Biomedical subjects

M Nigam

Publications and source records attributed to M Nigam.

At least 37 records · Page 2Linked to original sources

PubMed1992

Ryanodine-affinity chromatography purifies 106 kD Ca2+ release channels from skeletal and cardiac sarcoplasmic reticulum.

A 106 kD protein was isolated from skeletal sarcoplasmic reticulum (SR) vesicles and shown to have the properties of SR Ca2+ release channels, including blockade by 5 nM ryanodine. In view of extensive reports that the ryanodine-receptor complex consists of four 565 kD junctional feet proteins (JFPs) and is the 'physiological' Ca2+ release channel, we prepared ryanodine-affinity columns to isolate its receptor site(s). Conditions known to maximize the association and dissociation of ryanodine to SR proteins were respectively used to link, then elute, the receptor(s) from ryanodine-affinity columns. The method purified a protein at about 100 kD from both rabbit skeletal and canine cardiac SR vesicles. The skeletal and cardiac proteins isolated by ryanodine-affinity chromatography were identified as the low molecular weight Ca2+ release channel through their antigenic reaction with an anti-106 kD monoclonal antibody. Upon reconstitution in planar bilayers, both skeletal and cardiac proteins revealed the presence of functional SR Ca2+ release channels. Surprisingly, ryanodine-affinity columns did not retain JFPs but purified 106 kD Ca2+ release channels which are a minor component (0.1-0.3%) of SR proteins.

Animals↗

PubMed1991

Assessment of mitral valvar stenosis by echocardiography: utility of various methods before and after mitral valvotomy.

Cross-sectional and Doppler echocardiography are currently the most important non-invasive tests for the evaluation of mitral stenosis. Recent experience has, however, shown that parameters that are reliable before mitral valvotomy may not be valid after the procedure. We have studied the validity of estimation of the area of the mitral valve by echo-planimetry, by Doppler pressure half time and the transmitral end-diastolic pressure gradient calculated by continuous wave Doppler in 100 patients (aged 10-30 years) before and after balloon mitral valvoplasty (n = 70) or surgical closed mitral valvotomy (n = 30). These patients underwent cardiac catheterisation and echocardiographic studies before, immediately after and 8-12 (9.3 +/- 2.2) weeks following balloon valvoplasty or closed valvotomy. The area as estimated echocardiographically correlated well with that obtained by the Gorlin formula before (r = 0.80), but not immediately after (r = 0.67) or on follow up after mitral valvotomy. There was good correlation between Doppler pressure half time and the area as estimated by the Gorlin formula before (r = 0.89) and on follow up after valvotomy (r = 0.82), but the correlation was not as good in the immediate period after valvotomy (r = 0.60). The end-diastolic pressure gradients obtained by Doppler examination and at cardiac catheterisation correlated well with each other before (r = 0.94), immediately after valvotomy (r = 0.92) and on follow up (r = 0.94). Hence, the reliability of estimation of the area of the mitral valve by echo-planimetry and by Doppler pressure half time varies according to the time at which the examination is performed following commissurotomy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1990

Unusual thrombi in the setting of rheumatic heart disease.

We report two patients with unusual intracavitary thrombi in association with rheumatic mitral stenosis. One patient had a large free-floating left atrial thrombus immediately after successful closed mitral valvotomy causing recurrent acute pulmonary oedema in the post-operative phase. The other patient was detected to have multiple, discrete and calcified left ventricular thrombi in the presence of severe left ventricular systolic dysfunction. The diagnosis in both cases was made by cross-sectional echocardiography.

Adult↗

PubMed1989

Percutaneous balloon mitral valvuloplasty in children and young adults with rheumatic mitral stenosis.

Twenty-eight patients with mitral stenosis, 17 females and 11 males, underwent percutaneous balloon mitral valvuloplasty (BMV). The age range was 10 to 30 (mean 17.8 +/- 6.7) years and all were symptomatic (New York Heart Association [NYHA] class III, 12 patients; class IV, 16 patients). BMV was done with a single balloon in 10 patients and double balloon in 16 patients. Following BMV, there was a significant reduction in transmitral end-diastolic pressure gradient from 23.1 +/- 5.8 to 7.6 +/- 4.2 mm Hg (p less than 0.001) and a significant increase in mitral valve area from 1.06 +/- 0.29 to 2.64 +/- 1.35 cm2 (p less than 0.001), along with an increase in cardiac index from 3.40 +/- 1.18 to 4.26 +/- 1.46 L/min/m2 (p less than 0.01). Improvement in symptomatic status by at least one NYHA class was seen in all patients. Mild mitral regurgitation developed in four and moderate mitral regurgitation developed in one patient. Angiographic evidence of atrial septal defect was present in one patient. Follow-up at 8 to 12 weeks in 12 patients has shown sustained hemodynamic improvement. These short-term results indicate that BMV is an effective nonsurgical procedure for the management of patients with rheumatic mitral stenosis.

