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C Y Yang

Publications and source records attributed to C Y Yang.

At least 181 records · Page 10Linked to original sources
PubMed1994

Structure of human apolipoprotein D: locations of the intermolecular and intramolecular disulfide links.

We have determined the primary structure of human apolipoprotein D (apoD) by aligning peptides derived from digestions by cyanogen bromide, trypsin, and chymotrypsin. Our results confirm the primary structure derived from cDNA [Drayna et al. (1986) J. Biol. Chem. 261, 16535-16539]. ApoD consists of 169 amino acid residues, including 5 cysteines. Tryptic peptide analysis indicated that Cys41 and Cys16 are joined by a disulfide bridge. Using a combination of manual Edman degradations and mass spectrometric analysis on a purified cluster of chymotryptic fragments, we identified an intramolecular disulfide bridge between Cys8 and Cys114 and an intermolecular bridge between Cys116 of apoD and Cys6 of apoA-II. In addition, sites of N-glycosylation were found at Asn45 and Asn78. Because apoD contains two intramolecular disulfide linkages and has a high content of proline to disrupt alpha-helical structures, formation of the amphipathic helical regions that characterize the other soluble apolipoproteins is unlikely. We conclude that apoD binds to lipoprotein surfaces through structures other than alpha-helices, such as disulfide links.

Amino Acid Sequence↗
PubMed1994

Structure and orientation of apo B-100 peptides into a lipid bilayer.

Peptides corresponding to lipid binding domains of Apo B-100 were synthesized, purified, and incubated with dimyristoylphosphatidylcholine (DMPC) liposomes. The secondary structure of the apo B-100 peptide-lipid complexes was evaluated by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). Those peptides belonging to the hydrophobic "core" domain of apo B-100 when associated with phospholipids were rich in beta sheet structure; a predominant alpha helical conformation was shown to be associated with one peptide located in a surface region of apo B-100. IR dichroic spectra revealed, in the case of the "core" peptides, that the beta sheet component is the only oriented structure with respect to the phospholipid acyl chains. This orientation of the beta sheet was recently found in LDL particles after proteolytic digestion by trypsin (Goormaghtigh, E., Cabiaux, V., De Meutter, J., Rosseneu, M., and Ruysschaert, J. M., 1993, Biochemistry 32, 6104-6110). Altogether, the data suggest that beta sheet, present in a high proportion in the native apo B-100, is probably another protein structure in addition to the amphipathic helix which strongly interacts with the lipid outer layer surrounding the LDL particle.

Apolipoprotein B-100↗
PubMed1994

Rat C-reactive protein causes a charge modification of LDL and stimulates its degradation by macrophages.

We have previously shown the binding of low-density lipoprotein (LDL) to immobilized rat C-reactive protein (CRP) and the formation of a fluid-phase complex between these two proteins. In this report we used immunoelectrophoresis and agarose gel electrophoresis to show increased anodic migration of the LDL particle as a result of the modification of LDL by rat CRP. The degradation of the modified 125I-LDL by rat peritoneal macrophages was increased more than twofold in the presence of rat CRP. The increase in rat CRP-mediated 125I-LDL degradation by macrophages was dependent on the concentrations of 125I-LDL and rat CRP. This increased 125I-LDL degradation was inhibited by phosphorylcholine. In contrast, the degradation of 125I-acetyl-LDL by macrophages was not affected by rat CRP, although acetylated LDL inhibited the rat CRP-stimulated degradation of 125I-LDL. Increasing concentrations of LDL did not affect the degradation of rat 125I-CRP by the macrophages, which suggested that the rat CRP and the modified LDL did not enter the cell as a complex. Our results suggested that the increased degradation of 125I-LDL was caused by the charge modification of 125I-LDL by rat CRP, due to a fluid-phase complex formation between 125I-LDL and rat CRP, and that the degradation involved the scavenger receptor present on the macrophages.

Animals↗
PubMed1994

Regulation of PG synthase by EGF and PDGF in human oral, breast, stomach, and fibrosarcoma cancer cell lines.

