1,721,001 research outputs found
Application of (lamellar) keratoplasty and limbal stem cell transplantation for corneal clouding in the mucopolysaccharidoses - a review
No full textCorneal clouding or opacification is a prominent feature of mucopolysaccharidosis (MPS), particularly in MPS I and VI. In patients with marked corneal clouding and visual impairment, penetrating keratoplasty may be considered to improve the patient's vision, functional capacity and quality of life. In MPS, glycosaminoglycans mainly accumulate in the corneal stroma and not in Descemet's membrane or the endothelium, therefore deep anterior lamellar keratoplasty (DALK) may be preferred in these patients over penetrating keratoplasty. Although there are only limited data on the use of DALK in MPS (I and VI) patients, the results are generally favourable. Nonetheless, when deciding on whether to perform keratoplasty in patients with MPS, the risk of general anaesthesia due to potential concomitant cardio-pulmonary problems and cervical spine instability, the potential presence of other ocular manifestations that also impair vision (e.g. glaucoma, retinal degeneration and optic atrophy) and/or complications such as allograft rejection and the risk of re-opacification of the graft, all need to be taken into consideration. Limbal stem cell transplantation, which can be combined with keratoplasty, also holds potential promise in the treatment of these complex cases. A review of the indications, local and systemic risks, techniques of lamellar and penetrating keratoplasty, and the potential of limbal stem cell transplantation is provided in the context of corneal opacity in MPS
Correlation of central and peripheral keratometric parameters after corneal collagen cross-linking in keratoconus patients
No full textPurpose: To evaluate the difference in the central and peripheral keratometric parameters in patients with keratoconus after corneal collagen cross-linking (CXL). Methods: Forty-eight eyes of 32 patients (18 males, 16–28 years) affected by progressive keratoconus in different stages of evolution underwent CXL using the standard epithelium-off protocol. Corneal thickness and corneal curvature before CXL and after 6 and 12 months using the Sirius tomographer were analyzed. The values of the mean corneal thickness at the corneal apex (CAT), center of the pupil (PCT), thinnest point (CTTL) and along concentric circles of 2, 4, 6, 8, 8.5, 9, 9.5 and 10 mm diameter were evaluated; the values of the mean curvature at the corneal apex and at the points in which the inferior, superior, nasal and temporal meridians crossed the above-mentioned concentric circles were also evaluated. Results: The mean preoperative values for CAT, PCT and CTTL were 461.4 ± 30.3, 475.3 ± 30.5 and 441 ± 32.0, respectively. The values after 12 months of CXL were 444.6 ± 36.2, 451.6 ± 36.7 and 418.2 ± 41.4. The peripheral corneal thickness at the eight points ranged from 479 to 733 preoperatively. At 12-month post-CXL, the values ranged from 444.6 to 734.1. The mean posterior curvature from apex to periphery ranged from − 4.5 to − 9.1 days preoperatively and from − 4.5 to − 9.2 days at 12 months. These were not statistically significant (ANOVA and unpaired T test). Conclusions: Our data suggest that CXL over an 8-mm zone can stabilize the peripheral cornea. Longer-term follow-up studies on the peripheral cornea after CXL will provide useful information
Human Keratocytes from the Limbus and Cornea Both Express Epithelial Cytokeratin 3: Possible Mesenchymal-Epithelial Transition.
No full textBackground: The corneal limbus is the repository of epithelial stem cells (SC) that sustain the turnover of corneal epithelial cells. The limbus stroma contains mesenchymal SC that generates stromal keratocytes. Mesenchymal-epithelial transition is a phenomenon wherein cells of mesenchymal phenotype can transdifferentiate to epithelial phenotype. Our aim was to study whether limbal keratocytes, cytokeratin 3 (CK3) negative, could be induced to transdifferentiate into CK3 positive cells.
Methods: Human keratocytes were isolated from the limbus and cornea of cadaver donors, cultured and evaluated for CD34, CK3 and vimentin expression by immunofluorescence and RT-PCR and for keratocan by RT-PCR.
