Biomedical subjects

F Xie

Publications and source records attributed to F Xie.

At least 37 records · Page 2Linked to original sources

PubMed2001

Effect of pH and soybean cultivars on the quantitative analyses of soybean rhizobia populations.

Quantitative analyses of fast- and slow-growing soybean rhizobia populations in soils of four different provinces of China (Hubei, Shan Dong, Henan, and Xinjiang) have been carried out using the most probable number technique (MPN). All soils contained fast- (FSR) and slow-growing (SSR) soybean rhizobia. Asiatic and American soybean cultivars grown at acid, neutral and alkaline pH were used as trapping hosts for FSR and SSR strains. The estimated total indigenous soybean-rhizobia populations of the Xinjiang and Shan Dong soil samples greatly varied with the different soybean cultivars used. The soybean cultivar and the pH at which plants were grown also showed clear effects on the FSR/SSR rations isolated from nodules. Results of competition experiments between FSR and SSR strains supported the importance of the soybean cultivar and the pH on the outcome of competition for nodulation between FSR and SSR strains. In general, nodule occupancy by FSRs significantly increased at alkaline pH. Bacterial isolates from soybean cultivar Jing Dou 19 inoculated with Xinjiang soil nodulate cultivars Heinong 33 and Williams very poorly. Plasmid and lipopolysaccharide (LPS) profiles and PCR-RAPD analyses showed that cultivar Jing Dou 19 had trapped a diversity of FSR strains. Most of the isolates from soybean cultivar Heinong 33 inoculated with Xinjiang soil were able to nodulate Heinong 33 and Williams showed very similar, or identical, plasmid, LPS and PCR-RAPD profiles. All the strains isolated from Xinjiang province, regardless of the soybean cultivar used for trapping, showed similar nodulation factor (LCO) profiles as judged by thin layer chromatographic analyses. These results indicate that the existence of soybean rhizobia sub-populations showing marked cultivar specificity, can affect the estimation of total soybean rhizobia populations indigenous to the soil, and can also affect the diversity of soybean rhizobial strains isolated from soybean nodules.

China↗

PubMed2001

A prospective, randomized, comparative US trial of a combination hepatitis A and B vaccine (Twinrix) with corresponding monovalent vaccines (Havrix and Engerix-B) in adults.

In an open, randomized, multicenter, controlled clinical trial in the US, 773 adults were administered either a combination hepatitis vaccine (Twinrix: 720 EL.U inactivated hepatitis A antigen and 20 mcg recombinant hepatitis B surface antigen per milliliter) on a 0, 1, 6 month schedule or corresponding monovalent vaccines concurrently (Havrix, 1440 EL.U/ml of hepatitis A antigen at 0, 6 months and Engerix-B, 20 mcg of hepatitis B surface antigen at 0, 1, 6 months). Non-inferiority testing for the primary endpoint, severe soreness, and equivalence testing for the secondary endpoints, anti-HAV seroconversion and anti-HBs seroprotection, showed that safety and immunogenicity were comparable in the two groups.

Adult↗

PubMed2001

Real-time assessment of myocardial perfusion and wall motion during bicycle and treadmill exercise echocardiography: comparison with single photon emission computed tomography.

OBJECTIVES: We sought to determine the feasibility and accuracy of real-time imaging of myocardial contrast echocardiography (MCE) in detecting myocardial perfusion defects during exercise echocardiography compared with radionuclide tomography. BACKGROUND: Ultrasound imaging at a low mechanical index and frame rate (10 to 20 Hz) after intravenous injections of perfluorocarbon containing microbubbles has the potential to evaluate myocardial perfusion and wall motion (WVM) simultaneously and in real time. METHODS: One hundred consecutive patients with intermediate-to-high probability of coronary artery disease underwent treadmill (n = 50) or supine bicycle (n = 50) exercise echocardiography. Segmental perfusion with MCE and WM w ere assessed in real time before and at peak exercise using low mechanical index (0.3) and frame rates of 10 to 20 Hz after 0.3 ml bolus injections of intravenous Optison (Mallinckrodt Inc., San Diego, California). All patients had a dual isotope (rest thallium-201, stress sestamibi) study performed during the same exercise session, and 44 patients had subsequent quantitative coronary angiography. RESULTS: In the 100 patients, agreement between MCE and single photon emission computed tomography (SPECT) was 76%, while it was 88% between MCE and WM assessment. Compared with quantitative angiography, sensitivity of MCE, SPECT and WM was comparable (75%), with a specificity ranging from 81% to 100%. The combination of MCE and WM had the best balance between sensitivity and specificity (86% and 88%,respectively) with the highest accuracy (86%). CONCLUSIONS: The real-time assessment of myocardial perfusion during exercise stress echocardiography can be achieved with imaging at low mechanical index and frame rates. The combination of WM and MCE correlates well with SPECT and is a promising important addition to conventional stress echocardiography.

