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Biomedical subjects

D S Amorim

Publications and source records attributed to D S Amorim.

At least 19 recordsLinked to original sources
PubMed2005

Xylanases from fungi: properties and industrial applications.

Xylan is the principal type of hemicellulose. It is a linear polymer of beta-D-xylopyranosyl units linked by (1-4) glycosidic bonds. In nature, the polysaccharide backbone may be added to 4-O-methyl-alpha-D-glucuronopyranosyl units, acetyl groups, alpha-L-arabinofuranosyl, etc., in variable proportions. An enzymatic complex is responsible for the hydrolysis of xylan, but the main enzymes involved are endo-1,4-beta-xylanase and beta-xylosidase. These enzymes are produced by fungi, bacteria, yeast, marine algae, protozoans, snails, crustaceans, insect, seeds, etc., but the principal commercial source is filamentous fungi. Recently, there has been much industrial interest in xylan and its hydrolytic enzymatic complex, as a supplement in animal feed, for the manufacture of bread, food and drinks, textiles, bleaching of cellulose pulp, ethanol and xylitol production. This review describes some properties of xylan and its metabolism, as well as the biochemical properties of xylanases and their commercial applications.

Endo-1,4-beta Xylanases↗
PubMed1991

High output failure in patients with peripartum cardiomyopathy: a comparative study with dilated cardiomyopathy.

Although few studies have reported on relatively preserved ventricular function in patient with peripartum cardiomyopathy, the condition is usually believed to have the typical low-output congestive hemodynamic pattern of the dilated congestive cardiomyopathies. Two groups of patients, 14 with peripartum cardiomyopathy and 12 with dilated congestive cardiomyopathy who were matched for gender and age, were studied. They had normal blood pressure and similar New York Heart Association functional class, nutritional status, thyroid function and routine laboratory evaluation. All patients were catheterized during stable in-hospital compensation of heart failure, which was achieved by bed rest, sodium restriction, and administration of digoxin and diuretics long (more than 3 months) after delivery. Significant differences (p less than 0.05) between patients with peripartum cardiomyopathy and those with dilated congestive cardiomyopathy were observed in regard to: (1) cardiac index: 3.34 +/- 1.36 L/min/m2 versus 2.24 +/- 0.72 L/min/m2, (2) systemic vascular resistance: 1713 +/- 567 dynes.sec.cm-5 versus 2194 +/- 603 dynes.sec.cm-5, (3) right ventricular stroke work index: 8.6 +/- 4.2 g.M/m2 versus 14.8 +/- 8.2 g.M/m2 in the peripartum cardiomyopathy and the dilated congestive cardiomyopathy groups, respectively. Three of the patients with peripartum cardiomyopathy had resting cardiac index values that were even higher than the normal upper limit for our laboratory (4.5 L/min/m2): 4.80, 5.70, and 5.63 L/min/m2. They also had nearly normal left ventricular ejection fractions: 0.68, 0.41, and 0.51, respectively. These results indicate that, unlike the common dilated cardiomyopathy, the hemodynamic pattern in patients with peripartum cardiomyopathy is not homogeneous, and some patients have high-output failure and near normal left ventricular function.

Adult↗
PubMed1990

Age-associated changes in the number of neurons in the right atrium.

1. It has been demonstrated that chronotropic responses differ in healthy elderly subjects compared to those in younger normal adults. To evaluate the involvement of the autonomic nervous system, we determined the number of neurons in right atrial strips from six elderly individuals (aged 77 +/- 3.4 years) five of whom had died as the result of extracardiac causes, and from younger adult controls (aged 44.0 +/- 6.0 years) who had died in traffic accidents. 2. There was a significant reduction in the number of neurons of the group of hearts from the elderly (3587 +/- 445, mean +/- SEM) compared with the control group (6412 +/- 377) of five hearts from younger adults (P less than 0.001). 3. It is suggested that this decrease in the number of neurons contributes to the reduced chronotropic responses in the aged. The mechanisms responsible for the neuronal depopulation was not determined.

Adult↗
PubMed1987

Use of isometric exercise to demonstrate cardiac parasympathetic impairment in the digestive form of Chagas' disease.

