Biomedical subjects

J B Park

Publications and source records attributed to J B Park.

At least 19 recordsLinked to original sources

PubMed2006

Fabrication and investigation of nanostructures on transition metal dichalcogenide surfaces using a scanning tunneling microscope.

Nanometer-scale holes have been fabricated on the surfaces of the semiconducting transition metal dichalcogenides (TMDCs) molybdenum ditelluride (MoTe2) and molybdenum disulfide (MoS2) by applying voltage pulses from the tip of a scanning tunneling microscope (STM) operating in ultrahigh vacuum (UHV). It was found that the tip geometry (tip shape and sharpness) influences the formation and structure of the atomic-scale nanostructures. Threshold voltage ranges for the surface modification of MoTe2 (3.0 +/- 0.3 V) and MoS2 (3.4 +/- 0.3 V) were determined. Negative sample voltage pulses applied to a p-type MoTe2 surface produced much larger and deeper nanometer-scale holes when compared with those produced by positive voltage pulses. The existence of threshold voltages and the pulse polarity dependence of nanostructure fabrication suggests that an electric field evaporation mechanism is applicable. Support for this mechanism was obtained by nanostructuring metallic TMDC NbSe2, where both the produced features and the threshold voltages (3.0 +/- 0.3 V) were similar for both positive and negative voltage pulses.

Journal Article↗

PubMed2006

Prognosis after liver transplantation predicted by preoperative MELD score.

The model for end-stage liver disease (MELD) has been an excellent predictor of 3-month mortality among cirrhotic patients awaiting orthotopic liver transplantation (OLT). The aim of this study was to evaluate whether the preoperative MELD score predicts short-term prognosis after OLT. We enrolled 98 adult liver transplant patients performed at our center from January 2001 to December 2002. In univariate analysis of risk factors for death within 3 and 6 months after liver transplantation, serum total bilirubin, creatinine, MELD score, hyponatremia with ascites, Child-Turcotte-Pugh (CTP) score were statistically significant parameters (P < .05). By logistic regression, none of the risk factors were subjected to multivariate analysis showed statistical significance. The odds ratios of the MELD score, hyponatremia with ascites, CTP score within 3 months were 0.997, 1.151, and 0.726 with 95% confidence intervals of [0.899, 1.105], [0.102, 12.959], and [0.389, 1.352], respectively. The odds ratio of MELD score, hyponatremia with ascites, CTP score within 6 months were 0.996, 0.914, and 0.764, with 95% confidence intervals of [0.901, 1.102], [0.089, 9.369], and [0.417, 1.401], respectively. Although MELD score has been a good predictor of short-term prognosis before OLT, MELD did not show an influence on the short-term prognosis after liver transplantation in this study.

Analysis of Variance↗

PubMed2006

Outcomes of hepatitis B virus recurrence after liver transplantation.

The introduction of high doses of hepatitis B immune globulin (HBIG) and lamivudine for liver transplantation (OLT) prophylaxis has reduced the risk of hepatitis B recurrence and improved the survival of patients transplanted for hepatitis B virus (HBV)-related liver disease. But, posttransplant prophylaxis strategies to treat the recurrence of HBV have not yet been standardized. We analyzed 23 patients with HBV recurrence among 340 HBV-associated liver transplants performed from September 1996 to April 2004 (6.7%). Nine patients underwent deceased donor OLT and 14, living donor OLT. Mean follow-up was 37 months. Seroconversion after recurrence was observed in 6 of 23 patients (26%). Mean time to HBV recurrence tended to be shorter among the seroconversion (+) patients compared to seroconversion (-) patients (10 months vs 19.7 months; P = .062). Seroconversion rate after HBIG and lamivudine combination therapy for patients with HBV recurrence was 37.5% and time to seroconversion after HBV recurrence was 1.7 months. Seroconversion was best achieved when the pretransplant HBV DNA level was high and HBeAg was positive. Also, seroconversion rate was increased when HBV DNA level was low and the alanine transferase level high at the time of recurrence and when the time to recurrence after transplantation was short. Seroconversion after HBV recurrence, which was observed in 26%, may be increased in selected cases. Accordingly, aggressive treatment should be undertaken after HBV recurrence.

