scholarly journals GENETIC ANALYSIS OF GAMMA-RAY MUTAGENESIS IN YEAST. I. REVERSION IN RADIATION-SENSITIVE STRAINS

Genetics ◽  
1979 ◽  
Vol 93 (2) ◽  
pp. 361-373
Author(s):  
Richard H McKee ◽  
Christopher W Lawrence
Keyword(s):  
Ionizing Radiation ◽  
Genetic Analysis ◽  
Gamma Ray ◽  
Wild Type ◽  
Uv Mutagenesis ◽  
Major Pathway ◽  
Gene Functions ◽  
Γ Rays ◽  
Γ Ray ◽  
Type Strains

ABSTRACT The frequency of revertants induced by 6OCo γ rays of the ochre allele, cyc1-9, has been measured in radiation-sensitive strains carrying one of 19 nonallelic mutations and in wild-type strains. The results indicate that ionizing radiation mutagenesis depends on the activity of the RAD6 group of genes and that the gene functions employed are very similar, but probably not identical, to those that mediate UV mutagenesis. Repair activities dependent on the functions of the RAD50 through RAD57 loci, the major pathway for the repair of damage caused by ionizing radiation, do not appear to play any part in mutagenesis. A comparison between the γ-ray data and those obtained previously with UV (LAWRENCE and CHRISTENSEN 1976) and chemical mutagens (PRAKASH 1976) suggests that the RAD6 "mutagenic pathway" is in fact composed of a set of processes, some of which are concerned with error-prone, and some with error-free, recovery activities.

scholarly journals GENETIC ANALYSIS OF GAMMA-RAY MUTAGENESIS IN YEAST. II. ALLELE-SPECIFIC CONTROL OF MUTAGENESIS

Genetics ◽  
1979 ◽  
Vol 93 (2) ◽  
pp. 375-381 ◽  
Author(s):  
Richard H McKee ◽  
Christopher W Lawrence
Keyword(s):  
Genetic Analysis ◽  
Genetic Control ◽  
Gamma Ray ◽  
Uv Mutagenesis ◽  
Gene Functions ◽  
Allele Specific ◽  
Γ Rays ◽  
Specific Control

ABSTRACT We find that partially different sets of gene functions are required for the production of different kinds of mutations induced by 6OCo γ rays in Saccharomyces cereuisiae. This observation is very similar to others made previously with respect to UV mutagenesis (LAWRENCE and CHRISTENSEN 1978a,b, 1979) and confirms the conclusion that such distinctive patterns of genetic control reflect properties of the test alleles and their genetic locations, rather than the kinds of lesions required to revert them. The data also support the model of mutagenic repair outlined in the first paper of this series (MCKEE and LAWRENCE 1979), in which partially different sets of gene functions are required for the production of different kinds of mutations, the formation of mutations at different genetic sites and the induction of mutations by different mutagens.

scholarly journals Molecular Clouds Observed by the EGRET Gamma-Ray Telescope

1997 ◽  
Vol 170 ◽  
pp. 22-24 ◽  
Author(s):  
Seth. W. Digel ◽  
Stanley D. Hunter ◽  
Reshmi Mukherjee ◽  
Eugéne J. de Geus ◽  
Isabelle A. Grenier ◽  
...  
Keyword(s):  
Molecular Mass ◽  
Molecular Clouds ◽  
Gamma Ray ◽  
Angular Resolution ◽  
Cosmic Ray ◽  
High Energy ◽  
Background Rejection ◽  
Γ Rays ◽  
Γ Ray ◽  
Production Mechanisms

EGRET, the high-energy γ-ray telescope on the Compton Gamma-Ray Observatory, has the sensitivity, angular resolution, and background rejection necessary to study diffuse γ-ray emission from the interstellar medium (ISM). High-energy γ rays produced in cosmic-ray (CR) interactions in the ISM can be used to determine the CR density and calibrate the CO line as a tracer of molecular mass. Dominant production mechanisms for γ rays of energies ∼30 MeV–30 GeV are the decay of pions produced in collisions of CR protons with ambient matter and Bremsstrahlung scattering of CR electrons.

