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Biomedical subjects

A Jiang

Publications and source records attributed to A Jiang.

At least 19 recordsLinked to original sources
PubMed2006

Novel magnetic rings for rapid vascular reconstruction in canine liver transplantation model.

OBJECTIVE: Magnetic rings were used for rapid vascular reconstruction in a canine liver transplantation model. MATERIALS AND METHODS: Thirty-two adult mongrel dogs weighing 13 to 16 kg were randomly selected as donors or recipients of transplantations. The recipients were randomly divided into two groups: group A (n = 10) had magnetic rings used for vascular reconstruction without venovenous bypass; group B (n = 6) had vascular reconstruction performed by continuous suturing with splenojugular venovenous bypass. RESULTS: In group A, the entire operative period was 3.24 +/- 0.49 hours, the durations of clamping the portal vein and the infrahepatic vena cava of the recipient were 5.89 +/- 2.27 minutes and 3.89 +/- 0.73 minutes, respectively. In group B, the entire operative period was 4.12 +/- 0.51 hours with the duration of clamping portal vein and infrahepatic vena cava, 28.33 +/- 6.04 minutes and 12.16 +/- 3.72 minutes (P < .01 vs group A). In group A, mean arterial pressure dropped during the anhepatic phase but recovered quickly after reperfusion. The fluid infusion was about 730.56 +/- 50.56 mL in the group A and a pressor agent was unnecessary. In group B, blood pressure dropped during the anhepatic phase and slowly recovered. The fluid infusion was about 2241.67 +/- 390.78 mL and a pressor agent was used to maintain the blood pressure of the recipient. No twist or thrombus was discovered in the anastomoses group A and the endothelium at the site of anastomosis was entire. In group B, errhysis was common in the anastomotic stomas. Nine of 10 dogs in group A survived more than 3 days, the longest being 8 days, whereas four of the six dogs in group B survived less than 3 days. CONCLUSION: The results showed that the anhepatic time was significantly shortened (about 5.89 +/- 2.27 minutes) in group A compared with group B and venovenous bypass was unnecessary. Magnetic rings could be used for rapid vascular reconstruction in canine liver transplantation model. The long-term results of this procedure should be clarified before it is applied in clinical practice in the future.

Animals↗
PubMed2001

Regulation of membrane-type matrix metalloproteinase 1 activity by dynamin-mediated endocytosis.

Membrane-type matrix metalloproteinase 1 (MT1-MMP) plays a critical role in extracellular matrix remodeling under both physiological and pathological conditions. However, the mechanisms controlling its activity on the cell surface remain poorly understood. In this study, we demonstrate that MT1-MMP is regulated by endocytosis. First, we determined that Con A induces proMMP-2 activation in HT1080 cells by shifting endogenous MT1-MMP from intracellular compartments to cell surface. This phenotype was mimicked by the cytoplasmic truncation mutant MT1 Delta C with more robust pro-MMP-2 activation and cell surface expression than wild-type MT1-MMP in transfected cells. MT1 Delta C was subsequently shown to be resistant to Con A treatment whereas MT1-MMP remains competent, suggesting that Con A regulates MT1-MMP activity through cytoplasmic domain-dependent trafficking. Indeed, MT1-MMP was colocalized with clathrin on the plasma membrane and with endosomal antigen 1 in endosomes. Internalization experiments revealed that MT1-MMP is internalized rapidly in clathrin-coated vesicles whereas MT1 Delta C remains on cell surface. Coexpression of a dominant negative mutant of dynamin, K44A, resulted in elevation of MT1-MMP activity by interfering with the endocytic process. Thus, MT1-MMP is regulated by dynamin-dependent endocytosis in clathrin-coated pits through its cytoplasmic domain.

Animals↗
PubMed2001

Involvement of Bik, a proapoptotic member of the Bcl-2 family, in surface IgM-mediated B cell apoptosis.

