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Biomedical subjects

S A Silveira

Publications and source records attributed to S A Silveira.

13 recordsLinked to original sources
PubMed1994

[Mitral valve prolapse and cusp elasticity].

PURPOSE: To verify if systolic bulging of floppy mitral cusps can to elastic behavior of their myxomatous collagen tissue. METHODS: Five hearts with floppy mitral valves obtained from autopsies were distended with air (20 to 250 mmHg) through a catheter connected to the left ventricle. It was observed if some area of the atrial surface of the coapted cusps showed variable bulging according to the variation of air injection pressures. Molding of those surfaces (gypsum) allowed the same kind of analysis by other four researches. It was analyzed the cut surfaces of these radially sectioned molds. Lately, isolated tendinae chords were submitted to repeated tractions and observed if they exhibited elastic behavior. Histological study defined the presence of collagen myxomatous degeneration and quantified the amount of elastic tissue. RESULTS: In no case it was detected elastic bulding of mitral cusps. Cut surfaces of the molds confirmed that no increment of the prominent areas occurred, even in those regions with extensive, histologically confirmed, myxomatous substitution of the native collagen tissue. CONCLUSION: Increment of the degree of mitral bulging occurring during ventricular systole can not be ascertained to cusp elasticity but probably to papilar muscle traction.

Elasticity↗
PubMed1993

[Relationship between volume reduction of the left ventricle and the increase of mitral valve prolapse. An experimental study in dogs].

PURPOSE: To verify whether accentuated reductions of left ventricular volume lead to mitral valve prolapse. METHODS: Seven mongrel dogs were bled through the internal jugular vein, the systolic systemic pressure being kept between 100 and 140 mmHg by means of continuous infusion of dopamine; the inferior vena cava vein, in tree other dogs, was partially obstructed for 4 to 6 seconds; epicardial echocardiography was carried out in all cases. RESULTS: Reductions of volemia were about 50% of the estimated total blood volume. Systolic internal diameter of left ventricle decreased about 25% and systolic ostial diameter, about 12.5%. Three out of seven died suddenly from arrhythmia before one has reached a significant decrease in total blood volume; one showed momentary mitral valve prolapse, during a period of hypotension; however, this prolapse disappeared completely when systemic blood pressure was restored by increasing the dopamine dosage; one dog had slight systolic displacement of the anterior cusp toward left atrium (0.5mm) and the last two showed no change; one out of 3 dogs submitted to partial constriction of inferior vena cava had systolic displacement of anterior cusp of 1mm; in one case there was an equivalent degree of displacement of the anterior cusp toward the left ventricle and in the last one no change was detected. In all dogs there was a change in the dynamics of mitral valve closure: with accentuated reduction of left ventricular volume the posterior cusp became less mobile, the anterior cusp being the principal responsible for the systolic ostial occlusion. CONCLUSION: Accentuated reduction of dog's left ventricular volume does not, necessarily, cause mitral valve prolapse but only slight displacement of the anterior cusp toward the left atrium in some animals or no displacement at all.

Animals↗
PubMed1993

[Necropsy study of the mitral valve according to 5 different echocardiographic planes].

PURPOSE: To study, in anatomic specimens, the regions of the mitral valve transected by the parasternal long axis, the apical five chamber, the apical four chamber, the apical two chamber and the left ventricle apical long axis echocardiographic views. METHODS: 15 patients' hearts, after fixation through intra-ventricular injection of formalin, were cut according to the five above referred echocardiographic views. RESULTS: Only the apical five chamber view studied adequately the most anterior regions of both mitral cusps. The apical four chamber and the parasternal long axis views examine the most posterior segments of the mitral valve. Heart sections made according to the apical two chamber view are not adequate to study both cusps on a anatomo-pathologic view. The left ventricle apical long axis is the one which better defines the length of both cusps. CONCLUSIONS: Its necessary to know precisely the regions of the mitral valve sectioned by different longitudinal echocardiographic views in order to visualize through that method localized mitral valve prolapse.

Cadaver↗
PubMed1991

[Necropsy study of the mitral valve transected according to five echocardiographic planes].

PURPOSE: To study, in anatomic specimens, the regions of the mitral valve transected by the parasternal long axis, the apical 5 chamber, the apical 4 chamber, the apical 2 chamber and the left ventricle apical long axis echocardiographic views. METHODS: 15 patients' hearts, after fixation through intra-ventricular injection of formalin, were cut according to the five above referred echocardiographic views. RESULTS: Only the apical 5 chamber view studied adequately the most anterior regions of both mitral cusps. The apical 4 chamber and the parasternal long axis views examine the most posterior segments of the mitral valve. Heart sections made according to the apical 2 chamber view are not adequate to study both cusps on a anatomo-pathologic view. The left ventricle apical long axis is the one which better defines the length of both cusps. CONCLUSION: Its necessary to know precisely the regions of the mitral valve sectioned by different longitudinal echocardiographic views in order to visualize through that method localized mitral valve prolapse.

