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Biomedical subjects

A K Das

Publications and source records attributed to A K Das.

At least 19 recordsLinked to original sources
PubMed1992

Fatty acylation of a 55 kDa membrane protein of human erythrocytes.

The major palmitoylated human erythrocyte membrane protein has an M(r) of 55,000. It is distinct from the glucose transporter and is not derived from band 3 or ankyrin. It resists salt extraction suggesting a high affinity for the membrane. Pulse chase experiments demonstrate that palmitoylation is a dynamic process, and it may therefore have regulatory significance in membrane protein-protein or protein-lipid interaction. Slower dynamics of palmitoylation in erythrocytes from patients suffering from chronic myelogenous leukemia, which are less stable than normal erythrocytes, strengthen this view.

Acylation↗
PubMed1992

Biosynthesis of glycerolipid precursors in rat liver peroxisomes and their transport and conversion to phosphatidate in the endoplasmic reticulum.

The transport of glycerolipid intermediates, viz. palmitoyl dihydroxyacetone phosphate (DHAP) and lysophosphatidate from peroxisomes and their conversion to phosphatidate in endoplasmic reticulum (microsomes) were studied in cell-free systems. The lipids were biosynthesized from [32P]DHAP, palmitoyl-CoA, and freshly made rat liver peroxisomes and microsomes in the presence or absence of Mg2+, NADPH, and bovine serum albumin (BSA). After incubation, the soluble fraction and the membranes were separated, and the distribution of radioactive lipids in these fractions were determined. The results showed that palmitoyl-DHAP and lysophosphatidate were recovered in the supernatant when BSA was present or when BSA was absent, but Mg2+ was removed after incubation by chelation with EDTA (or ATP). At low optimum palmitoyl-CoA concentration or when palmitoyl-CoA was generated in peroxisomes, and in the absence of BSA, the biosynthesized keto ether and ester lipids and lysophosphatidate were similarly present in the supernatant. Phosphatidate, however, was always localized in the membranes. Further fractionation showed that phosphatidate was associated with the microsomes. The critical micellar concentrations of palmitoyl-DHAP and 1-palmitoyl-rac-glycerol 3-phosphate, under the incubation conditions used, were determined to be 58 and 70 microM, respectively. These results suggest that at physiological concentrations the biosynthesized lysolipids are water soluble, and therefore, a carrier protein is unnecessary for their transport. These lipids freely diffuse from peroxisomes to endoplasmic reticulum where they are converted to membrane-bound phosphatidate.

Acyltransferases↗
PubMed1992

Mutants in a macrophage-like cell line are defective in plasmalogen biosynthesis, but contain functional peroxisomes.

We have used a fluorescence-activated cytotoxicity protocol, 9-(1'-pyrene)nonanol (P9OH)/UV selection (Morand, O. H., Allen, L.-A. H., Zoeller, R. A., and Raetz, C. R. H. (1990) Biochim. Biophys. Acta 1034, 132-141), to isolate a series of plasmalogen-deficient mutants in a murine, macrophage-like cell line, RAW 264.7. Three of these mutants, RAW.7, RAW.12, and RAW.108, displayed varying degrees of plasmalogen deficiency (48, 17, and 14% of wild-type levels, respectively), and all three mutants were deficient in peroxisomal dihydroxyacetone phosphate (DHAP) acyltransferase activity (5% of wild-type). Unlike previously described Chinese hamster ovary (CHO) cell mutants, the RAW mutants contained intact, functional, peroxisomes and normal levels of alkyl-DHAP synthase activity, a peroxisomal, membrane-bound enzyme. In RAW.7 and RAW.108 cells, the loss of peroxisomal DHAP acyltransferase is the primary lesion. RAW.12 displayed not only a deficiency in the DHAP acyltransferase activity, but also displayed a second lesion in the biosynthetic pathway, a deficiency in delta 1'-desaturase activity (plasmanylethanolamine desaturase, EC 1.14.99.19), the final step in plasmenylethanolamine biosynthesis. The deficiencies expressed in the mutants represent unique lesions in plasmalogen biosynthesis. Since the RAW cell line is a macrophage-like responsive cell line, these mutants can be used to examine the role of plasmalogens in cellular functions such as arachidonic acid metabolism, prostaglandin synthesis, protein secretion, and signal transduction.

Acyltransferases↗
PubMed1992

Immunoelectron microscopy of cationized bovine serum albumin-induced glomerulonephritis in the rabbit.

