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J H Sim

Publications and source records attributed to J H Sim.

12 recordsLinked to original sources
PubMed2003

Molecular basis and characteristics of KATP channel in human corporal smooth muscle cells.

Relaxation of the corpus cavernosum smooth muscle is an absolute prerequisite for penile erection. Potassium channels play a role in the physiologic regulation of corporal smooth muscle tone. In spite of the physiological importance of K(ATP) channel in the modulation of corporal smooth muscle tone, there is a shortage of information available about the K(ATP) channel subtype(s) present in the corporal smooth muscle. The purpose of this study was to investigate the subunit type of K(ATP) channel, that is, the combinations of the Kir subunit and the SUR subunit in the human corporal smooth muscle and determine whether the electrophysiological kinetics and pharmacological properties of K(ATP) channels meet the subunit characteristics of the ion channel. We used cultured human corporal smooth muscle cells. To determine the presence of Kir and SURs subunits, RT-PCR was performed using Kir6.1, Kir6.2, SUR1, SUR2A, and SUR2B gene-specific primers. For electrophysiological recordings, the whole-cell, inside-out, and cell-attached configurations of the patch-clamp technique were used. We observed transcripts for Kir6.1, Kir6.2, and SUR2B in mRNA isolated from smooth muscle cells of cultured human corpus carvernosum. We recorded the unitary K(ATP) channel under the condition of intracellular and extracellular 140 mM [K(+)], and the slope conductance of the channel was 42.0+/-2.6 pS which is an intermediate conductance between that of either Kir6.1 or Kir6.2. The pinacidil (10 microM) increased the magnitude of the outward K(+) current (214.6+/-89.2%, n=12, < or = 0.05), which was blocked by the subsequent addition of the specific K(ATP) channel subtype selective blocker, glibenclamide (10 microM). The SIN-1(200 microM) induced increases in whole-cell outward K(+) currents (126.0+/-1.4%, n=4). The increased currents by SIN-1 were inhibited by glibenclamide (10 microM). We are the first to show that K(ATP) channel in human corporal smooth muscle is composed of Kir6.1-Kir6.2 construct expressed with SUR2B by RT-PCR. These findings, taken together with the electrophysiological results, suggest that K(ATP) channel in corporal smooth muscle cells is composed of heteromultimers of Kir6.1 and Kir6.2 with the ratio of 3 : 1 or 4 : 0 and SUR2B.

ATP-Binding Cassette Transporters↗
PubMed2001

Capsaicin inhibits the voltage-operated calcium channels intracellularly in the antral circular myocytes of guinea-pig stomach.

Studies of the effect of capsaicin (CAP) on the smooth muscle contractions have shown both contraction and relaxation in various preparations. The direct effect of CAP on gastric smooth muscle itself has not yet been reported, though CAP was reported to relax the isolated guinea-pig stomach by releasing nitric oxide from the CAP-sensitive sensory neurons. Here we showed an evidence that CAP evokes a prolonged relaxation of gastric antral circular smooth muscle (CAP-induced relaxation) by blocking the voltage-operated Ca2+ channels (VOCC) from inside of the cell. CAP suppressed dose-dependently the spontaneous contractions of guinea-pig gastric circular muscle strip under the condition without neural influence (IC50 = 5.8 microM). The inhibitory effects of CAP both on the high K+ contracture induced by 50 mM K+ Tyrode solution and on the slow waves recorded using a conventional intracellular microelectrode technique were similar to those of Ca2+ channel antagonists, indicating that Ca2+ influx through the VOCC is decreased by CAP. Ca2+ channel current (I(Ba)) decreased in a concentration-dependent manner on superfusing the physiological salt solution containing various concentrations of CAP. The steady-state activation and inactivation curves of I(Ba) were not affected by the treatment with CAP. The experiment using a synthetic water-soluble analog of CAP, DA-5018 x HCl, suggested that the acting site of CAP is present in the intracellular side. Spontaneous transient outward K+ currents (STOCs) recorded at a holding potential of 0 mV were also inhibited by CAP and verapamil, Ca channel blocker. Taken together, these results indicate that CAP-induced relaxation is associated with the direct inhibitory action on the VOCC from inside of the cell.

Animals↗
PubMed2001

Protein kinase C suppresses spontaneous, transient, outwards K+ currents through modulation of the Na/Ca exchanger in guinea-pig gastric myocytes.

