Abstract.One technique used to measure concentrations of the hydroperoxy radical (HO 2 ) in the atmosphere involves chemically converting it to OH by addition of NO and subsequent detection of OH. However, some organic peroxy radicals (RO 2 ) can also be rapidly converted to HO 2 (and subsequently OH) in the presence of NO, interfering with measurements of ambient HO 2 radical concentrations. This interference must be characterized for each instrument to determine to what extent various RO 2 radicals interfere with measurements of HO 2 and to assess the impact of this interference on past measurements. The efficiency of RO 2 -to-HO 2 conversion for the Indiana University laser-induced fluorescencefluorescence assay by gas expansion (IU-FAGE) instrument was measured for a variety of RO 2 radicals. Known quantities of OH and HO 2 radicals were produced from the photolysis of water vapor at 184.9 nm, and RO 2 radicals were produced by the reaction of several volatile organic compounds (VOCs) with OH. The conversion efficiency of RO 2 radicals to HO 2 was measured when NO was added to the sampling cell for conditions employed during several previous field campaigns. For these conditions, approximately 80 % of alkene-derived RO 2 radicals and 20 % of alkane-derived RO 2 radicals were converted to HO 2 . Based on these measurements, interferences from various RO 2 radicals contributed to approximately 35 % of the measured HO 2 signal during the Mexico City Metropolitan Area (MCMA) 2006 campaign (MCMA-2006), where the measured VOCs consisted of a mixture of saturated and unsaturated species. However, this interference can contribute more significantly to the measured HO 2 signal in forested environments dominated by unsaturated biogenic emissions such as isoprene.

Bombesin receptor subtype-3 (BRS-3) is an orphan G-protein-coupled receptor (GPCR) involved in the regulation of energy homeostasis. Mice deficient in BRS-3 develop late-onset mild obesity with metabolic defects, while synthetic agonists activating BRS-3 show antiobesity profiles by inhibiting food intake and increasing metabolic rate in rodent models. The molecular mechanisms and the neural circuits responsible for these effects, however, remain elusive and demand better characterization. We report here a comprehensive mapping of BRS-3 mRNA in the rat and mouse brain through in situ hybridization. Furthermore, to investigate the neurochemical characteristics of the BRS-3-expressing neurons, double in situ hybridization was performed to determine whether BRS-3 colocalizes with other neurotransmitters or neuropeptides. Many, but not all, of the BRS-3-expressing neurons were found to be glutamatergic, while few were found to be cholinergic or GABAergic. BRS-3-containing neurons do not express some of the well-characterized neuropeptides, such as neuropeptide Y (NPY), proopiomelanocortin (POMC), orexin/hypocretin, melanin-concentrating hormone (MCH), thyrotropin-releasing hormone (TRH), gonadotropin-releasing hormone (GnRH), and kisspeptin. Interestingly, BRS-3 mRNA was found to partially colocalize with corticotropin-releasing factor (CRF) and growth hormone-releasing hormone (GHRH), suggesting novel interactions of BRS-3 with stress- and growth-related endocrine systems. Our study provides important information for evaluating BRS-3 as a potential therapeutic target for the treatment of obesity.

Abstract. Reactions of the hydroxyl (OH) and peroxy (HO2 and RO2) radicals play a central role in the chemistry of the atmosphere. In addition to controlling the lifetimes of many trace gases important to issues of global climate change, OH radical reactions initiate the oxidation of volatile organic compounds (VOCs) which can lead to the production of ozone and secondary organic aerosols in the atmosphere. Previous measurements of these radicals in forest environments characterized by high mixing ratios of isoprene and low mixing ratios of nitrogen oxides (NOx) (typically less than 1–2 ppb) have shown serious discrepancies with modeled concentrations. These results bring into question our understanding of the atmospheric chemistry of isoprene and other biogenic VOCs under low NOx conditions. During the summer of 2015, OH and HO2 radical concentrations, as well as total OH reactivity, were measured using laser-induced fluorescence–fluorescence assay by gas expansion (LIF-FAGE) techniques as part of the Indiana Radical Reactivity and Ozone productioN InterComparison (IRRONIC). This campaign took place in a forested area near Indiana University's Bloomington campus which is characterized by high mixing ratios of isoprene (average daily maximum of approximately 4 ppb at 28 ∘C) and low mixing ratios of NO (diurnal average of approximately 170 ppt). Supporting measurements of photolysis rates, VOCs, NOx, and other species were used to constrain a zero-dimensional box model based on the Regional Atmospheric Chemistry Mechanism (RACM2) and the Master Chemical Mechanism (MCM 3.2), including versions of the Leuven isoprene mechanism (LIM1) for HOx regeneration (RACM2-LIM1 and MCM 3.3.1). Using an OH chemical scavenger technique, the study revealed the presence of an interference with the LIF-FAGE measurements of OH that increased with both ambient concentrations of ozone and temperature with an average daytime maximum equivalent OH concentration of approximately 5×106 cm−3. Subtraction of the interference resulted in measured OH concentrations of approximately 4×106 cm−3 (average daytime maximum) that were in better agreement with model predictions although the models underestimated the measurements in the evening. The addition of versions of the LIM1 mechanism increased the base RACM2 and MCM 3.2 modeled OH concentrations by approximately 20 % and 13 %, respectively, with the RACM2-LIM1 mechanism providing the best agreement with the measured concentrations, predicting maximum daily OH concentrations to within 30 % of the measured concentrations. Measurements of HO2 concentrations during the campaign (approximately a 1×109 cm−3 average daytime maximum) included a fraction of isoprene-based peroxy radicals (HO2*=HO2+αRO2) and were found to agree with model predictions to within 10 %–30 %. On average, the measured reactivity was consistent with that calculated from measured OH sinks to within 20 %, with modeled oxidation products accounting for the missing reactivity, however significant missing reactivity (approximately 40 % of the total measured reactivity) was observed on some days.

