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S Dey

Publications and source records attributed to S Dey.

At least 91 records · Page 5Linked to original sources
PubMed1996

Soft metal thiol chemistry is not involved in the transport of arsenite by the Ars pump.

The single cysteine in the ArsB protein subunit of the arsenite resistance pump was changed to serine and alanine residues. Resistance in cells expressing the two mutant arsB genes was the same as in the wild type, and the serine substitution had no effect on the arsenite transport properties. These results eliminate possible thiol chemistry in translocation. Thus, the pump uses soft metal chemistry for metalloactivation and nonmetal chemistry for oxyanion transport.

Adenosine Triphosphatases↗
PubMed1996

Chronic exercise alters EEG power spectra in an animal model of depression.

The EEG from frontal cortex, EMG and EOG were recorded from rats exposed to only exercise (Treadmill), only stress, exercise + stress and neither (control). In comparison with the control group, the percent of Delta activity in the awake was significantly increased in the depressed group and significantly decreased in the exercised groups, while for Beta-2, the reverse occurred; Theta increased and Beta-2 decreased in the NREM sleep state of the depressed group and the opposite happened for the exercised groups. Delta and Alpha-2 activity significantly increased in the depressed group, and they were significantly decreased in the exercised groups whereas the Beta-2 activity showed contrary changes in the REM sleep state. These findings indicate that exercise has the opposite effect from what stress has on qEEG and concomitant physical exercise reduces the effects of stress. Behavioral tests were done by Open Field (OF) and High Plus Maze (HPM). Slow EEG activity (Delta, Theta, Alpha) was significantly positively correlated with immobilization in the OF and defecation in both OF and HPM and negatively with the food intake, transfer latency in HPM; rearing, grooming and total ambulation in OF Whereas, fast activity (Beta-2) was significantly negatively correlated with immobilization in OF and defecation in OF and HPM, while positively with ambulation in the central squares of OF and time spent at the central cross and number of times arms crossed in the HPM.

Animals↗
PubMed1996

Aryl monooxygenase: a detoxifying enzyme from Candida pulcherrima MCMY2.

Characterization of partially purified aryl monooxygenase (1:14:14:1) from Candida pulcherrima MCMY2 was achieved using standard purification protocol. The molecular weight of the enzyme was 110 kDa and contained 3 subunits with pI 5.7, 7.4 and 7.6. The activity seemed to be related with pulcherrimin. The optimum pH and temperature for enzyme activity were 6.8 and 30 degrees C respectively. Activity was not substrate specific and Fe3+ FAD and NADH+ enhanced the activity substantially.

Aryl Hydrocarbon Hydroxylases↗
PubMed1995

Dual mode of energy coupling by the oxyanion-translocating ArsB protein.

The arsA and arsB genes of the ars operon of R-factor R773 confer arsenite resistance in Escherichia coli by coding for an anion-translocating ATPase. Arsenite resistance and the in vivo energetics of arsenite transport were compared in cells expressing the arsA and arsB genes and those expressing just the arsB gene. Cells expressing the arsB gene exhibited intermediate arsenite resistance compared with cells expressing both the arsA and arsB genes. Both types of cells exhibited energy-dependent arsenite exclusion. Exclusion of 73AsO2- from cells expressing only the arsB gene was coupled to electrochemical energy, while in cells expressing both genes, transport was coupled to chemical energy, most likely ATP. These results suggest that the Ars anion transport system can be either an obligatory ATP-coupled primary pump or a secondary carrier coupled to the proton motive force, depending on the subunit composition of the transport complex.

Adenosine Triphosphatases↗
PubMed1995

The ars operon of Escherichia coli confers arsenical and antimonial resistance.

The chromosomally encoded arsenical resistance (ars) operon subcloned into a multicopy plasmid was found to confer a moderate level of resistance to arsenite and antimonite in Escherichia coli. When the operon was deleted from the chromosome, the cells exhibited hypersensitivity to arsenite, antimonite, and arsenate. Expression of the ars genes was inducible by arsenite. By Southern hybridization, the operon was found in all strains of E. coli examined but not in Salmonella typhimurium, Pseudomonas aeruginosa, or Bacillus subtilis.

