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Jean-françois Payen - One of the best experts on this subject based on the ideXlab platform.

  • Measuring hemoglobin oxygen saturation during graded Hypoxic Hypoxia in rat striatum.
    Anesthesia and analgesia, 2006
    Co-Authors: Cécile Julien, Emmanuelle Grillon, Chantal Rémy, Adrian Bradu, Raphaël Sablong, Jacques Derouard, Jean-françois Payen
    Abstract:

    We evaluated in vivo reflectance spectroscopy of visible light as a method to assess brain tissue hemoglobin oxygen saturation in rat striatum (SstrO2). Seven anesthetized and mechanically ventilated rats were subjected to incremental reduction in the fraction of inspired oxygen (Fio2): 0.35, 0.25, 0.15, 0.12, and 0.10, followed by a reoxygenation period (Group 1). At each episode, local changes in SstrO2 and in cerebral blood flow (LCBF) were simultaneously determined in the two striatal regions, using reflectance spectroscopy and laser Doppler flowmetry, respectively. Another group of rats (Group 2, n = 6) was also studied to measure sagittal sinus blood hemoglobin saturation (SssO2) during graded Hypoxic Hypoxia. Corpus striatum exhibited a significant graded decrease in SstrO2, from 38% +/- 17% at Fio2 of 0.35 (control) to 16% +/- 10% at Fio2 of 0.12 and to 13% +/- 7% at Fio2 of 0.10 (P < 0.05), with no difference between the two hemispheres. These local changes in SstrO2 were associated with a significant graded increase in LCBF: 161% +/- 26% of control values and 197% +/- 34% during these 2 Hypoxic episodes, respectively (P < 0.05). All local changes were fully reversed during the reoxygenation period. In Group 2, SssO2 decreased from 38% +/- 8% at Fio2 of 0.35 (control) to 10% +/- 3% at Fio2 of 0.10, closely related to SstrO2 decreasing in Hypoxia. This study shows that reflectance spectroscopy of the visible light in rat striatum could be a possible measure of continuous changes in SstrO2. SssO2 and LCBF measurements during graded Hypoxic Hypoxia indicate that changes in SstrO2 reflect primarily those in brain venous oxygenation.

  • Assessment of vascular reactivity in rat brain glioma by measuring regional blood volume during graded Hypoxic Hypoxia.
    British journal of cancer, 2004
    Co-Authors: Julien C, Jean-françois Payen, Irène Troprès, Régine Farion, Emmanuelle Grillon, Olivier Montigon, Chantal Rémy
    Abstract:

    Assessment of vascular reactivity in rat brain glioma by measuring regional blood volume during graded Hypoxic Hypoxia

  • Regional response of cerebral blood volume to graded Hypoxic Hypoxia in rat brain
    British journal of anaesthesia, 2002
    Co-Authors: C. Julien-dolbec, Irène Troprès, Olivier Montigon, H. Reutenauer, A. Ziegler, M. Decorps, Jean-françois Payen
    Abstract:

    Background. The response of cerebral blood flow to Hypoxic Hypoxia is usually effected by dilation of cerebral arterioles. However, the resulting changes in cerebral blood volume (CBV) have received little attention. We have determined, using susceptibility contrast magnetic resonance imaging (MRI), changes in regional CBV induced by graded Hypoxic Hypoxia. Methods. Six anaesthetized rats were subjected to incremental reduction in the fraction of inspired oxygen: 0.35, 0.25, 0.15, and 0.12. At each episode, CBV was determined in five regions of each hemisphere after injection of a contrast agent: superficial and deep neocortex, striatum, corpus callosum and cerebellum. A control group (n=6 rats) was studied with the same protocol without contrast agent, to determine blood oxygenation level dependent (BOLD) contribution to the MRI changes. Results. Each brain region exhibited a significant graded increase in CBV during the two Hypoxic episodes: 10‐27% of control values at 70% SaO2 , and 26‐38% at 55% SaO2 . There was no difference between regions in their response to Hypoxia. The mean CBV of all regions increased from 3.6 (SD 0.6) to 4.1 (0.6) ml (100 g) ‐1 and to 4.7 (0.7) ml (100 g) ‐1 during the

  • Lactate Accumulation During Moderate Hypoxic Hypoxia in Neocortical Rat Brain
    Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism, 1996
    Co-Authors: Jean-françois Payen, Emmanuelle Lebars, Bernard Wuyam, Bernard Tropini, Jean-louis Pépin, Patrick Levy, Michel Décorps
    Abstract:

    Neocortical metabolism was studied during moderate Hypoxic Hypoxia, reoxygenation, and postmortem periods in anesthetized normocapnic rats using 1H nuclear magnetic resonance (NMR) spectroscopic imaging. Rats were prepared with unilateral common carotid occlusion to determine the ipsilateral metabolic effects of inadequate cerebral blood flow (CBF) response to Hypoxia. No difference in brain metabolism between the two hemispheres was found during the control period. Hypoxic Hypoxia (Pao2 = 54.1 ± 5.8 mm Hg) resulted in a significant rise in neocortical lactate peak in both hemispheres, with an additional marked rise in the clamped side compared to the unclamped side (53 ± 27 vs. 22 ± 13% of postmortem value, p < 0.001). These lactate changes were not reversible within 30 min of reoxygenation in the clamped hemisphere. No changes in neocortical lactate peak were observed while elevating arterial lactate via intravenous lactate infusion without Hypoxia. In addition, Hypoxic Hypoxia resulted in an apparent d...

Chantal Rémy - One of the best experts on this subject based on the ideXlab platform.

  • Measuring hemoglobin oxygen saturation during graded Hypoxic Hypoxia in rat striatum.
    Anesthesia and analgesia, 2006
    Co-Authors: Cécile Julien, Emmanuelle Grillon, Chantal Rémy, Adrian Bradu, Raphaël Sablong, Jacques Derouard, Jean-françois Payen
    Abstract:

    We evaluated in vivo reflectance spectroscopy of visible light as a method to assess brain tissue hemoglobin oxygen saturation in rat striatum (SstrO2). Seven anesthetized and mechanically ventilated rats were subjected to incremental reduction in the fraction of inspired oxygen (Fio2): 0.35, 0.25, 0.15, 0.12, and 0.10, followed by a reoxygenation period (Group 1). At each episode, local changes in SstrO2 and in cerebral blood flow (LCBF) were simultaneously determined in the two striatal regions, using reflectance spectroscopy and laser Doppler flowmetry, respectively. Another group of rats (Group 2, n = 6) was also studied to measure sagittal sinus blood hemoglobin saturation (SssO2) during graded Hypoxic Hypoxia. Corpus striatum exhibited a significant graded decrease in SstrO2, from 38% +/- 17% at Fio2 of 0.35 (control) to 16% +/- 10% at Fio2 of 0.12 and to 13% +/- 7% at Fio2 of 0.10 (P < 0.05), with no difference between the two hemispheres. These local changes in SstrO2 were associated with a significant graded increase in LCBF: 161% +/- 26% of control values and 197% +/- 34% during these 2 Hypoxic episodes, respectively (P < 0.05). All local changes were fully reversed during the reoxygenation period. In Group 2, SssO2 decreased from 38% +/- 8% at Fio2 of 0.35 (control) to 10% +/- 3% at Fio2 of 0.10, closely related to SstrO2 decreasing in Hypoxia. This study shows that reflectance spectroscopy of the visible light in rat striatum could be a possible measure of continuous changes in SstrO2. SssO2 and LCBF measurements during graded Hypoxic Hypoxia indicate that changes in SstrO2 reflect primarily those in brain venous oxygenation.

  • Assessment of vascular reactivity in rat brain glioma by measuring regional blood volume during graded Hypoxic Hypoxia.
    British journal of cancer, 2004
    Co-Authors: Julien C, Jean-françois Payen, Irène Troprès, Régine Farion, Emmanuelle Grillon, Olivier Montigon, Chantal Rémy
    Abstract:

    Assessment of vascular reactivity in rat brain glioma by measuring regional blood volume during graded Hypoxic Hypoxia

Risto A. Kauppinen - One of the best experts on this subject based on the ideXlab platform.

