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1.
Nezamzadeh M 《Magma (New York, N.Y.)》2012,25(4):285-296
Object
To understand the behavior of diffusion signal decays of water in white matter of human brain in vivo and to estimate tissue microstructure parameters such as exchange time of diffusing water molecules in human brain.Materials and methods
Diffusion decays were measured over an extended range of diffusion weightings (b-values) up to a maximum of 12,500?s/mm2 and diffusion times between 19.9 and 53.8?ms in eight healthy human subjects using MRI scans. The diffusion signal decays were all Rician noise corrected and then analyzed using multi-component non-negative least squares (NNLS) data analysis.Results
Three diffusion coefficients including one at (0.930?±?0.003)?×?10?3 (80?±?1%)?mm2/s, another at (0.067?±?0.002)?×?10?3 (19?±?1%)?mm2/s and a small contribution at (1.20?±?0.02)?×?10?2 (1.00?±?0.01%)?mm2/s were observed in the diffusion decay using the highest b-value. The diffusion decays show diffusion time dependence for the slow diffusion coefficient which has not previously been reported.Conclusion
This study presents the accurate diffusion parameters by the use of very large b-values along with Rician noise correction and multi-component data analysis. The experimental results are consistent with the theoretical predictions used to estimate the exchange time of diffusing water molecules for a model of human brain tissue. 相似文献2.
Hyperammonemia and chronic hepatic encephalopathy: an in vivo PMRS study of the rat brain 总被引:1,自引:0,他引:1
The brain energy metabolism of rats affected by chronic hepatic encephalopathy due to portacaval shunting was monitored by
in vivo31P-nuclear magnetic resonance spectroscopy before and after ammonium acetate administration. With respect to healthy unoperated
and to sham operated controls, portacaval shunting decreased the levels of the nuclear magnetic resonance (NMR) visible brain
phosphocreatine and nucleoside phosphates, and the intracellular [free Mg2+]. Ammonium acetate induced a further decrease of the levels of the NMR detectable phosphocreatine and nucleoside triphosphates
and of the [free Mg2+], while the PMR spectra of the brain of non-shunted rats did not show any significant change even after treatment with ammonium
acetate. 相似文献
3.
M. C. Delmas-Beauvieux S. Pietri M. Culcasi N. Leducq H. Valeins T. Liebgott P. Diolez P. Canioni J. L. Gallis 《Magma (New York, N.Y.)》1997,5(1):45-52
Detection of free radicals by electron spin resonance (ESR) proves the involvement of reactive oxygen species (ROS) in reperfused
organ injuries. Spin-traps are known to ameliorate hemodynamic parameters in an isolated postischemic heart. The effects of
5 mmol/L DMPO (5,5-dimethyl-1-pyrroline-N-oxide) or DEPMPO (5-(diethylphosphoryl)-5-methyl-1-pyrrolineN-oxide) on intracellular pH (pHin) and ATP level were evaluated by31P nuclear magnetic resonance on isolated rat liver submitted to 1 hour of warm ischemia and reperfusion. At the end of the
reperfusion period, during which pHin recovered to its initial value (7.16±0.03) in all groups, the ATP recovery level (expressed in percentage of initial value)
was similar in controls and DEPMPO (60%±5%,n=6 and 54%±4%,n=6, respectively), but only 37%±1% in DMPO-treated livers (n=6) (p<0.05 versus controls andp<0.05 versus DEPMPO). Oxidative phosphorylation was not affected by an addition of nitrones on isolated mitochondria extracted
from livers not submitted to ischemia-reperfusion. In contrast, mitochondria extracted at the end of the ischemia-reperfusion
showed an impairment in the phosphorylation parameters, particularly in the presence of DMPO. Mass spectrum of ischemic liver
perchloric acid extracts evidenced probable catabolites in treated groups. The differences in the effect of the two nitrones
on energetic metabolism may be explained by the production of deleterious catabolites by DMPO as compared to DEPMPO. Even
though a specific radical scavenging effect could be operative in the liver, our results indicate that catabolic effects were
predominant. The absence of deleterious effects of DEPMPO in contrast to DMPO on the liver energetic metabolism was evidenced,
allowing the use of DEPMPO for ESR detection. 相似文献