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Dissertations / Theses on the topic 'Lens of the Eye'
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1
Bateman, Orval. "The characterisation of eye lens crystallins." Thesis, Birkbeck (University of London), 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301285.
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Keenan, Jonathan. "Crystallin distribution patterns in the eye lens." Thesis, University of Ulster, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.554261.
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The lens is an ideal tissue to study growth and ageing since it continually grows throughout life accumulating cells with no protein turnover. The lenticular structural proteins, the crystallins, are distributed in layers that follow a chronological pattern. In this thesis, crystallin distribution patterns were investigated in concentric fractions of eye lenses from nine species. Clear lenses were used in order to examine changes occurring with development and ageing without the confounding factor of cataract. For the majority of species studied this was the first study to investigate and identify lens crystallin distributions. Lens proteins were separated using a fractionation technique following the lenticular growth mode. Individual crystallin subunits were further isolated and identified by size-exclusion chromatography, electrophoresis and mass spectrometry. Proportions of HMW, MMW and LMW proteins across each lens were determined by Bradford Assay. a, ~ and y-crystallin subunits were identified in each lens studied with comparable distribution patterns in phylogenetically similar species. a-crystallin proportions decreased from lens periphery to centre in all species and was not detected in the centre of amphibian and fish lenses. y-crystallins represented the most prominent soluble proteins in the lens centre with largest increases from the lens periphery seen in amphibian and fish, corresponding to their high refractive indices. Insoluble protein proportions increased towards the lens centre in all species. Taxon-specific crystallins were not identified in any species studied. Protein distribution patterns affect the optics of the lens; this structure/function relationship is important in understanding lens transparency. Protein distribution patterns in transparent lenses from in this thesis will assist understanding of changes in lenticular biochemistry taking place when transparency is compromised by cataract formation. Results from this thesis will also aid determination of phylogenetic relationships among species studied.
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Hott, John Lester. "Photochemical alterations of ocular lens proteins." Diss., Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/30087.
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Tomlinson, Julie. "Calcium in relation to lens physiology and pathology." Thesis, University of East Anglia, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292537.
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Chen, Wen-Lung. "Raman spectroscopic/imaging studies of eye lenses and lens proteins." Diss., Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/30431.
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Wilson, Cynthia Nicole. "A Fully Customizable Anatomically Correct Model of the Crystalline Lens." Thèse, Université d'Ottawa / University of Ottawa, 2011. http://hdl.handle.net/10393/20130.
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The human eye is a complex optical system comprised of many components. The crystalline lens, an optical component with a gradient index (GRIN), is perhaps the least understood as it is situated inside the eye and as a result is difficult to characterize. Its complex nonlinear structure is not easily measured and consequently not easily modeled. Presently several models of the GRIN structure exist describing the average performance of crystalline lenses. These models, however, do not accurately describe the performance of crystalline lenses on an individual basis and a more accurate individual eye model based on anatomical parameters is needed. This thesis proposes an anatomically correct, individually customizable crystalline lens model. This is an important tool and is needed both for research on the optical properties of human eyes and to diagnose and plan the treatment of optically based visual problems, such as refractive surgery planning. The lens model consisted of an interior GRIN with a constant refractive index core. The anterior and posterior surface was described by conic sections. To realize this eye model, the optical and biometric properties of mammalian lenses were measured and the correlation relationships between these measurements were used to simplify the model down to one fitting parameter which controls the shape of the GRIN. Using this data, an anatomically correct individualizable model of the lens was successfully realized with varying parameters unique to each lens. Using this customizable lens model, customizable human eye models based on measurements of the entire human eye can be realized.
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MacDonald, James Tomomi. "The unfolding and stability of eye lens crystallins." Thesis, Birkbeck (University of London), 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427680.
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Chandler, Heather Lynn. "Epithelial-mesenchymal transition in the anterior segment of the eye." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1154533588.
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Walker, Heather Mhairi. "Investigating the role of the lens in the growth and development of the vertebrate eye." Thesis, University of Aberdeen, 2014. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=225773.
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The eye forms through complex tissue interactions, and it still only partly understood. The developing vertebrate lens however, is crucial for coordinating eye development and eye growth, through releasing signals to surrounding eye structures. It is thought that the lens controls the growth of the eye through the production of the vitreous- the jelly-like substance that fills the main cavity of the eye and maintains the eye in its correct shape. Many components of the vitreous are produced by a region of the peripheral retina known as the ciliary body, and so it is believed that the lens controls eye growth through controlling the development of the ciliary body and thus, indirectly, the vitreous. This project addresses this concept. I have identified a previously unknown functional link between the lens and Vitamin A metabolism. The lens is important for maintaining retinoic acid production within the developing chick eye through controlling the expression of RDH10 in the presumptive ciliary body. RDH10 is important for the first step in retinoic acid synthesis, the conversion of Vitamin A into retinal, which is then converted into retinoic acid. The loss of RDH10 within the presumptive ciliary body is associated with a reduction in expression of other genes known to be involved in ciliary body development, BMP7, WNT2B and OTX1 along with a reduction in the growth of the eye. The reduction in retinoic acid production within the eye as a result of lens removal, in turn affects the synthesis of Collagen IX from the ciliary body, a major component of the vitreous. The data suggests that the lens controls retinoic acid production within the eye, through maintaining gene expression in the developing ciliary body. Retinoic acid signalling controls the synthesis of components of the vitreous, such as Collagen IX. The proper accumulation of the vitreous within the eye is crucial for the correct growth of the chick eye.
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Sparrow, John Martin. "The lens in diabetes." Thesis, University of Oxford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238162.
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Lin, Valentine, and Hamad Tarek Sayed. "3D Printing a Maxwell Fish Eye Lens With Periodic Structures." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-254262.
