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Y H Park

Publications and source records attributed to Y H Park.

At least 19 recordsLinked to original sources
PubMed2006

Evaluation of the photoneutron field produced in a medical linear accelerator.

The doses and spectra of photoneutrons produced in a medical linear accelerator with photon energies of 10 and 15 MV were evaluated. The Monte Carlo code, MCNPX, was used to simulate the transport of these photoneutrons around the head for 10 and 15 MV photons. The fully-described geometry of the accelerator head was used in this calculation. The photoneutron energy spectra and doses for various photon field sizes were calculated at each of 20 positions. The results indicate that the maximum dose equivalents are observed in 20 x 20 cm(2) case among photon fields. It was found the neutron average energy at isocenter for a 0 x 0 cm(2) field is 0.38 MeV for 10 MV and is 0.45 MeV for 15 MV. The neutron doses at 10 positions around the head in the treatment room of the operation facility at 10 and 15 MV were measured using the bubble detectors. Measurements were compared with the calculations under the same geometry in the experiment. It was found that the majority of the calculated results agreed to within the standard deviations of the measurements. These above results can be applied in the verification of maximum allowed neutron leakage percentage of treatment dose defined in the IEC. We have been employing them to derive the empirical formula for neutron dose equivalent level at the maze entrance of medical accelerator treatment rooms in a study that is still underway.

Algorithms↗
PubMed2006

A phase II study of capecitabine plus 3-weekly oxaliplatin as first-line therapy for patients with advanced gastric cancer.

Capecitabine plus oxaliplatin every 3 weeks (XELOX regimen) has proven efficacy in patients with colorectal carcinoma. We investigated this combination in patients with previously untreated advanced gastric carcinoma. The study population comprised patients with histologically confirmed nonresectable advanced gastric adenocarcinoma. Patients received intravenous oxaliplatin 130 mg m(-2) over 2 h on day 1 plus oral capecitabine 1000 mg m(-2) twice daily on days 1-14, every 3 weeks. Patients received a maximum of eight cycles. Twenty evaluable patients (17 men, 3 women) with a median age of 64 years (range 38-75) were enrolled. The overall response rate was 65% (95% confidence interval (CI), 44-86%), with complete responses in two patients and partial responses in 11 patients. Median progression-free survival was 7.5 months (95% CI, 3.2-11.7 months); median overall survival was not reached during the study period. There was no grade 4 and little grade 3 toxicity. The most common haematological adverse event was anaemia (65% of patients) and the most common nonhaematological toxicities were vomiting (65%), neuropathy (60%), diarrhoea (30%), and hand-foot syndrome (20%). In conclusion, XELOX is apparently as effective as triplet combinations and is well tolerated as first-line therapy for advanced gastric carcinoma. We are starting a large multi-institutional phase II study of XELOX in this setting.

Adenocarcinoma↗
PubMed2006

Sleep-related nocturnal erections and erections during midazolam-induced sedation in healthy young men.

This study was performed to evaluate the characteristics of penile erection during midazolam-induced sedation after nocturnal sleep deprivation (NSD) and to determine the effect of NSD on erectile episodes in healthy, sexually functional young men. This procedure might possibly prove to be a brief office-based method of assessing whether erectile dysfunction is psychogenic or biogenic. Nineteen volunteers between the ages of 20 and 29 years participated in this study. We measured the morning penile erection after midazolam (3-5 mg) administration intravenously and all subjects completed 42 tests. Of 42 test, 28 tests revealed erectile episodes, whereas no erectile episodes were observed in 14 tests. Nocturnal sleep deprivation rate was significantly higher in tests with erectile episodes than in tests without erectile episode (P=0.030). Test order or duration of test was not different between two test results. Number of erectile episodes (r=0.374, P=0.015), tip radial rigidity (r=0.412, P=0.007), base radial rigidity (r=0.366, P=0.017) and tip tumescence (r=0.447, P=0.003) correlated with the degree of NSD. When we determined whether NSD was discriminative with regard to erectile episodes, the area under the receiver operating characteristic curve was calculated at 0.705 (95% confidence interval, 0.527-0.883; P=0.032) for the possibility of erectile episodes. Nocturnal sleep deprivation might recover the inhibited rapid eye movement sleep during midazolam-induced sedation. Our findings suggest that erection monitoring during midazolam-induced sedation after NSD may be convenient. However, validation of midazolam-induced morning penile tumescence monitoring with a large population is mandatory.

Adult↗
PubMed2006

The effect of Epstein-Barr virus status on clinical outcome in Hodgkin's lymphoma.

