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Biomedical subjects

A Machado

Publications and source records attributed to A Machado.

At least 91 records · Page 5Linked to original sources
PubMed1996

Protection of the aged substantia nigra of the rat against oxidative damage by (-)-deprenyl.

1. We have studied the effect of (-)-deprenyl on the oxidative damage that the rat substantia nigra suffers during aging. 2. (-)-Deprenyl (2 mg kg-1, three times a week) administered for two months, beginning at 22 months of age, produced a significant increase in tyrosine hydroxylase (TH) activity (2.67 +/- 0.40 and 3.64 +/- 0.38 nmol mg-1 protein h-1 in untreated aged rats and treated aged rats respectively, P < 0.05) and in TH amount (0.072 +/- 0.012 and 0.128 +/- 0.38 absorbance 405 nm in untreated aged and treated aged rats respectively, P < 0.05). 3. The proteins of aged rat substantia nigra showed a significant decrease of carbonyl groups in treated animals compared with saline-injected control rats (136.2 +/- 21.8 and 71.5 +/- 13.2 c.p.m. microgram-1 protein in untreated aged and treated aged rats respectively, P < 0.05). 4. The carbonyl groups measured in TH enzyme showed a statistically significant decrease (42.3%) after (-)-deprenyl treatment (471.4 +/- 73.0 and 271.9 +/- 50.00 c.p.m. in untreated aged and treated aged rats respectively, P < 0.001). 5. All these results suggest that oxidative damage produced during aging is prevented by (-)-deprenyl treatment and could explain the effect of this drug in Parkinson's disease (PD) and other degenerative diseases such as Alzheimer's disease.

Aging↗
PubMed1995

Decrease in free-radical production with age in rat peritoneal macrophages.

The respiratory-burst reaction has been studied in rat peritoneal macrophages of different ages (3, 12 and 24 months) using phorbol 12-myristate 13-acetate (PMA) to stimulate NADPH oxidase. Production of O2-. and H2O2 decreased with age (about 50 and 75% respectively); however, no difference in NADPH oxidase activity was found. NO. production was also reduced with age (40%). Furthermore, a progressive and significant decrease in the pentose phosphate flux was detected as a function of age in control and PMA-stimulated macrophages. The NADPH/NADP+ ratio decreased with age in control and PMA-stimulated macrophages. Glucose uptake was lower in middle-aged (12 months) and old (24 months) animals but no differences were found between these groups.

Aging↗
PubMed1995

Implication of dopamine transporter system on 1-methyl-4-phenylpyridinium and rotenone effect in striatal synaptosomes.

The neurotoxic effect of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) seems to be produced by the inhibition of the respiratory chain by its metabolite 1-methyl-4-phenylpyridinium ion (MPP+). At the same time, its specific selectivity seems to be related especially to the dopamine uptake system. However, it is possible that other specific differences in dopaminergic neurons at the nigrostriatal system, such as constitutive metabolic deficiencies or other differences related to the energy capacity, could determine the greater vulnerability to MPP+. We have addressed this point by studying the effect of MPP+ and different inhibitors of the respiratory chain (rotenone, antimycin A and KCN) on the maximal respiratory rate from both synaptosomes and isolated synaptosomal mitochondria from different brain areas, i.e. cortex, hippocampus and striatum, and in isolated liver mitochondria. The results demonstrate the absence of differences in the effect of the inhibitors in isolated mitochondria. In contrast, a greater inhibition was found in striatal synaptosomes than in cortical or hippocampal synaptosomes when MPP+ and rotenone were used. Moreover, nomifensine or 1-[2-[bis(4-fluorophenyl)methoxy]ethyl]-4-(3-phenylpropyl) piperazine dihydrochloride (GBR-12909), inhibitor of the dopamine uptake system, has a protective effect in both cases. Our study indicates the great importance of the dopamine uptake system in the vulnerability of the dopamine striatum system. Moreover, our results show the low selectivity of this dopamine uptake system that is able to transport actively compounds with different chemical structures such as dopamine, MPP+ and rotenone.

1-Methyl-4-phenylpyridinium↗
PubMed1995

Changes in the histidine residues of Cu/Zn superoxide dismutase during aging.

