Mutual benefits from the symbiotic coexistence between bipolar Euplotes cells and Parafrancisella bacteria

Ciliates are common carriers of cytoplasmic bacteria, however little is known about the molecular basis of the symbiotic relationships with their host. Working on interbreeding bipolar (Arctic and Antarctic) populations of the ciliate Euplotes nobilii, members of these populations were found to stably host Parafrancisella γ-proteobacteria. These bacteria (originally isolated from an Antarctic population of another Euplotes species, E. petzi) are phylogenetically related to pathogenic Francisella species which are well known for their capacity to colonize eukaryotic cells, causing animal diseases known as francisellosis. The finding that Parafrancisella/Euplotes associations are common in polar marine environments suggested that both microbial partners benefit from their stable partnership. To inquire into mutual advantages, we carried out a genomic analysis of E. nobilii and its Parafrancisella symbionts. In the E. nobilii genome, no gene was detected encoding methionine sulfoxide reductase of type A (MsrA), an enzyme which is essential to face damages from oxidative stress imposed by the high (saturated) oxygen concentrations of the polar sea waters. At the same time, the Parafrancisella genome revealed genes encoding MsrA sequences endowed with a N-terminal signal peptide for the secretion into the host’s cytoplasm, and the effectiveness of this secretion was further supported by the identification of a complete gene set coding for the so-called ‘Type VI Secretion System’ that many Gram-negative bacteria use to transfer their proteins into target cells. On the other side, in the Parafrancisella genome no gene encoding enzymes involved in the biosynthetic pathways of cysteine, lysine, methionine, and threonine was detected, implying that Parafrancisella cells rely on their E. nobilii host to obtain these four essential amino acids

Temporal Variability of Polybrominated Diphenyl Ether (PBDE) Serum Concentrations over One Year

Polybrominated diphenyl ethers (PBDEs) are flame retardant chemicals used in consumer products. They are common contaminants in human serum and associated with adverse health effects. Our objectives were to characterize PBDE serum concentrations in a New England cohort and assess temporal variability of this exposure biomarker over a one-year period. We collected three repeated measurements at six-month intervals from 52 office workers from the greater Boston (MA, United States) area from 2010 to 2011. The intraclass correlation coefficient for BDEs 28, 47, 99, 100, and 153 ranged from 0.87 to 0.99, indicating that a single serum measurement can reliably estimate exposure over a one-year period. This was true for both lipid adjusted and nonlipid adjusted concentrations. The kappa statistics, quantifying the level of agreement of categorical exposure classification, based on medians, tertiles, or quartiles ranged from 0.67 to 0.90. Some congeners showed nonsignificant increases from sampling round 1 (winter) to round 2 (summer) and significant decreases from round 2 to round 3 (winter). This study highlights the high reliability of a single serum PBDE measurement for use in human epidemiologic studies

Polybrominated Diphenyl Ethers and Other Persistent Organic Pollutants in Serum Pools from the National Health and Nutrition Examination Survey: 2001–2002

Polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), and persistent pesticides have been measured in serum pools from participants 3–5, 6–11, 12–19, 20–39, 40–59, and ≥60 years of age from the 2001–2002 National Health and Nutrition Examination Survey. For 2,2′,4,4′-tetrabromodiphenyl ether (PBDE-47), the unweighted (not adjusted for sampling weights) arithmetic mean concentration (±95% confidence interval) was 3.4 times higher in 3–5-year-olds (216 ± 30 ng/g of lipid) than in 12–19-year-olds (64 ± 11 ng/g of lipid), with no apparent change with increasing age for adults ≥20 years of age. By contrast, unweighted arithmetic mean concentrations of traditional persistent organic pollutants (POPs) such as hexachlorobenzene (HCB) and 2,2′,3,3′,4,4′,5,5′-octachlorobiphenyl (PCB194) were 2- and 20-fold higher, respectively, in persons ≥60 years than in 12–19-year-old adolescents. Findings suggest higher exposures to PBDEs but lower exposures to traditional POPs in 3–5-year-old children than in adults

Polybrominated Diphenyl Ethers, Polychlorinated Biphenyls, and 2,2-Bis(4-chlorophenyl)-1,1-dichloroethene in 7- and 9‑Year-Old Children and Their Mothers in the Center for the Health Assessment of Mothers and Children of Salinas Cohort

