Nitrification, a key process in the global nitrogen cycle that generates nitrate through microbial activity, may enhance losses of fertilizer nitrogen by leaching and denitrification. Certain plants ...can suppress soil-nitrification by releasing inhibitors from roots, a phenomenon termed biological nitrification inhibition (BNI). Here, we report the discovery of an effective nitrification inhibitor in the root-exudates of the tropical forage grass Brachiaria humidicola (Rendle) Schweick. Named "brachialactone," this inhibitor is a recently discovered cyclic diterpene with a unique 5-8-5-membered ring system and a γ-lactone ring. It contributed 60-90% of the inhibitory activity released from the roots of this tropical grass. Unlike nitrapyrin (a synthetic nitrification inhibitor), which affects only the ammonia monooxygenase (AMO) pathway, brachialactone appears to block both AMO and hydroxylamine oxidoreductase enzymatic pathways in NITROSOMONAS: Release of this inhibitor is a regulated plant function, triggered and sustained by the availability of ammonium (NHFormula: see text) in the root environment. Brachialactone release is restricted to those roots that are directly exposed to NHFormula: see text. Within 3 years of establishment, Brachiaria pastures have suppressed soil nitrifier populations (determined as amoA genes; ammonia-oxidizing bacteria and ammonia-oxidizing archaea), along with nitrification and nitrous oxide emissions. These findings provide direct evidence for the existence and active regulation of a nitrification inhibitor (or inhibitors) release from tropical pasture root systems. Exploiting the BNI function could become a powerful strategy toward the development of low-nitrifying agronomic systems, benefiting both agriculture and the environment.
Nitrification, a microbial process, is a key component and integral part of the nitrogen (N) cycle. Soil N is in a constant state of flux, moving and changing chemical forms. During nitrification, a ...relatively immobile N-form (NH
4
+
) is converted into highly mobile nitrate-N (NO
3
−
). The nitrate formed is susceptible to losses via leaching and conversion to gaseous forms via denitrification. Often less than 30% of the applied N fertilizer is recovered in intensive agricultural systems, largely due to losses associated with and following nitrification. Nitrogen-use efficiency (NUE) is defined as the biomass produced per unit of assimilated N and is a conservative function in most biological systems. A better alternative is to define NUE as the dry matter produced per unit N applied and strive for improvements in agronomic yields through N recovery. Suppressing nitrification along with its associated N losses is potentially a key part in any strategy to improve N recovery and agronomic NUE. In many mature N-limited ecosystems, nitrification is reduced to a relatively minor flux. In such systems there is a high degree of internal N cycling with minimal loss of N. In contrast, in most high-production agricultural systems nitrification is a major process in N cycling with the resulting N losses and inefficiencies. This review presents the current state of knowledge on nitrification and associated N losses, and discusses strategies for controlling nitrification in agricultural systems. Limitations of the currently available nitrification inhibitors are highlighted. The concept of biological nitrification inhibition (BNI) is proposed for controlling nitrification in agricultural systems utilizing traits found in natural ecosystems. It is emphasized that suppression of nitrification in agricultural systems is a critical step required for improving agronomic NUE and maintaining environmental quality.
BackgroundAgriculture is the single largest geo-engineering initiative that humans have initiated on planet Earth, largely through the introduction of unprecedented amounts of reactive nitrogen (N) ...into ecosystems. A major portion of this reactive N applied as fertilizer leaks into the environment in massive amounts, with cascading negative effects on ecosystem health and function. Natural ecosystems utilize many of the multiple pathways in the N cycle to regulate N flow. In contrast, the massive amounts of N currently applied to agricultural systems cycle primarily through the nitrification pathway, a single inefficient route that channels much of this reactive N into the environment. This is largely due to the rapid nitrifying soil environment of present-day agricultural systems.ScopeIn this Viewpoint paper, the importance of regulating nitrification as a strategy to minimize N leakage and to improve N-use efficiency (NUE) in agricultural systems is highlighted. The ability to suppress soil nitrification by the release of nitrification inhibitors from plant roots is termed ‘biological nitrification inhibition’ (BNI), an active plant-mediated natural function that can limit the amount of N cycling via the nitrification pathway. The development of a bioassay using luminescent Nitrosomonas to quantify nitrification inhibitory activity from roots has facilitated the characterization of BNI function. Release of BNIs from roots is a tightly regulated physiological process, with extensive genetic variability found in selected crops and pasture grasses. Here, the current status of understanding of the BNI function is reviewed using Brachiaria forage grasses, wheat and sorghum to illustrate how BNI function can be utilized for achieving low-nitrifying agricultural systems. A fundamental shift towards ammonium (NH4+)-dominated agricultural systems could be achieved by using crops and pastures with high BNI capacities. When viewed from an agricultural and environmental perspective, the BNI function in plants could potentially have a large influence on biogeochemical cycling and closure of the N loop in crop–livestock systems.
