The effect of oxygen concentration on the X-ray induction of chromosome aberrations in human lymphocytes.

In vitro dose--response curves, for unstable chromosome aberration induction in human lymphocytes under conditions of full oxygenation or of anoxia, have been obtained using 250 kVp X-rays. Dicentric yields have been fitted to the quadratic function Y = alpha D + beta D2. An Oxygen Enhancement Ratio (OER) ranging from 7.2 to 2.7 was calculated from the coefficients of these curves possibly indicating that the data do not fit to the dose-modifying model of the oxygen effect although the differences are not statistically significant. A similar analysis of total aberration data yields an OER of 3.6 to 2.7 fitting much more satisfactorily to the dose-modifying model. Variations in dicentric yield induced by 3.0 Gy and 0.75 Gy of X-rays with increasing oxygen concentration were plotted and for each dose a constant dicentric yield was observed at oxygen levels of 2 and 250 ppm. Above 250 ppm yields increased steeply up to about 1% oxygen and then more gradually to a maximum at 100% oxygen.     

The RBE of neutrons for induced mitotic gene conversion in "error-prone repair" defective yeast

Mitotic gene conversion was induced in the diploid yeast strain D7.rad6 which lacks "error-prone repair" and thus does not mutate. Neutrons (14.5 MeV), 60Co gamma rays, and 150 kVp X rays delivered under oxic or anoxic conditions were compared for their ability to induce gene conversion. Doses were chosen to minimize cell killing. A lack of induced mutation in this strain at the ilv1-92 allele was confirmed. Gene conversion of the trp5-27/trp5-12 alleles was induced with a linear dose response, and the yield of convertants per gray was significantly enhanced over yields reported previously for a wild-type stain. The relative biological effectiveness (RBE) of neutrons relative to low-LET radiations was found to be about 2.2 for either oxic or anoxic radiation in contrast to wild-type where the oxic RBE was 1.7 and the anoxic RBE 2.7. Absence of the rad6 function was therefore associated with an altered RBE for the conversional end point. The oxygen enhancement ratio (OER) for gene conversion was found to be about 1.7 for all radiations in contrast to the wild type where the OER for neutrons was 1.7, but for low-LET radiations it was 2.7. As repair of ionizing damage in the rad6 strain did not lead to mutation, owing to the loss of "error-prone repair," the changes in yield, RBE, and OER were consistent with the hypothesis that some of the lesions processed by wild type to generate mutations could, in the rad6 strain, lead instead to gene conversion.     

Inactivation of aerobic and hypoxic cells from three different cell lines by accelerated (3)He-, (12)C- and (20)Ne-ion beams

The LET-RBE spectra for cell killing for cultured mammalian cells exposed to accelerated heavy ions were investigated to design a spread-out Bragg peak beam for cancer therapy at HIMAC, National Institute of Radiological Sciences, Chiba, prior to clinical trials. Cells that originated from a human salivary gland tumor (HSG cells) as well as V79 and T1 cells were exposed to (3)He-, (12)C- and (20)Ne-ion beams with an LET ranging from approximately 20-600 keV/micrometer under both aerobic and hypoxic conditions. Cell survival curves were fitted by equations from the linear-quadratic model and the target model to obtain survival parameters. RBE, OER, alpha and D(0) were analyzed as a function of LET. The RBE increased with LET, reaching a maximum at around 200 keV/micrometer, then decreased with a further increase in LET. Clear splits of the LET-RBE or -OER spectra were found among ion species and/or cell lines. At a given LET, the RBE value for (3)He ions was higher than that for the other ions. The position of the maximum RBE shifts to higher LET values for heavier ions. The OER value was 3 for X rays but started to decrease at an LET of around 50 keV/micrometer, passed below 2 at around 100 keV/micrometer, and then reached a minimum above 300 keV/micrometer, but the values remained greater than 1. The OER was significantly lower for (3)He ions than the others.     

The radiosensitivity of spermatogonial stem cells in C3H/101 F1 hybrid mice

The radiosensitivity of spermatogonial stem cells of C3H/HeH × 101/H F₁ hybrid mice was determined by counting undifferentiated spermatogonia at 10 days after X-irradiation. During the spermatogenic cycle, differences in radiosensitivity were found, which were correlated with the proliferative activity of the spermatogonial stem cells. In stage VIII_irr, during quiescence, the spermatogonial stem cells were most radiosensitive with a D₀ of 1.4 Gy. In stages XI_irr−V_irr, when the cells were proliferatively active, the D₀ was about 2.6 Gy. Based on the D₀ values for sensitive and resistant spermatogonia and on the D₀ for the total population, a ratio of 45:55% of sensitive to resistant spermatogonial stem cells was estimated for cell killing.

