Soil nitrogen fertilization reduces relative leaf nitrogen allocation to photosynthesis.

The connection between soil nitrogen availability, leaf nitrogen, and photosynthetic capacity is not perfectly understood. Because these three components tend to be positively related over large spatial scales, some posit that soil nitrogen positively drives leaf nitrogen, which positively drives photosynthetic capacity. Alternatively, others posit that photosynthetic capacity is primarily driven by above-ground conditions. Here, we examined the physiological responses of a non-nitrogen-fixing plant (Gossypium hirsutum) and a nitrogen-fixing plant (Glycine max) in a fully factorial combination of light by soil nitrogen availability to help reconcile these competing hypotheses. Soil nitrogen stimulated leaf nitrogen in both species, but the relative proportion of leaf nitrogen used for photosynthetic processes was reduced under elevated soil nitrogen in all light availability treatments due to greater increases in leaf nitrogen content than chlorophyll and leaf biochemical process rates. Leaf nitrogen content and biochemical process rates in G. hirsutum were more responsive to changes in soil nitrogen than those in G. max, probably due to strong G. max investments in root nodulation under low soil nitrogen. Nonetheless, whole-plant growth was significantly enhanced by increased soil nitrogen in both species. Light availability consistently increased relative leaf nitrogen allocation to leaf photosynthesis and whole-plant growth, a pattern that was similar between species. These results suggest that the leaf nitrogen-photosynthesis relationship varies under different soil nitrogen levels and that these species preferentially allocated more nitrogen to plant growth and non-photosynthetic leaf processes, rather than photosynthesis, as soil nitrogen increased.

Root mass carbon costs to acquire nitrogen are determined by nitrogen and light availability in two species with different nitrogen acquisition strategies.

Plant nitrogen acquisition requires carbon to be allocated belowground to build roots and sustain microbial associations. This carbon cost to acquire nitrogen varies by nitrogen acquisition strategy; however, the degree to which these costs vary due to nitrogen availability or demand has not been well tested under controlled conditions. We grew a species capable of forming associations with nitrogen-fixing bacteria (Glycine max) and a species not capable of forming such associations (Gossypium hirsutum) under four soil nitrogen levels to manipulate nitrogen availability and four light levels to manipulate nitrogen demand in a full-factorial greenhouse experiment. We quantified carbon costs to acquire nitrogen as the ratio of total root carbon to whole-plant nitrogen within each treatment combination. In both species, light availability increased carbon costs due to a larger increase in root carbon than whole-plant nitrogen, while nitrogen fertilization generally decreased carbon costs due to a larger increase in whole-plant nitrogen than root carbon. Nodulation data indicated that G. max shifted relative carbon allocation from nitrogen fixation to direct uptake with increased nitrogen fertilization. These findings suggest that carbon costs to acquire nitrogen are modified by changes in light and nitrogen availability in species with and without associations with nitrogen-fixing bacteria.

Assessment of Written Feedback for Emergency Medicine Residents.

OBJECTIVES: An essential component of resident growth is a learning environment with high-quality feedback. Criteria have been developed for characterizing and assessing written feedback quality in internal medicine residents by Jackson et al. Our primary goal was to describe feedback characteristics and assess the quality of written feedback for emergency medicine (EM) residents. Our secondary goals were to evaluate the relation between feedback quality and objective outcome measures. METHODS: This retrospective study was conducted between July 1, 2016 and July 1, 2018. EM residents with an Accreditation Council for Graduate Medical Education composite score (ACS), an in-service score, and written evaluations completed by an attending physician or EM resident in each of the 2 years of the study period were included. RESULTS: Overall, most of the evaluations contained 1 (21%), 2 (23%), or 3 (17%) feedback items. Feedback tended to be positive (82%) and the feedback quality of the evaluations was more likely to be high (44%). There was an association between feedback quality and ACS change (P < 0.0001), but not in-service score change (P = 0.63). Resident evaluations were more likely than attending evaluations to correlate with ACS change (P < 0.00001). CONCLUSIONS: The written evaluations contained few individual feedback items. Evaluations generally focused on the feedback characteristics of professionalism and interpersonal communication. The general feedback quality of evaluations tended to be high and correlated with an increase in ACSs.

