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Biomedical subjects

F Yan

Publications and source records attributed to F Yan.

At least 55 records · Page 3Linked to original sources
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↗
PubMed1999

Mesalamine blocks tumor necrosis factor growth inhibition and nuclear factor kappaB activation in mouse colonocytes.

BACKGROUND & AIMS: Derivatives of 5-aminosalicylic acid (mesalamine) represent a mainstay in inflammatory bowel disease therapy, yet the precise mechanism of their therapeutic action is unknown. Because tumor necrosis factor (TNF)-alpha is important in the pathogenesis of inflammatory bowel disease, we investigated the effect of mesalamine on TNF-alpha-regulated signal transduction and proliferation in intestinal epithelial cells. METHODS: Young adult mouse colon cells were studied with TNF-alpha, epidermal growth factor, or ceramide in the presence or absence of mesalamine. Proliferation was studied by hemocytometry. Mitogen-activated protein (MAP) kinase activation and IkappaBalpha expression were determined by Western blot analysis. Nuclear transcription factor kappaB (NF-kappaB) nuclear translocation was determined by confocal laser immunofluorescent microscopy. RESULTS: The antiproliferative effects of TNF-alpha were blocked by mesalamine. TNF-alpha and ceramide activation of MAP kinase were inhibited by mesalamine, whereas epidermal growth factor activation of MAP kinase was unaffected. TNF-alpha-stimulated NF-kappaB activation and nuclear translocation and the degradation of Ikappa-Balpha were blocked by mesalamine. CONCLUSIONS: Mesalamine inhibits TNF-alpha-mediated effects on intestinal epithelial cell proliferation and activation of MAP kinase and NF-kappaB. Therefore, it may function as a therapeutic agent based on its ability to disrupt critical signal transduction events in the intestinal cell necessary for perpetuation of the chronic inflammatory state.

Animals↗
PubMed1999

[Evaluation of the arterial phase of biphase enhanced SCT in the diagnosis of small HCC].

OBJECTIVE: To evaluate the value of the arterial phase (AP) of biphase enhanced SCT in the diagnosis of small HCC and investigate the criteria, initial time, ending time and duration of AP. METHODS: From May 1995 to March 1999, patients with small HCC proved by surgicopathology including 49 cases (N = 53) in the 1st group, 148 cases (N = 186) in the 2nd group and 52 cases (N = 52)n in the 3rd group were collected. Biphase dynamic enhanced SCT scans were performed in all patients of three groups and additional single-level dynamic scans only done in the 3rd group. The detectability, diagnostic accuracy of the lesions and enhancement of the lesion in AP were analyzed statistically. In addition, the initial time, ending time and duration of AP were measured. RESULTS: The results of the 1st group showed the detectability of small HCC was 88.68% in AP and 90.57% in both phases, higher than those by US. Markedly enhanced lesion in AP accounted for 76% and 78% in the 2nd and 3rd groups respectively. The initial, ending and duration times of AP measured on single-level dynamic scans were 16.9 s, 39.6 s and 22.7 s in average respectively. CONCLUSION: The biphase dynamic SCT especially its arterial phase appears to be very valuable in diagnosing small HCCs. In light of short duration of AP, understanding and strict control of AP is obviously imperative.

Adult↗
PubMed1999

[The value of MR cholangiopancreatograghy in diagnosis of obstructive jaundice].

OBJECTIVE: To evaluate the diagnostic value of MRCP in finding positions and causes of obstructive jaundice. METHODS: Fourty-two patients with obstructive jaundice received MRCP examination. All patients were finally onfirmed operatively. RESULTS: The correct diagnostic rate of finding obstructive positions in MRCP was 100% and the correct rate of finding obstructive causes 78.57%. MRCP combined with MRI raised the accuracy of diagnosis of obstructive causes. (90.48%). All pathogenic changes have their own characteristics. CONCLUSIONS: MRCP in diagnosing obstructive jaundice is quite effective and safe because of its clear pictures without use of contrast medium and no complications.

Adult↗
PubMed1998

Temperature-sensitive interactions between RPE and rod outer segment surface proteins.

