Comparison of venturi and peristaltic vacuum in phacoemulsification.

PURPOSE: To evaluate the efficiency of peristaltic-based and venturi-based vacuums. SETTING: John A. Moran Eye Center Laboratories, University of Utah, Salt Lake City, Utah, USA. DESIGN: Experimental study. METHODS: Porcine lenses were hardened with formalin and cut into 2.0 mm cubes. Time to fragment removal (efficiency) and fragment bounces off the tip (chatter) were measured using a Signature machine with the ability to switch between peristaltic-based and venturi-based vacuum. Micropulse longitudinal and transversal ultrasound motions were tested. RESULTS: Venturi-based vacuum had increased efficiency and decreased chatter compared with peristaltic-based vacuum at lower vacuum levels. CONCLUSION: Use of a venturi-based vacuum, when available, may result in reduced clearance time of lens material and mitigate chatter even under noisy conditions. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.

Effect of lanosterol on human cataract nucleus.

AIM: To study the effect of lanosterol on age-related cataractous human lens nuclei. MATERIALS AND METHODS: Forty age-related cataractous nuclei removed during manual small incision cataract surgery were obtained and randomly immersed in 25 mM lanosterol solution or in control solution and stored at room temperature for 6 days. Pre- and post-immersion photographs were graded by two masked observers and collated for the regression or progression of lens opacity. RESULTS: Both lanosterol and control groups showed progression or no change in the lens opacity at the end of 6 days. CONCLUSION: Lanosterol 25 mM solution did not reverse opacification of human age-related cataractous nuclei.

Porcine lens nuclei as a model for comparison of 3 ultrasound modalities regarding efficiency and chatter.

PURPOSE: To validate a porcine lens model by comparing density and ultrasound (US) with known human standards using the Infiniti Ozil with Intelligent Phacoemulsification (torsional), Whitestar Signature Micropulse (longitudinal), and Ellips FX (transversal) modalities. SETTING: Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA. DESIGN: Experimental study. METHODS: Lens nuclei were formalin soaked in hour-based intervals and divided into 2.0 mm cubes. Density was characterized by crushing experiments and compared with known human measures. Efficiency and chatter were examined. RESULTS: The mean weight to cut thickness in half ranged from 16.9 g ± 5.5 (SD) in the 0-hour group to 121.3 ± 47.5 gm in the 4-hour group. Lenses in the 2-hour group (mean 70.2 ± 19.1 g) best matched human density (P=.215). The mean efficiency ranged from 0.432 ± 0.178 seconds to 9.111 ± 2.925 seconds; chatter ranged from zero to 1.85 ± 1.927 bounces. No significant difference was detected when comparing the 2-hour formalin group with human lenses in torsional and transversal US. There was no significant difference between transversal and torsional modalities, consistent with human studies. Although longitudinal (6 milliseconds on, 12 milliseconds off) was significantly more efficient at 50% power than at 25%, there was no significant difference compared with transversal or torsional US. CONCLUSIONS: Animal lenses soaked for 2 hours in formalin were most comparable to human lenses. Longitudinal US may be an acceptable alternative to torsional and transversal US.

Triangular congenital cataract morphology associated with prenatal methamphetamine exposure.

Bilateral congenital cataracts are often characterized by morphology, etiology, and related conditions. We report a case of unique congenital cataracts with triangular morphology and associated prenatal methamphetamine exposure. Although this association is likely coincidental, the cataract's morphology in light of the specific timing of prenatal drug use deserves reporting.

Dietary linolenic acid intake is positively associated with five-year change in eye lens nuclear density.

OBJECTIVE: Dietary fat may affect lens cell membrane composition and function, which are related to age-related cataract. The present study was designed to examine the associations between dietary fat and the change in nuclear lens opacification over five years. METHODS: Women aged 52 to 73 years without previously diagnosed cancer, diabetes and cataracts from the Boston, Massachusetts area were selected from the Nurses' Health Study cohort. Four hundred forty women participated in a baseline (1993-95) and a follow-up (1998-2000) eye examination. Intakes of total fat and selected fatty acids were calculated as the average intake from five food frequency questionnaires that were collected between 1980 and baseline. Change in the degree of nuclear density (opacification) was characterized by the difference between baseline and follow-up in pixel density at the central clear zone in the Scheimpflug slit image of the lens. RESULTS: Intake of alpha-linolenic acid (ALA) was positively associated with change in nuclear density. The geometric mean nuclear density change was 16% greater in the highest quartile category of ALA intake than in the lowest quartile category (P for trend = 0.05). For women in the high tertile category of baseline nuclear lens opacification, the geometric mean change in the highest quartile category of ALA acid intake was 70% higher than the change in the lowest quartile category (P for trend = 0.01). There were no significant associations between other dietary fats and change in nuclear density. CONCLUSION: Higher ALA intake was associated with a greater age-related change in lens nuclear density.

