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At least 19 recordsLinked to original sources
PubMed1992

Indirect spectral transmission ratio measurements of the aging crystalline lens nucleus.

A new objective approach to characterize color and opalescence in the lens nucleus, using wavelength indexed transmission ratios (TR) is described. Transmission ratios, i.e. the transmissivity per unit lens thickness, for the whole visible spectral range (390-720 nm) were calculated using fast scanning spectral colorimetry (FSSC). The lowest transmission ratios values were obtained in the blue part of the spectrum in general and at 450 nm in particular. They inversely followed the subjectively determined LOCS II color grading. The difference between transmission ratios at the absorbed part of the spectrum (less than 500 nm) and the non-absorbed part (greater than 550 nm) also reflects the LOCS II color grading. The overall mean transmission ratios for all wavelengths in the spectrum gives an index that closely followed the nuclear opalescence grading of the LOCS II system. The transmission ratios are theoretically independent of the spectral characteristics of the incident light as long as it contains suprathreshold energies in the whole measured spectral range.

Absorption↗
PubMedDate not supplied

[Densitometric analysis of crystalline lens nucleus in the choice of strategy of surgical treatment of cataracts].

Computer analysis of TV images of the eye was used for quantitative evaluation of optic density of the lens nucleus in patients with cataracts in need of surgical treatment. Indications to cataract phacoemulsification were determined using classification of the degree of the lens nucleus maturity. This classification is based on the maximal values of optic density of the anterior third of the nucleus, obtained by the lens densitometry, coefficient of light absorption by the lens nucleus, and tentative subjective classification of the lens nucleus maturity by a color scale. In initial cataract (first degree) the mean maximal optic density of the anterior third of the nucleus is 55.8 +/- 5.7 arb. units and coefficient of the lens nucleus light absorption is 0.93, in nuclear brown cataract (fourth degree) these values are 158.7 +/- 24.4 arb units and 1.81, respectively. Cataract with brown enlarged nucleus involving the cortical layers of the lens and high optic density of these layers, with lens nucleus light absorption coefficient more than 2.5 is a contraindication to phacoemulsification.

Cataract↗
PubMed1984

Conformational changes in soluble lens proteins during the development of senile nuclear cataract.

Soluble crystallins were isolated, by gel filtration, from the nucleus and cortex of types I-IV cataractous lenses and neonatal lenses. Extinction coefficients were determined and used to calculate the proportion of the crystallins. alpha Crystallins were the major proteins in the cortex of the cataractous lens whereas beta crystallins predominate in the nucleus and in the neonatal lens. Electrophoretic and immunological data, indicated that there was very little soluble gamma crystallin in the cataractous tissue. Highly specific competitive radioimmunoassays were used to estimate the crystallin contents of the various extracts. Values obtained for the neonatal extracts agreed closely with those from gel filtration but, in general, the values found for the cataractous proteins were low. The immunological reactivity of beta crystallin decreased progressively with the development of nuclear colour whereas alpha crystallin reactivity decreased sharply with the onset of nuclear cataract (type II lens) and then partially recovered. No significant alterations were found in the micro-environments of tryptophan residues in any of the proteins indicating that there are no gross conformational changes in the soluble proteins during cataract development. It would appear that the losses of immunochemical reactivity are due to chemical and/or conformational alterations which are restricted to the surface of the protein molecules.

Aged↗
PubMed1989

A new cannula for nucleus hydrodissection.

This disposable 25-gauge cannula has a specially designed distal segment which facilitates crystalline lens nucleus hydrodissection or viscodissection. The injection of a fluid or viscous material creates a cleavage plane between the nucleus and cortex or capsule, thus facilitating extraction of the nucleus. The flattened, smooth, cannulated tip allows easier insertion and manipulation under the capsule.

Cataract Extraction↗
PubMed1992

Ageing and changes in protein conformation in the human lens: a Raman microspectroscopic study.

Using confocal Raman microspectroscopy with laser light of 660 nm the secondary and tertiary conformation of crystallins was studied in human lenses of varying age (20-75 years). Differences in cortical and nuclear proteins in individual lenses and among lenses of different age and differences between small equatorial opacities and adjacent clear sites were analysed using a difference spectrum approach. Intensity calibration allows assessment of local variations in protein content. The main findings and conclusions are as follows. (1) Irrespective of the age of the lens nuclear proteins proved to contain more aromatic amino acids, i.e. tryptophan, tyrosine and phenylalanine. This change most probably reflects differences in crystallin composition between nucleus and cortex as described in biochemical studies. (2) Changes in the amide bands indicate a more pronounced beta-sheet conformation of the nuclear proteins. Taking into account available biochemical evidence this most probably reflects a true post-translational change in the secondary conformation of the crystallins. (3) Cortical proteins in 'old' and 'young' lenses are largely identical indicating that ageing is not accompanied by gross alterations in the transcription/translation of the crystallin genes. (4) 'Old' and 'young' nuclear proteins deviate with respect to the amount of aromatic amino acids, being more abundant in 'young' nuclear proteins. (5) Proteins in small early opacities do not exhibit alterations in conformation. (6) A pronounced peak in the difference spectra in the region 1425-1435 cm-1 for nuclear proteins especially when compared with equatorial cortical proteins may be considered as evidence for the advanced photooxidation of tryptophan and/or deamidation of asparagine from superficial to deep regions of the lens.

