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Biomedical subjects

S Chetty

Publications and source records attributed to S Chetty.

14 recordsLinked to original sources
PubMed1998

Sympathetic and platelet adrenergic activity and salt sensitivity: an experimental study.

The objective of the study was to evaluate the advanced hypothesis that genetically predisposed salt-sensitivity contributes to an increased adrenergic susceptibility and platelet activity and both these factors play a role in the pathogenesis of hypertension in a Dahl rat model. The results showed: i) Dahl salt-sensitive rats (DS) gradually develop a diastolic hypertension by the end of 3 months of age, in spite of the diet they are fed. Low-Na diet (0.5% NaCl) does not prevent hypertension but delays its development. High-Na diet (8%) exacerbates their hypertension. ii) After 2 months of Na-loading, DS rats expressed significantly increased sodium and water retention and increased plasma volume by 15%, compared with 2.8% in Dahl salt-resistant (DR) rats on high-Na diet. iii) The increased activity of the sympathetic nervous system (SNS) in DS rats paralleled the development of hypertension and was stimulated by Na-loading. It was assessed by their catecholamines status and heart rate changes. iv) Platelet activity of DS rats was increased as reflected in collagen-induced nonstimulated and adrenaline-stimulated aggregation, and an increased plasma T x B2/6-keto PGF1 alpha ratio. Na-loading further increased platelet activity. v) Both DR and DS rat platelets displayed alpha 2-adrenoceptors (A2) of low binding capacity (Bmax 25 and 35 fmol/mg protein, respectively) and low affinity (KD 5.6 nM for both groups), suggesting that platelet alpha 2 adrenoceptors in this strain of rats might not play a significant biological role in their increased platelet activity. The fact that platelet alpha 2-adrenoceptors do not define the stimulation of SNS in DS rat do not exclude their participation in development of salt-dependent hypertension, since a genetic defect(s) of these ubiquitous receptors (brain, kidney, blood vessels) could still contribute to the pathogenesis of the disease.

Animals↗
PubMed1998

Regulation of renal alpha 2-adrenoceptor activity in Dahl salt-sensitive rats by dietary sodium changes.

The objective of the study was to evaluate the concept that genetically predisposed salt-sensitivity contributes to an increased adrenergic susceptibility and renal alpha 2-adrenoceptor (A2) abnormality in Dahl salt-sensitive hypertensive rats. The results showed: i) After 2 months of Na-loading (8% NaCl) Dahl salt-sensitive (DSS) rats expressed increased sodium and water retention which paralleled gradual development of diastolic hypertension. Low Na diet (0.5% NaCl) does not prevent hypertension but delays its development. ii) The increased activity of the sympathetic nervous system (SNS), in DSS rats corresponded to the development of hypertension and was stimulated by Na-loading. It was assessed by plasma catecholamine levels and heart rate changes. iii) The increased density of renal A2 by 29% was upregulated by high sodium diet, and coupled with increased norepinephrine level by 53%, only in DSS but not in DSR rats. iv) No strain renal A2 and epinephrine differences between DSS and DSR were found in weanling, prehypertensive rats, or in the adult DSS and DSR on low Na diet. By mediating an enhanced receptor-coupled response, such as increased proximal tubular sodium reabsorption during sodium loading, a genetic abnormality of renal alpha 2-adrenoceptors may contribute to some of the pathophysiologic derangements leading to hypertension in Dahl salt-sensitive rats.

Animals↗
PubMed1997

Cyclin D1 and retinoblastoma protein expression in oesophageal squamous cell carcinoma.

