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Biomedical subjects

K Park

Publications and source records attributed to K Park.

At least 109 records · Page 6Linked to original sources
PubMed2001

A new potential of blood oxygenation level dependent (BOLD) functional MRI for evaluating cerebral centers of penile erection.

It is well known that penile erection is dependent on commands from the central nervous system. However, there has been little research on the central control of penile erection. The aim of this study was to evaluate, for the first time, the cerebral centers of penile erection using BOLD-functional MRI. Functional magnetic resonance imaging (fMRI) on a 1.5T MR scanner was performed in 12 sexually potent male volunteers (mean age: 23) and two hypogonadal impotent patients. In this study, blood oxygenation level dependent (BOLD) technique was utilized to create fMRI reflecting local brain activities. Real-time visual stimulation was performed with an alternatively combined erotic and non-erotic film to identify and quantify the activated brain regions associated with sexual response. Subjective sexual arousal and penile erection responses were assessed using 5-point scales ranging from 1 (no change) to 5 (maximal increase). In normal volunteers, the mean scores on subjective sexual arousal and penile erection by sexual stimulation with erotic film were 3.0 and 3.3 respectively, whereas there were no changes by non-erotic stimulation. During the visual stimulation the occipital cortex was activated by either an erotic or non-erotic film, the erotic film gave 150-200% stronger activation. However, more than seven of the 12 healthy subjects were significantly activated in the areas of inferior frontal lobe, cingulate gyrus, insula gyrus, corpus callosum, thalamus, caudate nucleus, globus pallidus, and inferior temporal lobe by erotic stimulation. In the hypogonadal patients, brain activation in response to the erotic film decreased compared to normal volunteers, however, it was restored by testosterone supplementation. These results are the first demonstration to show the functional neuroanatomy of the brain associated with sexual arousal by visual sexual stimulation using BOLD-based fMRI. Further studies are needed to verify that fMRI provides an important new tool in evaluating the cerebral center of the penile erection.

Adult↗
PubMed2001

Decreased circulating levels of estrogen alter vaginal and clitoral blood flow and structure in the rabbit.

Aging and menopause related decline in circulating levels of estrogen has been shown to adversely affect female sexual arousal function. Our aim was to study the effects of circulating levels of estrogen on the hemodynamic mechanism of vaginal and clitoral engorgement and on the structure of the vaginal and clitoral cavernosal tissue in the rabbit. New Zealand White female rabbits (3.5-4 kg) were randomly divided into three groups with five rabbits in each group: control; bilateral oophorectomy; bilateral oophorectomy undergoing subcutaneous injection of estrogen (40 microg/kg/day). After 6 weeks, the serum levels of 17 beta-estradiol were measured and systemic blood pressure was monitored. Vaginal and clitoral cavernosal blood flows were measured with laser Doppler flowmeter before and after pelvic nerve stimulation. Cross sections of the clitoris and vagina were processed for histologic examination and histomorphometric image analysis. Serum level of 17 beta-estradiol (pg/ml; mean+/-s.d.) revealed a significant decrease in the oophorectomy group (25.4+/-5.1) compared with the control (38.5+/-7.6) and estrogen replacement (115.9+/-57.3) groups (P<0.05). Nerve stimulation-induced peak vaginal and clitoral intracavernosal blood flows in the oophorectomy group (28.9+/-16.3 and 6.1+/-1.4, respectively) were significantly less than those recorded in the control (48.9+/-6.5 and 11.0+/-2.4, respectively) or estrogen replacement (48.7+/-12.2 and 10.1+/-2.8, respectively) group (P<0.05). In histology, marked thinning of the vaginal epithelial layers, decreased vaginal submucosal microvasculature, and diffuse clitoral cavernosal fibrosis were evident in the oophorectomy group but not in the estrogen supplement and control groups. In histomorphometry, the percentage of clitoral cavernosal smooth muscle in the oophorectomy group (49.6+/-6.2) was significantly decreased compared with the control (56.8+/-2.6) and estrogen replacement (58+/-3.0) groups (P<0.05). Our studies show that decline in circulating levels of estrogen impairs the hemodynamic mechanism of vaginal and clitoral engorgement and leads to histopathologic changes in the vagina and clitoral cavernosal tissue. These observations suggest that decreased circulating levels of estrogen, a physiologic change in the menopausal state, may play a role in the development of female sexual arousal dysfunction.

