Biomedical subjects

Y Park

Publications and source records attributed to Y Park.

At least 91 records · Page 5Linked to original sources

PubMed2000

Expression pattern of germ cell-specific genes in the testis of patients with nonobstructive azoospermia: usefulness as a molecular marker to predict the presence of testicular sperm.

OBJECTIVE: To analyze the expression pattern of testis-specific genes of patients with various spermatogenic defects and their usefulness as a molecular marker to predict the presence of testicular spermatozoa in patients with nonobstructive azoospermia undergoing IVF. DESIGN: Prospective, controlled study. SETTING: Hospital-based infertility research laboratory. PATIENT(S): Fifty-eight men with azoospermia or severe oligozoospermia. INTERVENTION(S): Testicular biopsy was done in the patients with obstructive or nonobstructive azoospermia, including Sertoli cell-only syndrome, maturation arrest, severe hypospermatogenesis, and normal spermatogenesis. MAIN OUTCOME MEASURE(S): Reverse transcriptase polymerase chain reaction was performed using 1 microgram of total RNA extracted from testicular tissues. Three pairs of primers were used for amplification of male germ cell-specific genes (DAZ, transcribed in male germ cells; PGK2, in late spermatocytes and spermatids; protamine-2, in spermatids) as molecular markers. Testicular sperm was obtained by multiple testicular sperm extraction. RESULT(S): The DAZ, PGK2, and protamine-2 genes were expressed in 38, 30, and 21 of the 43 patients with nonobstructive azoospermia, respectively. Testicular spermatozoa were successfully extracted in 4 of 43 patients with nonobstructive azoospermia with the use of multiple testicular sperm extraction. Detection of protamine-2 transcripts predicted the presence or absence of spermatozoa in the testicular tissue in 39 of 43 patients (91%). CONCLUSION(S): Expression of the protamine-2 gene may be a useful molecular marker to predict the presence of testicular sperm in patients with nonobstructive azoospermia.

Adult↗

PubMed2000

Effect of hypercholesterolemia on the sequential changes of apoptosis and proliferation after balloon injury to rabbit iliac artery.

To evaluate the effect of hypercholesterolemia on apoptosis and proliferation after vascular injury, iliac arteries of hypercholesterolemic (HC) and normocholesterolemic (NC) rabbits were examined after balloon injury using TUNEL, immunohistochemical staining of PCNA, macrophages, smooth muscle actin and p53. In media, apoptosis occurred massively early after injury and then decreased. HC did not affect this early post-injury apoptosis but significantly increased apoptosis 14 days later (D14). Immediate apoptosis in media was followed by active proliferation. HC sustained a high activity of proliferation until D14. The changes of immunoreactivity to p53 over the same 14 day period parallel that of apoptosis. In intima, where cells were scarce initially, proliferative activity reached a peak at D7 and then decreased. HC significantly enhanced proliferation at D14. In intima proliferation was accompanied by a later low-level apoptosis. HC significantly enhanced this low-level apoptosis at D14. These effects of HC resulted in significantly increased areas of intima and media. The fundamental difference between HC and NC was the infiltration of macrophages in HC. In conclusion, balloon injury induces early massive p53-associated apoptosis followed by proliferation in media, whereas in intima, it induces active proliferation followed by a low-level apoptosis. Hypercholesterolemia does not affect the early post-injury apoptosis but enhances proliferation and low-level apoptosis at a later stage, which in turn results in intimal and medial hyperplasia.

Actins↗

PubMed2000

Ligament-sparing lumbar microdiscectomy: technical note.

BACKGROUND: The prevention or inhibition of postoperative adhesions is a significant goal for successful lumbar discectomy, not only to reduce the probable risk of recurrent radiculopathy, but also to improve the likelihood of success of re-operation. METHODS: We describe a new technique for sparing the ligamentum flavum in lumbar microdiscectomy. The superficial layer of the ligament is removed by horizontal splitting. Additional horizontal splitting of the ligament yields a paper-thin deep layer. Lateral vertical splitting and retraction is then carried out to provide a sufficient operative window. The split ligament returns to its original position after releasing the retraction, thereby closing the operative window. RESULTS: This method could preserve a layer of the ligamentum flavum to act as a physical barrier, which in turn greatly restricts the peridural fibrosis. CONCLUSIONS: This ligament-sparing technique enables surgeons to preserve the original anatomic plane and to reduce the extent of postoperative adhesion.

