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Biomedical subjects

J V Forrester

Publications and source records attributed to J V Forrester.

At least 109 records · Page 6Linked to original sources
PubMed1996

Prostaglandin E2 and monoclonal antibody to lymphocyte function-associated antigen-1 differentially inhibit migration of T lymphocytes across microvascular retinal endothelial cells in rat.

Lymphocyte-transendothelial cell migration is a complex event, and although much is known about the receptor-ligand interactions involved, little is understood about the intracellular events which accompany these interactions, or their regulation by inflammatory mediators. In this study we have shown that activation of T lymphocytes increased the proportion of cells migrating across monolayers of cultured retinal microvascular endothelial cells by both lymphocyte function-associated antigen-1 (LFA-1)-dependent and LFA-1-independent mechanisms. In preliminary experiments, it was found that activation of T cells with mitogens such as concanavalin (Con A) increased significantly T-cell migration across the endothelial monolayers. In contrast, activation of the endothelial monolayer with interferon-gamma (IFN-gamma) (96 hr) had no effect on transendothelial migration. Investigation of adhesion molecule requirements for transendothelial migration indicated that LFA-1 was necessary (P < 0.02) but that intracellular adhesion molecule-1 did not appear to be involved. Investigation of the role of prostaglandins in transendothelial migration revealed that, while prostaglandin E2 (PGE2) did not affect adhesion molecule expression on endothelial cells or T cells, treatment of either cell significantly blocked transendothelial migration (P < 0.05). Pretreatment with PGE2 combined with LFA-1 blockade had an additive effect on inhibition of T-cell transendothelial migration, indicating that two independent mechanisms were operative. PGE2 also had a direct inhibitory effect on T-cell adhesion to the endothelium. These results highlight the importance of considering non-adhesion receptor-mediated mechanisms, perhaps involving cytoskeletal and/or motility, in the migration of T cells across endothelial monolayers.

Animals↗
PubMed1996

Orientation and directed migration of cultured corneal epithelial cells in small electric fields are serum dependent.

Reorientation and migration of cultured bovine corneal epithelial cells (CECs) in an electric field were studied. Electric field application was designed to model the laterally directed, steady direct current electric fields which arise in an injured corneal epithelium. Single cells cultured in media containing 10% foetal bovine serum showed significant galvanotropism, reorienting to lie perpendicular to electric field vector with a threshold field strength of less than 100 mV/mm. Cells cultured in serum-free medium showed no reorientation until 250 mV/mm. Addition of EGF, bFGF or TGF-beta 1 singly or in combination to serum free medium significantly restored the reorientation response at low field strengths. Both the mean translocation rate and directedness of cell migration were serum dependent. Cultured in medium with serum or serum plus added EGF, single cells showed obvious cathodal migration at 100 mV/mm. Increasing electric field strength enhanced the cathodal directedness of single cell migration. Supplementing serum free medium with growth factors restored the cathodal directed migration of single cells and highest directedness was found for the combination of EGF and TGF-beta 1. Corneal epithelial sheets also migrated towards the cathode in electric fields. Serum or individual growth factors stimulated CEC motility (randomly directed). Applied fields did not further augment migration rates but added a vector to stimulated migration. Electric fields which are present in wounded cornea interact with other environmental factors and may impinge on CECs migration during wound healing. Therapies which combine the application of growth factors and electric fields may be useful clinically.

Animals↗
PubMed1996

Directed migration of corneal epithelial sheets in physiological electric fields.

PURPOSE: To characterize the effects of small applied electric fields (EFs) (100 to 250 mV/ mm) on cultured bovine corneal epithelial cell (CEC) sheets and to determine how EFs interact with other environmental cues in directing CEC sheet migration. METHODS: Primary cultures of bovine CECs were exposed to EFs in medium with or without serum, epithelial growth factor, basic fibroblast growth factor, or transforming growth factor-beta 1. Cell sheet migration was traced using an image analyzer. RESULTS: Cell sheets migrated toward the cathode (negative pole). The directional migration was voltage dependent, and, at low field strength (up to 200 mV/mm), it required serum in the medium. Sheets showed no migration responses up to 200 mV/mm in serum-free medium, whereas those in medium with serum showed evident migration toward the cathode, at an average rate of approximately 15 microns/h (n = 15 approximately 20) at 150 mV/mm. When serum was present, the threshold was below 100 mV/mm, very close to the measured wound field strength (approximately 42 mV/mm). After supplementing serum-free medium with individual growth factors or with combinations of epithelial growth factor, basic fibroblast growth factor, and transforming growth factor-beta 1, significant restoration of cathode-directed migration occurred at 150 mV/ mm. Lamellipodia were abundant at the leading edges of migrating sheets, extending the area of sheets covered. The extension of cell membranes toward the cathode was more prominent in cell sheets than in single cells. CONCLUSIONS: The endogenous EFs generated by wounded cornea could play an important role by interacting with other environmental factors to promote changes in shape and in directed migration of CEC sheets.

