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Background: Fat infiltration in skeletal muscle is related to declining muscle strength, whereas excess subcutaneous fat is implicated in the development of metabolic diseases. Methods: Using multi-slice axial T2-weighted (T2w) MR images, this retrospective study characterized muscle fat infiltration (MFI) and fat distribution in the lower extremity of 107 subjects (64M/43F, age 11–79 years) with diverse ethnicities (including White, Black, Latino, and Asian subjects). Results: MRI data analysis shows that MFI, evaluated by the relative intensities of the pixel histogram profile in the calf muscle, tends to increase with both age and BMI. However, statistical significance was found only for the age correlation in women (p < 0.002), and the BMI correlation in men (p = 0.04). Sex disparities were also seen in the fat distribution, which was assessed according to subcutaneous fat thickness (SFT) and the fibula bone marrow cross-sectional area (BMA). SFT tends to decrease with age in men (p < 0.01), whereas SFT tends to increase with BMI only in women (p < 0.01). In contrast, BMA tends to increase with age in women (p < 0.01) and with BMI in men (p = 0.04). Additionally, MFI is positively correlated with BMA but not with SFT, suggesting that compromised bone structure may contribute to fat infiltration in the surrounding skeletal muscle. Conclusions: The findings of this study highlight a sex factor affecting MFI and fat distribution, which may offer valuable insights into effective strategies to prevent and treat MFI in women versus men. [ABSTRACT FROM AUTHOR]

BACKGROUND: We identified peripherally limited patients using cardiopulmonary exercise testing and measured skeletal muscle oxygen transport and utilization during invasive single leg exercise testing to identify the mechanisms of the peripheral limitation. METHODS: Forty-five patients with heart failure with preserved ejection fraction (70±7 years, 27 females) completed seated upright cardiopulmonary exercise testing and were defined as having a (1) peripheral limitation to exercise if cardiac output/oxygen consumption (VO2) was elevated (=6) or 5 to 6 with a stroke volume reserve >50% (n=31) or (2) a central limitation to exercise if cardiac output/VO2 slope was =5 or 5 to 6 with stroke volume reserve <50% (n=14). Single leg knee extension exercise was used to quantify peak leg blood flow (Doppler ultrasound), arterial-to-venous oxygen content difference (femoral venous catheter), leg VO2, and muscle oxygen diffusive conductance. In a subset of participants (n=36), phosphocreatine recovery time was measured by magnetic resonance spectroscopy to determine skeletal muscle oxidative capacity. RESULTS: Peak VO2 during cardiopulmonary exercise testing was not different between groups (central: 13.9±5.7 versus peripheral: 12.0±3.1 mL/min per kg; P=0.135); however, the peripheral group had a lower peak arterial-to-venous oxygen content difference (central: 13.5±2.0 versus peripheral: 11.1±1.6 mLO2/dL blood; P<0.001). During single leg knee extension, there was no difference in peak leg VO2 (P=0.306), but the peripherally limited group had greater blood flow/VO2 ratio (P=0.024), lower arterial-to-venous oxygen content difference (central: 12.3±2.5 versus peripheral: 10.3±2.2 mLO2/dL blood; P=0.013), and lower muscle oxygen diffusive conductance (P=0.021). A difference in magnetic resonance spectroscopy-derived phosphocreatine recovery time was not detected (P=0.199). CONCLUSIONS: Peripherally limited patients with heart failure with preserved ejection fraction identified by cardiopulmonary exercise testing have impairments in oxygen transport and utilization at the level of the skeletal muscle quantified by invasive knee extension exercise testing, which includes an increased blood flow/VO2 ratio and poor muscle diffusive capacity. [ABSTRACT FROM AUTHOR]

[Objectives] Solid Oxide Fuel Cell-Micro Gas Turbine(SOFC-MGT) hybrid power generation system will help to improve the endurance and stealth of conventionally powered submarines. So in order to analyze the performance characteristics of this system in different operating modes,[Methods] the fuel cell AIP system improved by Matlab/Simulink is combined with Micro Gas Turbine(MGT)to form a top-level cyclic hybrid power generation system in this paper. And the dual-mode is proposed according to the sailing state of the submarine. The simulation model of SOFC-MGT hybrid power generation system and exhaust treatment system is established to analyze the performance indicators under design conditions, as well as the influences of current,water-carbon ratio,CH4 flow rate,air component and other factors on the system performance.[Results] The simulation results verify the validity and feasibility of the model; in these two modes,the power generation efficiency is 59.48% and 61.61%,and the maximum power is 217 kW and 223 kW,where the system net power in the mode 2 is higher. The submarine dual-mode SOFC-MGT hybrid power system can maintain stable output power and high power generation efficiency under different working conditions of the submarine,achieving obviously better performance than other AIP systems.[Conclusions] This study results can provide theoretical support for the application of SOFC-MGT hybrid power generation system to conventional submarines.

