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At least 19 recordsLinked to original sources
PubMed1994

Colloid osmotic pressure of steer alpha- and beta-crystallins: possible functional roles for lens crystallin distribution and structural diversity.

This study addresses the general mechanisms whereby the major cytoplasmic proteins from the adult bovine lens contribute both to transparency and maintenance of the refractive index gradient across the lens. Colloid osmotic properties and quaternary structure were measured for alpha- and beta-crystallins isolated from the steer lens, including low-molecular-weight crystallins from the cortex (alpha Le and beta L) and nucleus (alpha Ln) and high-molecular-weight crystallins from the nucleus (alpha H and beta H). In electron microscopic images of rotary-shadowed preparations alpha Le appears as spherical particles 16 nm in diameter, alpha Ln appeared as individual spheres or small aggregates of spherical subunits, alpha H contained large irregular aggregates as large as 180 nm, and both beta L and beta H appeared as elliptical particles of 7-9 nm diameter. Secondary osmometry showed that for all these crystallins colloid osmotic pressure increased monotonically in a non-linear fashion with protein concentration. For the alpha-crystallins, osmotic pressure rose more steeply with concentration for alpha Le than for either alpha Ln or alpha H, so that at 0.3 g ml-1 at 0.1 M ionic strength, the colloid osmotic pressure of alpha Le, alpha Ln and alpha H were approximately 2.6 x 10(5) dyn cm-2, 1.6 x 10(5) dyn cm-2 and 1.0 x 10(5) dyn cm-2, respectively. In a similar manner, osmotic pressure rose more steeply with concentration of beta L than for beta H, so that at 0.3 g ml-1 at 0.1 M ionic strength the colloid osmotic pressures of beta L and beta H were 2.6 x 10(5) dyn cm-2 and 1.1 x 10(5) dyn cm-2, respectively. The osmotic pressure of alpha Le dropped as ionic strength was increased from 0.02 to 0.4 M. For beta L and beta H, osmotic pressure dropped as ionic strength was increased from 0.02 to 0.1 M but was nearly the same at 0.1 M and 0.4 M ionic strength. The data for steer alpha Ln and beta H were similar to previous reports for calf cortical alpha L and beta-crystallins, respectively. The osmotic pressure isotherms for alpha Le, beta L and that previously reported for steer cortical extract were nearly identical, whereas the nuclear crystallins (alpha Ln, alpha H or beta H) generated slightly higher pressures than those previously reported for steer nuclear crystallin extracts. In all cases, osmotic pressure rose more steeply with concentration for the cortical crystallins than for the nuclear crystallins.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1998

Higher glycation of beta L- and beta S-crystallins in the anterior lens cortex and maximum glycation of gamma-crystallins in the bovine lens nucleus, demonstrated by frozen sectioning, isoelectric focusing and lectin staining.

The aim of the current study was to demonstrate glycation of beta L-, beta S- and gamma-crystallins in the young bovine lens. To establish which of the crystallins are glycated and where they are located in the lens, we carried out microsectioning of the lens, followed by isoelectric focusing (IEF). Four bovine lenses of 1.183 +/- 0.070 years were frozen-sectioned into equator and 11 layers. Water-soluble crystallins were separated by IEF and stained: (1) with Coomassie brilliant blue for proteins; (2) with the lectin concanavalin A, followed by horseradish peroxidase and diaminobenzidine, for glycated proteins. Experiments were performed with crystallins and proteins in native form, in the absence of denaturants. The crystallins were separated by IEF into alpha-crystallins of high molecular weight (HM), alpha L-, beta H-, beta L-, beta S- and gamma-crystallins. In the lectin staining experiments, only HM, beta L-, beta S- and gamma-crystallins were positive, whereas the alpha L- and beta H-crystallins were negative. Contrary to the glycated gamma-crystallins in the lens nucleus, the beta S- and beta L-crystallins were predominantly glycated in the anterior cortex and to a somewhat lower extent also in the posterior cortical regions. The degree of glycation (total densitometric readings of lectin-stained bands/Coomassie-blue-stained bands) is as follows: total gamma-crystallins 2.44, beta S-crystallins 0.77 and beta L-crystallins 0.28. Though glycation in the bovine lens is very low, lectin staining is sufficiently sensitive to detect the various glycated crystallins. The degree of glycation of gamma-crystallins was 3 times higher than that of beta S-crystallins and 9 times higher than that of beta L-crystallins.

