PubMed Health⌕ Search

Biomedical subjects

J V Forrester

Publications and source records attributed to J V Forrester.

At least 91 records · Page 5Linked to original sources
PubMed1998

In vivo cell tracking by scanning laser ophthalmoscopy: quantification of leukocyte kinetics.

PURPOSE: To image peripheral blood leukocyte traffic in the normal retinal and choroidal vasculature and to quantify the differences in the circulation dynamics between normal and concanavalin A (ConA)-activated leukocytes. METHODS: Normal or ConA-activated splenocytes were fluorescently labeled in vitro with 6-carboxyfluorescein diacetate (CFDA) and reinfused in vivo where they were tracked in the retinal and choroidal circulations of syngeneic rats by means of a scanning laser ophthalmoscope (SLO). Simultaneous digital and video images were captured for as long as 30 minutes, and the initial 15 seconds of image sequences and leukocyte dynamics were analyzed from digitized images by recording the velocity of trafficking cells and the number of stationary cells that accumulated with time, using a customized software package. RESULTS: Mean velocity (+/-SD) was 29.8 +/- 15.3 mm/sec in the retinal arteries, 14.7 +/- 7.2 mm/sec in the retinal veins, and 3.0 +/- 3.6 mm/sec in the retinal capillaries. Mean velocity in the choroidal vessels was 6.1 +/- 6.0 mm/sec. No significant difference in leukocyte velocity was found between activated and normal leukocytes in any of the vessel systems. However, activated leukocytes were observed to accumulate more within the choroidal vasculature (P < 0.001) and the retinal capillaries (P < 0.001) than in control animals, but not in larger retinal vessels. CONCLUSIONS: A technique to measure the kinetics of circulating leukocytes in vivo has been developed. Although leukocyte activation itself is insufficient to cause slowing of leukocyte velocity, the data indicate that leukocyte adherence to endothelium can be induced in the absence of local or systemic activating stimuli.

Animals↗
PubMed1997

Nitric oxide accelerates the onset and increases the severity of experimental autoimmune uveoretinitis through an IFN-gamma-dependent mechanism.

The production of large amounts of nitric oxide (NO) by inducible nitric oxide synthase (iNOS) has been described as a double-edged sword eliciting pro- or anti-inflammatory effects in different immune situations. Our aim, therefore, was to investigate its role in experimental autoimmune uveoretinitis (EAU), a model of ocular inflammation, induced in the Lewis rat following a single footpad injection of retinal Ags. iNOS enzyme was not detected in the normal Lewis rat eye, but was strongly expressed by infiltrating ED1+ macrophages during the acute inflammatory stages of EAU. Treating immunized animals with L-arginine increased urinary NO metabolite (NOx) levels, accelerated the inflammatory response, and increased disease severity, whereas treatment with the NOS inhibitor, N(G)-nitro-L-arginine methyl ester, reduced NOx excretion, delayed the onset, and reduced the clinical signs of EAU. Reverse transcription-PCR analysis of ocular tissue from untreated and treated animals detected iNOS mRNA at all stages of disease, and expression was up-regulated during peak disease. L-arginine treatment enhanced cytokine mRNA expression, particularly of IFN-gamma, which was detected earlier than in control animals, corresponding with the more rapid onset of disease and increased disease severity observed in this group. N(G)-nitro-L-arginine methyl ester had little or no effect on iNOS or inflammatory cytokine mRNA expression. These results suggest NO is central to the pathogenesis of EAU and highlight the importance of the macrophage as an effector cell in what is considered a CD4+ T cell-dependent disease. Furthermore, this study demonstrates the therapeutic potential of NOS inhibitors in the treatment of inflammatory and autoimmune mediated disease.

Animals↗
PubMed1997

Soluble leucocyte adhesion molecules in diabetic retinopathy stimulate retinal capillary endothelial cell migration.

