Search

The inwardly rectifying potassium current of the cardiomyocyte (IK1) is the main determinant of the resting potential. Ion channels Kir2.1, Kir2.2, and Kir2.3 form tetramers and are the molecular correlate of macroscopic IK1 current. Verapamil is an antiarrhythmic drug used to suppress atrial and ventricular arrhythmias. Its primary mechanism of action is via blocking calcium channels. In addition, it has been demonstrated to block IK1 current and the Kir2.1 subunit. Its effect on other subunits that contribute to IK1 current has not been studied to date. We therefore analyzed the effect of verapamil on the Kir channels 2.1, 2.2, and 2.3 in the Xenopus oocyte expression system. Kir2.1, Kir2.2, and Kir2.3 channels were heterologously expressed in Xenopus oocytes. Respective currents were measured with the voltage clamp technique and the effect of verapamil on the current was measured. At a concentration of 300 µM, verapamil inhibited Kir2.1 channels by 41.36% ± 2.7 of the initial current, Kir2.2 channels by 16.51 ± 3.6%, and Kir2.3 by 69.98 ± 4.2%. As a verapamil effect on kir2.3 was a previously unknown finding, we analyzed this effect further. At wash in with 300 µM verapamil, the maximal effect was seen within 20 min of the infusion. After washing out with control solution, there was only a partial current recovery. The current reduction from verapamil was the same at − 120 mV (73.2 ± 3.7%), − 40 mV (85.5 ± 6.5%), and 0 mV (61.5 ± 10.6%) implying no voltage dependency of the block. Using site directed mutations in putative binding sites, we demonstrated a decrease of effect with pore mutant E291A and absence of verapamil effect for D251A. With mutant I214L, which shows a stronger affinity for PIP2 binding, we observed a normalized current reduction to 61.9 ± 0.06% of the control current, which was significantly less pronounced compared to wild type channels. Verapamil blocks Kir2.1, Kir2.2, and Kir2.3 subunits. In Kir2.3, blockade is dependent on sites E291 and D251 and interferes with activation of the channel via PIP2. Interference with these sites and with PIP2 binding has also been described for other Kir channels blocking drugs. As Kir2.3 is preferentially expressed in atrium, a selective Kir2.3 blocking agent would constitute an interesting antiarrhythmic concept.

The global reach-scale “ICESat-2 River Surface Slope” (IRIS, https://doi.org/10.5281/zenodo.7098113) dataset comprises average and extreme water surface slopes (WSS) derived from ICESat-2 observations between October 2018 and August 2022 as a supplement to 121,583 reaches from the “SWOT Mission River Database” (SWORD, Altenau et al., 2021). WSS is required to calculate river discharge, which is among the Essential Climate Variables as defined by the Global Climate Observing System. To gain full advantage of ICESat-2’s unique measurement geometry with six parallel lidar beams, the WSS is determined across pairs of beams or along individual beams, depending on the intersection angle of spacecraft orbit and river centerline. The combined results of both approaches are validated against in-situ data in a regional study at 815 reaches in Europe and North America with a median absolute error of 23 mm/km, almost complying with the SWOT science requirements of 17 mm/km (Scherer et al., 2022). IRIS can be used to research river dynamics, estimate river discharge, and correct water level time series from satellite altimetry for shifting ground tracks. Additionally, by referencing SWORD as a common database, IRIS may be used in combination with observations from the recently launched SWOT mission and could be easily compared against WSS measurements from SWOT’s new wide-swath sensor.

