Changes in skeletal muscle diffusion parameters owing to intramyocellular lipid

IntroductionSeveral studies investigated the changes in diffusion of water molecules in skeletal muscle cells of lifestyle-related-disease patients who performed a hybrid training (HYBT) for six months. They reported that the apparent diffusion coefficient (ADC) and all diffusion eigenvalues (λ₁, λ₂, and λ₃) increased after the HYBT, owing to the enlargement of the intramyocellular diffusion space (intracellular space) caused by the muscular hypertrophy.We assumed that the HYBT promoted metabolism of the whole skeletal muscle including lipids, which reduced the amount of intramyocellular lipid (IMCL), and led to a secondary enlargement of the diffusion space in the skeletal muscle cells. However, the IMCL has to be a diffusion limiting factor in order to verify this hypothesis. Until now, there is no report on whether IMCL is a diffusion limiting factor for water molecules.The objective of this study was to examine whether the IMCL is a diffusion limiting factor in skeletal muscle cells.Materials and methodsWe performed a three-dimensional quantification of the IMCL in triceps surae muscles of lifestyle-related-disease patients and healthy volunteers. In addition, we measured the ADC in the volume of interest (VOI), diffusion anisotropy (FA), and diffusion eigenvalues (λ₁, λ₂, and λ₃), and evaluated the correlations between these diffusion parameters and IMCL.ResultsThe results showed that the amount of IMCL was positively and negatively correlated with the FA and λ₃, respectively, in lifestyle-related-disease patients. In addition, there was a weak negative correlation between IMCL and ADC, λ₁, and λ₂. There was no correlation between the amount of IMCL and diffusion parameters of healthy volunteers.DiscussionAbove a certain amount, the IMCL correlates with the diffusion parameters. A higher amount of IMCL leads to smaller diffusion eigenvalues. This result suggested that IMCL possibility of influencing diffusion of water molecules in skeletal muscle cells. However, in order for the influence of IMCL to be reflected in the diffusion eigenvalues, it was needed large amount of IMCL existed, and we thought that the influence was smaller than the influence by the already reported cell membrane.     

Investigation of proton diffusion in Nafion®117 membrane by electrical conductivity and NMR

The proton dynamics in Nafion ^®117 is investigated by comparison of the diffusion coefficient D_NMR estimated from PFG-NMR with that of D_σ estimated from electrical conductivity. At high water content region, D_σ is about two times higher than D_NMR as a result of Grotthuss mechanism. At low water content region, D_σ and D_NMR are in good agreement with each other. Both of the diffusion coefficients decrease steeply at low water content region. It can be explained as a result of the percolation transition due to the isolation of ion clusters, which is suggested by the recent small angle X-ray scattering data.     

Relaxation-Time and Diffusion NMR Microscopy of Single Neurons

Relaxation-time and diffusion-weighted NMR micrographs have been obtained for single neurons isolated from Aplysia californica. These images allow the nucleus and cytoplasm to be clearly differentiated, in contrast to proton spin-density images, which appear relatively homogenous. Images of the spatial distribution of T₁ and T₂ relaxivities and the diffusion coefficient (D), as well as average values for T₁, T₂, and D in the cytoplasm and nucleus, were calculated from sets of appropriately weighted images. In all cases, water in the nucleus had relaxation and diffusion properties markedly differing from those of cytoplasmic water, which in turn had properties which were distinct from those of free water. Additionally, the cytoplasmic T₂ was observed to triple following cell death, which is attributed to cytoplasmic dilution as water enters the cell. The work presented represents the first effort at a consistent exploration of the spatial distribution of NMR characteristics of water within intact single cells. These studies have implications both for modeling the NMR characteristics of water in neuronal tissues based on an understanding of the characteristics of water in different cell compartments and for understanding water/macromolecule interactions within cells. NMR microscopy studies such as these may help form a foundation for understanding and interpreting NMR characteristics measured from large assemblies of cells, i.e., spectroscopy and imaging of living tissues.     

