1,721,043 research outputs found
Footprints of unconventional mitochondrial inheritance in bivalve phylogeny: Signatures of positive selection on clades with doubly uniparental inheritance.
Full text linkThe doubly uniparental inheritance (DUI) of some bivalve mollusks is the major exception to the common maternal inheritance of mitochondria in animals. DUI involves two mitochondrial lineages with paternal and maternal transmission routes, and it appears as a complex phenomenon requiring both nuclear and mitochondrial adaptations. DUI distribution seems to be scattered among the Bivalvia, and there are several clues for its multiple origins. In this paper, we investigate whether the incipient DUI systems had left possible selective signatures on mitochondrial gen- omes. Alongside the outstanding divergence of amino acid sequences, we confirmed strong purifying selection to act on mitochondrial genes. However, we found evi- dence that distinct episodes of intense directional pressure are associated with the origins of different DUI systems: We interpret these signals as footprints of the coevolution with the nuclear genome that ought to take place at the base of a DUI clade. Six genes (atp6, cox1, cox2, cox3, nad4L, and nad6) seem to be more com- monly linked to the appearance of DUI. We also identified few putative DUI‐specific mutations, thus extending support to the hypothesis of multiple independent origins of this complex phenomenon
Molecular evolution and recombination in gender-associated mitochondrial DNAs of the manila clam Tapes philippinarum
No full textDoubly uniparental inheritance (DUI) provides an intriguing system for addressing aspects of molecular evolution and intermolecular recombination of mitochondrial DNA. For this reason, a large sequence analysis has been performed on Tapes philippinarum (Bivalvia, Veneridae), which has mitochondrial DNA heteroplasmy that is consistent with a DUI. The sequences of a 9.2-kb region (containing 29 genes) from 9 individuals and the sequences of a single gene from another 44 individuals are analyzed. Comparisons suggest that the two sex-related mitochondrial genomes do not experience a neutral pattern of divergence and that selection may act with varying strength on different genes. This pattern of evolution may be related to the long, separate history of M and F genomes within their tissue-specific "arenas." Moreover, our data suggest that recombinants, although occurring in soma, may seldom be transmitted to progeny in T. philippinarum
Mitochondrion-to-nucleus communication mediated by RNA export: A survey of potential mechanisms and players across eukaryotes
Full text linkThe nucleus interacts with the other organelles to perform essential functions of the eukaryotic cell. Mitochondria have their own genome and communicate back to the nucleus in what is known as mitochondrial retrograde response. Information is transferred to the nucleus in many ways, leading to wide-ranging changes in nuclear gene expression and culminating with changes in metabolic, regulatory or stress-related pathways. RNAs are emerging molecules involved in this signalling. RNAs encode precise information and are involved in highly target-specific signalling, through a wide range of processes known as RNA interference. RNA-mediated mitochondrial retrograde response requires these molecules to exit the mitochondrion, a process that is still mostly unknown. We suggest that the proteins/complexes translocases of the inner membrane, polynucleotide phosphorylase, mitochondrial permeability transition pore, and the subunits of oxidative phosphorylation complexes may be responsible for RNA export
SDS-PAGE identification of raw and cooked clams of the Veneridae family
No full textClam species belonging to the family Veneridae (Mollusca: Bivalvia) represent very important marine products, especially in the European countries. The increasing economic interest in marine edible molluscs has strongly enhanced the need for a routine method of unambiguous recognition of species in Fresh and preserved material, mainly intended to prevent mislabelling and commercial frauds. Here a procedure for identification of soft parts is proposed, by means of SDS-PAGE total protein patterning. In fresh material, this technique allowed recognition of four main regions of diagnostic bands, which have been named V1 (111-99 kDa), V2 (44 kDa), V3 (33-30 kDa) and V4 (19-13 kDa). The main diagnostic region appears to be the V3 band series. SDS-PAGE analysis allows the same technique to be used with denatured samples, such as cooked and preserved soft parts, giving reproducible results, very similar to those of fresh material
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
Polymerase chain reaction amplification of the Bag320 satellite family reveals the ancestral library and past gene conversion events in Bacillus rossius (Insecta Phasmatodea)
No full textPolymerase chain reaction amplifications of genomic DNA in 17 individuals of bisexual and parthenogenetic populations of three subspecies of Bacillus rossius (Insecta Phasmatodea) revealed that the species still harbours the whole variability of the ancestral Bag320 satellite family, since monomers of all non-hybrid Bacillus taxa plus private sequences occur in it. Bag320 monomers had not been rescued as a major satellite component in B. rossius, but possibly represent the remnant of a set of diverging sequences present in the Bacillus ancestor. Following the library hypothesis, these monomer variants have been differently amplified along the evolutionary pathways leading to present taxa in agreement with the mitochondrial phylogeny of the genus. The putative converted tracts observed are explained as the results of past gene conversion events. © 2003 Elsevier Science B.V. All rights reserved
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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