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PubMed1983

Age-related and distributional changes in the trypsin inhibitor activity of bovine lens.

Age-related changes in the bovine lens trypsin inhibitor activity were measured by assaying water soluble extracts of 10 concentric slices from the periphery to the center of the lens. Inhibitor assays were carried out at pH 7.0 and 7.9 using prenatal, calf and mature lenses. The inhibitor at pH 7.0 remained constant throughout the lens but the pH 7.9 activity decreased sharply in the lens nucleus. This was particularly true for the prenatal and calf lenses. Agarose A-15 m gel filtration of the water soluble inhibitor activity showed a decrease in inhibitor in the alpha-crystallin region and a corresponding increase in inhibitor activity in the HMW protein peak. Inhibitor assays were carried out on the water insoluble fractions following solubilization in 6.0 M-urea. Little or no inhibitor activity was seen in the outer cortical fractions but the inner cortex and nucleus contained high levels of inhibitor activity in the water insoluble fraction with specific activities 7- to 10-fold higher than the comparable crude lens extracts. These data suggest that the lens inhibitor activity at pH 7.0 and 7.9 aggregate into a HMW complex and with time preferentially enter the water insoluble fraction. The distribution of a purified 5.5 K inhibitor protein between the water soluble and the water insoluble fraction was measured. In the periphery all of this inhibitor was in the water soluble fraction, but toward the center of the lens this inhibitor began shifting to the water insoluble fraction. Slices taken from the lens nuclear region showed that all the inhibitor was in the water insoluble fraction as detected by both activity measurements and SDS-PAGE.

Aging↗
PubMed1991

Structural characterization of human lens membrane lipid by infrared spectroscopy.

Fourier transform infrared spectroscopy was used to measure the structural changes in lipid hydrocarbon chain and interface regions of membranes that were obtained from the cortex and the nucleus of the normal human lens. Temperature-dependent studies, ie, phase transitions, were performed to evaluate the differences in the thermodynamic properties of the nuclear and cortical lipids. The structure of the fatty acyl chain region showed a higher degree of order for the nuclear lipid membranes as compared with the cortical ones. At physiologic temperature, the acyl chains of lipid from the cortical region of a 51-yr-old lens showed a degree of disorder of 63 +/- 0.6% compared with 23 +/- 1% for the nuclear region. The gel-to-liquid crystalline-phase transition temperatures were 27.2 +/- 0.3 and 39.2 +/- 1 degree C for the cortical and nuclear lipids, respectively. From the phase transition data, the enthalpy (strength of lipid-lipid interactions), entropy (randomness of the bilayer), and cooperativity (influence of adjacent lipid molecules) were calculated to be 2.6, 1.8, and 2 times greater, respectively, for the nuclear lipid transition compared with the cortical lipid transition. These differences show stronger lipid interactions and higher order in the nuclear membranes as compared with those in the cortex. Energetic differences between the cortical and nuclear membranes may arise from differences in the level of hydration or in the packing at the interface region. This last possibility is supported by changes in the contour of the carbonyl band near 1743 cm-1.

Fourier Analysis↗
PubMed1982

Protein and electrolyte alterations in human senile cataract.

Water content, wet and dry weights of the crystalline lens, and protein, free amino acid and electrolyte levels in serum, aqueous humour and lens were determined in patients with nuclear senile cataract and at the different stages of the maturation of cortical cataract. In immature senile cortical cataract wet weight and sodium contents of the lens were significantly higher while potassium levels were low when compared with the nuclear cataract. With the maturation of cortical cataract water content, wet weight and sodium concentrations of the crystalline lens significantly increased while protein, free amino acid and potassium levels decreased. The possible role of these changes in various types of cataracts is discussed.

Aged↗
PubMed1992

Cortical cleaving hydrodissection.

In this technique, I/A of cortex as a separate step can be omitted, thereby eliminating that portion of the surgical procedure in which posterior capsular disruption most frequently occurs. Residual cortical cleanup is accomplished in the presence of a posterior chamber IOL which protects the poserior capsule by holding it remote from the aspiration port.

