117,285 research outputs found
Selection of methotrexate-resistant cell lines in Daucus carota: biochemical analysis and genetic characterization by protoplast fusion
No full textIn this work we report the isolation and characterization of carrot cell lines resistant to methotrexate (Mtx). Selection of spontaneous variants was accomplished by one step and two step exposure to Mtx. Among lines that showed normal Mtx uptake, no difference from the parental line was found in inactivation of the inhibitor or affinity of dihydrofolate reductase (DHFR) for Mtx.
One step resistant lines, when maintained in a medium lacking Mtx for at least 75 days, showed a DHFR specific activity and capacity to bind Mtx 3 -4 times that of the parental one and these values remained stable up to 6 months. DHFR activity appeared to be very low in cell lines grown with Mtx, due to the presence of an inhibitor, possibly Mtx itself, in the cell extract.
Nevertheless, measurement of the amount of DHFR using antibodies to the pure enzyme indicated that the level of the enzyme is about the same in lines maintained either in the presence or in the absence of Mtx. Genetic analysis by protoplast fusion has shown that resistance is a dominant or semidominant trait
SELECTION OF METHOTREXATE-RESISTANT CELL-LINES IN DAUCUS-CAROTA - BIOCHEMICAL-ANALYSIS AND GENETIC-CHARACTERIZATION BY PROTOPLAST FUSION
No full textLapidaster etteri Thuy 2013, sp. nov.
No full textLapidaster etteri sp. nov. urn:lsid:zoobank.org:act: DFBC69CF-37F1-4D39-A8F3-D8DA46708D05 Fig. 9: 1-5 p.p. Ophiopholis ? trispinosa Hess, 1965a: 1067, 1075, figs 16, 38-40 (non figs 36-37, referable to Ishidacantha trispinosa (Hess, 1965) comb. nov.) Diagnosis Species of Lapidaster gen. nov. with relatively large LAPs showing a weak constriction, a widened dorsal tip of the ridge on the inner side and a thickened ventral part. Etymology Species named in honour of Walter Etter (Naturhistorisches Museum Basel, Switzerland), who generously provided access to the original material of Hans Hess’s pioneering studies on ophiuroid micropalaeontology, inclusive of the type material of the new species. Type material Holotype NHMB M11209. Paratypes NHMB M11210, NHMB M11211, NHMB M11212 and NHMB M11213. Type locality and horizon Longecombe, France; Renggeri Member, Bärschwil Formation, early Oxfordian, Late Jurassic. Additional material 304 dissociated LAPs from Longecombe, France, the original material of Hess (1965a); 7 dissociated LAPs from Chapois, France, the original material of Hess (1965a). Description Holotype NHMB M11209 is a dissociated, medium-sized proximal lateral arm plate, slightly wider than long, with strongly concave proximal edge and strongly convex distal edge; ventro-proximal quarter of LAP protruding ventro-proximalwards; slight constriction, resulting in slightly concave dorsal edge; horizontal, elongate, moderately well-defined and prominent spur close to ventro-proximal tip of LAP. Outer surface with coarsely reticulate stereom with thickened trabeculae; trabeculae without tendency to develop into vertical striation; coarsely reticulate stereom evenly surrounding all spine articulations, grading into finely meshed stereom close to proximal edge. Four large, ear-shaped spine articulations, freestanding in continuous row close to distal edge of LAP, dorsal and ventral lobes forming continuous volute in all spine articulations; proximal edge of dorsalmost spine articulation overlapped by finely reticulate stereom; ventralmost and dorsalmost spine articulations smaller than two median ones; dorsalward increase in size of gaps separating spine articulations. Ventral edge of LAP with large, conspicuous and gently concave tentacle notch. Inner side of LAP with sharply defined, narrow, prominent ridge; dorsal half of ridge oblique and nearly straight, with rounded tip nearly twice wider than remaining dorsal half of ridge and not reaching dorsal or proximal edges of LAP; ventral half of ridge slightly wider than dorsal half, separated from the latter by rounded kink, less sharply defined and prominent than dorsal half but not confluent with thickened ventral edge of LAP. Single irregular perforation discernible on inner side of LAP near tentacle notch. Small, moderately well-defined, prominent and slightly oblique ridge on inner side of ventro-distal tip of LAP. Inner side of tentacle notch with coarsely reticulate and horizontally stretched stereom. Paratype supplements and variation NHMB M11210 is a dissociated median lateral arm plate, wider than high. Overall morphology well in agreement with that of holotype. Constriction stronger than in holotype, resulting in clearly concave dorsal edge of LAP. Spur near ventro-proximal edge of LAP poorly defined, hardly discernible. Three spine articulations in continuous row; median spine articulation slightly larger than others. Ventral edge of LAP with large, conspicuous tentacle notch. Inner side with well-defined, narrow, prominent ridge; dorsal half of ridge strongly oblique, straight, with slightly widened dorsal tip; ventral half of ridge wider than dorsal one but less well-defined, not confluent with thickened ventral edge of LAP. Small, very poorly defined and barely prominent spur on inner side of ventro-distal edge. NHMB M11211 is a dissociated distal LAP, almost three times wider than high, of rectangular