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22.
In clinical 13C infusion studies, broadband excitation of 200 ppm of the human brain yields 13C MR spectra with a time resolution of 2-5 min and generates up to 2000 metabolite peaks over 2h. We describe a fast, automated, observer-independent technique for processing [1H-decoupled] 13C spectra. Quantified 13C spectroscopic signals, before and after the administration of [1-13C]glucose and/or [1-13C]acetate in human subjects are determined. Stepwise improvements of data processing are illustrated by examples of normal and pathological results. Variation in analysis of individual 13C resonances ranged between 2 and 14%. Using this method it is possible to reliably identify subtle metabolic effects of brain disease including Alzheimer's disease and epilepsy. 相似文献
23.
Seong Cho Dana Jones Wilburn E. Reddick Robert J. Ogg R.Grant Steen 《Magnetic resonance imaging》1997,15(10):1133-1143
The goal of this study was to determine the expected normal range of variation in spin-lattice relaxation time (T1) of brain tissue in vivo, as a function of age. A previously validated precise and accurate inversion recovery method was used to map T1 transversely, at the level of the basal ganglia, in a study population of 115 healthy subjects (ages 4 to 72; 57 male and 58 female). Least-squares regression analysis shows that T1 varied as a function of age in pulvinar nucleus (R2 = 56%), anterior thalamus (R2 = 51%), caudate (R2 = 50%), frontal white matter (R2 = 47%), optic radiation (R2 = 39%), putamen (R2 = 36%), genu (R2 = 22%), occipital white matter (R2 = 20%) (all p < 0.0001), and cortical gray matter (R2 = 53%) (p < 0.001). There were no significant differences in T1 between men and women. T1 declines throughout adolescence and early adulthood, to achieve a minimum value in the fourth to sixth decade of life, then T1 begins to increase. Quantitative magnetic resonance imaging provides evidence that brain tissue continues to change throughout the lifespan among healthy subjects with no neurologic deficits. Age-related changes follow a strikingly different schedule in different brain tissues; white matter tracts tend to reach a minimum T1 value, and to increase again, sooner than do gray matter tracts. Such normative data may prove useful for the early detection of brain pathology in patients. 相似文献
24.
Response surface methodology (RSM) was used to optimize the formulation of a nanoemulsion for central delivery following parenteral administration. A mixture of medium-chain triglyceride (MCT) and safflower seed oil (SSO) was determined as a sole phase from the emulsification properties. Similarly, a natural surfactant (lecithin) and non-ionic surfactant (Tween 80) (ratio 1:2) were used in the formulation. A central composite design (CCD) with three-factor at five-levels was used to optimize the processing method of high energy ultrasonicator. Effects of pre-sonication ultrasonic intensity (A), sonication time (B), and temperature (C) were studied on the preparation of nanoemulsion loaded with valproic acid. Influence of the aforementioned specifically the effects of the ultrasonic processing parameters on droplet size and polydispersity index were investigated. From the analysis, it was found that the interaction between ultrasonic intensity and sonication time was the most influential factor on the droplet size of nanoemulsion formulated. Ultrasonic intensity (A) significantly affects the polydispersity index value. With this optimization method, a favorable droplet size of a nanoemulsion with reasonable polydispersity index was able to be formulated within a short sonication time. A valproic acid loaded nanoemulsion can be obtained with 60% power intensity for 15 min at 60 °C. Droplet size of 43.21 ± 0.11 nm with polydispersity index of 0.211 were produced. The drug content was then increased to 1.5%. Stability study of nanoemulsion containing 1.5% of valproic acid had a good stability as there are no significant changes in physicochemical aspects such as droplet size and polydispersity index. With the characteristisation study of pH, viscosity, transmission electron microscope (TEM) and stability assessment study the formulated nanoemulsion has the potential to penetrate blood–brain barrier in the treatment of epilepsy. 相似文献
25.
We study reflection diffuse optical tomography using two-dimensional (2D) continuous-wave source-detector arrays on the surface
of semi-infinite medium, aiming at imaging the perfusion and the hemoglobin oxygen saturation variation of human cerebral
cortex with brain activation. We had previously formulated the inverse problem with Moore-Penrose inversion. When we use simple
regularization in this inverse problem, the reconstruction sensitivity decreases markedly with the depth so that the signal
in the deep range may be masked by an unwanted signal in the shallow range. In this paper, we propose a depth-adaptive regularized
reconstruction, in which we assign a smaller regularization parameter with the depth. We demonstrate improvement of the three-dimensional
(3D) reconstruction uniformity using the proposed scheme. 相似文献
26.
