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Biomedical subjects

D K Das

Publications and source records attributed to D K Das.

At least 91 records · Page 5Linked to original sources
PubMed1997

Interrelationship between cellular calcium homeostasis and free radical generation in myocardial reperfusion injury.

This review describes the interrelationship between two important biological factors, intracellular calcium overloading and oxygen-derived free radicals, which play a crucial role in the pathogenesis of myocardial ischemic reperfusion injury. Free radicals are generated during the reperfusion of ischemic myocardium, and polyunsaturated fatty acids in the membrane phospholipids are the likely targets of the free radical attack. On the other hand, activation of phospholipases can provoke the breakdown of membrane phospholipids which results in the activation of arachidonate cascade leading to the generation of prostaglandins, and oxygen free radicals can be produced during the interconversion of the prostaglandins. In conclusion, it has been emphasized that the two seemingly different causative factors of reperfusion injury, intracellular calcium overloading and free radical generation are, in fact, highly interrelated.

Calcium↗
PubMed1997

Fine-needle aspiration diagnosis of carotid body tumor: report of a case and review of experience with cytologic features in four cases.

A 45-yr-old female presented with a left upper cervical swelling of 4 yr duration. The clinical suspicion of carotid body tumor (CBT) was confirmed by imaging findings, fine-needle aspiration (FNA) cytology, and histology of the resected tumor. Review of our experience with four cases including the present one during 10 yr (1984-1994) showed that the age of the patients ranged from 35 to 45 yr with a mean of 40.8 yr. All four cases were females and had left-sided upper cervical swelling. Clinically one case was diagnosed as cervical lymphadenopathy and there was clinical suspicion of CBT in two cases. Findings of digital subtraction angiogram in four cases and ultrasonography including Doppler ultrasound vascular imaging in three cases were consistent with CBT. The cytodiagnosis was CBT in three cases and inadequate (blood only) in one case. The analysis of detailed cytologic features in three cases revealed blood-rich aspirate with poor to moderate cellularity, indistinct cell outline, and acinar formation. Giant bare nuclei, spindle-shaped tumor cells, and cytoplasmic granulations were observed in two cases each. Histopathology of the resected tumors in two cases confirmed the cytodiagnosis of CBT. FNA cytology played a useful role in arriving at a tissue diagnosis of this rare neoplasm.

Adult↗
PubMed1997

High expression and activation of MAP kinase-activated protein kinase 2 in cardiac muscle cells.

Recently, three mammalian mitogen-activated protein (MAP) kinases, ERK, SAPK/JNK, and p38/HOG-1 have been identified, each with apparently unique signal transduction pathways. The p38 MAP kinase mediates an intracellular stress-activated signaling pathway by regulating down-stream molecules, such as MAP kinase-activated protein (MAPKAP) kinase 2. To study the tissue specificity of MAPKAP kinase 2, mRNA blots containing multiple human tissues were hybridized with a specific oligonucleotide probe corresponding to human MAPKAP kinase 2. The Northern blot analysis revealed that two mRNA species of MAPKAP kinase 2, with sizes of 4.8 and 3.3 kb, were expressed in high levels in both human heart and skeletal muscle tissues. To better understand how MAPKAP kinase 2 is regulated in myocardium, cultured rat cardiac myoblast (H9c2) cells were stimulated with heat shock, H2O2-induced oxidative stress, or phorbol ester (PMA). Enzymatic activity of cellular MAPKAP kinase 2 in the cell lysates was evaluated using an in vitro kinase assay. Exposure of H9c2 cells to heat shock or oxidative stress induced a transient increase of cellular MAPKAP kinase 2 activity, which reached its peak level within 5 min. In contrast, stimulation of H9c2 cells with PMA, a potential myocardial hypertrophic factor, induced a sustained increase of cellular MAPKAP kinase 2 activity that was detectable for over 1 h. In addition, in vitro protein phosphorylation analysis with recombinant MAPKAP kinase 2 showed that small heat shock protein (hsp25) served as a major substrate molecule for the kinase in H9c2 cells and the protein phosphorylation of cellular hsp25 was stimulated by H2O2-induced oxidative stress or PMA treatment in intact H9c2 cells. Moreover, exposure of H9c2 cells to H2O2-induced oxidative stress or PMA rapidly activated cellular p38 MAP kinase as detected by the induced protein phosphorylation of the kinase. Taken together, these results strongly suggest that MAPKAP kinase 2 may be involved in stress-activated signal transduction in myocardium.

