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Biomedical subjects

S J Ryu

Publications and source records attributed to S J Ryu.

At least 19 recordsLinked to original sources
PubMed2006

Role of Src-specific phosphorylation site on focal adhesion kinase for senescence-associated apoptosis resistance.

A decreased apoptotic response toward noxious stress is an issuing characteristic of the aging phenotype. Hydrogen peroxide or staurosporine induced apoptosis readily in young cells but not in senescent cells. We showed that focal adhesion kinase (FAK) expression and its phosphorylation at Tyr397, autophosphorylation site for focal adhesion formation, and Tyr577, Src-dependent phosphorylation site, were both increased in senescent cells. Moreover, FAK was inactivated proteolytically by apoptotic stimuli in young cells, but not in senescent cells. In addition, senescent cells whose FAK expression was downregulated by siRNA showed the increased level of apoptosis by staurosporine treatment via caspase-3 activation but not by hydrogen peroxide treatment. Interestingly dephosphorylation at Tyr577 of FAK by PP2 treatment, Src-family kinase inhibitor, induced the apoptosis by staurosporine in senescent cells but dephosphorylation at Tyr397 by downregulation of caveolin-1 was not affected. These data suggest that FAK might differently regulate apoptosis and focal adhesion formation through site-specific tyrosine phosphorylation in senescent cells.

Apoptosis↗
PubMed2004

Occurrence and characteristics of enterohemorrhagic Escherichia coli O157 in calves associated with diarrhoea.

Little is known of the association of enterohemorrhagic Escherichia coli O157:H7/NM (EHEC O157) with disease in naturally infected calves, although cattle have been known as a major source for EHEC O157 outbreaks in humans. In this study, we investigated the occurrence of EHEC O157 in calves associated with/without diarrhoea to examine if EHEC O157 is involved in calf diarrhoea and to characterize the isolates. Four hundred and ninety eight diarrhoeic and non-diarrhoeic young calves from 115 different farms were examined. Of 244 diarrhoeic calves, 24 (9.8%) were positive for EHEC O157, and of 254 non-diarrhoeic calves, 7 (2.8%) were positive. EHEC O157 was recovered from 12/76 (15.79%) of diarrhoeic calves less than 2-week-old, and no EHEC O157 was detected in this age group of non-diarrhoeic calves. This implicates EHEC O157 as a possible cause of the disease in naturally infected neonatal calves. The occurrence of EHEC O157 was relatively lower in the older calves (aged older than 8 weeks) and no significant difference was found in the occurrence rates between these diarrhoeic and non-diarrhoeic calves. PCR analysis of virulence markers revealed that the isolates carried various virulence genes such as Ehly, eae, stx1 and stx2, which underlines the potential importance of these attributes for the infection, colonization and possible pathogenesis of calf diarrhoea.

Age Factors↗
PubMed2001

Myxoma attached to both atrial and ventricular sides of the mitral valve: report of a case and review of 31 cases of mitral myxoma.

We report for the first time upon a case of myxoma that involved both atrial and ventricular sides of the anterior mitral valve leaflet. Electron beam tomography (EBT) showed that the tumor was attached to both the atrial and ventricular sides of the mitral valve, while echocardiography did not. EBT also diagnosed dynamic obstruction of left ventricular outflow tract caused by the tumor.

Adult↗
PubMed2001

CT and MR findings of primary cardiac lymphoma: report upon 2 cases and review.

Although primary cardiac lymphoma was a near fatal disease in the past, recent advances in imaging diagnosis and chemotherapy have dramatically improved survival. We describe the CT and MR findings of primary cardiac lymphoma in two immunocompetent subjects who recovered after chemotherapy. The primary cardiac lymphomas manifested as a poorly enhancing mass on CT, relatively hyperintense on a T2-weighted image and a heterogeneously enhanced mass on contrast-enhanced MR. The tumor also showed a predilection for right heart chambers and contiguous infiltration along adjacent structures.

Adult↗
PubMed2000

Purification and partial characterization of a novel glucanhydrolase from Lipomyces starkeyi KSM 22 and its use for inhibition of insoluble glucan formation.