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With the rise of high frequency communication systems such as 5G, new types of antennas has to be developed in order to meet the new requirements. In recent years, lens antennas made of periodic structures has been shown to have desirable performance when increasing operational frequency without increasing the size of the antennas. One way of manufacturing the lenses for the antennas are with 3D printers loaded with dielectrics with specified permittivity. This project group studied the process of designing and manufacturing a flat Maxwell fish eye lens at 5 GHz with a bandwidth of 3.5 GHz to 6 GHz. The resulting design is a lens based on a periodic configuration of cuboid unit cells made from dielectrics which consisted of a hole. By choosing the ratio of dielectric and holes in the unit cells, each part of the lens could be tuned to achieve a specific effective refractive index required for realising the Maxwell fish eye lens.
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Nichols, Jason Jay. "Evaporative tear film and contact lens factors associated with dry eye symptoms in contact lens wearers." The Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=osu1085771728.
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Banks, Eric A. "Connexin 45.6 in lens development : a dissertation /." San Antonio : UTHSC, 2007. http://proquest.umi.com/pqdweb?did=1400957401&sid=1&Fmt=2&clientId=70986&RQT=309&VName=PQD.
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Nichols, Jason J. "Evaporative tear film and contact lens factors associated with dry eye symptoms in contact lens wearers." Connect to this title online, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1085771728.
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Thesis (Ph. D.)--Ohio State University, 2004.Title from first page of PDF file. Document formatted into pages; contains xiii, 122 p.; also includes graphics Includes bibliographical references (p. 80-94). Available online via OhioLINK's ETD Center
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Slight, S. H. "Biochemical studies on the mammalian lens." Thesis, University of Salford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381703.
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Sousounis, Konstantinos. "Gene Expression During Newt Lens Regeneration and Cephalopod Eye Evolution." University of Dayton / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1405702826.
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Principi, Sara. "Development of methodologies for estimating the dose to the eye lens in interventional radiology : operational implications of the eye lens new dose limit." Doctoral thesis, Universitat Politècnica de Catalunya, 2017. http://hdl.handle.net/10803/620729.
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Recent epidemiological evidences on very late opacities or cataract manifestation, has led to a review of the actual limit for the eye lens (150 mSv/year) for workers exposed to ionizing radiation. ICRP 118 recommends reducing the limit to 20 mSv per year. This drastic change in the dose limit has been incorporated into the revised European and International Basic Safety Standards (European Commission 2013, International Atomic Energy Agency 2014) and it should be implemented in national legislation of member states in 2018. Up to now, eye lens dose is not routinely measured and there are no general international recommendations regarding procedures on how correctly estimate the dose to the eye lens.
The present work provides proposals regarding metrological, dosimetric and radiation protection needs associated to the new limit. At first, a calibration procedure and an easy-to use dosemeter for the eye lens have been set-up to accurately measure eye lens doses in terms of Hp(3) for photon radiation fields. Secondly, a measurement campaign on phantom was performed in order to test several dosimetric systems and to analyze the influence of the position of the eye lens dosemeter. The best position for an accurate assessment of the eye lens dose is to locate the dosemeter as close as possible to the most exposed eye. Measurements at four Spanish hospitals in real clinical conditions were performed in order to evaluate whether the risk of exceeding the new recommended eye lens dose limit of 20 mSv per year is of real concern. 24 physicians and 12 nurses were monitored. Results show that approximately 40% of the monitored physicians and 25 % of monitored nurses would exceed the new limit. The relation between the eye lens equivalent dose Hp(3) and other quantities, easier to measure such as Hp(0.07) with an unprotected whole body dosemeter situated at the chest or the KAP registered in the X-ray console have been investigated. Results highlight that the relation between Hp(3) and Hp(10) or Hp(0:07) measured on the chest or collar with an unprotected whole body dosemeter is more reproducible than the relationship between Hp(3) and KAP, in particular in the case of nurses. Large uncertainties are associated to the estimation of Hp(3) through other quantities (such as KAP or whole body doses). The relationship is dependent on the type of procedure, position of the monitored person and use of protection means. Thus, this methodology is only recommended for monitoring of staff exposed to eye lens doses below 6 mSv or in order to identify which individuals are likely to require regular eye lens monitoring. The recommended correction factor is Hp(3)=0.8Hp(0.07)thorax. For individuals at risk, the use of a dedicated eye lens dosemeter is strongly recommended.
Monte Carlo simulations were carried out in order to analyse the influence of several parameters on eye lens equivalent dose and to provide recommendations on eye lens dose reduction and on the effectiveness of the protective glasses. This thesis proposes simple precautions to reduce the dose, such as the positioning of the monitors away from the X-rays. A rotation of the head of 30º or 45º away from the tube is shown to reduce eye lens dose by approximately 50%, in particular at distances of 20cm and 40cm from the X-ray source. Furthermore, a correction factor of 0.3 for wraparound-style lead glasses and a more conservative value of 0.5 for any design of glasses is recommended. This correction should be applied when an eye lens dosemeter is used on an unprotected region close to the eye, as the measurement of the eye lens equivalent dose does not take into account the protection provided by the glasses. This proposal is in agreement with several published work and with the recommendations from ISO in 2015.
Finally, this thesis highlights the need of training to improve the use of the protection systems, in particular the ceiling shielding during clinical practice.Evidencias epidemiológicas sobre la manifestación precoz de cataratas u opacidades han comportado la revisión del límite anual de dosis equivalente al cristalino (150 mSv /año) para los trabajadores expuestos a la radiación ionizante. ICRP 118 recomienda reducir dicho límite a 20 mSv por año, promediado en un período de 5 años. Este cambio drástico en el límite de dosis se ha incorporado en las Normas básicas de protección radiológica europeas (Comisión Europea, 2014) e internacionales (IAEA, 2013) y deberán ser transpuestas a la legislación nacional de los Estados miembros en 2018. Actualmente, no se lleva a cabo el control dosimétrico de la dosis al cristalino y no se dispone de recomendaciones internacionales consensuadas sobre cómo llevar a cabo dicho control. Esta tesis presenta diversas propuestas para cubrir las nuevas necesidades metrológicas, dosimétricas y de protección radiológica en el ámbito de la cardiología y radiología intervencionista, asociadas al nuevo cambio legislativo. Se ha desarrollado y puesto a punto un procedimiento para la calibración de dosímetros personales de cristalino en unidades de Hp(3). También se ha caracterizado el dosímetro de cristalino UPC-ELD de acuerdo con la norma IEC 32687 (2012) para campos de radiación fotónica. Dicho dosímetro se ha utilizado en una campaña de medidas en maniquí antropomórfico para la validación de diversos sistemas dosimétricos y para analizar la influencia de la posición del dosímetro para la estimación de la medida de la dosis equivalente en cristalino. Se concluye que la posición óptima del dosímetro de cristalino, es sobre la oreja, en el lado correspondiente al ojo más expuesto, habitualmente el izquierdo. Se efectuaron mediciones en cuatro hospitales españoles utilizando el dosímetro UPC-ELD. Participaron 24 facultativos y 12 enfermeras. Los resultados muestran que aproximadamente el 40% de los médicos y el 25% de las enfermeras superarían el nuevo límite. Paralelamente se ha investigado la relación entre Hp (3) y otras magnitudes como Hp (0,07) determinado con un dosímetro de cuerpo entero situado a nivel de tórax encima del delantal plomado o el KAP registrado en la consola de rayos X. Los resultados ponen de manifiesto que la relación entre Hp (3) y Hp (10) o Hp (0:07), medidas en el tórax, es más reproducible que la relación entre Hp (3) y KAP, en particular en el caso de las enfermeras. La determinación indirecta de la dosis en cristalino presenta importantes incertidumbres puesto que la relación entre las distintas magnitudes depende del tipo de procedimiento, de la posición de la persona y del uso de los sistemas de protección. Por ello, esta metodología sólo se recomienda para la vigilancia individual, si es muy poco probable que la dosis equivalente anual en el cristalino supere 6 mSv, o bien si el objetivo consiste en identificar los puestos de trabajo que pueden requerir un control dosimétrico sistemático. El factor de corrección recomendado para estimar Hp (3) es: Hp (3)= 0.8Hp (0.07) tórax. Cuando no es improbable superar 6 mSv, se recomienda el uso de un dosimetro específico para el cristalino. Mediante simulaciones Monte Carlo se analiza la influencia de varios parámetros en la dosis equivalente en cristalino y se determina la atenuación de distintos tipos de gafas protectoras. En base a los resultados de las simulaciones se propone situar los monitores alejados del haz de rayos X y girar la cabeza de 30º a 45º en dirección opuesta al tubo de RX, dicha posición reduce la dosis en cristalino aproximadamente el 50%, en particular a distancias de 20 cm y 40 cm de la fuente de rayos X. Además, se ha determinado un factor de corrección igual a 0,3 para las gafas de plomo de estilo envolvente y un valor más conservador de 0,5 para otros diseños menos ajustados. Por último, esta tesis subraya la necesidad de mejorar la formación sobre el correcto uso de los sistemas
18
Li, Dongyun. "The effect of UV-laser radiation on lenses and lens proteins." Thesis, Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/27271.
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McClure, Kate Alexandra. "Tear Film Dynamics Associated with Contact Lens Wear." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1523579680091666.
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Bergbauer, Katrina L. "Laser raman spectroscopic studies of ocular lens aging and cataractogenesis." Diss., Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/30031.
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Poey, S. M. "Infrared thermography of the anterior eye during contact lens wear." Thesis, University of Manchester, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.494480.
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Evans, Paul James. "Circular dichroism spectroscopy studies of the eye lens crystallin proteins." Thesis, Birkbeck (University of London), 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437767.
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Circular dichroism spectroscopy is an established technique that is frequently used in the analysis of the confonnation of biological molecules. It has previously been reported that the deconvolution of circular dichroism spectra of vertebrate eye lens P'rcrystallin proteins gives exceptionally poor results, and that these spectra are heavily influenced by aromatic contributions in the far-ultraviolet. This thesis describes work undertaken to assess to what extent circular dichroism spectra of py-crystallins can be rationalised in tenus of secondary structure, and to determine if circular dichroism can be applied to investigations of the role of crystallin proteins in congenital and agerelated cataract. It Was found that in most py-crystallin spectra, aromatic interference is minor, and that the reported poor quality of py-crystallin deconvolution reflects inherent diffiCulties in deconvolution for most non-helical secondary structures. An instance of aromatic contributions to the far .. ultraviolet spectrum was identified, and investigated through mutagenesis. Synchrotron radiation circular dichroism was used in conjunction with other solution techniques to demonstrate that a loss in solubility of the folded P23T mutation of human yD .. crystallin is responsible for the congenital cataracts associated with this mutation. Finally, circular dichroism was used to investigate the stability and aggregation mechanisms of human fJB2-crystallin, and an assay method developed to show the interaction of fJB2-crystallin with the a.-crystallin molecular chaperone. Information from these experiments was used to describe the unfolding and subsequent aggregation and. chaperone-association of human PB2-crystallin.
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Maksimovic, Srdjan. "Unusual eye design: The compound-lens eyes of Strepsiptera and the scanning eyes of Sunburst Diving Beetle larvae." University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1285687000.