Results: All cells regardless of site expressed vimentin and some also expressed CD34 and CK3. Double immunofluorescence revealed three subpopulations: CK3−/CD34+, CK3+/CD34+ and CK3+/CD34−. Total CD34 cell yield was higher in the limbus with a peak time to confluence (TTC) of more than 30 days. Total CK3 cell yield was greater in the cornea with a peak TTC of less than 30 days. Increasing donor age corresponded to a decreased CD34 yield and an increased CK3 yield. CK3−/CD34+ and CK3+/CD34− cells behaved similarly to total CD34 and CK3 cells in relation to age, site and TTC while CK3+/CD34+ cells showed intermediate features. Keratocan was present in corneal samples.
Conclusions: Suspension cultured human keratocytes of the limbus behave as progenitor cells of corneal keratocytes being slower cycling and with a greater proportion expressing CD34. Cultured keratocytes both from the limbus and cornea are able to express CK3. This phenomenon may reflect mesenchymal-epithelial transition or, given the loss in vitro of the micro-anatomical features of the limbal-corneal area, may indicate the acquisition by keratocytes of a differentiation and migration pathway similar to that of the overlying epithelium. This suggests that the limbus/ corneal stromal niche may exhibit site-specific modulating abilities that direct the development of site-dependent intermediate filament repertoire of epithelial cells
Epithelial dendritic cell distribution in normal and inflamed human cornea: in vivo confocal microscopy study
No full textPURPOSE: To evaluate dendritic cell (DCs) density,
distribution, and morphology in central corneal and limbal
epithelium in normal subjects and patients with immunemediated
corneal inflammation using in vivo confocal
microscopy (IVCM).
DESIGN: Comparative case-controlled, observational
confocal microscopy study.
METHODS: A total of 135 eyes of 135 patients were
investigated. Group 1 (normal eyes) included 45 eyes
of 45 healthy volunteers, group 2 photorefractive keratectomy
(PRK-treated eyes) included 45 myopic eyes of
45 patients treated with PRK, and group 3 (inflamed
eyes) comprised 45 eyes of 45 patients affected by
immune-mediated corneal inflammation. The central cornea
and limbus were examined for epithelial dendriticshaped
cells using laser scanning IVCM. DCs density
was calculated using image analysis software.
RESULTS: Cells with a branching dendritic morphology
were visualized in the basal epithelial layer, basal
lamina, and subbasal nerve plexus, in the central cornea,
and in the basal layer and basal membrane of the limbal
epithelium. The limbal epithelium demonstrated DCs
in 93.3%, 89%, and 97.7% of eyes in group 1, 2, and
3, respectively (P ns). Central epithelial DCs were
observed in 20.0% and 13.3% of eyes in group 1 and 2
(P ns), while in 93.3% of eyes in group 3 (P < .001).
DCs were found to be significantly higher at the limbus
compared with central cornea in each group (P < .001).
Cell densities observed in group 3 were significantly
greater than groups 1 and 2, at both locations (P < .05).
CONCLUSIONS: Laser scanning IVCM is a useful
method for evaluating epithelial DCs distribution at the
limbus and central cornea in both healthy and diseased
eyes
Application of (lamellar) keratoplasty and limbal stem cell transplantation for corneal clouding in the mucopolysaccharidoses - a review
No full textCorneal clouding or opacification is a prominent feature of mucopolysaccharidosis (MPS), particularly in MPS I and VI. In patients with marked corneal clouding and visual impairment, penetrating keratoplasty may be considered to improve the patient's vision, functional capacity and quality of life. In MPS, glycosaminoglycans mainly accumulate in the corneal stroma and not in Descemet's membrane or the endothelium, therefore deep anterior lamellar keratoplasty (DALK) may be preferred in these patients over penetrating keratoplasty. Although there are only limited data on the use of DALK in MPS (I and VI) patients, the results are generally favourable. Nonetheless, when deciding on whether to perform keratoplasty in patients with MPS, the risk of general anaesthesia due to potential concomitant cardio-pulmonary problems and cervical spine instability, the potential presence of other ocular manifestations that also impair vision (e.g. glaucoma, retinal degeneration and optic atrophy) and/or complications such as allograft rejection and the risk of re-opacification of the graft, all need to be taken into consideration. Limbal stem cell transplantation, which can be combined with keratoplasty, also holds potential promise in the treatment of these complex cases. A review of the indications, local and systemic risks, techniques of lamellar andpenetrating keratoplasty, and the potential of limbal stem cell transplantation is provided in the context of corneal opacity in MPS
Epithelial dendritic cell distribution in normal and inflamed human cornea: in vivo confocal microscopy study
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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