds stresses in homogeneous flows do not need to be changed for the mean flow field but predictions for variances and correlations are still rather uncertain: in fact experimental results providing such information in variable-density flows are rare. The special problem of measuring turbulence in flows with density variations was discussed. In the discussions it was agreed that there are in fact strong similarities in the effects of density gradients on the dynamics of non-reacting flows and reacting flows despite the differences in the distributions of density gradients. Participants at the meeting from industry emphasized the importance of these flows to many different kinds of industrial and environmental problems.
Journal Article•
TL;DR: In this paper, a reverse phase high-performance liquid chromatography analysis coupled with a sensitive radioimmunoassay for α-melanocyte-stimulating hormone (α-MSH)-related peptides was used to characterize the αMSH-related peptide stored in the rat hypothalamus or released from perifused hypothalamic slices.
TL;DR: The present results show that large kainic acid lesions of the NRTP do not abolish optokinetic eye movements in the rat, in contrast to what has been reported after electrolytic lesions, and suggest that there is a failure of slow build-up of OKN slow phase velocity.
Abstract: The nucleus reticularis tegmenti pontis (NRTP) and adjacent pontine reticular formation were lesioned chemically using the neurotoxic agent kainic acid, and the effects of these lesions on horizontal ocular optokinetic and vestibular nystagmus were examined. Eye position was measured in the alert, NRTP-lesioned animals with the electromagnetic search coil technique. Optokinetic and vestibular stimuli consisted of steps of rotations or sinusoidal oscillations of a fullfield visual pattern surrounding the animal or of the animal in total darkness, respectively. In a first group of animals, small unilateral NRTP lesions were produced by placing a single kainic acid injection in the area of the left NRTP. In one third of the animals, ipsilateral quick phases of optokinetic and vestibular nystagmus were abolished. In the remaining animals, quick phases were deficient to various degrees or not affected at all. There were no changes in the characteristics of optokinetic step responses to ipsilateral pattern rotations which activate predominantly optokinetic pathways on the side of the brainstem lesion. In animals with ipsiversive quick phase deficits, contralateral pattern rotations elicited tonic eye deviations. In a second group of animals, large uni- or bilateral lesions were produced by injecting kainic acid into three separate rostral, middle and caudal levels of the right NRTP. These animals had uni- or bilateral quick phase deficits during optokinetic and vestibular nystagmus. Optokinetic nystagmus in response to velocity steps of pattern rotation towards the lesion side was strongly reduced in gain even in those animals that had no apparent deficits in the fast contraversive reset phases. In four out of six animals, responses to sinusoidal optokinetic pattern oscillations were reduced in gain and showed increased phase lags compared to controls. Vestibulo-ocular responses to velocity steps of head rotations were of normal gain but reduced in duration (measured from onset of stimulation to reversal of nystagmus). Sinusoidal vestibulo-ocular responses evoked by head oscillations exhibited reduced gain values and strongly increased phase leads in the frequency range below 0.5 Hz. The vestibular time constant was found to be around 4.5 s in animals with NRTP lesions compared to about 7.5 s in control animals. The present results show that large kainic acid lesions of the NRTP (and adjacent area) do not abolish optokinetic eye movements in the rat, in contrast to what has been reported after electrolytic lesions.(ABSTRACT TRUNCATED AT 400 WORDS)
TL;DR: The data indicate that acetylation of des-Nα-acetyl α-MSH may occur during the process of exocytosis, and suggest that regulation of the acetyltransferase activity could be a key mechanism to modulate the bioactivity of α- MSH-related peptides in the brain.
TL;DR: The differential distribution of POMC-related peptides suggests that α-MSH may act as a neurotransmitter or neuromodulator, whereas β-endorphin and ACTH might also exert neuroendocrine functions.
Abstract: The occurrence and distribution of the pro-opiomelanocortin (POMC)-derived peptides alpha-MSH, ACTH, and beta-endorphin in the brain of the dogfish Scyliorhinus canicula were investigated by immunocytochemistry using the indirect immunofluorescence and the peroxidase-antiperoxidase procedures. Immunoreactive perikarya were found in distinct regions of the hypothalamus. Alpha-MSH-like containing neurons were confined mainly in the dorso-caudal area of the hypothalamus within the nucleus tuberculi posterioris and the nucleus sacci vasculosi. A small number of immunoreactive cells were localized in the nucleus periventricularis. The hypothalamic dorso-caudal region contained a rich network of fine immunopositive fibers extending in the whole tuberculum posterioris toward the saccus vasculosi. Very few fibers were found coursing ventrally toward the nucleus periventricularis and within the thalamus and the basal mesencephalon. In the pituitary gland, only the melanotropic cells of the neurointermediate lobe were stained by the alpha-MSH antiserum.
ACTH-like-containing neurons and fibers were identified in the nucleus lateralis tuberis. Many of these cells appeared to be of the liquor-contacting type. Some immunoreactive cells were also found within the subependymal layers of the nucleus lobi lateralis. At the pituitary level, ACTH-positive cells were located in the rostral lobe of the pars distalis.
Beta-endorphin-like immunoreactive cells were seen mainly within the preoptic nucleus, bordering the ventral side of the anterior preoptic recess, and in the nucleus lateralis tuberis. Most of these immunoreactive cells were of the liquor-contacting type. Beta-endorphin immunoreactive fibers were found coursing through the lateral post-chiasmatic region and the hypothalamic floor. Scattered fibers were also found in the basal telencephalon. Occasionally, some positive cells were identified in the nucleus lobi lateralis. Beta-endorphin-positive cells were located in the neurointermediate lobe of the pituitary.