The association of Epstein-Barr virus (EBV) with Hodgkin's lymphoma (HL) has been investigated over the last few years. The impact of EBV on clinical outcome is still controversial, however. In this study, we investigated the effect of EBV status on clinical outcome of HL patients. Between January 1986 and September 2004, fifty-six patients, diagnosed as having HL, were included in the analysis. Clinical data were reviewed retrospectively from the patients' records. Tissues from 56 patients were analyzed for the presence of EBV using the in situ hybridization (ISH) for EBV-encoded RNA (EBER) and immunohistochemistry for latent membrane protein (LMP)1. EBV infection was identified in 41.1% of cases by EBER ISH, 26.8% by LMP1 expression, and 26.8% by LMP1 and EBER ISH. EBER-positive HL were significantly more frequent in mixed cellularity (MC) subtype (P=0.014) and advanced stage (P=0.034). There was a trend toward shorter overall survival in EBER-positive patients without statistical significance (P=0.238). LMP1 expression also correlated with MC subtype (P=0.006) and advanced stage (P=0.007), although it did not significantly influence the survival outcome. In subgroup analysis, both EBER and LMP1 positivities were associated with longer progression-free survival in patients with age <25 years old (P=0.045). Reverse trends were shown in patients > or =25 years old. In this study, we demonstrated that the impact of tumor EBV status on prognosis may be age dependent and young patients with latent EBV infection have favorable prognosis.

Adult↗
PubMed2006

Improved therapeutic outcomes of DLBCL after introduction of rituximab in Korean patients.

The addition of rituximab to cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) has been shown to improve the outcome in all age groups with newly diagnosed diffuse large B-cell lymphoma (DLBCL). We conducted a retrospective analysis to evaluate the impact of this combination therapy on DLBCL outcomes in Korea. From October 2001 to June 2004, newly diagnosed DLBCL patients in nine Korean institutes were included. All of these 81 patients were treated with three or more cycles of rituximab plus CHOP (R-CHOP) combination chemotherapy (R group), and followed for a minimum of 12 months. For comparison, a historical cohort of patients was used and analyzed for "Clinicopathologic characteristics of Korean non-Hodgkin's lymphomas (NHLs) based on Revised American Lymphoma (REAL) classification" in 1999. Among the 1,098 NHL patients, the data of 214 DLBCL patients, who were treated with CHOP chemotherapy in first-line, were analyzed (C group). We compared outcomes between the C group and the R group. A total of 295 patients were evaluated (C group, 214; R group, 81). The complete response (CR) rate was higher in R group (73 vs 91%, p=0.001). The 2-year event-free survival (EFS) rate was significantly higher in R group (78 vs 85%, p=0.0194). This survival benefit was maintained in high-risk patients according to the international prognostic index (IPI) (p=0.0039), regardless of age. However, there was no significant difference in low-risk patients. The addition of rituximab to CHOP combination chemotherapy for DLBCLs showed improved outcomes, particularly in high-risk group according to the IPI. Long-term follow-up results will be needed to confirm these results.

Adolescent↗
PubMed2006

High-dose chemotherapy with autologous stem cell transplantation in extranodal NK/T-cell lymphoma: a retrospective comparison with non-transplantation cases.

To determine the role of high-dose chemotherapy and autologous stem cell transplantation (HDC/ASCT) in extranodal NK/T-cell lymphoma patients, we conducted a retrospective analysis. In our previous study, we searched for patients who had received HDC/ASCT and identified 16 eligible patients and compared the treatment outcome with historical control group (n=246). Nine patients received HDC/ASCT in the first (CR1) or second complete remission (CR2), while seven patients received HDC/ASCT as salvage. Twelve of 16 patients achieved or maintained CR after HDC/ASCT. Among the 12 patients, five patients relapsed. Estimated 2-year overall survival (OS) and relapse-free survival (RFS) rates were 71.3+/-12.4% and 25.8+/-14.3%, respectively. There was a tendency of better survival in patients who received HDC/ASCT as compared to those who did not (P=0.091). In subset analysis, patients who underwent HDC/ASCT at CR (P=0.049) and patients with stage III or IV (P=0.001) had a favorable outcome. Patients with NKIPI 3,4 or EUNKTL, who underwent HDC/ASCT had more prolonged survival without statistical significance (P=0.055 and 0.056). In conclusion, HDC/ASCT may be considered as a treatment option for patients with extranodal NK/T-cell lymphoma, especially those in CR, with advanced disease (stage III/IV or EUNKTL) and high NKIPI scores.

