Hydration properties of the molecular chaperone alpha-crystallin in the bovine lens

Topographic studies of crystalline fractions from different morphological layers of the young adult bovine lens were conducted. Crystallin profiles were obtained for each lens layer, using thin-layer isoelectric focusing in polyacrylamide gel (IEF). Water soluble (WS) crystallins from the lens equator revealed a separation into HM (high molecular weight) alpha(L)-, beta(H)-, beta(L)-, beta(S)-, and gamma-crystallins. The nature of the water insoluble (WI) protein fraction in the separated lens layers reflected the aggregated state of alpha(L)-, beta(L)-, beta(S)-, and gamma-crystallins in different regions of the lens, concealed in the central cavity of the alpha-crystallin chaperone model. The IEF data demonstrate a possible chaperone-like function for alpha-crystallin in the nucleus and inner cortex of the lens, but not in the outer cortex. The water binding properties of bovine lens alpha-crystallin, calf skin collagen, and bovine serum albumin (BSA) were investigated with various techniques. The water adsorptive capacity was obtained in high vacuum desorption experiments volumetrically, and also gravimetrically in controlled atmosphere experiments. The NMR spin-echo technique was used to study the hydration of protein samples and to determine the spin-spin relaxation times (T(2)) from the protons of water adsorbed on the proteins. Isolated bovine lenses were sectioned into 11-12 morphological layers (from anterior cortex through nucleus to posterior cortex). The water content in relation to dry weight of proteins was measured in individual morphological lens layers. During water vapor uptake at relative humidity P/P(0) = 0.75, alpha-crystallin did not adsorb water suggesting that hydrophobic regions of the protein are exposed to the aqueous solvent. At relative humidity P/P(0) = 1.0, the adsorption of water by alpha-crystallin was 17% with a single component decay character of spin echo (T(2) = 3 msec). Addition of water to alpha-crystallin to about 50% of its weight/weight in the protein sample showed T(2) = 8 msec with only one single component decay of the spin-echo signal. The single component decay character of the spin echo indicates water tightly bound by alpha-crystallin. Under a relative humidity P/P(0) = 1.0, collagen and BSA adsorbed, correspondingly, 19.3 and 28% of water and showed a two-component decay curve with T(2) about 5 and 40 msec. The findings demonstrate the presence of two water fractions in collagen and BSA which are separated in space. The IEF data suggest a tight binding of water with alpha-crystallin with similar distribution patterns in the lens layers. To conclude, it was found that alpha-crystallin can immobilize water to a greater extent than other proteins such as collagen and BSA. These results shed new light on structural properties of alpha-crystallin and its superhydration properties and have important implications for understanding the mechanism of the chaperone-like action of this protein in the lens and non-ocular tissues.

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.

Analysis of tear proteins by one- and two-dimensional thin-layer iosoelectric focusing, sodium dodecyl sulfate electrophoresis and lectin blotting. Detection of a new component: cystatin C

BACKGROUND

Isoelectric focusing (IEF) of tear proteins has not yet been carried out in a satisfactory way. Two-dimensional (2D) electrophoresis, especially in the combination of IEF with SDS, is able to differentiate between proteins in detail. The purpose of this study was therefore to analyze tear proteins by 1D IEF alone and in combination with a 2D pattern, and by IEF followed by lectin staining.

METHODS

Ampholines, covering a broad range from pH 3 to pH 10, were applied. After IEF, semi-dry blotting and incubation with a group II lectin and two group V lectins was performed.

RESULTS

Tear proteins could be separated into 31 single bands. Tear-specific pre-albumin (TSPA), lactoferrin, sIgA, IgG and lysozyme were found to be main components. Isoelectric points (IEPs, pls) of all proteins separated were determined by comparison with IEF standards. 2D patterns of IEF and SDS electrophoresis were obtained for the main subunit components of lactoferrin, sIgA, TSPA, and lysozyme. An additional new component of considerable concentration was focused at pI 8.6 with a subunit MW of 14 kDa. With s-WGA a component at an IEP of 5.2 was visualized, representing transferrin. With SNA, lactoferrin stained as a sharp main band at pI 5.1 with three additional weaker bands at IEPs from 4.8 to 4.9. At IEPs between 4.4 and 6.1, multiple components of sIgA were stained with MAA. The sugar specificity of transferrin at pI 5.2 was beta-GlcNAc. Lactoferrin showed glycation with NANA-alpha-2-6-Gal or NANA-alpha-2-6-GalNAc, whereas the sugar specificity of sIgA was NANA-alpha-2-3-Gal.