Cu/Zn-Superoxide dismutase activity (Cu/Zn-SOD) was studied in liver from 3- and 24-month-old rat. A significant decrease of enzyme activity in liver of the aged rat was found. Various amino acid residues and protein carbonyl groups (CO) were measured in purified young and old enzyme. It was found that the 'old' enzyme had one histidine fewer and higher CO content than the 'young' Cu/Zn-SOD. Inactivation 'in vitro' of purified commercial bovine erythrocyte Cu/Zn-SOD led to a decrease in the enzymatic activity, an increase in the CO and one histidine residue modified. A similar behavior between aging and oxidation was suggested.

Aging↗
PubMed1995

Complex I inhibitor effect on the nigral and striatal release of dopamine in the presence and absence of nomifensine.

The effect of inhibitors of complex I respiratory chain--1-methyl-4-phenylpyridinium ion (MPP+, 10 microM) and rotenone (100 microM)--on the release and metabolism of dopamine was studied by in vivo microdialysis in the striatum and substantia nigra. Both compounds produced a marked increase in the release of dopamine in the striatum and substantia nigra, which was diminished when nomifensine (20 microM) was included in the perfusion fluid. The 3,4-dihydroxyphenylacetic acid (DOPAC) extracellular output was decreased under MPP+ (10 microM) perfusion in the striatum and substantia nigra, in the presence and in the absence of nomifensine (20 microM). However, perfusion of rotenone (100 microM) increased or had no effect on DOPAC outflow. Homovanillic acid levels were affected in the same way as DOPAC levels, but the changes were always much less pronounced. These results suggest that the neurotoxic action of MPP+ or rotenone is similar in the striatum and substantia nigra, indicating the importance of the dopamine uptake system in this neurotoxic action of MPP+ or rotenone, also suggesting that the dopamine uptake system could have low selectivity and also transports other substances such as rotenone.

1-Methyl-4-phenylpyridinium↗
PubMed1995

Intrastriatal quinolinic acid injections protect against 6-hydroxydopamine-induced lesions of the dopaminergic nigrostriatal system.

We tested the effect of intrastriatal quinolinic acid (QA) injections 2 weeks before subsequent intrastriatal injections of 6-hydroxydopamine (6-OHDA). Levels of DA and its metabolites were measured 2 days and 21 days after lesioning the dopaminergic nigrostriatal system with 6-OHDA. Intrastriatal 6-OHDA injections in the absence of prior treatment of QA significantly decreased dopamine (DA) and its metabolite levels in striatum but not in substantia nigra at day 2, and in striatum and substantia nigra at day 21, a clear indication of a time-dependent retrograde axonal degeneration of substantia nigra cell bodies. Intrastriatal QA injections 2 weeks before subsequent intrastriatal injection of 6-OHDA partially prevented the 6-OHDA-depleting effect on DA and its metabolite levels in both striatum and substantia nigra 21 days after 6-OHDA injection. However, no statistically significant differences were found between QA + 6-OHDA- and 6-OHDA-treated animals at day 2. Our results suggest that intrastriatal QA injections partially prevent the naturally-occurring retrograde axonal degeneration of substantia nigra cell bodies caused by 6-OHDA, and illustrate a target-derived interaction between dopaminergic nerve endings and cell bodies. We suggest that the protective effect found in the QA-injected animals against the neurotoxic action of 6-OHDA is mediated by neurotrophic agents released by activated astroglia.

Animals↗
PubMed1995

The effect of age on the monoamines of the hypothalamus.

Measurement of dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC) homovanillic acid (HVA), 3-methoxytyramine (3-MT), noradrenaline (NA), 3-methoxy-4-hydroxyphenyl glycol (MHPG) and serotonin (5-HT) and its main metabolite, 5-hydroxyindol-3-acetic acid (5-HIAA) was assessed in hypothalamus and median eminence of aged rats. Age-related changes were not observed in the concentration of NA and its metabolites in median eminence. In contrast, there was a significant NA decrease in aged hypothalamus compared with 12 months (no differences were found compared with 3 months). No significant differences were found in DA concentration and its metabolites in hypothalamus but DA decreased significantly in aged median eminence compared with 12 months. The ratio 5-HIAA/5-HT, indicative of 5-HT turnover, appeared to increase in the hypothalamus and median eminence of the aged rat. Morphological dissimilarities between hypothalamus of young and aged rats were demonstrated using serotonin-immunocytochemistry. A degeneration of the serotoninergic system, denoted by the appearance of enlarged or swollen varicosities, was observed in the hypothalamus of the aged rat. These aberrant serotoninergic fibers may reflect the local degeneration of serotoninergic hypothalamic afferents during ageing. Such differential age-dependent alterations of the serotoninergic system might be responsible for at least some of the functional deficits in aged animals.

