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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
281

Cbx4 regulates the proliferation of thymic epithelial cells and thymus function.

Liu, B., Liu, Y.F., Du, Y.R., Mardaryev, Andrei N., Yang, W., Chen, H., Xu, Z.M., Xu, C.Q., Zhang, X.R., Botchkarev, Vladimir A., Zhang, Y., Xu, G.L. January 2013 (has links)
No / Thymic epithelial cells (TECs) are the main component of the thymic stroma, which supports T-cell proliferation and repertoire selection. Here, we demonstrate that Cbx4, a Polycomb protein that is highly expressed in the thymic epithelium, has an essential and non-redundant role in thymic organogenesis. Targeted disruption of Cbx4 causes severe hypoplasia of the fetal thymus as a result of reduced thymocyte proliferation. Cell-specific deletion of Cbx4 shows that the compromised thymopoiesis is rooted in a defective epithelial compartment. Cbx4-deficient TECs exhibit impaired proliferative capacity, and the limited thymic epithelial architecture quickly deteriorates in postnatal mutant mice, leading to an almost complete blockade of T-cell development shortly after birth and markedly reduced peripheral T-cell populations in adult mice. Furthermore, we show that Cbx4 physically interacts and functionally correlates with p63, which is a transcriptional regulator that is proposed to be important for the maintenance of the stemness of epithelial progenitors. Together, these data establish Cbx4 as a crucial regulator for the generation and maintenance of the thymic epithelium and, hence, for thymocyte development.
282

Development of Novel Tumor-Targeted Theranostic Nanoparticles Activated by Membrane-Type Matrix Metalloproteinases for Combined Cancer Magnetic Resonance Imaging and Therapy

Ansari, C., Tikhomirov, G.A., Hong, S.H., Falconer, Robert A., Loadman, Paul, Gill, Jason H., Castaneda, R., Hazard, F.K., Tong, L., Lenkov, O.D., Felsher, D.W., Rao, J., Daldrup-Link, H.E. 27 August 2013 (has links)
No / A major drawback with current cancer therapy is the prevalence of unrequired doselimiting toxicity to non-cancerous tissues and organs, which is further compounded by a limited ability to rapidly and easily monitor drug delivery, pharmacodynamics and therapeutic response. In this report, the design and characterization of novel multifunctional “theranostic” nanoparticles (TNPs) is described for enzyme-specifi c drug activation at tumor sites and simultaneous in vivo magnetic resonance imaging (MRI) of drug delivery. TNPs are synthesized by conjugation of FDA-approved iron oxide nanoparticles ferumoxytol to an MMP-activatable peptide conjugate of azademethylcolchicine (ICT), creating CLIOICTs (TNPs). Signifi cant cell death is observed in TNP-treated MMP-14 positive MMTVPyMT breast cancer cells in vitro, but not MMP-14 negative fi broblasts or cells treated with ferumoxytol alone. Intravenous administration of TNPs to MMTV-PyMT tumor-bearing mice and subsequent MRI demonstrates signifi cant tumor selective accumulation of the TNP, an observation confi rmed by histopathology. Treatment with CLIO-ICTs induces a significant antitumor effect and tumor necrosis, a response not observed with ferumoxytol. Furthermore, no toxicity or cell death is observed in normal tissues following treatment with CLIO-ICTs, ICT, or ferumoxytol. These fi ndings demonstrate proof of concept for a new nanotemplate that integrates tumor specifi city, drug delivery and in vivo imaging into a single TNP entity through attachment of enzyme-activated prodrugs onto magnetic nanoparticles. This novel approach holds the potential to signifi cantly improve targeted cancer therapies, and ultimately enable personalized therapy regimens. / Yorkshire Cancer Research
283

Space and movement in an Iron Age oppidum: integrating geophysical and topographic survey at Entremont, Provence

Armit, Ian, Gaffney, Christopher F., Hayes, A. January 2012 (has links)
No / The famous Celtic site of Entremont, well known for its head cult and warrior statues, is a heritage gem of southern France. This naturally inhibits further excavation there, but the authors show just how much can be achieved through an integrated package of remote mapping techniques. Their exemplary methodology produced more than a high resolution plan of the unexcavated part of the site; this type of integrated procedure generates ground-breaking research, without breaking any ground. Here the investigation mobilised arguments for pre-urban monuments, and the activities, enclosures, entrances and circulation of the oppidum.
284

Metallohelices with activity against cisplatin-resistant cancer cells; does the mechanism involve DNA binding?

