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Biomedical subjects

C H Koh

Publications and source records attributed to C H Koh.

At least 19 recordsLinked to original sources
PubMed2001

Trace organic contaminants in sediment and water from Ulsan Bay and its vicinity, Korea.

Sediment and water samples collected from 32 locations in Ulsan Bay and adjacent inland areas were analyzed for polycyclic aromatic hydrocabons (PAHs), nonylphenol (NP), octylphenol (OP), bisphenol A (BPA), organochlorine (OC) pesticides (HCB, HCHs, CHLs, and DDTs), and polychlorinated biphenyls (PCBs) to characterize their spatial distribution and contamination status. PAHs were detected in nearly all sediment and water extracts from Ulsan Bay and its inland locations. The sedimentary PAH concentrations ranged from 17 to 3,100 ng/g on a dry weight basis (DW), which were predominated by two- and three-ring aromatic hydrocarbons in river and/or stream, and four- to six-ring compounds in Ulsan Bay sediment. Concentrations of PAHs in pore water samples were generally two or three orders magnitude less than those of corresponding sediment samples. Maximum concentrations of NP, OP, and BPA in sediments were 1,040, 120, and 54 ng/g DW, respectively. Concentrations of OP and BPA were, on average, 5- to 13-fold less than those of NP. PCB concentrations in sediment ranged from 1.4 to 77 ng/g DW, which were predominated by lower chlorinated congeners such as di- through pentachlorinated biphenyls. Among different OC pesticides analyzed, concentrations of DDTs were the greatest, ranging from 0.02 to 41.9 ng/g DW. NP concentrations were greater at inner locations proximal to municipal wastewater discharges into rivers and/or streams, whereas the concentrations of PCBs and PAHs were great near the sites of high industrial activities. Sediment-pore water partitioning coefficients correlated with those of reported Koc or Kow values for selected PAHs in Ulsan Bay, but these varied by an order of magnitude for stream and/or river sediments.

Chromatography, Gas↗
PubMed2001

In vitro bioassay determination of dioxin-like and estrogenic activity in sediment and water from Ulsan Bay and its vicinity, Korea.

Extracts of sediment and water samples collected from Ulsan Bay, Korea, were screened for their ability to induce dioxin-like and estrogenic gene expression in vitro. Each sample was tested as raw extract (RE) and fractionated extract (FE). Based on the initial screening of RE, 23 of 31 sediment samples showed significant dioxin-like activity in H4IIE-luc bioassay, whereas most sediment samples did not elicit estrogenic response in MVLN bioassay. Most of the activities associated with FE samples revealed that mid-polar (F2) and most polar (F3) fractions were responsible for the significant reporter gene expression in H4IIE-luc bioassay. The results suggest that complex interactions may have depressed the activities of the known arylhydrocarbon receptor (AhR) agonists present in F1 samples. The F2 samples were the most active fraction. All F2 samples except one induced significant dioxin-like activity, and over half of the F2 samples induced significant estrogenic activity. Ten of the F2 samples produced magnitudes of response in H4IIE-luc bioassay similar to those induced by a 2,3,7,8-tetrachlorodibenzo-p-dioxin standard. Sediment associated with F2 samples was estimated to contain 24.9-826 pg TCDD-EQ/g DW. Based on a qualitative mass balance analysis, polycyclic aromatic hydrocarbons (PAHs) appeared to account for both the estrogenic and dioxin-like responses observed. Over half of the F3 samples were either cytotoxic or caused morphological changes in both H4IIE-luc and MVLN cells. Known concentrations of alkylphenols and bisphenol A were not great enough to account for both the estrogenic response and cytotoxicity observed for F3 samples. Despite the apparent toxic or stressful effects, most of F3 samples induced significant dioxin-like activity in vitro, adding to a growing body of evidence that suggests the presence of unidentified, relatively polar, AhR agonists in sediment from some areas.

Animals↗
PubMed2001

Contamination of polychlorinated biphenyls (PCBs) in sediments from Kyeonggi Bay and nearby areas, Korea.

