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Biomedical subjects

P Simoens

Publications and source records attributed to P Simoens.

At least 73 records · Page 4Linked to original sources
PubMed1994

Jugular vein wall repair after intravenous injection in equids.

The evolution of the healing process of venous puncture wounds was studied macroscopically and light-microscopically in order to determine the time of venipuncture. Seven small equids of various ages, all in normal healthy condition, were experimentally injected in the external jugular vein with a physiological Hartmann solution at different times before euthanasia. Two types of needle diameters i.e. 16.5 G and 19 G, were used. A fairly good uniformity in the healing process was seen in the 7 animals. In most cases the lesions induced within 5 weeks before death were macroscopically visible, whereas older perforation sites became indistinct. Light-microscopic study enabled determination of the time lapse after intravenous injection. The needle diameter seemed hereby relatively unimportant. Points of reference were endothelium repair, presence of a fibrin plug containing red and white blood cells, neovascularization and healing of the connective tissue fibers.

Animals↗
PubMed1994

Morphometric analysis of the foramen magnum in Pekingese dogs.

The size and shape of the foramen magnum were studied in skulls from 75 adult and 5 juvenile Pekingese dogs. After maceration of the skulls, the height, width, and area of each foramen magnum were measured, and various skull indices were determined. The shape of the foramen varied from ovoid to rectangular and had a dorsal notch in all but 2 skulls. Prolapse of cerebellum or brain stem through the enlarged opening was prevented by a fibrous membrane covering the dorsal notch. Mean +/- SD area of the foramen was 138.1 +/- 26.1 mm2; its mean total height was 15.0 +/- 2.9 mm, and its mean maximal width was 13.3 +/- 1.1 mm. Statistically, variability in the area of the foramen was mainly correlated with total height of the foramen, including the dorsal notch. Total height of the foramen was not correlated with age or gender. The degree of dysplasia, notch index, and occipital index of each foramen magnum were determined. To allow a more accurate evaluation of the morphology of the foramen, the foramen magnum index, defined as the ratio between the maximal width and the total height of the foramen, was also computed. Mean +/- SD foramen magnum index was 91.8 +/- 17.1 in the adult Pekingese dogs. Foramen magnum index was not significantly correlated with age, but was significantly larger in male than in female dogs.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1993

[In vivo and in vitro study of experimental occlusion of choroidal and retinal blood vessels in the miniature pig].

Experimental occlusion of ocular blood vessels was performed in 25 eyes of 20 adult miniature pigs. The hyperacute, acute, subacute and chronic effects of these occlusions were studied by photography and fluorescein angiography of the ocular fundus in the living animals, and post-mortem by microscopic examination of histologic sections and stereomicroscopic study of vascular corrosion casts. Transection of the lateral posterior ciliary arteries was performed in eleven eyes and resulted in manifest chorioretinal ischaemic atrophy in confined areas of the ocular fundus. One month and longer after arterial transection, revascularization was found in the areas in which hypoperfusion had been induced, but no indications of neovascularization were observed. In one eye the lateral vortex veins were occluded by ligation. The subsequent fluorescein angiograms demonstrated only an insignificant local retardation of the choroidal filling. Filling defects of the choroidal vasculature and chorioretinal ischaemic lesions were not observed in the living animal nor in the vascular corrosion cast. Transection of the lateral posterior ciliary arteries was combined with ligation of the lateral vortex veins in seven eyes. These experiments resulted in lesions which were less severe than the sequels caused by transection of the lateral posterior ciliary arteries only. This observation was explained by the retrograde flow of venous blood which is rich in oxygen from the medial to the lateral choroidal quadrants. Consequently, ligation of the lateral vortex veins has a protective influence on the acute ischaemic lesions provoked by transection of the lateral posterior ciliary arteries. Simultaneous transection of the lateral posterior ciliary arteries and lateral chorioretinal arteries was performed in eight eyes. In the subacute and chronic stages, 1 and 4 months respectively after the vascular transection, proliferation of the retinal pigment epithelium and intraretinal neovascularization were observed in three out of five eyes examined. A fibrogliotic tissue mass containing newly formed blood vessels was found in between the reduplicated retinal pigment epithelium and the external layers of the sensory retina. The miniature pig offers an interesting ophthalmologic model because the ischaemic chorioretinal lesions and intraretinal gliovascular membranes which can be induced experimentally in this species present numerous similarities with the sequels of chorioretinal vascular occlusions in man.

