title: The effect of graded hypoxia on the embryonic chick heart.
abstract: Embryonic ventricular function in the chick was measured in response to graded levels of hypoxia. Myocardial contractility, as measured by cinephotoanalysis and expressed as shortening fraction, was significantly depressed after 1 hour of moderate hypoxia (6% O2) and after 5 hours of milder (16% O2 and 11% O2) levels of hypoxia (P less than .05). Microscopy confirmed associated myocyte damage with cell death noted after 5 hours of moderate hypoxic stress. Heart rate change was not related to the severity of hypoxia. The greatest level of tachycardia was noted with conditions of mildest hypoxia (16% O2). The data confirm that cardiac contractility, as measured by shortening fraction, is depressed on exposure to hypoxia, with impairment of function related to the severity of the hypoxic conditions.
mesh_terms: D000818:Animals; D002306:Cardiac Volume; D002467:Cell Nucleus / Q000648:ultrastructure; D002642:Chick Embryo; D006321:Heart / Q000196:embryology*; D006339:Heart Rate; D000860:Hypoxia / Q000473:pathology / Q000503:physiopathology*; D008854:Microscopy, Electron; D009040:Motion Pictures; D009200:Myocardial Contraction; D009206:Myocardium / Q000473:pathology