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Rodent models of Duchenne muscular dystrophy (DMD) often do not recapitulate the severity of muscle wasting and resultant fibro‐fatty infiltration observed in DMD patients. Having recently documented severe muscle wasting and fatty deposition in two preclinical models of muscular dystrophy (Dysferlin‐null and mdx mice) through apolipoprotein E (ApoE) gene deletion without and with cholesterol‐, triglyceride‐rich Western diet supplementation, we sought to determine whether magnetic resonance imaging and spectroscopy (MRI and MRS, respectively) could be used to detect, characterize, and compare lipid deposition in mdx‐ApoE knockout with mdx mice in a diet‐dependent manner. MRI revealed that both mdx and mdx‐ApoE mice exhibited elevated proton relaxation time constants (T2) in their lower hindlimbs irrespective of diet, indicating both chronic muscle damage and fatty tissue deposition. The mdx‐ApoE mice on a Western diet (mdx‐ApoEW) presented with greatest fatty tissue infiltration in the posterior compartment of the hindlimb compared with other groups, as detected by MRI/MRS. High‐resolution magic angle spinning confirmed elevated lipid deposition in the posterior compartments of mdx‐ApoEW mice in vivo and ex vivo, respectively. In conclusion, the mdx‐ApoEW model recapitulates some of the extreme fatty tissue deposition observed clinically in DMD muscle but typically absent in mdx mice. This preclinical model will help facilitate the development of new imaging modalities directly relevant to the image contrast generated in DMD, and help to refine MR‐based biomarkers and their relationship to tissue structure and disease progression. [ABSTRACT FROM AUTHOR]

The goal of this study was to determine whether changes in cardiac metabolism in Type 2 diabetes are associated with contractile dysfunction or impaired response to ischemia. Hearts from Zucker diabetic fatty (ZDF) and lean control rats were isolated and perfused with glucose, lactate, pyruvate, and palmitate. The rates of glucose, lactate, pyruvate, and palmitate oxidation rates and glycolysis were determined during baseline perfusion and low-flow ischemia (LFI: 0.3 ml/min for 30 min) and after LFI and reperfusion. Under all conditions, ATP synthesis from palmitate was increased and synthesis from lactate was decreased in the ZDF group, whereas the contribution from glucose was unchanged. During baseline perfusion, the rate of glycolysis was lower in the ZDF group: however, during LFI and reperfusion, there were no differences between groups. Despite these metabolic shifts, there were no differences in oxygen consumption or ATP production rates between the groups under any perfusion conditions. Cardiac function was slightly depressed before LFI in the ZDF group, but during reperfusion, function was improved relative to the control group despite the increased dependence on fatty acids for energy production. These data suggest that in this model of diabetes, the shift from carbohydrates to fatty acids for oxidative energy production did not increase myocardial oxygen consumption and was not associated with impaired response to ischemia and reperfusion. contractile dysfunction; ischemia; nuclear magnetic resonance spectroscopy; carbohydrate metabolism

Interventions that stimulate carbohydrate oxidation appear to be beneficial in the setting of myocardial ischemia or infarction. However, the mechanisms underlying this protective effect have not been defined, in part because of our limited understanding of substrate utilization under ischemic conditions. Therefore, we used [sup.1]H and [sup.13]C NMR spectroscopy to investigate substrate oxidation and glycolytic rates in a global low-flow model of myocardial ischemia. Isolated male Sprague-Dawley rat hearts were perfused for 30 min under conditions of normal flow (control) and low-flow ischemia (LFI, 0.3 ml/min) with insulin and [sup.13]C-labeled lactate, pyruvate, palmitate, and glucose at concentrations representative of the physiological fed state. Despite a ~50-fold reduction in substrate delivery and oxygen consumption, oxidation of all exogenous substrates plus glycogen occurred during LFI. Oxidative metabolism accounted for 97% of total calculated ATP production in the control group and ~30% in the LFI group. For controls, lactate oxidation was the major source of ATP; however, in LFI, this shifted to a combination of oxidative and nonoxidative glycogen metabolism. Interestingly, in the LFI group, anaplerosis relative to citrate synthase increased sevenfold compared with controls. These results demonstrate the importance of oxidative energy metabolism for ATP production, even during very-low-flow ischemia. We believe that the approach described here will be valuable for future investigations into the underlying mechanisms related to the protective effect of increasing cardiac carbohydrate utilization and may ultimately lead to identification of new therapeutic targets for treatment of myocardial ischemia. nuclear magnetic resonance spectroscopy; energy metabolism; lactate; pyruvate; ATP

