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  • 1.
    Abramenkovs, Andris
    et al.
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för immunologi, genetik och patologi, Medicinsk strålningsvetenskap.
    Stenerlöw, Bo
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för immunologi, genetik och patologi, Medicinsk strålningsvetenskap.
    Measurement of DNA-Dependent Protein Kinase Phosphorylation Using Flow Cytometry Provides a Reliable Estimate of DNA Repair Capacity2017Inngår i: Radiation Research, ISSN 0033-7587, E-ISSN 1938-5404, Vol. 188, nr 6, s. 597-604Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Uncontrolled generation of DNA double-strand breaks (DSBs) in cells is regarded as a highly toxic event that threatens cell survival. Radiation-induced DNA DSBs are commonly measured by pulsed-field gel electrophoresis, microscopic evaluation of accumulating DNA damage response proteins (e.g., 53BP1 or gamma-H2AX) or flow cytometric analysis of gamma-H2AX. The advantage of flow cytometric analysis is that DSB formation and repair can be studied in relationship to cell cycle phase or expression of other proteins. However, gamma-H2AX is not able to monitor repair kinetics within the first 60 min postirradiation, a period when most DSBs undergo repair. A key protein in non-homologous end joining repair is the catalytic subunit of DNA-dependent protein kinase. Among several phosphorylation sites of DNA-dependent protein kinase, the threonine at position 2609 (T2609), which is phosphorylated by ataxia telangiectasia mutated (ATM) or DNA-dependent protein kinase catalytic subunit itself, activates the end processing of DSB. Using flow cytometry, we show here that phosphorylation at T2609 is faster in response to DSBs than gamma-H2AX. Furthermore, flow cytometric analysis of T2609 resulted in a better representation of fast repair kinetics than analysis of gamma-H2AX. In cells with reduced ligase IV activity, and wild-type cells where DNA-dependent protein kinase activity was inhibited, the reduced DSB repair capacity was observed by T2609 evaluation using flow cytometry. In conclusion, flow cytometric evaluation of DNA-dependent protein kinase T2609 can be used as a marker for early DSB repair and gives a better representation of early repair events than analysis of gamma-H2AX.

  • 2. Claesson, Anna Kristina
    et al.
    Stenerlöw, Bo
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för onkologi, radiologi och klinisk immunologi, Enheten för biomedicinsk strålningsvetenskap.
    Jacobsson, Lars
    Elmroth, Kecke
    Relative biological effectiveness of the alpha-particle emitter At-211 for double-strand break induction in human fibroblasts2007Inngår i: Radiation Research, ISSN 0033-7587, E-ISSN 1938-5404, Vol. 167, nr 3, s. 312-318Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The purpose of this study was to quantify and to determine the distribution of DNA double-strand breaks (DSBs) in human cells irradiated in vitro and to evaluate the relative biological effectiveness (RBE) of the alpha-particle emitter (211)At for DSB induction. The influence of the irradiation temperature on the induction of DSBs was also investigated. Human fibroblasts were irradiated as intact cells with alpha particles from (211)At, (60)Co gamma rays and X rays. The numbers and distributions of DSBs were determined by pulsed-field gel electrophoresis with fragment analysis for separation of DNA fragments in sizes 10 kbp-5.7 Mbp. A non-random distribution was found for DSB induction after irradiation with alpha particles from (211)At, while irradiation with low-LET radiation led to more random distributions. The RBEs for DSB induction were 2.1 and 3.1 for (60)Co gamma rays and X rays as the reference radiation, respectively. In the experiments studying temperature effects, nuclear monolayers were irradiated with (211)At alpha particles or (60)Co gamma rays at 2 degrees C or 37 degrees C and intact cells were irradiated with (211)At alpha particles at the same temperatures. The dose-modifying factor (DMF(temp)) for irradiation of nuclear monolayers at 37 degrees C compared with 2 degrees C was 1.7 for (211)At alpha particles and 1.6 for (60)Co gamma rays. No temperature effect was observed for intact cells irradiated with (211)At. In conclusion, irradiation with alpha particles from (211)At induced two to three times more DSB than gamma rays and X rays.

