Absence of a dose-rate effect in the transformation of C3H 10T1/2 cells by α-particles

The findings of Hill et al. (1984) on the greatly enhanced transformation frequencies at very low dose rates of fission neutrons induced us to perform an analogous study with -particles at comparable dose rates. Transformation frequencies were determined with γ-rays at high dose rate (0·5 Gy/min), and with -particles at high (0·2 Gy/min) and at low dose rates (0·83-2·5 mGy/min) in the C3H 10T1/2 cell system. α-particles were substantially more effective than γ-rays, both for cell inactivation and for neoplastic transformation at high and low dose rates. The relative biological effectiveness (RBE) for cell inactivation and for neoplastic transformation was of similar magnitude, and ranged from about 3 at an -particle dose of 2 Gy to values of the order of 10 at 0·25 Gy. In contrast to the experiments of Hill et al. (1984) with fission neutrons, no increased transformation frequencies were observed when the -particle dose was protracted over several hours

Sound archaeology: terminology, Palaeolithic cave art and the soundscape

This article is focused on the ways that terminology describing the study of music and sound within archaeology has changed over time, and how this reflects developing methodologies, exploring the expectations and issues raised by the use of differing kinds of language to define and describe such work. It begins with a discussion of music archaeology, addressing the problems of using the term ‘music’ in an archaeological context. It continues with an examination of archaeoacoustics and acoustics, and an emphasis on sound rather than music. This leads on to a study of sound archaeology and soundscapes, pointing out that it is important to consider the complete acoustic ecology of an archaeological site, in order to identify its affordances, those possibilities offered by invariant acoustic properties. Using a case study from northern Spain, the paper suggests that all of these methodological approaches have merit, and that a project benefits from their integration

The Temperley-Lieb algebra and its generalizations in the Potts and XXZ models

We discuss generalizations of the Temperley-Lieb algebra in the Potts and XXZ models. These can be used to describe the addition of different types of integrable boundary terms. We use the Temperley-Lieb algebra and its one-boundary, two-boundary, and periodic extensions to classify different integrable boundary terms in the 2, 3, and 4-state Potts models. The representations always lie at critical points where the algebras becomes non-semisimple and possess indecomposable representations. In the one-boundary case we show how to use representation theory to extract the Potts spectrum from an XXZ model with particular boundary terms and hence obtain the finite size scaling of the Potts models. In the two-boundary case we find that the Potts spectrum can be obtained by combining several XXZ models with different boundary terms. As in the Temperley-Lieb case there is a direct correspondence between representations of the lattice algebra and those in the continuum conformal field theory.Comment: 49 page

Alteration of gene expression profiles during mycoplasma-induced malignant cell transformation

BACKGROUND: Mycoplasmas are the smallest microorganisms capable of self-replication. Our previous studies show that some mycoplasmas are able to induce malignant transformation of host mammalian cells. This malignant transformation is a multistage process with the early infection, reversible and irreversible stages, and similar to human tumor development in nature. The purpose of this study is to explore mechanisms for this malignant transformation. METHODS: To better understand mechanisms for this unique process, we examined gene expression profiles of C3H cells at different stages of the mycoplasma-induced transformation using cDNA microarray technology. A total of 1185 genes involved in oncogenesis, apoptosis, cell growth, cell-cycle regulation, DNA repair, etc. were examined. Differences in the expression of these genes were compared and analyzed using the computer software AtlasImage. RESULTS: Among 1185 genes screened, 135 had aberrant expression at the early infection stage, 252 at the reversible stage and 184 at the irreversible stage. At the early infection stage, genes with increased expression (92 genes) were twice more than those with decreased expression (42 genes). The global gene expression at the reversible stage appeared to be more volatile than that at any other stages but still resembled the profile at the early infection stage. The expression profile at the irreversible stage shows a unique pattern of a wide range of expression levels and an increased number of expressing genes, especially the cancer-related genes. Oncogenes and tumor suppressors are a group of molecules that showed significant changes in expression during the transformation. The majority of these changes occurred in the reversible and irreversible stages. A prolonged infection by mycoplasmas lead to the expression of more cancer related genes at the irreversible stage. CONCLUSION: The results indicate that the expression profiles correspond with the phenotypic features of the cells in the mycoplasma induced transformation process. The early mycoplasma infection stage shares a common phenomenon with many other acute infections, genes with increased expression significantly outnumbering those with decreased expression. The reversible stage is a transition stage between benignancy and malignancy at the molecular level. Aberrant expression of oncogenes and tumor repressors plays a key role in mycoplasma-induced malignant transformation

