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H D Kim

Publications and source records attributed to H D Kim.

At least 55 records · Page 3Linked to original sources
PubMed1999

Glucose starvation and hypoxia induce nuclear accumulation of proteasome in cancer cells.

Solid tumors commonly contain regions with glucose-starved and hypoxic conditions. Tumor cells under the adverse conditions can survive through the stress response, such as cell cycle arrest. In this study, we found that the stress conditions stimulated nuclear accumulation of proteasomes, large multicatalytic protease complexes, in human colon cancer HT-29 cells. The nuclear proteasome levels both in amount and in activity were increased approximately 4 and 2 times by glucose starvation and hypoxia, respectively. No changes were detected in the total expression levels of proteasome. The nuclear proteasome accumulation was also observed in ovarian cancer A2780 cells under glucose starvation, suggesting that this response was regardless of the origin of cancer cells. Our results indicate that the nuclear proteasome distribution is enhanced by glucose starvation and hypoxia, and suggest that the proteolysis by proteasome in the nucleus may play roles in the stress response of solid tumor cells.

Cell Cycle↗
PubMed1999

Glucose-regulated stresses cause degradation of DNA topoisomerase IIalpha by inducing nuclear proteasome during G1 cell cycle arrest in cancer cells.

The glucose-regulated stress response of cancer cells leads to a decreased expression of DNA topoisomerase IIalpha (topo IIalpha) and a cell cycle arrest at the G1 phase. In this study, we found that the topo IIalpha decrease occurred specifically during the G1 arrest in human colon adenocarcinoma HT-29 cells. The intracelluar level of topo IIalpha in HT-29 cells was relatively constant regardless of cell cycle position in the exponentially growing state, determined using a centrifugal elutriation technique and synchronizing the cells with a mitotic inhibitor nocodazole. Interestingly, when the cell cycle was arrested in the M phase by nocodazole, the topo IIalpha level remained high even in stressed cells. After the stressed cells were released from the M phase, topo IIalpha steeply decreased along with cell cycle progression followed by the next G1 arrest. This decrease in nuclear topo IIalpha protein was completely inhibited by selective inhibitors for proteasome. Furthermore, we found that proteasome activity was elevated three to fourfold in the nuclear extract of stressed cells over unstressed cells. Accordingly, there were increased amounts of nuclear proteasome subunits, although total intracellular content of the subunits did not change in stressed cells. These findings indicate that the expression of topo IIalpha in stressed cells is downregulated at the G1 phase by proteasome-mediated degradation and that the proteolysis of topo IIalpha can be facilitated by the nuclear accumulation of proteasome.

Antigens, Neoplasm↗
PubMed1999

Continual remodeling of postsynaptic density and its regulation by synaptic activity.

A postsynaptic density (PSD) protein, PSD-95, was tagged with green fluorescent protein (GFP-PSD-95) and expressed in cultured hippocampal neurons using recombinant adenoviruses. GFP-PSD-95 was selectively localized to excitatory postsynaptic sites. Time-lapse fluorescence imaging of hippocampal neurons revealed that >20% of GFP-PSD-95 clusters turned over within 24 hours. The appearance rate of clusters was higher than the disappearance rate, and this difference accounted for the gradual increase of the cluster density observed in culture. Dynamics of PSD-95 clusters were also inhibited by blockers of excitatory synaptic transmission. Continual PSD turnover and its regulation by synaptic activity may be important in activity-dependent remodeling of neuronal connections.

2-Amino-5-phosphonovalerate↗
PubMed1999

Geldanamycin induces heat shock protein expression through activation of HSF1 in K562 erythroleukemic cells.

