Changes in chemical composition of anterior lens capsules of cataractous human eyes as a function of age

Peczon, Benigno D.; Peczon, JoséD.; Cintron, Charles; Hudson, Billy G.

doi:10.1016/0014-4835(80)90109-8

Cited by 21 publications

(9 citation statements)

References 17 publications

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“…Age-relat ed changes in collagen IV, such as decreased amino acid content and alteration in the redu cible cross-links, have also been observed [24], In this study the capsular samples are from a very wide age range (49-91 years); the age-related changes in protein secondary structure of senile human lens capsules must therefore also be considered [25], In the cata ractous lens, the lens capsule has also been reported to have a higher degree of nonenzymatic glycosylation than cortex and nucleus [26]. This indicates that the lens capsule seems to play an important role in senile cata ract formation.…”

Section: Possible Pathway For Exacerbating Cataract Formationmentioning

confidence: 96%

“…This indicates that the lens capsule seems to play an important role in senile cata ract formation. In addition, the lens capsule of cataractous human lenses is almost com pletely glycosylated to increase stiffening and browning, especially in diabetic cataractous patients [24,27], Our finding suggests that the secondary structure of immature cataractous human lens capsules in patients with longer diabetic history was modified by decreasing the triple helix content and by markedly in creasing the random coil structure [8]. This once more suggests that the lens capsule is eas ily influenced by disease and might be associ ated with increased risk for senile cataracts.…”

Section: Possible Pathway For Exacerbating Cataract Formationmentioning

confidence: 99%

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Possible Mechanism of Exacerbating Cataract Formation in Cataractous Human Lens Capsules Induced by Systemic Hypertension or Glaucoma

Lee¹,

Lin

et al. 1997

Ophthalmic Res

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To clarify the role of the lens capsule in cataract formation, changes in the protein conformational structure of immature cataractous lens capsules from patients with systemic hypertension or glaucoma have been investigated, as compared to normal lens capsules. The protein secondary structure and composition of these capsular samples were determined using Fourier transform infrared microspectroscopy with second-derivative, deconvolution and curve-fitting methods. We found that the composition of both random coil and β-type (β-sheet and β-turn) structures in the immature cataractous human lens capsules was increasingly induced by systemic hypertension or glaucoma, but α-helix content clearly decreased, leading to the alteration of protein conformational structures in lens capsules. A possible pathway of cataract formation exacerbated by systemic hypertension or glaucoma is discussed. According to the results, we propose that systemic hypertension or glaucoma induce changes in the protein conformational structures of the lens capsule, then cause alteration of membrane transport and permeability for ions, and finally increase intraocular pressure, resulting in the exacerbation of cataract formation. The effect on the conformational structure of cataractous human lens capsules is more pronounced for systemic hypertension than for glaucoma. The present study implies that systemic hypertension or glaucoma can exacerbate cataract formation in senile patients by modifying the protein secondary structures in the lens capsule.

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Section: Possible Pathway For Exacerbating Cataract Formationmentioning

confidence: 96%

Section: Possible Pathway For Exacerbating Cataract Formationmentioning

confidence: 99%

Possible Mechanism of Exacerbating Cataract Formation in Cataractous Human Lens Capsules Induced by Systemic Hypertension or Glaucoma

Lee¹,

Lin

et al. 1997

Ophthalmic Res

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“…This may correlate with the known chemical and morphological changes which occur in the capsule with age. There is an increase in non-collagenous proteins in the capsule [36], and the capsule accumulates linear densities [25, 37]and loses its laminated structure [25, 38]. Krag et al [26]suggest that the shape of the load/strain curve is explained by the composition of the capsule.…”

