Biomedical subjects

Sung Min Park

Publications and source records attributed to Sung Min Park.

11 recordsLinked to original sources

PubMed2006

Dynamic behaviors in directed networks.

Motivated by the abundance of directed synaptic couplings in a real biological neuronal network, we investigate the synchronization behavior of the Hodgkin-Huxley model in a directed network. We start from the standard model of the Watts-Strogatz undirected network and then change undirected edges to directed arcs with a given probability, still preserving the connectivity of the network. A generalized clustering coefficient for directed networks is defined and used to investigate the interplay between the synchronization behavior and underlying structural properties of directed networks. We observe that the directedness of complex networks plays an important role in emerging dynamical behaviors, which is also confirmed by a numerical study of the sociological game theoretic voter model on directed networks.

Journal Article↗

PubMed2006

Effect of titanium ion and resistance encoding plasmid of Pseudomonas aeruginosa ATCC 10145.

Titanium and its alloys are technically superior and cost-effective materials, with a wide variety of aerospace, industrial, marine, and commercial applications. In this study, the effects of titanium ions on bacterial growth were evaluated. Six strains of bacteria known to be resistant to both metal ions and antibiotics were used in this study. Two strains, Escherichia coli ATCC 15489, and Pseudomonas aeruginosa ATCC 10145, proved to be resistant to titanium ions. Plasmid-cured P. aeruginosa resulted in the loss of one or more resistance markers, indicating plasmid-encoded resistance. The plasmid profile of P. aeruginosa revealed the presence of a 23-kb plasmid. The plasmid was isolated and transformed into DH5alpha. Interestingly, the untransformed DH5alpha did not grow in 300 mg/l titanium ions, but the transformed DH5alpha grew quite well under such conditions. The survival rate of the transformed DH5alpha also increased more than 3-fold compared to that of untransformed DH5alpha.

Culture Media↗

PubMed2005

Apolipoprotein C-II is a novel substrate for matrix metalloproteinases.

We previously reported an efficient proteomic approach to identify matrix metalloproteinase (MMP) substrates from complex protein mixture. Using the proteomic approach, apolipoprotein C-II (apoC-II), which is a cofactor of lipoprotein lipase (LPL) and a component of very-low density lipoprotein and chylomicron, has been identified as a putative MMP-14 substrate. Cleavage of apoC-II, with various MMPs, demonstrated that apoC-II is cleaved most efficiently by MMP-14, and also by MMP-7, among the tested MMPs. The 79-amino acid residue apoC-II was cleaved between Asn35 and Leu36 by MMP-14, and between Phe14 and Leu15 and between Asn35 and Leu36 by MMP-7. Cleavage of apoC-II by MMP-14 markedly decreased LPL activity and would thus impair hydrolysis of triglycerides in plasma and transfer of fatty acids to tissues. Our result suggests that cleavage of apoC-II by MMPs would be important for development of pathophysiological situations of apoC-II deficiency such as atherosclerosis.

Amino Acid Sequence↗

PubMed2005

Proteolytic cleavage of extracellular secreted {alpha}-synuclein via matrix metalloproteinases.

Although alpha-synuclein is the main structural component of the insoluble filaments that form Lewy bodies in Parkinson disease (PD), its physiological function and exact role in neuronal death remain poorly understood. In the present study, we examined the possible functional relationship between alpha-synuclein and several forms of matrix metalloproteinases (MMPs) in the human dopaminergic neuroblastoma (SK-N-BE) cell line. When SK-N-BE cells were transiently transfected with alpha-synuclein, it was secreted into the extracellular culture media, concomitantly with a significant decrease in cell viability. Also the addition of nitric oxide-generating compounds to the cells caused the secreted alpha-synuclein to be digested, producing a small fragment whose size was similar to that of the fragment generated during the incubation of alpha-synuclein with various MMPs in vitro. Among several forms of MMPs, alpha-synuclein was cleaved most efficiently by MMP-3, and MALDI-TOF mass spectra analysis showed that alpha-synuclein is cleaved from its C-terminal end with at least four cleavage sites within the non-Abeta component of AD amyloid sequence. Compared with the intact form, the protein aggregation of alpha-synuclein was remarkably facilitated in the presence of the proteolytic fragments, and the fragment-induced aggregates showed more toxic effect on cell viability. Moreover, the levels of MMP-3 were also found to be increased significantly in the rat PD brain model produced by the cerebral injection of 6-hydroxydopamine into the substantia nigra. The present study suggests that the extracellularly secreted alpha-synuclein could be processed via the activation of MMP-3 in a selective manner.

