Yasuaki Kokubo

Mice overexpressing rat heat shock protein 70 are protected against cerebral infarction

Increased expression of heat shock protein 70 (HSP70) in the brain has been extensively documented in association with a variety of insults, including ischemia, and is suggested to play a role in cell survival and recovery after ischemic injury. To more directly assess the protective role of HSP70 during ischemic brain damage, we used transgenic mice overexpressing the rat HSP70 (HSP70tg mice). In contrast to wild‐type (wt) littermates, high levels of HSP70 messenger RNA and protein were detected in brains of HSP70tg mice under normal conditions, and immunohistochemical analysis revealed primarily neuronal expression of HSP70. Heterozygous HSP70tg mice and their wt littermates were subjected to permanent focal cerebral ischemia by intraluminal blockade of the middle cerebral artery. Cerebral infarction after 6 hours of ischemia, as evaluated by Nissl staining, was significantly less in HSP70tg mice compared with wt mice. This reduction in infarction volume in HSP70tg mice was not attributable to an altered cardiovascular anatomy or to initial differences in body temperature or hemodynamic parameters. The HSP70tg mice were still protected against cerebral infarction 24 hours after permanent focal ischemia. The data suggest that HSP70 can markedly protect the brain against ischemic damage and that approaches aimed at inducing HSP70 may lead to new therapeutic interventions in cerebrovascular injuries. Ann Neurol 2000;47:782–791

Temporal profile of neurogenesis in the subventricular zone, dentate gyrus and cerebral cortex following transient focal cerebral ischemia

Abstract Background: In the adult mammalian brain, it is considered that neurogenesis persists in limited regions such as the hippocampal dentate gyrus (DG) and the subventricular zone (SVZ) of the lateral ventricle. On the other hand, neurogenesis in the cortex after cerebral ischemia and its role in post-stroke recovery have not been clarified yet. In this study, we investigated neurogenesis in the cortex and the spatiotemporal profile of neural progenitors in SVZ and DG of rats subjected to transient focal cerebral ischemia. Materials and methods: Male Sprague–Dawley rats (270–300 g) were subjected to 60 minute middle cerebral artery occlusion. Proliferating cells were labeled by the cumulative administration of BrdU 1, 2, 3, 4, 6 and 8 weeks after ischemia induction (at weeks 1–4, 6 and 8). Double labeling was also performed with antibodies against BrdU and NeuN. Results: BrdU-positive cells proliferated in DG and SVZ of the bilateral hemispheres, and their proliferation peaked at week 3 in SVZ and at week 4 in DG. In the peri-infarct zone of cerebral cortex, BrdU-positive cells co-expressed NeuN from weeks 3 to 8. Conclusion: Neurogenesis was observed in the cerebral cortex and proliferation of neural progenitors occurred in SVZ and DG of rats subjected to transient focal cerebral ischemia. Our data might indicate that endogenous dormant neural stem cells residing in the cortex were activated by ischemic insult to induce the proliferation of neural progenitors and differentiation into mature neurons.

The alterations of oligodendrocyte, myelin in corpus callosum, and cognitive dysfunction following chronic cerebral ischemia in rats.

Although the white matter lesions, so called leuko-araiosis, often seen in elderly people have been gaining attention due to their association with cognitive dysfunction (CD) and high risk of incident stroke, the pathological significance of these lesions still remains controversial. Therefore, in the present study, we investigated the alterations in oligodendrocytes (OLG), including oligodendrocytes progenitor cells (OPCs), myelin, and CD following chronic cerebral ischemia in rats. SD rats were subjected to bilateral common carotid artery occlusion. Immunohistochemical staining was performed at 2, 4, 6, 8, and 12weeks after the induction of ischemia with anti-NG2 (OPCs), anti-GST-π (OLG), and anti-MBP antibodies in paramedian corpus callosum (CC). CD was assessed by the Morris water maze test. There was a significant decrease in the number of GST-π positive cells at 2weeks after the start of ischemia compared with that seen in the sham group. There was a significant increase of the number of NG2 positive cells at 4weeks in the ischemia group compared with the sham group. In the ischemic group, the amount of MBP was observed to have decreased significantly at each time point compared with the sham group. CD was observed in the ischemic group than that in the sham group at all time points. Our results indicate that remyelination is strongly correlated with the recovery of cognitive dysfunction following chronic cerebral ischemia.

