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Biomedical subjects

D K Das

Publications and source records attributed to D K Das.

At least 253 records · Page 14Linked to original sources
PubMed1989

Improvement of myocardial function by trifluoperazine, a calmodulin antagonist, after acute coronary artery occlusion and coronary revascularization.

Activation of an intracellular calcium-calmodulin complex may play an important role in myocardial injury induced by ischemia and reperfusion. Trifluoperazine, a calmodulin antagonist, was used before ischemia to enhance myocardial preservation by preventing intracellular calcium accumulation. The experimental model used an isolated in situ pig heart (19 control animals and 15 trifluoperazine-treated animals) subjected to occlusion of the left anterior descending coronary artery for 60 minutes followed by 60 minutes of hypothermic potassium crystalloid cardioplegic arrest and 60 minutes of reperfusion. Myocardial segmental function measured by ultrasonic crystals showed that active systolic segment shortening was abolished in the distribution of the left anterior descending artery after 60 minutes of occlusion irrespective of the treatment, whereas that not in the distribution of the left anterior descending artery increased by about 15% in both groups of animals. Restoration of systolic segment shortening in the distribution of the left anterior descending artery 60 minutes after reperfusion was 12% and 42% of baseline levels in untreated and trifluoperazine-treated animals, respectively (p less than 0.01). This improvement in segmental function by trifluoperazine was reflected in significantly (p less than 0.05) better global myocardial contractility and compliance and in significantly (p less than 0.01) greater total coronary blood flow and myocardial oxygen consumption. Trifluoperazine also increased myocardial creatine phosphate content in the distribution of the left anterior descending artery (p less than 0.01) during reperfusion, and creatine kinase release was reduced (p less than 0.05). Our results suggest that trifluoperazine improved regional myocardial function after acute occlusion of the left anterior descending artery and reperfusion and that global cardiac performance was thereby improved. The beneficial effects of trifluoperazine may be exerted by prevention of myocardial injury associated with the calcium-calmodulin complex in ischemic and reperfused myocardium.

Adenosine Triphosphate↗
PubMed1988

Separation of fatty acid binding protein by high-performance mixed-mode chromatography.

Fatty acid binding protein (FABP) (14 kDa), can regulate the levels of tissue free fatty acids by binding them with high affinity. Since free fatty acids are known to accumulate in the ischemic myocardium, it is likely that FABP has a significant role in regulating their concentration in ischemic heart. FABP has recently been purified from other proteins, but the method requires several hours and special techniques. In this report, we describe a rapid high-performance liquid chromatographic method for separating and isolating the FABP from myocardial tissue biopsies. About 25-50 micrograms of rat heart cytosol was incubated with 2 nmol of the potassium salt of [9,10-3H]oleate (25,000 cpm) for 10 min at 37 degrees C. This was then injected onto a Bio-Rad (Richmond, CA, U.S.A.) TSK-125 column. The sample was run using a low-salt isocratic mobile phase containing 10 mM potassium phosphate buffer (pH 7) and 1 mM dithiothreitol, and at a flow-rate of 0.8 ml/min. The heart cytosol, when incubated with isotopic oleate, was resolved into two radioactive peaks, one eluting in the area of serum albumin (retention time 9.6 min) and the other corresponding to a retention time of 12.9 min. The sodium dodecyl sulfate polyacrylamide gel electrophoretic profile of the later peak revealed a major protein band of ca. 14 kDa. Rat heart FABP purified by gel filtration and ion-exchange chromatography coeluted with the second radioactive peak.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Novel dual-wavelength monitoring approach for the improved rapid separation and estimation of adenine nucleotides and creatine phosphate by high-performance liquid chromatography.

