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Biomedical subjects

D L Easty

Publications and source records attributed to D L Easty.

At least 73 records · Page 4Linked to original sources
PubMed1994

Response of epithelial (MDCK) cell junctions to calcium removal and osmotic stress is influenced by temperature.

Intercellular junctions could be targets of injury during both hypothermic storage and cryopreservation. Monolayers of Madin-Darby canine kidney (MDCK) cells, an epithelial cell line, were grown on microporous membrane filters, and junction integrity was monitored by transepithelial electrical resistance (TER). At 37 degrees C, TER was 196 ohm . cm2 (SD 58, n = 59): this rose with falling temperature to 278 (SD 54) and 409 (SD 110) ohm . cm2, respectively, at 22 and 0 degrees C. This initial increase was accounted for solely by the change in conductivity of the bathing medium, which declined with falling temperature. Prolonged exposure to reduced temperature, however, did cause a gradual decline in TER. Removal of calcium at 22 degrees C caused a rapid fall in TER owing to dissociation of calcium-dependent components of the junctional complex. This was followed by a gradual increase in TER over several hours when calcium was restored to the bathing medium. At 0 degrees C, TER declined slowly regardless of the presence or absence of calcium, which suggested that reduced temperature stabilized junctions with respect to their calcium dependence, but that low temperature itself was causing dissociation of junctions. Hypertonic stress (597 mOsmol/kg) caused a reduction in TER both at 22 and 0 degrees C, which, unlike the reduction caused by calcium removal at 22 degrees C, was reversed relatively rapidly on return to isotonic conditions. Hypotonic stress (201 mOsmol/kg) increased TER at 0 degree C, but had no effect at 22 degrees C. The lack of response at the higher temperature might have been the result of a cell volume regulatory mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Corneal graft survival and visual outcome. A multicenter Study. Corneal Transplant Follow-up Study Collaborators.

PURPOSE: The Corneal Transplant Follow-up Study has followed 2385 corneal transplants performed in the United Kingdom and the Republic of Ireland for up to 450 days to quantify factors influencing corneal graft survival and visual outcome 3 and 12 months postoperatively. METHODS: Multifactorial analyses of grafts registered by United Kingdom Transplant Support Service from July 1987 to June 1990 were used. Corrected visual acuity of functioning grafts was assessed at 3 and 12 months. RESULTS: Of 2385 corneal transplants followed, 214 failures were observed: graft survival was 95% at 3 months and 89% at 1 year. Similar factors affected outcome at each time. Decreased risk of failure was associated with surgeons reporting most grafts, and increased risk was associated with regrafts, patients younger than 10 years of age, nonvisual reasons for grafting, endothelial failure, and deep vascularization. Visual outcome was worse in older patients and was associated with cosmetic reasons for grafting, superficial vascularization preoperatively, and secondary endothelial failure. Visual acuity was better when the other eye had been grafted previously, or when the diagnosis was keratoconus or stromal dystrophy. CONCLUSIONS: Primary endothelial failure was associated with high failure rates but good visual results when functioning. Most other factors had similar effects on both outcome measures. Improved outcome under highest-reporting surgeons was slight, and indicated possible differences in postoperative care.

Adolescent↗
PubMed1994

Improved preservation of human corneal basement membrane following freezing of donor tissue for epikeratophakia.

Current methods for the production of lenticules for epikeratophakia involve rapid freezing, cryolathing, and slow warming of the donor cornea. We have found that this procedure causes structural damage to the epithelial basement membrane in the donor cornea which may subsequently contribute to poor postoperative re-epithelialisation of the implant, leading to graft failure. Endeavouring to overcome these problems, the effects of cryoprotection of donor cornea were investigated, using dimethyl sulphoxide, in conjunction with different cooling and warming rates as part of the protocol for cryolathing. The structural integrity of the epithelial basement membrane zone (BMZ) was then assessed by electron microscopy and by immunofluorescence microscopy using antibodies to types IV and VII collagen, components of the basal lamina and anchoring fibrils respectively, and an antibody to a component of the anchoring filaments. No differences in the pattern of immunostaining for these components were detected, indicating that the composition of the BMZ was unaltered by the different treatment regimens applied. However, electron microscopy showed that preservation of basement membrane ultrastructure was markedly improved when cornea was warmed rapidly rather than slowly, both in cryoprotected and non-cryoprotected tissue. Epithelial cell retention and preservation of stromal architecture appeared superior in cryoprotected samples, while keratocyte structure was heterogeneous throughout the experimental groups. Further work is in progress to assess the efficacy of these protocols in the preservation of keratocyte viability in association with improved basement membrane structure in donor tissue for epikeratophakia.

