Irradiation of Langmuir-Blodgett multilayer preparations of phospholipids and a fatty acid. 2: Effect of X-radiation.

X-irradiation of Langmuir-Blodgett (LB) preparations of stearic acid with doses up to a few thousand Gy produced no change of measured electrical conductance in the direction perpendicular to the stacked monolayers. However, irradiation of LB preparations of phospholipids resulted in increased conductance. The effect depended on dose, but not on dose rate and, unlike the corresponding effect of UV-radiation, did not reverse at room temperature. For doses up to about 2 kGy the increased conductance fell away over some tens of minutes if the temperature was raised above 45 degrees C. For doses between 2 and 60 kGy the conductance increased linearly, but less rapidly than the initial rise and the increase was only partly reversible by heating. The rate of increase of conductance rose again for doses above about 60 kGy and for these doses the increase could not be reversed on heating. It is suggested that X-irradiation left molecules in a damaged but reversible state similar to that found after UV irradiation; and that subsequent excitation and ionization damaged the molecules irreversibly.     

The role of higher-order chromatin structure in the yield and distribution of DNA double-strand breaks in cells irradiated with X-rays or alpha-particles

PURPOSE: To determine whether the non-random distributions of DNA double-strand breaks in cells observed after alpha-particle irradiation are related to the higher-order structure of the chromatin within the nucleus. MATERIALS AND METHODS: Chinese hamster V79 cells were irradiated as either cellular monolayers, nuclear monolayers with condensed chromatin or nuclear monolayers with relaxed chromatin, and the yields and distribution of DSB measured using two pulsed-field gel electrophoresis protocols capable of separating fragments of 10kbp to 5.7 Mbp. RESULTS: Using conventional FAR analysis, the effect of isolating nuclear monolayers and changing the chromatin condensation state was less for alpha-particle irradiated substrates than for X-irradiated ones. When the total number of breaks was measured by separating and quantifying all the fragments produced in the 10kbp to 5.7Mbp region, the difference between the observed yields of breaks in X-irradiated cells (7.3 x 10(-9) DSB/Gy/bp) relative to alpha-particles (12.1 x 10(-9) DSB/Gy/bp) was largely removed when nuclear monolayers with decondensed chromatin were exposed. The yields, although similar, increased to 44.4 x 10(-9) DSB/Gy/bp for X-irradiated decondensed nuclear monolayers and 46.6 x 10(-9) DSB/Gy/bp for alpha-particle irradiated monolayers. However, the alpha-particle DSB distributions remained non-random. CONCLUSIONS: Our results suggest that the non-random distribution of breaks observed in cells with alpha-particle irradiation, which leads to a high probability for the production of regionally multiply damaged sites, is not related to the underlying chromatin condensation state present in the nucleus.     

The role of higher-order chromatin structure in the yield and distribution of DNA double-strand breaks in cells irradiated with X-rays or α-particles

Purpose : To determine whether the non-random distributions of DNA double-strand breaks in cells observed after alpha-particle irradiation are related to the higher-order structure of the chromatin within the nucleus. Materials and methods : Chinese hamster V79 cells were irradiated as either cellular monolayers, nuclear monolayers with condensed chromatin or nuclear monolayers with relaxed chromatin, and the yields and distribution of DSB measured using two pulsedfield gel electrophoresis protocols capable of separating fragments of 10kbp to 5.7Mbp. Results : Using conventional FAR analysis, the effect of isolating nuclear monolayers and changing the chromatin condensation state was less for α -particle irradiated substrates than for Xirradiated ones. When the total number of breaks was measured by separating and quantifying all the fragments produced in the 10kbp to 5.7 Mbp region, the difference between the observed yields of breaks in X-irradiated cells (7.3 10 9 DSB/Gy/bp) relative to α -particles (12.1 10 -9 DSB/Gy/bp) was largely removed when nuclear monolayers with decondensed chromatin were exposed. The yields, although similar, increased to 44.4 10 -9 DSB/Gy/bp for X-irradiated decondensed nuclear monolayers and 46.6 10 9 DSB/Gy/bp for α -particle irradiated monolayers. However, the α -particle DSB distributions remained non-random. Conclusions : Our results suggest that the non-random distribution of breaks observed in cells with α -particle irradiation, which leads to a high probability for the production of regionally multiply damaged sites, is not related to the underlying chromatin condensation state present in the nucleus.     