Alzheimer Disease↗

PubMed2005

Cervical radiculopathy caused by neural foraminal migration of a herniated calcified intervertebral disk in childhood: a case report.

Childhood intervertebral disk calcification is a rare clinical entity. Although its clinical course is usually benign, nerve root irritation or spinal cord compression can occasionally occur. We present the clinical and radiologic findings of a 9-year-old boy with cervical radiculopathy due to a herniated calcified intervertebral disk, which developed suddenly after swimming for 1 hour. Radiologic findings indicated that a calcified nucleus pulposus at the C6-7 level herniated into the spinal canal and migrated far into the right C6-7 neural foramen. Surgical management was performed 8 weeks after the onset of symptoms, because the initial presenting symptoms persisted despite conservative treatment. In children, calcified intervertebral disks can cause cervical radiculopathy that requires surgical management when they herniate and migrate far into the neural foramen.

Calcinosis↗

PubMed2004

A proteomic approach to identify substrates of matrix metalloproteinase-14 in human plasma.

Matrix metalloproteinases (MMPs) are a family of zinc-containing endopeptidases that proteolyze extracellular matrix components as well as a variety of functional proteins. Here we describe a "degradomics" method that efficiently identifies substrates of MMP-14 in a complex protein mixture, such as plasma. Plasma proteins were incubated in the presence or absence of the MMP-14 catalytic domain and displayed on two-dimensional (2-D) gels. After a comparison of the gels, we selected 40 protein spots that reproducibly showed disparities. Upon in-gel digestion, mass determination, and peptide mass fingerprinting, we identified 15 different proteins from 31 spots. These proteins included six known substrates and nine potential substrates of MMP-14. Among the latter, the purified forms of apolipoprotein A-I, apolipoprotein E, and plasma gelsolin were cleaved in vitro by MMP-14, confirming that each of them is a novel substrate of MMP-14. These results demonstrate that our method rapidly and selectively identifies MMP-14 substrates from human plasma proteins. This method would thus constitute a powerful tool for identifying the substrates of MMPs and other proteases in highly complex mixtures of proteins and would enhance our understanding of the biological roles of these enzymes.

Amino Acid Sequence↗

PubMed2004

Cortical activation changes associated with motor recovery in patients with precentral knob infarct.

We investigated the cortical activation changes associated with motor recovery in six hemiparetic patients with precentral knob infarct. fMRI at 1.5 T with finger movements at a fixed rate was performed twice in each patient, 1 and 6 months after stroke onset. From the images obtained, the LI (laterality index) for the primary sensorimotor cortex (SM1) was calculated to measure the degree of the cortical activity concentration in the contralateral hemisphere. Our results showed that a greater improvement in motor function scores was significantly correlated with a greater increment in LI induced by affected finger movements (p < 0.05). Motor recovery after precentral knob infarct was found to be positively related with the concentration of SM1 activity in the ipsilesional hemisphere. This finding may imply motor recovery through cortical reorganization after precentral knob infarct in the human brain.

Aged↗

PubMed2004

Antioxidants and inhibitor of matrix metalloproteinase-1 expression from leaves of Zostera marina L.

In order to develop new anti-photoaging agents, we examined the antioxidative activity and the inhibition effect of matrix metalloproteinase-1 (MMP-1) on the extracts of a marine product, Zostera marina L., which is known for its potent activity. Three compounds (compounds 1, 2, and 3) were isolated from an ethyl acetate (EtOAc) soluble fraction of the product; they were identified as apigenin-7-O-beta-D-glucoside (1), chrysoeriol (2), and luteolin (3). These compounds were found to scavenge radicals and reactive oxygen species (ROS) and were measured to have SC50 values of 0.18 mM, 0.68 mM, and 0.01 mM against the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and 0.04 mM, 0.03 mM, and 0.01 mM against the superoxide radical in the xanthine/xanthine oxidase system, respectively. Compound 3 suppressed the expression of MMP-1 by up to 44% at 4.0 microM and inhibited the production of interleukin 6 (IL-6), which is known as a cytokine that induces MMP-1 expression. From these results, compound 3 and the other compounds were determined to have antioxidative activity and to inhibit MMP-1 expression. Thus, the three compounds are expected to be useful for preventing the photoaging of skin.

Antioxidants↗

PubMed2004

Alcohol neurolysis of tibial nerve motor branches to the gastrocnemius muscle to treat ankle spasticity in patients with hemiplegic stroke.