Diabetic retinal neovascularisation is considered to be a consequence of retinal ischaemia caused by capillary occlusion. Capillary occlusion is the result of microvascular thrombi in which erythrocytes, platelets and leucocytes each may play a role. We investigated the role of leucocytes in this process and the subsequent angiogenic response. We studied the serum levels of the soluble leucocyte adhesion molecules soluble E-Selectin, soluble vascular cell adhesion molecule-1 (sVCAM-1) and soluble intercellular adhesion molecule-1 (sICAM-1) in the serum of 93 patients with insulin-dependent diabetes (IDDM) and varying degrees of retinopathy and 47 healthy age and sex matched control subjects. We also measured the ability of serum to stimulate retinal capillary endothelial cell migration using an assay of angiogenesis in vitro. Soluble E-Selectin and sVCAM-1 levels were raised in all patients with IDDM (p < 0.001; p < 0.001) particularly those with retinopathy (p < 0.001; p < 0.001). Soluble E-Selectin levels were highest in the patients with severe non-proliferative diabetic retinopathy (p < 0.001) and sVCAM-1 levels were highest in patients with proliferative diabetic retinopathy (p < 0.01). In contrast soluble ICAM-1 levels were the same in patients and control subjects (p > 0.05). Soluble E-Selectin levels in diabetic patients were correlated with the level of glycated haemoglobin (p < 0.05). Retinal endothelial cell migration-inducing (ECMI) activity was increased in patients with IDDM (p < 0.01) in particular in those with retinopathy (p < 0.01). Furthermore, in vitro ECMI activity could be blocked by antibodies to sVCAM-1 and sE-Selectin. These data point to a functional role for leucocyte adhesion in the microvasculopathy of diabetic retinopathy and may have implications for the induction of retinal angiogenesis.

Adult↗
PubMed1997

Nasal administration of retinal antigens maintains immunosuppression of uveoretinitis in cyclosporin-A-treated Lewis rats: future treatment of endogenous posterior uveoretinitis?

PURPOSE: Current treatment of autoimmune endogenous posterior uveoretinitis (EPU) is limited by drug toxicity, unpredictable relapses on dose reduction and resistance to therapy. Administration of autoantigens via gastrointestinal or respiratory mucosa prior to antigen exposure induces immune hyporesponsiveness (mucosal tolerance) to further antigen sensitisation. In this study we assessed whether mucosal tolerance induction was possible after immunisation with retinal antigens in experimental autoimmune uveoretinitis (EAU) in animals that were short-term immunosuppressed with cyclosporin A (CsA) to determine whether mucosal administration of retinal antigens can maintain immunosuppression in sensitised and immunosuppressed individuals. METHODS: Female Lewis rats were immunised with retinal extract (RE) and then treated as follows. Group 1 received no specific therapy and served as control; group 2 were fed CsA from day 7 to day 20 post-immunisation; group 3 received inhalational tolerance therapy with RE in addition to CsA; tolerance therapy was continued after day 20 when CsA was stopped. Experiments varying the timing and dosage of both tolerising and immunising antigen were also performed, the details of which are described. Incidence, day of onset and clinical activity were recorded and histopathological assessment of intraocular inflammation, in particular the extent of autoimmune target-organ damage, was graded semiquantitatively. RESULTS: Compared with controls and group 2, group 3 showed both a marked delay in disease onset and a reduction in disease severity. This effect was both dose and dose-timing dependent. Tissue damage assessed in terms of preservation of rod outer segments was significantly less in group 3. CONCLUSIONS: The success of combination therapy, clinically, remains unknown at present but these results support continuing present clinical trials of mucosal tolerance therapy and in particular have future implications for either maintaining or inducing immunosuppression in autoimmune diseases in combination with present immunosuppressive therapies.

Administration, Intranasal↗
PubMed1997

A fully automated comparative microaneurysm digital detection system.

A fully automated digital image processing system, which provides an objective and repeatable way to quantify microaneurysms in digitised fluorescein angiograms, has been developed. The automated computer processing includes registration of same-eye retinal images for serial studies, cutting of regions-of-interest centred on the fovea, the detection of microaneurysms and the comparison of serial images for microaneurysm turnover. The microaneurysm detector was trained against a database of 68 images of patients with diabetes containing 394 true microaneurysms, as identified by an ophthalmologist. The microaneurysm detector achieved 82% sensitivity with 2.0 false-positives per image. An independent test set, comprising 20 images containing 297 true microaneurysms, was used to compare the microaneurysm detector with clinicians. The microaneurysm detector achieved a sensitivity of 82% for 5.7 false-positives per image, whereas the clinician receiver-operator-characteristic (ROC) curve gives 3.2 false-positives per image at a sensitivity of 82%. It is concluded that the computer system can reliably detect microaneurysms. The advantages of the computer system include objectivity, repeatability, speed and full automation.

Aneurysm↗
PubMed1997

Human corneal epithelial cells reorient and migrate cathodally in a small applied electric field.

