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L Leybaert

Publications and source records attributed to L Leybaert.

At least 19 recordsLinked to original sources
PubMed2005

Gap junctions and the propagation of cell survival and cell death signals.

Gap junctions are a unique type of intercellular channels that connect the cytoplasm of adjoining cells. Each gap junction channel is comprised of two hemichannels or connexons and each connexon is formed by the aggregation of six protein subunits known as connexins. Gap junction channels allow the intercellular passage of small (< 1.5 kDa) molecules and regulate essential processes during development and differentiation. However, their role in cell survival and cell death is poorly understood. We review experimental data that support the hypothesis that gap junction channels may propagate cell death and survival modulating signals. In addition, we explore the hypothesis that hemichannels (or unapposed connexons) might be used as a paracrine conduit to spread factors that modulate the fate of the surrounding cells. Finally, direct signal transduction activity of connexins in cell death and survival pathways is addressed.

Animals↗
PubMed2005

A simple and practical method to acquire geometrically correct images with resonant scanning-based line scanning in a custom-built video-rate laser scanning microscope.

Most currently available confocal or two-photon laser scanning microscopes (LSMs) allow acquisition rates of the order of 1-5 images s(-1), which is too slow to fully resolve dynamic changes in intracellular messenger concentration in living cells or tissues. Several technologies exist to obtain faster imaging rates, either in the video-rate range (30 images s(-1)) or beyond, but the most versatile technology available today is based on resonant scanners for horizontal line scanning. These scanning devices have several advantages over designs based on acousto-optical deflectors or Nipkow discs, but a drawback is that the scanning pattern is not a linear but rather a sinusoidal function of time. This puts additional constraints on the hardware necessary to read-in the image data flow, one of which is the generation of a pixel clock that varies in frequency with the position of the pixel on the scanned line. We describe a practical solution to obtain a variable pixel clock add-on that is easy to build and is easy to integrate into a custom-built LSM based on resonant scanning technology. In addition, we discuss some important hardware and software design aspects that simplify the construction of a resonant scanning-based LSM for high-speed, high-resolution imaging. Finally, we demonstrate that the microscope can be used to resolve calcium puffs triggered by photolytically increasing the intracellular concentration of inositol trisphosphate.

Journal Article↗
PubMed2002

Inositol 1,4,5-trisphosphate receptor function in human oocytes: calcium responses and oocyte activation-related phenomena induced by photolytic release of InsP(3) are blocked by a specific antibody to the type I receptor.

Type I inositol 1,4,5-trisphosphate-sensitive receptors (InsP(3)R) are expressed in human oocytes and may be involved in operating the Ca(2+) release triggered by the fertilizing sperm. This study examines the contribution of type I InsP(3)R in operating Ca(2+) release in human oocytes secondary to InsP(3) itself, using a specific function-blocking antibody in conjunction with photolytic release of microinjected InsP(3). Intracellular Ca(2+) responses were assessed in oocytes microinjected with only caged InsP(3) in experiment set A, while in experiment sets B and C, sibling oocytes were injected with caged InsP(3) and the blocking antibody or a corresponding volume of medium, prior to flash photolysis. In experiment set C, certain fertilization-related phenomena (cortical granule exocytosis and chromatin configurations) were assessed using optical sections and three-dimensional image reconstructions obtained from a confocal laser scanning microscope. In experiment set A, photolytic release of InsP(3) triggered a Ca(2+) response (increase from approximately 100 to 220 nmol/l followed by an exponential recovery, n = 8) and a wave in the oocytes that spread from the stimulation point to the opposite pole. In set B, photolytic InsP(3) release generated Ca(2+) responses in control oocytes (n = 9), but not in the antibody-injected oocytes (n = 7). In set C, cortical granule exocytosis and anaphase chromosome configurations were noted in the control oocytes after flash photolysis (n = 6). These changes were completely absent in antibody injected oocytes as their cortical granules were intact and the chromosomes were in metaphase. These oocytes had also lacked Ca(2+) responses as in set B (n = 5). This study demonstrates the functional presence of type I InsP(3)R-operated Ca(2+) channels in human oocytes and further suggests an active role of InsP(3) in triggering the Ca(2+) rise and secondary activation phenomena at fertilization.

Antibodies, Monoclonal↗
PubMed2001

Mitochondrial transmembrane potential changes support the concept of mitochondrial heterogeneity during apoptosis.

