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Biomedical subjects

S K Bhattacharya

Publications and source records attributed to S K Bhattacharya.

At least 163 records · Page 9Linked to original sources
PubMed2000

Anxiolytic activity of Indian Abies pindrow Royle leaves in rodents: an experimental study.

Putative anxiolytic activity of ethanolic extract of Indian A. pindrow Royle leaf was investigated in rats using various experimental paradigms of anxiety viz. open field exploratory behaviour, elevated plus maze (EPM) and elevated zero maze (EZM) tests. Pilot studies indicated that single dose administration of extract had little to no acute behavioural effects, hence the extract was administered orally at different dose levels once daily for three consecutive days, while lorazepam (LR) (0.5 mg/kg, i.p.) was administered acutely. Ethanolic extract of A. pindrow (AP) leaves (50 and 100 mg/kg, p.o.) showed significant anxiolytic effects on all the paradigms of anxiety. The results indicate that AP and LR induced a significant increase in open field ambulation and slight increase in rearings and activity in center, whereas grooming and faecal droppings remain unchanged. In EPM, significant augmentation of open arm entries, and time spent on open arms was noted in AP treated rats. In EZM test, significant increase in time spent on open arms and entries in open arms was observed, whereas slight increase in head dips and stretched attend postures was also observed. The AP extract showed consistent and significant anxiolytic activity in all the tests. The effects induced by ethanolic extract of AP were less marked than those of lorazepam were.

Animals↗
PubMed2000

Adaptogenic activity of Siotone, a polyherbal formulation of Ayurvedic rasayanas.

Siotone (ST) is a herbal formulation comprising of Withania somnifera, Ocimum sanctum, Asparagus racemosus, Tribulus terristris and shilajit, all of which are classified in Ayurveda as rasayanas which are reputed to promote physical and mental health, improve defence mechanisms of the body and enhance longevity. These attributes are similar to the modern concept of adaptogenic agents, which are, known to afford protection of the human physiological system against diverse stressors. The present study was undertaken to investigate the adaptogenic activity of ST against chronic unpredictable, but mild, footshock stress induced perturbations in behaviour (depression), glucose metabolism, suppressed male sexual behaviour, immunosuppression and cognitive dysfunction in CF strain albino rats. Gastric ulceration, adrenal gland and spleen weights, ascorbic acid and corticosterone concentrations of adrenal cortex, and plasma corticosterone levels, were used as the stress indices. Panax ginseng (PG) was used as the standard adaptogenic agent for comparison. Additionally, rat brain levels of tribulin, an endogenous endocoid postulated to be involved in stress, were also assessed in terms of endogenous monoamine oxidase (MAO) A and MAOB inhibitory activity. Chronic unpredictable footshock induced marked gastric ulceration, significant increase in adrenal gland weight and plasma corticosterone levels, with concomitant decreases in spleen weight, and concentrations of adrenal gland ascorbic acid and corticosterone. These effects were attenuated by ST (50 and 100 mg/kg, p.o.) and PG (100 mg/kg, p.o.), administered once daily over a period of 14 days, the period of stress induction. Chronic stress also induced glucose intolerance, suppressed male sexual behaviour, induced behavioural depression (Porsolt's swim despair test and learned helplessness test) and cognitive dysfunction (attenuated retention of learning in active and passive avoidance tests), and immunosuppression (leucocyte migration inhibition and sheep RBC challenged increase in paw oedema in sensitized rats). All these chronic stress-induced perturbations were attenuated, dose-dependently by ST (50 and 100 mg/kg, p.o.) and PG (100 mg/kg, p.o.). Chronic stress-induced increase in rat brain tribulin activity was also reversed by these doses of ST and by PG. The results indicate that ST has significant adaptogenic activity, qualitatively comparable to PG, against a variety of behavioural, biochemical and physiological perturbations induced by unpredictable stress, which has been proposed to be a better indicator of clinical stress than acute stress parameters. The likely contribution of the individual constituents of ST in the observed adaptogenic action of the polyherbal formulation, have been discussed.

Animals↗
PubMed2000

Anxiolytic activity of Indian Hypericum perforatum Linn: an experimental study.

