Elektronenmikroskopische Befunde am Ductus thoracicus

Identification of interstitial Cajal-like cells in the human thoracic duct

Interstitial Cajal-like cells (ICLCs) are speculated to be pacemakers in smooth muscle tissues. While the human thoracic duct (TD) is spontaneously active, the origin of this activity is unknown. We hypothesized that ICLCs could be present in the TD and using histological techniques, immunohistochemistry and immunofluorescence we have investigated the presence of ICLCs, protein markers for ICLCs and the cellular morphology of the human TD. Transmission electron microscopy was employed to investigate ultrastructure. Methylene blue staining, calcium-dependent fluorophores and confocal microscopy were used to identify ICLCs in live tissue. Methylene blue stained cells with morphology suggestive of ICLCs in the TD. Immunoreactivity localized the ICLC protein markers c-kit, CD34 and vimentin to many cells and processes associated with smooth muscle cells (SMCs): coexpression of c-kit with vimentin or CD34 was observed in some cells. Electron microscopy analysis confirmed ICLCs as a major cell type of the human TD. Lymphatic ICLCs possess caveolae, dense bands, a patchy basal lamina, intermediate filaments and specific junctions to SMCs. ICLCs were ultrastructurally differentiable from other interstitial cells observed: fibroblasts, mast cells, macrophages and pericytes. Lymphatic ICLCs were localized to the subendothelial region of the wall as well as in intimate association with smooth muscle bundles throughout the media. ICLCs were morphologically distinct with multiple processes and also spindle shapes. Confocal imaging with calcium-dependent fluorophores corroborated cell morphology and localization observed in fixed tissues. Lymphatic ICLCs thus constitute a significant cell type of the human TD and physically interact with lymphatic SMCs.

Immunoelectron microscopy on the localization of endothelin in the umbilical vein of perinatal rabbits

Immunoelectron microscopic localization of endothelin (ET) using the mouse monoclonal anti-ET sera was performed on the pre- and postnatal rabbit umbilical vein during stages when Weibel-Palade (WP) bodies increase in number in the endothelial cells. The immunoreactions are localized in the rough endoplasmic reticulum, Golgi cisterns, and WP bodies that are actively segregated from the Golgi apparatus. After degranulation and extracellular release of WP bodies was induced by compound 48/80, heavy immunoreactions were seen in both vascular lumen and cytoplasm near the degranulated WP bodies. These results indicate that ET is stored in WP bodies after segregation from the Golgi apparatus and released from the endothelial cells concomitantly with other components of these granules by exocytosis. Because the immunoreactions are also seen in pinocytotic vesicles that are occasionally in contact with WP bodies, it seems likely that WP bodies are also involved in the uptake and storage of ET from blood plasma.

Degranulation of endothelial specific granules of the toad aorta after treatment with compound 48/80

Incubation of isolated toad aortas in Ringer solution containing compound 48/80, a histamine liberator, resulted in marked degranulation of endothelial specific granules. Since incubation of these vessels in Ringer solution only did not show significant morphologic changes in these granules, these findings suggest that the degranulation was induced by histamine release from the granules, as in the case for mast cell degranulation, and that endothelial specific granules are a storage site of histamine in the toad aorta. The present morphologic data were supported by preliminary chromatography, which showed appreciable concentrations of histamine in the granule-containing pellets of subcellular fractions of homogenized toad aortas.