The morphology of the pecten oculi of the ostrich, Struthio camelus.

The pecten oculi is a structure peculiar to the avian eye. Three morphological types of pecten oculi are recognized: conical type, vaned type and pleated type. The pleated type has been well studied. However, there exists only scanty data on the morphology of the latter two types of pectens. The structure of the vaned type of pecten of the ostrich, Struthio camelus was investigated with light and electron microscope. The pecten of this species consists of a vertical primary lamella that arises from the optic disc and supports 16-19 laterally located secondary lamellae, which run from the base and confluence at the apex. Some of the secondary lamellae give rise to 2 or 3 tertiary lamellae. The lamellae provide a wide surface, which supports 2-3 Layers of blood capillaries. Pigmentation is highest at the distal ends of the secondary and tertiary Lamella where blood capillaries are concentrated and very scanty on the primary and the proximal ends of the secondary lamella where the presence of capillaries is much reduced. In contrast to the capillaries of the pleated pecten, the endothelium of the capillaries in the pecten of the ostrich exhibits very few microvilli. These observations suggest that the morphology of the pecten of the ostrich, a flightless ratite bird is unique to the pleated pecten and is designed to meet the balance between optimal vision and large surface area for blood supply and yet ensuring it is kept firmly erect within the vitreous.

Influence of a probiotic Enterococcus faecium strain on development of the immune system of sows and piglets.

The influence of the probiotic bacterium Enterococcus faecium SF68 on the immune system and the intestinal colonization of pigs were determined in a feeding experiment with sows and piglets. Mucosal immunity of the developing piglets was monitored by isolation and detection of intestinal lymphocyte cell populations from the proximal jejunal epithelium and the continuous Peyers patches by the use of flow cytometry. The levels of intestinal IgA in both groups of piglets were compared, as well as total IgG in the serum of sows and piglets. Feces of the sows and intestinal contents of the piglets were taken for determination of total anaerobe and coliform bacterial counts in both probiotic and control groups. Villus length and depth of the crypts were measured in the jejunum of sacrificed piglets to monitor the development of the intestinal mucosal surface amplification. Total serum IgG of the sows appeared to be unaffected. Piglets of both groups showed similar IgG levels up to 5 weeks after birth with a slight tendency toward lower values in the probiotic group. At an age of 8 weeks the total IgG levels of the probiotic animals were significantly lower (p<0.01). No differences were observed in the populations of CD4+ and CD8+ T cells in the Peyers patches. However, the levels of cytotoxic T cells (CD8+) in the jejunal epithelium of piglets of the probiotic group were significantly reduced. The depth of the jejunal crypts and length of the villi were similar in both groups, suggesting the relative T-cell population differences were not due to alterations in the epithelial cell numbers. The total anaerobe and coliform bacterial populations were not significantly affected by the probiotic treatment, either in sows or in the piglets. However, a remarkable decline in the frequency of beta-haemolytic and O141 serovars of Escherichia coli was observed in the intestinal contents of probiotic piglets, suggesting an explanation for the reduction in cytotoxic T-cell populations.

Morphology of the small intestine of weaned piglets and a novel method for morphometric evaluation.

The intestinal morphology of 7-week-old pigs was investigated by light (LM) and scanning electron microscopy (SEM). The piglets were fed either a semisynthetic or a cereal-based diet. The shapes of the intestinal villi and crypts of the duodenum, jejunum and ileum were examined. The villi were predominantly tongue-shaped. In the duodenum they were also ridged, branched and folded, and in the jejunum they were also leaf-like and ridged. At places with lymph follicles, the surface of the ileum was rugged with meandering fold-like villi. The crypts of the three segments of the small intestine were mainly coiled and sometimes branched. A novel morphometric evaluation method was introduced using the enlargement factors of each villus and crypt surface. The enlargement factor for the villus surface of the duodenum, jejunum and ileum was 3.13, 3.72 and 2.71, respectively. The factor for the crypt surface of the duodenum, jejunum and ileum was 9.07, 8.94 and 6.53, respectively. Furthermore, the relative proliferation rate and the epithelial renewal index were calculated for the first time. The relative proliferation rate of the duodenum, jejunum and ileum was 32.88, 34.78 and 50.77 proliferations per mm crypt perimeter, respectively. The diets consumed had an influence on the epithelial renewal index being higher for piglets fed the cereal-based diets.

