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H Ji

Publications and source records attributed to H Ji.

At least 73 records · Page 4Linked to original sources
PubMed1999

Trimerization specificity in HIV-1 gp41: analysis with a GCN4 leucine zipper model.

The envelope glycoprotein of human immunodeficiency virus type 1 (HIV-1) consists of a complex of two noncovalently associated subunits, gp120 and gp41. Formation of gp120/gp41 oligomers is thought to be dependent on a 4-3 hydrophobic (heptad) repeat located in the amino-terminal region of the gp41 molecule. We have investigated the role of this heptad repeat in determining the oligomeric structure of gp41 by introducing its buried core residues into the first (a) and fourth (d) positions of the GCN4 leucine-zipper dimerization domain. The mutant peptides fold into trimeric, helical structures, as shown by circular dichroism and equilibrium sedimentation centrifugation. The 2.4 A resolution crystal structure of one such trimer reveals a parallel three-stranded, alpha-helical coiled coil. Thus, the buried core residues from the gp41 heptad repeat direct trimer formation. We suggest that the conserved amino-terminal heptad repeat within the gp41 ectodomain possesses trimerization specificity.

Amino Acid Sequence↗
PubMed1999

Misexpression of the catenin p120(ctn)1A perturbs Xenopus gastrulation but does not elicit Wnt-directed axis specification.

Modulators of cadherin function are of great interest given that the cadherin complex actively contributes to the morphogenesis of virtually all tissues. The catenin p120(ctn) (formerly p120cas) was first identified as a src- and receptor-protein tyrosine kinase substrate and later shown to interact directly with cadherins. In common with beta-catenin and plakoglobin (gamma-catenin), p120(ctn) contains a central Armadillo repeat region by which it binds cadherin cytoplasmic domains. However, little is known about the function of p120(ctn) within the cadherin complex. We examined the role of p120(ctn)1A in early vertebrate development via its exogenous expression in Xenopus. Ventral overexpression of p120(ctn)1A, in contrast to beta-catenin, did not induce the formation of duplicate axial structures resulting from the activation of the Wnt signaling pathway, nor did p120(ctn) affect mesoderm induction. Rather, dorsal misexpression of p120(ctn) specifically perturbed gastrulation. Lineage tracing of cells expressing exogenous p120(ctn) indicated that cell movements were disrupted, while in vitro studies suggested that this may have been a consequence of reduced adhesion between blastomeres. Thus, while cadherin-binding proteins beta-catenin, plakoglobin, and p120(ctn) are members of the Armadillo protein family, it is clear that these proteins have distinct biological functions in early vertebrate development. This work indicates that p120(ctn) has a role in cadherin function and that heightened expression of p120(ctn) interferes with appropriate cell-cell interactions necessary for morphogenesis.

Animals↗
PubMed1999

The arthritogenic T cell receptor and its ligand in a model of spontaneous arthritis.

OBJECTIVE: Spontaneous arthritis in the KRN transgenic mouse model is due to the autoreactivity of the transgenic T cell receptor (TCR) against Ag7 major histocompatibility complex (MHC) molecules, which leads to strong but incomplete clonal deletion. We sought to determine whether other stimuli triggering this receptor might provoke arthritis, whether the apparently systemic reactivity might have some joint-preferential component explaining the paradoxical arthritic phenotype, and whether the transgenic receptor was the only one required or whether other TCRs might be ferried along in a leaky tolerance process. METHODS: Crosses and radiation chimeras involving a panel of transgenic and knockout mouse lines were used. The reactivity of the KRN TCR was tested in carboxyfluorescein diacetate succinimidyl ester-transfer experiments and in crosses with transgenic or inbred mice expressing other molecules that stimulate the KRN receptor (the mls-1a superantigen, the Aalpha(k69)Abeta(k) mutant MHC molecule). The arthritogenic capacity of T cells expressing only the KRN TCR was tested by crossing to recombination-activating gene-knockout mice, and constructing bone marrow chimeras with precursors to these strictly monoclonal T cells. RESULTS: The data show that the KRN TCR itself is the only receptor needed. It needs to be triggered by the Ag7 molecule loaded with self-peptides in order to provoke arthritis, but there is no indication of preferential presentation of joint-derived peptides. CONCLUSION: Arthritis can be generated by systemic recognition of self-MHC-peptide complexes by autoreactive T cells. This triggers B lymphocytes to produce arthritogenic antibodies, without the involvement of joint-specific T cell targets.

