Apparent resistance to immunosuppression of MHC-matched corneal transplants.
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Animals↗
Biomedical subjects
D L Easty
Publications and source records attributed to D L Easty.
Driving, glaucoma, and the law. Patients need more information.
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Automobile Driving↗
Differing effects of various cryoprotectants on intercellular junctions of epithelial (MDCK) cells.
The effects of 30 min exposure to 10% v/v cryoprotectant (glycerol, dimethyl sulfoxide, or propane-1,2-diol) on intercellular junctions were investigated in monolayers of epithelial (MDCK) cells. The cells were grown on microporous membrane filters and transepithelial resistance was monitored as an index of junction integrity. At 22 degrees C, Me2SO had the least effect of the three cryoprotectants, causing a gradual fall in transepithelial resistance of only 17% in 30 min. This compares with falls of 50% in 15 min and 37% over 30 min, respectively, with glycerol and propane-1,2-diol. At 0 degrees C, however, propane-1,2-diol had no effect on transepithelial resistance, whereas the effect of Me2SO was now similar to that of glycerol, viz. a sustained reduction in resistance of approximately 30% throughout the 30-min exposure. The results could not be explained solely in terms of osmotic effects and suggested that the cryoprotectants were directly affecting components of the junctional complex or associated elements of the cytoskeleton. During removal of the cryoprotectants by two-step dilution, changes in transepithelial resistance showed little consistency between the different cryoprotectants. This suggested that the pattern of change was dictated more by the state of the junctions immediately before removal of the cryoprotectants, with each cryoprotectant having affected the junctions to different extents and perhaps by different mechanisms, than by the removal of cryoprotectant itself. Thus, intercellular junctions in epithelial sheets were affected by even modest concentrations of cryoprotectant, but the effect was influenced by the type of cryoprotectant and by temperature of exposure.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Immune cell infiltration and persistence in the mouse trigeminal ganglion after infection of the cornea with herpes simplex virus type 1.
Following inoculation of the mouse cornea with herpes simplex virus type 1 (HSV-1), the spread of virus was investigated and the types of immune cell infiltrating the trigeminal ganglion (TG) were identified in low temperature paraffin wax sections. Virus antigen was first found on day 3 and was absent after day 14. Early presentation of antigen to T cells may occur since increased expression of major histocompatibility complex (MHC) class II antigens, including de novo expression on satellite and Schwann cells, was detected in foci of such antigen on day 3. A second large peak of such expression was detected on day 10 together with increasing numbers of B and T cells. Large numbers of these lymphocytes and extensive expression of MHC class II were seen in the TG well into the phase of virus latency; the significance of this is discussed.
Animals↗
Over-expression of a gelatinase A activity in keratoconus.
Keratoconus is an ocular disorder in which the central cornea becomes thin, conical and frequently scarred. We are exploring the possibility that this condition is induced and maintained by proteases that exist in the corneal matrix in an activated form. In this study, the activities of the proteases secreted in vitro and in vivo by keratocytes of normal, clear keratoconic, scarred keratoconic and traumatically scarred corneas have been compared and partially characterised. Data obtained by assaying acyl transferase activity showed that the matrix metalloproteinases account for a minimum of 95% of the total protease secreted by cultured keratocytes. Their summated specific activity was consistently and significantly higher in the culture medium of keratoconic keratocytes than in the medium of other keratocyte cultures. Analysis of the individual protease activities secreted by these corneal keratocytes in vitro and in vivo by SDS-gelatin polyacrylamide gel electrophoresis showed that a gelatinase of molecular weight 65,000 is the major protease secreted by normal keratocytes. Whereas clear keratoconic and traumatically scarred corneal keratocytes secrete an additional activity of molecular weight 61,000, scarred keratoconic corneal keratocytes generally produced little or none of this gelatinase activity. Both activities may be ascribed to gelatinase A, and although the 61,000 molecular weight form may be a significant feature of keratoconus, neither appears to be active as secreted.
Acyltransferases↗
Toxicity of antibiotics and antifungals on cultured human corneal cells: effect of mixing, exposure and concentration.
