Lens Core Research Articles

The optics of the spherical fish lens

The optical design of the fish eye is particularly simple because immersion renders the cornea optically ineffective and the lens is nearly spherical in shape. Measurements have shown that an approximately parabolic gradient of refractive index exists within the lens. If full internal and external spherical symmetry of the lens applies, the geometrical-optical behaviour of the lens is then a function only of the refractive index of the surrounding medium, that of the lens core and cortex, and of the form of the index gradient. The theoretical optical performance of models of the spherical fish lens is calculated by means of the ray-tracing program Drishti as a basis for understanding the optical design of real fish and aquatic eyes. Models based on the gradients proposed by earlier workers are shown to be unable to predict reported spherical aberration and image quality. A model of the fish lens with a polynomial gradient is proposed that yields spherical aberration, image quality and chromatic aberration similar to that reported for the fish.

Short-wave absorbing pigments in the ocular lenses of deep-sea teleosts

This study describes the spectral characteristics between 250 and 700 nm of lenses from 71 species of deep-sea teleost. The majority of these did not contain detectable amounts of short-wave absorbing pigment and transmitted all longer wavelengths to the same extent before cutting off smoothly and rapidly in the near-UV (50% transmission 310–348 nm). The lenses of 15 species, however, contained significant amounts of short-wave absorbing pigment. The majority of these lenticular pigments had smooth ‘bell-shaped’ absorbance spectra with a single peak in the near-UV. Such ‘simple’ pigments were extracted from four species (λmax: 360·8 nm, 36·50 nm, 395·7 nm, 324·8 nm) and detected in a further eight species, although insufficient material was available to allow their extraction from the latter group.The absorbance profiles of lenses from another three species were more complex, suggesting the presence of one and two carotenoid-like pigments respectively in the lenses ofArgyropelecus sladeniandA. affinis,and two as yet unidentified pigments in the lenses ofMalacosteus niger.This brings the total of short-wave absorbing pigments so far described in the lenses of deep-sea fish to at least eleven. InArgyropelecusspp. the pigmentation was most pronounced in the lens cortex, while inMalacosteus nigerit was restricted to the lens core. In all other species the pigment appeared freely diffusible throughout the lens. Several species showed an increase in the degree of lenticular pigmentation in older animals and two(Argyropelecus affinisandMalacosteus niger)demonstrated age-related changes in the relative concentrations of two different pigments within the lens.

Differential localization by in situ hybridization of specific crystallin transcripts during mouse lens development

Abstract The embryonic development of the mammalian lens is well known at the biochemical and histologi-cal level. However few data are available at the molecular level concerning gene expression during the continuous differentiation of the lens. In the present study, we have investigated by in situ hybridization the changes in the distribution of mouse crystallin mRNA as a marker of differentiated lens cells, during development of the lens primordium, when tissue interactions are known to be essential. The transcripts of α and β crystal-lins are first detected at the early elongation stage of primary fibres; γ-crystallin-transcripts do not appear until the late elongation phase. All areas of the lenses exhibited crystallin mRNA until the beginning of secondary fiber formation at 18 days of development. Hybridization for α and β crystallin is confined at that time to the equatorial part of the lens. The γ crystallin transcripts are no longer found in the equatorial region after 1 post-natal day, but remain in the lens core, decreasing gradually. A possible mechanism is discussed.

Carbonate Mud Bodies in Middle Mississippian Strata of Southern Indiana and Northern Kentucky: End Members of a Middle Mississippian Mud Mound Spectrum?

