Toxic effects of copper on cultured rat lenses

Lenses from 60-day-old rats were cultured for 24 hr at 35°C in Tyrode's medium containing copper sulfate at concentrations of 0, 10, 20, 50 and 100 μm. Lenses incubated with 0 or 10 μm copper remained clear. Lenses incubated with 20, 50 or 100 μm copper became cloudy, the cloudiness increasing with increasing copper concentration and being more intense in the equatorial than in the central region. Glucose utilization was inhibited, lens sodium and water contents were increased, and lens potassium was decreased with increasing copper concentration. At 10 μm, the copper concentration at which opacification first became observable, glucose utilization was inhibited 20% and lens sodium content was increased threefold compared to control lenses. Copper (100 μm) inhibited the active transport of ⁸⁶Rb and increased its passive transport to a substantially greater degree than it inhibited the glucose utilization of cultured lenses. EDTA in the medium afforded substantial protection from copper toxicity; d-penicillamine (used to treat diseases involving copper toxicity) and histidine afforded partial protection. Noteworthy clinical implications of these studies are discussed.     

Exposure of rabbit lens to hyperbaric oxygen in vitro: regional effects on GSH level

Previous studies have indicated that in vivo exposure to hyperbaric O2 may be associated with the development of nuclear cataract. In the present work, in vitro effects of hyperbaric O2 on rabbit lenses were investigated following culture of the lenses in an atmosphere of 99% O2 at pressures ranging between 1 and 100 atm. Treatment with O2 resulted in a significant decrease in the level of reduced glutathione (GSH) in the lenses even at the lower pressures studied (less than 8 atm). At 100 atm O2 the loss of GSH was 85% after a 3 hr exposure. At 8 atm O2 a significant drop in GSH concentration was shown to occur in the lens nucleus prior to loss of the tripeptide in the superficial cortex. O2-treated lenses became hazy in appearance, especially at the higher pressures, but did not become densely opaque. Pressures of N2 up to 100 atm had no effect on either lens transparency or on the concentration of GSH. Although oxidized glutathione (GSSG) was detected in the whole lens at pressures of O2 as low as 4 atm, no change in GSH level or evidence for GSSG accumulation was observed in the capsule-epithelium of the lens at pressures as high as 50 atm O2. Ninety percent of the GSSG present in lenses after exposure to 100 atm O2 could be reconverted to GSH by subsequent culture of the lenses under normal conditions. Exposure of lenses to 50 atm O2 produced a three-fold stimulation of hexose monophosphate shunt activity, equal to that which has been reported for treatment of lenses with 0.06 mM H2O2.(ABSTRACT TRUNCATED AT 250 WORDS)     

Controlled trial of hyperbaric oxygen treatment for alkali corneal burn in the rabbit

Purpose: To evaluate the efficacy of hyperbaric oxygen therapy in the treatment of alkali‐induced corneal burns in an animal model. Methods: Twenty‐four rabbits were randomized into a control group (n = 12) and hyperbaric oxygen treatment group (n = 12). After induction of anaesthesia, the alkali burn model was established by application of 1 N sodium hydroxide to one eye of each rabbit. The hyperbaric oxygen treatment group was treated each day for 21 days with hyperbaric oxygen at 2.4 Atmospheres Absolute (ATA) for 1 h. The eyes of the animals were examined daily for 2 weeks and then weekly until the end of the trial. The principal endpoint was that of perforation of the cornea at which time the animals were killed with a lethal dose of either intravenous or intraperitoneal barbiturate and the eyes immediately enucleated and fixed in 10% neutral buffered formalin. All animals in which complete healing took placed were also killed, the eyes removed, fixed and examined histologically. Photographs were taken of the rabbit's eyes at weekly intervals and the area of vascularization and epithelial defects in the hyperbaric and control groups were compared. Results: Equal numbers (seven) of the control and hyperbaric oxygen treated groups had perforated corneas and there was no statistical difference in the mean time to perforation (control 30.1 days; treated 30 days). There was also no statistical difference between the two groups with respect to epithelial defect size. Conclusion: Treatment with hyperbaric oxygen for 1 h daily for 21 days had no beneficial effect on alkali‐induced corneal burns.     

The effect of corneal contact lenses on the oxygen tension in the anterior chamber of the rabbit eye

The oxygen tension in the aqueous humor in the anterior chamber of rabbit eyes was measured continuously with a polarographic electrode. The normal oxygen tension in the anterior chamber was 23 +/- 2 mm Hg (mean +/- SD, n = 4). A contact lens was then placed on the cornea for at least 10 min and the drop in oxygen tension recorded. A hard polymethylmethacrylate lens reduced the oxygen tension by 16 +/- 4 mm Hg, and a larger hydroxyethylmethacrylate soft lens (Soflens) decreased oxygen tension by 17 +/- 4 mm Hg (mean +/- SD, n = 4). Comparable statistically significant decreases were seen with the Permalens, Polycon II, and Silcon lenses. Only the elastofilcon A lens (Silsoft) did not decrease the oxygen tension in the anterior chamber significantly.     