Angiography↗
PubMed1993

Elbow arthroscopy in clinically normal dogs.

After a detailed anatomic study to determine puncture sites, 10 cadaver elbows from 5 dogs were examined arthroscopically to study the normal intraarticular anatomy, as viewed from the medial side. Subsequent dissection revealed absence of neurovascular injury and only minor iatrogenic damage to the cartilage. The technique was clinically applied and evaluated in 13 dogs (26 joints). The dogs recovered without complications. The technique proved to be safe and reliable for direct examination of nearly the entire joint. More specifically, it allowed systematic inspection of the medial and lateral humeral condyles, the medial and lateral coronoid processes, the caudal and middle parts of the head of the radius, the olecranon (including the anconeal process), and the medial collateral ligament.

Animals↗
PubMed1992

Morphologic and clinical study of the retinal circulation in the miniature pig. A: Morphology of the retinal microvasculature.

The microvasculature of the retina was studied in 20 miniature pigs by means of vascular corrosion casts and semithin histological sections. These techniques provided information useful for a better understanding of retinal fluoangiography. Various characteristics of the porcine retinal vessels, which are similar in the human retinal vasculature, were demonstrated in this study: the holangiotic retina, the trilaminar organization of the retinal capillaries and the presence of particular avascular zones, radial peridiscal capillaries and initial annular constrictions of certain arteriolar side-branches. The intrinsic retinal vasculature also shows some dissimilarities between both species. The major retinal blood vessels of the pig lie very superficially in the nerve fibre layer, in contrast to their deeper location in man. The streak-shaped macular area of the pig contains no major vessels but, unlike the central fovea in the human eye, it is not completely avascular. Another interesting finding is the presence of a large anterior border venule in the porcine retina.

Animals↗
PubMed1992

Morphologic and clinical study of the retinal circulation in the miniature pig. B: Fluorescein angiography of the retina.

The retinal blood circulation was examined in 20 porcine eyes by studying fluoangiograms before and after occlusion of the temporal choroidal circulation. The use of a small intravenous bolus of 2.5 ml fluorescein provided high-resolution angiograms with detailed information of the retinal vascular bed. The lobular filling pattern of the choriocapillaris very closely resembles the human pattern. The intrinsic retinal vasculature of the miniature pig also has numerous characteristics in common with the human retina with regard to the extent of the vascular bed, the size of the blood vessels and the presence of radial peridiscal capillaries. Unlike the central fovea in the human eye, the porcine retina has a streak-like macular area which extends both temporally and nasally and which, although it is free of major blood vessels, is not completely avascular. This fluoangiographic study substantiates the results of the accompanying paper. It may be concluded that the miniature pig is a suitable experimental animal for applied research on the retinal vasculature.

Animals↗
PubMed1991

Morphological study of the development of the disseminate prostate in intact and castrated male pigs aged two to six months.

The light-microscopical and ultrastructural differentiation of the disseminate prostate was studied in 12 boars and 8 barrows, ranging in age from 8 to 28 and 12 to 27 weeks, respectively. The barrows had been castrated at the age of 8 weeks. In young boars the prostate is organized in an inner zone and an outer zone. The glandular tubules of the latter are more differentiated than those in the inner zone. Sexual maturation in the prostate is characterized by almost complete reduction of the inner zone and concomitant enlargement of the outer zone. This differentiation of the inner zone occurs progressively and is manifested by a higher density of the glandular tubules, by a decrease in the number of basal cells and by an increase in the secretory tubular cells containing more microvilli, organelles and secretory vesicles. A few weeks after castration, the characteristic morphology of the undifferentiated inner zone is found throughout the entire glandular layer. The number of glandular tubules in barrows has decreased, and their cells show minimal secretory activity, nuclear indentations and a decrease in their organelles. A further castration effect is vacuolization of the perinuclear cytoplasm in numerous glandular cells.

