Biomedical subjects

Jinzhong Xu

Publications and source records attributed to Jinzhong Xu.

8 recordsLinked to original sources

PubMed2006

Four new macrocyclic trichothecenes from two strains of marine-derived fungi of the genus Myrothecium.

Three new macrocyclic trichothecenes, named 12'-hydroxyroridin E (1), roridin Q (2), and 2',3'deoxyroritoxin D (3), were isolated from the marine-derived fungus Myrothecium roridum TUF 98F42, and a new macrocyclic trichothecene, named roridin R (4), was isolated from Myrothecium sp. TUF 02F6 together with roridins A and H and isororidin E. The structures of new compounds were determined on the basis of their spectral data. Compound 2 possessed a unique ether moiety at the 13' position of 1. Compound 4 was a 2',3'-dihydro-2'-hydroxy derivative of roridin H. The IC50 values of compounds 1, 2, and 4 against the murine leukemia cell line L1210 were 0.19, 31.2, and 0.45 microM, respectively. Compound 3 showed antiyeast activity to Saccharomyces cerevisiae at 1 microg/disc (inhibition zone: 12.2 mm), which was about 10 time more active than roritoxin D (10.2 mm at 10 microg/disc).

Antineoplastic Agents↗

PubMed2006

Melophlins P, Q, R, and S: four new tetramic acid derivatives, from two Palauan marine sponges of the genus Melophlus.

Four new tetramic acid derivatives, named melophlins P, Q, R, and S (1-4), were isolated from two marine sponges of the genus Melophlus collected at Palau, together with seven known melophlins A, D, E, G, H, I, and O. The structures of the new compounds were elucidated on the basis of their spectral data. The absolute stereochemistries at the tetramic acid moieties of the new compounds were determined as 1 : 1 mixtures (racemic) by ESI-LC/MS analysis of derivatives obtained by oxidation and hydrolysis of the respective parent compounds. Melophlins P-S (1-4) showed cytotoxicity against the murine leukemia cell line L1210 with IC(50) values of 20.0, 10.5, 0.85, and 5.13 microM, respectively.

Animals↗

PubMed2006

[Determination of three nitroimidazole residues in royal jelly by high performance liquid chromatography-tandem mass spectrometry].

A method for analysis of trace metronidazole (MTZ), dimetridazole (DMZ) and ronidazole (RNZ) residues in royal jelly was developed by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). After samples were dissolved in sodium hydroxide solution to disassociate target analytes from matrix, liquid-liquid extraction methods by ethyl acetate solvent were used. Matrix effects were minimized and good quantitation results were obtained by using highly-selective reaction monitoring (H-SRM) technology when deuterated dimetridazole (dimetridazole-D3) was selected as internal standard. Limits of detection (LODs) were 1.0 microg/kg for DMZ, 0.5 microg/kg for MTZ and RNZ (S/N > 5). Limits of quantitation (LOQs) were 2.0 microg/kg for DMZ, 1.0 microg/kg for MTZ and RNZ (S/N > 10). The linear ranges were 2.0 - 200 microg/L for all target analytes. Recoveries and relative standard deviations (RSDs) were in the ranges of 96.6% - 110.6% and 2.1% -7.4%, respectively. This method is suitable for statutory residue testing in the National Residue Surveillance Plan in China and meets the requirement for export.

China↗

PubMed2006

[Determination of metabolites of nitrofuran antibiotics in royal jelly by high performance liquid chromatography-tandem mass spectrometry].

Nitrofurans are a group of widely used veterinary antibiotics that have been banned in many countries. This has generated a great deal of interests and demands for assay of nitrofurans in animal food products. To our knowledge, this is the first time that a high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method has been successfully developed for simultaneously analyzing the metabolites of four nitrofuran antibiotics (furazolidone, furaltadone, nitrofurazone and nitrofurantoin) in royal jelly. Trichloroacetic acid solution was used both to precipitate proteins and to provide acidic reaction condition. Four isotope internal standards were utilized to improve the quantitative precision. The limits of detection (LODs) were 0.03 microg/kg for the metabolite of furaltadone and 0.05 microg/kg for the other three metabolites. The limits of quantitation were 0.20 microg/kg for the metabolite of furaltadone and 0.25 microg/kg for the other three metabolites. The linear range was 0.4-20 ng/mL for all the target analytes. The recoveries calibrated by internal standard were in the range of 97.7%-104.8 with the relative standard deviations (RSDs) of 2.7-9.7. It showed that this method could meet the requirements of national monitoring plan in China and the Minimum Required Performance Limits (MRPL) set by the European Union.

Anti-Bacterial Agents↗

PubMed2006

[Determination of lincosamide residues in honey using high performance liquid chromatography-electrospray tandem mass spectrometry].