Prostaglandins may inhibit or promote tumor cell replication, depending on the cell system that is investigated. In our laboratory, we have established and characterized four different specific human cancer cell lines. The objectives of this study were to examine and compare the prostaglandin endoperoxide synthase (PG synthase, EC 1.14.99.1) activity of these cell lines by measuring the conversion of arachidonate to 3H-PGE2 and 3H-PGF2 alpha. We found that the oral epidermal carcinoma cell line (OEC-M1) had a moderate degree of PG synthase activity. Enzyme activity could be partially blocked (statistically significant) by the addition of epidermal growth factor (EGF) at 20 ng/mL and almost completely inhibited by platelet-derived growth factor at (PDGF) 20 mU/mL. By contrast, we discovered that the human breast adenocarcinoma cell line (BC-M1) did not contain significant PG synthase, and enzyme activity could be significantly activated by the addition of epidermal growth factor at 20 ng/mL and platelet-derived growth factor at 20 mU/mL. We also found that the human stomach adenocarcinoma cell line (SCM-1) had a significant amount of PG synthase activity, and these PG synthase activities were not activated or inhibited by EGF at 20 ng/mL or PDGF at 20 mU/mL. Furthermore, the human fibrosarcoma (FS-M1) cell line also contained a moderate degree of PG synthase activity, which could be significantly inhibited by PDGF at 20 mU/mL but was not inhibited by EGF at 20 ng/mL. The results suggest that EGF and PDGF may be involved in the regulation of the PG synthase activities of human oral, breast, stomach, and fibrosarcoma cancer cells.

Adenocarcinoma↗
PubMed1994

Immunoreactivity of apolipoprotein B-100 in oxidatively modified low density lipoprotein.

Thirteen monoclonal antibodies (MAbs) against apolipoprotein B-100 (apo B) were used to analyze changes in immunoreactivity of human LDL resulting from oxidation mediated by cupric ions and oxygen. Decrease in immunoreactivity of oxidized LDL was demonstrated by competitive ELISA with MAbs 5F8, BL3, Mb43, 2G8, B3, B5, and BL7 for which the epitopes are located within residues 1-1297, 4235-4355, 4027-4081, 3728-4306, 2239-2331, 1854-1878, and in the vicinity of residue 2331, respectively. Immunoreactivity of the epitope B6 (2239-2331) increased during first 4 hours of oxidation and then diminished gradually. Epitope B1 (405-539) had slightly reduced immunoreactivity during first 8 h of LDL oxidation and then its minor increase was observed. MAb 12G10, specific to the epitope within apo B thrombin-digest fragment T4 (1-1297), displayed either weak or strong binding to LDL. LDL with weak binding pattern demonstrated significant increase in immunoreactivity upon oxidation. In contrast, LDL with strong binding pattern showed little to no change. Epitopes Mb47 (3441-3569) and 8G4 (1-1297) remained unchanged in oxidized LDL. Immunoreactivity of apo B-100 epitope recognized by MAb 4C11 (residues 2377-2658) was shown to be a function of oxidation time: it increased progressively up to 16 h and was stabilized for another 24 h of LDL oxidation. This epitope may be unmasked by LDL oxidation and may provide a useful immunochemical marker to monitor the extent of LDL oxidation.

Antibodies, Monoclonal↗
PubMed1994

Insulin autoimmune syndrome in a patient with methimazole and carbimazole-treated Graves' disease: a case report.

Insulin autoimmune syndrome (IAS) includes fasting or reactive hypoglycemia, hyperinsulinemia and the presence of insulin-binding antibodies in patients who have never been exposed to exogenous insulin. The report concerns a 34-year-old male patient with Graves' disease who had history of having taken methimazole for two months, without any consequence, 4 years previously. However, when methimazole was again administered for three weeks followed by a week of carbimazole, the patient suffered hypoglycemia 4 times during the next 4 weeks. He denied history of diabetes mellitus (DM), of taking any oral hypoglycemic agent or of having received insulin injection. Laboratory data showed total serum insulin level > 320 microU/mL, free insulin 55 microU/mL and insulin antibody 88.3%. Oral glucose tolerance test (OGTT) revealed DM pattern. Since the patient had history of allergy to anti-thyroid drugs before this event, so he was treated with radioiodine (131I). There was no episode of hypoglycemic attack during 15 months of follow-up.

