Biomedical subjects

Y S Hwang

Publications and source records attributed to Y S Hwang.

At least 19 recordsLinked to original sources

PubMed2002

Application of semiological seizure classification to epileptic seizures in children.

To better define seizure characteristics and to examine whether semiological seizure classification (SSC) can be appropriately applied to the seizures of infants and children, we studied 152 videotaped seizures recorded in 133 children. Seizure semiology was described on the basis of a series of behavioural, sensory, and motor phenomena according to SSC. Special emphasis was placed on whether one semiology can be representative of a patient's whole semiology sequence. If one semiology was able to represent the whole sequence, the seizure was classified according to SSC. Ninety of 152 seizures (59.2%) could be classified as a single seizure type by SSC. However, only 19 of 53 seizures (35.9%) consisting of two semiologies, three of 24 seizures (12.5%) consisting of three semiologies, and one of eight seizures (12.5%) consisting of four semiologies could be classified according to SSC. Although SSC is very efficient, it is more accurately a descriptive terminology for clinical ictal events than a classification system.

Adolescent↗

PubMed2001

Expression of the REB transcriptional activator in rice grains improves the yield of recombinant proteins whose genes are controlled by a Reb-responsive promoter.

The gene encoding the rice transcription factor, REB (rice endosperm bZIP) was cloned from a bacterial artificial chromosome library of rice. The cloned 6,227-bp-long Reb gene is composed of six exons and five introns and is flanked by a 1.2-kb 5' promoter and a 1.2-kb 3' terminator region. The function of the Reb gene was explored by a transient assay by using a rice immature endosperm system. The effector constructs containing the native gene or fusion genes linking Reb to the rice actin (Act) or globulin (Glb) gene promoters and the reporter gene construct Glb-beta-glucuronidase (GUS) were used in this study. When these effector constructs were cotransferred with the reporter uidA gene encoding GUS under the control of the Glb promoter into immature rice endosperm cells, the Glb promoter was activated. The transient GUS expression was 2.0 to 2.5-fold higher with the effector construct than without. When the upstream activation sequence containing the GCCACGT(A/C)AG motifs of the Glb promoter was deleted, the activation by REB was abolished. On the other hand, a gain-of-function experiment showed that inserting the upstream activation sequence into the glutelin-1 (Gt1) promoter made it responsive to activation by REB. When cotransformed with Reb gene, mature transgenic rice grains containing the human lysozyme gene driven by the Glb promoter produced 3.7-fold more lysozyme. Accumulation of recombinant lysozyme in mature seed ranged from 30.57 to 279.61 microg.mg(-1) total soluble protein in individual transformants from 30 independent transformation events. Thus, our results show that REB is not only a transcriptional activator, it can also be used to increase the expression of recombinant protein in transgenic rice grains.

Actins↗

PubMed2001

Molecular characterization of Hmg2 gene encoding a 3-hydroxy-methylglutaryl-CoA reductase in rice.

Three genes encoding 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR, EC1.1.1.34), which converts HMG-CoA into mevalonate in the early key step of the plant isoprenoid pathway, were isolated by RT-PCR and rice cDNA and genomic library screening. A genomic Southern blot analysis confirmed that HMGR genes are present in three copies in rice. Of the three, the HMGR 2 gene (Hmg2) obtained as a cDNA clone and its genomic clone had 4 exons and 3 introns, and encoded a 576 amino acid peptide containing an open reading frame of 1,728 bp with a calculated Mw. of 61,150. The structure of rice Hmg2 had common features, based on its nucleotide and deduced amino acid sequence homologies, with other plant HMGR genes published to date. Rice Hmg2 transcripts were constitutively detected in all parts of the rice plant, except in lamina and their levels were high particularly in the leaf part of the dark-grown seedlings and mature flowers. Our result showed that mRNA levels of rice Hmg2 were strongly induced in seedlings and influorescence in the early development stage. Rice Hmg2 possibly has a housekeeping role involved in the sterol biosynthesis, among the possible roles of plant HMGR genes that have been suggested in other plants [Weissenborn et al. (1995)].

Amino Acid Sequence↗

PubMed2001

Cyclophilin a binds to peroxiredoxins and activates its peroxidase activity.