To elucidate the characteristic distribution and contamination of polychlorinated biphenyls (PCBs) in sediments, 63 sediments and five benthic organisms from Kyeonggi Bay, Namyang Bay and Lake Shihwa, West coast of Korea, were analysed. Characterization of PCBs distribution in sediments was conducted by correlation between PCBs concentrations and environmental parameters, comparison of contamination level and composition of PCBs homologs between Kanechlor mixture (KC-mix) and sediments. The residues of PCBs in sediments were correlated with total organic carbon (TOC) and particulate organic carbon (POC) contents, not with mud contents and grain size distributions. Elevated concentrations of T-PCBs were found in sediments from Incheon North Harbor (INH) in Kyeonggi Bay. T-PCBs concentrations were decreased with distance increase from inner site of INH. The residues of T-PCBs in sediments from Namyang Bay were either non-detectable or near to detection limit. The contamination by PCBs in sediments from Lake Shihwa was also low. The PCBs congener profiles in INH were similar to those of KC-mix, while those in less contaminated sites showed relatively high percentage of lower chlorinated biphenyls. Sites K18 (580 ng/g or 48 ug/g-OC dry wt) and K19 (330 ng/g or 38 ug/g-OC dry wt) within INH exceeded the sediment quality criteria (SQC) (16 micrograms/g-OC as a KC-mix) derived from equilibrium partitioning (EqP) approach.

Environmental Monitoring↗
PubMed2001

Induction of the P450 reporter gene system bioassay by polycyclic aromatic hydrocarbons in Ulsan Bay (South Korea) sediments.

Polycyclic aromatic hydrocarbons (PAHs) and induction of the P450 reporter gene system (RGS) for 6- and 16-h exposure periods were determined in organic extracts of Ulsan Bay (South Korea) sediments to assess the utility of this bioassay as a screening tool for PAH contamination. The sum of the concentrations of 23 individual PAHs in 30 sediment samples (sigma PAH) based on GC-MS analysis ranged from 0.05 to 6.1 micrograms/g dry wt. P450 RGS fold induction ranged from 4.0 to 320 micrograms/g based on benzo[a]pyrene toxic equivalents (BaPEq). P450 RGS BaPEq and the 'chemical BaPEq', defined as the sum of the products of individual PAH concentrations and pre-determined toxic equivalency factors, exhibited very strong positive correlations with sigma PAH (r2 > 0.90; P < 0.001). Fold induction did not increase (and in some cases decreased) after the optimal incubation period (6 h) for PAHs, indicating that other compounds known to induce the P450 RGS (e.g. chlorinated organics) were not present at levels effecting significant induction. This was supported by GC-ECD analysis where non-ortho and mono-ortho polychlorinated biphenyls (PCBs) known to be strong P450 RGS inducers were found to be at very low or non-detectable levels in samples with the highest P450 RGS responses. The profound difference in PAH profiles for the two most contaminated sites suggested that this assay is especially sensitive for selected PAHs with greater than four rings. Combined with previous results, the P450 RGS shows promise as a useful screening tool for predicting deleterious biological effects resulting from CYP1A1-inducing, sediment-associated chemicals, particularly high molecular weight PAHs.

Biological Assay↗
PubMed2001

Distribution of organochlorine pesticides in sediments from Kyeonggi Bay and nearby areas, Korea.

The residues of oragnochlorine pesticides (OCPs) in 62 sediments from Kyeonggi Bay and nearby areas in the west coast of Korea were determined. The concentrations of chlordanes (CHLs) and DDTs showed a distinctive gradient of contamination between inner and outer sites of Incheon North Harbor (INH), whereas hexachlorocyclohexanes (HCHs) were uniformly distributed at most sites studied. The distribution of CHLs and DDTs was strongly correlated with total organic carbon contents in sediments while HCH residue levels were independent. Relationship between contaminant's concentration and environmental factors was analyzed by principal component analysis. Distribution patterns of T-CHLs, T-DDTs, and TOC were similar while those of T-HCHs, mud content, and grain size were similar. The notable contamination by CHLs and DDTs was found in INH where these levels were one or two orders of magnitude higher than other sites. The dominant OCPs in sediments were beta-HCH among HCH compounds, trans-chlordane among CHL compounds, and p,p'-DDD among DDT compounds. The higher concentrations and compositional pattern of OCPs in INH sediments indicate that INH is in the vicinity of the source.

Carbon↗
PubMed2001

Application of a sigmapolycyclic aromatic hydrocarbon model and a logistic regression model to sediment toxicity data based on a species-specific, water-only LC50 toxic unit for Hyalella azteca.

