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Biomedical subjects

F Xie

Publications and source records attributed to F Xie.

At least 19 recordsLinked to original sources
PubMed1999

In vivo microdialysis/liquid chromatography/tandem mass spectrometry for the on-line monitoring of melatonin in rat.

Liquid chromatography/tandem mass spectrometry (LC/MS/MS) has been coupled to in vivo microdialysis for on-line monitoring of melatonin in a freely moving rat for a period of 15 hours. A microdialysis probe was surgically implanted into the jugular vein of the rat, and deionized water was used as the perfusion medium at a flow rate of 1.0 microL/min. Microdialysis samples were collected in an on-line injector with sample injection every 30 minutes. Melatonin was dosed by intraperitoneal (i.p.) injection and then monitored by microdialysis/LC/MS/MS. The whole experiment, including the microdialysis sampling and sample injection into the LC/MS system, was fully automated. Metabolites of melatonin were identified off-line by LC/MSn experiments. Two metabolites were identified as 6-hydroxymelatonin and cyclic 2-hydroxymelatonin, consistent with ones found previously in the literature.

Animals↗
PubMed1999

Different role of antioxidants in endotoxin-induced late myocardial protection.

Previous studies have proposed that endogenous antioxidants play a protective role against cardiac ischemia-reperfusion injury in endotoxin pretreatment. However, the mechanism underlying this effect remains elusive. We therefore evaluated the role of endogenous antioxidants in delayed myocardial protection after different doses of endotoxin administration using cultured rat neonatal cardiomyocytes. Myocytes were treated with normal saline (control) or lipopolysaccharide (Escherichia coli, serotype O111) at doses of 40 and 80 microg/ml (ET40 and ET80). Also, antisense oligodeoxyribonucleotide (1.5 micromol/L) to manganese superoxide dismutase (Mn-SOD) and 3-amino-1,2,4-triazole (25 mg/ml) were added along with a 40 or 80 microg/ml endotoxin pretreatment in the IET40 and IET80 groups. Twenty-four hours later, Cells were subjected to hypoxia (pO2 < 1 kPa, 3 h) and reoxygenation (pO2: 19 kPa, 1 h). Compared with controls, cell viability enhanced significantly (65.3 +/- 5.9, 63.8 +/- 4.6, and 69.7 +/- 5.2% vs 47.2 +/- 4.3%, P < 0.05) and creatine kinase release decreased (7.34 +/- 1.76, 7.11 +/- 1.49, and 6.27 +/- 1.24 U/mg protein vs 11.23 +/- 2.49 U/mg protein, P < 0. 05) in ET40, IET40, and ET80 groups following reoxygenation. No statistically significant difference was found between the control and the IET80 groups. Furthermore, the levels of Mn-SOD (1.12 +/- 0. 31 vs 0.75 +/- 0.15 U/mg. protein, P < 0.05) and catalase activity (1265 +/- 109 vs 996 +/- 85 U/mg. protein, P < 0.05) were higher only in the ET80 group. The results suggest that at a dose of 40 microg/ml, cells were protected by mechanisms other than the augmentation of endogenous antioxidant activity which were more evident at a dose of 80 microg/ml. It seems that different doses of endotoxin pretreatment may induce delayed myocardial protection through various mechanisms.

Animals↗
PubMed1999

An evaluation of the safety and immunogenicity of a five-component acellular pertussis, diphtheria, and tetanus toxoid vaccine (DTaP) when combined with a Haemophilus influenzae type b-tetanus toxoid conjugate vaccine (PRP-T) in Taiwanese infants.

