Pododermal angioarchitecture in the equine hoof wall: A light and scanning electron microscopic study of the wall proper.

BACKGROUND: Blood supply is an important factor for the normal function of the equine hoof, but earlier studies present conflicting data on functional characteristics of its angioarchitecture. OBJECTIVE: Emphasis was laid on demonstration of the microvascularisation in the different hoof wall regions, aiming at assessment of specialised vascular structures, e.g. vascular sphincter mechanisms and arteriovenous anastomoses. METHODS: The angioarchitecture of the adult pododerma in the equine hoof wall was examined by scanning electron microscopy of micro-corrosion casts assisted by exemplary histological and immuno-histochemical characterisation of the pododermal vasculature. RESULTS: The microvasculature of the lamellae and terminal papillae in all hoof wall regions was described in detail. Focal dilations and microvascular sphincters were a common feature. In contrast to former investigations, true arteriovenous anastomoses were detected at the base of the primary lamellae and the terminal papillae only, while thoroughfare channels proved a regular element within the microvasculature of the wall proper. Bicuspid venous valves were detected as regular feature. For the first time, the alpha-smooth muscle actin-reactivity of the microvascularisation in the hoof wall was systematically assessed, verifying its specialised vasomotor devices. CONCLUSIONS: The vasculature of the hoof wall displays specific angio-adaptations to high pressure and tensile load.

Gross morphology and histology of the alimentary tract of the convict cichlid Amatitlania nigrofasciata.

The primary objectives of this study were to document the macroscopic and histological structure of the alimentary tract (AT) of the convict cichlid Amatitlania nigrofasciata, because there are no data available for this omnivorous freshwater fish of the family Cichlidae. The morphology of the AT of A. nigrofasciata resembles that of related species. While having morphological criteria of the AT typical of most omnivorous fishes, such as a blind sac stomach and medium length intestine, A. nigrofasciata also has some structural peculiarities: the oesophagus is lined by a uniform stratified squamous epithelial layer with interspersed goblet cells along its entire length. Additionally, it has well-developed layers of the tunica muscularis including muscle fibre bundles that ascend into its mucosal folds. Occasionally, taste buds are present. In the transitional area between oesophagus and stomach, a prominent torus-like closure device is present. The mucosa of the stomach cannot be divided into different regions according to mucosal and morphological properties. The simple pattern of intestinal loops of A. nigrofasciata has few variations, irrespective of sex, mass and length of the individual fish. The first segment of the intestine is characterized by the largest mucososerosal ratio and the most complex mucosal surface architecture. A distinction of midgut and hindgut was not possible in A. nigrofasciata due to lack of defining structural components as described for other fish species.

Porcine intestinal mast cells. Evaluation of different fixatives for histochemical staining techniques considering tissue shrinkage.

Staining of mast cells (MCs), including porcine ones, is critically dependent upon the fixation and staining technique. In the pig, mucosal and submucosal MCs do not stain or stain only faintly after formalin fixation. Some fixation methods are particularly recommended for MC staining, for example the fixation with Carnoy or lead salts. Zinc salt fixation (ZSF) has been reported to work excellently for the preservation of fixation-sensitive antigens. The aim of this study was to establish a reliable histological method for counting of MCs in the porcine intestinum. For this purpose, different tissue fixation and staining methods that also allow potential subsequent immunohistochemical investigations were evaluated in the porcine mucosa, as well as submucosa of small and large intestine. Tissues were fixed in Carnoy, lead acetate, lead nitrate, Zamboni and ZSF and stained subsequently with either polychromatic methylene blue, alcian blue or toluidine blue. For the first time our study reveals that ZSF, a heavy metal fixative, preserves metachromatic staining of porcine MCs. Zamboni fixation was not suitable for histochemical visualization of MCs in the pig intestine. All other tested fixatives were suitable. Alcian blue and toluidine blue co-stained intestinal goblet cells which made a prima facie identification of MCs difficult. The polychromatic methylene blue proved to be the optimal staining. In order to compare MC counting results of the different fixation methods, tissue shrinkage was taken into account. As even the same fixation caused shrinkage-differences between tissue from small and large intestine, different factors for each single fixation and intestinal localization had to be calculated. Tissue shrinkage varied between 19% and 57%, the highest tissue shrinkage was found after fixation with ZSF in the large intestine, the lowest one in the small intestine after lead acetate fixation. Our study emphasizes that MC counting results from data using different fixation techniques can only be compared if the respective study-immanent shrinkage factor has been determined and quantification results are adjusted accordingly.

