Light scattering in normal and cataractous lenses of farmed Atlantic salmon (Salmo salar): a slit lamp and Scheimpflug photographic study.

To investigate normal light scattering and cataract formation, the anterior eye segments of farmed Atlantic salmon (Salmo salar) reared in fresh water and sea water were documented in vivo for the first time with a Topcon SL-45 Scheimpflug camera. A total of 40 fish from the fresh-water-rearing period, obtained from 2 groups of identical age but showing a different growth rate, and 24 fish from the sea-water-rearing period, sampled from 2 groups with identical age but being fed different food brands, were included in this study. The fish were anaesthetized before examination. Due to the naturally wide pupil, no mydriatic compound was applied. All fish were removed from the water for photography, which was performed for each eye in 0 degrees = vertical slit position. Images were recorded on Kodak Tmax 400 black-and-white film. Microdensitometric image analysis of all negatives was performed using a Joyce-Loebl online microdensitometer. In spite of the virtual absence of an anterior chamber gap between cornea and lens and very little light scattering in the normal fish lens, a small number of distinct layers could be reproducibly identified in the lens. While there was little abnormal light scattering which could point to cataract development in young fish from the fresh water period, the evaluation of the lenses from the 2 sea water groups showed the presence of specific forms of cataract especially in the cortical and supranuclear layers. There were significant differences between the groups fed different food brands at the sea water site. In conclusion, Scheimpflug photography proved to be applicable to eye research in fish in vivo. It is suggested that this method should be employed for reproducible documentation as an extension to slit lamp monitoring in experimental research to reveal causative factors for cataracts in farmed fish.

Comparison of various calpain inhibitors in reduction of light scattering, protein precipitation and nuclear cataract in vitro.

PURPOSE: To compare effects of calpain inhibitors on in vitro light-scattering in rat lens soluble protein and calcium-ionophore (A23187)-induced cataract formation in cultured rat lenses. METHODS: Rat lens soluble protein was hydrolyzed for 24 hours by activation of endogenous lens calpain. Ten calpain inhibitors were tested in this model at 10 and 25 microM concentration. As an index of protein precipitation, light scattering was measured daily at 405 nm for 8 days. Lens proteins were analyzed by isoelectric-focussing. Subsequently, rat lenses were cultured for 5 days with 10 microM A23187. Calpain inhibitors (SJA6017, MDL28170, AK295 and PD150606), which inhibited light-scattering were tested at 100 microM concentration in this model. Cataract evaluation, isoelectric-focussing and calcium determinations were performed. RESULTS: At 25 microM concentration AK295, SJA6017, E-64, PD-150606 and MDL28170 produced greater than 25% inhibition of light-scattering. Isoelectric-focussing revealed that addition of Ca(2+) produced characteristic crystallin proteolysis and aggregation patterns. AK295, SJA6017, MDL28170 and E64c prevented these changes. Lenses cultured in A23187 exhibited nuclear cataract, elevated calcium and proteolysis and aggregation of crystallins. Co-culture with SJA6017, MDL28170 and E64c reduced A23187-induced nuclear opacities, proteolysis and aggregation of crystallins without affecting increased total calcium. CONCLUSIONS: Endogenous calpain-activation model and A23187-induced cataract model can be used sequentially to screen calpain inhibitors for potential anti-cataract activity. Proteolytic changes in lens cortex after exposure to A23187 are also due to calpain activation. AK295, SJA6017 and MDL28170 possess efficacy against calcium-induced models of rodent cataracts. Use of calpain inhibitors represents a promising approach to cataract therapy.

Higher glycation of beta L- and beta S-crystallins in the anterior lens cortex and maximum glycation of gamma-crystallins in the bovine lens nucleus, demonstrated by frozen sectioning, isoelectric focusing and lectin staining.

