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Biomedical subjects

B Hazra

Publications and source records attributed to B Hazra.

14 recordsLinked to original sources
PubMed2003

Antimycobacterial activity of diospyrin derivatives and a structural analogue of diospyrin against Mycobacterium tuberculosis in vitro.

Three derivatives and one structural analogue of diospyrin were synthesized and investigated for their inhibitory activity against Mycobacterium tuberculosis employing the rapid radiometric method in vitro. A novel aminoacetate derivative was found to be more active than the parent compound, the MICs being 50 and 100 mg/L, respectively, for a drug-susceptible strain, H37Rv, of M. tuberculosis. This derivative also exhibited an MIC of 50 mg/L for a few multidrug-resistant strains of M. tuberculosis. The other two derivatives and the analogue did not show any significant antimycobacterial activity at the highest concentration (100 mg/L) tested.

Antibiotics, Antitubercular↗
PubMed2000

Propranolol in primary and secondary prophylaxis of variceal bleeding among cirrhotics in India: a hemodynamic evaluation.

OBJECTIVE: In the present study, we attempted to complete the hemodynamic assessment of propranolol response in cirrhotics with esophageal varices at high risk of bleeding, in one sitting, so as to identify nonresponders at the earliest. Some noninvasive indicators of this response were also evaluated. METHODS: Hepatic venous pressure gradient (HVPG) was measured in 33 such cases (18 nonbleeders, 15 bleeders) before and 90 min after an oral dose of 80 mg propranolol, and reduction by > or =20% taken as responder. RESULTS: Twenty-two patients (66.67%) responded (HVPG reduction > or =26%), whereas 11 (33.33%) did not (HVPG reduction < or =6%). Postdrug HVPG between responders and nonresponders showed a significant difference (p < 0.001). Neither baseline HVPG (p > 0.1), baseline CI (p = 0.665), nor baseline stroke volume index (p > 0.1) could predict responder status. Difference of HVPG reduction (percent) between bleeders (21.49 +/- 35.53) and nonbleeders (40.58 +/- 23.95) approached, but did not reach, statistical significance (p = 0.076). However, logistic regression showed this difference to be significant (p = 0.026). Age of responders was found to be significantly lower than that of nonresponders (p approximately equals 0.05). During a follow-up of 9-38 months, only one of 22 responders (on propranolol) had an episode of variceal bleed. None in whom HVPG fell to < or = 12 mm Hg bled. CONCLUSION: The study suggests that single-sitting hemodynamic assessment of acute response to high-dose oral propranolol clearly differentiates between responders and nonresponders. Moreover, it appears that prior history of variceal bleeding and old age negatively influences the effect of propranolol.

Administration, Oral↗
PubMed2000

Effects of atovaquone and diospyrin-based drugs on ubiquinone biosynthesis in Pneumocystis carinii organisms.

The naphthoquinone atovaquone is effective against Plasmodium and Pneumocystis carinii carinii. In Plasmodium, the primary mechanism of drug action is an irreversible binding to the mitochondrial cytochrome bc(1) complex as an analog of ubiquinone. Blockage of the electron transport chain ultimately inhibits de novo pyrimidine biosynthesis since dihydroorotate dehydrogenase, a key enzyme in pyrimidine biosynthesis, is unable to transfer electrons to ubiquinone. In the present study, the effect of atovaquone was examined on Pneumocystis carinii carinii coenzyme Q biosynthesis (rather than electron transport and respiration) by measuring its effect on the incorporation of radiolabeled p-hydroxybenzoate into ubiquinone in vitro. A triphasic dose-response was observed, with inhibition at 10 nM and then stimulation up to 0.2 microM, followed by inhibition at 1 microM. Since other naphthoquinone drugs may also act as analogs of ubiquinone, diospyrin and two of its derivatives were also tested for their effects on ubiquinone biosynthesis in P. carinii carinii. In contrast to atovaquone, these drugs did not inhibit the incorporation of p-hydroxybenzoate into P. carinii carinii ubiquinone.

Antifungal Agents↗
PubMed2000

Effects of atovaquone and diospyrin-based drugs on the cellular ATP of Pneumocystis carinii f. sp. carinii.

Atovaquone (also called Mepron, or 566C80) is a napthoquinone used for the treatment of infections caused by pathogens such as Plasmodium spp. and Pneumocystis carinii. The mechanism of action against the malarial parasite is the inhibition of dihydroorotate dehydrogenase (DHOD), a consequence of blocking electron transport by the drug. As an analog of ubiquinone (coenzyme Q [CoQ]), atovaquone irreversibly binds to the mitochondrial cytochrome bc(1) complex; thus, electrons are not able to pass from dehydrogenase enzymes via CoQ to cytochrome c. Since DHOD is a critical enzyme in pyrimidine biosynthesis, and because the parasite cannot scavenge host pyrimidines, the drug is lethal to the organism. Oxygen consumption in P. carinii is inhibited by the drug; thus, electron transport has also been identified as the drug target in P. carinii. However, unlike Plasmodium DHOD, P. carinii DHOD is inhibited only at high atovaquone concentrations, suggesting that the organism may salvage host pyrimidines and that atovaquone exerts its primary effects on ATP biosynthesis. In the present study, the effect of atovaquone on ATP levels in P. carinii was measured directly from 1 to 6 h and then after 24, 48, and 72 h of exposure. The average 50% inhibitory concentration after 24 to 72 h of exposure was 1.5 microgram/ml (4.2 microM). The kinetics of ATP depletion were in contrast to those of another family of naphthoquinone compounds, diospyrin and two of its derivatives. Whereas atovaquone reduced ATP levels within 1 h of exposure, the diospyrins required at least 48 h. After 72 h, the diospyrins were able to decrease ATP levels of P. carinii at nanomolar concentrations. These data indicate that although naphthoquinones inhibit the electron transport chain, the molecular targets in a given organism are likely to be distinct among members of this class of compounds.

