Biomedical subjects

J F Pujol

Publications and source records attributed to J F Pujol.

At least 19 recordsLinked to original sources

PubMed1992

Somatotopic organization of tyrosine hydroxylase expression in the rat locus coeruleus: long term effect of RU24722.

Tyrosine hydroxylase (TH) tissue concentration was determined by immunostaining of tissue sections directly transferred onto nitrocellulose membranes in the restricted region of the noradrenergic perikarya of the locus coeruleus (LC) along its postero-anterior axis. TH containing cells were systematically counted on adjacent post fixed sections stained by immunohistochemistry. The absolute quantity of TH was estimated in each section and was found to be linearly related to the number of TH immuno-positive cells found in the adjacent section. The ratio between these two parameters was thus used as an index of the cellular concentration of TH in noradrenergic cells. In the LC of control rats, the TH cellular concentration was lower (-39%) in the anterior than in the posterior half of the structure. Three days after an injection of 20 mg/kg of RU24722, an eburnamine derivative known to increase the quantity of TH in the LC, increases in quantities of TH were found in both portions of the LC. Moreover in the posterior LC the increase in the amount of TH resulted from a significant increase in the number of TH-immunopositive cells. In the anterior part, however, it was primarily the result of a significant increase in TH cellular concentration. Throughout the LC there was an increase in the cellular concentration of TH which was inversely proportional to the concentrations found in control animals. TH mRNA content was measured by a quantitative in situ hybridization in sections of both the posterior and anterior LC one day after a single injection of RU24722 at the same dose. The quantity of TH mRNA was significantly increased in both parts. The number of TH mRNA-expressing neurons also increased, especially in the anterior LC. Thus the effects at the level of TH protein and TH mRNA were strikingly parallel though increase in TH protein occurred later than the increase in the TH mRNA. These results suggest that in the rat LC: (1) there is a significant population of 'sleeping cells' in which TH expression is either inactivated or, at a low level of activation; (2) TH cellular concentration could exert a retrocontrol on its own expression in cells of the LC that contained TH and (3) TH expression appears to be regulated by different selective mechanisms in these two different subpopulations of noradrenergic cells within the LC.

Animals↗

PubMed1992

Influence of long-term hypoxia on tyrosine hydroxylase in the rat carotid body and adrenal gland.

Tyrosine hydroxylase (TH) protein was measured in the carotid body and adrenal gland of rats exposed to normobaric hypoxia (10% O2 in nitrogen) for 3, 7, 14 or 22 days. After 22 days of hypoxia, a gradual increase in TH protein content was observed in the carotid body and in the adrenal gland, reaching 168% and 148% of the normoxic controls, respectively. To determine if the increase in TH protein content in the carotid body could alter catecholamine biosynthesis, in vitro TH activity and catecholamine turnover were measured in rats submitted to hypoxia for 14 days. TH activity was increased by 11.2-fold, while the turnover of dopamine and norepinephrine was increased by 14.8- and 5.4-fold, respectively. The data show that long-term hypoxia exerts a stimulatory influence on TH protein in the carotid body and adrenal gland in addition to an elevation in dopamine and norepinephrine biosynthesis in the carotid body.

Adrenal Glands↗

PubMed1992

[Cardiac failure by major arterial hypertension secondary to nephroblastoma].

The authors report on the case of a 7 week-old boy, in whom a renal mass was discovered after general symptoms were observed. Within 48 h, cardiac failure secondary to systemic arterial hypertension occurred, requiring intensive care. After a few days of mechanical ventilation and alternating elevated and low blood pressure, improvement was obtained with captopril and frusemide enabling further investigations to be carried out which lead to the diagnosis of Wilms tumor. During left-sided nephrectomy, elevated renin from the left renal vein was found. The post surgical course was excellent. Several authors have reported on the association between arterial hypertension and nephroblastoma as being the result of hyperreninism due to hilar compression; however severe hypertension was uncommon. Renin activity determination from the tumoral tissue had led to a different interpretation, ie primary hyperreninism: in the case of mesoblastic nephroma, only the non tumoral but compressed tissue contains a large quantity of renin; in the case of nephroblastomas, only the tumoral tissue contains renin. The question now is whether all or only certain nephroblastomas secrete renin.

Heart Failure↗

PubMed1991

Distribution of alpha-1 and alpha-2 binding sites in the rat locus coeruleus.