Relatively small, lens-shaped carbonate mud bodies are common features in the Ramp Creek Formation and Harrodsburg Limestone (Mississippian) of southern Indiana and northern Kentucky. The outcrop dimensions of the lenses range from approximately 10 cm thick and 3 m wide to as much as 2 m thick and in excess of 100 m wide; their three-dimensional geometry is unknown. The lens cores consist of dolomitic mudstone that grades laterally and vertically into increasingly more fossiliferous wackestone to grainstone with fenestrate bryozoans and echinoderms being the dominant fossils. The great abundance of fenestrate bryozoan fragments surrounding the lenses suggests that lens evolution was controlled by the trapping of carbonate mud by the baffling action of bryozoans. Wisps of organic material preserved in the lens cores may be remnants of some form of non-calcareous algae that also baffled and trapped carbonate mud. These mud lenses are end members of a spectrum of Mississippian carbonate mud bodies ranging in size from these small lenses to the classical Waulsortian mounds that may be hundreds of meters thick and a kilometer or more broad. All of these carbonate mud bodies may have in part formed by baffling and localizing of carbonate mud by organisms andmore » in part by local production of carbonate mud. The major difference between large and small bodies is the water depth in which each formed. The Ramp Creek-Harrodsburg mud lenses may be miniature Waulsortian mounds that developed at or above fair-weather wave base on a relatively shallow carbonate platform rather than on shelf-to-basin slopes as proposed for the classical Waulsortian mounds.« less

Age-related changes in proteolysis of aberrant crystallin in bovine lens cell-free preparations

Bovine α-crystalline fragments were prepared by H 2O 2/Cu 2+-mediated free-radical treatment (which generated 15.1 and 16.6 K M r fragments) and cyanogen bromide cleavage (which generated 8.4, 13.8 and 16.8 K M r fragments). Proteolysis of the fragments and native and denatured α-crystallin was then compared using bovine lens homogenates prepared from either cortex or cores of lenses obtained from animals of different ages (foetal, 1.5 years and 6.5 years old). In all preparations the fragments were more rapidly degraded than the denatured but uncleaved protein, while the untreated crystallin was only slightly susceptible to proteolytic attack. Both developmental and age-related differences in proteolytic activity towards the aberrant crystallins were detected, most notably a marked age-related decline in the fragment catabolism in preparations obtained from the cores. Should a similar decline occur in human lenses then the changes which we have detected may be important contributary factors towards cataractogenesis.

Site of carbamoylation of bovine gamma-II-crystallin by potassium [14C]cyanate.

One possible route to cataract formation may be via the carbamoylation of lens proteins due to increased concentrations of cyanate in the body resulting from uraemia associated with renal failure and with severe diarrhoea. Carbamoylation of gamma-II-crystallin, which is found in the lens core, could alter the surface charge network of the molecules, resulting in aggregation, increased light-scattering and hence cataract. We have attempted to locate the site(s) of carbamoylation in gamma-II-crystallin. gamma-II-Crystallin was isolated by gel chromatography and ion-exchange chromatography. gamma-II-Crystallin was then carbamoylated by incubation with potassium [14C]cyanate, followed by citraconylation and digestion with trypsin to give peptides that were separated by high-resolution ion-exchange chromatography. The amino acid compositions of the radioactive peptides were compared with the expected peptide composition for gamma-II-crystallin. The radioactive peptide compositions, which agreed with the theoretical peptides, all matched with the N-terminal region of gamma-II-crystallin and had in common the presence of the N-terminal glycine residue. It appears that the alpha-amino group of the N-terminal glycine was the main site of carbamoylation. This site forms part of the charge network on the surface of gamma-II-crystallin.

Tracing phylogeny in a fish group (groupers) through proteins of the layers of the eye lens core

1. 1. An initial study with tunas indicated that electrophoretic patterns of proteins from consecutively deeper layers of the lens core (nucleus) may reflect phylogenetic pathways. 2. 2. This approach was further evaluated in the present study with members of another fish group, the groupers. 3. 3. Densitometrically analyzed electrophoretic patterns of proteins from nuclear lens layers of the Warsaw, yellowedge, and red groupers agreed with generally accepted species relationships, plus reflected a picture of early and progressive divergence from separate ancestral stocks. 4. 4. This study supports the view that proteins in nuclear lens layers can be used to trace phylogenetic development.

