Biomedical subjects

H Suh

Publications and source records attributed to H Suh.

At least 37 records · Page 2Linked to original sources

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

Apoptotic activity of novel bile acid derivatives in human leukemic T cells through the activation of caspases.

The therapeutic efficacies of bile acids, such as ursodeoxycholic acid (UDCA) and chenodeoxycholic acid (CDCA), have been widely demonstrated in various liver diseases, suggesting that they might protect hepatocytes against common mechanisms of liver damage. Although they have been shown to prevent apoptotic cell death in certain cell lines, we have previously reported that a novel derivative (HS-1030) of UDCA significantly inhibited cell growth and induced apoptosis in cancer cells. To develop more effective agents, we synthesized several derivatives, named HS-1183, HS-1199 and HS-1200, based on the structure of UDCA and CDCA, and investigated them for anti-proliferative activity in Jurkat cells, a human leukemic T cell line. Whereas UDCA and CDCA had no significant effects on the growth of Jurkat cells in the concentration range tested, both HS-1199 and HS-1200 completely inhibited the cell proliferation, and HS-1183 showed only a weak inhibitory activity. Furthermore, chromatin condensation, DNA ladder formation and proteolytic cleavage of poly(ADP-ribose) polymerase (PARP) were observed after treatment of novel bile acids, indicating the occurrence of apoptotic cell death, which was associated with down-regulation of caspase-3 and -8. The apoptotic manifestations such as PARP cleavage and DNA fragmentation were abolished in the presence of the tripeptide caspase inhibitor zVAD-fmk or the specific caspase-3 inhibitor DEVD-fmk. Our data thus demonstrate that novel bile acid derivatives-induced apoptosis of leukemic T cells is dependent on caspase activation.

Apoptosis↗

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↗

PubMed2000

Differential potentiative effects of glutamate receptor antagonists in the production of antinociception induced by opioids administered intrathecally in the mouse.

The effect of (+/-)-5-methyl-10,11-dihydro-5H-dibenzo(a,d) cyclohepten-5, 10-imine maleate (MK-801) or 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) injected intrathecally (i.t.) on the inhibition of the tail-flick response induced by morphine, D-Ala(2)-NmePhe(4)-Gly-ol-enkephalin (DAMGO), beta-endorphin, D-Pen(2,5)-enkephalin (DPDPE), or ¿(trans-3, 4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl) cyclohexyl] benzeocetamide)¿ (U50, 488H) administered i.t. was studied in ICR mice. The i.t. injection of MK-801 (2 microg) or CNQX (1 microg) alone did not affect the basal tail-flick response. Morphine (0.2 microg), DAMGO (0.8 ng), beta-endorphin (0.1 microg), DPDPE (0.5 microg) or U50, 488H (6 microg) caused only slight inhibition of the tail-flick response. CNQX injected i.t., but not MK-801, enhanced the inhibition of the tail-flick response induced by i.t. administered morphine, DAMGO, DPDPE or U50, 488H. However, CNQX or MK-801 injected i.t. was not effective in enhancing the inhibition of the tail-flick response induced by beta-endorphin administered i.t. The potentiating effect of CNQX on tail-flick inhibition induced by morphine, DAMGO, DPDPE or U50, 488H was blocked by naloxone (from 1 to 20 microg), yohimbine (from 1 to 20 microg) or methysergide (from 1 to 20 microg) injected i.t. in a dose-dependent manner. Our results suggest that the blockade of AMPA/kainate receptors located in the spinal cord appears to be involved in enhancing the inhibition of the tail-flick response induced by stimulation of spinal mu-, delta-, and kappa-opioid receptors. Furthermore, this potentiating action may be mediated by spinal noradrenergic and serotonergic receptors. However, N-methyl-D-aspartate receptors may not be involved in modulating the inhibition of the tail-flick response induced by various opioids administered spinally.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗

PubMed2000

Reaction monitoring of succinylation of collagen with matrix-assisted laser desorption/ionization mass spectrometry.

Succinylated collagen was synthesized by the reaction of collagen with succinic anhydride under basic conditions for one hour. Using the matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) technique, the reaction products were directly identified without multi-step separation processes. MALDI-MS monitored the reaction more accurately than the conventional method of sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). From the change in molecular mass during the reaction, it is observed that about 28 succinyl groups are attached to the collagen strand.

Animals↗

PubMed2000

Heparinized bovine pericardium as a novel cardiovascular bioprosthesis.