Long-term nutrient intake and 5-year change in nuclear lens opacities.

OBJECTIVE: To determine if usual nutrient intake is related to a 5-year change in the amount of lens nuclear opacification assessed by computer-assisted image analysis. DESIGN: A sample of 408 Boston, Mass-area women from the Nurses' Health Study aged 52 to 74 years at baseline participated in a 5-year study related to nutrition and vision. Usual nutrient intake was calculated as the average intake from 5 food frequency questionnaires that were collected over a 13- to 15-year period before the baseline evaluation of lens nuclear density. Duration of vitamin supplement use before baseline was determined from 7 questionnaires collected during this same period. We assessed the degree of nuclear density (opacification) using computer-assisted image analysis of digital lens images with amount of nuclear density measured as a function of average pixel gray scale, ranging from 0 (clear) to 255 (black). RESULTS: Median (range) baseline and follow-up nuclear densities were 44 (19 to 102) and 63 (32 to 213). The median (range) 5-year change in nuclear density was 18 (-29 to 134) and was positively correlated with the amount of opacification at baseline (Spearman correlation coefficient = 0.35; P<.001). Geometric mean 5-year change in nuclear density was inversely associated with the intake of riboflavin (P trend = .03) and thiamin (P trend = .04) and duration of vitamin E supplement use (P trend = .006). CONCLUSION: Our results suggest that long-term use of vitamin E supplements and higher riboflavin and/or thiamin intake may reduce the progression of age-related lens opacification.

[Morphological and functional characteristics of the lens histamine-containing structures at the early stages of chemical irritation of the eye]. / Morfofunktsional'naia kharakteristika gistaminsoderzhashchikh struktur khrustalika v rannie sroki khimicheskogo razdrazheniia glaznogo iabloka.

The purpose of the present study was to determine, using the methods of light, fluorescence microscopy and cytospectrofluorometry, the morpho-functional changes in histaminergic structures of the lens as influenced by extrinsic chemical irritation of the eye (exposure to ether vapors). The experiments were conducted on 74 outbred male albino rats. Extremely fast simultaneous changes (demonstrated in all lens structures already 3 minutes after an irritation) were found in histamine content of the lens cells. According to the results of luminescence analysis, maximal increase in histamine content (by 53.3%) took place in the area of lens nucleus. In the cytoplasm of lens epitheliocytes, histamine content was increased by 22%, while in the cytoplasm of equatorial epithelial cells it was increased by 36.1%, and in the nuclei of central epithelial cells--by 26.4%. The data obtained suggests an existence of diffuse neurotransmission in the lens, that is not associated with neurons.

Long-term intake of vitamins and carotenoids and odds of early age-related cortical and posterior subcapsular lens opacities.

BACKGROUND: Proper nutrition appears to protect against cataracts. Few studies have related nutrition to the odds of developing cortical or posterior subcapsular (PSC) cataracts. OBJECTIVE: We assessed the relation between usual nutrient intakes and age-related cortical and PSC lens opacities. DESIGN: We studied 492 nondiabetic women aged 53-73 y from the Nurses' Health Study cohort who were without previously diagnosed cataracts. Usual nutrient intake was calculated as the average intake from 5 food-frequency questionnaires collected over a 13-15-y period before the eye examination. Duration of vitamin supplement use was determined from 7 questionnaires collected during this same period. We defined cortical opacities as grade > or = 0.5 and subcapsular opacities as grade > or =0.3 of the Lens Opacities Classification System III. RESULTS: Some lenses had more than one opacity. No nutrient measure was related to prevalence of opacities in the full sample, but significant interactions were seen between age and vitamin C intake (P = 0.02) for odds of cortical opacities and between smoking status and folate (P = 0.02), alpha-carotene (P = 0.02), beta-carotene (P = 0.005), and total carotenoids (P = 0.02) for odds of PSC opacities. For women aged <60 y, a vitamin C intake > or = 362 mg/d was associated with a 57% lower odds ratio (0.43; 95% CI: 0.2, 0.93) of developing a cortical cataract than was an intake <140 mg/d, and use of vitamin C supplements for > or = 10 y was associated with a 60% lower odds ratio (0.40; 0.18, 0.87) than was no vitamin C supplement use. Prevalence of PSC opacities was related to total carotenoid intake in women who never smoked (P = 0.02). CONCLUSIONS: Our results support a role for vitamin C in diminishing the risk of cortical cataracts in women aged <60 y and for carotenoids in diminishing the risk of PSC cataracts in women who have never smoked.

