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Biomedical subjects

H Yoo

Publications and source records attributed to H Yoo.

At least 19 recordsLinked to original sources
PubMed2006

PATRIC: the VBI PathoSystems Resource Integration Center.

The PathoSystems Resource Integration Center (PATRIC) is one of eight Bioinformatics Resource Centers (BRCs) funded by the National Institute of Allergy and Infection Diseases (NIAID) to create a data and analysis resource for selected NIAID priority pathogens, specifically proteobacteria of the genera Brucella, Rickettsia and Coxiella, and corona-, calici- and lyssaviruses and viruses associated with hepatitis A and E. The goal of the project is to provide a comprehensive bioinformatics resource for these pathogens, including consistently annotated genome, proteome and metabolic pathway data to facilitate research into counter-measures, including drugs, vaccines and diagnostics. The project's curation strategy has three prongs: 'breadth first' beginning with whole-genome and proteome curation using standardized protocols, a 'targeted' approach addressing the specific needs of researchers and an integrative strategy to leverage high-throughput experimental data (e.g. microarrays, proteomics) and literature. The PATRIC infrastructure consists of a relational database, analytical pipelines and a website which supports browsing, querying, data visualization and the ability to download raw and curated data in standard formats. At present, the site warehouses complete sequences for 17 bacterial and 332 viral genomes. The PATRIC website (https://patric.vbi.vt.edu) will continually grow with the addition of data, analysis and functionality over the course of the project.

Bioterrorism↗
PubMed2006

Measurement and restoration of the point spread function of fluorescence confocal microscopy.

The point spread function of an objective lens of a fluorescence confocal microscope was directly measured by imaging fluorescent beads. We analysed how the measurement of the point spread function was influenced by the diameter of the fluorescent beads and how the restoration technique with a deconvolution algorithm improved the measuring performance. Numerical and experimental results are presented for a typical point spread function and a zero-centred point spread function.

Journal Article↗
PubMed2005

Dihydroartemisinin enhances radiosensitivity of human glioma cells in vitro.

PURPOSE: The antimalarial agent, artemisinin, also confers cancer-specific cytotoxic effects by reacting with ferrous iron atoms to form free radicals. Here, we investigated the radiosensitizing effects of dihydroartemisinin on glioma cells and assessed some possible mechanisms for these effects. MATERIALS AND METHODS: U373MG glioma cells treated with various concentrations of dihydroartemisinin plus radiation, and efficiency of radiosensitization was assessed by clonogenic survival assay. Expression and activity of antioxidant enzymes, glutathione-S-transferase (GST) were quantified by western blot and enzymatic activity analyses, respectively. RESULTS: Dihydroartemisinin showed higher cytotoxicity in the glioma cell lines than in the liver, breast or cervical cancer cell lines. In clonogenic survival assays, treatment with dihydroartemisinin alone dose-dependently reduced the number of U373MG colonies, while treatment with dihydroartemisinin plus gamma-irradiation showed far lower clonal survival than cultures treated with radiation or dihydroartemisinin alone. The radiosensitizing effect of dihydroartemisinin was blocked significantly by the free radical scavengers, NAC and TIRON, indicating association with dihydroartemisinin-induced ROS generation. In addition, the radiation-induced expression of endogenous GST was suppressed by treatment with dihydroartemisinin. The radiosensitizing effect of dihydroartemisinin was also markedly enhanced by the addition of holotransferrin CONCLUSION: Taken together, our results strongly suggest that dihydroartemisinin triggers production of ROS and inhibits GST activity, leading to effective and therapeutically relevant radiosensitization of human glioma cells.

1,2-Dihydroxybenzene-3,5-Disulfonic Acid Disodium ↗
PubMed2005

Organochlorines and dioxin-like compounds in green-lipped mussels Perna viridis from Hong Kong mariculture zones.

