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  • 1
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Although hepatocyte growth factor (HGF) and its receptor are expressed in various regions of the brain, their effects and mechanism of action under pathological conditions remain to be determined. Over-activation of the N-methyl-d-aspartate (NMDA) receptor, an ionotropic glutamate receptor, has been implicated in a variety of neurological and neurodegenerative disorders. We investigated the effects of HGF on the NMDA-induced cell death in cultured hippocampal neurons and sought to explore their mechanisms. NMDA-induced cell death and increase in the number of terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL)-positive cells were prevented by HGF treatment. Although neither the total amounts nor the mitochondrial localization of Bax, Bcl-2 and Bcl-xL were affected, caspase 3 activity was increased after NMDA exposure. Treatment with HGF partially prevented this NMDA-induced activation of caspase 3. Although the amount of apoptosis-inducing factor (AIF) was not altered, translocation of AIF into the nucleus was detected after NMDA exposure. This NMDA-induced AIF translocation was reduced by treatment with HGF. In addition, increased poly(ADP-ribose) polymer formation after NMDA exposure was attenuated by treatment with HGF. These results suggest that the protective effects of HGF against NMDA-induced neurotoxicity are mediated via the partial prevention of caspase 3 activity and the inhibition of AIF translocation to the nucleus.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Tyrosine phosphorylation of the NMDA receptor has been implicated in the regulation of the receptor channel. We investigated the effects of transient (15 min) global ischemia on tyrosine phosphorylation of NMDA receptor subunits NR2A and NR2B, and the interaction of NR2 subunits with the SH2 domain of phosphatidylinositol 3-kinase (PI3-kinase) in vulnerable CA1 and resistant CA3/dentate gyrus of the hippocampus. Transient ischemia induced a marked increase in the tyrosine phosphorylation of NR2A in both regions. The tyrosine phosphorylation of NR2B in CA3/dentate gyrus after transient ischemia was sustained and greater than that in CA1. PI3-kinase p85 was co-precipitated with NR2B after transient global ischemia. The SH2 domain of the p85 subunit of PI3-kinase bound to NR2B, but not to NR2A. Binding to NR2B was increased following ischemia and the increase in binding in CA3/dentate gyrus (4.5-fold relative to sham) was greater than in CA1 (1.7-fold relative to sham) at 10 min of reperfusion. Prior incubation of proteins with an exogenous protein tyrosine phosphatase or with a phosphorylated peptide (pYAHM) prevented binding. The results suggest that sustained increases in tyrosine phosphorylation and increased interaction of NR2B with the SH2 domain of PI3-kinase may contribute to altered signal transduction in the CA3/dentate gyrus after transient ischemia.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Neurogenesis in the adult brain is promoted by various stimulations. NMDA receptor blockade enhances neurogenesis in the hippocampal dentate gyrus. There is no agreed conclusion, however, as to whether newly generated neurons after NMDA receptor blockade obtain functional properties. We investigated the functional maturation of newly generated neurons after NMDA receptor blockade. In the dentate gyrus, 80% of newly generated cells differentiated into the phenotype of mature neurons at 29 days after the single intraperitoneal injection of an NMDA receptor antagonist MK-801. The number of newly generated neurons after MK-801 treatment was significantly greater than that in the saline-treated group. The neurogenic basic helix-loop-helix transcription factor NeuroD protein in the dentate gyrus after MK-801 treatment was expressed transiently in proliferative cells, but not in mature neurons. To determine functional properties of newly generated neurons, we administered NMDA to the lateral ventricle. As an in vivo response, we assessed extracellular-regulating kinase (ERK) phosphorylation. The newly generated neurons showed ERK phosphorylation by NMDA administration as seen in surrounding mature neurons. The number of newly generated neurons, which responded to NMDA receptor stimulation, increased with time after MK-801 treatment. The present study provides evidence that newly generated neurons in the adult hippocampus after NMDA receptor blockade acquire biochemical function in vivo.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Cardiovascular drug reviews 10 (1992), S. 0 
    ISSN: 1527-3466
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-4919
    Keywords: calcium accumulation ; calcium uptake ; Ca2−, Mg2+-ATPase ; contractile function ; vitamin 133 ; myocardium ; mitochondria ; sarcolemma ; sarcoplasmic reticulum ; Na+, K+-ATPase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The present study was designed to induce massive accumulation of calcium in the myocardium and to evaluate the effect of calcium overload on myocardial contractile function and biochemical activity of cardiac subcellular membranes. Rats were treated with an oral administration of 500,000 units/kg of vitamin D3 for 3 consecutive days, and their hearts were sampled on the 5th day for biochemical analysis. On the 4th and 5th days, heart rate, mean aortic pressure, left ventricular systolic pressure and left ventricular dP/dt were significantly lowered in vitamin D3-treated rats, demonstrating the existence of appreciable myocardial