1,721,099 research outputs found
The integument of lungfish: General structure and keratin composition
No full textThe aquatic environment poses less restrictions on mechanical and barrier performances in the integument of both marine and freshwater vertebrates, mainly fish and some amphibians, in comparison to the skin of terrestrial vertebrates (Whitear 1977; Zaccone et al. 2001; Alibardi 2006). As a result, apart from specific locations of the body in a few species of fishes and amphibians, the epidermis of aquatic vertebrates resembles the relatively poorly keratinised multi-layered epithelia found in the mucoses lining the respiratory or alimentary canals of terrestrial vertebrates (Whitear 1986a,b). In particular a corneal layer is missing over the general epidermis of fishes and perennibranchiate amphibians. Th is includes also sarcopterygian fish, both crossopterygians (Latimeria, saltwater) and dipnoans (freshwater). Th is chapter is mainly concerned with the skin, especially the epidermis of the Australian lungfish, Neoceratodus forsteri, which is compared where studies are available, with the epidermis of other species of dipnoans (Kitzan and Sweeny 1968; Imaki and Chavin 1975a,b, 1984). In addition to a previously published study (Alibardi and Joss 2003), N. forsteri skin derived from two extra larval stages are described and the keratins have been partially characterised
The molecular organization of the beta-sheet region in Corneous beta-proteins (beta-keratins) of sauropsids explains its stability and polymerization into filaments
No full textThe hard corneous material of avian and reptilian scales, claws, beak and feathers is mainly derived from the presence of proteins formerly known as beta-keratins but now termed Corneous beta-proteins of sauropsids to distinguish them from keratins, which are members of the intermediate filament protein family. The modeling of the conserved 34 amino acid residues long central beta-sheet region of Corneous beta-proteins using an ab initio protein folding and structure prediction algorithm indicates that this region is formed by four antiparallel beta-sheets. Molecular dynamic simulations and Molecular Mechanics/Poisson Boltzmann Surface Area (MM-PBSA) analysis showed that the disposition of polar and apolar amino acids within the beta-region gives rise to an amphipathic core whose stability is further increased, especially in an aqueous environment, by the association into a dimer due to apolar interactions and specific amino-acid interactions. The dimers in turn polymerize into a 3 nm thick linear beta-filament due to van der Waals and hydrogen-bond interactions. It is suggested that once this nuclear core of anti-parallel sheets evolved in the genome of a reptilian ancestor of the extant reptiles and birds about 300 millions years ago, new properties emerged in the corneous material forming scales, claws, beaks and feathers in these amniotes based on the tendency of these unique corneous proteins to form stable filaments different from keratin intermediate filaments or sterical structures formed by other corneous proteins so far known
Skin structure of the slow worm lizard Anguis fragilis (Anguidae, Sauria, Reptilia) with emphasis on the epidermal micro‐ornamentation in relation to the animal movements
Full text linkSkin structure of the slow worm lizard Anguis fragilis (Anguidae, Sauria, Reptilia) with emphasis on the epidermal micro-ornamentation in relation to the animal movements (Acta Zoologica, Stockholm). The structure of the skin and superficial micro-ornamentation in the slow worm Anguis fragilis, a limbless lizard with a fossorial activity, was examined using histology, immunofluorescence, scanning and transmission electron microscopy. The scales, with a triangular to trapezoidal shape, are very overlapped and interlocked to form a smooth surface and are reinforced by osteoderms. The epidermis shows a thin Oberhautchen layer merged with a thicker beta-layer that contains corneous beta-proteins. The SEM survey detects a smooth surface made of tile-like patterned Oberhautchen cells with irregular perimeters that form an interlocking surface. Disk-like sensory organs of 15-20 mu m diameter are observed only on the head scales, the first to sense the environment and contact the ground. Numerous Oberhautchen denticles, namely corneous thorns of about 0.2-0.3 mu m, adorn the caudally directed perimeter of Oberhautchen cells in the ventral scales of the trunk and tail. This microstructure may determine gripping and increased friction with the substrate during the lateral undulating and forward movements of the slow worm. TEM observations reveal sparse short serrated protrusions of Oberhautchen cells that are largely merged with the underlying beta-cells. Altogether, the scale surface of the slow worm efficiently suites this limbless lizard to its environment and lifestyle
Low-cysteine alpha-keratins and corneous beta-proteins are initially formed in the regenerating tail epidermis of lizard
No full textProtein extracts from regenerating lizard tail show an inhibitory effect on human cancer cells cultivated in-vitro
No full textBackground: accumulating evidence indicates that during tail regeneration in lizards the initial stage of regenerative blastema is a tumor-like proliferative outgrowth that rapidly elongates into a new tail composed of fully differentiated tissues. Both oncogenes and tumor-suppressors are expressed during regeneration, and it has been hypothesized that an efficient control of cell proliferation avoids that the blastema is turned into a tumor outgrowth. Methods: in order to determine whether functional tumor-suppressors are present in the growing blastema we have utilized protein extracts collected from early regenerating tails of 3-5 mm that have been tested for a potential anti-tumor effect on in-vitro culture by using cancer cell lines from human mammary gland (MDA-MB-231) and prostate cancer (DU145).Results: at specific dilutions, the extract determines a reduction of viability in cancer cells after 2-4 days of culture, as supported by statistical and morphological analyses. While control cells appear viable, treated cells result damaged and produce an intense cytoplasmic granulation and degeneration.Conclusions: this negative effect on cell viability and proliferation is absent using tissues from the original tail supporting the hypothesis that only regenerating tissues synthesize tumor-suppressor molecules. The study suggests that the regenerating tail of lizard at the stages here selected contains some molecules that determine inhibition of cell viability on the cancer cells analyzed.& COPY; 2023 Elsevier GmbH. All rights reserved
Review: Evolution and diversification of corneous beta-proteins, the characteristic epidermal proteins of reptiles and birds
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
- …
