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Biomedical subjects

W Selvamurthy

Publications and source records attributed to W Selvamurthy.

At least 91 records · Page 5Linked to original sources
PubMed1992

Peripheral vascular response to local cold stress of tropical men during sojourn in the Arctic cold region.

Peripheral vascular response to local cold stress was studied on 4 groups of volunteers by eliciting cold-induced vasodilatation (CIVD) response during immersion of right hand in cold water (4 degrees C) for 30 min, to examine whether tropical men can get acclimatized to local cold compared to temperate zone people, during Arctic cold exposure. Group A and B (10 each) were drawn from tropical region of India, while Group C and D (6 each) from temperate zone of Russia and natives of Arctic, respectively. Initial study was conducted on control Group A at Delhi. Group B was airlifted to the Arctic (70 degrees N, 38 degrees E), where measurements were done on them during the seventh week of acclimatization, then they were flown back to Delhi and retested. For comparison, study was done at the Arctic on six migrants (Group C) from temperate zone of Russia and 6 natives (Group D) of the Arctic. There was a significant improvement of CIVD response and peripheral blood flow of tropical men due to acclimatization to Arctic environment, which was similar to that of the migrants but lower than the natives. Thus local cold acclimatization is possible even in tropical men as in those of the temperate zone people.

Acclimatization↗
PubMed1992

Auditory evoked response in patients of diabetes mellitus.

Brainstem auditory evoked response (BAER) and the mid latency response (MLR) were recorded in 25 diabetic men and compared with a group of 25 control subjects. The threshold of hearing was higher (P less than 0.001) in the patients. The BAER peak latencies were also significantly prolonged in both the ears; however, the degree of prolongation was more prominent in the right ear. The interpeak latencies of waves I-III were also prolonged (P less than 0.01) in the left ear, with non significant increase noticed in the right ear also. The wave V amplitude was lower (P less than 0.05) in diabetics. The MLR, on the other hand, was not affected in patients. These findings suggest functional impairment in the auditory pathway in patients of diabetes mellitus.

Adult↗
PubMed1991

Role of xanthinol nicotinate in the revival of monkeys subjected to acute haemorrhagic shock.

The therapeutic potential of xanthinol nicotinate in the revival of anaesthetised monkeys subjected to acute blood loss was investigated. The arterial pressure was lowered to 40 +/- 5 mmHg by rapid arterial bleeding and was maintained at this level for 2 h. Shed blood was then returned through infusion, to the animals. Animals alive at the end of 72 h observation period were considered as survivors. The test drug was infused 1/2 h prior to and 1/2 h, 1 h, 1 1/2 h and 2 h after the onset of oligaemic hypotension. The animals which received normal saline instead of test drug were treated as control. The physiological and biochemical parameters recorded prior to and after the onset of oligaemic hypotension were heart rate, pulse pressure, electrocardiogram, electroencephalogram (EEG), lactic acid, creatine phosphokinase, urea and glucose. The results showed tachycardia, narrowing of pulse pressure, depression of ST segment with occasional T inversion, slowing of EEG with increase in amplitude, rise in blood lactic acid, creatine phosphokinase, urea and glucose. The magnitude of these responses were proportional to the duration and severity of shock. These changes were markedly attenuated in the drug treated group. Enhancement of survival was observed in drug treated groups as compared to control. It was 10 per cent in control as against 60, 86, 71, 57 and 50 per cent in the groups which received the test drug 1/2 h prior to and 1/2 h, 1 h, 1 1/2 h and 2 h after the onset of oligaemic hypotension. It is concluded that the beneficial effect of the drug in the revival of monkeys subjected to acute haemorrhagic shock may be due to better maintenance of tissue perfusion.

Acute Disease↗
PubMed1991

In vivo experimental model to evaluate the insect repellent N-N, diethylphenylacetamide in Periplaneta americana Linn.

The responsiveness of insect antennae to bornyl acetate (BA), a sex pheromone mimic and N,N-diethyl phenylacetamide (DEPA), a multi-insect repellent has been studied. Electrical activity from the antennal lobe was quantified to observe the alterations in power and frequency spectrum in P. americana Linn. following exposure to these chemicals. Two distinct patterns of responses were exhibited on exposure to BA and DEPA, the former producing a marked excitation and the latter inhibition of electrical discharge during the exposure to these compounds at a concentration of 200 micrograms.

Acetamides↗
PubMed1990

Kainic acid induced epileptogenesis in developing normal & undernourished rats--a computerised EEG analysis.

