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Based on our morphologic and ultrastructural studies, we suggest that the characteristic lens opacities in Lowe's syndrome result from a genetic defect in the lens cells. This defect manifests early in embryogenesis, and the progression of the lens opacities is related to both the inherent genetic abnormality and the prevailing extralenticular environment. The defective formation and subsequent degeneration of the primary posterior lens fibers account for their loss and for the flattened, discoid, or ring-shaped cataract. The other findings, such as anterior polar cataract, subcapsular fibrous plaque, capsular excrescences, bladder cells, and posterior lenticonus are not necessarily specific for Lowe's syndrome. We believe that the pathogenesis of Lowe's cataract can be explained by Lyon's hypothesis, which implies that, very early in embryogenesis (at the stage of the primitive streak), one of the two X chromosomes in females is deactivated. We consider the high incidence of lens opacities in female carriers to be due to this random deactivation. In male probands, however, all lens cells are affected, since there is no normal X chromosome to nullify the effect of the Lowe gene.

Using freshly excised, pure, immature retinal vascular explants from neonatal rabbits as well as vascular cells harvested from such explants in a tissue culture environment, we established the direct cytocidal effect of hyperoxia on the vascular cells. One hundred percent oxygen at one atmosphere induced a marked cellular retraction after 4 to 6 hours of exposure and caused progressive increase in the number and size of lysosomal bodies and autophagic vacuoles. Between 12 to 18 hours, the Golgi apparatus enlarged and focal cytoplasmic degeneration ensued; the various changes in the endoplasmic reticulum, mitochondria, and nucleus became apparent between 18 to 24 hours. After 36 to 48 hours continuous exposure to hyperoxia, the cellular degradation with nuclear pyknosis led to granular and membranous debris. In contrast, the macrophages in the same culture were more resistant to the effect of hyperoxia. Our findings suggest multiple loci for oxygen toxicity in immature retinal vessels and cultured vascular cells. We believe that the cellular retraction is mediated through the prostanoid cascade. The initial event in cytotoxicity of hyperoxia is probably membrane injury, especially of the lysosomal system. The generation of the hydroxyl free radical invokes specific injury to the lysosomes; severe cellular damage occurs due to increased autophagocytosis, probably compounded upon by the inhibition of membrane pumps in the cell and the resulting intracellular acidosis. Injury to cell organelles such as mitochondria, endoplasmic reticulum, and nucleus which occurs at later stages and contributes to the final cell degeneration, may be partly related to the hyperoxic insult. The addition of vitamin E or gamma-aminobutryic acid to the culture medium partially retarded the hyperoxic injury to the vascular cells. In short term experiments, no significant damage occurred with exposure to 30% oxygen. The fact that immature, and not the mature, retinal vascular cells are rapidly and adversely affected by hyperoxia probably entails that the former are deficient in free radical scavenging enzymes but a protective mechanism against oxygen toxicity is acquired with the developmental maturity of these cells.

The histopathological manifestations in four eyes from two male patients with the oculo-cerebro-renal syndrome of Lowe included a small, discoid, cataractous lens, peculiar capsular and epithelial changes with aberrant formation of collagenous fibrous tissue, polar lenticular changes with anterior vitreous condensation, embryonic anterior chamber angle with anterior displacement of rudimentary ciliary processes, segmental hypoplasia of iris dilator muscle, and Lange's folds with peripheral retinal cystoid changes. Additional findings in one of the cases included bilateral corneal keloids, vitreous organization, hyalinized retinal vessels, and mild gliosis. We suggest that the congenital ocular abnormalities in Lowe's syndrome are related to an as yet unidentified, inherited enzymatic and/or biochemical defect, and that they progress further because of an abnormal aqueous humour environment. The role of aminoaciduria and mucopolysaccharidosis in the pathogenesis of systemic and ocular defects is discussed in the light of recent investigations.