A scanning electron microscope study of the luminal surface specializations in the blood vessels of the pecten oculi in a diurnal bird, the black kite (Milvus migrans).

The luminal surface of the pecten oculi of the black kite (Milvus migrans), a diurnally active bird of prey, was examined by scanning electron microscopy. In this species the blood vessels are generally of two types, the small-calibre capillaries and the large-calibre afferent and efferent vessels. The luminal surface of the efferent blood vessels possesses a few low microplicae. Conversely, the luminal surface of the afferent blood vessels is characteristically smooth except at the cell junctions and at the point of entry into the capillaries. The cells junctions are marked by low ragged ridges while the luminal surface is studded with low sparse pleiomorphic microprojections at the point of capillary emergence. The luminal surface of the blood capillaries is characterised by a labyrinth of closely disposed microplicae that projects into the lumen. These microplicae show no particular orientation with respect to either the longitudinal or transverse axis of the capillary. Instead, they are diffusely orientated. It is conjectured that such a heterogeneous design of the endothelium in the blood vessels of the pecten oculi has developed in order to augment the role of the pecten in the transport of nutrients to the avascular neural retina by an energy saving diffusion process. The process through which the design of the microfolds affects haemodynamics and their putatite role in facilitating the delivery of nutrients are discussed in the perspective of the available data.

Surface specialization of the capillary endothelium in the pecten oculi of the chicken, and their overt roles in pectineal haemodynamics and nutrient transfer to the inner neural retina.

The structure of the capillary endothelium in the pecten oculi of the domestic fowl was investigated by scanning and transmission electron microscopy. Scanning electron microscopy results demonstrated the existence of a vast array of irregular microplicae that projected from the luminal surface of the capillary endothelium. In between these microplicae were numerous crevices. The microplicae were closely packed and showed no preferred orientation regarding either the longitudinal or transverse plane of the capillaries. Transmission electron microscopy revealed the section profiles of the microplicae: their tortuity, branching, interdigitations and the magnitude of the crevices contained. The endothelial cytoplasm exhibited a few mitochondria and micropinocytotic vesicles. The apparent set-up of the luminal plasmalemmal infoldings seemed to be designed for effecting impedance to the pectineal blood flow and thereby facilitating passive permeation of blood-borne nutrients to the inner neural retina. The reasons of such passive transport operation mediated by the endothelial microplicae of the avian pecten oculi are discussed in the perspective of the existing literature.

A scanning electron microscope study of the pecten oculi of the black kite (Milvus migrans): possible involvement of melanosomes in protecting the pecten against damage by ultraviolet light.

The pecten oculi of the black kite (Milvus migrans), a diurnally active bird of prey, has been examined by scanning electron microscopy. In this species the pecten consists of 12 highly vascularised pleats, held together apically by a heavily pigmented 'bridge' and projects freely into the vitreous body in the ventral part of the eye cup. Ascending and descending blood vessels of varying calibre, together with a profuse network of capillaries, essentially constitute the vascular framework of the pecten. A distinct distribution of melanosomes is discernible on the pecten, the concentration being highest at its apical end, moderate at the crest of the pleats and least at the basal and lateral margins. Overlying and within the vascular network, a close association between blood vessels and melanocytes is evident. It is conjectured that such an association may have evolved to augment the structural reinforcement of this nutritive organ in order to keep it firmly erectile within the gel-like vitreous. Such erectility may be an essential prerequisite for its optimal functioning, as well as in its overt use as a protective shield against the effects of ultraviolet light, which otherwise might lead to damage of the pectineal vessels.

