Sex differences in stress reactivity of hippocampal BDNF in mice are associated with the female preponderance of decreased locomotor activity in response to restraint stress.

The incidence and prevalence of depression is higher in women than in men, but the cause of this sex discrepancy remains unknown. Brain-derived neurotrophic factor (BDNF) is a key protein for maintaining neuronal integrity. The purpose of this study was to investigate the female preponderance in behavioral responsivity to restraint stress focusing on the stress reactivity of BDNF in the hippocampus. Male and female ICR mice were exposed to a 3-h session of restraint stress. Plasma corticosterone was measured by high-performance liquid chromatography. BDNF mRNA expression in the whole hippocampus was measured by quantitative real-time reverse transcription-polymerase chain reaction. Wheel-running activity was monitored during the dark period. In response to restraint stress, the increase in levels of serum corticosterone was higher in female than in male mice. Restraint stress resulted in decreased voluntary wheel-running behavior that was greater in female than male animals. In addition to these sex differences in stress reactivity, we found a significant sex difference in BDNF levels in the hippocampus of restraint-stressed mice; total BDNF levels significantly decreased in female mice, but not in male mice in response to the stress. Furthermore, BDNF exon I and IV mRNA expression also showed the same tendency. These data indicate that the reduction in levels of voluntary wheel-running activity in response to stress can be significantly influenced by sex. Moreover, our findings suggest a link between the sex differences in this behavioral response to stress and differential stress reactivity in the production of BDNF in the hippocampus.

[Anti-diabetic effect of ethanol extract of Cyclolepis genistoides D. Don (Palo azul), made in Paraguay].

Extract of Cyclolepis genistoides D. Don (vernacular name Palo azul; Palo) are traditionally consumed in the Republic of Paraguay in South America for the treatment of diabetes and kidney disease, and is sold in Japan as dietary supplement. This study aimed to elucidate the mechanism of anti-diabetes activity of Palo, especially focused on insulin resistance. Palo promoted adipocytes differentiation and regulated adipokine profiles in 3T3-L1 adipocytes by modulation of PPARγ, a major regulator of adipose differentiation. Human adipocyte showed almost similar profile with 3T3-L1 against Palo treatment. Furthermore, Palo treatment (250 or 1000 mg/kg) was performed with C57BL/6J mice for 14 weeks, being fed high-fat-diet (HFD60) simultaneously. Palo 250 mg/kg exhibited a tendency to decrease subcutaneous adipose volume along with increase of PPARγ and its target, adiponectin mRNA expression. In addition, as the other insulin targeted cell, effect on muscle differentiation was examined. Palo increased differentiation of C2C12 mouse muscle myoblasts by increase of IGF-1, myogenin, and myosine heavy chain (MHC) as well as 5'-AMP-activated protein kinase (AMPK) activation. Palo subsequently promoted myotube formation under differentiation condition. From the above, it was clarified that Palo acts variously on the differentiation and maturation of both adipocytes and muscle cells, and from the viewpoint of the regulatory mechanism for adipocytes, PPARγ-inducing action was shown to be a mechanism that acts across species.

Neonatal exposure to diethylstilbestrol alters expression of DNA methyltransferases and methylation of genomic DNA in the mouse uterus.

Perinatal exposure to diethylstilbestrol (DES) can have numerous adverse effects on the reproductive organs later in life, such as vaginal clear-cell adenocarcinoma. Epigenetic processes including DNA methylation may be involved in the mechanisms. We subcutaneously injected DES to neonatal C57BL/6 mice. At days 5, 14, and 30, expressions of DNA methyltransferases (Dnmts) Dnmt1, Dnmt3a, and Dnmt3b, and transcription factors Sp1 and Sp3 were examined. We also performed restriction landmark genomic scanning (RLGS) to detect aberrant DNA methylation. Real-time RT-PCR revealed that expressions of Dnmt1, Dnmt3b, and Sp3 were decreased at day 5 in DES-treated mice, and that those of Dnmt1, Dnmt3a, and Sp1 were also decreased at day 14. RLGS analysis revealed that 5 genomic loci were demethylated, and 5 other loci were methylated by DES treatment. Two loci were cloned, and differential DNA methylation was quantified. Our results indicated that DES altered the expression levels of Dnmts and DNA methylation.

Perinatal exposure to brominated flame retardants and polychlorinated biphenyls in Japan.

