Factors Involved in the Loss of Spontaneous Contractile and Electrical Activity in Clusters of Cultured Cardiac Cells

1972 ◽  
Vol 50 (6) ◽  
pp. 523-532 ◽  
Author(s):  
O. F. Schanne
Keyword(s):  
Electrical Activity ◽  
Spontaneous Activity ◽  
Cardiac Cells ◽  
Pacemaker Activity ◽  
Newborn Rats ◽  
Cell Clusters ◽  
A Cell ◽  
Enzyme Pattern ◽  
Membrane Changes ◽  
Increasing Temperature

Beating cell clusters were obtained by trypsinization from hearts of newborn rats. Spontaneous activity ceased after several weeks while the cultures were still proliferating. Experiments were performed to identify the physiological determinant causing cessation of spontaneous activity. (a) Cell clusters having lost their spontaneous activity responded to extracellular stimulation. (b) Reduction of [K]o by 50% increased the number of beating cell clusters by 40%; doubling [K]o reduced the number of beating cell clusters by 49%. (c) Cell clusters which were in the process of losing their ability to contract spontaneously needed a progressively increasing temperature to induce spontaneous activity. These results suggest (1) that the pacemaker mechanism fails first when a cell cluster loses its spontaneous activity and (2) that shortly before the cluster fails to contract spontaneously, it requires more energy to maintain pacemaker activity because of possible structural membrane changes or changes in the enzyme pattern of the cells.

Ionic Determinants of Spontaneous Activity in Clusters of Cultured Cardiac Cells from Newborn Rats

1975 ◽  
Vol 53 (6) ◽  
pp. 1209-1213
Author(s):  
O. F. Schanne ◽  
C. Rivard ◽  
G. Doyon
Keyword(s):  
Spontaneous Activity ◽  
Cardiac Cells ◽  
Slow Inward Current ◽  
Heart Cells ◽  
Newborn Rats ◽  
Sodium Potassium ◽  
Inward Current ◽  
Cell Clusters ◽  
Beating Rate ◽  
Rat Heart Cells

The spontaneous activity of cell clusters derived from ventricle cells of newborn rats was studied using a recording television microscope. The influence of varying concentrations of sodium, potassium, calcium, tetrodotoxin (TTX), and that of 2 mM MnCl2 was tested. The spontaneous activity of the cell clusters persisted in TTX but it was abolished by Mn. The beating rate increased when [Ca]0 and [Na]0 were changed from 0.3 mM to 3.0 mM and from 30 mM to 75 mM; it decreased with a change of [Na]0 from 75 mM to 142 mM. It is concluded that electrogenesis in these cells is determined by a slow inward current and that these cell clusters are comparable in their behavior to very young embryonic rat heart cells or cells of the rabbit sinoauricular node.

Diastolic SR Ca efflux in atrial pacemaker cells and Ca-overloaded myocytes

1997 ◽  
Vol 273 (2) ◽  
pp. H886-H892 ◽  
Author(s):  
R. A. Bassani ◽  
J. W. Bassani ◽  
S. L. Lipsius ◽  
D. M. Bers
Keyword(s):  
Spontaneous Activity ◽  
Ventricular Myocytes ◽  
Cardiac Cells ◽  
Transport Systems ◽  
Pacemaker Activity ◽  
Pacemaker Cells ◽  
Sa Node ◽  
Ca Uptake ◽  
Rabbit Ventricular Myocytes ◽  
Ca Depletion

