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Biomedical subjects

H Kim

Publications and source records attributed to H Kim.

At least 163 records · Page 9Linked to original sources
PubMed2001

The highly conserved protein methyltransferase, Skb1, is a mediator of hyperosmotic stress response in the fission yeast Schizosaccharomyces pombe.

The p21-activated kinase, Shk1, is required for cell viability, establishment and maintenance of cell polarity, and proper mating response in the fission yeast, Schizosaccharomyces pombe. Previous genetic studies suggested that a presumptive protein methyltransferase, Skb1, functions as a positive modulator of Shk1. However, unlike Shk1, Skb1 is not required for viability or mating of S. pombe cells and contributes only modestly to the regulation of cell morphology under normal growth conditions. Here we demonstrate that Skb1 plays a more significant role in regulating cell growth and polarity under conditions of hyperosmotic stress. We provide evidence that the inability of skb1Delta cells to properly maintain cell polarity in hyperosmotic conditions results from inefficient subcellular targeting of F-actin. We show that Skb1 localizes to cell ends, sites of septation, and nuclei of S. pombe cells. Hyperosmotic shock results in substantial delocalization of Skb1 from cell ends and nuclei, as well as stimulation of Skb1 protein methyltransferase activity. Taken together, our results demonstrate a new role for Skb1 as a mediator of hyperosmotic stress response in fission yeast. We show that the protein methyltransferase activity of the human Skb1 homolog, Skb1Hs, is also stimulated by hyperosmotic stress in fission yeast, providing evidence for evolutionary conservation of a role for Skb1-related proteins as mediators of hyperosmotic stress response, as well as mechanisms involved in regulating this novel class of protein methyltransferases.

Carrier Proteins↗
PubMed2001

Human kallikrein gene 5 (KLK5) expression is an indicator of poor prognosis in ovarian cancer.

Kallikrein gene 5 (KLK5, also known as KLK-L2), located on chromosome 19q13.4, is one of the newly identified members of the kallikrein gene family, which is a subgroup of the serine protease enzyme family. In normal human tissues, KLK5 is highly expressed in skin, mammary gland and testis. Preliminary RT-PCR analysis has indicated that KLK5 is expressed in a subset of ovarian tumours. We have thus hypothesized that KLK5 may be a new prognostic indicator in ovarian cancer. We have examined the mRNA expression of KLK5 in 142 malignant ovarian tissues. Tumours were pulverized, total RNA was extracted, and cDNA was prepared by reverse transcription. KLK5 was amplified by PCR using gene specific primers, and the identity of the PCR product was verified by sequencing. Ovarian tissues were then classified as KLK5 positive or negative, based on ethidium bromide staining of the PCR product on agarose gels. KLK5 was found to be highly expressed in 58/142 (41%) of ovarian cancer samples while its level of expression was very low in normal ovarian tissues. We found a strong positive relation between KLK5 expression and tumour grade (P = 0.006) and disease stage (P = 0.027). Univariate survival analysis revealed that patients with ovarian tumours positive for KLK5 expression had an increased risk for relapse and death (P = 0.018 and 0.022, respectively). In multivariate analysis, KLK5 expression showed independent prognostic value only in the subset of tumours with lower grade disease (grades I and II). We conclude that KLK5 expression is associated with more aggressive forms of epithelial ovarian carcinoma and has indepdent prognostic value in low grade tumours.

Adult↗
PubMed2001

NO as an autocrine mediator in the apoptosis of activated microglial cells: correlation between activation and apoptosis of microglial cells.

