Left atrial (LA) volume (LAV) is used for the selection of patients with atrial fibrillation (AF) to rhythm control strategies. Calculation of LAV from the LA diameters and areas by two-dimensional (2D) echocardiography may result in significant error. Accuracy of atrial volume assessment has never been studied in patients with long-standing persistent AF (LSPAF) and significant atrial remodeling. This study investigated correlation and agreement between 2D echocardiographic (Simpson method) and electroanatomic (CARTO, Biosense Webster) left and right atrial (RA) volumes (LAVECHO vs. LAVCARTO and RAVECHO vs. RAVCARTO) in patients undergoing catheter ablation for LSPAF. The study enrolled 173 consecutive subjects (females: 21 %, age: 59±9 years). There was only modest correlation between LAVECHO (92±31 ml) and LAVCARTO (178±37 ml) (R=0.57), and RAVECHO (71±29 ml) and RAVCARTO (173±34 ml) (R=0.42), respectively. LAVECHO and RAVECHO underestimated LAVCARTO and RAVCARTO with the absolute bias (±1.96 standard deviation) of -85 (-148; -22) ml and -102 (-169; -35) ml, respectively, and with the relative bias of -48 (-75; -21) % and -59 (-88; -30) %, respectively (all P<0.000001 for their mutual difference). Significant confounders of this difference were not identified. In patients with LSPAF, 2D echocardiography significantly underestimated both LA and RA volumes as compared with electroanatomic reference. This disagreement was independent of clinical, echocardiographic and mapping characteristics., L. Škňouřil, Š. Havránek, V. Bulková, M. Dorda, T. Paleček, J. Šimek, Z. Fingrová, A. Linhart, J. Januška, D. Wichterle, M. Fiala., and Obsahuje bibliografii
a1_We hypothesize that hypokalemia-related electrolyte imbalance linked with abnormal elevation of intracellular free Ca2+ concentration can cause metabolic disturbances and subcellular alterations resulting in intercellular uncoupling, which favor the occurrence of malignant arrhythmias. Langendorff-perfused guinea pig heart (n = 44) was subjected to a standard Tyrode solution (2.8 mmol/l K+) followed by a K+-deficient solution (1.4 mmol/l K+). Bipolar ECG of the left atria and ventricle was continuously monitored and the incidence of ventricular fibrillation was evaluated. Myocardial tissue sampling was performed during stabilization, hypokalemia and at the onset of fibrillation. Enzyme activities of succinic dehydrogenase, glycogen phosphorylase and 5-nucleotidase were determined using in situ catalytic histochemistry. The main gap junction protein, connexin-43, was labeled using mouse monoclonal antibody and FITC conjugated goat antimouse antibody. Ultrastructure was examined by transmission electron microscopy. The free Ca2+ concentration was measured by the indo-1 method in ventricular cell cultures exposed to a K+-free medium. The results showed that sustained ventricular fibrillation appeared within 15-30 min of low K+ perfusion. This was preceded by ectopic activity, episodes of bigeminy and tachycardia. Hypokalemia induced moderate reversible and sporadically irreversible subcellular alterations of cardiomyocytes and impairment of intercellular junctions, which were heterogeneously distributed throughout myocardium. Patchy areas with decreased enzyme activities and diminished immunoreactivity of connexin-43 were found. Furthermore, lack of external K+ was accompanied by an increase of intracellular Ca2+. The prevention of Ca2+ overload by either 1 mmol/l Ni2+ (Na+/Ca2+ inhibitor), 2.5 mmol/l verapamil, 10 mmol/l d-sotalol or 10 mmol/l tedisamil was associated with the protection agains fibrillation., a2_The results indicate that hypokalemia induces Ca2+ overload injury and disturbances in intercellular coupling. Dispersion of these changes throughout the myocardium may serve as the basis for microreentry circuits and thus favor fibrillation occurrence., N. Tribulová, M. Manoach, D. Varon, L. Okruhlicová, T. Zinman , A. Shainberg., and Obsahuje bibliografii
Measuring of shape deviances, a surface roughness or a surface defects belongs to newly formed requirements in a serial production, especially in production of precise automotive parts. Methods, which are used so far, usually does not meet such requirements - their measuring capacity is not suitable, they cannot check a whole or at least a significant segment of a surface in a short time, they do not cover all the mentioned measuring parameters in one device, they are highly dependent on vibrations and fluctuation of temperature, etc. All of this can be solved using optical contactless dispersive methods. and Měření tvarových úchylek, drsnosti a často i povrchových defektů patří k novým požadavkům sériové výroby, zejména přesných autodílů. Dosud používané metody tyto požadavky většinou nesplňují - nevyhovují výkonem, neumožňují v krátkém čase oskenovat celou kontrolovanou plochu nebo alespoň její část, nezaručí jedním systémem proměřit uvedené parametry, jsou citlivé na vibrace, kolísání teploty atd. Problém je řešitelný až pomocí bezkontaktních optických disperzních metod.
