Biomedical subjects

S H Rhee

Publications and source records attributed to S H Rhee.

At least 19 recordsLinked to original sources

PubMed2004

The role of Coptidis Rhizoma extract in a renal ischemia-reperfusion model.

The effect of Coptidis Rhizoma extract on ischemia-reperfusion in rats was examined. The blood levels of urea nitrogen and creatinine increased significantly more in rats subjected to 24-h reperfusion than those subjected to 6-h reperfusion following 1-h ischemia, indicating functional kidney damage was more severe after the longer reperfusion time. These parameters were reduced by oral administration of Coptidis Rhizoma extract. Greater activity was found in rats given the extract for 30 days than in rats given the extract for 10 days prior to ischemia-reperfusion. In addition, the serum malondialdehyde level was lower, while the glutathione/glutathione disulfide ratio and the activities of the antioxidation enzymes, superoxide dismutase and catalase, were higher in rats given Coptidis Rhizoma extract orally for 30 consecutive days prior to 1-h ischemia and 24-h reperfusion in comparison with control rats given water. These results indicate that Coptidis Rhizoma has a protective action against the renal dysfunction caused by the ischemia and reperfusion process. Furthermore, renal DNA of rats given Coptidis Rhizoma extract orally showed a significantly lower DNA fragmentation rate, which was dose-dependent, implying that the extract afforded the kidneys protection against oxidative stress-mediated apoptosis during the process and ameliorated renal function impairment.

Animals↗

PubMed2002

Substance use, abuse and dependence in adolescence: prevalence, symptom profiles and correlates.

We present data on the lifetime prevalence of substance use, abuse and dependence in adolescents obtained through structured psychiatric interviews and self-report questionnaires. Most notably, we evaluate symptom profiles based on DSM-IV abuse and dependence criteria for tobacco, alcohol and marijuana, including a gender comparison. Participants are 3,072 adolescents (12-18 years) drawn from three community-based family samples in Colorado. Age trends suggest that substance use is a developmental phenomenon, which increases almost linearly from early to late adolescence. Substance use disorders are less common than experimentation in adolescence, but approximately 1 in 4 adolescents in the oldest cohorts meets criteria for abuse for at least one substance, and 1 in 5 meets criteria for substance dependence. By age 18 nearly 1 in 3 adolescents report daily smoking and 8.6% meet criteria for tobacco dependence. Although alcohol is the most commonly abused substance (10%), a slightly larger proportion of adolescents meet criteria for dependence on marijuana (4.3%) than alcohol (3.5%). Gender differences in prevalence of use more often show greater use in males than females. Males more frequently meet criteria for dependence on alcohol and marijuana in late adolescence, while females are more often nicotine dependent. A comparison of abuse and dependence symptom profiles shows some interesting variability across substances, and suggests that manifestations of a subset of symptoms are gender specific.

Adolescent↗

PubMed2001

Saturated fatty acids, but not unsaturated fatty acids, induce the expression of cyclooxygenase-2 mediated through Toll-like receptor 4.

Results from our previous studies demonstrated that activation of Toll-like receptor 4 (Tlr4), the lipopolysaccharide (LPS) receptor, is sufficient to induce nuclear factor kappaB activation and expression of inducible cyclooxygenase (COX-2) in macrophages. Saturated fatty acids (SFAs) acylated in lipid A moiety of LPS are essential for biological activities of LPS. Thus, we determined whether these fatty acids modulate LPS-induced signaling pathways and COX-2 expression in monocyte/macrophage cells (RAW 264.7). Results show that SFAs, but not unsaturated fatty acids (UFAs), induce nuclear factor kappaB activation and expression of COX-2 and other inflammatory markers. This induction is inhibited by a dominant-negative Tlr4. UFAs inhibit COX-2 expression induced by SFAs, constitutively active Tlr4, or LPS. However, UFAs fail to inhibit COX-2 expression induced by activation of signaling components downstream of Tlr4. Together, these results suggest that both SFA-induced COX-2 expression and its inhibition by UFAs are mediated through a common signaling pathway derived from Tlr4. These results represent a novel mechanism by which fatty acids modulate signaling pathways and target gene expression. Furthermore, these results suggest a possibility that propensity of monocyte/macrophage activation is modulated through Tlr4 by different types of free fatty acids, which in turn can be altered by kinds of dietary fat consumed.

