NRT1.1-Related NH4 + Toxicity Is Associated with a Disturbed Balance between NH4 + Uptake and Assimilation.

A high concentration of ammonium (NH4 +) as the sole source of nitrogen in the growth medium often is toxic to plants. The nitrate transporter NRT1.1 is involved in mediating the effects of NH4 + toxicity; however, the mechanism remains undefined. In this study, wild-type Arabidopsis (Arabidopsis thaliana Columbia-0 [Col-0]) and NRT1.1 mutants (chl1-1 and chl1-5) were grown hydroponically in NH4NO3 and (NH4)2SO4 media to assess the function of NRT1.1 in NH4 + stress responses. All the plants grew normally in medium containing mixed nitrogen sources, but Col-0 displayed more chlorosis and lower biomass and photosynthesis than the NRT1.1 mutants in (NH4)2SO4 medium. Grafting experiments between Col-0 and chl1-5 further confirmed that NH4 + toxicity is influenced by NRT1.1. In (NH4)2SO4 medium, NRT1.1 induced the expression of NH4 + transporters, increasing NH4 + uptake. Additionally, the activities of glutamine synthetase and glutamate synthetase in roots of Col-0 plants decreased and soluble sugar accumulated significantly, whereas pyruvate kinase-mediated glycolysis was not affected, all of which contributed to NH4 + accumulation. By contrast, the NRT1.1 mutants showed reduced NH4 + accumulation and enhanced NH4 + assimilation through glutamine synthetase, glutamate synthetase, and glutamate dehydrogenase. Moreover, the up-regulation of genes involved in ethylene synthesis and senescence in Col-0 plants treated with (NH4)2SO4 suggests that ethylene is involved in NH4 + toxicity responses. This study showed that NH4 + toxicity is related to a nitrate-independent signaling function of NRT1.1 in Arabidopsis, characterized by enhanced NH4 + accumulation and altered NH4 + metabolism, which stimulates ethylene synthesis, leading to plant senescence.

Nitrogen Use Efficiency Is Mediated by Vacuolar Nitrate Sequestration Capacity in Roots of Brassica napus.

Enhancing nitrogen use efficiency (NUE) in crop plants is an important breeding target to reduce excessive use of chemical fertilizers, with substantial benefits to farmers and the environment. In Arabidopsis (Arabidopsis thaliana), allocation of more NO3 (-) to shoots was associated with higher NUE; however, the commonality of this process across plant species have not been sufficiently studied. Two Brassica napus genotypes were identified with high and low NUE. We found that activities of V-ATPase and V-PPase, the two tonoplast proton-pumps, were significantly lower in roots of the high-NUE genotype (Xiangyou15) than in the low-NUE genotype (814); and consequently, less vacuolar NO3 (-) was retained in roots of Xiangyou15. Moreover, NO3 (-) concentration in xylem sap, [(15)N] shoot:root (S:R) and [NO3 (-)] S:R ratios were significantly higher in Xiangyou15. BnNRT1.5 expression was higher in roots of Xiangyou15 compared with 814, while BnNRT1.8 expression was lower. In both B. napus treated with proton pump inhibitors or Arabidopsis mutants impaired in proton pump activity, vacuolar sequestration capacity (VSC) of NO3 (-) in roots substantially decreased. Expression of NRT1.5 was up-regulated, but NRT1.8 was down-regulated, driving greater NO3 (-) long-distance transport from roots to shoots. NUE in Arabidopsis mutants impaired in proton pumps was also significantly higher than in the wild type col-0. Taken together, these data suggest that decrease in VSC of NO3 (-) in roots will enhance transport to shoot and essentially contribute to higher NUE by promoting NO3 (-) allocation to aerial parts, likely through coordinated regulation of NRT1.5 and NRT1.8.

Herniation of cartilaginous endplates in the lumbar spine: MRI findings.

