Biomedical subjects

J S Rhee

Publications and source records attributed to J S Rhee.

At least 55 records · Page 3Linked to original sources

PubMed1998

Developmental changes of GABA(A) receptor-chloride channels in rat Meynert neurons.

The developmental changes of GABA(A) receptors were investigated in Meynert neurons freshly dissociated from day 0, 2 week-, and 6 month-old rats using both nystatin and gramicidin perforated patch recording modes under voltage-clamp conditions. The age-related changes in the current amplitude and threshold concentration in the concentration-response relationships for GABA indicated the developmental alteration of the GABA(A) receptor subunits and the channel density. The GABA-induced E(Cl-) measured by the gramicidin perforated patch mode shifted to more negative with development. The decay time constant of GABAergic inhibitory postsynaptic spontaneous currents (sIPSCs) in the synaptic active zone accelerated with aging. The GABA-induced currents were potentiated in a concentration dependent manner in the presence of benzodiazepine (BZP) agonists, diazepam (DZP) and zolpidem (ZPM). The potentiation rate of DZP on the GABA(A) response decreased with aging, but not in the case of ZPM, which demonstrated a stronger action in the aging rat neurons. These results suggested that the GABA(A) receptor x Cl- channel complexes may thus change both the assembly and interaction of subunits as well as their functional roles with aging.

Animals↗

PubMed1998

Urinary bladder pseudolesions on contrast-enhanced helical CT: frequency and clinical implications.

OBJECTIVE: The goals of this study were to define the distinguishing characteristics and frequency of urinary bladder pseudolesions that are produced as opacified urine enters the bladder during contrast-enhanced helical CT of the abdomen and to evaluate the usefulness of delayed imaging in differentiating pseudolesions from true lesions. SUBJECTS AND METHODS: Contrast-enhanced routine CT scans of 184 patients were obtained prospectively. For each patient, we also obtained 5-min delayed images of the bladder. The images were evaluated for apparent focal thickening or polypoid lesions involving the bladder wall, findings that may represent bladder neoplasia, without knowledge of the indications for the scan, the patient's clinical history, or the patient's diagnosis. Apparent lesions that were visible on routine images and entirely absent on delayed images were considered to be pseudolesions. RESULTS: Apparent lesions were identified on 20 (10.9%+/-4.5% [limits of the 95% confidence interval]) of the routine CT scans. Using delayed images, the 21 apparent lesions in these 20 patients were resolved as 13 pseudolesions and eight true lesions. Pseudolesions were present in 6.5%+/-3.6% of patients. CONCLUSION: Pseudolesions of the bladder that are indistinguishable from true lesions pose a significant clinical problem in routine contrast-enhanced helical CT of the abdomen. Delayed imaging of the bladder is useful in distinguishing pseudolesions from true lesions.

Adult↗

PubMed1997

Age-related functional changes of the glutamate receptor channels in rat Meynert neurones.

1. The developmental changes of glutamate receptors (GluRs) in acutely dissociated rat Meynert neurones were investigated using the conventional whole cell and nystatin perforated patch recording modes under voltage-clamp conditions. 2. The neurones became less responsive to N-methyl-D-aspartic acid (NMDA) with age, most dramatically between 1 day and 2 weeks, while the responses to kainic acid (KA) and L-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) gradually increased. The metabotropic GluR response appeared a few days after birth, but thereafter no further change was observed. 3. The decrease in the NMDA response during postnatal development was due to an abrupt reduction in the number of receptors without affecting the affinity, voltage-dependent Mg2+ blockade or high Ca2+ permeability (PCa/PCs approximately 7.0). 4. PCa/PCs in the presence of KA decreased from 2.8 in the 1-day-old (1D) rat neurones to 1.1 and 0.44 in the 2-week-old (2W) and 6-month-old (6M) rat neurones, respectively. The concentration-response relationship for KA shifted to the left with age. The KA response was not affected by NS-102, a KA-selective antagonist, thus indicating that the increased affinity of the receptor for the ligand resulted from the change in the AMPA receptor channel subunits. 5. The AMPA response in the presence of 10(-4) M cyclothiazide showed a change in the inward rectifying current-voltage relationship with age. The KA response was strongly cross-desensitized by the addition of AMPA and was also blocked by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), whereas a rapid desensitization of the AMPA response was removed in a concentration-dependent manner by cyclothiazide. These results indicate that the non-NMDA receptor channels are assembled from the subunits of the AMPA receptor family without the GluR-2 subunit, thus resulting in a high Ca2+ permeability. 6. The L-glutamate (Glu)-induced responses were more sensitive to DL-2-amino-5-phosphonopentanoic acid (APV) in the 1D rat neurones than in the adult rat neurones. 7. Both NMDA and KA raised the intracellular Ca2+ concentration ([Ca2+]i) in all neurones of 1D, 2W and 6M rats, though the charybdotoxin-sensitive Ca(2+)-activated K+ current (IK(Ca)) did not appear in the 1D rat neurones. An age-related prolongation of both IK(Ca) decay and [Ca2+]i clearance was also seen after the removal of KA. 8. It was thus concluded that the age-related changes of ionotropic receptors appear to play a key role in the activities of immature and mature rat Meynert cholinergic neurones. The KA-induced IK(Ca), which developed with ageing, may thus function as one of the negative feedback systems, and thereby prevent excess cell excitation and neural damage, especially in adult rats.

