Biomedical subjects

D Debnath

Publications and source records attributed to D Debnath.

24 records · Page 2Linked to original sources

PubMed1990

Interactions of berberine with poly(A) and tRNA.

The interaction of berberine chloride with poly(A) and tRNA has been studied by various spectroscopic techniques. Binding parameters determined from spectrophotometric and spectrofluorimetric measurements by Scatchard analysis indicate a very high effective binding capacity of berberine to poly(A) as compared to DNA or tRNA. The circular dichroism studies show that binding of berberine to poly(A) causes a significant change in the circular dichroic spectrum of poly(A) itself, as manifested by (i) a decrease of both positive and negative bands and (ii) appearance of a conservative type of extrinsic circular dichroic spectrum in the wavelength range of 300-400 nm, while it does not cause any significant alteration to the A form structure of tRNA. It is concluded that berberine interacts stronger with poly(A) than DNA or tRNA. The results are interpreted in terms of its reported biological activities.

Berberine↗

PubMed1990

Effect of polymorphonuclear leukocyte-derived oxygen free radicals and hypochlorous acid on cardiac function and some biochemical parameters.

Polymorphonuclear (PMN) leukocyte activation is known to result in the production and release of oxygen free radicals and hypochlorous acid. Various clinical conditions are associated with PMN leukocyte stimulation. The present investigation deals with the effects of stimulated PMN leukocytes in the absence and in the presence of scavengers of oxygen free radicals (superoxide dismutase, catalase), hypochlorous acid quencher (methionine), and myeloperoxidase inhibitor (azide) on cardiac function and contractility; blood lactate, gases, and pH levels, blood and cardiac tissue malondialdehyde; and PMN leukocyte chemiluminescence activity in anesthetized dogs. Opsonised zymosan was used for stimulation of PMN leukocytes, and the effects were observed for 2 hours. The dogs were divided into four groups: group I, zymosan; group II, superoxide dismutase + catalase + zymosan; group III, methionine + zymosan; group IV, azide + methionine + zymosan. Zymosan produced a decrease in cardiac function and in indices of myocardial contractility and an increase in systemic and pulmonary vascular resistance. There was a decrease in blood pH and in PMN leukocyte chemiluminescense and an increase in the blood lactate and malondialdehyde. Superoxide dismutase plus catalase and methionine reduced the effect of zymosan on cardiac function and contractility and on blood malondialdehyde, lactate, and pH. The combination of azide and methionine did not prevent the deleterious effects of zymosan on cardiac function and contractility. Cardiac tissue malondialdehyde levels were lower in groups III and IV than in groups I and II which had values similar to each other. Methionine was superior to superoxide dismutase plus catalase in the prevention of the deleterious effects of PMN leukocyte stimulation on the various measured parameters. These results suggest that oxygen free radicals and hypochlorous acid are cardiac depressants and increase systemic and pulmonary vascular resistance in addition to causing tissue damage. Clinical situations with PMN stimulation may result in cardiac depression. The oxygen free radical scavenger and hypochlorous acid quencher may be beneficial in the counteraction of the deleterious effects of PMN leukocyte stimulation on the hemodynamic parameters and cellular integrity.

Animals↗

PubMed1989

Interaction of berberine chloride with deoxyribonucleic acids: evidence for base and sequence specificity.

The interaction of berberine chloride with natural and synthetic DNAs of differing base composition and sequences was followed by various spectroscopic and viscometric studies. The binding of berberine chloride was characterized by hypochromism and bathochromism in the absorption bands, enhancement of fluorescence intensity, stabilization against thermal denaturation, perturbations in the circular dichroic spectrum, increase in the contour length of sonicated rod-like DNA and induction of unwinding-rewinding process of covalently closed superhelical DNA, depending on the base composition and sequences of base pairs. Binding parameters determined from absorbance and fluorescence titration by Scatchard analysis, according to an excluded-site model, indicated a very high specificity of berberine to AT-rich DNAs and alternate AT polymer. Fluorescence quantum yield was maximum for the complexes with AT-rich DNAs and alternate AT polymer. Taken together, these results suggest that berberine chloride exhibits considerable specificity towards alternating AT polymer and binds to AT-rich DNAs by a mechanism of classical intercalation.

Berberine↗

PubMedDate not supplied

Study of quinalphos (an environmental oestrogenic insecticide) formulation (Ekalux 25 E.C.)-induced damage of the testicular tissues and antioxidant defence systems in Sprague-Dawley albino rats.

