Biomedical subjects

J C Park

Publications and source records attributed to J C Park.

At least 37 records · Page 2Linked to original sources

PubMed2001

A bone replaceable artificial bone substitute: cytotoxicity, cell adhesion, proliferation, and alkaline phosphatase activity.

Cellular toxicity, cell adhesion and proliferation, and alkaline phosphatase (ALP) activity were investigated for an artificial bone substitute composed of heated carbonate apatite (CAp) and Type I atelocollagen (AtCol) extracted from bovine tail skins (88/12 in %wt/wt). To enhance the intramolecular crosslinking between collagen molecules, the CAp-AtCol substitutes were irradiated by ultraviolet rays (wave length 254 nm) at 4 degrees C for 4 h or vacuum dried at 150 degrees C for 2 h. Cytotoxicity tests by a direct contact method and an extract dilution method revealed that the CAp-AtCol substitutes were cytocompatible for balb 3T3 fibroblasts. Osteoblast adhesion studies demonstrated that the substitute disks composed of 980 degrees C-heated CAp and AtCol were significantly more adhesive for osteoblasts than those of 1,200 degrees C-sintered CAp and AtCol (p < 0.05). Proliferation studies showed that the number of osteoblasts grown in the media containing substitutes of 980 degrees C-heated CAp and AtCol was statistically higher than grown in those of 1,200 degrees C-sintered CAp and AtCol after 5 days (p < 0.05). It was found that osteoblasts grown in the substitutes of 980 degrees C-heated CAp and AtCol only expressed similar ALP activity to the controls. These results suggested that the substitutes consisting of 980 degrees C-heated CAp and AtCol show more favorable interactions with osteoblasts than those of 1,200 degrees C-sintered CAp and AtCol.

3T3 Cells↗

PubMed2001

A bone replaceable artificial bone substitute: osteoinduction by combining with bone inducing agent.

Bone inducing agent (BIA) isolated from Saos-2 human osteosarcoma cells was added to an artificial bone substitute composed of 980 degrees C-heated carbonate apatite (CAp) and Type I atelocollagen (AtCol) extracted from bovine tail skins (88/12 in wt/wt %), and a CAp-AtCol-BIA substitute was prepared as an osteoinductive bone substitute. Rat calvaria osteoblasts treated by the isolated BIA demonstrated significantly increased alkaline phosphatase (ALP) activity after 3 days (p < 0.05). In vitro cell attachment and proliferation and ALP activity were investigated for the bone substitute combined with BIA. Osteoblasts cultured onto the surface of the CAp-AtCol-BIA substitute demonstrated remarkable morphological changes such as radial spreading, flattening, and projecting filopodia after 5 days. In comparison with the substitute without BIA, osteoblasts grown in the BIA-combined CAp-AtCol substitute expressed significantly increased proliferation and ALP activity, respectively (p < 0.05). Both the substitutes combined with and without BIA were implanted into artificial defects created in rabbit radii. After 4 weeks, the CAp-AtCol-BIA substitute implanted lesion was completely replaced by regenerated host bone in radiological observation whereas the substitute without BIA was partially resorbed. No histologic abnormalities appeared in the substitute either with or without BIA.

Alkaline Phosphatase↗

PubMed2001

Antibacterial effect of antibiotic solution on cellular viability in canine veins.

Pretreatment of tissue by using antibiotics is a critical step to prevent microbial contamination before venous transplantation. In this study, the optimal time and temperature of antibiotic solution treatment for maintaining cellular viability with antibacterial effect were investigated. The antibiotic-nutrient solutions were composed of cefoxitin, lincomycin, vancomycin, and polymyxin B in RPMI-1640 medium. After various antibiotic solution treatment times (4, 8, and 12 h) and temperatures (4, 25, and 37 degrees C), the viabilities of cells dissociated from veins (jugular vein, femoral vein, superior vena cava, and inferior vena cava) were determined. Double staining by Griffonia simplicifolia agglutins-fluorescein isothiocyanate (GS1-FITC) and propidium iodide was used. To measure the antibacterial effect of the antibiotic solution, canine veins were artificially infected by 3 kinds of bacteria (Staphylococcus aureus, Escherichia coli, and Klebsiella pneumoniae) and were treated by antibiotic solutions as viability test conditions. After the treatment with the antibiotic solution, the tissue was minced, and the homogenized tissue fraction was cultured on standard method agar. The colony that seemed to be resistant to the antibiotic solution was counted. At 37 and 25 degrees C, the viability of whole cells decreased significantly Asymptotic Significance 2-tailed (Asymp.Sig 2-tailed) < 0.05 after 4 h of antibiotic solution treatment, whereas at 4 degrees C it began to reduce significantly after 8 h of treatment. By antibiotic solution treatment at all 3 temperatures for 4 h, no significant difference in viability of the endothelial cells and whole cells was observed. To maintain the donor vein's cellular viability until transplantation, antibiotic solution treatment for 4 h at 4 degrees C is assumed to be appropriate.

