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A P Machado

Publications and source records attributed to A P Machado.

7 recordsLinked to original sources
PubMed1999

Tobacco smoking among Portuguese high-school students.

The aim of this study was to evaluate the prevalence, behavioural patterns, and determinants of smoking among a large sample of high-school students from Porto, the second largest city in Portugal, information on sociodemographic characteristics and personal history of tobacco, alcohol, coffee, and illicit drug use was obtained from 2974 students, aged 12-19 years (48.7% female, 51.3% male), using an anonymous self-administered questionnaire. Crude and adjusted odds ratios (OR) were calculated by logistic regression analysis to estimate the association between smoking and the characteristics evaluated. Overall, 35.8% students had never smoked, 39.4% had tried it ("experimental" smokers) but were not smokers, 3.3% were former smokers, 6.6% occasional smokers, and 14.9% regular smokers. The mean age for starting smoking was 13.4 +/- 2.1 years for males and 13.4 +/- 1.6 years for females. The prevalence of current smoking was higher among males than females, but the difference was not significant. Male students were significantly more likely to smoke more cigarettes per day than were females. The prevalence of smoking was significantly associated with the following variables: being aged > 12 years; having parents who had attended school for < 4 years; having a mother (OR = 1.88), siblings (OR = 1.96) or friends (OR = 1.75) who smoked; low academic performance (OR = 1.74 for one or two failures and OR = 2.27 for more than two failures at school); and consumption of coffee (OR = 2.90), alcohol (OR = 3.53), or illicit drugs (OR = 6.69). The prevalence of smoking among adolescents increased with age. There is therefore a need for school-based tobacco prevention programmes which also deal with family influences on smoking.

Adolescent↗
PubMed1995

[Nitric oxide-dependent endogenous and exogenous vasodilators. The mechanism of action of nitrates].

The concept of endothelium-dependent vasodilation was developed after the discovery in 1980 of the endothelium-derived relaxing factor (EDRF) by Furchtgott and Zawadzki. In 1987 Furchgott and Ignarro identified the EDRF with nitric oxide. In the same year Moncada and coworkers demonstrated that the liberation of nitric oxide by endothelial cells was responsible by the biologic activity of EDRF. Nitric oxide is the endogenous mediator responsible by the endothelium-dependent vasodilation and can be considered the endogenous nitrovasodilator. But nitric oxide has a more complex spectrum of action, because it participates in the regulation of platelet activity and preservation of the normal structure of the vessel wall. Nitric oxide is also the terminal product of the biotransformation of therapeutic nitrates responsible by guanylate cyclase activation. Nitrates can be classified as endothelium non dependent vasodilators because some of them release spontaneously nitric oxide from their metabolites, and others are biotransformed to nitric oxide in vascular smooth muscle cells.

Arteriosclerosis↗
PubMed1995

[Mother-child transmission of immunoglobulins G].

The placental transfer of immunoglobulins is made by active transport and only IgG class of immunoglobulins is transferred. In a full-term gestation IgG concentration is usually higher in the cord serum than in the mother serum. It has been shown that the ratio of cord/maternal IgG is higher when maternal IgG values are low. A series of 44 mother-child pairs from the north of Portugal were studied. Quantitative determination of IgG in all sera was made by single radial immunodiffusion and results were expressed in milligrams/deciliter (mg/dl). In the first 48 hours after delivery, mothers were interviewed and clinical, social and demographic data were collected. In 35 pairs, cord IgG exceeded the corresponding maternal concentration. The ratio of cord/maternal IgG ranged from 0.75 to 2.86 (mean 1.27). From all studied variables only maternal IgG concentration and age were correlated with that ratio. Transplacental concentration (ratio of cord/maternal IgG) was higher for lower levels of maternal IgG. Significant contribution of maternal age did not stand when a woman with extreme values of IgG and age was withdrawn from the analysis. Values found for this series of Portuguese mother-child pairs were similar to those found for other caucasian populations and are in agreement with current proposed models for placental transfer of IgG.

Adolescent↗
PubMed1994

Insights into the role of thromboxane A2 and serotonin in the pathogenesis of unstable angina.

