1,720,999 research outputs found
Characterisation of mouse limbal neurosphere cells: a potential cell source of functional neurons
No full textBACKGROUND/AIMS:To characterise the origin, ultrastructure and functional properties of corneal limbal neurospheres (LNS).METHODS:Limbal cells were isolated from the corneal limbus of adult mice and cultured in a serum-free sphere forming culture system. LNS were characterised by immunocytochemistry, Reverse-transcription-PCR and electron microscopy. LNS cells were also cocultured with neonatal mouse retinal cells. Phenotype and function were then assessed by immunofluorescence and a calcium influx/efflux assay.RESULTS:LNS cells displayed clonal growth and self-renewal, and expressed a wide range of stem cell and neural lineage markers. The acquisition of neural properties was concordant with expression of neural crest markers including CD34, Sca1, Sox9, Twist1, but not CD45. LNS exhibited similar morphology and microstructure to neurospheres derived from the central nervous system. Following culture in a conducive environment, the derived cells displayed mature neural markers and exhibited electrical excitability.CONCLUSIONS:Corneal limbal stromal progenitor cells are a potential and convenient autologous cell source to generate functional neurons
Children's exposure to second-hand smoke in the home: a household survey in the North of England
No full textExposure of children to second-hand smoke (SHS) leads to increased risk of health and social problems and uptake of smoking in the future. We aimed to assess the prevalence of children’s exposure to SHS in their homes, in a deprived area in the North of England and identify what people thought would help them achieve a smoke-free home (SFH). We performed a cross-sectional survey of 318 households with at least one child aged under 16 years in Beeston Hill, a deprived locality in Leeds, England in June 2008. One hundred and seventy-three households [54%, 95% confidence interval (C.I.) 49–60] had at least one smoker in the house. In 42% (95% C.I. 35–50) of these households (n = 73), smoking took place in the presence of children. The odds of allowing smoking in front of children were 2.2 (95% C.I. 1.1–4.5) times greater in households whose head had less than A-level (national exams at 18 years) or equivalent qualification than in homes with a more qualified head of household. 92% of respondents were aware that SHS has negative effects on children’s health. However, 71% felt more information about health risks to children would help reduce exposure to SHS in the home. Smoking in the presence of children takes place in a relatively high proportion of households with smoker(s), despite media awareness campaigns regarding the dangers of passive smoking launched alongside the recently enforced smoke-free public and workplaces legislation. Specific promotion of SFHs is needed to protect the health of children
The potential of limbal neurosphere cells to differentiate into retinal cell phenotypes
No full textPurpose: Neural colonies (neurospheres) can be generated from adult corneal limbus in vitro. We previously showed that neurospheres derived from limbus were of neural crest origin and can differentiate into functional neurons in vitro. The aim of this study was to investigate whether limbal neurosphere cells (LNS) could differentiate into retinal like cells in vitro and in vivo when exposed to a retinal developing microenvironment.Methods: Cells from adult (8-week old) murine corneal limbus were isolated and cultured in a serum-free sphere-forming system in the presence of mitogens. Following co-culture with developing retinal cells in vitro, LNS and their progeny were characterized using immunocytochemistry, reverse transcription-polymerase chain reaction (RT-PCR) and transmission electron microscopy (TEM). Enhanced Green Fluorescent Protein (eGFP) labelled limbal neurosphere cells were transplanted into the subretinal space (SRS) of neonatal mice. The potential for limbal cells to differentiate into retinal like cells and integrate into the host retina was assessed by immunohistochemistry after 2-5 weeks.Results: LNS cells formed a monolayer, with cells displaying neuronal morphologies following co-culture with neonatal retinal cells. Expression of retinal progenitor cell markers Pax6, Lhx2 and Six6 were observed by RT-PCR after 2-4 days of co-culture. Following 7-10 days in co-culture, LNS cells were immunopositive for the photoreceptor specific marker rhodopsin (13 ± 3%), the mature neuronal marker neurofilament 200 (31 ± 10%) and a major component of synapses within the retina Syntaxin3 (9± 2%)). LNS also displayed ultrastructural changes following differentiation. TEM revealed loss of junctions within the LNS and the presence of putative presynaptic dense bodies. In addition, non-motile primary cilia were also detected in differentiated LNS cells. Although not specific to retinal lineage cells, the same subtype of sensory cilia is present in photoreceptor and RPE cells. Following transplantation into the SRS of wildtype neonatal mice, rhodopsin was detected in eGFP labelled LNS cells.Conclusions: These data highlight that corneal limbal stromal stem/ progenitor cells can transdifferentiate to a retinal like phenotype in vitro and in vio. Therefore LNS cells could be a potential resource for autologous cell rescue of degenerative retinal diseases
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Optimisation of polymer scaffolds for retinal pigment epithelium (RPE) cell transplantation.