HSP90 is one of the most abundant heat shock proteins (HSPs) in eukaryotic cells and is found in complex with several regulatory proteins such as kinases and transcription factors. Geldanamycin (GA), a benzoquinone ansamycin, specifically binds to HSP90 and disrupts the interaction of HSP90 and target proteins. Thus, GA has been used as a specific inhibitor of HSP90. In this study, we examined whether GA could affect protein synthesis and gene expression in the human erythroleukemic cell line K562. Treatment with GA, but not herbimycin A (another benzoquinone ansamycin), highly induced a 70-kDa protein, which was revealed to be HSP70 by immunoblotting and immunoprecipitation with anti-HSP70 antibody. The expression of HSP28 was also enhanced by GA. Furthermore, GA induced the activation of heat shock factor 1 (HSF1), but not HSF2, as determined by electromobility shift and electromobility supershift assay. In addition, similar to heat shock treatment, GA induced the phosphorylation of HSF1. Heat shock element-binding activity and phosphorylation of HSF1 were attenuated 3 h after GA treatment. These results indicate that the functional inactivation of HSP90 by GA potentially stimulates the expression of heat shock proteins through activation of HSF1.

Antibiotics, Antineoplastic↗
PubMed1999

Geldanamycin induces cell cycle arrest in K562 erythroleukemic cells.

Geldanamycin (GA), a benzoquinone ansamycin, is one of the specific inhibitors of 90-kDa heat shock protein and induces growth inhibition and apoptosis in certain cancer cell lines. We have investigated the mechanism of GA-induced growth inhibition in K562 erythroleukemic cells. DNA flow-cytometric analysis indicated that GA-induced growth arrest was associated with G2/M phase arrest of the cell cycle. GA treatment down-regulated the expression of cyclin B1 and inhibited phosphorylation of Cdc2 protein, both key regulatory proteins at the G2/M boundary. GA also markedly inhibited the Cdc2 kinase activity, which may be in part a result of up-regulation of p27KIP1 by GA. The present results suggest a novel mechanism that p27KIP1 could be involved in the regulation of G2 to M phase transition.

Antibiotics, Antineoplastic↗
PubMed1999

ERK/MAPK pathway is required for changes of cyclin D1 and B1 during phorbol 12-myristate 13-acetate-induced differentiation of K562 cells.

Phorbol 12-myristate 13-acetate (PMA)-induced differentiation of human erythroleukemic K562 cells is characterized by growth arrest, morphological change, and expression of megakaryocyte-specific proteins. We examined the possible involvement of cell cycle regulators with PMA-induced growth arrest and megakaryocytic differentiation of K562 cells. The concentrations of cyclin D1 and p21Waf1/Cip1 were dramatically increased, whereas those of cyclin B1 and cdc2 were decreased, by PMA treatment. The concentrations of most cyclin-dependent kinases (Cdk2, Cdk4, and Cdk6), however, were unchanged by PMA treatment. PD98059, a specific inhibitor of MEK1, partially prevented the increase in cyclin D1 caused by PMA and fully reversed the down-regulation of cyclin B1 protein seen in response to PMA treatment. Thus, it is demonstrated here that the PMA-mediated changes of cyclin D1 and B1 are the result of a persistent increase in extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK) activity.

Cell Cycle↗
PubMed1999

Heat shock and 5-azacytidine inhibit nitric oxide synthesis and tumor necrosis factor-alpha secretion in activated macrophages.

To elucidate the role of stress response during macrophage activation, the effects of heat shock and the amino acid analog, 5-azacytidine on nitric oxide (NO) production, tumor necrosis factor-alpha (TNF-alpha) secretion, and heat shock protein (HSP) synthesis have been studied in murine peritoneal macrophages (C57BL/6). Heat shock (1 hr at 43 degrees C) or 5-azacytidine markedly inhibited the release of NO into the medium from interferon-gamma (IFN-gamma) plus lipopolysaccharide (LPS)-stimulated macrophages. Although heat shock significantly decreased TNF-alpha secretion only at the initiation stage of macrophage stimulation, 5-azacytidine treatment resulted in a more prolonged reduction in the secretion of TNF-alpha. When heat-shocked cells were stimulated with IFN-gamma plus LPS under normal culture conditions at 37 degrees C, the heat shock-induced inhibition of NO release reversed progressively with increasing recovery time. Although the total amount of cellular HSP72 measured by Western blot increased time-dependently over 7 hr, newly synthesized HSP72 measured by [35S]methionine incorporation was evident only after 1 and 3 hr of recovery time after heat shock treatment. At these time points, the lowest nitrite accumulation and TNF-alpha secretion into the medium was evident. It is concluded that signaling pathways related to newly synthesized HSP such as HSP72 are implicated in the down regulation of NO synthesis and TNF-alpha secretion in macrophages.