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Wei, Kang. "Bio-inspired Reconfigurable Elastomer-liquid Lens: Design, Actuation and Optimization." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429657034.
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Srikanthan, Durga. "Structural studies of small heat shock proteins and eye lens crystallins." Thesis, Birkbeck (University of London), 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414501.
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Najmudin, Shabir. "A structural analysis of eye lens proteins : refinement of yB crystallin." Thesis, Birkbeck (University of London), 1993. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.740998.
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Hook, Darren W. A. "Protection of enzymes by the molecular chaperone #alpha#-Crystalline." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300133.
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Miranda, Marco A. L. A. E. "Structural and Optical Changes in the Eye with Soft Contact Lens Wear." Thesis, University of Manchester, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.532229.
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Hennelly, Michelle Louise. "The light scattering characteristics of the normal and contact lens-wearing eye." Thesis, City University London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367322.
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Kivlan, Anna Karrer. "An eye for vulgarity : how MoMA saw color through Wild Bill's lens." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/39314.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Architecture, 2007.Includes bibliographical references (p. 67-71).
This thesis is an examination of the 1976 Museum of Modern Art exhibition of color photographs by William Eggleston-the second one-man show of color photography in the museum's history- with particular attention to the exhibition monograph, William Eggleston's Guide. From hundreds of slides, MoMA Director of Photography John Szarkowski dominated the process of selecting the 75 images for the exhibition and 48 to be carefully packaged in the Guide, a faux family photo album/road trip guidebook. It is my contention that, despite their verbal emphasis on the Modernist and universal (rather than Southern) nature of the images, the photographs can be read as being replete with the mythology of the Old South- its decay, vulgarity, and even horror. Through this act of manipulation, the images in the Guide appealed in a voyeuristic way to an elite Northern art world audience, ever eager to reinforce its own intellectual, economic, and ethical superiority over other parts of the country. Due to its presumed "vulgarity" and absence of aesthetic mystique at the time, color photography required for its inaugural moment at the museum a sharp distancing from the documentary tradition and advertising-the complete erasure of social context afforded by a Modernist aesthetic.
(cont.) The two-faced posture maintained by the curator and photographer combined a canny understanding of the cultural power of the images with an overtly Modernist disavowal of it.
by Anna Karrer Kivlan.
S.M.
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Best, Nigel. "The predictive ability of clinical tests for contact lens induced dry eye." Thesis, Aston University, 2013. http://publications.aston.ac.uk/19599/.
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Approximately half of current contact lens wearers suffer from dryness and discomfort, particularly towards the end of the day. Contact lens practitioners have a number of dry eye tests available to help them to predict which of their patients may be at risk of contact lens drop out and advise them accordingly. This thesis set out to rationalize them to see if any are of more diagnostic significance than others. This doctorate has found: (1) The Keratograph, a device which permits an automated, examiner independent technique for measuring non invasive tear break up time (NITBUT) measured NITBUT consistently shorter than measurements recorded with the Tearscope. When measuring central corneal curvature the spherical equivalent power of the cornea was measured as being significantly flatter than with a validated automated keratometer. (2) Non-invasive and invasive tear break-up times significantly correlated to each other, but not the other tear metrics. Symptomology, assessed using the OSDI questionnaire, correlated more with those tests indicating possible damage to the ocular surface (including LWE, LIPCOF and conjunctival staining) than with tests of either tear volume or stability. Cluster analysis showed some statistically significant groups of patients with different sign and symptom profiles. The largest cluster demonstrated poor tear quality with both non-invasive and invasive tests, low tear volume and more symptoms. (3) Care should be taken in fitting patients new to contact lenses if they have a NITBUT less than 10s or an OSDI comfort rating greater than 4.2 as they are more likely to drop-out within the first 6 months. Cluster analysis was not found to be beneficial in predicting which patients will succeed with lenses and which will not. A combination of the OSDI questionnaire and a NITBUT measurement was most useful both in diagnosing dry eye and in predicting contact lens drop out.
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Barron, Brent Christian. "Characterization of normal aging and cataractous processes in the eye lens by laser raman spectroscopy." Diss., Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/30052.
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Derham, Barry K. "The effects of ageing on #alpha#-crystallin, a molecular chaperone." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325297.
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Mizdrak, Jasminka. "Human lens chemistry: UV filters and age-related nuclear cataract." Australia : Macquarie University, 2007. http://hdl.handle.net/1959.14/16855.
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"A thesis submitted in partial fulfillment of the requirements for the award of the degree of Doctor of Philosophy".Thesis (PhD) -- Macquarie University, Division of Environmental and Life Sciences, Dept. of Chemistry and Biomolecular Sciences, 2007.
Bibliography: p. 243-277.
Introduction -- A convenient synthesis of 30HKG -- Facile synthesis of the UV filter compounds 30HKyn and AHBG -- Synthesis, identification and quantification of novel human lens metabolites -- Modification of bovine lens protein with UV filters and related metabolites -- Effect of UV light on UV filter-treated lens proteins -- Conclusions and future directions.