Acetylcholinesterase↗

PubMed1997

Investigation of refolding condition for Pseudomonas fluorescens lipase by response surface methodology.

Response Surface Methodology (RSM) was used to investigate optimal refolding conditions of Pseudomonas fluorescens lipase which was expressed as inclusion body in E. coli. Three interacting factors, protein concentration, pH and guanidine hydrochloride (GdnHCl) concentration were selected as the variables of RSM. The protein concentration did not affect the refolding yield within the selected range (50-340 micrograms ml-1) at low temperatures of 4 and -15 degrees C, but it was a critical factor at 25 degrees C and refolding yield significantly decreased with increasing protein concentration. The pH and GdnHCl were significant factors in all experimental conditions. But there was no trends of optimal pH depending on temperature and additives, just showing the optimum at neutral pH. Glycerol shifted optimal GdnHCl concentration to higher side, while arginine to lower side. Therefore, it was concluded that glycerol and arginine deprives and supplements GdnHCl, respectively. In this study, RSM made it possible to investigate successfully the optimal conditions of in vitro refolding and to elucidate interactions between refolding factors with a minimum number of experiments. Under the optimal condition determined by RSM, approximately 90% refolding yield was obtained and it was a 30% increase over the conventional method.

Arginine↗

PubMed1997

Effect of nilvadipine on high-voltage activated Ca2+ channels in rat CNS neurons.

The effect of nilvadipine, a dihydropyridine derivative, on high-voltage activated (HVA) Ca2+ channels was investigated in freshly dissociated rat frontal cortical neurons. The cortical neurons were observed to have five pharmacologically distinct HVA Ca2+ channel subtypes consisting of the L-, N-, P-, O- and R-types. Nilvadipine selectively inhibited the L-type Ca2+ channel current which comprised 23% of the total HVA Ca2+ channel current. A reversible inhibitory effect of nilvadipine on the L-type Ca2+ channel current was also observed in a concentration-dependent fashion without affecting the current-voltage relationship. The half-maximum inhibitory concentration was 3 x 10(-8) M. These results suggest that the inhibitory effect of nilvadipine on the neuronal Ca2+ influx, in combination with the cerebral vasodilatory action, may prevent neuronal damage during brain ischemia.

Animals↗

PubMed1997

Intraoperative mapping of sensate flaps. Electrophysiologic techniques and neurosomal boundaries.