The putative anxiolytic activity of 50% ethanolic extract of Indian Hypericum perforatum (IHp) was investigated in rats using various experimental paradigms of anxiety viz. open field exploratory behaviour (OFB), elevated plus maze (EPM), elevated zero maze (EZM), novelty induced suppressed feeding latency (FL) and social interaction (SI) tests. Pilot studies indicated that single dose administration of IHp had little to no acute behavioural effects, hence the extract of IHp was administered orally at different dose levels once daily for three consecutive days, while lorazepam (LR) (0.5 mg/kg, i.p.) was administered acutely. IHp extract (100 and 200 mg/kg, p.o.) showed significant anxiolytic effects on all the paradigms of anxiety. The results indicate that IHp and LR induced a significant increase in open field ambulation and slight increase in rearings and activity in centre, whereas grooming and fecal droppings remain unchanged. In EPM, significant augmentation of open arm entries, open arm/closed arm entries ratio and time spent on open arms was noted in IHp treated rats. In EZM test, significant increase in time spent on open arms and entries in open arms were observed, whereas slight increase in head dips and stretched attend postures were also observed. IHp and LR significantly attenuated the novelty induced increase in feeding latency. IHp treated rats also showed significant increase in social interaction in the novel environment. The IHp extracts showed consistent and significant anxiolytic activity in all the tests. The effects induced by 50% ethanolic extract of IHp were less marked than those of lorazepam were.

Administration, Oral↗
PubMed2000

Hypericum perforatum: nature's mood stabilizer.

Hypericum perforatum (HP), better known as St. John's Wort, has been used clinically for centuries. Modern usage is still quite diverse and includes kidney and lung ailments, insomnia and depression. Standardised extracts of HP are widely used in the treatment of psychovegetative disorders and especially for mild forms of depression. Several bioactive constituents of this plant may play important role in its well-known antidepressant activity, which are discussed in the present article. Furthermore, emphasis is also given on its botany, chemistry, pharmacology and clinical efficacy.

Antidepressive Agents↗
PubMed2000

An outbreak of Eltor cholera in Aizwal town of Mizoram, India.

During the months of May, June and through early part of July 1994, an unusual occurrence of severe dehydrating watery diarrhoea cases and deaths were reported from Aizwal town, the capital of Mizoram, a North-Eastern state of India. Vibrio cholerae 01 biotype Eltor, the causative agent responsible for this outbreak, was isolated from 50.0% of hospitalised cases. The disease affected older children and adults more (52.9%) than younger children below five years of age. Vibrio cholerae 01 strains isolated were uniformly resistant to furazolidone and co-trimoxazole, which are commonly advocated in the treatment of cholera specially in children of developing countries. Emergence of such resistant strain is alarming and is of great public health importance.

Adolescent↗
PubMed2000

Distribution of HIV-1 subtypes in female sex workers of Calcutta, India.

BACKGROUND & OBJECTIVES: Different routes for the transmission of HIV-1 in India have been reported and the majority of infections occurred through heterosexual route of transmission. In order to understand the dynamics of HIV-1 transmission, a systematic study was undertaken to determine the viral subtypes circulating among the female sex workers in Calcutta, India. METHODS: Peptide enzyme immunoassay (PEIA), heteroduplex mobility assay (HMA) and DNA sequence analysis were used to ascertain the HIV-1 subtypes. RESULTS: V3 serotyping of 52 HIV-1 seropositive samples identified 33 (60%) to be subtype C. A DNA fragment within C2-V3/C2-V5 regions of HIV-1 gp120 was amplified directly from the lymphocyte DNA to avoid any bias in selecting viral variants and used in HMA. Of the 40 samples analyzed, 38 (95%) belonged to subtype C and 2 were found to be non-typable. Further analysis of these 38 samples revealed that 26 (68%) had maximum homology to the C3-Indian reference strain (IND868), 11 (29%) were most homologous to C2-Zambian strain (ZM18) and 1 (3%) showed close resemblance to C1-Malawi strain (MA959). Nucleotide sequence of 11 subsamples encompassing about 325 base pairs was aligned for the Indian and other geographically distinct isolates. On distance and parsimony trees, most of the samples (8/11) clustered together as subtype C. INTERPRETATION & CONCLUSIONS: Subtype C was the major circulating HIV-1 strain in this geographical region, although variation within this subtype was also noticed. DNA sequence analysis was found to be the best method in determining the nature of the HIV-1 subtype followed by HMA and peptide enzyme immunoassay. These findings may have important implications for the design of effective vaccines in India and emphasizes the need for constant monitoring of the HIV-1 subtypes in different parts of India.

Amino Acid Sequence↗
PubMed2000

Severe cholera outbreak following floods in a northern district of West Bengal.