We report longitudinal serum concentrations of select persistent organic pollutants (POPs) in children at ages 7 and 9 years and in their mothers prenatally and again when the children were 9 years old. The participating families were enrolled in the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS), a longitudinal birth cohort study of low-income Hispanic families residing in the Salinas Valley, California. We observed decreasing concentrations in the mothers with year of serum collection (2009 vs 2011) for six out of seven polybrominated diphenyl ether (PBDE) congeners and for 2,2′,4,4′,5-pentachlorobiphenyl (CB-99; <i>p</i> < 0.05). The 9-year-old children had similarly decreasing serum concentrations of all seven PBDE congeners, CB-99, and 2,2′,3,4,4′,5′- and 2,3,3′,4,4′,6-hexachlorobiphenyl (CB-138/158) with year of serum collection (2009 vs 2011; <i>p</i> < 0.05). In mixed effect models accounting for weight gain as the children aged from 7 to 9 years, we observed an annual decrease (−8.3% to −13.4%) in tri- to hexaBDE concentrations (<i>p</i> < 0.001), except for 2,2′,3,4,4′-tetrabromodiphenyl ether (BDE-85) and 2,2′,4,4′,5,5′-hexabromodiphenyl ether (BDE-153). The concentrations of these congeners were not associated with time of serum collection and instead showed an −0.9% to −2.6% decrease per kilogram of weight gain during the study period (<i>p</i> < 0.05). In the case of tetra- to heptachlorobiphenyls, we observed −0.5% to −0.7% decrease in serum concentration per kilogram of weight gain (<i>p</i> < 0.05) and −3.0% to −3.7% decrease in serum concentration per year of aging (<i>p</i> < 0.05), except for 2,3′,4,4′,5-pentachlorobiphenyl (CB-118) and 2,2′,4,4′,5,5′-hexachlorobiphenyl (CB-153), which were not associated with time of serum draw. 2,2-Bis­(4-chlorophenyl)-1,1-dichloroethene (<i>p</i>,<i>p</i>′-DDE) decreased −2.4%/kg of weight gain between the two sampling points (<i>p</i> < 0.001). These findings suggest that as children grow, dilution in a larger body size plays an important role in explaining reductions in body burden in the case of traditional POPs such as PCBs and <i>p</i>,<i>p</i>′-DDE. By contrast, in the case of PBDEs, reductions are likely explained by reduction in exposure, as illustrated by decreased concentrations in more recent years, possibly amplified by presumed shorter biological half-life than other POPs

Polybrominated Diphenyl Ethers, Polychlorinated Biphenyls, and Persistent Pesticides in Serum from the National Health and Nutrition Examination Survey: 2003–2008

Polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), and persistent pesticides have been measured in pooled samples representative of the general noninstitutionalized population of the United States. The pools were made from individual sera from the National Health and Nutrition Examination Survey (NHANES) during 2005/06 and 2007/08. The pooled concentrations have been contrasted to NHANES 2003/04 individual measurements to evaluate changes in concentration over time and within survey period differences among age groups, race/ethnicity groups (Mexican American, non-Hispanic Black, non-Hispanic White), and sex. The arithmetic mean serum concentrations of several PCB congeners decreased from NHANES 2003/04 through 2007/08. Larger percentage reductions were seen for younger subjects (12–19 years) compared with older subjects (≥60 years). For example, the arithmetic mean concentration of 2,2′,4,4′,5,5′-hexachlorobiphenyl (PCB-153) was 36% lower in 12–19 year old adolescents when comparing NHANES 2007/08 with 2003/04; while for subjects over the age of 60 a 14% lower concentration was seen, although, the 95% confidence intervals overlapped. Similarly, the arithmetic mean serum concentrations of tri- to hexaBDEs were lower in NHANES 2007/08 than in 2003/04; however, most confidence intervals of the arithmetic means overlapped. These findings suggest that a reduction in PBDE serum concentrations cannot yet be detected following the discontinuation of pentaBDE in 2004

Flame Retardant Exposure among Collegiate United States Gymnasts

Gymnastics training facilities contain large volumes of polyurethane foam, a material that often contains additive flame retardants such as PentaBDE. While investigations of human exposure to flame retardants have focused on the general population, potentially higher than background exposures may occur in gymnasts and certain occupational groups. Our objectives were to compare PentaBDE body burden among gymnasts to the general United States population and characterize flame retardants levels in gym equipment, air, and dust. We recruited 11 collegiate female gymnasts (ages 18–22) from one gym in the eastern United States. The geometric mean (GM) concentration of BDE-153 in gymnast sera (32.5 ng/g lipid) was 4–6.5 times higher than in the general United States population groups. Median concentrations of PentaBDE, TBB, and TBPH in paired handwipe samples were 2–3 times higher after practice compared to before, indicating the gymnasts contacted these flame retardants during practice. GM concentrations of PentaBDE, TBB, and TBPH were 1–3 orders of magnitude higher in gym air and dust than in residences. Our findings suggest that these collegiate gymnasts experienced higher exposures to PentaBDE flame retardants compared to the general United States population and that gymnasts may also have increased exposure to other additive flame retardants used in polyurethane foam such as TBB and TBPH