No full textAim: to evaluate a variety of copolymers as suitable scaffolds to facilitate retinal pigment epithelium (RPE) transplantation. Methods: five blends of poly(L-lactic acid) (PLLA) with poly(D, L-lactic-glycolic acid) (PLGA) were manufactured by a solid-liquid phase separation technique. The blends were 10:90, 25:75, 50:50, 75:25, 90:10 (PLLA:PLGA). All blend ratios were validated by nuclear magnetic resonance spectroscopy. Samples of polymer blends were coated with laminin. Coated and uncoated blends were seeded with a human RPE cell line. Cell attachment, viability and retention of phenotype were assessed. Results: as the lactide unit content increased pore size generally became smaller. The 25:75 PLLA:PLGA blend was the most porous (44%) and thinnest (134?) scaffold produced. ARPE-19 cells survived with minimal cell death and maintained their normal phenotype for up to four weeks.. Cell density was maintained with only one of the fabricated ratios (25% PLLA:75% PLGA). There was a consistent decrease in apoptotic cell death with time on laminin coated samples of this blend. A decrease in polymer thickness concomitant with an increase in porosity characteristic of degradation was observed with all polymer blends. Conclusions: this study demonstrates that a 25:75 copolymer blend of PLLA:PLGA is a potentially useful scaffold for ocular cell transplantatio
Derivation of neural progenitor cells from adult mouse corneal limbus
No full textPurpose: cells from the adult rodent corneal limbal epithelium basal layer have been demonstrated to display neuronal potential and differentiate towards functional neurons in vitro. A sphere forming culture system has also been used to expand stem cells of a neural crest origin from mouse corneal stroma. The aim of this study was to investigate whether progenitors with neuronal potential could be cultured from adult murine limbus to form neuronal characteristics.Methods: cells from adult (8 weeks) murine corneal limbus were isolated and cultured in a serum-free sphere-forming system in the presence of mitogens. Cells were maintained in the presence or absence of the bone morphogenetic protein 4 (BMP4) inhibitor (Noggin). Sphere derived cells and their progeny were characterized using immunocytochemistry and/or reverse transcription-polymerase chain reaction (RT-PCR).Results: adult mouse limbal cells formed sphere colonies with the ability to self renew. The frequency of sphere-forming cells was 0.45-1.0% subject to culture conditions. Noggin did not have an effect on the efficiency of sphere formation. In the presence and absence of Noggin, sphere cells expressed ABCG2, Sox2, Nestin and beta-III tubulin (early differentiated neuron) but not P63 (epithelial stem cell marker) as shown by immunocytochemistry. Expression of neuronal stem/progenitor cells markers (nestin, Sox2, Musashi, beta-III tubulin) and neural crest markers (Twist1 and Slug) increased with time in culture and passage, concomitant with a decrease in expression of the epithelium lineage markers P63 and cytokeratin12, as shown by RT-PCR.Conclusions: the adult mouse corneal limbus contains stem / precursor cells which express neural stem cell markers in vitro. These stem cells/ progenitor cells appear to be neural crest & are likely to be derived from the corneal limbal strom
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