Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A considerable number of experimental, epidemiological and clinical studies are now available which point to an important role of Mg2+ in the etiology of cardiovascular pathology. In human subjects, hypomagnesemia is often associated with an imbalance of electrolytes such as Na+, K+ and Ca2+. Abnormal dietary deficiency of Mg2+ as well as abnormalities in Mg2+ metabolism play important roles in different types of heart diseases such as ischemic heart disease, congestive heart failure, sudden cardiac death, atheroscelerosis, a number of cardiac arrhythmias and ventricular complications in diabetes mellitus. Mg2+ deficiency results in progressive vasoconstriction of the coronary vessels leading to a marked reduction in oxygen and nutrient delivery to the cardiac myocytes. Numerous experimental and clinical data have suggested that Mg2+ deficiency can induce elevation of intracellular Ca2+ concentrations, formation of oxygen radicals, proinflammatory agents and growth factors and changes in membrane perrmeability and transport processes in cardiac cells. The opposing effects of Mg2+ and Ca2+ on myocardial contractility may be due to the competition between Mg2+ and Ca2+ for the same binding sites on key myocardial contractile proteins such as troponin C, myosin and actin. Stimulants, for example, catecholamines can evoke marked Mg2+ efflux which appears to be associated with a concomitant increase in the force of contraction of the heart. It has been suggested that Mg2+ efflux may be linked to the Ca2+ signalling pathway. Depletion of Mg2+ by alcohol in cardiac cells causes an increase in intracellular Ca2+, leading to coronary artery vasospasm, arrhythmias, ischemic damage and cardiac failure. Hypomagnesemia is commonly associated with hypokalemia and occurs in patients with hypertension or myocardial infarction as well as in chronic alcoholism. The inability of the senescent myocardium to respond to ischemic stress could be due to several reasons. Mg2+ supplemented K+ cardioplegia modulates Ca2+ accumulation and is directly involved in the mechanisms leading to enhanced post ischemic functional recovery in the aged myocardium following ischemia. While many of these mechanisms remain controversial and in some cases speculative, the beneficial effects related to consequences of Mg2+ supplementation are apparent. Further research are needed for the incorporation of these findings toward the development of novel myocardial protective role of Mg2+ to reduce morbidity and mortality of patients suffering from a variety of cardiac diseases.
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PMID:Protective role of magnesium in cardiovascular diseases: a review. 1234 4

We modeled changes in contractile element kinetics derived from the cyclic relationship between myoplasmic [Ca(2+)], measured by indo 1 fluorescence, and left ventricular pressure (LVP). We estimated model rate constants of the Ca(2+) affinity for troponin C (TnC) on actin (A) filament (TnCA) and actin and myosin (M) cross-bridge (A x M) cycling in intact guinea pig hearts during baseline 37 degrees C perfusion and evaluated changes at 1) 20 min 17 degrees C pressure, 2) 30-min reperfusion (RP) after 30-min 37 degrees C global ischemia during 37 degrees C RP, and 3) 30-min RP after 240-min 17 degrees C global ischemia during 37 degrees C RP. At 17 degrees C perfusion versus 37 degrees C perfusion, the model predicted: A x M binding was less sensitive; A x M dissociation was slower; Ca(2+) was less likely to bind to TnCA with A x M present; and Ca(2+) and TnCA binding was less sensitive in the absence of A x M. Model results were consistent with a cold-induced fall in heart rate from 260 beats/min (37 degrees C) to 33 beats/min (17 degrees C), increased diastolic LVP, and increased phasic Ca(2+). On RP after 37 degrees C ischemia vs. 37 degrees C perfusion, the model predicted the following: A x M binding was less sensitive; A x M dissociation was slower; and Ca(2+) was less likely to bind to TnCA in the absence of A. M. Model results were consistent with reduced myofilament responsiveness to [Ca(2+)] and diastolic contracture on 37 degrees C RP. In contrast, after cold ischemia versus 37 degrees C perfusion, A x M association and dissociation rates, and Ca(2+) and TnCA association rates, returned to preischemic values, whereas the dissociation rate of Ca(2+) from A x M was ninefold faster. This cardiac muscle kinetic model predicted a better-restored relationship between Ca(2+) and cross-bridge function on RP after an eightfold longer period of 17 degrees C than 37 degrees C ischemia.
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PMID:Cross-bridge kinetics modeled from myoplasmic [Ca2+] and LV pressure at 17 degrees C and after 37 degrees C and 17 degrees C ischemia. 1253 35

