An early case of de novo membranous nephropathy in a renal transplant patient.
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Adolescent↗
Biomedical subjects
F Carvalho
Publications and source records attributed to F Carvalho.
Central 5-HT3 receptor stimulation by m-CPBG increases blood glucose in rats.
The aim of the present study was to investigate the role of central 5-HT3 receptors on the control of blood glucose in stressed and non-stressed rats in both fasted and fed states. Adult Wistar male rats had each their third ventricle cannulated 7 days before the experiments. Injections of m-CPBG, a selective 5-HT3 receptor agonist, induced a significant increase in blood glucose in non-stressed rats in both fasted and in fed states. The same procedure was unable to modify stress-induced hyperglycemia. The hyperglycemic effect of m-CPBG central administration was blocked by pretreatment with ondansetron, a specific 5-HT3 receptor antagonist, indicating that the effects here obtained with m-CPBG were a result of its interaction with 5-HT3 receptors. Third ventricle injections of ondansetron alone were not able to modify blood glucose in non-stressed animals and did not change the hyperglycemic responses observed after immobilization stress. We conclude that pharmacological activation of the central 5-HT3 receptor induces a hyperglycemic effect in non-stressed animals.
Animals↗
Does the D(-)/D(+) production asymmetry decrease at large x(F)?
We have applied the meson cloud model to calculate the asymmetries in D and D(s) meson production in high-energy Sigma(-)-nucleus and pi(-)-nucleus collisions. We find a good agreement with recent data. Our results suggest that the asymmetries may decrease at large x(F).
Journal Article↗
Determination of amphetamine and its metabolite p-hydroxyamphetamine in rat urine by reversed-phase high-performance liquid chromatography after dabsyl derivatization.
The consumption of amphetamine is illicit and controlled due to both the elicited behavioural deviations and the toxicity effects reported in abusers. Thus, amphetamine levels in biological samples must be monitored in several clinical and forensic circumstances. In spite of the interspecies differences in the preferred route of biotransformation, benzylmethylketone, benzoic acid and 4-hydroxyamphetamine are the principal metabolites of amphetamine. However, the clinical and forensic studies are focused in the parent compound and in 4-hydroxyamphetamine since benzylmethylketone is a minor metabolite in human and benzoic acid is also an endogenous compound. In the present study amphetamine and its metabolite, 4-hydroxyamphetamine, are quantified in urine by HPLC after derivatization with 4-dimethylaminoazobenzene-4'-sulfonyl chloride (dabsyl chloride). This derivatization procedure transforms amphetamine and its hydroxylated metabolite in compounds with similar lipofilicity, enabling their quantitative and simultaneous extraction with an organic solvent. The precision of the HPLC technique was 7.3 and 10.0% for amphetamine and 4-hydroxyamphetamine derivatives, respectively. For the overall procedure, including enzymatic hydrolysis, derivatization and extraction of the derivatives, the obtained values were 9.3 and 6.2%. Recoveries obtained from spiked urines for amphetamine and 4-hydroxyamphetamine were better than 97% and 94% (mean value), respectively. The detection limits of the method was 10 ng for both compounds. The principal advantages of the present proposed method are the stability of the dabsyl derivatives at room temperature and the detection carried out in the visible region, reducing the interferences detected.
Amphetamine↗
Preimplantation genetic diagnosis for familial amyloidotic polyneuropathy (FAP).
Preimplantation genetic diagnosis (PGD) was developed more than a decade ago to offer an alternative to prenatal diagnosis for couples at risk of transmitting an inherited disease to their offspring. Portuguese-type familial amyloidotic polyneuropathy (FAP type I), is an autosomal dominant disease presenting an inherited mutation in the gene encoding the plasma protein transthyretin (TTR). We here report the first protocol for single-cell detection of the Met30 mutation in FAP type I and its application to PGD. A nested PCR reaction for exon 2 of the TTR gene was developed. The PCR product was then analysed by restriction enzyme analysis and SSCP allowing the detection of the point mutation. Ten clinical cycles were performed in seven couples. From the 93 metaphase II (MII) injected oocytes, 82 were normally fertilized and 78 were biopsied. A positive signal in the nested PCR reaction was obtained in 61 blastomeres, corresponding to a DNA amplification efficiency of 78.2%. No allele dropout (ADO) or contamination were detected. A biochemical pregnancy was obtained in three cases and a clinical pregnancy in one couple is actually in normal evolution.
