W. Selvamurthy

The role of free radicals in cold injuries

Cold injury is a tissue trauma produced by exposure to freezing temperatures and even brief exposure to a severely cold and windy environment. Rewarming of frozen tissue is associated with blood reperfusion and the simultaneous generation of free oxygen radicals. In this review is discussed the current understanding of the mechanism of action of free oxygen radicals as related to cold injury during rewarming. Decreased energy stores during ischaemia lead to the accumulation of adenine nucleotides and liberation of free fatty acids due to the breakdown of lipid membranes. On rewarming, free fatty acids are metabolized via cyclo-oxygenase and adenine nucleotides are metabolized via the xanthine oxidase pathway. These may be the source of free oxygen radicals. Leukocytes may also play a major role in the pathogenesis of cold injury. Oxygen radical scavengers, such as superoxide dismutase and catalase, may help to reduce the cold induced injury but their action is limited due to the inability readily to cross the plasma membrane. Lipid soluble antioxidants are likely to be more effective scavengers because of their presence in membranes where peroxidative reactions can be arrested.

Physiological effects of wearing heavy body armour on male soldiers

The effect of wearing two widely used body armours (BA) weighing 9.0 kg and 11.0 kg by the security personnel in India was evaluated. Six male soldiers underwent treadmill exercise in the laboratory (26-28[deg]C) at a fixed speed of 2.2 m [middle dot] sec-1 for 10 minutes with and without wearing the 11.0 kg BA over their regular uniform. Six other soldiers were exposed to a hot humid climatic chamber (34[deg]C Wet Bulb Globe Temperature/60% relative humidity) with and without 11.0 kg BA for one hour with light physical exercise. Pulmonary function test was conducted on 16 soldiers with 9.0 kg, 11.0 kg BA and without it. The heart rate (HR), minute ventilation (VE) and oxygen uptake (VO2) on wearing the 11.0 kg BA increased significantly (p -1, 9.4 1 [middle dot] min-1 and 6.0 ml [middle dot] kg-1 min-1 respectively, for HR, VE, and VO2. In hot humid exposure the HR and mean skin temperature () with 11.0 kg BA also increased significantly (p less than 0.05) as compared to without wearing it during exercise. Pulmonary functions deteriorated significantly with wearing BA and recorded further decrease with increase in weight of the armour. The significant increase in energy cost of physical task, increase cardiovascular strain in hot humid exposure and increase restrictive ventilatory effect which have been found when BA is worn have important practical implications. It is expected that the BA wearer would develop early onset of fatigue if they are to carry out the same task at the same rate as before without wearing BA. These factors need due consideration when planning work/rest cycles of BA wearer placed in demanding and/or endurance type of tasks.

Effect of vitamin E supplementation on carbogen-induced amelioration of noise induced hearing loss in man

The study explores the effect of occupational noise on oxidative stress status and prophylactic effect of Vitamin E and carbogen (5% CO 2 +95%O 2 ) breathing in alleviating the oxidative damage and conserving the hearing in human volunteers exposed to intense occupational noise. Plasma total antioxidant status, blood glutathione (GSH), malondialdehyde (MDA), antioxidant enzyme activities of GSH peroxidase (EC 1.11.1.9, GPx), superoxide dismutase (EC 1.15.1.1; SOD) in erythrocytes, nitric oxide and nitric oxide synthase in plasma were assessed before and after 6 days of administration of Vitamin E and Carbogen. Results of the study indicate that the exposure to noise for 6 days increased blood concentration of MDA, decreased concentrations of reduced GSH, antioxidant enzyme activity of SOD and plasma total antioxidant status in control (noise) group. Vitamin E- supplemented group showed decline in oxidative stress reflected by significant decrease in blood concentration of MDA and increase in antioxidant enzyme activity of erythrocyte SOD. Results of audiometric studies revealed that breathing of carbogen prevented the development of temporary threshold shift; thereby reducing the risk of noise induced hearing loss.

Role of neuropeptide Y and galanin in high altitude induced anorexia in rats.

