Influence of microbial activity on plant–microbial competition for organic and inorganic nitrogen

To investigate how the level of microbial activity in grassland soils affects plant–microbial competition for different nitrogen (N) forms, we established microcosms consisting of a natural soil community and a seedling of one of two co-existing grass species, Anthoxanthum odoratum or Festuca rubra. We then stimulated the soil microbial community with glucose in half of the microcosms and followed the transfer of added inorganic (¹⁵NH₄¹⁵NO₃) and organic (glycine-2-¹³C-¹⁵N) N into microbial and plant biomass. We found that microbes captured significantly more ¹⁵N in organic than in inorganic form and that glucose addition increased microbial ¹⁵N capture from the inorganic source. Shoot and root biomass, total shoot N content and shoot and root ¹⁵N contents were significantly greater for A. odoratum than F. rubra, whereas F. rubra had higher shoot and root N concentrations. Where glucose was not added, A. odoratum had higher shoot ¹⁵N content with organic than with inorganic ¹⁵N addition, whereas where glucose was added, both species had higher shoot ¹⁵N content with inorganic than with organic ¹⁵N. Glucose addition had equally negative effects on shoot growth, total shoot N content, shoot and root N concentrations and shoot and root ¹⁵N content for both species. Both N forms produced significantly more shoot biomass and higher shoot N content than the water control, but the chemical form of N had no significant effect. Our findings suggest that plant species that are better in capturing nutrients from soil are not necessarily better in tolerating increasing microbial competition for nutrients. It also appears that intense microbial competition has more adverse effects on the uptake of organic than inorganic N by plants, which may potentially have significant implications for interspecific plant–plant competition for N in ecosystems where the importance of organic N is high and some of the plant species specialize in use of organic N.     

Burn injuries inflicted on children or the elderly: a framework for clinical and forensic assessment

LEARNING OBJECTIVES: After studying this article, the participant should be able to: 1. Understand the difference between battery and assault in U.S. law and the concepts of the phrase "child abuse" and "elder abuse." 2. Understand that state statutes vary and can define abuse narrowly or with great specificity, and that either definition has inherent problems for physicians treating victims of abuse and neglect. 3. Know where to find the state-specific legal criteria for child or elder abuse and neglect, along with the corresponding standards for mandatory reporting and physician accountability. 4. Understand the relevant law regarding physician-patient privilege and the repercussions of incorrect but good faith reporting and of failing to report suspected abuse or neglect of children or the elderly. 5. Understand that there are no pathognomic signs for inflicted burn injury. 6. Clinically assess burned pediatric or elderly patients within a framework that will minimize the risk of missing or inappropriately suspecting injuries that stem from abuse or neglect. SUMMARY: This article deals with burns inflicted on children and the elderly, two particularly vulnerable societal groups. Though inflicted burning is a relatively rare method of inflicting physical abuse, failure to diagnose it has far-reaching ramifications. These injuries pose both medical and forensic problems for physicians, along with unique ethical dilemmas. This article is a collaboration between surgeons and lawyers providing a holistic, workable approach to the management of inflicted burn injury. The authors first describe the legal considerations that must be appreciated by U.S. physicians, then they suggest a rational and balanced clinical approach to the assessment of burn injuries that may have been inflicted intentionally or negligently on children and the elderly.     

Characterization of the phospholemman knockout mouse heart: depressed left ventricular function with increased Na-K-ATPase activity

