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Published on: November 22, 2013
Long-term measurement of heart rate in chicken eggs
R Akiyama1, A Matsuhisa, J T Pearson
1Department of Electrical and Electronic Engineering, Muroran Institute of Technology, Japan.
Insights
Chick embryo heart rate development shows increasing irregularities and an ultradian rhythm, but no circadian rhythm, before hatching. Breathing movements emerge later, impacting measurements.
Area of Science:
- Developmental physiology
- Embryology
- Cardiovascular research
Background:
- Understanding embryonic cardiovascular development is crucial for assessing fetal well-being.
- Acoustocardiography (ACG) offers a non-invasive method for monitoring fetal heart activity.
- Previous studies have not fully characterized the detailed development of heart rate patterns in late-stage chick embryos.
Purpose of the Study:
- To continuously measure chick embryo heart rate (HR) from day 12 until hatching using ACG.
- To investigate the development of heart rate irregularities (HRI), heart rate variability (HRV), and ultradian rhythms in mean HR (MHR).
- To determine the presence of a circadian rhythm in MHR during late embryonic development.
Main Methods:
- Continuous acoustocardiogram (ACG) recordings were performed on chick embryos from day 12 to hatching.
- Analysis focused on heart rate (HR), heart rate irregularities (HRI), heart rate variability (HRV), and mean heart rate (MHR).
- Breathing activities were recorded in the final days of incubation when ACG signals became disturbed.
Main Results:
- Heart rate irregularities (transient bradycardia and tachycardia) emerged around days 14-16 and increased with development.
- Mean HR peaked around days 14-15, then decreased, with baseline HRV (ultradian rhythm, 40-90 min) becoming prominent by days 17-18.
- No circadian rhythm in MHR was detected; breathing movements began around days 18-19, increasing in frequency before hatching.
Conclusions:
- Chick embryo heart rate exhibits significant developmental changes, including increasing irregularities and an ultradian rhythm, in late gestation.
- The absence of a detectable circadian rhythm suggests dominance of other regulatory mechanisms during this period.
- ACG is effective for monitoring embryonic cardiovascular development, though later stages are complicated by the onset of breathing.
Abstract:
Taking advantage of acoustocardiogram (ACG), we measured the heart rate (HR) of chick embryos continuously from day 12 until hatching and then investigated the development of HR irregularities (HRI), HR variability (HRV), and the existence of a circadian rhythm in mean HR (MHR). HRI comprised transient bradycardia and tachycardia, which first developed on day 14 and 16 in most embryos, respectively. Transient bradycardia increased in frequency and magnitude with embryonic development and occurred over periods of up to 30 min in some embryos. MHR was maximal on around days 14-15 and thereafter decreased to about 250-260 bpm on days 16-18. Baseline HRV, which is an oscillation of the MHR baseline, occurred as HR decreased from days 15-16 and became predominant on days 17-18. The magnitude of the baseline oscillations reached up to 50 bpm in some embryos and the period ranged between about 40-90 min (ultradian rhythm). A circadian rhythm of MHR was not found in late chick embryos. On days 18-19, embryonic activities were augmented and then breathing movements began to occur, disturbing ACG signals and thus making it difficult to measure the HR. Instead, the development of breathing activities was recorded. Breathing frequency was irregular at first and then increased to a maximum of about 1.5 Hz prior to hatching.
