Proton Transverse Relaxation Times Research Articles

In Vitro Digestion and Fermentation of Cowpea Pod Extracts and Proteins Loaded in Ca(II)-Alginate Hydrogels.

Antioxidants derived from food by-products are known for their bioactive properties and impact on human health. However, the gastrointestinal behavior is often poor due to their degradation during digestion. The development of Ca(II)-alginate beads supplemented with biopolymers and enriched with cowpea (Vigna unguiculata) extract could represent a novel environmentally friendly technological solution to produce functional ingredients in the food industry. The present study evaluates the impact of in vitro digestion/fermentation by analyzing global antioxidant response (GAR), production of short-chain fatty acids (SCFAs) as a modulation of gut microbiota, and behavior of proton transverse relaxation times by low-field nuclear magnetic resonance (as an indicator of gelation state and characterization of microstructure). Results revealed that guar gum and cowpea protein preserved a high GAR of total phenolic compounds and antioxidant capacity by ABTS and FRAP methods after digestion/fermentation, promoting an adequate protection of the bioactives for their absorption. Alginate-based beads have great potential as prebiotics, with the guar gum-containing system contributing the most to SCFAs production. Finally, the overall higher mobility of protons observed in the intestinal phase agrees with structural changes that promote the release of phenolic compounds during this stage. Beads are excellent carriers of bioactive compounds (cowpea phenolic compounds and peptides) with potential capacities.

Proton transverse relaxation times depending on the unsaturated fatty acids: a magnetic resonance relaxometric study on beef fat samples

ABSTRACT The unsaturated fatty acid content of beef meat is an important property that affects the health and sense of taste of the consumer and determines price. Fresh beef fat samples were measured by a bilateral low-field time-domain proton magnetic resonance (MR) apparatus. The proton transverse relaxation time (T2) for 18 fat samples were measured at 40.0°C using the Carr-Purcell-Meiboom-Gill method. The results showed that T2 increased linearly with unsaturated fatty acid content. By using the linear dependence of T2 on the unsaturated fatty acid content, we successfully estimated the contents of oleic acid, total monounsaturated fatty acid, and total unsaturated fatty acid with root-mean-square errors of 2.5, 2.8, and 3.2 wt%, respectively. The proposed T2-relaxometry-based method could be performed using a portable unilateral MR surface scanner, which would enable in-vivo nondestructive noninvasive measurements of live cattle for the optimization of the feeding and fattening timing from calf to adult and for the best choice of the shipment timing in terms of the maximization of unsaturated fatty acid content of beef meat.

Synergistic effects in cross-linked blends of ion-conducting PEO-/PPO-based unsaturated polyesters

Ion-conductive unsaturated polyesters (UP) were synthesised from poly(ethylene oxide) (Xn = 9, 13, 22, 90) or poly(propylene oxide) (Xn = 7, 13, 20, 34, 68) and maleic anhydride. Subsequently, the polyesters were doped with LiClO4 and cross-linked with styrene using a redox initiator. For PEO-based polyesters, the minimum resistivity is found at an O/Li+ molar ratio of 50/1. In contrast, more lithium is required to reach the minimum when using PPO (O/Li+ = 10/1). Unlike the PEO-based polyesters, cross-linking of the PPO types gives rise to decreasing resistivities at increasing molecular weight. This correlates well with the transverse proton relaxation time determined by single-sided NMR, which is an indicator of the chain mobility. The cross-linking reaction of these UP with styrene exactly follows the predictions based on the copolymerisation parameters and is, therefore, not dependent on the ratio of styrene to UP double bonds as previously reported. Due to the opposing effects of the molecular weight on the ion conductivity of PEO- and PPO-based UP, 1:1 blends of short-chain PPO and long-chain PEO polyesters were cross-linked with styrene. The resulting networks showed a resistivity of 4 kΩ m (σ = 2.5∙10−4 S∙m−1), which is 5 times lower than the pure PEO and 3 times lower than the pure PPO materials.

