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Biomedical subjects

A Saxena

Publications and source records attributed to A Saxena.

At least 253 records · Page 14Linked to original sources
PubMed1991

Late noninvasive evaluation of cardiac performance in mildly symptomatic older patients with Ebstein's anomaly of tricuspid valve: role of radionuclide imaging.

Ten patients 8 to 54 years of age with isolated Ebstein's anomaly of the tricuspid valve were evaluated by electrocardiography, maximal exercise treadmill testing, 24 h electrocardiographic (ECG) monitoring, echocardiography and rest radionuclide imaging of the left ventricle. The patients presented after the 1st year of life and had not undergone surgical intervention. All except one were in functional class II. No patient had preexcitation on the surface ECG, but abnormal tachyarrhythmias or bradyarrhythmias were seen in five patients on 24 h ECG monitoring. Subnormal exercise performance was observed in five patients. Echocardiography demonstrated typical variable tricuspid valve displacement and paradoxic interventricular septal motion. Left ventricular end-diastolic dimensions were normal in all patients, but posterior wall motion was reduced in two. Moderate to severe tricuspid regurgitation with a Doppler jet velocity less than 2.5 m/s was demonstrated in eight patients. Left ventricular radionuclide scintigraphy revealed a subnormal ejection fraction (less than 50%) in 5 of 10 patients; these 5 had previously shown suboptimal exercise performance. The two youngest patients (less than 15 years) had no arrhythmia, normal exercise performance and normal left ventricular ejection fraction. There was no correlation between the degree of tricuspid valve displacement or regurgitation and the presence of rhythm disturbance, exercise performance or radionuclide left ventricular function. Late evaluation of patients with Ebstein's anomaly may demonstrate significant unsuspected abnormalities in cardiac rhythm, exercise performance and left ventricular function. Radionuclide scintigraphy is a useful noninvasive technique for assessing left ventricular dysfunction in these patients.

Adolescent↗
PubMed1991

Identification of anomalous origin of one pulmonary artery from ascending aorta by two-dimensional and colour Doppler echocardiography.

The anomalous origin of the right pulmonary artery from the ascending aorta in a neonate was diagnosed by two-dimensional and colour directed Doppler echocardiography. An anomalous arterial vessel coursing towards the right lung originated from the posterolateral aspect of the ascending aorta. It could be visualized in parasternal and suprasternal views. The normal bifurcation of the pulmonary trunk was absent. Colour Doppler examination aided in clearer delineation and consequent correct identification of the anomalous vessel as the right pulmonary artery.

Aorta↗
PubMed1991

Non-specific aorto-arteritis (Takayasu's disease) in children.

Digital subtraction panaorto-arteriography was performed in 32 consecutive children (21 females, mean age 10.8 years) with non-specific aorto-arteritis to assess digital subtraction angiography (DSA) in imaging these children and to study the patterns of involvement in the Indian sub-continent. Diagnostic quality DSA images were obtained in 21 out of 27 intravenous and nine out of 11 intra-arterial studies. Obstructive lesions were present in all the patients and commonly involved the abdominal aorta (24 patients) and renal arteries (20 patients). Aneurysms were seen in five patients and predominantly involved the descending thoracic aorta. Pulmonary artery involvement was uncommon (five out of 20 patients) and clinically silent. Based on clinical and angiographic features, percutaneous transluminal angioplasty was performed for the management of uncontrolled hypertension in eight patients (10 lesions). Initial success was obtained in eight procedures (80%). Re-stenosis occurred after 5.5 months in one patient, but was successfully re-dilated. The follow-up period ranged between 5 and 16 months (mean 9 months). Long-term efficacy of transluminal angioplasty in the management of these children is awaited.

Adolescent↗
PubMed1990

Interaction of aromatic donor molecules with manganese(III) reconstituted horseradish peroxidase: proton nuclear magnetic resonance and optical difference spectroscopic studies.

