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Biomedical subjects

D Ghosh

Publications and source records attributed to D Ghosh.

At least 55 records · Page 3Linked to original sources
PubMed2000

Expression of vascular endothelial growth factor (VEGF) and placental growth factor (PlGF) in conceptus and endometrium during implantation in the rhesus monkey.

The aim of this study was to analyse the expression of transcripts and proteins for vascular endothelial growth factor (VEGF) and placenta growth factor (PlGF) in different compartments of the early conceptus at primary implantation sites during lacunar (n = 6), early villous (n = 9) and villous placenta (n = 6) stages of gestation in the rhesus monkey. During the lacunar stage, VEGF expression was observed in the cytotrophoblast cells lining the extraembryonic cavity, but these cells did not express PlGF. With further development, cytotrophoblast cells lining villi, forming columns, and constituting anchoring villi, expressed both VEGF and PlGF during early villous and villous placenta stages. In addition, chorion, amnion and villous stromal cells expressed both VEGF and PlGF proteins and mRNA. During the lacunar stage, all epithelial cells in maternal endometrium generally expressed VEGF, while PlGF expression was observed in the plaque epithelium only. As gestation advanced, the expression of VEGF and PlGF from plaque cells decreased, and in surface and glandular epithelium the expression of VEGF increased, while the expression of PlGF remained unaltered. Decidual stromal cells expressed VEGF and PlGF only at low levels during the lacunar stage, while the expression of both increased during the early villous and the villous placenta stages of implantation. It appears from the present study that the expression of VEGF and PlGF are regulated in a temporal and spatial manner during early stages of implantation and that their concerted actions in placental and maternal compartments play a critical role in the evolving pregnancy in the rhesus monkey.

Animals↗
PubMed2000

Macrophage protein kinase C: its role in modulating membrane microviscosity and superoxide in leishmanial infection.

Pretreatment of macrophages with, an agonist of PKC, showed diverse effects on degradation and survival of two virulent strains of Leishmania donovani promastigotes. Treatment of macrophages with PMA for 45 min at 37 degrees C generated significant amounts of superoxide anions and reduced the parasite burden of macrophages by up to 48 and 43% when AG83 and GE-1 strains were used for infection. Staurosporine, an inhibitor of PKC, inhibited PMA-dependent killing of the parasites, while tyrphostin AG 126, an inhibitor of protein tyrosine kinase, showed very little effect. Depletion of PKC by prolonged incubation with PMA drastically reduced the superoxide anion generation and increased the uptake and multiplication of the parasites. Finally, to understand the mechanism of higher uptake of the parasites by PKC-depleted macrophages, membrane microviscosity was measured by fluorescence depolarization. Membrane microviscosity was found to be approximately 40% lower in PKC-depleted macrophages than in normal macrophages, indicating the role of membrane fluidity in the infection process. Together, these data suggest PKC activation, superoxide generation, and membrane fluidity are essential factors in the efficient regulation of leishmanial infection.

Animals↗
PubMed2000

An empirical analysis of the purchaser-provider relationship in the NHS internal market.

Introduces the relationship marketing paradigm as a means of analysing the purchaser-provider relationship within the NHS internal market. This focus is justified in the context of the limitations of orthodox economic analysis. The research evidence is based upon a national survey of all NHS trust hospitals in England. The survey consisted of key questions relating to the process of relationship building strategies employed by NHS hospital trusts. In particular, emphasis was given to non-price competitive behaviour, i.e. the extent to which health care contracts were augmented or customized by providers. An empirical analysis is presented, identifying those factors driving such non-price competitive behaviour, based upon a LOGIT model. The results suggest the hypotheses tested are consistent with the evidence from our survey. Finally, the model is used to make some tentative predictions regarding the future of the purchaser-provider relationship within the reformed NHS.

Contract Services↗
PubMed2000

Nonparametric analysis of recurrent events and death.

This article is concerned with the analysis of recurrent events in the presence of a terminal event such as death. We consider the mean frequency function, defined as the marginal mean of the cumulative number of recurrent events over time. A simple nonparametric estimator for this quantity is presented. It is shown that the estimator, properly normalized, converges weakly to a zero-mean Gaussian process with an easily estimable covariance function. Nonparametric statistics for comparing two mean frequency functions and for combining data on recurrent events and death are also developed. The asymptotic null distributions of these statistics, together with consistent variance estimators, are derived. The small-sample properties of the proposed estimators and test statistics are examined through simulation studies. An application to a cancer clinical trial is provided.

