Association between somatosensory sensitivity and regional gray matter volume in healthy young volunteers: a voxel-based morphometry study.

Two-point discrimination (2PD) test reflects somatosensory spatial discrimination ability, but evidence on the relationship between 2PD and cortical gray matter (GM) volume is limited. This study aimed to analyze the relationship between cortical GM volume and 2PD threshold in young healthy individuals and to clarify the characteristics of brain structure reflecting the individual differences in somatosensory function. 2PD was measured in 42 healthy (20 females) volunteers aged 20-32 years using a custom-made test system that can be controlled by a personal computer. The 2PD of the right index finger measured with this device has been confirmed to show good reproducibility. T1-weighted images were acquired using a 3-T magnetic resonance imaging scanner for voxel-based morphometry analysis. The mean 2PD threshold was 2.58 ± 0.54 mm. Whole-brain multiple regression analysis of the relationship between 2PD and GM volume showed that a lower 2PD threshold (i.e. better somatosensory function) significantly correlated with decreased GM volume from the middle temporal gyrus to the inferior parietal lobule (IPL) in the contralateral hemisphere. In conclusion, a lower GM volume in the middle temporal gyrus and IPL correlates with better somatosensory function. Thus, cortical GM volume may be a biomarker of somatosensory function.

Cortical signature related to psychometric properties of pain vigilance in healthy individuals: A voxel-based morphometric study.

The Pain Vigilance and Awareness Questionnaire (PVAQ) is a questionnaire for non-clinical and clinical cases of patients, such as those suffering from chronic pain. Moreover, it is used for evaluation of two aspects of habitual attention to pain: attention to pain and attention to changes in pain. As the PVAQ assesses two different aspects of attention function, different neural basis may present. However, it remains unclear which brain regions are involved. Here, we performed voxel-based morphometry (VBM) in 30 healthy participants to determine the regional morphology associated with the two attention states. Multiple regression analysis was conducted between each score and the regional grey matter (GM) volume, which revealed that a decreased GM volume in the left anterior insular cortex (AIC) was associated with a higher attention to pain score. In contrast, no brain region was correlated with the attention to changes in pain score. Our VBM results demonstrate that attention to pain scores assessed by PVAQ are associated with morphological features of the left AIC. Moreover, they may contribute to the elucidation of the complex psychological and neurophysiological characteristics of patients with chronic pain.

Gray Matter Volume Variability in Young Healthy Adults: Influence of Gender Difference and Brain-Derived Neurotrophic Factor Genotype.

Although brain gray matter (GM) plastically changes during short-term training, it is still unclear whether brain structures are stable for short periods (several months). Therefore, this study aimed to re-test the short-term variability of GM volumes and to clarify the effect of factors (gender and BDNF-genotype) expected to contribute to such variability. The subjects comprised 41 young healthy adults. T1-weighted images were acquired twice with an interval of approximately 4 months using a 3 T-MRI scanner. Voxel-based morphometry (VBM) was used to calculate GM volumes in 47 regions. The intraclass correlation coefficient (ICC) and Test-retest variability (%TRV) were used as indices of variability. As a result, the ICCs in 43 regions were excellent (ICC > 0.90) and those in 3 regions were good (ICC > 0.80), whereas the ICC in the thalamus was moderate (ICC = 0.694). Women had a higher %TRV than men in 5 regions, and %TRV of the Val66Val group was higher than that of the Met carrier group in 2 regions. Moreover, the Female-Val66Val group had a higher %TRV than the Male-Met carrier group in 3 regions. These results indicate that although the short-term variability of GM volumes is small, it is affected by within-subject factors.

Induction of Relaxation by Autonomous Sensory Meridian Response.