Cataract Extraction↗
PubMed1993

Low and high Km forms of dinitrophenylglutathione-stimulated ATPase in bovine lens.

Dinitrophenyl S-glutathione (Dnp-SG) ATPase which catalyses the hydrolysis of ATP in the presence of GSH-conjugates has been implicated previously in the transport of these conjugates. In the present studies we demonstrate that Dnp-SG ATPase is present in bovine lens epithelium and cortex. The specific activity per mg membrane protein was found to be 75-fold higher in the epithelium as compared to the cortex. No enzyme was detected in the nuclear region of the lens. Dnp-SG ATPase was purified from bovine lens epithelium and cortex using Dnp-SG-Sepharose 6MB affinity chromatography. The partially purified Dnp-SG ATPase had two distinct Km values, 120 microM and 1.0 mM. The antibodies raised against human erythrocyte Dnp-SG ATPase cross-reacted with the bovine lens epithelium Dnp-SG ATPase which was identified by Western blot as a band corresponding to an approximate M(r) value of 80,000 Da.

Adenosine Triphosphatases↗
PubMedDate not supplied

Evaluation of lenticonus in Alport's syndrome: quantitative Scheimpflug analysis.

Anterior lenticonus is an ocular abnormality that can occur in Alport's syndrome. In this study, Scheimpflug slit imaging analyses were employed for quantitative and objective evaluation of lens changes associated with Alport's syndrome. It was determined that while the apices of the lenticular protrusions are central in the vertical plane, they are nasally displaced in the horizontal meridian. The eccentricity and dimensions of the diameters and thicknesses of the conical aberration are highly correlated in both eyes. Lens thickness and anterior chamber depth do not differ between eyes. Densitometrically similar differences are apparent in the cortex and nuclear regions although evidence of overt opacification may or may not be present. The data strongly suggest that the physical parameters of the lenticonus are consistent with the constraints imposed by the pupil. Changes observed in the cornea and the vitreous may be associated with the syndrome.

Adult↗
PubMed1983

An electron microscopic study of early reversible hydroxyurea cataracts in vitro.

The crystalline lenses of male white Wistar rats weighing 100 gr. were cultured in a culture fluid containing 5 X 10(-2) M hydroxyurea. The epithelial cells forming multiple layers in the equatorial region on the 4th day of incubation and swollen epithelial cells were studied by electron microscopy and the results are summarized as follows; The epithelial cells forming multiple layers retained a desmosome-like structure near the apical region. It was assumed that these cells preserve their epithelial properties. The cellular morphology and subcellular organela had the characteristics of epithelial cells. The scarcity of microtubules in the epithelial multiple layers was interpreted as reduced capacity of these cells for elongation.

Animals↗
PubMed1999

Human lens cholesterol concentrations in patients who used lovastatin or simvastatin.

OBJECTIVE: To determine whether long-term therapeutic use of the hypocholesterolemic drugs lovastatin and simvastatin significantly alters the distribution and concentration of cholesterol in the human lens. Such changes might precede observable alterations in lens structure. METHODS: Pairs of lenses (9-13 pairs) from patients (age range, 46-81 years) who had been taking lovastatin or simvastatin before their death (estimated for the previous 2-4 years) and lenses from similarly aged control subjects were divided into outer cortex and inner cortex plus nucleus by dissolution in a detergent-containing buffer. Ten minutes of dissolution removed 17% to 19% of the lens total volume, which accounted for about 20% of the width of the equatorial cortex and 75% of the width of the sagittal cortex. This fraction plus the residual lens was homogenized, saponified, and assayed for cholesterol by gas-liquid chromatography. RESULTS: The cortex of adult control lenses contained about 4 microg of cholesterol per cubic millimeter of volume. This concentration increased to 10 to 15 microg/mm3 in the adult nucleus and decreased to about 6 microg/mm3 in the juvenile and fetal nucleus. Treatment with neither lovastatin nor simvastatin significantly altered the concentration of cholesterol in either the cortex or nuclear fractions. CONCLUSIONS: Variations in concentration of cholesterol along the radii of the lens reflect differences in the density or packing of fiber cell membranes. The observed distribution of cholesterol supports the recent model of the adult lens structure, which, from surface to center, is the cortex, adult nucleus,juvenile nucleus, fetal nucleus, and embryonic nucleus. Finding no significant changes in concentration of cholesterol in the cortex formed during treatment with lovastatin or simvastatin reinforces the results of clinical studies that indicate a high lenticular safety of 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors. Nevertheless, caution is encouraged in assuming a similar ocular safety in newer drugs that inhibit cholesterol synthesis at later metabolic steps. CLINICAL RELEVANCE: Does clinical use of hypocholesterolemic drugs alter lens cholesterol?