A novel chemical modification of biological tissues was developed by the direct coupling heparin to bovine pericardium (BP). The heparinization involves pretreatment of BP using GA and followed by grafting heparin to BP by the reaction of residual aldehyde and amine group of heparin. BP was modified by direct coupling of heparin and the effect of heparin coupling on calcification was evaluated in vitro and in vivo. Heparinized BP was characterized by measuring shrinkage temperature, mechanical properties, digestion resistance to collagenase enzyme, in vitro cytotoxicity, and in vivo calcification. Thermal and mechanical properties showed that the durability of heparin-treated tissue increased as compared with fresh tissue and GA-treated tissue. Resistance to collagenase digestion revealed that heparin-treated tissue has greater resistance to enzyme digestion than did fresh tissue and GA-treated tissue. Heparinized tissue had shown to be non-cytotoxic, however, relatively high cytotoxicity was observed in the GA-treated tissues due to the release of GA. In vivo calcification study demonstrated much less calcium deposition on heparin-treated BP than GA-treated one. Obtained results attest to the usefulness of heparinized BP for cardiovascular bioprostheses.

Animals↗

PubMed2000

Antinociceptive mechanisms of dipsacus saponin C administered intrathecally in mice.

Dipsacus saponin C (DSC) administered intrathecally (i.t.) showed antinociceptive effect in a dose-dependent (from 3.75 to 30 microg) manner as measured by the tail-flick assay. The antinociception induced by DSC at the dose of 30 microg reached at peak 7.5 min and almost returned to the control level after 60 min. 5-Amino-valeric acid (5-AVA, a GABA(A) receptor antagonist, from 1 to 20 microg) and SR 95531 (a GABA(B) receptor antagonist, from 0.1 to 2 ng) dose-dependently attenuated i.t. administered DSC-induced increase of the inhibition of the tail-flick response. The i.t. injection of yohimbine (an alpha(2)-adrenergic receptor antagonist, from 1 to 20 microg) and methysergide (a serotonin receptor antagonist, from 1 to 20 microg), but not naloxone (from 2 to 8 microg), significantly attenuated inhibition of the tail-flick response induced by DSC (30 microg) administered i.t. Sulfated cholecystokinin (CCK, from 0.05 to 0.5 ng) injected i.t. significantly reduced the inhibition of the tail-flick response induced by DSC (30 microg) administered i.t. Our results suggest that DSC shows an antinociceptive effect when it is administered spinally and GABA(A), GABA(B), alpha(2)-adrenergic and serotonin receptors located at the spinal cord level, but not opioid receptors, may be involved in DSC-induced antinociception. Furthermore, CCK may play an important role for the modulation of i. t. injected DSC-induced antinociception.

Adrenergic alpha-Antagonists↗

PubMed2000

A novel in vitro assessment of tissue valve calcification by a continuous flow type method.

A dynamic flow type testing to study calcification was self-designed to investigate calcification in bioprosthetic heart valves. The apparatus consists of a container into which leaflets from a porcine aortic valve are placed, a chamber that contains calcium solution, and a peristaltic pump that provides a continuous supply of the solution toward the container. Efficacy of the apparatus was compared with the conventional batch type calcification testing at 37 degrees C through measuring the amount of calcium and phosphate deposited by inductively coupled plasma (ICP) and scanning electron microscope (SEM). After 14 days, calcium levels detected from the calcified deposit on leaflets were 470.4 +/- 37.0 microg/cm3 in the flow type testing whereas in the batch type testing levels were 81.0 +/- 6.7 microg/cm3. Though the calcium level on the leaflet increased as the exposure time to calcium solution increased in both testings, the rate and the tendency of calcification could be assessed very rapidly by flow type testing in comparison with batch type testing. [Ca]/[P] molar ratio decreased over time, and after 14 days, the ratio was close to 1.83 +/- 0.18 in the flow type testing. The ratio could not be determined in the batch type testing because the deposit was too small to assess. The descending rate of [Ca]/[P] molar ratio demonstrates that deposited calcium-complex at the earliest stage may interact with inorganic phosphate ions to create a calcified deposit mineral precursor. This in vitro dynamic flow type calcification testing was a favorable tool for rapid investigation of calcification.

Aortic Valve↗

PubMed2000

Specific determination of endothelial cell viability in the whole cell fraction from cryopreserved canine femoral veins using flow cytometry.