  • 3. Dasu, Alexandru
    et al.
    Denekamp, Juliana
    Inducible Repair and Intrinsic Radiosensitivity: A Complex but Predictable Relationship?2000Inngår i: Radiation Research, ISSN 0033-7587, E-ISSN 1938-5404, Vol. 153, nr 3, s. 279-288Artikkel i tidsskrift (Fagfellevurdert)
  • 4.
    Elmroth, Kecke
    et al.
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för onkologi, radiologi och klinisk immunologi, Enheten för biomedicinsk strålningsvetenskap.
    Stenerlöw, Bo
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för onkologi, radiologi och klinisk immunologi, Enheten för biomedicinsk strålningsvetenskap.
    DNA-incorporated 125I induces more than one double-strand break per decay in mammalian cells2005Inngår i: Radiation Research, ISSN 0033-7587, E-ISSN 1938-5404, Vol. 163, nr 4, s. 369-73Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Auger-electron emitter 125I releases cascades of 20 electrons per decay that deposit a great amount of local energy, and for DNA-incorporated 125I, approximately one DNA double-strand break (DSB) is produced close to the decay site. To investigate the potential of 125I to induce additional DSBs within adjacent chromatin structures in mammalian cells, we applied DNA fragment-size analysis based on pulsed-field gel electrophoresis (PFGE) of hamster V79-379A cells exposed to DNA-incorporated 125IdU. After accumulation of decays at -70 degrees C in the presence of 10% DMSO, there was a non-random distribution of DNA fragments with an excess of fragments <0.5 Mbp and the measured yield was 1.6 DSBs/decay. However, since these experiments were performed under high scavenging conditions (DMSO) that reduce indirect effects, the yield in cells exposed to 125IdU under physiological conditions would most likely be even higher. In contrast, using a conventional low-resolution assay without measurement of smaller DNA fragments, the yield was close to one DSB/decay. We conclude that a large fraction of the DSBs induced by DNA-incorporated 125I are nonrandomly distributed and that significantly more than one DSB/decay is induced in an intact cell. Thus, in addition to DSBs produced close to the decay site, DSBs may also be induced within neighboring chromatin fibers, releasing smaller DNA fragments that are not detected by conventional DSB assays.

  • 5.
    Elmroth, Kecke
    et al.
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för onkologi, radiologi och klinisk immunologi, Enheten för biomedicinsk strålningsvetenskap.
    Stenerlöw, Bo
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för onkologi, radiologi och klinisk immunologi, Enheten för biomedicinsk strålningsvetenskap.
    Influence of chromatin structure on induction of double-strand breaks in mammalian cells irradiated with DNA-incorporated 125I2007Inngår i: Radiation Research, ISSN 0033-7587, E-ISSN 1938-5404, Vol. 168, nr 2, s. 175-182Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study the induction of double-strand breaks (DSBs) was investigated in Chinese hamster V79-379A cells irradiated with the Auger-electron emitter (125)I incorporated into DNA. The role of chromatin organization was studied by pulse-labeling synchronized cells with (125)IdU before decay accumulation in early or late S phase. Pulsed-field gel electrophoresis and fragment-size analysis were used to quantify the distribution of DNA fragments in irradiated intact cells and naked DNA as well as in DNA from asynchronously labeled cultures in a different scavenging environment. The results show that in intact cells, after accumulation of decays at -70 degrees C in the presence of 10% DMSO, almost four times more DSBs were induced in late S phase compared with early S phase and the fragment distribution was clearly non-random with an excess of fragments <0.2 Mbp. The DSB yield was 0.6 DSB/cell and decay for cells irradiated in early S phase and 2.3 DSBs/cell and decay for cells irradiated in late S phase. When similar experiments were performed on naked genomic DNA or intact cells irradiated with gamma rays, the difference in yield was not as prominent. These data imply a role of chromatin organization in the induction of DSBs by DNA-incorporated (125)I. In summary, the results presented here suggest that the yield of DSBs as well as the fragment distribution induced by (125)IdU decay may vary significantly depending on the chromatin organization during S phase and the labeling procedure used.

