Biomedical subjects

H W Park

Publications and source records attributed to H W Park.

At least 19 recordsLinked to original sources

PubMed2006

Risk assessment of human exposure to cypermethrin during treatment of mandarin fields.

The potential dermal and respiratory exposure assessment and risk assessment for applicator were performed with cypermethrin EC. The pesticide was applied on a mandarin field using a power sprayer. Gloves were used for the hand exposure assessment, mask for face, and dermal patches for the other parts of the body. Personal air monitor equipped with a XAD-2 resin was used for the respiratory exposure assessment. During the application of cypermethrin in the field, the rate of potential dermal exposure ranged from 28.1 to 58.8 mg/h. The major exposure parts were upper-arms (22.1-24.6%) and legs (thigh and shin, 28.3-29.2%) for females and thigh (21.0-46.9%) and hand (14.9-19.3%) for males. Females were exposed more than males. No exposure was detected from the respiratory monitoring. For risk assessment, the potential dermal exposure (PDE), the absorbable quantity of exposure (AQE), and the margin of safety (MOS) were calculated. Among those four risk assessments, MOS was < 1 in only trial I, which indicated any possibility of risk. However, in the others, the possibility of risk was little. Moreover, the safe work time ranged from 3.61 h to 9.69 h.

Air Pollutants, Occupational↗

PubMed2005

Structural analysis of human liver glyceraldehyde-3-phosphate dehydrogenase.

The crystal structure of human liver glyceraldehyde-3-phosphate dehydrogenase (GAPDH) has been determined. This structure represents the first moderate-resolution (2.5 A) and crystallographically refined (Rfree = 22.9%) human GAPDH structure. The liver GAPDH structure consists of a homotetramer, each subunit of which is bound to a nicotinamide adenine dinucleotide (NAD+) molecule. The GAPDH enzyme has glycolytic and non-glycolytic functions, both of which are of chemotherapeutic interest. The availability of a high-quality human GAPDH structure is a necessity for structure-based drug design. In this study, structural differences between human liver and skeletal muscle GAPDHs are reported in order to understand how these two enzymes might respond to anti-trypanosomatid GAPDH inhibitors.

Animals↗

PubMed2003

The discomallear ligament and the anterior ligament of malleus: an anatomic study in human adults and fetuses.

According to some reports, movement of the malleus, resulting from anterior hypertension on the discomallear ligament (DML), could produce aural symptoms related with damage to middle ear structures. The aim of this study was to examine the topographic relationship of the DML and the anterior ligament of malleus (ALM). Four fetuses and 16 adult hemi-sectioned heads were used to determine the anatomic-clinical relevance of DML and ALM in temporomandibular disorder. In fetal specimens, the DML was distinctly interposed between the malleus and the disc of the temporomandibular joint (TMJ), and the ALM had a structure apparently composed of the superior and inferior lamellae, running anteriorly in continuation with the sphenomandibular ligament (SML) through the future petrotympanic fissure (PTF). In all adult specimens, the DML was inserted into the malleus, and it expanded broadly toward the disc and capsular region of the TMJ in a triangular shape and inserted into the disc and capsule of the TMJ. The two-lamellae structure of the ALM was not distinguishable in adult specimens. The overstretched ALM resulted in movement of the malleus in five cases, but similar tension applied to the DML did not cause any movement of the malleus. This result provides an indication of the clinical significance of the ALM, a ligamentous structure continuous with the SML. It is apparent that the ALM has the potential to cause aural symptoms as a result of damage to the middle ear structure.

Adult↗

PubMed2003

Economic burden of smoking in Korea.

OBJECTIVE: To support tobacco control policies in Korea by providing the estimated annual economic burden attributed to cigarette smoking. METHODS: The following two different approaches were used to estimate the cost: "disease specific" and "all causes". In the disease specific approach, we focused on estimating direct and indirect costs involved in treatments of cardiovascular, respiratory, and gastrointestinal diseases, and cancer as a result of smoking, by using an epidemiologic approach-the population attributable risk (PAR). To compute PAR, the relative risks of smoking in terms of physician visits, hospital admission, and death were estimated using the Cox proportional hazard model. In the all causes approach, we examined the differences in direct and indirect costs between smokers and non-smokers for all conditions and types of disease. The major data source was the Korea Medical Insurance Corporation cohort study, which had complete records of smoking status as of 1992 for 115 682 male and 67 932 female insured workers. RESULTS: By the disease specific approach, the estimated costs attributable to smoking in 1998 in Korea ranged from US 2269.42 million dollars (4.89 million dollars per 100,000 population; 0.59% of gross domestic product (GDP)) to 2956.75 million dollars (6.37 million dollars; 0.78% of GDP). The all causes approach yielded a minimum cost of 3154.75 million dollars (6.79 million dollars; 0.82% GDP) and a maximum of 4580.25 million dollars (9.86 million dollars; 1.19% GDP). CONCLUSION: The study confirms that smoking places a substantial economic burden on Korean society. In light of this, our study provides evidence for a strong need to develop a national policy to effectively control tobacco consumption in Korea.