Aged↗
PubMed2000

Light exposure and the risk of cortical, nuclear, and posterior subcapsular cataracts: the Pathologies Oculaires Liées à l'Age (POLA) study.

BACKGROUND: Exposure to light may be an important risk factor for the development of cataracts. OBJECTIVE: To present the relation of ambient solar radiation and professional and leisure exposures to light with the different types of cataracts. METHODS: Pathologies Oculaires Liées a l'Age (POLA) is a population-based study on cataract and age-related macular degeneration and their risk factors in 2584 residents of Sète (southern France). Cataract classification was based on lens examination at slitlamp according to Lens Opacities Classification System III. A questionnaire about light exposure was administered. RESULTS: After multivariate adjustment, participants who had higher ambient solar radiation had a 2.5-fold (95% confidence interval [CI], 1.2-5.0), 4.0-fold (95% CI, 2.0-8.0), and 2.9-fold (95% CI, 1.5-5.3) increased risk of cortical and mixed cataract and cataract surgery, respectively. Solar ambient radiation was not significantly associated with posterior subcapsular and nuclear cataracts. By contrast, posterior subcapsular cataracts were significantly associated with professional exposure to sunlight (odds ratio [OR], 1.63; 95% CI, 1.01-2.63) and frequent use of sunglasses (OR, 0.62; 95% CI, 0.43-0.90). Mixed cataract was also associated with professional exposure to artificial light (OR, 3.02; 95% CI, 1.03-8.82). CONCLUSION: Our study further confirms the role of sunlight exposure in the pathogenesis of cataract, in particular in its cortical localization.

Age Distribution↗
PubMed2004

Risk factors for incident cortical and posterior subcapsular lens opacities in the Barbados Eye Studies.

OBJECTIVE: To evaluate risk factors for the 4-year incidence of cortical and posterior subcapsular (PSC) lens opacities. DESIGN: Population-based cohort study with 85% participation at 4-year follow-up. PARTICIPANTS: Three thousand one hundred ninety-three black participants of the Barbados Eye Studies, Barbados, West Indies, of whom 2040 and 2954 were free of cortical and PSC lens opacities, respectively, at baseline. METHODS: The standardized protocol at baseline and follow-up included an interview, anthropometric and blood pressure measurements, and ophthalmic measurements including slitlamp lens grading, fundus photography, and an ophthalmologic examination. Factors associated with incident cortical and PSC opacities (Lens Opacities Classification System II, > or =2) were evaluated by logistic regression. Main Outcome Measure Relative risks (RRs) with 95% confidence intervals. RESULTS: The 4-year incidence of cortical lens opacities was 22.2% (452/2040); the factors increasing risk were older age, female gender (RR = 1.3), low socioeconomic status (RR = 1.4), and a history of diabetes mellitus (RR = 2.4), while aspirin use was associated with a lower RR (RR = 0.2; 95% confidence interval, 0.1-0.8), a result based on small numbers. The 4-year incidence of PSC opacities was lower at 3.3% (97/2954), and risk also increased with age and a history of diabetes mellitus (RR = 2.9). A dose-response relationship was evident between incident opacities and increased levels of glycosylated hemoglobin at baseline, with the highest risk of cortical (RR = 3.60; 95% confidence interval, 2.23-5.81) and PSC (RR = 4.93; 95% confidence interval, 2.69-9.05) opacities at more than an 11.5% glycosylated hemoglobin level. CONCLUSIONS: Diabetes mellitus and hyperglycemia are major modifiable risk factors for the development of cortical and PSC lens opacities in this African-descent population with a high rate of diabetes mellitus. Prevention and improved control of diabetes mellitus are likely to reduce the burden of cataract. The finding of a reduced incidence of cortical lens opacities in aspirin users merits further investigation, given its potential for cataract prevention.

