Biomedical subjects

K W Cho

Publications and source records attributed to K W Cho.

At least 19 recordsLinked to original sources

PubMed2003

Seroprevalence of canine dirofilariosis in South Korea.

Eight-hundred and forty eight dogs (480 females and 368 males) not on chemoprophylaxis were examined for Dirofilaria immitis infection from 2001 to 2002. Three-hundred and thirty nine (40.0%) of 848 samples tested with antigen detecting ELISA kits showed positive reaction for D. immitis antigen. More male (43.5%) than female (37.3%) dogs were affected in this study, although there was no significant difference between both groups. Chi2 analysis showed that female and male dogs of shoreline areas had higher significant prevalence than other areas (P<0.001), respectively. The mean overall positive rates of heartworm infection were 10.4% in dogs <2-year-old group, 46.5% in 2-4-year-old group, 48.4% in 4-6-year-old group and 50.3% in >6-year-old group. The older the age, the higher the prevalence of D. immitis infection in this study. Chi2 analysis revealed a significant higher prevalence in 4-6-year-old group (100%) of shoreline areas and in 2-4-old-year group (51.2%) of urban areas (Chungnam province), respectively (P<0.001), and also revealed that the over 6-year-old group (50.3%) in mean overall prevalence had the significant higher prevalence than other age group (P<0.001). In climate comparison, our data showed that shoreline areas (69.5%) had the significant higher prevalence than urban areas and mountain areas (P<0.001). This survey confirms that the prevalence of canine heartworm infection increases, and also that the prevalence in shoreline areas is higher than in other areas in South Korea.

Age Distribution↗

PubMed2002

Nociceptin/orphanin FQ increases ANP secretion in neonatal cardiac myocytes.

Nociceptin (N/OFQ) is a novel heptadecapeptide with an amino acid sequence similar to that of endogenous opioid peptide dynorphin A. Dynorphin have been reported to increase the secretion of atrial natriuretic peptide (ANP) via selective activation of kappa-opioid receptor in cultured atrial cardiocytes. The present study was designed to investigate the direct effect of N/OFQ on the ANP secretion in cultured neonatal rat cardiac myocytes via N/OFQ receptor (NOP) activation. The secretion of ANP from cultured neonatal cardiac myocytes was increased in terms of incubation time. N/OFQ, at a dose of 0.3, 1, 3, and 10 microM, caused increases in ANP secretion in a dose-dependent manner. The N/OFQ-induced ANP secretion was completely antagonized by antagonists of NOP, 1 microM each of [Phe1 (CH2-NH) Gly2] nociceptin (1-13)-NH2 ([FG]N/OFQ(1-13)NH2) or naloxone benzoylhydrazone. In contrast, naloxone (1 microM), the non-selective opioid receptor antagonist, did not alter ANP response to N/OFQ. N/OFQ at 3 microM inhibited basal and forskolin-stimulated cAMP production, which was partially antagonized with the pretreatment of [FG]N/OFQ(1-13)NH2. An increase in ANP secretion by N/OFQ was also partially blocked by the pretreatment of forskolin. Homologous competition studies in neonatal cardiomyocyte membranes revealed the presence of two distinct sites. The high affinity site (10.9 +/- 1.6 nM) was far less abundant than the low affinity site. Therefore, these results suggest that N/OFQ causes an increase in ANP secretion in cultured neonatal cardiac myocytes by decreasing cAMP through its binding sites.

Animals↗

PubMed2002

Comparison of effects of angiotensin peptides in the regulation of clitoral cavernosum smooth muscle tone.

The isometric tension measurement and in vitro autoradiography were used in clitoral cavernosum smooth muscle (CSM). Angiotensin ANG III, ANG IV, ANG II and ANG I induced contractions in clitoral CSM strips. ANG III and ANG I- induced contraction was five times less active than ANG II, whereas ANG IV-induced contraction was 1181-fold less potent than ANG II. Contractile responses to ANG III, ANG IV, ANG II and ANG I were significantly inhibited by type 1 ANG II (AT 1) receptor antagonist Dup 753 but not by type 2 ANG II (AT2) receptor antagonist PD 123,319. Pre-treatment with Nomega-nitro-L-arginine methyl ester, nitric oxide (NO) synthase inhibitor accentuated force of contraction induced by ANG III, ANG IV and ANG II. Amastatin, an aminopeptidase inhibitor enhanced ANG III- and ANG IV-induced contractions. Specific binding sites for 125I-ANG II were found in the clitoral CSM. Specific binding of 125I-ANG II was displaced by unlabeled ANG peptides. This study suggests that the contractile responses to all four peptides of the ANG family are mediated via AT1 receptors but not AT2 receptors. Further, the rank order of potency of contraction was as follows, ANG II> ANG I>ANG III>ANG IV. It is also suggested that peptides of the ANG family have a cross-talk with the NO system and aminopeptidase is involved in the modulation of the tone of clitoral CSM by ANG III and ANG IV.

