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Biomedical subjects

K Park

Publications and source records attributed to K Park.

At least 145 records · Page 8Linked to original sources
PubMed2000

Epithelial differentiation in developing murine eustachian tube and middle ear.

Detailed information on how an epithelial differentiation occurred in the developing eustachian tube and middle ear would be helpful in understanding both normal physiology and pathology of the tubotympanum. This study was undertaken to establish patterns of laminin and E-cadherin in the embryonic mouse eustachian tube and middle ear by use of immunohistochemistry at a stage when epithelial differentiation is taking place. This study was also designed to clarify the role of the middle ear mesenchyme. During the development of the eustachian tube, relatively high immunoreactivity to laminin was observed in the epithelium at gestational days 16 and 17, when the developments of ciliated and secretory cells were first observed. At the time of birth, in contrast to epithelium of the eustachian tube, epithelium of the middle ear cavity showed predominant expression of laminin and E-cadherin. These findings suggest that the expressions of laminin and E-cadherin may be correlated with maturation of the epithelium in the eustachian tube and middle ear and that the epithelial differentiation of the developing murine eustachian tube and middle ear may be controlled by epithelial-mesenchymal interaction and cell-to-cell interaction.

Animals↗
PubMed2000

Seasonal biochemical plasticity of a flight muscle in a bat, Murina leucogaster.

Cellular and biochemical responses of the pectoral muscle to variation in seasonal activity were studied in the bat, Murina leucogaster ognevi. We collected bats in mid-hibernation (February), end-hibernation (April), and mid-summer (August) to track major activity periods in their annual cycle. Our findings indicated that myofiber cross-sectional area decreased to 68% between mid- and end-hibernation, but returned to the winter level in mid-summer. Total soluble protein and total RNA concentrations were not altered over these sampling periods. Oxidative potential gauged by citrate synthase activity increased 1.47-fold from mid- to end-hibernation and then remained at the similar level in mid-summer. Glycolytic potential gauged by lactate dehydrogenase activity changed little between mid- and end-hibernation but increased 1.42-fold in summer, compared with the winter level. Thus, the myofibers underwent disuse atrophy during hibernation, while enzymatic catalytic function recovered towards the level of mid-summer.

Adenosine Triphosphatases↗
PubMed2000

Nickel-catalyzed cross-coupling of bromophenols with Grignard reagents in the solid phase synthesis.

Polymer-bound substituted bromophenols were found to readily undergo a Ni(0)-catalyzed cross-coupling reaction with Grignard reagents to give a variety of substituted phenols and hydroquinones, after cleavage from the support, in moderate to high yields. The requisite bromophenol derivatives, which were prepared from the corresponding phenols and hydroquinone using BTMA Br3 or TBA Br3, were attached to the solid support by the Mitsunobu reaction.

Biochemistry↗
PubMed2000

Atherosclerosis-induced chronic arterial insufficiency causes clitoral cavernosal fibrosis in the rabbit.

In our previous studies we found that aging-associated fibrosis of clitoral cavernosal tissue correlated with the prevalence of cardiovascular disease in elderly women. The aim of this study was to determine specifically, arterial insufficiency-related structural changes of clitoral cavernosal tissue in a rabbit model. New Zealand white female rabbits were divided into clitoral cavernosal ischemia (CCI, n = 5) and control (n = 5) groups. The CCI group underwent balloon endothelial injury of the iliac arteries and received 0.5% cholesterol diet. The control group received a regular diet. After 16 weeks, arteriography was performed then the animals were sacrificed. The iliac arteries and the entire clitoris were removed. Cross-sections of the iliac arteries and clitoris were processed for histologic evaluation The percentage of smooth muscle and connective tissue in trichrome stained sections of clitoral cavernosal tissue was determined by computer-assisted histomorphometry. Arteriography revealed diffused occlusive disease in the common iliac, internal iliac and pudendal arteries in the CCI group. Histology showed that arterial occlusive disease spreads from the site of balloon injury to the smaller branches involving the clitoral cavernosal arteries. Diffuse fibrosis was observed in the clitoral cross-sections of the CCI group. The percentage of clitoral cavernosal smooth muscle (mean +/- standard error) in the CCI group (53% +/- 0.9%) was significantly decreased compared with the control group (62% +/- 0.8%) (P = 0.0001). Chronic clitoral cavernosal ischemia causes significant fibrosis and loss of smooth muscle in the clitoral cavernosal tissue. These findings suggest that chronic clitoral cavernosal arterial insufficiency may play a role in the pathophysiology of female sexual arousal disorders.

