Electron Microscopy of Pre-Hatching Mammalian Embryos the Ultrastructure of Cattle, Swine and Horse Embryos

Abstract

All researchers working with stereo microscopical grading of mammalian embryos recognize the wish of turning the magnification zoom beyond its physical limit in order to assess the nature of structures that escape the resolution of the equipment. However, non-invasive microscopical techniques for embryo evaluation are hampered by on the one hand, the limit of resolution of the stereo microscope normally working within magnifications up to a few hundred times and, on the other hand, the thickness of the three dimensional structure of the embryo of 150 εm or even more. Transmission electron microscopy bypasses both of these limitations: The microscopical principle offers a much higher resolution in itself and the third dimension is almost eliminated by examining extremely thin sections of the specimen. The most obvious disadvantage by the electron microscopical approach is the inherent invasiveness including fixation, embedding and sectioning. Nonetheless, researchers who have had even limited experiences of revealing the electron microscopical structure, i.e. the ultrastructure, of embryos by either observing pictures or even sitting at the microscope themselves also recognize that knowledge of the ultrastructure allows for a much more detailed stereo microscopical assessment. A structure, the nature of which cannot be immediately distinguished by the stereo microscope, may very well reveal itself at this simple method of observation if it has previously been examined in the electron microscope.