Microwaves most commonly cause anterior and/or posterior subcapsular lenticular opacities in experimental animals and, as shown in epidemiologic studies and case reports, in human subjects. The formation of cataracts seems to be related directly to the power of the microwave and the duration of exposure. The mechanism of cataractogenesis includes deformation of heat-labile enzymes, such as glutathione peroxide, that ordinarily protect lens cell proteins and membrane lipids from oxidative damage. Oxidation of protein sulfhydryl groups and the formation of high-molecular-weight aggregates cause local variations in the orderly structure of the lens cells. An alternative mechanism is thermoelastic expansion through which pressure waves in the aqueous humor cause direct physical damage to the lens cells. Cataracts induced by ionizing radiation (e.g., X-rays and gamma rays) usually are observed in the posterior region of the lens, often in the form of a posterior subcapsular cataract. Increasing the dose of ionizing radiation causes increasing opacification of the lens, which appears after a decreasing latency period. Like cataract formation by microwaves, cataractogenesis induced by ionizing radiation is associated with damage to the lens cell membrane. Another possible mechanism is damage to lens cell DNA, with decreases in the production of protective enzymes and in sulfur-sulfur bond formation, and with altered protein concentrations. Until further definitive conclusions about the mechanisms of microwaves and ionizing radiation induced cataracts are reached, and alternative protective measures are found, one can only recommend mechanical shielding from these radiations to minimize the possibility of development of radiation-induced cataracts.

To characterize the pathophysiology of hyphema clearance, we studied changes in the facility of outflow in experimental hyphema in freshly enucleated rabbit eyes. Hyphemas, with washed normal or sickled red cells (RBCs) (suspended in isotonic phosphate buffer to obtain a hematocrit value comparable to that of whole blood) and occupying 50% to 100% of the anterior chamber volume, caused a marked cell "crowding" in the chamber angle and an increase in the outflow resistance; the facility stabilized at a value 60% lower than the control (p = < 0.001). No significant change in outflow facility was observed in hyphemas of either RBC type occupying 25% of the anterior chamber volume (p = N.S.). Whole blood hyphema occupying 50% of the anterior chamber volume reduced the facility of outflow by 80% of the control mock aqueous value (p = < 0.001); a comparison with 50% hyphema produced by washed RBCs indicated a significant contribution by the plasma (fibrin) component (p = 0.0025) in increasing the resistance to outflow.

With carmine particles used as markers, no significant difference was observed between the phagocytic activity of 1- to 3-week-old confluent monolayer cultures of normal and dystrophic retinal pigment epithelial (RPE) cells harvested from 1-day-old Royal College of Surgeons rats. The phagocytic activity of both normal and dystrophic RPE was markedly suppressed in a medium containing 1 mg/ml arachidonic acid (AA), and the cells rapidly assumed a rounded profile. With 100 micrograms/ml AA, the phagocytic activity of dystrophic RPE was differentially reduced compared with that of the normal sample (p greater than or equal to 0.001); this effect was subsequently accompanied by a gradual change in the shape of the cells. Lower concentrations of AA (5 microgram/ml and below) did not produce a significant effect in either group.

Two classes of ligand-binding molecules, (1) monoclonal antibodies (MABs) and (2) lectins, were used as probes to investigate the cell biology of human trabecular cells. We raised MABs by using human trabecular meshwork as the immunogen. One MAB (KAa25D7) consistently recognized two polypeptides with molecular weights of approximately 42 and 49 kilodaltons. The former comigrated with actin and the latter was shown by fractionation and extraction studies to be a macromolecular complex. Four lectins (wheat germ agglutinin, concanavalin A, Phaseolus vulgaris leukoagglutinin I, and Ulex europaeus agglutinin I) were used to identify the glycosylated polypeptides in human trabecular meshwork on Western blots. Compared to normal age-matched controls, there was a significant decrease in binding of the lectins to most polypeptides of the trabecular meshwork samples that were obtained from 4 eyes of 2 patients with primary open-angle glaucoma. Our preliminary studies show that lectins applied to Western blots and MABs are useful methods to probe the cell biology of human trabecular meshwork in health and disease.

