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Biomedical subjects

K H Choi

Publications and source records attributed to K H Choi.

At least 19 recordsLinked to original sources
PubMed2006

Placenta hominis protects osteoporosis in ovariectomized rats.

In China, Japan, and Korea, placenta hominis extracts (PHEs) are used clinically for the treatment of osteoporosis. The anti-osteoporotic effect of PHEs was studied. The trabecular bone area and thickness in OVX rats decreased by 50% from those in sham-operated rats; these decreases were completely inhibited by administration of PHEs for 7 weeks. Osteoclast numbers and the osteoblast surface were enhanced in OVX rats, but PHEs had no effect on these phenomena. Serum phosphorus and alkaline phosphatase in OVX rats increased compared to those in sham-operated rats, but the increases were not affected by the administration of PHEs. Thyroxine (T4) level was stimulated in OVX rats. The extracts inhibited the T4 level in the OVX rats. These results strongly suggest that PHEs be effective in preventing the development of bone loss induced by OVX in rats.

Animals↗
PubMed2005

Degradation of parathion and the reduction of acute toxicity in TiO2 photocatalysis.

Photocatalytic degradation of methyl parathion was done using a circulating TiO2/UV and TiO2/solar reactor. Indoor experimental results showed that, under the photocatalysis conditions, parathion was more effectively degraded than under the photolysis and TiO2 only conditions. Parathion (38 microM) was completely degraded under photocatalysis within 90 min, and more than 80% TOC decrease after 150 minutes. The main ionic byproducts during the photocatalysis were measured, and almost complete nitrogen recovery was achieved as mainly NO3- NO2-, and NH4+, and 80% of sulfur as recovered as SO4(2)-. Organic intermediates such as nitrophenol and methyl paraoxon were also identified during the photocatalysis of parathion, and these were further degraded after 90 minutes. Microtox bioassay using Vibrio fischeri was used in evaluating the toxicity of solutions treated by photocatalysis and photolysis of parathion. The results showed that the acute toxicity expressed as EC50 almost reduced after 90 min under the photocatalysis condition whereas only 40% reduction of toxicity as EC50 was achieved in photolysis condition. The outdoor results using a TiO2/solar system were similar to the TiO2 indoor system, indicating the possibility of applying TiO2/solar system for the treatment of parathion-contaminated water.

Biological Assay↗
PubMed2004

Risk of ovarian failure and pregnancy outcome in patients with lupus nephritis treated with intravenous cyclophosphamide pulse therapy.

This study was designed to investigate the risk of ovarian failure and the pregnancy outcomes in women treated with intravenous cyclophosphamide (IVCYC) pulse therapy for lupus nephritis. Sixty-seven women with proliferative lupus nephritis were studied. The clinical and laboratory data, SLEDAI and damage indices at IVCYC initiation, doses and numbers of IVCYC pulses, pregnancy and fetal outcomes were evaluated. During a follow-up of 74.4+/-20.6 months, amenorrhea occurred in 25 (37.3%) and was sustained permanently in 10 patients (14.9%). Thirteen women became pregnant with a total of 19 pregnancies. Seventeen pregnancies ended without complications and all babies were born healthy without any congenital anomalies or perinatal illnesses. Two pregnancies were terminated by induced abortion but no congenital anomaly was noted in these cases. Logistic regression analysis showed that old age, high damage index at the initiation of IVCYC pulse therapy and high cumulative dosage of IVCYC were the independent risk factors of ovarian failure, and that the presence of amenorrhea, regardless of its duration, was the risk factor of pregnancy failure. Pregnancy was possible with a favorable outcome after the withdrawal of IVCYC pulse therapy, unless amenorrhea develops.

Adolescent↗
PubMed2004

Integrated biological and electro-chemical treatment of swine manure.

A full-scale biogas plant was applied to the processing of 10 m3/d of swine manure. The plant consisted of an anaerobic digester and an engine-generator. The digester operation resulted in an 81% of COD removal, a 55% of VS reduction, and methane-rich biogas production that is used to generate electrical and thermal energies. To further treat the digested manure, for compliance with discharge limits, an electro-chemical oxidation with a dimensionally sable anode was investigated for the simultaneous elimination of both the remaining COD and ammonia nitrogen. It was able to reduce NH4+-N levels from as high as 1552 down to 25 mg/L in 160 min, and the COD from 1542 to 0.21 mg/L under the experimental conditions of 8 V, 30 A and 20,000 microS/cm. The amount of electricity required for a 90% removal of the residual COD and ammonia in 1 m3 of filtered digester manure, via electrochemical oxidation, were approximately 153 and 151 kWh, respectively. These values exceed the maximum potential capacity of the biogas-originated electricity through the digestion of swine manure containing normal VS content. However, approximately 50% of the required electricity for the electrochemical oxidation could be supplied from the engine-generator.