Standardized handgrip at 100% of maximal voluntary capacity was used to study heart rate responses to isometric exercise in patients with the digestive form of Chagas' disease. The chronotropic responses of the group were significantly lower (P less than 0.001) than those exhibited by control subjects, and comparable to those observed in a group of cardiac chagasic patients. These results show that severe impairment of autonomic control of the heart may occur in chagasic patients apparently having only digestive tract involvement.

Blood Pressure↗
PubMed1986

Effect of parasympathetic impairment on the haemodynamic response to handgrip in Chagas's heart disease.

Haemodynamic responses to sustained isometric exercise (handgrip at 30% of maximum voluntary capacity) were studied in 10 patients with Chagas's cardiopathy without previous or current heart failure. Five of the patients (group 1) had profound impairment of parasympathetic control of heart rate. They had no tachycardia in response to intravenous administration of atropine and no bradycardia during phase IV of the Valsalva manoeuvre. The other five (group 2) showed normal vagal regulation of heart rate, as judged by chronotropic responses to these tests. The heart rate change (mean (SD] elicited by the handgrip test was significantly lower in group 1 (from 93.0 (14.1) to 95.0 (16.7) beats/min) than in group 2 (from 78.2 (15.8) to 92.8 (18.1) beats/min). Pressor responses to handgrip were of similar magnitude (from 91.6 (7.8) to 109.0 (8.0) mm Hg in group 1 and from 88.6 (11.9) to 106.8 (20.9) mm Hg in group 2). In both groups no significant change in stroke index was detected during handgrip. Cardiac index increased during handgrip from 4.0 (1.2) to 4.8 (1.3) 1/min/m2 in group 2, but there was no significant change in group 1 (from 4.9 (0.7) to 4.8 (1.1) 1/min/m2). Changes in calculated systemic vascular resistance were significantly higher in group 1 (from 934 (175) to 1176 (383) dyn s cm-5) than in group 2 (from 1109 (404) to 1112 (424). This study shows that parasympathetic impairment adversely influences the haemodynamic pattern of response to isometric exercise in patients with Chagas's heart disease. In such conditions, the pressor response to handgrip is predominantly mediated by an increase in systemic vascular resistance rather than an increase in cardiac output.

Adult↗
PubMed1985

Current status of myocarditis and endomyocardial biopsy in Brazil.

The results presented here show the inadequate attention that has been paid to myocarditis as a clinical entity and to employing endomyocardial biopsy examination as a valuable tool for diagnostic and research purposes. The results must be interpreted with caution, as otherwise false conclusions may be drawn as far as the epidemiological profile of cardiovascular diseases in Brazil is concerned. The data are likely to be influenced by the striking regional differences in development which are reflected in the scientific output. The high incidence of positive serology in patients in endemic areas of Trypanosoma cruzi infection is a further complication. It is possible that Chagas' disease may be overestimated clinically, decreasing therefore the interest in clarifying diseases with comparable clinical features. Myocarditis (excluding a protozoal etiology) and dilated (congestive) cardiomyopathy may serve as examples. Considering these various points, together with the complex and multi-disciplinary requirements of obtaining and interpreting catheter biopsies of the heart explains the limited clinical application of this technique in Brazil.

Biopsy↗
PubMed1985

Chagas' heart disease: experimental models.

An experimental model embodies an evaluation procedure that helps the investigator to choose between possible alternatives. In this paper, consideration is given to a variety of aspects related to the host-parasite relationship in Trypanosoma cruzi infection and disease. Although several animal species have been used, there is still a lack of consistent experimental studies. A few examples of investigations mainly in dogs, monkeys, and rabbits are briefly described, showing the diversity of methodological approaches and, therefore, the difficulty experienced in comparing results and interpretations. Emphasis was given to the need for a suitable model presenting all possible stage of the infection as seen in man, as well as the functional and organic disorders commonly seen in this disease. The alterations of the autonomic nervous system involving the heart and other organs in Chagas' disease was stressed.

Acute Disease↗
PubMed1985

Subtle cardiac autonomic impairment in Chagas' disease detected by baroreflex sensitivity testing.

