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Biomedical subjects

A Ganguly

Publications and source records attributed to A Ganguly.

At least 19 recordsLinked to original sources
PubMed2006

Apoptosis is induced in leishmanial cells by a novel protein kinase inhibitor withaferin A and is facilitated by apoptotic topoisomerase I-DNA complex.

Protein kinase C (PKC) is an important constituent of the signaling pathways involved in apoptosis. We report here that like staurosporine, withaferin A is a potent inhibitor of PKC. In Leishmania donovani, the inhibition of PKC by withaferin A causes depolarization of DeltaPsim and generates ROS inside cells. Loss of DeltaPsim leads to the release of cytochrome c into the cytosol and subsequently activates caspase-like proteases and oligonucleosomal DNA cleavage. Moreover, in treated cells, oxidative DNA lesions facilitate the stabilization of topoisomerase I-mediated cleavable complexes, which also contribute to DNA fragmentation. However, withaferin A and staurosporine cannot induce cleavable complex formation in vitro with recombinant topoisomerase I nor with nuclear extracts from control cells. Taken together, our results indicate that inhibition of PKC by withaferin A is a central event for the induction of apoptosis and that the stabilization of topoisomerase I-DNA complex is necessary to amplify apoptotic process.

Animals↗
PubMed2006

SMAD4 mutations found in unselected HHT patients.

BACKGROUND: Hereditary haemorrhagic telangiectasia (HHT) is an autosomal dominant disease exhibiting multifocal vascular telangiectases and arteriovenous malformations. The majority of cases are caused by mutations in either the endoglin (ENG) or activin receptor-like kinase 1 (ALK1, ACVRL1) genes; both members of the transforming growth factor (TGF)-beta pathway. Mutations in SMAD4, another TGF-beta pathway member, are seen in patients with the combined syndrome of juvenile polyposis (JP) and HHT (JP-HHT). METHODS: We sought to determine if HHT patients without any apparent history of JP, who were undergoing routine diagnostic testing, would have mutations in SMAD4. We tested 30 unrelated HHT patients, all of whom had been referred for DNA based testing for HHT and were found to be negative for mutations in ENG and ALK1. RESULTS: Three of these people harboured mutations in SMAD4, a rate of 10% (3/30). The SMAD4 mutations were similar to those found in other patients with the JP-HHT syndrome. CONCLUSIONS: The identification of SMAD4 mutations in HHT patients without prior diagnosis of JP has significant and immediate clinical implications, as these people are likely to be at risk of having JP-HHT with the associated increased risk of gastrointestinal cancer. We propose that routine DNA based testing for HHT should include SMAD4 for samples in which mutations in neither ENG nor ALK1 are identified. HHT patients with SMAD4 mutations should be screened for colonic and gastric polyps associated with JP.

Activin Receptors, Type II↗
PubMed2005

Performance of a static-anode/flat-panel x-ray fluoroscopy system in a diagnostic strength magnetic field: a truly hybrid x-ray/MR imaging system.

Minimally invasive procedures are increasing in variety and frequency, facilitated by advances in imaging technology. Our hybrid imaging system (GE Apollo flat panel, custom Brand x-ray static anode x-ray tube, GE Lunar high-frequency power supply and 0.5 T Signa SP) provides both x-ray and MR imaging capability to guide complex procedures without requiring motion of the patient between two distant gantries. The performance of the x-ray tube in this closely integrated system was evaluated by modeling and measuring both the response of the filament to an externally applied field and the behavior of the electron beam for field strengths and geometries of interest. The performance of the detector was assessed by measuring the slanted-edge modulation transfer function (MTF) and when placed at zero field and at 0.5 T. Measured resonant frequencies of filaments can be approximated using a modified vibrating beam model, and were at frequencies well below the 25 kHz frequency of our generator for our filament geometry. The amplitude of vibration was not sufficient to cause shorting of the filament during operation within the magnetic field. A simple model of electrons in uniform electric and magnetic fields can be used to estimate the deflection of the electron beam on the anode for the fields of interest between 0.2 and 0.5 T. The MTF measured at the detector and the DQE showed no significant difference inside and outside of the magnetic field. With the proper modifications, an x-ray system can be fully integrated with a MR system, with minimal loss of image quality. Any x-ray tube can be assessed for compatibility when placed at a particular location within the field using the models. We have also concluded that a-Si electronics are robust against magnetic fields. Detailed knowledge of the x-ray system installation is required to provide estimates of system operation.