Effect of ultrasound on mill starch and protein in ultrasound-assisted laboratory-scale corn wet-milling

Ultrasound was applied to facilitate starch-protein separation during ultrasound-assisted laboratory-scale corn wet-milling. The effects of ultrasound on the properties of mill starch and protein were investigated to explore the possible mechanisms in this study. A higher starch yield was obtained with sonication treatment in starch-protein separation (15 min, 200 W) and the results showed that ultrasound did not induce damage to the product starch. The differences in the distribution of water proton transverse relaxation time for mill starch suggested that the interaction between starch granules and protein in mill starch was destroyed. The free sulfhydryl content increased by 37.21% and the disulfide bond content decreased by 43.66% of the separated proteins indicated that ultrasound destroyed the disulfide bonds effectively (p < 0.05). Sonication treatment for longer time or at higher power decreased α-helix and β-turn while increased β-sheet and random coil (p < 0.05). Ultrasound increased surface hydrophobicity and decreased the thermal stability of the protein (p < 0.05). The higher intensity of ultraviolet–visible spectroscopy and ultraviolet-difference absorption spectroscopy indicated the unfolding of protein by sonication treatments. Ultrasound may break down the disulfide bonds and hydrogen bonds of protein molecules, effectively releasing starch from the disintegrated protein agglomerates.

Time Domain Nuclear Magnetic Resonance (TD-NMR) to evaluate the effect of potato cell membrane electroporation

Time Domain-Nuclear Magnetic Resonance (TD-NMR) was used here for the first time to analyze potato specimens cut from tubers before and after electroporation. The proton transverse relaxation time, T2, was used to identify the modifications that occur at the cell level involving water molecules mobility in potato tubers after the electroporation treatment. Since electroporation modifies the tissue conductivity, the samples were also analyzed in terms of conductivity, water content, and microscopic morphology of the tissue. Comparison analyses were performed on dried potato (zero water content) and water-potato starch mixtures with different water contents. All the data confirm that the effect of the electroporation process can be identified with a variation of the position of the peaks in T2 distribution, associated to sub-cellular modifications.

Recent Advances of Bioresponsive Nano-Sized Contrast Agents for Ultra-High-Field Magnetic Resonance Imaging.

The ultra-high-field magnetic resonance imaging (MRI) nowadays has been receiving enormous attention in both biomaterial research and clinical diagnosis. MRI contrast agents are generally comprising of T1-weighted and T2-weighted contrast agent types, where T1-weighted contrast agents show positive contrast enhancement with brighter images by decreasing the proton's longitudinal relaxation times and T2-weighted contrast agents show negative contrast enhancement with darker images by decreasing the proton's transverse relaxation times. To meet the incredible demand of MRI, ultra-high-field T2 MRI is gradually attracting the attention of research and medical needs owing to its high resolution and high accuracy for detection. It is anticipated that high field MRI contrast agents can achieve high performance in MRI imaging, where parameters of chemical composition, molecular structure and size of varied contrast agents show contrasted influence in each specific diagnostic test. This review firstly presents the recent advances of nanoparticle contrast agents for MRI. Moreover, multimodal molecular imaging with MRI for better monitoring is discussed during biological process. To fasten the process of developing better contrast agents, deep learning of artificial intelligent (AI) can be well-integrated into optimizing the crucial parameters of nanoparticle contrast agents and achieving high resolution MRI prior to the clinical applications. Finally, prospects and challenges are summarized.

