1,720,959 research outputs found
Isolation and characterization of 14 polymorphic microsatellite markers for the blue and red shrimp, Aristeus antennatus (Crustacea, Decapoda)
No full textEighteen microsatellite loci were isolated and characterized from the blue and red shrimp, Aristeus antennatus Risso 1816, a commercially exploited marine crustacean widely distributed throughout the Mediterranean Sea and in the eastern Atlantic. Polymorphism was assessed in a population (n = 20) from the southwestern Sardinian seas; 14 loci resulted polymorphic and showed from three to 13 alleles. The observed heterozygosity ranged from 0.2 to 0.85. These microsatellites will be potentially useful for the study of A. antennatus population genetic structure
Studio del cariotipo di Gymnothorax tile (Osteichthyes, Anguilliformes) mediante bandeggio di replicazione
No full textStudio del cariotipo di Gymnothorax tile (Osteichthyes, Anguilliformes) mediante bandeggio di replicazione
ELISABETTA COLUCCIA, ANNA MARIA DEIANA, RITA CANNAS, SIMONA BUCCOLI, ANGELO CAU, SUSANNA SALVADORI
Dipartimento di Biologia Animale ed Ecologia, Università di Cagliari.
La famiglia Muraenidae comprende circa 200 specie, prevalentemente marine. Da un punto di vista citogenetico sono state studiate meno del 5% delle specie, la maggior parte di esse ha un numero diploide di 42 ma una differente struttura del cariotipo. In questo lavoro viene per la prima volta caratterizzato, mediante bandeggio di replicazione, il cariotipo di Gymnothorax tile (Hamilton, 1822), specie che vive in acque salmastre, sulla cui biologia si hanno scarsissime informazioni. Sono stati esaminati undici esemplari, tutti di sesso femminile, da cui sono stati ottenuti i preparati cromosomici mediante colture cellulari da sangue. Il bandeggio di replicazione precoce è stato ottenuto mediante incorporazione in vitro di BrdU e colorazione FPG. Il cariotipo è costituito da 42 coppie cromosomiche con un numero di bracci pari a 76, il più alto della famiglia, e comprende 8 coppie di metacentrici, 9 di submetacentrici e 4 di acrocentrici. Il pattern di bande a replicazione precoce ha permesso l’identificazione e la caratterizzazione delle coppie cromosomiche. Riproducibili pattern di replicazione precoce e tardiva sono state ottenute in altre due specie di murene (G. unicolor e Muraena helena); il loro confronto ha permesso l’identificazione di omeologie e riarrangiamenti, dimostrandosi un utile metodo nello studio dell’evoluzione del cariotipo tra specie correlate. Nei pesci le bande di replicazione rappresentano il metodo più valido per ottenere una differenziazione trasversale dei cromosomi in quanto le bande strutturali di tipo G, R e Q sono di difficile ottenimento. In G. tile sono state inoltre studiatate la distribuzione e struttura dell’eterocromatina e la localizzazione del NOR; con tutte le tecniche utilizzate il cariotipo di G. tile è risultato notevolmente differenziato rispetto a G. unicolor e M. helena
Sex chromosomes in Anguilliformes: a ZZ/ZW sex determination system in Dalophis imberbis (Ophichthidae).
No full textSex chromosomes in Anguilliformes: a ZZ/ZW sex determination system in Dalophis imberbis (Ophichthidae)
S. Salvadori, E. Coluccia, R. Cannas, S. Buccoli, A. Cau and A.M. Deiana
Dipartimento di Biologia Animale ed Ecologia, Università di Cagliari, Cagliari, Italy.
Among Anguilliformes, morphologically differentiated sex chromosomes have been described in 25% of the species studied. Interestingly, in this taxon the occurrence of different sex chromosome systems, both male and female heterogamety as well as a multiple chromosome system, has been reported. In this work we describe the karyotype and demonstrate the presence of a ZZ/ZW sex determination system in Dalophis imberbis (Delaroche, 1809). The chromosome preparations have been obtained from blood cell cultures. Dalophis imberbis has 46 chromosomes; its karyotype is made up of 4 metacentric and submetacentric pairs, 18 acrocentric and subtelocentric pairs and a sex chromosome pair, heteromorphic in females. By measuring with the Cromowin System software the relative length and the centromeric index of each chromosome pair, we have constructed the idiogram of this species. By C-banding we have located the constitutive heterochromatin in all centromeres; some chromosomes show peculiar banding patterns, in particular Z and W chromosomes present large heterochromatic blocks, probably related to mechanisms that lead to the inactivation and differentiation of sex chromosomes. Moreover, by replication banding, which represents the most effective karyotyping method in fishes, we have characterized each chromosome pair of D. imberbis. Furthermore, the 45S rDNA FISH has allowed to locate the ribosomal genes in two pairs of autosomes and in the subtelomeric region of the chromosome W. Ag-staining has shown in different individuals, three-four transcriptionally active NORs; the ribosomal clusters present on the W chromosome are often Ag-positive
Isolation and characterization of eight microsatellite loci in the icefish Chaenocephalus aceratus (Perciformes, Notothenioidea, Channichthyidae)
No full textWe characterized eight polymorphic microsatellites in the Scotia icefish Chaenocephalus aceratus (Perciformes, Notothenioidei, Channichthyidae) that is endemic of Southern Ocean waters surrounding the tip of the Antarctic Peninsula. Microsatellites were isolated from a partial genomic library enriched for an AC motif. The number of alleles ranged from two to 19 with a mean observed hererozygosity of 0.71. Loci were in Hardy–Weinberg equilibrium and no evidence for linkage disequilibrium was found. These molecular markers will be useful to investigate Scotia icefish genetic structure, possibly providing insights on its effective population size and demographic history
On the reappearance of the blue skate Dipturus batis (Linnaeus, 1758) off the Sardinian coasts (Western Mediterranean sea)
No full text
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
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