Biomedical subjects

Y K Park

Publications and source records attributed to Y K Park.

At least 19 recordsLinked to original sources

PubMed2002

Localization accuracy of single current dipoles from tangential components of auditory evoked fields.

We investigated the localization accuracy of single current dipoles from the tangential components of auditory evoked fields. The tangential fields were measured using planar gradiometers arranged in a way so as to detect two orthogonal field components parallel to a flat plane. Field responses to 1 kHz pure tones were recorded and equivalent current dipoles (ECDs) of N1m peak were estimated based on a locally fitted spherical conductor model. As a measure of localization accuracy, the standard deviation of the coordinates of the ECDs of N1m was obtained from repeated measurements for one subject. The estimated ECDs had a standard deviation of 5.5 mm and their mean location was at the supratemporal plane in the sylvian fissure on the MR image of the subject. In order to investigate the contribution of various errors to the localization accuracy, simulations using a sphere model and experiments using a realistically shaped skull phantom were performed. It was found that the background noise, which consisted of instrumental noise and spontaneous brain fields, was the main source of the errors that could explain the observed standard deviation. Further, the amount of systematic error was much less than the standard deviation due to the background noise. These results suggest that the volume currents in a non-spherical conductor shape such as the temporal region do not produce substantial errors in the localization of current dipoles from tangential components of auditory evoked fields.

Acoustic Stimulation↗

PubMed2002

Effects of apigenin and tt-farnesol on glucosyltransferase activity, biofilm viability and caries development in rats.

Propolis, a resinous hive product secreted by Apis mellifera bees, has been shown to reduce the incidence of dental caries in rats. Several compounds, mainly polyphenolics, have been identified in propolis. Apigenin and tt-farnesol demonstrated biological activity against mutans streptococci. We determined here their effects, alone or in combination, on glucosyltransferase activity, biofilm viability, and development of caries in rats. Sprague-Dawley rats were infected with Streptococcus sobrinus 6715 and treated topically twice daily as follows: (1) tt-farnesol, (2) apigenin, (3) vehicle control, (4) fluoride, (5) apigenin +tt-farnesol, and (6) chlorhexidine. Apigenin (1.33 mM) inhibited the activity of glucosyltransferases in solution (90-95%) and on the surface of saliva-coated hydroxyapatite beads (35-58%); it was devoid of antibacterial activity. tt-Farnesol (1.33 mM) showed modest antibacterial activity against biofilms and its effects on glucosyltransferases were minimal. The incidence of smooth-surface caries was significantly reduced by apigenin +tt-farnesol (60%), fluoride (70%), and chlorhexidine (72%) treatments compared to control (P < 0.05).

Analysis of Variance↗

PubMed2002

Stictodora lari (Digenea: Heterophyidae): the discovery of the first human infections.

Stictodora lari Yamaguti, 1939 (Digenea: Heterophyidae) was originally reported as an avian intestinal parasite and is here reported in humans. The patients were adults, aged 46-69 (2 men and 4 women), who resided in coastal villages in Sachon-gun, Kyongsangnam-do, or Shinan-gun, Chollanam-do. in the Republic of Korea. The worms were recovered after praziquantel treatment and purgation with magnesium salts. A total of 15 S. lari specimens (1-10 per individual) was collected, together with 5 other species of intestinal flukes. The flukes were morphologically characterized by a small body size (0.70-0.86 mm long and 0.27-0.36 mm wide), a ventrogenital sac, and a gonotyl armed with 70-80 spines in the form of a comma or reversed comma lying along their lateral margin. The patients had eaten the raw flesh of mullets and gobies that had been caught in an estuary near their villages. To the best of our knowledge, this is the first record of a human S. lari infection.

Aged↗

PubMed2002

Host specificity of Austropeplea ollula (Gastropoda: Lymnaeidae) to miracidial infection with a human intestinal fluke Neodiplostomum seoulense (Trematoda: Diplostomatidae) in Korea.

