Biomedical subjects

Tae Wan Kim

Publications and source records attributed to Tae Wan Kim.

9 recordsLinked to original sources

PubMed2006

The expression patterns of RGS transcripts in platelets.

Regulators of G protein signalling (RGS) are involved in the negative regulation of cell activation processes and are involved in the pathophysiology of cardiovascular diseases. To get some further evidence for a role of RGS proteins in platelets, we determined the expression profile of RGS-specific mRNA in rat platelets using reverse transcription-polymerase chain reaction (RT-PCR) with a poly dT18 primer and transcript-specific primers. We found that RGS2, RGS3, RGS5, RGS6, RGS10, RGS14, RGS16 and RGS18, Leukemia-associated Rho-GEF factor (LARG), and Galpha interacting protein (GAIP) were differentially expressed in platelets. The highest expression rate was found for RGS18 (about 1.3 fold when compared to GAPDH), followed by LARG, RGS6, RGS10 and RGS16 (0.7 to 0.95), whereas expression rates for RGS2, RGS3, RGS5, RGS14, and GAIP were in a range of 0.1 to 0.3. Our results suggest that G-protein-coupled receptor-mediated signalling in platelet may be regulated mainly by RGS 18, 16, 10, 6, and LARG.

Animals↗

PubMed2004

Enhanced immunodetection of cell-free synthesized erythropoietin under denaturing conditions.

A monoclonal antibody produced by hydridoma cell line, ATCC HB8209, was used to detect and purify erythropoietin synthesized in a cell-free system. The antibody was raised against the N-terminal 20 residues of erythropoietin. It retained anti-erythropoietin activity in 6 M urea in which most of the cell-free synthesized erythropoietin became soluble and gave an enhanced activity of the antibody.

Animals↗

PubMed2004

Bisphosphonates may reduce recurrence in giant cell tumor by inducing apoptosis.

Giant cell tumor of bone is an aggressive tumor characterized by extensive bone destruction and high recurrence rates. This tumor consists of stromal cells and hematopoietic cells that interact in an autocrine manner to produce tumoral osteoclastogenesis and bone resorption. This autocrine regulation may be disrupted by novel therapeutic agents. Nonspecific local adjuvant therapies such as phenol or liquid nitrogen have been used in the treatment of giant cell tumor, but specific adjuvant therapies have not been described. The bisphosphonates pamidronate and Zoledronate can induce apoptosis in giant cell tumor culture in a dose-dependent manner. We established giant cell tumor cultures from patients with extensive destruction of bone. One of the four cultures formed osteoclastlike giant cells in vitro after more than six passages without exogenous receptor activator of NF-kappaB ligand or macrophage colony stimulating factor. Annexin V staining, presence of active cleaved form of caspase-3, and disappearance of poly (ADP-ribose) polymerase on Western blotting indicated activation of apoptosis by bisphosphonates in giant cell tumor. These results indicate that topical or systemic use of pamidronate or zoledronate can be a novel adjuvant therapy for giant cell tumor by targeting osteoclastlike giant cells, mononuclear giant cell precursor cells, and the autocrine loop of tumor osteoclastogenesis.

Annexin A5↗

PubMed2004

Electroacupuncture ameliorates experimental colitis induced by acetic acid in rat.

The effect of electroacupuncture (EA) on experimental colitis was investigated in Sprague-Dawley rats. Colitis was induced by intracolonic instillation of 4% acetic acid. EA (2 Hz, 0.05 ms, 2 V for 20 min) was applied to bilateral Hoku (LI-4) and Zusanli (ST-36) on 12 hrs and 36 hrs after induction of colitis. EA-treatment significantly reduced the macroscopic damage and the myeloperoxidase activity of colonic samples at 3 days post-induction of colitis. Colitic colon showed a decreased in vitro motility. However, colonic motility of EA-treated group was not significantly different from that of normal group. The anti-inflammatory effect of EA was not inhibited by a glucocorticoid receptor antagonist, RU-486, but suppressed by a beta-adrenoceptor antagonist, propranonol. These results suggest that EA-treatment has a beneficial effect on colitis, and its anti-inflammatory effect is mediated by beta-adrenoceptor activation but not by endogenous glucocorticoiddependent mechanism.