scholarly journals Gamma-Ray Bursts and Binary Neutron Star Mergers

1996 ◽  
Vol 165 ◽  
pp. 489-502
Author(s):  
Tsvi Piran
Keyword(s):  
Neutron Star ◽  
Gravitational Radiation ◽  
Gamma Ray ◽  
Indirect Evidence ◽  
Gamma Ray Bursts ◽  
Binary Neutron Star ◽  
Merger Event ◽  
Γ Rays ◽  
Γ Ray ◽  
The One

Neutron star binaries, such as the one observed in the famous binary pulsar PSR 1913+16, end their life in a catastrophic merger event (denoted here NS2M). The merger releases ∼5 1053 ergs, mostly as neutrinos and gravitational radiation. A small fraction of this energy suffices to power γ-ray bursts (GRBs) at cosmological distances. Cosmological GRBs must pass, however, an optically thick fireball phase and the observed γ rays emerge only at the end of this phase. Hence, it is difficult to determine the nature of the source from present observations (the agreement between the rates of GRBs and NS2Ms providing only indirect evidence for this model). In the future a coinciding detection of a GRB and a gravitational-radiation signal could confirm this model.

scholarly journals A Possible Discovery of a Flaring 1012 eV Gamma-Ray Source near the Red Dwarf EV Lac

1995 ◽  
Vol 151 ◽  
pp. 78-79
Author(s):  
I.Yu. Alekseev ◽  
N.N. Chalenko ◽  
V.P. Fomin ◽  
R.E. Gershberg ◽  
O.R. Kalekin ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Electronic Device ◽  
Angular Size ◽  
High Energy ◽  
Optical Systems ◽  
Relativistic Electrons ◽  
Large Area ◽  
Γ Rays ◽  
Γ Ray ◽  
Ev Lac

During the 1994 coordinated observations of the red dwarf flare star EV Lac, the star was monitored in the very high energy (VHE) γ-ray range around 1012 eV with the Crimean ground-based γ-ray telescope GT-48. This telescope consists of two identical optical systems (Vladimirsky et al. 1994) which were directed in parallel on EV Lac.The detection principle of the VHE γ-rays is based on the Čerenkov radiation emitted by relativistic electrons and positrons. The latter are generated in the interaction of the γ-rays with nuclei in the Earth’s atmosphere that leads to an appearance of a shower of charged particles and γ-quanta. The duration of the Cherenkov radiation flash is very short, just about a few nanoseconds. The angular size of the shower is ∼ 1°. To detect such flashes we use an optical system with large area mirrors and a set of 37 photomultipliers (PMs) in the focal plane. Using the information from these PMs which are spaced hexagonally and correspond to a field of view of 2°.6 on the sky, we can obtain the image of an optical flash. The electronic device permits us to detect nanosecond flashes (40 ns exposure time and 12 μs readout dead-time).

scholarly journals Radiocarbon Production by the Gamma-Ray Component of Supernova Explosions

Radiocarbon ◽  
1995 ◽  
Vol 37 (2) ◽  
pp. 599-604 ◽  
Author(s):  
Paul E. Damon ◽  
Dai Kaimei ◽  
Grant E. Kocharov ◽  
Irina B. Mikheeva ◽  
Alexei N. Peristykh
Keyword(s):  
Cross Section ◽  
Tree Rings ◽  
Confidence Level ◽  
Gamma Ray ◽  
Visual Observation ◽  
Total Production ◽  
Average Increase ◽  
Supernova Explosions ◽  
Γ Rays ◽  
Γ Ray

We selected SN1006, the brightest and closest to Earth of all supernovas historically observed, for a study of 14C production by e−,e+-bremsstrahlung cascades initiated by hard γ rays (>10 MeV) from that event. During the cascade, bremsstrahlung energies eventually fall within a giant (n,γ), (n,2γ) cross-section, peaking at 23 MeV and approaching effectively zero below 10 MeV and above 40 MeV. The neutrons are absorbed primarily in the reaction 14N(n,p)14C. Cellulose from single-year tree rings from ad 1003 to ad 1020 was measured to determine ∆14C. Three years after the first visual observation of SN1006, ∆14C rose and remained above pre-ad 1009 values until ad 1018. Comparison of the 7 years before ad 1009 with the 9 years following show an average increase of 6.1 ± 1.6 (s.d.)‰ (significant at the 99.6% confidence level). Such a pulse of 14C requires a total production of neutrons of 17.1 × 107n cm−2e, implying an input of 11.3 × 104 ergs cm−2e γ-ray energy. This requires the total supernova γ-ray energy (>10 MeV) to have been 1 × 1050 ergs.

