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Epigenetic adaptation as a long lasting, but reversible adjustment to changed environmental conditions (without changes in DNA sequences) offers the possibility to explain increased adaptation of newborn to a changed environment. These adaptations can result in a higher survival as well as in illness/decreased health later on in life.
The bird embryo represents a nearly ideal model for investigation concerning the prenatal development under different ambient conditions. There are neither maternal compensations nor changes in nutrition supply during incubation.
The oxygen supply of bird embryos in incubation is a critical factor. There are many mechanisms of adaptation on a decreased oxygen supply described. Increases amount of erythrocytes; haemoglobin, 2,3 Diphosphoglycerate and of capillary density are part of this.
A very essential adaptation to oxygen deprivation could consist in a change of metabolism from aerobic to anaerobic energy production.
Some poikilotherm organisms show a high tolerance to less oxygen supply compared with homeotherm organisms, which consists partly in the ability of anaerobic energy production (glycolysis). The bird embryo is not able to regulate its body temperature until some days before hatching. The first time of incubation it is poikilotherm. So it is probable that the bird embryo is able to cope with a deprivation in oxygen supply using anaerobic energy production.
This work will examine the ability of anaerobic energy production of myocardium in chicken embryo during incubation. Furthermore it will be examined if there is a possibility for prenatal adaptation of myocardium to less oxygen supply.
A hint for the rate of increased glycolysis (anaerobic energy production) in tissue represents the ratio of pyruvate kinase (enzyme of glycolysis) to pyruvate kinase (enzyme of oxidative phosphorylation).
A sensible phase for long lasting changes of metabolism rate in chick embryo influenced by chronic hypoxia is described in the middle third of incubation.
In the experiment a oxygen deprivation will be during day (D) 6 to 12 of incubation. The enzymes will be determined directly after the chronically decreased oxygen supply (group 1), after incubation from D 12 to 18 with 21 % Oxygen (group 2) and at D 18 after a acute decreased oxygen supply (group 3). All these results will be compared with control groups, which will be treated the same way but without chronically oxygen deprivation from D6 to 12.