Search PubMed⌕ Search

Biomedical subjects

K Park

Publications and source records attributed to K Park.

At least 91 records · Page 5Linked to original sources
PubMed2001

Effect of compression on fast swelling of poly(acrylamide-co-acrylic acid) superporous hydrogels.

Superporous hydrogels (SPHs) swell to a large size in a very short time. In many applications it is preferred to compress SPHs to reduce the overall dimension in the dried state. The effects of compression on the swelling property of SPHs were examined. The swelling property of the compressed SPHs was dependent on the orientation of the SPHs during compression. If SPHs were compressed in an orientated manner so that they retained interconnected porous structure, they were able to swell to near equilibrium within 10 min of immersion in aqueous fluids. If SPHs were compressed in a manner that did not retain the open pore structure, the swelling rate was greatly reduced. The results showed that the SPHs could be compressed without significant sacrifice of the fast swelling property if compressed in a proper orientation. Because pores were formed owing to the generation of gas which rose from bottom to the top of the container, the compression parallel to the pore formation resulted in preservation of the pore structure, and thus fast swelling property. The ability to compress SPHs, maintaining the fast swelling property, is expected to be useful in various applications including development of gastric retention devices for oral drug delivery.

Acrylamides↗
PubMed2001

Type I interferons and IL-12: convergence and cross-regulation among mediators of cellular immunity.

Therapeutic use of type I IFN (IFN-alpha/beta) has become common. Many of the diverse diseases targeted are marked by pathogenetic abnormalities in cell-mediated immunity (CMI), these cellular immune responses either causing injury to the host, lacking sufficient vigor for virus or tumor clearance, or both. In general, therapeutic efficacy is limited. It is thus notable that the pleiotropic effects of type I IFN on CMI remain poorly understood. We characterized the effects of type I IFN on the production of IL-12, the central immunoregulatory cytokine of the CD4(+) T cell arm of CMI. We show that type I IFN are potent inhibitors of IL-12 production by human monocytes/macrophages. The underlying mechanism involves transcriptional inhibition of the IL-12p40 gene, marked by down-regulation of PU.1 binding activity at the upstream Ets site of the IL-12p40 promoter. Type I IFN have previously been shown to be able to substitute for IL-12 in driving IFN-gamma production from T and NK cells. The ability of IFN-alpha/beta to suppress IL-12 production while up-regulating IFN-gamma production suggests a possible mechanistic basis for the difficulties of employing these cytokines in diseases involving abnormalities of CMI.

Cells, Cultured↗
PubMed2001

Msx1 gene overexpression induces G1 phase cell arrest in human ovarian cancer cell line OVCAR3.

Recent evidence suggested an involvement of homeobox genes in tumorigenesis. Here we investigated whether one of homeobox-containing genes, Msx1, might be involved in the regulation of cell proliferation and cell cycle using Msx1 overexpressing human ovarian cancer cell line, OVCAR3. Overexpression of Msx1 in OVCAR3 cells inhibited cell proliferation by markedly increasing the length of the G1 phase of the cell cycle over control cells. Consistent with this result, dramatic suppression of cyclins D1, D3, E, cyclin-dependent kinase 4, c-Jun, and Rb was observed. Elevated expression of genes involved in the growth arrest and apoptosis (GADD153 and apoptotic cystein protease MCH4) and suppression of proliferation associated protein gene (PAG) in Msx1-overexpressing cells by cDNA expression array analysis provide further evidence for a potential repressor function of Msx1 in cell cycle progression.

Cell Division↗
PubMed2001

Effect of dust on the viability of Vibrio fischeri in the Microtox Test.

