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S-H Lee

Publications and source records attributed to S-H Lee.

At least 19 recordsLinked to original sources
PubMed2006

Food encounter rate of simulated termite tunnels in heterogeneous landscapes.

The aim of this study was to explore how a heterogeneous landscape affects food encounter rate in the Formosan subterranean termite, Coptotermes formosanus Shiraki. To do this, a lattice model was formulated to simulate the tunneling structure of the termite. The model made use of minimized local rules derived from empirical data. In addition, a landscape structure was generated on a lattice space by using a neutral landscape model. Each lattice cell has a value h, representing spatially distributed property of the landscape (e.g., temperature or moisture). The heterogeneity of the landscape was characterized by a parameter, H controlling aggregation of lattice cells with higher values of h. Higher H values correspond to higher aggregation levels. The effect of the landscape heterogeneity on the encounter rate was clear in the presence of higher food density than in lower density. The effect was also enhanced by the increase of the number of primary tunnels.

Animal Feed↗
PubMed2006

Mechanoelectrical feedback regulates the arrhythmogenic activity of pulmonary veins.

BACKGROUND: Atrial fibrillation is commonly associated with dilated pulmonary veins. Stretch has been shown to have mechano-electrical effects. OBJECTIVE: To investigate whether stretch can increase the arrhythmogenic activity of the pulmonary veins. METHODS: The transmembrane action potentials were recorded from rabbit pulmonary veins before and after stretch (100 and 300 mg). Gadolinium and streptomycin (stretch-activated ion channel blockers) were each perfused into the pulmonary veins under a 300-mg stretch. RESULTS: Stretch (0, 100 and 300 mg) force dependently increased the incidence of spontaneous activity (22%, 48% and 83%; p<0.05), mean (standard deviation (SD)) firing rates of spontaneous activity (1.7 (0.2), 2.1 (0.3) and 3 (0.2) Hz; p<0.05) and incidence of early post-depolarisations (9%, 26% and 61%; p<0.05) and delayed post-depolarisations (0%, 4% and 30%; p<0.05) in 23 pulmonary veins. In the seven preparations with spontaneous activity after the 300-mg stretch, gadolinium (1, 3 and 10 mumol/l) decreased the incidence of spontaneous activity by 43%, 29% and 14%, respectively (p<0.05), and decreased the firing rate from 2.9 (0.1) Hz to 0.8 (0.4), 0.3 (0.1) and 0.1 (0.1) Hz, respectively (p<0.05). Streptomycin (10 and 40 mumol/l) decreased the incidence of spontaneous activity by 71% and 29%, respectively (p<0.05), and decreased the firing rate from 2.9 (0.1) Hz to 1.6 (0.4) and 0.5 (0.3) Hz, respectively (p<0.05). CONCLUSION: Stretch is an important factor in the electrical activity of the pulmonary vein. Stretch-induced arrhythmogenic activity of the pulmonary vein may contribute to the genesis of atrial fibrillation.

Action Potentials↗
PubMed2006

Food encounter rates of simulated termite tunnels with variable food size/distribution pattern and tunnel branch length.

Subterranean termites excavate tunnels in a search pattern to encounter food in soil. To investigate the effect of food size, food distribution and the branch length of tunnels on food encounter rate we used a lattice gas model to simulate tunnels of the Formosan subterranean termite, Coptotermes formosanus Shiraki. The model made use of minimized local rules derived from empirical data to simulate termite tunnel patterns in featureless soil. Food distributions with three types (uniform, random, and clumped) were defined by using an I-index proposed by Zimmer and Johnson (1985). The food encounter rate was higher in a clumped than in non-clumped (uniform and random) distribution of food particles. When food particle size was varied in random distributions of food particles a maximum encounter rate was found, with particles of larger or smaller size being encountered less frequently. We also discussed the relationship between the branch tunnel length and the tunnel search pattern in minimizing the redundancy of overlapping branches.

Animals↗
PubMed2006

Reduction of prolonged bilateral temporomandibular joint dislocation by midline mandibulotomy.

Various surgical procedures have been used to reduce prolonged bilateral dislocation of the temporomandibular joint, but with some complications. A prolonged bilateral dislocation of the mandibular condyle was simply reduced by a midline mandibulotomy without any complications. One year postoperatively, joint function was unimpeded and there was no recurrence of condylar dislocation.