Three species of freshwater pulmonate snails of Lymnaeidae have been reported from Korea, Radix auricularia coreana, Austropeplea ollula, and Fossaria truncatula. Of these 3 species, only A. ollula was naturally infected with Neodiplostomum seoulense cercariae (prevalence, 0.3%). In experiments with the laboratory-reared snails, A. ollula was found to be susceptible to the N. seoulense miracidia (prevalence, 10%). This is the first report of A. ollula as the first molluscan intermediate host for N. seoulense in Korea.

Animals↗

PubMed2002

Cross-resistance between rifampicin and KRM-1648 is associated with specific rpoB alleles in Mycobacterium tuberculosis.

KRM-1648 resistant Mycobacterium tuberculosis strains were identified from a collection of rifampicin-resistant strains. Several strains had novel rpoB gene mutations in codons 512, 529 and 533 of the rpoB gene. The strains with mutations in codons 526 or 531, major mutation sites in rifampicin-resistant M. tuberculosis, were resistant to KRM-1648. Also, the strains with other mutations in the rpoB gene that were initially susceptible to KRM-1648 were prone to developing KRM-1648 resistance after further mutation. Thus, KRM-1648 is unlikely to be useful for the treatment of rifampicin-resistant tuberculosis.

Alleles↗

PubMed2001

Induction of glucose-regulated protein 78 by chronic hypoxia in human gastric tumor cells through a protein kinase C-epsilon/ERK/AP-1 signaling cascade.

The M(r) 78,000 glucose-regulated protein (GRP78) can be induced by physiological stresses such as glucose deprivation and hypoxia. In solid tumors, hypoxia can promote malignant progression and confer resistance to irradiation and chemotherapy by altering gene expression. Here, we investigated the molecular mechanisms and signaling pathway involved in the late and prolonged induction of the GRP78 gene by hypoxia in a human gastric cancer cell line, MKN28. Nuclear run-on assays and mRNA stability measurements revealed that transcriptional activation, not stabilization of mRNA, contributed to the dramatic induction of GRP78 gene under hypoxia. Induction of GRP78 by chronic hypoxia was completely abolished by pretreatment with PD98059 [a specific inhibitor of mitogen-activated protein/extracellular signal-regulated kinase (ERK) kinase (MEK1)] or by overexpression of a dominant-negative MEK1 mutant, demonstrating a direct involvement of ERK in the induction of transcription at the GRP78 promoter under these conditions. Furthermore, hypoxia increased the transcriptional activity of a 12-O-tetradecanoylphorbol-13-acetate response element-like motif on the GRP78 promoter and increased the abundance and DNA binding activity of AP-1 complex composed of c-Jun and c-Fos. A selective protein kinase C (PKC) inhibitor, GF109203X, inhibited the induction of GRP78 gene expression as well as the activities of both ERK and Raf-1. Among six PKC isoforms expressed in MKN28 cells, PKC-epsilon expression level and kinase activity were increased by hypoxia. Transfection of MKN28 cells with a dominant-negative PKC-epsilon blocked the induction of GRP78 through ERK by hypoxia, indicating that PKC-epsilon directly participated in GRP78 induction under hypoxia. Taken together, this study shows that a PKC-epsilon-Raf-1-MEK-ERK-AP1 signaling cascade acts on a 12-O-tetradecanoylphorbol-13-acetate response element-like element to mediate hypoxia-induced GRP78 expression in human gastric cancer cells. We also confirmed in vivo the overexpression of GRP78 in surgical specimens of human primary gastric tumors.

Adenocarcinoma↗

PubMed2001

Genetic alterations in gallbladder adenoma, dysplasia and carcinoma.

