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J H Cha

Publications and source records attributed to J H Cha.

68 records · Page 4Linked to original sources
PubMed1992

Multiple states of rat brain (RS)-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptors as revealed by quantitative autoradiography.

The binding of (RS)-alpha-[3H]amino-3-hydroxy-5-methylisoxazole-4-propionic acid ([3H]AMPA), a selective ligand for non-N-methyl-D-aspartate excitatory amino acid receptors, was investigated in rat brain using an autoradiographic receptor binding technique. [3H]AMPA binding sites were widely distributed throughout the rat central nervous system, and the rank order of potency of displacers of [3H]AMPA binding was quisqualate greater than AMPA greater than 6,7-dinitroquinoxaline-2,3-dione = 6-cyano-7-nitroquinoxaline-2,3-dione greater than beta-N-oxalylamino-L-alanine greater than glutamate greater than kainate. Potassium thiocyanate (0-100 mM) exerted a 4-fold stimulation of [3H]AMPA binding, without changing the relative regional distribution of [3H]AMPA binding densities among rat brain regions. Scatchard analysis of equilibrium saturation binding revealed high affinity and low affinity components of [3H]AMPA binding, even in the absence of potassium thiocyanate. Addition of potassium thiocyanate increased the number of high affinity [3H]AMPA binding sites without a change in affinity. In addition, the number of low affinity [3H]AMPA binding sites was unchanged in the presence of potassium thiocyanate, but the affinity of low affinity [3H]AMPA binding was greatly increased. [3H]AMPA thus binds specifically to two affinity conformations of postsynaptic binding sites that appear to be interconverted with potassium thiocyanate. The pharmacologic profile of these sites is consistent with that of the ion channel-linked ("ionotropic") quisqualate/AMPA class of excitatory amino acid receptor in the rat central nervous system.

Analysis of Variance↗
PubMed1991

2,4,5-Trihydroxyphenylalanine (6-hydroxy-dopa) displaces [3H]AMPA binding in rat striatum.

Excitatory amino acid (EAA) receptor-mediated events have recently been implicated in dopaminergic mechanisms of neurotoxicity. 2,4,5-Trihydroxyphenylalanine (6-hydroxy-DOPA, TOPA), the ortho-hydroxylated derivative of the dopamine precursor 2,4-dihydroxyphenylalanine (L-DOPA), has recently been reported to have neurotoxic properties which are blocked by CNQX, a specific antagonist of the AMPA class of non-N-methyl-D-aspartate (non-NMDA) EAA receptors. We report here that 6-hydroxy-DOPA is a selective displacer of [3H]AMPA binding in rodent brain. 6-Hydroxy-DOPA was as potent as kainate in displacing [3H]AMPA binding, with an IC50 value of 32 microM. Ineffective displacers of [3H]AMPA binding included dopamine, 6-hydroxydopamine, L-DOPA, D-DOPA, carbidopa, DOPAC, beta-methylamino-L-alanine, 2,4-dihydroxyphenylacetyl-L-asparagine, homogentisic acid, 2,4-dihydroxyphenylacetic acid, amantadine, and threo-DOPS. 6-Hydroxy-DOPA (100 microM) also displaced 20% of [3H]kainate binding, but did not displace binding to NMDA, phencyclidine (PCP), or dopaminergic (D1 and D2) receptors. These data raise the possibility that 6-hydroxy-DOPA or another abnormal metabolite of L-DOPA could act as an excitotoxic agent via action at AMPA receptors. Given that non-NMDA receptors are postulated to play a role in neurotoxic events, these data provide an additional mechanism via which EAA receptor-mediated events could produce neurodegeneration in areas of brain with dopaminergic innervation.

Animals↗
PubMed1991

Regional distribution and properties of [3H]MK-801 binding sites determined by quantitative autoradiography in rat brain.

[3H]MK-801 binding in rat brain was characterized using a quantitative autoradiographic binding assay. [3H]MK-801 binding (5 nM) reached equilibrium by 120 min at 23 degrees C. [3H]MK-801 appeared to label a single high affinity site with an affinity constant of approximately 11 nM. [3H]MK-801 binding was heterogeneously distributed throughout the brain with the following order of binding densities: hippocampal formation greater than cortical areas greater than striatum greater than thalamus. Competitive N-methyl-D-aspartate antagonists, DL-2-amino-5-phosphonopentanoic acid, DL-2-amino-7-phosphonoheptanoic acid, 3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid, and cis-4-phosphonomethyl-2-piperidine carboxylic acid, inhibited [3H]MK-801 binding. Glycine antagonists, 7-chlorokynurenic acid and kynurenic acid, also inhibited [3H]MK-801 binding. Furthermore, the inhibition of [3H]MK-801 binding by the quinoxalinedione compounds 6-cyano-7-nitroquinoxaline-2,3-dione and 6,7-dinitroquinoxaline-2,3-dione was reversed by glycine. [3H]MK-801 binding was also inhibited by zinc ions [3H]MK-801 binding was enhanced by glycine or N-methyl-D-aspartate. These results demonstrate that [3H]MK-801 can be used in a quantitative autoradiographic assay as a functional probe for the N-methyl-D-aspartate receptor complex.