Out-of-plane mirror symmetry-breaking provides a powerful tool for engineering the electronic properties and the exciton behavior of two-dimensional materials. Here, by combining time-domain density functional theory with nonadiabatic dynamics, we investigate the underlying mechanism of how the vertical dipole moment modulates the photoexcited carrier transport and the electron-hole recombination dynamics in polar Janus MoSSe/MoS2 stacked heterostructures. It is shown that the stronger nonadiabatic coupling, interlayer-state delocalization and the built-in electric field caused by charge redistribution facilitate a more rapid photocarrier separation across the interface in the S/S stacked bilayer compared with the S/Se bilayer, explaining the experimentally observed stronger photoluminescence quenching effect in the S/S heterostructure. We also found that the photocarrier recombination of the heterostructure with the S/Se interface has a timescale up to nanoseconds, which is ∼4 times longer than that of the S/S bilayer. Such a prolonged recombination time originates from the dipole-weakened nonadiabatic coupling between occupied and unoccupied states instead of quantum coherence and the band gap effect. Overall, Janus MoSSe/MoS2 heterostructures exhibit superior photocatalytic activity, reflecting the ultrafast photocarrier separation triggered by the built-in electric field, suppressed carrier recombination, high solar-to-hydrogen conversion efficiency and the strong absorption coefficient expanding from visible-light to near-infrared-light. The above atomistic and time-domain findings reveal the intrinsic dipole as an effective freedom to regulate the nonadiabatic photocarrier dynamics in Janus-based 2D heterostructures for efficient energy harvesting and optoelectronic applications. [ABSTRACT FROM AUTHOR]

31Phosphorus magnetic resonance spectroscopy (31P‐MRS) has been shown to detect altered energetic status (e.g. the ratio of inorganic phosphate to phosphocreatine: Pi/PCr), intracellular acid–base status, and free intracellular magnesium ([Mg2+]) in dystrophic muscle compared with unaffected muscle; however, the causes of these differences are not well understood. The purposes of this study were to examine 31P‐MRS indices of energetic status and sarcolemma integrity in young mdx mice compared with wild‐type and to evaluate the effects of downhill running to induce muscle damage on 31P‐MRS indices in dystrophic muscle. In vivo 31P‐MRS spectra were acquired from the posterior hindlimb muscles in young (4–10 weeks of age) mdx (C57BL/10ScSn‐DMDmdx) and wild‐type (C57BL/10ScSnJ) mice using an 11.1‐T MR system. The flux of phosphate from PCr to ATP was estimated by 31P‐MRS saturation transfer experiments. Relative concentrations of high‐energy phosphates were measured, and intracellular pH and [Mg2+] were calculated. 1H2O‐T2 was measured using single‐voxel 1H‐MRS from the gastrocnemius and soleus using a 4.7‐T MR system. Downhill treadmill running was performed in a subset of mice. Young mdx mice were characterized by elevated 1H2O‐T2 (p < 0.01), Pi/PCr (p = 0.02), PCr to ATP flux (p = 0.04) and histological inflammatory markers (p < 0.05) and reduced (p < 0.01) [Mg2+] compared with wild‐type. Furthermore, 24 h after downhill running, an increase (p = 0.02) in Pi/PCr was observed in mdx and wild‐type mice compared with baseline, and a decrease (p < 0.001) in [Mg2+] and a lower (p = 0.048) intracellular [H+] in damaged muscle regions of mdx mice were observed, consistent with impaired sarcolemma integrity. Overall, our findings demonstrate that 31P‐MRS markers of energetic status and sarcolemma integrity are altered in young mdx compared with wild‐type mice, and these indices are exacerbated following downhill running. [ABSTRACT FROM AUTHOR]