Adult↗
PubMed1994

The healing of grafts combining freeze-dried and demineralized allogeneic bone in rabbits.

The adjunctive role of demineralized bone matrix (DBM) in enhancing the incorporation of segmental freeze dried (FD)-allogeneic bone grafts has been studied in the rabbit ulna and fibula. The studies compared the healing patterns of fresh segmental autografts, FD-allografts, DBM-allografts, and FD-allografts supplemented at the graft-host junctions with FD- or DBM-allografts as particulates (ulna) or as segmental struts (fibula). The outcome was evaluated at five and ten weeks by a radiologic score, by biomechanical properties (breaking strength, energy to failure, stiffness), and histology. The ulnar autografts healed most rapidly (ten weeks = 100%), followed by DBM allografts (60%). By all criteria, FD-allografts were poorly incorporated (20-40%), and the process was not improved by supplements of FD- or DBM-particulate/strut bone. Histologically, the DBM component of composite fibular strut grafts was osteoinductive and united with host tissues within 35 days. The contiguous FD-allograft struts were not incorporated, showing fibrocartilaginous nonunions and resorptive foci. While the addition of DBM does not protect FD-allograft integrity in the rabbit, segmental mineralized FD-allografts could provide mechanical support for some intervals until, in such composite grafts, osteoinductive processes produced biomechanically competent new bone.

Animals↗
PubMed1993

Degradation of rat C-reactive protein by macrophages.

Rat C-reactive protein (CRP) is a serum glycoprotein belonging to the 'pentraxin' family of proteins. In this study we have shown the specific binding of 125I-CRP to rat peritoneal macrophages at 4 degrees C. This binding was dependent upon incubation time, CRP and cell concentrations, and was not inhibited by either phosphorylcholine or human IgG. At 37 degrees C, the surface-bound 125I-CRP was internalized and degraded. The degradation of 125I-CRP was measured by the formation of 125I-labelled trichloroacetic-acid-soluble CRP peptides by either precipitation assays or by h.p.l.c. of the incubation medium using a gel-filtration column. Since chloroquine and leupeptin inhibited CRP degradation, it was concluded that degradation of CRP occurred in the lysosomal compartment of the macrophage. There was an absolute requirement for the presence of bivalent cations (Ca2+ and Mg2+) in the incubation medium for the binding and degradation of CRP, which could be inhibited by EDTA but not by phosphorylcholine or human IgG. H.p.l.c. analysis of the medium obtained from incubation of macrophages with 125I-CRP revealed the presence of 125I-labelled low-M(r) peptides, the formation of which was dependent upon incubation time.

Animals↗
PubMed1993

The shear strength and the failure mode of plasma-sprayed hydroxyapatite coating to bone: the effect of coating thickness.

Plasma-sprayed hydroxyapatite coated (HAC) 50 and 200 microns thick on Ti-6Al-4V cylinders was transcortically implanted in the femora of canines to evaluate in detail the effect of coating thickness on the pushout shear strength and failure mode examined under scanning electron microscope after the periods of 4, 6, 8, and 12 weeks. The HAC coating exhibited higher shear strength at 50 microns than at 200 microns. Its failure mode was conclusively at or near the HAC-bone interface, and the slight attack of body fluid had not degraded the implant to the extent that failure occurred at the HAC-Ti alloy interface after 12 weeks of observation. For 200 microns-HAC, failure was found at the HAC-bond interface, inside the HAC lamellar splat layer and at the HAC-Ti alloy substrate interface, depending on the period of implantation. It was also deduced that the variation of failure mode of 200 microns-HAC with time could not be accounted for by the attack of body fluid alone; the degradation must be a synergetic adverse result of residual stress in the HAC and the attack of body fluid.

Analysis of Variance↗
PubMed1993

Liquid chromatographic analysis of amino acids: using dimethylamino-azobenzenesulfonyl chloride and Hypersil ODS column to analyze the composition of apo B peptides.

