Biomedical subjects

F Chen

Publications and source records attributed to F Chen.

At least 19 recordsLinked to original sources

PubMed2003

New features of the thermal Casimir force at small separations.

The difference of the thermal Casimir forces at different temperatures between real metals is shown to increase with a decrease of the separation distance. This opens new opportunities for the demonstration of the thermal dependence of the Casimir force. Both configurations of two parallel plates and a sphere above a plate are considered. Different approaches to the theoretical description of the thermal Casimir force are shown to lead to different measurable predictions.

Journal Article↗

PubMed2003

Injectable bone.

Temperature-dependent polymerising polyethylene oxide hydrogel was used as a vehicle to deliver bone marrow mesenchymal cells by injection in six nude mice, four mice acting as controls, to study generation of new bone in the cell-hydrogel complex. Mesenchymal cells were harvested by in vitro cell culture, and cells were seeded into polyethylene oxide solution. The density of the suspension was adjusted to 5 x 10(7)ml(-1). The hydrogel was obtained by adjusting the temperature to over 6 degrees C. Aliquots of 0.5 ml of the cell-hydrogel complexes were injected subcutaneously into the backs of the six experimental mice, and 0.5 ml of hydrogel alone was injected into the four controls. Generation of new bone was studied by gross inspection, radiographs, and histological examination. Two months after injection hard nodes had formed subcutaneously in all six mice, whereas in the control group the hydrogel had been absorbed completely and only soft tissue was present at the site of injection. A shadow could be seen on the radiographs of all cell-seeded mice. On histological examination of the nodes there was trabecular bone and some areas of neocartilage. This method of generating new bone might be of potential clinical use.

Animals↗

PubMed2003

Effect of Lactobacillus-fermented diets on bacterial translocation and intestinal flora in experimental prehepatic portal hypertension.

Spontaneous bacterial infections in cirrhosis and portal hypertension have been attributed to translocation of gut-derived bacteria, a process promoted by intestinal bacterial overgrowth and disruption of the gut mucosal barrier. Bacteriotherapy with Lactobacillus has been reported to correct bacterial overgrowth, stabilize mucosal barrier function, and decrease bacterial translocation in rat models of acute liver injury and failure. In this study we investigated the effect of Lactobacillus-supplemented diets on intestinal flora and on bacterial translocation rate in portal vein ligated rats. Lactobacillus-fermented milk (yogurt) containing at least 2 x 10(9) colony forming units/ml or placebo (water) was adminstrated by gavage twice daily (2 ml) for 9 days. Portal vein ligation was performed on day 7 of treatment. Bacterial translocation to mesenteric lymph nodes and quantification of intestinal flora was assessed by standard bacteriological cultures. Bacterial translocation was not significantly different between animals that received yogurt (82%) and those that received placebo (75%). Yogurt did not induce any significant changes in intestinal flora, whether it was produced with Lactobacillus acidophilus or Lactobacillus GG. In conclusion, in acute prehepatic portal hypertension, bacteriotherapy with Lactobacillus was unable to induce changes in bacterial translocation probably because it was unable to induce changes in bacterial flora.

Animals↗

PubMed2003

Major histocompatibility complex class I-restricted presentation of protein antigens without prior intracellular processing.

Proteins in their native form are incapable of stimulating antigen (Ag)-specific T cells, which can only recognize major histocompatibility complex (MHC)-bound peptides that have been generated by intracellular processing within antigen-presenting cells (APCs). Here, we show that APCs can trigger MHC class I-restricted T-cell responses after presenting proteins without conventional intracellular processing, provided the immunostimulatory MHC class I-binding peptide sequence is incorporated at the carboxy-terminal position. Such MHC-bound proteins do not stimulate T cells directly, because the contact between MHC/peptide complex and its cognate ligand is sterically hindered by the amino-terminal bulk of the protein. Removal of the latter via an extracellular Ag proteolysis by the T-cell- and/or APC-derived enzymes is required for effective T-cell stimulation. Our data challenge the established concept that only small peptides can bind to the MHC class I molecules.

