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Biomedical subjects

P De Backer

Publications and source records attributed to P De Backer.

At least 37 records · Page 2Linked to original sources
PubMed2001

The use of a Daphnia magna bioassay for rapid screening of acute intoxications with insecticides in dogs and cats.

Sudden death due to acute insecticide intoxications occurs frequently in dogs and cats. The absence of characteristic lesions at autopsy often renders post-mortem diagnosis dependent on the analysis of samples taken from the carcase at autopsy. In the present study, a bioassay utilizing Daphnia magna was proposed and tested as a rapid screening method for acute intoxications in dogs and cats. The bioassay was shown to be highly sensitive for detecting carbamate and organophosphate insecticides in the stomach contents. Generally. the mean survival time of the waterfleas in the control group was 5.17 h (SD = 1.24) and in the intoxicated group 1.32 h (SD = 1.49). during a 6 h observation period. If a cut-off is set at 4 h, this Daphnia bioassay gave 5.5% false negative results and 18.2% false positive results. using the results of toxicological analyses as a gold standard.

Animals↗
PubMed2001

Inhibition tests for detection and presumptive identification of tetracyclines, beta-lactam antibiotics and quinolones in poultry meat.

A combination of three plates, seeded with strains of Micrococcus luteus, Bacillus cereus or Escherichia coli, can be used for detection of residues of beta-lactam antibiotics, tetracyclines and fluoroquinolones. The sensitivity of each plate is optimal for only one of these groups, resulting in detection limits (LOD) lower than the corresponding maximum residue limits (MRL) and in distinct inhibition patterns typical for each antibiotic family. Beta-lactam antibiotics such as penicillin G, ampicillin and amoxicillin give only inhibition zones on the plate with M. luteus. Tetracyclines are detected up to the MRL level with B. cereus, and fluoroquinolones with E. coli. The LODs of the antibiotics tested were as follows: penicillin G (PENG) 0.9 ng, ampicillin (AMPI) 0.6 ng and amoxicillin (AMOX) 1.0 ng on the plate with M. luteus; tetracycline (TET) 4 ng, oxytetracycline (OXY) 3 ng, doxycycline (DOX) 0.6 ng, and chlortetracycline (CHL) 0.3 ng on the plate with B. cereus; enrofloxacin (ENRX) 1.5 ng, ciprofloxacin (CIPX) 0.5 ng and flumequine (FLUM) 1.5 ng on the plate with E. coli. The combination of plates enables the laboratory to select appropriate chromatographic techniques for identification and quantification of the residues. On the other hand, the three groups can also be detected on one plate seeded with Bacillus subtilis, although the limits of detection are higher: PENG 0.4 ng, AMPI and AMOX 3 ng, TET 5 ng, OXY 8 ng, DOX 1 ng, CHL 0.5 ng, ENRX 4 ng, CIPX 10 ng and FLUM 4 ng. The test was applied to 228 broiler fillets and to 27 turkey thighs, originating from different poultry slaughterhouses. Nineteen broiler fillets contained inhibiting substances. The positive results of the inhibition tests were confirmed with a chromatographic technique. Doxycycline residues were found in 16 samples and amoxicillin in two.

4-Quinolones↗
PubMed2000

Quantitative analysis of levamisole in porcine tissues by high-performance liquid chromatography combined with atmospheric pressure chemical ionization mass spectrometry.

This work presents the development and the validation of an LC-MS-MS method with atmospheric pressure chemical ionization for the quantitative determination of levamisole, an anthelmintic for veterinary use, in porcine tissue samples. A liquid-liquid back extraction procedure using hexane-isoamylalcohol (95:5, v/v) as extraction solvent was followed by a solid-phase extraction procedure using an SCX column to clean up the tissue samples. Methyllevamisole was used as the internal standard. Chromatographic separation was achieved on a LiChrospher 60 RP-select B (5 microm) column using a mixture of 0.1 M ammonium acetate in water and acetonitrile as the mobile phase. The mass spectrometer was operated in MS-MS full scanning mode. The method was validated for the analysis of various porcine tissues: muscle, kidney, liver, fat and skin plus fat, according to the requirements defined by the European Community. Calibration graphs were prepared for all tissues and good linearity was achieved over the concentration ranges tested (r>0.99 and goodness of fit <10%). Limits of quantification of 5.0 ng/g were obtained for the analysis of levamisole in muscle, kidney, fat and skin plus fat tissues, and of 50.0 ng/g for liver analysis, which correspond in all cases to half the MRLs (maximum residue limits). Limits of detection ranged between 2 and 4 ng/g tissue. The within-day and between-day precisions (RSD, %) and the results for accuracy fell within the ranges specified. The method has been successfully used for the quantitative determination of levamisole in tissue samples from pigs medicated via drinking water. Moreover the product ion spectra of the levamisole peak in spiked and incurred tissue samples were in close agreement (based on ion ratio measurements) with those of standard solutions, indicating the worthiness of the described method for pure qualitative purposes.

