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Biomedical subjects

S Ranganathan

Publications and source records attributed to S Ranganathan.

At least 19 recordsLinked to original sources
PubMed2004

Hodgkin-like posttransplant lymphoproliferative disorder in children: does it differ from posttransplant Hodgkin lymphoma?

Epstein-Barr virus (EBV)-mediated lymphoid proliferations occur in patients who are immunocompromised and are reported following bone marrow or solid organ transplantation. Most post-transplant lymphoproliferative disorders (PTLD) are polymorphic in appearance; some are monomorphic and can resemble conventional malignant lymphomas. PTLD that resembles Hodgkin lymphoma has been reported infrequently. We herein report seven cases of PTLD that have large numbers of Reed-Sternberg-like (RS-like) cells and highlight differences in the phenotype of these cases that may distinguish Hodgkin-like PTLD (HL-PTLD) from true Hodgkin lymphoma/disease (HD). All patients were in the second decade of life and were 8 months to 13 years following transplant. HL-PTLD involves lymph nodes that contain a mixed population of small to intermediate-sized lymphocytes with large mononuclear and occasionally binucleate RS-like cells. The large cells of HL-PTLD are pleomorphic B cells that react strongly for CD20 and/or CD79a, express CD30, but are usually negative for CD15 and have few mitoses. They are positive for EBV early RNA (EBER) using an EBER-1 probe, as are some of the background small lymphocytes. A single case of true Hodgkin lymphoma has highly atypical RS-like cells that contain numerous mitoses, does not have CD20 or CD79a reactivity, has CD15 and CD30 staining, and the EBER-1 probe is confined to the large cells only. All patients were managed by withdrawal of immunosuppression and variably treated with either antiviral or anti-CD20 monoclonal antibody, or with chemotherapy. A unique instance of evolution from a HL-PTLD to true HD is also illustrated. In conclusion, HL-PTLD and HD appear to be two related but immunophenotypically and biologically distinct forms of lymphoproliferation in post-transplant patients and may require different protocols for their management.

Adolescent↗
PubMed2003

Binary and multiparticle contributions to the velocity autocorrelation function.

A method for including the contribution of many-body correlation effects to the microscopically obtained results of the two-body contribution to the velocity autocorrelation has been proposed. A significant improvement over the results obtained through only binary contribution has been found, as can be judged by comparing the results for force and velocity autocorrelation functions of Lennard Jones fluids with that of molecular dynamic simulations. The agreement of results of self-diffusion coefficient is also quite good with simulation data over a wide range of densities and temperatures.

Journal Article↗
PubMed2003

Molecular dynamics study of a bilayer electron gas: single particle properties.

The single-particle dynamical properties of a strongly coupled, classical, symmetric electronic bilayer system have been investigated by molecular dynamics simulation. Results for the velocity correlation function, the single-particle scattering function, and their respective Fourier transforms have been calculated, and their behavior, as a function of the interlayer separation d, has been analyzed. The single-particle scattering function in particular, shows dramatic effects when the bilayer attains a staggered square lattice structure. This occurs when the interlayer separation is around 0.8a (a is the Wigner-Seitz radius), where our previous study showed a marked decrease in the diffusion coefficient.

Journal Article↗
PubMed2003

Diverse role of LDL receptor-related protein in the clearance of proteases and in signaling.

The low density lipoprotein receptor-related protein (LRP) is a large endocytic receptor that participates in several biological pathways and plays prominent roles in lipoprotein metabolism and in the catabolism of proteinases involved in coagulation and fibrinolysis. LRP also mediates the cellular entry of certain viruses and toxins and facilitates the activation of various lysosomal enzymes. Deletion of the LRP gene in mice is lethal, confirming an important role for this receptor in development, although its exact function in development is still not known. In addition to its role in the endocytosis of numerous ligands, recent studies are emerging that describe a signaling role for this receptor as well.

Animals↗
PubMed2002

Molecular dynamics study of diffusion in a bilayer electron gas.