Angiography↗
PubMed2000

Systemic administration of apomorphine improves the hemodynamic mechanism of clitoral and vaginal engorgement in the rabbit.

Clitoral and vaginal engorgement during sexual stimulation depend in part on the increase of arterial inflow. It has been shown that apomorphine (APO), a non-selective dopamine receptor agonist, produces penile erection by activating dopaminergic receptors in the central nervous system. Our aim was to study whether systemic administration of APO improves the hemodynamic mechanism of clitoral and vaginal engorgement in the rabbit. Female New Zealand white rabbits (3.5-4 kg, n=6) were anesthetized. To examine sexual arousal function, the vaginal/clitoral branch of the pelvic nerve was stimulated electrically and maximal increases in clitoral intracavernosal and vaginal wall blood flows and pressures were recorded. After this APO was injected intravenously in a dose-response manner (0.05, 0.1, 0.2, 0.3 and 0.4 mg/kg) and nerve stimulation was performed after each dose. Changes in nerve-stimulated increase of clitoral intracavernosal and vaginal blood flows and pressures after APO was compared to those recorded before APO. Electrical stimulation of the vaginal/clitoral branch of the pelvic nerve significantly increased clitoral intracavernosal and vaginal wall blood flows in the rabbit. Intravenous administration of APO caused concentration dependent increase in nerve stimulation-induced peak clitoral intracavernosal and vaginal wall blood flows reaching to statistically significant at the concentration of 0.1 and 0.2 mg/kg. Inravenous administration of APO greater than 0.2 mg/kg (0.3 and 0.4 mg/kg) were less effective or produced adverse effects on clitoral intracavernosal and vaginal wall blood flows. Intravenous APO also tended to increase nerve-stimulated increase of clitoral intracavernosal and vaginal wall pressures, but the effect was not statistically significant. In conclusion, our studies suggest that systemic administration of APO may improve clitoral and vaginal engorgement by increasing clitoral intracavernosal and vaginal wall arterial inflow.

Animals↗
PubMed2000

Association between hepatitis B virus infection and HLA-DR type in Korea.

Although the mechanism of susceptibility to chronic persistent hepatitis B virus (HBV) infection is not well clarified, immunogenetic factors of the host may have a role. Recently, a strong association between HLA-DR13 and the self-limited course of HBV infection has been reported. To determine whether the elimination of HBV is related to a particular HLA allele, we studied the HBV markers and HLA-DR phenotypes of 1,272 Koreans who had visited Yonsei University Medical Center for renal transplantation. They included 330 renal transplant donors. Subjects were categorized into 3 different groups: the "Unexposed Group" (UE; n = 946) with negative HBV markers, the "Chronic Carrier Group" (CC; n = 83), who were hepatitis B surface antigen (HBsAg)-positive, and the "Spontaneously Cleared Group" (SC; n = 243), who were HBsAg-negative with antibodies to HBsAg (anti-HBs) and hepatitis B core antigen (anti-HBc). HLA-DR4 was the most common type in all groups. HLA-DR6 was significantly more frequent in 69 of 243 subjects with SC (28. 4%) than in 8 of 83 subjects with CC (9.6%) (P <.001; relative risk [RR] = 3.72). HLA-DR9 was significantly more frequent in CC than in SC (P <.001; RR = 0.33). HLA-DR13 showed a stronger association with the clearance of HBV than the other HLA-DR6 subgroup. The distribution of HLA-DR phenotypes was similar regardless of renal disease. Our data indicate that HLA-DR6, especially HLA-DR13, is one of the host factors, which influences the immune response to HBV, and may be associated with self-elimination of HBV in Koreans.

Adult↗
PubMed2000

Race and sex influence clearance of nifedipine: results of a population study.