The aim of the current study was to demonstrate glycation of beta L-, beta S- and gamma-crystallins in the young bovine lens. To establish which of the crystallins are glycated and where they are located in the lens, we carried out microsectioning of the lens, followed by isoelectric focusing (IEF). Four bovine lenses of 1.183 +/- 0.070 years were frozen-sectioned into equator and 11 layers. Water-soluble crystallins were separated by IEF and stained: (1) with Coomassie brilliant blue for proteins; (2) with the lectin concanavalin A, followed by horseradish peroxidase and diaminobenzidine, for glycated proteins. Experiments were performed with crystallins and proteins in native form, in the absence of denaturants. The crystallins were separated by IEF into alpha-crystallins of high molecular weight (HM), alpha L-, beta H-, beta L-, beta S- and gamma-crystallins. In the lectin staining experiments, only HM, beta L-, beta S- and gamma-crystallins were positive, whereas the alpha L- and beta H-crystallins were negative. Contrary to the glycated gamma-crystallins in the lens nucleus, the beta S- and beta L-crystallins were predominantly glycated in the anterior cortex and to a somewhat lower extent also in the posterior cortical regions. The degree of glycation (total densitometric readings of lectin-stained bands/Coomassie-blue-stained bands) is as follows: total gamma-crystallins 2.44, beta S-crystallins 0.77 and beta L-crystallins 0.28. Though glycation in the bovine lens is very low, lectin staining is sufficiently sensitive to detect the various glycated crystallins. The degree of glycation of gamma-crystallins was 3 times higher than that of beta S-crystallins and 9 times higher than that of beta L-crystallins.

The glycation of bovine lens betaL-, betaS- and gamma-crystallins demonstrated by isoelectric focusing and lectin staining.

The aim of the current study is to detect glycation of betaL-, betaS- and gamma-crystallins in the young bovine lens. To determine which of the crystallins are glycated, we have made isoelectric focusing of the water-soluble crystallins of four bovine lenses of 1. 183+/-0.070 years. Samples are stained: (1) with Coomassie Brilliant Blue for proteins; (2) with the lectin Concanavalin-A, followed by horse-radish peroxidase (HRP) and diaminobenzidine (DAB). Experiments are performed with crystallins in native form, in absence of denaturants. The crystallins are separated by isoelectric focusing into: alpha-crystallins of high-molecular weight (HM)-, alphaL-, betaH-, betaL-, betaS- and gamma-crystallins. In the lectin staining experiments only HM-, beta L-, betaS- and gamma-crystallins are positive, whereas the alphaL- and betaH-crystallins do not stain. Though glycation in the bovine lens is very low, lectin staining is sufficiently sensitive to detect the various glycated crystallins.

Detection of glycated fetal human lens crystallins by concanavalin-A and aldehyde staining.

The binding of the lectin Concanavalin-A (Con-A) to crystallins was investigated. For this purpose, human fetal and juvenile lens crystallins were isofocused and specifically stained brown for glycoproteins by the lectin Con-A, and purple by the periodic acid Schiff's reagent (PAS). In reference experiments protein bands were stained with Coomassie Blue for proteins. Since Con-A is a protein with glucose-specific receptors, the following crystallins, glycated with this sugar, were visualized after isoelectric focusing: HM-, beta L-, beta S- and gamma-crystallins, but not alpha L- and beta H-crystallins. Glycation increased significantly with fetal age. The crystallins themselves could also function as sugar receptors, because it was shown that they possessed also receptors for glucose, like Con-A. This crystallin receptor staining revealed beta L-, beta S-, gamma- but hardly HM-crystallins. The PAS, Con-A and receptor stainings gave in principle identical results. The glycoproteins Con-A, horseradish peroxidase and lentil lectins were used as positive controls.

Staining of free sulfhydryl groups of proteins after separation by isoelectric focusing of Bio-Rad standards and lens crystallins.

In this study, we propose a new staining method for free sulfhydryl groups of proteins after having separated native samples by thin-layer isoelectric focusing (IEF) in absence of detergents. A comparison was made between proteins stained purple for free sulfhydryl groups (SH) and proteins stained blue by Coomassie blue (CB). A stainability factor, F = %SH/%CB, was calculated for each protein. The Bio-Rad IEF standards containing seven marker proteins for pH scale determination were stained purple, in the same way as they were designed for CB staining. To prove the validity of the currently proposed staining method for a defined protein system such as the eye lens crystallins, these proteins were also stained after IEF as described above. The factor F was calculated for all alpha-, beta-, and gamma-crystallin components that stained in both methods. We discovered that alpha-crystallins contained comparatively high amounts of free SH groups, while some beta- and gamma-crystallin components also contained considerable amounts of free SH groups. The SH staining procedure with 2,2'-dihydroxy-6,6'-dinaphthyl disulfide applied after IEF appeared to be useful, specific, and reproducible.

