It was previously shown that 4 hours´ lasting inhibition of nitric oxide synthesis by administration of an L-arginine analogue, the NG-nitro-L-arginine methyl ester (L-NAME) changed the affinity of the Na-binding site of Na,K-ATPase thus resulting in elevation of enzyme activity especially at higher concentrations of sodium. Using the same experimental model, we focused our attention in the present study to the question of binding of ATP to the enzyme molecule in the left ventricle (LV), ventricular septum (S) and the right ventricle (RV) of the dog heart. Activation of the enzyme by increasing concentrations of ATP revealed a significant increase of the Vmax only in septum (by 38 %). The KM increased significantly in septum (by 40 %) and in left ventricle (by 56 %) indicating an altered sensitivity of the ATP-binding site of Na,K-ATPase in the hearts of NO-deficient animals. The alterations of Na,K-ATPase in its ability to bind and hydrolyze ATP are localized to the tissue surrounding the cavity of the left ventricle., N. Vrbjar, M. Strnisková, O. Pecháňová, M. Gerová., and Obsahuje bibliografii
It is known that hypertension is accompanied by increased [Na+]i. The functional properties of Na,K-ATPase, which transports the Na+ out and K+ into myocardial cells during the relaxation phase, were investigated in the left ventricle (LV), septum (SV) and the right ventricle (RV) of anesthetized dogs with moderate acute blood pressure elevation elicited by short-term (4-hour) NO synthase inhibition. The NO-insufficiency was induced by administration of an L-arginine analogue, the NG-nitro-L-arginine methyl ester (L-NAME). Concerning the function of Na,K-ATPase under the conditions of lowered NO synthesis, we focused our attention to the binding of Na+ to the enzyme molecule. Activation of the enzyme by increasing Na+ concentrations revealed significant changes in both the maximal velocity (Vmax) and the affinity for Na+ (KNa) in all investigated heart sections. The Vmax increased by 27 % in LV, by 87 % in SV and by 58 % in RV. The KNa value increased by 86 % in LV, by 105 % in SV and by 93% in RV, indicating an apparent decrease in the sensitivity of the Na+-binding site in the Na,K-ATPase molecule. This apparently decreased pump affinity for Na+ together with the increase of Vmax suggest that, during the short-term inhibition of NO synthesis, the Na,K-ATPase is capable of extruding the excessive Na+ from the myocardial cells more effectively at higher [Na+]i as compared to the Na,K-ATPase of control animals., N. Vrbjar, M. Strnisková, O. Pecháňová, M. Gerová., and Obsahuje bibliografii
Adiponectin belongs to the group of biologically active substances secreted by adipocytes and referred to as adipokines. Disturbances in its secretion an d/or action are thought to be involved in the pathogenesis of some metabolic diseases. However, regulation of adiponectin secretion is poorly elucidated. In the present study, short-term regulation of adiponectin secretion in primary rat adipocytes was investigated. Isolated rat adipocytes were incubated in Krebs-Ringer buffer containing 5 mM glucose and insulin alone or in the combination with epinephrine, dibutyryl-cAMP, adenosine A 1 receptor antagonist (DPCPX), palmitate, 2-bromopalmitate or inhibitor of mitochondrial electron transport (rotenone). Adipocyte exposure for 2 h to insulin (1-100 nM) significantly increased secretion of adiponectin compared with secretion observed without insulin. Furthermore, secretion of adipon ectin from adipocytes incubated with glucose and insulin was reduced by 1 and 2 μ M epinephrine, but not by 0.25 and 0.5 μ M epinephrine. Under similar conditions, 1 and 2 mM dibutyryl-cAMP substantially diminished secretion of adiponectin, whereas 0.5 mM dibutyryl-cAMP was ineffective. Secretion of adiponectin was found to be effectively decreased by DPCPX. Moreover, ad ipocyte exposure to rotenone also resulted in a substantial diminution of secretory response of adipocytes incubated for 2 h with glucose and insulin. It was also demonstrated that palmitate an d 2-bromopalmitate (0.06-0.5 mM) failed to affect secretion of leptin. The obtained results indicated that in short-term regulation of adiponectin secretion, insulin and epinephrine exert the opposite effects. These effects appeared as early as after 2 h of exposure. Moreover, deprivation of energy or blockade of adenosine action substantially decreased secretion of adiponectin., T. Szkudelski, L. Nogowski, K. Szkudelska., and Obsahuje bibliografii a bibliografické odkazy