Internal Magnetic Field Gradients in Heterogeneous Porous Systems: Comparison Between Spin-Echo and Diffusion Decay Internal Field (DDIF) Method

Two techniques used for evaluating internal magnetic field gradient (G _i), spin-echo (SE) and diffusion decay internal field (DDIF), were investigated at 9.4 T and compared in porous systems characterized by different pores size ranging from 4 to 96 μm with magnetic susceptibility difference between solid and liquid phase, \(\Delta \chi\)  ≈ 1.6 ppm. Since diffusion of a fluid in a solid porous matrix plays a role in both SE and DDIF methods, we investigated these two different methods by highlighting their dependence on characteristic parameters and length scales used to describe diffusion behavior of fluids in porous systems. Therefore, G _i behavior as a function of the dephasing length (l _g), diffusion length (l _d) and pores size (l _s) was obtained. Moreover G _i was evaluated by using both free diffusion and measured apparent diffusion coefficient of water, to quantify diffusion effect in different porous samples. This study gives more insight into the physical dynamics process to explain contrast mechanisms recently exploited by DDIF and SE applications for cancellous bone quality measurements.     

In vivo lipid diffusion coefficient measurements in rat bone marrow

The diffusion coefficient of lipids, D_l, within bone marrow, fat deposits and metabolically active intracellular lipids in vivo will depend on several factors including the precise chemical composition of the lipid distribution (chain lengths, degree of unsaturation, etc.) as well as the temperature. As such, D_l may ultimately prove of value in assessing abnormal fatty acid distributions linked to diseases such as cystic fibrosis, diabetes and coronary heart disease. A sensitive temperature dependence of D_l may also prove of value for MR-guided thermal therapies for bone tumors or disease within other fatty tissues like the breast. Measuring diffusion coefficients of high molecular weight lipids in vivo is, however, technically difficult for a number of reasons. For instance, due to the much lower diffusion coefficients compared to water, much higher b factors than those used for central nervous system applications are needed. In addition, the pulse sequence design must incorporate, as much as possible, immunity to motion, susceptibility and chemical shift effects present whenever body imaging is performed. In this work, high b-factor line scan diffusion imaging sequences were designed, implemented and tested for D_l measurement using a 4.7-T horizontal bore animal scanner. The gradient set available allowed for b factors as high as 0.03 μs/nm² (30,000 s/mm²) at echo times as short as 42 ms. The methods were used to measure lipid diffusion coefficients within the marrow of rat paws in vivo, yielding lipid diffusion coefficients approximately two orders of magnitude smaller than typical tissue water diffusion coefficients. Phantom experiments that demonstrate the sensitivity of lipid diffusion coefficients to chain length and temperature were also performed.     

Extinguishment of propane/air co-flowing diffusion flames by fine water droplets

In the present study, extinguishment of propane/air co-flowing diffusion flame by fine water droplets was investigated experimentally. Water droplets are generated by piezoelectric atomizers with the maximum droplets flow rate of 1500 ml/h. When the fuel injection velocity U_f is low, an attached laminar diffusion flame with a premixed flame at the base is stabilized. At some distance from the burner rim, a transition from laminar to turbulent diffusion flame occurs, and a turbulent diffusion flame is formed in the downstream region. When the fuel injector rim is thin (δ = 0.5 mm), the flame stability deteriorates with increase of the co-flowing air stream velocity U_a and the water droplets flow rate Q_m. The stability mechanism can be explained by the balance of the gas velocity and the burning velocity of premixed flame formed at the base. However, when the injector rim is thick (δ = 5 mm), a recirculation zone is produced downstream of the injector rim. The dependence of the quenching distance H_q on U_f and Q_m is relatively weak, and the stability diagram shows curious features. It was shown that U_a is crucially important since it determines flow residence time; if U_a < 0.4 m/s, water droplets can evaporate when they go by the recirculation zone, and the water vapor can diffuse into the recirculation zone. However, if U_a > 0.4 m/s, the water droplets should pass by the recirculation zone without sufficiently evaporated and are not so effective to extinguish the flame. The supply velocity of droplet-laden air should be low enough so that water droplets can evaporate and water vapor can diffuse into the premixed region at the base to obtain sufficient effectiveness of water droplets for fire suppression.     