A reliable high-performance liquid chromatography (HPLC) method is described for the separation of dimethylamino-azobenzenesulfonyl-amino acid (DABS-AA). The separation is accomplished by reversed-phase chromatography on a Hypersil ODS column (4.6 x 150 mm) with a Hewlett-Packard liquid chromatography system. In addition to the developed sample and solvent preparation procedure, this precolumn modification method using dimethylaminoazobenzene sulfonyl chloride (DABS-CL) for amino acid analysis is proved reliable and sensitive. Five apolipoprotein B-100 tryptic peptides, two of them containing cysteine, were demonstrated as examples for the general application of this method in amino acid analysis. It is a useful method for analysis of cysteine- and cystine-containing peptide and, furthermore, for determination of sulfhydryl and disulfide linkages of proteins.

Amino Acid Sequence↗
PubMed1993

Primary structure of Beijing duck apolipoprotein A-1.

The primary structure of Beijing duck apolipoprotein A-1 was determined by sequencing peptide fragments derived from tryptic and endoproteinase Asp-N digestion of the protein, and alignment with homologous chicken apo A-1. All of the peptide fragments were isolated by high-pressure liquid chromatography (HPLC) with a Vydac C18 column using a trifluoroacetic acid (TFA) buffer system. The N-terminus of the protein was determined to be aspartic acid by directly sequencing 52 residues of the intact protein. The C-terminus was alanine. The protein contains 240 amino acid residues. By analysis of the whole protein and its tryptic peptides, a six amino acid (Arg-Tyr-Phe-Trp-Gln-His) prosegment was determined. No cross-reactivity between duck and human apo A-1 with a goat antiserum against human apo A-1 was found. Sequence analysis of apo A-1 of other species indicates that amino acid substitutions in rat are more extensive than in other mammals. Isoleucine residues in apo A-1 are inversely correlated to the homology of human to other species, except dog.

Amino Acid Sequence↗
PubMed1993

Proposed mechanisms for binding of apo[a] kringle type 9 to apo B-100 in human lipoprotein[a].

The protein component of human lipoprotein[a] consists primarily of two apolipoproteins, apo[a] and apo B-100, linked through a cystine disulfide(s). In the amino acid sequence of apo bd, Cys4057 located within a plasminogen kringle 4-like repeat sequence (3991-4068) is believed to form a disulfide bond with a specific cysteine residue in apo B-100. Our fluorescence-labeling experiments and molecular modeling studies have provided evidence for possible interactions between this apo[a] kringle type and apo B-100. The fluorescent probe, fluorescein-5-maleimide, was used in parallel experiments to label free sulfhydryl moieties in lipoprotein[a] and low-density lipoprotein (LDL). In apo B-100 of LDL, Cys3734 was labeled with the probe, but this site was not labeled in autologous lipoprotein[a]. The result strongly implicates Cys3734 of apo B-100 as the residue forming the disulfide linkage with Cys4057 of apo[a]. To explore possible noncovalent interactions between apo B-100 and apo[a], the crystallographic coordinates for plasminogen kringle 4 were used to generate molecular models of the apo[a] kringle-repeat sequence (3991-4068, LPaK9), the only plasminogen kringle 4 type repeat in apo[a] having an extra cysteine residue not involved in an intramolecular disulfide bond. The Cys4057 residue (henceforth designated as Cys67 in the LPaK9 sequence) is believed to form an intermolecular disulfide bond with a cysteine of apo B-100. In computer graphics molecular models of LPaK9, Cys67 is located on the surface of the kringle near the lysine ligand binding site. Selected segments of the LDL apo B-100 sequence that contain free sulfhydryl cysteines were subjected to energy minimization and docking with the ligand binding site and adjacent regions of the LPaK9 model. In the docking experiments, apo B-100 segment 3732-3745 (PSCKLDFREIQIYK) displayed the best fit and the largest number of van der Waals contacts with models of LPaK9. Other apo B-100 peptides with sulfhydryl cysteine were found to be less compatible when minimized with this kringle. These results support and extend previously suggested mechanisms for a complex interaction between apo[a] and apo B-100 that involve more than a simple covalent disulfide bond.

Amino Acid Sequence↗
PubMed1993

Effect of irrigation fluids on the articular cartilage: a scanning electron microscope study.