Electromagnetic Fields↗
PubMed2005

Photoluminescence and raman study of CdS-Al2O3 nanocomposite films prepared by sol-gel techniques.

The optical and microstructural properties of CdS-Al2O3 nanocomposite (CdS-Al2O3 = 20:80 to 50:50) thin films synthesized by sol-gel techniques were studied. Optical transmission spectra indicated a marked blue shift of the absorption edge due to quantum confinement. Band gaps of CdS-Al2O3 nanocomposites were found to vary in the range 3.69-2.61 eV. The sizes of the nanocrystals, estimated from the blue shift (0.2-1.2 eV) of the absorption edges and transmission electron microscopy, were found to vary in the range 2.8-7.0 nm. X-ray diffraction studies showed reflections from (111), (200), (220), and (311) planes of CdS in the cubic phase. Microstructural characterization by high-resolution transmission electron microscope (HRTEM) indicated well crystallinity of the nanoparticles and lattice fringes supported the cubic phase of CdS. Raman spectroscopy was carried out for CdS-Al2O3 nanocomposites, which indicated a prominent peak at approximately 299 cm(-1). Significant changes in the peak position and intensity of the Raman peak were observed with varying the annealing temperature (373-573 K). Photoluminescence measurements indicated a prominent broad peak at approximately 1.81 eV due to the surface defects in the CdS nanocrystallites. The present study revealed Al2O3 to be a good capping material for CdS nanoparticles.

Aluminum Oxide↗
PubMed2004

Camptothecin induced mitochondrial dysfunction leading to programmed cell death in unicellular hemoflagellate Leishmania donovani.

The parasites of the order kinetoplastidae including Leishmania spp. emerge from most ancient phylogenic branches of unicellular eukaryotic lineages. In their life cycle, topoisomerase I plays a significant role in carrying out vital cellular processes. Camptothecin (CPT), an inhibitor of DNA topoisomerase I, induces programmed cell death (PCD) both in the amastigotes and promastigotes form of L. donovani parasites. CPT-induced cellular dysfunction in L. donovani promastigotes is characterized by several cytoplasmic and nuclear features of apoptosis. CPT inhibits cellular respiration that results in mitochondrial hyperpolarization taking place by oligomycin-sensitive F0-F1 ATPase-like protein in leishmanial cells. During the early phase of activation, there is an increase in reactive oxygen species (ROS) inside cells, which causes subsequent elevation in the level of lipid peroxidation and decrease in reducing equivalents like GSH. Endogenous ROS formation and lipid peroxidation cause eventual loss of mitochondrial membrane potential. Furthermore, cytochrome c is released into the cytosol in a manner independent of involvement of CED3/CPP32 group of proteases and unlike mammalian cells it is insensitive to cyclosporin A. These events are followed by activation of both CED3/CPP32 and ICE group of proteases in PCD of Leishmania. Taken together, our study indicates that different biochemical events leading to apoptosis in leishmanial cells provide information that could be exploited to develop newer potential therapeutic targets.

Animals↗
PubMed2001

Cloning, expression and nuclear localization of human NPM3, a member of the nucleophosmin/nucleoplasmin family of nuclear chaperones.