Brominated flame retardants (BFRs) are used to prevent combustion in consumer products. Examples of BFRs are polybrominated diphenyl ethers (PBDEs), tetrabromobisphenol A (TBBPA), and tribromophenol (TBP). These compounds are reported to have adverse effects on human health and endocrine disrupting effects. The purpose of this study was to identify the Japanese perinatal exposure to PBDEs, hydroxylated PBDE metabolites (OH-PBDEs), TBBPA, and TBP compared with polychlorinated biphenyls (PCBs) and hydroxylated PCB metabolites (OH-PCBs). We investigated the concentrations of these compounds in maternal blood, maternal milk, cord blood, and umbilical cords from 16 Japanese mother-infant pairs by HRGC/HRMS. PBDEs were detected in all samples of maternal blood (mean+/-SD; median=25+/-23 pg/g; 18 pg/g wet weight), maternal milk (140+/-220 pg/g; 59 pg/g wet weight), cord blood (4.8+/-6.5 pg/g; 1.6 pg/g wet weight), and umbilical cords (3.1+/-3.1 pg/g; 2.1 pg/g wet weight). The mothers were divided into two groups, a high-concentration group and a low-concentration group. The percentage of BDE-47 showed the greatest difference between the two groups. 6-OH-BDE-47, TBBPA, and TBP were detected in all umbilical cord samples (mean+/-SD; median=8.4+/-8.1 pg/g; 8.0 pg/g, 16+/-5.5 pg/g; 15 pg/g, and 33+/-8.2 pg/g; 32 pg/g wet weight respectively), but not in all maternal blood or cord blood samples. These results indicate that OH-PBDEs, TBBPA, and TBP, in addition to PBDEs, PCBs, and OH-PCBs, pass through the blood-placenta barrier and are retained in the umbilical cord.

Strong correlation between the concentration of dioxins and total PCBs in current Japanese people.

The purpose of this study was to establish an economic and efficient method to screen total PCBs and total dioxins (PCDDs+PCDFs+Co-PCBs) in the highly exposed people in Japan. In this paper, we suggest use of total PCBs in human blood to represent other persistent organic pollutants, especially dioxins. Twenty blood samples were collected from Japanese volunteers. Total PCBs and total dioxins (PCDDs+PCDFs+Co-PCBs) were detected from all twenty blood samples. We carried out detailed analysis of correlation between concentration of total PCBs and each dioxin congener with both measured value and TEQ calculated value. The mean concentration of total PCBs was 250 ng g-fat(-1), and the mean concentration of total dioxins was 37 ng g-fat(-1) or 40 pg TEQ g-fat(-1). Correlations between the total PCBs (ng g-fat(-1)) and the total measured dioxins (ng g-fat(-1)), and between the total PCBs (ng g-fat(-1)) and the total dioxin TEQ calculated value (pg-TEQ g-fat(-1)) were 0.95 and 0.90, respectively. It became clear that the concentrations of total PCBs in human blood is a good indicator of the concentrations of total dioxins in Japan. If a mass screening is conducted on women of reproductive age in order to detect highly exposed women, it is possible that women with the highest contamination may be treated in order to decrease the levels of these chemicals before pregnancy. In conclusion, measurement of total PCBs concentration is useful for exposure assessment of dioxins in human blood.

The contamination levels of organochlorines and the pattern of gene expressions in human umbilical cords from intra-pairs of twins at delivery.

In this study, we examined the contamination levels of organochlorines and the patterns of gene expressions using umbilical cords of twins. The contamination levels of total PCBs, HCB and HCHs of intra-pair of twins were close to each other, but that of DDTs were not so as the others. It shows that the placental or fetal factor may influence the transfer or the accumulation of DDTs. The patterns of gene expressions of intra-pair of twins were similar to each other. It may because the environmental factor (sharing same mother), genetic factor or the both of twins are similar. This study gave us some information to understand the fetal exposure to organochlorines. Moreover, it showed the possibility that the pattern of gene expression in umbilical cord reflected the intra-uterine environment. However, the information from general pattern of the gene expression is limited. Therefore, further investigation is necessary to find new markers not only mRNA but also protein to estimate the effects of fetal exposure of multiple organochlorines.

Polychlorinated biphenyls alter the expression of endothelial nitric oxide synthase mRNA in human umbilical vein endothelial cells.