Animals↗
PubMed2004

Application of a sponge media (BioCube) process for upgrading and expansion of existing caprolactam wastewater treatment plant for nitrogen removal.

For the upgrade and expansion of an existing caprolactam wastewater treatment plant, a freely floating sponge media (BioCube) process was selected based on extensive pilot-plant tests, due to extreme space constraints. In order to protect nitrifier inhibition caused by high strength organics in caprolactam wastewater, the pilot plant consisted of an organics removal reactor, which functioned as a pretreatment for nitrification, and followed the nitrogen removal reactor. The suspended MLSS was 1,800-4,000 and the media attached MLSS was maintained at 22,000-26,000 mg/L. The final effluent COD was noticeably low, around 20.4-37 mg/L, even with fairly large fluctuations in the feed levels, between 1,400-6,770 mg/L. The removal of total nitrogen with the system, when denitrification was close to completion, was approximately 97.6%. For the entire run, complete nitrification of 99.6% was achieved, which might have been due to well-acclimatized nitrifiers attached in the BioCube media. Specifically, after adaptation, the nitrification continuously increased in the organics removal reactor, even under high residual organics conditions. From the numerous experimental results, the BioCube process seemed to be an effective method for the upgrading and expansion of the existing wastewater treatment plant, with minimum reactor enlargement.

Animals↗
PubMed2001

Snapshots of catalysis: the structure of fructose-1,6-(bis)phosphate aldolase covalently bound to the substrate dihydroxyacetone phosphate.

Fructose-1,6-bis(phosphate) aldolase is an essential glycolytic enzyme found in all vertebrates and higher plants that catalyzes the cleavage of fructose 1,6-bis(phosphate) (Fru-1,6-P(2)) to glyceraldehyde 3-phosphate and dihydroxyacetone phosphate (DHAP). Mutations in the aldolase genes in humans cause hemolytic anemia and hereditary fructose intolerance. The structure of the aldolase-DHAP Schiff base has been determined by X-ray crystallography to 2.6 A resolution (R(cryst) = 0.213, R(free) = 0.249) by trapping the catalytic intermediate with NaBH(4) in the presence of Fru-1,6-P(2). This is the first structure of a trapped covalent intermediate for this essential glycolytic enzyme. The structure allows the elucidation of a comprehensive catalytic mechanism and identification of a conserved chemical motif in Schiff-base aldolases. The position of the bound DHAP relative to Asp33 is consistent with a role for Asp33 in deprotonation of the C4-hydroxyl leading to C-C bond cleavage. The methyl side chain of Ala31 is positioned directly opposite the C3-hydroxyl, sterically favoring the S-configuration of the substrate at this carbon. The "trigger" residue Arg303, which binds the substrate C6-phosphate group, is a ligand to the phosphate group of DHAP. The observed movement of the ligand between substrate and product phosphates may provide a structural link between the substrate cleavage and the conformational change in the C-terminus associated with product release. The position of Glu187 in relation to the DHAP Schiff base is consistent with a role for the residue in protonation of the hydroxyl group of the carbinolamine in the dehydration step, catalyzing Schiff-base formation. The overlay of the aldolase-DHAP structure with that of the covalent enzyme-dihydroxyacetone structure of the mechanistically similar transaldolase and KDPG aldolase allows the identification of a conserved Lys-Glu dyad involved in Schiff-base formation and breakdown. The overlay highlights the fact that Lys146 in aldolase is replaced in transaldolase with Asn35. The substitution in transaldolase stabilizes the enamine intermediate required for the attack of the second aldose substrate, changing the chemistry from aldolase to transaldolase.

