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Biomedical subjects

L Lima

Publications and source records attributed to L Lima.

At least 55 records · Page 3Linked to original sources
PubMed1997

[3H]raclopride and [3H]spiroperidol binding to retinal membranes of the teleost Eugerres plumieri: effect of light and dark adaptation.

Monoamine and metabolites were determined in the retina of the teleost Eugerres plumieri after dark and light adaptation. Dopamine, homovanillic acid and 3,4-dihydroxyphenylacetic acid increased after light exposure. The results indicate an increase in the turnover rate of dopamine due to light exposure. Dopamine D2 receptors were studied by determining the binding parameters of [3H]spiroperidol and [3H]raclopride to retinal membranes. The results were best fitted to a two-site model, where the high-affinity site may correspond to D2 receptors and the low-affinity site could be D4 receptors, which have been recently described in the retina, although further research is needed to confirm this suggestion. The number of sites labeled with [3H]spiroperidol was lower than with [3H]raclopride. This may indicate the existence of monomer and dimer conformations of D2-like receptors in the retina, as has been shown in the brain. Light exposure increased the number of sites labeled with both ligands. Since D2 receptors are known to modulate the production of melatonin, the augmentation in the capacity of these receptors could contribute to the reduction of melantonin during light exposure.

Adaptation, Ocular↗
PubMed1997

Differential effect of taurine and serotonin on the outgrowth from explants or isolated cells of the retina.

The sulfur amino acid taurine and the indoleamine serotonin increases and decreases, respectively, the outgrowth from goldfish retinal explants. Taurine seems to be acting, at least partially, through an increase in calcium fluxes, and the serotonin-inhibiting effect appears to be mediated by serotonin1A receptors and cAMP. Isolated cells of postcrush goldfish retina and of retina from 5-day-old rats were cultured in the presence of taurine or serotonin. In the goldfish, the classical morphology of postcrush ganglion cells was observed. An antibody against the glycoprotein Thy-1 labelled three types of cells in the cultures of goldfish retina. The number of cells outgrowing and the length of the main neurite was measured at 5 days in culture in both species. The number of cells presenting neurites was increased in the goldfish retina by the addition of taurine, and decreased by serotonin. However, the length of the neurites was unaffected by the addition of the modulators. In the rat, only a slight decrease in the number of cells outgrowing was observed in the presence of serotonin. The incorporation of [3H]thymidine was not modified after 5 days in culture in the presence of taurine or serotonin, either in the goldfish or in the rat retina. The antibody Thy 1.1 can label retinal cells of the goldfish in vitro, one of them being ganglion cells. The trophic effect exerted by taurine in the postcrush goldfish retina needs the integrity of the tissue favoring the interaction of cells and factors, because outgrowth increases in retinal explants, but not in isolated cells.

Animals↗
PubMed1997

Video-assisted coronary bypass surgery: clinical results.

OBJECTIVE: Clinical experience with a video-assisted coronary artery bypass grafting procedure using the internal mammary artery is reported. The technique consists of a videoscopic harvesting of the left internal mammary artery (LIMA) to revascularise the left anterior descending artery (LAD) through a 4-cm left thoracotomy. METHODS: Between September 1995 and July 1996, we performed this procedure on 30 patients (29 males, 1 female; aged 38-71) with an isolated proximal LAD stenosis (n = 21) or occlusion (n = 9). All patients were symptomatic despite appropriate medication. A history of non-transmural myocardial infarction with myocardial viability was found in nine patients. Fourteen patients had a restenosis after previous percutaneous transluminal coronary angioplasty (PTCA). Mean left ventricular ejection fraction was 0.61 (< 0.3 in two patients). The LAD LIMA anastomosis was performed on the beating heart without cardiopulmonary bypass (CPB) in 26 patients. Femoral-femoral CPB was used in three patients because of unstable angina (n = 1) and intramyocardial LAD (n = 2). Conversion to sternotomy and standard CPB was necessary in one patient for extensive endarterectomy of the LAD. RESULTS: There were no operative complications and no reoperations for haemorrhage. Pulmonary infection was observed in one patient and wound infection in one patient. Patients who underwent the complete procedure on the beating heart without conversion or CPB were ready for discharge on the 5th postoperative day (36 h-13 days). Control coronary angiography was performed in 20 patients. In all cases, the graft was patent. In 17 cases, there was a patent graft with no evidence of anastomotic stenosis. An occlusion of the distal segment of the LAD with a retrograde perfusion of the proximal segment and septal branches by the LIMA was found in one case. This patient was symptom-free and the stress test was negative. An anastomotic stenosis was noted in two patients and was treated by angioplasty (n = 1) or conventional surgery (n = 1). CONCLUSION: In conclusion, the efficiency of this minimally invasive approach should be prospectively compared with similar revascularisation with PTCA or surgical approaches using sternotomy with or without CPB.