Precise anatomical distribution of alpha-1 and alpha-2 adrenergic binding sites has been investigated in the rat locus coeruleus (LC) using quantitative radioautography of brain sections incubated with 3H-prazosin or 3H-idazoxan. Distribution patterns of 3H-prazosin (alpha-1 sites) and 3H-idazoxan (alpha-2 sites) were heterogeneous and different along a postero-anterior axis in the LC. Comparison between distribution of alpha-2 binding sites and noradrenergic (NA) cellular density suggests that at least a fraction of these sites might be localized on NA perikarya or dendrites in this structure. Quantitative estimations of the binding parameters along this postero-anterior axis in the LC have revealed that the heterogeneous distributions of alpha-1 and alpha-2 binding sites are due not only to variations in the maximal densities of sites but also to variations in the affinities of these sites for their respective ligand.

Animals↗

PubMed1990

Variation of tryptophan-5-hydroxylase concentration in the rat raphe dorsalis nucleus after p-chlorophenylalanine administration. I. A model to study the turnover of the enzymatic protein.

An immunoblot procedure was developed to quantify the amount of tryptophan hydroxylase (TpOH), the rate limiting enzyme in the synthesis of serotonin, in the rat raphe dorsalis nucleus (NRD). Using this method we have studied the time course variations in TpOH protein level after a single p-chlorophenylalanine (PCPA) i.p. injection (300 mg/kg). PCPA provoked a rapid and large decrease of TpOH in the NRD, without affecting neuron-specific enolase in the NRD or TpOH in the locus coeruleus. The decrease in TpOH was maximum (-60% of the control value) 2 days after the drug administration and followed a monoexponential law which allowed us to estimate the half-life of this enzymatic protein as 1.43 days and to postulate that, during these 2 days, TpOH synthesis was inhibited. The neosynthesis of TpOH molecules from 2 to 7 days was estimated to be 57.8 U TpOH/NRD/day which was comparable to the initial steady state of synthesis (48.44 U TpOH/NRD/day). In vivo administration of 6-fluorotryptophan or in vitro incubation of raphe homogenates with either halogenated derivative had no effect on TpOH protein levels. PCPA should be an interesting tool to study the turnover rate of TpOH protein.

Animals↗

PubMed1990

Variation of tryptophan-5-hydroxylase concentration in the rat raphe dorsalis nucleus after p-chlorophenylalanine administration. II. Anatomical distribution of the tryptophan-5-hydroxylase protein and regional variation of its turnover rate.

Distribution of tryptophan-5-hydroxylase (TpOH)-containing cells and TpOH protein tissue concentrations were evaluated in the nucleus raphe dorsalis (NRD) of rat brain by immunocytochemistry and direct transfer onto nitrocellulose filters of unfixed adjacent brain sections. This work has demonstrated that: (1) the direct transfer onto nitrocellulose filters could be easily used for the quantitative analysis of TpOH protein distribution; (2) the origin of the TpOH in this brain nucleus was preferentially cellular; (3) classical subdivisions, qualitatively defined from morphometric and topographic observations could be precisely described in terms of cellular density, tissue and cellular concentrations and turnover of TpOH protein. Such differences could imply a physiological control of TpOH gene expression in the serotoninergic neurons.

Animals↗

PubMed1990

Light-microscopic localization of somatostatin binding sites in the locus coeruleus of the rat.

Somatostatin (SS14) binding sites within locus coeruleus (LC) were localized at the light microscope level by [125I][Tyr0,D-Trp8]SS14 radioautography combined with an immunohistochemical/neurotoxic lesioning approach. In intact rats, the dense accumulation of SS14 binding sites of LC conspicuously overlapped with the cluster of tyrosine hydroxylase (TH) immunoreactive neurons; SS14 specific binding was directly proportional to the number of TH immunostained (TH+) cell bodies per mg of tissue throughout LC. Complete lesion of catecholaminergic nerve cell bodies of LC by intracerebroventricular injection of 6-hydroxydopamine (6-OHDA) resulted in the total abolition of SS14 specific binding in the structure. In addition, specifically bound [125I][Tyr0, D-Trp8]SS14 and TH+ cell density were quantified serially in a set of rats bearing various partial neurotoxic lesions; a highly significant correlation was found between the two parameters at each of the 16 coronal levels of LC examined. The coefficient of proportionality was identical at all levels. These results strongly suggest that somatostatin binding sites are uniformly localized on all noradrenergic neurons of LC.

