Extracellular trafficking of Wnt signals in gastric cancer

Wnt proteins are secreted glycoproteins which signal in a tissue to regulate multiple cellular processes, such as cell differentiation, migration, and proliferation. However, post-translational modifications result in Wnt ligands being hydrophobic in nature. Thus, their ability to freely diffuse in the aqueous extracellular environment is restricted, and alternative mechanisms of transport have been proposed. In this thesis, I investigate and characterise the use of signalling filopodia – termed cytonemes – in the intercellular transport of Wnt3 ligands by gastric cancer cells, which display overactivated Wnt/β-catenin signalling. Additionally, I identify the membrane scaffolding protein Flotillin-2 (Flot2), which is overexpressed in gastric cancers, as a novel positive regulator of Wnt cytoneme formation and consequently proliferation. Mechanistically, I show that Flot2 is required for the intracellular transport, membrane localisation and thus signalling of the Wnt co-receptor Ror2; a known regulator of Wnt cytonemes. In parallel, I show that Flot2 also has a function in transducing signals in the Wnt- receiving cell. Here, Flot2 co-localises with the Wnt co-receptor Lrp6 and is involved in its endocytic uptake. Additionally, Flot2 knockdown results in the perinuclear accumulation of Lrp6 and its absence from recycling endosomes. Therefore, I suggest Flot2 may also be involved in the endosomal transport of Lrp6 following internalisation. Finally, following my observed co-localisations of both Ror2 and Lrp6 with Flot2, I found that these Wnt co-receptors co-localise with one another, as well as the cognate Wnt receptor Frizzled 7, in Flot2 microdomains. Expression of a mutant Ror2 missing its cysteine-rich domain, however, causes loss of co-localisation with Lrp6 and perturbed Wnt/β-catenin signalling. Together, these findings led me to propose a model whereby Frizzled 7, Ror2 and Lrp6 all interact and form one large complex, which I have termed the Wnt Receptor Supercomplex (WRS). I hypothesise that these receptors may interact, even in the absence of Wnt ligands, to regulate one another’s binding affinities for either Wnt/β-catenin or Wnt/PCP ligands. Here, I propose that flotillin microdomains provide the scaffold necessary for these interactions

An Analysis of the Broadband (22-3900 MHz) Radio Spectrum of HB3 (G132.7+1.3): The Detection of Thermal Radio Emission from an Evolved Supernova Remnant?

We present an analysis of the broadband radio spectrum (from 22 to 3900 MHz) of the Galactic supernova remnant (SNR) HB3 (G132.7+1.3). Published observations have revealed that a curvature is present in the radio spectrum of this SNR, indicating that a single synchrotron component appears is insufficient to adequately fit the spectrum. We present here a fit to this spectrum using a combination of a synchrotron component and a thermal bremsstrahlung component. We discuss properties of this latter component and estimate the ambient density implied by the presence of this component to be n \~ 10 cm^-3. We have also analyzed extracted X-ray spectra from archived {\it ASCA} GIS observations of different regions of HB3 to obtain independent estimates of the density of the surrounding interstellar medium (ISM). From this analysis, we have derived electron densities of 0.1-0.4 f^-1/2 cm^-3 for the ISM for the three different regions of the SNR, where f is the volume filling factor. By comparing these density estimates with the estimate derived from the thermal bremsstrahlung component, we argue that the radio thermal bremsstrahlung emission is emitted from a thin shell enclosing HB3. The presence of this thermal bremsstrahlung component in the radio spectrum of HB3 suggests that this SNR is in fact interacting with an adjacent molecular cloud associated with the HII region W3. By extension, we argue that the presence of thermal emission at radio wavelengths may be a useful tool for identifying interactions between SNRs and molecular clouds, and for estimating the ambient density near SNRs using radio continuum data.Comment: 5 pages, 2 figures, accepted for ApJ

The rodent uterotrophic assay: Critical protocol features, studies with nonyl phenols, and comparison with a yeast estrogenicity assay

The major protocol features of the immature rat uterotrophic assay have been evaluated using a range of reference chemicals. The protocol variables considered include the selection of the test species and route of chemical administration, the age of the test animals, the maintenance diet used, and the specificity of the assay for estrogens. It is concluded that three daily oral administrations of test chemicals to 21- to 22-day-old rats, followed by determination of absolute uterus weights on the fourth day, provide a sensitive and toxicologically relevant in vivo estrogenicity assay. Rats are favored over mice for reasons of toxicological practice, but the choice of test species is probably not a critical protocol variable, as evidenced by the similar sensitivity of rats and mice to the uterotrophic activity of methoxychlor. Vaginal opening is shown to be a useful, but nondefinitive, adjunct to the uterotrophic assay. The ability of test chemicals to reduce or abolish the uterotrophic response of estradiol is suggested to provide a useful extension of the uterotrophic assay for the purpose of detecting antiestrogens. The results of a series of studies on the environmental estrogen nonyl phenol (NP), and its linear isomer n -nonyl phenol, confirm that branching of the aliphatic side chain is important for activity. 17beta-Desoxyestradiol is shown to be of similar activity to estradiol in the uterotrophic assay and is suggested to represent the "parent" estrogen of NP. Benzoylation of NP and 17-desoxyestradiol did not affect their uterotrophic activity, in contrast to the enhancing effect of benzoylation on estradiol. Selected chemicals shown to be active in the immature rat uterotrophic assay were also evaluated in an in vitro yeast human estrogen receptor transactivation assay. Most of the chemicals gave similar qualitative responses to those seen in the uterotrophic assay, and the detection of the estrogen methoxychlor by the yeast assay evidenced a degree of intrinsic metabolic competence. However, the assay had a reduced ability (compared to rodents) to hydrolyze the benzoate ester of estradiol, and the estrogenic benzoate derivative of NP was not active in the yeast assay. These last results indicate that current metabolic deficiencies of in vitro estrogenicity assays will limit the value of negative data for the immediate future. The results described illustrate the intrinsic complexity of evaluating chemicals for estrogenic activities and confirm the need for rigorous attention to experimental design and criteria for assessing estrogenic activity

A revised chronostratigraphic framework for International Ocean Discovery Program Expedition 355 sites in Laxmi Basin, eastern Arabian Sea

AbstractInternational Ocean Discovery Program Expedition 355 drilled Sites U1456 and U1457 in Laxmi Basin (eastern Arabian Sea) to document the impact of the South Asian monsoon on weathering and erosion of the Himalaya. We revised the chronostratigraphic framework for these sites using a combination of biostratigraphy, magnetostratigraphy and strontium isotope stratigraphy. The sedimentary section at the two sites is similar and we divided it into six units bounded by unconformities or emplaced as a mass-transport deposit (MTD). Unit 1 underlies the MTD, and is of early–middle Miocene age at Site U1456 and early Paleocene age at Site U1457. An unconformity (U1) created by emplacement of the MTD (unit 2) during the late Miocene Epoch (at c. 9.83–9.69 Ma) separates units 1 and 2 and is identified by a marked change in lithology. Unit 3 consists of hemipelagic sediment with thin interbeds of graded sandstone of late Miocene age, separated from unit 4 by a second unconformity (U2) of 0.5–0.9 Myr duration. Unit 4 consists of upper Miocene interbedded mudstone and sandstone and hemipelagic chalk deposited between c. 8 and 6 Ma. A c. 1.4–1.6 Myr hiatus (U3) encompasses the Miocene–Pliocene boundary and separates unit 4 from unit 5. Unit 5 includes upper Pliocene – lower Pleistocene siliciclastic sediment that is separated from unit 6 by a c. 0.45 Myr hiatus (U4) in the lower Pleistocene sediments. Unit 6 includes a thick package of rapidly deposited Pleistocene sand and mud overlain by predominantly hemipelagic sediment deposited since c. 1.2 Ma

Impact on the phased abolition of co-payments on the utilisation of selected prescription medicines in Wales