OBJECTIVE: To estimate oral clearance of nifedipine and to determine demographic and clinical covariates that affect nifedipine clearance in a clinical population. METHODS: Apparent oral clearance of nifedipine and protein binding were measured in 226 patients receiving sustained-release nifedipine formulations for hypertension and coronary artery disease (black men, n = 111; black women, n = 27; white men, n = 64; white women, n = 24). Mean age +/- SD was 71 +/- 11 years, and mean weight was 86 +/- 17 kg. Nifedipine concentrations were analyzed by HPLC, protein binding was measured by equilibrium dialysis, clearance and covariate effects were estimated by a nonlinear mixed effects population model, and statistical analyses were performed by a nonlinear mixed-effects model (clearance) and ANOVA (protein binding). RESULTS: Clearance was significantly slower in black subjects (8.9 +/- 0.7 mL/min/kg; mean +/- SE) compared with white subjects (11.6 +/- 0.8 mL/min/kg; P = .00004) and in men compared with women (9.3 +/- 0.6 versus 12.1 +/- 1.5 mL/min/kg; P = .0021). Reported alcohol use (alcohol, 8.6 +/- 1.1 versus no alcohol, 10.8 +/- 0.6 mL/min/kg; P = .0002) and smoking status (smoker, 8.8 +/- 2.0 versus nonsmoker, 10.2 +/- 0.6 mL/min/kg; P = .0362) also affected nifedipine clearance. Race and sex had no effect on protein binding of nifedipine (P = .29 and P = .44, respectively). No effects of age, stable coronary artery disease, or reported intake of beta-blockers on nifedipine clearance were detected in this primarily elderly population with hypertension. CONCLUSIONS: The data suggest that race, sex, and environmental factors are identifiable sources of interindividual variation in the oral clearance of nifedipine, a CYP3A substrate. Our experience also suggests that data from clinical populations may be biased with regard to age, sex, and formulation selection, and covariates may not be independently distributed, which can limit analyses.

Aged↗
PubMed2000

Laparoscopic nephrectomy for nonfunctioning tuberculous kidney.

BACKGROUND AND PURPOSE: Although laparoscopic nephrectomy for benign renal disease has been widely accepted, use of the operation for tubercular pyelonephritic kidney is relatively contraindicated because of difficulties in dissecting the dense fibrotic adhesions and the risk of spillage of caseous materials with subsequent dissemination of the disease. However, with the accumulation of experience, laparoscopic surgery is expanding its applications. In this study, we tried to evaluate the efficacy and safety of the laparoscopic nephrectomy for renal tuberculosis. PATIENTS AND METHODS: At three centers, 13 laparoscopic nephrectomies were performed between April 1996 and March 1999. The patients consisted of eight men and five women with a mean age of 44.8 years (range 37-51 years). All patients had known renal tuberculosis with a nonfunctioning kidney and underwent nephrectomy after at least 3 months of chemotherapy with four antituberculous drugs. Nine patients underwent the transperitoneal approach and four patients, the retroperitoneal approach. The follow-up was from 2 to 35 months with a mean of 15.8 months. RESULTS: Kidneys were removed laparoscopically in 12 patients (92%). The mean operative time was 268 minutes (range 190-500 minutes), and the mean estimated blood loss was 227 mL. Although there had been some difficulties releasing the adhesions, no significant intraoperative and postoperative complications were observed. Conversion to open surgery was needed in only one patient. The mean hospital stay was 4 days, and the patients returned to normal activity within 10 days. Neither local recurrence nor distant dissemination of the disease was observed during the follow-up period. CONCLUSION: Laparoscopic nephrectomy for renal tuberculosis was safe and effective with minor complications. Therefore, tuberculosis should not be a contraindication to a laparoscopic approach.

Adult↗
PubMed2000

A phase II study of VP-16-fosfamide-cisplatin combination chemotherapy plus early concurrent thoracic irradiation for previously untreated limited small cell lung cancer.

BACKGROUND: At present the addition of thoracic irradiation to combination chemotherapy is a standard treatment for limited staged small cell lung cancer. However, there is still controversy about the optimum timing of chest irradiation. We conducted a phase II study of etoposide (VP-16)-ifosfamide-cisplatin (VIP) combination chemotherapy plus early concurrent thoracic irradiation for the patients with previously untreated limited small cell lung cancer in order to assess if the treatment modality could improve the response rate and the toxicity. METHODS: Forty-four patients with limited small cell lung cancer were treated with etoposide-ifosfamide-cisplatin and concurrent thoracic irradiation. Combination chemotherapy consisted of etoposide 100 mg/m2 (on days 1-3), ifosfamide 1000 mg/m2 (on days 1 and 2) and cisplatin 100 mg/m2 (on day 1). Concurrent thoracic irradiation consisted of a total of 4000 cGy over 4 weeks starting on the first day of the first chemotherapy. All patients who showed a complete response were given prophylactic cranial irradiation for 2.5 weeks. RESULTS: Forty-four of the 49 patients who entered the study from May 1994 to August 1998 were evaluable. The median age was 59 years and 40 patients had a performance status of 0 or 1. The median survival time was 22.5 months. Twenty-eight patients (62%) showed a complete response and 16 (38%) a partial response. Twenty-four patients (54%) developed grade 3 or 4 neutropenia; there was a 9% RTOG score 3 or 4 esophagitis. CONCLUSION: VIP combination chemotherapy and early concurrent thoracic irradiation for patients with limited stage small cell lung cancer revealed excellent antitumor response with tolerable toxicity.

