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Biomedical subjects

S Y Oh

Publications and source records attributed to S Y Oh.

At least 55 records · Page 3Linked to original sources
PubMed1998

Dietary habits, food intake and functional outcomes in those with a history of Hansen's disease in Korea.

This study shows that the nutrition and health status of ex-leprosy patients in Korea was marginal. Their nutrient intakes were low, especially from micronutrients which were associated with food from animal sources. Dietary quality was discriminated by food habits, such as skipping meals, irregularity of meals, food purchase and meal preparation. Dietary quality was best predicted by food habits followed by physical fitness and nutrition knowledge. Our subjects were nutrition-conscious, but they did not have accurate information. These findings suggest that our study population needs nutrition education.

Adult↗
PubMed1997

Reversal of 1,3-bis(2-chloroethyl)-1-nitrosourea-induced severe immunodeficiency by transduction of murine long-lived hemopoietic progenitor cells using O6-methylguanine DNA methyltransferase complementary DNA.

Bone marrow toxicity is a dose-limiting side effect of chloroethylnitrosourea (CNU) chemotherapeutic alkylating agents. A major determinant of CNU cytotoxicity is the methylation of guanine at the O6-position and the subsequent formation of interstrand DNA cross-links. O6-Methylguanine DNA methyltransferase (MGMT) removes alkyl groups from the O6 position of guanine and has been shown to repair CNU-induced DNA damage. We have previously demonstrated that transplantation of murine bone marrow cells transduced with a recombinant retroviral vector expressing MGMT via the human phosphoglycerate kinase promoter (PGK-MGMT) protects animals in vivo from acute myelotoxicity associated with CNU treatment. In the present study, we examined the effects of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), a commonly used CNU, on long term recovery of the lymphoid compartment, including thymus reconstitution, peripheral T and B cell populations, and lymphocyte mitogen responses in mice reconstituted with PGK-MGMT-transduced hemopoietic cells. Mice transplanted with either mock-infected control or PGK-MGMT-transduced stem cells were treated with five weekly doses of BCNU. Analysis of the lymphoid compartment demonstrated significant damage 3 mo after the last BCNU dose in control animals. In contrast, the profound deficiency in CD4+CD8+ double-positive thymocytes and mature lymphocytes observed in control mice surviving BCNU treatment was completely reversed in mice transplanted with PGK-MGMT-transduced bone marrow and was associated with molecular evidence of in vivo selection of transduced cells in the lymphoid compartment. Thus, long term immunodeficiency following CNU therapy may be prevented by genetic modification of murine hemopoietic stem cells with MGMT, leading to significant improvement in post-transplant immune function.

Animals↗
PubMed1997

Corneal endothelial cell loss from suture fixation of a posterior chamber intraocular lens.

PURPOSE: To evaluate the effect of suture fixation of a posterior chamber intraocular lens (PC IOL) on the corneal endothelium. SETTING: Seoul National University Hospital, Seoul, Korea. METHODS: Central corneal endothelial cell density was measured in 40 eyes that had planned extracapsular cataract extraction (P-ECCE) with PC IOL implantation and in 40 eyes that had PC IOL implantation by suture fixation (17 eyes with cataracts and 23 aphakic eyes). Central corneal endothelial cell counts were taken 1 day preoperatively and 1 and 3 months postoperatively by contact specular microscopy. RESULTS: One month postoperatively, mean central corneal endothelial cell loss was 10.1% in eyes that had P-ECCE with PC IOL implantation, 10.4% in eyes with cataracts that had PC IOL implantation by suture fixation, and 10.3% in aphakic eyes that had PC IOL implantation by suture fixation. At 3 months, it was 11.2%, 11.6%, and 11.7%, respectively. There was no statistically significant difference in the central corneal endothelial cell loss between the eyes that had PC IOL implantation by suture fixation and those that had P-ECCE with PC IOL implantation. CONCLUSIONS: Posterior chamber IOL implantation by suture fixation is a useful and safe method in patients who are aphakic or whose posterior capsule ruptures during cataract surgery.

Adult↗
PubMed1997

Real-time neural network based camera localization and its extension to mobile robot control.