Oxygen tracer diffusion in the magnéli phases TinO2n−1

Oxygen tracer diffusion was studied in rutile (TiO₂) at 1273 K and in the Magnéli phases Ti_nO_2n?1 (with 3 ? n < 8) at 1413 K. Mass spectrometry was used to analyse a gas atmosphere enriched in ¹⁸O; pure oxygen atmospheres were employed to study rutile, whilst studies on the Magnéli oxides utilised hydrogen/water buffers to set up the appropriate oxygen gas potentials. Anion diffusion is slower in the lower oxides than in rutile.     

Löslichkeit,Diffusion und Ultrarotabsorption von Wassermolekülen in Alkalihalogenidkristallen

Following a former communication, further experiments of solubility, diffusion and infraredabsorption of water molecules in KCl-, KBr- and KJ-crystals are given. Substituted mono- and bivalent ions to the refined crystals strongly increase the solubility of water at lower temperatures but there is practically no increase at higher temperatures. This points to two mechanisms for solubility: An interstitial at lower temperatures and probably by vacancies at higher temperatures. — The penetration of water into crystals containing K₂O orF-centers produces a colorless layer by chemical reaction. From investigation of such layers we get diffusion constants for the diffusion of water molecules. In crystals containingF-centers we find an additionalKH- layer. — The chemical reactions in the solid state produce H^?-, OH^?- and O^??-centers of well known concentration. This allows determination of the oscillator strengths of the characteristical ultraviolett absorptions. — The absorption in the near infrared by crystals containing water shows especially at low temperatures sharp peaks from single H₂O-molecules and broad peaks from precipitated water. An interstitial lattice model is discussed for the single H₂O-molecules.     

Ionic liquid type dye-sensitized solar cells: increases in photovoltaic performances by adding a small amount of water

Increases in photovoltaic performances for dye-sensitized solar cells having ionic liquid type electrolytes are reported. These results are explained by diffusion coefficient for I₃⁻, charge transfer resistances on counter electrodes, flat band potentials of TiO₂, redox potentials for I⁻/I₃⁻, electron diffusion constants, electron life time, and diffusion length in TiO₂ layers. Methylpropylimidazolium iodide is selected because of the lowest viscosity and the highest conductivity. Increases in the photovoltaic performance are observed when a small amount of water was added into the ionic liquid consisting of both LiI and t-butylpyridine as the additives. These improvements are brought about by enhancements of all of J_sc, ff and V_oc. The increases in J_sc and ff are associated with the decrease in charge transfer resistances on counter electrodes and increases in ionic conductivities. V_oc may be explained by an increase in the difference between redox potentials of I⁻/I₃⁻ and Fermi level.     

Protonic conductivity in hydrates

The protonic conductivity of three acid hydrates, HUO₂PO₄·4H₂O, Ce(HPO₄)₂·nH₂O,V₂O₅·nH₂O has been studied as a function of the partial pressure of water. The evolution of their conductivity is related to experimental water adsorption isotherms and to the theoretical Brunauer adsorption isotherms. Conclusions can then be drawn about the origin of the conductivity (bulk-type or surface conductivity) and about the type of water molecules involved in the protonic diffusion process. These three compounds are each representative of a different class of protonic conductors, the lattice hydrates, the particle hydrates, and the swelling hydrates respectively.     

