Complications of conjunctival surgery.
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Conjunctiva↗
Biomedical subjects
R A Thoft
Publications and source records attributed to R A Thoft.
Biosynthesis of stromal matrix proteoglycans and basement membrane components by human corneal fibroblasts.
The proteoglycans produced by intact human corneas and corneal cells in culture were compared by characterizing the biosynthetically radiolabeled proteoglycans and by using antibodies to detect their core proteins. Organ cultures of corneas primarily produce a keratan sulfate proteoglycan (KSPG) and a chondroitin and dermatan sulfate proteoglycan (decorin). Immunostaining with antibodies specific for the core proteins of KSPG and decorin showed that these proteoglycans are localized to the corneal stroma. The stroma also contained trace amounts of matrix that stained with antibodies to basement membrane heparan sulfate proteoglycan (perlecan) and laminin. Corneal fibroblasts in culture produced decorin, but the synthesis of KSPG appeared to be blocked at the level of core protein synthesis. Corneal fibroblasts in culture, however, produced perlecan in greater amounts than they did in organ cultures, and they synthesized both perlecan and laminin in greater amounts than did corneal epithelial cells in culture. These results indicate that the synthesis of proteoglycans by human corneal fibroblasts in culture is altered, resulting in increased production of basement membrane-associated proteoglycans and decreased synthesis of corneal stroma-associated proteoglycans.
Basement Membrane↗
Regulation of HLA class II antigen expression on cultured corneal epithelium by interferon-gamma.
The effect of recombinant human interferon gamma (IFN-gamma) on the induction of HLA class II (HLA-DR, -DP, -DQ) antigen expression on human corneal epithelial (HCE) cells was examined in different stages of culture. Primary cultures were established with limbal explants without endothelium. HCE cells in Stage 1 and Stage 2, with cells negative and positive for the 64K corneal keratin (the marker for advanced corneal epithelial differentiation), respectively, were prepared. HCE cells in both stages were treated with IFN-gamma at a concentration of 0 to 1000 U/ml for two to six days and were stained by the avidin-biotin peroxidase complex method. Class II antigens were not detected on HCE cells in either stage without IFN-gamma treatment. IFN-gamma induced three class II antigens on HCE cells in both stages in a dose- and time-dependent manner but at different levels for each antigen (DR greater than DP greater than DQ). In addition, DQ expression was related to cell differentiation, with DQ extremely rare at Stage 1 and more frequent at Stage 2 (5% vs. 20%). These findings indicate that the induction of class II antigens on HCE cells may be regulated by IFN-gamma independently for each of the antigens and that DQ induction may depend upon the differentiation of HCE cells in culture.
Cell Differentiation↗
Increased aggrecan (cartilage proteoglycan) production in the sclera of myopic chicks.
A previously characterized chick model of myopia was used to evaluate biochemical changes in the sclera which are associated with ocular enlargement and myopia. Chicks were monocularly occluded for 10 days and the DNA, hydroxyproline, and glycosaminoglycan contents of the sclera were compared between the normal and the myopic eyes. No significant differences could be detected in total DNA or hydroxyproline content. There was, however, a 34% increase in glycosaminoglycans and a 20.7% decrease in cell density within the posterior sclera of myopic eyes. The biosynthesis of scleral proteoglycans was determined by measuring 35SO4 incorporation in the sclera of chicks visually occluded for 5, 10, and 15 days. No differences could be detected in 35SO4 incorporation into the cornea or the anterior sclera. However, 35SO4 incorporation was significantly increased in the posterior sclera of myopic eyes by 64% at Day 5, 39% at Day 10, and 49% at Day 15. When fractionated on Sepharose CL-4B, scleral proteoglycans were resolved into two peaks which were identified by Western blot analysis as aggrecan (cartilage proteoglycan) and decorin. Furthermore, Western blot and dot blot analyses indicated that significantly more aggrecan core protein was present in the sclera of myopic eyes compared with equivalent amounts of sclera from control eyes. These results indicate that increased synthesis and accumulation of aggrecan, which increases the volume of extracellular matrix in the posterior sclera, are responsible for the ocular enlargement observed in this model of myopia.
Aggrecans↗
Regional heterogeneity in human corneal and limbal epithelia: an immunohistochemical evaluation.