The interaction of aromatic donor molecules with manganese(III) protoporphyrin-apohorseradish peroxidase complex [Mn(III)HRP] was investigated by optical difference spectroscopy and relaxation rate measurements of 1H resonances of aromatic donor molecules (at 500 MHz). pH dependence of substrate proton resonance line-widths indicated that the binding was facilitated by protonation of an amino acid residue (with a pKa of 6.1), which is presumably distal histidine. Dissociation constants were evaluated from both optical difference spectroscopy and 1H-NMR relaxation measurements (pH 6.1). The dissociation constants of aromatic donor molecules were not affected by the presence of excess of I-, CN- and SCN-. From competitive binding studies it was shown that all these aromatic donor molecules bind to Mn(III)HRP at the same site, which is different from the binding site of I-, CN- and SCN-. Comparison of the dissociation constants between the different substrates suggests that hydrogen bonding of the donors with distal histidyl amino acid and hydrophobic interaction between the donors and active site contribute significantly towards the associating forces. Free energy, entropy and enthalpy changes associated with the Mn(III)HRP-substrate equilibrium have been evaluated. These thermodynamic parameters were found to be all negative. Distances of the substrate protons from the paramagnetic manganese ion of Mn(III)HRP were found to be in the range of 7.7 to 9.4 A. The Kd values, the thermodynamic parameters and the distances of the bound aromatic donor protons from metal center in the case of Mn(III)HRP were found to be very similar as in the case of native Fe(III)HRP.

Horseradish Peroxidase↗
PubMed1990

Doppler assessment of interventricular pressure gradient across isolated ventricular septal defect.

Continuous wave Doppler ultrasound was used to estimate the pressure gradient between the right and left ventricle for assessment of pulmonary arterial systolic pressure in 30 patients with isolated ventricular septal defect and for subsequent comparison with similar data obtained on cardiac catheterization. The age of the patients ranged from 8 months to 45 years (6.8 +/- 8.6 years). No patient had right or left ventricular outflow tract obstruction. Doppler measurements were done within 24 h of cardiac catheterization. Pressure gradient across ventricular septal defect on cardiac catheterization ranged from 7 to 95 mmHg (48 +/- 24 mmHg) and that on Doppler assessment ranged from 8 to 78 mmHg (42 +/- 20 mmHg). Doppler measurements of interventricular pressure gradient correlated well with those obtained on cardiac catheterization (r = 0.90, p less than 0.001). Correlation was better in patients with pressure gradient across ventricular septal defect less than 75 mmHg (r = 0.96). Correlation was poor in three of five patients with very small ventricular septal defects (interventricular pressure gradient greater than 75 mmHg) because the jet used was not ideal. Thus continuous wave Doppler ultrasound is an accurate noninvasive means of measuring pressure gradient across ventricular septal defect, which is a useful parameter for assessment of pulmonary artery systolic pressure in patients with isolated ventricular septal defect without right and left ventricular outflow tract obstruction.

Adolescent↗
PubMed1990

Coronary arteriovenous fistula in tetralogy of Fallot: an unusual association.

A congenital coronary arteriovenous fistula is a rare anomaly, and only two cases have been previously reported in association with tetralogy of Fallot. We report one more patient with tetralogy of Fallot who had an associated fistulous communication between the left circumflex coronary artery and the coronary sinus. It is important to localize these left to right shunts preoperatively in order to plan optimal surgical management.

Adult↗
PubMed1990

Purification and characterization of the extracellular C3d-binding protein of Candida albicans.

A C3d-binding glycoprotein was purified from the culture filtrate of Candida albicans by preparative isoelectric focusing. The protein possessed a pI of 3.9 to 4.1 and could inhibit rosetting of EAC3d (sheep erythrocytes conjugated to C3d) by pseudohyphae of C. albicans. When analyzed by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate and mercaptoethanol, the protein migrated as a doublet with apparent molecular masses of 55 and 60 kilodaltons (kDa) and as a 50-kDa band in nonreducing gels. These results were observed with Aurodye stain for proteins. Western immunoblot, and concanavalin A stain, which indicates that both bands contain carbohydrate as well as antigenic determinants. The treatment of purified glycoprotein with endoglycosidase F but not endoglycosidases H, N, and O resulted in a complete conversion of the doublet into a faster-migrating broad band with an apparent molecular mass of 45 kDa. When the amino acid analysis of the C3d-binding protein was compared with that of the CR2 from B lymphocytes, significant differences were observed. These data indicate that C. albicans secretes a C3d-binding protein during growth in vitro which appears to be different from the mammalian C3d receptor.