Abstract: An efficient method for specifically determining the viability of endothelial cells (EC) from cells dissociated from the human saphenous vein was investigated. Three different methods, trypan blue staining assay, [3H]-proline incorporation assay, and flow cytometry (FCM), combined with the fluorescein isothiocyanate conjugated with Griffonia simplicifolia agglutins (GS1-FITC)/propidium iodide (PI) double staining, were used. Both trypan blue staining and [3H] proline incorporation assays demonstrated less sensitivity to determine viability of EC differentially from the other cells. FITC-GS1 showed prominent binding to the vascular EC and could be counted by FCM including PI on dead cells. Following the cryopreservation process, the GS1-FITC/PI FCM analytical method was adopted to test simultaneously the viability of whole cells and EC from the same tissue, human saphenous veins, and mongrel dogs' femoral veins after harvesting, antibiotic solution treatment, and thawing. The viability of the whole cells from veins decreased with a significant difference (p < 0.05) from that of EC after thawing.

Animals↗

PubMed2000

Calcification of leaflets from porcine aortic valves crosslinked by ultraviolet irradiation.

Glutaraldehyde (GA)-pretreated porcine aortic valves are generally used as a bioprosthetic valve, but gradual calcification of the leaflets often occurs. It has been hypothesized that the crosslinking agent, GA, stabilizes and perhaps modifies phosphorus-rich calcifiable structures in the bioprosthetic tissue. This is supported by our findings that calcium deposition is induced rapidly in GA-pretreated leaflets in comparison with ultraviolet (UV) irradiated leaflets. After 3 days of in vitro calcification test, calcium levels were 257.6 +/- 23.5 microg/cm3 in GA-pretreated, 57.7 +/- 10.2 microg/cm3 in the control, and 108.6 +/- 7.6 microg/cm3 in 24 h UV irradiated leaflets. The calcium level in all test groups increased as time proceeds and the calcium level of GA-pretreated leaflets was significantly higher than the control and UV irradiated leaflets during test. This rapid calcium deposition on the GA-pretreated leaflets may be due to residual aldehyde groups after pretreatment. The exposure time of UV irradiation was not significantly correlated with the extent of calcification. After 14 days of the test, calcium levels in leaflets UV irradiated for 1, 2, 4, and 24 h were 502.6 +/- 12.3 microg/cm3, 547.5 +/- 34.1 microg/cm3, 564.3 +/- 26.1 microg/cm3, and 543.0 +/- 55.5 microg/cm3. In all test groups, [Ca]/[P] molar ratio decreased toward that of hydroxyapatite as the predominant mineral phase as time proceeds. This study suggests that UV irradiation can be considerable as an efficient crosslinking method to surmount the side effects induced by GA-pretreatment and may endow tissue with mechanical property.

Animals↗

PubMed2000

A bone replaceable artificial bone substitute: morphological and physiochemical characterizations.

A composite material consisting of carbonate apatite (CAp) and type I atelocollagen (AtCol) (88/12 in wt/wt%) was designed for use as an artificial bone substitute. CAp was synthesized at 58 degrees C by a solution-precipitation method and then heated at either 980 degrees C or 1,200 degrees C. In this study, type I AtCol was purified from bovine tail skins. A CAp-AtCol mixture was prepared by centirfugation and condensed into composite rods or disks. The scanning electron-microscopic (SEM) characterization indicated that the CAp synthesized at 58 degrees C displayed a crystallinity similar to that of natural bone and had a high porosity (mean pore size: about 3-10 microns in diameter). SEM also revealed that the CAp heated at 980 degrees C was more porous than that sintered at 1,200 degrees C, and the 1,200 degrees C-heated particles were more uniformly encapsulated by the AtCol fibers than the 980 degrees C-heated ones. A Fourier transformed-infrared spectroscopic analysis showed that the bands characteristic of carbonate ions were clearly observed in the 58 degrees C-synthesized CAp. To enhance the intramolecular cross-linking between the collagen molecules, CAp-AtCol composites were irradiated by ultraviolet (UV) ray (wave length 254 nm) for 4 hours or vacuum-dried at 150 degrees C for 2 hours. Compared to the non cross-linked composites, the UV-irradiated or dehydrothermally cross-linked composites showed significantly (p < 0.05) low collagen degradation and swelling ratio. Preliminary mechanical data demonstrated that the compressive strengths of the CAp-AtCol composites were higher than the values reported for bone.

Animals↗

PubMed2000

Viability of cells in cryopreserved canine cardiovascular organs for transplantation.