Polychlorinated biphenyls (PCBs) are a group of persistent pollutants that are detected in maternal serum and umbilical cord, suggesting that fetal exposure also needs to be considered. The effects of dioxin-like PCB congeners 3,3',4,4'-tetrachlorobiphenyl (PCB77) and 3,3',4,4',5-pentachlorobiphenyl (PCB126) and a non-dioxin-like compound 2,2',4,4',5,5'-hexachlorobiphenyl (PCB153) on the expression of endothelial nitric oxide synthase (eNOS), known to maintain blood flow to the fetus, in human umbilical vein endothelial cells (HUVECs) were investigated. The mRNA levels of eNOS, aryl hydrocarbon receptor (AhR) and cytochrome P450 (CYP) 1A1 in cells treated with 5 microM PCBs for 24 hours were analysed by real-time RT-PCR. Cells were also treated with alpha-naphthoflavone (alpha NF), an AhR antagonist or ICI 182780, an estrogen receptor (ER) antagonist, one hour prior to PCB exposure, to observe the effects of these receptors on eNOS modulation. Each PCB increased the eNOS mRNA level by 4.5-fold that was markedly inhibited by alphaNF. ERs were also suspected of altering eNOS levels because ICI 182780 treatment resulted in a decrease in the eNOS level. These results suggest that the eNOS mRNA expression increases due to the action of PCBs related to both AhR and ERs in HUVECs, and that maternal PCB exposure could influence fetal circulation.

Reduction of dioxins and polychlorinated biphenyls (PCBs) in human body.

The accumulation of persistent lipophilic organic pollutants like dioxins and PCBs in human body is of great concern since many of these compounds may elicit adverse health effects on humans. To reduce dioxins and PCBs with long half-lives that are absorbed into the human body, we need to work actively to minimize accumulation of dioxins and PCBs taken. Lot of manner has been tested such as foods containing dietary fibers and chlorophyll, lipids (squalane etc) and anion exchange resins. Cholestyramine, a cholesterol lowering agent, was no efficacy in humans. Authors have conducted a pilot study to demonstrate the effect lowering dioxin in human bodies using colestimide. Nine patients on cdestimide for 6 months, showed mean 20% decrease respectively in both dioxin and PCB levels, and the maximum percentage decrease was approximately 40%. From a standpoint to avoid the influence on high-risk group and high-risk life stage other than next generation, the world-wide cooperation for reducing environmental chemicals is greatly appealed.

Neonatal administration of diethylstilbestrol has adverse effects on somatic cells rather than germ cells.

Neonatal administration of diethylstilbestrol (DES) to rodents has adverse effects on spermatogenesis. However, not many studies have been conducted to determine which type of cell - germ or somatic - is the major target of DES. In order to clarify this, we tried reciprocal germ cell transplantation--transplantation of germ cells from DES-treated mice into intact mice and germ cells from normal mice into DES-treated mice. The donor germ cells were tagged with the green fluorescent protein (GFP) gene in order to distinguish the exogenous germ cells from the endogenous cells. Moreover, to obtain a large number of spermatogonia from the testes of adult mice, we performed fractionation by centrifugation with Percoll. Consequently, we found that the germ cells collected from DES-treated mice have differentiated into normal sperms in normal seminiferous tubules. However, in the case of the transplantation of normal germ cells into the seminiferous tubules of DES-treated mice, defective spermatogenesis was observed. In conclusion, DES has adverse effects on the somatic cells that are involved in spermatogenesis rather than the germ cells.

Comparison of Elisa- and LC-MS-Based Methodologies for the Exposure Assessment of Bisphenol A.

Several types of methods, mainly liquid chromatography (LC), have been used for the analysis and assessment of bisphenol A (BPA) in human biological samples. Enzyme-linked immunosorbent assay (ELISA) is also being used for BPA measurement. In this study, we verified whether ELISA is suitable for measuring human samples, namely, serum and urine, by comparing the ELISA results with those obtained by liquid chromatography with multichannel colometric electrochemical detection (LC/ECD) and liquid chromatography coupled to a mass spectrometer (LC/MS/MS). Results of the measurement with LC/ECD showed urinary BPA concentrations to be 1.92 [1.45] +/- 1.99 (mean [median] +/- standard deviation) ng BPA/mL without the correction of urine volume and 1.20 [0.90] +/- 1.10 mug BPA/g creatinine; however, in serum, free and total BPA were not detected. In both samples, a good correlation of the values with the methods was not found. ELISA is one of the powerful measurement methods, since it is convenient and useful for screening bulk quantities. At this point, however, ELISA is not suitable for BPA measurement in human samples because of low levels of BPA in human samples, matrix effect, and specificity of anti-BPA antibody.

