Plasticity in the phenotypic expression of catecholamines and vasoactive intestinal peptide in adult rat superior cervical and stellate ganglia after long-term hypoxia in vivo.

Sympathetic ganglia in the adult rat contain various populations of nerve cells which demonstrate plasticity with respect to their transmitter phenotype. The plasticity of the neuronal cell bodies and of the small intensely fluorescent cells in the superior cervical and stellate ganglia in response to hypoxia in vivo (10% O2 for seven days) was assessed by studying the expression of catecholamines and vasoactive intestinal peptide. The levels of norepinephrine, dopamine, 3,4-dihydroxyphenylacetic acid and vasoactive intestinal peptide immunoreactivity were determined. In addition, the density of the immunohistochemical staining of cells for tyrosine hydroxylase and vasoactive intestinal peptide was evaluated. In the intact superior cervical ganglion, hypoxia increased the dopamine level as well as the density of small intensely fluorescent cells immunolabelled for tyrosine hydroxylase and vasoactive intestinal peptide. In the axotomized ganglion, hypoxia elicited a twofold rise in the level of the vasoactive intestinal peptide as well as enhancing the density of neuronal cell bodies immunostained for this peptide. Thus, the effect of hypoxia on the expression of vasoactive intestinal peptide expression in neurons was dependent on neural interactions. In the intact stellate ganglion, hypoxia alone induced a 1.5-fold increase in the density of neuronal cell bodies immunostained for vasoactive intestinal peptide. Thus, ganglia-specific factors appeared to play a role in determining changes in neuronal phenotype in response to hypoxia. The present study provides evidence for the involvement of dopamine and vasoactive intestinal peptide in ganglionic responses to long-term hypoxia as well as for differential responses by the two ganglionic cell populations, i.e. neuronal cell bodies and small intensely fluorescent cells. Changes in the expression of the vasoactive intestinal peptide during long-term hypoxia may be of energetic, trophic and/or synaptic significance. Hypoxia may be considered to be a vasoactive intestinal peptide-inducing factor in sympathetic ganglia.

Altered daily rhythms of brain and pituitary indolamines and neuropeptides in long-term hypoxic rats.

To determine whether sustained hypoxia alters daily rhythms in brain and pituitary neurotransmitters, the daily variations in vasoactive intestinal peptide-like immunoreactivity (VIP-LI), neuropeptide Y-like immunoreactivity (NPY-LI), serotonin (5-HT), and 5-hydroxyindole-3-acetic acid (5-HIAA) content were determined in discrete brain regions, pineal gland and anterior pituitary of hypoxic (10% O(2); 14 days) and normoxic rats. Hypoxia suppressed daily variations in VIP-LI in the suprachiasmatic nuclei (SCN) and the anterior pituitary, enhanced the daily rhythmicity in serotonergic elements of the caudal part of the dorsomedial medulla oblongata (DMMc), and even induced daily variations in NPY-LI in the DMMc as well as in the ventrolateral medulla oblongata. In addition, punctual alterations in the rhythmicity of 5-HT and 5-HIAA in the pineal gland and of plasma corticosterone were observed in hypoxic rats. Thus results of this study indicate that a permanent nonphotic stimulus, such as sustained hypoxia, may affect the functioning of the internal clock located in the SCN and may alter the daily rhythmicity in neurotransmitter content of some brain nuclei and the pituitary gland.

Effects of carotid sinus nerve transection on changes in neuropeptide Y and indolamines induced by long-term hypoxia in rats.

Long-term hypoxia induces changes in neuropeptide-Y-like immunoreactivity (NPY-LI) and/or in the content of serotonin (5-HT) and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) at the central level. To determine whether these alterations depend on the integrity of carotid body (CB) chemoreceptors, intact rats or those whose carotid sinus nerve was transected (CSNT) were exposed to hypoxia (10% O2) or to normoxia for 14 days. Thereafter, NPY-LI, 5-HT and 5-HIAA levels in discrete brain regions were determined. The increase in NPY-LI in the ventrolateral medulla oblongata (VLM) of intact hypoxic rats was mostly abolished after CSNT and therefore is mainly mediated by CB chemoreceptors. In contrast, other hypoxia-induced changes were similar or even enhanced in CSNT as compared to intact rats and therefore do not depend on the integrity of CB chemoreceptors. This was the case for the increase of NPY-LI in the striatum and the caudal dorsomedian medulla oblongata (DMM), as well as for all the changes in 5-HT and 5-HIAA in the DMM, the VLM, the raphe nuclei, the striatum and the frontal cortex. We propose that long-term hypoxia alters brain NPY-LI and indolamine content through the stimulation of CB chemoreceptors or ancillary chemoreceptors, as well as through local biochemical or morphological mechanisms.