Animals↗

PubMed2001

Effects of presurgical and post-surgical irradiation on the healing process of Medpor in dogs.

The purpose of this study was to determine the effect of irradiation on the healing process and the effect on the contact surface of Medpor and bone. Eighteen dogs were studied. The animals were divided into three groups. Six non-irradiated dogs served as controls (Group 1). Twelve dogs irradiated on the left femur, before and after implantation of Medpor, were studied. The dogs were euthanized 4 and 8 weeks after Medpor was implanted in presurgical irradiation subgroup animals (Group 2) and after the completion of irradiation in post-surgical irradiation subgroup animals (Group 3). Light microscopic and scanning electron microscopic examinations were performed. The appearance of osteoblasts and bone matrix formation were remarkably late and manifest slight reactions in post-surgical irradiation group compared to the control group presenting the osteoblasts at 4 weeks, and those osteoblasts were not visible in presurgical irradiation group in both the 4-week and 8-week observation. We concluded that the bone remodeling was delayed in the irradiated bone, especially in the presurgical group.

Animals↗

PubMed2001

The prevalence of trimethoprim-resistance-conferring dihydrofolate reductase genes in urinary isolates of Escherichia coli in Korea.

One-hundred and twenty-two urinary isolates of Escherichia coli were studied for trimethoprim resistance. Seventy-seven (63.1%) of the 122 isolates were found to be resistant to trimethoprim. Of the 77 trimethoprim-resistant isolates, 75 dfr genes were detected in 72 isolates as follows: the dfrA17 gene was the most prevalent, being found in 27 isolates, followed by dfrA12 in 26, dfrA1 in 15, dfrA5 in four and dfrA7 in three. Southern blot and PCR mapping analysis revealed that all of the dfrA17, dfrA12, dfrA5 and dfrA7 genes were located on class 1 integrons. The dfrA1 gene inserted as a gene cassette in class 1 integrons was found in 10 of 15 isolates, and the intI2 gene of Tn7 was detected in two out of five isolates. In conjugation experiments, the dfr genes inserted in class 1 integrons were transferred to a recipient E. coli in 32 (42.7%) of the 75 dfr genes. In conclusion, the dfrA17 and dfrA12 genes were the most prevalent genes responsible for trimethoprim resistance in urinary tract isolates of E. coli from Korea and the dfr genes inserted in integrons are more widespread than those that are not related to gene cassettes.

Anti-Bacterial Agents↗

PubMed2001

Clinical characteristics of unexplained sudden cardiac death in Korea.

In Western countries, sudden cardiac death (SCD) is closely related to coronary artery disease, but in Korea the clinical characteristics of SCD are not well determined. Over a 4-year period (June 1995 to May 1999), 186 cases of SCD, ranging in age from 16 to 75 years, were admitted to the Chonnam National University Hospital. In 82 (44.1%) of these, neither symptoms nor evidence of structural heart disease was found and so their clinical characteristics were investigated. There were 66 (80.5%) men and 16 (19.5%) women (male/female ratio = 4.1:1). The mean age was 50 +/- 14 years: 19 (23.2%) were in their 40s, 21 (25.6%) in their 50s, and 17 (20.7%) in their 60s. The time of circulatory collapse witnessed in 68 cases of SCD showed 2 peaks: between midnight and 03.00h (n=16, 23.5%) and between 09.00h and midday (n=15, 22.1%). Unexplained SCD occurred at home in 48 (64.9%) cases and on the street in 12 (16.2%); it occurred during normal daily routine activity in 23 (39.6%) and during sleep in 15 (25.9%). Thirty-three patients (40.2%) experienced various prodromal symptoms, including chest discomfort (n=13, 15.9%) and dyspnea (n=8, 9.8%). The electrocardiogram taken on arrival recorded asystole in 65 (79.3%) and ventricular fibrillation in 17 (20.7%). Idiopathic ventricular fibrillation was diagnosed in 14 (10 men, 4 women; 45 +/- 11 years) of 21 patients who recovered spontaneous circulation. Five (6.1%) patients were discharged alive, and an implantable cardioverter-defibrillator was implanted in 2. Unexplained SCD is common in Korea and develops predominantly in middle-aged males around midnight or in the late morning usually with no prodromal symptoms (59.8%). Idiopathic ventricular fibrillation is thought to be one of the important causes.

