Biomedical subjects

D Kim

Publications and source records attributed to D Kim.

At least 181 records · Page 10Linked to original sources

PubMed2000

Cytoplasmic unsaturated free fatty acids inhibit ATP-dependent gating of the G protein-gated K(+) channel.

This study reports the identification of an endogenous inhibitor of the G protein-gated (K(ACh)) channel and its effect on the K(ACh) channel kinetics. In the presence of acetylcholine in the pipette, K(ACh) channels in inside-out atrial patches were activated by applying GTP to the cytoplasmic side of the membrane. In these patches, addition of physiological concentration of intracellular ATP (4 mM) upregulated K(ACh) channel activity approximately fivefold and induced long-lived openings. However, such ATP-dependent gating is normally not observed in cell-attached patches, indicating that an endogenous substance that inhibits the ATP effect is present in the cell. We searched for such an inhibitor in the cell. ATP-dependent gating of the K(ACh) channel was inhibited by the addition of the cytosolic fraction of rat atrial or brain tissues. The lipid component of the cytosolic fraction was found to contain the inhibitory activity. To identify the lipid inhibitor, we tested the effect of approximately 40 different lipid molecules. Among the lipids tested, only unsaturated free fatty acids such as oleic, linoleic, and arachidonic acids (0.2-2 microM) reversibly inhibited the ATP-dependent gating of native K(ACh) channels in atrial cells and hippocampal neurons, and of recombinant K(ACh) channels (GIRK1/4 and GIRK1/2) expressed in oocytes. Unsaturated free fatty acids also inhibited phosphatidylinositol-4, 5-bisphosphate (PIP(2))-induced changes in K(ACh) channel kinetics but were ineffective against ATP-activated background K(1) channels and PIP(2)-activated K(ATP) channels. These results show that during agonist-induced activation, unsaturated free fatty acids in the cytoplasm help to keep the cardiac and neuronal K(ACh) channels downregulated by antagonizing their ATP-dependent gating. The opposing effects of ATP and free fatty acids represent a novel regulatory mechanism for the G protein-gated K(+) channel.

Acetylcholine↗

PubMed2000

Differential expression of eight chitinase genes in Medicago truncatula roots during mycorrhiza formation, nodulation, and pathogen infection.

Expression of eight different chitinase genes, representing members of five chitinase classes, was studied in Medicago truncatula roots during formation of arbuscular mycorrhiza with Glomus intraradices, nodulation with Rhizobium meliloti, and pathogen attack by Phytophthora megasperma f. sp. medicaginis, Fusarium solani f. sp. phaseoli (compatible interactions with root rot symptoms), Ascochyta pisi (compatible, symptomless), and F. solani f. sp. pisi (incompatible, nonhost interaction). In the compatible plant-pathogen interactions, expression of class I, II, and IV chitinase genes was enhanced. The same genes were induced during nodulation. Transcripts of class I and II chitinase genes accumulated transiently during early stages of the interaction, and transcripts of the class IV chitinase gene accumulated in mature nodules. The pattern of chitinase gene expression in mycorrhizal roots was markedly different: Expression of class I, II, and IV chitinase genes was not enhanced, whereas expression of three class III chitinase genes, with almost no basal expression, was strongly induced. Two of these three (Mtchitinase III-2 and Mtchitinase III-3) were not induced at all in interactions with pathogens and rhizobia. Thus, the expression of two mycorrhiza-specific class III chitinase genes can be considered a hallmark for the establishment of arbuscular mycorrhiza in Medicago truncatula.

Amino Acid Sequence↗

PubMed2000

The effects of plasma fentanyl concentrations on propofol requirement, emergence from anesthesia, and postoperative analgesia in propofol-nitrous oxide anesthesia.

