title: Capillaries and muscle fibers in the heart of the hyperoxic chick embryo.
abstract: Cardiomegaly was induced in chick embryos by incubation in 60% O2. On day 18 sections of heart were taken from these and from controls matched by egg weight before incubation in 21% O2. The ratio of left/right ventricular weight was the same in the two groups and so was the concentration of water in the ventricles. The densities of capillaries and of muscle fibers were determined in seven selected myocardial regions in order to establish (1) the cellular nature of the cardiomegaly, and (2) the effect of elevated O2 on capillary growth. In five of the regions no significant difference in capillary density was seen, but the cross-sectional area of the fibers rose significantly in all seven, especially in the right ventricle. Capillary density increased in the hyperoxic group in two areas immediately adjacent to the lumen of the right ventricle. These results suggest that oxygen causes hypertrophy of cardiac muscle fibers in the chick embryo without altering the capillary supply.
mesh_terms: D000818:Animals; D002196:Capillaries / Q000473:pathology; D006332:Cardiomegaly / Q000196:embryology / Q000473:pathology*; D002642:Chick Embryo; D003326:Coronary Circulation; D006321:Heart / Q000196:embryology; D009206:Myocardium / Q000473:pathology*; D010100:Oxygen / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D010100:Oxygen