PubMed Health⌕ Search

Biomedical subjects

M Nair

Publications and source records attributed to M Nair.

At least 19 recordsLinked to original sources
PubMed1999

Millisecond to microsecond time scale dynamics of the retinoid X and retinoic acid receptor DNA-binding domains and dimeric complex formation.

The all-trans retinoic acid and 9-cis retinoic acid receptors (RAR and RXR, respectively) belong to a family of ligand inducible transcription factors, which exert their effect via binding to hormone response elements. Both are members of the class II sub-family of nuclear receptors, which bind DNA as dimers, on tandem repeats of a hexamer motif separated by a variable spacer. The variability in spacer length and the head-to-tail organization of the hormone response elements result in different protein-protein interactions in each of the complexes. We show that the zinc-coordinating loop regions of RXR and RAR DNA-binding domains exhibit dynamics on the millisecond to microsecond time scale. The highly dynamic second zinc finger of RXR constitutes the primary protein-protein interface in many nuclear receptor assemblies on DNA. Dynamics is also observed in the first and second zinc fingers of RAR, which are implicated in dimeric interactions with RXR on response elements with spacers of 5 base pairs and 1 base pair, respectively. The striking correspondence between the regions that exhibit conformational exchange and the dimer interfaces of the proteins complexed with DNA suggests a functional role for the dynamics. The observed flexibility may allow the proteins to adapt to various partners and with different orientations upon assembly on DNA. Furthermore, the more extensive dynamics observed for RXR may reflect the greater ability of this protein to modulate its interaction surface since it participates in a wide variety of receptor complexes.

Amino Acid Sequence↗
PubMed1999

Malignant mesothelioma of the tunica vaginalis testis: a report of two cases and review of literature.

Two cases of rare malignant mesothelioma of tunica vaginalis testis are presented. Both cases were advanced on clinical and radiological studies. One patient was treated with surgical excision followed by chemotherapy and radiotherapy and the other patient was treated with surgery and chemotherapy. Despite aggressive therapy both the patients died within 18 months of treatment. Review of the literature with suggested treatment protocol is presented. The response of malignant mesothelioma to chemotherapy and radiotherapy is poor as indicated by both of our cases. Initial aggressive surgery and adjuvant procedures are necessary soon after diagnosis to achieve long-term survival.

Aged↗
PubMed1998

A comparison of Kodak Ektaspeed Plus film and the Siemens Sidexis digital imaging system for caries detection using receiver operating characteristic analysis.

OBJECTIVE: To evaluate the accuracy of proximal caries detection comparing enhanced and unenhanced Siemens Sidexis CCD-based digital images with Ektaspeed Plus films utilizing receiver operating characteristic analysis. STUDY DESIGN: Sixty extracted teeth (24 posterior and 36 anterior) were imaged under identical standardized geometric and exposure conditions. Six observers, using a 5-point confidence scale, rated 120 proximal surfaces for the presence or absence of carious lesions by means of three image modalities: (1) observer enhanced and (2) unenhanced Sidexis displays, and (3) Ektaspeed Plus films. The ground truth was determined by microscopic analysis of ground sections. Receiver operating characteristic curves were generated with calculated areas (AZ) analyzed with analysis of variance for effect of reader, reading, and modality. RESULTS: Analysis of variance demonstrated significant differences among readers, readings and modalities (mean square values of 0.012, 0.005, 0.004, F ratios of 13.604, 5.329, 5.100; p = values of 0.001, 0.043, and 0.030, respectively). Post-hoc paired comparisons of modalities using Tukey's statistic demonstrated that only film and enhanced Sidexis images were different from each other (p = 0.024). AZ scores were 0.7650, 0.7499, and 0.8008 respectively, for unenhanced Sidexis, enhanced Sidexis, and Ektaspeed Plus film. CONCLUSION: Unenhanced digital Sidexis images were equivalent to film for the detection of proximal caries in this in vitro study. Observer enhanced Sidexis images exhibited a statistically significant lower diagnostic accuracy than the unenhanced digital and film images.

Analysis of Variance↗
PubMed1997

Automatic arrhythmia identification using analysis of the atrioventricular association. Application to a new generation of implantable defibrillators. Participating Centers of the Automatic Recognition of Arrhythmia Study Group.

