Journal of neuropathology and experimental neurology
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J. Neuropathol. Exp. Neurol. · Apr 2003
ReviewSignaling of cell death and cell survival following focal cerebral ischemia: life and death struggle in the penumbra.
Focal ischemia by middle cerebral artery occlusion (MCAO) results in necrosis at the infarct core and activation of complex signal pathways for cell death and cell survival in the penumbra. Recent studies have shown activation of the extrinsic and intrinsic pathways of caspase-mediated cell death, as well as activation of the caspase-independent signaling pathway of apoptosis in several paradigms of focal cerebral ischemia by transient MCAO to adult rats and mice. The extrinsic pathway (cell-death receptor pathway) is initiated by activation of the Fas receptor after binding to the Fas ligand (Fas-L); increased Fas and Fas-L expression has been shown following focal ischemia. ⋯ Recent studies have shown the mitochondrial release of other factors; Smac/DIABLO (Smac: second mitochondrial activator of caspases: DIABLO: direct IAP binding protein with low pI) binds to and neutralizes the effects of the X-linked inhibitor of apoptosis (XIAP). Finally, apoptosis-inducing factor (AIF) translocates to the mitochondria and the nucleus following focal ischemia and produces peripheral chromatin condensation and large-scale DNA strands, thus leading to the caspase-independent cell death pathway of apoptosis. Delineation of the pro-apoptotic and pro-survival signals in the penumbra may not only increase understanding of the process but also help to rationalize strategies geared to reducing brain damage targeted at the periphery of the infarct core.
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J. Neuropathol. Exp. Neurol. · Mar 2003
Comparative StudyInsulin deficiency rather than hyperglycemia accounts for impaired neurotrophic responses and nerve fiber regeneration in type 1 diabetic neuropathy.
Diabetic polyneuropathy (DPN) shows more severe functional and structural changes in type 1 than in type 2 human and experimental diabetes. We have previously suggested that these differences may be due to insulin and/or C-peptide deficiencies in type 1 diabetes. To further explore these differences between type I and type 2 DPN, we examined factors underlying nerve fiber regeneration in the hyperinsulinemic type 2 BB/Z-rat and compared these with previous data obtained from the iso-hyperglycemic, insulin and C-peptide-deficient type 1 diabetic BB/Wor-rat. ⋯ Furthermore, type 2 BB/Z-rats showed the normal downregulation of low and medium molecular neurofilament (NF-L and NF-M, respectively), which did not occur in type 1 BB/Wor-rats. These findings were associated with significantly milder abnormalities in axonal elongation and caliber growth of regenerating fibers in type 2 compared to type 1 diabetic rats. These data suggest that impaired insulin signaling in type 1 diabetic nerve may be of greater significance in the regulation of neurotrophic and neurocytoskeletal protein synthesis than hyperglycemia in explaining the differences in nerve fiber regeneration between type 2 and type 1 diabetes.
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J. Neuropathol. Exp. Neurol. · Feb 2003
Ependymal cell reactions in spinal cord segments after compression injury in adult rat.
Recently, it has been suggested that neural stem cells and neural progenitor cells exist in the ependyma that forms the central canal of the spinal cord. In this study, we produced various degrees of thoracic cord injury in adult rats using an NYU-weight-drop device, assessed the degree of recovery of lower limb motor function based on a locomotor rating scale, and analyzed the kinetics of ependymal cell proliferation and differentiation by proliferating cell nuclear antigen (PCNA), nestin, glial fibrillary acidic protein (GFAP), or GAP-43 immunostaining. ⋯ No apoptotic cells in the ependyma were detectable by the TUNEL method. These results indicate that the ependymal cells of the spinal central canal are themselves multipotent, can divide and proliferate according to the severity of injury, and differentiate into reactive astrocytes within the ependyma without undergoing apoptosis or cell death.
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J. Neuropathol. Exp. Neurol. · Dec 2002
Genetic alterations commonly found in diffusely infiltrating cerebral gliomas are rare or absent in pleomorphic xanthoastrocytomas.
Pleomorphic xanthoastrocytoma (PXA) is a rare, usually well-circumscribed and superficially located neoplasm that preferentially arises in the cerebral cortex of children and young adults. The molecular aberrations that are associated with these tumors have not been studied systematically so far. We here report on a molecular genetic analysis of 62 PXAs (46 PXAs of World Health Organization [WHO] grade II and 16 PXAs with anaplastic features) for alterations of 5 candidate genes known to be frequently aberrant in diffusely infiltrating astrocytic gliomas, i.e. ⋯ Further analysis of 10 PXAs for inactivation of the CDKN2A. p14(ARF), and CDKN2B (p15(INK4b)) genes on 9p21 did not reveal any homozygous deletion, mutation, promoter hypermethylation, or complete loss of mRNA expression. Taken together, our results indicate that the chromosomal and genetic aberrations in PXAs are different from those typically associated with the diffusely infiltrating astrocytic and oligodendroglial gliomas. These genetic differences likely contribute to the more favorable behavior of PXAs and may be helpful for the molecular differential diagnosis of cerebral gliomas.
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J. Neuropathol. Exp. Neurol. · Sep 2002
Differential expression of vascular endothelial growth factor-A (VEGF-A) and VEGF-B after brain injury.
Our previous study demonstrated that vascular endothelial growth factor (VEGF), now referred to as VEGF-A, plays a significant role in blood-brain barrier (BBB) breakdown and angiogenesis after brain injury. In this study, VEGF-A expression was compared with that of VEGF-B in the rat cortical cold injury model over a period of 6 hours to 6 days post-injury. VEGF-A and VEGF-B mRNA were detected by in situ hybridization and their protein was detected by immunohistochemistry. ⋯ After brain injury, there was increased immunoreactivity for VEGF-B at the lesion site, this protein being present in the endothelium and vascular smooth muscle cells of pial vessels, in inflammatory cells, and later in proliferating endothelial cells, endothelium of neovessels, and astrocytes. Lesion vessels showing BBB breakdown to fibronectin showed endothelial VEGF-A protein but not VEGF-B protein. Constitutive expression of VEGF-B in normal endothelium suggests that it may have a role in maintenance of the BBB in steady states, while its induction at both the gene and protein level post-injury indicates that it has an essential role in angiogenesis and the repair processes after brain injury.