Toxic effects of topical drugs may be masked by manifestations of the disease they cure. The toxicity of drug mixtures has not been thoroughly studied. We therefore investigated cytopathic effects on primary cultures of human corneal cells of six topical antimicrobials singly and in combinations of any two, to determine the combined toxicity ranking and the interaction between duration of exposure and concentration. Preconfluent cultures were exposed to fixed dilutions of single drugs, or to equal-dilution mixtures of two drugs, for 7 and 14 days. Diminishing concentrations of single drugs were applied sequentially to cultures for 14 days. The number of metabolically competent cells was assessed by measuring hexosaminidase and total protein. Toxic effects depended on substance, concentration and exposure. The scale of toxicity determined for single drugs after 7 days of exposure was: gentamicin > econazole > or = methicillin > or = clotrimazole > or = miconazole > or = chloramphenicol. After 14 days this order changed: in particular chloramphenicol showed a highly increased toxicity. The order of diminishing effects was: gentamicin > chloramphenicol > or = methicillin > miconazole > econazole > clotrimazole. A clear reduction in cytopathic effects was observed when drug concentration was decreased progressively only in cultures treated with gentamicin or methicillin. All drug combinations were more toxic than their components at equal dilution. Combinations containing chloramphenicol ranked most toxic overall, those containing econazole least. A tapering off combination regime did not improve cell survival. These in vitro toxicity data complement clinical studies and suggest ways in which topical drugs can be chosen to minimise toxic effects to corneal surface.
Anti-Bacterial Agents↗
Cannalicular occlusion with cyanoacrylate adhesive: a new treatment for the dry eye.
One hundred microlitres (0.1 ml) of N-butyl cyano-acrylate adhesive was injected into the inferior cannaliculus of 8 patients with dry eye. The adhesive induced total (upper and lower) cannalicular occlusion in each patient which has not resolved to date (mean follow-up 15.2 months, range 11-19 months). Complications were minor and not specific to use of this adhesive. It is hoped that its ultimate reversibility will make the technique suitable for younger patients with dry eye.
Aged↗
Drug therapy in a murine model of Acanthamoeba keratitis.
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Acanthamoeba Keratitis↗
Non-MHC antigens and their relative resistance to immunosuppression after corneal transplantation.
We have used a high responder rat model to examine the role that non-MHC antigens play in corneal graft rejection. Recipients were backcross animals derived from a cross between two inbred strains, which mimicked the human outbred population in that donor and recipient could be matched or mismatched for MHC antigens, while non-MHC mismatches were variable and unknown. All mismatched grafts and 87% of matched grafts were rejected (median survival 11 and 17 days respectively). The high incidence of rejection of matched grafts indicates that several independently segregating non-MHC genes play a role in rejection. Moreover, the immune response to matched grafts appeared resistant to immunosuppression, suggesting that matching does not permit reduced dosage of immunosuppressants. A mechanism is discussed whereby matching at the class II locus may enhance presentation of mismatched histocompatibility antigens or viral peptides derived from infected graft cells, thereby prejudicing graft survival.
Animals↗
Preparation of Bruch's membrane and analysis of the age-related changes in the structural collagens.
AIMS/BACKGROUND: The morphological changes in Bruch's membrane and its constituent collagen seen during aging have been studied extensively but the chemical nature of the collagen and any aging changes have not previously been evaluated. METHODS: A method for preparing purified Bruch's membrane from human cadaver eyes by dissection preceded by trypsin digestion was developed. Following pepsin digestion, the constituent collagens were analysed by SDS-PAGE and by immunoblotting. Cyanogen bromide digestion was used to ascertain the solubility of the collagen and the proportion of type I to type III collagen. After hydrolysis of Bruch's membrane samples the constituent amino acids and collagen crosslinks were measured. RESULTS: The presence of collagen types I, III, IV, and V in Bruch's membrane was confirmed. The proportion of type III collagen as a percentage of total fibrous collagens was calculated as being between 35% and 39%, with no significant difference between different macular and peripheral sites or with age. There was a highly significant decline in the solubility of Bruch's membrane collagen with age, from near 100% in the first decade of life to 40-50% in the ninth decade at both macular and peripheral sites. There was no significant change in the amount of enzymatically formed collagen crosslinks with age. Amino acid analysis indicated a significant increase in the amount of non-collagen protein with age in macular but not peripheral sites. CONCLUSION: Changes in the constituent collagens may contribute to the accumulation of debris in Bruch's membrane with age and interfere with the function of the retinal pigment epithelium, with subsequent consequences for the overlying photoreceptors.
Adolescent↗
Acanthamoeba keratitis: risk factors and outcome.