Two models, a sigmapolycyclic aromatic hydrocarbon (PAH) model based on equilibrium partitioning theory and a logistic-regression model, were developed and evaluated to predict sediment-associated PAH toxicity to Hyalella azteca. A sigmaPAH model was applied to freshwater sediments. This study is the first attempt to use a sigmaPAH model based on water-only, median lethal concentration (LC50) toxic unit (TU) values for sediment-associated PAH mixtures and its application to freshwater sediments. To predict the toxicity (i.e., mortality) from contaminated sediments to H. azteca, an interstitial water TU, calculated as the ambient interstitial water concentration divided by the water-only LC50 in which the interstitial water concentrations were predicted by equilibrium partitioning theory, was used. Assuming additive toxicity for PAH, the sum of TUs was calculated to predict the total toxicity of PAH mixtures in sediments. The sigmaPAH model was developed from 10- and 14-d H. azteca water-only LC50 values. To obtain estimates of LC50 values for a wide range of PAHs, a quantitative structure-activity relationship (QSAR) model (log LC50 - log Kow) with a constant slope was derived using the time-variable LC50 values for four PAH congeners. The logistic-regression model was derived to assess the concentration-response relationship for field sediments, which showed that 1.3 (0.6-3.9) TU were required for a 50% probability that a sediment was toxic. The logistic-regression model reflects both the effects of co-occurring contaminants (i.e., nonmeasured PAH and unknown pollutants) and the overestimation of exposure to sediment-associated PAH. An apparent site-specific bioavailability limitation of sediment-associated PAH was found for a site contaminated by creosote. At this site, no toxic samples were less than 3.9 TU. Finally, the predictability of the sigmaPAH model can be affected by species-specific responses (Hyalella vs Rhepoxynius); chemical specific (PAH vs DDT in H. azteca) biases, which are not incorporated in the equilibrium partitioning model; and the uncertainty from site-specific effects (creosote vs other sources of PAH contamination) on the bioavailability of sediment-associated PAH mixtures.

Animals↗
PubMed2000

Influences of dietary uptake and reactive sulfides on metal bioavailability from aquatic sediments.

Understanding how animals are exposed to the large repository of metal pollutants in aquatic sediments is complicated and is important in regulatory decisions. Experiments with four types of invertebrates showed that feeding behavior and dietary uptake control bioaccumulation of cadmium, silver, nickel, and zinc. Metal concentrations in animal tissue correlated with metal concentrations extracted from sediments, but not with metal in porewater, across a range of reactive sulfide concentrations, from 0.5 to 30 micromoles per gram. These results contradict the notion that metal bioavailability in sediments is controlled by geochemical equilibration of metals between porewater and reactive sulfides, a proposed basis for regulatory criteria for metals.

Animals↗
PubMed2000

Instrumental and bioanalytical measures of persistent organochlorines in blue mussel (Mytilus edulis) from Korean coastal waters.

Blue mussels (Mytilus edulis) collected from 34 locations along the south and east coast of Korea were analyzed for polychlorinated biphenyls (PCBs) and organochlorine (OC) pesticides. Maximum concentrations of PCBs and total OC pesticides were 98.5 and 20.5 ng/g, wet weight, respectively. Extracts were fractionated by Florisil chromatography and each fraction was screened for dioxin-like activity in vitro, using recombinant rat hepatoma cells (H4IIE-luc). Fraction 2 (F-2), which contained hexachlorocyclohexanes, chlordanes, p,p'-DDD, and p,p'-DDT, generally elicited significant dioxin-like activity compared to control, whereas Fraction 1 (F-1), which contained PCBs, p,p'-DDE, and hexachlorobenzene, did not. The greatest magnitude of dioxin-like response observed was 44% of the maximum response elicited by a 2,000 pM 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) standard. The relatively low magnitudes of dioxin-like response observed for F-1 samples were consistent with the relatively low PCB concentrations. At concentrations equal to the maximum observed in the mussel samples, neither individual OC pesticides nor a mixture of OC pesticides yielded a significant dioxin-like response in the H4IIE-luc assay. Thus, the concentrations of OC pesticides in F-2 did not appear to have accounted for the dioxin-like activity observed. This suggests the presence of unidentified and/or unknown, acid-stable, dioxin-like compounds in F-2. This study suggests that in vitro bioassays are useful in assessing the contamination of mussels collected from coastal marine locations.

Animals↗
PubMed2000

The differentiation-specific factor CDP/Cut represses transcription and replication of human papillomaviruses through a conserved silencing element.

