1,721,106 research outputs found
Multiple-phase biometric relationships and sexual maturity in the atlantic bluefin tuna, thunnus thynnus (Osteichthyes: Scombridae)
Full text linkMost fish undergo distinct growth phases during ontogenesis. An extremely important passage from the juvenile to adult phase occurs at the onset of sexual maturity, which shows in body proportion and/or growth rate changes. These can be detected as change-points in biometric relationships. In this paper, the Atlantic bluefin tuna was analyzed to verify whether its somatic proportions show any sign of discontinuity during growth, i.e., whether any change-points may be detected in its somatic proportions. This fish has never been examined in this respect, and single-phase models, which are indeed easier to both compute and apply, are used in stock analyses. The following somatic relationships were analyzed in Atlantic bluefin tuna captured in the Mediterranean Sea between 1998 and 2010: “fork length–weight” regression, the von Bertalanffy growth equation, and “first dorsal spine cross section surface–fork length” regression. All of the examined relationships were found to be best modelled by multiple-phase regression equations, and all of them showed a change-point within the range of 101–110 cm fork length, which corresponds to 3–4 years of age. The present results, based on reproductive state-independent analyses, corroborate the disputed hypothesis that Atlantic bluefin tuna from the eastern stock in fact reproduce for the first time at this age
Immunohistochemical localization of FSH and LH in the pituitary of male ruin lizards (Podarcis sicula campestris De Betta)
No full textThe pars distalis from the pituitary gland of adult male ruin lizards (Podarcis sicula campestris De Betta), captured during the reproductive period (May and June), was studied immunohistochemically using specific antibodies against hFSHβ, hLHβ and oLHβ with the avidin-biotin-peroxidase complex (ABC) procedure to determine the localization of both gonadotropins The immunostaining with anti-hFSHβ and anti-hLHβ allowed identification of morphologically distinct FSH containing cells and LH containing cells, whereas anti-oLHβ serum showed cross-reactivity with cells immunostained with the anti-hFSHβ and anti-hLHβ sera. The gonadotropic cells took up approximatively 10.5% of the area of the pars distalis: 10% was positive for FSH, whereas only 0.5% was positive for LH. The FSH cells were distributed throughout the pars distalis, whereas the LH cells were only located in the rostral region. Double-immunostaining procedure did not reveal cells containing both gonadotropic hormones. The findings indicate that FSH and LH are produced in separate pituitary cells
Glycoconjugates during the annual sexual cycle in lizard epididymal ductuli efferentes: A histochemical study
No full textThe epididymal ductuli efferentes of the lizard Podarcis sicula campestris De Betta are lined with simple, columnar, nonciliated and ciliated cells. The use of lectin histochemistry has provided information about changes of sugars associated with glycoconjugates of epithelial cells and intraluminal spermatozoa which are conveyed from the longitudinal canal to the cranial region of the ductus epididymis. Epithelial cells exhibited residues of α-D-tnannose, N-acetylglucosamine, and β-D-galactose-(1-4)-N-acetylglucosamine as revealed with lectins Con A. WGA and RCA120 respectively, throughout the sexual cycle. An increase of RCA120 staining was observed on microvilli of nonciliated cells and in the cytoplasm of ciliated cells during the reproductive period. However, during the following refractory period, when the organ was in regression, there was a decreased staining with Con A on microvilli and the absorbent surface of nonciliated cells, with WGA in nonciliated cells and the cytoplasm of ciliated cells, and with RCA120 on microvilli and the cytoplasm of both cell types. Terminal α-D-galactose residues were increasingly stained from autumn up to the reproductive period with BS I-B4 on microvilli, the absorbent surface and cilia, whereas they were entirely lacking during the refractory period. UEA I revealed α-L-fucose residues on the absorbent surface of nonciliated cells during the abortive and reproductive periods, increasing in the latter period when cilia also expressed this sugar. Terminal α/β-D-N-acetylgalactosamine was evidenced with SBA on the absorbent surface of nonciliated cells during the reproductive period. The terminal β-D-galactose-(1-3)-N-acetylgalaclosamine dimer was never found with PNA, whereas O- and N-linked sialoglycoconjugates were present only during the reproductive period. The spermatozoa head exhibited N-linked glycaos with high-mannose content, and β-D-galactose-(1-4)-N-acetylglucosamine as well as O- and N-linked sialoglycoconjugates throughout the year. During the reproductive period, oligosaccharides with α-D-mannose residues increased, and oligosaccharides with terminal α-D-galactose, α-L-fucose and sialic acid-N-acetylgalactosamine dimer were also present. Unlike spermatozoa of seminiferous tubules, the spermatozoa head of the lizard epididymal ductuli efferentes exhibited seasonal variability in the lectin binding pattern which may be related to time-dependent changes in the glycoconjugate profiles of epithelial cells
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
Proliferation and Apoptosis of Cat (Felis catus) Male Germ Cells during Breeding and Non-Breeding Seasons
Full text linkThe domestic cat (Felis catus) is a seasonal-breeding species whose reproductive period starts when the day length increases. Since the existing information on cat spermatogenesis is limited and somewhat contradictory, in the present study, germ cell proliferation and apoptosis in feral adult tomcats orchiectomized during reproductive (reproductive group, RG; February–July) and non-reproductive (non-reproductive group, NRG; November and December) seasons were compared. Cross-sections taken from the middle third of the left testis were chemically fixed and embedded in paraffin wax. Histological sections were processed for the immunohistochemical detection of proliferating germ cells (PCNA) and for the identification of apoptotic cells (TUNEL method). The percentage of PCNA-positive spermatogonia was higher in the RG than in the NRG. On the contrary, germ cell apoptosis was higher in the NRG than in the RG. Our results confirm that cat spermatogenesis is modulated on a seasonal basis and suggests that spermatogenesis control involves changes in germ cell proliferation and apoptosis according to a common paradigm of seasonally breeding species
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
L. Boi, E.C. Corriero, Introduzione
No full textIl fascicolo comprende dieci saggi su Tilgher, Emo, Diano, Caracciolo, Carchia, Rensi, Pareyson, Masini. L’obiettivo è gettar luce su di un insieme di pensatori relativamente trascurati dalla critica e accomunati dall’aver affermato l’insuperabilità del conflitto tra i due poli caratterizzanti le nostre vite, siano essi forma ed evento, physis e logos, essere e dover essere. Caratteristica fondamentale di tale indirizzo di pensiero è, infatti, l’impossibilità di affrancarsi dalla natura dicotomica del reale, nella cui trama conflittuale va riconosciuta la matrice stessa del tragico
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