Lens and eye toxicity research最新文献

The effect of pyruvate on the progress of galactose cataract has been studied. Pyruvate was administered topically in the form of eye drops. Such treatment was found to delay the onset of the cataractous changes. Cataract formation was studied by visual inspection with pen light, as well as with slit lamp biomicroscopy in the intact animal. The delay in the formation of cataract was associated with the preservation of the levels of lens ATP, soluble proteins and the decreased accumulation of galactitol. In vitro organ culture experiments yielded similar results.

Two cases of chorioretinitis were caused by polymer material from the suture (Dexon) used in squint surgery. The lesions were macula edema, granulomatous uveitis and capillary occlusions on the ocular fundus located in the operated area. To confirm the cause of this injury, an immunological investigation was performed. Macrophage block and an incomplete adjuvant were necessary to lead delayed hypersensitivity against the synthetic polymer polyglycolic acid (PGA). The mice showed a strong reaction as hyperemia and swelling on their experimental footpads after the injection of PGA. Histologically the footpad accumulated a large quantity of lymphocytes in the swollen tissue but the control footpad had no reaction.

Because the corneal epithelium invariably encounters the full concentration of the preservative that is contained in multi-dose topical ophthalmic preparations, we investigated the cytotoxicity of several of these agents by using a sensitive model of human corneal epithelial cells in vitro. Primary cultures of epithelial cells were prepared from freshly enucleated globes. At confluence, all experimental cultures received a single dose of preservative at the concentration present in marketed formulations. The serum in the culture medium simulated the possible neutralizing effect of proteins present in the tear film in vivo. The cells were observed continuously by phase-contrast microscopy and time-lapse videomicrography for 24 hrs. Benzalkonium chloride at a concentration of 0.01% and chlorobutanol at 0.5% caused immediate cell retraction, as well as cessation of normal cytokinesis, cell movement, and mitotic activity; the epithelial cells degenerated within 2 hrs and 8 hrs, respectively. Cultures treated with chlorobutanol developed conspicuous blebs on the cell surface after 3 to 5 hrs of exposure. Thimerosal (0.001%) caused cell retraction, cessation of mitotic activity, and total cell destruction within 9 hrs. Sorbic acid (0.1% and 0.2%) greatly reduced cell movement and suppressed mitotic activity, but no cell death occurred. At concentrations of 50 ppm and 30 ppm, H2O2 instantaneously caused a marked retraction of the cells, followed by cessation of cytokinesis, cell movement, and mitosis. Retraction and death of the epithelial cells occurred within 12-24 hrs after exposure to 1 ppm H2O2 in serum-free medium. Polyquaternium ammonium chloride (0.001%) and polyaminopropyl biguanide (0.00005%) had no discernible effects on cytokinetic movement or on the mitotic activity of the epithelial cells. We relate our findings in vitro to those reported in vivo and discuss the mechanism of cytotoxicity of the various preservatives.

Normal and streptozotocin diabetic female Wistar rats were given normal diets with the following additions: 0, or 12,500 iu/kg food vitamin A (retinyl palmitate). At the end of 6 weeks, the rats were examined for weight gain or loss, general body condition, and cataracts. At sacrifice, blood was collected for measurement of serum glucose. gamma-Crystallin levels were determined in aqueous and vitreous humours using a radioimmunoassay. One lens (the right) was homogenized in 8 M guanidinium chloride for ATP analysis. In normal rats, gamma-crystallin was detected in both aqueous and vitreous humours, with a greater concentration found in the vitreous. Diabetes caused a 4-5 fold increase in gamma-crystallin in both aqueous and vitreous humours. Diabetes also led to a significant loss of body weight, and decrease in lens ATP levels. Addition of vitamin A to the diet resulted in reduction in gamma-crystallin leakage into the aqueous and vitreous humours. Vitamin A at 12,500 iu/kg food resulted in an increase in lens ATP for the diabetic rats. Neither streptozotocin diabetes nor vitamin A in the diet appeared to affect the weight of the lenses after 6 weeks. It is suggested that childhood vitamin A deficiency leading to latent fiber cell damage may be an important factor contributing to the high incidence of cataracts in the third world.

