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Biomedical subjects

J Yuan

Publications and source records attributed to J Yuan.

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

Immunogold labeling of Hrp pili of Pseudomonas syringae pv. tomato assembled in minimal medium and in planta.

Hypersensitive reaction and pathogenicity (hrp) genes are required for Pseudomonas syringae pv. tomato (Pst) DC3000 to cause disease in susceptible tomato and Arabidopsis thaliana plants and to elicit the hypersensitive response in resistant plants. The hrp genes encode a type III protein secretion system known as the Hrp system, which in Pst DC3000 secretes HrpA, HrpZ, HrpW, and AvrPto and assembles a surface appendage, named the Hrp pilus, in hrp-gene-inducing minimal medium. HrpA has been suggested to be the Hrp pilus structural protein on the basis of copurification and mutational analyses. In this study, we show that an antibody against HrpA efficiently labeled Hrp pili, whereas antibodies against HrpW and HrpZ did not. Immunogold labeling of bacteria-infected Arabidopsis thaliana leaf tissue with an Hrp pilus antibody revealed a characteristic lineup of gold particles around bacteria and/or at the bacterium-plant contact site. These results confirm that HrpA is the major structural protein of the Hrp pilus and provide evidence that Hrp pili are assembled in vitro and in planta.

Agar↗
PubMed2001

The thin-cap fibroatheroma: a type of vulnerable plaque: the major precursor lesion to acute coronary syndromes.

While the concept of plaque 'vulnerability' implies a propensity towards thrombosis, the term vulnerable was originally intended to provide a morphologic description consistent with plaques that are prone to rupture. It is now known that the etiology of coronary thrombi is diverse and can arise from entities of plaque erosion or calcified nodules. These findings have prompted the search for more definitive terminology to describe precursor lesions associated with rupture, now referred to as thin-cap fibroatheromas. This review focuses on the thin-cap fibroatheroma, as a specific cause of acute coronary syndromes. To put these issues into current perspective, we need to revisit some of the older literature describing plaque morphology in stable and unstable angina, acute myocardial infarction, and sudden coronary death. The morphology, frequency, and precise location of these thin-cap fibroatheromas are further discussed in detail. Potential mechanisms of fibrous cap thinning are also addressed, in particular emerging data, which suggests the role of cell death "apoptosis" in cap atrophy.

Acute Disease↗
PubMed2001

A non-potentiometric sensing method for the determination of pentoxyverine with PQC sensors based on ion-pair complexes.

The construction and general performance characteristics of three piezoelectric quartz crystal sensors responsive to the pentoxyverine are described here. This kind of non-potentiometric sensing method is based on use of ion-pair complexes of the pentoxyverine cation with three counter anions, namely, tungstophosphate, tetraphenylborate and picrolonate. The complexes were embedded in a PVC matrix. Adsorption of the pentoxyverine ion on the complex caused a frequency decrease of the crystal. The frequency decrease was proportional to the amount of adsorbed analyte. The influencing factors were investigated in detail, and then optimized. The proposed sensors exhibit reasonable selectivity and a higher sensitivity than the potentiometric sensors. For a sensor modified with pentoxyverine-phosphotungstate, the calibration graph was linear over concentration of 1.0 x 10(-7) - 5.0 x 10(-5) M with a detection limit of 6 x 10(-8) M at pH 5.4.

Antitussive Agents↗
PubMed2001

Lateral view flow system for studies of cell adhesion and deformation under flow conditions.

Physical interactions between circulating cells and the vascular wall play a central role in inflammation, metastasis, atherosclerosis, and therapeutic cell delivery. Unfortunately, traditional in vitro flow assays cannot be used to visualize the details of cell-surface interactions in blood flow because of inappropriate geometry and the poor penetration of light in erythrocyte solutions. To overcome these obstacles, we have developed an agarose-cast cylindrical vessel system to examine the profiles of cells interacting with surfaces under flow conditions. This design allows observation and quantification of cell deformation as cells adhere to surfaces under dynamic flow conditions without modifying the microscope or optical path. Furthermore, our flow system is uniquely suited for monitoring the profiles of adherent leukocytes deforming in response to erythrocyte suspension flow. We have used this flow system to study the role of erythrocytes in leukocyte-substrate interactions. Our results show that the cell deformation index (the ratio of the cell length to cell height) is higher in erythrocyte solutions compared to erythrocyte-free saline. This novel lateral view flow system provides a powerful technique for visualizing and quantifying the morphological changes of cells in contact with substrates exposed to shear stress.

