Biomedical subjects

Jong Hyun Kim

Publications and source records attributed to Jong Hyun Kim.

At least 19 recordsLinked to original sources

PubMed2006

Outcome of repeated radiosurgery for recurrent metastatic brain tumors.

OBJECTIVE: We investigated the outcome of repeated gamma knife radiosurgery (GKS) for local or remote recurrence after initial radiosurgery. MATERIAL AND METHODS: We retrospectively reviewed 204 patients who were treated with GKS. Among them 43 patients (21%) underwent GKS more than once. The second GKS was given for recurrence at the previously treated sites in 16 patients, new lesions at remote sites in 13, and both local recurrence and new lesions in 14. RESULTS: The median survival from the first GKS was 36 (7-190) weeks in all patients and 68 (16-156) weeks in 43 patients with repeated GKS. The median time from the first GKS to the second was 37 weeks. The median survival from the second radiosurgical intervention was 32 (7-132) weeks. Local control rate at 6 months after salvage GKS was 90.7%. RPA class was the commonly dominant prognostic factor in both initial and salvage GKS. CONCLUSION: Recurrence is common for patients with metastatic brain tumors after initial radiosurgery. Local control and survival time after salvage treatment are comparable with those after initial radiosurgery. GKS as a salvage treatment may provide additional survival benefit in selected patients.

Adult↗

PubMed2006

Phospholipase D2 acts as an essential adaptor protein in the activation of Syk in antigen-stimulated mast cells.

Mast cells are responsible for IgE-mediated allergic reactions. Phospholipase D1 (PLD1) and PLD2 regulate mast cell activation, but the mechanisms remain unclear. Here we show that PLD2 associates with and promotes activation of Syk, a key enzyme in mast cell activation. Antigen stimulation resulted in increased association and colocalization of Syk with PLD2 on the plasma membrane as indicated by coimmunoprecipitation and confocal microscopy. This association was dependent on tyrosine phosphorylation of Syk but not on PLD2 activity. In vitro, PLD2 interacted via its Phox homology (PX) domain with recombinant Syk to induce phosphorylation and activation of Syk. Furthermore, overexpression of PLD2 or catalytically inactive PLD2K758R enhanced antigen-induced phosphorylations of Syk and its downstream targets, the adaptor proteins LAT and SLP-76, while expression of a PLD2 siRNA blocked these phosphorylations. Apparently, the interaction of PLD2 with Syk is an early critical event in the activation of mast cells.

Adaptor Proteins, Signal Transducing↗

PubMed2006

Transient recovery of synaptic transmission is related to rapid energy depletion during hypoxia.

Transient recovery (TR) of evoked synaptic potential during the late stage of hypoxic hypoglycemia (HH) insult was investigated in rat hippocampal slices using extracellular recording methods. TR was observed in association with a rapid deterioration of antidromic population spikes (aPSs) following HH insult. TR was not elicited in normoglycemic hypoxia (NH), in which a gradual and delayed deterioration of aPSs was noted. TR was not modulated by either Ca(2+)- or PKC-dependent processes. When a glycolytic inhibitor was added, NH resulted in a rapid deterioration of aPSs and prompted appearance of TR. TR was also seen in slices using lactate to generate energy via oxidative phosphorylation, when hypoxic conditions were subsequently created. Other pharmacological interventions that aimed to cause rapid deterioration of aPSs without depleting energy stores failed to reproduce TR. The evidence thus suggests that the underlying mechanisms of TR appearance during HH insult are highly correlated with rapid energy depletion.

Animals↗

PubMed2006

Prognosis of non-small cell lung cancer with synchronous brain metastases treated with gamma knife radiosurgery.