The lack of specific agonists and antagonists has, until recently, precluded investigation of a role for dopamine receptors in the control of intraocular pressure. In the present study, we have examined the effects of fenoldopam, a novel selective dopamine1 (DA1) receptor agonist, on intraocular pressure, in eight healthy human volunteers. Fenoldopam, infused intravenously at 0.5 micrograms kg-1 min-1, increased intraocular pressure from 14.6 +/- 0.9 to 17.6 +/- 1.4 mmHg (P less than 0.05) while a control saline infusion had no effect. Pupil diameter and blood pressure did not change. In the same subjects, i.v. norepinephrine or angiotensin II both increased intraocular pressure--from 13.8 +/- 1.4- to 17.6 +/- 1.4 mmHg and from 13.4 +/- 1.3- to 17.5 +/- 1.7 mmHg respectively (P less than 0.05), and mean arterial pressure by about 20 mmHg. These data suggest that: (1) DA1 receptor activation can modulate intraocular pressure; (2) the intraocular pressure effects of the DA1 receptor agonist, fenoldopam, are independent of changes in systemic blood pressure, in contrast to those of norepinephrine or angiotensin II where intraocular and systemic blood pressures increase in parallel; (3) the ability of a DA1 receptor antagonist to lower intraocular pressure merits investigation.

Our study of a random series of more than 300 spoiled soft contact lenses reveals that virtually all lenses currently in use for daily or extended wear are subject to deterioration due to extraneous deposits, physical and chemical changes in the lens material, and microbial invasion. Common causes include ocular secretions, finger dirt and cosmetics, disinfecting and cleansing techniques, environmental factors, manufacturing defects and polymer impurities, mechanical stress and breakage, as well as aging and decay of the lens material. Mucoprotein-lipid deposits, with or without calcium, and calcareous deposits constitute the major forms of lens spoilage. Removal of encrusted deposits leaves surface irregularities and matrix defects which facilitate secondary spoilage including microbial invasion, and such lenses should be discarded. As virtually no soft lens material currently in use is "safe" for extended wear, the practitioner must carefully evaluated and follow his patients to identify those at risk of lens failure and spoilage complications. To eliminate spoilage, new lens materials and improved manufacturing techniques are needed. In the interim, for many patients, an inexpensive disposable soft lens which can be easily replaced, perhaps weekly or bi-weekly, may be the answer.

A wide-field contact specular microscope was used to examine and to photograph the corneal epithelium in 35 eyes with chronic corneal edema. Seven of the patients subsequently underwent corneal transplantation allowing for correlation of the in vivo findings with the light and electron microscopic appearance. The early findings on specular microscopy included loss of the clear superficial epithelial cell outlines with easy dislodgement of these cells and a fine pattern of edema outlining basal cells. Individual cellular edema and fluid-filled cysts occurring at various epithelial layers and subepithelially appeared with worsening swelling. Subepithelial connective tissue and anamalous basement membrane were present at later stages.

The statistical and epidemiologic literatures contain many examples of the reanalyses of medical databases. Some are confirmatory, such as the many reanalyses of the Stanford heart transplant data. Others, however, concern issues that differ from those that the data originally intended to address. We demonstrate in this paper that the second kind of reanalysis, if undertaken uncritically, can produce biased results. Utilizing a log-linear model, we show analytically that the reanalysis of a designed study without adjustment for the design variable can produce biased results. We express the magnitude of this bias as a function of second- and third-order interactions in the data. We demonstrate further that preliminary testing for the existence of second- and third-order interactions can provide substantial bias reduction.

A series of 75 spoilt soft lenses with opacities (mostly manifesting as discrete spots or as large areas of cloudiness, chalk-white in appearance) were subjected to histochemical, electron microscopical, electron probe x-ray microanalytical, x-ray diffraction, atomic absorption spectro-photometric, and biochemical analyses. The results showed that in many cases calcium was implicated in the deposit formation and that a broad correlation existed between the amount of calcium present and the degree of opacification. The possible mode of calcium deposition and resulting implications in lens intolerance are discussed. It is advocated that a search should be made for a modified or new soft lens material which does not permit calcium deposition, and that the medical practitioner should strive towards improved assessment of the systemic and ocular conditions which may help in identifying patients at risk of early lens failure.

