In vivo proton magnetic resonance spectroscopy of alcohol in rhesus monkey brain

Brain alcohol was measured in rhesus monkeys (Macaca mulatta) by proton magnetic resonance spectroscopy (MRS) following acute nasogastric alcohol administration (0.8 g/kg). Monkeys were anesthetized with ketamine and xylazine. A 1.5 T whole body imager and a 3-inch surface coil were used to acquire TE 30 and 270 ms spectra from a 7.5 cc voxel localized with a stimulated echo (STEAM) sequence. Venous blood samples were collected during spectral acquisitions for gas chromatographic determination of temporally concordant blood alcohol levels (BALs). Acute alcohol administration did not alter the resonance areas of N-acetylaspartate/N-acetyl containing compounds (NAA), choline containing compounds, or total creatine. The NAA resonance was used as an internal standard to calculate approximate brain alcohol concentrations, which averaged 27 ± 3% and 27 ± 8% of temporally concordant BALs (T₂-corrected TE 30 and TE 270 ms spectra, respectively). In addition to reconfirming results from prior studies finding incomplete detection of brain alcohol with MRS, these results demonstrate the feasibility of measuring brain alcohol in anesthetized nonhuman primates to examine relationships between alcohol exposure history and MRS-visibility of brain alcohol.     

1H magnetic resonance spectroscopy of the normal testis: preliminary findings

PURPOSE: The purpose of this study was to determine the pre- and postpubertal 1H magnetic resonance spectroscopic characteristics of the normal testis to establish baseline values for further clinical studies. MATERIALS AND METHODS: The subjects consisted of male volunteers, of whom 19 were prepubertal with ages between 7 and 13 years and 24 were postpubertal with ages between 19 and 39 years. Their testes were evaluated at 1.5 T with magnetic resonance spectroscopy; in addition, testis volumes were measured. Major metabolite peaks were identified and their ratios were calculated. Metabolite differences of testis between pre- and postpubertal age were analyzed. RESULTS: Major constituents of spectra were 3.21 ppm choline and 0.9-1.3 ppm lipid peaks. At the echo time (TE) spectrum of 31 ms, choline/lipid ratios ranged from 0.35 to 8.30 (mean=1.87) in postpubertal males and from 0.06 to 5.45 (mean=0.88) in prepubertal males (P<.013). At the TE spectrum of 136 ms, choline/lipid ratios ranged from 0.66 to 15.42 (mean=4.09) in postpubertal males and from 0.05 to 4.91 (mean=0.9) in prepubertal males (P<.016). CONCLUSIONS: Choline/lipid ratio was higher in the postpubertal period. The existence of higher choline peak in that age group should be due to the initiation of spermatogenesis. The decrease in the lipid peak may represent the effect of testosterone on testicular tissue or may be due to histochemical changes initiated by puberty. The significant decrease in choline/lipid ratio noted after puberty could represent the presence of spermatogenesis. This hypothesis should be evaluated by further studies on postpubertal subjects with impaired spermatogenesis.     

Proton magnetic resonance spectroscopy and biochemical investigation of type 2 diabetes mellitus in Asian Indians: observation of high muscle lipids and C-reactive protein levels

We report the determination of intramyocellular lipids (IMCLs) of the soleus muscle of patients with type 2 diabetes mellitus (T2DM) using proton magnetic resonance spectroscopy. In addition, the various anthropometric and biochemical profiles of these patients were determined, including estimation of C-reactive protein (CRP), an inflammatory marker of coronary heart disease, and insulin resistance [Homeostasis Model Assessment (HOMA-IR)]. The estimated CRP level and the IMCL content in these patients were correlated with body mass index, percentage of body fat, other measures of abdominal obesity, serum lipoproteins, fasting and post-oral glucose load serum insulin levels and other surrogate markers of insulin resistance. The IMCL content (P=.04), CRP (P=.008) and insulin resistance (P=.0007) were significantly higher in T2DM patients compared to healthy controls. However, IMCL content did not correlate with values of fasting insulin, HOMA-IR or CRP in either group. These findings have strong implications of increased cardiovascular risk in Asian Indians with T2DM. The absence of relationship between CRP and IMCL needs to be explored further in a study using a large sample size.     

