Metabolite changes with age measured by proton magnetic resonance spectroscopy in normal subjects

Abstract  To determine whether there are metabolite changes in the left medial temporal and frontal lobes with aging, we performed proton magnetic resonance spectroscopy in 36 normal subjects. The N-acetylaspartate/creatine-phosphocreatine ratio in the medial temporal lobe tended to be decreased in subjects over 60 years of age. The ratio decrease in the frontal lobe related to aging was lower than that in the medial temporal lobe. There were no significant differences in the metabolite ratios between males and females. These findings suggest that structures in the medial temporal lobe may be more susceptible to neuronal dysfunction associated with aging than those in the frontal lobe.     

Electrochemical and Raman spectroscopic studies of the effect of lanthanide ions on the activity of mitochondrial malate dehydrogenase

Chronoamperometry based on the ‘diffusion’ layer concept of the convective system was used to assay the activity of mitochondrial malate dehydrogenase (MDH). When the enzyme-catalysed reaction was initiated by adding the enzyme MDH into a well-stirred nicotinamide adenine dinucleotide (NADH, coenzyme) solution, the enzyme activity could be indicated by the continuous in-situ decrease in the limiting steady-state oxidation current of NADH. The effects of some lanthanide ions on the MDH activity were monitored. The La³⁺, Ce³⁺ and Eu³⁺ ions could activate markedly the enzyme MDH as the concentrations were lower. The activation mechanism would be that the lanthanide ions could interrupt the binding of NAD⁺ to MDH by combining preferentially to NAD⁺. This mechanism was proposed on the basis of voltammetric and Raman spectroscopic studies.     

Electrochemical impedimetry of electrodeposited poly(propylene imine) dendrimer monolayer

Voltammetric and electrochemical impedance spectroscopic (EIS) studies of generation one poly(propylene imine) (G1 PPI) dendrimer as an electroactive and catalytic nanomaterials both in solution and as an electrode modifier based on a simple one step electrodeposition method is presented. The G1 PPI exhibited a reversible one electron redox behaviour at E^0′ ca 210 mV in phosphate buffer pH 7.2 with diffusion coefficient and Warburg coefficient of 7.5 × 10⁻¹⁰ cm² s⁻¹ and 8.87 × 10⁻⁴ Ω s^−1/2 respectively. Cyclic voltammetric electrodeposition of a monolayer of G1 PPI on glassy carbon electrode was carried out between −100 mV and 1100 mV for 10 cycles. The nanoelectrode was electroactive in PBS at E^0′ ca 220 mV. Kinetic profiles such as time constant (4.64 × 10⁻⁵ s rad⁻¹), exchange current (1.55 × 10⁻⁴ A) and heterogeneous rate constant (4.52 × 10⁻³ cm s⁻¹) obtained from EIS showed that the dendrimer layer catalysed the redox reaction of Fe^2+/3+ in [Fe(CN)₆]^3−/4− redox probe.     

全面性发作癫(癎)患者记忆功能与海马质子磁共振波谱改变的相关性分析

目的 探讨原发性癫(癎)全面性发作患者记忆功能损害的特征以及磁共振波谱(magnetic resonance spectroscopy,MRS)检查与记忆功能的关系.方法 对45例癫(癎)全面性发作的患者和20例健康对照组进行临床记忆量表的测量,双侧海马行1H-MRS检测及体积测量,比较2组间记忆量表的各项量表分、记忆商和1H-MRS的各项指标,并对记忆量表的结果与海马1H-MRS结果进行相关分析.结果 癫(癎)组包括服药组(指向记忆15.68±4.79,联想学习18.70±5.84,图像自由回忆13.19±6.22,人像特点回忆12.02±4.31)与未服药组(指向记忆17.19±5.86,联想学习20.00±6.77,图像自由回忆18.44±6.62,人像特点回忆13.19±6.62)以及不同发作频率组的多数项量表分及记忆商(服药组74.64 ±18.52,未服药组79.07±20.20,≥3次/月组78.10±21.22,<3次/月组73.81±17.72)显著低于对照组(t=4.794-10.224,P<0.01);且癫(癎)服药组和发作频率≥3次/月组的各项量表分及记忆商显著低于服药组和发作频率<3次/月组(t=3.267～6.537,P<0.01).癫(癎)组海马体积(左侧2.45±0.25,右侧2.56±0.31)、N-乙酰天门冬氨酸(NAA,左侧12.93±1.73,右侧11.88±1.69)及NAA/胆碱(Cho)+肌酸(Cr,左侧0.48±0.08,右侧0.39±0.07)显著低于对照组,Cho(左侧15.02±0.86,右侧14.94±0.96)、Cr(左侧11.86±0.71,右侧10.71±0.42)显著高于对照组(t=4.103～5.768,P<0.01);癫(癎)组的各项量表分及记忆商与左右侧NAA浓度、NAA/Cho+Cr均呈明显正相关(r=O.489～0.727,P相似文献   

Intermittent theta-burst stimulation moderates interaction between increment of N-Acetyl-Aspartate in anterior cingulate and improvement of unipolar depression