The mechanism of human adipocere formation

In adipocere, some specific fatty acids possessing higher melting points, together with soap, play an important role in the formation and stabilization of adipocere. These fatty acids were shown to be mainly 10-hydroxy stearic and 10-hydroxy palmitic acids. Slight amounts of 10-oxo stearic and 10-oxo palmitic acids, which have higher melting points than those of hydroxy fatty acids (OHFAs), exist in the adipocere as well. The substantial adipocere is formed and stabilized mainly by these specific fatty acids. The OHFA and oxo fatty acid (OXOFA) are biosynthesized by some bacterial enzymes. Various aerobic and anaerobic bacteria are involved in the formation of adipocere. For instance, microbial conversion of various unsaturated fatty acids to 10-OHFA by Micrococcus luteus was investigated. It turned out that 10-OHFA was synthesized only from fatty acids possessing cis-9-unsaturatin. It was also shown that 10-OHFAs were converted to the corresponding 10-OXOFAs but 10-OXO compounds were inactive as substrates. It was further found that the enzyme preparations from Flavobacterium meningosepticum solubilized by sonication catalyzed not only hydration of oleic acid to produce 10-hydroxy stearic acid, but also dehydrogenation of this product in the presence of deuterium.On the other hand, we found out that there was 10-hydroxy-12-octadecenoic acid (10-OHODA) in the linoleic acid in human adipocere and that there were 9-chloro-10-methoxy (9-methoxy-10-chloro) palmitic acid and 9-chloro-10-methoxy (9-methoxy-10-chloro) stearic acid in human neonate adipocere.     

Effect of Ionizing Radiation on Artificial (Planar) Lipid Membranes. II. The Ion Carriers Valinomycin and Nonactin as Probes for Radiation Induced Structural Changes of the Membrane

Summary

Planar lipid membranes in the presence of the ion carriers valinomycin or nonactin were irradiated with 14 MeV electrons from a linear accelerator. A large increase of the membrane conductance by up to more than two orders of magnitude was found. The effect is virtually abolished either at high pH, or in the absence of oxygen, or in the presence of the radical scavenger ethanol. A further prerequisite for the effect is the presence of unsaturated fatty acid residues. A kinetic analysis of the carrier transport model based on current-voltage curves and on voltage-jump relaxation experiments was performed as a function of radiation dose. Only the translocation rate constant, k_MS, of the charged carrier-ion complex was found to be influenced by irradiation. The effect is interpreted as an increase of the polarity (dielectric constant) of the membrane interior induced by the presence of polar products of lipid peroxidation. A combined action of OH- and HO₂-radicals seems to be responsible for the phenomena. At large radiation doses (? 10³ Gy) a reduction of the membrane conductance was observed. This is interpreted as an increased microviscosity, possibly caused by cross-linking of fatty acid residues. Ion carriers represent sensitive probes of radiation induced membrane damage.     

Fast neutron beam radiotherapy of glioblastoma multiforme.

Twenty-one patients with glioblastoma multiforme were treated with fast neutron beam irradiation of the whole brain. Therapy was well tolerated up to calculated doses of 1.850 radn+y in 12-18 increments over 6 weeks. The survival rate 6 month after initiation of treatment was 62%, not significantly different from conventional photon therapy; average posttreatment survival appears to be shortened compared to photon therapy. No improvement or prolonged maintenance of existing neurologic function was observed. Autopsy findings in seven patients showed replacement of tumor by coagulative necrosis persisting at least 16 months posttreatment, paucity of tumor cells with infrequent mitosis, and suppression of macrophage response. These findings differ from those in conventionally irradiated patients. No treatment-related changes were documented by conventional gross and histologic studies of the irradiated brains distant from the tumors. Thus the deaths of patients in this study appear to be related to unexplained causes other than progressive growth of tumor.     

Determination of effective atomic number and electron density of some fatty acids by gamma-ray attenuation

Total photon mass attenuation coefficients of 7 fatty acids (lauric acid, palmitic acid, stearic acid, oleic acid, myristic acid, castor oil, mustard oil) have been measured in the energy range 356–1116 keV. The experimental results are analysed in terms of total cross sections, effective atomic numbers and electron densities.     

Biochemistry of late effects in rat lung after hemithoracic irradiation

The right hemithorax of rats was exposed to 1 kR of roentgen rays, the animals were killed at different times, and various physiologic and biochemic parameters (DNA, protein, collagen, sialic acid, lysosomal enzymes, fibrinolytic activity, peroxides and blood flow ratio between irradiated and non irradiated lung) were determined from 1 day until 11 months after irradiation. A decrease in relative blood flow was observed from 2 weeks until 11 months, a decrease in phospholipids from one to 3 months and a decrease in fibrinolytic activity from 1 day to 11 months after irradiation. At several times a decrease in sialic acid and cathepsin D was also noted. The changes are discussed with respect to the pathogenetic mechanisms of late lung damage.     

