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Biomedical subjects

L Burns

Publications and source records attributed to L Burns.

At least 37 records · Page 2Linked to original sources
PubMed1994

Application of monoclonal antibody-based sandwich ELISAs to detect verotoxins in cattle faeces.

b1p4wich ELISAs, which use monoclonal antibodies for both the capture and the completion stages, were developed for the detection of verotoxins I and II (non-variant). The ELISAs were used to investigate the incidence of verotoxins in 304 samples of bovine faeces collected from cases of enteritis, and 113 samples collected from normal animals. For most samples, the tests were carried out directly on faeces, and on colony sweeps which were taken from cultures grown from the faeces. These colonies were either grown directly from faeces (mixed colony sweep) or from a coliform culture purified from this (purified colony sweep). All the positive ELISA reactions were investigated by Vero cell cytotoxicity assays for the confirmation of verotoxins. The largest numbers of ELISA-positive reactions which were confirmed by cytotoxicity assays were obtained with mixed colony sweeps. Verotoxin activity was confirmed in 74 (24 per cent) of the samples from cases of enteritis and from 35 (31 per cent) of the normal faeces samples. The occurrence of ELISA reactions unconfirmed by cytotoxicity assays and high cytotoxicity levels with low ELISA readings indicated the presence of non-toxic verotoxin epitopes and the presence of toxic verotoxin variants in the samples.

Animals↗
PubMed1994

Gentamicin resistance in clinical isolates of Escherichia coli encoded by genes of veterinary origin.

Seven (27%) of 26 gentamicin-resistant human clinical isolates of Escherichia coli were resistant to the veterinary aminoglycoside antibiotic apramycin. A gentamicin-resistant Klebsiella pneumoniae isolate from a patient infected with gentamicin/apramycin-resistant E. coli was also resistant to apramycin. DNA hybridisation studies showed that all gentamicin/apramycin-resistant isolates contained a gene encoding the enzyme 3-N-aminoglycoside acetyltransferase type IV (AAC[3]IV) that mediates resistance to gentamicin and apramycin in bacteria isolated from animals. Seven of the eight gentamicin/apramycin-resistant isolates were also resistant to the veterinary antihelminthic agent hygromycin B, a phenomenon observed previously in gentamicin/apramycin-resistant Enterobacteriaceae isolated from animals. Resistance to gentamicin/apramycin and hygromycin B was co-transferable in six of the isolates. Restriction enzyme analysis of plasmids in apramycin-resistant transconjugants derived from E. coli and K. pneumoniae isolates from the same patient were virtually identical, suggesting that inter-generic transfer of plasmids encoding apramycin resistance had occurred in vivo. These findings support the view that resistance to gentamicin and apramycin in clinical isolates of E. coli results from the spread of resistant organisms from animals to man, with subsequent inter-strain or inter-species spread, or both, of resistance genes on transferable plasmids.

Acetyltransferases↗
PubMed1993

Luminescence studies with trp repressor and its single-tryptophan mutants.

Time-resolved and steady-state fluorescence, low-temperature phosphorescence, and optically detected magnetic resonance (ODMR) measurements have been made to resolve the luminescence contributions of the two intrinsic tryptophan residues in the subunits of trp aporepressor from Escherichia coli. Assignments of spectral information have been confirmed by use of the single-tryptophan mutants W19F and W99F. Solute fluorescence quenching studies show that both Trp19 and Trp99 are exposed to acrylamide and iodide, with Trp99 being the more exposed. Time-resolved and steady-state fluorescence measurements show Trp19 to have a bluer emission, a longer mean fluorescence decay time, a higher quantum yield, and essentially no independent rotational motion with respect to the protein. Trp99 is found to have a redder emission, a shorter mean fluorescence decay time, a lower quantum yield, and a significant degree of rotational freedom. Phosphorescence studies show a clear resolution of 0-0 vibronic transitions for each type of residue, with maxima at 407 and 415 nm that are assigned to Trp19 and Trp99, respectively. ODMR measurements show the zero-field splitting parameters to be quite characteristically different for each tryptophan residue. The existence of resonance energy transfer from Trp19 to Trp99, in the wild-type protein, is indicated by three types of data: comparison of the long-lived decay time (attributed to Trp19) in the absence (W99F) and presence (wild type) of the acceptor Trp99, comparison of the fluorescence quantum yield of the wild-type and mutant proteins, and deviations from the expected phosphorescence intensities for Trp19 and Trp99 in the absence of energy transfer.