Angioplasty, Balloon, Coronary↗
PubMed1996

Synthesis of serotonin from 5-hydroxytryptophan in the post-crush retina: inhibition of in vitro outgrowth by the intraocular administration of the precursor.

Serotonin is present in the retina of many species, in which plays roles as a neurotransmitter, as a modulator of regeneration, and as the precursor of melatonin. The turnover of serotonin in the goldfish retina is modified by the lesion of the optic nerve and, in postcrush goldfish retinal explants, serotonin inhibits the outgrowth. In the present study, the modification of the serotonergic system of the retina induced by the process of regeneration was explored. The addition of the precursor of serotonin, 5-hydroxytryptophan, to retinal explants, increased the levels of serotonin in a concentration-dependent manner. The concentration of serotonin differentially increased in control and postcrush explants cultured in the presence of 5-hydroxytryptophan for various periods of time, indicating a greater accumulation of the indoleamine at early periods of time in the control than in the postcrush tissue culture. This observation, together with the fact that serotonin concentration in postcrush retina cultured in the absence of 5-hydroxytryptophan and exposed to the precursor for 60 min increased less than in the control, indicates a saturation of the serotonergic system produced by the lesion. The addition of imipramine or citalopram, serotonin uptake blockers, did not significantly change the concentration of serotonin in the cultures, thus, the elevation of serotonin accumulation, especially in the post-crush tissue, might not be due to the transport from the medium. The intraocular injection of 5-hydroxytryptophan after the crush of the optic nerve resulted in a decrease in the outgrowth of retinal explants, supporting the in vivo role of serotonin during the regenerating process in situ. The lesion of the optic nerve did not affect the specific cells, since the number of serotonin-immunoreactive neurons in the retina were not modified by the crush. Taken together, retinal serotonin system is regulated after producing a lesion of the optic nerve, a modulation which has been demonstrated in vivo and in vitro. Thus, there is a reciprocal interaction, since serotonin influences outgrowth in the postcrush retina and the serotonergic system is modulated by the crush, indicating a mechanism of feed-back regulation.

5-Hydroxytryptophan↗
PubMed1996

5HT1A receptor agonist differentially increases cyclic AMP concentration in intact and lesioned goldfish retina. In vitro inhibition of outgrowth by forskolin.

5HT1A receptors occur in the retina of various species and the administration of 5HT1A agonists results in the inhibition of outgrowth from postcrush goldfish retinal explants. The levels of cyclic AMP (cAMP) play a role in the modulation of the outgrowth of the nevous system. Moreover, the stimulation of central 5HT1A receptors with the agonist 8-hydroxy-2-(di-n-propylamino)tetralin has been reported to produce an increase or decrease in the activity of adenylate cyclase. In the present investigation we studied the effect of adenylate cyclase stimulation by forskolin, as well as the modulatory effects of 5HT1A receptor agonists and antagonists on the production of cAMP in the goldfish retina, and on the outgrowth of this tissue in vitro. 8-Hydroxy-2-(di-n-propylamino)tetralin produced a significant and dose-dependent increase in cAMP concentration. This effect was not additive to the stimulation produced by forskolin. By contrast, as previously described, the 5HT1A agonist decreased cAMP concentration in the hippocampus of the rat. Both effects were significantly impaired by the 5HT1A antagonist WAY-100,135. A significant effect of the antagonist alone was observed only in the goldfish retina. The increase in cAMP levels was greater in the intact than in the postcrush retina. In addition, forskolin decreased the outgrowth of postcrush retinal explants in a dose-dependent manner, suggesting the importance of critical levels of cAMP in this process. Taken together, 5HT1A receptors seem to be positively coupled to adenylate cyclase in the goldfish retina, where cAMP plays a role as a modulator of outgrowth and regeneration. The inhibitory effect of 5HT1A receptor agonists on retinal outgrowth might be mediated through the production of cAMP. The activation of other subtypes of 5HT receptors positively coupled to adenylate cyclase by the 5HT1A agonist, such as 5HT7, cannot be discarded.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1996

