Feasibility of absolute quantification for 31 P MRS at 7 T.

PURPOSE: Phosphorus spectroscopy can differentiate among liver disease stages and types. To quantify absolute concentrations of phosphorus metabolites, sensitivity calibration and transmit field ( B1+ ) correction are required. The trend toward ultrahigh fields (7 T) and the use of multichannel RF coils makes this ever more challenging. We investigated the constraints on reference phantoms, and implemented techniques for the absolute quantification of human liver phosphorus spectra acquired using a 10-cm loop and a 16-channel array at 7 T. METHODS: The effect of phantom conductivity was assessed at 25.8 MHz (1.5 T), 49.9 MHz (3 T), and 120.3 MHz (7 T) by electromagnetic modeling. Radiofrequency field maps ( B1± ) were measured in phosphate phantoms (18 mM and 40 mM) at 7 T. These maps were used to assess the correction of 4 phantom 3D-CSI data sets using 3 techniques: phantom replacement, explicit normalization, and simplified normalization. In vivo liver spectra acquired with a 10-cm loop were corrected with all 3 methods. Simplified normalization was applied to in vivo 16-channel array data sets. RESULTS: Simulations show that quantification errors of less than 3% are achievable using a uniform electrolyte phantom with a conductivity of 0.23-0.86 S.m-1 at 1.5 T, 0.39-0.58 S.m-1 at 3 T, and 0.34-0.42 S.m-1 (16-19 mM KH2 PO4(aq) ) at 7 T. The mean γ-ATP concentration quantified in vivo at 7 T was 1.39 ± 0.30 mmol.L-1 to 1.71 ± 0.35 mmol.L-1 wet tissue for the 10-cm loop and 1.88 ± 0.25 mmol.L-1 wet tissue for the array. CONCLUSION: It is essential to select a calibration phantom with appropriate conductivity for quantitative phosphorus spectroscopy at 7 T. Using an 18-mM phosphate phantom and simplified normalization, human liver phosphate metabolite concentrations were successfully quantified at 7 T.

Unveiling a hidden 31 P signal coresonating with extracellular inorganic phosphate by outer-volume-suppression and localized 31 P MRS in the human brain at 7T.

PURPOSE: The study was undertaken to demonstrate that there is more than 1 component in the extracellular Pi31 P signal ( Piex) acquired from human head using nonlocalized 31 P MRS. METHODS: Outer-volume-suppression (OVS) saturation and 1D/2D 31 P CSI were utilized to reveal the presence of an additional component in the Piex signal. RESULTS: 67% of the head extracellular Pi signal was attenuated upon OVS saturation of the peripheral meningeal tissues, likely reflecting elimination of the Pi signal in the meningeal fluids (the blood and CSF). Localized 1D/2D CSI data provided further support for this assignment. Upon correction for the meningeal contribution, the extracellular Pi concentration was 0.51 ± 0.07 mM, whereas the intracellular Pi was 0.85 ± 0.10 mM. The extracellular pH was measured as 7.32 ± 0.04 when using OVS, as compared to 7.39 ± 0.03 when measured without OVS (N = 7 subjects). CONCLUSION: The extracellular Pi signal acquired from the human head using nonlocalized 31 P MRS contains a significant component likely contributed by peripheral blood and CSF in meninges that must be removed in order to use this signal as an endogenous probe for measuring extracellular pH and other properties in the brain.

Adiabatic excitation for 31 P MR spectroscopy in the human heart at 7 T: A feasibility study.