A rapid and improved method for the simultaneous quantification of adenine nucleotides, including adenosine triphosphate, adenosine diphosphate, adenosine monophosphate, as well as creatine phosphate by high-performance liquid chromatography is described. A programmable multi-wavelength UV detector was used to monitor the effluent initially at 210 nm for 4 min to measure creative phosphate, and then at 259 nm for 6 min to quantitate adenosine mono-, di- and triphosphate. The method is, thus, not only rapid, but also extremely sensitive because of the utilization of corresponding absorption maxima for creatine phosphate and adenine nucleotides, rather than measuring all of them at a single wavelength. In addition, computer-generated standard curves were used to estimate these compounds, thereby improving the accuracy of the measurements. Since myocardial high-energy phosphate levels are widely measured because they are reliable parameters for myocardial preservation during ischemia, these compounds were assayed in pig heart prior to and following ischemia. The results were compared with those obtained by conventional high-performance liquid chromatographic assay methods in order to examine the validity of this method. Our results indicate that this is indeed a novel method, which is more rapid as well as sensitive and accurate compared with other methods.

Adenine Nucleotides↗
PubMed1988

Analysis of tissue free fatty acids isolated by aminopropyl bonded-phase columns.

Gas chromatographic analysis revealed that polyunsaturated fatty acids such as arachidonic acid and total tissue free fatty acids isolated from an aminopropyl bonded-phase column yield a two- to three-fold higher recovery of arachidonic acid as compared to those isolated from thin-layer chromatographic plates. This method was further improved by packing the aminopropyl bonded phase in glass columns, since the glass column significantly eliminated the other contaminants (from polypropylene columns) coeluting with fatty acids in both a neutral lipid thin-layer chromatographic system and on a 5% DEGS-PS column of gas chromatographic analysis. In aminopropyl bonded-phase columns, the standard triglycerides and phospholipids were completely separated from free fatty acids as judged by gas chromatographic analysis. These results warrant the use of an aminopropyl bonded-phase column for the isolation of free fatty acids to obtain better recovery of polyunsaturated fatty acids.

Animals↗
PubMed1988

Improved myocardial performance induced by clofibrate during reperfusion after acute myocardial infarction.

The increase of cellular fatty acids appears to be one of the causes of the myocardial injury during ischemia and reperfusion. This study was designed to examine whether a hypolipidemic drug such as clofibrate can reduce the myocardial injury during ischemia and reperfusion. Clofibrate was fed to experimental pigs for 9 days. Isolated in situ hearts from both experimental and control pigs were subjected to 60 min of regional ischemia induced by occluding the left anterior descending coronary artery, followed by 60 min of global ischemia by hypothermic cardioplegic arrest and 60 min of reperfusion. The clofibrate feeding resulted in the better cardiac performance as judged by increased coronary blood flow, improved left ventricular function, and reduced myocardial injury as judged by creatine kinase release. Although the clofibrate-fed animals contained higher levels of thiobarbituric reactive materials, the free fatty acid levels of plasma and myocardium were much lower compared with control animals. The clofibrate feeding was also associated with increased peroxisomal catalase and beta-oxidation of fatty acids. These results suggest that decreased levels of free fatty acids in the plasma and the myocardium and increased catalase activity induced by antilipolytic therapy appear to provide beneficial effects to the myocardium during ischemia and reperfusion.

Animals↗
PubMed1988

Adenosine transport by the lung.

Adenosine, a nucleoside and potent vasodilator, has been found to be taken up by the lung and converted by deamination into inosine and hypoxanthine. In a single circulation through an isolated rat lung, 69.3 +/- 3.3% of infused [14C]adenosine (10 microM) was removed from the circulation. Uptake of [14C]adenosine remained unchanged when deamination of adenosine was inhibited by 8-azaguanine or coformycin. In a single passage of adenosine through the pulmonary artery, very little of the deaminated products appeared in the pulmonary circulation, but when adenosine was recirculated through the pulmonary circulation inosine and hypoxanthine appeared in the venous effluent. These adenosine metabolites were also taken up by the lung. A major portion of the circulating adenosine was transported into the lung, where it was used to synthesize adenine nucleotides. Inhibition of adenosine kinase by iodotubercidin resulted in reduced formation of ATP and ADP. Uptake of adenosine by the lung was saturable on a concentration gradient and was a passive process because it was not affected by the absence of glucose or the presence of ouabain. Km and Vmax for adenosine transport were 0.227 mM and 4.6 mumol.min-1.g lung-1, respectively. Adenosine transport was inhibited by adenosine analogues, and the inhibitions were found to be competitive in nature. These results suggest that a specific and rate-limiting transport system exists in the lung for adenosine.