Aging↗
PubMed1995

Increase in dopamine turnover and tyrosine hydroxylase enzyme in hippocampus of rats fed on low selenium diet.

We have studied the turnover of dopamine, noradrenaline, and serotonin and their metabolites in hippocampus of adult female rats that were fed control or selenium-deficient diets during 15 days. Under these circumstances, there was an increase of dopamine turnover (4-fold) in rats fed with selenium-deficient diet with respect to controls and also an increase in the tyrosine hydroxylase activity (75.8%), which was the result of the increase of the amount of the enzyme (2-fold), without significant change in the phosphorylation of the tyrosine hydroxylase. In addition the glutathione peroxidase, glutathione reductase, catalase, and superoxide dismutase activities have been studied. After selenium-deficient diet, the enzymatic activities of superoxide dismutase and catalase did not show change with respect to the controls; however glutathione reductase and glutathione peroxidase significantly decreased 15% and 29%, respectively. It is concluded that the increase in dopamine turnover seems to be associated with the induction of tyrosine hydroxylase enzyme. In these conditions the decrease in antioxidant capacity may produce a cascade of events, which accelerates the degenerative process, since the increase in dopamine turnover produces an increase in oxygen radical by monoamine oxidase activity.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1995

Aging-associated changes in the pharmacological properties of the benzodiazepine (omega) receptor isotypes in the rat hippocampus.

The aging-associated changes in hippocampal benzodiazepine (omega) receptor isotypes have been investigated in rats of the Wistar and Fischer 344 strains. Displacement experiments of [3H]flunitrazepam binding by zolpidem demonstrated that in hippocampal membranes from adult (3-month-old) Wistar strain rats, high (type I; omega 1)-, intermediate (type IIM; omega 2)-, and low (type IIL; omega 5)-affinity sites for this imidazopyridine account for 27.1 +/- 7.5, 44.2 +/- 7.5, and 28.8 +/- 5.1%, respectively. In hippocampal membranes from aged (24-month-old) rats of the same strain, the relative abundance of these sites was 42.8 +/- 9.3, 26.3 +/- 4, and 36.0 +/- 5.9%, respectively. In contrast, no significant difference was observed in the whole benzodiazepine (omega) binding site density between adult and aged rats. The increase in type I (omega 1) binding site density in the hippocampus of aged rats was also demonstrated in saturation experiments with [3H]zolpidem. This aging-induced increase in [3H]zolpidem binding was also observed in hippocampal membranes from Fischer 344 rats. Moreover, in both rat strains, GABA induced a greater enhancement of [3H]zolpidem (5 nM) binding to type I (omega 1) sites (GABA shift) in aged than in adult hippocampal membranes. Quantitative autoradiographic analysis of [3H]zolpidem binding to coronal brain sections from adult and aged Fischer 344 rats demonstrated that the aging-associated increases in the density of type I (omega 1) binding sites were restricted to the hippocampus. Moreover, increases in binding density were larger in the dentate gyrus and in the CA2 field than in the CA1 and CA3 fields.

Aging↗
PubMed1995

5-HT3 receptor agonist induced carrier-mediated release of dopamine in rat striatum in vivo.

1. In vivo microdialysis was used to study the effect of phenylbiguanide (PBG), a 5-hydroxytryptamine3 receptor agonist, on the extracellular output of dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) in the corpus striatum. 2. PBG produced a dose-related (10-500 microM) increase in the release of dopamine (280-2000%). DOPAC and HVA output decreased with the perfusion of PBG. This decrease was similar with 50-500 microM PBG. 5-HIAA output was not affected by any PBG concentration used. 3. When nomifensine (5 microM) was included in the Ringer solution, the effect of PBG on the release of dopamine was ameliorated or inhibited. However, the effect of PBG (50-500 microM) on the extracellular output of DOPAC and HVA was similar in the absence and in the presence of nomifensine (5 microM). 4. Perfusion of MDL 72222, a 5-hydroxytryptamine3 receptor antagonist, at doses of 50 and 100 microM produced similar decreases (50% of controls) and increases (120% of controls) in the extracellular output of dopamine and DOPAC, respectively. HVA and 5-HIAA output levels were not affected by either concentration of MDL 72222. MDL 72222 (10 microM) produced a slight and transient increase in the release of dopamine and a decrease in the extracellular output of DOPAC. HVA and 5-HIAA extracellular output was not affected by MDL 72222 (10 microM) perfusion. 5. Co-perfusion of MDL 72222 (10 and 100 microM) or tetrodotoxin (1 microM) with PBG (50 microM) did not modify the effect produced by PBG (50 microM) alone on the release of dopamine. 6 These results suggest that the effect of PBG on the release of dopamine is mainly carrier-mediated.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1995

