Lens and eye toxicity research最新文献

Our laboratory has demonstrated the potential of non-invasive biophysical methods in studying cataractogenesis. Initially these studies involved in vitro spectroscopic assays (UV, fluorescence and phosphorescence) on excised lenses or lens matter. In addition, we performed NMR pulse relaxation studies on extracted lenses which demonstrated an age-related increase in the T1 and T2 values of the normal lens. The in vitro fluorescence and NMR data suggested potential parameters for monitoring human and animal lenses in vivo. We then developed in vivo lens fluorescence densitography utilizing the Scheimpflug camera and have recently employed our Magnetic Resonance Imaging (MRI) method (using specially constructed small coils) to measure the moderately bound lens water compartment (T2) in vivo. Both of these in vivo methods correlate with our in vitro data and they demonstrate age-related changes in the normal lens; - i.e. - a progressive increase in fluorescence intensity and longer T2 values. Indices have been developed which permit us to detect abnormal lens fluorescence and changes in the moderately bound lens water (T2) compared with normal values for each specific age group by decade. These 2 non-invasive biophysical techniques can detect pre-cataractous changes in the living clear lens, months to years before any type of opacity becomes manifest with the conventional slit lamp method. The MRI technique can be performed in less than 20 minutes and the lens fluorescence method requires 4-6 minutes; thus they provide a rapid and objective in vivo measure of the status of the living lens as well as a method for evaluating anti-cataract drug efficacy.

The contour of OH stretching bands is very sensitive to any intra or intermolecular interactions. Thus it is interesting as a "marker" of cataractous stage of eye lens. Relative peak intensity and depolarization ratio of NH stretching band overlapping OH contour were estimated.

In 13 rabbits, 1 month to 1 year after posterior chamber lens implantation/polymethylmetacrylate/, the level of aqueous humor proteins was evaluated and the proteins separation in polyacylamide gel was performed. The studies were also carried out in unoperated eyes of the same animals and control group was composed of the eyes before surgery. It was found that in pseudophakic eyes an increased level of proteins remained during the whole year/the highest one month after surgery, slowly decreasing afterwards/, with the appearance of additional fractions. The moderate increase of the proteins concentration was also observed in unoperated eyes. The increase of aqueous humor proteins in pseudophakic eyes indicates that the presence of polymethyl metacrylate is not completely indifferent to the eyeball in spite of the suggestions derived from the clinical observations.

In order to establish the presence of Z-DNA sequences in the normal crystalline lens and to define their structure-function relationship, fixed and unfixed calf lens tissue sections were examined immunohistochemically. Polyclonal and monoclonal anti-Z-DNA antibodies were developed as immunoprobes, using brominated (Br-) poly(dG-dC).poly(dG-dC) as an antigen. The structure of the Z-helix antigen was confirmed by circular dichroism (CD) and U.V. spectroscopy. Whole rabbit and goat anti-Z-DNA sera; rabbit and goat IgG polyclonal anti-Z-DNA antibodies; and anti-Z-DNA monoclonal IgG antibodies were utilized as Z-DNA immunoprobes to localize the Z-DNA in calf lens tissue sections. Immunohistochemical examination using the peroxidase-antiperoxidase (PAP) method indicated that the cortex region of the lens reacted strongly with the anti-Z-DNA antibodies, while no immunoreaction could be observed in the nucleus region. Similar immunoreactive patterns were obtained whether whole sera, affinity purified IgG polyclonal antibodies or monoclonal antibodies were utilized. Immunobinding of anti-Z-DNA antibodies was low, effectively background type binding, in unfixed lens tissue sections. Various fixatives were tested to explore the potential antibody-Z-DNA interaction in calf lens tissue. Nuclear fixatives enhanced Z-DNA antibody immunoreactivity, while formalin, microanatomic and cytoplasmic fixatives produced lesser results. Digestion of the lens tissue with DNase I eliminated Z-DNA immunoreactivity, while RNase A and RNase T1 treatment had no effect. Actinomycin D also prevented Z-DNA immunoreactivity.