PURPOSE: Phosphorus magnetic resonance spectroscopy (31 P-MRS) provides a unique tool for assessing cardiac energy metabolism, often quantified using the phosphocreatine (PCr)/adenosine triphosphate (ATP) ratio. Surface coils are typically used for excitation for 31 P-MRS, but they create an inhomogeneous excitation field across the myocardium, producing undesirable, spatially varying partial saturation. Therefore, we implemented adiabatic excitation in a 3D chemical shift imaging (CSI) sequence for cardiac 31 P-MRS at 7 Tesla (T). METHODS: We optimized an adiabatic half passage pulse with bandwidth sufficient to excite PCr and γ-ATP together. In addition, the CSI sequence was modified to allow interleaved excitation of PCr and γ-ATP, then 2,3-DPG, to enable PCr/ATP determination with blood correction. Nine volunteers were scanned at 2 transmit voltages to confirm that measured PCr/ATP was independent of B1+ (i.e. over the adiabatic threshold). Six septal voxels were evaluated for each volunteer. RESULTS: Phantom experiments showed that adiabatic excitation can be reached at the depth of the heart using our pulse. The mean evaluated cardiac PCr/ATP ratio from all 9 volunteers corrected for blood signal was 2.14 ± 0.16. Comparing the two acquisitions with different voltages resulted in a minimal mean difference of -0.005. CONCLUSION: Adiabatic excitation is possible in the human heart at 7 T, and gives consistent PCr/ATP ratios. Magn Reson Med 78:1667-1673, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Efficient 31 P band inversion transfer approach for measuring creatine kinase activity, ATP synthesis, and molecular dynamics in the human brain at 7 T.

PURPOSE: To develop an efficient 31 P magnetic resonance spectroscopy (MRS) method for measuring creatine kinase (CK) activity, adenosine triphosphate (ATP) synthesis, and motion dynamics in the human brain at 7 Tesla (T). METHODS: Three band inversion modules differing in center frequency were used to induce magnetization transfer (MT) effect in three exchange pathways: (i) CK-mediated reaction PCr → γ-ATP; (ii) de novo ATP synthesis Pi → γ-ATP; and (iii) ATP intramolecular 31 P-31 P cross-relaxation γ-(α-) ↔ ß-ATP. The resultant MT data were analyzed using a 5-pool model in the format of magnetization matrix according to Bloch-McConnell-Solomon formalism. RESULTS: With a repetition time (TR) of 4 s, the scan time for each module was approximately 8 min. The rate constants were kPCr → γATP 0.38 ± 0.02 s-1 , kPi → γATP 0.19 ± 0.02 s-1 , and σγ(α) ↔ ßATP 0.19 ± 0.04 s-1 , corresponding to ATP rotation correlation time τc (0.8 ± 0.2) ·10-7 s. The T1 relaxation times were Pi 7.26 ± 1.76 s, PCr 5.99 ± 0.58 s, γ-ATP 0.98 ± 0.07 s, α-ATP 0.95 ± 0.04 s, and ß-ATP 0.68 ± 0.03 s. CONCLUSION: Short-TR band inversion modules provide a time-efficient way of measuring brain ATP metabolism and could be useful in studying metabolic disorders in brain diseases. Magn Reson Med 78:1657-1666, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

In-vivo31P-MRS of skeletal muscle and liver: A way for non-invasive assessment of their metabolism.

In addition to direct assessment of high energy phosphorus containing metabolite content within tissues, phosphorus magnetic resonance spectroscopy (31P-MRS) provides options to measure phospholipid metabolites and cellular pH, as well as the kinetics of chemical reactions of energy metabolism in vivo. Even though the great potential of 31P-MR was recognized over 30 years ago, modern MR systems, as well as new, dedicated hardware and measurement techniques provide further opportunities for research of human biochemistry. This paper presents a methodological overview of the 31P-MR techniques that can be used for basic, physiological, or clinical research of human skeletal muscle and liver in vivo. Practical issues of 31P-MRS experiments and examples of potential applications are also provided. As signal localization is essential for liver 31P-MRS and is important for dynamic muscle examinations as well, typical localization strategies for 31P-MR are also described.

Options of partners improve carbon for phosphorus trade in the arbuscular mycorrhizal mutualism.

The mutualism between plants and arbuscular mycorrhizal fungi (AMF) is widespread and has persisted for over 400 million years. Although this mutualism depends on fair resource exchange between plants and fungi, inequality exists among partners despite mechanisms that regulate trade. Here, we use (33) P and (14) C isotopes and a split-root system to test for preferential allocation and reciprocal rewards in the plant-AMF symbiosis by presenting a plant with two AMF that differ in cooperativeness. We found that plants received more (33) P from less cooperative AMF in the presence of another AMF species. This increase in (33) P resulted in a reduced (14) C cost per unit of (33) P from less cooperative AMF when alternative options were available. Our results indicate that AMF diversity promotes cooperation between plants and AMF, which may be an important mechanism maintaining the evolutionary persistence of and diversity within the plant-AMF mutualism.