Animals↗
PubMed1997

Cytohistological correlation as a measure of quality assurance of a cytology laboratory.

In a hospital-based cytology screening programme for the early detection of preinvasive lesions of the uterine cervix, 166 women with abnormal smears (human papillomavirus (HPV) changes, cervical intraepithelial neoplasia (CIN) and invasive carcinoma) were referred to the central colposcopy clinic between January 1989 and December 1991. The colposcopist (V.S.) was able to take a direct biopsy in 156 cases. In the remaining 10-cases, biopsy could not be taken because of unsatisfactory colposcopy. A cytohistological correlation was obtained in 121/156 (77.5%) cases, and the remaining 35 cases showed a disparity in diagnosis. These were reviewed by one of us (P.S.) and the reasons for underdiagnosis/false negatives and overdiagnosis/false-positive results were analysed. It was found that sampling error was the cause of false negativity and underdiagnosis in most cases while interpretative errors resulted in the overdiagnosis and false-positive smears. The reasons for interpretative errors were studied in detail.

Cytodiagnosis↗
PubMed1997

Ischemic preconditioning triggers phospholipase D signaling in rat heart.

Recent studies have indicated that repeated brief episodes of ischemia and reperfusion render the myocardium more tolerant to subsequent lethal ischemic injury. In view of the previous observations that ischemia-reperfusion potentiates phospholipase D signaling and that such signaling is beneficial for the heart, we investigated whether a similar phospholipase D signaling is responsible for the beneficial effects associated with repeated ischemia and reperfusion. Using an isolated perfused working rat heart model, we demonstrated that four brief episodes of 5 min of ischemia and 10 min of reperfusion reduced the incidence of ventricular arrhythmias, enhanced the postischemic ventricular performance, and decreased the release of creatine kinase from the reperfused heart, with simultaneous activation of phospholipase D generating the second messengers diacylglycerol and phosphatidic acid and leading to the translocation and activation of protein kinase C. The specific antiphospholipase D antibody blocked the activation of phospholipase D and attenuated the generation of diacylglycerol and phosphatidic acid and activation of protein kinase C. In concert, phospholipase D inhibition increased the incidence of ventricular arrhythmias, blocked the beneficial effects of preconditioning on the ventricular performance, and increased the amount of creatine kinase release from the coronary effluent. The results of this study indicate that repeated brief episodes of ischemia and reperfusion exert beneficial effects on the intact rat heart by triggering the activation of a phospholipase D signaling mechanism.

Animals↗
PubMed1997

Evaluation of antioxidant effectiveness of a few herbal plants.

We have screened a number of plants from the Indian soil for potential antioxidant properties out of which fifteen extracts were found to be positive. Leaves/bulk from the plants were crushed and extracted with organic solvents by three different ways. The first group of plants were extracted with CHCL3:CH3OH (2:1), evaporated, partitioned between petroleum ether and methanol (9:1), aqueous methanolic part re-partitioned between methanol:H2O (4:1) and dichloromethane. Methanol was evaporated from the aqueous methanolic part and extracted with n-butanol. The second group of plants were extracted with methanol followed by partitioning between petroleum ether and CH3OH. The rest of the extraction procedure was the same as above. A third extraction procedure was used for Ocimum sanctum which after extraction with CHCL3:CH3OH (2:1), partitioned between CCL4 and CH3OH:H2O (9:1). Aqueous methanolic part was repartitioned between CH3OH:H2O (4:1) and CHCl3 and CHCl3 soluble part was used for the study. Free radical scavenging activities of the plant extracts were examined by chemiluminescence method. Peroxyl radical was generated from 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH), superoxide radical (O2-) from xanthine/xanthine oxidase (XO) and hydroxyl radical (OH) from Xanthine/XO/FeCl3/ EDTA. In addition, O2- and OH. scavenging activities were also determined by cytochrome C reduction and deoxyribose oxidation methods, respectively. The results of this study demonstrate that these plant extracts possess potent antioxidant activities.