Acetylcholine↗

PubMed2002

Role of rho-kinase activity in angiotensin II-induced contraction of rabbit clitoral cavernosum smooth muscle.

Isometric tension measurement using a selective Rho-kinase inhibitor (+)- (R)-trans4-(1-aminoethyl)-N-(4-pyridyl)cyclohexanecarboxamide (Y-27632) and a selective myosin light chain kinase (MLCK) inhibitor 1-(5-iodonaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine hydrochloride (ML7) were used in rabbit clitoral cavernosum smooth muscle (CSM). N(G)-nitro-L-arginine methyl ester (L-NAME) was used to evaluate the relationship between NO release and Rho-kinase. Y-27632 significantly attenuated contractions induced by ANG II, dose-dependently. However, ML7 did not affect the contractile response to ANG II except in the high concentrations of ML7. Y-27632 inhibited contraction with phenylephrine (PhE), but ML7 did not inhibit contraction with PhE. Nitric oxide synthase inhibitor (NAME) did not affect the Y-27632-induced relaxation in the pre-contracted strip with PhE. The present study demonstrates that G-protein-coupled increase in myofilament Ca(2+) sensitivity mediated through the RhoA/Rho-kinase signal pathway is involved in the control by ANG II of the clitoral CSM tone. RhoA/Rho-kinase pathway acts in the ANG II-induced contraction independently of the NO pathway.

Amides↗

PubMed2001

Intracellular BMP signaling regulation in vertebrates: pathway or network?

Bone morphogenetic proteins (BMPs), members of the TGF-beta superfamily of secreted signaling molecules, have important functions in many biological contexts. They bind to specific serine/threonine kinase receptors, which transduce the signal to the nucleus through Smad proteins. The question of how BMPs can have such diverse effects while using the same canonical Smad pathway has recently come closer to an answer at the molecular level. Nuclear cofactors have been identified that cooperate with the Smads in regulating specific target genes depending on the cellular context. In addition, the pivotal role BMP signaling plays is underscored by the identification of factors that regulate members of this pathway at the cell surface, in the cytoplasm, and in the nucleus. Many of these factors are BMP-inducible and inhibit the BMP pathway, thus establishing negative feedback loops. Members of the BMP-Smad pathway can also physically interact with components of other signaling pathways to establish crosstalk. Finally, there is accumulating evidence that an alternative pathway involving MAP kinases can transduce BMP signals. The evidence and implications of these findings are discussed with an emphasis on early embryonic development of Xenopus and vertebrates.

Animals↗

PubMed2001

Accentuation of ANP secretion to endothelin-1 in hypertrophied atria.

To investigate modulation of ANP secretion by atrial hypertrophy, the secretion of ANP in response to stretch and endothelin-1 was studied using isolated perfused quiescent atria from rats treated with monocrotaline (MCT). Male Sprague-Dawley rats were given a single subcutaneous injection of 50 mg/kg MCT or saline and were sacrificed at 6 weeks. Rats with right heart hypertrophy showed an increase in ANP mRNA and decrease in tissue concentration of ANP in hypertrophied atria and a marked increase in plasma concentration of ANP. In isolated perfused hypertrophied right atria from MCT rats, changes in atrial volume induced by increased atrial pressure caused proportional increases in mechanically stimulated extracellular fluid (ECF) translocation and stretch-activated ANP secretion. Changes in atrial volume and mechanically stimulated ECF translocation in hypertrophied right atria were not different from those in control right atria. The stretch-activated ANP secretion was suppressed without significant difference in basal ANP secretion, as compared to control right atria. Therefore, the stretch-activated ANP secretion from hypertrophied right atria into the atrial lumen in relation to the ECF translocation (ANP concentration in the interstitium) was lower than that from control atria. A positive correlation between the stretch-activated ANP secretion in relation to the ECF translocation and tissue ANP content was found in control atria but not in hypertrophied atria. Endothelin-1 caused increases in stretch-activated ANP secretion in a dose-dependent manner, which were accentuated in hypertrophied right atria. Therefore, we suggest that atrial hypertrophy causes an attenuated response to stretch and accentuated response to endothelin-1 of ANP secretion.

