Biomedical subjects

F Yan

Publications and source records attributed to F Yan.

At least 37 records · Page 2Linked to original sources

PubMed2001

[Studies on the cell suspension culture of Saussarea medusa in a stirred tank bioreactor].

The cell suspension culture of Saussarea medusa in a 2L aerated and agitated bioreactor with a four-pitch-blade impeller was investigated. The effects of agitation speed, aeration and inoculum size on cell growth and flavonoids production were studied and it was found that cells had optimum growth and flavonoids production when cultivated at 75 r/min, 700-1000 L/min and an inoculum of 4.0-5.0 g/L. A high cell biomass of 13.8 g/L and flavonoids production of 416 mg/L were achieved after 12 days of cultivation. Time course study revealed that flavonoids biosynthesis was growth-associated. The studies on aggregates size distribution in the bioreactor showed that the aggregates break-up caused by hydrodynamic stress might adversely affect cell growth and lead to significant reduction of cell biomass and flavonoids production.

Bioreactors↗

PubMed2001

[Comparison of enhancement patterns of multi-phase scan of dynamic MRI and dynamic CT in small hepatocellular carcinoma].

OBJECTIVE: To study prospectively the enhancement features of multi-phase scan of dynamic MRI and spiral CT in the diagnosis of small hepatocellular carcinoma (SHCC) and to discuss the cause of dynamic MRI being superior to spiral CT. METHODS: Multi-phase contrast scanning of dynamic MR and spiral CT were done in 53 SHCC patients. The lesions were proved by surgery and pathology. The arterial-phase, portal venous-phase and delayed phase scan of spiral CT were carried out after the pre-contrast scanning of the entire liver. MRI was performed with SE sequence and FMPSPGR sequence dynamic multi-phase contrast scans. RESULTS: Seventy-six lesions were found in 53 patients. Sixty-nine lesions and 54 lesions were enhanced obviously in MR and spiral CT arterial-phase scans. The typical enhancement patterns of SHCC in the arterial-phase, portal venous-phase and delayed phase scan of MRI and spiral CT were hyper-hypo-hypointense (dense) and hyperintense (hyperdense), -isointense (isodense) and -hypointense (hypodense). Atypical enhancement patterns were hyperintense (hyperdense), -hyperintense (hyperdense), -hyperintense (hyperdense), -hyperintense (hyperdense), -isointense (isodense), -isointense (isodense) and -hypointense- (hypodense), -hypointense (hypodense) and -hypointense (hypodense). CONCLUSION: Both dynamic MRI and spiral CT multi-phase contrast scanning are able to demonstrate the enhancement features of SHCC, with arterial-phase scan of MRI being superior to spiral CT in reflecting the hypervascular characterization of SHCC. Combined with SE sequence in characterizing the SHCC, MRI is better than spiral CT.

Adult↗

PubMed2001

[A primary clinical analysis of artificial bone implantation of cleft palate].

OBJECTIVE: To observe whether repairing the hard palate can improve velopharyngeal function. METHODS: 40 patients with hard palate cleft were randomly divided into two groups: the control group and the implantation group. Each group had 20 patients. The patients in the implantation group were implanted with compound artificial bone of HA--Bone cement. All patients hag been followed up for three months postoperatively. The patients in the repaired group were examined using computer tomography. All patients were examined using NPF. RESULTS: The implanted artificial bone had no rejection. The computer tomography showed that the implanted artificial bone in hard palate had no shifting, subsidence or breakage. The movement of soft palate of the implantation group was greater than the control group. The velopharyngeal function of the implantation group was much better than the control group. CONCLUSION: Repairing the hard palate cleft with artificial bone can improve velopharyngeal function.

Biocompatible Materials↗

PubMed2001

Rapid analysis of momordicoside A in bitter melon by high performance liquid chromatography following solid phase extraction.