Animals↗

PubMed2003

Identification of bulb from Fritillaria cirrhosa by PCR with specific primers.

Bulb of Fritillaria cirrhosa is an important traditional Chinese herbal medicine. According to the Chinese Pharmacopoeia (1995), it is commonly used as an antitussive and expectorant. Many young bulbs from species of Fritillaria are similar to those of F. cirrhosa, but they are different in price and quality. Therefore, there are many young bulbs from species of Fritillaria that could fake those of F. cirrhosa on the commercial market. The coding region of 5S-rRNA is highly conserved in higher eukaryotes. The 5S-rRNA spacer region sequences of F. thunbergii, F. pallidiflora, F. ussuriensi, F. delavayi, F.cirrhosa, F. anhuiensis, F. puqiensis were cloned by PCR with a pair of primers located within the conserved coding region. Based on sequences analyses of the 5S-rRNA spacer region from the 7 species, a specific sequence was found in F. cirrhosa. A pair of specific primers was designed for differentiating the bulbs of F. cirrhosa from each other by PCR. This result indicated that the method is rapid, more accurate and applicable in identification of the bulbs of F. cirrhosa at the DNA level.

Base Sequence↗

PubMed2003

[Surgical treatment of pulmonary aspergillosis].

We studied clinically upon 10 surgical cases of pulmonary aspergillosis. There were 7 male and 3 female cases, and the median age was 59 years. Seven cases had underlying bronchopulmonary diseases, and 9 cases had underlying diseases including systemic diseases, such as diabetes mellitus. There were 3 wedge resections, and 6 lobectomies, and 1 two-staged surgery (cavernostomy + muscle transposition). Eight cases whose lesion extended beyond neither chest wall nor mediastinal pleura were treated successfully by pulmonary resections almost within one lobectomy. One case, who had a cavitary lesion and multiple patchy infiltrates in the other lobes, cured by lobectomy including a main cavitary lesion and postoperative treatment with an antifungal agent. All cases returned home almost uneventfully, but 1 case of two-staged surgery died at home suddenly of massive hemoptysis. Surgical treatments of pulmonary aspergillosis are recommended when the lesions can be resected completely, that is, when patients are relatively well, lesions extend beyond neither chest wall nor hilar bronchus or vessels, and when the lungs other than the lesions are not extensively destroyed.

Adult↗

PubMed2002

Demonstration of the lateral casimir force.

The lateral Casimir force between a sinusoidally corrugated gold coated plate and large sphere was measured for surface separations between 0.2 to 0.3 microm using an atomic force microscope. The measured force shows the required periodicity corresponding to the corrugations. It also exhibits the necessary inverse fourth power distance dependence. The obtained results are shown to be in good agreement with a complete theory taking into account the imperfectness of the boundary metal. This demonstration opens new opportunities for the use of the Casimir effect for lateral translation in microelectromechanical systems.

Journal Article↗

PubMed2002

Hyaluronic acid and chondroitin sulphate A rapidly promote differentiation of immature DC with upregulation of costimulatory and antigen-presenting molecules, and enhancement of NF-kappaB and protein kinase activity.

Dendritic cells (DCs) have been identified as effective antigen-presenting cells (APCs). We demonstrate that extracellular matrix (ECM), hyaluronic acid (HA) and chondroitin sulphate A (CSA), in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF), can rapidly promote the differentiation of monocyte-derived immature DCs, as characterized by the remarkable upregulation of human leucocyte antigen (HLA-DR), CD40, CD54, CD80 and CD86 expression to levels higher than those in the DCs generated by culturing with GM-CSF and interleukin (IL)-4 for 7 days and aggregation of the cells within 48 h. The upregulation of expression of HLA-DR, CD40, CD54, CD80 and CD86 was dose-dependent. Further studies showed that HA and CSA were able to augment nuclear factor (NF)-kappaB activity, as determined by gel mobility shift assay and promote protein phosphorylation. Inhibition of NF-kappaB by pyrolidine dithiocarbamate and sodium salicylate, and serine-threonine and tyrosine kinase by starosporine as well as phosphatidylinositide-3-kinase (PI-3-K) by wortmannin could prevent the effects of HA and CSA on the expression of HLA-DR, CD40, CD80 and CD86 in various degrees. Thus, our data demonstrate that HA or CSA can effectively and rapidly promote the differentiation of immature DC, suggesting that HA and CSA may possess a potential capacity in regulating immune responses.

