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Biomedical subjects

D J Coster

Publications and source records attributed to D J Coster.

At least 37 records · Page 2Linked to original sources
PubMed2000

Antimicrobial susceptibility of 19 Australian corneal isolates of Acanthamoeba.

PURPOSE: To determine the in vitro drug susceptibility of Australian corneal isolates of Acanthamoeba and to correlate the results with patient treatment and visual outcome. METHODS: Acanthomoeba isolates were obtained from a reference laboratory Cyst suspensions were prepared from 19 strains and exposed to 10 antimicrobial agents for 7 days. The minimum drug concentrations required to inhibit excystation were determined. Inhibited cells were then plated out to determine minimum cysticidal concentrations. RESULTS: Overall, propamidine proved to be the most active anti-Acanthamoeba agent tested. The disinfectant polyhexamethylene biguanide, either pure or in Baquacil, was also effective. Pentamidine, hexamidine, chlorhexidine and chloroxylenol had intermediate activity, while neomycin, amphotericin B and povidone-iodine had poor activity. There was no clear relationship between in vitro susceptibility and visual outcome. CONCLUSIONS: Propamidine and polyhexamethylene biguanide drops are recommended as initial choices for the treatment of Acanthamoeba keratitis. The variability in the susceptibility to any one agent suggests that individual testing of isolates is necessary to identify the most appropriate treatment. A number of factors influence visual outcome in these cases; further studies are required to resolve the importance or otherwise of in vitro susceptibility.

Acanthamoeba↗
PubMed2000

Current Australian practice in the prevention and management of corneal allograft rejection.

PURPOSE: To determine current practices in the prevention and management of corneal allograft rejection in Australia. METHODS: A questionnaire was circulated to attendees at the 1998 Eye Bank Meeting in Adelaide. Twenty-four responses were received and analysed. RESULTS: All respondents used topical corticosteroids for routine prophylaxis and to treat established rejection episodes. Prednisolone acetate was the most frequently prescribed topical corticosteroid. Systemic non-steroidal immunosuppression was prescribed almost exclusively for high-risk grafts. Seventy-five per cent of surgeons used systemic antiviral agents for the treatment of graft rejection in patients with Herpes simplex keratitis. CONCLUSION: There was a wide variation amongst surgeons in the choice of therapy for routine prophylactic immunosuppression as well as for the treatment of established corneal allograft rejection.

Administration, Topical↗
PubMed2000

Apoptosis is a prominent feature of acute anterior uveitis in the Fischer 344 rat.

AIMS: To examine the hypothesis that apoptosis of infiltrating cells contributes to spontaneous resolution of uveitis in clinically relevant rodent models. METHODS: Experimental melanin induced uveitis (EMIU) was induced in Fischer 344 rats by immunisation with 250 microg bovine ocular melanin. Endotoxin induced uveitis (EIU) was induced by injection of 200 microg Escherichia coli lipopolysaccharide. Formalin fixed, paraffin embedded ocular cross sections were stained by terminal deoxynucleotidyl transferase mediated deoxyuridine triphosphate biotin nick end labelling (TUNEL) to identify apoptotic cells. Indirect immunoperoxidase staining of paraformaldehyde lysine periodate fixed tissue cross sections was used to demonstrate expression of inducible nitric oxide synthase (iNOS). RESULTS: TUNEL positive mononuclear cells were observed in the anterior uvea during both EMIU and EIU at all selected time points. However, whereas the majority of mononuclear cells appeared apoptotic from the outset of disease, neutrophils were notably TUNEL negative at all time points examined. Many infiltrating neutrophils expressed iNOS. CONCLUSION: Apoptosis occurs early in the course of rat EMIU and EIU, and may contribute to resolution of these diseases. In general, infiltrating mononuclear cells die rapidly, while neutrophils survive, producing inducible nitric oxide synthase which may contribute to disease pathogenesis.

Acute Disease↗
PubMed1999

Experimental melanin-induced uveitis in the Fischer 344 rat is inhibited by anti-CD4 monoclonal antibody, but not by mannose-6-phosphate.

