Temporal and spatial properties of cellular Ca2+ flux in trout ventricular myocytes

2005 ◽  
Vol 288 (6) ◽  
pp. R1756-R1766 ◽  
Author(s):  
Holly A. Shiels ◽  
Ed White
Keyword(s):  
Cardiac Myocyte ◽  
Ventricular Myocytes ◽  
Bay K 8644 ◽  
Confocal Imaging ◽  
Cell Periphery ◽  
Dependent Manner ◽  
Spatial Properties ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
Temporal Properties ◽  
Temporal And Spatial

Confocal microscopy was used to investigate the temporal and spatial properties of Ca2+ transients and Ca2+ sparks in ventricular myocytes of the rainbow trout ( Oncorhynchus mykiss). Confocal imaging confirmed the absence of T tubules and the long (∼160 μm), thin (∼8 μm) morphology of trout myocytes. Line scan imaging of Ca2+ transients evoked by electrical stimulation in cells loaded with fluo 4 revealed spatial inhomogeneities in the temporal properties of Ca2+ transients across the width of the myocytes. The Ca2+ wavefront initiated faster, rose faster, and reached larger peak amplitudes in the periphery of the myocyte compared with the center. These differences were exacerbated by stimulation with the L-type Ca2+ channel agonist (−)BAY K 8644 or by sarcoplasmic reticulum (SR) inhibition with ryanodine and thapsigargin. Results reveal that the shape of the trout myocyte allows for rapid diffusion of Ca2+ from the cell periphery to the cell center, with SR Ca2+ release contributing to the cytosolic Ca2+ rise in a time-dependent manner. Spontaneous Ca2+ sparks were exceedingly rare in trout myocytes under control conditions (1 sparking cell from 238 cells examined). This is in marked contrast to the rat where a total of 56 spontaneous Ca2+ sparks were observed in 9 of 11 myocytes examined. Ca2+ sparklike events were observed in a very small number of trout myocytes (15 sparks from 9 of 378 cells examined) after stimulation with either (−)BAY K 8644 or high Ca2+ (6 mM). Reducing temperature to 15°C in intact myocytes or permeabilizing myocytes to adjust intracellular conditions to favor Ca2+ spark detection was without significant effects. Possible reasons for the rarity of Ca2+ sparks in a cardiac myocyte with an active SR are discussed.

scholarly journals Developmental Changes in Sensitivity to Spatial and Temporal Properties of Sensory Integration Underlying Body Representation

2017 ◽  
Vol 30 (6) ◽  
pp. 467-484 ◽  
Author(s):  
Katie Greenfield ◽  
Danielle Ropar ◽  
Kristy Themelis ◽  
Natasha Ratcliffe ◽  
Roger Newport
Keyword(s):  
Multisensory Integration ◽  
Body Representation ◽  
Proprioceptive Information ◽  
Tactile Information ◽  
Spatial Properties ◽  
Temporal Properties ◽  
Temporal Binding Window ◽  
Temporal And Spatial ◽  
Sensory Processes ◽  
Proprioceptive Inputs

The closer in time and space that two or more stimuli are presented, the more likely it is that they will be integrated together. A recent study by Hillock-Dunn and Wallace (2012) reported that the size of the visuo-auditory temporal binding window — the interval within which visual and auditory inputs are highly likely to be integrated — narrows over childhood. However, few studies have investigated how sensitivity to temporal and spatial properties of multisensory integration underlying body representation develops in children. This is not only important for sensory processes but has also been argued to underpin social processes such as empathy and imitation (Schütz-Bosbach et al., 2006). We tested 4 to 11 year-olds’ ability to detect a spatial discrepancy between visual and proprioceptive inputs (Experiment One) and a temporal discrepancy between visual and tactile inputs (Experiment Two) for hand representation. The likelihood that children integrated spatially separated visuo-proprioceptive information, and temporally asynchronous visuo-tactile information, decreased significantly with age. This suggests that spatial and temporal rules governing the occurrence of multisensory integration underlying body representation are refined with age in typical development.

