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

本研究采用冰冻切片和冷冻断裂法对胚胎胰腺和小肠组织以及体外培养的胚胎胰腺进行了研究。1.胰腺组织：妊娠13-16天，胰腺组织由未分化细胞组成，细胞间很少有小缝隙连接。孕17天腺泡细胞分化，开始产生大量酶原颗粒，孕18天腺泡细胞胞质内充满大量酶原颗粒。缝隙连接的数量和大小迅速增加。其生长过程如下：（1）在细胞膜的一个区域内，出现许多大的前体颗粒，（2）在分散的区域内出现六边形排列的大颗粒，（3）大颗粒之间的距离逐渐减小，形成常见的缝隙连接。2.肠上皮：妊娠13-14天，上皮由复层的未分化细胞组成。妊娠14-16天，分层细胞生长，靠近管腔。只有小的缝隙连接很少出现， ...更多信息 这些天妊娠17-18天，伴随原始绒毛的形成，上皮细胞由柱状变为柱状，管腔重新开放，上皮细胞不同于肠吸收细胞，具有较多的微绒毛。近年来，缝隙连接的数量和尺寸不断增加，并伴随着分散的、六边形排列的大颗粒。出生后，随着绒毛和隐窝的发育，缝隙连接仅分布于晶体细胞和潘氏细胞.培养胰腺：腺泡细胞在无血清培养基中的分化也不完全类似于胚胎腺泡细胞，但在不含胰岛素和转铁蛋白的培养基（不含激素的培养基）中也是如此。经环己脲（1 mg/l）处理后，未分化状态得以保留，无酶原颗粒和缝隙连接的产生，这些证据表明消化酶和缝隙连接颗粒的基因表达几乎同时开始。然而，细胞分化与缝隙连接位置信息之间的关系还需要进一步的证据来阐明。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