Biomedical subjects

A Machado

Publications and source records attributed to A Machado.

At least 109 records · Page 6Linked to original sources

PubMed1994

Molecular characterization of type I GABAA receptor complex from rat cerebral cortex and hippocampus.

The molecular composition of the native gamma-aminobutyric acidA (GABAA) receptor complex is actually unknown. In the present communication we report a novel approach to characterize the minimal molecular conformation of the native GABAA receptor complex. This novel approach is based on the combination of subunit specific antibodies and specific 3H-labeled ligands in immunoprecipitation experiments. We have determined the presence of beta 2/3 and gamma 2 subunits in the Type I GABAA receptor complex, from rat cerebral cortex and hippocampus, by using two antibodies, the monoclonal 62-3G1 (specific for beta 2/3) and the polyclonal anti-gamma 2 (to the large intracellular loop of the gamma 2 short form) together with the Type I-specific ligand [3H]zolpidem. The association of gamma 2 and beta 2/3 subunits with the GABAA receptor complex was also tested using [3H]flumazenil. The results indicated that both gamma 2 and beta 2/3 were the most abundant subunits associated to either Type I or total benzodiazepine receptors from both cortex and hippocampus. Between 70-80% of Type I or total benzodiazepine binding activity was immunoprecipitated by either antibody. In addition, we have also investigated the coexistence of both subunits as part of the same population of Type I GABAA receptor complex by cross-immunoprecipitation experiments with 62-3G1 and anti-gamma 2. The results indicated that, in cerebral cortex, both gamma 2 and beta 2/3 subunits were part of the same population of Type I receptors. In hippocampus, an additional 20% of Type I receptors displayed either gamma 2 or beta 2/3 but not both subunits.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Cumulative effects model: a response to Williams (1994)

The cumulative effects (CE) model explains free-operant choice by the ratio of total numbers of responses and reinforcements, a probability-like variable. Williams (1994) argues that the model is vulnerable to experiments that disprove melioration, a local probability model. The authors note critical differences between the nonlocal CE model and local probability models that allow the CE model to handle some data with which they are incompatible. All models are simplifications of reality; hence, a model's failures are as revealing as its successes. Williams suggests that simple models may need to be abandoned in favor of a "representational" account. The authors point out that representations must be both acquired and acted on. Acquisition requires processing of responses and reinforcers; action requires decision rules. Models are simply testable suggestions for what these rules and processes might be.

Behavior Therapy↗

PubMed1994

Effect of L-arginine/nitric oxide pathway on MPP(+)-induced cell injury in the striatum of rats.

1. Protection against 1-methyl-4-phenylpyridinium ion (MPP+) neurotoxicity by two nitric oxide-related compounds, N omega-nitro-L-arginine (L-NOARG) and L-arginine, was studied in the corpus striatum by means of two MPP+ perfusions separated by 24 h. Dopamine extracellular output after the second MPP+ (1, 5 and 10 mM) perfusion was considered as an index of the dopaminergic neurone damage produced by the first MPP+ (1, 5 and 10 mM) perfusion. 2. L-NOARG, systemically administered (10 mg kg-1, i.p., every 12 h for 4 days), failed to prevent the neurotoxic action of MPP+ (1 and 10 mM). On the contrary, the neurotoxic effect of MPP+ was increased by L-NOARG administration. 3. L-Arginine (10 mM) perfused 2 h before MPP+ perfusion did not protect against the neurotoxic action of high MPP+ concentrations (5 and 10 mM). At the highest MPP+ concentration used (10 mM), the increase in the extracellular output of dopamine after the second MPP+ perfusion was slower in L-arginine-treated rats than in control and L-NOARG-treated rats. 4. When MPP+ (1 mM) was perfused 2 h after L-arginine (10 mM) perfusion, there was a clear protection against MPP+ neurotoxicity. In the second MPP+ (1 mM) perfusion, the increase in the extracellular output of dopamine in L-arginine-treated rats was twice as high as for the control rats. 5. The results indicate that NO may exert a protective mechanism in the presence of a low ambient redox.

1-Methyl-4-phenylpyridinium↗

PubMed1994

Bone marrow transplantation with major ABO incompatibility. Experience of the Bone Marrow Transplantation Unit--Francisco Gentil Portuguese Institute of Oncology, Lisbon Centre.