PURPOSE: To test whether human corneal epithelial cells (HCECs) respond to small applied electric fields (EFs) in a similar manner to bovine corneal epithelial cells (BCECs), the orientation and directed migration in small EFs of both primary cultures and of a human corneal epithelial cell line were quantified. METHODS: Primary cultures of human corneal epithelial cells (PHCECs) and transformed human corneal epithelial cells (THCECs) were exposed to EFs (100 mV/mm-250 mV/mm) in different media. Cell migration was traced using an image analyser. RESULTS: PHCECs and THCECs reoriented and migrated towards the cathode (negative pole) when cultured in small direct current (dc) EFs. Both the reorientation and directional migration were voltage- and serum-dependent, as shown previously for bovine cells. PHCECs and THCECs showed significant perpendicular orientation in EFs at 150 mV/mm in medium with serum, while at the same voltage, no significant orientation was found in serum free medium. PHCECs started to show perpendicular reorientation around 30 min after onset of EF at 150 mV/mm. They showed significant directional migration at 150 mV/mm, with directedness of 0.35 +/- 0.07 and a migration rate of 9.1 +/- 0.7 microns/h (n = 90), both significantly higher than that of cells in serum free medium. Addition of EGF-induced significant reorientation and directional migration of THCECs at 100 mV/mm. Additionally, as for BCECs, which remained viable and responsive to electric fields for at least 75 h at 150 mV/mm, THCECs also remained viable and showed responsiveness during long periods of exposure to EFs (at least 20 h). CONCLUSIONS: Cultured human primary CECs and a human corneal epithelial cell line both responded to small EFs with perpendicular reorientation and cathodally-directed migration. Cell responses were qualitatively similar to those reported previously for bovine CECs. The endogenous EFs generated by wounded cornea may play an important role in promoting cell shape changes and directed migration of CECs during the healing process.

Animals↗
PubMed1997

Photoreceptor rim protein: partial sequences of cDNA show a high degree of similarity to ABC transporters.

PURPOSE: To isolate and sequence cDNA for bovine rim protein, a large membrane-bound glycoprotein found in photoreceptor outer segments. METHODS: Bovine rim protein was N-terminally sequenced (22 residues) and fragments were prepared by partial proteolysis. Two internal sequences of 21 and 18 amino acid residues were obtained from 35 kDa and 32 kDa fragments, respectively. Sense and anti-sense oligonucleotide primers were constructed, based on the peptide sequences derived from the 35 kDa and 32 kDa fragments, respectively, and the polymerase chain reaction (PCR) was used to amplify a 150 bp sequence from bovine retinal cDNA. RESULTS: The amplified sequence coded for the remainder of the peptide sequence determined from the 35 kDa fragment, which was not present in the primer, confirming that it was derived from the rim protein. The 150 bp sequence was translated to give a 50 amino acid peptide. Part of this peptide was compared with Dna sequence databases using the TFastA program, which found 94.6% identity with an EST derived from human retina and 86.1% identity to the mouse abc1 transporter. CONCLUSIONS: It is proposed that rim protein is a member of the ATP transporter family of proteins. It may be involved in transport of molecules involved in visual transduction across the photoreceptor disk membrane.

ATP-Binding Cassette Transporters↗
PubMed1997

Interphotoreceptor retinoid binding protein is a potent tolerogen in Lewis rat: suppression of experimental autoimmune uveoretinitis is retinal antigen specific.

AIMS: Administration of unfractionated retinal antigen(s) (retinal extract, RE) suppresses RE induced experimental autoimmune uveoretinitis (EAU) and offers a potential therapeutic alternative to non-specific immunosuppressive therapies for posterior uveitis and autoimmune diseases. S-Ag and interphotoreceptor retinoid binding protein (IRBP) are two major autoantigens within soluble RE. It was aimed to assess, firstly, as has previously been shown with S-Ag, if IRBP can induce intranasal tolerance and, secondly, the contribution of both these major autoantigens to tolerance induction by whole RE. METHODS: Animals were tolerised by intranasal administration with S-Ag or IRBP, either alone or in combination, or RE before immunisation with either IRBP or RE. Control animals were administered nasally either PBS or MBP. Daily clinical responses were recorded biomicroscopically and histological grades were obtained using a semiquantitative scoring system. Weekly serum antibody levels to retinal antigens were measured by ELISA and delayed hypersensitivity responses (DTH) were assessed by skin reactivity to intradermal inoculation with retinal or non-specific antigens. RESULTS: Microgram doses of IRBP successfully suppressed both clinically and histologically IRBP induced EAU. This suppression was accompanied by reduced antigen specific DTH reactivity but maintained T cell dependent (IgG2a) antibody responses. Furthermore, combined S-Ag and IRBP administration afforded equal suppression of RE induced EAU when compared with RE therapy alone. Suppression of RE induced EAU was not achieved with administration of a non-retinal specific autoantigen, MBP. Although individually, both S-Ag and IRBP suppressed RE induced EAU, whole RE was unable to protect against IRBP induced disease. CONCLUSIONS: Intranasal administration of IRBP suppressed IRBP induced EAU in the Lewis rat. S-Ag and IRBP are the major contributors to the tolerogenicity within RE, despite the known uveogenicity of other retinal antigens within RE and induction of tolerance was retinal antigen specific. Furthermore, suppression induced by single antigen administration is antigen specific although concomitant bystander suppression may also play a role. RE was unable to protect against IRBP induced disease despite tolerogenic levels of antigen within RE. Although this may be due in part to a dose effect of either tolerising or immunising antigen, further investigation into the possible antigen dominance of IRBP or mucosal processing of combinations of antigens is necessary so that the full efficacy of mucosal tolerance therapy can be assessed.

