Longitudinal assessment of infarct progression, brain metabolism and behavior following anterior cerebral artery occlusion in rats.

Background: Stroke patients suffering from occlusion of the anterior cerebral artery (ACAo) develop cognitive and executive deficits. Experimental models to investigate such functional impairments and recovery are rare and not satisfyingly validated.

New Method: We stereotactically injected the vasoconstrictor endothelin-1 (ET-1) close to the ACA of rats and assessed magnitude and course of CBF reduction using [(14)C]iodoantipyrine autoradiography and [(15)O]H2O-PET.

Vascular endothelial growth factor promotes pericyte coverage of brain capillaries, improves cerebral blood flow during subsequent focal cerebral ischemia, and preserves the metabolic penumbra.

Background And Purpose: Therapeutic angiogenesis aims at improving cerebral blood flow by amplification of vascular sprouting, thus promoting tissue survival under conditions of subsequent ischemia. It remains unknown whether induced angiogenesis leads to the formation of functional vessels that indeed result in hemodynamic improvements. Observations of hemodynamic steal phenomena and disturbed neurovascular integrity after vascular endothelial growth factor delivery questioned the concept of therapeutic angiogenesis.

Hyperlipidemia attenuates vascular endothelial growth factor-induced angiogenesis, impairs cerebral blood flow, and disturbs stroke recovery via decreased pericyte coverage of brain endothelial cells.

Objective: Therapeutic angiogenesis aims at the promotion of vascular growth, usually under conditions of atherosclerosis. It was unknown how hyperlipidemia, a risk factor that is closely associated with atherosclerosis of brain vessels in humans, influences vascular endothelial growth factor-induced angiogenesis and stroke recovery.

Approach And Results: Wild-type and apolipoprotein-E (ApoE)(-/-) mice were kept on regular or cholesterol-rich diet for mimicking different severities of hyperlipidemia.

Heterozygosity for the mutated X-chromosome-linked L1 cell adhesion molecule gene leads to increased numbers of neurons and enhanced metabolism in the forebrain of female carrier mice.

Mutations in the X-chromosomal L1CAM gene lead to severe neurological deficits. In this study, we analyzed brains of female mice heterozygous for L1 (L1+/-) to gain insights into the brain structure of human females carrying one mutated L1 allele. From postnatal day 7 onward into adulthood, L1+/- female mice show an increased density of neurons in the neocortex and basal ganglia in comparison to wild-type (L1+/+) mice, correlating with enhanced metabolic parameters as measured in vivo.

Conflict Processing in the Rat Brain: Behavioral Analysis and Functional μPET Imaging Using [F]Fluorodeoxyglucose.

Conflicts in spatial stimulus-response tasks occur when the task-relevant feature of a stimulus implies a response toward a certain location which does not match the location of stimulus presentation. This conflict leads to increased error rates and longer reaction times, which has been termed Simon effect. A model of dual route processing (automatic and intentional) of stimulus features has been proposed, predicting response conflicts if the two routes are incongruent.

Oxygen therapy improves energy metabolism in focal cerebral ischemia.

Oxygen therapy (OT) with hyperbaric oxygen (HBO) or normobaric hyperoxia (NBO) improves the oxygenation of penumbral tissue in experimental ischemic stroke. However, whether this results in the improvement of energy metabolism is unclear. We investigated the effect of both OTs on tissue acidosis and on ATP production.

Whiskers area as extracerebral reference tissue for quantification of rat brain metabolism using (18)F-FDG PET: application to focal cerebral ischemia.

Unlabelled: Diseases and dysfunction of the central nervous system are often associated with regional changes in cerebral glucose metabolism, which can be measured in vivo by PET using (18)F-FDG as the tracer. For quantification, the arterial tracer input function must be determined. For rodents in particular, direct measurement of blood radioactivity concentration is scarcely feasible for follow-up of individual animals because of the invasiveness of blood sampling.

Distinct spatiotemporal patterns of spreading depolarizations during early infarct evolution: evidence from real-time imaging.