Adult↗

PubMed2000

Effect of root and bone morphology on the stress distribution in the periodontal ligament.

To achieve predictable and physiologic orthodontic tooth movement, estimating the axis of rotation of a tooth and the level and location of maximum stress distributed in the periodontal ligament is essential. An extracted upper canine was scanned into a computer 2-dimensionally and divided into 80 nodes along the long axis of the tooth. A mathematical formula was derived, and stress was calculated on each node. The purpose of this study was to reveal the center of resistance, axis of rotation, and an ideal force magnitude associated with various periodontal conditions, such as potential root resorption, alveolar bone loss, and varying anatomic root shape by analyzing the stress distribution in the periodontal ligament. The study demonstrates that the location of center of resistance changes significantly with variation of shape and length of the root embedded in alveolar bone. In contrast, in response to alveolar bone loss, the relative location of the center of resistance to total root length remains constant. Analysis of the stress distribution pattern in our 2-dimensional model reveals that the relationship between location of force and axis of rotation is determined by s(2) (that is) a constant depends on shape and length of a root in alveolar bone. Tapered and short roots that result from alveolar bone loss or apical root resorption are prone to tipping. The optimal orthodontic force may vary depending on the maximum stress in the periodontal ligament.

Algorithms↗

PubMed2000

Effects of mixing on fed-batch fermentation of L-ornithine.

The effects of mixing on L-ornithine fermentation were studied using an L-arginine auxotrophic mutant of Brevibacterium ketoglutamicum ATCC 21092. Three different modes of fed-batch culture using two different impeller types were studied in a 7 l fermentor. The first two modes of fed-batch culture were carried out in a fermentor equipped with six-flat-blade disk-turbine impellers with top and bottom feeding. The third mode of fed batch culture was carried out using pitched-six-flat-blade disk-turbine impellers with top feeding. The titre of L-ornithine increased up to 1.8 fold with bottom-feeding or when the pitched-six-flat-blade disk-turbine impellers were used compared to when the six-flat-blade disk-turbine impellers with top-feeding were used. It was observed that the mixing time of the limiting nutrients varied significantly depending on both the direction of feeding and the impeller type. Since the profiles of the specific rates of CO2 evolution, oxygen and glucose uptakes were very similar for the three culture modes, it could be reasonably assumed that the microorganism exhibited similar growth rates for each mode used. However, different amino acid producing activities were observed in the three culture modes. From these results it is concluded that the productivity of L-ornithine fermentation is significantly improved by shortening the mixing time of the limiting nutrient in the fermentor.

Journal Article↗

PubMed2000

A comparative study of terazosin and tamsulosin for symptomatic benign prostatic hyperplasia in Japanese patients.

OBJECTIVE: To compare the efficacy and safety of an incremental-dose regimen of terazosin (1-2 mg daily) and a fixed-dose regimen of tamsulosin (0.2 mg daily), on Japanese patients with symptomatic benign prostatic hyperplasia (BPH). PATIENTS AND METHODS: This multicentre, single-blind, randomized trial compared terazosin and tamsulosin over 4 weeks, in 61 patients with symptomatic BPH randomly assigned to terazosin (n = 31) or tamsulosin (n = 30). Terazosin 0.5 mg twice daily was administered for 2 weeks, followed by 1 mg twice daily for 2 weeks. Tamsulosin (0.2 mg) was administered once daily for 4 weeks. Symptoms were evaluated using the International Prostate Symptom Score (IPSS), and quality of life (QOL) was assessed subjectively before treatment, and again after 2 and 4 weeks of treatment. Objective measurements taken before and after the treatment period were the maximum (Qmax) and average (Qave) urinary flow rates, and the percentage residual urine volume. Improvement was defined as a 25% decrease from baseline in IPSS, > 1 point increase in QOL score, and > 2.5 mL/s increase in Qmax. Adverse reactions potentially related to the study drugs were recorded throughout the treatment period. RESULTS: Both terazosin and tamsulosin produced statistically significant improvements in subjective and objective variables. Neither treatment affected systolic or diastolic blood pressure or pulse rate. Adverse reactions were noted in four patients (three in the terazosin group and one in the tamsulosin group). However, there was no statistically significant difference in the incidence of adverse effects between the groups. CONCLUSIONS: Despite the limitations of small sample size and relatively short treatment periods, terazosin and tamsulosin were equally effective in the treatment of symptomatic BPH in Japanese patients, using relatively lower doses than those used in Western countries.