A high spatial resolution 1H magnetic resonance spectroscopic imaging technique for breast cancer with a short echo time

The high sensitivity but low specificity of breast MRI has prompted exploration of breast (1)H MRS for breast cancer detection. However, several obstacles still prevent the routine application of in vivo breast (1)H MRS, including poor spatial resolution, long acquisition time associated with conventional multi-voxel MRS imaging (MRSI) techniques, and the difficulty of "extra" lipid suppression in a magnetic field with relatively poor achievable homogeneity compared to the brain. Using a combination of a recently developed echo-filter (EF) suppression technique and an elliptical sampling scheme, we demonstrate the feasibility of overcoming these difficulties. It is robust (the suppression technique is insensitive to magnetic field inhomogeneity), fast (acquisition time of about 12 min) and offers high spatial resolution (up to 0.6 cm(3) per voxel at 1.5 T with a TE of only 60 ms). This approach should be even better at 3 T with higher resolution and/or shorter TE.     

Potential of magnetic resonance spectroscopy to detect metastasis in axillary lymph nodes in breast cancer

Focused pathological evaluation of axillary lymph nodes in breast cancer is gaining importance. Nuclear magnetic resonance (NMR) spectroscopy that assesses the whole of the specimen has the potential in evaluating micrometastases. The biochemical changes associated with breast cancer metastases in axillary nodes by in vitro NMR and its use in the detection of axillary metastases in a clinical setting in comparison with conventional histopathology is presented in this study. Eighty-eight lymph nodes obtained from 30 patients with breast cancer were investigated. Histopathology revealed metastases in 20 nodes from 11 patients, while in vitro NMR spectroscopy revealed metastases in 22 nodes. Out of these 22 nodes, 16 were the same, which showed metastases on histopathology, while 6 nodes have shown metastases only on in vitro magnetic resonance spectroscopy (MRS). These 6 nodes with suspicion of metastases on MRS were subjected to reevaluation with serial sectioning and immunohistochemistry, but no additional metastases were revealed. Forty metabolites could be identified from the MR spectrum of lymph nodes. The levels of the glycerophosphocholine-phosphocholine (GPC-PC), choline, lactate, alanine and uridine diphosphoglucose were elevated significantly in nodes with metastases. In addition, the intensity ratio of GPC-PC/threonine (Thr) was higher in nodes with metastases, and using this as marker, MRS detected the axillary metastases with a sensitivity, specificity and accuracy of 80%, 91% and 88%, respectively. Neoadjuvant chemotherapy (NACT) lowered the concentrations of GPC-PC and GPC-PC/Thr ratio. The accuracy of MRS in detecting metastases was 75% in patients who received NACT (n=9) as compared to 96% in those who did not (n=21). Our results demonstrate the potential of in vitro MRS in characterizing the metabolite profile of the axillary nodes with breast cancer metastases. It detected axillary metastases with reasonable accuracy and can be complementary to histopathological evaluation and immunohistochemistry.     

Magnetic resonance spectroscopy outcomes from a comprehensive magnetic resonance study of children with fetal alcohol spectrum disorders

Magnetic resonance (MR) technology offers noninvasive methods for in vivo assessment of neuroabnormalities. A comprehensive neuropsychological/behavioral, MR imaging (MRI), MR spectroscopy (MRS) and functional MRI (fMRI) assessment was administered to children with fetal alcohol spectrum disorders (FASD) to determine whether global and/or focal abnormalities could be identified and to distinguish diagnostic subclassifications across the spectrum. The four study groups included (1) FAS/partial FAS; (2) static encephalopathy/alcohol exposed (SE/AE); (3) neurobehavioral disorder/alcohol exposed (ND/AE) as diagnosed with the FASD 4-Digit Code; and (4) healthy peers with no prenatal alcohol exposure. Results are presented in four separate reports: MRS (reported here) and neuropsychological/behavioral, MRI and fMRI outcomes (reported separately). MRS was used to compare neurometabolite concentrations [choline (Cho), n-acetyl-aspartate (NAA) and creatine (Cre)] in a white matter region and a hippocampal region between the four study groups. Choline concentration in the frontal/parietal white matter region, lateral to the midsection of the corpus callosum, was significantly lower in FAS/PFAS relative to all other study groups. Choline decreased significantly with decreasing frontal white matter volume and corpus callosum length. These outcomes suggest low choline concentrations may reflect white matter deficits among FAS/PFAS. Choline also decreased significantly with increasing severity of the 4-Digit FAS facial phenotype, increasing impairment in psychological performance and increasing alcohol exposure. NAA and Cre concentrations did not vary significantly. This study provides further evidence of the vulnerability of the cholinergic system in FASD.     