Chronic immune complex glomerulonephritis was induced in a group of New Zealand white rabbits by daily intravenous injections of cationized bovine serum albumin (cBSA). The animals were serially killed and renal tissue was embedded in the hydrophilic resin Lowicryl K4M for immunoelectron microscopy. The results demonstrate the progressive deposition of rabbit IgG in the glomerular basement membrane in this model, with aggregation of immunoglobulins occurring only in the subepithelial space. Proteinuria developed concurrently with this event. Glomerular visceral epithelial cell (GVEC) endocytosis of immune material was observed at various stages of the disease process, suggesting that GVECs may be part of a clearance mechanism acting within the glomerulus.

Animals↗
PubMed1992

Dietary ether lipid incorporation into tissue plasmalogens of humans and rodents.

Chronic feeding of 1-O-octadecyl-sn-glycerol (batyl alcohol) to patients suffering from congenital deficiency in tissue ether glycerolipids showed an increase in the plasmalogens content of their erythrocytes. However, nothing is known about the ether lipid content of other tissues in these patients. Feeding 1-O-heptadecyl-sn-glycerol to young rats showed that this uncommon ether lipid was incorporated to a high extent into the plasmalogens of all tissues except brain. Comparative studies with other precursors, such as 3-O-heptadecyl-sn-glycerol, heptadecanol and heptadecanoic acid, indicated a stereospecific incorporation of the dietary 1-O-alkyl-sn-glycerols into tissue plasmalogens without cleavage of the ether bond. Dietary ether lipids were also shown to be transferred from mothers to suckling rats, but not from pregnant rats to fetuses. The implication of these results to possible dietary ether lipid therapy for patients suffering from peroxisomal disorders is discussed.

Acyltransferases↗
PubMed1992

Pedunculated scrotal mass: leiomyoma of scrotum.

Scrotal leiomyomas of the tunica dartos are extremely rare and usually misdiagnosed. A case of a pedunculated mass observed expectantly over thirty years demonstrates the benign oncologic natural history of this lesion despite its capability for substantial growth. Only limited local surgical management of such lesions is indicated.

Humans↗
PubMed1992

The hemi-Kock ileocystoplasty: a versatile procedure in reconstructive urology.

The hemi-Kock system, constructed from approximately 40 cm. of terminal ileum, comprises a detubularized and remodeled ileal plate with a stapled ileoileal intussusception to form a 1-way valve. This system has been applied to reconstruct 30 varied cases in which the intussuscepted valve was used either for reflux prevention or as a continent stoma. The patients included 11 with intractable urinary incontinence and a devastated bladder outlet in whom the hemi-Kock pouch was anastomosed to the bladder after the bladder neck had been surgically closed, with the afferent limb of the nipple valve being routed through the abdominal wall as a continent stoma. In 9 patients who had previously undergone supravesical diversion, undiversion was accomplished with this system to augment the bladder, with the antireflux nipple being anastomosed to the prior ileal loop or ureters. In 5 patients in whom intractable bladder hyperactivity had led to devastated upper tracts with markedly dilated ureters this system was used for bladder augmentation, with the ureters being reimplanted into the afferent limb of the hemi-Kock system to prevent reflux. The final patients were those in whom the hemi-Kock pouch was converted into a complete reservoir and used for orthotopic bladder replacement. The hemi-Kock system proved to be successful in each of these roles. It created a capacious low pressure reservoir, protected the upper tracts from reflux and improved those that were previously dilated, and it proved to be a reliable continent stoma when applied to that use. The versatility of the hemi-Kock system in its application to a variety of reconstructive endeavors recommends it for use.

Adolescent↗
PubMed1992

Indirect atomic absorption spectrometric determination of sulfate in human blood serum.

An indirect method for the determination of sulfate by atomic absorption spectrometry (AAS) is described. Sulfate forms a stable ion-association complex, [Cu(neocuproine)2]2+(SO4(2-)), in neutral medium, which can be extracted into isobutyl methyl ketone in the presence of a polar medium (methanol) with an efficiency higher than 98.0% and the extract can be analysed directly for copper (and hence indirectly for sulfate) by AAS. Measurement of the copper atomic absorption signal from the organic phase allows the indirect determination of 0.14-1.12 micrograms ml-1 of sulfate, giving a 450-fold increase in sensitivity over the conventional method of precipitation with barium. The limit of detection (3 sigma) is 3.2 ng ml-1 which is better than that of ion chromatography (0.15 micrograms ml-1). Indirect AAS allows the accurate assay of inorganic sulfate anion in biological fluids and tissues. The sulfate concentration determined by the proposed method in human blood serum (n = 6 in each instance) was 35.4-43.3 micrograms ml-1 in normal persons, 50.3-62.5 micrograms ml-1 in jaundice patients and 83.3-155.6 micrograms ml-1 in diabetic patients. A good correlation between measured sulfate and the sulfate added to blood serum was obtained.