The kynurenine-based UV filters are unstable under physiological conditions and undergo side chain deamination, resulting in α,β-unsaturated carbonyl compounds. These compounds can react with free or protein bound nucleophiles in the lens via Michael addition. The key sites of the UV filters kynurenine (Kyn) and 3-hydroxykynurenine (3OHKyn) modification in human lenses include cysteine (Cys), and to a lesser extent, lysine (Lys) and histidine (His) residues. Recent in vivo studies have revealed that 3-hydroxykynurenine-O-β-D-glucoside (3OHKG) binds to Cys residues of lens crystallins in older normal human lenses. As a result of this binding, human lens proteins become progressively modified by UV filters in an age-dependent manner, contributing to changes that occur with the development of age-related nuclear (ARN) cataract. Upon exposure to UV light, free UV filters are poor photosensitisers, however the role of protein-bound species is less clear. It has been recently demonstrated that Kyn, when bound to lens proteins, becomes more susceptible to photo-oxidation by UV light. Therefore, the investigation of 3OHKG binding to lens proteins, and the effect of UV light on proteins modified with 3OHKG and 3OHKyn, were major aims of this study. As a result of the role of these compounds as UV filters and their possible involvement in ARN cataract formation, it is crucial to understand the nature, concentration and modes of action of the UV filters and their metabolites present in the human lenses. Therefore, an additional aim was to investigate human lenses for the presence of novel kynurenine-based human lens metabolites and examine their reactivity.--As 3OHKG is not commercially available, to conduct protein binding studies, an initial aim of this study was to synthesise 3OHKG (Chapter 2). Through the expansion and optimisation of a literature procedure, 3OHKG was successfully synthesised using commercially available and inexpensive reagents, and applying green chemistry principles, where toxic and corrosive reagents were replaced with benign reagents and solvent-free and microwave chemistry was used. A detailed investigation of different reaction conditions was also conducted, resulting in either the improvement of reaction yields or reaction time compared to the literature method. Applying the same synthetic strategy, and using key precursors from the synthesis of 3OHKG, the UV filters 3OHKyn and 4-(2-amino-3-hydroxyphenyl)-4-oxobutanoic acid-O-β-D-glucoside (AHBG), were also successfully synthesised (Chapter 3).
Chapter 4 describes the investigation of both normal and cataractous human lenses in an attempt to identify novel human lens metabolites derived from deaminated Kyn and 3OHKyn (Chapter 4, Part A). Initially, 4-(2-aminophenyl)-4-oxobutanoic acid (AHA), glutathionyl-kynurenine (GSH-Kyn), kynurenine yellow (Kyn yellow), 4-(2-amino-3-hydroxyphenyl)-4-oxobutanoic acid (AHB), glutathionyl-3-hydroxykynurenine (GSH-3OHKyn) and 3-hydroxykynurenine yellow (3OHKyn yellow) were synthesised and human lenses were examined for their presence. AHA and AHB were synthesised from similar precursors to those used in the synthesis of 3OHKG, while the GSH adducts and yellow compounds were synthesised from Kyn and 3OHKyn via base induced deamination. Following isolation and structural elucidation, AHA, AHB and GSH-Kyn were confirmed as novel human lens metabolites. They were quantified in low pmol/mg lens (dry mass) levels in normal and cataractous lenses of all ages, while GSH-3OHKyn, Kyn yellow and 3OHKyn yellow were not detected. In contrast to AHA, the lens metabolites AHB, GSH-Kyn and GSH-3OHKyn were found to be unstable at physiological pH. The spectral properties of these compounds suggest that they may act as UV filters. --Chapter 4 (Part B) also describes the identification and characterisation of a novel human lens UV filter, cysteinyl-3-hydroxykynurenine -O-β-D-glucoside (Cys-3OHKG). An authentic standard was synthesised via Michael addition of cysteine to deaminated 3OHKG. Cys-3OHKG was detected in low pmol/mg lens (dry mass) levels in normal lenses only after the 5th decade of life and was absent in cataractous lenses. Cys-3OHKG showed rapid decomposition at physiological pH.
Chapter 5 describes the identification and quantification of amino acids involved in covalent binding of 3OHKG to lens proteins. Model studies with bovine lens proteins and 3OHKG at pH 7.2 and 9.5 were undertaken. The amino acid adducts were identified via total synthesis and spectral analysis, and subsequently quantified upon acid hydrolysis of the modified lens proteins. Under both pH conditions, 3OHKG was found to react with lens proteins predominantly via Cys residues with low levels of binding also detected at Lys residues. Comparative studies with Kyn (pH 9.5) and 3OHKyn (pH 7.2 and 9.5) resulted in modified lens proteins at Cys residues, with only minor modification at Lys residues at pH 9.5. The extent of modification was found to be significantly higher at pH 9.5 in all cases. His adducts were not identified. 3OHKG-, Kyn- and 3OHKyn-modified lens proteins were found to be coloured and fluorescent, resembling those of aged and ARN cataractous lenses. In contrast, AHB and AHA, which can not form α,β-unsaturated carbonyl compounds, resulted in non-covalent modification of lens proteins. AHB may contribute to lens colouration and fluorescence as further reactions of this material yielded species that have similar characteristics to those identified from 3OHKyn modification. These species are postulated to arise via auto-oxidation of the o-aminophenol moiety present in both 3OHKyn and AHB.--In Chapter 6, the potential roles of 3OHKG and 3OHKyn, and the related species AHA and AHB, in generating reactive oxygen species and protein damage following illumination with UV light was examined. The UV filter compounds were examined in both their free and protein-bound forms. Kyn-modified proteins were used as a positive control. Exposure of these compounds to UV light (λ 305-385 nm) has been shown to generate H2O2 and protein-bound peroxides in a time-dependent manner, with shorter wavelengths generating more peroxides. The yields of peroxides were observed to be highly dependent on the nature of the UV filter compound and whether these species were free or protein bound, with much higher levels being detected with the bound species. Thus, protein-bound 3OHKyn yielded higher levels of peroxide than 3OHKG, with these levels, in turn, higher than for the free UV filter compounds. AHB-treated lens proteins resulted in formation of low but statistically significant levels of peroxides, while AHA-treated lens proteins resulted in insignificant peroxide formation. The consequences of these photochemical reactions have been examined by quantifying protein-bound tyrosine oxidation products (3,4-dihydroxyphenylalanine [DOPA], di-tyrosine [di-Tyr]) and protein cross-linking. 3OHKG-modified proteins gave elevated levels of di-Tyr, but not DOPA, whereas 3OHKyn-modified protein gave the inverse. DOPA formation was observed to be independent of illumination and most likely arose via o-aminophenol auto-oxidation. AHB- and AHA-treated lens proteins resulted in statistically insignificant di-Tyr formation, while a light independent increase in DOPA was observed for both samples. Both reducible (disulfide) and non-reducible cross-links were detected in modified proteins following illumination. These linkages were present at lower levels in modified, but non-illuminated proteins, and absent from unmodified protein samples.