Ethanol extract of Cyclolepis genistoides D. Don (palo azul) induces formation of myotubes, which involves differentiation of C2C12 myoblast cells.

In this study, we examined the cell differentiation effect of an ethanol extract of Cyclolepis genistoides D. Don, a herbaceous perennial belonging to the family Asteraceae (vernacular name: palo azul). Palo azul has numerous physiological effects that contribute to the prevention of metabolic syndromes, although the mechanism remains unclear. We previously suggested that palo azul has antidiabetic activity via an adipose differentiation effect. Here, we focused on whether palo azul promoted the differentiation of myoblasts. The mouse muscle myoblast cell line C2C12 was cultured and differentiated using horse serum with or without an ethanol extract of palo azul (12.5-200 µg/mL). Quantitative real-time polymerase chain reaction was performed to evaluate differentiation markers, including insulin-like growth factor-1 and myogenin. To evaluate myotube formation, myosin heavy-chain (MHC) expression and localization were detected by immunohistochemistry. Palo azul increased the expression of the differentiation markers. Furthermore, immunohistochemistry analysis revealed increased formation of MHC myotubes after palo azul treatment along with increased diameter and fusion indices of the myotubes. The expression level of MHC was also increased. In conclusion, palo azul may increase muscle mass in the body and improve insulin resistance conditions by facilitating the formation of myotubes by promoting myocyte differentiation.

Necessity to measure PCBs and organochlorine pesticide concentrations in human umbilical cords for fetal exposure assessment.

Three types of tissue samples--umbilical cord (UC), umbilical cord serum (CS), and maternal serum (MS)--have often been used to assess fetal exposure to chemicals. In order to know the relationship of contamination between mothers and fetuses, we measured persistent chemicals in comparable sets of the three tissue samples. Also, we analyzed the association between the chemicals in maternal and fetal tissues to know which tissue is the best sample for fetal exposure assessment. On a wet basis, the chemical concentrations were of the order MS > CS > UC, except for some chemicals such as cis-chlordane and endosulfan. On a lipid basis, the concentrations in UC were nearly equal or often higher than in MS, but the concentrations in CS were usually lower than in others. Hexachlorocyclohexanes and penta-, hexa-, and heptachlorinated biphenyls showed an association between the concentrations in UC versus MS, and UC versus CS. These chemicals also showed high correlation coefficients between the chemical concentrations in UC of first babies and maternal age. These chemicals were closely related to each other when grouped on the basis of their concentrations using cluster analysis. In conclusion, we insist that UC is the best sample to assess fetal contamination status of persistent chemicals. There is a possibility that the assessment based on the contamination levels in CS result in an underestimation.

Protective effect of young green barley leaf (Hordeum vulgare L.) on restraint stress-induced decrease in hippocampal brain-derived neurotrophic factor in mice.

BACKGROUND: Many health experts support the hypothesis that stressful lifestyles are the leading cause of illness, like depression. Therefore, from the standpoint of preventive medicine, it is important to reduce stress. Young green barley leaves are a good natural source of vitamins and minerals, and their juice is widely consumed as a functional food for health reasons in Japan. This study investigated the protective effect of young green barley leaves for stress control. MATERIALS AND METHODS: ICR outbred mice were exposed to 3-h sessions of restraint stress. Young green barley leaves (400 and 1,000 mg/kg) were administered orally 1 h before the sessions for 5 days. To analyze voluntary behavior, wheel-running activity was monitored during the dark period. Brain-derived neurotrophic factor (BDNF) messenger RNA (mRNA) expression in the whole hippocampus was measured by real-time quantitative polymerase chain reaction. RESULTS: Restraint stress resulted in a significant decrease in voluntary wheel-running behavior, but this decrease was ameliorated by the administration of young green barley leaves. The leaves also enhanced the decreased levels of BDNF mRNA induced by restraint stress; in particular, a significant protective effect was shown in the exon IV variant as compared to vehicle control mice. CONCLUSION: The findings suggest that young green barley leaves have potent anti-stress properties, as evidenced by preventing decreases in the levels of voluntary wheel-running activity and hippocampal BDNF mRNA in response to restraint stress. Our findings support the possibility that supplementation with young green barley leaves might be beneficial for preventing stress-related psychiatric disorders like depression.

Temporal changes in testis weight during the past 50 years in Japan.

