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Biomedical subjects

J Ye

Publications and source records attributed to J Ye.

At least 253 records · Page 14Linked to original sources
PubMed1994

Characterization of antigenic determinants in the core antigen of the hepatitis C virus.

Antibodies to the hepatitis C virus (HCV) core protein are present in the majority of patients with chronic HCV infection. To characterize the corresponding determinants, synthetic peptides and various deletion clones of the core gene expressed in Escherichia coli were used to test human anti-core positive sera or rabbit anti-peptide antibodies in enzyme-linked immunosorbent assays, immunoblots, and competition assays. Two distinct linear antigenic determinants which are located within aa 1 to 20 and between aa 30 and 47 were found. Further studies using reactive serum after preabsorption of antibodies with N- and C-terminal-deleted HCV core proteins or with peptides directed to the linear epitopes revealed an additional determinant that requires for presentation the participation of the N-terminal 69 amino acids. It is postulated that the HCV core protein forms a three-dimensional structure exposing two linear epitopes and, in addition, presents a conformational determinant within the N-terminal 69 amino acids. The remaining core amino acid sequence spanning from position 69 to 191 does not seem to expose further determinants to induce additional anti-core antibodies.

Animals↗
PubMed1994

Monoclonal antibody specific for alpha 2-->8-linked oligo deaminated neuraminic acid (KDN) sequences in glycoproteins. Preparation and characterization of a monoclonal antibody and its application in immunohistochemistry.

Two particular types of sialoglycoproteins have been detected in fish: polysialoglycoproteins containing alpha 2-->8-linked polysialic acid (-->8Neu5Gc alpha 2-->)n present in unfertilized Salmonidae fish eggs, and glycoproteins bearing oligo/polymers of deaminated neuraminic acids (KDN) found in the vitelline envelope of the eggs and ovarian fluid. We report the preparation and characterization of a monoclonal antibody specifically recognizing oligo/polymers of KDN sequences in glycoproteins and its application in immunohistochemistry. Fusion of spleen cells from a BALB/c mouse immunized with a KDN-rich glycoprotein (KDN-gp) containing (-->8KDN alpha 2-->)n-->6(KDN alpha 2-->3Gal beta 1-->3G alpha lNA-c alpha 1-->3) GalNAc alpha 1-->residues, with mouse myeloma cells yielded a hybrid cell line producing a monoclonal antibody that bound to KDN-gp, but not to KDN-gp depleted of KDN residues. The specificity of the monoclonal antibody, designated mAb.kdn8kdn, was determined by an enzyme-linked immunosorbent assay using KDN-gp samples that varied in KDN content. These antigens were prepared by the selective removal of KDN residues from the native KDN-gp. The mAb.kdn8kdn reacted most strongly with the intact KDN-gp and less strongly with KDN-gp samples containing decreased numbers of KDN residues.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

On-line respiratory artefact removal via adaptive FIR filters in rheopneumographic measurement.

Impedance rheopneumography is a simple non-invasive technique that can reflect the vascular condition in the human pulmonary circulatory system. However, the much larger and almost in-banding respiratory artefact present has greatly restricted its usefulness to only respiratory patients of a less severe type, in view of the existing practice of requiring the subject to stop breathing momentarily during measurement. Conventional fixed or adaptive filtering cannot satisfactorily remove the artefact in view of the non-time stationary characteristic of the latter. In the paper, a fast adaptive FIR filter design method, which is based on the filter coefficient look-up table (CLT) concept, is presented as a solution. The CLT is constructed with the coefficients indexed to the cut-off frequency to separate the two components of the plethysmogram. An on-line fast Fourier transform is calculated to track the cut-off frequency. This filter can adaptively change its coefficients, not only for different subjects, but also for the same subject during long-term monitoring. Results show that this filter design is capable of providing an almost respiratory artefact-free signal for a majority of patients. The high speed of implementation also renders it a possibility for real-time monitoring applications.

Humans↗
PubMed1994

An analytical approach to quantitative reconstruction of non-uniform attenuated brain SPECT.