饱和脂肪酸和不饱和脂肪酸对肺癌细胞增殖与自噬的影响

目的 研究饱和脂肪酸和不饱和脂肪酸对肺癌细胞增殖与自噬的影响.方法 用0、30、60、120、240μmol/L硬脂酸(饱和脂肪酸)和DHA(不饱和脂肪酸)分别处理肺癌细胞A549,绘制细胞生长曲线并计算克隆形成率以检测细胞增殖.采用硬脂酸和DHA分别处理A549细胞24h后,采用激光共聚焦显微镜从形态学方面观察细胞自噬情况.采用硬脂酸和DHA分别处理A549细胞12、24、36h后,用Western blotting检测细胞自噬相关蛋白的表达.结果 30~240μmol/L硬脂酸和DHA均有抑制A549细胞增殖的作用(P<0.05),硬脂酸、DHA处理A549细胞24h后均检测到细胞出现明显的自噬;Western blotting结果 显示,硬脂酸、DHA分别处理A549细胞12、24、36h后,LC3Ⅱ/LC3Ⅰ比值升高(P<0.05),哺乳动物雷帕霉素靶蛋白(ser2481)磷酸化水平降低(P<0.05).结论 饱和脂肪酸和不饱和脂肪酸均有抑制肺癌细胞增殖、诱导肺癌细胞自噬的作用,其机制可能与p-mTOR(ser2481)信号通路有关.     

Critical energies for SSB and DSB induction in plasmid DNA by low-energy photons: action spectra for strand-break induction in plasmid DNA irradiated in vacuum

PURPOSE: To measure action spectra for the induction of single-strand breaks (SSB) and double-strand breaks (DSB) in plasmid DNA by low-energy photons and provide estimates for the energy dependence of strand-break formation important for track-structure simulations of DNA damage. MATERIALS AND METHODS: Plasmid pMSG-CAT was irradiated as a monolayer, under vacuum, with 7 150eV photons produced by a synchrotron source. Yields of SSB and DSB were determined by the separation of the three plasmid forms by gel electrophoresis. RESULTS: The yields of SSB per incident photon increased from 1.4x 10(-15) SSB per plasmid per photon/cm2 at 7eV to 7.5 x 10(-14) SSB per plasmid per photon/cm2 at 150 eV. Direct induction of DSB was also detected increasing from 3.4 x 10(-17) DSB per plasmid per photon/cm2 at 7eV to 4.1 x 10(-15) DSB per plasmid per photon/cm2 at 150eV. When the absorption cross-section of the DNA was considered, the quantum efficiency for break formation increased over the energy range studied. Over the entire energy range, the ratio of SSB to DSB remained constant. CONCLUSIONS: These studies provide evidence for the ability of photons as low as 7 eV to induce both SSB and DSB. The common action spectrum for both lesions suggests that they derive from the same initial photoproducts under conditions where the DNA is irradiated in vacuum and a predominantly direct effect is being observed. The spectral and dose-effect behaviour indicates that DSB are induced predominantly by single-event processes in the energy range covered.     

Critical energies for SSB and DSB induction in plasmid DNA by low-energy photons: action spectra for strand-break induction in plasmid DNA irradiated in vacuum

Purpose : To measure action spectra for the induction of single-strand breaks (SSB) and double-strand breaks (DSB) in plasmid DNA by low-energy photons and provide estimates for the energy dependence of strand-break formation important for track-structure simulations of DNA damage. Materials and methods : Plasmid pMSG-CAT was irradiated as a monolayer, under vacuum, with 7-150 eV photons produced by a synchrotron source. Yields of SSB and DSB were determined by the separation of the three plasmid forms by gel electrophoresis. Results : The yields of SSB per incident photon increased from 1.4 x 10 -15 SSB per plasmid per photon/cm 2 at 7 eV to 7.5 x 10 -14 SSB per plasmid per photon/cm 2 at 150 eV. Direct induction of DSB was also detected increasing from 3.4 x 10 -17 DSB per plasmid per photon/cm 2 at 7 eV to 4.1 x 10 -15 DSB per plasmid per photon/cm 2 at 150 eV. When the absorption cross-section of the DNA was considered, the quantum efficiency for break formation increased over the energy range studied. Over the entire energy range, the ratio of SSB to DSB remained constant. Conclusions : These studies provide evidence for the ability of photons as low as 7 eV to induce both SSB and DSB. The common action spectrum for both lesions suggests that they derive from the same initial photoproducts under conditions where the DNA is irradiated in vacuum and a predominantly direct effect is being observed. The spectral and dose-effect behaviour indicates that DSB are induced predominantly by single-event processes in the energy range covered.     