Adrenergic alpha-Antagonists↗

PubMed2000

Mechanisms of action of conjugated linoleic acid: evidence and speculation.

Conjugated linoleic acid (CLA) has been shown to inhibit carcinogenesis and atherosclerosis, enhance immunologic function while protecting against the catabolic effects of immune stimulation, affect body composition change (reducing body fat gain while enhancing lean body mass gain), and stimulate the growth of young rats. We discuss possible biochemical mechanisms that underlie these physiological effects. We emphasize the importance of considering the effects, both individually and combined, of the two CLA isomers (cis-9, trans-11 CLA and trans-10, cis-12 CLA) that have been shown to exhibit biological activity and which appear to exert their effects via different biochemical mechanisms.

Animals↗

PubMed2000

Long-term therapy of chronic hepatitis B with lamivudine.

Lamivudine therapy induces improvements in chronic hepatitis B in a high proportion of patients, but prolonged therapy is limited by the development of viral resistance. We analyzed clinical responses and virologic resistance in 27 patients treated continuously with lamivudine for 2 to 4 years. Serum transaminases, hepatitis B virus (HBV) DNA by both branched DNA (bDNA) signal amplification and quantitative polymerase chain reaction were monitored at 4- to 8-week intervals. Virologic resistance to lamivudine was confirmed by the presence of mutations in the YMDD motif of the polymerase gene by restriction fragment-length polymorphism analysis. Serum HBV-DNA levels decreased rapidly in all treated patients, falling by 4 to 5 logs within 1 year. Transaminase levels also decreased and were normal in 70% of patients at 1 year, at which point liver histology had improved in 81% of patients. Viral resistance began to emerge after 8 months of therapy, eventually developing in 14 patients, including 76% of hepatitis B e antigen (HBeAg)-positive patients but only 10% of HBeAg-negative patients. Lamivudine withdrawal led to reappearance of wild-type HBV species, but retreatment led to more rapid reappearance of the mutant virus. Clinical, serum biochemical, and histologic improvements were maintained in the 13 patients who did not develop resistance. Thus, long-term therapy with lamivudine resulted in maintained improvements in virologic, biochemical, and histologic features of disease in most patients with HBeAg-negative chronic hepatitis B and in the subgroup of HBeAg-positive patients with high serum transaminase levels. A high rate of resistance limited efficacy, particularly in patients who remained HBeAg positive on therapy.

Adult↗

PubMed2000

Bronchoalveolar lavage cellular composition in acute asthma and acute bronchiolitis.

OBJECTIVE: To compare cellular inflammation in the airways between acute bronchiolitis and asthma. STUDY DESIGN: Using a bronchoalveolar lavage with flexible bronchoscopy procedure, we investigated the cellular constituents of BAL fluid in children with acute exacerbation of asthma (n = 18) and infants with acute bronchiolitis caused by respiratory syncytial virus (n = 20). These results were compared with those of healthy control subjects (n = 14). RESULTS: Total lavage fluid recovered was similar in all groups. The total cell numbers were highest in the bronchiolitis group. The BAL cellular profile in the asthma group was characterized by a higher median (interquartile range) ratio of eosinophils (2.4% [1.6%-9.5%]; P <.01) than in the bronchiolitis group (0% [0%-0%]) or the control group (0% [0%-0%]). Neutrophil ratio was higher in the bronchiolitis group (40.0% [26.5%-50.0%]; P <.01), with no difference found between the asthma group (3.3% [2.0%-7.9%]) and the control group (2.0% [0.8%-5.5%]). CONCLUSIONS: Asthma and acute bronchiolitis are characterized by an elevated cellular percentage of eosinophils and neutrophils, respectively, in bronchoalveolar lavage fluid.

