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The nonlinear, pseudo-periodic current of potassium ions through a high conductance locust K+ channel (BK channel) has been modelled by a two-parameter logistic map (“crowd model”). Data obtained by the patch clamp for different values of potential difference has been correlated with a mechanism of transport incorporating dynamical structure and morphology of pores in a membrane. The ordering influence of applied voltage upon ionic current behaviour has been found and explained within the “crowd model”.
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Biochemistry of magnesium

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Magnesium is essential for biochemical functions of cells. Since Mg2+ has a relatively low ionic radius in proportion to the size of the nucleus (0.86 versus 1.14 f A for Ca2+), it shows exceptional biochemical activity. Due to its physicochemical properties, intracellular magnesium can bind to the nucleus, ribosomes, cell membranes or macromolecules occurring in the cell’s cytosol. It is indispensable for the nucleus to function as a whole and for the maintenance of physical stability as well as aggregation of rybosomes into polysomes able to initiate protein synthesis. Mg2+ can also act as a cofactor for ribonucleic acid enzymes (ribozymes) capable of specifically recognizing and cleaving the target mRNA. As an essential cofactor in NER, BER, MMR processes, Mg2+ is required for the removal of DNA damage. An activator of over 300 different enzymes, magnesium participates in many metabolic processes, such as glycolysis, Krebs cycle, β-oxidation or ion transport across cell membranes. Mg2+ plays a key role in the regulation of functions of mitochondria, including the control of their volume, composition of ions and ATP production.
The aim of the experiment was to study the effects of selenium ions on the changes in membrane permeability for K and Ca in the leaves of rape during cadmium stress. The of stress level was determined by changes in the mass increment and lipid peroxidation (MDA concentration) in 3-week-old seedlings cultured in vitro on Murashige and Skoog [1962] medium (control) and on medium containing 600 µМ CdCl2. Selenium was added at the concentration of 2 µМ (Na2SeO4) to the control and medium containing cadmium ions. The level of K and Ca was determined with ionoselective electrodes after one hour of shaking leaf discs (membrane permeability) and heating to 100°C (total ion content). Cadmium present in the nutrient medium inhibited the mass increment and increased MDA concentration, and significantly decreased membrane permeability for K and Ca. In the mixtures of cadmium and selenium, selenium ions partially reduced the effects of the stress-inducing cadmium action on the studied physiological parameters and membrane permeability to the studied ions. The observed protective effect of selenium can be the result of the effect of this substance on both the activity of ion channels and peroxidation of membrane lipids.
The erythrocytes from Morris Hepatoma 5123 bearing rats took up Na+ and K+ ions from the incubation medium and released Na into the extracellular space at lower rates than did erythrocytes from intact control rats* The lipid composition of erythrocytes membranes from the tumor-bearing rats differed from that of membranes from unaffected rats, showing increased contents of phospholipid phosphorus and a decreased content of cholesterol, resulting in decreased choleste- rol: phospholipid molar ratios.
The present study aimed to identify the response of melon accessions and cultivars to salt stress in terms of ion exchange, enzyme activity, lipid peroxidation and photosynthetic pigment contents by mixture modelling. In mixture modeling, it is expected that the data set demonstrates a heterogeneous structure. This heterogeneity is characterized as unobservable heterogeneity. The data set’s heterogeneity produces severe deviations in the parameter assessments and the standard deviations. Heterogeneity is overcome when the data set separates itself into homogeneous sub-populations. Mixture modeling was performed using the Mclust mixture cluster program of the statistical software package R 5.2.3. Sub-populations were constructed by evaluating genotypes according to studied traits and correlation analysis was performed using the SPSS software package. The seedlings of 13 melon genotypes were harvested two weeks after salt application (0 mM or 50 mM NaCl) when symptoms of salt stress were observed. Nutrient contents and ratios (K, Ca, Na, K : Na and Ca : Na); superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) activities malondialdehyde (MDA) chlorophyll a, chlorophyll b, total chlorophyll and carotenoid contents were measured. Mixture modeling and correlation analysis were used in evaluating the experimental data sets. Differences in responses to salt application were observed among genotypes. While all genotypes exhibited negative responses in terms of K : Na ratio, which is an important parameter of salt tolerance, the smallest decreases in K : Na ratios were observed in the YYU-11 (–57.09%) and YYU-4 (–58.78%) genotypes, indicating them to be the most tolerant to salt stress. In general, enzyme activity decreased in response to salt application, although the responses varied among genotypes, especially with regard to CAT and APX activity. The YYU-29 genotype was notable as the genotype with the highest K : Na ratio (1.79) as well as the smallest change in MDA content under salt stress.