Adenoma and dysplasia in the gallbladder (GB) have been reported as precancerous lesions, but the genetic evidence of this is not clearly defined. The purpose of this study was to analyze the frequencies of K-ras, p53, and p16 gene mutations, of microsatellite instability (MI) and of loss of heterozygosity (LOH) in GB cancer, dysplasia, and adenoma. Tissues from 15 GB cancers, five dysplasias around cancerous tumors, and three adenomas were collected prospectively. The mutation rates of K-ras, p53, and p16 were 20.0, 35.7, and 30.7%, respectively, in GB cancers. However, no mutations were found in dysplasia or adenoma. Reduced staining for p16 was seen in 23% of carcinomas. All of the GB carcinomas and four out of five (80%) of the dysplasias showed LOH in a minimum of one locus, but one out of three (33%) cases of adenoma displayed LOH in only one locus. All of the loci of LOH in the dysplasias, except one, showed the same patterns of allelic loss as the adjacent carcinomas. Only one dysplasia showed multiple MI. In conclusion, multiple LOH may be associated with the development of dysplasia and the malignant transformation of GB carcinoma. Gene alterations of K-ras, p53, and p16 are important steps in the malignant changes of dysplasia. However, MI seems to have only a limited role in GB cancer development.

Adenoma↗

PubMed2001

Effects of capsaicin on Ca(2+) release from the intracellular Ca(2+) stores in the dorsal root ganglion cells of adult rats.

We have investigated the effect of capsaicin on Ca(2+) release from the intracellular calcium stores. Intracellular calcium concentration ([Ca(2+)](i)) was measured in rat dorsal root ganglion (DRG) neurons using microfluorimetry with fura-2 indicator. Brief application of capsaicin (1 microM) elevated [Ca(2+)](i) in Ca(2+)-free solution. Capsaicin-induced [Ca(2+)](i) transient in Ca(2+)-free solution was evoked in a dose-dependent manner. Resiniferatoxin, an analogue of capsaicin, also raised [Ca(2+)](i) in Ca(2+)-free solution. Capsazepine, an antagonist of capsaicin receptor, completely blocked the capsaicin-induced [Ca(2+)](i) transient. Caffeine completely abolished capsaicin-induced [Ca(2+)](i) transient. Dantrolene sodium and ruthenium red, antagonists of the ryanodine receptor, blocked the effect of capsaicin on [Ca(2+)](i). However, capsaicin-induced [Ca(2+)](i) transient was not affected by 2-APB, a membrane-permeable IP(3) receptor antagonist. Furthermore, depletion of IP(3)-sensitive Ca(2+) stores by bradykinin and phospholipase C inhibitors, neomycin, and U-73122, did not block capsaicin-induced [Ca(2+)](i) transient. In conclusion, capsaicin increases [Ca(2+)](i) through Ca(2+) release from ryanodine-sensitive Ca(2+) stores, but not from IP(3)-sensitive Ca(2+) stores in addition to Ca(2+) entry through capsaicin-activated nonselective cation channel in rat DRG neurons.

Animals↗

PubMed2001

Abrogation of disease development in plants expressing animal antiapoptotic genes.

An emerging topic in plant biology is whether plants display analogous elements of mammalian programmed cell death during development and defense against pathogen attack. In many plant-pathogen interactions, plant cell death occurs in both susceptible and resistant host responses. For example, specific recognition responses in plants trigger formation of the hypersensitive response and activation of host defense mechanisms, resulting in restriction of pathogen growth and disease development. Several studies indicate that cell death during hypersensitive response involves activation of a plant-encoded pathway for cell death. Many susceptible interactions also result in host cell death, although it is not clear how or if the host participates in this response. We have generated transgenic tobacco plants to express animal genes that negatively regulate apoptosis. Plants expressing human Bcl-2 and Bcl-xl, nematode CED-9, or baculovirus Op-IAP transgenes conferred heritable resistance to several necrotrophic fungal pathogens, suggesting that disease development required host-cell death pathways. In addition, the transgenic tobacco plants displayed resistance to a necrogenic virus. Transgenic tobacco harboring Bcl-xl with a loss-of-function mutation did not protect against pathogen challenge. We also show that discrete DNA fragmentation (laddering) occurred in susceptible tobacco during fungal infection, but does not occur in transgenic-resistant plants. Our data indicate that in compatible plant-pathogen interactions apoptosis-like programmed cell death occurs. Further, these animal antiapoptotic genes function in plants and should be useful to delineate resistance pathways. These genes also have the potential to generate effective disease resistance in economically important crops.