  • 6. Fakir, Hatim
    et al.
    Sachs, Rainer K.
    Stenerlöw, Bo
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för onkologi, radiologi och klinisk immunologi, Enheten för biomedicinsk strålningsvetenskap.
    Hofmann, Werner
    Clusters of DNA double-strand breaks induced by different doses of nitrogen ions for various LETs: experimental measurements and theoretical analyses2006Inngår i: Radiation Research, ISSN 0033-7587, E-ISSN 1938-5404, Vol. 166, nr 6, s. 917-927Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The yields and clustering of DNA double-strand breaks (DSBs) were investigated in normal human skin fibroblasts exposed to gamma rays or to a wide range of doses of nitrogen ions with various linear energy transfers (LETs). Data obtained by pulsed-field gel electrophoresis on the dose and LET dependence of DNA fragmentation were analyzed with the randomly located clusters (RLC) formalism. The formalism considers stochastic clustering of DSBs along a chromosome due to chromatin structure, particle track structure, and multitrack action. The relative biological effectiveness (RBE) for the total DSB yield did not depend strongly on LET, but particles with higher LET produced higher fractions of small DNA fragments, corresponding in the formalism to an increase in the average number of DSBs per DSB cluster. The results are consistent with the idea that DSB clustering along chromosomes is what leads to large RBEs of high-LET radiations for major biological end points. At a given dose, large fragments are less affected by the variability in LET than small fragments, suggesting that the two free ends in large fragments are often produced by two different tracks. The formalism successfully described an extra increase in small DNA fragments as dose increases and a related decrease in large fragments, mainly due to interlacing of DSB clusters produced along a chromosome by different tracks, since interlacing cuts larger DNA fragments into smaller ones.

  • 7.
    Fessé, Per
    et al.
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska och farmaceutiska vetenskapsområdet, centrumbildningar mm, Centrum för klinisk forskning, Gävleborg. Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för immunologi, genetik och patologi, Experimentell och klinisk onkologi.
    Qvarnström, Fredrik
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för immunologi, genetik och patologi, Experimentell och klinisk onkologi.
    Nyman, Jan
    Hermansson, Ingegerd
    Ahlgren, Johan
    Turesson, Ingela
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för immunologi, genetik och patologi, Experimentell och klinisk onkologi.
    UV-Radiation Response Proteins Reveal Undifferentiated Cutaneous Interfollicular Melanocytes with Hyperradiosensitivity to Differentiation at 0.05 Gy Radiotherapy Dose Fractions2019Inngår i: Radiation Research, ISSN 0033-7587, E-ISSN 1938-5404, Vol. 191, nr 1, s. 93-106Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    To date, the response activated in melanocytes by repeated genotoxic insults from radiotherapy has not been explored. We hypothesized that the molecular pathways involved in the response of melanocytes to ionizing radiation and ultraviolet radiation (UVR) are similar. Skin punch biopsies, not sun-exposed, were collected from prostate cancer patients before, as well as at 1 and 6.5 weeks after daily doses of 0.05-1.1 Gy. Interfollicular melanocytes were identified by ΔNp63- and eosin-periodic acid Schiff staining. Immunohistochemistry and immunofluorescence were performed to detect molecular markers of the melanocyte lineage. Melanocytes were negative for ΔNp63, and the number remained unchanged over the treatment period. At radiation doses as low as 0.05 Gy, melanocytes express higher protein levels of microphthalmia-associated transcription factor (MITF) and Bcl-2. Subsets of MITF- and Bcl-2-negative melanocytes were identified among interfollicular melanocytes in unexposed skin; the cell number in both subsets was reduced after irradiation in a way that indicates low-dose hyperradiosensitivity. A corresponding increase in MITF- and Bcl-2-positive cells was observed. PAX3 and SOX10 co-localized to some extent with MITF in unexposed skin, more so with radiation exposure. Low doses of ionizing radiation also intensified c-KIT and DCT staining. Nuclear p53 and p21 were undetectable in melanocytes. Apoptosis and proliferation could not be observed. In conclusion, undifferentiated interfollicular melanocytes were identified, and responded with differentiation in a hypersensitive manner at 0.05 Gy doses. Radioresistance regarding cell death was maintained up to fractionated doses of 1.1 Gy, applied for 7 weeks. The results suggest that the initial steps of melanin synthesis are common to ionizing radiation and UVR, and underline the importance of keratinocyte-melanocyte interaction behind hyperpigmentation and depigmentation to radiotherapy.