OBJECTIVE: The purpose of this study was to determine reliable MRI findings suggesting disk herniation with cartilage endplate herniation in the lumbar spine. MATERIALS AND METHODS: The records of 73 patients who underwent lumbar spinal MRI and lumbar microdiskectomy between March 2005 and January 2009 were searched to find those with the diagnosis of disk herniation with cartilage endplate herniation confirmed during surgery. The following morphologic features were assessed: posterior corners (posterior marginal nodes, dorsal corner defects, Modic changes, and posterior osteophytes), mid endplates (endplate irregularities, Modic changes), and heterogeneous low signal intensity of extruded material. The chi-square test and multiple logistic regression analysis with age, body mass index, and sex as covariates were used for the analysis. The ROC curve was obtained with scores of the statistically significant MRI findings. RESULTS: Posterior marginal nodes, posterior osteophytes, Modic changes in posterior corners, mid endplate irregularities, Modic changes in mid endplates, and heterogeneous low signal intensity of extruded material were significantly more frequent in patients with disk herniation with cartilage endplate herniation (0.000 < p < 0.009). The AUC for diagnosing disk herniation with cartilage endplate herniation with our scoring system of the six MRI findings (0-6) was 0.888. CONCLUSION: The presence of disk herniation with cartilage endplate herniation could be ascertained with the following MRI findings: posterior marginal nodes, posterior osteophytes, mid endplate irregularities, heterogeneous low signal intensity of extruded material, and Modic changes in posterior corners and mid endplates.

Potential for control of harmful cyanobacterial blooms using biologically derived substances: problems and prospects.

Water blooms of cyanobacteria have posed a worldwide environmental threat and a human health hazard in recent decades. Many biologically derived (but non-antibiotic) bioactive substances are known to inhibit the growth of aquatic bloom-forming cyanobacteria. Some of these biologically derived substances (BDSs) have no or low toxicity to aquatic animals and humans. Most BDSs are easily biodegradable in aquatic environments. These characteristics indicate that they may have potential for control and removal of harmful algae. However, BDSs also have the disadvantages of high cost of preparation, and possible damage to non-target aquatic organisms, and sometimes, low efficiency of algae removal. The ecological risks of most BDSs are still unknown. Here, we review recent research progress relative to the inhibitory effects of BDSs on cyanobacteria, and critically analyze the potential of BDSs as algicides with an emphasis on possible problems during the process of controlling harmful cyanobacteria. We suggest avenues of study to enhance effective use of BDSs in controlling of cyanobacterial blooms; these include guidelines for isolation and characterization of new effective BDSs, exploiting the synergistic effects of BDSs, the merits of controlling harmful cyanobacteria at the early stages of proliferation and evaluation of ecological risks of BDSs.

Feasibility and accuracy of dual-source dual-energy CT for noninvasive determination of hepatic iron accumulation.

PURPOSE: To retrospectively assess feasibility of dual-source dual-energy (DSDE) computed tomography (CT) for evaluation of hepatic iron accumulation in a liver phantom and liver transplantation candidates and to compare its accuracy with that of 3-T magnetic resonance (MR) imaging. MATERIALS AND METHODS: This study was approved by the institutional review board; informed consent was waived. A liver agar phantom containing six tubes of iron (concentrations, 100-5000 mg of iron per 100 mL of solution) was scanned at 80 and 140 kVp with both DSDE mode and single-source dual-energy (SSDE) CT with sequential scanning mode. Difference of averaged attenuation between 80 and 140 kVp at CT (ΔH) was measured and correlated with iron concentration. Thirty-two liver transplant recipients and 55 donors who underwent DSDE CT at 80 and 140 kVp were included. Twenty-three underwent 3-T liver MR with dual-echo in-phase and opposed-phase T1-weighted and spin-echo T2-weighted imaging. Hepatic ΔH was measured at CT. On T1- and T2-weighted MR images, iron indexes were calculated. Degree of iron accumulation and macrosteatosis were determined at histologic examination (reference). Diagnostic performance of ΔH at CT and iron indexes at MR for diagnosing clinically important iron accumulation was evaluated (receiver operating characteristic [ROC] analysis). RESULTS: For phantom study, ΔH obtained from both DSDE mode and SSDE CT with sequential scanning mode was correlated with iron concentration (correlation coefficient, 1.00 and 0.943, respectively; P = .173). ΔH (13.53) in 10 patients with clinically important (≥ 10%) iron accumulation was significantly higher than that (7.39) in 77 patients with normal or mild iron deposition (P < .001). ΔH was significantly correlated with degree of iron accumulation (correlation coefficient, 0.430; P < .001) but not with degree of hepatic macrosteatosis (P = .216). Area under the ROC curve for diagnosing clinically important iron accumulation was 0.881 and 0.897 with CT and MR, respectively (P = .851). CONCLUSION: DSDE CT is accurate for diagnosing clinically important hepatic iron accumulation without confounding influence of hepatic steatosis, with diagnostic performance on par with MR.

