Size changes of mouse ova during preparation for morphometric studies in the electron microscope

Summary The diameters of oocytes during successive steps of preparation for electron microscopy were measured in the light microscope. During glutaraldehyde fixation the diameter of the ova mainly reflected the osmolarity of the fixative vehicle. An increase in the diameter of the ova occurred with postfixation in OsO₄ depending on time of postfixation and also on osmolarity and OsO₄ concentration. During ethanol dehydration the cell diameter decreased to its lowest value and remained unchanged after embedment in Epon. A procedure that minimizes ova size changes during preparation for electron microscopy is elaborated.This investigation was supported by NIH PL 480 Research Agreement No. 05-030-1.