Land use drives the distribution of free, physically protected, and chemically protected soil organic carbon storage at a global scale.

Soil organic carbon (SOC) sequestration is increasingly emphasized as a climate mitigation solution, as scientists, policy makers, and land managers prioritize enhancing belowground C storage. To identify key underlying drivers of total SOC distributions, we compiled a global dataset of soil C stocks held in three chemical forms, reflecting different mechanisms of organic C protection: free particulate organic C (fPOC), physically protected particulate organic C (oPOC), and mineral-protected soil organic C (mSOC). In our dataset, these three SOC pools were differentially sensitive to the effects of climate, soil mineralogy, and ecosystem type, emphasizing the importance of distinguishing between physical and chemical C protection mechanisms. C stocks in all three pools varied among ecosystems: cropland soils stored the least amount in each pool, with forest and grassland soils both containing significantly more fPOC (40%-60% greater in each ecosystem) than croplands. oPOC stocks did not significantly differ from zero in croplands but were substantial in forest and grassland soils. Meanwhile, mSOC stocks were the greatest in grasslands and shrublands (90%-100% greater than croplands). In cropland soils, there were no major effects of tillage on C storage in any of the three pools, while manure addition enhanced mSOC stocks, especially when added with inorganic N. Thus, the human land use intensity in croplands appears to reduce SOC storage in all major pools, depending upon management; retaining native vegetation should be emphasized to maintain current global SOC stocks.

Improving Access to Specialty Pediatric Care: Innovative Referral and eConsult Technology in a Specialized Acute Care Hospital.

Background: The COVID-19 pandemic has exacerbated wait times for pediatric specialty care. Transformative technologies such as electronic referral (eReferral-automation of patient information) and electronic consultations (eConsult-asynchronous request for specialized advice by primary care providers) have the potential to increase timely access to specialist care. The objective of this study was to present an overview of the current state and characteristics of referrals directed to a pediatric ambulatory medical surgery center, with an emphasis on the innovative use of an eConsult system and to indicate key considerations for system improvement. Methods: This cross-sectional study was conducted at a specialized pediatric acute care hospital in Ottawa, Ontario. Secondary data were obtained over a 2-year period during the COVID-19 pandemic (2019-2022). To gain insights and identify areas of improvement related to the factors pertaining to referrals and eConsults at the process and system levels, quality improvement (QI) methodologies were employed. Descriptive statistics provide a summary of the trends and characteristics of referrals and the utilization of eConsult. Results: Among the 113,790 referrals received, 31,430 were denied. Most common reasons for referral denial were other/null (e.g., unspecified) (29.3%), inappropriate referrals (12.6%), and duplicate referrals (12.4%). Four clinics (e.g., endocrinology, cardiology, neurology, and neurosurgery) reported a total of 277 eConsults, with endocrinology accounting for 95.0% of all eConsults. QI findings revealed the need for standardized workflows among specialties and ensuring that eConsult options are accessible and integrated within the electronic medical record (EMR). Conclusions: Refining the pediatric referral management process and optimizing eConsult through existing clinical systems have the potential to improve the timeliness and quality of specialty care. The results inform future research initiatives targeting improved access to pediatric specialty care and serve as a benchmark for hospitals utilizing EMRs and eConsult.

Effectiveness of message framing in changing COVID-19 vaccination intentions: Moderating role of travel desire.

This research examines the effectiveness of message framing, message appeal and information content in changing respondents' COVID-19 vaccination intentions through influencing their vaccine risk perceptions. Furthermore, the moderating effect of travel desire on the relationship between vaccine risk perceptions and changing vaccination intentions is examined. In doing so, two rounds of data that were collected from the same respondents. The first survey recorded respondents' vaccination intentions, travel desire and socio demographics. A follow up survey tested cause-and-effect relationships on the proposed relationships using a 2 (message frame: gain, loss) x 2 (message appeal: rational, emotional) ×2 (information content: subjective, objective) between-subjects online experimental design. Findings suggest that loss-framed messages are more effective than gain-framed and emotional-rational messages in reducing risk perceptions and, thus, changing vaccination intentions. Travel desire is found to moderate the effect of vaccine risk perception on vaccination intentions by weakening the negative effect of vaccine risk perception on vaccination intention. Findings show the importance of travel desire along with message framing and message appeal on changing individuals' COVID-19 vaccination intentions in public health communications.