Metabolism of the colonic mucosa in patients with inflammatory bowel diseases: an in vitro proton magnetic resonance spectroscopy study

Metabolism of the colonic mucosa of patients with ulcerative colitis (UC; n=31) and Crohn's disease (CD; n=26) and normal mucosa (control, n=26) was investigated using in vitro high-resolution proton magnetic resonance spectroscopy. Of the 31 UC patients, 20 were in the active phase and 11 were in the remission phase of the disease. Out of 26 CD patients, 20 were in the active phase, while 6 were in the remission phase of the disease. Twenty-nine metabolites were assigned unambiguously in the perchloric acid extract of colonic mucosa. In the active phase of UC and CD, significantly lower (P相似文献   

Metabolite mapping of human filarial parasite, Brugia malayi with nuclear magnetic resonance

Metabolite mapping of human filarial parasite, Brugia malayi was carried out in vitro as well as in situ in host Mastomys coucha by ³¹P nuclear magnetic resonance (NMR) spectroscopy. Detection of parasites by visualizing contrast spots due to pathologic changes was observed by ¹H magnetic resonance imaging (MRI). Major metabolites of adult B. malayi observed by ³¹P-NMR spectroscopy were of sugar phosphates (SP), phosphomonoesters (PME), glycerophosphoryl-ethanolamine (GPE), -choline (GPC), phosphoenolpyruvate (PEP), inorganic phosphate (Pi), nucleoside diphosphosugar and nucleotides-mono, -di and -tri phosphates. PEP and GPC were present in high concentration; PEP being the major energy reservoir and GPC the major phospholipid in this species of filaria. The ³¹P NMR spectra of testis of mastomys, showed seven major peaks of SP, PME, phosphocreatine (PCr), phosphodiesters (PDE), Pi, and nucleotides di- and tri-phosphates. The ³¹P-NMR spectra of testis of B. malayi infected animal also consisted of seven major peaks with significant decrease in the SP and PME peak showing changes in the carbohydrate and lipid metabolism of filaria infected testis. Thus, in vivo ³¹P MRS provided a non-invasive assessment of tissue bioenergetics and phospholipid metabolism.     

Macroscopic tumor volume of malignant glioma determined by contrast-enhanced magnetic resonance imaging with and without magnetization transfer contrast

The purposes of this study were to compare the conspicuity and lesion volume of contrast-enhancing macroscopic malignant glioma determined by postcontrast magnetic resonance (MR) imaging with and without magnetization transfer (MT) saturation, and to discuss possible implications for radiotherapy planning. Nineteen patients (age 24–60 years) with histologically proven malignant glioma were prospectively examined by MR imaging. After the administration of gadolinium dimeglumine (0.1 mmol/kg body weight), the lesions were imaged with an MT-weighted FLASH (fast, low-angle shot) pulse sequence and with a conventional T₁-weighted spin-echo (SE) sequence without MT saturation. The mean tumor volumes of gliomas measured on MT-weighted FLASH images were significantly (p < .01) larger than those obtained from T₁-weighted SE images (45 ± 15 cm³ vs. 33 ± 10 cm³). The mean contrast-to-noise ratio of enhancing lesions on MT-weighted FLASH was 48 ± 14 compared with 30 ± 14 on SE images, representing a significant (p < .01) improvement. We conclude that the volume of contrast enhancement of malignant glioma identified on MT-weighted FLASH images represents the area of disrupted blood-brain barrier. If this volume of subtle contrast enhancement is caused by tumor infiltration and represents the boost target volume for stereotactic radiosurgery or brachytherapy, MT-weighted FLASH images would be better than T₁-weighted SE images to define these volumes. These improved delineation of areas at highest risk for recurrence following radiation therapy should enhance the efficacy of treatment planning for high-boost therapy.     

