Real-time monitoring of ischemic and contralateral brain pO2 during stroke by variable length multisite resonators

Purpose

Electron paramagnetic resonance (EPR) oximetry using variable length multi-probe implantable resonator (IR), was used to investigate the temporal changes in the ischemic and contralateral brain pO₂ during stroke in rats.

Material and methods

The EPR signal to noise ratio (S/N) of the IR with four sensor loops at a depth of up to 11 mm were compared with direct implantation of lithium phthalocyanine (LiPc, oximetry probe) deposits in vitro. These IRs were used to follow the temporal changes in pO₂ at two sites in each hemisphere during ischemia induced by left middle cerebral artery occlusion (MCAO) in rats breathing 30% O₂ or 100% O₂.

Results

The S/N ratios of the IRs were significantly greater than the LiPc deposits. A similar pO₂ at two sites in each hemisphere prior to the onset of ischemia was observed in rats breathing 30% O₂. However, a significant decline in the pO₂ of the left cortex and striatum occurred during ischemia, but no change in the pO₂ of the contralateral brain was observed. A significant increase in the pO₂ of only the contralateral non-ischemic brain was observed in the rats breathing 100% O₂. No significant difference in the infarct volume was evident between the animals breathing 30% O₂ or 100% O₂ during ischemia.

Conclusions

EPR oximetry with IRs can repeatedly assess temporal changes in the brain pO₂ at four sites simultaneously during stroke. This oximetry approach can be used to test and develop interventions to rescue ischemic tissue by modulating cerebral pO₂ during stroke.     

Berberine chloride can ameliorate the spatial memory impairment and increase the expression of interleukin-1beta and inducible nitric oxide synthase in the rat model of Alzheimer's disease

Background  

Berberine is the major alkaloidal component of Rhizoma coptidis, and has multiple pharmacological effects including inhibiting acetylcholinesterase, reducing cholesterol and glucose, lowering mortality in patients with chronic congestive heart failure and anti-inflammation etc. Thus berberine is a promising drug for diabetes, hyperlipemia, coronary artery disease and ischemic stroke etc. The present study was carried out to investigate the effect of berberine chloride on the spatial memory, inflammation factors interleukin-1 beta (IL-1beta) and inducible nitric oxide synthase (iNOS) expression in the rat model of Alzheimer's disease (AD) which was established by injecting Abeta (1–40) (5 microgram) into the rats hippocampuses bilaterally.     

Differences between arterial occlusive and cortical photothrombosis stroke models with magnetic resonance imaging and microtubule-associated protein-2 immunoreactivity

The differences between two models of cerebral ischemia [middle cerebral arterial transection (MCAT) and cortical photothrombosis (PT)] were explored with multiparametric MRI of apparent diffusion coefficient trace (ADCtr), cerebral blood flow (CBF) and T1. Microtubule-associated protein-2 (MAP2) immunoreactivity sections aligned with the MR images in the same coronal plane were used to map the infarct and to guide region-of-interest selection. In ischemic cortex, the larger T1 increase in PT versus MCAT (42+/-7% vs. 16+/-5%) is related to the different character of edema between these models; yet, neither CBF nor ADCtr discriminated between them at 3.5 h, suggesting that different mechanisms of ischemic damage to the brain cells resulted in the same ADCtr value. CBF and ADCtr were depressed in immediately adjacent ischemic border by 27+/-7% and 47+/-10%, respectively, in MCAT but not in PT, suggesting marginal perfusion in MCAT. CBF in homotopic normal cortex in the opposite hemisphere was higher for PT compared with MCAT (199+/-20 and 134+/-10 ml/100 g/min, respectively). Different pathological processes in the two models affect CBF, ADCtr and T1 in a unique, regionally specific manner. The PT model differs substantially from the MCAT and is not a model of cortical ischemia with an appreciable border zone.     

Decreased oxygen saturation in asymmetrically prominent cortical veins in patients with cerebral ischemic stroke

Decreased oxygen saturation in asymmetrically prominent cortical veins (APCV) seen in ischemic stroke has been hypothesized to correlate with an increase of de-oxygenated hemoglobin. Our goal is to quantify magnetic susceptibility to define APCV by establishing a cutoff above which the deoxyhemoglobin levels are considered abnormal. A retrospective study was conducted on 26 patients with acute ischemic stroke in one cerebral hemisphere that exhibited APCV with 30 age- and sex-matched healthy controls. Quantitative susceptibility mapping (QSM) was used to calculate the magnetic susceptibility of the cortical veins. A paired t-test was used to compare the susceptibility of the cortical veins in the left and right hemispheres for healthy controls as well as in the contralateral hemisphere for stroke patients with APCV. The change in oxygen saturation in the APCV relative to the contralateral side was calculated after thresholding the susceptibility using the mean plus two standard deviations of the contralateral side for each individual. The thresholded susceptibility value of the APCVs in the stroke hemisphere was 254 ± 48 ppb which was significantly higher (p < 0.05) than that in the contralateral hemisphere (123 ± 12 ppb) and in healthy controls (125 ± 8 ppb). There was a decrease of oxygen saturation in the APCV ranging from 16% to 44% relative to the veins of the contralateral hemisphere. In conclusion, APCV seen in SWI correspond to reduced levels of oxygen saturation and these abnormal veins can be identified using a susceptibility threshold on the QSM data.     