scholarly journals Kant’s Unconscious ‘Given’

1969 ◽  
Vol 2 (02) ◽  
Author(s):  
Patricia KITCHER
Keyword(s):  
Human Perception ◽  
Sensory Data ◽  
Spatial Properties ◽  
Temporal Properties ◽  
Temporal And Spatial ◽  
Temporal Representations

Kant appeals to unconscious representations for reasons that are deeply connected to his distinctive theory of cognition. He is an empirical realist, accepting the Empiricist claim that cognition must be based in sensory data. He is an idealist about spatial and temporal representations. He believes that human perception is always of objects or events with temporal and spatial properties. It follows from these three claims that the sensations that must begin the process of cognition lack spatial and temporal properties and so are not perceived, but unconscious.

Uptake of taurocholic acid and cholic acid in isolated hepatocytes from rainbow trout

1994 ◽  
Vol 267 (3) ◽  
pp. G380-G386 ◽  
Author(s):  
C. M. Rabergh ◽  
K. Ziegler ◽  
B. Isomaa ◽  
M. M. Lipsky ◽  
J. E. Eriksson
Keyword(s):  
Rainbow Trout ◽  
Bile Acids ◽  
Low Temperatures ◽  
High Efficiency ◽  
Isolated Hepatocytes ◽  
Metabolic Inhibitors ◽  
Dependent Manner ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
Transport Component ◽  
Efficient Uptake

The uptake of the bile acids cholate (CHA) and taurocholate (TCHA) was studied in isolated hepatocytes from rainbow trout (Oncorhynchus mykiss). Both CHA and TCHA were taken up in a concentration- and temperature-dependent manner with optimum temperature at 15 degrees C and a strikingly efficient uptake even at low temperatures (0-5 degrees C). The total uptake was a combination of a saturable [Michaelis-Menten constant (Km) for CHA, 20 microM; Km for TCHA, 19 microM] and a nonsaturable component. The maximal uptake rate of the saturable component was 416 and 805 pmol.mg protein-1.min-1 for CHA and TCHA, respectively. The uptake of both bile acids was shown to be energy dependent, since it was inhibited by the metabolic inhibitors antimycin A, oligomycin and carbonyl cyanide m-chlorophenylhydrazone. The uptake was clearly Na+ independent, since isosmotic replacement of extracellular Na+ by Li+, choline, or K+ did not inhibit the uptake. Furthermore, it seemed to be independent of the presence of extracellular Cl-, since it was not inhibited by replacement of Cl- with sodium gluconate. On the whole, our results show that the hepatocellular uptake of bile acids in rainbow trout is mediated by a Na(+)-independent carrier system, with characteristics resembling the corresponding transport component in mammalian hepatocytes, but with high efficiency even at low temperatures.

Fluid pressure modulates L-type Ca2+ channel via enhancement of Ca2+-induced Ca2+ release in rat ventricular myocytes

2008 ◽  
Vol 294 (4) ◽  
pp. C966-C976 ◽  
Author(s):  
Sunwoo Lee ◽  
Joon-Chul Kim ◽  
Yuhua Li ◽  
Min-Jeong Son ◽  
Sun-Hee Woo
Keyword(s):  
Ventricular Myocytes ◽  
Fluid Pressure ◽  
Inhibitory Effect ◽  
Cellular Mechanism ◽  
Confocal Imaging ◽  
Rat Ventricular Myocytes ◽  
Whole Cell Patch Clamp ◽  
Current Voltage ◽  
Intracellular Ca ◽  
High Concentrations

