1,462 research outputs found
Total PCBs, Dioxin-Furan TEQs and Total Mercury Concentrations in Mink In and Out of the Rochester Embayment Area of Concern Near and Inland from the Shore of Lake Ontario
In terms of reproductive and other adverse outcomes after exposure to polychlorinated biphenyls (PCBs), dioxins and furans, the mink (Mustela vison) is one of the most sensitive mammals. Our objective was to determine if there are differences in the concentrations of total mercury (Hg), total PCBs, and dioxin-furan toxic equivalents (TEQs) between mink living in and out of the Rochester Embayment of Lake Ontario (RELO) Area of Concern (AOC) and between mink living near the shore of Lake Ontario and inland. Concentrations of total Hg in brain, total PCB and dioxin-furan TEQ in adipose, and total PCB in liver were significantly higher for mink living near the shore of Lake Ontario than inland. For mink living in and out of the AOC, differences in total PCB and dioxin-furan TEQ in adipose and liver were substantial but not significant. Correlations between concentrations of total Hg, total PCB, and dioxin-furan TEQ in mink were high. Our results suggest that contamination of mink living near the southern shore of Lake Ontario primarily comes from contact with the Lake Ontario food web, not from sources in the RELO AOC
Model Estimates Bioaccumulation of Total PCBs, Dioxin-Furan TEQs, and Total Mercury in Mink Liver Based on Concentrations in Lake Ontario Water
We used stable isotope analysis and a bioaccumulation model to estimate concentrations of total polychlorinated biphenyls (PCB), dioxin-furan toxic equivalents (TEQ), and total mercury (Hg) in mink and to compare predicted ranges with their chemical concentrations in mink liver (PCB, TEQ) and brain (Hg). Actual concentrations were within predicted bounds for total PCB, dioxin-furan TEQ, and Hg except in two cases (lowest PCB and highest Hg) which were very close to predicted bounds. Based on 15N analysis, the trophic level of mink ranged from 3.4 to 3.9. Animals at the upper end of the range were exposed to Lake Ontario water and its food web while those at the lower end were captured at inland locations. Because of the complexity of wetland (an important habitat for mink in this study) food webs with pelagic, littoral, and terrestrial carbon sources and overlapping 13C signatures, whether the origins of mink diets were aquatic or terrestrial could not be determined. We have established a non-destructive biomonitoring tool to reasonably estimate concentrations of total PCB, TEQ and total Hg in mink tissues as concentrations of these chemicals change in their water supply
Histological Lesions in Mink Jaws are a Highly Sensitive Biomarker of Effect after Exposure to TCDD-like Chemicals: Field and Literature-based Confirmations
The mink (Mustela vison) is one of the most sensitive mammals to 2,3,7,8 tetrachlorodibenzo-p-dioxin (TCDD)-like chemicals. By literature review we established that a histological lesion of the jaw bone of mink, evidenced by squamous epithelial hyperplasia in the gingival tissue that forms nests or cords that infiltrate the periodontal ligament and alveolar bone causing osteolysis of the mandible and maxilla that could lead to squamous cell carcinoma, is the most sensitive known biomarker of effect following exposure of mink to TCDD-like chemicals. Lesions have been observed when total TCDD toxic equivalents (TEQ: dioxins, furans, co-planar polychlorinated biphenyls or PCBs) in liver exceed 40 ng/kg-ww or when total PCB exceeds 1,698 ng/g-ww. This is the second report of histological evidence of this lesion in wild-caught mink, and it is the first report of the lesion being grossly detectable in naturally exposed mink. Some mink living near the south shore of Lake Ontario (exposed to the lake’s food web) but not inland mink (not exposed to the lake’s food web) accumulate more than 40 ng total TEQ/kg or 2 1,698 ng total PCB/kg in liver. Because of its sensitivity, the jaw lesion biomarker is very useful for assessing the health of wildlife populations exposed to TCDD-like chemicals
Visible-light-induced intramolecular charge transfer in the radical spirocyclisation of indole-tethered ynones
Indole-tethered ynones form an intramolecular electron donor-acceptor complex that can undergo visible-light-induced charge transfer to promote thiyl radical generation from thiols. This initiates a novel radical chain sequence, based on dearomatising spirocyclisation with concomitant C-S bond formation. Sulfur-containing spirocycles are formed in high yields using this simple and mild synthetic protocol, in which neither transition metal catalysts nor photocatalysts are required. The proposed mechanism is supported by various mechanistic studies, and the unusual radical initiation mode represents only the second report of the use of an intramolecular electron donor-acceptor complex in synthesis
Two-dimensional carrier density distribution inside a high power tapered laser diode
The spontaneous emission of a GaAs-based tapered laser diode emitting at lambda = 1060 nm was measured through a window in the transparent substrate in order to study the carrier density distribution inside the device. It is shown that the tapered geometry is responsible for nonuniform amplification of the spontaneous/stimulated emission which in turn influences the spatial distribution of the carriers starting from below threshold. The carrier density does not clamp at the lasing threshold and above it the device shows lateral spatial hole-burning caused by high stimulated emission along the cavity center. (C) 2011 American Institute of Physics. (doi: 10.1063/1.3596445
