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In this study, the expression of estrogen receptor alpha (ERalpha) in the bovine ovary is described. ERalpha was visualized by immunohistochemistry on paraffin sections of ovaries obtained from 11 non-pregnant and 2 pregnant animals. In general, ERalpha was not observed in cells of primordial, primary and secondary follicles, whereas weak expression was noticed in cells of healthy and arteric tertiary follicles. In corpora lutea cells the expression of ERalpha was obvious. Intermediate to high ERalpha expression was present in thecal cells and in cells of the superficial and deep stroma, tunica albuginea and surface epithelium. Furthermore, the expression of ERalpha in stroma and tunica albuginea cells was in general, highest in cows with the lowest plasma progesterone levels, and lowest in cows with the highest plasma progesterone levels. Remarkably, the ERalpha expression in pregnant cows was in general, lower than in non-pregnant cows with similar plasma progesterone levels. The relatively high expression of ERalpha in thecal and stromal cells in comparison with that in follicle cells suggests an indirect effect of estrogen on the follicular development. However, the exact function of ERalpha in the bovine ovary together with the cycle-dependent variations in ERalpha expression remain to be elucidated.

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The objective of this study was to examine the diameter, extent, orientation and contents of dentinal tubules in order to validate the hypothesis of pigment penetration into the dental star of equine incisival occlusal surfaces. The time of appearance and the configuration of the dental star on the incisival occlusal surface are macroscopically visible features that, along with other more reliable parameters, are used for the determination of horses' age. Although dental stars are an integral part of the equine incisor occlusive surface, the exact nature and microstructure of the dental star are poorly documented. Therefore, equine incisor dentine was examined macroscopically and by scanning electron microscopy to elucidate numerical density, diameter and 3-dimensional organisation of the dentinal tubules in the dental star. The dental star is surrounded by primary dentine and consists of a central core of tertiary dentine, an intermediate ring of pale secondary dentine and a peripheral rim of darker, yellowish-brown secondary dentine. The central core of tertiary dentine contains relatively few dentinal tubules (<8000/mm2) that have small diameters (mean +/- s.d. 1.67 +/- 034 microm) and are arranged in an irregular pattern. The surrounding pale ring of secondary dentine comprises manifestly more and wider tubules that lie almost parallel to the occlusal surface. The dark peripheral rim of the dental star contains high numbers of tubules (28,000-58,000/mm2) that have wide luminal diameters (mean +/- s.d. 3.09 +/- 0.31 microm) and open perpendicular to the occlusal surface. In contrast, the primary dentine surrounding the dental star is made up by a lower number of dentinal tubules (<25,000/mm2). The tubules of primary dentine, which are initially mean +/- s.d. 5.15 +/- 0.80 microm wide, are narrowed by circumferential deposits of peritubular dentine and are obliquely exposed at the occlusal surface. From these observations, it was concluded that the regional differences in numerical density, diameter and spatial orientation of the dentinal tubules may influence the penetration of food pigments into the equine occlusal surface and result in the particular staining of the dental star.

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In this study the endometrial morphology of four dogs in oestrus and 10 dogs in late metoestrus was investigated with scanning electron microscopy. In early oestrus the cells were slightly convex with fairly long microvilli and cell boundaries that were apparent but situated on a deeper level than the cell surface. In late oestrus the cells were clearly convex with long and numerous microvilli masking the cell boundaries. At the beginning of late metoestrus the cells became less convex with many but short microvilli and prominent but lower situated cell boundaries. At the end of late metoestrus the cells were flat with very short microvilli and protruding cell borders. These morphological findings were correlated with the cyclic variations of the steroid hormone levels.

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Vascular corrosion casts of 12 equine, 15 bovine and 50 porcine eyes were studied scanning electron microscopically for the presence of posterior ciliary veins. These veins drain a postequatorial segment of the choroid and emerge near the posterior bulbar pole. They complement the four vorticose veins that emerge near or at the equatorial zone of the eyeball and the slender choroidoretinal veins that drain the peridiscal area of the choroid. Posterior ciliary veins were observed in all equine and bovine eyes examined. In these species they presented a large variation in size, number and position. In contrast, posterior ciliary veins were only present in two porcine eyes where they were represented by one and two vessels, respectively. The morphology and variability of these vessels is illustrated and their nomenclature and functional significance are discussed.

