Structural characterization of the capybara (Hydrochaeris hydrochaeris) tongue by light, scanning, and transmission electron microscopy.

Capybara is the largest rodent in the world and displays a seasonally dependent herbivore feeding behavior. Here, we present an anatomical contribution for understand this fact, by light, scanning, and transmission electron microscopy methodologies for tongue tissue analysis. The histological preparations revealed filiform, fungiform, vallate, and foliate papillae on the dorsal mucosa of the capybara tongue. The epithelial layer exhibited a lining of keratinized stratified squamous epithelial cells. The lamina propria was characterized by a dense connective tissue composed of the primary and secondary papillar projections. We also revealed the original aspects of the connective papillae. The shapes of the papillae varied by region of the tongue, and filiform, fungiform, vallate, and foliate papillae and subjacent layers of muscular fibers were observed. Pyriform taste buds occupying the epithelial layer of fungiform, vallate and foliate papillae were identified and the intracellular components of the taste buds and the intracorpuscular amyelinated nerve fibers were observed. The taste buds were characterized by the distribution of granular endoplasmic reticulum throughout the perinuclear area, the Golgi apparatus, and mitochondrial assemblies of various distinct diameters. Mitochondrial accumulation was also observed in the collagen bundle-surrounded amyelinated nerve fibers beside the basal cells. Therefore, these peculiar anatomical descriptions may contribute to understanding the adaptation of the feeding behavior of capybaras in a seasonally changing environment.

Ultrastructural characteristics of the gerbil pterygoid medial muscle after experimental occlusal alteration.

Ten male young adult gerbils Meriones unguiculatus weighing 55g were divided in two groups: experimental (n=5) animals submitted to exodontia of the left upper molars, and sham-operated were used as control (n=5) group. The aim of the present study was to investigate the ultrastructural effects of occlusal alteration induced by unilateral exodontia on medial pterygoid muscle. After 60 days, the animals were sacrificed by perfusion intracardially with a modified Karnovsky solution after anesthetized with overdose of urethane (3g/kg i.p.). The small samples of this muscle were fixed in 2.5% glutaraldehyde solution and post-fixed in 1% buffered osmium tetroxide solution, dehydrated in ascending concentration of ethanol, and embedded in Spurr resin. Several micrographs data showed that in this period of time, the unilateral teeth extraction was able to induce modifications on the medial pterygoid muscle fibers and capillaries at ultrastructural levels as compared to control muscles and to the ones in the contralateral side of the experimental animals. Ultrastructural changes suggest that injury was greater in the hypofunctional muscle, ipsilateral to teeth extraction.