Light scattering and reversible cataracts in the calf and human lens

Benedek, George B.; Clark, John I.; Serrallach, E. N.; Young, C. Y.; Mengel, L.; Sauke, T.; Bagg, Anne; Benedek, K.R.

doi:10.1098/rsta.1979.0100

Cited by 77 publications

(34 citation statements)

References 5 publications

(7 reference statements)

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“…A temperaturedependent reversible opacification can be induced in the nucleus of these young lenses (24)(25)(26)(27)(28). This behavior appears to be an intrinsic property of the concentrated mixture of crystallins, since it also can be induced in purified, membranefree cytoplasmic extracts of lens nucleus (27,(29)(30)(31)(32).…”

Section: Introductionmentioning

confidence: 93%

Opacification of gamma-crystallin solutions from calf lens in relation to cold cataract formation.

Siezen¹,

Fisch²,

Slingsby³

et al. 1985

Proc. Natl. Acad. Sci. U.S.A.

113

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To determine the molecular mechanisms for cold cataract formation in the nucleus of the young mammalian lens, we have investigated the thermally reversible opacification of -crystallin solutions isolated from calf lens. Coexistence curves (plots of opacification temperature Tc versus protein concentration) were determined for the individual y-crystallin fractions II, III, and IV as well as for the unfractionated -crystallin mixtures isolated from the nucleus and cortex. The coexistence curve of yIV-crystallin is remarkably elevated above those of y4I-and yIII-crystallin and the -crystallin mixtures. The yIV-crystallin fraction is the major determinant of the opacification temperature within the whole lens or isolated cytoplasm. Quasielastic light-scattering spectroscopy of yIV-crystallin solutions indicates that above Tc there are two populations of protein aggregates of distinctly different mean size. As the temperature is lowered towards Tc, both populations increase in size. Opacification occurs when the population of large scatterers, which is composed of <0.1% protein by weight, reaches an average radius of about 20,000 A.The cytoplasm in eye lens cells contains a highly concentrated solution of lens-specific proteins, the crystallins. Their concentration increases from =250 to 400 g/liter going from cortex to nucleus, thus establishing the refractive index gradient required for proper focusing of incident light (1). The cytoplasm is normally transparent because of short-range ordering of the crystallins (2, 3). Mammalian lenses contain primarily a-crystallins (Mr 700,000-1,200,000), l3-crystallins (Mr 50,000-300,000) and -crystallins (Mr 20,000) (1,4,5). Their relative proportions vary with age and location within the lens as a result of both differential synthesis during development and selective degradation and insolubilization with aging (4-15). The lens nucleus is highly enriched in -crystallins, which are monomeric, basic proteins rich in sulfhydryl groups (8,(16)(17)(18)(19). The majority of human cataracts represent an irreversible opacification of the lens nucleus that progresses with age, a condition that is accompanied by oxidation of sulfhydryl groups, aggregation, and insolubilization of the various crystallins (4,8,13,(20)(21)(22)(23).The cold cataract phenomenon observed in most young mammalian lenses (e.g., calf, rat, and rabbit) is a convenient model system to study the relationship between nuclear opacification and -crystallin aggregation. A temperaturedependent reversible opacification can be induced in the nucleus of these young lenses (24)(25)(26)(27)(28). This behavior appears to be an intrinsic property of the concentrated mixture of crystallins, since it also can be induced in purified, membranefree cytoplasmic extracts of lens nucleus (27,(29)(30)(31)(32). Cold cataract has been modeled as a reversible phase-separation phenomenon (26)(27)(28)(29)(30)(31)(32). Upon lowering the temperature below a critical value Tc, the cytoplasm separates into protein-rich and protein-poor d...

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Section: Introductionmentioning

confidence: 93%

Opacification of gamma-crystallin solutions from calf lens in relation to cold cataract formation.

Siezen¹,

Fisch²,

Slingsby³

et al. 1985

Proc. Natl. Acad. Sci. U.S.A.

