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Biomedical subjects

S Bhattacharya

Publications and source records attributed to S Bhattacharya.

At least 235 records · Page 13Linked to original sources
PubMed1997

The tautomeric state of histidines in myoglobin.

1H-15N HMQC spectra were collected on 15N-labeled sperm whale myoglobin (Mb) to determine the tautomeric state of its histidines in the neutral form. By analyzing metaquoMb and metcyanoMb data sets collected at various pH values, cross-peaks were assigned to the imidazole rings and their patterns interpreted. Of the nine histidines not interacting with the heme in sperm whale myoglobin, it was found that seven (His-12, His-48, His-81, His-82, His-113, His-116, and His-119) are predominantly in the N epsilon2H form with varying degrees of contribution from the Ndelta1 H form. The eighth, His-24, is in the Ndelta1H state as expected from the solid state structure. 13C correlation spectra were collected to probe the state of the ninth residue (His-36). Tentative interpretation of the data through comparison with horse Mb suggested that this ring is predominantly in the Ndelta1H state. In addition, signals were observed from the histidines associated with the heme (His-64, His-93, and His-97) in the 1H-15N HMQC spectra of the metcyano form. In several cases, the tautomeric state of the imidazole ring could not be derived from inspection of the solid state structure. It was noted that hydrogen bonding of the ring was not unambiguously reflected in the nitrogen chemical shift. With the experimentally determined tautomeric state composition in solution, it will be possible to broaden the scope of other studies focused on the electrostatic contribution of histidines to the thermodynamic properties of myoglobin.

Animals↗
PubMed1997

Temperature dependence of histidine ionization constants in myoglobin.

The standard enthalpy of ionization of six titratable histidines in horse metaquomyoglobin was determined by repeating proton NMR titrations as a function of temperature and using the van't Hoff relationship. It was found that deltaH degrees varies between 16 and 37 kJ mol(-1) in the protein, compared with a value of 29 kJ mol(-1) in free histidine. The standard entropy change was evaluated by combining the enthalpy and free energy changes derived from the pKa values. Although the entropy change could not be precisely and accurately obtained by this method, it could be established that it spans a wide range, from -60 to 0 J K(-1) mol(-1), about the value of -23 J K(-1) mol(-1) for the free histidine. The entropy change was used within the framework of enthalpy-entropy compensation to partition the solvation component from the standard thermodynamic quantities for each of the titrating residues. It was shown that the partitioning of the values in the protein is not readily understood in terms of solvent accessibility or electrostatic interactions. The contribution of solvation effects to the temperature response appeared to be significant only in the case of His-119 and His-48. The standard quantities were also used to explore the energetics of proton binding in the native state at temperatures below the onset of thermal denaturation.

Animals↗
PubMed1997

Characterization of EhCaBP, a calcium-binding protein of Entamoeba histolytica and its binding proteins.

A novel calcium-binding protein (EhCaBP) has been recently identified and characterized from the protozoan parasite Entamoeba histolytica. In order to decipher the function of this protein, a few basic properties were investigated and compared with the ubiquitous Ca(2+)-signal transducing protein calmodulin (CaM). Indirect immunofluorescence and immunoprecipitation analyses using specific antibodies against EhCaBP suggest that it is a soluble cytoplasmic protein with no major post-translational modification. EhCaBP did not stimulate cAMP-phosphodiesterase activity, differentiating it from all known CaMs. Affinity chromatography of [35S]methionine-labelled proteins of E. histolytica trophozoites using EhCaBP-sepharose column showed Ca(2+)-dependent binding of a group of proteins. Radiolabelled proteins from the same extract also bound to CaM-sepharose. However, the proteins bound to the two columns were different as revealed by sodium dodecyl sulphate polyacrylamide gel electrophoresis. At least one of the EhCaBP-binding proteins became phosphorylated as revealed by in vivo phosphorylation analysis. The binding-proteins could not be detected in E. invadens (a species that is pathogenic in reptiles) and E. moshkovskii (which is found in the human gut but is not pathogenic), two species in which EhCaBP-like protein has not been found. Two distinct Ca(2+)-dependent protein kinases, which get activated by EhCaBP and CaM respectively, were detected in E. histolytica. These kinases require different levels of Ca2+ for their maximal activities. Affinity chromatography also showed the binding of protein kinase(s) to EhCaBP in a Ca(2+)-dependent manner. Our data suggest that there may be novel Ca(2+)-signal transduction pathway in E. histolytica mediated by EhCaBP.

