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In Koo Hwang

Publications and source records attributed to In Koo Hwang.

69 records · Page 4Linked to original sources
PubMed2003

Presynaptic gamma-aminobutyric acid type B receptor-mediated regulation of vesicular gamma-aminobutyric acid transporter expression in the gerbil hippocampus.

Changes in vesicular gamma-aminobutyric acid (GABA) transporter (VGAT) expression in the gerbil hippocampus after treatment with baclofen (GABA(B) receptor agonist) or phaclofen (GABA(B) receptor antagonist) were investigated to identify the GABA(B) receptor-mediated regulation of VGAT expression. In the baclofen-treated seizure-resistant gerbils, VGAT expression was significantly reduced, as compared with the control animals, thus the VGAT immunoreactive pattern in these gerbils was similar to that in control seizure-sensitive (SS) gerbils. In the phaclofen-treated SS gerbils, VGAT expression was dramatically elevated, compared to SS gerbil controls. Our findings demonstrated that GABA(B) receptor-mediated regulation of VGAT expression may be another mechanisms for presynaptic GABA release, which is accompanied by a reduction in Ca(2+) conductance by the inhibition of voltage-gated Ca(2+) channels.

Animals↗
PubMed2003

Elevation of Na+-K+ ATPase immunoreactivity in GABAergic neurons in gerbil CA1 region following transient forebrain ischemia.

In a previous study, we suggested that GABAergic neurons might be resistant to ischemic insult, because of the maintenance of the GABA shunt, which is one of the ATP synthetic pathways in neurons. In the present study, we identified Na(+)-K(+) ATPase immunoreactivity in the gerbil hippocampus in order to determine whether changes in Na(+)-K(+) ATPase immunoreactivity correlate with GABA shunt following ischemic insult. At 12 h after ischemia-reperfusion, Na(+)-K(+) ATPase immunoreactivity accumulated in some neurons in the CA1 region. However, the protein content of Na(+)-K(+) ATPase was not altered. Interestingly, the density of Na(+)-K(+) ATPase immunoreactivity in neurons and the protein content in the CA1 region was intensified in the 24 h post-ischemic group. As a result of double immunofluorescence study, Na(+)-K(+) ATPase immunoreactive neurons were identified with GABAergic neurons. Therefore, our findings suggest that the increase of Na(+)-K(+) ATPase in GABAergic neurons may be able to explain the resistance of these cells to ischemic insult, and support our previous hypothesis that GABA may play an important role as a metabolite in the survival of GABAergic neurons after ischemic insult.

Animals↗
PubMed2003

Chronological alterations of calbindin D-28k immunoreactivity in the gerbil main olfactory bulb after ischemic insult.

We investigated spatial and temporal alterations of calbindin D-28k (CB) immunoreactivity in the gerbil main olfactory bulb after transient ischemia-reperfusion. In sham-operated animals, CB-immunoreactive (IR) neurons were found in the periglomerular layer, external plexiform layer and granule cell layer. At 1-4 days after ischemic insult, the number of CB-IR neurons significantly increased. This result suggests that the increased CB may buffer the intracellular calcium at an early time point after the ischemic insult. In contrast, 10-30 days after the ischemic insult, the number of CB-IR neurons significantly decreased as compared to sham-operated animals. This result suggests that a malfunction in olfactory process may have occurred in the olfactory bulb at a later time point after the ischemic insult.

Animals↗
PubMed2003

Effect of vigabatrin on glutamate dehydrogenase in the hippocampus of seizure prone gerbils.

Vigabatrin (VGB, gamma-vinyl-gamma-aminobutyric acid (GABA)), an irreversible inhibitor of GABA transaminase, increases regional inhibitory effects by elevating GABA concentration and reducing glutamate synthesis. In the present study, changes in glutamate dehydrogenase (GDH) activity and its immunoreactivity in the seizure prone gerbil hippocampus after treating VGB were investigated to identify the effect of VGB on energy and/or glutamate metabolism via GDH. In the VGB treated group, GDH immunoreactivity and its activity in the hippocampus were significantly decreased, as compared with those of controls. These findings suggest that VGB administration may suppress the development and spread of seizures not only by elevating the level of GABA, but also by affecting the glutamate signaling and energy metabolism in neurons.

