Biomedical subjects

C Park

Publications and source records attributed to C Park.

At least 163 records · Page 9Linked to original sources

PubMed1997

Deposition of Brownian Particles on Cylindrical Collectors in a Periodic Array

The capture of charged Brownian particles in an idealized square array of cylindrical collectors has been studied using a finite element method. In addition to varying the size of the cylindrical collectors and the porosity, the collector-particle interactions resulting from van der Waals attraction and electrostatic repulsion have been considered. In a typical filtration process where the particle capture is diffusion-limited, a critical value of surface potential appears to exist above which the filter coefficient decreases rapidly. It is due to the insurmountable repulsive barrier between the particles and collectors. While the value of the critical surface potential varies with the electrolyte concentration and the Hamaker constant, it apparently corresponds to a common value of about 10 kT for the height of the primary maximum of the interaction potential.

Journal Article↗

PubMed1997

Involvement of iclR and rpoS in the induction of acs, the gene for acetyl coenzyme A synthetase of Escherichia coli K-12.

Two independent pathways in Escherichia coli convert acetate to acetyl CoA: reversal of acetate production by phosphotransacetylase and acetate kinase, and the acetyl-CoA synthetase (Acs) pathway that scavenges acetate. We investigated acs gene expression by using a cat transcriptional fusion. It was observed that acs expression varies depending on the carbon sources used and occurs in the stationary phase of growth even in the absence of acetate. Mutations in iclR for the repressor of the glyoxylate shunt and in rpoS for the stationary phase sigma factor reduced the consumption of acetate mediated by Acs, indicating that both are involved in acs regulation.

Acetate-CoA Ligase↗

PubMed1997

Modulation of MMP-2 (gelatinase A) and MMP-9 (gelatinase B) by interferon-gamma in a human salivary gland cell line.

Gelatinases have been shown to be regulated by many cytokines and growth factors, and have been implicated in the pathogenesis of certain autoimmune diseases via tissue destruction. High levels of several cytokines, including IFN-gamma and TNF-alpha, have been demonstrated in the salivary gland microenvironment of patients with Sjogren's syndrome (SS). How these cytokines may be contributing to the pathogenesis of this disease is not well understood. We hypothesized that IFN-gamma with or without (+/-) TNF-alpha could be playing a role in the pathogenesis of SS via the regulation of matrix metalloproteinase (MMP) levels. This study examined the role of IFN-gamma and (+) TNF-alpha in the regulation of the matrix metalloproteinases, MMP-2 (72 kD gelatinase A) and MMP-9 (92 kD gelatinase B). A human salivary gland cell line (HSG) has been used as a possible in vitro model to study the role of IFN-gamma + TNF-alpha in the pathogenesis of SS. The HSG cell line, in the presence of IFN +/- TNF-alpha, displays increased MMP-2 and MMP-9 gelatinolytic activity, protein and RNA levels. The increase in MMP activity was partially blocked with an antibody against the IFN-gamma receptor, and this was associated with a complete inhibition of the previously described IFN-gamma +/- TNF-alpha antiproliferative effect. However, incubation of IFN-gamma treated HSG cells with the synthetic MMP inhibitor BB94 did not alleviate this antiproliferative effect. In addition, we demonstrate that there are very high levels of MMP-9 in the saliva of patients with SS when compared to healthy control subjects. These data suggest that cytokines could be regulating MMP production by salivary epithelial cells and thus indicate a potential role for these cells in the pathogenesis of SS.

Animals↗

PubMed1997

Analysis of expression and function of topoisomerase I and II during meiosis in male mice.

