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Biomedical subjects

W J McCaughey

Publications and source records attributed to W J McCaughey.

At least 37 records · Page 2Linked to original sources
PubMed1995

Determination of the concentrations of the steroids estradiol, progesterone and testosterone in bovine sera: comparison of commercial dissociation enhanced lanthanide fluorescence immunoassay kits with conventional radio and enzyme immunoassays.

The performance of three conventional enzyme and radioimmunoassays routinely used to detect residues of anabolic steroids in cattle sera were compared with dissociation enhanced lanthanide fluorescence immunoassay (DELFIA) kits designed for the hospital market. Slight modifications to the kit reagents were required for the analysis of bovine sera. Owing to the large sample volumes used in conventional assays, detection limits were generally better than those obtained with DELFIA kits, however, assay reproducibility was enhanced using the DELFIA technology. Comparison of sera obtained from cattle implanted with anabolic steroids revealed a good correlation between alternate methods (r2 from 0.91 to 0.97). The DELFIA kits offer a faster method for measuring estradiol, progesterone and testosterone with adequate sensitivity and in a safer environment than that encountered using radioimmunoassays.

Animals↗
PubMed1995

Detection of irradiated chicken meat by analysis of lipid extracts for 2-substituted cyclobutanones using an enzyme linked immunosorbent assay.

The means to detect the irradiation of food has been investigated for many years. In recent times radiolytic products, termed 2-alkylcyclobutanones (2-CBs), have been identified as excellent markers of irradiation in lipid-containing foods. An ELISA test was developed, which was capable of detecting a number of these compounds in irradiated chicken meat. A polyclonal antiserum was raised to a 2-CB containing a terminal carboxyl group conjugated to a carrier protein. This antiserum was highly specific for cyclobutanones containing C10 and C12 side chains. During assay validation the limit of detection of the assay was calculated to be 0.064 microgram of 2-CB per gram of fat, within- and between-assay variations ranged from 6.7 to 18%. During experimental studies, chicken meat irradiated at doses ranging from 2.5 to 10 kGy were assayed and correctly identified as being treated. Quantitative comparisons between the ELISA and GC-MS revealed a good correlation (r2 = 0.93) between the two methodologies in concentrations of 2-CB detected in irradiated samples.

Animals↗
PubMed1995

Residues of clenbuterol in cattle receiving therapeutic doses: implications for differentiating between legal and illegal use.

Clenbuterol (CBL) can be used legally in the treatment of respiratory diseases and illegally as a growth promoter in animals. Liver and eye have previously been shown to be effective matrices for the detection of residual concentrations of the drug. The pharmacokinetics of CBL in therapeutically treated cattle were investigated. During treatment, many body fluids and tissues contained residues of the drug. After a 14 day withdrawal only eyes (mean 27.1 micrograms/kg), and to a much lesser extent lung and kidney (mean 0.3 micrograms/kg), contained detectable residues. By day 28 of withdrawal only residues in eyes were present (mean, 6 micrograms/kg). These persisted to the end of the trial (42 days withdrawal). It is concluded that it is not possible to differentiate between the legal and illegal use of CBL solely on drug residue analysis. Other information must be made available to regulatory bodies to enforce control programmes.

Adrenergic beta-Agonists↗
PubMed1995

Possible naturally occurring zeranol in bovine bile in Northern Ireland.

Zeranol and two Fusarium toxins, alpha-zearalenol and beta-zearalenol, were confirmed by gaschromatography/mass spectrometry (GC/MS) in bovine bile samples referred to this laboratory for analysis. No evidence of zeranol abuse was found on-farm. Given the recent suggestion that zeranol might arise from the metabolism of these Fusarium toxins, and the finding of zeranol in bovine and ovine urine across the EU, it was concluded that the residues had arisen as a result of natural metabolism.

Animals↗
PubMed1994

Pathology and residues in veal calves treated experimentally with clenbuterol.

Six veal calves were medicated with clenbuterol at 20 micrograms kg bodyweight-1 day-1 for 42 days before they were slaughtered, to evaluate the lesions and residues in target organs. Compared with six unmedicated calves the most noticeable changes were tracheal dilatation, decreased uterine weight, slight mucous hypersecretion in the uterus and vagina and depletion of liver glycogen. The highest concentrations of clenbuterol (62 to 128 ng/g-1) were recorded in the choroid/retina, and the aqueous humour had the lowest concentration (0.5 to 2.4 ng ml-1). The residue concentrations were higher than the maximum residue level set for clenbuterol (0.5 ng g-1).