Analysis of ceftriaxone and ceftazidime distribution in cerebrospinal fluid of and cerebral extracellular space in awake rats by in vivo microdialysis.

In vivo microdialysis was used to estimate the extracellular concentrations of ceftazidime and ceftriaxone, two expanded-spectrum cephalosporins commonly used in the treatment of bacterial meningitis, in two brain regions (the right corpus striatum and the left lateral ventricle_ of awake, freely moving rats. Antibiotics were administered by constant intravenous infusion at 18 mg/h until steady-state levels were reached. Ceftriaxone levels measured at the steady state in the extracellular space of the corpus striatum (0.80 +/- 0.17 micrograms/ml) were statistically equivalent to those obtained in the cerebrospinal fluid of the lateral ventricle (0.71 +/- 0.15 micrograms/ml). The ratios of these levels in the brain to the steady-state levels in plasma were 0.5 +/- 0.1% for both regions. The postinfusion concentrations of ceftriaxone in the brain declined monoexponentially, with an elimination half-life similar to that obtained in plasma. However, the mean antibiotic concentration of ceftazidime in the striatum (2.2 +/- 0.4 micrograms/ml) was lower (P < 0.001) than that in the lateral ventricle (3.8 +/- 0.5% and 4.0 +/- 1.8%, respectively) were higher than those obtained with ceftriaxone. Moreover, the half-life of ceftazidime elimination from plasma was lower than that obtained in the two brain regions. It was concluded that the in vivo microdialysis technique yields useful data on antibiotic distribution in the extracellular space of the brain, that the distribution may not be homogeneous, and that the decay of postinfusion concentrations in the brain may be different from the decay of postinfusion concentrations in plasma.

Animals↗
PubMed1995

Effect of intraventricular injection of 1-methyl-4-phenylpyridinium: protection by acetyl-L-carnitine.

1-methyl-4-phenylpyridinium (MPP+) is the bioactivated product of 1-methyl-4-phenyl- 1, 2, 3, 6-tetrahydropyridine (MPTP). The neurotoxic action of MPP+ injected intracerebroventricularly (ICV) in the rat has been studied, using dopaminergic systems in the substantia nigra, striatum, olfactory bulb, median eminence and hypophysis. The following results were obtained: (1) Rats with ICV administration of 1 microliter MPP+ solution (62.5 micrograms of MPP+ rat) showed 50% mortality; (2) The ICV administration of MPP+ produced a decrease in dopamine (DA) concentration in different areas of rat CNS studied: striatum (83%), hypophysis (95%) and median eminence (70%). However, olfactory bulb and substantia nigra were not affected; (3) MPP+ by ICV administration produced neurotoxic effect on the dopaminergic system. We also studied the possible protective action of acetyl-L-carnitine (ALC) against the neurotoxic action of MPP+. Rats were intraperitoneally injected daily for 8 days with 100 mg kg-1 of ALC and 3 days from the beginning of the MPP+ treatment; (4) We found that the ALC treatment significantly protected against mortality produced by the ICV injection of MPP+. Rats treated with ALC showed no mortality; (5) We did not find a protective effect on the dopaminergic system studying either catecholamine concentration or measuring tyrosine hydroxylase, neurofilament or glial fibrillary acid protein; (6) The results suggest that the ALC protective action could be related to energy metabolism.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1994

Lectin effects on HIV-1 infectivity.

Lectins with specificity for terminal mannose residues and anti-mannan antibodies are assumed to neutralize HIV-1 by binding to the viral glycoproteins. In this report we demonstrate that one such agents, the lectin from Galanthus nivalis (GNA), blocks infection also at the target cell level.

Carbohydrate Sequence↗
PubMed1994

1-Methyl-4-phenylpyridinium has greater neurotoxic effect after selenium deficiency than after vitamin E deficiency in rat striatum.