Animals↗
PubMed2001

Amphiphysin IIb-1, a novel splicing variant of amphiphysin II, regulates p73beta function through protein-protein interactions.

p73 is a nuclear protein that is similar in structure and function to p53. Notably, the C-terminal region of p73 has a regulatory function, through interactions with a positive or negative regulator. In this study, we use the yeast two-hybrid technique to identify a novel p73beta binding protein, designated amphiphysin IIb-1. Amphiphysin IIb-1 is one of the splicing variants of amphiphysin II, and has a shorter protein product than amphiphysin IIb, which has been previously reported. We confirmed that amphiphysin IIb-1 binds full-length p73beta, both in vitro and in vivo. This association is mediated via the SH3 domain of amphiphysin IIb-1 and C-terminal amino acids 321-376 of p73beta. Double immunofluorescence patterns revealed that p73beta is relocalized to the cytoplasm in the presence of amphiphysin IIb-1. Overexpression of amphiphysin IIb-1 was found to significantly inhibit the transcriptional activity of p73beta in a dose-dependent manner. In addition, the cell death function of p73beta was inhibited by amphiphysin IIb-1. These findings offer a new insight into the regulation mechanism of p73beta, and suggest that amphiphysin IIb-1 modulates p73beta function by direct binding.

Alternative Splicing↗
PubMed2001

Inducible RGS2 is a cross-talk regulator for parathyroid hormone signaling in rat osteoblast-like UMR106 cells.

Parathyroid hormone (PTH) activates dual signal transduction systems via Galphas and Galphaq proteins. We now report a novel mechanism by which "cross-talk" may occur between the Galphas and Galphaq signaling pathways. RGS2 (Regulator of G protein Signaling 2) mRNA was rapidly and transiently increased only by PTH analogs (PTH1-84, 1-34, 1-31, and PTHrP) that activated the Galphas-mediated cAMP/PKA signaling pathway, whereas activation of the Galphaq-mediated Ca(2+)/PKC signaling pathway by PTH3-34 had no effect on RGS2 expression. Treatment of UMR106 cells with nonPTH activators of the cAMP/PKA signaling pathway such as cholera toxin, forskolin, 8-Br-cAMP, and dibutyryl-cAMP also significantly elevated RGS2 mRNA levels, while activator of the Galphaq pathway PMA did not. Pretreatment using the Galphas signaling pathway inhibitors SQ22536 and H89 significantly blocked PTH-induced RGS2 expression, but the Galphaq signaling pathway inhibitor bisindolylmaleimide I had no effect. Therefore, RGS2 expression is governed solely by the Galphas signaling pathway. Additionally, we demonstrate for the first time that RGS2 binds to both Galphas and Galphaq subunits in their transition state (GDP/AlF(-4)-bound) forms, suggesting that RGS2 has the potential to act as a bridge between the cAMP/PKA and Ca(2+)/PKC pathways, and that it may act as a cross-talk regulator for these two PTH signaling pathways.

Animals↗
PubMed2001

Bax-dependent apoptosis induced by ceramide in HL-60 cells.

Ceramide is an important lipid messenger involved in mediating a variety of cell functions including apoptosis. In this study, we show that antisense bax inhibits cytochrome c release, poly(ADP-ribose)polymerase cleavage and cell death induced by ceramide in HL-60 cells. In addition, ceramide induces translocation of Bax to mitochondria. The addition of the broad spectrum caspase inhibitor zVAD-fmk prevented ceramide-induced apoptotic cell death but did not inhibit translocation of Bax and mitochondrial cytochrome c release. Furthermore, ceramide inhibits the expression of the antiapoptotic protein Bcl-xL with an increase in the ratio of Bax to Bcl-xL. These data provide direct evidence that Bax plays an important role in regulating ceramide-induced apoptosis.

Amino Acid Chloromethyl Ketones↗
PubMed2001

Dextromethorphan affects cocaine-mediated behavioral pattern in parallel with a long-lasting Fos-related antigen-immunoreactivity.

In order to understand the underlying mechanisms responsible for the behaviors mediated by dextromethorphan (DM), we examined the effects of DM on locomotor activity and locomotor patterns in mice, and Fos-related antigen immunoreactivity (FRA-IR) of mouse brain following repeated administration of cocaine. Combined treatments (30 min prior to each cocaine administration) with DM dose-dependently decreased locomotor activity for high doses of cocaine (20 mg/kg, i.p./day x 7). DM combinations did not significantly affect hyperactivity for 10 mg cocaine/kg, i.p./day x 7. In contrast, combined treatments with DM increased the locomotor activity for 5 mg cocaine/kg, i.p./day x 7. These results were consistent with alterations in marginal activity. Repeated administration with cocaine or DM increased FRA-IR in the nucleus accumbens (NAc) and striatum which lasted for at least 7 days. Our results suggest that DM exhibits biphasic effects on the locomotor stimulation induced by cocaine, and that locomotor activities are in parallel with FRA-IR of the striatal complex. However, the role of FRA-IR regulated by DM or/and cocaine remains to be further determined.