Antiviral Agents↗

PubMed2006

Liver transplantation for hepatocellular carcinoma with bile duct thrombi.

In a few cases of hepatocellular carcinoma (HCC), jaundice results from obstructive causes, including tumor invasion or thrombi in the bile duct. We have reported herein our experience with liver transplantation (OLT) for HCC cares showing bile duct thrombi (BDT). From September 1996 to August 2004, 140 adult patients underwent OLT for HCC at our center. Four patients (2.9%) who had OLT performed for HCC had BDT and were included in this study. The patients were all men of mean age 57.0 years. The initial total bilirubin levels were in the range of 2.0 to 30.5 mg/dL. The sizes of the tumors ranged from 2.0 cm to 3.0 cm in diameter, all were single lesions. The median follow-up period was 20.6 months (range: 17.6 to 28.1 months). The only case in which the BDT was identified intraoperatively died 20 months after OLT due to multiple intrahepatic recurrences. The other three patients were alive, showing no evidence of recurrence at the end of follow-up. Although a series of four is too small to reach any conclusion, we suggest that OLT may be a treatment option for HCC with BDT in selected cases.

Adult↗

PubMed2006

Safety of donors with fatty liver in liver transplantation.

Steatotic liver graft transplantation affect donor safety as well as recipient survival. We investigated safety of donors according to the extent of fatty change. We retrospectively reviewed donors who underwent right hepatectomy from September 1999 to April 2005, dividing them into three groups according to degree of macrovesicular fatty change upon intraoperative liver biopsy. Group 1 included patients with macrovesicular steatosis of 0 approximately 9%: group 2, 10 approximately 19% and group 3, at least 20%. Two hundred forty-five donors were enrolled with a male to female ratio of 2.02:1 and mean age of 31.8 years. There were 163 donors in group 1, 75 in group 2, and seven in group 3. There was no statistically significant difference in body mass index, operative time, blood loss, postoperative peak serum bilirubin, and aspartate transaminase levels among groups 1, 2, and 3. Overall complication rate, including reoperation, biliary stricture, wound infection, ileus, transfusion, bile leak and fluid collection were not different between the groups. Postoperative hospital stay was also not different. Peak alanine transaminase level was different between each group, and prothrombin time between group 1 and 3, but days until return to normal levels in all measured laboratory parameters were not different. Residual liver volume percent was significantly smaller among group 1 compared to others. In conclusion, fatty livers with less than 30% macrovesicular steatosis may be good donor candidates without significant complications as long as sufficient residual liver volume is left for the donor.

Adolescent↗

PubMed2005

Characteristics of felodipine-located poly(epsilon-caprolactone) microspheres.

Felodipine-loaded poly (epsilon-caprolactone) (PCL) microspheres were prepared by two methods, the conventional emulsion solvent evapouration method and the quenching method. The aim of this work was to investigate the effects of process parameters such as emulsion type, drug loading, molecular-weight of the polymer, types of emulsion stabilizer and dispersed phase solvents, as well as preparation methods. The results show that, when conventional emulsion solvent evapouration method was used, the o/w-method produced smaller mean size and higher encapsulation efficiency compared with the o/o-method. The encapsulation efficiencies increased with an increase in the molecular weight and a decrease in crystallinity of PCL. The size of microspheres varied with the type of emulsion stabilizer used, smaller microspheres with PVA and narrow size distribution with Pol 237. The water solubility of the dispersed phase solvent was one of the critical factors in controlling the encapsulation efficiency and microsphere mean size. When water-soluble solvents such as acetonitrile and ethyl formate were used, the encapsulation efficiencies decreased due to higher evapouration rate. When quenching methods were used, in contrast to the conventional emulsion solvent evapouration method, very narrowly size-distributed but bigger microspheres were obtained.

Antihypertensive Agents↗

PubMed2004

The viability and function of cryopreserved hepatocyte spheroids with different cryopreservation solutions.

