Lens epithelium: a primary target of UVB irradiation

Cultured rabbit lenses and cultured rabbit lens epithelial cells were irradiated with UV to correlate morphological changes in the epithelium with physiological changes in the whole lens during the development of UV-induced cataract. Two UV spectral ranges were utilized; one spanned 290 to 340 nm and was designated near-UV, the other was a narrower, pure UVB region: 303 to 313 nm, designated UVB. Irradiation with either spectrum of the anterior surface of whole lenses caused opacification and a dose-dependent loss of ion homeostasis as measured by Na+ and Ca2+ concentrations in whole lenses. It was determined that cation pump activity, assessed by 86Rb uptake, continued to decline steadily during culture after UV irradiation. Whole mount preparations of the epithelial cell layer of UVB-irradiated lenses revealed morphological changes within 2 hr of irradiation and cell death after 20 hr. Following posterior irradiation of whole lenses, the epithelial cells remained viable and lenses remained transparent during 3 days of culture, presumably because UV photons did not reach the epithelium. Absorption of UV photons by posterior fiber cell membranes and proteins did not cause opacification. To learn more about the epithelial damage, cultured rabbit lens epithelial cells were irradiated, UVB treatment retarded growth over a 7-day period in cultured cells. The surviving cells at day 7 were abnormal in appearance and the potassium concentration was approximately 50% less than controls, a finding which may explain the previously reported reduction in protein synthesis by UVB irradiation. Collectively, the data suggest that UV cataract is initiated by damage to the epithelium, including a change in membrane permeability leading to loss of ion homeostasis in the lens.     

Time-dependent aspects of osmolyte changes in rat kidney, urine, blood and lens with sorbinil and galactose feeding

Sorbitol plus myo-inositol, betaine and glycerophosphorylcholine (GPC) are cellular osmolytes in the mammalian renal medulla. Galactosemia and hyperglycemia can cause excessive levels of galactitol or sorbitol in several organs via aldose reductase (AR) catalysis. AR inhibitors can reduce these polyols. To examine osmolyte responses to polyol perturbations, male Wistar rats were fed normal diet, the AR inhibitor sorbinil (at 40 mg/kg/d), 25% galactose, or a combination, for 10, 21 and 42 days. All animals at 21 days had higher apparent renal AR activity than at 10 or 42 days, possibly providing resistance to sorbinil. Sorbinil feeding alone tended to increase urinary, plasma and renal urea levels. It reduced AR activity and sorbitol contents in renal inner medulla, though less so at 21 days; other renal osmolytes, especially betaine, were elevated. Galactose feeding caused little change in renal AR activity, and resulted in high galactose and galactitol contents in renal medulla, urine, blood and lens (and higher renal Na+ contents at 10 days). Renal sorbitol, inositol and GPC decreased, while betaine contents trended higher at all times. Sorbinilgalactose feeding reduced renal AR activities and galactitol contents (again less so at 21 days), urine, blood and lens galactitol, and further reduced renal sorbitol contents. At 10 and 21 days it tended to raise renal betaine more, and restore inositol (but not GPC) contents to control levels. At 42 days it reduced renal and urinary Na+ and galactose, and decreased renal betaine to control levels. Under most conditions, total renal (non-urea) organic osmolyte contents (presumed to be mostly intracellular) and Na+ plus galactose contents (presumed mostly extracellular) changed together such that cell volumes may have been maintained. The exception was 10 days on galactose, where total osmolytes appeared too low. In galactose-fed animals, urine/plasma ratios suggest some renal galactitol efflux, and cellular galactitol probably helps maintain osmotic balance rather than cause swelling.     

Mineral metabolism in plasma, urine and bone of periparturient cows fed anionic diets with different calcium and phosphorous contents