This work has provided an optimised synthetic procedure for 3OHKG and other lens metabolites (Chapters 2 and 3). Four novel lens metabolites have been identified and quantified in normal and cataractous human lenses (Chapter 4). Subsequent experiments, described in Chapter 5, identified the major covalent binding sites of 3OHKG to lens proteins, while AHA and AHB showed non-covalent binding. Further work described in Chapter 6 showed that protein-bound 3OHKG, Kyn and 3OHKyn were better photosensitisers of oxidative damage than in their unbound state. Together, this research has provided strong evidence that post-translational modifications of lens proteins by kynurenine-based metabolites and their interaction with UV light appear, at least in part, responsible for the age-dependent colouration of human lenses and an elevated level of oxidative stress in older lenses. These processes may contribute to the progression of ARN cataract.
Mode of access: World Wide Web.
xxxix, 308 p. ill. (some col.)
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Pult, Heiko. "The predictive ability of clinical tests for dry eye in contact lens wear." Thesis, Cardiff University, 2008. http://orca.cf.ac.uk/54731/.
Full textAbstract:
Thirty to fifty percent of contact lens wearers discontinue contact lens wear. Therefore it is essential for the clinician to have a predictive method that can forecast the development of dryness symptoms in contact lens wear. Contact lens wear induces tear film instability leading to increased tear film evaporation and its associated hyperosmolarity. This in turn causes ocular surface inflammation resulting in the release of cytokines, impacting tear mucin production, which further destabilises the tear film. Since this mechanism can only be fully evaluated by an intensive laboratory-based approach, the clinician must rely on assessing those factors easily accessible within the practice situation: tear film stability and mucin loss/epithelial damage. These two factors are inter-related, and investigating one also provides information about the other. For this PhD, these two components of the mechanism have been investigated. This PhD has found that: (1) Bulbar and limbal redness are inter-related using the CCLRU grading scales, a limbal redness grade above 2.5 or a bulbar redness grade above 3.0 may be considered abnormal. (2) Symptomatic, experienced soft contact lens wearers exhibit significantly more lid wiper epitheliopathy (LWE) and lid parallel conjunctival folds (LIPCOF) but not corneal staining, bulbar hyperaemia or decreased Pre-lens break up time (PLBUT). LWE and LIPCOF are significantly correlated, suggesting that both are related to mechanical forces during blinking caused by a deficiency of the mucin layer. (3) LIPCOF and LWE are also positively correlated with symptoms amongst non-contact lens wearers. Using these two tests as a surrogate, the clinician has, for the first time, a useful indication of the mucin layer in contact lens patients. Returning then to the fundamental question—"Can the development of dryness symptoms in soft contact lens wearers be predicted?" This PhD has found that the clinician can use a combination of currently available tests to meet this question. The optimum combination of tests was found to be LIPCOF Sum plus NIBUT plus OSDI, termed the P-Test. The P-Test shows outstanding potential as a discriminator and predictor of contact lens induced dry eye.
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Sandilands, Aileen. "Characterisation of the intermediate filament proteins filensin and CP49 within the eye lens." Thesis, University of Dundee, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441633.
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Oppermann, Brian P. "Identification, localization and metal catalyzed induction of specific metallothionein isoforms expressed by the adult human lens." Morgantown, W. Va. : [West Virginia University Libraries], 2001. http://etd.wvu.edu/templates/showETD.cfm?recnum=1846.
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Thesis (M.S.)--West Virginia University, 2001.Title from document title page. Document formatted into pages; contains vi, 43 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 37-43).
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Hager, Michele LynnManeca. "A Study of Contact Lens Comfort in Patients Wearing Comfilcon A Soft Contact Lenses Compared to Their Habitual Soft Contact Lenses." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1243711014.
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Schultz, Kristin E. "Accommodative microfluctuations, crystalline lens tension, ciliary body thickness, and refractive error in children." Columbus, Ohio : Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1240445960.
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Dube, Zack. "Computational Reconstruction of the Physical Eye Using a New Gradient Index of Refraction Model." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34791.
Full textAbstract:
This thesis proposes and tests an individually customizable model of the human crystalline lens. This model will be crucial in developing both research on the human eye and driving diagnostic tools to help plan and treat optical issues, such as those requiring refractive surgery.
This thesis attempts to meet two goals: first, it will determine whether this new lens model can reproduce the major aberrations of real human eyes using a computational framework. Second, it will use clinical information to measure how well this model is able to predict post-operation results in refractive surgery, attempting to meet clinical standards of error.
The model of the crystalline lens proposed within this thesis is shown to be valid, as it is able to both reproduce individual patient's optical information, and correctly predicts the optical results of a refractive surgery of an individual human eye within clinical standards of error.
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Rueff, Erin. "Contact lens induced dry eye and binocular vision disorders: A study of similar symptoms." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1397167126.
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Ramamoorthy, Padmapriya. "HIGH MOLECULAR WEIGHT TEAR PROTEINS AND OCULAR SURFACE MUCINS IN CONTACT LENS-RELATED DRY EYE." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1316523981.
