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Biomedical subjects

C H Oh

Publications and source records attributed to C H Oh.

At least 19 recordsLinked to original sources
PubMed2006

Phase contrast radiography of Lewy bodies in Parkinson disease.

Parkinson's disease (PD), defined as a neurodegenerative disorder, is characterized by the loss of dopaminergic neurons and the presence of Lewy bodies in neurons. Morphological study of Lewy bodies is important to identify the causes and the processes of PD. Here, we investigate a possibility of phase contrast radiography using coherent synchrotron X-rays to explore the microscopic details of Lewy bodies in thick (approximately 3 mm) midbrain tissues. Autopsied midbrain tissues of a PD patient were sliced in 3 mm thickness and then examined using synchrotron X-rays from the 7B2 beamline of the Pohang Light Source. Refraction-enhanced phase contrast radiography and microtomography were adopted to identify dark core and dim edge of Lewy bodies in neurons. The morphology of Lewy bodies was clearly revealed by the phase contrast radiography in very thick (3 mm) midbrain tissues without any staining treatment. Three-dimensional volume rendered microtomography of the autopsied midbrain tissues demonstrates striking evidence that several Lewy bodies are agglomerated by dim edges in a neuron. We suggest that the phase contrast radiography could be a useful tool to morphologically investigate the causes or the processes in PD.

Dopamine↗
PubMed2005

Quantitative conditions do not guarantee the validity of the adiabatic approximation.

In this Letter, we point out that the widely used quantitative conditions in the adiabatic theorem are insufficient in that they do not guarantee the validity of the adiabatic approximation. We also reexamine the inconsistency issue raised by Marzlin and Sanders [Phys. Rev. Lett. 93, 160408 (2004)] and elucidate the underlying cause.

Comment↗
PubMed2005

Experimental quantum cloning with prior partial information.

When prior partial information about a state to be cloned is available, it can be cloned with a fidelity higher than that of universal quantum cloning. We experimentally verify this intriguing relationship between the cloning fidelity and the prior information by reporting the first experimental optimal quantum state-dependent cloner, using nuclear magnetic resonance techniques. Our experiments may further cast important implications into many quantum information processing protocols.

Journal Article↗
PubMed2004

Qutrit state engineering with biphotons.

The novel experimental realization of three-level optical quantum systems is presented. We use the polarization state of biphotons to generate a specific sequence of states that are used in the extended version of four-state QKD protocol quantum key distribution protocol. We experimentally verify the orthogonality of the basic states and demonstrate the ability to easily switch between them. The tomography procedure is employed to reconstruct the density matrices of generated states.

Journal Article↗
PubMed2004

Gisin's theorem for three qubits.

We present a theorem that all generalized Greenberger-Horne-Zeilinger states of a three-qubit system violate a Bell inequality in terms of probabilities. All pure entangled states of a three-qubit system are shown to violate a Bell inequality for probabilities; thus, one has Gisin's theorem for three qubits.

Journal Article↗
PubMed2004

Coincidence bell inequality for three three-dimensional systems.

We construct a Bell inequality for coincidence probabilities on a three three-dimensional (qutrit) system. We show that this inequality is violated when each observer measures two noncommuting observables, defined by the so-called unbiased six-port beam splitter, on a maximally entangled state of two qutrits. The strength of the violation agrees with the numerical results presented by Kaszlikowski et al, quant-ph/0202019. It is proven that the inequality defines facets of the polytope of local variable models.

Journal Article↗
PubMed2003

Observation of geometric phases for mixed states using NMR interferometry.

Examples of geometric phases abound in many areas of physics. They offer both fundamental insights into many physical phenomena and lead to interesting practical implementations. One of them, as indicated recently, might be an inherently fault-tolerant quantum computation. This, however, requires one to deal with geometric phases in the presence of noise and interactions between different physical subsystems. Despite the wealth of literature on the subject of geometric phases very little is known about this very important case. Here we report the first experimental study of geometric phases for mixed quantum states. We show how different they are from the well-understood, noiseless, pure-state case.

Journal Article↗
PubMed2003

Non-linear registration for brain images by maximising feature and intensity similarities with a Bayesian framework.

The objective of this work was to provide a new, precise registration of the cortical mantle with a non-linear transformation. Image registration is broadly classified into two types, using intensity similarity and feature similarity. Whereas the former approach has merit in global brain matching, the latter provides a fast registration centred on a region of interest. The hybrid registration proposed in this paper was achieved using a Bayesian framework, which consisted of a likelihood model including intensity similarity and a prior model including feature information and a smoothing constraint. In this approach, each voxel was spatially transformed, so that the distance between corresponding features was shortened and also so that the intensity correlation was maximised. The result of the hybrid method clearly showed a good match of global brain (r = 0.930) by including intensity similarity. Moreover, this method compensated for the approximated sulcus of the feature-based method with intensity information, so that the geometric shape and thickness of the sulcus at the feature-defined region was likely to be registered. The accuracy in the feature-defined area was improved by 33.4% and 7.5% compared with feature-based and intensity-based methods, respectively.