Evidence has shown that the sarcoplasmic reticulum (SR) of cardiac cells releases Ca not only during excitation-contraction coupling but also during diastole, albeit at a much lower rate. This diastolic SR Ca release (leak) has also been implicated in the generation of spontaneous depolarization in latent atrial pacemaker cells of the cat right atrium. In the present work, we sought to measure Ca transients in pacemaker and nonpacemaker cells of the cat using the fluorescent Ca indicator indo 1. Atrial latent pacemaker cells develop a slow Ca transient when rested in the presence of both Na- and Ca-free solution and thapsigargin [used to inhibit Na/Ca exchange and SR Ca adenosinetriphosphatase (Ca-ATPase), respectively]. This increase in cytosolic Ca concentration ([Ca]i) is probably caused by the rate of SR Ca leak exceeding the capacity of the remaining Ca transport systems (e.g., sarcolemmal Ca-ATPase and mitochondrial Ca uptake). However, neither cat sinoatrial (SA) node cells nor myocytes from cat atrium or ventricle exhibited a similar increase in [Ca]i during the same protocol. This indicates that SR Ca leak in these cells occurred at a rate low enough to be within the capacity of the slow Ca transporters, as observed previously in rabbit ventricular myocytes. When atrial and ventricular myocytes were stimulated at higher frequencies, sufficient to markedly increase diastolic and systolic [Ca]i and approach Ca overload (and spontaneous activity), they responded to inhibition of SR Ca-ATPase and Na/Ca exchange with a slow Ca transient similar to that normally observed in atrial latent pacemaker cells. Furthermore, the SR Ca depletion by thapsigargin did not affect spontaneous activity of SA node cells, but it prevented or slowed pacemaker activity in the atrial latent pacemaker cells. These findings suggest that enhanced diastolic SR Ca efflux contributes significantly to the generation of spontaneous activity in atrial subsidiary pacemakers under normal conditions and in Ca-overloaded myocytes but not in SA node cells.

Form follows function: how muscle shape is regulated by work

2000 ◽  
Vol 88 (3) ◽  
pp. 1127-1132 ◽  
Author(s):  
Brenda Russell ◽  
Delara Motlagh ◽  
William W. Ashley
Keyword(s):  
Muscle Cell ◽  
Cell Shape ◽  
Force Production ◽  
Cardiac Cells ◽  
Cross Sectional Area ◽  
Dynamic Responses ◽  
Mechanical Activity ◽  
Sectional Area ◽  
Cross Sectional ◽  
A Cell

What determines the shape, size, and force output of cardiac and skeletal muscle? Chicago architect Louis Sullivan (1856–1924), father of the skyscraper, observed that “form follows function.” This is as true for the structural elements of a striated muscle cell as it is for the architectural features of a building. Function is a critical evolutionary determinant, not form. To survive, the animal has evolved muscles with the capacity for dynamic responses to altered functional demand. For example, work against an increased load leads to increased mass and cross-sectional area (hypertrophy), which is directly proportional to an increased potential for force production. Thus a cell has the capacity to alter its shape as well as its volume in response to a need for altered force production. Muscle function relies primarily on an organized assembly of contractile and other sarcomeric proteins. From analysis of homogenized cells and molecular and biochemical assays, we have learned about transcription, translation, and posttranslational processes that underlie protein synthesis but still have done little in addressing the important questions of shape or regional cell growth. Skeletal muscles only grow in length as the bones grow; therefore, most studies of adult hypertrophy really only involve increased cross-sectional area. The heart chamber, however, can extend in both longitudinal and transverse directions, and cardiac cells can grow in length and width. We know little about the regulation of these directional processes that appear as a cell gets larger with hypertrophy or smaller with atrophy. This review gives a brief overview of the regulation of cell shape and the composition and aggregation of contractile proteins into filaments, the sarcomere, and myofibrils. We examine how mechanical activity regulates the turnover and exchange of contraction proteins. Finally, we suggest what kinds of experiments are needed to answer these fundamental questions about the regulation of muscle cell shape.

scholarly journals Experimental study of the stratification of polydisperse emulsions in a cell with heated walls

2021 ◽  
Vol 2057 (1) ◽  
pp. 012041
Author(s):  
V I Valiullina ◽  
A I Mullayanov ◽  
A A Musin ◽  
L A Kovaleva
Keyword(s):  
Experimental Study ◽  
Deposition Rate ◽  
Thermal Convection ◽  
Dispersion Medium ◽  
Experimental Studies ◽  
Oil Emulsion ◽  
Convective Flows ◽  
A Cell ◽  
Increasing Temperature ◽  
Water In Oil Emulsion

Abstract Experimental studies of the gravitational deposition of a polydisperse water-in-oil emulsion under heat influence are carried out. When the rate of thermal convection exceeds the rate of precipitation, partial delamination of the emulsion is found to occur. The viscosity of the dispersion medium decreases with increasing temperature, which contributes to an increase in the deposition rate of water droplets in the emulsion. In the presence of a temperature difference, convective flows occur in the liquid, while the drops of the emulsion coagulate and form larger agglomerates that settle faster to the bottom of the cell.

