Discrepancy between Onset of Early Lens Changes and Onset of Senile Cataract: The Case for Cellular Defense Systems in the Human Eye Lens

Vrensen, G.

doi:10.1159/000419947

Cited by 4 publications

(2 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…1989). In a series of studies on lenses ranging in age from 30 to 90 years and excised from donor eyes collected for cornea transplantation purposes, we have investigated the lens morphology and ultrastructure (Vrensen & Willekens 1988, Vrensen et al 1990a, Vrensen 1991). The presence of small opacities in the equatorial region of older lenses is a common observation (Fig.…”

Section: Ageing and Lens Transparencymentioning

confidence: 99%

Early cortical lens opacities: a short overview

Vrensen

2009

Acta Ophthalmologica

View full text Add to dashboard Cite

. Cataract is still the dominant cause of blindness worldwide. Cortical cataract is the most prevalent of the age‐related changes in the human lenses that require surgical intervention to restore vision. The absence of adequate cataract surgery in most developing countries is the main cause of the high prevalence of cataract blindness worldwide. Lens ageing is accompanied by dramatic increases in stiffness, light scattering and coloration of the lens nucleus. These changes start to become manifest as early as the fourth or fifth decade of life and lead to nuclear cataract in old age. In the same period the equatorial deep lens cortex starts to show small opaque shades, which eventually grow out to segmental and annular opacities. These opaque shades are filled with small vesicles and contain abnormal amounts of cross‐linked proteins, cholesterol and phospholipids. They are bordered by membranes that are rich in square arrays, have ‘degenerate’ gap junctions and have few intramembranous particles. It has been shown that the opaque shades represent cohorts of locally affected fibres segregated from unaffected neighbouring fibres by ‘non‐leaky’ membranes. This segregation is an effective mechanism delaying the outgrowth of these opacities to cuneiform cataracts entering the pupillary space and thus leading to blinding cortical cataracts. Although cataract formation is mostly considered to be a multi‐factorial disease, oxidative stress might be one of the leading causes for both nuclear and cortical cataract. In cortical cataracts shear stress between cortex and nucleus during accommodation may also play a significant role.

show abstract

Section: Ageing and Lens Transparencymentioning

confidence: 99%

Early cortical lens opacities: a short overview

Vrensen

2009

Acta Ophthalmologica

View full text Add to dashboard Cite

show abstract

“…Once inside the cell, glucose can be utilised in many metabolic processes to release energy in the form of ATP, which is required to maintain the structural integrity and, therefore, transparency of the lens ( Vrensen, 1991 ; Donaldson et al, 2017 ). In the lens, it is primarily metabolised by three pathways ( Figure 1 ), glycolysis ( Kinoshita, 1955 ), the pentose phosphate pathway (hexose monophosphate shunt) ( Giblin et al, 1981 ), and the polyol pathway ( Dvornik et al, 1973 ; Kinoshita, 1990 ).…”

Section: Introductionmentioning

confidence: 99%

Mapping Glucose Uptake, Transport and Metabolism in the Bovine Lens Cortex

et al. 2022

View full text Add to dashboard Cite

Purpose: To spatially correlate the pattern of glucose uptake to glucose transporter distributions in cultured lenses and map glucose metabolism in different lens regions.Methods:Ex vivo bovine lenses were incubated in artificial aqueous humour containing normoglycaemic stable isotopically-labelled (SIL) glucose (5 mM) for 5 min-20 h. Following incubations, lenses were frozen for subsequent matrix-assisted laser desorption/ionisation (MALDI) imaging mass spectrometry (IMS) analysis using high resolution mass spectrometry. Manually dissected, SIL-incubated lenses were subjected to gas chromatography-mass spectrometry (GC-MS) to verify the identity of metabolites detected by MALDI-IMS. Normal, unincubated lenses were manually dissected into epithelium flat mounts and fibre cell fractions and then subjected to either gel-based proteomic analysis (Gel-LC/MS) to detect facilitative glucose transporters (GLUTs) by liquid chromatography tandem mass spectrometry (LC-MS/MS). Indirect immunofluorescence and confocal microscopy of axial lens sections from unincubated fixed lenses labelled with primary antibodies specific for GLUT 1 or GLUT 3 were utilised for protein localisation.Results: SIL glucose uptake at 5 min was concentrated in the equatorial region of the lens. At later timepoints, glucose gradually distributed throughout the epithelium and the cortical lens fibres, and eventually the deeper lens nucleus. SIL glucose metabolites found in glycolysis, the sorbitol pathway, the pentose phosphate pathway, and UDP-glucose formation were mapped to specific lens regions, with distinct regional signal changes up to 20 h of incubation. Spatial proteomic analysis of the lens epithelium detected GLUT1 and GLUT3. GLUT3 was in higher abundance than GLUT1 throughout the epithelium, while GLUT1 was more abundant in lens fibre cells. Immunohistochemical mapping localised GLUT1 to epithelial and cortical fibre cell membranes.Conclusion: The major uptake site of glucose in the bovine lens has been mapped to the lens equator. SIL glucose is rapidly metabolised in epithelial and fibre cells to many metabolites, which are most abundant in the metabolically more active cortical fibre cells in comparison to central fibres, with low levels of metabolic activity observed in the nucleus.

show abstract

UV-B and early cortical and nuclear changes in the human lens

Vrensen

1995

Doc Ophthalmol

View full text Add to dashboard Cite

Experimental studies in mice and rats have shown that UV (B) irradiation leads to specific lens changes, viz. yellowing of the nucleus and a multilayered epithelium in the anterior pole with disrupted cortical fibres underneath. Biomicroscopic and ultrastructural studies on ageing human lenses revealed yellowing of the lens nucleus and locally ruptured membranes and small opacities in the equatorial cortex. No changes in the anterior pole were ever observed. This discrepancy between the human and animal lens, contraindicating UV as an important risk factor for human cataract, is discussed and may be due to several factors: (1) a difference between the high level acute and low level chronic irradiation; (2) species differences: nocturnal animals may be unable to cope with bright light exposure; (3) differences in scavenger and other defense mechanisms between humans and animals.

show abstract

Discrepancy between Onset of Early Lens Changes and Onset of Senile Cataract: The Case for Cellular Defense Systems in the Human Eye Lens

Cited by 4 publications

References 0 publications

Early cortical lens opacities: a short overview

Early cortical lens opacities: a short overview

Mapping Glucose Uptake, Transport and Metabolism in the Bovine Lens Cortex

UV-B and early cortical and nuclear changes in the human lens

Contact Info

Product

Resources

About