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Biomedical subjects

G Renard

Publications and source records attributed to G Renard.

At least 325 records · Page 18Linked to original sources
PubMedDate not supplied

Expanded polytetrafluoroethylene episcleral implants used as encircling scleral buckling. an experimental and histopathological study.

To investigate tissue changes induced by the implantation of expanded polytetrafluoroethylene (e-PTFE) used as encircling scleral buckling, an experimental and histopathological study was performed in rabbits. The eyes of 12 rabbits were implanted during 20-128 days with e-PTFE episcleral implants. Of these, 8 eyes were uncomplicated and enabled us to perform the histopathological study, 2 others were discarded for too short a time of implantation and, in 2 additional eyes, the episcleral implant was exposed with a wide conjunctival erosion. Surrounding the implant, a constant encapsulation was combined with numerous giant cells, forming a granuloma caused by irregularities of the implant outline. Its porous structure allowed a peripheral colonization by fibrovascular tissue. Scleral thinning and scleral invagination were the main scleral changes. No change of the conjunctiva made us suspect that a granuloma occurred before it was found histologically. The granulomatous changes did not seem to modify the apparently good experimental tolerance of the material after its implantation.

Animals↗
PubMedDate not supplied

Tropoelastin biosynthesis by corneal cells. Epithelial inhibition of keratocyte tropoelastin biosynthesis.

The vertebrate cornea is an avascular tissue and does not contain elastic fibers. We tested the capacity of corneal epithelial cells and stromal keratocytes to synthesize tropoelastin. Explant cultures and cell cultures were obtained from these two cell types in standard culture conditions. Their elastin-synthetic activity was compared to skin explant cultures and to dermal fibroblast cell cultures. Both corneal cell types synthesized tropoelastin as shown by the incorporation of a radioactive precursor followed by immunoprecipitation of tropoelastin. When serial cultures of keratocytes were tested, tropoelastin biosynthesis strongly increased after the 3rd passage and was at the 9th passage more than the double of that of the first passage. When cocultures were studied with or without cell contact, epithelial cells partially inhibited tropoelastin biosynthesis by keratocytes. This inhibition was somewhat stronger (-36%, p < 0.005) with cell-to-cell contact than keeping separate epithelial cells and keratocytes bathing in the same medium (-18%, p < 0.005). When human skin fibroblasts were substituted for keratocytes with cell-to-cell contact, their tropoelastin biosynthesis was also inhibited by corneal epithelial cells (-42%, p < 0.005), to the same extent as for keratocytes. In Transwell culture, this inhibition was again somewhat lower (-36%, p < 0.005). Some diffusible factor produced by epithelial cells is apparently involved. The epithelial inhibition of tropoelastin biosynthesis by stromal keratocytes might represent one of the mechanisms keeping corneal stroma exempt of elastin fibers.

Cell Communication↗
PubMedDate not supplied

Basal cell carcinomas of the eyelids.

Basal cell carcinomas (BCC) are the more frequent malignant tumors seen in France as in other western countries. They represent 20% of eyelid tumors and 90% of eyelid malignancies. Due to their local growth, problems may arise when treating BCC, and curative exeresis must be the preferred choice each time it is possible. BCC of the eyelids have a high risk of recurrence. Recurrences are more aggressive, infiltrative and destructive and have a considerably poorer rate of cure than primary tumors. Eyelid reconstructions can entail use of complex methods which should only be carried out by a trained ophthalmologist who is also able to treat any associated age-related ocular pathologies. BCC is the most common cause leading to eyelid reconstructive surgery; a surgery which has a triple objective: tumor removal, functionality and an esthetic outcome.

Basal Cell Carcinoma↗
PubMedDate not supplied

Studies on corneal wound healing. Effect of fucose on iodine vapor-burnt rabbit corneas.

Corneal wound healing often leads to the development of scar tissue with loss of transparency. Reconstitution of transparent corneal stroma depends on the regulation of the biosynthetic activities of postlesional keratocytes and also to a large extent on the limitation of matrix degradation, attributed essentially to the upregulation of matrix metalloproteases and especially MMP-9. Using a standardized method for the production of reproducible corneal lesions by burning with iodine vapors, we could show that the local application of 0.5 mg/ml L-fucose reduced significantly MMP-9 upregulation and accelerated the recovery of the epithelial layer of the cornea. The iodine vapor used in the experiments produces a rapid loss of epithelium with no or slight effect below the basement membrane. A relatively rapid regrowth of epithelium was observed. The speed of this reepithelialization was stimulated by the local application of fucose. At 48 h after burn, there was a difference between fucose-treated and control corneas (epithelial thickness was about 50 mum for fucose-treated corneas and 37 microm for control corneas). Culture media of in vivo fucose-treated corneas showed an important decrease of MMP-9 activity (-51%, n = 6, p < 0.01). It appears that the in vivo fucose treatment reduced the MMP-9 activity released in the media. This effect is significant 24 h after iodine vapor burn. In order to study the effect of fucose on normal corneas, it was added to rabbit as well as human cornea explant cultures, and the production and release of MMP-9 was determined by zymography. Fucose at a concentration of 0.5 mg/ml produced a 70% decrease of MMP-9 activity released in the medium by corneal explant cultures. Other mono- and oligosaccharides were also tested. Besides lactose, fucose-rich oligosaccharides also produced significant inhibition. Galactose, melibiose, mannose and glucose were inactive. These results justify the use of fucose for the local treatment of corneal wounds.

