Biomedical subjects

C Yang

Publications and source records attributed to C Yang.

At least 361 records · Page 20Linked to original sources

PubMed1997

[Micro-particle image processing based on an artificial neuron network with fluid properties].

The form of macro-particle is a close successive region in two-valued micro-particle image, and the detection of microparticles is actually that of close successive regions. Accordign to this theory, this paper present a new technique for micro-particles detecting based on an artificial neuron network modeled on the diffusing behaviour of real visual system, which has fluid properties. The results of simulation on computer shew that this method is very effect.

Blood Cell Count↗

PubMed1997

[The development of a laser back-scattering erythrocyte-aggregometer].

In this paper, an erythrocyte-aggregometer based on the analysis of the light intensity back-scattered by a blood suspension is presented and described in detail. It allows to approach aggregation phenomenon in terms of kinetics, structural and rheological parameters. A personal computer and a microcomputer are applied to automate the system's sampling, data-processing and data-restoring procedure.

Equipment Design↗

PubMed1997

[A four-box multi-function testing system of pharmacology reaction].

The organism position matrix method, a new method of testing pharmacology reaction is proposed. On the basis of the method, we have developed a four-box multi-function testing system which can test the spontaneous activity, analgesic effect, and learning and memory ability of 1 to 4 mice in three dimensions respectively. Four quantitative parameters, the total distance, the movement intensity, the vertical number and the jumping number are put forward to describe the spontaneous activity. The starting time of continuous jumping and the jumping number are used to describe the analgesic effect. The time from the electrical shock to escape onto a safety platform and the number of the electrical shock are used to describe the learning and memory ability. The system has the characteristics of good repeatability, high efficiency, quantitative and automatic control.

Animals↗

PubMed1997

[The clinical effect after locally using mitomycin C during trabeculectomy in glaucoma].

To improve the function of filtering blebs after trabeculectomy, we divided randomly 44 patients (60 eyes) with moderate or late glaucoma into mitomycin C and control groups (30 eyes per group). Two small surgical sponges were soaked with 0.2 mg.ml-1 mitomycin C solution. One sponge was put on the top of the superficial scleral flap, the other was placed underneath the scleral flap and contacted with the bed of the scleral flap. After 5 minutes the wound was then irrigated with normal saline. All patients were followed up from 1 to 12 months (7.9 +/- 4.0 months). We found that: (1) functional filtering blebs were 92.9% in the mitomycin C group and 55.2% in the control group (P < 0.01), (2) the decreasing percentage of intraocular pressure (IOP) in the mitomycin C group was much more than that in the control group (P < 0.05), (3) the successful rates of the operation in MMC group were higher than that of the control group, and the visual field was effectively maintained in MMC group.

Administration, Topical↗

PubMed1996

Quantitation of RT-PCR amplified cytokine mRNA by aequorin-based bioluminescence immunoassay.

We described here a bioluminescence-based immunoassay for the quantitation of RT-PCR amplified cytokine mRNA. This technique uses a standard RT-PCR procedure, with the following modifications. The forward primer in the PCR reaction is labeled with a 5' biotin molecule. Following PCR, a digoxigenin-conjugated oligonucleotide probe is hybridized to the target biotin-labeled DNA template. The hybridized duplex is captured onto a streptavidin-coated microtiter plate. The bound product is quantitated by adding digoxigenin-specific antibodies conjugated with the photoprotein aequorin. The amount of specific DNA captured onto the plate is quantitated by triggering the bioluminescence reaction through the addition of calcium ions. This technique detected as low as 40 amol of amplified cytokine products, or 500 copies of templates when 27 PCR cycles were used. The high sensitivity of this technique enables the quantitation of target DNA during the exponential phase of the PCR reaction. The aequorin-bioluminescence assay is an alterative non-radioactive method for the quantitation of PCR products.

Aequorin↗

PubMed1996

Coccidioides immitis antigen 2: analysis of gene and protein.

Antigen 2 is a glycosylated protein present in the cell walls of the dimorphic fungus Coccidioides immitis. Using oligodeoxyribonucleotide (oligo) primers based on the sequences of Ag2 cDNA, the gene encoding Ag2 was cloned from genomic DNA derived from the mycelial phase of C. immitis by PCR. Nucleotide (nt) sequence analyses showed a 582 base pair (bp) ORF disrupted by two introns which are 78 bp and 101 bp long. The deduced primary translation product consists of 194 amino acids (aa), contains an N-terminal putative signal sequence to allow transport into the endoplasmic reticulum, and a C-terminal putative signal sequence to enable a GPI anchor addition. Putative GPI anchor/cleavage site and O-glycosylation sites, as well as phosphorylation and myristoylation sites are also present. On the basis of these analyses, we predict that a prepro-Ag2 undergoes a post-translational modification to yield the mature glycosylated Ag2 protein which is anchored on the extracellular plasma membrane of mycelial and spherule-phase cells.

