Biomedical subjects

Y H Kim

Publications and source records attributed to Y H Kim.

At least 109 records · Page 6Linked to original sources

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

Photophysical properties of long rodlike meso-meso-linked zinc(II) porphyrins investigated by time-resolved laser spectroscopic methods.

The molecular design of directly meso-meso-linked porphyrin arrays as a new model of light-harvesting antenna as well as a molecular photonic wire was envisaged to bring the porphyrin units closer for rapid energy transfer. For this purpose, zinc(II) 5,15-bis(3,5-bis(octyloxy)phenyl)porphyrin (Z1) and its directly meso-meso-linked porphyrin arrays up to Z128 (Zn, n represents the number of porphyrins) were synthesized. The absorption spectra of these porphyrin arrays change in a systematic manner with an increase in the number of porphyrins; the high-energy Soret bands remain at nearly the same wavelength (413-414 nm), while the low-energy exciton split Soret bands are gradually red-shifted, resulting in a progressive increase in the exciton splitting energy. The exciton splitting is nicely correlated with the values of cos[pi/(N + 1)] according to Kasha's exciton coupling theory, providing a value of 4250 cm(-1) for the exciton coupling energy in the S(2) state. The increasing red-shifts for the Q-bands are rather modest. The fluorescence excitation anisotropy spectra of the porphyrin arrays show that the photoexcitation of the high-energy Soret bands exhibits a large angle difference between absorption and emission dipoles in contrast with the photoexcitation of the low-energy exciton split Soret and Q-bands. This result indicates that the high-energy Soret bands are characteristic of the summation of the individual monomeric transitions with its overall dipole moment deviated from the array chain direction, while the low-energy Soret bands result from the exciton splitting between the monomeric transition dipoles in line with the array chain direction. From the fluorescence quantum yields and fluorescence lifetime measurements, the radiative coherent length was estimated to be 6-8 porphyrin units in the porphyrin arrays. Ultrafast fluorescence decay measurements show that the S(2) --> S(1) internal conversion process occurs in less than 1 ps in the porphyrin arrays due to the existence of exciton split band as a ladder-type deactivation channel, while this process is relatively slow in Z1 (approximately 1.6 ps). The rate of this process seems to follow the energy gap law, which is mainly determined by the energy gap between the two Soret bands of the porphyrin arrays.

Journal Article↗

PubMed2001

Inhibition of neutrophil elastase prevents cathelicidin activation and impairs clearance of bacteria from wounds.

The host defense roles of neutrophil elastase in a porcine skin wound chamber model were explored. Analysis of wound fluid by acid-urea polyacrylamide gel electrophoresis, Western blot, and bacterial overlay confirmed that the neutrophil-derived protegrins constituted the major stable antimicrobial polypeptide in the wound fluid. The application to the wound of 0.10 and 0.25 mM N-methoxysuccinyl-alanine-alanine-proline-valine (AAPV) chloromethyl ketone, a specific neutrophil elastase inhibitor (NEI), blocked the proteolytic activation of protegrins and diminished the associated antimicrobial activity as detected by radial diffusion assay against Staphylococcus epidermidis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans or by bacterial gel overlay against S epidermidis and E coli. The application of the related cathepsin G inhibitor (CGI), benzyloxycarbonyl-glycine-leucine-phenylalanine (ZGLF) chloromethyl ketone, had no effect. In wound chambers that received 10(6) colony-forming unit (CFU)/mL of S epidermidis, the presence of NEI significantly decreased the 24-hour clearance of bacteria from the wound compared to wounds treated with CGI or solvent only. Neither inhibitor, at 0.10 or 0.25 mM concentration, affected leukocyte accumulation or degranulation in the wound chambers. The in vitro microbicidal decrement due to NEI was restored by an amount of the specific protegrin (PG-1), which was equivalent to the measured difference of protegrin between control and inhibited chambers. Administration of 1 microg/mL exogenous PG-1 4 hours after chamber preparation was sufficient to normalize in vivo antimicrobial activity. Although pharmacologic NEIs are promising candidates as anti-inflammatory drugs, they may impair host defense in part by inhibiting the activation of cathelicidins by neutrophil elastase.