The ever-increasing presence of environmental toxicants and their disruptive effect on the reproductive systems of wildlife raises the question of possible damage to the human reproductive system. Using medicolegal data from over 20,000 Japanese men subjected to necropsy from 1948 to 1998, we investigated temporal changes in testis weight to find possible evidence of male reproductive disorders. We also carried out a histological examination of 747 testes collected from 1978 to 1998. Our detailed analyses of the development of testis weight over the past 50 years have revealed four clear phenomena: (i) the age at which testis weight reaches its maximum has decreased; (ii) peak weight showed a general increase until it started to decline in boys born after 1960; (iii) the decline-rate at which testis weight decreases after its peak has greatly accelerated; and (iv) the onset of increasing testis weight of boys has occurred at a progressively younger age. Our quantitative analyses of testis weight indicate the possibility of a subtle reproductive disorder in Japanese men, especially in those born after 1960. Together with the accelerated development and decline in testis weight during the past 50 years, the decline in peak weight might be indicative of a subtle interference of environmental toxicants with male reproductive organogenesis.

Long-term alteration of gene expression without morphological change in testis after neonatal exposure to genistein in mice: toxicogenomic analysis using cDNA microarray.

In this study, we carried out toxicogenomic analysis using in-house cDNA microarray to ascertain the long-term effects of neonatal exposure to genistein, also known as phytoestrogen, on testicular gene expression in mice. Male ICR mice, 1 day after birth, were exposed for 5 days to genistein (1000 microg/mouse/day) or diethylstilbestrol (DES) (50 microg/mouse/day), used as an example of a potent estrogen, and their testes were used when they were 12 weeks old. Since exposure to DES was been reported to induce morphological changes and alteration of gene expression in reproductive organs, DES was used as a positive control. Genistein-treated mice did not show any histological abnormalities or increased apoptotic cells in testes, but these abnormalities and increases were found in DES-treated mice. On the other hand, mRNA expression analysis using in-house cDNA microarray revealed that 2 down-regulated genes (GeneBank accession No. W49392 and AI430907) were detected in genistein-treated mouse testes. Moreover, real-time PCR analysis revealed that mRNAs of the W49392 gene, estrogen receptor alpha (ERalpha) and androgen receptor (AR), were down-regulated in the testes of both genistein-treated and DES-treated mice. In our present study using toxicogenomic analysis, long-term alteration in testicular mRNA expression, without morphological change in testes, was detected after neonatal treatment with genistein, indicating that the W49392 gene, in addition to ERalpha and AR, might be useful as a biological marker for predicting the effects of neonatal exposure to DES and genistein.

Epigenetic alteration by the chemical substances, food and environmental factors.

Epigenetic alteration is one of the most important mechanisms for gene regulation; however, it is not changes in gene function with DNA sequence changes. Recently, epigenetics were studied in the wide ranging fields of research. In the present review, we introduce recent studies on epigenetic alteration, especially DNA methylation, by chemical exposure, food intake and environmental factors. In addition, we introduced our results on alteration of DNA methylation by transient exposure of neonatal mice to diethylstilbestrol. As these data suggest that chemical exposure, food intake and environmental factors are responsible for epigenetic alteration, we insist the necessity of the new risk assessment focusing on epigenetic alteration. (Reprod Med Biol 2004; 3: 115-121).

Polychlorinated biphenyl levels in the blood of Japanese individuals ranging from infants to over 80 years of age.

Individuals' exposure to various persistent organic pollutants (POPs), including polychlorinated biphenyls (PCBs), and its adverse health effects have been a cause of concern. We measured blood PCB concentrations from samples taken from 507 Japanese individuals ranging from infants to those over 80 years of age. The blood PCB levels increased with age for both male (Spearman's r = 0.69, p < 0.001) and female (Spearman's r = 0.70, p < 0.001) participants. Adult men and nulliparous women showed similar increases with age. However, the PCB levels of multiparous women were lower than those of nulliparous women in their thirties (p = 0.005), probably because the PCBs were transferred from the mothers to their children during pregnancy and lactation. Among infants (<2 years of age), some had as high levels of accumulated PCB levels as those in adults >30 years of age. In some cases, the PCB levels were over 0.8 ng/g wet weight, similar to levels observed in adults over 50 years of age. In the future, it will be necessary to do research on the health of the children who are exposed by high concentration level of POPs.

Cyclolepis genistoides D. Don (palo azul) promotes differentiation of adipocytes and regulates adipokine expression.