A 6-bp deletion in the Crygc gene leading to a nuclear and radial cataract in the mouse.

PURPOSE: A mouse mutant expressing a bilateral nuclear and radial cataract was found after paternal treatment with chlorambucil. The purpose of this study was to establish the linkage of the mutation to a particular chromosome to allow molecular characterization. Moreover, the mutants were examined morphologically. METHODS: Isolated lenses were photographed and histologic sections of the eye were analyzed according to standard procedures. The mutation was localized to chromosome 1 by allelism testing with the Cryge(nz) mutation. Candidate genes were amplified by PCR from cDNA or genomic DNA and sequenced. RESULTS: A novel mouse cataract was characterized by a nuclear and radial opacification of the lens. The lenses of the mutants are smaller than those of the wild type. The histologic analysis demonstrated degeneration of lens fibers in the lens core. Abnormal remnants of cell nuclei are present throughout the entire lens. Genetic analysis revealed allelism to the Cat2 group of dominant cataracts on mouse chromosome 1; therefore, the cluster of the Cryg genes and the closely linked Cryba2 gene were tested as candidates. A 6-bp deletion in exon 3 of the gammaC-crystallin encoding gene (Crygc) is causative for the cataract phenotype; the mutation is therefore designated CrygcChl3. The deletion of the bases 420 to 425 leads to a loss of two amino acids, Gly and Arg, in the fourth Greek-key motif. CONCLUSIONS: The CrygcChl3 is the first mutation in the mouse affecting the Crygc gene. Dominant mutations for five of the six Cryg genes on mouse chromosome 1 have now been characterized, demonstrating the importance of this gene cluster for lens transparency.

Hormone replacement therapy and lens opacities: the Salisbury Eye Evaluation project.

BACKGROUND: Data suggest a possible protective effect against lens opacity with use of hormone replacement therapy (HRT). However, no agreement exists on which opacity type is affected, and more exploration of the additional role of endogenous estrogen exposure is warranted. OBJECTIVE: To determine whether HRT and the prevalence of different lens opacity types are associated after controlling for endogenous estrogen exposure. DESIGN AND SETTING: Salisbury Eye Evaluation population-based prevalence survey of residents in an eastern US city. PARTICIPANTS: One thousand two hundred thirty-nine women aged 65 through 84 years. MAIN OUTCOME MEASURES: Nuclear, cortical, and posterior subcapsular opacity. RESULTS: We found a protective association between nuclear opacity and current (odds ratio [OR], 0.5; 95% confidence interval [CI], 0.3-0.7) and recent (OR, 0.4; 95% CI, 0.3-0.7) HRT use. Increasing number of births in younger women was also protective (test of trend, P =.05). Past HRT use protected against nuclear opacity only in women who had never been pregnant (OR, 0.2; 95% CI, 0.1-0.7). Past (OR, 0.2; 95% CI, 0.1-0.7) and current (OR, 0.3; 95% CI, 0.1-0.9) HRT use were associated with a lower prevalence of posterior subcapsular opacity. CONCLUSION: A protective association between the use of HRT and nuclear and posterior subcapsular opacities is reported, which should be confirmed in prospective studies.

Long-term nutrient intake and early age-related nuclear lens opacities.

