1,720,976 research outputs found
Performance Comparison of Downlink User Multiplexing Schemes in IEEE 802.11ac: Multi-user MIMO vs. Frame Aggregation
No full textIdentification of transacting factors responsible for the tissue-specific expression of human glucose transporter type 2 isoform gene - Cooperative role of hepatocyte nuclear factors 1 alpha and 3 beta
No full textWe investigated transacting factors binding to the cis-element important in tissue-specific expression of the human glucose transporter type 2 isoform (GLUT2) gene. By transient transfection assay, we determined that the 227-base pair fragment upstream of the ATG start site contained promoter activity and that the region from +87 to +132 (site C) was responsible for tissue-specific expression. DNase I footprinting and electrophoretic mobility shift assay indicated that site C contained one binding site for hepatocyte nuclear factor 1 (HNF1) and two binding sites for HNF3 The mutations at positions +101 and +103, which are considered to be critical in binding HNF1 and HNF3, resulted in a 53% decrease in promoter activity, whereas the mutation of the proximal HNF3 binding site (+115 and +117) reduced promoter activity by 28%. The mutations of these four sites resulted in marked decrease (70%) in promoter activity as well as diminished bindings of HNF1 and HNF3, A to G mutation, which causes conversion of the HNF1 and HNF3 binding sequence to the NF-Y binding site, resulted in a 22% decrease in promoter activity. We identified that both HNF1 and HNF3 function as transcriptional activators in GLUTS gene expression. Coexpression of the pGL+74 (+74 to +301) construct with the HNF1 alpha and HNF3 beta expression vectors in NIH 3T3 cells showed the synergistic effect on GLUTS promoter activity compared with the expression of HNF1 alpha, HNF3 beta, or a combination of HNF1 beta and HNF3 beta. These data suggest that HNF1 alpha and HNF3 beta may be the most important players in the tissue-specific expression of the human GLUTS gene
HNF1 and/or HNF3 may contribute to the tissue specific expression of glucokinase gene
No full textA possible role of hepatocyte nuclear factor 1 (HNF1) or HNF3, a predominant trans-acting factors of hepatic or pancreatic p-cells, was examined on the tissue specific interdependent expression of glucokinase (GK) in liver, H4IIE, HepG2, HIT-T15 and MIN6 cell line. The tissues or cell lines known to express GK showed abundant levels of HNF1 and HNF3 mRNA as observed in liver, H4IIE, HepG2, HIT-T15 and MIN6 cells, whereas they were not detected in brain, heart, NIH 3T3, HeLa cells. The promoter of glucokinase contains several HNF3 consensus sequences and are well conserved in human, mouse and rat. Transfection of the glucokinase promotor linked with luciferase reporter to liver or pancreatic beta cell lines showed high interacting activities with HNF1 and HNF3, whereas minimal activities were detected in the cells expressing very low levels of HNFs. The binding of HNF1 or HNF3 to the GK promoter genes was confirmed by electrophoretic mobility shift assay (EMSA). From these data, we propose that the expression of HNF1 and/or HNF3 may, in part, contribute to the tissue specific expression of GK
Analysis of polymorphism of the GLUT2 promoter in NIDDM patients and its functional consequence to the promoter activity
No full textGlucose transporter type 2 (GLUT2), along with glucokinase, has been implicated to participate in glucose-induced insulin secretion in pancreatic beta-cells. Recently, several sequence variations in the promoter of GLUT2 have been identified in patients with non-insulin dependent diabetes mellitus (NIDDM), but the functional effects of these polymorphisms on promoter activity have not previously been studied. We compared the incidence of sequence variations in the GLUT2 promoter in 100 normal subjects and 100 NIDDM patients. Sequencing of the promoter region (-294 to +301) revealed that an A-->G variant at position -44 was found in 45 of 100 NIDDM patients, but only in 23 of 100 normal subjects. In addition, -269 A-->C and +103 A-->G mutations were identified in a single diabetic patient. Electrophoretic mobility shift assays using double-stranded oligonucleotide containing -44A as a probe showed a clearly shifted band of DNA-protein. To examine whether the sequence variation at position -44 affects the promoter activity, we carried out in vitro transfection experiments. Site-specific mutagenesis at position -44 region from A to C, T or G resulted in reductions of CAT activity by 52.3%, 63.8%, and 63.6%, respectively. The -269 A-->C and +103 A-->G mutations also decreased the promoter activity. These results suggest that polymorphisms at positions -269, -44, or +103 may affect GLUT2 gene transcription, possibly associated with reduced expression of the GLUT2 gene in NIDDM patients
Identification and functional characterization of the peroxisomal proliferator response element in rat GLUT2 promoter
No full textWe identified the peroxisomal proliferator response element (PPRE) in the +68/+89 region of the rat GLUT2 gene. To identify whether the putative PPRE in the GLUTS gene (GLUT2-PPRE) is functional, GLUTS promoter-luciferase reporter constructs were transfected into CV-1 cells. Promoter activities were increased by coexpression of peroxisomal proliferator-activated receptor (PPAR)-gamma, retinoid X receptor (RXR)-alpha, and treatment of their ligands; troglitazone and g-cis retinoic acid potentiated the transactivational effects, Introduction of mutations in GLUT2-PPBE resulted in loss of transactivational effects of the PPAR-gamma/RXR-alpha heterodimer, Electrophoretic mobility shift assay using nuclear extracts of CV-1 cells, which were transfected with various combinations of PPARs or RXR-alpha expression plasmids, revealed that heterodimers of PPAR-gamma and RXR-alpha preferentially bound to GLUT2-PPRE. In HIT-T15 cells, promoter activity of the mt GLUTS gene was increased by troglitazone and g-cis retinoic acid, and mutations of GLUT2-PPRE resulted in reduction of promoter activity. In addition, we observed increased GLUTS transcription by troglitazone and 9-cis retinoic acid in isolated rat primary islets, These results suggested that the GLUT2-PPRE is functional and plays a significant role in gene expression of GLUTS in pancreatic beta-cells. This is the first report; identifying PPRE in a gene involved in glucose homeostasis, linking the effect; of troglitazone on the regulation of insulin secretion
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
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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