Relative biological effectiveness (RBE) and out-of-field cell survival responses to passive scattering and pencil beam scanning proton beam deliveries

The relative biological effectiveness (RBE) of passive scattered (PS) and pencil beam scanned (PBS) proton beam delivery techniques for uniform beam configurations was determined by clonogenic survival. The radiobiological impact of modulated beam configurations on cell survival occurring in- or out-of-field for both delivery techniques was determined with intercellular communication intact or physically inhibited. Cell survival responses were compared to those observed using a 6 MV photon beam produced with a linear accelerator. DU-145 cells showed no significant difference in survival response to proton beams delivered by PS and PBS or 6 MV photons taking into account a RBE of 1.1 for protons at the centre of the spread out Bragg peak. Significant out-of-field effects similar to those observed for 6 MV photons were observed for both PS and PBS proton deliveries with cell survival decreasing to 50-60% survival for scattered doses of 0.05 and 0.03 Gy for passive scattered and pencil beam scanned beams respectively. The observed out-of-field responses were shown to be dependent on intercellular communication between the in-and out-of-field cell populations. These data demonstrate, for the first time, a similar RBE between passive and actively scanned proton beams and confirm that out-of-field effects may be important determinants of cell survival following exposure to modulated photon and proton fields

The dynamics of arsenic in four paddy fields in the Bengal delta

Irrigation with arsenic contaminated groundwater in the Bengal Delta may lead to As accumulation in the soil and rice grain. The dynamics of As concentration and speciation in paddy fields during dry season (boro) rice cultivation were investigated at 4 sites in Bangladesh and West Bengal, India. Three sites which were irrigated with high As groundwater had elevated As concentrations in the soils, showing a significant gradient from the irrigation inlet across the field. Arsenic concentration and speciation in soil pore water varied temporally and spatially; higher As concentrations were associated with an increasing percentage of arsenite, indicating a reductive mobilization. Concentrations of As in rice grain varied by 2-7 fold within individual fields and were poorly related with the soil As concentration. A field site employing alternating flooded-dry irrigation produced the lowest range of grain As concentration, suggesting a lower soil As availability caused by periodic aerobic conditions.

Arsenic accumulation and phosphorus status in two rice (Oryza sativa L.) cultivars surveyed from fields in South China

The consumption of paddy rice (Oryza sativa L.) is a major inorganic arsenic exposure pathway in S.E. Asia. A multi-location survey was undertaken in Guangdong Province, South China to assess arsenic accumulation and speciation in 2 rice cultivars, one an Indica and the other a hybrid Indica. The results showed that arsenic concentrations in rice tissue increased in the order grain <husk <straw <root. Rice grain arsenic content of 2 rice cultivars was significant different and correlated with phosphorus concentration and molar ratio of P/As in shoot, being higher for the Indica cultivar than for the hybrid Indica, which suggests altering shoot phosphorus status as a promising route for breeding rice cultivars with reduced grain arsenic. Speciation of grain arsenic, performed using HPLC-ICP-MS, identified inorganic arsenic as the dominant arsenic species present in the rice grain.

Dynamics of Self-Generated, Large Amplitude Magnetic Fields Following High-Intensity Laser Matter Interaction

The dynamics of magnetic fields with an amplitude of several tens of megagauss, generated at both sides of a solid target irradiated with a high-intensity (~1019W/cm2) picosecond laser pulse, has been spatially and temporally resolved using a proton imaging technique. The amplitude of the magnetic fields is sufficiently large to have a constraining effect on the radial expansion of the plasma sheath at the target surfaces. These results, supported by numerical simulations and simple analytical modeling, may have implications for ion acceleration driven by the plasma sheath at the rear side of the target as well as for the laboratory study of self-collimated high-energy plasma jets. © 2012 American Physical Society.

A Kinetic-Based Model of Radiation-Induced Intercellular Signalling

It is now widely accepted that intercellular communication can cause significant variations in cellular responses to genotoxic stress. The radiation-induced bystander effect is a prime example of this effect, where cells shielded from radiation exposure see a significant reduction in survival when cultured with irradiated cells. However, there is a lack of robust, quantitative models of this effect which are widely applicable. In this work, we present a novel mathematical model of radiation-induced intercellular signalling which incorporates signal production and response kinetics together with the effects of direct irradiation, and test it against published data sets, including modulated field exposures. This model suggests that these so-called "bystander" effects play a significant role in determining cellular survival, even in directly irradiated populations, meaning that the inclusion of intercellular communication may be essential to produce robust models of radio-biological outcomes in clinically relevant in vivo situations.

A study of velocity fields in the transition region of ε Eri (K2 V)

Analyses of the widths and shifts of optically thin emission lines in the ultraviolet spectrum of the active dwarf e Eri (K2 V) are presented. The spectra were obtained using the Space Telescope Imaging Spectrograph on the Hubble Space Telescope and the Far Ultraviolet Spectroscopic Explorer. The linewidths are used to find the non-thermal energy density and its variation with temperature from the chromosphere to the upper transition region. The energy fluxes that could be carried by Alfvén and acoustic waves are investigated, to test their possible roles in coronal heating. Acoustic waves do not appear to be a viable means of coronal heating. There is, in principle, ample flux in Alfvén waves, but detailed calculations of wave propagation are required before definite conclusions can be drawn concerning their viability. The high sensitivity and spectral resolution of the above instruments have allowed two-component Gaussian fits to be made to the profiles of the stronger transition region lines. The broad and narrow components that result share some similarities with those observed in the Sun, but in e Eri the broad component is redshifted relative to the narrow component and contributes more to the total line flux. The possible origins of the two components and the energy fluxes implied are discussed. On balance our results support the conclusion of Wood, Linsky & Ayres, that the narrow component is related to Alfvén waves reaching to the corona, but the origin of the broad component is not clear.