The objective of this experiment was to evaluate the influences of Ca and P contents in an anionic diet on the mineral metabolism in plasma, urine and bone in periparturient diary cows. Fifteen multiparous Holstein-Friesian cows were divided into 3 dietary groups (5 cows/group) by dietary Ca and P contents and dietary cation-anion balance [(Na + K) - (Cl + S) mEq/kg DM]; diet 1 [low Ca (0.46%), low P (0.24%), cationic (+195.8 mEq/kg DM)]; diet 2 [low Ca (0.46%), low P (0.24%), anionic (-32.4 mEq/kg DM)]; and diet 3 [high Ca (0.93%), high P (0.60%), anionic (-41.0 mEq/kg DM)]. Cows were fed one of these 3 diets from approximately 4 weeks before the expected calving date to 5 days after calving. There was no outbreak of milk fever in any cows fed these 3 diets; however, plasma Ca levels at 1 and 2 days after calving tended to be higher in the cows fed diet 3 than those in the cows fed diets 1 or 2. Fractional urinary excretion of Ca in the cows fed diet 2 or 3 was higher than that in the cows fed diet 1. Fractional urinary excretion and plasma level of Pi were higher during the periparturient period in the cows fed diet 3 than those in the cows fed diets 1 or 2. There were no significant differences in plasma parathyroid hormone levels among the 3 groups. In the spongy substance of ilium at 5 days after calving, the Ca and Mg contents bone volume and trabecular thickness were the lowest, but not significant, in the cows fed diet 2. These data suggest that sufficient Ca and P contents in an anionic diet may be effective in maintaining plasma Ca and Pi levels of periparturient cows and further in preventing of potential bone damage brought about by increased urinary mineral excretion following the feeding of an anionic diet.     

An impediment to glutathione diffusion in older normal human lenses: a possible precondition for nuclear cataract

Human age-related nuclear cataract is associated with progressive and widespread oxidation of proteins, particularly in the centre of the lens. The reasons for the onset of cataract and why this disease should take place only in the lenses of older individuals remain unclear. However, a common feature of nuclear cataract is the low concentration of reduced glutathione (GSH) in the centre of the lens. GSH is the principal lenticular antioxidant of the lens and it is synthesized and regenerated in the lens cortex. In this study we investigated the diffusion of glutathione within the human lens as a function of age. Normal human lenses were incubated in artificial aqueous humor containing [35S]cysteine and the label was metabolically incorporated into GSH. After 48-h incubation, lenses were sectioned and phosphorimaging was used to determine the distribution of 35S label. In young lenses, label appeared to diffuse uniformly throughout the whole lens. By contrast, in lenses over the age of 30, very little 35S had penetrated to the centre of the lens. A distinct zonal pattern of label distribution was noted in the older lenses after 48 h incubation, which had dimensions of approximately 7.2 mm (diameter) by 2.8 mm (axial). In some older lenses this pattern was noticeable even after 96-h incubation. Thus a barrier to the diffusion of GSH was observed in older normal lenses which was not present in younger lenses. Furthermore, the internal zone thus delineated has dimensions that coincide with those of the coloured and sclerotic zone present in nuclear cataract lenses. Since nuclear cataract is a disease of the elderly, and maintenance of GSH is known to be vital for lens clarity, we propose that the development of a barrier to the movement of GSH from its site of synthesis and regeneration in the cortex, into the nucleus in older normal lenses, may over time allow oxidative modification of protein to take place in the nucleus, resulting ultimately in nuclear cataract.     

High galactose levels in vitro and in vivo impair ascorbate regeneration and increase ascorbate-mediated glycation in cultured rat lens

In contrast to conventional view that glucose is the sole glycating agent, ascorbate has now emerged as a potential precursor of advanced glycation products in lenses during cataractogenesis, owing to the high concentration present in human lens. The effects of high hexose environment in vitro and in vivo on the disruption of redox equilibrium of ascorbate (ASA) to dehydroascorbate (DHA), which is required for ascorbate-mediated crystallin modification by the Maillard reaction during cataractogenesis were examined. Organ culture experiments were performed with rat lenses that were first exposed to high galactose levels in vitro and in vivo and then incubated with 1-14C-labeled ASA, DHA or DKG (2,3-diketogulonic acid). Formation of ASA degradation products as a function of time was assessed by radiometric TLC method. Upon incubation with ASA or DHA, an elevated level of the degradation product, DKG, was detected in lenses exposed to galactose in vivo and in vitro. ASA uptake was significantly enhanced in the galactosemic lenses as compared to controls (P = 0.01). Regeneration of ASA from DHA in both galactose treated and galactosemic lenses was impaired when compared to control lens which completely converted DHA from the medium into ASA. Surprisingly, the galactose exposed lenses showed enhanced permeability to DKG which was picked up readily from the medium in contrast to normal healthy lenses which remained impermeable to DKG. Galactose exposed lenses both in vitro and in vivo showed a 5-9-fold increase in crystallin bound Schiff base-linked radioactivity when incubated with 1-14C-labeled ASA or DHA. As a preamble to the question of whether lens pigmentation predisposes towards ascorbate oxidation, lens homogenate from normal young and old pigmented cataractous lenses were incubated with [1-14C]ASA. After 2 days, ASA levels were found to have decreased by 74% and DKG levels increased by 48% in brunescent lens as compared to the young lens. These data demonstrated that profound abnormalities in ASA metabolism exist in lenses exposed to a high sugar environment suggestive of a breakdown of the redox equilibrium of ASA to DHA and a loss of membrane permeability barrier for DKG. The latter would further contribute toward a ASA-catalysed Maillard reaction in the redox impaired lens.     

