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Biomedical subjects

M Das

Publications and source records attributed to M Das.

At least 109 records · Page 6Linked to original sources
PubMed1997

Reductive and hydrolytic activities of enteric bacteria on food colours.

Reductive and hydrolytic activities on two food colours namely metanil yellow and indigo carmine by different strains of enteric bacteria were evaluated. Enteric bacteria possessed both reductive and hydrolytic capabilities which depended upon the incubation period and the type of strain. In certain bacterial strains, (Escherichia coli and Vibrio sp.), reductive activity was visible after 3 hr. Other enteric strains showed an increasing activity right from the beginning of incubation. Enterobacter cloacae appeared to be producing maximum reductive capability followed by Enterobacter aerogenes and E. coli. Even enteric bacterial strains demonstrated a good response in obtaining hydrolytic activity of indigo carmine during incubation upto 10 hr, establishing the fact that the gut microflora may cause health problem to consumers.

Adult↗
PubMed1997

Comparative azo reductase activity of red azo dyes through caecal and hepatic microsomal fraction in rats.

In order to study the rate of formation of toxic aromatic amines, anaerobic reduction of four red azo dyes viz. amaranth, carmoisine, fast Red E and ponceau 4R was investigated by incubating caecal content and hepatic microsomal fraction of rats with 37.5 microM concentration of dyes in sodium phosphate buffer pH 7.4 using NADPH generating system, glucose oxidase system and nitrogen as the gaseous phase. Caecal suspension exhibited higher azo reductase activity than that of hepatic microsomal fraction using any of the 4 azo dyes. Caecal microbes showed maximal azo reductase activity when ponceau 4R was used as a substrate followed by fast Red E and carmoisine, while with amaranth the activity was minimum. Similarly ponceau 4 R exhibited maximum hepatic microsomal azo reductase activity followed by fast Red E and carmoisine whereas, amaranth had minimum activity. Caecal flora possessed almost 17 fold higher degradative capability of ponceau 4 R and fast Red E colourants than the hepatic microsomal fraction. The higher reductive ability through caecal flora for ponceau 4R and fast Red E signifies the formation of more aromatic amines which may be re-absorbed through the intestine to be either eliminated through urine as conjugates or retained in the target tissues to elicit toxic effects.

Animals↗
PubMed1996

Is activation of lysosomal enzymes responsible for paracetamol-induced hepatotoxicity and nephrotoxicity?

Paracetamol overdose (300 mg kg(-1)) in mice resulted in a time-dependent increase in the liver weight; no change was seen for the kidney. The total acid phosphatase activities in the two tissues increased significantly 0.5 h after paracetamol overdose and remained elevated up to 3 h. Free as well as total cathepsin D activities increased significantly in both the tissues within 2-2.5 h of paracetamol treatment. Simultaneously tyrosine positive materials in the two tissues increased. RNAse II and DNAse II activities were low in liver and kidneys of the controls. Paracetamol treatment elevated both free and total RNAse II activity in the two tissues by 0.5 h. Maximum activity of DNAse II (free and total) was seen at 2.5 h after paracetamol administration. The results suggest that concerted action of cathepsin D, RNAse II and DNAse II may be responsible for paracetamol-induced hepatotoxicity and nephrotoxicity.

4-Nitrophenylphosphatase↗
PubMed1995

Cardiovascular and respiratory changes following exposure to a synthetic toxin of Ptychodiscus brevis.

The present study demonstrated cardiorespiratory effects of a synthetic phosphorus-containing ichthyotoxic metabolite elaborated by the marine dinoflagellate Ptychodiscus brevis in anaesthetised cats. The metabolite at a dose of 0.25-1.5 mg/kg i.v., resulted in a dose-dependent fall in blood pressure and such vasodepressor effect was associated with bradycardia. There is initial respiratory apnoea followed by increased rate and depth of respiration (hyperapnoea) following the administration of the toxin. The hypotensive response was accompanied by a decrease in aortic baroreceptor activity. The ECG showed atrioventricular conduction block, arrhythmia and depression of S-T segment and T wave which indicated coronary insufficiency. Vasodepressive property of the toxin is presumably muscarinic in nature as atropine counteracted the vasodepression.

Animals↗
PubMed1995

Characterization of a novel epidermal-growth-factor-receptor-related 200-kDa tyrosine kinase in tumor cells.