Apoproteins↗
PubMed1993

High density lipoprotein metabolism in the horse (Equus caballus).

1. Apolipoprotein A-I dependent lecithin:cholesterol acyl transferase (LCAT) activity was identified in equine lipoprotein deficient plasma (LPDP). 2. LCAT activity showed no breed or sex variation, and was unaltered postprandially. 3. There was no significant cholesteryl ester transfer activity in equine LPDP. 4. Hydrophobic interaction chromatography on phenyl sepharose failed to unmask transfer activity or identify an inhibitor of cholesteryl ester transfer. 5. In 12 Shetland ponies, plasma high density lipoprotein (HDL) concentrations were positively correlated with those of triglyceride, but not with the activities of LCAT, lipoprotein lipase or hepatic lipase.

Animals↗
PubMed1993

Effects of pregnancy and lactation on plasma lipid and lipoprotein concentrations, lipoprotein composition and post-heparin lipase activities in Shetland pony mares.

The incidence of hyperlipaemia in ponies is highest in mares in late gestation and then early in lactation. Plasma lipid and lipoprotein concentrations were measured to establish the metabolic basis for this and the lipoprotein composition of six healthy Shetland ponies was analysed before pregnancy, in the last six weeks of gestation and one month after foaling. In the pregnant ponies, the concentrations of cholesterol and triglyceride were significantly increased (both P < 0.05) because of increased concentrations of high density lipoproteins (HDL) and very low density lipoproteins (VLDL), respectively (both P < 0.05). The VLDL were significantly enriched in triglyceride and depleted of protein (P < 0.05 in each case), with the majority of cholesterol in the free rather than esterified form. These changes appeared to reflect increased hepatic triglyceride synthesis and VLDL secretion because the activities of lipoprotein lipase and hepatic lipase, the enzymes responsible for the catabolism of VLDL and their remnants, were unaltered. After foaling, the concentrations of triglyceride and VLDL decreased significantly (both P < 0.05) because of increased lipoprotein lipase activity consistent with the induction of the enzyme in mammary tissue to provide for milk fat synthesis. Plasma cholesterol and HDL concentrations remained high and non-esterified fatty acid concentrations were significantly increased (P < 0.05). The VLDL remained enriched in triglyceride but had normal cholesterol and protein compositions, although the mass of phospholipids was reduced. The changes in plasma VLDL concentration and composition found in the pregnant ponies mimicked those previously reported in ponies with hyperlipaemia and suggested a metabolic basis for the incidence of the disease in late gestation.

Animals↗
PubMed1992

Post-prandial lipoprotein metabolism in nephrotic syndrome.

Post-prandial lipaemia was investigated in a group of nine subjects with nephrotic syndrome by following the concentrations of triglyceride and retinyl palmitate in the d < 1.006 g ml-1 fraction of plasma after a standard oral fat load containing vitamin A. Lipoprotein lipase and hepatic triglyceride lipase activities were measured in post-heparin plasma. Subjects with other renal disease but insignificant proteinuria acted as controls. The time course of the lipaemic response was similar in both groups although individual patients demonstrated a prolonged lipaemia. Overall, there were no significant differences in the rise in triglyceride at 6 h (nephrotic--median 2.53 mmol l-1; range 0.87-4.76 vs. control 1.88; 0.38-4.12, P = 0.34), the peak concentration of retinyl palmitate (nephrotic 0.87 mg dl-1; 0.27-2.16 vs. control 0.65; 0.24-1.89, P = 0.97) or the areas under the curve from 0-24 h for triglyceride (nephrotic 10.5 mmol. h l-1; 2.9-43.6 vs. control 9.7; 4.3-27.0, P = 1.0) or retinyl palmitate (5.5 mg.h dl-1; 1.0-23.4 vs. 4.3; 1.5-12.4, P = 0.7). At baseline, the particles in the d < 1.006 g ml-1 fraction of plasma from nephrotic subjects had a higher free cholesterol:phospholipid ratio but this difference was no longer apparent 6 h after the test meal. There were no differences in total heparin-releasable lipase, lipoprotein lipase or hepatic triglyceride lipase activities between the two groups. These data suggest that impaired clearance of chylomicrons is not a major contributor to nephrotic hyperlipidaemia in man.