To investigate the regulation of the actomyosin crossbridge cycle in cardiac muscles, the effects of ATP, ADP, Pi, and creatine phosphate (CP) on the rate of force redevelopment (ktr) were measured. We report that CP is a primary determinant in controlling the actomyosin crossbridge cycling kinetics of cardiac muscles, because a reduction of CP from 25 to 2.5 mmol/L decreased ktr by 51% despite the presence of 5 mmol/L MgATP. The effects of CP on ktr were not a reflection of reduced ATP or accumulated ADP, because lowering ATP to 1 mmol/L or increasing ADP to 1 mmol/L did not significantly decrease ktr. Therefore, the effect of CP on the actomyosin crossbridge cycle is proposed to occur through a functional link between ADP release from myosin and its rephosphorylation by CP-creatine kinase to regenerate ATP. In activated fibers, the functional link influenced the kinetics of activated crossbridges without affecting the aggregate number of force-generating crossbridges. This was demonstrated by the ability of CP to affect ktr in maximally and submaximally activated fibers without altering the force per cross-sectional area. The data also confirm the important contribution of strong binding crossbridges to cardiac muscle activation, likely mediated by cooperative recruitment of adjacent crossbridges to maximize force redevelopment against external load. These data provide additional insight into the role of CP during pathophysiological conditions such as ischemia, suggesting that decreased CP may serve as a primary determinant in the observed decline of dP/dt.
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PMID:Creatine phosphate consumption and the actomyosin crossbridge cycle in cardiac muscles. 1279 10

The precise molecular basis for myocardial stunning remains unresolved, but protein damage within the myofibril is a likely mechanism. We used two-dimensional gel electrophoresis (2-DE) and mass spectrometry (MS) to identify protein modifications in stunned myocardium. In isolated, perfused rabbit hearts, low-flow ischemia (1 ml/min) and reperfusion resulted in impaired left-ventricular function (rate-pressure product (RPP) after 15-min ischemia: 65 +/- 5% pre-ischemia). We have characterised the sequence of ventricular myosin-regulatory light chain (MLC-2, 18 kDa) in rabbit myocardium and identified two non-phosphorylated (P(1) and P(2)) and two phosphorylated (P(3) and P(4) at Ser-14) isoelectric point variants. MS revealed that the acidic isoelectric point post-translational modification of P(1) and P(3), resulting in P(2) and P(4) respectively, was due to deamidation of asparagine to aspartate at residue 13, adjacent to Ser-14 phosphorylation site. After 15-min ischemia and reperfusion, a 15-kDa MLC-2 fragment was detected (MLC-2(14-165)), resulting from N-terminal cleavage between Asn/Asp-13 and Ser-14 of non-phosphorylated MLC-2, which accounted for 9.8% of visible non-phosphorylated MLC-2. Subsequent 2-DE of subcellular fractions showed that the fragment was lost from the myofilament. Treatment with an OH radical scavenger, N-(2-mercaptopropionyl) glycine (MPG, 3 mmol/l), preserved contractile function (RPP: 106 +/- 9% pre-ischemia) and prevented cleavage of MLC-2. Proteolytic damage to MLC-2, related to presence of OH radicals during reperfusion, correlates with myocardial stunning and may contribute to impaired contractility.
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PMID:Modifications of myosin-regulatory light chain correlate with function of stunned myocardium. 1281 74