Activity of tryptophan hydroxylase and content of indolamines in discrete brain regions after a long-term hypoxic exposure in the rat.

The influence of long-term hypoxia (10% O2, 14 days) on in vivo activity of tryptophan hydroxylase and on 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) concentration in discrete brain regions of rats was assessed. The activity of tryptophan hydroxylase was determined through 5-hydroxytryptophan accumulation (5-HTPacc) following the administration of NSD 1015. The 5-HTPacc was significantly decreased in the dorsal and median raphe (56 and 42%, respectively) and in the striatum (62%). Both 5-HTPacc and the ratio of the concentrations of 5-HIAA to 5-HT were decreased in the nucleus raphe magnus (46 and 27%, respectively), the dorsomedian medulla oblongata (52 and 51%), the locus coeruleus (62 and 40%) and the anterior hypothalamic nucleus (30 and 50%). In contrast, 5-HTPacc was increased in the ventrolateral medulla oblongata (55%) and the preoptic area (83%), but the 5-HIAA/5-HT ratio was lower in these two regions. Finally, 5-HIAA/5-HT ratio was also decreased in the periventricular nucleus and in the frontal cortex. Since various patterns of variations in 5-HTPacc and in 5-HIAA/5-HT ratio were observed, the factors affecting serotonin metabolism in hypoxic rats can be different among brain regions. These results show that, in the rat, long-term hypoxia induces changes in in vivo activity of tryptophan hydroxylase and in 5-HT and 5-HIAA content of some brain structures; some of these biochemical changes may be linked to adaptative mechanisms.

Effects of tianeptine, sertraline and clomipramine on brain serotonin metabolism: a voltammetric approach in the rat.

Tianeptine is a substance enhancing the serotonir uptake while sertraline and clomipramine inhibit it. By means of 5-hydroxyin-doleacetic acid (5-HIAA) voltammetric measurements, this study investigated their influence on serotonin metabolism which depends mainly upon the activity of monoamine oxidase type A. After tianeptine injection the 5-HIAA signal increased by about 60%. This effect was maintained when the animals were pre-treated with MDL 72145 (an inhibitor of monoamine oxidase type B) but reduced when clorgyline (an inhibitor of monoamine oxidase type A) was administered after tianeptine. Administration of sertraline or clomipramine reduced the 5-HIAA signal by about 30-50%, whether the animals were pre-treated with MDL 72145 or not. It is to be concluded that tianeptine, sertraline and clomipramine can regulate the 5-HT fraction present in the synaptic cleft, not only by acting at the level of the serotoninergic neurons, but also by favoring or reducing the access of the amine to monoamine oxidase type A which is synthesized within non-serotoninergic neurons and glial cells.

Alteration in central and peripheral substance P- and neuropeptide Y-like immunoreactivity after chronic hypoxia in the rat.

The influence of long-term hypoxia on substance P (SP) and neuropeptide Y (NPY)-like immunoreactivity (LI) in discrete brain areas and peripheral structures was assessed by radioimmunoassay. Rats were exposed to normobaric hypoxia (10% O2 in nitrogen) for 14 days. In the carotid bodies of hypoxic animals, NPY-LI was significantly increased (56% vs. normoxic controls) while SP-LI was unchanged. In the brain, NPY-LI was increased in the ventrolateral medulla oblongata (23%) and in the striatum (53%); however, SP-LI was unaltered in these two regions. In the anterior pituitary, NPY-LI was increased (99%), while SP-LI was decreased (37%). No significant alteration in NPY-LI and SP-LI was observed in other discrete brain areas or peripheral structures studied. These results show that, in the rat, long-term hypoxia induces changes in NPY-LI or SP-LI in a few central and peripheral structures; these biochemical alterations may be linked to adaptative mechanisms involving morphological changes in carotid bodies or alterations in sympathetic control and neuroendocrine function.