Estimation of shift between signals of two ultrasound images is the key of sonoelastography. Comparison of three methods - cross-correlation function and two versions of SAD (sum of absolute differences) has been conducted for various displacements and estimation parameters using a soft tissuemimicking gelatin phantom with harder inclusion. Resulting displacement maps were evaluated by comparison of average values and their standard deviations. and Obsahuje seznam literatury
This paper introduces an innovated plate anchor, increasing its bearing section area during uplift. In this experimental study, the influences of embedment depth of plate anchor and soil surface condition (restricted or free) on sand deformation field during uplift test are investigated. In order to study the soil deformation around the anchor, Particle Image Velocimetry (PIV) is used. The experimental setup consists of a camera, a new designed box, load cell, encoder and computer. During the uplift test on physical models, images are captured and used by PIV to depict the soil displacement field. Based on this study, it is found that pullout capacity and sand deformation zone are significantly influenced by anchor embedment depth. In shallow anchors, sand deformation zone lines are similar to a curve and cross the soil surface; however, in deep anchors, sand deformation zone is a bulb-shaped zone that extends from anchor to a distance of approximately two times its diameter above. Soil surface restriction increases anchor pullout capacity in shallow anchors up to 37 %, but in deep ones, there is no significant difference. Soil surface restriction changes shallow anchor behavior to deep anchors; however, it has no notable influence on deep anchors.
Increased levels of plasma cysteine predispose to obesity and metabolic disturbances. Our recent genetic analyses in spontaneously hypertensive rats (SHR) revealed mutated Folr1 (folate receptor 1) on chromosome 1 as a quantitative trait gene associated with reduced folate levels, hypercysteinemia and metabolic disturbances. The Folr1 gene is closely linked to the Folh1 (folate hydrolase 1) gene which codes for an enzyme involved in the hydrolysis of dietary polyglutamyl folates in the intestine. In the current study, we obtained evidence that Folh1 mRNA of the BN (Brown Norway) origin is weakly but significantly expressed in the small intestine. Next we analyzed the effects of the Folh1 alleles on folate and sulfur amino acid levels and consecutively on glucose and lipid metabolism using SHR-1 congenic sublines harboring either Folr1 BN and Folh1 SHR alleles or Folr1 SHR and Folh1 BN alleles. Both congenic sublines when compared to SHR controls, exhibited significantly reduced folate clearance and lower plasma cysteine and homocysteine levels which was associated with significantly decreased serum glucose and insulin concentrations and reduced adiposity. These results strongly suggest that, in addition to Folr1 , the Folh1 gene also plays an important role in folate and sulfur amino acid levels and affects glucose and lipid metabolism in the rat., J. Šilhavý, J. Krijt, J. Sokolová, V. Zídek, P. Mlejnek, M. Šimáková, V. Škop, J. Trnovská, O. Oliyarnyk, I. Marková, M. Hüttl, H. Malínská, L. Kazdová, F. Liška, V. Kožich, M. Pravenec., and Obsahuje bibliografii
By measurement of gas exchange and chlorophyll fluorescence, the effects of salt shock on photosynthesis and the mechanisms to protect photosynthetic machinery against photodamage during salt shock were investigated in leaves of Rumex seedlings. Salt shock induced significant decrease in photosynthesis both in 21 and 2 % O2. In 21 % O2, quantum yield of photosystem 2 (PS2) electron transport (ΦPS2) decreased slightly and qP remained constant, suggesting that the excitation pressure on PS2 did not increase during salt shock. In 2 % O2, however, both ΦPS2 and qP decreased significantly, suggesting that the excitation pressure on PS2 increased during salt shock. NPQ increased slightly in 21 % O2 whereas it increased significantly in 2 % O2. The data demonstrated that during salt shock a considerable electron flow was allocated to oxygen reduction in the Mehler-peroxidase reaction (MPR). Under high irradiance and in the presence of saturating CO2, the susceptibility of PS2 to photoinhibition in salt-shocked leaves was increased when the electron flow to oxygen in MPR was inhibited in 2 % O2. Hence, MPR is important in photoprotection of Rumex seedlings during salt shock. and H.-X. Chen ... [et al.].