Experimental melanin-induced uveitis (EMIU) is a rodent model of acute anterior uveitis which was described in 1993. We investigated strain susceptibility, and age and gender characteristics of the model, undertook histological and immunohistochemical studies to investigate underlying cellular mechanisms, and examined several treatment options. Rats were immunized with bovine ocular melanin (250 microg), and disease was followed by slit lamp examination. Lewis, Fischer 344 and Porton rats were found to be susceptible to EMIU, whereas Wistar-Furth, DA, and Hooded Wistar strains were resistant. EMIU was neither age- nor gender-dependent. In Fischer 344 rats, EMIU was characterized clinically by florid anterior segment inflammation. Histopathological findings included infiltration of ciliary body and iris with mononuclear cells and neutrophils. Both CD4+ and CD8+ T lymphocytes were prominent. Rats were then treated with intraperitoneal injections of anti-CD4, anti-CD8 or irrelevant isotype-matched MoAb on days -3, 0, 3, 6 and 9 with respect to melanin immunization. Incidence of uveitis was significantly reduced in rats treated with a non-depleting cocktail of anti-CD4 MoAbs (P = 0.007), whereas a depleting anti-CD8 antibody had no effect on the disease. Mannose-6-phosphate inhibits lymphocyte migration in some models of T cell-mediated inflammation. This simple sugar was administered to additional rats via intraperitoneal osmotic pumps for 14 days following disease induction, but did not influence the uveitis. We conclude that EMIU is controlled by CD4+ T cells, and disease may be abrogated by treatment with anti-CD4 MoAbs.

Animals↗
PubMed1999

A new model of orthotopic penetrating corneal transplantation in the sheep: graft survival, phenotypes of graft-infiltrating cells and local cytokine production.

BACKGROUND: Orthotopic penetrating keratoplasty in the sheep was developed as an outbred preclinical model to allow correlation of the cellular infiltrate during graft rejection with local production of cytokine mRNA. METHODS: Penetrating corneal autografts and allografts were performed in Merino sheep. Graft outcome was followed at the slit-lamp. Corneal infiltrates were examined by immunoperoxidase staining on postmortem specimens. Cytokine mRNA was detected by polymerase chain reaction. RESULTS: Corneal autografts survived indefinitely. Allografts became vascularized and underwent rejection at a median of 20 days postgraft. Both endothelial and epithelial rejection lines were observed. Immunohistochemical staining of rejecting grafts showed up-regulation of major histocompatibility complex class I molecules on corneal graft epithelium, damaged or absent graft endothelium and a marked, predominantly mononuclear cell infiltrate. CD4-positive T cells were observed in the graft within 2 days of the onset of rejection, followed several days later by CD8-positive T cells. Messenger RNA transcripts for interleukin (IL)-2, tumour necrosis factor (TNF)-alpha and IL-10 (but not for interferon (IFN)-gamma or IL-4) were found in autografted corneas. Proportionately, more allografts than autografts contained transcripts for IL-2 and TNF-alpha, and IFN-gamma was detected in three of four allografts. CONCLUSIONS: Corneal graft rejection in the sheep is macroscopically and histologically similar to human corneal graft rejection. Allografts become infiltrated by both CD4- and CD8-positive T cells and local production of pro-inflammatory cytokines occurs during graft rejection.

Animals↗
PubMed1999

Linear IgA disease.

PURPOSE: A case of linear IgA disease is reported to alert ophthalmologists and physicians to this unusual cause of chronic cicatrizing conjunctivitis. METHODS: Clinical records of a patient suffering from linear IgA disease were reviewed. RESULTS: A 65-year-old woman with a complicated medical history experienced rapidly progressive chronic cicatrizing conjunctivitis leading to corneal perforation. Undiagnosed gingivitis and palatal ulceration had been present for 5 years prior to the onset of ocular symptoms and vitamin C deficiency had followed the consequent dietary restrictions. A diagnosis of linear IgA disease was made on conjunctival biopsy, which demonstrated linear deposits of IgA along the epithelial basement membrane. The perforation was managed successfully with a conjunctival pediculate flap. Control of the inflammation was achieved with systemic prednisolone and cyclophosphamide but at the expense of serious systemic side-effects. CONCLUSIONS: Linear IgA disease causes progressive conjunctival cicatrization in many affected individuals. Although dapsone generally controls the inflammation, heavier systemic immunosuppression was required in this case. Involvement of skin or other mucosal surfaces may become symptomatic before the conjunctivitis, and physicians must be educated to refer patients for ophthalmological review on diagnosis. Conversely, ophthalmologists encountering ocular linear IgA disease should be aware of the possibility of other mucosal involvement requiring physician intervention.

