Human Senile Cataract Research Articles

Protein and electrolyte alterations in human senile cataract

Water content, wet and dry weights of the crystalline lens, and protein, free amino acid and electrolyte levels in serum, aqueous humour and lens were determined in patients with nuclear senile cataract and at the different stages of the maturation of cortical cataract. In immature senile cortical cataract wet weight and sodium contents of the lens were significantly higher while potassium levels were low when compared with the nuclear cataract. With the maturation of cortical cataract water content, wet weight and sodium concentrations of the crystalline lens significantly increased while protein, free amino acid and potassium levels decreased. The possible role of these changes in various types of cataracts is discussed.

Inhibition of lens and cataract aldose reductase by protein-bound anti-rheumatic drugs: Salicylate, indomethacin, oxyphenbutazone, sulindac

The protein bound anti-rheumatic drugs salicylate, indomethacin, oxyphenbutazone and sulindac inhibit human and calf lens aldose reductase. Against human cataract aldose reductase the IC50 is 1×10−7 m for sulindac, 1×10−5 m for indomethacin, 5×10−4 m for salicylate and 5×10−3 m for oxyphenbutazone. These drugs which have had widespread clinical use in humans inhibit human senile cataract aldose reductase non-competitively with either dl -glyceraldehyde or d -glucose as substrate. The effectiveness of the anti-rheumatic agents as inhibitors of aldose reductase may be enhanced by binding to lens proteins and retention inside the lens (or cataract) for prolonged periods of time.

Cation pump activity and membrane permeability in human senile cataractous lenses

The majority of human senile cataractous lenses show a progressive alteration of electrolyte levels resulting in increased lens sodium and decreased potassium, and a concomitant increase in lens water. These changes are known to be associated with the cortical type of senile cataract. The aim of this study was to investigate the mechanisms responsible for the osmotic imbalance in cortical cataract. Determination of Na,K-ATPase activity gave a wide range of values that were not significantly different from normal controls, but rubidium influx showed a normal accumulation in cataractous lenses demonstrating a normal functioning of the cation pump. Both sodium influx and rubidium efflux are increased in the cataractous lenses and the increase is proportional to the absolute level of lens sodium. These results suggest that the biochemical change responsible for the osmotic imbalance in human senile cataract is not a defect in the cation pump mechanism but rather an increase in lens membrane permeability.

Modelling cortical cataractogenesis. IV. Induction by hygromycin B in vivo (swine) and in vitro (rat lens)

The cataractogenic effect of the anthelminthic antibiotic hygromycin B was examined. Histochemical staining and scanning electron microscopy of field samples of cataracts from pigs fed hygromycin B were examined in vitro in isolated rat lenses, in vivo in pigs maintained on several defined dietary regimens. In vivo, field samples showed globular degeneration similar to that which we have previously found for human senile posterior cortical subcapsular cataracts (PCSC), including intensified immunofluorescence for α-, β- and γ-crystallins and actin, and similar morphology by scanning electron microscopy. Four dietary regimens were tested: (1) 66 g/t, continuously, (2) 13·2 g/t, continuously, (3) 13·2 g/t intermittently (8 weeks on, 8 weeks off), the manufacturer's suggested regimen, and (4) control. All but one pig on regimens 1 and 2 had developed cataracts with associated globular degeneration when the experiment was terminated after 14 months, but no pigs on regimens 3 and 4 had cataracts. In vitro, in rat lenses incubated in M199 cortical lenticular opacities (cataracts) with associated globular degeneration were found at concentrations of hygromycin B as low as 10 −10 m; vitamin E seemed to offer some protection, in that no cataracts were found at 10 −10 m-hygromycin if vitamin E (2·4 μ m) was also present. The possibility exists that this drug may provide another system for modelling human senile PCSC, as well as a potential cataractogenic agent for human population.

Isolation and partial characterization of fucose- and N-acetylglucosamine-containing neutral glycosphingolipids from human senile cataracts.