An analytical method for the determination of lincosamide antibiotic residues in honey was developed. In the procedure a solid-phase extraction for the isolation of lincomycin and clindamycin from diluted honey samples was employed. The residues of lincomycin and clindamycin were subsequently analyzed by reversed-phase high performance liquid chromatography (RP-HPLC) coupled with electrospray tandem mass spectrometry. Mass spectral acquisition was applied with selective reaction monitoring of two diagnostic transition reactions. The qualitative analysis was based on the retention time, the precursor ion and two product ions, and the quantitation was carried out with intension of the characteristic ion m/z 126. The linear ranges were from 1.0 microg/L to 200 microg/L for lincomycin and clindamycin and the correlation coefficients (r2) were all greater than 0.996. The average recoveries for lincomycin and clindamycin ranged from 80% to 110% in replicate sets of honey samples spiked with the drug concentrations of 1.0, 5.0 and 20.0 microg/kg, and the relative standard deviations (RSDs) were less than 8% for intra-day and 15% for inter-day determinations. The method detection limit and quantitation limit were 0.1 micro/kg and 0.5 microg/kg, respectively. The method is simple and suitable for routine analysis.

Chromatography, High Pressure Liquid↗

PubMed2005

Fabrication of a hydrogen peroxide biosensor based on a self-assemble composite oxide film.

A titania film with horseradish peroxidase (HRP) was immobilized on indium tin oxide (ITO) electrodes to act as a biosensor of hydrogen peroxide via the self-assembling and sol-gel route. The film was characterized by the atomic functional microscopy, electrochemical and UV-vis spectroscopy methods. The resulting biosensor exhibited fast amperometric response and good stability to hydrogen peroxide (H2O2). The linear range for H2O2 determination was from 2 x10(-6) to 1.45 x 10(-3) M, with a detection limit of 4 x10(-6) M based on S/N=3. The apparent Michaelis-Menten constant of the biosensor to H2O2 was estimated to be 1.5 mM, showing the HRP on the films had the higher biologic activities.

Biosensing Techniques↗

PubMedDate not supplied

Computer-based testing in family practice certification and recertification.

BACKGROUND: The member boards of the American Board of Medical Specialties have agreed to expand the scope of certification to include assessment of medical knowledge, practice-based learning and improvement, patient care, interpersonal and communication skills, systems-based practice, and professionalism. Multiple-choice examinations provide limited ability to assess these dimensions. METHODS: The American Board of Family Practice (ABFP) has developed a computer simulation system to facilitate more comprehensive candidate evaluation. The system consists of a knowledge base, a simulation program to create patient scenarios, an interface for presenting simulations to users, and an administrative database to track candidate performance and interactions with the system. The system uses population distributions for disease states to produce cases and evolves patients in response to candidate interventions, such as pharmacological and nonpharmacological therapies. We use Bayesian belief networks to model patient characteristics and comorbid condition interactions. RESULTS: Simulations have been created for 7 disease states; ultimately simulations will be available for 25 to 30 disease states. Initial testing will take place in regional examination centers but will ultimately use the Internet for convenient access for certification and recertification candidates. CONCLUSION: The ABFP will begin field-testing the system in early 2003 and will include simulations in the certification and recertification examination process in 2004.

Bayes Theorem↗

PubMedDate not supplied

Maintenance of certification for family physicians (MC-FP) self assessment modules (SAMs): the first year.

INTRODUCTION: In 2000, the American Board of Medical Specialties adopted Maintenance of Certification (MOC) to replace intermittent, periodic recertification. MOC consists of 4 components: demonstration of professionalism (part I); commitment to life-long learning (part II); demonstration of cognitive expertise (part III); and evaluation of performance in practice (part IV). The American Board of Family Medicine (ABFM) implemented Maintenance of Certification for Family Physicians (MC-FP) in 2004, with its MC-FP part II self-assessment modules (SAMs) as the focus of the first year's activities. METHODS: The SAMs use materials and resources provided at the ABFM's website (www.theabfm.org). As of April 2005, approximately 7000 Diplomates had successfully completed SAMs in essential hypertension (N = 2351) and type 2 diabetes mellitus (N = 4648). Participants completed categorical modified Likert scale evaluations to receive continuing education credit, and many offered unstructured free-text comments regarding the clinical simulation component. These free-text comments were entered into the AnSWR qualitative analysis program from the Centers for Disease Control and Prevention. Text coding was performed by 2 authors (MDH, DJI). As no inferential analyses or comparisons were anticipated, the authors conducted no studies of inter-rater consistency. Results are reported as means (SD) and medians for continuous data, and as frequencies for count data. RESULTS: Likert-scale ratings indicated generally favorable responses (predominantly 5 to 6 on a 6-point scale) to the hypertension and diabetes SAMs. In addition, over half (ie, 55% for hypertension and 54% for diabetes participants) of the respondents indicated that the experience would lead to changes in their practices. Navigation and system operation issues predominated in the free-text comments offered for the diabetes and hypertension simulations. CONCLUSION: The MC-FP SAMs received generally favorable ratings in the program's first year. The SAMs underwent a number of modifications and improvements during the first year, largely in response to feedback and suggestions from ABFM Diplomates.

Certification↗