Apoptosis plays a central role in shaping the repertoire of circulating mature B lymphocytes, but the underlying molecular mechanisms regulating B cell fate are not well understood. Human B104 B lymphoma cells undergo apoptosis after surface Ig (sIg)M, but not sIgD, ligation; sIgM-mediated apoptosis of B104 cells apparently requires new gene transcription because actinomycin D can inhibit the apoptotic response. Here we report that expression of Bik, a proapoptotic member of the Bcl-2 family, is greatly increased after sIgM ligation. Bik expression was tightly controlled at both transcriptional and post-transcriptional levels. Whereas a calcineurin-dependent pathway was essential for Bik mRNA induction, both the phosphatidylinositol 3-kinase (PI3K)- and the calcineurin-dependent pathways were required for the sustained production of Bik protein. Consistent with these findings, sIgD ligation, which leads to the similar calcium mobilization and increases in Bik mRNA, induced only a transient activation of PI3K and did not lead to sustained Bik protein expression. Furthermore, sustained Bik protein expression correlated with B cell apoptosis, as treatment with either a calcineurin inhibitor or PI3K inhibitors blocked both sIgM-mediated sustained Bik protein induction and apoptosis. In addition, sIgM ligation strongly increased the amount of Bik associated with endogenous Bcl-x, but sIgD ligation did not. Studies with caspase inhibitors also revealed that Bik and Bcl-x interacted upstream of caspases in the B cell apoptosis cascade. Thus, Bik protein induction and, subsequently, sequestering of antiapoptotic Bcl-x by Bik may play an important role in regulating B cell apoptosis.

Apoptosis↗
PubMed2000

Functional characterization of MT3-MMP in transfected MDCK cells: progelatinase A activation and tubulogenesis in 3-D collagen lattice.

MT3-MMP, a membrane-anchored matrix metalloproteinase, has been proposed to participate in the remodeling of extracellular matrix either by direct proteolysis or via activating other enzymes such as progelatinase A. To test this hypothesis, we analyzed the effect of exogenously transfected MT3-MMP in a tissue remodeling system: growth and tubulogenesis of Madin-Darby canine kidney (MDCK) cells in collagen gels. Although the parental cells require MMP activities for both growth and tubulogenesis, over-expression of wild-type MT3-MMP, but not its catalytically inactive mutant, leads to further enhancement of both processes, independent of its downstream substrate, progelatinase A. Mechanistically, MT3-MMP accomplishes such an effect by displaying on cell surfaces as active species, ready to activate progelatinase A or degrade ECM molecules. These data strongly suggest that MT3-MMP possesses the potential to directly enhance the growth and invasiveness of cells in vivo, two critical processes for development and carcinogenesis.

Animals↗
PubMed2000

Avian reticuloendotheliosis virus strain A and spleen necrosis virus do not infect human cells.

Spleen necrosis virus (SNV) and Reticuloendotheliosis virus strain A (REV-A) belong to the family of reticuloendotheliosis viruses and are 90% sequence related. SNV-derived retroviral vectors produced by the REV-A-based D17.2G packaging cell line were shown to infect human cells (H.-M. Koo, A. M. C. Brown, Y. Ron, and J. P. Dougherty, J. Virol. 65:4769-4776, 1991), while similar vectors produced by another SNV-based packaging cell line, DSH134G, are not infectious in human cells (reviewed by R. Dornburg, Gene Ther. 2:301-310, 1995). Here we describe a careful reevaluation of the infectivity of vectors produced from the most commonly used REV-A- or SNV-based packaging cells obtained from various sources with, among them, one batch of D17.2G packaging cells obtained from the American Type Culture Collection. None of these packaging cells produced vectors able to infect human cells. Thus, contrary to previously published data, we conclude that REV-based vectors are not infectious in human cells.

Cell Separation↗
PubMed2000

[Changes of genomic density polymorphism and quantitative expression of complement receptor type 1 in patients with liver diseases].

