Biomedical subjects

D H Yi

Publications and source records attributed to D H Yi.

8 recordsLinked to original sources

PubMed2006

Administration of donor-derived mesenchymal stem cells can prolong the survival of rat cardiac allograft.

BACKGROUND: Mesenchymal stem cells (MSCs) are multipotent adult elements that have recently been shown to have profound immunomodulatory effects both in vitro and in vivo. Herein we have examined the impact of intravenous infusion of donor MSCs on the survival of transplanted hearts in a rat allograft model. METHODS: Recipient Fisher344 rats were transplanted with hearts from inbred Wistar rats. Wistar rat MSCs were infused via the tail vein at designated intervals. In vitro mixed lymphocyte reaction (MLR) and cell-mediated lympholysis (CML) assays were performed to assess whether MSCs downregulated T-cell responses in vivo. Real-time polymerase chain reaction (PCR) was used to analyze the Th1/Th2 balance in MSC-treated and control groups. RESULTS: The MSCs cultured in vitro exhibited multipotential for differentiation. Survival of the allografts was markedly prolonged by administration of MSCs compared with the controls, namely mean survivals of 12.4 vs 6.4 days, respectively. Real-time PCR showed a shift in the Th1/Th2 balance toward Th2. By MLR and CML assays, untreated control rats showed greater alloreactivity than did MSC-treated rats. CONCLUSION: Our results indicated that MSCs suppressed allogeneic T-cell responses both in vitro and in vivo. Intravenous administration of MSCs prolonged the survival of transplanted hearts, possibly by induction of allograft tolerance through changing the Th1/Th2 balance.

Animals↗

PubMed2001

Surgically induced astigmatism after hyperopic and myopic photorefractive keratectomy.

PURPOSE: To compare the axis and magnitude of surgically induced refractive astigmatism (SIA) after hyperopic and myopic photorefractive keratectomy (PRK). SETTING: Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA. METHODS: In this single-center retrospective study, the VISX Star S2 excimer laser was used to create a peripheral annular ablation profile to correct spherical hyperopia in 23 eyes of 16 consecutive patients. Attempted corrections ranged from +0.50 diopter (D) to +4.25 D with 0 to 1.00 D of astigmatism. The same laser was used to create a central ablation profile to correct spherical myopia in 25 eyes of 17 consecutive patients. Attempted corrections ranged from -2.25 to -6.50 D with 0 to 1.00 D of astigmatism. The absolute change in refractive astigmatism was calculated by taking the difference in magnitudes of astigmatism before and after laser treatment without regard to axis. Axis and magnitude of SIA were analyzed by vector differences. Magnitudes were compared using the Student t test, and axial shifts were compared using the chi-square test. All patients were followed for a minimum of 6 months. RESULTS: The mean changes in absolute astigmatism were 0.29 +/- 0.28 D at 3 months and 0.34 +/- 0.29 D at 6 months after hyperopic PRK and 0.40 +/- 0.35 D at 3 months and 0.39 +/- 0.36 D at 6 months after myopic PRK. The mean vectoral magnitudes were 0.49 +/- 0.29 at 3 months and 0.52 +/- 0.25 at 6 months after hyperopic PRK and 0.48 +/- 0.39 at 3 months and 0.44 +/- 0.38 at 6 months after myopic PRK. The mean values for SIA (the centroid) were 0.10 +/- 0.57 D x 113 degrees at 3 months and 0.15 +/- 0.57 D x 131 degrees at 6 months after hyperopic PRK and 0.04 +/- 0.63 D x 160 degrees at 3 months and 0.08 +/- 0.58 D x 171 degrees at 6 months after myopic PRK. There was no statistically significant difference between the 2 groups in vectoral axis or magnitude of SIA. CONCLUSION: Surgically induced astigmatism after hyperopic PRK was comparable to astigmatism induced by myopic PRK. A peripheral annular ablation for hyperopic correction, similar to a central ablation in myopic PRK, did not appear to result in uneven corneal healing causing astigmatism.

