Biomedical subjects

D H Chung

Publications and source records attributed to D H Chung.

At least 19 recordsLinked to original sources

PubMed2002

Autologous cardiomyocyte transplantation in an ovine myocardial infarction model.

BACKGROUND: To evaluate the possibility of autologous cardiomyocyte transplantation, we transplanted cultured autologous cells into an infarct region developed by coronary artery ligation in an ovine model. MATERIALS AND METHODS: A chronic heart failure model with a considerable portion of myocardial infarction was created in sheep using sequential ligation of the homonymous artery and its diagonal branch. Autologous cardiomyocytes were cultured and isolated from the right ventricular infundibulum. After a predetermined interval (one animal for two months and the other for three months), the two animals were reanesthetized and a suspension of cultured autologous vetricular cells in 0.3 ml of culture medium (1.2 x 10(7) cells) was injected into the center of three out of the four sites in the infarcted area using a tuberculin syringe. The same amount of culture medium was injected with an identical procedure into the center of the remaining site, as control. The animals were kept alive for a further month, and then sacrificed for postmortem heart examinations. Light microscopic analysis and immunohistochemical study for myoglobin were done. RESULTS AND CONCLUSIONS: On postmortem gross examination, well-demarcated thin-walled anteroseptal infarcts with chamber enlargement were clearly seen in specimens from the two animals. Microscopic analysis showed homogenous fibrosis throughout the infarcted areas. In both animals, one of the three sites of cardiomycyte injection showed an islet of cardiomyocytes in the mid-myocardium, while none were observed in the control site of either animal. A layer of cardiomyocytes was observed in subendocardial regions, as it was in the control areas. In conclusion, cardiomyocyte transplantation into the infarct regions developed by coronary artery ligation in an ovine model was achieved with only limited success. An understanding of why only 33% of cardiomyocyte-injection sites demonstrated viable cardiomyocytes, in the form of tiny cell islets, remains to be elucidated.

Animals↗

PubMed2001

Competitive inhibition in vivo and skewing of the T cell repertoire of antigen-specific CTL priming by an anti-peptide-MHC monoclonal antibody.

We have recently described a mAb, KP15, directed against the MHC-I/peptide molecular complex consisting of H-2D(d) and a decamer peptide corresponding to residues 311-320 of the HIV IIIB envelope glycoprotein gp160. When administered at the time of primary immunization with a vaccinia virus vector encoding gp160, the mAb blocks the subsequent appearance of CD8(+) CTL with specificity for the immunodominant Ag, P18-I10, presented by H-2D(d). This inhibition is specific for this particular peptide Ag; another H-2D(d)-restricted gp160 encoded epitope from a different HIV strain is not affected, and an H-2L(d)-restricted epitope encoded by the viral vector is also not affected. Using functional assays and specific immunofluorescent staining with multivalent, labeled H-2D(d)/P18-I10 complexes (tetramers), we have enumerated the effects of blocking of priming on the subsequent appearance, avidity, and TCR Vbeta usage of Ag-specific CTL. Ab blocking skews the proportion of high avidity cells emerging from immunization. Surprisingly, Vbeta7-bearing Ag-specific TCR are predominantly inhibited, while TCR of several other families studied are not affected. The ability of a specific MHC/peptide mAb to inhibit and divert the CD8(+) T cell response holds implications for vaccine design and approaches to modulate the immune response in autoimmunity.

Animals↗

PubMed2001

Special phase matching of second-harmonic generation in helical ferroelectric liquid crystal cells.

The helical structures in ferroelectric liquid crystals can be utilized to realize a special phase matching for second-harmonic generation (SHG) when two counter fundamental waves propagate along the helical axis and the wavelength of SHG is near the photonic (selective reflection) band edge. On the basis of the exact theory [Drevensek-Olenik and Copic, Phys. Rev. E 56, 581 (1997)], a simple analytical description is derived and some characteristic features of the special phase matching are shown. (1) Special phase matching is definitely achieved under particular combinations of polarization. (2) The SH spectrum is related to a subsidiary oscillating structure in the selective reflection spectrum. The maximum SH intensity is realized at the first dip of the oscillation near one of the edges in the selective reflection band. (3) The thickness (d) dependence of the maximum SH intensity is d4 in thick cells, while it is d2 for conventional phase matching. (4) The linewidth for the SH peak is d(-3) dependent, which is much narrower than in conventional phase matching.