Animals↗
PubMed1990

Two types of quisqualate receptors are decreased in human olivopontocerebellar atrophy cerebellar cortex.

We used receptor autoradiography to study the distribution of ionotropic and metabotropic quisqualate (QA) receptors in normal human cerebellar cortex and cerebellar cortex from 7 cases of olivopontocerebellar atrophy (OPCA). In normal human cerebellar cortex, both types of QA receptors were densest in the molecular layer. Both ionotropic and metabotropic QA receptors were significantly diminished in the molecular layer of OPCA specimens. These results suggest that both ionotropic and metabotropic QA receptors are localized on Purkinje cell dendrites.

Autoradiography↗
PubMed1990

L-[3H]glutamate labels the metabotropic excitatory amino acid receptor in rodent brain.

A quantitative autoradiographic assay for a novel L-[3H]glutamate binding site in rodent brain has been developed. Binding to this site was distinguished by its high affinity for quisqualate (QA), ibotenate, glutamate and trans-1-amino-cyclopentyl-1,3-dicarboxylic acid (trans-ACPD), but low affinity for [RS]-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), kainate and N-methyl-D-aspartate (NMDA). 'AMPA-insensitive, QA-sensitive [3H]glutamate binding' (AiQsGB) had a heterogeneous distribution in rat brain with high levels observed in molecular layer of cerebellum, striatum, and lateral septum. AiQsGB was reduced in molecular layer of cerebellum in mice lacking Purkinje cells. AiQsGB appears to represent binding to the 'metabotropic' neuronal excitatory amino acid receptor linked to phosphoinositide metabolism.

Animals↗
PubMed1990

Autoradiographic characterization and localization of quisqualate binding sites in rat brain using the antagonist [3H]6-cyano-7-nitroquinoxaline-2,3-dione: comparison with (R,S)-[3H]alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid binding sites.

Using quantitative autoradiography, we have investigated the binding sites for the potent competitive non-N-methyl-D-aspartate (non-NMDA) glutamate receptor antagonist [3H]6-cyano-7-nitro-quinoxaline-2,3-dione ([3H]-CNQX) in rat brain sections. [3H]CNQX binding was regionally distributed, with the highest levels of binding present in hippocampus in the stratum radiatum of CA1, stratum lucidum of CA3, and molecular layer of dentate gyrus. Scatchard analysis of [3H]CNQX binding in the cerebellar molecular layer revealed an apparent single binding site with a KD = 67 +/- 9.0 nM and Bmax = 3.56 +/- 0.34 pmol/mg protein. In displacement studies, quisqualate, L-glutamate, and kainate also appeared to bind to a single class of sites. However, (R,S)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) displacement of [3H]CNQX binding revealed two binding sites in the cerebellar molecular layer. Binding of [3H]AMPA to quisqualate receptors in the presence of potassium thiocyanate produced curvilinear Scatchard plots. The curves could be resolved into two binding sites with KD1 = 9.0 +/- 3.5 nM, Bmax = 0.15 +/- 0.05 pmol/mg protein, KD2 = 278 +/- 50 nM, and Bmax = 1.54 +/- 0.20 pmol/mg protein. The heterogeneous anatomical distribution of [3H]CNQX binding sites correlated to the binding of L-[3H]glutamate to quisqualate receptors and to sites labeled with [3H]AMPA. These results suggest that the non-NMDA glutamate receptor antagonist [3H]CNQX binds with equal affinity to two states of quisqualate receptors which have different affinities for the agonist [3H]AMPA.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1990

Hydrogen peroxide stimulates rat colonic prostaglandin production and alters electrolyte transport.