UNLABELLED: To determine the effects of plasma fentanyl concentrations on intraoperative propofol requirements, emergence from anesthesia, and relief of postoperative pain, we studied 60 ASA physical status I and II patients undergoing spine fusion. The patients were randomly assigned to four study groups according to the expected intraoperative plasma fentanyl concentrations. Group I received an infusion of saline, and Groups II, III, and IV received fentanyl infusions to maintain the blood levels at 1.5, 3.0, and 4.5 ng/mL, respectively. An infusion rate of propofol was adjusted to keep the mean arterial pressure within 15% of the control value. Inspired nitrous oxide concentrations were maintained at 67%. The following were investigated in each group: 1) an average propofol infusion rate, 2) time to spontaneous eye opening and recovery of orientation (name, date, and place), and 3) total dose of fentanyl used for 24 h after admission to the postanesthetic care unit. Average propofol infusion rates were 10.1 +/- 2.5 (mean +/- SD), 7.5 +/- 1.2, 5.7 +/- 1.1, and 4.9 +/- 1.2 mg. kg(-1). h(-1), in Groups I, II, III, and IV, respectively. Groups receiving fentanyl infusion had significantly smaller infusion rates of propofol (P < 0.01) than the group receiving saline. Among the three fentanyl infusion groups, Group II (P < 0.01) had more than Groups III and IV. The time to spontaneous eye opening and the recovery of orientation were directly related to plasma fentanyl concentrations. The plasma fentanyl levels between Groups III and IV were the same. The total amount of IV patient-controlled analgesia fentanyl during postoperative 24 h increased significantly when the order of plasma fentanyl concentrations was reversed, 913.1 +/- 58.4, 553.4 +/- 129, 222.7 +/- 73.4, and 135.1 +/- 69.5 microg in Groups I, II, III, and IV, respectively. These results suggest that the addition of fentanyl infusions had ceiling effects that reduce the intraoperative propofol requirements according to the plasma fentanyl concentrations. The ceiling effect was demonstrated in the recovery of consciousness but not in the fentanyl requirements for postoperative analgesia. IMPLICATIONS: The addition of fentanyl, a potent opioid, reduced the intraoperative requirement of propofol, an IV anesthetic, in the order of the plasma fentanyl concentrations. The ceiling effects of fentanyl were demonstrated in the reduction of propofol requirements and recovery of consciousness but not in the fentanyl requirements for postoperative analgesia.

Adult↗

PubMed2000

Synchronization in a system of globally coupled oscillators with time delay

We study the synchronization phenomena in a system of globally coupled oscillators with time delay in the coupling. The self-consistency equations for the order parameter are derived, which depend explicitly on the amount of delay. Analysis of these equations reveals that the system in general exhibits discontinuous transitions in addition to the usual continuous transition, between the incoherent state and a multitude of coherent states with different synchronization frequencies. In particular, the phase diagram is obtained on the plane of the coupling strength and the delay time, and ubiquity of multistability as well as suppression of the synchronization frequency is manifested. Numerical simulations are also performed to give consistent results.

Journal Article↗

PubMed2000

Depinning of an anisotropic interface in random media: the tilt effect

We study the tilt dependence of the pinning-depinning transition for an interface described by the anisotropic quenched Kardar-Parisi-Zhang equation in 2+1 dimensions, where the two signs of the nonlinear terms are different from each other. When the substrate is tilted by m along the positive sign direction, the critical force F(c)(m) depends on m as F(c)(m)-F(c)(0) approximately -|m|(1.9(1)). The interface velocity v near the critical force follows the scaling form v approximately |f|(straight theta)Psi(+/-)(m(2)/|f|(straight theta+straight phi)) with straight theta=0.9(1) and straight phi=0.2(1), where f identical withF-F(c)(0) and F is the driving force.

Journal Article↗

PubMed2000

Phase diagram of congested traffic flow: An empirical study

We analyze traffic data from a highway section containing one effective on-ramp. Based on two criteria, local velocity variation patterns and expansion (or nonexpansion) of congested regions, three distinct congested traffic states are identified. These states appear at different levels of the upstream flux and the on-ramp flux, thereby generating a phase digram of the congested traffic flow. Observed traffic states are compared with recent theoretical analyses and both agreeing and disagreeing features are found.