Abnormal activation of microglial cells has been implicated in various neurodegenerative diseases. Microglial activation needs to be tightly regulated for physiological maintenance and normal functioning of the central nervous system. Potential mechanisms for the down-regulation of activated microglial cells are the deactivation or elimination of activated cells. We hypothesized that the elimination of activated microglial cells by apoptosis is one of the key mechanisms of auto-regulation of activated microglial cells. To test this hypothesis, we utilized BV-2 mouse microglial cells and rat primary microglial cultures exposed to activating agents such as lipopolysaccharide and interferon-gamma, and investigated a possible correlation between apoptosis and activation of these cells. We found that the activation of microglial cells led to apoptotic death, and the activation state of microglial cells inversely correlated with cell viability. We have also demonstrated that: (i) NO was produced by activated microglial cells in a manner dependent on time and dose of activating agents; (ii) inhibition of NO synthesis by iNOS inhibitor blocked the apoptosis of activated microglial cells; (iii) an exogenous NO donor induced apoptosis of microglial cells; and (iv) inhibition of TNFalpha or FasL using neutralizing antibodies did not affect activation-induced apoptosis of microglial cells. These results indicated that activation of microglial cells leads to the production of NO, which in turn acts as the major mediator of cellular apoptosis in an autocrine fashion. Our work suggests the presence of auto-regulatory mechanism for microglial activation, which may have relevance in the pathogenesis of various neurodegenerative diseases possibly resulting from 'over-activation' of microglial cells.

Animals↗
PubMed2001

Effects of nicotine on APP secretion and Abeta- or CT(105)-induced toxicity.

Several lines of evidence indicated that overexpression or aberrant processing of amyloid precursor protein (APP) is causally related to Alzheimer's disease (AD). Amyloid precursor protein is principally cleaved within the amyloid beta protein domain to release a large soluble ectodomain (APPs), known to have a wide range of trophic functions. The central hypothesis guiding this review is that nicotine may play an important role in APP secretion and protection against toxicity induced by APP metabolic fragments (beta-amyloid [Abeta], carboxyl terminal [CT]). Findings from our experiments have shown that nicotine enhances the release of APPs, which has neurotrophic and neuroprotective activities in concentration-dependent (>50 micromol/L) and time-dependent (>2 hours) manners. In addition, pretreatment of nicotine (>10 micromol/L for 24 hours) partially prevented Abeta or CT(105)-induced cytotoxicity in primary cultured neuron cells, and the effects of nicotine-induced protection were inhibited by the pretreatment with a nicotine alpha-bungarotoxin. Nicotine (>10 micromol/L for 24 hours) partially inhibited CT(105)-induced cytotoxicity when PC12 cells was transfected with CT(105). From these results, we proposed that nicotine or nicotinic receptor agonist treatment might improve the cognitive functions not only by supplementation of cholinergic neurotransmission, but also by protecting Abeta- or CT(105)-induced neurotoxicity probably through the increased release of APPs and the activation of nicotinic receptors.

Alzheimer Disease↗
PubMed2001

Interferon gamma (IFNgamma ) and tumor necrosis factor alpha synergism in ME-180 cervical cancer cell apoptosis and necrosis. IFNgamma inhibits cytoprotective NF-kappa B through STAT1/IRF-1 pathways.

We investigated the molecular mechanism of the synergism between interferon gamma (IFNgamma) and tumor necrosis factor alpha (TNFalpha) documented in a variety of biological occasions such as tumor cell death and inflammatory responses. IFNgamma/TNFalpha synergistically induced apoptosis of ME-180 cervical cancer cells. IFNgamma induced STAT1 phosphorylation and interferon regulatory factor 1 (IRF-1) expression. Transfection of phosphorylation-defective STAT1 inhibited IFNgamma/TNFalpha-induced apoptosis, whereas IRF-1 transfection induced susceptibility to TNFalpha. Dominant-negative IkappaBalpha transfection sensitized ME-180 cells to TNFalpha. IFNgamma pretreatment attenuated TNFalpha- or p65-induced NF-kappaB reporter activity, whereas it did not inhibit p65 translocation or DNA binding of NF-kappaB. IRF-1 transfection alone inhibited TNFalpha-induced NF-kappaB activity, which was reversed by coactivator p300 overexpression. Caspases were activated by IFNgamma/TNFalpha combination; however, caspase inhibition did not abrogate IFNgamma/TNFalpha-induced cell death. Instead, caspase inhibitors directed IFNgamma/TNFalpha-treated ME-180 cells to undergo necrosis, as demonstrated by Hoechst 33258/propidium iodide staining and electron microscopy. Taken together, our results indicate that IFNgamma and TNFalpha synergistically act to destroy ME-180 tumor cells by either apoptosis or necrosis, depending on caspase activation, and STAT1/IRF-1 pathways initiated by IFNgamma play a critical role in IFNgamma/TNFalpha synergism by inhibiting cytoprotective NF-kappaB. IFNgamma/TNFalpha synergism appears to activate cell death machinery independently of caspase activation, and caspase activation seems to merely determine the mode of cell death.

