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Biomedical subjects

Y Yuan

Publications and source records attributed to Y Yuan.

At least 73 records · Page 4Linked to original sources
PubMed2001

A case of Erdheim-Chester disease with bilateral orbital involvement.

PURPOSE: To describe a case of Erdheim-Chester disease with bilateral orbital involvement. METHODS: A 43-year-old female with bilateral proptosis was presented. Its clinical features, image findings, pathological character and therapeutic effect were evaluated. RESULTS: CT demonstrated bilateral, diffuse orbital mass. Histopathologic assessment revealed a diffuse xanthogranulomatous process with clusters of lipidladen histocytes. Numerous Touton giant cells were scattered throughout the lesion. Renal and heart failure happened during a 6-year follow-up period. Long bones roentgenogram demonstrated diffuse symmetrical sclerosis with extensive, lytic lesions. Systemic administration of corticosteroids, chemotherapy, immunoglobulin and traditional Chinese medicine showed good therapeutic result. CONCLUSIONS: An administration of systemic corticosteroids, chemotherapy, immunoglobin and traditional Chinese medicine can control Erdheim-Chester disease. Further exploration of its pathogenesis and collection of useful clinical data are required.

Adult↗
PubMed2001

[Study on the essential oil components in Thymus quinquecostatus Celak].

AIM: To analyse the essential oil components of Thymus quinquecostatus Celak. METHODS: Gas chromatography/mass spectrometry were used. RESULTS: A total of 78 components were separated. 34 of them were identified, which accounted for 95.93% of the total peak area. The main constituents are o-cymene, carvacrol, caryophyllene, 2-isopropyl-1-methoxy-4-methylbenzene and gamma-terpene. CONCLUSION: Thymus quinquecostatus Celak has perfume and medical development value.

Cymenes↗
PubMed2001

[3D-QSAR of antiinflammatory activities of 5,6-diaryl-2,3-dihydro-1-pyrrolizinone derivatives].

AIM: To study the SARs of 5,6-diaryl-2,3-dihydrol-1-pyrrolizinone derivatives to provide information for the design of new structural compounds. METHODS AND RESULTS: Three dimensional quantitative structure-activity relationship (3D-QSAR) model was constructed by Apex-3D. CONCLUSION: The antiinflammatory activities of 5, 6-diaryl-pyrrolizinones were related to the global hydrophobicity and volume, the properties of the group at 1-position of pyrrolizinone ring and the two secondary sites; improved the pi-electronic density of the group at 1-position of pyrrolizinone ring and lowered the global hydrophobicity and the volume of p-substituent of the phenyl ring at 6-position of pyrrolizinone contributed to the antiinflammatory activities of the title compounds.

Animals↗
PubMed2001

[Studied on docking of 5,6-diaryl-2,3-dihydro-1-pyrrolizinone derivatives with cyclooxygenase].

AIM: To theoretically explore the mechanism of action of 5,6-diaryl-2, 3-dihydro-1-pyrrolizinone derivatives. METHODS: The interactions of the compound ZZ-122 with cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) were modeled by docking method. RESULTS: According to the binding pattern, intermolecular energy and capacity to form H-bond, it was easy for ZZ-122 to bind to COX-2 and not easy to COX-1. CONCLUSION: Compound ZZ-122 may be a selective COX-2 inhibitor, which has to be confirmed by experiment.

Cyclooxygenase 1↗
PubMed2000

Synergistic adhesive interactions and signaling mechanisms operating between platelet glycoprotein Ib/IX and integrin alpha IIbbeta 3. Studies in human platelets ans transfected Chinese hamster ovary cells.

This study investigates three aspects of the adhesive interaction operating between platelet glycoprotein Ib/IX and integrin alpha(IIb)beta(3). These include the following: 1) examining the sufficiency of GPIb/IX and integrin alpha(IIb)beta(3) to mediate irreversible cell adhesion on immobilized von Willebrand factor (vWf) under flow; 2) the ability of the vWf-GPIb interaction to induce integrin alpha(IIb)beta(3) activation independent of endogenous platelet stimuli; and 3) the identification of key second messengers linking the vWf-GPIb/IX interaction to integrin alpha(IIb)beta(3) activation. By using Chinese hamster ovary cells transfected with GPIb/IX and integrin alpha(IIb)beta(3), we demonstrate that these receptors are both necessary and sufficient to mediate irreversible cell adhesion under flow, wherein GPIb/IX mediates cell tethering and rolling on immobilized vWf, and integrin alpha(IIb)beta(3) mediates cell arrest. Moreover, we demonstrate direct signaling between GPIb/IX and integrin alpha(IIb)beta(3). Studies on human platelets demonstrated that vWf binding to GPIb/IX is able to induce integrin alpha(IIb)beta(3) activation independent of endogenous platelet stimuli under both static and physiological flow conditions (150-1800 s(-)(1)). Analysis of the key second messengers linking the vWf-GPIb interaction to integrin alpha(IIb)beta(3) activation demonstrated that the first step in the activation process involves calcium release from internal stores, whereas transmembrane calcium influx is a secondary event potentiating integrin alpha(IIb)beta(3) activation.

