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Development of electrical rhythmic activity in early embryonic cultured chick double-heart monitored optically with a
Insights
Researchers created double-hearted chick embryos to study early heart development. They found the left half-heart typically beats faster than the right, offering insights into cardiac rhythm formation.
Area of Science:
- Developmental biology
- Cardiovascular research
- Embryology
Background:
- Early heart development involves the fusion of cardiac primordia.
- Understanding the initiation of cardiac rhythm is crucial for developmental studies.
Purpose of the Study:
- To investigate the electrophysiological properties of developing double-hearted chick embryos.
- To analyze the onset and characteristics of spontaneous contractions in nascent cardiac tissues.
Main Methods:
- Microsurgical separation of chick embryos at the 1- to 6-somite stage to create double-hearted formations.
- Whole-embryo culture and optical recording of electrical activity and contractions using a photodiode array and voltage-sensitive dye (NK 2761).
Main Results:
- Spontaneous action potentials were detected in bilateral half-hearts by the 7- to 8-somite stages.
- Regular electrical activity was observed in beating half-hearts, with a higher incidence than irregular rhythms in prebeating half-hearts.
- The left half-heart exhibited a faster heart rate compared to the right half-heart in most double-hearted embryos.
Conclusions:
- Bilateral cardiac primordia can initiate independent electrical activity prior to full fusion.
- Differential heart rates between left and right half-hearts suggest early functional asymmetry in cardiac development.
- This model provides a platform for studying the fundamental mechanisms of cardiac rhythmogenesis.
Abstract:
Double-hearted embryos were produced by whole-embryo culture of chick embryos which were microsurgically cut through the tissue of the anterior intestinal portal at the 1- to 6-somite developmental stage, at the time when the cardiac primordia have not yet fused in the bulboventricular region. The cultured embryos were removed from an incubator usually at the 7- to 10-somite stages of development, and then spontaneous electrical action potentials and/or contractions were optically recorded simultaneously from both the right and left half-hearts, using a 10 X 10- element photodiode matrix array together with a voltage-sensitive merocyanine-rhodanine dye (NK 2761). At the 7- to 8-somite stages, spontaneous action potentials were detected from bilateral prebeating half-hearts or sometimes from one half-heart. In each half-heart, the first spontaneous beating was often observed in the half-heart of the 9 somite embryos. In the beating half-hearts regular activity was always observed, while in the prebeating half-hearts at the 7- to 8-somite stages, both the regular and irregular rhythms of action potentials were detected, and the incidence of occurrence of regular activity significantly outnumbered that of the irregular rhythm. The heart rate in the left half-heart was faster than that in the right half-heart in the great majority of the prebeating and beating double-hearted embryos.