Apoptosis↗
PubMed2001

Perceived motion in orientational afterimages: direction and speed.

Two sets of experiments demonstrate new properties of motion in orientational after-effects. In a previous report, we showed that when observers adapted to a static bar grating whose elements varied in size or intensity from one side to the other, offset of the grating resulted in a motion after-effect, with the perceived motion in the direction of the largest or most intense bar. In the first new experiment, we show that similar results can be produced by varying the duration of the bar elements, with the direction of the motion after-effect toward the bar with the longest duration. In the second new experiment we demonstrate that the perceived speed of the motion after-effect is influenced by the spatial extent of the after-effect, with larger extents corresponding to faster speeds. The experimental findings are discussed in the context of a neural network theory of visual perception. In this theory, a moving oriented contour leaves a trail of activity among cortical cells tuned to orthogonal orientations. We hypothesize that the grating stimuli produce after-effects that mimic the pattern of oriented responses produced by a true moving contour, and the visual system interprets this pattern as a cue for motion. We also show how the model connects the properties of these motion after-effects to properties of visual persistence.

Figural Aftereffect↗
PubMed2001

Characterization of chromosomal aberrations in lung cancer cell lines by cross-species color banding.

Using cross-species color banding (RxFISH) and chromosome painting techniques, chromosomal aberrations were investigated in six lung cancer cell lines (NCI-H524, H865, H522, H1373, H358, A549). Each cell line had a variable number of numerical and structural cytogenetic aberrations. While NCI-H524, -H865, and -H522 had near diploidy, NCI-H358, -H1373, and A549 had near triploidy. The origins of the marker chromosomes were further identified by RxFISH and chromosome painting: Nonrandom chromosomal rearrangements were seen on 1p, 3q, 5p10-p15, 6q13-q21, 7q22-q31, 9p32, 15q22-qter, 17p, 17q21-q25, and 21. These abnormal cytogenetic findings indicate that multiple genetic lesions are associated with the development of lung cancer, and thus, these might be possible candidate regions for the abnormal genes involved in lung cancer.

Animals↗
PubMed2001

Frameshift mutations at coding mononucleotide repeats of the hRAD50 gene in gastrointestinal carcinomas with microsatellite instability.

Microsatellite instability (MSI) and frameshift mutations in genes containing nucleotide repeats have been reported in a subset of colorectal and gastric carcinomas. This study describes the analysis of MSI-positive colorectal (39 cases) and gastric carcinomas (36 cases) for the presence of frameshift mutations of the six genes known to be involved in DNA repair and containing mononucleotide repeats in their coding region. Our mutational study of the 75 MSI-positive tumors revealed frequent mutations in hRAD50 (23 cases, 31%), BLM (16 cases, 21%), and hMSH6 (16 cases, 21%); rare mutations in BRCA1 (1 case, 1%) and ATM (3 cases, 4%); and no mutation in NBS1. In contrast, no frameshift mutation was found in 60 MSI-negative colorectal and gastric carcinomas. The mutation of hRAD50, a gene that is involved in the response to cellular DNA damage and forms a complex with hMRE11 and NBS1, has not been reported previously. Our results suggest that frameshift mutations of hRAD50, BLM, and hMSH6 are selected and play a role in the tumorigenesis of colorectal and gastric carcinomas with MSI. The MSI targeting of the hRAD50 and BLM genes represents an additional link between MSI and DNA repair because alteration of these genes could accelerate defective DNA repair.

Acid Anhydride Hydrolases↗
PubMed2001

Establishment and characterization of chromosomal aberrations in human cholangiocarcinoma cell lines by cross-species color banding.