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The distribution of intratubular (peritubular) dentine was studied by scanning electron microscopy in 12 equine incisor teeth. High levels of intratubular dentine were found in the peripheral regions of the dentine. In these areas, a marked asymmetry occurred, as intratubular dentine was predominantly deposited onto the side of the dentinal tubular walls nearest to the dentino-enamel junction. The quantity and asymmetry of intratubular dentine were reduced towards the centre of the tooth. The significance of these variations in the amount and distribution of intratubular dentine between the different dentinal regions is discussed.

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This paper gives an anatomical overview of the dentinal structure in equine incisor teeth with special reference to the three-dimensional organization, the number and the diameter of the dentinal tubules. The spatial arrangement of equine dentine was examined by scanning electron microscopy of occlusal surfaces and longitudinally fractured teeth and by light microscopy of both decalcified and ground sections. The dentinal tubules of the peripherally situated primary dentine were directly continuous with those of the circumpulpal secondary dentine. The tubules had numerous side branches along their entire course and ramified into terminal branches near the dentino-enamel junction. Tubules of tertiary dentine, situated in the centre of the dental star, were few in number and not continuous with those of the surrounding secondary dentine. On non-etched incisors tubular orifices were clogged by an amorphous smear layer that covered the occlusal surface. On etched occlusal surfaces the numerical tubular density was calculated in different zones. The largest number of tubules per unit area was situated in the secondary dentine forming the dark periphery of the dental star, whereas the smallest number was present in the tertiary dentine located in the pale centre of the dental star. Dentinal tubular diameters were measured at various distances from the pulp. They were widest near the pulpal wall and narrowed progressively towards the dentino-enamel junction. Tubular widths measured on etched occlusal surfaces were considerably larger than those measured on undecalcified incisors due to the removal of intratubular dentine during the etching process.

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The dentinal tubules of 20 permanent equine incisors were investigated by scanning electron microscopy. Occlusal surfaces and longitudinal fracture planes of both etched and undecalcified teeth were examined. Three different types of structure were observed inside the dentinal tubular lumen. Odontoblastic processes could only be visualized in the circumpulpal parts of the tubules. The more peripheral parts were empty or housed cylindrical structures that probably correspond to the laminae limitantes. Collagen fibres were frequently observed in the tubular lumina and were most numerous in the circumpulpal parts of the tubules.

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The presence of hormone receptors is as important as the amount of hormone to predict hormone action. Therefore, the presence of estrogen receptors of the alpha subtype (ER-alpha) and progesterone receptors (PR) was evaluated in six pregnant uteri including the placenta and in three postpartum uteri of dogs. This preliminary study is part of our immunohistochemical research project on steroid hormone receptor distribution in the canine female genital tract. Specific staining for ER-alpha or PR was found only in cell nuclei. Staining for ER-alpha was rare in the various cell types of pregnant and postpartum uteri. Staining for PR was absent or weak in epithelial cells. Moderate staining for PR was observed in endometrial stromal cells and myometrial smooth muscle cells, two cell types playing an important role in the maintenance of pregnancy. Stromal cells stained more frequently positive for ER-alpha and PR than epithelial cells, indicating that both hormones may act on epithelial cells indirectly via stromal cells. In the placental labyrinth, fetal cells showed no evidence of ER-alpha or PR. In contrast, both receptors were present in maternal mesenchymal cells that were located around the basement membrane of the maternal blood vessels. These cells showed signs of decidualization. No difference in PR distribution was seen between pregnant and postpartum uterine tissue, suggesting that during parturition the decrease in serum progesterone levels and the concomitant increase in the estrogen/progesterone ratio are probably more important than the decline in receptor availability.