Animals↗
PubMed2001

Searching the Porphyromonas gingivalis genome with peptide fragmentation mass spectra.

An approach is described for genomic database searching based on experimentally observed proteolytic fragments, e.g., isolated from 1D or 2D gels or analyzed directly, that can be applied to unfinished prokaryotic genomic data in the absence of annotations or previously assigned open reading frames (ORFs). This variation on the database search is in contrast to the more familiar use of peptide mass spectral fragmentation data to search fully annotated inferred protein databases, e.g., OWL or SWISS-PROT. We compared the SEQUEST search results from a six reading frame translation of the Porphyromonas gingivalis genome DNA sequence with those from computationally derived ORFs created using publicly available genomics software tools. The ORF approach eliminated many of the artifacts present in output from the six reading frame search. The method was applied to uninterpreted tandem mass spectrometric data derived from proteins secreted by the periodontal pathogen Porphyromonas gingivalis in response to the gingival epithelial cell environment, a model system for the study of host-pathogen interactions relevant to human periodontal disease.

Bacterial Proteins↗
PubMed2001

Surgical tactics and outcome of treatment in jugular foramen schwannomas.

Seven patients with schwannomas of the jugular foramen were included our study in Samsung Medical Center between 1995 and 1999. Patients with neurofibromatosis were excluded. The records of the seven patients (six surgical case and one nonsurgical case) were retrospectively reviewed. There were six women and one man (mean age, 47 years) with a symptom duration ranging from 3 months to 14 years (mean, 47 months). The predominant symptoms were hearing difficulty, hemifacial spasm and hoarseness. Preoperative audiologic evaluation, computerised tomography (CT), magnetic resonance (MR) imaging, and angiography were performed in most patients. We classified tumours into four types using Kaye and Pellet classification on the basis of radiological and surgical findings. The tumours were: Type A (at cerebellopontine angle) in one; Type B (foraminal) in two; Type C (extracranial and/or foraminal) in two; and Type D (intra- and extracranial) in two cases. We used various surgical approaches such as retrosigmoid suboccipital craniectomy for Type A tumours, infratemporal fossa type A approach (ITFA) for Type C tumours, petro-occipital transsigmoid approach or modified transcochear approach for Type D tumours and ITFA with partial labyrinthectomy for Type B. In the selection of surgical approaches, we took consideration of tumour extension, tumour size, and preoperative hearing function. Facial nerve transposition was not used only in one case of ITFA because of small tumour size (1.5cm). Gross total removal was achieved in five cases, and subtotal removal in one case (Type D tumour) with a single-stage operation. Stereotactic radiosurgery was performed on residual mass in the subtotally removed case. Follow-up period ranged from 13 to 49 months (mean, 27.5 months). There was neither postoperative mortality nor recurrence on follow-up MR imaging. There were two cases of temporary facial nerve palsy and one aggravation of pre-existing low cranial palsy. Two case of sustained vocal cord palsy underwent thyroplasty, but there was no aspiration pneumonia. Persistent cerebrospinal fluid collection was improved with lumboperitoneal shunt. The surgical approaches of each case should be tailored according to their shape and the clinical manifestation. We obtain acceptable outcomes from one-stage operation.

Accessory Nerve↗
PubMed2001

Preoperative concurrent chemoradiotherapy for stage IIIA non-small cell lung cancer.

Thirty-one patients with stage IIIA non-small cell lung cancer (NSCLC) were treated with preoperative concurrent chemoradiotherapy (CCRT) followed by surgery. The treatment protocol could not be completed in eight patients. The acute hematologic toxicities of grade III or IV occurred in 48.4%, (15/31) after the first chemotherapy cycle, and in 39.1% (9/23) after the second cycle. The most common non-hematologic toxicity was radiation esophagitis. Surgery was attempted in 23 patients and successful in 22 patients (resection rate = 71.0%. Pathologic complete response and down-staging were achieved in 13.6% (3/22) and 68.2% (15/22). The median survival period, 2-year overall survival, local control and disease-free survival rates of all 31 patients and of 22 patients who underwent surgery were 19 months, 37.2%, 49.1%, 35.5%, and 19 months, 43.2%, 51.8%, 25.6%, respectively. On the basis of our observations, preoperative CCRT followed by surgery for stage IIIA NSCLC has resulted in outcomes comparable with those in previous reports.