Six distinct peroxiredoxin (Prx) proteins (Prx I-VI) from distinct genes have been identified in mammalian tissues. Prxs are members of a group of peroxidases that have conserved reactive cysteine residue(s) in the active site(s). An immediate physiological electron donor for the peroxidase catalysis for five Prx proteins (Prx I-V) has been identified as thioredoxin (Trx), but that for Prx VI (1-Cys Prx) is still unclear. To identify an immediate electron donor and a binding protein for Prx VI, we performed a Prx VI protein overlay assay. A 20-kDa binding protein was identified by the Prx VI protein overlay assay with flow-through fractions from a High-Q column with rat lung crude extracts. Using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF) and MS-Fit, we identified the 20-kDa Prx VI-binding protein as a cyclophilin A (CyP-A). The binding of recombinant human CyP-A (hCyP-A) to Prx VI was confirmed by using the hCyP-A protein overlay assay and Western immunoblot analysis with hCyP-A-specific antibodies. hCyP-A enhanced the antioxidant activity of Prx VI, as well as the other known mammalian Prx isotypes. hCyP-A supported antioxidant activity of Prx II and Prx VI both against thiol (dithiothreitol)-containing metal-catalyzed oxidation (MCO) systems and ascorbate-containing MCO systems. Prx II was reduced by hCyP-A without help from any other reductant, and the reduction was cyclosporin A-independent. These results strongly suggest that CyP-A not only binds to Prx proteins but also supports its peroxidase activity as an immediate electron donor. In addition, Cys(115) and Cys(161) of hCyP-A were found to be involved in the activation and the reduction of Prx.

Animals↗

PubMed2001

Correlation between increased airway responsiveness and severity of pulmonary edema.

To determine whether the severity of the pulmonary edema in sheep models of cardiogenic and non-cardiogenic pulmonary edema correlate with concomitant alterations in airway responsiveness using three separate measures of pulmonary edema: post-mortem wet-to-dry lung weight ratio (W/D), chest radiograph (CXR) scores, and small airway wall area. Cardiogenic pulmonary edema was induced by increasing left atrial pressure (increase PLA) and non-cardiogenic pulmonary edema was induced by intravenous administration of Perilla ketone (PK). There was a significant negative correlation between changes in airway responsiveness and changes in CXR grade (r=-0.749, P<0.05), W/D (r=-0.662, P<0.05), airway wall areas (r=0.784, P<0.05) after increases in both PLA and PK. Chest radiograph score, W/D, and airway wall area correlated with each other (CXR score and W/D r=0.657, P<0.05; CXR score and airway wall area r=0.678, P<0.05; airway wall area and W/D r=0.704, P<0.05). We speculate that the increased airway responsiveness observed during pulmonary edema may result from the mechanical effects of edema formation within the airways.

Airway Resistance↗

PubMed2001

MR diagnosis of cerebellar infarction due to vertebral artery dissection in children.

Posterior circulation infarction is uncommon in children. We describe the clinical presentation and radiological findings in two children with cerebellar infarction resulting from dissection of the vertebral artery. We emphasize that vertebral artery injury should be considered in a child with acute symptoms and signs of ischaemia in the posterior circulation. MRI and MRA may be helpful in the diagnosis of cerebellar infarction and vertebral artery abnormality.

Cerebellar Diseases↗

PubMed2001

Herpes simplex encephalitis: MRI findings in two cases confirmed by polymerase chain reaction assay.

Herpes simplex virus (HSV) type I causes a fulminant necrotising meningoencephalitis distinguished from other encephalitides by its focal and often haemorrhagic nature. Specific antiviral therapy with acyclovir can significantly improve the prognosis. We present MRI findings of two cases of herpes simplex encephalitis (HSE) confirmed by PCR analysis, focusing on the serial changes after acyclovir therapy: gyral swelling, high signal intensity on T2-weighted images in the subfrontal region, temporal lobe and insula in the initial stage, then regional extension with enhancement and haemorrhage despite appropriate acyclovir therapy, and finally encephalomalacia and brain atrophy.

Acyclovir↗

PubMed2001

Intractable epilepsy associated with brain tumors in children: surgical modality and outcome.

OBJECTS: The aim of this study was to evaluate the role of surgical modality in children with brain tumors and intractable epilepsy. METHODS: Twenty-three patients who were treated for brain tumors and intractable epilepsy between January 1985 and March 1998 were retrospectively reviewed. The most common tumors were dysembryoplastic neuroepithelial tumors (n=9), oligodendrogliomas (n=6), and gangliogliomas (n=5). Six patients exhibited cortical dysplasia. The mean duration of follow-up was 43.4 months (range 12 to 125 months). Seizure outcome was more favorable (Engel's classes I and II) in patients with a complete resection of tumor (14/14 vs 6/9 for incomplete resection; P<0.05). There was no significant difference in seizure outcome between lesionectomy (n=13) and epilepsy surgery (n=10). The likelihood of requiring postoperative antiepileptic drugs was not influenced by the extent of resection or type of surgery. CONCLUSIONS: On the basis of this study, we conclude that the complete resection of these tumors can be an appropriate initial treatment for children with brain tumors who experience intractable epilepsy.