Adult↗
PubMed1984

Cytoskeletal proteins of the ageing human lens.

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

Actins↗
PubMed1985

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↗
PubMed1989

Cigarette smoking and risk of nuclear cataracts.

The current study was undertaken to assess the relationship of smoking to the risk of lens opacities. The risk was evaluated separately for nuclear and cortical opacities and for both types together. We studied 838 watermen in Maryland by detailed ocular examination for the presence and severity of each cataract type. All subjects were interviewed regarding smoking history, and a cumulative smoking dose was calculated. The results suggest a significantly increased risk of pure nuclear opacities associated with cigarette smoking. The increase in smoking dose was associated with increasing severity of nuclear opacity. The risk of nuclear opacities increased with increasing cigarette dose and decreased if the subject had quit smoking. The effect of smoking was most striking in those less than 80 years old. No increased risk of nuclear opacities was observed with earlier age when smoking started, after adjusting for dose and cessation of smoking. Further investigations are warranted on the biochemical and physical damage to the nucleus of the lens from smoking cigarettes.

Adult↗
PubMed1986

Freezable and non-freezable water content of cataractous human lenses.

Twenty-nine cataractous human lenses between the ages of 36 and 93 were investigated. The total water content of cortex and nucleus were obtained by vacuum dehydration. The freezable water content was measured by differential scanning calorimetry. The non-freezable water content was obtained by difference. To measure the extent that syneresis contributes to cataract formation, an excess function was designed. The excess function represents the changes that occur, for example, in non-freezable water content due to cataractogenesis. It is calculated as the difference between the non-freezable water content of a normal lens and that of a cataractous lens of the same age. On the average, there is 7% less non-freezable water in the cortex of a cataractous lens than in the cortex of a normal lens. The corresponding number for the nucleus is 9%. This represents 29 and 36% changes, respectively, in the cortex and nucleus due to syneresis during cataractogenesis.

Adult↗
PubMed1984

HPLC analysis of lens GSH and GSSG.

A sensitive method for the analysis of reduced and oxidized glutathione in bovine lens fractions is described. Samples which have been derivatized with iodoacetic acid and dinitrofluorobenzene have been analyzed by high pressure liquid chromatography. Quantitation of reduced and oxidized glutathione in the sample at nanomole levels has been accomplished using a commercially available Bondapak-amine column. Values for reduced glutathione of approximately 30 mumoles/gm wet weight have been found for epithelium preparations while only 4 mumoles/gm wet weight were found in the nucleus. Only small amounts of oxidized glutathione were observed, increasing in the inner regions of the lens.

Animals↗
PubMed1991

Resonance Raman detection of a carotenoid in the lens of the deep-sea hatchetfish.

A laser scanning micro-probe has been used to elicit resonance Raman signals from frozen sections of the lens of the deep-sea hatchetfish, Argyropelecus affinis. The signals demonstrate with certainty the presence of a carotenoid and its distribution in the lens. The carotenoid exhibits characteristic resonance Raman vibrational modes at 1551 cm-1 (C = C stretch, v1), 1147 cm-1 (C-C stretch with C-H bend, v2), 2285 cm-1 (2v2) and 2681 cm-1 (v1 + v2), upon excitation at 441.6 nm. Unlike glycogen in the nucleus of dove lens, the carotenoid in the lens of A. affinis occurs at a higher concentration in the cortex, although its presence in the nucleus is established. A study of lenses of varying age showed that carotenoid incorporation is accelerated as the fish grows older and hence its concentration is highest in the cortex. Because of the extremely low concentration of the carotenoid in the nucleus, it was detectable only by the very sensitive resonance Raman technique.

Aging↗
PubMed1986

G6PD molecules devoid of catalytic activity are present in the nucleus of the rat lens.

The specific activity of glucoso-6-phosphate dehydrogenase (G6PD) in the rat lens declines as a function of animal age. G6PD activity could be found only in the cortex of the lens. Previous work showed that antibodies against the 'native' form of G6PD could not recognize any cross-reacting material (CRM) in the lens. It was speculated that this could be due either to disappearance of G6PD from the nucleus by degradation or by alterations of the molecules which resulted in the loss of their antigenic determinants. In order to investigate this question, an antibody was prepared against denatured G6PD. This antibody did not interact with 'native' (active) forms of the enzyme; it was shown, however, to recognize antigenically cross-reactive but catalytically inactive intact G6PD molecules in the nucleus of the lens. This finding suggests that altered enzyme molecules are at least partially denatured and accumulate in the lens without being further cleaved proteolytically.