Acute Disease↗

PubMed2000

The Kyonggi Shear Zone of the Central Korean Peninsula: Late Orogenic Imprint of the North and South China Collision.

The crustal-scale Kyonggi shear zone of central Korea has been identified as a major boundary between the Precambrian Kyonggi massif in the south and the Imjingang belt in the north. The latter is an eastward extension of the Qinling-Dabie-Sulu collisional belt of China. Field observations and microstructural analysis indicate that the extensional shear zone evolved from a deep crustal ductile regime to a shallow crustal brittle regime, associated with a rapid uplift of the Kyonggi massif following the Late Permian-Early Triassic collision between the Sino-Korean and Yangtze cratons. A Rb-Sr muscovite age (226+/-1.2 Ma) of the mylonite suggests that the extensional ductile shearing occurred during the Late Triassic.

Journal Article↗

PubMed2000

Telomere structure regulates the heritability of repressed subtelomeric chromatin in Saccharomyces cerevisiae.

Telomeres, the protein-DNA structures present at the termini of linear chromosomes, are capable of conferring a reversible repression of Pol II- and Pol III-transcribed genes positioned in adjacent subtelomeric regions. This phenomenon, termed telomeric silencing, is likely to be the consequence of a more global telomere position effect at the level of chromatin structure. To understand the role of telomere structure in this position effect, we have developed an assay to distinguish between the heritability of transcriptionally repressed and derepressed states in yeast. We have previously demonstrated that an elongated telomeric tract leads to hyperrepression of telomere-adjacent genes. We show here that the predominant effect of elongated telomeres is to increase the inheritance of the repressed state in cis. Interestingly, the presence of elongated telomeres overcomes the partial requirement of yCAF-1 in silencing. We propose that the formation of a specific telomeric structure is necessary for the heritability of repressed subtelomeric chromatin.

Chromatin↗

PubMed2000

The trans-10,cis-12 isomer of conjugated linoleic acid downregulates stearoyl-CoA desaturase 1 gene expression in 3T3-L1 adipocytes.

Conjugated linoleic acids (CLA) are a group of positional and geometric conjugated dienoic isomers of linoleic acid. The objective of this study was to determine the effects of the cis-9,trans-11 and trans-10,cis-12 isomers of conjugated linoleic acid on lipid composition and gene expression during the differentiation of mouse 3T3-L1 preadipocytes. Treatment of differentiating 3T3-L1 preadipocytes with trans-10,cis-12 conjugated linoleic acid (CLA) resulted in a dose-dependent decrease in the expression of the stearoyl-CoA desaturase 1 gene (SCD1). The expression of other adipocyte genes such as adipose P2 (aP2), fatty acid synthase (FAS), SCD2 and the key adipogenic transcription factors, peroxisome proliferator-activated receptor gamma2 (PPARgamma2) and CCAAT enhancer binding protein alpha (C/EBPalpha), remained elevated. Cells treated with trans-10,cis-12 CLA exhibited smaller lipid droplets, with reduced levels of the major monounsaturated fatty acids, palmitoleate and oleate. By contrast, the cis-9,trans-11 isomer did not alter adipocyte gene expression. Repression of the stearoyl-CoA desaturase gene expression in adipocytes by the trans-10,cis-12 isomer may contribute to the mechanisms by which CLA reduces body fat in mice.

3T3 Cells↗

PubMed2000

Regulation of the Porphyromonas gingivalis fimA (Fimbrillin) gene.

In common with many bacterial virulence genes, the fimbrillin (fimA) gene of Porphyromonas gingivalis is modulated in response to environmental fluctuation. The trans-acting components that comprise the regulatory system for transcriptional activity of the fimA gene in P. gingivalis were investigated. Three major proteins were found to bind to the upstream region of the fimA promoter. One of these proteins was fimbrillin itself, and the other two were a major arginine protease (Rgp) and lysine protease (Kgp). Production of these proteins was necessary for maximal fimA transcription. An exogenous fimA promoter-lacZ reporter was inactive when introduced into a strain of P. gingivalis carrying a mutation in the indigenous fimA gene. Furthermore, fimA mRNA levels were significantly decreased in rgp and kgp mutant strains. These data indicate that P. gingivalis has evolved multiple levels of control of fimbrial gene expression to enhance its survival in hostile environments.

