Biomedical subjects

Sung-Min Choi

Publications and source records attributed to Sung-Min Choi.

5 recordsLinked to original sources

PubMed2006

Polymerized rodlike nanoparticles with controlled surface charge density.

Stable rodlike nanoparticles with highly controlled surface charge density have been developed by the free radical polymerization of the mixture of polymerizable cationic surfactant, cetyltrimethylammonium 4-vinylbenzoate (CTVB), and hydrotropic salt sodium 4-styrenesulfonate (NaSS) in aqueous solution. The surface charge of the polymerized CTVB/NaSS rodlike nanoparticles was controlled by varying the NaSS concentration during the polymerization process, and the charge variation was interpreted in terms of the overcharging effect in colloidal systems. The SANS measurements show that the diameter of the polymerized CTVB/NaSS rodlike nanoparticles is constant at 4 nm and the particle length ranges from 24 to 85 nm, depending on the NaSS concentration. The polymerized particles are longest when the NaSS concentration is 5 mol % which corresponds to the charge inversion or neutral point. The SANS and zeta potential measurements show that the Coulomb interactions between the particles are strongly dependent on the NaSS concentration and the zeta potential of the polymerized CTVB/NaSS nanoparticles changes from positive to negative (+12.8 approximately -44.2 mV) as the concentration of NaSS increases from 0 to 40 mol %. As the NaSS concentration is further increased, the zeta potential is saturated at approximately -50 mV.

Journal Article↗

PubMed2006

Thermally reversible pluronic/heparin nanocapsules exhibiting 1000-fold volume transition.

Novel Pluronic/heparin composite nanocapsules that exhibit a thermally responsible swelling and deswelling behavior were synthesized. Pluronic F-127 preactivated with p-nitrophenyl chloroformate at its two terminal hydroxyl groups was dissolved in a methylene chloride phase. The organic phase was dispersed in an aqueous phase containing heparin. At an organic/aqueous interface, Pluronic-cross-linked heparin nanocapsules were produced. They exhibited a 1000-fold volume transition (ca. 336 nm at 25 degrees C; ca. 32 nm at 37 degrees C), and a reversible swelling and deswelling behavior when the temperature was cycled between 20 and 37 degrees C. The reversible volume transition of Pluronic nanocapsules was caused by micellization and demicellization of cross-linked Pluronic polymer chains within the nanocapsule structure in response to temperature. The morphological characters were investigated with transmission electron microscopy and small angle neutron scattering. Pluronic/heparin nanocapsules had an aqueous fluid-filled hollow interior with a surrounding shell layer below the critical temperature, but they became a collapsed core/shell structure similar to that of Pluronic micelles above it.

Heparin↗

PubMed2005

Two novel mutations in the C7 gene in a Korean patient with complement C7 deficiency.

Complement C7 deficiency is an autosomal recessive disorder well known to be associated with increased susceptibility to meningococcal infection and has mostly been reported in Caucasians. In the Korean population, no case of C7 deficiency has been reported to date. Recently we experienced an 11-yr-old girl with meningococcal meningitis who was diagnosed as having C7 deficiency based upon the undetectable serum C7 protein on radial immunodiffusion and the undetectable serum total and C7 hemolytic activities. To identify the genetic basis of the C7 deficiency of the patient, we performed a mutation analysis for the C7 gene and found two novel mutations; a point mutation at the 3' splice acceptor site of intron 4 (c.281-1G>T) and a large deletion mutation encompassing almost the whole C7 gene from exon 1 to exon 17 (c.1-?_2350+?del). A haplotype analysis showed that the large deletion mutation was inherited from the patient's father. To the best of our knowledge, this is the first confirmed case of C7 deficiency in Korea.

Child↗

PubMed2005

Cerebral infarction in IgG multiple myeloma with hyperviscosity.

Cerebral infarction is an uncommon complication in multiple myeloma with hyperviscosity. Serum hyperviscosity may cause a variety of clinical manifestations including bleeding from mucosal membranes, congestive heart failure, retinopathy, and various neurologic deficits. These manifestations have been attributed to the presence of large quantities of asymmetrical molecules of high molecular weight in the serum. We recently experienced a case of multiple myeloma with acute cerebral infarction, which caused by hyperviscosity, as an initial manifestation in IgG multiple myeloma, and reviewed the relevant literature of myeloma presenting with the stroke. A 68-yr-old woman abruptly developed hypesthesia and monoplegia in the left leg. The stroke confirmed by the brain MRI and MR angiography, which revealed acute infarction at the right anterior cerebral artery territory. On admission, routine blood tests showed a slight decrease in hemoglobin and a marked increase in erythrocyte sedimentation rate. Peripheral blood smear, serum protein electrophoresis, serum visocity, and bone marrow aspiration showed that she had IgG multiple myeloma with hyperviscosity. She was treated by chemotherapy with cyclophosphamide and discharged with the improved clinical condition.

Aged↗

PubMed2004

5-fluorouracil-induced oligodendrocyte death and inhibitory effect of cycloheximide, Trolox, and Z-VAD-FMK in murine cortical culture.

BACKGROUND: 5-fluorouracil (5-FU) is a widely used anticancer drug. One of the adverse effects of this drug is selective cerebral white matter injury, but to the authors' knowledge its mechanism has not been well documented. The current study was performed to investigate the mechanism of cerebral white matter injury caused by 5-FU and to develop the intervention to attenuate its injury in vitro. METHODS: Mixed oligodendrocyte/astrocyte cells were dissociated from specimens taken from approximately 2-day-old postnatal mouse cortex and cultured for 3-4 weeks. The culture cells were exposed to 5-FU, cycloheximide, emetine, Z-VAD-fmk, 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)-quinoxaline (NBQX), Trolox, and epigallocatechin gallate. Oligodendrocyte cell death was assessed by counting the number of viable galactocerebroside-positive cells per x 100 field. RESULTS: Mixed oligodendrocyte/astrocyte culture cells that were exposed to 5-FU (at doses of 10 microM, 30 microM, and 100 microM) for 24 hours ensued concentration-dependent oligodendrocyte death. The majority of oligodendrocytes, but few astrocytes, were injured by 100 microM 5-FU. Trolox, a vitamin E analog antioxidant, as well as cycloheximide (a protein synthesis inhibitor) and Z-VAD-fmk (a caspase inhibitor), significantly attenuated the 5-FU-induced oligodendrocyte death. However, NBQX, an alpha-amino-2,3-dihydro-5-methyl-3-oxo-4-isoxazolepropionic acid (AMPA) receptor antagonist, did not appear to effect the 5-FU-induced oligodendrocyte death. CONCLUSIONS: The findings of the current study suggested that 5-FU led to oligodendrocyte death rather than astrocyte death by way of the apoptotic process, whereas antioxidants may prevent the 5-FU-induced oligodendrocyte cell death in vitro.

Amino Acid Chloromethyl Ketones↗