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Biomedical subjects

P Mestres

Publications and source records attributed to P Mestres.

At least 55 records · Page 3Linked to original sources
PubMed1988

Occlusion of experimental artery aneurysms by intrasaccular injection of fibrin sealant.

Aneurysms were produced by grafting a vein pouch onto the cervical carotid artery of rabbits following the removal of an elliptical piece of the arterial wall. The diameter of the opening was 3-4 mm and the maximum height 8 mm. Through direct puncture of the aneurysm a clot of the fibrin sealant Tissucol was injected into the aneurysm. The sequential morphological changes were studied by light microscopy. One case was examined after 3 weeks by scanning electron microscopy. Complete resorption of the fibrin sealant was observed. The aneurysm cavity was filled with a dense connective tissue covered by a layer of newly formed endothelial cells.

Animals↗
PubMed1987

Experimental aneurysms in the rabbit: occlusion by intrasaccular injection of fibrin sealant.

Experimental aneurysms of the carotid artery were produced using the microsurgical technique of grafting a venous sack onto the artery in the neck of rabbits after the removal of an elliptical piece of arterial wall. Twenty-five aneurysms were occluded with the fibrin sealant Tissucol. Microscopic examination showed complete resorption of the fibrin clot and the formation of dense granulation tissue within the aneurysm, which was covered with a layer of endothelial cells after 2 weeks. The results are only tentative and require further experimental studies.

Animals↗
PubMed1986

Morphological aspects of the pharyngeal hypophysis in human embryos.

In human embryos the hypophyseal sac (Rathke's pouch) originates at the roof of the mouth until stage 15 as a broad rim. As the mandibular arch and the maxillary swelling enhance the mesodermal masses in forming the early palatal shelves the rim is reduced to a cleft of about 0.2 mm in broadness in stage 17. From stage 18 up to stage 23 there is a prominent papilla in the midline of the mouth's roof which later on may become recanalized. The different SEM-aspects of the pharyngeal hypophysis are demonstrated.

Humans↗
PubMed1985

Scanning electron microscopy of the lateral ventricle of the pigeon brain.

Adult pigeons of both sexes were used for this study. Depending upon the distribution of various surface profiles, for example cilia, microvilli and blebs, ependymal areas with differing surface patterns were distinguished in the lateral ventricle. The topographical locations of these areas with respect to the underlying forebrain nuclei were determined in accord with the atlas of Karten and Hodos (1967). The medial surface (A) of the ventricle was much more densely ciliated than the lateral surface (B). There did not appear to be any correlation between a given surface pattern and a specific type of underlying nervous tissue. Comparison of the cell patterns seen in the pigeon brain with those seen in the analogous areas of the rat brain showed that it is not feasible to extrapolate from one zoological group to another. With the exception of the Kolmer cells populating the choroid plexus, there were remarkably few supraependymal cells in the pigeon lateral ventricle. Supraependymal nerve fibers were also extremely rare. Particular attention was given to the ependyma associated with the nucleus stria terminalis, to that of the lateral septal organ and to the choroid plexus. The possible classification of these areas into the group of the circumventricular organs is considered.

Animals↗
PubMed1983

Effects of monosodium glutamate on the development of intraventricular axons in the rat hypothalamus.

The development of intraventricular axons in the infundibular recess of the young rat was investigated by correlative scanning and transmission electron microscopy (SEM-TEM). From the fourth through the fifteenth day of life such axons increase steadily in number. During subsequent weeks their number gradually decreases. In animals given monosodium glutamate on the fourth postnatal day there is widespread neuronal necrosis in the arcuate nucleus, and the development of intraventricular axons is greatly reduced. These findings suggest that the axons originate from the neurons of the arcuate nucleus.

Animals↗
PubMed1982

A contribution to the study of the afferents to the pigeon optic tectum.

The origins of several afferent pathways to the pigeon's tectum were studied using the horseradish peroxidase tracing technique. The results confirm the presence of several previously described afferents, and add further data on intertectal and hyperstriatofugal projections. Two new sources of afferents to the tectum, located in the hypothalamus and the septum, were identified. The latter is described in greater detail.

Afferent Pathways↗
PubMed1981

Supraependymal cell clusters in the rat brain.

The histological patterns of supraependymal cell clusters (CC) in rats of different ages (untreated, androgenized, and treated with monosodium glutamate) were investigated with light (LM)-, scanning- and transmission electron microscopy (SEM, TEM). These clusters were a frequent but not a constant finding. In 18 day- and older embryos, CC were always found in the recess of the olfactory bulb immediately prior to its obliteration. All other CC appear in the infundibular recess between the 3rd and the 6th postnatal day. Independent of age, all cell clusters exhibit small aggregates of subependymal tissue protruding through the ependyma. Both neurons (light cells) and neuroglia (dark cells) were found in the CC. By use of SEM, in the region of the infundibular recess it is possible to distinguish four forms of supraependymal cell clusters according to localization, size, number of cells, and presence of intraventricular axons. CC may be 1) receptors or have an additional secretory function; 2) Manifestations of a pathological type of reaction of the ventricular wall; 3) possible excrescences of the neural matrix, or 4) modifications of the ventricular wall in relation to the obliteration of the ventricular recesses. The first two interpretations are not tenable based on the present observations.

Aging↗
PubMed1981

The ventricular surface of the monkey mediobasal hypothalamus. A scanning electron microscopic study.