We have detected a tyrosine-phosphorylated 200-kDa protein in two human tumor cell lines, A1235 glioma and A172 glioblastoma. The protein is an integral plasma membrane sialoglycoprotein with tyrosine kinase activity. The interesting characteristic of this protein (gp200) is that it is recognized by a number of monoclonal and polyclonal antibodies to the 170-kDa epidermal-growth-factor (EGF) receptor; however, it lacks detectable EGF-binding activity. gp200 differs from three other EGF-receptor-related proteins, erb-B-2, erb-B-3 and erb-B-4 gene products, and hence appears to be yet another member of the EGF-receptor family of proteins. This is further strengthened by the fact that both gp200 and the EGF receptor contain a common epitope which is recognized by an anti-peptide IgG to the beta-type platelet-derived-growth-factor (PDGF) receptor. Our previous studies [Bishayee, S., Majumdar, S., Scher, C.D. & Khan, S. (1988) Mol. Cell. Biol. 8, 3696-3702] have demonstrated that this epitope in the PDGF receptor is highly susceptible to the phosphorylation state of the receptor and that such a conformational change appears to be important in biological message transmission. The expression of gp200, which appears to have tyrosine kinase activity and is immunologically related to the EGF receptor in tumor cells, suggests its possible involvement in cell growth.

Amino Acid Sequence↗
PubMed1995

Comparative nucleotide and amino acid sequence analysis of the sequence-specific RNA-binding rotavirus nonstructural protein NSP3.

NSP3, an acidic nonstructural protein, encoded by gene 7 has been implicated as the key player in the assembly of the 11 viral plus-strand RNAs into the early replication intermediates during rotavirus morphogenesis. To date, the sequence of NSP3 from only three animal rotaviruses (SA11, SA114F, and bovine UK) has been determined and that from a human strain has not been reported. To determine the genetic diversity among gene 7 alleles from group A rotaviruses, the nucleotide sequence of the NSP3 gene from 13 strains belonging to nine different G serotypes, from both humans and animals, has been determined. Based on the amino acid sequence identity as well as phylogenetic analysis, NSP3 from group A rotaviruses falls into three evolutionarily related groups, i.e., the SA11 group, the Wa group, and the S2 group. The SA11/SA114F gene appears to have a distant ancestral origin from that of the others and codes for a polypeptide of 315 amino acids (aa) in length. NSP3 from all other group A rotaviruses is only 313 aa in length because of a 2-amino-acid deletion near the carboxy-terminus. While the SA114F gene has the longest 3' untranslated region (UTR) of 132 nucleotides, that from other strains suffered deletions of varying lengths at two positions downstream of the translational termination codon. In spite of the divergence of the nucleotide (nt) sequence in the protein coding region, a stretch of about 80 nt in the 3' UTR is highly conserved in the NSP3 gene from all the strains. This conserved sequence in the 3' UTR might play an important role in the regulation of expression of the NSP3 gene.

Amino Acid Sequence↗
PubMed1995

Anti-hyperglycemic effect of black tea (Camellia sinensis) in rat.

Investigations were carried out to evaluate the effect of the hot water extract of black tea (Camellia sinensis (L.) O. Kuntze (Theaceae) on streptozotocin (STZ)-induced diabetes in rats. The extract significantly reduced the blood glucose level and was found to possess both preventive and curative effects on experimentally produced diabetes in rats. The study reveals that, like green tea, black tea also possesses antidiabetic activity.

Animals↗
PubMed1995

Enhanced growth of fetal and neonatal pulmonary artery adventitial fibroblasts is dependent on protein kinase C.

