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Biomedical subjects

M Nair

Publications and source records attributed to M Nair.

At least 19 recordsLinked to original sources
PubMed2001

Chronic atrial fibrillation in patients with rheumatic heart disease: mapping and radiofrequency ablation of flutter circuits seen at initiation after cardioversion.

BACKGROUND: There is little information concerning mapping and radiofrequency ablation (RFA) of arrhythmias seen during reinduction of atrial fibrillation (AF) after pharmacological and/or electrical cardioversion in patients with chronic AF and rheumatic heart disease. METHODS AND RESULTS: Seventeen patients with rheumatic heart disease and symptomatic chronic AF underwent multisite atrial mapping during reinduction of AF after cardioversion. An organized atrial arrhythmia of varying duration was seen to precede the AF in all patients. The earliest atrial activity during this organized rhythm was near the coronary sinus ostium (CS OS) in 14 patients and along the left side of the interatrial septum (IAS) in 3 patients. RFA was performed in 16 patients (14 near the CS OS and 2 along the IAS). Postablation AF was inducible in 1 patient in whom RFA was preformed near the CS OS and in both patients when it was performed along the IAS. At a follow-up of 6 to 56 weeks (mean, 32 weeks), 10 of the 13 patients who had successful ablation were in sinus rhythm. All patients in whom AF was reinducible immediately after RFA continue to be in AF. CONCLUSIONS: Induced AF in patients with rheumatic heart disease begins as a rapid organized arrhythmia with earliest atrial activity near the CS OS in most patients. RFA targeting the region of the CS OS is successful in suppressing the arrhythmia immediately in most of the patients and in most on follow-up.

Adult↗
PubMed2001

Papillary carcinoma of the thyroid and its variants: a cytohistological correlation.

Fine-needle aspiration cytology (FNAC) is considered highly specific for the diagnosis of papillary carcinoma of the thyroid (PCT). In recent years, several variants of PCT have been described. An attempt was made to gauge the accuracy of classification of variants of PCT on aspirates. Cytology smears from 124 of 150 cases of histologically proven PCT with a prior FNAC were reviewed over a 16-yr period. A diagnosis of papillary carcinoma on FNAC was made in 93 cases. Further subclassification of these cases was done on cytology and tissue sections independently. The variants of PCT classified on FNAC were classical PCT (PCT-CL), 76 cases; Hurthle-cell variant (PCT-HCV), 3 cases; follicular variant (PCT-FV), 6 cases; tall-cell variant (PCT-TCV), 2 cases; high-grade variant (PCT-HG), 2 cases; and 2 cases each which were debatably PCT-CL/PCT-FV and PCT-CL/PCT-HG. Cytology typing was accurate in 65 of the 72 classical variants, while only 7 of the 22 follicular variants were correctly identified on cytology. Two of the 3 high-grade papillary carcinomas (PCT-HG) were identified on FNAC, and the solitary case of tall-cell variant could readily be classified on cytology. In conclusion, identification of the various variants of PCT is possible, though difficulty is encountered in correctly categorizing the follicular variant, which is often mistaken for a follicular neoplasm. Also, identification of the solid variant and the papillary carcinoma with nodular fasciitis-like stroma was a problem on cytology. Another interesting observation in our series is that an admixture of various cell types was seen in the smears and corroborated on histology to be present in focal areas.

Biopsy, Needle↗
PubMed2001

Neurocysticercosis: a clinical and radiological appraisal from Kerala State, South India.

OBJECTIVES: Little has been published on Neurocysticercosis (NCC) in the State of Kerala, South India. This study was conducted to describe the clinical and radiological features of NCC in Kerala and also to study the frequency of NCC as seen in a tertiary referral setting. MATERIALS AND METHODS: We evaluated retrospectively 11 patients who were admitted with a diagnosis of NCC from 1986 to 1998. A pre-abstracted proforma containing detailed demographic data, dietary habits, clinical features and history of travel outside Kerala and neuroimaging findings were obtained from patient records and the data was tabulated and analysed. Follow up assessment was made three months after treatment. RESULTS: There were a total of 11 patients, including nine males and two females in the age range of 24 to 62 years and a mean age of 35.2 years. All were nonvegans, only 36% were pork eaters while 18% claimed consumption of salads and uncooked vegetables. 55% of patients were migrants. Migrants were defined as those who lived outside the state of Kerala for more than six months. Seizure was the most common presenting complaint and occurred in all patients (100%). Multiple ring enhancing lesions were seen on computerised tomography (CT) and magnetic resonance imaging (MRI) scans in 60%. Calcified lesions were noted in two patients. An isolated instance of miliary or disseminated cysticercosis with subcutaneous nodules and multiple brain lesions in MRI scan was observed. All patients received anticysticercal therapy besides anticonvulsants. CONCLUSIONS: It appears that NCC is rather uncommon in Kerala. Better socioeconomic status, high literacy rate, improved sanitation and health care in the state of Kerala could be reasons for this observation. A prospective case-control study of NCC in Kerala is needed to study these factors.