Study of Template Measurement of Plutonium Pit Based on Gamma-Ray Detection

2010 ◽  
Author(s):  
Changfan Zhang ◽  
Jian Gong ◽  
Junrui Teng ◽  
Suping Liu
Keyword(s):  
Spontaneous Fission ◽  
Counting Rate ◽  
Gamma Ray ◽  
Unique Property ◽  
Nuclear Disarmament ◽  
Neutron Counting ◽  
Neutron Counting Rate ◽  
Γ Rays ◽  
Γ Ray ◽  
Nuclear Warhead

Template measurement is an important method in deep nuclear disarmament. The gamma-ray spectrum of Plutonium pit shows unique property due to age, abundance, amounts and thickness of the Plutonium pit; that is, same designed pits yield similar gamma-ray spectra while different design give distinct spectra. Useful information is extracted from gamma-ray spectrum generated by the reliable Plutonium pit radiation as ‘template’. Comparison of the data from inspected objects with the template can give conclusion whether they are of the same type. This paper studies how to choose template data from gamma-ray spectrum and discusses the limits of the gamma-ray measurement. Because of the strong self-absorption of Plutonium, some characteristics of Plutonium pit can’t be identified only by gamma spectrum. MCNP simulation was employed to prove that in some cases, template depending on gamma-ray spectrum from the reliable Plutonium pit alone can’t effectively distinguish the spurious objects. And a further approach indicates that enhancing neutron counting rate of spontaneous fission of Plutonium can improve the problem. Neutron counting rate can be indirectly acquired by spontaneous fissile neutrons bombarding a 10B target. 478 keV γ rays are concomitant with the nuclear reaction 10B(n,α)7Li* from 7Li* nuclei’s deexcitation. Neutron information is gathered by detecting 478 keV γ photons. Using HPGe γ detector can both detect γ-ray spectrum and acquire neutron counting rate. This method efficiently increases confidence of template measurement and also ensures the dismantling process without revealing sensitive nuclear warhead design information.

Levels in 45Sc from Radiative Proton Capture in 44Ca

1974 ◽  
Vol 52 (2) ◽  
pp. 131-139 ◽  
Author(s):  
R. L. Schulte ◽  
J. D. King ◽  
H. W. Taylor
Keyword(s):  
Decay Scheme ◽  
Bound States ◽  
Gamma Ray ◽  
Angular Distributions ◽  
Distribution Data ◽  
Excitation Energies ◽  
Proton Capture ◽  
Resonant States ◽  
Γ Rays ◽  
Γ Ray

A total of 22 resonances has been observed in the 44Ca(p,γ)45Sc reaction within the incident proton energy range of 600 to 930 keV. Gamma-ray singles spectra and γ-ray angular distribution data were accumulated for resonances at Ep = 856 and 906 keV. Both of these resonant states have been found to have spin 3/2. The measured angular distributions of primary γ rays from the resonant states have given spin information on the intermediate bound states of 45Sc with excitation energies above 2 MeV. A γ-ray decay scheme has been derived from the γ-ray spectra. The data indicate new levels at 2151.0, 3525.2, 3548.5, 3584.0, and 3714.3 keV.

Radioprotection of 1,2-dimethylhydrazine-initiated colon cancer in rats using low-dose γ rays by modulating multidrug resistance-1, cytokeratin 20, and β-catenin expression

2015 ◽  
Vol 35 (3) ◽  
pp. 282-292 ◽  
Author(s):  
HM Nabil ◽  
BN Hassan ◽  
AA Tohamy ◽  
HF Waaer ◽  
AE Abdel Moneim
Keyword(s):  
Colon Cancer ◽  
Multidrug Resistance ◽  
Ionizing Radiation ◽  
Tumor Cells ◽  
Low Dose ◽  
Colorectal Tumor ◽  
Cytokeratin 20 ◽  
Γ Irradiation ◽  
Γ Rays ◽  
Γ Ray