Water-insoluble high-molecular-weight and alpha-crystallins as the source of the Scheimpflug light scattering pattern in the rat lens.

Lenses of 14-week-old rats were separated into 10 layers or fractions by a frozen-sectioning technique. The biochemical characteristics of these layers were assigned to corresponding parts of the densitometric reading obtained from the Scheimpflug negative, which enables a correlation of light scattering values recorded in vivo to protein patterns in the same area. Calculated as percentage of lens dry weight, all water-soluble crystallins show minima and the water-insoluble crystallins show maxima in the lens nucleus. This demonstrates that the nucleus contains the bulk of the water-insoluble high-molecular-weight and alpha-crystallins, being the source for the Scheimpflug light scattering pattern.

Crystallin profiles of calf and bovine lens microsections, stained for free sulfhydryl groups and proteins.

Calf and bovine lenses of 0.98 and 8.40 years old were separated mechanically into lens equator and inner cylinder. The inner cylinder was cut into 10 to 11 sections by a microsectioning device. These sections were investigated on the protein profiles of water-soluble crystallins, stained for proteins by Coomassie Blue (CB). These crystallins were also specifically stained purple for free sulfhydryl groups (SH). It appeared that all crystallins that were stained blue for proteins were also stained purple for sulfhydryl groups. This means that all crystallins contain free sulfhydryl groups. Going from anterior and posterior cortex to the nucleus of the lens, there was an appreciable increase of the percent of gamma-crystallins, whereas especially in the older lenses a decrease of gamma-crystallins could be observed in the lens equator and the anterior and posterior cortices. A stainability factor F = %SH/%CB was calculated for all crystallins. HM-, alpha- and beta s-crystallins exhibit high values of factor F. For the bovine lens, factor F of HM-crystallin displayed a maximum in the nucleus, whereas this factor decreased for gamma-crystallins towards the nucleus. This microsectioning technique allows for determining age-related differences between the sections obtained. This may lead to a comprehensive understanding of age-related changes within one lens, including cataractous changes.

Water-soluble and insoluble crystallins of the developing human fetal lens, analyzed by agarose/polyacrylamide thin-layer isoelectric focusing.

Eight human fetal lenses, selected on basis of normality, of a gestational age of 119 to 231 days were analyzed by thin-layer isoelectric focusing (IEF) in agarose/polyacrylamide gels. This method was adapted for the separation of lens crystallins into HM-, alpha-, beta- and gamma-crystallins. It is especially suitable for analysis under non-denaturing conditions of high-molecular-weight crystallins and of insoluble crystallins (WI) solubilized in formamide. The latter could be separated into HM-, alpha- and gamma-crystallins. During fetal development, a considerable increase of gamma-crystallin proportion was observed due to new synthesis. This increase was balanced by a decrease of alpha-crystallin proportion.

Correlation of Scheimpflug photography of the anterior eye segment with biochemical analysis of the lens. Application of a frozen-sectioning technique to investigate differences in protein distribution of single lens layers.

Normal and cataractous lenses were separated mechanically into lens equator and inner cylinder and the latter then sectioned in a freezing microtome. Fractions with 120-140 sections each were collected representing single lens layers, and the content of water-soluble and insoluble proteins was determined. Protein profiles for each lens layer were obtained by means of isoelectric focusing in special agarose gels. Using this microsectioning technique, it was possible to demonstrate differences in the protein distribution in single layers of both normal and cataractous human lenses. Comparison of the protein profiles of the normal lens and the lenses of different cataract morphology used in this study demonstrates the potential usefulness of this methodology for future research with cataract lenses.