Diffusion in thermotropic liquid crystals

Diffusion coefficients in mesophases of thermotropic liquid crystals have been measured to a considerable extent only during the last twelve years. Some theories on diffusion in mesophases have been developed too. Measurements in nematic, smectic A, smectic B, and smectic C mesophases have been carried out by mass transport techniques, detected by radio-tracers or optically, by NMR spin-echo techniques, and by quasi-elastic neutron scattering. The diffusion is anisotropic in most of the cases. In nematics self-diffusion parallel to the molecular director (D₆) is somewhat faster than perpendicular (D_⊥). Both diffusion coefficients show about the same activation energy. Impurity diffusion (small molecules dissolved in mesophases) demonstrates the same behaviour with less anisotropy. In smectics A and C the diffusion coefficients D₆ and D_⊥ can be nearly equal. The anisotropy is now shown in their respective activation energies with E₆>E_⊥. This effect is more pronounced in impurity than in self-diffusion. In addition impurity diffusion shows a strong anisotropy of the diffusion coefficients (D_⊥?D₆). In smectics B the activation energies E₆ and E_⊥ of self-diffusion seem again to be equal and the diffusion coefficients show a small anisotropy (D_⊥≥D₆).     

NMR study of tomato pericarp tissue by spin-spin relaxation and water self-diffusion

Pericarp tissues of tomato varieties Quest and Cameron were studied by low-field nuclear magnetic resonance (NMR) at a controlled temperature of 20°C. The spin-spin relaxation times and the water diffusion coefficients were measured with Carr-Parcell-Meiboom-Gill and pulsed field gradient multi-spin-echo (PFGMSE) NMR sequences. Four relaxing components were extracted from the spin-spin relaxation. The components withT ₂=11 ms,T ₂=65 ms,T ₂=430 ms andT ₂=1500 ms were related to the nonexchangeable protons and water proton in each cell compartment (i.e., cell wall-extracellular space, cytoplasm and vacuole, respectively). In contrast to the relative intensities, theT ₂ values appeared insensitive to variety and harvest period. The difference in relative intensity was related to the size of the pericarp cell. The water self-diffusion coefficients for each cell compartment were determined simultaneously with the PFGMSE sequence. The water self-diffusion coefficients for the vacuole and cytoplasm were not affected by the harvest date or variety. However, the water self-diffusion in the cell wall-extracellular space was significantly different between the two varieties.     

Transverse water relaxation in whole blood and erythrocytes at 3T, 7T, 9.4T, 11.7T and 16.4T; determination of intracellular hemoglobin and extracellular albumin relaxivities

Blood is a physiological substance with multiple water compartments, which contain water-binding proteins such as hemoglobin in erythrocytes and albumin in plasma. Knowing the water transverse (R₂) relaxation rates from these different blood compartments is a prerequisite for quantifying the blood oxygenation level-dependent (BOLD) effect. Here, we report the Carr-Purcell-Meiboom-Gill (CPMG) based transverse (R_2CPMG) relaxation rates of water in bovine blood samples circulated in a perfusion system at physiological temperature in order to mimic blood perfusion in humans. R_2CPMG values of blood plasma, lysed packed erythrocytes, lysed plasma/erythrocyte mixtures, and whole blood at 3 T, 7 T, 9.4 T, 11.7 T and 16.4 T were measured as a function of hematocrit or hemoglobin concentration, oxygenation, and CPMG inter-echo spacing (τ_cp). R_2CPMG in lysed cells showed a small τ_cp dependence, attributed to the water exchange rate between free and hemoglobin-bound water to be much faster than τ_cp. This was contrary to the tangential dependence in whole blood, where a much slower exchange between cells and blood plasma applies. Whole blood data were fitted as a function of τ_cp using a general tangential correlation time model applicable for exchange as well as diffusion contributions to R_2CPMG, and the intercept R_20blood at infinitely short τ_cp was determined. The R_20blood values at different hematocrit and the R_2CPMG values of lysed erythrocyte/plasma mixtures at different hemoglobin concentration were used to determine the relaxivity of hemoglobin inside the erythrocyte (r_2Hb) and albumin (r_2Alb) in plasma. The r_2Hb values obtained from lysed erythrocytes and whole blood were comparable at full oxygenation. However, while r_2Hb determined from lysed cells showed a linear dependence on oxygenation, this dependence became quadratic in whole blood. This possibly suggests an additional relaxation effect inside intact cells, perhaps due to hemoglobin proximity to the erythrocyte membrane. However, we cannot exclude that this is a consequence of the simple tangential model used to remove relaxation contributions from exchange and diffusion. The extensive data set presented should be useful for future theory development for the transverse relaxation of blood.     

