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Biomedical subjects

F Qian

Publications and source records attributed to F Qian.

At least 19 recordsLinked to original sources
PubMed2001

BAFF-R, a newly identified TNF receptor that specifically interacts with BAFF.

B cell homeostasis has been shown to critically depend on BAFF, the B cell activation factor from the tumor necrosis factor (TNF) family. Although BAFF is already known to bind two receptors, BCMA and TACI, we have identified a third receptor for BAFF that we have termed BAFF-R. BAFF-R binding appears to be highly specific for BAFF, suggesting a unique role for this ligand-receptor interaction. Consistent with this, the BAFF-R locus is disrupted in A/WySnJ mice, which display a B cell phenotype qualitatively similar to that of the BAFF-deficient mice. Thus, BAFF-R appears to be the principal receptor for BAFF-mediated mature B cell survival.

Amino Acid Sequence↗
PubMed2001

Fabrication and characterization of controlled release poly(D,L-lactide-co-glycolide) millirods.

A compression-heat molding procedure was developed to fabricate poly(D,L-lactide-co-glycolide) (PLGA) controlled release drug delivery devices for the local treatment of tumors. The drug delivery devices were designed in the shape of a cylindrical millirod (1.6-mm diameter, 10-mm length), which allows them to be implanted by a modified 14-gauge tissue biopsy needle into tumor tissues via image-guided interventional procedures. In this study, the prototype trypan blue-containing PLGA millirods were fabricated under a compression pressure of 4.6 x 10(6) Pa and different fabrication temperatures for 2 h. The scanning electron microscopy results showed complete polymer annealing for millirods fabricated at 80 and 90 degrees C, while the cross sections of the 60 and 70 degrees C millirods showed incompletely annealed PLGA microspheres and trypan blue powders. The density, flexural modulus, and release properties of the PLGA millirods were also characterized and compared. The average values of the density and flexural modulus of the millirods increased with an increase in fabrication temperature. The flexural modulus values of most PLGA millirods were above 1 x 10(8) Pa, which provides sufficient stiffness for implantation within the tumor tissue. In addition, a Delta c(p) method was developed to determine the loading density of trypan blue in the PLGA millirods by differential scanning calorimetry. Results from the Delta c(p) measurement showed that trypan blue was homogeneously distributed in the millirod. Release studies in phosphate-buffered saline showed that the release rate decreased for the millirods fabricated at higher temperatures. The times for the release of 50% trypan blue were 5, 25, 25, and 25 h for millirods fabricated at 60, 70, 80, and 90 degrees C, respectively. Millirods fabricated at 90 degrees C had the most reproducible release profiles. The results from this study established compression--heat molding as an effective method to fabricate controlled release PLGA millirods with sufficient mechanical strength and reproducible release profiles for local cancer therapy.

Biocompatible Materials↗
PubMed2001

L-selectin can facilitate metastasis to lymph nodes in a transgenic mouse model of carcinogenesis.

L-selectin mediates homing of lymphocytes to lymph nodes (LN). Transgenic mice that express rat insulin promoter regulated simian virus 40 Tag (RIP-Tag) develop large, local cancers that metastasize to liver but not LN. To test whether this lack of LN metastases reflects their absence from the circulation, transgenic mice were produced that express Tag (T), L-selectin (L), and Escherichia coli LacZ (Z), in pancreatic beta cells. LTZ mice developed insulinomas that specifically had LN metastases; metastasis was blocked by an anti L-selectin mAb. LacZ(+) tumor cells from these LN homed to secondary LN upon transfer. These results suggest that the highly vascularized islet carcinomas are shedding tumor cells into the bloodstream, which is a necessary but insufficient condition for metastasis to occur; L-selectin can facilitate homing of such tumor cells to LN, resulting in metastasis.

Animals↗
PubMed2001

Study of the frequency response of the thin film cold cathode electron source of a lighting element.

Details of the recent experimental and theoretical studies of the frequency characteristic of the field emission electron source of a lighting element are given. The response times at different frequencies (0.02-200 kHz) and applied gap fields, acting on cathode surface, have been studied. A correlation has been found to exist between the response time and the frequency of applied voltage pulse. The response time remains almost constant within a range of frequencies between 1 and 30 kHz, and it remains nearly constant with increasing applied gap field higher than the threshold field. Finally, the cutoff frequency of the electron source is found, and with the current design of the electron source, it can be as high as 40 kHz. An equivalent circuit model is proposed, and theoretical results based on this model agree well with experimental findings.

Journal Article↗
PubMed2001

Biochemical characterization of bona fide polycystin-1 in vitro and in vivo.