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The aim of this immunohistochemical study is to describe the normal distribution of progesterone receptors in the various cell types of the canine uterine horns, body and cervix. The results can be used for research on uterine and endocrinological pathology, since the impact of progesterone on different uterine cell types is partly determined by the receptor availability. Nuclear staining for progesterone receptors was observed in epithelial cells of the surface epithelium, glandular ducts and basal glands of the endometrium, in endometrial stroma cells and in myometrial smooth muscle cells. This staining was positively correlated with the estradiol-17 beta:progesterone ratio, and reflects the positive effect of estradiol-17 beta and the negative influence of progesterone on the receptors. Staining scores were high during proestrus and decreased through estrus to early metestrus. In late metestrus, staining scores of the stromal and smooth muscle cells increased again. In anestrus, high scores of the surface-epithelial cells contrasted with minimal scores of the basal glands. This finding suggests a different hormonal regulation of the progesterone receptor expression in both epithelial cell groups. The higher staining intensities for progesterone receptors in stromal cells compared with epithelial cells might be explained by the fact that stromal cells mediate some effects of steroid hormones on the epithelial cells in the genital tract. Therefore, the role of stromal cells in regulation of the cyclic endometrial changes and in pathologic changes of uterine tissue should not be underestimated.

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The accuracy of ageing mini-Shetland ponies and donkeys was assessed by correlating the appearance of specific dental features with the known ages of 106 mini-Shetland ponies and 63 donkeys. The ages of the animals ranged between 2 days and 26 years. In both species the eruption of the deciduous and permanent incisors occurred later than in horses. On the other hand, the appearance of the dental stars on the permanent incisors of mini-Shetlands and donkeys was seen at a younger age than in horses. As in most horse breeds, the disappearance of the cups, the clinical crown lengths, the presence of hooks on the upper corner and the presence of a Galvayne's groove are unreliable features for dental age determination in the pony and the donkey. Specific dental characteristics of both the mini-Shetland pony and the donkey are discussed.

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The microhardness of enamel, primary dentine and secondary dentine was determined in the incisor teeth of 39 horses of three different breeds, trotter horses, Belgian draft horses and Arab horses. Using a microhardness tester fitted with a Knoop diamond indenter, the overall Knoop Hardness Number was determined for each tissue, and the influence of breed and age on the hardness were evaluated. Enamel and secondary dentine were significantly harder in Arab horses than in trotters and Belgian draft horses, but there were no significant differences between draft horses and trotter horses in the hardness of their enamel and dentine.

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Cyclic changes in estrogen receptor expression in the uterine tissue of 60 female dogs were evaluated, using an immunohistochemical technique on formalin-fixed paraffin-embedded sections. The expression of estrogen receptors in the uterine horns, body and cervix was quantified by means of an immunohistochemical score. A negative correlation was found between staining scores in the uterine horns and serum progesterone levels. Generally, staining scores in the uterine horns were highest during proestrus, declined during estrus and were lowest during early metestrus. During anestrus high staining scores for estrogen receptors were observed, indicating sensitivity for estrogens in a sexual quiescence stage. Compared with the uterine horns, high staining scores were found in the uterine body and cervix during estrus and metestrus. No positive staining for estrogen receptors was detected in 1 pregnant uterus. Fluctuations in estrogen receptors were more pronounced in endometrial stroma cells than in epithelial cells of the uterine horns. The importance of stromal cells in the sexual cyclicity of the canine uterus should not be underestimated when studying uterine endocrinology and pathology.

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In the present study the age-related morphological characteristics of 948 equine incisors were investigated. After extraction, total incisival length and root length were measured at the vestibular side of the teeth. Equine incisors reach their maximal length 2-3 years after eruption. Notwithstanding severe occlusal wear, this maximal length is maintained during most of the horses' life due to prolonged root formation. Root formation, at the rate of 2.5 mm per year, starts at the age of 5-6 years and continues until the age of 17. As the root of the incisor develops, its apical foramen narrows and changes position. In young horses the apical foramen is situated at the apex of the tooth, whereas in older individuals it is located at the mesial, distal, or lingual side of the tooth at a distance of 5-15 mm from the dental apex. In horses aged over 20 years apical foramina are still present. Radiographic imaging is a good method with which to obtain reliable information concerning the total incisival length and the size and position of the apical foramen.

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The innervation pattern of the interosseus muscle of the forelimb was studied in two ponies and two horses. The nerves of the suspensory ligament were studied histologically after neurectomy of the ulnar and median nerve branches proximal to the carpal joint. The results demonstrated that the interosseus muscle is innervated by the deep branch of the lateral palmar nerve which emerges at the level of the midcarpal region and contains fibres from the ulnar and the median nerve. These findings provide evidence that an ulnar nerve block proximal to the accessory bone would fail to anaesthetise the entire suspensory ligament.