Basement Membrane↗
PubMed1994

An antimicrobial effect associated with rabbit primary aqueous humour.

Viability curves were recorded for a variety of bacteria suspended in rabbit primary aqueous humour. Controls included neat rabbit serum, dilute rabbit serum (1/50), dilute heat treated fetal bovine serum (1/50), and balanced salt solution. Rabbit aqueous humour was bactericidal in vitro for Staphylococcus aureus and Pseudomonas aeruginosa. Micrococcus spp, Streptococcus pneumoniae and Escherichia coli were not affected. The factor mediating the bactericidal effect survives filtration (0.2 micron porosity) and freezing in liquid nitrogen (-196 degrees C) but is labile when stored in air at temperatures of 4 degrees C, 25 degrees C, and 37 degrees C for 1 hour. The bactericidal effect was stable when aqueous humour was stored in an atmosphere of 5% CO2 at 37 degrees C for 3 hours. The antibacterial component in rabbit aqueous humour has yet to be identified.

Animals↗
PubMed1994

Effects of irrigation solutions on corneal endothelial function.

Rabbit corneas were perfused in vitro with an irrigation solution for 90 minutes. This was followed by 6 hours of perfusion with tissue culture medium TC199 during which endothelial function was assessed by monitoring rates of swelling during a period of perfusion in the absence of bicarbonate ions, and subsequent rates of thinning when bicarbonate ions were restored to the perfusate. Corneal thickness (measured with an ultrasonic pachymeter) immediately following excision was 401 microns (SD 19, n = 23). During the 90 minute perfusion at 35 degrees C, corneas exposed to balanced salt solution (BSS), Hartmann's solution or 0.9% NaCl (all initially at room temperature) swelled, respectively, at 14 (SD 2.3, n = 4), 11 (SD 2.6, n = 4), and 70 (SD 4.3, n = 4) microns/h. Cold Hartmann's solution (initially at 4 degrees C) caused corneas to swell at 9 (SD 2.3, n = 4) microns/h. On the other hand, corneas perfused with BSS Plus thinned at 9 (SD 3.4, n = 4) microns/h and TC199 with Earle's salts had little effect on thickness. Rates of swelling and thinning during the following assessment perfusion showed no apparent effects of prior exposure to any of the irrigation solutions on the barrier properties or pump function of the endothelium. Despite this, the increased thickness of corneas exposed initially to BSS, cold Hartmann's solution, or 0.9% NaCl was not fully reversed, even by the end of the 6 hour assessment perfusion. In contrast, the swelling observed in corneas exposed to Hartmann's solution at room temperature was reversed and these corneas had returned to their normal thickness by the end of the assessment period. All corneas, even those exposed to 0.9% NaCl, had an intact endothelial mosaic with no evidence of damage or cell loss, although morphological differences in cell shape and the appearance of cell borders were evident compared with freshly isolated cornea.

Animals↗
PubMed1994

Ocular penetration of topical ciprofloxacin and norfloxacin drops and their effect upon eyelid flora.

A double blind, prospective study was undertaken to compare aqueous humour penetration of topical 0.3% norfloxacin and 0.3% ciprofloxacin and their effect upon normal eyelid flora in 39 patients undergoing cataract surgery. Lid swabs were taken before and after six 1 hourly applications of single drops of ciprofloxacin or norfloxacin given before surgery. Aqueous humour was aspirated at surgery and antibiotic concentration assayed using high performance liquid chromatography. The mean aqueous humour concentrations were: ciprofloxacin 220 ng ml-1, norfloxacin 140 ng ml-1. Although this difference was not statistically significant (p = 0.112) the trend demonstrated may be relevant clinically, especially considering the greater activity of ciprofloxacin. Both coagulase negative staphylococcal (p = 0.004) and total bacterial (p = 0.019) lid counts dropped sixfold after ciprofloxacin treatment but the smaller reductions noted after norfloxacin application did not achieve statistical significance (p > 0.1). The reduction of external eye flora experienced with ciprofloxacin suggests that this may be a useful presurgical prophylactic agent.

Administration, Topical↗
PubMed1994

Ocular infection with herpes simplex virus in several strains of rat.