Four irrigation solutions, two for general arthroscopic examination and two for electrosurgery, were evaluated for their effects on the ultrastructure of the articular cartilage surface using an animal model with a scanning electron microscope (SEM). The murine knee joints were irrigated continuously for 1 or 2 h with normal saline, Ringer's lactate, 3% sorbitol, or distilled water, respectively. The articular cartilage of the patella was evaluated in situ; that is, the cartilage was kept intact as it related to the underlying bone tissue, so that artifacts during the biopsy procedure could be prevented. Results of the study showed no significant differences among the four solutions and the unirrigated control group. We conclude that Ringer's lactate, normal saline, distilled water, and 3% sorbitol can all be safely used as irrigation solutions in arthroscopic surgery.

Animals↗
PubMed1993

Complete membranous obstruction of the inferior vena cava: clinical characteristics of Chinese patients.

OBJECTIVES: To analyse the clinical presentations of membranous-type Budd-Chiari syndrome and the long-term outcome of balloon angioplasty. DESIGN: A case-control study. Patients who received abdominal sonography and were suspected of having hepatic venous outflow obstruction were advised to receive cardiac catheterization and angiography. SETTING: Patients were collected from Chung Hisao Hospital and Chang Gung Medical Centre. Angioplasty was done at Chang Gung Medical Centre. SUBJECTS: Seventeen patients who had the symptoms and signs of portal hypertension were suspected of having hepatic venous outflow obstruction after abdominal sonography and a radionuclide liver scan and eight of them were confirmed as having membranous-type obstruction. INTERVENTIONS: Simultaneous catheterization and contrast angiography was performed via the right brachial and femoral veins. Angioplasty was performed afterwards. MAIN OUTCOME MEASURES: The remission of clinical symptoms and signs and a decrease of the pressure gradient between the right atrium and inferior vena cava were used as indicators of successful intervention. RESULTS: All patients had remarkable remission of symptoms and signs. The average pressure gradient between right atrium and inferior vena cava dropped from 16.5 +/- 1.6 to 6.5 +/- 1 mmHg (mean +/- SD). CONCLUSION: The clinical presentations of membranous-type Budd-Chiari syndrome are somewhat different from hepatic vein occlusion. Balloon angioplasty may be a modality for curing this disease. A larger patient population is necessary to confirm this study.

Adult↗
PubMed1993

[The relationship between loading on the TMJ and occlusal splints]

The primary purpose of this study is to estimate loading conditions on the TMJ with five different occlusal splint.We developed a model that simulated dynamic relationship between dental occlusion,masticatory muscles and TMJ.It is demonstrated that loading on the condyle increases whatever kinds of splints are used.The anterior splint brings about larger loading on the condyle than any other splint.When the ratio force of the muscle on the non pivot is1,left-side pivot split makes loading on left condyle decrease and right increase.It was change on both condyles when posterior teeth are missing including loading, contact and unilateral mastication.

Journal Article↗
PubMed1993

[An investigation on public awareness, attitude and behavior toward drinking water quality in Taiwan].

The objective of this study was to investigate the public awareness, attitude and behavior toward drinking water quality. The results showed that (1) Overall, 80.6% of those responding to the survey rated their local drinking water quality as above average or better. (2) Even though most people were happy with the present quality of their drinking water, 79.2% of the public characterized themselves as concerned about encountering substances in drinking water in their lifetime that could lead to bad health effect or death. (3) 73.8% of the survey respondents never examined the water facilities for their own use.

Adult↗
PubMed1993

[Workplace risk factors associated with eye syndrome in office workers].

Four large sealed office buildings were investigated to determine the relationship between the prevalence of sick building syndrome and the indoor air quality. Questionnaires were distributed to all building occupants. Respondents suffered from upper airway, eye, lower airway and many less specific complaints. Multivariate logistic regression analyses were conducted to assess workplace risk factors associated with eye syndrome. Working with visual display terminals, glare, use of desk lamp, fabric-covered partitions, new carpet, too dim, too bright and lack of openable windows correlated significantly with the prevalence of eye syndrome.

Adult↗