  • 8. Jahnson, S
    et al.
    Christofferson, R H
    Gerdin, B
    Reduced mucosal perianastomotic capillary density in rat small intestine with chronic radiation damage.1998Inngår i: Radiation Research, ISSN 0033-7587, E-ISSN 1938-5404, Vol. 150, nr 5, s. 542-8Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Anastomoses in an intestine with chronic radiation damage are prone to leakage, possibly due to a reduced blood supply induced by a reduced capillary bed. In an animal model, the numerical capillary density in the perianastomotic area was investigated in intestine with or without chronic radiation damage. A 2-cm segment of rat ileum received a single dose of 21 Gy. Twenty weeks later, when the chronic radiation-induced changes were established, an anastomosis was constructed in this segment and in a corresponding segment in control rats. In situ perfusion fixation of the intestine was done 4 or 7 days after construction of the anastomosis, sections of the intestine were removed surgically, the specimens were embedded in methacrylate plastic and sectioned at 2.5 microm, and capillaries were counted under a light microscope. The circumferential mucosal capillary density was lower in irradiated than in nonirradiated animals at both 4 and 7 days (P < 0.001 and P = 0.04, respectively). This reduction was greater in the mesenteric quadrant than in the other quadrants around the circumference. These results are indicative of a reduced capillary bed in the vicinity of anastomoses in intestine with chronic radiation damage, which might lead to an impeded blood supply and subsequent leakage.

  • 9.
    Karlsson, Karin H
    et al.
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för onkologi, radiologi och klinisk immunologi, Enheten för biomedicinsk strålningsvetenskap.
    Radulescu, Irina
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för onkologi, radiologi och klinisk immunologi, Enheten för biomedicinsk strålningsvetenskap.
    Rydberg, Björn
    USA.
    Stenerlöw, Bo
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för onkologi, radiologi och klinisk immunologi, Enheten för biomedicinsk strålningsvetenskap.
    Repair of Radiation-Induced Heat-Labile Sites is Independent of DNA-PKcs, XRCC1 and PARP-12008Inngår i: Radiation Research, ISSN 0033-7587, E-ISSN 1938-5404, Vol. 169, nr 17, s. 506-512Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ionizing radiation induces a variety of different DNA lesions; in addition to the most critical DNA damage, the DSB, numerous base alterations, SSBs and other modifications of the DNA double-helix are formed. When several non-DSB lesions are clustered within a short distance along DNA, or close to a DSB, they may interfere with the repair of DSBs and affect the measurement of DSB induction and repair. We have shown previously that a substantial fraction of DSBs measured by pulsed-field gel electrophoresis (PFGE) are in fact due to heat-labile sites within clustered lesions, thus reflecting an artifact of preparation of genomic DNA at elevated temperature. To further characterize the influence of heat-labile sites on DSB induction and repair, cells of four human cell lines (GM5758, GM7166, M059K, U-1810) with apparently normal DSB rejoining were tested for biphasic rejoining after gamma irradiation. When heat-released DSBs were excluded from the measurements, the fraction of fast rejoining decreased to less than 50% of the total. However, the half-times of the fast (t(1/2) = 7-8 min) and slow (t(1/2) = 2.5 h) DSB rejoining were not changed significantly. At t = 0, the heat-released DSBs accounted for almost 40% of the DSBs, corresponding to 10 extra DSBs per cell per Gy in the initial DSB yield. These heat-released DSBs were repaired within 60-90 min in all cells tested, including M059K cells treated with wortmannin and DNA-PKcs-defective M059J cells. Furthermore, cells lacking XRCC1 or poly(ADP-ribose) polymerase 1 (PARP1) rejoined both total DSBs and heat-released DSBs similarly to normal cells. In summary, the presence of heat-labile sites has a substantial impact on DSB induction and DSB rejoining rates measured by pulsed-field gel electrophoresis, and heat-labile sites repair is independent of DNA-PKcs, XRCC1 and PARP.

  • 10.
    Rydberg, B.
    Uppsala universitet, The Svedberg-laboratoriet.
    The Rate of Strand Separation in Alkali of DNA of Irradiated Mammalian Cells2012Inngår i: Radiation Research, ISSN 0033-7587, E-ISSN 1938-5404, Vol. 178, nr 2, s. AV190-AV197Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Rydberg B. The Rate of Strand Separation in Alkali of DNA of Irradiated Mammalian Cells. Radiat. Res. 61, 274-287 (1975). When mammalian cells are treated with alkali of pH at about 12, the cells are lysed and the released DNA starts to uncoil. This process of DNA strand separation is accelerated if the cells have been exposed to ionizing radiation, and the effect is clearly detectable in the dose range 10-100 rads. The rate of strand separation is also influenced by temperature and ionic strength of the alkaline solution. The kinetics of DNA strand separation in alkali is studied for three conditions in terms of ionic strength and temperature, chosen in such a way that the effect of irradiation may conveniently be studied in the dose range 10 rads to 20 krads. The accelerating effect of ionizing radiation on DNA strand separation is probably due to DNA strand breakage and the technique described is thus a sensitive method of studying such damage to DNA. A model for the strand-separation process, based on the assumption that strand breakage causes the accelerating effect, is proposed and found to describe the experimental data adequately.