In vivo ³¹P-nuclear magnetic resonance studies of glyphosate uptake, vacuolar sequestration, and tonoplast pump activity in glyphosate-resistant horseweed.

Horseweed (Conyza canadensis) is considered a significant glyphosate-resistant (GR) weed in agriculture, spreading to 21 states in the United States and now found globally on five continents. This laboratory previously reported rapid vacuolar sequestration of glyphosate as the mechanism of resistance in GR horseweed. The observation of vacuole sequestration is consistent with the existence of a tonoplast-bound transporter. (31)P-Nuclear magnetic resonance experiments performed in vivo with GR horseweed leaf tissue show that glyphosate entry into the plant cell (cytosolic compartment) is (1) first order in extracellular glyphosate concentration, independent of pH and dependent upon ATP; (2) competitively inhibited by alternative substrates (aminomethyl phosphonate [AMPA] and N-methyl glyphosate [NMG]), which themselves enter the plant cell; and (3) blocked by vanadate, a known inhibitor/blocker of ATP-dependent transporters. Vacuole sequestration of glyphosate is (1) first order in cytosolic glyphosate concentration and dependent upon ATP; (2) competitively inhibited by alternative substrates (AMPA and NMG), which themselves enter the plant vacuole; and (3) saturable. (31)P-Nuclear magnetic resonance findings with GR horseweed are consistent with the active transport of glyphosate and alternative substrates (AMPA and NMG) across the plasma membrane and tonoplast in a manner characteristic of ATP-binding cassette transporters, similar to those that have been identified in mammalian cells.

Organic matter remineralization predominates phosphorus cycling in the mid-Bay sediments in the Chesapeake Bay.

Chesapeake Bay, the largest and most productive estuary in the U.S., suffers from varying degrees of water quality issues fueled by both point and nonpoint nutrient sources. Restoration of the Bay is complicated by the multitude of nutrient sources, their variable inputs, and complex interaction between imported and regenerated nutrients. These complexities not only restrict formulation of effective restoration plans but also open up debates on accountability issues with nutrient loading. A detailed understanding of sediment phosphorus (P) dynamics provides information useful in identifying the exchange of dissolved constituents across the sediment-water interface as well as helps to better constrain the mechanisms and processes controlling the coupling between sediments and the overlying waters. Here we used phosphate oxygen isotope ratios (δ(18)O(P)) in concert with sediment chemistry, X-ray diffraction, and Mössbauer spectroscopy on sediments retrieved from an organic rich, sulfidic site in the mesohaline portion of the mid-Bay to identify sources and pathway of sedimentary P cycling and to infer potential feedbacks on bottom water hypoxia and surface water eutrophication. Authigenic phosphate isotope data suggest that the regeneration of inorganic P from organic matter degradation (remineralization) is the predominant, if not sole, pathway for authigenic P precipitation in the mid-Bay sediments. This indicates that the excess inorganic P generated by remineralization should have overwhelmed any pore water and/or bottom water because only a fraction of this precipitates as authigenic P. This is the first research that identifies the predominance of remineralization pathway and recycling of P within the Chesapeake Bay. Therefore, these results have significant implications on the current understanding of sediment P cycling and P exchange across the sediment-water interface in the Bay, particularly in terms of the sources and pathways of P that sustain hypoxia and may potentially support phytoplankton growth in the surface water.

Comparison of three reference methods for the measurement of intracellular pH using 31P MRS in healthy volunteers and patients with lymphoma.