Adult↗
PubMed1993

The Lens Opacities Classification System III. The Longitudinal Study of Cataract Study Group.

OBJECTIVE: To develop the Lens Opacities Classification System III (LOCS III) to overcome the limitations inherent in lens classification using LOCS II. These limitations include unequal intervals between standards, only one standard for color grading, use of integer grading, and wide 95% tolerance limits. DESIGN AND RESULTS: The LOCS III contains an expanded set of standards that were selected from the Longitudinal Study of Cataract slide library at the Center for Clinical Cataract Research, Boston, Mass. It consists of six slit-lamp images for grading nuclear color (NC) and nuclear opalescence (NO), five retroillumination images for grading cortical cataract (C), and five retroillumination images for grading posterior subcapsular (P) cataract. Cataract severity is graded on a decimal scale, and the standards have regularly spaced intervals on a decimal scale. The 95% tolerance limits are reduced from 2.0 for each class with LOCS II to 0.7 for nuclear opalescence, 0.7 for nuclear color, 0.5 for cortical cataract, and 1.0 for posterior subcapsular cataract with the LOCS III, with excellent interobserver agreement. CONCLUSION: The LOCS III is an improved LOCS system for grading slit-lamp and retroillumination images of age-related cataract.

Aging↗
PubMed1984

Cytoskeletal proteins of the ageing human lens.

The cytoskeletal proteins of the human lens were studied by sodium dodecylsulphate-polyacrylamide gel electrophoresis, two-dimensional electrophoresis, and immunologically. Spectrin, vimentin and actin were identified in the superficial fibre cells of human lenses even to age 87 years. These proteins are lost from the deeper cortical and nuclear fibre cells, where a broad zone of water-insoluble proteins of Mr 36 000-45 000 emerges even in the transparent normal lens. Age-related changes in the water-soluble fraction include the increased prominence of W 56 and W 36 proteins in the cortex and of W 38 in the nucleus.

Actins↗
PubMed1985

A quantitative microprobe analysis of elements in cortical and nuclear cells of the calf lens.

The outer cortical cells in the calf lens remain transparent under conditions that produce opacity in central nuclear cells. The nuclear cells opacify by a mechanism of cellular restructuring that is associated with a cytoplasmic phase separation while cortical cells do not opacify by this mechanism. In this study the differences in elemental composition of nuclear and cortical cells were analyzed using X-ray emission spectroscopy (XES) of tissue that was prepared for scanning electron microscopy. It was necessary to develop special methods of fixation and dehydration to prevent significant distortion of lens tissue and minimize solubilization and redistribution of elements during the histological processing of the tissue. We calibrated the microprobe for the quantitative analysis using gelatin standards which contained known concentrations of sulfur, potassium, phosphorus, chlorine, and cesium. The standard curves were used to determine proportionality constants, which related the intensity of X-ray emission to the molar concentration of each element, and to determine the minimum detectable levels of each element. An important finding is that the intensity of the X-ray emission is dependent on sample density only at low protein concentration. At the high protein concentrations that exist in lens, the intensity is not affected by sample density.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1998

Modelling cortical cataractogenesis. XXIX. Calpain proteolysis of lens fodrin in cataract.

The relation between cataract and calpain proteolysis of lens fodrin was studied in two systems: elevated glucose (55.6 mM, diabetic model), and cytochalasin D (CD, 10(-2) mM, actin depolymerization-induced opacity model). Glucose treatment (48 h) caused a visible opaque layer and enzyme leakage, with a concomitant accumulation of ([Ca2+]i) around the lens equatorial cortex. CD caused both earlier and greater opacity and enzyme leakage than glucose. Lens fodrin digestion occurred in parallel with the timing and extent of calcium elevation. A calpain inhibitor peptide (CIP, 10(-2) mM) reduced the proteolysis of fodrin, opacity, and enzyme leakage in glucose-treated lenses but only partially retarded them in CD-treated lenses. These results suggest a mechanism in which calpain proteolysis of fodrin is a critical event in lens damage during opacification of cortical cataract.