Aged↗
PubMed1998

Diagnosing the systemic associations of anterior uveitis.

Up to one-half of patients with anterior uveitis suffer from related systemic diseases. The common associations are the seronegative arthropathies and, in children, juvenile chronic arthritis. Anterior uveitis may also occur in the context of sarcoidosis or Behçet's disease. Syphilis and tuberculosis remain a significant problem for specific populations and may be the cause of anterior uveitis in these groups. By thorough clinical history and the correct selection and interpretation of simple investigations, it is generally possible for the ophthalmologist to make or exclude a systemic diagnosis, predict the ocular prognosis and direct selected patients to the appropriate physician. Diseases that threaten the patient's wellbeing must certainly be recognized. In the present review we present a method for identifying the systemic associations of anterior uveitis.

Adolescent↗
PubMed1998

An instrument for assessment of subjective visual disability in cataract patients.

AIMS/BACKGROUND: The construction and validation of an instrument for the assessment of subjective visual disability in the cataract patient is described. This instrument is specifically designed for measuring the outcome of cataract surgery with respect to visual disability. METHODS: Visually related activities thought to be affected by cataract were considered for the questionnaire. These were reduced by pilot study and principal components analysis to 18 items. A patient's assessment of his/her ability to perform each task was scored on a four point scale. Scores were averaged to create an overall index of visual disability, as well as subscale indices for mobility related disability, distance/lighting/reading related disability, and near and related tasks visual disability. The questionnaire, administered verbally is entitled "The Visual Disability Assessment (VDA)". Reliability testing included test-retest reliability, interobserver reliability (p, the intraclass correlation coefficient), and internal consistency reliability (Cronbach's alpha). Construct validation, the process for proving that a test measures what it is supposed to measure, included consideration of content validity, comparison with the established Activities of Daily Vision Scale (ADVS) and empirical support with factor analysis. RESULTS: For the four indices, interobserver reliability varied from 0.92 to 0.94, test-retest reliability varied from 0.96 to 0.98, and internal consistency reliability varied from 0.80 to 0.93. The VDA compared favourably with the ADVS by correlation, but Bland-Altman analysis demonstrated that the two instruments were not clinically interchangeable. Factor analysis suggests that all test items measure a common theme, and the subgroupings reflect common themes. CONCLUSIONS: The VDA is easy to administer because it has a short test time and scoring is straightforward. It has excellent interobserver, test-retest, and internal consistency reliability, and compares favourably with the ADVS, another test of visual disability. Factor analysis demonstrated that the 18 items measure a related theme, which can be assumed to be visual disability. The VDA is a valid instrument which provides a comprehensive assessment of visual disability in cataract patients and is designed to detect changes within a patient over time.

Activities of Daily Living↗
PubMed1998

Uveal mast cells are not required for rodent uveitis.

Uveal mast cells have previously been considered to be vital mediators of experimental uveitis. We extended the study of these cells to experimental melanin-induced uveitis (EMIU), a recently described clinically relevant model, and re-examined their role in endotoxin-induced uveitis (EIU) using genetically mast cell-depleted mice on a single background. EMIU was induced in Fischer 344 rats by immunisation with bovine ocular melanin (250 microgram. Animals were killed immediately, and on days 1 and 3 of clinical disease. Numbers of uveal mast cells and the percentage of degranulated cells were counted in whole-mount preparations. There was no significant change in either measure across the selected time points. To induce EIU, normal and mast cell-depleted DBA/2 mice were injected with Escherichia coli lipopolysaccharide (400 microgram). Cells infiltrating the eye 24 h after injection were quantified in 5 micrometer ocular cross-sections. Disease was not significantly reduced in the mast cell-depleted mutants. We conclude that uveal mast cells are not required for the development of EMIU or, in contrast to earlier work, EIU.

Animals↗
PubMed1998

Mice deficient in tumor necrosis factor receptors p55 and p75, interleukin-4, or inducible nitric oxide synthase are susceptible to endotoxin-induced uveitis.