  • Gray matter nulled and vascular space occupancy dependent fMRI response to visual stimulation during Hypoxic Hypoxia
    NeuroImage, 2011
    Co-Authors: Yuji Shen, Rishma Vidyasagar, George M. Balanos, Xavier Golay, Risto A. Kauppinen
    Abstract:

    Two cerebral blood volume (CBV)-weighted fMRI techniques, gray matter nulled (GMN) and vascular space occupancy (VASO)-dependent techniques at spatial resolution of 2 × 2 × 5 mm(3), were compared in the study investigating functional responses in the human visual cortex to stimulation in normoxia (inspired O(2) = 21%) and mild Hypoxic Hypoxia (inspired O(2) = 12%). GMN and VASO signals and T(2)* were quantified in activated voxels. While the CBV-weighted signal changes in voxels activated by visual stimulation were similar in amplitude in both fMRI techniques in both oxygenation conditions, the number of activated voxels during Hypoxic Hypoxia was significantly reduced by 72 ± 22% in GMN fMRI and 66 ± 23% in VASO fMRI. T(2)* prolonged in GMN and VASO activated voxels in normoxia by 1.6 ± 0.5 ms and 1.7 ± 0.5 ms, respectively. In Hypoxia, however, T(2)* shortened in GMN-activated voxels by 0.7 ± 0.6 ms (p < 0.001 relative to normoxia), but prolonged in VASO-activated ones by 1.1 ± 0.6 ms (p < 0.05 relative to normoxia). The data show that the hemodynamic responses to visual stimulation were not affected by Hypoxic Hypoxia, but T(2)* increases by both CBV-weighted fMRI techniques were smaller in activated voxels in Hypoxia. The mechanisms influencing GMN fMRI signal in both oxygenation conditions were explored by simulating effects of the oxygen extraction fraction (OEF) and partial voluming with cerebral spinal fluid (CSF) and white matter in imaging voxels. It is concluded that while GMN fMRI data point to increased, rather than decreased OEF during visual stimulation in Hypoxia, partial voluming by CSF is likely to affect the CBV quantification by GMN fMRI under the experimental conditions used.

  • 31P magnetic resonance spectroscopy study of the human visual cortex during stimulation in mild Hypoxic Hypoxia.
    Experimental brain research, 2008
    Co-Authors: Rishma Vidyasagar, Risto A. Kauppinen
    Abstract:

    Effects of mild Hypoxic Hypoxia on cerebral energy state, as assessed by phosphocreatine (PCr)/γ-ATP and inorganic phosphate (Pi)/(Pi + PCr) ratios and intracellular pH (pHi) in the human visual cortex, were studied using 31P nuclear magnetic resonance spectroscopy (MRS) at 3 T. The working hypothesis that, during compromised O2 availability obtained by Hypoxic Hypoxia, both cerebral energy state and pHi decline due to insufficient O2 supply for energy metabolism was addressed. Under baseline Hypoxic Hypoxia, with blood O2 saturation ranging from 0.95 to 0.83, neither the PCr/γ-ATP and Pi/(Pi + PCr) ratios nor pHi was affected, thus, showing that cerebral energy metabolism was maintained. Contrary to the formulated hypothesis, visual stimulation during Hypoxic Hypoxia influenced neither the indicator ratios for energy state nor pHi in the occipital cortex. Taking these results, together with previous observations showing that cerebral blood flow responses are the same in size both in euoxia and in Hypoxia at this depth (Mintun et al. in Proc Natl Acad Sci USA 98:6859–6864, 2001; Tuunanen et al. in J Cereb Blood Flow Metab 26:263–273, 2006a), it is concluded that O2 delivery to the brain during mild Hypoxic Hypoxia meets the demand by the energy metabolism both under baseline and stimulated states.

Per Thorborg - One of the best experts on this subject based on the ideXlab platform.

  • Effect of Hypoxic Hypoxia and ritanserin on capillary flow and oxygenation in rabbit skeletal muscle
    Acta physiologica Scandinavica, 1994
    Co-Authors: U. Gustafsson, David H. Lewis, Folke Sjöberg, Per Thorborg
    Abstract:

    Gustafsson, U., Sjoberg, F., Lewis, D. H. & Thorborg, P. 1994. Effect of Hypoxic Hypoxia and ritanserin on capillary flow and oxygenation in rabbit skeletal muscle. Acta Physiol Stand 150, 39–45. Received 2 April 1993, accepted 21 July 1993. ISSN 0001–6772. Clinical Research Centre and the Burns Unit, Department of Hand and Plastic Surgery, and Department of Anaesthesiology, University Hospital, Linkoping, Sweden, and Dept of Anesthesiology, University of Rochester Medical Center, NY, USA. This study examined capillary flow and oxygenation in rabbit skeletal muscle during Hypoxic Hypoxia (inspired oxygen fraction = 0.10) and after administration of ritanserin (highly selective 5-Hydroxytryptamine-2-receptor antagonist). Capillary flow (hydrogen clearance) or oxygen pressure was measured with a multiwire micro-electrode which was placed on the surface of the left vastus medialis muscle. For measurement of regional microcirculatory blood flow a laser-Doppler flowmeter probe was placed on the contralateral muscle. An experimental sequence with normoxaemia (arterial Po2 12.5 kPa), followed by hypoxaemia (arterial Po2 3.9 kPa) and thereafter sustained hypoxaemia (arterial Po2 4.0 kPa) during which ritanserin (0.035 mg kg-1 i.v.) was administered, was used. During hypoxaemia a decrease was seen in mean arterial pressure (MAP) by 27%, capillary flow by 25%, muscle oxygen pressure by 32% and laser-Doppler flowmetry (LDF) flow by 24%. After the administration of ritanserin the mean arterial pressure was further reduced by 7%, whereas the capillary flow increased by 59% and the muscle oxygen pressure by 31 %. The LDF flow remained unchanged. These results demonstrate that, in this animal model, a decrease in skeletal muscle capillary flow and oxygenation during hypoxaemia can be reversed by the administration of ritanserin, despite a further reduction in blood pressure.

  • Skeletal muscle capillary flow and oxygenation in Hypoxic Hypoxia: effect of a 5-HT2 receptor antagonist.
    Advances in experimental medicine and biology, 1992
    Co-Authors: U. Gustafsson, David H. Lewis, Per Thorborg
    Abstract:

    Serotonin (5-HT) seems to be essential to mammal life, however, its various actions have hither to been difficult to assess due to their complexity; further more, it is not until the last few years that serotonin receptors have been typed and subtyped. Following this recent development of selective and pure serotonin receptor antagonists, it has been shown that serotonin is involved in the modulation of tissue blood flow and oxygenation in response to various stimuli. Hyperoxemia is known to cause arteriolar vasoconstriction, the disturbed tissue oxygenation and capillary flow in skeletal muscle can be normalized by ketanserin or ritanserin, 5-HT2 receptor antagonists (1,2). The purpose of the present study was to assess skeletal muscle capillary flow and oxygenation during Hypoxic hypoxemia with particular reference to the action of 5-HT2 receptors.

Irène Troprès - One of the best experts on this subject based on the ideXlab platform.

  • Assessment of vascular reactivity in rat brain glioma by measuring regional blood volume during graded Hypoxic Hypoxia.
    British journal of cancer, 2004
    Co-Authors: Julien C, Jean-françois Payen, Irène Troprès, Régine Farion, Emmanuelle Grillon, Olivier Montigon, Chantal Rémy
    Abstract:

    Assessment of vascular reactivity in rat brain glioma by measuring regional blood volume during graded Hypoxic Hypoxia

  • Regional response of cerebral blood volume to graded Hypoxic Hypoxia in rat brain
    British journal of anaesthesia, 2002
    Co-Authors: C. Julien-dolbec, Irène Troprès, Olivier Montigon, H. Reutenauer, A. Ziegler, M. Decorps, Jean-françois Payen
    Abstract:

    Background. The response of cerebral blood flow to Hypoxic Hypoxia is usually effected by dilation of cerebral arterioles. However, the resulting changes in cerebral blood volume (CBV) have received little attention. We have determined, using susceptibility contrast magnetic resonance imaging (MRI), changes in regional CBV induced by graded Hypoxic Hypoxia. Methods. Six anaesthetized rats were subjected to incremental reduction in the fraction of inspired oxygen: 0.35, 0.25, 0.15, and 0.12. At each episode, CBV was determined in five regions of each hemisphere after injection of a contrast agent: superficial and deep neocortex, striatum, corpus callosum and cerebellum. A control group (n=6 rats) was studied with the same protocol without contrast agent, to determine blood oxygenation level dependent (BOLD) contribution to the MRI changes. Results. Each brain region exhibited a significant graded increase in CBV during the two Hypoxic episodes: 10‐27% of control values at 70% SaO2 , and 26‐38% at 55% SaO2 . There was no difference between regions in their response to Hypoxia. The mean CBV of all regions increased from 3.6 (SD 0.6) to 4.1 (0.6) ml (100 g) ‐1 and to 4.7 (0.7) ml (100 g) ‐1 during the