Background: Autonomous sensory meridian response (ASMR) is used by young people to induce relaxation and sleep and to reduce stress and anxiety; it comprises somatosensation caused by audiovisual stimuli (triggers) that lead to positive emotions. Auditory stimuli play the most important role among the triggers involved in ASMR and have been reported to be more triggering than visual stimuli. On the other hand, classical music is also known to have a relaxing effect. This is the first study to clarify the difference in brain activation associated with relaxation effects between ASMR and classical music by limiting ASMR to auditory stimulation alone. Methods: Thirty healthy subjects, all over 20 years of age, underwent fMRI while listening to ASMR and classical music. We compared the differences in brain activation associated with classical music and ASMR stimulation. After the experiment, the subjects were administered a questionnaire on somatosensation and moods. After the experiment, the participants were asked whether they experienced ASMR somatosensation or frisson. They were also asked to rate the intensity of two moods during stimulation: "comfortable mood," and "tingling mood". Result: The results of the questionnaire showed that none of the participants experienced any ASMR somatosensation or frisson. Further, there was no significant difference in the ratings given to comfort mood, but there was a significant difference in those given to tingling mood. In terms of brain function, classical music and ASMR showed significant activation in common areas, while ASMR showed activation in more areas, with the medial prefrontal cortex being the main area of activation during ASMR. Conclusion: Both classical music and the ASMR auditory stimulus produced a pleasant and relaxed state, and ASMR involved more complex brain functions than classical music, especially the activation of the medial prefrontal cortex. Although ASMR was limited to auditory stimulation, the effects were similar to those of listening to classical music, suggesting that ASMR stimulation can produce a pleasant state of relaxation even if it is limited to the auditory component, without the somatic sensation of tingling. ASMR stimulation is easy to use, and appropriate for wellness purposes and a wide range of people.

Contribution of the brain-derived neurotrophic factor and neurometabolites to the motor performance.

Individual motor performance ability is affected by various factors. Although the key factor has not yet completely been elucidated, the brain-derived neurotrophic factor (BDNF) genotype as well as neurometabolites may become contibuting factors depending on the learning stage. We investigated the effects of the Met allele of the BDNF gene and those of the neurometabolites on visuomotor learning. In total, 43 healthy participants performed a visuomotor learning task consisting of 10 blocks using the right index finger (Val66Val, n = 15; Val66Met, n = 15; and Met66Met, n = 13). Glutamate plus glutamine (Glx) concentrations in the primary motor cortex, primary somatosensory cortex (S1), and cerebellum were evaluated using 3-T magnetic resonance spectroscopy in 19 participants who participated in the visuomotor learning task. For the learning stage, the task error (i.e., learning ability) was significantly smaller in the Met66Met group compared with that observed in the remaining groups, irrespective of the learning stage (all p values < 0.003). A significant difference was observed between the Val66Val and Met66Met groups in the learning slope (i.e., learning speed) in the early learning stage (p = 0.048) but not in the late learning stage (all p values> 0.54). Moreover, positive correlations were detected between the learning slope and Glx concentrations in S1 only in the early learning stage (r = 0.579, p = 0.009). The BDNF genotype and Glx concentrations in S1 partially contribute to interindividual variability on learning speed in the early learning stage.

Influence of Brain-Derived Neurotrophic Factor Genotype on Short-Latency Afferent Inhibition and Motor Cortex Metabolites.

The Met allele of the brain-derived neurotrophic factor (BDNF) gene confers reduced cortical BDNF expression and associated neurobehavioral changes. BDNF signaling influences the survival, development, and synaptic function of cortical networks. Here, we compared gamma-aminobutyric acid (GABA)ergic network activity in the human primary motor cortex (M1) between the Met (Val/Met and Met/Met) and non-Met (Val/Val) genotype groups. Short- and long-interval intracortical inhibition, short-latency afferent inhibition (SAI), and long-latency afferent inhibition were measured using transcranial magnetic stimulation (TMS) as indices of GABAergic activity. Furthermore, the considerable inter-individual variability in inhibitory network activity typically measured by TMS may be affected not only by GABA but also by other pathways, including glutamatergic and cholinergic activities; therefore, we used 3-T magnetic resonance spectroscopy (MRS) to measure the dynamics of glutamate plus glutamine (Glx) and choline concentrations in the left M1, left somatosensory cortex, and right cerebellum. All inhibitory TMS conditions produced significantly smaller motor-evoked potentials than single-pulses. SAI was significantly stronger in the Met group than in the Val/Val group. Only the M1 Glx concentration was significantly lower in the Met group, while the BDNF genotype did not affect choline concentration in any region. Further, a positive correlation was observed between SAI and Glx concentrations only in M1. Our findings provide evidence that the BDNF genotype regulates both the inhibitory and excitatory circuits in human M1. In addition, lower Glx concentration in the M1 of Met carriers may alter specific inhibitory network on M1, thereby influencing the cortical signal processing required for neurobehavioral functions.