Animals↗
PubMed1999

Calcitonin-suppressed expression of parathyroid hormone-related protein in breast cancer cells.

Parathyroid hormone-related protein (PTHrP) is a key factor behind humoral hypercalcemia of malignancy (HHM). It is produced in most breast tumors and may be an important local mediator of skeletal metastases due to breast cancer. PTHrP may mediate local bone destruction in the absence of increased circulating PTHrP. Calcitonin (CT) is used for treatment of HHM, but there are data showing that CT can increase PTHrP expression and secretion in vitro. We have therefore studied the effect of CT on PTHrP gene expression and secretion in MCF-7 breast cancer cells. PTHrP mRNA decreased significantly after 4, 8, and 16 h incubation with 10 nM salmon calcitonin (sCT) when compared with the respective controls. PTHrP mRNA also decreased significantly and dose-dependently after incubation with sCT at 0.1 to 10 nM for 16 h. The PTHrP levels in the conditioned medium also decreased in a similar dose-dependent manner. The adenylate cyclase agonist forskolin lowered the PTHrP mRNA dose-dependently. In cells exposed to varying concentrations of sCT for 15 min, the cAMP levels increased dose-dependently. In conclusion, sCT can suppress PTHrP gene expression in MCF-7 breast cancer cells. The suppressive effect is probably exerted mainly via the cAMP-protein kinase A pathways.

Calcitonin↗
PubMed1999

Failure to demonstrate human papillomavirus DNA in epithelial ovarian cancer by general primer PCR.

One of the recent controversies with substantial clinical interest is the role of HPV in pathogenesis of ovarian cancer. The available highly conflicting data are based on analysis of 175 ovarian carcinomas so far. As an attempt to further elucidate this issue, the first systematic study of HPV detection in ovarian cancer was carried out using a highly sensitive general primer PCR (confirmed by hybridization for low- and high-risk HPV types separately) in a series of 98 histologically and clinically well-characterized epithelial ovarian malignancies. Despite the high (fg) sensitivity and a wide HPV type coverage of the technique used, all 98 ovarian carcinomas failed to demonstrate any signs of HPV DNA whatsoever. The preexisting 12 reports comprising a total of 175 ovarian tumors analyzed for HPV were summarized, giving highly discrepant results (i.e., detection rates from 0 to 100%) with the overall HPV DNA detection rate of 25.7%. The reasons for these discrepant findings are most probably technical. Our data are consistent with those of the majority of the most recent reports failing to disclose HPV DNA in ovarian neoplasia. The present completely negative results make the authors inclined to conclude that HPV is highly unlikely to play any causal role in the pathogenesis of epithelial ovarian neoplasia.

Adenocarcinoma↗
PubMed1999

Antithrombotic effects of low-molecular-weight heparin calcium (LMWH-Ca) in experimental models.

The antithrombotic activity of low-molecular-weight heparin calcium (LMWH-Ca) was studied in venous and arterial thrombosis models, arterial thrombosis model in rats, arterio-venous shunt model and venous thrombosis model in rabbits. The data showed that LMWH-Ca reduced thrombus formation in a dose-dependent manner. It suggests that LMWH-Ca is a potent antithrombotic agent for venous thrombosis, and also may be a beneficial therapeutic agent in arterial thrombosis.

