1,720,955 research outputs found
Analyse fonctionnelle de deux nouvelles mutations récessives de l’AQP2 impliquées dans le diabète insipide néphrogénique par expression dans les ovocytes de Xenopus laevis
Full text linkLe diabète insipide néphrogénique (DIN) autosomal peut être causé par les
mutations du gène codant pour le canal à eau aquaporine-2 (AQP2). Un
modèle couramment utilisé pour l’étude des protéines membranaires telle
l’AQP2 est l’expression hétérologue dans les ovocytes de Xenopus laevis.
Malheureusement, les techniques déjà existantes de purification de membranes
plasmiques sont soit trop longues, trop difficiles ou demandent trop de matériel,
ne permettent pas l’analyse adéquate du ciblage des formes sauvage comme
mutantes, un élément crucial de ce type d’étude. Nous avons donc dans un
premier temps mis au point une technique rapide et efficace de purification de
membranes plasmiques qui combine la digestion partielle de la membrane
vitelline, sa polymérisation à la membrane plasmique suivi de centrifugations à
basse vitesse pour récolter les membranes purifiées. Nous avons utilisé cette
technique dans l’étude de deux nouveaux cas familiaux de patients
hétérozygotes possédant les mutations V24A et R187C dans un cas et K228E et
R187C dans le second cas. Pour chaque mutation, nous avons analysé autant
les éléments de fonctionnalité que les paramètres d’expression des protéines
mutantes. Les expériences de perméabilité membranaire démontrent que les
ovocytes exprimant AQP2-V24A (Pf = 16.3 ± 3.5 x 10-4 cm/s, 10 ng) et AQP2-
K228E (Pf = 19.9 ± 7.0 x 10-4 cm/s, 10 ng) ont des activités similaires à celle
exprimant la forme native (Pf = 14.4 ± 5.5 x 10-4 cm/s, 1 ng), tandis que AQP2-
R187C (Pf = 2.6 ± 0.6 x 10-4 cm/s, 10 ng) ne semble avoir aucune activité
comme ce qui est observé chez les ovocytes non-injectés (Pf = 2.8 ± 1.0 x 10-4
cm/s). Les études de co-expression ont démontré un effet d’additivité lorsque
AQP2-V24A et -K228E sont injectées avec la forme native et un effet
s’apparentant à la dominance négative lorsque AQP2-R187C est injecté avec la
forme native, avec AQP2-V24A ou avec –K228E. Les résultats obtenus par
immunobuvardage représente bien ce qui a été démontré précédemment, on
remarque la présence des mutations K228E, V24A et la forme sauvage à la
membrane plasmique, contrairement à la mutation R187C. Cependant, lorsque
les mutations sont exprimées dans des cellules mIMCD-3, il n’y a qu’une faible
expression à la membrane de la forme –K228E et une absence totale des formes
–V24A et –R187C à la membrane plasmique, contrairement à la forme native.
Les résultats de nos études démontrent que tout dépendant du système
d’expression les formes –K228E et –V24A peuvent être utiles dans l’étude des
problèmes d’adressage à la membrane à l’aide de chaperonne chimique. De
plus, la forme –R187C démontre des difficultés d’adressage qui devront être
étudiées afin de mieux comprendre la synthèse des formes natives.The autosomal nephrogenic diabetes insipidus (NDI) is caused by mutations of
the gene coding for the water channel aquaporine-2 (AQP2). An oftenly used
model for the study of membrane proteins such as AQP2 is the heterogenous
expression in Xenopus laevis oocytes. Unfortunately, the existing techniques of
plasma membranes purification are either too long, too difficult or require too
much material, which does not allow adequate analysis of targeting of the
native and mutants forms, which is crucial for this type of study. We developed
a fast and effective plasma membrane purification technique which combines
partial digestion of the vitellin membrane, its polymerization with the plasma
membrane followed by a serie of low speed centrifugations to collect the
purified membranes. We used this technique to study of two new family cases
of heterozygote patients carrying the V24A and R187C mutations in a case and
K228E and R187C in the second case. For each mutation, we analyzed the
functionality and the parameters of expression of the mutant proteins. The
membrane permeability experiments show that the oocytes expressing AQP2-
V24A (Pf = 16.3 ± 3.5 x 10-4 cm/s, 10 ng) and AQP2-K228E (Pf = 19.9 ± 7.0 x
10-4 cm/s, 10 ng) have similar activities to the oocytes expressing the native
form (Pf = 14.4 ± 5.5 x 10-4 cm/s, 1 ng), while AQP2-R187C (Pf = 2.6 ± 0.6 x
10-4 cm/s, 10 ng) doesn’t seem to have any activity like the un-injected oocytes
(Pf = 2.8 ± 1.0 x 10-4 cm/s). The coexpression studies showed an additive effect
when AQP2-V24A and -K228E are injected with the native form and an effect
being associated with negative dominance when AQP2-R187C was injected
with AQP2-V24A, -K228E and the native form. Western blot results
confirmed what was observed in the functionality studies. However, when the
mutations were expressed in mIMCD-3 cells, there was a slight expression of
the K228E mutation to the plasma membrane and a total absence of the
mutations –V24A and R187C at the plasma membrane. The results of our
studies showed that depending on the expression system the mutations –K228E
and -V24A can be used in targeting studies using chemical chaperones
Analyse fonctionnelle de deux nouvelles mutations récessives de l’AQP2 impliquées dans le diabète insipide néphrogénique par expression dans les ovocytes de Xenopus laevis
Full text linkLe diabète insipide néphrogénique (DIN) autosomal peut être causé par les
mutations du gène codant pour le canal à eau aquaporine-2 (AQP2). Un
modèle couramment utilisé pour l’étude des protéines membranaires telle
l’AQP2 est l’expression hétérologue dans les ovocytes de Xenopus laevis.