Blood Circulation↗
PubMed2001

[A new method for lowering noise of ECG signal].

In this article, a new method is introduced to reduce the noise in ECG signal. We use accumulation-division method in frequency area, which can solve the problem of locating the initial position. This problem exists definitely in time area. By using this method, automation in disposing the noise can be realized. The result of this disposing is an integrated and low noise level cycle of ECG signal, which contains all useful characteristic signals. We hope it will be convenient for doctors.

Algorithms↗
PubMed2001

The suitability of hepatocyte culture models to study various aspects of drug metabolism.

Since the liver is the main organ involved in the metabolism and the toxicity of xenobiotics, isolated rat hepatocytes have been increasingly used in recent years as a model to identify pharmacological and toxicological responses of drugs. However, it is generally recognised that isolated hepatocytes retain most of their functions only for a short period. For this reason, numerous models and techniques have been developed to study and improve the metabolic capacity of hepatocytes in vitro over an extended time period and in application for drug metabolism studies. In the present study, we compared four different cell culture models to fulfill these requirements and have therefore harvested hepatocytes and cultured them in different culture systems over two weeks. In order to prove certain advantages or disadvantages of each model, we compared the metabolic capacity, albumin secretion, the release of cytosolic and mitochondrial enzymes, as well as the capacity to metabolise diclofenac (DF). We found that rat hepatocytes in all studied culture models (except the Unisyn Bioreactor) were able to metabolise DF to the same extent as found in vivo. However, the concentration of metabolites was found to decrease with culture time using the monolayer although the DF metabolite level in the collagen Sandwich culture was higher than that of the monolayer culture. The 3D-membrane bioreactor preserved the metabolic capacity for a prolonged period of time. The concentrations of DF metabolites in the Unisyn hollow fiber bioreactor were below the detection limit, which corresponded to other parameters such as albumin secretion and cytochrome P450 activity, disqualifying this culture system clearly for the use of in vitro primary hepatocyte cultures. The other three systems all have their place in drug metabolism with different advantages. However, our studies clearly showed that hepatocytes cultured within a collagen sandwich or in the 3D-membrane bioreactor qualify to study various aspects of drug metabolisms over a long time period. Further studies are needed to prove if the later two culture models may really help to reduce animal testing.

Alanine Transaminase↗
PubMed2001

Rapid ocular angiogenic control via naked DNA delivery to cornea.

PURPOSE: To determine the efficacy and safety of naked plasmid gene therapy to the corneal stroma and epithelium. METHODS: Naked plasmid DNA was injected under pressure into the cornea of mice. The expression of genes coding for beta galactosidase (beta-gal), enhanced green fluorescent protein (EGFP), vascular endothelial growth factor (VEGF), and soluble Flt-1 (s-Flt) was recorded and measured with regard to dose, time course, and bioactivity. RESULTS: LacZ gene expression of the protein beta-gal was demonstrated as early as 1 hour, with expression persisting for 10 days. Plasmid-injected corneas remained clear and free of inflammation. EGFP was bicistronically expressed with VEGF to demonstrate the practicality of simultaneous in vivo analysis of gene expression and growth factor bioactivity. Corneal injection of a plasmid containing VEGF cDNA induced corneal and anterior chamber neovascularization. Moreover, corneal injection of plasmid containing the cDNA for the soluble form of the VEGF receptor Flt-1 effectively prevented corneal neovascularization. CONCLUSIONS: The cornea is readily accessible for gene therapy in the laboratory and in the clinic. The method described is safe, effective, titratable, and easily monitored. Naked DNA delivery to the cornea has the potential to alter the treatment of a wide variety of corneal and anterior segment diseases.

Animals↗
PubMed2001

Intravascular local gene transfer mediated by protein-coated metallic stent.