Adult↗

PubMed2003

Baculovirus expression vectors that incorporate the foreign protein into viral occlusion bodies.

Current baculovirus expression systems typically produce soluble proteins that accumulate within the infected insect cell or are secreted into the growth medium. A system has now been developed for the incorporation of foreign proteins, along with the matrix protein, polyhedrin, into baculovirus occlusion bodies. Initial studies showed that a recombinant virus expressing a translational fusion between polyhedrin and GFP did not form occlusion bodies. However, a baculovirus coexpressing native polyhedrin and the polyhedrin-GFP fusion protein formed occlusion bodies that fluoresced under UV light, demonstrating that they included the polyhedrin-GFP fusion protein. This was confirmed by immunoblot analysis. Thus, incorporation of a foreign protein into occlusion bodies depends on an interaction between native polyhedrin and the polyhedrin fusion protein. Electron microscopy demonstrated that the occlusion bodies containing GFP also incorporated virions as expected. These ColorPol occlusion bodies were as infectious to insect larvae as occlusion bodies produced by wild-type virus. This new system expands the capabilities for foreign gene expression by baculoviruses, which has implications for biopesticide design, novel vaccine delivery systems, and fusion protein purification applications.

Animals↗

PubMed2002

Spine needle biopsy simulator using visual and force feedback.

OBJECTIVE: Biopsy with an inserted needle is an important procedure for lesion detection in the spine, but is difficult to perform due to the presence of many critical organs near the spine. This article presents a spine needle biopsy simulator, based on visual and force feedback, which can be used to plan the optimal path of a needle and to practice the procedure without risk. MATERIALS AND METHODS: The simulator is composed of a 3D human model, a visual-feedback component, a force-feedback component, and an evaluation module. The human model is based on 3D CT data. The visual-feedback component provides an oblique section, multiplanar reformatting images, and a volume-rendered image. Of these, the oblique section display is very useful for planning a 3D path for the needle. During simulation, the force-feedback component generates and provides realistic forces acting on the biopsy needle in real time by synchronizing them to visual feedback. After each simulation, the evaluation module provides a performance analysis for the trainee. RESULTS: For an XCT abdomen volume data set of 256 x 256 x 256, the update rate of image rendering due to needle movement is over 25 Hz, with a force-feedback rate of 1 kHz. This performance proved to be good enough for the trainee to learn the relationship between visual and force feedback. CONCLUSIONS: The simulator is useful for the planning of and training in complicated 3D spine needle biopsy procedures. It may be used as an educational tool for beginners, a practice tool to increase expertise, or a test bed for new procedures.

Algorithms↗

PubMed2002

High prevalence of current asthma and active smoking effect among the elderly.

BACKGROUND: Although asthma is a common cause of morbidity in adults, relatively few objectively measured population studies of asthma prevalence in adult populations have been conducted. OBJECTIVE: To evaluate the prevalence of asthma, based on both a questionnaire and methacholine bronchial provocation test, and to determine the risk factors of asthma prevalence in an adult population. METHODS: A total of 2,467 adults, who were randomly selected from metropolitan urban, non-metropolitan urban and rural areas, responded to the modified ISAAC questionnaire, and underwent methacholine bronchial provocation tests and skin prick tests to locally common aeroallergens. RESULTS: The prevalence of current asthma based on the questionnaire and the methacholine challenge was 2.0% in adults younger than 40, 3.8% in 40- to 54-year-olds, 7.7% in 55- to 64-year-olds and 12.7% in those aged 65 or higher. For subjects of 55-64 years, active smoking was found to be significantly related with the prevalence of current asthma and bronchial hyper-responsiveness, although smoking was positively associated with percentage predictive value of forced expiratory volume of 1 s (FEV1). CONCLUSION: The prevalence of current asthma is common among the elderly, and active smoking may play an important role in the development of asthma and bronchial hyper-responsiveness among the elderly.

Adult↗

PubMed2001

A structural pathway for activation of the kinesin motor ATPase.