Adult↗
PubMed2001

Large-scale early in vitro response to actinobacillus actinomycetemcomitans suggests superantigenic activation of T-cells.

The mode of T-cell response to Actinobacillus actinomycetemcomitans is largely unknown. The present study sought to investigate the hypothesis that A. actinomycetemcomitans expresses superantigens, capable of antigen-non-specific T-cell activation. To that end, peripheral blood mononuclear cells were stimulated with A. actinomycetemcomitans, and T-cell expression of the early activation marker, CD69, was determined by flow cytometry. Results showed that A. actinomycetemcomitans activated a large number of T-cells with magnitude similar to that of staphylococcal enterotoxin superantigens. A. actinomycetemcomitans sonicate preferentially activated T-cells expressing Vbeta5.1 and Vbeta8, while the extracellular preparation activated Vbeta5.1+, Vbeta8+, and Vbeta12+ T-cells. T-cell response to A. actinomycetemcomitans was observed in the presence of autologous, as well as heterologous, antigen-presenting cells, suggesting a MHC-non-restricted response. Thus, the in vitro response to A. actinomycetemcomitans is characterized by large-scale T-cell activation in a Vbeta-specific and MHC-non-restricted manner, consistent with the involvement of superantigens.

Aggregatibacter actinomycetemcomitans↗
PubMed2001

Differential roles for signal transducers and activators of transcription 5a and 5b in PRL stimulation of ERalpha and ERbeta transcription.

PRL has been shown to stimulate mRNA expression of both ERalpha and ERbeta in the rat corpus luteum and decidua of pregnancy. To investigate whether PRL may stimulate ER expression at the level of transcription and which transcription factors may mediate this stimulation, we have cloned the 5'-flanking regions of both rat ER genes. A constitutively active PRL receptor (PRL-R(CA)) stimulated both ERalpha and ERbeta promoter activity, indicating that PRL is acting to stimulate ER transcription. Putative signal transducer and activator of transcription (Stat)5 response elements were identified at -189 in the ERalpha promoter and at -330 in the ERbeta promoter. Mutation of these response elements or overexpression of dominant negative Stat5 prevented stimulation of ERalpha and ERbeta promoter activity, indicating that PRL regulation of ER expression requires both intact Stat5 binding sites as well as functional Stat5. Interestingly, either Stat5a or Stat5b could stimulate ERalpha transcription while stimulation of ERbeta occurred only in the presence of Stat5b. Through mutational analysis, a single nucleotide difference between the ERalpha and ERbeta Stat5 response elements was shown to be responsible for the lack of Stat5a-mediated stimulation of ERbeta. These findings indicate that PRL stimulation of ER expression occurs at the level of transcription and that PRL regulation of ERalpha can be mediated by either Stat5a or Stat5b, while regulation of ERbeta appears to be mediated only by Stat5b.

Animals↗
PubMed2001

Increased burst firing in substantia nigra pars reticulata neurons and enhanced response to selective D2 agonist in hemiparkinsonian rats after repeated administration of apomorphine.

Intermittent administrations of dopaminergic agents in hemiparkinsonian rat enhances the behavioral response to subsequent administration of the drugs. This phenomenon is known as "priming" and thought as comparable to drug-induced dyskinesia in patients with Parkinson's disease. We investigated the behavioral and electrophysiological changes in 6-hydroxydopamine (6-OHDA)-lesioned hemiparkinsonian rats after repeated administrations of apomorphine. Administration of apomorphine (0.32 mg/kg, intraperitoneal, i.p.) twice daily for 6 days enhanced the rotation induced by apomorphine from 341 turns/hour at the beginning to 755 turns/hr at the end. At the same time, the response to selective D2 agonist quinpirole (0.26 mg/kg, i.p.) was also enhanced from 203 to 555 turns/hr. Extracellular single unit recording revealed no significant difference in the basal firing rates of substantia nigra pars reticulata (SNr) neurons between the ipsilateral and contralateral side of the 6-OHDA lesion regardless of the repeated administrations of apomorphine. In SNr of the lesion side, the units with burst firing pattern were found more frequently after repeated administrations of apomorphine and the suppressive effect of quinpirole on the firing rate was enhanced. These findings suggest that the increased percentage of the burst units is the important electrophysiological change in the development of enhanced response to selective D2 agonist.

Animals↗
PubMed2001

Long-term outcome of kidney transplantation in adult recipients with focal segmental glomerulosclerosis.