Animals↗
PubMed1997

Studies on antitussive activity of Drymaria cordata Willd. (Caryophyllaceae).

The methanol extract of Drymaria cordata Willd. was investigated for its effect on a cough model induced by sulfur dioxide gas in mice. It exhibited significant antitussive activity when compared with the control in a dose-dependent manner. The antitussive activity of the extract was comparable to that of codeine phosphate, a prototype antitussive agent. The D. cordata extract (100, 200, 400 mg/kg) showed 11.6%, 31.6% and 51.5% inhibition of cough with respect to the control group.

Animals↗
PubMed1997

Inorganic mercury binding to fish oocyte plasma membrane induces steroidogenesis and translatable messenger RNA synthesis.

Both in vitro and in vivo HgCl2 treatment demonstrated a remarkably high rate of progesterone synthesis accompanied by a low rate of conversion to 17 beta-estradiol in the oocyte of Channa punctatus. On depuration, however, there was a reversal of the steroidogenic scenario with a low progesterone and high estradiol level. The accumulation of progesterone was positively correlated with the significant increase in 3 beta-hydroxysteroid dehydrogenase activity in the Hg-treated fish. Thus, it was clear that at the early stage of intoxication Hg does play a role in the induction of 3 beta-hydroxysteroid dehydrogenase in the oocyte of fish at the spawning stage. The induction of this enzyme was found to be mediated by specific binding of Hg to the plasma membrane Na(+)-K(+)-ATPase (Bmax: 14 nmoles mg-1 protein; Ka 1.14 x 10(8) moles) and increase in the specific messenger RNA translating 3 beta-hydroxysteroid dehydrogenase. It is concluded that inorganic mercury is able to initiate translatable messenger RNA synthesis in fish oocyte at a low degree of intoxication.

3-Hydroxysteroid Dehydrogenases↗
PubMed1997

Specific binding of inorganic mercury to Na(+)-K(+)-ATPase in rat liver plasma membrane and signal transduction.

Specific binding of Hg2+ to ouabain-sensitive Na(+)-K(+)-ATPase of rat liver plasma membrane was demonstrated with a Ka of 2.64 x 10(9) and Bmax of 1.6 nmole mg-1 protein. The binding of mercury to the enzyme also causes significant inhibition of the enzyme, which is greater than its ouabain sensitivity. In the cytosol Hg2+ binding to reduced glutathione (GSH) is stimulated by GSH-S-transferase (GST), the activity of which was found to be significantly enhanced by 15 mM Na+ and 10 mM Hg2+. It is proposed that the transport of Hg2+ inside the cell takes place by increased dissociation of Hg2+ from the membrane due to greater avidity of Hg2+ towards cytosolar GSH binding. The GSH-Hg complex enters the nucleus where it dissociates to bind the metal response element (MRE) of the metallothionein (MT) gene to induce MT transcription.

Animals↗
PubMed1997

Protamine sulfate enhances lipid-mediated gene transfer.

A polycationic peptide, protamine sulfate, USP, has been shown to be able to condense plasmid DNA efficiently for delivery into several different types of cells in vitro by several different types of cationic liposomes. The monovalent cationic liposomal formulations (DC-Chol and lipofectin) exhibited increased transfection activities comparable to that seen with the multivalent cationic liposome formulation, lipofectamine. This suggests that lipofectamine's superior in vitro activity arises from its ability to condense DNA efficiently and that protamine's primary role is that of a condensation agent, although it also possesses several amino acid sequences resembling that of a nuclear localization signal. While the use of polycations to condense DNA has been previously reported, the of protamine sulfate, USP as a condensation agent was found to be superior to poly-L-lysine as well as to various other types of protamine. These differences among various salt forms of protamine appear to be attributable to structural differences between the protamines and not due to differences in the net charge of the molecule. The appearance of lysine residues within the protamine molecule correlate with a reduction in binding affinity to plasmid DNA as well as an observed loss in transfection enhancing activity. This finding sheds light on the structural requirements of condensation agents for use in gene transfer protocols. Furthermore, protamine sulfate, USP is an FDA-approved compound with a documented safety profile and could be readily used as an adjuvant to a human gene therapy protocol.

Amino Acid Sequence↗
PubMed1997

Familial glaucoma iridogoniodysplasia maps to a 6p25 region implicated in primary congenital glaucoma and iridogoniodysgenesis anomaly.