Excretion Profiles and Half-Lives of Ten Urinary Polycyclic Aromatic Hydrocarbon Metabolites after Dietary Exposure

Human exposure to polycyclic aromatic hydrocarbons (PAHs) can be assessed by biomonitoring of their urinary monohydroxylated metabolites (OH-PAHs). Limited information exists on the human pharmacokinetics of OH-PAHs. This study aimed to investigate the excretion half-life of 1-hydroxypyrene (1-PYR), the most used biomarker for PAH exposure, and 9 other OH-PAHs following a dietary exposure in 9 nonsmoking volunteers with no occupational exposure to PAHs. Each person avoided food with known high PAH-content during the study period, except for a high PAH-containing lunch (barbecued chicken) on the first day. Individual urine samples (<i>n</i> = 217) were collected from 15 h before to 60 h following the dietary exposure. Levels of all OH-PAHs in all subjects increased rapidly by 9–141-fold after the exposure, followed by a decrease consistent with first-order kinetics, and returned to background levels 24–48 h after the exposure. The average time to reach maximal concentration ranged from 3.1 h (1-naphthol) to 5.5 h (1-PYR). Creatinine-adjusted urine concentrations for each metabolite were analyzed using a nonlinear mixed effects model including a term to estimate background exposure. The background-adjusted half-life estimate was 3.9 h for 1-PYR and ranged 2.5–6.1 h for the other 9 OH-PAHs, which in general, were shorter than those previously reported. The maximum concentrations after barbecued chicken consumption were comparable to the levels found in reported occupational settings with known high PAH exposures. It is essential to consider the relatively short half-life, the timing of samples relative to exposures, and the effect of diet when conducting PAH exposure biomonitoring studies

Factors Associated with Serum Polybrominated Diphenyl Ether (PBDE) Levels Among School-Age Children in the CHAMACOS Cohort

Polybrominated diphenyl ethers (PBDEs) are a class of flame retardants historically used in textiles, furniture, and electronic products. Recent studies have documented widespread PBDE exposure to humans, with higher levels measured in children than adults. We analyzed 10 tri- to hepta-BDE congener levels in blood collected from 7-year old Mexican-American children living in an agriculture community in California (<i>n</i> = 272). The most frequently detected PBDE congeners in child serum were BDE-47, -99, -100, and -153, all of which were measured in >99% of the children. We used multiple linear regression models to examine associations between child total PBDE levels (ng/g lipid) and determinants of exposure. Factors positively associated with higher PBDE levels in the children were total PBDE levels in maternal serum during pregnancy, duration of exclusive breastfeeding, and having no safe places to play in their neighborhood. Child BMI was inversely associated with serum PBDE levels (regression p-values <0.05). Our findings confirm that exposure to the penta-BDE mixture is ongoing, and that Mexican-American children living in California may be experiencing higher PBDE exposure from their environment compared to children sampled from the general U.S. population. Additional research is needed to assess the health impacts of these exposures

Polybrominated Diphenyl Ethers, 2,2′,4,4′,5,5′-Hexachlorobiphenyl (PCB-153), and <i>p</i>,<i>p</i>′‑Dichlorodiphenyldichloroethylene (<i>p</i>,<i>p</i>′‑DDE) Concentrations in Sera Collected in 2009 from Texas Children

Polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs) and <i>p</i>,<i>p</i>′-dichlorodiphenyldichloroethylene (<i>p</i>,<i>p</i>′-DDE) have been measured in surplus serum collected in 2009 from a convenience sample of 300 Texas children (boys and girls) in the birth to 13 years of age range. Serum concentrations of traditional persistent organic pollutants such as 2,2′,4,4′,5,5′-hexachlorobiphenyl (PCB-153) and <i>p</i>,<i>p</i>′-DDE did not change consistently with age. By contrast, serum concentrations of tetra-, penta-, and hexa-BDEs were lowest in the youngest children (birth to two year old) and increased 3.0 to 7.9 times, depending on the analyte, for children in the >4 to 6 years of age group. From the apex concentration to the 10 to 13 years of age group, concentrations decreased significantly except for 2,2′,4,4′,5,5′-hexabromodiphenyl ether (PBDE-153), which also had a longer apex concentration of >4 to 8 years of age. This concentration trend for PBDE-153 is most likely due to a longer half-life of PBDE-153 than of other PBDE congeners. The observed PBDEs concentration patterns by age may be related, at least in part, to ingestion of residential dust containing PBDEs through hand-to-mouth behavior among toddlers, preschoolers, and kindergarteners. Further studies to characterize young children’s exposure to PBDEs are warranted and, in particular, to determine the lifestyle factors that may contribute to such exposures