Polymelous layer chick displaying additional malformations of the hind gut: case report and in-depth review of related literature.

A case report of a male 6-day-old male layer chick featuring incomplete polymelia of the hind limbs and hindgut malformations is presented. The chick was submitted to computed tomography (CT) examination and subsequent anatomical dissection. Apart from the two supernumerary hind limbs, the anatomical dissection revealed additional hindgut alterations: three uniform-sized caeca flanked the ileum, and the rectum branched into paired cloacae. The supernumerary hind limbs were localized caudal to the normal hind limbs in an inverted position and were attached to pelvic girdle elements and to a curtate pygostyle. They featured a prominent unpaired femur besides paired tibiotarsi, tarsometatarsi and species-specific phalanges of the toes. Additionally, two separate bones attached to the caudoventral aspect of the regular hip bones were developed. The supernumerary limbs were in part mobile and received nerve and vascular supply. Digital 3D-reconstruction based on the CT datasets revealed the osseous components of the malformed body parts. The possible morphogenesis including an in-depth literature review and the clinical implications of the reported malformations are discussed.

On the structure of the adrenal gland of the common seal (Phoca vitulina vitulina).

The adrenal gland is a vitally important endocrine gland that occupies a central role in the regulatory mechanisms of the body metabolism. Environmental stress factors lead to permanent strain and overload of the body resulting in structural alterations of the adrenals that in turn are followed by hormonal imbalances. This leads to an increased susceptibility to bacterial and viral diseases. The recurrence of numerous fatalities in the different seal populations of the North Sea (during the years 1988, 1989 and 2002), of the Baikal Lake and Caspian Sea (during the years 2000 and 2001) were the motive for a morphological investigation of the species-specific structure of the adrenal gland of the common seal in order to differentiate environmental stress-induced pathological alterations from the physiological structure of this organ. The study was based on adrenals of 112 common seals (Phoca vitulina vitulina) using light microscopic and transmission and scanning electron microscopic methods. The phocine adrenal gland displays several structural characteristics. Originating from the connective tissue organ capsule, narrow and broad septa intersperse the adrenal cortex. These septa contain blastemata as a reserve for the regeneration of hormone-producing cortical cells. Such blastemata are also occurring in the form of an intermediate zone in between the zona glomerulosa and zona fasciculata in the phocine adrenal cortex. Another species-specific characteristic is an inverse part of the adrenal cortex encircling the central vein of the organ. These structural features have to be considered in assessment and definition of pathological alterations of the adrenals as observed in the form of exhausted blastema cell pools in the adrenocortex of seals perished in the mentioned phocine mass mortalities.

Pododermal angioarchitecture of the bovine claw in relation to form and function of the papillary body: a scanning electron microscopic study.

The region-specific angioarchitecture of the bovine pododerma was examined using systematic scanning electron microscopy of micro-corrosion casts of juvenile and adult bovine claws. Particular emphasis was laid on the demonstration of specialised vascular structures such as arteriovenous anastomoses. Comparing the results of main and dew claws, respectively, of juvenile and adult claws, a relation between burdening of the claw and density and differentiation of the pododermal papillary and lamellar blood vessels was detected. The results suggest a possible influence of body weight (or age) and weight-bearing on the formation and vascularisation of the pododermal papillary body. The lamellar and papillary microvascularisation and microcirculation are discussed.

Microvasculature of the bovine claw demonstrated by improved micro-corrosion-casting technique.

A new and improved technique for microvascular corrosion casting was developed and verified by examination of corrosion casts of 90 bovine limbs. The described technique renders a complete filling of the vasculature of the claw even in regions that hitherto proved to be difficult regarding completeness of filling such as the dorsal area of the claw. This is demonstrated by an exemplary examination of all regions of the claw. The advantages and disadvantages of the new method are discussed.