Nectary photosynthesis contributes to the production of manuka (Leptospermum scoparium) floral nectar.

Current models of floral nectar production do not include a contribution from photosynthesis by green nectary tissue, even though many species have green nectaries. Manuka (Leptospermum scoparium) floral nectaries are green, and in addition to sugars, their nectar contains dihydroxyacetone (DHA), the precursor of the antimicrobial agent in the honey. We investigated causes of variation in manuka floral nectar production, particularly the effect of light incident on the nectary. Flower gas exchange, chlorophyll fluorescence, and the effects on nectar of age, temperature, light, sucrose, 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), pyridoxal phosphate, and 13 CO2 , were measured for attached and excised flowers. Flower age affected all nectar traits, whilst temperature affected total nectar sugar only. Increased light reduced floral CO2 efflux, increased nectar sugar production, and affected the ratio of DHA to other nectar sugars. DCMU, an inhibitor of photosystem II, reduced nectar sugar production. Pyridoxal phosphate, an inhibitor of the chloroplast envelope triose phosphate transporter, reduced nectar DHA content. Incubation of excised flowers with 13 CO2 in the light resulted in enrichment of nectar sugars, including DHA. Photosynthesis within green nectaries contributes to nectar sugars and influences nectar composition. Manuka nectar DHA arises from pools of triose phosphate that are modulated by nectary photosynthesis.

Longitudinal Links between Adolescent and Peer Conduct Problems and Moderation by a Sensitivity Genetic Index.

The most extensively studied influence on adolescent conduct problem behaviors is peers, and the literature points to genetics as one source of individual differences in peer influence. The purpose of this study was to test the hypothesis that an environmental sensitivity genetic index comprised of DRD4, 5-HTTLPR, and GABRA2 variation would moderate the association between peer and adolescent conduct problems. Latent growth modeling was applied to PROSPER project longitudinal data from adolescents and their peers. Results showed the hypothesis was supported; adolescents with more copies of putative sensitivity alleles were more strongly influenced by their peers. The interaction form was consistent with differential susceptibility in follow-up analyses. Strengths and weaknesses of genetic aggregates for sensitivity research are discussed.

Impact of cytochrome P450 variation on meperidine N-demethylation to the neurotoxic metabolite normeperidine.

1. Meperidine is an opioid analgesic that undergoes N-demethylation to form the neurotoxic metabolite normeperidine. Previous studies indicate that meperidine N-demethylation is catalyzed by cytochrome P450 2B6 (CYP2B6), CYP3A4, and CYP2C19.2. The purpose of this study was to examine the relative P450 contributions to meperidine N-demethylation and to evaluate the effect of CYP2C19 polymorphism on normeperidine generation. Experiments were performed using recombinant P450 enzymes, selective chemical inhibitors, enzyme kinetic assays, and correlation analysis with individual CYP2C19-genotyped human liver microsomes.3. The catalytic efficiency (kcat/Km) for meperidine N-demethylation was similar between recombinant CYP2B6 and CYP2C19, but markedly lower by CYP3A4.4. In CYP2C19-genotyped human liver microsomes, normeperidine formation was significantly correlated with CYP2C19 activity (S-mephenytoin 4´-hydroxylation).5. CYP2C19 inhibitor (+)-N-3-benzylnirvanol and CYP3A inhibitor ketoconazole significantly reduced microsomal normeperidine generation by an individual donor with high CYP2C19 activity, whereas donors with lower CYP2C19 activity were sensitive to inhibition by ketoconazole but not benzylnirvanol.6. These findings demonstrate that the relative CYP3A4, CYP2B6, and CYP2C19 involvement in meperidine N-demethylation depends on the enzyme activities in individual human liver microsomal samples. CYP2C19 is likely an important contributor to normeperidine generation in individuals with high CYP2C19 activity, but additional factors influence inter-individual metabolite accumulation.