Experimental and clinical studies indicate that waves of cortical spreading depolarization (CSD) appearing in the ischemic penumbra contribute to secondary lesion growth. We used an embolic stroke model that enabled us to investigate inverse coupling of blood flow by laser speckle imaging (CBF(LSF)) to CSD as a contributing factor to lesion growth already in the early phase after arterial occlusion. Embolization by macrospheres injected into the left carotid artery of anesthetized rats reduced CBF(LSF) in the territories of the middle cerebral artery (MCA) (8/14 animals), the posterior cerebral artery (PCA) (2/14) or in less clearly defined regions (4/14).

Changes of cerebral blood flow during the secondary expansion of a cortical contusion assessed by 14C-iodoantipyrine autoradiography in mice using a non-invasive protocol.

Although changes of cerebral blood flow (CBF) in and around traumatic contusions are well documented, the role of CBF for the delayed death of neuronal cells in the traumatic penumbra ultimately resulting in secondary contusion expansion remains unclear. The aim of the current study was therefore to investigate the relationship between changes of CBF and progressive peri-contusional cell death following traumatic brain injury (TBI). CBF and contusion size were measured in C57Bl6 mice under continuous on-line monitoring of (ETp)CO2 before, and at 15 min and 24 h following controlled cortical impact by 14C-iodoantipyrine autoradiography (IAP-AR; n = 5-6 per group) and by Nissl staining, respectively.

Shut-down of translation, a global neuronal stress response: mechanisms and pathological relevance.

Shut-down of translation is a global stress response required to block synthesis of proteins that cannot be correctly folded and thereby reduce the work load of the folding machinery, a primary target of the pathological process triggered by severe forms of stress. The short-term control of protein synthesis involves alterations in the activity of initiation factors mediated through changes in their phosphorylation states, the alpha subunit of eukaryotic initiation factor 2 being a key player in this process. While the stress-induced shut-down of translation is viewed as a protective response, the inability of vulnerable cells to restore protein synthesis after being exposed to a severe form of stress is a pathological process because it blocks the translation of messages coding for protective proteins required for restoration of function.

Establishing a photothrombotic 'ring' stroke model in adult mice with late spontaneous reperfusion: quantitative measurements of cerebral blood flow and cerebral protein synthesis.

This study sought to establish the photothrombotic 'ring' stroke model with late spontaneous reperfusion in adult mice. By applying a 3.0-mm diameter laser ring-beam (514 nm, 0.

Spreading depression activates unfolded protein response.

Preconditioning is a process where a preceding non-lethal form of stress activates a stress response that protects cells against an otherwise lethal form of stress. Preconditioning can be induced in various ways including short-term ischemia or spreading depression. Here we investigated the effect of 1 h repetitive spreading depression on the unfolded protein response (UPR), a stress response activated under conditions associated with endoplasmic reticulum (ER) dysfunction.

Granulocyte-macrophage colony-stimulating factor-induced arteriogenesis reduces energy failure in hemodynamic stroke.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a powerful arteriogenic factor in the hypoperfused rat brain. To test the pathophysiological relevance of this response, the influence of GM-CSF on brain energy state was investigated in a model of hemodynamic stroke. Sprague-Dawley rats were submitted to three-vessel (bilateral vertebral and unilateral common carotid artery) occlusion (3-VO) to induce unilaterally accentuated brain hypoperfusion.

Characterization of a novel chronic photothrombotic ring stroke model in rats by magnetic resonance imaging, biochemical imaging, and histology.

A novel photothrombotic ring stroke model was characterized by multiparametric magnetic resonance imaging, imaging of cerebral blood flow (CBF), adenosine triphosphate (ATP), pH, and histology. Ischemia was initiated by transosseous irradiation of a predefined brain area intravenously perfused by the photosensitive dye erythrosin B in male Wistar rats. In the region of the primary ring-lesion, the phototoxic reaction caused necrosis reflected by low relative ATP levels (28 +/- 15%), alkalosis (pH: 7.

Immunohistochemical analysis of protein expression after middle cerebral artery occlusion in mice.

The effect of transient focal cerebral ischemia on protein regulation was studied in mice using multiparametric immunohistochemistry. Injury was characterized by measurements of blood flow, regional protein synthesis and terminal transferase biotinylated-dUTP nick end labeling (TUNEL). The proteins studied were selected from a previously established list of differentially regulated proteins and included the GTPases dynamin, RhoB, CAS and Ran BP-1, the transcription factors Nurr1 and p-Stat 6, the protein kinase MAPK p49, the splicing factors SRPK1 and hPrp16, the cell cycle control proteins cyclin B1 and Nek2, the inflammatory proteins FKBP12 and Rag2, the cell adhesion protein paxillin and the folding protein TCP-1.