Body water volume is tightly regulated such that the daily variation in total body water content is less than 1%. Imbalances in fluid volume can occur when fluid is not freely available, and can lead ...to decrements in physical performance when water losses exceed 2% body mass. Thus, it is essential to assess strategies that promote fluid replacement and retention during and following exercise. Beverages containing milk permeate have been suggested to be an efficacious alternative to traditional sports drinks for restoring hydration and maintaining performance. However, no prior studies have examined how consumption of such a beverage following overnight fluid restriction affects exercise performance in recreationally active individuals, or how ad libitum (AD) consumption following exercise affects indices of hydration, compared to other beverages.
PURPOSE
We aimed to (1) determine how overnight fluid restriction and next‐day prescribed rehydration with either water (WAT), GatoradeÔ (GAT), or a milk permeate solution – GoodSportÒ (GS) – affects cycling time trial (TT) performance, and (2) compare the impact of ad libitum consumption of these three beverages on restoration of fluid balance and biomarkers of hydration status post‐TT.
HYPOTHESES
We hypothesized that (1) time‐trial performance would be similarly improved following consumption of GAT and GS compared to WAT, and 2) ad libitum fluid consumption post‐time‐trial would be greater for GAT and GS compared to WAT.
METHODS
Four (3M/1F) recreationally active (>150min/wk) young adults (25±1yr) completed 3 experimental visits consisting of a 15‐hr overnight fluid restriction prior to arrival at the laboratory for exercise trials. Subjects cycled at a moderate intensity (50% VO2max, 60 RPM) for one hour in a warm environment (30°C, 20% relative humidity) while consuming 2 mL/kg of randomly assigned fluid every 10 minutes, followed by a 5‐km TT. Following the TT, subjects cycled for one hour at 25% VO2max and were instructed to drink the randomly assigned fluid ad libitum.
RESULTS
TT performance, measured as both time and watts per kilogram (W/kg), was not different among trials (WAT: 562±36 sec, 2.2±0.4 W/kg; GAT: 570±58 sec, 2.3 ± 0.5 W/kg; GS 575±29 sec, 2.1 ± 0.6 W/kg; all p>0.21). AD consumption was not different among trials (WAT: 1148±638 mL; GAT: 1200±355 mL; GS: 1271±486 mL). There were no differences in percent change in plasma volume (%ΔPV) at any time point among beverage conditions (all p>0.28).
CONCLUSION
TT performance, measured as both time and W/kg, was not improved following prescribed consumption of a milk permeate solution (GS) or a traditional sports drink (GAT) compared to WAT. AD fluid consumption was not different among beverage conditions during the one‐hour recovery cycling period after the TT. Changes in plasma volume, an important indicator of hydration, was not different among drink conditions at any time‐point, indicating subjects were similarly hydrated among beverage conditions.
