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Biomedical subjects

A Vieira

Publications and source records attributed to A Vieira.

At least 19 recordsLinked to original sources
PubMed2001

Mediated imitation in 6-month-olds: remembering by association.

In two experiments with 72 6-month-olds, we examined whether associating an imitation task with an operant task affects infants' memory for either task. In Experiment 1, infants who imitated target actions that were modeled for 60 s on a hand puppet remembered them for only 1 day. We hypothesized that if infants associated the puppet imitation task with a longer-remembered operant task, then they might remember it longer too. In Experiment 2, infants learned to press a lever to activate a miniature train-a task 6-month-olds remember for 2 weeks-and saw the target actions modeled immediately afterward. These infants successfully imitated for up to 2 weeks, but only if the train memory was retrieved first. A follow-up experiment revealed that the learned association was bidirectional. This is the first demonstration of mediated imitation in 6-month-olds across two very different paradigms and reveals that associations are an important means of protracting memories.

Association Learning↗
PubMed2001

[Complete congenital atrioventricular block].

Congenital atrioventricular block is defined (Yater) as a documented conduction defect in a young subject with unquestionable bradycardia in the absence of a history of infection which might have caused the condition. This condition may be isolated or associated with structural cardiac disease. Isolated block is often observed in patients with mothers suffering from autoimmune disease, often clinically latent. Anti-Ro/SS-A and La/SS-B antibodies cross into the fetal circulation and cause inflammation of the fetal conduction system. The diagnosis of the conduction defect is sometimes made during fetal life by echocardiography. Echocardiography assesses fetal hemodynamic status and may detect signs of fetal deterioration. Long-term follow-up studies have revised the previously considered good prognosis of isolated congenital atrioventricular block but advances in cardiac pacing provide satisfactory treatment. Follow-up by Holter monitoring, exercise testing and echocardiography is justified in children and adolescents; the patients may become symptomatic at any age. Indications for permanent pacing in pediatric patients have been difficult to determine due to the lack of data from controlled studies and multicenter trials. Pacing is not always easy in children. Epicardial pacing is advocated in small patients (< 5 years of age or 30 kg in weight). A pacing mode which restores the normal atrioventricular sequence is theoretically superior to single ventricular pacing even with rate responsive frequency.

Adolescent↗
PubMed2000

Artificial neural network algorithm for analysis of rutherford backscattering data

Rutherford backscattering (RBS) is a nondestructive, fully quantitative technique for accurately determining the compositional depth profile of thin films. The inverse RBS problem, which is to determine from the data the corresponding sample structure, is, however, in general ill posed. Skilled analysts use their knowledge and experience to recognize recurring features in the data and relate them to features in the sample structure. This is then followed by a detailed quantitative analysis. We have developed an artificial neural network (ANN) for the same purpose, applied to the specific case of Ge-implanted Si. The ANN was trained with thousands of constructed spectra of samples for which the structure is known. It thus learns how to interpret the spectrum of a given sample, without any knowledge of the physics involved. The ANN was then applied to experimental data from samples of unknown structure. The quantitative results obtained were compared with those given by traditional analysis methods and are excellent. The major advantage of ANNs over those other methods is that, after the time-consuming training phase, the analysis is instantaneous, which opens the door to automated on-line data analysis. Furthermore, the ANN was able to distinguish two different classes of data which are experimentally difficult to analyze. This opens the door to automated on-line optimization of the experimental conditions.

Journal Article↗
PubMed1999

[Human leptospirosis. A short review concerning a caseload].

Leptospirosis, a zoonosis with worldwide distribution, may have a broad spectrum of clinical manifestations that can delay the diagnosis, especially in wet climates where other conditions may dissimulate the main aspects. The authors describe 42 cases of patients with leptospirosis admitted to the Infectious Diseases Unit of a general hospital since 1990. The goal was to analyse epidemiological features, clinical manifestations, laboratory findings, treatment and evolution. There were 23 males (54.7%) and 19 females (45.2%), with ages ranging from 17 to 82 years. Most cases occurred in occupational settings, especially in those in contact with animals or stagnant water. All the cases had serological confirmation (by MAT or ELISA methods). Anicteric forms represented 42.9% of the total, which implies that in many cases a diagnosis is not immediately evident. The main symptoms, other than fever (97.6%) and jaundice (57.1%), were myalgia (71.4%), headache (42.8%) and nausea (33.3%). Renal involvement was common (52%), but the most severe forms occurred in 3 patients who required hemodialysis; followed by D.I.C. in 9.5%; meningitis in 4.7% and pulmonary involvement in 2.3% of the cases. The serovars most commonly identified were L. icterohaemorraghiae (28.5%), L. australis (14.3%), L. grippothyphosa (11.9%) and L. canicola (9.5%). The patients were treated with penicillin G (83.3%) or doxycyclin (9.5%). Two of them deceased (4.7%) and the remainder had a good evolution. The diagnosis of leptospirosis may be delayed if physicians fail to include this infection in the initial differential diagnosis. In view of this, the authors emphasize that when nonspecific clinical manifestations occur, a good epidemiological history is useful in proposing this diagnosis.