Journal Article↗

PubMed2001

CD99 regulates the transport of MHC class I molecules from the Golgi complex to the cell surface.

The down-regulation of surface expression of MHC class I molecules has recently been reported in the CD99-deficient lymphoblastoid B cell line displaying the characteristics of Hodgkin's and Reed-Sternberg phenotype. Here, we demonstrate that the reduction of MHC class I molecules on the cell surface is primarily due to a defect in the transport from the Golgi complex to the plasma membrane. Loss of CD99 did not affect the steady-state expression levels of mRNA and protein of MHC class I molecules. In addition, the assembly of MHC class I molecules and the transport from the endoplasmic reticulum to the cis-Golgi occurred normally in the CD99-deficient cells, and no difference was detected between the CD99-deficient and the control cells in the pattern and degree of endocytosis. Instead, the CD99-deficient cells displayed the delayed transport of newly synthesized MHC class I molecules to the plasma membrane, thus causing accumulation of the molecules within the cells. The accumulated MHC class I molecules in the CD99-deficient cells were colocalized with alpha-mannosidase II and gamma-adaptin in the Golgi compartment. These results suggest that CD99 may be associated with the post-Golgi trafficking machinery by regulating the transport to the plasma membrane rather than the endocytosis of surface MHC class I molecules, providing a novel mechanism of MHC class I down-regulation for immune escape.

12E7 Antigen↗

PubMed2001

Local expression and distribution of a storage protein in the ovary of Hyphantria cunea.

Storage protein-1 (HcSP-1) is a major storage protein found in the hemolymph and fat body of Hyphantria cunea. HcSP-1 has a high methionine (6.0%) and low aromatic amino acid content (8.5%) (Cheon et al., 1998). In this study, the accumulation and expression of HcSP-1 in ovary was investigated using biochemical and immunocytochemical methods. HcSP-1 was detected in the ovaries in 6-day-old pupae and accumulated toward the end of pupal life, when HcSP-1 transcripts were detectable by Northern blot analysis and RT-PCR. In situ hybridization showed that the HcSP-1 mRNA was located in the nurse cells and follicular epithelial cells, but not in the oocyte. Though most of the HcSP-1 that is incorporated in the yolk bodies of the oocyte is probably sequestered from the surrounding hemolymph, HcSP-1 is an important yolk protein contributing to early yolk body formation before the development of patency by the follicular epithelium.

Animals↗

PubMed2001

Expression of leukemia-associated antigen, JL1, in bone marrow and thymus.

The identification of immunophenotypic markers with restricted expression has long been a critical issue in diagnostic and therapeutic advances for acute leukemias. We previously developed a monoclonal antibody against a new thymocyte surface antigen, JL1, and showed that JL1 is expressed in the majority of acute leukemia cases. In this study, using multiparameter flow cytometric analyses, we found that JL1 was uniquely expressed in subpopulations of normal bone marrow (BM) cells, implying the association of JL1 with the differentiation and maturation process. Although CD34(+) CD10(+) lymphoid precursors and some of maturing myeloid cells express JL1, neither CD34(+) CD38(-/lo) nor CD34(+) AC133(+) noncommitted pluripotent stem cells do. As for the myeloid precursors, CD34(+) CD33(+) cells do not express JL1. During lymphopoiesis, JL1 on the earliest lymphoid precursors disappear in the CD20(+) sIgM(+) stage of B-cell development or after CD1a down-regulation in thymocytes. Despite the highly restricted expression of JL1 in normal BM cells, most of the leukemias express JL1 irrespective of their immunophenotypes. These results indicate that JL1 is not only a novel differentiation antigen of hematopoietic cells, but also a leukemia-associated antigen. Therefore, we suggest that JL1 be a candidate molecule in acute leukemia for the diagnosis and immunotherapy that spares the normal BM stem cells.

