The Experts below are selected from a list of 120 Experts worldwide ranked by ideXlab platform
Hana Tejkalová - One of the best experts on this subject based on the ideXlab platform.
-
Effects of K^+-Depolarization, Arachidonic Acid, Ethanol, and Aging on the High-Affinity Choline Transport in Rat Hippocampus
Neurochemical Research, 1998Co-Authors: Zdena Kristofikova, Jan Klaschka, Hana TejkalováAbstract:The Na^+-dependent high-affinity choline uptake (HACU) transport and the [^3H]Hemicholinium-3 ([^3H]HC-3) specific binding were measured on hippocampal synaptosomes of young (3–6 months) and old (22 months) Wistar rats. In vitro effects of 100–300 μM arachidonic acid (AA) and of 5% ethanol were tested under basal as well as stimulated (55 mM KCl) conditions. The influence of AA (an irreversible decrease of HACU and a reversible increase of [^3H]HC-3 binding) was more marked under stimulated rather than basal conditions in brain tissue of young rats. The increased K^+-depolarization effect on HACU and the decreased influence of AA on [^3H]HC-3 binding were estimated in brain tissue of old compared to young rats. Results suggest the involvement of different pools of the high-affinity choline carrier and marked changes due to aging in the regulation of the HACU transport.
Zdena Kristofikova - One of the best experts on this subject based on the ideXlab platform.
-
The interaction of standard oxime reactivators with Hemicholinium-3 sensitive choline carriers
Toxicology Letters, 2012Co-Authors: Ondrej Soukup, Zdena Kristofikova, Vojtech Tambor, Daniela Ripova, Kamil KucaAbstract:Abstract Organophosphorus poisoning manifests as a cholinergic syndrome due to an inhibition of acetylcholinesterase. It is treated symptomatically by anticholinergics and oxime reactivators are used as causal antidotes. Reactivators possess a complex mechanism of action and interact at various levels of the cholinergic transmission. The aim of this study was to investigate the effect of standard oxime reactivators (HI-6, obidoxime, trimedoxime, methoxime and pralidoxime) on the Hemicholinium-3 sensitive carriers, which are involved in the high-affinity choline uptake (HACU) transport, a key regulatory step in the synthesis of acetylcholine. The activity of the carriers was estimated in vitro on hippocampal synaptosomes using the substrate (3H)-choline and the competitive inhibitor (3H)-Hemicholinium-3. Furthermore, the effect of the reactivators on the fluidity of hippocampal membranes was assessed. All tested compounds, except methoxime, showed an acute inhibitory effect on the carriers, however, only at μM concentrations. Trimedoxime showed the highest potency to inhibit HACU among all tested compounds ( I max 62%, IC 50 = 3 μM). All compounds, except HI-6, influenced also a membrane fluidity in the region of the hydrophilic heads of phospholipid bilayer, nevertheless, only methoxime was able to penetrate more deeply into the hydrocarbon core. We suggest that the direct interaction of oxime reactivators with the carrier protein (HI-6 and trimedoxime) and/or the changes in carrier conformation mediated by alterations in membrane fluidity (trimedoxime, obidoxime and pralidoxime) could occur here. The influence of reactivators on the carriers could be unfavorable in the case of their prolonged administration in vivo. From this point of view, the application of methoxime appears to be the best.
-
Effects of K^+-Depolarization, Arachidonic Acid, Ethanol, and Aging on the High-Affinity Choline Transport in Rat Hippocampus
Neurochemical Research, 1998Co-Authors: Zdena Kristofikova, Jan Klaschka, Hana TejkalováAbstract:The Na^+-dependent high-affinity choline uptake (HACU) transport and the [^3H]Hemicholinium-3 ([^3H]HC-3) specific binding were measured on hippocampal synaptosomes of young (3–6 months) and old (22 months) Wistar rats. In vitro effects of 100–300 μM arachidonic acid (AA) and of 5% ethanol were tested under basal as well as stimulated (55 mM KCl) conditions. The influence of AA (an irreversible decrease of HACU and a reversible increase of [^3H]HC-3 binding) was more marked under stimulated rather than basal conditions in brain tissue of young rats. The increased K^+-depolarization effect on HACU and the decreased influence of AA on [^3H]HC-3 binding were estimated in brain tissue of old compared to young rats. Results suggest the involvement of different pools of the high-affinity choline carrier and marked changes due to aging in the regulation of the HACU transport.