Phagocytosis of rod outer segments by the retinal pigment epithelium is distinguished by the two distinct temperature-dependent steps of binding and ingestion. This study was designed to see if retinal pigment epithelial (RPE) plasma membrane proteins interact with ROS plasma membrane proteins at temperatures favoring either binding or ingestion. A modified blot overlay assay was used whereby Western blots of RPE plasma membrane proteins were overlaid with biotinylated ROS plasma membrane proteins. RPE/ROS interactions were detected by streptavidin-HRP and the ECL method at 25 degrees C (ingestion), 15 degrees C (binding), and 4 degrees C (little or no binding or ingestion). Unlabeled ROS proteins served as the negative control. Competition with excess unlabeled ROS proteins were used to test the specificity of the protein interactions. Some protein interactions were somewhat temperature dependent. For example, two RPE plasma membrane proteins (200 kDa and 173 kDa) interacted with ROS plasma membrane proteins at both 25 degrees C and 15 degrees C, but not at 4 degrees C. A strongly labeled protein at 50 kDA protein was present at 25 degrees C but weakly labeled at 15 degrees C and at 4 degrees C. Other protein interaction were more clearly temperature dependent. For example, a 110 kDa RPE protein interacted with ROS proteins only at 25 degrees C. Another RPE protein (55 kDa) interacted only at 15 degrees C. These latter data provide correlations between binding events in the assay and previously described stages of phagocytosis.

Animals↗
PubMed1998

Adaptation of active proton pumping and plasmalemma ATPase activity of corn roots to low root medium pH

Corn (Zea mays L.) root adaptation to pH 3.5 in comparison with pH 6. 0 (control) was investigated in long-term nutrient solution experiments. When pH was gradually reduced, comparable root growth was observed irrespective of whether the pH was 3.5 or 6.0. After low-pH adaptation, H+ release of corn roots in vivo at pH 5.6 was about 3 times higher than that of control. Plasmalemma of corn roots was isolated for investigation in vitro. At optimum assay pH, in comparison with control, the following increases of the various parameters were caused by low-pH treatment: (a) hydrolytic ATPase activity, (b) maximum initial velocity and Michaelis constant (c) activation energy of H+-ATPase, (d) H+-pumping activity, (e) H+ permeability of plasmalemma, and (f) pH gradient across the membranes of plasmalemma vesicles. In addition, vanadate sensitivity remained unchanged. It is concluded that plasmalemma H+-ATPase contributes significantly to the adaptation of corn roots to low pH. A restricted net H+ release at low pH in vivo may be attributed to the steeper pH gradient and enhanced H+ permeability of plasmalemma but not to deactivation of H+-ATPase. Possible mechanisms responsible for adaptation of plasmalemma H+-ATPase to low solution pH during plant cultivation are discussed.

Journal Article↗
PubMed1997

Gray-scale liver enhancement in VX2 tumor-bearing rabbits using BR14, a new ultrasonographic contrast agent.

RATIONALE AND OBJECTIVES: We evaluated the potential of BR14, a novel gas-based echo contrast agent, for gray-scale liver imaging and VX2 tumor detection/delineation in the conventional and harmonic imaging modes. METHODS: A single dose (0.2 mL/kg) of BR14 was administered to eight VX2 tumor-bearing rabbits. Imaging was performed with an ATL-HDI 3000. The B-mode gray levels were analyzed by videodensitometry in areas selected in the liver tissue, tumors, aorta, and the portal vein from frames recorded up to 1 hour after injection. The tumors were further assessed using subjective scores just before and after contrast injection, as well as 15 minutes later in both conventional gray-scale and harmonic imaging modes. RESULTS: Gray-scale enhancement of the liver tissue was detectable soon after BR14 injection and remained at a high level even after clearance of the agent from the blood stream. On precontrast, of 42 observed tumors, 4 were perfectly detected (4/42). After injection of BR14, the number rose to 10/20 in the vascular phase and 12/20 in the delayed phase. In harmonic imaging, the corresponding numbers were even higher, 17/22 in the vascular phase and 18/22 in the delayed phase. The number of tumors perfectly delineated increased after BR14 from 1/42 to 3/20 in the vascular phase and 5/20 in the delayed phase. In the harmonic mode, 9 of 22 tumors were perfectly delineated in the vascular phase and 10 of 22 in the delayed phase. CONCLUSIONS: BR14 is a promising new agent for the study of tissue perfusion and in particular for liver imaging. It shows not only strong, but also persistent gray scale enhancement of the parenchyma but not of the tumors. The increased conspicuousness allows considerable improvements in tumor detection and tumor delineation in conventional imaging and even more so in harmonic imaging.

Animals↗
PubMed1997

Immobilized cells with endocellular enzymes improved by the permealizing and crosslinking treatment.

In order to achieve high activity of enzymatic catalysis, the method of permealizing and crosslinking treatment has been suggested for immobilizing cells with endocellular enzymes. Polyethene-polyamine and glutardehyde were used to enhance the activity and stability of E. coli having aspartase entrapped in k-carrageenan gel and intact P. dacunhae cells having aspartate-beta-decarbonoxylase. The strength and enlargement effects, which favor the performance of catalysis in a packed bed reactor and a membrane reactor, respectively, were also obtained from the experiment results.