Animals↗
PubMed1999

From systemic T cell self-reactivity to organ-specific autoimmune disease via immunoglobulins.

Rheumatoid arthritis is a common and debilitating autoimmune disease whose cause and mechanism remain a mystery. We recently described a T cell receptor transgenic mouse model that spontaneously develops a disease with most of the clinical, histological, and immunological features of rheumatoid arthritis in humans. Disease development in K/BxN mice is initiated by systemic T cell self-reactivity; it requires T cells, as expected, but B cells are also needed, more surprisingly. Here, we have identified the role of B cells as the secretion of arthritogenic immunoglobulins. We suggest that a similar scenario may unfold in some other arthritis models and in human patients, beginning with pervasive T cell autoreactivity and ending in immunoglobulin-provoked joint destruction.

Adoptive Transfer↗
PubMed1999

Gene gun-mediated DNA vaccination induces antitumor immunity against human papillomavirus type 16 E7-expressing murine tumor metastases in the liver and lungs.

DNA vaccination has emerged as an attractive approach for tumor immunotherapy. The aim of this study was to evaluate the potency of DNA vaccines in preventing and treating the liver and lung metastases of a human papillomavirus-16 (HPV-16) E7-expressing murine tumor (TC-1). We used the gene gun method to vaccinate C57BL/6 mice intradermally with DNA vaccines containing the HPV-16 E7 gene, the E7 gene linked to the sorting signals of the lysosome-associated membrane protein-1 (Sig/E7/ LAMP-1), or the 'empty' plasmid vector. The in vivo antitumor immunity was analyzed in both tumor prevention and tumor regression experiments. In addition, cytotoxic T lymphocyte (CTL) assays, enzyme-linked immunospot assay and enzyme-linked immunoabsorbent assay were used to assess the E7-specific T cell-mediated and humoral immunity. Mice vaccinated with Sig/E7/LAMP-1 DNA generated the strongest E7-specific CTL activities, the highest numbers of E7-specific CD8+ cell precursors and the highest titers of E7-specific antibodies. While both E7 DNA and Sig/E7/LAMP-1 DNA generated potent antitumor immunity in the liver and lung metastases models, the Sig/E7/LAMP-1 DNA was more potent under stringent conditions. DNA vaccination with E7-expressing plasmids was effective in controlling liver and lung metastases of an E7-expressing murine tumor. Our data suggest that antigen-specific DNA vaccination can potentially be applied to control liver and lung metastases of tumors with defined tumor-specific antigens.

Animals↗
PubMed1999

The prognostic significance of p53 expression quantitated by computerized image analysis in epithelial ovarian cancer.

The prognostic significance of p53 expression in 316 archival epithelial ovarian cancers was assessed using a static, computer-aided image analysis system (CAS 200). Using a 10% cut-off point, 26% of primary tumors and 35% of their metastases were positive for p53 protein. p53 positivity closely correlated with tumor grade (p < 0.001), stage (p < 0.001), residual tumor (p < 0.001), serous histologic type (p = 0.005), and tumor recurrence (p = 0.007). The overall 5-year survival was 37%. In univariate survival analysis, high grade, advanced stage, older age at diagnosis, and residual tumor > 2 cm were significant predictors of poor overall survival. In both the overall (p < 0.001) and recurrence-free (p < 0.001) survival, p53 immunopositivity predicted poor prognosis. p53 expression was a significant prognostic factor of multivariate recurrence-free survival (RR 1.93, p = 0.03), but not of overall multivariate survival. In addition, p53 positivity was a marker of poor overall survival in patients with well or moderately differentiated tumors, early stage tumors, or residual tumor. Quantitation of p53 immunoexpression by CAS may offer an objective means to identify patients who need more aggressive adjuvant therapy or new treatment strategies.

Adolescent↗
PubMed1999

Different modes of pathogenesis in T-cell-dependent autoimmunity: clues from two TCR transgenic systems.