Adolescent↗
PubMed2005

Effects of supplementation of beta-glucan on the growth performance and immunity in broilers.

Two experiments were conducted to evaluate the efficacy of beta-glucan on commercial broilers. In experiment 1, one hundred and forty-four broiler chicks were employed in a 2x3 factorial design with cage and open floor housing with three levels of beta-glucan viz. 0%, 0.02% and 0.04%. In experiment 2, ninety-six broilers were used with 4 treatments: No beta-glucan and antibiotic (T1), beta-glucan 0.03% (T2), antibiotic (T3), and beta-glucan 0.03% + antibiotic (T4) for 34 d with 3 replicates of 8 chicks each in both studies. During experiment 1 there was no significant effect of the feeding system or the beta-glucan levels on the performance from 0 to 17 d but during 18-34 days birds housed on the open floor had significantly (p<0.0001) higher weight gain compared with those in cages. In experiment 2, no significant effect was noticed on the weight gains when the effect of beta-glucan, antibiotic or their interaction were tested. The retention of dry matter increased in both experiments with beta-glucan supplementation. The CD8 and TCR 1 cells were significantly higher in the 0.04% beta-glucan group at 42 days as compared with the control. It could be concluded that beta-glucan supplementation was beneficial for broilers.

Animal Feed↗
PubMed2005

Nasal-type NK/T cell lymphoma: clinical features and treatment outcome.

Nasal-type NK/T cell lymphoma is an increasingly recognised disease entity of aggressive clinical behaviour. The objective of this study was to investigate clinical features and treatment outcomes in patients with nasal-type NK/T cell lymphoma. From January 1991 to December 2003, 26 patients diagnosed as nasal-type NK/T cell lymphoma were included in the analysis. One half of patients presented with poor performance status (ECOG > or =2); 46% of patients were categorised as high intermediate or high-risk group according to IPI; and 46% of patients were diagnosed at advanced stage. The median survival for 26 patients with nasal-type NK/T cell lymphoma was 7.4 months (95% CI, 0.1, 16.9). The treatment outcome of primary anthracycline-based chemotherapy was poor: 60% CR rate in localised disease and 0% CR rate in advanced disease. After a median follow-up of 24.4 months (range 3.1-99.0) in patients with localised disease who had achieved a CR (range 29.6-165.7), three patients (50.0%) developed disease recurrence at 6.1, 21.8, and 52.1 months, respectively, and all patients presented with locoregional failure. The predictive factors for poor survival were of age greater than 60, advanced stage and poor performance in multivariate analysis. In conclusion, Nasal-type NK/T cell lymphomas showed a poor response to the conventional anthracycline-based chemotherapy, and thus an investigation for an innovative therapy is urgently needed to improve survival in these patients.

Adult↗
PubMed2005

Application of remote monitoring and automatic control system using neural network for small wastewater treatment plants in Korea.

For this study, an automatic control system has been developed by using a neural network and internet-based remote monitoring system for efficient operation of plants that have a serious variance of influent loading and have difficulties in appropriate maintenance, just like small wastewater treatment plants in Korea. In the control algorithm, ORP was used as the main sensor for control. At the point where the ORP value was judged to reach the "nitrate knee" of denitrification and phosphorus release, ORP indicated the state of lower saturation read by the neural network and then changed the operating condition from the reduction state to the oxidation state. For example, if ORP indicates the state of higher saturation at the point of "nitrogen breakpoint" or "ammonia valley" of nitrification, the neural network reads it and cuts off the oxygen supply and mixing. The dORP data have been used as one of the main input for the neural network. After the operation of lab-scale cyclic aeration process using an automatic control system, it has been found that regardless of loading variance, more than 95% of organic matters and more than 60% of nitrogen and phosphorus have been removed. Assuming that an internet-connected computer and a basic web browser are available, this study has developed a remote monitoring system that can monitor the operating status of small plants or any troubles with them.

Automation↗
PubMed2005

Improvement of the thickening and dewatering characteristics of activated sludge by electroflotation (EF).

The performances of electroflotation (EF) on the thickening of activated sludge were investigated using laboratory scale batch flotation reactors. Four activated sludges including bulking sludges were tested. After 30 minutes of EF operation, 57-84% of sludge volume reduction could be achieved by EF, while only about 1.5-14% could be obtained by gravity thickening for the same period. After thickening the effluent water quality in terms of TCOD, SS, and turbidity was improved by EF operation for all sludge samples. In addition, the EF thickened sludge showed much better dewaterability both in SRF and cake solid content. It is induced that the air bubbles entrapped in the thickened sludge play a key role in the observed dewaterbility improvement.