Radioprotection of whole-body gamma irradiation induced alterations in lipid metabolism of liver and plasma by AET (S-2, aminoethyl isothiuronium Br. H. Br.) and serotonin in rats.

Radioprotective effect of AET, serotonin and their mixture has been studied on liver and plasma lipid metabolism 24 hrs and 48 hrs after irradiation in fasted male rats. AET and serotonin both gave significant radioprotection to certain liver and plasma lipid components, but the mixture of the two afforded a better protection. The non-radioprotection of plasma NEFA, phospholipids and phosphatidyl choline levels by serotonin observed in irradiated rats was because serotonin itself raised the levels of these lipids in control rats. Serotonin alone or in mixture effectively protected the radiation-induced increased incorporation of NaH2(32)PO4 into liver phospholipids. Mixture of AET and serotonin failed to protect the increased incorporation of aceae-1-14-C into liver total fatty acids and cholesterol, but it prevented this increased incorporation into liver triglycerides and phospholipids.     

Use of alanine for dosimetry intercomparisons among Italian radiotherapy centers.

A pilot program of postal dosimetry intercomparison among 16 Italian Radiotherapy Centers was performed using the ISS Alanine/EPR dosimetry as a transfer system. Dosimeters were irradiated at 10 Gy with high-energy photon beams, both in reference condition in a water phantom and in an anthropomorphic phantom during the simulated treatment of rectum cancer. Intercomparison design along with alanine performances analyzing the different contributions to the combined uncertainty in dose assessment are reported. Main results of the pilot intercomparison, terminated in 2002, are also presented.     

Effects of Carbon Photon Irradiation on Wound Healing in a Rat Full-thickness Wound Model

Objective: The present study was undertaken to examine the effect of carbon photon on healing of skin wounds in a rat model.Methods: One full-thickness skin wounds were created on the back of Wistar rats and irradiated by using carbon photon at peak wavelength 662 nm with 54 J/cm2,compared with injured sham-irradiation control rats. The animals were then killed after various intervals of wounding,and the wounded skin tissues were evaluated by histological test.. The wound re-epithelialization and healing qualification were examined by histological analysis.Cell proliferation was examined by Brd Uimmunohis through chemical staining.Results: The irradiation of carbon photon significantly accelerated wound healing rate compared with the control group at 7,14 and 21 days after wounding. At the histological level,the significant increasement in the degree of re-epithelialization,the content of collagen and the density of micro-vessel were observed in the wound sites in carbon photon treated group at 7,14 and21 days after wounding. Moreover,treatment with carbon photon increased Brd U-labeled cells at the edge of the wound sites after wounding at the indicated time.Conclusion: The results of the experiment showed that carbon photon therapy can accelerate wound healing and improve wound healing quality by stimulating cell proliferation.     

Measurement of high dose rates by photon activation of indium foils.

Photon activation of indium foils is proposed as a dosimetry technique for high dose rate measurements in a 60Co irradiation facility. The irradiated indium nuclei may be raised to its metastable isomers of 113mIn and 115mIn. The isomer 115mIn, with appreciable induced radioactivity, was selected for dose-rate measurements. Based on the photon flux distribution and the derived dose rates, which were simulated by the MCNP code, the dependence of dose rate measurement sensitivity of indium foils with respect to photon energy at various irradiation distances is described. For practical uses, the radioactivity of 115mIn was linearly related to the dose rate response at the specified irradiation positions. By comparing with a calibrated dosimetry system, the measurement deviation of the indium dosimeter, over dose rates ranging from 10 to 10(4) Gy/h, was evaluated and exhibited an uncertainty of +/- 7%. Other related characteristics including measurement sensitivity and range, linearity with respect to the variation of dose rate, and limitations of the indium dosimeter were evaluated to justify it as an alternative for monitoring dose rate in an irradiation field.     

