Search results for "otas"

The presence of KCl in the exposure medium strongly influences the mutagenicity of metabolites of polycyclic aromatic hydrocarbons in Escherichia col…

1994

Abstract Previous studies demonstrated that the ion composition of the exposure medium may strongly influence the mutagenicity of many compounds in the liquid preincubation modification of the reversion assay with his − Salmonella typhimurium strains. Similar influences were now observed in the reversion assay with trp − Escherichia coli strain WP2 uvrA . The exposure medium was 8 mM sodium phosphate buffer (pH 7.4), containing no other ions or 125 mM KCl. Omission of KCl resulted in an about 10-fold enhancement of the mutagenic activity of 7-methylbenz[ a ]anthracene 5,6-oxide, but in a strong decrease in the mutagenicity of 1-hydroxymethylpyrene sulphate, close to the limit of detection. …

Ion conductance changes associated with spike adaptation in the rapidly adapting stretch receptor of the crayfish.

1975

The time course of the repetitive impulse discharges has been investigated for two high intensities of maintained depolarizing currents, 30 nA and 50 nA, for which the receptor adaptation was complete within 70 msec. The changes in sodium and potassium conductance associated with the decline in spike activity have been analyzed at different instances of time by interrupting in successive experiments the various action potentials in the pulse trains either at the early phase by holding the potential at about -60 mV and recording the inward current (upstroke-gNa) or by evaluating the delayed outward current flowing as the result of a depolarizing voltage pulse which at the end of the action p…

Evidence for a selective and electroneutral K+/H+-exchange in Saccharomyces cerevisiae using plasma membrane vesicles

1996

The existence of a K+/H+ transport system in plasma membrane vesicles from Saccharomyces cerevisiae is demonstrated using fluorimetric monitoring of proton fluxes across vesicles (ACMA fluorescence quenching). Plasma membrane vesicles used for this study were obtained by a purification/reconstitution protocol based on differential and discontinuous sucrose gradient centrifugations followed by an octylglucoside dilution/gel filtration procedure. This method produces a high percentage of tightly-sealed inside-out plasma membrane vesicles. In these vesicles, the K+/H+ transport system, which is able to catalyse both K+ influx and efflux, is mainly driven by the K+ transmembrane gradient and ca…

High nucleo-cytoplasmic concentration gradient of chloride in rat liver.

1966

PREVIOUSLY, a high nucleo-cytoplasmic concentration gradient of sodium was found in rat liver and other tissues1,2. Since the concentration of potassium also was higher in the nucleus than in the cytoplasm, about 500 µequiv./g dry weight of anions should exist in the nucleus if the assumption is correct that nucleic acids and basic proteins approximately neutralize each other. This communication presents data which demonstrate a high concentration of chloride in the nucleus of the rat-liver cell.

Involvement of Kv3.1 potassium chanels in 7-ketocholesterol, 24S-hydroxycholesterol and C24 : 0-induced lipotoxicity on 158N and BV-2 cells : relatio…

2017

Potassium (K+) is involved in the regulation of cellular excitability, cell cycle regulation, cell viability, neuroprotection and maintenance of microglial and oligodendrocytic functions. Potassium dysfunction, described in several neurodegenerative diseases such as Alzheimer's Disease (AD), multiple sclerosis (MS), Parkinson's disease and Huntington's disease, may be a potential therapeutic target. The underlying toxic mechanisms of these neurodegenerative pathologies involve oxysterols, which are oxidized cholesterol derivatives, and fatty acids including those associated with peroxisomal metabolism. 7-ketocholesterol (7KC), 24S-hydroxycholesterol (24S-OHC) and tetracosanoic acid (C24:0),…

Investigation of magnesium phosphate cement hydration in diluted suspension and its retardation by boric acid

2016

Abstract Magnesium phosphate cements (MPCs) are used for rapid repair works, but they may also offer prospects for the stabilization/solidification of deleterious waste. MPCs contain calcined magnesium oxide and a water-soluble acid phosphate, such as potassium dihydrogen phosphate (KH 2 PO 4 ). The main precipitated hydrate is then K-struvite (MgKPO 4 ·6H 2 O). This work aims at giving new insight into the processes involved in its formation. Since cement hydration is very rapid, the second objective is to understand how boric acid, a common admixture for field application, retards cement hydration. A multi-stage process is evidenced in diluted suspension: MgHPO 4 ·7H 2 O likely precipitat…

Retention of alkali ions by hydrated low-pH cements: Mechanism and Na+/K+ selectivity

2013

Low-pH cements, also referred to as low-alkalinity cements, can be designed by replacing significant amounts of Portland cement by pozzolanic materials. Their pore solution is characterized by a pH near 11, and an alkali concentration much lower than that of Portland cement. This work investigates the retention of sodium and potassium by a hydrated low-pH cement comprising 60% Portland cement and 40% silica fume. It is shown that sorption of potassium is higher than that of sodium and mainly results from counterion charge balancing of the C-S-H negative surface charge. To explain the greater retention of potassium compared to sodium, it is postulated that potassium, unlike sodium, may enter…

The electrophysiology of adenosine in the mammalian central nervous system

1991

Immunoproteomic studies on paediatric opsoclonus-myoclonus associated with neuroblastoma

2016

We aimed to identify new cell-membrane antigens implicated in opsoclonus-myoclonus with neuroblastoma. The sera of 3 out of 14 patients showed IgG electron-microscopy immunogold reactivity on SH-SY5Y neuroblastoma cells. Immunoprecipitation experiments using rat brain synaptosomes and SH-SY5Y cells led to the identification of: (1) thirty-one nuclear/cytoplasmic proteins (including antigens HuB, HuC); (2) seven neuronal membrane proteins, including the Shaw-potassium channel Kv3.3 (KCNC3), whose genetic disruption in mice causes ataxia and generalized muscle twitching. Although cell-based assays did not demonstrate direct antigenicity, our findings point to Shaw-related subfamily of the pot…

Ceramide Mediates Acute Oxygen Sensing in Vascular Tissues

2014

AbstractAims: A variety of vessels, such as resistance pulmonary arteries (PA) and fetoplacental arteries and the ductus arteriosus (DA) are specialized in sensing and responding to changes in oxygen tension. Despite opposite stimuli, normoxic DA contraction and hypoxic fetoplacental and PA vasoconstriction share some mechanistic features. Activation of neutral sphingomyelinase (nSMase) and subsequent ceramide production has been involved in hypoxic pulmonary vasoconstriction (HPV). Herein we aimed to study the possible role of nSMase-derived ceramide as a common factor in the acute oxygen-sensing function of specialized vascular tissues. Results: The nSMase inhibitor GW4869 and an anticera…