Search PubMed⌕ Search

Biomedical subjects

M Nair

Publications and source records attributed to M Nair.

At least 73 records · Page 4Linked to original sources
PubMed1979

Impairment of cell-mediated immunity functions by dietary zinc deficiency in mice.

Several immunologic features were analyzed in mice on a zinc-deficient diet [Zn(-)], in mice pair-fed a diet containing zinc [Zn(+)], in mice fed a Zn(+) diet ad lib, and in mice fed laboratory chow ad lib. When placed on a Zn(-) diet, 6- to 8-week-old A/Jax, C57BL/Ks, and CBA/H mice showed loss of body weight, low lymphoid tissue weight, and profound involution of the thymus within 4-8 weeks after initiation of the regimen. Approximately 50% of the mice on the Zn(-) diet developed severe acrodermatitis enteropathica (lesions on tail and paws) and diarrhea. Pair-fed mice on the Zn(+) diet did not show any of these symptoms. Mice on the Zn(-) diet showed the following immune deficiencies: (i) depressed plaque-forming cells against sheep erythrocytes after in vivo immunization; (ii) depressed T killer cell activity against EL-4 tumor cells after in vivo immunization; and (iii) low natural killer cell activity. However, antibody-dependent cell-mediated cytotoxicity against chicken erythrocytes was normal in the mice on the Zn(-) diet. Deficiency of T killer cell activity was not observed when immunization with EL-4 allogeneic lymphoma cells was carried out in vitro. Progressive loss of relative and absolute number of Thy 1.2+ cells and a proportionate relative increase in cells bearing Fc receptors was seen in spleen and lymph nodes of Zn(-) animals. It appears that zinc is an essential element for maintenance of normal T cell and other immune functions in vivo.

Animals↗
PubMed1979

Studies in acute leukemia. I. Antibody-dependent and spontaneous cellular cytotoxicity by leukemic blasts from patients with acute nonlymphoid leukemia.

Leukemic blasts from patients with acute nonlymphoid leukemia were examined for the presence of Ig, receptors for IgGFc, and for their capacity to mediate antibody-dependent cellular cytotoxicity (ADCC) against chicken red blood cells (RBC) coated with IgG and spontaneous cell-mediated cytotoxicity (SCMC) against cells of K562 cell line. Leukemic blasts from acute myeloblastic leukemia (AML) patients lacked both Fc receptors and Ig on their surface, had no SCMC activity and majority, but not all of them, lacked ADCC activity. Leukemic blasts from patients with acute monocytic leukemia (AMOL) had Fc receptors, and 50% had IgG on their surface. IgG was cytophilic and appeared not to be directed against cell-surface antigens. This antibody did not interfere with the ADCC activity of leukemic cells. Leukemic blasts from majority of patients with AMOL mediated ADCC, but had no SCMC activity. An association between ADCC and presence of Fc receptor was observed.

Adult↗
PubMed1978

Spontaneous and antibody-dependent cell-mediated cytotoxicity by human T cell subpopulations.

Human peripheral blood non-T cells, T cells and their subpopulations (Tmu, Tgamma, Tphi, Tgamma-depleted cells, and Tmu-depleted cells) were assayed for their capacity to mediated spontaneous lymphocyte-mediated cytotoxicity (SLMC) or natural killer activity against K562 tumor cell line and antibody-dependent cellular cytotoxicity (ADCC) against chicken erythrocytes coated with antibody. Non-T cells, unseparated T cells, Tgamma cells, and Tmu-depleted (Tgamma-enriched) cells were found to have both SLMC (NK activity) and ADCC. Tmu, Tphi, and Tgamma-depleted cells had minimal or no SLMC and ADCC activity. This study demonstrates that SLMC and ADCC activity in T cells is mediated by Tgamma cell subpopulations. These two cytotoxic reactions were either mediated by two distinct subsets of Tgamma cells or by a single effector cell using two different mechanisms.

Antibody-Dependent Cell Cytotoxicity↗
PubMedDate not supplied

Circadian immune measures in healthy volunteers: relationship to hypothalamic-pituitary-adrenal axis hormones and sympathetic neurotransmitters.