When the present data were compared with data on translocation induction obtained in mice of the same genotype, a close fit was obtained when the translocation yield (Y; in % abnormal cells) after a radiation dose D was described by Y = e^τD, with τ = 1 for the sensitive and τ = 0.1 for the resistant spermatogonial stem cells, with a maximal e^τD of 100.     

Radiobiology of ultrasoft X rays. II. Cultured C3H mouse cells (10T1/2)

In the first paper of this series (Radiat. Res. 110, 396-412 (1987], using V79 cells, we reported that the relative biological effectiveness (RBE) of ultrasoft X rays was found to increase with decreasing energy, and the oxygen enhancement ratio (OER) was found to decrease with decreasing energy. In this report, we present RBE and OER results for 10T1/2 cells that are known to grow uniformly flat and are considerably thinner than V79 cells. Thus the variation in dose across the cell nucleus is considerably reduced. The OER results agree well with our earlier V79 results. However, the RBE values for 10T1/2 cells compared to V79 cells are systematically less for all soft X rays and especially for 0.28 keV carbon-K (1.3 compared to 3.4 for V79 cells). Some plausible explanations are presented to reconcile the apparent discrepancy between V79 and 10T1/2 results.     

The effectiveness of 20 mev protons at nanosecond pulse lengths in producing chromosome aberrations in human-hamster hybrid cells

Laser accelerated radiotherapy is a potential cancer treatment with proton and carbon-ion beams that is currently under development. Ultra-fast high-energy laser pulses will accelerate ion beams that deliver their dose to a patient in a "pulsed mode" that is expected to differ from conventional irradiation by increasing the dose delivery rate to a tissue voxel by approximately 8 orders of magnitude. In two independently performed experiments at the ion microprobe SNAKE of the 14 MV Munich tandem accelerator, A(L) cells were exposed either to protons with 1-ns pulse durations or to protons applied over 150 ms in continuous irradiation mode. A slightly but consistently lower aberration yield was observed for the pulsed compared to the continuous mode of proton irradiation. This difference was not statistically significant when each aberration type was analyzed separately (P values between 0.61 and 0.85 in experiment I and P values between 0.32 and 0.64 in experiment II). However, excluding the total aberrations, which were not analyzed as independent radiation-induced effects, the mean ratio of the yields of dicentrics, centric rings and excess acentrics scored together showed (with 95% CI) a significant difference of 0.90 (0.81; 0.98) between the pulsed and the continuous irradiation modes. A similar tendency was also determined for the corresponding RBE values relative to 70 kV X rays. Since the different findings for the comparisons of individual chromosome aberration types and combined comparisons could be explained by different sample sizes with the consequence that the individual comparisons had less statistical power to identify a difference, it can be concluded that 20 MeV protons may be slightly less effective in the pulsed mode.     

The induction by ionizing radiation of chromosomal aberrations in rhesus monkey pre-meiotic germ cells: effects of dose rate and radiation quality

The induction of reciprocal translocations in rhesus monkey stem-cell spermatogonia was studied using multivalent analysis at metaphase of primary spermatocytes. Animals were exposed to 1 Gy gamma-rays at dose rates of 140 and 0.2 mGy/min or to 0.25 Gy acute 2 MeV neutrons. Reduction of the dose rate from 140 mGy/min to 0.2 mGy/min did not result in a lowering of the frequencies of recovered translocations of 0.43%. The neutron data indicated an RBE (neutrons vs. X-rays) of 2.1, which is clearly lower than the value of 4 obtained in the mouse. It is made plausible that in general mammalian species with high sensitivities for the cytotoxic effects of ionizing radiation, such as the rhesus monkey, will exhibit relatively high threshold dose rates below which no further reduction in aberration yield occurs, whereas in more resistant species, such as the mouse, the threshold dose rate will be at a very low level. Similarly, resistant species will show relatively high RBE values for neutron irradiation and sensitive species low ones.     