Antigen Presentation↗

PubMed2002

[Surgical treatment of Marfan syndrome; analysis of the patients required multiple surgical interventions].

Without treatment, the life expectancy of patients with Marfan syndrome is reduced by the associated cardiovascular abnormalities. In this study, we reviewed our experience of the patients with Marfan syndrome who required multiple surgical interventions to identify the optimal treatment for these patients. Between January 1986 and December 2000, 44 patients with Marfan syndrome were operated on at Shizuoka City Hospital (SCH). Among them, 10 patients (22.7%) underwent multiple surgical interventions. There were 5 male and 5 female patients with a mean age of 40.6 +/- 16.1 years at the initial surgery. Only one patient was operated on at another hospital for his first, second, and third operations. His fourth operation was carried out at SCH. The remaining 9 patients underwent a total of 14 additional surgical procedures at SCH. Computed tomography (CT) scans were taken every 6 months postoperatively, and aortic diameter greater than 60 mm was considered as the indication for the additional surgery. There were no early death and one late death. The causes of additional surgery were enlargement of true aneurysm in 6, enlargement of residual dissection in 4, new dissection in 4, false aneurysm at the coronary anastomosis of Bentall procedure in 1. In 9 patients, both ascending and descending aorta were replaced. Among these 9 patients, only 3 patients underwent total arch replacement, and remaining 6 patients had their arch left in place with or without dissection. Our current strategy of the treatment of Marfan patients with acute type A dissection is total arch replacement with an elephant trunk at the initial emergent surgery.

Adolescent↗

PubMed2001

An anion-induced regio- and chemoselective acylation and its application to the synthesis of an anticancer agent.

[reaction--see text] An efficient Grignard- and organolithium-induced regio- and chemoselective anionic acylation is reported. A number of tricyclic ketones are prepared in good to excellent yields via this method. This method is complementary to the Frieldel-Crafts acylation for electron-deficient substrates. A novel anisole-based Grignard reagent was developed to effect the cyclization of sterically hindered substrates. This novel reagent has been successfully applied to the synthesis of Sch 66336, a candidate for oncologic treatment.

Acylation↗

PubMed2001

Application of statistically-based experimental designs for the optimization of eicosapentaenoic acid production by the diatom Nitzschia laevis.

Statistically based experimental designs were applied to the optimization of medium components and environmental factors for eicosapentaenoic acid (EPA) production by the diatom Nitzschia laevis in heterotrophic conditions. First, the Plackett-Burman design was used to evaluate the effects of variables including medium components and environmental factors on cell growth and EPA production. Among these variables, NaCl, CaCl(2), PI metal solution, pH, and temperature were identified to have the significant effects (with confidence level > 90 %). Subsequently, the concentrations of NaCl, CaCl(2), PI metal solution as well as the values of pH and temperature were optimized using central composite design. The cell growth and EPA production were found to respectively correlate to NaCl, CaCl(2), pH, and temperature that could be represented by second-order polynomial models. The optimal values of the four parameters were determined by response surface and numerical analyses as 8 g/L NaCl, 0.10 g/L CaCl(2), pH 8.5 and 19.8 degrees C for cell dry weight (DW), and 14 g/L NaCl, 0.10 g/L CaCl(2), pH 8.5 and 18 degrees C for EPA production, respectively. The subsequent verification experiments confirmed the validity of the models. This optimization strategy led to a DW of 9 g/L, an EPA yield of 280 mg/L and an EPA productivity of 28 mg/L/d, respectively, which were considerably higher than those obtained in the previous studies.

