Different Types Of Cataract Research Articles

Structure-Based Virtual Screening and Biological Evaluation of a Calpain Inhibitor for Prevention of Selenite-Induced Cataractogenesis in an in Vitro System.

Calpains belong to the family of calcium-dependent, structurally related intracellular cysteine proteases that exhibit significant functions in evolution of different types of cataracts in human as well as animal models. Application of calpain inhibitors generated through a virtual screening workflow may provide new avenues for the prevention of cataractogenesis. Hence, in the current study, compounds were first screened for potent calpain inhibitory activity by employing a structure-based approach, and the screening results were then validated through biological experiments in rat lenses. A hit compound, HTS08688, was obtained by structure-based virtual screening. A micromolar concentration of HTS08688 was found to prevent in vitro cataractogenesis in isolated Wistar rat lenses, while maintaining the antioxidant and calcium concentrations at near normal levels. Inhibition of superoxide anion generation, as observed through cytochemical localization studies, and maintenance of structural integrity, as demonstrated by histological analysis of lenticular tissue, also suggested that HTS08688 can ameliorate the cataractous condition induced by selenite in an in vitro rodent model. A cell proliferation assay was performed; the IC 50 value of the screened calpain inhibitor, HTS08688, against human lenticular epithelial cells-b3 was found to be 177 μM/mL. This combined theoretical and experimental approach has demonstrated a potent lead compound, HTS08688, that exhibits putative anticataractogenic activity by virtue of its potential to inhibit calpain.

Differences in Unfolded Protein Response Pathway Activation in the Lenses of Three Types of Cataracts.

PurposeTo investigate the activation of three unfolded protein response (UPR) pathways in the lenses of age-related, high myopia-related and congenital cataracts.Methods and MaterialsLens specimens were collected from patients during small incision cataract surgery. Lenses from young cadaver eyes were collected as normal controls. Real-time PCR and Western blotting were performed to detect the expression of GRP78, p-eIF2α, spliced XBP1, ATF6, ATF4 and p-IRE1α in the lenses of normal human subjects and patients with age-related, myopia-related or congenital cataracts.ResultsIn the lenses of the age-related and high myopia-related cataract groups, the protein levels of ATF6, p-eIF2α and p-IRE1α and the gene expression levels of spliced XBP1, GRP78, ATF6 and ATF4 were greatly increased. Additionally, in the congenital cataract group, the protein levels of p-eIF2α and p-IRE1α and the gene expression levels of spliced XBP1, GRP78 and ATF4 were greatly increased. However, the protein and gene expression levels of ATF6 were not up-regulated in the congenital cataract group compared with the normal control group.ConclusionsThe UPR is activated via different pathways in the lenses of age-related, high myopia-related and congenital cataracts. UPR activation via distinct pathways might play important roles in cataractogenesis mechanisms in different types of cataracts.

Analysis of Internal Optical Aberrations in Eyes with Different Types of Cataract

Purpose: The present study investigates the patterns of internal optical aberrations in eyes with different types of cataract. Methods: Eighty eyes of 70 cataract patients were included in the present study. Internal optical aberrations were measured with a KR-1W wavefront aberrometer before cataract operation. Types of cataract were classified into three groups; cortical, nuclear and posterior subcapsular cataracts. The differences in the results of the wavefront data of 6-mm pupil diameter zones were compared among three groups. The Kruskal-Wallis test and Mann-Whitney U test were used for comparing data. Results: A total of 80 eyes consisting of 30 cortical cataracts, 30 nuclear cataracts and 20 posterior subcapsular cataracts were found. In the 6-mm pupil diameter zone, the average internal spherical aberrations by original value were 0.042 μm of cortical cataracts, -0.092 μm of nuclear cataracts and -0.109 μm of posterior subcapsular cataracts. The average internal spherical aberrations by absolute value were 0.122 μm of cortical cataracts, 0.533 μm of nuclear cataracts and 0.202 μm of posterior subcapsular cataracts. The internal spherical aberrations by original value were not statistically significantly different, but by absolute value were statistically significantly different (p = 0.003, Kruskal-Wallis test). Nuclear cataracts have a much higher positive or negative value than other cataract groups in the distribution of internal spherical aberrations by original value for each type of cataract. Other than this difference, the internal astigmatism and internal high order aberrations were not statistically significantly different. Conclusions: The change in internal spherical aberrations of nuclear cataract from the original value was larger than cortical and posterior subcapsular cataract. Therefore, nuclear cataracts have much higher positive or negative values than other cataract groups. J Korean Ophthalmol Soc 2015;56(4):532-540