[The conjunctival epithelium of dogs. Light and electron microscopic investigations]. / Das Konjunktivalepithel des Hundes. Licht- und elektronenmikroskopische Untersuchungen.

The conjunctiva of the dog has a smooth surface on the inside of the upper and lower lid and of the bulbus oculi. In these areas the conjunctiva is covered by a stratified squamous epithelium, the polygonal surface cells of which have microvilli and microplicae which are different in number and show a great variety of shapes. In the passage towards the fornix conjunctivae a stratified cuboidal epithelium is to be discerned. In the fornix itself, the conjunctiva is arranged in small folds which are protruded by goblet cells and the openings of lacrimal glands. Here a stratified cuboidal or columnar epithelium can be observed which at the electron microscopic level shows in all epithelial layers--mostly however in the stratum superficiale--morphological signs of enhanced metabolic activities. The bulbar surface of the third eyelid which is covered by a stratified squamous epithelium has a three-dimensional moulded pattern of pads and grooves. The structure of the conjunctival epithelium to some extend is age dependent.

Development of gastrin-and somatostatin-containing cells in the pyloric gland region of the bovine abomasum.

The ontogeny of gastrin- and somatostatin-containing cells in the pyloric gland region of the abomasum was studied in bovine fetuses, newborns and adults, using immunohistochemical techniques. A clear-cut developmental increase in the two kinds of endocrine cells could not be observed. The region of the lesser curvature displays more D and G cells than the greater curvature. Cells of both open and closed types are found from the earliest stages examined and continue to be present throughout the complete differentiation of the pyloric mucosa.

Somatostatin cells in the gastric mucosa of small ruminants. Immunohistochemical study.

The distribution of somatostatin cells was investigated immunohistochemically in the epithelium of the abomasal mucous membrane of sheep and goats. Tissue samples were taken from different areas at the lesser and greater curvature of the glandular stomach. More somatostatin cells per 0.5 mm2 were found in sheep than in goats, predominantly in the pyloric gland region. In the pyloric area of both species the mucosa in the greater curvature contained more immunoreactive cells than the one in the lesser curvature. A few somatostatin cells with basal cytoplasmic processes of the 'open type' were observed over the entire abomasal mucosa.

[Fine structure of the fundic gland zone epithelium in various eastern African ruminants]. / Die Feinstruktur des Epithels der Fundusdrüsenzone einiger ostafrikanischer Wildwiederkäuer.

Light- and electron microscopic investigations were conducted on the epithelium of the area glandulae gastricae propriae of the abomasum, using material of 12 East African game ruminants of nine species. The members of the main feeding categories (Hofmann, Stewart 1972): concentrate selector, roughage eater and intermediate feeder did not differ much in the ultrastructure of the fundic stomach epithelium but showed greater differences with respect to the height and shape of the glandular tubules and the arrangement of the epithelial cell types. Specifically the following cell types were observed: mucoid cells, chief cells, parietal cells, seven different endocrine cells, tuft cells and two types of migrating cells. In some epithelial celltypes of the concentrate selector dikdik, cristalloid cytoplasmic inclusions were found.

The surface of the conjunctiva in domestic ruminants. A scanning electron microscopic investigation.

The surface of the conjunctiva was investigated in goats, sheep and bovines. The lid-facing surface of the nictitating membrane carries a serrated crest. At a low magnification the areas covered by a stratified squamous epithelium appear as a mosaic. In the superior and inferior conjunctival fornices the mucous membrane has a uniform appearance. Areas of goblet cells have an irregular appearance. Four functional stages can be observed in the goblet cells. At a high magnification the superficial cells of the palpebral and bulbar conjunctiva are covered by microplicae. In the fornix conjunctival microvilli project over the superficial cells.