OBJECTIVE: Immunologic interference particular to the Haemophilus influenzae type b (Hib) response has been observed with previous acellular pertussis-Hib combination vaccines. To test this hypothesis a clinical trial to assess the safety and immunogenicity of a five-component (pertussis toxoid [PT], filamentous hemagglutinin [FHA], pertactin [PRN], and fimbriae 2 and 3 [FIM]), pertussis vaccine combined with diphtheria and tetanus toxoids (DTaP) when given simultaneously with a lyophilized Hib-tetanus toxoid conjugate vaccine (PRP-T) in infants at 2, 4, 6, and 18 months of age was conducted. The study compared two methods of administration: both vaccines combined in a single syringe and administered as a single injection, or both vaccines administered concurrently but at separate sites of injection. METHODS: Healthy 2-month-old infants were enrolled at the National Taiwan University Hospital. DTaP, PRP-T, and oral poliomyelitis vaccine (OPV) were given at 2, 4, 6, and 18 months. Reaction information was collected by telephone 2 days after each vaccination. Serum was collected at 2, 6, 7, 18, and 19 months of age. RESULTS: One hundred thirty-five healthy infants were enrolled in Taiwan, of which 127 (94%) completed the 18-month booster: 68 received the combined vaccine and 67 the separate vaccines. All vaccines were well tolerated. No differences in rates of local and systemic reactions were seen between the two methods of administration. No serious adverse events were reported. Serologic responses were comparable between the groups. Pertussis responses (enzyme-liked immunoabsorbant assay units [EU]/mL) at 7 months were, for combined versus separate, PT (131 vs 105), FHA (116 vs 116), PRN (100 vs 77), and FIM (922 vs 702). At 19 months, pertussis results were, for combined versus separate, PT (216 vs 182), FHA (203 vs 200), PRN (263 vs 197), and FIM (892 vs 732). Only the 7-month PT response in the combined group was significantly higher (combined 131 EU/mL vs separate 105 EU/mL). After the third dose (age 6 months), all subjects achieved serologic serum antibody levels indicative of protection against Hib, diphtheria, tetanus, and poliovirus types 1, 2, and 3. In fact, 96% of children had anti-PRP levels indicative of protection (>/=0.15 microgram/mL) against Hib after only two doses. At 7 months, anti-PRP geometric mean titer values were 11.8 micrograms/mL in the combined group compared with 13.0 micrograms/mL in the separate group. The anti-PRP geometric mean titers after the 18-month booster were 58.5 micrograms/mL in the combined group versus 55.3 micrograms/mL in the separate group. CONCLUSION: The five-component DTaP vaccine may be combined with PRP-T vaccine without clinically significant immunologic interaction when given in a 2-, 4-, 6-, and 18-month schedule.

Diphtheria↗
PubMed1998

Role of pectinate muscle bundles in the generation and maintenance of intra-atrial reentry: potential implications for the mechanism of conversion between atrial fibrillation and atrial flutter.

To determine the role of pectinate muscle (PM) bundles in the formation of intra-atrial reentry, 10 isolated canine right atrial tissues were perfused with Tyrode's solution containing 1 to 2.5 micromol/L acetylcholine (ACh). The endocardium was mapped using 477 bipolar electrodes with 1.6-mm resolution. Reentry was induced by a premature stimulus (S2). Computer simulation studies were used to investigate the importance of regional myocardial thickness in reentry formation. A total of 40 episodes of reentry were induced; 28 episodes were stationary, and the remaining 12 were nonstationary. The stationary reentry was induced either immediately after the S2 stimuli (n=9) or after an initial period of irregular activations that lasted 1460+/-1077 ms (n= 19). Of 28 episodes, 20 were initiated by conduction block along large PM ridges, leading to wave break and the initiation of reentry. The reentrant wave fronts remained stationary and rotated around these ridges as anchoring sites. During the transition from the initial irregular activations to stationary reentry, the electrogram morphology converted from "fibrillation-like" to "flutter-like" activity. In 8 episodes, initially stationary reentry converted to irregular activations because of interference with outside wave fronts (n=5) or spontaneous separation of waves from the ridges (n=3). Compared with stationary reentry, nonstationary reentry always occurred over an area without large PMs, and the mean life span was much shorter (102+/-151 versus 3.8+/-1.1 rotations, P<0.001). Computer simulation studies showed that a critical ridge thickness is needed for reentry to anchor, thereby converting fibrillation to flutter. We conclude that PM ridge forms an area where wave break occurs, allowing the initiation of reentry. It also provides a natural anchor to the reentrant wave front, lengthening the life span of reentry. The attachment and detachment of the reentrant wave front to and from the ridge determine "flutter-like" or "fibrillation-like" activity.

Animals↗
PubMed1998

Safety and immunogenicity of a combined five-component pertussis-diphtheria-tetanus-inactivated poliomyelitis-Haemophilus B conjugate vaccine administered to infants at two, four and six months of age.