Animals↗

PubMed1990

Quantitative radioautographic study of somatostatin receptors heterogeneity in the rat extrahypothalamic brain.

The possible heterogeneity of extrahypothalamic somatostatin receptors was studied in rat brain by quantitative radioautography. The respective distribution and relative proportion of two somatostatin receptor sub-types (SS1 and SS2) were assessed by using two radioligands, the non-selective probe [125I]Tyr3-D-Trp8-somatostatin14 and the SS1 selective analogue [125I]Tyr3-SMS 201-995. For both ligands, adjacent brain sections were processed in the presence of micromolar concentrations of either a non-discriminative competitor (somatostatin14) or SS1-selective analogue (SMS 201-995). The comparative analysis of the specific binding remaining in the presence of each non-radioactive competitor permitted a semi-quantitative analysis of the proportion of SS1 and SS2 receptor sub-types in each brain region examined. Data obtained correlate well with homogenate binding results reported previously [Reubi J. C. (1984) Neurosci. Lett. 49, 259-263]. Although the distribution patterns obtained with both radioligands were similar, [125I]Tyr3-SMS 201-995 labelled only a fraction of [125I]Tyr0-D-Trp8-somatostatin14-labelled sites in certain brain regions. For example, both superficial and deep cortical laminae, as well as the basolateral amygdaloid nucleus and CA1 hippocampal area exhibited different binding densities with [125I]Tyr0-D-Trp8-somatostatin14 depending on the competitor used in the assay (somatostatin14 or SMS 201-995). On the other hand, [125I]Tyr3-SMS 201-995 binding was eliminated in an identical fashion by either competitor in these very same brain areas. This suggests the existence of SS1 and SS2 somatostatin receptor sub-types in these regions. In all other brain areas examined, somatostatin receptor sites are apparently of the SS1 sub-type. The heterogeneity of somatostatin receptors observed in certain regions may have relevance for the various biological effects induced by somatostatin in the central nervous system.

Animals↗

PubMed1990

Pharmacological and functional evidence for extracellular 3,4-dihydroxyphenylacetic acid as an index of metabolic activity of the adrenergic neurons: an in vivo voltammetry study in the rat rostral ventrolateral medulla.

Catecholamine metabolism was studied in vivo in the C1 adrenergic area of the rostral ventrolateral medulla oblongata in rats, using differential normal pulse voltammetry coupled with an activated carbon fiber microelectrode. Pharmacological evidence indicates that 3,4-dihydroxyphenylacetic acid, the major dopamine metabolite, is responsible for the electrochemical signal appearance in the C1 group, and that it reflects the catecholamine synthesis rate, as previously reported in the locus coeruleus. Indeed, 3,4-dihydroxyphenylacetic acid was estimated to be formed from 77% of the intracellular dopamine, since its synthesis was increased by only 23%, after blockade of the dopamine-beta-hydroxylase activity. Neuronal activation by retrograde electrical stimulation increased the electrochemical signal, as well as hemorrhage and hypotension, suggesting that the level of extracellular 3,4-dihydroxyphenylacetic acid is a good biochemical index of the C1 adrenergic cellular activity in baseline conditions and during cellular activation.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1990

Ontogeny of tyrosine hydroxylase concentration in locus coeruleus of newborn rats: long-term effects of RU24722.

The ontogenetic variations of tyrosine hydroxylase (TH) have been studied in locus coeruleus of developing rats. During the first 2 weeks after birth, a large increase in TH content (6.04-23.99 TH units) in the noradrenergic structure was observed, followed by a period of progressive increase of the protein concentration (42 TH units in adult rats). The expression of TH was studied in the same ontogenetic period after treatment by RU24722 (20 mg/kg, i.p.). The long-term increase in TH concentration produced by the drug was found to follow ontogenetic variations. It becomes significant around the middle of the second week after birth and gradually increases until the 24th day of postnatal development, indicating a maturation of the mechanisms involved in the inducing effect.

Aging↗

PubMed1989

RU 24722, a new eburnamine derivative, induces selective alterations in cerebral glucose utilization in freely moving rat.

