Ultrastructure of motor nerve terminals in the anterior third of Wistar rat tongue.

The nerve terminals of intrinsic muscular fibers of the tongue of adult wistar rats was studied by using silver impregnation techniques, transmission electron microscopy (TEM), and high resolution scanning electron microscopy (HRSEM) to observe the nerve fibers and their terminals. Silver impregnation was done according to Winkelman and Schmit, 1957. For TEM, small blocks were fixed in modified Karnovsky solution, postfixed in 1% buffered osmium tetroxide solution, and embedded in Spurr resin. For HRSEM, the parts were fixed in 2% osmium tetroxide solution with 1/15 M sodium phosphate buffer (pH 7.4) at 4 degrees C for 2 h, according to the technique described by Tanaka, 1989. Thick myelinated nerve bundles were histologically observed among the muscular fibers. The intrafusal nerve fiber presented a tortuous pathway with punctiform terminal axons in clusters contacting the surface of sarcolemma. Several myelinated nerve fibers involved by collagen fibers of the endoneurium were observed in HRSEM in three-dimensional aspects. The concentric lamellae of the myelin sheath and the axoplasm containing neurofilaments interspersed among the mitochondria were also noted. In TEM, myofibrils, mitochondria, rough endoplasmic reticulum, Golgi's apparatus, and glycogen granules were observed in sarcoplasm. It is also noted that the sarcomeres constituted by myofilaments with their A, I, and H bands and the electron dense Z lines. In areas adjacent to muscular fibers, there were myelinated and unmyelinated nerve fibers involved by endoneurium and perineurium. In the region of the neuromuscular junction, the contact with the sarcolemma of the muscular cell occurs forming several terminal buttons and showing numerous evaginations of the cell membrane. In the terminal button, mitochondria and numerous synaptic vesicles were observed.

High-resolution sem of intrinsic muscle fibers of anterior third rat's tongue

The characteristics of intrinsic muscle fibers in the anterior third of the adult rat tongue were studied employing light microscopy, SEM and high-resolution SEM (HRSEM) methods. For light microscopy, specimens were fixed in Bouin's solution and embedded in paraffin. In order to identify the muscle fibers and bundles of collagen fibers, frontal sections were stained with hematoxylin-eosin, azo-carmin and picro-sirius. The results showed that muscle fibers near the lamina propria are fixed with connective tissue, constituting several groups. The bundles of muscle fibers are arranged in longitudinal, vertical and transversal directions. For SEM, specimens were fixed in modified Karnovsky solution and freeze-fractured in liquid nitrogen revealed the collagen fibers and bundles of muscle fibers located in three-dimensional aspects. The samples treated in NaOH solution showed the original location of collagen fibers, constituting complex networks in three-dimensional SEM images. Under HRSEM, fractured specimens in DMSO revealed basement membrane of muscle cell containing sponge-like structures and networks of fine collagen fibrils. Cytoplasmic organelles, such as mitochondria with cristae mitochondriales and sarcoplasmic reticulum, were cleary seen in three-dimensional HRSEM images.

Conventional scanning electron microscopic study of the submandibular gland of the rat

The submandibular gland of rats was treated with HC1-collagenase and NaOH methods which remove respectively, the collagen fibers and cellular components of acinar and ductal structures. The results revealed that the acini are oval in shape and surrounded by basal lamina and fine fibrilar structures. The fractured surface revealed clearly the lobuli, the interlobular spaces containing the collagen fiber bundles and the acini formations of submandiblar glands. Numerous acini of differents diameters are seen. The surfaces of striated ductus showed the original disposition of collagen fiber bundles belonging to the capsular elements.