Phospholemman (PLM, FXYD1), abundantly expressed in the heart, is the primary cardiac sarcolemmal substrate for PKA and PKC. Evidence supports the hypothesis that PLM is part of the cardiac Na-K pump complex and provides the link between kinase activity and pump modulation. PLM has also been proposed to modulate Na/Ca exchanger activity and may be involved in cell volume regulation. This study characterized the phenotype of the PLM knockout (KO) mouse heart to further our understanding of PLM function in the heart. PLM KO mice were bred on a congenic C57/BL6 background. In vivo conductance catheter measurements exhibited a mildly depressed cardiac contractile function in PLM KO mice, which was exacerbated when hearts were isolated and Langendorff perfused. There were no significant differences in action potential morphology in paced Langendorff-perfused hearts. Depressed contractile function was associated with a mild cardiac hypertrophy in PLM KO mice. Biochemical analysis of crude ventricular homogenates showed a significant increase in Na-K-ATPase activity in PLM KO hearts compared with wild-type controls. SDS-PAGE and Western blot analysis of ventricular homogenates revealed small, nonsignificant changes in Na- K-ATPase subunit expression, with two-dimensional gel (isoelectric focusing, SDS-PAGE) analysis revealing minimal changes in ventricular protein expression, indicating that deletion of PLM was the primary reason for the observed PLM KO phenotype. These studies demonstrate that PLM plays an important role in the contractile function of the normoxic mouse heart. Data are consistent with the hypothesis that PLM modulates Na-K-ATPase activity, indirectly affecting intracellular Ca and hence contractile function.     

Do male ornaments signal immunity in the common yellowthroat?

Male ornaments may advertise genetic benefits to females choosingmates. These benefits may come in the form of genes for resistanceto parasites and disease. Thus, females that prefer more ornamentedmales as mates may receive genes for enhanced immune systemfunction for their offspring. The common yellowthroat (Geothlypistrichas) is the only species to date in which a male plumageornament (size of the black facial mask) is known to be relatedto extrapair mating, and extrapair young are more immunocompetentthan their within-pair half-sibs (at least in colder years).To investigate whether male mask size signals superior immunefunction, we examined male ornaments (mask and bib size andcolor) in relation to measures of overall health (hematocrit)and immune system function (plasma immunoglobulin G [IgG] concentrationand cutaneous immune activity). We also investigated the rolethat testosterone may play in mediating the relationship betweenornaments and immunity. Male mask size was correlated positivelywith IgG level, suggesting that male mask size may indicatehumoral immunity. However, mask size was correlated negativelywith hematocrit and cutaneous immune activity (our measure ofnestling immunocompetence). Bib size and color were not relatedto these indices of immune function or health. Plasma testosteronelevel was neither related to immune function or health nor tothe expression of male ornaments. These results suggest thatthere might be a trade-off between immune system components,as well as between immunity and the production or advertisementof male ornaments.     

The membrane dynamics of pexophagy are influenced by Sar1p in Pichia pastoris

Several Sec proteins including a guanosine diphosphate/guanosine triphosphate exchange factor for Sar1p have been implicated in autophagy. In this study, we investigated the role of Sar1p in pexophagy by expressing dominant-negative mutant forms of Sar1p in Pichia pastoris. When expressing sar1pT34N or sar1pH79G, starvation-induced autophagy, glucose-induced micropexophagy, and ethanol-induced macropexophagy are dramatically suppressed. These Sar1p mutants did not affect the initiation or expansion of the sequestering membranes nor the trafficking of Atg11p and Atg9p to these membranes during micropexophagy. However, the lipidation of Atg8p and assembly of the micropexophagic membrane apparatus, which are essential to complete the incorporation of the peroxisomes into the degradative vacuole, were inhibited when either Sar1p mutant protein was expressed. During macropexophagy, the expression of sar1pT34N inhibited the formation of the pexophagosome, whereas sar1pH79G suppressed the delivery of the peroxisome from the pexophagosome to the vacuole. The pexophagosome contained Atg8p in wild-type cells, but in cells expressing sar1pH79G these organelles contain both Atg8p and endoplasmic reticulum components as visualized by DsRFP-HDEL. Our results demonstrate key roles for Sar1p in both micro- and macropexophagy.     

Enzyme‐linked immunosorbent assay to quantitate serum ferritin in the northern fur seal (Callorhinus ursinus)

Serum ferritin concentration correlates with tissue iron stores in humans, horses, calves, dogs, cats, and pigs. Serum ferritin is considered the best serum analyte to predict total body iron stores in these species, and is more reliable than serum iron or total iron‐binding capacity, both of which may be affected by disorders unrelated to iron adequacy or excess (including hypoproteinemia, chronic infection, hemolytic anemia, hypothyroidism, renal disease, and drug administration). Iron overload has been documented to result in hemochromatosis in captive northern fur seals (Callorhinus ursinus); therefore, we developed an enzyme‐linked immunosorbent assay (ELISA) to measure serum ferritin in this species. The assay uses two murine anti‐canine ferritin monoclonal antibodies in a sandwich arrangement that was originally used in an ELISA to measure serum ferritin in dogs. Ferritin isolated from fur seal liver was used as a standard. Ferritin standards were linear from 0 to 50 ng/ml. Recovery of purified ferritin from fur seal serum varied from 89% to 99%. The within‐assay variability was 6%, and the assay‐to‐assay variability for two different samples was 10% and 16%. Zoo Biol 23:79‐84, 2004.© 2004 Wiley‐Liss, Inc.     