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

Response to high-dose intravenous immune globulin as a valuable factor predicting the effect of splenectomy in chronic idiopathic thrombocytopenic purpura patients.

This study was conducted to verify whether the response to high-dose intravenous immune globulin (IVIG) was related to the effect of splenectomy in chronic idiopathic thrombocytopenic purpura (ITP) patients. A total of 79 patients over 16 years of age were enrolled in this study. The response to the treatment was classified on the basis of the platelet count as no response (NR, <50 x 10(9)/l), incomplete response (IR, (50-150) x 10(9)/l), and complete response (CR, >150 x 10(9)/l). The response was evaluated after the infusion of high-dose IVIG, within 2 weeks after splenectomy (immediate response), and during a follow-up period of more than 6 months after splenectomy (sustained response), respectively. 58 patients (73.4%) showed responses (CR or IR) to high-dose IVIG. After splenectomy, immediate responses were observed in 73 patients (92%). The response to high-dose IVIG had no relationship with the immediate response to splenectomy (P = 0.333). A follow-up evaluation was possible with 58 patients; 6 patients with NR in immediate responses did not show any response during the follow-up period, and 17 patients relapsed within 6 months after immediate responses, so 35 patients (60.3%) had sustained responses. Responders to IVIG had significantly higher sustained response rates to splenectomy than non-responders (62% vs. 38%, P = 0.001). These results indicate that the response to high-dose IVIG could be a valuable factor predicting the sustained response to splenectomy in chronic ITP patients.

Adult↗

PubMed2001

Improved calcification resistance and biocompatibility of tissue patch grafted with sulfonated PEO or heparin after glutaraldehyde fixation.

A novel chemical modification of biological tissues was developed aimed at improving biocompatibility and calcification resistance. This method involved the additional grafting of sulfonated PEO (PEO-SO(3)) or heparin after conventional glutaraldehyde (GA) fixation of bovine pericardium (BP). The amino groups of PEO-SO(3) or heparin were utilized to react to the GA residues to block them. The PEO-SO(3) or heparin grafted tissues demonstrated a slightly higher shrinkage temperature and tensile strength, but greater resistance to collagenase digestion, than GA treated ones. These results suggest that modified tissues have improved durability due to the grafting and filling effect of PEO-SO(3) or heparin in addition to the GA cross-linking. At the direct contact cytotoxicity test in vitro, PEO-SO(3) or heparin grafted tissue was shown to be nontoxic, while relatively significant cytotoxicity was observed for the GA treated tissues, possibly due to the release of GA. From the in vivo calcification study, calcium contents deposited on the modified tissues were much less than those on GA treated tissues. Such a decreased calcification might be explained by the decrease of residual GA groups during the additional treatment, and the space-filling effect and the nonadhesive property and/or the blood compatibility of PEO-SO(3) or heparin grafted covalently. The newly modified tissue patch was observed to show improved pathological assessibility including less inflammation and tissue reactions. This simple modification method may be useful for calcification-resistant and blood-compatible tissue patches for cardiovascular implants.

Animals↗

PubMed2001

Inhibitory effects of Korean plants on HIV-1 activities.

In the search for novel anti-human immunodeficiency virus type 1 (anti-HIV-1) agents from natural sources, 49 MeOH extracts of Korean plants were screened for their inhibitory effects against RNA-dependent DNA polymerase (RT) and ribonuclease H (RNase H) activities of HIV-1 reverse transcriptase and HIV-1 protease, and anti-HIV-1 activity. Regarding the HIV-1 reverse transcriptase, Agrimonia pilosa (whole plant), Cornus kousa (stem and leaf), Limonium tetragonum (root) and Mallotus japonicus (stem) showed significant inhibitory activity on RT activity with 50% inhibitory activity (IC(50)) of 8.9, 6.3, 7.5 and 11.9 microg/mL, respectively, whereas Agrimonia pilosa was also active against RNase H activity (IC(50) = 98.4 microg/mL). Four plants, namely Agrimonia pilosa (whole plant), Atractylodes japonica (root), Clematis heracleifolia (whole plant) and Syneilesis palmata (whole plant), were appreciably active (<35%) against recombinant HIV-1 protease at a concentration of 100 microg/mL. Crinum asiaticum var. japonicum (root) showed significant anti-HIV-1 activity (ED(50) = 12.5 microg/mL) with a favourable SI value of 16.

