Tolerance of chick embryos to low temperatures in reference to the heart rate.
Ten-day-old embryos were exposed to 28, 18 and 8 degrees C environments and their electrocardiograms (ECG) monitored. Embryos in 28 and 18 degrees C environments maintained a constant heart rate averaging 97 and 25 beats/min, respectively, followed by arrhythmias and cardiac arrest at 101 and 59 hr. Embryos in an 8 degrees C environment went into cardiac arrest after 2-4 hr, but recovered 20 hr later upon rewarming to 38 degrees C. Six to 20-day-old embryos exposed to 8 degrees C were examined for tolerance time after cardiac arrest. The younger the embryo the longer its tolerance to prolonged cardiac arrest.
D000064:Acclimatization; D000818:Animals; D002642:Chick Embryo / Q000502:physiology*; D003080:Cold Temperature; D004562:Electrocardiography; D006321:Heart / Q000196:embryology*; D006323:Heart Arrest / Q000196:embryology; D006339:Heart Rate