Cyclolepis genistoides D. Don is a herbaceous perennial belonging to the family Asteraceae, and its vernacular name is "palo azul" (palo). Palo has been reported to exhibit many physiological effects that contribute to the prevention of metabolic syndromes, although its mechanism is unclear. Among palo's various activities, we investigated the hypothesis that palo promotes adipocytes differentiation and regulates adipokine profiles in 3T3-L1 adipocytes by modulation of peroxisome proliferator-activated receptor (PPAR) γ, a major regulator of adipose differentiation. 3T3-L1 adipocytes were cultured and differentiated in Dulbecco modified Eagle medium with 50 to 200 µg/mL palo for 7 days or were cultured with palo without differentiation protocol for 14 days. Palo down-regulated the expression of 2 types of expressed/secreted adipokines, leptin and resistin, in a concentration-dependent manner. Under a nondifferentiated condition, palo promoted the accumulation of lipid droplets in cells. Real-time polymerase chain reaction and luciferase reporter assay showed that palo up-regulated expression and transcriptional activity of PPARγ. Furthermore, palo increased the expression of insulin-sensitizing adipokine, adiponectin, which is a directly target of PPARγ, both at the messenger RNA level and at the protein level. In summary, palo demonstrated the potential to improve insulin resistance by promoting adipocyte differentiation via PPARγ activation. Results suggest an increase in adiponectin secretion and a decrease in insulin-resistant factors such as leptin and resistin.

Antidepressant-like effects of young green barley leaf (Hordeum vulgare L.) in the mouse forced swimming test.

BACKGROUND: Young green barley leaf is one of the richest sources of antioxidants and has been widely consumed for health management in Japan. In this study, we examined whether oral administration of young green barley leaf has an antidepressant effect on the forced swimming test in mice. MATERIALS AND METHODS: Mice were individually forced to swim in an open cylindrical container, one hour after oral administration of young green barley leaf (400 or 1000 mg / kg) or imipramine (100 mg / kg). Expression of mRNA for nerve growth factor (NGF), brain-derived neurotrophic factor, and glucocorticoid receptor in the brain was analyzed using real-time quantitative polymerase chain reaction (PCR). RESULTS: There was a significant antidepressant-like effect in the forced swimming test; both 400 and 1000 mg / kg young green barley leaves, as well as the positive control imipramine (100 mg / kg), reduced the immobility duration compared to the vehicle group. The expression of mRNA for NGF detected in the hippocampus immediately after the last swimming test was higher than that in the non-swimming group (Nil). Oral administration of imipramine suppressed this increase to the level of the Nil group. Young green barley leaf (400 and 1000 mg / kg) also showed a moderate decrease in the expression of mRNA for NGF, in a dose-dependent manner. CONCLUSION: Oral administration of young green barley leaf is able to produce an antidepressant-like effect in the forced swimming test. Consequently it is possible that the antidepressant-like effects of the young green barley leaf are, at least in part, mediated by an inhibition of the increase in the hippocampus levels of NGF.

Confirmation of polychlorinated biphenyl (PCB) distribution in the blood and verification of simple quantitative method for PCBs based on specific congeners.

We measured the concentration of each polychlorinated biphenyl (PCB) congener in whole blood, plasma and blood cells, and investigated the distribution of PCBs in human blood using high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS). The PCB concentrations in plasma and whole blood in terms of lipid concentrations were almost equal, with a correlation coefficient of r=0.972. In the blood, the ratio of PCBs in blood cells to those in plasma was generally about 1:9 and the congener distribution patterns in blood cells and plasma were similar. We performed verification of a simple mass screening method by obtaining information on the main PCB congeners for investigations on human accumulation and exposure. The total concentration of the seven PCB congeners (UNEP-7) proposed to the United Nations Environment Programme (UNEP) by Muir and Morita was about 50% of the total concentration of all PCB congeners, and UNEP-30 was about 80%. The seven main congeners in the blood (MCB-7) showed a value that was about 60%, and MCB-30 showed a value that was about 90%. Determinations with the main congeners in the blood showed a correlation of r=0.990 or more between the main eight congeners (MCB-7 plus #74) and the total PCB concentration for all congeners. The results suggest that, although total PCB concentration can be effectively estimated from the main seven congeners, the main eight congeners would be preferable, and that the use of these congeners in the simple mass screening method would be effective for populations in areas uncontaminated by PCBs.