Biomedical subjects

Byung-Woo Yoon

Publications and source records attributed to Byung-Woo Yoon.

26 records · Page 2Linked to original sources

PubMed2003

Human neural stem cells can migrate, differentiate, and integrate after intravenous transplantation in adult rats with transient forebrain ischemia.

Intraparenchymally transplanted rodent-origin neural and human-origin mesenchymal stem cells migrate and differentiate in neurological diseases. By intravenously injecting human neural stem cells, we showed that transplanted human neural stem cells migrate to the damaged hippocampus, proliferate and differentiate into mature neurons and astrocytes in the adult rat brain with transient forebrain ischemia. We also demonstrated the migratory course of implanted human neural stem cells after intravenous injection. Our findings show that transplanted human neural stem cells differentiate into mature neurons to replace lost neural cells in the adult hippocampus with human-rat neural chimeras.

Animals↗

PubMed2003

Cerebral cavernous malformations with dynamic and progressive course: correlation study with vascular endothelial growth factor.

BACKGROUND: Cerebral cavernous malformations (CCMs) are reported to exhibit a wide range of dynamic patterns including growth, regression, and de novo formation, which generally show slow and steady courses. Although the pathogenesis of CCMs is not well known, vascular endothelial growth factor (VEGF) has been suggested as a possible mediating factor. OBJECTIVES: To report CCMs showing rapid progression over a short period and to investigate these biological characteristics. DESIGN: Experimental study. SETTING: Tertiary referral center, neurology department. Patient A 40-year-old man was admitted because of a left-sided numbness, vertigo, and ataxia, which were attributed to a pontine hemorrhage. He had experienced a left-sided weakness 6 months before admission, and thereafter had complained of intermittent headache. Serial brain magnetic resonance images showed multiple intracerebral microhemorrhages throughout the cerebral hemispheres. A biopsy of the lesion confirmed the diagnosis of CCM. MAIN OUTCOME MEASURES: We investigated the expression of VEGF by immunohistochemistry of the biopsy specimen. Dynamic patterns of CCMs, obtained with spin-echo magnetic resonance images with gradient-echo sequences, were compared with serial serum VEGF concentrations, determined by enzyme-linked immunosorbent assay. RESULTS: Immunohistochemistry of the specimen displayed increased VEGF expression. Serial magnetic resonance images during 7 months showed dynamic signal changes of the preexisting lesions and 15 de novo formations in many cortices. The VEGF level in serum increased during this dynamic period and became normal during the steady and resolving stages. CONCLUSIONS: Cerebral cavernous malformations can be progressively deteriorating. The endothelial proliferation induced by VEGF is likely to be an important aspect of the pathogenetic mechanisms of CCMs.

Adult↗

PubMed2003

Nonpulsatile cerebral perfusion in Takayasu's arteritis.

A nonpulsatile cerebral perfusion may be encountered in an artificial cardiopulmonary bypass used in cardiac surgery, which is exceptional in physiological conditions. The authors report on a 37-year-old woman with Takayasu's arteritis (TA) who had been suffering from progressive visual loss and recurrent seizures. Ocular findings of chronic ischemia and multiple, subcortical, high-signal lesions in magnetic resonance (MR) imaging were indicative of significant hemodynamic impairment. MR angiography showed the complete occlusion of the innominate artery, the left common carotid artery (CCA), and the subclavian artery from the orifice of the aortic arch. The patient's transcranial Doppler (TCD) waveform was flat throughout all segments of the intracranial arteries. Intravenous acetazolamide injection confirmed the severe impairment of vasoreactivity. After a bypass graft from the aorta to the left CCA, flow velocity and pulsatility were dramatically increased without postoperative complications. A nonpulsatile cerebral perfusion indicates severe hemodynamic impairment and is partially reversible by a surgical bypass graft. TCD seems to be useful to detect "high-risk" patients and to follow up in TA.

Adult↗

PubMed2002

Ischemic intensity influences the distribution of delayed infarction and apoptotic cell death following transient focal cerebral ischemia in rats.