OBJECTIVE: To assess the relation between usual nutrient intake and subsequently diagnosed age-related nuclear lens opacities. SUBJECTS: Four hundred seventy-eight nondiabetic women aged 53 to 73 years from the Boston, Mass, area without previously diagnosed cataracts sampled from the Nurses' Health Study cohort. METHODS: Usual nutrient intake was calculated as the average intake from 5 food frequency questionnaires that were collected during a 13- to 15-year period before the evaluation of lens opacities. The duration of vitamin supplement use was determined from 7 questionnaires collected during this same period. We defined nuclear opacities as a nuclear opalescence grade of 2.5 or higher using the Lens Opacification Classification System III. RESULTS: The prevalence of nuclear opacification was significantly lower in the highest nutrient intake quintile category relative to the lowest quintile category for vitamin C (P<.001), vitamin E (P =.02), riboflavin (P =.005), folate (P =.009), beta-carotene (P =.04), and lutein/zeaxanthin (P =.03). After adjustment for other nutrients, only vitamin C intake remained significantly associated (P =.003 for trend) with the prevalence of nuclear opacities. The prevalence of nuclear opacities was significantly lower (P<.001) in the highest vitamin C intake quintile category relative to the lowest quintile category (odds ratio, 0.31; 95% confidence interval, 0.16-0.58). There were also statistically significant trends of decreasing prevalence of nuclear opacities with increasing duration of use of vitamin C (P =.004 for trend), vitamin E (P =.03 for trend), and multivitamin (P =.04 for trend) supplements, but only duration of vitamin C supplement use remained significantly associated with nuclear opacities after mutual adjustment for use of vitamin E (P =.05 for trend) or multivitamin (P =.02 for trend) supplements. The prevalence of nuclear opacities was significantly lower (P =.004) for women who used a vitamin C supplement for 10 or more years relative to women who never used vitamin C supplements (odds ratio, 0.36; 95% confidence interval, 0.18-0.72). Plasma measures of vitamins C and E taken at the eye examination were also inversely associated with the prevalence of nuclear opacities. CONCLUSION: These results provide additional evidence that antioxidant nutrients play a role in the prevention of age-related nuclear lens opacities.

Identification of a novel fluorophore, xanthurenic acid 8- O -beta-D-glucoside in human brunescent cataract.

We have identified the chemical structure of a novel protein-unbound fluorescent glucoside (Fl-Glc), found to be far more abundant in the human brunescent cataractous lens nuclei than in non-brunescent ones. Our earlier experiments showed that long-term incubation of the protein-free filtrate of non-brunescent cataractous nuclei generated increasing amounts of a particular yet to be characterized fluorophore (Fl-X). High performance liquid chromatography (HPLC) analyses revealed Fl-X and Fl-Glc to be identical. HPLC-electrospray ionization-mass spectrometry (HPLC-ESI-MS) disclosed the molecular weights (MW) of Fl-X and its beta-glucosidase-digest (Fl-X-aglycon) to be 367 and 205, respectively. Fl-X-aglycon and authentic xanthurenic acid (MW = 205) not only eluted at exactly the same retention time on HPLC but also revealed their protonated ions at the same m/z of 206.1 by positive ion analysis on HPLC-ESI-MS. These results suggest that Fl-X ( = Fl-Glc) is a beta-glucoside of xanthurenic acid. Fl-Glc was finally identified as xanthurenic acid 8- O -beta- D -glucoside because the retention times of both completely agreed with three kinds of HPLC conditions.

Induction of cataracts of varying degrees of hardness in human eyes obtained postmortem for cataract surgeon training.

PURPOSE: To report a method of inducing nuclear cataracts of varying degree of hardness using intralenticular injection of the Karnovsky solution. METHODS: Twelve postmortem human eyes were prepared according to the Miyake-Apple posterior video technique. After performing capsulorhexis and hydrodissection/delineation, 0.2 ml of the Karnovsky solution was injected into the lens nucleus of the eyes. Manual extracapular cataract extraction techniques and various two-handed phacoemulsification maneuvers were then practiced at various time intervals after the injection. RESULTS: Uniform nuclear cataracts with varying degrees of hardness were successfully induced in all globes. The optimum dose of the Karnovsky solution and time for induction of nuclear hardness of grade 3 (ideal for practicing two-handed phacoemulsification maneuvers) were 0.2 ml and 15 minutes, respectively. CONCLUSION: The Karnovsky solution can be successfully used for the induction of hard, uniform nuclear cataracts for learning/practicing extracapular cataract extraction and phacoemulsification.

