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Biomedical subjects

H Singh

Publications and source records attributed to H Singh.

At least 433 records · Page 24Linked to original sources
PubMed1984

A DNA primase that copurifies with the major DNA polymerase from the yeast Saccharomyces cerevisiae.

Biochemical fractionation of the yeast Saccharomyces cerevisiae has revealed a novel DNA primase activity that copurifies with the major DNA polymerase activity. In the presence of RNA precursors and single-stranded DNA (poly(dT), M13), the DNA primase synthesizes discrete length oligoribonucleotides (apparent length, 8-12 nucleotides) as well as longer RNA chains that appear to be multiples of a modal length of 11-12 nucleotides. When DNA precursors are also present, the oligoribonucleotides are utilized by the accompanying DNA polymerase as primers for DNA synthesis. Copurification of these two enzymatic activities suggests their association in a physical complex which may function in the synthesis of Okazaki fragments at chromosomal replication forks.

Chromatography, DEAE-Cellulose↗
PubMed1984

Monoacylglycerol lipase. Regulation and increased activity during hypoxia and ischemia.

The presence of monoacylglycerol lipase was established in extracts of acetone-dried powders from rat and bovine brains using thioester substrate analogs. At pH 7.4, the apparent Km and Vmax values for 1-S-decanoyl-1-mercapto-2,3-propanediol were 56 microM and 227 nmol/h/mg protein in bovine gray matter. The divalent metal ions Ca2+ and Mg2+ had no effect on enzymic activity, but Zn2+ at 500 microM produced a 50% inhibition of this enzyme. Free fatty acids also caused a marked inhibition of monoacylglycerol lipase activity. Norepinephrine and 5-hydroxytryptamine slightly stimulated the enzymic activity. Hypoxic-hypoxia and 30-s postdecapitation ischemia resulted in a considerable increase in monoacylglycerol lipase activity of rat brain. However, the increased activity of monoacylglycerol lipase returned to normal after 5 min of ischemia. The increased activity of monoacylglycerol lipase during hypoxic-hypoxia and short-time ischemia may be partially responsible for increased levels of free fatty acids during these processes.

Acetylcholine↗
PubMed1984

Effect of anionic polymeric hydrogels on spermatozoa motility.

The effects of a few synthetic polymers on the motility of human spermatozoa in vitro have been studied. An alternate copolymer of styrene and maleic anhydride, poly(S-MA), poly (styrene-maleic acid), poly(S-MC), poly(hydroxy-ethyl methacrylate-methacrylic acid) copolymer, poly(HEMA-MAC), poly(HEMA) homopolymer and poly(MAC) homopolymer were chosen for this purpose. It was found that all the carboxylic acid containing polymers are strong inhibitors of the motility of spermatozoa. Poly(HEMA) did not have any inhibitory effect on the motility of spermatozoa.

Contraceptive Agents, Male↗
PubMed1984

The titration of tetanus antitoxin I. Factors affecting the sensitivity of the indirect haemagglutination test.

Various factors affecting the indirect HA test for the titration of tetanus antitoxin have been evaluated with a view to obtaining maximum sensitivity in tests using unfixed sheep erythrocytes and sheep erythrocytes fixed with glutaraldehyde, formaldehyde and pyruvic aldehyde. The optimal concentration of tannic acid has been found to be 1/40 000 for tanning both fixed and unfixed sheep erythrocytes. Tanned sheep erythrocytes sensitized with 50 Lf/ml of tetanus toxoid at pH 7.2 for one hour were the most sensitive. Although the optimal temperature of sensitization was found to be 56 degrees C, unfixed cells tended to clump and lyse at this temperature. Thus a temperature of 37 degrees C was used to sensitize unfixed sheep erythrocytes. Sheep erythrocytes from different animals and the final concentration of sensitized sheep erythrocytes both had great effects on sensitivity. A final concentration of 0.5% of sensitized sheep erythrocytes was found suitable as a compromise between sensitivity and readability. The loss of sensitivity of fixed and sensitized erythrocytes was investigated by storing these cells at 4-8 degrees C for six to nine months.