Anti-HIV Agents↗

PubMed2001

Structural determination of lysophosphatidylcholines extracted from marine sponges by fast atom bombardment tandem mass spectrometry.

A series of lysophosphatidylcholines were isolated from the marine sponge Spirastrella abata by reversed-phase high performance liquid chromatography (HPLC) and analyzed by fast atom bombardment mass spectrometry (FAB-MS). Their structural elucidation was carried out with fast atom bombardment tandem mass spectrometry (FAB-MS/MS). The collision-induced dissociation (CID) of protonated and sodiated molecular ions produced diverse product ions via a series of dissociative processes. Because of the positive charge of the amine group at the end of the molecules, charge-remote fragmentation patterns of specific ions, [M + H](+) or [M + Na](+), were very helpful for the identification of product ions which are characteristic for choline and long hydrocarbon chains substituted at the glycerol back bone. Moreover, the CID-MS/MS spectra of sodium adducted molecular ions for lysophosphatidylcholines yielded common characteristic fragment ions for the choline moiety and characteristic ions [M + Na-103](+), [M + Na-85](+) and [M + Na-59](+) in the higher mass region.

Animals↗

PubMed2001

Heterogeneity of cingulate contributions to spatial attention.

Functional magnetic resonance imaging was used to investigate activation patterns within the cingulate region during tasks based on spatial attention. Subjects were asked to detect targets which appeared either at the site indicated by a cue or on the opposite side. A "cue effect" was identified by the presence of shorter reaction times to validly than invalidly cued targets, showing that an anticipatory bias had been generated in the direction of the cue. Target detection accuracy was consistently above 90% although cue effects and reaction times displayed substantial variations, from one task session to another. Activation within the anterior cingulate region was seen in 16 of the 26 sessions but showed no correlation with reaction time. Posterior cingulate activation was seen in only 6 of the 26 sessions. However, a random effects analysis showed that the task-related signal change in this region was strongly correlated with the speed of target detection. A post hoc analysis indicated that this correlation was significant only when cue effects were present. No other part of the cerebral cortex displayed significant correlations with reaction times or cue effects. These results suggest that the cingulate component of the attentional network has at least two functionally segregated sectors, an anterior one in BA 24/32 and a posterior cingulo-retrosplenial one in BA 23/29/30. The posterior sector appears to be associated with the speed of detecting spatial targets, especially when attention is under the influence of a cue-induced anticipatory bias. The anterior cingulate focus did not display such a relationship in our tasks and is likely to mediate other aspects of attentional deployment such as performance monitoring, response selection or target identification.

Adult↗

PubMed2001

A cytotoxic secocycloartenoid from Abies koreana.

Two triterpenoids, 24-methylene-3,4-seco-cycloart-4(28)-en-3-oic acid (1) and 3-oxo-9beta-lanosta-7,22Z,24-trien-26,23-olide (6) were isolated from Abies koreana, together with beta-sitosterol (2), maltol (3), beta-sitosterol-O-beta-D-glucoside (4), and hexacosylferulate (5). The structures of the compounds were established based on the spectroscopic data. The cytotoxic activities of triterpenoids have been evaluated using the sulforhodamine B (SRB) method. Compound 1 showed moderate cytotoxicities against human lung carcinoma (A549), ovarian carcinoma (SK-OV-3), malignant melanoma (SK-MEL-2), and colon carcinoma (HCT-15) cell lines.

Abies↗

PubMed2001

Quantitative determination of eleutheroside B and E from Acanthopanax species by high performance liquid chromatography.