Animals↗
PubMed1990

Anaesthesia for fluorescein angiography of the ocular fundus in the miniature pig.

A safe and reproducible procedure is described for anaesthesia and ophthalmic fluorescein angiography in the miniature pig. Twenty examinations were performed in five adult miniature pigs. A detailed description is given of the anaesthetic procedure, in particular of the techniques for endotracheal intubation and for intra-arterial and intravenous cannulation. All cardiovascular parameters recorded during the experiments remained within acceptable anaesthetic limits. The fluorescein angiographic technique, which is routinely used in human ophthalmology, was adapted for the pig. This procedure for in vivo examination of the porcine eye is interesting and useful for experimental ophthalmic research.

Anesthesia↗
PubMed1990

Development of the retina in the porcine fetus. A light microscopic study.

Morphogenesis of the porcine retina was studied using light microscopy from 4 weeks of gestation until birth (18 to 310 mm crown-rump length), and compared with the adult stage (6 months). Tissue samples were examined from the posterior and peripheral parts of the retina. At 18 mm the retina consists of an inner marginal layer and an outer layer of neuroblastic cells. At 18-40 mm the latter layer is divided into an inner and an outer neuroblastic layer by the transient layer of Chievitz. Subsequently, the development of the different retinal layers begins at the inner retinal border and moves progressively outwards; it also spreads from the posterior to the peripheral part of the neural retina. Many cells of the inner neuroblastic layer are prospective ganglionic cells which migrate inwards, thus forming the ganglion cell layer and the inner plexiform layer at 90 mm. At 120 mm, primitive horizontal cells appear within the outer neuroblastic layer. Separation of this layer into the inner nuclear, outer plexiform and outer nuclear layers is first evident at 180 mm. At this stage all retinal layers are present, except the layer of the photoreceptor cells which is not widespread until at 220 mm. The inner and outer segments of the photoreceptor cells lengthen considerably during the last month of gestation. During the late fetal stage the nerve fiber layer, the inner and outer plexiform layers and the layer of rods and cones all continue to increase in thickness. Concurrently, the ganglion cell layer and the inner and outer nuclear layers have reached their maximal thickness and become thinner. After the total thickness of the neural retina amounts to approximately 180 microns at two to three weeks before birth, it then thins to approximately 160 microns in the adult stage.

Animals↗
PubMed1990

The morphology of the equine iridocorneal angle: a light and scanning electron microscopic study.

The present investigation of 20 equine eyes shows that the iridocorneal angle of the horse is characterised by a very distinct pectinate ligament and a large ciliary cleft. The pectinate ligament consists of long and broad pigmented trabeculae which form a firm, flat and dense network that encircles the eye. On meridional sections, the ciliary cleft is visible as a wide triangular space comprising the trabecular meshwork which consists of two parts. The inner part is the larger and forms a three-dimensional network of large pigmented trabeculae with very wide intertrabecular spaces. The outer part occupies a much smaller area and fills the posterior angle of the ciliary cleft. It is a compact annular network consisting of small non-pigmented circularly orientated trabeculae. They enclose very narrow spaces which contain glycosaminoglycans. External to the outer network lies the angular aqueous plexus, which is rudimentary. This discontinuous plexus runs circularly and is composed of small slit-like vessels. The intrascleral venous plexus is also very weakly developed, whereas the internal collector channels and the episcleral venous plexus are clearly visible. The large ciliary cleft is supported by the strong trabeculae of both the pectinate ligament and the inner part of the trabecular meshwork, making collapse of the ciliary cleft practically impossible. This morphology of the equine iridocorneal angle helps to explain the rarity of glaucoma in the horse.

Animals↗
PubMed1990

Horner's syndrome in the horse: a clinical, experimental and morphological study.

A clinical case of Horner's syndrome is described in a Standardbred horse, and the various symptoms of cranial sympathetic denervation are studied in two ponies after experimental transection of the left cervical sympathetic trunk and vagosympathetic trunk, respectively. The most prominent symptoms of equine Horner's syndrome were ptosis, local sweating and increased cutaneous temperature in the denervated area. Enophthalmos, miosis and increased lacrimation were also observed but these symptoms were mild, variable and difficult to ascertain. Prolapse of the third eyelid was not noticed. Concomitant laryngeal hemiplegia was present in the clinical case and was provoked experimentally in one pony by transection of the left vagosympathetic trunk. The aetiology of each of these symptoms is discussed by comparing the results of pharmacological tests and histological findings in the three horses with the data from the literature.