Adult↗
PubMed2000

Connexin26 mutations associated with nonsyndromic hearing loss.

OBJECTIVE: Mutations in the GJB2 gene are a major cause of autosomal recessive and sporadic types of congenital deafness. The 35delG mutation is the most frequent type of mutation in white populations. However, several other forms were reported, such as 167delT among Ashkenazi Jews and R143W in Africans. The present study investigated the mutations of connexin26 (Cx26) found in patients with nonsyndromic hearing loss (NSHL) and newborns in the Korean population. STUDY DESIGN: The sequencing data for 147 unrelated patients with congenital NSHL and 100 audiologically screened newborns were included in this prospective study. METHODS: Genomic DNA samples from all patients and newborns were sequenced in both directions for detection of Cx26 mutations. RESULTS: Thirteen different types of mutations were found in the patients and newborns. V27I and E114G are the popular types of polymorphic mutations in both groups. 235delC-deletion and frameshift--was detected in patients (15 in 294 alleles) and newborns (1 in 200 alleles). 35delG was rarely found in both group. In addition to above mutations, several types of mutations--S85P, K41R, S72C, V84A, 176-191del, and 299-300del-were identified. The family study of the 235delC showed a typical autosomal recessive trait of NSHL in their audiological evaluation of hearing threshold. CONCLUSION: The frequency of 235delC allele showed much higher in the patients (5%) than in newborns (0.5%). We rarely found 35delC mutant in both groups. These results suggest that the different types of Cx26 mutations affect autosomal recessive NSHL according to ethnic background.

Adult↗
PubMed2000

Self-organized growth model for the quenched herring-mullin equation

We introduce a simple self-organized growth model mimicking the dynamics of a driven tensionless interface in a random medium near the depinning threshold. The roughness and growth exponents for the model are obtained as zeta approximately 1.93 and beta approximately 0.96, respectively. We discuss the possible continuum equation describing the motion of a driven interface in our model.

Journal Article↗
PubMed2000

Renormalization group analysis of the anisotropic nonlocal kardar-parisi-zhang equation with spatially correlated noise

We study an anisotropic nonlocal Kardar-Parisi-Zhang (KPZ) equation with spatially correlated noise by using the dynamic renormalization group method. When the signs of nonlinear terms in parallel and perpendicular directions are opposite, the correlated noise coupled with the long ranged nature of interaction produces a stable non-KPZ fixed point for d<d(c). For the uncorrelated noise, the roughness and dynamic exponents associated with the stable fixed point are different from those of the isotropic nonlocal KPZ equation, while for the correlated noise the exponents are the same as those of the isotropic case.

Journal Article↗
PubMed2000

Phase transitions in a simple growth model for a driven interface in random media

We introduce a simple growth model for a driven interface in random media, exhibiting a smoothing (roughening) transition as well as a pinning-depinning transition in a nonequilibrium (1+1)-dimensional system. At both transition points, the scaling exponents belong to the directed percolation universality class. The rough interface at the pinning-depinning transition point belongs to the quenched Kardar-Parisi-Zhang universality class. The two transitions are second order phase transitions. We also introduce a modified growth model exhibiting the pinning-depinning transition. In the modified model, the pinning-depinning transition is a first order phase transition in the directed percolation universality class.

Journal Article↗
PubMed2000

Growth of a driven interface in isotropic and anisotropic random media

We introduce a simple stochastic model for a driven interface in a random medium, in which we can control the degree of the anisotropy of a random medium. When there is no anisotropy of a random medium, the motion of a growing interface in our model can be well described by the quenched Edwards-Wilkinson equation. When there is anisotropy of a random medium, however, the motion of a growing interface can be described by the quenched Kardar-Parisi-Zhang (KPZ) equation. In the two interfaces, apart from one growing in an isotropic medium and the other growing in an anisotropic medium, the growth rule of our model is the same. Our results support the fact that the anisotropy of a random medium is a source of the KPZ nonlinearity.

