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Biomedical subjects

B Chen

Publications and source records attributed to B Chen.

At least 289 records · Page 16Linked to original sources
PubMed1998

Soluble fibronectin promotes migration of oral squamous-cell carcinoma cells.

We have shown that a fibronectin (FN) matrix is required for the organization of tenascin-C (TN-C) matrices by peritumor fibroblasts (PTF) cultured from tissue surrounding oral squamous-cell carcinoma (SCC). In the present study, we detected alternatively spliced FN containing both the EDA and EDB domains decorating the reactive stroma adjacent to the invading tumor nests in oral SCC biopsies. In vitro, PTF cells organized an extensive FN matrix rich in the EDA domain and containing a small amount of EDB. In contrast, normal human fibroblasts deposited a FN matrix which expressed only the EDA domain. PTF-conditioned medium (CM), shown to enhance migration of oral SCC cells on TN-C, was found to enhance their migration on FN and invasion of a reconstituted basement membrane. Addition of antibodies to FN to the PTF-CM inhibited SCC-cell migration on TN-C, and depletion of FN from the PTF-CM abolished its ability to induce migration or invasion by oral SCC cells, suggesting that FN promotes the migration and invasion of oral SCC cells. Western blots of the PTF-CM identified FN containing the EDA but not the EDB domain. When soluble FN was added to the control medium in the lower chamber of the Transwell system, SCC-cell migration increased significantly. These results demonstrate that both the EDA and the EDB domains of FN are expressed in the extracellular matrix of oral SCC in vivo and PTF in vitro and indicate that FN is the probable chemotactic factor in the PTF-conditioned medium.

Alternative Splicing↗
PubMed1998

Small espin: a third actin-bundling protein and potential forked protein ortholog in brush border microvilli.

An approximately 30-kD isoform of the actin-binding/ bundling protein espin has been discovered in the brush borders of absorptive epithelial cells in rat intestine and kidney. Small espin is identical in sequence to the COOH terminus of the larger ( approximately 110-kD) espin isoform identified in the actin bundles of Sertoli cell-spermatid junctional plaques (Bartles, J.R., A. Wierda, and L. Zheng. 1996. J. Cell Sci. 109:1229-1239), but it contains two unique peptides at its NH2 terminus. Small espin was localized to the parallel actin bundles of brush border microvilli, resisted extraction with Triton X-100, and accumulated in the brush border during enterocyte differentiation/migration along the crypt-villus axis in adults. In transfected BHK fibroblasts, green fluorescent protein-small espin decorated F-actin-containing fibers and appeared to elicit their accumulation and/or bundling. Recombinant small espin bound to skeletal muscle and nonmuscle F-actin with high affinity (Kd = 150 and 50 nM) and cross-linked the filaments into bundles. Sedimentation, gel filtration, and circular dichroism analyses suggested that recombinant small espin was a monomer with an asymmetrical shape and a high percentage of alpha-helix. Deletion mutagenesis suggested that small espin contained two actin-binding sites in its COOH-terminal 116-amino acid peptide and that the NH2-terminal half of its forked homology peptide was necessary for bundling activity.

Actins↗
PubMed1998

The synthesis and screening of a combinatorial peptide library for affinity ligands for glycosylated haemoglobin.

This paper reports the synthesis and screening of a combinatorial peptide library for new affinity ligands for glycosylated haemoglobin (HbA1c), which is an important indicator of diabetes control. The new ligands are suitable for large-scale synthesis and overcome the disadvantages of antibodies (unstable and expensive to produce etc.), while remaining as efficient as antibodies in binding to the analyte. The library consisted of 262,144 hexapeptides synthesised using the one-bead-one-compound technique. The hexapeptides attached onto beads were screened with glycosylated haemoglobin HbA1c. The structures of the peptides exhibiting high affinity were characterised by Edman microsequencing. Computer modelling simulation of one of the lead sequences has shown that this class of ligand has a high affinity and specificity for glycosylated haemoglobin.

Animals↗
PubMed1998

Weight functions, double reciprocity laws, and volume formulas for lattice polyhedra.