Molecular dynamics simulations of strongly coupled, classical electronic bilayers, interacting through the Coulomb potential, have been produced and studied. Values of the plasma coupling parameter Gamma between 10 and 80 and interlayer separations d from 0.1 to 3.0, (in units of Wigner-Seitz radius), were considered. The simulation results were used to calculate the intralayer and interlayer pair correlation functions and self-diffusion of charged particles in this system. The variation of self-diffusion with Gamma and d has been analyzed, and it is found that for the largest value of Gamma, the diffusion coefficient does not increase monotonically with layer separation, but has a distinct minimum for values of d slightly less than 1.

Journal Article↗
PubMed2002

A male-specific (cysteine-rich) protein of Oesophagostomum dentatum (Strongylida) with structural characteristics of a serine protease inhibitor containing two trypsin inhibitor-like domains.

A cDNA was isolated from an adult male Oesophagostomum dentatum gene library by screening with a male-specific, partial expressed sequence tag (EST) probe identified previously using a differential display technique. The full-length cDNA of 642 bp included 5' and 3' untranslated regions of 44 and 121 nucleotides, respectively, and encoded a predicted protein with a putative 18 amino acid signal sequence and a mature polypeptide of 14.7 kDa comprising approximately 15% cysteine residues. The amino acid sequence showed similarity with a number of proteins from Caenorhabditis elegans, parasitic nematodes, insects and amphibia, all of which contain a trypsin inhibitor-like cysteine-rich domain. A 3-dimensional structure model constructed for the O. dentatum protein (designated OdmCRP) inferred that it is composed of 2 domains, each with 5 disulfide bonds, which are indicative of the Ascaris family of serine protease inhibitors. These findings indicate that OdmCRP, with 2 structural domains relating to functionally active sites, is a new member of this inhibitor family.

Amino Acid Sequence↗
PubMed2002

Did earthworms contribute to the parasitic evolution of dermatophytes?

The survival of dermatophyte species in the gut of four species of earthworms was studied by feeding the fungi to the earthworms. Recovery of the dermatophyte species in culture from the guts was only possible for Microsporum gypseum and Chrysosporium keratinophilum. In the light of these findings, we presume that earthworms could have influenced the parasitic evolution of certain dermatophytes.

Animals↗
PubMed2002

The HIV protease inhibitor saquinavir impairs lipid metabolism and glucose transport in cultured adipocytes.

Treatment of HIV infection using protease inhibitors is frequently associated with lipodystrophy and impaired lipid and glucose metabolism. We examined the effect of saquinavir, one of the protease inhibitors, on lipid metabolism and glucose transport in cultured adipocytes. Saquinavir inhibited lipoprotein lipase (LPL) activity in 3T3-F442A and 3T3-L1 adipocytes. The inhibition of LPL was 81% at a concentration of 20 microg/ml. Another closely related drug, indinavir, had a small inhibitory effect. Saquinavir also inhibited the biosynthesis of lipids from [(14)C]-acetate. Saquinavir increased the lipolysis. Saquinavir had no significant effect on the cellular protein synthesis or protein content. Saquinavir increased the basal glucose transport threefold and decreased insulin-stimulated glucose transport by 35%. These studies suggest that some HIV protease inhibitors have direct effects on lipid and glucose metabolism. This inhibition of lipogenesis and glucose transport may explain some of the lipodystrophy, dyslipidemia and disturbed glucose metabolism with the clinical use of these drugs.

Acetates↗
PubMed2001

Modulation of endogenous beta-tubulin isotype expression as a result of human beta(III)cDNA transfection into prostate carcinoma cells.

Increases of individual beta tubulin isotypes in antimicrotubule drug resistant cell lines have been reported by several laboratories. We have previously described elevations in beta(III)and beta(IVa)isotypes in estramustine and paclitaxel resistant human prostate carcinoma cells. To investigate further the function of beta tubulin isotypes in antimicrotubule drug response, human prostate carcinoma cells that normally have very low to undetectable levels of beta(III)were stably transfected with beta(III)cDNA in pZeoSV system. An 18 bp haemagglutinin (HA) epitope tag was added at the 3' end prior to cloning into the vector. Cells were transfected with pZeoSV or pZeoSV-beta(III)plasmids and selected in the presence of Zeocin. Immunofluorescent staining of the transfectant cells have shown significant expression and incorporation of HA-tagged beta(III)tubulin into cellular microtubules. Quantitation of Western blots revealed the HA-tagged beta(III)levels to be approximately 7-fold higher than the vector control cells. RT-PCR analysis confirmed the increase at the transcript level and also revealed a collateral increase of beta(II)and beta(IVb)transcripts. Cell viability assays indicated that sensitivity of beta(III)transfected cells to various antimicrotubule agents was similar to vector transfected cells: IC50 values for estramustine, paclitaxel, colchicine and vinblastine were 4 microM, 4 nM, 22 nM and 2 nM, respectively for both cell lines. Thus, overexpression of beta(III)isotype in human prostate carcinoma cells by stable transfection failed to confer antimicrotubule drug resistance to these cells. Counterregulatory increases of endogenous beta(II)and beta(IVb)tubulin isotypes in these beta(III)transfected cells may be a compensatory mechanism used by the cells to overcome the effects of elevated beta(III)levels on the cellular microtubules. These results highlight the difficulty in isolating the contribution of single tubulin isotypes in drug response studies.

