Improved FBX chemical dosimeter system with enhanced radiochemical yield for reference dosimetry in radiobiology and radiotherapy research

Radiation dosimetry plays important role in the reproducibility of radiobiology experiments, in the replicability of results, as well as in the successful and safe use of radiotherapy procedures. The consistency and accuracy of the applied dosimetry methods pre-define the outcomes of these applications. This paper presents a version of the well-known ferrous sulphate – benzoic acid – xylenol orange (FBX) chemical dosimeter with improved sensitivity, accuracy and precision. Sensitivity is increased due to a slight modification in composition and the preparation procedures. We use stock solutions for the preparation of the dosimeter solution, which consists of 1 mM ferrous sulphate and 16 mM benzoic acid with 0.25 mM xylenol orange added post-irradiation. The nonlinear response to the absorbed dose of this system is eliminated by the increased ferrous sulphate concentration, permitting the calculation of the absorbed dose by a linear relationship between the absorbed dose and the optical absorbance of the solution. The measured chemical yield of our dosimeter is 9.08⋅10−6mol/J for 6 MV photon beams and 6.42⋅10−6mol/J for 250 kVp x-rays. This is a 24% enhancement over the original FBX solution, which permits a finer dose resolution. The accuracy and precision of our method is assured by a well-designed and consistently used practice. A custom designed multipurpose PMMA slab phantom was used for irradiation in reference conditions. This phantom can be used for irradiation in reference conditions of dosimetric solutions, dosimetric films and chemical or biological samples. The combined standard uncertainty of this system is 1.12%, which can be improved by using an appropriate temperature correction factor. Furthermore, a working protocol has been established which allows dosimetry measurements using less than 1 mL dosimetric solutions

Dietary phosphatidylcholine supplementation attenuates inflammatory mucosal damage in a rat model of experimental colitis

This study was designed to follow the time course of inflammatory activation in a rodent model of 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced colitis. We hypothesized that oral phosphatidylcholine (PC) pretreatment regimens may influence leukocyte-mediated microcirculatory reactions in this condition. In series I, Wistar rats were monitored 1 day after colitis induction (n = 24), and in series II (n = 24) on day 6 following a TNBS enema. The PC-pretreated animals received a 2% PC-enriched diet for 6 days before the TNBS enema (series I), or for 3 days before and 3 days after TNBS treatment (series II). The macrohemodynamics, serosal microcirculation (visualized by intravital videomicroscopy), colonic xanthine oxidoreductase, myeloperoxidase and nitric oxide end products, and changes in proinflammatory cytokine levels in plasma were measured. The mucosal structural injury was monitored in vivo by means of confocal laser scanning endomicroscopy. The TNBS enema induced a systemic hyperdynamic circulatory reaction with increased serosal capillary blood flow and significantly elevated colonic inflammatory enzyme activities, levels of nitric oxide production, and cytokine concentrations. Acute colitis caused disruption of the capillary network, whereas the morphologic damage was less severe in series II. The PC pretreatment protocols led to significant decreases in the serosal hyperemic reaction, the cytokine levels, and the inflammatory enzyme activities. The objective signs of tissue damage were reduced in both series, and the number of mucus-producing goblet cells in the resolving phase of colitis was increased. Dietary PC efficiently decreases the cytokine-mediated progression of inflammatory events and preserves the microvascular structure in the large intestine. © 2012 by the Shock Society

Terápiás lehetőségek a gyulladásos bélbetegség állatkísérletes modelljében – összehasonlító vizsgálat [Comparative study of novel therapeutic possibilities in animal experimental model of inflammatory bowel disease]