PURPOSE: To investigate the roles of tumor necrosis factor-alpha (TNF-alpha), interleukin-4 (IL-4), and inducible nitric oxide synthase (iNOS) in endotoxin-induced uveitis (EIU) using gene knock-out mice. METHODS: Mice (C57BL/6 x 129) either of normal phenotype or deficient in the genes encoding one or both tumor necrosis factor receptors (TNFR p55 and TNFR p75), IL-4, or iNOS were given footpad injections of 400 micrograms Escherichia coli lipopolysaccharide. Animals were killed 24 hours later, and infiltrating cells were counted on 5-micron ocular cross-sections through the optic nerve. RESULTS: All abnormal mouse phenotypes were susceptible to EIU. Yet, TNFR p55 and IL-4 gene knock-out mice experienced less ocular inflammation than control animals (P = 0.021 and 0.007, respectively), whereas disease was not reduced for iNOS-deficient mice. Mice deficient in TNFR p55 and TNFR p75 experienced milder EIU than mice lacking TNFR p75 alone (P = 0.046). CONCLUSIONS: Mice deficient in TNFR p55 and TNFR p75, IL-4, or iNOS retain the susceptibility to EIU, but TNF-alpha and IL-4 influence the influx of inflammatory cells to the eye during this disease.

Acute Disease↗
PubMed1997

Rethinking immunological privilege: implications for corneal and limbal stem cell transplantation.

Immunological privilege operates within the normal eye by multiple passive and active mechanisms, including antigen sequestration, maintenance of an immunosuppressive local environment and induction of apoptotic death in infiltrating cells of the immune system. Ocular privilege might have developed to protect the eye from the collateral damage associated with an inflammatory response to invading pathogens. Nevertheless, corneal grafts do undergo irreversible immunological rejection and, furthermore, corneal graft rejection is very similar at a histological level to the rejection processes that operate in vascularized organ grafts. Ocular privilege is thus relative. The question arises as to how corneal grafts are rejected in the face of so many mechanisms designed to prevent immune responses from operating inside the eye--a question that is still essentially unanswered.

Animals↗
PubMed1997

Cataract surgery reduces subjective visual disability.

PURPOSE: The present study examines the impact of cataract on visual disability (VD) and how cataract surgery alters VD. METHODS: Fifty-six patients were assessed pre- and at 3 months post cataract surgery. Cataract severity was measured with the Lens Opacities Classification System III (LOCS III). Visual disability was assessed by questionnaire. The relationship between LOCS III scores and total VD score was examined with linear regression. Repeated measures analysis of variance was used to determine whether the pre- and postoperative VD scores were different. RESULTS: The VD score was found to relate more closely to the LOCS III score in the least affected eye than in the most affected eye. The VD score is related to nuclear opacity (P = 0.01), and posterior subcapsular cataract (PSC; P = 0.0004), but not to cortical cataract (P = 0.51) (r2 = 0.43). The VD score is significantly greater before surgery (mean +/- SD) 1.81 +/- 0.67) than after (1.19 +/- 0.21; P < 0.001). CONCLUSIONS: Nuclear and PSC cataracts cause more visual disability than cortical cataracts. Visual disability is significantly reduced by cataract surgery.

Cataract↗
PubMed1997

Influence of advanced recipient and donor age on the outcome of corneal transplantation. Australian Corneal Graft Registry.

AIMS: The aims of this study were to examine the influence of advanced recipient and donor age on the long term outcome of corneal transplantation. METHODS: Records of 1036 penetrating corneal grafts in recipients aged > or = 80 years at surgery (defined as the elderly subset) and 8092 donor corneas used for transplantation were obtained from the Australian Corneal Graft Register database, Kaplan-Meier graft survival plots were compared using log rank statistics. RESULTS: Elderly recipients constituted 15% of the recipient pool. The major indication for corneal transplantation in the elderly was bullous keratopathy. Graft survival fell with increasing recipient age (p < 0.00001); the major cause of graft failure was rejection (33%). The desired outcome in 51% of cases was to improve vision and in 42% of cases to relieve pain; 23% of elderly recipients achieved a Snellen acuity of 6/18 or better in the grafted eye and 66% recorded improved acuity after transplantation. Elderly recipients suffered more complications and comorbidities in the grafted eye than did younger recipients. Donor age (stratified in 10 year intervals) did not influence corneal graft survival significantly (p = 0.10). CONCLUSIONS: Elderly graft recipients fared less well after corneal transplantation than did younger recipients, but outcomes in terms of long term graft survival and visual rehabilitation were still good. Donor age did not affect graft survival.

Age Factors↗