Perfusion in vivo of the porcine placenta. Fixation for EM

A method for vascular perfusion in vivo, especially for EM fixation, was developed with the porcine placenta. The effect of fixation at varying parameters was studied. Nine multiparous Danish Landrace sows ranging in gestation from 33 to 112 days and in body weight from 160 to 257 kg were used. After general and local anaesthesia laparotomy was undertaken on the left flank and the uterine horn was perfused through a. uterina with buffered glutaraldehyde. Local perfusion through a. umbilicalis was undertaken in one case, and installation of concentrated glutaraldehyde into the allantoic cavity was performed in five cases. Perfusion-fixed and fresh tissue samples were fixed in OsO4 and processed for electron microscopy. The osmolarity of the buffer was varied between 470 and 660 mOsm. At high tonicity cytoplasm was well preserved but the intercellular spaces of the uterine epithelium was dilated. At about 575 mOsm the preservation was still good and the spaces were occluded. At lower tonicity damage occurred in the cytoplasm. The trophoblast was generally better preserved than the uterine epithelium. A rapid perfusion flow was beneficial for fixation.