A rapid, simple and accurate method for the determination of momordicoside A has been established using solid phase extraction (SPE) followed by high performance liquid chromatography (HPLC). Sample was processed by SPE on a Carb cartridge (3 mL/250 mg), and was then determined by HPLC on a C18 column (4.6 mm i.d. x 250 mm, 5 microns) with V(acetonitrile):V(methanol):V(50 mmol/L potassium dihydrogen phosphate buffer) = 25:20:60 as mobile phase (0.8 mL/min) and UV detection at 208 nm. The calibration curves were linear from 10 mg/L to 1,000 mg/L (r2 = 0.9992). The analytical method was shown to be highly reproducible, giving all of the relative standard deviations and relative mean errors less than 10% for both intra-day and inter-day determinations. The absolute recoveries were greater than 90%.

Antineoplastic Agents, Phytogenic↗

PubMed2000

Polymer-supported and chemoenzymatic synthesis of the Neisseria meningitidis pentasaccharide: a methodological comparison.

Neisseria meningitidis trisaccharide [GlcNAc[(1-->3)Galbeta(1-->4)Glc-R], tetrasaccharide [Galbeta(1-->4)GlcNAcbeta(1--> 3)Galbeta(1-->4)Glc-R], and a pentasaccharide [Neu5Acalpha(2-->3)Galbeta(1-->4)GlcNAcbeta(1-->3)G albeta(1-->4)Glc-SPh] were prepared via conventional chemical synthesis, polymer-supported synthesis, and chemoenzymatic methods, starting from D-lactose. The polymer polyethyleneglycol monomethylether (MPEG) and the linker dioxyxylene (DOX) were used with a lactose-bound acceptor to improve the purification process. Several enzymes (LgtA, GalE-LgtB fusion, and CMP-Neu5Ac synthetase/sialyltransferase fusion) were used for syntheses of these oligosaccharides. Excellent stereo- and regioselectivities as well as high yield (> 90% from Gal(1-->4)Glc-SPh) of the pentasaccharide were obtained. Both of the convenient processes are suitable for efficient preparation of target oligosaccharides.

Antigens, Bacterial↗

PubMed2000

Nonphytate phosphorus requirement and phosphorus excretion of broiler chicks fed diets composed of normal or high available phosphate corn with and without microbial phytase.

A study was conducted to evaluate the ability of the young (0 to 3 wk) broiler chicken to utilize the P provided by a high available P corn [HAPC; 0.27% total P and 0.17% nonphytate P] in comparison with yellow dent corn (YDC; 0.23% total P and 0.03% nonphytate P), and to determine the extent to which supplementation with exogenous phytase enzyme could reduce the demands for dietary P and subsequently reduce P excretion. Diets prepared using the two types of corn differed in the amount of phytate-bound P, with the HAPC diets containing approximately 50% less phytate-bound P. Treatment diets were prepared by varying the amount of dicalcium phosphate, and ranged from 0.10 to 0.50% nonphytate P for YDC diets, and from 0.18 to 0.50% nonphytate P for HAPC diets. Sublots of each diet were supplemented with 800 units/kg phytase. Each diet was fed to six pens of five male chicks of a commercial broiler strain from 1 to 21 d of age. Regression analysis was used to estimate nonphytate P requirements for each corn type with and without phytase supplementation. The greatest need for nonphytate P was for maximum tibia ash, with requirements of 0.39, 0.29, 0.37, and 0.32% in diets with YDC, YDC plus phytase, HAPC, and HAPC plus phytase, respectively. Addition of phytase liberated approximately 50% of the phytate-bound P from each diet. These levels were sufficient to support body weight, feed conversion, and livability. Fecal P content of broilers fed diets with YDC at the NRC (1994) recommended level of 0.45% nonphytate P was 1.21%, whereas at the respective requirement points indicated above, the P content was 1.09, 0.87, 0.78, and 0.64% in feces from broilers fed diets with YDC, YDC plus phytase, HAPC, and HAPC plus phytase, respectively. Thus, fecal P output could be reduced while maintaining optimum performance by the use of reduced dietary nonphytate P, introduction of HAPC, and phytase supplementation. One of the greatest benefits of phytase supplementation appeared to be maintaining livability at lower dietary levels of nonphytate P.