Adult↗
PubMed2000

Changes in dynamical behavior of the retinoid X receptor DNA-binding domain upon binding to a 14 base-pair DNA half site.

The retinoid X receptor (RXR) is a prominent member of the nuclear receptor family of ligand-inducible transcription factors. Many proteins of this family exert their function as heterodimers with RXR as a common upstream partner. Studies of the DNA-binding domains of several nuclear receptors reveal differences in structure and dynamics, both between the different proteins and between the free- and DNA-bound receptor DBDs. We investigated the differences in dynamics between RXR free in solution and in complex with a 14 base-pair oligonucleotide, using (1)H and (15)N relaxation studies. Nano- to picosecond dynamics were probed on (15)N, employing Lipari-Szabo analysis with an axially symmetric tumbling model to estimate the exchange contributions to the transverse relaxation rates. Furthermore, milli- to microsecond dynamics were estimated qualitatively for (1)H and (15)N, using CPMG-HSQC and CPMG-T(2) measurements with differential pulse spacing. RXR shows hardly any nano- to picosecond time-scale internal motion. Upon DNA binding, the order parameters show a tiny increase. Dynamics in the milli- to microsecond time scale is more prevalent. It is localized in the first and second zinc fingers of the free RXR. Upon DNA-binding, exchange associated with specific/aspecific DNA-binding of RXR is observed throughout the sequence, whereas conformational flexibility of the D-box and the second zinc finger of RXR is greatly reduced. Since this DNA-binding induced folding transition occurs remote from the DNA in a region which is involved in protein-protein interactions, it may very well be related to the cooperativity of dimeric DNA binding.

Anisotropy↗
PubMed2000

Biochemical and compositional analyses of recombinant lecithin:cholesterol acyltransferase (LCAT) obtained from a hepatic source.

Lecithin:cholesterol acyltransferase (LCAT) is an important plasma glycoprotein which plays a central role in lipid metabolism. This protein is responsible for generation of cholesteryl esters in plasma and it has been proposed to play a pivotal role in the reverse cholesterol transport pathway. Structural and functional studies of LCAT have employed various expression systems for production of recombinant LCAT (rLCAT). However, recent studies have shown some differences in the oligosaccharide structure and composition of rLCAT. In this study, we have generated a new hepatic based expression system using McArdle-RH7777 (Mc-7777) cells to produce a recombinant protein most similar to human plasma LCAT. The expressed glycoprotein was compared to the LCAT expressed in previously characterized baby hamster kidney (BHK) cells. Both proteins were compared on the basis of their carbohydrate structure and composition as well as their functional properties. Although the functional properties of both glycoproteins were similar, the carbohydrate structure was significantly different. While BHK-LCAT contained bi-, tri-, and tetraantennary structures, Mc-7777 LCAT presented only biantennary oligosaccharide structures. The difference in glycosylation pattern of rLCAT from Mc-7777 and BHK cells underlines the importance of appropriate expression system, both in vivo and in vitro.

Animals↗
PubMed2000

Angiolymphoid hyperplasia with eosinophilia (epithelioid hemangioma) of the breast: report of a case.

We report herein the unusual case of a 35-year-old woman found to have angiolymphoid hyperplasia with eosinophilia (ALHE) of the breast. The patient was initially referred to our hospital for investigation of a well-circumscribed breast lump, 2.5 cm in diameter, and a clinical diagnosis of fibroadenoma was made. However, fine-needle aspiration cytology of the lump revealed an admixture of lymphocytes and eosinophils. Therefore, the lump was excised and microscopic examination showed features of ALHE. No evidence of recurrence of the lump has been seen in the 2 years since this excision. To the best of our knowledge, this is the first case to be documented of ALHE arising in the breast.

Adult↗
PubMed2000

False-positive exercise stress electrocardiogram due to accessory pathway in the absence of manifest preexcitation.

False-positive exercise testing in patients with an accessory pathway has been described only in patients with manifest preexcitation during exercise. We describe a patient in whom marked ST-segment changes were seen during an exercise test in the absence of any preexcitation of the QRS complexes. The role of the accessory pathway in producing the ST changes was reaffirmed by absence of this abnormality following catheter ablation of the accessory pathway.

Catheter Ablation↗
PubMed2000

Mitral regurgitation following percutaneous transvenous mitral commissurotomy: a single-center experience.