Safety And Feasibility Of Strength Training In Patients With Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is a rapidly progressive and currently incurable neuromuscular disease. Understanding the role of exercise is important for these patients as high-intensity or eccentric actions can be damaging in DMD yet a lack of loading may exacerbate muscle dysfunction. While a few studies show submaximal exercise may be safe and potentially delay the loss of muscle function in DMD, no study has systematically examined the potential of strengthening exercise to improve muscle function or attenuate disease progression. PURPOSE: To examine the safety and feasibility of a pilot, in-home strengthening intervention consisting of knee extensor (KE) and flexor (KF) exercise in DMD. METHODS: Eight ambulatory boys with DMD [9.3 (0.8) yrs, BMI 19.0 (4.6) kg/m2] on corticosteroid therapy were recruited to undergo 12 weeks of isometric exercise training of the bilateral KE and KF. Exercise prescription consisted of 4 sets x 6 reps, 3x/week at a target intensity of 50% maximal volitional contraction (MVC). At baseline (BL), MVC testing and training familiarization were done for one week on site. The exercise equipment (custom built chair, laptop, and load cell) was subsequently shipped allowing for in-home training and supervision via live video conferencing for each session. Safety outcome measures to assess muscle damage included magnetic resonance proton transverse relaxation time (T2) of KE and KF, pain assessment, and creatine kinase levels at BL, 1, 6, and 12wks. Peak strength (KE and KF MVC) and time to ascend/descend 4 steps were also assessed at BL and 12wks. RESULTS: The 7 boys who completed the strength training program had a compliance of 84.9 (9.0)% for the exercise sessions. The safety measures did not indicate signs of muscle damage [non-significant change in mean T2: KE=2.3 (3.6)% and KF= 0.4 (4.6)%]. Peak torque increased by 20.6% for KE (p<0.01) and 14.3% for KF (p<0.05), and the time to ascend (13.5%, p<0.05) and descend (22.7%, p<0.05) steps improved after exercise training. CONCLUSION: This in-home, 12-week supervised strength training program was safe, feasible, and improved strength and function in boys with DMD. Future research is required to optimize the strengthening protocol and further explore its potential efficacy and clinical application.

Silicon Nanoparticles Prepared by Plasma‐Assisted Ablative Synthesis: Physical Properties and Potential Biomedical Applications

Silicon (Si) nanoparticles (NPs) with small (10−3–10−1 at%) content of iron oxide (Fe2O3) are prepared by plasma‐assisted ablative synthesis. Powders of the prepared Si‐iron oxide (SIO) NPs are investigated by means of the transmission electron microscopy, Raman spectroscopy, electron paramagnetic resonance, and magnetic susceptibility measurements. Aqueous suspensions of the NPs are studied by using dynamic light scattering and nuclear magnetic resonance technique. The longitudinal and transverse relaxation times of protons in aqueous suspensions of the NPs are found to be dependent on the iron content. The stronger decrease of the proton relaxation is detected for the samples with higher iron content. Magnetic resonance imaging (MRI) experiments show that SIO NPs have properties of the MRI contrast agent and it is confirmed by in vivo experiments with cancer tumor. Aqueous suspensions of SIO NPs are explored as sensitizers of electromagnetic radio frequency hyperthermia and the highest heating rate is observed for the NPs with smaller hydrodynamic size (≈50 nm). The obtained results indicate possible ways for applications of SIO NPs in the MRI diagnostics and mild therapy of cancer.

Surface Characterization of TiO2 Polymorphic Nanocrystals through 1H-TD-NMR.

Nanocrystals (NCs) surface characterization is a fundamental step for understanding the physical and chemical phenomena involved at the nanoscale. Surface energy and chemistry depend on particle size and composition, and, in turn, determine the interaction of NCs with the surrounding environment, their properties and stability, and the feasibility of nanocomposites. This work aims at extracting more information on the surface of different titanium dioxide polymorphs using 1H-TD-NMR of water. Taking advantage of the interaction between water molecules and titanium dioxide NCs, it is possible to correlate the proton transverse relaxation times ( T2) as the function of the concentration and the specific surface area (δp· Cm) and use it as an indicator of the crystal phase. Examples of three different crystals phase, rutile, anatase, and brookite, have been finely characterized and their behavior in water solution have been studied with TD-NMR. The results show a linear correlation between relaxivity ( R2) and their concentration Cm. The resulting slopes, after normalization for the specific surface, represent the surface/water interaction and range from 1.28 g m-2 s-1 of 50 nm rutile nanocrystals to 0.52 for similar sized brookite. Even higher slopes (1.85) characterize smaller rutile NCs, in qualitative accordance with the trends of surface energy. Thanks to proton relaxation phenomena that occur at the NCs surface, it is possible to differentiate the crystal phase and the specific surface area of titanium dioxide polymorphs in water solution.