Adenocarcinoma↗

PubMed2001

Suppression of tumor cell growth both in nude mice and in culture by n-3 polyunsaturated fatty acids: mediation through cyclooxygenase-independent pathways.

Dietary n-3 polyunsaturated fatty acids (PUFAs), as compared with n-6 PUFAs, suppress cellular production of prostaglandins and tumor cell growth both in vitro and in vivo. However, the mechanism by which n-3 PUFAs suppress tumor growth is not understood. We investigated whether the suppression of tumor cell growth by dietary n-3 PUFAs is mediated through inhibition of cyclooxygenase (COX). A colon tumor cell line, HCT-116, that does not express COX was stably transfected with the constitutively expressed COX-1 or the inducible COX-2 cDNA using a retroviral transfection and infection system. Athymic nude mice transplanted with the cells expressing enzymatically active COX were fed isocaloric diets containing either safflower oil or fish oil for 2 weeks before the start of the experiment and for an additional 21 days after transplantation. Both tumor volume and tumor burden (tumor volume/body weight) were significantly reduced in mice fed the fish oil diet as compared with safflower oil-fed mice. This reduction occurred even in control mice that received injections with cells infected with the retroviral vector without COX-1 or COX-2 cDNA. The growth of tumor cells expressing COX was not different from the growth of those transfected with the vector alone in the nude mice and in soft agar. N-3 PUFAs, as compared with linoleic acid, also inhibited the growth of these cells in culture. This growth inhibition by n-3 PUFAs was not affected by COX-1 or COX-2 overexpression. Contrary to general belief, these results indicate that the suppression of tumor growth by dietary n-3 PUFAs is mediated through COX-independent pathways.

Animals↗

PubMed2001

Effects of stress management on pain behavior in rheumatoid arthritis.

OBJECTIVE: To examine the effects of stress management training on pain behavior exhibited by persons with rheumatoid arthritis (RA) and the relationship of change in pain behavior with certain patient characteristics as well as change in self-reported levels of pain. METHODS: Patients with RA (n = 131) were randomly assigned to 1 of 3 groups: a stress management group, an attention control group, or a standard care control group. The stress management and attention control groups received a 10-week intervention followed by a 15-month maintenance phase. RESULTS: The 3 groups did not differ significantly in the change in pain behavior at any of the assessment periods. However, persons with RA who had less disease activity tended to exhibit positive changes in pain behavior over time. Changes in self-reported pain were not significantly related to changes in pain behavior. CONCLUSION: The results indicate that stress management interventions do not reduce total pain behaviors exhibited by persons with RA. Changes in pain behaviors appear to be related to disease activity, age, and disease duration, but not to changes in self-reported measures of pain.

Arthritis, Rheumatoid↗

PubMed2001

Biomimetic configurational arrays of hydroxyapatite nanocrystals on bio-organics.

Biomimetic configurational arrays of hydroxyapatite (HAp) nanocrystals on several bio-organics, collagen (Col), chondroitin sulfate (ChS), and their mixture, were comparatively studied. The nanocomposites of HAp/Col, HAp/ChS, and HAp/Col/ChS were synthesized through a precipitation method with calcium hydroxide suspension and phosphoric acid solution containing Col, ChS, and their mixture, respectively. The (0 0 2) diffraction of the synthesized HAp crystals on a Col fiber showed an around 60 arching angle, while that on a ChS fiber showed just around 10 degrees. The same configurational arrays of HAp crystals could also be obtained on the mixture of Col and ChS fibers. The different electron diffraction patterns of the HAp crystals on the Col and ChS fibers were explained by the different macromolecular configurations of the Col and ChS fibrils which compose their fibers. The results may be applicable to develop a bone substitute which mimics the peculiar configurational arrays of HAp crystals found in bone and their detailed organic composition.