Intravenous Thrombolysis at 3.5 Hours From Onset of Pediatric Acute Ischemic Stroke.

Acute thrombolysis has a proven benefit for adults presenting with acute ischemic stroke, but data within the pediatric population are extremely limited. We report the case of a 14-year-old girl who presented with right-sided weakness and ataxia, loss of sensation, and altered mental status. Magnetic resonance imaging with diffusion-weighted imaging showed an acute lesion in the distribution of the left posterior cerebral artery, and magnetic resonance angiogram demonstrated occlusion of the third branch of the left posterior cerebral artery. With parental consent, clinicians decided to infuse an adult dose of weight-adjusted intravenous alteplase at 3.5 hours from onset of symptoms, with subsequent improvement in National Institutes of Health Stroke Scale score from 11 to 3. Computed tomography angiogram at 24 hours showed recanalization of the occluded vessel with no evidence of intracranial hemorrhage. Stroke Scale score at discharge was 3, with modified Rankin Scale scores at discharge of 1 and at 90 days of 0. This case highlights the importance of magnetic resonance imaging in diagnosing pediatric acute ischemic stroke and suggests consideration of thrombolysis in select confirmed pediatric stroke cases. However, a rigorous evidence base is lacking, and clinical trials have not been successful in recruiting patients.

Evaluation of a community-based dental screening program prior to radiotherapy for head and neck cancer: a single-center experience.

PURPOSE: Oral toxicities following radiation therapy (RT) for head and neck (HN) cancer can be profound and are associated with poor health outcomes. The Division of Oral Medicine and Dentistry at Brigham and Women's Hospital and Dana-Farber Cancer Institute therefore implemented a dental evaluation program designed for community-based (CB) dentists to evaluate and treat patients scheduled for HN RT. The aim of this retrospective single-center cohort study was to assess the compliance of CB dentists with this pre-RT dental evaluation program. METHODS: A retrospective analysis of dental evaluations completed by CB dentists from December 2013 to December 2015 was performed. Descriptive statistics were used to determine compliance. RESULTS: A total of 186 dental evaluations were received. Compliance with completion of dental treatment was as follows: scaling and prophylaxis: 94.5% (172/182); dental restorations: 78.7% (48/61); endodontic therapy: 76.9% (10/13); and dental extractions: 76.9% (30/39). Compliance of CB dentists with all requested components of the pre-RT evaluation and treatment was 77.4% (144/186). The median distance traveled by patients to the CB dentist and to the hospital was 5.2 miles (range 0.03-66.0) and 46.5 miles (range 0.8-1457; p < 0.01), respectively. CONCLUSION: In this study, the majority of patients completed their necessary dental treatment in a timely manner by their CB dentist in collaboration with an oral medicine specialist. Given the high compliance of CB dentists, this program could serve as a model for other cancer centers to optimize oral and dental health prior to RT.

High growth temperatures and high soil nitrogen do not alter differences in CO2 assimilation between invasive Phalaris arundinacea (reed canarygrass) and Carex stricta (tussock sedge).