Impact of Ionic Liquids on the Structure and Dynamics of Collagen.

The changes in the structure and dynamics of collagen treated with two different classes of ionic liquids, bis-choline sulfate (CS) and 1-butyl-3-methyl imidazolium dimethyl phosphate (IDP), have been studied at the molecular and fibrillar levels. At the molecular level, circular dichroic studies revealed an increase in molar ellipticity values for CS when compared with native collagen, indicating cross-linking, albeit pronounced conformational changes for IDP were witnessed indicating denaturation. The impedance was analyzed to correlate the conformational changes with the hydration dynamics of protein. Changes in the dielectric properties of collagen observed upon treatment with CS and IDP reported molecular reorientation in the surrounding water milieu, suggesting compactness or destabilization of the collagen. This was further confirmed by proton transverse NMR relaxation time measurements, which demonstrated that the water mobility changes in the presence of the ILs. At the fibrillar level, differential scanning calorimetry thermograms for rat tail tendon collagen fibers treated with CS show a 5 °C increase in denaturation temperature, suggesting imparted stability. On the contrary, a significant temperature decrease was noticed for IDP, indicating the destabilization of collagen fibers. The obtained results clearly indicate that the changes in the secondary structure of protein are due to the changes in the hydration dynamics of collagen upon interaction with ILs. Thus, this study on the interaction of collagen with ionic liquids unfolds the propensity of ILs to stabilize or destabilize collagen depending on the changes invoked at the molecular level in terms of structure and dynamics of protein, which also got manifested at the fibrillar level.

Analysis of masticatory muscle coordination during unilateral single-tooth clenching using muscle functional magnetic resonance imaging.

In a previous study, we used muscle functional magnetic resonance imaging to show that the anterior movement of the occlusal point increased the activity of the superior head of the ipsilateral lateral pterygoid muscle (ipsilateral SHLP) during unilateral single-tooth clenching. The purpose of this study was to verify the hypothesis that the increased activity of the ipsilateral SHLP described above serves to antagonise the occlusal force acting on the condyle. In total, 9 healthy volunteers were requested to perform left unilateral clenching at the first molar or first premolar region for 1minute at 20% or 40% maximum voluntary clenching force. Changes in the mean proton transverse relaxation time (∆T2) were examined from the magnetic resonance images obtained before and after each clenching act as an index of the activity in all masticatory muscles. Correlation analyses of the mean ΔT2 for each volume of interest were performed with the first molar or premolar clenches to analyse the correlation between the activities in each muscle. A statistically significant correlation was exhibited between the ipsilateral temporal and ipsilateral SHLP (r=.651, P=.003) during first premolar clenching. However, no significant correlations were observed in the ipsilateral SHLP during first molar clenching. The results of this study suggest that the ipsilateral SHLP may contribute to the pulling of the mandibular condyle forward against the occlusal force generated by the ipsilateral temporal muscle.

Unilateral NMR and Micro DSC Study of Artificially Aged Parchments

New and artificially aged parchments were studied by unilateral NMR and micro DSC. Samples were obtained by exposing new parchments to 80 �C and alternate 40 and 80% relative humidity for increasing times up to 32 days. The impact of accelerated ageing was assessed by measuring both the proton transverse relaxation times (T2eff) and thermodynamic parameters associated with thermal denaturation of fibrillar collagen. Depending on the ageing time, significant structural changes correlated with thermal stability and collagen heterogeneity were observed, in good agreement with changes in phase composition and relaxation times. The results suggest two ageing regimes depending on the balance between the two main processes which drive the behavior of parchments during thermal ageing, i.e. thermally induced cross linking and thermal destabilization and denaturation.

