Akira Koizumi

Induction of sister-chromatid exchanges in human lymphocytes by microsomal activation of benzene metabolites.

Metabolic activation of the benzene metabolites, catechol, hydroquinone, and phenol, by rat-liver microsomes and an NADPH-generating system (S9 mix) caused an increased induction of sister-chromatid exchanges (SCEs) in cultured human lymphocytes. There were different optimal concentrations of S9 mix for converting each benzene metabolite into further reactive forms that could induce SCE-forming lesions. The data indicate that catechol and hydroquinone can be optimally metabolized to produce reactive species, presumably benzo(semi)quinones, under conditions of lower metabolic activity than those necessary for phenol and benzene.

Trihalomethanes induce sister chromatid exchanges in human lymphocytes in vitro and mouse bone marrow cells in vivo

The four major trihalomethanes (THMs) found in chlorinated drinking water (CHCl3, CHCl2Br, CHClBr2, and CHBr3) have been investigated for their ability to induce sister chromatid exchanges (SCEs) and cell-cycle delays in human lymphocytes in vitro and to induce SCEs in mouse bone marrow cells in vivo. Each THM tested caused dose-dependent increases in SCE frequency and delays in the cell cycle. The THMs differed greatly in their ability to induce these cytological effects in vitro, with CHBr3 being the most active compound and CHCl3 the least active compound, whereas they were not markedly different in their ability to induce SCEs in vivo.

Health effects of volcanic ash: a repeat study.

The Mount Sakurajima volcano in Kyushu, Japan, is proximal to a large residential area, and it emits an enormous amount of volcanic ash during frequent eruptions. In our previous study, we investigated, for the first time, respiratory effects of chronic exposure to volcanic ash. The study demonstrated a low prevalence of respiratory symptoms, even in the area of highest exposure; only a slight excess prevalence of symptoms appeared to be associated with exposure to volcanic ash. To confirm the findings of our previous study, the prevalence study of chronic respiratory symptoms for residents was repeated in Kanoya and Tashiro, which are located 25 and 50 km, respectively, from the crater of Mt. Sakurajima. The concentration of suspended particulate matter in Kanoya frequently exceeded the national environmental quality standards and, during summer and winter, was 2-3 times higher than that found in Tashiro. Women who were 30-59 y of age and who had resided in Kanoya or Tashiro for more than 3 y completed a modified ATS-DLD questionnaire. The prevalence of nonspecific respiratory disease was low, i.e., 6.5% in Kanoya and 6.2% in Tashiro; similar prevalences were found in women who had never smoked. When we restricted the analysis to individuals without a history of occupational exposure to dusts and who had no exposure to passive smoking, there was a slightly higher prevalence of nonspecific respiratory disease in Kanoya than Tashiro, but the difference was not significant. Eye symptoms were equally prevalent in the two areas.(ABSTRACT TRUNCATED AT 250 WORDS)

Selenite prevents the induction of sister-chromatid exchanges by methyl mercury and mercuric chloride in human whole-blood cultures.

The protective effect of sodium selenite (Na2SeO3) against the cytogenetic toxicity of methyl mercury (CH3HgCl) and mercuric chloride (HgCl2) were investigated on human whole-blood cultures in relation to induction of sister-chromatid exchange (SCE). Both mercurials caused a dose-dependent increase in SCEs, methyl mercury being about 5 times more potent than mercuric chloride. Sodium selenite also induced SCEs. However, the simultaneous addition of selenite (1 x 10(-7) -3 x 10(-5) M) to cell cultures containing either methyl mercury (3 x 10(-6) M) or mercuric chloride (1 x 10(-5) M) prevented the induction of SCEs by the mercurial in a clear dose-related manner. When selenite and mercurial were simultaneously added at a molar ratio of 1:2 Na2SeO3:CH3HgCl, or 1:1 Na2SeO3:HgCl2, cells from treated cultures showed no increase in the SCE frequency. These results indicate that selenite and mercury mutually antagonize their ability to cause DNA damage leading to the formation of SCEs. The formation of bis(methylmercuric)selenide, (CH3Hg)2Se, from Na2SeO3 and CH3HgCl, or a high molecular complex consisting of glutathione-Se-Hg from Na2SeO3 and HgCl2 involving the participation of glutathione in RBCs might play a key role in this antagonism between mercury and selenium.

Bleomycin-induced chromosomal aberrations and sister chromatid exchanges in Down lymphocyte cultures

SummaryPeripheral blood lymphocytes from three patients with Down syndrome (DS; trisomy 21; aged 5–6 years) and three age-matched control children were studied for the induction of chromosomal aberrations and sister chromatid exchanges (SCEs).Cells in G0 were exposed to bleomycin (20–100 μg/ml) for 3 h, and then cultured in medium containing 5-bromodeoxyuridine and phytohemagglutinin for 66 h. By the sister chromatid differential staining method, chromosome analyses were performed on metaphase cells that had divided one, two, or three or more times after treatment. The results indicate that DS cells exposed to bleomycin are hypersensitive to the production of dicentric and ring chromosomes compared to normal cells. Bleomycin also led to a dose-related increase in the frequency of SCEs, but no difference was found between the SCE frequencies in DS or normal lymphocytes exposed to bleomycin.