Adenosine↗
PubMed1988

Alpha 1-adrenoceptor-mediated phosphoinositide breakdown and inotropic response in rat left ventricular papillary muscles.

alpha 1-Adrenoceptor stimulation of rat left ventricular papillary muscles by phenylephrine in the presence of propranolol resulted in rapid breakdown of phosphatidylinositol 4,5-bisphosphate (PI-4,5-P2) and a triphasic inotropic response in a concentration-dependent manner. The release of inositol trisphosphate (IP3) was maximum within 30 seconds and remained high for at least 30 minutes. The IP3 formation was associated with a rapid, but small, increase in contractile force followed by a transient decline in the contractility prior to the development of a sustained and more pronounced positive inotropic response. Inhibition of PI-4,5-P2 hydrolysis by the alpha 1-adrenergic antagonist prazosin or the PI-4,5-P2 phosphodiesterase inhibitor neomycin blocked all components of the inotropic responses. Combined addition of 2,3-diphosphoglyceric acid, a competitive inhibitor of IP3 phosphatase, with phenylephrine doubled the IP3 formation and potentiated the initial phases of inotropic responses but had no effect on the sustained positive inotropic response. Nifedipine and Mn2+ did not block the transient inotropic responses but inhibited the sustained positive inotropic response. alpha 1-Adrenoceptor stimulation resulted in restoration of slow responses in the high K+-depolarized muscles in the time course similar to that of the development in the sustained positive inotropic response. Addition of phorbol-12,13-dibutyrate alone or in combination with caffeine or A23187 failed to produce a sustained positive inotropic effect, but pretreatment with this phorbol ester (1-100 nM) for 30 minutes resulted in dose-dependent potentiation of alpha 1-adrenoceptor-mediated sustained positive inotropic effect associated with enhanced slow responses. These results suggest that the inotropic effects mediated by cardiac alpha 1-adrenoceptor stimulation occur through the phosphodiesteratic cleavage of PI-4,5-P2, such that IP3 may produce transient inotropic effects by mobilizing intracellular Ca2+, while diacylglycerol, along with cofactors that are also generated on alpha 1-adrenoceptor stimulation, may provoke a sustained positive inotropic effect by potentiating slow Ca2+ channels through activation of protein kinase C.

2,3-Diphosphoglycerate↗
PubMed1988

Enhanced phosphodiesteratic breakdown and turnover of phosphoinositides during reperfusion of ischemic rat heart.

In this study, we examined phosphoinositide metabolism during ischemia and reperfusion using an isolated and perfused rat heart. When myocardial phosphoinositides were prelabeled with [3H]inositol, reperfusion after 30 minutes of normothermic global ischemia resulted in significant accumulations of radiolabeled inositol phosphate, inositol bisphosphate, and inositol trisphosphate. Isotopic incorporation of [3H]inositol into phosphatidylinositol, phosphatidylinositol-4-phosphate, and phosphatidylinositol-4,5-bisphosphate was increased significantly in the heart reperfused with [3H]inositol after 30 minutes of ischemia compared with that perfused with [3H]inositol after 30 minutes of nonischemic perfusion. However, isotopic incorporation of [3H]glycerol into diacylglycerol, phosphatidic acid, and all of the three phosphoinositides was diminished in the reperfused hearts. Reperfusion of the ischemic heart prelabeled with [14C]arachidonic acid resulted in significant increases in [14C]diacylglycerol and [14C]phosphatidic acid. The enhanced accumulations of [3H]inositol phosphates during reperfusion were not affected by treatment with prazosin plus atropine or indomethacin, but were inhibited by hypoxic reperfusion, reperfusion with Ca2+-free buffer, or by mepacrine. These results suggest that myocardial reperfusion stimulates phosphodiesteratic breakdown and turnover of phosphoinositides, and increased Ca2+ influx caused by reperfusion may be involved in the mechanism of stimulation of phosphatidylinositol-specific phospholipase C activity in the rat heart.

