Biomedical subjects

Sang-Hoon Han

Publications and source records attributed to Sang-Hoon Han.

7 recordsLinked to original sources

PubMed2005

Oxaliplatin, folinic acid and 5-fluorouracil (FOLFOX-4) combination chemotherapy as second-line treatment in advanced colorectal cancer patients with irinotecan failure: a Korean single-center experience.

OBJECTIVE: This study was designed to determine the effectiveness and tolerance of oxaliplatin, folinic acid (FA) and infusional 5-fluorouracil (5-FU) (FOLFOX-4) chemotherapy when used as a second-line treatment in patients with advanced colorectal cancer for whom an irinotecan-containing regimen failed. METHODS: Thirty-eight patients with measurable colorectal cancer, progressive after previous irinotecan-containing chemotherapy for metastatic disease, were registered in this trial. Oxaliplatin was administered on day 1 at the dose of 85 mg/m(2) as a 2 h infusion, concurrently with FA 200 mg/m(2)/day, followed by bolus 5-FU 400 mg/m(2) and a 22 h infusion of 5-FU 600 mg/m(2) for two consecutive days. The treatment was repeated every 2 weeks until disease progression or unacceptable toxicity occurred or until a patient chose to discontinue the treatment. RESULTS: For 34 patients treated, a total of 183 chemotherapy cycles were administered. In an intent-to-treat analysis, six patients (16%) achieved a partial response that they maintained for 5.4 months. The median progression-free and overall survivals were 2 and 5 months, respectively. Frequently encountered toxicities were peripheral neuropathy and gastrointestinal side effects including diarrhea. Although there was one early death, toxicity profiles were generally predictable and manageable. CONCLUSION: Second-line FOLFOX-4 is a feasible regimen with modest activity for colorectal cancer patients with irinotecan failure. Further clinical trials incorporating novel biological agents are warranted.

Adult↗

PubMed2004

Visual search does not remain efficient when executive working memory is working.

Working memory (WM) has been thought to include not only short-term memory stores but also executive processes that operate on the contents of memory. The present study examined the involvement of WM in search using a dual-task paradigm in which participants performed visual search while manipulating or simply maintaining information held in WM. Experiments 1a and 2a involved executive WM tasks that required counting backward from a target digit and sorting a string of letters alphabetically, respectively. In both experiments, the search slopes in the dual-task condition were significantly steeper than those in a search-alone condition, indicating that performing the WM manipulation tasks influenced the efficiency of visual search. In contrast, when information was simply maintained in WM (Experiments 1b and 2b), search slopes did not differ between the single- and dual-task conditions. These results suggest that WM resources related to executive functions may be required in visual search.

Cognition↗

PubMed2003

Phylogenetical positions of Sorex sp. (Insectivora, Mammalia) from Cheju Island and S. caecutiens from the Korean Peninsula, inferred from mitochondrial cytochrome b gene sequences.

Phylogenetical positions of Sorex specimens unassigned to species from Cheju Island, Korea, and S. caecutiens from southern Korean Peninsula were investigated based on full nucleotide sequences (1,140 bp) of the mitochondrial cytochrome b gene, comparing specimens of the S. caecutiens/shinto group from locations throughout its range. In the phylogenetic tree obtained, S. caecutiens were separated into two main groups: Hokkaido and Continent-Sakhalin-Cheju clusters. Shrews from Cheju and Korean Peninsula were included in the latter cluster. Thus, we suggest that the shrew on Cheju Island should be ranked as S. caecutiens, although taxonomic description of the shrew has to be conducted elsewhere. The Cheju shrews formed a single sub-cluster while the peninsular shrews were not included in a single sub-cluster. The clustering of individuals in Continent-Sakhalin-Cheju cluster did not always reflect the geographical proximity of their capture locations. We interpret these findings as indicating ancestral isolation of a Hokkaido population and recent rapid range expansion of the modern population in Eurasian Continent-Sakhalin-Cheju.

Animals↗

PubMed2002

Determination of zeta potentials of polymeric nanoparticles by the conductivity variation method.