GlyCEST: Magnetic Resonance Imaging of Glycine-Distribution in the Normal Murine Brain and Alterations in 5xFAD Mice.

The glycine level in the brain is known to be altered in neuropsychiatric disorders, such as schizophrenia and Alzheimer's disease (AD). Several studies have reported the in vivo measurement of glycine concentrations in the brain using proton magnetic resonance spectroscopy (1H-MRS), but 1H-MRS is not capable of imaging the distribution of glycine concentration with high spatial resolution. Chemical exchange saturation transfer magnetic resonance imaging (CEST-MRI) is a new technology that can detect specific molecules, including amino acids, in tissues. To validate the measurements of glycine concentrations in living tissues using CEST from glycine to water (GlyCEST), we extracted the brain tissues from mice and performed biochemical tests. In wild-type C57BL/6 mice, GlyCEST effects were found to be higher in the thalamus than in the cerebral cortex (P < 0.0001, paired t-test), and this result was in good agreement with the biochemical results. In 5xFAD mice, an animal model of AD, GlyCEST measurements demonstrated that glycine concentrations in the cerebral cortex (P < 0.05, unpaired t-test) and thalamus (P < 0.0001, unpaired t-test), but not in the hippocampus, were decreased compared to those in wild-type mice. These findings suggest that we have successfully applied the CEST-MRI technique to map the distribution of glycine concentrations in the murine brain. The present method also captured the changes in cerebral glycine concentrations in mice with AD. Imaging the distribution of glycine concentrations in the brain can be useful in investigating and elucidating the pathological mechanisms of neuropsychiatric disorders.

Electrochemical Detection of Sesamol Dimer and its Application to Measurement of Radicals.

In this paper we propose a novel measurement for NO and ·OH by electrochemical detection using sesamol. Standard samples of the sesamol monomer and dimer were subjected to differential pulse voltammetry, resulting in their peaks being clearly separated and detected. Based on the oxidative dimerization of sesamol, the current simple, sensitive and selective method was successfully applied to preliminary measurements for NO and ·OH, respectively.

Longitudinal GluCEST MRI Changes and Cerebral Blood Flow in 5xFAD Mice.

Many of the focal neurological symptoms associated with Alzheimer's disease (AD) are due to synaptic loss. Glutamate chemical exchange saturation transfer (GluCEST) magnetic resonance imaging (MRI) is a candidate method to assess synaptic dysfunction. We assessed chronological changes in GluCEST in a 5xFAD mouse model of AD, comparing Glucest effects and regional cerebral blood flow (CBF). GluCEST effects and CBF in 5xFAD mice aged 1-15 months and their littermates (WT) were measured. Neurite orientation dispersion and density imaging (NODDI) MRI reflecting dendritic/axonal density was also measured and compared with GluCEST in 7-month-old mice. While regional CBF's decrease began at 7 months, GluCEST-reduction effects preceded hypoperfusion of the temporal cortex and hippocampus. While longitudinal 5xFAD mouse measurements revealed a correlation between the regional GluCEST effects and CBF, a generalized linear mixed model revealed statistically different correlations in cortical and basal brain regions. Further, NODDI-derived neurite density correlated with GluCEST effects in the parietal cortex, but not in the hippocampus, thereby revealing regional differences in pathophysiological mechanisms. Finally, GluCEST's effects correlated with regional synaptophysin. These results demonstrate that GluCEST can reflect subtle synaptic changes and may be a potential imaging method for AD diagnosis as well as serve as a biomarker of AD progression.

Binding Assays Using a Benzofurazan-Labeled Fluorescent Probe for Estrogen Receptor-Ligand Interactions.

Binding assays are widely used to study the estrogenic activity of compounds targeting the estrogen receptor (ER). The fluorescence properties of benzofurazan (BD), an environmentally sensitive fluorophore, are affected by solvent polarity. In this study, we synthesized BD-labeled estradiol (E2) derivatives hoping to develop a fluorescent ligand to be used in ER binding assays, without the separation of free- from bound-ligand. Three fluorescent ligands with a BD skeleton were obtained and their fluorescence properties were investigated. Analysis of the fluorescent ligands and human recombinant ERα (hr-ERα) interactions revealed that the fluorescence intensity increased in hydrophobic environments, such as the receptor-binding site. In saturation binding assays, ABD-E2 derivative 2c showed positive cooperative binding, and its dissociation constant (Kd) and Hill coefficient were 23.4 nM and 1.34, respectively. The estrogenic compounds affinity, assessed by competitive binding assays was well correlated with the results obtained by conventional studies, using the fluorescence polarization method. Overall, the developed assay using BD-labeled ligands was a simple, rapid, and reliable method for the evaluation of ER binding affinity.