contractile dysfunction. Marked increases in the myocardial calcium (67-fold increase) and mitochondrial calcium contents (24-fold increase) were observed by hypervitaminosis D3. Mitochondrial oxidative phosphorylation and ATPase activity were significantly reduced by this treatment. A decline in sarcolemmal Na+, K+-ATPase activity was also observed, while relatively minor or insignificant changes in calcium uptake and ATPase activities of sarcoplasmic reticulum were detectable. Electron microscopic examination revealed calcium deposits in the mitochondria after vitamin D3 treatment. The results suggest that hypervitaminosis D3 produces massive accumulation of calcium in the myocardium, particularly in the cardiac mitochondrial membrane, which may induce an impairment in the mitochondrial function and eventually may lead to a failure in the cardiac contractile function.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-4919
    Keywords: cardiac contraction ; cardiomyocyte ; encosapentaenoic acid ; ischemia and reperfusion injury ; perfused heart ; polyunsaturated fatty acid ; prostagalndin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The effects of eicosapentaenoic acid (EPA) and long-term treatment with EPA-ethylester (EPA-E) were examined in perfused rat hearts subjected to ischemia/reperfusion and adult rat cardiomyocytes subjected to hypoxia/reoxygenation. EPA (0.1 μM) improved postischmic contractile dysfunction of the ischemic/reperfused heart. EPA (10 μM) attenuated hypoxia/reoxygenation-induced morphological deterioration of cardiomyocytes. The results suggest the presence of direct cardioprotective effects of EPA. Rats were orally treated for 4 weeks with 1 g/kg/day of EPA-E to elucidate ex vivo effects of EPA, and the fatty acid composition of cardiac phospholipids was determined. The percent ratio of EPA in total fatty acids of cardiac phospholipids increased whereas that of arachidonic acid decreased. The percent ratio of n-3/n-6 fatty acid did not increase. Treatment with EPA-E did not improve the post-ischemic contractile function, but attenuated the ischemia/reperfusion-induced release of prostaglandins during reperfusion. Treatment with EPA-E preserved a better morphological appearance of the cardiomyocytes subjected to hypoxia/reoxygenation. The results suggest that the mechanisms responsible for cytoprotective effects of hypoxic/reoxygeanted cardiomyocytes or inhibition of metabolic alterations of the ischemic/reperfused heart by long-term EPA-E treatment did not contribute substantially to recovery of post-ischemic contractile dysfunction. The direct in vitro effects of EPA may play a role in the protection of the heart from ischemia/reperfusion or hypoxia/reoxygenation injury.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-4919
    Keywords: pressure overload ; gene expression ; subcellular remodeling ; sarcoplasmic reticulum Ca2+-handling ; anti-hypertensive therapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The effects of propranolol and verapamil on contractile dysfunction, subcellular remodeling and changes in gene expression in cardiac hypertrophy due to pressure overload were examined. Rats were subjected to banding of the abdominal aorta and then treated with either propranolol (10 mg/kg daily), verapamil (5 mg/kg daily) or vehicle for 8 weeks after the surgery. Depression of the left ventricular function in the hypertrophied heart was associated with decreases in myofibrillar and myosin CA2+ ATPase activities as well as Ca2+-pump and Ca2+-release activities of the sarcoplasmic reticulum (SR). The level of a-myosin heavy chain (α-MHC) mRNA was decreased while that of β-MHC mRNA was increased in the pressure-overloaded heart. The level of SR Ca2+-pump ATPase (SERCA2) mRNA and protein content for SERCA2 were decreased in the pressure overloaded heart. Treatment of the hypertrophied animals with propranolol or verapamil resulted in preservation of the left ventricular function and prevention of the subcellular alterations. Shift in the α- and β-MHC mRNA levels and changes in the expression in SERCA2 mRNA level and protein content were also attenuated by these treatments. The results suggest that blockade of β-adrenoceptors or voltage-dependent calcium channels normalizes the cardiac gene expression, prevents subcellular remodeling and thus attenuates heart dysfunction in rats with cardiac hypertrophy. Furthermore, both cardiac β-adrenoceptors and L-type Ca2+-channels may be involved in the genesis of cardiac hypertrophy due to pressure overload.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1435-1803
    Keywords: Key words Glycolysis – preconditioning – protein kinase C – mitochondria – rat heart
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Objectives. A possible link between activation of PKC and improvement of energy metabolism during reperfusion in ischemic preconditioning hearts was examined. Methods. Isolated perfused rat hearts were preconditioned by 5-min ischemia and 5-min reperfusion in the presence and absence of a PKC inhibitor polymyxin B (50 μM) and then subjected to 40-min sustained ischemia and subsequent 30-min reperfusion. In another set of experiments, the hearts pretreated with and without a PKC activator PMA (15 pmol/5 min) were subjected to the sustained ischemia and reperfusion. Myocardial high-energy phosphates, glycolytic intermediates and mitochondrial oxygen consumption capacity were determined at appropriate experimental sequences. Results. Preconditioning enhanced the recovery of cardiac function such as left ventricular