Animals↗
PubMed1989

The hyaloid vascular system of the pig. A light and scanning electron microscopic study.

The hyaloid vascular system of the pig was studied from 4 weeks of gestation until 2 weeks after birth by means of semithin sections and vascular corrosion casts. The vascular tunic of the lens is supplied by the posterior lens branches of the hyaloid artery (at the posterior lens pole), by the intermediate lens branches of the proper hyaloid arteries (at the lens equator) and by the anterior lens branches of the radial iridial arteries (at the anterior lens pole). Venous drainage takes place via the venous lens branches which leave the lens anteriorly and drain into the radial iridial veins. Regression of the vascular tunic of the lens occurs during the second half of fetal life and is nearly completed in the first postnatal days. The involution first affects the proper hyaloid arteries and their intermediate lens branches. Subsequently, the posterior lens branches regress, whereas the anterior lens branches in the pupillary membrane disappear in the perinatal period only.

Animals↗
PubMed1989

Retinal vascular patterns in domestic animals.

In this paper a morphological study of the retinal vascular patterns in various species of domestic animals is reported. A classification of these patterns into four well-defined groups is described. In the domestic ruminants, pigs and carnivores the retina contains a compact plexus of blood vessels located in the major part of the light-sensitive portion of the retina (euangiotic or holangiotic pattern). In other domestic animals blood vessels are present only in a smaller part of the retina. In the rabbit, vessels are confined to a broad horizontal band coincident with the area of dispersion of the myelinated nerve fibres. The larger of these vessels are readily visible macroscopically (merangiotic pattern). In the horse and the guinea pig the retinal blood vessels are minute and restricted to the direct neighbourhood of the optic disc (paurangiotic pattern). The avian retina is completely avascular (anangiotic pattern), but a densely vascularised pecten oculi is attached to the linear optic nerve head and protrudes far into the inferior part of the vitreous body.

Animals↗
PubMed1988

Topography and identification of the parathyroid glands in the calf.

There is considerable controversy in the literature concerning the topography of the parathyroid glands in the calf. In the present study, the position of the parathyroids III (external parathyroids) and of the parathyroids IV (internal parathyroids) was examined in 25 young calves, 10 veal calves and 5 adult oxen. Detailed data for the recognition and the collection of these glands are provided. The parathyroids III are well suited for removal in a fresh state, since they can readily be located. They are situated medial to the carotid bifurcation and ventrolateral to the vagus nerve, where the latter gives off the cranial laryngeal nerve. In all young calves and in most veal calves, they lie embedded in the sub-basilar portion of the thymus, from which they can usually be differentiated easily by their color. However, they should not be confused with lymph nodes and hemal nodes, which are located in the neighborhood. Light-microscopical substantiation is therefore advisable. The parathyroids IV are not suited for collection, since they cannot be distinguished macroscopically from the adjacent thyroid gland.

Animals↗
PubMed1984

Aetiology and pathogenesis of congenital torticollis and head scoliosis in the equine foetus.

In 214 cases of severe dystocia in mares, of which 141 (66 per cent) were Draught horses, deviation of the head and neck, with or without torticollis, malformed head and limbs were found to be the cause of dystocia. No evidence of a genetic lethal factor was found and torticollis was often combined with scoliosis of the head and, frequently, with malformation of one or more limbs. This is considered evidence of a common aetiology and pathogenesis of the syndrome of malformation. The malformations were found to be associated with an increased incidence of caudal and, particularly, transverse presentations. These findings are presented as evidence to support the hypothesis that, during the second half of pregnancy, the narrow tip of the uterine horns provides only limited space for the developing cranial half of the foetus. The surprisingly rapid and complete anatomical and functional recovery of severe malformations of the bones of the neck, head and limbs of surviving foals, born by caesarian section, is taken as further evidence that these malformations have no genetic basis, but originate from unfavourable intrauterine conditions.

Abnormalities, Multiple↗