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Biomedical subjects

I K Park

Publications and source records attributed to I K Park.

At least 19 recordsLinked to original sources
PubMed2005

Phase II study of concurrent chemoradiotherapy with capecitabine and cisplatin in patients with locally advanced squamous cell carcinoma of the head and neck.

We aimed to evaluate the efficacy and safety of concurrent chemoradiotherapy with capecitabine and cisplatin in patients with locally advanced squamous cell carcinoma of the head and neck (SCCHN). In total, 37 patients with stage III or IV SCCHN were enrolled on the study. The chemotherapy consisted of two cycles of intravenous cisplatin of 80 mg m(-2) on day 1 and oral capecitabine 825 mg m(-2) twice daily from day 1 to day 14 at 3-week intervals. The radiotherapy (1.8-2.0 Gy 1 fraction day(-1) to a total dose of 70-70.2 Gy) was delivered to the primary tumour site and neck. The primary tumour sites were as follows: oral cavity (n=6), oropharynx (n=11), hypopharynx (n=8), larynx (n=3), nasopharynx (n=6), and paranasal sinus (n=3). After the chemoradiotherapy, 29 complete responses (78.4%) and 6 partial responses (16.2%) were confirmed. Grade 3 or 4 neutropenia occurred only in two patients, plus grade 3 febrile neutropenia was observed only in one patient. At a median follow-up duration of 19.8 months, the estimated overall survival and progression-free survival rate at 2-year was 76.8 and 57.9%, respectively. Concurrent chemoradiotherapy with capecitabine and cisplatin was found to be well tolerated and effective in patients with locally advanced SCCHN.

Adult↗
PubMed2005

Galactose-carrying polymers as extracellular matrices for liver tissue engineering.

Extracellular matrix (ECM) plays important roles in tissue engineering because cellular growth and differentiation, in the two-dimensional cell culture as well as in the three-dimensional space of the developing organism, require ECM with which the cells can interact. Especially, the bioartificial liver-assist device or regeneration of the liver-tissue substitutes for liver tissue engineering requires a suitable ECM for hepatocyte culture because hepatocytes are anchorage-dependent cells and are highly sensitive to the ECM milieu for the maintenance of their viability and differentiated functions. Galactose-carrying synthetic ECMs derived from synthetic polymers and natural polymers bind hepatocytes through a receptor-mediated mechanism, resulting in enhanced hepatocyte functions. Attachment and functions of hepatocytes were affected by physico-chemical properties including ECM geometry as well as the type, density and orientation of galactose. Also, cellular environment, medium composition and dynamic culture system influenced liver-specific functions of hepatocytes beside ECM.

Animals↗
PubMed2005

Influence of air exposure and storage condition on serum ionized magnesium level.

The aim of this study was to evaluate whether reporting serum level of ionized magnesium (iMg) is appropriate when affected by various conditions such as exposure to air and delayed measurement. Serum levels of pH, iMg and normalized magnesium (nMg, normalized or adjusted concentration of iMg to pH 7.40) from 28 inpatients were measured at intervals of 3 min after exposing the samples to air at room temperature. Serum from 30 inpatients was stored in closed tubes at 4 degrees C and -20 degrees C and iMg and nMg levels were measured after 2 days. It was found that serum iMg and nMg concentrations exposed to air were decreased by 0.0023 mmol/l and 0.0001 mmol/l per minute, respectively. nMg did not display any significant changes compared with iMg at 0 min, whereas iMg showed significant changes, which exceeded between-day precision. For the stored serum, only iMg of serum at -20 degrees C showed no statistically significant changes (p = 0.169). It is concluded that to report the result as iMg, the sample should be kept anaerobically, and if exposed to air, the result should be reported as nMg. For storage, iMg of serum kept anaerobically at -20 degrees C is reliable.

Air↗
PubMed2005

A case report: isolated a heavy chain monoclonal gammopathy in a patient with polyneuropathy, organomegaly, endocrinopathy, monoclonal gammopathy and skin change syndrome.