31P magnetic resonance spectroscopy (31P MRS) can measure intracellular pH (pHi) using the chemical shift difference between pH-dependent inorganic phosphate (Pi) and a pH-independent reference peak. This study compared three different frequency reference peaks [phosphocreatine (PCr), α resonance of adenosine triphosphate (αATP) and water (using 1H MRS)] in a cohort of 10 volunteers and eight patients with non-Hodgkin's lymphoma (NHL). Well-resolved chemical shift imaging (CSI) spectra were acquired on a 1.5T scanner for muscle, liver and tumour. The pH was calculated for all volunteers and patients using the available methods. The consistency of the resulting pH was evaluated. The direct Pi­PCr method was best for those spectra with a very well-defined PCr, such as muscle (pH=7.05 ± 0.02). In liver, the Pi­αATP method gave more consistent results (pH=7.30 ± 0.06) than the calibrated water-based method (pH=7.27 ± 0.11). In NHL nodes, the measured pH using the Pi­αATP method was 7.25 ± 0.12. Given that the measured range includes some biological variation in individual patients, treatment-related changes of the order of 0.1 pH units should be detectable.

Accurate measurement of heteronuclear dipolar couplings by phase-alternating R-symmetry (PARS) sequences in magic angle spinning NMR spectroscopy.

We report a Phase-Alternating R-Symmetry (PARS) dipolar recoupling scheme for accurate measurement of heteronuclear (1)H-X (X = (13)C, (15)N, (31)P, etc.) dipolar couplings in MAS NMR experiments. It is an improvement of conventional C- and R-symmetry type DIPSHIFT experiments where, in addition to the dipolar interaction, the (1)H CSA interaction persists and thereby introduces considerable errors in the dipolar measurements. In PARS, phase-shifted RN symmetry pulse blocks applied on the (1)H spins combined with π pulses applied on the X spins at the end of each RN block efficiently suppress the effect from (1)H chemical shift anisotropy, while keeping the (1)H-X dipolar couplings intact. Another advantage over conventional DIPSHIFT experiments, which require the signal to be detected in the form of a reduced-intensity Hahn echo, is that the series of π pulses refocuses the X chemical shift and avoids the necessity of echo formation. PARS permits determination of accurate dipolar couplings in a single experiment; it is suitable for a wide range of MAS conditions including both slow and fast MAS frequencies; and it assures dipolar truncation from the remote protons. The performance of PARS is tested on two model systems, [(15)N]-N-acetyl-valine and [U-(13)C,(15)N]-N-formyl-Met-Leu-Phe tripeptide. The application of PARS for site-resolved measurement of accurate (1)H-(15)N dipolar couplings in the context of 3D experiments is presented on U-(13)C,(15)N-enriched dynein light chain protein LC8.

Mycorrhizal networks: common goods of plants shared under unequal terms of trade.

Plants commonly live in a symbiotic association with arbuscular mycorrhizal fungi (AMF). They invest photosynthetic products to feed their fungal partners, which, in return, provide mineral nutrients foraged in the soil by their intricate hyphal networks. Intriguingly, AMF can link neighboring plants, forming common mycorrhizal networks (CMNs). What are the terms of trade in such CMNs between plants and their shared fungal partners? To address this question, we set up microcosms containing a pair of test plants, interlinked by a CMN of Glomus intraradices or Glomus mosseae. The plants were flax (Linum usitatissimum; a C(3) plant) and sorghum (Sorghum bicolor; a C(4) plant), which display distinctly different (13)C/(12)C isotope compositions. This allowed us to differentially assess the carbon investment of the two plants into the CMN through stable isotope tracing. In parallel, we determined the plants' "return of investment" (i.e. the acquisition of nutrients via CMN) using (15)N and (33)P as tracers. Depending on the AMF species, we found a strong asymmetry in the terms of trade: flax invested little carbon but gained up to 94% of the nitrogen and phosphorus provided by the CMN, which highly facilitated growth, whereas the neighboring sorghum invested massive amounts of carbon with little return but was barely affected in growth. Overall biomass production in the mixed culture surpassed the mean of the two monocultures. Thus, CMNs may contribute to interplant facilitation and the productivity boosts often found with intercropping compared with conventional monocropping.

Increase in SNR for 31P MR spectroscopy by combining polarization transfer with a direct detection sequence.

