1180 Doaa M. Mokhtar et al.
Fig. 8. Digitally colored transmission electron microscope images of chromaffin cells in the treated group. a,b: Both adrenaline (A) and noradrenaline (NA) cells were engorged with granules. Note dilatated blood capillary (BC). c: The NA-cells contained mitochondria (M), Glycogen granules (g), Golgi apparatus (GA), and ribosomes (R). The cisternae of the endoplasmic reticulum (ER) were well represented. d: The A-cells were crowded with granules (G). In (c,d)Nerve endings (pink, asterisks) were scattered in both A- and NA-cells.
membrane, followed by movement of these vesicles through the cytoplasm to fuse with the plasma membrane.
Chromaffin cells–nerve fibers interaction The control group Few nerve endings invaginated the plasma membrane of the chromaffin cells for a short distance to form small clear synaptic vesicles (Fig. 10a). The treated group Nerve endings had been observed in large numbers in all treated specimens. Numerous large nerve endings penetrated the chromaffin cells for a long distance in a typical synaptic type of ending. During its intracellular course, the nerve endings were surrounded by tubular invagination of chromaffin cells’ plasma membranes. Multiple synaptic-type endings were recorded in a single chromaffin cell. Both plasma membrane of nerve endings and chromaffin cells approached to form synaptic thickening or regions of increased electron density, and the synaptic region may lie on the same plane as the remainder of the surface of the cell or may lie in a depression or tunnel produced by invagi- nation of the cell surface. Synapse on NA-cells was more numerous than A-cells. When nerve fibers penetrate the cell cords, they lose their Schwann cells (Fig. 10b).
Schwann cells and nerve fibers The control group Schwann cells (3.6±0.48 µm in dia- meter) occurred in proximity to nerve fibers in the
Fig. 9. Digitally colored transmission electron microscope images showing mode of chromaffin cells secretion in the treated group. a: Excessive granules discharged from the chromaffin cell mem- branes to the blood vessels. b: Small localized invaginations of the apical cell surface (red) and their granular contents could be observed being discharged intercellularly. c: Some granules showed varying degrees of contact and fusion with the plasma membrane of chromaffin cells (arrowheads). Note, release of granule materials (red) to the perivascular space. d: Ultrastructure suggestive of piecemeal degranulation in chromaffin cells as some granules in adrenaline (A)-cell showed irregular budding or tail- like profiles (arrowheads, square). Electron-lucent and moderately electron-dense vesicles (red) were observed free in the cytoplasm or attached to granules, in a process of fusion with or budding from the perigranule membrane (inserted figure).
connective tissue space between the chromaffin cell groups. Their nuclei contained dense patches of peripherally orien- ted heterochromatin with deep indentation. Their cytoplasm
had no secretory granules, but was provided with Ample filamentous cytoskeletons and mitochondria. Some of these cells extended tongue-shaped cell processes towards the nerve fibers, and most of them were nonmyelinated. The nerve fibers contained neurotubules, small synaptic vesicles with clear centers, and large vesicles with electron-dense cores typical of peptide storage vesicles (Fig. 10c). The treated group Chromaffin cells were covered externally by tongues of Schwann cell cytoplasm. Schwann cells were increased significantly in their diameter (5.1±0.54 µm, Table 1) and embraced bundles of nerve fibers. Their nucleus enlarged with more heterochromatin that arranged at the nuclear envelope mainly and at the nuclear sap and their cytoplasm were moderately electron dense. Bundles of unmyelinated nerve fibers containing synaptic vesicles, neurotubules, mitochondria, and sER had been observed lying partly embedded in Schwann cell cytoplasm and made synaptic contact with chromaffin cells (Fig. 10d).
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