Antineoplastic Agents↗
PubMed2001

The Gummelt decagon as a 'quasi unit cell'.

Steinhardt, Jeong, Saitoh, Tanaka, Abe & Tsai [Nature (London) (1998), 396, 55-57] have demonstrated that the structure of decagonal Al-Ni-Co can be built from overlapping clusters of a single type. The structure arises from a decoration of the decagons of a Gummelt covering. The unit (essentially a decagonal prism) was called by Steinhardt et al. a 'quasi unit cell'. In this work, a classification scheme is proposed for 'G patterns'--quasiperiodic patterns obtained by decorating a decagonal quasi unit cell. The classification makes use of the fact that G patterns can also be derived from decoration of a tiling. The tiles are analogues, for decagonal quasiperiodic patterns, of the 'asymmetric units' of a periodic pattern; they provide a simple mode of description and classification of the 'Gummelt-type structures'. Four existing models for decagonal phases are considered from this viewpoint.

Journal Article↗
PubMed2001

One-step transformation of tricyclopentabenzene (trindane, C(15)H(18)) to bicyclo(10.3.0)pentadec-1(12)ene- 2,6,7,11-tetrone (C(15)H(18)O(4)) and its aldol product, 12-hydroxy-16-oxatetracyclo(10.3.1.0.(1,5)0(7,11))hexadec-7(11)ene-2,6-dione (C(15)H(18)O(4)).

[reaction: see text] Ozonolysis of 1 largely results in 2 and 3, having features similar to several classes of natural products. The retention of the C(15) pericycle suggests preference for the cleavage of pi-bonds endo to the cyclopentane ring. This unique property of trindane offers opportunities for synthesis of complex natural products from this hydrocarbon that can be made in quantity by acid-catalyzed trimerization of cyclopentanone.

Bridged Bicyclo Compounds↗
PubMed2001

Ewald sum for electronic bilayer systems.

The potential energy of a bilayer two-dimensional system of charges, subject to periodic boundary conditions, is derived. The technique of the Ewald sum has been employed so that the formulas can be applied directly in Monte Carlo and molecular-dynamics computer simulations. Numerical evaluation of the potential energy is carried out to confirm the parameter independence.

Journal Article↗
PubMed2001

Electroanalytical performance of carbon films with near-atomic flatness.

Physicochemical and electrochemical characterization of carbon films obtained by pyrolyzing a commercially available photoresist has been performed. Photoresist spin-coated on to a silicon wafer was pyrolyzed at 1,000 degrees C in a reducing atmosphere (95% nitrogen and 5% hydrogen) to produce conducting carbon films. The pyrolyzed photoresist films (PPF) show unusual surface properties compared to other carbon electrodes. The surfaces are nearly atomically smooth with a root-mean-square roughness of <0.5 nm. PPF have a very low background current and oxygen/carbon atomic ratio compared to conventional glassy carbon and show relatively weak adsorption of methylene blue and anthraquinone-2,6-disulfonate. The low oxygen/carbon ratio and the relative stability of PPF indicate that surfaces may be partially hydrogen terminated. The pyrolyzed films were compared to glassy carbon (GC) heat treated under the same conditions as pyrolysis to evaluate the electroanalytical utility of PPF. Heterogeneous electron-transfer kinetics of various redox systems were evaluated. For Ru(NH3)6(3+/2+), Fe(CN)6(3-/4-), and chlorpromazine, fresh PPF surfaces show electron-transfer rates similar to those on GC, but for redox systems such as Fe3+/2+, ascorbic acid, dopamine, and oxygen, the kinetics on PPF are slower. Very weak interactions between the PPF surface and these redox systems lead to their slow electron-transfer kinetics. Electrochemical anodization results in a simultaneous increase in background current, adsorption, and electron-transfer kinetics. The PPF surfaces can be chemically modified via diazonium ion reduction to yield a covalently attached monolayer. Such a modification could help in the preparation of low-cost, high-volume analyte-specific electrodes for diverse electroanalytical applications. Overall, pyrolysis of the photoresist yields an electrode surface with properties similar to a very smooth version of glassy carbon, with some important differences in surface chemistry.