Human Health Situation and Chromosome Alterations: Sister Chromatid Exchange Frequency in Lymphocytes from Passive Smokers and Patients with Hereditary Diseases

Lymphocytes from passive smokers, and patients with FA, Alz, or FPC were studied for SCEs in cultures treated with MMC, 4NQO, or MNNG. Fanconi anemia lymphocytes were also studied for cell cycle Tab. 3. Mean SCE frequencies in FPC or normal cells. (Table; see text) kinetics, and CAs after completion of 1, 2, or 3 or more divisions in MMC-treated cultures. The results can be summarized as follows: (1) lymphocytes from passive smokers showed a slightly higher induction of SCEs than nonsmokers when exposed to MMC. (2) FA cells had about 1.4 times higher frequencies of SCEs than normal cells in both MMC-treated and untreated cultures while they showed several times higher frequencies of CAs in both cultures. Analyses of cell cycle kinetics by the sister chromatid differential staining method revealed that MMC treatments of FA and normal cells led to a clearly dose-related delay in cell turnover times, the duration of delay being much longer in FA than in normal cells. (3) Alz cells showed about 1.5 times higher induction of SCEs in MMC-treated cultures whereas they had only 10% as much SCEs as controls when exposed to 4NQO. Familial polyposis coli cells showed no significant difference in the induction of SCEs in untreated cultures and cultures treated with MMC, 4NQO, and MNNG.

Proliferative kinetics of human lymphocytes in culture measured by autoradiography and sister chromatid differential staining

A simple combination of autoradiography, to determine when a cell synthesized DNA, and sister chromatid differential staining, to determine how many times a cell has divided, was used to follow up the proliferating fate of human lymphocytes in culture. Cells were incubated continuously with 5-bromodeoxyuridine (BrdU) and pulse-labelled with 0.1 muCi/ml [3H]thymidine at various times after stimulation with phytohemagglutinin (PHA). The cells were then harvested at 4 h intervals up to 72 h, and the percentage of labelled mitoses was determined separately in first, second, or third division cells. The data showed that the cycling cells, whether they began cycling at earlier or later times after stimulation, had about the same generation times of 12--14 h. This confirms that the heterogeneity of cell generations seen in short-term lymphocyte cultures is in large part due to the difference in the times when cells began cell cycling in response to PHA.

In vitro biological effects of volcanic ash from Mount Sakurajima

Mount Sakurajima in the south of the Kyushu Island of Japan erupts hundreds of times a year and continuously emits large amounts of ash. More than a million people live under this ash plume, and there is considerable concern about the possible effects of this on their health. We have studied the physicochemical characteristics and in vitro effects of airborne ash collected at 8 km from the crater. More than 30% of the ash was found to be SiO2 (w/w) with most of the particles within the respirable size range. The ash did not inhibit the colony formation of V79-4 cells and failed to activate complement or generate chemotactic factor activity in samples of fresh human serum. It was minimally active in causing the release of lysosomal enzymes from human neutrophile, and did not cause arachidonic acid release from macrophage-like cells. These results were in accord with our epidemiological study, in which very low prevalences of nonspecific respiratory disease were demonstrated even at the area with highest ash exposure.

Adaptation-like response to the chemical induction of sister chromatid exchanges in human lymphocytes.

SummaryExperiments have been performed to determine whether human lymphocytes in primary cultures can show an “adaptive” response to the induction of cellular lesions (manifested as a production of sister chromatid exchanges, SCEs) as previously found in bacteria and established human and mammalian cell lines. Human lymphocytes were pretreated with various subtoxic concentrations (5–50ng/ml) of N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) once every 6h for 72h, and subsequently challenged by a high dose (4μg/ml) of MNNG. The lymphocytes in MNNG-challenged cultures had the lowest frequency of SCEs when pretreated with 10ng/ml MNNG. Further cross-resistance study revealed that repeaied pretreatments of lymphocytes with 10ng/ml MNNG for 72h can render the cells resistant to the induction of SCEs by the following challenge with a high dose of MNNG, but not of mitomycin C or ethyl nitrosourea. The data also suggest variations in the degree of the adaptation-like response among individuals.

Proliferative kinetics and mitomycin C-induced chromosome damage in Fanconi's anemia lymphocytes

SummaryLymphocytes from two sisters with Fanconis anemia (FA) were studied for cell cycle kinetics, sister chromatid exchanges (SCEs), and chromosomal aberrations when they had undergone one, two, or three or more divisions in mitomycin C (MMC)-treated cultures. Lymphocytes from the parents another sister of the probands, and a healthy unrelated adult were examined as controls. Analyses of cell cycle kinetics by the sister chromatid differential staining method revealed that the relative frequency of metaphase cells at their third or subsequent divisions was much smaller in untreated FA cultures than in normal cultures fixed at 96h after phytohemagglutinin stimulation. These data indicate that FA cells proliferate much more slowly than normal cells. MMC treatments of FA and normal cells led to a clearly dose-related delay in cell turnover times, the duration of delay being much longer in FA than in normal cells. FA cells had about 1.4 times higher frequencies of SCEs than normal cells in both MMC-treated and untreated cultures. FA cells also showed several times higher frequencies of chromosomal aberrations than normal cells, and the frequency of chromosomal aberrations decreased through subsequent mitoses by approximately 60% in both FA and normal cells.