Animals↗
PubMed2001

National trends in condom use among at-risk heterosexuals in the united states.

Based on national level surveys, we examined data relevant to the United States' overall effort to prevent the spread of HIV among heterosexual adults. We examined changes in condom use among at-risk heterosexuals over the past decade. The observed increases over time in condom use across all heterosexual at-risk population segments are consistent with the observed (declines) trends in HIV and syphilis in the 1990s. These results and findings from prior studies suggest that U.S. efforts to facilitate condom use and contain HIV and related sexually transmitted disease (STD)-cofactors among adult at risk heterosexuals was succeeding over most of the 1990s. The absence of national level behavioral trend data after 1996, and the ambiguities of HIV spread suggest some caution in projecting trends into this century. National and local efforts need to be directed at sustaining behavioral change and conducting more rigorous studies on population trends in HIV/STD-related behaviors/pathogens.

Adolescent↗
PubMed2001

beta-Cell dysfunction rather than insulin resistance is the main contributing factor for the development of postrenal transplantation diabetes mellitus.

BACKGROUND: Our study was undertaken to investigate the pathogenesis and possible risk factors for postrenal transplantation diabetes mellitus (PTDM). METHODS: We recruited 114 patients with normal glucose tolerance (NGT) and performed both 75-g oral glucose tolerance tests (OGTT) and short insulin tolerance tests 1 week before and 9-12 months after transplantation. RESULTS: The subjects were classified into three groups by World Health Organization criteria on the basis of OGTT after transplantation: (a) 36 (31.6%) subjects with normal glucose tolerance; (b) 51 (45.7%) subjects with impaired glucose tolerance (IGT); and (c) 27 (23.7%) subjects with postrenal transplantation diabetes mellitus. Dosages of steroid and cyclosporine were equivalent among the three groups. Before transplantation, the fasting and 2-hr plasma glucose and proinsulin/insulin (PI/I) ratios were significantly higher in the IGT and PTDM groups than in the NGT group, but the insulin sensitivity index (ISI) was not significantly different among the three groups. In addition, the area under the curve-insulin on OGTT was significantly lower in the PTDM group than in the NGT group. After transplantation, however, the ISI was increased in all groups. Furthermore, the ISI and PI/I ratios revealed significantly higher values in the PTDM group than in the NGT group after transplantation. CONCLUSIONS: These results revealed that fasting and 2-hr plasma glucose levels, as well as the proinsulin/insulin ratio before transplantation, are both possible indicators of beta-cell dysfunction and may be predictors for the development of PTDM. Furthermore, beta-cell dysfunction, rather than insulin resistance, was proven to be the main factor for the pathogenesis of PTDM.

Adult↗
PubMed2001

Positive and negative life events after counselling and testing: the Voluntary HIV-1 Counselling and Testing Efficacy Study.

INTRODUCTION: The results of the Voluntary HIV-1 Counselling and Testing Efficacy Study support the efficacy and cost-effectiveness of HIV voluntary counselling and testing (VCT) for reducing risk behaviors in three developing countries. METHODS: This report explores the social consequences of HIV VCT by examining the incidence of positive and negative life events at the first follow-up (an average of 7.3 months after recruitment). The incidence of positive and negative life events was compared between: (i) those who were randomly assigned to HIV VCT versus health information (HI); (ii) those who tested seronegative and those who tested seropositive; and (iii) those who disclosed their serostatus and those who did not. RESULTS: The occurrence of most negative life events was rare (0--4%); positive life events were more common (17--39%). With few exceptions, those assigned to HIV VCT were no more likely to experience negative life events than those who were assigned to HI. For individuals, positive serostatus was associated with increased support from health professionals, the break-up of a marriage and being neglected or disowned by their family. Serodiscordant couples with an HIV-positive woman were most likely to report the break-up of a marriage (20 versus 0--7% for other groups) and the break-up of a sexual relationship (45 versus 22--38% for other groups). Disclosure was associated with strengthening of a sexual relationship except for HIV-seropositive women. CONCLUSION: These findings, in combination with findings supporting the efficacy and cost-effectiveness of HIV VCT, support the dissemination of HIV VCT with appropriate support services in developing countries.