Water surface slope (WSS) of rivers is a key parameter in hydrological modelling, which allows for estimation of the transport and erosion capacity of a river, its flow velocity and discharge. On a local scale, WSS can be measured with a GNSS receiver installed on a boat, using remote sensing techniques (e.g. airborne lidar) or from a Digital Elevation Model (DEM). The most accurate method to measure WSS avoiding high-cost field campaigns is based on Water Surface Elevations (WSE) measured at in-situ stations. However, in poorly gauged rivers the neighboring gauges can be up to hundreds of kilometers apart, which inhibits a proper river profile observation. The gap in decreasing number of gauge readings is partially filled with satellite altimetry over rivers. Altimetry based WSE can be used to estimate WSS between neighboring measurements. Here, we present an innovative approach for estimating high-resolution WSS derived from multi-mission satellite altimetry for the largest Polish rivers.In this study, we used measurements from 9 altimetry missions: CryoSat-2, Envisat, ICESat-2, Jason-2/-3, SARAL, Sentinel-3A/-B, and Sentinel-6A. These observations cover the years from 2002 to 2022. We extracted the river centerlines from the global “SWOT Mission River Database” (SWORD). In order to validate the obtained results, we used WSE from 81 gauges, which are maintained by the Institute of Meteorology and Water Management – National Research Institute (Instytut Meteorologii i Gospodarki Wodnej – Państwowy Instytut Badawczy, IMGW-PIB). These measurements are referenced to the Kronsztadt’86 vertical datum and they range from 01.2016 to 05.2022. Additionally, we used the reach-scale “ICESat-2 River Surface Slope” (IRIS) and the DEM-derived WSS values from SWORD.To obtain WSS, we first determined WSE at each satellite pass crossing the studied river. Next, we split rivers into sections without dams and reservoirs. The Support Vector Regression (SVR) has been applied to reject outliers. Then, water levels were assigned to a given river kilometer (bin). For each of them a median WSE has been calculated. Finally, WSS were calculated at river sections between bins, excluding those disrupted by hydraulic structures. Finally, we weighted the section-wise WSS inversely proportional to the length of each section and applied a Least Square Adjustment with an additional Laplace condition to obtain bin-wise WSS for each river kilometer.To assess the accuracy of the proposed approach, we compared the obtained WSS with the slopes between IMGW-PIB gauges. For large rivers (Vistula, Odra, Warta), the multi-mission approach revealed high accuracy with preliminary Root Mean Squared Error (RMSE) below 30 mm/km. For smaller, mountain rivers (San, Dunajec) the preliminary errors were slightly larger (RMSE ~100 mm/km). We also compared our accuracies with those of the slopes based on DEM models, lidar data, ICESat-2 altimetry, and SWORD database. In general, the multi-mission approach revealed the highest accuracy. The research is supported by the National Science Centre, Poland, through the project no. 2020/38/E/ST10/00295.

For nearly three decades, satellite radar altimetry has provided measurements of the water surface elevation (WSE) of rivers. These observations can be used to calculate the water surface slope (WSS), which is an essential parameter for estimating flow velocity and river discharge. In this study, we calculate a high-resolution WSS of 11 Polish rivers based on multi-mission altimetry observations from 11 satellites in the period from 1994 to 2022. The proposed approach is based on a weighted such gauge stations adjustment with an additional Laplace condition and an a priori gradient condition. The processing is divided into river sections not interrupted by dams and reservoirs. After proper determination of the WSE for each river kilometer (bin), the WSS between adjacent bins is calculated. To assess the accuracy of the estimated WSS, it is compared with slopes between gauge stations, which are referenced to a common vertical datum. Such gauge stations are available for 8 investigated rivers. The root mean squared error (RMSE) ranges from 3 mm/km to 80 mm/km, with an average of 26 mm/km. However, the mean RMSE decreases to 10 mm/km when the 2 mountain rivers are excluded. The WSS accuracies are also compared with those of slope datasets based on digital elevation models, ICESat-2 altimetry, and lidar. For 6 rivers the estimated WSS showed the highest accuracy. The improvement was particularly significant for mountain rivers. The proposed approach allows an accurate, high-resolution WSS even for small and medium-sized rivers and can be applied to almost any river worldwide.

Geometry is a branch of mathematics that helps us to work with distances, volumes, and areas of the real world. But spatial geometry presents an unusual obstacle: how to understand the elements of a three-dimensional object when they are normally presented in a two-dimensional form. The study was conducted with two classes in the 2nd year of high school in a public school. Class 1 used traditional resources: textbook, blackboard, and chalk. Class 2 used augmented reality (FLARAS) and 3D visualization (Sketchup) and textbook. It was expected that, with the help of augmented reality, the students of Class 2 would perform better than Class 1. A better understanding of the content was achieved, as they would have better visualization of spatial objects. Consequently, better performance was achieved in the exercises and problem questions presented.

Compared to mechanical extraction methods, pulsed electric field (PEF) treatment provides an energy-efficient and gentle alternative. However, the biological processes involved are poorly understood. The unicellular green microalga Chlorella vulgaris was used as model organism to investigate the effect of PEF treatment on biological cells. A viability assay using fluorescein diacetate measured by flow cytometry was established. The influence of developmental stage on viability could be shown in synchronised cultures when applying PEF treatment with very low specific energies where one part of cells undergoes cell death, and the other part stays viable after treatment. Reactive oxygen species generation after similar low-energy PEF treatment could be shown, indicating that PEFs could act as abiotic stress signal. Most importantly, a cell-death inducing factor could be extracted. A water-soluble extract derived from microalgae suspensions incubated for 24 h after PEF treatment caused the recipient microalgae to die, even though the recipient cells had not been subjected to PEF treatment directly. The working model assumes that low-energy PEF treatment induces programmed cell death in C. vulgaris while specifically releasing a cell-death inducing factor. Low-energy PEF treatment with subsequent incubation period could be a novel biotechnological strategy to extract soluble proteins and lipids in cascade process.