In vivo and ex vivo regulation of visfatin production by leptin in human and murine adipose tissue : role of mitogen-activated protein kinase and phosphatidylinositol 3-kinase signaling pathways
Visfatin is an adipogenic adipokine with increased levels in obesity, properties common to leptin. Thus, leptin may modulate visfatin production in adipose tissue (AT). Therefore, we investigated the effects of leptin on visfatin levels in 3T3-L1 adipocytes and human/murine AT, with or without a leptin antagonist. The potential signaling pathways and mechanisms regulating visfatin production in AT was also studied. Real-time RT-PCR and Western blotting were used to assess the relative mRNA and protein expression of visfatin. ELISA was performed to measure visfatin levels in conditioned media of AT explants, and small interfering RNA technology was used to reduce leptin receptor expression. Leptin significantly (P < 0.01) increased visfatin levels in human and murine AT with a maximal response at leptin 10–9 M, returning to baseline at leptin 10–7 M. Importantly, ip leptin administration to C57BL/6 ob/ob mice further supported leptin-induced visfatin protein production in omental AT (P < 0.05). Additionally, soluble leptin receptor levels rose with concentration dependency to a maximal response at leptin 10–7 M (P < 0.01). The use of a leptin antagonist negated the induction of visfatin and soluble leptin receptor by leptin. Furthermore, leptin-induced visfatin production was significantly decreased in the presence of MAPK and phosphatidylinositol 3-kinase inhibitors. Also, when the leptin receptor gene was knocked down using small interfering RNA, leptin-induced visfatin expression was significantly decreased. Thus, leptin increases visfatin production in AT in vivo and ex vivo via pathways involving MAPK and phosphatidylinositol 3-kinase signaling. The pleiotropic effects of leptin may be partially mediated by visfatin
Comparison of polychlorinated biphenyl levels across studies of human neurodevelopment.
Polychlorinated biphenyls (PCBs) are persistent pollutants that are ubiquitous in the food chain, and detectable amounts are in the blood of almost every person in most populations that have been examined. Extensive evidence from animal studies shows that PCBs are neurotoxins, even at low doses. Interpretation of human data regarding low-level, early-life PCB exposure and subsequent neurodevelopment is problematic because levels of exposure were not similarly quantified across studies. We expressed the exposure levels from 10 studies of PCB and neurodevelopment in a uniform manner using a combination of data from original investigators, laboratory reanalyses, calculations based on published data, and expert opinion. The mainstay of our comparison was the median level of PCB 153 in maternal pregnancy serum. The median concentration of PCB 153 in the 10 studies ranged from 30 to 450 ng/g serum lipid, and the median of the 10 medians was 110 ng/g. We found that (a)) the distribution of PCB 153 exposure in most studies overlapped substantially, (b)) exposure levels in the Faroe Islands study were about 3-4-fold higher than in most other studies, and (c)) the exposure levels in the two recent U.S. studies were about one-third of those in the four earlier U.S. studies or recent Dutch, German, and northern Québec studies. Our results will facilitate a direct comparison of the findings on PCBs and neurodevelopment when they are published for all 10 studies
A new measurement of the Collins and Sivers asymmetries on a transversely polarised deuteron target
New high precision measurements of the Collins and Sivers asymmetries of
charged hadrons produced in deep-inelastic scattering of muons on a
transversely polarised 6LiD target are presented. The data were taken in 2003
and 2004 with the COMPASS spectrometer using the muon beam of the CERN SPS at
160 GeV/c. Both the Collins and Sivers asymmetries turn out to be compatible
with zero, within the present statistical errors, which are more than a factor
of 2 smaller than those of the published COMPASS results from the 2002 data.
The final results from the 2002, 2003 and 2004 runs are compared with naive
expectations and with existing model calculations.Comment: 40 pages, 28 figure
A systematic validation of hot Neptunes in TESS data
We statistically validated a sample of hot Neptune candidates applying a
two-step vetting technique using DAVE and TRICERATOPS. We performed a
systematic validation of 250 transit-like events in the Transiting Exoplanet
Survey Satellite (TESS) archive in the parameter region defined by d
and . Through our analysis, we identified 18 hot
Neptune-sized candidates, with a false positive probability . Nine of
these planet candidates still need to be confirmed. For each of the nine
targets we retrieved the stellar parameters using ARIADNE and derived
constraints on the planetary parameters by fitting the lightcurves with the
juliet package. Within this sample of nine candidates, we statistically
validated (i.e, with false positive probability < ) two systems (TOI-277
b and TOI-1288 b) by re-processing the candidates with TRICERATOPS along with
follow-up observations. These new validated exoplanets expand the known hot
Neptunes population and are high-priority targets for future radial velocities
follow-up.Comment: 24 pages, 20 figures. Accepted for publication on MNRA
- …