Adenosine Triphosphate↗
PubMed2000

Etiology based prevalence of Budd-Chiari syndrome in eastern India.

BACKGROUND: Diagnosis of Budd-Chiari syndrome (BCS) is often missed unless its possibility has been kept in mind. Obstruction of inferior vena cava (IVC) is reportedly the most frequent cause of BCS in Afro-Asian variety. AIM: An attempt was made to classify BCS (in an eastern Indian population) etiopathologically. PATIENTS AND METHODS: Thirty consecutive cases of BCS presenting over a period of five years were included. Following a thorough physical examination, necessary investigations (including coagulation profile, ultrasonography (with Doppler study) of hepatobiliary tract, hepatic vein and IVC angiography (n = 22) and liver biopsy (n = 26, including autopsy in two cases) were performed. RESULTS: Mean age at presentation was 32.7 +/- 10.36 years (range 12-60 years) with M:F = 21:9. Clinical presentations included, hepatomegaly in 28 (93.3%), ascites in 27 (90%), splenomegaly in 15 (50%), pain in abdomen in 26 (86.6%), jaundice in 10 (33.3%), back veins in 20 (66.6%) and gastrointestinal bleeding in three (10%) cases. Amongst the total of 30 patients, four, six and 20 cases presented as fulminant, acute and chronic BCS respectively. Twenty four cases of BCS could be diagnosed by ultrasonography alone, while the remainder required angiography for diagnosis. IVC and hepatic vein angiography revealed membranous obstruction in nine, partial stricture of IVC in six, and IVC and/or hepatic vein block in others. The etiopathological nature in 30 cases were as follows: idiopathic membranous obstruction in nine (30%), hepatocellular carcinoma in six (20%), idiopathic stricture in six (20%) cases and one case (3.3%) each of the following: cholangiocarcinoma, renal cell carcinoma, chronic pancreatitis, hydatid cyst in liver, protein S deficiency, oral contraceptive use, nephrotic syndrome (with antithrombin III deficiency), polycythemia rubra vera and chronic lymphatic leukemia. CONCLUSION: Idiopathic membranous obstruction and stricture of IVC are the commonest cause of BCS in the eastern part of India. Hepatocellular carcinoma is also a common cause, presenting in the fulminant form. Ultrasonography may be a helpful screening test for BCS, but IVC and hepatic vein catheterisation is essential for a complete work up of these patients.

Adolescent↗
PubMed1998

Diospyrin, a bisnaphthoquinone: a novel inhibitor of type I DNA topoisomerase of Leishmania donovani.

Diospyrin is a plant product that has significant inhibitory effect on the growth of Leishmania donovani promastigotes. This compound inhibits the catalytic activity of DNA topoisomerase I of the parasite. Like camptothecin, it induces topoisomerase I mediated DNA cleavage in vitro. Treatment of DNA with diospyrin before addition of topoisomerase I has no effect. Preincubation of topoisomerase I with diospyrin before the addition of DNA in the relaxation reaction increases this inhibition. Our results suggest that this bis-naphthoquinone compound exerts its inhibitory effect by binding with the enzyme and stabilizing the topoisomerase I-DNA "cleavable complex." Diospyrin is a specific inhibitor of the parasitic topoisomerase I. It does not inhibit type II topoisomerase of L. donovani and requires much higher concentrations to inhibit type I topoisomerase of calf thymus. The potent inhibitory effect of diospyrin on type I DNA topoisomerase from L. donovani can be exploited for rational drug design in human leishmaniasis.

Animals↗
PubMed1998

A study of mycetoma in eastern India.

Forty consecutive cases of mycetoma were studied with respect to clinico-epidemiological, histopathological and radiological features. The age of the patients ranged from 17 to 57 years mean being 32.4 +/- 8.68. The disease was equally distributed amongst the sexes. Most of the patients had a rural background and the disease occurred mainly among farmers and housewives. Actinomycetes (32 cases. 80%) were found to be the main pathogenic organism and Eumycetes in 4 cases (20%) only. Clinical features were more or less the same irrespective of the aetiologic agent, consisting of local swelling with discharging sinuses. History of trauma was present in only 20% cases and 80% were incidental. Foot (28/40 i.e. 70%) was the commonest site of infection. Radiological bony involvement was detected in 14 out of 18 cases examined (38.88%). Out of the 32 radiographed patients of actinomyetoma 10(31.25%) showed bony involvement whereas all the four. Eumycetoma cases radiographed, had bony involvement. The notable bony changes were sclerosis, erosions, periosteal thickening and osteoporosis.

Actinomycetales Infections↗
PubMedDate not supplied

Epidemiology of peptic ulcer in north Bengal, India.

A retrospective analysis of hospital records of inpatients of Medicine department of North Bengal Medical College and Hospital during the period between 1988-90 revealed that 6.2% of all medical admissions were on account of peptic ulcer and or acute gastritis. Duodenal ulcer was prevalent accounting for more than 50% of the cases of peptic ulcer and acute gastritis. Duodenal ulcer was more common in the working age groups (> 21 years) among males and more than 31 yrs among females. Gastric ulcer was more common among older age groups. In respect to ethnicity, Bengali speaking hindus showed high probability for gastric ulcers in both sexes. The probability for duodenal ulcer was within confidence limits among all social groups.

Acute Disease↗