Adenosine Triphosphatases↗
PubMed1995

Treatment of lead toxicity in calves.

Thiamine hydrochloride alone or in combination with calcium edetate (Ca-EDTA) was used to treat experimentally-induced lead toxicity in calves. In 12 calves lead toxicity was induced by po administration of 5 mg lead acetate/kg/d until the development of overt signs. The calves were divided into 3 groups: untreated control; thiamine-treated; and thiamine+Ca-EDTA-treated. The use of 25 mg thiamine/kg sc twice daily cured 2/4 calves, whereas 4/4 calves recovered with 25 mg thiamine+110 mg Ca-EDTA/kg iv twice daily. Lead concentrations in blood and tissues were significantly lower and histopathologic lesions were less pronounced in the treated calves. Treatment with thiamine+Ca-EDTA was more effective than the use of thiamine alone.

Administration, Oral↗
PubMed1995

Lead in blood and milk from urban Indian cattle and buffalo.

Lead levels were estimated in blood and milk collected from cattle and buffalo in 3 urban areas in India. Mean blood lead concentrations were above background levels. The highest mean blood lead was from Delhi/Ghaziabad (0.43 +/- 0.06) where 11.11% of the samples contained 0.80 ppm lead. Mean milk lead concentrations were 0.28 +/- 0.06 ppm in Ahmedabad, 0.28 +/- 0.05 ppm in Calcutta and 0.27 +/- 0.05 ppm in Delhi. More than 50% of the milk samples from these areas had higher lead concentrations than the background levels suggested for milk.

Animals↗
PubMed1994

ATP-dependent arsenite transport in everted membrane vesicles of Escherichia coli.

Resistance to toxic oxyanions of arsenic and antimony in Escherichia coli results from active efflux of these anions out of the cell. Extrusion is an active process mediated by an ATP-dependent pump composed of two types of subunits, the integral membrane ArsB protein and the catalytic ArsA subunit. An in vitro assay for transport in everted membrane vesicles of E. coli was developed. Uptake of 73AsO2- by everted vesicles was time- and temperature-dependent and required both pump subunits. Transport required ATP; no other nucleotide, including GTP, CTP, UTP, or the nonhydrolyzable analog adenosine 5'-O-(thiotriphosphate), could substitute for ATP. Protonophores, ionophores, or inhibitors of other types of ion-motive ATPases did not inhibit arsenite uptake. The sulfhydryl reagent N-ethylmaleimide was a potent inhibitor of ATP-dependent arsenite accumulation in vesicles. The apparent Km values for ATP and arsenite were approximately 2 and 0.1 mM, respectively. Antimonite, the most potent activator of the ArsA ATPase, inhibited arsenite uptake with an apparent Ki of 10 microM.

Adenosine Triphosphatases↗
PubMed1994

Contribution of the Leishmania P-glycoprotein-related gene ltpgpA to oxyanion resistance.

Oxyanions in the form of pentavalent antimony compounds are currently the drug of choice for treating leishmaniasis. Leishmania mutants resistant to high concentrations of the oxyanion arsenite were obtained in a stepwise selection procedure. Amplification of the H locus P-glycoprotein-related gene ltpgpA, as part of extrachromosomal circles, is a frequent event in arsenite-resistant cells, but was observed only in cells resistant to high concentrations of the metalloid salts. Revertants grown in the absence of the drug lost their ltpgpA-containing amplicon and part of their resistance. The results of previous transfection experiments in Leishmania had suggested that ltpgpA is only involved in low level resistance to arsenite and antimonite. The results of this study using transfection of ltpgpA alleles isolated from arsenite-resistant mutants or of whole circular amplicons containing ltpgpA demonstrate clearly that this P-glycoprotein-related gene is involved in low level resistance to oxyanions, including the pentavalent antimony-containing drug Pentostam. By site-directed mutagenesis, the LtpgpA protein was shown to require an intact nucleotide-binding site to confer arsenite resistance. Under the experimental conditions used, decreased accumulation of the 73AsO2- drug was not observed in the ltpgpA transfectants. One possibility is that LtpgpA-mediated arsenite resistance could result from sequestration of the toxic anion in an intracellular compartment. The results indicate that despite the fact that ltpgpA amplification is a frequent event in oxyanion-resistant mutants, it contributes only slightly to the overall resistance.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

Interaction of the catalytic and the membrane subunits of an oxyanion-translocating ATPase.