Adult↗

PubMed2001

Real-time perfusion imaging with low mechanical index pulse inversion Doppler imaging.

OBJECTIVES: We sought to determine how successful pulse inversion Doppler (PID) imaging would be in detecting myocardial perfusion defects during dobutamine stress echocardiography. BACKGROUND: By transmitting multiple pulses of alternating polarity (PID) at a low mechanical index, myocardial contrast enhancement from intravenously injected microbubbles can be detected using real-time frame rates. Pulse inversion Doppler imaging was performed in 117 patients during dobutamine stress echocardiography by using an intravenous bolus of a perfluorocarbon-filled, albumin-(Optison: n = 98) or liposome- (Definity: n = 19) encapsulated microbubble and a mechanical index of <0.3. The visual identification of myocardial contrast defects and wall motion abnormalities was determined by blinded review. Forty of the patients had quantitative angiography (QA) performed to correlate territorial contrast defects with stenosis diameter >50%. RESULTS: There was a virtual absence of signal from the myocardium before contrast injections in all patients. Bright myocardial opacification at peak stress was observed in at least one coronary artery territory at frame rates up to 25 Hz in 114 of the 117 patients during dobutamine stress echocardiography. Regional myocardial contrast defects at peak stress were observed in all 30 patients with >50% stenosis in at least one vessel (13 with single-vessel and 17 with multivessel disease). Contrast defects were observed in 17 territories subtended by >50% diameter stenosis that had normal wall motion at peak stress. Overall agreement between QA and myocardial contrast enhancement on a territorial basis was 83%, as compared with 72% for wall motion. CONCLUSIONS: Pulse inversion Doppler imaging allows the detection of myocardial perfusion abnormalities in real-time during stress echocardiography and will further add to the quality and sensitivity of this test.

Albumins↗

PubMed2001

Coexistence of multiple spiral waves with independent frequencies in a heterogeneous excitable medium.

We studied the interactions and coexistence of stable spiral waves with independent frequencies in a heterogeneous excitable medium, using numerical simulations of a spatial system based on the FitzHugh-Nagumo cell model. When the heterogeneity of the medium exceeded a critical value, a transition took place from a single dominant spiral wave to a coexistence of multiple spiral waves with independent frequencies and n:n-1 wave conduction blocks. In this case, multiple spiral waves could coexist because they are "insulated" from each other by chaotic regions.

Biological Clocks↗

PubMed2001

Inhibition of carotid artery neointimal formation with intravenous microbubbles.

Because therapeutic gene products such as synthetic antisense oligodeoxynucleotides (ODN) bind to albumin-coated microbubbles, we sought to determine whether IV perfluorocarbon-exposed sonicated dextrose albumin (PESDA) microbubbles could target their delivery to the carotid artery following balloon injury. In 5 pigs, the concentration of ODN taken up within the carotid vascular wall was found to be significantly increased when the IV antisense (ODN) was administered bound to PESDA (ODN-PESDA), and while transcutaneous low-frequency (20 kHz) ultrasound was applied over the carotid artery. Based on these results, a chronic model was then developed, in which 21 pigs received either IV ODN-PESDA, ODN alone, or control, following carotid balloon injury. At 30 days following balloon injury, percent area stenosis was only 8 +/- 2% in the ODN-PESDA groups compared to 19 +/- 8% and 28 +/- 3% in the other groups (p < 0.01). IV PESDA may be a method of noninvasively targeting the delivery of therapeutic genes.

Animals↗

PubMed2001

alpha- and beta-homogalactonojirimycins (alpha- and beta-homogalactostatins): synthesis and further biological evaluation.

