Biomedical subjects

Tae-Kyun Kim

Publications and source records attributed to Tae-Kyun Kim.

7 recordsLinked to original sources

PubMed2005

Occupational exposure to benzene in South Korea.

Benzene has been used in various industries as glues or solvents in Korea. Since 1981, a preparation containing more than 1% benzene is not allowed to be manufactured, used or dealt with in the workplace, except in laboratories and in those situations benzene must be used in a completely sealed process as specified in Industrial Safety and Health Act (ISHA). Claims for compensation of hematopoietic diseases related to benzene have been rising even though the work environment has been improved. This study was conducted to assess the status of benzene exposure in different industries in Korea. We reviewed the claimed cases investigated by the Korea Occupational Safety and Health Agency (KOSHA) between 1992 and 2000. The Survey of National Work Environment Status in 1998 was analyzed to assume the number of workers and factories exposed to benzene. In 2000, six factories were investigated to evaluate benzene exposure. Personal air monitoring was performed in 61 workers and urine samples were collected from 57 workers to measure trans,trans-muconic acid (t,t-MA). Hematologic examination has performed. Thirty-four cases of hematopoietic diseases were investigated by KOSHA including eight cases of myelodysplastic syndrome and eight cases of acute myelocytic leukemia. Eight cases were accepted as related to benzene exposure. The number of workers possibly exposed to benzene can be estimated to be 196,182 workers from 6219 factories based on the database. The geometric mean of benzene in air was 0.094 (0.005-5.311) ppm. Seven samples were higher than 1 ppm but they did not go over the 10 ppm occupational exposure limit (OEL) value in Korea. The geometric mean of trans,trans-muconic acid in urine was 0.966 (0.24-2.74) mg/g creatinine. The benzene exposure level was low except in a factory where benzene was used to polymerize other chemicals. The ambient benzene from 0.1 to 1 ppm was significantly correlated with urine t,t-MA concentration (r=0.733, p<0.01). Hematologic parameters did not show significant difference among groups divided into the level of exposure. Korean workers were not highly exposed to benzene and the level of exposure was mostly less than 1 ppm. However, there might be an excessive risk of hematopoietic disorders due to relatively high past exposure. The OEL value of benzene was amended to 1 ppm from 10 ppm in 2002 and was effective since July 2003.

Adult↗

PubMed2005

Locally linear discriminant analysis for multimodally distributed classes for face recognition with a single model image.

We present a novel method of nonlinear discriminant analysis involving a set of locally linear transformations called "Locally Linear Discriminant Analysis (LLDA)." The underlying idea is that global nonlinear data structures are locally linear and local structures can be linearly aligned. Input vectors are projected into each local feature space by linear transformations found to yield locally linearly transformed classes that maximize the between-class covariance while minimizing the within-class covariance. In face recognition, linear discriminant analysis (LDA) has been widely adopted owing to its efficiency, but it does not capture nonlinear manifolds of faces which exhibit pose variations. Conventional nonlinear classification methods based on kernels such as generalized discriminant analysis (GDA) and support vector machine (SVM) have been developed to overcome the shortcomings of the linear method, but they have the drawback of high computational cost of classification and overfitting. Our method is for multiclass nonlinear discrimination and it is computationally highly efficient as compared to GDA. The method does not suffer from overfitting by virtue of the linear base structure of the solution. A novel gradient-based learning algorithm is proposed for finding the optimal set of local linear bases. The optimization does not exhibit a local-maxima problem. The transformation functions facilitate robust face recognition in a low-dimensional subspace, under pose variations, using a single model image. The classification results are given for both synthetic and real face data.

Algorithms↗

PubMed2005

Musculoskeletal differentiation of cells derived from human embryonic germ cells.

Stem cells have the potential to significantly improve cell and tissue regeneration therapies, but little is understood about how to control their behavior. We investigated the potential differentiation capability of cells derived from human embryonic germ (EG) cells into musculoskeletal lineages by providing a three-dimensional environment with increased cell-cell contact and growth factors. Cells were clustered into pellets to mimic the mesenchyme condensation process during limb development. LVEC cells, an embryoid body-derived (EBD) cell culture generated from EG cells, were cultured in micromass pellets for 21 days in the presence of bone morphogenetic protein 2 (BMP2) and/or transforming growth factor beta-3 (TGFbeta3). Gene expression for cartilage-, bone-, and muscle-specific matrix proteins--including collagen types I, II, III, IX, X; aggrecan; cartilage proteoglycan link protein; cartilage oligomeric protein; chondroitin sulfate-4-S; and myf5--was upregulated in the pellets treated with TGFbeta3, while mRNAs for neurofilament heavy (NFH), a neuron marker, and flk-1, a hematopoietic marker, decreased. Total collagen and proteoglycan production exhibited a time-dependent increase in the pellets treated with TGFbeta3, further confirming the expression of characteristic musculoskeletal markers. Furthermore, our results indicate the ability to select or differentiate stem cells toward a musculoskeletal lineage from a heterogenous EBD cell line.