Experimental epilepsy was induced in developing normal, undernourished and subsequently rehabilitated rats by locally injecting graded doses of Kainic acid (KA) in the right frontal cortex. Frequency and power spectral analysis of EEG was carried out to assess the progressive changes in EEG during KA-epileptogenesis. Undernourished animals were highly susceptible to seizure discharge. They exhibited generalized tonic-clonic discharge and had episodes of clinical seizures even after temporary neuronal recovery. Increase in power of delta, theta and decrease in alpha power was observed in the compressed spectral array (CSA) of undernourished animals. Delayed neuronal recovery with reduced background EEG and marked electrosilence in response to intra-rectal sodium valproate was observed in undernourished animals. Rehabilitated animals exhibited partial recovery which was related to the body weight gain. Spike frequency, spike amplitude and neuronal recovery time were not significantly differet between normal and undernourished animals at lower doses of KA (7.5-60 ng) whereas at higher doses (120-500 ng) marked differences were observed in these parameters. In KA treated undernourished rats 3H-glycine incorporation was significantly higher than normal in the hippocampus and spinal cord and lower in the cerebellum.

Age Factors↗
PubMed1990

Acute toxicity of methyl isocyanate in mammals. III. Electroencephalographic changes in rabbits.

Electroencephalographic (EEG) changes in rabbits following subcutaneous administration of methyl isocyanate (MIC) remained essentially similar at both 0.5 LD50 and 1.0 LD50 except for the magnitude. There was slowing of the EEG, depicting a synchronized pattern with frequent delta waves. Compressed spectral analysis revealed a spreading of power to a higher frequency. Power spectral analysis showed a reduction in all four bands in the frontal-transverse leads. This study demonstrates that MIC intoxication leads to the impairment of brain function, probably through stagnant hypoxia.

Animals↗
PubMed1990

Seizure susceptibility & intra rectal sodium valproate induced recovery in developing undernourished rats.

The seizure threshold and therapeutic potential of intrarectal sodium valproate were studied in young developing normal and undernourished rats, using the penicillin model. Undernourished rats were highly susceptible to seizure discharge. They exhibited generalised electrocortical inhibition and repeated episodes of epileptic discharges even after temporary neuronal recovery. Delayed spontaneous and drug induced neuronal recovery, low spike frequency and amplitude (P less than 0.001) reduced background EEG and marked electrocortical silence in response to intrarectal (25 mg/kg) sodium valproate treatment, was observed in the undernourished animals. Rehabilitated animals exhibited partial neuronal recovery which was related to the improvement in body weight. Analysis of spike frequency, spike amplitude and neuronal recovery time showed that both normal and undernourished animals behaved in a similar fashion at lower doses of penicillin (2.5 to 15 IU). Significant differences in the electrophysiological parameters were observed between the two groups at higher doses of penicillin (20 to 30 IU).

Administration, Rectal↗
PubMed1988

Acute toxicity of methyl isocyanate, administered subcutaneously in rabbits: changes in physiological, clinico-chemical and histological parameters.

Subcutaneous administration of methyl isocyanate (MIC) in 0.5 LD50 and 1 LD50 doses in female rabbits resulted in significant changes in physiological, clinico-chemical and histological parameters. There was a fall in arterial blood pressure and cardioacceleration in both the 0.5 LD50 and 1 LD50 groups, while the respiration showed a differential response in these groups with the former showing hyperpnoea and the latter showing respiratory inhibition. A significant increase in the arterial blood lactic acid, lactate/pyruvate ratio and 2,3-diphosphoglycerate levels, and the significant changes in acid-base status of both arterial and venous blood indicated tissue hypoxia of a stagnant type. Histopathological observations revealed a mild to moderate degree of congestion, focal lymphocytic infiltrations and necrosis in all visceral organs examined. These findings suggest that acute toxicity of MIC in vivo may be mediated by its effects on vascular beds.

2,3-Diphosphoglycerate↗
PubMed1981

Autonomic responses of high-altitude natives during sojourn at plains and on return to altitude.

The study was conducted on 20 high-altitude natives (HAN-I) 19-32 years old, to evaluate the changes in autonomic responses during their 2-months sojourn on the plains, and on return to high altitude (HA). The autonomic indices measured were heart rate HR), blood pressure (BP), oral temperature (Tor), mean skin temperature (Tsk), respiratory rate (RR), Cold pressor response (CPR), HR-response to tilt at 70 degree, and alpha index (AI) of EEG (occipital). These indices were recorded periodically during the 2 months of their stay on the plains, and thereafter on return to altitude for a period of 1 month. For comparison, the same responses were studied on 10 lowlanders (LL) on the plains and on induction to HA along with HAN-I. The study was repeated at altitude, once on 10 HAN who had never been to the plains (HAN-II) and on 10 acclimatised lowlanders. The results suggest that the relative parasympathetic dominance observed in natives at HA showed a gradual decrease during their sojourn on the plains, probably due to the elevation in sympathetic activity. On return to high altitude, they showed further increase in sympathetic excitation, as observed in LL on acute induction, but the magnitude of this response was less in natives. However, they showed a trend to faster return of autonomic responses to their initial level compared to LL.

