Stroke penumbra defined by an MRI-based oxygen challenge technique: 2. Validation based on the consequences of reperfusion

Magnetic resonance imaging (MRI) with oxygen challenge (T2* OC) uses oxygen as a metabolic biotracer to define penumbral tissue based on CMRO2 and oxygen extraction fraction. Penumbra displays a greater T2* signal change during OC than surrounding tissue. Since timely restoration of cerebral blood flow (CBF) should salvage penumbra, T2* OC was tested by examining the consequences of reperfusion on T2* OC-defined penumbra. Transient ischemia (109±20 minutes) was induced in male Sprague-Dawley rats (n=8). Penumbra was identified on T2*-weighted MRI during OC. Ischemia and ischemic injury were identified on CBF and apparent diffusion coefficient maps, respectively. Reperfusion was induced and scans repeated. T2 for final infarct and T2* OC were run on day 7. T2* signal increase to OC was 3.4% in contralateral cortex and caudate nucleus and was unaffected by reperfusion. In OC-defined penumbra, T2* signal increased by 8.4%±4.1% during ischemia and returned to 3.25%±0.8% following reperfusion. Ischemic core T2* signal increase was 0.39%±0.47% during ischemia and 0.84%±1.8% on reperfusion. Penumbral CBF increased from 41.94±13 to 116.5±25 mL per 100 g per minute on reperfusion. On day 7, OC-defined penumbra gave a normal OC response and was located outside the infarct. T2* OC-defined penumbra recovered when CBF was restored, providing further validation of the utility of T2* OC for acute stroke management

Stroke penumbra defined by an MRI-based oxygen challenge technique: 1. validation using [14C]2-deoxyglucose autoradiography

Accurate identification of ischemic penumbra will improve stroke patient selection for reperfusion therapies and clinical trials. Current magnetic resonance imaging (MRI) techniques have limitations and lack validation. Oxygen challenge T2* MRI (T2* OC) uses oxygen as a biotracer to detect tissue metabolism, with penumbra displaying the greatest T2* signal change during OC. [14C]2-deoxyglucose (2-DG) autoradiography was combined with T2* OC to determine metabolic status of T2*-defined penumbra. Permanent middle cerebral artery occlusion was induced in anesthetized male Sprague-Dawley rats (n=6). Ischemic injury and perfusion deficit were determined by diffusion- and perfusion-weighted imaging, respectively. At 147±32 minutes after stroke, T2* signal change was measured during a 5-minute 100% OC, immediately followed by 125 μCi/kg 2-DG, intravenously. Magnetic resonance images were coregistered with the corresponding autoradiograms. Regions of interest were located within ischemic core, T2*-defined penumbra, equivalent contralateral structures, and a region of hyperglycolysis. A T2* signal increase of 9.22%±3.9% (mean±s.d.) was recorded in presumed penumbra, which displayed local cerebral glucose utilization values equivalent to contralateral cortex. T2* signal change was negligible in ischemic core, 3.2%±0.78% in contralateral regions, and 1.41%±0.62% in hyperglycolytic tissue, located outside OC-defined penumbra and within the diffusion abnormality. The results support the utility of OC-MRI to detect viable penumbral tissue follow

Pericentromeric location of the telomeric DNA sequences on the European grayling chromosomes

The chromosomal characteristics, locations and variations of the C-band positive heterochromatin and telomeric DNA sequences were studied in the European grayling karyotype (Thymallus thymallus, Salmonidae) using conventional C-banding, endonucleases digestion banding, silver nitrate (AgNO3), chromomycin A(3) and 4',6-diamidino-2-phenylindole staining techniques as well as fluorescence in situ hybridization (FISH) and primed in situ labelling. Original data on the chromosomal distribution of segments resistant to AluI restriction endonuclease and identification of the C-banded heterochromatin presented here have been used to characterize the grayling karyotype polymorphism. Structural and length polymorphism of the chromosome 21 showing a conspicuous heterochromatin block adjacent to the centromere seems to be the result of the deletion and inversion. Two pairs of nuclear organizer regions (NOR)-bearing chromosomes were found to be polymorphic in size and displaying several distinct forms. FISH with telomeric peptide nucleic acid probe enabled recognition of the conservative telomeric DNA sequences. The karyotype of the thymallid fish is thought to experienced numerous pericentric inversions and internal telomeric sites (ITSs) observed at the pericentromeric regions of the six European grayling metacentric chromosomes are likely relics of the these rearrangements. None of the ITS sites matched either chromosome 21 or NOR bearing chromosomes.University of Warmia and Mazury in Olsztyn, Poland (0804.0809)info:eu-repo/semantics/publishedVersio

Predictors of functional outcome vary by the hemisphere of involvement in major ischemic stroke treated with intra-arterial therapy: a retrospective cohort study

<p>Abstract</p> <p>Background</p> <p>Conflicting data exists regarding the effect of hemispheric lateralization on acute ischemic stroke outcome. Some of this variability may be related to heterogeneous study populations, particularly with respect to the level of arterial occlusion. Furthermore, little is known about the relationship between stroke lateralization and predictors of outcome. The purpose of this study was to characterize the impact of stroke lateralization on both functional outcome and its predictors in a well-defined population of anterior circulation proximal artery occlusions treated with IAT.</p> <p>Methods</p> <p>Thirty-five consecutive left- and 35 consecutive right-sided stroke patients with intracranial ICA and/or MCA occlusions who underwent IAT were retrospectively analyzed. Ischemic change on pre-treatment imaging was quantified. Reperfusion success was graded using the Mori scale. Good outcome at three months was defined as an mRS ≤ 2. Left- and right-sided strokes were compared for outcome and its predictors.</p> <p>Result</p> <p>Of 70 patients with median NIHSS score of 18 (IQR, 14-21), 19 (27.1%) had a good outcome. There were 21 terminal ICA and 49 MCA occlusions. There was no difference in the rate of good outcomes between left- (n = 9) and right-sided (n = 10) strokes (p = 0.99). There were no significant differences in occlusion level, age, ischemic change on initial imaging and degree of reperfusion between left- and right-sided strokes. Left-sided strokes had higher baseline NIHSS scores (p = 0.02) and lower admission SBP (p = 0.009). Independent predictors of outcome for left-sided strokes were NIHSS (p = 0.0002) and reperfusion (p = 0.006), and for right-sided strokes were age (p = 0.002) and reperfusion (p = 0.003). In univariate analysis, pre-treatment ischemic change on NCCT was associated with outcome only for left-sided strokes (p = 0.05).</p> <p>Conclusions</p> <p>In anterior circulation proximal artery occlusions treated with IAT, hemispheric lateralization influences the clinical and imaging predictors of outcome. Most notably, NIHSS predicts outcome only for the left-sided strokes in this population. This finding has important implications for outcome prediction in the acute setting and indicates a need for stroke severity scales more sensitive to right hemispheric deficits.</p