Animals↗
PubMed1985

Opacification of gamma-crystallin solutions from calf lens in relation to cold cataract formation.

To determine the molecular mechanisms for cold cataract formation in the nucleus of the young mammalian lens, we have investigated the thermally reversible opacification of gamma-crystallin solutions isolated from calf lens. Coexistence curves (plots of opacification temperature Tc versus protein concentration) were determined for the individual gamma-crystallin fractions II, III, and IV as well as for the unfractionated gamma-crystallin mixtures isolated from the nucleus and cortex. The coexistence curve of gamma IV-crystallin is remarkably elevated above those of gamma II- and gamma III-crystallin and the gamma-crystallin mixtures. The gamma IV-crystallin fraction is the major determinant of the opacification temperature within the whole lens or isolated cytoplasm. Quasielastic light-scattering spectroscopy of gamma IV-crystallin solutions indicates that above Tc there are two populations of protein aggregates of distinctly different mean size. As the temperature is lowered towards Tc, both populations increase in size. Opacification occurs when the population of large scatterers, which is composed of less than 0.1% protein by weight, reaches an average radius of about 20,000 A.

Animals↗
PubMed1985

Distribution of phosphatic metabolites in the crystalline lens.

The phosphatic metabolite content of specific anatomic regions within the crystalline lens was determined by phosphorus-31 nuclear magnetic resonance analyses performed on tissue perchloric acid (PCA) extracts. Anatomically distinct zones each were dissected from five sets of 10 porcine lenses, isolated, and frozen in liquid N2. Separate pooled-tissue PCA extracts were prepared for each set of lens tissue corresponding to the following anatomic regions: capsule with attached epithelium, cortex, and nucleus. Randomly selected tissues were evaluated by light microscopy to determine the accuracy of the described dissection technique. Thirty-four phosphorus-containing metabolites were detected and quantitated by P-31 NMR from each of the three zones studied. Included among the phosphatic metabolites of these lens tissues were 18 chemically unidentified compounds. Significant regional differences in the metabolite distribution pattern were detected. The levels of ATP in the capsule + epithelium and in the cortex were 2.2-fold and 3.2-fold higher, respectively, than in the nucleus. In contrast, the Pi content was 2.3-fold greater in the capsule + epithelium and nucleus than in the cortex. End products of phospholipid metabolism (eg, glycerol 3-phosphocholine) also varied according to the anatomic region, with the highest content found in the nucleus. The prominent unidentified lens metabolite at 6 delta was highest in the nucleus, 35% lower in the cortex, and quite low in the capsule + epithelium. When individual P-31 NMR spectral profiles from each zone were summed according to normalized weighting factors, which reflected the relative phosphorus concentration of each region, a spectral profile of the lens was generated that was essentially indistinguishable from that of the whole (undissected) lens.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1982

Visible changes of the lens with age.

Slit lamp photographs taken along the optical axis of human eyes were examined with a microdensitometer. This showed an increasing opacity in the lens nucleus, an increased opacity and thickness of the cortex and the anterior lens capsule with age. However, the opacity and width of the anterior disjunction zones decreases with age. Patients with clear lenses but who had chronic uveitis, retinal detachment and glaucoma treated with medication, showed large deviations in the behavior of the disjunction zone as compared with other lenses of the same age. In incipient cataract in the aged, the fogging in the lens cortex is greatest when vestiges of the disjunction zone still remain. The cortex is less affected if the disfunction zone is absent.

Adolescent↗
PubMed1989

Elucidation of intermediate (mobile) and slow (solidlike) protein motions in bovine lens homogenates by carbon-13 NMR spectroscopy.

