Podcasts about rcbf

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2022.08.30.505941v1?rss=1 Authors: Wong, A., Bhuiyan, M. I. H., Rothman, J., Drew, K., Pourrezaei, K., Sun, D., Barati, Z. Abstract: Timely and sensitive in vivo estimation of ischemic stroke-induced brain infarction are necessary to guide diagnosis and evaluation of treatments efficacy. The gold standard for estimation of the cerebral infarction volume is magnetic resonance imaging (MRI), which is expensive and not readily accessible. Measuring regional cerebral blood flow (rCBF) with Laser Doppler flowmetry (LDF) is the status quo for confirming reduced blood flow in experimental ischemic stroke models. However, rCBF reduction following cerebral artery occlusion often does not correlate with subsequent infarct volume. In the present study, we employed the continuous-wave near infrared spectroscopy (NIRS) technique to monitor cerebral oxygenation during 90 min of the intraluminal middle cerebral artery occlusion (MCAO) in Sprague-Dawley rats (n=8, male). The NIRS device consisted of a controller module and an optical sensor with two LED light sources and two photodiodes making up two parallel channels for monitoring left and right cerebral hemispheres. Optical intensity measurements were converted to deoxyhemoglobin (Hb) and oxyhemoglobin (HbO2) changes relative to a 2-min window prior to MCAO. Area under the curve (auc) for Hb and HbO2 was calculated for the 90-min occlusion period for each hemisphere (ipsilateral and contralateral). To obtain a measure of total ischemia, auc of the contralateral side was subtracted from the ipsilateral side resulting in {Delta}Hb and {Delta}HbO2 parameters. Infarct volume (IV) was calculated by triphenyl tetrazolium chloride (TTC) staining at 24h reperfusion. Results showed a significant negative correlation (r = -0.81, p = 0.03) between {Delta}Hb and infarct volume. In conclusion, our results show feasibility of using a noninvasive optical imaging instrument, namely NIRS, in monitoring cerebral ischemia in a rodent stroke model. This cost-effective, non-invasive technique may improve the rigor of experimental models of ischemic stroke by enabling in vivo longitudinal assessment of cerebral oxygenation and ischemic injury. Copy rights belong to original authors. Visit the link for more info Podcast created by PaperPlayer

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Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.09.02.280024v1?rss=1 Authors: Just, N., Adriaensen, H., Chevillard, P.-M., Batailler, M., Dubois, J.-P., Migaud, M. Abstract: Biomedical investigations in clinically relevant animal models is of crucial interest for faster and appropriate transfer to human. The ovine model has already demonstrated its potential compared to rodents and non-human primates (NHP) in various studies: sheep possess a gyrencephalic brain, captivity is not an issue and can undergo magnetic resonance imaging (MRI) in routine clinical scanners (1.5T, 3T) under identical conditions using similar techniques to humans. To date, the effects of anesthesia have been poorly explored and only few functional MRI (fMRI) studies were conducted in sheep. Here, Blood Oxygen Level dependent fMRI and perfusion MRI were conducted in lambs and adult ewes at 3 T. Robust but weak BOLD responses to visual stimulation were found in the lateral geniculate nucleus (LGN) up to 3% isoflurane anaesthesia. BOLD responses were weaker in adult sheep than in lambs while relative cerebral blood volumes (rCBV) and relative cerebral blood flows (rCBF) were significantly higher in lambs than in adult sheep for both gray and white matter in accordance with previous findings in the human. Assessment of functional responses in healthy individuals under adequate physiological conditions is essential for robust translational studies. Copy rights belong to original authors. Visit the link for more info