Safety, immunogenicity and lot consistency of five-component pertussis combination vaccine (CPDT-IPV//PRP-T) in infants were compared to that of whole cell pertussis combination vaccine (DPT-IPV//PRP-T), as were separate and combined injections of CPDT-IPV and PRP-T. No significant differences in adverse event rates were observed between lots of CPDT-IPV//PRP-T or between separate or combined injections of CPDT-IPV and PRP-T. Minor differences in antibody responses were observed between lots of component pertussis vaccine. Higher concentrations of diphtheria and tetanus antitoxins were induced by separate than by combined injection of CPDT-IPV and PRP-T, but no other differences in immunogenicity were observed. Adverse reactions were more than twice as frequent after whole cell than after component pertussis vaccines. Antibody responses to pertussis toxoid, filamentous hemagglutin and pertactin were significantly greater after component vaccines, while the response to type 3 poliovirus was higher after whole cell vaccine. No significant differences were observed for other vaccine components. CPDT-IPV//PRP-T was safe and immunogenic in infants. Antibody results were similar to those observed in a Swedish field trial that demonstrated CPDT to be 85% effective in preventing clinical pertussis.

Acetaminophen↗
PubMed1998

[Determination enzyme protein of CK-MB m-AST and ChE by immunological methods and survey of its applying values].

In recent decades, because considerable progress has been made due to rapid developments in basic theory and techniques in molecular biology and immunology, the determination of trace enzyme proteins is not difficult. We measured the serum concentration of Creatine kinase-MB (CK-MB) mitochondria aspartate aminotransferase (m-AST) and cholinesterase (ChE) immunologically and compared these findings with those of an assay of enzyme activity. Purification of enzyme protein and preparation of serum antibodies monoclonal antibodies established the immunological assay methods. Equipment and reagents for enzyme activity test use 7150 Biochemical Analyzer. CK-NAC AST and ChE were produced by trace kits (Australia). CK-MB and m-AST use immunological inhibition method. CK-MB m-AST ChE of protein determination used immunological turbidimetry. The normal group included 150 cases and the 1990 patient group. Results of the two methods did not significantly differ for normal controls, but were significantly different in the patient group. These results demonstrated that the two methods differ, although each may have specific clinical significance. How to evaluate these differences needs to be studied further, but immunological assay uses higher values for clinical diagnosis than enzyme activity assay.

Antibodies, Monoclonal↗
PubMed1997

Diphtheria and tetanus immunity among blood donors in Toronto.

OBJECTIVE: To determine the diphtheria and tetanus antitoxin levels among blood donors in Toronto. DESIGN: Cross-sectional seroprevalence study. SETTING: Two fixed-site blood-donation clinics in Toronto from September to November 1994. PARTICIPANTS: Blood donors 20 years of age or older were eligible to participate; of the 781 eligible donors, 710 (90.9%) participated in the study. MAIN OUTCOME MEASURES: Diphtheria and tetanus antitoxin levels and factors associated with disease susceptibility, such as vaccination history, country of birth, age and sex. A diphtheria antitoxin level lower than 0.01 lU/mL and a tetanus antitoxin level lower than 0.15 lU/mL were considered nonprotective. RESULTS: Among the participants, 147 (20.7%) had a diphtheria antitoxin level in the nonprotective range, and 124 (17.5%) had a tetanus antitoxin level that was nonprotective. Increasing age and lack of written vaccination records were associated with susceptibility to the 2 diseases. Birth outside Canada was significantly related to tetanus susceptibility. CONCLUSION: Adults over 50 years of age who did not know their vaccination history were the least likely to be protected against diphtheria and tetanus. The greatest benefit of any immunization strategy would be gained by targeting this group.

Adult↗
PubMed1997

Comparison of evidence for linkage from different analytic methods.

In a randomly chosen replicate of extended pedigrees from GAW10, we conducted robust multipoint genome scans for linkage using a dense marker map. For analysis of the quantitative traits, we selected sibships from the pedigrees, and for analysis of disease status, small families of affected relatives were selected. Lod-score likelihood analyses were conducted in the full pedigrees and in the affected relative families for selected regions. We located a flanking marker for MG1 on chromosome 5, and identified marker regions including MG2, MG4, and MG5 on chromosomes 8 and 9. The analytic methods were consistent for the major gene with a strong effect; false positive errors on chromosomes 1 and 10 could have been eliminated by requiring evidence from more than one method.