BACKGROUND & OBJECTIVES: An explosive epidemic of cholera in the district of Malda in the state of West Bengal, was induced by devastating floods resulting from overflowing of the two main rivers of the district, at the end of July 1998, affecting 15 blocks and 2 municipalities. Diarrhoeal outbreak occurred around the middle of August after receding of the flood waters. Within two weeks of its onset, the outbreak spread throughout the district. An investigation was conducted to understand the epidemiological characteristics, identify the etiological agent, rationalise clinical management and suggest control measures. METHODS: The team visited the Block Primary Health Centres, surrounding the affected villages and also the district hospital. Morbidity and mortality data were collected and 88 patients were interviewed and examined clinically. Epidemiological and clinical observations were recorded. Rectal swabs were collected from both hospitalised and domiciliary cases. RESULTS: During the period between August and October 1998, 16,590 cases were reported with 276 deaths (case fatality rate of 1.7%). Twenty one of 29 (72%) rectal swabs were positive for Vibrio cholerae O1, biotype ElTor, serotype Ogawa. All the strains were sensitive to tetracycline, norfloxacilin, ciprofloxacilin, gentamycin, chloramphenicol but resistant to furazolidine, co-trimoxazole, nalidixic acid, streptomycin and ampicilin. INTERPRETATION & CONCLUSIONS: Observations of the present study identified the epidemiological and clinical deficiencies in the management of the outbreak and recommendations were elaborated for its effective control.

Adolescent↗
PubMed2000

Antioxidant activity of tannoid principles of Emblica officinalis (amla) in chronic stress induced changes in rat brain.

Effect of tannoid principles emblicanin A, emblicanin B, punigluconin, and pedunculagin of E. officinalis was assessed on chronic unpredictable footshock-induced stress-induced perturbations in oxidative free radical scavanging enzymes in rat brain frontal cortex and striatum. Chronic stress, administered over a period of 21 days, induced significant increase in rat brain frontal cortical and striatal superoxide dismutase (SOD) activity, concomitant with significant reduction in catalase (CAT) and glutathione peroxidase (GPX) activity. The changes in the enzyme activities was accompanied by an increase in lipid peroxidation, in terms of augmented thiobarbituric acid-reactive products. Administration of Emblica tannoids (10 and 20 mg, po) for 21 days, concomitant with the stress procedure, induced a dose-related alteration in the stress effects. Thus, a tendency towards normalization of the activities of SOD, CAT and GPX was noted in both the brain areas, together, with reduction in lipid peroxidation. The results indicate that the reported antistress rasayana activity of E. officinalis may be, at least partly due to its tendency to normalize stress-induced perturbations in oxidative free radical scavenging activity, in view of the postulate that several stress-induced diseases, including the process of aging, may be related to accumulation of oxidative free radicals in different tissues.

Animals↗
PubMed1999

Construction of a multi RE module: exploitation of mechanochemistry of restriction endonucleases.

We describe the construction of a multi-immobilized restriction endonuclease module (Multi RE module). We demonstrate that the applied mechanical stress enables modulation of enzyme activity and modulation of recognition site selectivity (in oligonucleotides of approximately 200 bp) of immobilized restriction endonucleases. The central module which is consisted of different strips of immobilized restriction endonucleases allows limited digestion of a large DNA sample in a controlled manner as a function of applied mechanical stress on strips. The stress-activity relationship and the effect of repeated cycles of stress and relaxation on the immobilized strips are presented here. &copy 1999 John Wiley & Sons, Inc.

Bacterial Proteins↗
PubMed1999

DNA methylation is a reversible biological signal.

The pattern of DNA methylation plays an important role in regulating different genome functions. To test the hypothesis that DNA methylation is a reversible biochemical process, we purified a DNA demethylase from human cells that catalyzes the cleavage of a methyl residue from 5-methyl cytosine and its release as methanol. We show that similar to DNA methyltransferase, DNA demethylase shows CpG dinucleotide specificity, can demethylate mdCpdG sites in different sequence contexts, and demethylates both fully methylated and hemimethylated DNA. Thus, contrary to the commonly accepted model, DNA methylation is a reversible signal, similar to other physiological biochemical modifications.

5-Methylcytosine↗
PubMed1999

Kinetic mechanism of cytosine DNA methyltransferase MspI.