Electric Field-Assisted Positioning of Neurons on Pt Microelectrode Arrays

2003 ◽  
Vol 773 ◽  
Author(s):  
Shalini Prasad ◽  
Mo Yang ◽  
Xuan Zhang ◽  
Yingchun Ni ◽  
Vladimir Parpura ◽  
...  
Keyword(s):  
Electric Field ◽  
Electrical Activity ◽  
Electric Fields ◽  
Microelectrode Array ◽  
Electrode Array ◽  
Sprague Dawley ◽  
A Cell ◽  
Neuron Patterning

AbstractCharacterization of electrical activity of individual neurons is the fundamental step in understanding the functioning of the nervous system. Single cell electrical activity at various stages of cell development is essential to accurately determine in in-vivo conditions the position of a cell based on the procured electrical activity. Understanding memory formation and development translates to changes in the electrical activity of individual neurons. Hence, there is an enormous need to develop novel ways for isolating and positioning individual neurons over single recording sites. To this end, we used a 3x3 multiple microelectrode array system to spatially arrange neurons by applying a gradient AC field. We characterized the electric field distribution inside our test platform by using two dimensiona l finite element modeling (FEM) and determined the location of neurons over the electrode array. Dielectrophoretic AC fields were utilized to separate the neurons from the glial cells and to position the neurons over the electrodes. The neurons were obtained from 0-2-day-old rat (Sprague-Dawley) pups. The technique of using electric fields to achieve single neuron patterning has implications in neural engineering, elucidating a new and simpler method to develop and study neuronal activity as compared to conventional microelectrode array techniques.

scholarly journals The complement of desmosomal plaque proteins in different cell types.

1985 ◽  
Vol 101 (4) ◽  
pp. 1442-1454 ◽  
Author(s):  
P Cowin ◽  
H P Kapprell ◽  
W W Franke
Keyword(s):  
Guinea Pig ◽  
Cell Types ◽  
Cardiac Cells ◽  
Myocardial Tissue ◽  
Cell Type ◽  
Wide Range ◽  
Specific Manner ◽  
A Cell ◽  
Cell Type Specific ◽  
Different Cell Types

Desmosomal plaque proteins have been identified in immunoblotting and immunolocalization experiments on a wide range of cell types from several species, using a panel of monoclonal murine antibodies to desmoplakins I and II and a guinea pig antiserum to desmosomal band 5 protein. Specifically, we have taken advantage of the fact that certain antibodies react with both desmoplakins I and II, whereas others react only with desmoplakin I, indicating that desmoplakin I contains unique regions not present on the closely related desmoplakin II. While some of these antibodies recognize epitopes conserved between chick and man, others display a narrow species specificity. The results show that proteins whose size, charge, and biochemical behavior are very similar to those of desmoplakin I and band 5 protein of cow snout epidermis are present in all desmosomes examined. These include examples of simple and pseudostratified epithelia and myocardial tissue, in addition to those of stratified epithelia. In contrast, in immunoblotting experiments, we have detected desmoplakin II only among cells of stratified and pseudostratified epithelial tissues. This suggests that the desmosomal plaque structure varies in its complement of polypeptides in a cell-type specific manner. We conclude that the obligatory desmosomal plaque proteins, desmoplakin I and band 5 protein, are expressed in a coordinate fashion but independently from other differentiation programs of expression such as those specific for either epithelial or cardiac cells.

The effect of local cooling upon spontaneous and evoked electrical activity of cerebral cortex

1970 ◽  
Vol 48 (9) ◽  
pp. 640-652 ◽  
Author(s):  
Herbert H. Jasper ◽  
David G. Shacter ◽  
Jacques Montplaisir
Keyword(s):  
Cerebral Cortex ◽  
Electrical Activity ◽  
Auditory Evoked Potentials ◽  
Response Duration ◽  
Surface Cooling ◽  
Local Cooling ◽  
Cortical Responses ◽  
Increasing Temperature ◽  
Local Stimulation ◽  
Synaptic Mechanisms