We sought to evaluate the viability and function of cryopreserved hepatocyte spheroids using different cryopreservation solutions in order to elucidate the efficiency of cryopreservation. Hepatocytes isolated from a Sprague-Dawley rat were formed into spheroids by 24 hours of rotational culture. The spheroids were cryopreserved using a programmed linear freezer in a liquid nitrogen tank for 24 hours in four different cryopreservation solutions: UW solution (UW), William E media (WE), fetal bovine serum (FBS), and a mixture (MIX). After thawing, they were cultured for 4 days. With each hepatocyte spheroid, the viability using the MTT assay and hepatocyte-specific functions, such as ammonia clearance, urea nitrogen synthesis, and albumin secretion, were analyzed. The viabilities of cryopreserved hepatocyte spheroids were 64.8% +/- 10.2% (UW), 33.2% +/- 9.7% (WE), 69.3% +/- 8.7% (FBS), and 48.4% +/- 15.5% (MIX). Ammonia clearance of spheroids cyropreserved in UW solution was 0.93 +/- 0.13 mmol/L per well per day, which was not significantly different from freshly cultured spheroids. From the aspect of urea nitrogen synthesis, spheroids cryopreserved with UW, FBS, and MIX solution were not significantly different from freshly cultured spheroids. The amount of albumin secretion by the UW cryopreserved spheroids was significantly greater than that of other cryopreserved spheroids. Cryopreserved hepatocyte spheroids in UW solution were not significantly different from freshly cultured spheroids with respect to viability and function. UW solution was superior to other cryopreservation solutions for viability and functions.

Animals↗

PubMed2004

Ion channels of Fasciola hepatica incorporated into planar lipid bilayers.

Ion channels are important target sites of anthelmintics, but little is known about those in Fasciola hepatica. In this work, we applied a planar lipid bilayer technique to characterize the properties of single ion channels in F. hepatica. Under a 200/40 mM KCl gradient, a large conductance channel of 251 pS was observed in 18% of the membranes studied. The channel was selective to K(+) over Cl(-) with a permeability ratio of K(+) to Cl(-) (PK/PCl) of 4.9. Open state probability (Po) of the channel was less than 0.5 and dependent on voltage (-60 to approximately +40 mV) and Ca(2+) (approximately 100 microM). The other two types of single channels observed in 11 and 5% of membranes, respectively, were a K(+)-permeable channel of 80 pS (PK/PCl=4.6) and a Cl(-)-permeable channel of 64 pS (PK/PCl=0.058). Open state probability of both channels showed little voltage dependence. The results indicate that distinct single channels of 60 to approximately 251 pS are present in relative abundance and, in addition, that the planar lipid bilayer technique can be a useful tool for the study of single ion channels in F. hepatica.

Animals↗

PubMed2004

Subtypes of alpha1- and alpha2-adrenoceptors mediating noradrenergic modulation of spontaneous inhibitory postsynaptic currents in the hypothalamic paraventricular nucleus.

Noradrenergic inputs to the hypothalamic paraventricular nucleus (PVN) play important roles in the regulation of neuroendocrine and autonomic functions. Previous reports show that noradrenaline increases the frequency of spontaneous inhibitory postsynaptic currents (sIPSCs) in a subpopulation of type II neurones, acting via alpha(1)-adrenoceptors (ARs), but reduces this frequency in most type I and another subpopulation of type II neurones, via alpha(2)-ARs on presynaptic GABA neurones. Here, we identified the subtypes of alpha-ARs mediating noradrenaline-induced increases and decreases in the sIPSC frequency of PVN neurones, by using slice patch recordings from PVN neurones. In both type I and II neurones, the noradrenaline-induced decrease in sIPSC frequency was completely blocked by BRL44408 (alpha(2A)-AR antagonist) at 1-3 micro M, which is approximately 1/100 of its equilibrium dissociation constant (pA(2) = 8.0), but not by prazosin (20-100 micro M, alpha(2B/C)-AR antagonist; pA(2) = 7.5). The effect of noradrenaline was mimicked by guanfacine (alpha(2A)-AR agonist) with an EC(50) of 0.1 micro M. In type II neurones, the noradrenaline-induced increase in sIPSC frequency was not blocked by any of the following antagonists: RS17053 (10 micro M, alpha(1A)-AR antagonist), BMY7378 (2 micro M, alpha(1D)-AR antagonist), prazosin (0.1 micro M, alpha(1)-AR antagonist; pA(2) = 10.5), or chloroethylclonidine (10 micro M, alpha(1B/D)-AR antagonist). However, the effect of noradrenaline was blocked by higher concentrations of prazosin (1 micro M) or RS17053 (100 micro M), suggesting the involvement of alpha(1L)-subtype, a low affinity form of alpha(1A)-ARs. Collectively, our results indicate that the alpha(2A)-, or alpha(1L)-ARs on the GABA neurones mediate the noradrenaline-induced decreases, or increases in the frequencies of the sIPSCs of PVN neurones, respectively.