Differential cerebral protein synthesis and heat shock protein 70 expression in the core and penumbra of rat brain after transient focal ischemia

OBJECTIVEThe purpose of this study was to correlate the cerebral protein synthesis (CPS) reductions in the ischemic core and penumbra with the metabolic stress response indicated by heat shock protein 70 (HSP70) synthesis. METHODSRats were subjected to 90 minutes of temporary focal cerebral ischemia produced by occlusion of the middle cerebral artery, using the endovascular suture model. Regional CPS was qualitatively evaluated, with [35S]methionine autoradiography, after reperfusion for 2 to 72 hours. The observed changes were correlated with HSP70 immunoreactivity, as assessed in the same brain sections. The ischemic core in the striatum was characterized by HSP70 expression only in endothelial and/or glial cells, with an absence of expression in neurons. The penumbra was delineated as the cortical middle cerebral artery territory region in which HSP70 was also expressed in metabolically stressed neurons. RESULTSAfter 2 hours of reperfusion, CPS was reduced to 30 ± 16% of the homologous contralateral hemisphere value in the core and to 75 ± 22% in the penumbra (P < 0.05). This difference was still present at 72 hours, when CPS values were 62 ± 21% and 98 ± 29% of the nonischemic contralateral hemisphere values in the core and penumbra, respectively (P < 0.05). CONCLUSIONPersistent inhibition of CPS in regions in which neuronal HSP70 expression is absent may distinguish core areas of infarction from penumbral regions in which neuronal HSP70 is present, which eventually recover from sublethal metabolic stress during reperfusion after temporary focal ischemia.

Surgical resection of tumors located in subcortex of language area.

SummaryObject. Although functional mapping facilitates the planning of surgery in and around eloquent areas, the resection of tumors adjacent to language areas remains challenging. In this report, we took notice that the language areas (Broca’s and Wernicke’s) present at the perisylvian fissure. We posit that if there is non-essential language area on the inner surface of the Sylvian fissure, safe tumor resection may be possible even if the tumor is located under the language cortex. Methods. The study population consisted of 5 patients with intrinsic brain tumors (frontal glioma, n = 3; temporal cavernous angioma, n = 1; primary malignant central nervous system lymphoma, n = 1) located in the perisylvian subcortex, in the language-dominant hemisphere. All patients underwent awake surgery and we performed intra-operative bipolar cortical functional language mapping. When the tumor was located under the language area, the Sylvian fissure was opened and the inner surface of the opercular cortex was exposed with the patient asleep, and additional functional mapping of that cortex was performed. This enabled us to remove the tumor from the non-functioning cortex.In our series, 4 of 5 patients had not language function on the inner surface of the operculum. Only one patient, a 52-year-old man with frontal glioblastoma (Case 3) had language function on the inner surface of the frontal operculum. Conclusion. We suggest that even perisylvian tumors located in the subcortex of the language area may be resectable via the nonfunctioning intrasylvian cortex by a transopercular approach without resultant language dysfunction.

An esophageal neuroendocrine tumor metastatic to the pineal region

With the aging of society, the number of patients with cancer has been increasing, and cases of metastatic brain tumors have also been increasing. Autopsy studies to date have reported metastatic brain lesions in 10–15 % of cancer patients. The clinical incidence of metastatic brain lesions has been also reported to be 6–10 %. Primary tumors with a high incidence in adults include lung cancer (small cell carcinoma, adenocarcinoma), breast cancer, renal cell carcinoma, colon cancer, and malignant melanoma. However, the primary tumor is unknown in about 10 % of patients with metastatic brain lesions [1–3]. The presence of metastatic brain lesions indicates an advanced stage (stage 4) of the primary cancer and a poor prognosis. However, various neurological symptoms due to an intracranial tumor or due to treatment itself can also often markedly decrease QOL. Research on the treatment of metastatic brain tumors is being conducted at many institutions, and it is important not to impair QOL. A multicenter collaborative study of metastatic brain tumors is now also being conducted in Japan. Most metastatic brain tumors are located in the cerebral hemispheres, but a few occur in the cerebellum or meninges. However, pineal region metastases are very rare; according to recent statistics, they account for only 0.3 % of all intracranial metastases [3]. Moreover, the pineal region is a site of predilection for primary tumors of the pineal region and germ cell tumors. Thus, when lesions are seen in the pineal region, these tumors have higher priority in the differential diagnosis. The patient in this case report had an esophageal neuroendocrine tumor (NET), which itself is rare, as a primary tumor. Therefore, this very rare case is reported.

