Biomedical subjects

I Hayata

Publications and source records attributed to I Hayata.

At least 19 recordsLinked to original sources

PubMed2006

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. RESULTS: The ratio of acentric rings to dicentric chromosomes (termed RaD ratio) and that of excess fragments to dicentrics (termed EfD ratio) showed significant (p < 0.05) differences between the two groups of cancer patients, and these ratios for accidental victims were in between the values of the two groups of cancer patients. The in vitro studies using doses equivalent to 1 - 3 Gy of gamma-rays have confirmed that the EfD ratios were increased with the high LET (linear energy transfer) and RaD ratios decreased. CONCLUSION: The present data show that the RaD and EfD ratios can be used as cytogenetic biomarkers of exposure to high-LET radiation at least within a few years of exposure.

Aged↗

PubMed2004

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. RESULTS: In PCC preparations, cells in the late G(2) phase and late M phase were observed. In late M phase cells, 17-20% of ring chromosomes lacked one chromatid (single-chromatid ring), irrespective of dose. Both the distribution patterns of centromeres in rings and intercentromere distances in dicentric rings indicate that a considerable number of single-chromatid rings might be formed by SCE occurring in a chromosome-type ring, thereby joining strands of two rings, followed by a transformation into one ring. These single-chromatid rings were less stable in vivo than chromosome-type rings. CONCLUSION: Single-chromatid rings visualized clearly using PCC techniques indicate SCE in the respective rings. Contrary to the conventional SCE-detecting technique, this approach does not require the use of bromodeoxyuridine, which itself leads to SCE. Some of the observed SCE might be secondary products resulting from the repair of radiation-induced DNA damage, while others may be spontaneous.

Cell Cycle↗

PubMed2004

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. During the Georgian accident soldiers carried in their pockets small sources of 137Cs leading to partial and protracted body exposures. During the Tokai-mura accident, three employees involved in the process of 235U enrichment were exposed to very high doses of gamma rays and neutrons. During the Bialystok accident, five patients with breast cancer undergoing radiotherapy were exposed to a single dose of electrons which reached about 100 Gy. In the present paper the approaches chosen to estimate, by cytogenetic methods, the doses absorbed by the people involved in the accidents are described.

Breast Neoplasms↗

PubMed2004

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. On average 2,600 cells per subject were analyzed. 27 adults and six children in HBRA and 25 adults and eight children in CA were studied with respect to translocations. On average 4,741 cells per subject were examined. We found an increase of the frequency of dicentrics and rings in HBRA, where the natural radiation level is three to five times higher than in the control area. But the increase of translocations in HBRA was within the range of individual variation in the controls.

Adult↗

PubMed2002

Dynamic analysis of chromosome aberrations in three victims of the Tokai-mura criticality accident.

PURPOSE: To investigate the dynamics of chromosome aberrations in the blood cells of three workers severely exposed to neutrons and gamma-rays in a criticality accident that occurred in Tokai-mura, Japan, in 1999. MATERIALS AND METHODS: The change with time of the frequency of' chromosome aberrations in the three patients was examined using a new analysis to score drug-induced prematurely condensed ring chromosomes (PCC-R) and a conventional meta-phase analysis. RESULTS: The frequencies and cellular distributions of PCC-R, dicentrics and rings did not change significantly among the samples obtained at 9-48h after the accident while the first depletion of lymphocytes occurred. The distributions of these aberrations in the cells of two patients showed a slight overdispersion compared with a Poisson distribution reflecting neutron and non-uniform exposures. The dose response curve of rings paralleled that of dicentrics, but not PCC-R. The half-lives of PCC-R (8.5 months) and of rings (8.7 months) were shorter than that of dicentrics (13.5 months). CONCLUSIONS: In the three patients of the Tokai-mura accident, lymphocytes in the circulating and extravascular pools had reached equilibrium at 9h, and highly damaged lymphocytes did not selectively move away from the circulatory system during the first rapid depletion of lymphocytes after exposure. Data on the in vivo half-life of PCC-R as well as dicentrics and rings obtained in the present study may be useful for retrospective dosimetry.