Amino Acids↗
PubMed1990

Mannan composition of the hyphal form of two relatively avirulent mutants of Candida albicans.

We have previously reported the characteristics of mannans isolated from the yeast forms of two relatively avirulent Candida albicans strains, designated 4918-2 and 4918-10. Investigations have been expanded to include an analysis of mannans from the hyphal form of these strains as well as from the hyphal form of the parental strain, 4918. After extraction, mannans were further purified by high-pressure liquid chromatography on a Bio-gel TSK DEAE-5-PW column. Subsequent to either mild acid hydrolysis, alkali hydrolysis, or acetylation followed by acetolysis, the resulting products were fractionated by high-pressure liquid chromatography on an Aminex HPX-42A column. The results of acid hydrolysis showed only minor quantitative differences in the products released from each strain, with mannose constituting the vast majority of product liberated. The profiles of mannooligosaccharides obtained from either alkali hydrolysis or acetolysis for strain 4918-2 showed distinct quantitative differences compared with profiles of the other two strains. Finally, a general characteristic noted is a decrease in the average chain length of mannooligosaccharides in hyphal mannans compared with the yeast counterpart.

Acetylation↗
PubMed1990

Sequence requirements for proteolytic processing of glycoprotein B of human cytomegalovirus strain Towne.

Truncated versions of the human cytomegalovirus (CMV) strain Towne glycoprotein B (gB) gene were stably expressed in CHO cell lines. The calcium-specific ionophore A23187 inhibited proteolytic cleavage of C-terminal-truncated gB expressed by cell line 67.77. These inhibition studies also showed that the 93-kilodalton cleavage product most likely represents the N-terminal cleavage fragment of gB. The ionophore carboxyl cyanide m-chlorophenyl-hydrazone was used to show that proteolytic cleavage of gB did not occur in the endoplasmic reticulum. Two-dimensional polyacrylamide gel electrophoresis demonstrated that the N- and C-terminal cleavage products of gB remained associated by disulfide linkages after cleavage. Expression studies using constructs in which 80% or all of the N terminus was deleted demonstrated that the N terminus was required for secretion of the gB molecule. The amino acid sequence at the site of cleavage was shown to be critical for cleavage by a cellular protease. Our results indicate that an arginine-to-threonine change at either amino acid 457 or 460, a lysine-to-glutamine change at amino acid 459, or all three substitutions together block gB cleavage. The effect on proteolysis of the arginine-to-threonine amino acid change at residue 457 (position -4 relative to the cleavage site) demonstrated that a basic pair of amino acids at the endoproteolytic processing site is not the only requirement in cis for gB cleavage.

Amino Acid Sequence↗
PubMed1990

Use of balloon dilatation to treat supravalvar pulmonary stenosis developing after anatomical correction for complete transposition.

Eight balloon dilatations were performed in five patients (aged from 10 to 37 months) in whom supravalvar pulmonary stenosis developed after anatomical correction for complete transposition. The ratio of the maximum diameter of the inflated balloon to the narrowest pulmonary arterial diameter varied from 1.6 to 3.3. In three patients with an initial ratio of less than or equal to 2 dilatation was repeated with a larger balloon. The right ventricular systolic pressure ranged from 0.70 to 1.25 of the simultaneously measured femoral arterial systolic pressure. The major stenosis was in the main pulmonary artery in four patients and at the pulmonary arterial bifurcation in one. After balloon angioplasty in the four patients there was no significant improvement in the ratio of right ventricular to femoral arterial systolic pressure or in the angiographic appearance. There was no change in the pressure ratio after angioplasty in the patient who had a major stenosis of the pulmonary arterial bifurcation and mild main pulmonary artery narrowing. There seemed to be a slight angiographic improvement in the bifurcation stenosis but at restudy two months later the angiographic improvement had disappeared. Balloon angioplasty of supravalvar pulmonary stenosis developing after anatomical correction for complete transposition was not successful in eight procedures. This lack of success may be attributable to a small pulmonary annulus with consequent multiple levels of stenosis and distortion of the main pulmonary artery.