Reversed-phase high performance liquid chromatographic method was applied for the determination of eleutheroside B and E in the various Acanthopanax species collected in Korea. The stationary phase used was Zorbax 300 SB C18 and a mobile phase program was used, which started at 6% acetonitrile for 2 min, and then a linear gradient was operated for the next 18 min to 17% acetonitrile at a flow rate of 1.0 ml/min. The column effluent was monitored at UV 210 nm. Identification was carried out by comparing the retention time and the LC/MS spectrum of each peak corresponding to eleutheroside B and E from sample with those of standards. In general, the contents of eleutheroside B and E in stems were higher than those in roots. Acanthopanax species could be classified into two groups based upon the contents of eleutheroside B and E: one group contains no or very little eleutheroside B and another contains both eleutheroside B and E.

Araliaceae↗

PubMed2001

Long-term engraftment stability of peripheral blood stem cells cryopreserved using the dump-freezing method in a -80 degrees C mechanical freezer with 10% dimethyl sulfoxide.

In this study, we summarize our long-term follow-up data of 24 patients who underwent autologous peripheral blood stem cell transplantation (PBSCT) using the dump-freezing method in a -80 degrees C freezer. Collected peripheral blood mononuclear cells were mixed with a cryoprotectant solution consisting of autologous plasma and 20% dimethyl sulfoxide, then placed in a -80 degrees C freezer. The recovery rate of mononuclear cells (MNCs), colony-forming unit-granulocyte/macrophage (CFU-GM) colonies, and CD34+ cells were calculated. Engraftment time (with neutrophil count > 0.5 x 10(9)/L, platelet count > 50 x 10(9)/L) and normal hemopoiesis (neutrophil count > 2 x 10(9)/L, platelet count > 100 x 10(9)/L) were evaluated. Median duration of cryopreservation was 76 days. The mean recovery rates of MNCs, CFU-GM colonies, and CD34+ cells were 93.4%, 78.4%, and 95.3%, respectively. The median engraftment times of neutrophils and platelets were 8 and 27 days, respectively. The median normal hemopoiesis times of neutrophil and platelet were 31 and 45 days, respectively. Nine patients are alive and in complete remission (CR). Seven patients in first CR sustained normal hemopoiesis with a median duration of 35 months. Two patients, who achieved second CR after salvage chemotherapy due to a leukemia relapse after PBSCT, maintained engraftment status for 24 and 28 months, and 1 reached normal hemopoiesis. These results demonstrate that PBSCT using the dump-freezing method in a -80 degrees C freezer leads to acceptable long-term engraftment stability.

Adolescent↗

PubMed2001

Characterization of antidepressant-like effects of p-synephrine stereoisomers.

We previously reported that p-synephrine has antidepressant-like activity in the murine models of forced swimming and tail suspension. In the present study, we characterized antidepressant-like effects of p-synephrine stereoisomers in both in vivo and in vitro systems. In the tail suspension test, S-(+)-p-synephrine (3 mg/kg, p.o.) reduced the duration of immobility, while R-(-)-p-synephrine (0.3-3 mg/kg, p.o.) had no effect. S-(+)-p-synephrine (0.3, 1 and 3 mg/kg, p.o.) and R-(-)-p-synephrine (1 mg/ kg and 3 mg/kg, p.o.) significantly reversed the reserpine (2.5 mg/kg, i.p.)-induced hypothermia. S-(+)-p-synephrine was more effective than R-(-)-p-synephrine in inhibition of both [3H]noradrenaline uptake in rat cerebral cortical slices (maximal inhibition 85.7 +/- 7.8% vs. 59.8 +/- 4.3%; EC50 5.8 +/- 0.7 microM vs. 13.5 +/- 1.2 microM) and [3H]nisoxetine binding (Ki 4.5 +/- 0.5 microM vs. 8.2 +/- 0.7 microM). In contrast, R-(-)-p-synephrine was more effective than S-(+)-p-synephrine in stimulation of [3H]noradrenaline release from rat cerebral cortical slices (maximal stimulation 23.9 +/- 1.8% vs. 20.1 +/- 1.7%; EC50 8.2 +/- 0.6 microM vs. EC50 12.3 +/- 0.9 microM). The stimulatory effect of R-(-)-p-synephrine on [3H]noradrenaline release was inhibited by nisoxetine (100 nM), but tetrodotoxin (1 microM) and elimination of extracellular calcium had no effect. It is suggested that S-(+)-p-synephrine has more effective antidepressant-like activity than R-(-)-p-synephrine.