Adult↗
PubMed1998

ELISA-based assay for scatchard analysis of ligand-receptor interactions.

A simple, nonradioactive method is presented that can be used for performing large numbers of binding assays of cell membrane receptors with their ligands. The method adopts the simple membrane preparation and biotin-based quantitation methods of the semi-intact cell endocytosis assays. After binding of the biotinylated ligand to its receptors on the semi-intact cell membranes, a rapid centrifugation step separates the membranes from unbound ligand. Bound ligand is subsequently released by detergent, captured by a specific antibody coated on teh surface of microwells, and quantitated with peroxidase-conjugated streptavidin in a colorimetric assay. Using this assay, Scatchard analysis was performed on the data for the specific binding of iron-loaded transferrin to its receptors on mouse fibroblasts and yielded Kd values similar to those obtained with other published methods. The assay is sensitive, rapid, and also convenient, because aliquots of semi-intact cells can be stored frozen. The perforated plasma membrane of the cells offers the additional possibility of screening factors that interact with the cytoplasmic domain of the receptors for their possible effects on the parameters of the extracellular ligand-receptor interaction.

Animals↗
PubMed1998

Induction of labor with intravaginal administration of misoprostol.

OBJECTIVE: The purpose of this study was to evaluate the efficacy and safety of intravaginal misoprostol for labor induction. METHODS: 110 singleton term pregnancies with or without rupture of membranes were enrolled. Fractionated doses of misoprostol were applied (50-100 microg), every 6 h until a maximum of three doses or beginning of labor. RESULTS: The average interval (+/- S.D.) from vaginal application to the beginning of active labor and to delivery were, respectively, 9.5 +/- 5.7 h and 14.8 +/- 9.5 h. Failed labor induction was observed in two cases (2%). Cesarean section rate was 14%. The incidence of tachysystole was 18% and hypersystole 4%, but these situations were associated with abnormal fetal heart rate pattern (hyperstimulation) in only 3%. No maternal side effects and neonatal adverse effects were noted. CONCLUSIONS: Intravaginal misoprostol administration with low doses is an effective and safe method for labor induction in term pregnancies, with or without rupture of membranes.

Administration, Intravaginal↗
PubMed1998

Structural similarity of two T cell signaling regulators suggests a conserved and interactive mechanism of immunosuppression.

A primary structural element is identified which is present in the Nef protein of immunodeficiency viruses and in the cytoplasmic domain of a regulatory T cell protein, CTLA-4. In both proteins, conserved residues that lie within this element have been shown to be important for the regulation of cellular signaling and endocytic trafficking. The structural similarity identified suggests conserved and, possibly, interactive mechanisms for Nef- and CTLA-4-dependent modulation of T cell function.

Abatacept↗
PubMed1996

[Isolated right ventricular myxoma: report of a clinical case].

A clinical case of a 14 years old white female with asthenia and easy fatigue of two months duration is presented. The two-dimensional echocardiography study has identified a tumorous and homogeneous mass filling completely the right ventricle. During the cardiac surgery and with the help of extemporaneous biopsy the real nature of the tumor was confirmed-cardiac myxoma. In this report the authors discuss the incidence of cardiac tumors and particularly cardiac myxomas and point out the rarity of isolated myxomas in the right ventricle.

Adolescent↗
PubMed1994

[Gastric tuberculosis].

A 37 year old woman with duodenal ulcer not responsive to medical treatment was operated. Antrectomy, truncal vagotomy and Bilroth II gastrojejunostomy were performed. The histopathology revealed epithelioid cell granulomas with multinucleated cells and central ceseation, in the gastric side of the pylorus and in three isolated lymph nodes. With Ziehl-Neelsen staining there were multiple acid-fast bacilli. There was no evidence or previous history, personal or familial, or tuberculosis in an other localization. Epidemiology, pathology, diagnosis, and treatment of gastric tuberculosis are discussed according to the literature.

Adult↗
PubMed1993

Plasma concentrations of fluvoxamine and maprotiline in major depression: implications on therapeutic efficacy and side effects.