CONCLUSIONS

The investigative strategy applied here, including IEF alone, in combination with SDS-electrophoresis, and SDS-electrophoresis followed by lectin staining proved to be a reproducible method for tear protein analysis of hitherto unexperienced capacity. Lectin-stained bands of native tear proteins are not uniformly glycated by one sugar residue, but show various sugar specificities. IgA as a whole molecule is specifically glycated with NANA-alpha-2-3-Gal.

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.

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.

Comparative investigations on water-soluble crystallins of the embryonic, fetal, and postnatal human lens during development and ageing

To compare the crystallin composition of embryonic and fetal human lenses with those of postnatal and adult lenses, we investigated the crystallins of lenses of various ages (from the 5th gestational week to 55 years) by gel chromatography, isoelectric focusing, immunodiffusion, and immunoelectrophoresis. Age-related changes were calculated as relative percentages of the different classes and subclasses of crystallins. During prenatal lens development the percentages of both high- and low-molecular-weight alpha-crystallins as well as gamma-crystallins gradually increased, whereas the percentage of beta-crystallins decreased. A considerable change in crystallin composition was found immediately after birth: the relative percentage of beta-crystallins increased, whereas that of gamma-crystallins decreased. Gel-filtration analysis of crystallins from juvenile and adult lenses showed a high-molecular-weight peak, which was not found in extracts from fetal and new-born lenses.

Isoelectric focusing of crystallins in microsections of calf and adult bovine lens. Identification of water-insoluble crystallins complexing under nondenaturing conditions: demonstration of chaperone activity of alpha-crystallin

Topographic studies of crystallin fractions from the young adult bovine lens revealed that lenses do not have a homogeneous distribution of crystallins. There are, however, gradual differences between the cortices and the nucleus. The isolated lenses were separated mechanically into lens equator and inner cylinder. The latter was then sectioned in a special sectioning machine into 11-12 morphological layers (from anterior cortex through nucleus to posterior cortex). Matters of the lens sections were separated into water-soluble (WS) and water-insoluble (WI) crystallins. The WI fractions were solubilized with 100% formamide, or dissolved into 7 M urea. Crystallin profiles were obtained for each lens layer, using thin-layer isoelectric focusing in polyacrylamide gel. WS crystallins from the lens equator revealed a separation into HM-, alpha L-, beta H-, beta L-, beta S- and gamma-crystallins. The WI fractions of the layers dissolved in urea gave a separation into the individual HM- (3 components), alpha L- (4 components), beta- (6 component groups), beta S- (2 components) and gamma- (11 components) crystallins in the different morphological layers. The results confirm that a significant age-related increase in several beta- and gamma-crystallins incorporated into alpha-crystallins exists in the patterns of WI fractions of the different layers from lenses of 2.2 and 5.9 years. The WI crystallins solubilized in formamide showed only the presence of HM weight and alpha-crystallin moieties, due to the action of chaperone activity of alpha-crystallin. The nature of the WI protein fraction in the separated lens layers reflected to the aggregated state of: alpha L-, beta L-, beta S- and gamma-crystallins in the different regions of the lens, concealed in the central cavity of the alpha-crystallin chaperone model.