The protein profile of the trabecular meshwork from 44 normal human eyes of various ages, ranging from 5 months to 87 years, was investigated by using sodium dodecyl sulfate-polyacrylamide-gel (SDS-PAGE) electrophoresis and a highly sensitive silver-stain technique. Samples from each eye were analysed individually to avoid anomalies that may occur with tissue pooling. More than 20 protein bands were consistently visible at all ages and varied in molecular weight from 20,000 to 290,000 MW. The shifts which occurred in band prominence with increasing age included a consistent decrease in the intensity of bands at MWs 42,000 (tentatively identified as G-actin) and 58,000; a noticeable increase in the intensity of the bands at MWs 140,000 and 160,000 that correspond to alpha I and II components of type IV collagen; and a gradual disappearance of a faint band at MW 68,000 in eyes older than 31 years. Our study shows that molecular aging does occur in the trabecular meshwork. The data presented also provides a basis for comparison of the polypeptide alterations that may occur in primary open-angle glaucoma and in other disease processes.

Experimental retinal vein occlusion in monkeys was followed by an immediate increase in capillary permeability which was accompanied by retinal oedema. This functional capillary change was followed at about 6 hours after occlusion by structural damage to the capillary wall. Thrombus formation occurred in the damaged vessels, and areas of stasis were thus produced with associated retinal haemorrhages. Finally, there was complete loss of the capillary endothelium and pericytes, and the acellular capillaries were invaded by proliferating glial cell processes, so producing permanent capillary closure.

A firm, round tissue mass, measuring approximately 12 mm in diameter, was excised from a 5-month-old boy who had a history of a gradually enlarging swelling in the left lower nasal eyelid since birth. Histologically and ultrastructurally, the lesion appeared benign and was composed of a dense connective tissue stroma in which nests, lobules, tubules, cords, and sheets of large, pale-staining cuboidal and elongated epithelial cells were surrounded by an irregular, thick PAS-positive basement membrane having focal excrescences. The interior of the epithelial islands contained "bladder" cells, cellular debris, granuloamorphous material, and foci of dystrophic calcification; an unusual feature of the lesion was the formation of numerous psammoma bodies. Tumors of lenticular anlage are rare and probably result due to displacement of migration of the inferior lens placode cells; alternatively, it may originate from an additional locus of lens vesicle in the primitive surface ectoderm of the lower lid. The lesion enlarges because of the differentiation of the ectopic lenticular cells in an abortive attempt to form a lens within the extraocular and mesodermal environment of the lid.

Trabeculectomy specimens from three eyes with Sturge-Weber syndrome were examined histopathologically. Changes in the trabecular meshwork-Schlemm's canal system were similar to findings in old age and in primary open-angle glaucoma. Two mechanisms for glaucoma are theorized. In cases with buphthalmos and congenital glaucoma, the chamber angle is often anomalous, as in other types of congenital glaucoma. In later onset juvenile cases, the chamber angle more often appears normal. A premature aging of the trabecular meshwork Schlemm's canal complex, as shown by us histopathologically, is a primary cause of juvenile glaucoma. It is suggested that both mechanisms relate to the abnormal hemodynamics of episclera and chamber angle, due to persistence of Streeter's primordial vascular plexus.

Corneal mucus plaques adhered to the anterior corneal surface in 17 of 67 advanced cases of keratoconjunctivitis sicca. The plaques were translucent to opaque and varied in size and shape, from multiple isolated islands to bizarre patterns involving more than half the corneal surface. Ultrastructurally, they consisted of mucus mixed with desquamated degenerating epithelial cells and proteinaceous and lipoidal material. The condition may be symptomatic but can be controlled and prevented in most cases by topical ocular application of 10% acetylcysteine.