Molecular Diffusion in NMR Microscopy

The signal-to-noise ratio and the T₂ contrast in ¹H NMR microscopy are strongly affected by self-diffusion effects. Here, we investigate the free diffusion of water within imaging gradients. As a result we obtain an apparent relaxation time T₂ which in NMR microscopy is at least one order of magnitude smaller than the true T₂ value of water in the object. This apparent T₂ relaxation is considerably reduced by improving spatial resolution. We conclude that quantitative true T₂ values cannot be calculated from series of images with increasing echo time. Furthermore, from the knowledge of the apparent T₂, an optimum short echo time can be found in order to maximize signal-to-noise ratio. Our theoretical findings are confirmed by phantom experiments at 11.75 T field strength.     

Electrical conductivity and chemical diffusion in Perovskite-type proton conductors in H2-H2O gas mixtures

The electrical conductivities of SrZr_0.9Y_0.1O_3-δ (SZY10) and BaCe_0.95Y_0.05O_3-δ(BCY5) were measured as a function of hydrogen partial pressure P(H₂), oxygen partial pressure P(O₂), steam partial pressure P(H₂O) and temperature. Their relaxation processes were analyzed using the solution of Fick's diffusion equation to determine the chemical diffusion coefficients and surface reaction rate constants. There were the differences in chemical relaxation kinetics and the conductivity dependence on P(H₂O) between the both oxides. The chemical diffusion coefficients depend on temperature but are essentially independent of P(H₂), P(O₂) and P(H₂O). The ambipolar diffusion treatment can explain the temperature dependence of chemical diffusion coefficients quantitatively. The chemical diffusion coefficients of SZY10 is one or two order of magnitude smaller than those of BCY5 at low temperature. The sluggish conductivity relaxation in SZY10 was due to considerably small oxygen vacancy diffusion coefficients at low temperatures. The total conductivity depends on P(H₂O) in the case of SZY10, but not for BCY5. This different dependence on P(H₂O) is caused by the difference in the ratio between proton mobility and oxide-ion mobility.     

A Diffusion Model for Spin-Spin Relaxation of Compartmentalized Water in Wood

A diffusion model for spin-spin relaxation of compartmentalized water with a surface relaxation was verified for lumen water in wood. Spin-spin relaxation measurements were carried out on water in redwood sapwood, spruce sapwood, and spruce compression-wood samples, which possessed different cell-lumen radius distributions as measured by scanning electron microscopy. For the redwood sample, NMR measurements were made for seven temperatures between 4 and 55°C over which the average lumen-water T₂ decreased from 177 to 103 ms. The lumen-water theory and experiment were in agreement, and evidence of higher-order relaxation modes, theoretically predicted for low temperatures, was found. This model was extended to two water regions to characterize the surface relaxation in terms of the spin-spin relaxation and diffusion coefficient of the cell-wall water and the partition coefficient. Using the extension and measurements of the spin-spin relaxation times and relative populations of lumen and cell-wall-water, estimates for cell-wall-water diffusion in a maximally hydrated redwood varied from 0.92 × 10⁻⁶ cm²/s at 4°C to 5.89 × 10⁻⁶ cm²/s at 55°C. The activation energy for cell-wall-water diffusion in redwood sap-wood in this temperature range was 6700 cal/mol, about 40% higher than the free-water value of 4767 cal/mol.     

