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Biomedical subjects

J H Yoon

Publications and source records attributed to J H Yoon.

At least 55 records · Page 3Linked to original sources
PubMed2001

Candida thermophila sp. nov., a novel thermophilic yeast isolated from soil.

Yeast strain Y94T, which is capable of growth at high temperature, was isolated from soil in Korea. Characteristics of the strain include asexual reproduction by multilateral budding, the absence of extracellular starch-like compounds, a negative Diazonium blue B colour reaction, and the absence of arthrospores, ballistoconidia and ascospores; the strain can therefore be placed in the genus Candida. A maximum growth temperature of 50-51 degrees C, along with certain other physiological characteristics, and a unique 26S rDNA partial sequence separate this strain from other ascomycetous yeasts. Taken together, these results suggest that the strain is a novel species and the name Candida thermophila sp. nov. (type strain is Y94T = JCM 10994T = KCCM 50661T) is proposed.

Candida↗
PubMed2001

Drosophila Med6 is required for elevated expression of a large but distinct set of developmentally regulated genes.

Mediator is the evolutionarily conserved coactivator required for the integration and recruitment of diverse regulatory signals to basal transcription machinery. To elucidate the functions of metazoan Mediator, we isolated Drosophila melanogaster Med6 mutants. dMed6 is essential for viability and/or proliferation of most cells. dMed6 mutants failed to pupate and died in the third larval instar with severe proliferation defects in imaginal discs and other larval mitotic cells. cDNA microarray, quantitative reverse transcription-PCR, and in situ expression analyses of developmentally regulated genes in dMed6 mutants showed that transcriptional activation of many, but not all, genes was affected. Among the genes found to be affected were some that play a role in cell proliferation and metabolism. Therefore, dMed6 is required in most cells for transcriptional regulation of many genes important for diverse aspects of Drosophila development.

Alleles↗
PubMed2001

Drosophila Mediator complex is broadly utilized by diverse gene-specific transcription factors at different types of core promoters.

To decipher the mechanistic roles of Mediator proteins in regulating developmental specific gene expression and compare them to those of TATA-binding protein (TBP)-associated factors (TAFs), we isolated and analyzed a multiprotein complex containing Drosophila Mediator (dMediator) homologs. dMediator interacts with several sequence-specific transcription factors and basal transcription machinery and is critical for activated transcription in response to diverse transcriptional activators. The requirement for dMediator did not depend on a specific core promoter organization. By contrast, TAFs are preferentially utilized by promoters having a specific core element organization. Therefore, Mediator proteins are suggested to act as a pivotal coactivator that integrates promoter-specific activation signals to the basal transcription machinery.

Amino Acid Sequence↗
PubMed2001

The analgesic efficacy of bee venom acupuncture for knee osteoarthritis: a comparative study with needle acupuncture.

The aim of this investigation was to determine whether bee venom (BV) administered directly into an acupoint was a clinically effective and safe method for relieving the pain of patients with knee osteoarthritis (OA) as compared to traditional needle acupuncture. We evaluated the efficacy of BV acupuncture using both pain relief scores and computerized infrared thermography (IRT) following 4 weeks of BV acupuncture treatment. We observed that a significantly higher proportion of subjects receiving BV acupuncture reported substantial pain relief as compared with those receiving traditional needle acupuncture therapy. Furthermore, the IRT score was significantly improved and paralleled the level of pain relief.

Acupuncture Points↗
PubMed2001

Application of time-of-flight secondary ion mass spectrometry to automobile paint analysis.

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) provides a method of elemental analysis that can distinguish among automotive paint samples of the same or nearly the same color. TOF-SIMS survey spectra were employed to determine the relative abundances of elements in the surface layers of the paint chips. The depth profile of paint samples permitted the analysis of small paint chips, the reproducible results for specific elements, and the identification of each car paint. Seventy-three samples of blue, red, white, and silver automobile paints from the major manufacturers in Korea were investigated using high resolution TOF-SIMS technique. It was found that paints of the same color produced by different manufacturers could be distinguished by this technique. TOF-SIMS is a reliable, nondestructive, and small area analyzing method for characterization of the elemental composition of automotive paint chips.

Journal Article↗
PubMed2001

Association between polymorphisms of ethanol-metabolizing enzymes and susceptibility to alcoholic cirrhosis in a Korean male population.