The feasibility of using neural networks for camera localization and mobile robot control is investigated here. This approach has the advantages of eliminating the laborious and error-prone process of imaging system modeling and calibration procedures. Basically, two different approaches of using neural networks are introduced of which one is a hybrid approach combining neural networks and the pinhole-based analytic solution while the other is purely neural network based. These techniques have been tested and compared through both simulation and real-time experiments and are shown to yield more precise localization than analytic approaches. Furthermore, this neural localization method is also shown to be directly applicable to the navigation control of an experimental mobile robot along the hallway purely guided by a dark wall strip. It also facilitates multi-sensor fusion through the use of multiple sensors of different types for control due to the network's capability of learning without models.

Algorithms↗
PubMed1996

Blood and cell compatibility of gelatin-carrageenan mixtures cross-linked by glutaraldehyde.

Mixtures of gelatin and iota-carrageenan cross-linked by glutaraldehyde were prepared and their physical properties and blood and cell compatibility were compared to gelatin as a control material. According to scanning electron microscopic observation of fracture surfaces, the mixtures were composed of dispersed and continuous domains which might be generated by phase separation of carrageenan. The thermal degradation temperature of iota-carrageenan in the mixtures rose with increasing gelatin content. The swelling process in the mixtures proceeded slower than in gelatin. Tensile strengths of the mixtures, except that containing 50% iota-carrageenan, increased with increased amounts of iota-carrageenan in the mixtures. The iota-carrageenan contents at the surfaces of the mixtures were generally higher than those admixed originally. Static friction coefficients of the mixtures were lower than that of gelatin. Plasma recalcification times of the mixtures were longer than that of gelatin. Platelet adhesion of the mixtures was lower than that of gelatin, while cell adhesion and growth assays using Chinese hamster ovary cells showed that cell adhesion and growth were not dependent on adding iota-carrageenan. It was concluded that blood compatibility of the mixtures increased and cell compatibility did not decrease, compared to gelatin.

Animals↗
PubMed1995

Locally activated neural networks and stable neural controller design for nonlinear dynamic systems.

A stable neural control scheme using a locally activated neural network has been proposed for a class of nonlinear dynamic systems. The locally activated neural network, for a given input, essentially selects a small subset of the network hidden nodes for output computation using the CMAC-like content addressing mechanism. This network aims to maintain local representations of the system dynamics. Thus, the global control performance in the concerned state space is achieved by the cooperation of many local control efforts and furthermore, real-time control can be facilitated because only a small sized network is involved to control and learn at any given time. The proposed control scheme is composed of two stages: (1) prediction error based learning in which the network attempts to learn the nonlinear basis functions of the plant inverse dynamics by a modified backpropagation learning rule; and (2) tracking error based learning in which the network weights are further fine-tuned using the basis set obtained in (1). This basis set spans the locally partitioned vector space of the system inverse dynamics when the prediction error based learning is achieved within a prescribed error tolerance. For uniform stability, the sliding mode control is introduced as a safety mechanism when the network has not sufficiently learned the plant dynamics yet. With suitable assumptions on the controlled plant, global stability and tracking error convergence proof has been given. Finally, the proposed control scheme is verified with computer simulation.

Adaptation, Physiological↗
PubMed1995

Neural network based dynamic controllers for industrial robots.

The industrial robot's dynamic performance is frequently measured by positioning accuracy at high speeds and a good dynamic controller is essential that can accurately compute robot dynamics at a servo rate high enough to ensure system stability. A real-time dynamic controller for an industrial robot is developed here using neural networks. First, an efficient time-selectable hidden layer architecture has been developed based on system dynamics localized in time, which lends itself to real-time learning and control along with enhanced mapping accuracy. Second, the neural network architecture has also been specially tuned to accommodate servo dynamics. This not only facilitates the system design through reduced sensing requirements for the controller but also enhances the control performance over the control architecture neglecting servo dynamics. Experimental results demonstrate the controller's excellent learning and control performances compared with a conventional controller and thus has good potential for practical use in industrial robots.

Algorithms↗
PubMed1994

Lysophosphatidic acid inhibits gap-junctional communication and stimulates phosphorylation of connexin-43 in WB cells: possible involvement of the mitogen-activated protein kinase cascade.