Journal Article↗
PubMed2001

Laboratory method to study mutational effects on human erythrocyte spectrin tetramerization.

We have developed a laboratory method combining a random mutagenesis method and a yeast two-hybrid system to study effects of mutation on human erythrocyte spectrin tetramerization. A PCR-based procedure was used to generate random mutations in DNA fragments of the first 55 residues of alpha-spectrin. Each of the DNA fragments from random mutagenesis was fused with a DNA fragment of native spectrin consisting of residues 56 to 368 to give a DNA fragment of the first 368 residues in alpha-spectrin. The alpha-spectrin DNA fragment and a DNA fragment containing the last 449 residues in beta-spectrin were introduced into the yeast two-hybrid system for rapid screening of alpha- and beta-spectrin interaction. Yeast colonies with interacting alpha- and beta-peptides were blue, and those with non-interacting alpha- and beta-peptides were white. Six single amino acid mutations (R27G, Y35N, F38S, L49H, Y53N, and Y53C) and a double amino acid mutation (K16M, I24N) were identified from 8 white colonies, but no mutations were found in the DNA fragments of 14 blue colonies. Thus this simple laboratory method allows us to study effects of mutation on interactions of alpha- and beta-spectrin at the tetramerization site.

Binding Sites↗
PubMed2001

Effect of high altitude (7,620 m) exposure on glutathione and related metabolism in rats.

Reduced and oxidised glutathione (GSH and GSSG) contents, and glutathione reductase, and glutathione S-transferase activities were studied in the livers, muscles, and blood/erythrocytes of male Sprague-Dawley rats exposed to intermittent hypoxia (6 h.day-1) at a simulated altitude of 7,620 m for 1, 7, 14, and 21 days. Significant decreases in GSH and increases in GSSG contents were observed in the muscles and blood of hypoxia-exposed rats in comparison to unexposed rats. Significant declines in GSH content by 43% and 45% respectively in muscles and blood were observed in the group exposed for 1 day which tended to recover on subsequent exposure. Glutathione reductase and glutathione S-transferase activities were decreased in the livers and erythrocytes of hypoxia-exposed rats, but were increased significantly in muscle. Lipid peroxidation was also increased in the livers and muscles of exposed rats. The changes were indicative of an increased production of reactive oxygen species and an impairment of drug and xenobiotic metabolism during exposure to high altitude hypoxia.

Acclimatization↗
PubMed2001

Effect of an antidiabetic extract of Catharanthus roseus on enzymic activities in streptozotocin induced diabetic rats.

Hypoglycemic activity was detected in dichloromethane:methanol extract (1:1) of leaves and twigs of Catharanthus roseus (family Apocynaceae), a traditionally used medicinal plant, using streptozotocin (STZ) induced diabetic rat model. Extract at dose 500 mg/kg given orally for 7 and 15 days showed 48.6 and 57.6% hypoglycemic activity, respectively. Prior treatment at the same dose for 30 days provided complete protection against STZ challenge (75 mg/kg/i.p.x1). Enzymic activities of glycogen synthase, glucose 6-phosphate-dehydrogenase, succinate dehydrogenase and malate dehydrogenase were decreased in liver of diabetic animals in comparison to normal and were significantly improved after treatment with extract at dose 500 mg/kg p.o. for 7 days. Results indicate increased metabolization of glucose in treated rats. Increased levels of lipid peroxidation measured as 2-thiobarbituric acid reactive substances (TBARS) indicative of oxidative stress in diabetic rats were also normalized by treatment with the extract.

Animals↗