Quantification of hepatic macrosteatosis in living, related liver donors using T1-independent, T2*-corrected chemical shift MRI.

PURPOSE: To evaluate the diagnostic implications of the iterative decomposition of water and fat using echo-asymmetry and the least-squares estimation (IDEAL) technique to detect hepatic steatosis (HS) in potential liver donors using histopathology as the reference standard. MATERIALS AND METHODS: Forty-nine potential liver donors (32 male, 17 female; mean age, 31.7 years) were included. All patients were imaged using the in- and out-of-phase (IOP) gradient-echo (GRE) and IDEAL techniques on a 1.5 T MR scanner. To estimate the hepatic fat fraction (FF), two reviewers performed regions-of-interest measurement in 15 areas of the liver seen on the IOP images and on the IDEAL-FF images. The magnetic resonance imaging (MRI) and pathology values of macrosteatosis were correlated using the Pearson correlation coefficient. We analyzed the diagnostic performance of IOP imaging and IDEAL for detecting HS. RESULTS: The results of the hepatic-FF estimated on IDEAL were well correlated with the histologic degree of macrosteatosis (γ = 0.902, P < 0.001). IDEAL showed 100% sensitivity and 91% specificity for detecting HS, and IOP imaging showed 87.5% sensitivity and 97% specificity, respectively. CONCLUSION: IDEAL is a useful tool for the preoperative diagnosis of HS in potential living liver donors; it can also help to avoid unnecessary biopsies in these patients.

Culture-based indicators of fecal contamination and molecular microbial indicators rarely correlate with Campylobacter spp. in recreational waters.

Campylobacter spp. are the leading cause of gastroenteritis worldwide. Most human infections result from contaminated food; however, infections are also caused by recreational waterway contamination. Campylobacter culture is technically challenging and enumeration by culture-based methods is onerous. Thus, we employed qPCR to quantify Campylobacter spp. in fresh- and marine-water samples, raw sewage and animal feces. Multiplex PCR determined whether Campylobacter jejuni or C. coli, most commonly associated with human disease, were present in qPCR-positive samples. Campylobacters were detected in raw sewage, and in feces of all avian and mammalian species tested. Campylobacter-positive concentrations ranged from 68 to 2.3 × 106 cells per 500 mL. Although C. jejuni and C. coli were rare in waterways, they were prevalent in sewage and feces. Campylobacter-specific qPCR screening of environmental waters did not correlate with the regulatory EPA method 1600 (Enterococcus culture), nor with culture-independent, molecular-based microbial source tracking indicators, such as human polyomavirus, human Bacteroidales and Methanobrevibacter smithii. Our results suggest that neither the standard EPA method nor the newly proposed culture-independent methods are appropriate surrogates for Campylobacter contamination in water. Thus, assays for specific pathogens may be necessary to protect human health, especially in waters that are contaminated with sewage and animal feces.

Balance between nitrogen use efficiency and cadmium tolerance in Brassica napus and Arabidopsis thaliana.