Amyloid Neuropathies, Familial↗
Is hyperthermia the triggering factor for hepatotoxicity induced by 3,4-methylenedioxymethamphetamine (ecstasy)? An in vitro study using freshly isolated mouse hepatocytes.
The consumption of 3,4-methylenedioxymethamphetamine (ecstasy; MDMA) may cause hepatocellular damage in humans, a toxic effect that has been increasing in frequency in the last few years, although the underlying mechanisms are still unknown. The metabolism of MDMA involves the production of reactive metabolites which form adducts with intracellular nucleophilic sites, as is the case with glutathione (GSH). Also, MDMA administration elicits hyperthermia, a potentially deleterious condition that may aggravate its direct toxic effects. Thus, the objective of this study was to evaluate the extent of MDMA-induced depletion of GSH, induction of lipid peroxidation and loss of cell viability in freshly isolated mouse hepatocytes under normothermic conditions (37 degrees C) and to compare the results with the effects obtained under hyperthermic conditions (41 degrees C). By itself, hyperthermia was an important cause of cell toxicity. A rise in incubation temperature from 37 degrees C to 41 degrees C caused oxidative stress in freshly isolated mouse hepatocytes, reflected as a time-dependent induction of lipid peroxidation and consequent loss of cell viability (up to 40-45%), although the variations in GSH and GSSG levels were similar to those under normothermic conditions. MDMA (100, 200, 400, 800 and 1600 microM) induced a concentration- and time-dependent GSH depletion at 37 degrees C but had a negligible effect on lipid peroxidation and cell viability at this temperature. It is particularly noteworthy that hyperthermia (41 degrees C) potentiated MDMA-induced depletion of GSH, production of lipid peroxidation and loss of cell viability (up to 90-100%). It is therefore concluded that hyperthermia potentiates MDMA-induced toxicity in freshly isolated mouse hepatocytes.
Animals↗
Hydrogen peroxide production in mouse tissues after acute d-amphetamine administration. Influence of monoamine oxidase inhibition.
The toxicity of amphetamines is conditioned by a complex array of mechanisms, involving the increase of neurotransmission (e.g. leading to hyperthermia) and enzymatic and non-enzymatic oxidation of amphetamines and biogenic amines. Considering that all these processes may increase the generation of hydrogen peroxide (H2O2) by metabolic or non-metabolic redox pathways, the main objective of this work was to evaluate d-amphetamine-induced H2O2 production in mice liver, kidney and heart. The contribution of monoamine oxidase (MAO) to H2O2 production after d-amphetamine administration was studied using the MAO inhibitor pargyline. H2O2 production was measured indirectly using the catalase-H2O2 complex I irreversible inhibitor 3-amino-1,2,4-triazole (AT). Using this method, the measurement of residual catalase activity following administration of AT permits the monitoring of H2O2 production in vivo. Charles River CD-1 mice (30-35 g body weight) were injected with AT just before the injection of d-amphetamine sulphate (20 mg/kg). d-Amphetamine stimulated the production of H2O2 in all tissues studied, although to different degrees. MAO inhibition by itself led to a remarkable decrease of basal H2O2 production in the kidney and a slight decrease in the liver, although no effect was observed in the heart. d-Amphetamine-induced H2O2 production in the heart and kidney was reduced in MAO-inhibited mice. However, in the liver, H2O2 production was transiently potentiated at 30 min under MAO inhibition. In conclusion, d-amphetamine administration leads to an increase in H2O2 production in mouse liver, kidney and heart, and monoamine oxidase plays an important role in this effect.
Animals↗
Antioxidant activity of Centaurium erythraea infusion evidenced by its superoxide radical scavenging and xanthine oxidase inhibitory activity.
Centaurium erythraea Rafin. (Gentianaceae) has long been used in traditional medicine. This plant contains considerable amounts of polyphenolic compounds, namely, xanthones and phenolic acids as the main constituents. Because phenolic groups exhibit activity as radical scavengers and/or metal chelators, this study evaluated the superoxide radical scavenging properties of a lyophilized infusion obtained from C. erythraea flowering tops. Superoxide radical scavenging activity was assayed using enzymatic (xanthine/xanthine oxidase) and nonenzymatic (NADH/phenazine methosulfate) superoxide generating systems. This study provided evidence that C. erythraea exhibits interesting antioxidant properties, expressed either by the capacity to scavenge superoxide radical or to noncompetitively inhibit xanthine oxidase. The main phenolic compounds present in this extract were several esters of hydroxycinnamic acids, namely, p-coumaric, ferulic, and sinapic acids.