BACKGROUND: The desirability of restoring sensation to the upper aerodigestive tract has led to an expanded use of sensate flaps for reconstruction of mucosal defects. Sensation can be restored via preformed neural pathways through the anastomosis of recipient and donor nerves, provided that the sensate flap falls within the boundaries of the neurosome for the identified sensory nerve. OBJECTIVES: To perform detailed electrophysiologic mappings of neurosomes of potential sensate flap donor sites, to describe their variability, and to investigate the usefulness of intraoperative mapping in terms of flap design and harvesting. DESIGN: A case series of 27 patients who were undergoing free flap reconstruction of various postablative head and neck defects were examined. Two silver-silver chloride recording electrodes were placed in direct contact with the dissected sensory nerve, and the overlying skin was either mechanically or electrically stimulated. Auditory feedback, as well as visualization of the responses on an oscilloscope, determined whether the stimulated area fell within the neurosome. This technique was applied to the lateral antebrachial cutaneous nerve of the radial forearm flap (n = 15), the lateral sural cutaneous nerve of the fibula flap (n = 5), the subcostal nerve of the iliac crest flap (n = 6), and the dorsal cutaneous rami of spinal nerve T-1 or T-2 of the scapula flap (n = 1). RESULTS: The neurosome of the lateral antebrachial cutaneous nerve was relatively consistent with the variability only at the distal boundary (ie, the dorsum of the hand). The neurosome of the lateral sural cutaneous nerve was more variable, falling into 2 distinct innervation patterns: one showing innervation that was limited to the upper lateral and posterior portions of the calf and the other demonstrating significant extension into the lower half of the calf. The neurosome of the subcostal nerve showed little variability and consistently overlapped the proposed skin paddle. The neurosome of the T-1 or T-2 spinal nerve was mapped in 1 patient and is described. CONCLUSIONS: The consistency of neurosomal boundaries is dependent on the donor site. Intraoperative mapping of flap donor sites may not only assure the harvesting of a true sensate flap, but may also allow for intraoperative decision making with regard to possible modifications of flap design and harvesting techniques. Two new sensate flaps from the iliac crest and scapula are accurately described.

Adult↗

PubMed1997

Mechanisms of GABA- and glycine-induced increases of cytosolic Ca2+ concentrations in chick embryo ciliary ganglion cells.

We used fura-2 microfluorometry and the gramicidin-perforated patch clamp technique in an attempt to clarify the mechanisms underlying the GABA- and glycine-induced increases in the cytosolic Ca2+ concentration ([Ca]in) in acutely isolated chick embryo ciliary ganglion neurons. GABA, glycine, and isoguvacine, but not baclofen, increased [Ca]in in a dose- and a Ca2+-dependent manner. The GABA-induced [Ca]in increase was inhibited by bicuculline and picrotoxin, and potentiated by pentobarbital, flunitrazepam, and alphaxalone, whereas the glycine-induced [Ca]in increase was inhibited by strychnine but not by bicuculline or picrotoxin. L- and N-type Ca2+ channel blockers inhibited the GABA- and glycine-induced [Ca]in increases, whereas Bay K-8644 potentiated these responses. These responses were also substantially potentiated by blockers of various K+ channels and by lowering the external Cl- concentrations. The high KCI- and nicotine-induced [Ca]in increases were substantially reduced during continuous stimulation with either 2 microM GABA or 1 mM glycine. Electrophysiological studies indicated that the reversal potential of the GABA-induced current exhibited a more depolarized value than the resting membrane potential in 17 of the 25 cells examined. Taken together, these results suggest that both GABA and glycine depolarize the membrane potentials by increasing Cl- conductance via respective receptors and thus increase the Ca2+ influxes through L- and N-type voltage-dependent Ca2+ channels.

Animals↗

PubMed1997

Modulation of high-voltage activated Ca2+ channels in the rat periaqueductal gray neurons by mu-type opioid agonist.

The effect of mu-type opioid receptor agonist, D-Ala2,N-MePhe4,Gly5-ol-enkephalin (DAMGO), on high-voltage-activated (HVA) Ca2+ channels in the dissociated rat periaqueductal gray (PAG) neurons was investigated by the use of nystatin-perforated patch recording mode under voltage-clamp condition. Among 188 PAG neurons tested, the HVA Ca2+ channels of 38 neurons (32%) were inhibited by DAMGO (DAMGO-sensitive cells), and the other 80 neurons (68%) were not affected by DAMGO (DAMGO-insensitive cells). The N-, P-, L-, Q-, and R-type Ca2+ channel components in DAMGO-insensitive cells shared 26.9, 37.1, 22.3, 7.9, and 5.8%, respectively, of the total Ca2+ channel current. The channel components of DAMGO-sensitive cells were 45.6, 25.7, 21.7, 4.6, and 2.4%, respectively. The HVA Ca2+ current of DAMGO-sensitive neurons was inhibited by DAMGO in a concentration-, time-, and voltage-dependent manner. Application of omega-conotoxin-GVIA occluded the inhibitory effect of DAMGO approximately 70%. So, HVA Ca2+ channels inhibited by DAMGO were mainly the N-type Ca2+ channels. The inhibitory effect of DAMGO on HVA Ca2+ channels was prevented almost completely by the pretreatment of pertussis toxin (PTX) for 8-10 h, suggesting that DAMGO modulation on N-type Ca2+ channels in rat PAG neurons is mediated by PTX-sensitive G proteins. These results indicate that mu-type opioid receptor modulates N-type HVA Ca2+ channels via PTX-sensitive G proteins in PAG neurons of rats.