The standard Microtox test involving the bioluminescent bacterium Vibrio fischeri is a frequently used ecotoxicological bioassay whose EC50, values have been correlated to acute toxicity parameters of vertebrates, to irritancy measures, and to cytotoxicity indices. The aims were to explore the dependence of light output on viable cell number, with the latter estimated with the naked eye using a colorimetric tetrazolium salt method, the effects of dust on the bioluminescence and cell viability, how the viability of the cells is affected after spills, and how spills can be sampled. The lower limit of the linear dynamic range of the light-emitting bacterium was first defined to be 3.7 x 10(7) cells/ mL, compared with 37 x 10(7) cells/mL in the Microtox assay. The effects of dust were then explored in the working range by the method of standard additions by adding 5-, 10-, and 20-mg amounts of Standard Reference Material Urban Dust 1649a. This simulated dust samples collected by a cordless vacuum technique involving a filter cassette. A mass of 20 mg dust totally inhibited the Microtox test at all times (5, 15, and 30 min). Masses of 5 and 10 mg dust lowered the luminescence significantly by 20 and 64%, respectively, after 30 min. However, the viability test was totally inhibited by 5 mg of dust. A spectrophotometric modification of the viability test using a wavelength of 508 nm was developed that was twice as sensitive as the naked eye test, and was as sensitive as the Microtox test. Mechanical shock involved with spilling and sampling bacterial reagent on hard surfaces killed the luminescent bacteria as shown by inhibition of luminescence. The optimum filter cassette for Microtox reagent collection was a 25-mm 1.00-microm PTFE filter in a 25-mm Delrin holder operated at 4.0 L/min, with a Tygon sampling probe.

Calibration↗
PubMed2001

Investigation of juxtasellar and cerebellopontine angle meningiomas and neurogenic tumours: two-phase helical CT.

We performed two-phase helical CT in 31 patients with juxtasellar region and cerebellopontine angle tumours to evaluate its usefulness in differentiating meningiomas from neurogenic tumours. After the intravenous injection of 90 ml contrast medium at 3 ml/s, axial helical images were obtained with delays of 30 and 120 s. After the delayed axial images, we acquired coronal images. Changes in attenuation were assessed visually and quantitatively (by comparing the attenuation in Hounsfield units). There were 17 meningiomas and 14 neurogenic tumours, all pathologically proven. Two-phase helical CT showed a decrease in attenuation in 15 (88%) meningiomas and an increase in 14 (100%) neurogenic tumours from early to delayed axial images. Coronal images showed a decrease in attenuation in all 17 meningiomas and an increase in 13 (93%) of the neurogenic tumours. The mean HU and their ratios were significantly different between meningiomas and neurogenic tumours.

Adult↗
PubMed2001

Immunohistochemical study on proliferative activity of experimental cholesteatoma.

In this study, we induced canal ligation cholesteatoma using Mongolian gerbils and investigated the hyperproliferative nature of canal ligation cholesteatoma by using an immunohistochemical technique with proliferation markers (cytokeratin 13/16, PCNA, EGFR, thrombomodulin). Canal ligation cholesteatoma using Mongolian gerbils had a hyperproliferative character in the suprabasal cell layer similar to human cholesteatomas. This result will provide a good morphological basis for future cholesteatoma animal research concerning the pathogenesis of cholesteatoma.

Animals↗
PubMed2001

Long-term results of kidney transplantation between HLA-identical siblings.

Long-term data on HLA-identical renal transplants are scarce, and the advantages of using cyclosporine (CsA) over azathioprine (AZA) have yet to be elucidated. In 68 recipients from HLA-identical donors (37 under AZA-steroids and 31 under CsA-steroids), we estimated the graft and patient survival to posttransplant 120 months, and compared the results between patients on different protocols. Episodes of rejection, causes of graft loss or patient death, and longterm complications were also compared retrospectively. The 10-year patient/graft survivals were comparable: 82.7/67.6% for the AZA and 78.4/63.5% for the CsA patients. The incidence of acute rejection during the first year after transplant was also comparable. We lost 25 grafts. The major causes of graft loss were patient death (7/13 in AZA and 5/12 in CsA patients) and chronic rejection (3/13 in AZA and 3/12 in CsA patients). Four grafts were lost due to poor compliance. We lost 12 patients due mostly to cerebrovascular disease and infections. There was no difference in the prevalence of complications between patients. In conclusion, the long-term outcome was excellent in this subgroup of transplant patients. We could not find any advantages of using CsA over AZA in these patients after a long-term follow-up. To achieve better results, continued attention should be paid to the prevention of poor compliance and complications.