Aging↗
PubMed1990

[Lens position following planned capsular sac fixation: results of 200 consecutively surgically treated phacoemulsifications].

A total of 200 phacoemulsifications with planned in-the-bag fixation of one piece PMMA posterior chamber lenses implanted consecutively by one surgeon were examined on postoperative days 3-7. Special attention was given to both position of the haptics and centering of the lens. No sodium hyaluronate or other viscoelastic materials were used in any of the operated eyes. After capsulorhexis and phacoemulsification inside the bag we were able to confirm in-the-bag fixation in 190 implants (95%). In 197 of the 200 patients centering of the IOL was excellent. The capsular rim of the circular capsulorhexis was preserved in all cases due to phacoemulsification within the capsular bag. This procedure meets the best conditions for a secure in-the-bag insertion of the posterior chamber lens. Expression of the lens nucleus after capsulorhexis or through the so-called letter-box technique leads to a remarkably lower percentage of proven bag-bag fixation of the haptics.

Cataract Extraction↗
PubMed1983

Variation in proportion and molecular weight of native crystallins from single human lenses upon aging and formation of nuclear cataract.

Extracts of water-soluble proteins from cortex and nucleus of single human lenses have been analyzed by high-pressure gel permeation chromatography in combination with a size- and a concentration-sensitive detector. Using this rapid and accurate method, changes in molecular weight and proportion of the native crystallins upon aging and formation of nuclear cataract are observed. In the range from 30 to about 40 years the gamma-crystallin content of normal lenses increases and that of alpha-crystallin decreases; over 40 years the level of gamma-crystallin decreases and that of alpha-crystallin remains constant in the cortex (11%) as well as in the nucleus (1-2%). These changes are accompanied by an increase in the water-insoluble fraction. With progressing nuclear cataract an increase in beta 3- and a drastic decrease in gamma-crystallin content, especially in the nucleus, are accompanied by a steep increase in the water-insoluble fraction. The molecular weights of the crystallins do not change significantly, except that of alpha- and beta 1-crystallin which show an increase with age.

Aging↗
PubMed2003

Changes in the refractive index of lens fibre membranes during maturation--impact on lens transparency.

PURPOSE: Local variations in refractive index are the physical cause of light scattering in a material or tissue and also induce phase changes of propagating light waves. The goal of this study was to analyse local differences in refractive index by phase contrast microscopy of sections of human lenses. METHODS: Refractive index was estimated by immersion refractometry. Cryo-sections of quick-frozen human donor lenses were embedded in a graded series of bovine serum albumin solutions, and in immersion oil, ranging in refractive index from 1.34 to 1.52. RESULTS: Fibre membranes in the lens cortex prove to have a refractive index considerably above that of fibre cytoplasm at the same location. Fibre membranes in the lens nucleus have a refractive index approximately the same as that of fibre cytoplasm at the same location. CONCLUSION: In the lens cortex, transparency is obtained by a high spatial order of the lens fibre lattice to compensate for the light scattering caused by differences in refractive index between fibre membranes and cytoplasm. In the lens nucleus, high spatial order is less important, because the minor differences in the refractive index between fibre membranes and fibre cytoplasm lead only to minimal scattering.

Cryopreservation↗
PubMed1996

Electrical impedance tomography of the eye: in vitro measurements of the cornea and the lens.

This study was designed to perform multifrequency impedance measurements on the pig's eye. On one hand, impedance of the ocular tissues was measured from 10 kHz to 10 MHz. The aqueous and vitreous humours and the cornea showed no relaxation in this range of frequencies, whereas the lens and its parts (the cortex and the nucleus) did. On the other hand, multifrequency EIT and dynamic imaging were performed on the lens and on the whole eye. Data and images obtained after thermal and chemical injuries are presented and discussed.

Animals↗
PubMed1989

Local variation in absolute water content of human and rabbit eye lenses measured by Raman microspectroscopy.

Raman spectra were obtained from fresh, fixed and sliced rabbit lenses and from human lens slices. For all lenses and lens slices the ratio R, defined as the Raman intensity at 3390 cm-1 divided by the Raman intensity at 2935 cm-1, was measured at different locations along the visual and equatorial axis. The ratios R were transformed to absolute water mass percentages by measuring solutions with known protein concentrations. It was shown that fixation and slicing have very little effect on the absolute water content of the lenses. The values obtained for the absolute water content are comparable to values given in literature. It was also shown that the water content in rabbit and human lenses rapidly decreases from the immediate anterior and posterior subsurface region to the deep superficial cortex and is relatively constant in the nucleus. Raman microspectroscopy appears to be a reliable method for the measurement of the absolute water content of small volumes on defined positions in the lens. This can be very useful when analyzing the possible relation between local variations in water content and the occurrence of opacities in the lens.

Animals↗