Normal human lens—the distribution of protein

Fagerholm, Per; Philipson, Bo; Lindström, Bo

doi:10.1016/s0014-4835(81)80101-7

Cited by 153 publications

(82 citation statements)

References 9 publications

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“…The lens at birth can be considered as the nucleus of the adult lens and there is no compaction of the adult nucleus. (Fagerholm et al 1981; Asx The values shown in Fig 2 reflect the racemisation of both Asn and Asp in proteins, since the side chain amide of Asn is hydrolysed with acid. In a pattern that was also shown with another amino acid that racemised significantly (Ser), there was a more rapid increase in racemisation in the early years, with 4% inversion occurring between ages 0 and 12.…”

Section: Resultsmentioning

confidence: 99%

Racemisation and human cataract. d-Ser, d-Asp/Asn and d-Thr are higher in the lifelong proteins of cataract lenses than in age-matched normal lenses

Hooi

Truscott

2010

AGE

105

122

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Astract Several amino acids were found to undergo progressive age-dependent racemisation in the lifelong proteins of normal human lenses. The two most highly racemised were Ser and Asx. By age 70, 4.5% of all Ser residues had been racemised, along with >9% of Asx residues. Such a high level of inversion, equivalent to between 2 and 3 D -amino acids per polypeptide chain, is likely to induce significant denaturation of the crystallins in aged lenses. Thr, Glx and Phe underwent age-dependent racemisation to a smaller degree. In model experiments, D -amino acid content could be increased simply by exposing intact lenses to elevated temperature. In cataract lenses, the extent of racemisation of Ser, Asx and Thr residues was significantly greater than for agematched normal lenses. This was true, even for cataract lenses removed from patients at the earliest ages where age-related cataract is observed clinically. Racemisation of amino acids in crystallins may arise due to prolonged exposure of these proteins to ocular temperatures and increased levels of racemisation may play a significant role in the opacification of human lenses.

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Section: Resultsmentioning

confidence: 99%

Racemisation and human cataract. d-Ser, d-Asp/Asn and d-Thr are higher in the lifelong proteins of cataract lenses than in age-matched normal lenses

Hooi

Truscott

2010

AGE

105

122

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“…This is further supported by lens morphology [1,36], which shows a compaction of fibres toward the lens centre. Other differences have also been observed between the lens nucleus and cortex in terms of the protein gradient [13], refractive index [33] and acoustic parameters [26].…”

Section: Introductionmentioning

confidence: 99%

Stiffness gradient in the crystalline lens

Weeber

Eckert

Pechhold

et al. 2007

Graefes Arch Clin Exp Ophthalmol

140

147

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Background While the overall stiffness of the lens has been measured in a number of studies, the knowledge about the stiffness distribution within the lens is still limited. The purpose of this study was to determine the stiffness gradient in the human crystalline lens. A secondary purpose was to determine whether the stiffness gradient depends on age. Methods The local dynamic stiffness was measured in 10 human crystalline lenses (age range: 19 to 78 years). The lenses were stored at −70°C before being measured. The influence of freezing on the mechanical properties has been determined in a previous study. A small oscillating probe was used to measure the local dynamic shear modulus as a measure of lens stiffness. The measurements were taken in the cross-sectional plane through the lens equator. Results The local dynamic shear modulus varied with location for all tested lenses. The central stiffness of the oldest lens (78 years) was 10 4 times higher than the youngest (19 years) lens. The equatorial stiffness of the oldest lens was 10 2 times higher than the youngest lens. For the older lenses, the centre was 5.8-210 times stiffer than the periphery, as opposed to earlier results described by Fisher (1971), who found that the periphery was up to 3 times softer than the centre for lenses younger than 70-years-old. For the three youngest lenses (19 to 49 years), the periphery was 2.2-16.6 times stiffer than the centre. Conclusions The dynamic stiffness of the crystalline lens varies with location within the lens. The stiffness gradient depends on the age of the lens. The results of the 10 lenses indicate that the stiffness of both centre and periphery increase with age, but at a different rate.

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“…Their concentration increases from cortex to nucleus, thus establishing the protein concentration and refractive index gradient required for proper focusing of incident light (1)(2)(3). The cytoplasm is normally transparent, due to short-range ordering of the crystallins (4,5).…”

mentioning

confidence: 99%

Human lens gamma-crystallins: isolation, identification, and characterization of the expressed gene products.

Siezen¹,

Thomson²,

Kaplan³

et al. 1987

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

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We have isolated the individual y-crystallins expressed in young human lenses and identified with which of the six known human y-crystallin genes they each correspond.We find that at least 90% of the y-crystallins synthesized in the young human lens are the products of genes yG3 and yG4. We demonstrate that yG4-crystallin undergoes a temperaturedependent phase separation, and we have measured the lowconcentration branch of its coexistence curve (phase separation temperature vs. concentration) up to about 40 mg/ml. By comparison, we found no evidence of yG3-crystallin phase separating, even at lower temperatures and higher concentrations. This is consistent with predictions based on sequence homology between human and rat y-crystailins. The implications of these findings for human inherited and senile cataracts are considered.

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Normal human lens—the distribution of protein

Cited by 153 publications

References 9 publications

Racemisation and human cataract. d-Ser, d-Asp/Asn and d-Thr are higher in the lifelong proteins of cataract lenses than in age-matched normal lenses

Racemisation and human cataract. d-Ser, d-Asp/Asn and d-Thr are higher in the lifelong proteins of cataract lenses than in age-matched normal lenses

Stiffness gradient in the crystalline lens

Human lens gamma-crystallins: isolation, identification, and characterization of the expressed gene products.

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