BACKGROUND: Atrioventricular association is a key criterion for arrhythmia diagnosis. Its use in a defibrillator should significantly reduce the incidence of inappropriate shocks. Therefore, we evaluated the diagnostic accuracy of an algorithm that uses dual-chamber sensing and analysis of atrioventricular association to discriminate ventricular from supraventricular arrhythmias in a prototype of an implantable defibrillator. METHODS AND RESULTS: The algorithm performed a stepwise analysis of arrhythmias. The rhythm was first classified on the basis of cycle lengths. Each episode was then classified as supraventricular or ventricular in origin on the basis of the stability of cycle lengths and atrioventricular association. This algorithm was evaluated in 156 episodes of induced sustained tachycardias. Eighty-nine tachycardias were taken from the Ann Arbor electrogram library; the others were recorded in 50 patients during electrophysiological studies. The atrial and ventricular signals were stored on an external recorder and then injected into an external prototype of a defibrillator system. The algorithm correctly diagnosed 96% of ventricular tachycardia episodes, 100% of ventricular fibrillation episodes, and 92% of double-tachycardia episodes. The mean detection time for ventricular tachycardia was 2.6 +/- 0.8 seconds, and for ventricular fibrillation, it was 2.1 +/- 0.4 seconds. The positive predictive values for the diagnoses of atrial fibrillation and atrial flutter were 92% and 86%, respectively. For ventricular tachycardia and ventricular fibrillation, the values were 95% and 100%, respectively. CONCLUSIONS: Analysis of atrioventricular association promotes reliable differentiation between ventricular and supraventricular tachycardias and should enhance the diagnostic capabilities of implantable defibrillators.

Algorithms↗
PubMed1997

Marital rape.

Explore the source record for details and available documents.

Female↗
PubMed1996

Radiofrequency catheter ablation of atrial flutter. Further insights into the various types of isthmus block: application to ablation during sinus rhythm.

BACKGROUND: Radiofrequency ablation of type 1 atrial flutter (AF1) has recently evolved toward an anatomically guided procedure directed to isthmuses at the lower part of the right atrium (RA). However, different types of block at these isthmuses may be observed and potentially correlated with different late outcomes. In addition, because the ablation is anatomically guided, ablation should be possible during sinus rhythm. METHODS AND RESULTS: Forty-four patients underwent ablation of type 1 AF1 performed during ongoing tachycardia (33 patients) or sinus rhythm (11 patients). Evidence of inferior vena cava-tricuspid annulus isthmus block was assessed by changes in RA impulse propagation while pacing from both sides of the ablation site. Apparent complete isthmus block was achieved in 43 of 44 patients with 9 +/- 7 pulses. However, incomplete block mimicking complete block because of intra-atrial conduction delay but leading to a different low RA activation pattern was individualized. At the end of the procedure, isthmus block was complete in 35 patients and incomplete in 8, but since AF1 reinduction was no longer possible, patients were discharged. During a follow-up period of 12.1 +/- 5.5 months, 4 patients experienced AF1 recurrence; all had shown incomplete or no block. CONCLUSIONS: Detailed multiple-point low RA mapping is necessary to differentiate incomplete from complete isthmus block. Complete block is the best marker for long-term success of AF1 ablation, although incomplete block may be sufficient to prevent recurrence in a significant number of cases. Isthmus block is achievable during sinus rhythm, and AF1 induction is not mandatory.

Atrial Flutter↗
PubMed1996

Electrocardiographic patterns and results of radiofrequency catheter ablation of clockwise type I atrial flutter.

INTRODUCTION: Counterclockwise right atrial propagation is usually observed in common atrial flutter, but little is known regarding flutter with clockwise right atrial rotation. The aim of this study is to describe the ECG characteristics and results of catheter ablation of atrial flutter with clockwise right atrial rotation. METHODS AND RESULTS: Among the 38 patients with type I atrial flutter in this study population, right atrial impulse propagation was counterclockwise in 20 and clockwise in 8. In the remaining 10 patients, both clockwise and counterclockwise patterns were seen. Clinical and ECG parameters associated with clockwise flutter were compared to those of 28 cases of counterclockwise atrial flutter. Ablation was performed in 11 of 18 cases using a technique identical to that used for counterclockwise flutter. A classical "sawtooth" pattern of the flutter wave was observed in 28 of 28 counterclockwise and 14 of 18 clockwise flutter. A shorter plateau phase, a widening of the negative component of the F wave in the inferior leads, and a negative F wave in V1 were the most consistent findings in clockwise flutter. Coronary sinus recording always showed septal to lateral left atrial impulse propagation. Ablation was successful in 11 of 11 cases of clockwise flutter in whom this procedure was performed, with 9.5 +/- 11.6 radiofrequency pulses delivered between the tricuspid valve and the coronary sinus ostium (n = 5) or the inferior vena cava (n = 5), and in the proximal coronary sinus (n = 1). After a follow-up of 46.6 weeks, two recurrences of clockwise flutter were encountered, which were successfully treated with a second session. CONCLUSION: Contrary to commonly accepted concepts, clockwise rotation of atrial flutter is not an infrequent phenomenon and can mimic counterclockwise rotation. It can also be successfully ablated by radiofrequency pulses.