PURPOSE: To assess the suitability of the rat for studies of ocular infection with herpes simplex virus (HSV). METHODS: LEW, AO, DA, PVG, and (DAxLEW)F1 x LEW backcross generation rats, 7 to 9 weeks of age, were inoculated with HSV-1 McKrae. The course of primary disease was assessed by clinical observation using a slit lamp. Infectious virus was assayed in ocular and nervous tissue, and the incidence of latent infection was determined. RESULTS: LEW and AO strains were the most susceptible. All LEW rats died after an inoculum of 4 x 10(2) plaque-forming units (pfu) and developed severe corneal disease and uveitis. In contrast, all PVG rats survived 10(4) pfu, 60% survived 4 x 10(4) pfu, and eye disease was restricted to epithelial lesions, sometimes accompanied by mild stromal haze. This resolved, even in animals that developed central nervous system disease. The DA strain showed intermediate susceptibility. Resistance was dominant because disease in backcross generation (DA x LEW)F1 x LEW rats resembled that of the DA rather than the LEW strain. Resistance appeared to be linked to coat color (P < 0.001) rather than to major histocompatibility complex (MHC) type. Chronic stromal disease did not occur in survivors (DA, PVG, and hybrid strains only). CONCLUSIONS: The susceptibility of rat strains to infection of the cornea with HSV varies, and, as with mice, resistance seems to be controlled by non-MHC genes. Rats may prove useful for immunologic studies. Virus reactivation will be the subject of a future report.

Animals↗
PubMed1993

Absence of tolerance to noninherited maternal transplantation antigens expressed on skin and cornea.

Tolerance to noninherited maternal antigens (NIMAs) of the MHC was investigated in a rat model involving both skin and corneal transplants. Recipient animals were obtained by backcrossing F1 hybrids to parental strain animals. In one group of experiments, crosses were (DA[RT1a] x LEW[RT1(1)]) female-to-LEW male and, in a second group, (DAxPVG[RT1c]) female-to-PVG male. Homozygous backcross offspring (RT1(1/1) or RT1c/c) were putatively tolerant to DA NIMAs if the mother was a hybrid animal, having been exposed to these antigens in utero. The equivalent offspring of hybrid fathers, i.e., LEW female x (DAxLEW) male or PVG female x (DAxPVG) male, served as putatively nontolerant controls. Hemagglutinating antibody levels were measured against the class I RT1Aa antigen on days 7 and 14 after up to three consecutive subcutaneous DA strain skin grafts. Significantly lower titers were found in the putatively tolerant group 7 days after the first skin graft in the RT1a-to-RT1(1) combination (P < 0.05). Levels were not significantly different at any other time point, or at any time point in the RT1a-to-RT1c combination. Tolerance to a corneal graft was not demonstrated in either the strongly rejecting RT1a-to-RT1(1) combination or weakly rejecting RT1a-to-RT1c, whether or not animals were presensitized to RT1a antigens with DA skin grafts. We conclude that tolerance to NIMAs is unimportant in this clinical rat model of transplantation.

Animals↗
PubMed1993

Corneal transplantation in the United Kingdom and Republic of Ireland.

The Corneal Transplant Follow up Study has registered 4560 corneal grafts performed in the United Kingdom and Republic of Ireland from July 1987 to June 1991. Rates of reported grafts doubled during that time. This increase was greater for surgeons and regions reporting fewer grafts, but was consistent across patient factors. Eleven of 428 consultants were responsible for over 25% of grafts, and their patients' characteristics differed significantly from others. Overall, reasons for grafting were visual only (77%), visual and other (16%), and non-visual (7%). Most frequent diagnoses were endothelial failure (38%), inflammation (26%), and keratoconus (20%). Age ranged from 2 months to 97 years, and differed markedly with diagnosis. Eighteen per cent of transplants were regrafts, and 40% were vascularised preoperatively.

Adolescent↗
PubMed1993

Antigen presentation of herpes simplex virus by corneal epithelium--an in vitro and in vivo study.

Ia antigen (class II antigen) is a histocompatibility antigen that foreign peptides associate with, before antigen presentation to T cells and subsequent triggering of the CD4 T cells. Although corneal epithelium is normally Ia negative it may become Ia positive under abnormal circumstances but the functional significance of this is uncertain. In this study the expression of Ia antigen on corneal epithelium of mice during in vivo primary and secondary herpes simplex keratitis and the in vitro accessory function of corneal epithelium in the presentation of herpes simplex virus (HSV) antigen to in vivo HSV primed T cells were evaluated. Whole mount preparations of corneal epithelium were found to express Ia antigen on days 3, 5, and 7 following corneal inoculation with live HSV. The intensity of the Ia expression was greater in non-immune mice on day 7 after corneal inoculation compared with immune mice. A cellular suspension of corneal epithelium induced HSV primed T cells to proliferate in the presence of HSV antigen. Induction of Ia antigen on corneal epithelium during herpes simplex keratitis may functionally expand the population of antigen presenting cells in the cornea and contribute to T cell activation.

