Rapid astrocyte death induced by transient hypoxia, acidosis, and extracellular ion shifts

Glia ◽  
2001 ◽  
Vol 34 (2) ◽  
pp. 134-142 ◽  
Author(s):  
Alexander Bondarenko ◽  
Mitchell Chesler
Keyword(s):  
Ion Shifts

Effect of cicletanine on ischemia/reperfusion-induced ion shifts in isolated rat hearts

1990 ◽  
Vol 22 ◽  
pp. S64
Author(s):  
Arpad Tosaki ◽  
Matyas Koltai ◽  
Thierry Tarrade ◽  
Pierre Braquet
Keyword(s):  
Ischemia Reperfusion ◽  
Rat Hearts ◽  
Ion Shifts ◽  
Isolated Rat

Calcium dependence of rapid astrocyte death induced by transient hypoxia, acidosis, and extracellular ion shifts

Glia ◽  
2001 ◽  
Vol 34 (2) ◽  
pp. 143-149 ◽  
Author(s):  
Alexander Bondarenko ◽  
Mitchell Chesler
Keyword(s):  
Calcium Dependence ◽  
Ion Shifts

scholarly journals Extracellular pH Changes and Accompanying Cation Shifts During Ouabain-Induced Spreading Depression

2000 ◽  
Vol 83 (3) ◽  
pp. 1338-1345 ◽  
Author(s):  
G. Menna ◽  
C. K. Tong ◽  
M. Chesler
Keyword(s):  
Spreading Depression ◽  
Cyclopiazonic Acid ◽  
Stratum Radiatum ◽  
Ph Changes ◽  
Alkaline Shift ◽  
Gradual Onset ◽  
High K ◽  
Ion Shifts ◽  
Free Media ◽  
Peak Value

Interstitial ionic shifts that accompany ouabain-induced spreading depression (SD) were studied in rat hippocampal and cortical slices in the presence and absence of extracellular Ca2+. A double-barreled ion-selective microelectrode specific for H+, K+, Na+, or Ca2+ was placed in the CA1 stratum radiatum or midcortical layer. Superfusion of 100 μM ouabain caused a rapid, negative, interstitial voltage shift (2–10 mV) after 3–5 min. The negativity was accompanied by a rapid alkaline transient followed by prolonged acidosis. In media containing 3 mM Ca2+, the alkalosis induced by ouabain averaged 0.07 ± 0.01 unit pH. In media with no added Ca2+ and 2 mM EGTA, the alkaline shift was not significantly different (0.09 ± 0.02 unit pH). The alkaline transient was unaffected by inhibiting Na+-H+ exchange with ethylisopropylamiloride (EIPA) or by blocking endoplasmic reticulum Ca2+ uptake with thapsigargin or cyclopiazonic acid. Alkaline transients were also observed in Ca2+-free media when SD was induced by microinjecting high K+. The late acidification accompanying ouabain-induced SD was significantly reduced in Ca2+-free media and in solutions containing EIPA. The ouabain-induced SD was associated with a rapid but relatively modest increase in [K+]o. In the presence of 3 mM external Ca2+, the mean peak elevation of [K+]o was 12 ± 0.62 mM. In Ca2+-free media, the elevation of [K+]o had a more gradual onset and reached a significantly larger peak value, which averaged 22 ± 1.1 mM. The decrease in [Na+]o that accompanied ouabain-induced SD was somewhat greater. The [Na+]o decreased by averages of 40 ± 7 and 33 ± 3 mM in Ca2+ and Ca2+-free media, respectively. In media containing 1.2 mM Ca2+, ouabain-induced SD was associated with a substantial decrease in [Ca2+]o that averaged 0.73 ± 0.07 mM. These data demonstrate that in comparison with conventional SD, ouabain-induced SD exhibits ion shifts that are qualitatively similar but quantitatively diminished. The presence of external Ca2+ can modulate the phenomenon but is irrelevant to the generation of the SD and its accompanying alkaline pH transient. Significance of these results is discussed in reference to the propagation of SD and the generation of interstitial pH changes.