Administration, Intranasal↗
PubMed1997

Imaging of optic nerve head drusen with the scanning laser ophthalmoscope.

BACKGROUND: Optic nerve head drusen may present diagnostic difficulties in cases of disc swelling. Imaging of the nerve in a search for drusen is often inconclusive, especially in children, where drusen may be buried below the surface of the nerve head. METHODS: A small study was carried out using a scanning laser ophthalmoscope (SLO) with an infrared confocal facility to scan deep within optic discs in an attempt to image drusen. RESULTS: The SLO was able to demonstrate superficial and buried drusen (using the infrared confocal facility). The superiority of the SLO over ultrasound in the presence of lens opacity was revealed, as the SLO simultaneously demonstrated both drusen and the associated anomalous disc features which are not detected by ultrasound. CONCLUSION: The SLO can help in the diagnosis of optic disc drusen especially in difficult cases where lens opacity or buried drusen hinders their definitive diagnosis.

Adolescent↗
PubMed1997

Phenotypic analysis of retinal leukocyte infiltration during combined cyclosporin A and nasal antigen administration of retinal antigens: delay and inhibition of macrophage and granulocyte infiltration.

Nasal antigen administration successfully suppresses a model of organ-specific autoimmune disease, experimental autoimmune uveoretinitis (EAU), when administered prior to immunisation. We have previously shown that nasal antigen therapy for active disease or in primed, sensitised animals does not reliably or consistently suppress histological disease. However, when nasal antigen administration is combined with cyclosporin A (CsA) therapy, rod outer segment destruction (target organ) is reduced despite the presence of clinical and histological leukocytic infiltration of the eye. In this study, two colour flow cytometric phenotypic analysis of retinal and choroidal leukocytic infiltration of animals treated with either CsA alone, combined therapy with CsA and inhalational tolerance therapy with retinal antigens or sham treated controls was performed. There was no clinical difference between the two treated groups. Flow cytometric phenotypic analysis was performed in all groups at both maximal clinical disease and during resolution of clinical signs. Although the cell number within the infiltrate was reduced in combined treated group, CD4+ IL-2R+ T cells were still present in large numbers, in contrast to the markedly reduced numbers of ED7+ (macrophages/granulocytes) cells infiltrating during height of disease. In the CsA-nasal antigen treated group, when clinical inflammation had subsided, an increase in both macrophages and granulocyte numbers in the chorioretina was observed. The cell numbers were always less than CsA-only treated animals. Despite the late cellular influx of monocytes/macrophages, rod outer segment (ROS) integrity as determined histologically, was maintained. Nasal antigen administration of retinal antigens in CsA-only treated animals (combined therapy group) protects against target organ damage without inhibiting activated T cell traffic to the eye. These results suggest that recruitment of macrophages to the target tissue is central to autoimmune target organ damage, the mechanisms of which are discussed.

Administration, Intranasal↗
PubMed1996

Regulation of glucose transporters (GLUT-1 and GLUT-3) in human retinal endothelial cells.

The regulation of glucose transporters (GLUT-1 and GLUT-3), in terms of both mRNA and protein, in human retinal endothelial cells was investigated. The cells responded within 1 h of exposure to 5 mM glucose with an increase in the level of GLUT-3 mRNA that was due to an increase in the transcription of the 4.1 kb mRNA of the gene for GLUT-3. In the absence of glucose, the gene for GLUT-1 was not transcribed but the level of GLUT-3 mRNA was increased in these conditions and this was the result of an increase in the transcription of the 4.1 kb mRNA. The level of GLUT-1 and GLUT-3 mRNA was maximal when the cells were exposed to 15 mM glucose. These results are discussed in the light of the glucose regulatory potential of the retinal microvasculature and the implications that this may have for the mechanisms of diabetic retinopathy.