Etiolated sunflower cotyledons developed in complete darkness and lacking photosystem (PS) 2 were exposed to continuous 200 µmol(photon) m-2 s-1 "white light" for 1, 3, 6, 12, and 18 h prior to evaluations of excitation-energy dissipation using modulated chlorophyll a fluorescence. Photochemical potential of PS2, measured as the dark-adapted quantum efficiency of PS2 (FV(M)/FM), and thermal dissipation from the antenna pigment-protein complex, measured as the Stern-Volmer non-photochemical quenching coefficient (NPQ), increased to 12 h of irradiation. Following 12 h of irradiation, thermal dissipation from the antennae pigment-protein complex decreased while the efficiency of excitation capture by PS2 centers (F'V/F'M) and light-adapted quantum efficiency of PS2 (ΦPS2) continued to increase to 18 h of irradiation. The fraction of the oxidized state of QA, measured by the photochemical quenching coefficient (qP), remained near optimal and was not changed significantly by irradiation time. Hence during the development of maximum photochemical potential of PS2 in sunflower etioplasts, which initially lacked PS2, enhanced thermal dissipation helps limit excitation energy reaching PS2 centers. Changes of the magnitude of thermal dissipation help maintain an optimum fraction of the oxidized state of QA during the development of PS2 photochemistry. and J. G. Lebkuecher ... [et al.].
The impact of floodplain hydrology on the in-stream dissolved oxygen dynamics and the relation between dissolved oxygen and water temperature are investigated. This has been done by examining the time series of dissolved oxygen and water temperature coupled with meteorological and hydrological data obtained from two lowland rivers having contrasting hydrological settings. Spectral analysis of long-term oxygen variations in a vegetated river revealed a distinct scaling regime with slope ‘-1’ indicating a self-similar behaviour. Identical slopes were obtained for water temperature and water level. The same power-law behaviour was observed for an unvegetated river at small timescales revealing the underlying scaling behaviour of dissolved oxygen regime for different types of rivers and over various time scales. The results have shown that the oxygenation of a vegetated river is strongly related to its thermal regime and flow conditions. Moreover, analysis of short-term fluctuations in the unvegetated river demonstrated that physical factors such as rainfall and backwaters play a substantial role in the functioning of this ecosystem. Finally, the results show that the relation between water temperature and dissolved oxygen concentration at the diurnal timescale exhibits a looping behaviour on the variable plot. The findings of this study provide an insight into the sensitivity of rivers to changing hydro-physical conditions and can be useful in the assessment of environmental variability.
Kohonen's self-organizing maps are a recognized tool for finding representative data vectors and clustering the data. To what extent is it possible to preserve the topology of the data in the constructed planar map? We address the question looking at distal data points located at the peripherals of the data cloud and their position in the provided map. Several data sets have been investigated; we present the results for two of them: the Glass data (dimension d=7) and the Ionosphere data (dimension d=32). It was found that the distal points are reproduced either at the edges (borders) of the map, or at the peripherals of dark regions visualized in the maps.