Insertion Sequence Inversions Mediated by Ectopic Recombination between Terminal Inverted Repeats

Transposable elements are widely distributed and diverse in both eukaryotes and prokaryotes, as exemplified by DNA transposons. As a result, they represent a considerable source of genomic variation, for example through ectopic (i.e. non-allelic homologous) recombination events between transposable element copies, resulting in genomic rearrangements. Ectopic recombination may also take place between homologous sequences located within transposable element sequences. DNA transposons are typically bounded by terminal inverted repeats (TIRs). Ectopic recombination between TIRs is expected to result in DNA transposon inversions. However, such inversions have barely been documented. In this study, we report natural inversions of the most common prokaryotic DNA transposons: insertion sequences (IS). We identified natural TIR-TIR recombination-mediated inversions in 9% of IS insertion loci investigated in Wolbachia bacteria, which suggests that recombination between IS TIRs may be a quite common, albeit largely overlooked, source of genomic diversity in bacteria. We suggest that inversions may impede IS survival and proliferation in the host genome by altering transpositional activity. They may also alter genomic instability by modulating the outcome of ectopic recombination events between IS copies in various orientations. This study represents the first report of TIR-TIR recombination within bacterial IS elements and it thereby uncovers a novel mechanism of structural variation for this class of prokaryotic transposable elements

Radiation-induced cell transformation: transformation efficiencies of different types of ionizing radiation and molecular changes in radiation transformants and tumor cell lines

This study aims to compare the efficiencies of 5.4 keV soft X-rays, alpha-particles, and gamma-rays in transforming C3H 10T1/2 cells and to assess the sequence of cellular and molecular changes during the process of radiation-induced transformation of Syrian hamster embryo (SHE) cells. The somewhat more densely ionizing soft X-rays are more effective than gamma-rays both for cell inactivation and cell transformation. The relative biological effectiveness (RBE) appears to be independent of dose; it is approximately 1.3 for either end point. The RBE of alpha-particles versus gamma-rays, on the other hand, increases with decreasing dose; the dose dependence is somewhat more apparent for cell transformation than for cell inactivation. SHE cells transformed by different types of ionizing radiation and related tumor cell lines isolated from nude mice tumors were found to have a distinct growth advantage compared to primary SHE cells, documented by higher plating efficiencies, shorter doubling times, and higher cloning efficiencies in semisolid medium. Most transformed and tumor cell lines that were investigated have elevated mRNA levels for the H-ras gene, some of them show restriction fragment length polymorphisms of the H-ras gene, and some exhibit a substantially amplified c-myc gene. In a sequence analysis of the Syrian hamster H-ras gene of eight tumor cell lines from radiation transformants, we have not found any mutation in codons 12, 13, 59, 61, nor in the flanking regions of these codons. The transformed and tumor cell lines tend to have lower chromosome numbers than primary SHE cells

Accurate stationary densities with partitioned numerical methods for stochastic partial differential equations

We consider the numerical solution, by finite differences, of second-order-in-time stochastic partial differential equations (SPDEs) in one space dimension. New timestepping methods are introduced by generalising recently-introduced methods for second-order-in-time stochastic differential equations to multidimensional systems. These stochastic methods, based on leapfrog and Runge–Kutta methods, are designed to give good approximations to the stationary variances and the correlations in the position and velocity variables. In particular, we introduce the reverse leapfrog method and stochastic Runge–Kutta Leapfrog methods, analyse their performance applied to linear SPDEs and perform numerical experiments to examine their accuracy applied to a type of nonlinear SPDE