Female↗
PubMed1997

Generalized estimating equation model for binary outcomes with missing covariates.

This paper presents an approach to handling missing covariates in the generalized estimating equation (GEE) model for binary outcomes when the probability of missingness depends on the observed outcomes and covariates. The proposed method is to replace the missing quantities in the estimating function with consistent estimates. In special cases, the proposed model reduces to a weighted GEE model for the completely observed units, where the weight is the inverse of the probability of missingness. Our method can be viewed as an extension of the mean score method by Reilly and Pepe (1995, Biometrika 82, 299-314) to the GEE context. Under certain regularity conditions, the estimates of the regression coefficients obtained by the proposed method are consistent and asymptotically normally distributed. The finite sample properties of the estimates are illustrated via computer simulations. An application to the study of dementia among stroke patients is presented.

Aged↗
PubMed1997

Multiple imputation methods for the missing covariates in generalized estimating equation.

This paper discusses the missing covariates problem in the generalized estimating equation (GEE) model. Estimates by various multiple imputation techniques (MI) are examined and compared to the sample average imputation method (SA) through simulations and an example. The simulation results show that, under the correct model specification, the MI estimators have negligible bias and have fairly similar efficiencies as the SA estimator. A practical advantage of the MI estimates is that the standard errors can be more easily computed than the SA estimates.

Aged↗
PubMed1997

[A knowledge-based method for 3D segmentation and display of human brain].

From the view of the artificial intelligence, a new method of segmentation and display of human brain medical images is descrided. On the basis of the knowledge of brain anatomy and image processing, we have built the 3D knowledge mobel using frame as the main knowledge expression method. Under the guide of the knowledge, the main structures in the brain are segmented and displayed by means of the "inelligent ray-tracing".

Artificial Intelligence↗
PubMed1996

Improved myocardial contrast with second harmonic transient ultrasound response imaging in humans using intravenous perfluorocarbon-exposed sonicated dextrose albumin.

OBJECTIVES: The objectives of this study were to determine whether a new method of ultrasound imaging (transient response imaging) could improve the myocardial contrast after intravenous injections of perfluorocarbon-exposed sonicated dextrose albumin microbubble contrast medium in humans. BACKGROUND: We have shown in animals that very low doses of intravenous contrast medium can produce transient but significantly better myocardial contrast when diagnostic ultrasound pulses are interrupted (delivered only once per cardiac cycle) instead of conventional 25- to 30-Hz frame rate imaging. METHODS: In 14 patients with normal rest wall motion, the peak myocardial contrast produced by transient response imaging was compared with that produced by conventional harmonic ultrasound imaging after injections of low doses (0.0025 to 0.01 ml/kg) of intravenous contrast medium. All studies were performed with second harmonic imaging (2.0 to 2.5 MHz-transmitted frequency). Blood pressure, oxygen saturation, respiratory rate and pulse were monitored before and after each injection. RESULTS: The intravenous contrast medium in the doses given produced no hemodynamic changes and no significant side effects in any patients. Overall, the mean (+/-SD) anterior and posterior myocardial contrast produced was significantly greater with transient response imaging than with conventional harmonic ultrasound imaging (anterior: 37 +/- 20 U transient response imaging vs. 18 +/- 14 U conventional harmonic imaging; posterior: 17 +/- 14 U transient response imaging vs. 5 +/- 5 U conventional; p< 0.01). With the sample size of 14 patients, the study had 80% power to detect a true difference of 18 U for anterior myocardial contrast and 90% power to detect a difference of 12 U for posterior contrast. Visually evident anterior or apical myocardial contrast was observed in 14 of 15 patients with transient response imaging but in only 7 patients with conventional harmonic imaging. Posterior or basal myocardial contrast was evident in 10 patients with transient response imaging but in only 1 patient with conventional harmonic imaging. CONCLUSIONS: Transient response imaging produces significantly better myocardial contrast than conventional harmonic imaging in humans and can be produced safely with minute quantities of intravenous perfluorocarbon.