The motional dynamics of lens cytoplasmic proteins present in calf lens homogenates were investigated by two 13C nuclear magnetic resonance (NMR) techniques sensitive to molecular motion to further define the organizational differences between the cortex and nucleus. For the study of intermediate (mobile) protein rotational reorientation motion time scales [rotational correlation time (tau 0) range of 1-500 ns], we employed 13C off-resonance rotating frame spin-lattice relaxation, whereas for the study of slow (solidlike) motions (tau 0 greater than or equal to 10 microseconds) we used the solid-state NMR techniques of dipolar decoupling and cross-polarization. The frequency dependence of the peptide bond carbonyl off-resonance rotating frame spectral intensity ratio of the lens proteins present in native calf nuclear homogenate (42% protein) at 35 degrees C indicates the presence of a polydisperse mobile protein fraction with a tau 0,eff (mean) value of 57 ns. This mean value is consistent with the average value calculated from the known water-soluble nuclear lens protein polydispersity assuming a cytoplasmic viscosity 3 times that of pure water. Lowering the temperature to 1 degree C, a temperature which produces the cold cataract, results in an overall decrease in tau 0,eff to 43 ns, suggesting a selective removal of beta H-, LM-, and possibly gamma s-crystallins from the mobile lens protein population. The presence of solidlike or motionally restricted protein species was established by dipolar decoupling and cross-polarization. The fraction of motionally restricted protein in the nuclear region varied from 0.35 to 0.45 in the temperature range of 35-1 degree C. For native cortical homogenate (25% protein), the off-resonances rotating frame spectral intensity ratio frequency-dependent curves for the protein carbonyl resonance yielded tau 0,eff values of 34 and 80 ns at 35 and 1 degree C, respectively. Both values were reconciled with the known lens cortex soluble protein polydispersity using an assumed cytoplasmic viscosity 1.5 times that of pure water at the same temperature. Comparison of proton dipolar-decoupled and nondecoupled 13C NMR spectra of native cortical homogenate at 20 degrees C indicates the absence of significant contributions from slowly tumbling, motionally restricted species. This interpretation was confirmed by the failure to detect significant lens protein 13C-1H cross-polarization at this temperature. However, at 1 degree C, the fraction of solidlike protein was 0.15. Concentrated cortical homogenates at 20 degrees C (42% protein), by contrast, gave cross-polarization spectra with maximum absolute signal intensities 50-70% of native nuclear homogenates, but with similar magnetization parameters...

Animals↗
PubMed1984

Elemental profiles in cryosections and frozen-dried bulk specimens of the normal lens.

Energy-dispersive X-ray analysis was used to obtain distribution profiles of Na, K, Cl, P and S in rapidly frozen-dried bulk specimens, and in cryosections of the normal rat lens. Na and Cl are highly concentrated in the capsule, and K and P, in the epithelial cells. Profiles of the entire radius of a lens show relatively high concentrations of K and P in the outermost cells of the lens, with decreasing concentrations through the cortex, and a minimum throughout the nuclear region. S, on the other hand, shows increasing concentrations at deeper locations, with maximum values throughout the nuclear region.

Animals↗
PubMed1982

The "trap door" anterior capsulectomy technique for extracapsular cataract extraction with posterior chamber intraocular lens implantation in the capsular bag.

A technique for performing the anterior capsulectomy in extracapsular cataract extraction is described. The "trap door" anterior capsulectomy facilitates removal of 12 o'clock cortex by retracting the superior iris. Also, the anterior capsular flap acts as a lens glide during insertion of the IOL, and as a guide for the haptic during placement of the superior loop in the superior fornix of the capsular bag.

Cataract Extraction↗
PubMed1998

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.

Adolescent↗
PubMed1985

Distribution of calpain I, calpain II, and calpastatin in bovine lens.

Two types of Ca2+-requiring cysteine proteinase (calpain, EC 3.4.22.17), which required for full activation 100 microM Ca2+ (calpain I) and 1 mM Ca2+ (calpain II) were found to exist in the cytosolic fraction of bovine lens. Since calpain may play an important role on the degradation of lens proteins during the aging process of the lens, we attempted to study the distribution of calpain I, calpain II, and calpastatin (an endogenous specific inhibitor of calpain) in bovine lens. It was found that both the capsule-epithelium and cortex fiber cells contained calpains I and II and calpastatin, although the content of calpain I was much lower than that of calpain II. Calpains I and II and calpastatin activities were not detected in the nuclear region at all.

Animals↗
PubMed1989

Relative abundance of aldose reductase mRNA in rat lens undergoing development of osmotic cataracts.