Accidents, Traffic↗
PubMed2006

Lysophosphatidylcholine suppresses apoptotic cell death by inducing cyclooxygenase-2 expression via a Raf-1 dependent mechanism in human cholangiocytes.

PURPOSE: The high incidence of biliary tract carcinoma in patients with anomalous pancreaticobiliary ductal junction (APBDJ) implicates that a compositional alteration in bile may contribute to the genesis of this cancer. Lysophosphatidylcholine (LPC) is generated in the bile of these patients. Given the role of cyclooxygenase-2 (COX-2) in biliary tract carcinogenesis, we postulated that LPC induces COX-2 in cholangiocytes. METHODS: The effect of LPC on COX-2 expression in cholangiocytes was evaluated by immunoblot analysis, real-time PCR and reporter gene assay. Apoptosis was induced by TRAIL treatment, and quantified using DAPI staining. RESULTS: Lysophosphatidylcholine increased COX-2 protein expression in cholangiocytes in a concentration- and time-dependent manner. LPC-induced Raf-1 activation was responsible for this COX-2 induction. Accordingly, LPC increased COX-2 mRNA levels in a Raf-1 dependent manner by stabilizing COX-2 mRNA. Finally, LPC attenuated TRAIL-mediated apoptosis through a COX-2/PgE2 dependent mechanism. CONCLUSIONS: Collectively, these results implicate that LPC inhibits cholangiocyte apoptosis by inducing COX-2 expression via a Raf-1 dependent mechanism. This anti-apoptotic signaling may participate in biliary tract carcinogenesis in APBDJ patients, and therefore, its interruption may be a viable chemopreventative strategy.

Animals↗
PubMed2006

Up-regulation of IL-23p19 expression in rheumatoid arthritis synovial fibroblasts by IL-17 through PI3-kinase-, NF-kappaB- and p38 MAPK-dependent signalling pathways.

OBJECTIVE: To investigate the expression of interleukin (IL)-23p19 in human rheumatoid arthritis (RA) synovial fibroblasts and its up-regulation by IL-17 stimulation, and to define the signal pathways involved in the regulation of IL-23p19 expression in RA synovial fibroblasts. METHODS: Synovial fluid (SF) and serum levels of IL-23p19 in RA were determined by enzyme-linked immunosorbent assays. The levels of IL-23p19 mRNA and protein were measured after the RA synovial fibroblasts were treated with recombinant human IL-17 and various inhibitors of intracellular signal pathway molecules using reverse transcription (RT) polymerase chain reaction (PCR), real-time PCR and western blotting. RESULTS: Levels of IL-23p19 in the sera and SF were much higher in RA patients than in osteoarthritis patients or healthy controls. The expression of IL-23p19 mRNA and protein was enhanced in RA synovial fibroblasts by IL-17 stimulation. Such effects of IL-17 were completely blocked by inhibitors of phosphatidylinositol (PI)-kinase/Akt, nuclear factor (NF)-kappaB and p38 mitogen-activated protein kinase (MAPK). In accordance with the expression of IL-23p19, the phosphorylation of IkappaB, Akt and p38 MAPK in synovial fibroblasts also increased after IL-17 stimulation. CONCLUSION: IL-23p19 is over-expressed in RA synovial fibroblasts and IL-17 appears to up-regulate the expression of IL-23p19 in RA synovial fibroblasts via PI3-kinase/Akt, NF-kappaB- and p38-MAPK-mediated pathways. These results suggest that a disruption of interaction between IL-17 and IL-23p19 may provide a new therapeutic approach in the treatment of RA.

Adult↗
PubMed2006

PEGylated glucagon-like peptide-1 displays preserved effects on insulin release in isolated pancreatic islets and improved biological activity in db/db mice.