A 45-year-old South-Korean man presented with abdominal distension, progressive paresthesia and motor weakness of both lower extremities. Our case was identified as polyneuropathy, organomegaly, endocrinopathy, monoclonal gammopathy and skin change (POEMS) syndrome based on diagnostic criteria. Circulating M components of POEMS syndrome consist mainly of IgG or IgA-lambda and rarely IgM-lambda, IgG-kappa or isolated light chains. In this case, the M-band on serum protein electrophoresis and isolated IgA heavy chain on serum immunofixation electrophoresis were demonstrated, but there was no abnormal light chain. We suggest that this case may be associated with a pattern of abnormal secretion of monoclonal protein or a coincidence of a heavy chain disease in POEMS syndrome, even though the latter possibility may be very rare.

Bone Marrow↗
PubMed2003

Visualization of transfection of hepatocytes by galactosylated chitosan-graft-poly(ethylene glycol)/DNA complexes by confocal laser scanning microscopy.

Dual-labeled galactosylated chitosan-graft-poly(ethylene glycol) (PEG) (GCP)/DNA complexes were prepared and their hepatocyte-specific delivery and cellular distribution were investigated by confocal laser scanning microscopy (CLSM). The complexes were transfected into hepatocyte through specific interaction of galactose moiety of the GCP and asialoglycoprotein receptors (ASGPR) of the hepatocytes. The GCP/DNA complexes taken up by the hepatocytes were rapidly released into the cytoplasm, but nuclear trafficking of the released complexes was slow and rate-limiting process. The more efficient transfection of the complex occurred in the human-derived HepG2 cells than in primary hepatocytes.

Animals↗
PubMed2003

Galactosylated chitosan (GC)-graft-poly(vinyl pyrrolidone) (PVP) as hepatocyte-targeting DNA carrier. Preparation and physicochemical characterization of GC-graft-PVP/DNA complex (1).

Galactosylated chitosan was conjugated with poly(vinyl pyrrolidone) (PVP) as a hydrophilic group. The complex formation of GC-graft-PVP (GCPVP)/DNA complexes was confirmed by agarose gel electrophoresis. The morphology of the complex observed by atomic force microscopy had a compact and spherical shape, around 40 nm particle sizes at a charge ratio of 3. The binding strength of GCPVP 10K/DNA complex measured by ethidium bromide binding assay was superior to that of the GCPVP 50K/DNA one, probably attributable to its higher flexibility due to the smaller size, whereas the DNase I protection of GCPVP 10K/DNA complex was inferior to that of the GCPVP 50K/DNA one. This indicated that effective complex formation required both higher binding strength and minimal molecular weight of polycation enough to induce the condensation of DNA. The DNA-binding property of GCPVP mainly depended on the molecular weight of chitosan and composition of PVP.

Animals↗
PubMed2001

Receptor-mediated delivery of all trans-retinoic acid to hepatocyte using poly(L-lactic acid) nanoparticles coated with galactose-carrying polystyrene.

All trans-retinoic acid (RA)-loaded poly(L-lactic acid) (PLA) nanoparticles coated with galactose-carrying polymer, as hepatocyte-specific targeting material using galactose ligands as recognition signals to asialoglycoprotein receptors were prepared by the diafiltration method. Effects of released RA from its loaded nanoparticles on morphology and DNA synthesis of hepatocytes were studied. Receptor-mediated endocytosis of the nanoparticles was checked by fluorescence and confocal laser microscopy. It was found that the shapes of most hepatocytes attached onto polystyrene dish precoated with collagen solution were flat and spreading at low concentration of RA for the RA-loaded nanoparticles, whereas their shapes were round at even low concentration of RA when RA was mixed with the nanoparticles. From the fluorescence and confocal laser microscopic studies, it was suggested that the nanoparticles coated with galactose-carrying polymers were internalized by the hepatocytes through the receptor-mediated mechanism. The RA-loaded nanoparticles were more potent stimulators of hepatocyte DNA synthesis than the free RA system in the presence of epidermal growth factor (EGF) owing to the controlled release of RA from the RA-loaded nanoparticles.