Astigmatism↗

PubMed2001

Economic evaluation of the societal costs of hepatitis B in South Korea.

BACKGROUND AND AIMS: Hepatitis B (HBV) infection remains a major public health problem in South Korea, and accounts for considerable morbidity and mortality. At present, very little is known about the cost of HBV to the South Korean health-care system and society. The present study was therefore conducted to estimate the total annual cost of HBV infection in South Korea for a given year (1997). METHODS: The study was conducted from the South Korean societal perspective, taking into account the direct and indirect costs of HBV vaccination programs (prevention costs), and those related to the treatment of acute and chronic hepatitis, cirrhosis and liver cancer (disease costs). Several assumptions were made in arriving to actual cost estimates. RESULTS: The total societal cost of HBV in 1997 was 1078.3 billion Won ($US 959.7 million), 142.3 billion Won or 13.2% being attributable to prevention costs and 225.4 billion Won or 20.9% being attributable to indirect costs of HBV-related diseases. The total cost (direct plus indirect) associated with HBV-related diseases to the South Korean society was 936.1 billion Won ($US 833.1 million), of which 45.3% was attributable to cirrhosis-related costs. In terms of disease-related direct costs alone (710.5 billion Won or $US 632.3 million), the estimated annual spending per patient was 1.37 million Won ($US 1219). The direct costs of the HBV disease (prevention and disease treatment, amounting to 782.2 billion Won or $US 696.2 million) is equivalent to 3.2% of the national health-care expenditure for 1997. CONCLUSIONS: This study confirms that HBV is a significant cost burden to the South Korean society, and in the absence of an effective cure reinforces the importance of continued disease prevention via vaccination.

Fibrosis↗

PubMed2000

Protein kinase C activation by phorbol ester increases in vitro invasion through regulation of matrix metalloproteinases/tissue inhibitors of metalloproteinases system in D54 human glioblastoma cells.

To elucidate possible mechanisms of phorbol 12-myristate 13-acetate (PMA) induced in vitro invasiveness of glioblastoma cells, we examined expression levels of membrane-type 1 matrix metalloproteinase (MT1-MMP), MMP-2, MMP-9 and tissue inhibitor of metalloproteinase (TIMP)-1 and TIMP-2 using Western blotting and gelatin zymography assay, and found that PMA induced the secretion of MMP-9, activated MMP-2 proenzyme to fully active form of 59 kDa, down-regulated the TIMP-1 and TIMP-2 secretion, and increased MT1-MMP on the cell surface. However, PKC inhibitor Go 6983 reversed all of these effects brought about by PMA. We, therefore, conclude the activation of PKC by PMA in these cells plays a critical role in the regulation of MMPs/TIMPs system, which has a major role in tumor invasion and metastasis.

Brain Neoplasms↗

PubMed2000

Matrix metalloproteinases in human gliomas: activation of matrix metalloproteinase-2 (MMP-2) may be correlated with membrane-type-1 matrix metalloproteinase (MT1-MMP) expression.

To evaluate possible roles of matrix metalloproteinase (MMP)-1, -2, tissue inhibitor of metalloproteinase (TIMP)-1, -2 and membrane-type-1 matrix metalloproteinase (MT1-MMP) in invasion of human gliomas, expressions of these proteins were investigated in ten cases of human glioma and two meningioma tissues and eight human glioma cell lines. In gelatin zymography, MMP-2 activities of glioblastomas were higher than astrocytomas. The activated form of MMP-2 was seen in five of six cases of glioblastomas, but not in astrocytomas. MMP-9 activity was detected in all cases of malignant astrocytomas but the reactivity of MMP-9 was weaker than that of MMP-2. MT1-MMP mRNA expression in glioblastomas was higher than that in astrocytomas. Five cases of glioblastomas with activated form of MMP-2 had MT1-MMP expressions. In vitro, human glioma cell lines with high expression of MT1-MMP also showed high MMP-2 activity. TIMP-1 transcripts were constitutively present in almost all glioma tissues and cell lines, whereas TIMP-2 mRNA were weak especially in malignant gliomas. Imbalance of TIMP-2/MMP-2 was observed using immunoprecipitation analysis in a glioma cell line. High expression of MMP-2 and MT1-MMP is possibly involved in invasiveness of malignant glioma.