Purpose: To determine whether deuterated water (HDO) generated from the metabolism of [2H7]glucose is a sensitive biomarker of cerebral glycolysis and oxidative flux. Methods: A bolus of [2H7]glucose was injected through the tail vein at 1.95 g/kg into Sprague‐Dawley rats. A 2H surface coil was placed on top of the head to record 2H spectra of the brain every 1.3 minutes to measure glucose uptake and metabolism to HDO, lactate, and glutamate/glutamine. A two‐point Dixon method based on a gradient‐echo sequence was used to reconstruct deuterated glucose and water (HDO) images selectively. Results: The background HDO signal could be detected and imaged before glucose injection. The 2H NMR spectra showed arrival of [2H7]glucose and its metabolism in a time‐dependent manner. A ratio of the HDO to glutamate/glutamine resonances demonstrates a pseudo–steady state following injection, in which cerebral metabolism dominates wash‐in of HDO generated by peripheral metabolism. Brain spectroscopy reveals that HDO generation is linear with lactate and glutamate/glutamine appearance in the appropriate pseudo–steady state window. Selective imaging of HDO and glucose is easily accomplished using a gradient‐echo method. Conclusion: Metabolic imaging of HDO, as a marker of glucose, lactate, and glutamate/glutamine metabolism, has been shown here for the first time. Cerebral glucose metabolism can be assessed efficiently using a standard gradient‐echo sequence that provides superior in‐plane resolution compared with CSI‐based techniques. [ABSTRACT FROM AUTHOR]

This study investigates the clinical and imaging characteristics of coronavirus disease 2019 (COVID‐19) patients with false‐negative nucleic acids. Mild‐to‐moderate COVID‐19 patients, including 19 cases of nucleic acid false‐negative patients and 31 cases of nucleic acid positive patients, were enrolled. Their epidemiological, clinical, and laboratory examination data and imaging characteristics were analyzed. Risk factors for false negatives were discussed. Compared with the nucleic acid positive group, the false‐negative group had less epidemiological exposure (52.6% vs 83.9%; P =.025), less chest discomfort (5.3% vs 32.3%; P =.035), and faster recovery (10 [8, 13] vs 15 [11, 18.5] days; P =.005). The number of involved lung lobes was (2 [1, 2.5] vs 3 [2, 4] days; P =.004), and the lung damage severity score was (3 [2.5, 4.5] vs 5 [4, 9] days; P =.007), which was lighter in the nucleic acid false‐negative group. Thus, the absence of epidemiological exposure may be a potential risk factor for false‐negative nucleic acids. The false‐negative cases of COVID‐19 are worth noting because they have a risk of viral transmission without positive test results, lighter clinical manifestations, and less history of epidemiological exposure. Highlights: The clinical and imaging features of mild‐to‐moderate COVID‐19 patients with nucleic acid false negative have certain characteristics. These patients have less clear history of epidemiological exposure, lighter clinical symptoms, lower lung damage severity score, and laboratory test results are better than those with nucleic acid positive. [ABSTRACT FROM AUTHOR]

Research has been conducted on Nb-mu-O-Nb linkages. The authors demonstrate the formation of these linkages during acid condensation of A-alpha-[SiNb (sub)3 W (sub)9 O (sub)40] (super)7- to the tri-mu-oxo-bridged structure via the use of X-ray crystallography and variable-pD solution (super)183 W and (super)29 Si NMR spectroscopy.