The clinical outcome and prognostic factors of patients with synchronous brain metastases from non-small cell lung cancer (NSCLC) who were treated with gamma knife radiosurgery (GKS) were analyzed. A total of 35 patients with NSCLC underwent GKS as an initial treatment for metastatic brain lesions of synchronous onset. The period of survival and various prognostic factors such as age, gender, performance status, multiplicity of the brain lesions, intracranial tumor volume, and extent of the primary tumor were analyzed. The overall median survival time for this series was 12 months (range 0.75 to 43 months) from the diagnosis. Of the 21 patients who were no longer alive at the conclusion of this study, only 7 (33.3%) died of neurological causes. Multivariate analysis of these data revealed that N stage, whole-brain radiotherapy (WBRT), and chemotherapy were significant predictors for survival (p<0.05). Survival of patients with NSCLC and synchronous brain metastases is mainly dependent upon the progression of the systemic disease, provided that the cerebral lesions are treated adequately with local treatment modalities including radiosurgery. Application of radiosurgery as an initial treatment option and aggressive local and systemic modalities to control extracranial disease may improve survival.

Adult↗

PubMed2006

A pilot study of metronomic temozolomide treatment in patients with recurrent temozolomide-refractory glioblastoma.

Frequent regular administration of chemotherapeutic agents at low doses, known as 'metronomic chemotherapy', can increase the anti-angiogenic activity of the drugs, as has been confirmed by several other experimental tumor models. The aim of this pilot study was to evaluate the efficacy and safety of metronomic temozolomide (TMZ) treatment in twelve consecutive patients with recurrent TMZ-refractory glioblastoma. The patients were administered by metronomic treatment schedule (continuous low-dose chemotherapy) with TMZ at a daily dose of 40 mg/m(2). The median overall survival (OS) and progression-free survival (PFS) from the start of metronomic treatment were 11.0 months (95% CI, 5.2-10.5 months) and 6.0 months (95% CI, 0-12.3 months), respectively. During the follow-up period, complete response (CR) was not achieved in any patient, partial response (PR) in 2, and stable disease (SD) in 5 patients. Estimated PFS (CR+PR+SD) was 58.3% at 3 months. Grade III/IV toxicity according to the National Cancer Institute Common Toxicity Criteria (NCI CTC) was not found. These results suggest that the change of chemotherapeutic schedule from conventional to metronomic treatment overcomes the chemo-resistance in patients with recurrent TMZ-refractory glio-blastoma without any major toxicity.

Adult↗

PubMed2005

Changes in bone metabolism in a rat model of traumatic brain injury.

PRIMARY OBJECTIVE: To evaluate the process of bone metabolism after traumatic brain injury. RESEARCH DESIGN: Randomized controlled trial. METHODS AND PROCEDURES: Rats were randomly assigned to either the brain injury group or to the sham-operation group using a fluid percussion device. The BMDs of lumbar vertebrae and proximal femur and bone turnover markers, osteocalcin and carboxy-terminal telopeptide, were measured at three points: the day before surgery and 1 and 3 weeks post-operatively. The biomechanics (maximum load of tibia and femoral neck) were measured 3 weeks post-operatively. MAIN OUTCOMES AND RESULTS: There was significant change in the BMDs of lumbar vertebrae 1 week post-operatively and of both distal femurs 3 weeks post-operatively (p < 0.05). A significant change in the maximum load of femoral neck was also observed 3 weeks post-operatively between the brain injury and the sham-operation groups (p = 0.044). CONCLUSIONS: This finding suggests that brain injury could induce osteoporosis by immobilization.

Animals↗

PubMed2005

Phosphatidylinositol (3,4,5)-trisphosphate specifically interacts with the phox homology domain of phospholipase D1 and stimulates its activity.

Phospholipase D (PLD), which catalyzes the hydrolysis of phosphatidylcholine to phosphatidic acid and choline, plays key roles in cellular signal transduction by mediating extracellular stimuli including hormones, growth factors, neurotransmitters, cytokines and extracellular matrix molecules. The molecular mechanisms by which domains regulate the activity of PLD--especially the phox homology (PX) domain--have not been fully elucidated. In this study, we have examined the properties of the PX domains of PLD1 and PLD2 in terms of phosphoinositide binding and PLD activity regulation. Interestingly, the PX domain of PLD1, but not that of PLD2, was found to specifically interact with phosphatidylinositol (3,4,5)-trisphosphate (PtdIns(3,4,5)P3). We found that mutation of the conserved arginine at position 179 of the PLD1 PX domain to lysine or to alanine (R179A or R179K, respectively) disrupts PtdIns(3,4,5)P3 binding. In NIH-3T3 cells, the EGFP-PLD1 PX wild-type domain, but not the two mutants, localized to the plasma membrane after 5-minute treatment with platelet-derived growth factor (PDGF). The enzymatic activity of PLD1 was stimulated by adding PtdIns(3,4,5)P3 in vitro. Treatment with PDGF resulted in the significant increase of PLD1 activity and phosphorylation of the downstream extracellular signal-regulated kinases (ERKs), which was blocked by pre-treatment of HEK 293 cells with phosphoinositide 3-kinase (PI3K) inhibitor after the endogenous PLD2 had been depleted by siRNA specific for PLD2. Nevertheless, both PLD1 mutants (which cannot interact with PtdIns(3,4,5)P3) did not respond to treatment with PDGF. Moreover, PLD1 was activated in HepG2 cells stably expressing the Y40/51 mutant of PDGF receptor that is required for the binding with PI3K. Our results suggest that the PLD1 PX domain enables PLD1 to mediate signal transduction via ERK1/2 by providing a direct binding site for PtdIns(3,4,5)P3 and by activating PLD1.