Animals↗
PubMed1984

The titration of tetanus antitoxin II. A comparative evaluation of the indirect haemagglutination and toxin neutralization tests.

Serum samples from 77 guinea pigs immunized against tetanus have been titrated for tetanus antitoxin by a standardized indirect haemagglutination (IHA) test and the conventional toxin neutralization (TN) test. These sera were titrated before and after treatment of the sera with 2-mercaptoethanol (2-ME) by the IHA test using unfixed sheep erythrocytes and erythrocytes fixed with glutaraldehyde, formaldehyde and pyruvic aldehyde. The titres of these sera obtained by IHA using unfixed and glutaraldehyde-fixed sheep erythrocytes before treatment of the sera with 2-ME were two to six times higher than the TN titres, whereas the IHA-titres using formaldehyde- and pyruvic aldehyde-fixed sheep erythrocytes were 10 times higher than the TN titres in some of the sera. There was no statistically significant difference between TN and IHA titres using unfixed and glutaraldehyde-fixed sheep erythrocytes after the treatment of the sera with 2-ME.

Animals↗
PubMed1984

The titration of tetanus antitoxin III. A comparative evaluation of indirect haemagglutination and toxin neutralization titres of human sera.

The tetanus antitoxin titres of 174 serum samples from healthy adults were determined by a standardization indirect haemagglutination test (IHA) and the conventional toxin neutralization (TN) test. The serum samples were titrated by the IHA test using glutaraldehyde-fixed and toxoid sensitized sheep erythrocytes before and after the treatment of the sera with 2-mercaptoethanol (2-ME). The IHA method has been found to be very sensitive and specific for the estimation of tetanus antitoxin in human sera. The IHA titres before the treatment of the sera with 2-ME were generally about four times higher than the TN titres and the correlation coefficient between these titres was 0.94. The IHA titres after the treatment of the sera with 2-ME were in good agreement with the TN titres and there was no statistically significant differences between the titres by the two methods. The tetanus antitoxin titres of 50% of the sera were below the minimum protective titres of tetanus antitoxin (0.01 IU/ml). In 19.5% of the sera the antitoxin level (IU/ml) ranged from 0.01 to 0.1, in 20.1% from 0.1 to 1.0 and in 10.4% from 1.0 to 10.0.

Hemagglutination Tests↗
PubMed1984

Biochemical aspects of malabsorption in marasmus.

Sixty marasmic children and fifteen normal age-matched controls were investigated for the absorption of fats and proteins. Their duodenal juice samples were also analysed for bile salts and microflora. A significant amount of malabsorption, with respect to both the dietary ingredients, was observed in the majority of the marasmic children. The levels of conjugated bile acids in the duodenal juice samples of marasmic children were significantly lower as compared with those of normal controls, while the reverse was true for free bile acids and bacterial counts. Significant correlations were observed between bile acid levels and fat absorption and also between microflora and free bile acids. The pathophysiology of malabsorption in marasmus is discussed in the light of these findings.

Bacteria, Aerobic↗
PubMed1984

Use of alcuronium in patients undergoing renal transplantation.

Alcuronium 0.16 mg kg-1 was used to provide neuromuscular blockade in patients with chronic renal failure undergoing renal transplantation. Relaxation was found to be adequate for intubation and surgery. There were minimal alterations to cardiovascular variables. The dose required was small, and complete reversal occurred with neostigmine. Although the number of patients is small, the drug may be of value as an alternative to tubocurarine or pancuronium in such patients.

Adolescent↗
PubMed1984

The haemodynamic effects of left ventriculography in coronary artery disease and mitral valve disease: a comparison of high and low osmolality contrast media.