Five neutral glycosphingolipids were isolated from human cataracts using silicic acid column chromatography and preparative thin-layer chromatography. Three of these glycolipids were partially identified by gas-liquid chromatography as glucosylceramide, lactosylceramide, and trihexosylceramide. Two glucosamine-containing glycosphingolipids (one of which contained fucose) were also detected. One of these two lipids contained galactose, glucose, N-acetylglucosamine in the molar ratio of 2:1:1, while the other contained fucose, galactose, glucose, and N-acetylglucosamine with the molar ratio of 1:2:1:1. Dihydrosphingosine (sphinganine) was the major long-chain base detected in all these fractions. The fatty acids of these neutral glycosphingolipids were variable in chain length, although the majority of them were greater than 20 carbons. This represents the first time whereby a family of neutral glycosphingolipids has been detected in human cataracts. This is also the first demonstration of the existence of a neutral fucolipid in the lenses of any species.

Biochemical studies on human cataract lens. II. Opacity-related changes of cations, ATP and GSH in various types of human senile cataracts

To investigate the mechanism of senile cataract formation in human, detailed knowledge of biochemical changes occuring during opacification is first required. In the present paper, this subject is discussed in regards to opacity-related changes of cations, adenosine-5'-triphosphate (ATP) and glutathione, reduced form (GSH) in various types of human senile cataracts. Early cataract lenses had normal cation levels. However, when lenses were separated into nucleus and cortex, cation levels of the nucleus were higher than those of cortex in all stages of cataract. GSH level in lenses of the early cataract stage had already decreased, and its level in the anterior cortex region more decreased clearly compared with other regions of the mature cataract. ATP level in the lens decreased suddenly in the mature cataract. These results suggest that ATP levels are the same in all regions of the lens. In the nucleus during all stages of cataract, both GSH and ATP levels were always of a constant value. These levels were lower compared with other regions. Mg-ATPase maintained the same activity in the early cataract lens during all stages of cataract. However, Na, K-ATPase activity decreased remarkably in the immature cataract lens. These phenomena agreed with changes in the levels of Na+ and K+ during the cataract process. These results, when compared with those reported in our previous papers, illustrate the great difference in biochemical parameters of the human senile cataract by comparing it with the experimental cataract of animals. Taken together, these results, therefore, suggest the presence of many factors that may play a role during cataract formation in the human lens.

The Emory mouse cataract: an animal model for human senile cataract.

The Emory mouse cataract is a late-appearing lens opacity which may serve as an animal model for some human senile cataracts. It is inherited as an autosomal dominant trait and has a typical course of development. Lens opacities may become readily apparent as early as 6-8 months in mice having a familial history of early cataracto-genesis. Many gross morphologic and microscopic features resemble findings in human senile cataract. As an animal model it has many desirable characteristics. Its slow development permits studies of the lens at the pre-cataractous stage and makes it a good assay system for drugs or other factors affecting cataractogenesis. In this paper are given some morphologic and histologic aspects of the developing cataract.

Classification of human senile cataracts by nuclear colour and sodium content

Human cataractous lenses were photographed in vivo prior to surgery and then in vitro after extraction. They were also analysed for sodium concentration and protein content. The lenses were then classified according to a dual system taking into account the extent of nuclear involvement (colour groups I to V) and electrolyte changes (sodium bands A to E) in each lens. The protein data from lenses classified according to the above dual scheme confirmed that the colour of the lens is closely associated with the water-insoluble protein content of the lens but further demonstrated that an increase in the sodium concentration (osmotic involvement) is associated with a dramatic fall in the water-soluble and total protein content. As the osmotic and nuclear mechanisms lead to quite different changes in protein distribution and as most cataracts are mixed in nature, a dual classification system is essential in any study where it is intended to discriminate between the two mechanisms. It was found that both the in vivo and in vitro photographic methods gave a consistent measure of nuclear involvement. However, it was not always possible to relate the changes in lens sodium to the extent of light scattering seen either in the in vivo or in vitro photographs.

