Functional and morphological analysis of the main excretory duct IV.

在颌下腺主要排泄管上皮中发现的簇状细胞也存在于内胚层起源的中空器官中，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，平行于细胞轴的微管和微丝，顶端细胞质中有大量的囊泡和小管。然而，它们的功能仍然是未知的。下面的实验是为了确定它们的功能：1)含有丝状物质的囊泡和小管。用糖缀合细胞化学证实了丝状物质的性质。小泡、小管高尔基元及微绒毛质膜染色阳性。2)包埋水溶性树脂LRW，包埋后用凝集素/胶体金（CG）偶联物- con - a、PNA、SBA、UEA-1、DBA进行染色。在顶端细胞质的小泡和小管中观察到Con-A。3)采用扫描电镜和透射电镜观察出生后0、1、7、14、21、28和54天的簇毛细胞发育情况。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%。成虫期出现簇状细胞的频率约为7%。微绒毛较成虫小。在精细结构上，28天后的簇状细胞达到与出生时相同的水平。结论大鼠颌下腺主排泄管上皮的簇状细胞参与糖缀合物的分泌活动，可能与长微绒毛突出于管腔内有关。

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.