Calf lens alpha-crystallin, a molecular chaperone, builds stable complexes with beta s- and gamma-crystallins

Calf water-soluble (WS) crystallins consist of high-molecular weight (HM), alpha-, beta H-, beta L-, beta s- and gamma-crystallins. alpha-Crystallin as a molecular chaperone forms a structure with a central hole, known as Carver's model. The only crystallins fitting into this central cavity are beta s- and gamma-crystallins, with native molecular weights of 28 and 18.5-21 kD, respectively. The beta s-crystallin is loosely bound to this structure, whereas with the application of 7M urea in the sample, beta s-, may be some beta L-components and all gamma-crystallins emerge from the central hole. Although WS and water-insoluble (WI) crystallins display the same immunologic determinants, there is an appreciable difference in electrophoretic mobility already in the young calf lens. alpha-Crystallins from the WI part demonstrate a clear cathodic shift. WI beta- and gamma-crystallins show smaller but well perceptible cathodic shifts. The chaperone function of alpha-crystallin preserves the original structures of beta s- and gamma-crystallins for aggregation and other influences.

Distribution of water-soluble crystallins in microsectioned cataractous lenses from one hundred Egyptian patients

Morphologically classified lenses from 100 cataract patients from the Mansoura Eye Hospital (Egypt) were microdissected and the crystallin composition and distribution were analyzed by thin-layer isoelectric focusing (IEF). The IEF profiles of cataractous lenses were compared with each other, with those of sclerotic lenses and with a normal lens profile. The alterations in the composition of high-molecular-weight (HMW)-, alpha-, beta H-, beta L-, beta s-, and gamma-crystallins along with normal aging, are superimposed by pronounced cataract-related changes which are different for the various types of cataracts. The general feature includes a continuous loss of gamma-, beta s- and beta L-crystallins of higher IEPs and an increase of HMW material. This is highly pronounced in the nucleus of nuclear cataractous lenses. In cortical cataractous lenses, changes start in the cortical layers. No differences could be observed between alterations in Caucasian lenses and this extended Egyptian lens population.

Basic biochemical parameters of one hundred cataractous lenses from Egyptian patients

Cataractous lenses from an extended population of 100 Egyptian patients whose age, sex and case history had been recorded, were collected and classified morphologically. After determination of the lens wet weights, lenses were microsectioned and basic parameters such as wet weight, dry weight, water content and contents of water-soluble and water-insoluble crystallins of the samples were determined. The data obtained document moderate as well as drastic changes of the investigated parameters along with aging and cataractogenesis, and extend our knowledge from small numbers of hitherto investigated human lenses to a considerably high number of cases.

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.

Molecular mass distribution of water-soluble crystallins from the human foetal lens during development

The water-soluble crystallins of twenty human foetal lenses with gestational ages of 112-231 days were analysed by size-exclusion chromatography. The crystallin distribution showed similar patterns for all foetal lenses, but clear changes in the proportions of different crystallins were evident. The distribution showed that the water-soluble part of all the lenses already contained high-molecular-mass material. Also beta-crystallins of high molecular mass (beta H), formed by post-translational changes, were detected in all stages. During gestation, the percentage of high-molecular-mass crystallins and of alpha-crystallins of low molecular mass (alpha L) decreased significantly. The total beta-crystallins (beta T) and the total gamma-crystallins (gamma T) increased significantly. The low Mr crystallins were resolved into three peaks, designated beta s-, gamma H- and gamma L-crystallins. They increased significantly during development. These significant increases of the low Mr crystallins took place exclusively in the developing lens. The rate of protein synthesis of the low Mr crystallins was 23% of the total water-soluble crystallin synthesis rate.

Protein profiles of microsections of the fetal and adult human lens during development and ageing

The water-soluble proteins of the human fetal lens (175- and 285-day-old) contain HM-, pre-alpha-, alpha-, beta- and gamma-crystallins. Using the frozen-sectioning technique, it can be demonstrated that the fetal lens does not have an homogeneous distribution of crystallins, but there are gradual differences between the cortices and the nucleus. The frozen-sectioning technique shows for the adult lens significantly increasing amounts of beta-crystallins of pI 4.95-5.55, especially at the posterior supra-nuclear layer, increasing amounts of HM-crystallins and decreasing amounts of beta-crystallins of pI 5.80-7.05 in the nucleus. This microsectioning technique was correlated with Scheimpflug photographs of the fetal and adult lens. In the fetal lens, the anterior capsule and 2 peaks in the anterior and posterior supranuclear layers could be visualized after densitometry. In the adult lens 5 layers could be demonstrated, e.g. the anterior capsule, the anterior supranuclear layer, the nucleus, the posterior supranuclear layer and the anterior capsule.