Animals↗

PubMed2001

Homologues of Twisted gastrulation are extracellular cofactors in antagonism of BMP signalling.

Twisted gastrulation (TSG) is involved in specifying the dorsal-most cell fate in Drosophila embryos, but its mechanism of action is poorly understood. TSG has been proposed to modify the action of Short gastrulation (SOG), thereby increasing signalling by the bone morphogenetic protein (BMP) Decapentaplegic. SOG, an inhibitor of BMP signalling, is in turn inactivated by the protease Tolloid. Here we identify Tsg gene products from human, mouse, Xenopus, zebrafish and chick. Expression patterns in mouse and Xenopus embryos are consistent with in vivo interactions between Tsg, BMPs and the vertebrate SOG orthologue, chordin. We show that Tsg binds both the vertebrate Decapentaplegic orthologue BMP4 and chordin, and that these interactions have multiple effects. Tsg increases chordin's binding of BMP4, potentiates chordin's ability to induce secondary axes in Xenopus embryos, and enhances chordin cleavage by vertebrate tolloid-related proteases at a site poorly used in Tsg's absence; also, the presence of Tsg enhances the secondary axis-inducing activity of two products of chordin cleavage. We conclude that Tsg acts as a cofactor in chordin's antagonism of BMP signalling.

Amino Acid Sequence↗

PubMed2001

C-type natriuretic peptide system in rabbit oviduct.

C-type natriuretic peptide (CNP), a third member of the natriuretic peptide family, is known to be distributed mainly in brain and vascular endothelium and is considered to act as a local regulator in many tissues. The purpose of this study was to determine the presence of CNP system and its biological function in rabbit oviduct. The serial dilution curve of tissue extracts was parallel to the standard curve of CNP((1-22)) and a major peak of molecular profile of tissue extracts by HPLC was CNP((1-53)). mRNA of CNP which was the same size as positive control was also detected by Southern blot analysis. CNP increased the production of 3',5'-cyclic guanosine monophosphate (cGMP) in the purified membrane of oviduct, which was more in membranes derived from the isthmic portion than in the ampullar portion. The presence of mRNAs of natriuretic peptide receptor-A (NPR-A) and NPR-B was demonstrated by RT-PCR. Synthetic CNP((1-22)) inhibited both frequency and amplitude of basal motility of oviduct in a dose-dependent manner. The inhibitory effect of CNP on the basal motility was more potent in the isthmic portion than in the ampullar portion. These results demonstrate the presence of CNP system in the oviduct and regional differences in motility inhibition by CNP between isthmic and ampullar portions. Therefore, these findings suggest the possible existence of a CNP system that may exert a local regulator of basal motility, either alone or in concert with other hormones.

Animals↗

PubMed2001

C-type natriuretic peptide system in rabbit colon.

C-type natriuretic peptide (CNP) is mainly distributed in the brain and vascular endothelium and is considered to act as a local regulator in many tissues. The present study was aimed to determine the presence of CNP system and its biological function in rabbit colon. The serial dilution curves of tissue extracts were parallel to the standard curve of CNP-22. With gel permeation chromatography and reverse-phase HPLC, the major immunoreactive peak of CNP was observed at the same elution time corresponding to the synthetic CNP-53. The concentration of CNP in the mucosal layer of colon was 212.49 +/- 30.44 pg/g tissue wet weight (n = 7), which was significantly higher than that in the muscular layer. The presence of CNP mRNA was also detected by RT-PCR and Southern blot analysis. Production of cGMP by the activation of particulate guanylyl cyclase stimulated by BNP and CNP was higher in membranes obtained from the muscular layer than from mucosal layer. More cGMP was produced by CNP than by ANP. Both natriuretic peptide receptor-A and -B mRNAs were detected by RT-PCR and specific binding sites to 125I-[Tyr(0)]-CNP-22 were mainly localized to the muscular layer. Synthetic CNP inhibited basal tension, frequency and amplitude of basal motility of taenia coli of the right colon. This study showing the presence of CNP system and its biological function in colon suggests that endogenous CNP synthesized in the mucosal layer may have a paracrine function as a local regulator of colonic motility.