Malheureusement, les techniques déjà existantes de purification de membranes
plasmiques sont soit trop longues, trop difficiles ou demandent trop de matériel,
ne permettent pas l’analyse adéquate du ciblage des formes sauvage comme
mutantes, un élément crucial de ce type d’étude. Nous avons donc dans un
premier temps mis au point une technique rapide et efficace de purification de
membranes plasmiques qui combine la digestion partielle de la membrane
vitelline, sa polymérisation à la membrane plasmique suivi de centrifugations à
basse vitesse pour récolter les membranes purifiées. Nous avons utilisé cette
technique dans l’étude de deux nouveaux cas familiaux de patients
hétérozygotes possédant les mutations V24A et R187C dans un cas et K228E et
R187C dans le second cas. Pour chaque mutation, nous avons analysé autant
les éléments de fonctionnalité que les paramètres d’expression des protéines
mutantes. Les expériences de perméabilité membranaire démontrent que les
ovocytes exprimant AQP2-V24A (Pf = 16.3 ± 3.5 x 10-4 cm/s, 10 ng) et AQP2-
K228E (Pf = 19.9 ± 7.0 x 10-4 cm/s, 10 ng) ont des activités similaires à celle
exprimant la forme native (Pf = 14.4 ± 5.5 x 10-4 cm/s, 1 ng), tandis que AQP2-
R187C (Pf = 2.6 ± 0.6 x 10-4 cm/s, 10 ng) ne semble avoir aucune activité
comme ce qui est observé chez les ovocytes non-injectés (Pf = 2.8 ± 1.0 x 10-4
cm/s). Les études de co-expression ont démontré un effet d’additivité lorsque
AQP2-V24A et -K228E sont injectées avec la forme native et un effet
s’apparentant à la dominance négative lorsque AQP2-R187C est injecté avec la
forme native, avec AQP2-V24A ou avec –K228E. Les résultats obtenus par
immunobuvardage représente bien ce qui a été démontré précédemment, on
remarque la présence des mutations K228E, V24A et la forme sauvage à la
membrane plasmique, contrairement à la mutation R187C. Cependant, lorsque
les mutations sont exprimées dans des cellules mIMCD-3, il n’y a qu’une faible
expression à la membrane de la forme –K228E et une absence totale des formes
–V24A et –R187C à la membrane plasmique, contrairement à la forme native.
Les résultats de nos études démontrent que tout dépendant du système
d’expression les formes –K228E et –V24A peuvent être utiles dans l’étude des
problèmes d’adressage à la membrane à l’aide de chaperonne chimique. De
plus, la forme –R187C démontre des difficultés d’adressage qui devront être
étudiées afin de mieux comprendre la synthèse des formes natives.The autosomal nephrogenic diabetes insipidus (NDI) is caused by mutations of
the gene coding for the water channel aquaporine-2 (AQP2). An oftenly used
model for the study of membrane proteins such as AQP2 is the heterogenous
expression in Xenopus laevis oocytes. Unfortunately, the existing techniques of
plasma membranes purification are either too long, too difficult or require too
much material, which does not allow adequate analysis of targeting of the
native and mutants forms, which is crucial for this type of study. We developed
a fast and effective plasma membrane purification technique which combines
partial digestion of the vitellin membrane, its polymerization with the plasma
membrane followed by a serie of low speed centrifugations to collect the
purified membranes. We used this technique to study of two new family cases
of heterozygote patients carrying the V24A and R187C mutations in a case and
K228E and R187C in the second case. For each mutation, we analyzed the
functionality and the parameters of expression of the mutant proteins. The
membrane permeability experiments show that the oocytes expressing AQP2-
V24A (Pf = 16.3 ± 3.5 x 10-4 cm/s, 10 ng) and AQP2-K228E (Pf = 19.9 ± 7.0 x
10-4 cm/s, 10 ng) have similar activities to the oocytes expressing the native
form (Pf = 14.4 ± 5.5 x 10-4 cm/s, 1 ng), while AQP2-R187C (Pf = 2.6 ± 0.6 x
10-4 cm/s, 10 ng) doesn’t seem to have any activity like the un-injected oocytes
(Pf = 2.8 ± 1.0 x 10-4 cm/s). The coexpression studies showed an additive effect
when AQP2-V24A and -K228E are injected with the native form and an effect
being associated with negative dominance when AQP2-R187C was injected
with AQP2-V24A, -K228E and the native form. Western blot results
confirmed what was observed in the functionality studies. However, when the
mutations were expressed in mIMCD-3 cells, there was a slight expression of
the K228E mutation to the plasma membrane and a total absence of the
mutations –V24A and R187C at the plasma membrane. The results of our
studies showed that depending on the expression system the mutations –K228E
and -V24A can be used in targeting studies using chemical chaperones
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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