We extend the concept of manifold with boundary to weight and boundary weight functions. With the new concept, we obtained the double reciprocity laws for simplicial complexes, cubical complexes, and lattice polyhedra with weight functions. For a polyhedral manifold with boundary, if the weight function has the constant value 1, then the boundary weight function has the constant value 1 on the boundary and 0 elsewhere. In particular, for a lattice polyhedral manifold with boundary, our double reciprocity law with a special parameter reduces to the functional equation of Macdonald; for a lattice polytope especially, the double reciprocity law with a special parameter reduces to the reciprocity law of Ehrhart. Several volume formulas for lattice polyhedra are obtained from the properties of the double reciprocity law. Moreover, the idea of weight and boundary weight leads to a new homology that is not homotopy invariant, but only homeomorphic invariant.

Journal Article↗
PubMed1998

The role of tumor necrosis factor alpha in modulating the quantity of peripheral blood-derived, cytokine-driven human dendritic cells and its role in enhancing the quality of dendritic cell function in presenting soluble antigens to CD4+ T cells in vitro.

Because dendritic cells (DC) are critically involved in both initiating primary and boosting secondary host immune responses, attention has focused on the use of DC in vaccine strategies to enhance reactivity to tumor-associated antigens. We have reported previously the induction of major histocompatibility complex class II-specific T-cell responses after stimulation with tumor antigen-pulsed DC in vitro. The identification of in vitro conditions that would generate large numbers of DC with more potent antigen-presenting cell (APC) capacity would be an important step in the further development of clinical cancer vaccine approaches in humans. We have focused attention on identifying certain exogenous cytokines added to DC cultures that would lead to augmented human DC number and function. DC progenitors from peripheral blood mononuclear cells (PBMC) were enriched by adherence to plastic, and the adherent cells were then cultured in serum-free XVIVO-15 medium (SFM) for 7 days with added granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-4 (IL-4). At day 7, cultures contained cells that displayed the typical phenotypic and morphologic characteristics of DC. Importantly, we have found that the further addition of tumor necrosis factor alpha (TNFalpha) at day 7 resulted in a twofold higher yield of DC compared with non-TNFalpha-containing DC cultures at day 14. Moreover, 14-day cultured DC generated in the presence of TNFalpha (when added at day 7) demonstrated marked enhancement in their capacity to stimulate a primary allogeneic mixed leukocyte reaction (8-fold increase in stimulation index [SI]) as well as to present soluble tetanus toxoid and candida albicans (10- to 100-fold increases in SI) to purified CD4+ T cells. These defined conditions allowed for significantly fewer DC and lower concentrations of soluble antigen to be used for the pulsing of DC to efficiently trigger specific T-cell proliferative responses in vitro. When compared with non-TNFalpha-supplemented cultures, these DC also displayed an increased surface expression of CD83 as well as the costimulatory molecules, CD80 and CD86. Removal of TNFalpha from the DC cultures after 2 or 4 days reduced its enhancing effect on DC yield, phenotype, and function. Thus, the continuous presence of TNFalpha over a 7-day period was necessary to achieve the maximum enhancing effect observed. Collectively, our findings point out the importance of exogenous TNFalpha added to cultures of cytokine-driven human DC under serum-free conditions, which resulted in an enhanced number and function of these APC. On the basis of these results, we plan to initiate clinical vaccine trials in patients that use tumor-pulsed DC generated under these defined conditions.

Antigen Presentation↗
PubMed1998

[Polymorphism analysis of 4 loci of X-chromosome in a Chinese population of the Han nationality].

OBJECTIVE: To investigate the polymorphism of 4 loci of X-chromosome in the Hans. METHODS: Using PCR-SSLP, the authors analysed the polymorphism of DXS1068, DXS7132, DXS6804 and DXS6799 in the X-chromosome in 70 randomly selected female Hans. RESULTS: The number of alleles in the 4 loci were 5,5,5 and 6 respectively; there were no significant differences between the observed and estimated and genotype probabilities of the 4 loci; the estimates of heterozygosity of 4 loci were 0.6819, 0.6895, 0.7659 and 0.6483 respectively and there were no significant differences between the observed and estimated heterozygosity of the 4 loci. CONCLUSION: The distribution of alleles and genotype probabilities of 4 loci all observe the Hardy-Weinberg equilibrium.

Asian People↗
PubMed1998

Implications of a common polymorphism in intron 12 of the dystrophin gene for deletion detection by multiplex PCR.

