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Biomedical subjects

B K Bhattacharya

Publications and source records attributed to B K Bhattacharya.

At least 19 recordsLinked to original sources
PubMed1996

Development of malathion resistance in Culex quinquefasciatus Say (Diptera: Culicidae).

A malathion resistant colony of C. quinquefasciatus was developed in the laboratory. LC50 and LC90 for larvae were calculated at every generation and the values were 0.3 ppm and 1.13 ppm for first generation and 61.09 ppm, 136.3 ppm for 25th generation respectively. The fold increase in LC50 and LC90 were 2036 and 2726 folds respectively. Cross resistance against propoxur and chlorpyrifos showed 6.64 and 6.52 fold and 600 and 720 fold increase in their LC50 and LC90 values respectively. Triphenyl phosphate (TPP) and piperonyl butoxide (PB) were used as synergists and TPP indicated proportional decrease in LC50 and LC90 values while not much change was observed with PB. No change in biotic potential (larval hatchability, adult emergence and male and female ratio) between susceptible and malathion resistant colonies was observed.

Animals↗
PubMed1995

Synthesis and anti-DNA viral activities in vitro of certain 2,4-disubstituted-7-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)pyrrolo[2,3-d d pyrimidine nucleosides.

Several novel 2,4-disubstituted-7-(2-deoxy-2-fluoro-beta-D- arabinofuranosyl)pyrrolo[2,3-d]pyrimidines have been synthesized and evaluated for their anti-human cytomegalovirus (HCMV), anti-hepatitis B virus (HBV), and anti-herpes simplex virus (HSV) activities in vitro. These nucleosides were prepared starting from 2-amino-4-chloro-7-(2-deoxy-2-fluoro- 3,5-di-O-benzoyl-beta-D-arabinofuranosyl)pyrrolo[2,3-d]pyrimidine (3), which in turn was synthesized by direct glycosylation of the sodium salt of 2-amino-4-chloropyrrolo[2,3-d]pyrimidine (1) with 2-deoxy-2-fluoro-3,5-di-O-benzoyl-alpha-D-arabinofuranosyl bromide (2). Displacement of the 4-chloro group of 3 with OH, NH2, NHOH, SH, and SeH nucleophiles furnished the corresponding nucleosides 6-8, 12, and 14, respectively. The 3'-deoxygenation of 2-amino-4-chloro-7- (2-deoxy-2-fluoro-beta-D-arabinofuranosyl)pyrrolo[2,3-d]pyrimidine (4) and subsequent amination gave 2,4-diamino-2',3'-dideoxy derivative 19. Catalytic hydrogenation of 3 followed by debenzoylation afforded 2-aminopyrrolo[2,3-d]pyrimidine nucleoside 23. Among the compounds evaluated for their ability to inhibit the growth of HCMV (strain AD169) in MRC-5 cells using a plaque reduction assay, only 7 was significantly active in vitro with a 50% inhibitory concentration (IC50) of 3.7 micrograms/mL (TI > 125), whereas the IC50 value of ganciclovir (DHPG) was 3.2 micrograms/mL. Strain D16 of HCMV was more resistant to 7 (IC50 11 micrograms/mL) than the AD169 strain. When 7 was tested in combination with DHPG, the resultant anti-HCMV activity was found to be moderately synergistic with no evidence of antagonism. Nucleoside 7 also reduced episomal HBV replication in human hepatoblastoma 2.2.15 cells with an IC50 of 0.7 micrograms/mL (TI > 143). Development of cells harboring HBV which had become resistant to the drug was not observed with 7. Compound 7 also exhibited significant activity against herpes simplex virus types 1 and 2 (IC50 of 4.1 and 6.3 micrograms/mL, respectively) in Vero cells.

Animals↗
PubMed1995

Altered glycine transport by cerebral tissue and decreased Na+ and Ca++ pump activities during organophosphorus-ester-induced delayed neurotoxicity development period.

Uptake of [U-14C] glycine during the organophosphorus-ester-induced delayed neurotoxicity (OPIDN) development period was studied. Diisopropyl fluorophosphate (DFP), a delayed neurotoxic organophosphorus ester was administered to adult rats and hens. Results showed a decreased accumulation of glycine in hen cerebral cortex slices during the delayed neurotoxicity development period. An altered sensitivity toward transport inhibitors 2,4-dinitrophenol and ouabain was observed in DFP-treated hens. An altered neuronal membrane function during the OPIDN development period is reported in the present work. Brain Na+, K(+)-ATPase and Ca(++)-ATPase activities decreased during the neurotoxicity development period. The decrease in Ca(++)-ATPase activity persisted in hens until the complete development of neurotoxic symptoms. Decreased Ca++ pump activity is correlated with altered membrane function during OPIDN.

2,4-Dinitrophenol↗
PubMed1995

Inhibition of episomal hepatitis B virus DNA in vitro by 2,4-diamino-7- (2-deoxy-2-fluoro-beta-D-arabinofuranosyl)-pyrrolo[2,3-d]pyrimidine.