The life cycles of human papillomaviruses (HPVs) are intimately linked to the differentiation program of infected stratified epithelia, with both viral gene expression and replication being maintained at low levels in undifferentiated basal cells and increased upon host cell differentiation. We recently identified, in HPV-16, a negative regulatory element between the epithelial-cell-specific enhancer and the E6 promoter that is capable of silencing E6 promoter activity, and we termed this element a papillomavirus silencing motif (PSM) and the unknown cellular factor that bound to it PSM binding protein (PSM-BP). Here we show that the homologous genomic segments of six other distantly related genital HPV types contain a PSM that binds PSM-BP and is capable of repressing transcription. Conservation of the PSM suggests that it is indispensable for the HPV life cycle. Purification, electrophoretic mobility shift assay experiments, and the use of specific antibodies proved that the cellular factor PSM-BP is identical to a previously described transcriptional repressor, the CCAAT displacement protein (CDP), also referred to as the human Cut protein (Cut). CDP/Cut repression of HPV-16 may stem from the modification of specifically positioned nucleosomes, as suggested by transcriptional stimulation under the influence of the histone deacetylase inhibitor trichostatin A. CDP/Cut is an important developmental regulator in several different tissues. It was recently shown that CDP/Cut is expressed in basal epithelial cells but not in differentiated primary keratinocytes. This suggests the possibility that repression by PSM couples HPV transcription to the stratification of epithelia. In each of the studied HPV types, the two CDP/Cut binding sites of PSM overlap with the known or presumed binding sites of the replication initiator protein E1. Transfection of CDP/Cut expression vectors into cells that support HPV-16 or HPV-31 replication leads to the elimination of viral episomes. Similarly, two PSM-like motifs overlapping the E1 binding site of bovine papillomavirus type 1 bind CDP/Cut, and CDP/Cut overexpression reduces the copy number of episomally replicating BPV-1 genomes in mouse fibroblasts. CDP/Cut appears to be a master regulator of HPV transcription and replication during epithelial differentiation, and PSMs are important cis-responsive targets of this repressor.

Animals↗
PubMed1999

Assessment of metal pollution in Onsan Bay, Korea using Asian periwinkle Littorina brevicula as a biomonitor.

Cadmium (Cd), lead (Pb), copper (Cu) and zinc (Zn) concentrations in the marine gastropod, Littorina brevicula Philippi, were determined to assess the metal pollution in Onsan Bay, Korea. Samples of L. brevicula employed as a biomonitor and seawater were collected from 12 to 20 stations of Onsan Bay in November 1997, respectively. Dissolved metal concentrations in surface seawater were highest at the station near Onsan Non-ferrous Industrial Complex: 1.15 micrograms l-1 for Cd, 2.49 micrograms l-1 for Pb, 3.75 micrograms l-1 for Cu and 23.98 micrograms l-1 for Zn. These values were 1-2 orders higher than those shown at outer regions of the Bay. Metal concentrations in the soft body of periwinkles were highly variable at different sampling locations: 0.48-27.11 micrograms g-1 for Cd, 1.41-24.91 micrograms g-1 for Pb, 57-664 micrograms g-1 for Cu and 83-246 micrograms g-1 for Zn. The values from stations near the industrial complex were higher than those expected from relationships between body sizes and metal body burdens in periwinkles collected from the whole Korean coast. Spatial distribution of metal concentrations in the periwinkle and seawater indicated that Onsan industrial complex near the Bay is the input source of these metals. Especially, Cd and Pb concentrations in the periwinkle and seawater were distinctly decreased with distance from the Onsan industrial complex. Non-essential metals such as Cd and Pb in the periwinkle showed a strong correlation with dissolved metal concentrations in seawater. Conversely, essential Cu and Zn in the periwinkle were hardly explained by those in seawater, except at the most contaminated sites.

Animals↗
PubMed1999

Laparoscopic microsurgical tubal anastomosis.

The authors explored the feasibility of performing true microsurgery through the laparoscope in 1990. The first laparoscopic microsurgical tubal anastomosis was performed in February 1992. Operative laparoscopy will continue to expand as technical feasibility continues to improve, driven by both hardware advances and increased surgical dexterity. Laparoscopic microsurgery will introduce a new dimension to reproductive surgery and over time, will replace laparotomy for microsurgery.

Anastomosis, Surgical↗
PubMed1999

Laparoscopic microsurgery: current and future status.

The successful introduction of microsuturing and microinstruments for operative laparoscopy has allowed the convergence of laparoscopy and traditional microsurgery, resulting in the evolution of the 'new microsurgery'. This more dynamic approach overcomes the limitations of open microsurgery by providing continuous magnification and the benefits of a closed environment, making laparoscopy a complete surgical tool. The test model for microsurgery is tubal anastomosis, which is very dependent on operative technique to attain well-established pregnancy rates. Our cumulative pregnancy results for laparoscopic microsurgical tubal anastomosis of 76% at 12 months, 70% at 9 months, 67% at 6 months and 44% at 3 months, compares favorably to the best results achieved by traditional open microsurgery. With this validation the technique is now employed as a complete solution for all tubal surgery. The ability to effect microsurgical repair of the ureter, bladder, bowel and vessels has expanded the surgical repertoire, allowing radical excision of deep endometriosis, severe enterolysis, and adhesiolysis.