The multiplex polymerase chain reaction (PCR) is a reliable and efficient method for detecting dystrophin gene deletions in about 65% of patients with Duchenne or Becker muscular dystrophy (DMD or BMD). The 9-plex PCR assay, which simultaneously amplifies the muscle-specific promoter and exons 3, 6, 13, 43, 47, 50, 52 and 60, is one of the multiplex PCR assays used routinely to test for DMD and BMD deletions. In this study, we describe a previously unrecognized A to G base variation in intron 12 (nt -110 from exon 13) of the dystrophin gene. This variant, located within the annealing site of the exon 13 forward primer, prevented amplification of exon 13 in the 9-plex PCR assay. Present in 56% (25 of 45) of normal Caucasian alleles and 23% (3 of 13) of normal black American alleles, it is likely encountered frequently during dystrophin deletion analysis by multiplex PCR, and may complicate test result interpretation. Therefore, we suggest two modifications for the multiplex PCR detection of dystrophin gene deletion.

Alleles↗
PubMed1998

Tenascin-C matrix assembly in oral squamous cell carcinoma.

We previously showed that the extracellular matrix component tenascin-C (TN-C) is upregulated in oral squamous cell carcinoma (SCC) compared with the normal oral mucosa. In this study we examined oral biopsy specimens of mild to moderate dysplasia or carcinoma in situ to study TN-C expression. We found that carcinoma in situ is the stage at which TN-C becomes widely expressed, suggesting it may be involved in the initial stages of tumor progression. To study TN-C matrix production in vitro, we used an invasive oral SCC cell line (HSC-3) and peri-tumor fibroblasts (PTF). Neither cell type organized a TN-C matrix when cultured alone; however, when co-cultured with HSC-3 cells, PTF were able to assemble a TN-C matrix. PTF retained the ability to organize a TN-C matrix when separated from the HSC-3 cells by a semi-permeable membrane, indicating that cell-cell contact is not necessary for TN-C matrix organization and suggesting that soluble factors may be involved. Moreover, PTF were induced to assemble TN-C matrices when grown in medium conditioned by both the PTF and HSC-3 cells. Antibodies to fibronectin (FN) and to the first FN type III repeat blocked both FN and TN-C matrix assembly, indicating that TN-C matrix organization is dependent on an FN template. Antibodies to alpha5, alphav and beta1 integrins also blocked TN-C matrix formation. When seeded onto FN matrices, the co-cultures were unaffected by the anti-integrin and anti-FN antibodies and were able to organize a TN-C matrix. Our results suggest that progression of malignant oral SCC is accompanied by an alteration of the normal ECM to one rich in TN-C, and that the organization of a TN-C matrix is dependent on soluble cues provided by both the SCC cells and the PTF.

Carcinoma in Situ↗
PubMed1998

[A study of genetic patterns of idiopathic epilepsy].

OBJECTIVE: To explore genetic patterns of idiopathic epilepsy (IEP). METHODS: Using familial analysis, tests for multifactorial inheritance and segregation analysis, we studied 210 pedigrees with IEP found in a population survey in Shangdong province. RESULTS: The genetic pattern of IEP is not polygenic but is mainly influenced by autosomal recessive disorders. The results of segregation analysis indicate that the genetic pattern of U*U multiplex families and U*A group is autosomal recessive. Only a few cases in U*U group may accept the assumption of autosomal recessive inheritance while the other are sporadic cases. The frequency of sporadic cases is approximately 78.5%. Genetic heterogeneity may influence U*U(f) group and U*U group. CONCLUSION: Further and careful empirical scrutiny of U*U(f) group and the sporadic cases in U*U group offers the best hope for getting a clear understanding of genetic patterns and mechanisms in IEP.

Epilepsy↗
PubMed1998

[Cytochrome P450*2D6 gene polymorphism in Chinese population].

OBJECTIVE: To demonstrate the cytochrome P450*2D6(CYP*2D6) gene polymorphism distribution in Chinese. METHODS: The polymorphisms of CYP*2D6 gene in 100 Chinese people were studied with polymerase chain reaction and Xba I restriction fragment length polymorphic (RFLP) techniques. RESULTS: The frequencies of CYP*2D6 gene A, B, D and E mutations were 1%, 6.5%, 0.5% and 1%, respectively; the genotypes of 29kb/29kb,44kb/29kb and 44kb/44kb Xba I RFLP were 38%, 46% and 13%, respectively. It was found that 12% of B mutations were linked with even though A and B mutations were mainly associated with 29kb/29kb genotype. CONCLUSION: The frequencies of the four kinds of CYP*2D6 gene mutation in Chinese were lower than those of the European, but the frequency of Xba I 44kb allele was a little higher.