BACKGROUND: Studies suggest that the related proteins nucleoplasmin and nucleophosmin (also called B23, NO38 or numatrin) are nuclear chaperones that mediate the assembly of nucleosomes and ribosomes, respectively, and that these activities are accomplished through the binding of basic proteins via their acidic domains. Recently discovered and less well characterized members of this family of acidic phosphoproteins include mouse nucleophosmin/nucleoplasmin 3 (Npm3) and Xenopus NO29. Here we report the cloning and initial characterization of the human ortholog of Npm3. RESULTS: Human genomic and cDNA clones of NPM3 were isolated and sequenced. NPM3 lies 5.5 kb upstream of FGF8 and thus maps to chromosome 10q24-26. In addition to amino acid similarities, NPM3 shares many physical characteristics with the nucleophosmin/nucleoplasmin family, including an acidic domain, multiple potential phosphorylation sites and a putative nuclear localization signal. Comparative analyses of 14 members of this family from various metazoans suggest that Xenopus NO29 is a candidate ortholog of human and mouse NPM3, and they further group both proteins closer with the nucleoplasmins than with the nucleophosmins. Northern blot analysis revealed that NPM3 was strongly expressed in all 16 human tissues examined, with especially robust expression in pancreas and testis; lung displayed the lowest level of expression. An analysis of subcellular fractions of NIH3T3 cells expressing epitope-tagged NPM3 revealed that NPM3 protein was localized solely in the nucleus. CONCLUSIONS: Human NPM3 is an abundant and widely expressed protein with primarily nuclear localization. These biological activities, together with its physical relationship to the chaparones nucleoplasmin and nucleophosmin, are consistent with the proposed function of NPM3 as a molecular chaperone functioning in the nucleus.

Journal Article↗
PubMed2001

Caucasian family with two independent mutations: 2594delC in BRCA1 and 5392delAG in BRCA2 gene.

Germline mutations in two breast cancer susceptibility genes, BRCA1 and BRCA2, predispose individuals to early onset breast and ovarian cancer. The frequency of mutations in these genes in the general population is very low. Therefore, the prior probability of finding any family with mutations in both genes is even lower. This study reports the presence of two mutations, one in BRCA1 and a second in BRCA2, in a single family with variable expression. The BRCA1 mutation, 2594delC, was identified first in the proband. Analysis on a related family member with early onset bilateral breast cancer for the same mutation was negative. Further analysis on the same individual led to the identification of a second germline mutation, 5392delAG in BRCA2 gene in this family. Without the knowledge of the second mutation in this family, many asymptomatic individuals would have been given a negative test result and be falsely reassured. Further analysis reveals differential expression of the two mutations. The spectrum of cancers as well as the age of onset is variable between the mutations and the generations. Finally, the study exemplifies the fact that molecular analysis of a genetically heterogeneous disease can be very complex and requires a team effort of the patients and their family members, genetic counselors or referring physicians as well as the personnel from the testing laboratory.

BRCA1 Protein↗
PubMed2001

The cell cycle of Entamoeba invadens during vegetative growth and differentiation.

The cell division cycle of Entamoeba invadens was studied during vegetative growth of trophozoites and during their differentiation into cysts. During vegetative growth of trophozoites, it was observed that DNA synthesis typically continued after one genome content had been duplicated. During encystation, DNA synthesis was arrested after 4n genome content had been synthesised. Using multi-parameter flow cytometry, the light scattering properties of cysts and trophozoites were studied. The cytoplasmic granularity, reflected by the side scatter of light, was proportional to DNA content of trophozoites, whereas cysts with similar DNA contents showed heterogeneity in their cytoplasmic granularity. Dynamic changes in the intracellular calcium pools were observed during differentiation of trophozoites to cysts. Comparison of E. invadens and Entamoeba histolytica cell cycles suggest that both organisms may have similar regulatory processes during cell division and differentiation. Since E. histolytica cannot be induced to encyst in axenic culture, analysis of the E. invadens cell cycle during encystation may be useful for identifying homologous processes in E.histolytica.

Animals↗
PubMed2001

Unilateral dopamine depletion increases expression of the 2A subunit of the N-methyl-D-aspartate receptor in enkephalin-positive and enkephalin-negative neurons.