Animals↗
PubMed1999

Identification of heat shock protein 90-associated 84-kDa phosphoprotein.

In eukaryotic cells, HSP90 is associated with several protein kinases and regulates their activities. HSP90 was also reported to possess an autophosphorylase activity. In this study, we examined in vitro autophosphorylation of HSP90, which was purified from chick muscle. We show that HSP90 was not phosphorylated in vitro, but an 84-kDa protein (p84) was highly phosphorylated. P84 was neither HSP90 nor its degradative product, as it was not detected by an antibody (BF4) specific to HSP90 in denaturing immunoprecipitation and Western blot analysis. Phosphorylation of a protein similar to p84 was also detected with purified human brain and HeLa HSP90, indicating that p84 is present in many different types of cells. P84 appeared to exist as large complexes, as determined by HPLC and native gel electrophoresis. Native immunoprecipitation using anti-HSP90 (BF4)-conjugated Affi-gel revealed that this phosphoprotein is specifically associated with HSP90. The interaction of p84 and HSP90 was not affected by p84 phosphorylation. In addition, p84 phosphorylation was prevented by the presence of divalent cations such as Mg(2+) and Mn(2+). In contrast, p84 phosphorylation was significantly activated by addition of exogenous Ca(2+) between 100 and 500 microM, although it was blocked by higher concentrations (>1 mM) of Ca(2+). HSP90, but not p84, could be phosphorylated by casein kinase II. Finally, p84 phosphorylation was specifically prevented by hemin, but not by other kinase inhibitors, indicating that p84 phosphorylation may be regulated by heme-regulated protein kinase.

Animals↗
PubMed1999

The effect of nitric oxide on sperm cell function and embryo development.

PROBLEM: Nitric oxide (NO) has been known to have multifunctional roles both in the male and female reproductive systems. We investigated the effects of sodium nitroprusside (SNP)-dependent NO release on sperm cell function and embryo development to elucidate the mechanisms of action of NO. METHOD OF STUDY: Semen samples from 20 healthy men were processed by the swim-up method. Sperm motility, hyperactivation, and acrosome reaction were examined following incubation with various concentrations of SNP. The concentration of 10 nM to 1 mM was used for sperm motility and hyperactivation measurement and 1 microM to 1 mM for examining the effect on acrosome reaction. Embryo development to blastocyst stage was assessed using 100 nM to 1 mM of SNP added before transferring the mouse embryos into the culture medium. Finally, to understand the mechanism of action of NO, changes in embryo development were examined after zygotes were treated with various concentrations ranging up to 1 mM of 8-bromo-cGMP, an analog of cGMP. RESULTS: Both sperm motility and hyperactivation were significantly reduced at 100 microM and 1 mM concentrations of SNP after 6 hr of incubation. After 24 hr of incubation, they were greatly decreased with all, except the 10 nM concentration of SNP. The percentage of acrosomal-reacted spermatozoa was increased with the increasing concentration of SNP following incubation with 10 microM and 1 mM of SNP. Embryo development was arrested since the two-cell embryonic stage with all except the 100 nM concentration of SNP, and inhibited by 200 microM of SNP regardless of SNP treatment stage. However, embryo development was not influenced by 8-bromo-cGMP. CONCLUSIONS: We concluded that SNP-inhibited sperm cell function and embryo development in a dose- and time-dependent manner, and the inhibitory effect on embryo development, may not be a stage-specific treatment mediated via a cGMP-independent pathway. This result suggests that NO may be enough to affect the fecundity potential in vivo.

Acrosome↗
PubMed1999

Craniofacial arteriovenous malformation: preoperative embolization with direct puncture and injection of n-butyl cyanoacrylate.

