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Biomedical subjects

Y Cao

Publications and source records attributed to Y Cao.

At least 127 records · Page 7Linked to original sources
PubMed2001

[Reconstruction of corneal stroma using tissue engineering technique].

OBJECTIVE: To reconstruct new corneal stroma in order to provide a basis for future studies on the reconstruction of cornea. METHODS: The cultured corneal stromal cell-PGA complex was grafted to the subdermis of a female balb/c nude mouse. Six weeks after grafting, the new reformed tissue was fixed for histologic examination and transmission electron microscopy (TEM). At the same time, the new deposited collagen fibril diameter was measured. RESULTS: The reconstructed corneal stromal layer was formed in a waved, crossed-web structure, which was similar to the normal corneal stroma. Cell deposited collagen fibrils were similar in diameter to those seen in normal corneal stroma. CONCLUSIONS: The corneal stroma can be reconstructed by using tissue engineering technique. The reconstructed tissue which is similar to the normal cornea in key characteristics, including morphology and histologic structure provides an ideal experimental model for corneal physiological, pathologic, toxic and drug efficient testing and for future development of the tissue for implantation.

Animals↗
PubMed2001

[Effects of tetrandrine on the synthesis of collagen and scar-derived fibroblast DNA].

OBJECTIVE: To investigate the effects of tetrandrine on the synthesis of collagen and scar derived fibroblast DNA. METHODS: Scar-derived human fibroblasts were cultured in vitro. The changes in the levels of the synthesis of collagen and DNA of the fibroblasts were represented by the incorporation values of (3)H-TdR and (3)H-proline into the cells. Tetrandrine was added to the culture media of the cells, and its effects were studied. RESULTS: When the concentration of added tetrandrine increased from 5 mg/L to 80 mg/L, The (3)H-TdR values in scar-derived fibroblasts were 1162 plus minus 226 and 412 plus minus 82, respectively while that in control group was 1740 plus minus 165, showing an inhibition rate of 76.32%, and the difference (P < 0.01). In addition, the (3)H-proline incorporation values in the cells were 535 plus minus 141 and 341 plus minus 89, respectively, while that in control group was 1126 plus minus 193, with the inhibition rate of 69.71%, showing significant difference (P < 0.01). CONCLUSION: The synthesis of DNA and collagen in cultured scar-derived fibroblasts could be inhibited by tetrandrine in dose-dependent pattern. Tetrandrine might be a potential agent for the prevention and treatment of proliferative scars.

Alkaloids↗
PubMed2001

[Percutaneous testicular sperm aspiration and intracytoplasmic sperm injection in the treatment of severe male infertility].

OBJECTIVE: To investigate the efficacy of intracytoplasmic sperm injection (ICSI) combined with percutaneous testicular sperm aspiration (PTSA) in the treatment of severe male infertility. METHODS: From October 1998 to December 2000, 162 couples were enrolled, and ICSI and PTSA were adopted. Ovarian stimulation was achieved by the short protocol. All metaphase II (M II) oocytes were selected for ICSI. RESULTS: 1,517 M II oocytes were injected in 185 cycles, 990 fertilized (65.3%), and 152 embryo implanted. 54 couples achieved clinical pregnancy (35.5%). CONCLUSION: PTSA combined with ICSI is a rapid, convenient, painless and effective approach for the treatment of severe male infertility.

Adult↗
PubMed2001

[Shoulder pain after laparoscopic cholecystectomy].

OBJECTIVE: To detect the mechanism of shoulder pain after laparoscopic cholecystectomy(LC). METHODS: Ninety patients who had receive LC were randomly divided into three groups (each 30 patients): group A, no management after LC; group B, absorption of residual CO2 after LC; group C, O2 insufflation for three times followed by complete absorption of CO2 after LC. PO2 and PCO2 before and after LC were recorded. Postoperative shoulder pain was assessed with shoulder pain's rate and level. RESULTS: The PO2 difference of group C between before and after LC was significant as compared to groups A and B(P < 0.05). Postoperative shoulder pain developed in 13 patients (43.33%) of group A, in 8 (26.67%) of group B, and 21 (70%) of group C (P > 0.05 A vs B; P < 0.05 A vs C; and P < 0.01 B vs C). The shoulder pain's level was higher in group C than in groups A and B. CONCLUSIONS: Direct irritation to the diaphragm due to the residual CO2 pneumoperitoneum is not the main cause of shoulder pain. The excessive traction of the triangular ligament and over-stretching of the diaphragmatic fibers due to insufflation are the main cause of shoulder pain.