上皮生长因子在家兔视网膜色素上皮细胞培养中的作用

本研究对有色家兔视网膜色素上皮（ＲＰＥ）细胞进行体外培养，结果显示：低浓度上皮生长因子ＥＧＦ对ＲＰＥ细胞无刺激作用，而达到适当浓度时对ＲＰＥ细胞有明显刺激作用，但高浓度与适当浓度的作用相同。本文认为适当浓度的ＥＧＦ可促进ＲＰＥ培养细胞生长，缩短传代周期，细胞增殖速度快，细胞数量明显增多，且细胞形态不受影响。ＥＧＦ对体外培养ＲＰＥ细胞的最佳浓度为１０ｎｇ／ｍｌ，这为在体外大量培养ＲＰＥ细胞提供了新的实验数据     

The effects of injections of cultured fibroblasts into the rabbit vitreous

A comparison was made between rabbit's eyes which had an intravitreal injection of either 400,000 autologous or homologous skin fibroblasts. The follow-up period was up to 6 months with autologous and 10 weeks with homologous cells. The evaluation involved the clinical assessment of membrane formation, retinal detachment and anterior segment inflammation. In addition, a detailed histological, electron microscopic and autoradiographic study was made of membrane development and changes in the surrounding tissue. Clinical evaluations revealed little difference between the two models. However, on the basis of macroscopic and microscopic examination, homologous cells produced more extensive detachments and more pronounced retinal gliosis. Plasma cells were evident in the choroid 6 weeks after homologous fibroblast injection, but they were not associated to any appreciable extent with the autologous model. Fibrovascular proliferation from around the optic nerve head made a major contribution to the formation of membranes in the experiments with homologous fibroblasts but not those using the autologous cells.Presented at the 1984 meeting of the European Club for Ophthalmic Fine Structure (ECOFS) in Lund, Sweden     

Therapeutic contact lenses: the role of high-Dk lenses

Currently, the armamentarium of contact lenses that can be used for therapeutic effect provides a wider selection of lenses than ever before. If the therapeutic goal is protection and healing of the corneal epithelium, epithelial or stromal edema is best avoided, and the selection of a high-Dk silicone hydrogel (balafilcon A, lotrafilcon A) lens or a very thin membrane-type lens (crofilcon) is the best choice. If the goal is surface protection as well as stimulation of stromal wound vascularization, selection of a low-water content, thick, hydrophilic lens is the better option. If the patient is prone to lens loss or requires frequent replacement of the therapeutic lens, a prudent economic decision is to select a daily disposable moderate-water content lens. Specific circumstances may mandate the selection of a specific therapeutic lens. Patients with a prior history of active giant papillary conjunctivitis may be better served by the use of a crofilcon glyceryl methacrylate lens, which has a lower incidence of this complication. Patients who have dry eye may benefit from a higher-water content lens if adequate unpreserved tear supplementation is provided with or without punctal occlusion. The options when selecting a therapeutic contact lens are wider than ever before. Although the new generation of high-Dk lenses promises fewer limiting problems of vascularization and infection, one can use the older traditional therapeutic lenses when induced vascularization of the cornea is needed or when an economic necessity exists. Not all of the available lenses are FDA approved for therapeutic use, and such wear is an off-label use. The patient should be informed of the goal of therapy as well as the benefits and risks of therapeutic contact lenses.     

Aggregation of lens crystallins in an in vivo hyperbaric oxygen guinea pig model of nuclear cataract: dynamic light-scattering and HPLC analysis

PURPOSE: The role of oxygen in the formation of lens high-molecular-weight (HMW) protein aggregates during the development of human nuclear cataract is not well understood. The purpose of this study was to investigate lens crystallin aggregate formation in hyperbaric oxygen (HBO)-treated guinea pigs by using in vivo and in vitro METHODS: methods. Guinea pigs were treated three times weekly for 7 months with HBO, and lens crystallin aggregation was investigated in vivo with the use of dynamic light-scattering (DLS) and in vitro by HPLC analysis of water-insoluble (WI) proteins. DLS measurements were made every 0.1 mm across the 4.5- to 5.0-mm optical axis of the guinea pig lens. RESULTS: The average apparent diameter of proteins in the nucleus (the central region) of lenses of HBO-treated animals was nearly twice that of the control animals (P < 0.001). Size distribution analysis conducted at one selected point in the nucleus and cortex (the outer periphery of the lens) after dividing the proteins into small-diameter and large-diameter groups, showed in the O2-treated nucleus a threefold increase in intensity (P < 0.001) and a doubling in apparent size (P = 0.03) of large-diameter aggregate proteins, compared with the same control group. No significant changes in apparent protein diameter were detected in the O2-treated cortex, compared with the control. The average diameter of protein aggregates at the single selected location in the O2-treated nucleus was estimated to be 150 nm, a size capable of scattering light and similar to the size of aggregates found in human nuclear cataracts. HPLC analysis indicated that one half of the experimental nuclear WI protein fraction (that had been dissolved in guanidine) consisted of disulfide cross-linked 150- to 1000-kDa aggregates, not present in the control. HPLC-isolated aggregates contained alphaA-, beta-, gamma-, and zeta-crystallins, but not alphaB-crystallin, which is devoid of -SH groups and thus does not participate in disulfide cross-linking. All zeta-crystallin present in the nuclear WI fraction appeared to be there as a result of disulfide cross-linking. CONCLUSIONS: The results indicate that molecular oxygen in vivo can induce the cross-linking of guinea pig lens nuclear crystallins into large disulfide-bonded aggregates capable of scattering light. A similar process may be involved in the formation of human nuclear cataract.     