AIMS: To assess the immunoexpression of cyclin D1 and retinoblastoma in a cohort of oesophageal squamous cell carcinoma cases from South Africa to see whether there is a relation between these two proteins. In addition, protein expression was correlated with clinicopathological features. METHODS: Fifty biopsies and 30 oesophagectomy specimens were immunostained with commercially available antibodies to cyclin D1 and retinoblastoma proteins, following microwave antigen retrieval. RESULTS: Twenty three of the 80 cases (29%) showed cyclin D1 protein expression. However, only five cases had > 50% of the tumour cells displaying immunopositivity. Three of the four cases with lymph node spread were cyclin D1 positive in the primary tumour and the metastasis. Fifty three cases were immunoreactive with the antiretinoblastoma antibody; 29 of these cases showing > 50% of cells with immunolabelling. Of the 23 cyclin D1 positive cases, 18 were also retinoblastoma positive. No correlation was observed between cyclin D1 and retinoblastoma protein expression and age, sex, race, or histological grade. CONCLUSIONS: Cyclin D1 is expressed in a minority of cases of oesophageal squamous carcinomas from South Africa. However, three of four cases with lymph node spread were cyclin D1 positive, thus indicating that cyclin D1 positive tumours may have a greater propensity for spread. In addition, 18 of 23 cyclin D1 positive cases also expressed retinoblastoma protein. These findings suggest a possible relation between cyclin D1 and retinoblastoma proteins in a proportion of cases of oesophageal squamous.

Adult↗
PubMed1993

Percutaneous balloon mitral valvotomy in pregnant patients with tight pliable mitral stenosis.

Percutaneous balloon mitral valvotomy was attempted in severely symptomatic (New York Heart Association class III or IV) pregnant patients (mean age 30 years) with tight mitral stenosis. Nineteen patients were pregnant (mean gestation 30 weeks, range 26 to 34) and one patient was in the immediate postpartum period. All patients had undergone a trial of diuretic therapy and 16 were also taking atenolol. Percutaneous valvotomy was performed with the Inoue catheter (18 patients) or the Schneider-Medintag bifoil (2 x 19 mm) balloon catheter (2 patients). The fluoroscopy time was 9.2 +/- 3.4 minutes. After percutaneous valvotomy the mean mitral gradient decreased from 17.9 +/- 6.2 to 5.9 +/- 2.4 mm Hg (p < 0.001). The mitral valve area (pressure half time) increased from 0.8 +/- 0.2 to 1.7 +/- 0.2 cm2 (p < 0.001). These hemodynamic changes were accompanied by immediate symptomatic improvement by at least one New York Heart Association functional grade in all patients. Moderate (3+) mitral regurgitation developed in one patient. Eighteen patients had normal infants delivered vaginally at term without assistance, and one patient had a normal infant delivered by cesarean section at 35 weeks' gestation. We conclude that percutaneous balloon mitral valvotomy for pliable mitral stenosis in pregnancy is safe for both the mother and fetus. We recommend that it be performed in symptomatic patients with tight mitral stenosis so as to avoid hemodynamic complications in the latter stages of pregnancy.

Adult↗
PubMed1993

Balloon mitral valvotomy with a single catheter: a comparison between bifoil/trefoil and the Inoue balloon.

Results of percutaneous mitral valvotomy were compared in two groups undergoing the procedure at our institution. Group I: 100 patients having had percutaneous valvotomy with the Schneider-Medintag bifoil (2 x 19 mm) or trefoil (3 x 15 mm or 3 x 12 mm) catheters, and group II; 150 patients in whom the procedure was performed with the Inoue balloon (24-30 mm). Baseline clinical (age, gender, NYHA class and echo score) and haemodynamic variables were similar in both groups. Haemodynamic improvement occurred in both groups. Although the reduction in left atrial pressure did not differ significantly between the two groups, the increase in mitral valve area was significantly (P < 0.001) higher for group I (0.8 +/- 0.2 to 1.9 +/- 0.7 and 0.8 +/- 0.3 to 1.6 +/- 0.3 cm2 respectively for mitral area, and 22 +/- 6 to 13 +/- 5 and 21 +/- 6 to 13 +/- 5 mmHg respectively for mean left atrial pressure). The increase in cardiac output was statistically significant in group I (3.2 +/- 0.7 to 4.0 +/- 0.9 l.min-1, P < 0.05) but not in group II (3.5 +/- 2.0 to 3.7 +/- 0.9 l.min-1, ns). Inter-atrial shunting immediately after valvotomy was recorded in 19% of group I patients compared with 6% in group II (P < 0.001). The overall incidence of significant mitral regurgitation (3+ or 4+) was similar in both groups (5% and 4% respectively). However, when the stepwise dilatation technique was employed in group II, the incidence had dropped to 2.1%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Abnormal insulin receptor binding in cultured monocytes in myotonic muscular dystrophy.