Histopathologic study of lens epithelial cells in different types of cataracts

Background Cataract was directly associated with the damage to the structure and function of lens epithelial cells (LECs).In those patients who suffer from cataracts,morphologic changes of LECs is the most compelling evidence confirming loss of cellular structure and function of LECs.So,learning about the morphological changes of LECs of the different types of cataracts is very important for study on biological behaviors of LECs in different environments or diseases.Objective This study was to evaluate the morphological and ultrastructural changes of the LECs in different types of cataracts.Methods Anterior capsular member from age-related cataracts,diabetic cataracts and high myopia complicated cataract were obtained during the cataract surgery and 15 pieces for each.Trypan blue and alizarin red (TB-AR) stain,haematoxylin and eosin stain were performed in the samples to assess the viability and morphology of LECs.The ultrastructural change of LECs was observed under the transmission electron microscope.The features of the LECs were compared among the different types of cataract.Results TB-AR stain showed that LECs were polygon in shape with the mosaic arrangement and round cell nucleus,and a few dead cells were seen in the samples age-related cataract.In the diabetic samples,LECs largened from swelling with different sizes.More dead cells were found in the high myopia complicated cataract.Haematoxylin and eosin stain exhibited that the anterior capsular membrane presented a homogeneuous membrane,and monolayer LECs attached firmly anterior capsular membrane in the samples of related cataract.Majority of the cells had the intact structure.However,the interspaces between cells and capsular membrane were found in diabetic cataract.Also,smaller LECs were seen in high myopia complicated cataract with the irregular cell morphology.Under the transmission electron microscope,LECs presented the normal shape,intact intercellular tight junction and well attachment between cells and capsular membrane in the samples of the age-related cataract.In the samples of the diabetic cataract,edema of LECs and large intercellular spaces were seen.In addition,the jogged pump and vacuolar degeneration of cytoplasm were revealed in the high myopia complicated cataract.Conclusions The degeneration,necrosis and apoptosis was a common pathological basis of age-related cataract,diabetic cataract and high myopia complicated cataract.However,the damage of LECs was more serious in diabetic cataract and high myopia complicated cataract than that of agerelated cataract. Key words: Lens; Epithelial cell; Trypan blue and alizarin red stain; Haematoxylin and eosin stain; Ultrastructure

Linolenic and Linoleic Acid Induce the Opening of Connexin 43, 46 and 50 Hemichannel in Human Hela Cells

Abstract: Connexin (Cx) hemichannels (HC) located at the plasma membrane have a very low open probability, but under physiological conditions they can briefly open, allowing passage of both ions and small signaling molecules, thereby participating in the control of diverse cellular responses. Cx43, 46 and 50 are expressed in human lens and are essential to maintaining its transparency, since mutations in the genes coding for these Cxs have been identified, inducing the development of different types of cataracts. However, non-congenital cataracts may result from consumption of polyunsaturated fatty acids (PUFAs). While the consumption of omega-6 PUFAs, such as linoleic acid (ω-6LA) has been associated with development of cataracts, intake of omega-3linolenic acid (ω-3LA) has been associated with their decline. Here, we report the effects of ω-6LA and ω-3LA on HCs in HeLa cells that express Cx43, Cx46 or Cx50. Bath application of ω-6LA or ω-3LA induces opening of HCs (measured as Ethidium uptake) formed by Cx43, Cx46 or Cx50in HeLa cells and also in human lens epithelial cell line (HLE) that expresses endogenously Cx46 and Cx50 HCs, in a concentration- dependent manner and inhibited by HC blockers such as Lanthanum. Both PUFAs also increased the membrane current mediated by these HCs measured by patch clamp assays in the whole cell configuration in both cell types. Since PUFAs have demonstrated cytotoxic effects in HLE and also in organotypic cultures of bovine lens epithelial cells, their effect on HCs might be relevant to development and prevention of cataracts.

