Resolving the energy restriction at high altitude: variation in the digestive system of Phrynocephalus vlangalii

Hypothermic and hypoxic environments create strong selective pressure on native species by affecting, among other things, the relationship between energy intake and allocation. In order to detect the adaptation of Phrynocephalus vlangalii to such energy limitation, the morphological structure and argyrophil cells of the digestive tract of 80 individuals from two different altitudes in the Qinghai-Tibet Plateau were compared using overall anatomy as well as paraffin sectioning of specific organs. Compared with the low-altitude population, the high-altitude individuals were found to have a significantly longer stomach and duodenum, longer and wider villus in the small intestine, larger surface area in duodenum and jejunum, and more argyrophilic cells in stomach and duodenum. Our results indicate that the morphological and histological change of the digestive tract may be conductive to the plateau adaptability of P. vlangalii by enhancing the efficiency of digestion and absorption. For a more general conclusion to be drawn, comparison of more populations at both altitudes is required in addition to verifying how phenotypically flexible these traits are.

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

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 capybaraHydrochoerus 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.

Functional morphology of the esophagus of the tropical house gecko Hemidactylus mabouia (Squamata: Gekkonidae)

In order to understand the biology of species that easily establish themselves in new environments, morphological studies are essential. This study aimed to describe the esophageal functional morphology ofHemidactylus mabouia, indicating adaptations to food habits. Seventeen adult specimens were used for anatomical, topological, histological, and histochemical analyses. Histological sections were stained with toluidine blue or submitted to techniques for identification of argyrophil and argentaffin endocrine cells, proteins, and glycoconjugates. The esophagus ofH. mabouiais a tubular straight-lined organ, and its anterior portion is dilated, facilitating the swallowing of whole prey. The esophageal epithelium is pseudostratified, containing cells secreting neutral and acid mucins. At the esophagogastric transition, we found a mixture of this epithelium with a simple prismatic epithelium secreting neutral mucins. The esophagus lamina propria is thin and non-glandular. At the esophagogastric transition it becomes thick and filled by branched simple acinous glands, with cells secreting neutral mucins, zymogenic cells, and argentaffin endocrine cells, with no argyrophil cells. The mucins protect the esophageal mucosa and lubricate the channel to facilitate the passage of food, while pepsinogen in the stomach increases the levels of pepsin for proteolytic digestion. The muscular tunica is made up of smooth muscle cells. Ciliary action, in addition to muscle contractions, facilitates the swallowing of small prey.

Well-Differentiated Fetal Adenocarcinoma: Rare Tumor in the Pediatric Population

Well-differentiated fetal adenocarcinoma (WDFA) is a rare tumor of the lung, which has gone by many names over the years. The lesion was first described by Kradin et al., in 1982, who called it “pulmonary blastoma with argyrophil cells and lacking sarcomatous features (pulmonary endodermal tumor resembling fetal lung).” Since then, there have been at least 65 cases reported in the literature. Although there has been no consensus in the literature as to the best pathological term for this entity, the most recent World Health Organization classification of lung and pleural tumors uses the term well-differentiated fetal adenocarcinoma. Characteristically, this lesion consists of an epithelium, which recapitulates fetal lung at 3–5 months of gestation and demonstrates neuroendocrine differentiation. Although the classic age range is 30–40 years, there have been seven reports of WDFA in the pediatric age. We report an additional pediatric case of this tumor and review the pediatric cases in the existing literature.