Histological and Histochemical Studies on the Esophagus, Stomach and Small Intestines of Varanus niloticus

Morphological description of the digestive tract of the Amazonian Diving Lizard Uranoscodon superciliosus (Linnaeus, 1758) and its associations to the diet and foraging mode

The study aimed to characterize the digestive tract of Uranoscodon superciliosus and its associations to the diet and foraging behavior already described for the species. Five lizards were captured in forest areas near the city of Manaus, Amazonas, Brazil. Tongue, oesophagus, stomach, small and large intestines fragments were collected, fixed, and processed for light microscopy. Hyaline cartilage was present in the center of the tongue, and the papillae from the apex and glands from the radix showed positive reaction to Alcian blue. The oesophagus presented a folded mucosa, covered by an epithelium with mucous and goblet cells positive to PAS and Alcian blue. There was presence of gastric glands in the cardic and fundic stomach regions, plus all the regions reacted positively to PAS. Fold and villi variations in both small and large intestine were noted, as well as the number and arrangement of goblet cells. Mucous and goblet cells from the small intestine were positively stained in PAS, while only the goblet cells were Alcian blue positive. These findings indicate that the Amazonian Diving Lizard's digestive tract organs, mainly the tongue and stomach, present morphologies associated to ambush-type foraging and a specific diet largely based on small invertebrates.

Microscopic anatomy of the oesophagus in the southern white-breasted hedgehog (Erinaceus concolor) a histochemical, stereological, and scanning electron microscope study

The present work was designed to investigate the microscopic structure of the oesophagus in the southern white-breasted hedgehog (Erinaceus concolor) using histochemical staining, Scanning electron microscope (SEM), and stereological procedures. Four adult males were included in our study. Serial sections of the entire length of the oesophagus were stained with aldehyde fuchsin, alcian blue (pH 2.5), Periodic acid Schiff (PAS), and Masson's trichrome. Then, the total volume of the oesophagus, and the total volume of its different layers, were estimated using Cavalieri's principle. The oesophageal epithelium was a non-keratinized stratified squamous type. Muscularis mucosa was present as a thick layer between lamina propria and submucosa and its thickness was increased toward the stomach. Tunica submucosa was a loose connective tissue containing an oesophageal gland with PAS-positive and AB-positive reactions throughout the submucosa and become denser toward the stomach. The tunica muscularis consisted of two distinct striated muscle layers, and its thickness was decreased toward the stomach. On SEM images, the cervical and thoracic oesophagus showed shallow folding, while the abdominal part had deeper folds. The present findings indicate that the histological properties of the oesophagus in southern white-breasted hedgehogs have slight similarities with rodents and considering its epithelium, submucosal glands and tunica muscularis more resemble with dog oesophagus. The obtained results may be quite helpful to improve the current knowledge of the histophysiology of the hedgehog gastrointestinal tract as a member of eulipotyplan mammals and as a pet for biologists and veterinarians.

Comparative microanatomical and histochemical biodistribution profiles of different types of mucins in oesophageal gastric tract mucosa of some tetrapod representatives

The microanatomical features of the oesophageal gastric tract in tetrapod representatives and their function, especially those related to the mucosal layer, have not yet been fully investigated. The mucosal layer cells and their function in the oesophageal gastric tract differ structurally and functionally in tetrapod representatives based on interspecies difference and the type of food and feeding habits. The present study was, therefore, postulated to compare the mucosal microanatomical structure and histochemical biodistribution of different mucin types in oesophageal gastric tract tissues of four tetrapod species. A representative of each tetrapod class was selected, as follows: the Egyptian toad Bufo regularis, the lizard Trachylepis quinquetaeniata, the domestic pigeon Columba livia domestica and the albino mouse Mus musculus for Amphibia, Reptilia, Aves and Mammalia, respectively. Microanatomically, in lower tetrapods (toad and lizard), the mucosal layer of the oesophagus was composed of simple ciliated columnar epithelium with goblet cells, whereas in higher tetrapods (pigeon and mouse) it was composed of stratified squamous epithelium, with non-keratinised epithelium in the pigeon but keratinised epithelium in the mouse. However, the gastric mucosal layer of the stomach in lower tetrapods consists of simple columnar epithelium and gastric glands. Similarly, the mucosa of the pigeon's proventriculus consists of simple columnar epithelium with proventricular glands opened into the lumen, whereas mouse mucosa consists of simple columnar epithelium which folds and forms gastric glands with gastric pits having a variety of cell types. Histochemically, the neutral mucin profile biodistribution in the oesophagus mucosal layer was variable. It was strongly positive in the toad and lizard, but was weak in the pigeon and completely negative in the mouse. In contrast it was strongly positive in the gastric mucosa of the toad, lizard and pigeon, but was weak in the mouse's gastric mucosa. On the other hand, the signals of carboxylated and sulfated mucins were found to be different. They were strong in the mucosa of the lizard oesophagus. In contrast, the carboxylated mucins in the gastric mucosa were positive in all representatives except the mouse. The sulfated mucins were, however, seen localised in the mucosal layer cells of the lizard and pigeon only. The study revealed that the microanatomical structures and functions as well as mucin distribution profiles in the oesophageal gastric tract are in line with interspecies difference and the type of food and feeding habits. However, this may need further investigations including more tetrapod representatives.

