Biomedical subjects

S Balakrishnan

Publications and source records attributed to S Balakrishnan.

At least 19 recordsLinked to original sources

PubMed1999

Cytogenetic analysis of peripheral blood lymphocytes of occupational workers exposed to low levels of ionising radiation.

The incidence of chromosomal aberrations was analysed in peripheral blood lymphocytes of occupationally exposed people having cumulative doses of 500 mSv. The exposed individuals showed higher frequencies of dicentrics as well as acentrics than normal controls. Absorbed radiation dose was calculated by using in vitro dose response curve established for Cobalt-60 gamma rays. In the control constituting 17 healthy individuals, two dicentrics were detected among 3700 metaphases analysed. In the exposed group 27 dicentrics and one centric ring was detected among 8400 metaphases analysed. Due to small number of dicentrics scored in each individual, the dose estimate suffers from a large statistical uncertainty. The collective dose was found to be 1.89 Gy. This is in good agreement with the corrected physical doses, assuming a mean life of 10 years for the disappearance of lymphocytes. The physical doses accumulated during the last 10 years of occupation were also in good agreement with the biological dose estimate.

Adult↗

PubMed1999

Anticonvulsant profile of nimodipine and nitrendipine against pentylenetetrazole induced seizures in rats.

The activity of nimodipine and nitrendipine against pentylenetetrazole (PTZ) induced seizures in Albino rats was studied alone and in combination with valproate. The median effective dose [ED50] of valproate, nimodipine and nitrendipine were initially determined. All the 3 drugs were injected i.p. 30 min before the induction of seizures. Seizures were induced by PTZ 85 mg/kg i.p., and subsequently the effect of combining ED50 doses of nimodipine and nitrendipine with ED50 dose of valproate was evaluated. ED50 of valproate and nitrendipine were 129 and 2.5 mg/kg respectively. ED50 of nimodipine could not be established since a dose-response relationship was not obtained. Hence, for the purpose of combination studies, 4 mg/kg of nimodipine was used. Both nimodipine (4 mg/kg) and nitrendipine (2.5 mg/kg) decreased the ED50 of valproate from 129 to 40 mg/kg. Both nimodipine and nitrendipine potentiate the activity of valproate against PTZ induced seizures and can be considered as potential adjuvant anticonvulsants which merit further study.

Animals↗

PubMed1999

Role of nitric oxide in electroshock and pentylenetetrazole seizure threshold in rats.

There are contradictory reports on whether nitric oxide (NO) is a proconvulsant or anticonvulsant. Hence a study was designed to investigate the effect of NO donor l-Arginine and NO synthesis inhibitor N omega-nitro-L-arginine (NOARG) on electroshock- and pentylenetetrazole (PTZ)-induced seizure threshold in rats. L-arginine was tested in three doses (75, 150 and 300 mg/kg), and NOARG was administered in doses of 4, 8 and 16 mg/kg. L-Arginine increased the intensity of current required to produce a threshold seizure, whereas NOARG had the opposite effect. In PTZ-induced seizures, L-arginine significantly decreased the dose of PTZ required to produce a threshold seizure, while NOARG increased it. Hence, it was concluded that NO synthase inhibition had the opposite effect in electroshock- and PTZ-induced seizures, meriting further studies on the mechanism of effect.

Animals↗

PubMed1999

Role of nitric oxide on insulin induced seizures in mice.

The role of nitric oxide (NO) on acute hypoglycemia-induced seizures in mice was investigated using insulin as the hypoglycemic agent. The NO precursor L-arginine in the doses of 150, 500 and 750 mg/kg exhibited a dose-dependent protective effect against seizures induced by 8 mu/kg insulin. The NO synthase inhibitor (L-NMMA) at the doses of 50 and 100 mg/kg potentiated the subconvulsive doses of insulin (2 mu/kg). The onset, duration, number of seizures and the mortality were noted in a 2 hr study period. The results of this study suggest than NO plays an important protective role in acute hypoglycemia induced seizures which are known to occur through the activation of NMDA receptors.

Animals↗

PubMed1999

Cognitive dysfunction induced by phenytoin and valproate in rats: effect of nitric oxide.