Familial glaucoma iridogoniodysplasia (FGI) is a form of open-angle glaucoma in which developmental anomalies of the iris and irido-corneal angle are associated with a juvenile-onset glaucoma transmitted as an autosomal dominant trait. A single large family with this disorder was examined for genetic linkage to microsatellite markers. A peak LOD score of 11.63 at a recombination fraction of 0 was obtained with marker D6S967 mapping to chromosome 6p25. Haplotype analysis places the disease gene in a 6.4-cM interval between the markers D6S1713 and D6S1600. Two novel clinical appearances extend the phenotypic range and provide evidence of variable expressivity. The chromosome 6p25 region is now implicated in FGI, primary congenital glaucoma, and iridogoniodysgenesis anomaly. This may indicate the presence of a common causative gene or, alternatively, a cluster of genes involved in eye development/function.

Chromosome Mapping↗
PubMed1997

A new locus for dominant "zonular pulverulent" cataract, on chromosome 13.

Inherited cataract is a clinically and genetically heterogeneous disease that most often presents as a congenital autosomal dominant trait. Here we report the linkage of a new locus for dominant "zonular pulverulent" cataract (CZP) to chromosome 13. To map the CZP locus we performed molecular-genetic linkage analysis using microsatellite markers in a five-generation English pedigree. After exclusion of eight known loci and several candidate genes for autosomal dominant cataract, we obtained significantly positive LOD scores (Z) for markers D13S175 (maximum Z [Zmax] = 4.06; maximum recombination frequency [theta max] = 0) and D13S1236 (Zmax = 5.75, theta max = 0). Multipoint analysis gave Zmax = 6.62 (theta max = 0) at marker D13S175. Haplotype data indicated that CZP probably lies in the centromeric region of chromosome 13, provocatively close to the gene for lens connexin46.

Cataract↗
PubMed1997

Prediction of probable genes by Fourier analysis of genomic sequences.

MOTIVATION: The major signal in coding regions of genomic sequences is a three-base periodicity. Our aim is to use Fourier techniques to analyse this periodicity, and thereby to develop a tool to recognize coding regions in genomic DNA. RESULT: The three-base periodicity in the nucleotide arrangement is evidenced as a sharp peak at frequency f = 1/3 in the Fourier (or power) spectrum. From extensive spectral analysis of DNA sequences of total length over 5.5 million base pairs from a wide variety or organisms (including the human genome), and by separately examining coding and non-coding sequences, we find that the relative-height of the peak at f = 1/3 in the Fourier spectrum is a good discriminator of coding potential. This feature is utilized by us to detect probable coding regions in DNA sequences, by examining the local signal-to-noise ratio of the peak within a sliding window. While the overall accuracy is comparable to that of other techniques currently in use, the measure that is presently proposed is independent of training sets or existing database information, and can thus find general application. AVAILABILITY: A computer program GeneScan which locates coding open reading frames and exonic regions in genomic sequences has been developed, and is available on request.

Algorithms↗
PubMed1997

IsK and KvLQT1: mutation in either of the two subunits of the slow component of the delayed rectifier potassium channel can cause Jervell and Lange-Nielsen syndrome.

The Jervell and Lange-Nielsen syndrome (JLNS) comprises profound congenital sensorineural deafness associated with syncopal episodes. These are caused by ventricular arrhythmias secondary to abnormal repolarisation, manifested by a prolonged QT interval on the electrocardiogram. Recently, in families with JLNS, Neyroud et al. reported homozygosity for a single mutation in KVLQT1 , a gene which has previously been shown to be mutated in families with dominantly inherited isolated long QT syndrome [Neyroud et al . (1997) Nature Genet ., 15, 186-189]. We have analysed a group of families with JLNS and shown that the majority are consistent with mutation at this locus: five families of differing ethnic backgrounds were homozygous by descent for markers close to the KVLQT1 gene and a further three families from the same geographical region were shown to be homozygous for a common haplotype and to have the same homozygous mutation of the KVLQT1 gene. However, analysis of a single small consanguineous family excluded linkage to the KVLQT1 gene, establishing genetic heterogeneity in JLNS. The affected children in this family were homozygous by descent for markers on chromosome 21, in a region containing the gene IsK . This codes for a transmembrane protein known to associate with KVLQT1 to form the slow component of the delayed rectifier potassium channel. Sequencing of the affected boys showed a homozygous mutation, demonstrating that mutation in the IsK gene may be a rare cause of JLNS and that an indistinguishable phenotype can arise from mutations in either of the two interacting molecules.

