1,720,983 research outputs found
Mammalian tumor xenografts induce neovascularization in zebrafish embryos.
No full textThe zebrafish (Danio rerio)/tumor xenograft model represents
a powerful new model system in cancer. Here, we describe a
novel exploitation of the zebrafish model to investigate tumor
angiogenesis, a pivotal step in cancer progression and target
for antitumor therapies. Human and murine tumor cell lines
that express the angiogenic fibroblast growth factor (FGF) 2
and/or vascular endothelial growth factor (VEGF) induce the
rapid formation of a new microvasculature when grafted close
to the developing subintestinal vessels of zebrafish embryos at
48 h postfertilization. Instead, no angiogenic response was
exerted by related cell clones defective in the production of
these angiogenic growth factors. The newly formed blood
vessels sprout from the subintestinal plexus of the zebrafish
embryo, penetrate the tumor graft, and express the transcripts
for the zebrafish orthologues of the early endothelial markers
Fli-1, VEGF receptor-2 (VEGFR2/KDR), and VE-cadherin.
Accordingly, green fluorescent protein–positive neovessels
infiltrate the graft when tumor cells are injected in transgenic
VEGFR2:G-RCFP zebrafish embryos that express green fluorescent
protein under the control of the VEGFR2/KDR
promoter. Systemic exposure of zebrafish embryos immediately
after tumor cell injection to prototypic antiangiogenic
inhibitors, including the FGF receptor tyrosine kinase inhibitor
SU5402 and the VEGFR2/KDR tyrosine kinase inhibitor
SU5416, suppresses tumor-induced angiogenesis without
affecting normal blood vessel development. Accordingly,
VE-cadherin gene inactivation by antisense morpholino
oligonucleotide injection inhibits tumor neovascularization
without affecting the development of intersegmental and
subintestinal vessels. These data show that the zebrafish/
tumor xenograft model represents a novel tool for investigating
the neovascularization process exploitable for drug
discovery and gene targeting in tumor angiogenesis
Fibroblast Growth Factor 2-induced angiogenesis in zebrafish: the zebrafish yolk membrane (ZFYM) angiogenesis assay
No full textAngiogenesis plays a key role in tumour growth and metastasis. The teleost zebrafish (Danio rerio) represents a promising alternative model in cancer research. Here, we describe a zebrafish yolk membrane (ZFYM) angiogenesis assays based on the injection of 1-30 ng of human recombinant FGF2 (rFGF2) in the perivitelline space of zebrafish embryos in the proximity of developing subintestinal vein vessels (SIVs) at 48 hrs after fertilization. The rFGF2 induces a rapid and dose-dependent angiogenic response from the SIV basket, characterized by the ectopic growth of newly formed, alkaline phosphatase-positive blood vessels. These vessels are formed by proliferating cells that incorporate bromodeoxyuridine and express the endothelial cell markers vegfr2/kdr and fli1. Microangiography shows that rFGF2-induced vessels are patent and connected to the systemic circulation of the embryo. In keeping with these observations, fli1:EGFP(+) cells isolated from transgenic tg(fli1:EGFP)(y1) zebrafish embryos express the tyrosine kinase (TK) FGF receptor-1 (FGFR1) and activate extracellular signal-regulated kinase signalling when stimulated in vitro by rFGF2. The low molecular weight TK-FGFR1 inhibitor SU5402 and the high molecular weight FGF2 antagonist long-pentraxin 3 inhibit the angiogenic activity of rFGF2 when added to fish water or when co-injected with the growth factor, respectively. Moreover, similar to rFGF2, injection of the zebrafish form of vascular endothelial growth factor-A (VEGF-A) induces a significant angiogenic response in the ZFYM assay that is suppressed by the VEGF receptor-2/KDR TK inhibitor SU5416. The ZFYM assay represents a novel tool for testing the activity of low and high molecular weight inhibitors targeting a defined angiogenic growth factor in zebrafish. The assay may offer significant advantages when compared to other animal models
Antiangiogenic and vascular-targeting activity of the microtubule-destabilizing trans-resveratrol derivative 3,5,4'-trimethoxystilbene.