Thirteen patients submitted to bone marrow transplantation (BMT), HLA A and B identical, with mixed negative lymphocyte culture and major ABO incompatibility were retrospectively evaluated. Gravity sedimentation by hydroxyethyl starch was used in almost all cases to deplete erythrocytes from bone marrow (12/13): a removal rate of 90%--corresponding to an erythrocyte residual volume of 27,4 rate ml--and a nucleated cell recovery of 76% (mean values) were obtained. All patients underwent a hyperhydration regimen and received corticosteroid prophylaxis before bone marrow infusion. Considering the most important immunohematological problems associated to this type of transplant, we verified that seven patients developed minor complications and among them only one had long term consequences. In comparison with the control group, ABO identical and with minor incompatibility, the study group had delayed onset of erythropoiesis and needed greater erythrocyte transfusion support. We concluded that major ABO incompatibility does not constitute a drawback to BMT success in most patients.

ABO Blood-Group System↗

PubMed1994

[Macrocheilitis and Melkersson-Rosenthal syndrome. Review of 19 cases].

Melkersson-Rosenthal syndrome is an uncommon condition of unknown cause. The classical triad includes recurrent orofacial oedema involving predominantly the lips (macrocheilitis), intermittent peripheral facial palsy and scrotal tongue. Some authors consider Miescher's cheilitis as a monosymptomatic form of the syndrome. Nineteen cases (11 females and 8 males) of macrocheilitis seen at the Dermatologic Clinic, University of Coimbra, between 1966 and 1992, are reviewed. The complete triad of signs was present only in 4 patients (21%) and two features of the classic triad in 3 (16%) (macrocheilitis and lingua plicata in two; macrocheilitis and facial palsy in one). Twelve patients had only recorrent or persistent orofacial swelling. All 19 patients had macrocheilitis. Less commonly, the check, nose, forehead, eyelid, chin and buccal mucosa were also involved. Peripheral facial paralysis was present in 5 cases (26%), and scrotal tongue occurred in 6 (32%). Lip biopsies, performed in 17 patients, revealed the typical pathologic picture of granulomatous cheilitis only in 8 cases. Systemic corticosteroids and clofazimine were the most efficacious treatment.

Adolescent↗

PubMed1993

Age-related changes on monoamine turnover in hippocampus of rats.

After pargyline treatment the turnover rates of dopamine (DA), noradrenaline (NA), 3,4-dihydroxyphenylacetic acid (DOPAC), serotonin (5-hydroxytryptamine (5-HT) and 5-hydroxy-3-indolacetic acid (5-HIAA) has been measured in control and aged hippocampus of the rats. In addition, the tyrosine hydroxylase (TH) activity and monoamine oxidase-A and monoamine oxidase-B activities have also been studied. The TH activity did not change in aged hippocampus as compared to controls. The monoamine oxidase-B: monoamine oxidase-A ratio increased in 26-month-old rats compared with controls. The turnover of DA, DOPAC and NA did not show significant changes while 5-HT synthesis, 5-HT accumulation rate and 5-HIAA turnover increased in aged rats. Serotonin fibers showed morphological dissimilarities between the hippocampus of young and aged rats using immunocytochemistry techniques. In aged rats aberrant serotoninergic fibers mainly appear in the molecular layer of the dentate gyrus and molecular of the hippocampal CA1. It is suggested that the aberrant morphology of 5-HT fibers may reflect the local degeneration of serotoninergic hippocampal afferents during aging. Increase of 5-HT turnover in aged might be a signal of degeneration.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1993

Effect of ageing on monoamine turnover in the prefrontal cortex of rats.

Turnover of dopamine (DA), serotonin (5-hydroxytryptamine) (5-HT), noradrenaline (NA) and their metabolites has been measured in control and aged rats. In addition, tyrosine hydroxylase (TH) activity has been studied. After pargyline treatment, the turnover rates of DA, NA, 3,4-dihydroxyphenylacetic acid (DOPAC), 3-methoxytyramine (3-MT), 5-HT and 5-hydroxy-3-indolacetic acid (5-HIAA) and TH activity increased in aged rats with respect to controls. At the same time the DA and 3-MT turnover increase are consistent with the hypothesis that enhanced release of DA may participate in some degenerative processes in ageing. After probenecid treatment, the turnover of homovanillic acid (HVA) was lower in aged rats than in controls. However, DOPAC turnover was higher in the aged rats. The DOPAC increase seems to indicate a reinforcement of this pathway in aged rats.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1993

Regulation of the prefrontal cortical dopamine release by GABAA and GABAB receptor agonists and antagonists.