The natural variation in estrogen secretion throughout the female menstrual cycle impacts various organs, including estrogen receptor (ER)-expressed skeletal muscle. Many women commonly experience increased fatigue or reduced energy levels in the days leading up to and during menstruation, when blood estrogen levels decline. Yet, it remains unclear whether endogenous 17β-estradiol, a major estrogen component, directly affects the energy metabolism in skeletal muscle due to the intricate and fluctuating nature of female hormones. In this study, we employed 2D 31P FID-MRSI at 7T to investigate phosphoryl metabolites in the soleus muscle of a cohort of young females (average age: 28 ± 6 years, n = 7) during the early follicular (EF) and peri-ovulation (PO) phases, when their blood 17β-estradiol levels differ significantly (EF: 28 ± 18 pg/mL vs. PO: 71 ± 30 pg/mL, p < 0.05), while the levels of other potentially interfering hormones remain relatively invariant. Our findings reveal a reduction in ATP-referenced phosphocreatine (PCr) levels in the EF phase compared to the PO phase for all participants (5.4 ± 4.3%). Furthermore, we observe a linear correlation between muscle PCr levels and blood 17β-estradiol concentrations (r = 0.64, p = 0.014). Conversely, inorganic phosphate Pi and phospholipid metabolite GPC levels remain independent of 17β-estradiol but display a high correlation between the EF and PO phases (p = 0.015 for Pi and p = 0.0008 for GPC). The robust association we have identified between ATP-referenced PCr and 17β-estradiol suggests that 17β-estradiol plays a modulatory role in the energy metabolism of skeletal muscle. [ABSTRACT FROM AUTHOR]

Over the past four decades, ATP, the obligatory energy molecule for keeping all cells alive and functioning, has been thought to contribute only one set of signals in brain 31P MR spectra. Here we report for the first time the observation of two separate β-ATP peaks in brain spectra acquired from patients with myelin oligodendrocyte glycoprotein antibody-associated disorders (MOGADs) using 3D MRSI at 7 T. In voxel spectra with β-ATP line splitting, these two peaks are separated by 0.46 ± 0.18 ppm (n = 6). Spectral lineshape analysis indicates that the upper field β-ATP peak is smaller in relative intensity (24 ± 11% versus 76 ± 11%), and narrower in linewidth (56.8 ± 10.3 versus 41.2 ± 10.3 Hz) than the downfield one. Data analysis also reveals a similar line splitting for the intracellular inorganic phosphate (Pi) signal, which is characterized by two components with a smaller separation (0.16 ± 0.09 ppm) and an intensity ratio (26 ± 7%:74 ± 7%) comparable to that of β-ATP. While the major components of Pi and β-ATP correspond to a neutral intracellular pH (6.99 ± 0.01) and a free Mg2+ level (0.18 ± 0.02 mM, by Iotti's conversion formula) as found in healthy subjects, their minor counterparts relate to a slightly acidic pH (6.86 ± 0.07) and a 50% lower [Mg2+] (0.09 ± 0.02 mM), respectively. Data correlation between β-ATP and Pi signals appears to suggest an association between an increased [H+] and a reduced [Mg2+] in MOGAD patients. [ABSTRACT FROM AUTHOR]

A new ligand, 8[O.sub.2] 1,4,7,10-tetraazadodecane tetraacetic acid (DOTAM), is synthesized and its lanthanide complexes are examined as potential chemical exchange saturation transfer (CEST) agents. The analysis reveals that the increasing ionic radius of the lanthanide ion leads to an increase in the extent of the distortion, thereby leading to a complete loss of symmetry in the complex.

Both of the two new 1,7-disubstituted-1,4,7,10-tetraazacyclododecane ligands DO2P and DO2PME form 1:1 M:L complexes with lanthanide, alkaline, earth metal, Mn(2+) and Zn(2+) ions. According to 17O shifts, 1H relaxation rates and 31P nuclear magnetic resonance data, the nonprotonated Ln(3+) complexes are in an 'in-cage' position in LnHDO2P and are octacoordinate, with six ligand donors and two inner-sphere coordinated water molecules. In the diprotonated complexes, however, the Ln(3+) cation shifts to an 'out-of-cage' position.