Aldose reductase (AR) messenger RNA concentration was determined in normal rat lens and in lens from rats fed a 50% galactose diet over a period of 20 days. The AR mRNA was detected by using a previously described AR cDNA clone. The relative concentration of the AR mRNA was estimated by cpm of 35S-UTP labeled antisense RNA hybridized to dot-blots prepared from cytosols isolated from single lens, decapsulated lens (cortex) and its respective capsule (epithelia). The results demonstrated that the concentration of the AR mRNA in the epithelium doubled over the 20 day period. Correspondingly, an increase in the concentration of the DNA was also observed, suggesting that the increase in epithelial cytosolic mRNA might be partially due to the increase in the number of epithelial cells occurring in lens undergoing cataractogenesis. The increase in AR mRNA in the epithelia was gradual, and it doubled by day 12 on galactose, while the increase in DNA was rapid and reached an optimum level by about day 4. By day 4 the cortex AR mRNA concentration increased, then rapidly decreased to insignificant levels by day 20. Changes in AR mRNA and in DNA following a high influx of galactose in the lens might suggest a heightened gene response to changes in the cellular environment for the lens epithelium.

Aldehyde Reductase↗
PubMed1995

Simultaneous measurement of reduced and oxidized glutathione in human aqueous humor and cataracts by electrochemical detection.

A sensitive, electrochemical method was employed for the simultaneous measurement of reduced and oxidized glutathione in lens cortex, nucleus and capsule epithelia of rabbit lenses, normal human lenses and human cataracts. In addition, aqueous humor from cataract patients was also analyzed. The level of GSSG in the nucleus of human cataracts was significantly higher than that in the nucleus of normal eye bank lenses. The capsule epithelium of intracapsular extracted cataracts possessed high levels of reduced glutathione, despite the fact that much of the glutathione in the cortex and nucleus of the lenses was depleted. Levels of GSH in the aqueous humor of cataract patients were several times higher than those reported for normal aqueous humor. Electrochemical detection proved to be a useful technique for analysis of reduced and oxidized glutathione in lens and aqueous humor, especially when sample size is small, such as for capsule epithelium.

Aged↗
PubMed1997

Analysis of small GTP-binding proteins of the lens by GTP overlay assay reveals the presence of unique GTP-binding proteins associated with fiber cells.

Low molecular weight GTP-binding proteins are molecular switches which are thought to play pivotal roles in cell growth, differentiation, cytoskeletal organization and vesicular trafficking. In this study, members of this family of proteins have been identified and characterized in the eye lens, for the first time. [alpha 33P]GTP blot overlay assays of monkey and human lens water soluble and membranous insoluble fractions revealed the presence of specific GTP-binding proteins in the range of 20-30 kDa (small GTPases) in both fractions, with much higher amounts in the membranous insoluble fraction. In the insoluble fraction, in addition to 20-30 kDa GTPases, there are three distinct GTP-binding proteins, ranging from 33-45 kDa. The small GTPases (20-30 kDa) were present throughout the lens in epithelium, cortex and nucleus, while the 33-45 kDa GTP-binding protein bands were exclusively associated with the cortex and nucleus (fiber cells). Analysis of lens fractions by two-dimensional electrophoresis, immunoprecipitation using monoclonal and sequence specific polyclonal antibodies and C3 exoenzyme mediated ADP-ribosylation demonstrated the presence of Ras, Rap, Rho, Rac, Rab and several other small GTPases. The 33-45 kDa GTP-binding proteins that are associated with lens fiber cells appear to be distinct from the small GTPases and from heterotrimeric GTPases, and were not detected in brain or heart tissue. The presence of different complements of GTP-binding proteins in lens fibers and epithelial, cells suggests their involvement in important regulatory functions, possibly related to cell growth, differentiation and organization of the cytoskeleton.

Animals↗
PubMed1986

Ultrastructure of posterior subcapsular cataract in human lens.

In 20 eyes with posterior subcapsular cataract, ultrastructural changes were observed in the capsule and the subcapsular cortex. In 13 eyes, lens fibers of the subcapsular cortex were markedly swollen and liquefied, and contained granules of various sizes. In 4 eyes, various vacuoles or wide separations of the cell membrane were seen. In 3 eyes, the lens fibers became narrow and showed high electron density. The structure of human posterior subcapsular cataract affects the operation for posterior subcapsular cataract. In 1 case of posterior subcapsular cataract, a lamellar structure containing fine fibrils was observed in the deep layer of the posterior capsule and the epithelial cells which had a long nucleus and poor cytoplasm were scattered just under the posterior capsule. It is considered that these changes in the cells indicated a reduction of cellular function.

Adult↗
PubMed1987

The effect of neodymium:YAG laser shocks on the blood-aqueous barrier.