Adrenergic Uptake Inhibitors↗

PubMed2001

Unique properties of four lactobacilli in amino acid production and symbiotic mixed culture for lactic acid biosynthesis.

With four Lactobacilli--L. delbrueckii subsp. lactis (ATCC 12315), L. casei (NRRL-B1445), L. delbrueckii (NRRL-B445), and L. heveticus (NRRL-B1937)--the characteristics of cell growth and production of lactate and amino acids were investigated. Especially, the time-course variation in concentration of amino acids (classified into alanine, serine, aspartate, glutamate, aromatic amino acid, and histidine families) was estimated in detail, and the results were systematically compared. It was elucidated that L. delbrueckii (NRRL-B445) and L. helveticus (NRRL-B1937) had quite different characteristics in growth, lactic acid synthesis, and amino acid production. L. helveticus (NRRL-B1937) was superior in the production of amino acids as well as in cell growth, but showed very poor ability in lactic acid production. However, L. delbrueckii (NRRL-B445) showed higher yield of lactic acid despite repressed cell growth, but suffered from severe amino acid deficiency in culture. By modulating the initial concentration of each strain in the mixed culture containing both L. delbrueckii (NRRL-B445) and L. helveticus (NRRL-B1937), the lactic acid production (i.e., the amount of lactic acid produced and lactic acid yield to glucose consumed) was significantly improved, presumably via symbiotic interaction between the two strains.

Amino Acids↗

PubMed2001

Cyst fluid levels of carcinoembryonic antigen, carbohydrate antigen 19-9, squamous cell carcinoma antigen, and amylase in thyroglossal duct and branchial cleft cysts.

Cyst fluid was aspirated from five thyroglossal duct cysts (TDCs) and four branchial cleft cysts (BCCs). The cyst fluid levels of carcinoembryonic antigen (CEA), carbohydrate antigen (CA) 19-9, squamous cell carcinoma antigen (SCC), and amylase were measured and compared between the two types of cyst. The enzyme immunoassay technique was used for CEA and CA19-9, while SCC and amylase levels were measured by the immunoradiometric assay and nitrophenol method, respectively. Immunostaining for CEA, CA19-9, and amylase was also performed. The serum levels of these markers in both groups of patients were within the normal ranges. In contrast, their cyst fluid levels were extremely high. There was no significant difference in the cyst fluid levels of CEA and SCC between the two types of cyst; however, the cyst fluid from the TDCs showed significantly higher levels of CA19-9 and significantly lower levels of amylase compared with that from the BCCs. Immunostaining revealed expression of CA 19-9 in nearly half the columnar epithelial cells in the TDCs, but not in the squamous epithelial cells in the BCCs. CEA and amylase were not found in the epithelial cells of either type of cyst. These findings seem to reflect the difference in etiology between TDCs and BCCs.

Adult↗

PubMed2001

Chromosomal alterations in paired gastric adenomas and carcinomas.