6-Phytase↗

PubMed2000

Evaluation of normal yellow dent corn and high available phosphorus corn in combination with reduced dietary phosphorus and phytase supplementation for broilers grown to market weights in litter pens.

A study was conducted to determine the extent fecal P levels could be reduced while maintaining performance. Various strategies were employed including the use of a high available phosphorus hybrid of corn (HAPC), supplementation with phytase enzyme, and reduced dietary P levels. The use of HAPC resulted in a 50% reduction in phytate-bound dietary P as compared with a normal yellow dent corn (YDC) diet. Dietary nonphytate P was maintained at either NRC (1994) recommendations for appropriate age periods or reduced by 0.075 or 0.15%. Portions of the diets were supplemented with 1,000 units of phytase/kg. Male chicks of a commercial strain were grown to 56 d on the test diets. Broilers fed diets with HAPC had BW, feed conversion, livability, and tibia ash that were equal to or superior to those fed diets with YDC with considerably reduced fecal P content at any dietary level of nonphytate P. Phytase supplementation enabled birds to maintain live performance at lower levels of nonphytate P, further reducing the fecal P output. One of the greatest contributions of phytase was a reduction in mortality at the lower levels of nonphytate P. Dietary P levels could be reduced by 0.075% under NRC (1994) recommendations without adversely affecting live performance; a reduction of 0.15% in conjunction with phytase supplementation maintained BW, feed conversion, and livability but reduced tibia ash. The extent to which dietary P levels can be reduced over the entire feeding program is subject to further research.

6-Phytase↗

PubMed2000

Glycosaminoglycans in gingival crevicular fluid of patients with periodontal class II furcation involvement before and after guided tissue regeneration. A pilot study.

BACKGROUND: The levels of glycosaminoglycans in gingival crevicular fluid (GCF) are good indicators of underlying tissue turnover. We hypothesize that connective tissue elements in GCF may be used as indicators of tissue maturation underneath barrier membranes. Therefore, we investigated the levels of sulfated glycosaminoglycans in GCF at sites before and after guided tissue regeneration (GTR). METHODS: Six patients were selected on the basis of having at least one Class II buccal furcation involvement on a molar tooth. Each molar furcation was treated with the standard GTR surgical protocol using a non-resorbable expanded polytetrafluoroethylene membrane. Gingival crevicular fluid samples were taken at baseline (immediately prior to insertion of the membrane) and at 1, 2, 3, 4, 5, and 6 weeks (immediately prior to removal of the membrane). Glycosaminoglycan levels were determined using an Alcian blue dye detection system. RESULTS: The mean levels of chondroitin sulfate and total sulfated glycosaminoglycans in GCF significantly decreased during the first 4 weeks after GTR surgery. By week 5, the levels began to rise, and by week 6 the levels had returned to baseline levels. CONCLUSIONS: Sulfated glycosaminoglycans can be monitored in GCF at healing GTR sites. It is proposed that this is a useful means of monitoring the status of the regenerating tissues. However, further longitudinal studies are required to assess if the sulfated glycosaminoglycans can be used as indicators of tissue maturation under guided tissue membranes used to treat periodontal defects.

Adult↗

PubMed2000

[Study of expression of hepatitis C virus antigens and viral replication in extrahepatic tissues].