113

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“…4(b) (Glu104-Arg89). A delicate balance of protein-water versus protein-protein interaction is in play in the liquid-like lens as lowering the temperature causes light scattering because of separation into phases of uneven protein concentration (Benedek et al, 1979;Blundell et al, 1983). In the centre of older lenses, the protein is glass-like, and the protein concentration approaches that of crystals.…”

Section: Water-protein Interactionsmentioning

confidence: 99%

“…There is almost no protein turnover in the core regions of lenses (Wannermacher & Spector, 1969) and therefore the 3,-crystallins must have great stability in terms of their tertiary structures and their interactions with other cell components including water. Young mammalian lenses are liquid-like and exhibit cold cataract whereby the ")'-crystallins separate into phases of unequal density on cooling (Benedek et al, 1979, Broide, Berland, Pande, Ogun & Benedek, 1991Tardieu, V6r6tout, Krop & Slingsby, 1992). This core region of the human lens frequently turns opaque in senile cataract when "y-crystallins become cross-linked with other lens components (Harding, 1991).…”

Section: Introductionmentioning

confidence: 99%

An Eye Lens Protein–Water Structure: 1.2 Å Resolution Structure of γB-Crystallin at 150 K

Kumaraswamy¹,

Lindley²,

Slingsby³

et al. 1996

Acta Cryst D

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Abstract7B-crystallin is a structural protein of the eye lens with a role in the maintenance of an even distribution of protein and water over distances around the wavelength of light, preserving lens transparency. The structure of the 174-residue bovine protein has already been determined at room temperature to 1.47 A resolution. By flash freezing the protein crystals, data have now been collected to a nominal resolution limit of 1.2 A as radiation damage was essentially eliminated. The protein-water model has been refined against this data using the program RESTRAIN converging to an R factor of 18.5% with all data. Atomic positions are clearly indicated in the electron-density maps. Discrete bimodal disorder has been visualized for a few side chains. Out of a total of 498 water molecules present in the crystal asymmetric unit, 394 have been modelled and refined at unit occupancy. The solvent structure is extremely well ordered with an average B value of 23.4 A 2. Partially occupied sites have been identified where disorder in the protein induces concomitant disorder in the local solvent structure. The solvent structure covers 97% of the solvent-exposed surface of the protein in the crystal. 126 water molecules are distributed in second and higher hydration shells. There are networks of hydrogen-bonded solvent extending up to 64 molecules in a network, comprising trimers and tetramers as well as five-and six-membered water-ring structures. The hydration of the protein surface is dominated by arginine and aspartate side chains. Extensive cages of highly ordered solvent molecules are also observed around exposed non-polar groups.

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“…Any disruption of this uniformity leads to opacity (Benedek et al, 1979). The pooling hemolymph in the P. pugio tail (Fig.6) creates regions that have a low refractive index relative to the surrounding muscle fibers.…”

Section: The Physical Basis For the Loss Of Transparencymentioning

confidence: 99%

The effects of salinity and temperature on the transparency of the grass shrimp Palaemonetes pugio

Bhandiwad

Johnsen

2011

Journal of Experimental Biology

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SUMMARY Transparency is an effective form of camouflage, but it must be present throughout the entire volume of an animal to succeed. Certain environmental stressors may cause physiological responses that increase internal light scattering, making tissue less transparent and more conspicuous to predators. We tested this in the transparent grass shrimp, Palaemonetes pugio, which is found in shallow estuaries where both salinity and temperature change rapidly because of tidal cycles, evaporation and runoff. Animals originally kept at a salinity of 15 p.p.t. and a temperature of 20°C were placed into solutions with salinities of 0, 15, 25 or 30 p.p.t. and temperatures of 13, 20 or 27°C for 12 h (N=26 for each of 12 treatments). Under the control conditions of 15 p.p.t. at 20°C, the transparency of grass shrimp tails was 54±3% (mean ± s.e.). At higher salinities and at both higher and lower temperatures, transparency dropped significantly (P<0.001, two-way ANOVA), reaching 0.04±0.01% at 30 p.p.t. at 27°C. Confocal microscopy of P. pugio's tail suggested that the observed loss of transparency was due to the pooling of low refractive index hemolymph between the high index muscle fibers, creating many index boundaries that increased light scattering. Analysis of a year-long salinity and temperature record from a North Carolina estuary showed that changes of the order of those found in this study are relatively common, suggesting that P. pugio may undergo periods of reduced crypsis, potentially leading to increased predation.

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Light scattering and reversible cataracts in the calf and human lens

Cited by 77 publications

References 5 publications

Opacification of gamma-crystallin solutions from calf lens in relation to cold cataract formation.

Opacification of gamma-crystallin solutions from calf lens in relation to cold cataract formation.

An Eye Lens Protein–Water Structure: 1.2 Å Resolution Structure of γB-Crystallin at 150 K

The effects of salinity and temperature on the transparency of the grass shrimp Palaemonetes pugio

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