The earliest and most striking proliferative changes in the neonatal pulmonary arterial wall occur in the adventitia where the fibroblast resides. The protein kinase C (PKC) pathway is developmentally regulated and important in vascular cell growth. We tested the hypothesis that developmental differences in growth of pulmonary artery adventitial fibroblasts would be detectable in vitro and dependent on PKC. Fibroblasts were isolated from bovine fetal, neonatal, and adult pulmonary arteries. Growth was measured by [3H]thymidine incorporation and cell counts. Under serum-stimulated conditions, fetal and neonatal pulmonary artery fibroblasts grew faster and reached higher plateau densities than adult cells. Increased growth of fetal cells in vitro was dependent on time of harvest during fetal life (early > late). Under quiescent conditions, fetal and neonatal fibroblasts had increased DNA synthesis compared with adult cells in response to the PKC agonist phorbol 12-myristate 13-acetate. To test whether the developmental differences in fibroblast growth were dependent on PKC, three different inhibitor strategies were used (dihydrosphingosine, phorbol-ester-induced downregulation, and heparin). Fetal and neonatal fibroblasts were more susceptible than adult cells to each antagonist strategy. Finally, we measured whole cellular PKC catalytic activity and found it correlated with growth and susceptibility to PKC inhibition (i.e., fetal PKC activity > neonatal > adult). We conclude that PKC-dependent developmental differences in growth of pulmonary artery fibroblasts are detectable in vitro and that the enhanced growth capacity of fetal and neonatal cells may contribute to the dramatic adventitial thickening seen in vivo after hypoxic exposure in the neonatal calf.

Animals↗
PubMed1995

Bio-metabolic disposition of metanil yellow, orange II and their blend by caecal microflora of rats.

Caecal microflora were employed to study the degradation pattern, with time course of Metanil yellow and Orange II-two extensively used non-permitted food colours. Metanil yellow and Orange II showed the respective Degradation Index 50 (DI 50) values of 369 and 288 min. However, the blend of Metanil yellow and Orange II (1:1) resulted in the D1 50.value of 288 min. Metanil yellow, Orange II and their blend were resolved into respective metabolites in different solvent systems.

Animals↗
PubMed1994

Carbohydrate-binding profile of a pregnancy-associated rat uterine glycoprotein.

Sugar-binding proteins obtained from the peri-implantation uterine tissue have been thought in recent years to have significant roles in embryo implantation, where carbohydrate moieties of the protein are actively involved. Based on this rationale a mannose-containing glycoprotein/lectin (named uterine agglutinin or UA) was purified by Concanavalin A (Con A) affinity chromatography in a previous study. A modification of the original purification procedure to include a 33% ammonium sulfate fractionation improves the yield of the protein significantly. An alternative purification procedure by Mannan affinity matrix, indicates that apart from containing mannose, UA possesses mannose-binding properties as well. In this paper, we report some of the biochemical and more specifically, the carbohydrate-binding characteristics of UA. The protein is seen to contain mannose-6-phosphate (M-6-P)-binding sites, which is of importance since M-6-P receptors have a large number of biologically significant roles, including that of binding to growth factors. SDS-PAGE, gel filtration chromatography and alkaline PAGE indicate the homogenous nature of the protein with subunit molecular weights of 36 kDa and 19 kDa, and a native size of 64 kDa. Amino acid analysis shows glycine, glutamic acid and aspartic acid to be the major constituents. UA is a glycoprotein and shows presence of N-acetyl glucosamine and galactose, apart from mannose. De nove synthesis studies in the presence of tunicamycin show that the carbohydrate moiety of the glycoprotein is attached by N-linkage to the protein. Binding characteristics of the protein is studied quantitatively in which (125I)-labelled lectin is bound to Mannan-Sepharose affinity matrix.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylglucosamine↗
PubMed1994

Improved synthesis of Salmonella typhimurium enterotoxin using gene fusion expression systems.

Salmonella enterotoxin (Stn) is a virulence factor in S. typhimurium strain Q1 that causes both fluid secretion in ligated intestinal loops of rabbits and elongation of Chinese hamster ovary (CHO) cells. High-level expression systems are needed to provide Stn in soluble form for detailed study of the biological activity of Stn. To maximize the synthesis and solubility of Stn, we systematically compared the production of native Stn synthesized with a T7 RNA polymerase/promoter system to that of two fusion proteins: glutathione S-transferase::Stn (Gst::Stn) and thioredoxin A::Stn (TrxA::Stn). The latter fusion protein expression systems resulted in a 64-fold increase in Gst::Stn and TrxA::Stn antigen concentration, as measured by specific anti-peptide antibodies in an enzyme-linked immunosorbent assay (ELISA). Most of the toxin derived using these vector systems was insoluble; however, the solubility of the TrxA::Stn antigen increased by at least 50-fold, with a concomitant increase in CHO cell elongation activity. In addition, stn gene expression was enhanced more than 50-fold by addition of 0.2-0.4 M NaCl to Luria-Bertani medium. The biological activity of Stn also was increased in the high-osmolarity medium. Consequently, the expression of stn may be regulated by DNA supercoiling.