Dissipation of mitochondrial membrane potential (DeltaPsi(m)) and release of cytochrome c from mitochondria appear to be key events during apoptosis. The precise relationship (cause or consequence) between both is currently unclear. We previously showed in a model of serum-free cultured granulosa explants that cytochrome c is retained in a subset of respiring mitochondria until late in the apoptotic process. In this study we further investigated the issue of heterogeneity by using the DeltaPsi(m)-sensitive probe CM-H2TMRos in combination with a DNA fluorochrome. Changes of DeltaPsi(m) were assessed qualitatively by epifluorescence microscopy and were quantified using digital imaging microscopy. This approach yielded the following results: (a) CM-H2TMRos staining is a reliable and specific procedure to detect DeltaPsi(m) changes in granulosa cells explants; (b) dissipation of transmembrane potential is an early event during apoptosis preceding nuclear changes but is confined to a subpopulation of mitochondria within an individual cell; (c) in frankly apoptotic cells a few polarized mitochondria can be detected. These findings support the hypothesis that ATP needed for completion of the apoptotic cascade can be generated during apoptosis in a subset of respiring mitochondria and is not necessarily derived from anaerobic glycolysis.

Animals↗
PubMed2001

Astrocyte-endothelial cell calcium signals conveyed by two signalling pathways.

Astrocytes and endothelial cells are in close contact with each other at the blood-brain barrier, where important molecular transports take place. Despite these key morphological and functional properties, little is known regarding the dynamic signalling processes that occur between these two cell types. We investigated astrocyte-endothelial cell calcium signalling mechanisms in a coculture model prepared from primary rat cortical astrocytes and ECV304 cells. We used flash photolysis of caged inositol-trisphosphate (IP3) and gentle mechanical stimulation to trigger astrocyte-endothelial cell calcium signals and to investigate the underlying propagation mechanisms. Photolytically releasing IP3 in a single cell triggered increases in cytoplasmic calcium concentration that propagated between astrocytes and endothelial cells in either direction. These propagating calcium signals did not cross cell-free zones and were not affected by fast superfusion or by the purinergic inhibitors apyrase and suramin, indicating that they are communicated through an intracellular pathway in conjunction with gap junctions. Electrophysiological experiments confirmed a low degree of astrocyte-endothelial cell electrical cell-to-cell coupling. Mechanical stimulation of a single cell also triggered astrocyte-endothelial cell calcium signals but, in contrast to the former triggering mode, these signals crossed cell-free zones and were significantly inhibited by apyrase, thus indicating the involvement of an extracellular and purinergic messenger. Astrocyte-endothelial cell calcium signalling also occurred in cocultures prepared with astrocytes and primary rat brain capillary endothelial cells. We conclude that astrocytes and endothelial cells can exchange fast-acting calcium signals (time scale of seconds) that can be communicated through an intracellular/gap junctional pathway and an extracellular purinergic pathway.

Animals↗
PubMed2000

Ionic changes accompanying astrocytic intercellular calcium waves triggered by mechanical cell damaging stimulation.

Mechanically poking or damaging a single cell within a confluent astrocyte culture produces the so-called intercellular calcium (Ca(2+)) waves, that is, cell-to-cell propagating changes of intracellular free Ca(2+). We were interested whether intercellular Ca(2+) waves are also associated with changes in other intra- or extracellular ions. To that purpose, we investigated spatiotemporal changes of intracellular Ca(2+) (Ca(i)2+), sodium (Na(i)+) and protons (H(i)+) in primary cultures of rat cortical astrocytes using microfluorescence imaging with fura-2, SBFI and BCECF, respectively; changes of extracellular potassium (K(e)+) were monitored with K(+)-sensitive microelectrodes. Mechanical damage to a single cell by stimulation with a piezo-electrically driven micropipette initiated intercellular Ca(2+) waves that propagated to about 160 microm away from the stimulation point. Na(i)(+) increases could be detected in cells located 2-3 cell diameters from the stimulated cell, acidification was observed 1-2 cell diameters away and Ke(+) increases were measured up to 75 microm away. Kinetic analysis suggests that the Na(i)(+) and H(i)(+) changes occur after, and thus secondary to the Ca(i)(2+) changes. In contrast, K(e)(+) changes occurred very fast, even before the Ca(i)(2+) changes, but their propagation speed was too fast to implicate them as a trigger of Ca(i)(2+) changes. As Na(i)(+) is an important regulator of glycolysis in astrocytes, we hypothesize that astrocytic Na(i)(+) changes in cells located remotely from a damaged cell might be a signal that activates glycolysis thereby producing more lactate that is transferred to the neurons and increases their energy potential to survive the inflicted damage.

