EPR study of NO2 and NO3 produced in urea nitrate by uv irradiation, x‐irradiation, and constituent tritium atom decay

1976 ◽  
Vol 64 (2) ◽  
pp. 546-551 ◽  
Author(s):  
David E. Wood ◽  
George P. Lozos
Keyword(s):  
Uv Irradiation ◽  
Urea Nitrate ◽  
Tritium Atom ◽  
X Irradiation ◽  
Atom Decay

EPR study of free radicals produced in pyrrole by x‐irradiation and tritium atom decay

1978 ◽  
Vol 68 (4) ◽  
pp. 1813-1816 ◽  
Author(s):  
Roger V. Lloyd ◽  
Silvio DiGregorio ◽  
David E. Wood
Keyword(s):  
Free Radicals ◽  
Tritium Atom ◽  
X Irradiation ◽  
Atom Decay

COLONY MUTANTS OF COMPATIBLE NOCARDIAE DISPLAYING VARIATIONS IN RECOMBINING CAPACITY

Genetics ◽  
1972 ◽  
Vol 70 (3) ◽  
pp. 341-351
Author(s):  
George H Brownell ◽  
Richard S Walsh
Keyword(s):  
Uv Irradiation ◽  
Mating Type ◽  
Genome Recombination ◽  
X Irradiation ◽  
Increased Sensitivity ◽  
Colonial Morphology ◽  
Rec Genes

ABSTRACT Colonial morphology mutants of Nocardia erythropolis were isolated following ultraviolet (UV) irradiation. The alleles rou-1/smo-1 were located by recombinant analysis and found to be linked to previously mapped characters. On the basis of recombinant class type patterns obtained from various selective characters it was postulated that the rou-1 allele may span a region of unique nucleotides in the Mat-Ce genome. Recombination frequencies of rou-1 and smo-2 bearing mutants of the Mat-Ce mating type were found to differ by over 1000 fold. Attempts to demonstrate that low recombination frequencies produced by the Smo mutants were due to Rec- genes were unsuccessful. No increased sensitivity to either UV or X irradiation was observed by the Smo mutants. Acriflavine treatment of either Rou or Smo colony mutants failed to accelerate reversion or to alter the recombining potentials of the mutants.

scholarly journals H-NS Regulates DNA Repair inShigella

1998 ◽  
Vol 180 (19) ◽  
pp. 5260-5262 ◽  
Author(s):  
Sunil Palchaudhuri ◽  
Brandon Tominna ◽  
Myron A. Leon
Keyword(s):  
Dna Repair ◽  
Uv Irradiation ◽  
Shigella Flexneri ◽  
Virulence Gene ◽  
High Rate ◽  
High Survival ◽  
Virulence Gene Expression ◽  
E Coli ◽  
X Irradiation ◽  
K 12

ABSTRACT We report a new role for H-NS in Shigella spp.: suppression of repair of DNA damage after UV irradiation. H-NS-mediated suppression of virulence gene expression is thermoregulated inShigella, being functional at 30°C and nonfunctional at 37 to 40°C. We find that H-NS-mediated suppression of DNA repair after UV irradiation is also thermoregulated. Thus, Shigella flexneri M90T, incubated at 37 or 40°C postirradiation, shows up to 30-fold higher survival than when incubated at 30°C postirradiation. The hns mutants BS189 and BS208, both of which lack functional H-NS, show a high rate of survival (no repression) whether incubated at 30 or 40°C postirradiation. Suppression of DNA repair by H-NS is not mediated through genes on the invasion plasmid of S. flexneri M90T, since BS176, cured of plasmid, behaves identically to the parental M90T. Thus, inShigella the nonfunctionality of H-NS permits enhanced DNA repair at temperatures encountered in the human host. However, pathogenic Escherichia coli strains (enteroinvasive and enterohemorrhagic E. coli) show low survival whether incubated at 30 or 40°C postirradiation. E. coli K-12 shows markedly different behavior; high survival postirradiation at both 30 and 40°C. These K-12 strains were originally selected fromE. coli organisms subjected to both UV and X irradiation. Therefore, our data suggest that repair processes, extensively described for laboratory strains of E. coli, require experimental verification in pathogenic strains which were not adapted to irradiation.