Adolescent↗

PubMed1989

[Use of an antibioprophylaxis with pefloxacin and fosfomycin in cardiac surgery in patients with beta-lactam hypersensitivity].

An association of pefloxacin plus fosfomycin was used as antibioprophylaxis in beta lactam allergic patients who underwent cardiac surgery with cardiovascular-bypass. Pefloxacin (800 mg), was administered orally, one hour before anesthetic induction and fosfomycin (60 mg/kg) was injected at the time of induction. The whole course of prophylaxis wat 24 hours. Antibiotic concentrations were measured in serum before (P1, P2) during (C1, C2, C3, C4) and after cardiovascular-bypass (P3) and in bone, endocardiac and pleural tissues. The efficacy was evaluated on clinical and biological data. Antibiotic levels of pefloxacin were measured by HPLC and those of fosfomycin by bacteriological method. Antibiotic concentrations are high in blood and tissues, without evidence of cardiovascular-bypass influence. The tissue penetration of both drugs is excellent. Two patients have presented serious post-operative infections. The pharmacokinetic of pefloxacin associated with fosfomycin is appropriate during cardiovascular-bypass and the local antibiotic concentrations are above the MIC of the strains commonly responsible of post operative infections in cardiovascular surgery. The clinical efficacy of this prophylaxis must be studied in a large population of patients.

Aged↗

PubMed1988

Gd-DOTA: characterization of a new paramagnetic complex.

The relaxivity, biodistribution, and toxicity of the gadolinium-tetraazacyclododecanetetraacetic acid (Gd-DOTA) complex were evaluated. This cyclic complex has much greater in vitro stability (10(28)) than similar noncyclic complexes such as gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA) (10(23)) or gadolinium-ethylenediaminetetraacetic acid (Gd-EDTA) (10(17)). The T1 relaxivity of Gd-DOTA (meglumine salt) determined in saline and in liver tissue at 20 MHz was similar to the relaxivity of Gd-DTPA. Tissue proton relaxation enhancement (PRE) correlated closely with chemical measurement of tissue gadolinium concentration. In rats, the biodistribution of Gd-DOTA was similar to Gd-DTPA with a distribution half-life of 3 minutes and an elimination half-life of 18 minutes. The median lethal dose (LD50) in mice of Gd-DOTA was 93% higher than that of Gd-DTPA; the calculated safety factor (ratio of LD50 to effective dose) was 53 for Gd-DOTA and 28 for Gd-DTPA. The data suggest that in vitro stability correlates with in vivo safety.

Animals↗

PubMed1983

Tissue distribution of lymphocytes in rheumatic heart valves as defined by monoclonal anti-T cell antibodies.

Fresh cardiac valvular tissues and atrial appendages removed from 106 Indian patients with rheumatic heart disease at the time of corrective cardiac surgery were examined to determine the characteristics of valvular interstitial lymphocytic infiltrates using conventional histologic staining along with indirect immunofluorescent techniques. Precise identification of the phenotypic profiles of inflammatory mononuclear cells was attempted using anti-IgG, anti-Ia, and monoclonal mouse hybridoma reagents identifying T cells (OKT3) as well as T cell subsets (OKT4 helper/inducer and OKT8 suppressor/cytotoxic cells). A similar group of 21 patients undergoing cardiac valvular resection in Albuquerque was studied. The mean age of Indian patients providing valve tissues was 27.7, whereas in those in Albuquerque, it was 52 years. Twenty-five percent of rheumatic heart valves in Indian patients showed significant interstitial lymphoid infiltrates, and one third of the rheumatic valves from patients in Albuquerque showed similar mononuclear cell collections. Lymphoid infiltrates contained a predominance of T cells (70 to 80 percent) and only occasional B cells. Most of the T cells were OKT4-positive, with only a minor representation of suppressor/cytotoxic OKT8-positive T cells. In many instances, OKT4-positive helper T cell collections were closely juxtaposed to fibroblasts and collagen fibrils. These findings suggest that the chronic rheumatic scarring process may involve helper/inducer T cells as an ancillary factor in the indolent contracture and fibrosis of deformed cardiac valvular structures. Attempts to demonstrate residual streptococcal antigens by indirect immunofluorescence using a wide panel of heterologous rabbit F(ab')2 reagents with specificity for group A streptococcal membranes, cell wall mucopeptide, or group A carbohydrate gave negative results.

Adult↗

PubMed1983

Complications of rectal suction biopsy.

Complications following use of the rectal suction biopsy technique in the diagnosis of Hirschsprung's disease, are rare. In a series of 1,340 consecutive biopsies, complications included three clinical perforations of the bowel, one resulting in death, and three rectal hemorrhages requiring transfusion. A plea is made for the use of greater care in this technique.

Biopsy↗

PubMed1975