Biotin↗

PubMed2001

Preparative isolation and purification of salidroside from the Chinese medicinal plant Rhodiola sachalinensis by high-speed counter-current chromatography.

High-speed counter-current chromatography was applied to the isolation and purification of salidroside from the Chinese medicinal plant Rhodiola sachalinensis A. Bor. The crude salidroside was obtained by extraction with methanol from Rhodiola sachalinensis A. Bor. Preparative high-speed counter-current chromatography with a two-phase solvent system composed of n-butanol-ethyl acetate-water (2:3:5, v/v) was successfully performed yielding salidroside (32 mg) at 98% purity from 250 mg of the crude extract in a one-step separation.

Chromatography, High Pressure Liquid↗

PubMed2001

Characterization of the DNA-binding property of Smad5.

Activation of TGF-beta superfamily receptors leads to phosphorylation of Smad proteins which function as transcription factors to regulate gene expression. Previous studies have indicated that Smad5, together with Smad1 and Smad8, participates in signaling downstream of BMP receptors. To characterize the DNA-binding characteristics of Smad5, we used the GST-Smad5 N-terminal fusion protein to select for random oligonucleotide sequences that were able to binds the protein. As a result, we found that Smad5 is able to bind a consensus sequence TGTGC. We further used the Smad7 promoter sequence that contains a Smad-binding element (SBE), GTCTAGAC to determine how mutations in each nucleotide in the SBE affects the binding with Smad5, compared with the binding with Smad1, Smad2, Smad3, Smad4, and Smad8. Interestingly, Smad5, but not Smad1 and Smad8, was able to bind the SBE, at a level similar to the binding by Smad3 and Smad4. However, mutations at the SBE had different effect on the binding with Smad5, compared to that with Smad3 and Smad4. These studies suggest that even though Smad5 falls into the same subfamily with Smad1 and Smad8 in mediating the signaling by BMP receptors, it has an unique DNA-binding property that is similar to Smad3, which specifically transduces signaling for TGF-beta and activin receptors.

Animals↗

PubMed2001

EBNA promoter usage in EBV-negative Burkitt lymphoma cell lines converted with a neomycin-resistant EBV strain.

Latent Epstein-Barr virus (EBV) uses two alternative strategies to express the Epstein-Barr nuclear antigens (EBNAs). Resting normal B cells harboring latent virus and Burkitt's lymphoma (BL) cells use monocistronic messages generated from the Q promoter (restricted strategy). EBV-transformed immunoblasts express all EBNAs by using giant messages generated from the W/C promoter (full program). Whether the virus establishes the restricted program on primary infection of a BL cell (or its progenitor) or, alternatively, whether such cells are generated by phenotypic down-regulation from the immunoblast is unclear. We found previously that conversion of EBV-negative BL lines to EBV-positive sublines required repeated exposure to large virus doses. The converted sublines used the full program. However, the possibility that cells with a full program had a selective advantage during the long period of in vitro passage could not be excluded. We therefore infected EBV-negative BL lines with recombinant EBV carrying a neomycin resistance marker. Most convertants of the 12 lines tested were positive for YUK splicing, indicative of the full program, but some were also positive for the restricted QUK splice program. One convertant DG75 line showing both YUK and QUK was cloned and gave rise to stable QUK users. We conclude that EBV infection of established BL lines can give rise to subclones with either the full or the restricted program. The fact that all EBVs carrying BL lines use the restricted program in vitro may be a consequence of immunoselection.