Atrial Flutter↗
PubMed1995

Radiofrequency catheter ablation of type 1 atrial flutter. Prediction of late success by electrophysiological criteria.

BACKGROUND: Radiofrequency energy has demonstrated its efficacy in catheter ablation of atrial flutter (AFl). However, long-term recurrences of AFl have been reported frequently after initial, apparently successful ablation. To date, criteria for prediction of late recurrences are lacking. METHODS AND RESULTS: Twelve patients (10 men; mean age, 53.6 years; range, 26 to 69 years) were referred for AFl ablation. Duodecapolar and decapolar catheters were used for detailed mapping of the tricuspid ring, the inferior vena cavatricuspid annulus (IVC-TA) isthmus, and the coronary sinus ostium (CSOs) area. Additional multipolar catheters were used for recording activation of the coronary sinus and the CSOs-TA isthmus. AFl was present at baseline in 9 patients and was induced by proximal coronary sinus (PCS) pacing in 3. Counterclockwise right atrial activation was recorded in all patients. Primary success of ablation was defined as when AFl was no longer inducible even during isoproterenol infusion. AFl was successfully ablated in all 12 patients, with a median of 4 pulses delivered at the IVC-TA isthmus. In the 3 patients in whom AFl was induced, during PCS pacing in sinus rhythm before ablation, a collision of descending and ascending wave fronts was observed at the middle lateral right atrium (LRA). This activation pattern of the LRA also was noted after unsuccessful radiofrequency applications. Noninducibility of AFl after radiofrequency applications was associated with a change of activation pattern at the LRA and with an inversion of the activation sequence of the IVC-TA isthmus (from clockwise to counterclockwise) in 9 patients when pacing from the PCS. In 2 of 3 patients, despite noninducibility of atrial flutter, ablation was pursued to obtain evidence of permanent block of conduction at the IVC-TA isthmus. Finally, a completely descending LRA wave front was observed when pacing from the PCS in all patients except one. Low LRA pacing was also performed in 4 patients and showed evidence for block in the counterclockwise direction at the isthmus. During a follow-up of 9 +/- 3 months, AFl recurred in 1 patient; this was the only patient who showed no conduction block at the isthmus after the procedure. CONCLUSIONS: Direction of impulse propagation at LRA and block of propagation at the IVC-TA isthmus during PCS and low LRA pacing appear to be of interest in predicting long-term success of AFl ablation.

Adult↗
PubMed1994

Guillain-Barré syndrome. A prospective clinical study in 25 children and comparison with adults.

Children who fulfilled the recognized diagnostic criteria for Guillain-Barré syndrome (GBS) were studied prospectively from 1982. After detailed clinical evaluation and investigation, severity of disease was graded on a disability scale ranging from 1 to 6, and the time taken from the 1st day of illness to reach important clinical landmarks was noted. All children were monitored for a minimum of 1 year and observations on them were then compared with those on 92 adults with GBS seen during the same period. Twenty-five children, evenly distributed between the sexes, were seen between 1982 and 1989 and constituted 22% of all GBS patients seen during this period. Children had a more acute form of onset than adults, 80% becoming bedbound within 7 days, and a higher incidence of cranial nerve palsies (76% vs 55%). The incidence of respiratory paralysis was 40% and of dysautonomia 20%, which was similar to findings in adults. Children fared marginally better than adults: 72% were ambulant at 1 year, 12% bedbound and 16% decreased. The prognosis of ventilated patients was relatively poor in both groups, but children with the hyperacute form of the disease had twice the probability of adults to attain independent walking at 1 year (0.63 vs 0.33).

Activities of Daily Living↗
PubMed1993

Immediate and long-term results of balloon and surgical closed mitral valvotomy: a randomized comparative study.