AIMS/HYPOTHESIS: The rapid degradation and clearance of glucagon-like peptide-1 (GLP-1) by the enzymes dipeptidyl peptidase-IV and neutral endopeptidase 24.11 are the main impediments to the development of GLP-1 as a potential glucose-lowering agent. In this study, new enzyme-resistant polyethylene glycol (PEG)-conjugated GLP-1 analogues were designed and examined for metabolic stability and biological potency. MATERIALS AND METHODS: Two mono-PEGylated GLP-1 analogues, N-terminally modified N-PEG/GLP-1 and Lys-modified Lys-PEG/GLP-1, were prepared. Stability was tested in plasma and tissue extracts. In vitro insulin release studies were performed using isolated rat pancreatic islets, while in vivo glycaemic responses were measured in db/db mice. RESULTS: The half-life of Lys-PEG/GLP-1 was 40-, 10- and 28-fold longer than that of GLP-1 in plasma, liver and kidney homogenates, respectively. Lys-PEG/GLP-1 stimulated insulin secretion in the islets in a dose- and glucose-dependent manner, and was as potent as GLP-1. In contrast, N-PEG/GLP-1 showed extended metabolic stability but had significantly lower biological activity. The administration of Lys-PEG/GLP-1 (9 nmol/kg i.p.) to non-fasted db/db mice stabilised glycaemia (p<0.001), whereas GLP-1 (9 nmol/kg) only caused small changes in glucose level. During OGTT in fasted db/db mice, Lys-PEG/GLP-1 administered at 1, 3 and 9 nmol/kg (i.p.) reduced the glucose AUC(0-3h) by 48.7+/-9.4, 55.0+/-2.9 and 63.4+/-2.5%, respectively, compared with placebo (p<0.01), whereas GLP-1 (9 nmol/kg) lowered the glucose level by 39.5+/-12.9% (p<0.01). CONCLUSIONS/INTERPRETATION: This study demonstrates that site-specific PEGylated GLP-1 analogues are resistant to degradation. The enhanced biological potencies of these analogues highlight their potential as new, GLP-1-like glucose-lowering agents.

Animals↗
PubMed2006

Elevated serum levels of soluble receptor activator of nuclear factors-kappaB ligand (sRANKL) and reduced bone mineral density in patients with ankylosing spondylitis (AS).

OBJECTIVE: To assess bone mineral density (BMD), serum levels of soluble receptor activator of nuclear factors-kappaB ligand (sRANKL) and osteoprotegerin (OPG) in patients with ankylosing spondylitis (AS), and to determine their relationships with disease activities. METHODS: Serum levels of sRANKL and OPG in AS were measured by sandwich enzyme-linked immunosorbent assay. The disease activities were determined using Bath Ankylosing Spondylitis Disease Activity Score Index, Bath Ankylosing Spondylitis Functional Index , Bath Ankylosing Spondylitis Metrology Index and Bath Ankylosing Spondylitis Patient Global Score. BMD of femur and lumbar spine was measured by dual energy X-ray absorptiometry. Radiological grading was determined by New York criteria for sacroiliitis and modified Stoke Ankylosing Spondylitis Spine Score. RESULTS: Osteoporosis and osteopaenia of femoral neck were found in 33 and 41% of patients, respectively. BMD of femoral neck showed negative correlation with disease activity indexes, erythrocyte sedimentation rate and C-reactive protein. The serum sRANKL levels and the ratio of sRANKL to OPG were significantly higher in patients with AS than those of controls. The sRANKL/OPG ratio tended to increase in patients with reduced BMD and radiological findings of active inflammation. CONCLUSION: About 74% of AS patients have reduced BMD and this change reflects disease activity. Serum sRANKL levels and sRANKL/OPG ratios are up-regulated in patients with AS and have relationship with BMD and radiological changes. These results suggest that the imbalance between RANKL and OPG might be involved in the pathogenesis and clinical courses of osteoporosis in AS.

Absorptiometry, Photon↗
PubMed2006

Certified reference material for radionuclides in fish flesh sample IAEA-414 (mixed fish from the Irish Sea and North Sea).

A certified reference material (CRM) for radionuclides in fish sample IAEA-414 (mixed fish from the Irish Sea and North Seas) is described and the results of the certification process are presented. Nine radionuclides (40K, 137Cs, 232Th, 234U, 235U, 238U, 238Pu, 239+240Pu and 241Am) were certified for this material. Information on massic activities with 95% confidence intervals is given for six other radionuclides (90Sr, 210Pb(210Po), 226Ra, 239Pu, 240Pu 241Pu). Less frequently reported radionuclides (99Tc, 129I, 228Th, 230Th and 237Np) and information on some activity and mass ratios are also included. The CRM can be used for quality assurance/quality control of the analysis of radionuclides in fish sample, for the development and validation of analytical methods and for training purposes. The material is available from IAEA, Vienna, in 100 g units.