Anorexia causing weight loss at high altitude (HA) is a major problem. Neuropeptide Y (NPY) and galanin are considered to have appetite regulatory function. The present study was therefore undertaken to investigate the changes in these two peptides at simulated HA and its possible role in anorexia. Male Sprague-Dawley rats (n = 8 in each group) were exposed to simulated HA (7620 m) for 1, 7, 14 and 21 days for 6h a day and to an altitude of 6096 m for 72h to study the effect of intermittent and continuous exposure, respectively. NPY and galanin levels were estimated in different brain parts and plasma of exposed and unexposed control animals. Significant reduction in food intake was observed in rats during both intermittent as well as continuous exposure. In case of 72h continuous exposure severe reduction in food intake was observed (73.2%) with reduction in body mass (∼29.7 g/rat in 48h). Hypothalamic NPY levels were decreased by 54.7, 35.0 and 15.4% in 1, 7, and 14 days, respectively, in case of intermittent exposure to HA. However in case of 72 h HA exposure no significant change in hypothalamic and circulating NPY levels were observed. Plasma galanin levels were decreased in both intermittent and 72h continuous HA exposed rats. Hypothalamic galanin levels were also decreased in 72h exposed rats. The changes in levels of these peptides may be responsible for anorexia at HA.

Environmental impact on crew of armoured vehicles: Effects of 24 h combat exercise in a hot desert

A field study was undertaken to investigate the effects of combined noise, vibration and heat stress on the physiological functions of the crew of armoured vehicles during prolonged combat exercise in a desert. The sound pressure level of noise was measured with a sound level meter and accelerations by vibration analyser. The thermal load on the crew was evaluated by calculating the wet bulb globe temperature index. The physiological responses of the subjects (n=9), included significant increases in the heart rate, 24 h water intake and urinary catecholamine concentration. A significant decrease was recorded in body mass, peak expiratory flow rate and 24 h urinary output. The high heat load on the crew resulted in a hypohydration of 3% body mass and appeared to be the dominant factor in producing the physiological strain.

Acclimatization to High Altitude in the Tien Shan: A Comparative Study of Indians and Kyrgyzis

Abstract Objective.—To study the changes in pulmonary function of human male volunteers from 2 different populations: Indians and Kyrgyzis before and after ascent to 3200 m and during a 4-week stay at that altitude. Methods.—Ten healthy soldiers of the Indian army (22–25 years of age) and 10 Kyrgyzis recruits (19–20 years of age ), height and weight matched, were volunteers in this study. Their pulmonary functions were evaluated at baseline (Bishkek, 760 m); on days 2, 13, and 25 at a mountain clinic at Tuya Ashuu pass (3200 m) in the northern Tien Shan Range; and on return to Bishkek. A dry spirometer was used to measure lung function at each location. Results.—Results indicated that Kyrgyzis had significantly larger forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1) than those of the Indians, but their peak expiratory flow rate (PEF), forced expiratory flow rate at 25% to 75% of FVC (FEF25–75%), and maximal voluntary ventilation (MVV) measures were comparable. At high altitude (HA), FVC showed significant reduction on day 2, with subsequent recovery in the Kyrgyzis; but in the Indians, FVC showed gradual reduction, and on day 25, it was significantly reduced compared with the baseline value. FEV1 did not show any change with altitude in either group. Expiratory flow rates and MVV showed significantly higher values at HA in both groups. However, after air density correction for the 2 altitudes, PEF and MVV showed no changes from their baseline values, and the mid-expiratory flow rate (FEF25–75%) was actually reduced in both groups: on day 2 in the Kyrgyzis and on day 25 in the Indians. On day 2 of return from a 4-week stay at HA, all test measures were back to their baseline values. Conclusions.—The major difference between the 2 populations was larger lung volumes in the Kyrgyzis compared with the Indians, with no differences seen in their flow rate measures. Also, there was a different time schedule of altitude-induced reductions in FVC and FEF25–75%.

Effect of a carbohydrate supplement on feeding behaviour and exercise in rats exposed to hypobaric hypoxia

The effect of a carbohydrate supplement, offered as a diet option, on feeding behaviour, body weight gain, and endurance exercise was studied in rats exposed to hypobaric hypoxia. Male albino rats (n = 35) were randomly divided into 5 groups; hypoxic supplemented and control groups; normoxic supplemented and control groups, and an untreated control group. After treadmill training for 5 days, the hypoxic groups were exposed to simulated high altitude equivalent to 6960 m for 18 days continuously. Food and water intakes, body weight and endurance exercise were recorded before and during the exposure period. Blood glucose, insulin, muscle and liver glycogen were assayed at the end of the exposure period. Hypobaric hypoxia resulted in a significant decrease in food and water intake, and body weight, and reduced endurance exercise capacity compared to the basal and normoxic group values. The carbohydrate supplement did not ameliorate the hypoxia-induced loss in body weight, but however, significantly delayed the onset of fatigue during exercise in the supplemented rats compared to the hypoxic control group.