Biocompatible Materials↗

PubMed2000

Murine TOLL-like receptor 4 confers lipopolysaccharide responsiveness as determined by activation of NF kappa B and expression of the inducible cyclooxygenase.

Genetic evidence indicating that TOLL-like receptor 4 (Tlr4) is the lipopolysaccharide (LPS) receptor in mice was reported. However, biochemical evidence that murine Tlr4 confers LPS responsiveness has not been convincingly demonstrated. Inducible cyclooxygenase (COX-2) is selectively expressed in LPS-stimulated macrophages in part mediated through the activation of NF kappa B. Thus, we determined whether murine Tlr4 confers LPS responsiveness as evaluated by the activation of NF kappa B and COX-2 expression. Transfection of a murine macrophage-like cell line (RAW264.7) with the constitutively active form (delta Tlr4) of Tlr4 is sufficient to activate NF kappa B and COX-2 expression. However, the truncated form (delta Tlr4(P712H)) of the missense mutant Tlr4(P712H) found in LPS-hyporesponsive mouse strain (C3H/HeJ) inhibits LPS-induced NF kappa B activation and COX-2 expression. The inability of delta Tlr4(P712H) to activate NF kappa B and induce COX-2 expression is rescued by a constitutively active adapter protein myeloid differentiation factor 88 (MyD88), which interacts directly with the cytoplasmic domain of Tlr proteins. Furthermore, MyD88 is co-immunoprecipitated with the wild-type delta Tlr4 but not with the delta Tlr4(P712H) mutant. Together, these results indicate that Tlr4 confers LPS responsiveness in RAW264.7 cells and suggest that hyporesponsiveness of C3H/HeJ mice to LPS is attributed to the disruption of Tlr4-mediated signaling pathways that results from the inability of the mutant Tlr4(P712H) to interact with MyD88.

Animals↗

PubMed2000

Hydroxyapatite formation on cellulose cloth induced by citric acid.

Hydroxyapatite (HAp) formation on cellulose cloth with the aid of citric acid was investigated. The cellulose cloths were soaked in simulated body fluid (SBF) solutions (1.5 SBF) with ion concentrations 1.5 times that of SBF (1.0 SBF) with and without citric acid and carbonate containing HAp crystals were found to form only in the 1.5 SBF solution that contained citric acid. The results were explained in terms of hydrogen bonding of citric acid to the cellulose cloth and its chelating ability of calcium ions. Practical application may involve the inclusion of citric acid in the 1.5 SBF solution to promote formation of HAp on previously bioinert cellulose cloth.

Journal Article↗

PubMed2000

Triangular-shaped incisor crowns and crowding.

The purpose of this study was to establish if there is a correlation between the shape of the labial crowns of the incisors and crowding. Plaster cast models of 69 untreated individuals (30 males and 39 females) were evaluated. The casts were selected randomly from the collection at Seoul National University and Ajou University. With the use of Little's irregularity index, the sample was divided into 2 groups, a crowded group and a normal group. Repeated measurements of the maximum mesiodistal width of the incisal and cervical areas of the incisors were taken by means of a digital vernier caliper and a ratio of these measurements was calculated. The mean value for the crowded group was significantly larger in the incisal area (P <.01) and smaller in the cervical areas (P <.01) than corresponding values in the normal group. These ratios were correlated with the irregularity index (Pearson r(2) from 55% to 65%). The value obtained from the incisor width ratio in the normal group can be useful for the diagnosis and treatment of crowded malocclusion.

Case-Control Studies↗

PubMed2000

Stress management in rheumatoid arthritis: what is the underlying mechanism?