A novel approach to the simulation of nitroxide spin label EPR spectra from a single truncated dynamical trajectory

A simple effective method for calculation of EPR spectra from a single truncated dynamical trajectory of spin probe orientations is reported. It is shown that an accurate simulation can be achieved from the small initial fraction of a dynamical trajectory until the point when the autocorrelation function of re-orientational motion of spin label has relaxed. This substantially reduces the amount of time for spectra simulation compared to previous approaches, which require multiple full length trajectories (normally of several microseconds) to achieve the desired resolution of EPR spectra. Our method is applicable to trajectories generated from both Brownian dynamics and molecular dynamics (MD) calculations. Simulations of EPR spectra from Brownian dynamical trajectories under a variety of motional conditions including bi-modal dynamics with different hopping rates between the modes are compared to those performed by conventional method. Since the relatively short timescales of spin label motions are realistically accessible by modern MD computational methods, our approach, for the first time, opens the prospect of the simulation of EPR spectra entirely from MD trajectories of real proteins structures.     

Study on the phase transitions by nuclear magnetic resonance of α-type RbAl(SO4)2·12H2O and β-type CsAl(SO4)2·12H2O single crystals

The thermodynamic properties, spin–lattice relaxation times, T₁, and spin–spin relaxation times, T₂, of the ²⁷Al, ⁸⁷Rb, and ¹³³Cs nuclei in MAl(SO₄)₂·12H₂O (M=Rb and Cs) crystals were investigated, and the two crystals were found to lose H₂O with increases in temperature. From our results for T₁ and T₂, we conclude that the discontinuities near T_d in the T₁ curves of the two crystals correspond to structural changes. In both crystals, below T_d the water molecules surrounding the Al³⁺ and M⁺ nuclei form distorted octahedra, whereas above T_d the water molecules around the Al³⁺ and M⁺ nuclei form regular octahedra and the environment of the Al³⁺ and M⁺ nuclei has cubic symmetry. Further, the T₁ for the ²⁷Al and ⁸⁷Rb nuclei in RbAl(SO₄)₂·12H₂O below T_d were found to increase with increasing temperature, whereas the T₁ for the ²⁷Al and ¹³³Cs nuclei in CsAl(SO₄)₂·12H₂O were found to decrease. It is possible that this difference is due to the different characteristics of α- and β-type crystals.     

Surface chemistry and catalysis of oxide model catalysts from single crystals to nanocrystals

Fundamental understandings of surface chemistry and catalysis of solid catalysts are of great importance for the developments of efficient catalysts and corresponding catalytic processes, but have been remaining as a challenge due to the complex nature of heterogeneous catalysis. Model catalysts approach based on catalytic materials with uniform and well-defined surface structures is an effective strategy. Single crystals-based model catalysts have been successfully used for surface chemistry studies of solid catalysts, but encounter the so-called “materials gap” and “pressure gap” when applied for catalysis studies of solid catalysts. Recently catalytic nanocrystals with uniform and well-defined surface structures have emerged as a novel type of model catalysts whose surface chemistry and catalysis can be studied under the same operational reaction condition as working powder catalysts, and they are recognized as a novel type of model catalysts that can bridge the “materials gap” and “pressure gap” between single crystals-based model catalysts and powder catalysts. Herein we review recent progress of surface chemistry and catalysis of important oxide catalysts including CeO₂, TiO₂ and Cu₂O acquired by model catalysts from single crystals to nanocrystals with an aim at summarizing the commonalities and discussing the differences among model catalysts with complexities at different levels. Firstly, the complex nature of surface chemistry and catalysis of solid catalysts is briefly introduced. In the following sections, the model catalysts approach is described and surface chemistry and catalysis of CeO₂, TiO₂ and Cu₂O single crystal and nanocrystal model catalysts are reviewed. Finally, concluding remarks and future prospects are given on a comprehensive approach of model catalysts from single crystals to nanocrystals for the investigations of surface chemistry and catalysis of powder catalysts approaching the working conditions as closely as possible.