Cecilia M. Futsaether

Porphyrin sensitization and intracellular calcium changes in the prokaryote Propionibacterium acnes

Photosensitization induces intracellular free calcium changes ([Ca2+]i) in some eukaryotic cell systems which either contribute to or protect against cell inactivation. We have investigated whether or not similar changes can be induced in prokaryotes. The skin bacterium Propionibacterium acnes was sensitized using protoporphyrin IX (PP IX) or 5-aminolevulinic acid (ALA). Exogenous ALA resulted in either a preferential accumulation of protoporphyrin (ALA-PP) or of coproporphyrin and/or uroporphyrin (ALA-CP/UP) in P. acnes. For PP IX or ALA-PP sensitization, exposure to broad-band red light resulted in an increase in [Ca2+]i. For ALA-PP sensitization, this increase was transient and [Ca2+]i returned to basal levels within 5-10 min after irradiation. However, the elevated [Ca2+]i levels obtained after PP IX sensitization were maintained for at least 1 h after irradiation. In both cases, the reduction in the external calcium concentration led to an enhancement in the cell survival, indicating that induced [Ca2+]i changes may participate in photoinactivation. Sensitization by hydrophilic coproporphyrin and/or uroporphyrin (ALA-CP/UP) did not affect the [Ca2+]i levels, but higher levels of cell inactivation were obtained. It therefore appears that damage to membrane-associated components is at least partly responsible for [Ca2+]i alterations after photosensitization.

Visible foliar injury and infrared imaging show that daylength affects short-term recovery after ozone stress in Trifolium subterraneum

Tropospheric ozone is a major air pollutant affecting plants worldwide. Plants in northern regions can display more ozone injury than plants at lower latitudes despite lower ozone levels. Larger ozone influx and shorter nights have been suggested as possible causes. However, the effects of the dim light present during northern summer nights have not been investigated. Young Trifolium subterraneum plants kept in environmentally controlled growth rooms under long day (10 h bright light, 14 h dim light) or short day (10 h bright light, 14 h darkness) conditions were exposed to 6 h of 70 ppb ozone during daytime for three consecutive days. Leaves were visually inspected and imaged in vivo using thermal imaging before and after the daily exposure. In long-day-treated plants, visible foliar injury within 1 week after exposure was more severe. Multivariate statistical analyses showed that the leaves of ozone-exposed long-day-treated plants were also warmer with more homogeneous temperature distributions than exposed short day and control plants, suggesting reduced transpiration. Temperature disruptions were not restricted to areas displaying visible damage and occurred even in leaves with only slight visible injury. Ozone did not affect the leaf temperature of short-day-treated plants. As all factors influencing ozone influx were the same for long- and short-day-treated plants, only the dim nocturnal light could account for the different ozone sensitivities. Thus, the twilight summer nights at high latitudes may have a negative effect on repair and defence processes activated after ozone exposure, thereby enhancing sensitivity.

Classification of dynamic contrast enhanced MR images of cervical cancers using texture analysis and support vector machines.

Dynamic contrast enhanced MRI (DCE-MRI) provides insight into the vascular properties of tissue. Pharmacokinetic models may be fitted to DCE-MRI uptake patterns, enabling biologically relevant interpretations. The aim of our study was to determine whether treatment outcome for 81 patients with locally advanced cervical cancer could be predicted from parameters of the Brix pharmacokinetic model derived from pre-chemoradiotherapy DCE-MRI. First-order statistical features of the Brix parameters were used. In addition, texture analysis of Brix parameter maps was done by constructing gray level co-occurrence matrices (GLCM) from the maps. Clinical factors and first- and second-order features were used as explanatory variables for support vector machine (SVM) classification, with treatment outcome as response. Classification models were validated using leave-one-out cross-model validation. A random value permutation test was used to evaluate model significance. Features derived from first-order statistics could not discriminate between cured and relapsed patients (specificity 0%-20%, p-values close to unity). However, second-order GLCM features could significantly predict treatment outcome with accuracies (~70%) similar to the clinical factors tumor volume and stage (69%). The results indicate that the spatial relations within the tumor, quantified by texture features, were more suitable for outcome prediction than first-order features.