Electrochemistry↗
PubMed2004

Application of extended single-reaction multiplex polymerase chain reaction for toxin typing of Staphylococcus aureus isolates in South Korea.

The extended single-reaction multiplex PCR (esr-mPCR) developed in this study to detect staphylococcal enterotoxins (SEs), including SEA, SEB, SEC, SED, SEE, SEH, SEI, and SEJ, requires fewer sets of primers than other conventional multiplex PCRs and can be used to detect newly identified staphylococcal enterotoxins SEs more readily. Esr-mPCR analysis of 141 isolates of Staphylococcus aureus obtained from abattoir and livestock product samples revealed that 27 of the S. aureus isolates were toxigenic, and two were 2 multitoxigenic isolates. The most prevalent SE type was SEI followed by SEA and SEH. In addition, we investigated the clonal relatedness of toxigenic S. aureus isolates by arbitrarily primed PCR (AP-PCR). AP-PCR analysis of toxigenic S. aureus isolates revealed that the discriminatory power of AP-PCR was 9 (D=0.81), 8 (D=0.77), and 10 types (D=0.83) with primers AP1, ERIC2, and AP7, respectively. The combination of three each AP-PCR result could rearrange toxigenic S. aureus isolates into 10 types and five subtypes, with the D-value of 0.92. Interestingly, our data showed that toxigenic S. aureus isolates from different sources had different fingerprinting patterns although some of them carried the same types of SE genes. These data suggest that combinations of esr-mPCR and AP-PCR can provide a powerful approach for epidemiological investigation of toxigenic S. aureus isolates.

Abattoirs↗
PubMed2004

Repeated amphetamine couples norepinephrine transporter and calcium channel activities in PC12 cells.

Repeated intermittent amphetamine enhances efflux of dopamine through the dopamine transporter in rat basal ganglia and through the norepinephrine transporter in rat pheochromocytoma PC12 cells. Extracellular Ca2+ is required for the detection of this enhancement in the rat. In this study, we examined the role of Ca2+ and Ca2+ channels in the enhanced amphetamine-induced dopamine efflux that develops in PC12 cells following repeated intermittent amphetamine. Repeated pretreatment of PC12 cells with 1 microM amphetamine followed by a drug-free period increased amphetamine-induced efflux of dopamine compared with controls. The enhancement in amphetamine-induced dopamine efflux depended upon the presence of extracellular Ca2+ and was inhibited by the blockade of N-type and L-type Ca2+ channels. The enhanced dopamine efflux was not altered by tetanus toxin or reserpine, treatments that abrogate synaptic vesicle-mediated, exocytotic dopamine efflux. Measurement of intracellular Ca2+ concentrations using fura-2/acetoxymethyl ester revealed that amphetamine increased intracellular Ca2+ by a transporter-dependent mechanism. In amphetamine-pretreated cells, amphetamine elicited a greater increase in intracellular Ca2+; this increase depended upon the presence of extracellular Ca2+ and N- and L-type Ca2+ channel activity. The enhanced amphetamine-induced dopamine efflux requires Ca2+/calmodulin kinase activity. In vehicle-treated cells, 1 microM amphetamine inhibited the calmodulin kinase activity although it did not in amphetamine-pretreated cells. This study suggests that repeated intermittent amphetamine couples norepinephrine transporter activity and Ca2+ signaling.

Adrenergic Agents↗
PubMed2004

A phase II study of capecitabine and docetaxel combination chemotherapy in patients with advanced gastric cancer.

Capecitabine and docetaxel have considerable single-agent activity in gastric cancer with distinct mechanisms of action and no overlap of key toxicities. A synergistic interaction between these two drugs is mediated by taxane-induced upregulation of thymidine phosphorylase. We investigated the activity and the feasibility of capecitabine and docetaxel combination chemotherapy in patients with previously untreated advanced gastric cancer (AGC). From September 2001 to March 2003, 42 patients with AGC received 21-day cycles of oral capecitabine (1250 mg x m(-2) twice daily on days 1-14) and docetaxel (75 mg x m(-2) i.v. on day 1). The patients received a total of 164 cycles of chemotherapy. The median age was 53.5 years (range 33-73 years). The overall response rate in the 38 efficacy-evaluable patients was 60% (95% confidence interval, 45-74%). The median progression-free survival was 5.2 months (range, 1.0-15.5+ months) and the median overall survival was 10.5 months (range, 2.9-23.7+ months). The most common grade 3/4 adverse events were hand-foot syndrome (HFS: G3 50%), neutropenia (15%) and leucopenia (12%). Further studies of this combination are clearly warranted, albeit with lower doses of both agents (1000 mg x m(-2) twice daily and 60 mg x m(-2)) to reduce the rate of HFS and onycholysis.