Topoisomerases are nuclear enzymes that remove torsional stress in DNA. Their function is important for replication, transcription, chromosome condensation, and chromosome segregation during mitosis and meiosis. The goal of this work is to analyze both expression and function of topoisomerases during the meiotic stages of mammalian spermatogenesis. The patterns of expression of topoisomerase I and topoisomerase II alpha genes were followed on Northern blots of RNA from testes of mice of different ages and from specific germ cell populations. The transcript of the topoisomerase I gene was highest in somatic cells of the testis and in the mitotically proliferating spermatogonia and meiotic prophase spermatocytes, with the level of transcript decreasing dramatically in postmeiotic spermatids. In contrast, the levels of topoisomerase II alpha transcript were negligible in germ-cell free testes and highest in late meiotic prophase cells and round spermatids. Enzyme activity for both topoisomerase I and topoisomerase II was detected in both pachytene spermatocytes and in round spermatids; topoisomerase II exhibited a higher level of activity in meiotic spermatocytes than in round spermatids. In cultured cells, camptothecin, an inhibitor of topoisomerase I, caused some abnormalities of paired meiotic homologs, but did not inhibit the transition to metaphase. In contrast, teniposide and ICRF-193, inhibitors of topoisomerase II, dramatically inhibited the formation of metaphase chromosomes in cells induced to progress from prophase to metaphase. However, the disassembly of the synaptonemal complex was not inhibited, indicating that this process could be uncoupled from condensation of chromatin to form chromosomes. These studies constitute evidence for a functional requirement for topoisomerase II activity in the transition from meiotic prophase to meiotic metaphase I in mammalian spermatocytes.

Animals↗

PubMed1997

Application of genetic algorithms to parameter estimation of bioprocesses.

The paper explains the application of a genetic algorithm (GA) to the problem of estimating parameters for a kinetic model of a biologically reacting system. It is demonstrated that the GA is a powerful tool for quantifying the kinetic parameters using kinetic data. As the operation of the GA does not depend on the form of the model equation, it can be applied to the wide spectrum of kinetic modelling problems without any complex formulation procedure.

Algorithms↗

PubMed1997

Three-dimensional ultrasound device for rapid determination of bladder volume.

OBJECTIVES: We sought to assess the accuracy, reliability, and clinical utility of the noninvasive determination of bladder volume using an automated, compact three-dimensional (3-D) ultrasound device. METHODS: We prospectively tested 249 adult outpatients for accuracy (n = 182), by comparing scan versus catheter volumes, or reliability (n = 67), by comparing the scan readings of two independent observers. Two models of the bladder scan device were tested (BVI-2500, 1994 and 1995 models). RESULTS: Scan and catheter volumes were correlated (y = 1.02x + 12.6, R2 = 0.90, P < 0.001) across a range of zero to 1015 cc, regardless of which machine model was used. Scan volume underestimated catheter volume by an average of 10 cc in men and 20 cc in women. If a scan-predicted volume of 100 cc or greater were used as a cutpoint for clinical importance, the device exhibited a sensitivity of 97%, a specificity of 91%, and an overall accuracy of 94%. These results were not affected by age, gender, height, weight, diagnosis, uterine presence/prostate size, or user experience. The two observers, one a graduate physician and the other a college student, achieved essentially the same volume determinations (y = 0.96x + 0.13, R2 = 0.90, P < 0.001). CONCLUSIONS: Volume determinations obtained with the bladder scan device are accurate and reliable in adult outpatients. A special technician is not required. These results may be attributable to use of automated planimetry and 3-D volumetry, rather than a fixed geometric formula, to custom measure each bladder shape.

Adult↗

PubMed1997

Button-down procedure for correction of cleft earlobe malformation.

The button-down procedure for correction of a tag and cleft type of cleft earlobe malformation has been presented. The method is simple and easy to perform. We were able to add relative fullness with a natural look to several malformed earlobes that satisfactorily matched the contralateral earlobe in size and shape. The patients and their parents were pleased with our results.

Child↗

PubMed1997

Modification of two-flap method and framework construction for reconstruction of atypical congenital auricular deformities.