The authors studied the distribution of specific keratins within the superior, inferior, medial, and lateral regions of human limbus and cornea to determine whether the limbal epithelium exhibits regional heterogeneity in its microstructure. A corneal epithelial basic keratin (K3), recognized by monoclonal antibody AE5, was immunohistochemically undetectable in the basal layers of the limbus in these four regions, but was seen in all layers in the central cornea. The pattern of immunostaining with another monoclonal antibody, AE1, which recognizes several acidic keratins, was complementary to AE5 staining in that AE1 recognized a similar heterogeneity in the limbal epithelial cells. AE1 immunoreacted with the basal cells of the limbus, but not those of the central corneal epithelium. Limbal characteristics, as defined by AE1-positive and AE5-negative staining, extended deeply into peripheral cornea in the superior and inferior regions, but to a lesser extent in the lateral and medial regions. The broader regions of epithelium with limbal characteristics in the superior and inferior regions raises the possibility that these regions play an important role in corneal epithelial maintenance and wound healing.
Aged↗
Differentiation in cultured limbal epithelium as defined by keratin expression.
The authors investigated differentiation of cultured corneal and limbal epithelial cells by immunochemically evaluating the changes in the profiles of keratins recognized by two monoclonal antibodies: AE5, which recognizes K3, and AE1, which recognizes a group of acidic keratins including K16, which is present in the hyperproliferative cells. After 1 and 2 weeks in culture, the human epithelial cells did not react with AE5 but did react strongly with AE1. At 3 weeks, only suprabasal cells exhibited a moderate reactivity with AE5, whereas AE1 binding was seen in all of the cells. After 5 to 6 weeks in culture, all of the cells reacted moderately with AE5 and AE1. Treatment of 2-week-old limbally derived cultures with mitomycin C (mitosis inhibitor) did not inhibit subsequent K3 expression. Thus, K3 expression was associated with maturation or a later stage of differentiation that did not require an additional cell division. Unlike human epithelial cells, rabbit suprabasal epithelial cells expressed K3 (reactivity to AE5) after only ten days in culture. The epithelium derived from central human cornea lost K3 by 1 week in tissue culture but expressed keratin(s) recognized by AE1. Even after 4-6 weeks, cells derived from the central cornea did not become confluent and did not react with AE5. Thus, limbally derived human and rabbit epithelial cells undergo chronological changes in K3 expression similar to that seen in rabbit epithelial cells derived from central cornea. However, cultured human limbal epithelial cells take a significantly longer time to express K3 (a phenotypic characteristic of differentiated corneal epithelium) than do rabbit epithelial cells.
Animals↗
Treatment of Cogan's syndrome with FK 506: a case report.
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Female↗
Growth of acanthamoeba on human corneal epithelial cells and keratocytes in vitro.
Acanthamoebic keratitis, a potentially devastating infection usually associated with contact lens wear, has been recognized with increasing frequency in recent years. Once the Acanthamoeba organisms gain access to the human cornea, it is not clear which constituents of the corneal milieu provide a substrate for their growth. The growth of Acanthamoeba polyphaga was investigated on cultured monolayers of human corneal epithelial cells, stromal keratocytes, and stromal homogenate suspensions. Growth was determined through organism counts and observation of cytopathic effects on tissue culture dishes. Compared with tissue culture media controls, acanthamoebic growth was supported by cultured epithelial cells and keratocytes but not stromal homogenates. These results suggest that in acanthamoebic keratitis the organisms depend on the cellular components of the cornea as substrates for growth. This in vitro model may also provide further information on the pathogenesis of keratitis and a system for drug sensitivity testing.
Acanthamoeba↗
Indications for keratoepithelioplasty.
Thirteen patients with ocular surface failure were treated by keratoepithelioplasty using allografts of corneal limbal epithelial cells from donor eyes. The ocular surface was stabilized with long-term healing of persistent epithelial defects in five of eight eyes followed up for 4 to 19 months. The procedure was performed on an additional 5 patients with superficial keratopathies. Three of those five procedures resulted in a stable and clear optical surface. These results suggest that epithelial transplantation may be a useful option in the care of chronic ocular surface failure unresponsive to conventional medical management.
Adult↗
Healing of excimer laser ablated monkey corneas. An immunohistochemical evaluation.
