Just F, Walz B
Institut für Zoologie der Universität, Regensburg, Germany.
J Morphol. 1994 Apr;220(1):35-46. doi: 10.1002/jmor.1052200105.
We have reinvestigated the morphology of the salivary glands in the cockroach, Periplaneta americana, by light, electron, and confocal laser scanning microscopy. All secretory acini have a uniform structural layout. They consist of three cell types: peripheral cells, central cells, and duct cells. One pair of peripheral cells forms the base of each acinus. The central cells, arranged concentrically in a fourfold symmetry around the most proximal part of the acinar ducts, lie next downstream. In every acinus, duct cells accompany the central cells and form a thin sheet on the apical surface of the latter. This apical lining of the duct cells is regularly fenestrated, and the central cells secrete the contents of their secretory vesicles only through these openings into the lumen of the ducts. Peripheral cells and central cells are never in direct physical contact, because, apically, extensions of the inner acinar duct cells intervene between the cells. Basally, thin extensions of the basement membrane separate the cell types. We have found no morphological evidence for the existence of electrical coupling (gap junctions) between the saliva-producing cells. Our ultrastructural data support the view that the peripheral cells are responsible for water and electrolyte transport, whereas only central cells secrete the proteinaceous components of the saliva. We have found that the duct cells distal to the acini are also specialized for ion and water transport. They have a prominent basal labyrinth containing numerous mitochondria and a highly folded apical surface. The folded apical membrane surface is coated with electron-dense particles on its cytoplasmic side; these particles are probably portasomes. Our investigation provides morphological evidence that the duct cells distal to the secreting acini are able to modify primary saliva.
我们通过光学显微镜、电子显微镜和共聚焦激光扫描显微镜，对美洲大蠊唾液腺的形态进行了重新研究。所有分泌性腺泡都有统一的结构布局。它们由三种细胞类型组成：外周细胞、中央细胞和导管细胞。一对外周细胞构成每个腺泡的基部。中央细胞围绕腺泡导管最近端呈四重对称同心排列，位于下游相邻位置。在每个腺泡中，导管细胞与中央细胞相伴，并在中央细胞的顶端表面形成一层薄片。导管细胞的顶端内衬有规则的小孔，中央细胞仅通过这些开口将其分泌小泡的内容物分泌到导管腔内。外周细胞和中央细胞从不直接物理接触，因为在顶端，腺泡内导管细胞的延伸部分介于两者之间。在基部，基底膜的薄延伸部分将不同细胞类型分隔开。我们没有发现产生唾液的细胞之间存在电偶联（间隙连接）的形态学证据。我们的超微结构数据支持这样一种观点，即外周细胞负责水和电解质的运输，而只有中央细胞分泌唾液的蛋白质成分。我们发现腺泡远端的导管细胞也专门用于离子和水的运输。它们有一个突出的基部迷路，含有大量线粒体和高度折叠的顶端表面。折叠的顶端膜表面在其细胞质一侧覆盖有电子致密颗粒；这些颗粒可能是孔体。我们的研究提供了形态学证据，表明分泌腺泡远端的导管细胞能够改变初级唾液。
