Effect of Acute Hypoxia on the Motor Activity and Heart Rate of the 10- and 14-Day Chick Embryo

Abstract

Embryonic motility is an important component of development and may be a precursor of posthatching motor behavior. In chickens, it accompanies almost the entire embryogenesis and depends on environmental conditions, whose effects on embryonic motility have been poorly studied. The effect of acute hypoxia (10% O 2 for 10 min) on the temporal parameters of chick embryo motility on incubation days 10 (D10) and 14 (D14) was estimated; the results were compared with data on the heart rate (HR). A force transducer connected with an embryo limb was used to record embryonic movements simultaneously with HR video recording. In the control, the duration of the activity phase (APh) and HR increased, while the inactivity phase (IPh) decreased in the period from D10 to D14. In response to hypoxia, the APh did not change significantly on either day, but the IPh significantly increased on D14 and tended to increase on D10. A distinct pattern of the motor activity response to hypoxia was observed on D14: the IPh increased after 0.5-2.5 min of hypoxia, peaked at a value 6 times as large as the control one, and then partly recovered. Under hypoxia, the mean HR significantly decreased to 87% of the control value and then partly recovered, increasing to 93% on both days studied. The similarity of the hypoxic patterns of IPh and HR on D14 suggests that the hypoxic recovery of HR contributes to the recovery of the embryo motility under hypoxia in late embryos.

Age-related Changes in the Response of Embryonic Motility to Acute Hypoxia During the Third Quarter of Chick Embryogenesis

“…2A). The mean durations of APh and IPh on D10 and D14 were comparable with our earlier results for these embryonic ages [17]. The average duration of the motility cycle that consisted of the activity phase duration plus the duration of the subsequent inactivity phase remained unchanged from D10 to D15, and then was decreasing until D16 ( Fig.…”

“…We previously found a characteristic time course of the motility response to hypoxia on D14, but it was much less pronounced on D10 [17]. The time course showed that during hypoxic exposure the embryonic motility initially stopped and then was partly restored while the hypoxic exposure continued.…”

“…Eggs were opened over the air-cell side by making a window approximately 2 -2.5 cm in diameter in the egg shell above the developing embryo. A part of the inner shell membrane was removed, a small hole was cut in the chorioallantoic membrane and the amnion to reach the embryo, and the force transducer was attached to a limb of the embryo by means of a special grip (micro-serrefine); the signal from the transducer was recorded continuously and stored digitally on a computer [17]. The experimental setup is presented in Fig.…”

“…The durations of the activity phase (APh) and inactivity phase (IPh) were used to quantify the embryonic motility. As in previous studies [17], we defined an APh as any episode of embryonic movements (no shorter than 6 s) that was separated from other embryonic movements by at least 6 s of quiescence. When we studied the time-sequential changes in the APh and IPh, the durations of APh and IPh were represented as averages over every 5 min.…”

“…Earlier, we showed that acute hypoxia (10% O 2 10 min) inhibited cyclic (or periodic) motility as estimated by its temporal parameters. This effect was found to depend on embryonic age: the motility inhibition was weak on day 10 of embryogenesis (D10), but it was substantial on D14 [17]. At the same time, authors that estimated the overall motility of a chick embryo by measuring the pressure within the egg reported on variable and often insignificant effects of acute hypoxia (10% O 2 30 min) on body motion in the period D10-18, except for D16, when a significant decrease in the motility was observed [19].…”