1,720,957 research outputs found
Radioimmunoassay of dermorphin-like peptides in mammalian and non-mammalian tissues
No full textA selective RIA for D-Ala2-Dermorphin (Der), a natural peptide extracted from amphibian skin, has been developed using an antibody raised in rabbits against Der which has been coupled to BSA through its phenolic hydroxyl groups of tyrosine residues with 2,4-Dichloro-6-methoxy-1,3,5-triazine. The cross-reactivity of this antibody with dermorphin analogs, C- and N-terminal fragments of dermorphin molecule, some opioid and gastrointestinal peptides was tested. Der-like immunoreactivity has been identified in tissue extracts of rats, frog and cephalopoda. Der-like peptides were purified by passing methanol extracts of the tissues through a Sephadex G25 column (16x100 cm) eluted with 0.1 M acetic acid at 4°C. Der-like immunoreactivity from neural tissue of Dosidicus gigas, Eledone moscata, and rat brain showed a good agreement with an authentic sample of synthetic dermorphin
Occurrence and polymorphism of bombesin-like peptides in the gastrointestinal tract of birds and mammals
No full textThe gastrointestinal tract of mammals and birds, especially stomach and upper small intestine, contains bombesin-like peptides. This has been unequivocally demonstrated by radioimmunoassay and bioassay. Concentrations of bombesin-like activity may range from a few ng to 500-600 ng per g fresh tissue. Last values refer to the chicken proventriculus, which has been the object of a more thorough investigation. The bombesin-like peptide of the chicken proventriculus showed a marked heterogeneity. All forms probably stem from a pro-bombesin, a large precursor molecule which is insoluble in methanol, acetone, and even boiling water, but may be cleaved by acid hydrolysis. Methanol extracts contain at least 2 forms of the bombesin-like peptide; HCl extracts at least 3 forms; HCl extracts of the residue of methanol extraction at least 4 forms. Whereas some forms - for example, the methanol extractable forms - probably pre-exist in the tissue, other forms may be artefacts arising from acid treatment. The various forms may be distinguished from each other not only by their elution profile, but also by bioassay. In fact, though all forms show the activity spectrum characteristic for the amphibian bombesin-like peptides, they present considerable quantitative differences in activity. Pro-bombesin(s) probably occur also in the rat and guinea-pig stomach; similarly, a clear-cut heterogeneity is appreciable for the bombesin-like peptide of the human gastric mucosa
Occurrence of bombesin and alytesin in extracts of the skin of three European discoglossid frogs and pharmacological actions of bombesin on extravascular smooth muscle.
No full text1. Methanol extracts of the skin of Bombina bombina and Bombina variegata variegata, two European discoglossid frogs, contain an active tetradecapeptide, bombesin. Alytesin, a tetradecapeptide strictly related to bombesin is present in extracts of the skin of Alytes obstetricans, another European discoglossid frog. The American frog Rana pipiens, contains in its skin ranatensin, an endecapeptide related to bombesin and alytesin. 2. Passage of crude skin extracts of Bombina through a column of alumina yields eluates which may be considered free of other peptide contaminants and are suitable for the isolation of bombesin in a pure form. 3. Bombesin has a stimulant action on several preparations of intestinal, uterine and urinary tract smooth muscle. Sometimes the effect is easily repeatable and shows a fair proportionality to the dose, but at other times a prompt and intense tachyphylaxis is observed. Other smooth muscle preparations are poorly sensitive or insensitive to bombesin. The rat uterus, the kitten small intestine, the guinea-pig colon and the rat urinary bladder may be used for the quantitative bioassay of bombesin. 4. Bombesin-like peptides may easily be distinguished from all other naturally occurring peptides by parallel assay. They constitute a new group of active peptides possessing a peculiar spectrum of activity
Uperolein and other active peptides in the skin of the Australian leptodactylid frogs Uperoleia and Taudactylus
No full textMethanol extracts of the skin of the Australian leptodactylid frogs Uperoleia rugosa, Uperoleia marmorata and Taudactylus acutirostris contain several highly active polypeptides belonging to different peptide families. The most abundant peptide was uperolein, a tachykinin closely related to physalaemin and possessing the same spectrum of biological activity. Uperolein was present in the three species examined. Other tachykinins were represented by Rugosa uperolein II and Marmorata uperolein II, the structures of which still await full elucidation. Another peptide family represented in both Uperoleia and Taudactylus was that of bombesin like peptides. They were abundant in Uperoleia rugosa and scarce in Uperoleia marmorata and in Taudactylus. These bombesins are possibly similar to the bombesins, among which is litorin, present in the skin of other Australian leptodactylid frogs. Finally, Taudactylus contained a bradykinin like peptide and both the Uperoleia species an hitherto unclassified peptide. These new findings have further enriched the already considerable list of active peptides and biogenic amines occurring in the amphibian skin
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
Physalaemin- and bombesin-like peptides in the skin of the Australian leptodactylid frog Uperoleia rugosa.
No full text[No abstract available
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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