Adult↗
PubMed1998

The reaction of lanthanide ions with n-doxyl stearic acids and its utilization for the ESR study on the permeability of lipid-bilayer of erythrocyte membrane to gadolinium ions.

The reaction of lanthanide ions with n-doxyl stearic acid (nDS) spin labels (n = 5,7,12,16) was investigated by the electron spin resonance technique in aqueous solution. Among the lanthanides, the Gd3+, Tb3+, Tm3+ and Ce3+ ions strongly quenched the ESR signal of spin labels, but the effects of La3+, Eu3+ and Lu3+ are very weak. The quenching effects are featured by: (1) the dependence on the concentration of lanthanide ions; (2) no obvious changes of the ESR line shape in the presence of lanthanide ions; (3) the quenching constant decreases in the order: Gd3+ > Tb3+ > Tm3+ > Ce3+; (4) the quenching effects of lanthanide ions are found to strikingly correlate with their magnetic properties. These findings indicate that the interaction of lanthanide ions with nitroxide oxygen leading to the reduction of ESR signal amplitude is dominated by their magnetic characteristics rather than the coordination effect. By labeling erythrocyte membrane with nDS, n = 5,7,12,16 at different depths, we studied the diffusion of Gd3+ into the lipid-bilayer of erythrocyte membrane by monitoring the reduction processes of the ESR signals of nitroxide spin labels located at different depths of membrane lipid-bilayer after addition of Gd3+. These results revealed that the Gd3+ ions can penetrate into the lipid-bilayer, though the entry rate is slow. It was shown that the Gd3+ ions bind to the membrane and enhance the permeability of extracellular ascorbate into erythrocyte membrane. The transport mechanism of Gd3+ ions through the lipid-bilayer might be involved in the Gd3+ cation-induced pore formation in the surface of membrane.

Ascorbic Acid↗
PubMed1998

NIRS: dose dependency of local changes of cerebral HbO2 and Hb with pCO2 in parietal cortex.

Regional cerebral oxygenated hemoglobin and total hemoglobin increased systematically with increasing depth of hypercapnia, but the concentration of deoxygenated hemoglobin remained relatively constant. Relative mean changes of oxygenated and total hemoglobin increased nearly linearly, corresponding to the characteristic increase of the cerebral vascular dilation with increasing depth of hypercapnia.

Animals↗
PubMed1998

Diffusion and reaction of nitric oxide in suspension cell cultures.

A reaction-diffusion model was developed to predict the fate of nitric oxide (NO) released by cells of the immune system. The model was used to analyze data obtained previously using macrophages attached to microcarrier beads suspended in a stirred vessel. Activated macrophages synthesize NO, which is oxidized in the culture medium by molecular oxygen and superoxide (O2-, also released by the cells), yielding mainly nitrite (NO2-) and nitrate (NO3-) as the respective end products. In the analysis the reactor was divided into a "stagnant film" with position-dependent concentrations adjacent to a representative carrier bead and a well-mixed bulk solution. It was found that the concentration of NO was relatively uniform in the film. In contrast, essentially all of the O2- was calculated to be consumed within approximately 2 microm of the cell surfaces, due to its reaction with NO to yield peroxynitrite. The decomposition of peroxynitrite caused its concentration to fall to nearly zero over a distance of approximately 30 microm from the cells. Although the film regions (which had an effective thickness of 63 microm) comprised just 2% of the reactor volume and were predicted to account for only 6% of the NO2- formation under control conditions, they were calculated to be responsible for 99% of the NO3- formation. Superoxide dismutase in the medium (at 3.2 microM) was predicted to lower the ratio of NO3- to NO2- formation rates from near unity to <0.5, in reasonable agreement with the data. The NO3-/NO2- ratio was predicted to vary exponentially with the ratio of O2- to NO release rates from the cells. Recently reported reactions involving CO2 and bicarbonate were found to have important effects on the concentrations of peroxynitrite and nitrous anhydride, two of the compounds that have been implicated in NO cytotoxicity and mutagenesis.

Animals↗
PubMed1998

Mapping of Drosophila mutations using site-specific male recombination.