A single-stage two-flap method utilizing an anteriorly based subcutaneous pedicled skin flap and a mastoid fascial flap has been applied successfully for reconstruction of lobule-type microtia. This paper presents three modifications of the two-flap method, with which atypical congenital auricular deformities necessitating both framework construction and coverage were reconstructed successfully. In middle and upper auricular deformities such as a concha-type or a scapha-type microtia, a cranially based postauricular skin flap and lower mastoid fascial flap were used. For upper auricular deformities such as microtia representing lop-ear deformity, a narrow cranially based postauricular skin flap (Grotting flap) and upper mastoid fascial flap were used. For lower auricular deformities such as total absence of the earlobe, a cranially based skin flap and lower mastoid fascial flap were utilized. In each deformity the framework was totally or partially constructed with autogenous costal, conchal, or septal cartilage or their combination according to the size or shape of the defect. Fifty-two atypical auricular deformities were corrected with the modified two-flap method and framework construction. The follow-up has ranged from 4 months to 3 years (average 18 months). No major surgical complications occurred in this series. Representative cases reconstructed with each modified method are shown. While the shape of the cartilage framework is sculptured according to the type and degree of deformity in each patient, the modified two-flap method not only adequately covers the cartilage but also preserves the fabricated framework in its natural contour and position in the diverse varieties of atypical congenital auricular deformities.

Adolescent↗

PubMed1997

Clonality of large regenerative nodules in liver cirrhosis.

The role of the large regenerative nodule (RN) in hepatocarcinogenesis is not clear, although the incidence of hepatocellular carcinoma (HCC) is high in cirrhotic liver. This study was aimed at clarifying the preneoplastic nature of large RN without atypia. We analyzed the clonality of HCCs and large RNs, ranging in size from 0.6 to 1.2 cm, of cirrhotic liver by X-linked human androgen receptor (HUMARA) gene assay, using the principle of random X chromosome methylation and inactivation in females. Eleven cases of HCC and five cases of large RN without atypia from ten female patients were selected. All HCCs, large RNs and paired non-tumorous tissue from adjacent liver were selectively microdissected from deparaffinized hematoxylin and eosin stained slides. Genomic DNA was isolated and digested with Hha I. Polymerase chain reaction (PCR) amplification of the HUMARA gene was performed using a PCR mixture containing [alpha-32P]-dCTP. The PCR products were separated by gel electrophoresis and analysed by autoradiography. HUMARA was informative in nine out of ten female patients. In the informative 10 HCCs from nine patients, 9 HCCs were monoclonal and one case was polyclonal. The HCC case that showed polyclonality contained many inflammatory cells in the tumor. All of the large RNs were polyclonal. No allelic loss of chromosome 18q was present in the large RNs in constrast to the 3 out of 7 HCCs, which showed allelic deletion in chromosome 18q. We conclude that all or most of the cells composing the large RNs without atypia are polyclonal and the size of a nodule may not be important in hepatocarcinogenesis. This clonality assay may be informative for the differentiation between regenerative and preneoplastic nodules in cirrhotic liver.

Adult↗

PubMed1997

Bacterial DL-2-haloacid dehalogenase from Pseudomonas sp. strain 113: gene cloning and structural comparison with D- and L-2-haloacid dehalogenases.

DL-2-Haloacid dehalogenase from Pseudomonas sp. strain 113 (DL-DEX) catalyzes the hydrolytic dehalogenation of both D- and L-2-haloalkanoic acids to produce the corresponding L- and D-2-hydroxyalkanoic acids, respectively, with inversion of the C2 configuration. DL-DEX is a unique enzyme: it acts on the chiral carbon of the substrate and uses both enantiomers as equivalent substrates. We have isolated and sequenced the gene encoding DL-DEX. The open reading frame consists of 921 bp corresponding to 307 amino acid residues. No sequence similarity between DL-DEX and L-2-haloacid dehalogenases was found. However, DL-DEX had significant sequence similarity with D-2-haloacid dehalogenase from Pseudomonas putida AJ1, which specifically acts on D-2-haloalkanoic acids: 23% of the total amino acid residues of DL-DEX are conserved. We mutated each of the 26 residues with charged and polar side chains, which are conserved between DL-DEX and D-2-haloacid dehalogenase. Thr65, Glu69, and Asp194 were found to be essential for dehalogenation of not only the D- but also the L-enantiomer of 2-haloalkanoic acids. Each of the mutant enzymes, whose activities were lower than that of the wild-type enzyme, acted on both enantiomers of 2-haloacids as equivalent substrates in the same manner as the wild-type enzyme. We also found that each enantiomer of 2-chloropropionate competitively inhibits the enzymatic dehalogenation of the other. These results suggest that DL-DEX has a single and common catalytic site for both enantiomers.