OBJECTIVE: To explore the state of hepatitis C virus (HCV) infection and replication in extrahepatic tissues and its significance in hepatitis C patients. METHODS: Immunohistochemical assay and reverse transcriptase polymerase chain reaction (RT-PCR) were used respectively to detect HCV antigens (NS3, NS5 and CP10) and HCV RNA positive-and negative-strand in kidney, heart, pancreas, and intestine from 9 hepatitis C patients. RESULTS: Positive staining for HCV NS3, NS5 and CP10 in extrahepatic tissues was found in 6 of the 9 (66.7%) patients. The expression of HCV antigens was observed only in plasma of cells. The amount of positive-staining cells was less and there were a few differences between the kind, amounts and distribution of HCV antigen-positive-staining cells in different extrahepatic tissues. HCV RNA was detected in extrahepatic tissues from all the patients by RT-PCR. The detection rates of HCV RNA positive-and negative-strand were 64.5% and 35.5% in 31 extrahepatic tissues specimens, respectively. The positive of HCV RNA positive-and negative-strand detection was coincident with that of HCV antigens detection in these tissues (Kappa>0.40). CONCLUSIONS: These results suggest a possible presence of HCV infection and replication in extrahepatic tissues. Low-level of HCV extrahepatic infection and replication is possibly a major cause of a low positive rate and inconsistent results of HCV detection in extrahepatic tissues.

Adult↗

PubMed2000

[Primary identification of organic compounds in soybean rhizospheric soil on continuous and alternate cropping and their allelopathy on soybean seed germination].

Organic compounds extracted with ethanol (OCEWE) from soybean rhizospheic soil on continuous and alternate cropping at pod-string were identified by gas chromatography-mass spectrometry (GC-MS). The results showed the compounds mainly include organic acids, alcohol, acetone, aldehyde, naphthalene phenyl and furan hydrocarbon, many of which were reported as allelochemcals. Under this experiment condition, OCEWE did not show any allelopathy on soybean seed germination and radicle growth, which might be related with their critical toxicity concentrations. In addition, the relationship between allelopathy and barrier on soybean continuous and alternate cropping was also discussed.

Acids↗

PubMed2000

[Spiral CT features of hepatocellular caicinoma].

OBJECTIVE: To analyze the features of two-phase spiral scanning in 54 cases of hepatocellular carcinoma and to evaluate its usefulness in diagnosis and differential diagnosis. METHODS: Precontrast and postcontrast CT scans of the whole liver in all cases were carried out with GE-Hispeed Advantage spiral CT scanner. The arterial phase scanning was started at 25 sec after injection of contrast medium and the portal venous phase scanning at 70 sec. RESULTS: In the 54 cases examined, 72 lesions were found in the arterial phase. In 28 of these lesions, it was enhanced homogeneously, while in 40 lesions, the enhancement was not homogeneous. Supplying artery could be seen in 4 of them. The remaining 4 lesions had no enhancement. There were 62 lesiosns with low density in portal venous phase. Portal vein tumor thrombus was seen in 8 cases, and pseudocapsule was observed in 7 lesions. CONCLUSION: Two-phase spiral CT scanning is of value in the diagnosis and differential diagnosis of hepatocellular carcinoma.

Adult↗

PubMed2000

[An experimental study of myocardial injury by hydrofluoric acid in burned rabbits].

OBJECTIVE: To investigate the myocardial injury by hydrofluoric acid in burned rabbits METHODS: New Zealand white rabbits were injured with 2% TBSA III degree skin burn on the back by hydrofluoric acid. The blood and tissue samples were taken from the rabbit after injury for the detection of myocardial and related enzymes and the pathomorphological examination. RESULTS: (1) Postburn myocardial enzymes increased significantly compared to those before burn (P < 0.01). (2) All the myocardial enzymes reached their peak levels within 48 postburn hours and were higher than those before burn (P < 0.01). (3) Among all the enzymes, CPK increased by 97.5% and those of LDH, AST and CK-MB by 81.9%, 76.1% and 60.3%, respectively. (4) Pathomorphological findings with LM were the granular degeneration and focal necrosis of myocardial fibers, interstitial hemorrhage of myocardium accompanied with neutrophil and lymphocyte infiltration. Ultrastructural changes included myofibril decrease or even disappearing, severe cellular and mitochondrial swelling, disappearing of mitochondrial crista, endothelial swelling, decrease of electronic density with the exhibiting of bulla and deformation of myocardial cellular nucleus. CONCLUSION: Myocardial function could be damaged after hydrofluoric acid burn. Therefore, special attention should be paid to the protection of cardiac function after hydrofluoric acid burn by strengthening the monitoring of myocardial enzymes and ECG, etc.

