| Research Abstract |
Embryonic pancreas and small intestine, these adult tissues,and cultured embryonic pancreas were studied by ultrathin section and freeze fracture method.
1.Pancreatic tissue: 13-16 days of gestation, this tissue was consisted of undifferentiated cells which have rarely small gap junctions. 17 day of gestation, acinar cells differentiate and begin to product many zymogen granules and 18day of gestation, acinar cell cytoplasm is filled by numerous granules. Gap junctions rapidly increase in number and size. Growing process is as follows, (1) many large precursor particles appear dispersedly in a domain of cell membrane, (2) hexagonal arrayed large particles appear in dispersed area and (3) usual gap junctions are formed by decreasing of distance between large particles.
2.Intestinal epitbelium: 13-14 days of gestation, the epithelium consists of stratified undiffer- entiated cells. 14-16 days of gestation, growing of straified cells close a lumen. Only small gap junctions appear rarely in
… More
these days. 17-18 days of gestation, accompanied by formation of primordial villi, the epithelium changes columnar one, the lumen reopen, and epithelial cells different to intestinal absorptive cells with many microvilli. In these days, gap junctions increase in number and size, with accompanied by the dispersed and hexagonal arrayed large particles. As accomplished villi and crypt after the birth, gap junctions distribute to only crystal cells and Paneth cells.
3. Cultured pancreas: Acinar cells differentiate not also exactly similar to embryonic acinar cells in no-serum cultured medium, but also in medium without insulin and transferrin (no hormone contained medium). By the treatment of Cyclohexamide(1mg/l), the undifferentiated state are preserved , without zymogen granule production and gap junctions.
In these all evidences show that the gene expressions of digestive enzyme and gap junctional particles begin at almost same time. However, further evidences would be necessary to clarify the relationships between the cytodifferentiation and the positional information of gap junctions. Less
|