An analytical approach to quantitative brain SPECT (single-photon-emission computed tomography) with non-uniform attenuation is developed. The approach formulates accurately the projection-transform equation as a summation of primary- and scatter-photon contributions. The scatter contribution can be estimated using the multiple-energy-window samples and removed from the primary-energy-window data by subtraction. The approach models the primary contribution as a convolution of the attenuated source and the detector-response kernel at a constant depth from the detector with the central-ray approximation. The attenuated Radon transform of the source can be efficiently deconvolved using the depth-frequency relation. The approach inverts exactly the attenuated Radon transform by Fourier transforms and series expansions. The performance of the analytical approach was studied for both uniform- and non-uniform-attenuation cases, and compared to the conventional FBP (filtered-backprojection) method by computer simulations. A patient brain X-ray image was acquired by a CT (computed-tomography) scanner and converted to the object-specific attenuation map for 140 keV energy. The mathematical Hoffman brain phantom was used to simulate the emission source and was resized such that it was completely surrounded by the skull of the CT attenuation map. The detector-response kernel was obtained from measurements of a point source at several depths in air from a parallel-hole collimator of a SPECT camera. The projection data were simulated from the object-specific attenuating source including the depth-dependent detector response. Quantitative improvement (>5%) in reconstructing the data was demonstrated with the nonuniform attenuation compensation, as compared to the uniform attenuation correction and the conventional FBP reconstruction. The commuting time was less than 5 min on an HP/730 desktop computer for an image array of 1282*32 from 128 projections of 128*32 size.

Brain↗
PubMed1994

Quantitative reconstruction for myocardial perfusion SPECT: an efficient approach by depth-dependent deconvolution and matrix rotation.

An efficient reconstruction method for myocardial perfusion single-photon emission computed tomography (SPECT) has been developed which compensates simultaneously for attenuation, scatter, and resolution variation. The scattered photons in the primary-energy-window measurements are approximately removed by subtracting the weighted scatter-energy-window samples. The resolution variation is corrected by deconvolving the subtracted data with the detector-response kernel in frequency space using the depth-dependent frequency relation. The attenuated photons are compensated by recursively tracing the attenuation factors through the object-specific attenuation map. An experimental chest phantom with defects inside myocardium was used to test the method. The attenuation map of the phantom was reconstructed from transmission scans using a flat external source and a high-resolution parallel-hole collimator of a single-detector system. The detector-response kernel was approximated from measurements of a point source in air at several depths from the collimator surface. The emission data were acquired by the same detector setting. A computer simulation using similar protocols as in the experiment was performed. Both the simulation and experiment showed significant improvement in quantification with the proposed method, as compared to the conventional filtered-backprojection technique. The quantitative gain by the additional deconvolution was demonstrated. The computation time was less than 20 min on a HP/730 desktop computer for reconstruction of a 1282 x 64 array from 128 projections of 128 x 64 samples.

Algorithms↗
PubMed1994

Isolation and sequence analysis of polyketide synthase genes from the daunomycin-producing Streptomyces sp. strain C5.

A contiguous region of about 30 kbp of DNA putatively encoding reactions in daunomycin biosynthesis was isolated from Streptomyces sp. strain C5 DNA. The DNA sequence of an 8.1-kbp EcoRI fragment, which hybridized with actI polyketide synthase (PKS) and actIII polyketide reductase (PKR) gene probes, was determined, revealing seven complete open reading frames (ORFs), two in one cluster and five in a divergently transcribed cluster. The former two genes are likely to encode PKR and a bifunctional cyclase/dehydrase. The five latter genes encode: (i) a homolog of TcmH, an oxygenase of the tetracenomycin biosynthesis pathway; (ii) a PKS Orf1 homolog; (iii) a PKS Orf2 homolog (chain length factor); (iv) a product having moderate sequence identity with Escherichia coli beta-ketoacyl acyl carrier protein synthase III but lacking the conserved active site; and (v) a protein highly similar to several acyltransferases. The DNA within the 8.1-kbp EcoRI fragment restored daunomycin production to two dauA non-daunomycin-producing mutants of Streptomyces sp. strain C5 and restored wild-type antibiotic production to Streptomyces coelicolor B40 (act VII; nonfunctional cyclase/dehydrase), and to S. coelicolor B41 (actIII) and Streptomyces galilaeus ATCC 31671, strains defective in PKR activity.

Amino Acid Sequence↗
PubMed1994

Exogenous intracellular, but not extracellular, iron augments myocardial reperfusion injury.