OBJECTIVE: To assess the feasibility, efficiency and selectivity of adenovirus-mediated gene transfer to local arterial wall by protein-coated metallic stent. METHODS: A replication-defective recombinant adenovirus carrying the Lac Z reporter gene for nuclear-specific beta-galactosidase (Ad-beta gal) was used in this study. The coating for metallic stent was made by immersing it in a gelatin solution containing crosslinker. The coated stents were mounted on a 4.0 or 3.0 mm percutaneous transluminal coronary angioplasty (PTCA) balloon and submersed into a high-titer Ad-beta gal viral stock (2 x 10(10) pfu/ml) for 3 min, and then implanted into the carotid arteries in 4 mini-swines and into the left anterior descending branch of the coronary artery in 2 mini-swines via 8F large lumen guiding catheters. The animals were sacrificed 7 (n = 4), 14 (n = 1) and 21 (n = 1) days after implantation, respectively. The beta-galactosidase expression was assessed by X-gal staining. RESULTS: The results showed that the expression of transgene was detected in all animal. In 1 of carotid artery with an intact intima, the beta-gal expression was limited to endothelial cells. In vessels with denuded endothelium, gene expression was found in the sub-intima, media and adventitia. The transfection efficiency of medial smooth muscle cells was 38.6%. In 2 animals sacrificed 7 days after transfection, a microscopic examination of X-gal-stained samples did not show evidence of transfection in remote organs and arterial segments adjacent to the treated arterial site. CONCLUSIONS: Adenovirus-mediated arterial gene transfer to endothelial, smooth muscle cells and adventitia by protein-coated metallic stent is feasible. The transfection efficiency is higher. The coated stent may act as a good carrier of adenovirus-mediated gene transfer and have a potential to prevent restenosis following PTCA.

Adenoviridae↗
PubMed2001

Pharmacokinetics of anastrozole in Chinese male volunteers.

AIM: To compare pharmacokinetics of domestic and imported tablets of anastrozole. METHODS: Twenty male Chinese volunteers were enrolled in a randomized crossover study with a single oral dose of 1 mg of the two formulations respectively. The anastrozole in plasma was measured by gas chromatography with electron-captured detector. Area under the drug concentration-time curve was evaluated by variance analysis and two one-side t-test. RESULTS: A two-compartment model was adopted in anastrozole plasma concentration-time data analysis. The paramaters such as Cmax, Tmax, T1/2beta, and AUC(0-infinity) were (10 +/- 3) and (10.2 +/- 2.5) microg/L, (1.2 +/- 0.5) and (1.3 +/- 0.4) h, (42 +/- 14) and (41 +/- 26) h, (443 +/- 141) and (429 +/- 121) microg . h . L-1, respectively, and there were no significant differences between the two formulations. CONCLUSION: Domestic and imported anastrozole were of bioequivalence. The relative bioavailability of the domestic tablet was 100 % +/- 9 %.

Adult↗
PubMed2001

Miller Fisher syndrome: toward a more comprehensive understanding.

PURPOSE: To review recent knowledge on the clinical features, pathology and pathophysiology, diagnosis and treatment of Miller Fisher syndrome (MFS). DATA SOURCES: Clinical and laboratory studies on MFS in the past 10 years were included. RESULTS: A viral infection preceded neurological symptoms in 71.8% of MFS patients. Typical MFS consists of the triad of ataxia, areflexia and ophthalmoplegia. Other cranial nerves are also involved, which may overlap with limb weakness in typical Guillain-Barre syndrome (GBS). Lower cranial nerve variants of GBS, atypical MFS and ataxic neuropathies may overlap, and are thought of as variant forms of MFS. Recurrence and CNS involvement is found more frequently in MFS than in GBS. Antibody to GQ1b, a tetrasyaloganglioside (GQ1b antibody) which is found in close relation to ophthalmoplegia in MFS, is also associated with Campylobacter jejuni (C. jejuni) serotype Penner 2. This suggests that C. jejuni may induce MFS via the GQ1b structure. The GQ1b antibody may lead to the failure of acetylcholine release from motor nerve terminals, which has been confirmed by clinical neurophysiological results. CONCLUSIONS: Many studies have shown similarities in the pathogenesis of MFS and GBS. However, there are still some differences between them, especially in the areas of sensory and CNS involvement. The GQ1b antibody is thought of as one of the key factors in the pathogenesis of MFS, especially with ophthalmoplegia, and it may prove a useful clinical marker in the diagnosis of MFS.

Central Nervous System↗
PubMed2001

[Weak signal detection in every heart cycle].