Cytoprotective and immunomodulatory properties of Geriforte, a herbomineral preparation, in lymphocytes.

The study was designed to determine the cytoprotective and immunomodulatory properties of Geriforte, an indigenous herbomineral compound, using lymphocytes as a model system. The possible involvement of free radicals and the ability of Geriforte to inhibit the oxidative process induced by tert-butylhydroperoxide (tert-BHP) was also investigated. The production of free radicals (evaluated by fluorescent probe fluorescein-diacetate), level of malondialdehyde (MDA, as index of lipid peroxidation), and levels of anti-oxidants--reduced glutathione (GSH) and glutathione peroxidase (GPx) were determined. There was an increase in cytotoxicity and apoptosis significantly in the presence of tert-BHP (100 microM) over control. Addition of tert-BHP resulted in a marked increase in free radical production and MDA level with a concomitant decrease in GSH level in lymphocytes. Geriforte supplementation reduced cytotoxicity and apoptosis induced by tert-BHP. Further, Geriforte inhibited tert-BHP induced lipid peroxidation and maintained higher anti-oxidant levels. tert-BHP significantly inhibited the lymphocyte proliferation stimulated by mitogens (Lipopolysaccharide/Concanavalin A) and enhanced DNA fragmentation. Geriforte relieved the inhibitory effect of tert-BHP on lymphocyte proliferation and decreased DNA fragmentation appreciably. The results indicate that Geriforte possesses cytoprotective and immunomodulatory properties which could be due to its anti-oxidant activity.

Translating Physiological Knowledge to Health Application

Physiology forms the basis for medical practice. Earlier in India, physiological research undertaken by medical teachers and researchers was primarily focused towards publications rather than translating that knowledge into a device/technology/process. The Defence Physiological Research and Development endeavours have provided a new paradigm since 1960 with the establishment of Defence Institute of Physiology and Allied Sciences (DIPAS). Most of the research efforts were aimed at finding solution to problems encountered by soldiers operating in extreme operational environments such as high-altitude, cold, desert, underwater and aerospace environments. Even the basic physiological research had an ultimate aim of application for the well-being of the soldiers thereby focusing on translational component. To cite a few examples, physiological responses during high-altitude acclimatisation studied on sojourners were translated to formulate the staging of acclimatisation schedule at high altitude. The nitric oxide and oxygen therapy for treatment of high-altitude pulmonary oedema (HAPO) resulted from the pathophysiological studies undertaken on the patients with HAPE. This resulted in devising an equipment to deliver a precise concentration of nitric oxide and oxygen to the patients while monitoring the concentration of nitrogen dioxide. Studies carried out to assess the physiological effects of heat stress resulted in formulating an ergogenic drink to keep the fluid electrolyte balance, thereby optimising the physical and mental efficiency of soldiers operating in desert environment. Development of a radio sensitiser, namely, 2-deoxy-d-glucose (2DG), came out of physiological research to find a method to ameliorate the adverse effects of radiotherapy in cancer patients. Such examples of translational research in physiology led to the development of products/technologies/processes which helped in providing health solutions which are illustrated in this chapter.

Improvement in high altitude hypoxic stress tolerance in albino rats on oral glutamate supplementation

Hypoxia results in body weight loss due to anorexia and hypophagia and reduced human performance. The present study was undertaken to evaluate the role of oral glutamate administration with food and water in improvement in hypoxic tolerance, if any. The placebo controlled study revealed that supplementation of optimal dose of glutamate (Glu) promoted hypoxic tolerance in male Sprague Dawley Albino rats fed one dose daily for 5 days and exposed to continuous intermittent hypoxia of 6 hrs per day at 10,668m in an animal exposure chamber. Effect of varying dose of Glu on body weight (bw),food intake and water uptake were studied which revealed the optimal dose of Glu to be 27mgKg bw. Oral feeding of Glu resulted in improved tolerance of combined stress of cold and hypoxia as measured by fall in rectal temperature from 37’C to 23’C and faster rewarming. It enhanced 5.8 times hypoxic tolerance 36% bw gain and 24% food intake in hypoxia possibly by acting as a conditionally essential amino acid under hypoxia.