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Measurement of Local Partial Pressure of Oxygen in the Brain Tissue under Normoxia and Epilepsy with Phosphorescence Lifetime Microscopy.

Zhang C, Bélanger S, Pouliot P, Lesage F - PLoS ONE (2015)

Bottom Line: In this work a method for measuring brain oxygen partial pressure with confocal phosphorescence lifetime microscopy system is reported.When used in conjunction with a dendritic phosphorescent probe, Oxyphor G4, this system enabled minimally invasive measurements of oxygen partial pressure (pO2) in cerebral tissue with high spatial and temporal resolution during 4-AP induced epileptic seizures.Our results reveal a correlation between the percent change in the pO2 signal during the "initial dip" and the duration of seizure-like activity, which can help localize the epileptic focus and predict the length of seizure.

View Article: PubMed Central - PubMed

Affiliation: École Polytechnique de Montréal, Department of Electrical Engineering, C.P. 6079 succ.Centre-ville, Montreal, Quebec, Canada, H3C 3A7.

ABSTRACT
In this work a method for measuring brain oxygen partial pressure with confocal phosphorescence lifetime microscopy system is reported. When used in conjunction with a dendritic phosphorescent probe, Oxyphor G4, this system enabled minimally invasive measurements of oxygen partial pressure (pO2) in cerebral tissue with high spatial and temporal resolution during 4-AP induced epileptic seizures. Investigating epileptic events, we characterized the spatio-temporal distribution of the "initial dip" in pO2 near the probe injection site and along nearby arterioles. Our results reveal a correlation between the percent change in the pO2 signal during the "initial dip" and the duration of seizure-like activity, which can help localize the epileptic focus and predict the length of seizure.

No MeSH data available.


Related in: MedlinePlus

Obtained pO2 values in tissue near the focus and surround.(a) Grayscale angiogram of cortical surface and locations for pO2 measurement (red: focus; blue: surround). The artery was shown by the red arrows. Scale bar size: 0.2mm (b) Epileptic activity induced a transient dip in tissue pO2 followed by an increase in pO2 in the focus. A sustained increase in pO2 was seen in the surround. The dashed vertical lines show the ictal onset (left) and offset (right). (c) Distribution of percent of initial dip at multiple locations (color dotted) during epileptic activity. The 4-AP injection site is shown by green circle. The artery was shown by the red arrows. Scale bar size: 0.2mm.
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pone.0135536.g006: Obtained pO2 values in tissue near the focus and surround.(a) Grayscale angiogram of cortical surface and locations for pO2 measurement (red: focus; blue: surround). The artery was shown by the red arrows. Scale bar size: 0.2mm (b) Epileptic activity induced a transient dip in tissue pO2 followed by an increase in pO2 in the focus. A sustained increase in pO2 was seen in the surround. The dashed vertical lines show the ictal onset (left) and offset (right). (c) Distribution of percent of initial dip at multiple locations (color dotted) during epileptic activity. The 4-AP injection site is shown by green circle. The artery was shown by the red arrows. Scale bar size: 0.2mm.

Mentions: To study simultaneously changes of tissue oxygenation at the focus and surrounding areas, points were selected both adjacent and distant from injection site in 3 mice (Fig 6A). An example of change in pO2 in the focus and surrounding areas from a single animal is shown in Fig 6B. At the focus, the typical pO2 profile was biphasic with an early dip after ictal onset (deoxygenation), followed by a longer duration increase in pO2 (hyperoxygenation). The early dip in the focus was described in previous papers during seizures [7] and was present in most seizures measured here. At a distance from the ictal focus, the pO2 was monophasic and significantly increased, returning to the baseline at the offset of the seizure. These results were in agreement with tissue oxygen measured by oxygen microelectrodes [33]. To assess the spatial distribution of pO2 around the focus, points were scanned near the focus in the form of a spiral during epileptic activity, where initial dips were measured. Fig 6C shows an example of measured percent of initial dip for different locations overlaid on a grayscale anatomical image. The higher values were obtained near the focus, and pO2 decreased when points were farther away from the focus. These data indicated that the influx of blood into the focus was inadequate to perfuse the hypermetabolic neurons, after which there was a period of hyperperfusion and hyperoxygenation.