Alcohol is oxidized to acetaldehyde by alcohol dehydrogenase (ADH) and cytochrome P-4502E1 (CYP2E1), and then to acetate by aldehyde dehydrogenase (ALDH). Polymorphisms of these ethanol-metabolizing enzymes may be associated with inter-individual difference in alcohol metabolism and susceptibility to alcoholic liver disease. We determined genotype and allele frequencies of ALDH2, CYP2E1, ADH2, and ADH3 in male Korean patients with alcoholic cirrhosis (n=56), alcoholics without evidence of liver disease (n=52), and nondrinkers (n=64) by using PCR or PCR-directed mutagenesis followed by restriction enzyme digestion. The prevalences of heterozygous ALDH2*1/*2 plus homozygous ALDH2*2/*2 in patients with alcoholic cirrhosis (7.1%) and alcoholics without evidence of liver disease (3.8%) were significantly lower than that in nondrinkers (45.3%). The c2 allele frequencies of the CYP2E1 in alcoholic cirrhosis, alcoholics without evidence of liver disease, and nondrinkers were 0.21, 0.20, and 0.20, respectively. Allele frequencies of ADH2*2 in the three groups were 0.78, 0.74, and 0.77 and those of ADH3*1 were 0.94, 0.98, and 0.95. Therefore, we confirmed the observation that the ALDH2*2 gene protects against the development of alcoholism. However, the development of cirrhosis in Korean alcoholic patients was not associated with polymorphisms of ethanol-metabolizing enzymes.

Adult↗
PubMed2000

The efficient enzymatic synthesis of N-acetyllactosamine in an organic co-solvent.

In the presence of beta-galactosidase from Bifidobacterium bifidum, N-acetyllactosamine was synthesized in significantly enhanced yield compared with earlier routes. Different proportions of the (1-->4)- and (1-->6)-linked forms were obtained depending on the choice of enzyme and reaction conditions, viz. the nature of added organic co-solvent (20-80% of 2-ethoxy ethyl ether, trimethyl phosphate, or acetone). The beta-(1-->4)-linked disaccharide was the major product and the beta-(1-->6)-linked disaccharide was the minor product. With beta-galactosidases from P. multicolor, A. oryzae, B. longum the beta-(1-->6) linkage was exclusively synthesized. Procedures for optimising the yield of N-acetyllactosamine are discussed. An immobilized enzyme on a nylon powder column was used for the efficient recycling of enzyme and synthesizing the disaccharide.

Amino Sugars↗
PubMed2000

Identification of p53 gene mutations in breast cancers and their effects on transcriptional activation function.

Somatic mutations in the p53 tumor suppressor gene are the most common genetic alterations found in human malignancies. In the present study, we studied 36 primary human breast carcinomas, using a polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) and sequencing analysis of exons 2 through 9 for the presence of p53 gene mutations. Six of 36 (17%) breast cancers contained mutations within the core domain of the p53 protein responsible for sequence-specific DNA binding (codons 102-292); all 5 missense mutations clustered between codons 240 and 291 (codons 240, 243, 250, 285, and 291), whereas one nonsense mutation occurred at codon 199. By using recombinant PCR in vitro mutagenesis, we introduced point mutations at codons 199 from Gly to stop (gly199stop), 240 from Ser to Ile (ser240Ile), 250 from Pro to Ala (pro250ala), 285 from Glu to Lys (glu285lys), and 291 from Lys to Asn (lys291asn), and all the p53 sequences were subcloned into the CMVneoBam vector under the control of the cytomegalovirus (CMV) promoter. To test whether the mutants p53 were functionally wild-type (wt) or mutant, we transfected them to p53-null Saos-2 cells with a reporter plasmid containing a p53-responsive element, and performed chloramphenicol acetyltransferase (CAT) assay. Transient CAT assay for transcriptional activation revealed that one group, including gly199stop, ser240ile, glu285lys, and lys291asn, abolished the transcriptional activity, whereas the other group, including pro250ala, retained stronger transcriptional transactivation activity than that of wt p53.

Adult↗
PubMed2000

The DNA damage spectrum produced by simulated sunlight.