The transmembrane transport of NO3- and Cd2+ into plant cell vacuoles relies on the energy from their tonoplast proton pumps, V-ATPase and V-PPase. If the activity of these pumps is reduced, it results in less NO3- and Cd2+ being transported into the vacuoles, which contributes to better nitrogen use efficiency (NUE) and lower Cd2+ tolerance in plants. The physiological mechanisms that regulate the balance between NUE and Cd2+ tolerance remain unknown. In our study, two Brassica napus genotypes with differential NUEs, xiangyou 15 and 814, and Atclca-2 mutant and AtCAX4 over-expression line (AtCAX4-OE) of Arabidopsis thaliana, were used to investigate Cd2+ stress responses. We found that the Brassica napus genotype, with higher NUE, was more sensitive to Cd2+ stress. The AtCAX4-OE mutant, with higher Cd2+ vacuolar sequestration capacity (VSC), limited NO3- sequestration into root vacuoles and promoted NUE. Atclca-2 mutants, with decreased NO3- VSC, enhanced Cd2+ sequestration into root vacuoles and conferred greater Cd2+ tolerance than the WT. This may be due to the competition between Cd2+ andNO3- in the vacuoles for the energy provided by V-ATPase and V-PPase. Regulating the balance between Cd2+ and NO3- vacuolar accumulation by inhibiting the activity of CLCa transporter and increasing the activity of CAX4 transporter will simultaneously enhance both the NUE and Cd2+ tolerance of Brassica napus, essential for improving its Cd2+ phytoremediation potential.

Cyanobacterial bloom mitigation by sanguinarine and its effects on aquatic microbial community structure.

Sanguinarine has strong inhibitory effects against the cyanobacterium Microcystis aeruginosa. However, previous studies were mainly limited to laboratory tests. The efficacy of sanguinarine for mitigation of cyanobacterial blooms under field conditions, and its effects on aquatic microbial community structure remain unknown. To elucidate these issues, we carried out in situ cyanobacterial bloom mitigation tests. Our results showed that sanguinarine decreased population densities of the harmful cyanobacteria Microcystis and Anabaena. The inhibitory effects of sanguinarine on these cyanobacteria lasted 17 days, after which the harmful cyanobacteria recovered and again became the dominant species. Concentrations of microcystins in the sanguinarine treatments were lower than those of the untreated control except during the early stage of the field test. The results of community DNA pyrosequencing showed that sanguinarine decreased the relative abundance of the prokaryotic microorganisms Cyanobacteria, Actinobacteria, Planctomycetes and eukaryotic microorganisms of Cryptophyta, but increased the abundance of the prokaryotic phylum Proteobacteria and eukaryotic microorganisms within Ciliophora and Choanozoa. The shifting of prokaryotic microbial community in water column was directly related to the toxicity of sanguinarine, whereas eukaryotic microbial community structure was influenced by factors other than direct toxicity. Harmful cyanobacteria mitigation efficacy and microbial ecological effects of sanguinarine presented in this study will inform the broad application of sanguinarine in cyanobacteria mitigation.

A Pilot Study of Intralymphatic Immunotherapy for House Dust Mite, Cat, and Dog Allergies.

Several recent clinical trials reported that intralymphatic immunotherapy (ILIT) for some allergens, such as cat dander and pollen, induce tolerance more rapidly than conventional subcutaneous or sublingual immunotherapy, have a comparable duration of effect after only 3 injections, and do not provoke serious local or systemic reactions. However, the efficacy and safety of ILIT are using Dermatophagoides farinae (Df), Dermatophagoides pteronyssinus (Dp), and dog, which are indoor allergens that are commonly found globally, need to be evaluated. Furthermore, use of multiple allergens in ILIT should be investigated. We assessed the clinical efficacy and adverse effects of ILIT using aqueous Df, Dp, dog, and cat allergens or mixtures thereof in patients with allergic rhinitis. A total of 11 subjects with AR sensitized to Df, Dp, cat, and/or dog allergens received 3 intralymphatic inguinal injections of sensitized allergen extract (HollisterStier, New Orleans, LA, USA). Clinical parameters were assessed before ILIT, and 4 months and 1 year after the first injection. Rhinitis symptoms were alleviated and quality of life was improved 4 months after ILIT (P=0.012 and P=0.007, respectively), and these improvements lasted for 1 year after ILIT (P=0.047 and P=0.009, respectively). However, we observed 2 cases of anaphylaxis, one case of a moderate-to-severe systemic hypersensitivity reaction and the other case of a severe local reaction at the injection site after ILIT. In conclusion, ILIT can rapidly improve allergy symptoms and quality of life, and this effect lasts for 1 year. In hypersensitized patients, however, ILIT can provoke severe systemic and/or local hypersensitivity reactions when performed using aqueous allergen extracts.