Catheterization↗
PubMed1990

Interactions of macrophages from in vivo stimulated guineapigs & the trophozoites of Entamoeba histolytica.

The interactions between peritoneal macrophages obtained from guineapigs immunized with a Sephadex chromatographed fraction (FI) of crude amoebic extract proteins and trophozoites of axenic E. histolytica (NIH:200) were studied in vitro in the presence or absence of anti FI antiamoebic antibodies. Unstimulated macrophages killed trophozoites to some extent. Incorporation of anti FI antiamoebic antibodies or IgG of FI antibodies in the amoebae macrophages mixture significantly enhanced the cytotoxic potentials of both unstimulated and in vivo stimulated peritoneal macrophages. Transmission electron microscopy revealed a close contact between macrophages and E. histolytica trophozoites. A large number of lysosomal vacuoles were seen accumulating near the contact areas. The contact between peritoneal macrophages and amoebic trophozoites in the presence of anti FI antibodies led to extensive degeneration of amoebic trophozoites. The antiamoebic antibodies induced cytotoxicity by macrophages in an opsonic manner. The data suggest that antiamoebic IgG binding to the trophozoites by its Fab portion and to the macrophages by its Fc portion initiated the cytotoxic mechanism(s) of macrophages.

Animals↗
PubMed1989

Isolation and sequencing of cDNA clones encoding Drosophila chromosomal protein D1. A repeating motif in proteins which recognize at DNA.

Drosophila melanogaster D1 is a satellite DNA-associated protein which preferentially binds DNA sequences containing runs of AT base pairs. Clones encoding this polypeptide have been isolated from a lambda gt11 cDNA library by immunological screening with a D1 antiserum. The deduced sequence of the D1 polypeptide is 355 amino acids long and contains 10 copies of a repeating motif consisting of a glycine-arginine-proline (GRP) tripeptide located within a cluster of basic amino acids. Three copies of a similar motif have previously been observed in a mammalian satellite DNA-binding protein, high mobility group protein I (Lund, T., Dahl, K. H., Mork, E., Holtlund, J., and Laland, S. G. (1987) Biochem. Biophys. Res. Commun. 146, 725-730), suggesting that this motif may be a general feature of proteins which bind AT-rich satellite DNA and perhaps other AT-containing DNA as well.

Amino Acid Sequence↗
PubMed1989

Doppler echocardiographic assessment of transmitral gradients and mitral valve area before and after mitral valve balloon dilatation.

This is a comparative study of 60 sets of observations of mitral valve end-diastolic gradient, mean diastolic gradient, and mitral valve area obtained by Doppler echocardiography and cardiac catheterization. The studies were performed in 28 patients, 16 of whom underwent mitral valve balloon valvuloplasty. These 16 patients had studies performed before, immediately after valvuloplasty, and one week later. Thus 28 studies were performed before or without valvuloplasty (Group I) and 32 after valvuloplasty (Group II). The time interval between Doppler echocardiography and cardiac catheterization was less than 24 hours in 44 studies and 24 to 72 hours in 16 studies. In Doppler echocardiography the gradients were obtained by simplified Bernoulli's equation and the mitral valve area by pressure half-time method. There was excellent correlation between end-diastolic gradients (r = 0.96, p less than 0.001) and mean diastolic gradients (r = 0.92, p less than 0.001) measured by the two techniques. A statistically significant correlation also existed in the mitral valve area values (r = 0.53, p less than 0.005). On separate analysis Group I showed excellent correlation for all three variables (r values of 0.90, 0.87, and 0.82 for end-diastolic gradients, mean-diastolic gradients, and mitral valve area, respectively). Group II also showed excellent correlation of end-diastolic gradients (r = 0.80) and mean diastolic gradients (r = 0.87), but poor correlation of the mitral valve areas (r = 0.17; p = NS) by the two techniques. Doppler echocardiography can accurately measure transmitral gradients both before and after valvuloplasty.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