Biomedical subjects

W Selvamurthy

Publications and source records attributed to W Selvamurthy.

At least 73 records · Page 4Linked to original sources

PubMed1996

Effect of high-altitude hypoxia on feeding responses and hedonic matrix in rats.

Albino male rats (n = 78) were exposed to a simulated high altitude (HA) equivalent to 7,620 m for 6 h daily, contiguously for a period of 21 days, to study their feeding behavior and gustatory responses. Their food, water intake, and body weight were recorded daily, and blood sugar and blood insulin were estimated once a week. All the parameters were recorded for a period of 3 wk each before, during, and after exposure to simulated HA. The results show a decrease in daily food and water intakes and body weight and mild hyperglycemia and hyperinsulinemia during hypoxic exposure. The 1-h single-bottle taste solution test showed a preference for sweet solutions (13% glucose and 0.2% saccharine) over citric acid (0.16%), sodium chloride (0.9%), and quinine sulfate (0.001%) during exposure to simulated HA. The 1-h two-bottle test containing glucose (calories plus taste) and saccharine (taste but no calories) administration showed a preference for the glucose solution over the saccharine solution. The trend of the 1-h intake of all test solutions also showed a reversal to preexposure levels after termination of HA hypoxia. It would appear that high-altitude stress influences food intake in a manner that sensory cues (e.g., preference for sweet substances) become more important.

Altitude↗

PubMed1996

Effect of vitamin C in modulating the hypothermic influence on nerve conduction.

The study was carried out to evaluate the effect of different degrees of hypothermia on nerve conduction and the possible beneficial effect of vitamin C in the amelioration of the impairment in nerve conduction due to hypothermia. Sixty male Wistar rats, 225-250 g, were randomly divided into two equal groups of untreated controls and vitamin C treated experimental groups. Sciatic nerve conduction and nerve temperature (Tn) were recorded at different degrees of hypothermia by step-wise lowering of rectal temperature (Tr) from 38 to 20 degrees C. A regression analysis showed a positive linear relationship of Tr with nerve conduction velocity (NCV) and with Tn in both groups (p < 0.001). There was also a positive linear relationship between Tn and NCV in both groups: control, p < 0.001; experimental, p < 0.05. Comparisons between the regression equations of Tr with NCV, Tr with Tn, and Tn with NCV showed significant differences between the two groups (p < 0.001). There was no significant relationship between Tr and the amplitude of the action potential. Vitamin C may have a protective effect against the impairment of NCV due to hypothermia.

Animals↗

PubMed1996

Respiratory changes during initial days of acclimatization to increasing altitudes.

METHOD: The daily changes in respiratory function were monitored in 16 healthy male road inductees at sea level (SL) and at high altitudes (HA) of 3110 m, 3445 m, and 4177 m. Identical studies were also carried out on acclimatized low landers (ALL) staying at 3110 m and at 4177 m for 2 years. RESULTS: Ventilation, tidal volume, and respiratory rate showed significant increases on arrival at HA and remained high during the entire period of observation (p < 0.001). These parameters did not show any appreciable difference between 3110 m and 3445 m. Forced vital capacity (FVC) and forced expiratory volume (L) in 1.0-s (FEC1.0) also did not change on the first day of arrival at HA but decreased significantly (p < 0.001) on the second day at 3110 m. However, both FVC and FEV1.0(L) returned to SL values by day 3 but declined further at 3445 m and at 4177 m. Forced expiratory flow and maximum voluntary ventilation declined on arrival at HA. Peak expiratory flow rate, however, tended to decline during initial days but increased by day 3 and remained elevated during the subsequent residence. Respiratory adaptation to hypoxia in ALL appeared to be different at 3110 m as compared to that at 4177 m. At higher altitude the lung volumes and capacities were markedly decreased, whereas at lower altitudes these parameters were comparable to SL values. CONCLUSION: We conclude that initial respiratory adjustments in sojourners occur by day 3 at 3110 m and show further decrement at 4177 m with a cyclic variation on day 6, while ALL manifest variability in respiratory adaptation at different altitudes.

Acclimatization↗

PubMed1996

Involvement of a protease in tert-butylhydroperoxide-mediated activation of Ca2+ ATPase in microsomes of pulmonary smooth muscle.