AIDS Serodiagnosis↗
PubMed2001

Caspase-3-mediated cleavage of the NF-kappa B subunit p65 at the NH2 terminus potentiates naphthoquinone analog-induced apoptosis.

The transcription factor nuclear factor kappaB (NF-kappaB) plays a crucial role in immune and inflammatory response, and protects cells from apoptosis. In this report, we investigate whether the NF-kappaB signaling pathway is blocked during apoptosis induced by 2,3-dichloro-5,8-dihydroxy-1,4-naphthoquinone (NA), an analog of naphthoquinone. It is observed that NA triggers apoptotic cell death in HeLa cells and destroys resistance to apoptosis caused by tumor necrosis factor-alpha. Data presented in this study establish that p65/RelA, a subunit of NF-kappaB, is cleaved at Asp(97) by caspase-3 during apoptosis. Caspase-3-cleaved p65 loses transcriptional activity and potentiates NA-induced apoptosis, in contrast to an uncleavable mutant of p65, which protects the cell from apoptosis. Caspase-3, which is responsible for the cleavage of p65, is activated via the cytochrome c/caspase-9 signaling pathway rather than Fas/caspase-8 pathway during NA-induced apoptosis. Our results suggest that NA induces apoptosis by the negative regulation of cell survival through caspase-3-mediated cleavage of p65.

Apoptosis↗
PubMed2001

Live donor renal allograft in end-stage renal failure patients from immunoglobulin A nephropathy.

BACKGROUND: The purpose of this study was to attempt to resolve two important issues, i.e. to determine (1) whether the course of recurrent immunoglobulin A nephropathy (IgAN) is benign, and (2) whether it is advisable to use a related donor. METHODS: We evaluated the long-term outcome, in terms of recurrence and graft survival, after live related or unrelated donor renal transplantation, and assessed the validity of the use of related donors in 90 grafts in 89 IgAN patients. RESULTS: Ten-year graft survival for IgAN patients was 66%, compared with 84% for 107 reference recipients who had other kinds of glomerulonephritis (GN), and with 69% in 90 other recipients who had non-GN renal failure (P=0.27). In 43 grafts, 54 event graft biopsies were performed, documenting the presence of mesangial IgA deposits in 19 of those grafts. In eight grafts, lesions were accompanied by chronic rejection (CR). Ten-year cumulative recurrence was 44%. Ten grafts were lost: by CR (n=3) or acute rejection (n=1) in 24 recurrence-free recipients, by CR (n=2) or recurrence (n=2) in 19 recurrent patients, and by patient death (n=2) in 46 patients devoid of graft biopsy. We found no difference in 10-year graft survival between the recurrent and recurrence-free patients (63% vs. 74%, P=0.98), or the proportion of related donors (68% vs. 83%, P=0.25). The presence or matching of HLA B12, B35, or DR4 did not affect the recurrence. CONCLUSIONS: Recurrence increased to 44% with longer follow-up, but this did not limit the graft outcome. Recurrence was not affected by the kind of live donor. We conclude that live related or unrelated kidneys should be offered to IgAN patients.

Adult↗
PubMed2001

UVB-induced GM-CSF production is suppressed by dexamethasone in HaCaT cells.

BACKGROUND: Epidermal keratinocytes are important sources of a wide variety of cytokines that include the Granulocyte-macrophage Colony Stimulating Factor (GM-CSF). Glucocorticoids have been shown to inhibit the production of several cytokines. However, their effect on GM-CSF synthesis by keratinocytes is still unknown. METHODS: The effects of glucocorticoid on GM-CSF production by keratinocytes were evaluated using ELISA and RT-PCR analysis. RESULTS: GM-CSF secretion by HaCaT cells increased with increasing UVB exposure. Dexamethasone suppressed basal release of GM-CSE In addition, it strongly inhibited both the UVB-mediated augmentation of GM-CSF protein production and mRNA expression. Lincomycin enhanced slightly the inhibitory effect of dexamethasone on GM-CSF synthesis, while lincomycin itself had no effect on GM-CSF secretion. CONCLUSION: Results showed that dexamethasone suppressed basal release and UVB-induced production of GM-CSF by keratinocytes.

Anti-Bacterial Agents↗