Animals↗

PubMed1997

Effect of glutathione, catechin, and epicatechin on the survival of Drosophila melanogaster under paraquat treatment.

The biological effect of antioxidants which showed high superoxide-scavenging (SOS) activity in an in vitro analysis was examined by using Drosophila melanogaster. When the flies were exposed to paraquat as an endogenous source of the superoxide anion, their survival rapidly decreased. Although the SOS antioxidants did not have a preventive effect against paraquat toxicity, a supplement of each SOS antioxidants as glutathione, (+)-catechin and/or (-)-epicatechin to the diet had a reparative effect on flies damaged by the superoxide anion. The survival ratio of flies fed on a diet enriched with SOS antioxidants ranged from 77% to 87%, while that of the control group was 56%. When flies were exposed to paraquat in the presence of hydrogen peroxide or iron, each combination was more toxic than paraquat alone, since the two compounds could accelerate the generation of reactive oxygen species in vivo. The SOS antioxidants, however, allowed the flies to resist the combined toxicity of paraquat and ferrous iron.

Animals↗

PubMed1996

Modulation of glycine-induced chloride current in acutely dissociated rat periaqueductal gray neurons by mu-opioid agonist DAGO.

Effect of a mu-opioid agonist (D-Ala2,N-MePhe4,Gly5-ol-enkephalin, DAGO), on glycine (Gly)-induced chloride current (IGly) was investigated in the periaqueductal gray (PAG) neurons acutely dissociated 1-2-week-old Wistar rats by the use of nystatin-perforated patch recording configuration under voltage-clamp condition. At a holding potential (VH) of -40 mV, DAGO caused a sustained potentiation of IGly at the low concentrations (10(-6)-10(-5) M) but reduced slightly the Gly response at the high concentration (10(-4) M). The reversal potential of IGly was equal to the Cl- equilibrium potential (ECl) and was not changed in the presence of 10(-6) M DAGO. The 10(-5) M Gly response was inhibited by the simultaneous treatment of forskolin and 3-isobutyl-1-methylxanthine (IBMX). H-89, a protein kinase A (PKA) inhibitor, increased the 10(-5) M Gly response but had little effect on the 10(-4) M Gly response. DAGO increased 10(-5) M Gly response in the presence of forskolin and IBMX but, not more than in the absence of forskolin and IBMX. The 10(-5) M Gly response augumented by DAGO was not affected by adding H-89. The present results suggest that the glycine-induced chloride current is cAMP dependent and is inhibited by PKA, and that the potentiation of the glycine response by DAGO is also cAMP dependent and is due to the inhibition of PKA as that of H-89. We conclude that the potentiation of glycine response by DAGO is mediated by an inhibition of cAMP-dependent PKA in the PAG neurons.

Animals↗

PubMed1996

Interaction between the intracellular Ca2+ stores in rat dissociated hippocampal neurones.

