PubMed Health⌕ Search

Biomedical subjects

R Prabhu

Publications and source records attributed to R Prabhu.

At least 37 records · Page 2Linked to original sources
PubMed1984

The intracellular content of dihydrofolate reductase: possibilities for control and implications for chemotherapy.

Intracellular levels of DHFR can be modulated by mechanisms other than gene amplification. We found that MTX itself has an effect and the important features of this mechanism are as follows: (a) Sub-saturating doses of MTX induce intracellular DHFR activity by increasing DHFR synthesis; (b) The time-dependent effect seems quite specific for DHFR and is reversible (7); (c) Elevated DHFR synthesis is accompanied by disproportionate increases in DHFR mRNA; (d) The time scale for maximum induction is appreciably longer than the cell generation time. We suggest that part of the control involved is translational and we postulate that DHFR may regulate its own biosynthesis through feedback mechanisms. It is conceivable that the induction phenomenon could affect the clinical efficacy of MTX-therapy in some instances.

Cell Line↗
PubMed1984

Polymorphic ventricular tachycardia and other complex arrhythmias in organophosphate insecticide poisoning.

Organophosphate insecticide intoxication produces endogenous acetylcholine poisoning which may precipitate complex ventricular arrhythmias, a relatively unrecognized and potentially lethal aspect of this condition. A case is described in which sinus bradycardia, A-V dissociation, idioventricular rhythms, multiform ventricular extrasystoles, and prolongation of the PR, QRS, and QT intervals were observed. Polymorphic ventricular tachycardia--a chaotic ventricular rhythm characterized by extreme variability of QRS morphology and the R-R interval--which previously has not been reported with organophosphate poisoning, was also present in our case. Metabolic and electrolyte derangements, myocardial injury, autonomic dysfunction, and asynchronous repolarization variously may be involved in the genesis of arrhythmias in organophosphate intoxication. Management of these cases should take into account the possible occurrence of conduction abnormalities and arrhythmias, including polymorphic ventricular tachycardia.

Aged↗
PubMed1983

Continuous electrocardiographic monitoring in patients with sickle-cell anemia during pain crisis.

Electrocardiographic studies in patients with sickle-cell anemia have been performed during the normal resting state with routine twelve-lead ECGs. We studied 30 patients with sickle-cell disease in acute crisis with 24-hour continuous electrocardiographic monitoring. The standard ECG demonstrated a high incidence of abnormalities, but only three patients had arrhythmias. These findings contrasted sharply with the results of continuous monitoring, during which arrhythmias were detected in 24 of 30 patients. They were fairly evenly split between atrial (60%) and ventricular (67%). Nine of the patients had "complex arrhythmias" including two with episodes of ventricular tachycardia. Seventeen patients subsequently underwent equilibrium gated-blood pool scans. Eight patients had abnormal contractility and tended to have more arrhythmias on monitoring than those with normal contractility. Thus, continuous electrocardiographic monitoring of sickle-cell patients during crisis revealed a higher incidence of arrhythmias than previously thought.

Adolescent↗
PubMed1981

Hypercalcemia and idiopathic hypertrophic subaortis stenosis.

A patient presenting with hypercalcemia was found to have idiopathic hypertrophic subaortic stenosis and phenotypic Turner's syndrome. She has 3 daughters with phenotypic Turner's syndrome. 1 with a thickened interventricular septum and a son with asymmetric septal hypertrophy without obstruction and also possibly with hypercalcemia. Chromosome-banding studies revealed a normal 46,XX karyotype with no structural defects noted. The need for further studies of the incidence of hypercalcemia in idiopathic hypertrophic subaortic stenosis and in all the aortic outflow obstruction syndromes is suggested along with parathyroid function studies.

Aged↗
PubMed1980

Lymphomatoid granulomatosis. Report of a patient with severe anemia and clubbing.

We report a 31-year-old man in whom initially localized lymphomatoid granulomatosis was diagnosed at left pneumonectomy. He had severe anemia which is rare and clubbing of the fingers and toes, a feature not previously described. Five months following surgery, disease spread to the right lung, and atypical lymphomatous transformation occurred in cervical and mediastinal lymph nodes, leading to a superior vena cava syndrome. Chemotherapy with cyclophosphamide and prednisone resulted in significant resolution initially, but ultimately, the patient had progressive axillary node enlargement and succumbed. Clinical and roentgenographic improvement and later deterioration following pneumonectomy and improvement with chemotherapy were mirrored by changes in degree of clubbing, leukocytosis, and elevation of erythrocyte sedimentation rate.