The homoiminosugars alpha- and beta-homogalactonojirimycins were prepared from a common intermediate, tetra-O-benzyl-D-galacto-heptenitol 6, by way of highly stereoselective reaction sequences involving, as the key steps, an internal amidomercuration (alpha-epimer) and a double reductive amination (beta-epimer). alpha-Homogalactonojirimycin retains a large part of the potent activity of the parent galactonojirimycin and 1-deoxygalactonojirimycin as an inhibitor of alpha-galactosidases. However, by contrast with the parent iminosugars, it does not inhibit beta-galactosidases, with the exception of the Jack beans enzyme. beta-Homogalactonojirimycin is a weak alpha-galactosidase inhibitor and is completely devoid of activity towards beta-galactosidases. Thus, a marked selectivity toward one family of enzymes has been achieved by the addition of an alpha-CH(2)OH group in the structure of the parent iminosugars.

Amination↗

PubMed2001

Simvastatin inhibits noradrenaline-induced hypertrophy of cultured neonatal rat cardiomyocytes.

1. Oxidative mechanisms have been implicated in neonatal cardiomyocyte hypertrophy. We and others have shown that a HMG-CoA reductase inhibitor preserves endogenous antioxidant enzyme activity and inhibits cardiac hypertrophy in vivo. We therefore have examined whether noradrenaline (NA) induces the generation of reactive oxygen species (ROS) during its induction of neonatal cardiomyocyte hypertrophy and whether simvastatin, a HMG-CoA reductase inhibitor, attenuates ROS production and thus NA-induced hypertrophy of cardiomyocytes. 2. NA increased the intracellular ROS levels in a concentration-dependent manner. This increase of ROS was significantly inhibited by simvastatin and catalase. Prazosin partially suppressed NA-induced increase of ROS and beating, while preincubation with both prazosin and propranolol completely abolished NA-evoked increase of ROS and beating. Simvastatin did not affect NA-induced increase of beating. 3. The NA-induced increase of protein content was partially suppressed by prazosin and completely abolished by preincubation with both prazosin and propranolol. Simvastatin inhibited the increase of NA-induced increase of RNA content and [(3)H]-leucine incorporation in a concentration-dependent manner. Mevalonic acid (MVA) reversed the inhibition of NA-induced RNA and protein increase by simvastatin. Catalase also inhibited the NA-induced increase of RNA and protein. 4. We conclude that the inhibitory effects of simvastatin on myocyte hypertrophy were associated with its antioxidant effects and inhibition of MVA-metabolism pathway in neonatal rat cardiomyocytes. NA-induced increases of intracellular ROS and cardiomyocyte hypertrophy requires both alpha and beta adrenoceptors activation in neonatal rat cardiomyocytes. The increases of ROS induced by NA is required for hypertrophy.

Adrenergic alpha-Agonists↗

PubMed2001

Therapeutic ultrasound for gene delivery.

In vitro and in vivo studies using perfluorocarbon-exposed sonicated dextrose albumin (PESDA) microbubbles to enhance gene delivery are reviewed. In vitro studies show PESDA binds to oligonucleotides and that ultrasound can be used to deposit these nucleotides. In addition, in vitro studies show that drug release from microspheres is dependent on ultrasound transmission frequency as well as pulsed or continuous application. Early in vivo studies confirm that ultrasound in combination with microbubbles can be used to facilitate gene deposition. However, the role of ultrasound targeting gene delivery remains to be determined.

Animals↗

PubMed2001

Myocardial cavitational activity during continuous infusion and bolus intravenous injections of perfluorocarbon-containing microbubbles.

The 20-MHz component of broadband noise from inertial cavitation within the anterior myocardium of an open-chest dog was recorded during intravenous infusions or injections of perfluorocarbon-containing microbubbles during insonation with a 1.7-MHz harmonic transducer. Intramyocardial cavitational activity was evident even at a mechanical index of 0.2, but it increased significantly as frame rate and mechanical index were increased. The amount of myocardial contrast intensity produced by the microbubbles was increased by variables that reduced cavitational activity (eg, reducing frame rate to 1 every cardiac cycle or decreasing mechanical index). At a mechanical index of 0.2, myocardial contrast could still be observed at 10-Hz frame rates. These results confirm that intramyocardial cavitational activity is present during ultrasound imaging of microbubbles; imaging techniques that reduce cavitational activity increase the magnitude of myocardial contrast.