Introduction: The consequence of inflammatory bowel diseases (IBD) is cytokine-mediated severe local tissue damage. Our aim was to determine the extent of inflammatory response and to influence the morphologic changes during the subacute phase of trinitro-benzene sulfonic acid (TNBS)-induced experimental colitis by oral phosphatidylcholine (PC) and N-methyl-D-aspartate (NMDA) receptor antagonist kynurenic acid therapy. Methods: Sprague-Dawley rats were randomized to control, untreated colitis (ic TNBS), colitis fed with 2% PC-containing diet (3 days pre-treatment +3 days treatment after TNBS induction), colitis with kynurenic acid treatment (on day 6, n = 7) groups. The colitis was characterized by tissue myeloperoxidase and plasma TNF-alpha levels, the extent of tissue damage, structural changes in microvasculature (FITC-dextran staining) and mucosal injury (acridine orange staining) were determined by in vivo confocal laser scanning endomicroscopy (Optiscan Five1, Australia) and conventional histology (hematoxyilin-eosin staining). Results: Significant elevation in myeloperoxidase and TNF-alpha levels with remarkable damage in epithelial structure was detected in the colitis group. Both treatment regimens significantly decreased the level of inflammatory activation but only PC pretreatment could preserve the number of goblet cells and the epithelial structure. Treatment with kynurenic acid did not alter the morphology changes. Conclusion: Oral PC pretreatment is a promising possibility in the therapy of IBDs through decreasing inflammatory reaction and increasing the number of goblet cells

Analysis of Ionizing Radiation Induced DNA Damage by Superresolution dSTORM Microscopy

The quantitative detection of radiation caused DNA double-strand breaks (DSB) by immunostained γ-H2AX foci using direct stochastic optical reconstruction microscopy (dSTORM) provides a deeper insight into the DNA repair process at nanoscale in a time-dependent manner. Glioblastoma (U251) cells were irradiated with 250 keV X-ray at 0, 2, 5, 8 Gy dose levels. Cell cycle phase distribution and apoptosis of U251 cells upon irradiation was assayed by flow cytometry. We studied the density, topology and volume of the γ-H2AX foci with 3D confocal microscopy and the dSTORM superresolution method. A pronounced increase in γ-H2AX foci and cluster density was detected by 3D confocal microscopy after 2 Gy, at 30 min postirradiation, but both returned to the control level at 24 h. Meanwhile, at 24 h a considerable amount of residual foci could be measured from 5 Gy, which returned to the normal level 48 h later. The dSTORM based γ-H2AX analysis revealed that the micron-sized γ-H2AX foci are composed of distinct smaller units with a few tens of nanometers. The density of these clusters, the epitope number and the dynamics of γ-H2AX foci loss could be analyzed. Our findings suggest a discrete level of repair enzyme capacity and the restart of the repair process for the residual DSBs, even beyond 24 h. The dSTORM superresolution technique provides a higher precision over 3D confocal microscopy to study radiation induced γ-H2AX foci and molecular rearrangements during the repair process, opening a novel perspective for radiation research

Protective effects of l-alpha-glycerylphosphorylcholine on ischaemia-reperfusion-induced inflammatory reactions

Purpose Choline-containing dietary phospholipids, including phosphatidylcholine (PC), may function as anti-inflammatory substances, but the mechanism remains largely unknown. We investigated the effects of l-alpha-glycerylphosphorylcholine (GPC), a deacylated PC derivative, in a rodent model of small intestinal ischaemia-reperfusion (IR) injury. Methods Anaesthetized Sprague-Dawley rats were divided into control, mesenteric IR (45 min mesenteric artery occlusion, followed by 180 min reperfusion), IR with GPC pretreatment (16.56 mg kg-1 GPC i.v., 5 min prior to ischaemia) or IR with GPC post-treatment (16.56 mg kg-1 GPC i.v., 5 min prior to reperfusion) groups. Macrohaemodynamics and microhaemodynamic parameters were measured; intestinal inflammatory markers (xanthine oxidoreductase activity, superoxide and nitrotyrosine levels) and liver ATP contents were determined. Results The IR challenge reduced the intestinal intramural red blood cell velocity, increased the mesenteric vascular resistance, the tissue xanthine oxidoreductase activity, the superoxide production, and the nitrotyrosine levels, and the ATP content of the liver was decreased. Exogenous GPC attenuated the macro- and microcirculatory dysfunction and provided significant protection against the radical production resulting from the IR stress. The GPC pretreatment alleviated the hepatic ATP depletion, the reductions in the mean arterial pressure and superior mesenteric artery flow, and similarly to the post-treatments with GPC, also decreased the xanthine oxidoreductase activity, the intestinal superoxide production, the nitrotyrosine level, and normalized the microcirculatory dysfunction. Conclusions These data demonstrate the effectiveness of GPC therapies and provide indirect evidence that the anti-inflammatory effects of PC could be linked to a reaction involving the polar part of the molecule. © 2014 Springer-Verlag Berlin Heidelberg