Satomi Kameo

Intervention study on cardiac autonomic nervous effects of methylmercury from seafood.

To scrutinize whether the provisional tolerable weekly intake (PTWI, 3.4 microg/kg body weight/week) of methylmercury in Japan is safe for adults, we conducted an intervention study using heart rate variability (HRV) that has been considered to reflect cardiac events. Fifty-four healthy volunteers were recruited and divided into experimental and control groups. The experimental group was exposed to methylmercury at the PTWI level through consumption of bigeye tuna and swordfish for 14 weeks, and HRV parameters were compared between the two groups. In the experimental group, mean hair mercury levels, determined before and after the dietary methylmercury exposure and after 15-week wash-out period following the cessation of exposure, were 2.30, 8.76 and 4.90 microg/g, respectively. The sympathovagal balance index of HRV was significantly elevated after the exposure, and decreased to the baseline level at the end of this study. Still, such changes in HRV parameters were not found in the control group with a mean hair mercury level of around 2.1 microg/g. In conclusion, the PTWI does not appear to be safe for adult health, because methylmercury exposure from fish consumption induced a temporary sympathodominant state. Rather, long-term exposure to methylmercury may pose a potential risk for cardiac events involving sympathovagal imbalance among fish-consuming populations.

Assessment of exposure to methylmercury in pregnant Japanese women by FFQ.

OBJECTIVE To examine whether an FFQ can be used for assessing exposure to methylmercury (MeHg) by estimating MeHg intake from seafood consumption using the FFQ and confirming the accuracy of the estimated value. DESIGN Seafood consumption of pregnant women was assessed using the FFQ. Total mercury (T-Hg) concentrations of maternal red blood cells (RBC) and hair were measured as exposure indices of MeHg. SETTING A prospective birth cohort study, the Tohoku Study of Child Development (TSCD), which has been ongoing since 2001. SUBJECTS The subjects were 609 pregnant Japanese women who were enrolled in the TSCD. RESULTS MeHg intake was estimated from seafood consumption determined using the FFQ and the MeHg concentrations in each type of seafood. The accuracy of the estimated value was confirmed by comparison with T-Hg in RBC and hair. Estimated MeHg intake was 42.3 microg/week, and 43.0 % of that was from large predatory fish. Compared with the Japanese tolerable weekly intake, in total 12.5 % of the subjects exceeded it. T-Hg concentrations in RBC and hair were significantly correlated with estimated MeHg intake: r = 0.325 (P < 0.0001) for RBC and r = 0.305 (P < 0.0001) for hair. CONCLUSIONS Estimated MeHg intake based on the FFQ was significantly associated with T-Hg concentrations in RBC and hair. Although the estimated value involves uncertainties, the FFQ appears to be a useful tool for assessment of exposure to MeHg.

Simple Analysis Method for Metallothionein-1, -2 and -3 in the Brain by One-Step Size-Exclusion Column HPLC On-Line Coupling with Inductively Coupled Plasma Mass Spectrometry

A simple analysis method of metallothionein (MT) isoforms MT-1, MT-2, and MT-3 was developed based on the use of one-step size-exclusion column (SEC) HPLC and on-line coupling with inductively coupled plasma mass spectrometry (ICP-MS). For the elucidation of the functions of MT isoforms in the brain, it is necessary to have a simple method to determine these isoforms. A SEC TSK gel G2000 SWXL PEEK (7.8 mm I.D. × 30 cm) system was used in this study. The HPLC system was connected with a quadrupole ICP-MS. All of the connections were made using PEEK tubing. To induce MTs, cadmium (Cd) chloride was administered to MT-1, 2 null and 129/Sv mice at a dose of 4 mg/kg body weight by i.p. injection. Mice were sacrificed 24 h after treatment under anesthesia. Brains and livers were collected, and all the samples were stored at −80°C until subsequent analyses. Soluble extracts of the livers and brains from 129/Sv mice either treated with cadmium or untreated were analyzed. MT-1, MT-2, and MT-3 were clearly separated by the one-step SEC HPLC-ICP-MS system (monitored at 65Cu, 66Zn, 113Cd and 55Mn for element) using an appropriate buffer (25 mM Tris-12.5 mM HCl containing 20 mM KCl) and an ultrafiltration membrane filter to eliminate high molecular weight proteins over 30,000 MW and Cu, Zn-SOD. Retention times (RTs) of peaks of each isoform were distinguishable; RTs of MT-1, MT-2, and rMT-3 were 8.6, 8.1, and 7.6 min, respectively. MT-1, MT-2, and MT-3 were separated clearly using this system. This system would be a powerful tool for the separation and metal-component analysis of MT isoforms to elucidate further the biological functions of MTs in the brain.

Trends of body mass index distribution in schoolchildren in Sendai, Japan, 1989–2003

SUMMARY Accumulating evidence indicates a strong association between obesity and health problems. Childhood obesity increases the risk of adulthood obesity. Although it is reported that the number of obese children in Japan has increased, it is unclear whether the obesity index distribution pattern has changed. To clarify this distribution pattern, we analyzed the changes in the body mass index (BMI) of primary (6th grade, 12 years old) and junior high (3rd year, 15 years old) schoolchildren in the city of Sendai during the period from 1989 to 2003. Our department has accumulated information on the height and body weight of all the schoolchildren in the city of Sendai. BMI was calculated using both the height and body weight data. The change in median BMI for 15 years had a slightly upward trend every year with both gender and school year. Although the BMI distribution showed that there was little or no change over time in the lower (10th and 25th) percentiles, the increases in the 75th and 90th percentiles were more marked than that in the 50th percentile in primary school children. On the other hand, there was only a small increase in BMI in the 3rd year of junior high school. Our results indicated that the changes in BMI distribution were concentrated at the upper end of the distribution in primary school children. The shifts in the value of high percentiles might be due to effect modification of the corresponding exposure by another environmental exposure or genetic predisposition. It is suggested that the factors causing this change influenced only part of this population, and affected individuals might represent a susceptible subpopulation of the exposed children.: