1,721,002 research outputs found
Receptor Proteins for Nongenomic Actions of Thyroid Hormone.
No full textGenomic actions of thyroid hormone require the intranuclear binding by nuclear thyroid hormone receptors (TRs) of 3,5,3’-triiodo-L-thyronine (T3). Nongenomic actions of the hormone have been described that are initiated at the plasma membrane, in cytoplasm or in the mitochondrion. These are complex processes associated with maintenance of the cytoskeleton, control of cell respiration, cell proliferation—including tumor cell proliferation and angiogenesis—and nervous system function. We briefly review here the nature of the proteins which are now appreciated to initiate nongenomic actions of the hormone when they bind T3 or L-thyroxine (T4). These receptor proteins for nongenomic effects include truncated isoforms of TRalpha, cytoplasmic intact TRbeta, certain cytoplasmic enzymes and a structural protein of the plasma membrane, integrin alphaVbeta3
Thyroid Hormone and P- Glycoprotein in tumor cells.
No full textP-glycoprotein (P-gp; multidrug resistance pump 1, MDR1; ABCB1) is a plasma membrane efflux pump that when activated in
cancer cells exports chemotherapeutic agents. Transcription of the P-gp gene (MDR1) and activity of the P-gp protein are known to
be affected by thyroid hormone. A cell surface receptor for thyroid hormone on integrin v3 also binds tetraiodothyroacetic
acid (tetrac), a derivative of L-thyroxine (T4) that blocks nongenomic actions of T4 and of 3,5,3-triiodo-L-thyronine (T3) at
v3. Covalently bound to a nanoparticle, tetrac as nanotetrac acts at the integrin to increase intracellular residence time of
chemotherapeutic agents such as doxorubicin and etoposide that are substrates of P-gp. This action chemosensitizes cancer cells.
In this review, we examine possible molecular mechanisms for the inhibitory effect of nanotetrac on P-gp activity.Mechanisms for
consideration include cancer cell acidification via action of tetrac/nanotetrac on the Na+/H+ exchanger (NHE1) and hormone
analogue effects on calmodulin-dependent processes and on interactions of P-gp with epidermal growth factor (EGF) and
osteopontin (OPN), apparently via v3. Intracellular acidification and decreasedH+ efflux induced by tetrac/nanotetrac viaNHE1
is the most attractive explanation for the actions on P-gp and consequent increase in cancer cell retention of chemotherapeutic
agent-ligands of MDR1 protein
Nongenomic regulation by thyroid hormone of plasma membrane ion and small molecule pumps
No full textThe sodium/proton (Na/H) exchanger, Na,K-ATPase, and Ca2+-ATPase are membrane ion pumps whose basal activities may be regulated by local nongenomic actions of thyroid hormone and hormone analogues via a hormone receptor on plasma membrane integrin αvβ3. System A amino acid transport and the activity of P-glycoprotein (P-gp; ABCB1), a multidrug efflux pump, are also modulated by thyroid hormone and αvβ3. Where signal transduction has been studied, the presence of the hormone at the receptor is transduced by mitogen-activated protein kinase (MAPK) isoforms (ERK1/2; p38) or phosphatidylinositol 3-kinase into local actions. The existence of the cell surface receptor offers opportunities to pharmacologically modify actions of these important transport functions with nanoparticulate formulations of T4 and T3 that do not enter the cell. Such formulations may reverse complex intracellular accumulations of H+, Na+, and Ca2+ that occur in clinical settings such as ischemia. In addition, nanoparticulate tetraiodothyroacetic acid (tetrac), a thyroid hormone analogue that inhibits binding of T4 and T3 to integrin αvβ3 as well as certain other functions of the integrin, may reverse P-gp-dependent resistance to anti-cancer drugs in tumor cells
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
Molecular mechanisms of actions of formulations of the thyroid hormone analogue, tetrac, on the inflammatory response.
No full textBACKGROUND: Tetraiodothyroacetic acid (tetrac) and its nanoparticulate formulation (Nanotetrac) act at a cell surface receptor to block angiogenesis and tumor cell proliferation.
OBJECTIVE: The complex anti-angiogenic properties of tetrac and Nanotetrac caused us to search in the literature and in certain of our unpublished mRNA experiments for evidence that these agents affect the early inflammatory response, perhaps through actions on specific cytokines and chemokines.
RESULTS AND DISCUSSION: Tetrac and Nanotetrac inhibit expression in tumor cells of cytokine genes, e.g., specific interleukins, and chemokine genes, such as fractalkine (CX3CL1), and chemokine receptor genes (CX3CR1) that have been identified as high priority targets in the development of inflammation-suppressant drugs. The possibility is also examined that tetrac formulations have an effect on the function of inflammatory cells
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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