Animals↗

PubMed2001

Data mining approach to policy analysis in a health insurance domain.

This study examined the characteristics of the knowledge discovery and data mining algorithms to demonstrate how they can be used to predict health outcomes and provide policy information for hypertension management using the Korea Medical Insurance Corporation database. Specifically, this study validated the predictive power of data mining algorithms by comparing the performance of logistic regression and two decision tree algorithms, CHIAD (Chi-squared Automatic Interaction Detection) and C5.0 (a variant of C4.5) using the test set of 4588 beneficiaries and the training set of 13,689 beneficiaries. Contrary to the previous study, the CHIAD algorithm performed better than the logistic regression in predicting hypertension, and C5.0 had the lowest predictive power. In addition, the CHIAD algorithm and the association rule also provided the segment-specific information for the risk factors and target group that may be used in a policy analysis for hypertension management.

Algorithms↗

PubMed2001

New xenicane diterpenoids from the gorgonian Acalycigorgia inermis.

Eight diterpenes and norditerpenes including five new xenicane metabolites (4--8) have been isolated from the gorgonian Acalycigorgia inermis. The structures of these compounds have been determined by combined spectroscopic analysis. The new compounds exhibited significant cytotoxicity against a human leukemia cell-line.

Animals↗

PubMed2001

New lactone-containing metabolites from a marine-derived bacterium of the genus Streptomyces.

Six novel metabolites containing a lactone moiety as a common structural feature, along with the previously described (-)-blastmycinolactol, have been isolated from the cultivation broth of a bacterium of the genus Streptomyces isolated from marine sediment. On the basis of the results of combined spectroscopic analysis, the structures of the new compounds have been determined as butenolides and 3-hydroxy-gamma-butyrolactones.

Antifungal Agents↗

PubMed2001

New triterpenoid saponins from the sponge Erylus nobilis.

Erylosides G--J (1--4), four new triterpenoid saponins, were isolated from the sponge Erylus nobilis collected from Jaeju Island, Korea. On the basis of the results of combined chemical and spectral analyses, the structures of the aglycones were determined to be lanostane-based, modified penasterols. The oligosaccharide portions were composed of one unit each of L-arabinose, D-galactose, and 2-N-acetyl-D-glucosamine (1 and 3) or two units of L-arabinose and one unit of 2-N-acetyl-D-glucosamine (2 and 4). These compounds exhibited moderate cytotoxicty against a human leukemia cell line.

Animals↗

PubMed2001

New farnesylhydroquinone glycosides from the gorgonian Euplexaura anastomosans.

Euplexides F (3) and G (4), novel farnesylhydroquinone glycosides, have been isolated as minor constituents of the gorgonian Euplexaura anastomosans. The structures of these compounds have been determined by combined spectroscopic methods. These compounds exhibited moderate cytotoxicity and inhibitory activity against PLA2.

Animals↗

PubMed2001

Attenuation of inhibitory effect of CNP on the secretion of ANP from hypertrophied atria.

It has been shown that atrial natriuretic peptide (ANP) influences proliferation of cardiac cells. To define the possible role of C-type natriuretic peptide (CNP) in cardiac hypertrophy, the influence of CNP on the secretion of ANP was studied with the use of perfused nonbeating atria from monocrotaline-treated rats. Increases in atrial volume caused proportional increases in ANP secretion that were markedly suppressed by CNP (10(-6) M) in nonhypertrophied left atria and control right atria but not in hypertrophied right atria. However, increases in atrial volume and mechanically stimulated extracellular fluid (ECF) translocation by CNP were similar to those in the control group. Therefore, the secretion of ANP in terms of ECF translocation was decreased by CNP in nonhypertrophied left and control right atria but not in hypertrophied atria. However, the inhibitory effect of 8-bromo-cGMP on the secretion of ANP was observed in both atria. The cGMP productions from perfused hypertrophied atria and their membranes exposed to CNP were significantly lower than those from nonhypertrophied atria. No significant difference in natriuretic peptide receptor-B transcript was found. Therefore, attenuation of the inhibitory effect of CNP on the ANP secretion in hypertrophied atria may be due to lack of cGMP production. The results showing the relief of CNP-induced negative inhibition of ANP secretion by atrial hypertrophy suggest that CNP may be a contributing factor to delay the development of cardiac hypertrophy.

Animals↗

PubMed2001

High glucose dialysis solutions increase synthesis of vascular endothelial growth factors by peritoneal vascular endothelial cells.

