10 research outputs found
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
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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
Determinants of Serum Polybrominated Diphenyl Ether (PBDE) Levels among Pregnant Women in the CHAMACOS Cohort
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