The aim of this study was to investigate whether the apoptotic process contributes to the delayed infarction that follows a middle cerebral artery (MCA) occlusion of 20 min (mild ischemia group) and to compare this with the delayed component of infarct following 2 h of MCA occlusion (severe ischemia group). Adult male Sprague-Dawley rats underwent left MCA occlusion for either 20 min or 2 h and were reperfused for 12, 24 and 72 h. On 2,3,5-triphenyltetrazolium chloride-stained coronal sections, delayed infarction was observed to develop in the whole MCA territory after mild ischemia, and also in the frontoparietal cortex after severe ischemia. At 24 h after 20 min of MCA occlusion, characteristic apoptotic features, including chromatin condensation and apoptotic bodies were frequently observed by electron microscopy. In both ischemic groups, Hoechst 33342 staining showed typically condensed and fragmented nuclei in the area showing delayed infarction, where TdT-dUTP nick end labeling (TUNEL)-positive cells were also significantly increased. Caspase-3 activity was also found to be elevated 24 and 72 h after reperfusion and this peaked at 24 h in both groups. These findings suggest that ischemic severity may influence the distribution of delayed infarction, and that apoptosis is the underlying pathophysiologic mechanism.

Animals↗

PubMed2002

Lesion patterns and mechanism of ischemia in internal carotid artery disease: a diffusion-weighted imaging study.

CONTEXT: Although embolism and low-flow phenomenon are the 2 main mechanisms of stroke in internal carotid artery (ICA) occlusive disease, the mechanism of border-zone infarction remains controversial. Diffusion-weighted imaging (DWI) can more easily detect small or multiple ischemic lesions than conventional imaging. OBJECTIVES: To investigate the ischemic lesion patterns on DWI and to discuss the mechanisms of stroke in ICA disease. DESIGN: Case series. SETTING: A tertiary referral center. PATIENTS: We enrolled 35 consecutive patients who had an acute ischemic stroke and (> or = 70%) stenosis or an occlusion of the extracranial ICA confirmed by cerebral angiography and an acute relevant stroke lesion on DWI within 1 week of onset, but without cardiac sources of embolism and tandem intracranial arterial disease. MAIN OUTCOME MEASURES: The lesion pattern on DWI was categorized as territorial or border zone. Multiple ischemic lesions were defined as noncontiguous lesions on DWI in more than 1 vascular territory. RESULTS: There were 3 distinctive stroke lesion patterns. (1) A territorial lesion without a border-zone lesion was found in 21 patients: superficial and superficial territorial in 9, superficial and deep territorial in 7, and single in 5. (2) A border-zone lesion with or without a territorial lesion was found in 10 patients: border zone and territorial in 9 and border zone alone in 1. (3) Bilateral hemispheric lesions were found in 4 patients. Multiple ischemic lesions were found in 29 (82.9%) of the 35 patients. No patient had episodes of hemodynamic compromise. CONCLUSIONS: An acute ischemic lesion in ICA occlusive disease is mainly multiple. Border-zone infarction was mostly associated with territorial infarction. These results support the fact that embolism is the predominant stroke mechanism in ICA occlusive disease.

Aged↗

PubMed2002

Gradient echo magnetic resonance imaging in the prediction of hemorrhagic vs ischemic stroke: a need for the consideration of the extent of leukoariosis.

BACKGROUND: Multifocal signal loss lesion (MSLL) on gradient echo magnetic resonance imaging (GE-MRI) may reflect bleeding-prone microangiopathy. However, MSLLs are also known to be associated with leukoariosis; leukoariosis is commonly associated with occlusive-type vascular lesions. OBJECTIVE: To determine whether MSLL on GE-MRI is significantly associated with the type of stroke--intracerebral hemorrhagic (ICH) stroke more often than an ischemic stroke (infarction)--regardless of the extent of leukoariosis. PATIENTS AND METHODS: We studied 91 patients who had an acute stroke and were admitted to the Department of Neurology, Seoul National University Hospital, Seoul, South Korea, from March 1, 1997, to July 31, 1998. These patients underwent both conventional MRI and GE-MRI. The GE-MRI was used to count MSLLs. We also counted lacunae and classified leukoariosis (none or mild and advanced). Multiple logistic regression analysis was used to test for MSLL-leukoariosis interaction association with the type of stroke (ICH over infarction) and to evaluate the relative contribution of an MSLL--adjusted for age, sex, and lacunae--in discriminating the type of stroke. RESULTS: The association between MSLL and ICH statistically significantly differed by leukoariosis (P =.003 for MSLL-leukoariosis interaction term). The MSLL count on GE-MRI was significantly associated with the type of stroke (ICH over infarction; odds ratio, 2.46; 95% confidence interval, 1.38-4.39) when leukoariosis was classified as none or mild. When leukoariosis was classified as advanced, there was a decrease in the odds ratio of MSLL to 0.99 (95% confidence interval, 0.94-1.04). CONCLUSIONS: Our findings indicate that MSLL on GE-MRI is a predictor of ICH vs infarction in patients with no or mild leukoariosis, but not in patients with advanced leukoariosis. Therefore, in the evaluation of GE-MRI for a bleeding-prone microangiopathy, the extent of leukoariosis should be considered.