Amino Acid Sequence↗

PubMed1996

The evidence for the incorporation of fulvic acid into the bone and cartilage of rats.

In animal testing, abdominal injection of commercial fulvic acid (FA) to Wistar rats resulted in the coloration of the bone. Free radical signal was detected by ESR spectra of the bone, which were shown to be dependent upon the dosage of FA injected. The fluorescence spectra, UV spectra and gel permeation chromatography of the alkaline extracts of the bone showed similar characteristics to FA. In in-vivo rat tests and in-vitro experiments of cultured chicken cartilage tissue with tritium labeled FA, the results showed that 3H-FA could be incorporated into the bone and cartilage of rats.

Animals↗

PubMed1996

Molecular cloning and characterization of DdCAD-1, a Ca2+-dependent cell-cell adhesion molecule, in Dictyostelium discoideum.

Dictyostelium discoideum expresses EDTA-sensitive cell-cell adhesion sites soon after the initiation of development, and a Ca2+-binding protein of Mr 24,000 (designated DdCAD-1) has been implicated in this type of adhesiveness. We have previously purified DdCAD-1 to homogeneity and characterized its cell binding activity (Brar, S. K., and Siu, C.-H. (1993) J. Biol. Chem. 268, 24902-24909). In this report, we describe the cloning of DdCAD-1 cDNAs. DNA sequencing revealed a single open reading frame coding for a polypeptide containing 213 amino acids. The identity of the cDNA was confirmed by amino acid sequences of two cyanogen bromide peptides. The deduced amino acid sequence of DdCAD-1 exhibits a relatively high degree of sequence similarity with members of the cadherin family and protein S of Myxococcus xanthus. Unlike the other cadherins, the carboxyl-terminal region of DdCAD-1 contains a Ca2+-binding motif. Although analyses of the sequence suggest that the polypeptide lacks a signal peptide sequence and a transmembrane domain, immunofluorescence microscopy demonstrates the association of DdCAD-1 with the ecto-surface of the plasma membrane. To investigate the structure/function relationships of DdCAD-1, glutathione S-transferase fusion proteins containing different DdCAD-1 fragments were expressed and assayed for their 45Ca2+ and cell binding activities. These studies revealed that the cell binding activity is dependent on the amino-terminal segment and not the carboxyl-terminal Ca2+-binding domain and showed additional Ca2+-binding site(s) within the amino-terminal segment.

Amino Acid Sequence↗

PubMed1996

Palmitoylation of the murine leukemia virus envelope glycoprotein transmembrane subunits.

The envelope protein of Friend murine leukemia virus is modified by fatty acylation of the transmembrane (TM) protein subunit. The labeling by [3H]palmitic acid was found to be sensitive to treatment with the reducing reagents 2-mercaptoethanol and hydroxylamine, indicating the presence of a thioester linkage. Pulse-chase experiments showed that the precursor protein can be labeled by [3H]palmitic acid prior to its cleavage into the surface and TM subunits. By using site-directed mutagenesis, we determined that palmitoylation occurs on a cysteine residue, Cys 606, located in the transmembrane domain. A thin-layer chromatography assay after acid hydrolysis showed that incorporated label comigrated with palmitic acid. When another cysteine residue was introduced into the cytoplasmic tail 22 amino acids from the transmembrane domain, no palmitoylation was observed to occur on this cysteine residue, demonstrating the importance of the position of the cysteine residue for palmitoylation. Sequence comparison revealed that most retrovirus envelope proteins have one or two conserved cysteine residues in their transmembrane domain. Mutations that change the palmitoylation state of the murine leukemia virus envelope protein did not affect its transport, processing, surface expression, or cell fusion activity. The palmitate-deficient viral envelope proteins were incorporated into virus particles, and replication of the virus in vitro was not affected significantly by the mutation of the palmitoylation site.

3T3 Cells↗

PubMed1996

Multiple protein factors interact with the cis-regulatory elements of the proximal promoter in a cell-specific manner and regulate transcription of the dopamine beta-hydroxylase gene.

