Ionizing radiation and hydrogen peroxide induced oxidative DNA base damage in two L5178Y cell lines

Seven oxidized DNA bases were quantified, by gas GC/MS-SIM, in chromatin from gamma-rays and H2O2 treated mouse lymphoma L5178Y (LY) cells, inversely cross-sensitive to these agents. In H2O2 treated cells (2 mM, 1 h, 37 degrees C) we found more damage in LY-R cells than in LY-S cells. On the contrary, in gamma-rays (400 Gy) treated cells we found more damaged DNA bases in LY-S cells. The yield of damaged bases in control cells was similar in both cell lines, with the exception of 8OHAde and FapyGua that were found at a much higher level in LY-S cells. The yields of damaged bases were related to cellular sensitivity to damaging agent; this observation points to a relationship between DNA base damage induction, antioxidant defense system in the intracellular milieu and cell sensitivity.     

Effects of simultaneous displacive and ionizing radiations and of electric field on radiation damage in ionic crystals

We summarize our recent progress on the formation process of radiation-induced defects, their stability, and cation- and anion-disordering in ionic crystals, such as magnesium aluminate spinel and alpha alumina, under simultaneous displacive and ionizing radiations or under electric field. In those crystals, suppression of dislocation loop formation is observed under simultaneous ionizing and displacive radiations. Cation and anion disordering are also detected through newly developed analytica electron microscopy. Furthermore, the electric field suppresses the formation of dislocation loops and enhances their growth in thinner specimens of ionic crystals. Those results are discussed in terms of the instability of defect clusters under electronic excitation and displacements of structure vacancies and of the interaction between charged defects and electric fields. This article is based on a presentation in the symposium “Terence E. Mitchell Symposium on the Magic of Materials: Structures and Properties” from the TMS Annual Meeting in San Diego, CA in March 2003.     

Sensitivity of selected bacterial species to UV radiation

The effect of exposure of bacterial suspensions to UV radiation by means of the dose-response curves was assessed. The D37 and D10 values were used for subsequent statistical analysis of the results. The aim of this article is to evaluate the sensitivity to UV radiation of several microorganisms of different habitats (Rhizobium meliloti, Rhodobacter sphaeroides, Escherichia coli, and Deinococcus radiodurans), two mutants with nonfunctional SOS DNA repair system (R. meliloti recA- and E. coli recA-), and a mutant in the synthesis of carotenoids (R. sphaeroides crtD). The results reveal that D. radiodurans was an extremely resistant bacterium, R. meliloti was more resistant than R. sphaeroides, and E. coli was the most sensitive bacterium tested. The high sensitivity of recA- mutants was also verify. Moreover, it seems that the possession of pigments had no important effect in the sensitivity of R. sphaeroides to UV radiation.     

Environmental damage of a cast nickel base superalloy

Exposure in air in the temperature range 900 to 1100 °C produces a major loss in stress rupture life and ductility of IN738. The sensitivity to this environmental damage increases with decreasing test temperature in the range 1000 to 700 °C. Oxygen is identified as the source of the damage for air exposure and indirect evidence supports grain boundary penetration of the gas to considerable depth. It is argued that oxygen segregation can lead to grain boundary immobilization and unstable intergranular fracture at intermediate temperatures. It is shown that compositional modifications, particularly boron and hafnium additions, may reduce the oxygen damage susceptibility, and that a cobalt base coating effectively eliminates the susceptibility. The relevance of these observations in understanding the effect of test environment on creep-rupture and fatigue crack propagation is considered.     