As glucagon is known to cause a receptor-mediated increase in intracellular calcium and cyclic AMP, we have developed a novel method of evaluating the integrity of the signal transduction and transport system using glucagon-induced changes in indocyanine green (ICG) excretion. The kinetics of the hepatocellular concentration of ICG at 4-second intervals was analyzed by near-infrared spectroscopy in vivo on the liver surface. After intravenous injection of 0.5 mg/kg ICG to rabbits, absorbance of ICG increased and then decreased according to the two-compartment model: ICG(t) = -Aexp(-alphat) + Bexp(-betat), where alpha and beta (min(-1)) indicate the time constants of uptake and excretion, respectively. During the excretion phase, 40 microg/kg glucagon was infused as a bolus via the portal vein. A biphasic acceleration and retardation of ICG excretion from the baseline exponential decay was observed in the controls. In order to perturb the glucagon response, colchicine, ouabain, wortmannin and an ischemia-reperfusion insult were employed. Colchicine, ouabain and wortmannin abolished the biphasic acceleration and retardation of ICG excretion. Glucagon response was absent upon the ischemia-reperfusion insult. The observed biphasic response to glucagon clearly indicates that glucagon modulates bile canalicular contraction and peristalsis via the two glucagon receptors and these second messengers. The glucagon response requires the integrity of signal transduction, cytoskeleton structure, myosin function, and bile canalicular pump.
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PMID:Receptor-mediated biphasic alteration of hepatocellular transport from hepatocyte to bile canaliculi as measured by near-infrared spectroscopy: a novel test with glucagon for biliary excretion. 1459 29

Chronic heart failure is a slowly progressive disease. Hemodynamic deterioration activates various neuro-humoral factors and increases stresses, such as catecholamine, angiotensin II (AII), cytokines, endothelin, wall stress, ischemia, tachycardia, and oxidative stress. These factors affect the myocardium to cause phenotype switching, leading to ventricular remodeling. We investigated the effects of pharmacological blocking for neuro-humoral factors in rats with dilated cardiomyopathy. Experimental autoimmune myocarditis (EAM) was elicited in Lewis rats by immunization with cardiac myosin. After acute inflammation healed, rats were treated with angiotensin converting enzyme inhibitors (ACEI), type 1 AII receptor blockers, and amiodarone. These agents had favorable effects on hemodynamics and myocardial contractility, prevented fibrosis, suppressed the expression of ANP, and reversed phenotypic change of cardiac myosin. AII receptor blockers were less effective than ACEI. In order to prevent ventricular remodeling in chronic heart failure, wide and complete blocking of neuro-humoral factors is important.
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PMID:[Effects of humoral factors on left ventricular remodeling under chronic heart failure]. 1474 25

Reinnervation, muscle regeneration, density of microvessels, and muscle-type specific atrophy were studied 3-4 years after surgery in surgically nonreinnervated free microvascular muscle flaps to 13 patients transplanted to the upper or lower extremities. Routine histology and immunohistochemistry for PGP 9.5 and S-100 (neuronal markers), Ki-67 (cell proliferation), myosin (muscle fiber types), and CD-31 (endothelium) were carried out, and results were analyzed morphometrically. Three to 4 years after surgery, severe atrophy of predominantly slow-type fibers was seen in 9 cases. In 4 cases, muscle-fiber diameter and fiber-type distribution were close to normal. Long intraoperative muscle ischemia and postoperative immobilization were associated with poor muscle bulk in flaps. The density of microvessels in flaps did not differ from control muscles. PGP 9.5 and S-100 immunopositive nerve fibers were detected in 7 patients. Reinnervation was associated with good muscle bulk. In 4 patients, activation of satellite cells was evident. The results suggest that in some cases, spontaneous reinnervation may occur in free muscle flaps, and that several years after microvascular free flap transfer, the muscle still attempts to regenerate.
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PMID:Long-term morphometric and immunohistochemical findings in human free microvascular muscle flaps. 1474 22

