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Biomedical subjects

F Carvalho

Publications and source records attributed to F Carvalho.

67 records · Page 4Linked to original sources
PubMed1989

Uptake inhibitors do not change the effect of imidazoline alpha 2-adrenoceptor agonists on transmitter release evoked by single pulse stimulation in mouse vas deferens.

The present study was undertaken to compare the presynaptic interaction of neuronal noradrenaline uptake inhibitors with imidazoline and phenylethylamine alpha 2-adrenoceptor agonists under two different conditions: at low and high noradrenaline concentrations in the biophase. Isolated mouse vasa deferentia were stimulated with trains of 7 pulses given at 0.2 Hz and the inhibition by the alpha 2-adrenoceptor agonists clonidine, alpha-methylnoradrenaline, and UK-14,304 of twitch responses was measured in the absence and in the presence of either cocaine (12 mumol/l) or desipramine (40 nmol/l). The effects were determined for the first (equivalent to single pulse stimulation) and the last stimulus of each train. Both uptake inhibitors antagonized the presynaptic inhibitory effects of imidazolines (clonidine and UK-14,304) on the last twitch; the effects on the first twitch remained unchanged. In contrast, the uptake inhibitors potentiated the inhibitory effect of the phenylethylamine (alpha-methylnoradrenaline) on both the first and the last twitches. These results support the view that the concentration of noradrenaline in the biophase plays a decisive role in the inhibition by alpha 2-adrenoceptor agonists of the electrically evoked release of noradrenaline. Agonists that are not substrates of neuronal uptake (i.e., clonidine, UK-14,304) become less effective when noradrenaline is present in the biophase while substrates of neuronal uptake (i.e., alpha-methylnoradrenaline) do not. The results argue against the hypothesis that uptake inhibitors interact directly with presynaptic alpha 2-adrenoceptors or act at some link between uptake and receptor sites.

Adrenergic alpha-Agonists↗
PubMed1986

[Value of aspiration biopsy of subcutaneous fat in amyloidosis].

Fine-needle aspiration of subcutaneous fat (FNAF) was performed in 24 patients, 12 with previously diagnosed amyloidosis presenting with proteinuria or nephrotic syndrome, and 12 presenting a nephrotic syndrome without amyloidosis on renal biopsy. FNAF was positive in 10 of 12 patients with amyloidosis (sensitivity: 83%) and negative in 12 of 12 patients with non-amyloid nephrotic syndrome (specificity: 100%). Considering a 2.5 to 10% prevalence of amyloidosis in adult patients with proteinuria or nephrotic syndrome, a positive FNAF is diagnostic of amyloidosis, and a negative FNAF rules out the diagnosis with a probability of 98 to 99%. FNAF is a simple and safe method which can be useful in patients who cannot undergo a renal biopsy.

Adipose Tissue↗
PubMed1985

Interstitial foam cells in the nephrotic syndrome belong to the monocyte/macrophage lineage.

Interstitial foam cells are occasionally seen in patients with the nephrotic syndrome. In a group of patients with the nephrotic syndrome we were able to demonstrate that these cells express markers characteristic of the monocyte/macrophage lineage. Their presence was related to the previous duration of proteinuria, but they had no apparent influence on the subsequent evolution of renal function. The mechanisms leading to their presence are unknown.

Adult↗
PubMed1984

Lead and cadmium concentrations in the hair of fishermen from the Subae River basin, Brazil.

Previous studies have shown heavy pollution by lead and cadmium in the Subae River basin, State of Bahia, Brazil, caused by a lead smelter. Concentrations of these metals were determined in scalp hair of fishermen from three riverside towns and from a reference town. Increased levels for both metals were associated with increasing proximity to the smelter. Mean concentrations of lead and cadmium were higher among fishermen with straight hair than among those with curly hair. The effects of hair washing, hair type, and color and age on metal concentrations in fishermen's hair were studied.

Absorption↗
PubMedDate not supplied

Hyperglycemia induced by acute central fluoxetine administration: role of the central CRH system and 5-HT3 receptors.

Brain serotonin and CRH systems participate in the control of blood glucose levels. We have previously demonstrated that the pharmacological stimulation of central 5-HT3 receptors, the target for several therapeutic agents used as antiemetics in the course of chemotherapy, induces hyperglycemia. The aim of the present study was to investigate the participation of the brain CRH component and 5-HT3 receptors in basal blood glucose levels as well as in the hyperglycemia induced by third ventricle injections of fluoxetine, a serotonin reuptake inhibitor with a broad range of clinical use. In this study, we used fasted adult Wistar male rats (220 +/- 20 g) whose third ventricles were cannulated 7 days prior to the experiments. Acute third ventricle injections of fluoxetine caused a significant increase in plasma glucose levels throughout the experiment. Pretreatment with alpha-helical CRH, a selective CRH antagonist, significantly blunted fluoxetine-induced hyperglycemia. Also, pretreatment with two distinct selective 5-HT3 receptor antagonists (LY-278,584 and ondansetron) significantly impaired the rise in plasma glucose levels observed in fluoxetine-treated animals pretreated with isotonic saline solution. None of these antagonists was able to modify blood glucose levels when injected alone into the third ventricle. Animals receiving third ventricle injections of fluoxetine, in spite of being hyperglycemic, presented plasma insulin levels similar to those displayed by normoglycemic, saline-treated controls. It is suggested that the acute increase in brain serotonergic activity caused by third ventricle injections of fluoxetine induces a hyperglycemic response that requires the functional integrity of the brain CRH system and 5-HT3 receptors. Also, it is proposed that the absence of a compensatory increase in plasma insulin levels may contribute to the generation of a hyperglycemic response after central fluoxetine administration.