Measurement of Local Partial Pressure of Oxygen in the Brain Tissue under Normoxia and Epilepsy with Phosphorescence Lifetime Microscopy.

Zhang C, Bélanger S, Pouliot P, Lesage F - PLoS ONE (2015)

Obtained pO2 values in tissue near the focus and surround.(a) Grayscale angiogram of cortical surface and locations for pO2 measurement (red: focus; blue: surround). The artery was shown by the red arrows. Scale bar size: 0.2mm (b) Epileptic activity induced a transient dip in tissue pO2 followed by an increase in pO2 in the focus. A sustained increase in pO2 was seen in the surround. The dashed vertical lines show the ictal onset (left) and offset (right). (c) Distribution of percent of initial dip at multiple locations (color dotted) during epileptic activity. The 4-AP injection site is shown by green circle. The artery was shown by the red arrows. Scale bar size: 0.2mm.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4549327&req=5

pone.0135536.g006: Obtained pO2 values in tissue near the focus and surround.(a) Grayscale angiogram of cortical surface and locations for pO2 measurement (red: focus; blue: surround). The artery was shown by the red arrows. Scale bar size: 0.2mm (b) Epileptic activity induced a transient dip in tissue pO2 followed by an increase in pO2 in the focus. A sustained increase in pO2 was seen in the surround. The dashed vertical lines show the ictal onset (left) and offset (right). (c) Distribution of percent of initial dip at multiple locations (color dotted) during epileptic activity. The 4-AP injection site is shown by green circle. The artery was shown by the red arrows. Scale bar size: 0.2mm.
Mentions: To study simultaneously changes of tissue oxygenation at the focus and surrounding areas, points were selected both adjacent and distant from injection site in 3 mice (Fig 6A). An example of change in pO2 in the focus and surrounding areas from a single animal is shown in Fig 6B. At the focus, the typical pO2 profile was biphasic with an early dip after ictal onset (deoxygenation), followed by a longer duration increase in pO2 (hyperoxygenation). The early dip in the focus was described in previous papers during seizures [7] and was present in most seizures measured here. At a distance from the ictal focus, the pO2 was monophasic and significantly increased, returning to the baseline at the offset of the seizure. These results were in agreement with tissue oxygen measured by oxygen microelectrodes [33]. To assess the spatial distribution of pO2 around the focus, points were scanned near the focus in the form of a spiral during epileptic activity, where initial dips were measured. Fig 6C shows an example of measured percent of initial dip for different locations overlaid on a grayscale anatomical image. The higher values were obtained near the focus, and pO2 decreased when points were farther away from the focus. These data indicated that the influx of blood into the focus was inadequate to perfuse the hypermetabolic neurons, after which there was a period of hyperperfusion and hyperoxygenation.

Bottom Line: In this work a method for measuring brain oxygen partial pressure with confocal phosphorescence lifetime microscopy system is reported.When used in conjunction with a dendritic phosphorescent probe, Oxyphor G4, this system enabled minimally invasive measurements of oxygen partial pressure (pO2) in cerebral tissue with high spatial and temporal resolution during 4-AP induced epileptic seizures.Our results reveal a correlation between the percent change in the pO2 signal during the "initial dip" and the duration of seizure-like activity, which can help localize the epileptic focus and predict the length of seizure.

View Article: PubMed Central - PubMed

Affiliation: École Polytechnique de Montréal, Department of Electrical Engineering, C.P. 6079 succ.Centre-ville, Montreal, Quebec, Canada, H3C 3A7.

ABSTRACT
In this work a method for measuring brain oxygen partial pressure with confocal phosphorescence lifetime microscopy system is reported. When used in conjunction with a dendritic phosphorescent probe, Oxyphor G4, this system enabled minimally invasive measurements of oxygen partial pressure (pO2) in cerebral tissue with high spatial and temporal resolution during 4-AP induced epileptic seizures. Investigating epileptic events, we characterized the spatio-temporal distribution of the "initial dip" in pO2 near the probe injection site and along nearby arterioles. Our results reveal a correlation between the percent change in the pO2 signal during the "initial dip" and the duration of seizure-like activity, which can help localize the epileptic focus and predict the length of seizure.

No MeSH data available.


Related in: MedlinePlus