A number of clinical neurological pathologies are associated with increased permeability of the blood brain barrier (BBB). Induced changes of the homeostatic mechanisms in the brain microenvironment lead among others to cellular changes in the CNS. The question was whether some of these changes can be induced by osmotic opening of BBB in an in vivo experiment and whether they can be detected in cerebrospinal fluid (CSF). CSF was taken via the suboccipital puncture from 10 healthy rats and six rats after the osmotic opening of the BBB. In all 16 animals, concentration of myelin basic protein (MBP ng/ml), Neuron-specific enolase (NSE ng/ml) and Tau-protein (Tau pg/ml) were determined in CSF by ELISA. Values in both groups were statistically evaluated. Significant difference between the control and experimental group was revealed only for the concentration of myelin basic protein (p<0.01). The presented results indicate that osmotic opening of the BBB in vivo experiment without the presence of other pathological conditions of the brain leads to a damage of myelin, without impairment of neurons or their axons., P. Kozler, O. Sobek, J. Pokorný., and Obsahuje bibliografii
In some patients, heart failure (HF) is associated with increased pulmonary vascular resistance (PVR). The magnitude and the reversibility of PVR elevation affect the HF management. Sildenafil has been recently recognized as potent PVR-lowering drug in HF. The aim of the study was to compare hemodynamic effects and pulmonary selectivity of sildenafil to prostaglandin E1(PGE1). Right-heart catheterization was performed in 13 euvolemic advanced HF patien ts with elevated PVR (6.3±2 Wood's units). Hemodynamic parameters were measured at the baseline, during i.v. infusion of PGE1 (alprostadil 200 ng·kg-1·min-1 ) and after 40 mg oral do se of sildenafil. Both drugs similarly reduced systemic vascular resistance (SVR), but sildenafil had higher effect on PVR (-28 % vs. -49 %, p=0.05) and transpulmonary pressu re gradient than PGE1. The PVR/SVR ratio - an index of pulmonary se lectivity, did not change after PGE1(p=0.7) but it decreased by -32 % (p=0.004) after sildenafil. Both drugs similarly reduced pulmonary artery mean and wedge pressures and increa sed cardiac index (+27 % and +28 %). Sildenafil led more often to transplant-acceptable PVR while causing smaller drop of mean systemic pressure than PGE1. In conclusion, vasodilatatory effects of sildenafil in patients with heart failure are more pronounced in pulmonary than in systemic circulation., H. Al-Hiti ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy
Ischemic postconditioning and remote conditioning are potentially useful tools for protecting ischemic myocardium. This study tested the hypothesis that 2,3-dehydrosilybin (DHS), a flavonolignan component of Silybum marianum , could attenuate cardiomyocyte damage following hypoxia/ reoxygenation by decreasing the generation of reactive oxygen species (ROS). After 5-6 days of cell culture in normoxic conditions the rat neonatal cardiomyocytes were divided into four groups. Control group (9 h at normoxic conditions), hypoxia/ reoxygenation group (3 h at 1 % O2 , 94 % N2 and 5 % CO2 followed by 10 min of 10 μmol·l -1 DHS and 6 h of reoxygenation in normoxia) and postconditioning group (3 h of hypoxia, three cycles of 5 min reoxygenation and 5 min hypoxia followed by 6 h of normoxia). Cell viability assess ed by propidium iodide staining was decreased after DHS treatment consistent with increased levels of lactatedehydrogenase (LDH) after reoxygenation. LDH leakage was significantly reduced when cardiomyocytes in the H/Re group were exposed to DHS. DHS treatment reduced H2O2 production and also decreased the generation of ROS in the H/Re group as evidenced by a fluorescence indicator. DHS treatment reduces reoxygenation-induced injury in cardiomyocytes by attenuation of ROS generation, H2O2 and protein carbonyls levels. In addition, we found that both the postconditioning protocol and the DHS treatment are associated with restored ratio of phosphorylated/total protein kinase C epsilon, relative to the H/Re group. In conclusion, our data support the protective role of DH S in hypoxia/reperfusion injury and indicate that DHS may act as a postconditioning mimic., E. Gabrielová, V. Křen, M. Jabůrek, M. Modrianský., and Obsahuje bibliografii
