scholarly journals Functional pacemaking area in the early embryonic chick heart assessed by simultaneous multiple-site optical recording of spontaneous action potentials.

1988 ◽  
Vol 91 (4) ◽  
pp. 573-591 ◽  
Author(s):  
K Kamino ◽  
H Komuro ◽  
T Sakai ◽  
A Hirota
Keyword(s):  
Action Potentials ◽  
Optical Recording ◽  
Measuring System ◽  
Embryonic Chick ◽  
Multiple Site ◽  
Optical Signals ◽  
Chick Heart ◽  
Embryonic Chick Heart ◽  
Spontaneous Action ◽  
Spontaneous Action Potentials

Pacemaking areas in the early embryonic chick hearts were quantitatively assessed using simultaneous multiple-site optical recordings of spontaneous action potentials. The measuring system with a 10- X 10- or a 12 X 12-element photodiode array had a spatial resolution of 15-30 microns. Spontaneous action potential-related optical signals were recorded simultaneously from multiple contiguous regions in the area in which the pacemaker site was located in seven- to nine-somite embryonic hearts stained with a voltage-sensitive merocyanine-rhodanine dye (NK 2761). In the seven- to early eight-somite embryonic hearts, the location of the pacemaking area is not uniquely determined, and as development proceeds to the nine-somite stage, the pacemaking area becomes confined to the left pre-atrial tissue. Analysis of the simultaneous multiple-site optical recordings showed that the pacemaking area was basically circular in shape in the later eight- to nine-somite embryonic hearts. An elliptical shape also was observed at the seven- to early eight-somite stages of development. The size of the pacemaking area was estimated to be approximately 1,200-3,000 micron2. We suggest that the pacemaking area is composed of approximately 60-150 cells, and that the pacemaking area remains at a relatively constant size throughout the seven- to nine-somite stages. It is thus proposed that a population of pacemaking cells, rather than a single cell, serves as a rhythm generator in the embryonic chick heart.

Effects of taurine on the electrical and mechanical activities of embryonic chick heart

1986 ◽  
Vol 64 (5) ◽  
pp. 649-655 ◽  
Author(s):  
Akihiko Sawamura ◽  
Nick Sperelakis ◽  
Junichi Azuma ◽  
Susumu Kishimoto
Keyword(s):  
Action Potentials ◽  
Cultured Cells ◽  
Negative Inotropic Effect ◽  
Embryonic Chick ◽  
Inotropic Action ◽  
Positive Inotropic Action ◽  
Chick Heart ◽  
Embryonic Chick Heart ◽  
Electrical And Mechanical Activities ◽  
Slow Action Potentials

The effect of taurine (2-aminoethanesulphonic acid) on myocardial slow action potentials (APs) and accompanying contractions was examined in isolated perfused chick hearts and reaggregated cultured cells. Isoproterenol (ISO), histamine (HIS), or tetraethylammonium (TEA) induced slow APs and contractions in hearts whose fast Na+ channels had been inactivated by elevated K+. Taurine (10 mM) not only failed to induce slow APs, but actually decreased ISO (10−8 M), HIS (10−4 M), or TEA (10 mM) induced slow APs and contractions transiently (about 30s –2 min after the addition of taurine). The properties of the slow APs recovered to control levels by 7–13 min after the addition of the taurine; at this time, there was an increase in developed tension of the contraction accompanying the slow APs. These results suggest that the positive inotropic action of taurine is not mediated through an increase in the slow inward Ca2+ current. However, the transient depression of Ca2+-dependent slow APs by taurine probably explains the transient negative inotropic effect of taurine.

scholarly journals Effects of calcium on electrical propagation in early embryonic precontractile heart as revealed by multiple-site optical recording of action potentials.

1985 ◽  
Vol 85 (3) ◽  
pp. 365-382 ◽  
Author(s):  
H Komuro ◽  
A Hirota ◽  
T Yada ◽  
T Sakai ◽  
S Fujii ◽  
...  
Keyword(s):  
Intercellular Communication ◽  
Action Potentials ◽  
Optical Recording ◽  
Fusion Line ◽  
Ionophore A23187 ◽  
Multiple Site ◽  
Optical Signals ◽  
Photodiode Array ◽  
Electrical Propagation

The effects of Ca2+ on electrical propagation in early embryonic precontractile chick hearts were studied optically using a voltage-sensitive merocyanine-rhodanine dye. Spontaneous optical signals, corresponding to action potentials, were recorded simultaneously from 25 separate regions of the eight-to-nine-somite embryonic primitive heart, using a square photodiode array. Electrical propagation was assessed by analyzing the timing of the signals obtained from different regions. Electrical propagation in the heart was suppressed by either lowering or raising extracellular Ca2+. Similar effects were produced by a Ca2+ ionophore (A23187). We have also found that electrical propagation across the primordial fusion line at the midline of the heart was enhanced by increasing, and depressed by lowering, external Ca2+. One possible interpretation is that intercellular communication in the embryonic precontractile heart is regulated by the level of the intracellular Ca2+ concentration, and it is suggested that intercellular communication across the primordial fusion line strongly depends on external Ca2+.

scholarly journals The Electrophysiological Organization of the Embryonic Chick Heart

1965 ◽  
Vol 49 (2) ◽  
pp. 351-363 ◽  
Author(s):  
Melvyn Lieberman ◽  
Antonio Paes de Carvalho
Keyword(s):  
Action Potentials ◽  
Adult Rabbit ◽  
Embryonic Chick ◽  
Surface Electrodes ◽  
Transmembrane Potentials ◽  
Functional Regions ◽  
Purkinje System ◽  
Chick Heart ◽  
Embryonic Chick Heart ◽  
The Right

Both intracellular and surface electrodes were employed to record electrical activity from embryonic chick hearts between the ages of 3 and 20 days. Cells from the sinus venosus, sinoatrial (SA) valves, atrium, atrioventricular (AV) ring, and ventricle were localized and characterized on the basis of shape, amplitude, rise time, and duration of transmembrane potentials. The differences in transmembrane potentials from these various regions provided the basis for a hypothesis concerned with the distribution of pacemaker potentiality and one related to the origin of the His-Purkinje system. Action potentials recorded along the entire embryonic AV ring were comparable to those of the adult rabbit AV nodal cells in both configuration and sequence of activation and were thus categorized into three functional regions (AN, N, NH). Histological sections of 7 and 14 day hearts demonstrated muscular continuity between the right atrium and ventricle across the muscular AV valve.

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