scholarly journals Factors Limiting the Number of Radiation-Induced Chromosome Exchanges

1958 ◽  
Vol 4 (4) ◽  
pp. 365-372 ◽  
Author(s):  
Sheldon Wolff ◽  
K. C. Atwood ◽  
M. L. Randolph ◽  
H. E. Luippold
Keyword(s):  
Dose Fractionation ◽  
Fast Neutrons ◽  
Root Tip ◽  
X Rays ◽  
X Ray ◽  
Linear Dose ◽  
Radiation Induced ◽  
Short Fractionation ◽  
Chromosome Exchanges ◽  
Aberration Yield

Soaked seeds of Vicia faba were exposed to fractionated doses of x-rays or x-rays and fast neutrons. When the two-hit (exchange) chromosome aberrations were scored at the first mitosis of the root tip, it was observed that with short fractionation times the radiation-induced breaks from the two x-ray doses could rejoin with one another to form exchanges in proportion to the square of the total dose. If, however, one dose was x-rays and the second neutrons, then no quantitatively determinable interaction occurred between the breaks induced by each of the doses, and the aberration yield was simply the sum of that induced by each fraction. The phenomenon of non-interaction as observed by these dose fractionation studies and also by the linear dose response curve for two-break aberrations induced by neutrons has led to calculations of the distance over which two breaks can rejoin. The distance is evidently much smaller than the previously accepted value of 1 µ.

X-ray radiation-induced amorphization of metal–organic frameworks

2019 ◽  
Vol 21 (23) ◽  
pp. 12389-12395 ◽  
Author(s):  
Remo N. Widmer ◽  
Giulio I. Lampronti ◽  
Nicola Casati ◽  
Stefan Farsang ◽  
Thomas D. Bennett ◽  
...  
Keyword(s):  
Radiation Damage ◽  
Metal Organic Frameworks ◽  
X Rays ◽  
X Ray ◽  
P Accumulation ◽  
Metal Organic ◽  
Radiation Induced ◽  
Crystalline Metal

Accumulation of radiation damage from synchrotron X-rays leads to complete amorphization of the initially crystalline metal–organic frameworks ZIF-4, ZIF-62, and ZIF-zni. The mechanism of this transformation is studied as a function of time and temperature and is shown to be non-isokinetic.

FINE STRUCTURE MAPPING IN YEAST WITH SUNLAMP RADIATION

Genetics ◽  
1974 ◽  
Vol 76 (4) ◽  
pp. 723-733
Author(s):  
Christopher W Lawrence ◽  
Roshan Christensen
Keyword(s):  
Fine Structure ◽  
Dose Response ◽  
Gamma Ray ◽  
X Rays ◽  
Structure Mapping ◽  
Mapping Procedure ◽  
X Ray ◽  
Linear Dose ◽  
Near Ultraviolet ◽  
Ionizing Radiations

ABSTRACT The X-ray mapping procedure of Manney and Mortimer (1964) is the most widely applicable and convenient method for fine structure analysis in yeast, but suffers the disadvantage that suitable X-ray machines or gamma ray sources are very expensive. Although many other recombinogens are known, none gives a linear dose-response like X-rays and few are as convenient or give as reproducible results. Experiments with Saccharomyces cerevisiae reported in this paper show, however, that the near-ultraviolet radiation emitted by fluorescent sunlamps gives linear dose-response relations, as reproducible results as ionizing radiations, and map distances which correlate highly with those obtained by using 60Co gamma rays. It is suggested that this convenient recombinogen may be a suitable low-cost substitute for ionizing radiations in fine structure mapping.