Amino Acid Sequence↗

PubMed2000

Coinvasion of dentinal tubules by Porphyromonas gingivalis and Streptococcus gordonii depends upon binding specificity of streptococcal antigen I/II adhesin.

Cell wall-anchored polypeptides of the antigen I/II family are produced by many species of oral streptococci. These proteins mediate adhesion of streptococci to salivary glycoproteins and to other oral microorganisms and promote binding of cells to collagen type I and invasion of dentinal tubules. Since infections of the root canal system have a mixed anaerobic bacterial etiology, we investigated the hypothesis that coadhesion of anaerobic bacteria with streptococci may facilitate invasive endodontic disease. Porphyromonas gingivalis ATCC 33277 cells were able to invade dentinal tubules when cocultured with Streptococcus gordonii DL1 (Challis) but not when cocultured with Streptococcus mutans NG8. An isogenic noninvasive mutant of S. gordonii, with production of SspA and SspB (antigen I/II family) polypeptides abrogated, was deficient in binding to collagen and had a 40% reduced ability to support adhesion of P. gingivalis. Heterologous expression of the S. mutans SpaP (antigen I/II) protein in this mutant restored collagen binding and tubule invasion but not adhesion to P. gingivalis or the ability to promote P. gingivalis coinvasion of dentin. An isogenic afimbrial mutant of P. gingivalis had 50% reduced binding to S. gordonii cells but was unaffected in the ability to coinvade dentinal tubules with S. gordonii wild-type cells. Expression of the S. gordonii SspA or SspB polypeptide on the surface of Lactococcus lactis cells endowed these bacteria with the abilities to bind P. gingivalis, penetrate dentinal tubules, and promote P. gingivalis coinvasion of dentin. The results demonstrate that collagen-binding and P. gingivalis-binding properties of antigen I/II polypeptides are discrete functions. Specificity of antigen I/II polypeptide recognition accounts for the ability of P. gingivalis to coinvade dentinal tubules with S. gordonii but not with S. mutans. This provides evidence that the specificity of interbacterial coadhesion may influence directly the etiology of pulpal and periapical diseases.

Adhesins, Bacterial↗

PubMed2000

A new method for the study of chylomicron kinetics in vivo.

Our understanding of the metabolism of chylomicrons, the lipoprotein that transports dietary fat from the intestine to peripheral tissues, is incomplete. The present studies were conducted to determine whether a labeled intravenous lipid emulsion could be used to estimate chylomicron triglyceride (TG) rate of appearance (R(a)) and thereby quantify the rate of intestinal fat absorption. After an overnight fast, healthy volunteers (n = 6) sipped a (3)H-labeled drink over 6.5 h at a rate of 175 mg fat. kg(-1). h(-1). Beginning at hour 5, an HPLC-purified, (14)C-labeled lipid emulsion was infused intravenously for 90 min. During the study, plasma total and chylomicron TG concentrations increased from 100 +/- 21 to 237 +/- 40 mg/dl and from undetectable to steady-state levels of 35 +/- 13 mg/dl, respectively. After a minor correction for VLDL contamination, tracer-determined chylomicron TG R(a) was 175 +/- 30 mg. kg(-1). h(-1), equal to the presumed ingestion rate. In summary, a radiolabeled intravenous lipid emulsion is able to accurately estimate chylomicron TG R(a) and therefore can be used to measure in vivo fat absorption rates.

Adult↗

PubMed2000

An optimization approach to design of generalized BSB neural associative memories.