Concentrations of persistent organic pollutants including polychlorinated biphenyls (PCBs), organochlorine (OC) pesticides and dioxin-like compounds were measured in green-lipped mussels, Perna viridis, collected from seven mariculture zones in Hong Kong between September and October in 2002 in order to evaluate the status, spatial distribution and potential sources of pollution in these areas. Concentrations ranged from 300 to 4400 ng/g lipid weight for total OCs and 170-1000 ng/g lipid weight for total PCBs (based on 28 congeners). Relatively smaller DDT concentrations in mussels compared with previous studies suggest reduced discharges of DDTs from nearby regions into Hong Kong waters. Detection of a mixture of HCH isomers in the mussels indicated that Hong Kong waters were predominantly contaminated by technical HCHs rather than lindane. Mussel samples from all sampling locations elicited significant dioxin-like activity in the H4IIE-luc bioassay. The greatest magnitude of dioxin-like response (39 pg TEQ/g wet wt.) was detected in mussels from Ma Wan in the western waters of Hong Kong, which is strongly influenced by the Pearl River discharge. Human health risk assessment was undertaken to evaluate potential risks associated with the consumption of the green-lipped mussels. Risk quotient (RQ) for dioxin-like compounds was greater than unity suggesting that adverse health effects may be associated with high mussel consumption.

Animals↗
PubMed2001

The genome of the natural genetic engineer Agrobacterium tumefaciens C58.

The 5.67-megabase genome of the plant pathogen Agrobacterium tumefaciens C58 consists of a circular chromosome, a linear chromosome, and two plasmids. Extensive orthology and nucleotide colinearity between the genomes of A. tumefaciens and the plant symbiont Sinorhizobium meliloti suggest a recent evolutionary divergence. Their similarities include metabolic, transport, and regulatory systems that promote survival in the highly competitive rhizosphere; differences are apparent in their genome structure and virulence gene complement. Availability of the A. tumefaciens sequence will facilitate investigations into the molecular basis of pathogenesis and the evolutionary divergence of pathogenic and symbiotic lifestyles.

Agrobacterium tumefaciens↗
PubMed2001

An angiographic lesion mimicking pseudo-aneurysm in cerebral arteriovenous malformation.

In cerebral arteriovenous malformations (AVMs), a pseudo-aneurysm represents rupture site, and its presence is known as a factor for rebleeding. We report a case of cerebral AVM presenting with intracerebral haemorrhage in which cerebral angiography showed a lesion mimicking pseudo-aneurysm. Although the patient needed urgent surgical decompression, it was delayed because early haematoma evacuation would induce rebleeding from the rupture site. The authors attempted to occlude the pseudoaneurysm interventionally before surgery. After surgical excision, the lesion that was believed to be a pseudo-aneurysm was revealed as a partially thrombosed venous sac having a thick fibrous wall. In this report, the authors discuss the pitfalls in the interpretation of pseudo-aneurysms in angiographic AVM architecture.

Adolescent↗
PubMed2001

Multiple meningiomas of different pathological features: case report.

Meningioma is a common intracranial tumour and it may occur not infrequently as one of the multiple tumours, especially in patients with neurofibromatosis. The incidence of multiple meningiomas (MMs) without the stigmata of neurofibromatosis is rare, ranging from 1 to 9% of all meningiomas in the literature. Multiple meningiomas with different pathologic features are even rarer, and most of them are benign histologies. The authors report an extremely rare case of MMs which were presented with malignant and benign histological features simultaneously. The underlying mechanism of MM formation is still unclear, however, subarachnoid spread was thought to be the most likely mechanism. The findings of most of MMs showed identical histopathological features and several molecular biologic studies provided evidence for the monoclonal origin of MMs to back up the above hypothesis. However, different histological features among the reported multiple meningioma cases including our particular one, suggests their origin from multicentric neoplastic foci activated by a supposed tumour-producing factor. However, we cannot completely exclude the possibility of independent progression from monoclonal origin.

Aged↗
PubMed2001

Epithelioid haemangioendothelioma of the sphenoid bone.