Animals↗
PubMed2001

Galactosylated chitosan-graft-poly(ethylene glycol) as hepatocyte-targeting DNA carrier.

Lactobionic acid bearing galactose group was coupled with chitosan for liver specificity, and poly(ethylene glycol) (PEG) was grafted to galactosylated chitosan (GC) for stability in water and enhanced cell permeability. Complex formation of galactosylated chitosan-graft-PEG (GCP)/DNA complexes was confirmed by agarose gel electrophoresis. Compared to GC/DNA complex, the stability of GCP/DNA complex could be enhanced. Particle sizes of GCP/DNA complexes decreased as the charge ratio of GCP to DNA increased and had a minimum value around 27 nm at the charge ratio of 5. Conformational change of DNA did not occur after complex formation with GCP compared to conformation of DNA itself. GCP/DNA complexes were only transfected into Hep G2 having asialoglycoprotein receptors (ASGR), indicative of specific interaction of ASGR on cells and galactose ligands on GCP.

Chitin↗
PubMed2001

NAD+ inhibits the self-splicing of the group I intron.

We investigated the effects of the coenzyme NAD+ (nicotinamide adenine dinucleotide) and its analogs on the self-splicing of primary transcripts of the phage T4 thymidylate synthase gene (td). Of all the nicotinamide coenzymes and analogs tested, NADP+ was the strongest inhibitor, with a potency approximately threefold that of NAD+. Kinetic analysis demonstrated that NAD+ acts as a mixed type noncompetitive inhibitor for the td intron RNA with a K(i) of 4.1 mM. The splicing specificity inhibition by NAD+ is predominantly due to changes in Km and kcat, and was Mg2+ concentration dependent. The results suggest that both the ADP and nicotinamide moieties are the key structural features in NAD+ responsible for the inhibition of splicing.

Adenosine Diphosphate↗
PubMed2001

Molecular cloning and characterization of a novel regulator of G-protein signaling from mouse hematopoietic stem cells.

A novel regulator of G-protein signaling (RGS) has been isolated from a highly purified population of mouse long-term hematopoietic stem cells, and designated RGS18. It has 234 amino acids consisting of a central RGS box and short divergent NH(2) and COOH termini. The calculated molecular weight of RGS18 is 27,610 and the isoelectric point is 8.63. Mouse RGS18 is expressed from a single gene and shows tissue specific distribution. It is most highly expressed in bone marrow followed by fetal liver, spleen, and then lung. In bone marrow, RGS18 level is highest in long-term and short-term hematopoietic stem cells, and is decreased as they differentiate into more committed multiple progenitors. The human RGS18 ortholog has a tissue-specific expression pattern similar to that of mouse RGS18. Purified RGS18 interacts with the alpha subunit of both G(i) and G(q) subfamilies. The results of in vitro GTPase single-turnover assays using Galpha(i) indicated that RGS18 accelerates the intrinsic GTPase activity of Galpha(i). Transient overexpression of RGS18 attenuated inositol phosphates production via angiotensin receptor and transcriptional activation through cAMP-responsive element via M1 muscarinic receptor. This suggests RGS18 can act on G(q)-mediated signaling pathways in vivo.

Amino Acid Sequence↗
PubMed2001

Effects of nicotinamide coenzymes on the stability of enzyme activities and proteins in niacin-deficient quail tissues against trypsin treatment.

The stability of liver and muscle enzymes and proteins in niacin-deficient quail towards trypsin treatment in the presence and absence of coenzymes, NAD or NADP, was characterized. The protection of liver dehydrogenases by coenzymes was low when they are subjected to trypsin digestion for 60 min. In contrast, in the muscle there was substantial protection against trypsin inactivation of glyceraldehyde-3-phosphate dehydrogenase by NAD and of 6-phosphogluconate dehydrogenase by NADP. Among all enzymes tested, glyceraldehyde-3-phosphate dehydrogenase showed the greatest protection against trypsin inactivation by NAD. SDS-polyacrylamide gel electrophoresis demonstrated that muscle proteins from the niacin-deficient group were more substantially protected compared to control and pair-fed groups when liver and muscle extracts were spiked with NAD and subjected to trypsin digestion. Overall results suggest that niacin deficiency exerted specific destabilizing effects on the stability of enzymes and proteins in muscle.