Cx43, ZO-1, alpha-catenin and beta-catenin in cataractous lens epithelial cells

Specimens of the anterior lens capsule with an attached monolayer of lens epithelial cells (LECs) were obtained from patients (n=52) undergoing cataract surgery. Specimens were divided into three groups based on the type of cataract: nuclear cataract, cortical cataract and posterior subcapsular cataract (PSC). Clear lenses (n=11) obtained from donor eyes were used as controls. Expression was studied by immunofluorescence, real-time PCR and Western blot. Statistical analysis was done using the student's t-test. Immunofluorescence results showed punctate localization of Cx43 at the cell boundaries in controls, nuclear cataract and PSC groups. In the cortical cataract group, cytoplasmic pools of Cx43 without any localization at the cell boundaries were observed. Real-time PCR results showed significant up-regulation of Cx43 in nuclear and cortical cataract groups. Western blot results revealed significant increase in protein levels of Cx43 and significant decrease of ZO-1 in all three cataract groups. Protein levels of alpha-catenin were decreased significantly in nuclear and cortical cataract group. There was no significant change in expression of beta-catenin in the cataractous groups. Our findings suggest that ZO-1 and alpha-catenin are important for gap junctions containing Cx43 in the LECs. Alterations in cell junction proteins may play a role during formation of different types of cataract.

Gaps between lens epithelial cells due to contractions

AbstractPurpose The purpose of the study was to characterize the contractions of human anterior lens capsule epithelial cells that create gaps between cells, and to assess the physiological mechanisms and a possible association of the contractions with cataract formation.Methods Lens capsules obtained during cataract surgery were stained with fluorescent dye Fura‐2. Its fluorescence, upon excitation at 360 and 380 nm, was imaged to monitor changes in cell morphology and cytosolic free Ca2+ concentrations ([Ca2+]i) in response to pharmacological stimulation by acetylcholine and to mechanical stimulation. Contractions were also studied by scanning electron microscope.Results Epithelial cells contracted in about a third of preparations after stimulation. Contractions started either before or at best simultaneously with the rise in [Ca2+]i. They also occurred when there was hardly any change in [Ca2+]i upon application of physiological saline alone. The probability of contractions occurring did not differ significantly among cortical, nuclear and combined cortical+nuclear cataract.Conclusion The contractions of the anterior lens epithelial cells occur in significant part of human lens anterior capsule postoperative preparations. They can be mechanically induced, are localized and reversible, have a fast response and did not differ among different types of cataract. They are at least partly independent of changes in [Ca2+]i. This mechanism could represent physiological basis of cataract formation in phakic intraocular lenses that touch the crystalline lens.

Human anterior lens capsule epithelial cells contraction

Human anterior lens epithelial cells, attached to surgically isolated capsules, were found to contract upon stimulation. The purpose of this study was to characterize these contractions, which create gaps between cells, and to assess the underlying physiological mechanisms and their possible association with cataract formation. Lens capsules obtained during cataract surgery were stained with fluorescent dye Fura-2. Its fluorescence, upon excitation at 360 and 380 nm, was imaged to monitor changes in cell morphology and cytosolic free Ca(2+) concentrations ([Ca(2+) ](i) ) in response to pharmacological stimulation by acetylcholine (ACh) and to mechanical stimulation by flow of saline or direct contact. Epithelial cells contracted in approximately a third of preparations when stimulated by either ACh application, fluid movement or direct mechanical contact. Contractions started either before or at best simultaneously with the rise in [Ca(2+) ](i). Contractions also occurred when there was hardly any change in [Ca(2+) ](i) upon application of physiological saline alone. The probability of contractions occurring did not differ significantly among cortical, nuclear and combined cortical + nuclear cataract. This study provides the evidence that contractions of the anterior lens epithelial cells take place in significant portion of human lens anterior capsule postoperative preparations after non-specific stimulation. Contractions are at least partially independent of changes in [Ca(2+) ](i). They can be mechanically induced, are localized and reversible and have a fast response and did not differ among different types of cataract. Physiological and clinical significance of this phenomenon remains to be elucidated.