Induction of chromosome aberrations by Sr β-particles in cultured human lymphocytes

Human blood was irradiated with β-particles from an external source of ⁹⁰Sr. The source was a rolled piece of silver foil, active dimensions: 100 × 12.5 mm, incorporating 3.7 × 10⁸ Bq (10 mCi) of ⁹⁰Sr/⁹⁰Y. After culturing for 48 h, the dicentric yield in the lymphocytes at the first metaphase was measured as a function of the dose in the blood. The aberration yield fitted the linear-quadratic function well, which is consistent with the single-track and two-track model for aberration formation at low LET radiation. The curve for ⁹⁰Sr β-rays was compared with a curve for ⁶⁰Co γ-rays. The main difference between the coefficients was in the values. With respect to ⁶⁰Co γ-rays, the RBE calculated from the dose-effect relationships for dicentric production was 2.8 at the dose of 0.14 Gy; it decreased with increasing doses. The distribution of dicentrics was consistent with the Poisson distribution but showed a tendency to over-dispersion in the region of higher doses. A reason for these discrepancies is discussed.     

The magnetic susceptibility of reduced cytochrome P-450cam

The magnetic susceptibility of singly reduced, camphor-complexed cytochrome P−450 from Pseudomonas putida has been measured at various temperatures. Computer analysis using a spin Hamiltonian gives values of D between 15K and 25K, which agrees with a value of D = 20K found by low-field variable temperature Mössbauer spectroscopy. This result is compared with those from deoxyhemoglobin and deoxy-myoglobin.     

Aberrations induced by fission neutrons in human peripheral lymphocytes

Analysis of dose-response relationship was carried out for chromosome aberrations produced in human peripheral lymphocytes by fission neutrons at doses of 25, 50, 100 or 200 rad.Statistical treatment showed experimental data to be fitted by a regression curve described by the mathematical model Y = a+bD. A linear relation to dose characterized both one-break and two-break aberration yields. Numerical values of coefficients are reported for yields of dicentrics, chromosome fragments, minutes, aberrant cells, total number of aberrations, and total breakage.Based on chromosome fragments and aberrant cells, relative biological efficiency (RBE) value derived for fission neutrons relative to 180 kV X-rays for chromosome fragments was 2.53, and for aberrant cells it was 2.80.     

Assessment of relative biological effectiveness of tritium using chromosome aberration frequency in human blood lymphocytes

The aim of this work is to determine Relative Biological Effectiveness (RBE) of tritium beta-irradiation using chromosome aberration frequency in peripheral blood lymphocytes after radiation exposure in vitro and in vivo. The results of the experimental estimation of tritium beta-irradiation RBE in comparison with 60Co gamma-irradiation using analysis of unstable chromosome aberration frequencies in peripheral blood lymphocytes in reference to concrete conditions of the investigation were presented. It was demonstrated that tritium beta-irradiation is in total more effective than gamma-irradiation up to 1 Gy. RBE of tritium beta-irradiation was determined as 2.2 at minimum doses and decreased at higher doses (1 Gy) up to 1.25. For the first time results of the comparative analysis of frequencies of stable chromosome aberrations in two groups of professional nuclear workers (town Sarov) exposed to chronic tritium beta- and gamma-irradiation in remote period were presented. The grater RBE of tritium beta-irradiation was demonstrated. It has been estimated as 2.5.     

The FLUKA Monte Carlo code coupled with an OER model for biologically weighted dose calculations in proton therapy of hypoxic tumors

IntroductionThe increased radioresistance of hypoxic cells compared to well-oxygenated cells is quantified by the oxygen enhancement ratio (OER). In this study we created a FLUKA Monte Carlo based tool for inclusion of both OER and relative biological effectiveness (RBE) in biologically weighted dose (ROWD) calculations in proton therapy and applied this to explore the impact of hypoxia.MethodsThe RBE-weighted dose was adapted for hypoxia by making RBE model parameters dependent on the OER, in addition to the linear energy transfer (LET). The OER depends on the partial oxygen pressure (pO₂) and LET. To demonstrate model performance, calculations were done with spread-out Bragg peaks (SOBP) in water phantoms with pO₂ ranging from strongly hypoxic to normoxic (0.01–30 mmHg) and with a head and neck cancer proton plan optimized with an RBE of 1.1 and pO₂ estimated voxel-by-voxel using [¹⁸F]-EF5 PET. An RBE of 1.1 and the Rørvik RBE model were used for the ROWD calculations.ResultsThe SOBP in water had decreasing ROWD with decreasing pO₂. In the plans accounting for oxygenation, the median target doses were approximately a factor 1.1 lower than the corresponding plans which did not consider the OER. Hypoxia adapted target ROWDs were considerably more heterogeneous than the RBE_1.1-weighted doses.ConclusionWe realized a Monte Carlo based tool for calculating the ROWD. Read-in of patient pO₂ and estimation of ROWD with flexibility in choice of RBE model was achieved, giving a tool that may be useful in future clinical applications of hypoxia-guided particle therapy.     