Carbon Dioxide↗
PubMed2001

[A preliminary study on relationship between concentrations of human growth hormone in urine (HGH-U) and puberty].

OBJECTIVE: The aim of this study is to investigate relationship between the concentration of human growth hormone in urine (HGH-U) and puberty, and to find a simple, accurate, and acceptable way of judging puberty of patients. METHODS: The concentration of HGH-U was measured by using radioimmunoassay in 277 students of Chengdu, and students were divided into three different groups, according to their ages (9, 13, 17 years old). Half of them are male. In order to evaluate the relationship between the concentration of HGH-U and puberty, the information of age, height, weight, growth velocity and sex character of all individuals were obtained, and analyzed their relation with the concentration of individuals' HGH-U. RESULTS: 1. There was no significant difference in the concentration of HGH-U between the 9-year-old group and the 13-year-old group, but there is significant difference between the concentration of HGH-U in the 9-year-old, 13-year-old groups and that of the 17-year-old group, and the concentration in the latter group is lower than those of the former two groups. 2. The concentration of HGH-U was negatively correlated with height, body weight, age, sex character and growth velocity (P < 0.05), but the correlation coefficient is low. 3. The coefficients of variation of HGH-U in all group were higher than 30%, which indicated a low dispersion degree. CONCLUSION: The concentration of HGH-U cannot be used as an independent indicator to evaluate puberty of children.

Adolescent↗
PubMed2001

[Study of the reconstruction methods after vertical partial laryngectomy for glottic carcinoma of the larynx].

OBJECTIVE: To study the reconstruction methods after vertical partial laryngectomy for glottic carcinoma of the larynx. METHOD: 58 cases with glottic carcinoma of the larynx were treated with vertical partial laryngectomy or extended vertical partial laryngectomy. The clinical materials of these cases were retrospectively studied. RESULT: The total decannulation rate was 93.1% and the 3- and 5-year survival rates were 87.2% and 80.5% respectively. The voice was socially acceptable in 93.1%(54/58) of the patients. Aspiration was only 3. All resumed mouth-food-taking. CONCLUSION: The reconstruction methods after vertical partial laryngectomy were mainly decided by the extent of the laryngeal defect. If the laryngeal defect of the framework was small, the pedicle muscular flap was the best reconstruction method in comparison with other reconstruction methods. If the laryngeal defect of the framework was too big, allograft nasal septal cartilage or epiglottic laryngoplasty should be performed.

Aged↗
PubMed2001

[Observation of the biological characterizations of nasopharyngeal epithelial cells by EB virus infection in early phase of immortalization].

The multi-stage cell model of the nasopharyngeal carcinoma development in vitro by Epstein-Barr virus transformation is beneficial for the elucidation of the mechanism of nasopharyngeal cancer. To observe the biological changes of primary human nasopharyngeal epithelial cells in early phase of immortalization, in this study, we have detected the morphological changes and the expression profile of senescence-associated beta-galactosidase (SA-beta-Gal) in primary culture. In addition, the expression of EB virus latent membrane protein 1 (LMP1) and the growth curve of primary cells were also detected. Our results showed a low percentage of cells infected with EB virus expressing SA-beta-Gal activity at the late primary culture. In morphology, the cells also formed multilayer foci, and the cell population doubling time was showed. These results demonstrated that the nasopharyngeal epithelial cells by EB virus infection have passed through the senescence and entered the early phase of immortalization. These cells have some of the transformed characteristics. Our results provided the data for further study on the mechanism of immortalization and the establishment of human nasopharyngeal epithelial cell line.

Cell Transformation, Viral↗
PubMed2001

[Epstein-Barr virus latent membrane protein 1 induces the telomerase activity in human nasopharyngeal epithelial cells].