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.

The quantification of eight enzymes from the ageing rat lens, with respect to sex differences and special reference to aldolase

Eight enzymes, e.g. lactate dehydrogenase, malate dehydrogenase, fructose-diphosphate aldolase, sorbitol dehydrogenase, glucose-6-phosphate dehydrogenase, hexokinase, phosphofructokinase and pyruvate kinase were estimated quantitatively in the rat lens from 37 to 1,211 days of age, by spectrophotometric methods. The activity was expressed as mU/g LWW. All enzymes measured showed declining activities, but LDH, ALD, SDH, G-6-PDH, HK and PFK gave a significant decrease during ageing when plotted semi-logarithmically from 37 to 1,211 days. SDH and G-6-PDH showed a statistically significant difference between the enzymes from the male and the female lenses. The female lens always had a lower activity than the male lens. Of all enzymes the specific activity, expressed as mU/l mg protein, was calculated. This specific activity appeared to be rather constant during ageing, except for ALD. In the female lenses, the specific activity of 7 enzymes was lower than in the male lenses. For ALD the specific activity decreased significantly in the male lens from 5.32 at 37 days to 0.88 at 1,211 days. In the female lens this significant decrease was from 4.97 to 0.81.

Alterations of lens metabolism with experimentally induced cataract in rats

Rat lenses with experimentally induced cataract (either by naphthalene or by streptozotocin) were analyzed biochemically. Both noxae had some effects in common. Water-soluble protein and aldose reductase activity decreased, and glucose-6-phosphate dehydrogenase, phosphofructokinase and glutathione reductase activity increased. A specific effect of streptozotocin was the rise in glucose, fructose and sorbitol. A specific effect of naphthalene was increased amounts of water-insoluble protein.

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.

Age-related changes in water and crystallin content of the fetal and adult human lens, demonstrated by a microsectioning technique

By means of a microsectioning technique, human fetal and adult lenses were divided into 8-16 fractions. The dry weight (DW), the water content, and the amounts of water-soluble (WS) crystallins and water-insoluble (WI) lens fraction were determined in each layer or fraction. Within the lens, the changes of these parameters are gradual and continuous. The lens nucleus contains the highest amounts of DW and WI fraction, and the lowest amounts of water and WS crystallins. There is a relative dehydration of the lens during development and ageing, most pronounced in the lens nucleus.

Age-related variations in the distribution of crystallins within the bovine lens

The native water-soluble proteins of equator, anterior cortex, posterior cortex and nucleus from bovine lenses in the age range 0.3-33.7 years were analyzed by high-pressure gel-permeation chromatography and high-pressure ion-exchange chromatography. Unlike the equator and cortices, the nucleus shows a gradual decrease in alpha-crystallin proportion with age which is not compensated for by an increase in HM-crystallin. The beta 6H-crystallin species, almost the only beta H-component in the youngest lens, is largely replaced by at least four fractions with higher and lower molecular weights in the older lenses. In the nucleus a beta L-component (39,000 MW) increasingly seems to replace the major beta L-crystallin (beta 2L, 50,000 MW). Moreover, a switch in the synthesis of monomeric crystallins is demonstrated. This study clearly reveals an age-related increase in the size heterogeneity of the native soluble crystallins with age.

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.

Human fetal lens: wet and dry weight with increasing gestational age

The lens wet weight (LWW) and its relationship with fetal age was determined for 32 lenses between gestational ages of 119 and 242 days. In addition to the water content, lens dry weight, water-soluble (WS) and water-insoluble (WI) protein content were determined. The increase in LWW with increasing fetal age appeared to be exponential. The WS protein content increased from 2.9 to 15.3 mg and that of the WI from 0.07 to 0.53 mg. The lens water decreased from 82.2 to 75.7%. This decrease reflects the protein increase during gestation. A formula expressing the relation between LWW and fetal age was calculated and compared with formulae calculated from results obtained by other authors.