Animals↗
PubMed1995

Quantitative image analysis of macular drusen from fundus photographs and scanning laser ophthalmoscope images.

Drusen are common features in the ageing macula and are associated with exudative age-related macular degeneration (ARMD). They appear as characteristic structures in indirect mode infrared scanning laser ophthalmoscope (SLO) images. Manual counting of drusen area in SLO images has shown no significant difference from that in standard fundus photographs in 6 eyes of 5 patients (p > 0.5). Computerised image processing techniques have been applied to digitised colour fundus photographs and indirect mode images to quantify the area of the macula affected by drusen in an automated fashion. Application of these methods may permit objective and repeatable assessment of the natural history of macular drusen. For a specificity of 90%, a sensitivity of 60% for colour fundus photographs and 35% for SLO images has been achieved, when compared with manual counting. The colour fundus photograph method also showed superior reproducibility compared with the SLO technique.

Aged↗
PubMed1995

Fundus imaging in patients with cataract: role for a variable wavelength scanning laser ophthalmoscope.

AIMS: An investigation was carried out to compare the image quality of the ocular fundus obtained clinically, photographically, and with the scanning laser ophthalmoscope (SLO) at visible and infrared wavelengths in patients with significant cataract. METHODS: Nineteen patients admitted for routine cataract extraction were examined clinically by two independent observers to ascertain cataract type and clarity of fundus view with an indirect ophthalmoscope. Fundus photography and both confocal and direct (non-confocal) SLO imaging at 590 nm, 670 nm, and 830 nm were carried out after pupillary dilatation. Images obtained were graded independently using a recognised grading system. RESULTS: Quality of SLO images appeared to be superior to indirect ophthalmoscopy (p < 0.01) and fundus photography (p < 0.001) when graded subjectively. Quantitative analysis of contrast of retinal vessels demonstrated significantly higher contrast for the SLO compared with digitised fundus photographs at all wavelengths tested (p < 0.001), with highest contrast at 590 nm. Use of a confocal aperture significantly improved vessel contrast but may reduce overall image intensity. CONCLUSIONS: Scanning laser ophthalmoscopy may offer a method to observe and record fine fundus detail in patients who have marked cataract.

Cataract↗
PubMed1995

Flow cytometric identification of a minority population of MHC class II positive cells in the normal rat retina distinct from CD45lowCD11b/c+CD4low parenchymal microglia.

AIMS: This study aimed to isolate and classify by flow cytometry, the cell surface phenotype of microglia in the normal rat retina with a view to identifying putative antigen presenting cells (APC) within the retina, which has to date not been possible by immunohistochemistry. METHODS: Normal rat retinal microglia were isolated and classified using a modification of an isolation technique employing graduated Percoll density gradient cell separation and flow cytometric phenotypic criteria used for CNS microglia. RESULTS: Retinal microglia can be defined by flow cytometry on the basis of their CD45lowCD11b/c+CD4low cell surface expression. Constitutive MHC class II expression in the normal rat retina was confined almost exclusively to a very minor population of cells expressing neither low (microglia) nor high levels of CD45. Three colour flow cytometric analysis confirmed that these MHC class II positive cells were ED2+. CONCLUSIONS: Using this sensitive isolation technique we have identified the cell surface characteristics of ramified, resident microglia, and found that they do not constitutively express MHC class II. There is, however, constitutive MHC class II expression on a phenotypically distinct population of cells (CD45low/highED2+). We propose these cells are the counterpart of the perivascular macrophages found in the CNS which present antigen to extravasating T cells, although their exact retinal location can only be confirmed by immunohistochemical analysis. The role of parenchymal microglia as APC remains undefined. Future isolation of microglia and putative perivascular cells using this technique will help identify the role these cells play in the initiation and perpetuation of immune responses within the retina.