Quantitative two-dimensional ultrashort echo time magnetization transfer (2D UTE-MT) imaging of cortical bone.

To investigate quantitative 2D ultrashort echo time magnetization transfer (UTE-MT) imaging in ex vivo bovine cortical bone and in vivo human tibial cortical bone. Data were acquired from five fresh bovine cortical bone samples and five healthy volunteer tibial cortical bones using a 2D UTE-MT sequence on a clinical 3T scanner. The 2D UTE-MT sequence used four or five MT powers with five frequency offsets. Results were analyzed with a two-pool quantitative MT model, providing measurements of macromolecular fraction (f), macromolecular proton transverse relaxation times (T2m ), proton exchange rates from water/macromolecular to the macromolecular/water pool (RM0m /RM0w ), and spin-lattice relaxation rate of water pool (R1w ). A sequential air-drying study for a small bovine cortical bone chip was used to investigate whether above MT modeling parameters were sensitive to the water loss. Mean fresh bovine cortical bone values for f, T2m , R1w , RM0m , and RM0w were 59.9 ± 7.3%, 14.6 ± 0.3 μs, 9.9 ± 2.4 s-1 , 17.9 ± 3.6 s-1 , and 11.8 ± 2.0 s-1 , respectively. Mean in vivo human cortical bone values for f, T2m , R1w , RM0m and RM0w were 54.5 ± 4.9%, 15.4 ± 0.6 μs, 8.9 ± 1.1 s-1 , 11.5 ± 3.5 s-1 , and 9.5 ± 1.9 s-1 , respectively. The sequential air-drying study shows that f, RM0m , and R1w were increased with longer drying time. UTE-MT two-pool modeling provides novel and useful quantitative information for cortical bone. Magn Reson Med 79:1941-1949, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Sub-Micrometer Magnetic Nanocomposites: Insights into the Effect of Magnetic Nanoparticles Interactions on the Optimization of SAR and MRI Performance.

There is increasing interest in the development of new magnetic polymeric carriers for biomedical applications such as trigger-controlled drug release, magnetic hyperthermia (MH) for the treatment of cancer, and as contrast agents in magnetic resonance imaging (MRI). This work describes the synthesis of sub-micrometer and magnetic polymer nanocomposite capsules (MPNCs) by combining in one single platform the biodegradable polymer poly-ε-caprolactone (PCL) and different concentrations of ∼8 nm oleic acid (OA)-functionalized magnetite nanoparticles (Fe3O4@OA), employing the oil-in-water emulsion/solvent evaporation method. The MPNCs showed a significant increase in particle size from ∼400 to ∼800 nm as the magnetic loading in the organic-inorganic hybrids increases from 1.0% to 10%. The MPNCs presented high incorporation efficiency of Fe3O4@OA nanoparticles, good colloidal stability, and super-paramagnetic properties. Interestingly, electron microscopy results showed that the Fe3O4@OA nanoparticles were preferentially located at the surface of the capsules. Evaluation of the magnetic properties showed that the saturation magnetization and the blocking temperature of the MPNCs samples increased as a function of the Fe3O4@OA loading. All the MPNCs exhibited heating when subjected to MH, and showed good specific absorption rates. Use of the formulations decreased the longitudinal (T1) and transverse (T2) relaxation times of water protons' nuclei, with excellent transverse relaxivity (r2) values, especially in the case of the formulation with lowest Fe3O4@OA loading. Furthermore, the MPNCs-cell interaction was studied, and MPNCs showed lower cellular toxicity to normal cells compared to cancer cells. These findings help in understanding the relationships between magnetic nanoparticles and polymeric capsules, opening perspectives for their potential clinical uses as simultaneous heating sources and imaging probes in MH and MRI, respectively.