Gastroesophageal tube of the Iguana iguana (Iguanidae): histological description, histochemical and immunohistochemical analysis of 5-HT and SS cells

The work aims were to describe the histological and histochemical structure of the gastroesophageal tube of Iguana iguana and verify the occurrence and distribution of immunoreactive serotonin (5-HT) and somatostatin (SS) cells. Fragments of the gastrointestinal tract (GIT) of five iguanas were which underwent standard histological and immunohistochemistry technique. Immunoreactive cells for 5-HT and SS were quantified using the STEPanizer. The oesophagus has ciliated columnar pseudostratified epithelium with staining Alcian blue (AB) + and goblet cells highly reactive to periodic acid Schiff (PAS). In the cervical oesophagus, the numerical density of 5-HT cells per unit area (QA [5-HT cells]/µm2) was 4.6x10-2 ± 2.0 and celomatic oesophagus presented QA = 4.0x10-2 ± 1.0. The epithelium of the stomach is simple columnar, PAS and AB +. The cranial and middle regions of the stomach presented (QA [5-HT cells]/µm2) = 6.18x10-2 ± 3.2 and the caudal region, QA = 0.6x10-2 ± 0.2. The SS cells were only observed in the caudal stomach, with numerical density (QA [SS cells]/µm2) = 1.4x10-2 ± 0.9 In I. iguana, variation was observed in terms of the distribution of mucus secretions and the pattern of occurrence of serotonin and somatostatin-secreting enteroendocrine cells in the TGI, which possibly will result in an interspecific adaptive response.

Histomorphometrical and stereological study of the oesophagus in the adult male Persian squirrel (Sciurus anomalus)

The Persian squirrel (Sciurus anomalus) is habitat in the Middle East countries and feed on pine acorns and other seeds. The present study was carried out to investigate the histological and volumetric features of the oesophagus in Persian squirrels. Five adult male Persian squirrels were included in the study. The cervical, thoracic and abdominal oesophagus of all subjects were processed routinely and sectioned in a serial manner. Then, the total volume of the oesophagus and its different layers were estimated using Cavalieri's principle. Histological assessment revealed a non-keratinized stratified squamous epithelium lining the mucosa. No glands were seen in the lamina propria and submucosa. Lamina muscularis was present as a distinct layer of smooth muscle cells separating the lamina propria from the tunica submucosa. The tunica muscularis consisted of two distinct layers of striated muscle fibres: inner circular and outer longitudinal that was intermingled with few scattered smooth muscle fibres especially in the abdominal region. The thoracic region contained more amount of the lamina muscularis and tunica muscularis in comparison to the cervical or abdominal regions. The obtained results revealed that the histological structure of the Persian squirrel oesophagus has differences and similarities with other rodents and even with other species of squirrel. These findings would be useful to improve the knowledge in the areas of histological structure of the rodent digestive system.

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.

Histological, histochemical and ultrastructural analysis reveals functional division of the oesophagogastric segment in freshwater tubenose goby Proterorhinus semilunaris Heckel, 1837

Histological and histochemical features of the oesophagogastric segment of the alimentary canal as well as ultrastructure of gastric gland cells of freshwater tubenose goby Proterorhinus semilunaris were examined. The studies revealed that despite the lack of anatomical distinction, the oesophagogastric segment is histologically divided into the oesophagus, oesogaster and stomach, which provides evidence for the functional compartmentation of this organ. The oesophagus was characterised by the presence of numerous goblet cells secreting mainly a mixture of neutral and acid mucopolysaccharides. In the stomach, the apical zone of the surface epithelial cells contained neutral mucopolysaccharides. Numerous proliferating cells were scattered throughout the surface epithelium. In the lamina propria of the stomach, a well-developed layer of gastric glands was observed. The glands were of the alveolar type and occupied nearly the entire length of the stomach except the pyloric region. The gastric gland cells were varied into light and dark; however, their ultrastructure was identical. All cells had numerous mitochondria and a well-developed tubulovesicular system typical for the oxynticopeptic cells, but pepsinogen granules were not present in the cytoplasm of these cells. These findings contribute new evidence to literature reports that not all gobiid fish are stomachless. Moreover, they suggest higher adaptation of the species to utilise protein-rich food compared to stomachless fish, and its ability to adjust the alimentary canal quickly to changing diet. How this may facilitate establishment of P. semilunaris in invaded environments remains an open question.

Morphological and histochemical investigations of esophagogastric tract of a lizard, Laudakia stellio (Agamidae, Linnaeus 1758)

Histological structures of esophagus and stomach tissue samples of Lacerta stellio have been studied, and glycosaminoglycan (GAG) distribution has been histochemically determined. Histologically, esophagus and stomach of L. stellio are composed of four layers: mucosa, submucosa, muscularis mucosae and serosa. Mucosa of esophagus is covered by simple columnar ciliated epithelium with many mucous secreting goblet cells and contains branched tubular glands.Stomach of L. stellio is composed of fundus (oral and aboral) and pylorus regions. Mucosa is covered by columnar epithelium. Fundic glands are branched tubular glands while pyloric glands are usually simple tubular glands. In both regions of the stomach, glands are subdivided into three areas as base, neck and isthmus. Both in the esophagus and stomach, muscular layer is in the form of smooth muscle having inner circular and outer longitudinal layers.According to the results obtained by Alcian Blue (pH 5.8)/Periodic Acid Schiff staining, stomach is similar to esophagus in that neutral mucins and hyaluronic acid (HA) are dominant in isthmus and neck regions of gland tissue of stomach. In the base of the stomach, only neutral mucins have been observed. HA has been observed to be dominant in all other regions of both stomach and esophagus, along with some but not much sulphated GAGs.