106 research outputs found
Dynamic light scattering study on phase separation of a protein-water mixture: Application on cold cataract development in the ocular lens
We present a detailed dynamic light scattering study on the phase separation
in the ocular lens emerging during cold cataract development. Cold cataract is
a phase separation effect that proceeds via spinodal decomposition of the lens
cytoplasm with cooling. Intensity auto-correlation functions of the lens
protein content are analyzed with the aid of two methods providing information
on the populations and dynamics of the scattering elements associated with cold
cataract. It is found that the temperature dependence of many measurable
parameters changes appreciably at the characteristic temperature ~16+1 oC which
is associated with the onset of cold cataract. Extending the temperature range
of this work to previously inaccessible regimes, i.e. well below the phase
separation or coexistence curve at Tcc, we have been able to accurately
determine the temperature dependence of the collective and self-diffusion
coefficient of proteins near the spinodal. The analysis showed that the
dynamics of proteins bears some resemblance to the dynamics of structural
glasses where the apparent activation energy for particle diffusion increases
below Tcc indicating a highly cooperative motion. Application of ideas
developed for studying the critical dynamics of binary protein/solvent
mixtures, as well as the use of a modified Arrhenius equation, enabled us to
estimate the spinodal temperature Tsp of the lens nucleus. The applicability of
dynamic light scattering as a non-invasive, early-diagnostic tool for ocular
diseases is also demonstrated in the light of the findings of the present
paper
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Corneal collagen crosslinking in patients treated with dextran versus isotonic hydroxypropyl methylcellulose (HPMC) riboflavin solution: a retrospective analysis
Abstract Background Corneal collagen crosslinking (CXL) is a widely used treatment for halting the progression of keratoconus. Although initial studies of CXL were performed with a riboflavin solution containing dextran, recent protocols for CXL have indicated the use of a riboflavin solution containing isotonic hydroxypropyl methylcellulose (HPMC). This study was performed to investigate differences in visual outcomes and Scheimpflug (Pentacam) analysis in patients who have undergone epithelium-off CXL with riboflavin solution containing either 20% dextran versus 1.1% HPMC. Methods All patients in this non-randomized, non-masked, retrospective cohort analysis were treated at Edward S. Harkness Eye Institute, Columbia University Medical Center, New York, NY, USA. Thirty-seven eyes of 33 patients were crosslinked with a dextran solution and 19 eyes of 19 patients crosslinked with an isotonic HPMC solution, both using an epithelium-off 30-min, 3 mW/cm2 protocol. All patients had a diagnosis of keratoconus or post-refractive surgery ectasia. Best spectacle corrected visual acuity (BSCVA) and Pentacam parameters were compared at all follow up visits (1, 6, 12, and 24 months). Differences between groups treated with HPMC and dextran were compared using student’s t-test. Differences between treated eye and fellow eye were calculated and compared between HPMC and dextran groups using paired t-test. Results Patients treated with a dextran solution had significantly greater improvement in BSCVA at 1, 6, and 24 months (p < 0.05) compared to the isotonic HPMC-treated group. Kmax increased in both groups at 1 month; however, HPMC-treated patients had a greater increase compared to dextran-treated patients (p = 0.01). Kmax decreased in both groups at 6 and 12 months, although this finding was only significant in the HPMC-treated group at 12 months. Conclusions Our data suggest that crosslinking with the dextran solution may result in significantly better visual outcomes (demonstrated by visual acuity) compared to the isotonic HPMC riboflavin solution. Dextran solutions may have other potential advantages intrinsic to its biochemical properties facilitating more efficient crosslinking. Further research and long-term evidence regarding the use of dextran versus HPMC riboflavin solutions in collagen crosslinking is necessary
Aliphatic β-Nitroalcohols for Therapeutic Corneoscleral Cross-linking: Chemical Mechanisms and Higher Order Nitroalcohols
More effective agents have been identified based on an understanding of the chemical mechanisms involved in therapeutic nitroalcohol corneoscleral cross-linking
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