BackgroundIntermittent theta-burst stimulation (iTBS), a novel repetitive transcranial magnetic stimulation (rTMS) technique, appears to have antidepressant effects when applied over left dorsolateral prefrontal cortex (DLPFC). However, its underlying neurobiological mechanisms are unclear. Proton magnetic resonance spectroscopy (¹H-MRS) provides in vivo measurements of cerebral metabolites altered in major depressive disorder (MDD) like N-acetyl-aspartate (NAA) and choline-containing compounds (Cho). We used MRS to analyse effects of iTBS on the associations between the shifts in the NAA and Cho levels during therapy and MDD improvement.MethodsIn-patients with unipolar MDD (N = 57), in addition to treatment as usual, were randomized to receive 20 iTBS or sham stimulations applied over left DLPFC over four weeks. Single-voxel ¹H-MRS of the anterior cingulate cortex (ACC) was performed at baseline and follow-up. Increments of concentrations, as well as MDD improvement, were defined as endpoints. We tested a moderated mediation model of effects using the PROCESS macro (an observed variable ordinary least squares and logistic regression path analysis modeling tool) for SPSS.ResultsImprovement of depressive symptoms was significantly associated with decrease of Cho/NAA ratio, mediated by NAA. iTBS had a significant moderating effect enhancing the relationship between NAA change and depression improvement.ConclusionsOur findings suggest a potential neurochemical pathway and mechanisms of antidepressant action of iTBS, which may moderate the improvement of metabolic markers of neuronal viability. iTBS might increase neuroplasticity, thus facilitating normalization of neuronal circuit function.     

Cellular mechanisms of hereditary photoreceptor degeneration – Focus on cGMP

The cellular mechanisms underlying hereditary photoreceptor degeneration are still poorly understood, a problem that is exacerbated by the enormous genetic heterogeneity of this disease group. However, the last decade has yielded a wealth of new knowledge on degenerative pathways and their diversity. Notably, a central role of cGMP-signalling has surfaced for photoreceptor cell death triggered by a subset of disease-causing mutations.In this review, we examine key aspects relevant for photoreceptor degeneration of hereditary origin. The topics covered include energy metabolism, epigenetics, protein quality control, as well as cGMP- and Ca²⁺-signalling, and how the related molecular and metabolic processes may trigger photoreceptor demise. We compare and integrate evidence on different cell death mechanisms that have been associated with photoreceptor degeneration, including apoptosis, necrosis, necroptosis, and PARthanatos. A special focus is then put on the mechanisms of cGMP-dependent cell death and how exceedingly high photoreceptor cGMP levels may cause activation of Ca²⁺-dependent calpain-type proteases, histone deacetylases and poly-ADP-ribose polymerase. An evaluation of the available literature reveals that a large group of patients suffering from hereditary photoreceptor degeneration carry mutations that are likely to trigger cGMP-dependent cell death, making this pathway a prime target for future therapy development.Finally, an outlook is given into technological and methodological developments that will with time likely contribute to a comprehensive overview over the entire metabolic complexity of photoreceptor cell death. Building on such developments, new imaging technology and novel biomarkers may be used to develop clinical test strategies, that fully consider the genetic heterogeneity of hereditary retinal degenerations, in order to facilitate clinical testing of novel treatment approaches.     

The Effect of Microstructural Changes on Mechanical and Electrochemical Corrosion Properties of Duplex Stainless Steel Aged for Short Periods

This work reports the effects of Microstructural changes due to the secondary phases, in particular sigma (σ), on the mechanical properties and electrochemical behavior of thermally aged duplex stainless steel (DSS). Structural, morphological, mechanical, and electrochemical characterizations were performed. Sigma phase content increased with increasing aging treatment time. It had a net-like shape, as observed by electron backscatter diffractometry (EBSD). Its presence directly damaged mechanical properties. The corrosion assessment included electrochemical impedance spectroscopy (EIS) in 1 M NaCl solution at temperatures of 25, 40, and 65 °C. EIS results demonstrate that an increase in the σ phase content decreased the corrosion resistance (21.1–0.8, 3.5–0.3, and 3.1–0.2 kΩ cm² at 25, 40, and 60 °C, respectively).     

Methodological considerations for near-infrared spectroscopy to assess mitochondrial capacity after spinal cord injury

Background: Skeletal muscle mitochondrial activity is reduced by?～?50–60% after SCI, resulting in impaired energy expenditure, glucose utilization and insulin sensitivity. Near infra-red spectroscopy (NIRS) is a non-invasive tool that can be used to assess mitochondrial capacity.

Objectives: (1) Highlight methodological limitations impacting data acquisition and analysis such as subcutaneous adipose tissue (SAT) thickness, movement artifacts, inadequate muscle stimulation, light interference, and ischemic discomfort. (2) Provide technical considerations to improve data acquisition and analysis. This may serve as guidance to other researchers and clinicians using NIRS.

Study Design: cross-sectional observational design.

Settings: Clinical research medical center.

Participants: Sixteen men with 1?>?year post motor complete SCI.

Methods: NIRS signals were obtained from right vastus lateralis muscle utilizing a portable system. Signals were fit to a mono-exponential curve.

Outcome Measures: Rate constant and r ² values for the fit curve, indirectly measures mitochondrial capacity.

Results: Only four participants produced data with accepted rate constants of 0.002–0.013?s^?1 and r ² of 0.71–0.87. Applications of studentized residuals ≥2.5 resulted in sparing data from another four participants with rate constants of 0.010–0.018?s^?1and r ² values ranging from 0.86–0.99.

Conclusions: Several limitations may challenge the use of NIRS to assess mitochondrial capacity after SCI. Acknowledging these limitations and applying additional data processing techniques may overcome the discussed limitations and facilitate data sparing.