Adult↗
PubMed1992

Plasma lipids, lipoproteins and post-heparin lipases in ponies with hyperlipaemia.

The metabolic origins of equine hyperlipaemia were investigated by analysing the concentration and composition of plasma lipoproteins in 18 ponies with the condition. The mean concentrations of cholesterol, triglyceride and very low density lipoproteins (VLDL) were increased by 4-, 52- and 19-fold, respectively, compared with a control group of 18 healthy ponies. These increases were due to the appearance of a buoyant VLDL fraction (VLDL1) not present in healthy ponies. The mean diameter of VLDL1 particles was 44% greater than control VLDL, and the particles were enriched in triglyceride and free cholesterol and depleted of cholesteryl esters, phospholipid and protein. The apolipoprotein (apo) B-100 content of VLDL1 was reduced and the ratio of apoB-100 to apoB-48 particles was 1:1, compared with 2:1 in control VLDL. The VLDL1 was also enriched in apoE, but had normal complements of apoC-II and apoC-III. The conventional VLDL (called VLDL2), LDL and HDL fractions were moderately enriched with triglyceride, and HDL contained increased amounts of apoE, apoC-II and apoC-III. The activities of lipoprotein lipase and hepatic lipase, the enzymes responsible for the catabolism of VLDL and their remnants, were increased by 2- and 3-fold, respectively, in response to the increased concentrations of their substrates. The composition of VLDL1 suggested that the liver was maximising the secretion of triglyceride by producing larger number of VLDL particles that accommodated a greater mass of triglyceride by having apoB-48 rather than apoB-100 as their structural protein. Plasma free fatty acid (FFA) concentrations were elevated in 17 of the 18 ponies, suggesting that increased FFA flux might be the stimulus for hepatic triglyceride synthesis and VLDL secretion. We conclude that overproduction, rather than defective catabolism, of VLDL was the cause of the hyperlipidaemia and that lipid lowering agents which reduce VLDL synthesis, by decreasing adipose lipolysis and FFA flux, are candidates for the management of hyperlipaemia.

Animals↗
PubMed1992

Selective measurement of lipoprotein lipase and hepatic triglyceride lipase in heparinized plasma from horses.

Affinity chromatography on heparin sepharose was used to identify 2 lipolytic enzymes in heparinized plasma from horses. One enzyme was typical of hepatic triglyceride lipase (HTGL), because it was resistant to inactivation by high concentrations of NaCl, and it did not require the addition of serum for activity. The other enzyme was identified as lipoprotein lipase (LPL), because of its inactivation at NaCl concentrations in excess of 0.2M, and its dependency on addition of serum as a source of apolipoprotein C-II activator. The enzymes were purified by 347-(HTGL) and 442- (LPL) fold, with yields of 54 and 58%, respectively. The partially purified enzymes were used to design incubation conditions that gave optimal activities for each enzyme in vitro. A selective assay was then developed for direct measurement of LPL and HTGL activities in heparinized plasma from horses. Analysis of HTGL took advantage of the almost complete inactivation of LPL when serum cofactor was excluded from the assay at the NaCl concentration that gave optimal HTGL activity. Prior incubation of heparinized plasma with sodium dodecyl sulfate to inhibit HTGL was necessary for measurement of LPL, because HTGL retained 67% of its activity at the NaCl concentration required for optimal LPL activity. Activity of each enzyme was measured in heparinized plasma from 12 Shetland ponies. The mean activity +/- SD for LPL was 3.22 +/- 1.04 mumol of fatty acids/ml of heparinized plasma/h (mumol of FA/ml/h. The mean activity for HTGL was 4.9 +/- 1.56 mumol of FA/ml/h. The performance of the assay was assessed by replicate analysis of pools of each enzyme with high and low activities.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

The BRMD BOMAB phantom family.