Preventive action of vitamin E-containing liposomes on cataractogenesis in young adult rats fed a 25% galactose diet

The preventive action of vitamin E (Vit. E)-containing liposomes on cataractogenesis was examined in male Wistar rats (five weeks old) fed a 25% galactose diet. Vit. E-containing liposomes prepared with dipalmitoylphosphatidylcholine were instilled into both eyes three times a day over a 45-day period. Cataract appeared at 18-day galactose feeding and developed gradually thereafter. Simultaneous Vit. E-containing liposome instillation delayed this cataractogenesis. Lenses of 18-day galactose-fed rats showed decreases in Vit. E and reduced glutathione (GSH) contents and Na+, K(+)-ATPase activity and increases in lipid peroxide (LPO), galactitol, and water contents. Lenses of 45-day galactose fed rats showed decreases in GSH content and Na+,K(+)-ATPase activity and increases in Vit. E, LPO, galactitol, and water contents. Serum Vit. E and cholesterol levels decreased in 18-day galactose-fed rats, while both levels increased in 45-day galactose-fed rats. Simultaneous Vit. E-containing liposome instillation prevented these changes except for the changes of lenticular galactitol and water contents and serum Vit. E and cholesterol levels. These results indicate that simultaneously instilled Vit. E-containing liposomes can delay cataractogenesis in young adult rats fed a 25% galactose diet mainly by the antioxidative action of Vit. E contained in the instilled liposomes.     

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.     

Differential cataractogenic potency of TGF-beta1, -beta2, and -beta3 and their expression in the postnatal rat eye

PURPOSE: Transforming growth factor-beta has been shown to induce cataractous changes in rat lenses. This study assesses the relative cataractogenic potential of TGF-beta1, TGF-beta2, and TGF-beta3 and their expression patterns in the rat eye. METHODS: Lens epithelial explants and whole lenses from weanling rats were cultured with TGF-beta1, TGF-beta2, or TGF-beta3 at concentrations ranging from 0.025 ng/ml to 4 ng/ml for 3 to 5 days. Cataractous changes were monitored daily by phase contrast microscopy and by immunofluorescent detection of cataract markers alpha-smooth muscle actin and type I collagen. Expression of TGF-beta was studied by immunofluorescence and in situ hybridization on eye sections from neonatal and weanling rats. RESULTS: All three isoforms induced morphologic changes in lens epithelial explants and cultured lenses that are typically associated with human subcapsular cataract. Transforming growth factor-beta2 and TGF-beta3 were approximately 10 times more potent than TGF-beta1. All three isoforms were expressed in the eye in spatially distinct but overlapping patterns. Transforming growth factor-beta1 and TGF-beta2 and their mRNA were detected in most ocular tissues, including the lens. Although TGF-beta3 was immunolocalized in lens epithelium and fibers and in other ocular tissues, its mRNA was detected only in the retina and choroid. CONCLUSIONS: All three isoforms of TGF-beta are potentially available to lens cells and have the potential to induce cataractous changes. The results suggest that TGF-beta activity is normally tightly regulated in the eye. Activation of TGF-beta in the lens environment, such as may occur during injury, in wound healing, or in pathologic conditions may contribute to cataractogenesis in vivo.     