Telomerase activation has been linked to cell immortalization in vitro and tumorigenicity in vivo. In this study, for the first, we reported that Epstein-Barr virus activated the telomerase activity of human nasopharyngeal epithelial cells in the early stage of immortalization as tested by the PCR-ELISA. The telomerase activity in nasopharyngeal epithelial cells was only observed in presenescent cells. It was implicated that Epstein-Barr virus induced the escape of nasopharyngeal epithelial cells from senescence via the activation of telomerase. We further showed that telomerase activation in infected cells was dependent on the protein level of latent membrane protein 1 (LMP1) encoded by Epstein-Barr virus using a Tetracycline regulatory cell line expressing LMP1, pTet-on-LMP1-HNE2. The activity of telomerase in nasopharyngeal cells was decreased when the protein level of LMP1 was blocked by antisense LMP1 plasmid DNA. And the activity of telmerase was also related to the carboxyl terminus of LMP1. It was implicated that the ability of Epstein-Barr virus to suppress senescence is associated with telomerase activation by LMP1.

Cell Transformation, Viral↗
PubMed2001

[Study on the Apriona germari(Hope) larvae's intestinal bacterial flora].

Intestinal flora of 47 Apriona germari(Hope) larvae, collected from fields, had been isolated and identified. The results showed that the predominant bacteria were Staphylococcus. Its viable count was 7.63 +/- 0.21, and the detection rate was 100%. Meanwhile, a strain of cellulose-utilizing bacterium was isolated from the fore-midgut fluid of A. germari larvae with the cellulose-congo red agar medium. The bacterium was tentatively identified as Cellulomonas. The detection rate of the cellulolytic bacterium was 23.40%, and the count was 3.84 +/- 0.54 approximately. Its contribution to the borer's cellulose digestion needs further investigations.

Animals↗
PubMed2001

[Fluorescence spectra of the rare earth complex-PAA-g-PE films].

The acrylic acid (AA) was grafted onto the PE film surface through UV photograft polymerization. With certain pH value, the grafted films were made to react with the alcohol-water solution of Eu3+ and alpha-thenoyltrifluoroacetone (TTA) or with the chloroform-water solution of Tb3+ and acetyl actone (AcAc), thus causing the preparation of the red or green fluorescent films. As compared with the corresponding Eu(TTA)3.(H2O)2 or Tb(AcAc)3.(H2O)2 solid complexes, both the excitation and emission spectra of the fluorescent films changed remarkably. It's predictable that chemical bond combination has occurred between the rare earth complexes and the macromolecular material. In addition, the IR spectra of the fluorescent films were also observed.

Acrylates↗
PubMed2000

Phylogenetic position of turtles among amniotes: evidence from mitochondrial and nuclear genes.

Maximum likelihood analysis, accounting for site-heterogeneity in evolutionary rate with the Gamma-distribution model, was carried out with amino acid sequences of 12 mitochondrial proteins and nucleotide sequences of mitochondrial 12S and 16S rRNAs from three turtles, one squamate, one crocodile, and eight birds. The analysis strongly suggests that turtles are closely related to archosaurs (birds+crocodilians), and it supports both Tree-2: (((birds, crocodilians), turtles), squamates) and Tree-3: ((birds, (crocodilians, turtles)), squamates). A more traditional Tree-1: (((birds, crocodilians), squamates), turtles) and a tree in which turtles are basal to other amniotes were rejected with high statistical significance. Tree-3 has recently been proposed by Hedges and Poling [Science 283 (1999) 998-1001] based mainly on nuclear genes. Therefore, we re-analyzed their data using the maximum likelihood method, and evaluated the total evidence of the analyses of mitochondrial and nuclear data sets. Tree-1 was again rejected strongly. The most likely hypothesis was Tree-3, though Tree-2 remained a plausible candidate.

Animals↗
PubMed2000

Interordinal relationships and timescale of eutherian evolution as inferred from mitochondrial genome data.