Animals↗
PubMed2000

ATP-dependent astrocyte-endothelial calcium signaling following mechanical damage to a single astrocyte in astrocyte-endothelial co-cultures.

In the brain, endfeet of perivascular astrocytes make close contact with capillary endothelial cells that form the blood-brain barrier. The aim of the present work was to investigate whether and how calcium signals can be communicated from astrocytes to endothelial cells following acute mechanical cell damage. The experiments were performed on astrocyte-endothelial co-cultures prepared from primary rat brain astrocytes and an endothelial cell line (ECV304). A single astrocyte was acutely damaged by mechanical stimulation of sufficient strength with a micropipette, and the resulting cytoplasmic calcium changes were monitored using fura-2 and digital calcium imaging. Mechanical damage to a single astrocyte triggered a large intercellular calcium wave that propagated to surrounding astrocytes and also to even remotely located (several hundred micrometers) endothelial cells. Astrocyte-endothelial calcium waves induced by mechanical cell damage were largely deflected by fast superfusion, were able to cross a cell-free lane, were dose-dependently inhibited by suramin, a P2-purinoceptor blocker, and were largely reduced in size in the presence of the ATP-degrading enzyme apyrase. Our results indicate that mechanical damage to a single astrocyte can produce far reaching calcium signals that are propagated by the release of a calcium mobilizing P2-purinergic agonist and that can be communicated to endothelial cells. As endothelial cytoplasmic calcium is an important factor in the regulation of blood-brain barrier permeability and transport, mechanical cell damage-induced astrocyte-endothelial calcium signals are hypothesized to play a role in the initiation of brain edema and the stimulation of brain glucose uptake.

Adenosine Triphosphate↗
PubMed2000

Intercellular calcium waves in HeLa cells expressing GFP-labeled connexin 43, 32, or 26.

This study was undertaken to obtain direct evidence for the involvement of gap junctions in the propagation of intercellular Ca(2+) waves. Gap junction-deficient HeLa cells were transfected with plasmids encoding for green fluorescent protein (GFP) fused to the cytoplasmic carboxyl termini of connexin 43 (Cx43), 32 (Cx32), or 26 (Cx26). The subsequently expressed GFP-labeled gap junctions rendered the cells dye- and electrically coupled and were detected at the plasma membranes at points of contact between adjacent cells. To correlate the distribution of gap junctions with the changes in [Ca(2+)](i) associated with Ca(2+) waves and the distribution of the endoplasmic reticulum (ER), cells were loaded with fluorescent Ca(2+)-sensitive (fluo-3 and fura-2) and ER membrane (ER-Tracker) dyes. Digital high-speed microscopy was used to collect a series of image slices from which the three-dimensional distribution of the gap junctions and ER were reconstructed. Subsequently, intercellular Ca(2+) waves were induced in these cells by mechanical stimulation with or without extracellular apyrase, an ATP-degrading enzyme. In untransfected HeLa cells and in the absence of apyrase, cell-to-cell propagating [Ca(2+)](i) changes were characterized by initiating Ca(2+) puffs associated with the perinuclear ER. By contrast, in Cx-GFP-transfected cells and in the presence of apyrase, [Ca(2+)](i) changes were propagated without initiating perinuclear Ca(2+) puffs and were communicated between cells at the sites of the Cx-GFP gap junctions. The efficiency of Cx expression determined the extent of Ca(2+) wave propagation. These results demonstrate that intercellular Ca(2+) waves may be propagated simultaneously via an extracellular pathway and an intracellular pathway through gap junctions and that one form of communication may mask the other.

Adenosine Triphosphate↗
PubMed2000

First and second messenger role of calcium. Survival versus apoptosis in serum-free cultured granulosa explants.

