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E Grillon

Publications and source records attributed to E Grillon.

6 recordsLinked to original sources
PubMed2004

Assessment of vascular reactivity in rat brain glioma by measuring regional blood volume during graded hypoxic hypoxia.

While morphological and molecular events during angiogenesis in brain glioma have been extensively studied, the functional properties of tumour vessels have yet received little attention. We have determined changes in regional blood volume (BV) during graded hypoxic hypoxia using susceptibility contrast magnetic resonance imaging in a model of rat brain glioma. Nine anaesthetised and ventilated rats with C6 glioma were subjected to incremental reduction in the fraction of inspired oxygen (FiO(2)): 0.35, 0.25, 0.15, 0.12, 0.10 and reoxygenation to 0.35. At each episode, BV was determined in peritumoral, intratumoral and contralateral regions. Baseline BV values (FiO(2) of 0.35) were higher in peritumoral than in the contralateral and intratumoral regions. Progressive hypoxia resulted in a graded increase in BV in contralateral and peritumoral regions. At FiO(2) of 0.10, BV increases were comparable between these two regions: 49+/-22% (s.d.) and 28+/-17% with respect of control values, respectively. These BV changes reversed during the reoxygenation episode. By contrast, the intratumoral region had a significant increase in BV at FiO(2) of 0.10 only, with no evidence of return to the basal value during reoxygenation. Immunohistochemical staining of alpha-smooth muscle actin confirmed reactivity of vessels in the peritumoral region. Our findings indicate that peritumoral vessels present a vascular reactivity to hypoxia, which is comparable to that of nontumoral vessels. A method is thus available for noninvasively demonstrating whether any particular vascular modifying strategy results in the desired outcome in terms of tumour blood volume changes.

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PubMed2001

Vessel size imaging.

Vessel size imaging is a new method that is based on simultaneous measurement of the changes Delta R(2) and Delta R(2)(*) in relaxation rate constants induced by the injection of an intravascular superparamagnetic contrast agent. Using the static dephasing approximation for Delta R(2)(*) estimation and the slow-diffusion approximation for Delta R(2) estimation, it is shown that the ratio Delta R(2)/Delta R(2)(*) can be expressed as a function of the susceptibility difference between vessels and brain tissue, the brain water diffusion coefficient, and a weighted mean of vessel sizes. Comparison of the results with 1) the Monte Carlo simulations used to quantify the relationship between tissue parameters and susceptibility contrast, 2) the experimental MRI data in the normal rat brain, and 3) the histologic data establishes the validity of this approach. This technique, which allows images of a weighted mean of the vessel size to be obtained, could be useful for in vivo studies of tumor vascularization. Magn Reson Med 45:397-408, 2001.

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PubMed2001

Xenon-129 MR imaging and spectroscopy of rat brain using arterial delivery of hyperpolarized xenon in a lipid emulsion.

Hyperpolarized (129)Xe dissolved in a lipid emulsion constitutes an NMR tracer that can be injected into the blood stream, enabling blood-flow measurement and perfusion imaging. A small volume (0.15 ml) of this tracer was injected in 1.5 s in rat carotid and (129)Xe MR spectra and images were acquired at 2.35 T to evaluate the potential of this approach for cerebral studies. Xenon spectra consistently showed two resonances, at 194.5 ppm and 199.0 ppm relative to the gas peak. The signal-to-noise ratio (SNR) obtained for the two peaks was sufficient (ranging from 12 to 90) to follow their time courses. 2D transverse-projection xenon images were obtained with an in-plane resolution of 900 microm per pixel (SNR range 8-15). Histological analysis revealed no brain damage except in two rats that had received three injections.

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PubMed2000

Nuclear factor-kappa B activation in permanent intraluminal focal cerebral ischemia in the rat.

Nuclear factor-kappa B (NF-kappa B) is an oxidative stress responsive transcription factor known to be activated in response to transient middle cerebral artery intraluminal occlusion. Since oxidative stress activation may largely occur during reperfusion, the aim of this study was to determine if permanent middle cerebral artery intraluminal occlusion without reperfusion induces NF-kappa B activation and the relationship of NF-kappa B activation to HSP70 expression and neuronal cell death. Our results suggest that permanent intraluminal occlusion is sufficient to induce NF-kappa B activation 7 h after the onset of occlusion. Interestingly, this activation seems to occur specifically in dying neurons of the penumbra area devoid of any HSP70 neuronal immunoreactivity. These findings are consistent with the suggested protective role of HSP70 expression and suggest that NF-kappa B activation observed in the penumbra area has a role in neuronal cell death after permanent intraluminal cerebral ischemia.

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PubMed2000

In vivo 129Xe NMR in rat brain during intra-arterial injection of hyperpolarized 129Xe dissolved in a lipid emulsion.

Hyperpolarized 129Xe was dissolved in a lipid emulsion and administered to anaesthetized rats by manual injections into the carotid (approximately 1-1.5 mL in a maximum time of 30 s). During injection, 129Xe NMR brain spectra at 2.35 T were recorded over 51 s, with a repetition time of 253 ms. Two peaks assigned to dissolved 129Xe were observed (the larger at 194 +/- 1 ppm assigned to intravascular xenon and the smaller at 199 +/- 1 ppm to xenon dissolved in the brain tissue). Their kinetics revealed a rapid intensity increase, followed by a plateau (approximately 15 s duration) and then a decrease over 5 s. This behaviour was attributed to combined influences of the T1 relaxation of the tracer, of radiofrequency sampling, and of the tracer perfusion rate in rat brain. Similar kinetics were observed in experiments carried out on a simple micro-vessel phantom. An identical experimental set-up was used to acquire a series of 2D projection 129Xe images on the phantom and the rat brain.

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