Although previous studies using iron chelators suggest that iron-catalyzed reactions exacerbate myocardial injury, a direct demonstration of the timing, sites, and mechanisms of iron-mediated damage during reperfusion has been lacking. Catalytic doses of redox-active iron react with exogenously administered oxygen radical-generating systems to exacerbate myocardial injury. In an analogous manner, catalytic doses (5 microM) of excess iron present during early reperfusion should augment oxidative injury, if the redox-active iron is present in the same compartment as both the oxygen radicals generated during reperfusion as well as the critical biochemical targets of oxidative injury. We determined whether catalytic doses of iron given during early reperfusion could exacerbate myocardial injury and whether iron-catalyzed injury required intra- or extracellular iron. Buffer-perfused rabbit hearts underwent 30 min of 37 degrees C global ischemia and 30 min of reperfusion. Iron (5 microM), attached to ligands that either restrict iron to the extracellular space (ADP) or facilitate the entry of iron into myocytes (omadine, tropolone), was infused during the last 3 min of ischemia and the first 4 min of reperfusion. Recovery of developed pressure was decreased (P < 0.05) in omadine-iron and tropolone-iron compared with ADP-iron and noniron hearts treated with ligands alone. Tissue lipid peroxide levels, an index of oxidative injury, were increased (P < 0.05) by omadine-iron and tropolone-iron, but not ADP-iron. The oxidative damage caused by omadine-iron was blocked by pretreatment with dimethylthiourea, a cell-permeable scavenger of the hydroxyl radical.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Diphosphate↗
PubMed1994

Prevention of lipid peroxidation does not prevent oxidant-induced myocardial contractile dysfunction.

We tested whether, with exposure to an extraneous iron-catalyzed free radical-generating system, prevention of lipid peroxidation with U74006F, a 21-aminosteroid, could also prevent myocardial contractile dysfunction. Rabbits received either U74006F (10 mg/kg iv) or vehicle (V). Thirty minutes later the hearts were excised and perfused by a non-recirculating Langendorff technique. Six U74006F- and six V-treated hearts were exposed for 7.5 min to a .OH-generating system (H2O2 and Fe(2+)-ADP chelate). Myocardial lipid peroxides were measured by glutathione peroxidase-catalyzed oxidation of exogenous glutathione. With exposure to .OH, cytosolic lipid peroxide levels were increased threefold in V-treated hearts, but there was no increase in U74006F-treated hearts. After 30 min of recovery, developed pressure and maximum first derivative of left ventricular pressure were greater in U74006F-treated hearts than in V-treated hearts but were still 50 and 44% of levels in saline hearts, respectively. Coronary flow was markedly reduced after exposure to free radicals and was only slightly less depressed when U74006F was administered. When coronary flow following oxidant exposure was increased by nitroglycerin, U74006F again only modestly improved systolic function. Thus, although U74006F blocked lipid peroxidation, it only slightly improved the ventricular dysfunction caused by .OH. Therefore, factors other than lipid peroxidation play a major role in oxidant-induced myocardial stunning.

Adenosine Diphosphate↗
PubMed1994

Dexamethasone induced proliferation of cultured retinal pigment epithelial cells.

Dexamethasone (DEX) is a glucocorticoid that is widely used after vitreoretinal surgery and may have mitogenic properties. This study was initiated to determine if human cultured retinal pigment epithelium (RPE) cells express glucocorticoid receptor and proliferate in response to DEX stimulation. Glucocorticoid receptor mRNA was detected in RPE cells by means of reverse transcriptase polymerase chain reaction. To determine the effect of DEX on RPE cell proliferation in vitro, we cultured human RPE cells with various concentrations for DEX for 5 days and determined the effects on cell number and incorporation of tritiated thymidine. DEX treatment with a DEX dose of 1 microgram/ml in the presence or absence of serum resulted in a maximal 2-3 times increase in cell number. Autoradiography after thymidine incorporation revealed a greater than 2-fold increase in incorporating cells at this same dose. These results indicate that DEX causes cultured human RPE cells to proliferate and suggest that it may have a growth factor-like action.

Cell Count↗
PubMed1994

Cytokine effect on fibronectin release by retinal pigment epithelial cells.