Time course of lithium-induced alterations in renal and endocrine function in normal and Brattleboro rats with hypothalamic diabetes insipidus

1. A lithium chloride (1.1 g/kg) supplemented diet was given to Long Evans (LE) and Brattleboro (DI) rats to investigate its actions in the presence (LE) and absence (DI) of vasopressin. 2. During the first 24 h, Li-supplemented LE rats displayed an initial water deficit (drinking less than renal output), increased plasma antidiuretic (ADH) titres and slightly increased plasma renin activities (PRA) and plasma osmolarities. Such changes were qualitatively similar to those seen in rats fed a normal diet, but deprived of water for 24 hours. After 12 days, the Li-supplemented rats had elevated plasma ADH titres, but reduced pituitary oxytocic and antidiuretic activities. 3. The urinary losses of Na, K and Cl exceeded dietary intakes in LE rats on the introduction of the Li-supplement, and the urinary osmolarity fell by 50%. Electrolyte balances were gradually re-established, although drinking and urine production increased in parallel to reach twice the control values by day 12 of the supplement. 4. Aldosterone and corticosterone secretory rates and their peripheral plasma concentrations were unchanged both after 24 h and 28 days of the Li-supplement. 5. Li elicited no water deficit or saluresis in DI rats, and although the polyuria and polydipsia were exacerbated, urinary osmolarity did not change over the 12 day observation period. 6. Li increased Ca excretion in both rat types; after 12 days the PRA of DI but not LE animals were increased. 7. It is concluded that the overall renal actions of Li are tempered by vasopressin rather than adrenocorticosteroids.     

Distribution and quantification of pyridinium cross-links of collagen within the different maturational zones of the chick growth plate

The levels of alanine, aspartate and glutamine transaminase increase considerably in some diseases. We measured the activity of these enzymes and of the transaminase of 3-hydroxykynurenine, an aminoacid, which acts as a UV lens filter. Alanine and glutamine transaminases (carboxypeptidase) were not detected in normal and cataractous human lenses, and aspartate transaminase was found only in the cortex of normal lenses. 3-hydroxykynurenine transaminase was not found in lenses from persons below thirty years of age, but was found in lenses at about fifty years of age, and in cataractous lenses. Transamination of 3-hydroxykynurenine leads to the formation of xanthurenic acid and its derivatives. These substances appear to be responsible for the increase of lens fluorescence during cataract development.     

Human age-related cataract and lens epithelial cell death

PURPOSE: To evaluate the importance of lens epithelial cell death in age-related cataract. To determine whether the large percentage of terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labeling (TUNEL)-positive lens epithelial cells previously reported in human capsulotomy specimens results from apoptosis or necrosis. METHODS: Capsulotomy specimens from patients who had undergone cataract surgery and epithelia from cataractous lenses of eye bank eyes were compared with epithelia from noncataractous lenses of eye bank eyes. DNA fragmentation was assayed using the TUNEL method. Cell membrane integrity was tested using a fluorescent stain for DNA, BOBO-3, that is excluded from living cells. Cell proliferation was assayed by labeling with 5-bromo-2'-deoxyuridine (BrdU). The number of cells in different regions of the lens epithelium was measured by digital imaging and computerized counting of nuclei after staining with methyl green. RESULTS: TUNEL-positive cells were sometimes detected adjacent to denuded regions of capsulotomy specimens, especially when epithelia were not fixed immediately after surgery. TUNEL-stained cells usually stained with BOBO-3, indicating loss of plasma membrane integrity. No BrdU-labeled cells were detected in capsulotomy specimens. Cell density in cataractous lens epithelia was similar to that in normal lens epithelia. In cataractous lenses from eye bank eyes, cell density in the region of the epithelium overlying the cataract was higher than cell density in the region of the epithelium overlying the transparent part of the lens. No correlation was found between cell density and cataract severity or between cell density and age. CONCLUSIONS: TUNEL staining of lens epithelial cells in capsulotomy specimens most likely results from necrotic cell death caused by damage during or soon after cataract surgery. Loss of cells from the lens epithelium, by apoptosis or other mechanisms of cell death, does not seem to play a major role in age-related cataract formation.     