Extensive phylogenetic analyses of the updated sequence data of mammalian mitochondrial genomes were carried out using the maximum likelihood method in order to resolve deep branchings in eutherian evolution. The divergence times in the mammalian tree were estimated by a relaxed molecular clock of the mitochondrial proteins calibrated with multiple references. A Chiroptera/Eulipotyphla (i.e. bat/mole) clade and a close relationship of this clade to Fereuungulata (Carnivora+Perissodactyla+Cetartiodactyla) were reconfirmed with high statistical significance. However, a support for a monophyly of Fereuungulata relative to the Chiroptera/Eulipotyphla clade was fragile, and we suggest that the three branchings among Carnivora, Perissodactyla, Cetartiodactyla and Chiroptera/Eulipotyphla occurred successively in a short time period, estimated to be approximately 77Myr BP. The Chiroptera/Eulipotyphla divergence was estimated to roughly coincide with the Cretaceous-Tertiary boundary (65Myr BP). The monophyly of Rodentia, the Lagomorpha/Rodentia clade (traditionally called Glires), and the Afrotheria/Xenarthra clade were preferred over alternative relationships, but the supports of these clades were not strong enough to exclude other possibilities. Although several super-order taxa of eutherians were strongly supported by the analyses of the mitochondrial genome data, the branching order in the deepest part of the eutherian tree remained ambiguous from the data presently available.

Animals↗
PubMed2000

Metalloprotease-disintegrin ADAM 12 binds to the SH3 domain of Src and activates Src tyrosine kinase in C2C12 cells.

ADAM 12, a member of the ADAM (protein containing a disintegrin and metalloprotease) family of metalloprotease-disintegrins, has been implicated in the differentiation and fusion of skeletal myoblasts, and its expression is dramatically up-regulated in many cancer cells. While the extracellular portion of ADAM 12 contains an active metalloprotease and a cell-adhesion domain, the function of the cytoplasmic portion is much less clear. In this paper, we show that the cytoplasmic tail of ADAM 12 mediates interactions with the non-receptor protein tyrosine kinase Src. The interaction is direct, specific, and involves the N-terminal proline-rich region in the cytoplasmic tail of ADAM 12 and the Src homology 3 (SH3) domain of Src. ADAM 12 and Src co-immunoprecipitate from transfected C2C12 cells, suggesting that the two proteins form a complex in vivo. Co-expression of Src and ADAM 12, but not ADAM 9, in C2C12 cells results in activation of the recombinant Src. Moreover, endogenous ADAM 12 associates with and activates endogenous Src in differentiating C2C12 cells. These results indicate that ADAM 12 may mediate adhesion-induced signalling during myoblast differentiation.

ADAM Proteins↗
PubMed2000

Eradication of breast cancer xenografts by hyperthermic suicide gene therapy under the control of the heat shock protein promoter.

To investigate the usefulness of heat shock protein (HSP) promoter for breast cancer gene therapy, hyperthermia and HSV thymidine kinase (tk) suicide gene combination therapy was examined with mouse mammary cancer cell line FM3A. HSP promoter activity was markedly increased after heat shock (41-45 degrees C), with maximum activation (about 400-fold) at 3 hr. An in vitro cytotoxic assay showed that HSP-tk-transduced FM3A cells became more sensitive (more than 50,000 times) to ganciclovir (GCV) with heat shock, but untreated cells showed no increased cytotoxic sensitivity to GCV compared with control FM3A cells. In addition to promoter-oriented selective cell killing, a "chemosensitization effect" as a bystander effect was demonstrated by hyperthermia and suicide gene combination therapy, using a non-heat-inducible promoter. Immunohistochemical analysis revealed that this synergistic killing effect was dependent on apoptotic cell death with upregulation of both Fas and FasL (Fas ligand) expression. We also examined the efficacy of HSP-tk gene therapy in vivo by implanting breast cancer in subcutaneous and intraperitoneal models of BALB/c nude mice targeted by the HVJ-anionic liposome method. Significant tumor regression was observed in HSP-tk-transduced tumors followed by hyperthermia therapy, but no such inhibition was noted in either the mock vector transfection or hyperthermia group compared with control tumor-bearing mice. Our results demonstrate that this combination system is synergistically effective in mediating Fas-dependent apoptosis for a specific gene therapy targeting HSP-expressing mammary carcinomas, even in advanced and heat-resistant breast cancer.

Animals↗
PubMed2000

Dynamin II regulates hormone secretion in neuroendocrine cells.