Regulating nitrification could be a key strategy in improving nitrogen (N) recovery and agronomic N-use efficiency in situations where the loss of N following nitrification is significant. A highly ...sensitive bioassay using recombinant luminescent Nitrosomonas europaea, has been developed that can detect and quantify the amount of nitrification inhibitors produced by plants (hereafter referred to as BNI activity). A number of species including tropical and temperate pastures, cereals and legumes were tested for BNI in their root exudate. There was a wide range in BNI capacity among the 18 species tested; specific BNI (AT units activity g-¹ root dry wt) ranged from 0 (i.e. no detectable activity) to 18.3 AT units. Among the tested cereal and legume crops, sorghum Sorghum bicolor (L.), pearl millet Pennisetum glaucum (L.) R. Br., and groundnut Arachis hypogaea (L.) showed detectable BNI in root exudate. Among pasture grasses, Brachiaria humidicola (Rendle) Schweick, B. decumbens Stapf showed the highest BNI capacity. Several high- and low-BNI genotypes were identified within the B. humidicola species. Soil collected from field plots of 10 year-old high-BNI genotypes of B. humidicola, showed a near total suppression (>90%) of nitrification; most of the soil inorganic N remained in the NH ₄ ⁺ form after 30 days of incubation. In contrast, soils collected from low-BNI genotypes did not show any inhibitory effect; most of the soil inorganic N was converted to NO ₃ - after 30 days of incubation. In both the high- and low-BNI genotypes, BNI was detected in root exudate only when plants were grown with NH ₄ ⁺ , but not when grown with NO ₃ - as the sole source of N. BNI compounds when added to the soil inhibited nitrification and the relationship was linear (r ² = 0.92**; n = 12). The BNI from high- and low-BNI types when added to N. europaea in pure culture, blocked both the ammonia monooxygenase (AMO) and the hydroxylamine oxidoreductase (HAO) pathways. Our results indicated that BNI capacity varies widely among and within species; and that some degree of BNI capacity is likely a widespread phenomenon in tropical pasture grasses. We suggest that the BNI capacity could either be managed and/or introduced into pastures/crops with an expression of this phenomenon, via genetic improvement approaches that combine high productivity along with some capacity to regulate soil nitrification process.
Ongoing growth in health care expenditures and changing patterns in the demand for health care challenge societies worldwide. The Chronic Care Model (CCM), combined with classification for care needs ...based on Kaiser Permanente (KP) Triangle, may offer a suitable framework for change. The aim of the present study is to investigate the effectiveness of Embrace, a population-based model for integrated elderly care, regarding patient outcomes, service use, costs, and quality of care.
The CCM and the KP Triangle were translated to the Dutch setting and adapted to the full elderly population living in the community. A randomized controlled trial with balanced allocation was designed to test the effectiveness of Embrace. Eligible elderly persons are 75 years and older and enrolled with one of the participating general practitioner practices. Based on scores on the INTERMED-Elderly Self-Assessment and Groningen Frailty Indicator, participants will be stratified into one of three strata: (A) robust; (B) frail; and (C) complex care needs. Next, participants will be randomized per stratum to Embrace or care as usual. Embrace encompasses an Elderly Care Team per general practitioner practice, an Electronic Elderly Record System, decision support instruments, and a self-management support and prevention program - combined with care and support intensity levels increasing from stratum A to stratum C. Primary outcome variables are patient outcomes, service use, costs, and quality of care. Data will be collected at baseline, twelve months after starting date, and during the intervention period.
This study could provide evidence for the effectiveness of Embrace.
The Netherlands National Trial Register NTR3039.
Sodium-A Functional Plant Nutrient Subbarao, G. V.; Ito, O.; Berry, W. L. ...
Critical reviews in plant sciences,
09/2003, Letnik:
22, Številka:
5
Journal Article
Recenzirano
Plant scientists usually classify plant mineral nutrients based on the concept of "essentiality" defined by Arnon and Stout as those elements necessary to complete the life cycle of a plant. Certain ...other elements such as Na have a ubiquitous presence in soils and waters and are widely taken up and utilized by plants, but are not considered as plant nutrients because they do not meet the strict definition of "essentiality." Sodium has a very specific function in the concentration of carbon dioxide in a limited number of C
4
plants and thus is essential to these plants, but this in itself is insufficient to generalize that Na is essential for higher plants. The unique set of roles that Na can play in plant metabolism suggests that the basic concept of what comprises a plant nutrient should be reexamined. We contend that the class of plant mineral nutrients should be comprised not only of those elements necessary for completing the life cycle, but also those elements which promote maximal biomass yield and/or which reduce the requirement (critical level) of an essential element. We suggest that nutrients functioning in this latter manner should be termed "functional nutrients." Thus plant mineral nutrients would be comprised of two major groups, "essential nutrients" and "functional nutrients." We present an array of evidence and arguments to support the classification of Na as a "functional nutrient," including its requirement for maximal biomass growth for many plants and its demonstrated ability to replace K in a number of ways, such as being an osmoticium for cell enlargement and as an accompanying cation for long-distance transport. Although in this paper we have only attempted to make the case for Na being a "functional nutrient," other elements such as Si and Se may also confirm to the proposed category of "functional nutrients."