Malonaldehyde, superoxide dismutase and human cataract

UV-spectrophotometry and fluorometry were used to study Malonaldehyde (MDA) and Superoxide Dismutase (SOD) in normal, cataractous human lenses and red blood cells of the patients with cataract. MDA content of senile and complicated cataractous lenses was significantly higher than that of normal human lenses, while that of complicated cataract was significantly higher than that of senile cataract. SOD activity of senile and complicated cataractous lenses was significantly lower than that of normal human lenses, while there was no marked difference between senile and complicated cataractous lenses. Significant correlation between cataractous lenses and red blood cells was not found in MDA content and SOD activity. There was a negative correlation between SOD and MDA in normal human lenses, but no correlation between SOD and MDA in cataractous lenses. The study shows that lipid peroxidation may be one of the possible mechanisms of cataractogenesis in human, and emphasizes the role of SOD in prevention of photoperoxidative damages to the tissues.     

Cataract induction in lenses cultured with transforming growth factor-beta

PURPOSE: Anterior subcapsular cataracts are characterized by the appearance of opaque plaques of abnormal cells. Distinctive spindle-shaped cells containing alpha-smooth muscle actin are present and are associated with wrinkling of the overlying lens capsule. Accumulations of extracellular matrix, including type I collagen, also are found. The authors previously reported that transforming growth factor-beta (TGF-beta) induces similar aberrant morphologic changes in lens epithelial explants. More recently, they identified alpha-smooth muscle actin in explants cultured with TGF-beta. The aim of this study was to determine whether TGF-beta induces comparable cataractous changes in whole lenses and to examine the effects of this treatment on the transparency of the lens. METHODS: Whole lenses from 21-day-old rats were cultured in defined serum-free medium with TGF-beta 2 or without added growth factors for 5 days. Lenses were then photographed and prepared for histology and immunolocalization. RESULTS: Lenses cultured with TGF-beta developed distinct anterior opacities just beneath the lens capsule. Histologically, clumps of abnormal cells corresponded with these opacities. Spindle-shaped cells, which contained alpha-smooth muscle actin, were present, and the overlying capsule was often wrinkled. The clumps contained accumulations of type I collagen, laminin, and heparan sulphate proteoglycan. In contrast, lenses cultured without growth factors remained transparent, retained normal lens morphology, and did not accumulate alpha-smooth muscle actin or type I collagen. CONCLUSIONS: These results show that TGF-beta induces whole lenses to form opacities that contain morphologic and biochemical markers for subcapsular cataract.     

Effect of ammonia via prepyriform cortex on regulation of food intake in the rat

Studies were made on whether ammonia, which is an obligatory intermediate of amino acid metabolism, depresses the food intake of rats fed a low-casein (basal) diet containing imbalanced amino acid mixtures (imbalanced diets). Bilateral lesions in the prepyriform cortex caused normalization of food intake of rats fed amino acid-imbalanced diets, confirming the work of Leung and Rogers (Am. J. Physiol. 221:929-935, 1971). Unlike normal rats, animals with prepyriform cortical lesions consumed as much of a diet containing 3% NH4Cl as they did of the basal diet. However, like normal rats, they rejected a diet containing a mixture of keto acids. Unilateral injection of NH4Cl into prepyriform cortical areas reduced the food intake to a greater extent than injection of NaCl into these areas or injection of NH4Cl into other parts of the brain. These results suggest that ammonium ions influence the appetite through their effect on prepyriform cortical areas.     

Physical interpretation of information entropy: Numerical evidence of the Collins conjecture

The effect of altering the dietary Ca:P ratio during critical points of growth (based on reproductive and skeletal age) on kidney calcification in female rats was investigated. Groups of weanling animals were fed one of three nutritionally complete but calcium-altered diets (0.25, 0.5 or 1.0 g Ca/100 g diet) from 4 to 12 wk of age (Phase 1). Phosphorus concentration remained constant at 0.4 g/100 g diet resulting in Ca:P molar ratios of 0.48, 0.96 and 1.92, respectively. During Phase 2, the same animals within each diet group were then rerandomized into one of the above diets and fed for an additional 25 wk. Each group contained five rats. The data from the nine treatment groups were analyzed statistically using a two-way ANOVA (Phase 1 dietary Ca level by Phase 2 dietary Ca level). The level of dietary Ca during Phase 1 only exerted a significant influence on kidney Ca accumulation. Rats fed the two lower dietary Ca levels, and hence lower dietary Ca:P molar ratios, during Phase 1 had two- to threefold greater kidney Ca concentration and kidney ash Ca concentration than rats fed the diet with the highest dietary Ca level (1.92 Ca:P molar ratio) during Phase 1, regardless of the Ca intake during Phase 2. In contrast, the dietary Ca:P molar ratio during Phase 2 had little effect either positively or negatively on the kidney Ca concentration that had been established during Phase 1. The results indicate that dietary-induced nephrocalcinosis in female rats is irreversible and is induced primarily before the completion of adolescence (approximately 12 wk of age) in Sprague-Dawley female rats.     