This study examines whether fluid pressure (FP) modulates the L-type Ca2+ channel in cardiomyocytes and investigates the underlying cellular mechanism(s) involved. A flow of pressurized (∼16 dyn/cm2) fluid, identical to that bathing the myocytes, was applied onto single rat ventricular myocytes using a microperfusion method. The Ca2+ current ( ICa) and cytosolic Ca2+ signals were measured using a whole cell patch-clamp and confocal imaging, respectively. It was found that the FP reversibly suppressed ICa (by 25%) without altering the current-voltage relationships, and it accelerated the inactivation of ICa. The level of ICa suppression by FP depended on the level and duration of pressure. The Ba2+ current through the Ca2+ channel was only slightly decreased by the FP (5%), suggesting an indirect inhibition of the Ca2+ channel during FP stimulation. The cytosolic Ca2+ transients and the basal Ca2+ in field-stimulated ventricular myocytes were significantly increased by the FP. The effects of the FP on the ICa and on the Ca2+ transient were resistant to the stretch-activated channel inhibitors, GsMTx-4 and streptomycin. Dialysis of myocytes with high concentrations of BAPTA, the Ca2+ buffer, eliminated the FP-induced acceleration of ICa inactivation and reduced the inhibitory effect of the FP on ICa by ≈80%. Ryanodine and thapsigargin, abolishing sarcoplasmic reticulum Ca2+ release, eliminated the accelerating effect of FP on the ICa inactivation, and they reduced the inhibitory effect of FP on the ICa. These results suggest that the fluid pressure indirectly suppresses the Ca2+ channel by enhancing the Ca2+-induced intracellular Ca2+ release in rat ventricular myocytes.

Abstract 425: Development of a Vascular Cell Adhesion Molecule-1 Targeted Esterase Nanofiber that Binds Activated Endothelial Cells

2014 ◽  
Vol 34 (suppl_1) ◽  
Author(s):  
Mazen S Albaghdadi ◽  
Charles Rupert Perez ◽  
Amanda Worthy ◽  
Edward S Bahnson ◽  
Clifford Carpenter ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Adhesion Molecule ◽  
Free Cholesterol ◽  
Confocal Imaging ◽  
Atherosclerotic Plaques ◽  
Atherosclerotic Cardiovascular Disease ◽  
Dependent Manner ◽  
Cholesterol Esters ◽  
Binding Peptide ◽  
N Terminus

Introduction: Novel therapies capable of directly targeting and regressing atherosclerotic plaques would provide tremendous benefit to patients with atherosclerotic cardiovascular disease. Molecular imaging studies have shown the feasibility of targeting vascular adhesion molecule (VCAM-1) for non-invasive atherosclerosis imaging. Histidine contains an imidazole ring with esterase activity that can convert cholesterol esters to free cholesterol. Thus, we hypothesize that a peptide amphiphile (PA) functionalized with a VCAM-1 binding peptide and histidine will spontaneously form a targeted nanofiber that binds activated endothelium and liberates free cholesterol from cholesterol esters. Methods: PAs were synthesized by solid phase methods and purified by reversed phase HPLC. Three different VCAM-1 binding peptide sequences were conjugated to the PAs (free N-terminus, free C-terminus, and cyclic). To assess 3-dimensional structure of the co-assembled PAs, cryogenic transmission electron microscopy (TEM) was used. To assess targeting of the VCAM-PAs (50μM), human umbilical endothelial cells (HUVECs) were stimulated with TNFα (10ng/ml). To assess the ability of the histidine-PA to liberate free cholesterol, a modified Amplex Red Cholesterol Assay was used. Results: Using TEM, we demonstrated that the co-assembled VCAM- and histidine-PAs formed characteristic nanofibers with diameters of 5-8nm and lengths ranging from 300nm to 1μm. TNFα-activated HUVECs were confirmed to express VCAM-1 protein by Western blot analysis. Confocal imaging revealed that the VCAM-1 binding peptide with a free N-terminus conjugated to the PA had the greatest binding affinity to the TNFα-activated HUVECs. Co-incubation of the histidine-PA with cholesterol esters demonstrated that free cholesterol was liberated from cholesterol esters in a concentration-dependent manner with a five-fold increase in free cholesterol release with 25μM of PA versus 1μM. Conclusion: We have designed and characterized a VCAM-1 targeted nanofiber that successfully binds activated endothelium and generates free cholesterol from cholesterol esters. This novel therapeutic nanotechnology has the capacity to target and regress atherosclerotic plaques.