Focal segmental glomerulosclerosis (FSGS) is an important cause of nephrotic syndrome and end-stage renal disease. FSGS recurrence after renal transplantation has a potentially detrimental course leading to the loss of renal function. In order to establish FSGS recurrence rates and evaluate the course of the disease on living-related-donor renal transplantation in ethnic Korean adults (> or = 18 years), we reviewed our experiences of 27 kidney transplantations with FSGS over the last 15 years. Of the 27 renal allografts, 13 were found to have recurrent FSGS by graft biopsy. In comparison with background data upon patients with and without recurrence of FSGS, the donor age of patients with recurrent FSGS was significantly higher than that of those without recurrence (median, 39 years vs 26, p < 0.05). In terms of, age at transplantation, length of dialysis period, and mode of dialysis no differences were found between recurrent and nonrecurrent cases. The graft survival rate of recipients from a kidney donor of age less than 40 years was significantly higher than that of recipients from a kidney donor of age more than 40 years, at 5 and 10 years, respectively (87% vs 33%, 41% vs 0%, p < 0.05). The association between clinical variables and recurrence was assessed by multiple logistic regression analysis, and donor age was found to be a risk factor of FSGS recurrence (p<0.05). Variables such as HLA-mismatch numbers and immunosuppression were not found to be associated. In conclusion, the recurrence rate of FSGS in adult recipients with FSGS was 48% and patients that received kidney from an older donor appear to be at higher risk of developing recurrence. The use of a renal graft from a younger donor is considered advisable for adult recipients with FSGS.

Adult↗
PubMed2001

Granzyme B and TIA-1 expression in chronic and acute on chronic renal allograft rejection.

Although active inflammation may be deleterious and indicate immunologic activation in chronically rejected grafts, the underlying mechanism of tissue destruction has been little studied. Twenty-four cases of chronic rejection (CR) with or without acute rejection (AR) were stained with antibodies against CD3, CD8, CD68, granzyme B and TIA-1, and the number of positive cells were counted. Eleven cases of AR served as controls. The number of CD3 and CD8 positive cells increased in the acute on CR group compared to the CR group. About a half of CD3 positive T cells were CD8 positive in both groups, however, the proportion of TIA-1 or granzyme B positive cells was higher in the acute on CR group. The numbers of CD3, CD68, granzyme B and TIA-1 positive cells were higher in the AR group than the acute on CR group, however, no significant difference was found between the two groups. Serum creatinine level and proteinuria at the time of biopsy and the percentages of late onset AR and graft failure rate were higher in the acute on CR group than the CR group. Summarizing, these results suggest that infiltration of activated T cells containing cytotoxic granules plays a role in graft destruction in acute on CR.

Adult↗
PubMed2001

Experimental and modeling evaluation of upward and downward velocities in the coaxial flotation column.

This study was conducted to show the influence of upward velocity in the inner column and downward velocity in the outer column of the coaxial cylinder-type flotation column on the solids removal efficiency, solids concentration in the treated water, and so on. The SIMPLE (Semi-Implicit Method for Pressure Linked Equation) solution was applied to the coaxial flotation column to simulate the velocity vectors of the elements of water flowing in the column. The effects of solids loading and residence time in the agglomerate separation zone on the solids removal efficiency were also tested. In the pilot scale coaxial DAF column experiments with solids concentration of 1,000-2,000 mg of SS per liter and solids loading less than 350 kg/m2/day, approximately 90% of the solids removal efficiencies were obtained using the upward velocity of up to 110 cm/min in the contact zone of the inner column and the downward velocity of up to 30 cm/min in the outer column. In the simulation, similar results were observed as in the experiments. The solids loading in the excess of 350 kg/m2/day caused the instability of the sludge float layer and aggravated the quality of the treated water.

Air↗
PubMed2001

Expression of phospholipase C-gamma1 in experimental cholesteatoma using Mongolian gerbils.

Phospholipase C (PLC)-gamma1 is known to play a central role in ligand-mediated signal transduction for cell proliferation. The purpose of this study was to elucidate the distribution of PLC-gamma1 in deep meatal skin, retroauricular skin and cholesteatoma matrix of experimental animals. We induced canal ligation cholesteatoma using Mongolian gerbils and investigated the expression of PLC-gamma1 in this model by using Western blot analysis and immunohistochemistry. By Western blot analysis, considerably higher levels of PLC-gamma1 protein were detectable in experimental cholesteatoma. On immunohistochemistry, experimental cholesteatoma showed more intense immunolabeling of PLC-gamma1 protein than deep meatal skin and retroauricular skin. In conclusion, overexpression of PLC-gamma1 may in part contribute to abnormal proliferation and differentiation of experimental cholesteatoma in Mongolian gerbils.