Antineoplastic Agents, Alkylating↗
PubMed2000

High throughput and global approaches to gene expression.

In the past several years, a new set of technologies based on whole genome analysis have revolutionized the study of gene expression. These microarray or "gene chip" technologies, which arose out of the development of large-scale sequencing approaches, are now coming into increasing use, generating a far greater volume of data than the data representing the sequences themselves. This review focuses on the current state of development of these technologies, and the available approaches to manage and analyze the information they generate. The applicability of this technology to general problems in biomedicine is also discussed.

Electronic Data Processing↗
PubMed2000

Gelastic epilepsy possibly following antirabies vaccine.

A case of child with gelastic epilepsy following administration of antirabies vaccine is presented. No associated structural brain could be identified in the patient. Possibility of relationship between antirables vaccine and gelastic epilepsy is discussed.

Brain↗
PubMed1999

Co-occupancy of the interferon regulatory element of the class II transactivator (CIITA) type IV promoter by interferon regulatory factors 1 and 2.

Class II transactivator (CIITA) activates the expression of major histocompatibility class II genes, which encode antigen-presenting molecules recognized by the T-cell receptor of CD4+ T cells. IFN-gamma induced CIITA transcription in many cell types is directed by the CIITA Type IV promoter. Here we report that the human CIITA Type IV promoter IRF-E binds IRF-1 and can be activated by exogenous expression of IRF-1. Surprisingly, the CIITA Type IV promoter IRF-E is also activated by IRF-2, another member of the IRF family that generally acts as a transcriptional repressor. In addition, we found that IRF-1 and IRF-2 synergistically activate the CIITA Type IV promoter. Electrophoretic mobility shift assays revealed that IRF-1 and IRF-2 can simultaneously occupy the IRF-E of the CIITA Type IV promoter, suggesting a novel mechanism for the role of these two proteins in promoter activation. Our results also indicate that IRF-1 and IRF-2 can cooperatively activate and co-occupy the IRF-E of the guanylate binding protein (GBP) promoter. Finally, CIITA induction by IFN-gamma does not occur in a pancreatic tumor cell line that expresses a mutated IRF-2, representing the first IRF-2 mutation identified in a human tumor cell line.

DNA-Binding Proteins↗
PubMed1999

Structure of Ustilago maydis killer toxin KP6 alpha-subunit. A multimeric assembly with a central pore.

Ustilago maydis is a fungal pathogen of maize, some strains of which secrete killer toxins. The toxins are encoded by double-stranded RNA viruses in the cell cytoplasm. The U. maydis killer toxin KP6 contains two polypeptide chains, alpha and beta, having 79 and 81 amino acids, respectively, both of which are necessary for its killer activity. The crystal structure of the alpha-subunit of KP6 (KP6alpha) has been determined at 1.80-A resolution. KP6alpha forms a single domain structure that has an overall shape of an ellipsoid with dimensions 40 A x 26 A x 21 A and belongs to the alpha/beta-sandwich family. The tertiary structure consists of a four-stranded antiparallel beta-sheet, a pair of antiparallel alpha-helices, a short strand along one edge of the sheet, and a short N-terminal helix. Although the fold is reminiscent of toxins of similar size, the topology of KP6alpha is distinctly different in that the alpha/beta-sandwich motif has two right-handed betaalphabeta split crossovers. Monomers of KP6alpha assemble through crystallographic symmetries, forming a hexamer with a central pore lined by hydrophobic N-terminal helices. The central pore could play an important role in the mechanism of the killing action of the toxin.

Hydrogen Bonding↗
PubMed1999

Equilin.

3-Hydroxyestra-1,3,5(10),7-tetraen-17-one, C18H20O2, crystallizes in space group P2(1)2(1)2(1) from ethyl acetate. The planarity of the B ring, and the difference in puckering of the C and D rings from that of estrone, are due to the presence of the C7 = C8 double bond, which may explain its function as an inhibitor of human type 1 17 beta-hydroxysteroid dehydrogenase, instead of being its substrate.