Microsomes isolated from bovine pulmonary artery smooth muscle tissue treated with the oxidant t-buOOH stimulated Ca2+ ATPase activity dose-dependently as also protease activity when tested with a synthetic substrate N-benzoyl-DL-arginine p-nitroanilide. At 300 microM, t-buOOH optimally stimulated these activities. Treatment of the microsomes with t-buOOH stimulated ATP dependent Ca2+ uptake while Na+ dependent Ca2+ uptake was inhibited by t-buOOH. Pretreatment of the microsomes with vitamin E (1 mM) and aprotinin (1 mg/ml) prevented t-buOOH caused stimulation of protease activity and Ca2+ ATPase activity, and also stimulation of ATP dependent Ca2+ uptake while t-buOOH caused inhibition of Na+ dependent Ca2+ uptake was reversed by vitamin E and aprotinin. Treatment of the microsomes with trypsin (1 microgram/ml) stimulated Ca2+ ATPase and ATP dependent Ca2+ uptake while Na+ dependent Ca2+ uptake was inhibited. Pretreatment of the microsomes with aprotinin prevented trypsin caused stimulation of Ca2+ ATPase and ATP dependent Ca2+ uptake, while trypsin caused inhibition of Na+ dependent Ca2+ uptake was reversed by aprotinin.

Animals↗

PubMed1996

Effect of Sahaja yoga practice on seizure control & EEG changes in patients of epilepsy.

The effect of Sahaja yoga meditation on seizure control and electroencephalographic alterations was assessed in 32 patients of idiopathic epilepsy. The subjects were randomly divided into 3 groups. Group I (n = 10) practised Sahaja yoga for 6 months, Group II (n = 10) practised exercises mimicking Sahaja yoga for 6 months and Group III (n = 12) served as the epileptic control group. Group I subjects reported a 62 per cent decrease in seizure frequency at 3 months and a further decrease of 86 per cent at 6 months of intervention. Power spectral analysis of EEG showed a shift in frequency from 0-8 Hz towards 8-20 Hz. The ratios of EEG powers in delta (D), theta (T), alpha (A) and beta (B) bands i.e., A/D, A/D + T, A/T and A + B/D + T were increased. Per cent D power decreased and per cent A increased. No significant changes in any of the parameters were found in Groups II and III, indicating that Sahaja yoga practice brings about seizure reduction and EEG changes. Sahaja yoga could prove to be beneficial in the management of patients of epilepsy.

Adolescent↗

PubMed1996

Clinical observations on tropical men during their sojourn over the Arctic region.

In the present study, besides a detailed clinical evaluation, roentgenographic changes in cardio-respiratory system in Indian soldiers (IS) during their 60 days stay at the arctic have been observed. These results have been compared with the responses at Delhi (before cold acclimatisation) and on return to Delhi (deacclimatisation). An attempt has also been made to compare the same physiological variables with those of Russian Migrants (RM) and Russian Natives (RN) in the arctic region to review significant differences if any. Heart Rate (HR) did not show much change; there was a tendency to increase in both systolic and diastolic blood pressure; and Kerdo's index inclined towards increased sympathetic activity in IS. X-ray chest (PA View) did not show any appreciable change in the lungs in the three groups. One subject amongst IS showed cardiac enlargement and RN subjects showed prominence of pulmonary artery and pulmonary vascular markings. All these physiological changes aim at increasing the cardiac output to overcome the ill effects of cold. Pneumopathy, a clinical condition of increased pulmonary haemodynamics could have resulted in the prominence of pulmonary artery and pulmonary blood flow in the RN. Most of the physiological changes reverted to the baseline value on return to Delhi thus proving that there were no permanent changes during short stay at extreme cold conditions.

Acclimatization↗

PubMed1995

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.

Adult↗

PubMed1995

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.

Animals↗

PubMed1995

Auditory evoked responses in tropical men during sojourn over the arctic region.

The influence of an arctic environment on auditory evoked responses, both brainstem and cognitive, were evaluated in 10 Indian soldiers. They were first tested in Delhi and then flown to an arctic region where they were tested in the first week and again in the eighth week of their stay. Two migrants from Moscow, their usual place of residence, and six natives, born and brought up in the arctic, were also tested for comparison. The Indians, on their return to India, were tested again. The auditory evoked responses were recorded using the Nicolet (USA) Compact 4 Instrument. The Indians showed a delay in all the waves of the auditory brainstem response (ABR) during their induction in the arctic and these persisted even on their return to India whereas the migrants and the natives had relatively higher ABR latency values.

Acclimatization↗

PubMed1995

Acclimatization at high altitude in gradual and acute induction.