进境美国大豆中值得关注的真菌Diaporthe novem

采用常规平板分离法,从一批进境的美国大豆样品中获得1株可疑的间座壳属菌株MDD57.经形态学观察发现,该菌株在PDA培养基上产生分生孢子器,且同时产生大量α型和β型分生孢子,未见有性阶段.经ITS和tef1α基因扩增、核酸序列比对分析,发现该菌株同GenBank中2株Diaporthe novem菌株的基因序列同源性达...     

Extracting absolute titanium-alkyl and-hydride bond enthalpies from relative D(TiR(H)) in (silox)2(Bu3SiNH)TiR: electronegativity and ECT models

Relative D(Ti-R)_rel have been measured previously for (silox)₂(^tBu₃SiNH)TiR (1-R). Pauling and Matcha equations of D(MR) that contain elements of electronegativity, D(MM), D(HH) and D(RH) were used to estimate absolute D(TiR) in 1 with minimal success. The electronegativity approaches need a variety of substituents with a wide spread in χ_R, hence examination of 1-H and 1-R are heavily and incorrectly weighted by D(TiH)-D(TiR). Absolute D(TiR) generated in this manner approach those of related systems only when χX_Ti = 2.9, a value shown to be irrational. Drago's ECT parameters were used in the hope that the three parameter fit would compensate for inadequacies in electronegativity-based methods. The limited set of alkyl parameters available, and a lack of distinguishing parameters that can significantly differentiate one alkyl from another, render this potentially useful method imprecise.     

Mathematical modeling and study of mass transfer parameters in supercritical fluid extraction of fatty acids from Trout powder

Mathematical modeling of fatty acids (FAs) extraction from Trout powder by supercritical carbon dioxide was performed in the present work. Trout powder with its low cost contains high amount of essential FAs and it is commonly available as a proper source of FAs. The effect of process parameters, such as pressure (25, 28, 31, 34 and 37 MPa) and temperature (310, 318 and 326 K) of extraction and void fraction of the bed (0.25, 0.35 and 0.45, v/v) on the yield of FAs extraction was examined in a series of experiments conducted in a laboratory scale apparatus. The results indicated a significant increase of extraction yield with an increase of pressure from 25 to 34 MPa, but working at the higher pressure (37 MPa) caused reduction of the extract. Increasing the temperature higher than 318 K revealed significant reduction of the FAs yield and increasing the bed void fraction from 0.25 to 0.45 showed enhancement of the extraction.

The mathematical model was developed considering diffusion-controlled regime in the particle and film mass transfer resistance around the particle with axial dispersion of the bulk phase at dynamic conditions. Henry law was used to describe the equilibrium state of solid and fluid phases. The proposed mass balance equations were numerically solved using implicit finite difference method and the model parameters were correlated using the experimental results of the outlet FAs concentration in the oil extracted at dynamic conditions. Well-known Nelder–Mead method was applied to estimate the four parameters of the model, namely, mass transfer coefficient (k_f), axial dispersion coefficient (D_ax) in the bulk phase, effective diffusivity (D_eff) into the pores and Henry coefficient (H). In the range of studied conditions, the higher extraction efficiency with higher pressure resulted lower correlated H, although the temperature increasing which showed a retrograde phenomena in the FAs yield, revealed H passing though a minimum.     

贵州梨芽枯间座壳菌属Diaporthe的种类

为明确引起贵州梨芽枯病的间座壳菌种类,本研究进行了病害调查、病芽采集和病菌分离及纯化,根据其菌落特征与ITS序列鉴定,共获得94个间座壳属Diaporthe菌株,从中选取40个代表菌株进行多基因(ITS、TEF、CAL、HIS和TUB)系统发育分析和形态学观察,结果显示它们分属于间座壳属的8个种,包括核桃间座壳菌D. biguttulata、榆树间座壳菌D. eres、椭圆间座壳菌D. ellipsoidea、梭状间座壳菌D. fusicola、香港间座壳菌D. hongkongensis、塞纳间座壳菌D. sennae、大豆间座壳菌D. sojae和蜜柑间座壳菌D. unshiuensis,其中D. ellipsoidea、D. biguttulata和D. sennae为侵染梨的首次报道。玉露香梨离体枝条接种结果显示,8种间座壳的代表菌株均可产生与田间相同的症状,分离比最高的D. eres致病力较强,表明它们均为梨芽枯病的病原菌,其中D. eres为病原优势种。本研究首次报道了引起梨芽枯的间座壳菌种类组成,为该病的发生规律及防控技术研究提供了理论依据。     