Adaptation, Physiological↗
PubMed1978

Effect of altitude acclimatization on thermoregulation efficiency of man.

A study has been conducted on 20 sojourners (SJs) at a high altitude (HA) of 3500 m to evaluate the changes in thermoregulation efficiency (ThE) during acclimatization for 3 weeks, by observing the rate and pattern of rewarming of palm skin temperature (Tsk) after dipping the hand in water of 10 +/- 1 degrees C for 2 min (Tromp's water bath test). The ThE of the SJs was compared to that of 10 acclimatized lowlanders (ALs) staying at the same altitude for about 1 year and 10 high-altitude natives (HANs). In SJ, at sea level (SL), the effect of seasonal variation and ambient temperature on ThE was also studied. The initial Tsk of the palm (29.9 degrees C) was lower at altitude as compared to SL value (32.2 degrees C) in SJs inspite of similar ambient temperature (21 +/- 1 degrees C). There was a prolongation of rewarming time in all the subjects during stay at altitude. The rewarming curve showed a shift towards the right, indicating slower rewarming. The rewarming response of ALs and SJs was comparable at altitude. In HANs, the rewarming at altitude was faster and resembled those of SJs at SL. The rewarming improved in the season following cold months, and at higher ambient temperature in the same season, on the plains. It may be concluded that thermoregulation efficiency of man deteriorates at high altitude, and the peripheral vascular responses to local cold stress do not reach the level attained by natives even after 1 year of acclimatization. General cold acclimatization improves the rewarming response.

Acclimatization↗
PubMed1978

Changes in EEG pattern during acclimatization to high altitude (3500 m) in man.

This study was conducted on 30 healthy soldiers to observe EEG changes during acclimatization to high altitude. Of these subjects, 10 were lowlanders (LL), 10 were acclimatized low landers (AL), and 10 10 were high-altitude natives (HAN). The EEG was recorded by the 10-20 international system of electrode placement in LL at sea level (SL) during rest and hyperventilation (HV). Then they were air-lifted to an altitude of 3500 m where periodic recordings of EEG were made for 4 weeks. For comparison, the altitude recordings were also made in AL and HAN. The quantitative analysis of EEG (occipital) was done to determine alpha index (AI) and average amplitude. The mean AI was 25.5% at SL in LL, which changed to 45.7%, 15.8%, 28.0%, 30.3%, and 33.2% on days 2, 7, 14, 21, and 28, respectively. The average amplitude was 17.3 microV at SL, which changed to 23.3 microV, 11.8 microV, 16.2 microV, 17.3 microV, and 19.8 microV on days 2, 7, 14, 21, and 28, respectively. In two subjects, spiking was seen along with the desynchronized pattern of EEG on days 7 and 14. The AI and average amplitude of AL and HAN were significantly more than those of LL. The magnitude of buildup during HV was greater at altitude. These results indicate that there is cerebral cortical depression in the initial phase of induction which changes to cortical desyncronization in the latter part of the first week of induction. During acclimatization, there is gradual buildup of EEG waves, as observed in AL and HAN.

Acclimatization↗
PubMed1977

Cold-induced vasodilatation and peripheral blood flow under local cold stress in man at altitude.

The cold-induced vasodilatation (CIVD) response was studied on 17 lowlanders (20-30 years) at Delhi, using a water bath maintained at 4 degrees+/-0.2 degreesC. The temperatures were measured at the tip of the index finger, centre of the palm, over a prominent wrist vein, and orally. Then the subjects were air-lifted to an altitude of 3500 m, where the measurements were repeated at weekly intervals for a period of 3 weeks. After this, they were flown back and retested. For comparison, the study at altitude was done on 10 acclimatised lowlanders and on 10 high-altitude natives. The peripheral blood flow under a local cold stress was calculated. Three types of CIVD responses--viz. typical hunting, proportional control, and continuous rewarmin--were observed. At altitude, the pattern was more or less the same but there was a significant reduction in the response. The responses of the natives were more or less identical to those of the lowlanders at sea level, and responses of the acclimatized lowlanders were better than the fresh inductees, but much less than the natives. The changes in peripheral blood flow was in accordance with the CIVD response.

Acclimatization↗