George H. Paff

Electrical and Mechanical Properties of Chick Embryo Heart Chambers

Electrical and mechanical events of the atrium, ventricle and conus of the 72-hour chick embryo heart were recorded by a specially designed instrument. The electrical-mechanical delay and the time of muscular contraction differed among the chambers, the atrium being the most rapid and the conus, the slowest. Muscular relaxation times of the atrium and ventricle were approximately one-half that of the conus. Mechanical performance, gaged by the approximations of work and power, was greatest for the ventricle, but based on the muscle mass (protein), values for the ventricle and conus were similar. Electrical activation of the ventricle followed a consistent pathway, suggesting the existence of a preferential conduction system prior to the development of the His bundle.

Free Wandering Cells and Cortisone

Conclusion In tissue cultures of embryonic skin it can be demonstrated that, of the cell types present, the free wandering cells are the most sensitive to the hormone. All wandering cell movement can be brought to a stop in cultures in which fibroblastic activity remains undisturbed. This observation is supported by the behavior of cortisone-treated spleen fragments.

Effects of Different Oxygen and Carbon Dioxide Concentrations on the Activity of the Embryonic Chick Heart

The 72 hour chick embryo heart reacts to progressive hypoxia by the appearance of arrhythmias and asystole. In the presence of 4 per cent CO2, complete anoxia is tolerated for a period of 30 min. with carbon dioxide apparently augmenting the buffering capacity of the plasma clot which supports the heart. A gaseous environment of 4 per cent O2/4 per cent CO2/92 per cent N2 induced a steady and entirely reversible state of cardiac stress.