The Human Monitoring Laboratory (HML) has used the International Commission on Radiological Protection's Report on Reference Man and Canadian anthropomorphic data as guidance to design and construct a family of phantoms corresponding to Reference Man (PM), Reference Woman (PF), Reference Ten-Year-Old (P10), Reference Four-Year-Old (P4), Ninety-five Percentile Man (PM95), and Five Percentile Man (PM5). The PM series also has an accessory chest section (PMacc) to better simulate lung depositions. The phantoms are constructed from high-density polyethylene and fitted with end-recessed filling caps to minimize leakage problems. This paper describes the methodology of construction and presents data so that the phantoms can be reproduced. The phantoms have been used in Canada's National in-vivo Intercomparison Program, and results show that all Canadian in-vivo counting facilities have size-dependent calibrations. Selected data are presented to exemplify this dependence.

Adult↗
PubMed1991

The isolation, characterisation and quantification of the equine plasma lipoproteins.

Plasma lipoproteins were isolated from eight Thoroughbred horses and eight Shetland ponies on the basis of particle size by gel filtration chromatography and according to density using rate-zonal ultracentrifugation. Three major classes corresponding to very low density lipoproteins (VLDL), low density lipoproteins (LDL) and high density lipoproteins (HDL) were identified and characterised by their lipid and apolipoprotein compositions. The particle size distributions of each class were determined by electron microscopy and non-denaturing polyacrylamide gradient gel electrophoresis. HDL was found to dominate the equine lipoprotein spectrum, accounting for 61 per cent of the total plasma lipoprotein mass (VLDL 24 per cent, LDL 15 per cent). The VLDL class was isolated as a single population of particles that were triglyceride rich and cholesterol, phospholipid and protein poor. Equine LDL was characteristically cholesterol rich and was found to be polydisperse comprising three subfractions that were discrete with respect to particle size and lipid composition. The HDL class was composed of homogeneous particles that were typically protein rich. Apolipoprotein (apo) B was the major protein of VLDL and LDL, and presented two components on polyacrylamide gel electrophoresis with molecular weights in the region of human apoB-100 and a third in VLDL similar to that of apoB-48. ApoA-I was the predominant protein in equine HDL. Although there were no breed differences in the physical or chemical properties of each lipoprotein class, the Shetland ponies had higher plasma triglyceride and VLDL concentrations than their Thoroughbred counterparts.

Animals↗
PubMed1990

Predictive value of susceptibility tests for the outcome of antibacterial therapy.

A total of 510 charts of patients who received antibacterial agents were examined for clinical outcome and microbiology findings. A total of 382 patients (75%) had one or more specimens submitted for culture and susceptibility tests before the administration of the drugs; 298 (78%) of these had positive cultures and susceptibility tests were done. A total of 18 species were isolated. Of the 298 patients with organisms of known susceptibilities, 271 (91%) received antibacterial agents to which the respective organisms were susceptible and 219 of these patients (81%) improved (P less than 0.05). This high rate of good infectious diseases practice is probably due to two factors: (1) susceptibility tests results were available in most cases the next day after the submission of a specimen; (2) the medical board distributed guidelines for the use of antibiotics and monitored the compliance closely. The patients treated with antibacterial agents to which the bacteria were resistant improved in 3% and did not improve in 82% (P less than 0.05) of the patients. This study shows that choosing an antibacterial agent in accordance to the susceptibility test resulted in a high rate of improvement. When the choice of agent disregarded bacterial resistance in vitro, therapy almost always ended in failure. Therefore, susceptibility tests in vitro have a good predictive value for the outcome of antibacterial therapy.