Synthesis and enzymatic processing of oligodeoxynucleotides containing tandem base damage

Several studies have shown that ionizing radiation generates a wide spectrum of lesions to DNA including base modifications, abasic sites, strand breaks, crosslinks and tandem base damage. One example of tandem base damage induced by @OH radical inX-irradiated DNA oligomers is N -(2-deoxy-beta-d- erythro -pentofuranosyl)-formylamine/8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo). In order to investigate the biological significance of such a tandem lesion, both 8-oxo-7,8-dihydroguanine and formylamine were introduced into synthetic oligonucleotides at vicinal positions using the solid phase phosphoramidite method. For this purpose, a new convenient method of synthesis of 8-oxodGuo was developed. The purity and integrity of the modified synthetic DNA fragments were assessed using different complementary techniques including HPLC, polyacrylamide gel electrophoresis, electrospray and MALDI-TOF mass spectrometry. The piperidine test applied to the double modified base-containing oligonucleotides revealed the high alkaline lability of formylamine in DNA. In addition, various enzymatic experiments aimed at determining biochemical features of such multiply damaged sites were carried out using the synthetic substrates. The pro-cessing of the vicinal lesions by nuclease P1, snake venom phosphodiesterase, calf spleen phospho-diesterase and repair enzymes including Escherichia coli endonuclease (endo) III and Fapy-glycosylase was studied and is reported.     

Comparison of oxidative base damage in mitochondrial and nuclear DNA

In 1994-1995, a child and five dogs from villages located between Jerusalem and Tel-Aviv, Israel were diagnosed with visceral leishmaniasis (VL). Based on these findings, the distribution of VL in domestic and wild canids in central Israel was examined. In the two villages where canine index cases were identified, a substantial proportion (11.5%, 14 of 122) of the dogs examined were seropositive. However, the rate of infection in five neighboring villages was only 1% (1 of 99). Parasites were cultured from 92% (12 of 13) of the seropositive dogs biopsied and the strains were characterized as Leishmania infantum by a clamped polymorphic-polymerase chain reaction, monoclonal antibodies, and/or excreted factor serology. The discovery of VL close to major urban centers is an important public health issue. The disease appears to have emerged recently in this area, and it is unclear whether the parasite was re-introduced or was continuously present at low levels in this region. The presence of seropositive wild canids, jackals (7.6%, 4 of 53) and red foxes (5%, 1 of 20), in central Israel, and the reappearance of the jackal population after near extinction suggests that wild canids may play a role in spreading this disease.     

Oceanic protection of prebiotic organic compounds from UV radiation

It is frequently stated that UV light would cause massive destruction of prebiotic organic compounds because of the absence of an ozone layer. The elevated UV flux of the early sun compounds this problem. This applies to organic compounds of both terrestrial and extraterrestrial origin. Attempts to deal with this problem generally involve atmospheric absorbers. We show here that prebiotic organic polymers as well as several inorganic compounds are sufficient to protect oceanic organic molecules from UV degradation. This aqueous protection is in addition to any atmospheric UV absorbers and should be a ubiquitous planetary phenomenon serving to increase the size of planetary habitable zones.     

Analytical electron microscopy studies of radiation damage

Analytical electron microscopy (AEM) has provided structural, crystallographic, and compositional characterization to aid in the understanding of radiation damage processes, especially in multiphase materials. The range of AEM techniques is based on the use of as many of the signals produced by the interaction of an electron beam with a specimen as possible. This paper briefly discusses the origins, capabilities, and current developments of AEM, including the spatial resolution of the various techniques. Several important applications of AEM in radiation damage studies, including radiation-induced segregation and phase instability in austenitic stainless steels, will be reviewed. From the comparison of phase equilibria under irradiation to that under thermal aging, principles for alloy development in non-nuclear applications will be discussed. This paper is based on a presentation made in the symposium “Irradiation-Enhanced Materials Science and Engineering” presented as part of the ASM INTERNATIONAL 75th Anniversary celebration at the 1988 World Materials Congress in Chicago, IL, September 25-29, 1988, under the auspices of the Nuclear Materials Committee of TMS-AIME and ASM-MSD.     

Evidence that the Rad1 and Rad10 proteins of Saccharomyces cerevisiae participate as a complex in nucleotide excision repair of UV radiation damage

A newly characterized rad1 missense mutation (rad1-20) in the yeast Saccharomyces cerevisiae maps to a region of the Rad1 polypeptide known to be required for Rad1-Rad10 complex formation. The UV sensitivity of the rad1-20 mutant can be partially and specifically corrected by overexpression of wild-type Rad10 protein. These results suggest that complex formation between the Rad1 and Rad10 proteins is required for nucleotide excision repair.     