Animals↗
PubMed1994

Investigation of dissociation enhanced lanthanide fluoroimmunoassay as an alternative screening test for veterinary drug residues.

Both the number of drugs used in veterinary medicine and the diversity of procedures employed to detect their residues are ever increasing. Many laboratories that carry out such testing have employed a variety of immunoassays to serve as rapid screening tests. Owing to the high sensitivity, good reproducibility and availability of multi-analyte assays dissociation enhanced time-resolved fluorescence immunoassay (dissociation enhanced lanthanide fluoroimmunoassay, DELFIA) kits have become a market leader in the human clinical field. No commercial DELFIA kits are presently available for veterinary drug analysis. A DELFIA method was developed for the quantitative analysis of residues of medroxyprogesterone (MP) in bovine bile. Commercially available DELFIA reagents were used in a microtitre assay format. Within- and between-assay sr values (relative standard deviation) were 4.2-9.9 and 5.1-8.5%, respectively. Detection limits were calculated (mean + 3 s of a known negative population) as being 0.52 and 4.91 micrograms l-1 for male and female animals, respectively. A second study was carried out to optimize the labelling of haptens with a range of lanthanide metals. Purification of the hapten-lanthanide conjugates produced was achieved using fast protein liquid chromatography. Sensitive standard curves were produced for nortestosterone and diethylstilbestrol (curve mid-points of 30 and 40 pg, respectively). By using two different lanthanide labels (Eu and Tb) the simultaneous measurement of these compounds in a single assay system was achieved. Use of a third lanthanide label (Sm) yielded a product of low signal intensity and sensitivity.

Anabolic Agents↗
PubMed1994

Origin of chlortetracycline in pig tissue.

Violative chlortetracycline (CTC) residues in excess of the maximum residue limit (MRL) have been identified in 0.9% of all pigs tested at slaughter in Northern Ireland. Three experiments were carried out to investigate the possible reasons. In Experiment 1, pigs were fed CTC at therapeutic levels (300 mg kg-1 head-1 d-1) for 7 days and were slaughtered at day 0, 2, 4, 6, 8 and 10 following CTC withdrawal. Muscle, liver and kidney cortex and medulla samples were analysed for CTC residues by using high-performance liquid chromatography (HPLC). In all tissues, residues were less than the MRL from day 2 onwards. Mean CTC concentrations in kidney cortex were greater than medulla concentrations (p < 0.05). In Experiment 2, feed spiked with a sub-therapeutic dose of CTC (40 mg kg-1) was fed to six pigs that were slaughtered after 4, 8 and 12 days of medication. Violative CTC residues were not detected. In Experiment 3, short term supra-therapeutic administration was examined. Eight pigs received 500 mg kg-1 CTC head-1 d-1 for 1 or 2 days and were killed in pairs, 24 and 48 h following the final medicated feed. Violative levels were detected in both groups after 24 h only. It is concluded that: firstly, recommended CTC withdrawal periods are sufficient to avoid violative carcass residues; secondly, violative residues do not arise from sub-therapeutic dosing but can arise from supra-therapeutic dosing which could occur with inadequately mixed feed; and thirdly, the difference in kidney cortex and medullary CTC concentrations is significant from a regulatory perspective.

Animal Feed↗
PubMed1993

Liquid chromatography-thermospray mass spectrometric assay for trenbolone in bovine bile and faeces.

A liquid chromatography-thermospray mass spectrometric assay was developed and validated to confirm the presence of illegal residues of the synthetic androgenic growth promoter, trenbolone acetate, in cattle. The assay was specific for 17 alpha-trenbolone, the major bovine metabolite of trenbolone acetate. Methods were developed for the determination of 17 alpha-trenbolone in both bile and faeces, the most appropriate matrices for the control of trenbolone acetate abuse. The clean-up procedure developed relied on enzymatic hydrolysis, followed by sequential liquid-liquid and liquid-solid extraction. The extracts were then subjected to immunoaffinity chromatography. 17 alpha-Trenbolone was detected by selected ion monitoring at m/z 271 using positive ion thermospray ionisation. The limit of detection was approximately 0.5 ng/g in faeces and 0.5 ng/ml in bile.

Animals↗
PubMed1993

Observations on the effects of long-term withdrawal on carcass composition and residue concentrations in clenbuterol-medicated cattle.