Animals↗
PubMedDate not supplied

The study of oxidative stress in freshly isolated Ca(2+)-tolerant cardiomyocytes from the adult rat.

Cardiotoxicity studies using isolated heart cells are becoming increasingly advocated as a supplement to, and sometimes as a replacement for, whole heart or whole animal experimentation. In fact, the use of isolated cardiomyocytes has the great advantage of enabling mechanistic and comparative studies of compounds, which are directly toxic to cardiomyocytes. Since the 1970s, different procedures have been developed in order to obtain Ca(2+)-tolerant cardiomyocytes. The advances in this field will be reviewed and an optimised method to obtain freshly isolated Ca(2+)-tolerant cardiomyocytes from the adult rat for use in toxicological studies will be described. With this procedure, a high number of rod-shaped cells can be obtained (6-7 x 10(6)/heart corresponding to 70% of total number of cells). It is also possible to maintain cell viability, glutathione content and enzymatic activity of glutathione reductase (GR), glutathione peroxidase (GPX) and glutathione S-transferase (GST) in acceptable levels for 4 hours. Cardiotoxicity studies performed with isoproterenol (ISO) in the presence of copper and with the model toxic substance tert-butylhydroperoxide (t-BHP) demonstrate the importance of oxidative stress as a cardiotoxic mechanism elicited by these molecules. The results obtained are also good indicators for future applications of this methodology to other cardiotoxicity studies.

Animals↗
PubMedDate not supplied

Do metals inhibit acetylcholinesterase (AChE)? Implementation of assay conditions for the use of AChE activity as a biomarker of metal toxicity.

The enzymatic activity of acetylcholinesterase (AChE) has been shown to be altered by environmental contaminants such as metals. However, the available literature illustrates a background of contradictory results regarding these effects. Therefore, the main purpose of this study was to investigate the potential of five metal ions (nickel, copper, zinc, cadmium and mercury) to inhibit AChE activity in vitro. First, to accomplish this objective, the possible interference of metals as test toxicants in the Ellman's assay, which is widely used to assess AChE activity, was studied. The potential influence of two different reaction buffers (phosphate and Tris) was also determined. The results suggest that the selected metals react with the products of this photometric technique. It is impossible to ascertain the artefactual contribution of the interaction of the metals with the technique when measuring AChE inhibition. This constitutes a major obstacle in obtaining accurate data. The presence of phosphate ions also makes enzymatic inhibition difficult to analyse. Attending to this evidence, an assay using the substrate o-nitrophenyl acetate and Tris buffer was used to investigate the effects of metals on AChE activity. O-nitrophenyl acetate is also a substrate for esterases other than cholinesterases. It is therefore only possible to use it for the measurement of cholinesterase activity with purified enzymes or after a previous verification of the absence of other esterases in the sample tissue. Under these conditions, the results indicate that with the exception of nickel, all tested metals significantly inhibit AChE activity.

Acetylcholinesterase↗
PubMedDate not supplied

[An anthropological investigation of old age and concepts concerning arterial hypertension].

Anthropology and sociology are joining epidemiology, clinical investigation, and pathophysiology in studies on the aging process of the Brazilian population. The objectives of the present study were: a) to identify the concepts of the elderly population of the municipality of Araraquara, São Paulo, Brazil, towards the etiology of arterial hypertension (AH) and the relevance of the different signs and symptoms that accompany the disease; b) to improve elderly people's concepts towards the relevance and utilization of different treatment categories for AH. Structured interviews were conducted with 29 individuals, the majority aged 60 years or over, who were being treated for hypertension at the Araraquara municipal gerontology outpatient clinic in August 1996. Patients were properly informed by the health team about problems related to AH, as clearly perceived in the discourse of the elderly. Folkloric concepts pertaining to etiology also appeared in the interviews and should be taken into consideration in the implementation of health education activities. Care provided by an interdisciplinary team was valued by the elderly. The most frequent complaint was the lack of free distribution of prescription medication for AH at the clinic.

Adolescent↗
PubMedDate not supplied

[The hemolytic-uremic syndrome].

The microangiopathic thrombotic syndromes--thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS)--are characterized by microangiopathic hemolytic anemia, thrombocytopenia, renal dysfunction, fever and central nervous system abnormalities. Today they are considered as two extremes of a continuous spectrum named TTP--HUS. The syndrome is an uncommon disease with a high mortality rate, despite treatment. The authors describe a case of hemolytic uremic syndrome in a young adult patient. Initially the clinical course and the first biopsy suggested a favourable prognosis, but the early recurrence with severe hypertension was followed by a fatal outcome 6 months later. Concerning this clinical case, the authors present a review of the most recent aspects of the pathogenesis and treatment of this syndrome.

Adolescent↗