Abstract 172: Thrombopoietin Receptor Agonists Protect Human Cardiac Myocytes from Injury by Activation of Cell Survival Pathways

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
John E Baker ◽  
Jidong Su ◽  
Stacy Koprowski ◽  
Anuradha Dhanasekaran ◽  
Tom P Aufderheide ◽  
...  
Keyword(s):  
Cardiac Myocytes ◽  
Cardiac Myocyte ◽  
Apoptotic Cell ◽  
Ischemia Reperfusion ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Survival Pathways ◽  
Thrombopoietin Receptor ◽  
Reoxygenation Injury ◽  
Hypoxia Reoxygenation

Thrombopoietin confers immediate protection against injury caused by ischemia/reperfusion in the rat heart at a dose that does not increase platelet levels. Eltrombopag is a small molecule agonist of the thrombopoietin receptor; the physiological target of thrombopoietin. Administration of thrombopoietin and eltrombopag result in a dose- and time-dependent increase in platelet counts in patients with thrombocytopenia. However, the ability of eltrombopag and thrombopoietin to immediately protect human cardiac myocytes against injury and the mechanisms underlying myocyte protection are not known. Human cardiac myocytes (7500 cells, n=10/group) were treated with eltrombopag (0.1- 30.0 μM) or thrombopoietin ( 0.1 - 30.0 ng/ml) and then subjected to 5 hours of hypoxia (95% N 2 /5%CO 2 ) and 16 hours of reoxygenation to determine their ability to confer resistance to necrotic and apoptotic myocardial injury . The thrombopoietin receptor (c-Mpl) was detected in unstimulated human cardiac myocytes by western blotting. Eltrombopag and thrombopoietin confer immediate protection to human cardiac myocytes against injury from hypoxia/reoxygenation by decreasing necrotic and apoptotic cell death in a concentration-dependent manner with an optimal concentration of 3 μM for eltrombopag and 1.0 ng/ml for thrombopoietin. The extent of protection conferred to cardiac myocytes with eltrombopag is equivalent to that of thrombopoietin. Eltrombopag and thrombopoietin activate multiple pro-survival pathways; inhibition of JAK-2 (AG-490, 10 μM), p38 MAPK (SB203580, 10 μM), p44/42 MAPK (PD98059, 10 μM), Akt/PI 3 kinase (Wortmannin, 100 nM), and src kinase (PP1, 20 μM) prior to and during hypoxia abolished cardiac myocyte protection by eltrombopag and thrombopoietin. These inhibitors had no effect on hypoxia/reoxygenation injury in myocytes when used alone. Eltrombopag and thrombopoietin may represent important and potent agents for immediately and substantially increasing protection of human cardiac myocytes, and may offer long-lasting benefit through activation of pro-survival pathways during ischemia.

Abstract 208: Mitochondrial-targeted Grk2 Increases Superoxide Formation And Impairs Cardiomyocyte Respiratory Reserve Capacity

2014 ◽  
Vol 115 (suppl_1) ◽  
Author(s):  
Priscila Y Sato ◽  
J K Chuprun ◽  
Jessica Ibetti ◽  
John W Elrod ◽  
Walter J Koch
Keyword(s):  
Heart Failure ◽  
Ventricular Myocytes ◽  
Permeability Transition ◽  
Fold Increase ◽  
Confocal Imaging ◽  
Neonatal Rat ◽  
Redox Stress ◽  
Mitochondrial Oxidative Stress ◽  
Neonatal Rat Ventricular Myocytes ◽  
Cellular Dysfunction