Anti-Bacterial Agents↗

PubMed2001

Formation of neurofibrillary tangles in P301l tau transgenic mice induced by Abeta 42 fibrils.

beta-Amyloid plaques and neurofibrillary tangles (NFTs) are the defining neuropathological hallmarks of Alzheimer's disease, but their pathophysiological relation is unclear. Injection of beta-amyloid Abeta42 fibrils into the brains of P301L mutant tau transgenic mice caused fivefold increases in the numbers of NFTs in cell bodies within the amygdala from where neurons project to the injection sites. Gallyas silver impregnation identified NFTs that contained tau phosphorylated at serine 212/threonine 214 and serine 422. NFTs were composed of twisted filaments and occurred in 6-month-old mice as early as 18 days after Abeta42 injections. Our data support the hypothesis that Abeta42 fibrils can accelerate NFT formation in vivo.

Aged↗

PubMed2001

The role of AP-1 in the transcriptional regulation of the rat apical sodium-dependent bile acid transporter.

Ileal reclamation of bile salts, a critical determinant of their enterohepatic circulation, is mediated primarily by the apical sodium-dependent bile acid transporter (ASBT=SLC10A2). We have defined mechanisms involved in the transcriptional regulation of ASBT. The ASBT gene extends over 17 kilobases and contains five introns. Primer extension analysis localized two transcription initiation sites 323 and 255 base pairs upstream of the initiator methionine. Strong promoter activity is imparted by both a 2.7- and 0.2-kilobase 5'-flanking region of ASBT. The promoter activity is cell line specific (Caco-2, not Hep-G2, HeLa-S3, or Madin-Darby canine kidney cells). Four distinct specific binding proteins were identified by gel shift and cross-linking studies using Caco-2 or rat ileal nuclear extracts. Two AP-1 consensus sites were identified in the proximal promoter. DNA binding and promoter activity could be abrogated by mutation of the proximal AP-1 site. Supershift analysis revealed binding of c-Jun and c-Fos to this AP-1 element. Co-expression of c-Jun enhanced promoter activity in Caco-2 cells and activated the promoter in Madin-Darby canine kidney cells. Region and developmental stage-specific expression of ASBT in the rat intestine correlated with the presence of one of these DNA-protein complexes and both c-Fos and c-Jun proteins. A specific AP-1 element regulates transcription of the rat ASBT gene.

Animals↗

PubMed2001

Preparative isolation and purification of astaxanthin from the microalga Chlorococcum sp. by high-speed counter-current chromatography.

High-speed counter-current chromatography was applied to the isolation and purification of astaxanthin from microalgae. The crude astaxanthin was obtained by extraction with organic solvents after the astaxanthin esters were saponified. Preparative high-speed counter-current chromatography with a two-phase solvent system composed of n-hexane-ethyl acetate-ethanol-water (5:5:6.5:3, v/v) was successfully performed yielding astaxanthin at 97% purity from 250 mg of the crude extract in a one-step separation.

Chlorophyta↗

PubMed2001

Preparative isolation and purification of six diterpenoids from the Chinese medicinal plant Salvia miltiorrhiza by high-speed counter-current chromatography.

A high-speed counter-current chromatography (HSCCC) method was developed for the preparative separation and purification of six diterpenoids. dihydrotanshinone I, cryptotanshinone, methylenetanshiquinone, tanshinone I, tanshinone IIA and danshenxinkun B from the Chinese medicinal plant Salvia miltiorrhiza Bunge. The crude diterpenoids were obtained by extraction with ethanol-n-hexane (1:1, v/v) from S. miltiorrhiza Bunge. Preparative HSCCC with the two-phase solvent systems A composed of n-hexane-ethanol-water (10:5.5:4.5, v/v) and B composed of n-hexane-ethanol-water (10:7:3, v/v) was successfully performed in a stepwise elution yielding six relatively pure diterpenoids from 300 mg of the crude extract in a single run. The purities of dihydrotanshinone I, cryptotanshinone, methylenetanshiquinone, tanshinone I, tanshinone IIA and danshenxinkun B were 88.1, 98.8, 97.6, 93.5, 96.8 and 94.3%, respectively.

Chromatography, High Pressure Liquid↗