The most common form of autosomal dominant polycystic kidney disease (PKD) results from mutation of the PKD1 gene on chromosome 16p13.3. The gene encodes a 14-kb messenger RNA that is predicted to express a 462-kd membrane protein. The gene product, polycystin-1, has a large extracellular portion composed of a novel combination of protein-protein interacting domains and is postulated to be a plasma membrane receptor involved in cell-cell/matrix interactions. However, slow progress has been made in the characterization of polycystin-1 or the determination of its function. In fact, the protein is expressed at very low levels in tissues and cell lines and previous efforts directed at expression of recombinant protein had been largely unsuccessful. We have recently developed constructs of full-length human PKD1 complementary (cDNA) that can be expressed in both a stable and transient fashion in mammalian cells. We used these systems to characterize our antibodies and to track the protein in vivo. We report here the first biochemical characterization of recombinant polycystin-1 and show that the protein is a 520-kd glycosylated polypeptide with an unglycosylated core of 460 kd. Subcellular fractionation as well as biotinylation studies confirmed that the protein is plasma-membrane associated. Furthermore, we show that the recombinant protein localizes to cell-cell junctions in polarized madin darby canine kidney cells as revealed by indirect immunofluorescence. Our data represent the first characterization of polycystin-1 performed under highly controlled conditions.

Animals↗
PubMed2001

Parathyroid hormone receptor internalization is independent of protein kinase A and phospholipase C activation.

Parathyroid hormone (PTH) and PTH-related peptide (PTHrP) binding to their common receptor stimulates second messenger accumulation, receptor phosphorylation, and internalization. LLC-PK(1) cells expressing a green fluorescent protein-tagged PTH/PTHrP receptor show time- and dose-dependent receptor internalization. The internalized receptors colocalize with clathrin-coated pits. Internalization is stimulated by PTH analogs that bind to and activate the PTH/PTHrP receptor. Cell lines expressing a mutant protein kinase A regulatory subunit that is resistant to cAMP and/or a mutant receptor (DSEL mutant) that does not activate phospholipase C internalize their receptors normally. In addition, internalization of the wild-type receptor and the DSEL mutant is stimulated by the PTH analog [Gly(1),Arg(19)]hPTH-(1-28), which does not stimulate phospholipase C. Forskolin, IBMX, and the active phorbol ester, phorbol-12-myristate-13-acetate, did not promote receptor internalization or increase PTH-induced internalization. These data indicate that ligand-induced internalization of the PTH/PTHrP receptor requires both ligand binding and receptor activation but does not involve stimulation of adenylate cyclase/protein kinase A or phospholipase C/protein kinase C.

1-Methyl-3-isobutylxanthine↗
PubMed2001

Nitric oxide synthase as a marker in colorectal carcinoma.

Elevated inducible nitric oxide synthase (iNOS) activity has been found in 60 per cent of colon adenomas and 20 to 50 per cent of adenocarcinomas. We postulated that high levels of iNOS may increase the invasive and metastatic potential of colon carcinoma and could be indicative of survival potential. Data were reviewed for 52 patients with colorectal carcinoma diagnosed in 1991 and 1992. Specimens were stained for iNOS and catalogued as low-activity staining (LAS) or high-activity staining (HAS) on the basis of visual evaluation by three pathologists. Thirty patients were LAS and 22 HAS. Age, sex, preoperative carcinoembryonic antigen, tumor and nodal status, and American Joint Committee on Cancer staging were not different between groups. Forty-six per cent of the HAS group remained alive after 5 years versus 71 per cent in the LAS group. Survival was significantly lower and metastatic status significantly higher in the HAS group. Results indicated that iNOS activity may be a prognostic indicator of long-term survival potential after treatment for colon cancer. In addition results suggested that metastasis was greater in colon carcinoma specimens that maintain an activated iNOS and that these cells clinically react more aggressively. Conclusions are tempered by the fact that results were based on a limited sample size.

Adult↗
PubMed2001

[Pathogen detection in the myocardial lesion using in situ RT-PCR in mice induced by experimental CoxB(3m) virus infection].

OBJECTIVE: To detect the location of pathogens in myocardium using in situ RT-PCR technique in order to study the pathogenetic course of the myocardial lesion induced by CoxB(3m) virus infection in mice. METHODS: (1) Thirty and fifty Balb/c mice were used respectively to establish the acute and chronic CoxB(3m) infected models, with another 25 healthy mice as the controls; (2) KS400 image analysis system (Germany) was used to measure the cardiac chamber area and the left ventricular wall thickness of the chronic infected mice and the controls; (3) CoxB(3m) virus in myocardial tissue was detected using in situ RT-PCR by direct incorporated technique which employed nucleotide labeling by anti-digoxin antibody and bonded with alkaline phosphatase (anti-dig-AKP method). RESULTS: Picture analysis indicated that the left ventricular chamber area was enlarged and the left ventricular wall was thinner in the chronic repeated virus infected models than those of the controls. With in situ RT-PCR, positive signals for Coxsackie virus B(3m) RNA were detected not only in the myocardium of the acute Balb/c mice models but also in the myocardium of the chronic mice models. CONCLUSION: Coxsackie virus B(3m) is able to induce pathologic lesions by exhibiting positive CVB-RNA signals in both acute and chronic models in mice. In the chronic experimental models, the cardiac chamber is enlarged while the ventricular wall is thinned which demonstrates the association with persistent infection of Coxsackie virus B(3m) virus.