To determine applicability of the cryopreservation procedure for vessel grafts, the viability of endothelial cells (ECs) among the whole cells in three kinds of organs artery, vein, trachea in mongrel dogs was evaluated on the basis of histological analysis. The Griffonia simplicifolia agglutins-fluorescein isothiocyanate (GSA-FITC) and propidium iodide (PI) double staining methods were combined with flow cytometry (FCM), which was able to simultaneously determine the viability of whole cells and ECs from the same tissue, were performed after harvesting, after antibiotic solution treatment, and after cryopreservation and thawing. In most cases, the viability of ECs is lower than that of whole cells from veins and arteries. The viability of whole cells in veins was maintained until the antibiotic solution treatment and then decreased significantly after cryopreservation and thawing, while the ECs began to decrease significantly after the antibiotic solution treatment and more markedly decreased after thawing. The viability of ECs and whole cells from arteries was similar to that of the veins' conditions. The viability of whole cells from the trachea decreased with a similar pattern to that of the ECs from vessels. In consideration of maintaining cell viability among the three kinds of organs, the viability of arteries was better than that of the others. The cells in the trachea demonstrated a lower viability than the vessels. The effect of antibiotic solution treatment on the reduction of cell viability depends on the treatment time and temperature.

Animals↗

PubMed2000

Tissue restoration, tissue engineering and regenerative medicine.

Recently, thanks to the rapid progress of new technologies in cell modulation, extracellular matrix fabrication and synthetic polymers mimicking bodily structures, the self-regeneration of bodily defects by host tissue has been considered by many researchers. The conventional science of art in biomaterials has been concerned with restoring damaged tissue using non-biological materials such as metals, ceramics and synthetic polymers. To overcome the limitations of using such non-viable materials, several attempts to construct artificial organs mimicking natural tissue by combining modulated cells with extracellular matrix-hybridized synthetic polymers have produced many worthy results with biologically functioning artificial tissues. The process involved in manufacturing biomaterials mimicking living tissue is generally called tissue engineering. However recently, the extension of knowledge about cell biology and embryology has naturally moved the focus from tissue restoration to tissue regeneration. Especially, embryonic and mesenchymal stem cells are attractive resources due to their potential for the differentiation of various tissue cells in response to signal transduction mediated by cytokines. Although no one knows yet what is the exact factor responsible for a stem cell's ability to differentiate between specific cells to generate specific tissue, what has been agreed is that delivering stem cells into the body provides a strong potential for the regeneration of tissue. In this review, the historical issues and future possibilities involved in medical tissue restoration and tissue regeneration are discussed.

Animals↗

PubMed2000

Viability evaluation of engineered tissues.

Biohybrid artificial organs encompass all devices capable of substituting for an organ or tissue function and are fabricated from both synthetic materials and living cells. The viability of engineered tissue could be related to the viability of implanted cells. The system of viability assay for mammalian cell culture can be applied to the determination of cell viability for engineered tissue. This review explores various methods of cell viability assay which can be applied to the viability evaluation of engineered tissue. The major criteria employed in viability assays include survival and growth in tissue culture, functional assay, metabolite incorporation, structural altercation, and membrane integrity. Each viability assay method is based on different definitions of cell viability, and has inherent advantages and disadvantages. In order to be able to assess the viability of cells with one assay method, it is desirable to compare the viability measurements from various assays derived from different criteria.

Animals↗

PubMed1999

Inhibition of initiation of simian virus 40 DNA replication in vitro by the ursodeoxycholic acid and its derivatives.

In this study, the effects of the ursodeoxycholic acid (UDCA), and its derivatives, on DNA replication were examined using simian virus (SV40) DNA replication in vitro. We found that UDCA and its derivatives inhibited SV40 DNA replication, and predominantly inhibited the initiation stage of DNA replication. UDCA and its derivatives inhibited the DNA cleavage by topoisomerase I (topo I). Among them, HS-1183 significantly reduced the activity of topo I. UDCA, at 100 microM, significantly reduced polymerase alpha-primase (pol alpha-primase) activity, but HS-1030 and HS-1183 showed a weak inhibitory effect. The ssDNA binding activity of replication protein A (RPA) was little affected by UDCA and HS-1030, but was weakly inhibited by HS-1183. Based on their properties, we suggest that UDCA and its derivatives might inhibit some molecules that is required to establish replication forks during the initiation reaction and their cytotoxicity might be related to the inhibitory effect they have on this fundamental cellular process.

Antineoplastic Agents↗