Both short- (1 week) and longer-term (7 week) studies have been made on a series of silicone oils to determine their effects on blood-retinal barrier permeability. About 25% of the vitreous humor was replaced with the test oil, and fluorophotometric determinations made after intravenous fluorescein at intervals after oil injection. The short-term studies revealed a uniform disturbance of the eye at 24 hours after oil injection that probably represents the physical disturbance of the eye during injection. For most oils the readings on day 4 and day 7 after oil injection revealed no difference between the experimental and the paired control eye. Adatomed 5000 cps oil and a Japanese 1000 cps oil caused more sustained aqueous humor fluorescein values over the first week. Longer-term studies, with two oils shown in prior studies on corneal endothelium to increase permeability and one oil that had no influence on endothelial permeability, revealed no effects on fluorescein penetration into any ocular compartment. It is apparent that the corneal endothelium offers a more sensitive paradigm for examining the toxicity of oils for predictive behavior of long-term exposure of the retina.

Corneal clarity is dependent upon maintenance of the corneal endothelial barrier and pump. Mechanical trauma is usually considered to be the most significant factor in corneal endothelial damage during cataract surgery resulting in postoperative corneal edema. However, corneal decompensation out of proportion to the degree of trauma seen during surgery does occur. These cases of unexpected corneal edema can often be traced to unrecognized preoperative endothelial dysfunction or to toxicity of intraocular medications used during surgery. This paper reviews the role of viscoelastics in reducing surgical trauma, their toxicity, and the risks of toxicity inherent in the use of re-usable cannulas and irrigating solution additives. Disposable cannulas should be used whenever possible. The use of re-usable cannulas with viscoelastics is highly likely to result in toxic residues being introduced onto the eye, and must be avoided. Irrigating solution additives should be tested with in-vitro human donor cornea perfusions prior to clinical use.

We have made an ESR study on the UV-photolysis of lens and identified the origins of free radicals involved in the initial photochemical process by spin trapping technique. Two spin adducts were detected on irradiation of canine lens in the presence of a spin trapping reagent (DMPO); a spin adduct of sulfur centered radical derived from glutathione and the protonated adduct of hydrated electron. A free radical mechanism of initial photochemical injury in UV-irradiated lens was discussed, comparing with a photolysis of tryptophan plus cysteine solution.

One of the research programs of the Australian Cataract Research Foundation (ACRF) is aimed at investigating the possibility that senile cataract both cortical and nuclear, may result from the interaction of reactive metabolites with proteins in the lens. In particular we are exploring the potential role of tryptophan metabolites for example, 3-hydroxyanthranilic acid, in this disease. This article examines briefly some aspects of this approach.

The purpose of this study was to reveal the presence of Z-helical conformation in normal crystalline lens DNA. Z-DNA antigen was prepared against poly(dG-dC).poly(dG-dC), which had been converted to the Z-helix conformation in high salt and then stabilized by bromination. Circular dichroism (CD) spectra confirmed the presence of left-handed Z-helix DNA. Antibodies to Z-DNA were raised in three rabbits immunized with brominated (Br-) poly(dG-dC).poly(dG-dC). These antibodies do not cross-react with polynucleotides in the B-helical form, but are specific to the left-handed Z-DNA conformation. DNA was isolated from three different regions of the calf lens. Anti-Z-DNA antisera, affinity purified IgG polyclonal anti-Z-DNA antibodies and monoclonal anti-Z-DNA antibodies were used as immunoprobes to detect the presence of S-DNA sequences. DNA from the cortex region of the lens reacted strongly with the anti-Z-DNA antibodies, but no binding could be observed in the DNA from the nucleus region. Digestion of lens DNA with DNase 1 dramatically decreased Z-DNA antibody binding, while RNase A and T1 treatment had no effect on Z-DNA immunoreactivity. This study has demonstrated that: (a) Z-DNA antibodies developed for our study can bind in high salt solutions (4M NaCl) to purified lens DNA sequences isolated from a variety of different calf lens cell types. By this criterion, lens DNA contains sequence determinants which may assume or are in the Z-helix conformation.

Freshly isolated rabbit lenses were cultured with and without attached iris-ciliary (IC)-complex for 24 hours in TC-199 medium. Subsequent morphological analysis revealed that the IC-complex cannot be maintained in serum-free medium. In addition an observed effect of the IC-complex on the co-cultured lenses could not be due only because of the cellular degeneration of the IC-complex. To test this possibility lenses with attached IC-complexes were incubated in 20% serum-containing TC-199 medium. The IC-complex cultured in 20% serum containing medium retained its normal morphology. However co-cultured lens cells displayed vacuoles and other signs of degeneration. The protein synthetic and Na+/K+ pump activities of these lenses were also significantly depressed. These data indicated that the observed effects of IC-complex on the lens were not due to its cellular degradation. Preliminary experiments showed that the IC-complex contains water soluble factor(s) which could effectively inhibit lens protein synthesis and Na+/K+ pump.