Adult↗

PubMed2001

cDNA sequence and gene expression of storage protein-2--a juvenile hormone-suppressible hexamerin from the fall webworm, Hyphantria cunea Drury.

We isolated and sequenced a cDNA clone corresponding to storage protein-2 (SP-2) from the fall webworm, Hyphantria cunea. The cDNA for SP-2 (2572 bp) codes for a 747-residue protein with a predicted molecular mass of 88.5 kDa. The calculated isoelectric point is 7.6. Multiple alignment analysis of amino acid sequence revealed that SP-2 is most similar to BJHSP2 (74.3% identity). According to both the phylogenetic analyses and criteria for amino acid composition, SP-2 belongs to the subfamily of moderately methionine-rich storage proteins (3.2% methionine, 11.8% aromatic amino acid). Topical application of the JH analog, methoprene, after head ligation of larvae, suppressed transcription of the SP-2 gene, indicating hormonal effects at the transcriptional level. The SP-2 transcript was detected by Northern blot analysis in Malpighian tubules, in addition to the fat body where it was most abundant. The local expression of SP-2 in Malpighian tubules suggests that it may have some function in that organ.

Amino Acid Sequence↗

PubMed2001

Positional change of the hyoid bone after bilateral sagittal split osteotomy with rigid and wire fixation.

The purpose of this study was to compare positional changes of the hyoid bone and the amount of postsurgical compensation in mandibular position in patients who received either wire or rigid fixation after surgery. Data were analyzed from 97 patients (25 males and 72 females) who were randomized to receive wire (43) or rigid (54) fixation after mandibular advancement surgery as part of a multicenter clinical trial. Radiographs were digitized before surgery (T2), immediately after surgery (T3), and 8 weeks (T4), 6 months (T5), 1 year (T6), and 2 years (T7) after surgery. The wire group had greater sagittal relapse of the hyoid bone at T6 (P =.007), which persisted at T7 (P =.02). Both groups showed upward movement of the hyoid bone after surgery. There was no relationship between the vertical change in the the hyoid bone position and the vertical position of mandible (B point y coordinate, mandibular plane). However, there was a relationship between the horizontal hyoid bone position and B point during the postsurgical period (rigid, r = 0.450; wire, r = 0.517). The direct distance from the hyoid bone to basion increased (P <.001) in both groups at T3 and then recovered its original length after 8 weeks (P <.001). The rigid group showed no significant change in distance from the hyoid to the genial tubercles, but the wire group showed recovery of the muscle length at T6 (P <.05) and T7 (P <.05).

Bone Wires↗

PubMed2001

Butyrate sensitizes human colon cancer cells to TRAIL-mediated apoptosis.

BACKGROUND: Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), a novel member of the tumor necrosis factor family, induces apoptosis in TRAIL-sensitive tumors through the activation of the caspase pathway. Sodium butyrate (NaBT) induces differentiation and apoptosis in certain colorectal cancers; the molecular mechanisms for these effects have not been clearly defined. The purpose of our study was to determine whether NaBT sensitizes TRAIL-resistant human colon cancer cells to the effects of TRAIL. METHODS: Human colon cancer cells (KM12C, KML4A, and KM20) that are resistant to TRAIL treatment alone were treated with TRAIL (100 ng/mL), NaBT (5 mmol/L), or a combination of these agents and harvested for total RNA and protein. Western blots were performed to assess intracellular expression of Flice-like inhibitory protein (FLIP), a caspase inhibitor. Percent-specific apoptosis, relative caspase-3 activity, and Annexin-V immunofluorescence were determined at 24 and 48 hours. Cell cycle--related gene expression was assessed by RNase protection. RESULTS: Treatment with NaBT for 24 and 48 hours decreased FLIP protein expression in all cell lines. Furthermore, NaBT sensitized these resistant cancer cells to the effects of TRAIL with significant increases noted in cell death, caspase-3 activity, and Annexin-V staining compared with NaBT alone. CONCLUSIONS: Our findings suggest that the reduction of FLIP protein levels by NaBT renders TRAIL-resistant human colon cancer cells sensitive to TRAIL-mediated apoptosis. The combination of TRAIL with agents (such as NaBT, which target proteins that prevent cell death) may provide a more effective and less toxic regimen for the treatment of resistant colon cancers.