In this article, a new approach is introduced to lowering the myo-electronic noise in weak ECG signals. We use artificial neural network to make the noise be white, and then we adopt an adaptive filter of which the reference signal is achieved by extracting from other ECG cycle. The outcome is the reduction of both white noise and non-white noise in ECG signal. Satisfactory results have been achieved by using this method in the experiment of late potential detection.

Action Potentials↗
PubMed2001

[The role of released cytochrome C from mitochondria in the apoptosis of HUVECs induced by hydrogen peroxide].

OBJECTIVE: To explore the role of mitochondria and from which released cytochrome C in the apoptosis of HUVECs induced by H2O2. METHODS: HUVECs were cultured with H2O2 of 100 mol/L for 24 hrs. H2O2 was added after that HUVECs were precultured with CsA (cyclosporin A) for 30 mins. The cell samples were collected at different time points for DAPI staining and counting of apoptotic cell number. Simultaneously, the changes of mitochondrial permeability was observed by Rhoadmine 123 accumulation. The changes of the cytochrome C concentrations in plasma and mitochondria were determined by western blot. RESULTS: HUVECs exhibited obvious apoptosis after being processed by H2O2. The apoptotic cell number increased since 4 hrs of culturation of HUVECs with H2O2, and reached peak level at 12 hrs. And the HUVEC apoptosis induced by H2O2 could be inhibited significantly by CsA. H2O2 could lead to the decrease of mitochondrial cytochrome C concentration, which in turn lead to the increase of cytoplasmic cytochrome C concentration. Similarly, mitochondrial Rhoadmine 123 concentration decreased and the mitochondrial permeability increased. But CsA could obviously inhibit the changes of both mitochondrial Rhoadmine 123 and permeability. CONCLUSION: H2O2 could induce cytochrome C releasing to cytoplasma which lead to endothelial apoptosis. And CsA could inhibit the apoptosis by maintaining the normal function of mitochondrial membrane.

Apoptosis↗
PubMed2001

[Cytotoxic natural killer/T-cell lymphomas of the lymph nodes].

OBJECTIVE: To investigate the clinicopathologic features of cytotoxic natural killer (NK)/T-cell lymphomas of the lymph nodes. METHODS: Clinicopathologic observations and follow up on 5 cases of cytotoxic NK/T-cell lymphomas of the lymph nodes, immunohistochemical staining for CD45RO, CD8, CD56, CD30, CD20, TIA-1 and in situ hybridization for EBER1/2 were performed. RESULTS: (1) The clinicopathologic features of cytotoxic NK-T-cell lymphomas of the lymph nodes were summarized; (2) The tumor cells were positive for CD45RO in 4 of the 5 cases, in which 3 cases were also positive for CD56. One case was of null cell type. The tumor cells were positive for TIA-1 and EBER1/2 in all 5 cases. CONCLUSIONS: The clinicopathological features and special immunophenotypes of cytotoxic NK/T-cell lymphomas of the lymph nodes were present in all 5 cases. Clinically, this entity tends to be an aggressive process with poor prognosis.

Adult↗
PubMed2001

[An experimental study on the release of endotoxin from gram negative bacteria induced by antibiotics].

OBJECTIVE: To explore the characteristics and possible mechanism of LPS released from Gram negative bacteria induced by antibiotics, so as to improve clinical management of endotoxemia and sepsis. METHODS: Cultures containing PA103 subtype of Pseudomonas aeruginosa (PA) and E coli 25922 subtype of E coli were treated with four kinds of antibiotics as Imipenam (IMP), ceftazidime (CTZ), amikacin (AMN) and pefloxacine (PFX) in four concentrations of 0.5, 1, 5 and 10 MIC for 8 hours. The changes in the bacterial quantity and morphology and the supernatant levels of free LPS of the culture media were observed at different time points. RESULTS: All the four kinds of antibiotics could kill the tested bacteria in similar degree, but lead to the different types of morphological changes of the bacteria. In detail, IMP could convert the bacteria into spherical shape, while CTZ and PFX made the bacteria to filamentous shape. But AMN could induce lysis of bacterial thallus. Under same condition, the ability of different kinds and concentrations of antibiotics to induce LPS release ranked as CTZ > PFX > IMP > AMN, 0.5MIC > 1MIC > 5MIC > 10MIC. Along with the prolongation of the action time, the LPS release increased. Furthermore, PA103 released less endotoxin than E. coli after the action of antibiotics. CONCLUSION: All of the four antibiotics, i,e, IMP, CTZ, AMN and PFX could induce PA103 and E coli 25922 to release different levels of LPS, which was related to bacterial morphological changes. The LPS release from the bacteria was correlated to the antibiotics applied, concentrations, action time and the bacterial features. Antibiotics with less ability of inducing LPS release were recommended for clinical management of the sepsis and/or septic shock caused by Gram negative bacteria.