Although recombination does not usually occur in the male Drosophila germline, site-specific recombination can be induced at the ends of P elements. This finding suggested that male recombination could be used to map Drosophila mutations. In this article, we describe the general method and its application to the mapping of two EMS-induced female-sterile mutations, grauzone and cortex. Within two months, the grauzone gene was mapped relative to seven different P-element insertion sites, and cortex was mapped relative to 23 different P-elements. The results allowed us to map grauzone to a region of about 50 kb, and cortex distal to the chromosomal region 33E. These experiments demonstrate that P-element-induced site-specific male recombination is an efficient and general method to map Drosophila autosomal mutations.

Animals↗
PubMed1998

Antenatal corticosteroids in preterm premature rupture of membranes.

It is clear that there is no unequivocal indication for the use of antenatal corticosteroids in the preterm gestation with PROM. Extrapolating the effects seen in gestations with intact membranes, however, there are potential benefits in reduction of neonatal respiratory disease and intracranial hemorrhage at the expense of increased risks of maternal postpartum infection. Because the lifetime harm from the neonatal grave and the sequelae of infection in the mother are usually mild, we recommend that antenatal corticosteroids be administered to patients with PPROM between the gestational ages of 24-33 weeks in the absence of frank maternal or fetal infection or fetal compromise. With the increasing acceptance of antenatal corticosteroid therapy, it is unlikely that any further prospective randomized trials will be possible because withholding corticosteroids may expose patients to unacceptable potential harm. Therefore, clinical judgments may have to made based solely on the limited data presently available. Hopefully, future clinical investigations will provide useful information about the relation between antenatal corticosteroids and perinatal infections of the mother and infant in the setting of prophylactic antibiotic exposure. Additionally, there is also a need for information establishing a clinical profile for the patient with PPROM that accurately predicts when she is likely to enter spontaneous labor, thus allowing clinicians to increase the likelihood of appropriately administering corticosteroids within 1 week of delivery to maximize potential neonatal benefit.

Adrenal Cortex Hormones↗
PubMed1998

Differential expression of alphav integrins in K1735 melanoma cells.

Tumor cell adherence to and migration on the extracellular matrix is an important aspect of cancer progression. This interaction with the extracellular matrix is mediated primarily through the integrin class of cell adhesion molecules. We identified a restricted expression of alphavbeta3 in highly metastatic K1735M2 and of alphavbeta5 in poorly metastatic K1735C23 murine melanoma cells. The highly metastatic cells were ten times more motile on vitronectin and fibronectin and approximately three times more invasive through a reconstituted basement membrane than the poorly metastatic cells. This motility was inhibited by addition of anti-beta3 antibodies. Injection of the alphavbeta3-negative K1735C23 cells into syngeneic mice resulted in the generation of a metastatic variant (K1735C23PM) that neo expressed the alphavbeta3 complex, indicating that expression of alphavbeta3 is required for K1735 melanoma metastasis. Injection of highly metastatic K1735M2 cells in the presence of blocking antibody to beta3 reduced tumor size by approximately 80%. Treatment of the K1735M2 cells with a retroviral antisense beta3 construct significantly reduced their expression of alphavbeta3 and also reduced their motility on extracellular matrix ligands and their invasion through a reconstituted basement membrane. In contrast, when the K1735C23 cells were treated with a construct containing the full-length beta3 cDNA, their motility on extracellular matrix proteins and invasion of a reconstituted basement membrane were significantly increased. These results indicate that alphavbeta3 is required for migration and invasion of K1735 melanoma cells in vitro and primary tumor growth and metastasis in vivo.

Animals↗
PubMed1998

Evaluation of radiation effects against C6 glioma in combination with vaccinia virus-p53 gene therapy.

The primary objective of this study was to evaluate the antitumor effects of recombinant vaccinia virus-p53 (rVV-p53) in combination with radiation therapy against the C6 rat glioma, a p53 deficient tumor that is relatively radioresistant. VV-LIVP, the parental virus (Lister strain), was used as a control. Localized treatment of subcutaneous C6 tumors in athymic mice with either rVV-p53 or VV-LIVP together with tumor irradiation resulted in low tumor incidence and significantly slower tumor progression compared to the agents given as single modalities. Assays of blood and spleen indicated that immune system activation may account, at least partly, for the enhance tumor inhibition seen with combined treatment. No overt signs of treatment-related toxicity were noted.

Animals↗