Animals↗
PubMed1995

Peripheral CD25 positive T lymphocytes with biased T cell receptor Vbeta gene usage in autoimmune endogenous posterior uveitis.

Aims-To determine T cell receptor (TCR) Vbeta gene usage in peripheral blood T lymphocytes of patients with endogenous posterior uveitis (EPU). If biased TCR variable (V) gene usage occurs in this autoimmune disease, it should be detectable in immune activated peripheral blood T cells in vivo.Methods-Relative proportions of each Vbeta gene family expressed in total peripheral blood lymphocytes (PBL) and in vivo activated (CD25+) T cells from patients with EPU and controls were determined using the anchored polymerase chain reaction (anchored PCR) in conjunction with a novel hybridisation assay. The TCR Vbeta repertoires seen in these cell populations were then compared.Results-Vbeta1 usage within the CD25+ lymphocytes of patients with EPU was substantially elevated (mean +/- SD 15 +/-9%) compared with control CD25+ cells (3.3 +/-2.4%).Conclusions-By contrasting the repertoires of these cell populations, biased TCR Vbeta gene usage was detected in patients with EPU, namely increased usage of Vbeta1 in CD25+ T cells from peripheral blood of these patients. This approach of directly analysing the activated T cells in blood, using bulk PBL as an internal control, has wide applicability where specific T cell subpopulations are thought to play an important aetiopathological role.

Journal Article↗
PubMed1995

TGF-beta and IL-1 beta act in synergy to enhance IL-6 and IL-8 mRNA levels and IL-6 production by human retinal pigment epithelial cells.

Cytokines produced by human retinal pigment epithelial (RPE) cells may function as important regulators of intraocular inflammation. We investigated the effect of transforming growth factor-beta (TGF-beta) on interleukin-1 beta (IL-1 beta) induction of IL-6 and IL-8 mRNA levels and protein production by human RPE cells. Both TGF-beta and IL-1 beta alone induce IL-6 mRNA and IL-6 production in human RPE cells and synergize to enhance IL-6 mRNA levels and IL-6 production over a range of TGF-beta (0.1-10 ng/ml) and IL-1 beta concentrations (5-500 U/ml). TGF-beta was also found to enhance IL-1 beta induction of IL-8 mRNA levels at lower IL-1 beta concentrations (50 U/ml) but had no effect at higher IL-1 beta concentrations (500 U/ml). However, TGF-beta had no synergistic effect on IL-1 beta induction of IL-8 secretion. These results suggest that expression of IL-6 and IL-8 in human RPE cells is regulated by different transcriptional and translational mechanisms, and that RPE cells are important regulators of cytokine production within the ocular microenvironment.

Adult↗
PubMed1994

Immunomodulation of experimental autoimmune uveoretinitis: a model of tolerance induction with retinal antigens.

Experimental autoimmune uveoretinitis (EAU) is a CD4+ T-lymphocyte mediated inflammation of the uveal tract and retina. As a model of human posterior uveitis it permits further understanding of the underlying immunopathogenesis of uveitis. It also allows for preclinical trials of immunosuppressive therapies and in vivo assessment of alternative strategies for immunointervention. This review highlights possible immunostrategic modalities which prevent the initiation or perpetuation of the immune response, and in particular reports on the novel effect of intranasal induction of tolerance with retinal antigens, prior to immunisation with retinal antigens. The mechanisms and potential application of this 'natural' method of immunosuppression in the treatment of autoimmune disease are discussed.

Adjuvants, Immunologic↗
PubMed1994

Performance measurements of an infrared digital scanning laser ophthalmoscope.

Direct digital acquisition of images using a scanning laser ophthalmoscope (SLO) offers several advantages over the conventional fundus camera; in particular, the ability to produce tomographic images using a confocal aperture. This note describes measurements of the performance of an SLO. Spatial resolution, measured by the modulation transfer function, MTF, was shown to be worse along the direction of scan. As expected, image uniformity was good, with a coefficient of variation of 1.9%. While the effect of using a 100 microns diameter confocal aperture instead of one with a 400 microns diameter was to reduce slice thickness from 2600 microns to 975 microns, image intensity was reduced by a factor of 30.

Humans↗