Amino Acid Sequence↗

PubMed1997

Organization and regulation of the D-xylose operons in Escherichia coli K-12: XylR acts as a transcriptional activator.

The metabolism of D-xylose in Escherichia coli K-12 is known to be mediated by the xylAB gene. However, the nearby xylFGHR genes were found by genome sequencing and predicted to be responsible for transport and regulation for xylose based on their sequence similarities to other functionally related genes. Here, we investigated transcriptional organization and functions of the xyl genes. An analysis with random transposon insertions revealed that the xyl genes are organized into two major transcriptional units, xylAB and xylFGHR, governed by the promoters PA and PF, respectively. However, there is an additional weak promoter, PR, which is specific for xylR. Sites of transcription initiation were determined by primer extension analysis. When studied with operon fusions to lacZ, the PA and PF promoters were activated by D-xylose and repressed by glucose. In contrast, the PR promoter was not regulated by these sugars. A mutation in xylR completely abolished expression from the PA and PF promoters, causing a defect in both growth and transport. Binding of XylR to the xyl promoter was enhanced by the presence of D-xylose, suggesting that transcription was positively regulated by XylR. In vivo footprinting analysis revealed that XylR binds to at least two DNA regions, IA and IF, each with a direct repeat. It is very likely that XylR interacts with IA and IF as a dimer. The presumed binding sites are located just upstream of the promoter consensus sequences (-35), while IA is additionally flanked by a cyclic AMP receptor protein-binding site on the other side. The proposed structure of xyl promoters is consistent with the regulation of xyl gene expression and with phenotypes of transposon insertions obtained in the promoter regions.

Bacterial Proteins↗

PubMed1997

The D-allose operon of Escherichia coli K-12.

Escherichia coli K-12 can utilize D-allose, an all-cis hexose, as a sole carbon source. The operon responsible for D-allose metabolism was localized at 92.8 min of the E. coli linkage map. It consists of six genes, alsRBACEK, which are inducible by D-allose and are under the control of the repressor gene alsR. This operon is also subject to catabolite repression. Three genes, alsB, alsA, and alsC, appear to be necessary for transport of D-allose. D-Allose-binding protein, encoded by alsB, is a periplasmic protein that has an affinity for D-allose, with a Kd of 0.33 microM. As was found for other binding-protein-mediated ABC transporters, the allose transport system includes an ATP-binding component (AlsA) and a transmembrane protein (AlsC). It was found that AlsE (a putative D-allulose-6-phosphate 3-epimerase), but not AlsK (a putative D-allose kinase), is necessary for allose metabolism. During this study, we observed that the D-allose transporter is partially responsible for the low-affinity transport of D-ribose and that strain W3110, an E. coli prototroph, has a defect in the transport of D-allose mediated by the allose permease.

Biological Transport↗

PubMed1997

Expression of alpha-1-antichymotrypsin in prostate carcinoma.

Prostate specific antigen (PSA) is a glycoprotein with the enzymatic activity of serine protease, the gene which is encoded in the human glandular kallikrein gene locus. Catalytically active PSA released into serum may be inactivated by a complex formation with alpha 1ACT (ACT) and alpha 2MG (MG), two major protease inhibitors. The serum complex-to-total PSA ratio can be used as a marker for the differentiation between prostate carcinoma (PCa) and a benign lesion because of a significant elevation of PSA binding to ACT in PCa. Apparently higher immunohistochemical expressions of PSA and ACT have been reported in PCa of low Gleason scores when compared with benign lesions. The fact that only normal secretory epitheliums are capable of producing ACT was recently proved by immunohistochemical and in situ hybridization methods. Our immunohistochemical study of ACT showed a tendency toward stronger expression in high Gleason grade PCa than in low Gleason grade Pca. Prostate intraepithelial neoplasia (PIN), as well as BPH, seldom react to ACT. Expression of ACT in normal ducts or acini was influenced by their location. In a normal prostate, expression of ACT was predominantly in secretory epithelial cells, with a minority of basal cells and rarely in the interdigitating neuroendocrine cells. Whereas the potency of ACT production in epithelial cells almost always appeared to be suppressed under normal conditions, it was noted that a strong expression of ACT was apparent in the normal ducts or acini near a high grade carcinoma with a weak reaction to ACT. ACT expression is much more enhanced in high grade carcinomas and in the residual normal acini adjacent to carcinomas of low ACT expression, presumably representing scale down the elevated PSA.