Adult↗

PubMed2001

Structural analysis of heavy ion radiation-induced chromosome aberrations by atomic force microscopy.

Heavy ion radiation (high linear energy transfer, LET, radiation) induces various types of chromosome aberration. In this report, we describe a new method employing an atomic force microscope (AFM) for nanometer-level structural analysis of chromosome damage induced by heavy ion irradiation. Metaphase mouse chromosomes with chromatid gap or chromatid breaks induced by heavy ion irradiation were marked under a light microscope. Then the detailed structure of chromosomes of Giemsa-stained or unstained samples was visualized by the AFM. The height data of chromosomes obtained by AFM provided useful information to distinguish chromatid gaps and breaks. A fibrous structure was observed on the unstained chromosome, the average width of which was about 45.8 nm in the image of AFM. These structures were considered to be 30-nm fibers on the chromosome. The structure of the break point regions induced by neon- or carbon-ion irradiation was imaged by AFM. In some cases, the fibrous structure of break points was detected by AFM imaging after carbon ion irradiation. These observations indicated that AFM is a useful tool for analysis of chromosome aberrations induced by heavy ion radiation.

Animals↗

PubMed2001

Fas-independent apoptosis induced by UVC in p53-mutated human epithelial tumor A431 cells through activation of caspase-8 and JNK/SAPK.

A431 cells/UVC-induced apoptosis/Caspase 8/Fas/JNK/PAPK. We previously observed that p53-mutated human epithelial tumor A431 cells underwent apoptosis after ultraviolet C (UVC) irradiation through the caspases-8 and -3 pathway. Fas/FasL is known to initiate apoptosis in several cell lines via caspase-8 activation. Then, to determine if Fas/FasL mediates apoptosis in A431. we investigated Fas expression and modulation in UVC-irradiated A431 cells. A431 constitutively expressed Fas, which gradually decreased after UVC-irradiation. Pretreatment with a neutralizing anti-Fas antibody, ZB4, did not abrogate the UVC-induced apoptosis. An agonistic anti-Fas antibody, CH11, very slowly induced apoptosis in A431. suggesting that the constitutively expressed Fas had a low functional potential. Hence, UVC-induced apoptosis in A431 seems to occur independent of the Fas signal. Interestingly, however, a pretreatment with CH11 remarkably potentiated UVC-induced apoptosis. An inhibitor of caspase-8, Ac-IETD-CHO, partially inhibited UVC-induced apoptosis. JNK was phosphorylated immediately after exposure to UVC. prior to apoptotic chromatin condensation. Our data suggest that the activation of caspase-8 occurs independent of Fas upregulation, and that JNK/ SAPK contributes to UVC-induced apoptosis in human epithelial A431 cells.

Apoptosis↗

PubMed2001

Chromosome aberration analysis in persons exposed to low-level radiation from the JCO criticality accident in Tokai-mura.

Chromosome aberrations were studied in peripheral blood lymphocytes of 43 persons who were exposed to low-level radiation of mixed neutrons and gamma-rays resulting from the JCO criticality accident. When the age-adjusted frequencies of dicentric and ring chromosomes were compared with the dose calibration curve established in vitro for 60Co gamma-rays as a reference radiation, a significant correlation was observed between the chromosomally estimated doses and the documented doses evaluated by physical means. The regression coefficient of the chromosomal doses against the documented doses, 1.47 +/- 0.33, indicates that the relative biological effectiveness of fission neutrons at low doses is considerably higher than that currently adopted in the radiation protection standard.

Adult↗

PubMed2001

Cytogenetical dose estimation for 3 severely exposed patients in the JCO criticality accident in Tokai-mura.