Adenosine Diphosphate↗
PubMed2000

Cytoskeletal regulation of the platelet glycoprotein Ib/V/IX-von willebrand factor interaction.

Shear-induced binding of von Willebrand factor (vWf) to the platelet glycoprotein (GP) Ib/V/IX complex plays a key role in initiating platelet adhesion and aggregation at sites of vascular injury. This study demonstrated that pretreating human platelets with inhibitors of actin polymerization, cytochalasin D or latrunculin B, dramatically enhances platelet aggregation induced by vWf. The effects of these inhibitors were specific to the vWf-GPIbalpha interaction because they enhanced vWf-induced aggregation of Glanzmann thrombasthenic platelets and Chinese hamster ovary (CHO) cells transfected with GPIb/V/IX. Moreover, cytochalasin D enhanced the extent of platelet aggregation induced by high shear stress (5000 s(-1)) and also lowered the shear threshold required to induce aggregation from 3000 s(-1) to as low as 500 s(-1). Studies of CHO cells expressing GPIbalpha cytoplasmic tail truncation mutants that failed to bind actin-binding protein-280 (deletion of residues 569-610 or 535-568) demonstrated that the linkage between GPIb and actin-binding protein-280 was not required for vWf-induced actin polymerization, but was critical for the enhancing effects of cytochalasin D on vWf-induced cell aggregation. Taken together, these studies suggest a fundamentally important role for the cytoskeleton in regulating the adhesive function of GPIb/V/IX.

Actin Cytoskeleton↗
PubMed2000

Complete genome sequence of Pseudomonas aeruginosa PAO1, an opportunistic pathogen.

Pseudomonas aeruginosa is a ubiquitous environmental bacterium that is one of the top three causes of opportunistic human infections. A major factor in its prominence as a pathogen is its intrinsic resistance to antibiotics and disinfectants. Here we report the complete sequence of P. aeruginosa strain PAO1. At 6.3 million base pairs, this is the largest bacterial genome sequenced, and the sequence provides insights into the basis of the versatility and intrinsic drug resistance of P. aeruginosa. Consistent with its larger genome size and environmental adaptability, P. aeruginosa contains the highest proportion of regulatory genes observed for a bacterial genome and a large number of genes involved in the catabolism, transport and efflux of organic compounds as well as four potential chemotaxis systems. We propose that the size and complexity of the P. aeruginosa genome reflect an evolutionary adaptation permitting it to thrive in diverse environments and resist the effects of a variety of antimicrobial substances.

Bacterial Proteins↗
PubMed2000

A small-molecule nitroimidazopyran drug candidate for the treatment of tuberculosis.

Mycobacterium tuberculosis, which causes tuberculosis, is the greatest single infectious cause of mortality worldwide, killing roughly two million people annually. Estimates indicate that one-third of the world population is infected with latent M. tuberculosis. The synergy between tuberculosis and the AIDS epidemic, and the surge of multidrug-resistant clinical isolates of M. tuberculosis have reaffirmed tuberculosis as a primary public health threat. However, new antitubercular drugs with new mechanisms of action have not been developed in over thirty years. Here we report a series of compounds containing a nitroimidazopyran nucleus that possess antitubercular activity. After activation by a mechanism dependent on M. tuberculosis F420 cofactor, nitroimidazopyrans inhibited the synthesis of protein and cell wall lipid. In contrast to current antitubercular drugs, nitroimidazopyrans exhibited bactericidal activity against both replicating and static M. tuberculosis. Lead compound PA-824 showed potent bactericidal activity against multidrugresistant M. tuberculosis and promising oral activity in animal infection models. We conclude that nitroimidazopyrans offer the practical qualities of a small molecule with the potential for the treatment of tuberculosis.

Animals↗
PubMed2000

Kinetics of two-liquid-phase Taxus cuspidata cell culture for production of Taxol.

The effects of different organic solvents (paraffin, organic acid, alcohol and ester) and their volumetric fractions on the cell growth and Taxol production were studied in two-liquid-phase and the two-stage culture. A kinetic model, incorporated the effects of the toxicity of organic solvents was developed for two-liquid-phase culture of Taxus cuspidata in the two-stage Taxol production. The results showed that the proposed kinetic model could fit the experimental data satisfactorily. The results also showed that Taxol production could reach the optimal value when 10-logP was in the range of 2 to 5 and the volumetric fraction of the organic solvents at the corresponding the highest Taxol production should be lower when 10-logP was high.

