1,720,963 research outputs found
STUDY OF THE PORCINE ELECTRORETINOGRAM AS PRECLINICAL MODEL FOR THE TREATMENT OF THE HUMAN RETINA HEREDITARY DEGENERATIONS
No full textThe present work has the aim to analyze, for the first time, the physiological activity of the pig’s retina using a standardized human electoretinogram protocol approved by the International Society for Clinical Electrophysiology of Vision (ISCEV). The experiment was conducted at the Livestock and Animal Testing unit of the Physiology service of the Department of Veterinary Medical Sciences of the University of Bologna, in accordance with the national and international guidelines on animal experimentation. All procedures were examined by the Ethics Committee of the University of Bologna, authorized in derogate by the Ministry of Health and controlled by the Central Veterinary Service of the University of Bologna during the implementation phase. The subjects are 30 healthy females piglets of 3 months old and weighing 30 kg. The pre medication is performed using Azaperone (2mg/kg of Stresnil) by intramuscular injection behind the ear. Then, the Ketamine (20mg/Kg of Ketavet), Medetomidine (0,04mg/kg of Medetor) and Atropine (0.04 mg/kg of Atropine sulfate) mixture is injected intramuscularly. The subject is left alone until the loss of the righting reflex. Two drops of mydriatic (Tropicamide 1%) per eye are instilled to obtain the necessary paralysis of the pupil. The instrument used for the retinal exam, is a Ganzfeld Stimulator Model GS-MAX for use in humans. The electrical signal data is recorded, amplified and analyzed by the program EREV2000 previously set for ERG sessions running in series. The electrodes are ERG-jet metal conductor model to transfer the bioelectric signal to the amplifier and they are divided in: subcutaneous or inox needle and corneals. Four different light stimulations are sent in order to record the photoreceptors response and to compare the average amplitudes for each protocol with the human and mouse data present in literature. This study confirm that a high cone density and the particular pig’s photoreceptor topography allow this animal to be the better choice for experimental modelling of human cone diseases than mouse. Additionally, this wide data background is a good resource for researchers involved in ophthalmic studies to choose the correct animal model for their experiment and to use the smallest possible number of animals needed to obtain a scientifically valid result
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
Transcriptional Repression of the Human Rhodopsin Gene by Artificial Zinc Finger Protein Recovers Retinal Function in a Model of Autosomal Dominant Retinitis Pigmentosa
No full textRetinitis Pigmentosa (RP) represents a heterogeneous group of
severe retinal degenerations. Rhodopsin (Rho) is the gene most
commonly associated to the autosomal dominant form of RP
(ADRP) with over 150 mutations identifi ed. The objective of this
study is to treat ADRP by silencing the Rho gene expression at the
transcriptional level in a mutation independent fashion to potentially
treat all ADRP due to rhodopsin mutations. To this end we have
used artifi cial zinc fi nger transcription factors (ZF-TFs) targeted to
human Rhodospin promoter. Through the modular assembly method
we generated 10 DNA Binding Domains (DBDs) targeted to hRho
promoter and we fused them to the KRAB or VP64 domains to
assemble specifi c Rho transcriptional repressors (ZFRs) and activators (ZFAs), respectively. We selected the most effi cient and selective
hRho transcription inhibitor using the luciferase reporter system.
Twenty percent success rate (2 out of 10) was obtained in generating
artifi cial ZF-TFs that robustly and specifi cally repress expression of
luciferase driven by hRho promoter in vitro. As further demonstration
of specifi city, the 2 selected ZF-TFs, when fused to VP64 domain,
are also able to effi ciently transactivate the targeted promoter as
well as directly bind it as assessed through Electromobility shift
assay (EMSA) experiments. The therapeutic potential of the two
selected hRho specifi c repressors (ZFR-2 and ZFR-6) was assessed
by transduction experiments on Retinal Stem Cells (RSC) explanted
from adult P347S ADRP transgenic mouse model. These cells die
once differentiated in vitro because of the expression of the mutated
copy of hRho gene. Retroviral delivery of the selected ZFRs to RSC
resulted in selective repression of the mutated human Rhodopsin as
measured by quantitative Real Time PCR analysis, and remarkably
in 90% reduction of apoptotic cells compared to controls. To assess
the feasibility of such approach in vivo, we generated an AAV 2/8
harbouring the ZFR-6 driven by a Rhodopsin kinase promoter.
One month after vector delivery RT-PCR analysis showed specifi c
repression of RHO transcript. Remarkably a significant retinal
morphological and functional recovery was observed. Taken together
these results demonstrate that artifi cial Zinc Finger transcription
factors repress hRho gene in vitro and in vivo, underscoring the
potential impact of this novel strategy to treat ADRP
The mouse model for ocular albinisin type 1 (OA1) as a tool to study Oa1 function in RPE development
No full textPurpose: Ocular Albinism type 1 (OA1) is an X-linked form of albinism isolated to the eye. The disease causes a severe visual handicap in affected males, manifesting foveal hypoplasia, horizontal and rotatory nystagmus, strabismus, photophobia and lack of stereoscopic vision. Histological analysis of patient melanocytes from the RPE and the skin reveals giant melanosomes (macromelanosomes). Mutations causing this disease were identified in OA1 gene. OA1 is specifically expressed in the retinal pigment epithelium (RPE) and in skin melanocytes . The protein is localized on the melanosomal membrane and displays characteristics typical of the seven transmembrane G protein coupled receptors. In order to understand the biological function of OA1, we generated a mouse model for the disease.
Methods: To generate Oa1 null mice, we deleted the first exon of Oa1 by homologous recombination in ES cells. Histological studies were performed on RPE of wild-type and mutant mice. Interactions of Oa1 with other melanosomal proteins was investigated by mating Oa1 null mice with p and c mice. Ultrastructural and biochemical analyses were conducted in double mutant mice.
Results: Histological analysis of the eyes in Oa1 mutants showed that the RPE was more lightly pigmented. Abnormally large melanosomes (macromelanosomes) could be identified by electron microscopy within the RPE. Interestingly, macromelanosomes could be seen just after birth in mutant mice. Oa1 knock-out mice display a misrouting of the optic fibers as in OA1 patients. A significant decrease of ipsilateral optic fibers could be measured in Oa1 knock-out mice as found in other albino mice. To investigate the function of Oa1 on the melanosomal membrane and its interaction with other genes causing different forms of albinism, we mated Oa1 null mice with p and c mice. Ultrastructural and biochemical analyses were performed in double mutant mice, finding a correlation of the macromelanosomal phenotype and level of pigmentation. We have also studied genes regulating Oa1 expression during development (e.i. Mitf) and we have started experiments aimed to the identification of genes downstream to it.
Conclusion: We developed a mouse model for OA1. Our data demonstrate that the Oa1 knock-out mouse is indeed a good model for the study of OA1 pathology. Furthermore the mouse model will be valuable for the identification of factors mediating RPE influence on retinal development
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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