Carcinoma↗

PubMed1997

A case of extragastrointestinal anisakiasis involving a mesocolic lymph node.

In a 43-year-old Korean man who underwent radical gastrectomy due to a malignant stromal tumor, was found to have an enlarged lymph node at transverse mesocolon. The lymph node exhibited histologically necrotizing eosinophilic granuloma formed around a track containing sections of a nematode larva. The well preserved nematode sections revealed polymyarian muscle cells, Y-shaped lateral cord, a large excretory gland cell, intestine and eosinophilic cuticle. The nematode sections were identified as a larva of Anisakis species. In Korea, this is the first case of extragastrointestinal anisakiasis.

Adult↗

PubMed1997

Triton X-100 induces apoptosis in human hepatoma cell lines.

The detergent Triton X-100 was used to establish a model for apoptosis in hepatoma cell lines. The electrophoresis of DNA extracted from 0.01% Triton X-100 treated hepatoma cell lines showed DNA ladder formation, a hallmark of apoptosis. The DNA fragmentation appeared within less than 60 min of the Triton X-100 treatment. Chromatin condensation and apoptotic bodies were observed by hematoxylin and eosin (H & E) stain, and fragmented nucleosome was detected by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labelling (TUNEL) test. Apoptosis was semi-quantitated by measuring the lactate dehydrogenase (LDH) level for cytotoxity. It was found that apoptosis had been induced in more than 90% of the cells treated with Triton X-100 for 150 min. These data show that Triton X-100 efficiently induces the apoptotic cell death in hepatoma cell lines.

Apoptosis↗

PubMed1997

The effect of aflatoxin B1 on the expression of early response genes and transforming growth factor-alpha in CCl4 induced rat liver injury.

Aflatoxin B1 (AFB1), a fungal toxin produced by Aspergillus flavus, is known to be a possible hepatocarcinogen. But the molecular biologic changes which may occur following exposure to AFB1 are not known and thus the carcinogenesis is not yet understood. This study was performed to examine the expressions of c-myc, c-fos and TGF-alpha genes and to investigate the possible role of those molecular biologic changes in hepatic regeneration and in the development of hepatocellular carcinoma (HCC). Sprague-Dawley rats were divided into 3 groups: Carbon tetrachloride (CCl4) only was administered to group I, AFB1 only was administered to group II and a combination of AFB1 and CCl4 was administered to group III. The animals were sacrificed at 0.5, 1, 2, 6, 12, 24, 48, and 72 hours after treatment. In addition to the examination of the hematoxylin-eosin stained sections, hepatic regeneration and apoptosis were analyzed quantitatively by bromodeoxyuridine (BrdU)-anti-BrdU immunohistochemistry and TUNEL assay utilizing apoptosis kit, respectively. The hepatic expressions of c-myc, c-fos and transforming growth factor-alpha (TGF-alpha) were examined by immunohistochemistry and studied by Western blot. The number of BrdU labelled cells and the degree of necrosis/apoptosis were comparable among the different groups. Livers of the group II rats showed nearly normal histology without regeneration and necrosis/apoptosis. In groups I and III, the number of BrdU- labelled cells showed an increase at 48 hours after treatment, and the increment was significantly higher in group I than in group III. Most BrdU-labelled cells were mature hepatocytes in group I, whereas in group III they appeared to be less mature. In group I, apoptosis showed an increase at around 24 hours, but appeared in group III as early as 12 hours after treatment and persisted through 48 hours. The expression of c-myc and c-fos were also different between the experimental groups. The expression intensity of c-myc in group I was highest at 1 hour and decreased thereafter. In groups II and III, the expressions were much more intense than in group I, except at 1 hour, and the increased intensity persisted throughout the experiment. Group II in particular showed a peak intensity at 30 minutes and at 6 hours after treatment. In group I, c-fos was strongly expressed only at 24 hours, but in group III, there was progressively increased expression with peak intensity at 24 hours. TGF-alpha was expressed in similar intensities in all groups throughout the experiment. These results suggest that AFB1 may evoke an intense and protracted expression of c-myc, provocating the CCl4-induced necrosis of hepatocytes, and a prolonged expression of c-fos, including persistent signals for regeneration which in turn may activate the replication of immature cells. These findings will aid further investigation of molecular biologic and histologic characteristics of the hepatotoxic and hepatocarcinogenic mechanism of AFB1 in rats. And these results in rats, together with clinico-epidemiologic and molecular biologic investigations in humans and other animals, suggest that AFB1 may supply hepatocarcinogenic background in early exposure time in AFB1-contaminated areas of China and Korea.

