We previously reported that the blood-brain barrier (BBB) function was deteriorated in vessels located in the hippocampus, but not the cerebral cortex, in 3-month-old stroke-prone spontaneously hypertensive rats (SHRSP). Recently published data suggest that matrix metalloproteinase (MMP)-2 and MMP-9 play a critical role in the BBB disruption in stroke or cerebral ischemia. In this study, we examined gene and protein expressions of MMPs in the BBB-damaged hippocampal vessels of 3-month-old SHRSP, in the cerebral cortical vessels without BBB damage of SHRSP, and in the hippocampal and cerebral cortical ones without BBB damage of 3-month-old Wistar Kyoto (WKY) rats. The expressions of MMPs were examined by real-time quantitative reverse transcriptase-PCR (RT-PCR), western blotting and immunohistochemical techniques. The gene and protein expressions of MMP-13 were significantly increased in the hippocampal samples of SHRSP compared with samples without BBB damage, such as cerebral cortical samples of SHRSP or hippocampal samples of WKY. Immunostaining of MMP-13 was seen in the cytoplasm of ED-1-positive perivascular cells in both rats and was colocalized with those of type IV collagen or osteopontin. The type IV collagen was also localized in the basement membrane. These findings indicate that the expression of MMP-13 is increased in BBB-damaged hippocampal vessels in hypertensive SHRSP compared with vessels without BBB impairment in normotensive WKY rats and may be involved in vascular remodeling. Keywords: blood-brain barrier; MMP-13; SHRSP INTRODUCTION A causative role of blood-brain barrier (BBB) impairment is suggested in the pathogenesis of vascular dementia with leakage of serum components from small vessels leading to neuronal and glial damage. 1 To clarify the roles of BBB impairment in vascular dementia, we have examined BBB function in various conditions related to vascular dementia, such as hypertension, acute ischemia with reperfusion, chronic cerebral hypoperfusion and aging with or without memory deficits. [2][3][4] Consequently, among these animal models, the most localized BBB impairment was clearly seen in the hippocampus, but not the cerebral cortex, of 3-month-old spontaneously hypertensive rats (SHR), especially of 3-month-old stroke-prone SHR (SHRSP), 4 which were established by Okamoto and Aoki 5 and are described in detail elsewhere. 6,7 It is known that the neuronal loss occurs with a reduction of gray matter volume in the CA1 subfield and dentate gyrus of the hippocampus in SHR at the age of 6 months or order, indicating that SHR can be a good animal model of vascular

Reported herein is a case of medulloblastoma with myogenic differentiation in a 3-year-old girl who died 1 year after appearance of clinical signs. Magnetic resonance imaging indicated a mass lesion in the cerebellar vermis. She underwent total resection of the tumor, followed by chemotherapy and radiotherapy in the brain and spinal cord. The resected specimen mainly consisted of densely packed cells with round-to-oval highly chromatic nuclei surrounded by scanty cytoplasm and focally of long spindle-shaped cells with elongated nuclei and eosinophilic cytoplasm showing discernible cross-striations. Immunohistochemistry indicated partial expression of synaptophysin in the former area and focal expression of desmin in the latter area. The diagnosis was medulloblastoma with myogenic differentiation, also known as medullomyoblastoma. Autopsy indicated disseminated proliferation of immature neuroglial cells with highly chromatic nuclei and scanty cytoplasm showing partial expression of synaptophysin, neurofilaments, and GFAP, and focal proliferation of round-to-oval immature cells showing immunoreactivity of myoglobin. The tumor cells had large nuclei, frequent mitoses, apoptoses, nuclear molding, and cell wrapping, indicating moderate anaplasia. Their Ki-67 labeling index was 54%. In addition, some tumor cells had double immunopositivity for synaptophysin or neurofilament and myoglobin, suggesting that the neuroectodermal cells may undergo differentiation into rhabdomyoblasts.