Clinical significance of incidentally detected aneurysms of the membranous ventricular septum in adults by multidetector computed tomography.

Although the clinical relevance of aneurysm of the membranous ventricular septum (AMVS) in adults is unclear, the frequency of AMVS detection has been increased because cardiac multidetector computed tomography has been widely adopted for the evaluation of coronary artery disease. Therefore, we aimed to assess the clinical significance of AMVS in a longitudinal study. In 30,120 adults with suspected coronary artery disease who underwent cardiac multidetector computed tomography in 3 hospitals, 52 patients with AMVS were retrospectively selected. We evaluated the clinical symptoms and electrocardiographic abnormalities (cross-sectional study) and the prevalence of embolic stroke (observational study) during a median 40-month (range 6 to 74 months) observation period. For the assessment of embolic stroke, we excluded 9 patients with other explainable embolic sources. Conduction abnormalities were noted in 13 of 52 adults (25%) with AMVS on electrocardiography and embolic stroke occurred in 6 of 43 patients (14%). The mean age and the prevalence of hypertension were significantly higher in the embolic stroke group than in the event-free group (p <0.05). Thrombi were detected in the 11.6% of AMVS, which was significantly related with embolic stroke (p <0.05). The size and morphology did not change in 15 patients with serial follow-up images. In conclusion, our study suggests that AMVS in adults should not be ignored because AMVS may be related to conduction abnormality or embolic stroke, and it does not spontaneously resolve or diminish in size.

Toxicity comparison of biosurfactants and synthetic surfactants used in oil spill remediation to two estuarine species.

The relative environmental toxicities of synthetic and biogenic surfactants used in oil spill remediation efforts are not well understood. Acute and chronic toxicities of three synthetic surfactants and three microbiologically produced surfactants were determined and compared in this study for the estuarine epibenthic invertebrate, Mysidopsis bahia and the inland silverside, Menidia beryllina. The toxicities of the surfactant were determined in standard laboratory static and static-renewal tests of 4-7 d duration. Results were specific to the surfactant, response parameter and test species. The LC50 values (nominal concentrations) for M. bahia ranged from 3.3 mg/l (Triton X-100) to >1000 mg/l (PES-61) and 2.5 mg/l (Triton X-100) to 413.6 mg/l (PES-61) for M. beryllina. Chronic first-effect concentrations (mg/l) for the six surfactants ranged from 2.3 to 465.0 (M. beryllina) and 1.0 to >1000.0 (M. bahia) based on reductions in growth and fecundity. Few generalizations could be made concerning the results due to their variability but M. bahia was generally the more sensitive species and the toxicities of the biosurfactants were intermediate to those of the synthetic surfactants.

C2 nerve root on magnetic resonance imaging of occipital neuralgia.

STUDY DESIGN: Review and grade the morphology of the C1-C2 neural foramina, from the MR images of patients who underwent C1-C2 spinal surgery, and determine the relationship with ON. OBJECTIVE: To evaluate the feasibility of MRI for C1-C2 neural foramen evaluation with a new grading system and to correlate the C1-C2 neural foramen grade with ON. SUMMARY OF BACKGROUND DATA: There have been no MRI studies of patients with and without ON in relation to C2 nerve root ganglion findings. METHODS: Among the registry of 124 patients who underwent C1-C2 spinal surgery between July 2004 and May 2012 in Seoul National University Bundang Hospital, we enrolled 101 patients who had information about ON and a relevant preoperative cervical spine MR image. A total of 202 neural foramina were evaluated with our new C1-C2 neural foramen grading system (grade, 0-3) using consensus reading by 2 experienced radiologists who were blinded to the clinical information. The relationship between the C1-C2 grading system and ON was assessed using a χ test and Fisher exact test. Inter- and intraobserver reliability agreement was assessed using the κ statistic. RESULTS: All C1-C2 neural foramina were delineated on T2 parasagittal images. Among 202 C1-C2 neural foramina, grade zero was found in 49 foramina (24.3%), grade 1 in 95 (47.0%), grade 2 in 30 (14.9%), and grade 3 in 28 (13.9%). Grade 1 stenosis was most frequently noted. The grade 2 group had the most frequent prevalence of ON (43.3%), followed by grade 3 (35.7%), grade zero (30.6%), and grade 1 (29.5%). However, the relationship between the grade and ON was not statistically significant. Inter- and intraobserver agreements were substantially high. CONCLUSION: C1-C2 neural foramina can be depicted on MR image. However, the relationship between the new grading system for C1-C2 neural foramina and ON was not statistically significant. LEVEL OF EVIDENCE: 4.