Induction of the Antioxidant Response by the Transcription Factor NRF2 Increases Bioactivation of the Mutagenic Air Pollutant 3-Nitrobenzanthrone in Human Lung Cells.

3-Nitrobenzanthrone (3-NBA) is a suspected human carcinogen present in diesel exhaust. It requires metabolic activation via nitroreduction in order to form DNA adducts and promote mutagenesis. We have determined that human aldo-keto reductases (AKR1C1-1C3) and NAD(P)H:quinone oxidoreductase 1 (NQO1) contribute equally to the nitroreduction of 3-NBA in lung epithelial cell lines and collectively represent 50% of the nitroreductase activity. The genes encoding these enzymes are induced by the transcription factor NF-E2 p45-related factor 2 (NRF2), which raises the possibility that NRF2 activation exacerbates 3-NBA toxification. Since A549 cells possess constitutively active NRF2, we examined the effect of heterozygous (NRF2-Het) and homozygous NRF2 knockout (NRF2-KO) by CRISPR-Cas9 gene editing on the activation of 3-NBA. To evaluate whether NRF2-mediated gene induction increases 3-NBA activation, we examined the effects of NRF2 activators in immortalized human bronchial epithelial cells (HBEC3-KT). Changes in AKR1C1-1C3 and NQO1 expression by NRF2 knockout or use of NRF2 activators were confirmed by qPCR, immunoblots, and enzyme activity assays. We observed decreases in 3-NBA activation in the A549 NRF2 KO cell lines (53% reduction in A549 NRF2-Het cells and 82% reduction in A549 NRF2-KO cells) and 40-60% increases in 3-NBA bioactivation due to NRF2 activators in HBEC3-KT cells. Together, our data suggest that activation of the transcription factor NRF2 exacerbates carcinogen metabolism following exposure to diesel exhaust which may lead to an increase in 3-NBA-derived DNA adducts.

Role of Human Aldo-Keto Reductases in the Metabolic Activation of the Carcinogenic Air Pollutant 3-Nitrobenzanthrone.

3-Nitrobenzanthrone (3-NBA) is a potent mutagen and suspected human carcinogen detected in diesel exhaust particulate and ambient air pollution. It requires metabolic activation via nitroreduction to promote DNA adduct formation and tumorigenesis. NAD(P)H:quinone oxidoreductase 1 (NQO1) has been previously implicated as the major nitroreductase responsible for 3-NBA activation, but it has recently been reported that human aldo-keto reductase 1C3 (AKR1C3) displays nitroreductase activity toward the chemotherapeutic agent PR-104A. We sought to determine whether AKR1C isoforms could display nitroreductase activity toward other nitrated compounds and bioactivate 3-NBA. Using discontinuous enzymatic assays monitored by UV-HPLC, we determined that AKR1C1-1C3 catalyze three successive two-electron nitroreductions toward 3-NBA to form the reduced product 3-aminobenzanthrone (3-ABA). Evidence of the nitroso- and hydroxylamino- intermediates were obtained by UPLC-HRMS. Km, kcat, and kcat/ Km values were determined for recombinant AKR1C and NQO1 and compared. We found that AKR1C1, AKR1C3, and NQO1 have very similar apparent catalytic efficiencies (8 vs 7 min-1 mM-1) despite the higher kcat of NQO1 (0.058 vs 0.012 min-1). AKR1C1-1C3 possess a Km much lower than that of NQO1, which suggests that they may be more important than NQO1 at the low concentrations of 3-NBA to which humans are exposed. Given that inhalation represents the primary source of 3-NBA exposure, we chose to evaluate the relative importance of AKR1C1-1C3 and NQO1 in human lung epithelial cell lines. Our data suggest that the combined activities of AKR1C1-1C3 and NQO1 contribute equally to the reduction of 3-NBA in A549 and HBEC3-KT cell lines and together represent approximately 50% of the intracellular nitroreductase activity toward 3-NBA. These findings have significant implications for the metabolism of nitrated polycyclic aromatic hydrocarbons and suggest that the hitherto unrecognized nitroreductase activity of AKR1C enzymes should be further investigated.

