1,720,966 research outputs found
The biology and evolution of the Dilp8-Lgr3 pathway: A relaxin-like pathway coupling tissue growth and developmental timing control
Get PDFMany insects, like cockroaches, moths, and flies, can regenerate tissues by extending the growth-competent phases of their life cycle. The molecular and cellular players mediating this coordination between tissue growth and developmental timing have been recently discovered in Drosophila. The insulin/relaxin-like peptide, Dilp8, was identified as a factor communicating abnormal growth status of Drosophila larval imaginal discs to the neuroendocrine centers that control the timing of the onset of metamorphosis. Dilp8 requires a neuronal relaxin receptor for this function, the Leucine rich repeat containing G protein coupled receptor, Lgr3. A review of current data supports a model where imaginal disc-derived Dilp8 acts on four central nervous system Lgr3-positive neurons to activate cyclic-AMP signaling in an Lgr3-dependent manner. This causes a reduction in ecdysone hormone production by the larval endocrine prothoracic gland, which leads to a delay in the onset of metamorphosis and a simultaneous slowing down in the growth rates of healthy imaginal tissues, promoting the generation of proportionate individuals. We discuss reports indicating that the Dilp8-Lgr3 pathway might have other functions at different life history stages, which remain to be elucidated, and review molecular evolution data on invertebrate genes related to the relaxin-pathway. The strong conservation of the relaxin pathway throughout animal evolution contrasts with instances of its complete loss in some clades, such as lepidopterans, which must coordinate growth and developmental timing using another mechanism. Research into these areas should generate exciting new insights into the biology of growth coordination, the evolution of the relaxin signaling pathway, and likely reveal unforeseen functions in other developmental stages.Fil: Gontijo, Alisson M.. Universidade Nova de Lisboa; PortugalFil: Garelli, Andres. Universidade Nova de Lisboa; Portugal. Universidad Nacional del Sur; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Investigaciones Bioquímicas de Bahía Blanca. Universidad Nacional del Sur. Instituto de Investigaciones Bioquímicas de Bahía Blanca; Argentin
Retrotransposition causes age-dependent neuronal function decline
No full textTese de mestrado, Engenharia Biomédica e Biofísica, Universidade de Lisboa, Faculdade de Ciências, 2022Retrotransposable elements (RE) are DNA sequences that have the ability to change position within
the genome. They are present in most organisms and often comprise a large part of their genome. Because of their mobilization, REs are an intrinsic source of DNA damage and mutations that can alter
gene activity. Even though some of these mutations can eventually drive evolutionary novelty at the
population and species scales, more often, the RE-driven mutations are deleterious and lead to genomic
instability and disease at the individual scale. It comes as no surprise, therefore, that hosts have evolved
transcriptional and post-transcriptional mechanisms that repress REs activity.
Recent studies have correlated increased expression of REs with age and age-related diseases, such
as neurodegenerative disorders, which is suspected to be due to the tendency of RE silencing mechanisms
to fail over time. However, it remains unclear whether RE de-repression is a cause or a consequence of
the age-dependent cellular loss of function.
The goal of this project is to determine if retrotransposition of long interspersed nuclear element-1
(LINE1 or L1) can be a cause of neurodegeneration and neural function decline if it is not repressed
by the organism. To evaluate the effects of continuous expression of L1 in the nervous system in such a
context, we developed a heterologous system that allows tissue-specific expression, using the GAL4-UAS
system, of an L1 of the mosquito Anopheles gambiae (AgL1) in the evolutionary-distant fly Drosophila
melanogaster. Mosquitos and flies have evolved separately for about 250 million years, so it is expected
that their anti-RE systems no longer recognize each other.
We confirmed the expression of AgL1 transcripts in the adult fly nervous system using reverse
transcription-quantitative real-time polymerase chain reaction (RT-qPCR), and of the AgL1-encoded
proteins, ORF1p and ORF2p, by immunohistochemistry using antibodies against V5 and HA epitopes,
which respectively tag each protein in our construct. Further immunohistochemistry assays using an
anti-phosphorylated histone H2Av antibody, which indicates the presence of DNA double strand breaks
(DSBs), showed that AgL1-expressing flies had higher DSB levels in neural cells than their controls.
However, immunostaining using anti-activated caspase, a programmed-cell death indicator, revealed similar levels of neuronal death in both conditions.