Animals↗
PubMed2006

Correlation of antiviral T-cell responses with suppression of viral rebound in chronic hepatitis B carriers: a proof-of-concept study.

Despite recent advances in the chemotherapy of chronic hepatitis B (CHB), an effective viral suppression after cessation of therapy has not yet been achieved. To investigate whether hepatitis B virus (HBV)-specific T-cell responses are inducible and can contribute to the viral suppression after cessation of the therapy, we conducted a proof-of-concept study with a DNA vaccine comprising of most HBV genes plus genetically engineered interleukin-12 DNA (IL-12N222L) in 12 CHB carriers being treated with lamivudine (LAM). When the ex vivo and/or cultured IFN-gamma enzyme-linked immunospot (ELISPOT) assay was performed, the detectable HBV-specific IFN-gamma secreting T-cell responses were observed at the end of treatment and during a follow-up. These type 1T-cell responses, particularly CD4(+) memory T-cell responses could be maintained for at least 40 weeks after the therapy and correlated with virological responses, but not with alanine aminotransferase elevation. Moreover, DNA vaccination under LAM treatment appeared to be well-tolerated and showed 50% of virological response rate in CHB carriers. Thus, a combination therapy of the DNA vaccine with chemotherapy may be one of new immunotherapeutic methods for the cure of CHB.

Adult↗
PubMed2006

Prevertebral soft tissue swelling after anterior cervical discectomy and fusion with plate fixation.

Airway complications after anterior cervical surgery are rare but potentially lethal. The purpose of this study was to identify the natural course of prevertebral soft tissue swelling after one- or two-level anterior cervical discectomy and fusion (ACDF) in order to prevent lethal airway obstruction after ACDF. Eighty-seven patients scheduled for one- or two-level ACDF were studied prospectively. Lateral radiographs of the cervical spine were taken preoperatively, postoperatively on the day of surgery and on the first, second, third, fourth, and fifth days after operation. Prevertebral soft tissue was measured from C2 to C6 on cervical spine lateral radiographs. The anteroposterior (AP) thickness of the prevertebral soft tissue was measured at each cervical level from C2 to C6. Prevertebral soft tissue swelling occurred postoperatively and increased markedly on the second day after operation. The maximum swelling was found on the second and third days. In fusions above C5 swelling was most prominent at C2, 3. Gradual decrease in swelling was observed after the fourth postoperative day. Prominent swelling was noted at the second, third, and fourth cervical levels. There was no significant difference in swelling when comparing one-level and two-level ACDF. Only one patient required reintubation (1.1%). In conclusion, in this prospective study of 87 patients fused at one or two levels in the cervical spine peak prevertebral soft tissue swelling was observed on the second and third days after the surgery.

Adult↗
PubMed2006

Metastatic tumours to the jaws and oral soft tissues: a retrospective analysis of 41 Korean patients.

This article describes a pooled analysis of 41 Korean patients with metastatic oral tumours. The data reviewed are from Korean dental and medical case reports published between 1983 and 2004. The mean age was 55.2 years, and the male-to-female ratio was 1.9:1. There were more metastases in the jawbone than in oral soft tissues. The lung was the most common primary site for jawbone metastases, whereas the liver was for those of oral soft tissues. In contrast to reports in Western literature of the breast being the most common primary site, the liver was the most common primary site, followed by the lung and thyroid. These differences may be caused by a relatively high incidence rate of hepatocellular carcinoma in Korea.

Adult↗
PubMed2006

Nanomagnetic droplets and implications to orbital ordering in LA(1-x)Sr(x)CoO3.