Apoptosis↗

PubMed2001

Molecular mechanisms contributing to necrotizing enterocolitis.

OBJECTIVE: To examine the cellular mechanisms involved in the pathogenesis of necrotizing enterocolitis (NEC). SUMMARY BACKGROUND DATA: Necrotizing enterocolitis is a major cause of death and complications in neonates; the cellular mechanisms responsible for NEC are unknown. The inducible form of cyclooxygenase (i.e., COX-2) is activated by the transcription factor nuclear factor (NF)-kappaB and is thought to play a role in inflammation. METHODS: Segments of perforated and adjacent uninvolved small intestine from neonates with NEC were analyzed for COX-2 expression by immunohistochemistry. NEC was induced in weanling (18 days old) rats by occlusion of superior mesenteric vessels for 1 hour and intraluminal injection of platelet activating factor (50 micro/kg). Small intestine was harvested for protein extraction. Western immunoblot was performed to determine expression of COX-2. Gel shift assays were performed to assess NF-kappaB binding activity. RESULTS: Immunohistochemical analysis showed increased COX-2 protein expression in the perforated intestinal sections of all 36 neonates but not in adjacent normal intestine. Increased expression of COX-2 protein and NF-kappaB binding activity was noted in the small intestine of weanling rats at 0 and 3 hours after induction of NEC. CONCLUSIONS: Increased COX-2 expression was identified in all neonatal intestinal segments resected for perforated NEC. In addition, a coordinate induction of COX-2 expression and NF-kappaB binding was noted in a rodent model of NEC. These findings suggest that the COX-2/NF-kappaB pathway may play a role in the pathogenesis of NEC. Therapeutic agents that target this pathway may prove useful in the treatment or possible prevention of NEC.

Animals↗

PubMed2001

LMP1-induced downregulation of CD99 molecules in Hodgkin and Reed-Sternberg cells.

Hodgkin's and Reed-Sternberg (H-RS) cells are morphological hallmarks of Hodgkin's disease (HD). So far, several characteristics frequently seen in H-RS cells from different origins have been described, such as the high expression of Epstein-Barr virus latent membrane protein 1 (LMP1), the elevation of NF-kappaB activity, and the aberrant expression of molecules such as CD15, CD30, and CD99. Despite extensive studies on the nature of H-RS cells, the molecular mechanism by which H-RS cells are generated remained elusive. Recently, the forced down-regulation of CD99 was reported to induce typical H-RS phenotypes in vitro in a B cell line. Furthermore, it was revealed that LMP1 markedly reduces the CD99 expression at the transcriptional level. Since the presence of LMP1 is known to be associated with the H-RS cell formation, the data provide a possibility of linkage between LMP1 and HD via CD99, thus suggesting that, at least in part, the loss of CD99 may play a critical role in the pathogenic sequence to the formation of H-RS cells in HD. In this review, the role of CD99 in the generation of H-RS cells and its molecular mechanism will be suggested.

12E7 Antigen↗

PubMed2001

Incidence and characterization of Listeria spp. from foods available in Korea.