Journal Article↗
PubMed2000

DNA repair and recombination factor Rad51 is over-expressed in human pancreatic adenocarcinoma.

Molecular processes that could contribute to differences in chemo- and radioresistance include variations in DNA repair mechanisms. In mammalian cells, the product of the rad51 gene mediates DNA repair via homologous recombination. We describe that in contrast to conventional monolayer cell systems Rad51 protein accumulates to high-levels in three-dimensional cell culture models as well as in orthotopic xeno-transplants of human pancreatic cancer cells. Strikingly, over-expression of wild-type Rad51 was also found in 66% of human pancreatic adenocarcinoma tissue specimens. Functional analysis revealed that Rad51 over-expression enhances survival of cells after induction of DNA double strand breaks. These data suggest that perturbations of Rad51 expression contribute to the malignant phenotype of pancreatic cancer. Oncogene (2000).

Adenocarcinoma↗
PubMed2000

Adsorbed Layers of Ferritin at Solid and Fluid Interfaces Studied by Atomic Force Microscopy.

The adsorption of the iron storage protein ferritin was studied by liquid tapping mode atomic force microscopy in order to obtain molecular resolution in the adsorbed layer within the aqueous environment in which the adsorption was carried out. The surface coverage and the structure of the adsorbed layer were investigated as functions of ionic strength and pH on two different charged surfaces, namely chemically modified glass slides and mixed surfactant films at the air-water interface, which were transferred to graphite substrates after adsorption. Surface coverage trends with both ionic strength and pH indicate the dominance of electrostatic effects, with the balance shifting between intermolecular repulsion and protein-surface attraction. The resulting behavior is more complex than that seen for larger colloidal particles, which appear to follow a modified random sequential adsorption model monotonically. The structure of the adsorbed layers at the solid surfaces is random, but some indication of long-range order is apparent at fluid interfaces, presumably due to the higher protein mobility at the fluid interface. Copyright 2000 Academic Press.

Journal Article↗
PubMed2000

The role of TGF-beta 1 in mice hepatic fibrosis by Schistosomiasis Japonica.

To investigate the role of transforming growth factor-beta 1 (TGF-beta 1) in mice with hepatic fibrosis caused by Schistosomiasis Japonica, ELISA, VG staining and multimedia color hieroglyph quantitative analysis were used to study the change of the serum TGF-beta 1, liver collagen fiber and reticular fiber in mice. The level of serum TGF-beta 1 in experimental group was significantly higher than that in control group (P < 0.01 or P < 0.05) 8, 10, 12 weeks after infected by schistosomiasis. After infection, the level of liver collagen fiber and reticular fiber, and that of TGF-beta 1 increased over time (P < 0.01 or P < 0.05). In mice infected by Schistosomiasis Japonica, the level of TGF-beta 1 increased with prolongation of infection time, and with the increase of liver collagen fiber and reticular fiber. TGF beta 1 plays an important role of immunomodulation in hepatic fibrosis formation caused by Schistosomiasis Japonica.

Animals↗
PubMed2000

In-vitro antibacterial activities of cefpiramide and other broad-spectrum antibiotics against 440 clinical isolates in China.

The in-vitro antibacterial activity of cefpiramide was compared with those of 15 other broad-spectrum cephalosporins. A total of 440 clinical strains of bacteria, including 9 bacterial species, were isolated from our hospital in 1998. The minimum inhibitory concentrations (MICs) of cefpiramide and five other antibiotics were determined for each species, using the agar-dilution method. The MIC of cefpiramide for Escherichia coli and Klebsiella pneumoniae was higher than those of three other third-generation cephalosporins, (ie, cefoperazone, ceftazidime, and ceftriaxone). Fifty-one percent (26/51) of Enterobacter cloacae isolates were resistant to cefpiramide. Cefoperazone/sulbactam and cefepime had greater activity against E. cloacae (resistance, 3.9% and 19.6%, respectively) than cefpiramide. Cefpiramide was more active against Pseudomonas aeruginosa (resistance rates, 12%) than cefoperazone, ceftazidime, ceftriaxone, aztreonam, and cefepime. Cefpiramide-resistant P. aeruginosa strains were resistant to ceftazidime, but 27% of ceftazidime-resistant strains were susceptible to cefpiramide; 15.3% of cefpiramide-resistant S. maltophilia strains were also susceptible to ceftazidime, but 50% of ceftazidime-resistant strains were still susceptible to cefpiramide. Cefoperazone/sulbactam was the most active agent against Acinetobacter baumannii, showing a resistance rate of 2%. Ampicillin/sulbactam, ceftazidime, and cefpiramide were the second most active agents, and about 50% of the tested strains were susceptible to these three antibiotics. Cefpiramide had an activity comparable to that of all tested beta-lactams against oxacillin-susceptible Staphylococcus aureus (MIC90, 2 microg/ml). Against Streptococcus pneumoniae and Haemophilus influenzae, cefpiramide had good activity, with an MIC90 concentration at which 90% of the strain was inhibited of 1 microg/ml and 0.5 microg/ml, respectively. These results indicated that cefpiramide was more active against glucose non-fermenting bacteria than against Enterobacteriaceae, and was very active against oxacillin-susceptible Staphylo-coccus aureus, S. pneumoniae, and H. influenzae. Thus, cefpiramide may be a good choice of drug for the treatment of patients with infections with glucose non-fermenting bacteria and community acquired infections.