Vapor pressure deficit predicts epiphyte abundance across an elevational gradient in a tropical montane region.

PREMISE OF THE STUDY: Tropical Montane Cloud Forests (TMCFs) are important ecosystems to study and preserve because of their high biodiversity and critical roles in local and regional ecosystem processes. TMCFs may be particularly affected by changes in climate because of the narrow bands of microclimate they occupy and the vulnerability of TMCF species to projected increases in cloud base heights and drought. A comprehensive understanding of the structure and function of TMCFs is lacking and difficult to attain because of variation in topography within and across TMCF sites. This causes large differences in microclimate and forest structure at both large and small scales. METHODS: In this study, we estimated the abundance of the entire epiphyte community in the canopy (bryophytes, herbaceous vascular plants, woody epiphytes, and canopy dead organic matter) in six sites. In each of the sites we installed a complete canopy weather station to link epiphyte abundance to a number of microclimatic parameters. KEY RESULTS: We found significant differences in epiphyte abundance across the sites; epiphyte abundance increased with elevation and leaf wetness, but decreased as vapor pressure deficit (VPD) increased. Epiphyte abundance had the strongest relationship with VPD; there were differences in VPD that could not be explained by elevation alone. CONCLUSIONS: By measuring this proxy of canopy VPD, TMCF researchers will better understand differences in microclimate and plant community composition across TMCF sites. Incorporating such information in comparative studies will allow for more meaningful comparisons across TMCFs and will further conservation and management efforts in this ecosystem.

Selected weight management interventions for military populations in the United States: a narrative report.

Overweight and obesity continues to be a significant public health burden in the US and particularly among military personnel. Although the US Department of Defense mandates standardized physical activity requirements for military members, incidence and prevalence of overweight and obesity among military personnel continue to increase. Each military department controls their own interventional strategies for physical fitness and weight control. However, unique challenges such as geographic transients, lack of central standardization and empirical efficacy data across military departments, and chronic stress associated with military service adversely affect program outcomes. This brief narrative report explores overweight and obesity interventions among military populations from 2006 to 2016 and includes programmatic reviews of eight overweight and obesity interventions: The Prevention of Obesity in Military Community; Health Eating, Activity, and Lifestyle Training Headquarters (H.E.A.L.T.H); ArmyMOVE!; L.I.F.E.; Look AHEAD; Nutrition-focused Wellness Coaching; Go for Green; and LE3AN. A majority of these interventions did not report significant weight loss 6 months post intervention, and did not mention a theoretical foundation within the interventions. Further research to examine the importance of theory-based programming is warranted to improve process and outcome objectives.

Ivermectin prescription fill rates among U.S. Military members during the coronavirus disease 2019 (COVID-19) pandemic.

This report describes ivermectin prescription fill rates among U.S. active component service members (ACSM) over time during the early phases of the COVID-19 pandemic. Information about the unsubstantiated benefits of ivermectin for coronavirus 2019 (COVID-19) prevention and treatment was widely available online early in the COVID-19 pandemic. Ivermectin prescription fill rates increased among ACSM during periods of Alpha and Delta coronavirus variant predominance, but not during the predominance of the Omicron variant. At the peak of the fill rate curve, in August 2021, rates were higher among men compared to women, older compared to younger age groups, senior officers compared to junior officers, senior enlisted compared to junior enlisted service members, and those with a bachelor's or advanced degree compared to those without a bachelor's degree. Ivermectin prescriptions were more likely to have been filled at a retail pharmacy than at a military hospital or clinic. During the COVID-19 pandemic fill rates for ivermectin prescriptions among ACSM increased, including those without a qualifying diagnosis. Rates peaked in August 2021 but subsequently declined. The decrease in ivermectin fill rates was coincident with vigorous efforts to correct previous misinformation and implement pre-authorization requirements for prescriptions. Research on the impact of unproven online claims about clinical and public health interventions has potential to curtail future unnecessary and potentially harmful treatments.