Crystallography, X-Ray↗
PubMed1999

Structure of the ternary complex of human 17beta-hydroxysteroid dehydrogenase type 1 with 3-hydroxyestra-1,3,5,7-tetraen-17-one (equilin) and NADP+.

Excess 17beta-estradiol (E2), the most potent of human estrogens, is known to act as a stimulus for the growth of breast tumors. Human estrogenic 17beta-hydroxysteroid dehydrogenase type 1 (17beta-HSD1), which catalyzes the reduction of inactive estrone (E1) to the active 17beta-estradiol in breast tissues, is a key enzyme responsible for elevated levels of E2 in breast tumor tissues. We present here the structure of the ternary complex of 17beta-HSD1 with the cofactor NADP+ and 3-hydroxyestra-1,3,5,7-tetraen-17-one (equilin), an equine estrogen used in estrogen replacement therapy. The ternary complex has been crystallized with a homodimer, the active form of the enzyme, in the asymmetric unit. Structural and kinetic data presented here show that the 17beta-HSD1-catalyzed reduction of E1 to E2 in vitro is specifically inhibited by equilin. The crystal structure determined at 3.0-A resolution reveals that the equilin molecule is bound at the active site in a mode similar to the binding of substrate. The orientation of the 17-keto group with respect to the nicotinamide ring of NADP+ and catalytic residues Tyr-155 and Ser-142 is different from that of E2 in the 17beta-HSD1-E2 complex. The ligand and substrate-entry loop densities are well defined in one subunit. The substrate-entry loop adopts a closed conformation in this subunit. The result demonstrates that binding of equilin at the active site of 17beta-HSD1 is the basis for inhibition of E1-to-E2 reduction by this equine estrogen in vitro. One possible outcome of estrogen replacement therapy in vivo could be reduction of E2 levels in breast tissues and hence the reduced risk of estrogen-dependent breast cancer.

Amino Acid Sequence↗
PubMed1999

Object oriented Transcription Factors Database (ooTFD).

ooTFD is an object-oriented database for the representation of information pertaining to transcription factors, the proteins and biochemical entities which play a central role in the regulation of gene expression. Given the recent explosion of genome sequence information, and that a large percentage of proteins encoded by fully sequenced genomes fall into this category, information pertaining to this class of molecules may become an essential aspect of biology and of genomics in the 21st century. In the past year, there was a small increase in the size of this database, and a number of new tools to facilitate data access and analysis have been added at the MIRAGE (Molecular Informatics Resource for the Analysis of Gene Expression) web site. ooTFD and associated tools and resources can be accessed at http://www.ifti.org/

Databases, Factual↗
PubMed1999

Structure of rabbit liver fructose 1,6-bisphosphatase at 2.3 A resolution.

The three-dimensional structure of the R form of rabbit liver fructose 1,6-bisphosphatase (Fru-1,6-Pase; E.C. 3.1.3.11) has been determined by a combination of heavy-atom and molecular-replacement methods. A model, which includes 2394 protein atoms and 86 water molecules, has been refined at 2.3 A resolution to a crystallographic R factor of 0.177. The root-mean-square deviations of bond distances and angles from standard geometry are 0.012 A and 1.7 degrees, respectively. This structural result, in conjunction with recently redetermined amino-acid sequence data, unequivocally establishes that the rabbit liver enzyme is not an aberrant bisphosphatase as once believed, but is indeed homologous to other Fru-1,6-Pases. The root-mean-square deviation of the Calpha atoms in the rabbit liver structure from the homologous atoms in the pig kidney structure complexed with the product, fructose 6-phosphate, is 0.7 A. Fru-1,6-Pases are homotetramers, and the rabbit liver protein crystallizes in space group I222 with one monomer in the asymmetric unit. The structure contains a single endogenous Mg2+ ion coordinated by Glu97, Asp118, Asp121 and Glu280 at the site designated metal site 1 in pig kidney Fru-1,6-Pase R-form complexes. In addition, two sulfate ions, which are found at the positions normally occupied by the 6-phosphate group of the substrate, as well as the phosphate of the allosteric inhibitor AMP appear to provide stability. Met177, which has hydrophobic contacts with the adenine moiety of AMP in pig kidney T-form complexes, is replaced by glycine. Binding of a non-hydrolyzable substrate analog, beta-methyl-fructose 1,6-bisphosphate, at the catalytic site is also examined.