Acetic Acid↗

PubMed2003

Muscarinic regulation of pacemaker frequency in murine gastric interstitial cells of Cajal.

Peristaltic contractions in the stomach are regulated by the spread of electrical slow waves from the corpus to the pylorus. Gastric slow waves are generated and propagated by the interstitial cells of Cajal (ICC). All regions distal to the dominant pacemaker area in the corpus are capable of generating slow waves, but orderly gastric peristalsis depends upon a frequency gradient in which the corpus pacemaker frequency exceeds the antral frequency. Cholinergic, muscarinic stimulation enhances pacemaker frequency. We investigated this phenomenon using intact murine gastric muscles and cultured ICC. Acetylcholine (ACh) increased the frequency of slow waves in antrum and corpus muscles. The increase was significantly greater in the antrum. ACh and carbachol (CCh) increased the pacemaker currents in cultured ICC. At high doses of CCh, transient pacemaker currents fused into sustained inward currents that persisted for the duration of stimulation. The effects of CCh were blocked by low doses of the M(3) receptor antagonist 1-dimethyl-4-diphenylacetoxypiperidinium. Frequency enhancement by CCh was not affected by forskolin, but the phospholipase C inhibitor U-73122 inhibited both the increase in frequency and the development of tonic inward currents. 2-Aminoethyldiphenyl borate also blocked the chronotropic responses to CCh. Inhibitors of protein kinase C did not block responses to CCh. These studies show that mice are an excellent model for studying mechanisms that regulate gastric slow-wave frequency. CCh, apparently via production of inositol 1,4,5-trisphosphate, accelerates the frequency of pacemaker activity. High concentrations of CCh may block the entrainment of pacemaker currents, resulting in a tonic inward current.

Acetylcholine↗

PubMed2002

A Ca(2+)-inhibited non-selective cation conductance contributes to pacemaker currents in mouse interstitial cell of Cajal.

Interstitial cells of Cajal (ICC) provide pacemaker activity in some smooth muscles. The nature of the pacemaker conductance is unclear, but studies suggest that pacemaker activity is due to a voltage-independent, Ca(2+)-regulated, non-selective cation conductance. We investigated Ca(2+)-regulated conductances in murine intestinal ICC and found that reducing cytoplasmic Ca(2+) activates whole-cell inward currents and single-channel currents. Both the whole-cell currents and single-channel currents reversed at 0 mV when the equilibrium potentials of all ions present were far from 0 mV. Recordings from on-cell patches revealed oscillations in unitary currents at the frequency of pacemaker currents in ICC. Voltage-clamping cells to -60 mV did not change the oscillatory activity of channels in on-cell patches. Depolarizing cells with high external K(+) caused loss of resolvable single-channel currents, but the oscillatory single-channel currents were restored when the patches were stepped to negative potentials. Unitary currents were also resolved in excised patches. The single-channel conductance was 13 pS, and currents reversed at 0 mV. The channels responsible were strongly activated by 10(-7) M Ca(2+), and 10(-6) M Ca(2+) reduced activity. The 13 pS channels were strongly activated by the calmodulin inhibitors calmidazolium and W-7 in on-cell and excised patches. Calmidazolium and W-7 also activated a persistent inward current under whole-cell conditions. Murine ICC express Ca(2+)-inhibited, non-selective cation channels that are periodically activated at the same frequency as pacemaker currents. This conductance may contribute to the pacemaker current and generation of electrical slow waves in GI muscles.

Analgesics↗

PubMed2002

Regulation of pacemaker frequency in the murine gastric antrum.