Animals↗

PubMed2000

[The change in placental estradiol-progesterone ratio and its relationship with the fetal membrane's response to IL-1 beta in labor].

This study was designed to investigate the local changes in the levels of placental estradiol and progesterone and their ratio during term labor and to determine whether the PGE2-generating ability of the fetal membrane in response to IL-1 beta at term labor is greater than that at term not-in-labor. Forty pregnant women were divided into two groups: term labor and term not-in-labor. Placental estradiol and progesterone were measured by radioimmunoassay. The levels of fetal membrane PGE2 were measured by enzymoimmunoassay. The results showed that the placental concentration of estradiol and progesterone remained unchanged at the onset of labor, but the ratio of estradiol to progesterone increased significantly (P < 0.05). IL-1 beta stimulated fetal membrane to produce more PGE2 at term labor, and at term not-in-labor, too. But the increment of PGE2 generated by fetal membrane at term labor was greater than that at term not-in-labor. It is concluded that the change in placental estradiol to progesterone ratio may play an important role in the initiation of labor by altering the PGE2-generating ability of fetal membrane in response to cytokines.

Adult↗

PubMed2000

[The evaluation of cervical lymph node metastasis of laryngeal cancer using magnetic resonance imaging (MRI)].

OBJECTIVE: To assess the potential or limitation of MRI for demonstrating the pathological cervical lymphnodes. METHOD: A prospective diagnostic study on cervical lymphnode metastasis from laryngeal carcinoma was performed for 19 cases undergone neck dissection (5 cases undergone bilateral neck dissection, 24 specimens of neck dissection were collected in total). With pathological findings as the criterion, sensitivity and specificity and accuracy were calculated for palpation and MRI examination of all patients. RESULT: MRI had obviously higher sensitivity specificity and accuracy than palpation. Besides the changes in size and shape of the metastatic lymphnodes, the intensity of MRI inside the metastatic lymphnodes was showed as mixed hypo-isointensity in T1WI and hyper intensity in T2WI. CONCLUSION: MRI examination was accurate in detecting cervical lymphnode metastasis and could image occult lymphnodes which are inaccessible on palpation. Thus, MRI will probably play an important role in the evaluation of malignant lymphnode metastasis.

Adult↗

PubMed2000

A comparison of the effects of two kinds of glass-ionomer cement on human gingival fibroblast attachment, proliferation and morphology in vitro.

The aim of this study was to compare the response of cultured human gingival fibroblasts to two kinds of glass-ionomer cement in vitro with regards to understanding the biocompatibility of these materials and their suitability for use as subgingival restorative materials. The glass-ionomer cements tested were Ketac Fil, and GC Fuji II. These cements were mixed according to the manufacturers' directions and condensed into tissue culture wells or cavities prepared on the root surfaces of extracted teeth. Healthy root slices and untreated tissue culture wells were used as controls. Several features such as attachment, proliferation and morphology of cells were studied. The results indicated that cells could not attach to the glass-ionomer cements unless they had been washed with distilled water and tissue culture media. No significant difference in initial attachment (1.5h) and long term attachment (48h) between the groups tested was noted. No significant difference was observed between levels of proliferation for human gingival fibroblasts grown on Ketac Fil, Fuji II, root slices and culture wells. No significant alterations of the cytomorphology could be detected in glass-ionomer cement compared with root slices. These results indicate that provided the surface is adequately washed, Ketac Fil, and Fuji II may be acceptable subgingival root surface restorative materials.

Analysis of Variance↗

PubMed1999

Aminosalicylic acid inhibits IkappaB kinase alpha phosphorylation of IkappaBalpha in mouse intestinal epithelial cells.