PREMISE OF THE STUDY: Global change in temperature and soil nitrogen availability could affect plant community composition, potentially giving an advantage to invasive species compared to native species. We addressed how high temperatures affected CO2 assimilation parameters for invasive Phalaris arundinacea and a sedge, Carex stricta, it displaces, in natural and controlled environments. METHODS: Photosynthetic parameters were measured in a wetland in Indiana, USA during the abnormally warm year of 2012. In a growth chamber, photosynthetic parameters were measured on the plants grown under three levels of nitrogen and exposed to optimum temperatures followed by 2012-like summer conditions and then hot temperatures with an autumn-like photoperiod. KEY RESULTS: In the wetland, C. stricta exhibited signs of midsummer leaf senescence, whereas P. arundinacea maintained CO2 assimilation at ambient pCO2 (Aamb ) through mid-October. In the chamber, 2012-like conditions reduced Aamb for both species through reductions in maximum carboxylation (Vcmax ) and electron transport (Jmax ) without further change during subsequent hot, autumn-like conditions, whereas the quantum efficiency of carbon assimilation (qe) declined throughout the experiment. However, P. arundinacea had higher values of Aamb , Jmax , and qe than C. stricta. A general, the positive effect of increasing nitrogen availability occurred for photosynthetic processes for both species in hot conditions. CONCLUSIONS: Our data suggest that C. stricta is more susceptible to excessive light stress than P. arundinacea during hot, sunny periods, leading to leaf senescence. Field confirmation of this idea is needed, but frequent heat waves should favor P. arundinacea over C. stricta with or without eutrophication.

Intravenous Tissue Plasminogen Activator for Wake-Up Stroke: A Propensity Score-Matched Analysis.

GOAL: To evaluate the safety and efficacy of intravenous (IV) tissue plasminogen activator (tPA) in the treatment of wake-up stroke (WUS) using propensity score (PS) analysis. MATERIALS AND METHODS: Consecutive acute ischemic stroke patients meeting inclusion criteria were retrospectively identified from our stroke registry between July 2008 and May 2014, and classified as stroke onset less than or equal to 4.5 hours treated with tPA (control; n = 369), tPA-treated WUS (n = 46), or nontreated WUS (n = 154). The primary outcome of interest for safety was symptomatic intracerebral hemorrhage (sICH), defined as parenchymal hemorrhage associated with a greater than or equal to 4-point increase in National Institutes of Health Stroke Scale (NIHSS) score. Multivariate logistic regression with adjustment for confounders and PS for receiving IV tPA assessed outcomes, along with PS-matched average treatment effect on the treated (ATT). FINDINGS: No significant difference was found in rates of sICH between tPA-treated WUS, nontreated WUS, and controls (2.2%, .7%, and 3%, respectively), or in the odds of sICH between tPA-treated WUS and controls (OR = .53, 95% CI = .06-4.60, P = .568). Among WUS patients, tPA treatment was significantly associated with higher odds of good functional outcome in fully adjusted analyses (OR = 7.22, 95% CI = 2.28-22.88, P = .001). The ATT of tPA for WUS patients demonstrated a significantly greater decrease in NIHSS score at discharge when compared to nontreated WUS patients (-4.32 versus -.34, P = .032). CONCLUSIONS: Comparable rates of sICH between treated WUS and stroke onset less than or equal to 4.5 hours treated with tPA suggest that tPA may be safely used to treat WUS. Superior outcomes for tPA-treated versus nontreated WUS subjects may suggest clinical efficacy of the treatment.

Plasticity of nitrogen allocation in the leaves of the invasive wetland grass, Phalaris arundinacea and co-occurring Carex species determines the photosynthetic sensitivity to nitrogen availability.

Phalaris arundinacea displaces the slower-growing, native sedge, Carex stricta, where nitrogen availability is high. Our aim was to address whether morphological and physiological traits associated with carbon gain for P. arundinacea and C. stricta responded to nitrogen supply differently and if the species exhibited different degrees of plasticity in these traits. The plants were grown in gravel and provided modified Hoagland's solution containing four nitrogen concentrations from 0.15 to 15 mM for 6 to 7 weeks. Supplied nitrogen affected the leaf nitrogen content to the same degree for both species. Increasing supplied nitrogen strongly increased CO2 assimilation (A), photosynthetic nitrogen use efficiency (PNUE), and respiration for P. arundinacea but had only a small effect on these parameters for C. stricta. Relative to growth at 15 mM nitrogen, growth at 0.15 mM for young leaves decreased carboxylation capacity and efficiency and the capacity for electron transport for P. arundinacea and a larger, stouter Carex species, Carex lacustris, by 53 to 70% but only 20 to 24% for C. stricta. Leaf nitrogen decreased approximately 50% for all species, but vacuolar nitrate did not decrease for P. arundinacea and C. stricta, suggesting that it does not serve as a nitrogen reserve for use during nitrogen deprivation in these species. After 4 months of nitrogen deprivation, P. arundinacea doubled A in 12 days after being supplied 15 mM nitrogen, whereas A for C. stricta increased only 22%. We propose that one factor linking P. arundinacea abundance to nitrogen availability involves this species' plastic response of carbon gain to nitrogen supply. C. stricta appears to be adapted to tolerate low nitrogen availability but cannot respond as rapidly and extensively as P. arundinacea when nitrogen supply is high.