Expression of the Yersinia enterocolitica pYV-encoded type III secretion system is modulated by lipopolysaccharide O-antigen status

We show that the expression of a Yersinia enterocolitica O:8 pYV-encoded type III secretion system was altered in a rough mutant (YeO8-R) due to elevated levels of FlhDC. H-NS might underlie flhDC upregulation in YeO8-R, and the data suggest a relationship between the absence of O antigen and the expression of H-NS.

The spark of life:The role of electric fields in regulating cell behaviour using the eye as a model system

Endogenous electric fields (EF) have long been known to influence cell behaviour during development, neural cell tropism, wound healing and cell behaviour generally. The effect is based on short circuiting of electrical potential differences across cell and tissue boundaries generated by ionic segregation. Recent in vitro and in vivo studies have shown that EF regulate not only cell movement but orientation of cells during mitosis, an effect which may underlie shaping of tissues and organs. The molecular basis of this effect is founded on receptor-mediated cell signalling events and alterations in cytoskeletal function as revealed in studies of gene deficient cells. Remarkably, not all cells respond directionally to EF in the same way and this has consequences, for instance, for lens development and vascular remodelling. The physical basis of EF effect may be related to changes induced in 'bound water' at the cell surface, whose organisation in association with trans-membrane proteins (e.g. receptors) is disrupted when EF are generated. Copyright © 2007 S. Karger AG.

Complement expression in retinal pigment epithelial cells is modulated by activated macrophages

Complement activation is involved in a variety of retinal diseases. We have shown previously that a number of complement components and regulators can be produced locally in the eye, and that retinal pigment epithelial (RPE) cells are the major source of complement expression at the retina-choroidal interface. The expression of complement components by RPE cells is regulated by inflammatory cytokines. Under aging or inflammatory conditions, microglia and macrophages accumulate in the subretinal space, where they are in close contact with RPE cells. In this study, we investigated the effect of activated macrophages on complement expression by RPE cells. Mouse RPE cells were treated with the supernatants from un-activated bone marrow-derived macrophages (BM-DMs), the classically activated BM-DMs (M1) and different types of the alternatively activated BM-DMs (M2a by IL-4, M2b by immune complex and lipopolysaccharide (LPS), M2c by IL-10). The expression of inflammatory cytokines and complement genes by RPE cells were determined by real-time RT-PCR. The protein expression of CFB, C3, C1INH, and C1r was examined by Western blot. Our results show that un-stimulated RPE cells express a variety of complement-related genes, and that the expression levels of complement regulators, including C1r, factor H (CFH), DAF1, CD59, C1INH, Crry, and C4BP genes are significantly higher than those of complement component genes (C2, C4, CFB, C3, and C5). Macrophage supernatants increased inflammatory cytokine (IL-1ß, IL-6, iNOS), chemokine (CCL2) and complement expression in RPE cells. The supernatants from M0, M2a and M2c macrophages mildly up-regulated (2~3.5-fold) CFB, CFH and C3 gene expression in RPE cells, whereas the supernatants from M1 and M2b macrophages massively increased (10~30-fold) CFB and C3 gene expression in RPE cells. The expression of other genes, including C1r, C2, C4, CFH, Masp1, C1INH, and C4BP in RPE cells was also increased by the supernatants of M1 and M2b macrophages; however, the increment levels were significantly lower than CFB and C3 genes. M1 and M2b macrophage supernatants enhanced CFB (Bb fragment) protein expression and C3 secretion by RPE cells. M1 macrophages may affect complement expression in RPE cells through the STAT1 pathway. Our results suggest that under inflammatory conditions, activated macrophages could promote the alternative pathway of complement activation in the retina via induction of RPE cell CFB and C3 expression.

Quantification of interpoint topographic correlations of threshold values in glaucomatous visual fields

Purpose: The authors sought to quantify neighboring and distant interpoint correlations of threshold values within the visual field in patients with glaucoma. Methods: Visual fields of patients with confirmed or suspected glaucoma were analyzed (n = 255). One eye per patient was included. Patients were examined using the 32 program of the Octopus 1-2-3. Linear regression analysis among each of the locations and the rest of the points of the visual field was performed, and the correlation coefficient was calculated. The degree of correlation was categorized as high (r > 0.66), moderate (0.66 = r > 0.33), or low (r = 0.33). The standard error of threshold estimation was calculated. Results: Most locations of the visual field had high and moderate correlations with neighboring points and with distant locations corresponding to the same nerve fiber bundle. Locations of the visual field had low correlations with those of the opposite hemifield, with the exception of locations temporal to the blind spot. The standard error of threshold estimation increased from 0.6 to 0.9 dB with an r reduction of 0.1. Conclusion: Locations of the visual field have highest interpoint correlation with neighboring points and with distant points in areas corresponding to the distribution of the retinal nerve fiber layer. The quantification of interpoint correlations may be useful in the design and interpretation of visual field tests in patients with glaucoma.