Striatal efferent neurons receive dopamine- and glutamate-utilizing afferents. Previous studies have shown that dopamine depletion increases gene expression in striatopallidal neurons and decreases it in striatonigral neurons. Previous work has also reported increased expression of the 2A subunit of the N-methyl-D-aspartate receptor in the dopamine-depleted striatum. The purpose of this study therefore was to determine whether dopamine depletion differentially alters the expression of the 2A subunit of the N-methyl-D-aspartate receptor in rat striatal neurons. 6-Hydroxydopamine (8microg/2microl) was infused unilaterally into the medial forebrain bundle. Rats were killed three weeks later. Double-label in situ hybridization was performed using an 35S-labeled ribonucleotide probe directed against the messenger RNA of the 2A subunit and a digoxigenin-labeled ribonucleotide probe directed towards preproenkephalin messenger RNA to mark striatopallidal neurons. Analysis of single-labeled film autoradiograms revealed a significant increase in the expression of 2A subunit messenger RNA in the ipsilateral, but not the contralateral, striatum of dopamine-depleted animals, consistent with other studies in the literature. Cellular analysis of 2A subunit expression indicated that as a consequence of dopamine depletion there is a significant increase in the expression of this subunit in both enkephalin-positive and enkephalin-negative neurons. From this study we conclude that dopamine depletion increases messenger RNA expression of the 2A subunit of the N-methyl-D-aspartate receptor in striatopallidal and presumed striatonigral (enkephalin-negative) neurons. Such alterations may affect the pharmacology and function of the resultant receptor, and thus alter glutamate transmission in both populations of medium spiny neurons after dopamine depletion.

Animals↗
PubMed2001

Hyperinsulinism and hyperammonemia syndrome: report of twelve unrelated patients.

Hyperinsulinism and hyperammonemia syndrome has been reported as a cause of moderately severe hyperinsulinism with diffuse involvement of the pancreas. The disorder is caused by gain of function mutations in the GLUD1 gene, resulting in a decreased inhibitory effect of guanosine triphosphate on the glutamate dehydrogenase (GDH) enzyme. Twelve unrelated patients (six males, six females) with hyperinsulinism and hyperammonemia syndrome have been investigated. The phenotypes were clinically heterogeneous, with neonatal and infancy-onset hypoglycemia and variable responsiveness to medical (diazoxide) and dietary (leucine-restricted diet) treatment. Hyperammonemia (90-200 micromol/L, normal <50 micromol/L) was constant and not influenced by oral protein, by protein- and leucine-restricted diet, or by sodium benzoate or N-carbamylglutamate administration. The patients had mean basal GDH activity (18.3 +/- 0.9 nmol/min/mg protein) not different from controls (17.9 +/- 1.8 nmol/min/mg protein) in cultured lymphoblasts. The sensitivity of GDH activity to inhibition by guanosine triphosphate was reduced in all patient lymphoblast cultures (IC(50), or concentrations required for 50% inhibition of GDH activity, ranging from 140 to 580 nM, compared with control IC(50) value of 83 +/- 1.0 nmol/L). The allosteric effect of ADP was within the normal range. The activating effect of leucine on GDH activity varied among the patients, with a significant decrease of sensitivity that was correlated with the negative clinical response to a leucine-restricted diet in plasma glucose levels in four patients. Molecular studies were performed in 11 patients. Heterozygous mutations were localized in the antenna region (four patients in exon 11, two patients in exon 12) as well as in the guanosine triphosphate binding site (two patients in exon 6, two patients in exon 7) of the GLUD1 gene. No mutation has been found in one patient after sequencing the exons 5-13 of the gene.

Adolescent↗
PubMed2001

Hyperinsulinism/hyperammonemia syndrome in children with regulatory mutations in the inhibitory guanosine triphosphate-binding domain of glutamate dehydrogenase.

The hyperinsulinism/hyperammonemia (HI/HA) syndrome is a form of congenital hyperinsulinism in which affected children have recurrent symptomatic hypoglycemia together with asymptomatic, persistent elevations of plasma ammonium levels. We have shown that the disorder is caused by dominant mutations of the mitochondrial enzyme, glutamate dehydrogenase (GDH), that impair sensitivity to the allosteric inhibitor, GTP. In 65 HI/HA probands screened for GDH mutations, we identified 19 (29%) who had mutations in a new domain, encoded by exons 6 and 7. Six new mutations were found: Ser(217)Cys, Arg(221)Cys, Arg(265)Thr, Tyr(266)Cys, Arg(269)Cys, and Arg(269)HIS: In all five mutations tested, lymphoblast GDH showed reduced sensitivity to allosteric inhibition by GTP (IC(50), 60--250 vs. 20--50 nmol/L in normal subjects), consistent with a gain of enzyme function. Studies of ATP allosteric effects on GDH showed a triphasic response with a decrease in high affinity inhibition of enzyme activity in HI/HA lymphoblasts. All of the residues altered by exons 6 and 7 HI/HA mutations lie in the GTP-binding domain of the enzyme. These data confirm the importance of allosteric regulation of GDH as a control site for amino acid-stimulated insulin secretion and indicate that the GTP-binding site is essential for regulation of GDH activity by both GTP and ATP.