Physiological effects of UVB irradiation on cultured rabbit lens.

The purpose of this study was to investigate the physiological effects of irradiation in the spectral range 295-340 nm in cultured rabbit lenses. Ultraviolet B cataract was produced in lenses exposed to low levels of irradiation, 1-2 mW/cm2. Opacification was assessed by laser transmittance measurements. The changes observed during lens culture after a 1 hr dose (4 J/cm2) include a gradual increase in hydration, sodium concentration, and calcium levels. Loss in membrane voltage and a rise in 36Cl accumulation indicate that membrane permeability was increased. The cation pump was impaired within 20 hr of irradiation, as concluded by an observed fall in 22Na efflux. Availability of glucose for cation transport was diminished based on the reduced rate of uptake of tritiated 3-o-methylglucose in irradiated lenses, but this reduced accumulation was observed much later than was sodium elevation. Ionic imbalances and opacification required less than 1 d of culture for 4-12-wk-old lenses and required nearly 7 d of culture for 100-wk-old lenses.     

Toxic effects of ophthalmic preservatives on cultured rabbit corneal epithelium

We investigated the effects of the ophthalmic preservatives thimerosal and sorbic acid on the proliferation and survival of rabbit corneal epithelial cells in tissue culture. Normally, explants of corneal epithelium grow vigorously during the first 7 days in culture. With 0.004% thimerosal present in the culture medium, the normal proliferation of corneal cells is suppressed completely. When 0.1% sorbic acid is present, proliferation is delayed and the lifespan of the corneal cells is reduced. After a 1-h exposure to concentrations of thimerosal of 0.0005% or greater, virtually all corneal cells present in established cultures are killed. These results suggest that use of ophthalmic preparations containing these chemicals may affect the metabolic and proliferative capacity of the corneal epithelium adversely.     

The effects of fenestrating soft contact lenses on corneal swelling: a re-examination

Previous studies have suggested that central corneal oedema during hydrogel lens wear can be reduced by placing peripheral fenestrations in the lens. In this study, optical pachometry was used to monitor central and peripheral corneal swelling in response to a peripherally fenestrated hydrogel lens. The experiment was conducted in a double-masked, randomized manner on 10 unadapted subjects. Fenestrations did not alter central corneal oedema, but peripheral corneal oedema was reduced by 34% (p > 0.001). Fenestrations may therefore provide a useful strategy for minimizing lens-induced corneal oedema. Clinical trials with fenestrated lenses are now indicated.     

高压氧在视网膜动脉阻塞治疗中的作用观察

目的 探讨高压氧配合常规药物治疗视网膜动脉阻塞的疗效。方法 明确诊断为视网膜动脉阻塞患者32例(32只眼)，全身应用血管扩张剂的同时，加压吸人纯氧。结果 32例(32只眼)中显效21例，有效8例，无效3例。总有效率90．6％。结论 高压氧在配合常规药物治疗视网膜动脉阻塞中起到了重要的作用。     

丝裂霉素对体外培养兔角膜内皮细胞的毒性影响

目的探讨丝裂霉素C(mitomycinC,MMC)对角膜内皮细胞的毒性作用。方法体外培养家兔角膜内皮细胞,接种于96孔板,加入不同浓度的MMC,分别为1×10-6g·L-1、1×10-5g·L-1、1×10-4g·L-1、1×10-3g·L-1、1×10-2g·L-1、1×10-1g·L-1,动态观察细胞的形态变化和增殖情况,加药22h后MTT法检测吸光度值,应用t检验比较各组间的差异。结果10-2g·L-1、10-1g·L-1浓度组8h后细胞部分死亡,20h细胞几乎全部死亡,其余各组变化不明显。统计学结果显示:10-6g·L-1、10-5g·L-1组和对照组比较无显著性差异(P>0.05),10-4g·L-1组有显著性差异(0.01相似文献