Lysophosphatidic acid (LPA) was shown to be a powerful inhibitor of gap-junctional communication between cultured rat liver WB cells, as determined by the transfer of Lucifer Yellow, with 50% inhibition obtained at about 0.3 microM LPA. Inhibition of communication was rapid (5 min) and was maintained for at least 80 min. After incubation for 3 h with LPA, communication competence was partially restored and dye transfer was refractory to further addition of LPA. Communication in LPA-refractory cells retained sensitivity to inhibition by phorbol ester and by epidermal growth factor (EGF). LPA-induced inhibition was associated with phosphorylation of connexin-43 protein, as detected by slower migration of the protein detected on Western blots, which could be eliminated by incubation of samples with alkaline phosphatase. A close correspondence was observed between the time- and dose-dependency of LPA effects on communication and the induction of mitogen-activated protein kinase (MAP kinase). Activation of both the 42 kDa and 44 kDa subspecies were confirmed by mobility shifts on Western blots using an anti-(MAP kinase R1) (erk 1-III) antibody and by fractionation on Mono Q columns. Cells pretreated with phorbol ester for 24 h were insensitive to phorbol ester inhibition of communication or activation of MAP kinase, but retained their sensitivity to LPA. The results indicate that LPA initiates the activation of protein kinase cascades in WB cells that are probably independent of protein kinase C and identifies connexin-43 as one substrate for the activated kinases.

Animals↗
PubMed1994

Effects of dietary alkylglycerols in lactating rats on immune responses in pups.

Alkylglycerols (AG) are glyceryl ether lipid and are present in human and cow's milk and the hematopoietic organs such as bone marrow, spleen, and liver. The biologic effects of AG include stimulation of blood leukocyte and thrombocyte production and activation of macrophage and anti-tumor activity. The present study was conducted to determine the effects of dietary AG in lactating rats on AG levels in milk and development of certain immune responses in the pups. Lactating rats were fed diets supplemented with various levels of AG. Milk samples were expressed from the dams and blood was collected from the pups on postpartum d 8, 16, and 24. Concentrations of AG in milk from the dams fed AG were significantly greater than those of the controls (p < 0.05). Peripheral blood granulocytes were significantly elevated in pups from the dams fed AG, but there were no differences in peripheral blood lymphocyte numbers. Plasma levels of immunoglobulins were significantly greater for IgG (p < 0.01) and IgM (p < 0.001) in pups from the dams fed AG than in the control pups. The supplementation of AG in the diets of lactating dams significantly elevated AG levels in the milk, and the increased AG in the milk subsequently stimulated certain immune responses in the pups.

Animals↗
PubMed1994

Five-year results of radial keratotomy in the myopia over 6 diopters.

A number of studies have documented the reasonable efficacy and safety of radial keratotomy, but most based upon results obtained in low or moderate myopia or short term follow up after surgery. We complied 5 year and longer follow up data on 91 consecutive radial keratotomy surgeries on high myopia (over -6.00 diopters) performed by one surgeon 5 year-follow up was obtained on 21 (23%) of these eyes. The mean spherical equivalent before surgery was -11.02 diopters (D), the average keratometry value was 44.40 D, and all of the eyes had an uncorrected visual acuity of 0.04 or less. The average change in spherical equivalent was 3.44 D for eyes examined at 1 year, compared with 3.05 D for eyes at 3 years and 2.87 D at 5 years after surgery. Average keratometry value were 42.30 D at 1 year, 41.60 D at 3 years, and 41.30 D at 5 years after surgery. In our study, the decrease in spherical equivalent of 0.57 D was statistically significant (P < 0.05), as was the reduction in average keratometry value of 1.00 D. The effect of the surgery on spherical equivalent continued to regress through all the 5 years of follow up. However, the keratometric measurement decreased up to 5 years which indicated progressive flattening of the cornea. Also we divided these eyes into 2 groups, lower-myopic group (-6.00 D-(-)9.75 D) and higher-myopic group (over -10.00 D). In each category, the changes in spherical equivalent were 3.60 D, 2.21 D at 5 years, compared with 3.65 D, 3.25 D at 1 year respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

The effects of intraoperative mitomycin-C or 5-fluorouracil on glaucoma filtering surgery.

