1,721,017 research outputs found
Characterization of phospholipase A2 from the pyloric ceca of two species of starfish, Coscinasterias acutispina and Plazaster borealis
Get PDFPhospholipase A (PLA) activities in the pyloric ceca and viscera from seven species of marine invertebrates (four starfish, one sea urchin, and two shellfish) were determined. Relatively high PLA specific activities were found in the pyloric ceca of two species of starfish (Coscinasterias acutispina and Plazaster borealis). Phospholipase A2s (PLA2s) were partially purified from the pyloric ceca of the starfish, C. acutispina PLA2 (C-PLA2) and P. borealis PLA2 (P-PLA2). The C-PLA2 and P-PLA2 mainly released oleic acid from 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine. Temperature optima of the C-PLA2 and P-PLA2 were at around 60 °C and 50 °C, respectively, and pH optima of the C-PLA2 and P-PLA2 were both at around pH 10.0. The activities of the C-PLA2 and P-PLA2 were enhanced by sodium deoxycholate and 1 mM or higher concentration of Ca2+. The C-PLA2 and P-PLA2 did not show the fatty acid specificity for hydrolysis of phosphatidylcholine. Unlike porcine pancreatic PLA2, the C-PLA2 and P-PLA2 hydrolyzed phosphatidylcholine more effectively than phosphatidylethanolamine
Characteristics of phospholipase A2 mutant of the starfish Asterina pectinifera
Get PDFSite-directed mutagenesis study of phospholipase A2 (PLA2) from the pyloric ceca of starfish Asterina pectinifera was used to probe the relationship between polar-group specificity and structure of the pancreatic loop region. The sequence of the cDNA encoding the starfish PLA2 was exchanged by the oligonucleotide-directed dual amber-long and accurate polymerase chain reaction method to insert Lys residue between Cys-62 and Gly-63. The modified cDNA was inserted into the expression plasmid pET-16b, and PLA2 mutant was expressed in Escherichia coli Origami™ B (DE3) by induction with isopropyl-beta-d(−)-thiogalactopyranoside. The starfish PLA2 mutant showed essentially the same properties as the starfish native PLA2 with respect to substrate positional specificity, optimum pH, optimum temperature, Ca2+ requirement, and sodium deoxycholate requirement. However, the specific activity of the starfish PLA2 mutant for egg yolk PC (950 U/mg) was extremely lower than that of native PLA2 (119,000 U/mg), but close to that of porcine pancreatic PLA2 (4300 U/mg). Moreover, the ratio of specific activity of the PLA2 mutant for phosphatidylcholine to phosphatidylethanolamine (98 times) was highly lower than that of native PLA2 (2650 times), but similar to that of porcine pancreatic PLA2 (25 times). Therefore, it was suggested that the charge and structure of pancreatic loop region of the starfish PLA2 might carry out important role on polar-group specificity
Isolation and characteristics of trypsin from pyloric ceca of the starfish Asterina pectinifera
Get PDFTrypsin was purified from pyloric ceca of the starfish Asterina Pectinifera by ammonium sulfate precipitation, gel filtration, and cation-exchange chromatography. Final enzyme preparation was nearly homogeneous in sodium dodecyl sulfate-polyacrylamide gel electrophoresis and its molecular weight was estimated as approximately 28 000. Optimum pH and temperature of A. pectinifera trypsin for hydrolysis of Nα-p-Tosyl--arginine methyl ester hydrochloride were approximately pH 8.0 and 55 °C, respectively. A. pectinifera trypsin was unstable at above 50 °C and below pH 5.0, and was not activated by adding Ca2+. The N-terminal amino acid sequence of A. pectinifera trypsin, IVGGHEF, was found
Isolation and characteristics of carboxypeptidase B from the pyloric ceca of the starfish Asterias amurensis
Get PDFCarboxypeptidase B was purified from the pyloric ceca of the starfish Asterias amurensis. The final enzyme preparation was nearly homogeneous in polyacrylamide gel electrophoresis and its molecular weight was estimated as approximately 34 000. The optimum pH and temperature of the enzyme for hydrolysis of benzoyl-glycyl--arginine were at approximately pH 7.5 and 55 °C, respectively. The enzyme was unstable at above 50 °C and at below pH 5.0. The enzyme was activated by Co2+, but was inhibited by EDTA and Hg2+. The N-terminal amino acid sequence of A. amurensis carboxypeptidase B was ASFDYNVYHSYQEIMNWITN
Purification and properties of phospholipase A2 isozymes from pyloric ceca of the starfish (asterina pectinifera)
Get PDFPhospholipase A2 isozyme II (PLA2 II) which showed different mobility on native PAGE from that of the PLA2 isozyme I (PLA2 I) isolated previously was purified from pyloric ceca of the starfish (Asterina pectinifera). The PLA2 II was mainly released oleic acid from 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine. N-terminal amino acid sequence of the PLA2 II was SVYQF. Temperature and pH optimums of the PLA2 II were at around 50C and pH 9.0, respectively, and the enzyme activity was enhanced by sodium deoxycholate and 1 mM or higher concentration of Ca2+. The PLA2 II did not show the fatty acid specificity for hydrolysis of phosphatidylcholine (PC). Specific activity of the PLA2 II was about 10 times higher than that of commercially available porcine pancreatic PLA2. The PLA2 II hydrolyzed PC more effectively than phosphatidylethanolamine. These characteristics of the PLA2 II were the same as those of the PLA2 I.The definitive version is available at www.blackwell-synergy.co
Purified sardine and king crab trypsin display individual differences in PAR-2-, NF-kB-, and IL-8 signaling
No full textRespiratory symptoms occur in workers processing a great variety of seafood. Studies previously showed that salmon trypsin increases transcriptional activity of NF-κB and induces secretion of IL-8 from airway epithelial cells by activating PAR-2. The aim of this study was to explore if purified trypsins from king crab (Paralithodes camtschaticus) and sardine (Sardinops melanostictus) are able to induce similar effects in cell stimulation assays. The knowledge that crustaceans seem to display dissimilar irritant potency compared to fish inspired us to investigate if one could detect differences in intracellular signaling pathways coupled to IL-8 in human airway epithelial cells (A549). Both sardine and king crab trypsin induced secretion of IL-8 from human airway epithelial cells in a concentration-dependent manner and increased transcriptional activity of NF-κB. With the use of siRNA data indicate that these effects are both mediated, at least partly, through the activation of PAR-2. Additionally, the king crab and sardine trypsin display individual differences in transformation of the NF-κB signal into subsequent IL-8 secretion. The contribution of MEK/ERK, p38, and NF-κB to the secretion of IL-8 following stimulation with sardine and king crab trypsins were examined with the use of specific inhibitors. The results demonstrated that MEK/ERK and NF-κB are both required for sardine and king crab trypsin-induced secretion of IL-8 but via separate pathways. P38 was also found to contribute to the secretion of IL-8 seemingly by NF-κB-dependent processes
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
- …