Animals↗
PubMed1997

Extracellular Mg++ manipulation prevents the proarrhythmic activity of cromakalim in ischemic/reperfused diabetic hearts.

Cromakalim, an adenosine triphosphate-sensitive potassium channel opener, shows proarrhythmic activity at moderate doses (1-10 micromol/liter) in the ischemic and reperfused myocardium. We studied the effects of extracellular Mg++ ([Mg++]o) on the incidence of reperfusion-induced ventricular fibrillation and ventricular tachycardia in isolated working hearts (n = 12 in each group) subjected to 20 min of global ischemia followed by 30 min of reperfusion, a model eliciting a low incidence of reperfusion arrhythmias, obtained from 8-wk streptozotocin-induced diabetic rats. Cromakalim, at a concentration of 3 micromol/liter, perfused 5 min before the induction of ischemia and throughout reperfusion increased the incidence of ventricular fibrillation and ventricular tachycardia from their drug-free diabetic control values of 25 and 42% ([Mg++]o = 1.2 mmol/liter) to 92% (P < .05) and 100% (P < .05), respectively. Glibenclamide at a concentration of 3 micromol/liter prevented the proarrhythmiac activity of cromakalim. Increasing concentration of [Mg++]o to 2.4, 3.6 and 4.8 mmol/liter in the perfusion buffer, the arrhythmogenic effect of cromakalim was also abolished. Thus, with 2.4, 3.6 and 4.8 mmol/liter of [Mg++]o perfused before the administration of cromakalim and the onset of ischemia, the incidence of reperfusion-induced ventricular tachycardia was reduced from 92% (in cromakalim treated group) to 67%, 42% (P < .05), and 25% (P < .05), respectively. The incidence of reperfusion-induced ventricular tachycardia showed the same pattern. Elevated [Mg++]o prevented the cromakalim-induced cellular Na+ gain and K+ loss, measured by atomic absorption spectrophotometer. [Mg++]o could prevent the proarrhythmic activity of cromakalim, and the use of cromakalim as an antihypertensive or antiischemic agent may be of particular concern in the population of postischemic diabetic subjects who are known to be at high risk of sudden coronary death.

Animals↗
PubMed1997

Reduction in the cumulative incidence rate of cervical cancer by one life time selective screening.

Mass scale cervical cytology which is the most accepted strategy for the control of cervical cancer cannot be undertaken in developing countries in view of paucity of resources, hence a need arises to examine alternate strategy. The present exercise attempts to study the reduction in cumulative incidence rate of cervical cancer by one life time selective screening. The results revealed that cumulative incidence rate (CIR) of cervical cancer per 100,000 in cohort of women during the age of 20 to 64 years was found to be 2555.0 in the absence of screening. One life time selective screening at the age of 40 and 45 years showed the reduction of 11.6 and 17.2% in CIR respectively where as respective estimates in case of complete screening at mentioned age groups were found to be 21.5% and 25%. In order to further conserve the resources the strategy seems to be optimum for developing countries.

Adult↗
PubMed1996

Ischemic preconditioning triggers the activation of MAP kinases and MAPKAP kinase 2 in rat hearts.