We compared the success rate of filtering surgery of a single 5-minute intraoperative application of mitomycin-C (MMC) or 5-fluorouracil (5-FU). Animal experiment and clinical study were done. In animal study, thirty pigmented rabbits (60 eyes) weighing 2.0 to 2.5 Kg were enrolled. We divided into 4 groups, such as BSS, 5-FU 50 mg/ml, MMC 0.2 mg/ml and MMC 0.4 mg/ml subconjunctival soaked group. Each group consisted of 15 eyes. In each group, 10 eyes was for examination of bleb survival and complications, 3 eyes for light microscopic examination and 2 eyes for electron microscopic examination. Bleb was survived 6.1 days (3 to 13 days) for BSS treated group, 16.3 days (9 to 23 days) for 5-FU 50mg/ml treated group, 32.7 days (17 to 55 days) in MMC 0.2 mg/ml treated group, and 64.4 days (49 to 84 days) in MMC 0.4 mg/ml treated group. Duration of bleb survival was significantly prolonged in 5-FU, MMC 0.2 mg/ml and MMC 0.4 mg/ml group respectively. In clinical study, fifty-five eyes of 40 patients were enrolled. 29 eyes of 21 patients were treated with MMC 0.2 mg/ml and 26 eyes of 19 patients were treated with 5-FU 50 mg/ml. The success rate was 89.7% in MMC 0.2 mg/ml treated group and 84.6% in 5-FU 50 mg/ml treated group at postoperative 3 months, and postoperative 6 months 89.7% in MMC 0.2 mg/ml treated group and 76.9% in 5-FU 50 mg/ml treated group. There was no statistical significance at postoperative 3 months (P > 0.05), but statistical significance at postoperative 6 months (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Restoration of gap-junctional intercellular communication in a communication-deficient rat liver cell mutant by transfection with connexin 43 cDNA.

To study the biochemical basis of gap-junctional intercellular communication (GJIC) and its role in tumorigenesis, a mammalian cell expression vector carrying both a rat connexin 43 (Cx43) cDNA and an amplifiable dihydrofolate reductase (DHFR) gene was transfected into the GJIC-deficient rat liver mutant cell line aB1. Two stable transfectants were selected for further amplification of the transfected Cx43 gene by increasing stepwise the concentration of methotrexate (MTX) in the culture medium. The results indicate that GJIC was restored in these two Cx43 cDNA transfectants after they became highly resistant to MTX but not in the control-vector transfectants, in which the DHFR gene was similarly amplified. The amount of Cx43 DNA revealed by Southern blot analysis and the expression of Cx43 gene revealed by northern and western blot analyses were concomitantly increased in the Cx43 cDNA transfectants resistant to high concentrations of MTX. Western blot analysis, using an antipeptide antibody that specifically recognizes Cx43 protein, further revealed that an approximately 46-kDa phosphorylated Cx43 protein that was prominent in the parental GJIC-competent cells was absent in the aB1 cells. This Cx43 protein, however, reappeared in the two Cx43 cDNA transfectants after amplification. After treatment of the membrane proteins with alkaline phosphatase in vitro, the approximately 46- and 44-kDa proteins disappeared, whereas the approximately 42-kDa proteins remained with increasing intensity, indicating that the higher molecular-weight proteins were the phosphorylated Cx43. These results indicate that a defect in posttranslational phosphorylation of Cx43 protein associated with low expression of the Cx43 gene might be responsible for the GJIC deficiency in aB1 cells and that increased expression of Cx43 by gene amplification might restore this phosphorylated Cx43 protein and so reestablish GJIC.

Animals↗
PubMed1993

Radioprotection of mice by dietary squalene.