Animals↗
PubMed2003

Gastrodin decreases immunoreactivities of gamma-aminobutyric acid shunt enzymes in the hippocampus of seizure-sensitive gerbils.

Gastrodin is one of the natural compound isolated from Gastrodia elata and has known anticonvulsant effects, although the exact pharmacological principles of this natural compound and its effects on other aspects of gamma-aminobutyric acid (GABA) metabolism in vivo have not been explored. Therefore, in the present study, the effects of gastrodin on GABA metabolism in the gerbil hippocampus were examined, in an effort to identify the antiepileptic characteristics of this substance. Gastrodin reduced the seizure score in the treated group, although the immunoreactivities of GABA synthetic enzymes and GABA transporters were unaltered in gastrodin-treated animals. Interestingly, in the gastrodin-treated group, GABA transaminase (GABA-T) immunoreactivity in the hippocampus, particularly in neurons, was significantly decreased. In the gastrodin-treated group, both succinic semialdehyde dehydrogenase (SSADH) and succinic semialdehyde reductase (SSAR) immunoreactivities in the hippocampus was also decreased significantly, which stood in contrast to the nontreated group, in which strong SSADH and SSAR immunoreactivities were detected. From the neuroanatomical viewpoint, these findings suggest that gastrodin may cause the elevation of GABA concentration by inhibiting the GABA shunt.

Animals↗
PubMed2003

Changed vesicular GABA transporter immunoreactivity in the gerbil hippocampus following spontaneous seizure and vigabatrin administration.

To identify the roles of vesicular gamma-aminobutyric acid (GABA) transporter (VGAT) in epileptogenesis and the recovery mechanisms in spontaneous seizure, we conducted a chronological and comparative analysis of VGAT expression. VGAT immunoreactivity was stronger in the seizure resistant group than that in the pre-seizure group of seizure sensitive (SS) gerbils. In 3 h postictal group, the density of VGAT immunoreactivity was significantly increased in the hippocampus, as compared to pre-seizure group. In 24 h postictal group, VGAT immunodensity had recovered to its pre-seizure level. In addition, VGAT immunoreactivity in the hippocampus was also increased by vigabatrin (GVG) administration. These results suggest that decreased VGAT expression in the SS gerbil hippocampus may affect epileptogenesis in this animal, and that the subsequent alteration in its expression induced by seizure and the administration of GVG may reflect a modulation of GABA release to alleviate seizure activity.

Animals↗
PubMed2003

The altered expression of GABA shunt enzymes in the gerbil hippocampus before and after seizure generation.

In the present study, the distribution of succinic semialdehyde dehydrogenase (SSADH) and succinic semialdehyde reductase (SSAR) in the hippocampus of the Mongolian gerbil and its association with various sequelae of spontaneous seizure were investigated in order to identify the roles of GABA shunt in the epileptogenesis and the recovery mechanisms in these animals. Both SSADH and SSAR immunoreactivities in the GABAergic neurons were significantly higher in the pre-seizure groups of seizure sensitive (SS) gerbil as compared to those seen in the seizure resistant (SR) gerbils. The distributions of both SSADH and SSAR immunoreactivities in the hippocampus showed significant differences after the on-set of seizure. At 3 h postictal, when compared to the pre-seizure group of SS gerbils, a decline in the immunoreactivities in the perikarya was observed. At 12 h after seizure on-set, the densities of both SSADH and SSAR immunoreactivities were begun to recover to the pre-seizure level of SS gerbils. These results suggest that the GABAergic neurons in the hippocampal complex of the SS gerbil may be highly activated. In addition, the imbalance of GABA shunt expressions in the GABAergic neurons may imply a malfunction of the metabolism of GABAergic neurons in the SS gerbils, and this defect may trigger seizure on-set. Therefore, the initiation of seizure, at least in gerbils, may be the result of a malfunction in GABA shunt in the GABAergic neurons.