The association between refractive errors and cataract: The Tehran eye study

Purpose:To determine the association between refractive errors and different types of cataract in Tehran, Iran.Materials and Methods:In a cross-sectional survey with a stratified cluster sampling approach, refractive errors were tested under cycloplegia. Myopia and hyperopia were defined as a spherical equivalent refractive error <-0.5 diopters (D) and more than +0.5 D, respectively. Cataract was graded according to the Lens Opacities Classification System III classification and the association between refractive errors and cataract was assessed. Of 1434 participants over the age of 40 years who participated in the study, data from 1313 right eyes were analyzed.Results:The mean age of the participants was 52.7 ± 10.0 years, and 58.3% (n = 767) were female. Overall, myopia was more prevalent among those with cataract (odds ratio [OR]: 2.00, 95% confidence interval [CI]: 1.38–2.89). Based on the type of cataract and refractive errors, the odds of myopia was significantly higher with nuclear cataracts (OR: 1.81, 95% CI: 1.14–2.87). The odds of myopia was higher for cases of nuclear cataract with some degrees of posterior subcapsular cataract (PSC) (OR: 3.33, 95% CI: 1.42–7.80). Of nine participants with cortical cataract, seven participants had hyperopia (OR: 3.77, 95% CI: 0.78–18.31).Conclusion:Individuals with nuclear and PSC showed a significantly higher prevalence of myopia while the prevalence of hyperopia was lower in those with cataract. High myopia was seen in higher grades of nuclear cataract. The high percentage of hyperopia was also significant in patients with cortical cataract. More studies are necessary to clarify the correlation between cortical cataract and hyperopia.

Pathophysiologie der Katarakt-Entwicklung nach Vitrektomie

Cataract formation is one of the most common complications after vitrectomy and cataract extraction in such cases will have to be performed under more difficult conditions. A knowledge of the different types of cataract, their frequency and causes may help to develop strategies to prevent this complication. In addition to a progressive nuclear opacification, which may occur after any type of vitrectomy, transient feathering of the lens often occurs after intraocular gas tamponade, while permanent subcapsular opacification may occur in silicone oil-filled eyes. Nuclear opacification after vitrectomy morphologically and histologically resembles age-related cataracts, but shows a faster progression: two years after vitrectomy half of the eyes require cataract extraction and there seems to be an age limit: the opacification progresses faster in patients over 50 years old. The main cause for nuclear cataracts most probably is oxidative stress. Oxygen in the avascular lens is provided by diffusion, meaning that the surrounding oxygen content is crucial for the oxygen content within the lens and thus for the formation of reactive oxygen species. In rabbits and also in humans the partial oxygen pressure is highly elevated in the vitreous cavity after vitrectomy and posterior to the lens since the vitreous is lacking as a diffusion barrier for the oxygen. The partial oxygen pressure might be additionally elevated by ventilation with oxygen and a high oxygen pressure in the infusion fluid during surgery. This elevated partial oxygen pressure may lead to increased oxygen stress and thus to lens opacification by oxidation of structural proteins. The key for the prevention of cataract formation therefore seems to be avoidance of oxidative stress, factors that might increase the protective or repair systems are so far not available. Ventilation with oxygen should be minimised as should be the partial oxygen tension in the infusion fluid. New hydrogels as vitreous substitutes might have a beneficial influence on intraocular partial oxygen tension.

A and B mode ultrasonography in preoperative evaluation of lens and posterior segment of dogs eyes with cataract

Ultrasonography of the lens and posterior segment is an indispensable step in the preoperative evaluation of dogs with cataracts, since ophthalmoscopy is not feasible when there is opacification of the lens. This study evaluated the echographic conditions of cataractous lens and fundus of the eye in dogs affected by cataracts. The study was conducted in 30 dogs (56 eyes), 10 males and 20 females, with different types of cataracts at different stages of development. Echography in A and B modes, simultaneously, was carried out for the examination of the lens and posterior segment. The examinations revealed anterior cortical, posterior cortical and nuclear cataract in 12 eyes (21.4%), anterior cortical, posterior cortical, nuclear and posterior capsular in 23 eyes (41%), anterior cortical, posterior cortical and posterior capsular cataract in one eye (1.7%), anterior cortical and nuclear cataract in one eye (1.7%), anterior cortical, nuclear and posterior capsular cataract in five eyes (8.9%), and anterior cortical cataract in seven eyes (12.5%). Abnormal ultrasonographic alterations were observed in the posterior segment in 26 eyes evaluated (46.4%). Vitreal degeneration was detected in 12 eyes (21.4%), images of vitreal exudate or hemorrhage in seven eyes (12.5%), persistence of hyaloid artery in four eyes (7.1%) and lens subluxation in three eyes (5.3%). The results obtained reiterate the importance of ultrasonography in canine patients presented for cataract surgery given that alterations of the posterior segment are difficult to identify in a clinical examination when the lens is opacified.