黄土高原北部典型灌丛枝条生物量估算模型

于2015年8月末在陕西神木县六道沟小流域采集200个柠条和210个沙柳枝条,测定枝条的基径(D)、长度(H)、含水量(W₀)、鲜质量(W_F)和干质量(W),选用指数函数和异速生长方程建立了4种由枝条形态指标估算枝条生物量的简易模型,并对模型的拟合效果进行验证. 结果表明: 对于柠条和沙柳灌丛,基于D、H二者组合变量(D²H)的异速生长方程是估算枝条生物量的最优模型,该模型经线性转化后可以消除生物量数据的异方差性,且拟合效果最优,决定系数(R²)最大,平均误差(ME)、平均绝对误差(MAE)、总相对误差(TRE)、平均系统误差(MSE)和平均绝对百分误差(MPSE)整体上最小,基本满足生态学研究的精度要求.     

RBE and OER values of negative pion beams from growth inhibition of Vicia Faba roots

Summary Two pion beams of different momentum width have been used to expose meristems of Vicia Faba roots under aerobic and hypoxic conditions. The measurements of the resulting 10 days growth inhibition after exposures at various locations on the pion beam axes have been made and RBE and OER values evaluated for 50% effects compared to⁶⁰Co ti-rays. The results have been related to the fractional doses from star products defined by telescope measure ments of stopped pions along the same beams. It has been found that the RBE value increases with the fractional star dose up to a maximum after which the RBE decreases. The OER values, however, were found to decrease with increas ing star dose fraction rather rapidly after which it was found to be independent of the star dose contribution.     

Dose-response relations for dicentric yields in GO lymphocytes of man and crab-eating monkey following acute and chronic gamma-irradiations.

A comparison has been made of dicentric yields in G₀ lymphocytes between man and crab-eating monkey, Macaca fascicularis, after acute and chronic γ-irradiations. With acute irradiation (49.6 rad/min) there was no significant difference between them, but for the chronic irradiation (17.1 rad/h) a significant difference was observed between the species. When the dose-response relations were fitted to the linear-quadratic model (Y = D + βD²), the species-difference observed for chronic irradiation was almost entirely due to change in the value of β. In addition, after chronic irradiation the β-value for monkey was almost negligible, but that for man was significant. Post-irradiation incubation experiment showed that cells with dicentrics were partly eliminated during the course of chronic irradiation, because there were appreciable reductions of dicentric yields (ca. 25% for both man and monkey at 400 rad) together with mitotic indices (ca. 30% and 60% for man and monkey, respectively, at 400 rad). Accordingly, it would be reasonable to postulate that G₀ repair for dicentrics other than selection mechanism must play a major role in the effects of low dose rate. It can be further suggested that G₀-repair capacity for chromosal damages leading to dicentrics may be different among different primate species.     

Chromosome aberrations induced by X-ray therapy and myxovirus infection in human peripheral leukocytes

The dose-response relationships and the distribution of breaks induced by irradiation were studied in phytohemagglutinin-stimulated peripheral lymphocytes from female patients treated with X-rays for cancer of the breast. The yield of dicentrics and rings was expressed by the formula y = 0.0086 + 1.53 (± 0.15) · 10⁻⁵ D, and the yield of fragments by y = 0.022 + 1.68 (± 0.17) · 10⁻⁵ D, where D is the accumulated skin dose in rad. The percentage of damaged cells, however, reached a plateau of 22% at about 6000 rad. In all dose ranges, the distribution of cells with various numbers of breaks deviated significantly from a Poisson distribution, which should have been obtained if all cells in the blood had been exposed to irradiation. It was possible to calculate the number of undamaged cells present in excess and, when these were omitted, a close agreement with a Poisson distribution was obtained. The results suggested that almost 30% of the circulating lymphocytes had been exposed to irradiation with the fractionated partial body procedure utilized.

The effect of Newcastle disease, Sendai, measles and mumps virus infection in vitro on peripheral blood lymphocytes from irradiated patients was also studied. Virus treatment caused a decrease in the frequency of chromosome-type damage. No effect, or a slight decrease of chromatid-type damage, was seen as compared with controls treated with normal allantoic fluid.