The authors examined various structures of human and rhesus monkey eyes for the presence of tissue plasminogen activator (t-PA) by using the peroxidase-antiperoxidase immunohistochemical technique with a monoclonal antibody specific for human t-PA. Positive staining for t-PA was observed both intracellularly and in the extracellular matrix of many tissues in both species. The tissues which stained intensely for t-PA included the corneal endothelium, corneal epithelium, trabecular meshwork, lens epithelium, peripheral vitreous, uveal tract, inner retina, and all vascular endothelia. The apparent minor difference in staining intensity between human and monkey eyes may be related to the time-dependent degradation of t-PA, to variations in the tissue content of t-PA, or to the difference in animal species. The discussion includes a consideration of the fibrinolytic activity of t-PA and of its emerging role in the destructive remodeling of the extracellular matrix in various ocular structures.

Acanthamoeba keratitis is a serious complication of contact lens wear. The majority of reports documented in the literature are from the USA. The typical features of this condition are reported and illustrated by personal observations. Clinically, Acanthamoeba keratitis can be misdiagnosed as viral, especially Herpes simplex, fungal, or bacterial keratitis. Culture and microscopic examination of corneal scrapings, biopsy, or of the disc obtained at keratoplasty, and special staining techniques, including indirect immunofluorescence, can provide the definitive diagnosis. We discuss the medical and surgical management of this disease, as well as the risk factors and preventive measures. Knowledge of the factors which are responsible for the low incidence of contact lens-associated Acanthamoeba keratitis in Europe, would be helpful in understanding the epidemiology of this disease.

Of a family with 40 members, 12 had autosomal dominant optic atrophy. The affected members were aware of reduced vision from the first decade. Visual loss was moderate to severe, 6/12 (20/40) to 3/60 (10/200). The affected members showed similar centrocecal scotomata. Most affected patients had severe unclassified color defects. Electroretinography measurements were normal in all but one patient who had a small reduction in the scotopic response. The pathologic changes in a patient with autosomal dominant optic atrophy showed diffuse atrophy of the ganglion cell layer of the retina with a loss of myelin and nerve tissue within the optic nerves. We suggest that autosomal dominant atrophy is a primary degeneration of retinal ganglion cells.

Primary confluent cultures of retinal pigment epithelium (RPE) cells harvested from porcine eyes were challenged with latex spheres. The extracellular release of tissue plasminogen activator (t-PA) that was associated with phagocytosis of the beads by the RPE was measured by using enzyme-linked immunosorbent and chromogenic substrate assays. In the presence of serum and as compared to the controls, the phagocytosis of latex spheres produced a 5.5-fold increase in the amount of t-PA released into the ambient medium. Cell lysis was not a significant feature in either treated or control groups. Because the RPE in vivo is exposed to serum through the fenestrated choriocapillaris, and because phagocytosis by the RPE outer segments shed by the photoreceptors contributes to the maintenance of the functional integrity of the neural retina, we suggest that the release of t-PA associated with the phagocytic activity of RPE cells is an important physiologic event.

The proteins from 30 samples of normal human aqueous humor were separated into major fractions by sodium dodecyl-sulfate polyacrylamide gel electrophoresis, transferred to nitrocellulose, and probed with lectins to characterize the glycated polypeptides. The lectins used were derived from Canavalia ensiformis (concanavalin-A), Phaseolus vulgaris (erythroagglutinin), Arachis hypogaea (peanut agglutinin), and Ulex europaeus agglutinin-I. Using this microanalytical technique, the glycated polypeptides in the aqueous humor were separated into nine major fractions with apparent molecular weights of 17, 41, 50, 55, 61, 77, 80, 120 and 151 kDa. The predominant oligosaccharides detected on these fractions were complex chains usually with sialic acid residues. The possible roles of the glycated polypeptides in the aqueous humor in health and disease are discussed. Our investigation of these molecules in human aqueous humor provides baseline data for a rapid diagnostic analysis of microsamples of this fluid obtained from diseased eyes.