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Background: Cerebral edema is an important risk factor for death and poor outcome following subarachnoid hemorrhage (SAH). However, underlying mechanisms are still poorly understood. Matrix metalloproteinase (MMP)-9 is held responsible for the degradation of microvascular basal lamina proteins leading to blood-brain barrier dysfunction and, thus, formation of vasogenic cerebral edema. The current study was conducted to clarify the role of MMP-9 for the development of cerebral edema and for functional outcome after SAH. Methods: SAH was induced in FVB/N wild-type (WT) or MMP-9 knockout (MMP-9(-/-)) mice by endovascular puncture. Intracranial pressure (ICP), regional cerebral blood flow (rCBF), and mean arterial blood pressure (MABP) were continuously monitored up to 30 min after SAH. Mortality was quantified for 7 days after SAH. In an additional series neurological function and body weight were assessed for 3 days after SAH. Subsequently, ICP and brain water content were quantified. Results: Acute ICP, rCBF, and MABP did not differ between WT and MMP-9(-/-) mice, while 7 days' mortality was lower in MMP-9(-/-) mice (p = 0.03; 20 vs. 60%). MMP-9(-/-) mice also exhibited better neurological recovery, less brain edema formation, and lower chronic ICP. Conclusions: The results of the current study suggest that MMP-9 contributes to the development of early brain damage after SAH by promoting cerebral edema formation. Hence, MMP-9 may represent a novel molecular target for the treatment of SAH. Copyright (C) 2011 S. Karger AG, Basel

Introduction: Stroke is the third leading cause of death, and is the leading cause of disabilities worldwide. Although stroke may result from localized cerebral ischemia, intracerebral hemorrhage, subarachnoid hemorrhage or venous sinus thrombosis, ischemic stroke is the most frequently cause of the total cases. In ischemic stroke, occlusion of the MCA or its branches accounts for more than 3/4 of infarcts and two thirds of all first strokes. The main mechanisms causing ischemic strokes are embolism and arterial thromboembolism. No matter what the mechanism an ischemic stroke is, they eventually lead to a focal reduction of perfusion in the brain. In the hyperacute stage the recognition of the ischemia using both clinical assessment and routine neuroimaging technique implies some uncertainties, which in turn makes it difficult to predict the outcome, either to improve or to reverse spontaneously, to persist or worsen. The concept of diffusion/perfusion mismatch attracted great attention since it may represent the tissue at risk or at least an index of penumbra. Our interest was to investigate whether the hemodynamic parameters had correlation with clinical severity and if they were useful for prediction of outcome in the mismatch region. Since diffusion/perfusion mismatch was recognized as a simple and feasible means to identify the ischemic penumbra, we evaluated the hemodynamic parameters in acute stroke patients and compared these parameter to the stroke scale NIHSS and to the outcome score MRS to investigate our hypothesis. Materials and Methods: 35 acute stroke patients (male:female=20:15, age: 61.3±15.2 years) who met the study inclusion and exclusion criteria were selected. Significant cerebrovascular risk factors were recorded in 27 patients. The NIHSS assessment was immediately performed at the patients’ admission by a neurologist. Functional outcome was measured on the day of hospital discharge following MRS. Routine MRI sequences and DWI and PWI (dynamic susceptibility contrast-enhanced [DSC] imaging) were employed in our patients study. The perfusion maps were processed with MEDx® and the parameters were obtained by identifying ROIs on both ischemic core and mismatch region, and the normal mirror region. Relative values of the hemodynamic perfusion parameters were used in the evaluation. Statistic treatment was used to test the significance of the result. Results: The NIHSS score ranged from 0 to 19 (10.2±4.4) and the outcome MRS scale ranged from 0 to 6 (mean: 3.23). Between the good outcome group (MRS 0 to 3) and the poor outcome group (MRS 4 to 6), time to scan, type of treatment, DW/PW volume ratio, and age and female/male ratio did not show significant differences. In ischemic core: rCBF showed a remarkable decrease in all patients on average by 59.3±33.7% (range: 23.2 - 97.4%). rCBV decreased in 29 patients by 41.7±23.7% (range 19.6 - 55.6%), while 6 patients showed an increase of rCBV by 60.4±57.1% (range 0.7 -139%). The mean rCBV change of the entire group was 26.3±52.5%. MTT, TTP and T0 prolonged for 4.7 (SD=15.1), 2.8 (SD=12.9) and 0.5 (SD=10.4) seconds, respectively. In mismatch region: rCBF decreased in 15 patients by 26.2±19.9% (range: 5.3-58.4%) and increased in 20 patients by 35±23.2% (range: 6.8–74.4%). The change of the rCBF of the whole patients group was 5.8±38.4%. rCBV decreased in 7 patients by 14.7±16.5% (range: 0.8-44.5%) and increased in 28 patients by 39.5±36% (range: 2.2-91.1%). The mean change of the rCBV of the whole group was 19.9±31.2%. The mean value of MTT, TTP and T0 prolonged for 2.7 (SD=8.5), 3.2 (SD=5.2) and 1.3 (SD=4.2) seconds respectively. In both core and mismatch region, rCBF showed statistically significant regression to MRS. The more the rCBF decreased the higher the MRS (poor outcome) was. Also, the MTT delay in the core region was significantly related to MRS. TTP delay, in both core and mismatch region, was related to both NIHSS and MRS significantly. No statistic significance was found comparing CBV and T0 in relation with NIHSS or MRS. Conclusion: The hemodynamic parameters derived from perfusion MR imaging may be helpful adjunct to predict the outcome and severity in acute stroke patients. In mismatch region, the rCBF and TTP are predictive for the stroke outcome.