The dopamine beta-hydroxylase (DBH) gene is expressed selectively in noradrenergic and adrenergic neurons and neuroendocrine cells in the nervous system. A cAMP response element (CRE) residing at -181 to -174 bp from the transcription start site of the human DBH gene seems to be essential for DBH transcription. Potential cis-regulatory motifs such as AP1 and YY1 occur proximal to and overlap this CRE, endowing the area with a composite promoter structure. Using the DBH-expressing human neuroblastoma SK-N-BE(2)C and DBH-negative HeLa cell lines as model systems, we report here that this CRE/YY1/AP1 area interacts with multiple nuclear proteins, including CRE-binding protein (CREB) and transcription factor YY1 in a cell-specific manner. In support of the notion that multiple proteins bind to the CRE/YY1/AP1 area, DNase I foot-printing analysis has demonstrated that nuclear extracts protect an extended region (from -186 to -150 bp) relative to that protected by the purified CREB (from -186 to -171 bp). Site-directed mutational analysis has revealed differential roles of potential cis-regulatory motifs in regulation of DBH transcription. Strikingly, the YY1 element positively regulated basal DBH transcription while simultaneously regulating cAMP-mediated induction negatively, which is a novel mechanism of promoter function. Furthermore, three additional DNA-binding sites have been identified by DNase I footprint analysis in the upstream 260 bp promotor region of the human DBH gene, of which two sites are cell-specific. These results support a model whereby multiple proteins bind to the 5'-proximal area in a cell-specific manner and coordinately regulate the cell type-specific transcriptional activation of the DBH gene.

Base Sequence↗

PubMed1996

Analysis of left-handed Z-DNA formation in short d(CG)n sequences in Escherichia coli and Halobacterium halobium plasmids. Stabilization by increasing repeat length and DNA supercoiling but not salinity.

To evaluate the relative importance of alternating d(CG) sequence length, DNA supercoiling, and salt in left-handed Z-DNA formation, plasmids containing short d(CG)n sequences (n = 3-17) with the capability of replicating in either Escherichia coli or the halophilic archaeum Halobacterium halobium were constructed. Z-DNA conformation in the d(CG)n sequences was assayed by (i) a band shift assay using the Z-DNA-specific Z22 monoclonal antibody (ZIBS assay); (ii) an S1 nuclease cleavage-primer extension assay to map B-Z junctions; and (iii) a BssHII restriction inhibition assay. Using the ZIBS assay on plasmids purified from E. coli, the transition from B-DNA to Z-DNA occurred from d(CG)4, to d(CG)5, with 20% of d(CG)4, and 90% of d(CG)5 in Z-DNA conformation. These findings were consistent with the results of S1 nuclease cleavage observed at B-Z junctions flanking d(CG)4 and d(CG)5 sequences. Resistance to BssHII restriction endonuclease digestion was observed only in supercoiled plasmids containing d(CG)8 or longer sequences, indicating that shorter d(CG)n sequences are in dynamic equilibrium between B- and Z-DNA conformations. When a plasmid containing d(CG)4, was isolated from a topA mutant of E. coli, it contained 25% greater linking deficiency and 40% greater Z-DNA conformation in the alternating d(CG) region. In plasmids purified from H. halobium, which showed 30% greater linking deficiency than from E. coli, 20-40% greater Z-DNA formation was found in d(CG)4-6 sequences. Surprisingly, no significant difference in Z-DNA formation could be detected in d(CG)3-17 sequences in plasmids from either E. coli or H. halobium in the NaCl concentration range of 0.1-4 M.

Base Composition↗

PubMed1996

Development of an optimal protocol for antigen retrieval: a 'test battery' approach exemplified with reference to the staining of retinoblastoma protein (pRB) in formalin-fixed paraffin sections.