Journal Article↗

PubMed2000

Path-integral formulation of stochastic processes for exclusive particle systems

We present a systematic formalism to derive a path-integral formulation for hard-core particle systems far from equilibrium. Writing the master equation for a stochastic process of the system in terms of the annihilation and creation operators with mixed commutation relations, we find the Kramers-Moyal coefficients for the corresponding Fokker-Planck equation (FPE), and the stochastic differential equation (SDE) is derived by connecting these coefficients in the FPE to those in the SDE. Finally, the SDE is mapped onto field theory using the path integral, giving the field-theoretic action, which may be analyzed by the renormalization group method. We apply this formalism to a two-species reaction-diffusion system with drift, finding a universal decay exponent for the long-time behavior of the average concentration of particles in arbitrary dimension.

Journal Article↗

PubMed2000

Neural pathways regulating Brunner's gland secretion in guinea pig duodenum in vitro.

This study examined the neural pathways innervating Brunner's glands using a novel in vitro model of acinar secretion from Brunner's glands in submucosal preparations from the guinea pig duodenum. Neural pathways were activated by focal electrical stimulation and excitatory agonists, and videomicroscopy was used to monitor dilation of acinar lumen. Electrical stimulation of perivascular nerves evoked large dilations that were blocked by TTX (1 microM) or the muscarinic receptor antagonist 4-diphenylacetoxy-N-(2-chloroethyl)-piperidine hydrochloride (1 microM). The nicotinic agonist 1,1-dimethyl-4-phenylpiperazinium iodide (100 microM) had no effect, and the nerve-evoked responses were not inhibited by hexamethonium (200 microM). Dilations were abolished in preparations from chronically vagotomized animals. Activation of submucosal ganglia significantly dilated submucosal arterioles but not Brunner's glands. Effects of electrical stimulation of perivascular and submucosal nerves were not altered by guanethidine. Capsaicin and substance P also dilated arterioles but had no effect on Brunner's glands. Cholinergic (choline acetyltransferase-immunoreactive) nerve fibers were found in Brunner's glands. These findings demonstrate that Brunner's glands are innervated by cholinergic vagal fibers but not by capsaicin-sensitive or intrinsic enteric nerves.

Animals↗

PubMed2000

Increased nitrovasodilator sensitivity in endothelial nitric oxide synthase knockout mice: role of soluble guanylyl cyclase.

Endogenously produced nitric oxide (NO) modulates nitrovasodilator-induced relaxation. We investigated the underlying mechanism in wild-type (WT) mice and endothelial NO synthase knockout (eNOS(-/-)) mice to determine whether a chronic lack of endothelial NO alters the soluble guanylyl cyclase (sGC) pathway. In aortic segments from eNOS(-/-) mice, the vasodilator sensitivity to sodium nitroprusside (SNP) was significantly greater than that in WT mice. There was no difference in sensitivity to the G-kinase I activator 8-para-chlorophenylthio-cGMP or to cromakalim. N(omega)-Nitro-L-arginine had no effect on the SNP-induced relaxation in eNOS(-/-) but increased the sensitivity in WT mice so it was no longer different than that of eNOS(-/-). Basal cGMP levels in aortic rings were significantly lower in eNOS(-/-) mice than in WT mice. SNP (300 nmol/L) induced a significantly greater cGMP accumulation in eNOS(-/-) mice than in WT mice. The maximal SNP-induced (10 micromol/L) increase in cGMP was similar in both strains. SNP-stimulated sGC activity was significantly greater in eNOS(-/-) mice than in WT mice. Incubation of aortic segments from WT mice with N(omega)-nitro-L-arginine increased sGC activity, an effect prevented by coincubation with SNP (10 micromol/L). The aortic expressions of the sGC alpha1 and beta1 subunits in WT and eNOS(-/-) mice were identical as determined with Western blot analysis. These data suggest that chronic exposure to endothelium-derived NO, as well as acute exposure to nitrovasodilator-derived NO, desensitizes sGC to activation by NO but does not alter sGC expression. Both the acute cessation of endothelial NO formation in WT mice and the chronic deficiency of NO in eNOS(-/-) mice restore the NO sensitivity of sGC and enhance vascular smooth muscle relaxation in response to nitrovasodilator agents.