These findings indicate that substances related to POMC-derived peptides are located in distinct neuronal centers of the hypothalamus of Scyliorhinus. The differential distribution of POMC-related peptides suggests that α-MSH may act as a neurotransmitter or neuromodulator, whereas β-endorphin and ACTH might also exert neuroendocrine (i.e., hypophysiotropic) functions.
TL;DR: Investigation of the presence of ACTH, alpha-MSH and beta-endorphin, three peptides which derive from the multifunctional precursor protein proopiomelanocortin (POMC) in the brain of the rainbow trout Salmo gairdneri suggests that expression and processing of POMC in the fish brain is similar to that occurring in pituitary melanotrophs.
TL;DR: The notion that the neurotransmitter GABA may play a physiological role in the regulation of α-MSH release by hypothalamic neurons is supported, as the presence of an abundant network of GABAergic nerve terminals in the basal hypothalamus supports the notion.
TL;DR: The view that atrial natriuretic factor may act as a neurotransmitter or a neuromodulator in various regions of the frog brain is supported by the results of in vitro receptor autoradiography.
Abstract: The distribution of atrial natriuretic factor (ANF) binding sites was investigated in the central nervous system of the frog Rana ridibunda using the technique of in vitro receptor autoradiography by means of [125I]-labeled ANF-28. The anatomic distribution of ANF recognition sites was determined on Kodak ARX films apposed onto tissue sections, and their distribution was examined in greater detail by analysis of autoradiograms generated by using emulsion-coated sections. The highest levels of ANF binding sites were found in the olfactory bulb, the dorsal pallium, the septum, the habenular nucleus, the dorsal infundibular nucleus, the interpeduncular nucleus, and in the tectum. Moderate levels of ANF binding sites were observed in the thalamus and throughout the mesencephalon, whereas low levels were detected in the lateral and medial pallium, the medial forebrain bundle, and the nucleus rotondus. In the pituitary gland, the neural and distal lobes were densely loaded with ANF binding sites, whereas no autoradiographic labeling was observed in the pars intermedia. In general, there was a good correlation between the location of ANF receptors and the distribution of ANF-containing neurons, as previously determined by immunocytochemistry. Together these results support the view that ANF may act as a neurotransmitter or a neuromodulator in various regions of the frog brain.
TL;DR: In this paper, the formation of 1:1 or 1:2 borate-sugar complexes by sugars having ribo configurations has been studied by 11B- and 13C-n.m. spectroscopy.
TL;DR: It is demonstrated that the neuropeptide TRH both stimulates Ca2+-sensitive K+ channels and inhibits voltage-dependent K+ current in pituitary melanotrophs and that TRH-induced secretion of alpha-MSH is not a direct consequence of the lowering of K+ conductance.
Abstract: Modulation of the activity of K+ channels by TRH and the possible involvement of this modulation in TRH-induced release of alpha-MSH were studied in cultured frog melanotrophs, using patch-clamp and perifusion techniques. Pars intermedia cells were enzymatically dispersed and cultured in Leibovitz medium. In order to test the viability of cultured cells, the amount of alpha-MSH released into the medium was measured by radioimmunoassay every day for 1 week of culture. The total amount of alpha-MSH released during the first 4 days of culture was 8.6 times higher than the intracellular content of alpha-MSH on day 1. Melanotrophs were identified by an indirect immunofluorescence technique using a specific antiserum to alpha-MSH. Recordings obtained in whole-cell, cell-attached and excised patch-clamp configurations showed that TRH induced a transient polarization concomitant with an increase in the probability of opening of Ca2+-activated K+ channels. This transient response was followed by a depolarization accompanied by an enhanced frequency of action potential discharge. TRH also induced a decrease in voltage-dependent K+ conductance. Application of tetraethylammonium, a K+ channel blocker, depolarized the cells and increased the basal secretory level without noticeable changes in TRH-evoked alpha-MSH release. These results demonstrate that the neuropeptide TRH both stimulates Ca2+-sensitive K+ channels and inhibits voltage-dependent K+ current in pituitary melanotrophs. Our data indicate that TRH-induced secretion of alpha-MSH is not a direct consequence of the lowering of K+ conductance. It thus appears that basal and TRH-induced alpha-MSH release occur through distinct pathways; the spontaneous release of alpha-MSH is probably linked to membrane potential, while modulation of the electrical activity is not directly involved in TRH-induced activation of the secretory process.
TL;DR: A prototype of an immobilized-cell photobioreactor based on a composite agar layer/microporous membrane structure is described and might be readily applied to other light-dependent bioreactions having more short-term economic interest than hydrogen photoproduction.
Abstract: A prototype of an immobilized-cell photobioreactor based on a composite agar layer/microporous membrane structure is described. This photobioreactor has been tested for hydrogen-gas production using viable cells ofRhodospirillum rubrum and a phosphate buffer supplemented with malate and glutamate as nutrient medium. The major problem was the high diffusional resistance of the immobilized-cell layer at high cell population. The device has been patented and might be readily applied to other light-dependent bioreactions having more short-term economic interest than hydrogen photoproduction.
TL;DR: In this paper, a potentiometric study showed that aldoses of the lyxo -series: d -lyxose, d -mannose and l -rhamnose, form dinuclear anionic complexes with tungstate or molybdate ions in acidic solutions.