The study assessed physiological responses to induction to high altitude first to 3,500 m and then to 4,200 m and compared the time course of altitude acclimatization in two groups of male volunteers. The acutely inducted group was transported by aircraft (AI) to 3,500 m in 1 h, whereas the gradually inducted group was transported by road (RI) in 4 days. Baseline recordings of basal cardiovascular, respiratory, and blood gas variables were monitored at sea level as well as at 3,500 m on days 1, 3, 5, and 7. Blood gases were measured on day 10 also. After 15 days at 3,500 m, the subjects were inducted to 4,200 m by road, and measurements were repeated on days 1, 3, and 5, except blood gas variables, which were done on day 10 only. Acute mountain sickness symptoms were recorded throughout. The responses of RI were stable by day 3 of induction at 3,500 m, whereas it took 5 days for AI. Four days in transit for RI appear equivalent to 2 days at 3,500 m for AI. Acclimatization schedules of 3 and 5 days, respectively, for RI and AI are essential to avoid malacclimatization and/or high-altitude illness. Both groups took 3 days at 4,200 m to attain stability for achieving acclimatization.

Acclimatization↗

PubMed1995

Effect of Sahaja yoga practice on stress management in patients of epilepsy.

An attempt was made to evaluate the effect of Sahaja yoga meditation in stress management in patients of epilepsy. The study was carried out on 32 patients of epilepsy who were rendomly divided into 3 groups: group I subjects practised Sahaja yoga meditation for 6 months, group II subjects practised postural exercises mimicking Sahaja yoga and group III served as the epileptic control group. Galvanic skin resistance (GSR), blood lactate and urinary vinyl mandelic acid (U-VMA) were recorded at 0, 3 and 6 months. There were significant changes at 3 & 6 months as compared to 0 month values in GSR, blood lactate and U-VMA levels in group I subjects, but not in group II and group III subjects. The results indicate that reduction in stress following Sahaja yoga practice may be responsible for clinical improvement which had been earlier reported in patients who practised Sahaja yoga.

Adolescent↗

PubMed1994

Effect of yogic exercises on thyroid function in subjects resident at sea level upon exposure to high altitude.

Using radioactive iodine, the effect of 1 month's yogic exercises has been investigated on the thyroid function of subjects resident at sea level (SL) specially after their exposure to high altitude (HA). The results have been compared with a group of SL subjects who underwent physical training (PT) exercises for the same duration. Ten healthy male volunteers in the age range of 20-30 years were used as test subjects in this study with each serving as his own control. The subjects were randomly divided into two groups of 5 each. One group practised hatha yogic exercises, while the other group performed the regular PT exercises. The thyroidal accumulation and release of radioactive iodine have been measured in each of the subjects of both groups before and after 1 month of their respective exercises at SL. One month of yogic exercises at SL has been observed to cause a significant reduction in the trans-thyroidal availability of radioiodine. The thyroid radioactivity in this group of subjects was always below normal levels with the exception of two peaks of radioactive iodine uptake, when the levels of radioactivity in the thyroid were similar to the control values of pre-yogic exercises. The release of radiolabel at 24-48 h was significantly increased after yogic exercises. In contrast, the subjects performing PT exercises for the same duration at SL showed significant thyroid uptake of radioactive iodine at 24 h. Subsequently their 131I uptake continued to rise slowly until 72 h without any demonstrable thyroidal release of radiolabel. This indicated that increased thyroid activity was induced by conventional PT exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1994

Personality traits and performance of military parachutist trainees.

Fifty-two Indian military parachutist trainees were studied throughout the training period to investigate effects of stress in parachutist training on performance efficiency. Stress attributable to fear, anxiety, and apprehension about the inherent risk of paratrooping was studied along with physiological and biochemical changes. An attempt is made to correlate personality traits with performance efficiency. In cognitive and psychomotor tests, maximum deterioration was seen before the tower jump and aircraft jump. The deterioration was correlated with the level of anxiety and urinary catecholamine levels. Inter-correlations between anxiety, catecholamine, and blood pressure were positive, and the level of anxiety was seen to be affecting the quality of performance adversely.

Adult↗

PubMed1993

Respiratory changes due to extreme cold in the Arctic environment.