The present study was designed to assess the extent of the protective effect of antioxidative capacity of dopaminergic neurons against the possible oxidative stress produced by 1-methyl-4-phenylpyridinium. We have studied the direct effect of 1-methyl-4-phenylpyridinium on striatum slices from rats fed with selenium-deficient or vitamin E-deficient diets for 30 days. Glutathione peroxidase activity decreased significantly after selenium dietary restriction. Our results showed that the effect of 1-methyl-4-phenylpyridinium on dopamine and its metabolites 3,4-dihydroxyphenylacetic acid, homovanillic homovanillic acid and 3-methoxytyramine in animals with both restriction diets was higher than in controls. However, this effect was significantly greater in animals with low selenium diets than with vitamin E-deficient diets in terms of dopamine, 3,4-dihydroxyphenylacetic acid and homovanillic acid, which were all significantly more depleted by 1-methyl-4-phenylpyridinium in selenium-deficient rats than in vitamin E-deficient rats. Therefore, considering changes in the levels of dopamine and its metabolites as an index of 1-methyl-4-phenylpyridinium toxicity, our results seem to indicate that the glutathione-glutathione peroxidase system has a greater protector effect than vitamin E.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1994

Molecular heterogeneity of the type I GABAA/benzodiazepine receptor complex.

We have investigated the presence of alpha 1, gamma 2 and beta 2-3 subunits as part of the type I (high affinity for [3H]zolpidem) GABAA/benzodiazepine receptor from rat cerebral cortex. Three subunit specific antibodies have been used (anti-alpha 1, to the C-terminal of rat alpha 1 subunit; anti-gamma 2, to the large intracellular loop of the gamma 2 subunit short form and the monoclonal 62-3G1, specific to beta 2-3 subunits) in immunoprecipitation experiments of the [3H]zolpidem binding activity or the 51,000 Da [3H]Ro 15-4513 photoaffinity labeled peptide (P51). The results indicated that alpha 1 subunit was present in the whole population (90%) of the GABAA/benzodiazepine receptors with high affinity for [3H]zolpidem. We cannot exclude the presence of other alpha subunits co-localized with alpha 1. On the one hand, 70-75% of type I GABAA/benzodiazepine receptor from rat cortex have co-existing alpha 1, beta 2-3 and gamma 2 subunits. We call this type Ia. On the other hand, 20-25% of the type I GABAA/benzodiazepine receptor complex should be constructed by the association of alpha 1 with subunits other than beta 2-3 and gamma 2. We call this type Ib. The identity of these subunits is currently unknown.

Animals↗
PubMed1994

Reduction of 1-methyl 1,2,3,4-tetrahydroisoquinoline level in substantia nigra of the aged rat.

The compounds 1,2,3,4-tetrahydroisoquinoline (TIQ) and 1-methyl-1,2,3,4-tetrahydroisoquinoline (1-MeTIQ) are endogenous in humans and rats. Whereas TIQ seems to have neurotoxicity, 1-MeTIQ has been described as having a protective effect. In this paper, we report the concentration of TIQ and 1-MeTIQ in two areas especially influenced by aging and Parkinson's disease, the substantia nigra (SN) and striatum (ST), of the rat at different ages. 1-MeTIQ and TIQ were detected in both structures using gas chromatography-mass spectrometry with the higher content of both being in the SN. During the aging process there is a significant decrease (50%) in 1-MeTIQ levels in the SN, but TIQ levels did not change significantly in either of the studied regions.

Aging↗
PubMed1994

The effect of a vitamin E-deficient diet on amino acid levels in the substantia nigra, striatum and hippocampus of rats.

The effects of a vitamin E deficiency diet for 15 days on amino acid concentrations have been studied in the substantia nigra, striatum and hippocampus of the rat. The substantia nigra showed an increase in glutamate and GABA and a decrease of tryptophan concentration compared with controls. In the striatum, aspartate and glycine decreased, no changes were found in the amino acid concentrations in the hippocampus. The substantia nigra and striatum showed opposite results-an increase and decrease of amino acids respectively. The increase of glutamate found in substantia nigra is particularly interesting as it may suggest possible links to degenerative processes. These results suggest that vitamin E could play a crucial role in substantia nigra degeneration and that the substantia nigra could be more sensitive to an oxidative stress than other brain structures.

Amino Acids↗