Converting the Iranian heavy water reactor IR-40 to a more proliferation-resistant reactor

This article assesses the feasibility and benefits of converting the Iranian heavy water research reactor, IR-40, from using natural uranium to low-enriched uranium fuel. Based on neutronics calculations for a detailed model of the two reactor configurations, a conversion would result in a smaller core with a subsequent reduction and degradation of plutonium production. It is argued that the proposed conversion will provide Iran with a research reactor that is better suited for scientific experiments and radioisotope production than in its original configuration. It is proposed to introduce the converted IR-40s fuel consumption requirements as a natural cap for Irans future enrichment efforts.

Photomorphogenesis and pigment induction in lentil seedling roots exposed to low light conditions

Although roots are normally hidden in soil, they may inadvertently be exposed to low light levels in experiments or in natural conditions through cracks or light transmittance through the soil. Light has been implicated in root morphogenesis. Thus, effects of low light conditions on lentil (Lens culinaris L. cv. Verte du Puy) root morphology and root pigmentation were studied. Lentil seedlings were grown in peat or transparent, nutrient-fortified agar at a 12-h light (PAR 240 μmol · m(-2) · s(-1)), 12-h dark cycle. Roots were exposed to low levels (≈ 1-10 μmol · m(-2) · s(-1)) of broadband white light, either directly or indirectly by aboveground light penetrating the growth medium. Control roots were grown in darkness. In situ spectroscopy was used to measure transmittance and reflectance spectra of intact root tissue by mounting the upper part of the primary root directly in a spectrophotometer equipped with an integrating sphere attachment. The transmittance and reflectance spectra were used to calculate the in situ root absorbance spectrum. Absorbance bands were found in the regions 480-500 nm and 650-680 nm, possibly due to low levels of root-localised carotenoids and chlorophylls, respectively. Low light levels (≈ 1-10 μmol · m(-2) · s(-1) ) transmitted through the growth medium significantly increased root pigment concentration and root biomass, and altered root morphology by enhancing lateral root formation and inhibiting root elongation relative to roots grown in complete darkness. The light-induced changes in root morphogenesis and pigmentation appear to be primarily due to upper root light perception.

Effects of the Nordic Photoperiod on Ozone Sensitivity and Repair in Different Clover Species Studied Using Infrared Imaging

Abstract Plants in Nordic regions can be more ozone sensitive at a given ozone concentration than plants at lower latitudes. A recent study shows that the Nordic summer photoperiod, particularly the dim nighttime light, can increase visible foliar injury and alter leaf transpiration in subterranean clover. Effects of photoperiod on the ozone sensitivity of white and red clover cultivars adapted to Nordic conditions were investigated. Although ozone induced visible foliar injury and leaf transpirational changes in white clover, the effects were independent of photoperiod. In red clover, ozone combined with a long photoperiod with dim nights (8 nights) induced more severe visible injuries than with a short photoperiod. Furthermore, transpirational changes in red clover depended on photoperiod. Thus, a long photoperiod can increase ozone sensitivity differently in clover cultivars with different degrees of adaptation to northern conditions, suggesting that ozone indices used in risk analysis should take this effect into account.

Cluster analysis of dynamic contrast enhanced MRI reveals tumor subregions related to locoregional relapse for cervical cancer patients

Abstract Background: Solid tumors are known to be spatially heterogeneous. Detection of treatment-resistant tumor regions can improve clinical outcome, by enabling implementation of strategies targeting such regions. In this study, K-means clustering was used to group voxels in dynamic contrast enhanced magnetic resonance images (DCE-MRI) of cervical cancers. The aim was to identify clusters reflecting treatment resistance that could be used for targeted radiotherapy with a dose-painting approach. Material and methods: Eighty-one patients with locally advanced cervical cancer underwent DCE-MRI prior to chemoradiotherapy. The resulting image time series were fitted to two pharmacokinetic models, the Tofts model (yielding parameters Ktrans and νe) and the Brix model (ABrix, kep and kel). K-means clustering was used to group similar voxels based on either the pharmacokinetic parameter maps or the relative signal increase (RSI) time series. The associations between voxel clusters and treatment outcome (measured as locoregional control) were evaluated using the volume fraction or the spatial distribution of each cluster. Results: One voxel cluster based on the RSI time series was significantly related to locoregional control (adjusted p-value 0.048). This cluster consisted of low-enhancing voxels. We found that tumors with poor prognosis had this RSI-based cluster gathered into few patches, making this cluster a potential candidate for targeted radiotherapy. None of the voxels clusters based on Tofts or Brix parameter maps were significantly related to treatment outcome. Conclusion: We identified one group of tumor voxels significantly associated with locoregional relapse that could potentially be used for dose painting. This tumor voxel cluster was identified using the raw MRI time series rather than the pharmacokinetic maps.