In order to elucidate the causal relationship between increased intracellular free calcium ([Ca2+]i) and induction of apoptosis, serum-free cultured granulosa cell (GC) explants were subjected to various experimental protocols interfering with normal Ca2+ homeostasis. Modulation of apoptotic indices was calculated on DAPI-stained GC explants. In some experiments [Ca2+]i was measured with the Ca2+ probe fura-2 in combination with epifluorescence microscopy. Buffering of [Ca2+]i with BAPTA-AM resulted in inhibition of apoptosis, while increasing extracellular Ca2+ (otherwise called [Ca2+]e load) resulted in a biphasic response characterized by an initial inhibitory effect on apoptosis followed by a delayed phase of increased apoptosis that became apparent at 4 h after withdrawal of the [Ca2+]e load. The initial inhibitory effect of the [Ca2+]e load on apoptosis was dependent on the concentration of the load (range 2-50 mM), was augmented when the [Ca2+]e load was applied in the presence of the Ca2+ channel blocker methoxyverapamil, and was mimicked by applying Mg2+ and Gd3+, two Ca(2+)-receptor agonists. These observations point towards the involvement of an extracellular Ca(2+)-sensing receptor (CaR). Measurements of [Ca2+]i showed that the ion was increased just after [Ca2+]e load, followed by recovery that was complete at 2 h after the load. Collectively these data suggest that a [Ca2+]e load initiates apoptosis, becoming manifest 4 h later, by the provoked [Ca2+]i increase, and this effect is preceded by an apoptosis-inhibiting phase presumably involving CaR activation. We conclude that Ca2+ may act as a first (extracellular) messenger promoting cell survival and as a second (intracellular) messenger activating the cell death pathway.

Animals↗
PubMed1999

Chemically, mechanically, and hyperosmolarity-induced calcium responses of rat cortical capillary endothelial cells in culture.

The purpose of the present work was to characterize calcium responses of brain-capillary endothelial cells (BCEC), the cells forming the blood-brain barrier, to chemical, hyperosmolar and mechanical stimulation. Confluent BCEC cultures were grown from capillary fragments isolated from rat cerebral cortex. Intracellular free calcium ([Ca2+]i) was measured using fura-2 and digital imaging. Our experiments show large endothelial calcium responses to substance P and ATP, up to a peak value of approximately 1000 and 600 nM, respectively, and these responses were observed in 2/3 of the cells. Calcium responses to bradykinin, histamine, and hyperosmolar sucrose or mannitol were smaller, attaining a peak in the range 180-340 nM, and were observed in a smaller fraction of the cells. No calcium responses were observed to high-potassium, L-glutamate, serotonin, carbachol, noradrenaline, and nitric-oxide donors. Consecutive superfusion of the cultures with ATP, bradykinin, and histamine showed that cells with a certain response pattern were spatially grouped; the response pattern itself varied widely between experiments. Mechanical stimulation of a single cell caused a calcium response in the stimulated cell in primary cultures and triggered an intercellularly propagating calcium wave in passaged cultures. Given the important effect of endothelial [Ca2+]i on blood-brain barrier permeability and transport, we conclude that substance P and ATP are potential modulators of blood-brain barrier function. Hyperosmolarity-induced blood-brain barrier opening is probably not mediated through endothelial [Ca2+]i.

Adenosine Triphosphate↗
PubMed1998

A simple method for high temporal resolution calcium imaging with dual excitation dyes.

Calcium-sensitive dual excitation dyes, such as fura-2, are now widely used to measure the free calcium concentration ([Ca2+]) in living cells. Preferentially, [Ca2+] is calculated in a ratiometric manner, but if calcium images need to be acquired at high temporal resolution, a potential drawback of ratiometry is that it requires equally fast switching of the excitation light between two wavelengths. To circumvent continuous excitation switching, some investigators have devised methods for calculating [Ca2+] from single-wavelength measurements combined with the acquisition of a single ratiometric pair of fluorescence images at the start of the recording. These methods, however, are based on the assumption that the concentration of the dye does not change during the experiment, a condition that is often not fulfilled. We describe here a method of single-wavelength calcium imaging, in which the dye concentration is estimated from ratiometric fluorescence image pairs acquired at regular intervals during the recording period, that furthermore includes a correction for the changing dye concentration in the calculation of [Ca2+].

Animals↗
PubMed1998

Apoptotic granulosa cells have moderately increased intracellular free calcium during phosphatidylserine exposure and a normal resting calcium level during DNA fragmentation.