Molecular motors move along actin or microtubules by rapidly hydrolyzing ATP and undergoing changes in filament-binding affinity with steps of the nucleotide hydrolysis cycle. It is generally accepted that motor binding to its filament greatly increases the rate of ATP hydrolysis, but the structural changes in the motor associated with ATPase activation are not known. To identify the conformational changes underlying motor movement on its filament, we solved the crystal structures of three kinesin mutants that decouple nucleotide and microtubule binding by the motor, and block microtubule-activated, but not basal, ATPase activity. Conformational changes in the structures include a disordered loop and helices in the switch I region and a visible switch II loop, which is disordered in wild-type structures. Switch I moved closer to the bound nucleotide in two mutant structures, perturbing water-mediated interactions with the Mg2+. This could weaken Mg2+ binding and accelerate ADP release to activate the motor ATPASE: The structural changes we observe define a signaling pathway within the motor for ATPase activation that is likely to be essential for motor movement on microtubules.

Amino Acid Substitution↗

PubMed2001

Construction and characterization of a recombinant Bacillus thuringiensis subsp. israelensis strain that produces Cry11B.

The mosquitocidal bacterium Bacillus thuringiensis subsp. israelensis (Bti) produces four major endotoxin proteins, Cry4A, Cry4B, Cry11A, and Cyt1A, and has toxicity in the range of many synthetic chemical insecticides. Cry11B, which occurs naturally in B. thuringiensis subsp. jegathesan, is a close relative of Cry11A, but is approximately 10-fold as toxic to Culex quinquefasciatus. To determine whether the addition of Cry11B to Bti would improve its toxicity, we produced this protein in Bti. High levels of Cry11B synthesis were obtained by expression of the cry11B gene under the control of cyt1A promoters and the STAB-SD sequence. This construct was cloned into the shuttle vector pHT3101, yielding the derivative plasmid pPFT11Bs, which was then transformed by electroporation into acrystalliferous (4Q7) and crystalliferous (IPS-82) strains of Bti. Synthesis of Cry11B in Bti 4Q7 produced crystals approximately 50% larger than those produced with its natural promoters without STAB-SD. However, less Cry11B was produced per unit culture medium with this construct than with the wild-type construct, apparently because the latter construct produced more cells per unit medium. Nevertheless, the Bti IPS-82 strain that produced Cry11B with pPFT11Bs was twice as toxic as the parental IPS-82 strain (LC(50) = 1.4 ng/ml versus 3.3 ng/ml, respectively) to fourth instars of C. quinquefasciatus. Against fourth instars of Aedes aegypti, no statistically significant difference between parental Bti IPS-82 (LC(50) = 4.7 ng/ml) and the Bti IPS-82 recombinant producing Cry11B (LC(50) = 3.5 ng/ml) was found in toxicity.

Aedes↗

PubMed2001

The transport of a hepatoprotective agent, isopropryl 2-(1-3-dithiethane-2-ylidene)-2[N-(4-methyl-thiazole-2-yl) carbamoyl] acetate (YH439), across Caco-2 cell monolayers.

Isopropryl 2-(1-3-dithiethane-2-ylidene)-2[N-(4-methyl-thiazole-2-yl) carbamoyl] acetate (YH439) is currently under phase II clinical trials by the Yuhan Research Center for use as a hepatoprotective agent. Unfortunately, the oral bioavailbility of YH439, which is sparingly soluble in water (i.e., 0.3 microg/ml or 0.91 microM at room temperature), reportedly, is negligible regardless of the dose administered to rats in the 10-300 mg/kg range. The bioavailability of the compound increased up to 24%, when administered in the form of a micellar solution (700 microg/ml or 2.1 mM for YH439) at a dose of 10 mg/kg, suggesting that its limited solubility is associated with its negligible bioavailability. In order to obtain additional information concerning the bioavailability of YH439, the mechanism(s) involved in gastrointestinal (GI) absorption were investigated in the present study. For this purpose, the transport of YH430 across a Caco-2 cell monolayer was measured in a Transwell. A permeability of 4.07 x 10(-5) cm/s was obtained for the absorptive (i.e., apical to basolateral direction) transport of 0.42 pM YH439, implicating that the in vivo GI absorption is nearly complete. The absorptive transport exhibited a slight concentration-dependency with an intrinsic clearance (CLi) of 0.38 microLL/cm2/sec, which accounted for 28.1% of the total intrinsic clearance (i.e., CLi plus the intrinsic clearance for the linear component) of the transport. Thus, saturation of the absorption process appears to be a minor factor in limiting the bioavailability of the compound. The apparent permeability of YH439 from the basolateral to the apical direction (i.e., efflux, 6.67 x 10(-5) cm/s) was comparable to that for absorptive transport, but, interestingly, a more distinct concentration-dependency was observed for this transport. However, the efflux does not appear to influence the bioavailability of the compound, as evidenced by the sufficiently high permeability in the absorption direction. Rather, a reportedly extensive first-pass hepatic metabolism appears to be a principal factor in limiting the bioavailability. In this respect, reducing the first-pass metabolism by some means would lead to a higher bioavailability of the compound. Thus, elevation of the absorption rate of YH439 becomes a necessity. From a practical point of view, increasing the concentration of YH439 in the GI fluid appears to be a feasible way to increase the absorption rate, because the compound is primarily absorbed via a linear mechanism. In summary, the solubilization of YH439, as previously demonstrated for a micellar solution of the compound, appears to be a practical way to increase the oral bioavailability of YH439.