Animals↗
PubMed2000

Determination and quantification of sulfadiazine and trimethoprim in swine tissues using liquid chromatography with ultraviolet and mass spectrometric detection.

High-performance liquid chromatographic procedures with ultraviolet detection were developed for the quantitative determination of sulfadiazine (SDA) and trimethoprim (TMP) in swine tissues (kidney, liver, muscle, fat and fat + skin). In addition, high-performance liquid chromatography with atmospheric pressure chemical ionization mass spectrometry was used for the confirmation of the identity of the analytes of interest. Chromatographic separation was achieved on a Spherisorb ODS-2 column (250 x 4.6 mm id, dp 5 microns). The mobile phase for SDA analysis consisted of 1% acetic acid in water-acetonitrile (85 + 15, v/v). For TMP analysis a 80 + 15 + 5 (v/v/v) mixture of 0.25% triethylammonium acetate in water, acetonitrile and methanol was used as the eluent. Sulfamerazine and ormethoprim were used as the internal standards for SDA and TMP analysis, respectively. For the isolation of the compounds of interest from biological samples, a liquid-liquid extraction with acetone and ethyl acetate, followed by a clean-up using a solid-phase extraction column (aminopropyl and benzenesulfonic acid for SDA, benzenesulfonic acid for TMP) was performed. Calibration graphs were prepared for all tissues and linearity was achieved over the concentration ranges tested (50-1000 ng g-1 for SDA, r > or = 0.9979; 25-500 ng g-1 for TMP, r > or = 0.9994). The method was validated at the maximum residue level (MRL, 100 ng g-1 for SDA and 50 ng g-1 for TMP), at half the MRL and at double the MRL for both SDA and TMP. The accuracy and precision (expressed as the within-day repeatability) were found to be within the required ranges for each specific concentration. The quantification limits were 50 ng g-1 for SDA and 25 ng g-1 for TMP. The limits of detection were below one half the MRLs. Both methods were selective for the determination of SDA and TMP. Biological samples (kidney, liver, muscle, fat and fat + skin) from pigs that received a commercial SDA-TMP preparation with the feed for five consecutive days (dose rate: 25 mg SDA and 5 mg TMP kg body weight-1 day-1) were analyzed using the described methods. The quantitative results were used to calculate a withdrawal time (12 days) to reach residue levels below the respective MRLs. This calculation was performed according to the recommendations of the European Agency for the Evaluation of Medicinal Products (EMEA/CVMP/036/95).

Animals↗
PubMed1998

Liquid chromatographic separation of doxycycline and 4-epidoxycycline in a tissue depletion study of doxycycline in turkeys.

Liver and muscle tissue residues of doxycycline in turkeys were determined following administration of 25 mg doxycycline x HCl/kg BW in the drinking water under field conditions. Quantitation was performed using a validated HPLC method with fluorescence detection. The method was able to separate doxycycline and its 4-epimer, 4-epidoxycycline. This epimer was found in both liver and muscle tissue. The detection limits of the method were estimated at 1.2 ng/g and 1.0 ng/g of doxycycline in liver and muscle tissue, respectively, using a signal-to-noise ratio of 3:1. The recovery of doxycycline was determined from spiked tissues and was 63+/-3.8% and 66+/-3.1% for liver and muscle, respectively (n = 6). Within-day and between-day imprecision, expressed as the R.S.D. was below 7.4%. Linear calibration curves (r>0.997) were obtained in spiked liver between 0 and 1500 ng/g and in spiked muscle between 0 and 500 ng/g. A good stability of doxycycline was observed in liver samples after storage for 22 days at -20 degrees C. The correlation between the residues in the liver and the muscle was expressed as the correlation coefficient r and was 0.9884. The depletion kinetics of doxycycline fitted a one-compartment model. The elimination half-life (T1/2) of doxycycline was 77.7 h and 78.0 h in muscle and liver, respectively. Furthermore, the residue depletion kinetics were used to establish a withdrawal period in conformity with official guidelines. The withdrawal times necessary to reach concentrations below maximum residue limits (MRLs), as imposed by the EU, were 12 days and 17 days for liver and muscle tissue, respectively.