Adult↗

PubMed2002

Atypical brainstem encephalitis caused by herpes simplex virus 2.

BACKGROUND: Herpes simplex encephalitis is one of the most common and serious sporadic encephalitides of immunocompetent adults. Herpes simplex virus 2 (HSV-2) infections of the central nervous system usually manifest as subacute encephalitis, recurrent meningitis, myelitis, and forms resembling psychiatric syndromes. OBJECTIVES: To report and discuss magnetic resonance imaging (MRI) findings and clinical features in atypical brainstem encephalitis and facial palsy associated with HSV-2. SETTING: Neurology department of a tertiary referral center. PATIENT: A 37-year-old woman was admitted to the hospital with fever, diplopia, left hemiparesis, sensory change in the face and limbs, personality changes, frontal dysexecutive syndrome, and a stiff neck. Brain MRI showed multifocal high-signal intensities in the pons, midbrain, and frontal lobe white matter on T2-weighted and fluid-attenuated inversion recovery images. Cerebrospinal fluid (CSF) polymerase chain reaction (PCR) amplification analysis was positive for HSV-2. Acyclovir therapy was started, and the encephalitic symptoms disappeared with a negative conversion of HSV-2 PCR in the CSF. However, after the discontinuation of acyclovir therapy, peripheral facial palsy occurred on the left side. A possible relapse or delayed manifestation of the HSV-2 infection was suspected, and the acyclovir therapy was restarted. A complete remission was achieved 3 days after the treatment. She was discharged without any neurologic sequelae. CONCLUSIONS: We describe a patient who developed atypical encephalitis due to HSV-2 and peripheral facial palsy, which could also be related to the HSV-2. This case suggests that HSV-2 should be considered among the possible causes of atypical or brainstem encephalitis and that the PCR amplification method of the CSF can help reveal the possible cause of HSV-2.

Acyclovir↗

PubMed2002

Low concentration of serum total cholesterol is associated with multifocal signal loss lesions on gradient-echo magnetic resonance imaging: analysis of risk factors for multifocal signal loss lesions.

BACKGROUND AND PURPOSE: Multifocal signal loss lesions (MSLLs) on T2*-weighted gradient-echo (GE) MRI are believed to be microbleeds histopathologically. Previous epidemiological studies suggested that low serum cholesterol is associated with the increased risk of intracerebral hemorrhage. We investigated risk factors of MSLLs and the relationship between lipid profiles and MSLLs on GE-MRI. METHODS: We included consecutively 172 patients who underwent brain MRI. MSLLs on GE-MRI were counted by 2 neurologists separately and graded by consensus. The concentrations of lipid profiles were categorized as quartiles, and the MSLLs were graded as absent (total count, 0), mild (1 to 2), moderate (3 to 10), and severe (>10). RESULTS: The mean concentrations of total cholesterol and low-density lipoprotein cholesterol were significantly lower in patients with a severe degree of MSLLs than in those without MSLL (P<0.05). By multivariate analysis, MSLLs were significantly correlated with hypertension (odds ratio [OR], 3.42; 95% CI, 1.17 to 9.97), leukoaraiosis (OR, 4.62; 95% CI, 2.87 to 7.41), the lowest quartile of serum total cholesterol (<4.27 mmol/L; OR, 10.91; 95% CI, 3.98 to 25.57), and the highest quartile of high-density lipoprotein (>1.47 mmol/L; OR, 3.5; 95% CI, 1.45 to 8.29). CONCLUSIONS: Our results suggest that both the lipid profile levels and the severity of hypertension may be closely associated with MSLLs on GE-MRI.

Adult↗