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Biomedical subjects

S Roy

Publications and source records attributed to S Roy.

At least 451 records · Page 25Linked to original sources
PubMed1995

A study of aggregation of 9-(dicyano-vinyl)julolidine.

Di(cyano vinyl)julolidine (DCVJ) is a fluorescent probe which has been used to monitor the local mobility of its binding sites on proteins. It shows a concentration dependence of its emission spectrum in water. At higher DCVJ concentrations, a longer wavelength band appears. The latter increases relative to the shorter wavelength band as a function of increased DCVJ concentration. Absorption and excitation spectra indicate that the concentration dependent emission in the longer wavelength is a consequence of association in the ground state and subsequent excimer formation. DCVJ forms two types of complexes with gamma-cyclodextrin, one of which shows the longer wavelength emission band. Analysis of stoichiometry of association also suggests that longer wavelength emission band may be a consequence of association of two molecules of DCVJ in the gamma-cyclodextrin cavity. Possible uses of such excimer formation in biological systems have also been discussed.

Fluorescent Dyes↗
PubMed1994

Magnesium-induced structural changes in tubulin.

Exogenously added Mg2+, in the intracellular concentration range, has significant effect on the conformation of tubulin as monitored by tryptophan fluorescence. This magnesium-induced conformational change is reflected in the change of the slope and intercept of the Lehrer plot. The off-rate of colchicine from colchicine-tubulin complex is also decreased severalfold upon the addition of exogenous magnesium. The conformational change is magnesium-specific, and magnesium can only be replaced by manganese. GTP, CaCl2, and NaCl have no effect. Magnesium, however has no effect on tryptophan accessibilities of tubulin-S. Implications of these results are discussed in terms of C-terminal tail-body interaction.

Animals↗
PubMed1994

New albumin gene 3' adjacent to the alpha 1-fetoprotein locus.

The albumin multigene family encodes proteins synthesized in the liver and secreted in the serum to fulfill ligand-carrier functions. The albumin (ALB), alpha 1-fetoprotein (AFP), and vitamin D-binding protein genes are syntenic, the ALB and AFP genes are organized in tandem, and the AFP gene is selectively expressed in the fetal liver. We now report the existence of a fourth member of the albumin gene family, located 10 kilobases downstream from the AFP locus. The new gene, named alpha-albumin (alpha ALB), is selectively expressed in the liver at late stages of development. The alpha ALB mRNA sequence encodes a predicted secreted protein with the typical triple domain disulfide cross-linked structure. Comparisons of coding and promoter sequences suggest that alpha ALB could be a phylogenetic intermediate between the ALB and AFP genes. The developmental switch between alpha ALB gene activation and AFP gene repression suggests new regulatory interplays at the albumin locus and adult stage-specific ligand binding functions carried out by the alpha ALB gene product.

Albumins↗
PubMed1994

Overexpression of any fibrinogen chain by Hep G2 cells specifically elevates the expression of the other two chains.

Earlier studies showed that overexpression of B beta fibrinogen chains, by transfection of Hep G2 cells with B beta cDNA, specifically enhanced the synthesis of all three fibrinogen chains (Roy, S. N., Mukhopadhyay, G., and Redman, C. M. (1990) J. Biol. Chem. 265, 6389-6393). To determine whether overexpression of any of the three component chains of fibrinogen affects the synthesis of the other two chains, we developed stable Hep G2 cell lines transfected with individual fibrinogen chain cDNAs. As a control, cells were also transfected with expression vector, which did not contain fibrinogen cDNA. Transfection with any fibrinogen cDNA increased the synthesis of all three fibrinogen chains but not of other plasma proteins. Hep G2 cells transfected with B beta cDNA produced 3-4-fold more fibrinogen than control cells, and cells transfected with A alpha or gamma cDNA made about 2-fold more fibrinogen. Northern blot analyses showed that levels of all 3 fibrinogen mRNAs were increased and were highest in Hep G2-B beta cells. Nuclear run-on transcription assays demonstrated that increased expression of the chains was due to increased transcriptional activity. These studies show that transcription of the three fibrinogen chains is tightly linked, and increased expression of any chain specifically leads to increased synthesis of the other two chains.

Blood Proteins↗
PubMed1994

The role of programmed cell death (apoptosis) in thymic involution following sepsis.