Animals↗
PubMed1993

Activated T cells in an animal model of allergic conjunctivitis.

The aim of this study has been to determine whether the presence of lymphocytic infiltrates observed in the histology of ocular allergic conditions in humans or in the late phase of ocular anaphylactic reactions in experimental animals is a non-specific event dependent only on the degranulation of mast cells, or is conditioned by a specific response to antigen. With this in mind, responses to antigen and to a non-immunological mast cell degranulator (compound 48/80) were compared in an experimental model of allergic conjunctivitis. Rats were sensitised to ovalbumin and challenged topically in the left conjunctival sac either with ovalbumin or compound 48/80. The presence of T cells and activated T cells in the infiltrate was studied by immunohistochemical staining on conjunctival tissue obtained at 4, 24, and 48 hours after challenge. Ovalbumin sensitised and challenged rats showed increased numbers of T cells in the conjunctival infiltrate, statistically significant when compared with compound 48/80 challenged rats at 48 hours and with controls at 4, 24, and 48 hours. The number of T cells was significantly higher in compound 48/80 challenged rats only at 48 hours when compared with controls. As for the number of activated T cells, only ovalbumin sensitised and challenged rats showed significantly increased levels of these cells compared with both sensitised animals challenged with compound 48/80 and controls at 4 and 24 hours after challenge. These results suggest that the infiltration of the conjunctiva by activated T lymphocytes is, at least in part, dependent on a specific response to antigen.

Animals↗
PubMed1993

Penetrating keratoplasty in the United Kingdom: an interim analysis of the corneal transplant follow-up study.

1. Clinical corneal transplantation has been performed for over a century, but many elements leading to a successful outcome have yet to be identified. 2. Because there are limitless supplies of tissue, the supply of corneas need never fall short of demand. Nevertheless, retrieval rates vary widely among regions in the UK due to uneven organization of services. 3. Organ culture of corneas improves the quality of transplanted tissues because it allows time for substandard material to be discarded. The outcome appears to equal other storage methods. 4. Between 1987 and 1991, 4,560 corneal transplants were performed by 428 surgeons at 216 centers in the UK and were registered with CTFS. Of these, 3,213 were evaluable for graft survival, rejection, and other measures of visual outcome. 5. Unifactorial analysis revealed that the percentage of graft survival at one year was 89% and rejection-free survival was 87%. However, the hazard of rejection appeared to increase at or after the time of suture removal. 6. The percentage of recipients in whom CVA was 6/24 or better (able to read normal text with correction) improved from 16% preoperatively to 59% at 3 and 70% at 12 months postoperatively overall. In patients transplanted purely for visual reasons, improvement was 78% and 83% at 3 and 12 months, respectively. 7. Interim results of multifactorial analysis suggest that the risk of graft failure, rejection, and decreased CVA increased in association with the following factors: surgeons who reported fewer than 50 transplants to the study; recipients under 10 years of age; previously failed grafts (the more failed grafts, the greater the risk); grafting for nonvisual reasons; certain diagnoses; and vascularization of the corneal bed prior to transplantation. 8. Astigmatism was investigated in 880 cases at 3 months postoperatively. Preliminary analysis indicated that the risk of severe astigmatism was influenced by suturing technique and large differences between (> 0.25 mm) donor and recipient trephine size. 9. The effects of HLA matching were evaluated in 542 transplants. HLA-A and B matching reduced the risk of rejection during the first 450 days posttransplant, but HLA-DR matching appeared to increase the risk of rejection. 10. A rat model designed to simulate clinical corneal grafting was used to investigate the interaction between immunosuppression and matching. Whereas MHC mismatching could be overcome with topical dexamethasone, non-MHC mismatching appeared resistant.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1992

Suitability for day case cataract surgery.

Areas of concern about day case surgery are highlighted. A group of 442 patients underwent cataract surgery with lens implant. They were randomly allocated to day case or inpatient groups. Questionnaires were used to assess opinions about day case cataract surgery and how patients felt they would manage. None of the areas of concern were actually a problem. Difficulties encountered by patients and clinicians in the postoperative period are discussed. Most patients appear suitable for day case surgery provided they are well informed.

Activities of Daily Living↗