Tumor necrosis factor alpha (TNFalpha)-stimulated nuclear factor (NF) kappaB activation plays a key role in the pathogenesis of inflammatory bowel disease (IBD). Phosphorylation of NFkappaB inhibitory protein (IkappaB) leading to its degradation and NFkappaB activation, is regulated by the multimeric IkappaB kinase complex, including IKKalpha and IKKbeta. We recently reported that 5-aminosalicylic acid (5-ASA) inhibits TNFalpha-regulated IkappaB degradation and NFkappaB activation. To determine the mechanism of 5-ASA inhibition of IkappaB degradation, we studied young adult mouse colon (YAMC) cells by immunodetection and in vitro kinase assays. We show 5-ASA inhibits TNFalpha-stimulated phosphorylation of IkappaBalpha in intact YAMC cells. Phosphorylation of a glutathione S-transferase-IkappaBalpha fusion protein by cellular extracts or immunoprecipitated IKKalpha isolated from cells treated with TNFalpha is inhibited by 5-ASA. Recombinant IKKalpha and IKKbeta autophosphorylation and their phosphorylation of glutathione S-transferase-IkappaBalpha are inhibited by 5-ASA. However, IKKalpha serine phosphorylation by its upstream kinase in either intact cells or cellular extracts is not blocked by 5-ASA. Surprisingly, immunodepletion of cellular extracts suggests IKKalpha is predominantly responsible for IkappaBalpha phosphorylation in intestinal epithelial cells. In summary, 5-ASA inhibits TNFalpha-stimulated IKKalpha kinase activity toward IkappaBalpha in intestinal epithelial cells. These findings suggest a novel role for 5-ASA in the management of IBD by disrupting TNFalpha activation of NFkappaB.

Animals↗

PubMed1999

Phenylalanine 138 in the second intracellular loop of human thromboxane receptor is critical for receptor-G-protein coupling.

Eicosanoid receptors exhibit a highly conserved ERY(C)XXV(I)XXPL sequence in the second intracellular loop. The carboxyl end of this motif contains a bulky hydrophobic amino acid (L,I,V, or F). In human thromboxane A2 receptor (TXA(2)R), phenylalanine 138 is located at the carboxyl end of this highly conserved motif. This study examined the function of the F138 in G protein coupling. F138 was mutated to aspartic acid (D) and tyrosine (Y), respectively. Both mutants F138D and F138Y showed similar ligand binding activity to that of the wild type TXA(2)R. The Kd and Bmax values of either mutant were comparable to those of the wild type receptor. However, both mutants showed significant impairment of agonist induced Ca(2+) signaling and phospholipase C activation. These results suggest that the F138 plays a key role in G protein coupling.

Amino Acid Sequence↗

PubMed1999

Conversion of TNF alpha from antiproliferative to proliferative ligand in mouse intestinal epithelial cells by regulating mitogen-activated protein kinase.

The mechanisms regulating the balance between intestinal epithelial cell proliferation and differentiation are essential to maintaining an intact mucosal barrier. Mitogen-activated protein (MAP) kinases appear to be key transducers of extracellular signals in these pathways. The goal of this study was to investigate the regulation of MAP kinase by tumor necrosis factor alpha (TNFalpha) and epidermal growth factor (EGF) in intestinal epithelial cells. The young adult mouse colon cell line was studied for TNFalpha and/or EGF regulation of MAP kinase in the presence or absence of the MAP kinase kinase (MEK1) inhibitor PD 98059. Proliferation was determined by hemocytometry, and activated MAP kinase was identified by Western blot analysis, in vitro kinase assay, and confocal laser immunofluorescent microscopy. TNFalpha stimulated sustained nuclear MAP kinase activity, while EGF stimulated transient cytoplasmic MAP kinase activity. Changing TNFalpha's sustained MAP kinase activation to transient converted TNFalpha from an anti-proliferative to a proliferative ligand. These findings demonstrate that both TNFalpha and EGF activate MAP kinase in intestinal epithelial cells. The kinetics and subcellular distribution of this enzyme activity may be pivotal in the transduction of divergent cellular responses in the intestinal epithelium with implications for altered proliferative signals in inflammatory bowel disease.

Animals↗