Adrenergic alpha-Agonists↗

PubMed2003

Preliminary study of interfacial shear strength between PMMA precoated UHMWPE acetabular cup and PMMA bone cement.

Followed by successful demonstration of high interfacial tensile strength in a new design of cemented all-polyethylene acetabular cup, interfacial shear strength was investigated in this study, with the use of canine-size prototypes of polymethylmethacrylate (PMMA) precoated UHMWPE acetabular cups. In addition to the PMMA precoated prototypes, three different types of controls were also prepared and tested: grooved UHMWPE cups, PMMA (bone cement) cups, and noncoated, plain UHMWPE cups. The interfacial shear strength of the precoated prototypes was 10.1 +/- 0.69 MPa (n = 6), whereas it was 24.3 +/- 0.78 MPa (n = 2) for the PMMA cup, 6.95 +/- 0.21 MPa (n = 2) for the grooved UHMWPE cup, and 0.34 +/- 0.47 MPa (n = 2) for the UHMWPE cup. These results indicate benefits of the PMMA precoating to stabilize the polyethylene acetabular cup securely when applied with bone cement in simulated clinical applications. Analysis of the failed PMMA precoated UHMWPE prototype cups suggested that the chemically induced bonds between precoated PMMA layer and bone cement played a key role in developing high shear strength. After the interfacial shear test of the PMMA precoated prototypes, major disruptions at the interface between treated UHMWPE and precoated PMMA layer were observed by scanning electron microscopy (SEM), which was a unique failure pattern, not found with other prototypes.

Animals↗

PubMed2003

The microbial community analysis of a 5-stage BNR process with step feed system.

The microbial communities of 5-stage BNR activated sludge samples were analyzed using fluorescence in-situ hybridization (FISH) and 16S rDNA characterization. The total cell numbers of each reactor were from 2.36 x 10(9) cells/ml to 2.83 x 10(9) cells/ml. From 56.5% to 62.0% of total DAPI cell counts were hybridized to the most bacterial specific probe EUB 338. Among them, beta-proteobacteria were most dominant in each tank. The number of phosphate accumulating organisms (PAOs) was almost 50% of the total cell number in anoxic-1 tank, and these results indicate that this process has a high content of denitrifying phosphorus accumulating organisms (dPAOs). In contrast with FISH, 16S rDNA analysis showed that dominant groups were the Cytophaga-Flavobacterium group and high G+C% gram-positive bacteria, which were determined as PAOs in anoxic-1 tank. The beta subclass Proteobacteria did not accumulate a large amount of polyphosphate. The overall results indicate that high G+C% gram-positive bacteria and the Cytophaga-Flavobacterium group might play a key role as dPAOs in this process.

Bioreactors↗

PubMed2002

Preparation and characterization of chitosan microparticles intended for controlled drug delivery.

Chitosan microparticles were prepared with tripolyphosphate (TPP) by ionic crosslinking. The particle sizes of TPP-chitosan microparticles were in range from 500 to 710 microm and encapsulation efficiencies of drug were more than 90%. The morphologies of TPP-chitosan microparticles were examined with scanning electron microscopy. As pH of TPP solution decreased and molecular weight (MW) of chitosan increased, microparticles had more spherical shape and smooth surface. Release behaviors of felodipine as a model drug were affected by various preparation processes. Chitosan microparticles prepared with lower pH or higher concentration of TPP solution resulted in slower felodipine release from microparticles. With decreasing MW and concentration of chitosan solution, release behavior was increased. The release of drug from TPP-chitosan microparticles decreased when cross-linking time increased. These results indicate that TPP-chitosan microparticles may become a potential delivery system to control the release of drug.

Chitin↗

PubMed2002

Preparation of alginate beads for floating drug delivery system: effects of CO(2) gas-forming agents.