Distribution of ions and volume regulation of epithelial cells of lenses cultured in the presence and absence of vitreous humor were examined. Ion levels of the epithelial cells were measured using energy dispersive x-ray analysis(EDX) and computer-assisted morphometry was used for volume measurements. Data from these experiments revealed that the epithelial cells in the pre-equatorial region of lenses cultured without attached vitreous humor are larger and have significantly altered ionic balance. The cell volumes and ionic balances of central epithelial cells of the lenses cultured without attached vitreous humor also displayed discernible changes. However, overall data indicated that the epithelial cells in the pre-equatorial regions of the lenses are most susceptible to the effects of vitreous humor. Experiments performed in our laboratory have demonstrated that vitreous humor contains some factor(s) which can effectively inhibit protein synthesis. It was also reported that this factor(s) is not a direct inhibitor of protein synthesis. Therefore it was assumed that the inhibition of protein synthetic activity was mediated via some other pathway. One of these possible routes could be altered cytoplasmic ion fluxes. Earlier we reported that the ion levels of the lenses cultured with or without adhered vitreous humor were similar. Ion levels were measured from intact lenses. It is possible that there were regional differences in ion levels, which could be masked in whole lenses. It is also known that the epithelial cells are major participant in ion-pump activity, whereas cortical and nuclear areas of the lens may not contribute significantly to the ion transport. It has also been proposed that the epithelial cells of the pre-equatorial region are the main site of the Na+, K+ pump. Variation in ion levels of the epithelial cells could also affect protein synthesis activities of the lens. To test these possibilities, experiments were performed to measure ion levels in various areas of the lenses by energy dispersive x-ray analysis techniques. Altered cytoplasmic ion level can also change the volumes of the epithelial cells. This possibility was investigated by employing computer-assisted morphometry in measurements of two- and three-dimensional parameters of the lens epithelial cells and capsule.

The morphological sequelae of intracameral injections of hydrogen peroxide on the corneal endothelium were examined under different conditions. In animals pretreated with either intravenous 3-aminotriazole (3AT) alone, to suppress catalase activity, or intravitreal buthionine sulfoximine alone (BSO), to inhibit gamma-glutamyl synthetase activity, the endothelium was normal. The intracameral administration of 10 microliters of 10 mM hydrogen peroxide caused no response after 3AT and some small morphological but not physiological changes after BSO pretreatment. The intracameral injection of 10 microliters of 25 mM hydrogen peroxide caused no additional change in 3AT pretreated rabbits, but caused substantial morphological and physiological changes in BSO pretreated rabbits. The correlation between the present morphological changes and those seen earlier in physiological studies is excellent. The data confirm that the glutathione redox system may be more important than catalase in maintaining the integrity of the corneal endothelium at low aqueous humor concentrations of hydrogen peroxide while catalase assumes greater importance at higher peroxide concentrations.

A systematic study of the temperature dependence of progressive saturation relaxation spectra was carried out on the nucleus and cortex of normal and cataractous eye lenses at different temperatures below freezing. A more complicated fine structure was detected, than was previously thought. The method utilized may well be applied in tomography as well.

The loss of transparency of the ocular lens is caused by the increase of light scattering as a result of structural changes and by the increased absorption of the visible light due to the accumulation of pigments. Following light absorption, these pigments undergo non-radiative and radiative (luminescence) processes which can be monitored spectroscopically. The paper presents some new results concerning the excitation spectra, decay times and polarization of the lenticular fluorescence. Fluorophore heterogeneity manifests itself in all the experimental data. A striking behaviour of the emission anisotropy as a function of temperature is found, particularly for cortical cataract lenses, indicating temperature-induced structural changes at about 20 degrees C.

Histopathological findings in 33 intracapsularly removed lenses and 35 enucleated eye-balls are presented. Anterior and posterior subcapsular cataracts were mostly seen in traumatic and advanced senile cataracts. Characteristic features of the latter were cortical degeneration and liquefaction with formation of Morgagnian globules and nuclear sclerosis. Anterior lens epithelium had more tendency to undergo fibrous pseudometaplasia, while equatorial epithelium migrated posteriorly with "bladder cell" formation. In complicated and traumatic cataracts, apart from abnormal proliferation of lens epithelium, frequent synechiae with iris and/or cyclitic membranes were seen. Phacoanaphylactic uveitis was observed in 6 eyes with capsular defects. Pseudoexfoliative material was found in 5 cases. It is suggested, that domination of proliferative changes in traumatic and complicated cataracts, in contrast to senile cataracts, results from the availability of different mitogenic factors in injured and inflammed eyes and may be due to the younger age of patients in this group.

Beagles were treated with bisoprolol, a beta 1-selective adrenoceptor antagonist, for 30 days with the following daily doses: oral: 30 mg/kg; conjunctival: 0.5% solution (approx. 0.04 mg/kg) and 5% solution (approx. 0.4 mg/kg). Drug concentrations were determined in plasma and various eye tissues on days 1, 16, and 30, and on day 59, i.e. on day 29 of the follow-up period. Bisoprolol concentrations in plasma and most eye tissues were considerably higher after oral than after conjunctival treatment. The highest tissue concentrations were observed in the iris (+ciliary body) and retina (+choroid) with tissue/plasma concentration ratios between 100 and 150 after oral and 1000 to 3000 after conjunctival instillation (5% solution). In plasma no accumulation of the drug was observed which is in accordance with its plasma half-life of 4 to 5 h. In contrast to this, concentrations in the iris and retina increased from day 1 to day 16 and 30 by 3 to 8 times and the half-life of bisoprolol in these tissues was estimated to be between 3 to 5 days.