We examined the relationship between plasma concentrations of specific acting antidepressants (fluvoxamine/maprotiline) and clinical improvement as well as the impact of the magnitude of the plasma concentration of these antidepressants on side effects. Patients (32 patients with major depression) were treated within a double-blind parallel trial for four weeks and plasma concentrations were obtained before, on days 8 and 28 of the trial. Although there was a fixed-flexible dosage design it was apparent that 16 patients (89%) of the fluvoxamine group and all patients of the maprotiline group received a dosage between 200 and 300 mg/day in the last week of the trial. Plasma concentrations (mean +/- SD micrograms/l) of fluvoxamine were 125 +/- 91 and 142 +/- 108 on days 8 and 28, respectively and the range of fluvoxamine plasma concentrations on day 28 was from 20 to 417 micrograms/l. Plasma concentrations (mean +/- SD micrograms/l) of maprotiline were 146 +/- 62 and 202 +/- 134 on days 8 and 28, respectively and the range of maprotiline plasma concentration on day 28 was from 12 to 428 micrograms/l. There was no linear relationship between plasma concentrations of both antidepressants (fluvoxamine/maprotiline) and oral dosage. Whereas there was no correlation between fluvoxamine concentration and clinical response there was a tendency that higher maprotiline concentrations were associated with a better antidepressive efficacy at the end of the trial. Higher concentrations of fluvoxamine as well as of maprotiline were significantly (P < 0.05) associated with more side effects.

Adult↗
PubMed1992

Automaticity and preattentive processing.

The characteristics of automatized performance resemble those of preattentive processing in some respects. In the context of visual search tasks, these include spatially parallel processing, involuntary calling of attention, learning without awareness, and time-sharing with other tasks. However, this article reports some evidence suggesting that extended practice produces its effects through different mechanisms from those that underlie preattentive processing. The dramatic changes in search rate seem to depend not on the formation of new preattentive detectors for the task-relevant stimuli, nor on learned abstracted procedures for responding quickly and efficiently, but rather on changes that are very specific both to the particular stimuli and to the particular task used in practice. We suggest that the improved performance may depend on the accumulation of separate memory traces for each individual experience of a display (see Logan, 1988), and we show that the traces differ for conjunction search in which stimuli must be individuated and for feature search where a global response to the display is sufficient.

Attention↗
PubMed1991

Heparin sensitivity and resistance in the neonate: an explanation.

Based on in vitro tests, newborns are reported to be both sensitive and resistant to standard heparin (SH) compared to adults. The sensitivity to SH occurs in assays based on de novo thrombin generation, and SH resistance occurs in systems where exogenous thrombin is added to newborn plasma. We hypothesized that this apparent paradox is related to the antithrombin III to (pro) thrombin ratio associated with each test. Since SH catalyses the activity of antithrombin III, any imbalance in the antithrombin III/(pro)thrombin ratio in newborns compared to adults would be amplified by SH. If the ratio of antithrombin III/(pro)thrombin is defined as 1 in adults, in comparison newborns have a ratio of 1.5. We compared how various doses of SH (0.1 to 0.6 u/ml) inhibited the generation of endogenous thrombin in defibrinated newborn (N) and adult (A) plasma. Following contact activation and recalcification of each plasma, thrombin activity was measured using a chromogenic substrate and quantitated by measuring the area under the curve. In the presence of SH, newborn plasma was more sensitive to SH than adult plasma and generated relatively less thrombin (N:6.1 vs A:9.1% sec/u/ml; p less than 0.01). When the ratio of antithrombin III/(pro)thrombin in newborns was altered to 2.5 by exogenous antithrombin III, the SH sensitivity was increased. This plasma now generated no detectable thrombin in the presence of only 0.1 u/ml of SH. In contrast, when the ratio of antithrombin III/(pro) thrombin of the newborn was altered by exogenous prothrombin to 0.6, this plasma now became resistant to SH and generated more thrombin than adults in the presence of SH (N:11.6 vs A:9.1; p less than 0.01). Because of the potential use of low molecular weight heparins (LMWH) in newborns, a LMWH, Choay 222, was also tested in a similar fashion and gave similar results to SH. Thus, the ratio of antithrombin III/(pro)thrombin likely determines the in vitro sensitivity or resistance of newborn plasma to SH and LMWH. There are no clinical studies that determine if newborns require more or less SH than the adult to successfully treat thrombotic complications. Current practice is a simple extrapolation of therapeutic ranges from adults. We speculate that the efficacy and safety of SH in the newborn in vivo can be improved by altering the antithrombin III/(pro)thrombin ratio.

Adult↗
PubMed1991

Therapeutic sleep deprivation and antidepressant medication in patients with major depression.

