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Biomedical subjects

F Becquet

Publications and source records attributed to F Becquet.

31 records · Page 2Linked to original sources
PubMed1997

Flow cytometry in impression cytology specimens. A new method for evaluation of conjunctival inflammation.

PURPOSE: To investigate feasibility and potential uses of flow cytometry in impression cytology as a new procedure to assess and quantify conjunctival inflammation. METHODS: Specimens for cytology were collected by impression from 30 patients with various chronic ocular surface disorders and from 10 normal subjects. Two specimens were obtained in each eye: One was transferred onto a glass slide and processed by immunofluorescence with antibodies to human leukocyte antigen (HLA)-DR antigens; cells from the other were suspended in phosphate-buffered saline for flow cytometry. Monoclonal antibodies to HLA-DR antigens and CD23, the low affinity receptor to immunoglobulin E, were used. RESULTS: Abnormal expression of HLA-DR and CD23 by conjunctival cells was found in 13 of 18 dry eyes and in 20 of 22 eyes with chronic conjunctivitis, whereas specimens remained almost negative (less than 10% of cells were positive) in normal eyes. Percentages of positive cells ranged between 20% and 98% of all conjunctival cells. Correlation between the two methods, immunocytology and flow cytometry, was highly significant (coefficient of correlation 0.77, P = 0.0001). Moreover, HLA-DR positivity, at its strongest intensity, was observed in a minority of cells (1% to 12%), most of which were resident class II-expressing dendritic cells. Percentages of those cells expressing high levels of HLA-DR were 3 +/- 1.2% in normal eyes, 5.8 +/- 4% in dry eyes (P = 0.05), and 5.9 +/- 3.5% in eyes with chronic conjunctivitis (P = 0.02). CONCLUSIONS: Results of this preliminary study confirm that conjunctival epithelial cells may abnormally express inflammatory markers in chronic ocular surface disorders. Development of flow cytometry in analysis of cytologic specimens provides a new, sensitive, and objective tool for exploring conjunctival pathology.

Antibodies, Monoclonal↗
PubMed1996

[Immunophenotype of dendritic cells of the human conjunctiva].

PURPOSE: To examine dendritic cells from human conjunctiva and to characterize their surface markers immunologically. METHODS: Conjunctival cells were isolated by conjunctival impression cytology from 150 patients: controls (65 patients, 126 eyes) or with various chronic inflammatory conditions (85 patients, 160 eyes); and by conjunctival biopsies from 25 patients: controls (10 patients) or treated topically for primary open angle glaucoma (15 patients). Immunostaining was performed using antibodies to investigate expression of 21 different membrane markers relevant to immunologic functions of dendritic cells. RESULTS: Conjunctival dendritic cells exhibited surface markers both in normal and inflammatory conditions: class II antigens HLA-DR and HLA-DQ, CD1a, vimentin, CD11a and CD18 (LFA-1), CD22, CD45RO and CD50. Some markers were more occasionally found CD4, CD11b, CD29, CD32, CD45RA and CD54, others being almost totally absent. Conjunctival inflammation induced the migration of dendritic cells from the stroma to the epithelium and thus increased their density. CONCLUSION: We conclude that conjunctival dendritic cells show common immunophenotypic features with those of other nonlymphoid tissues. Thus, conjunctival dendritic cells may be important in the immune regulation of the anterior segment.

Adult↗
PubMed1994

Nitric oxide decreases in vitro phagocytosis of photoreceptor outer segments by bovine retinal pigmented epithelial cells.

The presence of nitric oxide synthase (NOS) in the retina, the constitutive isoform in photoreceptor outer segments and the inducible form in retinal pigmented epithelial (RPE) cells, has been demonstrated, but the role of the free radical NO produced, remains unknown. We have investigated the effect of NO on the process of rod outer segment (ROS) phagocytosis. Using an in vitro assay for phagocytosis in primary cultures of bovine RPE cells, we demonstrate that NO released by SIN-1 (3-morpholinosydnonimine) in the culture medium inhibits the phagocytosis of ROS. Furthermore, endogenous NO, produced by RPE cells cotreated with lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma), is also able to decrease RPE cell phagocytic activity. This effect depends upon the continuous presence of NO during the assay and is abolished by the scavenging of NO by hemoglobin or by the inhibition of NO synthase activity by L-arginine analog, NG-monomethyl-L-arginine. Pretreatment of ROS with SIN-1 failed to impair subsequent phagocytosis, demonstrating that NO directly affects the RPE cells ability to phagocytose ROS. The inhibitory effect of NO is cGMP independent, since 8-bromo-cGMP does not modify this process. This decrease of ROS phagocytosis by RPE cells caused by NO may occur as a result of retinal inflammation, and could lead to photoreceptor degeneration.

Animals↗
PubMed1994

Superoxide inhibits proliferation and phagocytic internalization of photoreceptor outer segments by bovine retinal pigment epithelium in vitro.