Adolescent↗

PubMed2001

Huge calcified aneurysm of the sinus of Valsalva.

Aneurysms of the sinus of Valsalva often remain undiagnosed until they rupture. A 61-year-old man had a huge, heavily calcified unruptured aneurysm, originating from the right sinus of Valsalva, detected incidentally on a chest radiograph taken for the diagnosis of cardiomegaly. Two-dimensional echocardiography revealed pericardial effusion with a huge calcified mass compressing the right ventricular outflow tract. The Doppler color-flow echocardiogram showed blood flow from the aortic root into the aneurysm. A chest computed tomographic scan revealed a large thrombosed aneurysm originating from the aortic root and measuring 10x10 cm. After pericardiocentesis, cardiac catheterization was performed, which showed that the right ventricular systolic pressure had elevated to 80 mmHg. Aortic root aortography demonstrated a huge unruptured calcified aneurysm in the sinus of Valsalva arising from the right coronary sinus. The patient underwent surgical correction to prevent aneurysmal rupture and to relieve the right ventricular outflow obstruction.

Aortic Aneurysm↗

PubMed2001

The levels of MDM2 protein are decreased by a proteasome-mediated proteolysis prior to caspase-3-dependent pRb and PARP cleavages.

MDM2 is a substrate of caspase-3 in p53-mediated apoptosis. In addition, MDM2 mediates its own ubiquitination in a RING finger-dependent manner. Thus, we investigated whether MDM2 is degraded through a ubiquitin-dependent proteasome pathway in the absence of p53. When HL-60 cells, p53 null, were treated with etoposide, MDM2 was markedly decreased prior to caspase-3-dependent retinoblastoma tumor suppressor protein (pRb) and poly (ADP- ribose) polymerase (PARP) cleavages. Moreover, down-regulation of MDM2 level was not coupled with its mRNA down-regulation. However, the level of MDM2 was partially restored by proteasome inhibitors such as LLnL and lactacystin, even in the presence of etoposide. Our results suggest that, in the p53 null status, MDM2 protein level is decreased by proteasome-mediated proteolysis prior to caspase-3-dependent PARP and pRb cleavages.

Antineoplastic Agents, Phytogenic↗

PubMed2001

A case of torsade de pointes associated with hypopituitarism due to hemorrhagic fever with renal syndrome.

We describe a 51-yr-old man presenting with syncope due to torsade de pointes. The torsade de pointes was refractory to conventional medical therapy, including infusion of isoproterenol, MgSO4, potassium, lidocaine, and amiodarone. His past history, physical findings, and hormone study confirmed that QT prolongation was caused by anterior hypopituitarism that developed as a sequela of hemorrhagic fever with renal syndrome. The long QT interval with deep inverted T wave was completely normalized 4 weeks after starting steroid and thyroid hormone replacement. Hormonal disorders should be considered as a cause of torsade de pointes, because this life-threatening arrhythmia can be treated by replacing the missing hormone.

Hemorrhagic Fever with Renal Syndrome↗

PubMed2001

A case of successful primary coronary intervention for the total occlusion of left main stem with the aid of abciximab.

A 61-yr-old male patient presented with severe chest pain with cardiogenic shock due to an extensive anterolateral myocardial infarction. Two-dimensional echocardiogram showed severe left ventricular systolic dysfunction (ejection fraction=17%). Emergent coronary angiogram obtained immediately after placing temporary pacing electrode revealed total thrombotic occlusion in the left main stem. We performed direct coronary intervention using kissing balloon technique with the aid of Abciximab (ReoPro) infusion. Residual stenosis with thrombus remained even after high pressure balloon dilatations, therefore we placed two stents, one in the ostia of left anterior descending (LAD) and the other in left circumflex artery (LCX). Coronary angiogram after kissing stents showed improved LAD and LCX flows without residual stenosis. Chest pain resolved and blood pressure normalized after coronary intervention. The whole procedure time was 15 min. Follow-up coronary angiogram taken one week later showed patent previous stented arteries, and echocardiography demonstrated 40% of left ventricular ejection fraction. The clinical course for one-year follow-up was uneventful.

Abciximab↗

PubMed2001

Characterization of UV-irradiated dense/porous collagen membranes: morphology, enzymatic degradation, and mechanical properties.