Adult↗
PubMed2001

Identification and regulation of K+ and Cl- channels in human parotid acinar cells.

The properties of K+ channels in these cells were studied using patch-clamp methods. Two channels, with conductances of 165+/-13 pS (n=6) and 30+/-1 pS (n=3), were identified in single-channel experiments. In cell-attached patches the reversal potentials were -67+/-8 and -74+/-2 mV for the large and small conductance channel, respectively, suggesting that both channels are K+-selective. The large conductance channel was also shown to be K+-selective in inside-out patches. The open probability (P(o)) of this channel was increased at depolarizing potentials and by increasing intracellular Ca2+ concentration ([Ca2+]i). These properties suggest that the large conductance channel is a 'maxi' Ca2+-activated K+ channel (BK(Ca)). The small conductance channel was not observed in inside-out patches. Carbachol (CCh; 10(-5) M) activated the BK(Ca) channel, but not the small conductance channel, in cell-attached patches. CCh also caused a dose-dependent increase in [Ca2+]i measured by fura-2 in microspectrofluorimetric studies, with a half-maximal response at approximately 3x10(-6) M. Neither isoproterenol (10(-5) M) nor substance P (10(-6) M) affected K+-channel activity or [Ca2+]i. In whole-cell experiments, CCh caused an increase in outward current. Charybdotoxin (10(-7) M), a BK(Ca) blocker, inhibited a large component of the CCh-induced current. A large component of the charybdotoxin-insensitive current may be carried by Ca2+-activated Cl- channels, which were also observed in human parotid acinar cells. The results indicate that BK(Ca) channels make a significant contribution to the whole-cell conductance in human parotid acinar cells.

Adult↗
PubMed2001

Altered responsiveness to stress and NMDA following prenatal exposure to cocaine.

Pregnant Sprague--Dawley rats were treated once daily with 40-mg/kg cocaine or saline from gestation days (GD) 12 to 21. A third group of pregnant dams was used as a pairfed control. Male and female offspring were examined for stress endurance response as determined by the cold-water swim test on postnatal days (PND) 21, 30, 40, and 60. Male and female offspring exposed to cocaine in utero were found to have diminished tolerance and altered hormonal response to stress. Moreover, prenatal cocaine exposure has been associated with significant increases in severity of N-methyl-D-aspartate (NMDA; 35 mg/kg) behavioral responses (tail twitches, wetdog shaking, and convulsion) as compared to control. Examining the experimental groups for pain sensitivity using the tail-flick and the hot-plate methods indicated that prenatal cocaine exposure altered pain sensitivity. NMDA receptor binding studies showed an increase in receptor density in the hippocampus and hypothalamus of the cocaine-treated group. These results indicate that gestational cocaine exposure is associated with long-term alterations in response to stress, NMDA receptor, and pain sensitivity in the rat offspring.

Aging↗
PubMed2001

Blood-oxygenation-level-dependent functional magnetic resonance imaging for evaluating cerebral regions of female sexual arousal response.