Animals↗
PubMed1988

Fine needle aspiration cytology (FNAC) of the testes in childhood acute lymphoblastic leukemia and non-Hodgkin's lymphoma: preliminary report.

Eighteen patients with childhood acute lymphoblastic (ALL) or non-Hodgkin's lymphoma (NHL) in remission and 2 patients with ALL in suspected testicular relapses were studied by testicular fine needle aspiration cytology (FNAC). Well-preserved testicular cells, both singly and in small clusters, were considered indicative of an adequate aspiration. Of 18 patients in remission, 17 had at least one adequate sample from each testis and one showed evidence of leukemic infiltrate. None of these patients experienced a relapse during a median follow up of 4 years. In 2 other patients with clinically suspected testicular relapses, the smears from fine needle aspirates contained numerous malignant lymphoid cells that could be readily distinguished from seminiferous tubular cells. The observations indicate that FNAC is a promising new approach to study testicular conditions in childhood ALL and NHL. A larger prospective study and accumulation of additional follow-up data is required before a definitive evaluation of the technique can be made.

Adolescent↗
PubMed1988

Immunohistochemical identification of human papillomavirus infection in tissues from cervical precancerous and early cancerous lesions among Indian women.

Paraffin sections of 50 cervical condyloma biopsies from patients with precancerous and early cancerous lesions of the uterine cervix were screened for human papillomavirus (HPV) antigen by peroxidase-antiperoxidase (PAP) staining using genus specific anti-bovine papillomavirus serum (rabbit). The intra-nuclear HPV positivity was observed in 20 percent (10/50) of biopsies studied. Further, proportionately larger number of cases with moderate dysplasia (CIN II) associated with koilocytotic changes were found to be positive for HPV antigen (40%). No HPV positivity was detected from inflammation and mild dysplasia (CIN I) cases. The study strongly supports the association of HPV infection in the process of neoplastic transformation of the uterine cervix.

Antigens, Viral↗
PubMed1988

Positive inotropic effect and phosphoinositide breakdown mediated by arachidonic acid and prostaglandin F2 alpha.

We investigated the mechanism of arachidonate- and prostaglandin-induced alteration of cardiac contractile activity in isolated rat left ventricular papillary muscles. Superfusion with 10(-6) to 10(-4) M arachidonic acid resulted in a slow developing positive inotropic effect (PIE) in a concentration-dependent manner. The PIE was abolished by pretreatment with 10(-5) M indomethacin. Prostaglandin (PG) F2 alpha also produced a significant PIE in a concentration-dependent manner, but the EC50 value was approximately 2 orders of magnitude lower and the maximum contractile response was 2-fold higher than those of arachidonate. PGE2 and PGI2 were without an effect on contractile force at concentrations ranging from 10(-9) to 10(-6) M. Both arachidonate and PGF2 alpha provoked slow responses in the partially depolarized muscles in a time course similar to that of development in the PIE. Neither arachidonate nor PGF2 alpha affected tissue levels of cyclic AMP and cyclic GMP, but these molecules increased accumulations of [3H]inositol phosphates (IPs) in a concentration-dependent manner similar to that observed for their PIE. The enhanced accumulation of [3H]IPs induced by arachidonate was abolished by pretreatment with 10(-5) M indomethacin. Although an increase in [3H]IP level was relatively rapid in PGF2 alpha-treated tissues, maximum accumulations of [3H]IPs were identical between arachidonate- and PGF2 alpha-treated tissues. Thus, for comparable increases in [3H]IPs, there was a greater PIE with PGF2 alpha than with arachidonate.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Potential use of indium-111-labeled polymorphonuclear leukocytes for the detection of lung microvascular injury.