Aflatoxin B1↗

PubMed1997

Zinc and platelet membrane microviscosity in Alzheimer's disease. The in vivo effect of zinc on platelet membranes and cognition.

OBJECTIVES: To investigate the effects of oral zinc supplementation on: (i) plasma zinc concentrations; (ii) platelet membrane microviscosity in vivo; and (iii) cognitive function of Alzheimer's disease (AD) patients. DESIGN: An open-labelled pilot study. SETTING: University of Stellenbosch Medical School and Stikland Hospital. SUBJECTS: Six volunteer AD patients. OUTCOME MEASURES: Plasma zinc levels, platelet membrane microviscosity and cognition (MMSE and ADAS-cog tests). RESULTS: Oral zinc supplementation (30 mg/day) did not increase plasma zinc levels significantly, but significantly increased platelet membrane microviscosity (P = 0.02; 6 patients). Four patients, who underwent 12 months of evaluation, showed modest cognitive improvement on psychometric testing (Mini-Mental State Examination and the cognitive portion of the Alzheimer's Disease Assessment scale scores). CONCLUSIONS: While earlier literature promoted the use of zinc in AD patients, a recent study has contradicted this and implicated zinc in the aetiology of Alzheimer's disease. On the basis of the above results, it may be premature to single out zinc as a causal agent in AD.

Aged↗

PubMed1996

Na(+)-translocating cytochrome bo terminal oxidase from Vitreoscilla: some parameters of its Na+ pumping and orientation in synthetic vesicles.

Vitreoscilla cytochrome bo ubiquinol oxidase is similar in some properties to the Escherichia coli enzyme, but unlike the latter, the Vitreoscilla oxidase functions as a primary Na+ pump. When purified Vitreoscilla cytochrome bo is incorporated into liposomes made from Vitreoscilla phospholipids and energized with a quinol substrate, it translocates Na+, not H+, across the vesicle membrane. Since protonophores CCCP (carbonyl cyanide m-chlorophenylhydrazone) and DTHB (3,5-di-tert-butyl-4-hydroxybenzaldehyde) stimulated the Na+ pumping, it is unlikely that it is a secondary effect due to the presence of Na+/H+ antiporter activity in the preparations. The efficiency of the Na+ pumping was 3.93 Na+ pumped per O2 consumed when ascorbate/TMPD was used as the substrate. The cytochrome has a K(m) and Kcat for Na+ of 2.9 mM and 277 s-1, respectively. When ferricytochrome c was entrapped within liposomes prepared from Vitreoscilla phospholipids, it was reduced by Q1H2 (ubiquinol-1) but not by ascorbate/TMPD (N,N,N',N'-tetramethyl-1,4-phenylenediamine). Although Q1H2 was oxidized by cytochrome bo in solution at a rate approximately 14 times that of the latter substrate, the rate of accumulation of Na+ within cytochrome bo vesicles driven by the membrane impermeable ascorbate/TMPD was 1.23 times that of the membrane permeable ubiquinol. These data allowed a calculation that in these synthetic proteoliposomes the cytochrome bo molecules are only 51% directed inward; a value of 61% inward-directed was estimated by measuring the ascorbate/TMPD oxidase activity of the proteoliposomes before and after disrupting them with Triton X-100. A random orientation of the E. coli cytochrome bo oxidase in proteoliposomes has also been reported.

Ascorbic Acid↗