A novel glucanhydrolase from a mutant of Lipomyces starkeyi ATCC 74054 was purified. The single protein (100 kDa) showed either dextranolytic or amylolytic activity. We referred to the glucanhydrolase as a DXAMase. The DXAMase was produced in a starch medium and it was 3.75-fold more active for hydrolysis of the purified insoluble-glucan of Streptococcus mutans than Penicillium funiculosum dextranase. Aggregation of S. mutans cells with dextran and adherence to glass were eliminated by incubating with the DXAMase. The addition of DXAMase (0.1 IU/ml) to the mutansucrase reaction digest with sucrose reduced the formation of insoluble-glucan about 80%. Also the DXAMase (0.5 IU/ml) removed 80% of the pre-formed sucrose-dependent adherent film. These in vitro properties of L. starkeyi KSM 22 DXAMase are desirable for its application as a dental plaque control agent.

Dental Materials↗
PubMed1999

Retroperitoneal multilocular bronchogenic cyst adjacent to adrenal gland.

Bronchogenic cysts are generally found in the mediastinum, particularly posterior to the carina, but they rarely occur in such unusual sites as the skin, subcutaneous tissue, pericardium, and even the retroperitoneum. A 30-year-old Korean man underwent surgery to remove a cystic adrenal mass incidentally discovered during routine physical checkup. At surgery, it proved to be a multilocular cyst located in the retroperitoneum adjacent to the left adrenal gland. Microscopically, the cyst was lined by respiratory epithelium over connective tissue with submucous glands, cartilage and smooth muscle, thereby histologically confirming bronchogenic cyst. This is the first reported case of retroperitoneal bronchogenic cyst in an adult without other congenital anomalies in Korea.

Adrenal Glands↗
PubMed1998

Chronic inorganic mercury induced peripheral neuropathy.

We report the clinical features, electrophysiological studies, and morphometric analysis of sural nerve pathology in a patient with polyneuropathy due to inorganic mercury intoxication. He developed slowly progressive generalized paralysis of all limbs after 3 months ingestion of herb drugs which contained mercuric sulfate. Electrophysiologic studies revealed axonal polyneuropathy involving both motor and sensory fibers. Sural nerve biopsy demonstrated axonal degeneration with demyelination and a predominant loss of large myelinated fibers. His muscle strength showed only mild improvement after 2 years' follow-up. We concluded that inorganic mercury exposure may induce severe axonal sensorimotor polyneuropathy in humans and that neurological deficits may persist in severe cases.

Biopsy↗
PubMed1997

Carotid floating plaques associated with multiple cerebral embolic strokes. Case reports.

The authors describe 2 patients with multiple cerebral infarcts and hemorrhagic transformation caused by artery-to-artery emboli. Ulcerated plaques with free-floating thrombus adherent to the plaque were detected at the carotid bifurcation by duplex sonography. No other embolic source could be found. One patient developed an occipital infarction due to carotid emboli passing through a fetal-type posterior communicating artery. Both patients recovered well without recurrence of stroke or transient ischemic attack with antiplatelet treatment only. Follow-up carotid duplex sonography showed disappearance of floating thrombus in 1 patient and consolidation of the lesion in the other.

Adult↗
PubMed1997

Mixed meningococcal and tuberculous meningitis.

Meningococcal meningitis is one of the most common bacterial infections of the meninges worldwide, and tuberculous infection is the most common cause of chronic meningitis in Taiwan. However, mixed meningococcal and tuberculous meningitis is rare. We describe a 27-year-old woman with a case of culture-proven meningococcal and tuberculous meningitis verified by polymerase chain reaction on a cerebrospinal fluid specimen. The patient was initially treated with intravenous antibiotics including penicillin G and chloramphenicol. Though the patient responded well to therapy initially, her subsequent clinical deterioration was finally controlled by long-term antituberculous medications.

Adult↗
PubMed1997

Lacunar infarctions presenting as memory loss and mental changes: four cases report.