Animals↗
PubMedDate not supplied

Ultrasound biomicroscopy of Baikoff anterior chamber phakic intraocular lenses.

BACKGROUND: The purpose of the study was to analyze qualitatively and quantitatively anatomic relationships of anterior chamber Baikoff phakic intraocular lenses (IOL) to the cornea, angle, iris, and lens in myopic eyes. METHODS: Thirteen phakic myopic eyes (-9.00 to -15.00 diopters) corrected by minus power, angle-supported, anterior chamber intraocular lenses of the ZB5M style (Chiron-Domilens), with a mean follow-up of 25 months (range 18 to 36 months), were examined clinically and by ultrasound biomicroscopy. RESULTS: The mean distance (+/- SD) between the central cornea and the IOL was 2.05 +/- 0.18 mm (range 1.8 to 2.47 mm); mean distance between the corneal periphery and the IOL was 1.56 +/- 0.17 mm (range 1.33 to 1.95 mm); and the mean distance between the IOL and the lens was 0.58 +/- 0.12 mm (range 0.48 to 0.81 mm). IOL footplates seemed to be correctly positioned in the angle in all eyes. We observed no goniosynechiae. In six eyes, we found localized posterior indentation of the iris caused by the haptics. Four of these six eyes exhibited oval pupils associated with an oversized IOL. CONCLUSIONS: High frequency ultrasound biomicroscopy can define anatomic relationships of anterior chamber phakic IOLs, and help analyze the mechanisms of corneal and iris complications.

Adult↗
PubMedDate not supplied

[Cost of managing cataracts. Evaluation of traditional hospitalization and ambulatory surgery].

OBJECTIVE: Demonstrate eventual differences and evaluate the medical costs of treatment of a cataract in traditional hospitalisation and out-patient surgical conditions. METHODS: We conducted a study of minimisation costs in 3 ophthalmologic hospital departments. This retrospective study randomly selected the medical files of 250 patients (100 operated in the out-patient surgical department and 150 operated in traditional surgical conditions). Costs were evaluated on direct hospital costs, according to the standard costs method and the method of true costs. RESULTS: The mean total cost of a cataract is of 10,984 F in traditional hospital conditions and of 7,683 F in out-patient surgical conditions. DISCUSSION: In terms of direct hospital costs, treatment of cataracts in out-patient surgery appears more economic compared with traditional surgery. The difference in cost concerned the fixed hospital charges (structures and staff). CONCLUSION: Out-patient surgery will progress in France in the next few years, but traditional hospitalisation will still be required in ophthalmologic practice.

Ambulatory Surgical Procedures↗
PubMedDate not supplied

[Electron microscopic study of the corneal endothelium in 2 cases of keratitis. Herpetic disciform keratitis. Neuroparalystic keratitis with dry keratitis].

Study of corneal endothelium by scanning and transmission electron microscopy in two cases of corneal disease. In one case of herpetic keratitis with stromal oedema, there is no cellular reaction. The endothelium is damaged with cellular necrosis and nucleus irregularity. Intercellular junctions are abnormal. With TEM it is possible to say that there are two layers of cells on some places with cellular necrosis. In one case of corneal dryness with lesions of corneal anaesthesia the cells are very damaged and a retrocorneal membrane if formed by many layers of cells. The intercellular junctions are almost normal.

Cornea↗
PubMedDate not supplied

[Organotypic culture of the rabbit cornea. Evaluation of its morphologic criteria].

A report of a study on the cellular and tissue morphology of organotypic cultures of rabbit cornea using a method conforming to physiological conditions. The results demonstrate that in the first few hours there exist structural changes in the tissues as well as on ordinary histology, scanning and electron microscopy. These affect the endothelium primarily, whereas the keratocytes and epithelium seem to be more resistant, the latter having the tendency to invade the surfaces of the explant and to transform itself into fibroblastic cells. Certain reservations should therefore be expressed about the use of these explants, whether they are intended to preserve pathological corneas of different origin, or to be used in transplants.

Animals↗
PubMedDate not supplied

Damage to the corneal endothelium by minus power anterior chamber intraocular lenses.

We present 16 phakic myopic eyes (from -10.00 to -25.00 diopters) corrected by minus power intraocular lenses implanted in the anterior chamber whose corneal endothelium was observed by specular microscopy during a postoperative period from 6 to 18 months. Significant morphologic endothelial changes were noted in three eyes along the border of the lens optic. Around dark zones, which appeared acellular, endothelial cells were enlarged, deformed, and separated. These findings may be produced by intermittent contact between the endothelium and lens. Corneal indentation during specular microscopy occasionally caused a curvilinear reflection which corresponded to the optic border. In three eyes, dark areas without cellular abnormality were observed near the curved edge of the lens. These findings probably resulted from the disturbance of the specular reflection on part of the endothelium due to this edge.

Anterior Chamber↗
PubMedDate not supplied

[Trephination using an Excimer laser].

We compared histologically and ultrastructurally donor buttons and recipient beds trephined mechanically with those trephined by the Excimer laser at 193 nm. The laser allowed for superior cutting precision and perfect centering. This non-contact method obviated the need for any pressure or suction during trephination, thereby eliminating problems associated with distortion of corneal topography. We studied wound healing after penetrating keratoplasty with mechanical and laser trephination in an animal model. The laser did not adversely affect wound healing processes.

Animals↗