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A Novel Ex Ovo Banding Technique to Alter Intracardiac Hemodynamics in an Embryonic Chicken System
Published on: May 13, 2016
Cardiac rhythms of late pre-pipped and pipped chick embryos exposed to altered oxygen environments
A H Khandoker1, E M Dzialowski, W W Burggren
1Department of Electrical and Electronic Engineering, Muroran Institute of Technology, 050-8585, Muroran, Japan.
Insights
Chick embryo respiration transitions from chorioallantoic membrane (CAM) gas exchange to pulmonary respiration. Heart rate responses to hypoxia and hyperoxia differ significantly between pre-pipped and pipped embryos during this critical developmental stage.
Area of Science:
- Developmental Physiology
- Avian Embryology
- Respiratory Physiology
Background:
- Chick embryos transition from chorioallantoic membrane (CAM) gas exchange to pulmonary respiration near hatching.
- This transition involves internal pipping (IP), marking the initiation of lung breathing.
- Understanding cardiorespiratory adjustments during this period is crucial for avian development.
Purpose of the Study:
- To investigate the heart rate (HR) and HR fluctuation patterns of late-stage chick embryos under hyperoxic and hypoxic conditions.
- To compare the responses of pre-pipped and internally pipped (IP) embryos during the respiratory transition.
- To explore potential autonomic nervous system contributions to observed cardiorespiratory changes.
Main Methods:
- Chick embryos at 16, 18, 19 (pre-IP and IP), and 20 (externally pipped - EP) days of incubation were exposed to 100% O2 (hyperoxia) or 10% O2/N2 (hypoxia) for 2 hours.
- Internal pipping (IP) was identified using an acoustorespirogram.
- Baseline heart rate (HR) and instantaneous heart rate (IHR) fluctuation patterns were analyzed.
Main Results:
- Hyperoxia: Baseline HR was unchanged in pre-pipped embryos but depressed in pipped embryos (IP and EP).
- Hypoxia: Baseline HR was depressed in 16-day pre-pipped embryos but elevated in pipped embryos (IP and EP).
- Hypoxia increased transient decelerations of IHR in late pre-pipped embryos and markedly depressed HR fluctuations in pipped embryos, while hyperoxia had minimal effect on fluctuation patterns.
Conclusions:
- Pipped chick embryos exhibit distinct cardiorespiratory responses to hypoxia and hyperoxia compared to pre-pipped embryos.
- These differential responses suggest altered autonomic nervous system regulation, potentially involving increased vagal tone in hyperoxia and adrenergic activity in hypoxia.
- Hypoxia significantly impacts HR variability in pipped embryos, highlighting the challenges of pulmonary respiration during this transitional phase.
Abstract:
During the final stages of embryonic development in chickens, diffusive gas exchange through the chorioallantoic membrane (CAM) is progressively replaced by pulmonary respiration that begins with internal pipping (IP) of the CAM. Late chick embryos going through the transition from CAM respiration to pulmonary respiration were exposed to hyperoxic (100% O(2)) and hypoxic (10% O(2)/N(2)) environments for 2-h and the responses of baseline heart rate (HR), and HR fluctuation patterns were investigated. 16- and 18-day-old (referred to as 18-d) embryos and 20-d externally pipped (EP) embryos were examined as pre-pipped embryos and pipped embryos, respectively. 19-d embryos were divided into two groups: embryos that had not yet internally pipped (Pre-IP embryos) and embryos that had internally pipped (IP embryos). IP was identified by detecting the breathing signal with a condenser microphone attached hermetically on the eggshell (i.e. acoustorespirogram) on day 19 of incubation. In the hyperoxic environment, HR baseline of pre-pipped embryos remained unchanged and that of pipped embryos was depressed. In the hypoxic environment, HR baseline of 16-d pre-pipped embryos was depressed and that of pipped (IP and EP) embryos elevated. These different responses in pipped embryos might be partially attributed to increased cholinergic input from the vagus nerve in hyperoxia and increased adrenergic response in hypoxia. While hyperoxia did not induce marked modification of instantaneous heart rate (IHR) fluctuation patterns, hypoxia tended to augment transient decelerations of IHR in late pre-pipped embryos and markedly depressed HR fluctuations in pipped embryos.
