Bush Lupine Mortality, Altered Resource Availability, and Alternative Vegetaion States

Nitrogen-fixing plants, by altering the availability of soil N, potentially facilitate plant invasion. Here we describe how herbivore-driven mortality of a native N-fixing shrub, bush lupine (Lupinus arboreus), increases soil N and light availability, which promotes invasion by introduced grasses to the detriment of a native plant community. Soils under live and dead lupine stands contained large amounts of total N, averaging 3.14 mg N/g dry mass of soil (398 g/m2) and 3.45 mg N/g dry mass of soil (438 g/m2), respectively, over four years. In contrast, similar lupine-free soil was low in N and averaged only 1.66 mg N/g dry mass of soil (211 g/m2) over three years. The addition of N fertilizer to lupine-free soil produced an 81% increase in aboveground plant biomass compared to plots unamended with N. Mean rates of net N mineralization were higher under live lupine and where mass die-off of lupine had occurred compared to soils free of bush lupine. At all sites, only 2.5–4.2% of the total soil N pool was mineralized annually. Soil enriched by lupine is not available to colonists while lupines are alive. The dense canopy of lupine shades soil under shrubs, reducing average photon-flux density in late spring from 1725 μmol·m−2·s−1 (full sunlight) to 13 μmol·m−2·s−1 (underneath shrubs). Stand die-off due to insect herbivory exposed this bare, enriched soil. In January, when annual plants are establishing, average photon-flux density under dead lupines killed by insect herbivores was 370 μmol·m−2·s−1, compared to the photon-flux density under live lupines of the same age, which averaged 83 μmol·m−2·s−1. The availability of bare, N-rich patches of soil enabled nonnative annuals (primarily Lolium multiflorum and Bromus diandrus) to colonize sites, grow rapidly, and dominate the plant assemblage until lupines reestablished after several years. The N content of these grasses was significantly greater than the N content of the mostly native plants that occupied adjacent coastal prairie devoid of bush lupine. Between 57 and 70% of the net amount of N mineralized annually was taken up by introduced grasses and subsequently returned to the soil upon the death of these annuals. Even in the absence of further N inputs, we estimate that it would take at least 25 yr to reduce the soil N pool by 50%, indicating that the reestablishment of the native prairie flora is likely to be long term

Restoring Enriched Grasslands: Effects of Mowing on Species Richness, Productivity, and Nitrogen Retention

Species-rich grasslands that become enriched with nitrogen often suffer decreases in species richness, increases in plant biomass, and invasion by weedy exotic species. Suitable techniques to restore enriched grasslands and reestablish native communities are increasingly needed. Here we report results of a 5-yr experiment in enriched coastal prairie grasslands (Bodega Marine Reserve, Bodega Bay, California, USA), to determine the combined effects of mowing and biomass removal on total soil nitrogen, net rates of mineralization, nitrogen retention, and species richness and biomass. We mowed and removed plant biomass from plots in areas where the N-fixing shrub, bush lupine (Lupinus arboreus), had greatly enriched the soil, and where the community was composed of weedy introduced plants. Our goal was to facilitate the establishment of the native grassland assemblage such as was found at nearby low soil nitrogen sites. Mowing and biomass removal resulted in a dramatic change in the species assemblage, from exotic annual grasses to a mixed exotic/native forb community composed primarily of perennials. Species richness was significantly greater in treated plots than in control plots; weedy exotic grasses diminished in abundance, and both native and exotic forb species increased. In mowed vs. control plots, there was significantly less mean aboveground biomass, but significantly greater belowground biomass. This shift in species composition had significant impacts on nitrogen retention. In late fall and winter when plant-available N was highest, much nitrogen leached from the effectively fallow control plots where germination of annual grasses did not peak until midwinter. In contrast, mowed plots retained substantially greater amounts of nitrogen, due to the presence of perennial plants possessing large amounts of belowground biomass early in the season. Despite the cumulative removal of 22 g N/m2 in biomass over 5 yr, there was no difference between mowed and control plots in total soil N, pool sizes of inorganic N, or net rates of N mineralization. The results indicate that removal of plant biomass by mowing shifted this plant community from an annual grass to a perennial forb assemblage. However, in doing so, N retention by vegetation was increased, making it more difficult to reduce soil N

Lunar Lander Offloading Operations Using a Heavy-Lift Lunar Surface Manipulator System

This study investigates the feasibility of using a heavy-lift variant of the Lunar Surface Manipulator System (LSMS-H) to lift and handle a 12 metric ton payload. Design challenges and requirements particular to handling heavy cargo were examined. Differences between the previously developed first-generation LSMS and the heavy-lift version are highlighted. An in-depth evaluation of the tip-over risk during LSMS-H operations has been conducted using the Synergistic Engineering Environment and potential methods to mitigate that risk are identified. The study investigated three specific offloading scenarios pertinent to current Lunar Campaign studies. The first involved offloading a large element, such as a habitat or logistics module, onto a mobility chassis with a lander-mounted LSMS-H and offloading that payload from the chassis onto the lunar surface with a surface-mounted LSMS-H. The second scenario involved offloading small pressurized rovers with a lander-mounted LSMS-H. The third scenario involved offloading cargo from a third-party lander, such as the proposed ESA cargo lander, with a chassis-mounted LSMS-H. In all cases, the analyses show that the LSMS-H can perform the required operations safely. However, Chariot-mounted operations require the addition of stabilizing outriggers, and when operating from the Lunar surface, LSMS-H functionality is enhanced by adding a simple ground anchoring system