Indirect tissue electrophoresis: A new method for analyzing solid tissue protein

1. 1. The eye lens core (nucleus) has been a valuable source of molecular biologic information. 2. 2. In these studies, lens nuclei are usually homogenized so that any protein information related to anatomical subdivisions, or layers, of the nucleus is lost. 3. 3. The present report is of a new method, indirect tissue electrophoresis (ITE), which, when applied to fish lens nuclei, permitted (a) automatic correlation of protein information with anatomic layer, (b) production of large, clear electrophoretic patterns even from small tissue samples and (c) detection of more proteins than in liquid extracts of homogenized tissues. 4. 4. ITE seems potentially applicable to a variety of solid tissues.

The Subthermocline Lens D1. Part II: Kinematics and Dynamics

Abstract The dynamics of a subthermocline lens observed during the POLYMODE Local Dynamics Experiment are examined using density data and measurements of the velocity field obtained by an absolute velocity profiler. It is shown that the momentum balance is nonlinear. The lens' potential vorticity contours are closed in the horizontal and vertical, trapping low-salinity water at the lens core. The lens's dynamics are explained by a series of elementary models based on the classical Bessel-tunction vortex. The models show that nonlinearity enters in two ways, through the nonlinear momentum balance and through the finite character of the stretching vorticity. The models suggest a lens anatomy: the core; a boundary layer at the velocity maximum; a buffer zone; and a geostrophic region. The first two terms are self-explanatory. The buffer zone extends from the velocity maximum to a radius we term the geostrophic radius; at which there is a salinity front. On either side of this front the character of the mixin...

New medium for solubilizing proteins of the eye lens core (Nucleus)

1. 1. The eye lens core (nucleus) is a practical source of proteins for use as genetic markers. 2. 2. A new, simple extraction solution for these proteins is described. The solution was tested on fish (mullet, rockfish, and barracuda) lens nuclei, which produced weak extracts with other extraction media. 3. 3. A new solution, in addition to producing the strongest extracts, demonstrated desirable qualities relating to electrophoresis and storage. 4. 4. This solution may serve as a general extraction solution for nuclear lens proteins.

New applications and innovations in the electrophoretic separation of proteins from the eye lens core (nucleus)

1. 1. The electrophoretic separation of proteins from the eye lens core (nucleus) has been a useful procedure in population and taxonomic studies. 2. 2. The possibility exists that this method may be applied to obtaining behavioral, environmental, and perhaps other types of information. 3. 3. Because of the increasing usefulness of this approach with nuclear lens proteins, efforts to optimize the methodology are continually being made. 4. 4. A complete system, incorporating new developments and applied to four fish species, is described in this report.

Normal human lens—the distribution of protein

The distribution of dry mass and protein was determined in 21 normal human lenses of different age. The lenses were obtained from enucleated tumor eyes and were immediately prepared for quantitative microradiography. The measurements were performed along the lens axis. In the anterior and posterior subcapsular cortex the dry mass content was about 0·2 g/cm 3 From this region there was an even and continuous increase over a distance of about 0·5 mm to a level of about 0·45 g/cm 3 . This level was fairly constant in the center of the lens. These results allowed a subdivision of the lens into a central lens core with a constant high concentration of dry mass and a peripheral zone with an increasing concentration from the periphery. No major changes with age in the dry mass levels could be found.

Aging of pyruvate kinase isozymes in rabbit lens

Using acrylamide gel electrofocusing, several bands of pyruvate kinase activity were found, corresponding to “M” bands; the isoelectric points of these bands differed according to the zones of rabbit lens: four bands were seen in the epithelium (where protein synthesis is active), and only two bands in the core of the adult lens (where there is no protein biosynthesis). On the contrary, the four bands exist in the lens core of 12-day-old rabbits. Kinetic results and thermostability experiments confirmed that the bands of the adult lens core correspond to the “M 1” and “M 4” isozymes. It seems that the disappearance of certain molecular forms of pyruvate kinase may be due to their shorter life-span. These modifications may have some physiological or pathological consequences.

Ultraviolet radiation in the aging and cataractous lens. A survey.