Objectives: It is well known, that acidosis-induced dilation of the middle cerebral artery (MCA) in normonatremia depends on BKCa channel activation in smooth muscle cells of the arterial wall. Our studies on the effect of hyponatremia on the regulation of the rat MCA have demonstrated, that acute hyponatremia causes BKCa channel dysfunction manifested by its reduced sensitivity to agonists. The aim of our present experiments was, therefore, to study whether the response of MCA to acidosis is decreased during hyponatremia and if so, whether BKCa channel activator applied in subthreshold dose restores the response of MCA to lowering of extravascular pH. Method: MCAs were isolated from male Wistar rats brains and placed in the arteriograph chamber filled 3-(N-morpholino) propanesulfonic acid (MOPS) buffered saline solution containing 1% BSA. The vessels were perfused (100 µl/ min) and set at a hydrostatic pressure of 80 mmHg. The MCA images were recorded using a microscope equipped with a camera coupled to a monitor. The measured parameter was the internal diameter of the vessel. Acute hyponatremia was induced in the chamber by decreasing Na+ concentration in the extra- and intravascular fluid from 144 mM to 120 mM. After equilibration of the MCA for 1 hour in normonatremic buffer, responses of this artery to BKCa channel activator (NS1619, 10- 5M) in normo- and hyponatremia, to lowering of extravascular pH from 7.4 to 7.0 in normonatremia, in hyponatremia and in hyponatremia in the presence of NS1619 (10-5M) were studied. Results: NS1619 administration led to MCA dilation by 16 ± 1% (P<0.001) in normonatremia but had no effect on the vessel diameter in hyponatremia. Reducing pH from 7.4 to 7.0 resulted in the dilation of MCA by 18 ± 2% (P<0.001) in normonatremia whereas in hyponatremia constriction of the MCA by 4 ± 2% (P<0.01) in response to reduced pH was observed. The presence of BKCa channel activator restored the response of the MCA to acidosis during hyponatremia. Conclusion: These results confirm our previous findings that during acute hyponatremia, BKCa channels sensitivity in the wall of MCA is reduced. This explains lack of the dilation of this artery to extracellular acidosis in hyponatremia. This study was financially supported by statutory activities of the Mossakowski MRC PAS
W doświadczeniu wazonowym przebadano wpływ węglanu wapnia, gipsu i fosfogipsu na plon i skład chemiczny roślin oraz pH i zawartość Ca²⁺, Mg²⁺, K⁺ w roztworze glebowym. Do badań została użyta gleba lekka, pochodząca z warstwy ornej niewapnowanego obiektu NPK, trwałego doświadczenia nawozowego prowadzonego w Wydziałowej Stacji Doświadczalnej SGGW w Skierniewicach. Roślinami testowymi były: gorczyca biała (Sinapis alba L.) oraz koniczyna czerwona (Trifolium pratense L.). Dawki wapnia w użytych substancjach wyliczono na podstawie 1,2 i 4 Hh. Największy przyrost plonów uzyskano stosując CaCO₃, natomiast użyte do nawożenia odpady na ogół zmniejszały plony uprawianych roślin. Węglan wapnia powodował wzrost zawartości Ca i Mg i spadek zawartości K w roślinach. Pobranie Ca, Mg i K przez rośliny było największe na obiektach z węglanem wapnia, mniejsze na obiektach z gipsem i najmniejsze na obiektach z fosfogipsem. Zastosowanie największych dawek odpadów było przyczyną zaburzenia gospodarki jonowej roślin w wyniku, którego dochodziło do rozszerzenia stosunku K : (Ca + Mg). Dominującym jonem roztworu glebowego gleby silnie kwaśnej był potas, deficytowym zaś magnez. Wapnowanie zwiększyło zawartość wapnia, a zmniejszyło zawartość magnezu w roztworze glebowym po zbiorze roślin. Na obiektach z gipsem i fosfogipsem zawartość wszystkich badanych jonów była wielokrotnie większa niż na obiektach wapnowanych (CaCO₃), a dominującym jonem był kation wapnia.
W pracy przedstawiono wyniki badań jakości wód rzeki Drwinki. Woda badanego cieku przepływa przez tereny o zróżnicowanym zagospodarowaniu. W górnym biegu jest to teren przemysłowy oraz miejski, następnie tereny użytkowane rolniczo z zabudową osadniczą wiejską oraz zalesione tereny Puszczy Niepołomickiej, a w końcowym biegu wiejskie tereny zabudowane. W celu określenia jakości wody w Drwince przeprowadzono badania zawartości związków azotu, fosforu, potasu, sodu, wapnia, magnezu, siarczanów, chlorków, zawiesiny, a także pH, przewodności elektrolitycznej i substancji rozpuszczonych w sześciu wybranych punktach poboru próbek wody. Wodę do analiz pobierano w odstępach miesięcznych w latach 2009 i 2010. Wyniki badań mogą być przydatne przy planowaniu zagospodarowania terenów zlewni służącemu ograniczeniu zanieczyszczeń wprowadzanych do wód Drwinki.
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