Trp53 activity is repressed in radio-adapted cultured murine limb bud cells.

Understanding the effects of of ionizing radiation (IR) at low dose in fetal models is of great importance, because the fetus is considered to be at the most radiosensitive stage of the development and prenatal radiation might influence subsequent development. We previously demonstrated the existence of an adaptive response (AR) in murine fetuses after pre-exposure to low doses of X-rays. Trp53-dependent apoptosis was suggested to be responsible for the teratogenic effects of IR; decreased apoptosis was observed in adapted animals.

Chromosome aberrations in peripheral blood lymphocytes of individuals living in high background radiation areas of Ramsar, Iran.

In order to investigate the biological effects of exposure to low-dose radiation and to assess the dose-effect relationship in residents of high background radiation areas (HBRAs) of Ramsar, cytogenetic investigation of unstable-type aberrations was performed in 15 healthy elderly women in a HBRA of Ramsar, Talesh mahalle, and in 10 elderly women living in a nearby control area with normal background radiation. In total, 77,714 cells were analyzed; 48,819 cells in HBRA residents and 28,895 cells in controls. On average, 3,108 cells per subject were analyzed (range 1,475-5,007 cells).

The dose response of chromosome aberrations in human lymphocytes induced in vitro by very low-dose γ rays.

This paper considers the dose-effect relationship for unstable chromosome aberration yields in human lymphocytes in very low-dose range. Data are presented for (60)Co γ-ray doses of 0, 10, 20, 40 and 1000 mGy. More than 5,000 metaphases were scored for each data point at the very low doses, and each cell was double-checked using a semi-automated metaphase finding/relocation system.

Low-cost metaphase finder system.

In counting chromosome aberrations at low-dose radiation exposure in biological dosimetry, an automation technique has been required to process a large number of sample preparations. The metaphase finder is an automated optical microscope system, which automatically scans and finds metaphase cells on the slide glass in low magnification and relocates metaphase cells to the center of the field of view of the microscope to observe chromosomes in high magnification. The authors have constructed a cost-effective metaphase finder system by assembling commercially-available components, such as microscopes, motorized sample stages, personal computers and general-purpose image analysis software, instead of purchasing one dedicated system.

Human exposure to high natural background radiation: what can it teach us about radiation risks?

Natural radiation is the major source of human exposure to ionising radiation, and its largest contributing component to effective dose arises from inhalation of (222)Rn and its radioactive progeny. However, despite extensive knowledge of radiation risks gained through epidemiologic investigations and mechanistic considerations, the health effects of chronic low-level radiation exposure are still poorly understood. The present paper reviews the possible contribution of studies of populations living in high natural background radiation (HNBR) areas (Guarapari, Brazil; Kerala, India; Ramsar, Iran; Yangjiang, China), including radon-prone areas, to low dose risk estimation.

Adaptive response in embryogenesis: vi. Comparative microarray analysis of gene expressions in mouse fetuses.

Purpose: Exposure of sublethal doses of ionizing radiation can induce protective mechanisms against a subsequent higher dose irradiation. This phenomenon, called radiation-induced adaptive response (AR), has been described in a wide range of biological models. We previously demonstrated the existence of AR in mice during late organogenesis.

Dose limits below which the effect of radiation on health becomes undetectable due to background variation.

To clarify the low-dose limit at which the effect of radiation on health becomes undetectable is important in the regulation of radiation. As one of a series of cytogenetical studies on the effect of radiation on health, we present low-dose limits determined by analyzing the background frequencies of translocations in the lymphocytes of people living in normal circumstances. The frequencies of translocations in the lymphocytes were analyzed in 20 non-smokers (61.

International study of factors affecting human chromosome translocations.

Chromosome translocations in peripheral blood lymphocytes of normal, healthy humans increase with age, but the effects of gender, race, and cigarette smoking on background translocation yields have not been examined systematically. Further, the shape of the relationship between age and translocation frequency (TF) has not been definitively determined. We collected existing data from 16 laboratories in North America, Europe, and Asia on TFs measured in peripheral blood lymphocytes by fluorescence in situ hybridization whole chromosome painting among 1933 individuals.