scholarly journals RESTORATION INDUCED BY CATALASE IN IRRADIATED MICROORGANISMS

1952 ◽  
Vol 35 (3) ◽  
pp. 455-470 ◽  
Author(s):  
Raymond Latarjet ◽  
Luis Renato Caldas ◽  
Keyword(s):  
Uv Irradiation ◽  
General Problem ◽  
None None ◽  
Chemical Nature ◽  
Coli Strain ◽  
E Coli ◽  
Physiological Conditions ◽  
X Irradiation ◽  
Phage Production ◽  
K 12

1. E. coli, strain K-12, and B. megatherium 899, irradiated in strict but still undefined physiological conditions with certain heavy doses of ultraviolet light, are efficiently restored by catalase, which acts on or fixes itself upon the bacteria in a few minutes. This restoration (C. R.), different from photorestoration, is aided by a little visible light. 2. At 37° the restorability lasts for about 2 hours after UV irradiation; the restored cells begin to divide at the same time as the normal survivors. 3. C. R. is not produced after x-irradiation. 4. B. megatherium Mox and E. coli, strain B/r show little C. R.; E. coli strain B shows none. None of these three strains is lysogenic, whereas the two preceding catalase-restorable strains are. 5. Phage production in the system "K-12 infected with T2 phage" is restored by catalase after UV irradiation, whereas phage production in the system "infected B" is not. 6. With K-12, catalase does not prevent the growth of phage and the lysis induced by UV irradiation (Lwoff's phenomenon). 7. Hypotheses are discussed concerning: (a) the chemical nature of this action of catalase; (b) a possible relation between C. R. and lysogenicity of the sensitive bacteria; (c) the consequences of such chemical restorations on the general problem of cell radiosensitivity.

scholarly journals Replication-dependent sister chromatid recombination in rad1 mutants of Saccharomyces cerevisiae.

Genetics ◽  
1993 ◽  
Vol 133 (3) ◽  
pp. 469-487 ◽  
Author(s):  
L C Kadyk ◽  
L H Hartwell
Keyword(s):  
Dna Replication ◽  
Gene Conversion ◽  
Uv Irradiation ◽  
Sister Chromatid ◽  
Mammalian Cells ◽  
Excision Repair ◽  
Yeast Cells ◽  
Sister Chromatids ◽  
X Irradiation ◽  
Sister Chromatid Recombination

Abstract Homolog recombination and unequal sister chromatid recombination were monitored in rad1-1/rad1-1 diploid yeast cells deficient for excision repair, and in control cells, RAD1/rad1-1, after exposure to UV irradiation. In a rad1-1/rad1-1 diploid, UV irradiation stimulated much more sister chromatid recombination relative to homolog recombination when cells were irradiated in the G1 or the G2 phases of the cell cycle than was observed in RAD1/rad1-1 cells. Since sister chromatids are not present during G1, this result suggested that unexcised lesions can stimulate sister chromatid recombination events during or subsequent to DNA replication. The results of mating rescue experiments suggest that unexcised UV dimers do not stimulate sister chromatid recombination during the G2 phase, but only when they are present during DNA replication. We propose that there are two types of sister chromatid recombination in yeast. In the first type, unexcised UV dimers and other bulky lesions induce sister chromatid recombination during DNA replication as a mechanism to bypass lesions obstructing the passage of DNA polymerase, and this type is analogous to the type of sister chromatid exchange commonly observed cytologically in mammalian cells. In the second type, strand scissions created by X-irradiation or the excision of damaged bases create recombinogenic sites that result in sister chromatid recombination directly in G2. Further support for the existence of two types of sister chromatid recombination is the fact that events induced in rad1-1/rad1-1 were due almost entirely to gene conversion, whereas those in RAD1/rad1-1 cells were due to a mixture of gene conversion and reciprocal recombination.