The effect of long-term UV radiation exposure on the skin autonomous microflora and on body nonspecific resistance

Hairless mice of strain HRS were exposed to vertical UV-B-irradiation (280-320 nm) at daily doses of 1 or 2 kJ/m2 (biologically effective doses 200 and 400 J/m2) five days a week for 13 and 6 weeks. As the length of exposure increased, the abundance of automicroflora of the dorsal skin first decreased, then exceeded the control value, was normalized, and remained at the normal level until the end of the experiment. The rates of effect appearance and disappearance, just as its amplitude, increased with the daily doses. No changes were found in resistance to staphylococcal alpha-toxin after its post-irradiation intraperitoneal injection.     

Effect of strain rate on damage evolution in a cast Al-Si-Mg base alloy

An important aspect of damage evolution in cast Al-Si-Mg base alloys is fracture/cracking of Si particles. This microstructural damage is quantitatively characterized as a function of strain rate in the range 10⁻⁴ to 3.7 × 10⁺³, at an approximately constant uniaxial compressive strain level (20 to 25 pct). It is shown that the fraction of damaged silicon particles, their average size, and size distribution do not vary significantly with the strain rate, and at all strain rates studied, larger Si particles are more likely to crack than the smaller ones. However, the stress-strain curves are sensitive to the strain rate. These observations have implications for modeling of deformation and fracture of cast components under high strain rate crash conditions.     

Effects of altitude and latitude on ambient UVB radiation

PURPOSE: Spitting as an ictal automatism has been rarely reported. We aimed to establish its potential lateralizing and localizing significance. METHODS: Review of patients undergoing surgery for intractable epilepsy at two comprehensive epilepsy centers. RESULTS: Five patients were found who had spitting as a stereotyped automatism of their complex partial seizures. All had evidence of right temporal ictal onset and underwent resective surgery. Two had tumors; one, a cavernous angioma; one, hippocampal gliosis, and one, hippocampal sclerosis. We found no instances of ictal spitting in patients with left hemisphere onset. CONCLUSIONS: Spitting as an automatism in complex partial seizures, although uncommon, may be a localizing sign to the nondominant temporal lobe.     

Interaction between radiation and drug damage in mammalian cells. II. The effect of actinomycin-D on the repair of the sublethal radiation damage in plateau phase cells

The effect of actinomycin-D (AMD) on radiation damage repair was studied in plateau phase V79 Chinese hamster cells. Sublethal radiation damage repair, as demonstrated by survival fluctuations following two x-ray exposures separted by time, was observed in our plateau phase cells. Plateau phase cells exposed to 0.01-0.04 mug/ml AMD (a nontoxic regimen to 8 hours) between x-ray exposures were less able to repair sublethal damage. If plateau phase cells were plated at low dilutions into fresh medium (conditions for resuming exponential growth) immediately after the first x-ray dose, and exposed to 0.01--0.04 mug/ml AMD until the second dose, inhibition of sublethal damage repair and additional cell killing were observed particularly at 0.04 mug/ml AMD. It is suggested that radiation-drug damage interactions should be studied in plateau phase cells and in cells resuming exponential growth after plateau phase (possibly analogous to "recruitment"), as well as in exponential phase cultures.     

Effect of ATP on radiation damage to DNA caused by prolonged irradiation

The influence of bradykinin and kallikrein on the action of norepinephrine, epinephrine, isoprenaline, phentolamine, propranolol, aminophylline and theophylline on blood pressure was studied. The kinins potentiated the hypertensive action of norepinephrine and epinephrine, weakened the hypotensive action of isoprenaline, potentiated the hypotensive action of propranolol, and had no effect on the action of phentolamine, aminophylline and theophylline.     

Effects of DL-ethionine on mouse liver tRNA base composition

Treatment of mice with DL-ethionine and adenine causes a reduction of all methylated bases of liver tRNA. This effect is dose-dependent and specific for the methylated bases. Individual methylated components are affected to different extents, m22G being most sensitive to inhibition.