The effect of quinalphos (O-O-diethyl-O-[quinoxalinyl-(2)-thionophosphate]), an environmental oestrogenic organophosphorus insecticide pollutant, was studied on Sprague-Dawley albino rats at doses of 250 and 500 microgram kg(-1) body wt. i.p. for 3, 8 and 15 days, respectively. After the treatment with quinalphos there was an increase in the lipid peroxides (as measured by manoldialdehyde production) and a decrease in the total lipid content for the testicular membrane. The effects were more pronounced at the low doses than at the higher doses, indicating that some physiological defence mechanisms were in operation at higher doses. The free-radical-scavenging enzymes (superoxide dismutase, catalase and glutathione peroxidase) showed significantly higher activity at high dose in comparison to their activities at low-dose treatment. Glutathione content was gradually reduced after quinalphos treatment, both in low and high doses. Histomorphohological studies showed that after the low-dose treatment shrinkage of the tubular diameter and testicular atrophy leading to degenerative changes in the germinal epithelium were observed. But at high dose, gradual recovery of various germ cell layers and significant expansion of seminiferous tubules of Sprague-Dawley rat testes were found; the latter is generally believed to be a useful index of testicular activity through the hypothalamo-hypophyseal-gonadal axis. The present study indicates that quinalphos caused damage and degeneration of the testicular tissues due to free-radical-mediated lipid peroxidation at low doses. We have also demonstrated that, in response to the damage, an endogenous antioxidant enzyme defence system became operative at the higher dose of treatment.

Animals↗

PubMedDate not supplied

Structural perturbation of proteins in low denaturant concentrations.

The presence of very low concentrations of the widely used chemical denaturants, guanidinium chloride and urea, induce changes in the tertiary structure of proteins. We have presented results on such changes in four structurally unrelated proteins to show that such structural perturbations are common irrespective of their origin. Data representative of such structural changes are shown for the monomeric globular proteins such as horseradish peroxidase (HRP) from a plant, human serum albumin (HSA) and prothrombin from ovine blood serum, and for the membrane-associated, worm-like elongated protein, spectrin, from ovine erythrocytes. Structural alterations in these proteins were reflected in quenching studies of tryptophan fluorescence using the widely used quencher acrylamide. Stern-Volmer quenching constants measured in presence of the denaturants, even at concentrations below 100 mM, were higher than those measured in absence of the denaturants. Both steady-state and time-resolved fluorescence emission properties of tryptophan and of the extrinsic probe PRODAN were used for monitoring conformational changes in the proteins in presence of different low concentrations of the denaturants. These results are consistent with earlier studies from our laboratory indicating structural perturbations in proteins at the tertiary level, keeping their native-like secondary structure and their biological activity more or less intact.

Acrylamide↗

PubMedDate not supplied

Effect of hydrocortisone on the hemodynamics and serum CK and MBCK enzymes in acute myocardial infarct in dogs.

The effects of hydrocortisone on the hemodynamics and plasma creatine kinase (CK) in dogs with acute myocardial infarction were investigated. Acute myocardial infarction was produced by ligating the anterior descending branch of the left coronary artery and the effects on hemodynamics and plasma CK were observed for two hours. Complete coronary ligation produced a decrease in the cardiac index and left ventricular work index following two hours of coronary ligation. Other hemodynamic parameters (systemic and pulmonary arterial pressure, left ventricular pressure, right atrial pressure, pulmonary arterial wedge pressure, systemic and pulmonary vascular resistance, heart rate, cardiac effort) were essentially unaffected. There was a tendency for an increase in (dp/dt)/IIP but the increase was not significant. In hydrocortisone treated dogs, all the hemodynamic parameters were unaffected except the cardiac index which decreased significantly. Partial coronary ligation produced an increase in the systemic and pulmonary vascular resistance and a decrease in the cardiac index. The other hemodynamic parameters were unaffected. Plasma CK and MBCK increased significantly in dogs with partial or complete ligation of coronary artery. The serum CK was more in partially ligated than in complete coronary ligated dogs. Although hydrocortisone pretreatment decreased the rise of plasma CK it did not change the rise in MBCK observed in coronary ligated dogs without hydrocortisone treatment. These results indicate that hydrocortisone prevents, although not completely, the deleterious effects of ischemia on the plasma CK but has no effect on the increase in plasma MBCK and decrease in the cardiac index.

Animals↗