Antioxidants↗
MUC1 gene polymorphism in the gastric carcinogenesis pathway.
MUC1 like most mucin genes shows extensive length polymorphism in the central core region. In a previous study it was shown that individuals with small MUC1 alleles/genotypes have an increased risk for development of gastric carcinoma. Our aim was to see if MUC1 gene polymorphism was involved in susceptibility for the development of conditions that precede gastric carcinoma: chronic atrophic gastritis (CAG) and intestinal metaplasia (IM). We evaluated MUC1 polymorphism in a population of 174 individuals with chronic gastritis (CG) displaying (CAG) and/or intestinal metaplasia (IM). The population of patients with CG shows MUC1 allele frequencies significantly different from the gastric carcinoma patients and blood donors population. A significantly lower frequency of CAG and IM was observed in MUC1 VNTR heterozygotic patients. Within the group of patients with IM, MUC1 large VNTR homozygotes show a significantly higher frequency of complete IM while small VNTR homozygotes show a significantly higher frequency of incomplete IM. These findings show that MUC1 polymorphism may define different susceptibility backgrounds for the development of conditions that precede gastric carcinoma: chronic atrophic gastritis (CAG) and intestinal metaplasia (IM).
Adult↗
Cardiotoxicity studies using freshly isolated calcium-tolerant cardiomyocytes from adult rat.
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Animals↗
Copper enhances isoproterenol toxicity in isolated rat cardiomyocytes: effects on oxidative stress.
Sustained high levels of circulating catecholamines may result in cardiotoxicity. Although cardiotoxicity could occur primarily via adrenoceptor activation, there is increasing evidence that it may also occur through oxidative mechanisms. In fact, catecholamines can be converted into aminochromes by auto-oxidation, enzymatically or metal catalyzed, with the concomitant production of reactive intermediates and free radicals. Nevertheless, there is only scarce information concerning the effects of the catecholamine oxidation process on isolated cardiomyocytes. The aim of this work was to evaluate the cardiotoxic effects of isoproterenol (ISO) and its oxidation process in freshly isolated adult rat cardiomyocytes by assessing the cell shape, lactate dehydrogenase leakage, reduced and oxidized glutathione content, and glutathione reductase, peroxidase, and transferase activities. ISO was incubated at concentrations of 0.1, 0.5, and 1 mM in cardiomyocyte suspensions at subphysiological and physiological Ca2+ concentrations for 4 h. The same study was repeated in the presence of 20 microM of Cu2+. The levels of ISO in the incubation medium were monitored throughout the assays. Isoproterenol (1 mM) induced both glutathione oxidation and conjugation, but this effect decreased at subphysiological Ca2+ concentrations. The concomitant incubation with Cu2+ increased ISO oxidation and increased the glutathione oxidation but decreased the extent of glutathione conjugation. Although only a partial ISO oxidation was observed for all studied ISO concentrations in the presence of copper, the underlying oxidative process or its oxidation products, or both, were sufficient to induce a loss of cardiomyocyte viability and a decrease in the glutathione reductase, peroxidase, and transferase activities. Thus, the results suggest that the oxidation of catecholamines could be a major mechanism for catecholamine-induced cardiotoxicity.
Adrenergic beta-Agonists↗
Simultaneous determination of reduced and oxidized glutathione in freshly isolated rat hepatocytes and cardiomyocytes by HPLC with electrochemical detection.
Glutathione and glutathione disulphide constitute an essential thiol redox system present in the cell. The balance in favour of the latter is an indication of oxidative stress. Glutathione and glutathione disulphide quantification in isolated cells may therefore be essential for the evaluation of mechanistic and comparative studies of toxic xenobiotics. In this study, a rapid and sensitive isocratic reverse-phase high-performance liquid chromatographic method using coulometric detection was implemented for the simultaneous detection of glutathione and glutathione disulphide, in freshly isolated hepatocytes and cardiomyocytes of the rat. The method implemented proved to be effective for the measurement of glutathione and glutathione disulphide in control conditions and for the detection of variations in this redox system, induced by tert-butylhydroperoxide. tert-Butylhydroperoxide is an organic peroxide, which has been used as a model molecule for inducing oxidative stress in isolated cells. A comparative study with a previously published HPLC-electrochemical detection method was performed.