OBJECTIVE: To test whether change in cognitive-behavioral variables (such as self-efficacy, coping strategies, and helplessness) is a mediator in the relation between cognitive behavior therapy and reduced pain and depression in persons with rheumatoid arthritis (RA). METHODS: A sample of patients with RA who completed a stress management training program (n = 47) was compared to a standard care control group (n = 45). A path analysis testing a model including direct effects of comprehensive stress management training on pain and depression and indirect effects via change in cognitive-behavioral variables was conducted. RESULTS: The path coefficients for the indirect effects of stress management training on pain and depression via change in cognitive-behavioral variables were statistically significant, whereas the path coefficients for the direct effects were found not to be statistically significant. CONCLUSION: Decreases in pain and depression following stress management training are due to beneficial changes in the arenas of self-efficacy (the belief that one can perform a specific behavior or task in the future), coping strategies (an individual's confidence in his or her ability to manage pain), and helplessness (perceptions of control regarding arthritis). There is little evidence of additional direct effects of stress management training on pain and depression.

Adaptation, Psychological↗

PubMed1999

A confirmatory factor analysis of the Center for Epidemiologic Studies Depression Scale in rheumatoid arthritis patients: additional evidence for a four-factor model.

OBJECTIVE: To examine the factor structure of the Center for Epidemiologic Studies Depression Scale (CES-D) in a sample of patients with rheumatoid arthritis (RA), testing all of the alternative models suggested by the previous evidence. METHODS: The CES-D was administered to a group of RA patients (n = 685) during a structured telephone interview. The telephone interview was repeated 6 months later (n = 537) and 12 months later (n = 453). Confirmatory factor analyses were conducted to test alternative models. RESULTS: The correlated 4-factor model and the second-order 4-factor model were the best fitting models. CONCLUSION: The factor structure of the CES-D previously found in the general population was replicated in an RA sample. The results are consistent with previous evidence of criterion contamination in the CES-D when used in an RA sample and provide support for the view that a single summary score may not be the most informative index of the CES-D.

Arthritis, Rheumatoid↗

PubMed1999

A logistic regression extension of the transmission disequilibrium test for continuous traits: application to linkage disequilibrium between alcoholism and the candidate genes DRD2 and ADH3.

The transmission disequilibrium test (TDT) recently has become a popular method of testing for linkage in the presence of association due to its simplicity and advantages over other within-family analytic methods. In this paper, we describe a logistic regression extension to the TDT that can be used to test for differences in linkage disequilibrium as a function of one or more continuous and/or categorical explanatory variables. We highlight important features of this method and demonstrate some of its possible uses. We applied these analyses to test for linkage disequilibrium between the dopamine receptor D2 (DRD2) and alcohol dehydrogenase 3 (ADH3) genes and both diagnostic and quantitative indices of alcoholism. Using data from the Collaborative Study on the Genetics of Alcoholism data set, we found evidence suggesting linkage disequilibrium between DRD2 and ADH3 and quantitative indices of alcoholism and correlated phenotypes corresponding to smoking and personality. None of the evidence for linkage disequilibrium varied by sex or age.

Age Factors↗

PubMed1999

Inhibition of tyrosinase by green tea components.

The pigment melanin in human skin is a major defense mechanism against ultraviolet light of the sun, but darkened skin color, which is the result of increased and redistributed epidermal melanin, could be a serious aesthetic problem. Epidemiologically, it is well known that the consumption of green tea may help prevent cancers in humans and also reduce several free radicals including peroxynitrite. In the present study, to assess the efficacy of the inhibition of mushroom tyrosinase (monophenol monooxygenase EC 1.14.18.1), ten kinds of Korean traditional teas were screened for their tyrosinase inhibitory activity. Green tea was the strongest inhibitor, and the major active constituents in the tea are (-)-epicatechin 3-O-gallate (ECG), (-)-gallocatechin 3-O-gallate (GCG), and (-)-epigallocatechin 3-O-gallate (EGCG). All are catechins with gallic acid group as an active site. The kinetic analysis for inhibition of tyrosinase revealed a competitive nature of GCG with this enzyme for the L-tyrosine binding at the active site of tyrosinase.

