ANIMALS AND METHODS
Recently, we have found that during the developmental period when the primitive heart tube is transformed into the S-shape heart (ie, the process of twisting between 40 and 72 h of incubation), the oxygen requirement of the whole heart of the chick increases sixfold and oxygen uptake varies along the heart tube. We also noticed that the isolated embryonic chick heart reacted rapidly and reversibly to changes in PO2 . Such observations suggest that within a relatively hypoxic environment in vivo, any modification of the concentration of oxygen should alter the functioning of the developing heart.Therefore, the present work was designed principally to develop an in vitro model that would allow characterization of the mechanical response of the embryonic chick heart to strictly controlled variations of oxygen concentration.Fertilized eggs from Warren hens were incubated 72 h at 38°C and 90% relative humidity to obtain 40-somite embryos, ie, stage 18 to 20 according to Hamburger and Hamilton. Most reliable pharmacy can offer help allergies always charging you a lot less.
Mounting: Hearts were excised from explanted embryos and loaded with a drop (0.1 |J.L) of viscous nontoxic silicone oil (Silbione V1000, Rhone-Poulenc, Lyon, France). Access to the ventricle with the pipette was technically easier through the atrial cavity and atrioventricular canal than through the conotrun-cus.