Amino Acid Sequence↗

PubMed2005

Cytotoxicity of rat marrow stromal cells against malignant glioma cells.

OBJECTS: Marrow stromal cells (MSCs) have been shown to have the capacity of orthodox and unorthodox plasticity. In this study, the authors tried to access in vitro cytotoxicity of MSCs from rat and also to differentiate MSCs into immune effector cell. METHODS: Rat MSCs (rMSCs) were isolated by standard methodology and were activated by interleukin-2 (IL-2), interleukin-15 (IL-15), granulocyte macrophage colony stimulating factor, and combinations, which were effector cells. Cytotoxicity of rMSCs and activated rMSCs against the target cells (9L rat glioma cell line) was estimated using visual survival cell assay. Phenotypes of these various activated cells were determined using flow cytometry. The secreted protein from effector cells was estimated by enzyme-linked immunosorbent assay. The expression of immune response-related genes in activated cells was measured. RESULTS: There was a significant cytotoxicity of rMSCs activated with various cytokine combinations. After various cytokine activations of rMSCs, the population of immune effector cells (CD8, CD161a) and immune reaction-related proteins (IL-4, gamma-INF) might increase. Apoptosis may be one of the lysis mechanisms of target cells by activated rMSCs. The contributing genes could be gamma-INF, FasL, and perforin. CONCLUSION: This study suggests that rMSC may be used as adoptive transfer therapy in patients suffering from malignant brain tumor, but we have to investigate orthotopic animal study for the proper translation.

Animals↗

PubMed2005

ACNU-cisplatin continuous infusion chemotherapy as salvage therapy for recurrent glioblastomas: phase II study.

PURPOSE: To evaluate the activity and the toxicity of ACNU (1-(4-amino-2-methyl-5-pyrimidinyl)-methyl-3-(2-cholroethyl)-3-nitrosourea hydrochloride) administered with cisplatin by intravenous infusion for 72 h in select patients with recurrent glioblastoma. PATIENTS AND METHODS: From April 1996 to 2002, 37 patients with histologically proven glioblastoma, who showed recurrence on image study after operation and radiation, met the eligibility criteria of our cohort. The mean time to recurrence was 9.7+/-7.0 (1-26 months). Treatment response was evaluated every 6 weeks using magnetic resonance imaging (MRI). Complete blood counts were collected every week to monitor and treat possible bone marrow suppression from the treatment. Survival rates were analyzed using the Kaplan-Meier and log rank test. RESULTS: Post-chemotherapy MRI was available in 36 of 37 patients. Response to treatment was observed in 19 patients (53%) including two cases of complete remission. Six patients (17%) showed progression (PD) and 11 patients (31%) had stable disease (SD). Two or more cycles of chemotherapy was the only factor that predicted response to treatment. The overall median survival for all patients was 17.0+/-5.5 months. Age (< 40 years) and time to recurrence (>or=1 year) were the clinical factors that predicted improved overall survival. Survival gain after chemotherapy was 9 months. Patients who responded and those with SD after treatment (11 months) had a longer median survival compared to PD (5 months) (P=0.01). Myelosuppression was severe (grade III/IV leukopenia in 15 patients (40%) and grade III/IV thrombocytopenia in 19 patients (52%)) but most recovered more than WHO grade II at the end of the chemotherapy cycles. There was only one fatality due to sepsis from pneumonia during the initial leukopenic state. CONCLUSION: ACNU and cisplatin chemotherapy can be an effective salvage therapy for recurrent glioblastoma patients. Myelosuppression from the chemotherapy regimen was the greatest side-effect but was manageable.