Evaluation of (Z)-9-tricosene baited targets for control of the housefly (Musca domestica) in outdoor situations

Houseflies (Musca domestica L.) are a major pest species in a variety of outdoor situations, notably on and around livestock farms and landfill used for the disposal of domestic waste. Currently no effective options are available for control of houseflies outdoors, because many populations exhibit at least some resistance to all available synthetic pesticides. (Z)‐9‐tricosene is the only commercially available pheromone for use in lure‐and‐kill approaches to housefly control, and it is widely used in indoor livestock units in combination with sugar/insecticide bait. Here we examine the potential of this approach for use outdoors, on a landfill site. We investigate the efficacy of toxic targets painted with a sugar/insecticide/(Z)‐9‐tricosene mix. The effects of target size and pheromone concentration were examined in two replicate trials, conducted in June and September 2003. As expected, catch consisted largely of males, was consistently higher on larger traps, and generally increased with (Z)‐9‐tricosene concentration even up to very high levels. However, in repeated trials, and despite mass release of marked flies, catch rates appeared to be insufficient to provide adequate control. We suggest that this is probably because (Z)‐9‐tricosene is primarily a short‐range attractant, and fly populations in outdoor situations are generally distributed over a large area. Catch declined rapidly to zero within 2 weeks, indicating that improved formulation or target design is needed to slow the weathering of active ingredients on the targets. It seems unlikely that (Z)‐9‐tricosene is sufficiently attractive to houseflies to provide an effective and economic lure in outdoor situations.     

Likelihood-based clustering (LiBaC) for codon models, a method for grouping sites according to similarities in the underlying process of evolution

Models of codon evolution are useful for investigating the strength and direction of natural selection via a parameter for the nonsynonymous/synonymous rate ratio (omega = d(N)/d(S)). Different codon models are available to account for diversity of the evolutionary patterns among sites. Codon models that specify data partitions as fixed effects allow the most evolutionary diversity among sites but require that site partitions are a priori identifiable. Models that use a parametric distribution to express the variability in the omega ratio across site do not require a priori partitioning of sites, but they permit less among-site diversity in the evolutionary process. Simulation studies presented in this paper indicate that differences among sites in estimates of omega under an overly simplistic analytical model can reflect more than just natural selection pressure. We also find that the classic likelihood ratio tests for positive selection have a high false-positive rate in some situations. In this paper, we developed a new method for assigning codon sites into groups where each group has a different model, and the likelihood over all sites is maximized. The method, called likelihood-based clustering (LiBaC), can be viewed as a generalization of the family of model-based clustering approaches to models of codon evolution. We report the performance of several LiBaC-based methods, and selected alternative methods, over a wide variety of scenarios. We find that LiBaC, under an appropriate model, can provide reliable parameter estimates when the process of evolution is very heterogeneous among groups of sites. Certain types of proteins, such as transmembrane proteins, are expected to exhibit such heterogeneity. A survey of genes encoding transmembrane proteins suggests that overly simplistic models could be leading to false signal for positive selection among such genes. In these cases, LiBaC-based methods offer an important addition to a "toolbox" of methods thereby helping to uncover robust evidence for the action of positive selection.     

Simulation of stent deployment in a realistic human coronary artery

Background  

The process of restenosis after a stenting procedure is related to local biomechanical environment. Arterial wall stresses caused by the interaction of the stent with the vascular wall and possibly stress induced stent strut fracture are two important parameters. The knowledge of these parameters after stent deployment in a patient derived 3D reconstruction of a diseased coronary artery might give insights in the understanding of the process of restenosis.