While much is known about the beneficial effects of myocardial stress adaptation, relatively less information is available about the adaptive mechanisms. To explore the signaling pathways of stress adaptation, isolated working rat hearts were divided into three groups. Group I was adapted to stress by conventional technique of repeated ischemia and reperfusion consisting of 5 min of ischemia followed by 10 min of reperfusion, repeated four times. Group II was treated with 100 microM of genistein, a tyrosine kinase inhibitor, followed by preconditioning as described for group I. The third group, perfused with buffer only for 60 min, served as control. All hearts were subjected to 30 min of ischemia followed by 30 min of reperfusion. The results of our study demonstrated better postischemic myocardial functions in the preconditioned hearts as evidenced by increased aortic flow, coronary flow, developed pressure and lesser amount of tissue injury as evidenced by the decreased creatine kinase release. The preconditioning effects were associated with enhancement of phospholipase D activity in the heart. The preconditioning effect was almost abolished by the genistein treatment which also prevented the enhancement of phospholipase D activities. Additionally, preconditioning of the rat hearts stimulated protein kinase C, MAP kinase, and MAPKAP kinase 2 activities which were inhibited by genistein. The results identifies for the first time tyrosine kinase-phospholipase D as potential signaling pathway for ischemic preconditioning, and implicates the involvement of multiple protein kinases in myocardial adaptation to ischemia.

Animals↗
PubMed1996

Nitric oxide/carbon monoxide. A molecular switch for myocardial preservation during ischemia.

BACKGROUND: In heart, NO is produced from L-arginine catalyzed by NO synthase, and CO is formed during the conversion of bilirubin from heme by the action of heme oxygenase. NO, which exerts its biological actions through cGMP and heme, has recently been implicated in myocardial protection during ischemia and reperfusion. We hypothesized that the intracellular signaling by NO may be modulated by heme oxygenase. METHODS AND RESULTS: To test this hypothesis, isolated rat hearts were perfused for 10 minutes with one of the following: (1) buffer alone; (2) 3 mmol/L L-arginine, a precursor for NO; (3) 650 mumol/L zinc protoporphyrin, a heme oxygenase inhibitor; (4) 3 mmol/L L-arginine plus 650 mumol/L zinc protoporphyrin; (5) 15 mumol/L methylene blue, a cGMP inhibitor; or (6) 3 mmol/L L-arginine plus 15 mumol/L methylene blue. Hearts were then made ischemic for 30 minutes, followed by 30 minutes of reperfusion. L-Arginine afforded significant myocardial protection, as evidenced by increased developed pressure (DP) (53.3 +/- 4.3 versus 35.4 +/- 1.8 for control), dP/dtmax (2405 +/- 125 versus 1758 +/- 117 for control), aortic flow (23 +/- 1.5 versus 9.4 +/- 1.6 for control), and coronary flow (CF) (23.0 +/- 0.8 versus 19.0 +/- 1.6 for control) at the end of reperfusion. Protoporphyrin tended to reduce these values compared with L-arginine alone (DP, 27.5 +/- 1.4; dP/dtmax, 1400 +/- 78; CF, 17 +/- 0.5), suggesting a contribution of heme oxygenase in addition to NO for myocardial preservation. Increased mRNAs for the heme oxygenase were noticed in the ischemic reperfused myocardium. Contents of cGMP, the second messenger for NO signaling, increased in the L-arginine group (1.6 +/- 0.1 versus 1.1 +/- 0.1 for control) and were reduced by protoporphyrin. cGMP was completely inhibited by methylene blue, which also retarded postischemic myocardial functional recovery. Malonaldehyde formation, a presumptive marker for free radical generation, was decreased in the L-arginine group (0.053 +/- 0.003) compared with control (0.089 +/- 0.005) but was increased in the protoporphyrin group (0.09 +/- 0.003) compared with the L-arginine group. In vitro studies demonstrated that NO was able to reduce the reactive oxygen species produced by myoglobin, especially oxoferrylmyoglobin, which either are present in heart or are formed in high concentrations during the reperfusion of ischemic myocardium. CONCLUSIONS: The results suggest that NO contributes to myocardial preservation by both cGMP-dependent and cGMP-independent mechanisms, the former being modulated by CO signaling and the latter by virtue of its antioxidant action.