ATM and RAD51 Repair Pathways in Human Lymphocytes Irradiated with 70 MeV Therapeutic Proton Beam

2021 ◽  
Author(s):  
Agnieszka Panek ◽  
Justyna Miszczyk
Keyword(s):  
Proton Beam ◽  
Human Lymphocytes ◽  
Strand Break ◽  
Double Strand Break ◽  
Double Strand Break Repair ◽  
X Rays ◽  
X Ray ◽  
Post Irradiation ◽  
Repair Protein ◽  
Radiation Induced

The repair of radiation-induced DNA damage is a key factor differentiating patients in terms of the therapeutic efficacy and toxicity to surrounding normal tissue. Proton energy substantially determines the types of cancers that can be treated. The present work investigated the DNA double-strand break repair systems, represented by phosphorylated ATM and Rad51. The status of proton therapy energy used to treat major types of cancer is summarized. Here, human lymphocytes from eight healthy donors (male and female) were irradiated with a spread-out Bragg peak using a therapeutic 70 MeV proton beam or with reference X rays. For both types of radiation, the kinetics of pATM and Rad51 repair protein activation (0–24 h) were estimated as determinants of homologous and non-homologous double-strand break repair. Additionally, γ-H2AX was used as the gold standard marker of double-strand breaks. Our results showed that at 30 min postirradiation there was significantly greater accumulation of γ-H2AX (0.6-fold), pATM (2.0-fold), and Rad51 (0.6-fold) in the proton-irradiated cells compared with the X-ray-treated cells. At 24 h post irradiation, for both types of radiation and all investigated proteins, the foci number was still significantly higher when compared with control. Furthermore, the mean value of pATM and Rad51 repair effectiveness was higher in cells exposed to protons than in cells exposed to X rays; however, the difference was significant only for pATM. The largest inter-individual differences in the repair capabilities were noted for Rad51. The association between the frequency of repair protein foci and the frequency of lymphocyte viability at 1 h post irradiation showed a positive correlation for protons but a negative correlation for X rays. These findings indicate that the accumulation of radiation-induced repair protein foci after proton versus X-ray irradiation differs between patients, consequently affecting the cellular responses to particle therapy and conventional radiation therapy.

scholarly journals Thiamine prevents X-ray induction of genetic changes in human lymphocytes in vitro.

2004 ◽  
Vol 51 (3) ◽  
pp. 839-843 ◽  
Author(s):  
Maria Konopacka ◽  
Jacek Rogoliński
Keyword(s):  
Nuclear Division ◽  
Morphological Changes ◽  
Human Lymphocytes ◽  
Vitamin B1 ◽  
X Rays ◽  
Genetic Changes ◽  
X Ray ◽  
Radiation Induced ◽  
Nuclear Division Index

The effects of thiamine (vitamin B1) on the level of spontaneous or radiation-induced genetic changes in human lymphocytes in vitro were studied. Cultured lymphocytes were exposed to increasing concentrations of thiamine (0-500 microg/ml) and irradiated with X-rays. The DNA damage was estimated as the frequency of micronuclei and apoptotic or necrotic morphological changes in fixed cells. The results show that thiamine alone did not induce genetic changes. A significant decrease in the fraction of apoptotic and necrotic cells was observed in lymphocytes irradiated in the presence of vitamin B1 at concentrations between 1-100 microg/ml compared to those irradiated in the absence of thiamine. Vitamin B1 at 1 and 10 microg/ml decreased also the extent of radiation-induced formation of micronuclei. Vitamin B1 had no effect on radiation-induced cytotoxicity as measured by nuclear division index. The results indicate that vitamin B1 protects human cells from radiation-induced genetic changes.

The effects of x-ray radiation on the eye development of zebrafish

2014 ◽  
Vol 33 (10) ◽  
pp. 1040-1050 ◽  
Author(s):  
R Zhou ◽  
J Si ◽  
H Zhang ◽  
Z Wang ◽  
J Li ◽  
...  
Keyword(s):  
Eye Development ◽  
Model Organism ◽  
Control Group ◽  
X Rays ◽  
Heterogeneous Distribution ◽  
X Ray ◽  
Radiation Induced ◽  
High Doses ◽  
Lens Formation ◽  
Nuclear Cell

The toxic effects of x-ray radiation on eye development was measured using zebrafish as a model organism. Zebrafish embryos at 8 h post-fertilization (hpf) were irradiated using X-rays at doses of 1, 2, 4, and 8 Gy. At 24 and 48 hpf, x-ray radiation induced a significant increase in reactive oxygen species (ROS) content and cell apoptotic signals. Both of these increases were dose dependent and there were significant positive relationships between them at 24 hpf. At 48 and 72 hpf, the increase of ROS concentration can be eliminated by increasing activities of superoxide dismutase and catalase. Although the ROS generated by x-ray radiation caused a significant increase in cell apoptosis at 24 and 48 hpf, the cellular layers of the retina and lens formation in the irradiated groups were not significantly disrupted at 144 hpf compared with the control group, with the exception of a heterogeneous distribution of the cells in inner nuclear cell layer and a significant decrease in the diameters of whole eyes after 8 Gy irradiation. X-Ray radiation at later stages of gastrulation may not cause distinct optic complications; however, there is still a risk of microophthalmia at high doses of irradiation.

