Functional and morphological analysis of the main excretory duct IV.

在颌下腺的主要排泄管上皮中发现的簇状细胞也存在于内胚层来源的中空器官中，如呼吸系统和消化系统。它们的共同特征是指状的长微绒毛，微管和微丝平行于细胞轴排列，顶端细胞质中有大量的小泡和小管。然而，它们的功能仍不清楚。为了确定它们的功能，进行了以下实验：1)含有丝状物质的小泡和小管。用糖结合细胞化学方法证实了丝状物质的性质。2)将微绒毛细胞包埋于LRW中，用凝集素/胶体金(CG)结合物-Con-A、PNA、SBA、UEA-1、DBA进行包埋后染色，观察顶端细胞质中的囊泡和小管中的Con-A。3)通过扫描和透射电子显微镜观察不同发育阶段的绒毛细胞的发育。簇状细胞在出生时就已经被识别出来了。它们的数量约占上皮细胞总数的6%。成虫期绒毛细胞的出现频率约为7%。但微绒毛小于成体绒毛。结论大鼠颌下腺主要排泄管上皮细胞中的簇状细胞似乎参与了糖结合物的分泌活动，这可能与长的微绒毛突入颌下腺管腔内而导致接受有关。

The tuft cells found in the main excretory duct epithelium of the submandibular gland are also present in the hollow organs of endodermal orgin such as the respiratory systems and the alimentary systems. Their common chracteristics are the finger-like long microvilli, microtubules and microfilaments running parallel to the cell axis, and a lot of vesicles and tubules in the apical cytoplasm. However, their functions are still unknown. The following experiments were done to establish their functions1)Vesicles and tubules contained the filamentous substance. Glycoconjugate cytochemistry were performed to prove the character of the filamentous substance. Vesicles, tubules Golgi elements and plasma membrane of the microvilli stained positive.2)The tuft cells were studied by embedding water soluble resin LRW and postembedded staining with lectin/ colloidal-gold (CG) conjugate-Con-A,PNA,SBA,UEA-1, DBA.Con-A was observed in the vesicles and tubules in the apical cytoplasm.3)The postnatal development of tuft cells at various stages, 0,1,7,14,21,28 and 54 days, was investigated by scanning and transmission electron microscopy. Tuft cells were already recognized at birth. Their number reached approximately 6% of the total epithelial cells. The frequency of tuft cells in the adult stage was about 7%. However, microvilli were smaller than the adult ones. In fine structure, the tuft cells at 28 days after birth reached the same level as that at birth.ConclusionThe tuft cells in the main excretory duct epithelium of the rat submandibular gland seem to engage in secretory activity of glycoconjugates, which may be related to the reception because of long microvilli protruding into the lumen.