Animals↗
PubMed2001

Effects of neurotoxin 6-aminonicotinamide on levels of enzyme activities and metabolites in quail plasma.

Effects of 6-aminonicotinamide (6-AN) on the levels of proteins, metabolites and enzyme activities in the plasma of Japanese quail were investigated. The concentrations of soluble proteins in the pectoral and hindlimb muscle of the 6-AN treated and the pair-fed groups were significantly reduced compared to the control group. In the plasma, the levels of total proteins and albumin were not affected, but the levels of globulin were significantly lower than those of the control and pair-fed groups. In contrast, the levels of glucose and creatine were significantly elevated. Cellulose acetate gel electrophoresis showed that 6-AN induced a new synthesis of prealbumin and also increased the levels of beta-globulin relative to the control and pair-fed groups. In contrast, the levels of gamma-globulin were markedly lower than those of the control group, whereas the levels of alpha-globulin were not affected. The specific activity of alkaline phosphatase of the 6-AN group was significantly lower than that of the control and pair-fed groups and that of aspartate aminotransferase only lower than that of the control group but not the pair-fed group. The specific activities of creatine phosphokinase and lactate dehydrogenase of the 6-AN group were the greatest among the three groups, whereas those of the pair-fed group were greater than those of the control group. The results suggest that 6-AN may interfere with the proper maintenance of energy charges and the immune system function.

6-Aminonicotinamide↗
PubMed2001

The clinical and ocular manifestations of Takayasu arteritis.

PURPOSE: To evaluate the clinical and ocular manifestations of Takayasu arteritis and the fundus fluorescein angiography (FFA) characteristics of Takayasu retinopathy (TR). PATIENTS AND METHODS: Medical records and fundus fluorescein angiograms of 156 eyes of 78 patients with Takayasu arteritis were reviewed. Fundus FA using a wide-field fundus camera (60 degrees) was performed in 19 patients, and conventional angiography or spiral computed tomographic angiography was performed in all 78 patients. RESULTS: The series included 67 female and 11 male patients; mean age at time of diagnosis was 26.7 years (range, 4-61 years). Hypertension was found in 44 (56.4%) patients, ischemic cerebrovascular symptoms in 18 (23.1%) patients, and amaurosis fugax in 20 (25.6%) patients. On fundus examination, no retinopathy was found in 87 (55.8%) eyes; hypertensive retinopathy was found in 48 (30.8%) eyes; and TR was found in 21 (13.5%) eyes. Patients with TR had carotid artery or aortic arch involvement, and patients with hypertensive retinopathy had involvement of the descending aorta or renal artery and sparing of the carotids. Best-corrected visual acuity in TR Stage 1 to 3 ranged from 20/15 to 20/30, but in Stage 4, it ranged from 20/200 to hand motions because of secondary ocular complications. On FFA, the arm-to-retina circulation time was prolonged in all 21 eyes with TR (mean, 22.7+/-8.9 seconds), but only 14 eyes showed delayed arteriovenous filling time, which was mainly found in chronic, moderate to severe TR, Stage 3 or 4. Arteriovenous anastomosis was found in all 12 eyes with Stage 3 and 4 TR. CONCLUSIONS: Delayed arm-to-retina circulation time is shown in all cases of TR, but delayed arteriovenous filling time is mostly found in moderate and severe TR. During ophthalmic examination, the delay of arteriovenous filling time and formation of arteriovenous anastomosis must be examined carefully to prevent visual deterioration.

Adolescent↗
PubMed2000

Galactosylated chitosan-graft-dextran as hepatocyte-targeting DNA carrier.