The mutagenic effects of ultraviolet and solar irradiation are thought to be due to the formation of DNA photoproducts, most notably cyclobutane pyrimidine dimers (CPDs) and pyrimidine (6-4) pyrimidone photoproducts ((6-4)PPs). Experimental systems for determining the levels and sequence dependence of photoproduct formation in DNA have often used high doses of short-wave (UVC) irradiation. We have re-assessed this issue by using DNA sequencing technologies and different doses of UVC as well as more physiologically relevant doses of solar irradiation emitted from a solar UV simulator. It has been questioned whether hot alkali treatment can detect (6-4)PPs at all sequence positions. With high UVC doses, the sequence distribution of (6-4)PPs was virtually identical when hot alkali or UV damage endonuclease (UVDE) were used for detection, which appears to validate both methods. The (6-4)PPs form at 5'-TpC and 5'CpC sequences but very low levels are seen at all other dipyrimidines including 5'-TpT. Contrary to expectation, we find that (6-4) photoproducts form at almost undetectable levels under conditions of irradiation for up to five hours with the solar UV simulator. The same treatment produces high levels of CPDs. In addition, DNA glycosylases, which recognize oxidized and ring-opened bases, did not produce significant cleavage of sunlight-irradiated DNA. From these data, we conclude that cyclobutane pyrimidine dimers are at least 20 to 40 times more frequent than any other DNA photoproduct when DNA or cells are irradiated with simulated sunlight.

Alkalies↗
PubMed2000

Augmentation of urea-synthetic capacity by inhibition of nitric oxide synthesis in butyrate-induced differentiated human hepatocytes.

We have recently developed an in vitro differentiation model of immortalized non-transformed human hepatocytes using butyrate, and observed the induction of inducible NO synthase (iNOS). In this study, we analyzed the effect of NO on the urea-synthetic capacity of these cells. The inhibition of iNOS during butyrate treatment significantly increased the urea-synthetic capacity as compared to that of butyrate treatment alone, possibly through the further induction of ornithine transcarbamylase expression. Therefore, the inhibition of NO production might be useful for obtaining more differentiated hepatocytes in the process of in vitro induction of hepatocyte-specific differentiation.

Argininosuccinate Synthase↗
PubMed2000

Mapping of altromycin B-DNA adduct at nucleotide resolution in the human genomic DNA by ligation-mediated PCR.

The ligation-mediated PCR was used to map DNA alkylation sites induced by altromycin B at nucleotide resolution in genomic DNA purified from cultured human colon carcinoma. Altromycin B, one of the pluramycin group of antitumor antibiotics, is characterized as intercalator with the added ability to alkylate N7 guanine. DNA adducts formed in genomic DNA were cleaved into DNA strand breaks by hot piperidine treatment, and fragments containing ligatable breaks were then amplified in a single-sided, ligation-mediated PCR. The alkylation sites observed in exon 9 of the p53 gene revealed that the most high reactivity sites for altromycin B were found to be N7 of guanine in a 5'-AG* sequence. Determination of the DNA alkylation sites in naked radiolabeled plasmid DNA also showed that altromycin B preferred N7 of guanine in a 5'-AG* sequence. Thus, it can be concluded that the sequence selective DNA adduct formation induced by the intercalating alkylator, altromycin B, in genomic DNA is similar to that observed in naked plasmid DNA.

Alkylation↗
PubMed2000

Recurrent hepatocellular carcinoma after spontaneous regression.

The prognosis of untreated hepatocellular carcinoma (HCC) is usually grave, although there have been a few case reports of spontaneous regression. Tumor recurrence after spontaneous regression has been rarely reported, and there have been no previous reports of recurrent hepatocellular carcinoma after spontaneous regression. Two cases of hepatocellular carcinoma that spontaneously regressed and subsequently recurred are presented. The patients' tumors spontaneously regressed, as reflected by the radiologically evidenced reduction in tumor size and markedly decreased alpha-fetoprotein levels. Subsequent tumor recurrences after regression were evidenced by radiologic findings of newly growing nodules and appreciably increased alpha-fetoprotein levels. To the authors' knowledge, these two patients represent the first reported cases of hepatocellular carcinoma recurrence after spontaneous regression. In both of these patients, new hepatocellular carcinomas recurred at different sites before the spontaneous regression of the original HCCs was complete. Although the precise causes of the regression and the subsequent recurrence remain to be further investigated, this phenomenon suggests that multicentric hepatocarcinogenicity and intratumoral events in each hepatocellular carcinoma nodule may be involved.

Adult↗
PubMed2000

Epigenetic inactivation of a RAS association domain family protein from the lung tumour suppressor locus 3p21.3.