By quantitative analysis of tissue plasminogen activator (TPA) in the trabecular endothelium, corneal endothelium, and iris in the eyes of monkeys and dogs, we found significant levels of TPA activity. In a [125I]fibrin-coated well assay, the levels for the dog and monkey were, respectively: trabecular endothelium, 0.2 and 0.5; corneal endothelium, 0.8 and 0.5 IU per mg protein. The iris tissue showed high TPA activity, but its protein content could not be measured with the techniques employed. Activity in the aqueous humor was not detectable. By the ELISA technique, the values (in ng TPA/mg tissue protein) for the dog and monkey were, respectively: trabecular endothelium, 0.16 and 0.44; corneal endothelium, 0.48 and 0.92. Again, iris tissue showed high TPA activity, whereas the aqueous humor showed low activity (0.86 ng/ml). The data obtained with the two methods showed a reasonable consistency, although a direct comparison was not possible because two separate standards were used. The presence of TPA in the trabecular endothelium, corneal endothelium, and iris may be important in modulating the resistance to aqueous outflow under normal conditions as well as those of hyphema.

By exposing primary cultures of human corneal epithelial cells to a single dose of either benzalkonium chloride or chlorobutanol, evaluated the cytotoxicity of these two preservatives which are commonly used in artificial tear solutions and other topical ophthalmic medications. Control and experimental cultures were analyzed by continuous time-lapse videomicrographic recordings as well as by sequential phase-contrast microscopy. Both benzalkonium chloride at a concentration of 0.01% and chlorobutanol at 0.5% caused immediate cessation of normal cytokinesis and mitotic activity, and epithelial cells degenerated within two hours and eight hours, respectively.

The clincopathological features and pathogenesis of secondary mosaic degeneration of the cornea (anterior crocodile shagreen of Vogt) are described. The structural basis for the normal anterior corneal mosaic pattern seems to lie in the particular arrangement of many prominent collagen lamellae of the anterior stroma that thake an oblique course to gain insertion into Bowman's layer. Since, at normal intraocular pressure, Bowman's layer is under tension, when viewed from the anterior surface the cornea appears smooth. By releasing the tension, however, a reproducible polygonal ridge pattern becomes manifest. It is suggested that a prolonged phthisical state of the eye is one condition wherein the mosaic pattern may become permanent and that, as a secondary event, this is followed by irregular calcification of Bowman's layer which particularly involves the ridges projecting into the epithelium. Biomicroscopically these ridges corresponded to the branching reticular arrangement of the mosaic opacities.

Corneal changes in passive Arthus reaction are essentially the same as that reported to occur in active Arthus reaction and consist of accumulation of polymorphonuclear leucocytes around the deposits of immune complexes, release of lysosomes and fragmentation and dissolution of collagen fibrils. In addition, degenerative changes were found in the corneal endothelium and Descemet's membrane.

Hypotheses were tested regarding the effects of subjective current, retrospected, and anticipated person-environment fit on affective and somatic strain and well-being. Two-hundred seven university students preparing for annual academic examinations at an Indian university completed self-administered questionnaires measuring parameters of the hypotheses. A distinction was made between cognitive (e.g., meeting demands for intelligence, good memory) and motivational (e.g., being able to muster the effort) fit. Cognitive poor fit had a greater effect on predicting high levels of strain across all time frames but did best in the past and current frames. Motivational poor fit had its greatest effect on strain when poor fit dealt with anticipated or current fit. These findings are discussed in terms of hypotheses, which suggest that the more subjectively uncontrollable a dimension of fit, the more salient it is in the past time frame, whereas the more subjectively controllable the dimension, the more salient it is in the future time frame.