Male C3H mice were fed a diet containing 2% squalene for 14 d prior to and 30 d subsequent to exposure to 6, 7 or 8 Gy of whole body gamma-irradiation (Cesium-137). After 14 d on squalene-supplemented diet, plasma and jejunal tissue squalene levels were 2X and 15X that of controls. Seven days after irradiation, total white cell counts and total lymphocyte counts were substantially depressed in a radiation dose-dependent manner. Although counts in the squalene group were consistently (18-119%) higher than those in the corresponding dietary control group, the differences between dietary groups at any single dose were not significant. Nuclear area of villus cells in the jejunum of both dietary groups was significantly reduced (20%) by day 11 post-irradiation but the nuclear area in squalene-fed mice was significantly greater (15%) than in controls, before and after irradiation. There were no differences in body weight as a function of either diet or radiation dose prior to the first observations of animal lethality. Animal survival was decreased from 100 to 0% at 30 d post-irradiation by radiation doses of 6-8 Gy, with the greatest difference between dietary groups being observed at 7 Gy (median survival times of 12 and 16 d for control and squalene groups, respectively). Overall, survival of squalene-fed mice was significantly prolonged compared with control-fed mice (P = 0.0054 by censored multiple regression analysis). It is concluded that squalene conferred some cellular and systemic radioprotection to mice receiving these lethal whole-body radiation doses.

Animals↗
PubMed1993

Epidermal growth factor inhibits gap junctional communication and stimulates serine-phosphorylation of connexin43 in WB cells by a protein kinase C-independent mechanism.

Epidermal growth factor (EGF) stimulated the phosphorylation of connexin43 (Cx43) in WB cells as evidenced by the formation of multiple immunoreactive Cx43 proteins of higher molecular mass which were abolished by treatment with alkaline phosphatase. Phosphorylation of Cx43 occurred within 10 min of EGF stimulation, was sustained for 1 h, and was associated with almost complete inhibition of gap junctional communication in these cells. EGF-induced phosphorylation and communication inhibition were retained in cells pretreated with phorbol 12-myristate 13-acetate (PMA) to deplete protein kinase C. These results show that the EGF inhibition of communication is tightly linked to protein kinase C-independent phosphorylation of Cx43. Further, Cx43 phosphorylated in the presence of EGF did not react with phosphotyrosine antibodies and in 32Pi incorporation experiments was shown to contain only phosphoserine indicating that the tyrosine kinase activity of the EGF receptor was not directly involved.

Animals↗
PubMed1993

Characterization of gap junctional communication-deficient mutants of a rat liver epithelial cell line.

To understand the mechanism(s) regulating gap junctional communication, we isolated gap junctional intercellular communication-deficient (GJIC-) mutant clones of a rat liver epithelial cell line, WB F-344, which is hypoxanthine-guanine phosphoribosyl transferase deficient (HGPRT-). The cells were exposed to a mutagenesis regimen and cocultured with the wild type HGPRT+ cells. Four GJIC- and one positive clones were characterized in the present study. Northern analysis of RNA isolated from both mutant and parental cells showed a single RNA species of about 3.0 kb which hybridized to connexin43 (Cx43) cDNA. Western blot analysis confirmed the expression of this junctional protein in all these clones. However, in the GJIC- clones the slowest migrating band corresponding to a hyperphosphorylated form, P2, of Cx43 protein (approximately 46 kDa) was absent suggesting that loss of this phosphorylated form of Cx43 may be involved in the failure of the mutants to establish cell-cell communication. Immunofluorescence analysis of the mutants did not reveal any differences in the distribution and localization of Cx43 between GJIC+ and GJIC- clones suggesting that the loss of phosphorylation did not affect the membrane association of this protein. Taken together, these data suggest that one mechanism for the loss of communication in these GJIC- mutants may be the consequence of a change in the intrinsic phosphorylation state of Cx43 protein.

Animals↗
PubMed1991

Phorbol ester induces phosphorylation and down-regulation of connexin 43 in WB cells.

Western blot analysis indicated that WB cells contained multiple proteins of molecular mass 42-47 K which reacted with anti-connexin 43 antibody. Incubation of cells with 12-O-tetradecanoylphorbol-13-acetate (TPA) for 5 min caused the inhibition of dye transfer and the appearance of reactive material of 50 K which was abolished by acid phosphatase. Longer term incubation with TPA caused loss of connexin 43 protein.

Animals↗