OBJECTIVE: Increased peritoneal vasculature has been reported in long-term peritoneal dialysis (PD), and vascular endothelial growth factors (VEGFs) have been found in dialysate. High concentrations of glucose or lactate, glucose degradation products (GDPs), and low pH of dialysis solutions are all possible factors in increased peritoneal VEGF synthesis. In this study, we investigated the effects of high glucose dialysis solutions on VEGF synthesis by peritoneal vascular endothelial cells (PVECs). METHODS: The PVECs were isolated from rat omentum and were incubated for 4 hours in three different culture media [M199 media (control), conventional dialysis solutions containing 4.25% glucose diluted with an equal volume of M199 media (HGD), and M199 media containing 118 mmol/L mannitol as an osmolar control (mannitol)]. Levels of VEGF protein in the culture supernatant were measured by ELISA, and mRNA expression was determined by Northern blot analysis. Data are presented as percent of control. RESULTS: After incubation for 4 hours, the number of cells did not differ between the 3 groups. Levels of VEGF in culture supernatant were significantly higher in the HGD group (124% +/- 19%, p = 0.006) as compared with the control and mannitol (85% +/- 10%) groups. The mRNA expression of VEGF appeared to be higher in the HGD group (128% +/- 49%) than in the control and mannitol (94% +/- 18%) groups. CONCLUSION: High glucose dialysis solutions increased VEGF synthesis by PVECs. The relationship between VEGF synthesis by PVECs and neovascularization of the peritoneum observed in long-term peritoneal dialysis patients has to be studied further.

Animals↗

PubMed2000

Effects of pituitary adenylate cyclase activating polypeptide27 on cyclic AMP efflux and atrial dynamics in perfused beating atria.

Although pituitary adenylate cyclase activating polypeptide (PACAP) has been shown to increase cardiac force of contraction and to change the heart rate, the effect of PACAP on cyclic (c) AMP production in the atrium still has to be defined. In the present experiments, a simple protocol was developed for the evaluation of cAMP production in real-time base in the perfused beating left atria. The PACAP27-induced cAMP efflux in the atrial perfusate reflected changes in the production of cAMP in the atrial tissue. cAMP efflux was measured as an indicator of cAMP production in beating perfused rabbit atria. PACAP27 increased cAMP production in a dose- and time-dependent manner with a minor effect on atrial dynamics. These results suggest that PACAP27 has other roles besides control of force of contraction through cAMP production in the atrium.

1-Methyl-3-isobutylxanthine↗

PubMed2000

Xlim-1 and LIM domain binding protein 1 cooperate with various transcription factors in the regulation of the goosecoid promoter.

The homeobox genes Xlim-1 and goosecoid (gsc) are coexpressed in the Spemann organizer and later in the prechordal plate that acts as head organizer. Based on our previous finding that gsc is a possible target gene for Xlim-1, we studied the regulation of gsc transcription by Xlim-1 and other regulatory genes expressed at gastrula stages, by using gsc-luciferase reporter constructs injected into animal explants. A 492-bp upstream region of the gsc promoter responds to Xlim-1/3m, an activated form of Xlim-1, and to a combination of wild-type Xlim-1 and Ldb1, a LIM domain binding protein, supporting the view that gsc is a direct target of Xlim-1. Footprint and electrophoretic mobility shift assays with GST-homeodomain fusion proteins and embryo extracts overexpressing FLAG-tagged full-length proteins showed that the Xlim-1 homeodomain or Xlim-1/Ldb1 complex recognize several TAATXY core elements in the 492-bp upstream region, where XY is TA, TG, CA, or GG. Some of these elements are also bound by the ventral factor PV.1, whereas a TAATCT element did not bind Xlim-1 or PV.1 but did bind the anterior factors Otx2 and Gsc. These proteins modulate the activity of the gsc reporter in animal caps: Otx2 activates the reporter synergistically with Xlim-1 plus Ldb1, whereas Gsc and PV.1 strongly repress reporter activity. We show further, using animal cap assays, that the endogenous gsc gene was synergistically activated by Xlim-1, Ldb1, and Otx2 and that the endogenous otx2 gene was activated by Xlim-1/3m, and this activation was suppressed by the posterior factor Xbra. Based on these data, we propose a model for gene interactions in the specification of dorsoventral and anteroposterior differences in the mesoderm during gastrulation.

Animals↗