Animals↗
PubMed1998

Pharmacokinetics and efficacy of amoxycillin in the treatment of an experimental Streptococcus bovis infection in racing pigeons (Columba livia).

The pharmacokinetics of amoxycillin in pigeons (Columba livia) and the efficacy of amoxycillin treatment in pigeon streptococcosis, were investigated. After intravenous administration of 150 mg.kg-1 amoxycillin, the drug plasma concentration-time profile fitted an open two-compartment model. Amoxycillin was quickly cleared from the circulation with a mean half-life of 66 min and showed a distribution volume of 0.9 L.kg-1. The absolute oral bioavailability of amoxycillin was 50.1%. A 5-day drinking water treatment with amoxycillin (1500 mg.L-1, corresponding to 112.0 mg.kg-1.day-1 during day-light hours) significantly reduced the postinoculation morbidity in pigeons experimentally infected with Streptococcus bovis, compared to untreated infected controls.

Amoxicillin↗
PubMed1998

Detection of residues of tetracycline antibiotics in pork and chicken meat: correlation between results of screening and confirmatory tests.

Residues of the tetracycline group of antibiotics were quantified in pork and chicken muscle tissue that had previously been screened with a microbiological inhibition test and an immunological method. Pieces of frozen pork and chicken meat were screened on a pH 6 culture medium seeded with Bacillus subtilis. An aqueous extract of the inhibitor-positive samples was then screened with a group-specific commercial ELISA kit, able to detect levels of oxytetracycline, chlortetracycline, tetracycline and doxycycline corresponding with the European MRL or lower. The cut-off value of the ELISA was set at a B/B0 value of 75%. Finally, confirmation and quantification were performed using a validated HPLC method with fluorescence detection. The fluorescence was induced by complexation of the tetracyclines with the zirconium cation which is added post-column to the HPLC eluate. This fluorescence makes it possible to quantitate residues below one-half of the MRL. To gain additional qualitative information some samples were also analysed with LC-MS-MS. ELISA analysis demonstrated the presence of residues of tetracyclines in 12 out of 19 inhibitor-positive pork samples and in 19 out of 21 inhibitor-positive chicken samples. Doxycycline was detected with HPLC in 10 of these 12 pork samples and in 18 out of 19 chicken samples. The two other ELISA positive pork samples contained oxytetracycline, while no tetracyclines were found in one ELISA positive chicken meat sample. The correlation between the ELISA B/B0 values and the actual levels determined with the HPLC method was poor, whereas a better correlation was observed between the inhibition zones and the doxycycline levels. Our results indicate that an inhibition test with a medium at pH 6 and B. subtilis as test organism is well suited to screen pork and chicken muscle tissue for residues of tetracycline antibiotics. Since many positive samples contained doxycycline levels below the MRL, a confirmatory method is necessary to quantify the residues.

Animals↗
PubMed1998

Residue study of doxycycline and 4-epidoxycycline in pigs medicated via-drinking water.

A study was performed to determine the residues in edible tissues of healthy pigs after continuous administration of doxycycline with drinking water for five consecutive days at a dose rate of 10.5 mg doxycycline kg-1 body weight (BW) per day. Quantitation was performed using a validated HPLC method with fluorescence detection. The method was able to separate doxycycline and its 4-epimer, 4-epidoxycycline. This epimer was found in kidney, liver, skin, fat and muscle tissue. The method was validated at the maximum residue limit (MRL), at half the MRL and at double the MRL for both doxycycline and 4-epidoxycycline. Linear calibration curves were obtained in spiked tissues (r > 0.99). The accuracy of the calibrators of the calibration curves was within -20% to +10%. The accuracy and precision (expressed as the within-run repeatability) were found to be within the required ranges for the specific concentration. The limits of detection and limits of quantification were below one-half of the MRL. The quantification limits were 50 micrograms kg-1 for doxycycline and 100 micrograms kg-1 for 4-epidoxycycline in kidney and liver, 20 micrograms kg-1 for doxycycline and 50 micrograms kg-1 for 4-epidoxycycline in skin and fat and 10 micrograms kg-1 for doxycycline and 50 micrograms kg-1 for 4-epidoxycycline in muscle tissue. The withdrawal time was calculated according to the recommendations of the European Agency for the Evaluation of Medicinal Products (EMEA/CVMP/036/95) and was set at 3 days. The plasma concentration of doxycycline and the stability of doxycycline in drinking water were also determined during the treatment period. The mean plasma concentration of doxycycline during the treatment period ranged from 0.83 to 0.96 microgram ml-1. Thirty-six hours after the withdrawal from medicated drinking water, no plasma levels could be detected. Samples of medicated water were taken at time zero and at 24 h after addition of doxycycline to the drinking water. No statistically significant difference in the mean drinking water concentration was seen at time zero and at time 24 h (Student's t-test, alpha = 0.05).