-
Effect of postmortem storage on the [3H]Hemicholinium-3 binding site in the rat brain. Preliminary study for investigations of human patients with Alzheimer's disease.
Archives of Gerontology and Geriatrics, 1993Co-Authors: Zdena Kristofikova, Jan Klaschka, V. Němcová, E. Majer, E. FalesAbstract:Abstract The effect of postmortem storage at room temperature (24–26°C, 0–4 h) and cold-room temperature (4°C, (0–24 h) on the [ 3 H]Hemicholinium-3 binding sites in the brain hippocampus, cortex and cerebellum of 3-month-old Wistar rats was studied. A slow decrease in the density of the binding sites was observed at both temperatures, which was best fit by a linear model common for all three brain regions. No systematic alterations of the affinity of the binding sites for Hemicholinium-3 were found. The values obtained from experiments with animals were compared with the values measured in the frontal cortex of old men. Approaches to the evaluation of data obtained from postmortem samples of human brain tissue of patients with Alzheimer's disease are proposed.
Nicholas J. Lenn - One of the best experts on this subject based on the ideXlab platform.
-
hemicholinium 3 binding sites in subnuclei of the rat interpeduncular nucleus quantitative in vitro autoradiography
Brain Research Bulletin, 1990Co-Authors: Jonathan W Bekenstein, Nicholas J. LennAbstract:Abstract The interpeduncular nucleus (IPN) receives dense cholinergic input from the medial habenulae (MH) via the fasciculus retroflexus (FR). This projection is known to terminate in the rostral, central and intermediate subnuclei. Correspondingly, the concentration of Hemicholinium-3 (HC-3) binding sites in these subnuclei was equal to or greater than that reported in any other brain areas. Moderate values in the distal FR and in the lateral subnuclei indicate that choline uptake sites are located on nonterminal portions of MH afferent axons as well. Possible relationships of HC-3 binding to the unusual metabolic properties of FR and IPN, and to the distribution of choline acetyltransferase-containing axons and terminals in FR and IPN are suggested.
Jan Klaschka - One of the best experts on this subject based on the ideXlab platform.
-
Effects of K^+-Depolarization, Arachidonic Acid, Ethanol, and Aging on the High-Affinity Choline Transport in Rat Hippocampus
Neurochemical Research, 1998Co-Authors: Zdena Kristofikova, Jan Klaschka, Hana TejkalováAbstract:The Na^+-dependent high-affinity choline uptake (HACU) transport and the [^3H]Hemicholinium-3 ([^3H]HC-3) specific binding were measured on hippocampal synaptosomes of young (3–6 months) and old (22 months) Wistar rats. In vitro effects of 100–300 μM arachidonic acid (AA) and of 5% ethanol were tested under basal as well as stimulated (55 mM KCl) conditions. The influence of AA (an irreversible decrease of HACU and a reversible increase of [^3H]HC-3 binding) was more marked under stimulated rather than basal conditions in brain tissue of young rats. The increased K^+-depolarization effect on HACU and the decreased influence of AA on [^3H]HC-3 binding were estimated in brain tissue of old compared to young rats. Results suggest the involvement of different pools of the high-affinity choline carrier and marked changes due to aging in the regulation of the HACU transport.
-
Effect of postmortem storage on the [3H]Hemicholinium-3 binding site in the rat brain. Preliminary study for investigations of human patients with Alzheimer's disease.
Archives of Gerontology and Geriatrics, 1993Co-Authors: Zdena Kristofikova, Jan Klaschka, V. Němcová, E. Majer, E. FalesAbstract:Abstract The effect of postmortem storage at room temperature (24–26°C, 0–4 h) and cold-room temperature (4°C, (0–24 h) on the [ 3 H]Hemicholinium-3 binding sites in the brain hippocampus, cortex and cerebellum of 3-month-old Wistar rats was studied. A slow decrease in the density of the binding sites was observed at both temperatures, which was best fit by a linear model common for all three brain regions. No systematic alterations of the affinity of the binding sites for Hemicholinium-3 were found. The values obtained from experiments with animals were compared with the values measured in the frontal cortex of old men. Approaches to the evaluation of data obtained from postmortem samples of human brain tissue of patients with Alzheimer's disease are proposed.