Journal Article↗
PubMed2000

Behavioral responses to repeated cocaine exposure in mice selectively bred for differential sensitivity to pentobarbital.

Mice from the 20th generation of three lines divergently selected for response to pentobarbital-induced sedation times [long-sedation time (LST), short sedation time (SST), and randomly bred control (RBC)] were used to study cocaine-induced behavioral sensitization. These lines showed variable degrees of locomotor activities in response to cocaine. At a low cocaine dose and long withdrawal period (10 mg/kg, twice a day for 5 days followed by a 14-day withdrawal), the LST mice showed tolerance development. In response to cocaine, the locomotor activities of the SST were not significantly different from the RBC group. At a higher dose and a shorter withdrawal period (20 mg/kg, daily for 7 days followed by a 3-day withdrawal), the SST mice showed behavioral sensitization similar to the RBC mice, but the LST mice did not develop sensitization. The different responses in locomotor activity induced by cocaine suggest that genetic factors may play a role in determining the magnitude of response to this drug. Dopamine (DA) levels did not differ significantly in either striatum (STR) or nucleus accumbens (NAC) for the cocaine-treated animals to their corresponding saline-treated controls. The affinity (Kd) of D2 in the NAC decreased significantly, without changes in density (Bmax), in the cocaine-treated SST and RBC mice. On the other hand, the density of D2 binding sites in the SST and the RBC mice in the STR was significantly increased in cocaine-treated groups without change in Kd. The LST mice did not show any changes in the Kd and Bmax in either the STR or the NAC. Taken together, these findings suggest that the changes in the Kd of D2 in the NAC and the Bmax of D2 in the STR may contribute to the differences in locomotor responses to cocaine exposure in these mouse lines.

Analysis of Variance↗
PubMed2000

The interaction of bacteriophage P2 B protein with Escherichia coli DnaB helicase.

Bacteriophage P2 requires several host proteins for lytic replication, including helicase DnaB but not the helicase loader, DnaC. Some genetic studies have suggested that the loading is done by a phage-encoded protein, P2 B. However, a P2 minichromosome containing only the P2 initiator gene A and a marker gene can be established as a plasmid without requiring the P2 B gene. Here we demonstrate that P2 B associates with DnaB. This was done by using the yeast two-hybrid system in vivo and was confirmed in vitro, where (35)S-labeled P2 B bound specifically to DnaB adsorbed to Q Sepharose beads and monoclonal antibodies directed against the His-tagged P2 B protein were shown to coprecipitate the DnaB protein. Finally, P2 B was shown to stabilize the opening of a reporter origin, a reaction that is facilitated by the inactivation of DnaB. In this respect, P2 B was comparable to lambda P protein, which is known to be capable of binding and inactivating the helicase while acting as a helicase loader. Even though P2 B has little similarity to other known or predicted helicase loaders, we suggest that P2 B is required for efficient loading of DnaB and that this role, although dispensable for P2 plasmid replication, becomes essential for P2 lytic replication.

Amino Acid Sequence↗
PubMed2000

Immunogenicity of antigens in boiled alginate microspheres.

Vaccine efficacy can be enhanced by delivery of antigens in synthetic microspheres. The process of antigen incorporation into microspheres can expose fragile antigens to damaging conditions, such as high temperatures, and to bacterial contamination. Maintenance of immunogenicity of several antigens and reduction of bacterial load in alginate microspheres following boiling was evaluated. Mice were immunized subcutaneously, initially and again 21 days later, with either non-boiled or boiled microspheres containing ovalbumin (OVA), a culture supernatant vaccine of Pasteurella haemolytica (PHV), or a potassium thiocyanate extract of P. multocida (PTE). Serum samples were obtained prior to immunization and at the time of euthanasia 28 days later. Culture of microspheres showed that boiling completely eliminated aerobic bacterial growth for OVA-containing microspheres, and reduced growth by a factor of 10(4) for PTE microspheres. More bacteria were cultured after boiling than before for PHV microspheres. ELISA performed on serum and intestinal lamina propria explant supernatants showed that immunogenicity of PHV microspheres was not altered by boiling. Boiled OVA microspheres were still able to stimulate a significant serum IgG anti-OVA titer in mice, but boiled PTE microspheres completely lacked immunogenicity. Elispot assays of spleens showed that only PHV microspheres were able to retain immunogenicity after boiling. Results indicate that boiling is not an effective means for reducing the bacterial load of alginate microspheres and that the process is associated with a diminution of vaccine immunogenicity.

Alginates↗