PURPOSE: To evaluate the use of n-butyl cyanoacrylate (NBCA) for preoperative embolization of craniofacial arteriovenous malformation. MATERIALS AND METHODS: Fourteen patients with craniofacial arteriovenous malformation (forehead [n = 9], deep facial [n = 3], occipital [n = 1], or lip [n = 1] lesion) were treated with injection of NBCA. Forehead lesions were supplied by ophthalmic (n = 6) and/or superficial temporal arteries (n = 7); and facial and scalp lesions, by bilateral internal maxillary (n = 4), facial (n = 2), and/or occipital arteries (n = 1). Lesions were percutaneously punctured with a 20-gauge needle in the area of arteriovenous connection. Direct angiography was performed before and after compression of venous drainage, and NBCA diluted 30%-50% with iodized oil was injected during venous compression. RESULTS: Postembolization arteriograms showed that six lesions were completely devascularized after single or multiple (one to nine) injections, and five were effectively devascularized (> or = 90%). Although three lesions were 60%-70% devascularized after injection, two of these were successfully extirpated with no notable blood loss. In nine patients, the ophthalmic arterial supply had disappeared after embolization. There were no procedure-related complications. CONCLUSION: Direct-puncture embolization with NBCA is an effective and safe technique for preoperative devascularization of craniofacial arteriovenous malformation. For safe and effective devascularization, compression of draining venous channels is thought to be important.

Adolescent↗
PubMed1999

Changes in refraction and axial length according to the viscosity of intraocular silicone oil.

We performed this study to evaluate the changes in refraction and axial length induced by intraocular silicone oil, and to compare with various clinical parameters between 1,000 and 5,000 cSt silicone oil. The refraction length was measured with an autorefractometer, and the axial length was measured with A-scan ultrasonography. These measurements were performed before and after removal of the silicone oil, using a clear cornea technique in which the silicone oil was injected in combination with pars plana vitrectomy. The mean age of the 25 patients was 38.73 years. On average the intraocular retention after the removal of the silicone oil lasted 5.13 months, and the follow-up time following silicone oil removal was 4.37 months. The changes in refraction and axial length were 6.32 diopters and 12.02 mm, respectively. Eyes injected with 5,000 cSt (11 eyes) tended to have higher changes in the refraction (5.84 vs 6.86 diopters) and axial length (11.70 vs 12.34 mm) than did eyes injected with 1,000 cSt silicone oil (14 eyes). Statistically significant differences were shown for the changes in refraction (p = 0.010) and intraocular pressure (0.63 vs 2.00 mmHg; p = 0.006), whereas but not for the changes in axial length (p = 0.306) and visual acuity (14/100 vs 15/100; p = 0.125). Intraocular silicone oil induced changes in refraction and axial length, and these changes seemed to vary with different viscosities.

Adolescent↗
PubMed1999

Comparison of MR imaging with PET and ictal SPECT in 118 patients with intractable epilepsy.

BACKGROUND AND PURPOSE: MR imaging, PET, and ictal SPECT have been studied extensively as individual techniques in the localization of epileptogenic foci, but only a few comparative studies have been done. We evaluated the concordance rates of ictal video/EEG, MR imaging, PET, and ictal SPECT to compare the sensitivities of these imaging methods in the lateralization of epileptogenic foci. METHODS: The study included 118 consecutive patients who underwent surgery for medically intractable epilepsy and who were followed up for 12 months or more. MR imaging was compared retrospectively with ictal video/EEG, FDG-PET, ictal 99mTc-HMPAO SPECT, and invasive EEG as to their ability to localize the epileptogenic focus; the pathologic findings served as the standard of reference. RESULTS: MR imaging was concordant with video/EEG, PET, and ictal SPECT in 58%, 68%, and 58% of patients, respectively. With the pathologic diagnosis as the standard of reference, MR imaging, PET, and ictal SPECT correctly lateralized the lesion in 72%, 85%, and 73% of patients, respectively. Of the patients with good outcomes, MR imaging, PET, and ictal SPECT were correct in 77%, 86%, and 78%, respectively. In the good outcome group, MR imaging was concordant with PET and ictal SPECT in 73% and 62% of patients, respectively. Of 45 patients who underwent invasive EEG, MR imaging was concordant with the invasive study in 47%; PET in 58%; and ictal SPECT in 56%. Of 26 patients with normal MR findings, PET and ictal SPECT correctly lateralized the lesion in 80% and 55%, respectively. CONCLUSION: Overall concordance among the techniques is approximately two thirds or less in lateralizing epileptogenic foci. PET is the most sensitive, even though it provides a broad approximate nature of the epileptogenic zone, which is not adequate for precise surgical localization of epilepsy. PET and/or ictal SPECT may be used as complementary tools in cases of inconclusive lateralization with ictal video/EEG and MR imaging.

