Newstead J D
Department of Anatomy, University of Saskatchewan, Saskatoon, Canada.
Cell Tissue Res. 1987 Nov;250(2):401-11. doi: 10.1007/BF00219084.
The medullary pyramid of renculi in kidneys of ringed seals (Phoca hispida) is enclosed by a basket composed of ribbons of stromal tissue continuous with the wall of the calyx. Branched smooth muscle cells with well-developed Golgi complexes and rough endoplasmic reticulum and only an incomplete external lamina are the principal cells in sites near the origin of the ribbons from the calycal wall. Deeper in the corticomedullary junctional region, smooth muscle is progressively replaced with stellate or spindle-shaped cells exhibiting structural characteristics intermediate between those of fibroblasts and smooth muscle fibers. These myofibroblast-like cells contain arrays of parallel microfilaments 6-8 nm thick with associated focal densities and subplasmalemmal dense plaques, caveolae, elongate, often deeply wrinkled nuclei, and well-developed Golgi complexes and rough endoplasmic reticulum. Material resembling external lamina is associated with parts of the surfaces of most myofibroblast-like cells and intermediate junctions are present. Fibroblasts lacking arrays of parallel microfilaments are a minority at any level in the stromal ribbons. Interstitial cells in the vicinity of the corticomedullary junction show similar myofibroblast-like characteristics. The smooth muscle and myofibroblast-like cells presumably assist expression of urine from the papilla and calyx, and possibly participate as pacemakers for the urinary tract.
环斑海豹（Phoca hispida）肾脏肾锥体的肾乳头被一个由与肾盏壁相连的基质组织带组成的篮状结构所包围。在这些带从肾盏壁起始处附近，具有发育良好的高尔基体复合体和粗面内质网且仅具不完整外板的分支平滑肌细胞是主要细胞。在皮质髓质交界区更深的部位，平滑肌逐渐被星状或梭形细胞取代，这些细胞表现出介于成纤维细胞和平滑肌纤维之间的结构特征。这些肌成纤维细胞样细胞含有6 - 8纳米厚的平行微丝束，伴有附着斑和质膜下致密斑、小窝、细长且常深度皱缩的细胞核，以及发育良好的高尔基体复合体和粗面内质网。类似外板的物质与大多数肌成纤维细胞样细胞表面的部分区域相关联，并且存在中间连接。在基质带的任何层面，缺乏平行微丝束的成纤维细胞都是少数。皮质髓质交界附近的间质细胞表现出类似肌成纤维细胞样的特征。平滑肌和肌成纤维细胞样细胞可能有助于尿液从乳头和肾盏排出，并且可能作为泌尿道的起搏点发挥作用。