A total of 410 domestic Korean food samples were analyzed for the presence of Listeria spp. by the conventional U.S. Department of Agriculture protocol, and presumptive strains were identified by morphological, cultural and biochemical tests according to Bergey's manual and confirmed by API-Listeria kit. Among the total 410 food samples, 46 samples (11.2%) were found to be contaminated with Listeria species. Among the 46 strains of Listeria spp. isolates, 8 strains (17.42%) for Listeria monocytogenes, 3 strains (6.5%) for Listeria seeligeri, 33 strains (71.7%) for Listeria innocua, and 2 strains (4.4%) for Listeria welshimeri were identified, respectively. Also, only beef, chicken, pork, frozen foods, and sausage were contaminated with L. monocytogenes, and the other products were free of L. monocytogenes. Of 46 Listeria spp. isolates, L. innocua (71.7%) was the most predominantly isolated in a variety of foods compared to other Listeria spp. An in vitro virulence assay for Listeria spp. using myeloma and hybridoma cells from murine and human sources was performed. The result showed that only L. monocytogenes killed approximately 95 to 100% hybridoma cells after 6 h and the other Listeria species, such as L. innocua, L. seeligeri, and L. welshimeri strains had about 0 to 10% lethal effect on hybridoma cells. Also, an antibiotic susceptibility test showed that Listeria spp. isolates were very susceptible to the antibiotics tested, except for nalidixic acid. Also, serotyping results showed 75% of L. monocytogenes isolates from beef, chicken, and frozen pizza belonged to serotype 1 and 25% from sausage were type 4.

Animals↗

PubMed2000

Mapping the ligand of the NK inhibitory receptor Ly49A on living cells.

We have used a recombinant, biotinylated form of the mouse NK cell inhibitory receptor, Ly49A, to visualize the expression of MHC class I (MHC-I) ligands on living lymphoid cells. A panel of murine strains, including MHC congenic lines, was examined. We detected binding of Ly49A to cells expressing H-2D(d), H-2D(k), and H-2D(p) but not to those expressing other MHC molecules. Cells of the MHC-recombinant strain B10.PL (H-2(u)) not only bound Ly49A but also inhibited cytolysis by Ly49A(+) effector cells, consistent with the correlation of in vitro binding and NK cell function. Binding of Ly49A to H-2D(d)-bearing cells of different lymphoid tissues was proportional to the level of H-2D(d) expression and was not related to the lineage of the cells examined. These binding results, interpreted in the context of amino acid sequence comparisons and the recently determined three-dimensional structure of the Ly49A/H-2D(d) complex, suggest a role for amino acid residues at the amino-terminal end of the alpha1 helix of the MHC-I molecule for Ly49A interaction. This view is supported by a marked decrease in affinity of an H-2D(d) mutant, I52 M, for Ly49A. Thus, allelic variation of MHC-I molecules controls measurable affinity for the NK inhibitory receptor Ly49A and explains differences in functional recognition in different mouse strains.

Amino Acid Sequence↗

PubMed2000

Antibodies directed against the MHC-I molecule H-2Dd complexed with an antigenic peptide: similarities to a T cell receptor with the same specificity.

alphabeta TCRs, which use an Ab-like structure to form a combining site, recognize molecular complexes consisting of peptides bound to MHC class I (MHC-I) or class II (MHC-II) molecules. To explore the similarities and differences between Ab and T cell recognition of similar structures, we have isolated two mAbs, KP14 and KP15, that specifically bind H-2D(d) complexed with an HIV envelope gp160-derived peptide, P18-I10. These Abs are MHC and peptide specific. Fine specificity of mAb binding was analyzed using a panel of synthetic peptides, revealing similarities between the mAb and a cloned TCR with the same specificity. These two mAbs used the same V(H) and J(H) gene segments, but different D, Vkappa, and Jkappa genes. Administered in vivo, mAb KP15 blocked the induction of CTL specific for recombinant vaccinia virus-encoded gp160, indicating its ability to bind endogenously generated MHC/peptide complexes. Analysis of the fine specificity of these mAbs in the context of their encoded amino acid sequences and the known three-dimensional structure of the H-2D(d)/P18-I10 complex suggests that they bind in an orientation similar to that of the TCR. Thus, the plasticity of the B cell receptor repertoire and the structural similarities among BCR and TCR allow Abs to effectively mimic alphabeta TCRs. Such mAbs may be useful in the therapeutic modulation of immune responses against infectious agents or harmful self Ags as well as in tracing steps in Ag processing.

Amino Acid Sequence↗

PubMed2000

Mannose trimming targets mutant alpha(2)-plasmin inhibitor for degradation by the proteasome.

