Large-scale evaluation of the current level of polybrominated diphenyl ethers (PBDEs) in breast milk from 13 regions of Japan

Polybrominated diphenyl ethers (PBDEs) were measured in 2004 in 105 breast milk samples collected from 13 regions of Japan (Hokkaido, Akita, Miyagi, Tokyo, Gifu, Fukui, Kyoto, Hyogo, Wakayama, Shimane, Yamaguchi, Kochi and Okinawa). Six congeners (BDE-28, BDE-47, BDE-99, BDE-100, BDE-153 and BDE-154) were determined by gas chromatography /mass spectrometry (GC/MS). Total PBDE levels ranged from 0.01 to 23.0 ng/g lipid (geometric mean (GM), 1.34 ng/g lipid). BDE-47 (GM, 0.66 ng/g lipid, 59% of sigmaPBDE) was the most abundant congener present in breast milk and was detected in 99% of the samples. Total PBDE levels were higher in northern Japan than in other regions. We analyzed the effects of occupation, age, smoking status, alcohol consumption and number of deliveries on total PBDE levels. None of these factors were significantly associated with the level of PBDEs. The present study revealed that the current level of exposure to PBDEs in Japan is lower than that in the USA or Sweden. GMs (ng/g lipid) (GSD, geometric standard deviation) and medians (ng/g lipid) of PBDE levels in each district are as follows: Hokkaido 2.70 (1.70), 2.74; Akita 4.49 (2.19), 5.44; Miyagi 1.77 (4.37), 1.11; Tokyo 1.39 (2.09), 1.63, Gifu 2.83 (4.79), 2.23; Fukui 1.05 (2.34), 1.18; Kyoto 1.31 (2.95), 1.33; Hyogo 1.02 (2.69), 0.88; Wakayama 1.33 (3.80), 1.70; Shimane 0.83 (2.51), 0.66; Yamaguchi 1.74 (2.82), 1.76; Kochi 0.50 (2.69), 0.74 and Okinawa 1.91 (2.75), 1.22. This is the first large-scale study of current PBDE levels in breast milk in Japan.     

Contamination status of persistent organochlorines in human breast milk from Japan: recent levels and temporal trend

Contamination levels of persistent organochlorines (OCs) such as polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), biphenyls (PCBs), dichlorodiphenyltrichloroethane and its metabolites (DDTs), hexachlorocyclohexane isomers (HCHs), hexachlorobenzene (HCB), and chlordane compounds (CHLs) was examined in human breast milk collected during 2001-2004 from Fukuoka prefecture in Japan. The concentrations of OCs such as dioxins and related compounds, DDTs, CHLs and HCB in human breast milk from primiparae were comparable to or slightly higher than the data obtained during 1998, indicating that the levels of these contaminants in Japanese human breast milk have not decreased since 1998 and Japanese are continuously exposed to these chemicals, presumably via fish intake. In addition, OC levels in human breast milk from primiparae were significantly higher than those from multiparae, implying elimination of OCs via lactation. Furthermore, significant positive correlations were observed between levels of OCs in human breast milk and the age of primiparae. These results indicate that the mothers with higher age may transfer higher amounts of OCs to the first infant than to the infants born afterwards through breast-feeding, and hence the first born children might be at higher risk by OCs.     

Isolation of antifungal bacteria from Japanese fermented soybeans, natto

An inhibitory effect of a traditional Japanese fermented food, natto, was found against plant pathogens such as Rhizoctonia solani and Fusarium oxysporum, and the bacteria which showed inhibition were isolated from the natto. Among isolated bacteria, BC-1 and GAc exhibited a strong antagonistic effect in vitro against plant pathogens on an agar medium. The supernatant of bacterial culture also showed strong activity against R. solani, which meant the antimicrobial substances were produced and secreted into the medium. Both of the bacteria were estimated as Bacillus amyloliquefaciens from a partial sequence of the 16s rRNA gene. High performance liquid chromatography analysis clearly showed the production of the lipopeptide antibiotic iturin A by BC-1 and GAc.     

Organohalogen compounds in human breast milk from Republic of Buryatia, Russia

Human breast milk samples collected during 2003/04 in Buryatia, a Russian autonomous republic, were analyzed in order to assess human exposure to organohalogen compounds including organochlorine pesticides, polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs). When compared with available worldwide data, levels of HCB (23-880 ng/g lipid wt.), PCBs (69-680 ng/g lipid wt.), and HCHs (100-3700 ng/g lipid wt.) were relatively high, indicating elevated human exposure to these organochlorines (OCs) in Buryatia. In contrast to OCs, PBDE concentrations were low (0.46-1.7 ng/g lipid wt.). Out of 14 BDE congeners analyzed, BDE-28, BDE-47, BDE-100, BDE-153, BDE-197, and BDE-207 were detected. Estimated daily intakes (EDIs) of HCHs, HCB, CHLs, and PCBs by infants solely from human milk for 100%, 43%, 34%, and 17% of the samples, respectively, exceeded guideline thresholds. Although high EDIs raise concern for possible toxic effects of OCs, women in Buryatia are recommended to breastfeed due to numerous advantages of breastfeeding for mother and child.     