Chromosomes, Human, Pair 21↗
PubMed1997

How effective is patient-controlled analgesia? A randomized comparison of two protocols for pain relief during oocyte recovery.

Although the conventional method of pain relief during outpatient oocyte recovery involves physician-administered drugs, patient-controlled analgesia (PCA) offers an alternative technique with the potential to give women more control over peroperative analgesia. We conducted a prospective randomized study to compare the effect of fentanyl administered either through a PCA delivery system or by a physician. Thirty-nine women were randomized to PCA during egg collection while 42 were allocated to receive intermittent doses administered by a physician. Pain was evaluated by means of a 100 mm linear analogue scale. The mean (SD) pain score in the PCA group was 38.5 (19.8) while in the other group it was 46.1 (21.3) (P = 0.1). In the PCA group, 64% of women felt very satisfied with their analgesia as compared with 57% in the non-PCA group (P = 0.6). Among the PCA users, 39% of demands were successful. Significantly more fentanyl (97.5 microg) was used in the PCA group than in the other group (84.6 microg) (P = 0.03). Though intraoperative PCA with fentanyl is an effective alternative to physician-administered techniques, many women still feel the need for more analgesia during the procedure.

Adult↗
PubMed1997

Stimulation of cyclic AMP, 17beta-oestradiol and protein synthesis by human chorionic gonadotrophin in human endometrial cells.

Human endometrial tissue was collected from 30-37 year old ovulatory women and enzymatically dispersed and processed to obtain endometrial stromal cells. Cells (2 x 10(4)/well) were incubated in vitro in the absence (control) or presence of human chorionic gonadotrophin (HCG) (10 IU/well) either for 1 h (to determine cAMP) or for 4 h (to estimate protein synthesis, 17beta-oestradiol and aromatase activity). HCG significantly stimulated cellular cAMP content and release in comparison to control. Both cellular accumulation and release of cAMP reached the peak at 10 min and then sharply declined in the absence of phosphodiesterase (PDE) inhibitor or remained steady for 1 h in the presence of PDE inhibitor. Content and release of 17beta-oestradiol from stromal cells steeply increased from 30 min to 1 h and then slowly increased for 4 h in response to HCG. Incubation of cells with HCG significantly stimulated (P < 0.01) cellular aromatase activity in comparison to control. HCG stimulated protein synthesis of the cells in two phases, initially at 15 min which remained steady for 1 h and then significantly increased (P < 0.01) between 1 and 2 h. The initial phase of protein synthesis appears to be the direct effect of HCG while the later phase was due to the higher concentration of oestradiol caused by HCG. The initial phase of protein synthesis was inhibited by cycloheximide but not by actinomycin D, whereas the later phase of protein synthesis was inhibited both by cycloheximide and actinomycin D. Results therefore indicate a probable mechanism of HCG action on stromal cells and demonstrate the physiological relevance of gonadotrophin receptor in human endometrial cells reported earlier from this laboratory.

Adult↗
PubMed1997

A pragmatic randomised comparison of transcervical resection of the endometrium with endometrial laser ablation for the treatment of menorrhagia.

OBJECTIVE: To compare endometrial laser ablation (ELA) with transcervical resection of the endometrium (TCRE) in the treatment of menorrhagia. DESIGN: Randomised controlled trial. SETTING: Gynaecology department of a large teaching hospital. PARTICIPANTS: Women with menorrhagia due to dysfunctional uterine bleeding (n = 372) were randomly allocated to ELA (n = 188) or TCRE (n = 184). MAIN OUTCOME MEASURES: Operative complications, post-operative recovery, relief of menstrual and other symptoms, need for further surgical treatment, satisfaction with treatment after 6 and 12 months, and differential resource use. RESULTS: TCRE was significantly quicker, with lower rates of fluid overload. Perioperative morbidity was low and similar in both groups. Outcome at 12 months was also similar: 72 women (45%) had either amenorrhoea or brown discharge in the ELA group compared with 71 (49%) in the TCRE group; 79 (49%) versus 68 (46%) had lighter periods. Thirty (16%) versus 36 (20%) had received further surgical treatment: 9 (5%) compared with 25 (14%) had had a hysterectomy and 21 (11%) versus 11 (6%) had received repeat ablation. Anxiety and depression, dysmenorrhoea and pre-menstrual symptoms were improved by both procedures and bladder symptoms were affected by neither. At 12 months 148 (90%) women in the ELA group and 140 (91%) women in the TCRE group were satisfied with their treatment. The estimated additional cost of ELA was Pound 145 per procedure. CONCLUSIONS: At one year there was no clear difference in clinical outcome between ELA and TCRE. Both procedures were associated with low morbidity. ELA was the more costly procedure. Despite the need for further surgery for about one in six women, satisfaction rates were high following both ELA and TCRE.