An increase in the insoluble protein levels, in fluorescence, and a decrease in the SH concentration are three specific aging parameters in the mammalian lens. These can be markedly accelerated in human, rat and mouse lenses by in vitro exposure (for at least 4 h) to UV radiation (above 300 nm) and 3‐aminotriazole (AT) and in vivo by exposing mice to UV and parenteral AT for 4–6 weeks. UV, fluorescence, electron paramagnetic resonance (EPR) and Lasar Raman Spectroscopy were performed on normal and UV plus AT exposed 4–6 week old rat lenses and normal and experimental human lenses (1 day to 75 years of age). These data demonstrate the presence and/or induction of at least one fluorescent compound (fluorogen) (360 nm activation, 440 nm emission) derived from tryptophan by a free radical induced photooxidation reaction. Similar studies on purified lens proteins and peptides indicate that this fluorogen is tightly bound to at least one specific peptide. The age related increase in the concentration of fluorescent compounds enhances the yellowing of the lens core and accompanies polymerization of soluble protein precursors into the insoluble protein fraction. There is also a progressive fall in SH levels (with age or UV exposure) and an increase in SS bonds without any significant alteration in the secondary configuration of the lens proteins (which remain mainly in the anti‐parallel beta‐pleated configuration). It is postulated that UV radiation (300–380 nm) plays a role in lenticular aging, particularly nuclear sclerosis and its extreme state characterized by the Brunescent Cataract.

Contact and fracture ultramafic assemblages from Norway: Rb-Sr evidence for crustal contamination

Strontium isotopes are used as tracers of crustal contamination of alpine-type ultramafic rocks from the Basal Gneiss Complex of the Caledonides of southern Norway. Minerals from anhydrous assemblages that occur in the cores of these ultramafic lenses give Sr87/Sr86 ratios (0.7011 to 0.7047) that reflect the expected ambient Sr87/Sr86 conditions of the ancient upper mantle. Rb-Sr evidence for crustal contamination is found in hydrous assemblages that occur within fractures and around the margins of the ultramafio bodies. Olivine, enstatite, amphibole, and magnesite from these assemblages have present-day Sr87/Sr86 ratios (0.7049 to 0.7085) that are significantly higher than those of compositionally equivalent minerals from the interiors of the ultramafic bodies. The high Sr87/Sr86 values were acquired as a result of the reaction between the ultramafic rock and ion-charged hydrous solutions carrying strontium with the ambient Sr87/Sr86 ratio (around 0.713) of the enclosing country rook during the waning phases of the Caledonian Orogeny. Mineral separates from the interiors of these ultramafic bodies can yield useful information on the ancient upper mantle. Wholerock samples, however, will show some evidence of contamination from the crust as a result of the formation of at least trace amounts of secondary hydrous minerals. Most whole-rook Sr87/Sr86 ratios from alpine-type ultramafic rocks from other orogenic belts show evidence of this contamination.

Diffusion of sodium in extracellular space of the crystalline lens.