Adolescent↗

PubMed2001

Behavior of osteoblasts on a type I atelocollagen grafted ozone oxidized poly L-lactic acid membrane.

With oxidizing poly-L-lactic acid (PLLA) surface by ozone, peroxide groups are easily generated on the surface. Those peroxides are broken down by redox-coupling reaction, and provide active species that initiate grafting by reaction with the collagen molecules. The surface density of generated peroxide on a PLLA surface was determined by an iodide method. The maximum concentration of peroxide was about 2.87 x 10(-8) mol/cm2 when ozone oxidation was performed at 60 V for 60 min. After the surface oxidation, type I atelocollagen was grafted onto PLLA surface. All physical measurements on the collagen-grafted surface indicated that the PLLA surface was effectively grafted with type I atelocollagen. Behavior of rat calvaria osteoblasts on type I atelocollagen grafted PLLA (PLLA + COL) surface was observed. Initial attachment of osteoblasts on the surface was significantly enhanced, and it is assumed that the atelocollagen matrix supported the initial attachment and growth of cells. Collagenous protein synthesis of osteoblasts was maintained at relatively low level in the early stage of proliferation due to the primarily existing grafted type I atelocollagen, and then increased in 7 days as the osteoblast differentiated. After 7 days, collagenous protein synthesis in osteoblasts was activated. Alkaline phosphatase (ALPase) activity and mineralization by osteoblasts were promoted on PLLA + COL surface. In comparison with PLLA + COL, non-treated PLLA and tissue culture plate (TCPS) did not show any feature expressed in osteoblasts' maturation up to 9 days in this experiment. The grafted type I atelocollagen provided a favorable matrix for cell migration in relation with collagenase expression. Ozone oxidation might be a favorable method for surface modification of PLLA membranes by collagen grafting, and cell behavior could be modulated by the grafted collagen.

Animals↗

PubMed2001

National survey on West syndrome in Korea.

AIM: To investigate and analyze the current epidemiological and clinical data for West syndrome (WS) in Korea, including treatments and outcome. METHODS: Prepared survey forms were sent to hospitals located all over Korea to collect data on cases of WS treated between January 1997 and June 2000. Data from 21 institutes were returned. RESULTS: Data were collected for 358 children (219 boys and 139 girls) who were diagnosed and treated for WS. The incidences of WS were 112 cases in 1997, 104 cases in 1998, 108 cases in 1999, and 34 cases in the first half of 2000. Based on these figures, the presumed annual incidence of WS in Korea was derived to be one in 4000 live births, although there was a great inter-district variability. Regarding the etiology, 138 cases (38.5%) were cryptogenic. For the 220 symptomatic cases, hypoxic-ischemic encephalopathy (HIE) was the most common etiologic factor (50.8%), followed by central nervous system anomaly including malformation of cortical development (21.4%), and neurocutaneous syndrome (8.6%). Clinically flexor type spasms were most common (59.2%) and 199 cases (55.6%) revealed typical hypsarrhythmia, electroencephalographically. During 1997 and 1998, vigabatrin (VGB) was used most frequently for the treatment of WS, followed by valproic acid and adrenocorticotropic hormone (ACTH). In 1999 and 2000, the use of ACTH diminished and topiramate was used more frequently than ACTH. Spasms were controlled in 230 cases (64.2%) and evolution to other seizure types was observed in 44 cases (11.2%). Developmental and/or mental retardation were noticed in 270 cases (75.4%). CONCLUSIONS: The yearly incidence of WS did not show significant change in Korea between 1997 and 2000. Among symptomatic WS, HIE was the most common cause. During the period of this study, VGB was the most popular therapeutic regimen possibly because of shortage of ACTH. Recently, topiramate has showed promising signs as a therapy for WS.

Adrenocorticotropic Hormone↗

PubMed2001

Hemifacial seizure of cerebellar ganglioglioma origin: seizure control by tumor resection.