Floating beads were prepared from a sodium alginate solution containing CaCO(3) or NaHCO(3) as gas-forming agents. The solution was dropped to 1% CaCl(2) solution containing 10% acetic acid for CO(2) gas and gel formation. The effects of gas-forming agents on bead size and floating properties were investigated. As gas-forming agents increased, the size and floating properties increased. Bead porosity and volume average pore size, as well as the surface and cross-sectional morphology of the beads were examined with Mercury porosimetry and Scanning Electron Microscopy. NaHCO(3) significantly increased porosity and pore diameter than CaCO(3). Incorporation of CaCO(3) into alginate solution resulted in smoother beads than those produced with NaHCO(3). Gel strength analysis indicated that bead strength decreased with increasing gas-forming agent from 9 to 4 N. Beads incorporating CaCO(3) exhibited significantly increased gel strength over control and NaHCO(3)-containing samples. Release characteristics of riboflavin as a model drug were studied in vitro. Release rate of riboflavin increased proportionally with addition of NaHCO(3). However, increasing weight ratios of CaCO(3) did not appreciably accelerate drug release. The results of these studies indicate that CaCO(3) is superior to NaHCO(3) as a gas forming agent in alginate bead preparations. The enhanced buoyancy and sustained release properties of CaCO(3)-containing beads make them an excellent candidate for floating drug dosage systems (FDDS).

Alginates↗

PubMed2002

A gadolinium and pH-sensitive hyperpolarization-activated cation current in acutely isolated single neurones from Fasciola hepatica.

Fasciola hepatica, a parasitic flatworm belonging to the Class Trematoda, is one of the first metazoan groups to possess a centralized nervous system. However, the electrophysiological properties of neurones in F. hepatica are largely unknown. In the present study, we acutely isolated viable neurones from F. hepatica and characterized their electrophysiological properties. A hyperpolarization-activated cation current was recorded in the cells using the whole-cell patch-clamp. The current was found to be activated slowly at membrane potentials negative to 0 mV and did not display any time-dependent inactivation. This current was reduced by 1 mM Gd3+ to the level of the leak current, while 3 mM of Cs+ had no effect. However, the current was inhibited by extracellular acidosis in the pH range 7.0-7.8, and the membrane potentials of these cells were depolarized by extracellular alkalosis in the pH range of 5.8 to 8.2. Gd3+ (1 mM), which inhibited the pH-sensitive hyperpolarization-activated cation current, also hyperpolarized the cells. In summary, we isolated single neurones from F. hepatica, and these were found to express a pH-sensitive hyperpolarization-activated cation current. This current may participate in the membrane depolarization of F. hepatica neurones during alkaline challenge.

Animals↗

PubMed2001

The proteins of synaptic vesicle membranes are affected during ageing of rat brain.

Low molecular weight GTP-binding proteins are molecular switches that are believed to play pivotal roles in cell growth, differentiation, cytoskeletal organization, and vesicular trafficking. Rab proteins are key players in the regulation of vesicular transport, while Rho family members control actin-dependent cell functions, i.e. the regulation of cytoskeletal organization in response to extracelluar growth factors and in dendritic neuron development. In this study, we have examined the regulation of small GTP-binding proteins that are implicated in neurosecretion and differentiation of neuron during ageing processes. Comparison of small GTP-binding proteins from the synaptosome and crude synaptic vesicles (LP2 membranes) of 2 months and 20 months old rat brain respectively showed no difference in the level of Rab family proteins (Rab3A and Rab5A). However, Rho family proteins such as RhoA and Cdc42 were elevated in LP2 membranes of the aged brain. The dissociation of Rab3A by Ca2+/calmodulin (CaM) from SV membranes was not changed during aging. Ca2+/CaM stimulated phosphorylation of the 22 and 55-kDa proteins in SV membranes from the aged rat brain, and inhibited phosporylation of 30-kDa proteins. GTPgammaS inhibited phosphorylation of the 100-kDa proteins and stimulated phosphorylation of the 70 kDa in LP2 membranes from both the young and aged rat brains, whereas GDPbetaS caused just the opposite reaction. These results suggest that protein phosphorylation and regulation of Rho family GTPases in rat brain appears to be altered during ageing processes.

Aging↗

PubMed2001

Creatine kinase B is a target molecule of reactive oxygen species in cervical cancer.

