Sophie N. Chu

Prenatal exposure to allergen, DNA methylation, and allergy in grandoffspring mice

Prenatal allergen exposure has been linked to both induction and protection of allergic sensitization in offspring. We hypothesized that prenatal exposure of mice (F0) to Aspergillus fumigatus (A. fumigatus) would be associated with decreased immunoglobulin (Ig) E and airway eosinophilia and alterations in CpG methylation of T‐helper genes in third‐generation mice (F2).

In Situ Sensor Technology for Simultaneous Spectrophotometric Measurements of Seawater Total Dissolved Inorganic Carbon and pH

A new, in situ sensing system, Channelized Optical System (CHANOS), was recently developed to make high-resolution, simultaneous measurements of total dissolved inorganic carbon (DIC) and pH in seawater. Measurements made by this single, compact sensor can fully characterize the marine carbonate system. The system has a modular design to accommodate two independent, but similar measurement channels for DIC and pH. Both are based on spectrophotometric detection of hydrogen ion concentrations. The pH channel uses a flow-through, sample-indicator mixing design to achieve near instantaneous measurements. The DIC channel adapts a recently developed spectrophotometric method to achieve flow-through CO2 equilibration between an acidified sample and an indicator solution with a response time of only ∼ 90 s. During laboratory and in situ testing, CHANOS achieved a precision of ±0.0010 and ± 2.5 μmol kg(-1) for pH and DIC, respectively. In situ comparison tests indicated that the accuracies of the pH and DIC channels over a three-week time-series deployment were ± 0.0024 and ± 4.1 μmol kg(-1), respectively. This study demonstrates that CHANOS can make in situ, climatology-quality measurements by measuring two desirable CO2 parameters, and is capable of resolving the CO2 system in dynamic marine environments.

High-frequency spectrophotometric measurements of total dissolved inorganic carbon in seawater.

A new spectrophotometric method was developed to achieve continuous measurements of total dissolved inorganic carbon (DIC) in seawater. It uses a countercurrent flow design and a highly CO2-permeable membrane (Teflon AF 2400) to achieve flow-through CO2 equilibration between an acidified sample and an indicator solution with a fast response time of ~22 s. This method improves the spatiotemporal resolution by more than 1 order of magnitude compared to the existing spectrophotometric method. The flow-through equilibration allows for continuous (~1 Hz) detection and real-time data smoothing. The method had a short-term precision of ± 2.0 μmol kg(-1) for a given flow-through sample. It achieved a field precision of ± 3.6 μmol kg(-1) and successfully captured high DIC variability down to minute scales. Measurements by the new method over the typical range of oceanic DIC showed good agreement with measurements made by an established method (mean differences -1.6 to 0.3 μmol kg(-1) with 1σ ± 6.0-6.7 μmol kg(-1)). This level of precision and accuracy is comparable to that of the existing spectrophotometric method. The characteristics of the new method make it particularly suitable for high-frequency, submerged measurements required for mobile observing platforms in the ocean. It can also be adapted for high-frequency, spectrophotometric measurements of seawater CO2 fugacity.

Prenatal and Postnatal Polycyclic Aromatic Hydrocarbon Exposure, Airway Hyperreactivity, and Beta-2 Adrenergic Receptor Function in Sensitized Mouse Offspring

Despite data associating exposure to traffic-related polycyclic aromatic hydrocarbons (PAH) in asthma, mechanistic support has been limited. We hypothesized that both prenatal and early postnatal exposure to PAH would increase airway hyperreactivity (AHR) and that the resulting AHR may be insensitive to treatment with a β 2AR agonist drug, procaterol. Further, we hypothesized that these exposures would be associated with altered β 2AR gene expression and DNA methylation in mouse lungs. Mice were exposed prenatally or postnatally to a nebulized PAH mixture versus negative control aerosol 5 days a week. Double knockout β 2AR mice were exposed postnatally only. Prenatal exposure to PAH was associated with reduced β 2AR gene expression among nonsensitized mice offspring, but not increases in DNA methylation or AHR. Postnatal exposure to PAH was borderline associated with increased AHR among sensitized wildtype, but not knockout mice. In the first study that delivers PAH aerosols to mice in a relatively physiological manner, small effects on AHR and β 2AR gene expression, but not β 2AR agonist drug activity, were observed. If confirmed, the results may suggest that exposure to PAH, common ambient urban pollutants, affects β 2AR function, although the impact on the efficacy of β 2AR agonist drugs used in treating asthma remains uncertain.

Changes in anthropogenic carbon storage in the Northeast Pacific in the last decade

In order to understand the oceans role as a sink for anthropogenic carbon dioxide (CO2), it is important to quantify changes in the amount of anthropogenic CO2 stored in the ocean interior over time. From August to September 2012, an ocean acidification cruise was conducted along a portion of the P17N transect (50°N 150°W to 33.5°N 135°W) in the Northeast Pacific. These measurements are compared with data from the previous occupation of this transect in 2001 to estimate the change in the anthropogenic CO2 inventory in the Northeast Pacific using an extended multiple linear regression (eMLR) approach. Maximum increases in the surface waters were 11 µmol kg−1 over 11 years near 50°N. Here, the penetration depth of anthropogenic CO2 only reached ∼300 m depth, whereas at 33.5°N, penetration depth reached ∼600 m. The average increase of the depth-integrated anthropogenic carbon inventory was 0.41 ± 0.12 mol m−2 yr−1 across the transect. Lower values down to 0.20 mol m−2 yr−1 were observed in the northern part of the transect near 50°N and increased up to 0.55 mol m−2 yr−1 toward 33.5°N. This increase in anthropogenic carbon in the upper ocean resulted in an average pH decrease of 0.002 ± 0.0003 pH units yr−1 and a 1.8 ± 0.4 m yr−1 shoaling rate of the aragonite saturation horizon. An average increase in apparent oxygen utilization of 13.4 ± 15.5 µmol kg−1 centered on isopycnal surface 26.6 kg m−3 from 2001 to 2012 was also observed.