[Video-surgery for pericardial effusion. Technique and results].

Videosurgery is a relatively non-invasive method of draining the pericardium by the creation of a pleuropericardial window. It provides an excellent view of the thoracic cavity and allows selection of pericardial and pleural, pulmonary or mediastinal biopsy sites. The authors report their preliminary results with this technique. Between May 1994 and May 1995, 22 patients with pericardial effusions were operated by videosurgery at the Pitié Hospital. None of the patients had clinical signs of tamponade. The technique consists in introducing, through 2 or 3 thoracic incisions of 15 mm, trocarts allowing passage of an endoscopic camera and different surgical instruments. Access to the thoracic cavity enabled assessment of the pleura, evacuation of pleural effusions (n = 8) and biopsy of pleural nodules (n = 2). One pulmonary biopsy was performed. Opening the pericardium enabled evacuation of pericardial effusions averaging 622 ml. Pericardial biopsies showed appearances suggesting tuberculosis (n = 2), lupic vasculitis (n = 1) and post-radiation pericarditis (n = 1). In other cases, a histologic diagnosis of non-specific pericarditis was made. A biopsy of a pleural nodule showed undifferentiated carcinoma in one case. A pulmonary biopsy revealed the presence of relatively undifferentiated carcinoma. There were no complications related to the technique. There was one recurrence of pericardial effusion at one month in a patient with carcinoma of the lung who had previously had subxiphoid drainage. There were no cases of secondary pericardial constriction. Therefore, videosurgery is a relatively non-invasive and effective technique of pericardial drainage and biopsy. When there is no emergency, it is probably the method of choice in the treatment and diagnosis of pericardial effusions.

Adult↗
PubMed1995

Chronic alcoholization alters the expression of 5-HT1A and 5-HT1B receptor subtypes in rat brain.

The expression of central 5-HT1A and 5-HT1B receptors was studied in several brain areas of rats subjected to a 2-week period of chronic alcoholization, followed by 18 h withdrawal. Quantitative autoradiography indicated that the ethanol treatment provoked an increase (approximately +30%) in the labeling by [3H]8-hydroxy-2-(di-n-propylamino)tetralin ([3H]8-OH-DPAT) and [3H]N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl) cyclohexane carboxamide ([3H]WAY-100635) of 5-HT1A autoreceptors in the dorsal raphe nucleus, accompanied by a concomitant decrease in the labeling of postsynaptic 5-HT1A receptors in the hippocampus (approximately -20%), anterior (approximately -30%) and posterior (approximately -32%) cortices. These changes were associated with a tendency toward an increase and decrease in 5-HT1A mRNA levels in the anterior raphe area and hippocampus, respectively, suggesting that the changes observed are due to modifications in 5-HT1A receptor protein synthesis. The autoradiographic labeling of 5-HT1B receptors by serotonin-O-carboxymethylglycyl[125I]iodotyrosinamide ([125I]GTI) was found to increase (+55%) in the globus pallidus of alcoholized rats. Interestingly, a significant increase (+57%) in 5-HT1B receptor mRNA levels was observed in the striatum, which contains cell bodies of neurons projecting into the globus pallidus. These data suggest that altered sensitivity of chronically alcoholized rats to 5-HT1A and 5-HT1B receptor ligands may result from alcohol-induced changes in the transcription of the genes encoding these receptors.

