https://ogma.newcastle.edu.au/vital/access/ /manager/Index en-au 5 https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:34969 d = 121 ± 14 nM. Ex-vivo phosphorylation/dephosphorylation experiments suggested that the divergent CaM regulation of healthy and failing human RyR2 was caused by differences in RyR2 phosphorylation by protein kinase A and Ca-CaM-dependent kinase II. Ca²⁺-spark measurements in murine cardiomyocytes harbouring RyR2 phosphomimetic or phosphoablated mutants at S2814 and S2808 suggest that phosphorylation of residues corresponding to either human RyR2-S2808 or S2814 is both necessary and sufficient for RyR2 regulation by CaM. Our results challenge the current concept that CaM universally functions as a canonical inhibitor of RyR2 across species. Rather, CaM's biological action on human RyR2 appears to be more nuanced, with inhibitory activity only on phosphorylated RyR2 channels, which occurs during exercise or in patients with heart failure.]]> Wed 24 Jun 2020 11:42:42 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:38725 Wed 19 Jan 2022 10:25:02 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:4526 Wed 11 Apr 2018 16:51:00 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:26914 cyt) of cells trans-differentiating to a transfer cell morphology was tested. This hypothesis was examined using Vicia faba cotyledons. On transferring cotyledons to culture, their adaxial epidermal cells synchronously trans-differentiate to epidermal transfer cells. A polarized and persistent Ca²⁺ signal, generated during epidermal cell trans-differentiation, was found to co-localize with the site of ingrowth wall formation. Dampening Ca²⁺ signal intensity, by withdrawing extracellular Ca²⁺ or blocking Ca²⁺ channel activity, inhibited formation of wall ingrowth papillae. Maintenance of Ca²⁺ signal polarity and persistence depended upon a rapid turnover (minutes) of cytosolic Ca²⁺ by co-operative functioning of plasma membrane Ca²⁺-permeable channels and Ca²⁺-ATPases. Viewed paradermally, and proximal to the cytosol-plasma membrane interface, the Ca²⁺ signal was organized into discrete patches that aligned spatially with clusters of Ca²⁺-permeable channels. Mathematical modelling demonstrated that these patches of cytosolic Ca²⁺ were consistent with inward-directed plumes of elevated [Ca²⁺]_cyt. Plume formation depended upon an alternating distribution of Ca²⁺-permeable channels and Ca²⁺-ATPase clusters. On further inward diffusion, the Ca²⁺ plumes coalesced into a uniform Ca²⁺ signal. Blocking or dispersing the Ca²⁺ plumes inhibited deposition of wall ingrowth papillae, while uniform wall formation remained unaltered. A working model envisages that cytosolic Ca²⁺ plumes define the loci at which wall ingrowth papillae are deposited.]]> Wed 11 Apr 2018 16:31:50 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:13451 Wed 11 Apr 2018 16:22:13 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:1395 Wed 11 Apr 2018 15:40:46 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:17232 2+_ concentration but may influence mitochondrial function as both antioxidant treatments modulated mitochondrial membrane potential. These suggest that the antioxidant-sensitive subpopulations of LC neurons may be more susceptible to oxidative stress (e.g., due to ATP depletion and/or overactivation of Ca²⁺_ dependent pathways). Indeed it may be that this subpopulation of LC neurons is preferentially destroyed in neurological pathologies such as Parkinson’s disease. If this is the case, there may be a protective role for antioxidant therapies.]]> Wed 11 Apr 2018 14:36:25 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:3114 Wed 11 Apr 2018 14:34:07 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:16822 2+ release from sarcoplasmic/endoplasmic reticulum Ca²⁺-ATPase (SERCA) -dependent intracellular Ca²⁺ stores; and 3) c-Kit and/or vimentin immunoreactive ICs have a role in pacemaking. Methodology/Principal Findings: Vaginal and cervical contractions were measured in vitro, as was the distribution of c-Kit and vimentin positive interstitial cells (ICs). Cervical smooth muscle was spontaneously active in estrus and metestrus but quiescent during proestrus and diestrus. Vaginal smooth muscle was normally quiescent but exhibited phasic contractions in the presence of oxytocin or the K⁺ channel blocker tetraethylammonium (TEA) chloride. Spontaneous contractions in the cervix and TEA-induced