Maternal characteristics associated with the dietary intake of nitrates, nitrites, and nitrosamines in women of child-bearing age: a cross-sectional study

<p>Abstract</p> <p>Background</p> <p>Multiple <it>N</it>-nitroso compounds have been observed in animal studies to be both mutagenic and teratogenic. Human exposure to <it>N</it>-nitroso compounds and their precursors, nitrates and nitrites, can occur through exogenous sources, such as diet, drinking water, occupation, or environmental exposures, and through endogenous exposures resulting from the formation of <it>N</it>-nitroso compounds in the body. Very little information is available on intake of nitrates, nitrites, and nitrosamines and factors related to increased consumption of these compounds.</p> <p>Methods</p> <p>Using survey and dietary intake information from control women (with deliveries of live births without major congenital malformations during 1997-2004) who participated in the National Birth Defects Prevention Study (NBDPS), we examined the relation between various maternal characteristics and intake of nitrates, nitrites, and nitrosamines from dietary sources. Estimated intake of these compounds was obtained from the Willet Food Frequency Questionnaire as adapted for the NBDPS. Multinomial logistic regression models were used to estimate odds ratios and 95% confidence intervals for the consumption of these compounds by self-reported race/ethnicity and other maternal characteristics.</p> <p>Results</p> <p>Median intake per day for nitrates, nitrites, total nitrites (nitrites + 5% nitrates), and nitrosamines was estimated at 40.48 mg, 1.53 mg, 3.69 mg, and 0.472 μg respectively. With the lowest quartile of intake as the referent category and controlling for daily caloric intake, factors predicting intake of these compounds included maternal race/ethnicity, education, body mass index, household income, area of residence, folate intake, and percent of daily calories from dietary fat. Non-Hispanic White participants were less likely to consume nitrates, nitrites, and total nitrites per day, but more likely to consume dietary nitrosamines than other participants that participated in the NBDPS. Primary food sources of these compounds also varied by maternal race/ethnicity.</p> <p>Conclusions</p> <p>Results of this study indicate that intake of nitrates, nitrites, and nitrosamines vary considerably by race/ethnicity, education, body mass index, and other characteristics. Further research is needed regarding how consumption of foods high in nitrosamines and <it>N</it>-nitroso precursors might relate to risk of adverse pregnancy outcomes and chronic diseases.</p

Polychaete invader enhances resource utilization in a species-poor system

Ecosystem consequences of biodiversity change are often studied from a species loss perspective, while the effects of invasive species on ecosystem functions are rarely quantified. In this experimental study, we used isotope tracers to measure the incorporation and burial of carbon and nitrogen from a simulated spring phytoplankton bloom by communities of one to four species of deposit-feeding macrofauna found in the species-poor Baltic Sea. The recently invading polychaete Marenzelleriaarctia, which has spread throughout the Baltic Sea, grows more rapidly than the native species Monoporeia affinis, Pontoporeia femorata (both amphipods) and Macoma balthica (a bivalve), resulting in higher biomass increase (biomass production) in treatments including the polychaete. Marenzelleria incorporated and buried bloom material at rates similar to the native species. Multi-species treatments generally had higher isotope incorporation, indicative of utilization of bloom material, than expected from monoculture yields of the respective species. The mechanism behind this observed over-yielding was mainly niche complementarity in utilization of the bloom input, and was more evident in communities including the invader. In contrast, multi-species treatments had generally lower biomass increase than expected. This contrasting pattern suggests that there is little overlap in resource use of freshly deposited bloom material between Marenzelleria and the native species but it is likely that interference competition acts to dampen resulting community biomass. In conclusion, an invasive species can enhance incorporation and burial of organic matter from settled phytoplankton blooms, two processes fundamental for marine productivity

Diffusion mechanisms of DNA in agarose gels: NMR studies and Monte Carlo simulations

We report on the diffusion mechanism of short, single-stranded DNA molecules with up to 100 nucleobases in agarose gels with concentrations of up to 2.0% with the aim to characterize the DNA-agarose interaction. The diffusion coefficients were measured directly, i.e., without any model assumptions, by pulsed field gradient nuclear magnetic resonance (PFG-NMR). We find that the diffusion coefficient decreases, as expected, with an increase in both DNA strand length and gel concentration. In addition, we performed Monte Carlo simulations of particle diffusion in a model network of polymer chains, considering our experimental conditions. Together, the Monte Carlo simulations and the PFG-NMR results show that the decrease in diffusion coefficients in the presence of the agarose gel is due to a temporary adhesion of the DNA molecules to the surface of gel fibers. The average adhesion time to a given gel fiber increases with the length of the DNA strands but is independent of the number of gel fibers. The corresponding magnitude of the binding enthalpies of DNA strands to gel fibers indicates that a mixture of van der Waals interactions and hydrogen bonding contributes to the decreased diffusion of DNA in agarose gels

Stimulation of b cells by poly a.poly U and poly i.poly C in vitro.

Both poly I:poly C and poly A:poly U stimulate [(3)H]thymidine incorporation by spleen cells derived from normal or from cortisone-treated mice. The highest rate of stimulation was detected in the spleen cells of nude mice. Compared with spleen cells, thymus cells and cortisone-resistant thymus cells gave only a small but reproducible response. The results suggest that double-stranded polynucleotides act preferentially on B cells in the same way as dextran sulphate

SSM/I sea ice remote sensing for mesoscale ocean-atmosphere interaction analysis

Two algorithms have been used in a hybrid scheme in order to obtain sea iceconcentration maps at 12 km resolution from 19, 37, and 85 GHz SSM/I data.The first one is an algorithm based on the polarization difference near 90GHz and the second one is the NASA Team algorithm which uses the 19 and 37GHz SSM/I channels. Ice concentrations are calculated using the 85 GHzchannels. In addition, the lower frequency channels are used to decidewhether the data points belong to the ice-free ocean or to the ice-coveredarea. This combination of high and low frequency channels eliminatesincorrect high ice concentrations caused by weather effects over the in factice-free ocean using the rather weather independent low frequencies whileretaining high resolution over ice with the high frequency. The estimationof proper tie points for the 85 GHz algorithm was a major task. Astatistical linear regression method for reference brightness temperatureestimation was applied in order to avoid misarranged guesses of the tiepoints. This method requires independent ice concentration reference datawhich were derived from aircraft dual-polarized passive microwavemeasurements at 19 and 37 GHz and optical line scanner images. ERS-2 SARimages were used to analyze the capability of the SSM/I to resolve featuressuch as the evolution of the marginal ice zone in the Fram Strait and theStorfjorden Polynya. Two different numerical atmospheric models were used toanalyze the effect of an increased resolution of ice data from 50 to 12 kmon the model results. It was found that the representation of the ice edgezone significantly influences the modelled atmospheric boundary-layertemperatures. The temperatures obtained with the high resolution ice dataagree significantly better with aircraft observed data