Impairment of higher cortical functions is usually not considered as a typical presentation of lacunar infarction. However, a small discrete lesion at strategically important locations may produce memory loss and mental changes. We report 4 patients with lacunar infarctions manifested as acute amnesia and mental changes. One patient had left thalamic infarction, one had left capsular genu infarction, one had right capsular genu infarction, and one had left capsular genu infarction extending to the ipsilateral thalamus. The mental and memory impairment was transient in one patient but was persistent in the other 3 patients. Our report reconfirms that a lacunar infarction can cause impairment of higher cortical functions.

Aged↗
PubMed1996

Coexistence of cerebral venous sinus and internal carotid artery thrombosis associated with exogenous sex hormones. A case report.

A forty-six year-old premenopausal woman developed headache, nausea and vomiting, left hemiparesis and seizure two days after parenteral use of progesterone and estradiol. Diabetes mellitus (DM) was found during admission. Computed tomography showed a hemorrhagic infarct in the right frontal lobe and increased density in the superior sagittal sinus (SSS). Left carotid angiography found occlusion of the left internal carotid artery (ICA). Right carotid angiograms failed to show the SSS and inferior sagittal sinus, suggestive of venous sinus thrombosis. Coexistence of the cerebral artery and the venous sinus occlusion has been described infrequently. In this case, the authors postulate that the use of estradiol and progesterone and the underlying DM increased vascular thrombogenicity, which provided a common denominator for thrombosis of both the ICA and the venous sinus.

Carotid Artery Thrombosis↗
PubMed1995

Ginseng-associated cerebral arteritis.

We report a 28-year-old woman who had a severe headache after ingesting a large quantity of ethanol-extracted ginseng. Cerebral angiograms showed "beading" appearance in the anterior and posterior cerebral and superior cerebellar arteries, consistent with cerebral arteritis. The close temporal association between intake of ginseng and cerebral arteries suggests a causal relationship.

Adult↗
PubMed1995

Common carotid artery occlusion: evaluation with duplex sonography.

PURPOSE: To demonstrate the efficacy of carotid duplex ultrasound to diagnose common carotid artery occlusion (CCAO) and to define the clinical features of CCAO. METHODS: We reviewed 5400 carotid duplex ultrasonograms obtained over a 7-year period for suspected carotid artery disease. In cases of CCAO, medical records were reviewed. RESULTS: Thirteen cases (0.24%) of CCAO were diagnosed by carotid duplex ultrasonography, including five cases of isolated CCAO. Seven cases were proved by cerebral angiography. Cerebral angiography failed to demonstrate patent internal carotid arteries in two cases of isolated CCAO. Mean age of onset was 67 +/- 9 years. The main clinical presentation was stroke in nine cases (69%). The most common vascular risk factors were hypertension (62%) and heart diseases (54%). Three patients had a history of radiation therapy to the neck. Two of five patients with isolated CCAO had major stroke, with good recovery in one, whereas five of eight patients with CCAO had major stroke; among them, only one had good recovery. CONCLUSION: Patients with isolated CCAO may have a better outcome than patients with CCAO. Duplex sonography, particularly with color-coded flow imaging, provides an accurate examination to define the patency of the arteries distal to the carotid bifurcation. The clinical features of CCAO are similar to those of internal carotid artery occlusion except for the low prevalence of CCAO.

Aged↗
PubMed1995

Transcranial color-coded sonography in normal Chinese adults and its clinical applications.

We have performed transcranial color-coded sonography to 150 normal adults. Through the temporal, orbital and foraminal windows, by using a 2 MHz pulsed-wave transducer, we were able to directly insonate the brain parenchyma, and to obtain color-coded Doppler vascular imagings and flow velocities of the intracranial basal cerebral arteries. There was no significant difference of blood flow velocities and resistance index between the right and left hemispheres. The mean velocities was highest in the middle cerebral artery and lowest in the ophthalmic artery while which had the highest resistance index. Female had higher mean velocity in basilar artery. The mean velocity, peak systolic velocity, as well as end diastolic velocity decreased significantly with age in middle cerebral artery, anterior cerebral artery and basilar artery. Four illustrative cases with abnormal findings were presented to compare with normal control. Some pitfalls in ultrasonography were also described.

Adolescent↗
PubMed1995

Clinical features and carotid duplex sonography in patients with carotid transient ischemic attacks.