VII. Experiments on the Skin of Pigs with Fast Neutrons and 8 MV X Rays, including some Effects of Dose Fractionation

1963 ◽  
Vol 36 (422) ◽  
pp. 107-115 ◽  
Author(s):  
D. K. Bewley ◽  
J. F. Fowler ◽  
R. L. Morgan ◽  
J. A. Silvester ◽  
B. A. Turner
Keyword(s):  
Dose Fractionation ◽  
Fast Neutrons ◽  
X Rays

The inhibition of p21 on irradiation-induced apoptosis in EL-4 cells.

2012 ◽  
Vol 30 (15_suppl) ◽  
pp. e13558-e13558
Author(s):  
Feng-qin Yan ◽  
Jian-qiu Wang ◽  
Shi-bo Fu ◽  
Fang-zheng Wang ◽  
Zhen-fu Fu ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Ionizing Radiation ◽  
Time Course ◽  
Apparent Difference ◽  
X Rays ◽  
X Ray ◽  
Radiation Induced ◽  
Induced Apoptosis ◽  
Diploid Cells

e13558 Background: To elucidate the effect of p21 on ionizing radiation-induced apoptosis in EL-4 cells. Methods: In EL-4 cells, RT-PCR, immunocytochemistry and flow cytometry (FCM) were used to analyze the changes in the expression of p21 with time and doses caused by ionizing radiation; RNAi was used to silence the expression of p21 in EL-4 cells; FCM was applied to analyze the distribution of cell cycle,the number of the chromosome and the apoptosis in wild or p21-silencing EL-4 cells exposed to X-rays. Results: In EL-4 cells, p21 protein level was markedly increased at 8 ~ 72 h after exposure in 4.0 Gy of X-ray in vitro (p<0.01), as well as exposed in 1.0 ~ 4.0 Gy of X-ray at 24 h in vitro (p<0.05). Results of time-course experiments showed that, in EL-4 cells exposed to 4.0 Gy X-rays, the percentage in G0/G1 phase increased while that in S phase decreased, significantly different with the sham-irradiated groups (p<0.05), during 8-48h after exposure; the percentage of diploid cells increased significantly during 8-48 h (p<0.01), and the percentage of tetraploid and octoploid cells decreased significantly at 2 h and 8 h (p<0.05); the percentage of apoptosis during 2-72 h increased significantly (p<0.05-p<0.01). Compared with wild EL-4 cells, in p21-silencing EL-4 cells, the distribution of cell cycle had no apparent difference; the percentage of diploid cells decreased significantly and the percentage of octoploid cells increased significantly (p<0.01); the percentage of apoptosis increased significantly (p<0.05). Conclusions: p21 inhibited the apoptosis induced by ionizing radiation in EL-4 cells.

Room-temperature performance of 3 mm-thick cadmium–zinc–telluride pixel detectors with sub-millimetre pixelization

2020 ◽  
Vol 27 (5) ◽  
pp. 1180-1189
Author(s):  
Antonino Buttacavoli ◽  
Fabio Principato ◽  
Gaetano Gerardi ◽  
Manuele Bettelli ◽  
Nicola Sarzi Amadè ◽  
...  
Keyword(s):  
Room Temperature ◽  
Cadmium Zinc Telluride ◽  
Zinc Telluride ◽  
High Rate ◽  
X Rays ◽  
X Ray ◽  
Temperature Performance ◽  
Pixel Detectors ◽  
Radiation Induced ◽  
Cadmium Zinc