Collagen-based membranous materials of various shapes (gel, film, sponge) are known to be the most promising materials in terms of facilitating the regeneration of dermal defects. In this study, dense and porous collagen membranes were fabricated using air-drying and freeze-drying processes, respectively, and the effect of ultraviolet (UV) radiation on the degree of membrane crosslinking was evaluated by in vitro biodegradation and mechanical testing. A non-irradiated membrane group was used as the negative control and a glutaraldehyde (GA) treated group as the positive control. Scanning electron microscopy showed that, as the freezing temperature decreased to -196 degrees C, the resultant mean pore sizes also decreased; optimal pore size was obtained at a freezing temperature of -70 degrees C. In vitro biodegradation and mechanical testing demonstrated that GA treatment or 4 hours of exposure to UV radiation significantly increased both resistance to collagenase and mechanical strength versus the untreated controls, regardless of the collagen membrane type (dense or porous). Our results suggest that UV treatment is a useful tool for the fabrication of collagen membranes designed to be used as dermal dressings.

Animals↗

PubMed2001

Preparation of collagen modified hyaluronan microparticles as antibiotics carrier.

Hyaluronan (HA), a natural glycoaminoglycan featuring an extracellular matrix, has been suggested as an effective biocompatible material. In this study, the effectiveness of HA microparticles as a carrier system for antibiotics was evaluated, and their physicochemical characteristics were determined. Microparticles were fabricated by the gelation of sulfadiazine (SD) loaded HA solution with calcium chloride through either a granulation (GR-microparticles) or encapsulation (EN-microparticles) process, and atelocollagen was incorporated into the microparticles as an additive in order to improve their physical properties. The characteristics of the microparticles were examined by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and swelling test. In vitro release experiments were performed for 7 days and the released amount of SD was determined using high-performance liquid chromatography (HPLC). Microscopic observations revealed that the collagen incorporated HA particles had a more compact surface than the HA particles. DSC analysis determined a loss of SD crystallinity in the particles. Calcium chloride retarded the swelling of particles, whereas the loaded drug contents did not affect this property. Both GR-and EN-microparticles sustained SD release with initial bursting effect. SD release from EN-microparticles was faster than from GR-microparticles. In addition, the release rate was dependent on the SD content in the microparticles. These results suggest that collagen modified HA microparticles have a potential as a release rate controlling material for crystalline drugs such as SD.

Anti-Bacterial Agents↗

PubMed2001

Calcification comparison of polymers for vascular graft.

Polytetrafluoroethylene (PTFE), polyurethane (PU) and silicone are widely known biocompatible polymers which are commonly used for vascular grafts. However, in vitro and in vivo calcifications of these polymers have been found to seriously compromise their quality as biomaterials. In consideration of this problem, the present study compared the calcification rate and extent of PTFE, PU and silicone. Using the in vitro flow-type method, PTFE, PU and silicone films were tested for 1, 4, 7, 10, 14 and 21 days. After 21 days of in vitro calcification test, the calcium levels on PTFE, PU and silicone were 35.89 +/- 5.01 microg/cm2, 23.73 +/- 0.68 microg/cm2 and 19.86 +/- 5.28 microg/cm2, respectively. The higher observed calcium level for PTFE may be due to the effect of the rough surface of PTFE in accumulating calcium ions on the polymer surface. From the 7th day of test, the [Ca]/[P] molar ratio started to decrease over time, and PTFE showed a faster calcification process. This decreasing [Ca]/[P] molar ratio demonstrated the typical calcification mechanism consisting of phosphorus ion accumulation following calcium ion accumulation. This study concluded that PU and silicone are less calcified than PTFE film, a finding in good agreement with previously published studies.

Biocompatible Materials↗

PubMed2001

Effect of centrifugal force on cellular activity of osteoblastic MC3T3-E1 cells in vitro.

The effects of centrifugal force on growth and differentiation of osteoblastic cells cultured in alpha-MEM containing 1% Fetal bovine serum were investigated by assays of DNA synthesis, alkaline phosphatase activity and osteocalcin-production in osteoblastic MC3T3-E1 cells. Centrifugation of the cells in low concentrations (1%) of fetal bovine serum caused a 1.9-fold increase of [3H]thymidine incorporation on day 3 from the start of centrifugation, and gradually decreased with culture up to day 9. Alkaline phosphatase activity was not affected by centrifugal force until day 5, and increased rapidly after day 7. Stimulation of DNA synthesis by centrifugation was abolished in the presence of H-7, an inhibitor of protein kinase C. These results suggest that centrifugal force stimulates the proliferation of osteoblastic cells through an autocrine secretion of some diffusable growth- promoting activity. Additional centrifugation of the cells also slightly stimulated alkaline phosphatase activity, although this did not directly influence the cell's osteocalcin-production activity.