Phenytoin (PHT) and Valproate (VPA) are known to induce cognitive dysfunction, in terms of long term memory loss. Nitric oxide (NO) on the other hand is said to help in long term potentiation and hence enhance memory. The effects of nitric oxide donor L-arginine (L-Arg) and nitric oxide synthase inhibitor N-W-L-Nitroarginine (L-NOARG) were studied on the cognitive dysfunction, induced by PHT and VPA in normal healthy rats, using the step-through passive avoidance test (PAT). It was observed that combining L-Arg with PHT significantly enhanced long term memory while, combining PHT with L-NOARG decreased it, as compared to PHT alone. When combined with VPA, L-Arg and L-NOARG increased the retention latency as compared to PVA alone but this was not statistically significant. We conclude that the No donor L-Arg is able to increase the difference in LTE in acquisition and retention trials with both PHT and VPA, but with VPA the increase is not statistically significant.

Animals↗

PubMed1998

Radiotelemetric versus externalized catheter monitoring of blood pressure: effect of vasopressin in spontaneous hypertension.

The changes in arterial pressure that follow withdrawal of a 3-h intravenous infusion of arginine vasopressin (AVP; 20 ng/kg/min) in spontaneously hypertensive rats (SHR) were monitored by radiotelemetry or conventional externalized femoral arterial catheters connected to pressure transducers. Baseline control arterial pressure was lower in the telemetry group compared to the externalized group. After withdrawal of the AVP infusion, blood pressure fell below preinfusion levels in both groups but the decrease was much less in the telemetry group. Strikingly, absolute blood pressure values recorded both during and after the vasopressin infusion were remarkably similar in the two groups. Responses in rats with externalized catheters implanted 7 days before infusion of AVP, a protocol similar to the telemetry group, were similar to those in rats with catheters implanted 24 h earlier. Blood pressure remained decreased in SHR infused with AVP for several days with complete recovery requiring 6-7 days. In contrast, physical activity decreased only on the first day following withdrawal of the infusion. Thus, the mechanism accounting for the blood pressure decrease must be of a long duration and unrelated to a change in gross physical activity. The results emphasize the value of radiotelemetry for recording blood pressure responses.

Animals↗

PubMed1998

Effect of nimodipine on the efficacy of commonly used antiepileptic drugs in rats.

Effect of nimodipine was studied alone and in combination with phenytoin and valproate in maximal electroshock seizures in rats. The test drug was injected i.p. and seizures elicited by a 60 Hz alternating current of 150 mA intensity for 0.25 sec duration through corneal electrodes. The median effective dose (ED50) of phenytoin, valproate and nimodipine were found to be 13, 255 and 4 mg/kg respectively. Addition of ED50 of nimodipine to ED50 of phenytoin and valproate produced an additive effect. Addition of ED25 of nimodipine to ED25 of phenytoin and valproate produced asynergistic effect. Our results show that addition of nimodipine significantly potentiates the anticonvulsant efficacy of phenytoin and valproate.

Animals↗

PubMed1997

Effect of nimodipine on the cognitive dysfunction induced by phenytoin and valproate in rats.

Anticonvulsant effects of phenytoin (PHT) and valproate (VPA) were studied alone and in combination with nimodipine (NMD) against maximal electroshock (MES)-induced seizures in rats. PHT and VPA induce cognitive deficit in terms of long-term memory loss. The effect of NMD on the cognitive deficit induced by PHT and VPA was studied through the step-through passive avoidance test (PAT). It was seen that there was a potentiation of antielectroshock effect of PHT and VPA when NMD at a dose of 4 mg/kg was combined with PHT or VPA. NMD reversed the long-term memory loss induced by PHT and VPA in the PAT.

Animals↗

PubMed1996

Cardiac output mediates the antihypertensive effect of vasopressin in spontaneous hypertension.

The contribution of cardiac output and total peripheral resistance to the fall in arterial pressure that follows cessation of a 3-h intravenous infusion of arginine vasopressin (AVP; 20 ng.kg-1.min-1) was studied in conscious spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats instrumented with radiotelemetric probes for recording of blood pressure and ultrasonic transit-time flow probes for measuring cardiac output. Cessation of a 3-h infusion of AVP resulted in a significant decrease in arterial pressure in SHR (14-17 mmHg below preinfusion control levels) but not in WKY or in vehicle-treated controls. The fall in pressure persisted for several days. The fall in pressure was associated with a large decrease in cardiac output of 22 +/- 2 ml/min below control levels in SHR, and the time course of the cardiac output response over several days approximated the time course of the pressure response. By contrast, total peripheral resistance remained elevated for some time on withdrawal of the AVP infusion. We conclude that the withdrawal-induced antihypertensive phenomenon in SHR is mediated by a fall in cardiac output and not by a decline in total peripheral resistance.

