Drought Reduces Root Respiration In Sugar Maple Forests

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/117195/1/eap199883771.pd

Anthropogenic N deposition and the fate of 15 NO 3 − in a northern hardwood ecosystem

Human activity has substantially increased atmospheric NO 3 − deposition in many regions of the Earth, which could lead to the N saturation of terrestrial ecosystems. Sugar maple ( Acer saccharum Marsh.) dominated northern hardwood forests in the Upper Great Lakes region may be particularly sensitive to chronic NO 3 − deposition, because relatively moderate experimental increases (three times ambient) have resulted in substantial N leaching over a relatively short duration (5–7 years). Although microbial immobilization is an initial sink (i.e., within 1–2 days) for anthropogenic NO 3 − in this ecosystem, we have an incomplete understanding of the processes controlling the longer-term (i.e., after 1 year) retention and flow of anthropogenic N. Our objectives were to determine: (i) whether chronic NO 3 − additions have altered the N content of major ecosystem pools, and (ii) the longer-term fate of 15 NO 3 − in plots receiving chronic NO 3 − addition. We addressed these objectives using a field experiment in which three northern hardwood plots receive ambient atmospheric N deposition (ca. 0.9 g N m −2 year −1 ) and three plots which receive ambient plus experimental N deposition (3.0 g NO 3 − -N m −2 year −1 ). Chronic NO 3 − deposition significantly increased the N concentration and content (g N/m 2 ) of canopy leaves, which contained 72% more N than the control treatment. However, chronic NO 3 − deposition did not significantly alter the biomass, N concentration or N content of any other ecosystem pool. The largest portion of 15 N recovered after 1 year occurred in overstory leaves and branches (10%). In contrast, we recovered virtually none of the isotope in soil organic matter (SOM), indicating that SOM was not a sink for anthropogenic NO 3 − over a 1 year duration. Our results indicate that anthropogenic NO 3 − initially assimilated by the microbial community is released into soil solution where it is subsequently taken up by overstory trees and allocated to the canopy. Anthropogenic N appears to be incorporated into SOM only after it is returned to the forest floor and soil via leaf litter fall. Short- and long-term isotope tracing studies provided very different results and illustrate the need to understand the physiological processes controlling the flow of anthropogenic N in terrestrial ecosystems and the specific time steps over which they operate.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42478/1/10533_2004_Article_5147148.pd

Obeticholic acid for the treatment of non-alcoholic steatohepatitis: interim analysis from a multicentre, randomised, placebo-controlled phase 3 trial

Background Non-alcoholic steatohepatitis (NASH) is a common type of chronic liver disease that can lead to cirrhosis. Obeticholic acid, a farnesoid X receptor agonist, has been shown to improve the histological features of NASH. Here we report results from a planned interim analysis of an ongoing, phase 3 study of obeticholic acid for NASH. Methods In this multicentre, randomised, double-blind, placebo-controlled study, adult patients with definite NASH,non-alcoholic fatty liver disease (NAFLD) activity score of at least 4, and fibrosis stages F2–F3, or F1 with at least oneaccompanying comorbidity, were randomly assigned using an interactive web response system in a 1:1:1 ratio to receive oral placebo, obeticholic acid 10 mg, or obeticholic acid 25 mg daily. Patients were excluded if cirrhosis, other chronic liver disease, elevated alcohol consumption, or confounding conditions were present. The primary endpointsfor the month-18 interim analysis were fibrosis improvement (≥1 stage) with no worsening of NASH, or NASH resolution with no worsening of fibrosis, with the study considered successful if either primary endpoint was met. Primary analyses were done by intention to treat, in patients with fibrosis stage F2–F3 who received at least one dose of treatment and reached, or would have reached, the month 18 visit by the prespecified interim analysis cutoff date. The study also evaluated other histological and biochemical markers of NASH and fibrosis, and safety. This study is ongoing, and registered with ClinicalTrials.gov, NCT02548351, and EudraCT, 20150-025601-6. Findings Between Dec 9, 2015, and Oct 26, 2018, 1968 patients with stage F1–F3 fibrosis were enrolled and received at least one dose of study treatment; 931 patients with stage F2–F3 fibrosis were included in the primary analysis (311 in the placebo group, 312 in the obeticholic acid 10 mg group, and 308 in the obeticholic acid 25 mg group). The fibrosis improvement endpoint was achieved by 37 (12%) patients in the placebo group, 55 (18%) in the obeticholic acid 10 mg group (p=0·045), and 71 (23%) in the obeticholic acid 25 mg group (p=0·0002). The NASH resolution endpoint was not met (25 [8%] patients in the placebo group, 35 [11%] in the obeticholic acid 10 mg group [p=0·18], and 36 [12%] in the obeticholic acid 25 mg group [p=0·13]). In the safety population (1968 patients with fibrosis stages F1–F3), the most common adverse event was pruritus (123 [19%] in the placebo group, 183 [28%] in the obeticholic acid 10 mg group, and 336 [51%] in the obeticholic acid 25 mg group); incidence was generally mild to moderate in severity. The overall safety profile was similar to that in previous studies, and incidence of serious adverse events was similar across treatment groups (75 [11%] patients in the placebo group, 72 [11%] in the obeticholic acid 10 mg group, and 93 [14%] in the obeticholic acid 25 mg group). Interpretation Obeticholic acid 25 mg significantly improved fibrosis and key components of NASH disease activity among patients with NASH. The results from this planned interim analysis show clinically significant histological improvement that is reasonably likely to predict clinical benefit. This study is ongoing to assess clinical outcomes