to barlike outline; distal edge gently convex, proximal edge concave; slight constriction, resulting in very gently concave dorsal edge and clearly concave ventral edge of LAP; no spurs discernible on outer proximal edge. Two spine articulations, nearly equal in size. Large tentacle perforation near ventral spine articulation. Inner side with two very small, irregular, diffuse, slightly prominent and widely separate knobs. Large tentacle perforation in centre of distal half of LAP. NHMB M11212 is a median arm fragment composed of two articulated segments. LAPs well in agreement with type specimens; ventral arm plates T shaped, with narrow proximal half, concave lateral edges, distal half almost three times wider than proximal half, distal edge straight to slightly concave. Tentacle openings clearly larger than half the width of the ventral arm plates. Dorsal arm plates very thin, wedge shaped, with strongly acute proximal angle, outline of distal edge not clearly discernible. Single arm spine preserved, attached to ventral spine articulation, conical, with coarse outer surface, broken tip but probably not much longer than half the width of a LAP. NHMB M11213 are two distal arm fragments composed of five intact arm segments. One LAP preserving two arm spines in place, ventral one broken, dorsal one intact, shorter than half the width of a LAP, conspicuously claw shaped with point facing ventralwards. Remarks When Hess (1965a) described a new species, Ophiopholis ? trispinosa, on the basis of dissociated LAPs and articulated arm fragments from the Oxfordian of France, he lumped two entirely different LAP types under a single species. A re-examination of the original material has now revealed that one type, figured in the original description (Hess 1965a: figs 16, 38-40) along with the second type, bears a striking similarity to the LAPs of extant Ophiologimus. The presence of a spur on the outer proximal and inner distal edges places this type of LAPs in Lapidaster gen. nov. In view of the fact that the holotype of O. ? trispinosa is a LAP of the second type (see below for a detailed reassessment), however, the species name cannot be used for the LAPs assigned to Lapidaster gen. nov. The latter are therefore here described as a new species. Greatest similarities are shared with the LAPs of Lapidaster lukenederi sp. nov., especially on account of the slight constriction. The LAPs of Lapidaster etteri sp. nov., however, differ in being more markedly thickened near their ventral edge and in having a better-developed spur on the outer proximal and inner distal edges and a dorsally widened tip of the ridge on the inner side. Lapidaster etteri sp. nov. is the sole species of the genus of which arm spines and ventral and dorsal arm plates are available. Hook-shaped spines on distal arm segments, as observed in the articulated arm fragments of L. etteri sp. nov. described above are commonly found in extant species of Ophiologimus (e.g. O’Hara & Stöhr 2006; Martynov 2010). In addition, tentacle pores of the distalmost arm segments developed as within-plate perforations rather than between-plate openings, as observed in L. etteri sp. nov., are regularly seen in extant species of Ophiologimus. The hook-shaped arm spines and within-plate tentacle openings in distalmost arm segments provide additional evidence for the close ties between both genera. Occurrence Early Oxfordian of France.Published as part of Thuy, Ben, 2013, Temporary expansion to shelf depths rather than an onshore-offshore trend: the shallow-water rise and demise of the modern deep-sea brittle star family Ophiacanthidae (Echinodermata: Ophiuroidea), pp. 1-242 in European Journal of Taxonomy 48 on pages 39-42, DOI: 10.5852/ejt.2013.48, http://zenodo.org/record/382283
Selection of methotrexate-resistant cell lines in Daucus carota: biochemical analysis and genetic characterization by protoplast fusion.
No full textBiochemical and somatic cell genetic analysis of a carrot cell line resistant to methotrexate
No full textGoing Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Square Dancing with the Stars to Enhance Dynamic Hirschman Linkages?
No full textIn this Presidential Address, the author takes the reader on a reconnaissance of his life and time as a regional scientist. He points out scenery he found scintillating along the way, hoping that some may pick up the banner and chew on a few of the ideas for a while. He suggests a revisit to Albert O. Hirschman’s notion of key sectors and more empirical analysis related to Marcus Berliant’s and Masahisa Fujita’s notion of knowledge creation and transfer.Presidential Address, San Antonio, Texas, March 29, 2014 (53rd Meetings of the Southern Regional Science Association
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe 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
Letter from unknown writer to Jesse L. Boyce
No full textLetter to Jesse L. Boyce from unknown author (possibly Jack) about the investigation into the powder magazine located in the Grand Canyon. Some personal news is included in the letter such as the writer's marriage to the daughter of C.A. Taylor, former Supervisor of Cochise County
Dispelling the Myths Behind First-author Citation Counts
No full textWe 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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