ARTICLESDiffusion of sodium in extracellular space of the crystalline lensCA Paterson, and DM MauriceCA Paterson, and DM MauricePublished Online:01 Jan 1971https://doi.org/10.1152/ajplegacy.1971.220.1.256MoreSectionsPDF (2 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInEmailWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformationCited ByThe lens internal microcirculation system delivers solutes to the lens core faster than would be predicted by passive diffusionEhsan Vaghefi and Paul J. Donaldson27 November 2018 | American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, Vol. 315, No. 5Homeostasis in the vertebrate lens: mechanisms of solute exchange27 April 2011 | Philosophical Transactions of the Royal Society B: Biological Sciences, Vol. 366, No. 1568Visualization of transverse diffusion paths across fiber cells of the ocular lens by small animal MRI9 September 2009 | Physiological Measurement, Vol. 30, No. 10Biology of the Lens: Lens Transparency as a Function of Embryology, Anatomy, and PhysiologyRegulation of potassium transport in human lens epithelial cellsExperimental Eye Research, Vol. 82, No. 1ATPases and lens ion balanceExperimental Eye Research, Vol. 78, No. 3Transport of fluid by lens epitheliumJorge Fischbarg, Friedrich P. J. Diecke, Kunyan Kuang, Bin Yu, Fengying Kang, Pavel Iserovich, Yansui Li, Heinz Rosskothen, and Jan P. Koniarek1 March 1999 | American Journal of Physiology-Cell Physiology, Vol. 276, No. 3An Oneiropenic Account of an Ophthalmological CareerExperimental Eye Research, Vol. 66, No. 2Membrane cholesterol and phospholipid in consecutive concentric sections of human lenses.Journal of Lipid Research, Vol. 26, No. 5Steady state voltages in the frog lens2 July 2009 | Current Eye Research, Vol. 4, No. 4An analysis of 45 Ca fluxes in the rabbit lens2 July 2009 | Current Eye Research, Vol. 2, No. 11Lanthanum and Procion yellow as extracellular markers in the crystalline lens of the ratExperimental Eye Research, Vol. 28, No. 1Transport in Eye Epithelia: The Cornea and Crystalline LensThe toad's (Bufo marinus) lens and urinary bladder as mural membranes: A comparisonExperimental Eye Research, Vol. 15, No. 6The potential difference of the frog lensExperimental Eye Research, Vol. 15, No. 4Bioelectric measurements in the frog lensExperimental Eye Research, Vol. 15, No. 2ReferecnesActa Physiologica Scandinavica, Vol. 85Pharmaceutical Sciences—1971: Literature Review of PharmaceuticsJournal of Pharmaceutical Sciences, Vol. 61, No. 7Distribution and movement of ions in the ocular lens1 April 1972 | Documenta Ophthalmologica, Vol. 31, No. 1 More from this issue > Volume 220Issue 1January 1971Pages 256-263 Copyright & PermissionsCopyright © 1971 by American Physiological Societyhttps://doi.org/10.1152/ajplegacy.1971.220.1.256PubMed5538660History Published online 1 January 1971 Published in print 1 January 1971 Metrics

Lens of the rat eye: an electron microscope and freeze-etch study

The structure of lens fibers has been reinvestigated utilizing electron microscopy and the freeze-etch technique. Interest was focused particularly on the nature of cellular interfaces in relation to the paucity of extracellular space. While cortical fibers exhibit regular, parallel interfaces with frequent and extensive occluded zones, at the equator and in the lens core the interfaces are complicated by extensive interdigitating processes. In the replicas, two dissimilar membrane surfaces result from fracture of an interface, one with a high particle content, and the other with few associated particles. These findings are discussed in relation to current theories concerning the plane of membrane fracture.

Morphogenesis of the eye lens in a mouse strain with hereditary cataracts.

AbstractMice carrying the gene “Shrivelled, ” also known as “Cataract‐Fraser” or “Cataracta hereditaria subcapsularis, ” invariably develop lens opacities which are visible when the animals open their eyes on the fourteenth postnatal day.Lens development in normal and mutant embryos is the same until day 14 of gestation. At this stage the nuclei of the lens fibers in the controls are large and vesicular with prominent nucleoli. In the mutants the centrally located nuclei are smaller and darker with indistinct nucleoli. The nuclei of normal fibers remain large and open even after birth; those in the mutants continue to undergo pyknosis after passing through the equatorial zone in the regular fashion. The nuclear degeneration is followed, with a delay of about 24–48 hours, by swelling and vacuolization of the fibers concerned. In the adult the lens core forms an amorphous eosinophilic mass or may partly be resorbed. The cortical fibers remain normal. Anterior polar cataracts develop: the epithelial cells proliferate to form multiple layers of atypical cells, surrounded by lens capsule‐like material.The fiber degeneration may be caused by precocious cessation of protein synthesis after the cell nucleus becomes defunct. The late epithelial aberrations may be secondary to the changes in the underlying fibers and are possibly related to the reactivation of cell replication in the central part of lens epithelium seen after traum.