Aldehyde Oxidoreductases↗
PubMed2003

Morphological characteristics of dopaminergic immunoreactive neurons in the olfactory bulb of the common marmoset monkey (Callithrix jacchus).

The present study describes the distribution of tyrosine hydroxylase (TH)-immunoreactive (IR) elements in the olfactory bulb of the common marmoset monkey (Callithrix jacchus), a primate species by immunohistochemistry. We identified six layers of the olfactory bulb of the common marmoset monkey in sections stained with cresyl violet. The majority of TH-IR cells were found in the glomerular layer. A few TH-IR cells were present in the external plexiform and granule cell layers. TH-IR fibers were identified in all layers of the olfactory bulb. The density of these nerve fibers was high in the internal plexiform and granule cell layers. The results in the olfactory bulb of the common marmoset monkey are generally similar to previous reports in some mammals. These data suggest that TH in the olfactory bulb of the common marmoset monkey may play a role in olfactory transmission via the glomeruli like in other mammals.

Animals↗
PubMed2002

Changes in pyridoxal kinase immunoreactivity in the gerbil hippocampus following spontaneous seizure.

To identify the roles of pyridoxal kinase (PLK) in epileptogenesis and the recovery mechanisms in spontaneous seizure, a chronological and comparative analysis of PLK expression in the gerbil hippocampus was conducted. PLK immunoreactivity in a pre-seizure group of seizure sensitive (SS) gerbils was more strongly detected than that in a seizure resistant (SR) group. The density of PLK immunoreactivity in a 30-min postictal group was significantly lower than that of a pre-seizure group. In a 12 h postictal group, PLK immunodensity recovered to pre-seizure level. The over-expression of PLK in the hippocampus of pre-seizure SS gerbils suggests that PLP play an important role in the modulation of GAD activity and GABA reuptake as mediated by membrane transporter via neurons.

Animals↗
PubMed2002

Age-related change of calbindin D-28k immunoreactive neurons in the rat main olfactory bulb.

We examined the aged-related changes of calbindin D-28k (CB)-immunoreactive (IR) neurons in the rat main olfactory bulb (MOB). The localization of CB-IR neurons was found to be almost entirely restricted to the glomerular layer. However, a few CB-IR neurons were observed in the granular layer. Prior to the 6th postnatal month (PM 6), the CB-IR neurons had long processes, and the population of CB-IR neurons had increased significantly compared to PM 12 and 24. At PM 12, CB-IR neurons showed a tendency to be smaller and have fewer dendrites than at guess. This phenomenon became remarkable at PM 24. The distinct reduction of CB-IR dendrites in glomeruli may be due to age-related functional restrictions. Increased calcium levels in the MOB neurons may be induced to allow cytotoxic event detection in the MOB neurons, and unbalanced Ca(2+)/Mg(2+)-ATPase may also induce aging-related MOB morphological changes.

Aging↗
PubMed2002

Chronological changes in pyridoxine-5'-phosphate oxidase immunoreactivity in the seizure-sensitive gerbil hippocampus.

To identify the roles of pyridoxine-5'-phosphate (PNP) oxidase in epileptogenesis and the recovery mechanisms in spontaneous seizure, a chronological and comparative analysis of PNP oxidase expression was conducted. PNP oxidase immunoreactivity in a preseizure group of seizure-sensitive (SS) gerbils was detected more strongly than that in a seizure-resistant (SR) group. The density of PNP oxidase immunoreactivity in a 30 min postictal group was significantly lower than that in a preseizure group. In a 12 hr postictal group, PNP oxidase immunodensity had recovered to a preseizure level. The overexpression of PNP oxidase in the hippocampus of preseizure SS gerbils suggests that PNP or pyridoxal 5'-phosphate plays an important role in the modulation of glutamic acid decarboxylase activity and gamma-aminobutyric acid reuptake as mediated by membrane transporter via neurons. In addition, this change in the PNP oxidase immunoreactivity following seizure may be a compensatory response designed to reduce epileptic activity in this animal.