Therapeutic induction of arteriogenesis in hypoperfused rat brain via granulocyte-macrophage colony-stimulating factor.

Background: Colony-stimulating factors (CSFs) have been shown to effectively induce arteriogenesis in the hindlimb. Moreover, clinical trials demonstrated positive effects of CSFs on arteriogenesis in patients with coronary artery disease. However, patients with cerebrovascular disease have not yet profited from treatments aimed at the growth of brain vessels.

Arteriogenesis in hypoperfused rat brain.

Experimental and clinical studies have provided evidence for spontaneous and therapeutically induced arteriogenesis after occlusion of major peripheral or cardiac vessels. Such evidence is lacking for the cerebrovascular system. In halothane-anesthetized rats, different degrees of brain hypoperfusion were induced by one- to four-vessel occlusion, that is, one or both common carotid arteries in combination with or without bilateral vertebral artery occlusion.

Biochemical changes and gene expression following traumatic brain injury: Role of spreading depression.

The effects of spreading depression-like DC depolarizations on biochemical changes and gene expression were examined following trau-matic neocortical lesions, as induced by transcranial cold injury. The surrounding of traumatic cold lesions was characterized by increased glu-cose and lactate contents, without major disturbances of protein synthesis or energy state. A transient pH decrease by 0.

Mechanisms underlying suppression of protein synthesis induced by transient focal cerebral ischemia in mouse brain.

Transient global cerebral ischemia triggers suppression of the initiation step of protein synthesis, a process which is controlled by endoplasmic reticulum (ER) function. ER function has been shown to be disturbed after transient cerebral ischemia, as indicated by an activation of the ER-resident eIF2alpha kinase PERK. In this study, we investigated ischemia-induced changes in protein levels and phosphorylation states of the initiation factors eIF2alpha, eIF2B epsilon, and eIF4G1 and of p70 S6 kinase, proteins playing a central role in the control of the initiation of translation.

Down-regulation of parkin protein in transient focal cerebral ischemia: A link between stroke and degenerative disease?

Ubiquitylated protein aggregates are characteristic features of neurodegenerative disorders that are also found in acute pathological states of the brain such as stroke. Many of the proteins connected to neurodegenerative diseases play a role in the ubiquitin-proteasomal pathway. Mutation of one of these proteins, the E3 ubiquitin ligase parkin, is the cause of autosomal recessive juvenile Parkinson's disease.

Phosphorylation state, solubility, and activity of calcium/calmodulin-dependent protein kinase II alpha in transient focal ischemia in mouse brain.

During and after middle cerebral artery occlusion in mice, CaMKII alpha protein was irreversibly translocated from the soluble to the Triton X-100-nonsoluble fraction. This decrease in solubility had a strong effect on activity: CaMKII alpha was almost completely inactivated after being translocated. Results from solubilization experiments suggest that different mechanisms underlie the conversion of CaMKII alpha protein from a soluble to a detergent nonsoluble form in ischemic as opposite to nonischemic tissue.

Ischemia induces a translocation of the splicing factor tra2-beta 1 and changes alternative splicing patterns in the brain.

Alternative splice-site selection is regulated by the relative concentration of individual members of the serine-arginine family of proteins and heterogeneous nuclear ribonucleoproteins. Most of these proteins accumulate predominantly in the nucleus, and a subset of them shuttles continuously between nucleus and cytosol. We demonstrate that in primary neuronal cultures, a rise in intracellular calcium concentration induced by thapsigargin leads to a translocation of the splicing regulatory protein tra2-beta1 and a consequent change in splice-site selection.

Ischemic injury in experimental stroke depends on angiotensin II.

Since pharmacological interactions of the renin-angiotensin system appear to alter the neurological outcome of stroke patients significantly, we examined the effect of elevated levels of angiotensin II and the role of its receptor subtype AT1 in brain infarction in transgenic mice after focal cerebral ischemia. Angiotensinogen-overexpressing and angiotensin receptor AT1 knockout mice underwent 1 h or 24 h permanent middle cerebral artery occlusion (MCAO). The current study revealed a much smaller penumbra size, i.