Enzyme Inhibitors↗
PubMed2000

Effects of MK-801 on D1 dopamine receptor-mediated immediate early gene expression in the dopamine-depleted striatum.

Previous work indicates that intrastriatal administration of MK-801 does not completely block D1 agonist-induced gene expression in dopamine-depleted rats. The present study examined the effects of systemic MK-801 on such gene expression. A low dose of MK-801 did not affect induction of c-fos or zif268. A high dose completely blocked induction of c-fos, but only slightly suppressed zif268. The data suggest that NMDA receptor activity may not always be necessary for D1-induced gene expression.

Animals↗
PubMed2000

Clinical correlations of alpha2,6-sialyltransferase expression in colorectal cancer patients.

We have previously demonstrated a link between alpha2,6-Sialyltransferase (alpha2,6-ST; E.C. 2.4.99.1) expression and differentiation of colon tumors. So far, information is not available relative to the expression of alpha2,6-ST in tumors and the survival of patients with colorectal cancer. We have examined the expression of alpha2,6-ST in a variety of colorectal adenocarcinomas (n = 46) at different stages of differentiation (G1 to G3) by immunoperoxidase assay using monoclonal antibody (MAb) 6B9. Clinical outcome of the patients in a 5-year follow-up study has been correlated with the expression of alpha2,6-ST in tumors surgically removed from the same patients. No significant difference in the alpha2,6-ST expression was noted when age, sex, and tumor locations (colon, rectum) were included as parameters. However, 52% of the moderate (G2) and well-differentiated (G1) adenocarcinomas showed stronger alpha2,6-ST expression compared with poorly differentiated (G3) adenocarcinomas. Notably, absence to moderate levels of tumor alpha2,6-ST expression was correlated with 100% survival in patients with stage I and II tumors compared with 64% survival in patients with strong tumor alpha2,6-ST expression (p < 0.01). These studies suggest a negative correlation between the expression of alpha2,6-ST in tumors and a good clinical outcome in colorectal cancer patients.

Adenocarcinoma↗
PubMed1998

High throughput fluorescence-based conformation-sensitive gel electrophoresis (F-CSGE) identifies six unique BRCA2 mutations and an overall low incidence of BRCA2 mutations in high-risk BRCA1-negative breast cancer families.

Mutational analysis of cancer susceptibility genes has opened up a new era in clinical genetics. In this report we present the results of mutational analysis of the BRCA2 coding sequences in 105 high-risk individuals affected with breast cancer and/or ovarian cancer and previously found to be negative for mutations of the BRCA1 coding sequence in our laboratory. These individuals have a positive family history with three or more cases of breast cancer and/or ovarian cancer at any age from the same side of the family tree. In order to perform a high throughput and reliable mutational analysis of the BRCA genes, we have adapted the conformation-sensitive gel electrophoresis mutation-scanning assay to a fluorescent platform. The advantages are speed, reproducibility and enhanced resolving power of the scanning method. Four unique mutations, including one missense and three frameshift mutations, were identified in the pool of 60 non-Jewish patients (7%). Two cases of the 6174delT mutation were identified in the 45 Ashkenazi Jewish individuals studied (5%). In addition, two novel frameshift mutations, not characteristic of the Jewish subgroup, were identified. Thus there were four mutations in total in this ethnic subgroup (9%). The six mutations identified in this combined patient pool, excluding the 6174delT mutations, are novel and have not been previously reported in the Breast Cancer Information Core (BIC) database. The results indicate that BRCA2 mutations account for the disease in less than 10% of this patient population. In addition, there is no significant difference in frequency of BRCA2 mutations between the Ashkenazi Jewish and non-Jewish families in our clinical patient pool.

Adult↗