An easy method of measurement of the zeta potentials of sub-50-nm polymeric nanoparticles is suggested. Although zeta potential measurements of nanoparticles or emulsions above 50 nm have been successfully carried out, zeta potentials of emulsions or nanoparticles below 50 nm could not be precisely measured in the region of extremely low conductivity by conventional electrophoresis with a He-Ne laser. However, zeta potentials of sub-50-nm nanoparticles were measured in the region of thin electrical double layers by addition of sodium chloride and zeta potentials in the condition without sodium chloride could be predicted by extrapolation of the measured potentials. The electrophoretic mobility of 150-nm nanoparticles stabilized with sodium dodecylsulfate was the same as that calculated from extrapolation of the measured ones. The zeta potentials of sub-50-nm nanoparticles stabilized with sodium dodecylsulfate could be calculated by the same procedure.

Journal Article↗

PubMed2002

Self-aggregates of poly(2-hydroxyethyl aspartamide) copolymers loaded with methotrexate by physical and chemical entrapments.

Amphiphilic copolymers based on poly(2-hydroxyethyl aspartamide) (PHEA) formed self-aggregates for the entrapment and release of methotrexate (MTX) by physical entrapment and chemical conjugation. In physical entrapment, MTX was partitioned into hydrophobic domains in self-aggregates of PHEA grafted with octadecyl chains (PHEA-C18) and the amount of the entrapped drug increased linearly by 3.39 mg per the degree of substitution of grafted octadecyl groups. The amphiphilic nature of the drug induced a large initial release in the buffer medium, irrespective of the amount of octadecyl chains. However, PEG-grafted PHEA-C18 copolymers conjugated with MTX, ConG, formed a micelle-like structure by self-association of the conjugates and suppressed the initial large release. The alkyl grafting lowered the CAC, meaning enhancement of aqueous stability. The release was accelerated in pH 10.0 by rapid hydrolysis of ester linkage by base-catalyzed cleavage, while it was significantly reduced at pH 5.0.

Antimetabolites, Antineoplastic↗

PubMed2002

A spatial aspect on mitochondrial DNA genealogy in Apodemus peninsulae from East Asia.

Apodemus peninsulae is a field mouse that inhabits the broad-leafed forests of temperate Eurasia. We examined the mitochondrial cytochrome b gene in 57 in dividuals of A. peninsulae from northeastern Asia, including Siberia, Primorye, Magadan region, Sakhalin, Hokkaido, and the Korean Peninsula. The genealogy of the mitochondrial DNA (mtDNA) in A. peninsulae was shown to have substantial geographic affinity, suggesting geographic architecture of northeastern Asia, including the islands of Sakhalin and Hokkaido, played important roles on the cladogenesis. Taking into account the presence of region-specific anciently divergent mtDNA types, three parts of the regions of Primorye, Siberia, and the Korean Peninsula can be denoted as refugia for A. peninsulae during the substantial period of the Quaternary glacial ages. Among the geographic regions examined, Primorye is likely to be the most influential one, from which the mtDNA is thought to have migrated to the neighboring regions of Sakhalin, Hokkaido, the Magadan region, and Siberia during the evolution of this species.

Animals↗

PubMedDate not supplied

The stabilization of L-ascorbic acid in aqueous solution and water-in-oil-in-water double emulsion by controlling pH and electrolyte concentration.

This study presents a new approach that can stabilize effectively L-ascorbic acid in water-in-oil-in-water (w/o/w) double emulsions. Basically, the behavior of L-ascorbic acid in the aqueous phase was observed, considering its molecular deformation. Then, it was found that the stability determined in the aqueous phase by high-performance liquid chromatography (HPLC) showed that the collapse of ionization of L-ascorbic acid played a crucial role in protecting the molecular deformation. Then, the stable aqueous system was incorporated into the internal aqueous phase of the double emulsions. From the HPLC analysis, it was observed that the L-ascorbic acid in an appropriate system showed high molecular stability for a long time. Moreover, in the measurement of in vitro skin permeation, the L-ascorbic acid stabilized in this study showed considerable skin permeation ability, indicating its potential applicability in pharmaceutics and cosmetics.

Animals↗