Extended mutualism between termites and gut microbes: nutritional symbionts contribute to nest hygiene

All higher eukaryotes have established symbiotic relationships with diverse microorganisms. One of the most well-characterized symbiotic systems is that of termites and their intestinal microorganisms, which digest cellulose. Recently, diverse types of symbioses between gut microbes and host organisms including humans have received growing attention for various features of their complex interactions beyond nutrition. In termites, researchers are beginning to explore such function of gut symbionts, but only the contribution to internal immunity against entomopathogen is known in a few species. Here, we report that gut symbionts of the dampwood termite Zootermopsis nevadensis protect nests from the spread of the commensal bacterium Serratia marcescens, which has pathogenic potential. Defaunated termites dispersed S. marcescens in the surrounding environment by feeding on the bacteria, which then survived passage through their alimentary tracts, while non-defaunated termites did not. Loss of gut symbionts caused a significant reduction in intestinal acetate, which is an important carbon source for termites. Culture experiments showed that acetate had significant inhibitory effects on S. marcescens at a concentration as low as 12 mM, which indicated that the intestinal acetate of non-defaunated termites (40–130 mM) was capable of suppressing this bacterium. These results suggest that digestive derivatives produced by intestinal symbionts play an essential role in nest hygiene in addition to their nutritional function for termites. Our study provides a better understanding of the multifunctionality of symbiotic relationships in diverse organisms beyond nutrition.     

Soil contamination by halogenated polycyclic aromatic hydrocarbons from open burning of e-waste in Agbogbloshie (Accra,Ghana)

Detailed composition of chlorinated and brominated polycyclic aromatic hydrocarbons (Cl-PAHs and Br-PAHs) generated during informal recycling of e-waste and their toxic relevance are still poorly understood. This study investigated the occurrence of Cl-PAHs and Br-PAHs in surface soil samples from the Agbogbloshie e-waste recycling site (Accra, Ghana) using quantitative gas chromatography–mass spectrometry (GC–MS) and comprehensive two-dimensional GC–time-of-flight mass spectrometry (GC × GC–ToFMS) profiling. The results of GC–MS analysis showed elevated concentrations in open e-waste burning areas (160–220 and 19–46 ng/g dry weight for Cl- and Br-PAHs, respectively) with substantial contribution from unidentified compounds (respectively, more than 36 and 70%, based on the total areas of potential peaks). Cl- and Br-PAHs from e-waste burning had a distinctive composition dominated by ring–ring compounds. Several homologue groups not monitored with GC–MS were found using GC × GC–ToFMS: PAHs with up to 5Cl or 3Br, mixed halogenated PAHs and chlorinated methylPAHs. The dioxin-like toxic equivalents of the identified Cl-/Br-PAHs in soils, estimated from their in vitro AhR agonist potencies relative to 2,3,7,8-tetrachlorodibenzo-p-dioxin, were much lower than the range reported for chlorinated and brominated dioxins. However, the toxicity of the unidentified halogenated PAHs remained unclear.     

Population dynamics of Müllerian mimicry under interspecific competition

We ask what the effects of mutualism on population dynamics of two competitive species are. We model the population dynamics of mutualistic interactions with positive density- and frequency-dependences. We specifically assume the dynamics of Müllerian mimicry in butterflies, where the mortality of both species is reduced depending on the relative frequency of the other species. We assume that the two species are under Lotka–Volterra density-dependent competition. The equilibria are compared with the cases of competition alone. Unlike the traditional model of positive density-dependence, population explosion does not appear in the current dynamics, but the new equilibrium is simply achieved. It is because the effects of positive density- or frequency-dependence are restricted to parts of mortality. Both positive density- and frequency-dependences do promote coexistence of the mimetic species. However, the two models show a distinctive difference for coexistence. The effects of positive density-dependence are rather limited. In contrast, positive frequency-dependence always promotes coexistence, irrespective of environmental conditions. The results may imply that the evolutionary origin of Müllerian mimicry may depend on frequency-dependence (and density-dependence), but that its current population dynamics may depend solely on density-dependence. The role of frequency- and density-dependences on evolutionary dynamics is an open question.