developed pressure, heart rate and rate-pressure product of the reperfused heart, suppressed the release of creatine kinase, enhanced the reperfusion-induced restoration of myocardial high-energy phosphates, attenuated the reperfusion-induced accumulation in glucose 6-phosphate and fructose 6-phosphate contents, abolished the ischemia-induced increase in tissue lactate content and prevented the ischemia-induced decrease in mitochondrial oxygen consumption capacity. Treatment of the perfused heart with PMA mimicked the effects of preconditioning on post-ischemic contractile function, enzyme release, levels of myocardial energy store, glycolytic intermediates and lactate, and mitochondrial function. Polymyxin B-treatment abolished the preconditioning-induced recovery of post-ischemic contractile function, the suppression of the release of CK, the restoration of myocardial energy store, and the preservation of mitochondrial function, whereas it did not cancel the improvement of glycolytic intermediate levels and the reduction in tissue lactate accumulation. Post-ischemic contractile function was closely related to restoration of high-energy phosphates and mitochondrial oxygen consumption capacity in all hearts subjected to ischemia/reperfusion. Conclusion. The results suggest that activation of PKC and preservation of mitochondrial function are closely linked with each other in the preconditioned heart, which may lead to the improvement of post-ischemic contractile function.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-1106
    Keywords: Acetylcholine ; Asparte ; Brain ischemia Glutamate ; Microsphere embolism Naftidrofuryl oxalate ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Effects of naftidrofuryl oxalate (naftidrofuryl) on neurotransmitter, acetylcholine, and amino acid content of brain regions following microsphere-induced cerebral embolism were examined to elucidate its possible therapeutic effects on ischemic brain. Rats received 900 microspheres (48 μm in diameter) via the right internal carotid artery, followed by ligation of the right common carotid artery; and histological and biochemical alterations were examined on the 3rd, 5th, and 28th days after embolism. The embolism induced increases in triphenyltetrazolium chloride-(TTC)-unstained areas and decreases in acetylcholine, glutamate, aspartate, and γ-aminobutyric acid (GABA) contents in the cerebral cortex, striatum, and hippocampus of the right hemisphere, suggesting that microsphere embolism causes severe damage to these brain regions. Hematoxylin-eosin staining of the right cortical sections after embolism showed degeneration and necrosis of nerve cells with chromatolytic nuclei and eosinophilic cytoplasm. Changes in neurotransmitters of the left hemisphere were relatively small. Treatment with naftidrofuryl of the embolized rats with stroke-like symptoms took place from postoperative day 1 to 28. Treatment resulted in a reduction in TTC-unstained areas, less morphological damage to cerebral cortex on the 3rd and 5th days, and an appreciable restoration of acetylcholine content of three brain regions of the right hemisphere throughout the experiment, but restoration of neurotransmitter amino acids was observed to a smaller degree. The results suggest that naftidrofuryl is capable of preventing the development of ischemia-induced, sustained damage to brain regions vulnerable to oxygen deficiency, particularly by improving impaired acetylcholine metabolism.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1573-4919
    Keywords: arachidonic acid ; fatty acid composition ; heart failure ; lipid metabolism ; myocardial infarction ; remodeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Changes in fatty acid composition of myocardial lipids were examined in rats with heart failure following myocardial infarction. Left ventricular systolic pressure (LVSP) was decreased and left ventricular end-diastolic pressure (LVEDP) was elevated 24 h, 1 and 12 weeks after left coronary artery ligation (CAL), suggesting the development of heart failure at these periods in this model. Hearts were isolated 24 h, 1 week and 12 weeks after the operation. Myocardial lipids in the infarcted scar tissue, non-infarcted remaining left ventricle including interseptum and right ventricle were separated into phospholipid (PL), triacylglycerol (TG), diacylglycerol (DAG) and free fatty acid (FFA) fractions. In the scar tissue PL content markedly decreased whereas TG, DAG and FFA contents increased 24 h after CAL. Despite a marked decrease in constituted fatty acids of PL fraction in the scar tissue the percentage of arachidonic acid in PL was elevated 12 weeks after CAL, suggesting that release of arachidonic acid during PL degradation was suppressed. In the non-infarcted viable left ventricle PL content remained unchanged throughout the experiment whereas TG, DAG and FFA contents were elevated 24 h after CAL. Despite no changes in PL and other lipid contents in the non-infarcted tissue the percentage of linoleic acid in PL was reduced and that of docosahexaenoic acid in PL was elevated 12 weeks after CAL. Our findings showed that myocardial lipid composition of the non-infarcted left ventricle was altered only in an early stage of the development of heart failure and fatty acid compositions of PL was exchanged in a late stage of the development of heart failure. The exchange may be related to cardiac dysfunction or myocardial remodelling in the rat with heart failure.
    Type of Medium: Electronic Resource
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