Intercellular junctions on cytodifferentiation of gastro-intestinal tract and pancreas.

采用超薄切片和冷冻断裂法对胚胎胰腺和小肠、成体组织及体外培养胚胎胰腺进行了研究。胰腺组织：妊娠13-16天，该组织由未分化的细胞组成，很少有小间隙连接。妊娠第17天，腺泡细胞分化并开始产生许多酶原颗粒，妊娠第18天，腺泡细胞质被大量颗粒填充。缝隙连接的数量和尺寸迅速增加。生长过程如下：(1)许多大前体颗粒分散出现在细胞膜的一个区域，(2)分散区域出现六边形排列的大颗粒，(3)大颗粒之间的距离减小形成通常的间隙连接。肠上皮：妊娠13-14天，肠上皮由未分化的细胞组成。妊娠14-16天，成排细胞生长闭合管腔。只有小的缝隙连接很少出现在……妊娠17-18天，伴原始绒毛形成，上皮变为柱状，管腔重新开放，上皮细胞与肠吸收细胞不同，微绒毛较多。近年来，缝隙连接的数量和大小都在增加，并伴随着分散和六边形排列的大颗粒。作为出生后发育的绒毛和隐窝，间隙连接只分布在晶体细胞和潘氏细胞上。胰腺培养：在无血清培养基中，腺泡细胞的分化与胚胎腺泡细胞并不完全相似，但在不含胰岛素和转铁蛋白的培养基中（不含激素的培养基），腺泡细胞的分化也与胚胎腺泡细胞完全相似。经环己胺（1mg/l）处理，保持未分化状态，不产生酶原颗粒和间隙连接。这些证据表明，消化酶和间隙连接颗粒的基因表达几乎是同时开始的。然而，需要进一步的证据来阐明细胞分化与间隙连接位置信息之间的关系。少

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