T lymphocytes constantly flirt with reactivity to self peptides, a price they pay for their ability to recognize foreign peptides presented by self-MHC molecules, and autoreactivity in the T compartment occasionally gives rise to autoimmune disease. Pathology from T-cell autoimmunity can manifest itself through radically different strategies, as we have observed recently in two transgenic models. In the BDC2.5 diabetes model, T cells express a transgene-encoded T-cell receptor (TCR) with reactivity against a pancreatic antigen. This leads to a massive, if often controlled, infiltration of the pancreatic islets. Target cell destruction then results from the local consequences of this local immune/inflammatory process. On the other hand, the arthritic manifestations of the KRN transgenic model are indirect: the transgenic TCR confers a broad autoreactivity, through which T cells stimulate B cells to produce arthritogenic immunoglobulins. These molecules are then sufficient to produce the disease, even in the complete absence of any lymphocytes. Although important questions subsist in this model--how the KRN T cells interfere with B-cell tolerance, what the target of arthritogenic IgG is--its implication is that an isolated T-cell dysregulation may manifest itself through an Ig-mediated disease.

Animals↗
PubMed1999

Inhibition of human immunodeficiency virus type 1 infectivity by the gp41 core: role of a conserved hydrophobic cavity in membrane fusion.

The gp41 envelope protein of human immunodeficiency virus type 1 (HIV-1) contains an alpha-helical core structure responsible for mediating membrane fusion during viral entry. Recent studies suggest that a conserved hydrophobic cavity in the coiled coil of this core plays a distinctive structural role in maintaining the fusogenic conformation of the gp41 molecule. Here we investigated the importance of this cavity in determining the structure and biological activity of the gp41 core by using the N34(L6)C28 model. The high-resolution crystal structures of N34(L6)C28 of two HIV-1 gp41 fusion-defective mutants reveal that each mutant sequence is accommodated in the six-helix bundle structure by forming the cavity with different sets of atoms. Remarkably, the mutant N34(L6)C28 cores are highly effective inhibitors of HIV-1 infection, with 5- to 16-fold greater activity than the wild-type molecule. The enhanced inhibitory activity by fusion-defective mutations correlates with local structural perturbations close to the cavity that destabilize the six-helix bundle. Taken together, these results indicate that the conserved hydrophobic coiled-coil cavity in the gp41 core is critical for HIV-1 entry and its inhibition and provides a potential antiviral drug target.

Amino Acid Sequence↗
PubMed1999

Subdomain folding and biological activity of the core structure from human immunodeficiency virus type 1 gp41: implications for viral membrane fusion.

The envelope glycoprotein of human immunodeficiency virus type 1 (HIV-1) consists of two subunits, gp120 and gp41. The extraviral portion (ectodomain) of gp41 contains an alpha-helical domain that likely represents the core of the fusion-active conformation of the molecule. Here we report the identification and characterization of a minimal, autonomous folding subdomain that retains key determinants in specifying the overall fold of the gp41 ectodomain core. This subdomain, designated N34(L6)C28, is formed by covalent attachment of peptides N-34 and C-28 by a short flexible linker in place of the normal disulfide-bonded loop sequence. N34(L6)C28 forms a highly thermostable, alpha-helical trimer. Point mutations within the envelope protein complex that abolish membrane fusion and HIV-1 infectivity also impede the formation of the N34(L6)C28 core. Moreover, N34(L6)C28 is capable of inhibiting HIV-1 envelope-mediated membrane fusion. Taken together, these results indicate that the N34(L6)C28 core plays a direct role in the membrane fusion step of HIV-1 infection and thus provides a molecular target for the development of antiviral pharmaceutical agents.

Amino Acid Sequence↗
PubMed1999

Fatty acid oxidation affects food intake by altering hepatic energy status.