Animals↗

PubMed1993

Poor cognitive task performance of insulin-dependent diabetic children (6-12 years) in India.

UNLABELLED: Cognitive function was assessed in 22 diabetic and 39 healthy children, all in the age group of 6-12 years. Wechsler's coding, digit span test and Raven's colored progressive matrices were included in the battery of tests. The diabetic children underscored on all these tasks compared to the healthy children. The raw scores (mean +/- S.D.), of the diabetic and healthy children were: Wechsler's coding: 17.4 +/- 6.48, 37.4 +/- 9.33; digit span: 22.0 +/- 8.8, 44.1 +/- 7.67 and on Raven's A+AB+B: 16.2 +/- 3.5. 24.1 +/- 6.26; P < 0.001 in each instance, respectively. Duration of diabetes did not correlate with any of the test scores. No significant differences were noted between the early onset (IDDM starting before the age of 5 years) and late onset (IDDM starting after 5 years) diabetic children in their performance. We attribute the very low scores in our diabetic children to the psycho-social factors in addition to the metabolic control. CONCLUSIONS: (1) specific cognitive dysfunction is present in children with IDDM compared to the healthy children; (2) duration of diabetes did not correlate with cognitive function scores; (3) IDDM manifesting after the age of 5 years also had hitherto unknown detrimental effects on the cognitive process.

Age of Onset↗

PubMed1992

A psychological study of spinal cord injured patients involved in the Madras Paraplegia Project.

The psychological features of spinal cord injured (SCI) patients involved in the Madras Paraplegia Project are described. Three hundred and twenty-eight patients were studied. Based on personality tests, 11% were extroverts, 14% were introverts and 76% were neither extroverts nor introverts. Twenty-four percent of the subjects were neurotic, 11% had a depressive illness, and 26% had pathological anxiety. The study has highlighted the psychological status of SCI patients, and the usefulness of a psychiatric team in the multidisciplinary care of such patients. This is probably the first large psychological study of SCI patients from a developing country.

Adult↗

PubMed1991

Rupture of the pregnant uterus--a 21-year review.

Uterine rupture is still a common problem in developing countries although even here the incidence varies from urban to rural settings. This article is a review of uterine rupture in an urban referral hospital in Malaysia. It examines aetiology, clinical presentation, complications and management of the problem. Meticulous screening of patients together with optimal antenatal and intrapartum care will markedly reduce the incidence of uterine rupture. Early diagnosis and prompt treatment will further help reduce morbidity and mortality to both mother and fetus.

Cesarean Section↗

PubMed1991

Serum zinc/copper ratio in subtypes of leprosy and effect of oral zinc therapy on reactional states.

Serum zinc and copper levels and zinc/copper ratios were studied in 86 healthy controls, 45 cases of borderline tuberculoid (BT), 31 cases of borderline lepromatous (BL), 117 cases of lepromatous (LL) leprosy patients, 16 cases with severe erythema nodosum leprosum (ENL) reaction, and 16 cases with ENL reaction receiving oral zinc therapy. A significant reduction in serum zinc levels was noticed in all types of leprosy, the maximum decrease being seen in cases with ENL reaction. Conversely, the copper levels were significantly increased from BT to LL cases with ENL reaction in a progressive manner. A very good negative correlation (r = -0.998) was noticed between mean serum zinc and copper levels from healthy controls to active LL cases with ENL reaction. After oral zinc therapy, the serum zinc levels were significantly increased in all of the 16 LL patients with ENL reaction. In contrast, the copper levels were not decreased, indicating that oral zinc therapy can restore normal zinc levels in leprosy patients but is unable to reduce the increased copper levels.

Administration, Oral↗

PubMed1990

Reye and Reye-like syndromes: results of a pilot study in Peninsular Malaya, 1986.