Although there is a body of literature on the therapeutic efficacy of sleep deprivation (SD) there are only a few investigations in which the relevance of antidepressive medication for the clinical efficacy of SD has been studied. Based on the literature and on our own investigations with major depressed patients it seems that for the day-1 response it does not matter if and what type of antidepressive medication the patient receives. Furthermore, the results of our double blind study reveal that the day-1 response to total sleep deprivation (TSD) is not associated with a clear relationship to the outcome after 4 weeks treatment with either fluvoxamine or maprotiline. On the other hand, our data indicate that the day-2 response to TSD is significantly correlated with a beneficial outcome after subchronic treatment with maprotiline.

Antidepressive Agents↗
PubMed1990

Multiple hormone responses to stimulation with dl-fenfluramine in patients with major depression before and after antidepressive treatment.

The authors investigated 31 drug-free inpatients with major depression using dl-fenfluramine (dl-FEN) as a serotonin probe (fenfluramine stimulation test, FFT). The FFT was performed in the same individuals (intraindividual comparison) with and without application of dl-FEN and before and after antidepressive treatment. Blood samples were analyzed for prolactin, cortisol, thyrotropin (TSH), growth hormone (HGH), dl-FEN and its major metabolite dl-norfenfluramine. There was no difference in the conditions before and after treatment as regards peak plasma levels of dl-FEN. Compared with saline, significant (P less than 0.01) increases were detected for dl-FEN-stimulated cortisol and prolactin values. A significantly (P less than 0.01) lower increase in dl-FEN-stimulated prolactin values was found after treatment compared with the situation before treatment, a finding which was dependent on the type of medication which the patients were receiving at the time when the test procedure took place. Baseline and dl-FEN-stimulated cortisol values were significantly (P less than 0.001) lower and TSH values were significantly (P less than 0.01) higher in the condition after compared with the one before treatment. Patients' mean peak delta prolactin responses to dl-FEN before treatment were significantly (P less than 0.05) correlated with those of patients after subchronic treatment with fluvoxamine. Hormonal responses were neither associated with the severity of the illness nor with a specific psychopathological profile.

Adult↗
PubMed1990

Response to total sleep deprivation before and during treatment with fluvoxamine or maprotiline in patients with major depression--results of a double-blind study.

To test the hypothesis that the antidepressant effects of total sleep deprivation (TSD) are linked to the serotonergic and/or noradrenergic system the authors carried out a double-blind study (fluvoxamine versus maprotiline) in 42 inpatients with endogenous depression (ICD). Patients were randomized to a four-week treatment with either fluvoxamine (100-300 mg/day) or maprotiline (100-300 mg/day). In addition, patients underwent a TSD procedure before and after one week of antidepressant medication. There was a statistically significant reduction of depression ratings (HDRS) in both the fluvoxamine and maprotiline group. The day-1 response to TSD before antidepressive medication was not associated with a clear relationship to the outcome after four weeks of treatment with either fluvoxamine or maprotiline. On the other hand, the day-2 response to TSD was significantly correlated with a good outcome to subchronic treatment with maprotiline. Furthermore, the results of the authors' data suggest that a favorable short-term outcome of TSD may be connected to antidepressants enhancing the serotonergic neurotransmission. The global comparison between fluvoxamine and maprotiline revealed that the group of patients treated with fluvoxamine had a significantly higher efficiency index (CGI) than the maprotiline group; fluvoxamine was rated to be tolerated excellently in 70% of the patients whereas this percentage was only 43% in the maprotiline group. There was also significantly more vertigo and dry mouth in the maprotiline group whereas the fluvoxamine group was rated to have significantly more sleep disturbances during the trial.

Adult↗
PubMed1988

Nocturnal TSH and prolactin secretion during sleep deprivation and prediction of antidepressant response in patients with major depression.

In order to test the hypothesis that changes in the hypothalamic-pituitary axis during sleep deprivation are related to the antidepressant effects of this procedure, we measured thyroid-stimulating hormone (TSH) and prolactin levels in 32 depressed patients at 2:00 AM during a night before, during, and after total sleep deprivation (TSD). TSH levels increased significantly (p less than 0.05) during TSD, and prolactin levels decreased significantly (p less than 0.0001). When we divided the patients into responder and nonresponder groups based on a 30% reduction in the Hamilton Rating Scale, there was no difference between the two groups in their hormone levels on the baseline, TSD, or recovery nights. Changes in prolactin or TSH were not correlated with clinical improvement when the two groups were considered together or in the responder/nonresponder groups separately. Baseline values of both hormones were significantly (p less than 0.01) correlated with their respective levels during TSD and recovery sleep. These findings indicate that the relative levels of nocturnal TSH and prolactin are stable even within acutely depressed individuals and that changes in their levels are not related to the clinical response to sleep deprivation.

Adult↗