Animals↗
PubMed1995

The selective 5-HT1A antagonist radioligand [3H]WAY 100635 labels both G-protein-coupled and free 5-HT1A receptors in rat brain membranes.

The tritiated derivative of the novel silent 5-HT1A receptor antagonist WAY 100635 [N-(2-(4-(2-methoxyphenyl)-1-piperazinyl)ethyl)-N-(2-pyridinyl) cyclohexane carboxamide] was tested as a potential radioligand of 5-HT1A receptors in the rat brain. Binding assays with membranes from various brain regions showed that [3H]WAY 100635 specifically bound to a homogeneous population of sites, with a Kd of 0.10 nM. The regional distribution of [3H]WAY 100635 specific binding sites, as assessed in membrane binding assays and by autoradiography of labelled brain sections, superimposed exactly over that of 5-HT1A receptors specifically labelled by [3H]8-hydroxy-2-(di-n-propylamino) tetralin ([3H]8-OH-DPAT). Furthermore, the positive correlation (r = 0.96) between the respective pKi values of a large series of ligands as inhibitors of the specific binding of [3H]WAY 100635 and [3H]8-OH-DPAT in hippocampal membranes indicated that their pharmacological properties were similar. Nevertheless, marked differences also existed between [3H]8-OH-DPAT and [3H]WAY 100635 specific binding, as the former was inhibited by 1-100 microM GTP and GppNHp, whereas the latter was enhanced by these guanine nucleotides. In contrast, Mn2+ (1-10 mM) increased the specific binding of [3H]8-OH-DPAT, but inhibited that of [3H]WAY 100635. Treatment of membranes with N-ethylmaleimide (1-5 mM) markedly reduced their capacity to specifically bind [3H]8-OH-DPAT, but slightly increased (at 1 mM) or did not affect (at 5 mM) their [3H]WAY 100635 specific binding capacity. Finally, the Bmax of [3H]WAY 100635 specific binding sites was regularly 50-60% higher than that of [3H]8-OH-DPAT in the same membrane preparations from various brain regions (hippocampus, septum, cerebral cortex). These data are compatible with the idea that whereas [3H]8-OH-DPAT only binds to G-protein-coupled 5-HT1A receptors, [3H]WAY 100635 is a high affinity ligand of both G-protein-coupled and free 5-HT1A receptor binding subunits in brain membranes.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1995

Serotonin turnover rate, [3H]paroxetine binding sites, and 5-HT1A receptors in the hippocampus of rats subchronically treated with clonazepam.

Selective central benzodiazepine agonists, such as clonazepam, are known to modify serotonin and 5-hydroxyindoleacetic content in the brain. In order to further study the effect of this benzodiazepine on serotonin turnover rate, rats received clonazepam, 10 mg/kg for 10 days, and the concentrations of serotonin and 5-hydroxyindoleacetic acid were determined in the hippocampus after inhibition of monoamineoxidase with pargyline. The results indicate a reduction in the turnover rate of the monoamine. In addition, the systemic administration of clonazepam produced a decrease in the Bmax of [3H]DPAT binding to 5-HT1A sites in the hippocampus. By contrast, this effect was not observed if clonazepam was delivered into the dorsal raphe nucleus by osmotic minipumps. The binding of [3H]paroxetine to 5-HT reuptake sites was increased by the treatment with clonazepam. The present observations indicate that clonazepam produces a reduction of serotonin turnover rate in the hippocampus of the rat concomitant with a down-regulation of 5-HT1A binding sites, probably by an effect at the forebrain projections. There is also an up-regulation of the serotonin transporter, which might contribute to a reduction in the synaptic availability of serotonin during clonazepam treatment.

Animals↗
PubMed1995

Clonidine potentiates the growth hormone response to a growth hormone releasing hormone challenge in hypothalamic growth hormone releasing hormone deficient rats.

