1,720,971 research outputs found
Mapping CAP-A satellite DNAs by FISH in Sapajus cay paraguay and S. macrocephalus (Platyrrhini, Primates)
Full text linkSatellite DNAs such as Cap-A sequences are potentially informative taxonomic and phylogenetic markers useful for characterizing primate genomes. They have
also been used as cytogenetic markers facilitating species identification in many taxa.
The aim of this work is to map Cap-A sequences by FISH (fluorescent in situ hybridization) on two Platyrrhini (Primates) species genomes, Sapajus cay paraguay and S.
macrocephalus, in order to study their distribution pattern on chromosomes. The CapA probes showed bright signals with almost the same interstitial pattern of distribution in correspondence with C and CMA3 rich regions on six pairs of chromosomes
in both Sapajus species. An additional pair was detected on S. macrocephalus. The
analysis of the results, compared with previous literature data on other phylogenetically
close New World species, shows that Cap-A satellite sequences have a genus-specific
pattern, but with slight species-specific patterns that are useful as phylogenetic and taxonomic markers
Centromeric enrichment of LINE-1 retrotransposon in two species of South American monkeys Alouatta belzebul and Ateles nancymaae (Platyrrhini, Primates)
Full text linkLINE-1 sequences have been linked to genome evolution, plasticity and speciation; however, despite their importance, their chromosomal distribution is poorly known in primates. In this perspective, we used fluorescence in situ hybridiza-tion (FISH) to map LINE-1 probes onto two representative platyrrhine species, Aotus nancymaae (Cebidae) and Alouatta belzebul (Atelidae), both characterized with highly rearranged karyotypes, in order to investigate their chromosomal distribution and role and to better characterize the two genomes. We found centromeric enrichment of LINE-1 sequences on all biarmed and acrocentric chromosomes co-localized with heterochromatin C-positive bands. This distribution led us to hypothesize that LINE 1 sequences may have a role in the centromere architecture and karyotype organization of platyrrhine genome
Chromosome Painting in Cercopithecus petaurista (Schreber, 1774) Compared to Other Monkeys of the Cercopithecini Tribe (Catarrhini, Primates)
Full text linkThe Cercopithecini tribe includes terrestrial and arboreal clades whose relationships are
controversial, with a high level of chromosome rearrangements. In order to provide new insights
on the tribe’s phylogeny, chromosome painting, using the complete set of human syntenic probes,
was performed in Cercopithecus petaurista, a representative species of the Cercopithecini tribe. The
results show C. petaurista with a highly rearranged karyotype characterized by the fission of human
chromosomes 1, 2, 3, 5, 6, 8, 11, and 12. These results compared with the literature data permit us to
confirm the monophyly of the Cercopithecini tribe (fissions of chromosomes 5 and 6), as previously
proposed by chromosomal and molecular data. Furthermore, we support the monophyly of the
strictly arboreal Cercopithecus clade, previously proposed by the molecular approach, identifying
chromosomal synapomorphies (fissions of chromosomes 1, 2, 3, 11, 12). We also add additional
markers that can be useful for deciphering arboreal Cercopithecini phylogeny. For example, the
fission of chromosome 8 is synapomorphy linking C. petaurista, C. erythrogaster, and C. nictitans among
the arboreal species. Finally, a telomeric sequence probe was mapped on C. petaurista, showing only
classic telomeric signals and giving no support to a previous hypothesis regarding a link between
interspersed telomeric sequences in high rearranged genome
Molecular Cytogenetic Characterization of the Sicilian Endemic Pond Turtle Emys trinacris and the Yellow-Bellied Slider Trachemys scripta scripta (Testudines, Emydidae)
Full text linkTurtles, a speciose group consisting of more than 300 species, demonstrate karyotypes with
diploid chromosome numbers ranging from 2n = 26 to 2n = 68. However, cytogenetic analyses have
been conducted only to 1/3rd of the turtle species, often limited to conventional staining methods.
In order to expand our knowledge of the karyotype evolution in turtles, we examined the topology of
the (TTAGGG)n telomeric repeats and the rDNA loci by fluorescence in situ hybridization (FISH)
on the karyotypes of two emydids: the Sicilian pond turtle, Emys trinacris, and the yellow-bellied
slider, Trachemys scripta scripta (family Emydidae). Furthermore, AT-rich and GC-rich chromosome
regions were detected by DAPI and CMA3 stains, respectively. The cytogenetic analysis revealed that
telomeric sequences are restricted to the terminal ends of all chromosomes and the rDNA loci are
localized in one pair of microchromosomes in both species. The karyotype of the Sicilian endemic
E. trinacris with diploid number 2n = 50, consisting of 13 pairs of macrochromosomes and 12 pairs
of microchromosomes, is presented here for first time. Our comparative examination revealed
similar cytogenetic features in Emys trinacris and the closely related E. orbicularis, as well as to other
previously studied emydid species, demonstrating a low rate of karyotype evolution, as chromosomal
rearrangements are rather infrequent in this group of turtles
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
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