Search PubMed⌕ Search

Biomedical subjects

M Das

Publications and source records attributed to M Das.

At least 145 records · Page 8Linked to original sources
PubMed1991

Biochemical toxicology of argemone oil. I. Effect on hepatic cytochrome P-450 and xenobiotic metabolizing enzymes.

The in vivo effect of argemone oil on hepatic xenobiotic metabolizing enzymes was investigated in albino rats following either a single (10 ml kg-1 body wt.) or multiple intraparenteral doses (5 ml kg-1 body wt.) for three days. Animals sacrificed 72 h after a single intraparenteral dose of argemone oil exhibited a significant loss of hepatic cytochrome P-450 (35%) and cytochrome b5 (34%) contents and inhibition of aminopyrine-N-demethylase (APD), aryl hydrocarbon hydroxylase (AHH) and ethoxycoumarin-O-deethylase (ECD) activities (21-39%). Three successive 24-hourly intraparenteral injections of argemone oil followed by sacrificing the animals after 24 h of the last injection, showed a greater degree of inhibition of the content of cytochrome P-450 (58%) and its dependent mixed-function oxidases (35-63%). Also, multiple treatment of argemone oil caused a depletion of endogenous hepatic glutathione (GSH) content (72%) with a concomitant increase in lipid peroxidation (177%) and decrease in glutathione-S-transferase (GST) activity (30%). A significant decrease in relative liver weight (39%) was observed in animals treated with multiple treatment of argemone oil. These results suggest that argemone oil can alter both membrane and cytosolic defences and destabilizes the hepatic cytochrome P-450 dependent mixed-function oxidase system, so that it tips in the direction of autooxidative peroxidation of lipids.

Animals↗
PubMed1991

Interaction of benzanthrone with cytochrome P450: altered patterns of hepatic xenobiotic metabolism in rats.

Benzanthrone, an anthraquinone dye intermediate, is commonly used for the synthesis of a number of polycyclic vat and disperse dyes. Our prior studies have shown that benzanthrone can be metabolized by rat hepatic microsomal cytochrome P450 (P450) (Biochem. Int., 18, 1989, 1237). In this study, the interaction of benzanthrone with rat hepatic microsomal P-450 and its effect on xenobiotic metabolism have been investigated. Parenteral administration of benzanthrone (40 mg/kg body weight) for 3, 7, or 21 days caused no change in the relative body weight or organ weight of rats. The levels of P450 were found to be reduced (33%-50%) in all the benzanthrone-exposed animals at all the time periods. In vitro addition of benzanthrone caused a spectral change with oxidized P450 and concentration-dependent reduction in the carbon monoxide spectrum of dithionite-reduced P450. The addition of benzanthrone to hepatic microsomes prepared from phenobarbital-treated rats resulted in spectral changes characterized by an absorbance maximum at 397 nm indicative of type I binding. In vitro addition of benzanthrone showed a concentration-dependent inhibition of hepatic aminopyrine N-demethylase (APD) and ethoxyresorufin-O-deethylase (ERD) activities with respective I50 values of 9.5 x 10(-4) and 8.0 x 10(-5) M. However, the inhibition of aryl hydrocarbon hydroxylase (AHH) even at the highest concentration of benzanthrone (10(-2) M), was of the order of only 29%. In vivo administration of benzanthrone also led to the inhibition of APD, AHH, and ERD activities at all treatment times although the magnitude of inhibition was of a lower order.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Role of antioxidants and scavengers on argemone oil-induced toxicity in rats.

The role of antioxidants and scavengers on argemone oil-induced enzymatic and non-enzymatic hepatic lipid peroxidation was investigated in rats. Multiple treatment of argemone oil caused a significant stimulation of NADPH-dependent enzymatic or FeSO4 or FeSO4/ADP-or ascorbic acid-dependent non-enzymatic hepatic microsomal lipid peroxidation. In vitro addition of antioxidants such as tannic acid, quercetin, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), alpha-tocopherol, riboflavin or glutathione (GSH) in the assay system resulted in significant protection against argemone oil-induced microsomal NADPH, or FeSO4/ADP-dependent lipid peroxidation. In vitro addition of scavengers of the superoxide anion (O2-.) radical and hydrogen peroxide (H2O2) such as superoxide dismutase (SOD) and catalase, respectively, prevented argemone oil augmented microsomal lipid peroxidation to a lesser extent as compared to the scavengers of singlet oxygen (1O2) such as 2,5-dimethylfuran (DMF), beta-carotene, and histidine or hydroxyl (OH.) radical scavengers such as ethanol, mannitol and sodium benzoate. These results suggest that primarily 1O2 and OH. radicals are involved in argemone oil-induced hepatic microsomal lipid peroxidation, and that bio-antioxidant vitamins including riboflavin, beta-carotene and alpha-tocopherol may prove useful in reducing argemone oil-induced hepatotoxicity.