The sensitivity of baroreflex bradycardia and tachycardia was determined in fourteen patients with Chagas' disease who seemed to be normal with respect to cardiac autonomic control evaluated in terms of heart rate responses to the conventional atropinization and Valsalva maneuver tests. Eleven normal subjects were studied for comparison. Baroreflex sensitivity was determined by relating the beat-to-beat pulse intervals to systolic pressure values during transient phenylephrine- and amyl nitrite-induced changes in arterial pressure. Chagasic patients showed mean bradycardia sensitivity (10.1 +/- 1.3 ms/mmHg) which was significantly lower than that obtained for the control group (16.7 +/- 2.1 ms/mmHg). When only the subgroup of ten patients with overt disease (cardiac and/or digestive form) was considered, the value fell to 8.6 +/- 1.4 ms/mmHg. The lowest individual values were exhibited by the majority of patients with exclusive cardiac or associated cardiac and digestive disease. Patients with only digestive disease or without overt disease (indeterminate form) had values within the normal range. Tachycardia sensitivity (6.3 +/- 0.8 ms/mmHg) was similar to that obtained for the control group (6.6 +/- 1.0 ms/mmHg). Only one patient with associated disease presented a reduced value. These data show that the estimation of baroreflex sensitivity can be used to identify impaired cardiac autonomic control in chronic Chagas' disease not detectable by conventional tests. The reduced baroreflex sensitivity appears to be due to the subtle impairment of the parasympathetic influence on the heart. Furthermore, there is a relationship between the degree of baroreflex sensitivity and the clinical form of organic involvement in Chagas' disease.

Adult↗
PubMed1983

Intraoperative measurement of the orifice area in patients with mitral valve stenosis.

This study was carried out in ten patients in order to compare results of mitral valve area evaluated by a new intraoperative technique and those provided by conventional hemodynamic methods. The results obtained correlated very well (r = 0.95) with values calculated by the Gorlin formula. Paired data checking were closer than 0.3 cm2 in all but one of patients with moderately severe mitral stenosis. It is concluded that the method for intraoperative measurement of the mitral valve area is simple, safe and reliable.

Adolescent↗
PubMed1982

Assessment of heart neurons in dilated (congestive) cardiomyopathy.

Pathological studies in seven hearts from patients with dilated cardiomyopathy have shown that the number of neurons is significantly reduced in these compared with five hearts from normal subjects. The number of ganglion cells was counted in a strip of right atrial wall between the venae cavae and sectioned serially. The mechanism responsible for the neuronal depopulation in this type of cardiomyopathy could not be determined. Previous viral infection may be causally related. Three hearts of patients suffering from chronic Chagas's heart disease were also studied. Depopulation of neurons was most severe in the hearts with Chagas's disease and less severe in those with dilated cardiomyopathy, though neurons were still significantly reduced in number in the latter compared with normal controls. Despite the lack of a specific, definite cause for the depopulation of neurons, physiological evidence of parasympathetic impairment in patients with dilated cardiomyopathy is in agreement with the pathological findings. It is suggested that on the basis of our findings neuronal depopulation in some patients with dilated cardiomyopathy may be of aetiological significance.

Adult↗
PubMed1982

Chagas' heart disease as an experimental model for studies of cardiac autonomic function in man.

Patients presented here include apparently healthy persons who had diagnostic evidence of chronic cardiac Chagas' disease in the form of a positive complement-fixation test and an abnormal electrocardiogram. They had never been in heart failure. All were examined for autonomic cardiac function. Normal persons served as controls. Patients with Chagas' disease with sole involvement of hollow viscera were also included. In patients with cardiac Chagas' disease, failure of the heart rate to increase after administration of atropine and greatly reduced reflex changes in cardiac rate are believed to be a functional disorder related to degeneration of the neuronal supply to the sinoatrial region of the heart. It is concluded that Chagas' disease is a model of spontaneous denervation of the heart which may be used for the assessment of autonomic control of cardiac function in man.

Adult↗
PubMed1981

Is there autonomic impairment in congestive (dilated) cardiomyopathy?

Autonomic function was investigated in patients with congestive (dilated) cardiomyopathy and compared with that in controls. Heart-rate and blood-pressure were recorded during physiological and pharmacological interventions and plasma noradrenaline concentration was measured at rest and when the physiological interventions produced a peak response. The results indicate that even at an early (pre-failure) stage of the disease parasympathetic function is impaired but no significant increase in sympathetic activity occurs at this stage.

Autonomic Nervous System↗