Cadmium–zinc–telluride (CZT) pixel detectors represent a consolidated choice for the development of room-temperature spectroscopic X-ray imagers, finding important applications in medical imaging, often as detection modules of a variety of new SPECT and CT systems. Detectors with 3–5 mm thicknesses are able to efficiently detect X-rays up to 140 keV giving reasonable room-temperature energy resolution. In this work, the room-temperature performance of 3 mm-thick CZT pixel detectors, recently developed at IMEM/CNR of Parma (Italy), is presented. Sub-millimetre detector arrays with pixel pitch less than 500 µm were fabricated. The detectors are characterized by good room-temperature performance even at high bias voltage operation (6000 V cm−1), with energy resolutions (FWHM) of 3% (1.8 keV) and 1.6% (2 keV) at 59.5 keV and 122.1 keV, respectively. Charge-sharing investigations were performed with both uncollimated and collimated synchrotron X-ray beams with particular attention to recovering the charge losses at the inter-pixel gap region. High rate measurements demonstrated the absence of high-flux radiation-induced polarization phenomena up to 25 × 106 photons mm−2 s−1.

Radiation Exposure in the Neonatal Intensive Care Unit in Newborns and Staff

2021 ◽  
Author(s):  
Salih Cagri Cakir ◽  
Bayram Ali Dorum ◽  
Nilgun Koksal ◽  
Hilal Ozkan ◽  
Zeynep Yazici ◽  
...  
Keyword(s):  
Intensive Care ◽  
Radiation Exposure ◽  
Premature Infants ◽  
Neonatal Intensive Care ◽  
Diagnostic Procedures ◽  
Skin Dose ◽  
X Rays ◽  
X Ray ◽  
Radiation Induced ◽  
The Mean

Objective Portable X-rays remain one of the most frequently used diagnostic procedures in neonatal intensive care units (NICU). Premature infants are more sensitive to radiation-induced harmful effects. Dangers from diagnostic radiation can occur with stochastic effects. We aimed to determine the radiation exposure in premature infants and staff and determine the scattering during X-ray examinations in the NICU. Study Design In this prospective study, dosimeters were placed on premature infants who were ≤1,250 g at birth and ≤30 weeks of gestational age who stayed in the NICU for at least 4 weeks. The doses were measured at each X-ray examination during their stay. The measurements of the nurses and the doctors in the NICU were also performed with dosimeters over the 1-month period. Other dosimeters were placed in certain areas outside the incubator and the results were obtained after 1 month. Results The mean radiation exposure of the 10 premature infants, monitored with dosimeters, was 3.65 ± 2.44 mGy. The mean skin dose of the six staff was 0.087 ± 0.0998 mSV. The mean scattered dose was 67.9 ± 26.5 µGy. Conclusion Relatively high exposures were observed in 90% of the patients and two staff. The radiation exposure levels of premature infants and staff may need to be monitored continuously. Key Points

scholarly journals THE INDUCTION OF MITOTIC GENE CONVERSION BY X-IRRADIATION OF HAPLOID SACCHAROMYCES CEREVISIAE

Genetics ◽  
1973 ◽  
Vol 74 (2) ◽  
pp. 243-258
Author(s):  
D A Campbell
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Gene Conversion ◽  
Colony Formation ◽  
X Rays ◽  
Zygote Formation ◽  
X Ray ◽  
Sister Chromatids ◽  
X Irradiation ◽  
Radiation Induced ◽  
Mitotic Gene Conversion

ABSTRACT Mitotic recombination in Saccharomyces cerevisiae was examined by means of experiments in which one of the haploid parents was X-irradiated prior to zygote formation. By this method radiation-induced lesions are restricted to only one of the two non-sister chromatids that may be expected to undergo mitotic exchange in the diploid. The principal results of this work are: (1) X-irradiated haploid cells that are incapable of further vegetative growth (colony formation) are efficiently rescued into viable diploids by mating with unirradiated haploid cells. (2) X-rays delivered to only one of the two haploid parents are recombinogenic in the resultant diploid. The frequency of detected recombinational events increases as a probable linear function of the X-ray dose. (3) A majority of the induced recombinational events are nonreciprocal in nature (mitotic gene conversion). These results complement those obtained from X-irradiation of the vegetative diploid itself, where the induced genetic exchanges are principally reciprocal.

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