Nitric oxide (NO) is an endogenous vasodilator and inhaled NO is a promising therapeutic agent for the treatment of pulmonary hypertension. However, NO's mechanism of action is not completely understood. Previous studies have shown that NO increases intracellular levels of cyclic guanosine 3',5'-monophosphate (cGMP) and that leads to activation of calcium-gated potassium channels in vascular smooth muscle cells. Resulting cell membrane hyperpolarization causes vasorelaxation. The potassium channel activation by NO is inhibited by a blockade of cyclic nucleotide-dependent protein kinases, suggesting a key role of these enzymes in NO-induced vasodilation. To further examine this mechanism, we tested the hypothesis that pharmacological stimulation of the cGMP-dependent protein kinase will simulate the activating effect of NO on potassium channels. Indeed, we found that (Sp)-guanosine cyclic 3’,5'-phosphorothioate (1 /¿M), a selective activator of the cGMP-dependent protein kinase, dramatically increased potassium currents measured by the whole-celi patch clamp technique in freshly dispersed pulmonary artery smooth muscle cells. These currents were inhibited by an inhibitor of calcium-gated potassium channels, charybdotoxin. Our results support the hypothesis that the effect of NO on potassium channels is mediated by the cGMP-dependent protein kinase.
Trusses are suitable load-bearing structural systems for heavy concentrated loads. In this paper, it is shown that it is possible to use active control mechanisms to enhance the load-bearing capacity of the trusses. Under heavy loading, some elernents of a truss might experience high stresses and show non-linear behavior, resulting in large deformations in the truss. Under such a condition, some elernents of the truss might damage which can lead to the collapse of the truss. Application of control forces on some of the degrees of freedom of the truss can render help the truss tolerate larger forces before its collapse. A neural network can then be trained to learn the relationship between the Information about the external loads on the truss, as input, and the required control forces, as output, and act as a neuro-controller for the truss. This method is explained and then tested on a smáli truss to show the capabilities of the method.
Non-invasive assessment of the sensitivity of cardiac baroreflex was performed by recording each RR-interval and each blood pressure cycle (Finapres®). In sequences of at least three cardiac cycles in which systolic blood pressure and RR-interval had changed in the same direction, the slope of linear regression of RR duration as a function of the change in systolic arterial pressure was taken for estimating the sensitivity of the spontaneous cardiac baroreflex. This technique was used in healthy humans to examine how a postural change from supine to upright by either active standing up or 60° head-up tilting modified the sensitivity of the spontaneous baroreflex. We observed that the slope of the spontaneous baroreflex averaged 14.6 ±2 ms.mm Hg_1 during rest in the supine position, and decreased to 7.8 ± 1.2 ms.mm Hg"1 (p<0.05) after active standing, while the number of sequences was significantly increased in the upright as compared to the supine position. Head-up tilting by 60° led to values similar to those following active standing. The adjustment of baroreflex slope to either postural change occurred in a few seconds, so that posture-characteristic values were obtained from five-minute records. We conclude that non- invasive recording of spontaneous sequences of related changes in blood pressure and RR-interval during several minutes provides reproducible values of the slope of cardiac baroreflex in the supine and upright position. This easy and reliable determination of the sensitivity of the cardiac baroreflex might prove to be useful when assessment of baroreflex function is needed.
This paper examines the results of fault microdisplacement analyses obtained from sites located both at the surface and underground in western Slovakia. The results of surface monitoring showed significant annual climatic effects on the various displacement components. In contrast, the results of underground monitoring in caves showed minimal climatic effects. It is seen that the influence of climate decreases markedly with depth. The yearly peak-to-peak amplitude of climatic variations may be as high as 1 mm at the surface but only 0.1 mm underground. The amount of tectonic displacement can be determined once such climatic considerations have been taken into account. Our fault displacement measurements show horizontal strike-slip rates of tenths of mm or hundredths of mm per year. In addition, vertical displacements have been recorded at Prekážka Quarry, Driny Cave, and Slopy Cave. The network is sufficiently dense to identify changes in displacement activity recorded during recent, significant, earthquake events. Furthermore, three gauges have also helped to determine the local stress orientation in Driny Cave., Miloš Briestenský, Blahoslav Košťák, Josef Stemberk, Ľubomír Petro, Jozef Vozár and Lucia Fojtíková., and Obsahuje bibliografii
One of the leaved out fault active systems at Southern Moravian can be considered the so called Diendorf - Čebín tectonic zone (DCTZ), that is seismically active in its southern segment (in Austrian). The Waitzendorf fault is a part of the DCTZ, with intensive morphological signs. The terrain recognizance along the eastern margin of the Dyje Dome confirmed many indi cations showing evidence of geodynamic activity. The facets, old land slides and rock falls indicate recent activity in the environs of Znojmo area. The paper offers interpretation of the geodetic results (GPS) using morphological and geophysical data from all area of the DCTZ ., Lubomil Pospíšil, Pavel Roštínský, Otakar Švábenský, Josef Weigel and Michal Witiska., and Obsahuje bibliografické odkazy
Four groups of goldfish were exposed to cadmium in a concentration of 20 mg Cd/l water under aquarium conditions. The duration of exposure was 1, 4, 7 and 15 days. It was shown that the activity of superoxide dismutase (SOD) in the red blood cells (RBC) significantly decreased after the first day of cadmium exposure. However, the SOD activity increased after 7 and 15 days of cadmium treatment. Elevated activity of catalase (CAT) was found in erythrocytes of cadmium-treated fishes after 15 days, whereas plasma GOT levels was increased after 7 and 15 days and GPT levels after 1, 4, 7 and 15 days of cadmium treatment. This was accompanied by a significant decrease of blood hemoglobin concentrations (after 15 days) and hematocrit values (after 7 and 15 days). However, the concentration of blood glucose significantly increased after 1, 4, 7 and 15 days of cadmium exposure. These results indicate that cadmium causes oxidative stress and tissue damage in the exposed fishes., R.V. Žikić, A. Š. Štajn, S. Z. Pavlović, B. I. Ognjanović, Z. S. Saičić., and Obsahuje bibliografii
Total superoxide dismutase (SOD, EC 1.15.1.1) and catalase (CAT, EC 1.11.1.6) activities in erythrocytes and the glutamic acid-oxalacetic acid-transaminase (GOT, EC 2.6.1.1) and glutamic acid-pyruvic acid-transaminase (GPT, EC 2.6.1.2) activities in the plasma were measured in experimental groups of carps (Cyprinus carpio L.) exposed to cadmium in a concentration of 20 mg Cd/1 water under aquarium conditions for 6, 12, 18 and 24 hours and in control fishes. It was shown that the total activity of SOD in the erythrocytes is significantly decreased after 12, 18 and 24 hours of cadmium exposure. Increased activities of CAT (after 24 hours) in the erythrocytes and GOT and GPT in the plasma were found in cadmium-treated fishes. At the same time the concentration of blood haemoglobin and haematocrit values were significantly diminished. These results indicate that cadmium causes oxidative stress and tissue damage in the exposed fishes.