The changes in short circuit current (electrogenic Cl- secretion) of rat colon brought about by xanthine/xanthine oxidase in the Ussing chamber were inhibited by catalase and diethyldithiocarbamate, but not by superoxide dismutase. These results, the reproduction of the response with glucose/glucose oxidase and with exogenous H2O2, and the lack of effect of preincubation with deferoxamine or thiourea implicate H2O2, and not O2- or OH., as the important reactive oxygen metabolite altering intestinal electrolyte transport. 1 mM H2O2 stimulated colonic PGE2 and PGI2 production 8- and 15-fold, respectively, inhibited neutral NaCl absorption, and stimulated biphasic electrogenic Cl secretion with little effect on enterocyte lactic dehydrogenase release, epithelial conductance, or histology. Cl- secretion was reduced by cyclooxygenase inhibition. Also, the Cl- secretion, but not the increase in prostaglandin production, was reduced by enteric nervous system blockade with tetrodotoxin, hexamethonium, or atropine. Thus, H2O2 appears to alter electrolyte transport by releasing prostaglandins that activate the enteric nervous system. The change in short circuit current in response to Iloprost, but not PGE2, was blocked by tetrodotoxin. Therefore, PGI2 may be the mediator of the H2O2 response. H2O2 produced in nontoxic concentrations in the inflamed gut could have significant physiologic effects on intestinal water and electrolyte transport.

Animals↗
PubMed1989

Estrous cycle-dependent variation in amphetamine-induced behaviors and striatal dopamine release assessed with microdialysis.

Estrous cycle-dependent variation in amphetamine (AMPH)-stimulated behaviors and striatal dopamine (DA) release were determined for freely moving rats undergoing intracerebral microdialysis. There was greater AMPH-stimulated striatal DA release in the striatum of rats in estrus, during the period from 20 min to 100 min post-AMPH, compared with the response of rats in diestrus (P less than 0.05). Animals in estrus also showed less general activity and greater intensity of stereotyped behaviors than did animals in diestrus (P less than 0.05). Independent experiments examining estrous cycle-dependent differences in AMPH-stimulated striatal DA release in vitro also found that AMPH-stimulated striatal DA release was greater on estrus than on diestrus (P less than 0.05). Thus, striatal DA release and behaviors induced by AMPH are modulated by ovarian hormones. The heightened responsiveness to AMPH during estrus suggests that estrogen and/or progesterone potentiate the striatal DA response to AMPH.

Animals↗
PubMed1989

Contamination of commercially available quisqualic acid by glutamate-like and aspartate-like substances.

Six different batches of the glutamic acid analogue quisqualic acid were analyzed with high-pressure liquid chromatography (HPLC). All batches examined showed contaminant peaks. Different batches had different contaminant peaks and differing amounts of each contaminant. Every batch of quisqualic acid tested demonstrated a contaminant peak which co-eluted with exogenously added glutamic acid. Certain batches possessed a contaminant which co-eluted with aspartic acid. The levels of glutamate-like contamination ranged from 0.08 to 0.60%, and the levels of aspartate-like contamination ranged from undetectable amounts to 0.80%. The amount of combined glutamate- and aspartate-like contamination of each batch of quisqualate correlated very highly with the ability of that batch to interact with non-quisqualate receptors in an autoradiographic binding assay. These non-quisqualate receptors are likely N-methyl-D-aspartate (NMDA) receptors. Thus, when high concentrations of quisqualate are used experimentally, contamination is likely to produce spurious effects at non-quisqualate glutamate receptors. Quisqualate itself may be a more specific agonist than assumed previously.

Aspartic Acid↗
PubMed1988

Thiocyanate stabilizes AMPA binding to the quisqualate receptor.

Calcium and chloride ions stimulated [3H]glutamate binding to quisqualate-sensitive [3H]glutamate binding sites 4-fold, as measured by quantitative autoradiography, whereas 100 mM potassium thiocyanate had no additional effect. In contrast, calcium and chloride had little effect on the binding of [3H](RS)-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid ([3H]AMPA), but 100 mM thiocyanate stimulated binding 4-fold. AMPA displaced little [3H]glutamate binding from quisqualate-sensitive binding sites in the molecular layer of the cerebellum in the absence of thiocyanate. However, in the presence of thiocyanate AMPA became a more effective displacer, but still displaced only 44% of the quisqualate-sensitive [3H]glutamate binding. The distribution of [3H]glutamate binding to quisqualate-sensitive sites was similar to but not identical with that of [3H]AMPA binding. However, the distribution of AMPA-displaceable [3H]glutamate binding correlated highly (r = 0.97, P less than 0.0005) with that of [3H]AMPA binding. The results suggest that AMPA binds to a subclass of quisqualate-sensitive [3H]glutamate binding sites that are highly influenced by ionic environment and that quisqualate-sensitive binding sites exist in several states.

Animals↗
PubMed1988

Properties of quisqualate-sensitive L-[3H]glutamate binding sites in rat brain as determined by quantitative autoradiography.