New research about platelet and endothelial functions is allowing us to better understand the pathogenesis of myocardial ischemic episodes in patients with unstable angina, creating new perspectives for the rational utilization of therapies. In patients with unstable angina, the episodes of symptomatic and silent ischemia are caused by repeated reductions of coronary blood flow. They are the result of the mechanical effect of the growing thrombus, which causes intermittent episodes of partial obstruction of the arterial lumen, in association with vasoconstriction at the stenotic site and dependent coronary arterial bed, produced by the cyclic release of platelet derived vasoactive products, namely thromboxane A2 and serotonin. Several studies, many of them in animal models of thrombosis, suggest that serotonin and thromboxane A2 are mediators of platelet aggregation, adynamic obstruction and coronary artery thrombosis. Because they cause coronary cyclic flow reductions, they are implicated in the pathogenesis of myocardial ischemic episodes during unstable angina. Drugs that interfere with the arachidonate pathway, and the 5-HT2-receptor antagonists, have been proven to decrease or abolish coronary cyclic flow variations in animal models and man. However, further studies should be done to test the hypothesis that the association of a 5-HT2-receptor antagonist with aspirin may contribute to decrease myocardial ischemia and prevent coronary occlusion in patients with unstable angina. Continuous Holter monitoring during the first week after admission in the hospital should be a good method to evaluate the eventual efficacy of this new class of drugs in abolishing or decreasing the frequency, intensity and duration of myocardial ischemic episodes in patients with unstable angina. The central role of serotonin in the pathogenesis of thrombotic events, and the presumed preventive effect of ketanserin, were the bases of a national multicenter pilot controlled study designed to evaluate the safety and efficacy of ketanserin plus aspirin in the secondary prevention of patients with unstable angina and non-Q wave myocardial infarction (KATUA Trial).

Angina, Unstable↗
PubMed1989

[Comparison of Holter electrocardiography and thallium 201 scintigraphy in the detection of myocardial ischemia].

OBJECTIVE OF THE STUDY: To compare ischemic changes (I) detected by Holter ECG (H ECG) to the myocardial perfusion defects found in 201 TI myocardial perfusion scintigraphy. DESIGN: 201 TI exercise test was made during the performance of a 24 hours H ECG. The validation of ST segment changes detected by H ECG during the exercise test was made on basis of reversible myocardial perfusion defects (RPD) detected on 201 TL and a relation between ST segment changes detected during the remaining 24 hours recording period and 201 TI (TI) RPD was established. SETTING: The patients (pt) included in the study have come from Cardiology and Heart Surgery Clinics of a Central teaching hospital. MATERIAL AND METHODS: 20 pt with a high coronary artery disease prevalence have been submitted to a two lead (V5 and aVF) 24 hour H ECG during which they have performed a symptom limited bicycle exercise test followed by an injection of 201 TI with acquisition 5 minutes later. Ischemic episodes detected on H ECG were quantified and their relation with heart rate and symptoms was established. As far as 201 TI studies are concerned the fixed and reversible perfusion defects as well as their location were evaluated. RESULTS: 1. H ECG: 6 pt (30%) presented ST changes on H ECG during the exercise test and a total of 9 pt (45%) had ST changes during exercise and during the remaining period of H ECG. 2. TI: 19 pt presented perfusion defects images (fixed in 7, reversible in 14, both kinds of defects in 7). 3. H ECG validation: H ECG during exercise presented I in 6 out of 14 pt with RPD on TI (sensitivity = 43%). Six of these 8 pt, with negative H and positive TI, had a chronic myocardial infarction. All the 6 pt with negative TI had negative H ECG (specificity = 100%). 4. H ECG TI comparison: 7 (50%) of the 14 pt with RPD had ST changes on 24 hrs H ECG. Seven of 11 pt with negative H ECG had RPD in TI. Two pt with negative TI had positive H ECG. These 2 pt had during H ECG a higher heart rate (HR) than the HR recorded during the exercise test. CONCLUSIONS: 1. In pt with known CAD, TI has a high sensitivity and specificity to show perfusion defects. 2. Considering TI as gold standard, H ECG showed to be a useful method to detect I in the studied population (sens. = 43%; spec. = 100%). 3. H ECG revealed to be an important diagnostic tool in detecting additional I episodes beyond the ones recorded during TI exercise test.

Adult↗
PubMedDate not supplied

[Craniofacial pain].

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Diagnosis, Differential↗