Adolescent↗
PubMed1998

Molecular cloning of a novel GTP-binding protein induced in fish cells by rhabdovirus infection.

We have cloned and sequenced a cDNA encoding GTP-binding protein from a fish cell, CHSE-214. The clone was 1493 bp long and contained an open reading frame encoding 364 amino acids. It has the five sequence motifs G1-G5 that are conserved in all GTP-binding proteins. Its amino acid sequences are strikingly different from those of the well-characterized G-proteins. However, sequences closely related to this protein are found in various kinds of species including human, Arabidopsis, Drosophila and archaebacteria, suggesting a novel subfamily within the superfamily of the GTP-binding proteins. Northern analysis indicates that this gene is constitutively expressed at a low level in normal cells but is induced by fish rhabdovirus infection at about 24 h post infection and disappears thereafter. Based on these observations, we propose that this protein represents an evolutionarily conserved novel subfamily of GTP-binding proteins which may play an important role in fish rhabdovirus infection.

Amino Acid Sequence↗
PubMed1998

Cloning, expression, and characterization of a novel guanylate-binding protein, GBP3 in murine erythroid progenitor cells.

We report the molecular cloning of a novel guanylate-binding protein (GBP), termed mouse GBP3 (mGBP3) in Friend virus-induced mouse erythroid progenitor (FVA) cells. The 71-kDa mGBP3 belongs to a family of known GBPs that contain the first two consensus motifs, GXXXXGK(S/T) and DXXG, but lack the third element, (N/T)KXD, found in typical GTP-binding proteins. Recombinant mGBP3 protein, expressed using a baculovirus expression system, binds to agarose-immobilized guanine nucleotides (GTP, GDP and GMP). Moreover, mGBP3 has been found to have an intrinsic GTPase activity with K(m) and Vmax values of 77 +/- 4 microM and 21 +/- 0.5 pmol min-1 microgram-1 of protein, respectively. The mGBP3 is distinct from the other GBPs, in that it does not have an isoprenylation/methylation motif CAAX at the carboxyl terminus. The mGBP3 appears to be localized in the cytosol based on immunofluorescence staining. Although the mGBP3 transcript is expressed to a varying degree in numerous mouse tissues, the message is most abundant in FVA cells. The mGBP3 transcript increases in FVA cells undergoing differentiation to a maximum within a few hours and then decreases to an undetectable level by 24 h. These results, taken together, suggest that mGBP3 is a novel member of a family of guanylate-binding proteins, which plays a role in the erythroid differentiation. The nucleotide sequence reported in this paper has been submitted to the GenBank with accession number U44731.

Amino Acid Sequence↗
PubMed1998

Acute occlusion of the middle cerebral artery: early evaluation with triphasic helical CT--preliminary results.

PURPOSE: To evaluate use of triphasic helical computed tomography (CT) for early diagnosis of occlusion and assessment of ischemia in cases of acute middle cerebral arterial occlusion. MATERIALS AND METHODS: Thirty-five patients with acute ischemia underwent triphasic helical CT within 6 hours after symptom onset. Early arterial, perfusion, and delayed phase CT scans were obtained 18, 30, and 80 seconds, respectively, after contrast material administration. Eighteen patients had proximal middle cerebral arterial occlusion diagnosed at magnetic resonance (MR) or digital subtraction angiography. Follow-up CT or MR imaging was performed in all patients. Two independent observers interpreted images for signs of arterial occlusion, collateral vessels, and the ischemic zone. RESULTS: One observer found at least one of three signs in 17 of the 18 patients with occlusion, and the other found at least one sign in all 18: Early decreased arterial contrast enhancement was seen by both observers in 11 patients (kappa = 0.77), a nonenhancing arterial segment was seen by the two observers in 12 and 14 (kappa = 0.73), and delayed asymmetric arterial enhancement was seen in 13 and 16 (kappa = 0.49). Triphasic CT findings of the ischemic zone were consistent with follow-up CT or MR imaging findings in seven of 12 patients. CONCLUSION: Triphasic helical CT is useful for early diagnosis of acute proximal middle cerebral arterial occlusion and assessment of the ischemic zone.

