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Biomedical subjects

C K Nair

Publications and source records attributed to C K Nair.

At least 19 recordsLinked to original sources
PubMed1996

Nuclear matrix bound DNA polymerase-beta in mouse fibrosarcoma: effect of gamma-radiation.

Nuclear matrices isolated from the mouse fibrosarcoma tumour cells contain the eukaryotic replicative enzyme DNA polymerase-alpha and the presumptive repair enzyme DNA polymerase-beta. Exposure of tumors to various doses of gamma-radiation (1.95 to 6.5 Gy) causes a 2-fold increase in the levels of only DNA polymerase-beta in the nuclear matrix. The increase in the levels of this enzyme is not discernible if the matrices are isolated 24 hr after irradiation. The rise in the levels of the repair enzyme DNA polymerase-beta could be indicative of radiation stress response of the tumour cells and their repair ability.

Animals↗
PubMed1992

Ten-year experience with mitral valve replacement in the elderly.

Limited data are available on mitral valve replacement in the elderly patient. Therefore we report our 10-year experience including predictors of perioperative mortality and subsequent long-term cardiac mortality in elderly patients with mitral valve replacement compared to younger patients. Of the 126 consecutive patients with mitral valve replacement, 26 were older (77 +/- 4, group 1) and 100 were younger (62 +/- 9, group 2) than 70 years. Bioprostheses were used more frequently in patients in group 1 (65% vs 7%, p less than 0.0001). Of the 21 clinical, ECG, hemodynamic, and angiographic variables studied, patients in group 1 had higher pulmonary artery systolic pressure (57 +/- 15 vs 48 +/- 19, p less than 0.05), fascicular block on ECGs (70% vs 33%, p less than 0.005), and greater pump time on cardiopulmonary bypass (160 +/- 75 vs 120 +/- 50 minutes, p less than 0.025). A trend toward a higher perioperative mortality rate was also seen in group 1 (27% vs 12%, p = 0.058). Predictors of perioperative mortality by multivariate analysis were the presence of aortic calcification and prolonged pump time on cardiopulmonary bypass in group 1 and coronary artery disease, female sex, elevated mean pulmonary artery pressure, and postoperative complete atrioventricular block in group 2. During a mean 4-year follow-up period, cardiac mortality and total mortality rates were 42% and 54%, respectively, for group 1 compared to 24% and 35%, respectively, for group 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1991

Chemical radiosensitization by misonidazole: production and repair of DNA single-strand breaks in Yoshida ascites tumor cells.

Formation of strand-breaks in DNA and its repair in Yoshida ascites tumor cells exposed to gamma radiation (100-400 Gy) in presence and absence of misonidazole (10 mM) were studied. The methodology involved pre-labelling of cellular DNA by 3H-thymidine during cell proliferation in rats, irradiation of cells in vitro and analysing sedimentation profile of DNA by ultracentrifugation in alkaline sucrose density gradients. Irradiation under euoxic conditions resulted in formation of about 1.5 times greater number of strand breaks as compared to those formed during irradiation under hypoxic conditions. Misonidazole (10 mM) by its presence along with the cells during irradiation under hypoxic conditions caused a 3-fold increase in the number of single strand breaks, but under euoxic conditions of irradiation the presence of misonidazole did not enhance the strand break formation. Incubation of cells irradiated in absence of misonidazole for 1 hr in tissue culture medium at 37 degrees C resulted in repair of substantial fraction of the strand breaks while there was no repair of the DNA strand breaks in cells irradiated in the presence of the chemical.

Animals↗
PubMed1990

Ten-year results with the St. Jude Medical prosthesis.