Influence of high-dose verapamil on beagle lens proteins (chronic toxicity test)

After oral long-term administration to beagle dogs at doses within toxic and lethal ranges, some animals showed impaired lens transparency. These changes could not be reproduced in rats, even with specifically designed investigations. In man a comparable influence on lens transparency could not be observed either. In the course of further experiments it was demonstrated that the beagle lens changes are a 'species-specific process' which may be attributed to the species-specificity of dog lens proteins. In this study verapamil's influence on the composition of water-soluble and water-insoluble dog lens proteins was tested. 4 beagle dogs were treated daily with a very high dose of 81 mg/kg b.w. verapamil X HCl for 19 months. 3 untreated animals were available as controls. During the mentioned test period microscopic observations with the slit lamp did not reveal any pathological lens findings. In the verapamil-treated animals, however, a lower lens fresh weight and a lower content of water-soluble proteins occurred at the end of the experiment, compared to the control animals of the same age. This indicates a slowing down of lens growth. The distribution of the water-soluble crystallin fractions of dog lenses was determined using thin-layer isoelectric focusing. Significant changes in the single crystallin fractions were demonstrated only in the equator of the lens and in the anterior layer of the cortex. The alpha-crystallin fraction was found to be increased, the beta-crystallin fraction to be decreased.(ABSTRACT TRUNCATED AT 250 WORDS)

Isotachophoresis of human fetal lens crystallins with increasing gestational age

Eight selected fetal lenses of 119-231 days of gestation were analyzed by capillary isotachophoresis. A reproducible separation into pre-alpha-, alpha-, beta- and gamma-crystallins was achieved. During development, an increase was observed in beta s- and gamma-crystallins, balanced by a decrease in total alpha- and beta-crystallins. Isotachophoresis enabled a separation into at least 48 main crystallin components.

Isotachophoresis and immunoelectrophoresis of water-soluble and -insoluble crystallins of the ageing bovine lens

Water-soluble (WS) and water-insoluble (WI) crystallins were prepared from calf and bovine lenses. The WS-crystallins were analyzed by capillary isotachophoresis and by immunoelectrophoresis with polyvalent and alpha-, beta-, gamma-crystallin specific antisera. The WI-crystallins were first solubilized in formamide and then analyzed by the same methods. The WS-crystallins, which increase in weight, but decrease in % with increasing age, show an increase of alpha-crystallins from 36 to 43%, an increase of beta-crystallins from 42 to 48% and a decrease of gamma-crystallins from 22 to 9%. In the WI-crystallins, which increase in weight and in % with increasing age, the alpha-crystallins form the main portion with an increase from 54 to 61%. The beta-crystallins in WI remain fairly constant at about 37% and the gamma-crystallins decrease from 8 to 2%. Quantitatively, the alpha-crystallin is the major constituent of the lens. The alpha-crystallin and the beta-crystallin components are increasingly incorporated in WI with increasing age. The gamma-crystallin components are selectively incorporated into WI-protein. Immunologically, alpha-, beta- and gamma-crystallins were detected by the polyvalent and specific antisera in WS- and in WI- crystallins.

Biochemistry of the ageing rat lens. II. Isoelectric focusing of water-soluble crystallins

Thin-layer isoelectric focusing of the water-soluble crystallins shows with increasing age of the animals an increase of alpha-crystallins of high and low molecular weight and of the total beta-crystallins content. The beta-crystallin components of high molecular weight also increased during ageing, but the beta-crystallins of lower molecular weight decreased considerably. The total gamma-crystallin content, as well as certain gamma-crystallin components also decreased considerably with increasing age, or vanished completely. From 429 to 1,211 days of age the male gamma-crystallins as percent of the water-soluble moiety, were higher than the female gamma-crystallins. As a consequence of ascending age, the content of water-insoluble proteins of the rat lens increased gradually and continuously, e.g. by a process of insolubilization of soluble beta- and gamma-crystallins.

