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Biomedical subjects

G Shearer

Publications and source records attributed to G Shearer.

At least 73 records · Page 4Linked to original sources
PubMed1979

A prospective evaluation of the pulsatile assist device.

Conversion of roller pump flow to pulsatile flow by the pulsatile assist device (PAD) is said to result in improved myocardial preservation and a decrease in the incidence of perioperative myocardial infarction. The clinical advantages of the PAD were evaluated in a prospective randomized study of 100 consecutive coronary artery bypass operations. Serial electrocardiograms, creatine phosphokinase isoenzyme studies, and myocardial scans with technetium-labeled pyrophosphate failed to demonstrate any signficiant difference between patients with the PAD and those receiving nonpulsatile flow. Plasma hemoglobin levels were significantly higher in the PAD group indicating increased blood trauma. Other potential disadvantages of the PAD are discussed. Based on this study, we see few advantages of the PAD in routine coronary bypass operations.

Coronary Artery Bypass↗
PubMed1979

Multiple coronary bypass grafting: current mortality and morbidity.

Although coronary artery bypass surgery has become increasingly popular in recent years, recent critical reports have cast doubt on its efficacy in certain groups of patients. Our report reviews a recent experience with multiple coronary bypass grafting for triple vessel disease. From March 1976 to October 1978, 276 patients received from three to nine coronary bypass grafts. Combined procedures including valve replacement and ventricular aneurysmectomy are included. There were two operative deaths (30 days) for a 0.7% operative mortality. Eleven patients (4%) sustained a perioperative infarction. Other nonfatal operative complications are reviewed. The overall safety and low morbidity allow us to recommend coronary bypass surgery to certain controversial subsets of patients, ie, those with high-grade double and triple vessel disease with stable angina.

Arrhythmias, Cardiac↗
PubMedDate not supplied

Determination of synthetic growth promoters in bile.

To monitor the use of synthetic growth promoting hormones in red meat animals requires a sensitive and rapid method of analysis. This paper describes the development of such a method for these agents in bile, based on a high pressure liquid chromatographic purification procedure with detection and estimation by radioimmunoassay.

Anabolic Agents↗
PubMedDate not supplied

Ammonia caramels: specifications and analysis.

Twenty three UK commercially produced ammonia caramels and eight experimentally produced ammonia caramels have been analysed by a range of physical and chemical tests, which include solids content, nitrogen levels, colour intensity and pH. A statistical treatment of the results is reported.

Ammonia↗
PubMedDate not supplied

A method for the analysis of lincomycin in porcine and bovine kidney.

A method of analysis has been developed for the estimation of lincomycin in porcine and bovine kidney. The method employed high performance liquid chromatography and Sep-Pak clean-up of methanolic tissue extracts and nitrogen specific gas chromatographic detection. Using spiked (0.1 mg kg-1) extracts recoveries in the range 40-50% were obtained. Analysis at the 0.05 mg kg-1 level is possible. Fifty four samples of kidney destined for UK sale were analysed for the presence of this drug. No samples were found to contain lincomycin.

Animals↗
PubMedDate not supplied

Analysis of trace residues of tetracyclines in animal tissues and fluids using metal chelate affinity chromatography/HPLC.

A novel method of analysis for the trace residue determination of tetracyclines in animal tissues and fluids has been developed. Clean-up of sample extracts is based upon the specific ability of tetracyclines to chelate with divalent metal ions (metal chelate affinity chromatography, MCAC) and determination made by high-performance liquid chromatography. The method has been tested for the determination of oxytetracycline (OTC), tetracycline (TC) and chlortetracycline (CTC) in porcine kidney and muscle, ovine kidney, bovine kidney and milk, and trout muscle. Recoveries at the 0.05 mg/kg level for OTC, TC and CTC respectively were 75%, 63%, 73% in porcine kidney, 77%, 79%, 76% in porcine muscle, 85%, 54%, 53% in bovine kidney, 78%, 63%, 57% in ovine kidney, 75%, 58%, 56% in fish (trout) muscle, and 80%, 59%, 59% in bovine milk. At this level both within- and between-batch precision, as measured by the coefficient of variation (CV), was less than 10%. Determination to the 0.01 mg/kg level was carried out in all cases, although the method becomes less precise. The method has been used for several months and found to be both reliable and sufficiently rapid for use as a routine quantitative screening procedure. When coupled with liquid chromatography-mass spectrometry (LC-MS) it is suitable for use as a confirmatory method. Analysis of animals treated with tetracyclines has been carried out.