Biochar mitigates negative effects of salt additions on two herbaceous plant species.

Addition of pyrolyzed biomass ("biochar") to soils has commonly been shown to increase crop yields and alleviate plant stresses associated with drought and exposure to toxic materials. Here we investigate the ability of biochar (at two dosages: 5 and 50 t ha(-1)) to mitigate salt-induced stress, simulating road salt additions in a factorial glasshouse experiment involving the broadleaved herbaceous plants Abutilon theophrasti and Prunella vulgaris. Salt additions of 30 g m(-2) NaCl to unamended soils resulted in high mortality rates for both species. Biochar (Fagus grandifolia sawdust pyrolyzed at 378 °C), when applied at 50 t ha(-1) as a top dressing, completely alleviated salt-induced mortality in A. theophrasti and prolonged survival of P. vulgaris. Surviving A. theophrasti plants that received both 50 t ha(-1) biochar and salt addition treatments showed growth rates and physiological performance similar to plants without salt addition. Biochar treatments alone also substantially increased biomass of P. vulgaris, with a ∼50% increase relative to untreated controls at both biochar dosages. Biochar did not significantly affect photosynthetic carbon gain (Amax), water use efficiency, or chlorophyll fluorescence (Fv/Fm) in either species. Our results indicate that biochar can ameliorate salt stress effects on plants through salt sorption, suggesting novel applications of biochar to mitigate effects of salinization in agricultural, urban, and contaminated soils.

Incidence of Colorectal Cancer Among Active Component Service Members, 2010-2022.

Colorectal cancer, which is more predominant among men than women, has been shown to be associated with environmental and occupational risk factors experienced by military members. The Defense Medical Surveillance System (DMSS) was used to determine the crude and age-adjusted incidence rates of colorectal cancer among active component service members from all military services from January 1, 2010 to December 31, 2022. Results from this analysis show higher crude incidence rates of colorectal cancer among those who are older and male. The overall age-adjusted incidence rate throughout the surveillance period ranged from 3.56 (95% CI: 2.54-4.58) to 7.92 (95% CI: 5.98-9.86) cases per 100,000 person-years. Age-adjusted colorectal cancer rates were similar for males and females (4.46 and 4.33 cases per 100,000 person-years, respectively) and rates were relatively similar by service as well as race and ethnicity. This finding could be attributed to the small number of cases in this study due to better screening practices in the Military Health System (MHS). Although non-Hispanic Black service members have historically had the highest incidence of colorectal cancer within the U.S. military, this study observed similar rates of colorectal cancer for all races and ethnicities after adjusting for age. Incident rates of colorectal cancer within the U.S. military increase monotonically with age, with service members over the age of 45 with the highest incidence, re-enforcing the need to promote wellness screening among military populations. The importance of the DHA guideline changes that decreased colorectal screenings to age 45 years is significant.

Trends in the Incidence of Eating Disorders Among Active Component Service Members, 2017 to 2021.

From 2017 through 2021, a total of 2,454 active component U.S. military service members received incident diagnoses for 1 of the following eating disorders: anorexia nervosa (AN), bulimia nervosa (BN), binge eating disorder (BED), or "other/unspecified eating disorder" (OUED). The incidence rate of any eating disorder was 3.6 cases per 10,000 person-years (p-yrs). The case defining diagnoses OUED, BN, and BED accounted for nearly 89% of total incident cases. The incidence rate of any eating disorder among women was more than 8 times the rate among men. Overall rates were highest among service members under 30 years of age. Crude annual incidence rates of total eating disorders increased in 2021, following the COVID-19 pandemic. Increased prevalence of major life stressors and mental health conditions were reported on Periodic Health Assessment (PHA) forms completed in the 1-year period after an eating disorder diagnosis. These data suggest the need for increased attention to eating disorder prevention. Additionally, treatment programs could be warranted as continued effects of the COVID-19 pandemic are elucidated within the military population.