Animals↗
PubMed1991

Possible existence of dopaminergic receptors on cholinergic nerve terminals in the guinea-pig Auerbach's plexus.

In the Auerbach's plexus of guinea-pig ileum lower concentrations of oxotremorine (Oxo-T) produced an increase, whereas higher concentrations of Oxo-T caused inhibition of evoked acetylcholine (ACh) release, measured by bioassay using dorsal muscle of leech. Dopamine inhibited the increase in evoked release of ACh induced by Oxo-T as a function of its concentration and this inhibitory effect was nullified in presence of pimozide, the dopamine receptor antagonist. The results demonstrate existence of presynaptic dopamine receptors having inhibitory influence on excitatory presynaptic muscarinic receptors on regulation of ACh release. However, no physiological role of dopamine could be observed on ACh release in this preparation.

Acetylcholine↗
PubMed1991

An investigation of environmental impact on health of workers at retail petrol pumps.

Ninety-four male pump workers, employed in 41 petrol filling stations in Kanpur (formerly Cawnpore) and Lucknow--both in the Ganges plain of north India--were clinically examined. Headache, redness in eyes, lacrimation and signs like coated and/or furred tongue, throat and/or conjunctival congestion and carious teeth were significantly higher (P less than 0.05) in workers exposed to petrol fumes than in controls, as also was the level of phenol in urine (P less than 0.01). Environmental measurements revealed higher concentrations of benzene, sulphur dioxide and photoionizable dust in the air at petrol stations, and most of the symptoms and signs could be attributed to petrol fumes and other environmental pollution.

Adolescent↗
PubMed1990

EGF stimulates the processing and export of a secreted form of EGF receptor.

Human A431 cells express a 100 kDa EGF-receptor homolog that contains only the external domain. The kinetics of its maturation and export are slow and comparable to those of the transmembrane receptor. Here we demonstrate that exogenously added EGF stimulates post-translational processing and export of this receptor through a pathway that is insensitive to inhibitors of protein synthesis. The results suggest that EGF may influence one or more of the rate determining steps that control receptor export from endoplasmic reticulum. This may constitute one of the pathways by which EGF regulates the expression of its receptor.

1-Deoxynojirimycin↗
PubMed1990

Cytochrome P-450 dependent monooxygenases in neuronal and glial cells: inducibility and specificity.

Distribution of the mixed function oxidases (MFO's) catalyzed by presence of multiple forms of cytochrome P-450 (P-450) was investigated in the neuronal and glial cells of the brain. The neuronal cells exhibited 2-3 fold higher activity of P-450 dependent arylhydrocarbon hydroxylase (AHH), 7-ethoxycoumarin-o-deethylase (ECOD) and 7-ethoxy-resorufn-o-deethylase (EROD) than the glial cells. Pretreatment with phenobarbital (PB) significantly increased (60-85%) the activity of ECOD in neuronal and glial cells, while a 140% increase was observed in neuronal AHH activity. Exposure to 3-methylcholanthrene (MC) resulted in a significant induction of the activity of AHH (102-345%), ECOD (115-150%) and EROD (75-120%) in the neuronal and glial cell preparations. The neurons, in general, exhibited greater sensitivity towards PB and MC induction. The present data indicate the differential sensitivity of these enzymes in neuronal and glial cells which could be used as a model to understand the selective action of certain neurotoxic agents.

7-Alkoxycoumarin O-Dealkylase↗
PubMed1990

Control of expression and maturation of epidermal growth factor receptor.

Epidermal growth factor (EGF)-receptor is a 170 kDa transmembrane glycoprotein that contains a ligand-binding external domain, and a catalytically active cytoplasmic region. The expression of this receptor as well as a 100 kDa homolog that contains only the external domain is enhanced by the ligand EGF. EGF acts at transcriptional and post-transcriptional levels. To dissociate these pre-translational effects and the effects of EGF on receptor polypeptide synthesis from these on receptor export, pulse-chase experiments were conducted. These studies indicate that EGF stimulates post-translational transport and processing of the receptor, and this stimulation can occur in the absence of new protein synthesis. Other studies show that EGF accelerates at least two slow events in receptor maturation--the deoxynojirimycin sensitive processing in endoplasmic reticulum (ER) and the swainsonine sensitive processing in Golgi. The results suggest that EGF may influence one or more of the rate determining steps that control receptor export from ER, and this may represent yet another aspect of EGF action that contributes to the positive regulation of EGF-receptor protein expression.