Autopsy↗
PubMed1989

[Parasitism of the vena cava and adrenal veins in chronic chagasic patients].

The occurrence of nest of trypanosoma cruzi in the smooth muscle cells of the central veins of the adrenal glands and the inferior vena cava was studied in 21 chronic Chagas' patients, by serial sections. Nine patients presented parasites in the adrenal veins, with a total of 24 nests, and only one nest was found in the inferior vena cava. The area of muscular tissue examined was of 2944.3 mm2 for the adrenal veins and of 47808.6 mm2 for the vena cava, giving a relation of 0.815 nests/100 mm2 for the adrenal vein and of 0.002 for the vena cava. Thus the smooth muscle of the adrenal vein was 407 times more parasited than the muscular wall of the inferior vena cava. This higher parasitism of the adrenal vein by trypanosoma cruzi in chronic Chagas' disease may be determined by its greater corticosteroid concentration, which can reduce the anti-trypanosomal defenses.

Adrenal Glands↗
PubMedDate not supplied

Possible role of an adrenal parasite reservoir in the pathogenesis of chronic Trypanosoma cruzi myocarditis.

The possible contribution of parasitism of the central vein of the adrenal gland (CVAG) to chronic Trypanosoma cruzi myocarditis was assayed by comparing the occurrence of nests of amastigotes in the left ventricular myocardium (LVM) and determining the number and extent of areas of focal leucocyte exudate (FLE) in Chagas disease patients with and without CVAG parasitism. The frequency of occurrence of T. cruzi nests in the LVM, as well as the FLE number and area, were greater among patients with CVAG parasitism. We therefore suggest that CVAG parasitism plays a role in the onset and intensity of chronic T. cruzi myocarditis.

Adrenal Glands↗
PubMedDate not supplied

[Comparison of parasitology of the central vein of the adrenal gland and the other tissues in chronic chagas disease].

By morphological and morphometric analyses of serial sections the occurrence of T. cruzi nests in the central vein and in the parenchyma of adrenal glands, in the left ventricular wall and in the inferior vena cava wall in chronic Chagasic patients was studied. Of 36 cases 50% showed parasites in the adrenal central vein wall (total 29 nests), 3.1% showed parasites in the vena caval wall (only I nest) and 16.8% we found parasites in the myocardiocytes (total 23 nests). The density of parasites measured in the nests for each 100mm2 of the tissue examined, was 0.585 for the adrenal vein, 0.001 for the vena cava and 0.01 for the myocardium. No nest was found in 269103.1mm2 of adrenal parenchyma. Although the central vein area examined was smaller, it showed the largest frequency of T. cruzi nests. Since a basic difference between these tissues is the great quantity of corticoids in the blood of the adrenal central vein, this prevalence may be because of this hormonal ambient, which with its immunosuppressor and anti-inflammatory effects could help T. cruzi survival.

Adrenal Glands↗
PubMedDate not supplied

[Malnutrition and hypovitaminosis A in AIDS patients].

Anthropometric measurements and biochemical determinations were performed on HIV-infected individuals and on patients with AIDS from the Ribeirão Preto region, SP, Brazil, in order to evaluate their nutritional and vitamin A status. Plasma retinol was measured by HPLC, and hepatic vitamin A stores were evaluated by the relative dose response (RDR) test. Patients with AIDS presented significant undernutrition, with more marked alterations in the body fat compartment and a relative preservation of the parameters related to muscle mass (pattern of malnutrition predominantly of the marasmus type). Plasma retinol values below 1.05 mumol/L were observed in 25% of the patients with AIDS and in 17.3% of HIV-infected patients and RDR values indicating low body stores of vitamin A were detected in 28% of the subjects. There was no correlation between serum retinol levels and CD4 lymphocyte counts, clinical diagnosis of AIDS, low BMI or AFI. On the other hand, hypovitaminosis A status was associated with low BMI.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

[Survival and infectious processes in pacients with AIDS: analysis based on initial serum vitamin A levels].

Patients with Aids (n = 39) were followed up for a maximum period of 36 weeks, after which the types and topographies of infectious complications presented and patient survival were analyzed and correlated with the vitamin A levels presented by the patients at the beginning of clinical follow-up. Twenty-one (53,8%) patients presented serum retinol levels below 1.6 micromol/L, 12 (57%) of whom had values lower than 1.05 micromol/L. There was no correlation between low serum vitamin A levels and the types or topographies of the infectious complications that occurred during the follow-up period. Although mean survival at the end of the 36 months follow-up period was similar for the two groups, patients with retinol deficiency presented a lower probability of survival during the first 24 months of follow-up compared to patients without hypovitaminosis A (8.44 x 1.42 months; p = 0.003).

AIDS-Related Opportunistic Infections↗