Chronic hypoxia affects peripheral and central vasoactive intestinal peptide-like immunoreactivity in the rat.

The influence of long-term hypoxia on vasoactive intestinal peptide-like immunoreactivity (VIP-LI) in discrete brain areas and peripheral structures was assessed by RIA. Rats were exposed to normobaric hypoxia (10% O2-90% N2) for 14 days. VIP-LI was significantly increased in carotid bodies of hypoxic animals (204% vs. normoxic animals). On the other hand, VIP-LI was decreased in the anterior pituitary (-68%), suprachiasmatic nuclei (-29%) and periventricular nuclei (-26%). No significant variation in VIP-LI was observed in other peripheral structures and discrete brain area studied. These results suggest that long-term hypoxia induces alterations in VIP systems implicated in chemoreception, biological rhythms and neuroendocrine functions.

Daily variations in in vivo tryptophan hydroxylation and in the contents of serotonin and 5-hydroxyindoleacetic acid in discrete brain areas of the rat.

The in vivo rate of brain tryptophan hydroxylation was determined through 5-hydroxytryptophan accumulation (5-HTPacc) following the administration of NSD 1015, a L-aromatic amino-acid decarboxylase inhibitor. This measurement was performed every 4 h throughout a 24 h hour period in 10 discrete brain areas of rats maintained on a regular 12 h/12 h light-dark cycle. The concentrations of 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) were also determined in untreated rats. Daily variations in 5-HTPacc were found in all the areas studied, the 5-HTPacc being higher during the dark period in most structures. These results strongly suggest that tryptophan hydroxylation is involved in the control of the 5-HT biosynthesis circadian rhythm. However, various patterns of 5-HT and 5-HIAA daily variations were observed, suggesting that the circadian factors affecting serotonin metabolism can be different among brain areas.

Isolation and some properties of an arylamidase from Flavobacterium IIb.

A constitutive L-leucylarylamidase (EC 3.4.11) hydrolase able to cleave L-aminoacyl-beta naphthylamide and L-aminoacyl-4 nitroanilide substrates, was isolated from sonicated cells of Flavobacterium IIb and partially purified with a 0.9% yield and a 159-fold recovery. Its molecular weight was estimated to be about 170,000 +/- 10%. This arylamidase exhibited optimum activity at pH 7.0 and 28 degrees C for the hydrolysis of L-leucine-4NA and is inhibited strongly by metal chelating agents, and to a weaker extent, by some sulfhydryl and reducing agents. Heavy metal ions: Cd2+, Zn2+, Cu2+, Hg2+ and Co2+, markedly inhibit it, and Zn2+ is a competitive inhibitor. This metalloenzyme, free of carboxypeptidase, proteinase and L-leucine aminopeptidase (L-leucylglycine substrate) activities, hydrolyzes aminoacyl-beta NA, aminoacyl-4NA and some dipeptides with unsubstituted amino groups of the L-configuration. The lowest Km values are associated with substrates having neutral or basic residues, with large side chains.

[Demonstration of a proteolytic activity on intracellular origin in Aeromonas hydrophila LP 50]. / Essai de mise en évidence d'une activité protéolytique d'origine intracellulaire chez Aeromonas hydrophila LP 50.

Aeromonas hydrophila LP 50, isolated from packaged pasteurized milk, was grown in glucose-polypeptone medium at 30 degrees C. The proteolytic activity of A. hydrophila LP 50, optimum at the stationary phase of growth, is attributed to extracellular or membrane protease; no intracellular proteolytic activity was shown.

[Partial purification of the extracellular proteolytic system of Aeromonas hydrophila LP50: comparative chromatographic and electrophoretic study]. / Purification partielle du système protéolytique extracellulaire de Aeromonas hydrophila LP50: étude comparative chromatographique et électrophorétique.

A complex extracellular proteolytic system was produced by Aeromonas hydrophila LP50 on glucose- polypeptone medium. Partial purification of this system was accomplished by ammonium sulphate precipitation, acetone precipitation, gel filtration on Sephacryl- S200 and chromatography on DEAE-Sephacel. Every stage was controlled by electrophoresis. This proteolytic system was constituted of three aminopeptidase and two endopeptidase components.