Humans↗
PubMed1992

The acyl dihydroxyacetone phosphate pathway enzymes for glycerolipid biosynthesis are present in the yeast Saccharomyces cerevisiae.

The presence of the acyl dihydroxyacetone phosphate (acyl DHAP) pathway in yeasts was investigated by examining three key enzyme activities of this pathway in Saccharomyces cerevisiae. In the total membrane fraction of S. cerevisiae, we confirmed the presence of both DHAP acyltransferase (DHAPAT; Km = 1.27 mM; Vmax = 5.9 nmol/min/mg of protein) and sn-glycerol 3-phosphate acyltransferase (GPAT; Km = 0.28 mM; Vmax = 12.6 nmol/min/mg of protein). The properties of these two acyltransferases are similar with respect to thermal stability and optimum temperature of activity but differ with respect to pH optimum (6.5 for GPAT and 7.4 for DHAPAT) and sensitivity toward the sulfhydryl blocking agent N-ethylmaleimide. Total membrane fraction of S. cerevisiae also exhibited acyl/alkyl DHAP reductase (EC 1.1.1.101) activity, which has not been reported previously. The reductase has a Vmax of 3.8 nmol/min/mg of protein for the reduction of hexadecyl DHAP (Km = 15 microM) by NADPH (Km = 20 microM). Both acyl DHAP and alkyl DHAP acted as substrates. NADPH was the specific cofactor. Divalent cations and N-ethylmaleimide inhibited the enzymatic reaction. Reductase activity in the total membrane fraction from aerobically grown yeast cells was twice that from anaerobically grown cells. Similarly, DHAPAT and GPAT activities were also greater in aerobically grown yeast cells. The presence of these enzymes, together with the absence of both ether glycerolipids and the ether lipid-synthesizing enzyme (alkyl DHAP synthase) in S. cerevisiae, indicates that non-ether glycerolipids are synthesized in this organism via the acyl DHAP pathway.

Acyltransferases↗
PubMed1992

Evaluation of the cariogenic potential of the intense natural sweeteners stevioside and rebaudioside A.

Stevioside and rebaudioside A, two intense natural sweeteners, that are constituents of the South American plant Stevia rebaudiana, were tested for cariogenicity in albino Sprague-Dawley rats. Sixty rat pups colonized with Streptococcus sobrinus were divided into four groups and fed stevioside, rebaudioside A or sucrose added to basal diet 2000 as follows: group 1, 30% sucrose; group 2, 0.5% stevioside; group 3, 0.5% rebaudioside A, and group 4, no addition. All four groups were sacrificed after 5 weeks. S. sobrinus counts were made and caries was evaluated according to Keyes' technique. There were no differences in food and water intake and weight gains between the four groups. There were significant differences in sulcal caries scores (p < 0.02) and S. sobrinus counts (p < 0.05) between group 1 and the other three groups. There were no significant differences between the stevioside, rebaudioside A and no-addition groups. It was concluded that neither stevioside nor rebaudioside A is cariogenic under the conditions of this study.

Animals↗
PubMed1992

Acute filarial myositis.

An uncommon case of filariasis presenting as acute myositis is described. The patient was treated initially with steroids and antihistamines with no response. Later on with the confirmation of filariasis he was treated with diethyl carbamazine with complete recovery.

Acute Disease↗
PubMed1992

An extended SQL for temporal data management in clinical decision-support systems.

We are developing a database implementation to support temporal data management for the T-HELPER physician workstation, an advice system for protocol-based care of patients who have HIV disease. To understand the requirements for the temporal database, we have analyzed the types of temporal predicates found in clinical-trial protocols. We extend the standard relational data model in three ways to support these querying requirements. First, we incorporate timestamps into the two-dimensional relational table to store the temporal dimension of both instant- and interval-based data. Second, we develop a set of operations on timepoints and intervals to manipulate timestamped data. Third, we modify the relational query language SQL so that its underlying algebra supports the specified operations on timestamps in relational tables. We show that our temporal extension to SQL meets the temporal data-management needs of protocol-directed decision support.

Acquired Immunodeficiency Syndrome↗