Apoptosis↗

PubMed2001

1,4-dioxane-fused 4-anilinoquinazoline as inhibitors of epidermal growth factor receptor kinase.

The 4-anilinoquinazoline PD 153035 (1) is a potential antitumor agent which acts by inhibiting tyrosine kinase activity of epidermal growth factor receptor (EFGR) via competitive binding at the ATP site of enzyme. A series of cyclic analogues of PD 153035 bearing the 1,4-dioxane ring was prepared by reaction of 6-chloro derivative 5 with several aniline nucleophiles. These were evaluated for their ability to inhibit the EGFR kinase and the growth of primary human tumor cell cultures. All of the new 4-anilinoquinazolines exhibited less potency than PD 153035 against EGFR kinase. However, compounds 2b, 2c, 2e, 2g, and 2h showed higher inhibitory activities than PD 153035 against the growth of A431 tumor cell line. The compound 2b containing 3-chloroaniline ring was as potent as PD 153035 against EGFR kinase and showed about 5.4-fold better potency than PD153035 in the inhibition of growth of A431 cell line with good selectivity.

Antineoplastic Agents↗

PubMed2001

Inhibitory effect of glycolic acid on ultraviolet-induced skin tumorigenesis in SKH-1 hairless mice and its mechanism of action.

Glycolic acid, an alpha-hydroxy acid derived from fruit and milk sugars, has been used commonly as a cosmetic ingredient since it was discovered to have photoprotective and anti-inflammatory effects and antioxidant effects on ultraviolet (UV)B-irradiated skin. Little is known, however, about the functional role of glycolic acid on UV-induced skin tumorigenesis. In the present study, we examined the effect of glycolic acid on UV (UVA + UVB)-induced skin tumorigenesis and assessed several significant contributing factors in SKH-1 hairless mice. Inbred hairless female mice (15 animals/group) were irradiated for 5 d/wk at a total dose of 74.85 J/cm(2) UVA and 2.44 J/cm(2) UVB for 22 wk. Glycolic acid was applied topically twice a week at a dose of 8 mg/cm(2) immediately after UV irradiation. Glycolic acid reduced UV-induced skin tumor development. The protective effect of glycolic acid was a 20% reduction of skin tumor incidence, a 55% reduction of tumor multiplicity (average number of tumors/mouse), and a 47% decrease in the number of large tumors (larger than 2 mm). Glycolic acid also delayed the first appearance of tumor formation by about 3 wk. The inhibitory effect of glycolic acid on UV-induced tumor development was accompanied by decreased expression of the following UV-induced cell-cycle regulatory proteins: proliferating cell nuclear antigen (PCNA), cyclin D1, cyclin E, and the associated subunits cyclin-dependent kinase 2 (cdk2) and cdk4. In addition, the expression of p38 kinase, jun N-terminal kinase (JNK), and mitogen-activated protein kinase kinase (MEK) also was lower in UV + glycolic acid-treated skin compared with expression in UV-irradiated skin. Moreover, transcription factors activator protein 1 (AP-1) and nuclear factor kappaB (NF-kappaB) activation was significantly lower in UV + glycolic acid-treated skin compared with activation in UV-irradiated skin. These results show that glycolic acid reduced UV-induced skin tumor development. The decreased expression of the cell-cycle regulatory proteins PCNA, cyclin D1, cyclin E, cdk2, and cdk4 and the signal mediators JNK, p38 kinase, and MEK may play a significant role in the inhibitory effect of glycolic acid on UV-induced skin tumor development. In addition, the inhibition of activation of transcription factors AP-1 and NF-kappaB could contribute significantly to the inhibitory effect of glycolic acid.

Animals↗

PubMed2001

Microinvasive video-assisted thoracoscopic sympathicotomy for primary palmar hyperhidrosis.