Brian Collier - One of the best experts on this subject based on the ideXlab platform.
-
Stereoselectivity of the Inhibition of [3H]Hemicholinium‐3 Binding to the Sodium‐Dependent High‐Affinity Choline Transporter by the Enantiomers of a‐ and β‐Methylcholine
Journal of Neurochemistry, 2008Co-Authors: S. S. G. Ferguson, Brian CollierAbstract:: In a previous report, we showed that the enantiomers of alpha- and beta-methylcholine inhibited choline uptake with stereoselectivity, but that their transport by the choline carrier of nerve terminals showed stereospecificity. The present experiments used the same choline analogues to determine if either of the above characteristics pertains to their ability to interact with the [3H]-Hemicholinium-3 binding site present on striatal membranes and synaptosomes. [3H]Hemicholinium-3 binding to striatal membranes could be inhibited stereoselectively by the enantiomers of beta-methylcholine, but R(+)-alpha-methylcholine was little better than its enantiomer in this test. However, [3H]Hemicholinium-3 binding to striatal synaptosomes was inhibited stereoselectively by the enantiomers of both alpha- and beta-methylcholine. This difference between the properties of [3H]Hemicholinium-3 binding to membranes or to synaptosomes appears related to the presence of two ligand binding states. The [3H]Hemicholinium-3 binding site could be shifted to a low-affinity state by ATP treatment and to a high-affinity state by EDTA washing. When the [3H]Hemicholinium-3 binding site existed in its low-affinity state, binding was inhibited stereoselectively by the enantiomers of both alpha- and beta-methylcholine, but when shifted to its high-affinity state, it was inhibited stereoselectively only by the enantiomers of beta-methylcholine. We conclude that Hemicholinium-3 interacts with the substrate recognition site of the high-affinity choline transporter, but that the stereoselectivity of this site changes depending on its affinity state.
-
Regulation of Rat Brain Synaptosomal [3H]Hemicholinium‐3 Binding and [3H]Choline Transport Sites Following Exposure to Choline Mustard Aziridinium Ion
Journal of Neurochemistry, 2002Co-Authors: S. S. G. Ferguson, R. J. Rylett, Brian CollierAbstract:: Choline uptake by cholinergic nerve terminals is increased by depolarization; the literature suggests that this results from either the appearance of occult transporters or the increased activity of existing ones. The present experiments attempt to clarify the mechanism by which choline transport is regulated by testing if the preexposure of synaptosomes to choline mustard aziridinium ion prevents the stimulation-induced appearance of Hemicholinium-3 binding sites and/or choline transport activity. Choline mustard inhibited irreversibly most of the "ground-state" (basal) high-affinity choline transport but only 50% of "ground-state" Hemicholinium-3 binding sites. Exposure of both striatal and hippocampal synaptosomes to the mustard, before stimulation, inhibited K(+)-stimulated increases in choline transport and of [3H]-Hemicholinium-3 binding. We conclude that the mechanism by which choline transport is regulated involves the increased activity of a pool of transport sites that are occluded to Hemicholinium-3 but are available to choline mustard aziridinium ion, and presumably to choline, before stimulation. However, the concentration of mustard needed to inhibit the stimulation-induced increase of [3H]-Hemicholinium-3 binding and choline transport was lower for striatal synaptosomes than for hippocampal synaptosomes. In the absence of extracellular Ca2+ or presence of high Mg2+ levels, the choline mustard did not prevent the appearance of extra striatal Hemicholinium-3 binding sites. Also, high Mg2+ levels removed the ability of the mustard to inhibit K(+)-stimulated increases of either [3H]-Hemicholinium-3 binding or choline transport by hippocampal synaptosomes. In contrast, the preexposure of hippocampal synaptosomes to the mustard in the presence of a calcium ionophore (A23187) reduced the concentration of inhibitor needed to prevent the activation of [3H]Hemicholinium-3 binding and choline uptake. Thus, we conclude that the ability of the choline mustard to alkylate the pool of choline transporters that are activated by stimulation appears dependent on the entry of extra-cellular Ca2+.