Inhibition of fatty acid oxidation stimulates feeding behavior in rats. To determine whether a decrease in hepatic fatty acid oxidation triggers this behavioral response, we compared the effects of different doses of methyl palmoxirate (MP), an inhibitor of fatty acid oxidation, on food intake with those on in vivo and in vitro liver and muscle metabolism. Administration of 1 mg/kg MP selectively decreased hepatic fatty acid oxidation but did not stimulate food intake. In contrast, feeding behavior increased in rats given 5 or 10 mg/kg MP, which inhibited hepatic fatty acid oxidation to the same extent as did the low dose but in addition suppressed fatty acid oxidation in muscle and produced a marked depletion of liver glycogen. Dose-related increases in food intake tracked dose-related reductions in liver ATP content, ATP-to-ADP ratio, and phosphorylation potential. The findings suggest that a decrease in hepatic fatty acid oxidation can stimulate feeding behavior by reducing hepatic energy production.

Adenosine Diphosphate↗
PubMed1999

Metabolic, gastrointestinal, and CNS neuropeptide effects of brain leptin administration in the rat.

To investigate whether brain leptin involves neuropeptidergic pathways influencing ingestion, metabolism, and gastrointestinal functioning, leptin (3.5 micrograms) was infused daily into the third cerebral ventricular of rats for 3 days. To distinguish between direct leptin effects and those secondary to leptin-induced anorexia, we studied vehicle-infused rats with food available ad libitum and those that were pair-fed to leptin-treated animals. Although body weight was comparably reduced (-8%) and plasma glycerol was comparably increased (142 and 17%, respectively) in leptin-treated and pair-fed animals relative to controls, increases in plasma fatty acids and ketones were only detected (132 and 234%, respectively) in pair-fed rats. Resting energy expenditure (-15%) and gastrointestinal fill (-50%) were reduced by pair-feeding relative to the ad libitum group, but they were not reduced by leptin treatment. Relative to controls, leptin increased hypothalamic mRNA for corticotropin-releasing hormone (CRH; 61%) and for proopiomelanocortin (POMC; 31%) but did not reduce mRNA for neuropeptide Y. These results suggest that CNS leptin prevents metabolic/gastrointestinal responses to caloric restriction by activating hypothalamic CRH- and POMC-containing pathways and raise the possibility that these peripheral responses to CNS leptin administration contribute to leptin's anorexigenic action.

Animals↗
PubMed1999

The N-terminus of gp130 is critical for the formation of the high-affinity interleukin-6 receptor complex.

Interleukin-6 (IL-6) mediates its activity through binding to two cell-surface receptors. The high-affinity human IL-6 receptor complex consists of two transmembrane anchored subunits: a ligand-specific, low-affinity IL-6 receptor and the high-affinity converter and signal transducing, gp130. Previously, using recombinant forms of human IL-6 and the extracellular ('soluble') domains of the IL-6 receptor (sIL-6R) and gp130 (sgp130), we have shown that the high-affinity IL-6R complex is hexameric, consisting of two molecules each of IL-6, sIL-6R and sgp130 (Ward et al., 1994, J. Biol. Chem. 269: 23286-23289). This paper investigates the role of the N-terminal region of gp130 in the formation of the high-affinity IL-6R complex. Using recombinant sgp130 produced with a FLAG octapeptide epitope (DYKDDDDK) at the N-terminus (sgp130-FLAG), we demonstrate, using biosensor analysis and size-exclusion chromatography, that modification of the N-terminus of sgp130 interferes with the in vitro in solution formation of the stable hexameric IL-6 receptor complex. Rather, sgp130-FLAG interacts with IL-6 and sIL-6R with a much lower affinity and forms a stable lower-order ternary complex. However, this lower-order complex is inconsistent with the solution molecular weight of a trimeric complex, as measured by size-exclusion chromatography. In contrast, N-terminal modification of the sgp130 with the FLAG epitope did not interfere with the binding of leukemia inhibitory factor or oncostatin-M (other cytokines that signal through gp130) to sgp130. These data support our model of the hexameric IL-6 receptor complex, which is biased towards the association of two IL-6.IL-6R.gp130 trimers, and postulates the critical involvement of the N-terminal Ig-like domain of gp130 in tethering the two trimers to form the stable hexamer (Simpson et al., 1997, Prot. Sci. 6: 929-955).

