Structural, histochemical and immunocytochemical study of the forestomach mucosa in domestic ruminants.

The forestomach plays an important role in the digestion physiology of ruminants. The aim of this study is to clarify the morpho-functional role of the mucosa in each of the three compartments of the forestomach in three domestic ruminants species, viz cattle, buffalo and sheep, by means of structural, histochemical and immunocytochemical methods, including transmission electron microscopy, light microscopy and scanning electron microscopy. These methods were chosen to demonstrate the indirect evidence for the presence of nitric oxide (NO) employing NADPHd and nitric oxide synthase I (NOS I). The various cell layers of the forestomach epithelium are described and illustrated in detail. An intense NADPHd staining was observed in the granulosa, spinosa and basal layers of the epithelium, in particular in the cytoplasm over the nucleus. NOS I immunoreactivity was found in all specimens of the forestomach mucosa. The results of this study might reflect a possible role of NO in delaying the onset of cellular apoptosis in the forestomach mucosa of the domestic ruminants, by playing a role in the production of cell energy.

Functional morphology of unguiculiform papillae of the reticular groove in the ruminant stomach.

The arrangement of the ruminant stomach in four gastric compartments with specialized mucosal papillae along the gastric groove (GG) has been previously described. However, a debate remains about functional implications of these morphological pecularities. This study was aimed to elucidate the relation between the papillar morphology and its putative functions. The GG was obtained from adult bovine stomachs (n=10) and subdivided into (1) proximal, (2) middle, (3) distal portion of the reticular groove (RG) and (4) the area of the reticulo-omasal sphincter (ROS). The specimens were processed for scanning electron microscopy and stereomicroscopy to analyze the density, shape and location of the papillae. Whereas the proximal portion of the RG was characterized by small (1.5mm), conically shaped, smooth papillae, the middle portion exhibited larger papillae (4mm) with sharp borders covered by keratin. Towards the ROS the papillae further increased in size (3-11mm) and showed compound or single processes resembling the shape of arrows, twisted hooks or thorns (unguiculliform papillae). At the ROS the unguiculliform papillae were distributed in clusters groups and along the border of the sphincter. Due to their peculiar morphological features it is suggested that unguiculliform papillae functions as a filter barrier preventing the passage of large-sized food particles into the omasum and avoiding subsequent obstruction of both the RG and the ROS. The data give further evidence that unguiculliform papillae are actively involved in the complex mechanisms of food processing taking place within the ruminant pluricavity stomach.

Análisis morfológico comparado de la región fúndica entre un cánido (canis familiaris) y un camélido sudamericano (lama glama) / Comparative morphological analysis of the fundic region between a canidae (canis familiaris) and a southamerican camelidae (lama glama)

Los hábitos alimentarios que presentan los cánidos (monogástricos) respecto de los camélidos (poligástricos), son diferentes. Los primeros consumen dietas pobres en fibras, en tanto que los camélidos consumen una dieta rica en fibra que consiste en pastos cortos y duros (bofedal). Sin embargo son capaces de aprovechar eficientemente estos alimentos. Por ello, fueron analizados comparativamente las regiones fúndicas de ambas especies, donde encontramos diferencias morfológicas adaptativas. Para la realización del presente trabajo, se obtuvieron muestras de las regionnes fúndicas, provenientes de estómagos de perro (Canis familiaris) y de llama (Lama glama), adultos. estas muestras fueron procesadas de acuerdo a las técnicas histológicas corrientes e histoquímica de Picrosirius y analizadas comparativamente al microscopio óptico. Los resultados revelaron que existen diferencias importantes en las regiones fúndicas de ambas especies en estudio. Estas diferencias se encuentran especialmente a nivel de la mucosa, donde la profundidad de las glándulas fúndicas, número de células parietales (oxínticas) y la irrigación sanguínea son mucho mayores en la llama. La pared abdomasal presenta un refuerzo de tejido conjuntivo compacto de haces paralelos, entre la serosa y la muscular longitudinal externa. Estas adaptaciones redundarían en una mayor eficiencia digestiva por parte de los camélidos, dadas las características de su dieta habitual

[SEM study on the mucosa of the pre-stomach in Bubalus buffalus]. / Studio al SEM sulla mucosa dei prestomaci in Bubalus buffalus.

Morpho-structural features of pre-stomach mucosa in the first period of post-natal life in Bubalus buffalus have been studied by SEM. The rumen presents a well defined morpho-structural architecture from 10 to 100 days of life, while in reticulum and in omasum numerous morphological variations have been noticed. During the development, in fact, in these organs the establishment of a typical morphological pattern has been observed.

[Ultrastructure of the subepithelial capillaries and venules in the forestomach of sheep]. / Ultrastruktura na subepitelialnite kapiliari i venuli v predstomashiiata na ovtsata.

Described is the ultrastructure of the subepithelial capillaries and venules in the forestomach, of sheep. The vessels have proved to be fenestrated, with an entire endothelial lining, the fenestrae being closed by a well contoured membrane (diaphragm). Certain differences were established in the wall of the subepithelial vessels of the individual compartments of the forestomach. The fenestral portions are usually located at the side that is closer to the basal epithelium, while within the deeper layers they are replaced by nonfenestrated endothelium. A well defined pericapillary space, full of cross, olblique, and longitudinal collagen fibres was found between capillaries and epithelial basal cells. There were a number of ultrastructural findings in the walls of the capillaries, venules, and epithelium, which could be referred to as morphologic indices of the active transport of metabolic substances.

The origin and significance of the Langerhans cell granules.

Preliminary evidence indicates that the Langerhans cell granules (also known as Birbeck granules) may really be intercellular desmosomal discs of the more superficial layers of stratified squamous epithelium that have been taken up by the interdigitating dendritic processes of the Langerhans cells. They should therefore be considered as phagosomes whose only significance is in indicating that their hosts had traversed one or other of the various types of stratified squamous epithelium of the body. When seen in this light variable presence in Langerhans cells or occasional presence in melanocytes or keratinocytes can be satisfactorily explained. Although the Langerhans cells form the first line of immunologic defence as antigen detectors, it is unlikely that their granules play any role at all in the immune response.

Langerhans cells in the epithelium of the bovine forestomach: their role in the primary immune response.

Dendritic, migratory, lymphoid cells identical to the Langerhans cells of the epidermis, have been found in the epithelium of the bovine forestomach. They also possess the characteristic Langerhans cell granules. It can be assumed that these epithelial lymphocytes, (or Langerhans cells) as has been reported for the epidermal Langerhans cells, are antigen detectors and therefore form the first line of defence in the general immunological response of the body. The author suggests that the Langerhans cells of the forestomach be named epithelial lymphocytes. The existence of Langerhans cell granules has not yet been reported in the epithelial lymphocytes of the true stomach, intestines and respiratory epithelium.