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OPPOSING EFFECTS OF ASCORBATE ON COLLAGEN AND ELASTIN DEPOSITION IN THE NEONATAL RAT AORTA
No full textAscorbic acid plays an important role in connective tissue metabolism, where, among other effects, it acts as a reducing factor in the reactions catalyzed by prolyl and lysyl hydroxylases. In vitro, ascorbic acid has been shown to have a positive influence on collagen synthesis at pre- and/or post-translational levels and a negative effect on elastin production. In the present work, the effects of vitamin C on extracellular matrix deposition have been studied in vivo. Stereological analysis on electron micrographs showed, compared to age-matched controls, a 50 to 60% increase of collagen deposition in the media and in the adventitia of the aorta of rats treated for 30 days from the 18th day of life with 10% ascorbate in their drinking water. By contrast, elastin volume density was significantly reduced by the treatment at all ages examined. These morphological data were supported by in situ hybridization observations showing enhanced collagen type I mRNA and reduced elastin mRNA expression upon treatment. Although vitamin C did not inhibit lysyl oxidase activity in vivo, being only slightly higher than in controls, enzyme activity was significantly reduced, when high doses of ascorbate were added in vitro. Lysyl oxidase activity may be a function of enhanced collagen metabolism rather than a direct effect of the vitamin on the enzyme activity. These data indicate that ascorbate exerts opposite effects on the deposition of two major components of the extracellular matrix in vivo, at least during periods of rapid growth
STRUCTURE AND COMPOSITION OF THE ELASTIN FIBER IN NORMAL AND PATHOLOGICAL CONDITIONS
No full textElastin fibres are present in all connective tissues of vertebrates, and are particularly abundant in those undergoing physiological mechanical stress. Elastin, the main component of the fibres, is secreted as soluble tropoelastin molecules, that are crosslinked into insoluble aggregates in the extracellular space. Tropoelastin is highly hydrophobic and is encoded by a single copy gene, localized on chromosome 7 in humans; the primary transcript undergoes alternate splicing giving rise to different tropoelastin molecules, whose distribution and physiological significance are still under investigation. Elastin shows a transient developmental expression, with barely detectable turnover during adult life. In thin sections, elastin fibres appear rather compact and consist of an amorphous material (true elastin) and of longitudinal strips, probably made of various components. By freeze-fracture and negative staining, the elastin fibre has been shown to be made of a loose irregular network of beaded filaments, which can be oriented by stretching. Cytochemical and immunocytochemical approaches have shown that elastin fibres contain proteoglycans as well as sites recognized by antibodies to lysyl oxidase and microfibrillar components. It has been suggested that microfibrils and proteoglycans might have a role in elastin fibrogenesis. Elastin fibres undergo irreversible alterations during aging and in pathological conditions. These alterations consist mainly of accumulation of ions and of abnormal matrix constituents, and/or swelling and disaggregation of the fibre itself
ROLE OF THE EXTRACELLULAR-MATRIX IN AGE-RELATED MODIFICATIONS OF THE RAT AORTA - ULTRASTRUCTURAL, MORPHOMETRIC, AND ENZYMATIC EVALUATIONS
No full textConnective tissues such as blood vessels are known to be greatly affected by age because of impaired functional properties and increased susceptibility to diseases. With the aim of providing further information on the role of the extracellular matrix in age-related modifications, we investigated the aorta in the rat model from birth to senescence by means of morphological and morphometric observations and by evaluation of lysyl oxidase activity. Results focused on the dramatic vascular rearrangements due to progressive fibrosis of the extracellular matrix and on prominent elastin modifications. The presence of lysyl oxidase activity, even in the oldest animals, might be at least partly responsible for the increased stiffness of the aging extracellular matrix. The striking age-related remodeling of the aortic architecture and the alterations of the interactions between cellular and extracellular compartments might greatly influence the functional properties of the arterial wall in senescence, at least contributing to the consequences of some apparently age-related vascular disorders
The effect of caloric restriction on the aortic tissue of aging rats
No full textConnective tissue shows peculiar and complex age-related modifications, which can be, at least in part, responsible for altered functions and increased susceptibility to diseases. Food restriction has long been known to prolong life in rodents, having antiaging effects on a variety of physiologic and pathologic processes. Therefore, the aorta has been investigated in rats fed normal or hypocaloric diet, from weaning to senescence. Compared with controls, caloric-restricted animals showed less pronounced age-dependent alterations such as elastic fiber degradation, collagen accumulation and cellular modifications. Immunocytochemical analyses revealed that elastic fibers were positively labelled for biglycan, decorin, ApoB100 (LDL), ApoAl (HDL) and elastase and that the intensity of the reactions was time- and diet-dependent, With age, the major changes affecting aortic elastic fibers were increased positivity for decorin, LDL and elastase, Compared with age-matched normal fed rats, caloric restricted animals revealed lower content of LDL, decorin and elastase and higher positivity for HDL. These data suggest that a caloric restricted diet might influence the aging process of the arterial wall in rats, delaying the appearance of age-related degenerative features, such as structural alterations of cells and matrix and modified interactions of elastin with cells and with other extracellular matrix molecules
The De Barsy syndrome
No full textBackground: In 1968, De Barsy reported on a girl exhibiting an aged aspect, 'dwarfism, oligophrenia, and degeneration of the elastic tissue in cornea and skin'. The disorder was recognized as a subgroup of cutis laxa syndrome and termed De Barsy-Moens-Dierckx syndrome. The pathogenesis of the disorder is unknown. Methods: To improve the comprehension of the pathogenetic mechanisms involved in the De Barsy syndrome, we performed an ultrastructural, morphometric, immunocytochemical study on a skin biopsy of a boy with the De Barsy phenotype, who has been clinically followed for 12 years from birth. Moreover, the lysyl oxidase activity was measured on skin fibroblasts cultured in vitro. Results: Light and electron microscopy, morphometry, and immunocytochemical observations showed a significant reduction of the elastic fibers in the papillary and in the reticular dermis of patient compared to an age-matched control (p < 0.05). By contrast, the collagen structure, content, and the distribution were normal, as well as lysyl oxidase activity in the medium of in vitro fibroblasts (12,323 DPM/10(6) cells). The immunoreaction for antibodies recognizing fibrillin-1, neutrophilic elastase, and tumor necrosis factor-alpha was stronger, whereas that for antibodies against transforming growth factor-beta was less pronounced in the dermis of the De Barsy boy compared to control. Conclusions: Clinical, phenotypic, and structural data were consistent with the diagnosis of De Barsy syndrome. This is the first case described in Italy. Clinical and structural data confirm that the elastic component is mostly affected in this disorder. Moreover, ultrastructural and immunochemical findings suggest that both elastic fiber degradative and very likely synthetic processes are involved
Study of elastic fiber organization by scanning force microscopy
No full textElastic fibers of beef ligamentum nuchae were observed by atomic force microscopy and data compared with those obtained by conventional and freeze-fracture electron microscopy. Fresh isolated elastin fibers as well as thin sections of ligament fragments, which were fixed and embedded either in relaxed or in stretched, conditions, were analysed. The results confirm that, at least in beef ligamentum nuchae, elastic fibers consist of beaded filaments which can be oriented by stretching in the direction of the force applied. Moreover, atomic force microscopy revealed that these beaded filaments are laterally connected by periodical bridges which become more pronounced upon stretching. The data clearly show that elastin molecules are organized in a rather ordered array, at least at the super-molecular level, and a depiction of the elastin organization in beef ligament um nuchae is attempted
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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