Animals↗

PubMed1997

Surgical repair of patients with tetralogy of Fallot and unilateral absence of pulmonary artery.

UNLABELLED: BACKGROUND; Patients with tetralogy of Fallot and unilateral absence of pulmonary artery are a high-risk group for whom there is no consensus on the correct approach to medical management. The purpose of this report is to review a 29-year experience in the treatment of those patients. METHODS: Between May 1966 and February 1995, 2,511 patients underwent correction of tetralogy of Fallot in our department, 24 of those patients with unilateral absence of pulmonary artery (20 had absence of the left pulmonary artery, 4 had absence of the right pulmonary artery). Valved conduits were used in 9 patients, right ventricular patches were used in 4 patients, and transannular patches with a monocusp that was made of the patient's pericardium were used in 11 patients. RESULTS: There were two operative deaths; both were in patients with hypoplasia of the left ventricle. All survivors had good early and late results. CONCLUSIONS: A right ventricular patch should be used in patients with tetralogy of Fallot and infundibular stenosis; a transannular patch with a monocusp should be used in patients with tetralogy of Fallot and stenosis of the left or right pulmonary artery's origin as well as the pulmonary trunk. A homograft valved conduit is suitable for patients with anomalous coronary artery or pulmonary atresia.

Abnormalities, Multiple↗

PubMed1994

Linkage of a human brain malformation, familial holoprosencephaly, to chromosome 7 and evidence for genetic heterogeneity.

Holoprosencephaly (HPE) is a common malformation of the developing forebrain and midface characterized by incomplete penetrance and variable expressivity. Familial HPE has been reported in many families with autosomal dominant inheritance in some and apparent autosomal recessive inheritance in others. We have examined 125 individuals from nine families with autosomal dominant HPE. Expression in gene carriers varied from alobar HPE and cyclopia through microforms such as microcephaly or single central incisor to normal phenotype. We performed linkage studies by either Southern blot or polymerase chain reaction analyses with DNA markers (D7S22, D7S550, and D7S483) that are deleted from some patients with sporadic HPE and flank a translocation breakpoint in 7q36 associated with HPE. The strongest support for linkage was with D7S22, which was linked with no recombination to autosomal dominant HPE in eight of nine families with a combined logarithm of odds score of 6.4 with an affected-only model-free analysis and 8.2 with a reduced-penetrance model and all phenotypes. Close linkage to this region could be excluded in one family, and there was significant evidence of genetic heterogeneity. These results show that a gene for autosomal dominant HPE is located in a chromosomal region (7q36) known to be involved in sporadic HPE with visible cytogenetic deletions. They also demonstrate genetic heterogeneity in familial HPE. We hypothesize that mutations of a gene in 7q36, designated HPE3, are responsible for both sporadic HPE and a majority of families with autosomal dominant HPE.

Adolescent↗

PubMed1990

[Experimental study of a new calcification reducing monocusp patch].

The glutaraldehyde (GA)-treated porcine pericardium was modified chemically with epoxychlopropane (EC). Monocusp patches were made and implanted in the right ventricular outflow tract of dogs (n = 10). The GA or chloroacetic treated porcine pericardium monocusp patches was used as the control groups. At 6 months after implantation, the calcium of the samples were detected qualitatively (by von Kossa staining technique and with light microscopic observation), quantitatively (by a tomic absorption) and ultrastructurally. The stability and mechanical properties of tissue after modification with EC were assessed. The results of this study prove that chemically modified porcine pericardium with EC can reduce the calcification of tissue, and can preserve its structural intactness, good tissue stability, good tensile strength and function.

Animals↗