Application of backscattered electron imaging to enzyme histochemistry of lymphatic capillaries

A backscattered electron imaging (BEI) in scanning electron microscope (SEM) was applied to the observation of lymphatic capillaries on cryostat-cut tissue blocks of monkey stomachs with enzyme-histochemical method. The differentiation of the lymphatics from blood capillaries was established on cryostat sections using 5'-nucleotidase (5'-Nase)-alkaline phosphatase double-staining method. On the tissue surface, 5'-Nase-positive lymphatic capillary walls were seen as highlights with good contrast and resolution by the BEI. A pair of the backscattered and secondary electron imaging in the same area clearly reveals the correlation between the enzyme activity and surface structure of the tissue. Observation of stereo-pairs of the BEIs increases the information on the three-dimensional architecture of lymphatic capillaries. The present study demonstrates the applicability of the BEI of 5'-Nase reaction to SEM histochemistry of lymphatic capillaries stained with heavy metal.