A pilot epidemiologic study of all cases of Reye and Reye-like syndromes was undertaken at 8 representative major hospitals in Peninsular Malaya from January 1st to December 31st 1986. The cases were classified as definitive Reye's syndrome, clinical Reye's syndrome and encephalo-hepatopathies. Less than 50% of cases reviewed fulfilled the National Center for Disease Control criteria for clinical Reye's syndrome. Causes of Reye-like syndromes/encephalo-hepatopathies included fulminant hepatitis, Japanese B encephalitis, dengue, septicaemia, and complex febrile fits. It was not possible to differentiate clinical Reye's syndrome from the other encephalo-hepatopathies by either the clinical features (except for jaundice) or biochemical parameters. Liver biopsy is necessary for a definitive diagnosis of Reye's syndrome in Malaysia, because of the high prevalence of Reye-like diseases. The mortality rate in the 2 groups of patients is similar. Ingestion of salicylates was not found to be significantly associated with Reye and Reye-like syndromes in this study.

Diagnosis, Differential↗

PubMed1989

Hyperbilirubinaemia and erythrocytic glucose 6 phosphate dehydrogenase deficiency in Malaysian children.

Cord blood from 8,975 babies delivered in Hospital Sultanah Aminah Johor Bahru over a period of eight months (1st August 1985 to 31st March 1986) were screened for G6PD deficiency. The overall incidence was 4.5% in Chinese, 3.5% in Malays and 1.5% in Indian babies. One hundred of these babies were observed in the nursery for seven days and their daily serum bilirubin recorded. The serum bilirubin peaked at 96 hours to a value of 12mg%. None of the babies in the nursery developed a serum bilirubin level of more than 15mg%. Six of the babies with G6PD deficiency that were sent home were readmitted with hyperbilirubinaemia that needed exchange transfusion.

Asian People↗

PubMed1989

Sub clinical infection and the relative risk of developing leprosy: a statistical approach.

Subclinical infection in contacts of leprosy patients was identified by FLA-ABS test and Serum Antibody Competition Test (SACT). The risk of developing leprosy and the confidence intervals were worked out. The importance of expressing the risk ratio and confidence interval of the tests is brought out. This method is a useful adjunct to the routine statistical methods in epidemiological studies.

Antibodies, Monoclonal↗

PubMed1989

Investigations into the haemolytic effects of dapsone therapy in leprosy patients.

Investigations into the haemolytic effects of dapsone therapy were carried out in forty four leprosy patients admitted to the Sacred Heart Leprosy Centre, Kumbakonam. They received weight based dapsone dosages varying from 1.3-3.3 mg/kg body weight. Blood levels and urinary Dapsone/creatinine ratio were assessed at 1 day, 7 days and 30 days of Dapsone treatment. At the same points of time, haematological observations were also carried out. Serum bilirubin as well as blood mathaemoglobin were also examined. The findings showed a reduction in Hb levels at 30 days observation in a good proportion of cases on 100 mg. In one case (child) weighing 15 kg and receiving 50 mg dapsone increased mathaemoglobin was observed. It is suggested that dapsone dosage be regulated to body weight and preferably not to exceed 1.5 mg/kg body weight.

Adolescent↗

PubMed1988

Influence of acetylator phenotype of the leprosy patient on the emergence of dapsone resistant leprosy.

The half time of disappearance of dapsone and monoacetyl dapsone and the acetylator phenotype of the leprosy patients who harboured dapsone sensitive and dapsone resistant M. leprae was assessed in 27 subjects. Sixteen patients were rapid acetylators, five were slow and six were intermediate acetylators. The mean T 1 1/2 lives of dapsone (30.26 +/- 11.0) and monoacetyl dapsone (31.11 +/- 12.0) were also studied in the above patients. The percentage of different acetylators in both resistant and sensitive groups were similar showing no correlation between the emergence of drug resistance and the phenotype of the patient. The mean time of disappearance of DDS and MAD in the different acetylators did not show significant difference. The ratios of MAD/DDS in an individual at 3, 6 or 24 hours after the dose were similar. The mean T 1 1/2 lives of DDS and MAD in resistant and sensitive patients also showed no difference. Neither T 1 1/2 lives of DDS or MAD nor the acetylator phenotype seem to influence the emergence of dapsone resistance.

Acetylation↗