Allosteric Site↗
PubMed1999

Structure of an activity suppressing Fab fragment to cytochrome P450 aromatase: insights into the antibody-antigen interactions.

The crystal structure of a Fab fragment (Fab3-2C2) of a monoclonal antibody raised against aromatase cytochrome P450 P450arom) has been determined at 3.0 A resolution. P450arom is a membrane bound enzyme responsible for the catalysis of indrogens to estrogens, the process of aromatization, and hence has been implicated in hormone-dependent breast cancer. The Fab fragment of MAb3-2C2 IgG suppresses P450arom activity in a dose dependent manner. The Fab3-2C2 molecule crystallizes n the space group P2(1)2(1)2(1) with a unit cell of a= 154.89 A, b = 73.51 A, and c= 36.90 A. The crystal structure consists of a light and a heavy chain in the asymmetric unit, each characterized by the greek-key antiparallel beta barrel folding seen in all Fab structures. The average elbow angle between the two domains is 143 degrees. Modeling of the interactions between the variable domains of the antibody and a known model of P450arom maps the epitope to a region of the enzyme that is consistent with the available biochemical data and the activity-suppressing function of the antibody. The epitope mapping result is further supported by the inability of MAb3-2C2 IgG to suppress the activity of, or to interact with placental porcine P450arom, which is 81% identical (86% similar) to human P450arom but has a few key substitutions in the putative epitope region.

Amino Acid Sequence↗
PubMed1999

Statistical methods for analyzing repeated measures.

Repeated measurements arise frequently in biomedical research. In many situations, the scientific question of interest concerns finding differences in the measurements between groups. This question is frequently addressed by using analysis of variance-type methods that fail to incorporate information regarding the repeated sampling design of the experiment. In this paper, we provide an introduction to nonstatisticians of two approaches for analyzing such data. The procedures can be performed by using available software. These methods are illustrated on data from a preclinical study conducted by ZymoGenetics.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1999

Immunohistochemical localization of receptors for progesterone and oestradiol-17 beta in the implantation site of the rhesus monkey.

The aim of the present study was to examine the cellular basis of the involvement of oestradiol and progesterone in blastocyst implantation in the primate. To this end, the cellular distribution of receptors for oestradiol (ER) and progesterone (PR) in fetal trophoblast cells and in endometrial compartments of timed lacunar (pre-villous) and villous stages of placentation in primary implantation sites collected on days 13-22 of gestation were investigated in rhesus monkeys. Both in pre-villous stage tissue and in villous stage tissue, cytotrophoblast cells and syncytiotrophoblast cells and other trophoblast derived cells were PR positive, while they were generally ER negative. Maternal endometrial cells were ER negative, while epithelial cells, stromal cells and vascular endothelial cells in maternal endometrium showed heterogeneous staining patterns for PR depending on their relative location; these patterns, however, correlated well with glandular hyperplasia and differentiation, stromal-decidual transformation and vascular response seen during blastocyst implantation.

Animals↗
PubMed1999

Determination of a protein structure by iodination: the structure of iodinated acetylxylan esterase.

Enzymatic and non-enzymatic iodination of the amino acid tyrosine is a well known phenomenon. The iodination technique has been widely used for labeling proteins. Using high-resolution X-ray crystallographic techniques, the chemical and three-dimensional structures of iodotyrosines formed by non-enzymatic incorporation of I atoms into tyrosine residues of a crystalline protein are described. Acetylxylan esterase (AXE II; 207 amino-acid residues) from Penicillium purpurogenum has substrate specificities towards acetate esters of D-xylopyranose residues in xylan and belongs to a new class of alpha/beta hydrolases. The crystals of the enzyme are highly ordered, tightly packed and diffract to better than sub-angström resolution at 85 K. The iodination technique has been utilized to prepare an isomorphous derivative of the AXE II crystal. The structure of the enzyme determined at 1.10 A resolution exclusively by normal and anomalous scattering from I atoms, along with the structure of the iodinated complex at 1.80 A resolution, demonstrate the formation of covalent bonds between I atoms and C atoms at ortho positions to the hydroxyl groups of two tyrosyl moieties, yielding iodotyrosines.

Acetylesterase↗