3 year simvastatin treatment and lens nuclear back scattering.

AIM: To determine if 3 year treatment of hypercholesterolaemia with simvastatin causes an increase of lens nuclear back scattering. METHODS: 160 patients with hypercholesterolaemia in the Scandinavian Simvastatin Survival Study (4S) were followed for 3 years. Half (80) of the patients took simvastatin and half (80) received placebo. The lens was photographed with a Topcon SL-45 slit lamp camera at the beginning and at 1 year intervals. A common lens nuclear area was used for measuring lens nuclear back scattering. RESULTS: Nuclear back scattering increased with age and there was more pronounced scattering in women than in men. Lens nuclear back scattering did not differ significantly between the simvastatin and placebo groups, but the power was low (0.2). Lens nuclear back scattering increased during the study period independently of baseline back scattering, age, and sex for both groups. CONCLUSION: Although no significant difference was found between the simvastatin and placebo groups, the currently available data are insufficient for exclusion of the possibility that taking simvastatin during a 3 year period increases nuclear back scattering. However, a possible minor increase of nuclear back scattering is clinically irrelevant considering known beneficial effects of simvastatin on coronary heart disease.

Comparison of various calpain inhibitors in reduction of light scattering, protein precipitation and nuclear cataract in vitro.

PURPOSE: To compare effects of calpain inhibitors on in vitro light-scattering in rat lens soluble protein and calcium-ionophore (A23187)-induced cataract formation in cultured rat lenses. METHODS: Rat lens soluble protein was hydrolyzed for 24 hours by activation of endogenous lens calpain. Ten calpain inhibitors were tested in this model at 10 and 25 microM concentration. As an index of protein precipitation, light scattering was measured daily at 405 nm for 8 days. Lens proteins were analyzed by isoelectric-focussing. Subsequently, rat lenses were cultured for 5 days with 10 microM A23187. Calpain inhibitors (SJA6017, MDL28170, AK295 and PD150606), which inhibited light-scattering were tested at 100 microM concentration in this model. Cataract evaluation, isoelectric-focussing and calcium determinations were performed. RESULTS: At 25 microM concentration AK295, SJA6017, E-64, PD-150606 and MDL28170 produced greater than 25% inhibition of light-scattering. Isoelectric-focussing revealed that addition of Ca(2+) produced characteristic crystallin proteolysis and aggregation patterns. AK295, SJA6017, MDL28170 and E64c prevented these changes. Lenses cultured in A23187 exhibited nuclear cataract, elevated calcium and proteolysis and aggregation of crystallins. Co-culture with SJA6017, MDL28170 and E64c reduced A23187-induced nuclear opacities, proteolysis and aggregation of crystallins without affecting increased total calcium. CONCLUSIONS: Endogenous calpain-activation model and A23187-induced cataract model can be used sequentially to screen calpain inhibitors for potential anti-cataract activity. Proteolytic changes in lens cortex after exposure to A23187 are also due to calpain activation. AK295, SJA6017 and MDL28170 possess efficacy against calcium-induced models of rodent cataracts. Use of calpain inhibitors represents a promising approach to cataract therapy.

Nuclear cataract and light scattering in cultured lenses from guinea pig and rabbit.