The authors report a case of cranial EH occurred in the left sphenoid bone that was totally excised without transfusion. A 26-year-old woman presented with a 1-year history of progressing exophthalmos in the left eye. A cranial X-ray showed a mixed osteolytic and sclerotic expansile mass lesion in the left sphenoid bone. Neuroradiologic imaging study revealed a left temporosphenoidal extra-axial expansile mass lesion with heterogeneous enhancement after contrast enhancement associated with destruction and erosion of the temporal and sphenoid bones. The cerebral parenchyma and orbital contents were compressed without any sign of infiltration. Bone scan showed hot uptake in the left orbital region. Angiogram demonstrated marked neoplastic angiogenesis from the middle meningeal artery and other branches of left external carotid artery, for which preoperative embolisation was tried in vain. Cranio-orbito-zygomatic approach was undergone in two stages because of the patient's religious belief (patient was Jehovah's witness) and profuse bleeding during the first surgery. Two weeks after initial operation, second surgery was carried out with total excision of the residual mass in the left orbital ridge. Histopathological examination revealed typical epithelioid cell cords or nests in myxoid stroma with a positive immunoreactivity to factor VIII-related antigen. The authors report an unusual case of EH involving sphenoid and temporal bone in a young woman. Preoperative embolisation is thought to be absolutely essential before removal. Because there is no convincing data to advise radiation/chemotherapy, total resection and close follow-up may be reasonable.

Adult↗
PubMed2001

Effect of SKI 306X, a new herbal anti-arthritic agent, in patients with osteoarthritis of the knee: a double-blind placebo controlled study.

SKI 306X is a purified extract from a mixture of three oriental herbal medicines (Clematis mandshurica, Trichosanthes kirilowii and Prunella vulgaris) that have been widely used for the treatment of inflammatory diseases such as lymphadenitis and arthritis in far East Asia. A double-blind, controlled study was performed to evaluate the efficacy and safety of SKI 306X with placebo in 96 patients with classical osteoarthritis of the knee. Patients were randomized to four treatment groups: placebo, 200 mg, 400 mg and 600 mg of SKI 306X t.i.d.. Clinical efficacy and safety were evaluated for 4 weeks continuous treatment. SKI 306X demonstrated its clinical efficacy, as assessed by 100 mm visual analogue scale (VAS), Lequesne index and patients' and investigators opinion of the therapeutic effect compared with placebo (p<0.01). No significant adverse events were observed in patients treated with SKI 306X. This study demonstrated that SKI 306X, a new herbal anti-arthritic agent provided clinical efficacy in patients with osteoarthritis.

Adult↗
PubMed2001

Acetate injection into anaerobic settled sludge for biological P-removal in an intermittently aerated reactor.

Injecting acetate into the sludge layer during the settling and decanting periods was adopted to enhance phosphorus release inside the sludge layer during those periods and phosphorus uptake during the subsequent aeration period in a KIST Intermittently Decanted Extended Aeration (KIDEA) process. The relationship among nitrification, denitrification and phosphorus removal was investigated in detail and analyzed with a qualitative floc model. Dependencies of nitrification on the maximum DO level during the aerobic phase and phosphorus release on residual nitrate concentration during the settling phase were significant. High degree of nitrification resulted that phosphorus release inside the sludge layer was significantly interfered with nitrate due to the limitation of available acetate and the carbon sources from influent. Such limitation was related to the primary utilization of organic substance for denitrification in the outer layer of the floc and the retarded mass transfer into the inner layer of the floc. Nevertheless, effects of acetate injection on both denitrification and phosphorus release during the settling phase were significant. Denitrification rate after acetate injection was two times as high as that before acetate injection, and phosphorus release reached about 14 mg PO4(3-)-P/g MLVSS/hr during the decanting phase after the termination of denitrification inside the sludge layer. Extremely low level of maximum DO (around 0.5 mg/L) during the aerobic phase may inhibited nitrification, considerably, and thus nearly no nitrate was present. However, the absence of nitrate increased when the phosphorus release rate was reached up to 33 mg PO4(3-)-P/g MLVSS/hr during the settling and decanting phase, and nearly all phosphorus was taken up during subsequent aerobic phase. Since the sludge layer could function as a blocking layer, phosphorus concentrations in the supernatant was not influenced by the released phosphorus inside the sludge layer during the settling and decanting period. Phosphorus removal was directly (for uptake) and indirectly (for release) dependent on the median and maximum DO concentration during the aerobic phase, and those optimal values may exist within the range from 0.2 to 0.6 mg/L and 0.4 to 1.2 mg/L, respectively.