The interaction between the Ca(2+)-activated K+ currents (IK(Ca)) induced by acetylcholine (ACh), 1-aminocyclopentane-1S,3R-dicarboxylic acid (1S,3R)-ACPD) and caffeine in rat hippocampal CA1 neurones was investigated to examine the functional independence between IP3- and Ca(2+)-sensitive Ca2+ stores. Pretreatment with either ACh or (1S,3R)-ACPD almost completely suppressed the subsequent IK(Ca) induced by another. Pretreatment with caffeine partially suppressed the IK(Ca) induced by either ACh or (1S,3R)-ACPD, although the inhibitory effect varied among the neurones, while pretreatment with either ACh or (1S,3R)-ACPD also partially inhibited the caffeine-induced IK(Ca). Continuous treatment with ryanodine and thapsigargin nonselectively decreased both the caffeine- and ACh-induced IK(Ca). These results thus indicate a close interaction between IP3- and Ca(2+)-sensitive stores and also suggest that the relative size of both stores and the closeness between them differ among neurones.

Animals↗

PubMed1996

Serotonin modulates high-voltage-activated Ca2+ channels in rat ventromedial hypothalamic neurons.

The modulation of high-voltage-activated (HVA) Ca2+ channels by serotonin (5-HT) was studied in ventromedial hypothalamic (VMH) neurons acutely dissociated from 12-14-day-old Wistar rats using the whole-cell and nystatin perforated-patch recording configurations. 5-HT inhibited the HVA Ca2+ channels in a concentration-, time- and voltage-dependent manner. This inhibition was mimicked by the 5-HT1A agonist 8-hydroxy-dipropylaminotetralin and was prevented by pretreatment with pertussis toxin (PTX). omega-Conotoxin-GVIA, omega-agatoxin-IVA, nicardipine and omega-conotoxin-MVIIC blocked each fraction of HVA Ca2+ channel currents, suggesting the existence of N-, P-, L- and Q-types of HVA Ca2+ channels. A component of the current resistant to these Ca2+ channel antagonists also existed in the VMH neurons. Among these five components of HVA Ca2+ channel currents, the N- and Q-type currents were significantly inhibited by 5-HT. These findings suggest that the activation of 5-HT1A receptors produces the selective inhibition of N- and Q-type Ca2+ channels through a PTX-sensitive G-protein in rat VMH neurons.

Animals↗

PubMed1996

Mutations in a cyclic nucleotide-gated channel lead to abnormal thermosensation and chemosensation in C. elegans.

The C. elegans tax-4 mutants are abnormal in multiple sensory behaviors: they fail to respond to temperature or to water-soluble or volatile chemical attractants. We show that the predicted tax-4 gene product is highly homologous to vertebrate cyclic nucleotide-gated channels. Tax-4 protein expressed in cultured cells functions as a cyclic nucleotide-gated channel. The green fluorescent protein (GFP)-tagged functional Tax-4 protein is expressed in thermosensory, gustatory, and olfactory neurons mediating all the sensory behaviors affected by the tax-4 mutations. The Tax-4::GFP fusion is partly localized at the sensory endings of these neurons. The results suggest that a cyclic nucleotide-gated channel is required for thermosensation and chemosensation and that cGMP is an important intracellular messenger in C. elegans sensory transduction.

Amino Acid Sequence↗

PubMed1996

Reappraisal of the inferior epigastric flap: a new neurovascular flap model in the rat.

An anatomic, histologic, and electrophysiologic study was carried out in order to determine the distribution and cutaneous sensory territory of the epigastric nerve in the rat. Results for nerve staining (Sihler's method) and electrophysiologic nerve mapping indicate that the neurosome of the epigastric nerve has a different autonomy than the vascular territory of the inferior epigastric artery. Based on these findings, an experimental model for neurovascular free-tissue transfer is proposed.

Abdomen↗

PubMed1996

A novel autonomously replicating sequence (ARS) for multiple integration in the yeast Hansenula polymorpha DL-1.

