The effects of exogenous growth factors on matrix metalloproteinase secretion by human brain tumour cells

Matrix metalloproteinases (MMPs) are a growing family of zinc-dependent endopeptidases that are capable of degrading various components of the extracellular matrix. These enzymes have been implicated in a variety of physiological and pathological conditions including embryogenesis and tumour invasion. The synthesis of many MMPs is thought to be regulated by growth factors, cytokines and hormones. In this study, we investigated the effects of five exogenous growth factors known to be expressed by gliomas [epidermal growth factor (EGF), basic growth factor (bFGF), transforming growth factor beta (TGF-β1,2) and vascular endothelial growth factor (VEGF)] on MMP-2 and MMP-9 expression in an ependymoma, two grade III astrocytomas, a grade III oligoastrocytoma and a benign meningioma. Zymogram analysis revealed that the effects of the growth factors depended upon the cell lines used in the study. Growth factors generally up-regulated MMP-2 and MMP-9 expression in the gliomas but were least effective in the meningioma; the effect being most prominent with TGF-β1 and TGF-β2 in all the cell lines. It is hypothesized that paracrine growth factor interplay may be crucial in the regulation of MMP expression by glioma invasion of the normal brain. © 2000 Cancer Research Campaig

Constraining sub-grid physics with high-redshift spatially-resolved metallicity distributions

Aims. We examine the role of energy feedback in shaping the distribution of metals within cosmological hydrodynamical simulations of L* disc galaxies. While negative abundance gradients today provide a boundary condition for galaxy evolution models, in support of inside-out disc growth, empirical evidence as to whether abundance gradients steepen or flatten with time remains highly contradictory. Methods. We made use of a suite of L* discs, realised with and without "enhanced" feedback. All the simulations were produced using the smoothed particle hydrodynamics code Gasoline, and their in situ gas-phase metallicity gradients traced from redshift z similar to 2 to the present-day. Present-day age-metallicity relations and metallicity distribution functions were derived for each system. Results. The "enhanced" feedback models, which have been shown to be in agreement with a broad range of empirical scaling relations, distribute energy and re-cycled ISM material over large scales and predict the existence of relatively "flat" and temporally invariant abundance gradients. Enhanced feedback schemes reduce significantly the scatter in the local stellar age-metallicity relation and, especially, the [O/Fe]-[Fe/H] relation. The local [O/Fe] distribution functions for our L* discs show clear bimodality, with peaks at [O/Fe] = -0.05 and +0.05 (for stars with [Fe/H] > -1), consistent with our earlier work on dwarf discs. Conclusions. Our results with "enhanced" feedback are inconsistent with our earlier generation of simulations realised with "conservative" feedback. We conclude that spatially-resolved metallicity distributions, particularly at high-redshift, offer a unique and under-utilised constraint on the uncertain nature of stellar feedback processes

The role of feedback in shaping the structure of the interstellar medium

We present an analysis of the role of feedback in shaping the neutral hydrogen (H I) content of simulated disc galaxies. For our analysis, we have used two realizations of two separate Milky Way-like (similar to L star) discs - one employing a conservative feedback scheme (McMaster Unbiased Galaxy Survey), the other significantly more energetic [Making Galaxies In a Cosmological Context (MaGICC)]. To quantify the impact of these schemes, we generate zeroth moment (surface density) maps of the inferred H I distribution; construct power spectra associated with the underlying structure of the simulated cold interstellar medium, in addition to their radial surface density and velocity dispersion profiles. Our results are compared with a parallel, self-consistent, analysis of empirical data from The H I Nearby Galaxy Survey (THINGS). Single power-law fits (P proportional to k(gamma)) to the power spectra of the stronger feedback (MaGICC) runs (over spatial scales corresponding to similar to 0.5 to similar to 20 kpc) result in slopes consistent with those seen in the THINGS sample (gamma similar to -2.5). The weaker feedback (MUGS) runs exhibit shallower power-law slopes (gamma similar to -1.2). The power spectra of the MaGICC simulations are more consistent though with a two-component fit, with a flatter distribution of power on larger scales (i.e. gamma similar to -1.4 for scales in excess of similar to 2 kpc) and a steeper slope on scales below similar to 1 kpc (gamma similar to -5), qualitatively consistent with empirical claims, as well as our earlier work on dwarf discs. The radial H I surface density profiles of the MaGICC discs show a clear exponential behaviour, while those of the MUGS suite are essentially flat; both behaviours are encountered in nature, although the THINGS sample is more consistent with our stronger (MaGICC) feedback runs

Yoga for anxiety: a systematic review of the research evidence

Between March and June 2004, a systematic review was carried out of the research evidence on the effectiveness of yoga for the treatment of anxiety and anxiety disorders. Eight studies were reviewed. They reported positive results, although there were many methodological inadequacies. Owing to the diversity of conditions treated and poor quality of most of the studies, it is not possible to say that yoga is effective in treating anxiety or anxiety disorders in general. However, there are encouraging results, particularly with obsessive compulsive disorder. Further well conducted research is necessary which may be most productive if focused on specific anxiety disorders

Proceedings of the workshop "Standard Model at the LHC" University College London 30 March - 1 April 2009

Proceedings from a 3-day discussion on Standard Model discoveries with the first LHC dataComment: 9 contributions to the proceedings of the LHC Standard Model worksho

The stellar metallicity distribution of disc galaxies and bulges in cosmological simulations

By means of high-resolution cosmological hydrodynamical simulations of Milky Way-like disc galaxies, we conduct an analysis of the associated stellar metallicity distribution functions (MDFs). After undertaking a kinematic decomposition of each simulation into spheroid and disc sub-components, we compare the predicted MDFs to those observed in the solar neighbourhood and the Galactic bulge. The effects of the star formation density threshold are visible in the star formation histories, which show a modulation in their behaviour driven by the threshold. The derived MDFs show median metallicities lower by 0.2-0.3 dex than the MDF observed locally in the disc and in the Galactic bulge. Possible reasons for this apparent discrepancy include the use of low stellar yields and/or centrally-concentrated star formation. The dispersions are larger than the one of the observed MDF; this could be due to simulated discs being kinematically hotter relative to the Milky Way. The fraction of low metallicity stars is largely overestimated, visible from the more negatively skewed MDF with respect to the observational sample. For our fiducial Milky Way analog, we study the metallicity distribution of the stars born "in situ" relative to those formed via accretion (from disrupted satellites), and demonstrate that this low-metallicity tail to the MDF is populated primarily by accreted stars. Enhanced supernova and stellar radiation energy feedback to the surrounding interstellar media of these pre-disrupted satellites is suggested as an important regulator of the MDF skewness.Comment: 20 pages, 14 figures, MNRAS, accepte