The sensitivity of (31)P MRS can be increased using higher magnetic fields, but also by using (1)H to (31)P polarization transfer techniques where the sensitivity is determined by the polarization of the proton spins and thus the signal-to-noise per unit time is unaffected by the slow T(1) relaxation properties of the (31)P spins. This implies that (31)P spins can be manipulated during the T(1) relaxation of the (1)H spins without affecting the signal-to-noise of the (1)H to (31)P polarization transferred spins. It is shown here that by combining (1)H to (31)P polarization transfer with a direct (31)P detection sequence in one repetition time, one can gain more signal-to-noise per unit of time as compared to a polarization transfer sequence alone. Proof of principle was demonstrated by phantom measurements and additionally the method was applied to the human calf muscle and to the human breast in vivo at 7 T.

Improve the selectively refocused INEPT pulse sequence for detecting phosphomonoesters and phosphodiesters.

In application of the (31)P selectively refocused insensitive nuclei enhanced polarization transfer (srINEPT) technique to the detection of phosphomono- and diesters in tissues, homonuclear couplings between the CH(2)O protons and the NCH(2) protons seriously attenuate the sensitivity. These couplings can be conventionally removed by two soft 180° pulses in the (1)H evolution period which selectively invert the NCH(2) magnetizations. However, the srINEPT pulse sequence can be simplified by replacing the pulse train "soft 180°-hard 180°-soft 180°" with a single soft 180° pulse that selectively inverts the CH(2)O magnetizations. Theoretical analysis in this study demonstrates the correctness of this approach in principle. Validation on a milk phantom allowed us to investigate and discuss advantages and disadvantages of the proposed srINEPT with respect to the original srINEPT. Furthermore, comparison of different selective pulses made it possible to demonstrate that the proposed srINEPT experiment is not sensitive to errors in pulse length, offset, and B(1) field strength of the selective pulse when ReBurp pulse is used for selective refocusing.

Quantitative 31P magnetic resonance spectroscopy of the human breast at 7 T.

This study presents quantified levels of phosphorylated metabolites in glandular tissue of human breast using (31)P magnetic resonance spectroscopy at 7 T. We used a homebuilt (1)H/(31)P radiofrequency coil to obtain artifact-free (31)P MR spectra of glandular tissue of healthy females by deploying whole breast free induction decay (FID) detection with adiabatic excitation and outer volume suppression. Using progressive saturation, the estimated apparent T(1) relaxation time of (31)P spins of phosphocholine and phosphoethanolamine was 4.4 and 5.7 s, respectively. Quantitative measures for phosphocholine and phosphoethanolamine levels in glandular tissue were established based on MR imaging. We used a 3D (1)H image of the breast to segment the glandular tissue; this was matched to a 3D (31)P image of the B1- field of the (31)P coil to correct for differences in glandular tissue volume and B(1) inhomogeneity of the (31)P coil. The (31)P MR spectra were calibrated using a phantom with known concentration. Average levels of phosphocholine and phosphoethanolamine in 11 volunteers were 0.84 ± 0.21 mM and 1.18 ± 0.41 mM, respectively. In addition, data of three patients with breast cancer showed higher levels of phosphocholine and phosphoethanolamine compared with healthy volunteers. This may indicate a potential role for the use of (31)P magnetic resonance spectroscopy for characterization, prognosis, and treatment monitoring in breast cancer.

Electron spray ionization mass spectrometry and 2D 31P NMR for monitoring 18O/16O isotope exchange and turnover rates of metabolic oligophosphates.

A new method was here developed for the determination of (18)O-labeling ratios in metabolic oligophosphates, such as ATP, at different phosphoryl moieties (α-, ß-, and γ-ATP) using sensitive and rapid electrospray ionization mass spectrometry (ESI-MS). The ESI-MS-based method for monitoring of (18)O/(16)O exchange was validated with gas chromatography-mass spectrometry and 2D (31)P NMR correlation spectroscopy, the current standard methods in labeling studies. Significant correlation was found between isotopomer selective 2D (31)P NMR spectroscopy and isotopomer less selective ESI-MS method. Results demonstrate that ESI-MS provides a robust analytical platform for simultaneous determination of levels, (18)O-labeling kinetics and turnover rates of α-, ß-, and γ-phosphoryls in ATP molecule. Such method is advantageous for large scale dynamic phosphometabolomic profiling of metabolic networks and acquiring information on the status of probed cellular energetic system.