Resistance to arsenical and antimonial compounds in Escherichia coli is due to active extrusion of these compounds from cells expressing the ars operon. The arsenical pump is an ion-translocating ATPase which consists of two polypeptide components, the ArsA and ArsB proteins. The ArsB protein, the inner membrane component of the pump, has been shown to function as the membrane anchor for the catalytic subunit, the ArsA protein. The properties and nature of interaction between these two components of the pump were investigated using an in vitro binding assay. Purified ArsA protein bound to the membrane in a saturable manner. In the absence of arsenite or antimonite an apparent positive cooperativity in the binding of the ArsA protein to membrane vesicles containing the ArsB protein was observed. In the presence of arsenite or antimonite binding became hyperbolic, with a 10-fold decrease in the concentration of ArsA protein required for half-maximal binding, without any change in the stoichiometry of the complex. Addition of ATP had little affect on membrane binding of the ArsA ATPase subunit. In the presence or absence of the anionic substrates binding was maximal in a pH range 7.5-8.5.

Adenosine Triphosphatases↗
PubMed1994

A functional chimeric membrane subunit of an ion-translocating ATPase.

A chimeric transport protein was made by expression of a fusion of the arsB genes from Escherichia coli plasmid R773 and Staphylococcus aureus plasmid pI258. The two genes were fused to encode a functional protein with first eight membrane spanning alpha-helices of the S. aureus and the last four helices of the E. coli protein. The hybrid protein provided arsenite resistance and transport. When an arsA gene was expressed in trans with the ArsB proteins encoded by the R773, pI258 and fusion genes, arsenite efflux was dependent on chemical but not electrochemical energy. The Ars system is hypothesized to be a novel transport system that functions as a primary ATP-driven pump or a secondary carrier, depending on the subunit composition of the complex.

Adenosine Triphosphatases↗
PubMed1994

Physical exercise as a novel antidepressant agent: possible role of serotonin receptor subtypes.

Long-term exercise is associated with an antidepressant effect in patients with mild to moderate forms of nonbipolar depression and appears to be a promising new approach to its treatment. Adaptive changes in serotonin (5-HT) receptor functioning appears to play an important role in mediating the action of various antidepressant treatments. We investigated the adaptive changes in behavioral sensitivity of the 5-HT receptor subtype following 4 weeks of swimming exercise in normal rats, as well as in an animal model of depression (3 week, variety of chronic stressors). 5-HT1A autoreceptor sensitivity was assessed by hyperphagic response induced by 8-OH-DPAT (0.25 mg/kg, IP); 5-HT1A postsynaptic receptor by 5-HT syndrome induced by 8-OH-DPAT (0.75 mg/kg, IP), and 5 Me-ODMT (5 mg/kg, IP); and 5-HT2 receptor by wet dog shakes response induced by quipazine (1 mg/kg, IP) and 5MeODMT (5 mg/kg, IP). It was observed that exercise training in normal rats resulted in enhanced sensitivity of the 5-HT2 receptors along with subsensitivity of 5-HT1A autoreceptors. Exercise, given prophylactically along with chronic stressors, was able to prevent the development of behavioral deficit in the open-field test, and the animals developed remarkably enhanced sensitivity of 5-HT2 receptors. This adaptive supersensitivity of 5-HT2 receptor is also seen after various antidepressant treatments and may play an important role in mediating the antidepressant action of exercise.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1994

High level arsenite resistance in Leishmania tarentolae is mediated by an active extrusion system.

