Pimonidazole binding in C6 rat brain glioma: relation with lipid droplet detection

Item does not contain fulltextIn C6 rat brain glioma, we have investigated the relation between hypoxia and the presence of lipid droplets in the cytoplasm of viable cells adjacent to necrosis. For this purpose, rats were stereotaxically implanted with C6 cells. Experiments were carried out by the end of the tumour development. A multifluorescence staining protocol combined with digital image analysis was used to quantitatively study the spatial distribution of hypoxic cells (pimonidazole), blood perfusion (Hoechst 33342), total vascular bed (collagen type IV) and lipid droplets (Red Oil) in single frozen sections. All tumours (n=6) showed necrosis, pimonidazole binding and lipid droplets. Pimonidazole binding occurred at a mean distance of 114 microm from perfused vessels mainly around necrosis. Lipid droplets were principally located in the necrotic tissue. Some smaller droplets were also observed in part of the pimonidazole-binding cells surrounding necrosis. Hence, lipid droplets appeared only in hypoxic cells adjacent to necrosis, at an approximate distance of 181 microm from perfused vessels. In conclusion, our results show that severe hypoxic cells accumulated small lipid droplets. However, a 100% colocalisation of hypoxia and lipid droplets does not exist. Thus, lipid droplets cannot be considered as a surrogate marker of hypoxia, but rather of severe, prenecrotic hypoxia

Hemispheric language dominance testing by means of fMRI.

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fMRI assessment of hemispheric language dominance using a simple inner speech paradigm.

International audienceHemispheric language dominance (HLD) has been determined by means of functional MRI (fMRI) using a simple, inner speech, word fluency paradigm. During the task periods, subjects perform mental imagery of visual scenes and generate silently the nouns of all objects visualized. During the control periods, subjects attend to the scanner noise. Activated areas have been identified by means of cross-correlation analysis. HLD indices have been determined by comparing the number of activated pixels detected in both hemispheres within predefined cortical areas (Brodmann areas 6, 9, 10, 39, 40 and 44-47). The paradigm has been assessed on 10 healthy, right-handed volunteers. A volume 35 mm thick, centered on the inferior frontal gyrus, was imaged. A conventional GRE MR sequence was used on a 1.5 T clinical MR scanner. HLD indices were compared with those determined for overt speech. Robust fMRI responses were obtained. HLD indices indicated left hemispheric language dominance for all subjects examined. They correlated well with those obtained for overt speech (R(2) = 0.93, regression coefficient = 0.998, with p < 10(-4)). Thus, an inner speech paradigm based on visual imagery is well adapted for assessment of HLD by means of fMRI

In vivo assessment of tumoral angiogenesis.

Vessel size imaging (VSI) for brain tumor characterization was evaluated and the vessel size index measured by MRI (VSIMRI) was correlated with VSI obtained by histology (VSIhisto). Blood volume (BV) and VSI maps were obtained on 12 rats by simultaneous measurements of R2* and R2, before and after the injection of a macromolecular contrast agent, AMI-227. Immunostaining of collagen IV in vessels was performed. An expression was derived for evaluating VSI from stereologic measurements on histology data (VSIhisto). On BV and VSI images obtained from large-size tumors (n = 9), three regions could be distinguished and correlated well with histological sections: a high BV region surrounding the tumor, a necrotic area where BV is very low, and a viable tumor tissue region showing lower BV but higher VSI than the normal rat cortex, with the presence of larger vessels. The quantitative analysis showed a good correlation (Spearman rank's rho = 0.74) between VSIhisto and VSIMRI with a linear regression coefficient of 1.17. The good correlation coefficient supports VSI imaging as a quantitative method for tumor vasculature characterization

NMR imaging of thermally polarized helium-3 gas.

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Possible involvement of primary motor cortex in mentally simulated movement: a functional magnetic resonance imaging study.

International audienceThe role of the primary motor cortex (M1) during mental simulation of movement is open to debate. In the present study, functional magnetic resonance imaging (fMRI) signals were measured in normal right-handed subjects during actual and mental execution of a finger-to-thumb opposition task with either the right or the left hand. There were no significant differences between the two hands with either execution or simulation. A significant involvement of contralateral M1 (30% of the activity found during execution) was detected in four of six subjects. Premotor cortex (PM) and the rostral part of the posterior SMA were activated bilaterally during motor imagery. These findings support the hypothesis that motor imagery involves virtually all stages of motor control

Cryopreservation of organs: NMR follow-up of cryoprotectant perfusion in rabbit kidneys.

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