The gamma-aminobutyric acid-dopamine (GABA-DA) relationship was studied by intracerebral microdialysis in the prefrontal cortex. Nomifensine (5 microM) was included in the Ringer solution during all the dialysis experiments. Muscimol, a GABAA receptor agonist (50 and 500 microM) did not affect the extracellular output of DA and 3,4-dihydroxyphenylacetic acid (DOPAC). Baclofen, a GABAB receptor agonist (50 microM) significantly decreased the extracellular output of DA and DOPAC. On the other hand, picrotoxin and phaclofen, GABAA and GABAB receptor antagonists respectively, at a concentration of 50 microM, both significantly increased the release of DA. While the DOPAC level was affected only by picrotoxin perfusion. The present study indicates that GABA could control the release of DA in the prefrontal cortex.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1993

Respiratory burst reaction changes with age in rat peritoneal macrophages.

The respiratory burst reaction, estimated as O2.- production, has been studied in rat peritoneal macrophages of different age (3, 12 and 24 months). To stimulate NADPH oxidase, the enzyme responsible for the respiratory burst, various stimuli that act in different ways have been used: PMA (phorbol myristate acetate), Con-A (concanavalin A) and N-FMLP (N-formyl-methionyl-leucyl-phenylalanine). All produced a decrease in response with age, with that from PMA being the greatest. The PMA-induced decrease in the O2.- production may be related to the inactivation of NADPH-producing enzymes such as glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase that we have found with age. Glutathione reductase, an enzyme that participates in the maintenance of the redox status in the cell, also showed an age-related decrease. Enzymes that participate in oxygen species scavenging, such as glutathione peroxidase and Cu/Zn superoxide dismutase, did not change with age, although an age-related decrease in catalase activity was found.

Aging↗

PubMed1993

Age-dependent modification of lipid composition and lipid structural order parameter of rat peritoneal macrophage membranes.

The effect of aging on the lipid composition and fluidity of rat peritoneal macrophage membranes has been determined using young (3 months), mature (12 months) and aged (24 months) Wistar rats. In the aged animals, total phospholipid decreased significantly (P < 0.05), whereas cholesterol increased (P < 0.01), with an age-dependent increase in the molar ratio of cholesterol/phospholipid. The most marked change in phospholipid content was the significant (P < 0.001) age-dependent increase of phosphatidylserine and cardiolipin and the significant decrease of phosphatidylcholine and phosphatidylinositol. During aging there was a considerable decrease in arachidonic acid and docosapentanoic acid (about 50% in both cases). In contrast, an increase in the levels of oleic, linoleic and docosahexanoic acid was observed. Steady-state fluorescence polarization using 1,6-diphenyl-1,3,5-hexatriene as the probe was used to estimate the lipid structural order parameter of macrophage membranes. There was a highly significant (P < 0.001) age-dependent increase in the lipid structural order parameter, which correlated well with the increased molar ratio of cholesterol/phospholipid in the membranes isolated from aged animals. The data suggests alteration in membrane lipid-protein interactions in aging, and are consistent with the hypothesis of the aging process.

Aging↗

PubMed1993

Regulation of prefrontal cortical dopamine release by dopamine receptor agonists and antagonists.

The effect of dopamine D1 and D2 receptors agonists and antagonists on extracellular dopamine release was evaluated by microdialysis in the prefrontal cortex. Nomifensine (5 microM) was included in the Ringer solution during the experiments. Cortical dopamine release was tetrodotoxin- and calcium-dependent and was stimulated by high potassium (60 mM) Ringer solution. 1-Methyl-4-phenylpyridinium ion (MPP+) (10 mM) increased the extracellular output of dopamine. SKF-38393 decreased the release of dopamine in a dose-related manner to about 80, 40 and 0% of the control values at 0.1, 1 and 10 microM, respectively. The decrease produced by SKF-38393 (10 microM) was partially antagonized by SCH-23390 at a concentration of 1 microM. Perfusion of CY-208243 (10 microM) produced a decrease in the release of dopamine to about 70% of controls. Quinpirole, at a concentration of 10 microM, produced a decrease in the release of dopamine to about 65% of controls. SCH-23390 and sulpiride, at 10 microM, increased the extracellular output of dopamine to about 150% of controls. These results indicate that dopamine D1 and D2 receptors are implicated in the autoregulation of dopamine release in the prefrontal cortex.