Adult↗
PubMed1979

A perfused canine right bundle branch-septal model for electrophysiological studies.

UNLABELLED: As documented in the literature, isolated ventricular muscle preparations perfused with protein-free media become edematous and deteriorate. We hypothesized that the addition of colloid oncotic pressure to the perfusion medium might affect favorably the electrical characteristics and survival of an isolated right bundle branch-septal muscle preparation perfused via the anterior septal artery. Perfusion with protein-free Tyrode solution produced edema formation and a loss of transmembrane potential of Purkinje and muscle cells within 5.9 +/- 0.40 h. Addition of bovine albumin, 4 g/100 ml, to the Tyrode solution or perfusion with horse serum greatly reduced the formation of edema. Furthermore, intact electrical activity continued for more than 9 +/- 0.31 h (P less than 0.001). The preparations showed a greater diastolic potential and action potential amplitude during perfusion than during superfusion with Tyrode solution. IN CONCLUSION: 1) a viable, perfused septal muscle preparation was developed for electrophysiological studies, and 2) colloid oncotic pressure in the perfusion medium is essential to preserve the integrity of the capillary circulation and to eliminate edema formation and tissue death.

Animals↗
PubMed1978

Diet-induced atherosclerosis and experimental hypertension in stumptail macaques (Macaca arctoides). Effects of antihypertensive drugs and a non-atherogenic diet in the evolution of lesions.

This study was carried out to determine the evolution of atherosclerotic lesions during a therapeutic period during which regression might be appreciated. We produced aortic and coronary atherosclerosis in 27 young adult stumptail macaques (Macaca arctoides) by feeding a diet supplemented with 2% cholesterol and 25% fat. Hypertension was produced by bilateral or unilateral narrowing of the renal artery. After six months of this regimen, four monkeys were killed (group 1) and 23 monkeys were divided into three groups: group 2 received unsupplemented diet; group 3 received the same diet as group 2 and drug treatment for hypertension; group 4 was continued on the atherogenic diet and received antihypertensive drug treatment. The results indicate that deleting the atherogenic diet leads to a decrease in the lipid content of the lesions and a transformation of the lipid laden atherosclerotic plaques into lipid-poor, fibro-collagenous lesions, with a decrease in the amount of coronary luminal narrowing. Partial control of systolic hypertension by antihypertensive drugs did not accelerate the involution of the atherosclerotic lesions over the relatively short period of this study. No statistically significant correlation by regression analysis was observed between the level of blood pressure elevation, the plasma renin activity, or the degree of the drug response, and the severity and extent of the atherosclerotic lesions. Furthermore, severe arterial hypertension without an atherogenic diet (group 5) produced arteriosclerosis of the aorta, and intensified branch cushions in the coronary arteries, without inducing lipid deposition in either vascular bed.

Animals↗
PubMed1977

Potential pitfalls in quantification of pericardial effusions by echocardiography.

In the echocardiographic assessment of patients with pericardial effusions, the apparent width of the echo-free space between the left ventricular posterior wall and the parietal pericardium is commonly used to estimate the amount of pericardial fluid present. In 4 patients with pericardial effusions, we showed a distinct disparity between the widths of the posterior pericardial space at different levels of the left ventricular posterior wall. In 2 of them, a 'swinging heart' appearance was recorded when the ultrasoound beam was directed caudally, but not when its direction was cephalad or less caudad. It is suggested that the left ventricle should be scanned at all possible sites to minimise potential errors in estimating the amount of a pericardial effusion.

Adult↗
PubMed1977

Echocardiographic features of second degree atrioventricular block.

Echocardiographic studies demonstrated abnormalities of motion of the pulmonary valve, the aortic root and valve, the mitral and tricuspid valves, the left ventricle, and the left atrium in two patients with second-degree atrioventricular block. During Wenckebach 3:2 atrioventricular conduction, ventricular beats exhibited alternately long and short periods of systolic opening of the pulmonary and aortic valves and alternately large and small left ventricular stroke volumes. During 4:3 and 3:2 Wenckebach atrioventricular conduction, the left ventricular stroke volume was directly proportional to the preceding end-diastolic volume. During 2:1 atrioventricular conduction, the blocked atrial contractions may produce movements of the left atrial wall, thereby revealing the true atrial rate when the blocked P waves are obscured in the electrocardiogram by their superimposition on preceding T waves.