Relationship of human-associated microbial source tracking markers with Enterococci in Gulf of Mexico waters.

Human and ecosystem health can be damaged by fecal contamination of recreational waters. Microbial source tracking (MST) can be used to specifically detect domestic sewage containing human waste, thereby informing both risk assessment and remediation strategies. Previously, an inter-laboratory collaboration developed standardized PCR methods for a bacterial, an archaeal, and a viral indicator of human sewage. Here we present results for two subsequent years of field testing in fresh and salt water by five laboratories across the U.S. Gulf Coast (two in Florida and one each in Mississippi, Louisiana and Texas) using common standard operating procedures (SOPs) developed previously. Culturable enterococci were enumerated by membrane filtration, and PCR was used to detect three MST markers targeting domestic sewage: human-associated Bacteroides (HF183), Methanobrevibacter smithii and human polyomaviruses BK and JC (HPyVs). Detection of sewage markers in surface waters was significantly associated with higher enterococci levels and with exceedance of the recreational water quality standard in four or three regions, respectively. Sewage markers were frequently co-detected in single samples, e.g., M. smithii and HF183 were co-detected in 81% of Louisiana samples, and HPyVs and M. smithii were co-detected in over 40% of southwest Florida and Mississippi samples. This study demonstrates the robustness and inter-laboratory transferability of these three markers for the detection of pollution from domestic sewage in the waters impacting the Gulf of Mexico over a coastal range of over 1000 miles.

A filter-based propidium monoazide technique to distinguish live from membrane-compromised microorganisms using quantitative PCR.

Propidium monoazide (PMA) was used to differentiate live from membrane-compromised bacteria in PCR methods. We have adapted this technique for use on membrane-filtered water samples and determined its efficacy using qPCR. Independent labs at three institutions replicated these findings.

Response of estuarine biofilm microbial community development to changes in dissolved oxygen and nutrient concentrations.

The information content and responsiveness of microbial biofilm community structure, as an integrative indicator of water quality, was assessed against short-term changes in oxygen and nutrient loading in an open-water estuarine setting. Biofilms were grown for 7-day periods on artificial substrates in the Pensacola Bay estuary, Florida, in the vicinity of a wastewater treatment plant (WWTP) outfall and a nearby reference site. Substrates were deployed floating at the surface and near the benthos in 5.4 m of water. Three sampling events covered a 1-month period coincident with declining seasonal WWTP flow and increasing dissolved oxygen (DO) levels in the bottom waters. Biomass accumulation in benthic biofilms appeared to be controlled by oxygen rather than nutrients. The overriding effect of DO was also seen in DNA fingerprints of community structure by terminal restriction fragment length polymorphism (T-RFLP) of amplified 16S rRNA genes. Ribotype diversity in benthic biofilms at both sites dramatically increased during the transition from hypoxic to normoxic. Terminal restriction fragment length polymorphism patterns showed pronounced differences between benthic and surface biofilm communities from the same site in terms of signal type, strength, and diversity, but minor differences between sites. Sequencing of 16S rRNA gene clone libraries from benthic biofilms at the WWTP site suggested that low DO levels favored sulfate-reducing prokaryotes (SRP), which decreased with rising oxygen levels and increasing overall diversity. A 91-bp ribotype in the CfoI-restricted 16S rRNA gene T-RFLP profiles, indicative of SRP, tracked the decrease in relative SRP abundance over time.