Evaluation of Risk Factors for Cataract Types in a Competing Risks Framework

Purpose: In prospective studies of incident cataract, a person may have developed two or all three of cortical, nuclear sclerotic and posterior subscapsular cataract at the time when clinically significant cataract is apparent. One can compare the impact of risk factors on different types of cataract with methods of competing risk survival analysis that account for tied events. Methods: We studied risk factors for incident cataract among 20,599 participants in the Physicians' Health Study; 1,923 of whom developed cataract that reduced visual acuity over a median follow-up of 13.0 years. Among incident cases, 45% had two types of cataract and an additional 12% had all three. Proportional hazards models, adjusted for tied failures through use of generalized estimating equations, provided comparisons across different cataract types. Stratified analyses by type with age as the time scale were used to accommodate the strong but different relationships of age with occurrence of different cataract types. Results: Analyses found different relationships of diabetes and body mass index, but similar relationships of smoking, family history of coronary disease and multivitamin use, across different cataract types. A simplified model provided common estimates for relative risks associated with those characteristics with similar effects across cataract types. Conclusions: Whereas polytomous logistic regression has proven useful for comparisons of risks across cataract types in retrospective and cross-sectional studies, this approach based on methods of survival analysis has greater flexibility in prospective studies with variable follow-up and frequently tied event times for different cataract types.

Matrix metalloproteinase-9 activity in human lens epithelial cells of cortical, posterior subcapsular, and nuclear cataracts

To evaluate the level of matrix metalloproteinase-9 (MMP-9) activity in lens epithelial cells (LECs) derived from different types of cataract in patients having phacoemulsification. Iladevi Cataract & IOL Research Centre, Memnagar, Ahmedabad, India. This observational study of 275 patients having phacoemulsification was performed to evaluate the level of MMP-9 activity in LECs. All anterior lens capsules harboring the LECs and derived from the surgical curvilinear capsulorhexis were obtained during phacoemulsification. The anterior lens capsule samples were processed to analyze MMP-9 activity using a succinylated gelatin assay. The samples were grouped based on age and on pure cataract type. The level of MMP-9 activity in LECs was highest in eyes with cortical cataract. A significant difference in the level of MMP-9 activity was found in different types of cataract (P<.001). The highest level of MMP-9 activity was in patients older than 60 years. The MMP-9 activity increased gradually with age irrespective of cataract type (P<.001). A significant difference was observed in the level of MMP-9 activity between different types of cataract. The activity of MMP-9 was highest in eyes with cortical cataract. The level of MMP-9 activity increased with age in the LECs of patients with age-related cataract.

The acutely isolated human anterior lens capsule as a tool to study the physiology of human lens epithelial cells

Abstract Purpose The defects in functional characteristics of lens capsule epithelial cells, can lead to the formation of the cataract, especially as cortical cataract. In the germinative zone of the lens the same progenitor cells, which also form the epithelil cells, differentiate also into the fiber cells, which make up the inside of the lens and through their activity also keep the lens clear. When their function is impaired the nuclear cataract ensues. We set out to make a preparation of the human anterior capsule from cataract surgery, which would allow functional studies of the physiology of capsule epithelial cells from patients with different types of cataract, using cell physiological methods. Methods We used the entire anterior capsules, with the cells still attached. Cell contacts were preserved and allowed the communication between the cells. In addition all the contacts to the basement membrane were largely preserved although some parts of the capsule were denuded of the epithelium – possibly due to manipulation during the surgery itself, or to epithelial cell apoptosis. The remaining cells were viable and the capsules usable for experimentation for at least a day when kept in a tissue culture incubator. For experimentation using an inverted microscope, the capsules were weighed down with a harp as the one used for electrophysiological experiments. In a series of pilot experiments the lens epithelial cells were loaded with fura‐2. Results They exhibited normal [Ca2+]i responses to agonist application such as Ach. Conclusion We conclude that this preparation represents a useful tool to study many aspects of the lens epithelial cell physiology.

