Том 50, № 10 (2019)

Data on long-term persistence of nitroxide radicals typically are focused on solid samples. Less information is available for nitroxides in fluid solution. Sealed deoxygenated solutions of a doxyl nitroxide in tetrahydrofuran and a piperidinyl nitroxide in toluene in 4 mm EPR tubes were kept in a laboratory environment at ambient temperature and without protection from light. After more than 40 years, the concentrations of the solutions had decreased by about factors of 12 and 6, respectively. The longevity in solution probably depends strongly on the purity of the solvent, but these results indicate remarkable persistence.

Previously using ³¹P magnetic resonance spectroscopy (MRS) we have demonstrated that one hyperbaric oxygenation (HBO) session (with O₂ pressure 1.2 atm) directly activates cerebral energetics: the decrease in creatine phosphate (PCr) and, possibly, the increase in nicotinamide adenine dinucleotide. The aim of this study is to elucidate the effect of one HBO session on the concentrations of metabolites detectible by ¹H MRS, and on the connectivity in Default Mode Network. Absolute concentrations of the metabolites were calculated. The reduction of N-acetyl aspartate by 3% was found in mediolateral prefrontal cortex (MPFC) with p < 0.05 and in posterior cingulate cortex (p < 0.1). The resting-state functional connectivity between these zones was elevated by ~ 40%, p < 0.05 after HBO session. Glutamate levels remained unchanged after HBO. There is an indication in support of lactate growth in MPFC after HBO session. The demonstrated metabolic changes, as well as the decrease in PCr shown in previous study, may signify the activation of power supply processes to compensate the energy expenses connected with the enhancement of cerebral functional connectivity even after one HBO session.

Experiments on sodium (²³Na) magnetic resonance imaging (MRI) of human organs, including the construction of whole body (WB) MRI, on a clinical 0.5-T scanner are described. The specificity of the research is their conduct in the presence of radio frequency (RF) interference, characterized by the frequency drift of the parasitic RF signal, which complicates its filtering. To solve this problem, the receiver bandwidth (BW) was set as narrow as possible, which, in turn, determined the low sampling rate and pulse sequence with relatively long echo time (TE)—12 ms, which is comparable to the transverse relaxation time of sodium nuclei. ²³Na MRI on a 0.5-T clinical scanner was achieved without significant modifications in the hardware—only 20-cm square-shaped frame coil was made as a transceiver probe head. Scanning was performed using gradient echo method with in-plane resolution of (6.6 × 6.6) mm² without slice selection. After processing the data in K-space, including exponential apodization, images were obtained in which human organs are represented with signal-to-noise ratio (SNR) up to several tens. The scans from nine individual segments of the human body in prone and supine positions were acquired to produce ²³Na WB MRI. The time for one body segment scan was 30 min. The results of the work can be used to assess the potential capabilities of scanners of this class and to compare them with the data obtained using more advanced tools to assess their effectiveness.

The high-order perturbation formulas of the electron paramagnetic resonance (EPR) parameters for an orthorhombically elongated octahedral 3d⁹ cluster are adopted to analyze the local distortions of divalent copper in Ba₂Zn(HCOO)₆·4H₂O (BZFA). The doped Cu²⁺ may substitute the host Zn²⁺ in the lattice, with different local environments from the original Zn²⁺, which can strongly affect its EPR parameters. In the calculations, the admixture of d-orbitals in the ground state for the impurity Cu²⁺ ion under orthorhombic symmetry is considered, and the required molecular orbital coefficients are determined from the cluster approach. The orthorhombic field parameters are correlated with the local lattice distortion (characterized by the axial elongation δz and the relative perpendicular bond length variation δr) and can be calculated from the superposition model. The theoretical EPR parameters based on the above local structure are in good agreement with the observed values, and the results are discussed.

In the print published article, some equations were published incorrectly, the correct equations are given below.