Agaricales↗

PubMed1999

Effect of citric acid on the nucleation of hydroxyapatite in a simulated body fluid.

The role of citric acid in a simulated body fluid (SBF) was examined with the main focus on its induction ability of hydroxyapatite (HAp) nucleation on a bioinert collagen membrane. Collagen membranes were soaked in the SBF with citric acid concentrations in the range of 0-4 mM; then, carbonate-containing HAp crystals grew within a limited range, i.e., 0.3-2 mM. The results were explained in terms of chemical interaction among calcium ion, citric acid and collagen membrane, especially strong chelation ability of citric acid with the calcium ion.

Animals↗

PubMed1999

Receptor-mediated signaling pathways: potential targets of modulation by dietary fatty acids.

Extracellular signals are transmitted to intracellular targets through many signal-transduction pathways. Each signaling pathway is composed of a network of interacting signaling molecules that regulate diverse cellular responses. A modulation of the functional activities of these signaling molecules as a result of altered nutritional status could lead to qualitative and quantitative changes in cellular responses to extracellular signals. Growing evidence now suggests that fatty acids can directly and indirectly modulate signaling pathways at multiple levels. Elucidating the mechanism of this modulation could help us to understand how different types of dietary fat modify the risks of many chronic diseases.

1-Phosphatidylinositol 4-Kinase↗

PubMed1999

Selective interference with verbal and spatial working memory in young and older adults.

Young and older adults were administered digit and location memory span tasks with and without verbal and spatial secondary tasks. Age differences were greater in location span than in digit span; however, there were no age differences in either the magnitude or pattern of effects of secondary tasks. There were also no age differences in the effects of secondary tasks on a combined (digit and location) task. On the digit and location span tasks, both young and older adults showed only domain-specific interference: naming colors selectively interfered with memory for digits, leaving memory for locations unaffected; pointing to matching colors selectively interfered with memory for locations, leaving memory for digits unimpaired. The results of the present study suggest a greater age deficit in spatial working memory than in verbal working memory, but provide no evidence of an age deficit in susceptibility to interference by secondary tasks in either domain.

Adolescent↗

PubMed1994

Antimutagenic effect of plant flavonoids in the Salmonella assay system.

The antimutagenic effects of 27 kinds of plant flavonoids on the mutagenicity of aflatoxin B1(AFB1) and N-methyl-N'-nitro-N-nitrosoguanidine(MNNG) in Salmonella typhimurium TA100 were investigated. In the mixed applications of AFB1 (1 microgram/plate) with the flavonoids (300 micrograms/plate) in the presence of a mammalian metabolic activation system (S9 mix), chrysin, apigenin, luteolin and its glucoside, kaempferol, fisetin, morin, naringenin, hesperetin, persicogenin, (+)-catechin and (-)-epicatechin showed the antimutagenic effect against AFB1 with more than 70% inhibition rate. A little or no antimutagenicities except flavone against MNNG (0.5 microgram/plate) were observed. For the antimutagenicity of the flavonoids on AFB1, the flavonoid structure that contains the free 5-, 7-hydroxyl group seemed to be essential. However, saturation of the 2,3-double bond or elimination of the 4-keto group did not affect the activity.

Aflatoxin B1↗

PubMed1983

Viral membrane glycoproteins: comparison of the amino terminal amino acid sequences of the precursor and mature glycoproteins of three serotypes of vesicular stomatitis virus.

The NH2-terminal amino acid sequences of the envelope glycoproteins and the in vitro synthesized, nonglycosylated precursors of the glycoproteins of three serotypes, namely Indiana (Toronto), Cocal, and New Jersey (Concan) of vesicular stomatitis virus were determined. A comparison of the sequences showed little homology in the signal peptides present in the nonglycosylated precursors except for their high hydrophobic amino acid content. In contrast, the NH2-terminal amino acid sequences of the mature envelope glycoproteins revealed extensive homology suggesting that this region is conserved and may be involved in essential biological function(s) of the rhabdovirus.

Amino Acid Sequence↗