Bayes Theorem↗
PubMed2001

Synthesis and biological properties of C-2, C-8, N-9 substituted 6-(3-chloroanilino)purine derivatives as cyclin-dependent kinase inhibitors. Part II.

In this study, C-2, C-8, N-9 substituted 6-(3-chloroanilino)purine derivatives were synthesized and their inhibitory effects on cyclin-dependent kinases (CDK2, 4) as well as their cytotoxicities were evaluated. The effects of substituents at the C-2, C-8, and N-9 positions of the substituted purine were investigated. Among the compounds tested, [6-(3-chloroanilino)-2-(2-hydroxymethyl-4-hydroxypyrrolidyl)-9- isopropylpurine] (4h) was the most active inhibitor of CDK2 with IC50 of 0.3 microM, i.e. a two-fold increased inhibitory activity as compared to roscovitine. Results from structure-activity relationship studies should allow the design of more potent and selective CDK2 inhibitors, which may provide an effective therapy for cancer or other CDK-dependant diseases.

Antineoplastic Agents↗
PubMed2001

Quantitative histopathologic findings of erythromelanosis follicularis faciei et colli.

BACKGROUND: Even though only 33 cases of Erythromelanosis follicularis faciei et colli (EFFC) have been reported around the world, there have been no quantitative clinicopathological studies yet. The purpose of this study is to examine quantitatively clinical and histopathological evaluations of EFFC using image analysis system. METHOD: Clinical grading of its severity was assessed. Many parameters of the horny layer, granular layer, epidermis and the dermal components were measured and compared to controls by image analysis. The correlation between the histological findings and clinical grading was assessed. RESULT: Thickness and compactness of the horny layer was significantly increased in EFFC. There were no significant differences in the number of melanocytes and severity of pigmentation between EFFC and controls; however, melanization was slightly increased in EFFC. The percent area of the superficial blood vessels was significantly increased and correlated with visual grading of erythema. Diameters of hair shafts and outer root sheaths, and thickness of inner root sheaths were decreased. Basal layer pigmentation was correlated with the clinical features of pigmentation. CONCLUSION: This study supported the findings of hyperkeratosis and dilatation of superficial dermal blood vessels in EFFC. The pigmentation of the basal layer and the percent area of the inner spaces of the superficial dermal blood vessels may reflect the clinical severity more than the other parameters. Although follicular plugging is a characteristic clinical feature of EFFC, enlargement of hair follicles and hair shafts were not characteristic pathologic changes EFFC in our study.

Adolescent↗
PubMed2001

Solar damage in skin tumors: quantification of elastotic material.

BACKGROUND: The elastotic changes of the dermis are thought to be the primary indicator of the cumulative sun exposure of the dermis. The changes of elastotic material have been evaluated by several previous methods, but these did not quantitatively measure the amount of elastic tissue. OBJECTIVE: The purpose of this study was to quantify dermal elastosis and to assess the significance of sun exposure in the pathogenesis of nonmelanomatous skin tumors such as basal cell carcinoma (BCC), squamous cell carcinoma (SCC) and Bowen's disease (BD). METHODS: Ninety-nine sections from biopsy specimens of histopathologically proven BCC, SCC and BD were stained with Verhoeff-van Gieson stains. We studied the amount of elastotic material adjacent to the tumor by image analysis. RESULTS: There was a 3- to 4-fold increase in the amount of elastotic material in BCC and SCC compared to the sun-exposed skin of normal controls (p < 0.0001). The amount of elastotic material was increased 1.3 times in BD as compared with the nonexposed skins of normal controls (p < 0.01). CONCLUSION: We demonstrated a quantitative relationship between cumulative solar exposure and skin cancer such as SCC, BCC and BD.

Adult↗
PubMed2001

Congenital esophageal stenosis in adults: clinical and radiographic findings in seven patients.

OBJECTIVE: The purpose of this study was to determine the clinical and radiographic findings in seven adults with congenital esophageal stenosis. CONCLUSION: In young or middle-aged individuals, particularly men with long-standing dysphagia, an upper or mid esophageal stricture with multiple ringlike constrictions is a characteristic appearance of congenital esophageal stenosis on double-contrast esophagography.

Adult↗
PubMed2001

A modified method for intubation of a patient with ankylosing spondylitis using intubating laryngeal mask airway (LMA-Fastrach)--a case report.

We present an instance of successful use of an intubating laryngeal mask airway (LMA-Fastrach) and a Cook airway exchanger (CAE) for ventilation and intubation in a patient with severe ankylosing spondilitis (AS) receiving total hip arthroplasty. This measure may serve as an effective alternative for airway management in patients with difficult airway. A 61-year-old male was scheduled for right total hip arthroplasty because of degenerative osteoarthritis. He had been suffering from extensive ankylosing spondylitis, with the cervical spine markedly fixed in anterior flexion. Besides he could not open his mouth widely (35 mm when fully open) also because of ankylosis of jaw. Although we advised an awake fiberoptic tracheal intubation for anesthesia but he refused owing to a previous painful experience. After induction of anesthesia with glycopyrrolate, fentanyl, thiamylal sodium and succinylcholine, we inserted a # 5 Fastrach ILMA for primary airway maintenance. Then through the lumen of the ILMA we introduced the CAE as a guide for endotracheal tube (ETT) intubation. After applying the RAPI-FIT adapter to the CAE, we connected it to the capnography monitor for the confirmation of airway. We finally inserted an endotracheal tube into the trachea using the CAE as a guide. The whole procedure was uneventful and smooth. In sum, the modified Fastrach intubation method may facilitate tracheal intubation in patients with severe ankylosing spondilitis. It may be an alternative way for successful airway management in patients with difficult airway.