Effects of acute exposure and acclimatisation to cold stress on respiratory functions were investigated in healthy tropical Indian men (n = 10). Initial baseline recordings were carried out at Delhi and thereafter serially thrice at the arctic region and once on return to Delhi. For comparison the respiratory functions were also evaluated on Russian migrants (RM; n = 7) and Russian natives (RN; n = 6). The respiratory functions were evaluated using standard methodology on a Vitalograph: In Indians, there was an initial decrease in lung vital capacity (VC), forced vital capacity (FVC), forced expiratory volume 1st s (FEV1), peak expiratory flow rate (PEFR) and maximum voluntary ventilation (MVV) on acute exposure to cold stress, followed by gradual recovery during acclimatisation for 4 weeks and a further significant improvement after 9 weeks of stay at the arctic region. On return to India all the parameters reached near baseline values except for MVV which remained slightly elevated. RM and RN showed similar respiratory functions at the beginning of acute cold exposure at the arctic zone. RN showed an improvement after 10 weeks of stay whereas RM did not show much change. The respiratory responses during acute cold exposure are similar to those of initial altitude responses.

Acclimatization↗

PubMed1993

Effect of intermittent chronic exposure to hypoxia on feeding behaviour of rats.

Healthy albino male rats were exposed to a simulated high altitude (HA) equivalent to 25,000 ft (7620 m) for 6 h daily, continuously for 21 days to study the feeding behaviour. The 24-h food and water intake and body weight once in 3 days were recorded. Blood samples were drawn once a week from the retro-orbital venous plexus for blood sugar analysis. All the parameters were recorded before, during and after exposure to simulated HA. The results show a decrease in 24-h food and water intake and decreased gain in body weight during hypoxic exposure, which showed a tendency to come back to control during the post-exposure period. The blood sugar reflected a state of mild hyperglycaemia during exposure to HA.

Altitude↗

PubMed1993

Biomedical applications of simulated environments.

Environmental physiology assumes great significance in our national context in view of the diverse climatic conditions prevailing in different regions. Troops have to operate in diverse environmental conditions guarding the frontiers. Hence, the research in this area has been focused on the usage of field studies in the natural environments or simulated environments in the laboratory. Besides, the application of the simulation chambers in the research on the physiological effects of diverse environments, these studies may have applications in the control and management of certain clinical disorders. Some simulation chambers and specialised set-ups have been designed and developed at the Defence Institute of Physiology and Allied Sciences to carry out simulation studies. This paper describes these developments and the potentials of these biomedical applications of simulated environments.

Acclimatization↗

PubMed1993

Experimental studies on the treatment of frostbite in rats.

The effect of treatment by high dose of vitamin C, rapid rewarming by 37 degrees C water alone and with vitamin C, rapid rewarming by 37 degrees C decoction of Indian black tea alone and with vitamin C for experimentally produced frostbite was evaluated in 6 groups (25 each) of rats. Frostbite was produced experimentally in the hind limbs by exposing the animals at -15 degrees C for 1h using the harness technique. The degree of injury was assessed and classified on the basis of tissue necrosis at the end of 15 days. Administration of high dose of vitamin C for prolonged period and rapid rewarming at 37 degrees C water bath immediately after cold exposure apparently reduced the tissue damage. High dose of vitamin C therapy preceded by rapid rewarming in plain water showed additional benefit. Rapid rewarming in decoction of Indian tea resulted in identical beneficial effect. The degree of tissue preservation was highest with rapid rewarming in tea decoction followed by high dose of vitamin C.

Animals↗

PubMed1993

Responses of Arctic and tropical men to a standard cold test and peripheral vascular responses to local cold stress in the Arctic.

Thermoregulatory, metabolic and peripheral vascular responses to cold were studied in two groups (six each) of healthy men during exposure to the natural cold environment of the Arctic. Group A comprised of two arctic natives and four temporary residents who had migrated from the temperature zone of Russia. Group B consisted of six soldiers from a tropical region (India). Group B was airlifted to the arctic (70 degrees N, 38 degrees E). Both groups stayed in a field camp. The experiments were conducted during the 7th week of the stay. The volunteers were subjected to a standard cold test at 10 degrees C for 2 h wearing only shorts. Their heart rate, blood pressure, ventilation, oxygen consumption, oral temperature, mean skin and extremity temperatures were recorded initially and at 30 min intervals during standard cold test. The cold-induced vasodilatation response in both groups was also studied separately. The tropical natives (Group B) were flown back to Delhi and retested after 6 weeks. The physiological responses to general cold exposure as well as peripheral vascular response to local arctic cold stress were similar in both groups. The observation suggested that cold acclimatization in tropical men is similar to that of the people of Russian origin from a temperature zone.

Acclimatization↗