Cholangiocarcinoma (CC), a malignant neoplasm of the biliary epithelium, is usually fatal because of difficulty in early diagnosis and lack of availability of effective therapy. Furthermore, little is known about the genetics and biology of CC. Only a few reports concerning cytogenetic studies of CC have been published, and few cell lines have been established. We recently established four CC cell lines, designated as SCK, JCK, Cho-CK, and Choi-CK, and report the first application of cross-species color banding (RxFISH) and multiple chromosome painting for the characterization of the chromosomal rearrangements of these CC cell lines. Each cell line had unique modal karyotypic characteristics and showed a variable number of numerical and structural clonal cytogenetic aberrations. Chromosomes 3, 6, 7, 8, 12, 14, 17, and 18 were commonly involved in structural abnormalities. Homogeneously staining regions were determined in SCK and JCK, and double minute chromosomes were found in Cho-CK. The chromosomal aberrations of the four CC cell lines were effectively analyzed by RxFISH and FISH with multiple chromosome painting probes. The nonrandom rearrangements suggest candidate regions for isolation of genes related to CC.

Aged↗
PubMed2001

Soluble tubulin complexes in oocytes of the common leopard frog, Rana pipiens, contain gamma-tubulin.

Oocytes of the leopard frog, Rana pipiens, contain soluble tubulin which was previously shown to exist predominantly in megadalton (MDa) fractions and that fails to readily assemble in vitro. In order to further characterize these tubulin complexes, DEAE Sepharose chromatography, Sephacryl S-300 size exclusion columns and specific immunoprecipitation were used. The results revealed the presence of alpha-, beta-, and gamma-tubulin associated with several other proteins in the soluble fraction of Rana pipiens ovarian oocytes. These Rana oocyte tubulin complexes appear to be analogous to those recently reported in Xenopus ovulated eggs as gamma-tubulin ring complexes. This seems true since both size (estimates, i.e. approximately 2MDa) and protein components are similar. Furthermore, both alpha- and gamma-tubulin antibodies immunoprecipitated identical protein bands from Rana oocyte soluble fraction. These putative Rana gamma-tubulin ring proteins include 107, 97, 95, 90 and 75 kDa components which are similar in size to those found in Xenopus and other species. Rana appears to belong to a select group in which gamma-tubulin complexes contain significant alpha- and beta-tubulin (i.e., Xenopus and sheep), while other species such as Drosophila, Aspergillus, Saccharomyces, human cells and many other mammalian cells tested lack the other tubulin components. The heterogeneity in both size and protein components of Rana oocyte gamma-tubulin ring complexes may reflect different states of tubulin complex assembly. The lower vertebrate oocyte is hypothesized to act as a repository and prestaging point for the assembly of gamma-tubulin ring complexes which will become the maternal contribution to the centrosomes of the embryo. While the gamma-tubulin ring complexes of vertebrate eggs have been described previously, this is the first report biochemically characterizing soluble gamma-tubulin complexes in vertebrate ovarian oocytes.

Animals↗
PubMed2001

Molecular cloning and expression analysis of the turkey vasoactive intestinal peptide receptor.

Vasoactive intestinal peptide (VIP) is a prolactin (PRL)-releasing factor whose activity in avian species is believed to be mediated by a specific VIP receptor (VIP-R). Circulating PRL levels are closely related to hypothalamic VIP immunoreactivity, hypothalamic VIP mRNA content, and hypophysial-portal blood VIP concentrations in turkeys. In the present study, a turkey VIP-R (tVIP-R) cDNA was cloned and its mRNA abundance was quantified in various tissues during different reproductive stages. The 2347-bp tVIP-R cDNA encoded a 457 amino acid protein, with a predicted Mr of 52 kDa. The full-length cDNA shares approximately 55% similarity with the mammalian VIP receptor-1. Northern blot analysis revealed that a major 2.7-kb transcript was expressed in laying hen pituitaries. Furthermore, two minor tVIP-R transcripts of 3.7 and 3.4 kb were observed. Semiquantitative reverse transcription polymerase chain reaction (RT-PCR) was performed using RNA from various turkey brain and peripheral tissues throughout the reproductive cycle. The steady-state levels of pituitary tVIP-R mRNA changed during the reproductive cycle, whereas mRNA expression in other tissues was not affected. The steady-state levels of tVIP-R mRNA were only affected in the pituitary, whereas mRNA expression in any of the other tissues examined following the immunization of turkeys against VIP were not affected.

Amino Acid Sequence↗
PubMed2001

Characterization of microsatellite markers adjacent to AP-4 on chromosome 16p13.3.