Alterations in intracellular free calcium concentration ([Ca2+]i) are instrumental in apoptosis. We have previously shown that a [Ca2+]i increase above 1000 nM is related to the appearance of apoptosis in serum-free cultures of granulosa cell sheets. In the present study examined how the [Ca2+]i increase relates to indicators of distinct phases of the apoptotic cascade. We used a double staining technique whereby loading with the Ca2+ indicator fura-2 and capture of a [Ca2+]i image, was followed by staining with annexin-V, as an early apoptotic marker or with acridine orange, marking the late degradation phase. Calcium imaging showed a large heterogeneity of cellular [Ca2+]i levels. [Ca2+]i was moderately increased to approximately 230 nM in annexin positive cells but was at resting level in cells with nuclear manifestations of apoptosis as evidenced by acridine orange. Our results suggest that a modest [Ca2+]i increase is related to phosphatidylserine translocation and that [Ca2+]i has already recovered in apoptotic cells displaying chromatin condensation and/or nuclear fragmentation. Granulosa cells with [Ca2+]i above 1000 nM were never observed to strain positive for the apoptotic markers used; therefore, large [Ca2+]i increases are probably related to the apoptosis initiation phase occurring upstream of phosphatidylserine exposure.

Journal Article↗
PubMed1998

Inositol-trisphosphate-dependent intercellular calcium signaling in and between astrocytes and endothelial cells.

Interactions between astrocytes and endothelial cells are believed to play an important role in the control of blood-brain barrier permeability and transport. Astrocytes and endothelial cells respond to a variety of stimuli with an increase of intracellular free calcium ([Ca2+]i) that is propagated to adjacent cells as an intercellular Ca2+ wave. We hypothesized that intercellular Ca2+ signaling also occurs between astrocytes and endothelial cells, and we investigated this possibility in co-cultures of primary astrocytes and an endothelial cell line using caged messengers. Intercellular Ca2+ waves, induced by mechanical stimulation of a single cell, propagated from astrocytes to endothelial cells and vice versa. Intercellular Ca2+ waves could also be induced by flash photolysis of pressure-injected caged inositol trisphosphate (IP3) and also by applying the flash to remote noninjected cells. Ca2+ waves induced by flash photolysis propagated from endothelial cells to astrocytes but not from astrocytes to endothelial cells even though caged IP3 diffused between the two cell types. Flash photolysis of caged Ca2+ (NP-EGTA) resulted in an increase of [Ca2+]i but did not initiate an intercellular Ca2+ wave. We conclude that an increase of IP3 in a single cell is sufficient to initiate an intercellular Ca2+ wave that is propagated by the diffusion of IP3 to neighboring cells and that can be communicated between astrocytes and endothelial cells in co-culture. By contrast, Ca2+ diffusion via gap junctions does not appear to be sufficient to propagate an intercellular Ca2+ wave. We suggest that intercellular Ca2+ waves may play a role in astrocyte-endothelial interactions at the blood-brain barrier.

Animals↗
PubMed1997

Intracellular free calcium related to apoptotic cell death in quail granulosa cell sheets kept in serum-free culture.

The relationship between apoptosis and resting intracellular free calcium ([Ca2+]i) was studied in serum-free cultures of granulosa cell sheets isolated from preovulatory quail follicles. Apoptosis was detected by acridine orange, in situ end-labeling of fragmented DNA and electron microscopy. [Ca2+]i was measured using fura-2. [Ca2+]i averaged 525 mM in freshly isolated sheets. In 24 h cultures no apoptosis was detected but [Ca2+]i became very dispersed, 20% of the sheets showing values above 1000 nM. At 48 h, apoptosis was obvious and [Ca2+]i remained dispersed. At 72 h, apoptosis and also the fraction of sheets with high [Ca2+]i were at their maximum. At 96 h apoptosis was subsiding and [Ca2+]i normalized. FSH depressed apoptosis and [Ca2+]i in the 72 h cultures. We conclude that at 24 h apoptosis is initiated at high [Ca2+]i foci. At later stages apoptosis is associated with high [Ca2+]i, but it is not clear whether this is cause or consequence.

Journal Article↗
PubMed1996

Changes of intracellular free calcium during intracytoplasmic sperm injection.