  • 11.
    Steffen, Ann-Charlott
    et al.
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för onkologi, radiologi och klinisk immunologi, Enheten för biomedicinsk strålningsvetenskap.
    Göstring, Lovisa
    Tolmachev, Vladimir
    Carlsson, Jörgen
    Differences in sensitivity for 211At-(ZHER2:4)2 treatment between three HER-2 overexpressing cell lines2006Inngår i: Radiation Research, ISSN 0033-7587, E-ISSN 1938-5404Artikkel i tidsskrift (Fagfellevurdert)
  • 12.
    Turesson, Ingela
    et al.
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för immunologi, genetik och patologi, Experimentell och klinisk onkologi.
    Simonsson, Martin
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för immunologi, genetik och patologi, Experimentell och klinisk onkologi.
    Hermansson, Ingegerd
    Univ Göteborg, Sahlgrenska Univ Hosp, Dept Oncol, Gothenburg, Sweden..
    Book, Majlis
    Uppsala Univ, Dept Immunol Genet & Pathol, Expt & Clin Oncol, Uppsala, Sweden..
    Sigurdadottir, Sunna
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för immunologi, genetik och patologi, Experimentell och klinisk onkologi.
    Thunberg, Ulf
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för immunologi, genetik och patologi, Experimentell och klinisk onkologi.
    Qvarnström, Fredrik
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för immunologi, genetik och patologi, Experimentell och klinisk onkologi.
    Johansson, Karl-Axel
    Univ Göteborg, Sahlgrenska Univ Hosp, Dept Radiophys, Gothenburg, Sweden..
    Fessé, Per
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska och farmaceutiska vetenskapsområdet, centrumbildningar mm, Centrum för klinisk forskning, Gävleborg.
    Nyman, Jan
    Univ Göteborg, Sahlgrenska Univ Hosp, Dept Oncol, Gothenburg, Sweden..
    Epidermal Keratinocyte Depletion during Five Weeks of Radiotherapy is Associated with DNA Double-Strand Break Foci, Cell Growth Arrest and Apoptosis: Evidence of Increasing Radioresponsiveness and Lack of Repopulation; the Number of Melanocytes Remains Unchanged2020Inngår i: Radiation Research, ISSN 0033-7587, E-ISSN 1938-5404, Vol. 193, nr 5, s. 481-496Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    During fractionated radiotherapy, epithelial cell populations are thought to decrease initially, followed by accelerated repopulation to compensate cell loss. However, previous findings in skin with daily 1.1 Gy dose fractions indicate continued and increasing cell depletion. Here we investigated epidermal keratinocyte response with daily 2 Gy fractions as well as accelerated and hypofractionation. Epidermal interfollicular melanocytes were also assessed. Skin-punch biopsies were collected from breast cancer patients before, during and after mastectomy radiotherapy to the thoracic wall with daily 2 Gy fractions for 5 weeks. In addition, 2.4 Gy radiotherapy four times per week and 4 Gy fractions twice per week for 5 weeks, and two times 2 Gy daily for 2.5 weeks, were used. Basal keratinocyte density of the interfollicular epidermis was determined and immunostainings of keratinocytes for DNA double-strand break (DSB) foci, growth arrest, apoptosis and mitosis were quantified. In addition, interfollicular melanocytes were counted. Initially minimal keratinocyle loss was observed followed by pronounced depletion during the second half of treatment and full recovery at 2 weeks post treatment. DSB foci per cell peaked towards the end of treatment. p21-stained cell counts increased during radiotherapy, especially the second half. Apoptotic frequency was low throughout radiotherapy but increased at treatment end. Mitotic cell count was significantly suppressed throughout radiotherapy and did not recover during weekend treatment gaps, but increased more than threefold compared to unexposed skin 2 weeks post-radiotherapy. The number of melanocytes remained constant over the study period. Germinal keratinocyte loss rate increased gradually during daily 2 Gy fractions for 5 weeks, and similarly for hypofractionation. DSB foci number after 2 Gy irradiation revealed an initial radioresistance followed by increasing radiosensitivity. Growth arrest mediated by p21 strongly suggests that cells within or recruited into the cell cycle during treatment are at high risk of loss and do not contribute significantly to repopulation. It is possible that quiescent (G(0)) cells at treatment completion accounted for the accelerated post-treatment repopulation. Recent knowledge of epidermal tissue regeneration and cell cycle progression during genotoxic and mitogen stress allows for a credible explanation of the current finding. Melanocytes were radioresistant regarding cell depletion.