BACKGROUND: Transient ischemic attack (TIA) is recognized as a precursor of cerebral infarction. It is prompted by an embolism from extracranial carotid artery disease. However, extracranial carotid disease is less prevalent in Chinese patients. Non-invasive duplex sonography has been used for initial screening for extracranial carotid artery disease. METHODS: One hundred and twenty-seven consecutive patients with carotid TIA were divided into two groups according to sonographic results, Group I: < or = 50%, and Group II: > 50% stenosis of the carotid artery. The two groups were compared for the clinical manifestations, risk factors, brain computed tomography (CT) findings and subsequent stroke. An age and sex-matched group of patients with lacunar stroke was also collected from the same neurosonological data bank for further comparative analysis. RESULTS: The mean age at onset was 59 +/- 12 (mean SD) years. Hypertension was the most common risk factor. The most common symptom was transient focal motor deficit (73%) with or without other complaints. Eighty-two percent of the TIA episodes were less than one hour in duration. In Group I, there were 114 patients (90%) with stenosis < or = 50% ipsilateral to the symptomatic side. Group II included only 13 patients (10%) with the ipsilateral carotid artery stenosis > 50%. Mean age was older and cigarette smoking was more common in Group II (p < 0.05). Otherwise, no significant difference was noted between the two groups in initial characteristics of TIAs, risk factors, brain CT findings or subsequent stroke. Further, there was no statistical significant difference between the TIA and lacunar stroke groups in the degree of carotid stenosis. CONCLUSIONS: Hypertension was the most common risk factor for carotid TIAs. The prevalence of extracranial carotid artery disease was low in Chinese patients with carotid TIAs. The severity of the carotid artery was not predictive of recurrence of TIA or of subsequent stroke. There was no significant difference between patients with TIA and with lacunar stroke in sonographic findings of extracranial carotid arteries.

Adult↗
PubMed1994

Carotid duplex and transcranial color-coded sonography in evaluation of carotid-cavernous sinus fistulas.

We performed carotid duplex and transcranial color-coded sonography in three patients with traumatic and one patient with spontaneous carotid-cavernous fistulas. High flow and low resistance were detected by carotid Doppler imaging in the extracranial internal carotid artery in three cases and in the external carotid artery in one case. The fistula could be demonstrated directly as heterogenous color flashes with turbulent flow by transcranial color-coded sonography through the orbital or temporal window. The transorbital approach showed that the ophthalmic venous flow was normal or to-and-fro bidirectional in patients without proptosis and was retrograde, away from the cavernous sinus with arteriolization in patients with proptosis. Combination of carotid duplex and transcranial color-coded sonography provides a noninvasive method for more accurate hemodynamic study of cerebral circulation and direct imaging of CCF.

Adult↗
PubMed1993

Sudden bilateral hearing impairment in vertebrobasilar occlusive disease.

BACKGROUND: Bilateral hearing impairment is rare in vertebrobasilar occlusive disease. SUMMARY OF COMMENT: Between 1986 and 1991, we encountered seven patients (four men, three women; median age, 61 years; range, 46-71 years) who had sudden bilateral hearing impairment among 503 patients with vertebrobasilar occlusive disease. The main initial neurological symptoms were sudden bilateral hearing impairment, tinnitus, and vertigo. Acute labyrinthitis or Ménière's disease was the initial diagnosis until subsequent brain stem or cerebellar signs appeared. Brain stem auditory evoked potentials were abnormal bilaterally in six patients but had unilateral attenuation of the IV-V complex in the remaining one patient. Computed tomographic scans in all six patients showed multiple hypodense lesions in the brain stem and the cerebellum. Cerebral angiography showed complete occlusion on both vertebral arteries in one patient, occlusion on the left with small caliber on the right in another, and severe stenosis on both sides in a third. There was no opacification of internal auditory arteries in these three patients. The remaining patient had arteriosclerotic changes with faint opacification of the bilateral internal auditory arteries. Five patients had a poor prognosis, with locked-in state in four and severe truncal ataxia in one. CONCLUSIONS: We conclude that sudden bilateral hearing impairment in vertebrobasilar occlusive disease is more common than previously recognized and that it may indicate a grave prognosis.

Aged↗