Recently, a procedure for detecting ROS-sensitive proteins that contain active cysteine residues was devdoped. The method is based on the fact that biotin-conjugated iodoacetamide (BIAM) and ROS competitively and selectively react with the active cysteine residues in ROS-sensitive proteins. To investigate the role of ROS in cervical cancer, BIAM labeling on cytosolic proteins in normal and cancer tissues was performed, respectively. The BIAM labeling proteins are separated by 2-dimensional electrophoresis, and then identified by MALDI-TOF mass analysis. ROS-sensitive protein is identified as creatine kinase B containing cysteine residue in active center. Activity of creatine kinase B in normal tissue is higher than that of oxidized form in cervical cancer tissues. The result suggests that ROS play an important role in metabolic regulation in cervical cancer cells. However, molecular mechanisms that ROS and creatine kinase B are integrated into a physiological signal leading to the cellular transformation remain to be elucidated.

Amino Acid Sequence↗

PubMed2001

Simple bone cyst of lamina of lumbar spine: a case report.

STUDY DESIGN: A case report and literature review. OBJECTIVE: To describe an extremely rare simple bone cyst involving the lamina of the lumbar spine. SUMMARY OF BACKGROUND DATA: Simple bone cysts involving the spine are very rare. Moreover, the authors are unaware of any published report of a simple bone cyst involving the lamina of the spine. METHODS: A cystic lesion, incidentally identified in a patient with lumbar disc herniation of L5-S1, located at the left lamina of L5, was surgically treated with complete resection of the involved lamina and discectomy of L5-S1. Medical records, imaging studies, histologic findings, and related literature are reviewed in this study. RESULTS: Histologic examination of a section of the cystic lesion showed a thin fibrous lining membrane of the cyst surrounded by well-vascularized new bone formation. This result is consistent with the findings of previously reported simple bone cysts in other sites of the body, including the spine. CONCLUSION: This study suggests that a simple bone cyst may be included in the differential diagnosis of a cystic lesion of the posterior elements, especially laminae, of the spine.

Adult↗

PubMed2001

Quantitative analysis of transforming growth factor-beta 1 in ligamentum flavum of lumbar spinal stenosis and disc herniation.

STUDY DESIGN: The concentration of transforming growth factor-beta 1 (TGF-beta1) was examined in the ligamentum flavum of lumbar spinal stenosis and disc herniation. OBJECTIVE: To investigate the role of TGF-beta1 on hypertrophy of the ligamentum flavum in lumbar spinal stenosis compared with that of lumbar disc herniation. SUMMARY OF BACKGROUND DATA: The hypertrophy of the ligamentum flavum is known to be related to degenerative changes that are secondary to the aging process or mechanical instability. However, there has been no study to investigate the effect of biochemical factors, such as growth factors, associated with hypertrophy of the ligamentum flavum. METHODS: The concentrations of TGF-beta1 were analyzed in the surgically obtained ligamentum flavum specimens from lumbar spinal stenosis (n = 10; mean age 62.8 years) and disc herniation (n = 10; mean age 35.6 years) by enzyme-linked immunosorbent assay. The localization of TGF-beta1 within the ligamentum flavum was determined using immunohistochemical study. The thickness of the ligamentum flavum was measured with axial T1-weighted magnetic resonance imaging. The biochemical and radiologic results were compared for these two conditions. RESULTS: The mean concentration of TGF-beta1 was 123.78 pg/100 microg protein (range 11-374 pg/100 microg protein) in lumbar spinal stenosis and 38.56 pg/100 microg protein (range 0-155 pg/100 microg protein) in lumbar disc herniation; the difference between lumbar spinal stenosis and disc herniation was statistically significant (P = 0.029). The mean thickness of the ligamentum flavum was 4.44 mm (range 3.4-5.4 mm) in lumbar spinal stenosis and 2.44 mm (range 1.8-4.0 mm) in lumbar disc herniation; the difference between lumbar spinal stenosis and disc herniation was statistically significant (P = 0.001). On immunohistochemical study TGF-beta1 was positively stained on the fibroblasts within the ligamentum flavum specimens. CONCLUSION: The current results suggest that higher expression of TGF-beta1 by fibroblasts might be related to the development of hypertrophy of the ligamentum flavum in lumbar spinal stenosis.

Aged↗