An accurate in vitro model of the E. coli envelope

Gram-negative bacteria are an increasingly serious source of antibiotic-resistant infections, partly owing to their characteristic protective envelope. This complex, 20 nm thick barrier includes a highly impermeable, asymmetric bilayer outer membrane (OM), which plays a pivotal role in resisting antibacterial chemotherapy. Nevertheless, the OM molecular structure and its dynamics are poorly understood because the structure is difficult to recreate or study in vitro. The successful formation and characterization of a fully asymmetric model envelope using Langmuir-Blodgett and Langmuir-Schaefer methods is now reported. Neutron reflectivity and isotopic labeling confirmed the expected structure and asymmetry and showed that experiments with antibacterial proteins reproduced published in vivo behavior. By closely recreating natural OM behavior, this model provides a much needed robust system for antibiotic development

Viral Endomyocardial Infection Is an Independent Predictor and Potentially Treatable Risk Factor for Graft Loss and Coronary Vasculopathy in Pediatric Cardiac Transplant Recipients

ObjectivesThis study sought to evaluate the outcome and prevalence of viral endomyocardial infection after cardiac transplantation.BackgroundViral myocardial infection causes heart failure, but its role after cardiac transplantation is unclear. We hypothesized that viral infection of the cardiac allograft reduces graft survival.MethodsBetween June 1999 and November 2004, 94 pediatric cardiac transplant patients were screened for the presence of viral genome in serial endomyocardial biopsies (EMBs) using polymerase chain reaction (PCR) assays. Graft loss, advanced transplant coronary artery disease (TCAD), and acute rejection (AR) were compared in the PCR-positive (n = 37) and PCR-negative (n = 57) groups, using time-dependent Kaplan-Meier and Cox regression analyses. From November 2002 to November 2004, intravenous immunoglobulin therapy (IVIG) was administered to patients with PCR-positive EMBs. The outcomes of the IVIG-treated, PCR-positive patients (n = 20) were compared with IVIG-untreated, PCR-positive patients (n = 17).ResultsViral genomes were detected in EMBs from 37 (39%) patients; parvovirus B19, adenovirus, and Epstein-Barr virus (EBV) were the most common. The PCR-positive group (n = 37, 25% graft loss at 2.4 years) had decreased graft survival (p < 0.001) compared with the PCR-negative group (n = 57, 25% graft loss at 8.7 years) and developed advanced TCAD prematurely (p = 0.001). The number of AR episodes was similar in both groups. On multivariate analysis, presence of viral genome was an independent risk factor for graft loss (relative risk: 4.2, p = 0.015). The time to advanced TCAD after becoming PCR-positive was longer in the IVIG-treated patients (p = 0.03) with a trend toward improved graft survival (p = 0.06).ConclusionsViral endomyocardial infection is an independent predictor of graft loss in pediatric cardiac transplant recipients. This effect appears to be mediated through premature development of advanced TCAD. IVIG therapy in this subgroup may improve survival and merits further investigation

Differences in Presentation and Outcomes between Children with Familial Dilated Cardiomyopathy and Children with Idiopathic Dilated Cardiomyopathy: A Report from the Pediatric Cardiomyopathy Registry Study Group

Research comparing the survival of children with familial dilated cardiomyopathy (FDCM) to that of children with idiopathic dilated cardiomyopathy (IDCM) has produced conflicting results

Phenotypic and molecular characterisation of CDK13-related congenital heart defects, dysmorphic facial features and intellectual developmental disorders

Background: De novo missense variants in CDK13 have been described as the cause of syndromic congenital heart defects in seven individuals ascertained from a large congenital cardiovascular malformations cohort. We aimed to further define the phenotypic and molecular spectrum of this newly described disorder. Methods: To minimise ascertainment bias, we recruited nine additional individuals with CDK13 pathogenic variants from clinical and research exome laboratory sequencing cohorts. Each individual underwent dysmorphology exam and comprehensive medical history review. Results: We demonstrate greater than expected phenotypic heterogeneity, including 33% (3/9) of individuals without structural heart disease on echocardiogram. There was a high penetrance for a unique constellation of facial dysmorphism and global developmental delay, as well as less frequently seen renal and sacral anomalies. Two individuals had novel CDK13 variants (p.Asn842Asp, p.Lys734Glu), while the remaining seven unrelated individuals had a recurrent, previously published p.Asn842Ser variant. Summary of all variants published to date demonstrates apparent restriction of pathogenic variants to the protein kinase domain with clustering in the ATP and magnesium binding sites. Conclusions: Here we provide detailed phenotypic and molecular characterisation of individuals with pathogenic variants in CDK13 and propose management guidelines based upon the estimated prevalence of anomalies identified. Keywords: CDK13, CHDFIDD, De novo variant, Neurodevelopmental disorders, Agenesis of the corpus callosum, Hypertelorism, Developmental delay, Cyclin-dependent kinase, Undiagnosed Diseases Networ