The healing response of the cornea following excimer laser anterior keratomileusis (a 4-mm-diameter ablation to a depth of 11, 23, or 46 microns) was analyzed immunohistochemically in adult rhesus monkeys. The ablated surface had reepithelialized and the synthesis of type VII collagen (a major component of anchoring fibrils) was evident by 7 days; the reestablishment of a nearly continuous anchoring fibril zone was evident after 12 weeks. Stromal fibroblasts, activated in response to wounding, expressed a fetal antigen for approximately 6 weeks. Although fibronectin and type VII collagen were present only transiently in the regenerating subepithelial stromal matrix in the subepithelial regions, some other alterations, including the presence of type III collagen, increased levels of keratan sulfates, and discontinuities in the anchoring fibril zone were evident even 18 months after wounding. The depths of the regenerated stroma, which were estimated from the depths of remnant staining for type VII collagen in the stromal matrix, generally, but not always, corresponded to the depths of the calculated ablation.
Animals↗
Perforating eye injury in Allegheny County, Pennsylvania.
From 1980 through 1986, acute perforating eye injury (ICD codes 871.0-871.9) was diagnosed in 345 residents of Allegheny County, Pennsylvania. The mean incidence rate was 3.49 per 100,000 person years. There was no significant change in incidence over the seven-year period. The largest number of injuries occurred among individuals working with tools, of which 47 percent were occupational. Males had a 6.5-fold risk of injury relative to females. Blacks had a risk of 2.2 times that of Whites, mainly due to an excess of assaultive injuries. Individuals who had had recent ocular surgery accounted for 4.6 percent of cases overall, and for 31.6 percent of cases in those over age 60.
Adolescent↗
Survival of Acanthamoeba in contact lens rinse solutions.
Acanthamoeba may cause a severe keratitis in contact lens wearers. Since most sterilization techniques require rinsing the lenses prior to insertion, contaminated solutions represent a potential vector for transmission of Acanthamoeba. The ability of rinse solutions to sustain an inoculum of Acanthamoeba polyphaga was investigated. A. polyphaga was exposed to 0.1% benzalkonium chloride, 0.001% thimerosal/0.1% edetate disodium, 0.1% edetate disodium, saline, tap water, and distilled water. The status of the organism was evaluated with direct microscopic counts and cultures to confirm viability. Incubation with 0.1% edetate disodium, saline, tap water, and distilled water resulted in the maintenance of reduced populations of viable organisms for 7 days. Benzalkonium chloride preserved saline and solutions containing thimerosal with edetate rendered the Acanthamoeba nonviable.
Acanthamoeba↗
Antibasement membrane antibody-mediated experimental conjunctivitis.
In ocular cicatricial pemphigoid, the binding of circulating antibodies to conjunctiva is believed to initiate an antibody-mediated cytotoxic response that results in inflammation and tissue damage. To develop a model of antibody-mediated conjunctival inflammation, we examined the effect on conjunctiva of local or systemic administration of a murine monoclonal antibody against basement membrane of stratified squamous epithelium. Neonatal rabbits were given either a single subconjunctival or intraperitoneal injection of the antibody. Eyes were graded clinically for inflammation and conjunctival biopsies were performed. After subconjunctival injection, clinical and histologic inflammation as well as murine antibody and rabbit complement binding to conjunctival basement membrane were detected. With systemic administration there was post-injection clinical inflammation, and conjunctival basement membrane-bound murine antibody was detected. There was no difference observed in conjunctival mitotic rate or goblet cell frequency between treatment groups and controls, following either route of administration. We have created, therefore, a model for antibody-mediated conjunctivitis in rabbits by local or systemic administration of a monoclonal antibody against a component of stratified squamous epithelial basement membrane.
Analysis of Variance↗
Unique parameters in the healing of linear partial thickness penetrating corneal incisions in rabbit: immunohistochemical evaluation.
The healing of penetrating nonperforating linear corneal incisions in rabbit was analysed immunohistochemically. Regeneration of the basement membrane (BM) zone was evaluated by analysing the following components using monoclonal antibodies (MAbs): 1) an antigen designated AgHEBM1 (a 66k Mr polypeptide), 2) type VII collagen which is associated with anchoring fibrils and 3) an antigen designated Ag63/D7 which is associated with the lamina densa and anchoring plaques. Concomitant activity in the regenerating stroma was evaluated by analysing the distribution of 1) fibronectin, 2) keratan sulfate and 3) a fetal antigen, designated AgM12, (an intermediate filament associated protein with a Mr of 130k). Synthesis of the BM zone components was not evident at day 2 postwounding but was seen at day 7, only at the deepest aspects of the wounds. Re-establishment of a continuous BM zone was evident by day 60. The stromal regeneration had started by day 7, at the deepest aspect of the wounds, as judged from the distribution of stromal antigens including the fetal antigen AgM12. The number of activated cells (cells expressing AgM12) had decreased significantly by day 30 and diminished by day 60. Between day 30 and day 180 the thickness of the regenerated tissues had not increased significantly although the stroma had not yet reached its normal thickness. Even after six months, the epithelial plug persisted and the concentration of the sulfated epitopes of keratan sulfates in the regenerated stromal matrix were less than in the surrounding nonwounded regions. The cessation of expression of AgM12, by the cells in regenerating stroma, coincided with the relative decrease in extracellular matrix syntheses. The return of the stromal cells to the quiescent state also coincided with re-establishment of a continuous BM zone between the epithelium and the stroma in the regenerated tissue. These observations suggested that the synthesis, assembly and remodeling of stromal and epithelial extracellular matrices during the healing of penetrating corneal wounds may be influenced by the interactions between activated stromal cells and epithelial cells.