A dose estimation by chromosome analysis was performed on the 3 severely exposed patients in the Tokai-mura criticality accident. Drastically reduced lymphocyte counts suggested that the whole-body dose of radiation which they had been exposed to was unprecedentedly high. Because the number of lymphocytes in the white blood cells in two patients was very low, we could not culture and harvest cells by the conventional method. To collect the number of lymphocytes necessary for chromosome preparation, we processed blood samples by a modified method, called the high-yield chromosome preparation method. With this technique, we could culture and harvest cells, and then make air-dried chromosome slides. We applied a new dose-estimation method involving an artificially induced prematurely condensed ring chromosome, the PCC-ring method, to estimate an unusually high dose with a short time. The estimated doses by the PCC-ring method were in fairly good accordance with those by the conventional dicentric and ring chromosome (Dic+R) method. The biologically estimated dose was comparable with that estimated by a physical method. As far as we know, the estimated dose of the most severely exposed patient in the present study is the highest recorded among that chromosome analyses have been able to estimate in humans.

Chromosome Aberrations↗

PubMed2001

Rescue of lethally irradiated mice from hematopoietic death by pre-exposure to 0.5 Gy X rays without recovery from peripheral blood cell depletion and its modification by OK432.

Exposing mice to 0.5 Gy X rays 2 weeks before lethal irradiation has been reported to induce marked radioresistance and to rescue them from hematopoietic death. Here we examined effects of the 0.5-Gy pre-exposure on hematological changes in C57BL mice that were lethally irradiated with 6.5 Gy X rays. Approximately 77% of pre-exposed mice survived 30 days after this irradiation, whereas 80% of mice that did not receive this pre-exposure died by day 20. However, regardless of the pre-exposure, peripheral blood cell counts decreased markedly by day 3 and reached a nadir at day 20. CFU-S in femur and CFU-GM in spleen had started to recover at day 10 and 14, respectively, but recovery of functional peripheral blood cells occurred later. The effect of pre-exposure on survival was altered by OK432, a bioresponse modifier; the effect depended on the timing of its administration. OK432 given 2 days before 0.5 Gy enhanced the protective effect of pre-exposure, resulting in the survival of 97% of the mice. In contrast, injection of OK432 1 day before or 2 days after pre-exposure led to 100% mortality. Thus the survival-promoting effect of 0.5 Gy could be altered by OK432. The OK432-induced changes in the survival of mice could not be attributed solely to hematological changes, as shown by blood cell counts and progenitor cell contents. These results suggest that radioresistance induced by pre-exposure to 0.5 Gy X rays is not stable, but rather varies with the physiological conditions, and can be modulated by factors such as OK432.

Animals↗

PubMed2000

Analysis of radiation damage of DNA by atomic force microscopy in comparison with agarose gel electrophoresis studies.

DNA damage induced with ionizing radiation is considered one of the main causes of cell inactivation. Several methods including gel electrophoresis, pulsed-field gel electrophoresis, neutral filter elution method, neutral sedimentation and electron microscopy have been applied to analyze this type of DNA damage. A new method employing an atomic force microscope (AFM) for nanometer-level-structure analysis of DNA damage induced with gamma-irradiation is introduced in this report. Structural changes of plasmid DNA on a molecular size scale of about 3 kbp were visually analyzed by AFM after irradiation with 60Co gamma-rays at doses of 1.9, 5.6, and 8.3 kGy. Three forms of plasmid DNA, closed circular (intact DNA), open circular (DNA with a single strand break) and linear form (DNA with a double strand break) were visualized by dynamic force mode AFM after gamma-irradiation. The torsional feature of the plasmid DNA was visualized better with AFM than with a transmission electron microscope (TEM). All three forms of plasmid DNA were observed in the sample irradiated with gamma-rays at the dose of 1.9 kGy. Open circular and linear forms were observed in the samples irradiated with gamma-rays at doses of 5.6 and 8.3 kGy, though no closed circular form was observed. A shortening of the length of a linear form of DNA irradiated with 5.6 and 8.3 kGy gamma-rays was observed by AFM. Structural changes of DNA after gamma-irradiation were visualized by AFM at nanometer level resolution. In addition, shortening of the length of the linear form of DNA after radiation exposure was observed by AFM.