OBJECTIVE: To study the changes of genomic density polymorphism and quantitative expression of complement receptor type 1 (CR1) on erythrocytes in patients with liver diseases. METHODS: Polymerase chain reaction (PCR) and Hind III restriction enzyme digestion and the quantitative assay of erythrocytic CR1 were used. RESULTS: The spot mutation rate (25.0% approximately 30.3%) of erythrocyte CR1 density gene in patients with liver diseases was not significantly different with that of healthy individuals (28.0%). The amount of erythrocytic CR1 in patients with liver diseases, except for those with normal liver function, was significantly lower than that of healthy individuals (t=10.44, P<0.0001). The quantitative expression of erythrocytic CR1 in decompensated cirrhosis was obviously lower than that of compensated cirrhosis (t=2.21, P<0.05). CONCLUSION: Defective expression of CR1 in liver diseases is acquired through central and/or peripheral mechanisms. It is very important to study the quantitative expression in the evaluation of the development of liver diseases.

Erythrocytes↗
PubMed1999

A genetically engineered spleen necrosis virus-derived retroviral vector that displays the HIV type 1 glycoprotein 120 envelope peptide.

We reported that SNV-derived retroviral vectors, which display single-chain antibodies on the viral surface, enable cell type-specific gene delivery into various human cells. In particular, the SNV cell type-specific gene delivery vector system appears to be well suited to transduce genes into cells of the human hematopoietic system (Jiang et al., J. Virol. 72:10148-10156, 1998). Here, we report the construction of SNV vector particles that display the complete gp120 surface unit of the envelope protein of human immunodeficiency virus type 1 (HIV-1) on the viral surface. The complete gp120-coding region of a T cell-tropic HIV-1 strain (LAI/BRU) was fused to a short peptide spacer coding region [(Gly4Ser)3] linking it to the SNV TM-coding region. The corresponding protein was expressed as a single 145-kDa peptide as expected. This peptide was nontoxic and could be stably expressed in dog D17 SNV-derived packaging cells. Particles harvested from stable packaging lines infected CD4+ human hematopoietic cells with titers exceeding 10(5) CFU/ml supernatant tissue culture medium. Titers in other, CD4- cell lines expressing various coreceptors of HIV-1 were 100-fold lower than titers obtained in CD4+ cells. Specificity of infection was demonstrated by antibody inhibition assays or by preincubating cells with SDF-1alpha, the ligand, which binds to the CXCR4 coreceptor, to which this gp120 binds. Our data indicate that binding of the HIV-1 gp120 to either CD4 or CXCR4 is sufficient to enable infection of human cells with SNV vector particles. We constructed retroviral vector particles that display chimeric HIV-1-SU-SNV-TM proteins plus wild-type SNV envelope on the viral surface. Such particles allowed efficient infection of CD4-positive human T lymphocytes, and, at a lower efficiency, also cells expressing CXCR4 without CD4. These data coincide with our earlier hypothesis that the chimeric envelope is required only to bind the vector particle to a cell surface receptor of the target cell, while membrane fusion is mediated by wild-type Env, which alone is not sufficient to enable infection of human cells.

Animals↗
PubMed1999

Syk and Bruton's tyrosine kinase are required for B cell antigen receptor-mediated activation of the kinase Akt.