Anti-Bacterial Agents↗
PubMed1988

Infections caused by central venous catheters in patients with acquired immunodeficiency syndrome.

We assessed infectious complications of long-term percutaneous central venous catheterization in patients with acquired immunodeficiency syndrome (AIDS). We evaluated 98 consecutive patients, accounting for 6,298 catheter days. Catheter-associated bacteremia occurred in 3% of patients, a rate of 0.128%/patient-catheter day. Only bacterial pathogens--Pseudomonas, Serratia, and Staphylococcus species--were isolated. Five patients had infection at the catheter exit site. The length of time catheters were indwelling was not significantly different in patients with and those without infections. Percutaneous, multiple-use central venous catheters are safe and well accepted by patients with AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Voice restoration after total laryngopharyngectomy and cervical esophagectomy using the duckbill prosthesis.

We have presented a series of 10 patients who were successfully rehabilitated using the tracheoesophageal puncture technique for voice restoration. These patients underwent total laryngopharyngectomy or laryngopharyngoesophagectomy and reconstruction with visceral transposition (five patients), myocutaneous flaps (four patients), and skin graft and cervical flaps (one patient). All patients were able to produce adequate voice and carry on a conversation. Clinical evaluation of voice quality and acoustic analysis of voice samples indicate that the voice obtained in these patients was intelligible, and had adequate intensity, low pitch, and limited pitch variation. There were no complications related to the voice restoration procedure. It appears from our data and the limited experience reported in the literature that the tracheoesophageal prosthesis can be used successfully and safely for the speech rehabilitation of patients who undergo total laryngopharyngectomy, cervical esophagectomy, or both, regardless of the reconstructive method used.

Aged↗
PubMed1987

Treatment of patients with stage IV cancer: do the ends justify the means?

Most experienced head and neck surgeons recommend aggressive treatment--including radical surgery--for patients with resectable Stage IV cancers. Yet, given the poor overall cure rate of 15% and the deformity and disability often associated with treatment, one of the most frequently asked questions at our conference on tumors was: Are we really helping these patients? We found little data in the relevant literature to answer this or other questions. Are there subgroups with a better outlook? What is the evidence for palliation in the 85% of patients who fail treatment and how is it best achieved? How do patients and their families view their treatment in retrospect? To find the answers, we studied the records of 76 consecutive patients (previously untreated) who presented with Stage IV carcinoma of the upper aerodigestive tract in 1981-82. We also interviewed surviving patients or family members and friends by phone. Overall mean survival was 15 months, with a 2-year disease-free survival rate of 16%. More to the point, resectable patients treated with curative intent had a mean survival of 19.4 months, and 12 of 42 patients (29%) were disease-free at 2 years. Patients with laryngeal cancer had the best survival results, and patients with sinus cancers had the worst (25.2 vs. 10.5 months). Those with N2A staging lived longer than other groups (24.1 vs. 12.1 months). T4 lesions portend a particularly poor prognosis; mean survival was just 7.5 months and only 1 of 28 patients (3.6%) was alive and disease-free at 2 years. Twenty-five percent of patients returned to normal function, but 75% had significant problems eating or speaking.(ABSTRACT TRUNCATED AT 250 WORDS)

Activities of Daily Living↗
PubMed1980

Pharmacokinetics of oral and intravenous indomethacin in preterm infants.

The pharmacokinetic profile of indomethacin administered either orally or intravenously in 13 preterm infants with significant patent ductus arteriosus (PDA) is reported. 9 infants received oral indomethacin and 4 received intravenous therapy. Plasma half-life was significantly prolonged as compared to adult values and demonstrated significant correlation with gestational age. Mean half-life in neonates less than 32 weeks gestation was 17.2 (0.8) vs. 12.5 (0.5) h for neonates greater than 32 weeks gestation. Bioavailability of the oral dosage based on AUC was 13% but no difference was observed in the plasma protein binding or distribution volume of drug as compared to adult values. No serious complications could be attributed to the use of indomethacin at these dose levels in the premature infant.

Administration, Oral↗