The 1400 kb genomic sequence between the markers D16S406 and D16S423 on chromosome 16p13.3 has been recently sequenced and the interval contains a transcription factor, AP-4, that was identified as a ligand for immunoglobulin-kappa promoter E-box elements,(1)suggesting that AP-4 may be related to immunodeficiency diseases. In addition, chromosome 16p13.3 includes a number of genes including the PKD1 gene,(2,3)the autosomal dominant polycystic kidney disease (ADPKD) gene. ADPKD is characterized by progressive development and enlargement of renal cysts.(4)The size and genomic complexity of the PKD1 gene makes it impractical to detect mutations for prenatal diagnosis. Therefore, pedigree-based linkage analysis remains useful for diagnosis of ADPKD. To increase the number of polymorphic markers in the region around AP-4 gene, we performed database searches of 1400 kb of genomic sequence (from contig NT000677 to NT001573: http://www.ncbi.gov/genome/seq.cgi) across the 16p13.3. A number of dinucleotide or tetranucleotide repeats were found, and 20 microsatellites that contain more than 15 contiguous repeats were chosen for further investigation.

Adult↗
PubMed2001

Synergetic analysis of spatio-temporal EEG patterns: Alzheimer's disease.

A spatio-temporal analysis has been employed on EEG signals recorded in groups of patients with Alzheimer's disease (AD). The so-called Karhunen-Loeve analysis method was applied to four groups of subjects: 12 patients who were diagnosed as having severe AD, 8 mild AD patients, 10 vascular dementia patients, and 10 normal aged controls, to obtain the spatio-temporal eigenpatterns. The local difference of the global EEG pattern in mild AD patients from that of normal controls was expanded to the frontal regions in the case of severe AD. The analysis showed significant bilateral temporal functioning differences and inter-hemispheric connection difficulty, along with remarkable intra-hemispheric correlation in severe AD patients. Compared to the normal controls, severe AD patients' brains exhibit only weak local connections and correlations, resulting into limited harmonious inter-hemispheric information processing. The results from the spatio-temporal EEG study of AD patients can be considered to be due to a change in the relative activity of the brain corresponding to the pathologic variation in AD, and the results are in accordance with reported clinical studies.

Alzheimer Disease↗
PubMed2001

Cloning of the cel9A gene and characterization of its gene product from marine bacterium Pseudomonas sp. SK38.

The yellow-pigmented bacterial strain causing green spot rot and death of layer was isolated from Porphyra dentata. This strain has been identified as Pseudomonas sp., harboring agarase, xylanase, and protease activity, as well as carboxymethyl-cellulase (CMCase). Using genomic DNA from the Pseudomonas sp. SK38 digested with Sau3AI and ligated into pBluescript II KS+, we isolated a cel gene encoding a CMCase in Pseudomonas sp. SK38. A 4.5-kb fragment was subcloned into pKR400. The structure of the cel9A gene consists of an open reading frame of 1,521 bp starting with a GTG start codon and ending with a TAG stop codon. It thus encodes 506 amino acid residues of a protein with a calculated molecular weight of 52,636 daltons plus a signal peptide of 22 amino acids. The deduced amino acid sequence of the cel9A protein is similar to the same protein of Clostridium thermocellum. It contains, in particular, the two conserved regions of the glycoside hydrolase family 9. The apparent molecular mass of the Cel9A protein is 52 kDa as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme is most active at pH 6-7 and an optimal temperature of around 30 degrees C.

Amino Acid Sequence↗
PubMed2001

Effect of interferon-gamma on the susceptibility to Fas (CD95/APO-1)-mediated cell death in human hepatoma cells.