Acetates↗
PubMed2000

Enhanced delivery of antisense oligonucleotides with fluorophore-conjugated PAMAM dendrimers.

PAMAM dendrimers are cationic polymers that have been used for the delivery of genes and oligonucleotides to cells. However, little is known about the behavior of dendrimer-nucleic acid complexes once they reach the cell interior. To pursue this issue, we prepared dendrimers conjugated with the fluorescent dye Oregon green 488. These were used in conjunction with oligonucleotides labeled with a red (TAMRA) fluorophore in order to visualize the sub-cellular distribution of the dendrimer-oligonucleotide complex and of its components by two-color digital fluorescence microscopy. The 2'-O:-methyl antisense oligonucleotide sequence used in these studies was designed to correct splicing at an aberrant intron inserted into a luciferase reporter gene; thus effective delivery of the antisense agent results in the expression of the reporter gene product. The dendrimer-oligonucleotide complex remained associated during the process of uptake into vesicular compartments and eventual entry into the nucleus. Since the pharmacological activity of the antisense compound was manifest under these conditions, it suggests that the dendrimer-oligonucleotide complex is functionally active. A surprising result of these studies was that the Oregon green 488-conjugated dendrimer was a much better delivery agent for antisense compounds than unmodified dendrimer. This suggests that coupling of relatively hydrophobic small molecules to PAMAM dendrimers may provide a useful means of enhancing their capabilities as delivery agents for nucleic acids.

Biological Transport↗
PubMed2000

Real-time fluorescence assay for O6-alkylguanine-DNA alkyltransferase.

O6-alkylguanine-DNA alkyltransferase (AGT) is a DNA-repair protein that reverses the effects of alkylating agents by removing DNA adducts from the O6-position of guanine. We developed a real-time AGT assay that utilizes a fluorescent guanosine analog (3-methylisoxantopterin, 3-MI). 3-MI fluorescence is quenched in DNA and fluorescence intensity increases substantially with digestion of the oligonucleotide and release of 3-MI. The substrate is a doubled-stranded oligonucleotide with 3'-overhangs on each end and a PvuII recognition site. PvuII is inhibited by O6-methylguanine, positioned within the restriction site. 3-MI is incorporated in the opposite strand just outside of the PvuII restriction site. AGT repairs O6-methylguanine; PvuII cleaves at its restriction site, yielding a blunt-ended double strand, which is then digested by exonuclease III. This releases 3-MI from the oligonucleotide, resulting in an increase in fluorescence intensity. All reaction components (100-microL volume) are monitored in a single microcuvette. Rate of increase in fluorescence intensity is related to the amount of AGT in the reaction mixture. We measured AGT levels in extracts from a leukemia cell line, from leukemic lymphoblasts from patients, and from peripheral blood mononuclear cells from normal controls. This method may prove useful for mechanistic studies of AGT.

Base Sequence↗
PubMed2000

Meningioma manifesting intracerebral haemorrhage: a possible mechanism of haemorrhage.

We present a possible mechanism of intracerebral peritumoural haemorrhage in meningioma based on the clinical data of three of our cases. A meningioma manifesting intracerebral haemorrhage is uncommon and some sporadic case reports have been presented, but without any proven mechanisms. We are presenting three cases of convexity meningioma manifesting spontaneous intracerebral haemorrhage with apoplectiform onset. All three patients had no evidence of bleeding tendency or other predisposing factors for haemorrhage. Preoperative radiological studies showed a solid mass attached to the dura with intracerebral peritumoural haematoma. Total removal of the tumour and haematoma could be achieved in every case. Histological investigation revealed extensive tumour infarction in two cases and fibrosis related to pre-existing ischaemia in the other case. The diagnoses were atypical meningioma in two cases and transitional type in one case. We suggest that extensive tumour infarction might be a cause of spontaneous intracerebral peritumoural haemorrhage in our series of patients.

Aged↗
PubMed2000

In vitro transport and delivery of antisense oligonucleotides.