Adult↗
PubMed1997

JAK2 is required for induction of the murine DUB-1 gene.

Cytokine receptors activate multiple signal transduction pathways, resulting in the induction of specific target genes. We have recently identified a hematopoietic cell-specific immediate-early gene, DUB-1, that encodes a growth-regulatory deubiquitinating enzyme. The DUB-1 gene contains a 112-bp enhancer element that is specifically induced by the beta c subunit of the interleukin-3 (IL-3) receptor. To investigate the mechanism of DUB-1 induction, we examined the effects of dominant-negative forms of JAK kinases, STAT transcription factors, and Raf-1 in transient transfection assays. In Ba/F3 cells, IL-3 induced a dose-dependent activation of DUB-1-luciferase (luc) and GAS-luc reporter constructs. A dominant-negative form of JAK2 (truncated at amino acid 829) inhibited the induction of DUB-1-luc and GAS-luc by IL-3. A dominant-negative form of STAT5 (truncated at amino acid 650) inhibited the induction of GAS-luc but not DUB-1-luc. A dominant-negative form of Raf-1 inhibited the induction of DUB-1-luc but had no effect on the induction of GAS-luc by IL-3. The requirement for JAK2 in the stimulation of the DUB-1 enhancer was further supported by the suppression of DUB-1 induction in Ba/F3 cells stably expressing the dominant-negative JAK2 polypeptide. We hypothesize that IL-3 activates a JAK2/Raf-1 signaling pathway that is required for DUB-1 induction and is independent of STAT5.

Animals↗
PubMed1997

Detection of small hepatocellular carcinomas in cirrhotic livers using iodised oil computed tomography.

BACKGROUND: The detection of hepatocellular cancers (HCC) is a major role of preoperative imaging in patients with end stage liver disease being considered for orthotopic liver transplantation (OLT). AIMS: To assess the sensitivity of iodised oil computed tomography (IOCT). PATIENTS AND METHODS: A prospective evaluation in 50 consecutive patients undergoing OLT included ultrasound scan, contrast enhanced CT, angiography (with intra-arterial injection of iodised oil), and a second CT (IOCT) 10 days later. Following transplantation the explant liver was serially sectioned for pathological evaluation. Soft tissue radiographs of the liver slices were used to match histological lesions with CT findings. RESULTS: Eleven patients were excluded due to protocol violations. Of the remaining 39, histological evaluation revealed no cancers in 33 explant livers, in keeping with negative preoperative imaging. Six explant livers contained 55 HCCs, 84% of which were less than 1 cm in diameter. Pretransplant IOCT detected 3/6 patients with cancer (50%) but only 7% of cancerous lesions. Ultrasound, contrast CT, and angiography each detected 2/6 patients with cancer and 4% of cancerous lesions. CONCLUSION: IOCT is an insensitive method for the detection of small HCCs in livers with advanced cirrhosis but in this study was slightly superior to ultrasound, CT, and angiography.

Carcinoma, Hepatocellular↗
PubMed1997

Enhancement of membrane damage by saponins isolated from Acacia auriculiformis.

Acaciaside A and B, two acylated triterpenoid bisglycosides isolated from the funicles of Acacia auriculiformis, are known to have antihelmintic activity. Since the saponins contain a conjugated unsaturated system that is highly susceptible to peroxidation, we investigated the interaction of saponins and membrane using rat liver microsomes as our model. Microsomal membranes were incubated with saponins at 30 degrees C for 2 hr. Following incubation, lipid peroxidation was measured in terms of malondialdehyde and conjugated diene. Our results showed that incubation of microsomal membranes with saponins increased both malondialdehyde and conjugated diene. The results suggest that in our model, saponins enhance the membrane lipid peroxidation.

Acacia↗