Biochemistry of the ageing rat lens. I. Lens wet weight and lens dry weight with respect to sex differences

The lens wet weight differed from the age of 136 days: the male lenses were significantly heavier than the female lenses. The dry weight, in percent of the lens wet and dry weight, of the water-soluble proteins decreased and the dry weight of the water-insoluble proteins increased during ageing. At an age of 870 days, when the dry weight curves crossed each other, the lens contains equal amounts of water-soluble and water-insoluble proteins. At the end of the life expectancy, the relation between the water-soluble and water-insoluble moiety was 0.7 for the rat and 3.5 for the bovine lens. The dry weight percent of the water-soluble proteins was lower for the female lens, whereas that of the water-insoluble proteins was higher for the female lens. The male lens, on the contrary, showed a higher percentage of water-soluble and a lower percentage of water-insoluble proteins with increasing age. The ratio R of the dry weight of water-soluble to water-insoluble proteins was, from the age of 429 days, lower for the female lens. During ageing, the proportion of the lens-water was higher for the male lens.

Age-related changes of glyceraldehyde-3-phosphate-dehydrogenase (E.C. 1.2.1.12), 3-phosphoglyceratekinase (E.C. 2.7.2.3), phosphoglyceratemutase (E.C. 2.7.5.3), and enolase (E.C. 4.2.1.11) in bovine lenses

The specific activities of the four investigated enzymes of the carbohydrate metabolism decrease with ageing. In the old tissue, phosphoglyceratemutase and enolase sustain changes in their molecular weight, and their substrate affinity is modified.

Immunological properties of rat lens gamma-crystallins. III. Changes during development and ageing

The rat lens contains three immunologically different gamma-crystallins, gamma 1-, gamma 2-, and gamma 3-crystallins. With the aid of specific antisera, it could be established that partial identity exists between gamma 1- and gamma 2-crystallins, and non-identity between gamma 1- and gamma 3-, and between gamma 2- and gamma 3-crystallins. The occurrence of these three crystallins has been investigated in rat lenses, aged 5-1,162 days, by isoelectric focusing, immunofocusing and immunodiffusion. The gamma 1- and gamma 2-crystallins are already present in 5-day-old lenses, but diminish during ageing and finally disappear. In contrast, gamma 3-crystallin develops first in 10-day-old lenses, it remains present during progressed ageing.

Age-dependent variations in the distribution of rat lens water-soluble crystallins. Size fractionation and molecular weight determination

In order to obtain deeper insights into the mechanisms that are responsible for the age-related changes in the eye lens, the water-soluble proteins of 6-day-old to over 3-year-old rat lenses were analyzed by high-performance gel-permeation chromatography. Using this technique eleven crystallin fractions could be discerned: HM-, alpha-, three beta H-, two beta L-, beta S- and three gamma-crystallins. The concentrations of the higher molecular weight crystallins (HM-, alpha- and beta H-crystallin) seem to increase with age while those of the lower molecular weight (beta L- and gamma-crystallin) decrease. Taking into account the gradual increase of water-insoluble protein with aging, the relative amount of alpha-crystallin decreases from an age of 0.5 year after an initial increase. Additionally, an age-dependent increase in its molecular weight was found: from 7 . 10(5) to over one million. It appears that the gamma-crystallins are directly involved in the insolubilization process, while alpha- and beta L-crystallin first take part in aggregation processes leading to HM- and beta H-crystallin aggregates. These aggregation and insolubilization processes proceed gradually with increasing age. A steep decrease in gamma-crystallin concentration in the early phase of life, which also causes the relative increase in alpha-crystallin content in this period, may originate from a decrease in biosynthesis of certain gamma-crystallins.

Immunological properties of rat lens gamma-crystallins. II. Characterization of low molecular weight components

Two low molecular weight proteins with isoelectric points above pH 8 occur in the water-soluble proteins of the 24-day-old rat lens. Their molecular weights, estimated by SDS gel electrophoresis, are 9,500 and 10,500 daltons. The 9,500-dalton protein cross-reacts with gamma 1-crystallin. The 10,500-dalton protein designated gamma 3-crystallin is nonidentical with gamma 1 and gamma 2-crystallins and shows no cross-reactivity with alpha- and beta-crystallins.

