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Biomedical subjects

G Renard

Publications and source records attributed to G Renard.

At least 271 records · Page 15Linked to original sources
PubMed1978

Ultrastructural study of the cornea in the chick embryo.

The study of the development of the cornea in the chick embryo by transmission and scanning electron microscopy allows us to observe the differences between the aspect of thin sections and the surface of the cells. When studied with the T.E.M. both endothelium and epithelium have a rather normal and mature aspects on the 9th day of development. Observed with the S.E.M., the aspect of the surface of the epithelium becomes mature no earlier than on the 19th day, whereas the development of the endothelium is completed only after hatching. The development of apical junctional complexes occurs at a later stage in the organisation of the endothelial layer.

Animals↗
PubMed1978

Endothelial cell junctions in the ciliary body microvasculature. A freeze-fracture study in the rabbit.

Endothelial cells of the microvasculature (arterioles, fenestrated capillaries, and small venules) of the rabbit ciliary body have been examined in freeze-fracture replicas in ultrahigh vacuum and at very low temperatures, with special regard to their junctional boundaries. The junctional complexes of fenestrated capillaries and venular endothelium are discontinuous and do not seal the interendothelial clefts. They cannot be compared with zonulae occludentes or tight junctions, while the junctions in the arteriolar endothelium are continuous and well organized, suggesting a very low degree of paracellular permeability. It would be of interest to know if these structural differences at the junctional level in each segment of the microvasculature correspond to different paracellular permeability properties.

Animals↗
PubMed1978

Hyperacute form of experimental autoimmune uveo-retinitis in Lewis rats; electron microscopic study.

One systemic injection of retinal tissue or extract mixed with Freund's complete adjuvant induces uveo-retinitis in several animal species: guinea pig [6], rabbit [5, 7], monkey [4] and rat [8]. Rod outer segments may be used as the pathogenic antigenic preparation [1, 3, 9]. This study reports on the conditions of induction of experimental autoimmune uveo-retinitis (EAU) in rats (susceptible strains of rats, optimal doses of antigen and adjuvant) and the histopathological features of the lesions in the early stages of the disease. In several species one systemic injection of retinal tissue or extract mixed with Freund's complete adjuvant induces an ocular inflammatory disease, whose main features are an inflammatory infiltration of the uvea and a destruction of the external layers of the retina. With adequate doses of guinea pig retinal extract and adjuvant, the disease was induced in all cases in albino rats of the Lewis strain. The vascular and tissular lesions, and the infiltrates with a predominance of PMN's and basophils seem to be the result of immune complexe deposition.

Animals↗
PubMed1978

Corneal changes due to alkali burns.

Rabbit corneal epithelium and endothelium were destroyed in vivo with 0.5 normal sodium hydroxide applied to the anterior surface of the cornea for 1 minute. Specimens were studied by transmission and scanning electron microscopy. Cellular necrosis is intense during the first day and healing begins on the third day on both surfaces of the cornea. The epithelial side is covered with new cells in 12 days and the eptihelium is normal on the 21st day, but there is a transformation of part of the corneal epithelium by conjunctival epithelium. On the endothelial side, healing is very slow and for this there seems to be two reasons: (1) Persistent cellular necrosis, (2) Inflammatory reaction which disorganizes the regenerating process. The overstimulation caused by this slow cicatrization leads to the formation of a retrocorneal membrane similar to those observed in human pathology.

Animals↗
PubMed1977

Ultrastructure of the blood-aqueous barrier in normal condition and after paracentesis A freeze-fracture study in the rabbit.

There is in the ciliary epithelium a barrier which prevents the passage of plasma proteins into the posterior chamber of the eye. The anatomical site of this blood-aqueous barrier is at the zonulae occludentes (tight junctions) located between the lateral plasma-membranes of the nonpigmented epithelial cells. Using the freeze-fracture technique we have studied these junctions in the pars plicata. As in many epithelia, they are formed by an anastomosing network of ridges on the fracture PF face and by a complementary set of furrows on the fracture EF face of plasma membranes. Features of these junctions are the presence of frequent parallel and closely associated double or triple ridges, and a few small gap junctions, associated with tight junctional elements of the zonulae occludentes. We also show that the number of junctional strands (ridges and furrows from apex to base) varies from a few strands to about 15, according to their position around the nonpigmented epithelial cells. These observations suggest that the rabbit's ciliary epithelium is to be classified among the 'tight' or 'very tight' epithelia (Claude and Goodenough, 1973). After paracentesis, we observed no breakdown of the zonulae occludentes. This supports the hypothesis that the site of leakage of the plasma proteins is elsewhere than ciliary epithelium.

Animals↗
PubMed1977

The action of sensitized lymphocytes on the corneal endothelium of rabbits.

A host versus graft reaction is induced by the injection of sensitized lymphocytes into the anterior chamber of rabbit eyes. The reaction of these lymphocytes against the corneal endothelium is studied with S.E.M. and T.E.M. On the first and second days the transformation of lymphocytes into active cells with uropods is observed. These immunologic cells destroy the endothelium, but the endothelial cells regenerate quickly. On the sixth day there appear macrophages coming from the host, indicating that the lesions are being cleaned. These experiments present a good model for the study of the interaction between immunologic cells and an organized cellular structure.

Animals↗