  • 13.
    Villegas, Fernanda
    et al.
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för immunologi, genetik och patologi, Medicinsk strålningsvetenskap.
    Tilly, Nina
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för immunologi, genetik och patologi, Medicinsk strålningsvetenskap. Elekta Instrument AB.
    Ahnesjö, Anders
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för immunologi, genetik och patologi, Medicinsk strålningsvetenskap.
    Target size variation in microdosimetric distributions and its impact on the linear-quadratic parameterization of cell survival.2018Inngår i: Radiation Research, ISSN 0033-7587, E-ISSN 1938-5404, Vol. 190, s. 504-512Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The linear-quadratic (LQ) parameterization of survival fraction SF(D) inherently assumes that all cells in a population get the same dose D, albeit the distribution of specific energy z over the individual cells f(z,D) can be very wide. From these microdosimetric distributions, which are target size dependent, we estimate the size of the cellular sensitive volume by analysing its influence on the LQ parameterization of cell survival. A Monte Carlo track structure code was used to simulate detailed tracks from a 60Co source as well as proton and carbon ions of various energies. From these tracks, f(z,D) distributions were calculated for spherical targets with diameters ranging from 10 nm to 12 µm. A cell survival function based on f(z,D) was fitted to published experimental LQ α values, revealing an intrinsic limitation that target size imposes on the usage of f(z,D) to describe the linear term of the LQ parameterization. The results indicate that such threshold volume arises naturally from the relationship between the particle´s probability of no-hit and the probability of cell survival. Further analysis led to the proposal of a radiobiological property yf,MID, defined as the mean lineal energy corresponding to the target size that allows equivalence between the mean inactivation dose (MID) and the mean specific energy z1.  The fact that z1 is an increasing continuous function of target size within the range of biological targets of interest in radiobiology, ensures the uniqueness of yf,MID for any radiation quality, thus, its potential usefulness in modelling. In conclusion, an accurate estimation of such threshold volumes may be useful for improving modelling of cell survival curves.

    Fulltekst (pdf)
    2018-Villegasetal
  • 14. Waldeland, Einar
    et al.
    Hole, Eli Olaug
    Stenerlöw, Bo
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för onkologi, radiologi och klinisk immunologi, Enheten för biomedicinsk strålningsvetenskap.
    Grusell, Erik
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för onkologi, radiologi och klinisk immunologi, Avdelningen för sjukhusfysik.
    Sagstuen, Einar
    Malinen, Eirik
    Radical formation in lithium formate EPR dosimeters after irradiation with protons and nitrogen ions2010Inngår i: Radiation Research, ISSN 0033-7587, E-ISSN 1938-5404, Vol. 174, nr 2, s. 251-257Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Radical formation in polycrystalline lithium formate monohydrate after irradiation with gamma rays, protons and nitrogen ions at room temperature was studied by continuous-wave electron paramagnetic resonance (EPR) spectroscopy. The linear energy transfer (LET) of the various radiation beams was 0.2, 0.7-3.9 and 110-164 keV/microm for gamma rays, protons and nitrogen ions, respectively. Doses between 5 and 20 Gy were given. The EPR reading (the area under the EPR absorption resonance) increased linearly with dose for all types of radiation. As the LET increased, the relative effectiveness (the EPR reading per dose relative to that for gamma rays) decreased, while the EPR line width increased. Track structure theory and modeling of detector effectiveness predicted the dosimeter response observed after proton and nitrogen-ion irradiation. A semi-empirical line broadening model including dipolar spin-spin interactions was developed that explained the dependence of the line width on LET. The findings indicate that the local radical density in lithium formate is increased after high-LET irradiation.

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