Use of 1H and 31P HRMAS to evaluate the relationship between quantitative alterations in metabolite concentrations and tissue features in human brain tumour biopsies.

Quantitative multinuclear high-resolution magic angle spinning was performed in order to determine the tissue pH values of and the absolute metabolite concentrations in 33 samples of human brain tumour tissue. Metabolite concentrations were quantified by 1D (1)H and (31)P HRMAS using the electronic reference to in vivo concentrations (ERETIC) synthetic signal. (1)H-(1)H homonuclear and (1)H-(31)P heteronuclear correlation experiments enabled the direct assessment of the (1)H-(31)P spin systems for signals that suffered from overlapping in the 1D (1)H spectra, and linked the information present in the 1D (1)H and (31)P spectra. Afterwards, the main histological features were determined, and high heterogeneity in the tumour content, necrotic content and nonaffected tissue content was observed. The metabolite profiles obtained by HRMAS showed characteristics typical of tumour tissues: rather low levels of energetic molecules and increased concentrations of protective metabolites. Nevertheless, these characteristics were more strongly correlated with the total amount of living tissue than with the tumour cell contents of the samples alone, which could indicate that the sampling conditions make a significant contribution aside from the effect of tumour development in vivo. The use of methylene diphosphonic acid as a chemical shift and concentration reference for the (31)P HRMAS spectra of tissues presented important drawbacks due to its interaction with the tissue. Moreover, the pH data obtained from (31)P HRMAS enabled us to establish a correlation between the pH and the distance between the N(CH(3))(3) signals of phosphocholine and choline in (1)H spectra of the tissue in these tumour samples.

A new experimental approach and signal processing scheme for the detection and quantitation of ³¹P brain neurochemicals from in vivo MRS studies using dual tuned (¹H/³¹P) head coil.

Brain (31)P-neurometabolites play an important role in energy and membrane metabolism. Unambiguous identification and quantification of these neurochemicals in different brain regions would be a great aid in advancing the understanding of metabolic processes in the nervous system. Phosphomonoester (PME), consisting of phosphoethanolamine (PE) and phosphocholine (PC), is the "building block" for membranes, while phosphodiesters (PDE), consisting of glycerophosphocholine (GPC) and glycerophosphoethanolamine (GPE) metabolites are involved in the membrane breakdown process. In the clinical setting, generating well-resolved spectra for PC, PE, GPC, and GPE could be crucial phospholipids in providing information regarding membrane metabolism. We present here a new experimental approach for generating well-resolved (31)P spectra for PC and PE as well as for GPC, GPE, and other (31)P metabolites. Our results (based on uni-dimensional (1D) and multi-voxel (31)P studies) indicate that an intermediate excitation pulse angle (35°) is best suited to obtain well-resolved PC/PE and GPC/GPE resonance peaks. Our novel signal processing scheme allows generating metabolite maps of different phospholipids include PC/PE and GPC/GPE using the 'time-domain-frequency-domain' method as referred to in the MATLAB programming language.

Nonalcoholic fatty liver disease: detection of elevated nicotinamide adenine dinucleotide phosphate with in vivo 3.0-T 31P MR spectroscopy with proton decoupling.