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Parker, Nicole Renee. "The role of kynurenine and UV light in lens protein modification." Access electronically, 2005. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20060720.111305/index.html.
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Thesis (Ph.D.)--University of Wollongong, 2005.Typescript. EMBARGOED - This thesis is subject to a 12 month embargo (07/03/06 to 07/03/07) and may only be viewed and copied with the permission of the author. For further information please Contact the Archivist. Includes bibliographical references: leaf 236-266.
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Arnberg, Philip, and Petersson Oscar Barreira. "Design of a Maxwell Fish-Eye Lens in PCB Technology With a Glide-Symmetric Metasurface." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-254263.
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The aim of this project is to design a cost-effective planar Maxwell fish-eye lens in PCB technology operating at the center frequency 5 GHz with a bandwidth of 20 %. An approach to design a cost-effective lens is to use a metasurface, which is commonly realized as a periodic structure of unit cells. In this project, a study was made by comparing different unit cells and considering the effect of applying glide symmetry to the unit cells. Comparing different unit cells withand without glide symmetry demonstrates that glide symmetry is necessary to achieve a 20 % bandwidth. Introducing glide symmetry showed a reduction in dispersive behavior, an increaseof isotropy and effective refractive index. Simulations of the full lens show a functioning lens with a power transfer of 67 % at 5.46 GHz. In conclusion, glide symmetry will improve the performance of the lens and is necessary to fulfill the requirement of a 20 % bandwidth.
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Colom, diego Adai. "From eye lens cells to lens membrane proteins : Development and application of a hybrid high-speed atomic force microscopy/optical microscopy setup." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4033.
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Je utilise le AFM et le HS-AFM pour étudier les caractéristiques mécaniques du cellule du cristallin et aussi des protéines de membrane de la cellule, AQP0 et Connexon. L’énergie d'interaction de la AQP0 est -2.7 kBT, très nécessaire pour former les microdomaines de jonctions (junctional microdomain). Aussi c' est la première fois qu il est possible de voir des protéines individuel et son mouvement en cellules vivants. La formation de microdomaines est important pour la transparence du cristallin, et le AQP1 ne le peux faireI used the AFM and HS-AFM for characterise the eye lens and the eye lens membrane protein, AQP0 and connexon.A QP0-AQP0 interaction energy is -2.7kBT, it is important for the formation of junctional microdomains, which keep the distance between the cells lens and lens transparency. this is the first report which is present time the visualization of unlabelled membrane proteins on living cells under physiological conditions. AQP1 can not maintain the lens transparency because it does not form junctional microdomains
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Yao, Jianchao, and 姚劍超. "Predicting the 3D structure of human aquaporin-0 protein in eye lens using computational tools." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B2948540X.
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Flaugh, Shannon L. "Folding, stability and aggregation of the long-lived eye lens protein human gamma D crystallin." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/34572.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Biology, 2006.Vita.
Includes bibliographical references (p. 179-194).
Human [gamma]D crystallin (H[gamma]D-Crys) is a monomeric, two domain, primarily P-sheet protein found in high concentrations in the human eye lens. H[gamma]D-Crys and other crystallins are found in insoluble protein inclusions associated with the eye disease cataract. H[gamma]D-Crys is expressed in utero and does not regenerate during life, thus necessitating high stability and solubility. Covalent damage, including glutamine deamidation, of the lens crystallins increases with age and as a result of exposure to environmental insults. Such covalent damage may cause partial-unfolding into aggregation-prone confomations that cause cataract. The in vitro stability of H[gamma]D-Crys was analyzed in the denaturant guanidine h[gamma]Drochloride at pH 7.0 and 370C. An off-pathway aggregation reaction that competed with refolding was previously reported when H[gamma]D-Crys was refolded to less than 1 M GuHC1. Equilibrium transitions of H[gamma]D-Crys were best fit to a three-state model suggesting the presence of a partially-folded intermediate that likely had a structured C-terminal domain (C-td) and unstructured N-terminal domain (N-td). Similarly, previous analyses revealed a sequential domain refolding pathway where the C-td refolds first followed by the N-td.
(cont.) These findings suggest that the inter-domain interface of H[gamma]D-Crys is important in both folding and stability. The domain interface of H[gamma]D-Crys contains a central h[gamma]Drophobic cluster of six residues and two pairs of peripheral interacting residues. To test this importance of these residues in folding and stability, site-directed alanine mutants were constructed at all ten positions and properties of the mutant proteins were analyzed. Single mutations of h[gamma]Drophobic domain interface residues caused a decrease in stability of the N-td, but did not affect stability of the C-td. Similarly, stability of the N-td but not the C-td was reduced as a result of single and double mutations of peripheral interface residues. Minimal to no interaction energy was observed for the peripheral residues suggesting they contribute to stability indirectly, perhaps by shielding the central h[gamma]Drophobic cluster from solvent. Both the h[gamma]Drophobic and peripheral domain interface alanine mutants also had reduced rates of productive refolding for the N-td while refolding rates for the C-td were unchanged. These results suggest a productive folding pathway where the C-td refolds first and domain interface residues of the structured C-td act as a nucleating center for refolding of the N-td.