OBJECTIVES: To evaluate, for the first time, the cerebral regions associated with female sexual arousal evoked by visual stimulation using noninvasive blood-oxygenation-level-dependent (BOLD) functional magnetic resonance imaging (fMRI). METHODS: A total of 6 healthy right-handed female volunteers (mean age 33 years, range 25 to 41) underwent fMRI on a 1.5-T MR scanner, in which the BOLD technique was used to create fMR images reflecting local brain activities. Real-time visual stimulation was performed with alternatively combined erotic and nonerotic films to identify the activated brain regions associated with sexual response. The perceived sexual arousal response was assessed using a scale ranging from 1 (no change) to 5 (maximal increase). RESULTS: The mean score for perceived sexual arousal by erotic visual stimulation was 2.7 on the 5-point scale and was unchanged by nonerotic stimulation. During the visual task, the occipital cortex was activated by both the erotic and the nonerotic films; however, the following cerebral areas were significantly (P <0.05) activated, varying from 4 of 6 to 6 of 6 women: inferior frontal lobe, cingulate gyrus, insula gyrus, corpus callosum, thalamus, caudate nucleus, globus pallidus, and inferior temporal lobe. CONCLUSIONS: This study is the first to evaluate noninvasive BOLD-fMRI in identifying cerebral regions associated with sexual arousal response evoked by visual stimulation in women.

Adult↗
PubMed2001

Marrow-derived cells populate scaffolds composed of xenogeneic extracellular matrix.

INTRODUCTION: The source of cells that participate in wound repair directly affects outcome. The extracellular matrix (ECM) and other acellular biomaterials have been used as therapeutic scaffolds for cell attachment and proliferation and as templates for tissue repair. The ECM consists of structural and functional proteins that influence cell attachment, gene expression patterns, and the differentiation of cells. OBJECTIVE: The objective of this study was to determine if the composition of acellular matrix scaffolds affects the recruitment of bone marrow-derived cellular elements that populate the scaffolds in vivo. METHODS: Scaffolds composed of porcine tissue ECM, purified Type I collagen, poly(L)lactic coglycolic acid (PLGA), or a mixture of porcine ECM and PLGA were implanted into subcutaneous pouches on the dorsum of mice. The origin of cells that populated the matrices was determined by first performing bone marrow transplantation to convert the marrow of glucose phosphate isomerase 1b (Gpi-1(b)) mice to cells expressing glucose phosphate isomerase 1a (Gpi-1(a)). RESULTS: A significant increase in Gpi-1(a) expressing cells was present in sites implanted with the porcine ECM compared to sites implanted with either Type I collagen or PLGA. Use of recipient mice transplanted with marrow cells that expressed beta-galactosidase confirmed that the majority of cells that populated and remodeled the naturally occurring porcine ECM were marrow derived. Addition of porcine ECM to the PLGA scaffold caused a significant increase in the number of marrow-derived cells that became part of the remodeled implant site. CONCLUSION: The composition of bioscaffolds affects the cellular recruitment pattern during tissue repair. ECM scaffolds facilitate the recruitment of marrow-derived cells into sites of remodeling.

Animals↗
PubMed2001

Quantitative analysis of errors in fractionated stereotactic radiotherapy.

Fractionated stereotactic radiotherapy (FSRT) offers a technique to minimize the absorbed dose to normal tissues; therefore, quality assurance is essential for these procedures. In this study, quality assurance for FSRT of 58 cases, between August 1995 and August 1997 are described, and the errors for each step and overall accuracy were estimated. Some of the important items for FSRT procedures are: accuracy in CT localization, transferred image distortion, laser alignment, isocentric accuracy of linear accelerator, head frame movement, portal verification, and various human errors. A geometric phantom, that has known coordinates was used to estimate the accuracy of CT localization. A treatment planning computer was used for checking the transferred image distortion. The mechanical isocenter standard (MIS), rectilinear phantom pointer: (RLPP), and laser target localizer frame (LTLF) were used for laser alignment and target coordinates setting. Head-frame stability check was performed by a depth confirmation helmet (DCH). A film test was done to check isocentric accuracy and portal verification. All measured data for the 58 patients were recorded and analyzed for each item. 4-MV x-rays from a linear accelerator, were used for FSRT, along with homemade circular cones with diameters from 20 to 70 mm (interval: 5 mm). The accuracy in CT localization was 1.2+/-0.5 mm. The isocentric accuracy of the linear accelerator, including laser alignment, was 0.5+/-0.2 mm. The reproducibility of the head frame was 1.1+/-0.6 mm. The overall accuracy was 1.7+/-0.7 mm, excluding human errors.