Aspartate Ammonia-Lyase↗
PubMed1995

Allozyme differentiation among nine populations of the corn borer (Ostrinia) in China.

To test the hypothesis of the migration of the corn borer, the allozymes of nine populations of the corn borer (Ostrinia) in China were checked using vertical-slab polyacrylamide gel electrophoresis. Eight loci of six allozymes were analyzed. The mean of the genetic identities among the nine populations calculated from the allele frequencies was 0.99068, much closer than that of other species and geographical populations. The mean (0.97955) of the genetic identities between the XJYN population (Ostrinia nubilalis Hübner, collected from Yining, Xinjiang Autonomous Region) and each of the other eight populations (O. furnacalis Guenée) was significantly smaller than that between the pairs of the eight populations (0.99386; t test, P < 0.01). Although the population XJYN clearly deviates from the other eight populations in the dendrogram, the relationship of the two species of corn borer was very close. It is possible that the speciation of corn borer may have resulted from single-gene substitutions.

Animals↗
PubMed1995

BR1: a new ultrasonographic contrast agent based on sulfur hexafluoride-filled microbubbles.

RATIONALE AND OBJECTIVES: The basic characteristics of BR1, a novel echo contrast agent based on stabilized sulfur hexafluoride (SF6) microbubbles have been evaluated. METHODS: The authors determined the physicochemical properties (bubble concentration, bubble size distribution, resistance to pressure, and stability) and the acoustic properties (backscatter and attenuation coefficients) of BR1. The diagnostic value of BR1 was evaluated further in minipigs. Left heart images were recorded before and after injection of different doses of BR1. RESULTS: BR1 is formulated as a lyophilized product, which after addition of saline, provides a suspension containing 2 x 10(8) SF6 microbubbles/mL with a number mean diameter of 2.5 microns. More than 90% of the bubbles are below 8 microns. The use of SF6 rather than air provides an improved resistance to pressure increases such as the ones occuring in the left heart during systole. After reconstitution, the echogenicity and the bubble characteristics are unchanged for more than 8 hours. The high echogenicity remains almost constant over the entire medical frequency range (1-10 MHz). BR1 injections in animals resulted in a homogenous, dose-dependent opacification of the left heart. CONCLUSIONS: Considering its high echogenicity, outstanding stability, and resistance to pressure changes, BR1 is a very promising ultrasound contrast agent.

Animals↗
PubMed1995

Characterization of rod outer segment plasma membrane proteins which bind to the mannose receptor.

Previous work by our laboratory has demonstrated that rod outer segment (ROS) phagocytosis can be mediated by mannose-receptor dependent activity. This study was designed to probe for potential ligands on the ROS surface which could interact with the mannose receptor during the phagocytic cycle. Solubilized ROS plasma membranes were passed over a mannose receptor-Sepharose column in the presence of CaCl2. Proteins specifically bound to the column were eluted using methyl-D-mannoside and EDTA and characterized by gel electrophoresis, lectin blots, and immunoblots. Silver stained gels of ROS plasma membrane proteins eluted from the mannose-receptor column demonstrated six bands: a major band at 36 kD, identified by monospecific antibodies as rhodopsin, and bands of Mr = 39 kD, 67 kD, 76 kD, 97 kD and 100 kD. Lectin blots of the eluted fractions confirmed that all six proteins in these fractions could bind concanavalin A. In summary, these results showed that rhodopsin and several other mannose-containing glycoproteins on ROS plasma membranes were bound to a mannose receptor column, and thus could serve as ligands for mannose receptor-mediated ROS phagocytosis.

Animals↗
PubMed1995

[Relationship between levels of aspartate aminotransferase in gingival crevicular fluid and periodontal disease activity].

This paper describes a longitudinal study in which clinical parameters and aspartate aminotransferase (AST) in gingival crevicular fluid (GCF) were monitored bimonthly over a 6-12 months period in 970 sites from 7 treated periodontitis patients. In this study, 21 out of 970 sites exhibited new attachment loss (AL) of at least 2mm between two consecutive visits. The GCF-AST levels and clinical parameters at sites with active tissue destruction (> or = 2mm AL within two months) were significantly higher than those at control sites on the same tooth. The GCF-AST levels and clinical parameters at sites with active tissue destruction decreased significantly after re-treatment. The measurement of GCF-AST could be an useful adjunctive criterion for detection of disease activity. However, it seems to be unsatisfactory in predicting disease activity.

Aspartate Aminotransferases↗
PubMed1995

[Alkaline phosphatase levels in gingival crevicular fluid of periodontitis before and after periodontal treatment].