OBJECTIVE: To evaluate the effectiveness of alcohol neurolysis of tibial nerve motor branches to the gastrocnemius muscle for the treatment of ankle plantarflexor spasticity in patients with hemiplegic stroke. DESIGN: Case series. SETTING: Inpatient and outpatient clinics in the rehabilitation department of a university hospital. PARTICIPANTS: Twenty-two patients with hemiplegic stroke (mean age, 48y). INTERVENTIONS: Motor branch block (MBB) of the tibial nerve to the gastrocnemius muscle with 50% ethyl alcohol in cases of spastic ankle. MAIN OUTCOME MEASURES: The severity of spasticity was assessed using the Modified Ashworth Scale (MAS) score of ankle plantarflexor, clonus score of the ankle, and the passive range of motion (PROM) of ankle dorsiflexion. RESULTS: The MAS score was reduced in 17 (77%) of 22 patients during the 6-month follow-up, and spasticity reappeared at the level of the pre-MBB state in 5 patients (23%). The mean values of all parameters were significantly improved. The changes of mean values from the pre-MBB to the 6-month post-MBB stage were as follows: MAS score, 3.3+/-0.7 versus 1.7+/-1.1; clonus score, 1.6+/-0.7 versus 0.4+/-0.8; and PROM, 17.1 degrees +/-13.0 degrees versus 28.6 degrees +/-4.7 degrees. No serious complications were observed during the 6-month follow-up period. CONCLUSIONS: MBB of the tibial nerve to the gastrocnemius muscle is an effective and safe procedure for relieving localized spasticity of the ankle plantarflexors.

Adult↗

PubMed2003

Oxidant-induced cell death in renal epithelial cells: differential effects of inorganic and organic hydroperoxides.

This study was undertaken in order to examine the roles of lipid peroxidation and poly (ADP-ribose) polymerase (PARP) activation in oxidant-induced renal cell death. Opossum kidney cell cultures were used as the renal epithelial cell model, and an inorganic hydroperoxide H2O2 and an organic hydroperoxide t-butylhydroperoxide were employed as model oxidants. Cell death by both oxidants could be prevented by thiols (dithiothreitol and glutathione), iron chelators (deferoxamine and phenanthroline), and hydroxyl radical scavengers (dimethylthiourea and pyruvate). Phenolic antioxidants N,N'-diphenyl-p-phenylenediamine (DPPD) and butylated hydroxyanisole had no effect on the H2O2-induced cell death. However, the t-butylhydroperoxide-induced cell death was effectively prevented by these antioxidants. The PARP inhibitor 3-aminobenzamide prevented the cell death induced by H2O2, but not cell death by t-butylhydroperoxide. The PARP activity was increased in cells exposed to H2O2 but not t-butylhydroperoxide. Unlike in opossum kidney cells, in rabbit renal cortical slices both oxidants H2O2 and t-butylhydroperoxide induced cell death through a lipid peroxidation-dependent and PARP-independent mechanism. Effects of DPPD and 3-aminobenzamide on H2O2-induced cell death in primary cultured rabbit proximal tubular cells were similar to those in opossum kidney cells. These results indicate that 1) the H2O2-induced cell death in cultured renal epithelial cells is associated with PARP activation but not lipid peroxidation, whereas the t-butylhydroperoxide-induced cell death is mediated by lipid peroxidation, and 2) the role of lipid peroxidation in H2O2 cytotoxicity may be different between freshly isolated renal tubular cells and cultured renal epithelial cells.

Animals↗

PubMedDate not supplied

Ventricular assist device implantation using a right thoracotomy.

Most patients needing implantation of a ventricular assist device (VAD) require repeated sternotomy; some after cardiac surgery, and others later for heart transplantation. The purpose of this study was to establish the right thoracotomy technique as an alternative for VAD implantation to reduce repeated sternotomy-related morbidity and mortality. We performed a right thoracotomy in animals, preclinical cadaver fitting tests, and a clinical case. A total of 20 various animals underwent right thoracotomy for implantation of bi-VAD (BVAD, n = 17) and left VAD (LVAD, n = 3). The right chest cavity was entered through the fourth intercostal space with partial resection of the fifth rib. There was no procedure-related morbidity or mortality, except for one calf with right anterior leg paralysis. Preclinical fitting tests were performed on 7 human cadavers to observe the anatomical feasibility of BVAD cannulation from the right side of the heart. In humans, the ascending aorta, interatrial groove, right atrium, and main pulmonary artery were identified as optimal cannula insertion sites for BVAD implantation. A patient with cardiogenic shock underwent a right thoracotomy for implantation of an external LVAD. Cardiac function recovered after 3 weeks, and the device was successfully explanted through a repeat right thoracotomy. In conclusion, a right thoracotomy can be an alternative method to the standard median sternotomy for patients who need repeated sternotomy because of previous cardiac surgery, transplantation at a later date, or those with mediastinal infections.

Aged↗