This study was designed to further investigate our postulate regarding the inhibitory role played by central alpha 2-adrenergic pathways on hypothalamic somatostatin (SS) release in rats. The growth hormone (GH) responses to exogenous GH-releasing factor (GRF; 3 micrograms/kg i.v.) or clonidine (CLO; 100 micrograms/kg i.v.), either given alone or in combination, were tested in 3-month-old male rats made GH-releasing hormone (GH-RH) deficient neonatally by administration of monosodium glutamate (MSG; 4 mg/g body weight s.c.). To prevent the presumable decrease in the pituitary GH content in these animals from leading to an erroneous interpretation of the results obtained, half of these rats were given GRF (MSG-GRF rats; 30 micrograms/kg s.c.) for 3 days immediately prior to GH testing. The other half of MSG-treated and non MSG-treated rats received saline during these days (MSG-S and controls, respectively). To establish the efficiency of GRF priming, the pituitary GH content was measured in other MSG-GRF, MSG-S, and control animals. The mean (+/- SEM) GH peaks in response to GRF challenge were significantly higher in controls than in MSG-GRF rats (125.2 +/- 28.5 vs. 67.5 +/- 19.4 micrograms/l; p < 0.05), while no significant GRF-induced GH release was observed in the MSG-S group. Most likely these results are related to the different pituitary GH content, significantly (p < 0.01) higher in controls than in MSG-GRF rats, and in the latter higher than in MSG-S animals (p < 0.05). CLO administration did not evoke a significant GH release in MSG rats, whether primed with GRF or not.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Increase of the serotonin metabolite, 5-hydroxyindoleacetic acid, in cerebro-spinal fluid and spinal cord of bovines affected with the paraplegic syndrome.

The paraplegic syndrome of bovines is a condition characterized by impairment of locomotion, hypoalgesia and finally death within 72 h. The pathogenesis of the syndrome has not been established. In the present work we determined the levels of monoamines and their metabolites in cerebro-spinal fluid and spinal cord of affected animals in order to investigate the functional state of these neurotransmitters. The content of the main metabolite of serotonin, 5-hydroxyindoleacetic acid, was elevated in the cerebro-spinal fluid and in the gray matter of the spinal cord of paraplegic bovines. Serotonin content in the spinal cord did not differ with respect to control animals, but was decreased in the cerebro-spinal fluid of affected animals. Modifications in the noradrenergic system were also observed, but were less consistent, for which reason further studies are needed. These observations indicate an increase in the turnover rate of serotonin in the paraplegic syndrome. The meaning of the described alterations is unknown at the moment.

Animals↗
PubMed1994

Selective in vivo labelling of brain 5-HT1A receptors by [3H]WAY 100635 in the mouse.

The novel selective 5-HT1A receptor antagonist radioligand [3H]WAY 100635 ([O-methyl-3H]N-(2-(4-(2-methoxyphenyl)-1-piperazinyl)ethyl)-N-(2- pyridyl)cyclohexane-carboxamide) was injected i.v. to mice in an attempt to label in vivo central 5-HT1A receptors. Although 5 min after the i.v. injection of [3H]WAY 100635 (4-7.6 muCi per mouse) the amount of tritium found in the whole brain only accounted for 1.5-1.8% of the injected radioactivity, regional differences in 3H accumulation already corresponded to those of 5-HT1A receptor density. Optimal data were obtained 1 h after [3H]WAY 100635 injection as the distribution of 3H in brain was exactly that of 5-HT1A receptor binding sites in mouse brain sections labelled in vitro with [3H]WAY 100635. In particular, high level of labelling was found in the lateral septum, gyrus dentatus and CA1 area of Ammon's horn in the hippocampus, dorsal raphe nucleus and entorhinal cortex. No labelling was found in he substantia nigra, and 3H accumulated in the cerebellum represented only 12-14% of that found in the hippocampus. Pretreatment with various drugs indicated that only 5-HT1A receptor ligands were able to decrease the accumulation of 3H in all the brain areas examined except in the cerebellum. Assuming that only non-specific binding took place in the latter structure, it was possible to calculate the ID50 values of 5-HT1A receptor agonists (8-OH-DPAT (8-hydroxy-2-(di-n-propylamino)tetralin), S 14506 (1-[2-(4-fluorobenzoylamino)ethyl]-4-(7-methoxynaphthyl+ ++)piperazine) and S 20499 ((+)-4-[N-(5-methoxy-chroman-3-yl)-N-propylamino]butyl-8- azaspiro-(4,5)-decane-7,9-dione)) and antagonists (spiperone, (-)-tertatolol, (+)-WAY 100135 (N-tert-butyl-3,4-(2-methoxyphenyl)piperazin-1-yl-2-phenyl- propanamide)) as inhibitors of 3H accumulation in the hippocampus of [3H]WAY 100635-injected mice. Comparison of these values with the in vitro affinity of the same ligands for hippocampal 5-HT1A receptors revealed marked variations in the capacity of 5-HT1A receptor agonists and antagonists to reach the brain when injected via the subcutaneous route in mice.