Biological Availability↗

PubMed2001

Treatment of severe equinus deformity associated with extensive scarring of the leg.

Nine severe equinus deformities of the foot associated with extensive scarring of the leg and ankle were corrected using a hinged Ilizarov apparatus and free-tissue transfer. The average duration of followup was 38 months (range, 28-54 months). Free tissue transfer was done in all patients; a parascapular flap was used in seven patients, and a groin flap was used in two patients. The results were evaluated using two objective criteria and one subjective assessment: the degree of active dorsiflexion, the range of active movement of the ankle, and daily activities. For active dorsiflexion of the ankle and activities, the results were good in seven patients and fair in two patients. For range of active motion of the ankle, the results were good in six patients and fair in two patients. One patient with ankle arthrodesis was excluded. This study showed that severe equinus deformities associated with extensive scarring of the leg and ankle can be corrected effectively with heel cord lengthening, free-tissue transfer, and a hinged Ilizarov technique.

Adolescent↗

PubMed2001

The licC gene of Streptococcus pneumoniae encodes a CTP:phosphocholine cytidylyltransferase.

The licC gene product of Streptococcus pneumoniae was expressed and characterized. LicC is a nucleoside triphosphate transferase family member and possesses CTP:phosphocholine cytidylyltransferase activity. Phosphoethanolamine is a poor substrate. The LicC protein plays a role in the biosynthesis of the phosphocholine-derivatized cell wall constituents that are critical for cell separation and pathogenesis.

Amino Acid Sequence↗

PubMed2001

Clinical characteristics of unexplained sudden cardiac death in Korea.

In Western countries, sudden cardiac death (SCD) is closely related to coronary artery disease, but in Korea the clinical characteristics of SCD are not well determined. Over a 4-year period (June 1995 to May 1999), 186 cases of SCD, ranging in age from 16 to 75 years, were admitted to the Chonnam National University Hospital. In 82 (44.1%) of these, neither symptoms nor evidence of structural heart disease was found and so their clinical characteristics were investigated. There were 66 (80.5%) men and 16 (19.5%) women (male/female ratio = 4.1:1). The mean age was 50 +/- 14 years: 19 (23.2%) were in their 40s, 21 (25.6%) in their 50s, and 17 (20.7%) in their 60s. The time of circulatory collapse witnessed in 68 cases of SCD showed 2 peaks: between midnight and 03.00h (n=16, 23.5%) and between 09.00h and midday (n=15, 22.1%). Unexplained SCD occurred at home in 48 (64.9%) cases and on the street in 12 (16.2%); it occurred during normal daily routine activity in 23 (39.6%) and during sleep in 15 (25.9%). Thirty-three patients (40.2%) experienced various prodromal symptoms, including chest discomfort (n=13, 15.9%) and dyspnea (n=8, 9.8%). The electrocardiogram taken on arrival recorded asystole in 65 (79.3%) and ventricular fibrillation in 17 (20.7%). Idiopathic ventricular fibrillation was diagnosed in 14 (10 men, 4 women; 45 +/- 11 years) of 21 patients who recovered spontaneous circulation. Five (6.1%) patients were discharged alive, and an implantable cardioverter-defibrillator was implanted in 2. Unexplained SCD is common in Korea and develops predominantly in middle-aged males around midnight or in the late morning usually with no prodromal symptoms (59.8%). Idiopathic ventricular fibrillation is thought to be one of the important causes.

Adolescent↗

PubMed2001

Embryological background for fetal surgery.