Sodium pump research using excess-salt-free formulations of the 23Na shift reagent TmDOTP5 (DOTP8- = 1,4,7,10-tetraazacyclododecane-1,4,7,11-tetrakis(methylene-phosphonate)) and 0.32 molar solutions of (N-methylglucamine H4)HTmDOTP and Co(en)3]4/3HTmDOTP shows that ion-pairing interactions between Co(en)3(super 3+) and TmDOTP5- inhibit 23Na activity.

Guanosine diphosphate mannose (GDP‐Man) is the donor substrate required for mannosylation in the synthesis of glycoproteins, glycolipids and the newly discovered glycoRNA. Normal GDP‐Man biosynthesis plays a crucial role in support of a variety of cellular functions, including cell recognition, cell communication and immune responses against viruses. Here, we report the detection of GDP‐Man in human brain for the first time, using 31P MRS at 7 T. The presence of GDP‐Man is evidenced by the detection of a weak 31P doublet at −10.7 ppm that can be assigned to the phosphomannosyl group (Pβ) of the GDP‐Man molecule. This weak but well‐resolved signal lies 0.9 ppm upfield of UDP(G) Pβ‐multiplet from a mixture of UDP‐Glc, UDP‐Gal, UDP‐GlcNAc and UDP‐GalNAc. In reference to ATP (2.8 mM), the concentration of GDP‐Man in human brain was estimated to be 0.02 ± 0.01 mM, about 15‐fold lower than the total concentration of UDP(G) (0.30 ± 0.04, N = 17) and consistent with previous reports of UDP‐Man in cells and brain tissue extracts measured by high‐performance liquid chromatography. The reproducibility of the measured GDP‐Man between test and 2‐week retest was 21% ± 15% compared with 5% ± 4% for UDP(G) (N = 7). The measured concentrations of GDP‐Man and UDP(G) are linearly correlated ([UDP(G)] = 4.3 [GDP‐Man] + 0.02, with R = 0.66 and p = 0.0043), likely reflecting the effect of shared sugar precursors, which may vary among individuals in response to variation in nutritional intake and consumption. Given that GDP‐Man has another set of doublet (Pα) at −8.3 ppm that overlaps with NAD(H) and UDP(G)‐Pα signals, the amount of GDP‐Man could potentially interfere with the deconvolution of these mixed signals in composition analysis. Importantly, this new finding may be useful in advancing our understanding of glycosylation and its role in the development of cancer, as well as infectious and neurodegenerative diseases. [ABSTRACT FROM AUTHOR]

Nucleotide sugars are required for the synthesis of glycoproteins and glycolipids, which play crucial roles in many cellular functions such as cell communication and immune responses. Uridine diphosphate‐glucose (UDP‐Glc) was previously believed to be the only nucleotide sugar detectable in brain by 31P‐MRS. Using spectra of high SNR and high resolution acquired at 7 T, we showed that multiple nucleotide sugars are coexistent in brain and can be measured simultaneously. In addition to UDP‐Glc, these also include UDP‐galactose (UDP‐Gal), ‐N‐acetyl‐glucosamine (UDP‐GlcNAc) and ‐N‐acetyl‐galactosamine (UDP‐GalNAc), collectively denoted as UDP(G). Coexistence of these UDP(G) species is evident from a quartet‐like multiplet at −9.8 ppm (M−9.8), which is a common feature seen across a wide age range (24–64 years). Lineshape fitting of M−9.8 allows an evaluation of all four UDP(G) components, which further aids in analysis of a mixed signal at −8.2 ppm (M−8.2) for deconvolution of NAD+ and NADH. For a group of seven young healthy volunteers, the concentrations of UDP(G) species were 0.04 ± 0.01 mM for UDP‐Gal, 0.07 ± 0.03 mM for UDP‐Glc, 0.06 ± 0.02 mM for UDP‐GalNAc and 0.08 ± 0.03 mM for UDP‐GlcNA, in reference to ATP (2.8 mM). The combined concentration of all UDP(G) species (average 0.26 ± 0.06 mM) was similar to the pooled concentration of NAD+ and NADH (average 0.27 ± 0.06 mM, with a NAD+/NADH ratio of 6.7 ± 2.1), but slightly lower than previously found in an older cohort (0.31 mM). The in vivo NMR analysis of UDP‐sugar composition is consistent with those from tissue extracts by other modalities in the literature. Given that glycosylation is dependent on the availability of nucleotide sugars, assaying multiple nucleotide sugars may provide valuable insights into potential aberrant glycosylation, which has been implicated in certain diseases such as cancer and Alzheimer's disease. [ABSTRACT FROM AUTHOR]