We have taken advantage of a natural experiment to measure the impact of the phased abolition of prescription co-payments in Wales. We investigated 3 study periods covering the phased abolition: from £6 to £4, £4 to £3, and £3 to £0. A difference-in-difference modelling was adopted and applied to monthly UK general practice level dispensing data on 14 selected medicines which had the highest percentage of items dispensed subject to a co-payment prior to abolition. Dispensing from a comparator region (North East of England) with similar health and socio-economic characteristics to Wales, and where prescription co-payments continued during the study periods, was used to isolate any non-price effects on dispensing in Wales. Results show a small increase in dispensing of 14 selected medicines versus the comparator. Compared with NE England, monthly average Welsh dispensing was increased by 11.93 items (7.67%; 95% CI [7.2%, 8.1%]), 6.37 items (3.38%; 95% CI [2.9%, 3.7%]) and 9.18 items (4.54%; 95% CI [4.2%, 4.9%]) per practice per 1,000 population during the periods when co-payment was reduced. Price elasticities of the selected medicines utilisation were -0.23, -0.13, and -0.04 in 3 analyses, suggesting the abolition of co-payment had small effect on Welsh dispensing

Os avanços da aqüicultura.

A produção global da aqüicultura tem apresentado elevados níveis de crescimento nas últimas duas décadas, e no Brasil, esta expansão está expressa no aumento do consumo per capita de pescados, de 6 para 8kg/ano. Este aumento na produção tem gerado excedentes exportáveis que tornaram a balança comercial brasileira superavitária desde 2001 (MDIC/SECEX)

Automatic Detection of Expanding HI Shells Using Artificial Neural Networks

The identification of expanding HI shells is difficult because of their variable morphological characteristics. The detection of HI bubbles on a global scale therefore never has been attempted. In this paper, an automatic detector for expanding HI shells is presented. The detection is based on the more stable dynamical characteristics of expanding shells and is performed in two stages. The first one is the recognition of the dynamical signature of an expanding bubble in the velocity spectra, based on the classification of an artificial neural network. The pixels associated with these recognized spectra are identified on each velocity channel. The second stage consists in looking for concentrations of those pixels that were firstly pointed out, and to decide if they are potential detections by morphological and 21-cm emission variation considerations. Two test bubbles are correctly detected and a potentially new case of shell that is visually very convincing is discovered. About 0.6% of the surveyed pixels are identified as part of a bubble. These may be false detections, but still constitute regions of space with high probability of finding an expanding shell. The subsequent search field is thus significantly reduced. We intend to conduct in the near future a large scale HI shells detection over the Perseus Arm using our detector.Comment: 39 pages, 11 figures, accepted by PAS

Enhanced abundances in three large-diameter mixed-morphology supernova remnants

We present an X-ray study of three mixed-morphology supernova remnants (SNRs), HB 21, CTB 1 and HB 3, using archival ASCA and ROSAT data. These data are complemented by archival Chandra X-ray Observatory data for CTB 1 and XMM-Newton X-ray Observatory data for HB 3. The spectra from HB 21 and HB 3 are well-described with a single-temperature thermal plasma in ionization equilibrium, while a two-temperature thermal plasma is found in CTB 1. We found enhanced abundances in all three SNRs. The elemental abundance of Mg is clearly enhanced in CTB 1, while HB 21 has enhanced abundances of Si and S. The situation is not so clear in HB 3 -- the plasma in this SNR either has significantly enhanced abundances of O, Ne and Mg, or it has marginally enhanced abundances of Mg and under-abundant Fe. We discuss the plausibility of mixed-morphology SNR models for the three SNRs and the presence of enhanced abundances. We revise a list of MM SNRs and their properties, compare the three SNRs studied here with other members of this class, and discuss the presence of enhanced elemental abundances in MM SNRs. We also report the ASCA detection of a compact source in the southern part of HB 3. The source spectrum is consistent with a power law with a photon index of ~2.7, and an unabsorbed X-ray flux of ~10^{-12} erg/cm^2/s in the 0.5--10.0 keV band. The column density towards this source differs from that towards the SNR, and it is therefore unlikely they are related.Comment: 26 pages, 15 figures, revised version (minor changes), accepted for publication in ApJ (10 Aug 2006