phasic contractions in the vagina persisted in the presence of cyclopiazonic acid (CPA), a blocker of the SERCA that refills intracellular SR Ca²⁺ stores, but were inhibited in low Ca²⁺ solution or in the presence of nifedipine, an inhibitor of L-type Ca²⁺channels. ICs were found in small numbers in the mouse cervix but not in the vagina. Conclusions/Significance: Cervical smooth muscle strips taken from mice in estrus, metestrus or late pregnancy were generally spontaneously active. Vaginal smooth muscle strips were normally quiescent but could be induced to exhibit phasic contractions independent on phase of the estrus cycle or late pregnancy. Spontaneous cervical or TEA-induced vaginal phasic contractions were not mediated by ICs or intracellular Ca²⁺ stores. Given that vaginal smooth muscle is normally quiescent then it is likely that increases in hormones such as oxytocin, as might occur through sexual stimulation, enhance the effectiveness of such pacemaking until phasic contractile activity emerges.]]> Wed 11 Apr 2018 13:40:08 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:14540 Wed 11 Apr 2018 10:55:00 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:14381 Wed 11 Apr 2018 10:04:10 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:1132 Wed 11 Apr 2018 09:44:22 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:16993 450% immediately after MCAo. Collateral diameter changed minimally. Second, we determined the effect of ICP elevation on collateral and watershed penetrating arteriole flow. Intracranial pressure was artificially raised in stepwise increments during MCAo. The ICP increase was strongly correlated with collateral and penetrating arteriole flow reductions. Changes in collateral flow post-stroke appear to be primarily driven by the pressure drop across the collateral vessel, not vessel diameter. The ICP elevation reduces cerebral perfusion pressure and collateral flow, and is the possible explanation for 'collateral failure' in stroke-in-progression.]]> Wed 11 Apr 2018 09:23:28 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:53689 Wed 10 Jan 2024 10:35:05 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:45587 2+) release-refill cycle of Ca²⁺ stores. This occurs through opening of inositol 1,4,5-trisphosphate receptor (IP₃R)- and/or ryanodine receptor (RyR)-operated Ca²⁺ release channels in the sarcoplasmic/endoplasmic (SR/ER) reticulum and refilling by the SR/ER reticulum Ca²⁺ATPase (SERCA). Released Ca²⁺ from stores near the plasma membrane diffuse through the cytosol to open Ca2²⁺-activated chloride (Cl⁻) channels, this generating inward current through an efflux of Cl⁻. The resultant depolarisation leads to the opening of voltage-dependent Ca²⁺ channels and possibly increased production of IP3, which through Ca²⁺-induced Ca²⁺ release (CICR) of IP₃Rs and/or RyRs and IP₃R-mediated Ca²⁺ release provide a means by which store oscillators entrain their activity. Intercellular entrainment normally involves current flow through gap junctions that interconnect mural cells and in many cases this is aided by additional connectivity through the endothelium. Once entrainment has occurred the substantial Ca²⁺ entry that results from the near-synchronous depolarisations leads to rhythmical contractions of the mural cells, this often leading to vessel constriction. The basis for venous/venular vasomotion has yet to be fully delineated but could improve both venous drainage and capillary/venular absorption of blood plasma-associated fluids.]]> Wed 02 Nov 2022 09:13:14 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:37505 Wed 02 Mar 2022 14:28:59 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:47001 Tue 13 Dec 2022 10:59:25 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:43873 Tue 04 Oct 2022 12:29:00 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:36209 c but does not exclude action at intracellular microdomains. Further to this, the incubation of slices with cytochalasin D, an agent that depolymerises the actin cytoskeleton, inhibited the hyperpolarizing response indicating an involvement of the actin cytoskeleton. The data are consistent with the hypothesis that there is a crosstalk between mitochondria and L-type Ca²⁺ channels leading to modulation of noradrenergic neuronal activity mediated by the actin cytoskeleton.]]