The ventricular lining of the infundibular recess of monkey brains of both sexes was investigated with SEM. Based on the distribution patterns of surface profiles regional differences in the tanycytic ependyma are described. Variations in the number of surface profiles were observed in females during the ovarian cycle. These variations may be an indication not only of absorptive and/or secretory activities, but may also be related to cell membrane redistribution and membrane turnover in dependence of endocrine factors. In the males such variations were not registered. An essental sexual dimorphism does not seem to exist in the tanycytic ependyma of the monkey, only the reaction pattern is different. Supraependymal macrophages (SEC) were more numerous in the ovulating females than in the males or menstruating females. In addition to these SEC some monkeys had a second SEC type which was arranged in sheets. These are interpreted to be glioses. A variable number of axons can also be found in the lower regions of the infundibular recess. Their morphology suggests the presence of several types of axons, but they do not appear to constitute an organized network. No significant sexual differences were registered in relation to the axons.

Animals↗
PubMed1980

Effects of cytochalasin B on the ependyma.

In order to analyse whether or not surface morphology and intracellular skeleton are interdependent, Cytochalasin B (CB), an agent which interferes with microfilaments, was introduced ino the brain ventricular system of adult rats. Following intraventricular application of CB for different periods of time (up to 6h) the animals were sacrificed and the ventricular wall examined with both transmission and scanning electron microscopes. The first signs of cellular alteration after short periods of CB application were an increase in the number of microfilaments within the cytoplasm and the appearance of a multitude of small knobs on the surface of the cilia of the cuboidal ependymal cells, whereas the tanycytes exhibited extensive blebbing at their apical poles. When the duration of CB perfusion was lengthened, entire ciliated cells became rounded up and were loosened from the epithelium, especially in the transition zone of the third ventricle where the ependyma is composed of both tanycytes and ciliated cells. The significance of the CB-induced changes in the ependyma are discussed in relation to the ependymal surface modifications seen under physiological and other experimental conditions.

Animals↗
PubMed1980

Trinitrophenol lesions of the ventricular wall: a SEM-TEM study.

These experiments were performed in order to study the ventricular walls of the brain following more or less extensive lesioning of the ependyma and during the process of repair. Trinitrophenol (TNP, 1% in saline) was injected into the ventricular system of adult rats of both sexes. The animals were fixed for SEM/TEM 26th or 5, 7, 11, 21, 30 and 40d post injection. TNP caused areas of irreversible lesions in ependymal cells but the surrounding unlesioned cells showed no signs of a regenerative reaction. The number of supraependymal cells increased considerably at the sites of lesion, their shapes being markedly different from those of comparable cells in control animals. The subependymal tissue presented spongiosis. After a phase in which the lesioned ventricular surface was covered with abundant cell debris, the subependymal astroglia cell debris, the subependymal astroglia proliferated, producing an extensive layer of cell processes which substituted for the missing ependymal cells. This investigation has given us the opportunity to study the formation and morphological characteristics, particularly as visualized with the SEM, of an experimentally induced gliosis in the ventricular wall of adult rats.

Animals↗
PubMed1980

Reaction of the hypothalamic ventricular lining following systemic administration of MSG.

Monosodium glutamate (MSG) was used to create a lesion in the CNS of the infant rat. Subcutaneous injections of MSG in four day old rat pups caused a high degree of cell necrosis in the arcuate nucleus of the hypothalamus. The tanycytic ependyma overlying this nucleus was examined at different post injection intervals with both the SEM and the TEM. Four hours following treatment the tanycytic cell bodies appear swollen and their apical surfaces have lost most of their microvilli. Within 24 hours the affected ependymal area possesses a dense population of supraependymal cells. During the following days these alterations regress so that by the 14th day of life the ependymal surface of a treated animal is indistinguishable from that of a control animal. The changes taking place in the tanycytes are compared to those occurring in astrocytes within the body of the lesion. The morphological and ultrastructural features of the supraependymal cells are considered in their similarity to those of microglia.

Animals↗
PubMed1976

Morphology and distribution of supraependymal cells in the third ventricle of the albino rat.

The supraependymal cells (SEC) are a normal component of the wall of the cerebral ventricles. In the hypothalamic area of the third ventricle they are restricted, in healthy animals, to the ependymal projection of the hypophyseotropic area. Here the SEC show great polymorphism. In addition to bipolar, multipolar and stellate or spider-like cells, transitional forms between these types can be seen. Their perikarya and processes can either remain at some distance from the ependyma or be in close contact with it. The processes may protrude between the ependymal cells or show surface differentiations that resemble the thin cytoplasmic folds of the mesenchymal wandering cells. Considering this and the variations in the number of cells, for example during the ovarian cycle, the SEC can be interpreted as mesenchymal cells, probably related to microglial cells of the subependymal layer. It is suggested that the SEC have a phagocytotic function and may be involved in the normal renewal of the ependyma. A definitive explanation for the restriction of the SEC to the hypophyseotropic area as well as the elucidation of their function remain to be found.

Animals↗
PubMed1975

Modification by calcium dobesilate of histamine effects on capillary ultrastructure.

The ultrastructure of blood capillaries and venules are studied in rat skin. After i.v. injection of histamine the luminal surface of the endothelial cells show protrusions of variable size. Numerous gaps have been found in the capillary wall, specially in the venules. These alterations are not observed in the animals that were treated with calcium dobesilate before the administration of histamine. In these cases the capillary structure are indistinguishable of the controls. The possible effects of the histamine and calcium dobesilate on the cell coat and cell junctions of the endothelial capillary cells are discussed.

Animals↗