Activation of Akt by multiple stimuli including B cell antigen receptor (BCR) engagement requires phosphatidylinositol 3-kinase and regulates processes including cell survival, proliferation, and metabolism. BCR cross-linking activates three families of non-receptor protein tyrosine kinases (PTKs) and these are transducers of signaling events including phospholipase C and mitogen-activated protein kinase activation; however, the relative roles of PTKs in BCR-mediated Akt activation are unknown. We examined Akt activation in Lyn-, Syk- and Btk-deficient DT40 cells and B cells from Lyn(-/-) mice. BCR-mediated Akt activation required Syk and was partially dependent upon Btk. Increased BCR-induced Akt phosphorylation was observed in Lyn-deficient DT40 cells and Lyn(-/-) mice compared with wild-type cells suggesting that Lyn may negatively regulate Akt function. BCR-induced tyrosine phosphorylation of the phosphatidylinositol 3-kinase catalytic subunit was abolished in Syk-deficient cells consistent with a receptor-proximal role for Syk in BCR-mediated phosphatidylinositol 3-kinase activation; in contrast, it was maintained in Btk-deficient cells, suggesting Btk functions downstream of phosphatidylinositol 3-kinase. Calcium depletion did not influence BCR-induced Akt phosphorylation/activation, showing that neither Syk nor Btk mediates its effects via changes in calcium levels. Thus, BCR-mediated Akt stimulation is regulated by multiple non-receptor PTK families which regulate Akt both proximal and distal to phosphatidylinositol 3-kinase activation.

Agammaglobulinaemia Tyrosine Kinase↗
PubMed1999

In vivo cell type-specific gene delivery with retroviral vectors that display single chain antibodies.

Cell type-specific gene delivery will be essential for in vivo gene therapy. Our laboratory has previously developed retroviral vector particles, derived from spleen necrosis virus, SNV, which display the antigen-binding site of an antibody on the viral surface. Such particles infected only human cells in vitro, which expressed a receptor recognized by the antibody. To test cell type-specific gene delivery in vivo, a mouse model system has been developed. Antibiotic resistant human target and non-target cells were injected into the peritoneum of SCID mice. Subsequently, a vector solution containing 106 infectious particles, which display scAs against the human her2neu cell surface protein, was injected. Cells were recovered from the peritoneum, subjected to antibiotic selection, and tested for the expression of a lacZ gene transduced by the retroviral vector. We found that human target cells, which express her2neu, were infected in vivo. However, neither human cells that do not express her2neu, nor normal mouse cells were infected by such viral particles. These data give proof of principle that retroviral vector-mediated, cell type-specific gene delivery can be obtained in vivo.

Animals↗
PubMed1998

Identification and characterization of a new splicing variant of vascular endothelial growth factor: VEGF183.

We report the discovery of a new splicing variant of vascular endothelial growth factor named VEGF183. It is six amino acids shorter than its closest relative, VEGF189, due to the utilization of a conserved alternate splicing donor site within exon 6a. Highly expressed in heart tissue, VEGF183 is detected in transiently transfected COS cells as 28-32-kDa monomers under reduced condition, and 46-kDa dimers under non-reduced condition - the functional unit for all VEGF isoforms.

Alternative Splicing↗
PubMed1998

Involvement of guanosine triphosphatases and phospholipase C-gamma2 in extracellular signal-regulated kinase, c-Jun NH2-terminal kinase, and p38 mitogen-activated protein kinase activation by the B cell antigen receptor.

Mitogen-activated protein (MAP) kinase family members, including extracellular signal-regulated kinase (ERK), c-Jun NH2-terminal kinase ( JNK), and p38 MAP kinase, have been implicated in coupling the B cell antigen receptor (BCR) to transcriptional responses. However, the mechanisms that lead to the activation of these MAP kinase family members have been poorly elucidated. Here we demonstrate that the BCR-induced ERK activation is reduced by loss of Grb2 or expression of a dominant-negative form of Ras, RasN17, whereas this response is not affected by loss of Shc. The inhibition of the ERK response was also observed in phospholipase C (PLC)-gamma2-deficient DT40 B cells, and expression of RasN17 in the PLC-gamma2-deficient cells completely abrogated the ERK activation. The PLC-gamma2 dependency of ERK activation was most likely due to protein kinase C (PKC) activation rather than calcium mobilization, since loss of inositol 1,4,5-trisphosphate receptors did not affect ERK activation. Similar to cooperation of Ras with PKC activation in ERK response, both PLC-gamma2-dependent signal and GTPase are required for BCR-induced JNK and p38 responses. JNK response is dependent on Rac1 and calcium mobilization, whereas p38 response requires Rac1 and PKC activation.