A variety of techniques are currently available to enhance the cellular uptake and pharmacological effectiveness of antisense oligonucleotides in the in vitro setting. The choice of technique will depend on the context of investigation, the likelihood of cytotoxity due to the delivery agents, and the ease and convenience of the approach. The considerations for the delivery of antisense molecules in the in vivo setting are likely to be quite different from the cell culture situation emphasized in this article.

Amino Acid Sequence↗
PubMed2000

Long-term outcome and growth rate of subtotally resected petroclival meningiomas: experience with 38 cases.

OBJECTIVE: To evaluate the long-term outcome of a subtotally resected residual tumor and to assess its growth rate, we analyzed the records of 38 patients with residual petroclival meningioma. METHODS: Clinical records and radiological findings of 38 cases of petroclival meningioma that were diagnosed and subtotally resected at Seoul National University Hospital between 1981 and 1997 were carefully reviewed. Follow-up imaging studies were reviewed, and Karnofsky performance scale scores at the last follow-up were recorded. The duration of follow-up ranged from 6 to 141 months (mean, 47.5 mo; median, 30 mo). Tumor progression and progression-free survival rates were assessed. The growth rate of a residual tumor was evaluated by measuring the equivalent diameter and the tumor volume serially; the tumor doubling time was calculated, and the predictive factors for determining the growth pattern in residual tumors and the prognosis were analyzed. RESULTS: In 33 (87%) of the 38 patients, Karnofsky performance scale scores at the last follow-up were 80 or above. The median progression-free survival time among patients with subtotally resected tumors was 66 months, and the 5-year progression-free survival rate was 60%. The growth rate of residual tumors was low (volume increase, 4.94 cc/yr; diameter increase, 0.37 cm/yr). The mean tumor doubling time was 8 years. Although there were no significant predictive factors, age and extent of tumor resection seemed to influence the progression-free survival rate. Significant factors affecting the growth rate were age and occurrence of menopause. CONCLUSION: Subtotal resection with or without radiation or radiosurgery should be considered as a suitable treatment option for patients with petroclival meningiomas, especially the elderly, because the growth rate of residual tumors is low.

Adolescent↗
PubMed2000

Aspects of the transport and delivery of antisense oligonucleotides.

This article will examine recent developments concerning the cellular uptake and subcellular trafficking of antisense oligonucleotides. It will also examine the merits of various delivery strategies for oligonucleotides. The use of conjugates of oligonucleotides with 'cell penetrating peptides' as a promising delivery technology will be emphasized.

Administration, Oral↗
PubMed1999

Novel cationic amphiphiles as delivery agents for antisense oligonucleotides.

There has been great interest recently in therapeutic use of nucleic acids including genes, ribozymes and antisense oligonucleotides. Despite recent improvements in delivering antisense oligonucleotides to cells in culture, nucleic acid-based therapy is still often limited by the poor penetration of the nucleic acid into the cytoplasm and nucleus of cells. In this report we describe nucleic acid delivery to cells using a series of novel cationic amphiphiles containing cholic acid moieties linked via alkylamino side chains. We term these agents 'molecular umbrellas' since the cationic alkylamino chains provide a 'handle' for binding of nucleic acids, while the cholic acid moieties are likely to interact with the lipid bilayer allowing the highly charged nucleic acid backbone to traverse across the cell membrane. Optimal gene and oligonucleotide delivery to cells was afforded by a derivative (amphiphile 5) containing four cholic acid moieties. With this amphiphile used as a constituent in cationic liposomes, a 4-5 log increase in reporter gene delivery was measured. This amphiphile used alone provided a 250-fold enhancement of oligo-nucleotide association with cells as observed by flow cytometry. A substantial fraction of cells exposed to complexes of amphiphile 5 and fluorescent oligo-nucleotide showed nuclear accumulation of the fluorophore. Enhanced pharmacological effectiveness of antisense oligonucleotides complexed with amphiphile 5 was observed using an antisense splicing correction assay that activates a Luciferase reporter. Intracellular delivery, nuclear localization and pharmacological effectiveness of oligonucleotides using amphiphile 5 were similar to those afforded by commercial cytofectins. However, in contrast to most commercial cytofectins, the umbrella amphiphile showed substantial delivery activity even in the presence of high concentrations of serum.

3T3 Cells↗