MRI phantom for tissue simulation with respect to diffusion coefficient and kurtosis - Validation with injection of liposomal theranostics

This study presents gelatine-based and agar-based phantoms with an addition of glycerol, safflower oil, silicone oil and cellulose microcrystalline with a potential to cover the entire range of tissue diffusion coefficients and kurtosis values. Forty types of phantoms were prepared and examined for NMR relaxation times T₁ and T₂ and diffusional metrics D, K and ADC. Wide ranges of values of D (0.0003–0.0031 mm²s⁻¹), K (0.00–7.24) and ADC (0.0002–0.0031 mm²s⁻¹) were observed. Two of the phantoms closely mimic muscle and cortical gray matter with respect to water diffusion parameters. Although many of the presented phantoms display both D and K values within the range of human tissues, they match different tissues with respect to D and K. The imaging results for the gray matter simulating phantom injected with the liposomal solution, bear a resemblance to the particle size effect described in the literature. The phantoms presented in this work are simple in preparation and affordable tissue-simulating materials to be used primarily in development of diffusion kurtosis-based MRI methods and possibly in a preliminary assessment of MRI contrast agents. Further adjustments of the chemical compositions could potentially lead to development of new types of phantoms mimicking diffusional properties of more kinds of soft tissues.     

Synthesis of MoO2 particles during oxidation of bulk molybdenum samples by supercritical water

It was found that bulk samples of molybdenum 〈Mo〉 are oxidized by supercritical water forming nanoparticles of monocline MoO₂. The average size of nanoparticles obtained at uniform heating of 〈Mo〉 with supercritical water was about 27 nm, and the size of agglomerates of nanoparticles was ≤ 1 μm. From time dependence of the amount of formed H₂ n _H2(t), we have determined kinetic parameters of 〈Mo〉 transition to MoO₂ particles. The dependence dn _H2/dt is characterized by the presence of two pronounced maxima. This is explained by the change of mutual diffusion of H₂ and H₂O molecules along with the growth of thickness of the layer of MoO₂ nanoparticles.     

Ignition model of boron particle based on the change of oxide layer structure

The oxide layer of boron particle is generally regarded as a two-layer structure the inner layer is B₂O₃ and the outer is (BO)_n. However, under lower temperature, a tiny layer of B₂O₃ can be generated at the surface of the (BO)_n and form a three-layer structure during the ignition process, which has been proven by experimental phenomenon. Accordingly, a parameter xo is adopted to represent the thickness of the outer B₂O₃(l) layer (outermost layer), and a simplified kinetic and diffusion model for the ignition process of boron particles in dry and wet atmosphere is developed with considering the generation and consumption process of the outermost layer. The ignition process is divided into two parts (ignition delay and first-stage combustion) by the parameter xo. The ignition temperature is defined as the particle temperature at the moment that xo reaches 0. When xo?>?0, the particle is under the ignition delay process, and the evaporation product is B₂O₃(g). When xo?=?0, the particle turns to the first-stage combustion process. (BO)_n is exposed to the environment, the evaporation products are B₂O₂(g) and B₂O₃(g), and the particle is under the two-layer structure. The oxygen diffusion inward is available during these two processes. The ignition time which is predicted by this model is in good agreement with published experimental data. Under a real ramjet condition, higher ambient temperature and concentration of water vapor can reduce both the maximum value of xo and the ignition time. The ignition temperature decreases with higher water vapor concentration, but increases with the higher ambient temperature.     

NMR studies of hydrogen diffusion in β-LaNi5−yAly hydrides

Proton relaxation times have been measured in β-phase LaNi_5?yAl_yH_x, where 0<y<1.2, to determine the role of Al on hydrogen diffusion. Al substitution significantly increases the observed activation energy with a corresponding 100-fold decrease in the room temperature (300K) diffusion constant between y=0 and y=1.2. Comparisons are also made with previous studies of β-LaNi₅H_x and possible diffusion mechanisms are suggested.