Cobalt Radioisotopes↗

PubMed2000

UVC-induced apoptosis in human epithelial tumor A431 cells: sequence of apoptotic changes and involvement of caspase (-8 and -3) cascade.

Human epidermoid tumor A431 cells underwent apoptosis following exposure to ultraviolet C (UVC). The apoptosis was of the interphase death type, and mostly occurred within one cell cycle, independent of the cell-cycle phases. We further examined the detailed sequential order of apoptotic changes in cells after UVC exposure and the involvement of caspases using six caspase inhibitors. The loss of mitochondrial transmembrane potential (delta psi m) appeared in the earliest phase; subsequently, the chromatin condensation and DNA-fragmentation occurred. Cell shrinkage and loss of the plasma-membrane integrity, judged by propidium iodide (PI) staining, were observed in the later phase. A broad-spectrum caspase inhibitor, z-VAD-fmk, completely prevented all apoptotic changes, except for the depletion of delta psi m. Both Ac-DEVD-CHO and Ac-IETD-CHO, inhibitors of caspase -3 and -8, respectively, effectively inhibited typical chromatin condensation to almost the same extent. However, the nuclei still showed partial condensation. A caspase -9 inhibitor, Ac-LEHD-CHO, did not prevent chromatin condensation, though it partially inhibited cell-size reduction and PI-stainability. None of the caspase inhibitors could inhibit the delta psi m reduction. These results strongly suggest that the collapse of delta psi m is not a part of the central apoptotic machinery, and that caspase cascade(s), especially caspase-8 to -3, play an important role in UVC-induced apoptosis in A431.

Apoptosis↗

PubMed2000

Dose-effect relationship of dicentric and ring chromosomes in lymphocytes of individuals living in the high background radiation areas in China.

Chromosomes of 39 healthy family members (3 generations from 13 families) living both in the high-level background radiation areas (HBRA) and the control areas (CA) were studied. Cumulative dose from birth to the time of blood sampling was estimated by calculating measured exposure rate in each individual. The cumulative doses ranged 30.9-358.9 and 6.0-59.2 mGy for HBRA and CA, respectively. Peripheral lymphocyte chromosome preparations were made according to our improved method. Dicentric and ring chromosomes (Dic + Rc) were scored in average 2,527 cells per individual in HBRA and 2,694 cells in CA under a microscope equipped with an automated stage. A positive correlation between Dic + Rc and age was found in HBRA, while no such dose relationship was clear in CA. The frequency of Dic + Rc linearly increases over lifetime due to chronic low dose exposure and it is likely that the activation of repair enzymes is not triggered in the present HBRA. Threshold dose (rate) of the induction of chromosome aberrations, if any, is below the present dose (rate) level.

Adult↗

PubMed2000

Chromosome translocation in residents of the high background radiation areas in southern China.

We performed a cytogenetical study using chromosome painting analysis on 9 residents of the naturally high background radiation areas (HBRA) and 8 residents of the control areas in southern China. The estimated dose (air kerma) of each resident measured by an electric pocket dosimeter showed 2.20-4.23 mGy/year in HBRA and 0.56-0.70 mGy/year in the control areas. A total of 14,096 cells (1,566 cells/case) in the former and 17,522 cells (2,190 cells/case) in the latter were analyzed. Children, both in HBRA and in the control areas, had translocations at low frequencies. The frequency of translocations among elder individuals varied widely and it was not possible to detect dose effect although it was detected in dicentrics. The effect of radiation on the induction of chromosome aberrations, which have a statistically potential risk of causing malignant or congenital diseases, seems to be less significant than those of metabolic factors and/or mutagenic agents (excluding radiation) even in HBRA in China.

Aged↗

PubMed2000

Adaptive response in embryogenesis. III. Relationship to radiation-induced apoptosis and Trp53 gene status.