Action of antiepileptic drugs in immature brain may differ from that in adult brain. The aim of our study was to study an anticonvulsant action of lamotrigine and phenytoin, i.e. two drugs active against partial seizures in adult experimental animals as well as human patients, in a model of simple partial seizures in immature rats. Epileptic foci were induced by local application of bicuculline methiodide on sensorimotor cortical area of 12-dayold rat pups. The animals were pretreated with lamotrigine (LTG, 10 or 20 mg/kg i.p.) or phenytoin (PHT, 15, 30 or 60 mg/kg i.p.). Control rats for LTG received saline, controls for PHT solvent composed of propyleneglycol, ethanol and water. Influence of either drug on interictal activity was negligible. High doses of both LTG and PHT suppressed the transition into ictal phases and shortened the duration of persisting seizures. The tricomponent solvent exhibited moderate activity against ictal activity if compared with saline controls. The two drugs exhibited similar action in our model, i.e. the suppression of secondary generalization from epileptic focus. This action is comparable to that described for human patients and adult experimental animals. In favor of lamotrigine speaks the absence of serious side effects., K. Bernášková, P. Mareš., and Obsahuje bibliografii a bibliografické odkazy
Aerobic exercise showed beneficial influence on cardiovascular systems in aging, and mechanisms underlying vascular adaption remain unclear. Large-conductance Ca2+ -activated K+(BKCa) channels play critical role s in regulating cellular excitability and vascular tone. This study determin ed the effects of aerobic exercise on aging -associated functional changes in BK Ca channels in cerebrovascular myocytes, Male Wistar rats aged 20- 22 mo nths were randomly assigned to sedentary (O -SED), low training frequency (O-EXL), and high training frequency group (O -EXH). Young rats were used as control. Compared to young rats, w hole -cell BK Ca current was decreased, and amplitude of spontaneous transient outward currents were reduced. The open probability and Ca2+/voltage sensitivity of single BK Ca channel were declined in O -SED, accompanied with a reduction of tamoxifen-induced BK Ca activation; the mean open time of BK Ca channels was shortened whereas close time was prolonged. Aerobic exercise training markedly alleviated the aging-associated decline independent of training frequency. Exercise three times rather than five times weekly may be a time and cost-saving training volume required to offer bene ficial effects to offset the functional declines of BK Ca during aging., Na Li, Bailin Liu, Sharon Xiang, Lijun Shi., and Obsahuje bibliografii
The cytoskeleton plays a key role in cellular proliferation, cellshape maintenance and internal cellular organization. Cells are highly sensitive to changes in microgravity, which can induce alterations in the distribution of the cytoskeletal and cell proliferation. This study aimed to assess the effects of simulated microgravity (SMG) on the proliferation and expression of major cell cycle-related regulators and cytoskeletal proteins in human umbilical cord mesenchymal stem cells (hucMSCs). A WST-1 assay showed that the proliferation of SMG-exposed hucMSCs was lower than a control group. Furthermore, flow cytometry analysis demonstrated that the percentage of SMG-exposed hucMSCs in the G0/G1 phase was higher than the control group. A western blot analysis revealed there was a downregulation of cyclin A1 and A2 expression in SMG-exposed hucMSCs as well. The expression of cyclin-dependent kinase 4 (cdk4) and 6 (cdk6) were also observed to be reduced in the SMG-exposed hucMSCs. The total nuclear intensity of SMG-exposed hucMSCs was also lower than the control group. However, there were no differences in the nuclear area or nuclear-shape value of hucMSCs from the SMG and control groups. A western blot and quantitative RT-PCR analysis showed that SMG-exposed hucMSCs experienced a downregulation of β-actin and α-tubulin compared to the control group. SMG generated the reorganization of microtubules and microfilaments in hucMSCs. Our study supports the idea that the downregulation of major cell cycle-related proteins and cytoskeletal proteins results in the remodeling of the cytoskeleton and the proliferation of hucMSCs., Ho Nguyen Quynh Chi, Hoang Nghia Son, Doan Chinh Chung, Le Dinh Huan, Tran Hong Diem, Le Thanh Long., and Obsahuje bibliografii