OBJECTIVE: The purpose of this study is to examine the circadian pattern of specific immunologic measures and to compare observed circadian rhythms of these measures with the well-established circadian rhythms of hypothalamic-pituitary-adrenal axis hormones and sympathetic neurotransmitters. METHODS: Blood samples were collected every 2 hours for a total of 24 hours from nine healthy volunteers. The blood samples were assayed for hormones and immune measures, including adrenocorticotropic hormone (ACTH), cortisol, norepinephrine, and epinephrine. The immune measures included percentage and absolute number of neutrophils, lymphocytes, the lymphocyte subsets CD3+ (T cells), CD4+ (T helper/inducer), CD8+ (T suppressor/cytotoxic), CD56+ (natural killer [NK] cells) and NK cell activity (NKCA). RESULTS: The following immune measures exhibited a significant circadian rhythm: the percentages of neutrophils, CD4+ cells, and CD56+ cells; the absolute numbers of total lymphocytes, CD3+ cells, CD4+ cells, and CD8+ cells; and NKCA. Cross-correlations between the circadian rhythms of selected hormones and immune measures indicated a strong inverse association between the circadian rhythms of cortisol and the different T cell subsets on the one hand, and a strong direct association between the rhythms of cortisol and the percentage of CD56+ and NKCA on the other. Cross-correlations involving the circadian rhythms of norepinephrine and the same immune measures were in general much weaker and statistically nonsignificant. CONCLUSION: In healthy individuals, both enumerative and functional immune measures exhibit circadian rhythms that seem to be associated most closely with the circadian rhythm of cortisol.

Adrenocorticotropic Hormone↗
PubMedDate not supplied

Radiofrequency catheter ablation of common atrial flutter--acute and follow-up results.

Atrial flutter with a structurally well-defined macro-reentrant circuit in the right atrium has recently become amenable to radiofrequency ablation with the recognition of isthmus as a narrow zone of slow conduction. This study describes 20 consecutive and symptomatic patients with atrial flutter (15 males, 5 females; mean age 38.5 +/- 10.2 years) who underwent radiofrequency ablation in our institute in the last 18 months. Fourteen patients had structurally normal hearts, while the remaining six patients had specific disorders (prior surgery for closure of atrial septal defect-2, idiopathic restrictive cardiomyopathy-1, primary sinus node dysfunction-2, tachycardiomyopathy-1). The endpoints of a complete isthmus block and conversion to sinus rhythm were achieved in 19 of the 20 patients. Total number of pulses needed to attain the endpoints was a mean of 4.2 (range 1-5), each pulse being delivered for 90 seconds. At a mean follow up of 9.4 +/- 3.2 months (range 6-12 months), recurrence of atrial flutter was seen in one patient, atrial fibrillation in two and sinus node reentrant tachycardia in one. These results are comparable to those reported in the literature. Achievement of a complete isthmus block appears to be an important endpoint in obtaining optimal results. The issues of alternative sites of ablation, long-term results and advantages of an 8 mm tip catheter need to be examined further. In conclusion, radiofrequency ablation appears to be the preferred mode of treatment for patients with atrial flutter with excellent short-term and mid-term results.

Adolescent↗
PubMedDate not supplied

Recording of double atrial potentials as a marker for isthmus block during ablation of atrial flutter.

Radiofrequency ablation is an established method for treatment of type I atrial flutter. The assessment of creation of complete bidirectional isthmus block following linear ablation of the isthmus is an integral part of ablation procedure. Conventionally, bidirectional isthmus block is tested by pacing on either side of ablation line and looking for reversal of activation sequence in the right atrium. We looked at the feasibility of recording double potentials, separated by an isoelectric interval along the ablation line as an alternative method to demonstrate bidirectional isthmus block. An attempt was made to record the double potentials following linear ablation of the cavotricuspid isthmus. Following ablation, bidirectional isthmus block was also tested by pacing from the coronary sinus os and the low-lateral right atrium. We could demonstrate double potentials in 9 of the 11 patients in whom we attempted to record them following linear ablation of flutter. The presence of bidirectional block by pacing from coronary sinus os and low lateral right atrium could be demonstrated in 10 (91%) patients. Thus, double atrial potentials, separated by an isoelectric interval can be demonstrated following ablation of atrial flutter. Double potentials, if demonstrable on coronary sinus os and low lateral right atrium pacing, could serve as an alternative marker of isthmus block.