Lactobionic acid bearing galactose group was coupled with chitosan for liver specificity, and dextran was grafted to galactosylated chitosan (GC) for stability in water. Compared to the GC/DNA complex, the stability of the galactosylated chitosan-graft-dextran (GCD)/DNA complex could be enhanced. The particle size of the GCD/DNA complexes decreased as the charge ratio of GCD to DNA increased. Conformational change of DNA did not occur after complex formation with GCD compared with the conformation of DNA itself. The GCD/DNA complexes were only transfected into Chang liver cells and that of Hep G2 having asialoglycoprotein receptors (ASGR), indicative of specific interaction of ASGRs on cells and galactose ligands on chitosan.

Asialoglycoprotein Receptor↗
PubMed2000

K(+) and Mg(2+) ions promote the self-splicing of the td intron RNA inhibited by spectinomycin.

The effects of Mg(2+) and K(+) ions on the self-splicing inhibition of the td (thymidylate synthase gene) intron RNA by spectinomycin were investigated. The maximum splicing activity occurred at 20 mM KCl. The K(m) and V(max) values for GTP in the presence of 5 mM Mg(2+) are 2.25 microM and 0.55 min(-1), whereas those for GTP both in the presence of 5 mM Mg(2+) and 5 mM K(+) are 1.23 microM and 0. 46 min(-1), respectively. Spectinomycin at 10 mM concentration inhibited the splicing by about 10%, but at 20 mM concentration, the splicing rate was inhibited by about 63%. The splicing inhibition by the low concentration of spectinomycin was overcome markedly as the concentration of Mg(2+) ion was raised. At 30 mM spectinomycin, however, the splicing inhibition was not significantly affected by increasing the concentration of Mg(2+). A similar activation of the splicing rate was observed as the concentration of K(+) ion was increased. The concentration of K(+) ion required for the normal recovery of the splicing was much higher than that of Mg(2+) ion. Unlike Mg(2+) ion, 30 mM K(+) ion effectively alleviated the splicing inhibition by spectinomycin at its high concentration. The results indicate that K(+) and Mg(2+) ions may show mechanistically different interactions with spectinomycin in the self-splicing reaction of the td intron RNA.

Animals↗
PubMed2000

The flavin coenzymes: a new class of group I intron inhibitors.

Effects of the coenzyme flavin mononucleotide (FMN) and its analogs on the self-splicing of primary transcripts of the phage T4 thymidylate synthase gene (td) have been investigated. Among all flavins and analogs tested, the lumichrome was the most inhibitory. The kinetic analysis demonstrated that FMN acts as a competitive inhibitor for the td intron RNA with a Ki of 1.86 mM although it does not possess a guanidino group in its structure. FMN is able to inhibit the first step of the self-splicing, thus identifying FMN as a novel class of group I intron splicing inhibitors. The specificity of the splicing inhibition by FMN is predominantly due to changes in Km but not k(cat). The splicing inhibition is believed to be due to the interference with the affinity of GTP for the intron RNA. The analysis of the inhibitory concentration and structural examination suggests that the key structural features in FMN responsible for the inhibition of splicing may be an alloxazine group.

Bacteriophage T4↗
PubMed2000

Spectinomycin inhibits the self-splicing of the group 1 intron RNA.

Effects of the aminoglycoside spectinomycin on the self-splicing of primary transcripts of the phage T4 thymidylate synthase gene (td) have been investigated. The kinetic analysis demonstrated that spectinomycin acts as a mixed noncompetitive inhibitor for the td intron RNA with a K(i) of 7.2 mM. Increasing the spectinomycin concentration raised the K(m) values with the corresponding decrease of V(max) and k(cat) values. The specificity of the splicing inhibition by spectinomycin is due to changes in both K(m) and k(cat). The splicing inhibition by spectinomycin is dependent on pH changes and Mg(2+) concentration, indicating electrostatic interactions with the intron RNA. It has been proposed that the key structural features in spectinomycin responsible for the inhibition of splicing may be the hydroxyl groups on the antibiotic.

Guanosine Triphosphate↗