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Biomedical subjects

B Rajagopalan

Publications and source records attributed to B Rajagopalan.

119 records · Page 7Linked to original sources
PubMed1979

Blood flow in pulmonary veins: III. Simultaneous measurements of their dimensions, intravascular pressure and flow.

Vein flow in the large extraparenchymal pulmonary veins is pulsatile and its wave form has an inverse relationship to left atrial pressure. Extraparenchymal pulmonary veins are thin walled and collapsible. This enables them to behave as highly compliant structures. Dimensional measurements of their cross sectional area in living open chested dogs showed them to be non circular at low left atrial pressures. They rapidly assumed a circular cross section as left atrial pressure rose. Only at pressures above 1.5 kPa (11 mmHg) were the pulmonary veins circular in cross section. The aggregate volume of the large extraparenchymal pulmonary veins, when fully distended, was found to be equal to or greater than one stroke volume of the heart. The extraparenchymal pulmonary veins act as a reservoir to the left atrium so that left ventricular stroke volume can be maintained relatively unaffected by beat by beat changes in right ventricular stroke output. Their behaviour at normal mean left atrial pressures also enables them to isolate the lung capillaries from retrograde transmission of positive pressure transients from the left atrium, which could otherwise impede venous outflow of blood from the lung capillary bed.

Animals↗
PubMed1979

Cerebral complications in the treatment of accelerated hypertension.

The malignant phase of hypertension is invariably fatal unless treated, and rapid reduction of arterial pressure is thought to be the treatment of choice. Ten patients with accelerated hypertension are described in whom abnormal neurological signs developed following the rapid reduction of arterial pressure. Three patients died without recovering from the neurological damage. A fourth died of an unrelated cause a month later. Areas of ischaemic damage were found in the brains of three of these cases. Of the six survivors, four were left with some permanent neurological disability. It is likely that these changes resulted from the inability of the cerebral circulation in patients with severe hypertension to autoregulate blood flow to the brain, so that a rapid reduction in arterial pressure led to ischaemia, especially of the watershed areas of the brain. Cerebrovascular autoregulation is likely to be compromized in patients with cerebral oedema, stenosis of major cranial vessels or in those patients with long-standing severe hypertension. It is suggested that the blood pressure in patients with accelerated hypertension should be lowered gently over a period of several hours or even days in order to allow time for the cerebrovascular autoregulatory mechanisms to recover.

Adult↗
PubMed1978

The physcial properties of human pulmonary arteries and veins.

1. We have studied the extensibility of circumferential strips of main pulmonary artery and large pulmonary veins obtained at post mortem from patients of all ages, dying from conditions other than heart and lung disease. 2. The vessel strips were submitted to increasing loads in a tension balance. The pulmonary arteries were found to be readily extensible. This extensibility became less with increasing age. The pulmonary veins were virtually inextensible at all ages. 3. It is postulated that the large extraparenchymal pulmonary veins have a capacitative role in supplying blood from the lungs to the left atrium. This may be accomplished by their collapsible nature, as they have little capability of distension.

Adolescent↗
PubMedDate not supplied

Quantitative analysis by 31P magnetic resonance spectroscopy of abnormal mitochondrial oxidation in skeletal muscle during recovery from exercise.

We use the hyperbolic relationship between cytosolic [ADP] and the rate of phosphocreatine (PCr) resynthesis after exercise to estimate the apparent maximum rate of oxidative ATP synthesis (QMAX). We examine data from some human diseases in which mitochondrial oxidation may be impaired (due to reduced mitochondrial numbers, intrinsic mitochondrial defect or impaired vascular supply). Muscle responds to impaired oxidation by stimulating anaerobic ATP synthesis and/or by increasing [ADP], the stimulus to the mitochondrion. However, these responses interact: [ADP] depends on pH and [PCr], and lactic acid production tends to lower [ADP] (by lowering pH), while proton efflux has the opposite effect. We identify four patterns of results: (A) in mitochondrial myopathy, apparent QMAX is reduced and [ADP] is appropriately increased, because increased proton efflux reduces the pH change in exercise despite increased lactic acid production; (B) in some conditions (e.g., cyanotic congenital heart disease) apparent QMAX is reduced but there is no compensatory rise in [ADP], probably because anaerobic ATP synthesis during exercise is increased without increase in proton efflux; (C) in other conditions (e.g., myotonic dystrophy) [ADP] is increased during exercise but apparent QMAX is normal, suggesting either an increase in proton efflux and/or decrease in anaerobic ATP synthesis during exercise; (D) there are also conditions (e.g., respiratory failure) where, despite impaired oxygen supply, both apparent QMAX and end-exercise [ADP] are normal. We also discuss the metabolic conditions under which end-exercise [ADP] is increased by a mitochondrial defect.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Diphosphate↗
PubMedDate not supplied

No effect of blood transfusion on muscle metabolism.

31Phosphorus magnetic resonance spectroscopy allows examination of skeletal muscle bioenergetics in vivo. The forearm muscle of four male patients receiving regular blood transfusions for myelodysplastic anaemia showed increased acidification and phosphocreatine depletion during exercise (compared to six age-matched male controls). Transfusion produced no significant improvement in these measurements or in the estimated maximum oxidative capacity of the muscle. We conclude that transfusion of patients with chronic anaemia (haemoglobin of 8-9 g/dl) does not improve skeletal muscle oxidative metabolism.

Aged↗
PubMedDate not supplied

Psychiatric morbidity among dermatology inpatients.

BACKGROUND: Research on psychiatric morbidity among patients with dermatological diseases generally focuses on outpatients and questionnaire-based surveys. The aim of this study was to determine the prevalence and nature of psychiatric morbidity among dermatological inpatients with diagnosis being made by psychiatric interview, and ascertain whether demographic and clinical details in dermatological inpatients with psychiatric morbidity differed from those without it. METHODS: Charts of all inpatients admitted by the dermatology department between 1 January 1991 and 31 July 1995 were analysed for socio-demographic data, clinical features, treatment and course in hospital. For those patients who were referred to a psychiatrist, all records of the psychiatric consultation were obtained and analysed. RESULTS: A total of 1073 patients were admitted during the study period. Ninety-eight patients (9%) were diagnosed to have a psychiatric illness. Patients with psychiatric illness were likely to have had more admissions and longer duration of hospital stay. The most common psychiatric diagnoses were depressive episodes (34%) and adjustment disorders (29%). The highest rates of psychiatric morbidity were found among patients with chronic urticaria, exfoliative dermatitis and sexually transmitted diseases, including human immunodeficiency virus infection. The prevalence of psychiatric disorders was significantly higher in those who had received long term (more than six weeks) treatment with high-dose steroids (more than 1 mg/kg body weight of prednisolone). CONCLUSION: Some dermatology inpatients have psychiatric morbidity, which affects the course of the dermatological condition as well as the duration of hospitalization. The availability of psychiatric consultation at dermatology clinics and regular liaison between psychiatrists and dermatologists are essential for appropriate management.

Adjustment Disorders↗