Biological Transport↗
PubMed1996

CD59 and CD48 expressed by rat retinal pigment epithelial cells are major ligands for the CD2-mediated alternative pathway of T cell activation.

The alternative CD2-mediated pathway of T cell activation, which is independent of MHC/peptide recognition by the TCR/CD3 complex, is dependent upon two signals being received by the CD2 molecule. The natural ligand for CD2 is CD58, but controversy exists over alternative or additional ligands that could deliver the second signal in vivo. We have used rat retinal pigment epithelial cells (RPE), which lack temperature-insensitive ligands for CD2 adhesion, to study Ag-independent T cell activation. Rat RPE cells expressed high levels of CD59 and low levels of another potential CD2 ligand, CD48, both in vitro and in the in vivo model of experimental autoimmune uveoretinitis. When increasing numbers of syngeneic T cells were added to microwell cultures of rat RPE cells, the T cells, even in the absence of any exogenous stimulant in the cultures, underwent spontaneous proliferation. This effect required metabolically active RPE cells, and was IL-2 driven and enhanced in the presence of indomethacin. Proliferation was modulated by phosphatidylinositol-phospholipase C treatment of the RPE, and blocked by mAbs to CD59. Ab cross-linking of CD48 but not CD59 on the RPE was found to induce messenger RNA expression for IL-1 beta, which together with constitutively expressed IL-6 are required costimulatory factors for T cell activation through CD2. This is the first demonstration in a fully syngeneic system that bi-directional signaling involving CD59 and CD48 molecules expressed by physiologically normal, nonhematopoietic, cells can trigger T lymphocyte activation and proliferation through autocrine IL-2 production in the absence of Ag.

Animals↗
PubMed1996

Inhibition of tumor necrosis factor activity minimizes target organ damage in experimental autoimmune uveoretinitis despite quantitatively normal activated T cell traffic to the retina.

Recent studies demonstrated that administration of a p55-tumor necrosis factor (TNF) receptor IgG-fusion protein (TNFR-IgG) prevented the clinical onset of experimental autoimmune encephalomyelitis but did not alter the number or tissue distribution of autoantigen-specific CD4+ effector T cells which trafficked into the central nervous system. To determine whether specific target tissues of autoimmune damage remain intact after TNFR-IgG treatment despite the presence of inflammatory cells within the tissues, we examined rats with experimental autoimmune uveoretinitis (EAU), as in this model, the main target of autoreactive CD4+ T cells, the retinal rod outer segments (ROS), can be examined readily by light microscopy. As judged by direct ophthalmoscopy, the onset of inflammation in the anterior chamber of the eye in EAU following administration of TNFR-IgG was delayed by 6 days compared to untreated controls, but the magnitude of the response was only slightly less than controls. Histological examination of the retinae and direct assessment of retinal inflammation revealed a disproportionate sparing of ROS in the TNFR-IgG-treated animals despite a level of retinal inflammation not substantially less than controls in which ROS damage was marked. Analysis of retinal leukocytes by immunofluorescence microscopy and flow cytometry indicated that approximately equal numbers of CD4+ alpha beta TCR+ lymphocytes were present in treated and control retinae, more than 30% of CD4+ cells in both experimental groups expressed the CD25 or MRC OX40 activation markers and most cells, which would include the CD4+ T lymphocytes, were activated as evidenced by MHC class II expression. Fewer activated macrophages and granulocytes were present in the treated retinae, possibly reflecting the lower level of tissue damage and subsequent accumulation of these inflammatory cells. The results demonstrate directly that a tissue specifically targeted for autoimmune destruction can be protected despite the influx of fully activated CD4+ T cells.

Animals↗
PubMed1996

An image-processing strategy for the segmentation and quantification of microaneurysms in fluorescein angiograms of the ocular fundus.

Digital image-processing techniques can provide an objective and highly repeatable way of quantifying retinal pathology. This study describes an image-processing strategy which detects and quantifies microaneurysms present in digitized fluorescein angiograms. After preprocessing stages, a bilinear top-hat transformation and matched filtering are employed to provide an initial segmentation of the images. Thresholding this processed image results in a binary image containing candidate microaneurysms. A novel region-growing algorithm fully delineates each marked object and subsequent analysis of the size, shape, and energy characteristics of each candidate results in the final segmentation of microaneurysms. The technique is assessed by comparing the computer's results with microaneurysm counts carried out by five clinicians, using Receiver Operating Characteristic (ROC) curves. The performance of the automated technique matched that of the clinicians' analyses. This strategy is valuable in providing a way of accurately monitoring the progression of diabetic retinopathy.

Algorithms↗