Evaluation of masticatory activity during unilateral single tooth clenching using muscle functional magnetic resonance imaging.

Masticatory muscle activity during teeth clenching is affected by occlusal pattern. However, few studies have performed simultaneous evaluation of all masticatory activities during teeth clenching under various occlusal conditions. The aim of this study was to use muscle functional magnetic resonance imaging (mfMRI) to evaluate the effects of changes in occlusal point on masticatory activity during single tooth clenching. Changes in mean proton transverse relaxation time (∆T2) as an index of activity in all masticatory muscles during left unilateral clenching at the first molar or first premolar for 1 min were examined in nine healthy volunteers. Bite force was maintained at 40% of the maximum voluntary clenching force. The ∆T2 values of the masseter and lateral pterygoid muscles were analysed separately for superficial and deep layers, and for superior and inferior heads. The ∆T2 values for the ipsilateral deep masseter were significantly lower, and for the superior head of the ipsilateral lateral pterygoid muscles were significantly higher, after left first premolar clenching compared to left first molar clenching. These results quantitatively demonstrate a significant increase in activity of the superior head of the ipsilateral lateral pterygoid muscle and a significant decrease in activity of the ipsilateral deep masseter muscle with forward displacement of the occlusal contact point during unilateral tooth clenching.

Effect of Pressure Intensity of Compression Short-Tight on Fatigue of Thigh Muscles

Existing studies have failed to provide evidence of a positive effect on exercise performance by wearing compression short tights covering only both thighs. This could be due to an inadequate pressure intensity that otherwise has a significant effect if applied on the crucial point in the thigh. This study aimed to examine the effect of pressure intensity of elastic compression short-tights on the metabolic state of thigh muscles during submaximal running. Two groups of 11 male subjects performed treadmill running at 12 km · h(-1) in three conditions in each of experiment 1 (short-tights with a compression intensity at the thigh of 8 mm Hg (LOW) and 15 mm Hg (MID) and noncompression shorts as control (CON1)) and experiment 2 (short-tights with 20 mm Hg (MID-HIGH) and 25 mm Hg (HIGH) and CON2). Before and immediately after the running exercises, T2-weighted magnetic resonance images of the right thigh were obtained without testing garments. From the images, skeletal muscle proton transverse relaxation time (T2) of each muscle in the thigh was calculated. T2 was significantly increased after the treadmill running in all conditions in the hamstring and adductor muscles. In experiment 1, after the running, T2 elevation was significantly smaller in MID than that in CON1 for the biceps femoris, semimembranosus, adductor longus, and adductor magnus muscles. In experiment 2, after the running, T2 elevation was significantly lower in MID-HIGH than that in CON2 and HIGH for the biceps femoris, semimembranosus, and adductor longus. The findings suggest that wearing compression short tights with a pressure intensity of 15-20 mm Hg at the thigh can reduce development of fatigue of exercising muscles during submaximal running exercise in healthy adult males.

Molecular dynamics simulations of proton transverse relaxation times in suspensions of magnetic nanoparticles

In this work we have analyzed the influence of various factors on the transverse relaxation times T2 of water protons in suspension of magnetic nanoparticles. For that purpose we developed a full molecular dynamics force field which includes the effects of dispersion interactions between magnetic nanoparticles and water molecules, electrostatic interactions between charged nanoparticles and magnetic dipole–dipole and dipole–external field interactions. We also accounted for the magnetization reversal within the nanoparticles body frames due to finite magnetic anisotropy barriers. The force field together with the Langevin dynamics imposed on water molecules and the nanoparticles allowed us to monitor the dephasing of water protons in real time. Thus, we were able to determine the T2 relaxation times including the effects of the adsorption of water on the nanoparticles’ surfaces, thermal fluctuations of the orientation of nanoparticles’ magnetizations as well as the effects of the core–shell architecture of nanoparticles and their agglomeration into clusters. We found that there exists an optimal cluster size for which T2 is minimized and that the retardation of water molecules motion, due to adsorption on the nanoparticles surfaces, has some effect in the measured T2 times. The typical strengths of the external magnetic fields in MRI are enough to keep the magnetizations fixed along the field direction, however, in the case of low magnetic fields, we observed significant enhancement of T2 due to thermal fluctuations of the orientations of magnetizations.