Surgical Outcomes Following Robotic Single-Site Versus Multiport Hysterectomy for Treatment of Endometrial Cancer: A Systematic Review and Meta-Analysis.

Robotic single-site hysterectomy (RSSH) has emerged as a novel surgical approach for the treatment of endometrial cancer and atypical endometrial hyperplasia (AEH). Current research regarding the benefits of RSSH compared to robotic multiport hysterectomy (RMPH) for these indications has been inconclusive. Our team sought to compare surgical outcomes between these two approaches of robotic hysterectomy via systematic review and meta-analysis to ensure optimal surgical practices. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 Checklist guided our review. MEDLINE, Clinicaltrials.gov, and Cochrane Library were searched, yielding 59 results. Articles were filtered by title and abstract and then reviewed in full for inclusion and exclusion criteria. Inclusion criteria required that (1) studies compared outcomes for RSSH and RMPH, (2) hysterectomy was indicated for endometrial cancer or hyperplasia with atypia, and (3) studies were available in English. Excluded studies (1) compared single-site and multiport laparoscopic approaches, (2) compared robotic approaches to laparoscopic or abdominal (open) techniques, and (3) employed hysterectomy for benign conditions. Publication bias was assessed using the Egger Regression Correlation analysis. Four studies complied with the selection criteria, comprising 138 patients in the RSSH group and 259 in the RMPH group. Similar outcomes were noted across all measures, including conversion rate (relative risk [RR] = 1.84 and confidence interval [CI] = 0.99-3.43), blood loss (Cohen's d = 1.05 and Z = 18.62), operating time (Cohen's d = 0.29 and Z = 4.38), and length of hospital stay (Cohen's d = 1.06 and Z = 3.86). Publication bias was deemed minimal as indicated by Egger regression values of less than 0.05. These findings suggest that either a surgical approach or AEH with the proper standard of care can provide patients with endometrial cancer.

Update: Exertional rhabdomyolysis, active component, U.S. Armed Forces, 2017-2021.

Among active component service members in 2021, there were 513 incident cases of exertional rhabdomyolysis, for an unadjusted incidence rate of 38.6 cases per 100,000 person-years (p-yrs). Subgroup-specific rates in 2021 were highest among males, those less than 20 years old, non-Hispanic Black service members, Marine Corps or Army members, recruits, and those in "other" and combat-specific occupations. During 2017­2021, crude rates of exertional rhabdomyolysis reached a peak of 43.1 per 100,000 p-yrs in 2018 after which the rate decreased to 38.4 and 38.6 per 100,000 p-yrs in 2020 and 2021, respectively. Compared to those in other race/ethnicity groups, non-Hispanic Black service members had the highest overall rate of exertional rhabdomyolysis in every year of the period. Overall and annual rates were highest among Marine Corps members, intermediate among those in the Army, and lowest among those in the Air Force and Navy. Most cases of exertional rhabdomyolysis were diagnosed at installations that support basic combat/recruit training or major ground combat units of the Army or the Marine Corps. Medical care providers should consider exertional rhabdomyolysis in the differential diagnosis when service members (particularly recruits) present with muscular pain or swelling, limited range of motion, or the excretion of darkened urine after strenuous physical activity, especially in hot, humid weather.

Light-driven Oxidative Demethylation Reaction Catalyzed by a Rieske-type Non-heme Iron Enzyme Stc2.