Animals↗

PubMed2000

Thyrotropin modulates interferon-gamma-mediated intercellular adhesion molecule-1 gene expression by inhibiting Janus kinase-1 and signal transducer and activator of transcription-1 activation in thyroid cells.

TSH is known as an important hormone that plays the major role not only in the maintenance of normal physiology but also in the regulation of immunomodulatory gene expression in thyrocytes. The adhesion molecule intercellular adhesion molecule-1 (ICAM-1) was identified as one of the proteins that are abnormally expressed in the thyroid gland during autoimmune thyroid diseases. In this study we found that TSH inhibits interferon-gamma (IFNgamma)-mediated expression of the ICAM-1 gene, and we investigated the involved mechanisms in rat FRTL-5 thyroid cells. After exposure to IFNgamma, ICAM-1 expression is positively regulated at the level of transcription. This effect occurs via the IFNgamma-activated site (GAS) element in the ICAM-1 promoter as a consequence of the activation of STAT1 (signal transducer and activator of transcription-1), but not of STAT3. On the other hand, after exposure to TSH plus IFNgamma, ICAM-1 transcription is negatively modulated. We found that this inhibitory effect of TSH also occurs via the GAS element. Electrophoretic mobility shift assays confirmed that the IFNgamma-induced DNA-binding activities of STAT1 were reduced by TSH. Furthermore, our results showed that the inhibitory effect of TSH on IFNgamma signaling is caused by inhibition of tyrosine phosphorylation on STAT1, Janus kinase-1 (Jak1), and IFNgamma receptor a, but not Jak2. In conclusion, we have identified a novel mechanism in which TSH modulates the IFNgamma-mediated Jak/STAT signaling pathway through the inhibition of Jak1 and STAT1.

Animals↗

PubMed2000

Concanavalin A-induced discharge of glycocalyx of raphidophycean flagellates, Chattonella marina and Heterosigma akashiwo.

Chattonella marina and Heterosigma akashiwo, known as red tide phytoplankton, are naturally wall-less and have quite fragile cell structures. In this study, we found that an equilibrium dialysis technique allowed the study of lectin binding to these flagellates. The results suggested that concanavalin A (Con A) binds to these flagellate cells through the specific carbohydrate moieties on the cell surface. Interestingly, the binding of an excess of Con A on the cell surface caused morphological changes concomitant with discharge of glycocalyx, a polysaccharide-containing common structure on the external cell surface of these flagellates. Fluorescent microscopic observation using FITC-labeled Con A (F-Con A) confirmed that F-Con A molecules are localized on the discharged glycocalyx.

Animals↗

PubMed2000

Purification and partial characterization of a novel glucanhydrolase from Lipomyces starkeyi KSM 22 and its use for inhibition of insoluble glucan formation.

A novel glucanhydrolase from a mutant of Lipomyces starkeyi ATCC 74054 was purified. The single protein (100 kDa) showed either dextranolytic or amylolytic activity. We referred to the glucanhydrolase as a DXAMase. The DXAMase was produced in a starch medium and it was 3.75-fold more active for hydrolysis of the purified insoluble-glucan of Streptococcus mutans than Penicillium funiculosum dextranase. Aggregation of S. mutans cells with dextran and adherence to glass were eliminated by incubating with the DXAMase. The addition of DXAMase (0.1 IU/ml) to the mutansucrase reaction digest with sucrose reduced the formation of insoluble-glucan about 80%. Also the DXAMase (0.5 IU/ml) removed 80% of the pre-formed sucrose-dependent adherent film. These in vitro properties of L. starkeyi KSM 22 DXAMase are desirable for its application as a dental plaque control agent.