The retinoblastoma (RB) gene, which encodes the nuclear RB protein (pRB), is believed to be involved in cell cycle control and cell differentiation. Studies have demonstrated that loss of RB function may play a role in tumour formation and progression of a variety of human tumours, such as bladder, lung, breast, and prostate cancers. The immunohistochemical detection of pRB expression in formalin-paraffin sections of human cancer has potential advantages of convenience, economy, and compatibility with routine surgical pathology practice. In practice, however, results using pRB antibodies on routinely processed, paraffin-embedded tissue have been inconsistent. In this study, the antigen retrieval (AR) method has been applied to the immunohistochemical detection of pRB in paraffin-embedded tissues and a 'test battery' approach has been developed to identify the principal variables that result in the optimal AR protocol. This approach includes the use of buffered solutions at pH 1, 6, and 10 with three different heating conditions (temperatures 120 degrees C, 100 degrees C, and 90 degrees C). In the example described here with antibody RB-WL-1, the low pH solution with the microwave heating at 100 degrees C proved most effective. Both fresh and routinely processed formalin-paraffin tissues of normal and bladder carcinoma were used for a comparison of the pRB immunostaining. The AR method was evaluated by comparing the immunohistochemical staining result on routinely processed formalin-paraffin sections with frozen sections of the same tumour. A consistent intensity of immunohistochemical staining for pRB was achieved using the identified optimal AR protocol on formalin-paraffin sections. All slides showed positive staining of pRB in normal mesenchymal and epithelial tissues. The pattern of pRB localization and intensity of staining was similar to that obtained in frozen sections, though the intensity obtained by AR treatment on paraffin sections was slightly to moderately stronger than that obtained in frozen sections. Once the protocol was identified, it was tested using routinely processed paraffin tissue sections of 245 cases of bladder carcinoma, with consistent pRB immunostaining results. The protocol described is simple to perform and gives reproducible results for evaluation of pRB expression by immunohistochemistry.

Cryopreservation↗

PubMed1996

Plasmodium falciparum: involvement of additional receptors in the cytoadherence of infected erythrocytes to microvascular endothelial cells.

The involvement of additional ligands in the cytoadhesion of PRBC to endothelial cells was studied by the use of human microvascular endothelial cells (HMEC-1), brain microvascular endothelial cells (HBEC-51), umbilical vein endothelial (HUVEC), and C32 melanoma cells as well as soluble CD36, ICAM-1, and thrombospondin in the adhesion assays. Immunostaining showed that ICAM-1 and thrombospondin were expressed by all cell lines, whereas CD36 and VCAM-1 were expressed constitutively only by C32 melanoma cells and HBEC-51, respectively; none of these cells had basal expression of E-selectin. Bindings of the parental HB3 parasite strain to HMEC-1 and HUVEC were higher than that to HBEC-51 and C32 melanoma cells. Selections by panning the parental HB3 through HMEC-1 (HB3EC-6 line) or C32 melanoma cells (HB3C32-6 to HMEC-1 was higher than that to C32 melanoma cells. Antibody or peptide blockade against CD36, ICAM-1, and thrombospondin or preincubation of target cells with TNF-alpha and IFN-gamma did not significantly alter the binding intensity of HB3EC-6 to HMEC-1 and HB3C32-6 to C32 melanoma cells. Preincubation of HMEC-1 with IL-4, however, reduced its binding with HB3EC-6. In vitro selection did not enhance the binding of PRBC to plate-bound CD36 or thrombospondin; binding to ICAM-1 was negligible. The binding of both selected lines was inhibited by dextran sulfate and sulfatides, but not by chondroitin sulfate A. These results suggested that in addition to CD36 and thrombospondin, sulfated glycoconjugates were probably concurrently utilized by these PRBC as receptors. Experiments with freshly isolated Kenyan parasites indicated that they also exhibited a similar mechanism of binding to endothelial cells.

Animals↗

PubMed1996

Human hepatitis B virus and hepatocellular carcinoma. I. Experimental infection of tree shrews with hepatitis B virus.

Tree shrews (Tupaia belangeri chinenesis) can be experimentally infected with human hepatitis B virus (HBV) by inoculation with human serum positive for HBV, the experimental infection rate being 55.21%. Successive infections have been passed through five generations among the tree shrews inoculated with HBV-positive sera from the infected animals, the average infection rate being 94.0%. The experimental infection of tree shrews with HBV may be prevented by immunization with hepatitis B vaccine, the protection rate being 88.89%. Standard serum containing HBV at 10(8) CID (chimpanzee infection dose)/ml, was diluted 10(-6), 10(-7), 10(-8), 10(-9), and 10(-10) and produced infection rates of 80.0%, 88.8%, 66.7%, 55.6% and 42.9% respectively. Thus the CID50 in tree shrews may reach a dilution of 10(-9), which shows that tree shrews are sensitive to HBV infection. These results successfully establish tree shrews as a reliable and useful animal model for research on HBV infection and its relation to hepatocarcinogenesis.

Animals↗

PubMed1996

Human hepatitis B virus and hepatocellular carcinoma. II. Experimental induction of hepatocellular carcinoma in tree shrews exposed to hepatitis B virus and aflatoxin B1.