Allelic loss at the short arm of chromosome 3 is one of the most common and earliest events in the pathogenesis of lung cancer, and is observed in more than 90% of small-cell lung cancers (SCLCs) and in 50-80% of non-small-cell lung cancers (NSCLCs). Frequent and early loss of heterozygosity and the presence of homozygous deletions suggested a critical role of the region 3p21.3 in tumorigenesis and a region of common homozygous deletion in 3p21.3 was narrowed to 120 kb (ref. 5). Several putative tumour-suppressor genes located at 3p21 have been characterized, but none of these genes appear to be altered in lung cancer. Here we describe the cloning and characterization of a human RAS effector homologue (RASSF1) located in the 120-kb region of minimal homozygous deletion. We identified three transcripts, A, B and C, derived from alternative splicing and promoter usage. The major transcripts A and C were expressed in all normal tissues. Transcript A was missing in all SCLC cell lines analysed and in several other cancer cell lines. Loss of expression was correlated with methylation of the CpG-island promoter sequence of RASSF1A. The promoter was highly methylated in 24 of 60 (40%) primary lung tumours, and 4 of 41 tumours analysed carried missense mutations. Re-expression of transcript A in lung carcinoma cells reduced colony formation, suppressed anchorage-independent growth and inhibited tumour formation in nude mice. These characteristics indicate a potential role for RASSF1A as a lung tumour suppressor gene.

5-Methylcytosine↗
PubMed2000

Infantile fibromatosis in childhood: findings on MR imaging and pathologic correlation.

AIM: The objective of this study was to analyse the MR imaging findings of infantile fibromatosis of childhood and to correlate them with histopathological features. MATERIALS AND METHODS: Seven patients with histologically proven infantile fibromatosis were included in this study. The findings on MR images were retrospectively evaluated and then correlated with the pathological features. Findings on MR imaging evaluated included signal intensity, extent of hyperintense area on T2-weighted images, margins of the lesion, the degree and pattern of enhancement and the presence of fatty tissue. Pathological features evaluated included cellularity, collagenization, and myxoid change. A five point scale was used for the evaluation of the extent of hyperintense area on MR imaging, and each of pathological features. RESULTS: On T1-weighted images, the lesions were iso-intense in two patients; iso- and hypointense in three; and iso-, hypo- and hyperintense in two. On T2-weighted images, iso-, hypo- and hyperintense areas were mixed in all patients, the hyperintense area being the largest portion of the lesion. The margins of the lesions were infiltrative in four patients (57%), smooth in two (29%) and mixed in one (14%). Enhancement was marked in five patients (72%) and diffuse in five (71%). Regardless of the hyperintense signal intensity on T2-weighted images, the grades of each pathologic feature were variable. CONCLUSION: Infantile fibromatosis on MR imaging causes an enhancing mass, that is largely hyperintense on T2-weighted images. Areas of high signal intensity on T2-weighted images corresponded to variable grades of cellularity, collagenization, or myxoid change.

Child↗
PubMed2000

Odontogenic ghost cell carcinoma: a case report with reference to the relation between apoptosis and ghost cells.

The neoplastic variant of calcifying odontogenic cyst has various designations, and its malignant counterpart has been reported as aggressive epithelial odontogenic ghost cell tumor or odontogenic ghost cell carcinoma. We present a case of odontogenic ghost cell carcinoma with reference to the relation between the ghost cells and apoptosis. A 33-year-old man complained of a mandibular mass. The mass occupied the entire right side of the mandible with destruction of both buccal and lingual bone. The mass also infiltrated into submandibular and sublingual spaces. Histologically, the mass was composed of a solid proliferation of hyperchromatic and pleomorphic epithelial cells with abnormal mitoses. Islands of ghost cells were frequently admixed with nucleated cells, and there were foci of ameloblastic differentiation. Immunohistochemical stains for cytokeratins, involucrin, and apoptosis-related proteins such as Bcl-2, Bcl-X(L), and Bax were done. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling (TUNEL) assay was also performed. The nucleated cells adjacent to the ghost cells expressed cytokeratins and involucrin, but the ghost cells had no reaction. Bcl-2 was negative. Both Bcl-X(L) and Bax were demonstrated in the nucleated cells adjacent to the ghost cells. The ghost cells exhibited Bax protein. Some nucleated cells adjacent to the ghost cells were positive with TUNEL assay. The above results indicate that ghost cells undergo abnormal terminal differentiation as an apoptotic process.

Adult↗