We have previously characterized the molecular and cellular mechanisms of alpha(2)-plasmin inhibitor (alpha(2)PI) deficiency. The mutant alpha(2)PI-Nara and alpha(2)PI-Okinawa proteins were found to be retained and degraded in cells stably expressing these mutant forms of alpha(2)PI. Degradation of the two mutant alpha(2)PI proteins, mediated by proteasomes, occurred after a lag time of 1.5 h during which glucose trimming took place. The mutant alpha(2)PI proteins were not ubiquitinated. Inhibition of mannosidase activity blocked the degradation of the mutant alpha(2)PI proteins without resulting in any changes in their binding to calnexin. Inhibition of glucose removal completely blocked the interaction between the alpha(2)PI proteins and the molecular chaperone calnexin. Under these conditions, mannose residues were removed from the oligosaccharides even when glucose residues were not processed. With mannose removal, the glucose-untrimmed mutant forms of alpha(2)PI, which failed to bind to calnexin, were degraded by proteasomes. The initiation of mannose trimming was a prerequisite for their degradation. Our findings show that modification of oligosaccharides of the mutant forms of alpha(2)PI determines their recognition by the degradation apparatus and that mannose trimming is important for targeting the mutant alpha(2)PI proteins for the degradation pathway.

1-Deoxynojirimycin↗

PubMed2000

Segmenting skin lesions with partial-differential-equations-based image processing algorithms.

In this paper, a partial-differential equations (PDE)-based system for detecting the boundary of skin lesions in digital clinical skin images is presented. The image is first preprocessed via contrast-enhancement and anisotropic diffusion. If the lesion is covered by hairs, a PDE-based continuous morphological filter that removes them is used as an additional preprocessing step. Following these steps, the skin lesion is segmented either by the geodesic active contours model or the geodesic edge tracing approach. These techniques are based on computing, again via PDEs, a geodesic curve in a space defined by the image content. Examples showing the performance of the algorithm are given.

Algorithms↗

PubMed2000

Three cases of pancreas allograft dysfunction.

We present dincopathologic features of three cases of biopsy-proven pancreas allograft dysfunction in Korea. All patients had advanced insulin-dependent diabetes mellitus (IDDM). Case 1 was a 30-year-old woman who underwent a simultaneous pancreas-kidney transplantation. Urinary infection developed 6 days after the operation, which remitted and reappeared, when urine amylase level was normal. Since the 55th day after the operation, intermittent hematuria has persisted. Cytomegalovirus inclusions were detected on the urinary bladder and grafted duodenal mucosa. The graft was removed due to perforation of the grafted duodenum and panperitonitis. Case 2 was a 27-year-old man undergoing pancreas transplantation alone (PTA). Ten days after the transplatation, the level of 24 urine amylase decreased and the graft was not delineated by 99mTc DTPA scintigraphy. Allograft needle biopsy revealed multiple acinar cell necrosis and mild lymphocytic infiltration which were compatible with mild acute rejection. Case 3 was a 25-year-old man undergoing cadevaric PTA. Three months after the transplantation, graft was removed due to gastric perforation associated with cytomegalovirus and angiodestructive fungal infection. Various causes of pancreas allograft dysfunction can be diagnosed by needle biopsy, thus appropriate biopsy specimen should be taken using improved biopsy technique.

Adult↗

PubMed2000

A novel point mutation of the splicing donor site in the intron 2 of the plasmin inhibitor gene.

Plasmin inhibitor (PI) is a major physiological inhibitor of plasmin-mediated fibrinolysis; hence, its deficiency results in a severe haemorrhagic diathesis. We analyzed the PI gene of a French boy apparently homozygous for PI deficiency and his heterozygous parents. Both alleles of the homozygous patient had a novel G to A transition at the consensus splicing donor site in the intron 2 of the PI gene. In an expression assay using the heterologous cells transfected with the mutant PI expression vector, 3 types of aberrant transcripts using a cryptic splicing donor site within the intron 2 were detected. All of these mRNAs had a stop codon upstream of the cryptic splicing site and encode only 25 amino acids, comprising the first 21 amino acids of the signal peptide (27 amino acids) plus 4 new amino acids. This mutant was designated as PI-Paris-Trousseau.

Animals↗