Cell Line↗
PubMed1990

Effect of chromium administration on glutathione cycle of rat intestinal epithelial cells.

Acute oral administration of K2Cr2O7 (1500 mg/kg body wt/day) for 3 days to rats led to the decrease in activities of glucose-6-phosphate dehydrogenase, glutathione peroxidase, glutathione reductase, glutathione-S-transferase, superoxide dismutase and catalase of intestinal epithelial cells. Glutathione and total thiol contents were decreased while lipid peroxidation was increased markedly using the whole homogenate of the intestinal epithelial cells. Chronic oral administration of K2Cr2O7 (300 mg/kg body wt/day) for 30 days to rats on the other hand, led to marked increase in superoxide dismutase and glutathione peroxidase activities with no appreciable change in glucose-6-phosphate dehydrogenase, glutathione reductase and catalase activities. However, glutathione-S-transferase activity was decreased significantly. In the whole homogenate of rat intestine, glutathione and total thiol contents were decreased not so significantly but there was a slight enhancement in lipid peroxidation value.

Animals↗
PubMed1990

Differential response of cadmium toxicity towards Mg2(+)-ATPase activity in hepatic and renal nuclear membrane in rats.

Treatment with cadmium chloride (40mg/kg body wt/day) for three days led to a marked inhibition of Mg2(+)-ATPase activity in rat liver nuclear membrane, whereas it stimulated the enzyme in renal nuclear membrane. On 30 days treatment (15 mg/kg body wt/day) the effect was totally different i.e. stimulation of enzyme activity in the liver and inhibition in the kidney tissue. Arrhenius plot analysis of the enzyme activity showed significant increase in phase transition temperature only in liver tissue of rats subjected to acute treatment. Lineweaver Burk plots also showed differential effect of cadmium toxicity on the enzyme activity, i.e. while both Km and Vmax were changed in the liver, there was change only in Km of enzyme from kidney.

Animals↗
PubMed1990

Maturation and externalization of EGF-receptor: a cell-surface located oncoprotein.

The EGF-receptor is a proto-oncogene encoded membrane protein related to the verb-B oncogene product of avian erythroblastosis virus. Here we report studies on expression and maturation characteristics of this receptor. The expression of intact 170 kDa EGF-receptor as well as a 100 kDa homologue that contains only the external domain is enhanced by the ligand EGF. EGF acts at transcriptional and post-transcriptional levels. To dissociate these pre-translational effects and the effects of EGF on receptor polypeptide synthesis from those on receptor export, pulse-chase experiments were conducted. These studies indicate that EGF stimulates post-translational transport and processing of the receptor, and this stimulation can occur in the absence of new protein synthesis. Other studies show that EGF accelerates at least two slow events in receptor maturation--the deoxynojirimycin-sensitive processing in endoplasmic reticulum (ER) and the swainsonine-sensitive processing in golgi, suggesting that EGF may influence one or more of the rate determining steps that control receptor export from ER. Overall the results demonstrate that EGF controls EGF-receptor expression at multiple levels, viz. at transcriptional, pre-translational and post-translational pathways of receptor biosynthesis.

Blotting, Northern↗
PubMed1990

Coitus induced changes in oviductal motility & effect of progesterone.

Motility of different oviductal segments of conscious rabbits was recorded through permanently implanted sensors using the technique of impedance plethysmography. The implants were around the oviductal wall and therefore did not obstruct its lumen. Pre-ovulatory ampullary motility was always less than the isthmic motility. Coitus induced ovulation produced a characteristic oviductal motility pattern consisting of (i) initial relaxation of both isthmus and ampulla (4-12 h) followed by (ii) increased isthmic motility in the face of a continually relaxed ampulla (36-48 h), and finally phase (iii) leading to restitution of both ampullary and isthmic motility to the base-line at 72-96 h. Estimation of ova positions indicated the presence of fertilized eggs in the ampulla and ampullo-isthmic junction at 48 h and the ova could come to the end of the isthmic segment only at 72 h or after. Increased isthmic motility thus served to counter the transportation of ova and their retention in the ampulla. Rabbits in which oviducts were not taken out for ova positioning achieved normal pregnancy. Administration of progesterone (im, 2.5 mg) produced complete relaxation of both isthmus and ampulla, did not produce increased isthmic contractility on coitus, accelerated the ovum transport rate and inhibited pregnancy, again emphasising the ova retentive role of oviductal motility.

Animals↗