The effect of protein kinase C (PKC) on the Ca2+-activated K+ current (IK,Ca) in guinea-pig gastric myocytes was studied using the whole-cell voltage-clamp technique. At a holding potential of 0 mV, IK,Ca, recorded as spontaneous, transient, outwards currents (STOCs), was markedly inhibited, both in mean amplitude (54 +/- 5%) and frequency (60 +/- 8%) by 1 microM phorbol 12, 13 dibutyrate (PDBu, n = 6). These effects were antagonized by pretreatment with 10 nM bisindolylmaleimide I (n = 5), a selective inhibitor of PKC. The possibility that the inhibition of STOCs was due to direct channel inhibition by PKC was addressed using inside-out or open-cell-attached patch-clamp techniques, the latter established using beta-escin. PDBu did not alter the conductance or open probability of the KCa channel in any mode, suggesting that PKC does not inhibit the KCa channel directly. To study the involvement of the Na/Ca exchanger in the inhibition of STOCs by PDBu, its operation was prevented by replacing Na+ in the internal solution by tris(hydroxymethyl)aminomethane (TRIS) and external Na+ by equimolar K+ and Ca2+-activated inwards K+ currents recorded at a holding potential of 0 mV. Neither the mean amplitude (96 +/- 8%) nor the frequency of these currents was inhibited significantly by 1 microM PDBu (n = 5). Like PDBu, 5 microM 2-(2-[4-(4-nitrobenzyloxy)phenyl]ethyl) isothiourea methanesulphonate (KB-R7943), a selective inhibitor of the reverse mode Na/Ca exchanger, also inhibited the mean amplitude (45 +/- 6%) and frequency (26 +/- 2%) of STOCs at the holding potential of 0 mV (n=6). The results suggest that the suppression of STOCs by PKC is mediated by inhibition of the Na/Ca exchanger.

Animals↗
PubMed2001

The properties of carbachol-activated nonselective cation channels at the single channel level in guinea pig gastric myocytes.

We investigated the properties of carbachol (CCh)-activated nonselective cation channels (NSC(CCh)) at the single channel level in the gastric myocytes of guinea pigs using a magnified whole-cell mode or an outside-out mode. The channel activity (NPo) recorded in a magnified whole-cell mode increased with depolarization (from -120 to -20 mV) and had the half activation potential of -81 mV under the symmetrical 140 mM Cs+ condition. The single channel conductance depended upon the extracellular monovalent cations with the order of Cs+ (35 pS) > Na+ (25 pS) > Li+ (21 pS). The channel activities markedly diminished or disappeared when external Cs+ was replaced with Na+ or N-methyl-D-glucamate (NMDG+). With Cs+ and Na+ as external cations, the channel showed a monotonic increase in NPo with the increased mole fraction of Cs+ over Na+, and it had an intermediate conductance value in solution containing 67% Cs+ with 33% Na+. These data suggested that the extracellular monovalent cations regulate the whole-cell current of NSC(CCh) by modulating both the open state probability and the unitary conductance, and there is one binding site for the extracellular cations within the pore.

Animals↗
PubMed2000

Background nonselective cationic current and the resting membrane potential in rabbit aorta endothelial cells.

The ion channel conductances that regulate the membrane potential was investigated by using a perforated patch-clamp technique in rabbit aorta endothelial cells (RAECs). The whole-cell current/voltage (I-V) relation showed a slight outward rectification under physiological ionic conditions. The resting membrane potential was -23.3 +/- 1.1 mV (mean +/- SEM, n = 19). The slope conductances at the potentials of -80 and 50 mV were 31.0 +/- 4.0 and 62.8 +/- 7.1 pS pF(-1), respectively (n = 15). Changes in the extracellular and intracellular Cl(-) concentrations did not affect the reversal potential on I-V curves. The background nonselective cationic (NSC) current was isolated after the K(+) current was suppressed. The relative permeabilities calculated from the changes in reversal potentials using the constant-field theory were P(K):P(Cs):P(Na):P(Li) = 1:0.87:0.40:0.27 and P(Cs):P(Ca) = 1:0.21. Increases in the external Ca(2+) decreased the background NSC current in a dose-dependent manner. The concentration for half block by Ca(2+) was 1.1 +/- 0.3 mM (n = 7). Through the continuous recording of the membrane potential in a current-clamp mode, it was found that the background NSC conductance is the major determinant of resting membrane potential. Taken together, it could be concluded that the background NSC channels function as the major determinant for the resting membrane potential and can be responsible for the background Ca(2+) entry pathway in freshly isolated RAECs.

Animals↗
PubMed1999

Gamma Knife radiosurgery for functioning pituitary microadenoma.

Transsphenoidal microsurgery remains the treatment of choice for pituitary microadenomas One hundred and six patients were treated with Gamma Knife radiosurgery (GKRS) for pituitary adenomas, and of these, 23 patients (1 male, 22 female) had microadenomas. Twenty-two of these patients were followed up and endocrinological tests were available for 15 of these 22. Thirteen of these 15 had prolactinomas, while the remaining 2 had acromegaly. The follow-up period was from 3 to 26 months (median 12 months). The mean age was 33.6 years (range 21 to 60 years). The mean maximum tumor dose was 35.7 Gy and the mean margin dose was 22 Gy. Serum prolactin (PRL) was normalized in three patients, decreased in eight and unchanged in two. The growth hormone (GH) secretion in the acromegalic patients has remained unchanged through the follow-up period. Thus, GKRS is a valuable adjuvant to transsphenoidal microsurgery for patients with pituitary microadenomas.

Acromegaly↗
PubMed1999

A case of very large cyst formation with Gamma Knife radiosurgery for an arteriovenous malformation.