PGE(2) has been linked to the production of gastric arrhythmias such as tachygastria. The interstitial cells of Cajal (ICC) generate electrical rhythmicity in gastrointestinal muscles, and may therefore be a target for PGE(2) in gastric muscles. We cultured ICC from the murine gastric antrum, verified that cells were Kit immunoreactive, and measured spontaneous slow waves. These events were caused by spontaneous inward (pacemaker) currents that were not blocked by nifedipine. Forskolin and 8-bromoadenosine 3':5'-cyclic monophosphate (8-Br-cAMP) reduced the frequency of pacemaker currents in ICC and of slow waves in intact antral muscles. The effects of forskolin and 8-Br-cAMP were not blocked by inhibitors of protein kinase A, suggesting that cAMP has direct effects on pacemaker activity. PGE(2) mimicked the effects of forskolin and 8-Br-cAMP on ICC, but increased slow-wave frequency in intact muscles. Therefore, the chronotropic effects of specific prostaglandin EP receptor agonists were examined. Butaprost and ONO-AE1-329, EP(2) and EP(4) receptor agonists, mimicked the effects of forskolin and 8-Br-cAMP on ICC and intact muscles. Sulprostone (EP(3)>EP(1) agonist), GR63799, and ONO-AE-248 (EP(3) agonists) enhanced the frequencies of pacemaker currents in ICC and slow waves in intact muscles. The effects of sulprostone were not blocked by SC-19220, an EP(1) receptor antagonist. These observations suggest that the positive chronotropic effects of PGE(2) in intact muscles are mediated by EP(3) receptor stimulation. The effects of PGE(2) in intact muscles may be dependent upon the relative expression of EP receptors and/or proximity of receptors to sources of PGE(2).

8-Bromo Cyclic Adenosine Monophosphate↗

PubMedDate not supplied

Development of an optimal medium for continuous ferrous iron oxidation by immobilized Acidothiobacillus ferrooxidans cells.

This study was aimed at developing an immobilized bioreactor system in which long-term continuous ferrous iron oxidation can be realized with no formation of jarosite, which causes clogging of support pores and reactor lines. For this purpose, a medium with no jarosite formation was developed first by selecting optimal nitrogen and phosphate sources and their concentrations. Then with the developed medium containing ammonium phosphate instead of ammonium sulfate and potassium phosphate, repeated batch and continuous operations of ferrous iron oxidation by Acidothiobacillus ferrooxidans cells immobilized in a depth filter were successfully performed for an extended period of time. For about 510 h of operation including 450 h of continuous operation at dilution rates of 0.1, 0.2, and 0.3 h(-)(1), no formation of jarosite and thus no clogging of the reactor system were observed. The maximum ferrous iron oxidation rate was as high as 2.6 g/(L.h) at a dilution rate of 0.3 h(-)(1).

Air Pollutants↗

PubMedDate not supplied

Production of soluble human interleukin-6 in cytoplasm by fed-batch culture of recombinant E. coli.

The major objective of this study is to identify fed-batch culture conditions optimal for the production of human interleukin-6 (hIL-6) in a soluble form. Five different expression vectors were constructed for the expression of hIL-6 and hIL-6s fused with NusA, maltose binding protein (MBP), thioredoxin (Trx) or ubiquitin (Ubi). A series of flask cultures were conducted in LB medium at 37 degrees C. The intact hIL-6 was expressed mostly in the form of inclusion body. More than 95% of the hIL-6 fused with NusA (NusA/hIL-6) and about 90% of MBP/hIL-6 were expressed in a soluble form, whereas Trx/hIL-6 and Ubi/hIL-6 were expressed mostly in the form of inclusion body. Based on this result, NusA was selected as the fusion partner for the production of hIL-6 in the subsequent experiments. A series of pH-stat fed-batch cultures of an E. coli BL21(DE3) transformed with a NusA/hIL-6 expression vector were conducted in a bioreactor with a working volume of about 3 L. As the amount of nitrogen source was increased in the feeding medium, more soluble NusA/hIL-6 was produced, while the total amount was not significantly changed. Under the best conditions tested, about 90% of NusA/hIL-6 was produced in the soluble form. In this case, the concentration of soluble NusA/hIL-6 was 7.5 g/L with a volumetric productivity of 0.43 g/L-h.

Base Sequence↗