1-Methyl-4-phenylpyridinium↗

PubMed1993

Absence of modifications of the pharmacological properties of the GABAA receptor complex during aging, as assessed in 3- and 24-month-old rat cerebral cortex.

We have investigated the possible modifications of the pharmacological properties of Type I and Type II benzodiazepine binding sites of the gamma-aminobutyric acidA (GABAA) receptor complex in cortical membranes from 3- and 24-month-old Wistar or Fischer rats. No major changes were found in the binding parameters of [3H]zolpidem (a Type I-specific ligand) or [3H]flunitrazepam (a non-selective benzodiazepine). Neither the Kd values nor the Bmax for either ligand were modified during aging in cortical membranes from Wistar or Fischer rats. Consequently, the proportion of Type I binding sites was also unmodified in aged cortical membranes. The absence of modifications of Type I and Type II binding sites was also confirmed by Cl 218,872 displacement of [3H]flunitrazepam binding in aged cortical membranes from Wistar rats. Furthermore, the [3H]muscimol binding and the allosteric interactions between Type I or total benzodiazepine binding sites and GABA binding sites also remained unaltered with aging in cortical membranes from Wistar rats. Moreover, the pattern and proportion of the [3H]flunitrazepam photoaffinity labeled peptides were also unmodified by aging. These results demonstrate the absence of modifications in Type I or total benzodiazepine binding sites of the GABAA receptor complex from adult and aged cortical membranes in Fischer or Wistar rats.

Affinity Labels↗

PubMed1993

Protective effect of deprenyl against 1-methyl-4-phenylpyridinium neurotoxicity in rat striatum.

Rats were treated with deprenyl for 3 weeks. Afterwards, slices of the corpus striatum were incubated with 1-methyl-4-phenylpyridinium ion (MPP+). Concentrations of dopamine and its metabolite concentrations were assayed. The effect of MPP+ in animals treated with deprenyl was smaller than in controls, indicating that deprenyl protects against MPP+. We also measured superoxide dismutase (SOD) and catalase activities and carbonyl group content of the proteins. Both activities increased in deprenyl-treated rats, and the amount of carbonyl groups was unchanged. These results suggest that the protective effect of deprenyl is independent of the monoamine oxidase-B inhibitor and of the induction of SOD and catalase activities.

1-Methyl-4-phenylpyridinium↗

PubMed1993

Turnover of monoamines in hippocampus of rats fed on vitamin E-deficient diet.

Turnover of noradrenaline (NA), dopamine (DA), serotonin (5-hydroxytryptamine; 5-HT) and their metabolites has been measured after a 15-day vitamin E-deficient diet in adult hippocampus. Moreover, we have measured in vitro receptor binding of [3H]5-HT in hippocampal membranes from control and vitamin E-deficient rats. Turnover rates of 3,4-dihydroxyphenylacetic acid (DOPAC) and 5-hydroxy-3-indolacetic acid (5-HIAA) have been assayed from the disappearance rates after blocking by pargyline inhibition of monoamine oxidase (MAO). DA, NA, 5-HT, normetanephrine (NMN) and 3-methoxytyramine (3-MT) turnover rates have been measured as accumulation rates of DA, NA, 5-HT, NMN and 3-MT after pargyline inhibition of MAO. An increase was found in the turnover rate of DA between control and experimental animals. In contrast, no changes were found in the turnover rate of 3-MT and DOPAC. No change was found in the turnover rate of NA although there was an increase of the turnover rate of NMN in vitamin E-deficient diets. No changes was found in the turnover rate of 5-HT although there was a decrease of 5-HIAA turnover rate in the animals fed on a low vitamin-E diet. With respect to the 5-HT1 receptors, no changes were found in the affinity (kd) but the receptor number (Bmax) was increased in vitamin E-deficient rats.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1993

Regional differences in the enhancement by GABA of [3H]zolpidem binding to omega 1 sites in rat brain membranes and sections.