Because fibronectin (FN) is known to be present in membranes in proliferative vitreoretinopathy, we sought to identify cytokines that regulate the release of FN by retinal pigment epithelial cells (RPE). Levels of FN in the supernatant of cultured human RPE cells were quantified with an ELISA, after which the cells were stimulated with human recombinant cytokines, interleukin-1 beta (IL-1 beta), tumor necrosis factor alpha (TNF alpha), interleukin-6 (IL-6), interferon gamma (IFN-gamma), transforming growth factor beta 1 and 2 (TGF-beta), and phorbol myristate acetate (PMA). Protein kinase C (PKC) was blocked by 2 nM calphostin C or 1 mM staurosporine. RPE cells released FN into the supernatant constitutively. TGF-beta 1 and TGF-beta 2 upregulated the FN release in a dose- and time-dependent manner. The other cytokines tested were without effect. In combination, IFN-gamma and IL-1 beta reduced the effect of TGF-beta. PMA, which is a PKC activator, also increased the release of FN in a dose-dependent manner. Blocking of PKC with specific inhibitors abolished the effects of TGF-beta and PMA. The results show that TGF-beta is a potent stimulator of FN release by RPE cells, and exerts its effects via signal transduction involving PKC. Its effect is reduced by IFN-gamma.

Cells, Cultured↗
PubMed1994

High density cultivation of a recombinant CD-1 cell line producing prourokinase using a Biosilon microcarrier culture system.

CD-1, a genetically-engineered CHO cell line, was cultivated with a Biosilon microcarrier culture system. We successfully cultivated CD-1 cells to a very high density (over 1 x 10(7) cells/ml). Prourokinase was stably secreted at about 180 IU/10(6) cells/24 h. Experiments showed that CD-1 cells growing on Biosilon microcarriers were able to spontaneously release from the microcarriers, then reattach and proliferate on fresh microcarriers. This makes it very easy to scale up production. The microcarriers could be reused several times without affecting adhesion, proliferation and prourokinase secretion. With CM-PECC membrane radial flow chromatography and MPG chromatography, the prourokinase in conditioned medium could be purified to a specific activity of 1 x 10(5) IU/mg of protein. The purification factor was about 600 fold, and approximately 90% of the biological activity was recovered.

Animals↗
PubMed1994

Aging increases ischemia-reperfusion injury in the isolated, buffer-perfused heart.

Survival after acute myocardial infarction is decreased in elderly patients as compared with the overall adult population. Although several cardiac and noncardiac causes could contribute to the increased mortality rate, little is known regarding the relative susceptibility of aging myocardium to injury during ischemia and reperfusion. We hypothesized that the elderly heart is intrinsically more susceptible to damage than the adult heart. The recovery of isolated, buffer-perfused rat hearts from elderly animals (Fischer 344 rats, 24 months of age) was compared with that of adult hearts (6 months of age) obtained from the same strain. Hearts underwent 25 minutes of ischemia followed by 30 minutes of reperfusion. Hemodynamic recovery was decreased in elderly (n = 5) as compared with adult (n = 5) hearts, including developed pressure (% of preischemic baseline: elderly 31% +/- 4% vs adult 57% +/- 4%, p < 0.01). Elderly hearts also sustained greater tissue damage, with a markedly increased release of creatine kinase (elderly 2950 +/- 500 U vs adult 860 +/- 345 U, p < 0.01) during the 30-minute reperfusion period. The release of total protein and lactate dehydrogenase, other markers of myocyte injury, was also increased. Thus the elderly rat heart is more susceptible than the adult rat heart to ischemia-reperfusion injury. Greater injury during ischemia and reperfusion in an experimental model of aged myocardium raises the possibility of a more rapid progression of ischemic damage in elderly patients suffering acute myocardial infarction.

Aging↗
PubMed1994

Synthesis and cloning of the human lysozyme gene.

The human lysozyme is an enzyme with potential importance in clinical and industrial application. Owing to the limitation of its natural resource, we are making an attempt to produce the enzyme with the aid of recombinant DNA technology. Twenty-four segments with length ranging from 26 to 38 nucleotides were chemically synthesized by solid phase. The oligonucleotides were joined to form DNA duplexes by two different ligation methods. The entire gene covers a start signal ATG and a BamHI restriction site at its 5' end, and two stop signals TAA TGA and a SphI restriction site at its 3' end, besides the structural gene of human lysozyme. The synthetic gene was cloned into vector M13. The positive colonies were confirmed by dot-blot hybridization and analysis by restriction enzymes. The DNA sequence of the cloned enzyme gene was proved to be correct by M13 dideoxynucleotide chain termination method. The study on gene expression is under way.

Base Sequence↗