Dental Materials↗

PubMed2000

Specific toxic effect of dinoflagellate Heterocapsa circularisquama on the rotifer Brachionus plicatilis.

Heterocapsa circularisquama (Dinophyceae), a noxious red tide dinoflagellate, is known to have a specifically lethal effect on shellfish, especially bivalves such as pearl oyster (Pinctada fucata), but no detrimental effects of this alga on fishes have not been observed so far. In this study, we found that H. circularisquama was toxic to a microzooplankton, a rotifer (Brachionus plicatilis) in a cell concentration-dependent manner, while the cultured supernatant or ultrasonic ruptured H. circularisquama had no significant toxic effect on the rotifer. Since no such toxic effects on the rotifer were observed in Chattonella marina, Heterosigma akashiwo, or Cochlodinium polykrikoides, other species of harmful red tide plankton, H. circularisquama may have a strictly specific toxic mechanism against the rotifer as well as bivalves.

Animals↗

PubMed2000

Galacturonic-acid-induced increase of superoxide production in red tide phytoplankton Chattonella marina and Heterosigma akashiwo.

Red tide phytoplankton, Chattonella marina and Heterosigma akashiwo, are known to generate superoxide anion (O2-). We found that galacturonic acid (GaLUA) stimulated C. marina and H. akashiwo to generate increased amounts of O2-. Since such effect was not observed in any other monosaccharides tested, our results suggest that the binding of GalUA to specific sites on the flagellate cell surface may induce the increase of 02- production.

Culture Media↗

PubMed2000

The human L-pipecolic acid oxidase is similar to bacterial monomeric sarcosine oxidases rather than D-amino acid oxidases.

L-Pipecolic acid oxidase activity is deficient in patients with peroxisome biogenesis disorders (PBDs). Because its role, if any, in these disorders is unknown, the authors cloned the human gene to order to further study its functions. BLAST search of the translated sequence showed greatest homology to Bacillus sp. NS-129 monomeric sarcosine oxidase. The purified enzyme could use either L-pipecolic acid or sarcosine as a substrate. No homology was found to the peroxisomal D-amino acid oxidases. A further comparison of L-pipecolic acid oxidase to the two D-amino acid oxidases in peroxisomes showed that the proteins differed in many ways. First, both D-amino acid oxidase and L-pipecolic acid oxidase showed no enzyme activity in liver from Zellweger syndrome patients; D-aspartate oxidase activity was unchanged from control levels. Although all were targeted to peroxisomes, their targeting signals differed. No L-pipecolic acid oxidase was found in brain or other tissues outside of liver and kidney. The D-amino acid oxidases were similarly and more widely distributed. Finally, although D-amino acid degradation is limited to peroxisomes in mammals, L-pipecolic acid can be oxidized in either mitochondria or peroxisomes, or both.

Bacillus↗

PubMed2000

Improved recombinant retroviral titers utilizing trichostatin A.

Recombinant retroviruses are a common vehicle to deliver an exogenous gene to a target cell, which makes them a useful tool in the field of gene therapy. A major drawback to using recombinant retroviruses is the low titer achieved, resulting in a limited number of target cells infected and subsequently poor expression of a transgene. In this study, we created an ecotropic producer cell line that contained recombinant mouse nerve growth factor (NGF) and the reporter gene LacZ. This cell line, termed psi 2/LIG/NGF, was treated with the drug trichostatin A, an inhibitor of histone deacetylase. At a concentration of 3 microM trichostatin A, the retroviral titer of this producer cell line was increased 34-fold relative to untreated control cells and 3.4-fold compared to the commonly used hyperacetylating compound sodium butyrate. Producer cells treated with trichostatin A also increased the number of primary rat marrow stromal cells infected 5.8-fold compared to untreated producer cells. These results offer a simple and effective solution for converting low titer producer cell clones to higher titer clones, which can be easily tested and applied.