(cont.) Effects on N-td refolding rates were most prominent for the h[gamma]Drophobic residues indicating the importance of proper h[gamma]Drophobic burial during refolding. The peripheral domain interface residues of H[gamma]D-Crys include a pair of two glutamines that are targets for covalent damage during aging. Deamidation mimics at these sites were constructed by site directed mutagenesis of glutamine to glutamate. Properties of the mutants were analyzed to assess the affects of deamidation on stability and folding. Similar to the alanine mutants at these sites, the deamidation mutants had a destabilized N-td but not C-td at pH 7.0. In contrast, stabilities of the mutants were indistinguishable from wild type at pH 3.0. The N-td of the deamidation mutants also unfolded faster than that of wild type during kinetic unfolding. These results indicate that deamidation of domain interface glutamines destabilizes H[gamma]D-Crys and lowers the kinetic barrier to unfolding. A reduction in the thermodynamic and kinetic stability as a result of domain interface deamidation could result in the population of partially-unfolded conformations in the lens that may aggregate through mechanisms such as domain swapping or loop-sheet insertion.
by Shannon L. Flaugh.
Ph.D.
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Mills-Henry, Ishara Amenti Rakem. "Stability, unfolding, and aggregation of the gamma D and gamma S human eye lens crystallins." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/38627.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Biology, 2007.Includes bibliographical references (v. 2, leaves 189-208).
The transparency of the human eye lens depends on the properties of the a- crystallin and py-crystallin families of proteins, which accumulate to very high concentrations in mature lens fiber cells. The 0- and y-crystallins are thought to be primarily structural proteins while a-crystallin possess an additional chaperone activity. Aggregation of partially unfolded or covalently damaged forms of these proteins results in cataract, which is the leading cause of blindness in the world. The biochemical basis of the very high crystallin stability, and the nature of the misfolded, modified, or aggregated states, are thus of considerable importance in understanding the etiology of loss of lens transparency. All vertebrate P- and y-crystallins are homologous and contain two highly symmetrical domains with a hydrophobic interface connected by an interdomain linker. The overall sequences, fold topology, and domain interfaces of vertebrate py-crystallins are highly conserved. The two domain 0- and y-crystallins are believed to have evolved by gene duplication and fusion from an ancestral single domain py-crystallin. This thesis is focused on stability and aggregation properties of human yD crystallin (yDwT) and human yS crystallin (ySwT), two of the most abundant proteins in the human lens.
(cont.) Terminally differentiated fiber cells in the central nucleus of the lens are enucleated and devoid of organelles. The yD crystallins synthesized in utero must remain stable and soluble throughout life. The yS protein is more prevalent in the cortical regions of the lens, where protein degradation and synthesis do occur. Given the importance of long-term solubility for the crystallins, it seems likely that selection for the two-domain form is related to the need for very long-term stability. Comparison of the stabilities of the isolated domains and the intact protein indicated that the domain interface contributes a AGH20 of~ 4.2 kcal*mol-l to the stability of the complete yDwT two-domain protein. The differential stability observed for the yD isolated domains was not as distinct for the yS isolated domains. These results support the idea that selection for increased thermal stability was one of the factors leading to the evolution of two domain crystallins. A distinct hysteresis occurs during equilibrium unfolding and refolding, due to a kinetic barrier in the unfolding pathway. By extrapolating kinetic unfolding results from denaturing GuHCl concentrations to buffer, I show that the ti2 for the initial unfolding step is -19 years. The value extrapolated for the YSwT is not as long, though still significant. This supports the earlier conclusion that the domain interface is an important source of stability.
(cont.) Previous studies had shown that upon dilution from denaturant partially folded intermediates of yD crystallin formed highly ordered fibrous aggregates that were not amyloid in nature. This aggregation reaction of yDwT polypeptide chains competing with productive refolding provided a model for cataractogenesis in vitro. The structurally homologous ySwT crystallin did not exhibit an off-pathway aggregation under the same conditions as yDwT. This suggested that the pathway of aggregation involved specific amino acids or sequences essential for association and was not a general feature of the y- crystallins. To investigate this disparity between two structurally similar crystallins, chimera proteins were created in an attempt to narrow down regions of the protein that promoted aggregation in DwTr or regions in ySwT that inhibited aggregation. The aggregation behavior upon refolding was analyzed for the chimeras and isolated single domains. Partitioning of refolding chains into the aggregation pathway was strongest for the full-length proteins that retained the yD interface. This result is consistent with a domain swapping mechanism for the off-pathway aggregation of the crystallins. This aggregation reaction may be coupled to the increased stability of the yD-protein, as a kind of evolutionary cost of the extremely stable and long-lived native state conformation.
by Ishara Amenti Rakem Mills-Henry.
Ph.D.
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Bailey, Sheldon T. "Transparent Tissues and Porous Thin Films: A Brillouin Light Scattering Study." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1357248652.
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Day, Kevin Douglas. "The mechanics of a hydrogel contact lens on the human eye with a lubricating tear layer." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/43596.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1997.Includes bibliographical references (p. 113-114).
The mechanics governing the fit of a soft contact lens on the eye are examined through the development of a finite element analysis model. A linearly elastic lens is placed on a rigid eye with a lubricating viscoelastic tear layer. The mechanics of fit are described in terms of the pressure distribution through the tear layer, the contact pressure at the lens/tear interface, the tear film thickness, and the bending and membrane stresses in the contact lens itself. A parametric study is performed to investigate the impact of model assumptions of initial tear film thickness, tear film material properties, and eye geometries on the results predicted by the numerical simulations. Further study is performed to investigate the impact of certain geometric lens parameters and how variations in lens thickness, sagittal height, bevel curve design, and back surface design affect the mechanics of the contact lens. A three dimensional model is also developed to investigate mobility and stability issues. The strain energy is monitored as the lens is moved across the eye as it would move during a blink of the eye. Mobility is measured both through the total strain energy present in the lens and the strain energy gradient near the equilibrium position of the lens as a function of displacement on the eye. In addition to strain energy values, the force required to move the lens across the surface of the eye is monitored. The long term goal of this work is to develop a numerical tool to assist in the design and development of new lens geometries for better fit and mobility of soft contact lenses.
by Kevin Douglas Day.
S.M.