Cartilage↗

PubMed2005

Cervical facet joint injections in the neck and shoulder pain.

The effects from cervical facet joint injections in those patients who have been complaining cervical zygapophyseal joint pain were compared. The patients were diagnosed originally as myofascial pain syndrome (MPS), cervical herniated nucleus pulposus (HNP), and whiplash-associated disorders (WAD). Patients with the zygapophyseal joints pain of C5-6 and C6-7 were classified by their pain origin as MPS, HNP, and WAD. All patients had been undergone cervical zygapophyseal joints injections with the mixture of lidocaine and triamcinolone unilaterally or bilaterally through the posterior approach under C-arm imaging guide. The therapeutic effects were compared with reduction of numeric rating scale (NRS) of pain before and immediately after blockade and symptom-free periods in each group after 12 months. Symptom durations before injections were 16.1+/-9.6, 4.6+/-1.9 and 4.1+/-1.1 months in each MPS, HNP, and WAD groups. The reductions of NRS immediately after the blockade among the three groups were not different. However, the symptom-free duration after blockade lasted longer in the HNP group than the other two groups. In patients with cervical zygapophyseal pain syndromes, the analgesic effect from cervical facet joint blocks lasted longer in cervical HNP than MPS or WAD.

Adolescent↗

PubMed2005

Indigo carmine for the selective endoscopic intervertebral nuclectomy.

This study was undertaken to prove that the selectively infiltrated parts of nucleus pulposus with indigo carmine was degenerated parts of nucleus pulposus. This study was done, between August and October 2002, in 5 patients, who received endoscopic discectomy, due to intervertebral disc herniation. Discogram was done with mixture of indigo carmine and radioactive dye. Blue discolored part was removed through endoscope, and small undiscolored part was removed together for the control. The two parts were stained with hematoxylin and eosin and compared under the microscope. Undiscolored part was normal nucleus pulposus, composed of chondrocytes with a matrix of type II collagen and proteoglycan, mainly aggrecan. However, in discolored part, slits with destruction of collagen fiber array and ingrowth of vessel and nerve were observed. Using indigo carmine in endoscopic discectomy gives us selective removal of degenerated disc.

Chondrocytes↗

PubMed2005

Percutaneous vertebroplasty and facet joint block.

It is surprising that about 24% of patients with benign osteoporotic vertebral fracture die within a year from respiratory infection and urinary tract infection because of coughing and voiding difficulties, depending on the sites of compression fractures. We reviewed 500 patients on whom percutaneous vertebroplasty (PVP) was performed, at 612 levels in terms of patient selection, operation technique, medication, and clinical outcomes during the follow-up course for 2 yr study period. To confirm the most painful level among the multiple fracture sites, physical examination after facet joint block under the fluoroscope was the most reliable method. The mean total lumbar spine fracture threshold of bone mineral density was 0.81+/-0.05 g/cm2. The mean changes of numeric rating scale scores, Oswestry Disability Index except sex life, and Karnofsky performance status were -72.00, -83.50 and +60.62% in the osteoporosis group and -51.89, -45.02, and 69.03% in the tumor group. Complications related to the procedure were lateral spinal cord damage, transient paresthesia and transient hypotension. PVP with facet joint block is a profitable method for the vertebral compression fracture because of low risk and short duration of procedure with a high chance to result in pain relief and early mobilization.

Aged↗

PubMed2002

Evaluation of lead exposure in workers at secondary lead smelters in South Korea: with focus on activity of erythrocyte pyrimidine 5'-nucleotidase (P5N).

To evaluate lead exposure among secondary lead-smelting workers with a focus on erythrocyte pyrimidine 5'-nucleotidase (P5N) activity, blood lead concentration (PbB), activity of P5N and other biological variables were examined in 88 exposed workers in five secondary lead smelters and in 24 non-exposed workers in Korea. All of the mean values of air lead concentration (PbA) in the three processes, scrap pretreatment, blast furnace smelting, and refining and casting of the secondary lead smelters, markedly exceeded 0.05 mg/m3. In this survey, 29 (97%) of 30 air samples for lead exceeded 0.05 mg/m3. The highest mean PbA and PbB values were found in the section of blast furnace smelting. All of the mean PbB values in all the sections were higher than 30 microg/dl. PbB of 71 (81%) of the 88 exposed workers exceeded 30 microg/dl. In 31 (35%) of the exposed workers, PbB was above 60 microg/dl. Compared with the non-exposed group, zinc protoporphyrin (ZPP) in the exposed group was significantly increased, whereas erythrocyte P5N activity and activity of erythrocyte delta-aminolevulinic acid dehydratase (ALAD) were significantly inhibited. Erythrocyte P5N activity had valid biological correlation with PbB and with other biological variables, such as ALAD activity or ZPP. Lead exposure affected hemoglobin levels via inhibition of P5N activity, as well as the heme biosynthetic pathway, in the high-exposure state.

5'-Nucleotidase↗