Relationships among habitat quality and measured condition variables in Gulf of Mexico mangroves

Ecosystem condition assessments were conducted for 12 mangrove sites in the northern Gulf of Mexico. Nine sites were selected randomly; three were selected a priori based on best professional judgment to represent a poor, intermediate and good environmental condition. During single visits a visual assessment generated numerical scores for each site relative to the reference condition range. Relationships were examined among variables to evaluate relevance of visual observations and empirical data of environmental condition. Sites in poorest visual condition possessed low concentrations of soil contaminants as hydrological attributes that restricted contaminant inflow lowered visual scores. Bacterial abundance related to the greatest number of variables, and was the only indicator that correlated with the visually derived score (0.60, p < 0.05). Soil enzymatic activity ratios within classes provided estimates of microbial nutrient status. Low peptidases/phosphatase and glycosidases/phosphatase ratios supported the conclusion reached from the molar ratios of nutrients, that mangrove soils were phosphorous limited. A positive correlation (0.71, p < 0.05) observed between C:N ratios in leaf tissue and soil from all mangrove sites indicated that relative molar ratios of major nutrients in leaf tissue were reflective of limitations in the soil. Principal components analysis guided a reduction in variables retained for analysis, and provided an ordination of the sites which grouped into three clusters and two outliers. Grouping was primarily influenced by soil C:N. In future studies measuring major nutrients in soil, C:N:P, could possibly function as a single, cost effective indicator to validate rapid visual condition assessments of mangroves.     

Cell death mediated by the N-terminal domains of a unique and highly conserved class of NB-LRR protein

Plant genomes encode large numbers of nucleotide-binding, leucine-rich repeat (NB-LRR) proteins, many of which are active in pathogen detection and defense response induction. NB-LRR proteins fall into two broad classes: those with a Toll and interleukin-1 receptor (TIR) domain at their N-terminus and those with a coiled-coil (CC) domain at the N-terminus. Within CC-NB-LRR-encoding genes, one basal clade is distinguished by having CC domains resembling the Arabidopsis thaliana RPW8 protein, which we refer to as CCR domains. Here, we show that CCR-NB-LRR-encoding genes are present in the genomes of all higher plants surveyed, and that they comprise two distinct subgroups: one typified by the Nicotiana benthamiana N-required gene 1 (NRG1) protein and the other typified by the Arabidopsis activated disease resistance gene 1 (ADR1) protein. We further report that, in contrast to CC-NB-LRR proteins, the CCR domains of both NRG1- and ADR1-like proteins are sufficient for the induction of defense responses, and that this activity appears to be SGT1-independent. Additionally, we report the apparent absence of both NRG1 homologs and TIR-NB-LRR-encoding genes from the dicot Aquilegia coerulea and the dicotyledonous order Lamiales as well as from monocotyledonous species. This strong correlation in occurrence is suggestive of a functional relationship between these two classes of NB-LRR proteins.     

The identification of 4,7-disubstituted naphthoic acid derivatives as UDP-competitive antagonists of P2Y14

A weak, UDP-competitive antagonist of the pyrimidinergic receptor P2RY₁₄ with a naphthoic acid core was identified through high-throughput screening. Optimization provided compounds with improved potency but poor pharmacokinetics. Acylglucuronidation was determined to be the major route of metabolism. Increasing the electron-withdrawing nature of the substituents markedly reduced glucuronidation and improved the pharmacokinetic profile. Additional optimization led to the identification of compound 38 which is an 8 nM UDP-competitive antagonist of P2Y₁₄ with a good pharmacokinetic profile.     

ARGONAUTE2 mediates RNA-silencing antiviral defenses against Potato virus X in Arabidopsis

RNA-silencing mechanisms control many aspects of gene regulation including the detection and degradation of viral RNA through the action of, among others, Dicer-like and Argonaute (AGO) proteins. However, the extent to which RNA silencing restricts virus host range has been difficult to separate from other factors that can affect virus-plant compatibility. Here we show that Potato virus X (PVX) can infect Arabidopsis (Arabidopsis thaliana), which is normally a nonhost for PVX, if coinfected with a second virus, Pepper ringspot virus. Here we show that the pepper ringspot virus 12K protein functions as a suppressor of silencing that appears to enable PVX to infect Arabidopsis. We also show that PVX is able to infect Arabidopsis Dicer-like mutants, indicating that RNA silencing is responsible for Arabidopsis nonhost resistance to PVX. Furthermore, we find that restriction of PVX on Arabidopsis also depends on AGO2, suggesting that this AGO protein has evolved to specialize in antiviral defenses.     

Antipsychotic drugs increase N-acetylaspartate and N-acetylaspartylglutamate in SH-SY5Y human neuroblastoma cells

N -Acetylaspartate (NAA) and N -acetylaspartylglutamate (NAAG) are related neuronal metabolites associated with the diagnosis and treatment of schizophrenia. NAA is a valuable marker of neuronal viability in magnetic resonance spectroscopy, a technique which has consistently shown NAA levels to be modestly decreased in the brains of schizophrenia patients. However, there are conflicting reports on the changes in brain NAA levels after treatment with antipsychotic drugs, which exert their therapeutic effects in part by blocking dopamine D₂ receptors. NAAG is reported to be an agonist of the metabotropic glutamate 2/3 receptor, which is linked to neurotransmitter release modulation, including glutamate release. Alterations in NAAG metabolism have been implicated in the development of schizophrenia possibly via dysregulation of glutamate neurotransmission. In the present study we have used high performance liquid chromatography to determine the effects of the antipsychotic drugs haloperidol and clozapine on NAA and NAAG levels in SH-SY5Y human neuroblastoma cells, a model system used to test the responses of dopaminergic neurons in vitro . The results indicate that the antipsychotic drugs haloperidol and clozapine increase both NAA and NAAG levels in SH-SY5Y cells in a dose and time dependant manner, providing evidence that NAA and NAAG metabolism in neurons is responsive to antipsychotic drug treatment.     