Daily changes in VPD during leaf development in high air humidity increase the stomatal responsiveness to darkness and dry air

Previous studies have shown that plants developed under high relative air humidity (RH>85%) develop malfunctioning stomata and therefor have increased transpiration and reduced desiccation tolerance when transferred to lower RH conditions and darkness. In this study, plants developed at high RH were exposed to daily VPD fluctuations created by changes in temperature and/or RH to evaluate the potential improvements in stomatal functioning. Daily periods with an 11°C temperature increase and consequently a VPD increase (vpd: 0.36-2.37KPa) reduced the stomatal apertures and improved the stomatal functionality and desiccation tolerance of the rosette plant Arabidopsis thaliana. A similar experiment was performed with only a 4°C temperature increase and/or a RH decrease on tomato. The results showed that a daily change in VPD (vpd: 0.36-1.43KPa) also resulted in improved stomatal responsiveness and decreased water usage during growth. In tomato, the most effective treatment to increase the stomatal responsiveness to darkness as a signal for closure was daily changes in RH without a temperature increase.

Autodelineation of cervical cancers using multiparametric magnetic resonance imaging and machine learning

Abstract Background: Tumour delineation is a challenging, time-consuming and complex part of radiotherapy planning. In this study, an automatic method for delineating locally advanced cervical cancers was developed using a machine learning approach. Materials and methods: A method for tumour segmentation based on image voxel classification using Fisher?s Linear Discriminant Analysis (LDA) was developed. This was applied to magnetic resonance (MR) images of 78 patients with locally advanced cervical cancer. The segmentation was based on multiparametric MRI consisting of T2- weighted (T2w), T1-weighted (T1w) and dynamic contrast-enhanced (DCE) sequences, and included intensity and spatial information from the images. The model was trained and assessed using delineations made by two radiologists. Results: Segmentation based on T2w or T1w images resulted in mean sensitivity and specificity of 94% and 52%, respectively. Including DCE-MR images improved the segmentation model?s performance significantly, giving mean sensitivity and specificity of 85?93%. Comparisons with radiologists? tumour delineations gave Dice similarity coefficients of up to 0.44. Conclusion: Voxel classification using a machine learning approach is a flexible and fully automatic method for tumour delineation. Combining all relevant MR image series resulted in high sensitivity and specificity. Moreover, the presented method can be extended to include additional imaging modalities.

Effects of 50 Hz electric currents and magnetic fields on the prokaryote Propionibacterium acnes

The effects of 50 Hz sinusoidal electric currents and magnetic fields on the Gram-positive skin bacterium Propionibacterium acnes were investigated. Intracellular free calcium ([Ca(2+)](i)), intracellular pH (pH(i)), and cell viability were examined, based on their relevance to ELF field studies and on previous studies conducted on P. acnes (UVA irradiation, photosensitization using porphyrin-based sensitizers, and broad-band red light). The [Ca(2+)](i) and the pH(i) were measured spectrofluorimetrically using the fluorescent probes fura-2 and BCECF, respectively. Sham-exposed controls were used to assess the field exposed samples. Cell suspensions were exposed to 50 Hz, 0.2 mT sinusoidal magnetic fields generated by using Helmholtz coils for up to 30 min. The estimated maximum induced electric field was 0.2 mV/m. Changes in [Ca(2+)](i) and cell viability were not detected. Ag/AgCl electrodes were used to expose cell suspensions to 50 Hz sinusoidal electric currents. The current densities were in the range 0.015-1500 A/m(2) (corresponding electric fields congruent with0.01-1000 V/m). Changes in [Ca(2+)](i) were not observed after current exposure. Current densities of 800 A/m(2) (electric field E congruent with550 V/m) were required for a 50% reduction in cell viability. Current densities greater than 800 A/m(2) were required for a reduction in pH(i). However, a pH gradient across the cell membrane (inside alkaline) was maintained even when exposure resulted in less than 0. 2% survival (1400 A/m(2), E congruent with950 V/m). Thus, dissipation of the pH gradient across the cell membrane and changes in [Ca(2+)](i) were not a consequence of cell inactivation by 50 Hz electric currents. This is in contrast to inactivation of P. acnes by UVA irradiation or photosensitization, where such changes have been obtained.