Lens-specific antigens and cytodifferentiation in the developing lens

Polycrylamide gel electrophoresis of chicken lens proteins showed 17 crystallins, divided over three groups. Within each group physicochemical heterogeneity was combined with (partial) immunological homogeneity. It is assumed that more than one gene is involved in the synthesis of any crystallin species. During development of the chicken embryo, α-crystallin was first demonstrated by immunofluorescence in centrally located lens fibers at 3 days. At 8 days the epithelium became positive and the fibers lost some fluorescence. This continued until in 5-week-old chickens the lens core was negative. Lens placode cells showed immunofluorescence for δ-crystallin at 52 hours, mainly in their basal parts. The reaction gradually spread and at 3 days the entire lens was positive. From 8 days on the epithelium reacted progressively weaker, but the fibers remained positive. Five weeks after hatching, epithelium and cortex were negative, while the center still showed strong fluorescence. The behavior of β-crystallin was intermediate between that of the other two. Immunoelectrophoresis suggested a differential production onset for the components of each single crystallin type. Under normal conditions no crystallins were found outside the lens. Therefore, crystallin synthesis occurs after placode formation has taken place and must be restricted to the lens itself. Autoradiography after 3H-thymidine treatment indicated that all placode cells still replicate, though some already produce crystallins. A generation time of 8 to 10 hours was determined with an M phase of 30 minutes, an S phase of 6 hours, and a G2 of 2 ½ hours. During DNA synthesis the nuclei were located in the basal parts of the cells, and for mitosis they migrated to the lumen. Autoradiography after 3H-glucosamine application suggested that the placode cells take active part in the synthesis of the basement membrane interposed between lens rudiment and optic cup. This membrane later becomes the lens capsule, and in mice with the “shrivelled” gene, abnormal masses of anterior epithelial cells also clearly produce extra capsule material. This results in anterior polar cataracts. Several of the above findings are in disagreement with some of the current theories on the regulation of lens differentiation. No substitutes are presently offered, however.

Macromolecular events during differentiation of the chicken lens: Paper from the symposium ȁlens proteins and related subjects,ȁ Ghent, Belgium, June, 1967

The synthesis of lens proteins during differentiation of the chicken lens was studied with antisera to adult lens and to fractions isolated by polyacrylamide gel electrophoresis. δ-Crystallin (FISC) was first detected by immunoelectrophoresis at 60 hr. Lens placode cells showed immunofluorescence at 52 hr, mainly in their basal parts. Autoradiography after exposure to [3H]thymidine showed that their nuclei undergo interkinetic migration. During interkinesis they are located in the basal parts of the cells, but for mitosis the cells contract to the lumen. Following division the daughter cells again elongate and the nuclei return to the retinal side. Thus it is not surprising that δ-crystallin first appears here. At 57 hr the reaction had spread throughout the posterior wall, and at 3 days the epithelium was positive. At 8 days the latter reacted progressively weaker but the fibers remained positive. In 5-week-old chicks and in adults the cortex was negative while the center still showed strong fluorescence. α-Crystallin was detectable by immunoelectrophoresis on the fourth day of incubation. It was first demonstrated with immunofluorescence in centrally located lens fibers at 3ȁ3½ days. At 8 days the epithelium became positive and the fibers lost some fluorescence. This continued until in 5-week-old chicks the lens core was negative. The β-crystallins of the adult chicken consist of 8 or 9 immunologically related proteins. At 7 days the first component was seen immunoelectrophoretically. The pattern became more complicated until it was comparable at 17 days of embryonic life with that of the adult. Fluorecence was first observed in 28-somite embryos in the same location as δ-crystallin. At 3½ days the epithelium began to react and at 4 days the complete lens was positive. The reaction disappeared from the nucleus at a faster rate than that for α-crystallin. γ-Crystallins were not found. Fluorescence was never seen outside the lens. We conclude that crystallin synthesis is restricted to the lens itself and first occurs after placode formation has taken place. The most plausible explanation is that lens differentiation is dependent on differential gene activity at the level of the lens cell nuclei.