We compared the haemodynamic effects of a low osmolality contrast medium Hexabrix 320 (meglumine/sodium ioxaglate) with a high osmolality medium Urografin 370 (meglumine/sodium diatrizoate) in 32 patients. Each underwent left ventriculography with both media, which caused similar small and transient increases in heart rate and systolic pressure. In 15 patients with coronary artery disease, the mean left ventricular end-diastolic pressure increased by 4 mmHg after hexabrix compared with 10 mmHg after urografin (P less than 0.01); it returned to normal more quickly after hexabrix. Changes after both media did not correlate with baseline end-diastolic pressure, ejection fraction, or extent of coronary artery disease, and thus left ventriculography was unhelpful as a stress test. In 14 patients with mitral stenosis, hexabrix produced a smaller increase in left ventricular end-diastolic pressure (P less than 0.001), left atrial pressure (P less than 0.01) and mitral valve gradient (P less than 0.05) than urografin. Patients preferred the low osmolality medium (P less than 0.01). There was no difference in angiographic quality. We advocate low osmolality contrast media for patients with poor left ventricular function or severe mitral stenosis.

Adult↗
PubMed1984

Haemodynamics and plasma concentrations following sublingual GTN and intravenous, or inhaled, isosorbide dinitrate.

We measured plasma nitrate levels and haemodynamics following sublingual glyceryl trinitrate (GTN) (0.5 mg), or isosorbide dinitrate (ISDN) administered intravenously (0.5 mg) or by inhalation (1.25 mg) in 23 patients undergoing cardiac catheterisation for investigation of chest pain. Peak levels were detected at 90 s and 5 min following intravenous and inhaled ISDN respectively and at 3 min following sublingual GTN. Intravenous and inhaled ISDN produced similar plasma levels at 30 s and both were significantly greater than following sublingual GTN. Plasma levels were maintained for longer following inhaled ISDN than intravenous ISDN or sublingual GTN. Haemodynamic responses were qualitatively similar following each treatment; reduction in pulmonary vascular resistance and pressure and left ventricular end diastolic pressure occurred in each group. Heart rate, cardiac output and LV dP/dt.P-1 remained unchanged. Maximal haemodynamic responses were greater following ISDN than GTN, with little difference between the two preparations of ISDN. Haemodynamic responses were more sustained following inhaled ISDN than following sublingual GTN or intravenous ISDN, the latter two being similar in this respect. These findings suggest that inhaled ISDN may provide more rapid and sustained relief from angina than sublingual GTN.

Absorption↗
PubMed1984

Immunochemical identification of normal and variant hemoglobins after electrophoretic separation and transfer to nitrocellulose membranes.

A highly specific method for the conclusive identification of normal and variant human hemoglobins is described in this communication. The method employs the standard electrophoretic technique in combination with the immunoblot technique using monospecific antisera raised in rabbits. Various hemoglobins such as Hb, S, C, A2, and F were separated on an alkaline polyacrylamide gel or a cellulose-acetate membrane, and transferred to a nitrocellulose membrane and the individual hemoglobins were identified by the immunoblot procedure. With this method hemoglobins with similar or identical electrophoretic mobilities can be definitively identified with the use of monospecific antisera.

Electrophoresis, Cellulose Acetate↗
PubMed1984

Identification and quantification of hemoglobins A2 and Barts with an enzyme-labeled immunosorbent assay.

The presence and quantity of hemoglobins Barts and A2 in hemolysates from normal donors and individuals with alpha- and beta-thalassemia trait, respectively, were determined with an enzyme-labeled immunosorbent assay (ELISA). This technique requires the incorporation of monospecific antisera capable of specifically reacting only with these hemoglobins, e.g., with the delta chain of Hb A2 and gamma 4 chains of Hb Barts. By the ELISA, the mean percentage of Hb Barts in hemolysates from normal persons and persons with alpha-thalassemia was 0.25 (SD 0.07) and 6.1 (SD 0.40), respectively. Corresponding values for Hb A2 in hemolysates from normals and persons with beta-thalassemia were 3.1 (SD 0.22) and 5.9 (SD 0.21), respectively. The results obtained by the ELISA procedure were in good agreement with those determined by radioimmunoassay or microcolumn chromatography. The ELISA technique is more sensitive and specific than biochemical assays currently used to measure these hemoglobins and can detect 250 ng of Hb Barts in 100 micrograms of hemoglobin or 50 ng of Hb A2 in 5 micrograms of hemoglobin.

Adult↗