Several autonomously replicating sequences of Hansenula polymorpha DL-1 (HARSs) with the characteristics of tandem integration were cloned by an enrichment procedure and analyzed for their functional elements to elucidate the mechanism of multiple integration in tandem repeats. All plasmids harboring newly cloned HARSs showed a high frequency of transformation and were maintained episomally before stabilization. After stabilization, the transforming DNA was stably integrated into the chromosome. HARS36 was selected for its high efficiency of transformation and tendency for integration. Several tandemly repeated copies of the transforming plasmid containing HARS36 (pCE36) integrated into the vicinity of the chromosomal end. Bal 31 digestion of the total DNA from the integrants followed by Southern blotting generated progressive shortening of the hybridization signal, indicating the telomeric localization of the transforming plasmids on the chromosome. The minimum region of HARS36 required for its HARS activity was analyzed by deletion analyses. Three important regions, A, B, and C, for episomal replication and integration were detected. Analysis of the DNA sequences of regions A and B required for the episomal replication revealed that region A contained several AT-rich sequences that showed sequence homology with the ARS core consensus sequence of Saccharomyces cerevisiae. Region B contained two directly repeated sequences which were predicted to form a bent DNA structure. Deletion of the AT-rich core in region A resulted in a complete loss of ARS activity, and deletion of the repeated sequences in region B greatly reduced the stability of the transforming plasmid and resulted in retarded cell growth. Region C was required for the facilitated chromosomal integration of transforming plasmids.

Base Sequence↗

PubMed1995

Regional difference of high voltage-activated Ca2+ channels in rat CNS neurones.

The diversity of high voltage-activated (HVA) Ca2+ channels in rat CNS neurones was investigated with the nystatin perforated patch recording configuration. The neurones were freshly dissociated from rat substantia nigra, ventromedial hypothalamus, tuberomammillary nucleus, nucleus tractus solitarius, hippocampal CA1 region and cerebellum. Five different types of HVA Ca2+ channels were distinguished pharmacologically; dihydropyridine sensitive L-type, omega-conotoxin-GVIA sensitive N-type, omega-agatoxin-IVA sensitive P-type, omega-conotoxin-MVIIC sensitive Q-type, and R-type which is insensitive to these organic Ca2+ antagonists. The results showed clearly that the five subtypes of HVA Ca2+ channels differ considerably in their distribution among various CNS regions.

Animals↗

PubMed1995

Measurement of superoxide dismutase-like activity of natural antioxidants.

The superoxide dismutase (SOD)-like activity of natural antioxidants was evaluated by measuring the inhibition of pyrogallol autoxidation that is catalyzed by the superoxide radical. Among 22 water-soluble antioxidants tested, L-ascrobic acid, L-ascorbic acid 6-palmitate, glutathione (reduced form), (+)-catechin, and (-)-epicatechin showed effective SOD-like activity. To analyze lipophilic antioxidants, an optically clear organic system composed of diethyl ether, surfactant (dioctyl sulfosuccinate, AOT) and water, called reverse micelles, was developed. The optimum concentrations of AOT, water and pyrogallol for determining SOD-like activity were found to be 50 mM, 1.3 M, and 40 mM, respectively. After proving that pyrogallol autoxidation was mediated by the superoxide anion in that system, the SOD-like activity of 24 lipophilic antioxidants was measured. Cinnamon oil, gamma-oryzanol, extract of rosemary leaf, L-alpha-lecithin, and L-alpha-cephalin exhibited activity, although the activity of some antioxidants could not be measured because of the intense color or low solubility.

Antioxidants↗

PubMed1995

Inhibition of PDGF-induced phosphoinositide-turnover by glucopiericidin A.

In the search for a substance which would specifically block a particular step in the signal transduction cascade, we identified glucopiericidin A produced by Streptomyces sp. as an inhibitor of phosphoinositide (PI)-turnover in phospholipase-Cgamma1 (PLC-gamma1) overexpressing NIH 3T3 fibroblasts (NIH 3T3gamma1). Glucopiericidin A inhibited the formation of inositol phosphate (IPt) in platelet-derived growth factor (PDGF)-stimulated NIH 3T3gamma1 cells with an IC50 of 5.0 microM. In vitro enzyme assay showed the compound had no inhibitory effect on PLC-gamma1 even at 100 microM concentration. Glucopiericidin A reduced PDGF-induced tyrosine phosphorylations of proteins, including PDGF receptor and PLC-gamma1, in the cells. In contrast, glucopiericidin A showed only a slight inhibitory effect on epidermal growth factor (EGF)-induced IPt production and protein tyrosine phosphorylations in A431 cells. These results suggest that glucopiericidin A inhibits PDGF-induced activation of PLC-gamma1 by reducing the tyrosine kinase activity of the PDGF receptor and it more potently inhibits PI-turnover induced by PDGF than by EGF.

3T3 Cells↗