Brabec, V., Howson, S.E., Kaner, R.A., Lord, Rianne M., Malina, J., Phillips, Roger M., Abdallah, Qasem M.A., McGowan, P.C., Rodger, A., Scott, P. 12 1900 (has links)
Yes / Enantiomers of a relatively rigid DNA-binding metallo-helix are shown to have comparable activity to that of cisplatin against the cell lines MCF7 (human breast adenocarcinoma) and A2780 (human ovarian carcinoma) but are ca five times more active against the cisplatin-resistant A2780cis. The cell-line HCT116 p53+/+ (human colon carcinoma) is highly sensitive giving IC50 values in the nM range, far lower than the cisplatin control. The hypothesis that the biological target of such metallohelices is DNA is probed by various techniques. Tertiary structure changes in ct-DNA (formation of loops and intramolecular coiling) on exposure to the compounds are demonstrated by atomic force microscopy and supported by circular/linear dichroism in solution. Selectivity for 50-CACATA and 50-CACTAT segments is shown by DNase I footprinting. Various three- and four-way oligonucleotide junctions are stabilised, and remarkably only the L metallo-helix enantiomer stabilizes T-shaped 3WJs during gel electrophoresis; this is despite the lack of a known helix binding site. In studies with oligonucleotide duplexes with bulges it is also shown for the first time that the metallo-helix binding strength and the number of binding sites are dependent on the size of the bulge. In contrast to all the above, flexible metallo-helices show little propensity for structured or selective DNA binding, and while for A2780 the cancer cell line cytotoxicity is retained the A2780cis strain shows significant resistance. For all compounds in the study, H2AX FACS assays on HCT116 p53+/+ showed that no significant DNA damage occurs. In contrast, cell cycle analysis shows that the DNA binders arrest cells in the G2/mitosis phase, and while all compounds cause apoptosis, the DNA binders have the greater effect. Taken together these screening and mechanistic results are consistent with the more rigid helices acting via a DNA binding mechanism while the flexible assemblies do not.
285

DNA from keratinous tissue. Part I: Hair and nail

Bengtsson, C.F., Olsen, M.E., Brandt, L.O., Bertelsen, M.F., Willerslev, E., Tobin, Desmond J., Wilson, Andrew S., Gilbert, M.T.P. January 2012 (has links)
No / Keratinous tissues such as nail, hair, horn, scales and feather have been used as a source of DNA for over 20 years. Particular benefits of such tissues include the ease with which they can be sampled, the relative stability of DNA in such tissues once sampled, and, in the context of ancient genetic analyses, the fact that sampling generally causes minimal visual damage to valuable specimens. Even when freshly sampled, however, the DNA quantity and quality in the fully keratinized parts of such tissues is extremely poor in comparison to other tissues such as blood and muscle – although little systematic research has been undertaken to characterize how such degradation may relate to sample source. In this review paper we present the current understanding of the quality and limitations of DNA in two key keratinous tissues, nail and hair. The findings indicate that although some fragments of nuclear and mitochondrial DNA appear to be present in almost all hair and nail samples, the quality of DNA, both in quantity and length of amplifiable DNA fragments, vary considerably not just by species, but by individual, and even within individual between hair types.
286

Effect before cause: supramodal recalibration of sensorimotor timing

Heron, James, Hanson, James Vincent Michael, Whitaker, David J. January 2009 (has links)
Yes / Our motor actions normally generate sensory events, but how do we know which events were self generated and which have external causes? Here we use temporal adaptation to investigate the processing stage and generality of our sensorimotor timing estimates. Methodology/Principal Findings: Adaptation to artificially-induced delays between action and event can produce a startling percept¿upon removal of the delay it feels as if the sensory event precedes its causative action. This temporal recalibration of action and event occurs in a quantitatively similar manner across the sensory modalities. Critically, it is robust to the replacement of one sense during the adaptation phase with another sense during the test judgment. Conclusions/Significance: Our findings suggest a high-level, supramodal recalibration mechanism. The effects are well described by a simple model which attempts to preserve the expected synchrony between action and event, but only when causality indicates it is reasonable to do so. We further demonstrate that this model successfully characterises related adaptation data from outside the sensorimotor domain.
287

Mechanical Investigations on Agar Gels Using Atomic Force Microscopy: Effect of Deuteration.