Effect of measurement CO \u3c inf\u3e 2 concentration on sugar maple root respiration

Accurate estimates of root respiration are crucial to predicting below ground C cycling in forest ecosystems. Inhibition of respiration has been reported as a short-term response of plant tissue to elevated measurement [CO2]. We sought to determine if measurement [CO2] affected root respiration in samples from mature sugar maple (Acer saccharum Marsh.) forests and to assess possible errors associated with root respiration measurements made at [CO2]s lower than that typical of the soil atmosphere. Root respiration was measured as both CO2 production and O2 consumption on excised fine roots (≤ 1.0 mm) at [CO2]s ranging from 350 to \u3e 20,000 μl l-1. Root respiration was significantly affected by the [CO2] at which measurements were made for both CO2 production and O2 consumption. Root respiration was most sensitive to [CO2] near and below normal soil concentrations ( \u3c 1500 μl l-1). Respiration rates changed little at [CO2]s above 3000 μl l-1 and were essentially constant above 6000 μl l-1 CO2. These findings call into question estimates of root respiration made at or near atmospheric [CO2], suggesting that they overestimate actual rates in the soil. Our results indicate that sugar maple root respiration at atmospheric [CO2] (350 μl l-1) is about 139% of that at soil [CO2]. Although the causal mechanism remains unknown, the increase in root respiration at low measurement [CO2] is significant and should be accounted for when estimating or modeling root respiration. Until the direct effect of [CO2] on root respiration is fully understood, we recommend making measurements at a [CO2] representative of, or higher than, soil [CO2]. In all cases, the [CO2] at which measurements are made and the [CO2] typical of the soil atmosphere should be reported

Fine root respiration in northern hardwood forests in relation to temperature and nitrogen availability

We examined fine-root ( \u3c 2.0 mm diameter) respiration throughout one growing season in four northern hardwood stands dominated by sugar maple (Acer saccharum Marsh.), located along soil temperature and nitrogen (N) availability gradients. In each stand, we fertilized three 50 x 50 m plots with 30 kg NO3/--N ha-1 year-1 and an additional three plots received no N and served as controls. We predicted that root respiration rates would increase with increasing soil temperature and N availability. We reasoned that respiration would be greater for trees using NO3/- as an N source than for trees using NH4/+ as an N source because of the greater carbon (C) costs associated with NO3/- versus NH4/+ uptake and assimilation. Within stands, seasonal patterns of fine-root respiration rates followed temporal changes in soil temperature, ranging from a low of 2.1 μmol O2 kg-1 s-1 at 6 °C to a high of 7.0 μmol O2 kg-1 s-1 at 18 °C. Differences in respiration rates among stands at a given soil temperature were related to variability in total net N mineralized (48-90 μg N g-1) throughout the growing season and associated changes in mean root tissue N concentration (1.18- 1.36 mol N kg-1). The hypothesized increases in respiration in response to NO3/- fertilization were not observed. The best-fit model describing patterns within and among stands had root respiration rates increasing exponentially with soil temperature and increasing linearly with increasing tissue N concentration: R = 1.347N e(0.0727T) (r2 = 0.63, P \u3c 0.01), where R is root respiration rate (μmol O2 kg-1 s-1), N is root tissue N concentration (mol N kg-1), and T is soil temperature (°C). We conclude that, in northern hardwood forests dominated by sugar maple, root respiration is responsive to changes in both soil temperature and N availability, and that both factors should be considered in models of forest C dynamics

The cost of complications following major resection of malignant neoplasia

Background: Rising healthcare costs have led to increased focus on the need to achieve a higher value of care. As value-maximization efforts expand to include more complex surgical patients, evidence to support meaningful implementation of complication-based initiatives is lacking. The objective of this study was to compare incremental costs of complications following major gastrointestinal (GI) resections for organ-specific malignant neoplasia using nationally representative data. Methods: National (Nationwide) Inpatient Sample data, 2001-2014, were queried for adult (≥ 18 years) patients undergoing major resections for malignant neoplasia. Based on system-based complications considered relevant to the long-term treatment of GI disease, stratified differences in risk-adjusted incremental hospital costs and complication probabilities were compared. Differences in surgical outcomes and costs over time were also assessed. Results: A total of 293,967 patients were included, weighted to represent 1,408,117 patients nationwide. One fourth (26.1%; 95% CI, 25.7-26.4%) experienced ≥ 1 pre-discharge complication (range, 45.3% esophagectomy to 24.0% rectal resection). Resultant annual risk-adjusted incremental hospital costs totaled $540 million nationwide (19.5$20,900 per patient). Costs varied substantially with both cancer/resection type and complication group, ranging from $76.7 million for colectomies with infectious complications to$0.2 million for rectal resections with urinary complications. For each resection type, infectious ($154.7 million), GI ($85.5 million), and pulmonary ($77.9 million) complications were among the most significant drivers of increased hospital cost. Conclusions: Quantifying and comparing the impact of complications on an indication-specific level in more complex patients offers an important step toward allowing providers/payers to meaningfully prioritize the design of novel and adaptation of existing value-maximization approache