Balloon mitral valvotomy (BMV) constitutes an important alternative to surgical closed mitral valvotomy (CMV) for the treatment of rheumatic mitral stenosis. To compare the immediate and long-term results of these procedures, 200 patients with rheumatic mitral stenosis were randomly assigned to undergo either BMV (n = 100) or CMV (n = 100). The age range was 10 to 30 (mean 19.4 +/- 6.5) years. Both procedures resulted in significant and similar increases in mitral valve area (BMV: 0.85 +/- 0.26 to 2.39 +/- 0.94 cm2; CMV: 0.79 +/- 0.21 to 2.2 +/- 0.85 cm2; p = NS). Mitral regurgitation developed in 14 patients after BMV and in 12 patients after CMV. Eighty patients in each group have now been followed for a mean period of 22 +/- 6.3 (range 6 to 38) months by repeat echocardiographic study. Restenosis (defined as a loss of more than 50% of the achieved increase in mitral valve area) was seen in four (5%) patients after BMV and in three (4%) after CMV. Symptomatic restenosis was seen in only one patient who at follow-up examination 20 months after CMV had a mitral valve area of 0.8 cm2 and underwent successful balloon valvotomy. We conclude that the immediate and long-term results obtained with percutaneous BMV and surgical closed mitral commissurotomy are comparable.

Adolescent↗
PubMed1993

Immune function in alcoholism: a controlled study.

Several studies have shown an increased risk for infection and cancer in alcoholic patients. The mechanisms for such observations remain largely unknown. In an effort to investigate the possibility of immunological dysfunction in alcoholism, we studied three immune parameters in 47 hospitalized chronic alcoholic patients and 47 age- and sex-matched normal controls. The immune measures were: (1) lymphocyte phenotyping, with estimates of percentages of T cells, B cells, T helpers, T suppressors, natural killer (NK) cells, and cells carrying the activation markers IL2R1 and I2; (2) NK cell activity; and (3) lymphokine-activated killer cell activity. Results indicate a significant increase in the IL2R and I2 lymphocyte markers in alcoholic patients compared with matched controls. We also found a nonsignificant trend for a decrease in the percentage of suppressor T cells in the alcoholic group, as well as a trend for a negative correlation between the percentage of T suppressor cells and age. There were no significant differences in either NK or lymphokine-activated killer cell activities between the two groups. Furthermore, there were no significant associations between duration and intensity of alcohol consumption and any of the immune measures. These results suggest subtle alterations in immune regulation in alcoholic patients that cannot be explained solely on the basis of duration and/or amount of alcohol consumed.

Adult↗
PubMed1992

Balloon angioplasty of the aorta in Takayasu's arteritis: initial and long-term results.

Percutaneous transluminal balloon angioplasty for stenosis of the aorta was performed in 36 patients with Takayasu's arteritis (age range, 8 to 36 years; mean, 19.1 +/- 7.7 years). Balloon dilatation was successful in 34 patients and resulted in a decrease in the mean peak systolic pressure gradient (PSG) from 75.2 +/- 29.1 mm Hg to 24.8 +/- 19 mm Hg (p less than 0.001) and a mean increase in the diameter of the stenosed segments from 4.5 +/- 2.2 mm to 9.6 +/- 3.8 mm (p less than 0.001). Hemodynamic and angiographic restudy, which was performed in 20 patients at a mean follow-up period of 7.7 +/- 4.1 months (range, 3 to 24 months), showed a further decrease in PSG (greater than or equal to 15 mm Hg) in seven patients (from 40.0 +/- 11.2 mm Hg to 15.7 +/- 10.2 mm Hg; p less than 0.01), no significant change in PSG in 12 patients (17.1 +/- 13.6 mm Hg vs 16.6 +/- 12.7 mm Hg; p = NS), and an increase in PSG from 15 mm Hg to 85 mm Hg in one patient. The patient who showed restenosis underwent successful redilatation. Six patients who underwent late recatheterization and angiography at 36 to 60 months (mean, 43 +/- 9.4 months) show continued relief of stenosis (mean PSG, 8.8 +/- 7.8 mm Hg). Patients with short-segment (less than 4 cm) stenosis experience more relief than patients with long-segment (greater than or equal to 4 cm) stenosis (residual PSG, 18.6 +/- 8.2 mm Hg vs 40 +/- 16 mm Hg; p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