Although the hemodynamic characteristics and durability of the St. Jude valve prosthesis have been reported, the need for and the degree of anticoagulation in patients who receive these valves remain uncertain. Our 10-year experience with 165 patients (100 men and 65 women, mean age of 58 +/- 13 years), who underwent valve replacement with St. Jude prostheses, is reported. Of the 165 patients, 147 were treated with warfarin. A prothrombin time 1.3 to 1.8 times control (range 15 to 20 seconds) was maintained in 134 patients with single valve and 1.8 to 2 times control (range 20 to 25 seconds) in 13 patients with double valve prostheses. The 10-year actuarial event-free incidence from thromboembolic and hemorrhagic complications was 84 and 95%, respectively. Of the 8 patients receiving antiplatelet therapy alone, 4 had thromboembolic events. Of the 10 patients on neither warfarin nor antiplatelet therapy, 3 had thromboembolic events. The 10-year actuarial event-free incidence from valve failure was 95%. The 10-year actuarial patient survival was 55%. Thus, the St. Jude valve is a safe and reliable prosthesis with acceptable overall long-term performance in patients given a modest anticoagulation regimen. Patients who receive St. Jude prosthetic valves without anticoagulants have a high incidence of thromboembolic events despite therapy with antiplatelet agents.

Adolescent↗
PubMed1989

Long-term follow-up of patients with echocardiographically detected mitral anular calcium and comparison with age- and sex-matched control subjects.

One hundred seven patients with echocardiographically documented mitral anular calcium (MAC) and 107 age- and sex-matched control subjects without MAC were studied and followed for a mean of 4.4 +/- 2.4 (standard deviation) years. Fourteen (7%) patients were lost to follow-up. Compared with the control group, patients with MAC had higher frequency of precordial murmurs (p less than 0.0001), cardiomegaly (p less than 0.0001), left atrial enlargement (p less than 0.0001), and rhythm and conduction disturbances (p less than 0.0001). During the follow-up, patients with MAC had higher incidence of valve replacement (p less than 0.0025), permanent pacemaker implantation (p less than 0.0025), congestive heart failure (p less than 0.0001), thromboembolic cerebrovascular event (p less than 0.01), sudden death (p less than 0.001) and total cardiac death (p less than 0.0001). However, the frequencies of myocardial infarction, coronary artery bypass surgery and angioplasty, endocarditis or noncardiac death were not significantly different between patients with MAC and the control subjects. Thus, patients with MAC have higher frequencies of precordial murmurs, cardiomegaly, left atrial and ventricular enlargement, rhythm and conduction disturbances. They more frequently undergo valve replacement and permanent pacemaker implantation, develop congestive heart failure and die of cardiac causes than age- and sex-matched control subjects.

Adult↗
PubMed1989

Purification and characterisation of an inducible beta-galactosidase from Corynebacterium murisepticum.

The beta-galactosidase (EC 3.2.1.32) of Corynebacterium murisepticum (inducible by lactose and galactose) was purified by successive column chromatography on Sephadex G-200, DEAE-Sephadex A-50 and DEAE-cellulose (DE52). The enzyme was found to be a dimer of identical subunits of molecular mass 100,000 daltons. The Km values of the enzyme for the substrates lactose and o-nitrophenyl-beta-D-galactopyranoside (ONPG) are 16.7 mM and 4.4 mM, respectively, indicating, its low affinity for the substrates. The Ouchterlony immunodiffusion method exhibited immunological homogeneity of the enzyme preparation. The catalytic site of the enzyme does not take part in antigen-antibody reaction.

Chromatography↗
PubMed1989

Previously unreported adverse reaction to encainide.

We describe a patient with recurrent atrial fibrillation who suffered a previously unreported adverse reaction to encainide therapy manifested by fever, chills, diaphoresis and myalgia. The patient had a similar response upon rechallenging with encainide, which resolved on discontinuation of therapy.

Aged↗
PubMed1988

Clinical significance of exercise-induced bundle branch block.