The potential heterogeneity in the allosteric coupling between GABA and omega 1 binding sites within the native GABAA receptor complex has been evaluated in the rat by measuring the enhancement by GABA of [3H]zolpidem binding to omega 1 site in membranes from three rat brain structures (neocortex, cerebellum and hippocampus) and brain sections. The maximal stimulatory effect of GABA was significantly higher (265 +/- 47%) in cortical membranes than in cerebellar (165 +/- 48%) or in hippocampal (118 +/- 17%) membranes. These differences are not due either to the presence of different amounts of residual GABA in the membrane preparations or to the labeling, in presence of GABA, of binding sites other than omega 1 since: (1) the pharmacological properties of the [3H]zolpidem binding sites were similar in the three regions; (2) the degree of allosteric enhancement was unrelated to the relative proportion of omega 1 sites in each structure; and (3) GABA did not increase the Bmax for [3H]zolpidem. Regional differences in the effect of 100 microM GABA on [3H]zolpidem binding were also observed by quantitative autoradiography. Regions where the strongest (3-4-fold) effects of GABA in [3H]zolpidem binding were observed included the substantia nigra, lateral geniculate body, olfactory tubercule and red nucleus. A large increase in [3H]zolpidem binding was also demonstrated in the cingulate and frontoparietal cortices with higher effects in deep (4.2-fold) rather than in superficial layers (3.3-fold). Heterogeneous subregional increases in [3H]zolpidem binding in the presence of GABA were quantified within the cerebellum, hippocampus and superior colliculus.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗

PubMed1993

Effects of age and dopamine agonists and antagonists on striatal dopamine release in the rat: an in vivo microdialysis study.

The in vivo microdialysis technique was used to measure the extracellular output of dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) in adult and aged rats; as well as in response to the perfusion of dopamine agonists and antagonists, high-potassium Ringer solution and 1-methyl-4-phenyl-pyridinium ion (MPP+). The DA basal release before the drug treatment was higher in adult rats compared with the aged animals. The perfusion of dopaminergic drugs (nomifensine, sulpiride and quinpirole) through the probe at 1 microM concentration produced the same effect on DA, DOPAC and HVA outflow in adult and aged rats. 5-HIAA levels were not affected. The application of a high-potassium (60 mM) Ringer solution did not produce any significant difference on DA, DOPAC, HVA and 5-HIAA extracellular content when adult and aged rats were compared. The perfusion of MPP+ (1 mM) for 15 min produced a greater increase in DA release in aged than in adult rats. Greater susceptibility in the adult rats could explain these results.

1-Methyl-4-phenylpyridinium↗

PubMed1993

Ageing and monoamine turnover in the lateral geniculate nucleus and visual cortex of the rat.

The effects of ageing on the turnover of dopamine, noradrenaline and serotonin in the lateral geniculate nucleus and the visual cortex were evaluated, using high performance liquid chromatography (HPLC) with electrochemical detection. Compared to adult animals, aged rats showed more changes in the visual cortex than in the lateral geniculate nucleus, with dopamine turnover decreased in both structures and noradrenaline turnover unaltered. Changes in serotonin turnover were witnessed only in the visual cortex. A decrease in the monoamine oxidase-A to -B ratio was also observed with increased age for both the lateral geniculate nucleus and visual cortex.

Aging↗

PubMed1993

Effects of a short period of vitamin E-deficient diet in the turnover of different neurotransmitters in substantia nigra and striatum of the rat.

Measurement of turnover of dopamine, noradrenaline and serotonin and their metabolites was assessed in striatum and substantia nigra of adult female rats that were fed control or vitamin E-deficient diets over 15 days. The levels and turnover of dopamine increased and the levels of serotonin decreased in both structures whereas serotonin turnover decreased only in striatum. No change was found in the turnover rate of noradrenaline between control and experimental animals. However, the most striking result was the increase of dopamine turnover found in substantia nigra. This dopamine increase was accompanied by an increase in 3-methoxytyramine turnover which seems to indicate an increase in dopamine release after vitamin E deficiency. The present study indicates that the nigrostriatal dopamine neurons are susceptible to the deficiency of vitamin E. Moreover, these data suggest that substantia nigra may be more susceptible to damage from vitamin E deficiency than striatum.

3,4-Dihydroxyphenylacetic Acid↗