An animal model demonstrates that the acute inflammation seen after neodymium: YAG (Nd:YAG) capsulotomy is related to the presence of disrupted tissue suspended in the aqueous, rather than to the mechanical insults by the repeated shock waves. Seven rabbits were treated in the lens cortex of one eye with 20 bursts of 4 pulses, 24 mJ each, and followed fluorophotometrically using albumin labelled with fluorescein. This allowed transmission of shock waves to the anterior segment without releasing debris in five eyes that showed no inflammation. Two eyes with inadvertent capsular rupture showed marked blood-aqueous barrier breakdown. This suggests the use of a capsulotomy technique that relies on discission rather than pulverization of the membrane and avoids the thicker portions of the membrane when possible.

Animals↗
PubMed1989

Bendazac lysine in selected types of human senile cataract. A long-term double-masked placebo-controlled clinical trial with multilinear densitometric image analysis of Scheimpflug photographs.

A double-masked placebo-controlled clinical trial with hard data evaluation by image analysis of Scheimpflug photographs taken at baseline and 6, 12 and 18 months after starting treatment was performed to assess the efficacy of bendazac lysine in four different types of senile cataract. The study had a classical split-plot design. For statistical evaluation, the analysis of variance and covariance for repeated measures were used for three different lens sections: anterior capsule and superficial layer, anterior cortex and nucleus. In the entire group of 53 evaluable patients (without separation into cataract-type subgroups), there was a significantly less increase over time in light scattering (i.e. film blackening) of the anterior cortex and nucleus with bendazac lysine than with placebo. There was also a strong trend in favour of the active drug at the anterior capsular level. Patients with water clefts and spokes showed a significantly less light scattering of the anterior capsule and cortex when treated with bendazac lysine. Those with nuclear changes also showed significantly less light scattering of the anterior cortex and nuclear region with the active drug than with placebo. The number of patients with subcapsular and wedge-shaped (cuneiform) cataracts was too small to be adequately assessed by statistical procedures. Nevertheless, there were indications of a beneficial effect of bendazac lysine on all the lens sections in patients with subcapsular cataracts and on the anterior cortical region in those with wedge-shaped cataracts. In conclusion, this study showed that the increase in light scattering over time, i.e. the progression of cataract, is less in bendazac lysine-treated patients than in those treated with placebo.

Adult↗
PubMed1989

Lesion and regeneration of the anterior and posterior lens capsule and cortex in rabbits Nd:YAG laser.

With a mode-locked Nd:YAG laser set at various energy levels, anterior and posterior capsular and cortical lesions were produced in the lens of rabbits. Biomicroscopic and Scheimpflug examinations showed the anterior lesion to be healing in a whitish scar that was restricted to the area of the original lesion. Histology and transmission electron microscopy (TEM) demonstrated the proliferation of epithelial cells that produced a new, continuous, basement membrane-like capsule. In the area of the lesion collagenous material, myofibroblast-like cells and macrophages were found. Laser-induced lesions in the posterior lens capsule and lens protein resulted in damage to the capsule and grey opacity of the lenticular proteins, which remained unchanged for 6 weeks. Neither inflammatory nor epithelial cells appeared within the locally damaged lens. Macrophages migrated from the vitreous into the lesion; they were observed either in intercellular clefts or within a lens fibre, almost completely taking up their cross section.

Animals↗
PubMed1989

Excimer laser ablation of the human lens at 308 nm with a fiber delivery system.

A 308 nm excimer laser has been used with a fiber delivery system to perform ablation of the human lens. Preliminary results demonstrate the system's ability to ablate lens nucleus and cortex selectively, preserving the anterior and posterior capsules. The total delivered energy necessary to ablate a human lens ranged from 35 to 63 joules. Laser tissue interaction and ablation rates were computed for the different components of the human lens (capsule, cortex, nucleus) for the operatively useful energy densities (fluences). Operative experience suggests that cortex and nucleus can be ablated while preserving the capsule if an adequate irrigation and aspiration system is developed. These results also suggest that this modality may be adequate for performing endocapsular cataract extraction. Laser tissue interactions were also computed at variable distances between the fiber tip and tissue. As this distance increased, the spread of the beam increased and a significant increase in energy was necessary to induce tissue ablation. This was due to the decrease in fluence with increasing distance to the target tissue and/or the absorption and scattering of the delivered energy within a short distance from the fiber tip by the ablated material. Evidence of a sonic effect was also present.

Aged↗