Animals↗
PubMedDate not supplied

Analysis of enrofloxacin and its metabolite ciprofloxacin in bovine and porcine muscle by high-performance liquid chromatography following cation exchange clean-up.

A simple and rapid method of analysis for the trace residue determination of enrofloxacin and its metabolite ciprofloxacin has been developed. Clean-up of the samples is by cation exchange solid phase extraction (SPE) and determination made by high-performance liquid chromatography using a base-deactivated column and fluorescence detection. The method has been validated for the determination of residues in bovine and porcine muscle tissue and bacon. Recoveries at the 0.010 mg kg-1 level for enrofloaxacin and ciprofloxacin respectively were 90%, 75% in bovine muscle, 75%, 54% in porcine muscle and 81%, 63% in bacon. Determination to the 0.001 mg kg-1 level in bovine muscle and to the 0.002 mg kg-1 level in porcine muscle and bacon was also carried out. The method has been used as a quantitative screening procedure.

Animals↗
PubMedDate not supplied

The effect of cooking on veterinary drug residues in food: 1. Clenbuterol.

The heat stability of clenbuterol was investigated. The drug was shown to be stable in boiling water at 100 degrees C. In cooking oil at 260 degrees C, losses were observed, indicating a half-life of about 5 min. The effect of a range of cooking processes (boiling, roasting, frying, microwaving) on clenbuterol residues in fortified and incurred tissue was studied. No net change in the amount of clenbuterol was observed in any of the cooking processes investigated except for deep frying using extreme conditions. There was little observed migration from the tissue into the surrounding liquid or meat juices. Clenbuterol residues were found not to be evenly distributed in the incurred raw tissue used for the investigation. The findings of this investigation show that data obtained from measurements on raw tissue are applicable for use in consumer exposure estimates and dietary intake calculations.

Animals↗
PubMedDate not supplied

Development of multi-residue methodology for the HPLC determination of veterinary drugs in animal tissues.

The application of solid-phase extraction and HPLC with UV-diode array detection to the multi-residue determination of veterinary drugs is described. A two-stage SPE clean-up was employed, using C18 and silica cartridges. HPLC analysis was carried out on a base-deactivated C8 column using gradient elution systems at two pH values. The procedure establishes the basis of a method for routine screening of pig kidney samples for some sulphonamides, benzimidazoles, nitroimidazoles and nitrofurans at concentrations at or below the UK Maximum Residue Limits (MRLs). Limits of detection of 2-18 micrograms/kg could be achieved for these analytes at recoveries of 40-70%. UV spectra measured on-line were used for confirmation of peak identities at these concentrations. The possibility of extension of this procedure to a wider range of analyses is discussed.

Animals↗
PubMedDate not supplied

The effect of cooking on veterinary drug residues in food: 2. levamisole.

The heat stability of levamisole was investigated. Results obtained indicated that the drug was stable in boiling water at 100 degrees C, but unstable at 260 degrees C in cooking oil, with a half-life of about 5 minutes. The effect of cooking (microwaving, boiling, roasting, grilling and frying) on levamisole residues in a range of fortified and incurred tissue was studied. No evidence of instability was obtained in any of the cooking methods investigated. Most observed net changes fell within the limits of the precision of the method once allowance for weight loss during cooking was made to counter an apparent increase in concentration. Roasting was the only method of cooking where a net loss of levamisole was observed. Insufficient juices were produced to permit analysis in this instance. The net loss of levamisole in the cooked tissue was similar to that found with other cooking methods, where the levamisole lost was found in the cooking liquid or juices. An assessment of homogeneity of the incurred tissue used in the investigation was made. The pig muscle was found not to be homogeneous with larger differences seen between different areas of the animal than within the same muscle. The findings of this investigation showed that data obtained from measurements on raw tissue are suitable for use in consumer exposure estimates and dietary intake calculations.