Plant dieback under exceptional drought driven by elevation, not by plant traits, in Big Bend National Park, Texas, USA.

In 2011, Big Bend National Park, Texas, USA, experienced the most severe single year drought in its recorded history, resulting in significant plant mortality. We used this event to test how perennial plant response to drought varied across elevation, plant growth form and leaf traits. In October 2010 and October 2011, we measured plant cover by species at six evenly-spaced elevations ranging from Chihuahuan desert (666 m) to oak forest in the Chisos mountains (1,920 m). We asked the following questions: what was the relationship between elevation and stem dieback and did susceptibility to drought differ among functional groups or by leaf traits? In 2010, pre-drought, we measured leaf mass per area (LMA) on each species. In 2011, the percent of canopy dieback for each individual was visually estimated. Living canopy cover decreased significantly after the drought of 2011 and dieback decreased with elevation. There was no relationship between LMA and dieback within elevations. The negative relationship between proportional dieback and elevation was consistent in shrub and succulent species, which were the most common growth forms across elevations, indicating that dieback was largely driven by elevation and not by species traits. Growth form turnover did not influence canopy dieback; differences in canopy cover and proportional dieback among elevations were driven primarily by differences in drought severity. These results indicate that the 2011 drought in Big Bend National Park had a large effect on communities at all elevations with average dieback for all woody plants ranging from 8% dieback at the highest elevation to 83% dieback at lowest elevations.

Antecedent hypoglycemia impairs autonomic cardiovascular function: implications for rigorous glycemic control.

OBJECTIVE: Glycemic control decreases the incidence and progression of diabetic complications but increases the incidence of hypoglycemia. Hypoglycemia can impair hormonal and autonomic responses to subsequent hypoglycemia. Intensive glycemic control may increase mortality in individuals with type 2 diabetes at high risk for cardiovascular complications. We tested the hypothesis that prior exposure to hypoglycemia leads to impaired cardiovascular autonomic function. RESEARCH DESIGN AND METHODS: Twenty healthy subjects (age 28 +/- 2 years; 10 men) participated in two 3-day inpatient visits, separated by 1-3 months. Autonomic testing was performed on days 1 and 3 to measure sympathetic, parasympathetic, and baroreflex function. A 2-h hyperinsulinemic [hypoglycemic (2.8 mmol/l) or euglycemic (5.0 mmol/l)] clamp was performed in the morning and in the afternoon of day 2. RESULTS: Comparison of the day 3 autonomic measurements demonstrated that antecedent hypoglycemia leads to 1) reduced baroreflex sensitivity (16.7 +/- 1.8 vs. 13.8 +/- 1.4 ms/mmHg, P = 0.03); 2) decreased muscle sympathetic nerve activity response to transient nitroprusside-induced hypotension (53.3 +/- 3.7 vs. 40.1 +/- 2.7 bursts/min, P < 0.01); and 3) reduced (P < 0.001) plasma norepinephrine response to lower body negative pressure (3.0 +/- 0.3 vs. 2.0 +/- 0.2 nmol/l at -40 mmHg). CONCLUSIONS: Baroreflex sensitivity and the sympathetic response to hypotensive stress are attenuated after antecedent hypoglycemia. Because impaired autonomic function, including decreased cardiac vagal baroreflex sensitivity, may contribute directly to mortality in diabetes and cardiovascular disease, our findings raise new concerns regarding the consequences of hypoglycemia.