Acute Disease↗
PubMed1998

Regulation of intestinal Cl- and HCO3-secretion by uroguanylin.

Uroguanylin is an intestinal peptide hormone that may regulate epithelial ion transport by activating a receptor guanylyl cyclase on the luminal surface of the intestine. In this study, we examined the action of uroguanylin on anion transport in different segments of freshly excised mouse intestine, using voltage-clamped Ussing chambers. Uroguanylin induced larger increases in short-circuit current (Isc) in proximal duodenum and cecum compared with jejunum, ileum, and distal colon. The acidification of the lumen of the proximal duodenum (pH 5.0-5.5) enhanced the stimulatory action of uroguanylin. In physiological Ringer solution, a significant fraction of the Isc stimulated by uroguanylin was insensitive to bumetanide and dependent on HCO3- in the bathing medium. Experiments using pH-stat titration revealed that uroguanylin stimulates serosal-to-luminal HCO3- secretion (Js-->lHCO3-) together with a larger increase in Isc. Both Js-->lHCO3- and Isc were significantly augmented when luminal pH was reduced to pH 5.15. Uroguanylin also stimulated the Js-->lHCO3- and Isc across the cecum, but luminal acidity caused a generalized decrease in the bioelectric responsiveness to agonist stimulation. In cystic fibrosis transmembrane conductance regulator (CFTR) knockout mice, the duodenal Isc response to uroguanylin was markedly reduced, but not eliminated, despite having a similar density of functional receptors. It was concluded that uroguanylin is most effective in acidic regions of the small intestine, where it stimulates both HCO3- and Cl-secretion primarily via a CFTR-dependent mechanisms.

Animals↗
PubMed1998

Half-dose gadolinium-enhanced MR imaging with magnetization transfer technique in brain tumors: comparison with conventional contrast-enhanced MR imaging.

OBJECTIVE: The purpose of this study was to determine whether half-dose enhanced MR imaging with magnetization transfer (MT) saturation can replace standard-dose enhanced MR imaging without MT saturation in patients who have brain tumors. SUBJECTS AND METHODS: Three sets of enhanced T1-weighted MR images were prospectively obtained for each of 25 patients with 32 brain tumors; the first conventional MR images without MT were obtained after administration of standard-dose (0.1-mmol/kg) gadopentetate dimeglumine. Within 1 week, patients underwent administration of one half-dose (0.05 mmol/kg) of the contrast medium, and then two sets of enhanced T1-weighted images were obtained with and then without MT. The degree of contrast enhancement was assessed qualitatively for all 32 tumors and quantitatively for 26 tumors. In the quantitative analysis, we compared mean values for tumor-brain contrast-to-noise ratios in three sets of images. RESULTS: The visual conspicuity of enhancing lesions in half-dose T1-weighted MR images with MT was comparable with that of standard-dose conventional T1-weighted MR images in 43% of cases including most extraaxial tumors. In approximately 75% of cases, the degree of enhancement of the lesions was similar for half-dose T1-weighted images obtained with and without MT. Overall, mean values for tumor-brain contrast-to-noise ratios were significantly lower in half-dose T1-weighted images with MT than in standard-dose T1-weighted images. Also, mean values for tumor-brain contrast-to-noise ratios were significantly higher in half-dose T1-weighted images with MT than in half-dose T1-weighted images without MT. CONCLUSION: Because half-dose enhanced MR imaging with MT yields enhancement comparable with that of standard-dose enhanced conventional MR imaging in less than 50% of cases, the former technique would replace the latter in only limited cases such as selected extraaxial tumors.

Adult↗