A kinetic analysis of MspI DNA methyltransferase (M.MspI) is presented. The enzyme catalyzes methylation of lambda-DNA, a 50-kilobase pair linear molecule with multiple M.MspI-specific sites, with a specificity constant (kcat/KM) of 0.9 x 10(8) M-1 s-1. But the values of the specificity constants for the smaller DNA substrates (121 and 1459 base pairs (bp)) with single methylation target or with multiple targets (sonicated lambda-DNA) were less by an order of magnitude. Product inhibition of the M.MspI-catalyzed methylation reaction by methylated DNA is competitive with respect to DNA and noncompetitive with respect to S-adenosylmethionine (AdoMet). The S-adenosylhomocysteine inhibition of the methylation reaction is competitive with respect to AdoMet and uncompetitive with respect to DNA. The presteady state kinetic analysis showed a burst of product formation when AdoMet was added to the enzyme preincubated with the substrate DNA. The burst is followed by a constant rate of product formation (0.06 mol per mol of enzyme s-1) which is similar to catalytic constants (kcat = approximately 0.056 s-1) measured under steady state conditions. The isotope exchange in chasing the labeled methyltransferase-DNA complex with unlabeled DNA and AdoMet leads to a reduced burst as compared with the one involving chase with labeled DNA and AdoMet. The enzyme is capable of exchanging tritium at C-5 of target cytosine in the substrate DNA in the absence of cofactor AdoMet. The kinetic data are consistent with an ordered Bi Bi mechanism for the M.MspI-catalyzed DNA methylation where DNA binds first.

DNA-Cytosine Methylases↗
PubMed1999

Modified oligonucleotides as bona fide antagonists of proteins interacting with DNA. Hairpin antagonists of the human DNA methyltransferase.

The study of the biological role of DNA methyltransferase (DNA MeTase) has been impeded by the lack of direct and specific inhibitors. This report describes the design of potent DNA based antagonists of DNA MeTase and their utilization to define the interactions of DNA MeTase with its substrate and to study its biological role. We demonstrate that the size, secondary structure, hemimethylation, and phosphorothioate modification strongly affect the antagonists interaction with DNA MeTase whereas base substitutions do not have a significant effect. To study whether DNA MeTase is critical for cellular transformation, human lung non-small carcinoma cells were treated with the DNA MeTase antagonists. Ex vivo, hairpin inhibitors of DNA MeTase are localized to the cell nucleus in lung cancer cells. They inhibit DNA MeTase, cell growth, and anchorage independent growth (an indicator of tumorigenesis in cell culture) in a dose-dependent manner. The inhibitors developed in this study are the first documented example of direct inhibitors of DNA MeTase in living cells and of modified oligonucleotides as bona fide antagonists of critical cellular proteins.

Base Sequence↗
PubMed1999

A mammalian protein with specific demethylase activity for mCpG DNA.

DNA-methylation patterns are important for regulating genome functions, and are determined by the enzymatic processes of methylation and demethylation. The demethylating enzyme has now been identified: a mammalian complementary DNA encodes a methyl-CpG-binding domain, bears a demethylase activity that transforms methylated cytosine bases to cytosine, and demethylates a plasmid when the cDNA is translated or transiently transfected into human embryonal kidney cells in vitro. The discovery of this DNA demethylase should provide a basis for the molecular and developmental analysis of the role of DNA methylation and demethylation.

Amino Acid Sequence↗
PubMed1999

Structure-activity profiles of eleutherobin analogs and their cross-resistance in Taxol-resistant cell lines.

PURPOSE: Eleutherobin, a natural product, is an antimitotic agent that promotes the polymerization of stable microtubules. Although its mechanism of action is similar to that of Taxol, its structure is distinct. A structure-activity profile of synthetic eleutherobin derivatives that have modifications at C3, C8 and C15 was undertaken to define the structural requirements for microtubule stabilization and cross-resistance in Taxol-resistant cell lines. METHODS: The biological activity of five eleutherobin analogs was assessed using three techniques: (1) cytotoxicity and drug-resistance in three paired Taxol-sensitive and -resistant cell lines; (2) polymerization of microtubule protein in vitro in the absence of GTP and (3) induction of microtubule bundle formation in NIH3T3 cells. RESULTS: Eleutherobin had an IC50 value comparable to that of Taxol, whereas neoeleutherobin, which has a carbohydrate domain that is enantiomeric with that of the parent compound, was less cytotoxic and had 69% of the maximum microtubule polymerization ability of eleutherobin. Both of these compounds exhibited cross-resistance in MDRI-expressing cell lines. Removal or replacement of the C15 sugar moiety resulted in reduced microtubule polymerization and cytotoxicity compared to eleutherobin and loss of cross-resistance in the cell lines SKVLB and J7-T3-1.6, both of which express high levels of P-glycoprotein. By contrast, removal of the urocanic acid group at C8 resulted in virtually complete abrogation of biological activity. The compound lost its ability to polymerize microtubules, and its cytotoxicity was reduced by a minimum of 2000-fold in lung carcinoma A549 cells. CONCLUSIONS: Removal or modification of the sugar moiety alters the cytotoxic potency of eleutherobin and its pattern of cross-resistance in Taxol-resistant cells, although such compounds retain a small percentage of the microtubule-stabilizing activity of eleutherobin. The N(1)-methylurocanic acid moiety of eleutherobin, or perhaps some other substituent at the C8 position, is essential for Taxol-like activity. These findings will be important for the future design and the synthesis of new and more potent eleutherobin derivatives.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1999