Leishmania tarentolae cells selected for resistance to the oxyanions pentavalent or trivalent antimonials or to trivalent arsenicals exhibited cross-resistance to the other oxyanions. The basis for resistance in these mutants was studied by transport experiments using radioactive arsenite. All mutants exhibiting high level resistance to arsenite showed a marked decrease in the steady-state accumulation of arsenite. Decreased accumulation was also observed in antimonials-resistant mutants cross-resistant to various concentrations of arsenite. Cells depleted of endogenous energy reserves with metabolic inhibitors were loaded with radioactive arsenite; following addition of glucose, rapid efflux of arsenite was observed from arsenite mutant cells. Mutants resistant to high levels of arsenicals exhibited amplification of the P-glycoprotein related gene ltpgpA or of a linear amplicon of unknown function. However, the efflux-mediated arsenite resistance did not correlate with the amplification of the ltpgpA gene or with the presence of the linear amplicon. The calcium channel blocker verapamil and arsenite act in synergy in cells exhibiting the efflux system. Overall the oxyanion efflux system in Leishmania shares several properties with other resistance efflux systems mediated by transporters.

Animals↗
PubMed1994

Production of some extracellular enzymes by a lignin peroxidase-producing brown rot fungus, Polyporus ostreiformis, and its comparative abilities for lignin degradation and dye decolorization.

Polyporus ostreiformis produced Mn peroxidase, acid protease, alpha-amylase, and lignin peroxidase, with maximum activities of 40, 8,300, and 4,200 U liter-1 and 50 nkat liter-1, respectively, in nitrogen-limited liquid media. The fungus removed only 18.6% lignin from rice straw in 3 weeks but effected 99% decolorization of Congo red dye in 9 days.

Amylases↗
PubMed1994

Prevalence of serum IgG and IgM antibodies against Epstein-Barr virus capsid antigen in Indian patients with respiratory tract carcinomas.

Antibodies against Epstein-Barr virus capsid antigen (EBV-VCA) were measured in sera of Indian patients with respiratory tract carcinomas (lung, larynx, laryngopharynx, nasopharynx) using a commercial enzyme linked immunosorbent assay (ELISA) kit. Nineteen out of thirty-three (19/33) lung cancer, 12/22 laryngeal cancer, 11/16 laryngopharyngeal cancer, 6/9 nasopharyngeal carcinoma cases and 3/29 matched controls were positive for IgG antibody to VCA. None were positive for the IgM antibody to VCA. The antibody positivity was evaluated on the basis of immune status ratio (ISR) of the sera as described in the manual of the kit. Prevalence of the antibody was more pronounced among smokers with laryngeal and laryngopharyngeal carcinoma than among lung cancer cases. The results indicated that the antibody positivity rate among the patients declined with the advanced stages of the diseases. Serum IgG and IgM levels were raised in the patients who were tested positive for the viral antibody.

Adolescent↗
PubMed1993

Orphan enzyme or patriarch of a new tribe: the arsenic resistance ATPase of bacterial plasmids.

The plasmid-determined arsenite and antimonite efflux ATPase of bacteria differs from other membrane transport ATPases, which are classified into several families (such as the F0F1-type H(+)-translocating ATP synthases, the related vacuolar H(+)-translocating ATPases, the P-type cation-translocating ATPases, and the superfamily which includes the periplasmic binding-protein-dependent systems in Gram-negative bacteria, the human multidrug resistance P-glycoprotein, and the cystic fibrosis transport regulator). The amino acid sequences of the components of the arsenic resistance system are not similar to known ATPase proteins. New findings with the arsenic resistance operons of bacterial plasmids suggest that instead of being an orphan the Ars system will now be the first recognized member of a new class of ATPases. Furthermore, fundamental questions of energy-coupling (ATP-driven or chemiosmotic) have recently been raised and the finding that the arsC gene product is a soluble enzyme that reduces arsenate to arsenite changes the previous picture of the functioning of this widespread bacterial system.

Adenosine Triphosphatases↗