PURPOSE: To determine if 3.0-T proton-decoupled phosphorus 31 ((31)P) magnetic resonance (MR) spectroscopy can be used to differentiate between stages of nonalcoholic fatty liver disease (NAFLD) by resolving the components of phosphomonoester (PME) and phosphodiester (PDE) and enabling detection of a greater number of other phosphorus-containing compounds. MATERIALS AND METHODS: This study was approved by the ethics committee of Helsinki University Central Hospital, and written informed consent was obtained from all study subjects. A 3.0-T clinical imager was used to obtain proton-decoupled (31)P MR spectra in the liver of control subjects (n = 12), patients with biopsy-proved simple steatosis due to nonalcoholic causes (nonalcoholic fatty liver, n = 13; nonalcoholic steatohepatitis [NASH], n = 9), and patients with cirrhosis (n = 9) to determine PME, phosphoethanolamine (PE), phosphocholine, PDE, glycerophosphocholine (GPC), glycerophosphoryl ethanolamine, uridine diphosphoglucose, nicotinamide adenine dinucleotide phosphate (NADPH), inorganic phosphate, phosphoenolpyruvate, and alpha-, beta- and gamma-nucleotide triphosphate levels. Liver fat was determined with hydrogen 1 MR spectroscopy. Differences between the disease groups were analyzed with one-way analysis of variance. RESULTS: The PME/(PME + PDE), PME/PDE, and PE/(PME + PDE) ratios were higher and the GPC/(PME + PDE) ratio was lower in patients with cirrhosis than in the other study groups (P < or = .001, one-way analysis of variance). The NADPH/(PME + PDE) ratio was higher in patients with NASH and those with cirrhosis than in control subjects (P < .05, post hoc analyses) and correlated with disease severity (P = .007). CONCLUSION: NADPH, a marker of inflammation and fibrinogenic activity in the liver, is increased in patients with NASH and those with cirrhosis. Proton-decoupled (31)P 3.0-T MR spectroscopy shows promise in the differentiation of NAFLD stages.

In vivo 31P and 13C NMR investigations of Rhodococcus rhodochrous metabolism and behaviour during biotransformation processes.

AIMS: The strain Rhodococcus rhodochrous OBT18 was isolated from a water treatment plant used to decontaminate industrial effluents containing benzothiazole derivatives. Aims of the work are to study the central metabolism of this strain and more specifically its behaviour during biodegradation of 2-aminobenzothiazole. METHODS AND RESULTS: In vivo(13)C and (31)P NMR experiments showed that this strain contains storage compounds such as polyphosphates, glycogen and trehalose and produces biosurfactants containing trehalose as sugar unit. Trehalose can be synthesized after reversion of the glycolytic pathway. In vivo(31)P NMR experiments showed that energy metabolism markers such as the intracellular pH and the ATP concentration did not change during biotransformation processes when R. rhodochrous was exposed to potentially toxic compounds including iron complexes and (* )OH radicals. Also R. rhodochrous recovers the normal values of ATP and pH after anoxia/reoxygenation cycle very quickly. CONCLUSIONS: Rhodococcus rhodochrous carbon and energy metabolism is well adapted to different stresses and consequently to live in the environment where conditions are constantly changing. SIGNIFICANCE AND IMPACT OF THE STUDY: The results of this study can be used to understand the behaviour of this bacterium in natural environments but also in water treatment plants where iron and UV light are present.

Phosphorus forms and chemistry in the soil profile under long-term conservation tillage: a phosphorus-31 nuclear magnetic resonance study.

In many regions, conservation tillage has replaced conventional tilling practices to reduce soil erosion, improve water conservation, and increase soil organic matter. However, tillage can have marked effects on soil properties, specifically nutrient redistribution or stratification in the soil profile. The objective of this research was to examine soil phosphorus (P) forms and concentrations in a long-term study comparing conservation tillage (direct drilling, "No Till") and conventional tillage (moldboard plowing to 20 cm depth, "Till") established on a fine sandy loam (Orthic Humo-Ferric Podzol) in Prince Edward Island, Canada. No significant differences in total carbon (C), total nitrogen (N), total P, or total organic P concentrations were detected between the tillage systems at any depth in the 0- to 60-cm depth range analyzed. However, analysis with phosphorus-31 nuclear magnetic resonance spectroscopy showed differences in P forms in the plow layer. In particular, the concentration of orthophosphate was significantly higher under No Till than Till at 5 to 10 cm, but the reverse was true at 10 to 20 cm. Mehlich 3-extractable P was also significantly higher in No Till at 5 to 10 cm and significantly higher in Till at 20 to 30 cm. This P stratification appears to be caused by a lack of mixing of applied fertilizer in No Till because the same trends were observed for pH and Mehlich 3-extractable Ca (significantly higher in the Till treatment at 20 to 30 cm), reflecting mixing of applied lime. The P saturation ratio was significantly higher under No Till at 0 to 5 cm and exceeded the recommended limits, suggesting that P stratification under No Till had increased the potential for P loss in runoff from these sites.