We reported previously that a radiation-induced adaptive response existed in the late period of embryogenesis, and that radiation-induced apoptosis in the predigital regions was responsible for digital defects in embryonic ICR mice. To investigate the possible involvement of the Trp53 gene and radiation-induced apoptosis in radiation-induced adaptive responses in embryogenesis, the present study was conducted using Trp53 wild-type (Trp53(+/+)) and Trp53 heterozygous (Trp53(+/-)) embryonic mice of the C57BL/6 strain. The existence of a radioadaptive response in the Trp53(+/+) embryonic mice was demonstrated by irradiating the embryos with 5 or 30 cGy on embryonic day 11 prior to a challenging irradiation at 3 Gy on embryonic day 12. The two conditioning doses at 5 and 30 cGy significantly suppressed the induction of apoptosis by the challenging dose in the predigital regions of limb buds in the Trp53(+/+) embryonic mice, while no such effect was found in the Trp53(+/-) embryonic mice. These findings indicate that induction of a radioadaptive response in embryogenesis is related to Trp53 gene status and the occurrence of radiation-induced apoptosis.

Abnormalities, Radiation-Induced↗

PubMed2000

Prenatal radiation-induced limb defects mediated by Trp53-dependent apoptosis in mice.

We reported previously that in utero radiation-induced apoptosis in the predigital regions of embryonic limb buds was responsible for digital defects in mice. To investigate the possible involvement of the Trp53 gene, the present study was conducted using embryonic C57BL/6J mice with different Trp53 status. Susceptibility to radiation-induced apoptosis in the predigital regions and digital defects depended on both Trp53 status and the radiation dose; i.e., Trp53 wild-type (Trp53(+/+)) mice appeared to be the most sensitive, Trp53 heterozygous (Trp53(+/-)) mice were intermediate, and Trp53 knockout (Trp53(-/-)) mice were the most resistant. These results indicate that induction of apoptosis and digital defects by prenatal irradiation in the later period of organogenesis are mediated by the Trp53 gene. These findings suggest that the wild-type Trp53 gene may be an intrinsic genetic susceptibility factor that is responsible for certain congenital defects induced by prenatal irradiation.

Abnormalities, Radiation-Induced↗

PubMed1999

Allocyclic X chromosome visualized by drug-induced premature chromosome condensation.

Calyculin A, an inhibitor of serine/threonine protein phosphatases, can induce premature chromosome condensation (PCC) in human peripheral lymphocytes. In female lymphocytes treated with calyculin, one highly condensed chromosome per nucleus was frequently observed at early to middle S phase. When these PCC spreads were hybridized with a whole chromosome-painting probe for the X chromosome, one large spot and a cluster of small spots were observed in a cell. Judging from the Giemsa stained image, the former seemed to have finished DNA replication, while the latter was in the process of replication. Because this large spot was seldom observed in male PCC spreads, it was considered an inactive X chromosome. The inconsistency of this observation with earlier reports that the inactive X chromosome replicates later than autosomes and the active homolog is discussed.

Chromosome Painting↗

PubMed1999

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. Calyculin A induced PCC in 5-Gy-irradiated and unirradiated samples at almost the same frequency in the lymphocytes, whereas the efficacy was considerably lower in irradiated fibroblasts than in unirradiated ones. Calcium ionophore enhanced the induction of PCC in irradiated fibroblasts, although PCC frequencies were still much lower than those in the lymphocytes. The frequency of ring chromosomes observed in 2- and 5-Gy-irradiated fibroblasts was too low to be used as a marker for cytogenetic dosimetry, and that of excess fragments, scored as the observed chromosome number minus 46, might be substituted. The frequency of excess fragments for 2-, 5-, and 10-Gy-irradiated fibroblasts was less than 0.75, about 1 and a few per cell, respectively, although these values changed with the culture period. The prospects and limitations of the application of PCC techniques to fibroblasts are discussed.

Cell Cycle↗