BACKGROUND: Although video-assisted thoracoscopic surgery for palmar hyperhidrosis is now widely accepted as the approach of choice, the optimal technique has remained a subject of controversy. We have used 2-mm dual port video-assisted thoracoscopic sympathicotomy for primary palmar hyperhidrosis. This study evaluates the short-term results of the technique. METHODS: A retrospective review was carried out of 45 patients, 20 men and 25 women, with a mean age of 24.2 years. In the period from April 1998 to August 1999, 90 consecutive video-assisted sympathicotomy for primary palmar hyperhidrosis either in isolation (n = 56) or in combination with axillary and plantar hyperhidrosis (n = 34) was performed. The mean follow-up period was 11.3 months. Attention was focused on patient's satisfaction, complications, and morbidity. RESULTS: Dry limbs were immediately achieved in all patients after surgery. There was no operative mortality and one case of transient Horner's syndrome developed. Eight of 20 with plantar hyperhidrosis showed simultaneous improvement. The overall mean satisfaction rate was 92% +/- 2% with a median 93% improvement using a visual linear analogue scale from 0% (poor) to 100% (excellent). Only 2 patients were dissatisfied with the operative results owing to compensatory hyperhidrosis, which occurred in 25 patients and improved in 20 patients within the follow-up period. CONCLUSIONS: The video-assisted thoracoscopic sympathicotomy with 2-mm endoscope is a speedy and safe way of controlling hyperhidrosis with excellent cosmetic results while minimizing complications.

Adolescent↗

PubMed2001

Anti-AIDS agents. 48.(1) Anti-HIV activity of moronic acid derivatives and the new melliferone-related triterpenoid isolated from Brazilian propolis.

A new triterpenoid named melliferone (1), three known triterpenoids, moronic acid (2), anwuweizonic acid (3), and betulonic acid (4), and four known aromatic compounds (5-8) were isolated from Brazilian propolis and tested for anti-HIV activity in H9 lymphocytes. Moronic acid (2) showed significant anti-HIV activity (EC(50) <0.1 microg/mL, TI >186) and was modified to develop more potent anti-AIDS agents.

Anti-HIV Agents↗

PubMed2001

Livedoid vasculitis responding to PUVA therapy.

BACKGROUND: Livedoid vasculitis is a chronic disorder manifested as recurrent, painful, reticulated, and ulcerative lesions of the legs, which result in ivory atrophic scars with peripheral telangiectasia and hyperpigmentation. Its etiology remains obscure and therapy is difficult. In this study, we evaluated the clinical efficacy of psoralen plus UVA (PUVA) therapy and its side-effects in the treatment of livedoid vasculitis. METHODS: Eight South Korean patients with livedoid vasculitis were treated with UVA and 8-methoxypsoralen (8-MOP). Systemic PUVA was started with 4 J/cm2 of UVA two or three times a week, and then the dose was increased by 0.5 or 1 J/cm2 increments at each subsequent treatment as tolerated. The effects of treatment were evaluated using photographs of before, during, and after the study. RESULTS: All patients experienced rapid cessation of new lesion formation, significant symptom relief, and complete healing of primary lesions. The mean times for each of the above were 3.6, 5.9, and 10 weeks, and the mean cumulative doses of UVA for each of the above were 55.9, 96.8, and 197.9 J/cm2, respectively. The patients tolerated PUVA therapy well without unacceptable side-effects. CONCLUSIONS: We propose that systemic PUVA using 8-MOP should be investigated further as an alternative treatment for patients with livedoid vasculitis.

Adult↗

PubMed2001

Multicentric telangiectatic osteosarcoma.

A rare case of multicentric telangiectatic osteosarcoma in a 29-year-old woman is described. A plain X-ray showed a pure osteolytic lesion of the navicular, cuboid and I, II, III cuneiform bones. On magnetic resonance images, a T1-weighted image showed heterogeneous low signal intensity. A T2-weighted image showed heterogeneous high signal change with multicentric cystic foci and fluid-fluid levels. Histologically, the lesion showed typical telangiectatic osteosarcoma with numerous atypical giant cells.

Adult↗

PubMed2001

Intestinal protein and LPH synthesis in parenterally fed piglets receiving partial enteral nutrition and enteral insulinlike growth factor 1.