Amino Acid Sequence↗
PubMed1995

A high phosphotyrosine phosphatase activity is present in differentiating bovine lens cells.

Activity of phosphotyrosine-protein phosphatases (PTPases) has been investigated in the different cellular regions of bovine eye lens. PTPases were tested in cellular detergent extracts using phospholabelled synthetic peptides and p-nitrophenyl phosphate. We show that a high PTPase activity is only present in cells which undergo differentiation, namely the equatorial epithelium and cortex fiber cells. Since this activity is found to be severely inhibited by a specific inhibitor of receptor-type PTPases, it can be suggested that one or more members of this class of PTPases might play an important role in the lens differentiation process.

Animals↗
PubMed1993

Structural characterization of lipid membranes from clear and cataractous human lenses.

Lipid composition related structural changes in human cataractous lenses was explored by characterizing the hydrophobic hydrocarbon chains in lipid membranes corresponding to twelve Indian cataractous lenses and eight American clear lenses of similar age. The nuclear-lipid phase transitions corresponding to the clear lenses exhibited significantly higher average transition temperatures (nucleus 33 degrees C, cortex 26.3 degrees C) and cooperativities, 38.1, as compared to the value of 24.1 for the cortical-lipid phase transitions. At 36 degrees C, the phase transitions corresponding to cortical and nuclear lipids indicate a similar degree of disorder, 63%, in the hydrocarbon chains, i.e., similar relative amounts of gauche and trans rotomers. The twelve cataractous lenses investigated all had nuclear opacities, four were brunescent and four had cortical opacities. No significant differences were observed in the phase transition parameters (temperature, cooperativity, magnitude, enthalpy) evaluated for the nuclear-lipid membranes corresponding to the different types of cataracts. Furthermore, for the cataractous membranes, the phase transition parameters obtained for the nuclear lipids were comparable to those evaluated for the cortical lipid membranes. However, the cortical lipids exhibited the highest order in membranes from nuclear cataracts without cortical opacity. The cortical lipids from clear, non-cataractous lenses had the lowest level of order. At 36 degrees C, the degree of order in the cortical lipid from clear lenses was comparable to that from nuclear cataractous lenses without cortical opacity. The transition temperature, and cooperativity were significantly higher for cortical lipids from cataractous lenses as compared to those from clear lenses. At 36 degrees C, the degree of order in the cortical lipid membranes was lower for all cataract types vs. clear lens fractions. Our results suggest the possibility that lipid-lipid interactions could be different in cataractous lens membranes. Lipid compositional and chemical differences must account for these altered lipid interactions. These studies will provide a basis for studying lipid-protein interactions and structure-function relationships in the lens membrane.

Adult↗
PubMed1994

Actin filament bundles are associated with fiber gap junctions in the primate lens.

A unique association between actin filament bundles and gap junctions in cortical fiber cells of human and monkey lenses was studied with thin-section electron microscopy and immunocytochemistry. Thin-section electron microscopy showed that distinct layers of filament bundles (approximately 55 nm thick) were consistently associated with fiber gap junctions (approximately 16 nm thick) from intermediate to deep cortical regions in both species studied. The filament bundle was composed of 6-8 nm microfilaments which lay along both cytoplasmic surfaces of the junction. Fluorescence microscopy revealed a patchy pattern of F-actin labeling along the fiber cell membranes in the intermediate and deep cortical regions of the lens. The size and distribution pattern of F-actin labeling appear to correlate well with those of filament bundles/gap junctions seen in thin-section electron microscopy. By immunoelectron microscopy, the anti-actin antibody was shown to be localized to filament bundles/gap junctions in the intermediate cortical fibers of human lens, indicating that filament bundles are F-actin in nature. The identical filament bundle/gap junction association was not found in other species examined, including rodent, bird and fish, by the same procedure, suggesting that an association between actin bundles and gap junctions has a special functional role in the primate lens. It is proposed that gap junction-associated actin bundles may provide added structural stability for the primate lens.

Actins↗