The effect of a new eburnamine derivative, RU 24722, a putative phasic activator of catecholaminergic systems on local cerebral glucose utilization was studied in freely moving rats 15 min, 90 min and 6 h after the intraperitoneal administration of the drug (25 mg/kg). Of the 53 brain regions examined, 9 exhibited significant time-dependent increases of glucose utilization (up to 45-55%). Some changes were early and transient, as in the substantia nigra reticulata and the paraventricular nuclei. Other areas showed sustained (median septal nucleus) or delayed increases of glucose utilization (lateral septum, dorsal subiculum, hippocampal fimbria, fronto-parietal motor cortex and ventral cochlear nucleus). No significant alterations of glucose utilization could be elicited in the locus coeruleus and raphe nuclei, and none of the brain regions showed a decrease in glucose consumption. Our findings suggest that RU 24722 preferentially stimulates the activity in some brain areas involved in cognitive, vegetative and locomotor functions.

Animals↗

PubMed1989

Fentanyl increases catecholamine oxidation current measured by in vivo voltammetry in the rat striatum.

A proposed mechanism for fentanyl-induced muscular rigidity is the effect of opioids on dopaminergic transmission in the striatum. The objective of this study was to observe the effect of fentanyl on the rat striatal catechol oxidation current (CA.OC) which reflects extracellular DOPAC (3-4,dihydroxyphenylacetic acid) concentration (a major metabolite of dopamine), as measured by in vivo voltammetry. Male Sprague-Dawley rats, anaesthetized with halothane, were stereotaxically implanted with carbon fibre electrodes in the striatum and after an initial stabilization period of an hour were given a control saline IV injection followed 30 min later by fentanyl 10 micrograms.kg-1 IV over 10 min and at 70 min by the monoamine oxidase inhibitor pargyline 70 mg.kg-1 IP. Fentanyl produced a significant (P less than 0.05 Anova) increase in CA.OC in all animals. This reached a plateau 15 min following the administration of fentanyl and was at a maximum of 148 +/- 10.2 per cent of control 35 min after the administration of fentanyl. Pargyline produced a rapid decline in CA.OC peak height which went from 143 +/- 11.6 to 39 +/- 6.8 per cent of control over 30 min. There were no significant differences between the pH, PaO2 and PaCO2 during the saline and fentanyl injection periods and there was no significant variation of blood pressure throughout the experiment. This study shows that under stable physiological conditions, fentanyl produces a significant increase in CA.OC in the rat striatum.

Animals↗

PubMed1989

Subcellular distribution of tyrosine hydroxylase in some catecholaminergic rat brain areas determined by a quantitative immunoblot assay.

The subcellular distribution of the protein tyrosine hydroxylase (TH) after fractionation of rat brain tissue was studied by a sensitive technique of immunoblot quantification in the dopaminergic nigrostriatal and the dorsal noradrenergic pathways and in the ventrolateral medulla. This repartition indicates that in all catecholaminergic regions of the cell bodies studied, the contribution of the nerve endings to the total TH amount is very low (less than 7%), in contrast to that observed in the terminal fields. The correlative subcellular determination of the TH amount and activity in the same tissue could be a useful approach for studying experimentally induced mechanisms of catecholamine synthesis modulation in different brain catecholaminergic pathways.

Animals↗

PubMed1989

Direct transfer into nitrocellulose and quantitative radioautographic anatomical determination of brain tyrosine hydroxylase protein concentration.

An improved quantitative immunochemical determination of brain tyrosine hydroxylase (TH) concentrations was designed using direct transfer into nitrocellulose from 20-microns thick brain sections, followed by immunodetection and quantitative radioautography in three reference brain structures (locus ceruleus, substantia nigra, and ventral tegmental area). Results obtained by this methodology were similar to those obtained after extraction and Western blotting of the TH protein in control and reserpine-treated animals. Moreover, this methodology allows the combination of high sensitivity and high anatomical resolution in the study of the distribution of pharmacological effects. The locus ceruleus exhibited a significant posteroanterior distribution of TH protein concentration in control and reserpine-treated animals.

Animals↗

PubMed1989

Fentanyl decreases catecholamine metabolism measured by in vivo voltammetry in the rat locus coeruleus.