AIMS/BACKGROUND: This study was initiated to investigate risk factors for and outcome of Acanthamoeba keratitis. METHODS: Results of treatment were studied in 22 patients (23 eyes) presenting to Bristol Eye Hospital between 1985 and February 1995. Details related to the use and disinfection of contact lenses were also obtained. An additional two patients who were seen at Bristol but mainly treated elsewhere were surveyed for contact lens related information only. RESULTS: The incidence of Acanthamoeba keratitis rose substantially in the 1990s: three patients presented before 1990, while the remaining 21 presented between January 1990 and February 1995. Eleven patients have presented since january 1994. All of the patients in this series were contact lens wearers, 16 (67%) using daily wear disposable contact lenses. Contact lens disinfection data were available in 22 patients of whom 11 (50%) were using chlorine disinfectant. Other types of disinfection were much less common. Four patients (18%) had not used any disinfectant. During the course of the series the average diagnostic delay has fallen markedly, although in 77% of patients a diagnosis of a viral keratitis, most commonly herpes simplex, was made on first presentation. All but three of the series were treated with a combination of polyhexamethylene biguanide and propamidine isethionate. Penetrating keratoplasty was performed in 9/23 eyes (39%); in all of these eyes diagnosis was delayed for at least 6 weeks. All but one of the eyes in the series achieved a visual acuity of 6/9 or better after treatment, and 18 eyes (78%) saw 6/6 or better. CONCLUSIONS: Most patients with Acanthamoeba keratitis can now expect a good visual result and cure by medical therapy alone is favoured by early diagnosis.
Acanthamoeba Keratitis↗
Changes in the collagenous matrix of the aging human lamina cribrosa.
AIMS: The age-related changes in the biochemical composition of the collagenous matrix of the human lamina cribrosa were investigated. METHODS: An age range (3 weeks to 92 years old) of human laminae cribrosae, dissected free of any surrounding structures which contained collagen, were analysed for collagen solubility (n = 58) total collagen content (n = 46), proportion of collagen types (n = 38), and collagen cross linking (n = 30), using hydroxyproline analysis, scanning densitometry of peptides after cyanogen bromide digestion, and high performance liquid chromatography, respectively. RESULTS: Age-related changes included an increase in total collagen and a decrease in the proportion of type III collagen within the lamina cribrosa. The collagen cross link pyridinoline was present at low levels, but demonstrated no trend with age. An age-related increase was found in pentosidine, an advanced glycation product. CONCLUSION: These changes in collagen composition imply that the mechanical properties of the lamina cribrosa are altered, resulting in a stiffer, less resilient structure with age. Such alterations in structure may contribute to the increased susceptibility of the elderly to axonal damage in chronic open angle glaucoma.
Adolescent↗
Florid xanthelasmata (yellow lids) in orbital Wegener's granulomatosis.
AIMS: A new sign of florid xanthelasmata is described in four male patients with orbital manifestations of Wegener's granulomatosis. METHODS: The case notes of four patients with Wegener's granulomatosis, with orbital involvement accompanied by yellow lid lesions, are reviewed. RESULTS: All the patients had active Wegener's granulomatosis at the time the lid lesions were most florid. The lesions gradually resolved as the inflammatory disease was controlled with immunosuppressive agents. The lesions displayed marked asymmetry and predominantly involved the side with the most severe inflammation. Abnormalities of lipid metabolism were not identified and it is believed that the lesions developed in a susceptible anatomical region affected by a vasculitic process. CONCLUSION: A 'yellow lid' associated with orbital inflammation and is a strong pointer to the clinical diagnosis of Wegener's granulomatosis.
Adult↗
Topical 0.3% ciprofloxacin, norfloxacin, and ofloxacin in treatment of bacterial keratitis: a new method for comparative evaluation of ocular drug penetration.