3T3 Cells↗

PubMed2000

Expression of leptin receptor (Ob-R) in human atherosclerotic lesions: potential role in intimal neovascularization.

Neovascularization of the adventitial vasa vasorum with extension into the intima of atherosclerotic lesions is frequently observed, but its pathophysiological significance is still subject to debate. Recently, leptin, the product of the Ob gene, was identified. Leptin, via activation of the endothelial receptor (Ob-R), generates a growth signal involving a tyrosine kinase-dependent intracellular pathway and promotes angiogenic processes. We hypothesized that a high concentration of leptin within vasa vasorum and plaque itself, may influence inflammatory and vascular neovascularization coupling with functional upregulation of the vascular endothelial growth factor (VEGF). Microscopic computerized tomography was utilized for the spatial distribution of vasa vasorum and intimal neovascularization from atherosclerotic human coronary arteries. Atherosclerotic coronary arteries showed a dense plexus of microvessels in the adventitia and plaque itself. Microscopic analysis from human atherosclerotic aortas revealed an increase in the intimal thickness with neovascularization. The immunoreactivity for Ob-R, VEGF and matrix metalloproteinase (MMP) increased in atherosclerotic plaque, predominantly in the endothelial lining of the intimal neovessel and macrophages/foam cells. Our observation of a prominent colocalization between Ob-R, VEGF and MMP supports this hypothesis and these factors participate in the neovascularization of atherosclerotic lesions. The present study is the first report on vascular tissue and it opens a promising perspective concerning future investigations of leptin-dependent modulation of atherogenesis and vascular neovascularization under pathophysiolgical conditions.

Adult↗

PubMed2000

Coexpression of cyclooxygenase-2 and matrix metalloproteinases in human aortic atherosclerotic lesions.

Inflammation appears to have a major role in the development of atherosclerosis. Cyclooxygenase-2 (COX-2) is involved in the inflammatory response via the generation of prostanoids that, in turn, are involved in the production of matrix metalloproteinases (MMPs). This study aimed to investigate atherosclerosis in human aortas for in situ tissue distribution of COX-2, MMPs including MMP-9 and membrane type 1 MMP (MT1-MMP), and tissue inhibitor of metalloproteinase-2 (TIMP-2). Immunohistochemical studies were performed on atherosclerotic lesions of aortas from patients with aortic aneurysms (n = 4) and dissections (n = 3) by using antibodies to COX-2, MMP-9, MT1-MMP, and TIMP-2. Control tissues were obtained from traumatically dissected aortas (n = 2). All specimens from diseased aortas had atherosclerotic lesions ranging from fatty streak to atheromatous plaques. In control, there was no expression of COX-2, MMP-9, and MT1-MMP in all aortic layers. Immunoreactivity for COX-2 was predominantly noted in macrophages and smooth muscle cells (SMCs) of the intima including atherosclerotic plaque itself and the medial layer of the plaque base, as well as in SMCs and endothelial lining of the vasa vasorum in the adventitia. Immunoreactivity for MMP-9 and MT1-MMP was found in the same distribution as that of COX-2. Additionally, the expression of TIMP-2 increased in relation to MMP-9 expression. This study demonstrates that COX-2 is coexpressed with MMP-9 and MT1-MMP, not only by macrophages and SMCs in atherosclerotic lesions, but also in endothelial lining of the vasa vasorum of human aortas. Thus, vascular inflammatory reactions may influence extracellular matrix remodeling by coactivation of MMPs in the development of atherosclerosis and, in turn, the progression of disease.

Animals↗