PURPOSE: To compare calcium ionophore-induced cataract formation and in vitro light scattering in cultured lenses from guinea pig and rabbit. METHODS: Lenses from guinea pig and rabbit were cultured for 5 or 6 days with calcium ionophore A23187. To assess the involvement of calpain in cataract formation; SDS-PAGE, immunoblotting and calcium determinations were performed. For in vitro light scattering, lens soluble proteins from rabbit were hydrolyzed for 24 h by either endogenous lens calpain, or by addition of purified m-calpain and then further incubated for up to 10 days. Light scattering was measured daily at 405 nm. RESULTS: Lenses from younger guinea pigs cultured in A23187 first developed outer cortical opacities followed by nuclear cataract. Total calcium was markedly increased by A23187 in lenses of all ages. Proteolysis of crystallins and alpha-spectrin were observed in nuclear cataract in younger guinea pigs. This was attenuated with age, in association with the attenuation of cataract formation with age. Calpain 80 kDa subunit in the lenses cultured with A23187 was also decreased. Co-culture with SJA6017 or E64d (reversible and irreversible inhibitors of calpain, respectively) reduced A23187-induced nuclear opacities, proteolysis of crystallins and alpha-spectrin, and loss of calpain without affecting increased total calcium. In contrast, rabbit lenses cultured in A23187 did not develop nuclear cataract, although biochemical changes in cultured rabbit lenses were similar to those in cultured guinea pig lenses. Furthermore, no appreciable in vitro light scattering occurred in soluble proteins from rabbit lenses after activation of endogenous m-calpain, or after addition of exogenous purified m-calpain, although crystallins were partially hydrolyzed by calpain. CONCLUSIONS: Both rabbit and guinea pig lenses undergo calpain-induced proteolysis upon elevation of lenticular calcium. However, factors in intact guinea pig lenses may promote light scattering and insolubilization after proteolysis by calpain, but these factors were not functional in rabbit lenses. Discovery of the factors promoting light scatter and insolubilization after proteolysis will help to explain the role of certain crystallin polypeptides in cataract formation.

Loss of cytoskeletal proteins and lens cell opacification in the selenite cataract model.

This study of lens protein composition found that some cytoskeletal proteins were degraded during the earliest stages of cataract formation. Cataract was induced in 13-14 day old rats by a single subcutaneous injection of sodium selenite (19 mumol kg-1). By 24 hr after the injection of selenite, the ratio of insoluble to soluble protein increased as lens opacification began. The increase in insoluble protein aggregates was correlated with an accelerated loss of proteins having molecular weights of 42, 55/57 and 235 kDa which reacted with antibodies to the cytoskeletal proteins actin, tubulin/vimentin and spectrin, respectively. We observed the loss of 49, 60 and 90 kDa proteins which were not identified. In the lenses of animals protected from protein aggregation and opacification by administration of 1.5 mmol kg-1 pantethine, the pattern of proteins in SDS-PAGE gels resembled the pattern for proteins from transparent lenses of normal untreated animals and loss of cytoskeletal proteins was prevented.

Age-related decline in ubiquitin conjugation in response to oxidative stress in the lens.

Accumulation of damaged proteins is a major age-related change in lenses of virtually all species and is associated with lens opacification. Proteolytic removal of the damaged proteins may play an important role in maintaining the transparency of the lens. In many tissues, selective removal of abnormal or damaged proteins occurs via a ubiquitin-dependent proteolytic pathway. Ubiquitin, an 8.5 kDa polypeptide, selectively binds to proteins to form ubiquitin-protein conjugates. This ubiquitin-protein conjugate is, in most cases, a signal for protein degradation. In this work, age-related changes in rat lens in the following aspects were detected: (a) levels of the ubiquitin-protein conjugates, (b) some of the enzymes involved in ubiquitin conjugation in rat lenses, and (c) ability to respond to oxidative damage. Endogenous ubiquitin-protein conjugates were detected in epithelium, cortex and nucleus of lenses from young and old rats. The levels of endogenous high molecular weight (HMW) ubiquitin-protein conjugates in each developmental zone of the lenses from young rats were higher than that in the counterparts of lenses from old animals. Peroxide-treatment generally resulted in elevated levels of endogenous HMW ubiquitin-protein conjugates although masses of bulk proteins remain unchanged. The increases in ubiquitin-protein conjugates in the epithelial sections of young and old lenses upon oxidative stress were comparable. In the cortex of young lenses, there was a significant oxidation-related increase in ubiquitin-protein conjugates. There was a similar trend but diminished response in the cortex of old lenses. Nuclear fibers from young lenses also showed an oxidation-induced increase in the level of ubiquitin-protein conjugates. This response was not observed in nuclear fibers of old lenses. The ability to form HMW-ubiquitin conjugates with exogenous 125I-labeled ubiquitin in the lens also increased upon oxidative stress. The extent of the increase in the de-novo ubiquitin conjugating activity upon exposure to oxidation in old lens was much smaller than in young lens. Ubiquitin-activating enzyme (E1), and ubiquitin conjugating enzymes (E2(17k), E2(20k) and E2(25k) were detected by thiol ester assays or Western blot analysis. No significant age-related changes in the levels of E1, E2(17k), E2(20k) and E2(25k) were detected. The activity of E1 and E2(17k) increased upon exposure to H2O2. These data indicate that lens has the ability to increase ubiquitin conjugation activity in response to oxidative stress and this ability is attenuated upon aging. The age-related decrease in the ability to mount a ubiquitin-dependent response upon oxidation may contribute to the accumulation of damaged proteins in the old lenses.