Combined genotoxic effects of radiation and a tobacco-specific nitrosamine in the lung of gpt delta transgenic mice.

It is important to evaluate the health effects of low-dose-rate or low-dose radiation in combination with chemicals as humans are exposed to a variety of chemical agents. Here, we examined combined genotoxic effects of low-dose-rate radiation and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), the most carcinogenic tobacco-specific nitrosamine, in the lung of gpt delta transgenic mice. In this mouse model, base substitutions and deletions can be separately analyzed by gpt and Spi- selections, respectively.

Investigation of new cytogenetic biomarkers specific to high-LET radiation using in vivo and in vitro exposed human lymphocytes.

Purpose: To find detectable cytogenetic biomarkers that can offer information about the radiation quality of in vivo exposure retrospectively.

Materials And Methods: Chromosome-type aberrations of peripheral lymphocytes of uterine cancer patients that received internal gamma- and external X-ray therapy or carbon beam therapy and of victims severely exposed to neutrons and gamma-rays in a criticality accident that occurred in Tokai-mura, Japan were analysed. Data obtained from in vitro irradiation experiments using 60Co gamma-rays and 10 MeV neutrons were compared with the in vivo exposure data.

Visualization of the interaction between archaeal DNA polymerase and uracil-containing DNA by atomic force microscopy.

Deamination of cytosine to uracil is a hydrolytic reaction that is greatly accelerated at high temperatures. The resulting uracil pairs with adenine during DNA replication, thereby inducing G:C to A:T transitions in the progeny. Interestingly, B-family DNA polymerases from hyperthermophilic Archaea recognize the presence of uracil in DNA and stall DNA synthesis.

Regulation of radiation-induced protein kinase Cdelta activation in radiation-induced apoptosis differs between radiosensitive and radioresistant mouse thymic lymphoma cell lines.

Protein kinase Cdelta (PKCdelta) has an important role in radiation-induced apoptosis. The expression and function of PKCdelta in radiation-induced apoptosis were assessed in a radiation-sensitive mouse thymic lymphoma cell line, 3SBH5, and its radioresistant variant, XR223. Rottlerin, a PKCdelta-specific inhibitor, completely abolished radiation-induced apoptosis in 3SBH5.

Analysis of interaction between DNA and Deinococcus radiodurans PprA protein by atomic force microscopy.

A DNA repair-promoting protein, PprA, was isolated from a radiation resistant bacterium, Deinococcus radiodurans [I. Narumi, K. Sato, S.

Effects of prenatal irradiation with an accelerated heavy-ion beam on postnatal development in rats: I. Neurophysiological alterations.

Effects on postnatal neurophysiological development in offspring were studied after exposure of pregnant Wistar rats to accelerated carbon-ion beams with an LET of about 13 keV/ mum at doses ranging from 0.1 Gy to 2.5 Gy on the 15th day of gestation.

An improved culture system of mouse peripheral blood lymphocytes for analysis of radiation-induced chromosome aberrations.

There is an incentive to develop a culture system of mouse peripheral blood lymphocytes (PBLs) to serve as models for studying genotoxic effects in humans exposed to mutagens, including ionizing radiation. However, many past approaches have been laborious, complex and only partly reproducible. In the present study, we established an improved culture system of mouse PBLs by removing blood and/or plasma, which was found to inhibit in vitro mitotic stimulation or proceeding cell cycles of lymphocytes.

Effect of smoking on chromosomes compared with that of radiation in the residents of a high-background radiation area in China.

Cytogenetic investigation of stable-type aberrations (translocations) was carried out with our improved methods on 28 elderly individuals in a high-background radiation area (HBRA) in China, and on 24 elderly individuals in a control area (CA). The level of radiation in HBRA is 3 to 5 times higher than in CA. The mean frequencies of translocations per 1,000 cells in HBRA and CA were 12.

Characterization of ionizing radiation-induced ring chromosomes by atomic force microscopy.