Activity of superoxide dismutase isoenzymes in lens epithelial cells derived from different types of age-related cataract

To evaluate the level of superoxide dismutase (SOD) and SOD isoenzyme activity in lens epithelial cells (LECs) derived from different types of cataract in patients having phacoemulsification. Iladevi Cataract & IOL Research Centre, Memnagar, Ahmedabad, India. This observational study of 109 patients having phacoemulsification was performed to evaluate the level of activity in LECs of total superoxide dismutase (TSOD) and 2 superoxide dismutase isoenzymes: copper- (Cu) and zinc (Zn)-dependent SOD (Cu/Zn-SOD) and manganese (Mn)-dependent SOD (Mn-SOD). The curvilinear capsulorhexis (lens capsule) harboring LECs was obtained during phacoemulsification. The anterior lens capsule samples were processed for assaying SOD activity using the nitro blue tetrazolium reduction assay. The samples were grouped based on age and on pure cataract types. The highest level of TSOD, Cu/Zn-SOD, and Mn-SOD activity was in patients 50 years or younger. The activity declined gradually with age (P<.001). The level of TSOD activity increased in cortical cataract. The level of Cu/Zn-SOD and Mn-SOD isoenzyme activity in LECs was higher in cortical cataracts. A significant difference in the level of TSOD and Cu/Zn-SOD activity was found with different types of cataract (P<.001). The level of TSOD, Cu/Zn-SOD, and Mn SOD isoenzyme activity decreased with age in LECs of patients with age-related cataract. A significant difference in the level of TSOD and Cu/Zn-SOD isoenzyme activity between different types of cataract was observed. The activity of all 3 SOD isoenzymes was highest in cortical cataracts.

Dose-response relationship between ingested arsenic and cataracts among residents in Southwestern Taiwan

This association study was carried out to examine the effect of long-term exposure to ingested arsenic on various types of cataract. A total of 349 residents living in arseniasis-hyperendemic villages of southwestern Taiwan were recruited. Cumulative arsenic exposure was derived from the history of consuming artesian well water and the arsenic level in well water. The Lens Opacities System III was used to classify different types of cataract. The cataract surgery prevalence was 10% for the age group of 50 or more years. Cortical opacity was most common (35%), while nuclear and posterior subcapsular opacities were observed in 24% and 22% of subjects, respectively. Diabetes mellitus was a significant risk factor for all types of cataract. Occupational sunlight exposure was associated with cortical and posterior subcapsular opacities in a dose–response relationship. The cumulative exposure to arsenic from artesian well water and the duration of consuming artesian well water were associated with an increased risk of all types of lens opacity. But statistically significant dose-response relations with the cumulative arsenic exposure and the duration of consuming artesian well water were observed only for posterior subcapsular opacity (P = 0.014 and P = 0.023, respectively) after adjustment for age, sex, diabetes status, and occupational sunlight exposure. It was concluded that there was an increasing prevalence of posterior subcapsular opacity with the increase in exposure to ingested arsenic.

Determining the Acoustic Properties of the Lens Using A High-Frequency Ultrasonic Needle Transducer

Ultrasonic parameters including sound velocity and attenuation coefficient have recently been found to be useful in characterizing the cataract lens noninvasively. However, the regional changes of these acoustic parameters in the lens cannot be detected directly by those ultrasonic measurements. This prompted us to fabricate a 46-MHz needle transducer (lead magnesium niobate-lead titanate [PMN-PT] single crystal) with an aperture size of 0.4 mm and a diameter of 0.9 mm for directly measuring the sound velocity and frequency-dependent attenuation coefficient in lenses. These parameters have been shown to be related to the hardness of a cataract, and hence this technique may allow surgeons to detect the acoustic properties of the cataract via a small incision on the cornea before/during phacoemulsification surgery. To verify the performance of the needle transducer, experiments were performed on porcine lenses in which two types of cataracts (nucleus and cortical) were induced artificially. The needle transducer was mounted on a positioning system and its tip was inserted into the lens, allowing the anterior-to-posterior profiles of acoustic parameters along the lens axis to be obtained immediately. The experimental results show that the acoustic parameters are not constant within a single normal lens. The sound velocity and ultrasound attenuation coefficient (at 46 MHz) were 1701.2 ± 8.4 m/s (mean ± SD) and 9.42 ± 0.57 dB/mm, respectively, at the nucleus, and 1597.2 ± 9.6, 1589.3 ± 6.1 m/s and 0.42 ± 0.26 and 0.40 ± 0.33 dB/mm close to the anterior and posterior capsules, respectively. Finally, the data obtained demonstrate that regional variations in the acoustic properties of lenses corresponding to the hardness of different types of cataract can be detected sensitively by a needle transducer. (E-mail: j648816n@ms23.hinet.net)