BACKGROUND: Providing partial enteral nutrition (PEN) supplemented with insulinlike growth factor-1 (IGF-1) to parenterally fed piglets increases lactase-phlorizin hydrolase (LPH) activity, but not LPH mRNA. The current aim was to investigate potential mechanisms by which IGF-1 up-regulates LPH activity. METHODS: Newborn piglets (n = 15) received 100% parenteral nutrition (TPN), 80% parenteral nutrition + 20% parenteral nutrition (PEN), or PEN + IGF-1 (1.0 mg. kg-1. d-1) for 7 days. On day 7, [2H3]-leucine was intravenously administered to measure mucosal protein and brush border LPH (BB LPH) synthesis. RESULTS: Weight gain, nutrient intake, and jejunal weight and length were similar among the treatment groups. Partial enteral nutrition alone increased mucosal weight, villus width and cross-sectional area, LPH activity, mRNA expression, and high mannose LPH precursor (proLPHh) abundance compared with TPN (P<0.05). Insulinlike growth factor-1 further increased mucosal weight, LPH activity, and LPH activity per unit BB LPH approximately twofold over PEN alone (P < 0.05) but did not affect LPH mRNA or the abundance of proLPHh (one of the LPH isoforms) or mature LPH. Isotopic enrichment of [2H3]-leucine in plasma, mucosal protein, and LPH precursors, and the fractional and absolute synthesis rates of mucosal protein and LPH were similar among the treatment groups. Insulinlike growth factor-1 treatment increased total mucosal protein synthesis (60%, P < 0.05) but not LPH synthesis compared with the other two groups. CONCLUSIONS: Because IGF-1 did not affect the fractional synthesis rate of either mucosal protein or LPH, the authors suggest that enteral IGF-1 increases mucosal protein mass and LPH activity by suppressing mucosal proteolytic degradation.

Animals↗

PubMed2001

Accumulation of intraventricular fat in an intracranial epidermoid tumor: case report.

OBJECTIVE AND IMPORTANCE: A fat component within the ventricles or subarachnoid space in fat-containing tumors such as an epidermoid or a dermoid has been observed in rare instances. However, there have been no reports regarding an increase in the size of such a fat component. We describe the case of an epidermoid tumor with intraventricular fat that showed an increase in size and amount. CLINICAL PRESENTATION: A 26-year-old woman was admitted with headache and diplopia. Computed tomography and magnetic resonance imaging of the brain revealed a fat-containing suprasellar tumor and widespread fat globules in adjacent sulci and cisterns and within the frontal horn of the lateral ventricle. INTERVENTION: The patient underwent a pterional craniotomy. Removal of the suprasellar tumor was nearly total. Histopathological examination revealed an epidermoid tumor. Sequential magnetic resonance imaging throughout the ensuing 65-month period revealed no evidence of tumor recurrence; however, the intraventricular fat remained and increased in size. The patient underwent surgery via the transcallosal approach at 69 months after the initial operation, and the presence of free-floating oily fat globules was confirmed. CONCLUSION: In the case of a fat-containing tumor with free fat in the cerebrospinal fluid spaces, careful serial examination is necessary, with particular attention to the possibility of changes in size.

Adult↗

PubMed2001

Expression of cspH, encoding the cold shock protein in Salmonella enterica serovar Typhimurium UK-1.

Both Salmonella enterica serovar Typhimurium and Escherichia coli contain the cspH gene encoding CspH, one of the cold shock proteins (CSPs). In this study, we investigated the expression of cspH in S. enterica serovar Typhimurium and found that it was induced in response to a temperature downshift during exponential phase. The cspH promoter was activated at 37 degrees C, and its mRNA was more stable than the other csp mRNAs at 37 degrees C. Moreover, lacZ expression of the translational cspH-lacZ fusion was induced at that temperature. Interestingly, the cspH mRNA had a much shorter 5'-untranslated region than those in the other cold-shock-inducible genes, and the promoter sequence, which was only 55 bp, was sufficient for cspH expression. The 14-base downstream box located 12 bases downstream of the initiation codon of cspH mRNA was essential for its cold shock activation.

5' Untranslated Regions↗