Peroxy radicals were measured in a mixed deciduous forest atmosphere in Bloomington, Indiana, USA, during the Indiana Radical, Reactivity and Ozone Production Intercomparison (IRRONIC) during the summer of 2015. Total peroxy radicals ([XO 2 ] ≡ [HO 2 ] + [RO 2 ]) were measured by a newly developed technique involving chemical amplification using nitric oxide (NO) and ethane (C 2 H 6 ) followed by NO 2 detection by cavity-attenuated phase-shift spectroscopy (hereinafter referred to as ECHAMP -Ethane CHemical AMPlifier). The sum of hydroperoxy radicals (HO 2 ) and a portion of organic peroxy radicals ([HO * 2 ] = [HO 2 ] + α i [R i O 2 ], 0 < α < 1) was measured by the Indiana University (IU) laser-induced fluorescence-fluorescence assay by gas expansion instrument (LIF-FAGE). Additional collocated measurements include concentrations of NO, NO 2 , O 3 , and a wide range of volatile organic compounds (VOCs) and meteorological parameters. XO 2 concentrations measured by ECHAMP peaked between 13:00 and 16:00 local time (LT), with campaign average concentrations of 41 ± 15 ppt (1σ ) at 14:00 LT. Daytime concentrations of iso-prene averaged 3.6 ± 1.9 ppb (1σ ), whereas average concentrations of NO x ([NO] + [NO 2 ]) and toluene were 1.2 and 0.1 ppb, respectively, indicating a low impact from anthropogenic emissions at this site.We compared ambient measurements from both instruments and conducted a calibration source comparison. For the calibration comparison, the ECHAMP instrument, which is primarily calibrated with an acetone photolysis method, sampled the output of the LIF-FAGE calibration source which is based on the water vapor photolysis method and, for these comparisons, generated a 50 %-50 % mixture of HO 2 and either butane or isoprene-derived RO 2 . A bivariate fit of the data yields the relation [XO 2 ] ECHAMP = (0.88± 0.02; [HO 2 ] + [RO 2 ]) IU_cal + (6.6 ± 4.5) ppt. This level of agreement is within the combined analytical uncertainties for the two instruments' calibration methods.A linear fit of the daytime (09:00-22:00 LT) 30 min averaged [XO 2 ] ambient data with the 1 min averaged [HO * 2 ] data (one point per 30 min) yields the relation [XO 2 ] = (1.08±0.05)[HO * 2 ]−(1.4±0.3). Day-to-day variability in the Published by Copernicus Publications on behalf of the European Geosciences Union. 9564 S. Kundu et al.: Peroxy radical measurements by ethane [XO 2 ]/[HO * 2 ] ratio was observed. The lowest [XO 2 ]/[HO * 2] ratios between 13:00 and 16:00 LT were 0.8 on 13 and 18 July, whereas the highest ratios of 1.1 to 1.3 were observed on 24 and 25 July -the same 2 d on which the highest concentrations of isoprene and ozone were observed. Although the exact composition of the peroxy radicals during IRRONIC is not known, zero-dimensional photochemical modeling of the IRRONIC dataset using two versions of the Regional Atmospheric Chemistry Mechanism (RACM2 and RACM2-LIM1) and the Master Chemical Mechanism (MCM 3.2 and MCM 3.3.1) all predict afternoon [XO 2 ]/[HO * 2 ] ratios of between 1.2 and 1.5. Differences bet...