Grant, Colin A., Twigg, Peter C., Savage, M.D., Woon, W.H., Greig, D. 25 August 2011 (has links)
No / The isotopic effect of exchanging deuterium with hydrogen on the mechanical and surface properties of agar gel is examined. The elastic modulus of the D2O gels obtained by AFM nanoindentation is significantly higher (factor of 1.5¿2) than the modulus found in H2O agar gels. Furthermore, the modulus is independent of loading rate. Surface imaging reveals that the surface roughness gets progressively smaller with increasing agar concentration. All these data suggest that the isotopic replacement of deuterium enhances the mechanical properties of the agar gel, with significant advantages in its use as a biphasic scaffold. / MRC
288

High resolution imaging of bio-molecular binding studies using a widefield surface plasmon microscope

Jamil, M. Mahadi Abdul, Youseffi, Mansour, Twigg, Peter C., Britland, Stephen T., Liu, S., See, C.W., Zhang, J., Somekh, M.G., Denyer, Morgan C.T. January 2008 (has links)
No / Surface plasmon microscopes are mostly built around the prism based Kretschmann configuration. In these systems, an image of a sample can be obtained in terms of an intensity map, where the intensity of the image is dependent on the coupling of the light into the surface plasmons. Unfortunately the lateral resolution of these systems relies on the ability of plasmons to propagate along the metallised layer and is usually limited to a few microns unless special measures are taken. The widefield surface plasmon microscope (WSPR), used here enables surface plasmon imaging at significantly higher lateral resolutions than prism based systems. In this study we demonstrate the functionality of the WSPR by imaging a sequence of binding events between micro-patterned extracellular matrix proteins and their specific antibodies. Using the WSPR system a change in contrast was observed with each binding event. Images produced via the WSPR system were analyzed and compared qualitatively and quantitatively. Consequently, we confirm that the WSPR microscope described here can be used to study sequential monomolecular layer binding events on a micron scale. These results have significant implications in the development of new micron scale bioassays.
289

Characterisation of granule structure and strength made in a high shear granulator

Rahmanian, Nejat, Ghadiri, M., Jia, X., Stepanek, F. January 2009 (has links)
No / Results of a study of the influence of impeller speed on the strength, structure and morphology of granules produced in a type of high shear mixer granulators are reported. Calcium carbonate particles (Durcal 65) have been granulated in a Cyclomix with a capacity of 5 L. An aqueous solution of polyethylene glycol was used as the binder. The granules produced have been dried and their structure visualized using X-ray micro-tomography equipment, Nanotom, with a resolution of less than 1 μm. It is shown that the operation of the granulator at high impeller tip speeds produces granules with a higher strength and lower porosity than those produced at medium and low impeller speeds. Two different granule micro-structures and morphologies are produced at high and low impeller speeds. Structure descriptors such as phase volume fraction (as representative of porosity), chord length distribution and auto-correlation function (as indices of homogeneity of structure) are used to quantify the internal structure of granules in 3D, which in turn affects the granule strength.
290

Effects of process parameters on granules properties produced in a high shear granulator

Rahmanian, Nejat, Naji, A., Ghadiri, M. January 2011 (has links)
No / Results of a study on the influence of process parameters such as impeller speed, granulation time and binder viscosity on granule strength and properties are reported. A high shear granulator (Cyclomix manufactured by Hosokawa Micron B.V., The Netherlands) has been used to produce granules. Calcium carbonate (Durcal) was used as feed powder and aqueous polyethylene glycol (PEG) as the binder. The dried granules have been analysed for their strength, density and size distribution. The results show that increasing the granulation time has a great affect on granules strength, until an optimum time has been reached. The underlying cause is an increase in granule density. Granules are consolidated more at higher impeller speeds. Moreover, the granule size distribution seems not to be affected significantly by an increase in impeller speed. Granules produced with high binder viscosity have a considerably lower strength, wide strength distribution due to poor dispersion of binder on the powder bed. Binder addition methods have showed no considerable effect on granule strength or on granule size distribution.

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