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Synthesis of elastin in aortas from chick embryos. Conversion of newly secreted elastin to cross-linked elastin without apparent proteolysis of the molecule.
No full textThe biosynthesis of elastin was examined in matrix-free cells isolated by enzymic digestion of aortas from 17-day old chick embryos. After the cells were incubated with [14C]proline and then were rapidly boiled in buffer containing high concentrations of protease inhibitors and sodiumdodecyl sulfate, about one-quarter of the intracellular 14C-labeled protein was recovered as an elastin component with an apparent molecular weight of about 72 000. Examination of the medium from the cell suspension indicated that the largest elastin component secreted by the cells also had an apparent molecular weight of about 72 000. Pulse-chase experiments with intact aortas demonstrated that about two-thirds of the 72 000-dalton component disappeared in 2 h, apparently because it was converted to cross-linked fibers. When cross-linking was inhibited with penicillamine, the 72 000-dalton component persisted in the tissue 5 h. When cross-linking was inhibited with beta-aminopropionitrile, the elastin component of 72 000 daltons persisted for about 2 h, but thereafter it was gradually degraded to small peptides which were recovered in the incubation medium. The results suggest that elastin is secreted by cells in chick aorta as a polypeptide of about 72 000 daltons and that the secreted protein is incorporated into elastin fibers without cleavage to a protein of considerably smaller size
Is newly-secreted elastin cleaved to a smaller molecule before being incorporated into crosslinked elastin fibers?
No full textThe biosynthesis of elastin was examined in matrix-free cells isolated by enzymatic digestion of aortas from 17 day old chick embryos. When the cells were incubated with (14C) proline and then were rapidly boiled in buffer containing high concentrations of protease inhibitors and sodium dodecylsulfate, about one-quarter of the intracellular (14C)-protein was recovered as an elastin component with apparent molecular weight of about 72,000. Examination of the medium from the cell suspension indicated that the largest elastin component secreted by the cells also had an apparent molecular weight of about 72,000
Kinetics of the incorporation of tropoelastin into elastic fibers in embryonic chick aorta.
No full textMatrix-free cells isolated by enzymic digestion of chick embryo aortas were labeled with [14C]proline for 20 to 60 min and the kinetics of the secretion of tropoelastin were followed by chasing the label and assaying [14C]tropoelastin in the cells and in the medium. The results indicated that secretion of tropoelastin followed the kinetics of a single first order process with a half time of 60 min. In parallel experiments tissue explants of chick embryo aortas were labeled with [14C]proline and the kinetics for the incorporation of tropoelastin into elastic fibers were followed by chasing the label and assaying the soluble [14C]tropoelastin and insoluble [14C]elastin in tissues. It was found that the incorporation of tropoelastin into elastic fibers also followed a single first order process with a half time of 85 min, similar to the secretion of tropoelastin from cells. In further studies, antibodies directed against tropoelastin were utilized to isolate soluble [14C]elastin components in the tissues after 0 to 4 hr chase of the 14C label. The results demonstrated that all soluble elastin components were recovered as monomeric tropoelastin and no soluble oligomeric elastin could be detected. These results are consistent with the proposition that elastic fiber growth occurs by addition of individual tropoelastin molecules to existing fibers and that oligomers of elastin were not intermediates in the process
Demonstration by immunofluorescence that the same cells from chick embryo aortas synthesize elastin and collagen types I and III.
No full textCells were isolated from the aortas of 17-day old chick embryos and they were stained with fluorescent antibodies specific for Type I collagen, Type I procollagen, Type III collagen, elastin and prolyl hydroxylase. The results indicated that the same cells simultaneously synthesize Type I procollagen, Type III procollagen and elastin. The synthesis of procollagens, and the presence of prolyl hydroxylase, in the same cells which synthesize elastin may well explain why elastin contains hydroxy-proline
Synthesis of an elastin component of molecular weight about 70,000 by polysomes from chick embryo aortas.
No full textPolysomes were isolated from aortas of 17-day-old chick embryos, and the syntehsis of the nascent polypeptide chains was completed in vitro. When a mixture of a labeled amino acids found in elastin was used, the major radioactive product obtained was of molecular weight about 70,000 and was similar to elastin by several criteria. The 70,000 molecular weight product was extractable in propanol-butanol, it was not labeled with (35)S-methionine, and it was precipitated by antibodies against elastin. Polypeptides lager than 70,000 molecular weight were also synthesized, but these lager polypeptides incorporated relatively small amounts of (14)C-valine, and they appeared to represent pro-alpha chains of procollagen. These results suggest that the major gene product for elastin has a molecular weight of about 70,000
Intracellular-localization of the precursors of type-I-collagen as shown by immunoperoxidasic and immunoradioautographic techniques
No full textPT: J; CR: CARNEIRO J, 1959, EXP CELL RES, V18, P291 CARNEIRO J, 1966, J HISTOCHEM CYTOCHEM, V14, P334 CHUNG E, 1974, SCIENCE, V183, P1200 COURNIL I, 1979, J HISTOCHEM CYTOCHEM, V27, P1059 EPSTEIN EH, 1974, J BIOL CHEM, V249, P3225 FORSGREN A, 1967, J IMMUNOL, V99, P19 KARIM A, 1979, J HISTOCHEM CYTOCHEM, V27, P1070 KEFALIDES NA, 1973, INT REV CONNECTIVE T, V6, P63 LEBLOND CP, 1963, ANN HISTOCHIM, V8, P43 LEBLOND CP, 1980, BASIC MECHANISMS CEL MILLER EJ, 1973, CLIN ORTHOPAEDICS, V92, P260 PAIEMENT J, 1977, J CELL BIOL, V74, P992 PROCKOP DJ, 1979, NEW ENGL J MED, V301, P13 TRAUB W, 1971, ADV PROTEIN CHEM, V25, P243 VONDERMARK K, 1977, DEV BIOL, V59, P75 WEINSTOCK M, 1974, J CELL BIOL, V60, P92 WEINSTOCK M, 1975, EXTRACELLULAR MATRIX, P119 WEINSTOCK M, 1977, J ULTRASTRUCT RES, V61, P218; NR: 18; TC: 5; J9: ACTA HISTOCHEM CYTOCHEM; PG: 12; GA: JM029Source type: Electronic(1
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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