β-adrenergic receptors (βARs) are powerful regulators of cardiovascular function and are impaired in heart failure (HF). Signal transduction of βARs is canonically shut down by phosphorylation via G protein-coupled receptor kinase 2 (GRK2) and the subsequent binding of β-arrestins. This process of receptor desensitization is enhanced in HF via the up-regulation of GRK2 and contributes to disease progression. We have recently reported non-canonical actions of GRK2, which contribute to the development of HF independent of βAR desensitization. We have previously shown that GRK2 can act as a pro-death kinase in cardiomyocytes bytranslocating to mitochondria and activating mitochondria permeability transition. This study was designed to gain more understanding of the mitochondrial function of GRK2. We isolated adult cardiomyocytes from cardiac-specific transgenic mice overexpressing GRK2 at levels found in human HF (TgGRK2), and examined superoxide production using the redox sensitive reporter MitoSox Red. Confocal imaging revealed a 4.6 fold increase in superoxide levels in cardiomyocytes overexpressing Grk2 as compared to non-transgenic (NLC) cardiomyocytes (corrected total cell fluorescence 11.59±1.06, TgGRK2 (n= 3 hearts, 88 cells) vs 2.54±0.02 NLC (n=3 hearts, 52 cells), (p<0.001). This indicates that the chronic elevation of GRK2 induces mitochondrial oxidative stress priming the myocyte for enhanced injury. To further explore the mitochondrial actions of GRK2 and consequences of redox stress we examined oxidative phosphorylation by performing oxygen consumption measurements in neonatal rat ventricular myocytes overexpressing GRK2 or GFP-expressing control myocytes. Seahorse analysis showed that cells overexpressing GRK2 have a significant decrease in spare respiratory capacity indicating that cells with elevated GRK2 levels have an impaired capacity to generated ATP during times of stress. Further studies with mutants that limit GRK2 kinase activity or mitochondrial localization demonstrate that mitochondrial GRK2 may be a significant contributor to cellular dysfunction as seen in heart failure.

Protein kinase C-ζ modulates thromboxane A2-mediated apoptosis in adult ventricular myocytes via Akt

2002 ◽  
Vol 282 (1) ◽  
pp. H320-H327 ◽  
Author(s):  
Yukitaka Shizukuda ◽  
Peter M. Buttrick
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Cardiac Myocytes ◽  
Ventricular Myocytes ◽  
Kinase Assay ◽  
Dependent Manner ◽  
Adult Rat ◽  
Kinase C ◽  
Adult Cardiac Myocytes ◽  
Pkc Ζ

We hypothesized that thromboxane A2 (TxA2) receptor stimulation directly induces apoptosis in adult cardiac myocytes. To investigate this, we exposed cultured adult rat ventricular myocytes (ARVM) to a TxA2 mimetic [1S-[1α,2α(Z),3β(1E,3S*),4α]]-7-[3-[3-hydroxy-4-(4-iodophenoxy)-1-butenyl]-7-oxabicyclo[2.2.1]hept-2-yl]-5-heptenoic acid (I-BOP) for 24 h. Stimulation with I-BOP induced apoptosis in a dose-dependent manner and was completely prevented by a TxA2 receptor antagonist, SQ-29548. We further investigated the role of protein kinase C (PKC) in this process. TxA2 stimulation resulted in membrane translocation of PKC-ζ but not PKC-α, -βII, -δ, and -ε at 3 min and 1 h. The activation of PKC-ζ by I-BOP was confirmed using an immune complex kinase assay. Treatment of ARVM with a cell-permeable PKC-ζ pseudosubstrate peptide (ζ-PS) significantly attenuated apoptosis by I-BOP. In addition, I-BOP treatment decreased baseline Akt activity and its decrease was reversed by treatment with ζ-PS. The inhibition of phosphatidylinositol 3-kinase upstream of Akt by wortmannin or LY-294002 abolished the antiapoptotic effect of ζ-PS. Therefore, our results suggest that the activation of PKC-ζ modulates TxA2 receptor-mediated apoptosis at least, in part, through Akt activity in adult cardiac myocytes.

Temporal and spatial properties of some deep moonquake clusters

2007 ◽  
Vol 112 (E9) ◽  
Author(s):  
R. C. Bulow ◽  
C. L. Johnson ◽  
B. G. Bills ◽  
P. M. Shearer
Keyword(s):  
Spatial Properties ◽  
Temporal And Spatial
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