1,720,960 research outputs found
A family of non-collagen-based cartilages in the skeleton of the sea lamprey, Petromyzon marinus
No full textCartilage structures of the sea lamprey, Petromyzon marimus, have previously been reported to stain by the Verhoeff method for elastin and to have a morphology similar to that of elastic cartilage of higher vertebrates. Earlier we showed that lamprin, the major matrix protein of lamprey annular cartilage, although not identical to elastin, cross-reacted with antibodies to elastin and shared significant sequence and structural similarities. Here we demonstrate that the majority of the skeletal cartilage of the lamprey is noncollagenous in character, remaining intact after treatment of the tissues with cyanogen bromide. However, unlike annular and neurocranial cartilages, which consist mainly of lamprin, evidence from amino acid compositions, immunohistochemistry, and western and northern blotting indicates that the major matrix protein of branchial and pericardial cartilage is not lamprin, but a second cyanogen bromide-insoluble protein or group of proteins with similarities to elastin. These results suggest that the skeletal cartilage of lower vertebrates consists of a family of noncollagenous, elastin-like proteins. The relationships among members of this family of cartilaginous proteins and between these proteins and vertebrate elastins, and the implications of these relationships for understanding the evolutionary lineage of elastin will await further characterization of these proteins. (C) 1997 Elsevier Science Inc.PT: J; NR: 22; TC: 13; J9: COMP BIOCHEM PHYSIOL PT B; PG: 8; GA: YE823Source type: Electronic(1
Cartilage in the Atlantic hagfish, Myxine glutinosa
No full textLight and electron microscopic observations and biochemical analysis of the lingual cartilages from the Atlantic hagfish, Myxine glutinosa, reveal two different types of cartilage, designated types 1 and 2, respectively. The anterior and medial lingual are type 1, while the posterior lingual cartilage is type 2. Chondrocytes in type 1 cartilage are similar to those found in other vertebrate cartilages. The presence within the Golgi elements of material that resembles a component of the extracellular matrix suggests the involvement of active chondrocytes in the synthesis of the matrix. The matrix of the type 1 cartilage contains fibrils arranged to form concentric lamellae in the territorial matrix and irregularly arranged, branched fibrils in the interterritorial matrix. Biochemical analysis of the type 1 cartilage reveals that it is composed primarily of a cyanogen bromide (CNBr)-insoluble protein of unique composition that we have termed " myxinin ." Myxinin appears to be similar, but not identical, to lamprin . Type 2 cartilage bears no resemblance to any other known vertebrate cartilage. The principal cells are hypertrophied and are characterized by masses of cytoplasmic filaments. The appearance of the organelles in smaller nest cells suggests that nest cells are active in the production of some of the matrix, which consists primarily of collagen. Microfibrils and a basal lamina-like material are also present. Biochemical analysis of the type 2 cartilage reveals that the CNBr-insoluble material is different from myxinin . Comparisons of lamprey and hagfish cartilages prompt the concept that these two agnathans probably followed long-independent evolutionary histories
The unusual cartilaginous tissues of jawless craniates, cephalochordates and invertebrates
No full textA collagenous extracellular matrix was previously considered to be a requirement for classification of true cartilage. Data from the lamprey and hagfish now clearly indicate that both of these jawless craniates have extensive non-collagenous, yet cartilaginous endoskeletons. Non-collagenous cartilages are present in the cephalochordates (amphioxus) and in the invertebrates, although collagen-containing cartilages also are found in the invertebrates. This review summarizes current knowledge of the morphological, biochemical and molecular characteristics of the unusual non-collagenous cartilages in jawless craniates and the cartilaginous tissues in amphioxus and invertebrates. A least two types of non-collagenous cartilage matrix proteins are found in both the hagfishes and the lampreys, all of which are resistant to digestion by cyanogen bromide (CNBr). Although all four of these matrices show some similarities with each other, suggesting a family of non-collagenous, elastin-like proteins, it is clear that the major matrix proteins of each are different. New morphological and biochemical information on the cartilaginous tissues in squid, horseshoe crab and amphioxus reveals the presence of CNBr-insoluble, non-collagenous matrix proteins, potentially extending the jawless craniate family of cartilaginous proteins into the invertebrates. Details of the evolutionary relationships between these non-collagenous matrix proteins and the significance of the occurrence of these proteins as the major components of the cartilaginous tissues of jawless craniates, amphioxus, horseshoe crab and squid, all of which are capable of producing a variety of collagens in other tissues, remain to be investigated
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
Lamprin: a new vertebrate protein comprising the major structural protein of adult lamprey cartilage
No full textPT: J; CR: HARDISTY MW, 1979, BIOL CYCLOSTOMES HUBBS CL, 1971, BIOLOGY LAMPREYS, V1, P1 JOHNSON RG, 1980, CLIN ORTHOPAEDICS, V146, P282 KELLY RE, 1967, SCIENCE, V155, P208 MATHEWS MB, 1967, BIOL REV, V42, P499 MATHEWS MB, 1975, CONNECTIVE TISSUE MA ROBERT L, 1976, METHODOLOGY CONNECTI, P81 SAGE EH, 1977, ADV EXP MED BIOL, V79, P291 SAGE H, 1979, COMP BIOCHEM PHYS B, V64, P313 SAGE H, 1980, COMP BIOCHEM PHYS B, V66, P13 SAGE H, 1981, COMP BIOCHEM PHYS B, V68, P473 SAJDERA SW, 1969, J BIOL CHEM, V244, P77 SCHAFFER J, 1930, HDB MIKROSKOPISCHEN STARCHER BC, 1976, ANAL BIOCHEM, V74, P441 STOCKWELL RA, 1979, BIOL CARTILAGE CELLS WRIGHT GM, 1983, AM J ANAT; NR: 16; TC: 27; J9: EXPERIENTIA; PG: 3; GA: QR956Source type: Electronic(1
Distinct non-collagen based cartilages comprising the endoskeleton of the Atlantic hagfish, Myxine glutinosa
No full textPrevious evidence from our laboratories showed that collagen is not the major matrix protein of the cartilaginous endoskeleton of the lamprey (Petromyzon marinus). Here we have characterized the cartilage matrix proteins of the only other extant agnathan, the hagfish (Myxine glutinosa). Using morphological, immunochemical and biochemical methods, we show that the structural proteins of the cartilaginous endoskeleton of the hagfish are also non-collagenous in nature. Although these hagfish cartilage proteins share properties both with each other and with lamprey cartilage proteins, including resistance to solubilization with cyanogen bromide and an usual amino acid composition rich in glycine and non-polar amino acids, it is clear that at least two and probably more hagfish cartilage proteins can be distinguished, with distinct distributions in different cartilage structures. Furthermore, in spite of their similarities, matrix proteins from hagfish cartilage are not identical to the proteins we have previously characterized in lamprey cartilage. These results suggest the existence of a larger family of similar but not identical proteins that form the major structural elements of cartilage tissues of agnathans. These data also support our previous conclusion that type II collagen became the predominant structural protein of cartilage only after the divergence of the agnathans from the ancestral line of the vertebrates.PT: J; NR: 26; TC: 13; J9: ANAT EMBRYOL; PG: 10; GA: 361PKSource type: Electronic(1
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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