Animals↗
Immunohistochemical study of the expression of MUC6 mucin and co-expression of other secreted mucins (MUC5AC and MUC2) in human gastric carcinomas.
To investigate the expression of MUC6 mucin in gastric carcinomas, we generated a novel monoclonal antibody (MAb CLH5) using an MUC6 synthetic peptide. MAb CLH5 reacted exclusively with the MUC6 peptide and with native and deglycosylated mucin extracts from gastric tissues. MAb CLH5 immunoreactivity was observed in normal gastric mucosa restricted to pyloric glands of the antrum and mucopeptic cells of the neck zone of the body region. In a series of 104 gastric carcinomas, 31 (29.8%) were immunoreactive for MUC6. The expression of MUC6 was not associated with histomorphological type or with clinicopathological features of the carcinomas. Analysis of the co-expression of MUC6 with other secreted mucins (MUC5AC and MUC2) in 20 gastric carcinomas revealed that different mucin core proteins are co-expressed in 55% of the cases. MUC6 was co-expressed and co-localized with MUC5AC in 45% and with MUC2 in 5% of the cases. Expression of MUC2 alone was observed in 25% of the cases. All carcinomas expressing MUC2 mucin in more than 50% of the cells were of the mucinous type according to the WHO classification. The co-expression of mucins was independent of the histomorphological type and stage of the tumors. In conclusion, we observed, using a novel well-characterized MAb, that MUC6 is a good marker of mucopeptic cell differentiation and is expressed in 30% of gastric carcinomas, independent of the clinicopathological features of the cases. Furthermore, we found that co-expression and co-localization of mucins in gastric carcinomas is independent of histomorphology and staging. Finally, we observed that intestinal mucin MUC2 is expressed as the most prominent mucin of the mucins tested in mucinous-type gastric carcinomas.
Animals↗
Effect of d-amphetamine repeated administration on rat antioxidant defences.
The purpose of this study was to evaluate rat tissue antioxidant status after repeated administration of d-amphetamine. Three groups of four rats each were used: control, d-amphetamine sulphate dosed (s.c., 20 mg/kg per day), and pair-fed. After 14 days of d-amphetamine daily administration, superoxide dismutase (CuZnSOD and MnSOD), catalase, glutathione peroxidase (GPx), glutathione reductase (GRed), glutathione-S-transferase (GST), glutathione (GSH), cysteine and thiobarbituric acid reactive substances (TBARS) were measured in liver, kidney, and heart. Various serum and urine parameters were also analysed. d-Amphetamine treatment induced an increase of liver GSH, as well as a decrease of cysteine and MnSOD levels in this organ. A small increase in serum transaminases was also observed in comparison to the pair-fed group. Hepatic levels of TBARS, GPx, GRed and CuZnSOD were found to be similar among the three groups of rats. d-Amphetamine treatment induced an increase of kidney GST, GRed and catalase levels, and an elevation of N-acetyl-beta-D-glucosaminidase efflux to the urine, accompanied by a decrease in urinary creatinine, compared to the pair-fed group. In d-amphetamine treated animals, heart cysteine levels were significantly depleted when compared to the pair-fed group, but all three groups of rats were found to have similar heart antioxidant enzyme levels. These results indicate that repeated administration of d-amphetamine caused a certain degree of stress in liver and kidney, which was followed by adaptations of antioxidant defences. The mechanisms involved in d-amphetamine-induced toxicity may explain the different adaptations observed for the studied organs.
Animals↗
Mucins and mucin-associated carbohydrate antigens expression in gastric carcinoma cell lines.