Many tumors, including hepatocellular carcinomas (HCCs), resist Fas-mediated cell death, which is one of the effector mechanisms in the host's anti-tumor response; however, this resistance can be abolished by interferon-gamma (IFN-gamma). IFN-gamma may sensitize Fas-mediated cell death in several ways, but the exact mechanism in HCCs is uncertain. In this study, we thoroughly investigated the effect of IFN-gamma on the susceptibility of one human normal liver cell line and 12 HCC cell lines to Fas-mediated cell death. We also investigated the effect of IFN-gamma on the expression of various apoptosis-related genes such as the Fas/TNF-related genes, the bcl-2 family, and the caspase family of genes. Although most cell lines showed considerable constitutive expression of Fas, all tested cell lines resisted Fas-mediated cell death without IFN-gamma. When cells were pretreated with IFN-gamma, only three cell lines were made significantly susceptible to Fas-mediated cell death (SNU-354, SNU-387 and SNU-423); the other 10 cell lines were not affected. IFN-gamma increased the mRNA expression of Fas, TRAIL and caspase-1, and surface Fas was also increased. The strongly sensitized cell lines (SNU-354, SNU-387 and SNU-423) showed a particularly potent increment in surface Fas after IFN-gamma treatment (increase in surface Fas > 1.7-fold). This result enabled us to conclude that a potent increment of surface Fas expression is a major sensitizing mechanism of IFN-gamma. We conclude that IFN-gamma cannot play a sensitizing role in most HCC cell lines and that IFN-gamma makes HCC cells susceptible to Fas-mediated cell death through a marked up-regulation of surface Fas in some HCC cells.

Apoptosis↗
PubMed2001

Production of a novel compound, 7,10,12-trihydroxy-8(E)-octadecenoic acid from ricinoleic acid by Pseudomonas aeruginosa PR3.

The production and its potential use of a novel trihydroxy unsaturated fatty acid, 7,10,12-trihydroxy-8(E)-octadecenoic acid (TOD), were investigated. TOD was formed by Pseudomonas aeruginosa PR3 (NRRL B-18602) in a culture supplied with exogenous ricinoleic acid. The yield of TOD production was always higher in a rich culture medium than in minimal screening medium. Extending the conversion time from 48 to 72 h prior to lipid extraction led to a 65% reduction in yield, indicating that TOD was further metabolized by strain PR3 and that control of reaction time is important to achieving a maximum yield. The optimum culture density, reaction time, pH, temperature, and substrate concentration for the production of TOD were: 20-24 h culture growth, 48 h, 7.0, 25 degrees C, and 1% (vol/vol), respectively. Under optimum conditions, the yield of TOD production was greater than 45%. TOD was found to be an antifungal agent most active against the fungus that causes blast disease in rice plants, the most important fungal disease affecting rice production worldwide.

Culture Media↗
PubMed2001

Urinary 1-hydroxypyrene and 2-naphthol concentrations in male Koreans.

OBJECTIVE: Urinary 1-hydroxypyrene (1-OHP) has been used as a biological marker of exposure to polycyclic aromatic hydrocarbons (PAHs), and urinary 2-naphthol is suggested as a new marker for route-specific exposure to airborne PAHs. We analyzed urinary 1-OHP and 2-naphthol concentrations in 292 male Koreans (129 university students and 163 shipyard workers) to define the distribution pattern in Koreans with no or low occupational exposure to PAHs. METHOD: Histories of cigarette smoking and the eating of PAH-containing foods were obtained by a self-administered structured questionnaire. Urine samples were collected and urinary 1-OHP and 2-naphthol concentrations were measured using high-performance liquid chromatography (HPLC). RESULTS: The arithmetic (geometric) means of urinary 1-OHP and 2-naphthol concentrations for all students, expressed as micromoles per mole of creatinine, were 0.04 (0.04) and 3.12 (2.22), for non-smokers 0.03 (0.03) and 1.78 (1.30) and for smokers 0.05 (0.03) and 4.36 (3.62), respectively. Among shipyard workers, the arithmetic (geometric) means of urinary 1-OHP and 2-naphthol concentrations were 0.69 (0.31) and 4.37 (2.62) for all, 0.27 (0.18) and 2.46 (1.16) for nonsmokers, and 0.97 (0.44) and 5.60 (4.44) for smokers, respectively. Mean urinary 1-OHP and 2-naphthol concentrations differed significantly between nonsmokers and smokers both in students and in shipyard workers. In smokers, some variables related to smoking habit were positively correlated with urinary 1-OHP and with 2-naphthol concentrations. The latter showed better correlations with the variables related to smoking amount than the former. None of the food-related factors was significantly correlated with urinary 1-OHP or 2-naphthol concentration. CONCLUSION: These results suggest that urinary 2-naphthol concentration is more sensitively affected by smoking status than urinary 1-OHP concentration and that urinary 2-naphthol is a sensitive marker for low-level inhalation of PAHs.

Chromatography, High Pressure Liquid↗