Animals↗
Inhibition of vascularization in rabbit corneas by heparin: cortisone pellets.
The purpose of this work was to study the effectiveness of heparin plus cortisone, and of cortisone alone in control of corneal vascularization in rabbit eyes. Corneal vascularization was induced by de-epithelialization of the cornea and limbus and part of the bulbar conjunctiva with concurrent trephination and excision of a central 2-mm diameter corneal button. Inhibition of vascularization by polymer pellets impregnated with heparin (Panheprin, Abbott Laboratories; Chicago, IL) and cortisone, or neither drug was studied by implanting the pellets into the eyes at the time of injury and following the eye clinically and histologically. Wounded corneas with empty pellets developed vascularization extending from the limbus to the central cornea within 3 wk (n = 10). In other wounded eyes, heparin:cortisone pellets prevented vascularization (n = 10) while cortisone pellets slowed, but did not totally inhibit vascularization (n = 6). In other eyes, clear autografts were transplanted into vascularized eyes; and the ability of the drug-impregnated pellets to inhibit grafts vascularization was evaluated. In eyes with heparin:cortisone pellets inserted into the donor button at the time of keratoplasty, the autografts remained clear for at least 6 wk (n = 10) but subsequently vascularized if the sutures were not removed, while cortisone pellets slowed but did not block vascularization (n = 6). If heparin:cortisone pellets were inserted into the vascularized host tissue, rather than into the donor button, vascularization of the graft occurred (n = 6). Thus, heparin (Panheprin, Abbott Laboratories; Chicago IL) plus cortisone inhibited vascularization in rabbit cornea in the models studied: The effect of other commercially available heparins remains to be studied.
Animals↗
Factors related to corneal epithelial complications after closed vitrectomy in diabetics.
In a series of 30 vitrectomy patients, postoperative corneal complications developed in 14 (47%). Thirteen (92%) of the 14 patients with complications were diabetic. Other factors that were positively correlated with the development of corneal complications included decreased corneal sensitivity, intraoperative lensectomy, and intraoperative epithelial debridement. The corneal complications involved the epithelium in 11 (78%) of the 14 complicated cases, with involvement of the endothelium (as manifested by stromal edema) in five (35%) cases. The diabetic human corneal epithelium contains considerable levels of sorbitol and fructose, which indicates the probable presence of the sorbitol pathway. As in the lens, this pathway may lead to osmotic changes that make the diabetic corneal epithelium more vulnerable to damage intraoperatively. Postoperatively, reepithelialization is delayed because of a probable failure of adhesion of cells to the underlying basement membrane.
Cornea↗
Conjunctival transplantation as an alternative to keratoplasty.
Rehabilitation of the ocular surface is frequently desired following severe chemical and thermal injury. While keratoplasty, both lamellar and penetrating, has been the usual mode of therapy, chronic healing deficits and graft rejections as a result of heavy vascularization often lead to an unsatisfactory result. In unilateral injury, conjunctival transplantation from the opposite, uninvolved eye offers an alternative therapy which avoids both intraocular surgery and the introduction of immunologically foreign tissue. Seven of ten cases of unilateral chemical or thermal injury showed marked reduction in vascularization and scarring following conjunctival transplantation. The characteristic early vascularization of the peripheral conjunctival grafts showed marked regression one to four months postoperatively. At the same time, the central cornea, whose superficial vessels and scarring were removed by keratectomy, showed reepithelialization and smoothing, without attendant vascularization. Three cases were optical failures partially as a result of deep scarring that could not be adequately excised with keratectomy. Preoperative evaluation must be directed primarily toward evaluation of the corneal thickness and the extent of deep vascularization to select those patients most likely to be improved by conjunctival transplantation.
Adult↗
Ocular surface response to trauma.
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Adult↗