Adolescent↗
PubMed1976

Flutter of left ventricular structures in patients with aortic regurgitation, with special reference to patients with associated mitral stenosis.

Echocardiography was performed in 45 patients with aortic regurgitation. Forty showed a high frequency diastolic flutter of the mitral valve, which was holodiastolic in all but the patients with associated mitral stenosis. Of four patients with coexisting mitral stenosis, mitral flutter was absent in two; in the other two, in atrial fibrillation, mitral flutter occurred, but only during a fixed interval after mitral valve opening, irrespective of cycle length. A fine flutter of similar frequency was observed on the left ventricular aspect of the ventricular septum in 12 patients. In six of these it was of slight degree and restricted to early diastole and the high septum; in four others (three of whom had associated mitral stenosis), the septal flutter was more marked, holodiastolic, and present over all parts of the septum scanned; in two, it was holodiastolic over the high septum but early diastolic at lower septal levels. Aortography performed in 19 patients showed that septal flutter was present in seven of 12 patients in whom the regurgitant aortic jet was directed forward to the ventricular septum, whereas in the other seven patients with no septal flutter, the jet was directed away from the septum. Septal flutter is useful as an echocardiographic sign of aortic regurgitation, especially in the presence of mitral stenosis when mitral flutter may be absent or exceeded by septal flutter in both amplitude and duration, and when the mitral valve has been replaced by a prosthetic valve. Vibration of the septum appears to be attributable to the regurgitant aortic jet impinging on it and may contribute to the production and radiation of the characteristic diastolic murmur of aortic regurgitation.

Adolescent↗
PubMed1976

Echocardiography in mechanical alternans. With a note on the findings in discordant alternans within the left ventricle.

We described the echocardiographic manifestations of mechanical alternation of left ventricular (LV) contraction during regular sinus rhythm. Chronic LV dilatation and failure existed in all our four cases. Alternation was observed with respect to the following echocardiographic variables: amplitude and rate of increase of amplitude of systolic excursions of the LV posterior wall and ventricular septum (VS); reciprocal changes in the duration of LV ejection and pre-ejection periods (on the aortic valve echo) such that the total duration of LV electromechanical systole remained constant; reciprocal changes in the duration of RV ejection and pre-ejection periods (on the pulmonic valve echo) such that the total duration of RV electromechanical systole remained constant; systolic anterior excursion of the aortic root as a whole; steepness of the mitral EF slope; septal and LV posterior wall diastolic position; and end-systolic LV diameter. In two patients, discordant alternans of the motion of the LV posterior wall and the VS was observed.

Adult↗
PubMed1975

Diagnosis of cardiac tamponade by echocardiography: changes in mitral valve motion and ventricular dimensions, with special reference to paradoxical pulse.

The echocardiographic findings in three patients who presented with pericardial effusion and cardiac tamponade are described. Cyclic respiratory changes affected the diastolic movement of the anterior mitral leaflet, viz., during inspiration its anterior excursion decreased in amplitude and the E-F slope diminished. This inspiratory alteration in mitral valve motion was accompanied by an increase in right ventricular dimensions and a reciprocal decrease in left ventricular dimensions. Pericardial paracentesis confirmed the presence of effusion and relieved cardiac tamponade in all the patients. Repeat echocardiography, performed in two of the patients immediately after the pericardial tap, showed that the E-F slope had become steeper and that phasic respiratory variations in the diastolic motion of the anterior mitral leaflet were no longer present. The compatibility of our observations with the theories which endeavor to explain the mechanism of the paradoxical pulse in pericardial effusion with cardiac tamponade is discussed. We suggest that the abnormalities in anterior mitral leaflet motion defined by echocardiography constitute a useful addition to the study of patients with suspected cardiac tamponade resulting from pericardial effusion.

Adult↗
PubMedDate not supplied

Laparoscopic management of hydatid cyst of liver.

We describe the laparoscopic excision of a hydatid cyst in the liver. During the procedure, done after treatment with the scolicidal agents praziquantel and albendazole, care was taken to prevent spillage of scolices during evacuation of contents and to excise the entire germinal epithelium. The patient had no immediate or short-term complications and is asymptomatic 3 months later.

Adult↗