> Tue 03 Mar 2020 15:35:08 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:494 Thu 25 Jul 2013 09:09:56 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:53989 Thu 25 Jan 2024 13:03:51 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:34620 Thu 04 Apr 2019 14:26:20 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:9604 Sat 24 Mar 2018 08:39:39 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:9515 Sat 24 Mar 2018 08:35:35 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:1976 Sat 24 Mar 2018 08:33:14 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:1619 Sat 24 Mar 2018 08:30:33 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:1408 Sat 24 Mar 2018 08:28:15 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:1733 Sat 24 Mar 2018 08:27:27 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:12355 Sat 24 Mar 2018 08:18:31 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:9917 Sat 24 Mar 2018 08:13:33 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:10403 Sat 24 Mar 2018 08:07:46 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:18980 i = 10 µM at 100 nM Ca²⁺) that was similar to RyR2 from rat and sheep obtained under the same experimental conditions. However, in the presence of 0.1 mM Ca²⁺, RyR2s from human were 3.5-fold less sensitive to cytoplasmic Mg²⁺ inhibition than those from sheep and rat. The Kₐ values for luminal Ca²⁺ activation were similar in the three species (35 µM for human, 12 µM for sheep, and 10 µM for rat). From the relationship between open probability and luminal [Ca²⁺], the peak open probability for the human RyR2 was approximately the same as that for sheep, and both were ~10-fold greater than that for rat RyR2. Human RyR2 also showed the same sensitivity to luminal Mg²⁺ as that from sheep, whereas rat RyR2 was 10-fold more sensitive. In all species, modulation of RyR2 gating by luminal Ca²⁺ and Mg²⁺ only occurred when cytoplasmic [Ca²⁺] was <3 µM. The activation response of RyR2 to luminal and cytoplasmic Ca²⁺ was strongly dependent on the Mg²⁺ concentration. Addition of physiological levels (1 mM) of Mg²⁺ raised the Kₐ for cytoplasmic Ca²⁺ to 30 µM (human and sheep) or 90 µM (rat) and raised the Kₐ for luminal Ca²⁺ to ~1 mM in all species. This is the first report of the regulation by Ca²⁺ and Mg²⁺ of native RyR2 receptor activity from healthy human hearts.]]> Sat 24 Mar 2018 07:58:52 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:27526 Sat 24 Mar 2018 07:28:58 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:26905 Sat 24 Mar 2018 07:23:35 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:4460 Sat 24 Mar 2018 07:18:30 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:22802 2+ release. Although dantrolene inhibits Ca²⁺ release from the sarcoplasmic reticulum of skeletal and cardiac muscle preparations, its mechanism of action has remained controversial, because dantrolene does not inhibit single ryanodine receptor (RyR) Ca²⁺ release channels in lipid bilayers. Here we test the hypothesis that calmodulin (CaM), a physiologic RyR binding partner that is lost during incorporation into lipid bilayers, is required for dantrolene inhibition of RyR channels. In single channel recordings (100 nM cytoplasmic [Ca²⁺] + 2 mM ATP), dantrolene caused inhibition of RyR1 (rabbit skeletal muscle) and RyR2 (sheep) with a maximal inhibition of P_o (E_max) to 52 ± 4% of control only after adding physiologic [CaM] = 100 nM. Dantrolene inhibited RyR2 with an IC₅₀ of 0.16 ± 0.03 µM. Mutant N98S-CaM facilitated dantrolene inhibition with an IC₅₀ = 5.9 ± 0.3 nM. In mouse cardiomyocytes, dantrolene had no effect on cardiac Ca²⁺ release in the absence of CaM, but reduced Ca²⁺ wave frequency (IC₅₀ = 0.42 ± 0.18 µM, E_max = 47 ± 4%) and amplitude (IC₅₀ = 0.19 ± 0.04 µM, E_max = 66 ± 4%) in the presence of 100 nM CaM. We conclude that CaM is essential for dantrolene inhibition of RyR1 and RyR2. Its absence explains why dantrolene inhibition of single RyR channels has not been previously observed.]]> Sat 24 Mar 2018 07:12:18 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:34698 75% of its contraction capability. The effects of resveratrol on uterine contractions under hypoxia were attenuated by tetraethylammonium (10 mM) and almost abolished by glibenclamide (10 µM). Our results show regenerative and protective effects of resveratrol in non-pregnant murine uteri under hypoxia and describes for the first time that these effects are mediated by blockade of ATP-sensitive potassium channels.]]> Fri 12 Apr 2019 15:45:10 AEST ]]>