Amino Acid Sequence↗
PubMed1999

[Surgical management of subglottic carcinoma].

OBJECTIVE: To explore the clinical features and the methods of surgery and functional restoration of subglottic carcinoma. METHODS: Thirteen cases with primary subglottic carcinoma were treated surgically in this department from 1981 to 1997. Among them, six had T1-2N0 lesions, one had T3N0 lesion and six had T3-4N1-2 lesions. Four cases underwent total laryngectomy and nine had subglottic partial laryngectomy. The extensive subglottic partial laryngectomy was performed on patients with tracheal invasion. The defects of larynx were reconstructed by using unilateral or bilateral pedicled musculocutaneous flap, myofascial flap accordingly. T-shape silastic tube was placed in to the reconstructed cavity of larynx during the operation and the patients were decannulated in 2 to 6 months. Unilateral radical neck dissection was performed on 4 patients and bilateral on 2. RESULTS: All cases had restored the function of phonation except for 4 who underwent total laryngectomy. Five out of 9 (55.6%) were decannulated. The swallowing function was restored in all patients. The 3-year and 5-year survival rates were 100% and 66.7% in the cases with total laryngectomy, 88.9% and 75.0% with subglottic partial laryngectomy, respectively. CONCLUSION: It is possible to detect early subglottic carcinoma by using fiberoptic laryngoscopy routinely with the combination of stroboscopy, CT, MRI in male patients over 40 with hoarseness. It is practical that the whole or partial function of larynx could be restored in most cases with subglottic carcinoma after partial laryngectomy or subtotal laryngectomy. Unilateral or bilateral neck dissection should be performed on patients with T3 or T4 lesion. Postoperative radiotherapy is necessary.

Adult↗
PubMed1998

Antigen-specific immunotherapy for murine lung metastatic tumors expressing human papillomavirus type 16 E7 oncoprotein.

An important goal of cancer immunotherapy is to prevent and treat tumor metastasis. We have previously reported a recombinant vaccinia-based vaccine (Sig/E7/LAMP-1) that demonstrated significant anti-tumor effect in a subcutaneous tumor challenge model. In this study, we investigated the potency of the Sig/E7/ LAMP-1 vaccine in preventing and treating metastatic tumors. A tumor metastasis model was generated by injecting human papillomavirus type 16 (HPV-16) E6/E7 expressing tumor cells, designated TC-1, into the tail vein of syngeneic C57BL/6 mice. All the naive mice injected with 1 x 10(6) TC-1 cells developed tumors confined exclusively to the lungs within 1 month. For in vivo tumor prevention experiments, mice were vaccinated with Sig/E7/ LAMP-1 followed by tumor challenge. While tumor growth was observed in all of the mice (10/10) in the control groups, 8 of 10 vaccinated mice (80%) remained tumor-free 2 months post-tumor challenge. For in vivo treatment experiments, mice were first inoculated with TC-1 cells and then vaccinated with Sig/E7/ LAMP-1. Treatment with Sig/E7/LAMP-1 was effective in eliminating preexisting tumor cells in 4 of 5 vaccinated mice. Most importantly, treatment with Sig/E7/LAMP-1 resulted in regression of fully established lung tumors in 10% (5/10) of vaccinated mice. Our data suggest that the Sig/E7/LAMP-1 vaccine is effective in controlling the hematogenous spread of TC-1 tumor cells. In addition, the TC-1 lung metastasis model can be used to test the efficacy of various E6/E7-specific vaccines and immunotherapeutic strategies.

Animals↗