Endothelial cells lining the vasculature have close cell-cell associations that maintain separation of the blood fluid compartment from surrounding tissues. Permeability is regulated by a variety of growth factors and cytokines and plays a role in numerous physiological and pathological processes. We examined a potential role for the p21-activated kinase (PAK) in the regulation of vascular permeability. In both bovine aortic and human umbilical vein endothelial cells, PAK is phosphorylated on Ser141 during the activation downstream of Rac, and the phosphorylated subfraction translocates to endothelial cell-cell junctions in response to serum, VEGF, bFGF, TNFalpha, histamine, and thrombin. Blocking PAK activation or translocation prevents the increase in permeability across the cell monolayer in response to these factors. Permeability correlates with myosin phosphorylation, formation of actin stress fibers, and the appearance of paracellular pores. Inhibition of myosin phosphorylation blocks the increase in permeability. These data suggest that PAK is a central regulator of endothelial permeability induced by multiple growth factors and cytokines via an effect on cell contractility. PAK may therefore be a suitable drug target for the treatment of pathological conditions where vascular leak is a contributing factor, such as ischemia and inflammation.
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PMID:p21-activated kinase regulates endothelial permeability through modulation of contractility. 1533 33

During heart failure, alterations occur in contractile protein expression and phosphorylation, which may influence the effects of Ca2+ -sensitizers. To quantify the magnitude of these effects, isometric force was studied in mechanically isolated Triton-skinned myocytes from end-stage failing and non-failing donor hearts under control conditions (pH 7.2; no added inorganic phosphate (Pi)) and under mimicked ischemic conditions (pH 6.5; 10 mM Pi). Two different Ca2+ -sensitizers were used: EMD 53998 (10 microM), which exerts its influence through the actin-myosin interaction, and OR-1896 (10 microM) (the active metabolite of levosimendan), which affects the Ca2+ -sensory function of the thin filaments. The maximal force (Po) measured at saturating Ca2+ concentration and the resting force (Prest) determined in the virtual absence of Ca2+ (pCa 9) did not differ between the failing and non-failing myocytes, but the Ca2+ concentration required to induce the half-maximal force under control conditions was significantly lower in the failing than in the non-failing myocytes (DeltapCa50=0.15). This difference in Ca2+ -sensitivity, however, was abolished during mimicked ischemia. EMD 53998 increased Po and Prest by approximately 15% of Po and greatly enhanced the Ca2+ -sensitivity (DeltapCa50 > 0.25) of force production. OR-1896 did not affect Po and Prest, and provoked a small, but significant Ca2+ -sensitization (DeltapCa50 approximately 0.1). All of these effects were comparable in the donor and failing myocytes, but, in contrast with OR-1896, EMD 53998 considerably diminished the difference in the Ca2+ -sensitivities between the failing and non-failing myocytes. The action of Ca2+ -sensitizers under mimicked ischemic conditions was impaired to a similar degree in the donor and the failing myocytes. Our results indicate that the Ca2+ -activation of the myofibrillar system is altered in end-stage human heart failure. This modulates the effects of Ca2+ -sensitizers both under control and under mimicked ischemic conditions.
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PMID:Effects of Ca2+ -sensitizers in permeabilized cardiac myocytes from donor and end-stage failing human hearts. 1546 85

Thanks to advances in molecular biology during the last decade, the etiology of hypertrophic cardiomyopathy has been elucidated. Although more than 150 causal mutations of 9 genes that encode contractile proteins have been identified, many of the pathogenetic mechanisms remain unclear. In this review we discuss the current state of knowledge of the functional effects of some mutations, particularly two of the most lethal beta-myosin mutations -Arg403Gln and Arg723Gly (Barcelona mutation)- and their contributions to the pathogenesis of hypertrophy, sudden death and ischemia. Their potential roles in diagnostic and therapeutic strategies are emphasized.
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PMID:[Hypertrophic cardiomyopathy. Genetic basis and clinical implications]. 1551 86


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