Animals↗

PubMed2001

Electrophysiological heterogeneity and stability of reentry in simulated cardiac tissue.

Generation of wave break is a characteristic feature of cardiac fibrillation. In this study, we investigated how dynamic factors and fixed electrophysiological heterogeneity interact to promote wave break in simulated two-dimensional cardiac tissue, by using the Luo-Rudy (LR1) ventricular action potential model. The degree of dynamic instability of the action potential model was controlled by varying the maximal amplitude of the slow inward Ca(2+) current to produce spiral waves in homogeneous tissue that were either nearly stable, meandering, hypermeandering, or in breakup regimes. Fixed electrophysiological heterogeneity was modeled by randomly varying action potential duration over different spatial scales to create dispersion of refractoriness. We found that the degree of dispersion of refractoriness required to induce wave break decreased markedly as dynamic instability of the cardiac model increased. These findings suggest that reducing the dynamic instability of cardiac cells by interventions, such as decreasing the steepness of action potential duration restitution, may still have merit as an antifibrillatory strategy.

Action Potentials↗

PubMed2001

Effects of simulated ischemia on spiral wave stability.

Regional hyperkalemia during acute myocardial ischemia is a major factor promoting electrophysiological abnormalities leading to ventricular fibrillation (VF). However, steep action potential duration restitution, recently proposed to be a major determinant of VF, is typically decreased rather than increased by hyperkalemia and acute ischemia. To investigate this apparent contradiction, we simulated the effects of regional hyperkalemia and other ischemic components (anoxia and acidosis) on the stability of spiral wave reentry in simulated two-dimensional cardiac tissue by use of the Luo-Rudy ventricular action potential model. We found that the hyperkalemic "ischemic" area promotes wavebreak in the surrounding normal tissue by accelerating the rate of spiral wave reentry, even after the depolarized ischemic area itself has become unexcitable. Furthermore, wavebreak and fibrillation can be prevented if the dynamical instability of the normal tissue is reduced significantly by targeting electrical restitution properties, suggesting a novel therapeutic approach.

Action Potentials↗

PubMed2001

Effectiveness of transcranial and transthoracic ultrasound and microbubbles in dissolving intravascular thrombi.

OBJECTIVE: To examine the effectiveness of 1 -MHz and 40-kHz ultrasound with and without microbubbles in fragmenting thrombi in attenuated conditions. METHODS: First, an vitro transcranial model was used to examine the ability of these frequencies to fragment thrombi in the presence or absence of perfluorocarbon-exposed sonicated dextrose albumin microbubbles. Second, an in vivo transthoracic model was used to test the effectiveness of these same frequencies with intravenous perfluorocarbon-exposed sonicated dextrose albumin in fragmenting left circumflex coronary thrombotic occlusions. RESULTS: In the in vitro model, both transcranial 1-MHz and 40-kHz ultrasonic frequencies were effective at fragmenting thrombi only in the presence of microbubbles. In the in vivo model, 1-MHz ultrasound with intravenous perfluorocarbon-exposed sonicated dextrose albumin angiographically recanalized only 4 of 14 occlusions but was consistently effective at improving myocardial blood flow to the risk area even in the absence of angiographic recanalization. Both 40-kHz and 1-MHz ultrasound with perfluorocarbon-exposed sonicated dextrose albumin improved regional wall-thickening and electrocardiographic abnormalities (P < .05 compared with control or ultrasound alone). CONCLUSIONS: Transcranial and transthoracic ultrasound in the presence of intravenous microbubbles can improve flow to ischemic regions and should be considered as a supplement to current pharmacologic therapy.

Adult↗

PubMed2001

[Coding region cDNA sequence cloning of rat neuroglobin gene, its polymorphism feature and tissue expression profile analysis].