Adolescent↗

PubMed2005

Novel functions of the phospholipase D2-Phox homology domain in protein kinase Czeta activation.

It has been established that protein kinase Czeta (PKCzeta) participates in diverse signaling pathways and cellular functions in a wide variety of cells, exhibiting properties relevant to cellular survival and proliferation. Currently, however, the regulation mechanism of PKCzeta remains elusive. Here, for the first time, we determine that phospholipase D2 (PLD2) enhances PKCzeta activity through direct interaction in a lipase activity-independent manner. This interaction of the PLD2-Phox homology (PX) domain with the PKCzeta-kinase domain also induces the activation loop phosphorylation of PKCzeta and downstream signal stimulation, as measured by p70 S6 kinase phosphorylation. Furthermore, only the PLD2-PX domain directly stimulates PKCzeta activity in vitro, and it is necessary for the formation of the ternary complex with phosphoinositide-dependent kinase 1 and PKCzeta. The mutant that substitutes the triple lysine residues (Lys101, Lys102, and Lys103) within the PLD2-PX domain with alanine abolishes interaction with the PKCzeta-kinase domain and activation of PKCzeta. Moreover, breast cancer cell viability is significantly affected by PLD2 silencing. Taken together, these results suggest that the PLD2-mediated PKCzeta activation is induced by its PX domain performing both direct activation of PKCzeta and assistance of activation loop phosphorylation. Furthermore, we find it is an important factor in the survival of breast cancer cells.

3-Phosphoinositide-Dependent Protein Kinases↗

PubMed2005

Clinical features and long-term results of spontaneous intracranial hypotension.

OBJECTIVE: Although spontaneous intracranial hypotension (SIH) is an increasingly recognized syndrome, the long-term outcomes have not been established. We conducted a long-term follow-up study to clarify the clinical features and long-term outcomes of patients with this disorder. METHODS: We performed a retrospective study in 13 consecutive patients with SIH treated between 1998 and 2003. The diagnosis of intracranial hypotension was made on the basis of clinical symptoms, lumbar puncture, radiological studies (e.g. brain magnetic resonance imaging, spine magnetic resonance imaging, computed tomographic myelography) and radionuclide cisternography. We collected follow-up clinical information of the patients by telephone or by examination at an outpatient clinic. RESULTS: All patients were treated by nonsurgical conservative treatments, such as absolute bed rest, intravenous hydration and repetitive epidural blood patch (5 patients). The mean duration of follow up was 51.4 months (range, 15-80 mo). Among 13 patients included in this study, only one patient (7.7%) developed recurrent SIH, and the other patients improved from orthostatic headache. Although 7 of 13 patients had complete resolution of headache at a minimum of 2 years follow-up, 4 patients had mild headache and 2 patients continued to have moderate headache at the final examination. CONCLUSION: In this series, the outcome of SIH after conservative treatment was not as satisfactory as that reported in previous studies. We conclude that periodic follow-up examinations must be performed and a more effective treatment modality developed to achieve complete resolution of SIH.

Adult↗

PubMed2005

Clinical and radiological prognostic factors of anaplastic oligodendroglioma treated by combined therapy.

The clinical and radiological prognostic factors were investigated in 32 patients with newly diagnosed anaplastic oligodendroglioma treated by combined therapy using surgery, postoperative radiation therapy, and adjuvant chemotherapy between September 1994 and December 2002. Surgery aimed at total removal was followed by radiotherapy, and 3 weeks later by adjuvant chemotherapy repeated at 6- to 7-week intervals. Survival analysis showed that younger age, absence of preoperative headache, good postoperative Karnofsky Performance Status (KPS) score (>or=80), and relatively small tumor volume (<50 cm3) were predictors for longer survival in univariate analysis (p<0.05). Age and good postoperative KPS score were independent prognostic factors in multivariate analysis (p<0.05). Median survival was 58 months after diagnosis, and the 5-year survival rate was 49%.

