Neuroendocrine structures of the small intestine of the capybara Hydrochoerus hydrochaeris (Mammalia, Rodentia)

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A complex network of nerve fibers of the enteric nervous system and enteroendocrine cells is known to regulate the gastrointestinal tract. The distribution and frequency of the argyrophil, argentaffin and serotonin immunoreactive endocrine cells and of the submucosal and myenteric nervous ganglia were studied in the small intestine of the capybara Hydrochoerus hydrochaeris, aiming to verify the existence of possible numerical correlations between endocrine cells and nervous ganglia. Fragments of the duodenum, jejunum and ileum of adult animals were collected and processed according to routine histological techniques. To study the nervous ganglia, hematoxylin and eosin staining was used, while specific staining techniques were used to study the argyrophil, argentaffin and serotonin immunoreactive endocrine cells: Grimelius, modified Masson-Fontana and peroxidase anti-peroxidase, respectively. Endocrine cells were more abundant in the area of the crypts and, in relation to their morphology, ‘open type’ endocrine cells prevailed. The population of argyrophil cells was larger than that of argentaffin cells, and these cells were larger than serotonin immunoreactive cells. The frequency of endocrine cells was apparently greater in the duodenum, indicating the importance of this intestinal segment in digestive and absorptive functions. Prominent nervous ganglia were observed in the submucosal and myenteric plexi, and were larger and more frequent in the myenteric plexus. A numerical correlation was found among the endocrine cells (argentaffin and serotonin immunoreactive cells) and the myenteric nervous ganglia, suggesting the presence of physiological interactions among the endocrine and nervous systems for the control of intestinal activities. The findings in this study contribute to the understanding of the digestive processes of this species, which may also help in its conservation and future survival.

Neuroendocrine structures of the small intestine of the capybara Hydrochoerus hydrochaeris (Mammalia, Rodentia)

in Animal Biology



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    Histological sections of the mucosa of the small intestine of the capybara Hydrochoerus hydrochaeris, emphasizing the distribution and morphology of endocrine cells. A and B: Argyrophil endocrine cells visualized with Grimelius stain. C and D: Argentaffin endocrine cells visualized with modified Fontana-Masson stain. E and F: Endocrine cells immunoreactive for serotonin visualized with PAP technique. Abbreviatons: cag, argentaffin endocrine cells; car, argyrophil endocrine cells; cr, crypts; csr, endocrine cells immunoreactive for serotonin; gi, infranuclear granules; ms, mast cell; n, nucleus. The red arrows indicate the apical extension of the endocrine cell. The green arrows indicate the dilated basal portion of the endocrine cell. Scale bars for A, C and E are 70 μm; for B, D and F are 30 μm.

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    Number of argyrophil, argentaffin and immunoreactive to serotonin endocrine cells per mm2 of the mucosa layer (mean ± standard deviation) in different portions and subsections (cranial, median, caudal) of the small intestine of the capybara Hydrochoerus hydrochaeris.

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    Histological sections of the submucosal and myenteric nerve plexus of the small intestine of the capybara Hydrochoerus hydrochaeris. Hematoxylin-eosin stain. A. Submucosal nerve ganglion. B. Myenteric nerve ganglion. Abbreviations: cn, perikarya; csm, submucosal layer; gm, myenteric nerve ganglion; gs, submucosal nerve ganglion; mci, internal circular muscle sublayer; mle, outer longitudinal muscle sublayer; mm, muscularis mucosae. Scale bars represent 30 μm.

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    Number of submucosal nerve ganglia per mm2 of the submucosa and number of myenteric nerve ganglia per mm2 of the muscular layer (mean ± standard deviation) in different portions and subsections (cranial, median, caudal) of the small intestine of the capybara Hydrochoerus hydrochaeris.

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