Search results for "Potassium"
showing 10 items of 930 documents
Shell structure of potassium isotopes deduced from their magnetic moments
2014
\item[Background] Ground-state spins and magnetic moments are sensitive to the nuclear wave function, thus they are powerful probes to study the nuclear structure of isotopes far from stability. \item[Purpose] Extend our knowledge about the evolution of the $1/2^+$ and $3/2^+$ states for K isotopes beyond the $N = 28$ shell gap. \item[Method] High-resolution collinear laser spectroscopy on bunched atomic beams. \item[Results] From measured hyperfine structure spectra of K isotopes, nuclear spins and magnetic moments of the ground states were obtained for isotopes from $N = 19$ up to $N = 32$. In order to draw conclusions about the composition of the wave functions and the occupation of the …
Membrane potential of rat calvaria bone cells: dependence on temperature.
1990
The membrane potentials of bone cells derived from calvaria of new born rats was shown to be strongly dependent on temperature. When we lowered the temperature from 36 degrees C to 26 degrees C, cells with spontaneous resting membrane potentials (MP) of -80 to -50 mV depolarized (mean amplitude 8 mV; n = 33), and the membrane resistance increased by approximately 80% (n = 20). The temperature response depended on the actual MP, the reversal potential being in the range of -80 to -90 mV. With the application of ouabain (0.1-1 mmol/liter; n = 12), cells depolarized. Simultaneously, the reversal potential of the temperature response was shifted towards more positive values and approached the a…
Versuche zur Bestimmung des wahren K-Efflux im Rattenzwerchfell
1960
In an isolated muscle loaded with 42K the potassium efflux through the muscle fibre membrane can be calculated from the rate constant of the loss of 42K into an inactive bathing solution. The calculation can only be valid if the amount of 42K leaving all the individual fibres is equivalent to the amount of 42K entering the bathing solution from the surface of the whole muscle. It seems possible that 42K ions which have already left a muscle cell can be taken up again into a muscle fibre before diffusing into the bathing solution. Thus the calculated potassium efflux might be smaller than the real efflux.
SOIL CHARACTERISTICS, MINERAL NUTRIENTS, BIOMASS, AND CARDENOLIDE PRODUCTION INDIGITALIS OBSCURAWILD POPULATIONS
2002
Mature leaves of wild-growing Digitalis obscura plants and soil samples were collected in four different regions. Soil and leaf mineral nutrient contents as well as biomass and cardenolide productions were determined. The soils in the four collection sites, basic and highly calcareous, showed significant interpopulation differences in phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), manganese (Mn), copper (Cu), and zinc (Zn). Foliar mineral nutrients and cardenolides also varied among populations. Highest cardenolide yield was found in those Digitalis populations presenting a better development. The cardenolide content exhibited significant negative correlations with the levels …
Agronomic treatments to avoid seed presence in ‘Nadorcott’ mandarin I. Effect on in vivo pollen tube growth
2022
Abstract Fresh market demands high quality fruit and, therefore, citrus growers and researchers are constantly looking for solutions to avoid seed presence. Current horticultural techniques have low effectiveness or high cost. The objective of this study is to evaluate the inhibition effect of seven products on the in vivo pollen tube growth in Nadorcott mandarin, which is a high-value seedy variety. To achieve this main objective, three inorganic fertilizers (ammonium nitrate, potassium nitrate, sulfur), and four saccharides (saccharose, methyl cellulose, callose, chitosan) were applied to Nadorcott stigmas 24 h before and after hand pollination. Pollen tubes were counted 1, 3, and 5 days …
Short-term low-severity spring grassland fire impacts on soil extractable elements and soil ratios in Lithuania
2017
Abstract Spring grassland fires are common in boreal areas as a consequence of slash and burn agriculture used to remove dry grass to increase soil nutrient properties and crop production. However, few works have investigated fire impacts on these grassland ecosystems, especially in the immediate period after the fire. The objective of this work was to study the short-term impacts of a spring grassland fire in Lithuania. Four days after the fire we established a 400 m2 sampling grid within the burned area and in an adjacent unburned area with the same topographical, hydrological and pedological characteristics. We collected topsoil samples immediately after the fire (0 months), 2, 5, 7 and …
Gill ATPase activity in Procambarus clarkii as an indicator of heavy metal pollution.
1989
Lake Albufera and the surrounding rice field waters are subjected to very heavy loads of sewage and toxic industrial residues, including heavy metals, from the many urban and waste waters of this area. The American red crayfish, Procambarus clarkii have a high resistance to toxic effects of heavy metals. The sublethal effects of heavy metals on gills of fish and aquatic invertebrates have been extensively studied. Some metabolic disturbances and histologic damages have been reported, as well as osmoregulation alterations. However, little work has been done about the effect of heavy metals on Na,K and Mg-ATPases of freshwater invertebrate gills. Na,K-ATPase is the prime mediator of ion trans…
UV-photometrisch bestimmte relative molare massen von anionisch erzeugten polyäthylenoxiden mit unterschiedlichen endgruppen
1976
Athylenoxid wurde mit Kalium-4-(phenylazo)benzylalkoholat (1f) polymerisiert, die gereinigten Produkte fraktioniert und anschliesend acyliert. Die UV-photometrische Bestimmung der Endgruppen ergab, das HO-Endgruppen, verglichen mit den Starterendgruppen, in grosem Uberschus vorhanden waren. Aus den Endgruppenwerten liesen sich Zahlenmittel des Molekulargewichts (Mn) ableiten. Sie wurden mit osmotisch bestimmten Mn-Werten und Viskositatsmittel (Mη)-verglichen und bestatigten die angenommene Struktur der Polyathylenoxide. Ethylene oxide was polymerized with potassium 4-(phenylazo)benzylalcoholate (1f). The purified and fractionated products were acylated. The ultra-violet measurement of the e…
Pore-forming toxins activate MAPK p38 by causing loss of cellular potassium.
2009
Mitogen activated protein kinase (MAPK) p38 has emerged as a survival protein in cells that are attacked by bacterial toxins forming small membrane pores. Activation of p38 by pore forming toxins (PFT) has been attributed to osmotic stress, but here we show that loss of K+ is likely to be the critical parameter. Several lines of evidence support this conclusion: first, osmoprotection did not prevent p38-phosphorylation in alpha-toxin-loaded cells. Second, treatment of cells with a K+ ionophore, or simple incubation in K+-free medium sufficed to cause robust p38-phosphorylation. Third, media containing high [K+] prevented p38-activation by Staphylococcus aureus alpha-toxin, Vibrio cholerae c…
TRESK channel contributes to depolarization-induced shunting inhibition and modulates epileptic seizures.
2020
Glutamatergic and GABAergic synaptic transmission controls excitation and inhibition of postsynaptic neurons, whereas activity of ion channels modulates neuronal intrinsic excitability. However, it is unclear how excessive neuronal excitation affects intrinsic inhibition to regain homeostatic stability under physiological or pathophysiological conditions. Here, we report that a seizure-like sustained depolarization can induce short-term inhibition of hippocampal CA3 neurons via a mechanism of membrane shunting. This depolarization-induced shunting inhibition (DShI) mediates a non-synaptic, but neuronal intrinsic, short-term plasticity that is able to suppress action potential generation and…