Connexins in Lens Development and Cataractogenesis

The lens is an avascular organ that transmits and focuses light images onto the retina. Intercellular gap junction channels, formed by at least three different connexin protein subunits, alpha1 (connexin43 or Gja1), alpha3 (connexin46 or Gja3) and alpha8 (connexin50 or Gja8), are utilized to transport metabolites, ions and water in the lens. In combination with physiological and biochemical analyses, recent genetic studies have significantly improved our understanding about the roles of diverse gap junction channels formed by alpha3 and alpha8 connexin subunits during lens development and cataract formation. These studies have demonstrated that alpha3 connexin is essential for lens transparency while alpha8 connexin is important for lens growth and transparency. Diverse gap junction channels formed by alpha3 and alpha8 subunits are important for the differentiation, elongation and maturation of lens fiber cells. Aberrant gap junction communication, caused by alterations of channel assembly, channel gating or channel conductance, can lead to different types of cataracts. These findings provide some molecular insights for essential roles of connexins and gap junctions in lens formation and the establishment and maintenance of lifelong lens transparency.

External factors in the development of cataract

To provide an update on the risk factors for cataract development. Review of the literature. Age and heredity are the most important risk factors associated with the different types of cataract. While the hereditary component is self-explanatory, increasing age serves as a surrogate for a number of potential external risk factors, the effect of which is cumulative. Identification of the risk factors that have a causal effect on cataract development may provide means for cataract prevention. There are only a few risk factors that satisfy the criteria for causal effect: smoking, which results in the increased risk of nuclear cataract, excessive UV-B exposure and diabetes that increase the risk of cortical cataract, and steroidal treatment, diabetes and ionising radiation that lead to the formation of posterior subcapsular opacity. The effect of medications on cataract development requires further study, since the effect of the diseases should be distinguished from that of treatment. 'Stop Smoking' and 'UV-B protection' campaigns are gaining momentum as preventative measures, while the attempts to actively prevent cataract with antioxidants have not been successful. Cataract research has been facilitated lately by improvements of precision and standardisation in measuring lens opacities. However, measurement precision on its own cannot give us a solution to this problem. The major studies repeatedly measure the exposure to the traditional health hazards, while the missing parts in the equation are those risk factors that we do not know about and therefore do not measure. New approaches and new hypotheses are needed.

Accumulation and Aberrant Modifications of α-Crystallins in Anterior Polar Cataracts

Crystallins are the major proteins found in the lens, and the localization of specific crystallins is well known. Overexpression and accumulation of alphaB-crystallin has been observed in response to stress conditions or in certain diseases, such as brain tumors and neurodegenerative diseases. The purpose of this study was to examine whether alpha-crystallins are modified during pathological myofibroblastic changes in lens epithelial cells. Lens epithelial cells attached to the anterior capsules of patients with nuclear or anterior polar cataracts were analyzed quantitatively for alpha-crystallin proteins and mRNAs using Western blot and RT-PCR analysis., respectively. The degree of modification of alpha-crystallins was determined by 2-dimensional gel electrophoresis followed by Western blotting. Higher molecular weight protein bands that were immunoreactive to anti-alphaA- and anti-alphaB-crystallin antibodies around 45 kDa accumulated more in the anterior polar cataract samples than in those with the nuclear type of cataracts. Also monomeric alphaB-crystallins accumulated more in lens epithelial cells of patients with anterior polar cataracts. By comparison, no significant changes were found in the levels of the mRNAs encoding alphaA- and alphaB-crystallins in the different types of cataracts. Both alphaA- and alphaB-crystallin proteins seemed to undergo more extensive modification in anterior polar cataracts. Conclusion. In addition to fibrotic changes, which accompany increased levels of extracellular matrix molecules, accumulation and abnormal modification of alpha-crystallins might be implicated in the pathogenic mechanism of this type of cataract.