The cerebellum is known to have an inhibitory effect on seizures. Nevertheless, cerebellar dysplastic lesions can be epileptogenic. A 4-month-old infant had paroxysmal facial contractions; tachypnea and nystagmoid eyeball and tremulous movements were occasionally combined. These evolved to stereotypic clinical patterns and frequencies, which increased despite administration of antiepileptic drugs (AEDs). Magnetic resonance imaging (MRI) demonstrated a mass arising from the superior cerebellar peduncle, although video-scalp EEG monitoring revealed no abnormal findings. Positron emission tomography with [(18)F]fluorodeoxyglucose revealed focal hypermetabolism in the same area identified by MRI. A depth electrode implanted in the mass revealed focal spike-and-wave discharges. The lesion was partly removed; pathologic diagnosis was ganglioglioma. Because of incomplete seizure control and residual tumor visible on MRI, a second operation was performed. After complete excision of the tumor, the patient became seizure free without AEDs. This case confirms the presence of seizure originating from the cerebellum and emphasizes the need for the complete removal of an epileptogenic lesion.

Cerebellar Neoplasms↗

PubMed2001

Methimazole as an antioxidant and immunomodulator in thyroid cells: mechanisms involving interferon-gamma signaling and H(2)O(2) scavenging.

The antithyroid drug, methimazole (MMI) is used to treat patients with Graves' hyperthyroidism. The major action of MMI is to inhibit synthesis of thyroid hormone in the thyroid gland. However, MMI also has antioxidant and immunomodulatory effects on thyrocytes and/or immune cells. This study identifies novel antioxidant and immunomodulatory effects of MMI involving the interferon-gamma (IFN-gamma) signaling pathway in thyroid cells. MMI inhibits transcription of the intercellular adhesion molecule-1 (ICAM-1) gene by modulating the function of transcription factor STAT1 (signal transducer and activator of transcription 1), which binds to the IFN-gamma activated site of the ICAM-1 promoter. Furthermore, MMI rapidly eliminates H(2)O(2) produced by IFN-gamma treatment in thyroid cells and thus inhibits the H(2)O(2)-mediated phosphorylation of tyrosine 701 in STAT1. MMI also eliminates H(2)O(2) in vitro. MMI facilitates electron transfer from NADPH to H(2)O(2) using thioredoxin or glutathione, fulfilling a role similar to peroxiredoxin or glutathione peroxidase, respectively. MMI prevents the IFN-gamma and H(2)O(2)-mediated reversible inactivation of phosphatases. These effects inhibit full activation of the IFN-gamma-induced Janus kinase(JAK)/STAT signaling pathway in FRTL-5 thyroid cells. These results may in part explain the antioxidant and immunomodulatory effects of MMI in thyroid cells of Graves' disease patients.

Adjuvants, Immunologic↗

PubMed2001

Characterization of UV-irradiated dense/porous collagen membranes: morphology, enzymatic degradation, and mechanical properties.

Collagen-based membranous materials of various shapes (gel, film, sponge) are known to be the most promising materials in terms of facilitating the regeneration of dermal defects. In this study, dense and porous collagen membranes were fabricated using air-drying and freeze-drying processes, respectively, and the effect of ultraviolet (UV) radiation on the degree of membrane crosslinking was evaluated by in vitro biodegradation and mechanical testing. A non-irradiated membrane group was used as the negative control and a glutaraldehyde (GA) treated group as the positive control. Scanning electron microscopy showed that, as the freezing temperature decreased to -196 degrees C, the resultant mean pore sizes also decreased; optimal pore size was obtained at a freezing temperature of -70 degrees C. In vitro biodegradation and mechanical testing demonstrated that GA treatment or 4 hours of exposure to UV radiation significantly increased both resistance to collagenase and mechanical strength versus the untreated controls, regardless of the collagen membrane type (dense or porous). Our results suggest that UV treatment is a useful tool for the fabrication of collagen membranes designed to be used as dermal dressings.

Animals↗

PubMed2001

Calcification comparison of polymers for vascular graft.

Polytetrafluoroethylene (PTFE), polyurethane (PU) and silicone are widely known biocompatible polymers which are commonly used for vascular grafts. However, in vitro and in vivo calcifications of these polymers have been found to seriously compromise their quality as biomaterials. In consideration of this problem, the present study compared the calcification rate and extent of PTFE, PU and silicone. Using the in vitro flow-type method, PTFE, PU and silicone films were tested for 1, 4, 7, 10, 14 and 21 days. After 21 days of in vitro calcification test, the calcium levels on PTFE, PU and silicone were 35.89 +/- 5.01 microg/cm2, 23.73 +/- 0.68 microg/cm2 and 19.86 +/- 5.28 microg/cm2, respectively. The higher observed calcium level for PTFE may be due to the effect of the rough surface of PTFE in accumulating calcium ions on the polymer surface. From the 7th day of test, the [Ca]/[P] molar ratio started to decrease over time, and PTFE showed a faster calcification process. This decreasing [Ca]/[P] molar ratio demonstrated the typical calcification mechanism consisting of phosphorus ion accumulation following calcium ion accumulation. This study concluded that PU and silicone are less calcified than PTFE film, a finding in good agreement with previously published studies.