Experiments were performed to investigate the effect of free radical damage on two aspects of retinal pigmented epithelium (RPE) metabolism, namely, proliferation and phagocytosis. Bovine RPE cells were maintained in monolayer cultures, either as passaged (for proliferation and lysosomal activity assays) or primary cultures (for phagocytosis measurements). Free radicals (superoxide anions) were generated by a xanthine oxidase (XO)-hypoxanthine (HX) reaction. Total phagocytosis (binding plus ingestion of rod outer segments (ROS)) was quantitated by radioimmunoassay using a specific anti-opsin antibody and iodinated secondary antibody. In some cases, agents with known or possible protective influences against oxidative damage, i.e., superoxide dismutase (SOD), vitamin E, and basic fibroblast growth factor (bFGF), were tested for their activity in this model system. RPE cell proliferation was inhibited in a HX-XO dose-dependent manner, in the absence of cell toxicity. Modifications of cell morphology were also noticed. Either simultaneous exposure of RPE cells to ROS membranes and HX-XO or pretreatment of ROS membranes with HX-XO prior to their addition to RPE monolayers led to a statistically significant 20-30% decrease in phagocytosis relative to control values. This decrease was essentially observed in the binding phase of phagocytosis, indicating damage to ROS surface molecules as the primary event. Addition of SOD or vitamin E prevented this loss of phagocytic activity, whereas bFGF had no effect. Superoxide radicals did not, however, affect phagocytosis when RPE cells were exposed to them alone, prior to incubation with ROS; nor did they alter a later stage in the phagocytic process, acid phosphatase activity. This tissue culture model represents a convenient system for analyzing free radical damage in different aspects of RPE-photoreceptor behavior and may be useful in studying this phenomenon in several retinal disorders.

Acid Phosphatase↗
PubMed1993

Protection against light-induced retinal degeneration by an inhibitor of NO synthase.

The existence of nitric oxide synthase (NOS) in retinal rod outer segments and pigmented epithelial cells suggests that NO in excess could impair the interaction between these cells, resulting in photoreceptor degeneration. To test this hypothesis, NG-nitro-L-arginine methyl ester (L-NAME), an NOS inhibitor, was intraperitoneally injected daily into rats subjected to constant illumination for 7 days in order to destroy their photoreceptors. By measuring photoreceptor nuclear layer thicknesses, we found that L-NAME partially protects (by up to 35%) against the degeneration of photoreceptors and acts to maintain their organization. Thus NO may be involved in the process by which photoreceptor degeneration results from constant illumination of the retina.

Amino Acid Oxidoreductases↗
PubMed1993

Differential regulation of inducible nitric oxide synthase by fibroblast growth factors and transforming growth factor beta in bovine retinal pigmented epithelial cells: inverse correlation with cellular proliferation.

Bovine retinal pigmented epithelial (RPE) cells express, after activation with interferon gamma (IFN-gamma) and lipopolysaccharide (LPS), an inducible nitric oxide synthase (NOS). Experiments were done to investigate the effects of the transforming growth factor beta 1, epidermal growth factor, and fibroblast growth factors (FGFs), which are abundant in the retina, on NOS activity. Transforming growth factor beta 1 slightly increases the production of nitrite, an oxidation product of NO, induced by LPS plus IFN-gamma, whereas acidic and basic FGFs markedly inhibit the nitrite release due to LPS/IFN-gamma in a concentration-dependent manner, and epidermal growth factor did not modify LPS/IFN-gamma-induced NOS activity. The growth factors alone did not stimulate nitrite release. We have attempted to elucidate the mechanism of FGF inhibition. Results with heparin, suramin, and tyrphostin suggest involvement of the high-affinity receptor for FGF in its inhibition of LPS/IFN-gamma-stimulated NOS activity. Continued stimulation of RPE cells with LPS/IFN-gamma was essential for the induction of NO synthesis, and maximal inhibition was obtained when FGF was present during stimulation with LPS/IFN-gamma, suggesting that FGF inhibits NOS induction. Furthermore, an antiproliferative action of NO was demonstrated by an inverse correlation between the amounts of nitrite or citrulline produced in response to different stimuli (LPS/IFN-gamma or LPS/IFN-gamma with growth factors) and the level of cellular proliferation. Similar inhibition of growth was obtained when RPE cells were incubated with an NO donor, sydnonimide. Because NO acts as a cytotoxic compound in the retina, FGF, by inhibiting the induction of NOS in RPE cells, may have beneficial effects in protecting the retina from cytokine and endotoxin-mediated tissue damage.

Amino Acid Oxidoreductases↗
PubMedDate not supplied

Nitric oxide in the eye: multifaceted roles and diverse outcomes.

Recent works have highlighted the role of nitric oxide in a wide array of disease entities, including septic shock, hypertension, cerebral ischemia, and chronic degenerative diseases of the nervous system. The functions of nitric oxide appear very diverse, having actions on vascular tone, neurotransmission, immune cytotoxicity, and many others. Nitric oxide is an important mediator of homeostatic processes in the eye, such as regulation of aqueous humor dynamics, retinal neurotransmission and phototransduction. Changes in its generation or actions could contribute to pathological states such as inflammatory diseases (uveitis, retinitis) or degenerative diseases (glaucoma, retinal degeneration). Localization in the eye and biochemical characteristics of nitric oxide will be reviewed. A better understanding of the nitric oxide pathway will be the key to the development of new approaches to the management and treatment of various ocular diseases.

Administration, Topical↗
PubMedDate not supplied

Management of delayed massive suprachoroidal hemorrhage: a clinical retrospective study.

Suprachoroidal hemorrhages, both expulsive and delayed non-expulsive, are among the most devastating complications of intraocular surgery. We reviewed the charts of 13 patients with a delayed non-expulsive suprachoroidal hemorrhage (DNSCH) after cataract extraction (3 patients), glaucoma filtering surgery (6 patients), penetrating keratoplasty (3 patients), or vitrectomy (1 patient). All had large hemorrhagic choroidal detachments with nine eyes presenting kissing choroidal detachment, five eyes with associated retinal detachment, and one eye with intravitreous hemorrhage. All patients were treated with systemic corticosteroids before surgery. Eleven eyes underwent anterior drainage sclerotomy, followed by SF6 gas injection in eight eyes, and pars plana vitrectomy with silicon oil tamponade in three eyes. Mean follow-up was 22 months. These procedures gave good anatomical results in eleven cases and good visual results in nine. The results suggest that not all DNSCH need to be drained surgically but that, when surgical drainage is indicated, the use of gas to maintain internal tamponade appears to be beneficial.

Adolescent↗