Visualizing the Distribution of Matrix Metalloproteinases in Ischemic Brain Using In Vivo 19F-Magnetic Resonance Spectroscopic Imaging.

Matrix metalloproteinases (MMPs) damage the neurovascular unit, promote the blood-brain barrier (BBB) disruption following ischemic stroke, and play essential roles in hemorrhagic transformation (HT), which is one of the most severe side effects of thrombolytic therapy. However, no biomarkers have presently been identified that can be used to track changes in the distribution of MMPs in the brain. Here, we developed a new 19F-molecular ligand, TGF-019, for visualizing the distribution of MMPs in vivo using 19F-magnetic resonance spectroscopic imaging (19F-MRSI). We demonstrated TGF-019 has sufficient sensitivity for the specific MMPs suspected in evoking HT during ischemic stroke, i.e., MMP2, MMP9, and MMP3. We then utilized it to assess those MMPs at 22 to 24 hours after experimental focal cerebral ischemia on MMP2-null mice, as well as wild-type mice with and without the systemic administration of the recombinant tissue plasminogen activator (rt-PA). The 19F-MRSI of TGN-019-administered mice showed high signal intensity within ischemic lesions that correlated with total MMP2 and MMP9 activity, which was confirmed by zymographic analysis of ischemic tissues. Based on the results of this study, 19F-MRSI following TGN-019 administration can be used to assess potential therapeutic strategies for ischemic stroke.

Proton Affinitive Derivatization for Highly Sensitive Determination of Testosterone and Dihydrotestosterone in Saliva Samples by LC-ESI-MS/MS.

In this study, proton affinitive derivatization using picolinic acid and its analogs (3- and 6-methylpicolinic acid and 5-butylpicolinic acid) with proton affinitive moieties was performed for the highly sensitive determination of testosterone (T) and 5α-dihydrotestosterone (DHT) in saliva by LC-ESI-MS/MS. T and DHT were converted to their corresponding picolinate esters and their chromatographic behavior was investigated with a reversed phase column. The picolinate ester of each steroid exhibited a clear single peak and elution occurred in the following order: picolinate, 3/6-methylpicolinate, and 5-butylpicolinate. Estimation and understanding of the separation and retention time of each picolinate ester was made simple using the develop method. Although the peaks of picolinate and 3/6-methylpicolinate esters were suppressed by interference from the saliva background (matrix effect), the 5-butylpicolinate esters were only marginally affected.

Magnetic Resonance Imaging of Neurotransmitter-Related Molecules.

Molecular imaging implies the method capable of pictorially displaying distribution of target molecules and their relative concentration in space. In clinical medicine, where non-invasiveness is mandatory, diagnostic molecular imaging has been considered virtually identical to positron emission tomography (PET). However, there is another powerful, apparently underutilized molecular imaging, namely, proton magnetic resonance spectroscopic imaging (1H-MRSI). The technique can detect target molecules endogenous in brain in virtue of their own specific resonance frequencies (chemical shift) and can create quantitative images of each molecule. 1H-MRSI is conventionally utilized for imaging relatively easily detectable molecules such as N-acetyl-aspartate or lactate. More recently, however, the method is extended into imaging of more challenging molecules such as glutamate or γ-aminobutyric acid (GABA). In this small review, we summarize basic concept of 1H-MRSI and introduce an advanced technique, i.e. chemical exchange saturation transfer magnetic resonance imaging (CEST MRI), which made realistic glutamate imaging in vivo possible.

Recent development of chemical derivatization in LC-MS for biomedical approaches.