Ionizing radiation is a widely used therapy for solid tumors. However, high-dose ionizing radiation causes apoptosis, transforms normal cells into tumor cells, and impairs immune functions, leading to the defects in the removal of damaged or tumor cells. In contrast, low-dose radiation has been reported to exert various beneficial effects in cells. This experimental study investigated the effect of γ rays at low dose on the development of colorectal tumor in a 1,2-dimethylhydrazine (DMH)-induced colon cancer. Colorectal tumor model was induced in Wistar rats by subcutaneous injection of DMH (20 mg/kg) once a week for 15 weeks. Starting from zero day of DMH injection, a single low dose of whole-body γ irradiation of 0.5 Gy/week was applied to the rats. A significant reduction in lipid peroxidation, nitric oxide, and elevation in the glutathione content and antioxidant enzyme activity (superoxide dismutase and catalase) were observed after γ irradiation comparing with DMH group. Moreover, γ ray reduced the expressions of multidrug resistance 1 (MDR1), β-catenin, and cytokeratin 20 (CK20) those increased in DMH-treated rats. However, survivin did not change with γ ray treatment. A histopathological examination of the DMH-injected rats revealed ulcerative colitis, dysplasia, anaplasia, and hyperchromasia. An improvement in the histopathological picture was seen in the colon of rats exposed to γ rays. In conclusion, the present results showed that low-dose γ ray significantly inhibited DMH-induced colon carcinogenesis in rats by modulating CK20, MDR1, and β-catenin expression but not survivin expression.

scholarly journals Genetic Analysis of the Sinorhizobium meliloti BacA Protein: Differential Effects of Mutations on Phenotypes

2001 ◽  
Vol 183 (21) ◽  
pp. 6444-6453 ◽  
Author(s):  
Kristin LeVier ◽  
Graham C. Walker
Keyword(s):  
Amino Acids ◽  
Genetic Analysis ◽  
Protein Function ◽  
Sinorhizobium Meliloti ◽  
Null Allele ◽  
Biological Function ◽  
Wild Type ◽  
Phenotypic Characteristics ◽  
Multiple Phenotypes ◽  
Type Strains

ABSTRACT Sinorhizobium meliloti strains lacking BacA function are impaired in symbiosis with alfalfa host plants and display altered sensitivities to a number of compounds relative to wild-type strains. With the goal of finding clues to the currently unknown biological function(s) of BacA, we carried out a genetic analysis to determine which amino acids are critical for protein function and to attempt to ascertain whether the multiple phenotypes that result from abacA-null allele were the result of a common cause or whether BacA has multiple functions. We have created a set of 20 site-directed mutants in which selected individual amino acids inbacA were replaced with glycine residues. The resulting mutants were characterized to determine how the various amino acid changes affected a number of phenotypes associated with loss of BacA function. Mutants H165G, W182G, D198G, and R284G had null phenotypes for all functions assayed, while mutants W57G, S83G, S231G, and K350G were indistinguishable from wild-type strains. The remaining 12 site-directed mutants demonstrate mixed phenotypic characteristics and fall into a number of distinctly different groups. These observations may be consistent with a role for BacA in multiple, nonoverlapping functions.

Comparison of Lu3Al5O12:Ce and LaBr3:Ce Scintillators in Gamma-Ray Spectrometry

2011 ◽  
Vol 418-420 ◽  
pp. 922-927
Author(s):  
Weerapong Chewpraditkul ◽  
Chalerm Wanarak ◽  
Marek Moszynski ◽  
Lukasz Swiderski
Keyword(s):  
Energy Resolution ◽  
Gamma Ray ◽  
Light Yield ◽  
Gamma Ray Spectrometry ◽  
Timing Resolution ◽  
Intrinsic Resolution ◽  
Γ Rays ◽  
Γ Ray ◽  
Coincidence Timing ◽  
Better Than

The performances of Ce-doped Lu3Al5O12(LuAG:Ce) and LaBr3(LaBr3:Ce) scintillators were compared for γ-ray detection using photomultiplier tube ( XP5500B PMT) readout. For 662 keV γ-rays (137Cs source), an energy resolution of 3.5% obtained for LaBr3:Ce is much better than that of 6.7% obtained for LuAG:Ce, while the estimated photofraction of 28.0% for LuAG:Ce is higher than that of 16.2% for LaBr3:Ce. The light yield non-proportionality and energy resolution versus γ-ray energy were measured and the intrinsic resolution of the crystals was calculated. The coincidence timing resolution, obtained in this work for 511 keV annihilation quanta, was 583 ps and 204 ps, respectively, for LuAG:Ce –BaF2and LaBr3:Ce – BaF2detectors.

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