AIMS: This study was designed to assess the relative corneal penetration of topical drops of three antibiotics and to relate those levels to minimum inhibitory concentrations for organisms associated with bacterial keratitis. METHODS: Four drops of each of ciprofloxacin, norfloxacin, and ofloxacin (0.3% topical ophthalmic preparations) were given to 12 patients undergoing corneal transplantation. After the recipient tissue was removed, corneal drug penetration was measured using high performance liquid chromatography. RESULTS: Intracorneal concentrations of ofloxacin (geometric mean 0.81 mg kg-1) were significantly higher than both ciprofloxacin (0.60 mg kg-1; p = 0.048) and norfloxacin (0.54 mg kg-1; p = 0.012). Ciprofloxacin and norfloxacin concentrations did not differ significantly (p = 0.33). CONCLUSIONS: Review of the minimum inhibitory concentrations of the fluoroquinolones against ocular pathogens reveals that ciprofloxacin is more potent than ofloxacin against many bacteria; ofloxacin is in turn more potent than norfloxacin. These data favour the selection of ciprofloxacin and ofloxacin rather than norfloxacin for the empirical treatment of corneal infection. The greater potency of ciprofloxacin offsets the superior penetration of ofloxacin. There is a need for improved clinical trial data concerning the use of fluoroquinolone eyedrops in ulcerative keratitis; some encouraging data are available for ciprofloxacin but not (in humans) for norfloxacin or ofloxacin.
Adolescent↗
Immunohistochemical detection of T-cell subsets and other leukocytes in paraffin-embedded rat and mouse tissues with monoclonal antibodies.
We describe a method for immunohistochemical localization of T-cells, CD4+ T-cells, CD8+ T-cells, B-cells, activated lymphocytes, major histocompatibility complex (MHC) class II antigens, macrophages, dendritic cells, and granulocytes in rat and mouse tissue fixed in periodate-lysine-paraformaldehyde (PLP) and embedded in paraffin. Rat and mouse spleen and eyes were fixed in PLP for 18-24 hr, rapidly dehydrated, infiltrated under vacuum with paraffin at 54 degrees C, sectioned, and stained with appropriate monoclonal antibodies (MAbs). Sections of PLP-fixed, paraffin-embedded spleen were compared with acetone-fixed frozen spleen sections with respect to morphology and staining quality. Nine of 10 MAbs to rat antigens and eight of nine MAbs to mouse antigens stained paraffin sections equally or more intensely than frozen sections. The two MAbs that showed weaker staining still gave good staining on paraffin sections. Paraffin-embedded rat and mouse eyes were easier to section serially than frozen eyes, showed superior morphology, and individually stained cells were readily identified. Therefore, a combination of PLP fixation and low-temperature paraffin embedding permits detection of the major types of immune cell in rat and mouse tissues while maintaining good morphology, particularly in diseased, damaged, or delicate tissues.
Animals↗
Negative effect of HLA-DR matching on corneal transplant rejection.
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CD4-Positive T-Lymphocytes↗
The Bristol Shared Care Glaucoma Study: study design.
The purpose of this study was the evaluation of community based optometric monitoring of stable glaucoma patients and glaucoma suspects compared to the routine Hospital Eye Services (HES) monitoring. Four hundred and five subjects were recruited from routine outpatient clinics at the Bristol Eye Hospital. All eligible participants were seen in the routine hospital clinic and then within two months were given a 'Gold Standard Assessment' (GSA) by an independent research team. Participants then visited one of 12 glaucoma-trained optometrists, for a standard battery of tests. Randomisation resulted in 204 subjects being allocated to community care, with reviews on a six monthly basis, with 201 who remained a control group within the hospital. Referral criteria were established to enable optometric detection of apparent glaucomatous progression. A questionnaire was used to assess patient satisfaction with both care types. Additionally a cost analysis exercise was performed.
Community Health Services↗
Influence of donor and histocompatibility factors on corneal graft outcome.
The Corneal Transplant Follow-up Study has followed 2311 penetrating keratoplasties for up to 450 days after transplant. A total of 207 failures were observed, including 65 classical rejections and 35 endothelial decompensations. At 12 months, graft survival was 89%, and survival free from rejection was 87%. For surviving grafts, risk of failure reduced from 4.8% in the first 75 days and stabilized after 5 months at 1.2% in each 75-day interval. Risk of rejection initially followed a similar pattern, but then increased after 12 months. Multifactorial analyses accounted for differences in recipient characteristics and interrelationships of donor factors. Donor age, sex, cause of death, and method of corneal storage were not found to influence significantly either time to graft failure or time to first rejection. Grafts in prospectively tissue-typed donor-recipient pairs were generally considered before surgery to be at increased risk of either graft failure or rejection. With due allowance, increasing risk of rejection was associated with increasing numbers of mismatches at HLA-A and HLA-B broad antigens. The opposite was true at HLA-DR broad antigens, where increased risk of rejection was observed with no mismatches.
Adult↗