No full textGoing 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
Fibroblast growth factor receptor-1 is essential for in vitro cardiomyocyte development.
No full textFibroblast growth factor (FGF)/FGF receptor (FGFR) signaling plays a crucial role in mesoderm formation and patterning. Heartless mutant studies in Drosophila suggest that FGFR1, among the different FGFRs, may play a role in cardiogenesis. However, fgfr1-/- mice die during gastrulation before heart formation. To establish the contribution of FGFR1 in cardiac development, we investigated the capacity of murine fgfr1+/- and fgfr1-/- embryonic stem (ES) cells to differentiate to cardiomyocytes in vitro. Clusters of pulsating cardiomyocytes were observed in >90% of 3-dimensional embryoid bodies (EBs) originated from fgfr1+/- ES cells at day 9 to 10 of differentiation. In contrast, 10% or less of fgfr1-/- EBs showed beating foci at day 16. Accordingly, fgfr1-/- EBs were characterized by impaired expression of early cardiac transcription factors Nkx2.5 and d-Hand and of late structural cardiac genes myosin heavy chain (MHC)-alpha, MHC-beta, and ventricular myosin light chain. Homozygous fgfr1 mutation resulted also in alterations of the expression of mesoderm-related early genes, including nodal, BMP2, BMP4, T(bra), and sonic hedgehog. Nevertheless, fgfr1+/- and fgfr1-/- EBs similarly express cardiogenic precursor, endothelial, hematopoietic, and skeletal muscle markers, indicating that fgfr1-null mutation exerts a selective effect on cardiomyocyte development in differentiating ES cells. Accordingly, inhibitors of FGFR signaling, including the FGFR1 tyrosine kinase inhibitor SU 5402, the MEK1/2 inhibitor U0126, and the protein kinase C inhibitor GF109 all prevented cardiomyocyte differentiation in fgfr1+/- EBs without affecting the expression of the hematopoietic/endothelial marker flk-1. In conclusion, the data point to a nonredundant role for FGFR1-mediated signaling in cardiomyocyte development
FGF2-induced upregulation of DNA polymerase-delta p12 subunit in endothelial cells.
No full textp12 represents the smallest, so far poorly characterized subunit of the mammalian DNA polymerase delta (pol delta) heterotetramer. Previously, to gain a molecular understanding of endothelial cell activation by fibroblast growth factor-2 (FGF2), we identified an upregulated transcript in FGF2-overexpressing murine aortic endothelial cells (FGF2-T-MAE cells) showing 89\% identity with human p12. Here, we cloned the open reading frame of the murine p12 cDNA and confirmed the capacity of overexpressed or exogenously added FGF2 to upregulate p12 mRNA and protein in endothelial and NIH3T3 cells with no effect on the other pol delta subunits. p12 expression was instead unaffected by serum and different mitogens. Also, anti-p12 antibodies decorated FGF2-T-MAE cell nuclei and their chromosome outline during metaphase. Small interfering RNA-mediated knockdown of p12 caused a significant decrease in FGF2-driven proliferation rate of FGF2-T-MAE cells, in keeping with a modulatory role of p12 in pol delta activity. Immunoistochemistry of FGF2-embedded Matrigel plugs and FGF2-overexpressing tumor xenografts demonstrated a nuclear p12 staining of angiogenic CD31(+) endothelium. p12 immunoreactivity was also observed in the CD45(+)/CD11b(+) inflammatory infiltrate. Thus, FGF2 upregulates p12 expression in endothelial cells in vitro and in vivo. p12 expression in infiltrating inflammatory cells may suggest additional, cell proliferation-unrelated functions for this pol delta subunit
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
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