Biocompatible Materials↗

PubMed2001

A rapid and successful treatment for airbag-related traumatic macular hole.

A 28-year-old female was diagnosed as having an airbag-related traumatic macular hole in the right eye 9 days subsequent to a traffic accident. Four weeks after the trauma, the patient's visual acuity was deteriorating to 20/600. Following vitrectomy, membrane peeling, use of autologous serum and intraocular gas tamponade, the hole healed within 12 days, more rapidly than the expected interval for the treatment of a traumatic macular hole. The visual acuities at the 3-month and 1-year follow-up examinations were 20/50, much better than the conventional surgical treatment of idiopathic macular hole and comparable to previous reports of the treatment of traumatic macular hole. Vitrectomy procedure has been proved to be effective for the treatment of traumatic macular hole. Vitrectomy combined with membrane peeling, autologous serum and intraocular gas tamponade can heal the traumatic macular hole more rapidly than the conventional treatment with vitrectomy only.

Accidents, Traffic↗

PubMed2000

Type I atelocollagen grafting onto ozone-treated polyurethane films: cell attachment, proliferation, and collagen synthesis.

An approach is presented for the graft copolymerization of type I atelocollagen onto the surface of polyurethane (PU) films treated with ozone. Through inducing oxidization to modify PU surface by ozone, peroxide groups are easily generated on the surface. Those peroxides are broken by redox-polymerization, and provide active species which initiate graft polymerization by reacting with amines in the collagen molecules. The ozone oxidation time and voltage could readily control the amount of peroxide production. The surface density of generated peroxides on PU surface was determined by iodide method. The maximum concentration of peroxide was about 10.20 x 10(-8)mol/cm(2) when ozone oxidation was performed at 60 V for 30 min. After the reaction of PU by ozone oxidation, type I atelocollagen was graft-copolymerized onto the PU film. All the physical measurements on the collagen-grafted surface indicated that the PU surface was effectively covered with type I atelocollagen. The interaction of the collagen-grafted PU surface with fibroblasts could be greatly enhanced by the surface graft polymerization with type I atelocollagen. Attachment and proliferation of fibroblasts on the grafted type I atelocollagen were significantly enhanced, and it is assumed that the atelocollagen matrix supported the initial attachment and growth of cells. In the early stage of proliferation, collagen synthesis in fibroblasts was not activated and remained at a relatively low level due to the grafted type I atelocollagen, increasing only with fibroblast differentiation.

Animals↗

PubMed2000

Molecular cloning and expression analysis of 3-ketoacyl-ACP synthases in the immature seeds of Perilla frutescens.

We report the isolation and expression analysis of two cDNAs encoding 3-ketoacyl-acyl carrier protein synthases (KAS) that are involved in the de novo synthesis of fatty acids in plastids of perilla (Perilla frutescens L.). The cDNAs, designated PfFAB1 and PfFAB24, encoded polypeptides with high sequence identities to those of KAS I and KAS II/IV, respectively, of various plants. Genomic Southern blots revealed that there was a single PfFAB1 gene but two PfFAB24 genes in the perilla genome. Of interest is that the expression of both genes was developmentally regulated in seeds. Their mRNA expression patterns in seeds were also discussed in comparison with the profile of fatty acid accumulation.

3-Oxoacyl-(Acyl-Carrier-Protein) Synthase↗

PubMed2000

Molecular cloning and functional expression of Perilla frutescens 3-ketoacyl-(acyl carrier protein) synthase III.

The 3-ketoacyl-acyl carrier protein synthase III (KAS III) is a condensing enzyme catalyzing the initial step of fatty acid biosynthesis. We isolated two KAS III cDNA isoforms (PfKAS3a and PfKAS3b) from a cDNA library specific to Perilla frutescens immature seeds. Two cDNAs coded for 401 and 400 amino acids, respectively, which showed high degree of sequence similarity to corresponding enzymes from various sources. Results of Southern hybridization indicated that the PfKAS3a gene is present as two copies, whereas the PJKAS3b gene is a single copy. While both genes were equally expressed in high levels during early stages of seed maturation in a development-specific manner, the PfKAS3b transcript showed more prolonged appearance. Expression of the functional recombinant perilla KAS III increased the myristate level in E. coli but it exerted no appreciable effect on cell growth.

3-Oxoacyl-(Acyl-Carrier-Protein) Synthase↗