The dynamin family of GTP-binding proteins has been implicated as playing an important role in endocytosis. In Drosophila shibire, mutations of the single dynamin gene cause blockade of endocytosis and neurotransmitter release, manifest as temperature-sensitive neuromuscular paralysis. Mammals express three dynamin genes: the neural specific dynamin I, ubiquitous dynamin II, and predominantly testicular dynamin III. Mutations of dynamin I result in a blockade of synaptic vesicle recycling and receptor-mediated endocytosis. Here, we show that dynamin II plays a key role in controlling constitutive and regulated hormone secretion from mouse pituitary corticotrope (AtT20) cells. Dynamin II is preferentially localized to the Golgi apparatus where it interacts with G-protein betagamma subunit and regulates secretory vesicle release. The presence of dynamin II at the Golgi apparatus and its interaction with the betagamma subunit are mediated by the pleckstrin homology domain of the GTPase. Overexpression of the pleckstrin homology domain, or a dynamin II mutant lacking the C-terminal SH3-binding domain, induces translocation of endogenous dynamin II from the Golgi apparatus to the plasma membrane and transformation of dynamin II from activity in the secretory pathway to receptor-mediated endocytosis. Thus, dynamin II regulates secretory vesicle formation from the Golgi apparatus and hormone release from mammalian neuroendocrine cells.

Amino Acid Sequence↗
PubMed2000

Intracellular unesterified arachidonic acid signals apoptosis.

Cyclooxygenase-2 (COX-2) is up-regulated in many cancers and is a rate-limiting step in colon carcinogenesis. Nonsteroidal antiinflammatory drugs, which inhibit COX-2, prevent colon cancer and cause apoptosis. The mechanism for this response is not clear, but it might result from an accumulation of the substrate, arachidonic acid, an absence of a prostaglandin product, or diversion of the substrate into another pathway. We found that colon adenocarcinomas overexpress another arachidonic acid-utilizing enzyme, fatty acid-CoA ligase (FACL) 4, in addition to COX-2. Exogenous arachidonic acid caused apoptosis in colon cancer and other cell lines, as did triacsin C, a FACL inhibitor. In addition, indomethacin and sulindac significantly enhanced the apoptosis-inducing effect of triacsin C. These findings suggested that unesterified arachidonic acid in cells is a signal for induction of apoptosis. To test this hypothesis, we engineered cells with inducible overexpression of COX-2 and FACL4 as "sinks" for unesterified arachidonic acid. Activation of the enzymatic sinks blocked apoptosis, and the reduction of cell death was inversely correlated with the cellular level of arachidonic acid. Inhibition of the COX-2 component by nonsteroidal antiinflammatory drugs restored the apoptotic response. Cell death caused by exposure to tumor necrosis factor alpha or to calcium ionophore also was prevented by removal of unesterified arachidonic acid. We conclude that the cellular level of unesterified arachidonic acid is a general mechanism by which apoptosis is regulated and that COX-2 and FACL4 promote carcinogenesis by lowering this level.

Adenocarcinoma↗
PubMed2000

Human plasmin enzymatic activity is inhibited by chemically modified dextrans.

Some synthetic dextran derivatives that mimic the action of heparin/heparan sulfate were shown to promote in vivo tissue repair when added alone to wounds. These biofunctional mimetics were therefore designated as "regenerating agents" in regard to their in vivo properties. In vitro, these biopolymers were able to protect various heparin-binding growth factors against proteolytic degradation as well as to inhibit the enzymatic activity of neutrophil elastase. In the present work, different dextran derivatives were tested for their capacity to inhibit the enzymatic activity of human plasmin. We show that dextran containing carboxymethyl, sulfate as well as benzylamide groups (RG1192 compound), was the most efficient inhibitor of plasmin amidolytic activity. The inhibition of plasmin by RG1192 can be classified as tight binding hyperbolic noncompetitive. One molecule of RG1192 bound 20 molecules of plasmin with a K(i) of 2.8 x 10(-8) m. Analysis with an optical biosensor confirmed the high affinity of RG1192 for plasmin and revealed that this polymer equally binds plasminogen with a similar affinity (K(d) = 3 x 10(-8) m). Competitive experiments carried out with 6-aminohexanoic acid and kringle proteolytic fragments identified the lysine-binding site domains of plasmin as the RG1192 binding sites. In addition, RG1192 blocked the generation of plasmin from Glu-plasminogen and inhibited the plasmin-mediated proteolysis of fibronectin and laminin. Data from the present in vitro investigation thus indicated that specific dextran derivatives can contribute to the regulation of plasmin activity by impeding the plasmin generation, as a result of their binding to plasminogen and also by directly affecting the catalytic activity of the enzyme.

Dextrans↗