The nucleoside analog 2,4-diamino-7-(2-deoxy-2-fluoro-beta-D- arabinofuranosyl)pyrrolo[2,3-d]pyrimidine (T70080) and several related compounds were evaluated for anti-hepatitis B virus (HBV) activity by using cultured 2.2.15 cells. T70080 reduced episomal viral replication in these cells by 50% at a concentration of 0.7 microgram/ml. At the same time, T70080 reduced cellular proliferation by 50% at a concentration in excess of 100 micrograms/ml, yielding a therapeutic index of > 143. In cells cultured for 12 days in the presence of 10 or 50 micrograms of T70080 per ml and then with drug-free medium, for an additional 12 days, viral DNA replication was completely inhibited initially but resumed between 6 and 12 days post-drug removal. In view of the potent anti-HBV activity shown, T70080 is a good candidate for further evaluation as a treatment of human HBV infection.

Antiviral Agents↗
PubMed1994

Sulfinosine congeners: synthesis and antitumor activity in mice of certain N9-alkylpurines and purine ribonucleosides.

A number of N9-alkyl-substituted purines and purine ribonucleosides have been synthesized as congeners of sulfinosine and evaluated for their antileukemic activity in mice. NaH-mediated alkylation of 6-chloropurine (4) and 2-amino-6-chloropurine (5) with certain alkyl bromides gave N7- and N9-alkylated derivatives (7a-d and 6a-d), the N9-isomer being the major product. Treatment of 6a-d and 7a-d with thiourea furnished the corresponding 6-thio derivatives (9a-d and 8a-d). Amination of 9a-e with aqueous chloramine solution afforded the corresponding purine-6-sulfenamides (10-a-e), which on controlled oxidation with 3-chloroperoxbenzoic acid (MCPBA) gave the respective (R,S)-9-alkylpurine-6-sulfinamides (11a-e). A similar oxidation of 2-amino-6-(methyl/benzylthio)-9-beta-D-ribofuranosylpurine (12a and 12b) and 2-amino-9-(2-deoxy-beta-D-erythro-pentofuranosyl)-6- (methylthio)-purine (12c) with MCPBA gave the corresponding sulfoxides (13a-c), which on further oxidation furnished the respective sulfones (14a-c). Of the 20 compounds evaluated, six exhibited biologically significant anti-L1210 activity in BD2F1 mice and reduced body burdens of viable L1210 cells more than 90-97% by single treatment. Although compounds 9b and 9c at 44 mg and 40 mg/kg per day x 1 showed a T/C of 147 and 149, respectively, this group of compounds was found to be less effective than some of the sulfur-containing drugs that we previously described (e.g. sulfenosine and sulfinosine).

Animals↗
PubMed1990

Growth inhibition and induction of cellular differentiation of human myeloid leukemia cells in culture by carbamoyl congeners of ribavirin.

A series of 1,2,3-triazole (2), pyrazole (3 and 5), and pyrrole (4) ribonucleosides with two adjacent carbamoyl groups have been synthesized and evaluated for cell growth inhibition and induction of cellular differentiation of HL-60 cells in culture. Glycosylation of the TMS derivatives of dimethyl 1,2,3-triazole-4,5-dicarboxylate (6) and diethyl pyrazole-3,4-dicarboxylate (7) with 1-O-acetyl-2,3,5-tri-O-benzoyl-D- ribofuranose (8) in the presence of TMS triflate gave predominantly the beta-nucleosides 9 and 14, respectively. Ammonolysis of 9 and 14 furnished 2-beta-D-ribofuranosyl-1,2,3-triazole-4,5-dicarboxamide (2) and 1-beta-D-ribofuranosylpyrazole-3,4-dicarboxamide (3), respectively. Stereoselective ring annulation of 1-deoxy-1-hydrazinyl-2,3-O-isopropylidene-D- ribose (16) with tetracyanoethylene (15) gave 5-amino-1-(2,3-O-isopropylidene-beta-D-ribofuranosyl)pyrazole-3,4- dicarbonitrile (17). Deisopropylidenation of 17, followed by oxidative hydrolysis of the reaction product (18), gave the 5-amino derivative of 3 (5). Stereospecific glycosylation of the sodium salt of preformed diethyl pyrrole-3,4-dicarboxylate (22) with 1-chloro-2,3-O-isopropylidene-5-O-(tert-butyldimethylsilyl)-alpha-D- ribofuranose (23) was accomplished to furnish blocked nucleoside 24, which on ammonolysis and deisopropylidenation gave 1-beta-D-ribofuranosylpyrrole-3,4-dicarboxamide (4). The structures of 2 and 3 were assigned by single-crystal X-ray diffraction studies, which showed extensive inter- and intramolecular hydrogen bonding. Nucleosides 2-5 are devoid of significant cytotoxic properties against L1210 and WI-L2 leukemia cells in culture. However, these compounds were found to be inducers of cellular differentiation of HL-60 cells in the range of 30-60 microM and were comparable to ribavirin in this regard.