Animals↗
PubMed2001

[Induced expression of the variable region of AMA-1 from Plasmodium falciparum].

OBJECTIVE: To express the variable region of AMA-1 gene from Plasmodium falciparum in Escherichia coli. METHODS: Genomic DNA of FCC1/HN was used as template and the variable region of AMA-1 gene was amplified by polymerase chain reaction(PCR). The PCR products were digested by endonuclease BamH I and Hind III, cloned into pBlu2KSP. The nucleotide sequences of the variable region of AMA-1 gene were determined by sequencing. The AMA-1 gene fragment was subcloned into plasmid pQE, expressed in E. coli and induced by IPTG. The fusion product as identified by SDS-PAGE gel electrophoresis and Western blotting were proceeded with anti-AMA-1 sera from rabbit. RESULTS: The size of the variable region of AMA-1 gene from FCC1/HN was 506 bp and encoded 168 amino acids. On SDS-PAGE gel dyed with Coomassie brilliant blue R250, no specific protein band can be discerned, but Western blotting proceeded with anti-AMA-1 sera from rabbit demonstrated that the specific protein band was about 23.0 kDa. CONCLUSION: The variable region of AMA-1 gene from FCC1/HN was able to be expressed in E. coli and analysis of Western blotting demonstrated that the AMA-1 fussion protein contained specific antigenic epitopes.

Amino Acid Sequence↗
PubMed2000

A soluble form of B cell maturation antigen, a receptor for the tumor necrosis factor family member APRIL, inhibits tumor cell growth.

A proliferation-inducing ligand (APRIL) is a ligand of the tumor necrosis factor (TNF) family that stimulates tumor cell growth in vitro and in vivo. Expression of APRIL is highly upregulated in many tumors including colon and prostate carcinomas. Here we identify B cell maturation antigen (BCMA) and transmembrane activator and calcium modulator and cyclophilin ligand (CAML) interactor (TACI), two predicted members of the TNF receptor family, as receptors for APRIL. APRIL binds BCMA with higher affinity than TACI. A soluble form of BCMA, which inhibits the proliferative activity of APRIL in vitro, decreases tumor cell proliferation in nude mice. Growth of HT29 colon carcinoma cells is blocked when mice are treated once per week with the soluble receptor. These results suggest an important role for APRIL in tumorigenesis and point towards a novel anticancer strategy.

3T3 Cells↗
PubMed2000

BAFF mediates survival of peripheral immature B lymphocytes.

B cell maturation is a very selective process that requires finely tuned differentiation and survival signals. B cell activation factor from the TNF family (BAFF) is a TNF family member that binds to B cells and potentiates B cell receptor (BCR)-mediated proliferation. A role for BAFF in B cell survival was suggested by the observation of reduced peripheral B cell numbers in mice treated with reagents blocking BAFF, and high Bcl-2 levels detected in B cells from BAFF transgenic (Tg) mice. We tested in vitro the survival effect of BAFF on lymphocytes derived from primary and secondary lymphoid organs. BAFF induced survival of a subset of splenic immature B cells, referred to as transitional type 2 (T2) B cells. BAFF treatment allowed T2 B cells to survive and differentiate into mature B cells in response to signals through the BCR. The T2 and the marginal zone (MZ) B cell compartments were particularly enlarged in BAFF Tg mice. Immature transitional B cells are targets for negative selection, a feature thought to promote self-tolerance. These findings support a model in which excessive BAFF-mediated survival of peripheral immature B cells contributes to the emergence and maturation of autoreactive B cells, skewed towards the MZ compartment. This work provides new clues on mechanisms regulating B cell maturation and tolerance.

Animals↗
PubMed2000

BAFF binds to the tumor necrosis factor receptor-like molecule B cell maturation antigen and is important for maintaining the peripheral B cell population.

The tumor necrosis factor (TNF) family member B cell activating factor (BAFF) binds B cells and enhances B cell receptor-triggered proliferation. We find that B cell maturation antigen (BCMA), a predicted member of the TNF receptor family expressed primarily in mature B cells, is a receptor for BAFF. Although BCMA was previously localized to the Golgi apparatus, BCMA was found to be expressed on the surface of transfected cells and tonsillar B cells. A soluble form of BCMA, which inhibited the binding of BAFF to a B cell line, induced a dramatic decrease in the number of peripheral B cells when administered in vivo. Moreover, culturing splenic cells in the presence of BAFF increased survival of a percentage of the B cells. These results are consistent with a role for BAFF in maintaining homeostasis of the B cell population.