Gold microspheres: a selective technique for producing biologically effective dose enhancement

PURPOSE: To investigate dose enhancement and radiosensitization associated with electrons produced and scattered from gold particles suspended in cells in vitro and with tumour cells growing in vivo irradiated with low-energy photons. MATERIALS AND METHODS: CHO-K1, EMT-6 and DU-145 cells were irradiated with kilovoltage X-ray and Cs-137 beams in slowly stirred suspensions in the presence of various concentrations of gold particles ( 1.5-3.0 microm); cell survival was measured by clonogenic assay. Gold particles were injected directly into EMT-6 tumours growing in scid mice prior to their irradiation. Tumour cell killing was assayed by an in vivo-in vitro technique. RESULTS: Dose enhancement was confirmed by both Fricke dosimetry and cell killing for 100, 140, 200 and 240 kVp X-rays, but not for Cs-137 gamma-rays. For the chemical dosimeter, a dose enhancement (DMF) of 1.42 was measured for 1% gold particle solutions irradiated with 200 kVp X-rays. When rodent and human cells were irradiated in the presence of 1% gold particles, DMF values at the 10% survival level ranged from 1.36 to 1.54, with an overall average value of 1.43. Preliminary attempts to deliver these gold particles to tumour cells in vivo by intra-tumour injection resulted in modest radiosensitization but extremely heterogeneous distribution. CONCLUSIONS: An increased biologically effective dose can be produced by gold microspheres suspended in cell culture or distributed in tumour tissue exposed to kilovoltage photon beams. With the increasing use of interstitial brachytherapy with isotopes that produce low-energy photons, high-Z particles might find a role for significantly improving the therapeutic ratio.     

Determining soil contamination profiles from intensities of capture-gamma rays using above-surface neutron sources.

Four methods are presented to estimate contaminant concentration profiles in soil from the intensities of neutron-induced capture-gamma photon intensities measured at the soil surface. In particular, the method of linear regularization with and without an iterative positivity constraint, the Backus-Gilbert method, and the maximum entropy method are applied to the soil contamination problem. Example results obtained with the four methods are given for photon intensities calculated for idealized test contaminant profiles in soil irradiated by neutron sources above the surface.     

Determining soil contamination profiles from intensities of capture-gamma rays using above-surface neutron sources.

Four methods are presented to estimate contaminant concentration profiles in soil from the intensities of neutron-induced capture-gamma photon intensities measured at the soil surface. In particular, the method of linear regularization with and without an iterative positivity constraint, the Backus-Gilbert method, and the maximum entropy method are applied to the soil contamination problem. Example results obtained with the four methods are given for photon intensities calculated for idealized test contaminant profiles in soil irradiated by neutron sources above the surface.     

Gold microspheres: a selective technique for producing biologically effective dose enhancement

Purpose : To investigate dose enhancement and radiosensitization associated with electrons produced and scattered from gold particles suspended in cells in vitro and with tumour cells growing in vivo irradiated with low-energy photons. Materials and methods : CHO-K1, EMT-6 and DU-145 cells were irradiated with kilovoltage X-ray and Cs-137 beams in slowly stirred suspensions in the presence of various concentrations of gold particles (1.5-3.0 μ m); cell survival was measured by clonogenic assay. Gold particles were injected directly into EMT-6 tumours growing in scid mice prior to their irradiation. Tumour cell killing was assayed by an in vivo-in vitro technique. Results : Dose enhancement was confirmed by both Fricke dosimetry and cell killing for 100, 140, 200 and 240kVp X-rays, but not for Cs-137 γ-rays. For the chemical dosimeter, a dose enhancement (DMF) of 1.42 was measured for 1% gold particle solutions irradiated with 200 kVp X-rays. When rodent and human cells were irradiated in the presence of 1% gold particles, DMF values at the 10% survival level ranged from 1.36 to 1.54, with an overall average value of 1.43. Preliminary attempts to deliver these gold particles to tumour cells in vivo by intra-tumour injection resulted in modest radiosensitization but extremely heterogeneous distribution. Conclusions : An increased biologically effective dose can be produced by gold microspheres suspended in cell culture or distributed in tumour tissue exposed to kilovoltage photon beams. With the increasing use of interstitial brachytherapy with isotopes that produce low-energy photons, high-Z particles might find a role for significantly improving the therapeutic ratio.     

Inverse planning for photon and proton beams.

The concept of inverse planning for intensity-modulated radiation therapy and its application for photon and charged particle beams is presented. Starting from theoretical solutions of the "inverse problem" in radiation therapy, a clinically applied optimization approach is discussed. A central topic is the mathematical formulation of clinical objectives in terms of physical parameters such as dose levels and irradiated volumes. Examples for practical inverse treatment planning and its clinical application for photon beams are provided. Inverse treatment planning of dose delivery techniques with charged particle beams is discussed by extending the conventional planning concept. A new multimodality inverse planning tool is described and applied to an example of comparative planning between photon and proton IMRT.