Neuronal performance of ageing flies was analyzed using negative geotaxis (climbing) assays 2, 20,
30, and 40 days after eclosion. We observed a statistically significant decrease in climbing ability in
flies expressing AgL1 in the neurons, compared to their age-matched controls. Expression of AgL1 in
glial cells, in contrast, had no significant effect on climbing ability, suggesting that neurons are particularly sensitive to AgL1 activity. Feeding stavudine - a known retrotransposition inhibitor - to ageing
flies expressing AgL1 in neurons partially rescued their decreased climbing ability, suggesting AgL1
retrotransposition or its attempts had a causal role in the locomotor function decrease.
AgL1 retrotransposition capability was further evaluated using an established exogenous cell culture retrotransposition assay for human cells and a custom-modified retrotransposition assay for fly cells. We were able to demonstrate AgL1 retrotransposition in human HeLa cells, but not in Drosophila
melanogaster DL2 cells. This suggests that the decrease in climbing ability of AgL1-expressing flies is
the result of DNA damage caused by L1 retrotransposition attempts, rather than full retrotransposition
events
Retrotransposition causes age-dependent neuronal function decline
No full textTese de mestrado, Engenharia Biomédica e Biofísica, Universidade de Lisboa, Faculdade de Ciências, 2022Retrotransposable elements (RE) are DNA sequences that have the ability to change position within
the genome. They are present in most organisms and often comprise a large part of their genome. Because of their mobilization, REs are an intrinsic source of DNA damage and mutations that can alter
gene activity. Even though some of these mutations can eventually drive evolutionary novelty at the
population and species scales, more often, the RE-driven mutations are deleterious and lead to genomic
instability and disease at the individual scale. It comes as no surprise, therefore, that hosts have evolved
transcriptional and post-transcriptional mechanisms that repress REs activity.
Recent studies have correlated increased expression of REs with age and age-related diseases, such
as neurodegenerative disorders, which is suspected to be due to the tendency of RE silencing mechanisms
to fail over time. However, it remains unclear whether RE de-repression is a cause or a consequence of
the age-dependent cellular loss of function.
The goal of this project is to determine if retrotransposition of long interspersed nuclear element-1
(LINE1 or L1) can be a cause of neurodegeneration and neural function decline if it is not repressed
by the organism. To evaluate the effects of continuous expression of L1 in the nervous system in such a
context, we developed a heterologous system that allows tissue-specific expression, using the GAL4-UAS
system, of an L1 of the mosquito Anopheles gambiae (AgL1) in the evolutionary-distant fly Drosophila
melanogaster. Mosquitos and flies have evolved separately for about 250 million years, so it is expected
that their anti-RE systems no longer recognize each other.
We confirmed the expression of AgL1 transcripts in the adult fly nervous system using reverse
transcription-quantitative real-time polymerase chain reaction (RT-qPCR), and of the AgL1-encoded
proteins, ORF1p and ORF2p, by immunohistochemistry using antibodies against V5 and HA epitopes,
which respectively tag each protein in our construct. Further immunohistochemistry assays using an
anti-phosphorylated histone H2Av antibody, which indicates the presence of DNA double strand breaks
(DSBs), showed that AgL1-expressing flies had higher DSB levels in neural cells than their controls.
However, immunostaining using anti-activated caspase, a programmed-cell death indicator, revealed similar levels of neuronal death in both conditions.
Neuronal performance of ageing flies was analyzed using negative geotaxis (climbing) assays 2, 20,
30, and 40 days after eclosion. We observed a statistically significant decrease in climbing ability in
flies expressing AgL1 in the neurons, compared to their age-matched controls. Expression of AgL1 in
glial cells, in contrast, had no significant effect on climbing ability, suggesting that neurons are particularly sensitive to AgL1 activity. Feeding stavudine - a known retrotransposition inhibitor - to ageing
flies expressing AgL1 in neurons partially rescued their decreased climbing ability, suggesting AgL1
retrotransposition or its attempts had a causal role in the locomotor function decrease.
AgL1 retrotransposition capability was further evaluated using an established exogenous cell culture retrotransposition assay for human cells and a custom-modified retrotransposition assay for fly cells. We were able to demonstrate AgL1 retrotransposition in human HeLa cells, but not in Drosophila
melanogaster DL2 cells. This suggests that the decrease in climbing ability of AgL1-expressing flies is
the result of DNA damage caused by L1 retrotransposition attempts, rather than full retrotransposition
events
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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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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