Even though one of the characteristic features of myotonic dystrophy (MyD) is the high level of circulating insulin, 125I-insulin-binding data in MyD have been controversial. In the present study we utilized cultured monocytes to avoid problems of reproducibility and variability in age, and examined the affinity and binding characteristics of 125I-insulin binding in MyD patients and controls. The Bmax and mean affinity constant, Ka, were significantly lower, while the number of receptors per cell had increased in the patient group as compared to the controls. The data confirm our earlier findings that there is no primary defect in insulin receptors in MyD, and the disturbed insulin response may be due to an abnormality in the membrane environment. Since the insulin receptor is an integral membrane protein, abnormal plasma membrane lipid composition may lead to impaired lipid-protein interactions, and hence affect the binding characteristics in MyD.

Humans↗
PubMed1991

Balloon valvuloplasty versus closed commissurotomy for pliable mitral stenosis: a prospective hemodynamic study.

Closed surgical mitral valvotomy is the procedure of choice in most patients with symptomatic pliable mitral stenosis in developing countries. The procedure is efficacious and safe. Mitral valvotomy performed with a balloon has shown similar good results, with infrequent complications in selected subjects. Because there is a paucity of studies comparing the two techniques, this study was undertaken to compare the results of percutaneous balloon mitral valvuloplasty with those of closed commissurotomy as determined by catheterization studies. Forty-five patients with tight pliable mitral stenosis were randomly assigned to one of two groups: 23 patients had balloon valvuloplasty by the single catheter technique (group I) and 22 underwent closed surgical valvotomy (group II). The two groups were similar with regard to clinical and hemodynamic findings before intervention. Mitral valve area increased from 0.8 +/- 0.3 to 2.1 +/- 0.7 cm2 in group I (p less than 0.001) and from 0.7 +/- 0.2 to 1.3 +/- 0.3 cm2 in group II (p less than 0.001). Pulmonary artery pressure and pulmonary vascular resistance decreased in both groups, but these changes did not reach statistical significance in group II. Treadmill exercise time increased from 3.8 +/- 2.3 to 7.3 +/- 2.6 min in group I (p less than 0.001) and from 4 +/- 2.6 to 5.6 +/- 2.6 min in group II (p less than 0.001). There were no deaths. One patient in each group developed moderate (3+) mitral regurgitation. A small interatrial shunt (less than 1.5:1) was detected in three patients in group I immediately after the procedure.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Pulmonary hypertension in aortic regurgitation: early surgical outcome.

A review of the haemodynamic data of 139 patients with isolated, severe, chronic aortic regurgitation revealed severe pulmonary hypertension (pulmonary artery systolic pressure of greater than or equal to 60 mmHg) in 34 (24 per cent). The left ventricular end-diastolic pressure was high in all patients, suggesting that pulmonary hypertension was a consequence of severe long-standing regurgitation with ventricular dysfunction. Aortic valve replacement was performed in 69 patients, 33 of whom had normal or mildly elevated pulmonary artery systolic pressure (less than 39 mmHg; group I) and 36 of whom had moderate or markedly elevated pulmonary artery systolic pressures (less than 40 mmHg; group II). There was no difference in mortality or prevalence of post-operative complications between these two groups of patients. Furthermore, New York Heart Association (NYHA) functional class and cardiothoracic ratio were similar in both groups at the six-month assessment. The pulmonary vascular resistance fell from 4.7 +/- 3.5 to 1.5 +/- 0.8 units x m2 in 13 of 17 patients who had repeat catheterization after surgery. Pulmonary artery systolic pressure reverted to normal in 10 of these 13 patients. It is concluded that pulmonary hypertension consequent upon raised left ventricular end-diastolic pressure is common in severe aortic regurgitation, is largely reversible, and does not influence the early outcome after aortic valve replacement.

Adult↗
PubMed1990

Arrhythmias in idiopathic dilated cardiomyopathy. A preliminary study.

