Techniques for cryosectioning and x-ray microanalysis in the study of normal and injured myocardium

An improved system has been developed for analytical electron microscopic studies of diffusible electrolytes in normal and diseased myocardium. The rabbit interventricular septum preparation was used for an in vitro perfusion model system. Thin (0.5mm diameter) right ventricular papillary muscles were left attached to the septa during perfusions. The muscles were subsequently positioned in a special clamp device, removed from the septa, and quick frozen in liquid nitrogen-cooled propane. The muscles were used for cryoultramicrotomy and freeze substitution. Modifications of the ultratome cryochamber and methods of improved cryosectioning also were made. The methods reported here resulted in reproducible cryosections with good ultrastructure and relatively mild ice crystal damage. Good preservation of intracellular electrolytes also was demonstrated by analytical electron microscopy.