Quisqualate, a glutamate analogue, displaced L-[3H]glutamate binding in a biphasic manner, corresponding to "high-affinity" and "low-affinity" binding sites. High-affinity quisqualate sites were termed "quisqualate-sensitive L-[3H]glutamate" binding sites. Quisqualate-sensitive L-[3H]glutamate binding was regionally distributed, with the highest levels present in the cerebellar molecular layer. This binding was stimulated by millimolar concentrations of chloride and calcium. The stimulatory effects of calcium required the presence of chloride ions, whereas chloride's stimulatory effects did not require calcium. All of the L-[3H]glutamate binding stimulated by chloride/calcium was quisqualate sensitive and only weakly displaced by N-methyl-D-aspartate, L-aspartate, or kainate. At high concentrations (1 mM), the anion blockers 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid and 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid both reduced, by 41 and 43%, respectively, the stimulatory effects of chloride. At concentrations of 100 microM, kynurenate, L-aspartate, (RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), and L-2-amino-4-phosphonobutyric acid (L-APB) failed to displace quisqualate-sensitive L-[3H]glutamate binding in the cerebellar molecular layer. In the presence of KSCN, however, 100 microM AMPA displaced 44% of binding. Quisqualate-sensitive L-[3H]glutamate binding was not sensitive to freezing, and, in contrast to other chloride- and calcium-dependent L-[3H]glutamate binding sites that have been reported, quisqualate-sensitive binding observed by autoradiography was enhanced at 4 degrees C compared with 37 degrees C. Quisqualate-sensitive L-[3H]glutamate binding likely represents binding to the subclass of postsynaptic neuronal glutamate receptors known as quisqualate receptors, rather than binding to previously described APB receptors, chloride-driven sequestration into vesicles, or binding to astrocytic membrane binding sites.

Animals↗
PubMed1986

Effects of D-aspartate on excitatory amino acid-induced release of [3H]GABA from goldfish retina.

The rate of release of [3H]GABA from isolated intact goldfish retinas was studied. Release of [3H]GABA is markedly stimulated by the inclusion in the incubation medium of the photoreceptor neurotransmitter candidates L-glutamate (L-Glu) and L-aspartate (L-Asp), and the glutamate analogs, kainate and quisqualate. At micromolar concentrations, kainate and quisqualate are effective releasers of [3H]GABA, whereas millimolar concentrations of L-Glu and L-Asp are required to release comparable amounts of [3H]GABA. The D-isomers of aspartate (D-Asp) and glutamate (D-Glu) are able to release [3H]GABA, but only when applied at high concentrations (3-30 mM). In the presence of 5 mM D-Asp, the effect of L-Glu in releasing [3H]GABA was markedly potentiated. This dose-response curve of L-Glu was shifted to the left in the presence of D-Asp, although the maximal amount of release was unchanged. D-Asp at 5 mM only slightly increased the GABA release induced by quisqualate, and it did not increase the GABA release induced by kainate. Finally, low concentrations of L-Asp were potentiated by D-Asp, but higher concentrations of L-Asp (3-10 mM) were clearly inhibited by this agent. This biphasic effect of D-Asp on L-Asp-induced release of [3H]GABA is a possible explanation for previously conflicting reports of D-Asp's effect on L-Asp action. Our data suggest that D-Asp has both pre- and postsynaptic sites of action.

Amino Acids↗
PubMedDate not supplied

Preoperative evaluation of Klatskin tumor: accuracy of spiral CT in determining vascular invasion as a sign of unresectability.

BACKGROUND: To assess the accuracy of spiral computed tomography (CT) in predicting the resectability of Klatskin tumor as determined by vascular invasion. METHODS: Twenty-one consecutive patients with Klatskin tumor who had undergone laparotomy were included in this study. The preoperative thin-section (5-mm-thick) spiral CT scans of these patients were assessed for the surgical resectability of tumor by evaluating the vascular invasion. The criterion for vascular invasion indicating unresectability was the tumoral invasion of the proper hepatic artery or main portal vein or simultaneous invasion of one side of the hepatic artery and the other side of the portal vein. RESULTS: All nine patients with tumors thought to be unresectable on the basis of CT findings had tumors that were unresectable at surgery (positive predictive value, 100%). Of 12 patients with tumors thought to be resectable, six had resectable tumors (negative predictive value, 50%). Spiral CT failed to detect small hepatic metastasis (n = 1), lymph node metastasis (n = 1), extensive tumor (n = 2) and variation of bile duct (n = 2), which precluded surgical resection. CONCLUSION: Spiral CT is a reliable method for detecting vascular invasion and unresectable tumors. However, it has limitations in detecting variations of the bile duct or the intraductal extent of tumor.

Adult↗