Animals↗
PubMed2002

Immunohistochemical studies of brain pyridoxine-5'-phosphate oxidase.

A total of six hybridoma cell lines, which produce monoclonal antibodies (mAbs) against the sheep brain pyridoxine-5'-phosphate oxidase (PNP oxidase), were established. Isotype analysis revealed that all antibodies corresponded to the IgG 2B kappa subclass. Immunoblotting with various tissue homogenates indicated that all the mAbs specifically recognize a single protein band of 30 kDa. They also appear to be extensively cross-reactive among different mammalian and avian sources. These results demonstrated that only one type of immunologically similar PNP oxidase is present in all of the mammalian tissues tested. When the purified PNP oxidase was incubated with the mAbs, the enzyme activity was inhibited up to a maximum of 81%. Furthermore, these antibodies were successfully applied in immunohistochemistry in order to detect PNP oxidase in various regions of rat brain tissues. The immunoreactive neurons in PNP oxidase were found in cerebellar cortex, hippocampus, amygdala, paraventricular nucleus, cerebral cortex and ependyma. This result suggests that PNP oxidase may play an important role in the neuronal metabolism.

Animals↗
PubMed2002

Changes in Na(+)-K(+)-Cl(-) cotransporter immunoreactivity in the gerbil hippocampus following transient ischemia.

We examined alterations in Na(+)-K(+)-Cl(-) cotransporter 1 (NKCC1) immunoreactivity following ischemia. Twelve hours after ischemia, NKCC1 immunoreactivity in the CA1 region and in the hilar region was significantly diminished. Twenty-four hours after ischemia, NKCC1 immunoreactivity was intensified in these hippocampal regions as well as CA2-3. Two days after ischemia, NKCC1 immunoreactivity in the CA1 and the hilar neurons had disappeared, although in the CA2-3 and the granule cell layer NKCC1 immunoreactivities had recovered to the sham level. This finding suggests that NKCC1 may play an important role in the ischemic neuronal injury induced by excitotoxicity as well as neuronal edema.

Animals↗
PubMed2002

The decreases in calcium binding proteins and neurofilament immunoreactivities in the Purkinje cell of the seizure sensitive gerbils.

In previous studies, it has been reported that Purkinje cell degeneration during seizure is evoked by excitotoxicity due to an increase in the intracellular Ca(2+) level, though calbindin D-28k (CB) and parvalbumin (PV), intracellular free calcium buffers, are abundantly colocalized in these cells. In the present study, we investigated the expressions of CB, PV, neurofilament (NF) 68, 150, 200, and polyphosphorylated epitope in NF (RT 97), in the cerebellum of gerbils to identify the mechanism of Purkinje cell damages induced by seizure. In seizure resistant gerbils, nearly all the Purkinje cells showed CB, PA, NF 150, NF 200 and RT 97 immunoreactivity. In SS gerbils, however, a clear decrease in the number of CB(+) and PV(+) Purkinje cells was observed. The NF and RT 97 immunoreactivities, in the Purkinje cells was also lower (except NF 68), but not absent. These results suggest several points. First, the decrease in the concentrations of CB and PV may render the Purkinje cells more susceptible to intermittent Ca(2+) fluctuations and more prone to accumulating intolerable quantities of Ca(2+). Second, during the Ca(2+)-PV interaction PV plays an important role in facilitating donations of Mg(2+), which is a potent enzyme activator in phosphorylation. Thus the decline in PV concentration also implicated the defects of phosphorylation in the NF. Third, increases in both the intracellular Ca(2+) level and dephosphorylation trigger the degradation of the NF, particularly NF 200. Finally, these degradations in the NF induce the functional defects in Purkinje cell, which then cause Purkinje cell degeneration.

Animals↗