Perisylvian white matter connectivity in the human right hemisphere

Background  

By using diffusion tensor magnetic resonance imaging (DTI) and subsequent tractography, a perisylvian language network in the human left hemisphere recently has been identified connecting Brocas's and Wernicke's areas directly (arcuate fasciculus) and indirectly by a pathway through the inferior parietal cortex.     

Delayed minocycline inhibits ischemia-activated matrix metalloproteinases 2 and 9 after experimental stroke

Background  

Matrix metalloproteinases 2 and 9 (MMP-2 and MMP-9) are increased in the brain after experimental ischemic stroke in rats. These two proteases are involved with the degradation of the basal lamina and loss of stability of the blood brain barrier that occurs after ischemia and that is associated with thrombolytic therapy in ischemic stroke. Minocycline is a lipophilic tetracycline and is neuroprotective in several models of brain injury. Minocycline inhibits inflammation, apoptosis and extracellular matrix degradation. In this study we investigated whether delayed minocycline inhibits brain MMPs activated by ischemia in a model of temporary occlusion in Wistar rats.     

Enhanced expressions of microvascular smooth muscle receptors after focal cerebral ischemia occur via the MAPK MEK/ERK pathway

Background  

MEK1/2 is a serine/threonine protein that phosphorylates extracellular signal-regulated kinase (ERK1/2). Cerebral ischemia results in enhanced expression of cerebrovascular contractile receptors in the middle cerebral artery (MCA) leading to the ischemic region. Here we explored the role of the MEK/ERK pathway in receptor expression following ischemic brain injury using the specific MEK1 inhibitor U0126.     

Detrimental effects of tropisetron on permanent ischemic stroke in the rat

Background  

Recent in vitro evidence indicates that blockade of 5-hydroxytryptamine (5-HT) receptor 3 (5-HT₃) is able to confer protection in different models of neuronal injury. The purpose of the present study was to investigate the effect of tropisetron, a 5-HT₃ receptor antagonist, on infarct size and neurological score in a model of ischemic stroke induced by permanent middle cerebral artery occlusion (pMCAO) in the rat.     

Longitudinal MRI evaluation of neuroprotective effects of pharmacologically induced hypothermia in experimental ischemic stroke

Pharmacologically induced hypothermia (PIH) shows promising neuroprotective effects after stroke insult. However, the dynamic evolution of stroke infarct during the hypothermic therapy has not been understood very well. In the present study, MRI was utilized to longitudinally characterize the infarct evolution in a mouse model of ischemic stroke treated by PIH using the neurotensin agonist HPI201. Adult male C57BL/6 mice underwent permanent occlusion of the right middle cerebra artery (MCA). Each animal received a vehicle or HPI201 intraperitoneal injection. The temporal changes of stroke lesion were examined using T2-weighted imaging and diffusion-weighted imaging (DWI) in the acute phase (1 − 3h) and 24 h post stroke. Significantly reduced infarct and edema volumes were observed in PIH treated stroke mice, in agreement with TTC staining findings. Also, the TUNEL staining results indicated apoptotic cells were widely distributed among the ischemic cortex in control group but limited in PIH treated mice. Dramatically reduced growth rate of infarction was seen in PIH treated stroke mice. These results demonstrate HPI201 has strong neuroprotection effects during acute stroke. In particular, MRI with the numerical modelling of temporal infarct evolution could provide a unique means to examine and predict the dynamic response of the PIH treatment on infarct evolution.     

Delayed neuronal cell death in brainstem after transient brainstem ischemia in gerbils

Background  

Because of the lack of reproducible brainstem ischemia models in rodents, the temporal profile of ischemic lesions in the brainstem after transient brainstem ischemia has not been evaluated intensively. Previously, we produced a reproducible brainstem ischemia model of Mongolian gerbils. Here, we showed the temporal profile of ischemic lesions after transient brainstem ischemia.     