Perspective on allogeneic melanoma lysates in active specific immunotherapy

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.     

Lp82 calpain during rat lens maturation and cataract formation

PURPOSE: To measure changes in levels of Lp82 during maturation and selenite cataract formation in rat lens. Lp82 is a lens-specific, calcium-activated isozyme from the calpain family of cysteine proteases (EC 34.22.17). METHODS: Competitive RT-PCR was used to assess Lp82 and m-calpain mRNA concentrations. Immunoblotting and ELISA after DEAE chromatography measured Lp82 and m-calpain protein levels. Casein zymography assessed proteolytic activities in regions and whole lenses from maturing rats. RESULTS: Levels of Lp82 mRNA, protein, and caseinolytic activity decreased more rapidly during maturation of rat lens than for m-calpain. Unexpectedly, the water-insoluble fraction of rat lens contained enzymatically active Lp82. Selenite injection also caused major loss of Lp82 protein during cataract formation. CONCLUSIONS: Lp82 is a proteolytic enzyme likely functioning in early lens development and maturation. The rapid loss of Lp82 activity during lens maturation is probably caused by three factors: autodegradation associated with the proteolysis of soluble and insoluble proteins occurring in the rat lens nucleus, association of Lp82 with the lens insoluble fraction, and loss of Lp82 mRNA. Lp82 may function early in lens maturation along with m-calpain, which then is predominant in the latter stages of maturation. Proteolysis in selenite cataract is partially caused by over-activation of Lp82.     

Magnetic resonance imaging of the galactosemic dog eye using magnetization transfer contrast

Magnetization transfer contrast (MTC) enhanced magnetic resonance (MR) imaging is a technique that generates high contrast images based on characteristic tissue differences resulting from the interaction of water and macromolecules. In this study, the feasibility of applying this technique to documenting the progression of osmotic sugar cataract formation was investigated in male beagles, initially 6 or 24 month old, fed a diet containing 30% galactose. MTC enhanced magnetic resonance imaging was periodically conducted on these animal's eyes at 2-Tesla. The lens MR images were compared to photographs obtained by photo-slit lamp and retroillumination photography. The MTC technique provided improved image details of the lens and anterior segment that documented osmotic changes from initial cortical vacuole formation to cortical and nuclear changes associated with advanced sugar cataracts. The latter could not be observed by photo-slit lamp or retroillumination photography.     

Quantitative trait loci for blood glucose confirm diabetes predisposing and protective genes, Iddm4 and Iddm5r, in the spontaneously diabetic BB/OK rat

Rats were given a single injection of streptozotocin. They became diabetic with a blood sugar of around 300 mg dL-1. They were divided into three groups of six rats each. Group II was the diabetic control. Each one of group III diabetic rats received daily 2 ml of 2% solution of lysine supplement orally. Group IV received daily 2 ml of a 2% solution of a mixture of amino acids supplement for 120 days. In addition there were 6 rats as normal control (Group I). Periodically ophthalmic examination was done by slit lamp. Blood glucose, proteins, hemoglobin, free amino acids, glycosylated hemoglobin and glycated lens proteins were also analysed. Body weight was recorded. The diabetic controls decreased in body weight. The blood sugar levels were lowered from about 295 mg dL-1 to 99 mg dL-1 in the lysine-fed group and from 268 mg dL-1 to 126 mg dL-1 in the amino acids mixture-fed group. The levels of glycosylated hemoglobin and glycated lens proteins increased in diabetic controls while they were normal in other groups. The free amino acid levels in blood were lower in groups receiving lysine or amino acids than in diabetic controls indicating their better utilization. In diabetic control, all the animals developed cataract in 70-90 days; five out of six did not develop cataract in the lysine supplemented group. Four of six did not develop cataract in the amino acid mixture-supplemented group. None developed cataract in normal controls. Lysine and amino acids have anticataractous and antidiabetic effects.