286 



CELLS, TISSUES, AND ORGANISMS 



encountered enlarged cyst-like structures in the epidermis, such as 

 Taban reported, which seemed to be extensions into the epidermis of 

 subepidermal blisters that sometimes form spontaneously in the regen- 

 erate ( see below ) . 



In the electron microscope, boundaries between adjacent cells are 

 distinct in normal and regenerate epithelium ( see Figures 1 and 2 ) . The 

 border of the cells is irregular ( sometimes "oak-leaf" ) , and the contours 

 of adjacent cells follow each other. Adjacent cells are bound across the 

 intercellular spaces by cytoplasmic bridges, the desmosomes, which ap- 

 pear identical to the intercellular attachments described by Porter 

 (1954) and elaborated upon by Selby (1955) and Odland (1958). The 



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Figure 1. Electron micrograph of part of two epidermal cells ten days after 

 infusion of 0.03 molar beryllium nitrate into a moderate early regenerate 

 amputated ten days previously. Large intracytoplasmic inclusions (7) are 

 present. Note the intercellular space (S) crossed by cytoplasmic bridges (B) 

 containing characteristic plaques. These cells and inclusions are much like 

 those seen in normal regenerate epithelium. Fixation: osmium tetroxide. N: 

 nucleus. Magnification: approximately 10,000 X. 