Animals↗
PubMed1994

Dopamine and serotonin turnover rate in the retina of rabbit, rat, goldfish, and Eugerres plumieri: light effects in goldfish and rat.

The concentration of dopamine, and its metabolites 3,4-dihydroxyphenylacetic and homovanillic acids, as well as serotonin and its metabolite 5-hydroxyindoleacetic acid, were determined in the retina of two teleosts, C. auratus (goldfish) and E. plumieri (mojarra), and two mammals, R. norvegicus (rat) and O. cuniculus (rabbit). The turnover rate of these monoamines were investigated in the four species by the calculation of the ratio monoamine/metabolite as an indirect index, and in goldfish and rat by the inhibition of the synthesis with alpha-methyl-p-tyrosine or p-chlorophenylalanine, by the increase in dopamine or serotonin by the corresponding precursors, 3,4-dihydroxyphenylalanine or 5-hydroxytryptophan, and by inhibition of monoaminooxidase with pargyline. The modulation by light and dark stimulation was studied in the goldfish and the rat. Differences in the concentration and turnover rate were observed among the species. Serotonin concentration was higher in the teleosts. The administration of inhibitors of dopamine and serotonin synthesis differentially decreased the levels of the monoamines in the retina of goldfish and rat. The rate of formation of dopamine and serotonin by the corresponding precursors was much higher in the goldfish than in the rat. Pargyline administration decreased 3,4-dihydroxyphenylacetic and 5-hydroxyindoleacetic acids at different rates and time dependency in the retina of goldfish and rat. Dopamine and serotonin concentration did not exhibit high modifications by the inhibitor, suggesting the function of regulatory mechanisms or additional effect of pargyline at other sites different from monoaminooxidase.(ABSTRACT TRUNCATED AT 250 WORDS)

3,4-Dihydroxyphenylacetic Acid↗
PubMed1994

Serotonin inhibits outgrowth of goldfish retina and impairs the trophic effect of taurine.

The regeneration of explants prepared from goldfish retinas with a prior crush of the optic nerve is stimulated by the sulphur amino acid, taurine. Serotonin has been reported to modify survival, proliferation, and outgrowth of nervous tissue. In the present work we evaluated the effect of serotonin and some serotonergic agonists on the neuritic outgrowth from goldfish retinal explants. Serotonin, its precursor, 5-hydroxytryptophan, and the 5HT1A receptor agonists, 8-hydroxy-2-(di-n-propylamino)tetralin and buspirone, inhibited the outgrowth. The blockers of serotonin uptake, imipramine and citalopram, were also inhibitors of neurite sprouting. Imipramine favoured the inhibitory effect of serotonin at 10 days in culture. The concentration of serotonin and its metabolite, 5-hydroxyindoleacetic acid, decreased in the retina at 3 and 5 days after the crush of the optic nerve. Serotonin levels started to recover after 5 days post-lesion, and the metabolite also increased. This indicates that the lesion increases the turnover rate of serotonin and this may be related to its role in regeneration. Serotonin concentration was elevated by the intraocular administration of its precursor, 5-hydroxytryptophan, indicating that the capacity for synthesis was preserved after the crush, but that it was smaller in the post-lesioned retinas. The trophic effect of taurine was impaired by a low concentration of serotonin, probably by opposing the final effect on growth via different targets. These results support a role of serotonin in the regeneration of goldfish retina probably through 5HT1A receptors.

5-Hydroxytryptophan↗