Brain Neoplasms↗
PubMed2001

Improvement of the physical properties of reprocessed paper by using biological treatment with modified cellulase.

A primary need for waste paper reprocessing is to preserve optical properties and the physical strength of the paper fibers. In this study, modified cellulase with copolymer, polyethylene oxide (PEO) derivatives and maleic anhydride (MA) was applied to the reprocessing of mixed office waste (MOW). Modified cellulase was prepared by a chemical reaction between amino groups of the cellulase and the MA functional groups of the copolymer. In MOW reprocessing, modified cellulase improved several physical properties of the paper including freeness, optical properties, and physical strength compared to the conventional process. Even though native cellulase improved the physical properties, paper treated with modified cellulase exhibited an increase in physical properties such as tensile strength and internal bond over those of unmodified cellulase. From these results, modified cellulase method is a new biological treatment that will save pulp resources, which are added to waste paper reprocessing to maintain the strength of paper.

Cellulase↗
PubMed2001

Phase II study of high-dose lovastatin in patients with advanced gastric adenocarcinoma.

Lovastatin, an inhibitor of mevalonate synthesis, demonstrated in vitro antitumor activity against a variety of human cancer cells, especially in gastric adenocarcinoma cells at pharmacologically achievable concentrations. To determine the antitumor activity of this drug in advanced measurable gastric adenocarcinoma as well as to assess the toxicities and the pharmacokinetic features, we carried out a phase II study of high-dose lovastatin. Patients received lovastatin 35 mg/kg/day for 7 consecutive days, with ubiquinone (60 mg qid p.o.) to prevent rhabdomyolysis. The treatment was repeated every 28 days. From March 1996 to January 1997, 16 patients (median age, 57 years; range, 34-68) were entered into the study, 14 of whom were evaluated for response and toxicity. No patient achieved a response. A total of 28 cycles were administered. The median number of cycles was 2 (range, 1 to 4). Anorexia was the most common toxicity (64%), but decreased oral intake was observed only in 3 cycles. Two patients developed myalgia with elevated muscle enzyme. When used in this dosage and schedule, lovastatin does not appear to be effective for patients with advanced gastric adenocarcinoma.

Adenocarcinoma↗
PubMed2001

Glucose-binding property of pegylated concanavalin A.

PURPOSE: Concanavalin A (Con A) has been used in the development of sol-gel phase-reversible hydrogels for modulated insulin delivery. The usefulness of Con A has suffered from its poor aqueous solubility and stability. The goal of this study was to modify Con A with poly(ethylene glycol) (PEG) and examine the water solubility and stability of the PEGylated Con A. METHODS: Con A was PEGylated using monomethoxy poly(ethylene glycol) p-nitrophenol carbonates, and the extent of PEGylation was determined by the fluorescamine method. The stability of the PEGylated Con A was examined by measuring the time-dependent absorbance at 630 nm. The binding affinities of glucose and allyl glucose to native- and PEGylated-Con A were measured by the equilibrium dialysis method. RESULTS: The total number of PEG molecules that can be grafted to Con A was 10. As the number of grafted PEG chains per each Con A was increased up to 5, the binding affinity of glucose was gradually increased and reached the maximum. The solubility and stability of PEGylated Con A were improved significantly over those of native Con A. The binding affinity of allyl glucose to Con A was not changed much by PEGylation. When the extent of PEGylation was excessive (i.e., the number of grafted PEG chains per each Con A was larger than 5), however, the binding affinities of both glucose and allyl glucose were decreased significantly. CONCLUSIONS: PEGylation of Con A resulted in improved aqueous solubility and stability of Con A. The binding affinity of glucose increased and reached the maximum when the extent of PEGylation was 50%. Advantages of PEGylated Con A over native Con A are improved aqueous solubility, enhanced long-term stability, and higher glucose sensitivity.