利用光纤光谱仪和光纤探头建立脑组织血氧饱和度(hemoglobin oxygen saturation, SO2)微创在位测量系统。将悬乳液和全血的混合溶液作为生物组织模型,获取模型在不同SO2下可见光区实时吸收光谱与血氧分析仪所测SO2数据的样本集,将吸收光谱作归一化处理后取得500nm~600nm区间的4个光谱特征参量,通过统计分析建立特征参量与血氧饱和度的经验公式。结果表明:利用该系统获得了30只大鼠脑皮层不同深度的血氧饱和度SO2,其范围为64%~76%。这种方法有助于脑外科微创手术中实时在位测试脑组织血氧饱和度研究。 相似文献
27.
We investigate transcranial magneto–acoustical stimulation(TMAS) for noninvasive brain neuromodulation in vivo.TMAS as a novel technique uses an ultrasound wave to induce an electric current in the brain tissue in the static magnetic field. It has the advantage of high spatial resolution and penetration depth. The mechanism of TMAS onto a neuron is analyzed by combining the TMAS principle and Hodgkin–Huxley neuron model. The anesthetized rats are stimulated by TMAS, resulting in the local field potentials which are recorded and analyzed. The simulation results show that TMAS can induce neuronal action potential. The experimental results indicate that TMAS can not only increase the amplitude of local field potentials but also enhance the effect of focused ultrasound stimulation on the neuromodulation. In summary, TMAS can accomplish brain neuromodulation, suggesting a potentially powerful noninvasive stimulation method to interfere with brain rhythms for diagnostic and therapeutic purposes. 相似文献
28.
随着人口老龄化的不断加剧,衰老相关疾病已成为全球关注的问题.神经系统功能的退行性改变居于衰老相关疾病的首位,其机制尚不明了.该文旨在通过核磁共振磷谱(~(31)P NMR)检测不同月龄大鼠脑组织中小分子物质的改变,明确能量相关的含磷化合物随大鼠年龄增长的变化,从而揭示脑组织中年龄相关代谢物的变化规律.该研究萃取了不同年龄(幼年、中年及老年)Sprague-Dawley(SD)大鼠脑组织中的小分子物质,进行了~(31)P NMR检测分析.结果显示:老年大鼠脑组织中能量代谢相关物质——磷酸肌酸的含量显著升高,而磷脂酰胆碱及磷酸肌醇含量显著降低,并且出现了磷酸化葡萄糖.这一发现有助于理解衰老相关的脑结构和功能下调,为神经退行性疾病的发生提供依据. 相似文献
29.
Tomoko KANEKO-ISHINO Fumitoshi ISHINO 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2015,91(10):511-538
Mammals, including human beings, have evolved a unique viviparous reproductive system and a highly developed central nervous system. How did these unique characteristics emerge in mammalian evolution, and what kinds of changes did occur in the mammalian genomes as evolution proceeded? A key conceptual term in approaching these issues is “mammalian-specific genomic functions”, a concept covering both mammalian-specific epigenetics and genetics. Genomic imprinting and LTR retrotransposon-derived genes are reviewed as the representative, mammalian-specific genomic functions that are essential not only for the current mammalian developmental system, but also mammalian evolution itself. First, the essential roles of genomic imprinting in mammalian development, especially related to viviparous reproduction via placental function, as well as the emergence of genomic imprinting in mammalian evolution, are discussed. Second, we introduce the novel concept of “mammalian-specific traits generated by mammalian-specific genes from LTR retrotransposons”, based on the finding that LTR retrotransposons served as a critical driving force in the mammalian evolution via generating mammalian-specific genes. 相似文献
30.
de Graaf RA Brown PB Rothman DL Behar KL 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2008,193(1):63-67
Oxygen is an abundant element that is present in almost all biologically relevant molecules. NMR observation of oxygen has been relatively limited since the NMR-active isotope, oxygen-17, is only present at a 0.037% natural abundance. Furthermore, as a spin 5/2 nucleus oxygen-17 has a moderately strong quadrupole moment which leads to fairly broad resonances (T(2)=1-4 ms). However, the similarly short T(1) relaxation constants allow substantial signal averaging, whereas the large chemical shift range (>300 ppm) improves the spectral resolution of (17)O NMR. Here it is shown that high-quality, natural abundance (17)O NMR spectra can be obtained from rat brain in vivo at 11.74 T. The chemical shifts and line widths of more than 20 oxygen-containing metabolites are established and the sensitivity and potential for (17)O-enriched NMR studies are estimated. 相似文献