Albumins↗
PubMed1996

Thrombolytic enhancement with perfluorocarbon-exposed sonicated dextrose albumin microbubbles.

Whereas low-intensity, high-frequency ultrasound (US) alone appears to cause minimal thrombolysis, US combined with air-filled microbubbles does increase the amount of urokinase (UK)-mediated clot lysis (CL). Because this phenomenon may be mediated by cavitation-induced streaming, we hypothesized that perfluorocarbon-exposed sonicated dextrose albumin (PESDA) microbubbles, which are more stable than air-filled microbubbles, may also enhance US-induced thrombolysis. We measured the percentage CL of equally sized thrombi (1.0 +/- 0.1 mg) made from freshly drawn blood incubated for 2 hours and then exposed to 20 kHz US (0.846 MPa peak negative pressure). The thrombi were bathed in 4 ml of saline solution, UK alone (20,000 U), PESDA alone, or a combination of PESDA with UK. The percentage CL achieved with PESDA and therapeutic US was also compared with the percentage CL achieved with room air-filled sonicated dextrose albumin (RASDA) microbubbles. When compared with US alone (24% +/- 13% CL) or UK alone (17% +/- 3% CL), PESDA plus US produced significantly better CL (43% +/- 17%; p< 0.05). PESDA combined with US also produced significantly greater CL than RASDA combined with US (28% +/- 9%; p < 0.05). The optimal CL was achieved with a combination of PESDA with UK with US (60% +/- 14% CL). We conclude that PESDA microbubbles alone may be capable of inducing thrombolysis when insonified with a low-frequency transducer.

Contrast Media↗
PubMed1996

Myocardial perfusion abnormalities during low-dose dobutamine after coronary reperfusion can be demonstrated with intravenous perfluorocarbon-exposed sonicated dextrose albumin ultrasound contrast.

We measured background-subtracted peak myocardial videointensity (PMVI) in the left anterior descending and left circumflex perfusion zones in open-chest dogs after intravenous injection of perfluorocarbon-exposed sonicated dextrose albumin ultrasound contrast (PESDA) after reperfusion of a coronary occlusion. These measurements were repeated during low-dose dobutamine (LDD). The ratio of PMVI in the reperfused zone (RZ) compared with the adjacent normal zone (NZ) was measured at baseline and during LDD. Dogs with a >50% diameter residual stenosis were group I (n = 10), and those with <50% residual stenosis were group II (n = 13). Wall-thickening (WT) responses to LDD were not different between groups. Although the PMVI ratio (PMVI(RZ)/PMVI(NZ)) was the same in both groups at baseline, it decreased by >0.1 during LDD in 8 of 10 in group I compared with only 3 of 13 in group II dogs (p = 0.01). PMVI in the RZ increased by > or = 1.5 U in 12 of 13 group II dogs during LDD, but only in 3 of 10 group I dogs. Therefore, intravenous PESDA can be combined with WT responses to define both myocardial function and flow after reperfusion.

Adrenergic beta-Agonists↗
PubMed1996

Detection of regional perfusion abnormalities during adenosine stress echocardiography with intravenous perfluorocarbon-exposed sonicated dextrose albumin.

Although perfluorocarbon-exposed sonicated dextrose albumin (PESDA) microbubbles produce myocardial contrast after intravenous injection, it is unknown whether their use can accurately identify myocardial blood-flow abnormalities during stress echocardiography. Accordingly, we compared the background-subtracted peak myocardial videointensity (PMVI) after intravenous injections of PESDA before and during adenosine stress (100 to 140 units/kg/min) in 10 open-chest dogs with angiographically significant left circumflex artery disease. The ratios of PMVI in the ischemic region compared with the adjacent normal left anterior descending perfusion bed were measured, as were wall-thickening and coronary-flow ratios. In the dogs with a >50% diameter stenosis, there was a decrease in PMVI ratio during adenosine stress by >0.20 in 9, whereas wall-thickening ratios decreased in only 5. PMVI in the ischemic zone increased by <1.5 units during adenosine infusion in 8 of 10 dogs, whereas it increased by >1.5 units in 8 of 1O adjacent normal zones. We conclude that regional myocardial-perfusion abnormalities can be detected with intravenous PESDA during adenosine stress echocardiography.

Adenosine↗