Adaptor Proteins, Signal Transducing↗
PubMed1998

Different protein tyrosine kinases are required for B cell antigen receptor-mediated activation of extracellular signal-regulated kinase, c-Jun NH2-terminal kinase 1, and p38 mitogen-activated protein kinase.

B cell antigen receptor (BCR) cross-linking activates three distinct families of nonreceptor protein tyrosine kinases (PTKs): src-family kinases, Syk, and Btk; these PTKs are responsible for initiating downstream events. BCR cross-linking in the chicken DT40 B cell line also activates three distinct mitogen-activated protein kinases (MAPKs): extracellular signal-regulated kinase (ERK)2, c-jun NH2-terminal kinase (JNK)1, and p38 MAPK. To dissect the functional roles of these PTKs in MAPK signaling, activation of MAPKs was examined in various PTK-deficient DT40 cells. BCR-mediated activation of ERK2, although maintained in Lyn-deficient cells, was abolished in Syk-deficient cells and partially inhibited in Btk-deficient cells, indicating that BCR-mediated ERK2 activation requires Syk and that sustained ERK2 activation requires Btk. BCR-mediated JNK1 activation was maintained in Lyn-deficient cells but abolished in both Syk- and Btk-deficient cells, suggesting that JNK1 is activated via a Syk- and Btk-dependent pathway. Consistent with this, BCR-mediated JNK1 activation was dependent on intracellular calcium and phorbol myristate acetate-sensitive protein kinase Cs. In contrast, BCR-mediated p38 MAPK activation was detected in all three PTK-deficient cells, suggesting that no single PTK is essential. However, BCR-mediated p38 MAPK activation was abolished in Lyn/Syk double deficient cells, demonstrating that either Lyn or Syk alone may be sufficient to activate p38 MAPK. Our data show that BCR-mediated MAPK activation is regulated at the level of the PTKs.

Agammaglobulinaemia Tyrosine Kinase↗
PubMed1998

Expression of a p53 mutant in the epidermis of transgenic mice accelerates chemical carcinogenesis.

To develop an in vivo model for studying the role of the p53 tumor suppressor in skin carcinogenesis, a murine p53(172H) mutant (equivalent to human p53(175H)) was expressed in the epidermis of transgenic mice, utilizing a targeting vector based on the human keratin 1 gene (HK1.p53m). HK1.p53m mice developed normally and did not exhibit an obvious epidermal phenotype or develop spontaneous tumors. However, these mice demonstrated an increased susceptibility to a two-stage chemical carcinogenesis protocol, with the rate of formation and number of papillomas being dramatically increased as compared to non-transgenic controls. The majority of papillomas in control mice regressed after termination of 12-O-tetradecanoylphorbol-13-acetate (TPA) treatment, whereas p53m papillomas progressed to carcinomas and metastases. In addition, more advanced malignancy, i.e., undifferentiated spindle cell carcinomas, were exclusively observed in p53m mice. Increased bromodeoxyuridine (BrdU) labeling, accompanied by decreased expression of p21, was observed in HK1.p53m papillomas. In situ examination of centrosomes in HK1.p53m papillomas also revealed marked abnormalities, with 75% of the cells containing > or = 3 centrosomes/cell, whereas centrosome numbers in papillomas from control animals remained normal. These data suggest that the accelerated tumorigenesis observed in chemically-treated p53m mice is most likely due to increased genomic instability resulting from an inhibition of G1 arrest and abnormal amplification of centrosomes.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1998

Analysis of centrosome abnormalities and angiogenesis in epidermal-targeted p53172H mutant and p53-knockout mice after chemical carcinogenesis: evidence for a gain of function.