Mucins are high-molecular-mass glycoproteins with high carbohydrate content and marked heterogeneity both in the apoprotein and in the oligosaccharide side chains. Mucin genes are expressed in a regulated manner, namely in the human stomach. The first aim of the present study was to characterise the expression of mucins and mucin-associated carbohydrate antigens in seven gastric carcinoma cell lines, and to compare their expression profiles with those of normal gastric tissues and human gastric carcinomas. Secondly, we aimed to see whether or not there is an association between the expression of mucins and mucin-associated carbohydrate antigens. Our results show that mucin expression in gastric carcinoma cell lines: (a) follows in part the mucin expression profile of normal gastric mucosa and gastric carcinomas with wide expression of MUC1 and MUC5AC; (b) parallels the aberrant pattern of mucin expression observed in human gastric carcinomas with occasional expression of MUC2, MUC3, MUC4 and MUC5B; (c) does not include, at least in our series, the expression of MUC6 mucin; and (d) follows in part the differentiation pattern of the carcinomas from which the cell lines originated, keeping S-Tn expression in cell lines derived from glandular carcinomas. Our results further demonstrate that there is no apparent relationship between the mucin core proteins and the simple mucin-type or Lewis carbohydrate antigens.
Antigens, Tumor-Associated, Carbohydrate↗
MUC1 gene polymorphism does not explain the different incidence of gastric cancer in Portugal and Denmark.
MUC1 is a highly polymorphic mucin type glycoprotein expressed on the surface of many epithelia, including gastric mucosa, and is present in several body fluids and mucous secretions. A genetic polymorphism due to variation in length of a 60 bp tandemly repeated sequence domain constitutes more than half of the coding region of the glycoprotein. We demonstrated previously in a Portuguese population sample that the frequency of small MUC1 alleles is increased in patients with gastric carcinoma, suggesting that the possession of small MUC1 alleles confers increased risk for gastric carcinoma development. This finding raised the possibility that the very high prevalence of gastric carcinoma in Portugal could be partly due to a high frequency of small MUC1 alleles in the Portuguese population. In the present study we compared the MUC1 allele distribution in a population of Danish blood donors with the distribution in a population of Portuguese blood donors. The frequency of small MUC1 alleles was significantly higher in the Danish than in the Portuguese sample, thus failing to lend support to the hypothesis that a relatively higher frequency of the small MUC1 alleles might account for the high prevalence of gastric carcinoma in Portugal when compared to Denmark.
Adult↗
Cystic duplication of the rectum--report of two clinical cases.
The authors present two case reports of cystic rectal duplication which presented as rectal prolapse. Two girls, caucasian race, 8 months and 12 years old, went to the emergency department because of a rectal prolapse. After the diagnosis surgical excision was performed by transanal approach. The post-operative period was short and uneventful. Histological examination confirmed a rectal cystic duplication.
Child↗
Cardiac valve calcification in haemodialysis patients: role of calcium-phosphate metabolism.
BACKGROUND: Cardiac valve calcification (VC) has been detected with increased frequency in haemodialysis (HD) patients, making it necessary to determine the potential pathogenic factors in uraemic patients. METHODS: A total of 92 chronic HD patients (39 female, 53 male) and 92 age and gender-matched nondialysis control subjects were evaluated by echocardiography and a severity score for VC was determined. Calcium phosphate metabolism was evaluated at the beginning of haemodialysis. RESULTS: We found a greater prevalence of VC in dialysis patients than in normal patients (mitral annulus 44.5% vs 10%, P = 0.02; aortic annulus 52% vs 4.3%, P = 0.01). HD patients with mitral calcification were found to be older than patients without calcification, were on long-term renal replacement therapy, had longer duration of predialysis arterial hypertension, had greater values of the highest value of mean calcium phosphate product in 6 successive months (CaxP) and the highest absolute value of calcium-phosphate product (CaxPmax). We also found a positive correlation between calcification score, age, and CaxP. No correlation was found between actual VC and arterial hypertension or parathyroid hormone. Multiple stepwise regression analysis selected age and CaxP as the most predictive parameters for mitral calcification (r = 0.47). Mitral calcification was associated more frequently with rhythm and cardiac conduction defects, valvular insufficiency and with peripheral vascular calcification. Aortic calcification was correlated with age (r = 0.42) and longer duration of predialysis arterial hypertension. CONCLUSION: Our study confirmed an increased prevalence of VC in HD patients and selected age and calcium phosphate product as the most predictive parameters. These findings support careful monitoring of calcium metabolism beginning at the early stages of end-stage renal failure to reduce the risk of heart disease.
Aged↗