Amikacin↗
PubMed2001

[The effect of Lipopolysacharide (LPS) on morphology and function of human umbilical endothelial cells (HUVECs)].

OBJECTIVE: To study the effects of LPS on the morphology and function of HUVECs, so as to explore the roles of activated vascular endothelial cells (VEC) by LPS in systemic inflammatory reaction, sepsis and MOF. METHODS: HUVECs primarily cultured in vitro were employed as the model. Inverted microscope was used to observe the effects of LPS on the morphology of HUVECs. ELISA was used to assess the IL-6 content. The expression of ICAM-1 was determined by immunofluorescent staining method with confocal laser-scanning fluorescence microscope. RESULTS: The morphology of HUVECs could be altered by LPS to become long cord-like in shape. The smallest dose of LPS for stimulating the secretion of IL-6 from HUVEC was 1 ng/ml, and the effect was enhanced parallel to the increase of the concentration of LPS and reached top level at 8 postburn hours. The expresson of ICAM-1 on the nucleic and cytoplasmic membrane of HUVECs increased obviously after HUVECs was cultured with LPS (10 ng/ml) for 24 hours when observed by laser confocal scanning light microscope. CONCLUSION: The morphology and function of HUVECs could be evidently affected by LPS. As a result, LPS might play important roles in the increase of vascular permeability, the promotion of leukocytic adherence, and the initiation of inflammatory cascade reaction.

Cell Line↗
PubMed2001

[Purification and some properties of D-hydantoinase produced by Pseudomonas 2262].

A D-hydantoinase produced by Pseudomonas 2262 was purified to electrophoretic homogeneity by the steps of thermal treatment, (NH4)2SO4 fractionation and column chromatography with Q-Sepharose fast flow, phenyl-Sepharose fast flow and Superose 12. Purification of about 60 fold was achieved with an overall yield of 16%. The relative molecular mass of the native enzyme is 109 kD and that of subunit is 53.7 kD by the analysis of Native and SDS-PAGE as well as gel filtration respectively. Some properties of the enzyme such as the sensitivity to thiol reagent and the effects of metal ions, for instance inhibited by Zn2+ and activited by Mn2+, Mg2+ are identical to dihydropyrimidinase. The optimum temperature and pH for enzymatic catalysis are 70 degrees C and 8.0 respectively. The enzyme activity is stable under 60 degrees C and in the pH range of 6-10. The N-terminal sequence for 10 amino acid residues is MDKLIKNGTI.

Amidohydrolases↗
PubMed2000

Fluoxetine increases the anorectic and long-term dopamine-depleting effects of phentermine.

The anorectic drug phentermine produces dose-related toxic effects on brain dopamine (DA) neurons in animals. Until recently, phentermine was widely used in combination with fenfluramine for purposes of appetite suppression and weight loss. With the recent withdrawal of fenfluramine from the market, many people have begun combining phentermine with fluoxetine, a serotonin reuptake inhibitor which also produces mild anorectic effects. Fluoxetine, in addition to inhibiting serotonin reuptake, inhibits hepatic mixed function oxidase, which plays an important role in the metabolic degradation of amphetamines. The purpose of the present study was to assess the effects of fluoxetine on the anorectic and DA neurotoxic effects of phentermine in mice. Phentermine, in combination with fluoxetine, produced greater reductions in food intake and body weight than phentermine alone. The phentermine/fluoxetine combination also produced greater long-term reductions in brain DA levels than phentermine alone, likely reflecting greater DA neurotoxicity of the drug combination. Brain concentrations of phentermine were also found to be higher in animals pretreated with fluoxetine. These findings indicate that fluoxetine potentiates both the anorectic and DA neurotoxic effects of phentermine, probably by increasing phentermine brain levels. The clinical significance of these findings remains to be ascertained.

Animals↗