Rieske-type non-heme iron oxygenases/oxidases catalyze a wide range of transformations. Their applications in bioremediation or biocatalysis face two key barriers: the need of expensive NAD(P)H as a reductant and a proper reductase to mediate the electron transfer from NAD(P)H to the oxygenases. To bypass the need of both the reductase and NAD(P)H, using Rieske-type oxygenase (Stc2) catalyzed oxidative demethylation as the model system, we report Stc2 photocatalysis using eosin Y/sulfite as the photosensitizer/sacrificial reagent pair. In a flow-chemistry setting to separate the photo-reduction half-reaction and oxidation half-reaction, Stc2 photo-biocatalysis outperforms the Stc2-NAD(P)H-reductase (GbcB) system. In addition, in a few other selected Rieske enzymes (NdmA, CntA, and GbcA), and a flavin-dependent enzyme (iodotyrosine deiodinase, IYD), the eosin Y/sodium sulfite photo-reduction pair could also serve as the NAD(P)H-reductase surrogate to support catalysis, which implies the potential applicability of this photo-reduction system to other redox enzymes.

Benchmark Dose Modeling Approaches for Volatile Organic Chemicals Using a Novel Air-Liquid Interface In Vitro Exposure System.

Inhalation is the most relevant route of volatile organic chemical (VOC) exposure; however, due to unique challenges posed by their chemical properties and poor solubility in aqueous solutions, in vitro chemical safety testing is predominantly performed using direct application dosing/submerged exposures. To address the difficulties in screening toxic effects of VOCs, our cell culture exposure system permits cells to be exposed to multiple concentrations at air-liquid interface (ALI) in a 24-well format. ALI exposure methods permit direct chemical-to-cell interaction with the test article at physiological conditions. In the present study, BEAS-2B and primary normal human bronchial epithelial cells (pHBEC) are used to assess gene expression, cytotoxicity, and cell viability responses to a variety of volatile chemicals including acrolein, formaldehyde, 1,3-butadiene, acetaldehyde, 1-bromopropane, carbon tetrachloride, dichloromethane, and trichloroethylene. BEAS-2B cells were exposed to all the test agents, whereas pHBECs were only exposed to the latter 4 listed above. The VOC concentrations tested elicited only slight cell viability changes in both cell types. Gene expression changes were analyzed using benchmark dose (BMD) modeling. The BMD for the most sensitive gene set was within one order of magnitude of the threshold-limit value reported by the American Conference of Governmental Industrial Hygienists, and the most sensitive gene sets impacted by exposure correlate to known adverse health effects recorded in epidemiologic and in vivo exposure studies. Overall, our study outlines a novel in vitro approach for evaluating molecular-based points-of-departure in human airway epithelial cell exposure to volatile chemicals.

Plant community responses to stand-level nutrient fertilization in a secondary tropical dry forest.

The size of the terrestrial carbon (C) sink is mediated by the availability of nutrients that limit plant growth. However, nutrient controls on primary productivity are poorly understood in the geographically extensive yet understudied tropical dry forest biome. To examine how nutrients influence above- and belowground biomass production in a secondary, seasonally dry tropical forest, we conducted a replicated, fully factorial nitrogen (N) and phosphorus (P) fertilization experiment at the stand scale in Guanacaste, Costa Rica. The production of leaves, wood, and fine roots was monitored through time; root colonization by mycorrhizal fungi and the abundance of N-fixing root nodules were also quantified. In this seasonal forest, interannual variation in rainfall had the largest influence on stand-level productivity, with lower biomass growth under drought. By contrast, aboveground productivity was generally not increased by nutrient addition, although fertilization enhanced growth of individual tree stems in a wet year. However, root growth increased markedly and consistently under P addition, significantly altering patterns of stand-level biomass allocation to above- vs. belowground compartments. Although nutrients did not stimulate total biomass production at the community scale, N-fixing legumes exhibited a twofold increase in woody growth in response to added P, accompanied by a dramatic increase in the abundance of root nodules. These data suggest that the relationship between nutrient availability and primary production in tropical dry forest is contingent on both water availability and plant functional diversity.