The aim of this study was to determine the difference in functional outcomes after open reduction and internal fixation (ORIF) with and without arthroscopic debridement in adults with displaced ...intra-articular distal radius fractures. In this multicentre trial, 50 patients were randomized between ORIF with or without arthroscopic debridement. The primary outcome measure was the Patient-Rated Wrist Evaluation (PRWE) score. Secondary outcome measures were Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire, pain scores, range of wrist motion, grip strength, and complications. Median PRWE was worse for the intervention group at 3 months and was equal for both groups at 12 months. The secondary outcome measures did not show consistent patterns of differences at different time-points of follow-up. We conclude that patients treated with additional arthroscopy to remove intra-articular hematoma and debris did not have better outcomes than those treated with ORIF alone. We therefore do not recommend arthroscopy for removal of hematoma and debris when surgically fixing distal radius fractures.
Level of evidence: I
In the past several years, an increase in open reduction and internal fixation (ORIF) for intra-articular distal radius fractures has been observed. This technique leads to a quicker recovery of ...function compared to non-operative treatment. However, some patients continue to have a painful and stiff wrist postoperatively. Arthroscopically assisted removal of intra-articular fracture haematoma and debris may improve the functional outcomes following operative treatment of intra-articular distal radius fractures. The purpose of this randomised controlled trial is to determine the difference in functional outcome, assessed with the Patient-Rated Wrist Evaluation (PRWE) score, after ORIF with and without an additional wrist arthroscopy in adult patients with displaced complete articular distal radius fractures.
In this multicentre trial, adult patients with a displaced complete articular distal radius fracture are randomised between ORIF with an additional wrist arthroscopy to remove fracture haematoma and debris (intervention group) and conventional fluoroscopic-assisted ORIF (control group). The primary outcome is functional outcome assessed with the PRWE score after three months. Secondary outcomes are wrist function assessed with the Disability of the Arm, Shoulder and Hand (DASH) score, postoperative pain, range of motion, grip strength, complications and cost-effectiveness. Additionally, in the intervention group, the quality of reduction, associated ligamentous injuries and cartilage damage will be assessed. A total of 50 patients will be included in this study.
Although ORIF of intra-articular distal radius fractures leads to a quicker resume of function compared to non-operative treatment, some patients continue to have a painful and stiff wrist postoperatively. We hypothesise that, due to the removal of fracture haematoma and debris by an additional arthroscopy, functional outcomes will be better compared to the non-arthroscopically treated group.
ClinicalTrials.gov, NCT02660515 . Registered on 13 January 2016.
Instability of the distal radioulnar joint and scapholunate dissociation may cause pain, functional impairment and subsequent arthrosis. There is no consensus about whether these injuries should be ...treated acutely in patients undergoing surgery for distal radial fractures. We conducted a prospective cohort study to determine whether concomitant distal radioulnar joint instability or scapholunate dissociation negatively influence patient-related outcomes in these patients. The primary outcome was the patient-reported wrist/hand evaluation at 6 and 12 months after surgery. Out of 62 patients, 58% and 27% had intraoperative distal radioulnar joint instability and scapholunate dissociation, respectively. No significant differences were found in patient-reported scores at follow-up between patients with stable and unstable distal radioulnar joints, nor between patients with and without scapholunate dissociation. Sixty-three per cent of patients with an unstable distal radioulnar joint during surgery were stable on retesting after 6 months. Our study suggests that a wait-and-see policy in these patients therefore seems reasonable.
Level of evidence: III
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