Hemispheric biases and the control of visuospatial attention: an ERP study

Background  

We examined whether individual differences in hemispheric utilization can interact with the intrinsic attentional biases of the cerebral hemispheres. Evidence suggests that the hemispheres have competing biases to direct attention contralaterally, with the left hemisphere (LH) having a stronger bias than the right hemisphere. There is also evidence that individuals have characteristic biases to utilize one hemisphere more than the other for processing information, which can induce a bias to direct attention to contralateral space. We predicted that LH-biased individuals would display a strong rightward attentional bias, which would create difficulty in selectively attending to target stimuli in the left visual field (LVF) as compared to right in the performance of a bilateral flanker task.     

Src kinase up-regulates the ERK cascade through inactivation of protein phosphatase 2A following cerebral ischemia

Background  

The regulation of protein phosphorylation requires a balance in the activity of protein kinases and protein phosphatases. Our previous data indicates that Src can increase ERK activity through Raf kinase in response to ischemic stimuli. This study examined the molecular mechanisms by which Src activates ERK cascade through protein phosphatases following cerebral ischemia.     

Reduced blood brain barrier breakdown in P-selectin deficient mice following transient ischemic stroke: a future therapeutic target for treatment of stroke

Background  

The link between early blood- brain barrier (BBB) breakdown and endothelial cell activation in acute stroke remain poorly defined. We hypothesized that P-selectin, a mediator of the early phase of leukocyte recruitment in acute ischemia is also a major contributor to early BBB dysfunction following stroke. This was investigated by examining the relationship between BBB alterations following transient ischemic stroke and expression of cellular adhesion molecule P-selectin using a combination of magnetic resonance molecular imaging (MRMI), intravital microscopy and immunohistochemistry. MRMI was performed using the contrast, gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA) conjugated to Sialyl Lewis X (Sle^x) where the latter is known to bind to activated endothelium via E- or P selectins. Middle cerebral artery occlusion was induced in male C57/BL 6 wild-type (WT) mice and P-selectin-knockout (KO) mice. At 24 hours following middle cerebral artery occlusion, T₁ maps were acquired prior to and following contrast injection. In addition to measuring P- and E-selectin expression in brain homogenates, alterations in BBB function were determined immunohistochemically by assessing the extravasation of immunoglobulin G (IgG) or staining for polymorphonuclear (PMN) leukocytes. In vivo assessment of BBB dysfunction was also investigated optically using intravital microscopy of the pial circulation following the injection of Fluorescein Isothiocyanate (FITC)-dextran (MW 2000 kDa).     

Effects of brain polarization on reaction times and pinch force in chronic stroke

Background  

Previous studies showed that anodal transcranial DC stimulation (tDCS) applied to the primary motor cortex of the affected hemisphere (M1_{affected hemisphere}) after subcortical stroke transiently improves performance of complex tasks that mimic activities of daily living (ADL). It is not known if relatively simpler motor tasks are similarly affected. Here we tested the effects of tDCS on pinch force (PF) and simple reaction time (RT) tasks in patients with chronic stroke in a double-blind cross-over Sham-controlled experimental design.     

Iron-dependent formation of reactive oxygen species and glutathione depletion after accumulation of magnetic iron oxide nanoparticles by oligodendroglial cells

Magnetic iron oxide nanoparticles (IONP) are currently used for various neurobiological applications. To investigate the consequences of a treatment of brain cells with such particles, we have applied dimercaptosuccinate (DMSA)-coated IONP that had an average hydrodynamic diameter of 60 nm to oligodendroglial OLN-93 cells. After exposure to 4 mM iron applied as DMSA–IONP, these cells increased their total specific iron content within 8 h 600-fold from 7 to 4,200 nmol/mg cellular protein. The strong iron accumulation was accompanied by a change in cell morphology, although the cell viability was not compromized. DMSA–IONP treatment caused a concentration-dependent increase in the iron-dependent formation of reactive oxygen species and a decrease in the specific content of the cellular antioxidative tripeptide glutathione. During a 16 h recovery phase in IONP-free culture medium following exposure to DMSA–IONP, OLN-93 cells maintained their high iron content and replenished their cellular glutathione content. These data demonstrate that viable OLN-93 cells have a remarkable potential to deal successfully with the consequences of an accumulation of large amounts of iron after exposure to DMSA–IONP.     

Spectral-luminescent manifestation of the damaging action of brain ischemia on blood serum components

With the aid of spectral-luminescent analysis, our hypothesis on the determining role of free-radical oxidation in damage of blood serum components (low-density lipoproteins) in ischemia has been confirmed. An increase in the luminescence intensity of the blood serum of animals that suffered from brain ischemia as against that of healthy animals is registered. Lipoperoxide free-radical damage of phospholipids of the amphipathic layer of low-density lipoproteins after an ischemic procedure has also been confirmed by fluorescent probes (rhodamine 6G and Nile Blue). __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 6, pp. 827–831, November–December, 2005.     