Animals↗
PubMed2000

Polycystin-1, the gene product of PKD1, induces resistance to apoptosis and spontaneous tubulogenesis in MDCK cells.

The major form of autosomal dominant polycystic kidney disease (ADPKD) results from mutation of a gene (PKD1) of unknown function that is essential for the later stages of renal tubular differentiation. In this report, we describe a novel cell culture system for studying how PKD1 regulates this process. We show that expression of human PKD1 in MDCK cells slows their growth and protects them from programmed cell death. MDCK cells expressing PKD1 also spontaneously form branching tubules while control cells form simple cysts. Increased cell proliferation and apoptosis have been implicated in the pathogenesis of cystic diseases. Our study suggests that PKD1 may function to regulate both pathways, allowing cells to enter a differentiation pathway that results in tubule formation.

Animals↗
PubMed2000

[Expression of prourokinase in different mammalian cells].

Comparison studies of recombinant prourokinase(pro-UK) in various host cells, and expression vectors were carried out. Expression levels of vectors constructed in this study in different cell lines were compared. Mammalian cells expressing pro-UK were established. The levels of pro-UK expression in recombinant Namalwa, Vero and Sp2/0 cells are 200, 12.5 and 50 IU/(10(6) cells 24 h). pro-UK purities separated by immunoaffinity chromatograph are above 90%. Immunoabsorbent assay showed the ratio of pro-UK in CHO cells is lower than that from Vero and Namalwa cells. This study provide new host cells for pro-UK production.

Animals↗
PubMed2000

[Inducible expression of MSP1 gene of Plasmodium falciparum by a tetracycline controlled promoter in Salmonella typhi CVD908 strain].

OBJECTIVE: To investigate the inducible expression of MSP1 gene of Plasmodium falciparum in Salmonella typhi CVD908 vaccine strain using a tetracycline-controlled PLtetO promoter. METHODS: The recombinant plasmid pZE11/MSP1-42 was transferred into the CVD908/tetR strain by electroporation. Detections of the expression of MSP1-42 both in vitro and in vivo were carried out using SDS-PAGE, Western blot and immunofluorescence assay. RESULTS: The CVD908/tetR/MSP1-42 strain was constructed and the expression of MSP1-42 was dependent on the presence of tetracycline in vitro. The yield of the inducible expression was higher than that of constitutive system. Moreover, the MSP1-42 was expressed in the liver and spleen of mice inoculated with the CVD908/tetR/MSP1-42 strain in the presence of tetracycline, whereas no expression was detected in the absence of the inducer. CONCLUSION: The recombinant Salmonella typhi strain which expresses the MSP1-42 fragment of Plasmodium falciparum induced by tetracycline has been established successfully.

Animals↗
PubMed2000

[Inducible expression of MSP1 gene of Plasmodium falciparum by a tetracycline-controlled promoter].

OBJECTIVE: To express the entire MSP1 gene of Plasmodium falciparum and its C-terminal 42 kDa fragment using a tetracycline-controlled PLtetO-1 promoter. METHODS: The entire MSP1 gene and 42 kDa fragment gene were cloned into the plasmid of pZE11, and transformed into E. coli DH5 alpha Z1. Restriction enzyme analysis, SDS-PAGE and Western blotting were used to examine two recombinant plasmids and their expression in E. coli DH5 alpha Z1. RESULTS: The recombinant plasmids of pZE11/MSP1 and pZE11/MSP1-42 were constructed successfully. The expressive products about 190 kDa and 42 kDa of two genes in E. coli DH5 alpha Z1 were identified by SDS-PAGE and Western blotting. CONCLUSION: Tightly controlling expression of the MSP1 gene in E. coli is essential to reduce the toxicity of the product to its host cells as well as to provide a feasibility to construct Salmonella vaccine strain which can inducibly express the important malarial vaccine candidate gene.

Animals↗
PubMed1999

Comparison of statistical methods to predict the time to complete a series of surgical cases.

We present a statistical model for predicting the time to complete a series of successive, elective surgical cases. The use of sample means of case times and turnover times when scheduling cases does not minimize the operating room labor costs associated with errors in predicting times to complete series of cases. The problem of minimizing associated labor costs (both under and over utilization) can be converted to the problem of least absolute deviation regression. The dependent variables are the times to complete series of cases. The independent variables are the numbers of cases in each series that are in various categories (i.e., combinations of scheduled procedures and surgeons). Although the computational method is preferred on theoretical grounds to that involving sample means, application of both methods shows that the more practical method is to use the sample means of previous case times and turnovers.

Elective Surgical Procedures↗