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1
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Role of calcium in glutamate-mediated toxicity: mechanisms of calcium fluxes in rabbit hippocampus in vivo investigated with microdialysis

100%
Lazarewicz J. W., Salinska E.
Acta Neurobiologiae Experimentalis
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1993
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vol. 53
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issue 1
3-13
EN
Calcium ions are known to play a key role in the mechanism of excitotoxic and ischemic neuronal injury.< Hippocampal CA1 neurons> are selectively susceptible to this kind of damage. Although various have been identified in the hippocampal neurons, it is not clear what the main pathway for Ca?+ entry is during overexcitation. These studies were aimed to estimate a potential contribution of different types of calcium ionophores in calcium redistribution to hippocampal neurons in vivo.The local microdialysis technique, combined with the 45Ca?+ utilizing method was used to measure the changes in extracellular Ca?+ concentrations ([Ca?+]e) in the rabbit hippocampus in vivo, and to apply active substances directly to the hippocampus. The application of N-methyl-D-aspartate (NMDA) resulted in a large, dose-dependent decrease of [Ca?+]e, which was sensitive to APV and MK-801, but was only slightly reduced by and . The effect of high potassium medium was less pronounced and only slightly inhibited by nimodipine. However it was inhibited by 75% in the presence of MK-801 and then completely cancelled by nimodipine. To visualize the depolarization-induced calcium influx to hippocampal cells, KC1-induced cellular swelling and resulting shrinkage of the extracellular space, monitored with [U-14C]sucrose , was taken into account in calculating these data. These results indicate that calcium redistribution into hippocampal neurons through NMDA channels may highly exceed calcium fluxes in the hippocampus, attributable to a stimulation of the L-type voltage-sensitive calcium channels.
2
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Effect of K+ accumulation removal and high extracellular osmolarity on K+ current in insect axonal membrane

100%
Stankiewicz M., Pelhate M., Pancerzynska I., Zienkiewicz A., Kadziela^W., Kadziela W.
Acta Neurobiologiae Experimentalis
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1996
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vol. 56
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issue 1
95-102
EN
The effect of removal of K+ accmulation on K+ current in insect axonal membrane was observed. Experiments were performed on isolated giant axon of a cockroach using double oil gap technique. K+ accumulation was reduced by: (1) an outward water flow induced by non-electorlytes (urea, glucose) added to extracellular saline and (2) by an increase of non-specific permeability of axonal glial layer obtained after the application of DMSO. The conclusions are: (1) osmolar effect depends on the type of molecule used for osmotic shock, (2) increase of outward K+ current in conditions of high extraaxonal osmotic pressure is attributed to the decrease of K+ accumulation and outward water flow, (3) removal of K+ accumulation doesn't affect the kinetics and the time course of K+ current, (4) experiments confirmed the presence of an inactivating component in the axonal outward K+ current, (5) DMSO must be used cautiously as a solvent in electophysiological experiments.
3
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ATP-sensitive K+ transport in adrenal chromaffin granules

75%
Szewczyk A., Lobanov N. A., Kicinska A., Wojcik G., Nalecz M. J.
Acta Neurobiologiae Experimentalis
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2001
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vol. 61
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issue 1
1-12
EN
In the present study the influx of 86Rb+, a K+ analogue, was studied in mitochondria, microsomes and chromaffin granules prepared from adrenal gland medulla. The most active electrogenic 86Rb+ transport was found in the membrane fraction identified as chromaffin granules by marker enzyme estimation. The transport was found to be sensitive to ATP, ATPS, ADP and to the triazine dyes, but not to AMP and cAMP. The inhibition induced by ATP was observed in the absence of externally added Mg2+, suggesting that a free nucleotide, rather than the ATP-Mg complex, was required for inhibition. Furthermore, the 86Rb+ influx was found to be inhibited by Mg2+ alone, but not by Ca2+ and antidiabetic sulfonylureas. The 86Rb+ influx was not stimulated by potassium channel openers. In conclusion, our results indicate that an electrogenic, ATP-sensitive potassium transport system operates in the chromaffin granule membrane.
4

Motile activities of Dictyostelium discoideum differ from those in Protista or vertebrate animal cells

75%
Waligorska A., Wianecka-Skoczen M., Korohoda W.
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2007
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vol. 55
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issue 3-4
87-93
EN
Cell movement in the amoebae Dictyostelium discoideum has been examined in media differing in monovalent cation concentration (i.e. Na+ and K+). Under isotonic or even slightly hypertonic conditions, the cells move equally well in solutions in which either potassium or sodium ions dominate. However, in strongly hypertonic solutions the amoebae showed motility in a 2% potassium chloride solution, but remained motionless in a hypertonic 2% sodium chloride solution. This inhibition of D. discoideum amoebae movement in a hypertonic sodium chloride solution was fully reversible. Such behaviour corresponds to that of plant, fungi, and some invertebrate animal cells rather than protozoan or vertebrate cells. These observations suggest that studies using D. discoideum as a model for cell motility in vertebrate animal tissue cells should be considered with caution, and would seem to confirm the classification of cellular slime moulds as related rather to Fungi than to Protista. This also shows that the cell membrane models should consider the asymmetry in sodium /potassium ion concentrations found in vertebrate animal cells as one of various possibilities.
5
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Isulfhydryl reagents with K+ transport in adrenal chromaffin granules

63%
Szewczyk A., Lobanov N. A., Nowotny M., Nalecz M. J., Berent U., Mroczkowska J. E., Nalecz K. A.
Acta Neurobiologiae Experimentalis
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1997
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vol. 57
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issue 4
329-332
EN
In the present study the functional role of SH groups in the Ca2+ -independent K+ selective channel activity in the membrane of bovine adrenal gland chromaffin granules has been studied. Ionic channel activity has been estimated using 86Rb+, a K+ analogue, flux measurements. The inhibition of chromaffin granules K+ channel by SH modifying agents, such as N ethylmaleimide, mersalyl and phenylarsenoxide, is described.
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