Precataractous changes affect lens transparency in the selenite cataract.

Selenite treatment of the preweanling rat stabilized the transparency of the lens nucleus to decreasing temperature. Hence, we compared properties of the cortex and nucleus from lenses of selenite-treated and age-matched control rats. A subcutaneous dose of 30 nmol Na2SeO3/g body weight was administered to 10- to 13-day-old Sprague-Dawley rats. Uninjected, age-matched littermates served as controls. As required, lenses were frozen in liquid N2 and separated into nuclear and cortical-epithelial fractions. Transparency of solutions of lens proteins (90-100 mg per ml) was monitored from 30 to 2 degrees C as percent transmittance (%T) at 490 nm. The critical phase separation temperature, Tc, was the temperature at 80%T. Protein associations were monitored with gel filtration chromatography. The nuclear 'cold cataract', in intact lenses, formed at similar temperatures at 14 and 15 days of age, but at a significantly lower temperature when the lenses were from a selenite-treated rat. The Tc, however, was greater by 1.5-2 degrees C for solutions of proteins isolated from whole lenses or lens nuclei from rats 24 and 48 h after treatment with selenite. Further, less gamma-crystallin was associated with the alpha-crystallin fraction in extracts from the nucleus of lenses from treated rats. Altered phase separation properties occurred as an early event in the etiology of selenite cataract. The different in vivo and in vitro responses to temperature indicated that properties of lens crystallins do not solely establish transparency in the intact lens.

Nuclear light scattering, disulfide formation and membrane damage in lenses of older guinea pigs treated with hyperbaric oxygen.

Nuclear cataract, a major cause of loss of lens transparency in the aging human, has long been thought to be associated with oxidative damage, particularly at the site of the nuclear plasma membrane. However, few animal models have been available to study the mechanism of the opacity. Hyperbaric oxygen (HBO) has been shown to produce increased nuclear light scattering (NLS) and nuclear cataract in lenses of mice and human patients. In the present study, older guinea pigs (Initially 17-18 months of age) were treated with 2.5 atmospheres of 100% O2 for 2-2.5-hr periods, three times per week, for up to 100 times. Examination by slit-lamp biomicroscopy showed that exposure to HBO led to increased NLS in the lenses of the animals after as few as 19 treatments, compared to lenses of age-matched untreated and hyperbaric air-treated controls. The degree of NLS and enlargement of the lens nucleus continued to increase until 65 O2-treatments, and then remained constant until the end of the study. Exposure to O2 for 2.5 instead of 2 hr accelerated the increase in NLS; however, distinct nuclear cataract was not observed in the animals during the period of investigation. A number of morphological changes in the experimental lens nuclei, as analysed by transmission electron microscopy, were similar to those recently reported for human immature nuclear cataracts (Costello, Oliver and Cobo, 1992). O2-induced damage to membranes probably acted as scattering centers and caused the observed increased NLS. A general state of oxidative stress existed in the lens nucleus of the O2-treated animals, prior to the first appearance of increased NLS, as evidenced by increased levels of protein-thiol mixed disulfides and protein disulfide. The levels of mixed disulfides in the experimental nucleus were remarkably high, nearly equal to the normal level of nuclear GSH. The level of GSH in the normal guinea pig lens decreased with age in the nucleus but not in the cortex; at 30 months of age the nuclear level of GSH was only 4% of the cortical value. HBO-induced changes in the lens nucleus included loss of soluble protein, increase in urea-insoluble protein and slight decreases in levels of GSH and ascorbate; however, there was no accumulation of oxidized glutathione. Intermolecular protein disulfide in the experimental nucleus consisted mainly of gamma-crystallin, but crosslinked alpha-, beta- and zeta-crystallins were also present.(ABSTRACT TRUNCATED AT 400 WORDS)