Adult↗
PubMed2004

Differences in p53 gene polymorphisms between Korean schizophrenia and lung cancer patients.

The reduced incidence of cancer observed in schizophrenia patients may be related to differences in genetic background. It has been suggested that genetic predisposition towards schizophrenia is associated with reduced vulnerability to lung cancer, and p53 gene is one of the candidate genes. We tested the genetic association between schizophrenia and lung cancer by analyzing polymorphic sites in the p53 gene. Genotype and allele frequencies at two polymorphic sites in the p53 gene (BstUI and MspI restriction sites in exon 4 and intron 6, respectively) were studied in Korean schizophrenia (n=179) and lung cancer patients (n=104). Comparisons of the genotype and allele frequencies of the MspI polymorphism revealed significant differences between schizophrenia and lung cancer patients. The results suggest that the p53 polymorphism specifically found in schizophrenia patients may be associated with reduced vulnerability to lung cancer.

Adult↗
PubMed2004

Comparison of survival probabilities for living-unrelated versus cadaveric renal transplant recipients.

UNLABELLED: Any attempt to improve organ donation would be of benefit due to the growing shortage of cadaveric sources for transplantation. OBJECTIVE: We compared the graft survivals and possible predictive variables among renal transplant recipients with organs from living unrelated (LURD) versus cadaveric donors (CD). METHOD: Among 104 consecutive renal transplants performed from July 1992 to February 2003, 41 were from LURD and 24 from CD. Immunosuppressive regimens were based on cyclosporine and steroids with mycophenolate mofetil added after 1998. Patient and graft survivals were estimated using the Kaplan-Meier method and compared using log-rank tests. The significance level of predictive variables was analyzed with the Cox proportional hazard model. The follow-up period was 2 to 127 months (median 46 months). RESULTS: Eight recipients lost their grafts (six from LURD and two from CD) due to four chronic rejections, one acute rejection, one recurrence of primary disease, and one death with a functioning graft. The graft survival rates at 1, 3, 5, and 7 years were 97.6%, 91.9%, 88.5%, and 82.2% for LURD transplants versus 95.5%, 90.9%, 90.9%, and 90.9% for CD transplants, respectively (P > .05). Delayed graft function and donor age (>55 years old) were statistically significant predictors of graft survival among LURD transplants. Donor age (>55 years old) and multiple preoperative transfusion history were significant in CD transplants. CONCLUSION: LURD transplant survival was similar to that of CD transplants in our series. LURDs are an excellent source of organs to expand the donor pool.

Actuarial Analysis↗
PubMed2004

Risk factors on graft survival of living donor kidney transplantation.

UNLABELLED: Living donors have always been the basic resources of transplantation in our country, where cadaveric harvesting is still hampered for various reasons. OBJECTIVE: The aim of this study was to compare graft survival rates between living unrelated donor (LURD) and living related donor (LRD), to assess the potential risk factors for the graft survival, and to discuss the role of LURD. METHOD: From October 1991 to February 2003, 77 living donor renal transplants were performed: 41 were LURD and 36 were LRD transplants. The analyzed variables were donor relationship, recipient age and sex, donor age and sex, HLA-DR mismatching, nonspecific blood transfusion history of donor, acute rejection episodes, repeated rejection episode (more than 3 times), delayed graft function, recurred primary disease, and immunosuppressive regimen. Graft survival rate was assessed with the Kaplan-Meier method and the significance of possible variables with the Cox proportional hazard model. RESULTS: Eleven recipients lost their grafts (6 from LURD and 5 from LRD), most of them are due to chronic rejection (n = 7). Overall 3-, 5- and 10-year graft survival in live donors were 92.8%, 86.6%, and 76.9%, respectively. Graft survival at 3, 5, and 10 years being 91.9%, 88.5%, and 74.7% for the LURD versus 94%, 84%, and 78.8% for LRD transplants (P > .05). Acute rejection episodes, especially more than 3 times (risk ratio [RR] = 11.1) and preoperative multiple transfusion history (RR = 4.2) were significant factors on graft survival in our series. CONCLUSION: Acute rejection episodes markedly decreased the long-term graft survival in live donor renal transplants. The use of LURD transplants provides graft survival comparable with LRD transplants and proper management to acute rejection is essential for long-term graft survival.

Adult↗