Acetylation↗
PubMed1987

Inhibition of rat brain cytochrome oxidase activity by pyrolysed products of methyl isocyanate.

The effects were studied of methyl isocyanate (MIC) and its thermally degraded products (dMIC) on rat brain cytochrome oxidase activity. Pure MIC did not inhibit brain cytochrome oxidase activity. A significant inhibition of brain cytochrome oxidase activity by dMIC was observed both in vivo and in vitro. The presence of cyanide in pyrolysed products of MIC has also been confirmed by chemical methods.

Animals↗
PubMed1986

Elderly patients' views on cardiopulmonary resuscitation.

A survey was conducted by means of a questionnaire to assess elderly patients' perception of cardiopulmonary resuscitation (CPR) as it might be applied to themselves. Nearly half (47%) of patients were unaware of the existence and practice of this procedure. The majority of patients felt that selective application of CPR in the elderly was appropriate. Factors that may influence selection are discussed. A considerable proportion of patients wished to be resuscitated if the need arose--a fact not in keeping with the scant information available on the subject. Significantly more men than women favoured resuscitation. Some elderly people interviewed, favoured resuscitation of elderly patients other than themselves. Patients welcomed an opportunity to discuss and express their views on their position.

Aged↗
PubMed1978

Positive inotropic and blood pressure lowering activity of a diterpene derivative isolated from Coleus forskohli: Forskolin.

Forskolin is a diterpene derivative isolated from the Indian plant Coleus forskohli. Forskolin has positive inotropic action on the isolated guinea pig heart, on the isolated left atrium of the guinea pig heart and on the dog and cat heart in situ. It increases the heart rate. The positive inotropic effect on the increase of heart rate are not blocked by beta-blockers. On reserpinized dogs the actions on the heart could also be seen. With high doses the action potential of the guinea pig papillary muscle is shortened. The positive inotropic effect could be differentiated from the effects of theophylline, cardiac glycosides and veratrine. Forskolin lowers the blood pressure in dogs and cats and also in spontaneously hypertensive and renal hypertensive rats.

Action Potentials↗
PubMed1977

Possible role of dopamine in central effects of cocaine as measured by apomorphine gnawing test in mice.

Apomorphine (10mg/kg, s.c.) does not induce in mice a compulsion to gnaw, but pretreatment with cocaine (10-40 mg/kg, i.p.) caused gnawing activity. This effect of cocaine was inhibited by pretreatment with alpha-methyl-p-tyrosine, haloperidol, and physostigmine, but not with FLA-63, phenoxybenzamine and tetrabenazine. These findings would suggest that dopaminergic mechanism plays a significant role in the potentiation of apomorphine gnawing activity by cocaine and also support the view that inhibition of dopamine uptake is responsible for the stimulatory action of cocaine.

Animals↗
PubMed1977

Vascular reactivity of perfused vascular bed in spontaneously hypertensive and normotensive rats.

1 Hypertensive and normotensive rats of the same age group were isolated from an inbred colony of spontaneously hypertensive rats. 2 The perfused hindquarter and mesenteric artery preparations obtained from hypertensive and normotensive rats exhibited an increased reactivity to noradrenaline (NA) and angiotensin II. 3 Dose-response curves to NA obtained from hypertensive and normotensive rats exhibited a steeper slope and higher maximum than those from control rats. 4 These findings suggest that increased vascular reactivity of blood vessels is independent of the development or maintenance of elevated blood pressure.

Angiotensin II↗
PubMed1976

Influence of pheniramine and chlorpheniramine on apomorphine induced compulsive gnawing in mice.

In mice, apomorphine (10 mg/kg s.c.) does not induce a compulsion to gnaw, but pretreatment with antihistamines, viz. pheniramine, chlorpheniramine and mepyramine, in doses ranging from 30 to 60 mg/kg i.p. caused gnawing activity. Mepyramine showed significantly less effect when compared to the other two agents. Antihistamines are known to influence the activity of biogenic amines in central nervous system. The potentiation of apomorphine-induced gnawing by antihistamines might depend upon the reciprocal balance between dopaminergic and cholinergic systems. This was tested by blocking biosynthesis of biogenic amines or by blocking their receptors. The potentiation of gnawing was antagonised by physostigmine (0.25 mg/kg) or blocked by pretreatment with alpha-methyl-p-tyrosine (alpha-MPT) (4 X 150 mg/kg) and bis-(4-methyl-1-homopiperazinylthiocarbonyl)-disulphide (FLA) (40 mg/kg), while p-chlorophenyl alanine (p-CPA) (3 X 100 mg/kg) had no effect. Similarly, phenoxybenzamine (30 mg/kg) and haloperidol (1.0 mg/kg) inhibited gnawing activity, but methysergide (10 mg/kg) had no effect. Furthermore, pretreatment with tetrabenazine (20 mg/kg) and L-Dopa (200 mg/kg) did not affect gnawing activity. It is concluded that both pheniramine and chlorpheniramine potentiate apomorphine gnawing by upsetting the cholinergic and dopaminergic balance in favour of dopaminergic dominance.

Animals↗