Adult↗

PubMed2005

Spinal epidural synovial sarcoma: a case of homogeneous enhancing large paravertebral mass on MR imaging.

We report the MR imaging findings in a 44-year-old man with a low-grade synovial sarcoma. There was a right-sided epidural and paravertebral mass, widening of the ipsilateral neural foramen at the L4-L5 level, and focal erosion of the right superior articular process of the L5 vertebra. The mass was relatively homogeneous, hyperintense to muscle and isointense to fat on T2-weighted images, and isointense to muscle on T1-weighted images, and it demonstrated moderate homogeneous enhancement.

Adult↗

PubMed2004

Inhibition of muscarinic receptor-linked phospholipase D activation by association with tubulin.

Mammalian phospholipase D (PLD) is considered a key enzyme in the transmission signals from various receptors including muscarinic receptors. PLD activation is a rapid and transient process, but a negative regulator has not been found that inhibits signal-dependent PLD activation. Here, for the first time, we report that tubulin binding to PLD2 is an inhibition mechanism for muscarinic receptor-linked PLD2 activation. Tubulin was identified in an immunoprecipitated PLD2 complex from COS-7 cells by peptide mass fingerprinting. The direct interaction between PLD2 and tubulin was found to be mediated by a specific region of PLD2 (amino acids 476-612). PLD2 was potently inhibited (IC50 <10 nM) by tubulin binding in vitro. In cells, the interaction between PLD2 and tubulin was increased by the microtubule disrupting agent nocodazole and reduced by the microtubule stabilizing agent Taxol. Moreover, PLD2 activity was found to be inversely correlated with the level of monomeric tubulin. In addition, we found that interaction with and the inhibition of PLD2 by monomeric tubulin is important for the muscarinic receptor-linked PLD signaling pathway. Interaction between PLD2 and tubulin was increased only after 1-2 min of carbachol stimulation when carbachol-stimulated PLD2 activity was decreased. The expression of the tubulin binding region of PLD2 blocked the later decrease in carbachol-induced PLD activity by masking tubulin binding. Taken together, these results indicate that an increase in local membrane monomeric tubulin concentration inhibits PLD2 activity, and provides a novel mechanism for the inhibition of muscarinic receptor-induced PLD2 activation by interaction with tubulin.

Animals↗

PubMed2004

Lymphokine activated killer cells from umbilical cord blood show higher antitumor effect against anaplastic astrocytoma cell line (U87) and medulloblastoma cell line (TE671) than lymphokine activated killer cells from peripheral blood.

OBJECTS: The aims of this study were to assess the cytotoxic capability of lymphokine-activated killer (LAK) cells from umbilical cord blood (UCB), to compare them with those of peripheral blood (PB)-derived cells against anaplastic astrocytoma cell line (U87) and medulloblastoma cell line (TE671), and to identify which mechanism and genes were involved in cytotoxicity. METHODS: The effector cells were generated by interleukin-2 from UCB and PB. The antitumor property of effector cells against the target cells (U87, TE671) were estimated using a visual survival cell assay. The mixed target and effector (UCB) cells were analyzed for whether DNA fragmentation was present or not. Reverse transcription polymerase chain reaction analysis was then performed to estimate the statement of the perforin and FasL genes in activated and inactivated cells from UCB. RESULTS: The higher in vitro antitumor properties of the LAK cells from UCB were observed in comparison to the LAK cells from PB against the U87 and the TE671 ( p<0.05). Apoptosis may be one of the lysis mechanisms of target cells by the LAK cells from UCB. The contributing genes could be FasL and perforin. CONCLUSIONS: This study suggests that UCB may be used as a source of LAK cells in adults and children suffering from anaplastic astrocytoma or medulloblastoma.

Adult↗

PubMed2004

Computational study of conformational preferences of thioamide-containing azaglycine peptides.