Composition and synthesis in vivo of water-insoluble proteins in the rat ocular lens: Normal and cataractous

This study describes the composition and synthesis in vivo of the water-insoluble proteins in normal and cataractous rat ocular lens. Cataracts of the lens nucleus were induced by treatment of the young rat with U18666A, 3β-(2-diethylaminoethoxy)androst-5-en-17-one. HCl. Opaque lens contained more insoluble proteins and incorporated more intraocularly injected [ 3H]leucine into these proteins than clear lens. Insoluble proteins from both clear and opaque lens consisted of classes in three mol. wt. ranges; > 68 000, 35 000–60 000 and 16 000–22 000. Treatment with mercaptoethanol produced changes in the electrophoretic profiles of the 35 000–60 000 and 16 000–22 000 mol. wt. classes of proteins from both normal and opaque lens; however, the higher mol. wt. class from only the opaque lens was reduced to smaller components. The lowest mol. wt. class accounted for over 50% of the total water-insoluble protein in both types of lens. [ 3H]leucine was incorporated into the protein classes roughly proportionate to their relative concentrations, although there was a tendency for normal lens to incorporate more label into peak 1 and 2 proteins and for cataractous lens to incorporate more into peak 3 proteins. In general, however, the greater concentration of water-insoluble protein in this cataract appeared due to a proportionately increased formation of the same proteins present in normal lens. In contrast to human senile cataracts, the opaque rat lens did not preferentially accumulate disulfidelinked very high mol. wt. insoluble protein. However, the aged (i.e. pre-existing) higher mol. wt. insoluble proteins of the U18666A cataract appeared different from those newly synthesized, since the aged proteins were reduced under conditions not affecting those newly synthesized.

A Study of Human Senile Cataract: Growth and Differentiation of Lens Epithelial Cells in in vitro culture

Epithelial cells of human senile cataractous lenses from aged patients (over 60) were cultured <i>in vitro</i>. They began to grow from the 4th to 6th day of culture and formed typical epithelial cell sheets. The lentoid identified by immunochemical methods as a mass of lens fibers were found to develop at the terminal period of the primary culture. From the secondary passage of the culture, the growth potential of the cells decayed rapidly. It was also demonstrated clearly that the senile cataractous lenses still contained a small number of active epithelial cells exhibiting rather high growth and differentiation potentials, No signficant relationships between activities of epithelial cells and the condition of cataract have been observed so far.

Cataracts in the aging rat lens. Morphology and acid phosphatase histochemistry of incipient forms

The present investigation deals with morphological and certain histochemical changes that precede and accompany cataracts associated with aging in the rat. The cataracts were of two types: supranuclear (SNC) and posterior subcapsular (PSC). The initial biomicroscopie lesions, which were associated with the auterior and posterior lens suture systems, respectively, were attributed to cytological alterations of the ends of the superficial fiber cells. Cortical alterations common to both types of cataract included segmental cellular swelling, and the formation of assorted globular and multilamellar inclusions. With SNC, large multilamellar bodies corresponded to anterior sutural vacuolar opacities; while swelling and dissociation of the fiber cell bodies were associated with the formation of lamellar separations, lesions which eventually appeared in the peripheral cortex. Posterior subcapsular intercellular vacuoles, many of which developed a lamellated outer structure, were characteristic of the early form of PSC. An acid phosphataso which served as a marker for lysosomal hydrolases was demonstrated in the intercellular spaces of lenses with early forms of degeneration. The major source of the extracellular enzyme appeared to be the Golgi/lysosomal system within the epithelium and cortex, although the cortical smooth endoplasmic reticulum was not ruled out. Our studies support the concept that the swelling and degeneration of cortical fibers occurring in the initial stages of the cataracts might have been caused by intercellularly located hydrolases. The value of the aged rat lens as a model for human senile cataract was reinforced by the many similarities between the murine and human forms of the disease.

Distribution of glycolytic enzymes in nuclear and peripheral lens secretions of the human senile cataract.

Human nuclear cataracts soon after surgery, were dissected and the nuclear and clearer peripheral portions individually homogenized with physiological saline and centrifuged. The filtrates were analyzed for aldolase, phosphohexose isomerase and lactic dehydrogenase and the 3 enzymes found to range 6—14 times higher in the peripheral than in the nuclear portions of the lens. The LDH isozyme patterns of the peripheral tissue homogenates indicated greater glycolytic activity.