Gastric adenoma is a precancerous lesion of the stomach and its malignant transformation is thought to result from accumulative series of gene alterations. The aim of this study was to determine the pattern of chromosomal changes during gastric carcinogenesis. Pairs of adenoma and carcinoma tissues from 15 gastrectomy cases containing both adenomas and carcinomas in the same (adjacent pairs, 6 cases) and different (non-adjacent pairs, 9 cases) lesions, were analyzed for chromosomal alterations of 39 non-acrocentric chromosomal arms by comparative genomic hybridization (CGH). CGH analysis identified frequent chromosomal alterations in most of the gastric adenomas (14/15, 93%) and all of the carcinomas. The mean number of chromosomal alterations was higher in carcinoma (5.5 for adenoma and 11.7 for carcinoma; P = 0.006, by nonparametric Wilcoxon's test). Losses on the short arm of chromosome 17 were most common in both adenomas (43%) and carcinomas (67%). The pattern of chromosomal alterations in paired gastric adenomas and carcinomas showed greater similarity compared to the non-case pairs and this similarity was increased in the adjacent pairs. Deletion mapping analysis on chromosome 17p also demonstrated that the conserved deletion area was more frequent in the adjacent pairs. Among these 6 adjacent pairs, all had common deletion areas. In contrast, among the 9 non-adjacent pairs, 2 (22%) had common area of deletion, 5 (56%) showed deletion only in the carcinoma, and the remaining 2 (22%) had no deletion on 17p, suggesting diverse genetic changes might be involved in the multiple tumor formation. Our results that common clonal genetic changes between adjacent pairs of gastric adenomas and carcinomas and accumulated genetic changes in the carcinomas provide evidences for the stepwise mode of gastric carcinogenesis through the accumulation of a series of genetic alterations.

Adenoma↗

PubMed2001

Fractionation and characterization of dissolved organic matter in a shallow eutrophic lake, its inflowing rivers, and other organic matter sources.

Dissolved organic matter (DOM) in water from eutrophic Lake Kasumigaura, its inflowing rivers, and several other DOM sources in the lake catchment area was fractionated using resin adsorbents into five classes: aquatic humic substances (AHS), hydrophobic neutrals (HoN), hydrophilic acids (HiA), bases (BaS), and hydrophilic neutrals (HiN). The DOM-fraction distribution pattern and the ultraviolet absorbance to dissolved organic carbon ratio (UV/DOC ratio) were found remarkably effective for evaluating the characteristics of DOM in water. DOM-fraction distribution patterns were significantly different depending on the origin of the sample. AHS and HiA were found to be the dominant fractions in DOM in all samples studied. HiA prevailed over AHS in the lake water, whereas AHS were slightly more abundant than HiA in the river waters. AHS were in the great majority in forest streams and plowed-field percolates. HiA abounded in paddy-field outflow, domestic sewage, and sewage-treatment-plant effluent. Only domestic sewage contained a significant amount of HoN. The UV/DOC ratio also varied depending on the origin of the sample: the ratios in total DOM, AHS, and HiA were greater in river waters than in the lake water. The greatest ratio of AHS was found in paddy-field outflow and the lowest in domestic sewage. The UV/DOC ratios in the sewage-treatment-plant effluent were very similar to those in the lake water.

Absorption↗

PubMed2001

Immobilization of poly(ethylene glycol) or its sulfonate onto polymer surfaces by ozone oxidation.

A novel surface modification method has been developed to improve biocompatibility of polymeric biomaterials. This approach involves ozonation and then followed by graft polymerization with acrylates containing PEG, sulfonated PEG or by coupling of PEG derivatives. All the reactions were confirmed by ATR FT-IR and ESCA. The degree of ozonation measured by the iodide method was dependent on the ozone permeability of the polymers used. Surface hydrophilicity was investigated by measuring the contact angles. Ozonation itself yielded a slight increase in hydrophilicity and a decrease in platelet adhesion, but PEG immobilization showed a significant effect on surface hydrophilicity and platelet adhesion to confirm well-known PEG's passivity which minimize the adhesion of blood components on polymer surfaces. Both graft polymerization and coupling were effective for PU. In contrast, only grafting gave enough yields for PMMA and silicone. Platelet adhesion results demonstrated that all PEG modified surfaces adsorbed lower platelet adhesion than untreated or ozonated ones. Polymers coupled with sulfonated PEG exhibited the lowest platelet adhesion when compared with control and PEG coupled ones by virtue of the synergistic effect of non-adhesive PEG and negatively charged SO3 groups. This PEG or sulfonated PEG immobilization technology using ozonation is relatively simple for introducing uniform surface modification and therefore very useful for practical application of blood contacting medical devices.

Biocompatible Materials↗