The detection of the illegal use of clenbuterol (CBL) as a growth promoter has relied on detecting residual concentrations of the drug in body fluids or tissues. Analysis of retinal extracts has recently been shown to considerably extend the detection period following withdrawal. The withdrawal periods required to eliminate residues from the liver and retina were investigated by medicating 20 cattle with CBL for 30 days; 6 control animals remained unmedicated. Residual concentrations were monitored throughout this period and for the subsequent 140 days. Concurrent changes in muscle areas and backfat thicknesses were recorded by ultrasound. CBL was detectable in liver up to the 56th day of withdrawal (0.35 ng/g, SD = 0.5), but retinal concentrations remained well above detectable concentrations throughout the withdrawal period (22.5 ng/g, SD = 6.5). There were small gains (3-4%) in the muscle areas of treated cattle during medication as compared to controls (p > 0.05). These comparative gains remained during withdrawal. Backfat thicknesses in treated animals were 40% lower than in controls at the end of medication (p < 0.01). However, by 70 days after withdrawal this difference had disappeared (p > 0.05) owing to accelerated fat deposition in the treated group. The retina has been shown to be a highly effective target matrix for detecting CBL administration after long withdrawal periods.

Adipose Tissue↗
PubMed1993

Effective laboratory monitoring for the abuse of the beta-agonist clenbuterol in cattle.

The use of the beta-agonist clenbuterol (CBL) as a growth promoter has been outlawed in European meat production. The detection of its illegal use is dependent on CBL residues persisting in animal tissues for longer than the withdrawal times given by abusers. A comparison of urine, bile and liver matrices indicated that analysis of the liver offered the best possibility for CBL detection. However, an experimental study showed that CBL detection following withdrawal could be further extended (up to 56 d) if the retina was used as the target tissue. Analysis of 703 retina and liver samples from cattle suspected of CBL medication revealed that 96 cattle had CBL residues present in their retinas, only 46 of these were liver positive. There were no instances of liver CBL residues being detected without the associated retina also being positive.

Animals↗
PubMed1991

Sulphadimidine in drinking troughs at bacon factories.

Water troughs in the lairages of three bacon factories were examined. Pigs were observed drinking from the troughs, some of which were contaminated with faeces. Some of the troughs contained detectable concentrations of sulphadimidine, and the highest concentration recorded was 17 micrograms/ml. Pigs which drank this contaminated water before slaughter could contain tissue residues of sulphadimidine above the permitted concentration.

Abattoirs↗
PubMed1991

Rumen succinate production may ameliorate the effects of cobalt-vitamin B-12 deficiency on methylmalonyl CoA mutase in sheep.

When lambs were fed a cobalt-deficient whole barley diet there was a rapid and massive increase in rumen succinate concentrations. Within 2 d of feeding the Co-deficient diet, the rumen succinate concentrations rose 200-fold and peaked at a level 1000-fold higher than that in Co-sufficient controls. Rumen propionate concentrations decreased, suggesting that an alteration in the balance between succinate- and propionate-producing microorganisms had occurred. The rumen succinate can be absorbed and thus may lead to elevated plasma succinate concentrations in Co-deficient animals, whether fed barley or grass. Thus, the absorbed succinate can at least partially overcome the effect on gluconeogenesis of a decreased activity of methylmalonyl CoA mutase induced by Co-deficiency. These findings suggest that impaired propionate metabolism may not be the primary metabolic defect in ovine Co-deficiency.

Absorption↗
PubMed1990

Carry-over of sulphadimidine in the faeces and urine of pigs fed medicated feed.

In two experiments sulphadimidine-free pigs were placed in pens previously occupied by pigs fed a diet containing 100 ppm sulphadimidine. Faeces, urine and spilled feed had been removed by scraping the surface of the pens before the new pigs were introduced. The concentration of sulphadimidine in the tissues of the medicated pigs fell below 100 ng/g within 72 hours of withdrawal of the medicated diet and in the fluids the concentration fell below 500 ng/ml within 96 hours. The concentrations in the tissues of the pigs housed in the contaminated pens exceeded 100 ng/g for up to 24 hours but then fell to acceptable concentrations; the concentration of sulphadimidine in body fluids occasionally exceeded 500 ng/ml.

Animal Feed↗
PubMed1990

Sulphadimidine in the urine of experimentally fed pigs.

An enzyme-linked immunoassay for the detection of sulphadimidine in unextracted pig urine is described. Twenty-four hour urine samples from six individually caged pigs, four treated and two controls, were examined during a 10-day treatment and a 12-day withdrawal period. The concentration of sulphadimidine in the urine of the treated pigs increased rapidly after feeding started and decreased on withdrawal. The maximum concentration in a control pig was 308 ng/ml, and this concentration was probably due to contamination of the environment. By the seventh day after withdrawal of the drug its concentration in the urine of the treated pigs was less than 500 ng/ml.

Animals↗