Animals↗
PubMedDate not supplied

The effect of cooking on veterinary drug residues in food: 3. Sulphamethazine (sulphadimidine).

The heat stability of sulphamethazine was investigated. The drug was shown to be stable in boiling water at 100 degrees C. In cooking oil at 260 degrees C, losses were observed, indicating a half-life of about 5 min. At 180 degrees C in cooking oil, sulphamethazine was unstable with a half-life of about 2 h. The effect of a range of cooking processes (boiling, roasting, grilling, frying, pressure cooking and microwaving) on sulphamethazine residues in incurred animal tissue was studied. Once allowance for weight loss during cooking had been made no net unaccountable change in concentration of sulphamethazine was observed in any of the cooking processes investigated. During frozen storage, sulphamethazine residues were found to be stable over a period of 3 months. It was found during this investigation that the method used for analysis which involved acid extraction converted the N4-metabolites to parent sulphamethazine, and hence only sulphamethazine was measured. Sulphamethazine was found to be evenly distributed in the raw incurred tissue used for analysis. Migration from the tissue into the surrounding liquid or meat juices was observed during the cooking process. The findings of this investigation show that surveillance data obtained from measurements on raw tissue are applicable for use in consumer exposure and dietary intake calculations, but only if an acidic extraction method which converts the N4-metabolites to parent sulphamethazine is used for the surveillance. This may not however conform to current Maximum Residue Limit legislation which refers to total parent sulphonamides. Different methods of analysis for sulphonamides are likely to give rise to inter-laboratory variation.

Animal Diseases↗
PubMedDate not supplied

Determination of penicillins in animal tissues at trace residue concentrations: II. Determination of amoxicillin and ampicillin in liver and muscle using cation exchange and porous graphitic carbon solid phase extraction and high-performance liquid chromatography.

A method for the determination of the basic penicillins, amoxicillin and ampicillin, in animal tissue is described. The method used aqueous extraction with tungstate to remove proteins followed by cation exchange solid phase extraction (SPE) clean-up. This extract was further purified using porous graphitic carbon (PGC) SPE. Extracted residues were derivatized with acetic anhydride followed by triazole/mercuric chloride prior to reversed phase HPLC with UV determination at 325 nm. At the Maximum Residue Limit of 50 micrograms/kg in fortified cattle muscle validation gave mean recoveries for amoxicillin of 57% and 50% on two different days with relative standard deviations of 19% and 15% respectively. For ampicillin the recoveries were 72% and 59% with relative standard deviations of 15% and 19% respectively.

Amoxicillin↗
PubMedDate not supplied

The effect of cooking on veterinary drug residues in food: 7. Ivermectin.

The stability to heat and cooking of ivermectin was investigated. The drug was insufficiently soluble in water to allow the effect of heating in simple aqueous solutions to be studied. The effect of a range of cooking processes was investigated on pig muscle and liver, cattle muscle and liver and salmon muscle. The drug was found to be stable to the effect of cooking. Some leaching of ivermectin with juices as they exuded from the foods as they were cooked was observed; in one case this amounted to about 50% of the total residue.

Animals↗
PubMedDate not supplied

Aspects of extraction, spiking and distribution in the determination of incurred residues of chloramphenicol in animal tissues.

Studies of distribution, extraction procedures and spiking protocols in the determination of incurred chloramphenicol residues in animal tissues have been carried out. An extraction procedure involving glucuronidase enzyme digestion was found to extract 10 times more incurred chloramphenicol from pig kidney than direct extraction without digestion. However, neither protease digestion nor ultrasonic probe treatment resulted in improved chloramphenicol extraction. Chloramphenicol was found to be inhomogeneously distributed within kidney from a treated pig. Highest concentrations were detected in the renal medulla. Muscle tissues from the same animal were found to contain a lower concentration of chloramphenicol residues, but no chloramphenicol residues were detectable in the liver. Chloramphenicol recovery from spiked pig liver was found to be lower than that from kidney, but was improved by the addition of piperonyl butoxide before extraction. This additive had no effect on recovery from spiked pig or cattle kidney. The implications of these results for regulatory surveillance of animal tissue for chloramphenicol residues are discussed.

Animals↗