Animals↗
PubMed1998

Detection of human chorionic gonadotrophin misuse in sports.

The peptide hormone human chorionic gonadotrophin (hCG) was measured in the urine of 5663 male athletes collected for doping analysis in Flanders during the period 1993-1996. Using the Abbott IMx hCG procedure, the free and whole molecule associated beta-subunit of human chorionic gonadotrophin was determined. Statistical evaluation of the data results in a far outside value of 2.28 mIU/ml. The decision limit, i.e. the concentration at which a sportsman will be considered positive, is set at 5 mIU/ml to ensure with the greatest possible degree of certainty that no false positive results are reported.

Adolescent↗
PubMed1997

Disposition of human drug preparations in the horse. VI. Tiaprofenic acid.

Urinary and plasma concentrations of the nonsteroidal anti-inflammatory drug tiaprofenic acid were determined following oral and intramuscular administration of a dose of 1 g to five fasted horses. Quantitation was performed by high-performance liquid chromatography (HPLC). The limit of quantitation (LOQ) was 0.1 microg/ml and 0.5 microg/ml in 2 ml plasma and 1 ml urine, respectively. Assay precision and extraction recovery were between acceptable values. Tiaprofenic acid pharmacokinetics were described by non-compartment analysis of the data. Absorption was faster after oral administration as maximum plasma concentrations (oral: 6.0+/-3.3 microg/ml; intramuscular: 6.6+/-2.5 microg/ml) were obtained after 1 h (oral) compared to 1.6+/-0.4 h (intramuscular) post dosage. Plasma binding (66+/-3%) was lower than measured in other species. Tiaprofenic acid was detected in urine for at least 24 h. The percentage of the parent drug excreted in the first 12 h after oral and intramuscular administration was 38+/-6% and 34+/-5%, respectively.

Absorption↗
PubMed1997

Administration of doxycycline hydrochloride via drinking water to turkeys under laboratory and field conditions.

A series of experiments were carried out in order to determine doxycycline hydrochloride (DoxHCl) plasma levels in 6-wk-old turkeys medicated via drinking water containing DoxHCl at a concentration of 250 mg/L under laboratory and field conditions. Maximal plasma concentration (Cmax) values of 5.7 (+/-1.0) microgram/mL and 4.9 (+/-1.4) micrograms/mL obtained after DoxHCl administration during 2 and 7 d, respectively, were not significantly different. A significant difference was found between the area under the plasma concentration-time profile, calculated between 0 and 168 h (AUC(0-168)), Cmax, and the minimal plasma concentration (Cmin) values obtained after medication with a DoxHCl solution at a concentration of 250 mg/L (431.9 +/- 96.6 micrograms.h/mL, 4.9 +/- 1.4 micrograms/mL and 0.7 +/- 0.3 microgram/mL) and after medication with a DoxHCl solution at a concentration of 750 mg/L (1,176.5 +/- 201.8 micrograms.h/mL, 12.5 +/- 2.7 micrograms/mL and 2.9 +/- 0.4 micrograms/mL), respectively. The increase in body weight was also significantly higher for turkeys medicated with a DoxHCl solution at a concentration of 750 mg/L (83.7 g/d) than for the lower concentration (35.6 g/d). The DoxHCl solution uptake significantly decreased with the increase of DoxHCl concentration. A Cmax value of 1.7 +/- 0.6 micrograms/mL and a Cmin value of 0.5 +/- 0.1 microgram/mL were observed during the field experiment. Water consumption under laboratory conditions was followed for tap water (70 +/- 50 mL/kg.d) and for a DoxHCl solution at a concentration of 250 mg/L supplemented with 1 g anhydrous citric acid/L (119 +/- 6 mL/kg.d) and revealed to be not significantly different. The variability was significantly higher for tap water than for the DoxHCl solution. The stability of the DoxHCl solution containing 1 g citric acid/L over 24 h was 99% expressed as the percentage of the initial concentration.

Administration, Oral↗
PubMed1996

Threshold level for theophylline in doping analysis.