Three patients who initially presented to the ophthalmologist with a history of gradual deterioration of visual acuity showed, on biomicroscopic examination, a linear meshwork of opacities in the vitreous attached to the posterior surface of the lens in the form of pseudopodia lentis. Amyloidosis of the vitreous associated with systemic amyloid disease was diagnosed because of the characteristic nature of the opacities. This was confirmed initially in two of the cases by light and electron microscopical examination of a biopsy of the clinically normal conjunctiva, subsequently by systemic investigations, and finally, by direct histochemical and elecron microscopical examination of the vitreous which became available after vitrectomy in all three cases. It was not possible to examine other members of the families. The relevant literature on vitreous amyloidosis is reviewed in relation to our own findings and the importance of a diagnostic conjunctival biopsy is emphasized. This paper is the first British report on primary vitreous amyloidosis. The pathogenesis of vitreous amyloid opacities is discussed in the light of current concepts of amyloidosis. Since the vitreous opacities due to amyloid deposits appear to be one of the manifestations of systemic amyloid disease, surgical removal of the opacities by vitrectomy may not produce longlasting results. Moveover, in contemplating surgical treatment the ophthalmologist should bear in mind the poor prognosis of systemic amyloidosis.

Epinephrine exerts a direct effect on cell morphology, phagocytosis and mitotic activity of human trabecular endothelium in primary culture. Its action is probably mediated through both beta and alpha adrenoceptors in a dose-time dependent manner. Younger cells and cells that were loosely attached to the substrate were found to be affected more rapidly and severely than were older cells and those in confluent regions where cell-to-cell attachment and stress fibers were well established. Continuous exposure to epinephrine at a concentration of 10(-5) M led to cessation of the normal cytokinetic cell movements, inhibition of mitotic and phagocytic activity, marked cell retraction, separation from the substrate, and, by 4-5 days, degeneration of cells. Similar, but less marked changes were seen with a concentration of 10(-6) M, the cell degeneration becoming apparent after one week of exposure. A still weaker concentration of epinephrine, 10(-7) M, did not result in cell degeneration even after 10 days of exposure and observation. On complete withdrawal of the drug, the cellular effects were reversible even after 3 days' exposure to 10(-5) M and 5-7 days' exposure to 10(-6) M epinephrine. The action of epinephrine was partially blocked by pretreatment of cultured trabecular cells with the beta-blocker, timolol. Available evidence suggests that the mechanism of action of epinephrine is mediated through both beta and alpha adrenoceptors, and that it intimately involves the cytoskeletal system of the cells. Extrapolation of our findings in vitro suggests that use of maximal doses of epinephrine over a prolonged time may contribute to tissue damage in certain conditions of glaucoma.

To investigate the possible side effects of epinephrine on the aqueous outflow pathway, we studied the response of human trabecular cells in vitro exposed daily to the drug at various concentrations. Epinephrine at 10(-6) M caused abnormal cytokinesis and cell retraction, inhibited mitosis and phagocytosis, and induced a 4- to 5-fold increase in cAMP. After 7-10 days of exposure, notable degenerative changes were observed in the trabecular cells. Within certain limits, these effects were reversible when the drug was withdrawn. Exposure to epinephrine at 10(-5) M caused cell death within 96 hours. When a 10(-7) M concentration of epinephrine was administered for up to 10 days, no degenerative changes were seen, but mitotic activity was reduced somewhat. Pretreatment with timolol reduced, but did not completely eliminate, the cytotoxic effects of epinephrine. Cells with loose contact to the substrate were affected most. The morphologic changes and the observed loss of intracellular actin filaments indicate that the deleterious effects of epinephrine are probably mediated through damage to cellular contractile proteins. Although the precise cytotoxic action of epinephrine in vivo remains to be established, our results for primary cell cultures indicate a toxic action of this drug at concentrations of 10(-6) M or higher on human trabecular cells and suggest that, for prolonged use, the maximal dose of this drug at target sites should be in the region of 10(-7) M.

By using an enzyme-linked immunosorbent assay, we detected a significant amount of tissue plasminogen activator (0.8 +/- 0.17 ng/ml) in the aqueous humor of ten normal human eyes. It was also identified on Western blot analysis. The ratio of tissue plasminogen activator to total protein in aqueous humor was about 30 times greater than the ratio of tissue plasminogen activator to total protein in plasma. There was evidence that at least some of the tissue plasminogen activator in the aqueous humor was synthesized locally by the structures bordering the anterior chamber of the eye. Tissue plasminogen activator may be a useful therapeutic modality in clinical conditions of delayed dissolution of fibrin in the eye.