Cefazolin↗
PubMed2000

Kinetic effects of FPL 64176 on L-type Ca2+ channels in cardiac myocytes.

To characterize the effects of the Ca2+ channel agonist FPL 64176 on L-type Ca2+ current in isolated rat ventricular myocytes, certain of its effects were compared with those of a better known agonist, S (-) Bay K 8644. Both drugs enhance currents elicited by depolarizing pulses and enhance and slow the decay of tail currents elicited by subsequent repolarization. Both drugs shift the voltage dependence of activation and of inactivation approximately 10 mV in the negative direction, but FPL 64176 slows the rate of both activation and the decline of Ca2+ current during a depolarization, whereas Bay K 8644 accelerates the rate of current decay under the same conditions. In single channel studies in on-cell recording mode, FPL 64176 produced a great lengthening of the channel open time, produced very long openings when the channels were repolarized after a depolarizing stimulus, and had only modest effects on mean closed times and on first latency distributions. FPL 64176 and Bay K 8644 also had minimal effects on L-type channel "on" gating currents, while the "off" gating currents were slowed, particularly at positive potentials. However, the effects on gating currents were too small to account for the prolonged tails observed in FPL 64176. Once the channel is open, FPL 64176 slows transitions to closed or inactivated channel states.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed2000

In vitro activity of meropenem and four other antibiotics against 554 clinical strains obtained from Beijing in 1999.

In 1999, a surveillance study was initiated in a hospital in Beijing to monitor the potency and spectrum of five extended-spectrum beta-lactam antimicrobial agents (meropenem, imipenem, cefepime, ceftazidime, and cefoperazone/sulbactam) tested against 554 strains of bacteria. Five groups of organisms were tested by the E-test method, with results validated by concurrent quality control strain analysis. Results were tabulated, and 100% of quality assurance tests (16/16 tests) were within ranges recommended by the National Committee for Clinical Laboratory Standards. Of the five beta-lactam drugs tested, meropenem and imipenem were the most active against all isolates tested. Overall, the rank order of activity of the five agents was: meropenem (94.6% susceptible) > imipenem (90.1%) > cefepime (77.6%), cefoperazone/sulbactam (77.5%), ceftazidime (76.6%). Ninety-five percent of Enterobacter were to meropenem, while 82% were susceptible to imipenem. Meropenem was more active than imipenem against Pseudomonas aeruginosa. The minimum inhibitory concentration (MIC) of meropenem was eightfold lower than that of imipenem. Meropenem had excellent activity against Haemophilus influenzae, Streptococcus pneumoniae, and oxacillin-susceptible staphylococci.

Anti-Bacterial Agents↗
PubMed2000

Platelets and the injured vessel wall-- "rolling into action": focus on glycoprotein Ib/V/IX and the platelet cytoskeleton.

Blood platelets play a key role in maintaining the integrity of the vascular system through their ability to arrest bleeding (haemostasis) and promote repair of injured blood vessels. Considerable progress has been made in the last few years in our understanding of the adhesion mechanisms utilized by platelets to adhere to sites of vascular injury. Studies have helped define the precise role of von Willebrand factor (vWf), and its platelet receptor, glycoprotein (GP) Ib/V/IX, in initiating platelet-vessel wall and platelet-platelet adhesion contacts. In addition to its adhesive role, recent studies have highlighted the importance of GPIb/V/IX in regulating the cytoskeleton of platelets. GPIb/V/IX not only maintains the normal cytoskeletal architecture of resting platelets but also induces cytoskeletal reorganization following engagement of vWf. Somewhat surprisingly, the physical link between GPIb/V/IX and the membrane skeleton does not appear necessary for GPIb/V/IX-induced cytoskeletal reorganization. In contrast, this linkage appears critical for GPIb/V/IX to maintain cell adhesion under high shear and also for the ability of the cytoskeleton to exert negative regulatory effects on the GPIb-vWf interaction. Thus a complex functional relationship appears to exist between GPIb/V/IX and the membrane skeleton that goes well beyond preserving the normal cytoskeletal architecture of resting platelets.

Blood Platelets↗