OBJECTIVE: To test the hypothesis that thymic involution following peritoneal sepsis is secondary to thymocyte programmed cell death. DESIGN: We investigated the temporal response of thymic weight and thymic DNA fragmentation following peritoneal sepsis induced by cecal ligation and puncture in a rat model. We investigated the possible role of decreased interleukin (IL)-2 synthesis in the induction of apoptosis using rat thymocytes in primary culture. Finally, we studied IL-2 gene expression and IL-2 protein synthesis in phytohemagglutinin and IL-1 beta-treated thymocytes derived from the cecal ligation and puncture model of sepsis. RESULTS: We demonstrated that (1) there is a significant decrease in thymic weight and an increase in thymic DNA fragmentation with the characteristic apoptotic DNA "ladder" fragmentation pattern on agarose gel electrophoresis following peritoneal sepsis; (2) thymocytes in primary culture sustain a significant increase in thymocyte apoptosis following IL-2 withdrawal; and (3) peritoneal sepsis results in inhibition of phytohemagglutinin and IL-1 beta-induced thymocyte IL-2 messenger RNA accumulation and protein synthesis. CONCLUSIONS: Thymic involution following peritoneal sepsis is associated with increased thymocyte programmed cell death. Thymocyte apoptosis induced by sepsis may be the result, in part, of inhibition of IL-2 gene expression.

Animals↗
PubMed1994

Iliocaval reconstruction with metallic stents.

Percutaneous stenting is now the preferred first line of treatment for occlusive lesions of the great veins. A case is presented in which multiple metallic stents were used to reestablish communication between the suprahepatic inferior vena cava and both iliac veins. The clinical result was satisfactory: venous claudication was relieved, and the progress of chronic venous insufficiency arrested. Stent implantation offers a minimally invasive therapeutic option even when extensive revascularisation is indicated.

Blood Vessel Prosthesis↗
PubMed1994

Fructose 3-phosphate and 5-phosphoribosyl-1-pyrophosphate formation in perfused human erythrocytes: 31P NMR studies.

31P NMR was used to study the formation of fructose 3-phosphate (F3P) and 5-phosphoribosyl-1-pyrophosphate (PRPP) in perfused human erythrocytes, in the presence of 10 different combinations and concentrations of glucose, inosine, pyruvate, fructose, and inorganic phosphate (Pi). (1) The cells were immobilized in alginate-coated agarose threads and perfused with a medium containing fructose, and the level of F3P increased continuously over more than 10 h. The net rate of F3P formation was independent of the concentration of 2,3-bisphosphoglycerate (2,3-DPG) present in the cells. (2) PRPP was formed in high concentrations, relative to normal, in immobilized cells when they were perfused with a medium containing Pi at a low pH (6.6). (3) The 2,3-DPG level decreased simultaneously when the sample was perfused with a medium containing fructose, but without inosine or pyruvate. The measured intracellular pH and free Mg2+ concentration were constant in these experiments. (4) The experiments confirmed the presence of fructose-3-phosphokinase (E.C. 2.7.1.-) and ribose-phosphate pyrophosphokinase (E.C. 2.7.6.1) activity in the human erythrocytes and that the biosynthetic pathways are active in immobilized cells at 37 degrees C. (5) The rates of accumulation of 2,3-DPG and phosphomonoesters (PME) appeared to be strongly correlated.

2,3-Diphosphoglycerate↗
PubMed1994

Collagen type IV gene expression in human optic nerve heads with primary open angle glaucoma.

Previous studies have demonstrated proliferation of basement membranes in the optic nerve head in primary open angle glaucoma (POAG). We used in situ hybridization (ISH) of a radiolabeled riboprobe specific for human collagen IV, a ubiquitous component of basement membranes, to identify cells actively synthesizing basement membranes in the optic nerve head in POAG. In addition, to detect and further characterize the collagen IV mRNA transcripts, we used reverse transcriptase-polymerase chain reaction (RT-PCR) in total RNA extracted from individual optic nerve heads with POAG and from age-matched normal controls. ISH results demonstrate that, in POAG, numerous astrocytes in the prelaminar region expressed collagen IV mRNA. Lamina cribrosa cells and astrocytes in the compressed lamina cribrosa hybridized the probe. Few astrocytes and lamina cribrosa cells hybridized the probe in the optic nerve head of normal age-matched controls. RT-PCR products for collagen IV and for glyceraldehyde-3-dehydrogenase (G3PDH), a reference gene, were detected by agarose electrophoresis as single bands of the expected sizes and positively identified by Southern hybridization using specific cDNA probes in normal and POAG samples. No additional products (bands) were observed in RT-PCR experiments, indicating that there was no genomic DNA contamination in the total RNA extract. The lack of additional bands suggests that, at least in the ten samples used in this study, there were no alternatively spliced RNA products in any of the amplified sequences. Semi-quantitative analyses using densitometry showed a two-fold increase in collagen type IV PCR present in POAG samples. No differences were detected in levels of G3PDH PCR products between POAG and normal samples. This investigation provides evidence of increased biosynthesis of collagen type IV at the mRNA level in optic nerve heads with POAG. Whether this phenomenon represents a response to elevated intraocular pressure or a reparative mechanism to the loss of axons remains to be determined.