The objective of this study was to investigate under controlled conditions the effects of fentanyl on the rat locus coeruleus catechol oxidation current. Using differential normal pulse voltammetry combined with electrochemically treated carbon fiber electrodes to measure the catechol oxidation current, catecholamine metabolism can be reliably monitored. Male Sprague-Dawley rats weighing 500-600 g had carbon fiber electrodes implanted into the locus coeruleus under halothane - O2 - air anesthesia with controlled ventilation and muscle relaxation. Experiments consisted of four groups of rats given the following treatments: (A) saline (n = 6); (B) fentanyl, 10 micrograms.kg-1 i.v. (n = 6); (C) naloxone, 800 micrograms.kg-1 i.v. followed 2 min later by fentanyl, 10 micrograms.kg-1 (n = 5); (D) clonidine, 200 micrograms.kg-1 i.p. (n = 6). There was no significant change in the catechol oxidation current following saline. Fentanyl produced a significant (ANOVA, p less than 0.05) decrease in the catechol oxidation current (maximum 32 min postinjection was 75.8 +/- 4.6% of baseline). This decrease was prevented by a prior injection of naloxone. Clonidine produced a significant decrease in catechol oxidation current (maximum 40 min postinjection was 54.1 +/- 7.0% of baseline). Systolic blood pressure was significantly decreased following clonidine and there were no significant changes in arterial blood gases throughout the experiments. The alpha 2-adrenergic agonist clonidine and the opioid fentanyl produced a decrease in locus coeruleus catechol oxidation current measured by in vivo voltammetry, which monitors catecholamine turnover.

Animals↗

PubMed1988

Long-term effects of RU24722 on tyrosine hydroxylase of the rat brain.

The effects of RU24722 (14,15-dihydro-20,21-dinoreburnamine-14-ol) on tyrosine hydroxylase in central catecholaminergic neurons were studied in rats treated with different quantities of the molecule, and a time course was done for the minimal dose that gave the maximal effect. RU24722 induced increases in tyrosine hydroxylase activities and specific protein content in noradrenergic cells of the locus ceruleus and decreased all these parameters in dopaminergic neurons of the substantia nigra and ventral tegmental area. The results pointed out that the specific activity of newly synthesized tyrosine hydroxylase in the loci cerulei was potentially greater but was not expressed "in vivo" except 7 days after injection. The phenotypic specificity and the time course pattern of the action could be considered as a consequence of an induction mechanism. The comparison of long-term change in tyrosine hydroxylase values after piperoxane, RU24722, clonidine, and combined RU24722-clonidine treatment demonstrated that an activation during a few hours did not induce tyrosine hydroxylase in central noradrenergic neurons. Clonidine antagonized the activating effect of RU24722 following its injection but did not affect its long-term induction properties.

Animals↗

PubMed1987

Baroreflex-linked variations of catecholamine metabolism in the caudal ventrolateral medulla: an in vivo electrochemical study.

In vivo electrochemical recordings of the metabolism of catecholamines were obtained in the caudal ventrolateral medulla in anesthetized rats submitted to various experimental changes in systemic arterial pressure. Hypertension induced with phenylephrine and reversal of hypovolemia decreased the catechol metabolic activity. In contrast, controlled or hypovolemic hypotension, induced respectively with sodium nitroprusside or blood withdrawal (30% of blood volume), reversibly elicited the opposite pattern. This was suppressed by deafferentation. The changes in catechol metabolic activity in response to hypovolemia were accompanied by similar trends of variations of plasma vasopressin levels. By contrast with the increased catechol metabolic activity secondary to hypotension induced by either prazosin, sodium nitroprusside or hypovolemia, clonidine elicited a decrease in catechol metabolic activity. These data show a dynamic and specific involvement of the metabolism of catecholamines themselves promoted by changes in systemic arterial pressure. This pattern of functioning of catechol metabolism in the caudal ventrolateral medulla appears to be negatively related to systemic arterial pressure changes, a finding which does not fit with the proposed vasodepressor role of the A1-group.

Animals↗

PubMed1987

Clonidine modulates the ventrolateral medullary catechol metabolic hyperactivity induced by hypotension.

In vivo electrochemistry allowed recording of a catechol oxidation current in the ventrolateral medulla, caudal to the obex, in anesthetized rats whose ventilatory, metabolic and hemodynamic parameters were rigorously controlled. Hemorrhage or controlled hypotension induced an increase in the metabolism of catecholamines in the A1 noradrenergic group, which remained activated after full hemodynamic recovery. Clonidine (200 micrograms.kg-1 i.p.) given 30 min prior to hemorrhage or immediately before controlled hypotension suppressed partially the increased metabolism of catecholamines especially during the recovery period. This suggests that clonidine preserved phasic reactivity upon circulatory disturbances and decreased tonic hyperactivity following circulatory recovery.

Animals↗