This article is concerned with the synthesis of the optimally performing GBSB (generalized brain-state-in-a-box) neural associative memory given a set of desired binary patterns to be stored as asymptotically stable equilibrium points. Based on some known qualitative properties and newly observed fundamental properties of the GBSB model, the synthesis problem is formulated as a constrained optimization problem. Next, we convert this problem into a quasi-convex optimization problem called GEVP (generalized eigenvalue problem). This conversion is particularly useful in practice, because GEVPs can be efficiently solved by recently developed interior point methods. Design examples are given to illustrate the proposed approach and to compare with existing synthesis methods.

Association Learning↗

PubMed2000

Common susceptibility and transmission pattern of human leukocyte antigen DRB1-DQB1 haplotypes to Korean and Caucasian patients with type 1 diabetes.

The incidence of type 1 diabetes in Korea is less than 1/10th of that in the United States, and it has been suggested that human leukocyte antigen (HLA) alleles of Asian patients associated with diabetes differ from those of Caucasians. In this study we analyzed the common susceptibility and transmission pattern of a series of HLA DRB1-DQB1 haplotypes to Korean and Caucasian patients with type 1 diabetes. We performed HLA DR and DQ typing of 158 type 1 diabetic patients in a case control study, 140 nondiabetic subjects from the same geographical area, 49 simplex families from Seoul, and 283 families from the Human Biological Data Interchange. Although the haplotype frequencies in the two populations are quite different, when identical haplotypes are compared, their odds ratios are nearly the same. For all parental haplotypes, the transmission to diabetic offspring was similar for Korean and Caucasian families (r = 0.8; P: < 10(-)(4)). Allowing for ethnic differences in allelic associations due to different frequencies of DRB1 and DQB1 haplotypes (linkage disequilibrium), these data show, not only by case-control comparison but also by transmission analyses of the haplotypes, that the susceptibility effects of DRB1-DQB1 haplotypes are consistent in Koreans and Caucasians. Thus, the influence of class II susceptibility and resistance alleles appears to transcend ethnic and geographic diversity of type 1 diabetes.

Adolescent↗

PubMed2000

Synergistic activation of the inhibin alpha-promoter by steroidogenic factor-1 and cyclic adenosine 3',5'-monophosphate.

The inhibin alpha-subunit gene is expressed in the ovary, testis, adrenal, and pituitary. Because this pattern of expression corresponds to that of the orphan nuclear receptor, steroidogenic factor-1 (SF-1), we hypothesized that the inhibin alpha promoter might be regulated by SF-1. Expression of exogenous SF-1, in an SF-1 deficient cell line, caused modest stimulation of the inhibin alpha promoter. However, activation of the cAMP pathway, which is known to regulate inhibin alpha expression, greatly enhanced the actions of SF-1. Coexpression of SF-1 with the catalytic subunit of cAMP-dependent protein kinase A caused greater than 250-fold stimulation, whereas only 4- or 7-fold stimulation was seen by the SF-1 or protein kinase A pathway alone. Synergistic stimulation by SF-1 and the cAMP pathway was also seen in GRMO2 granulosa cells, which express endogenous SF-1. Deletion and site-directed mutagenesis localized a novel SF-1 regulatory element (TCA GGGCCA; -137 to -129) adjacent to a variant cAMP-response element (CRE; -120 to -114). The synergistic property of SF-1 and cAMP stimulation was inherent within this composite inhibin alpha fragment (-146 and -112), as it was transferable to heterologous promoters. Mutations in either the CRE or the SF-1 regulatory element completely eliminated synergistic activation by these pathways. The binding of SF-1 and CRE binding protein (CREB) to the inhibin alpha regulatory elements was relatively weak in gel mobility shift assays, consistent with their deviation from consensus binding sites. However, SF-1 was found to interact with CREB using an assay in which epitope-tagged SF-1 was expressed in cells and used to pull down in vitro translated CREB. Expression of CREB binding protein (CBP), a coactivator that interacts with SF-1 and CREB, further enhanced transcription by these pathways. Stimulation by the SF-1 and cAMP pathways was associated with increased histone H4 acetylation, suggesting that chromatin remodeling accompanies their actions. We propose a model in which direct interactions of SF-1, CREB, and associated coactivators like CBP induce strongly cooperative transactivation by pathways that individually have relatively weak effects on transcription.

Acetylation↗