To evaluate the diagnostic significance and long-term follow-up data of patients with exercise-induced bundle branch block (BBB), 10,176 consecutive patients' exercise test data were reviewed and 50 patients found to have exercise-induced BBB. Clinical, exercise test and arteriographic data were analyzed along with follow-up data during a mean of 43 months. Of the 50 patients, 37 had exercise-induced left BBB and 13 had exercise-induced right BBB. Significant coronary artery disease (CAD) was diagnosed in 26 of 37 patients (70%) with exercise-induced left BBB and in all 13 patients (100%) with exercise-induced right BBB. In patients who underwent coronary arteriography, data demonstrated a high prevalence of proximal left anterior descending disease (17 of 20, 85%). Follow-up data revealed that exercise-induced BBB was associated with a 36% (18 of 50) incidence of coronary events, including 16 patients who underwent coronary artery bypass grafting and 2 hospitalized for congestive heart failure. Results indicated that exercise-induced BBB was infrequent and occurred primarily in association with CAD, had a high prevalence of proximal left anterior CAD, infrequently had similar onset and offset heart rates, was reproducible and associated with a greater incidence of coronary artery bypass grafting than had been previously reported, although the incidence of cardiac events was similar to those investigations.

Adult↗
PubMed1988

Mitral annular calcification and coarctation of aorta.

Although coarctation of the aorta is associated with various cardiac abnormalities, its association with mitral annular calcification (MAC) is not reported. We therefore report a 37-year-old patient with postductal coarctation of the aorta and MAC. Considered to be a degenerative process, MAC is usually seen in elderly patients. It is uncommon in patients less than 50 years old and rare before the age of 40 years. Previous studies have reported increased frequency of cardiac conduction disturbances in patients with MAC compared to age- and sex-matched controls. This is in agreement with complete right bundle-branch block noted on the electrocardiogram of our patient. Clinicopathologic correlative studies and long-term follow-up may determine how such conduction disturbances develop and progress.

Adult↗
PubMed1987

Calcific valvular aortic stenosis with and without mitral anular calcium.

Seventy-six consecutive patients, mean age 66 +/- 9 years (+/- standard deviation), with isolated aortic valve replacement for calcific valvular aortic stenosis (AS) were studied. Mitral anular calcium (MAC) was detected by echocardiography in 45 patients (59%). Patients with MAC were older (p less than 0.01), had greater peak systolic aortic valve gradients (p less than 0.025), lower cardiac indexes (p less than 0.025) and smaller valve areas (p less than 0.05) than patients without MAC. Thirty-three percent of patients (15 of 45) with MAC required permanent pacemaker implantation after aortic valve replacement, compared with only 10% of patients (3 of 31) without MAC (p less than 0.025). During the follow-up of 7 years (mean 3.8 +/- 1.6), 27% of patients (12 of 45) with MAC died from cardiac causes, compared to only 7% (2 of 31) without MAC (p less than 0.025). Thus, patients with AS and MAC are older, have more severe AS, more frequently undergo permanent pacemaker implantation after aortic valve replacement and more frequently die of cardiac causes than patients with AS and no MAC during follow-up.

Adult↗
PubMed1984

Clinical characteristics of patients younger than 60 years with mitral anular calcium: comparison with age- and sex-matched control subjects.

The clinical characteristics of 107 patients younger than 60 years with mitral anular calcium (MAC) were compared with those of 107 age- and sex-matched control subjects. The patients with MAC included 55 men and 52 women, mean age 51 years. The control group included 55 men and 52 women, mean age 51 years. Patients with MAC had a higher prevalence of cardiomegaly on chest x-ray (p less than 0.0001), left atrial and left ventricular enlargement by echocardiography (p less than 0.0001), precordial murmurs (p less than 0.0001), diabetes mellitus (p less than 0.0001), systemic hypertension (p less than 0.025) and total conduction defects on surface electrocardiograms (p less than 0.0001) compared with the age- and sex-matched control subjects. The mean serum phosphorus and product of serum calcium and phosphorus were higher in patients with MAC (p less than 0.0025) than in the control subjects. The prevalence of coronary heart disease, aortic stenosis and hypertrophic cardiomyopathy and the mean serum cholesterol, triglyceride, total protein, albumin, creatinine, alkaline phosphatase and calcium levels were not significantly different between patients with MAC and the control subjects.

Adult↗