Inelastic cold-neutron scattering on LaCoO3 provided evidence for a distinct low energy excitation at 0.6 meV coincident with the thermally induced magnetic transition. Coexisting strong ferromagnetic (FM) and weaker antiferromagnetic correlations that are dynamic follow the activation to the excited state, identified as the intermediate S = 1 spin triplet. This is indicative of dynamical orbital ordering favoring the observed magnetic interactions. With hole doping as in La(1-x)Sr(x)CoO3 , the FM correlations between Co spins become static and isotropically distributed due to the formation of FM droplets. The correlation length and condensation temperature of these droplets increase rapidly with metallicity due to the double exchange mechanism.

Journal Article↗
PubMed2006

The influence of facet tropism on herniation of the lumbar disc in adolescents and adults.

We carried out a study to determine the effect of facet tropism on the development of adolescent and adult herniation of the lumbar disc. We assessed 149 levels in 140 adolescents aged between 13 and 18 years and 119 levels in 111 adults aged between 40 and 49 years with herniation. The facet tropism of each patient was measured at the level of the herniated disc by CT. There was no significant difference in facet tropism between the herniated and the normal discs in both the adolescent and adult groups, except at the L4-L5 level in the adults. Facet tropism did not influence the development of herniation of the lumbar disc in either adolescents or adults.

Adolescent↗
PubMed2005

Statics and dynamics of incommensurate spin order in a geometrically frustrated antiferromagnet CdCr2O4.

Using elastic and inelastic neutron scattering we show that a cubic spinel, CdCr2O4, undergoes an elongation along the c axis (c > a = b) at its spin-Peierls-like phase transition at T(N) = 7.8 K. The Néel phase (T < T(N)) has an incommensurate spin structure with a characteristic wave vector Q(M) = (0, delta,1) with delta approximately 0.09 and with spins lying on the ac plane. This is in stark contrast to another well-known Cr-based spinel, ZnCr2O4, that undergoes a c-axis contraction and a commensurate spin order. The magnetic excitation of the incommensurate Néel state has a weak anisotropy gap of 0.6 meV and it consists of at least three bands extending up to 5 meV.

Journal Article↗
PubMed2005

Dynamics of prey-flock escaping behavior in response to predator's attack.

The dynamic behavior of prey-flock in response to predator's attack was investigated by using molecular dynamics (MD) simulations in a two-dimensional (2D) continuum model. By locally applying interactive forces between prey individuals (e.g. attraction, repulsion, and alignment), a coherently moving state in the same direction was obtained among individuals in prey-flock. When a single predator was introduced to the prey population, the prey-flock was correspondingly deformed by the predator's continuous attacks towards the prey-flock's center. In response to the predator's attack, three regimes in the flock size (compression (Regime I), expansion (Regime II), compression (Regime III)) were revealed if the predator's attack speed (kappa) was comparatively low to the escape speed of prey-flock. If noise was added to the predator's attacking course, a higher degree of variation was observed in the patterns of compression and expansion in the prey-flock size. However, the scaling behavior in the changes in prey-flock size was present in different levels of noise with the increase in predation risk (R) when kappa takes an appropriately low value. During the procedure of escaping, order breaking in alignment (phi) of prey population was observed, while the degree of alignment was dependent upon the changes in parameters of kappa and R.

Animals↗
PubMed2005

Patterns of size sexual dimorphism in Australopithecus afarensis: another look.

Size sexual dimorphism is one of the major components of morphological variation and has been associated with socio-ecology and behavioral variables such as mating patterns. Although several studies have addressed the magnitude and pattern of sexual dimorphism in Australopithecus afarensis, one of the earliest hominids, consensus has yet to be reached. This paper uses assigned re-sampling method, a data re-sampling method to estimate the magnitude of sexual dimorphism without relying on individual sex assessments, to examine the fossil hominid sample from Hadar. Two questions are asked: first, whether sexual dimorphism in a selected sample of skeletal elements of A. afarensis is the same as that in living humans, chimpanzees, or gorillas; and second, whether different skeletal elements reflect variation in sexual dimorphism in the same way. All possible metric variables were used as data in applying the method, including seven variables from three elements (mandibular canine, humerus, femur). Analyses show that A. afarensis is similar in size sexual dimorphism to gorillas in femoral variables, to humans in humeral variables, and to chimpanzees in canine variables. The results of this study are compatible with the hypothesis that the pattern of sexual dimorphism in A. afarensis is different from any that are observed in living humans or apes.

Animals↗