We applied atomic force microscopy (AFM) to the structural analysis of radiation-induced ring chromosomes. Constrictions observed on the metaphase ring chromosome were found to correspond to the centromere regions of the ring chromosome in comparison with the AFM image of the centromere of rod chromosomes and with the fluorescence in situ hybridization (FISH) technique. Section analysis by AFM revealed that some ring-like chromosome fragments and ring-like chromatid fragments were thicker than standard chromosomes or chromatids, suggesting that they were ring chromosomes viewed edge on.

Chemically induced premature chromosome condensation in human fibroblast cell lines: fundamental study for applications to the biodosimetry of local exposure.

The premature chromosome condensation (PCC) of human peripheral lymphocytes treated with inhibitors of protein phosphatase has been demonstrated to be an excellent tool for the estimation of high-dose whole-body exposure. To develop a new biodosimetry for local exposure, the cytogenetical reaction of human fibroblast lines to PCC inducers was examined and compared with that of lymphocytes. The efficiency of the induction by calyculin A was greater than that by okadaic acid in both cell types.

Sister chromatid exchanges in ring chromosomes following X-irradiation of human lymphocytes.

Purpose: To examine whether X-rays induce sister chromatid exchanges (SCE).

Materials And Methods: Peripheral lymphocytes irradiated in vitro or in vivo were cultured and treated with okadaic acid to generate premature chromosome condensation (PCC). When identical spreads were analysed using conventional Giemsa staining and pan-centromeric fluorescence in situ hybridization painting, ring chromosomes were observed.

Effect of high-level natural radiation on chromosomes of residents in southern China.

To study the effect of low-dose (rate) radiation on human health, we analyzed chromosomes of peripheral lymphocytes of residents in a high background radiation area (HBRA) and compared the results with those obtained from residents in a control area (CA) in Guangdong Province, China. Unstable types of chromosome aberrations (dicentrics and rings) were studied in 22 members of eight families in HBRA and 17 members of five families in CA. Each family consists of three generations.

Cytogenetic damage in lymphocytes for the purpose of dose reconstruction: a review of three recent radiation accidents.

The analysis of chromosomal aberrations in peripheral blood of radiation accident victims is an established method of biological dosimetry. The dose estimate on the basis of an in vitro calibration curve is straightforward when the radiation exposure is homogeneous and the analysis not delayed. In recent years three radiation accidents occurred, where the irradiation or sampling conditions precluded a simple estimation of the dose.

Involvement of protein kinase C-related anti-apoptosis signaling in radiation-induced apoptosis in murine thymic lymphoma(3SBH5) cells.

Protein kinase C (PKC; also known as PRKC) is known to be an important participant in radiation-induced apoptosis. However, its role is not fully clarified. Using 3SBH5 cells, which are radiation-sensitive thymic lymphoma cells, the involvement and functions of PKC were assessed in radiation- induced apoptosis.

Adaptive response in embryogenesis: V. Existence of two efficient dose-rate ranges for 0.3 Gy of priming irradiation to adapt mouse fetuses.

The adaptive response is an important phenomenon in radiobiology. A study of the conditions essential for the induction of an adaptive response is of critical importance to understanding the novel biological defense mechanisms against the hazardous effects of radiation. In our previous studies, the specific dose and timing of radiation for induction of an adaptive response were studied in ICR mouse fetuses.

Adaptive response in embryogenesis: IV. Protective and detrimental bystander effects induced by X radiation in cultured limb bud cells of fetal mice.

The radioadaptive response and the bystander effect represent important phenomena in radiobiology that have an impact on novel biological response mechanisms and risk estimates. Micromass cultures of limb bud cells provide an in vitro cellular maturation system in which the progression of cell proliferation and differentiation parallels that in vivo. This paper presents for the first time evidence for the correlation and interaction in a micromass culture system between the radioadaptive response and the bystander effect.

An accidental exposure by a medical linear accelerator under construction.

A radiation accident occurred at a medical linear accelerator facility under construction in Japan. The radiation source was a 3- and 6-MV potential drop accelerator designed to produce X-rays for radiation therapy. This accelerator was also capable of producing a 5 to14-MV swept electron beam.