The effect of thioamide substitution on the conformational stability of an azaglycine-containing peptide, For-AzaGly-NH2 (1), was investigated for the sake of finding possible applications by using ab initio and DFT methods. As model compounds, For-[psiCSNH]-AzaGly-NH2 (2), For-AzaGly-[psiCSNH]-NH2 (3), and For-[psiCSNH]-AzaGly-[psiCSNH]-NH2 (4) were used. Two-dimensional phi-psi potential energy surfaces (PESs) for 2-4 were calculated at the B3LYP/6-31G*//HF/6-31G* level in gas (epsilon = 1.0) and in water (epsilon = 78.4) by applying the isodensity polarizable continuum model (IPCM) method. On the basis of these PESs, the minimum energy conformations for 2-4 were characterized at the B3LYP level with 6-31G*, 6-311G**, and 6-31+G** basis sets. The remarkable structural effect of thioamide substitution for 2-4 is that beta-strand structure is observed as a global or local minimum. The minima of 2-4 are also compared with those for glycine and thioamide-containing glycine peptides. Our theoretical results demonstrate that compounds 2-4 would be used to design controllable secondary structures.

Glycine↗

PubMed2004

Munc-18-1 inhibits phospholipase D activity by direct interaction in an epidermal growth factor-reversible manner.

Mammalian phospholipase D (PLD) has been reported to be a key enzyme for epidermal growth factor (EGF)-induced cellular signaling, however, the regulatory mechanism of PLD is still unclear. In this report, we found that Munc-18-1 is a potent negative regulator of PLD in the basal state and that its inhibition is abolished by EGF stimulation. We investigated PLD-binding proteins obtained from rat brain extract, and identified a 67-kDa protein as Munc-18-1 by peptide-mass finger-printing. The direct association between PLD and Munc-18-1 was confirmed by in vitro binding analysis using the purified proteins, and their binding sites were identified as the phox homology domain of PLD and multiple sites of Munc-18-1. PLD activity was potently inhibited by Munc-18-1 in vitro (IC50 = 2-5 nm), and the cotransfection of COS-7 cells with Munc-18-1 and PLD inhibited basal PLD activity in vivo. In the basal state, Munc-18-1 coprecipitated with PLD and colocalized with PLD2 at the plasma membrane of COS-7 cells. EGF treatment triggered the dissociation of Munc-18-1 from PLD when PLD was activated by EGF. The dissociation of the endogenous interaction between Munc-18-1 and PLD, and the activation of PLD by EGF were also observed in primary cultured chromaffin cells. These results suggest that Munc-18-1 is a potent negative regulator of basal PLD activity and that EGF stimulation abolishes this interaction.

Amino Acid Sequence↗

PubMed2004

A molecular basis for the efficacy of magnesium treatment following traumatic brain injury in rats.

Magnesium ions have been shown to be a promising treatment for brain lesions caused by traumatic brain injury (TBI), as well as for the associated acute neurodegeneration and progressive functional deficits. This study investigated the effects of magnesium on the expression of the cell death/survival related proteins following TBI. Male Sprague-Dawley (SD) rats (n = 66, 280-320 g body weight) were subjected to sham surgery alone (n = 14), or to the surgery followed by a lateral fluid percussion brain injury of moderate severity (n = 52, 2.4-2.7 atm). The injured rats were randomly treated with an intravenous bolus of magnesium chloride (n = 26, 125 micromol) or saline vehicle (n = 26). The coronal brain sections were quantitatively analyzed for cell apoptosis and the expression of p53-related proteins, Bcl-2, cyclin D1 and PCNA at 1, 2, and 4 days post-injury by immunohistochemistry or in situ hybridization. Tissue damage was observed primarily in the ipsilateral cortex of the injured region with the induction of apoptosis and p53 mRNA level at 2 days after TBI. The expression of p53 and responding proteins (p21(WAF1/CIP1), Mdm2 and Bax) showed a temporal pattern similar to the apoptotic events in the time course experiments. They were induced in the early time points of days 1-2, decreasing by day 4 after TBI. In contrast, the expression of the cell survival related proteins - Bcl-2, cyclin D1, and PCNA - was most significant at day 4 post-injury, when the rate of apoptosis decreased. Magnesium treatment resulted in a reduction in apoptosis and expression of p53-related proteins. However, it had only a slight additive effect on the expression of the survival related proteins in the same time-course. These results provide a molecular basis for the efficiency of magnesium in treating TBI-induced tissue damage.

Animals↗