MRI assessment of amplitude of low-frequency fluctuation in rat brains with acute cerebral ischemic stroke.

To investigate fluctuations in the amplitude of low-frequency blood oxygenation level-dependent (BOLD) fMRI during acute brain ischemia, and to evaluate the use of amplitude of low-frequency fluctuations (ALFFs) in resting state fMRI for assessing super-acute focal cerebral ischemic stroke. A super-acute stroke model with middle cerebral artery occlusion (MCAO) in the rat was employed. Spontaneous fluctuations were recorded using a series of gradient echo-planar imaging (EPI) images before and 30 min, 60 min, 2 h, 6 h, 12 h, and 24 h after MCAO. After preprocessing, serial fMRI data were obtained by fast Fourier transformation to calculate the ALFFs. Statistical parametric mapping software was used for the statistical analysis of ALFFs. T2-weighted images and diffusion weighted images (DWI) were also performed to detect the ischemic lesion. The signal intensities of abnormal ALFFs increased and migrated from the core of the ischemic lesion areas to the edge of lesion following MCAO. The dynamic changes in the ALFF maps demonstrated that the sizes of the ALFF regions exceeded beyond the borderline of the DWI lesions during the super-acute ischemic stroke stage. There was a significant difference in the ALFFs maps between the ischemic stroke group and the control group (P<0.005; cluster size>10 voxels), which mainly occurred in the periphery of the ischemic region in the cortex. These data suggest that ALFF maps provide hemodynamic BOLD information on neural activity, and have potential for predicting survival and prognosis of acute ischemic brain tissues.

[Functional connectivity analysis of super acute cerebral ischemia in rats: a resting-state functional MRI empirical study].

OBJECTIVE: To investigate the change of low-frequency blood-oxygenation-level-dependent fluctuation (LFBF) after cerebral ischemia by functional connectivity analysis in the resting state. METHODS: Super acute stroke rat-models with middle cerebral artery occlusion (MCAO) were employed in this study. Spontaneous fluctuations were recorded using a series of gradient-recalled echo-planar imaging (EPI) images before creation of the MCAO, and the same scan protocols were duplicated at the time of 60 min, 2 h after creation of the MCAO. FMRI signal time series from the different ROIs of ischemic cortex and normal cortex were preprocessed and low pass filtered. After preprocessing, the serial fMRI data was obtained by fast Fourier transformation to calculate the amplitude of the low-frequency fluctuations. Meanwhile, time course signal changes from a seed voxel of normal cortex were correlated with every voxel in the brain. Statistical analysis was performed across all rats to determine the extent of spatial correlation between regions. RESULTS: The amplitude of LFBF in the ischemic cortex between 0.01 and 0.1 Hz was lightly decreased during the super acute ischemic stroke. Howerever, the amplitude of LFBF in contralateral cortex was increased after 2 hours. Spatial distribution of LFBF, from cross-correlation analysis, indicates that the substantial inter-hemispheric synchrony of ischemic region was decreased and of contralateral cortex was enhanced during the super acute ischemic stroke. CONCLUSION: The contrast behavior of the resting state BOLD signal fluctuations and a intra-hemispheric symmetry in the LFBF with similar phase characteristics in most other regions during super acute ischemic stroke can be implied a new approach to detect the physiological activity functions and the distinct resting neural networks after the acute ischemic stroke takes place.

Efficient nano iron particle-labeling and noninvasive MR imaging of mouse bone marrow-derived endothelial progenitor cells.