Congenital malformations are one of the main topics, which must be addressed in the 21st century. Fetal surgery is expected to become a routine procedure for malformed fetal patients in the near future. This paper presents some important aspects of the embryological background required for fetal surgery and shows normal human embryos between the 4th and the 8th week of development.

Congenital Abnormalities↗

PubMed2001

Parapharyngeal second branchial cyst manifesting as cranial nerve palsies: MR findings.

SUMMARY: We report the MR findings of parapharyngeal branchial cleft cyst manifesting as multiple, lower cranial nerve palsies in a 35-year-old woman. On MR images, a well-marginated cystic mass was detected in the right parapharyngeal space, with displacement of both the right internal carotid artery and the right internal jugular vein on the posterolateral side. The cyst contained a whitish fluid that was slightly hyperintense on T1-weighted images and slightly hypointense to CSF on T2-weighted images. No enhancement on contrast-enhanced T1-weighted images was present. The right side of the tongue showed high signal intensity on T2-weighted images, suggesting denervation.

Adult↗

PubMed2001

[The Gurhigae Jejoongwon: its size and activities].

This article explores the location, size of the site, and medical activities of the Gurhigae Jejoongwon. Relevant documents such as reminiscences, diplomatic notes, newspaper accounts, maps, and photographs were referred for this study. The Gurhigae Jejoongwon located on a hill that, at present, covers the area from Ulchi-ro to MyungDong Cathedral. Its main entrance was towards Ulchi-ro. Real estate including the buildings of the Gurhigae Jejoongwon was returned to the Chosun government in 1905, and the estimated size of its site varied from 1,810 pyung to 5,036 pyung. The site of the Gurhigae Jejoongwon was 2 - 5 times larger than the 862.16-pyung-site of the Jejoongwon in its Jaedong days. With such larger size, the Jejoongwon could take care of more patients. Dr. Avison started medical education again. The Gurhigae Jejoongwon took the central part in medical treatment activities for public in Seoul, as it carried out the prevention activities against Cholera in 1895. The Chosun government highly recognized its medical treatment activities for the common people.

History, 19th Century↗

PubMed2001

[Social status and role of students entering Jejoongwon: focus on Kyum-Rae Lee].

This study considers the social class and social role of the entering students of Jejoongwon at that time in light of its very first medical graduate, Kyum-Rae Lee. Foremost, Kyum-Rae Lee was confirmed to have been from a middle-class family. However, unlike other chungin-class families, his family belonged to the minority. He seemed to have entered medical school to seek opportunity to move up in social class by taking advantage of special government provisions, which allowed him to learn English and Western medicine. Afterwards, he performed heroic services in the peasant-war, proceeded up to administration and participated in the modernization of Great Han Empire. With his knowledge of Western concepts, he became involved in numerous social activities, such as organizing the Enlightenment Society and leading the Enlightenment Movement. In much the same way, most early students were from low-class background with exceptional personal abilities and were able to pass aptitude examinations. Such achievements allowed them to apply for positions in the military and administrative management. Ten years later, medical education to train medical professionals was revived with changes in attitudes of people of Chosun Dynasty toward Western medicine and with creation of formal medical study.

Education, Medical↗

PubMed2000

Structural basis for the feedback regulation of Escherichia coli pantothenate kinase by coenzyme A.

Pantothenate kinase (PanK) is a key regulatory enzyme in the coenzyme A (CoA) biosynthetic pathway and catalyzes the phosphorylation of pantothenic acid to form phosphopantothenate. CoA is a feedback inhibitor of PanK activity by competitive binding to the ATP site. The structures of the Escherichia coli enzyme, in complex with a nonhydrolyzable analogue of ATP, 5'-adenylimido-diphosphate (AMPPNP), or with CoA, were determined at 2.6 and 2.5 A, respectively. Both structures show that two dimers occupy an asymmetric unit; each subunit has a alpha/beta mononucleotide-binding fold with an extensive antiparallel coiled coil formed by two long helices along the dimerization interface. The two ligands, AMPPNP and CoA, associate with PanK in very different ways, but their phosphate binding sites overlap, explaining the kinetic competition between CoA and ATP. Residues Asp(127), His(177), and Arg(243) are proposed to be involved in catalysis, based on modeling of the pentacoordinate transition state. The more potent inhibition by CoA, compared with the CoA thioesters, is explained by a tight interaction of the CoA thiol group with the side chains of aromatic residues, which is predicted to discriminate against the CoA thioesters. The PanK structure provides the framework for a more detailed understanding of the mechanism of catalysis and feedback regulation of PanK.

Adenosine Triphosphate↗