Arthroplasty, Replacement, Hip↗
PubMed2000

Arachidonic acid metabolites in antrochoanal polyp and nasal polyp associated with chronic paranasal sinusitis.

The aim of this study was to investigate the role of arachidonic acid metabolites (AAMs) in the pathogenesis of antrochoanal polyp (ACP). Using high-performance liquid chromatography (HPLC), we assayed the tissue concentrations of 6-keto-PGF1alpha, leukotrienes (LTs) and hydroxyeicosatetraenoic acids (HETE). Concentrations of AAMs in ACP were compared with the level in the control turbinate tissues and nasal polyps associated with chronic paranasal sinusitis (NPS). The concentrations of 6-keto-PGF1alpha were not significantly different in the control turbinate, ACP and NPS groups. In ACP, concentrations of LTC4, 15-HETE and 12-HETE were significantly lower than in the control turbinate. The striking differences in the profile of AAMs between ACP and NPS included a lack of production of LTD4 and LTE4 in ACP, also detectable in NPS, and markedly lower concentrations of 15-HETE and 12-HETE in ACP. The results of this study indicate that decreased lipoxygenase pathway products in arachidonic acid metabolism may be involved in the pathogenesis of ACP. However, in the pathogenesis of NPS, increased production of LTD4 and LTE4 may have an important role. Taken together, our results demonstrate a difference in pathogenesis between ACP and NPS, particularly in terms of arachidonic acid metabolism.

6-Ketoprostaglandin F1 alpha↗
PubMed1999

Low convulsive activity of a new carbapenem antibiotic, DK-35C, as compared with existing congeners.

Since carbapenems and cephalosporins have been suggested to induce convulsive side effects through an inhibitory action on the central gamma-aminobutyric acid (GABA)-mediated inhibitory transmission, the present study evaluated the convulsive activity of a new carbapenem antibiotic (1R,5S,6S)-6[(R)-1-hydroxyethyl]-2-[(3S,5S)-5(S-methyl-4thiomorpholin ylcarbonyl)pyrrolidin-3-thio]-l-methylcarbapen-2-em-3- carboxylic acid (DK-35C) in in vitro and in vivo experiments, in comparison with cefazolin, imipenem and meropenem. In in vitro experiments, their abilities to inhibit [3H]muscimol (5 nM) binding to GABA(A) receptors were measured using crude synaptic membranes prepared from the rat cerebral cortex. The concentrations (mM) of the antibiotics which inhibit 50% of the specific binding, were 0.6 for imipenem, 1.8 for cefazolin, 15.4 for DK-35C and 27.6 for meropenem. In in vivo experiments, intracerebroventricular (i.c.v.) injections of cefazolin, imipenem and DK-35C induced convulsions in a dose-dependent manner in rats. The doses (nmol/rat) of the antibiotics which induce convulsions in 50% of rats, were 57 for imipenem, 96 for cefazolin, 377 for DK-35C and >3000 for meropenem. In the mouse pentylenetetrazole (PTZ) convulsive model, intravenous pretreatment with cefazolin (800 mg/kg) or imipenem (200 mg/kg) shifted the dose-response curve of PTZ (i.p.) to the left, indicating enhancement of the convulsive activity of PTZ. However, pretreatment with cefazolin, meropenem or DK-35C at a dose of 400 mg/kg did not produce any marked effects on the convulsive activity of PTZ compared with the saline vehicle-pretreated control. The results clearly demonstrate a good correlation between in vitro GABA(A) receptor binding assay and in vivo i.c.v. convulsive model using rats, and suggest that DK-35C may possess a relatively weak convulsive activity mediated through an interaction with GABA(A) receptors.

Animals↗
PubMed1999

Characterization of a novel unconjugated pteridine glycoside, cyanopterin, in Synechocystis sp. PCC 6803.

A new pteridine glycoside, called cyanopterin, was isolated from Synechocystis sp. PCC 6803 and its structure was elucidated as 6-[1-(4-O-methyl-(alpha-d-glucuronyl)-(1, 6)-(beta-d-galactosyloxy]methylpterin by chemical degradation and 1H- and 13C-NMR spectroscopic means. Cyanopterin is constitutively synthesized at a relatively high intracellular concentration that is comparable to that of chlorophyll a in a molar ratio of approximately 1 to 1.6. The in vivo oxidation state of cyanopterin is primarily the fully reduced 5,6,7,8-tetrahydro form. The cellular function is unknown at present. The findings have established a model system, using Synechocystis sp. PCC 6803, for studies of the physiological functions of unconjugated pteridine glycosides found mostly in cyanobacteria.

Chromatography, High Pressure Liquid↗