Search results for "Potassium"
showing 10 items of 930 documents
Accumulation and discharge behavior of Cs-137 by zebra fish (Brachydanio rerio) in different aquatic environments
1990
The uptake and release kinetics of137Cs from water by the tropical fishBrachydanio rerio has been studied under controlled laboratory condition. The accumulation of this radionuclide from food was avoided by feeding the fishes separately in an inactive environment. A steep inverse dependence of bioconcentration factor (BCF) with potassium concentration has been observed. This can formally be described by the equation BCF=5.2 · [K+]−0.44. The elimination rate constant K in fresh water conditions has been found to have a magnitude of 0.014±0.03 d−1 which corresponds to a biological half-life of 51±10 days. The uptake and release kinetics ofBrachydanio rerio has been compared with earlier stud…
The effect of reaction conditions on the chain end structure and functionality during dehydrochlorination oftert-chlorine-telechelic polyisobutylene …
1998
Dehydrochlorination of tert-chlorine-telechelic polyisobutylene with potassium tert-butoxide in refluxing tetrahydrofuran is quantitative after 22 h, but results in ca. 3% endo olefin chain ends which are not reactive in some subsequent functionalization reactions. The formation of these undesired structures is most likely due to simultaneous thermally induced HCl loss. Lower temperatures and longer reaction times led to exclusive formation of external double bonds in some cases but to incomplete dehydrochlorination.
Potassium demineralization of coconut fiber via combined hydrothermal treatment and washing: Effect on pyrolysis kinetics, mechanisms, and bio-oil co…
2021
Abstract Producing clean energy from waste biomass via pyrolysis is critical in reducing dependence on fossil fuels and alleviating their environmental impacts. Inherent potassium in low energy density coconut fibers reduces bio-oil yield and compromises bio-oil quality and the integrity of reactors within which pyrolysis occurs. The effect of consecutive hydrothermal treatment (180°C-220 °C) and water washing on coconut fiber demineralization, pyrolysis behavior, and bio-oil composition was investigated. Chemical fractionation method classified the most occurring inorganic (potassium) as ~76% water-soluble, ~19% ion-exchangeable, and ~5% acid-soluble species. Demineralization results show …
Determination of total ribonucleotide pool in plant materials by high-pH anion-exchange high-performance liquid chromatography following extraction w…
2005
A new, improved method that only requires a potassium hydroxide extraction procedure is presented for the analysis of a full nucleotide pool in plant materials. Quantification was performed by high-pH anion-exchange chromatography (HPAEC) with UV detection after a potassium hydroxide extraction, and allowed the quantification of 13 linear ribonucleotides in a single run. The method has been validated by comparison of six extraction methods and also by measurement of the intracellular nucleotide levels of three plant species (cell cultures and leaves). The evolution of the nucleotide pool of Nicotiana tabacum cell culture during growth has also been measured, and showed an increase in the po…
Guanosine modulates K+ membrane currents in SH-SY5Y cells: involvement of adenosine receptors
2022
AbstractGuanosine (GUO), widely considered a key signaling mediator, is implicated in the regulation of several cellular processes. While its interaction with neural membranes has been described, GUO still is an orphan neuromodulator. It has been postulated that GUO may eventually interact with potassium channels and adenosine (ADO) receptors (ARs), both particularly important for the control of cellular excitability. Accordingly, here, we investigated the effects of GUO on the bioelectric activity of human neuroblastoma SH-SY5Y cells by whole-cell patch-clamp recordings. We first explored the contribution of voltage-dependent K+ channels and, besides this, the role of ARs in the regulation…
Potassium uptake system Trk2 is crucial for yeast cell viability during anhydrobiosis
2013
Yeasts grow at very different potassium concentrations, adapting their intracellular cation levels to changes in the external environment. Potassium homeostasis is maintained with the help of several transporters mediating the uptake and efflux of potassium with various affinities and mechanisms. In the model yeast Saccharomyces cerevisiae, two uptake systems, Trk1 and Trk2, are responsible for the accumulation of a relatively high intracellular potassium content (200-300 mM) and the efflux of surplus potassium is mediated by the Tok1 channel and active exporters Ena ATPase and Nha1 cation/proton antiporter. Using a series of deletion mutants, we studied the role of individual potassium tra…
Response of the Saccharomyces cerevisiae Mpk1 Mitogen-Activated Protein Kinase Pathway to Increases in Internal Turgor Pressure Caused by Loss of Ppz…
2004
ABSTRACT The Mpk1 pathway of Saccharomyces cerevisiae is a key determinant of cell wall integrity. A genetic link between the Mpk1 kinase and the Ppz phosphatases has been reported, but the nature of this connection was unclear. Recently, the Ppz phosphatases were shown to be regulators of K + and pH homeostasis. Here, we demonstrate that Ppz-deficient strains display increased steady-state K + levels and sensitivity to increased KCl concentrations. Given these observations and the fact that K + is the major determinant of intracellular turgor pressure, we reasoned that the connection between PPZ1 and - 2 and MPK1 was due to the combination of increased internal turgor pressure in Ppz-defic…
Il management dell’ipersensibilità dentinale: dalla ricerca alla clinica
2014
Obiettivi. Scopo di questo lavoro è presentare le più recenti acquisizioni in tema di epidemiologia, diagnosi, eziopatogenesi e management clinico dell’ipersensibilità dentinale. Vengono inoltre descritti i prodotti disponibili per il suo trattamento e gli studi sperimentali e clinici condotti per valutarne l’efficacia. Materiali e metodi. Attraverso la banca dati Medline/Pubmed sono stati selezionati i lavori originali, le revisioni della letteratura e le linee guida pubblicate in lingua inglese e in italiano sull’argomento dal 2009 al 2013. Altre fonti sono state selezionate dai riferimenti bibliografici individuati. Risultati e conclusioni. Il management dell’ipersensibilità prevede il c…
Evaluation of changes in salivary composition in renal failure patients before and after hemodialysis
2017
Background Saliva plays a major role in preserving the integrity of oral tissues. The oral health of renal failure patients could be negatively affected by the underlying pathology, the dialysis treatment, or an altered salivary composition. Major systemic changes occur during hemodialysis (HD), which could affect the flow rate and biochemical composition of saliva. Therefore, the aim of this study was to evaluate the effects of HD on the salivary flow rate, pH and biochemical composition before and after completion of a dialysis session. Material and methods Thirty Renal failure patients undergoing hemodialysis were selected based on the inclusion and exclusion criteria set forth for the s…
K-region oxides and imines derived from alkylated benz[α]anthracene congeners: synthesis, stability in aqueous media and mutagenicity
1994
The K-region oxides and imines of benz[a]anthracene, 1-methylbenz[a]anthracene, 7-methylbenz[a]anthracene, 7-ethylbenz[a]anthracene and 7,12-dimethylbenz[a]anthracene were synthesized and characterized (melting point, 1H-NMR and electron impact mass spectra, elemental analysis, IR spectroscopy). All 10 compounds showed high mutagenic activity in Salmonella typhimurium (reversion of his- strains TA97, TA98, TA100 and TA104). The arene imines were more potent than the corresponding arene oxides. Alkyl substitutions strongly influenced the activities. Furthermore, all compounds were more active when exposure took place in the absence of inorganic ions than when KCl (125 mM) was present. The in…