Section: Organisation and Remodelling In The Lensmentioning

confidence: 99%

The Ageing Lens

et al. 2000

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The human lens grows by a process of epithelial cell division at its equator and the formation of generations of differentiated fibre cells. Despite the process of continuous remodelling necessary to achieve growth within a closed system, the lens can retain a high level of light transmission throughout the lifetime of the individual, with the ability to form sharp images on the retina. Continuous growth of the lens solves the problem imposed by terminal differentiation within a closed, avascular system, from which cells cannot be shed. The lens fibre tips arch over the equator to meet anteriorly and posteriorly and form branching sutures of increasing complexity. The stages of branching may create the optical zones of discontinuity seen on biomicroscopy. The lens is exposed to the cumulative effects of radiation, oxidation and postranslational modification. These later proteins and other lens molecules in such a way as to impair membrane functions and perturb protein (particularly crystallin) organisation, so that light transmission and image formation may be compromised. Damage is minimised by the presence of powerful scavenger and chaperone molecules. Progressive insolublisation of the crystallins of the lens nucleus in the first five decades of life, and the formation of higher molecular weight aggregates, may account for the decreased deformability of the lens nucleus which characterises presbyopia. Additional factors include: the progressive increase in lens mass with age, changes in the point of insertion of the lens zonules, and a shortening of the radius of curvature of the anterior surface of the lens. Also with age, there is a fall in light transmission by the lens, associated with increased light scatter, increased spectral absorption, particularly at the blue end of the spectrum, and increased lens fluorescence. A major factor responsible for the increased yellowing of the lens is the accumulation of a novel fluorogen, glutathione-3-hydroxy kynurenine glycoside, which makes a major contribution to the increasing fluorescence of the lens nucleus which occurs with age. Since this compound may also cross-link with the lens crystallins, it may contribute to the formation of high-molecular-weight aggregates and the increases in light scattering which occur with age. Focal changes of microscopic size are observed in apparently transparent, aged lenses and may be regarded as precursors of cortical cataract formation.

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“…This thickening is accompanied by the nonenzymatic glycosylation of macromolecules, among them basement membrane collagen [Monnier and Cerami, 1982;Trueb et al, 1984], The nonenzymatic glycosylation of collagen is significantly higher in the skin of diabetic patients than in control subjects, although this parameter itself does not corre late with age, duration of diabetes or, for example, severity of retinopathy [Vishwanath et al, 1986]. In cataractous human lenses, the lens capsule has the highest degree of nonenzymatic glycosylation, followed by the cortex and finally the nucleus [Oimomi et al, 1988], In contrast to skin collagen, the anterior lens capsule of cataractous human lenses is almost fully glycosylated on the hydroxylysine residues [Peczon et at., 1980], Such glycosylation increases the stiffness and thermal stability [Andreassen and Oxlund, 1985], Eaton [1986] has proposed that stiffening of the collagen matrix may be the result of increased hydration of bound and/or entrapped water in the collagen fiberpolysaccharide matrix that alters the physi cochemical properties.…”

Section: Introductionmentioning

confidence: 99%

“…Changes in lens capsule charac teristics have been observed in aging [Peczon et al, 1980], in cataractogenesis [Gorthy and Abdelbaki, 1974] and in diabetes [Paterson and Heath, 1967], The most characteristic change in long-term diabetes mellitus is the thickening of basement membranes. This thickening is accompanied by the nonenzymatic glycosylation of macromolecules, among them basement membrane collagen [Monnier and Cerami, 1982;Trueb et al, 1984], The nonenzymatic glycosylation of collagen is significantly higher in the skin of diabetic patients than in control subjects, although this parameter itself does not corre late with age, duration of diabetes or, for example, severity of retinopathy [Vishwanath et al, 1986].…”

Section: Introductionmentioning

confidence: 99%

Bound Water Content of Bovine Lens Capsules

Popdimitrova

Bettelheim²

1989

Ophthalmic Res

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The anterior parts of bovine lens capsules have been incubated in media with different glucose contents. The freezable water content of the lens capsule was obtained by differential scanning calorimetry and the total water content by thermogravimetric analysis. The bound (nonfreezable) water content was calculated as the difference between total and freezable water. The bound water as percent of the total water increases with the degree of glycosylation of the bovine lens capsules.

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Changes in chemical composition of anterior lens capsules of cataractous human eyes as a function of age

Cited by 21 publications

References 17 publications

Possible Mechanism of Exacerbating Cataract Formation in Cataractous Human Lens Capsules Induced by Systemic Hypertension or Glaucoma

Possible Mechanism of Exacerbating Cataract Formation in Cataractous Human Lens Capsules Induced by Systemic Hypertension or Glaucoma

The Ageing Lens

Bound Water Content of Bovine Lens Capsules

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