LC-MS/MS is currently the most powerful system in biomedical analysis. At the same time, chemical derivatization is a useful technique to enhance the detection sensitivity of nonionizable or poorly ionizable molecules in LC-MS/MS. Derivatization improves the ionization efficiency, the chromatographic separation and/or the chemical stability. This article presents an overview of the recent development of chemical derivatization reagents and reactions for the quantitative analysis of xenobiotic and endogenous molecules such as pharmaceuticals, amino acids, peptides, proteins, steroids, biomarkers and industrial products by LC-MS.

Development of a highly sensitive chemiluminescent assay for hydrogen peroxide under neutral conditions using acridinium ester and its application to an enzyme immunoassay.

We developed a highly sensitive chemiluminescent (CL) assay for hydrogen peroxide using 10-methyl-9-(phenoxycarbonyl) acridinium fluorosulfonate (PMAC) that produced chemiluminescence under neutral conditions and applied it to an enzyme immunoassay (EIA). One picomole of hydrogen peroxide could be detected using the optimized PMAC-CL method and 6.2 × 10(-20) mol ß-D-galactosidase (ß-gal) could be detected by combining an indoxyl derivative substrate and the proposed PMAC-CL method. This highly sensitive CL ß-gal assay was applied to an EIA for thyroid-stimulating hormone (TSH) using ß-gal as a label enzyme; 0.02-100.0 µU/mL TSH in human serum could be assayed directly and with high reproducibility.

Accuracy of lung nodule density on HRCT: analysis by PSF-based image simulation.

A computed tomography (CT) image simulation technique based on the point spread function (PSF) was applied to analyze the accuracy of CT-based clinical evaluations of lung nodule density. The PSF of the CT system was measured and used to perform the lung nodule image simulation. Then, the simulated image was resampled at intervals equal to the pixel size and the slice interval found in clinical high-resolution CT (HRCT) images. On those images, the nodule density was measured by placing a region of interest (ROI) commonly used for routine clinical practice, and comparing the measured value with the true value (a known density of object function used in the image simulation). It was quantitatively determined that the measured nodule density depended on the nodule diameter and the image reconstruction parameters (kernel and slice thickness). In addition, the measured density fluctuated, depending on the offset between the nodule center and the image voxel center. This fluctuation was reduced by decreasing the slice interval (i.e., with the use of overlapping reconstruction), leading to a stable density evaluation. Our proposed method of PSF-based image simulation accompanied with resampling enables a quantitative analysis of the accuracy of CT-based evaluations of lung nodule density. These results could potentially reveal clinical misreadings in diagnosis, and lead to more accurate and precise density evaluations. They would also be of value for determining the optimum scan and reconstruction parameters, such as image reconstruction kernels and slice thicknesses/intervals.

Development of RNA aptamer and its ligand binding assay on microchip electrophoresis.

Microchip electrophoresis (ME) coupled with fluorescence detection was used to estimate the binding activity of aptamer in each systematic evolution of ligands by exponential enrichment (SELEX) round for a target molecule. This approach is a non-radioisotopic, rapid and simple platform, and electrophoretic separation appears to be an effective technique for aptamers of oligonucleotide molecules. We tried to obtain gonadotropin-specific RNA aptamer by the above approach. As a result, the peaks of aptamers based on the conformational differences between them were separated and detected on the electropherograms. Moreover, the intensity of peak of unbound aptamer was decreased with progression through the SELEX rounds, suggesting that RNA aptamer with high affinity was obtained by the proposed method.

New fluorimetric assay of horseradish peroxidase using sesamol as substrate and its application to EIA.

Horseradish peroxidase (HRP) is generally used as a label enzyme in enzyme immunoassay (EIA). The procedure used for HRP detection in EIA is critical for sensitivity and precision. This paper describes a novel fluorimetric assay for horseradish peroxidase (HRP) using sesamol as substrate. The principle of the assay is as follow: sesamol (3,4-methylenedioxy phenol) is reacted enzymatically in the presence of hydrogen peroxide to produce dimeric sesamol. The dimer is fluorescent and can be detected sensitively at ex. 347 nm, em. 427 nm. The measurable range of HRP was 1.0×10-18 to 1.0×10-15 mol/assay, with a detection limit of 1.0×10-18 mol/assay. The coefficient of variation (CV, n=8) was examined at each point on the standard curve, with a mean CV percentage of 3.8%. This assay system was applied to thyroid stimulating hormone (TSH) EIA using HRP as the label enzyme.