BACKGROUND AND AIM OF THE STUDY: Percutaneous transvenous mitral commissurotomy (PTMC) has revolutionized the treatment of patients with symptomatic mitral stenosis and is now established as the procedure of choice. Despite high technical expertise in PTMC using the Inoue balloon, mitral regurgitation (MR) remains a major procedure-related complication. We retrospectively analyzed our data of PTMC using the Inoue balloon with regard to the incidence of MR, its likely causative mechanism, and follow up of these patients. METHODS: During the past ten years, PTMC was performed in 3,650 patients (median age 26 years; range: 8-76 years), of whom 910 (24.9%) were juveniles. Preprocedure mitral valve area (MVA) was 0.9 +/- 0.4 cm2 (range: 0.3-1.3 cm2); MR was mild in 1,396 cases (38.2%), moderate in 394 (10.8%) and severe in 22 (0.6%). None of the patients was rejected on the basis of echocardiographic score. RESULTS: The procedure was successful in 3,276 (89.8%), with post-procedure MVA of 1.7 +/- 0.6 cm2 (range: 1.4-2.6 cm2), and without development of any major complication. Severe MR was seen in 120 patients (3.3%), of whom 66 (1.8%) required urgent mitral valve replacement (MVR). Echocardiography in these latter patients showed leaflet rupture in 48 (72.7%), chordal rupture in 12 (18.2%) and excessive commissural tear in six (9.1%). Fifty-four patients (1.5%) with severe MR post PTMC were followed with medical treatment; echocardiography in these patients revealed chordal rupture in 40 (74.1%) and excessive commissural tear in 14 (25.9%). Follow up data were available in 49 patients (1.3%); 30 (0.8%) required MVR and 19 (0.5%) were in NYHA class II at a median follow up of 24 months. Moderate MR was seen in 188 cases (5.1%), with predominant causative mechanisms of excessive commissural tear in 120 (63.8%) and chordal rupture in 68 (36.2%). Severity of MR worsened in 30 cases (0.8%), of which 20 (0.6%) required elective MVR on follow up. MR decreased in 58 patients (1.6%), in whom excessive commissural tear was the causative mechanism. CONCLUSION: Significant MR (moderate or severe) after PTMC was seen in 308 patients (8.4%), of whom 116 (3.2%) required MVR urgently or on follow up. All patients with leaflet rupture during PTMC developed severe MR and required urgent MVR. There was a tendency for the severity of MR to decrease with time in cases where excessive commissural tear was the causative mechanism.

Adolescent↗
PubMed2000

The cardiovascular and hemodynamic effects of erythropoietin in chronic renal failure.

OBJECTIVE: Left ventricular hypertrophy (LVH) has been identified as an independent risk factor for mortality in patients with chronic renal failure (CRF) and anemia has been proposed to contribute to LVH. The cardiovascular and hemodynamic effects of correction of anemia with recombinant human erythropoietin (rHU EPO) was assessed in a 12 week prospective study in patients with CRF. METHODS: Biochemical parameters and echocardiography were studied at the start and after three months therapy with EPO in 24 patients with CRF--11 predialysis (Group I) and 13 dialysis (Group II). RESULTS: The mean haemoglobin (Hb)--g/dl increased significantly from 7.5 +/- 1.0 to 10.1 +/- 1.1 in group I and from 6.7 +/- 0.6 to 9.4 +/- 0.8 in group II (p < 0.05) on EPO therapy. The left ventricular mass index (LVMi)--g/m2 reduced significantly from 185.6 +/- 44.6 to 158.3 +/- 4.1 in group I and from 158.0 +/- 26.9 to 131.6 +/- 22.1 in group II (p < 0.05 in both). The interventricular septal thickness (IVST) also showed a significant decline in both groups, 1.17 +/- 0.06 to 1.14 +/- 0.05 (group I) and 1.09 +/- 0.25 to 1.01 +/- 0.21 (group II), p < 0.05 in both. The thickness of the left ventricular posterior wall remained unchanged. The left ventricular end diastolic and systolic diameters (LVEDD and LVESD) significantly reduced from their baseline values in both the groups (p < 0.05). The diastolic filling parameters across the mitral valve remained unchanged in both the groups. The cardiac index (CI)--L/min/m2 decreased from 3.53 +/- 0.3 to 3.03 +/- 0.27 in group I and from 3.31 +/- 0.64 to 2.80 +/- 0.60 in group II (p < 0.05) and the total peripheral resistance (TPR)--dynes/cm5/sec increased from 1567 +/- 164.8 to 1883 +/- 190.7 in group I and from 1618 +/- 375.7 to 2004 +/- 437.3 in group II. The differences in all the parameters at the start and after 3 months of EPO were comparable in groups I and II. The mean arterial pressure (MAP) changed insignificantly in both the groups. CONCLUSIONS: To conclude, this study has shown that the decrease in LVMi with EPO reflects the role of anemia in the genesis of LVH and that the correction of anemia with EPO in CRF results in regression of LVMi and has a favourable effect on cardiovascular hemodynamics.

Adolescent↗
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↗