Alkaline Phosphatase↗

PubMed2001

Comparative study on motility of the cultured fetal and neonatal dermal fibroblasts in extracellular matrix.

One of the differences between fetal and adult skin healing is the ability of fetal wounds heal without contraction and scar formation. Extracellular matrix (ECM) provides a substratum for cells adhesion, migration, and proliferation and can directly influence the form and function of cells. As motility is essential for many important biological events, including wound healing, inflammatory response, embryonic development, and tumor metastasis, this study was designed to compare the motilities cultured dermal fetal and neonatal fibroblasts in the extracellular matrix. The motility of cultured fetal and neonatal fibroblasts was compared using a video-microscopy system that was developed in combination with a self-designed CO2 mini-incubator. To determine migration speed, cells were viewed with a 4X phase-contrast lens and video recorded. Images were captured using a color CCD camera and saved in 8-bit full-color mode. We found that cultured fetal fibroblasts move faster than neonatal fibroblast on type I collagen (fetal fibroblast, 15.1 micrometer/hr; neonatal fibroblast, 13.7 micrometer/hr), and in fibronectin (fetal fibroblast, 13.2 micrometer/hr; neonatal fibroblast, 13.0 micrometer/hr) and hyaluronic acid (fetal fibroblast, 11 micrometer/hr; neonatal fibroblast, 9.8 micrometer/hr).

Cell Movement↗

PubMed2001

A case of spontaneous pneumomediastinum and pneumopericardium in a young adult.

Spontaneous medialstinal emphysema (pneumomediastinum) and pneumopericardium may be defined as the presence of free air or gas in the mediastinal structures and in the pericardial sac without an apparent precipitating cause. It most frequently occurs in young healthy adults without serious underlying pulmonary disease. Although pneumomediastinum and pneumopericardium is often asymptomatic, it may cause pain in the neck and chest, dysphonia and shortness of breath. Treatment is supportive unless the patient has a history of trauma from foreign body aspiration. The course of spontaneous pneumomediastinum and pneumopericardium is usually benign and self-limited. A case of spontaneous pneumomediastinum, pneumopericardium and subcutaneous emphysema in a 20-year-old male is reported in this paper.

Adult↗

PubMed2001

Bidirectional incremental parsing for automatic pathway identification with combinatory categorial grammar.

As the importance of automatically extracting and analyzing various natural language assertions about protein-protein interactions in biomedical publications is recognized, many uses of natural language processing techniques are proposed in the literature. However, most proposals to date make rather simplifying assumptions about the syntactic aspects of natural language due to various reasons including efficiency. In this paper, we describe an implemented system that utilizes combinatory categorical grammar known to be competent in modeling natural language, with a controlled mechanism for the parser to operate bidirectionally and incrementally. We discuss the performance of the system on a large set of abstracts in Medline with quite encouraging results.

Data Interpretation, Statistical↗

PubMed2000

Type I atelocollagen grafting onto ozone-treated polyurethane films: cell attachment, proliferation, and collagen synthesis.

An approach is presented for the graft copolymerization of type I atelocollagen onto the surface of polyurethane (PU) films treated with ozone. Through inducing oxidization to modify PU surface by ozone, peroxide groups are easily generated on the surface. Those peroxides are broken by redox-polymerization, and provide active species which initiate graft polymerization by reacting with amines in the collagen molecules. The ozone oxidation time and voltage could readily control the amount of peroxide production. The surface density of generated peroxides on PU surface was determined by iodide method. The maximum concentration of peroxide was about 10.20 x 10(-8)mol/cm(2) when ozone oxidation was performed at 60 V for 30 min. After the reaction of PU by ozone oxidation, type I atelocollagen was graft-copolymerized onto the PU film. All the physical measurements on the collagen-grafted surface indicated that the PU surface was effectively covered with type I atelocollagen. The interaction of the collagen-grafted PU surface with fibroblasts could be greatly enhanced by the surface graft polymerization with type I atelocollagen. Attachment and proliferation of fibroblasts on the grafted type I atelocollagen were significantly enhanced, and it is assumed that the atelocollagen matrix supported the initial attachment and growth of cells. In the early stage of proliferation, collagen synthesis in fibroblasts was not activated and remained at a relatively low level due to the grafted type I atelocollagen, increasing only with fibroblast differentiation.

Animals↗