On the basis of the successful establishment of an animal model in tree shrews experimentally infected with human hepatitis B virus (HBV), a study on the hepatocarcinogenic effects of HBV and/or aflatoxin B1 (AFB1) was conducted. The results showed that the incidence of hepatocellular carcinoma (HCC) was significantly higher in the animals both infected with HBV and exposed to AFB1 (52.94%) than in those solely infected with HBV (11.11%) or exposed to AFB1 (12.50%). No HCC of precancerous lesions were found in the controls that were neither HBV-infected nor AFB-1 exposed. Precancerous lesions, including liver cell dysplasia and enzyme-altered hyperplastic hepatocyte foci, were observed before the occurrence of HCC, and the frequency of their appearance correlated well with the incidence of HCC. HBV DNA and the protein it encodes were detected in the cancer cells and/or the surrounding hepatocytes. Integration of HBV DNA into the host liver genome was found during hepatocarcinogenesis among the animals infected by HBV. These results suggest that exposure to HBV and AFB1 may play a synergistic role in the development of HCC, and support the viewpoint of an aetiological relationship between HBV and HCC.

Aflatoxin B1↗

PubMed1996

Surgical treatment of ascending aortic dissecting aneurysm--clinical application of modified Cabrol's operation.

This paper reported 3 cases of ascending aortic dissecting aneurysm treated by modified Cabrol's operation. An 8 mm Gore-Tex connected with coronary arteries was employed to prevent high tension, intimal tearing and bleeding of anastomosis. Unremoved aneurysmal wall used as a sac for enclosing conduit graft could minimize the bleeding and oozing so that leaked blood can be drained to right atrium via a bypass.

Adult↗

PubMed1996

Preconcentration of trace elements from natural water with palladium precipitation.

Palladium salts can be used as a coprecipitation carrier for the preconcentration of trace elements from natural water prior to their measurement by atomic spectrometry (AAS). The palladium is subsequently reduced by the introduction of hydrogen gas into the sample solution. The procedure is applied to the determination of Cu, Pb and Cd in seawater (enrichment factor 50) and synthetic water samples. Operating conditions have been optimized for the analysis of real samples. With the technique established an enrichment factor (500 fold) is feasible in synthetic samples. The recoveries of Cu, Cd and Pb from seawater are 95, 103 and 100%, respectively. This simple and rapid method can be applied in a wide pH-range and with complex matrices.

Journal Article↗

PubMed1996

Regulation of 5-hydroxytryptamine-induced calcium mobilization by cAMP-elevating agents in cultured canine tracheal smooth muscle cells.

The effects of increases in cellular adenosine 3'5'-cyclic monophosphate (cAMP) on 5-hydroxytryptamine-(5-HT-) induced generation of inositol phosphates (IPs) and increases in intracellular Ca2+ ([Ca2+]i) were investigated using canine cultured tracheal smooth muscle cells (TSMCs). Cholera toxin and forskolin induced concentration- and time-dependent cAMP formation with half-maximal effects (-logEC50) produced at concentrations of 7.0 +/- 0.5 and 4.9 +/- 0.4 respectively. Pretreatment of TSMCs with either forskolin or dibutyryl cAMP inhibited 5-HT-stimulated responses. Even after treatment for 24h, these agents still inhibited the 5-HT-induced Ca2+ mobilization. The inhibitory effects of these agents produced both depression of the maximal response and a shift to the right of the concentration response curves of 5-HT. The water-soluble forskolin analogue L-858051 [7-deacetyl-7beta-(gamma-N-methylpiperazino)-butyryl forskolin] significantly inhibited the 5-HT-stimulated accumulation of IPs. In contrast, the addition of 1,9-dideoxy forskolin, an inactive forskolin analogue, had little effect on this response. Moreover, SQ-22536 [9-(tetrahydro-2-furanyl)-9-H-purin-6-amine], an inhibitor of adenylate cyclase, and both H-89 [N-(2-aminoethyl)-5-isoquinolinesulphonamide] and HA-1004[N-(2-guanidinoethyl)-5-isoquinolinesulphonamide], inhibitors of cAMP-dependent protein kinase (PKA), attenuated the ability of forskolin to inhibit the 5-HT-stimulated accumulation of IPs. These results suggest that activation of cAMP/PKA was involved in these inhibitory effects of forskolin. The AlF4--induced accumulation of IPs was inhibited by forskolin, suggesting that G protein(s) are directly activated by AlF4-- and uncoupled from phospholipase C by forskolin treatment. These results suggest that activation of cAMP/PKA might inhibit the 5-HT-stimulated phosphoinositide breakdown and consequently reduce the [Ca2+]i increase or inhibit both responses independently.

Adenine↗