Unique receptor repertoire in mouse uterine NK cells

Uterine NK (uNK) cells are a prominent feature of the uterine mucosa and regulate placentation. NK cell activity is regulated by a balance of activating and inhibitory receptors, however the receptor repertoire of mouse uNK cells is unknown. We describe herein two distinct subsets of CD3(-)CD122(+) NK cells in the mouse uterus (comprising decidua and mesometrial lymphoid aggregate of pregnancy) at mid-gestation: a small subset indistinguishable from peripheral NK cells, and a larger subset that expresses NKp46 and Ly49 receptors, but not NK1.1 or DX5. This larger subset reacts with Dolichus biflores agglutinin, a marker of uNK cells in the mouse, and is adjacent to the invading trophoblast. By multiparametric analysis we show that the phenotype of uNK cells is unique and unprecedented in terms of adhesion, activation, and MHC binding potential. Thus, the Ly49 repertoire and the expression of other differentiation markers strikingly distinguish uNK cells from peripheral NK cells, suggesting that a selection process shapes the receptor repertoire of mouse uNK cells.     

The coiled-coil and nucleotide binding domains of the Potato Rx disease resistance protein function in pathogen recognition and signaling

Plant genomes encode large numbers of nucleotide binding and leucine-rich repeat (NB-LRR) proteins, some of which mediate the recognition of pathogen-encoded proteins. Following recognition, the initiation of a resistance response is thought to be mediated by the domains present at the N termini of NB-LRR proteins, either a Toll and Interleukin-1 Receptor or a coiled-coil (CC) domain. In order to understand the role of the CC domain in NB-LRR function, we have undertaken a systematic structure-function analysis of the CC domain of the potato (Solanum tuberosum) CC-NB-LRR protein Rx, which confers resistance to Potato virus X. We show that the highly conserved EDVID motif of the CC domain mediates an intramolecular interaction that is dependent on several domains within the rest of the Rx protein, including the NB and LRR domains. Other conserved and nonconserved regions of the CC domain mediate the interaction with the Ran GTPase-activating protein, RanGAP2, a protein required for Rx function. Furthermore, we show that the Rx NB domain is sufficient for inducing cell death typical of hypersensitive plant resistance responses. We describe a model of CC-NB-LRR function wherein the LRR and CC domains coregulate the signaling activity of the NB domain in a recognition-specific manner.     

Amount and distribution of biochemical-genetic variation among wild populations and a hatchery stock of Atlantic salmon, Salmo salar L., from north-east Ireland

The effects of tributyltin (TBT) compounds on gill morphology were examined in the mummichog, Fundulus heteroclitus , in 96-h LC50 and 6-week sublethal exposures. Morphometry was used for the identification and quantification of effects with the light microscope. A 96-h LC50 of 17.2 μg 1 ¹ was determined. Morphometric analysis of gill tissues revealed hypertrophy of the lamellar epithelium in fish exposed to 17.2 μg 1–1. Relative diffusing capacity was significantly decreased (−41 %); ( P <0.05, ANOVA, Bonferroni t -test). At 35.6 μg 1⁻¹, TBT exposure resulted in a significant reduction (− 40%) in the volume of the lamellar blood channels. Both of these observations occurred in fish that showed signs of acute poisoning including loss of equilibrium. In fish exposed to sublethal concentrations of 0.105–2.000 μg TBT 1⁻¹ for 6 weeks, there were no pathological changes in the gill. There were no treatment-related changes in the surface morphology of the gills of fish from both experiments upon scanning electron microscopic examination. Although gill pathology was observed in acutely toxic exposures, it does not appear to be a major mechanism of TBT toxicity.     

Atrial natriuretic peptide levels during development of chronic heart failure after myocardial infarction in rats

Serum levels of atrial natriuretic peptide (ANP) are elevated in chronic heart failure presumably due to dilatation of the left atrium resulting from increases in intracardiac pressures. To define the time course of changes in serum ANP levels and to determine the relationship to left ventricular end-diastolic pressure, rats were subjected to coronary artery ligation to produce myocardial infarction and left ventricular failure. Atrial natriuretic peptide levels were measured weekly for four weeks thereafter. In rats with myocardial infarction and elevation of left ventricular end-diastolic pressure there was no change in ANP levels at 7 and 14 days. However, at day 21 and 28, ANP levels were elevated more than 3 fold. There was a correlation between ANP levels and left ventricular end-diastolic pressures. There was no correlation between ANP levels and right atrial pressures or serum sodium concentrations. We conclude that the chronic elevation of left ventricular end-diastolic pressure is required to produce an increase in ANP after myocardial infarction which results in chronic heart failure.