Action Potentials↗
PubMedDate not supplied

Catheter ablation of retrograde fast pathway in patients with atrioventricular nodal reentrant supraventricular tachycardia.

Atrioventricular (AV) nodal reentrant tachycardia is a common cause of supraventricular tachycardia. The present study describes catheter ablation of this form of tachycardia in 23 patients using direct current shocks. The aim of ablation was to abolish conduction through the retrograde pathway while preserving the anterograde conduction. All patients had symptomatic, drug resistant, slow-fast variety of dual atrioventricular nodal reentrant tachycardia. Using the retrograde atrial activation in the His bundle catheter as the reference, the optimal ablation site was selected by positioning an electrode catheter to obtain atrial activation synchronous with or earlier than the atrial activation at the reference electrode. Shocks of 100-300 joules were delivered at this site resulting in blockade of retrograde conduction in all patients. Ventriculo-atrial conduction studied 24 hours after the procedure was still absent in 16, modified in 2 and resumed in 3 patients. Two patients developed permanent complete heart block and were given pacemakers. At repeat electrophysiologic study performed after 2-4 months in 10 patients, the supraventricular tachycardia could not be induced. The AH interval was 67 +/- 10 msec during control study and to 115 +/- 39 msec at restudy (p < 0.001). The ventriculo-atrial conduction was absent in 7 cases and had been modified in 1 case. Over a follow up period of 1-30 months (mean 10.8 +/- 7.1 mo) 17 patients (73%) remained free of the arrhythmia without medication or pacemaker. Three other patients were easily controlled with digoxin. Thus, catheter modification of AV node results in permanent cure of the AV nodal tachycardia in majority of patients.

Adolescent↗
PubMedDate not supplied

Percutaneous transluminal coronary angioplasty of distal lesions: comparison of results with proximal lesions.

The results of percutaneous transluminal coronary angioplasty (PTCA) of 57 distal lesions were compared with 55 proximal lesions in 42 patients, aged 31 to 66 years (mean +/- SD: 51 +/- 9 yrs). Twenty nine (69%) had multivessel and 13 (31%) single vessel disease. The lesions classified as distal were located in left anterior descending (LAD) artery beyond the origin of second diagonal (D2), left circumflex (LCx) after the main obtuse marginal (OM) and right coronary artery (RCA) after the origin of acute marginal branch. Also included in this category were lesions in the second diagonal and obtuse marginal branches, two centimeters from their origin and stenosis in the posterior descending and posterolateral left ventricular branches of RCA. Out of 57 distal lesions 18 were 'complex' because of tandem location (5 patients), ulceration (6 lesions) and intraluminal thrombi (2 lesions). There was no significant difference in the mean luminal diameter stenosis between distal and proximal lesions, before and after PTCA. The primary success rate of angioplasty was 89.5% for the distal and 94.5% for the proximal lesions (P = NS). Inability to position the balloon across the lesion accounted for more failures in distal (3) compared to proximal (1) location. There were no major complications. Our results show that PTCA of distal lesions can be performed with a high rate of success, which is comparable to those with classical proximal lesions in the same patients.

Adult↗
PubMedDate not supplied

Evaluation of lesions suitable for percutaneous transluminal coronary angioplasty after thrombolytic therapy of acute myocardial infarction.

Forty-two patients of acute myocardial infarction (AMI) and clinically successful thrombolysis underwent coronary angiography 7.6 +/- 3.6 days after the AMI. The infarct related artery was patent in 33 of 42 (78.5%) patients, and 27 of these 33 (82%) had residual diameter stenosis of 70 per cent or more. Arteries showing more than 70 per cent luminal diameter narrowing were considered suitable for percutaneous transluminal coronary angioplasty (PTCA) if the lesion was less than 1 cm in length and there was no significant left main or distal lesion. Based on the above criteria, 22 of the 33 patients (66%) with recanalised infarct-related artery were found to have lesions suitable for PTCA. Thus, after successful thrombolysis, significant proportion of patients of acute myocardial infarction have residual lesions that are suitable for PTCA.

Adult↗
PubMedDate not supplied

Non-surgical mitral valvuloplasty for rheumatic mitral stenosis.