The effect of local cooling of the surface of the cerebral cortex by means of a metal chamber implanted in the skull was studied while recording evoked and spontaneous electrical activity from the center of a cooled area of 1 cm2. Direct cortical responses to local stimulation of the cortical surface decreased rapidly and progressively to disappear at surface temperatures of 20–22 °C. Onset and peak latencies were prolonged with a Q10 of 1.4 and 1.7 respectively. Response duration was prolonged with decreasing amplitude, having a Q10 of about 2.6. Surface cooling to 8–12 °C was necessary to abolish all postsynaptic components of somatic and auditory evoked potentials, recruiting responses, and spontaneous barbiturate spindles. Latencies of these responses were also increased with a Q10 of 1.3–1.4 while the Q10 for amplitude was consistently higher (2.0–2.6). Allowing for a gradient of increasing temperature from surface to depth it is concluded that all synaptic processes are blocked at temperatures of 20–22 °C. Synaptic mechanisms determining latency were consistently different from those determining amplitude as judged by consistent differences in the Q10 of latency and amplitude for all postsynaptic responses studied in these experiments.

Pacemaker activity in the insect (T. molitor) heart: role of the sarcoplasmic reticulum

2011 ◽  
Vol 301 (6) ◽  
pp. R1838-R1845 ◽  
Author(s):  
Danielle F. Feliciano ◽  
Rosana A. Bassani ◽  
Pedro X. Oliveira ◽  
José W. M. Bassani
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Cardiac Cells ◽  
Pacemaker Activity ◽  
Electrophysiological Properties ◽  
Chronotropic Response ◽  
Different Types ◽  
Mealworm Beetle ◽  
Beating Rate

The electrophysiological properties of the myogenic cardiac cells of insects have been analyzed, but the mechanisms that regulate the pacemaker activity have not been elucidated yet. In mammalian pacemaker cells, different types of membrane ion channels seem to be sequentially activated, perhaps in a cooperative fashion with the current generated by Ca2+ extrusion mediated by the electrogenic Na+/Ca2+ exchanger, which is sustained by the diastolic sarcoplasmic reticulum (SR) Ca2+ release. The objective of the present work was to investigate the role of the SR function on the basal beating rate (BR), and BR modulation by extracellular Ca2+ concentration ([Ca2+]o) and neurotransmitters in the in situ dorsal vessel (heart) of the mealworm beetle Tenebrio molitor . The main observations were as follows: 1) basal BR was reduced by 50% by inhibition of SR function, but not affected by perfusion with CsCl or ZD7288; 2) spontaneous activity was abolished by Cd2+; 3) a robust positive chronotropic response could be elicited to serotonin (5-HT), but not to norepinephrine or carbamylcholine; 4) SR inhibition abolished the sustained chronotropic stimulation by [Ca2+]o elevation and by 5-HT, while the latter was unaffected by CsCl. It is concluded that, in T. molitor heart, BR is markedly, but not exclusively, dependent on the SR function, and that BR control and modulation by both [Ca2+]o and 5-HT requires a functional SR.

scholarly journals The Ionic Basis of Electrical Activity in Embryonic Cardiac Muscle

1968 ◽  
Vol 52 (3) ◽  
pp. 666-681 ◽  
Author(s):  
Billy K. Yeh ◽  
Brian F. Hoffman
Keyword(s):  
Electrical Activity ◽  
Sodium Concentration ◽  
Cardiac Cells ◽  
Resting Potential ◽  
Extracellular Potassium ◽  
Embryonic Chick ◽  
Extracellular Potassium Concentration ◽  
Chick Heart ◽  
Extracellular Sodium ◽  
Ionic Basis

The intracellular sodium concentration reported for young, embryonic chick hearts is extremely high and decreases progressively throughout the embryonic period, reaching a value of 43 mM immediately before hatching. This observation suggested that the ionic basis for excitation in embryonic chick heart may differ from that responsible for electrical activity of the adult organ. This hypothesis was tested by recording transmembrane resting and action potentials on hearts isolated from 6-day and 19-day chick embryos and varying the extracellular sodium and potassium concentrations. The results show that for both young and old embryonic cardiac cells the resting potential depends primarily on the extracellular potassium concentration and the amplitude and rate of rise of the action potential depend primarily on the extracellular sodium concentration.

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