Long-lived spin state of a tripeptide in stretched hydrogel

The longitudinal (T 1), transverse (T 2), and singlet state (T s) relaxation times of the geminal backbone protons (CH2) of L-Leu-Gly-Gly were studied by NMR spectroscopy at 9.4 T in a bovine hide gelatin gel composed in D2O at 25 °C. Gelatin granules were dissolved in a hot solution of the tripeptide and then the solution was allowed to gel inside a flexible silicone tubing. With increases in gelatin content, the T 2 and T s of the CH2 protons correspondingly decreased (T s/T 2 ~ constant), while the change in T 1 was relatively small. The largest observed T s/T 1 value was 3.3 at 46% w/v gelatin that was the lowest gelatin content examined. Stretching the tubing, and hence the gel, brought about anisotropic alignment of the constituents resulting in residual quadrupolar splitting of the resonance from D2O in (2)H NMR spectra, and residual dipolar splitting of the CH2 resonance in (1)H NMR spectra. WALTZ-16 decoupling during the relaxation intervals extended the singlet state relaxation time, but the efficacy diminished as the gels were stretched. Theoretically predicted T 1, T 2, and T s values, assuming intramolecular dipolar coupling as the only source of relaxation, were within the same order of magnitude as the experimentally observed values. Overall we showed that it is possible to observe a long-lived spin state in an anisotropic medium when T 2 is shorter than T 1 in the presence of non-zero residual dipolar couplings.

Longitudinal measurements of MRI-T2 in boys with Duchenne muscular dystrophy: Effects of age and disease progression

Duchenne muscular dystrophy (DMD) is characterized by an increased muscle damage and progressive replacement of muscle by noncontractile tissue. Both of these pathological changes can lengthen the MRI transverse proton relaxation time (T2). The current study measured longitudinal changes in T2 and its distribution in the lower leg of 16 boys with DMD (5–13years, 15 ambulatory) and 15 healthy controls (5–13years). These muscles were chosen to allow extended longitudinal monitoring, due to their slow progression compared with proximal muscles in DMD. In the soleus muscle of boys with DMD, T2 and the percentage of pixels with an elevated T2 (⩾2SD above control mean T2) increased significantly over 1year and 2years, while the width of the T2 histogram increased over 2years. Changes in soleus T2 variables were significantly greater in 9–13years old compared with 5–8years old boys with DMD. Significant correlations between the change in all soleus T2 variables over 2years and the change in functional measures over 2years were found. MRI measurement of muscle T2 in boys with DMD is sensitive to disease progression and shows promise as a clinical outcome measure.

Multidisciplinary approach to study the effect of water status and mobility on the activity of peroxidase in solutions

The effect of water mobility on horseradish peroxidase (HRP) activity in solutions was investigated by measuring water activity (aw), freezable water content, 1H proton transverse relaxation time and water self-diffusivity determined by nuclear magnetic resonance. The effect of system mobility as described by viscosity and glass transition temperature (T′g) was also studied.The aw and viscosity of aqueous solutions were modulated using ligands (glucose, sorbitol and trehalose) and a thickener (maltodextrin).The effectiveness of a solute in the inhibition of HRP activity was better related to its ability to reduce the mobility of the system than to its water mobility depleting effect.The relationship among viscosity and peroxidase activity was influenced by the type of enzyme but not by the substrate. Bovine lactoperoxidase activity was hindered by viscosity changes more than HRP activity (tested in the same system) due to the higher molecular weight of the former enzyme.