The present experiments were undertaken to investigate whether the procedure of intracytoplasmic sperm injection (ICSI) is associated with changes in the intracellular free calcium concentration ([Ca2+]i). [Ca2+]i was measured, using the calcium-sensitive dye fura-2, during and after impalement of mouse oocytes with an ICSI pipette and injection of a small amount of medium alone or of medium containing a normal human spermatozoon. Forty-five oocytes were injected with medium. Two different responses were observed: 20 of these cells showed a large increase of [Ca2+]i upon impalement; the other 25 cells did not show any change of [Ca2+]i, neither in the acute period nor in a late period 4 hr after impalement. All the cells that responded with an increase of [Ca2+]i subsequently lysed within the first 30 min following impalement, while all the cells with no [Ca2+]i change remained intact. This observation suggests that only traumatic impalement is associated with an increase of [Ca2+]i. Thirty-one oocytes were successfully, i.e., without subsequent cell lysis, injected with a normal mouse or human spermatozoon. In none of these cells could any acute or late change of [Ca2+]i be observed. The experiments illustrate that successful performance of the ICSI procedure, i.e., ICSI not followed by cell lysis, is not associated with changes of [Ca2+]i in mouse oocytes. This suggests that the ICSI technique, by itself, does not help in activating the oocyte via manipulation-induced changes of [Ca2+]i.

Animals↗
PubMed1996

Changes of intracellular free calcium following mechanical injury in a spinal cord slice preparation.

Intracellular calcium ions are, in addition to free radicals, an important mediator of tissue destruction following traumatic injury to the spinal cord. In vivo measurements of calcium in the interstitial space and in the tissue suggest the occurrence of a posttraumatic shift of calcium from the extracellular to the intracellular compartment at the injury site. No information is, however, available on the posttraumatic changes of calcium in the intracellular compartment, where the ion exerts its crucial messenger function. We developed an in vitro model of local traumatic spinal injury, using a spinal cord slice preparation, allowing us to investigate injury-related changes of intracellular free calcium. The injury consisted of the impact of a small needle, and intracellular free calcium was measured with fura-2. Application of the injury at different places within the gray matter caused a transient and reproducible increase in the fura-2 fluorescence ratio. This injury-induced ratio increase was largely, but not completely, suppressed under zero extracellular calcium conditions. It was also largely depressed in the presence of high extracellular potassium and in the absence of extracellular sodium. It was modestly depressed by the calcium channel blocker nifedipin, by the calcium release channel blocker dantrolene, and by the gap junction blockers halothane and octanol. The calcium channel blocker flunarizine, the N-methyl D-aspartate (NMDA)-receptor-channel blocker MK-801 and the endoplasmic reticulum calcium-ATPase blocker thapsigargin had no effect. The experiments suggest that injury is associated with an increase in intracellular free calcium that is mediated by calcium influx, in part via L-type calcium channels. They furthermore give evidence that sodium influx and gap junctions are involved in these injury-associated changes of intracellular free calcium.

Animals↗
PubMed1994

Interstitial and tissue cations and electrical potential after experimental spinal cord injury.

Interstitial and tissue cations and electrical potential were studied in an experimental model of spinal cord contusion injury in anaesthetised cats. Measurements of interstitial ion activity in the grey matter at the injury site (with ion-selective electrodes), showed a decrease of sodium and calcium, an increase of potassium, a small acidification and a negative shift in the electrical potential 5 min after injury. The interstitial ionic changes were completely reversible within 90 min following injury. Measurements of the ion content in a tissue sample from the injury site (flame photometry) showed an increase of sodium and calcium and a decrease of potassium 5 min after injury. The magnitude of the post-injury sodium change was much larger than the potassium change, both for interstitial and tissue measurements. Treatment of the animals with the calcium entry blocker flunarizine before the injury did not influence the magnitude of post-injury interstitial calcium decrease but significantly increased the rate of subsequent recovery. Pre-injury flunarizine treatment also significantly increased the recovery rate of the electrical potential. The experiments suggest the occurrence of a net ionic shift towards the intracellular space, which may contribute to oedema formation in the very early post-injury period. The post-injury decrease of interstitial calcium activity is probably not mediated by flunarizine-sensitive calcium entry mechanisms; such mechanisms may, however, be involved in the subsequent recovery period for interstitial calcium activity. Calcium ions may be involved in the recovery process of the negative electrical potential after injury.

Animals↗