Characteristics of alpha-crystallin in human senile cataract

Studies on alpha-crystallin separated from human senile lenses, either transparent or with different degrees of senile cataractous changes, have not shown appreciable differences in the relative amount of the high and low molecular weight fractions of this protein. Both in human normal senile lens and in senile cataract the larger-sized population, with molecular weight above 1 × 10 7, accounts for about 85% of all the alpha-crystallin extracted from the whole lens. Gel electrophoresis analysis in the presence of urea or of sodium dodecylsulphate, and amino acid composition gave essentially similar results in normal and cataractous alpha-crystallin. Titration of sulphydryl groups of alpha-crystallin indicated a lower availability to p-mercuribenzoate in advanced stages of cortical and nuclear cataracts. Under the experimental conditions used, no evidence has been found that lens opacification in human senile cataract is associated with the accumulation of a high molecular weight population of alpha-crystallin.

Glutathione and NADP linked enzymes in human senile cataract

Oxidized and reduced free glutathione were measured in clear and cataractous human lenses. Total glutathione decreases with the course of cataract. There exists a clear difference between different types of cataract. Lenses showing biomicrosopically superficial opacities as well as total opaque lenses contain only small levels of reduced glutathione whereas the level of the oxidized glutathione seems to be less changed. Since the enzyme activities of glutathione reductase and of enzymes linked to hydrogen producing pathways show only slight alterations, except in the mature cataract, the differences of the glutathione content in the various types of cataract may not be explained by the deficiency of enzyme activities. It is assumed that a loss of the reduced glutathione in human lenses occurs under two perhaps independent conditions: (1) the presence of a large amount of opaque lens material (for example nuclear cataract); (2) the occurrence of a superficial destruction of the lens even if the lens is nearly clear (for example subcapsular cataracts). There seems to exist a connection between the reduced glutathione level in the lens and a cation shift.

Chemical and mechanical dissolution of human senile cataracts in vitro.

The effects of mechanical and chemical dissolution on 100 human senile cataracts were tested in vitro. Senile cataracts obtained immediately after surgical removal were grouped in three classes according to transparency, color and hardness (resistance to perforation). Dissolution of the lenses by various chemicals during push‐pull aspirations was tested by weighing and by photography of cataracts before and after treatment. Mechanical forces deaggregated senile cataracts depending on the specific cataract types. Guanidine hydrochloride in 1 Molar concentration accelerated the rate of cataract breakdown in vitro.

Immunochemical Studies on Crystallins and Albuminoids in Human Senile Cataracts

Absorption experiments as well as organ-specific cross-reactions were used for immunochemical comparison of human normal and senile cataract lens. All the experiments revealed an identity of antigenic specificities in the crystallin as well as in the albuminoid fractions of human normal and senile cataract lenses. The human senile cataract lens crystallins contained a decreased amount of at least one immunologically specific β-crystallin antigen. A similar observation was made previously in experimental galactose cataract which occurs only in the young. The potential role of this protein in albuminoid formation is discussed. Under equal immunization procedures the cataract lens proteins tended to produce a stronger antibody response than the normal ones.

Changes in Weight and in Protein-Water Ratio of the Lens in Human Senile Cataracts

Changes in wet weight, dry weight and water content have been studied in different types of senile cataract and compared With transparent control lenses. While nuclear brunescent cataractous lens show normal weight, protein and water content, cortical opacification is characterized by a progressive decrease of total lens proteins associated with important terminal alterations of the percentage of water content. Posterior subcapsular cataracts in very early stages of the disease have a significantly lower wet weight than control lenses, but a normal protein-water ratio; this is interpreted as a decreased lens growth starting far back in time and producing apparently normal lens substance. The question is raised whether this could be interpreted as a manifestation of the same pathogenetic cause which determines the appearance of this type of lens opacification.

Enzyme Activity Patterns and some Intermediates in Human Senile Cataract

In nuclear cataract and cortical cataract, the enzyme activity pattern of the cortex shows slight alterations, indicating a change in the protein composition. The ATP content of these lenses is high a

Problems in Cataract Research

A general review concerning human senile cataract makes many unsolved problems obvious. Future research on these problems requires a generally accepted classification of these cataracts and well-organized co-operation between the ophthalmologist and the biologist. If research groups are established fulfilling these necessities in their studies of special problems, great progress can be achieved in a relatively short period of time.

Changes in weight and in the protein/water ratio of the lens in human senile cataracts

Changes in weight and in the protein/water ratio of the lens in human senile cataracts