| 1. |
- Bjerager, Jakob, et al.
(författare)
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Long-term development of lens fluorescence in a twin cohort : Heritability and effects of age and lifestyle
- 2022
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 17:5 May
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Tidskriftsartikel (refereegranskat)abstract
- The blue-green autofluorescence of the ocular lens increases with age, glycemia and smoking, as the irreplaceable structural proteins of the lens slowly accumulate damage from the encounter with reactive molecular species. We have conducted a prospective study of lens autofluorescence over two decades in a twin cohort. The study included 131 phakic, non-diabetic adult twins (median age at follow-up 58 years, range 41–66 years) who were examined twice at an interval of 21 years. Change in anterior lens peak autofluorescence was analyzed in relation to age, current and baseline glycemia, cumulative smoking and heritability. The level of lens autofluorescence in the study population increased as a function of age and smoking (p ≤.002), but not as a function of glycemia (p ≥.069). Lens autofluorescence remained a highly heritable trait (90.6% at baseline and 93.3% at follow-up), but whereas the combined effect of age and cumulative smoking explained 57.2% of the variance in lens autofluorescence at baseline in mid-life, it only accounted for 31.6% at followup 21 years later. From mid to late adulthood, the level of blue-green fluorescence remained overwhelmingly heritable, but became less predictable from age, smoking habits and glycemic status. Presumably, as the lens ages, its intrinsic characteristics come to dominate over environmental and systemic factors, perhaps in a prelude to the development of cataract.
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| 2. |
- Herbst, Kristina, et al.
(författare)
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Intrinsically photosensitive retinal ganglion cell function in relation to age : A pupillometric study in humans with special reference to the age-related optic properties of the lens.
- 2012
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Ingår i: BMC Ophthalmology. - : BioMed Central (BMC). - 1471-2415. ; 12:4
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Tidskriftsartikel (refereegranskat)abstract
- Background: The activity of melanopsin containing intrinsically photosensitive ganglion retinal cells (ipRGC) can be assessed by a means of pupil responses to bright blue (appr.480 nm) light. Due to age related factors in the eye, particularly, structural changes of the lens, less light reaches retina. The aim of this study was to examine how age and in vivo measured lens transmission of blue light might affect pupil light responses, in particular, mediated by the ipRGC.Methods: Consensual pupil responses were explored in 44 healthy subjects aged between 26 and 68 years. A pupil response was recorded to a continuous 20 s light stimulus of 660 nm (red) or 470 nm (blue) both at 300 cd/m2 intensity (14.9 and 14.8 log photons/cm2/s, respectively). Additional recordings were performed using four 470 nm stimulus intensities of 3, 30, 100 and 300 cd/m2. The baseline pupil size was measured in darkness and results were adjusted for the baseline pupil and gender. The main outcome parameters were maximal and sustained pupil contraction amplitudes and the postillumination response assessed as area under the curve (AUC) over two time-windows: early (0–10 s after light termination) and late (10–30 s after light termination). Lens transmission was measured with an ocular fluorometer.Results: The sustained pupil contraction and the early poststimulus AUC correlated positively with age (p = 0.02, p = 0.0014, respectively) for the blue light stimulus condition only.The maximal pupil contraction amplitude did not correlate to age either for bright blue or red light stimulus conditions.Lens transmission decreased linearly with age (p < 0.0001). The pupil response was stable or increased with decreasing transmission, though only significantly for the early poststimulus AUC to 300 cd/m2 light (p = 0.02).Conclusions: Age did not reduce, but rather enhance pupil responses mediated by ipRGC. The age related decrease of blue light transmission led to similar results, however, the effect of age was greater on these pupil responses than that of the lens transmission. Thus there must be other age related factors such as lens scatter and/or adaptive processes influencing the ipRGC mediated pupil response enhancement observed with advancing age.
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| 3. |
- Kessel, Line, et al.
(författare)
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Impact of UVR-A on whole human lenses, supernatants of buffered human lens homogenates, and purified argpyrimidine and 3-OH-kynurenine
- 2005
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Ingår i: ACTA OPHTHALMOLOGICA SCANDINAVICA. - : Wiley. - 1395-3907. ; 83:2, s. 221-7
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Yellow chromophores and fluorescent compounds accumulate in the lens with age. Some of these compounds are photochemically active. The present study aimed to examine the photochemical effect of ultraviolet radiation-A (UVR-A) on the human lens.Methods: Intact human lenses and supernatants of buffered lens homogenates were exposed to UVR-A. The effect of UVR-A was evaluated by time-resolved and steady-state fluorescence spectroscopy, visual evaluation of colour and protein gel electrophoresis.Results: Intact lenses exposed to UVR-A showed no changes in time-resolved or steady-state fluorescence properties but the yellow coloration was visibly attenuated. The supernatants of buffered lens homogenates exposed to UVR-A demonstrated a reduction in time-resolved and steady-state fluorescent properties and protein cross-linking.Conclusions: Exposure of the intact lens to UVR-A causes chromophore bleaching without affecting fluorescence, indicating that non-fluorescent chromophores have been destroyed. After homogenization, both chromophores and fluorophores from the lens suffer damage and proteins aggregate. This indicates that powerful mechanisms of protection against UVR-A found in the intact lens are disturbed by homogenization of the lens, suggesting that isolated lens proteins cannot be used as a model system for studying cataractogenesis. Hypothetically, the protective mechanism could be related to the rigidly packed three-dimensional structure of the lens proteins or to the abundance of antioxidative and free radical scavenging defence systems.
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| 4. |
- Vergmann, Anna Stage, et al.
(författare)
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Heritability of retinal vascular fractals : A twin study
- 2017
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Ingår i: Investigative Ophthalmology and Visual Science. - : Association for Research in Vision and Ophthalmology (ARVO). - 0146-0404. ; 58:10, s. 3997-4002
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE. To determine the genetic contribution to the pattern of retinal vascular branching expressed by its fractal dimension. METHODS. This was a cross-sectional study of 50 monozygotic and 49 dizygotic, same-sex twin pairs aged 20 to 46 years. In 50º, disc-centered fundus photographs, the retinal vascular fractal dimension was measured using the box-counting method and compared within monozygotic and dizygotic twin pairs using Pearson correlation coefficients. Falconer’s formula and quantitative genetic models were used to determine the genetic component of variation. RESULTS. The mean fractal dimension did not differ statistically significantly between monozygotic and dizygotic twin pairs (1.505 vs. 1.495, P = 0.06), supporting that the study population was suitable for quantitative analysis of heritability. The intrapair correlation was markedly higher (0.505, P = 0.0002) in monozygotic twins than in dizygotic twins (0.108, P = 0.46), corresponding to a heritability h2 for the fractal dimension of 0.79. In quantitative genetic models, dominant genetic effects explained 54% of the variation and 46% was individually environmentally determined. CONCLUSIONS. In young adult twins, the branching pattern of the retinal vessels demonstrated a higher structural similarity in monozygotic than in dizygotic twin pairs. The retinal vascular fractal dimension was mainly determined by genetic factors, which accounted for 54% of the variation. The genetically predetermination of the retinal vasculature may affect the retinal response to potential vascular disease in later life.
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