Idiopathic dilated cardiomyopathy is second to valvular heart disease as a cause of congestive heart failure in blacks in southern Africa. The disease has a deteriorating clinical course with high mortality. More than half these deaths are sudden and have been related to arrhythmias. In a preliminary study of 20 black patients in congestive heart failure caused by dilated cardiomyopathy, 24-hour ambulatory ECG monitoring was used to assess the prevalence, type and clinical significance of arrhythmias. Eighteen of the 20 patients (90%) had arrhythmias. Supraventricular arrhythmias were detected in 17 (85% of the total), and 18 (90%) had complex ventricular arrhythmias. Eleven (55%) had non-sustained ventricular tachycardia (VT). There was no correlation between complex ventricular arrhythmia and clinical features, resting ECG, chest radiograph or echocardiographic data. Over a 3-year period 13 patients died (65%), half these deaths being unexpected. All 13 had complex ventricular arrhythmias, and those who died suddenly had non-sustained VT. This small prospective study shows that ventricular arrhythmias are common in dilated cardiomyopathy in blacks and are frequently complex and dangerous. Sudden death is common and is more than likely to be related to VT in the presence of an already poorly functioning left ventricle.

Adolescent↗
PubMed1988

High-dose oral amoxycillin in the treatment of infective endocarditis.

Oral antibiotic therapy for infective endocarditis is not yet widely accepted. A study was undertaken to assess the efficacy of oral amoxycillin in this condition. Fifteen patients were treated with high-dose oral amoxycillin for 6 weeks. Twelve responded to treatment and remain well at 3 years. There were 3 deaths--1 at day 7 due to sudden aortic cusp rupture, and 2 late deaths due to pulmonary and cerebral embolism respectively. There was 1 relapse of streptococcal prosthetic valve endocarditis 8 weeks after oral treatment, but this responded to conventional intravenous therapy. Oral amoxycillin is effective in uncomplicated streptococcal endocarditis, and should not be used with prosthetic valve infections.

Administration, Oral↗
PubMed1980

Arrhythmia in hypertrophic cardiomyopathy: exercise and 48 hour ambulatory electrocardiographic assessment with and without beta adrenergic blocking therapy.

Submaximal treadmill exercise electrocardiography and 48 hour ambulatory electrocardiographic monitoring were performed in 30 patients with hypertrophic cardiomyopathy both with and without beta adrenergic blocking therapy. During ambulatory electrocardiographic monitoring 1 patient (3 percent) had no arrhythmia, 14 patients (46 percent) had supraventricular tachycardia or paroxysmal atrial fibrillation, 13 (43 percent) had multiform or paired ventricular extrasystoles and 8 (26 percent) had ventricular tachycardia. The frequency of these ventricular arrhythmias was almost identical with and without beta adrenergic blocking drugs (mean dose in "propranolol equivalents" 280 mg daily). With beta blocking therapy fewer patients had supraventricular tachycardia; however, the difference was not significant. During exercise testing 18 patients (60 percent) had ventricular extrasystoles and 3 patients (10 percent) had paired ventricular extrasystoles and the frequency was almost identical with and without beta adrenergic blocking therapy. No routine echocardiographic or hemodynamic measurement predicted the serious ventricular arrhythmias. It is concluded that asymptomatic ventricular arrhythmia is a common occurrence in patients with hypertrophic cardiomyopathy and its frequency is not reduced with beta adrenergic blocking therapy. Because occult arrhythmia may be the cause of sudden death it is important to detect it in these patients so that an effort can be made to improve prognosis with specific antiarrhythmic treatment.

Adrenergic beta-Antagonists↗
PubMed1976

Bilateral renal cortical necrosis: a report of 2 cases.

Two cases of renal cortical necrosis, one of which occurred after an obstetric complication (abruptio placentae) and the other after postpartum haemorrhage, are described. The diagnosis was made by percutaneous renal biopsy, intravenous pyelography and selective nephro-angiography. Immunofluorescence studies of the kidney showed no abnormality in one patient, but showed the presence of IgM in the glomerular basement membrane in the second patient. Hypotension was not observed when anuria occurred. Both patients survived. The importance of prolonged haemodialysis is stressed, since one patient was oliguric for 57 days and required intermittent haemodialysis for 5 months, while the second patient was oliguric for 17 days, required haemodialysis for 5 months and now has established hypertension.

Abruptio Placentae↗