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The dentition of 170 Arab horses of known ages was examined and compared with the dental characteristics of trotter horses and Belgian draft horses of the same ages. The results indicated that inaccuracies in the determination of the age of horses by their dentition may result, at least partly, from differences between the breeds of horse involved because there were some major differences between the three breeds examined. These differences increased as the horses' true age increased. In general, the rate of dental wear was slower in the Arab horses than in trotter horses and Belgian draft horses.

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The estrogen receptor (ER) was visualized immunohistochemically in paraffin sections of the canine uterus using a monoclonal antibody. The ER-expression was quantified by means of an immunohistochemical score. In the uterine horns highest scores were found during proestrus and lowest scores during early metestrus. Staining scores in the uterine body and cervix were high during estrus and metestrus compared with the uterine horns. A negative correlation was found between serum progesterone levels and immunohistochemical staining for ER in the uterine horns. The fluctuations in immunohistochemical scores were more pronounced in the endometrial stroma cells than in the epithelial cells of the uterine horns and therefore stromal cells may be of higher importance than epithelial cells concerning cyclic endometrial changes and uterine pathology.

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The accuracy of ageing horses by their dentition was assessed by comparing the dental features with the known dates of birth of 212 trotter horses and 189 Belgian draft horses. The horses ranged in age from two to 25 years. In both breeds it was observed that the shedding of the incisors and the appearance of the dental stars were the most reliable features for age determination. In young animals, the dental configuration was similar in both breeds. With increasing age the incisor teeth of draft horses were more liable to abrasion than those of trotter horses. The sequential changes in appearance of the permanent incisors occurred earlier in draft horses than in trotters.

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The pectinate ligaments of ten horses, two donkeys, five oxen, five sheep, ten goats, five dogs, five cats, thirty pigs and two rabbits were studied under the stereomicroscope and the scanning electron microscope. In the horse and the donkey, the pectinate ligament was very prominent and was characterized by sturdy interconnected strands and relatively small intertrabecular spaces. The pectinate ligaments of ruminants were composed of shorter strands, separated by relatively larger spaces. Fusion between adjacent strands, resulting in the formation of fenestrated sheets, was regularly observed in these species, in particular in the superior and inferior ocular segments. In the dog and the cat, the pectinate ligament consisted of slender strands that were separated by large intertrabecular spaces. The strands of the pectinate ligaments of the pig and the rabbit were shorter and their diameters were intermediate between those of the herbivores and the carnivores. The clinical relevance of the normal variability in the structure of the pectinate ligament and proposals for a uniform anatomical nomenclature are discussed.

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Orbital and intrabulbar arteries were studied in 20 equine eyes by means of latex injections and methylmethacrylate casts. The orbital branches of the external ophthalmic artery arise far caudal to the posterior pole of the eyeball and present a variable topographic arrangement. The intrabulbar arteries are supplied by ciliary and choroidoretinal arteries. Dependent on their entrance into the eyeball, the ciliary arteries are subdivided into a posterior and an anterior group. The posterior ciliary arteries perforate the sclera post equatorially and consist of 4 major vessels that penetrate in the lateral, medial, dorsal and ventral meridian of the eyeball, respectively. The lateral and medial of these arteries follow a long intrabulbar trajectory after having supplied several short posterior ciliary arteries to the choroid. The anterior ciliary arteries consist of a dorsal and a ventral vessel which penetrate the eyeball in the pericorneal area. The choroidoretinal arteries form an arterial network around the optic nerve at the posterior pole of the eyeball. They give rise to all retinal arterioles and some peridiscal choroidal branches. The larger part of the choroid is supplied by branches of the posterior ciliary arteries. Additionally, the anterior choroid receives recurrent branches from an arterial circle that lies externally in the ciliary ring. The iris contains a major arterial circle formed by the lateral and medial long posterior ciliary arteries and both anterior ciliary arteries. A minor iridic arterial circle nor central retinal artery could be found in the equine eyes examined.

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