Aged↗
PubMed1994

Immobilization methods for NMR studies of cellular metabolism--a practical guide.

Nuclear magnetic resonance (NMR) can be used in a nondestructive manner to study cellular metabolism in intact cell samples such as a suspension of cells. However, many different cell types require a well-regulated medium that includes a buffered pH, as well as a continuous supply of oxygen. A series of methods that have been used for the maintenance of the extracellular conditions involves the immobilization of cells, followed by perfusion of the immobilized cell sample. NMR studies can then be performed for extended periods of time, as well as under sterile conditions. We discuss methodology, with perfused erythrocytes and thymocytes as specific examples.

Alginates↗
PubMed1994

The differential diagnostic value of urinary enzyme and amino acid excretion in children with nephrotic syndrome.

Urinary enzymes N-acetyl-beta-D-glucosaminidase (NAG) and gamma-glutamyl transpeptidase (gamma-GT) are sensitive markers of specific renal cell damage. Excessive urinary amino acid excretion may also be an indicator of renal tubular damage. We have evaluated urinary excretion of NAG, gamma-GT and 37 amino acids, phospholipids and dipeptides in 30 children (aged 2.3-18.1 years) with nephrotic syndrome (NS), 23 with minimal change nephrotic syndrome (MCNS), 7 with focal segmental glomerulosclerosis (FSGS) and 16 healthy age-matched controls. Nine MCNS patients were in relapse and 14 in remission. Enzyme activity is expressed as micromoles per milligram urinary creatinine. In FSGS, NAG excretion correlated with the following: blood urea nitrogen (BUN) (r = 0.8), serum protein (r = 0.57), serum cholesterol (r = 0.85), serum albumin (r = -0.68) and proteinuria (r = 0.56). In FSGS the gamma-GT excretion was not significantly different from MCNS in remission or in relapse. In FSGS, gamma-GT excretion correlated with the following: BUN (r = 0.48), serum creatinine (r = -0.66), serum protein (r = -0.54), serum albumin (r = -0.68) and serum cholesterol (r = 0.87). Compared with controls, the urinary excretion of 5 amino acids was increased in FSGS patients as a possible indicator of tubular damage. The value for 7 amino acids was reduced in MCNS patients. Urinary amino acid excretion was not different from controls for the other amino acids in either FSGS or MCNS.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylglucosaminidase↗
PubMed1994

Urinary mineral excretion among normal Taiwanese children.

Prompted by a large population of children with renal stones seen in 20 of our country's teaching hospitals over the past 10 years, this study of urinary mineral excretion in normal children was performed. Fasting urine from 1,072 normal Taiwanese school children and 24-h urine collections from 125 children separated into three age groups were analysed for calcium (Ca), phosphate, magnesium (Mg), uric acid, sodium (Na) and creatinine (Cr). Fasting Ca/Cr ratios were not different between the sexes. Ca/Cr ratios were higher in the 17- to 18-year age group as were 24-h urinary Ca excretions. Urinary Mg/Cr ratios were higher in girls than boys and 24-h urinary Mg excretion was highest in the younger age groups. Urinary Mg excretion in Taiwanese children is 54%-86% lower than previously reported in Caucasian children. Both uric acid/Cr ratios and 24-h urinary uric acid excretion were highest in the youngest children. Urinary Na/Cr ratios and 24-h urinary Na excretion were higher in the two younger age groups. There was no correlation between 24-h urinary Ca and Na excretion.

Adolescent↗
PubMed1994

A prospective, double-blind study of growth failure in children with chronic renal insufficiency and the effectiveness of treatment with calcitriol versus dihydrotachysterol. The Growth Failure in Children with Renal Diseases Investigators.

