Rodlet cells in teleosts: new ultrastructural observations on the distribution of the cores in trout (Oncorhynchus mykiss, Salmo trutta L.).
The distribution of released rodlet cores was ultrastructurally analysed in the epithelia of intestine, kidney tubules and gill of trout (Oncorhynchus mykiss, Salmo trutta L.). In all three tissues, membrane -- bounded cores extruded from the rodlet cells were observed undissolved at the surface of the epithelia, often attached to or between the microvillar borders. Occasionally, in the medium zone of the comparatively high intestinal epithelium, rodlet cells were seen to shed their rodlet sacs into neighbouring intestinal cells. At the epithelial surface the released cores displayed often a conspicuously undulating limiting membrane apparently developing tubular elements (psi 25-30 nm). Additionally, discharged cores were observed in the apical cytoplasm or even in nuclei of damaged or apoptotic cells and in an intraepithelial lymphocyte. In these cases, the cores were often lacking the membrane but showed association with the mentioned tubular elements. In developing rodlet cells the cores originated near or in contact with the nuclear envelope and displayed a polygonal outline and crystalloid substructure. The observed distribution and morphology is unusual assuming the current interpretation of the rodlet cell as defensive, possibly blood-cell derived secretory cell correlated to stress. As crystalline inclusions and undulating, tubulo-reticular endoplasmic reticulum are typical e.g., in excessive protein synthesis, alternative explanations seem worth while considering.
Bielek
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Institute for Histology and Embryology, Unit for Comparative Histology, University of Vienna, Austria. Edith.Bielek@univie.ac.at
D000818:Animals; D004848:Epithelium / Q000648:ultrastructure*; D005880:Gills / Q000648:ultrastructure; D007422:Intestines / Q000648:ultrastructure; D007684:Kidney Tubules / Q000648:ultrastructure; D008871:Microvilli / Q000648:ultrastructure; D017686:Oncorhynchus mykiss / Q000033:anatomy & histology*