One hundred and twenty-six patients of rheumatic mitral stenosis (MS), aged 10-30 (mean 19.5 +/- 5.9) years underwent balloon mitral valvuloplasty (BMV). All valvuloplasties were done by the anterograde transvenous, transatrial route. The procedure was successful in 120 (95%) cases. Single balloon was used in 10 patients early in the series and double balloon was used in the other 110 patients. BMV resulted in a significant increase in the mitral valve area (MVA) from 0.96 +/- 0.35 to 2.3 +/- 0.8 cm2 (p less than 0.0001) and a significant fall in the transmitral pressure gradient (TMG) from 28.2 +/- 3.2 to 7.4 +/- 4.8 mmHg (p less than 0.001). The MVA achieved by BMV was found to have a significant positive correlation with the balloon diameter to body surface area ratio (BD/BSA) (r = 0.69, p less than 0.001). New mitral regurgitation (MR) developed in 15 patients--trivial in 11, 2+ in 2 and 3+ in 2. One patient required emergency mitral valve replacement. Procedure induced MR did not have a significant relation to the balloon size, degree of mitral sub-valvular pathology or the severity of mitral stenosis. Iatrogenic atrial septal defect was detected by oximetry in none, by angiography in one patient, and by Doppler color flow imaging in 5 patients. Cardiac tamponade was the most frequent serious complication, occurring in 6 patients, 4 of whom died following emergency surgery. Sixty-five patients have been followed up for at least 6 months (range 6-30, mean 16.3 +/- 6.3 months) following BMV.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMedDate not supplied

Long term performance of dual chamber pacemakers.

Records of 98 patients who had dual chamber pacemakers implanted at our institution and had a follow up for at least 6 months (range 6-90 months, mean 47.8 months) were analysed for long term performance of the pacemakers. There were 78 males and 20 females in the age range of 14 to 81 (mean 51.1 +/- 13.6) years. The mode of pacing was VDD in 12, DVI in 9 and DDD in 77 patients. Atrial malsensing was seen in 15 (16.7%) cases and generally occurred within the first week of implantation. Atrial lead dislodgement occurred in 4 cases (4.1%). Most of the problems related to atrial lead could be managed conservatively and re-operation was performed in only 4 cases. Other problems encountered on follow up included cross talk in one, endless loop tachycardia in 4, and pulse generator pocket erosion or infection in 4 (4.1%) patients. There were two instances of ventricular undersensing and one instance of insulation failure in the ventricular lead. A total of 16 patients underwent elective replacement of pulse generator 53-84 months (mean 66.3) following the initial implants. It is concluded that the incidence of pacemaker malfunction and other problems with dual chamber pacemaker implantation are not high; and most cases can be managed by conservative measures such as reprogramming.

Adolescent↗
PubMedDate not supplied

Clinical and haemodynamic effects of oral metoprolol therapy in dilated cardiomyopathy.

The clinical and haemodynamic effects of oral metoprolol therapy were assessed in thirty patients of dilated cardiomyopathy, aged 14-58 (33 +/- 10.9) years. After baseline haemodynamic study, metoprolol was administered in a dose of 25-100 mg/day (mean 87.0 +/- 25.1 mg/day). Before start of therapy, 13 patients were in NYHA symptom class IV, 14 were in NYHA class III and 3 were in NYHA class II. Symptomatic improvement was seen on oral metoprolol therapy in all patients except one. Six months after therapy 13 patients were asymptomatic, 16 were in NYHA class II, while 1 patient continued to be in NYHA class III. Repeat haemodynamic study in 15 patients done at a mean of 5.7 months showed a significant fall in the right ventricular end diastolic pressure (from 9.1 +/- 4.4 to 5.7 +/- 2.9 mm Hg, p less than 0.01), mean pulmonary artery pressure (from 32.3 +/- 13 to 24.5 +/- 10.3 mmHg, P less than 0.01) and mean pulmonary capillary pressure (from 23.3 +/- 10.3 mmHg to 14.7 +/- 7.4 mmHg, P less than 0.01). The left ventricular ejection fraction increased from 18.8 +/- 6.3 to 24.0 +/- 7.3 per cent, (P less than 0.05), while no significant change was observed in the cardiac index (2.43 +/- 0.47 to 2.66 +/- 0.83 L/min/m2, p = NS). These data suggest improvement in diastolic and systolic left ventricular function after metoprolol therapy.

Administration, Oral↗