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Biomedical subjects

A K Shukla

Publications and source records attributed to A K Shukla.

28 records · Page 2Linked to original sources
PubMed1985

Structural analysis of underivatized sialic acids by combined high-performance liquid chromatography-mass spectrometry.

Mass spectra of chemically ionized, positive ions of underivatized N,O-acylated sialic acids, 2-deoxy-2,3-didehydro-N-acetylneuraminic acid and sialyl-alpha(2-3)-lactose were obtained by combined high-performance liquid chromatography--mass spectrometry, using a direct liquid inlet system. The mass spectra of the different compounds for which fragmentation schemes are proposed enable the differentiation between sialic acids, although the localization of O-substituents is not possible. However, since the various sialic acids separated well on high-performance liquid chromatography, combined high-performance liquid chromatography-mass spectrometry allowed their unequivocal characterization.

Animals↗
PubMed1985

The receptor-destroying enzyme of influenza C virus is neuraminate-O-acetylesterase.

The nature of the receptor-destroying enzyme (RDE) of influenza C virus has been elucidated by analyzing its effect on the haemagglutination inhibitors rat alpha 1-macroglobulin (RMG) and bovine submandibulary mucin (BSM), respectively. The inhibitory activity of both compounds is abolished by incubation with influenza C virus. After inactivation, RMG and BSM were found to contain reduced amounts of N-acetyl-9-O-acetylneuraminic acid (Neu5,9Ac2) and increased amounts of N-acetylneuraminic acid (Neu5Ac). H.p.l.c. analysis revealed that purified Neu5,9Ac2 is converted to Neu5Ac by incubation with influenza C virus. These results demonstrate that RDE of influenza C virus is neuraminate-O-acetylesterase [N-acyl-9(4)-O-acetylneuraminate O-acetylhydrolase (EC 3.1.1.53)]. The data also indicate that haemagglutination-inhibition (HI) by RMG and BSM and most likely virus attachment to cell surfaces involves binding of influenza C virus to Neu5,9Ac2.

Acetylesterase↗
PubMed1984

New techniques for the investigation of structure and metabolism of sialic acids.

Sialic acid analysis in biological material including gangliosides is often confronted with the necessity to determine trace amounts of various N,O-substituted species. Therefore, techniques of high sensitivity and resolution are required, such as capillary gas-liquid chromatography (GLC) and high performance liquid chromatography (HPLC). Both methods in combination with mass spectrometry allow structural analysis of the different neuraminic acid derivatives. Thus, the number of natural sialic acids known so far has increased to more than 30, including non only saturated, but also 2,3-unsaturated and 2,7-anhydro-sialic acids. Furthermore, HPLC has proved to be especially useful for the study of enzyme reactions, as the sialic acids of enzyme assay mixtures in most cases can be analyzed without prior extensive purification or derivatization.

Animals↗
PubMed1984

Identification of a disialoganglioside (GD1a) containing terminal N-acetyl-9-O-acetylneuraminic acid in rat erythrocytes.

Gangliosides containing 350 micrograms of sialic acids were isolated from 2.85 X 10(11) rat erythrocytes and found to be mainly composed of GD1a and an unknown alkali-labile species which was converted to GD1a after treatment with ammonia. Smaller amounts of GM1 and Fuc-GM1 were also present. Identification of the sialic acids of the novel species by thin-layer chromatography, high performance liquid chromatography and gas-liquid chromatography--mass spectrometry revealed the presence of both N-acetylneuraminic acid and N-acetyl-9-O-acetyl-neuraminic acid in about equimolar amounts. Incubation of the isolated ganglioside with Vibrio cholerae sialidase released N-acetyl-9-O-acetyl-neuraminic acid. Non O-acetylated GM1 was identified as the only remaining ganglioside by thin-layer chromatography. Thus this novel ganglioside has the following structure: Neu5,9Ac2 alpha 2-3Gal beta 1-3GalNAc beta 1-4(Neu5Ac alpha-2-3)Gal beta 1-4Glc beta 1-1'Cer.

Animals↗
PubMed1982

Fluorimetric determination of unsubstituted and 9(8)-O-acetylated sialic acids in erythrocyte membranes.

A method is described for all quantitative determination of free or glycosidically bound sialic acids with special reference to erythrocyte membranes. Sialic acids, unsubstituted in their side chains, quantitatively yield formaldehyde after mild periodate oxidation (1 mM NaIO4, 15 min, 4 degrees C, in the dark). The formaldehyde is determined by the reaction with acetylacetone and ammonium acetate which leads to a sensitive fluorogen (F 410/510 nm). Sialic acids O-acetylated at C-9 or C-8 are not oxidized under these conditions. Therefore, they can be determined quantitatively by measuring the increase of fluorogen after O-deacetylation by 0.1 M NaOH. A minimum amount of 100 ng of sialic acids can be determined. Total sialic acids (microgram/ml packed erythrocytes) and the relative amount of 9(8)-mono-O-acetylated sialic acids were determined by this procedure in erythrocytes from the following mammals (data in brackets): donkey (360; 8%), horse (350; 4%), mouse (300; 60%), rat (280; 40%), cow (200; 0%), cat (190; 25%), man (180; 0%), guinea pig (160; 22%), pig (130; 12%) and rabbit (70; 20%).

Animals↗
PubMedDate not supplied

Radiation surface doses to patients and staff during positron emission tomography.

In view of the complexities involved in estimating individual organ doses in positron emission tomography, the present study was undertaken to measure radiation surface doses in 23 patients undergoing PET studies using specially designed CaSO4: Tm TL dosimeters. In patients with brain disorders, the mean radiation surface doses to the chest and gonads were 0.52 mGy and 0.47 mGy, respectively. In patients with cardiac disorders, the mean surface doses to the forehead and gonadals were, respectively, 0.29 mGy and 0.41 mGy. It was possible to measure the radiation surface doses to all the intended sites in patients with liver malignancies, and maximum surface doses of 0.50 mGy and 0.49 mGy were recorded at the chest and gonadals, respectively. The measurement of radiation surface doses enables easy, quick, and reliable intercomparison of radiation load to patients and staff in various PET procedures.

Brain Diseases↗
PubMedDate not supplied

Esophageal atresia: tragedies and triumphs over two decades in a developing country.

During a period of two decades, 1972-1991, 303 patients with esophageal atresia and/or tracheo-esophageal fistula were treated at the department of Pediatric Surgery, SMS Medical College, Jaipur, India. More than half of our patients fall into Waterston's risk category C. To evaluate the improvement in our results, the patients were divided into four phases of 5 years each. Over the period of observation, the incidence of new cases as well as the number of associated anomalies has considerably increased. With time, more patients are being diagnosed and referred early for treatment. This has resulted in more patients being treated by primary repair with or without a gastrostomy. Extrapleural approach and single layer end-to-end anastomosis has been practised in all cases. Results have shown a steady improvement primarily because of early recognition, improved perioperative care and newer antibiotics. Although postoperative pulmonary complications and anastomotic leak have shown a decreasing trend, but the presence of severe associated anomalies, pulmonary complications and sepsis still remain the major killers in our set-up. Although our results may not match those from the developed countries, we have still come a long way, improving our overall survival rate of 4.6% in 1972-76 to 45.7% in 1987-91. Through the present article, we wish to highlight the practical problems faced in the management of these patients in underprivileged developing countries.

Developing Countries↗