Electron Microscopic Examination of a Transplantable Rat Mammary Carcinoma

1968 ◽  
Vol 26 ◽  
pp. 20-21
Author(s):  
S. Shirahama ◽  
G. C. Engle ◽  
R. M. Dutcher
Keyword(s):  
Electron Microscope ◽  
Osmium Tetroxide ◽  
Electron Microscopic Examination ◽  
Undifferentiated Carcinoma ◽  
Uranyl Acetate ◽  
Sprague Dawley ◽  
Electron Microscopic ◽  
North West ◽  
X Irradiation ◽  
Tissue Specimens

A transplantable carcinoma was established in North West Sprague Dawley (NWSD) rats by use of X-irradiation by Engle and Spencer. The tumor was passaged through 63 generations over a period of 32 months. The original tumor, an adenocarcinoma, changed into an undifferentiated carcinoma following the 19th transplant. The tumor grew well in NWSD rats of either sex at various ages. It was invariably fatal, causing death of the host within 15 to 35 days following transplantation.Tumor, thymus, spleen, and plasma from 7 rats receiving transplants of tumor at 3 to 9 weeks of age were examined with an electron microscope at intervals of 8, 15, 22 and 30 days after transplantation. Four normal control rats of the same age were also examined. The tissues were fixed in glutaraldehyde, postfixed in osmium tetroxide and embedded in Epon. The plasma was separated from heparanized blood and processed as previously described for the tissue specimens. Sections were stained with uranyl acetate followed by lead citrate and examined with an RCA EMU-3G electron microscope.

The Response of Testis Cells to Low Dose X-Irradiation

1981 ◽  
Vol 39 ◽  
pp. 542-543
Author(s):  
D. E. Philpott ◽  
W. Sapp ◽  
C. Williams ◽  
Joann Stevenson ◽  
S. Black
Keyword(s):  
Electron Microscopy ◽  
Stem Cell ◽  
Light Microscopy ◽  
Dose Level ◽  
Cross Sections ◽  
Low Dose ◽  
Light And Electron Microscopy ◽  
Cellular Responses ◽  
Post Irradiation ◽  
X Irradiation

The response of spermatogonial cells to X-irradiation is well documented. It has been shown that there is a radiation resistent stem cell (As) which, after irradiation, replenishes the seminiferous epithelium. Most investigations in this area have dealt with radiation dosages of 100R or more. This study was undertaken to observe cellular responses at doses less than 100R of X-irradiation utilizing a system in which the tissue can be used for light and electron microscopy.Brown B6D2F1 mice aged 16 weeks were exposed to X-irradiation (225KeV; 15mA; filter 0.35 Cu; 50-60 R/min). Four mice were irradiated at each dose level between 1 and 100 rads. Testes were removed 3 days post-irradiation, fixed, and embedded. Sections were cut at 2 microns for light microscopy. After staining, surviving spermatogonia were identified and counted in tubule cross sections. The surviving fraction of spermatogonia compared to control, S/S0, was plotted against dose to give the curve shown in Fig. 1.

Eds Of Radioactive Particles By Self-Induced Fluorescence

1990 ◽  
Vol 48 (2) ◽  
pp. 238-239
Author(s):  
Gregory L. Finch ◽  
Richard G. Cuddihy
Keyword(s):  
Electron Beam Irradiation ◽  
Nuclear Reactor ◽  
X Rays ◽  
Reactor Accident ◽  
Internal Radiation ◽  
X Ray ◽  
External Sources ◽  
X Irradiation ◽  
Available Information ◽  
Individual Particles

The elemental composition of individual particles is commonly measured by using energydispersive spectroscopic microanalysis (EDS) of samples excited with electron beam irradiation. Similarly, several investigators have characterized particles by using external monochromatic X-irradiation rather than electrons. However, there is little available information describing measurements of particulate characteristic X rays produced not from external sources of radiation, but rather from internal radiation contained within the particle itself. Here, we describe the low-energy (< 20 KeV) characteristic X-ray spectra produced by internal radiation self-excitation of two general types of particulate samples; individual radioactive particles produced during the Chernobyl nuclear reactor accident and radioactive fused aluminosilicate particles (FAP). In addition, we compare these spectra with those generated by conventional EDS.Approximately thirty radioactive particle samples from the Chernobyl accident were on a sample of wood that was near the reactor when the accident occurred. Individual particles still on the wood were microdissected from the bulk matrix after bulk autoradiography.

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