A case of Langerhans cell histiocytosis of the skull in which preoperative methionine positron emission tomography was useful in comprehending the spreading of the lesion.

Background: The problem with treatments against skull lesions of Langerhans cell histiocytosis (LCH) is that invasions often reach the bones and dura mater, making it difficult to accurately comprehend the range thereof prior to surgery. We herein report that 11C-methionine positron emission tomography (PET) (Met-PET) carried out prior to surgery was useful in comprehending the spreading of the lesion. Case Description: A 20-year-old female presented with swelling and dull pain on the left side of the head. A slightly heterogeneously reinforced tumor was observed inside the bone defect in the gadolinium-enhanced T1-wighted image upon magnetic resonance imaging (MRI) and the dura mater contacting the tumor was observed with an enhancing effect. Accumulation was poor in the center of the tumor upon Met-PET, and accumulation with a well-defined border was observed in the border thereof as well as the area adjacent to the brain. Surgical resection was performed; the pathological diagnosis was LCH. An invasion of tumor cells was observed in the dura mater with accumulation observed according to Met-PET. Moreover, the accumulation of tumor cells was observed in the area observed with accumulation inside the bone; however, the center part with poor accumulation lacked tumor cells, with fibrous tissue accounting for most parts. Conclusion: Met-PET was believed to be helpful in comprehending the spreading of the tumor in the surroundings of the brain surface for skull lesions.

In vivo imaging of cerebral hemodynamics and regional oxygen saturation in rats with a digital red-green-blue camera

The concentrations of oxygenated and deoxygenated hemoglobin and regional oxygen saturation in rat brains were visualized based on the RGB images acquired while changing fraction of inspired oxygen.

A case report: C2 radiculopathy induced by neck flexion due to the cord compression of C2 segmental type vertebral artery relieved by microvascular decompression

Background: Decompression of an anomalous vertebral artery (VA) may effectively treat cervical myelopathy/radiculopathy due to resultant spinal cord or nerve compression. Here we report a case of C2 radiculopathy induced by neck flexion due to cord compression of the C2 segmental type VA relieved by microvascular decompression. Case Description: A 30-year-old female presented with left occipitalgia, sensory abnormalities in the left upper and lower extremities, and neck pain induced by neck flexion. The magnetic resonance imaging (MRI) revealed an abnormal flow void, confirming that the VA was compressing the spinal cord at the C1 level. Three-dimensional computed tomography (3D-CT) showed an anomalous course of the left VA, which entered the spinal canal between the axis and atlas. Microvascular decompression was performed by transposing the artery (e.g., anchoring it to the dura using PTEF): this effectively relieved cord compression. Conclusion: An anomalous VA rarely causes cervical radiculopathy induced by neck flexion. When it occurs, microvascular decompression effectively relieves pressure resulting in a resolution of symptoms.

In Vivo Evaluation of Cerebral Hemodynamics and Tissue Morphology in Rats during Changing Fraction of Inspired Oxygen Based on Spectrocolorimetric Imaging Technique

During surgical treatment for cerebrovascular diseases, cortical hemodynamics are often controlled by bypass graft surgery, temporary occlusion of arteries, and surgical removal of veins. Since the brain is vulnerable to hypoxemia and ischemia, interruption of cerebral blood flow reduces the oxygen supply to tissues and induces irreversible damage to cells and tissues. Monitoring of cerebral hemodynamics and alteration of cellular structure during neurosurgery is thus crucial. Sequential recordings of red-green-blue (RGB) images of in vivo exposed rat brains were made during hyperoxia, normoxia, hypoxia, and anoxia. Monte Carlo simulation of light transport in brain tissue was used to specify relationships among RGB-values and oxygenated hemoglobin concentration (CHbO), deoxygenated hemoglobin concentration (CHbR), total hemoglobin concentration (CHbT), hemoglobin oxygen saturation (StO2), and scattering power b. Temporal courses of CHbO, CHbR, CHbT, and StO2 indicated physiological responses to reduced oxygen delivery to cerebral tissue. A rapid decrease in light scattering power b was observed after respiratory arrest, similar to the negative deflection of the extracellular direct current (DC) potential in so-called anoxic depolarization. These results suggest the potential of this method for evaluating pathophysiological conditions and loss of tissue viability.