The coding region cDNA sequence of rat neuroglobin (NGB) was obtained by RT-PCR technique using a degeneracy PCR primer pair based on previously reported cDNA sequence of human and mouse NGB gene. Result demonstrated that the coding region cDNA sequence of rat NGB gene is 456 bp in length, which could encode a protein of 151 amino acids. The rat NGB gene is highly homology with mouse (96%) and human (88%) NGB gene. However, several polymorphism sites were also detected in the rat NGB coding region: 113 t/c [L38P], 133 a/g [N45D], 388 a/g[R130G], 417 t/c. The cDNA sequence of rat NGB gene has been registered in GenBank under the accession number AF333245. Moreover, highly expression level of rat NGB in brain, liver, kidney, heart and skeletal muscle was detected by using multiple tissue RT-PCR technique, indicating the functional importance of this novel gene.

Amino Acid Sequence↗

PubMed2001

[Interspecific association of dominant species in Betula luminifera natural forest communities of Shaowu, Fujian Province].

chi 2 test with 2 x 2 contingency table and Jaccard indices shows that the interspecific association of 16 dominant species in Betula luminifera communities of Shaowu, Fujian Province was of little significant level with few exceptions. The relationships between B. luminifera and Phyllostachys pubescens, and B. luminifera and Alniphyllum fortunei were significantly positive, showing that there was a high association degree between B. luminifera and Schima superba, B. luminifera, and Castanea henrgi, and B. luminifera and Pinus massoniana based on Jaccard indices.

Trees↗

PubMed2001

[Studies on hereditary deficiency of coagulation factor V].

OBJECTIVE: To explore the mechanisms of hereditary deficiency of coagulation factor V (FV). METHODS: The amount of FV in plasma and platelets was assayed by immunological and biochemical method, FV gene analysis by PCR product sequencing and restriction enzyme analysing, and the biostructural pathology of the identified mutation by molecular modeling. RESULTS: No detectable FV fragments and FV activity were found in the plasma and platelets from the proband of the affected family. His gene analysis revealed a 1763A-->C substitution in a FV allele gene. The mutation might cause the loss of the hydrogen bond between conservative Tyr530 and Glu330, and form a cavity in the protein core. CONCLUSION: The 1763A-->C mutation might cause the instability of FV and be the important mechanism for the hereditary deficiency of FV.

Adult↗

PubMed2001

[Diversity of Sinorhizobium fredii strains].

Rhizobial strains were isolated from soils growing with soybean cultivar Heilong 33 and Willimas. Fifty Sinorhizobium fredii strains were chosen, and their biological characteristics including growth velocity, acid-alkali endurance, resistance of intrinsic antibiotics, utilization of carbon and nitrogen sources, absorption of congo red, ability of melanin production, and plasmid profiles were comparatively researched. The dendrogram was described using the method of cluster analysis, and the biodiversity of Sinorhizobium fredii from different soils was proved.

Carbon↗

PubMed2001

An experimental study on drugs for improving blood circulation and removing blood stasis in treating mild chronic hepatic damage.

Large and small doses of drugs for improving blood circulation and removing blood stasis were used in model rats to treat mild chronic hepatic damage induced by carbon tetrachloride (CCl4). The results show that large dose of Dang Gui ([symbol: see text] Radix Angelicae Sinensis) and Dan Shen ([symbol: see text] Radix Salviae Miltiorrhizae) (drugs for regulating blood flow) and small dose of Yu Jin ([symbol: see text] Radix Curcumae) and Niu Xi ([symbol: see text] Radix Achyranthis Bidentatae) (drugs for activating blood flow) can significantly elevate the activity of SOD (P < 0.05) and/or lower the T/K ratio, markedly reduce the MDA content (P < 0.05 or P < 0.01) and significantly decrease the activities of ALT and AST (P < 0.05 or P < 0.01), demonstrating that these drugs are effective in combating oxygen free radicals (OFR) in chronic liver damage. On the contrary, large dose of Tu Bie Chong ([symbol: see text] Eupolyphaga seu Steleophaga) and E Zhu ([symbol: see text] Rhizoma Curcumae) (drugs for removing blood stasis) tend to increase the ALT and AST (P < 0.05) activities. The results suggest that the synergism of elevation of the SOD activity and reduction of T/K ratio contributes to the action of drugs for improving blood circulation and removing blood stasis in combating the liver damage induced by CCl4.

Alanine Transaminase↗