Immunological properties of rat lens gamma-crystallins. I. Characterization of the major components

Rat lens gamma-crystallins were separated by preparative flat bed isoelectric focusing (pH 7-11). The fractions obtained were submitted to analytical isoelectric focusing, fused rocket immunoelectrophoresis and immunodiffusion. The results demonstrate that rat lens gamma-crystallins are electrophoretically and immunologically heterogenous. Evidence is given that there are two immunologically different groups. Rat gamma 1-crystallin, the prominent and immunologically homogeneous part, is identical to calf lens gamma-crystallin. The second group of proteins, gamma 2-crystallins, is heterogeneous and shows only partial identity with gamma 1-crystallin.

Immunological characterization of calf lens gamma-crystallins, separated by preparative isoelectric focusing

Calf gamma-crystallins were separated by preparative flat-bed isoelectric focusing and characterized according to their immunological properties, molecular weights and isoelectric points. Immunologically 4 different groups of gamma-crystallins (gamma 1a-1d-crystallin) could be detected. The main immunological component, the gamma 1b-crystallin corresponds to two polypeptides with molecular weights of 20,500 and 22,000. The two minor components, the gamma 1c- and gamma 1d-crystallin, are immunologically partial identical with the main component gamma 1b-crystallin. One of these minor components, the gamma 1d-crystallin, has a MW of 29,000. The 4th antigen (gamma 1a-crystallin), which has a MW of 21,000, seems to have only remote relationship with the major gamma-crystallin component.

Experimental cataracts in rats due to tryptophan-free diet

A tryptophan-free diet induces posterior subcapsular cataracts and reversible corneal opacities in young Wistar rats. Compared to the controls there is a significant decrease of body weight, lens fresh weight, and water-soluble lens protein. Protein separation by isoelectric focusing shows diminished alpha-, beta-, and gamma-crystallin fractions. If tryptophan is restored to the diet after 24 days, new clear lens fibers are laid down again, indicating that the mechanism of protein synthesis has not been permanently damaged by tryptophan-deficiency.

The thin-layer isoelectric focusing of lactate dehydrogenase isoenzymes in rabbit lens parts and in intraocular tissues

Lactate dehydrogenase (LDH) isoenzymes of rabbit lens and other intraocular tissues are separated by thin-layer isoelectric focusing and localized as discrete groups of multiple bands with defined isoelectric points after staining by the tetrazolium method. In the rabbit lens parts, the predominant isoenzymes are LDH-4 and LDH-5. The bands show microheterogeneity, are composed of 2-4 subcomponents, and the pattern shows a distribution of the liver type. The activity of the LDH-4 decreases and that of LDH-5 increases in an order given by the equator, anterior and posterior cortex, and nucleus. LDH-3 remains almost constant in all lens parts. LDH-4 is composed of two subcomponents, one of which, the most cathodic with higher isoelectric point, is almost absent in the lens nucleus. Of the LDH localized in the rabbit intraocular tissues, only the retina shows a pattern of five isoenzymes also of the liver type. In all intraocular tissues LDH-3, -4, and -5 are very prominent, show also microheterogeneity of their isoenzyme bands, and are each composed of 4-6 subcomponents. LDH-1 and -2 show only one isofocused component. Species specificity is shown of the LDH isoenzymes in the rabbit, mouse, dog, and calf lens.

[The immunological characterization and isoelectric focusing of water-soluble proteins in the lens related to aging (author's transl)]

Immunelectrophoresis, antigen/antibody crossed electrophoresis and isoelectric focusing are applied to characterize lens crystallins. Using isoelectric focusing alpha-, beta- and gamma-crystallins are determined in bovine lens nucleus and equator. The data obtained are compared with those of rat and human lenses. In these three species a disappearance of specific beta- and gamma-crystallin components is observed depending on age. Further, the presence of crystallins is demonstrated in cornea and vitreous body.