Gingival crevicular fluid (GCF) samples were collected from 204 teeth from 35 subjects, including 8 rapidly progressive periodontitis (RPP), 14 chronic adult periodontitis (CAP), 7 marginal gingivitis (MG) and 6 healthy subjects (H). The results of alkaline phosphatase (ALP) examination indicated that the ALP levels from CAP and RPP patients were significantly higher than those from H subjects and MG patients. The ALP levels were closely related to the amount of GCF flow and various clinical periodontal parameters, especially to probing depth and attachment loss. The ALP levels and the various clinical parameters decreased significantly after periodontal therapy. The present study suggests that the measurement of GCF--ALP could be an useful adjuctive criterion for detection of periodontal inflammatory status and extent of tissue destruction.

Adult↗
PubMed1992

Fibrinogen adsorption on Pyrex glass tubes: a continuous kinetic study.

We present an experimental system to record continuously the adsorption kinetics of radiolabeled proteins, following an earlier study (Voegel et al., Colloids Surfaces 10 (1984) 9). We found results in accordance with the Lévêque equation at a wall shear rate of 50 s-1, for adsorption from fibrinogen solutions in Tyrode's buffer on Pyrex glass tubes. Dependence on concentration in the range 4 to 200 micrograms/mL and on distance to the tube entrance were examined. At the highest concentrations, a second slower regime appeared when coverage exceeded about 0.14 micrograms/cm2.

Adsorption↗
PubMed1992

Polymeric microballoons as ultrasound contrast agents. Physical and ultrasonic properties compared with sonicated albumin.

Air-filled polymeric microballoons were prepared with number-mean diameters of approximately 3 microns, volume-mean diameters of approximately 5 microns, and narrow particle-size distributions (standard deviation [SD] = 1.2 microns in number and SD = 2.0 microns in volume). More than 99% of the particles were below 8 microns. These particles were found to be highly echogenic for ultrasound, showing backscatter coefficients at 7.5 MHz, similar to the ones obtained with sonicated albumin microspheres. However, at 2.25 MHz, microballoons were less echogenic than albumin microspheres. These results are consistent with ultrasound attenuation measurements, which showed a maximum at 8 to 9 MHz for the microballoons compared with a reported value of 3.5 to 4.5 MHz for albumin microbubbles. Polymeric microballoons were found to be stable in plasma or under applied pressure as evidenced by unchanged particle concentration and echogenicity. Albumin microspheres were particularly unstable to applied pressure (150 mm Hg) and showed a rapid decrease in both particle counts and echogenicity.

Air↗
PubMed1992

Influence of a preadsorbed terpolymer on human platelet accumulation, fibrinogen adsorption, and ex vivo blood activation in hemodialysis hollow fibers.

Results are presented on kinetics of platelet accumulation in charged polyacrylonitrile (AN69) hollow fibers by continuous data recording under flow conditions (wall shear rate 108-1050 s-1), using suspensions of washed 111In-labeled human platelets in Tyrode's-albumin buffer, containing washed red blood cells (0-40%). Preadsorption of a terpolymer of acrylonitrile, poly(ethyleneoxide) methacrylate and trimethylaminoethyl chloride methacrylate leads to very efficient passivation with respect to platelet accumulation and fibrinogen adsorption. In human ex vivo tests, evaluation of complement peptide C3a, platelet beta-thromboglobulin, leucocyte-polymorphonuclear neutrophile elastase and fibrinopeptide A shows no detectable activation. Furthermore, preadsorption appears to result in simultaneous improvement in hemocompatibility of the blood lines leading to and from the dialysis module. This single pretreatment of dialysis membranes should allow injection of lower doses of anticoagulant to patients submitted to hemodialysis.

Acrylic Resins↗
PubMed1991

Study on induction of differentiation of a human megakaryoblastic leukemia cell line (HIMeg) by 1,25-dihydroxyvitamin D3.

It is reported that 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), a physiological factor, has an inductive effect on the differentiation of a novel human megakaryoblastic leukemia cell line (HIMeg) in vitro. At the concentrations ranging from 10(-9) to 10(-6) mol/L, 1,25(OH)2D3 showed inhibition of proliferation on HIMeg cells which was demonstrated by count of survival cells and cloning efficiency. Meanwhile, using light/electron microscopy, stain of cytochemistry (including immunoenzymatic technique) and flow cytometry, we found that HIMeg cells could be further induced into more mature cells in megakaryocytic lineage confirmed by a series of evidence, including the changes of cell morphology/structure and cytochemistry, increased expression of differentiation antigens on the cell surface, and polyploidization. So, it is possible for 1,25(OH)2D3 to promote the differentiation of the cells in megakaryocytic lineage in vivo and to be used to treat acute megakaryoblastic leukemia and other diseases with malignant megakaryocytosis.

Calcitriol↗