In this study, we sought to label mouse bone marrow-derived endothelial progenitor cells (EPCs) with Resovist(®) in vitro and to image them using 7.0 Tesla (T) magnetic resonance imaging (MRI). Mouse bone marrow-derived EPCs were cultured in endothelial basal medium with endothelial growth supplement. They were then characterized by immunocytochemistry, flow cytometry, and fluorescence quantitative polymerase chain reaction. Their functions were evaluated by measuring their uptake of 1,1-dioctadecyl-3,3,3,3-tetramethylindocarbocyanine-labeled acetylated low-density lipoprotein (Dil-Ac-LDL), binding of fluorine isothiocyanate (FITC)-labeled Ulex europaeus agglutinin (UEA), and formation of capillary-like networks. EPCs were labeled with superparamagnetic iron oxide (SPIO) and their proliferation was then assessed in a water-soluble tetrazolium (WST-8)-based cell proliferation assay. Spin echo sequence (multislice, multiecho [MSME]) and gradient echo sequence (2D-FLASH) were used to detect differences in the numbers of labeled cells by 7.0 T MRI. The results showed that the cultured cells were of "cobblestone"-like shape and positive for CD133, CD34, CD31, von Willebrand factor, kinase domain receptor, and CD45, but negative for F4/80. They could take up Dil-Ac-LDL, bind FITC-UEA, and form capillary-like networks on Matrigel in vitro. Prussian-blue staining demonstrated that the cells were efficiently labeled with SPIO. The single-cell T2* effect was more obvious in the 2D-FLASH sequence than in the MSME sequence. Further, there were almost no adverse effects on cell vitality and proliferation. In conclusion, mouse bone marrow-derived EPCs can be efficiently labeled with SPIO and imaged with 7.0-T MRI. They may thus be traced by MRI following transplantation for blood vessel disorders and cancer treatment.

[A study of ischemic penumbra by perfusion and diffusion-weighted imaging at high-field MRI (7.0 T)].

OBJECTIVE: To approach the value of perfusion-weighed and diffusion-weighted imaging at high field intensity (7.0 T) MR in research of the ischemic penumbra in acute cerebral infarction of rats. METHODS: Acute cerebral infarction of rat was induced by occluding middle cerebral artery (MCAO) with suture. Sixty SD rats were divided into six groups randomly of ten including sham operation group, and groups of MCAO for 0.5, 1.5, 3, 6, 24 h. Then all rats were examined by PWI, DWI, T1WI, T2WI and MRA at corresponding time point. Regional cerebral blood volume (rCBV), relative cerebral blood flow (rCBF), mean transit time (MTT) topographical maps were reconstructed and the relative values of rCBV, rCBF, MTT, DWI-derived (rVD) and PWI-derived (rVP) lesion volume were calculated. The outcomes of serial MRI were compared with TTC stain and pathological findings. RESULTS: Neither abnormal signal of MRI nor TTC stain or pathological changes were found in sham operation group. The rCBV, rCBF was significantly decreased but rMTT obviously extended of the area of middle cerebral artery blood-supply of each group of MCAO. The core of infarction was more serious than the edge of infarction. Abnormal signals were found in the MCA-supplying regions in the DWI and PWI of all of the groups of MCAO. The size of rVD became bigger with the time going on but no significant difference of rVP. The size of rVP was larger than rVD before MCAO of 6 h (P < 0.05). There was no significant difference between PWI and DWI after 6 h (P > 0.05) and also between TTC at 24 h and DWI after 3 h (P > 0.05). CONCLUSION: Perfusion-weighed and diffusion-weighted imaging at high field intensity (7.0 T) MR dynamic displaying the existence and the process of ischemic penumbra in acute cerebral infarction of rats provides a basis for further study.

Benzo (a) pyrene residue surveillance in retail food in the city of Xiamen, China: report from 121 samples / 中华预防医学杂志

<p><b>OBJECTIVE</b>To investigate Benzo (a) pyrene (BaP) residue in retail food of Xiamen.</p><p><b>METHODS</b>BaP residue in 121 retail food samples collected from Xiamen were determined by a rapid BaP detector based on derivative constant-energy synchronous fluorescence technique.</p><p><b>RESULTS</b>BaP was detected in 84.3% samples and the concentration were ranged from 0.17 to 59.0 microg/kg. There were 49.6% samples exceeding 5.00 microg/kg, and most of them were roasting food (1.44 - 54.10 microg/kg), processed meat products (0.17 - 59.00 microg/kg) and aquatic products (2.79 - 36.80 microg/kg). The BaP concentration in 34 samples collected from roadside stands were 1.78 - 49.60 microg/kg, of which the rate of the samples exceeding 5.00 microg/kg was 88.2%.</p><p><b>CONCLUSION</b>The BaP contamination in retail food samples from Xiamen is serious.</p>