Stability of Zn–Ni–TiO<Subscript>2</Subscript> and Zn–TiO<Subscript>2</Subscript> nanocomposite coatings in near-neutral sulphate solutions

Zn–Ni–TiO₂ and Zn–TiO₂ nanocomposites were prepared by galvanostatic cathodic square wave deposition. X-ray diffraction analysis and scanning electron microscopy revealed that the occlusion of TiO₂ nanoparticles (spherical shaped with diameter between 19.5 and 24.2 nm) promotes the formation of the γ-Ni₅Zn₂₁ phase, changes the preferred crystallographic orientation of Zn from (101) and (102) planes to (002), and decreases the particle size of the metallic matrices. The stability of the nanocomposites immersed in near-neutral 0.05 mold m⁻³ Na₂SO₄ solution (pH 6.2) was investigated over 24 h. The initial open circuit potential for the Zn–Ni–TiO₂ and Zn–TiO₂ coatings were −1.32 and −1.51 V (vs. Hg/Hg₂SO₄), respectively, and changed to −1.10 and –1.49 V (vs. Hg/Hg₂SO₄) after 24 h of immersion. Data extracted from the steady state polarization curves demonstrated that the metal–TiO₂ nanocomposites have, with respect to the metal coatings, a higher corrosion potential in the case of the Zn–Ni alloy composite; a lower corrosion potential in the case of Zn-based nanocomposite albeit the predominant (002) crystallographic orientation; and a lower initial corrosion resistance due to the smaller grain size and higher porosity in the Zn–Ni–TiO₂ and Zn–TiO₂ nanocomposites. Morphological and chemical analyses showed that a thicker passive layer is formed on the surface of the Zn–Ni–TiO₂ and Zn–TiO₂ deposits. After 24 h of immersion in the sulphate solution, the Zn–Ni–TiO₂ coating has the highest corrosion stability due to the double-protective action created by the deposit’s surface enrichment in Ni plus the higher amount of corrosion products.     

Direct EPR Detection of Nitric Oxide in Mice Infected with the Pathogenic Mycobacterium Mycobacterium tuberculosis

It has been shown that treatment of mice preinfected with Mycobacterium tuberculosis with spin NO traps (iron complexes with diethyldithiocarbamate) enables detection of large amounts of NO in internal organs 2 and 4 weeks after infection (up to 55–57 μmol/kg of wet lung tissue accumulated with spin NO traps during 30 min). The animals were infected with the drug-sensitive laboratory strain H37Rv and a clinical isolate nonrespondent to antituberculous drugs (the multidrug-resistant strain of M. tuberculosis) obtained from a patient with an active form of tuberculosis. Two weeks after infection with the multidrug-resistant strain, the NO level in the lungs, spleen, liver and kidney increased sharply concurrently with slight lesions of lung tissue. A reverse correlation, i.e., low level of NO in the lungs and other internal organs and extensive injury of lung tissue, was established for H37Rv-infected mice. Four weeks after infection, NO production in the lungs increased dramatically for both M. tuberculosis strains resulting in 80–84% damage of lung tissue. The lesion is suggested to be due to the development of defense mechanisms in M. tuberculosis counteracting NO effects.     

Immunological impact of magnetic nanoparticles (Ferucarbotran) on murine peritoneal macrophages

Ferucarbotran, a clinically used superparamagnetic iron oxide, is widely developed as a magnetic resonance imaging (MRI) contrast agent and has the potential to improve the monitoring of macrophage recirculation in vivo. However, the biological effect of Ferucarbotran or magnetic nanoparticles (MNPs) on macrophage is not clearly understood yet. This study is aimed to examine the immunological impact of Ferucarbotran toward murine peritoneal macrophages. Cells treated with Ferucarbotran demonstrated a dose–responsive increase of granularity in the cytoplasm. After 24 h of incubation, viability and cytotoxicity in macrophages treated with 200 μg Fe/mL of Ferucarbotran were not affected. Macrophages loaded with Ferucarbotran above 100 μg Fe/mL showed a significant (p < 0.01) increase in cytokine (TNF-α, IL-1β, IL-6) secretion and mRNA expression, followed by nitric oxide (NO) secretion and iNOS mRNA expression. Chemotactic responses of Ferucarbotran-preloaded macrophages toward CX3CL1 were significantly (p < 0.05) lower than those of untreated macrophages. Taking together, Ferucarbotran at high dose (100 μg Fe/mL) could induce murine peritoneal macrophages activation in pro-inflammatory cytokine secretion and NO production.