Animals↗
PubMed1994

Pulmonary fat embolism: a distinct cause of severe acute chest syndrome in sickle cell anemia.

The etiology of most cases of acute chest syndrome (ACS) in sickle cell disease (SCD) is unknown. Although pulmonary fat embolism (PFE) is frequently found on autopsy, it is rarely considered in the differential diagnosis in pediatric patients. We conducted a study to determine if we could identify PFE in SCD patients with ACS, define the clinical and laboratory course of PFE, and determine if bronchoalveolar lavage is safe and useful in diagnosis of PFE. Twenty-seven SCD patients with ACS were evaluated and compared with 43 control patients. Serial tests (complete blood count, platelet count, nucleated red blood cells [NRBCs], chest x-ray, and oxygen saturations) were compared with steady-state results. Diagnosis of PFE was made by quantitative evaluation of pulmonary macrophages for intracellular fat. No serious complications from bronchoscopy were observed. In the SCD patients with ACS, 12 were PFE+ and 15 were PFE-. The clinical course of the two groups was quite different. All PFE+ patients experienced bone pain and 11 of 12 had chest pain. In contrast, only 6 of 15 of PFE- patients had bone or chest pain. Neurologic symptoms developed in 6 of 12 of the PFE+ group and in none of the PFE- group. Mean hospital days for PFE+ was 13 compared with 7 for PFE-. Laboratory studies in PFE+ showed a significant decrease in hemoglobin (-2 g, P < .05), platelet count (-293,000, P < .001), and an increase in NRBCs/100 white blood cells (+8.3, P < .001) compared with PFE-. These results indicate that when PFE is associated with ACS, it is characterized by a distinct clinical course, and that bronchial lavage is a safe and useful test in diagnosing PFE in patients with ACS.

Acute Disease↗
PubMed1994

Biodegradation of malachite green and rhodamine B by caecal microflora of rats.

Bio-degradation of two non-permitted dyes namely Malachite green and Rhodamine B, commonly encountered in the food commodities, through rat caecal microflora was studied. Malachite green was biotransformed by caecal microflora to one fluorescent metabolite with a Rf value of 0.09. Incubation of Rhodamine B with caecal microflora resulted in two fluorescent metabolites with Rf values of 0.72 and 0.09. The DI50 value of Malachite green was quite low (10 min), while that of Rhodamine B could not be derived as the maximum degradation was only 32%. The results suggest that Malachite green and Rhodamine B are biotransformed to different metabolites by rat caecal microflora which may help in delineating the mechanism of carcinogenic potential of these two dyes.

Animals↗
PubMed1994

Attenuation of benzanthrone toxicity by ascorbic acid in guinea pigs.

Oral administration of benzanthrone (BA) (50 mg/kg body wt/day) to guinea pigs for 30 days resulted in depletion of ascorbic acid (ASA) in the liver, adrenals, and blood serum and in growth retardation (36%) and an increase (18%) in relative liver weight when compared to controls. BA treatment showed a tendency toward normocytic anemia with a decrease in hemoglobin content, reduction in RBC counts, and lowered packed cell volume. Guinea pigs treated with BA showed histopathological changes in liver including fibrosis, bile duct proliferation, and focus necrosis. Testes showed marked damage of seminiferous tubules with vacuolar degeneration and irregular and distorted interstitial spaces. BA showed evidence of patchy glomerular congestion, tubular lesions, and damaged epithelial cells in kidney, while urinary bladders had mild congestion in lamina propria and submucosa. Hepatic GOT, GPT, and LDH were found to be significantly decreased (17.5-33.5%), whereas activities of these enzymes showed a significant elevation in serum of BA-exposed guinea pigs. BA treatment also led to significant decrease of testicular hyaluronidase (29.8%) and LDH (19.8%) and significant depletion of lactic acid content (14.7%). Prior daily oral supplementation with ASA (50 mg/kg body wt) to BA-administered guinea pigs resulted in marked improvement of histopathological and biochemical changes observed in liver, testis, kidney, and urinary bladder of BA-exposed animals. These results suggest that extra supplementation of ASA could attenuate the toxic manifestations of BA.

Animals↗