Mucoid presentation of acute enterocolitis in children: a hospital-based case-control study.

A hospital-based case-control study was carried out to clarify the characteristics of mucoid presentation of acute enterocolitis in children. One hundred sixty-eight cases of acute mucoid enterocolitis (study population) were compared with 200 cases of watery diarrhoea and 118 cases of blood dysentery (control groups) on the basis of clinical characteristics and findings on stool examination. Study and control groups were comparable with respect to age, body weight and nutritional status. There was no significant difference in clinical characteristics (duration of diarrhoea, stool frequency, presence of vomiting, fever and dehydration) between patients suffering from mucoid enterocolitis and blood dysentery. However, watery diarrhoea patients had significantly high frequencies of vomiting (p=0.00001) and dehydration (p=0.00001). High numbers of microscopic red blood cells (mean +/- SD: 40.8 +/- 16.8) and white blood cells (40.6 +/- 18.0) were present in faecal samples of the patients with mucoid enterocolitis, which is indicative of infection caused by enteroinvasive enteropathogens. Shigella was a commonly identified enteropathogen in patients with mucoid enterocolitis (40.5%) and in patients with dysentery (46.6%), with no statistically significant difference (p = 0.30). Isolation of Salmonella was statistically similar in study and control groups. However, Entamoeba histolytica was detected in significantly high frequency in patients with mucoid enterocolitis as compared to the patients with dysentery (p = 0.0004) and watery diarrhoea (p = 0.00004). Our results indicate that mucoid enterocolitis patients are infected with enteroinvasive enteropathogens, and that stool examination is useful in establishing the aetiological diagnosis.

Acute Disease↗
PubMed1999

Killed oral Shigella vaccine made from Shigella flexneri 2a protects against challenge in the rabbit model of shigellosis.

The protective efficacy of an orally administered heat-killed virulent strain of Shigella flexneri 2a (5 weekly oral doses) was evaluated in 25 rabbits (14 immunized and 11 non-immunized controls) against challenge with the same strain of Shigella using the rabbit model of shigellosis. All 11 non-immunized rabbits developed bloody diarrhoea following challenge and 6 (54%) died. None of the 14 immunized rabbits developed diarrhoea (all had pellet stools) but 3 (21%) died from causes not associated with diarrhoea. Protection from diarrhoea and dysentery following oral immunization with a killed Shigella species was 100% and highly significant. Death following challenge was 2.5-fold higher in the non-immunized group (p = 0.115) but was not significant. These promising results suggest that further studies should be undertaken to develop a killed oral vaccine against shigellosis.

Administration, Oral↗
PubMed1999

Clonal diversity among recently emerged strains of Vibrio parahaemolyticus O3:K6 associated with pandemic spread.

The genomes of the O3:K6 strains of Vibrio parahaemolyticus which abruptly emerged in Calcutta, India, in February 1996 and which demonstrated an unusual potential to spread and an enhanced propensity to cause infections were examined by different molecular techniques to determine clonality. No restriction fragment length polymorphism (RFLP) in the gene encoding the thermostable direct hemolysin was observed among the O3:K6 isolates of V. parahaemolyticus. Clonal diversity among the O3:K6 strains became evident by examining the RFLPs of the rrn operons and by the use of pulsed-field gel electrophoresis. Five ribotypes were distinguished among the O3:K6 strains examined, with ribotype R4 constituting the major type. Strains of O3:K6 isolated between June and August 1996 showed different pulsotypes compared to the pulsotypes of strains isolated before and after this period, indicating genetic reassortment among these strains, but those isolated between August 1996 and March 1998 showed identical or nearly similar pulsotypes. It is clear that there is a certain degree of genomic reassortment among the O3:K6 clones but that these strains are predominantly one clone.

Bacterial Typing Techniques↗