HPLC in the reversed-phase mode is used to assay methylxanthines including theobromine, paraxanthine, theophylline and caffeine in urine. The calibration graphs show good linearity in the concentration range 0-10 micrograms/ml. The limit for accurate quantitation of theophylline was 0.25 microgram/ml. Between 6 and 20% of the parent drug is recovered in urine (0-12 h) after the oral administration of sustained release preparations containing 150 and 250 mg theophylline to four volunteers. Theophylline levels above 0.25 microgram/ml were found in 1539 out of 3885 urine samples collected from athletes during unannounced doping control in Flanders. Statistical evaluation of the results gives a far outside value [75th percentile+(3 x interquartile range)] of 2.25 micrograms/ml. The ratio theophylline paraxanthine (TP/PX) as an indicator for the non-dietary intake of theophylline seems to be more reliable. The far outside ratio was 0.20. To ensure with the greatest possible degree of certainty that no false-positive result is reported, decision limits of 5 micrograms/ml and 0.50, for theophylline and the ratio TP/PX respectively, are proposed.

Caffeine↗
PubMed1996

Validation of a high-performance liquid chromatographic method for the determination of doxycycline in turkey plasma.

A high-performance liquid chromatographic method for the analysis of doxycycline in turkey plasma samples using demeclocycline hydrochloride as the internal standard was developed, optimized and validated. A one-step extraction procedure and an isocratic HPLC method with UV detection were used. No interferences with endogenous compounds or with the anticoagulant were observed. Linear calibration curves (r2 > 0.99) were obtained in water and plasma between 0 and 600 micrograms ml-1. Good recoveries for doxycycline (> 66%) and demeclocycline (> 72%) were seen both in water and in plasma. The coefficient of variation was < 9.86% for within-day reproducibility and < 7.53% for the between-day reproducibility. The deviation between the mean value found and the true value was < 14.5% (accuracy). The limit of detection was 0.1 microgram ml-1 in plasma samples. A good stability of doxycycline was observed in water and in plasma samples after storage for six months at -20 degrees C (recovery > 91%).

Animals↗
PubMed1996

Pharmacokinetics and bioavailability of doxycycline in turkeys.

The pharmacokinetic parameters of doxycycline (DOX) were determined in 3 day, 3-, 6- and 12-week-old fasted turkeys, after a single intravenous (i.v.) dose of 25 mg doxycycline. HCl/kg body weight. Doxycycline disposition fitted an open two-compartment model. The mean (+/-SD) elimination half-life was 10.6 +/- 0.7, 10.8 +/- 1.5, 7.9 +/- 1.4 and 10.0 +/- 0.9 h in 3 day, 3-, 6- and 12-week-old turkeys, respectively. Mean (+/- SD) total body clearance was 0.19 (+/-0.01), 0.27 (+/-0.03), 0.11 (+/-0.03) and 0.06 (+/-0.01) L/h.kg in 3 day, 3-, 6- and 12-week-old turkeys, respectively. The steady-state volume of distribution was 1.77 (+/-0.2), 2.1 (+/-0.2), 0.7 (+/-0.4) and 0.5 (+/-0.2) L/kg in turkeys of the above mentioned ages, respectively. The AUC value significantly increased with the age of the turkeys. An oral doxycycline solution at a single dose of 25 mg/kg of body weight was administered to 3 day. 3-, 6- and 12-week-old turkeys. The maximal plasma concentrations in fasted turkeys were 3.8, 5.6, 7.4 and 5.7 micrograms/mL. with tmax values of 4.7, 1.5, 2.8 and 5.4 h, for the different ages, respectively. In fed turkeys the Cmax values were 2.5, 6.1, 4.8 and 3.0 micrograms/mL. with tmax values of 4.2, 5.3, 4.5 and 7.5 h, respectively. The absolute bioavailability in fasted turkeys varied between 25.0 +/- 9.0% (for 12-week-old birds) and 63.5 +/- 7.1% (for 3-week-old birds). The relative bioavailability varied between 40.0 +/- 13.0% (for 12-week-old birds) and 83.7 +/- 14.3% (for 3-week-old birds).

Administration, Oral↗
PubMed1993

Pharmacokinetics and anthelmintic efficacy of febantel in the racing pigeon (Columba livia).

This paper reports on the pharmacokinetics and the efficacy of febantel against Capillaria obsignata and Ascaridia columbae in the racing pigeon. Febantel was rapidly cleared from the circulation and highly metabolized. The efficacy of febantel against Capillaria and Ascaridia was studied on lightly and heavily infected pigeons. The efficacy against Ascaridia was 100% for the faecal egg count reduction (FECR) as well as for the worm reduction in all treated pigeons. After two treatments with febantel against Capillaria in heavily infected pigeons the FECR amounted to 96.7% and worm reduction was 95%. In order to effectively remove both parasites from the host, repeated treatments with febantel at a short interval could be the treatment of choice.

Animals↗