The early stages of microvascular injury are often difficult to detect due to the lack of a suitable marker to assess such an injury. We utilized the well known phenomenon of polymorphonuclear leukocyte (PMN) migration to the microvascular bed as a result of acute inflammatory reactions originating from the damaged cells. A radiotracer technique was developed, employing indium-111-labeled PMN for the detection of microvascular injury induced by hyperoxia. New Zealand white rabbits exposed to either 100% oxygen or air for various intervals of time were injected with indium-111-tropolone or oxine-labeled PMNs. Influx of radioactive PMN into the lung was detected in 72 hr/oxygen-exposed animals using gamma scintigraphic technique. Analysis of dry/wet ratios and histological examinations of the lung biopsies indicated noncardiogenic edema formation at this stage. Mortality was 50% beyond 96 hr/oxygen exposure. Our study thus provided a means to detect early microvascular injury during 72 hr/oxygen-exposure, which was not detectable by any other noninvasive techniques. The use of indium-111-labeled PMN thus appears to be a potentially important tool for the clinical assessment of lung microvascular injury.

Animals↗
PubMed1988

Role of polymorphonuclear leukocytes in hyperoxic lung injury. Prevention of neutrophil influx into the lung endothelium during oxygen exposure by ibuprofen.

The present study examines the role of PMN in hyperoxic lung injury using a nonsteroidal anti-inflammatory drug, ibuprofen. New Zealand white rabbits were exposed to 100% oxygen or air for 1 to 4 days. The animals were divided into two groups: the treatment group received ibuprofen with drinking water, and the control group received water alone. After exposure to oxygen or air, the rabbits were injected with indium-III-oxine labeled PMN. Influx or radioactive PMN into the lung was detected using gamma scintigraphic technique only in 72 h and 96 h oxygen-exposed animals which were not treated with ibuprofen. Ibuprofen-treated animals did not exhibit any PMN influx into the lung. Blood gas analysis of all 72 h oxygen-exposed animals did not show any abnormal values, although analysis of dry/wet weight ratios and histopathological examinations indicated noncardiogenic edema formation. After 96 h of oxygen exposure, both ibuprofen-treated and untreated groups suffered from severe acidosis. Gross cytoplasmic edema and partial destruction of lung endothelium were also observed. Mortality was 50% after 96 h of oxygen exposure. Our study, thus, demonstrates that ibuprofen cannot prevent hyperoxic lung injury although it inhibits the influx of PMN into the injured lung, suggesting that PMN are not directly involved in the injury process.

Animals↗
PubMed1988

Effect of ischemia and reperfusion of the myocardium on in vitro beta-oxidation of fatty acids.

The in vivo oxidation of perfused [14C]-labeled fatty acids has been shown to decrease dramatically in hypoxic hearts. This study addresses the influence of ischemia and reperfusion on the enzymic activities of beta-oxidation of fatty acids in mitochondria and of peroxisomal origin. The rate of beta-oxidation of fatty acids in the isolated mitochondria from myocardium of swine fed control diet declined about 20% by the ischemic insult induced by hypothermic cardioplegic arrest. Upon reperfusion, the rate of mitochondrial beta-oxidation returned to a normal level. In clofibrate-fed animals, the rate of mitochondrial beta-oxidation did not vary significantly between control, ischemic, and perfused tissues. Furthermore, neither in control nor in clofibrate-fed animals did the rates of peroxisomal beta-oxidation of fatty acids vary significantly in the ischemic or reperfused tissues as compared to that of preischemic controls. These results suggest that ischemia does not contribute to any loss of enzymic activity in beta-oxidation of fatty acid cycles either in mitochondria or peroxisomes. Furthermore, the feeding of 0.5% (w/w) clofibrate to pigs increased the rate of mitochondrial beta-oxidation of fatty acids only by 50% while that of peroxisomes increased threefold. A similar threefold increase in catalase activity was also produced by clofibrate feeding. These results suggest that the heart plays a role in the hypolipidemic action of clofibrate.

Animals↗