Effects of Some Environmental Factors on the Amnion Rhythmic Contractions in Chick Embryogenesis

Abstract

We studied the rhythmic contractions of the chick amnion in the egg at different developmental stages, performing continuous recording using a force transducer under normal conditions and under short-term changes of environmental factors (lowered temperature, acute hypoxia, hyperoxia, and hypercapnia). Acute hypoxia (10 and 15% O2) for periods of 10^20 minutes inhibited or arrested contractions of the amnion. During a 10 minute application of gas, 2% CO2 inhibited and 100% O2 accelerated the amniotic contractions. Lowering of temperature slowly decreased the frequency of the amnion contractions, and they stopped at 32^29 C. These changes of the amnion rhythmic contractions were reversible and the frequency of the amnion contractions restored after the returning to the normal conditions. The data on the isolated rostral part of amnion on day 8 of incubation demonstrated that the effect of temperature on the amnion contractions in egg is mainly a result of its direct influence. The morphological study of the smooth muscles described their distribution in this part of amnion, as the background for the contractile activity. Thus, the amnion rhythmic contractions are involved in short-term response of the embryo to the environmental factors that suggests their participation in the environmental adaptation during embryogenesis. As the amnion contractions produce mixing of the amniotic fluid, we propose that in combination with the other factors the changes in the amnion contractile activity could influence the level of the metabolic processes in the developing egg.