Binding, Competitive↗
PubMed2001

CHOP followed by involved field radiation: is it optimal for localized nasal natural killer/T-cell lymphoma?

The present study aimed to analyse the treatment outcome of four cycles of CHOP (cyclophosphamide-vincristine-doxorubicin-prednisolone) followed by involved field radiation therapy (IF RT) for the treatment of stage I-II nasal natural killer (NK)/T-cell lymphoma. From March 1995 to December 1999, 17 patients (median age 41 years; range 30-66) with localized nasal NK/T-cell lymphoma were enrolled. B symptoms were noted in five patients (31%). Sixteen of seventeen patients (94%) were of low risk when classified according to the International Prognostic Index (IPI). The treatment plan consisted of four cycles of CHOP chemotherapy followed by IF RT of 45 Gy. Two patients received radiation during the first or second cycle of CHOP because of bleeding from the primary tumour site. Both patients achieved complete responses (CRs). In the remaining 15 patients, after 4 cycles of CHOP, 6 CRs and 3 partial responses (PRs) were achieved (53% of response rate). IF RT was given to six patients (four in CR, one in PR and one in PD), and all six patients achieved CR. Overall, CR was achieved in 10 of 17 patients (58%). The planned sequential chemoradiotherapy was completed in only 6 of 17 patients (35%) because of the progression during chemotherapy. None of the patients who achieved CR experienced relapse of lymphoma during follow-up. The estimated overall three-year survival rate was 59%. In univariate analysis, B symptoms and stage were significant prognostic factors for response and overall survival (P < 0.05). The present study suggests that four cycles of CHOP followed by IF RT is not satisfactory for treating patients with localized nasal NK/T-cell lymphoma, and that further exploration for improved therapy is needed.

Adult↗
PubMed2001

P16INK4a protein expression is associated with poor survival of the breast cancer patients after CMF chemotherapy.

Immunohistochemical assay for p16 protein expession was performed in 192 breast carcinoma patients treated with adjuvant chemotherapy. p16 expression was observed in 78 cases (40.6%). The frequency of p16 expression significantly decreased in moderately differentiated (histologic grade II) cancers, 20 (19.6%) of 102. In poorly differentiated cancers (histologic grade III), p16 expression was not observed in all 16 cases. p16 expression was significantly associated with histologic grade of the breast carcinomas (p < 0.001). The proliferative index (PI: S + G2/M) of individual tumors was measured by DNA flow cytometry. In 114 tumors with PI less than 20%, p16 expression was observed in 59 tumors (49.1%). In the tumors with PI equal or more than 20%, p16 expression was observed in 22 (28.2%) of 78 cases. p16 expression was significantly decreased in the tumor with higher PI (p =0.003). For the other clinicopathologic variables, no significant association was found with p16 expression status. Immunohistochemical assay for p53 protein expression was performed on the same breast carcinomas. There was no significant association between p16 and p53 expression in breast carcinomas. During median follow-up period of 52 months (range: 40-72 months), 46 patients (25.8%) had recurrent disease and 32 patients (18.91%) died of recurrent disease. p16 expression was observed in 20 (43.5%) of 46 patients with recurrent disease, while its expression was observed in 58 patients (39.7%) of 146 patients who were free of recurrence during the study period. p16 expression had no significant impact on predicting recurrence of breast carcinoma. Fourteen patients (12.2%) of 114 patients whose tumors did not show p16 expression died of recurrent breast carcinoma, whereas 18 patients (23.1%) of 78 patients with p16 expressing tumor died during the follow-up period. There was a significant difference of patient survival according to p16 expression status (p = 0.039). These results indicate that p16 expression is useful in predicting response to chemotherapy in breast cancer patients. p16 protein seems to have a role in tumor growth and differentiation of the breast carcinoma.

Antineoplastic Combined Chemotherapy Protocols↗