Animals↗
PubMed1996

Critical timing of nitric oxide supplementation in cardioplegic arrest and reperfusion.

BACKGROUND: It has been shown that increased nitric oxide (NO) generation is associated with improved myocardial preservation during ischemia/reperfusion. This study sought to determine the optimal timing for NO supplementation in the setting of cardioplegic arrest, regional ischemia, and reperfusion. METHODS AND RESULTS: Isolated working rat hearts were arrested with normothermic oxygenated potassium cardioplegia for 5 minutes, followed by 60 minutes of normothermic continuous cardioplegic administration with left anterior descending coronary artery (LAD) occlusion. The hearts were divided into four groups. Hearts in group 1 were ischemic/reperfused controls without L-arginine treatment. Hearts in group 2 were perfused with 3 mmol/L L-arginine for 5 minutes before cardioplegic arrest. Hearts in group 3 were perfused with 3 mmol/L L-arginine in the cardioplegia solution. Hearts in group 4 were perfused with 3 mmol/L L-arginine for 5 minutes only during initial reperfusion. Myocardial contractile function after 30 minutes of reperfusion was significantly better in group 2 compared with the other groups and was significantly lower in group 4 than group 1. Coronary flow, although decreased from base line in all groups at 30 minutes of reperfusion, was highest in group 2. The tissue accumulation of cGMP in groups 2 and 3 increased significantly after L-arginine infusion compared with the control group (group 1). In contrast, the LAD regional cGMP after reperfusion in group 4 was comparable to group 1 and significantly lower than groups 2 and 3, whereas the circumflex region cGMP in group 4 was significantly increased over group 1, comparable to groups 2 and 3. LDH release in groups 2 and 3 was significantly lower compared with groups 1 and 4. CONCLUSIONS: As assessed by myocardial function and LDH release, L-arginine is most beneficial when given before cardioplegic arrest, effective during cardioplegic arrest, and detrimental during reperfusion. This suggests that L-arginine given during reperfusion is deleterious to optimal recovery of myocardial function in this ischemic model and that the effect of NO generation in the ischemic/reperfused myocardium may be dependent on the condition of the endothelium.

Animals↗
PubMed1996

Phospholipase D plays a role in ischemic preconditioning in rabbit heart.

BACKGROUND: Activation of protein kinase C (PKC) is thought to be a critical step in ischemic preconditioning. Many receptor agonists activate PKC via stimulation of phospholipase C (PLC), which degrades membrane phospholipids to diacylglycerol (DAG), an important PKC cofactor. However, adenosine receptors, critical components of the prototypical preconditioning pathway, are not thought to couple to PLC in the cardiomyocyte. We therefore tested whether ischemic preconditioning or adenosine might instead activate phospholipase D (PLD) to produce DAG. METHODS AND RESULTS: PLD activity was measured in isolated rabbit hearts. Ischemic injury was evaluated in either isolated rabbit hearts or dispersed myocytes. PLD activity doubled from a control level of 74.8 +/- 10.0 to 140.0 +/- 11.5 mumol.min-1.g-1 (P < .025) after two 5-minute periods of global ischemia separated by 5 minutes of reperfusion. A similar increase was noted after the heart had been exposed to (R)-N6-(2-phenylisopropyl)-adenosine [(R)-PIA] for 20 minutes. When sodium oleate, which activates PLD, was administered to isolated hearts before a 30-minute coronary occlusion, infarct size (15.6 +/- 2.0% of the risk zone) was significantly smaller than in untreated hearts (30.4 +/- 2.2%; P < .01). Exposure to sodium oleate significantly prolonged the rate of isolated myocyte survival during simulated ischemia. Propranolol 100 mumol/L, which blocks DAG production from metabolites produced by PLD catalysis, completely abolished the protective effects of both metabolic preconditioning and (R)-PIA exposure in myocytes. CONCLUSIONS: We conclude that PLD stimulation is involved in the protection of ischemic preconditioning in the rabbit heart.

Adenosine↗