We previously developed a transgenic mouse model that expresses in the epidermis a murine p53172R-->H mutant (p53m) under the control of a human keratin-1-based vector (HK1.p53m). In contrast to mice with wild-type p53 and p53-knockout mice, HK1.p53m mice exhibit increased susceptibility to chemical carcinogenesis, with greatly accelerated benign papilloma formation, malignant conversion, and metastasis. In the study presented here, we examined the expression pattern of several differentiation markers and observed that p53m tumors exhibited a less differentiated phenotype than tumors elicited in non-transgenic mice. Metastasis in p53m tumors was also associated with a poorly differentiated phenotype. To determine whether genomic instability was associated with a putative gain-of-function role for this p53m, in situ examination of centrosomes was performed in HK1.p53m and equivalent p53-null papillomas. In contrast to HK1.p53m papillomas, which had centrosome abnormalities at high frequencies (75% of cells contained more than three centrosomes/cell), p53-null tumors exhibited few abnormal centrosomes (4% of cells contained more than three centrosomes/cell). To determine whether angiogenesis played a role in the rapid progression of p53m tumors, the expression of vascular endothelial growth factor, a promoter of angiogenesis, and thrombospondin-1, an inhibitor of angiogenesis, was examined in tumors derived from either p53m or p53-knockout mice. Regardless of their p53 status (wild type, p53m, p53-/-), all of the papillomas exhibited similar levels of vascular endothelial growth factor expression and decreased expression of thrombospondin-1 as did normal epidermis. In addition, tumors from different p53 genotypes showed a similar density of blood vessels. Because p53 status did not appear to play an overt role in angiogenesis, these data suggest that p53m accelerates tumorigenesis primarily by exerting a gain of function associated with genomic instability.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1998

Cell-type-specific gene transfer into human cells with retroviral vectors that display single-chain antibodies.

The successful application of human gene therapy protocols on a broad clinical basis will depend on the availability of in vivo cell-type-specific gene delivery systems. We have developed retroviral vector particles, derived from spleen necrosis virus (SNV), that display the antigen binding site of an antibody on the viral surface. Using retroviral vectors derived from SNV that displayed single-chain antibodies (scAs) directed against a carcinoembryonic antigen-cross-reacting cell surface protein, we have shown that an efficient, cell-type-specific gene delivery can be obtained. In this study, we tested whether other scAs displayed on SNV vector particles can also lead to cell-type-specific gene delivery. We displayed the following scAs on the retroviral surface: one directed against the human cell surface antigen Her2neu, which belongs to the epidermal growth factor receptor family; one directed against the stem cell-specific antigen CD34; and one directed against the transferrin receptor, which is expressed on liver cells and various other tissues. We show that retroviral vectors displaying these scAs are competent for infection in human cells which express the antigen recognized by the scA. Infectivity was cell type specific, and titers above 10(5) CFU per ml of tissue culture supernatant medium were obtained. The density of the antigen on the target cell surface does not influence virus titers in vitro. Our data indicate that the SNV vector system is well suited for the development of a large variety of cell-type-specific targeting vectors.

Animals↗
PubMed1998

[Application of CT virtual endoscopy in larynx].

OBJECTIVE: To evaluate the clinical application of CT virtual endoscopy in larynx. METHODS: The virtual endoscopy images were compared with that of actual laryngoscopy in 16 patients(4 normal larynx, 9 laryngeal carcinomas, 1 bilateral glottic polyps, one laryngeal fibrous hyperplasis and 1 airway striction caused by infiltration of the laryngeal carcinoma after laryngectomy). All the lesions were pathologically proved. RESULTS: CT virtual endoscopy showed the normal anatomical structure of larynx as actual laryngoscopy. The location and extension of the lesions of larynx showed in CT virtual endoscopy agreed with that of actual laryngoscopy. In addition, CT virtual laryngoscopy revealed the structure of subglottic region and distal portion of strictured airway from feet to head, which were not available in actual laryngoscopy. CONCLUSION: CT virtual laryngoscopy is a good complemental method of fiber optic laryngoscopy.

Glottis↗