Animals↗
PubMed2000

Chemotherapeutic drug, adriamycin, restores the function of p53 protein in hepatitis B virus X (HBx) protein-expressing liver cells.

Hepatitis B virus X (HBx) protein implicated in the development of liver cancer may inhibit the function of p53 tumor suppressor protein through cytoplasmic retention of p53 protein. Here, we attempt to investigate whether the functional inhibition of p53 protein by HBx protein is reversible. First, we provide the evidence for the association of endogenous p53 protein with HBx by co-immunoprecipitation in stable Chang cells that express HBx protein in an inducible manner (ChangX-34). By immunofluorescence microscopy, the major location of p53 protein of ChangX-34 cells was confirmed at the nuclear periphery as well as in the cytoplasm where HBx protein is mainly expressed. Surprisingly, anticancer drug, adriamycin induces the nuclear translocation of p53 protein sequestered in the cytoplasm. This change is accompanied by the restoration of p53 activity, which results in increased transcriptional activity at the p53-responsive DNA elements as well as increase of p21WAF1 mRNA expression. Further, we observed the induction of cell death and G1 arrest in these cells upon adriamycin treatment regardless of HBx expression. Together, we demonstrate that functional inhibition of p53 protein through its cytoplasmic retention by HBx protein is reversible. These results may be extended into other tumors of which p53 activity is modulated by viral oncoproteins.

Antineoplastic Agents↗
PubMed2000

Surface modification of polyethylene terephthalate using PEO-polybutadiene-PEO triblock copolymers.

The initial step of thrombus formation on blood-contacting biomaterials is known to be adsorption of blood proteins followed by platelet adhesion. It is generally accepted that surface modification of the biomaterials with poly(ethylene oxide) (PEO) substantially reduces protein adsorption and cell adhesion. Dacron(R) (polyethylene terephthalate) fabric, which is one of the biomaterials commonly used in blood-contacting devices, was grafted with PEO. A simple two-step procedure for covalent grafting of PEO onto the surface of Dacron(R) fabric was used. The surface was first treated with PEO-polybutadiene-PEO (PEO-PB-PEO) triblock copolymer, to introduce a layer of double bonds onto the surface. The Dacron(R) surface was then exposed to a solution of Pluronic(R) F108 (PF108), a commercially available PEO-poly(propylene oxide)-PEO (PEO-PPO-PEO) triblock copolymer. The surface with two adsorbed layers of PEO-PB-PEO and PF108 was gamma-irradiated in the presence of PF108 in the bulk solution for a total radiation dose of 0.8 Mrad. The bulk concentrations of PEO-PB-PEO and PF108 were varied to maximize the efficiency of PEO grafting. Fibrinogen adsorption on PEO-grafted surfaces was reduced more than 90%, compared with that on control surfaces, irrespective of the bulk concentrations of polymers used for grafting. Platelet adhesion was also reduced substantially by PEO grafting. Only a few round platelets were able to adhere to the PEO-grafted surface, while the control surface was fully covered with aggregates of activated platelets. PEO grafting on polyethylene terephthalate using PEO-PB-PEO and PEO-PPO-PEO block copolymers is a simple approach that can be used for various other biomaterials.

Journal Article↗
PubMed2000

Discovery of selective metal-binding peptoids using 19F encoded combinatorial libraries.

A method for encoding solid-phase split/mix combinatorial libraries using the chemical shift of synthetic fluoroarenes ('F-codes') has been developed. They have wide chemical shift dispersion and are detectable at the sub-micromol level. 19F NMR is used for decoding. Nine fluoroarenes bearing linkers for attachment to solid-phase synthesis supports through a photocleavable group were prepared. A library of 90 N-alkylglycines bearing substituted succinamides was prepared on solid phase from nine amines, in which the amine is encoded by the fluorinated tag, and 10 anhydrides. Metal binding studies followed by decoding identified unique, specific binders of copper(II) and iron(III) with microM K(D)s.

Amides↗