Anisotropic and heterogeneous diffusion in the turtle cerebellum: implications for volume transmission

1993 ◽  
Vol 70 (5) ◽  
pp. 2035-2044 ◽  
Author(s):  
M. E. Rice ◽  
Y. C. Okada ◽  
C. Nicholson
Keyword(s):  
Time Course ◽  
Granular Layer ◽  
Volume Fraction ◽  
Molecular Layer ◽  
Extracellular Volume ◽  
Striking Difference ◽  
Volume Transmission ◽  
Anisotropic Porous Media ◽  
Parallel Fibers ◽  
Ion Shifts

1. Measurements of extracellular diffusion properties were made in three orthogonal axes of the molecular and granular layers of the isolated turtle cerebellum with the use of iontophoresis of tetramethylammonium (TMA+) combined with ion-selective microelectrodes. 2. Diffusion in the extracellular space of the molecular layer was anisotropic, that is, there was a different value for the tortuosity factor, lambda i, associated with each axis of that layer. The x- and y-axes lay in the plane parallel to the pial surface of this lissencephalic cerebellum with the x-axis in the direction of the parallel fibers. The z-axis was perpendicular this plane. The tortuosity values were lambda x = 1.44 +/- 0.01, lambda y = 1.95 +/- 0.02, and lambda z = 1.58 +/- 0.01 (mean +/- SE). By contrast, the granular layer was isotropic with a single tortuosity value, lambda Gr = 1.77 +/- 0.01. 3. These data confirm the applicability of appropriately extended Fickian equations to describe diffusion in anisotropic porous media, including brain tissue. 4. Heterogeneity between the molecular and granular layer was revealed by a striking difference in extracellular volume fraction, alpha, for each layer. In the molecular layer alpha = 0.31 +/- 0.01, whereas in the granular layer alpha = 0.22 +/- 0.01. 5. Volume fraction and tortuosity affected the time course and amplitude of extracellular TMA+ concentration after iontophoresis. This was modeled by the use of the average parameters determined experimentally, and the nonspherical pattern of diffusion in the molecular layer was compared with the spherical distribution in the granular layer and agarose gel by computing isoconcentration ellipsoids. 6. One functional consequence of these results was demonstrated by measuring local changes in [K+]o and [Ca2+]o after microiontophoresis of a cerebellar transmitter, glutamate. The ratios of ion shifts in the x- and y-axes in the granular layer were close to unity, with a ratio of 1.04 +/- 0.08 for the rise in [K+]o and 1.03 +/- 0.17 for the decrease in [Ca2+]o. In contrast, ion shifts in the molecular layer had an x:y ratio of 1.44 +/- 0.14 for the rise in [K+]o and 2.10 +/- 0.42 for the decrease in [Ca2+]o. 7. These data demonstrate that the structure of cellular aggregates can channel the migration of substances in the extracellular microenvironment, and this could be a mechanism for volume transmission of chemical signals. For example, the preferred diffusion direction of glutamate along the parallel fibers would help constrain an incoming excitatory stimulus to stay "on-beam."

The development of a perfusate to minimize water and ion shifts in perfused rabbit kidneys

Cryobiology ◽  
1974 ◽  
Vol 11 (6) ◽  
pp. 569-570
Author(s):  
D.E. Pegg ◽  
A.L. Doggett ◽  
C.J. Green
Keyword(s):  
Ion Shifts

Application of TEM to the Characterisation of Commercial BaTiO3 Capacitors

1981 ◽  
Vol 39 ◽  
pp. 170-171
Author(s):  
M. L. Mecartney
Keyword(s):  
Dielectric Constant ◽  
Phase Transformation ◽  
High Dielectric Constant ◽  
Pure Material ◽  
Ferroelectric State ◽  
Wide Range ◽  
Ferroelectric Domains ◽  
Perovskite Crystal ◽  
Ion Shifts ◽  
High Dielectric

Ferroelectric BaTiO3 with its high dielectric constant is a material widely used for miniature high capacitance capacitors. Pure BaTiO3 has the perovskite crystal structure (cubic) above 120°C and undergoes a phase transformation to a ferroelectric state at 120°C: the electric dipole is created as the Ti+4 ion shifts slightly along a <100> direction, resulting in a slightly tetragonal structure (c/a 1.01). Ferroelectric domains form to minimize strain energy. Commercial polycrystalline BaTiO3 contains various impurities and dopants and the purpose of this TEM study is to assess whether similar behaviour occurs compared to the pure material.BaTiO3 capacitors from several industrial sources were examined, containing up to several atomic per cent of various oxides (Bi, Zr, Sn, Ca) which stabilize the high dielectric constant over a wide range of temperatures and “tie up” oxygen vacancies. Previous TEM work in the present study using EDS has shown that the presence of impurities prevents the ferroelectric phase transformation and the formation of ferroelectric domains at room temperature. No ferroelectric domains exist in region A of fig. 1(d) where Bi, Sn, and Ca impurities were detected, while conversely in the ferroelectric region B no impurities could be found. (Delta fringes from overlapping ferroelectric domains delineate the ferroelectric portion of the grain.) It is thought that impurity ions substituting on the BaTiO3 lattice distort the lattice sufficiently to prevent the phase transformation from occuring.

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