A 17-year-old male patient underwent Gamma Knife radiosurgery (GKRS) for a left parietal arteriovenous malformation (AVM), which presented with hemorrhage. The 15.0 cm3 nidus was covered with the 50% isodose. The maximum dose was 50 Gy and the margin dose was 25 Gy. Eleven months later he developed a right hemiparesis and MRI showed a large cyst. Cerebral angiography showed partial obliteration of the AVM nidus. Stereotactic removal of cyst fluid (about 70 cm3) was performed, and an Ommaya reservoir was inserted. Cyst formation after GKRS for cerebral arteriovenous malformation is a is side effect of radiosurgery about which we need to learn more.

Adolescent↗
PubMed1998

Protein kinase C mediates the desensitization of CCh-activated nonselective cationic current in guinea-pig gastric myocytes.

The possibility of the protein kinase C (PKC) pathway being a mechanism underlying the desensitization of carbachol- (CCh-)activated nonselective cationic current (ICCh) was investigated in a study of guinea-pig gastric myocytes. Using the conventional whole-cell patch-clamp technique with symmetrical CsCl-rich solution in pipette and bath, ICCh was induced by bath application of 50 microM CCh. With 0.5 mM EGTA [ethyleneglycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid] in the pipette solution (0.5 mM [EGTA]i), ICCh decayed spontaneously (desensitization of ICCh) to around 20% within 10 min. Desensitization of ICCh was significantly attenuated with 2 mM [EGTA]i. At a concentration of 20 microM OAG (1-oleoyl-2-acetyl-sn-glycerol), a PKC activator, inhibited ICCh at 0.5 mM [EGTA]i but far less at 2 mM [EGTA]i (18% and 81% of control, respectively). The same cationic current induced by intracellular guanosine-5'-O-(3-thiotriphosphate) (GTP[gamma-S]) was not inhibited by OAG with 0.5 mM [EGTA]i. The pretreatment of gastric myocytes with PKC inhibitors, either 1 microM chelerythrine or 1 microM peptide inhibitor, attenuated the desensitization of ICCh. [Ca2+]i was also measured by single cell microfluorometry using fura-2. Under CCh stimulation with 2 mM [EGTA]i, [Ca2+]i did not increase above 100 nM while it increased to around 260 nM with 0.5 mM [EGTA]i. These results suggest that the desensitization of ICCh is partly due to the Ca2+-dependent PKC pathway in guinea-pig gastric myocytes.

Amino Acid Sequence↗
PubMed1998

Suppression of the carbachol-activated nonselective cationic current by antibody against alpha subunit of Go protein in guinea-pig gastric myocytes.

In this study, we investigated which subtype of GTP-binding protein (G protein) is related to muscarinic activation of nonselective cation (NSC) channels in gastric smooth muscle. Inward cationic current was activated by the application of 50 microM carbachol (ICCh) at a holding potential of -60 mV with the same CsCl-rich solution in both pipette and bath. The same cationic current as ICCh was slowly activated by the dialysis of guanosine 5'-O-(3-thiotriphosphate) (GTP[gamma-S]) through the pipette. Since it is known that pertussis toxin pretreatment can block ICCh, antibodies (Abs) against Galpha,i (anti-Galpha,i) or Galpha,o (anti-Galpha,o) were tested. Activation of ICCh was blocked by the addition of anti-Galpha,o. However, anti-Galpha,i Abs had no significant effect on ICCh. The expression of Galpha,o in guinea-pig gastric smooth muscle was confirmed by Western immunoblot analysis. These results suggest that Go-type protein may mediate signals from the muscarinic receptor to NSC channel in guinea-pig gastric myocytes.

Animals↗
PubMed1998

Intracranial aneurysms in Korea.

We have 32 university hospitals and 18 general hospitals for neurosurgical training in Korea. Recently I have analyzed intracranial aneurysm cases which had an operation in 28 university hospitals and nine general hospitals. I have reported 2863 aneurysm operation cases. The location of aneurysm consisted of 865 aneurysms (30.2%) in the anterior communicating artery, 724 aneurysms (25.3%) in the internal carotid artery, 687 aneurysms (24.0%) in the middle cerebral artery, 129 aneurysms (4.5%) in the anterior cerebral artery, 152 aneurysms (5.3%) in the posterior circulation, and 306 (10.7%) multiple aneurysms. The overall approximation of the operation rate of aneurysm is approximately 6.6 cases per 100,000 population in 1996 in Korea.

Humans↗
PubMed1996

Separation of recombinant human growth hormone from Escherichia coli cell pellet extract by capillary zone electrophoresis.

Free zone capillary electrophoresis (FZCE) was used to resolve recombinant human growth hormone (rhGH) and its variants from very crude mixtures of Escherichia coli (E. coli) cell paste extract. The methodology employs a phosphate deactivated fused-silica capillary and a 250 mM phosphate (pH 6.8), 1% (v/v) propylene glycol buffer with a high field strength of 600 V/cm. Resolution of rhGH and its variants from very crude mixtures did not change after 80 injections for the PSC capillaries. Bare silica and PVA coated capillaries had a more limited lifetime when injected with the same crude mixtures (10 to 30 injections). This FZC method provides a very powerful tool for assessing rhGH modification during the fermentation and isolation of rhGH that is not possible with other current analytical techniques.

Cell Extracts↗