Untersuchung über die Aminosäure L-Arginin/Stickstoffmonoxid als Vasodilatator in der Penumbra einer transienten fokalen zerebralen Ischämie bei der Ratte. Methode: Hierzu wurde bei narkotisierten, beatmeten Ratten der rCBF während und nach fokaler Ischämie und Reperfusion (Fadenmodell) mit der LDF-Methode simultan in beiden Hemisphären gemessen. Untersucht wurde der Einfluß auf den rCBF von L-Arginin, des NOS-Hemmers L-Nitro-Arginin und CO2 in der Reperfusionsphase bei unterschiedlicher Länge der Ischämie (5 und 20 min). Ergebnis: Es konnte gezeigt weren, daß eine Hyperkapnie und L-Arginin den CBF im nichtischämischen Hirn erhöhten. D-Arginin veränderte den CBF nicht. In der Reperfusionsphase nach 20-minütiger Ischämie ist die CBF-Reaktion auf L-Arginin und Hyperkapnie signifikant reduziert. Eine 5-minütige Ischämie hatte keinen Einfluß. Eine Vorbehandlung mit L-NA, einem unselektivem NOS-Inhibitor, stellte die Reaktivität auf L-Arginin nach 20-minütiger Ischämie teilweise wieder her, nicht jedoch die Hyperkapnieantwort. Schlußfolgerung: Der Vasodilatator L-Arginin hatte nur nach sehr kurzfristigen Ischämien eine Verbesserung der Durchblutung zur Folge und erscheint als klinische Therapie nicht erfolgversprechend. Allerdings zeigen die Versuche mit L-NA, daß der Verlust der Vasoreaktivität nach längerdauernder Ischämie nicht einer generellen Vasoparalyse gleich kommt, sondern selektiv beeinflussbar ist. Dies sollte in weiteren Versuchen genauer untersucht werden.

The aims of the present study were to investigate regional cerebral blood flow (rCBF) in heroin-dependent patients during withdrawal and to assess the relation between these changes and duration of heroin consumption and withdrawal data. The rCBF was measured using brain SPECT with Tc-99m-HMPAO in 16 heroin-dependent patients during heroin withdrawal. Thirteen patients received levomethadone at the time of the SPECT scans. The images were analyzed both visually and quantitatively, a total of 21 hypoperfused brain regions were observed in 11 of the 16 patients. The temporal lobes were the most affected area, hypoperfusions of the right and left temporal lobe were observed in 5 and 5 patients, respectively. Three of the patients had a hypoperfusion of the right frontal lobe, 2 patients showed perfusion defects in the left frontal lobe, right parietal lobe and left parietal lobe. The results of the quantitative assessments of the rCBF were consistent with the results of the qualitative findings. The stepwise regression analysis showed a significant positive correlation (r = 0.54) between the dose of levomethadone at the time of the SPECT scan and the rCBF of the right parietal lobe. Other significant correlations between clinical data and rCBF were not found. The present results suggest brain perfusion abnormalities during heroin withdrawal in heroin-dependent patients, which are not due to the conditions of withdrawal.