Because controlled trials in adults have shown accelerated deterioration of renal function in a small number of patients receiving calcitriol for renal osteodystrophy, we initiated a prospective, randomized, double-blind study of the use of calcitriol versus dihydrotachysterol in children with chronic renal insufficiency. We studied children aged 1 1/2 through 10 years, with a calculated glomerular filtration rate between 20 and 75 ml/min per 1.73 m2, and with elevated serum parathyroid hormone concentrations. Ninety-four patients completed a mean of 8.0 months of control observations and were randomly assigned to a treatment period; 82 completed the treatment period of at least 6 months while receiving a calcitriol dosage (mean +/- SD) of 17.1 +/- 5.9 ng/kg per day or a dihydrotachysterol dosage of 13.8 +/- 3.3 micrograms/kg per day. With treatment the height z scores for both calcitriol- and dihydrotachysterol-treated groups showed no differences between the two groups. In relation to cumulative dose, there was a significant decrease in glomerular filtration rate for both calcitriol and dihydrotachysterol; for calcitriol the rate of decline was significantly steeper (p = 0.0026). The treatment groups did not differ significantly with respect to the incidence of hypercalcemia (serum calcium concentration > 2.7 mmol/L (> 11 mg/dl)). We conclude that careful follow-up of renal function is mandatory during the use of either calcitriol or dihydrotachysterol because both agents were associated with significant declines in renal function. There was no significant difference between calcitriol and dihydrotachysterol in promoting linear growth or causing hypercalcemia in children with chronic renal insufficiency. Dihydrotachysterol, the less costly agent, can be used with equal efficacy.

Calcitriol↗
PubMed1994

Cell culture studies on human nerve sheath tumors.

The main controversy about nerve sheath tumors (NSTs) has been their histogenesis. A Schwann cell origin has been proposed by many investigators for both schwannomas and neurofibromas. However Erlandson and Woodruff observed that while schwannomas appeared to be composed predominantly of Schwann cells, neurofibromas consisted of mainly perineurial cells. In addition, variable numbers of fibroblast-like cells and intermediate cells also have been reported in the 2 lesions. Whether these represent distinct cell types or variants of Schwann cells is still debatable. In an attempt to solve this controversy, the present study was undertaken to observe the morphology and the behaviour of these tumors in culture. These studies showed that all nerve sheath tumors are basically of Schwann cell origin and that intermediate cells and fibroblasts are variants of Schwann cell. Tissue culture studies done chiefly on schwannomas showed that the morphological features of schwannomas are preserved in 'in vitro culture' condition and therefore the difference between neurofibroma and schwannoma appears to be due to inherent differentiating property of the Schwann cells along with some environmental stimulus.

Adolescent↗
PubMed1994

Interventional radiology in the management of superior thyroid artery injury which presents as a diagnostic dilemma.

Following a forgotten iron splinter injury, a 19 year old male developed a slowly increasing extrathyroidal haematoma, which presented as a diagnostic dilemma. Surgical exploration failed to establish a diagnosis and was complicated by severe haemorrhage. Emergency angiography demonstrated injury to the superior thyroid artery. Therapeutic embolization and surgical exploration resulted in functional and anatomical recovery of the thyroid lobe.

Adult↗
PubMed1994

Purification, pore-forming ability, and antigenic relatedness of the major outer membrane protein of Shigella dysenteriae type 1.

The major outer membrane protein (MOMP), the most abundant outer membrane protein, was purified to homogeneity from Shigella dysenteriae type 1. The purification method involved selective extraction of MOMP with sodium dodecyl sulfate in the presence of 0.4 M sodium chloride followed by size exclusion chromatography with Sephacryl S-200 HR. MOMP was found to form hydrophilic diffusion pores by incorporation into artificial liposome vesicles composed of egg yolk phosphatidylcholine and dicetylphosphate, indicating that MOMP of S. dysenteriae type 1 exhibited significant porin activity. However, the liposomes containing heat-denatured MOMP were barely active. The molecular weight of MOMP found by size exclusion chromatography was 130,000, and in sodium dodecyl sulfate-10% polyacrylamide gel it moved as an oligomer of 78,000 molecular weight. Upon boiling, fully dissociated monomers of 38,000 molecular weight were seen for S. dysenteriae type 1. However, among the four Shigella spp., the monomeric MOMP generated upon boiling ranged from 38,000 to 35,000 in molecular weight. Antibody raised in BALB/c mice immunized with MOMP of S. dysenteriae type 1 reacted strongly with purified MOMP of S. dysenteriae type 1 in an enzyme-linked immunosorbent assay (ELISA). The antibody reacted with whole-cell preparations of S. dysenteriae type 1 in an ELISA, suggesting that MOMP possessed surface components. Moreover, MOMP could be visualized on the bacterial surface by immunoelectron microscopy with anti-MOMP antibody. S. dysenteriae type 1 MOMP-specific immunoglobulin eluted from MOMP bound to a nitrocellulose membrane was found to cross-react with MOMP preparations of S. flexneri, S. boydii, and S. sonnei, indicating that MOMPs were antigenically related among Shigella species. The strong immunogenicity, surface exposure, and antigenic relatedness make MOMP of Shigella species an immunologically significant macromolecule for study.

Animals↗