Anastomosis, Surgical↗
PubMed1998

A new technique and system for simplifying total laparoscopic hysterectomy.

Because total laparoscopic hysterectomy (TLH) is technically challenging, laparoscopic-assisted vaginal hysterectomy is often the operation of choice, even in patients in whom it may not be successful. To encourage greater performance of TLH, I developed a technique and instrumentation that should enable gynecologists to do the operation successfully more often. The system consists of a pneumo-occluder and a cup, combined with a uterine manipulator. The cup, which is both visible and palpable, is placed over the cervix to delineate vaginal fornices, thus ensuring safe desiccation and avoiding ureteral dissection. Acceptable operating times allow TLH to be combined with other procedures, including excision of endometriosis, colposuspension, and enterocele repair.

Equipment Design↗
PubMed1998

A novel YY1-independent silencer represses the activity of the human papillomavirus type 16 enhancer.

Regulation of the human papillomavirus type 16 (HPV-16) E6 promoter is a complex process in which transcriptional repression as well as activation plays an important role. Here, we identify a negative regulatory element that in the context of a continuous long control region fragment overcomes the activation of the HPV-16 enhancer. This silencing element, which we have termed a PSM (papillomavirus silencing motif), consists of two copies of the sequence 5'-TAYAATAAT-3' that overlap the origin of replication. Each copy of this 9-bp sequence binds the same unknown cellular factor, which we refer to as PSM-BP (PSM binding protein). Both copies of the binding sequence are required for transcriptional repression, and we provide evidence that suggests that this particular organization results in the stabilization of a PSM-BP dimer. The silencing motif, while functioning in either orientation, showed a positional requirement between the enhancer and the promoter. Experiments with both a heterologous enhancer and a promoter also demonstrated a general ability of this element to function as a transcriptional silencer in non-HPV systems. Our findings provide an important addition to our understanding of HPV-16 gene regulation and an interesting model for the study of transcriptional repression.

Base Sequence↗
PubMed1998

Vinorelbine induces apoptosis and caspase-3 (CPP32) expression in leukemia and lymphoma cells: a comparison with vincristine.

Vinorelbine (NVB) is a novel vinca alkaloid FDA approved for use in some advanced carcinomas. However, its role in non-Hodgkin's lymphoma (NHL) is still not well defined. NVB is an antimicrotubule agent, but as yet, it is not known whether it induces apoptosis. By flow cytometry using nuclear staining (propidium iodide) and annexin V, we demonstrated that NVB and vincristine (VCR) induced both mitotic arrest and apoptosis in leukemia and lymphoma cells, in a drug exposure time dependent manner. Cell cycle kinetics in 3 different cell lines varied during vinca alkaloid treatment. The annexin V method showed that apoptosis, as opposed to necrosis, was the dominant mode of cell kill of chemosensitive leukemia and lymphoma cells. Phosphatidylserine expression on the cell surface was detectable as a hallmark of apoptosis at earlier drug exposure when compared to conventional flow cytometry with PI staining. By Western blot analysis, we demonstrated that CPP32 or caspase-3, a critical apoptosis inducer, and its active subunits p20 and p11 were upregulated in chemo- and apoptosis-sensitive lymphoma and leukemia cells treated with NVB. Our data contributes to the emerging hypothesis suggesting that widely divergent exogenous stimuli and chemotherapeutic agents can effect apoptosis in cancer cells via different pathways involving the caspases. We believe that vinorelbine may be a potentially important drug in the treatment of NHL in the future.

Annexin A5↗
PubMed1995

A ring-shaped lateral meniscus.

Ring-shaped lateral meniscus has not previously been reported. We report a case of ring-shaped lateral meniscus with ruptured anterior cruciate ligament.

Adult↗
PubMed1987

Chronic myeloid leukemia presenting as a gynecological emergency.

An unusual case of chronic myeloid leukemia presenting to the gynecological unit as a case of septic abortion is presented. Though history and clinical examination suggested the possibility of double pathology of septic abortion and chronic myeloid leukemia, histology of the products removed from the uterus showed it to be leukemic deposits. The diagnosis of leukemia was confirmed by marrow aspiration (trephine biopsy). Careful clinical examination and systematic investigation helped in diagnosing the pathology and to treat her appropriately.

Abortion, Septic↗