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Biomedical subjects

P M Scott

Publications and source records attributed to P M Scott.

At least 19 recordsLinked to original sources
PubMed1998

Peritonsillar abscess appearance on intra-oral ultrasonography.

The ultrasound appearances of peritonsillar abscesses (PTA) in 15 patients with clinically suspected peritonsillar infection were assessed using intra-oral sonography and computed tomography (CT). The ultrasonic appearances of an isoechoic rim with a hypoechoic centre were seen in the majority of cases, but a homogeneous isoechoic pattern was also recognized. The different ultrasonic appearances did not correlate with the number of symptomatic days. A central hypoechoic area with a surrounding isoechoic rim pattern was less likely if the volume of pus relative to the whole abscess was less than 10% on CT. Although the percentage of necrosis within the abscesses increased with time, the homogeneous isoechoic appearing abscesses, with less than 10% necrosis, did not fit in temporally and based on our findings it was not possible to predict the ultrasound appearances according to the duration of symptoms.

Adolescent↗
PubMed1998

Survey of Canadian human blood plasma for ochratoxin A.

Blood plasma samples collected from 144 healthy volunteers in 16 locations across Canada in 1994 were analysed for ochratoxin A (OTA). The method of analysis included cleanup by C18 solid phase extraction and immunoaffinity columns followed by liquid chromatography (LC) with fluorescence detection, which gave 86.5% (s.d. = 9.7) recovery (n = 31) of OTA (added at 2 ng/ml) with a detection limit of 0.15 ng/ml. The arithmetic mean concentration found in the plasma samples, corrected for volume of anticoagulant added, was 0.88 ng/ml with a standard deviation of 0.35 ng/ml and a range of 0.29-2.37 ng/ml. Confirmation of identity of OTA was by methyl ester formation for 65 samples and by LC-tandem mass spectrometry for 17 samples (some of which were included in pooled samples). Statistical analysis, by ANOVA of the log OTA plasma concentrations, showed a highly significant effect due to location in Canada (p = < 0.0001) but no effect due to age, sex or blood group of donors. The highest mean concentration was found in Winnipeg, significantly different (p = 0.05) by the Student-Newman-Keuls multiple range test from the lowest levels found in Toronto, Vancouver and Saint John.

Adult↗
PubMed1997

Gas chromatography-mass spectrometry of Alternaria mycotoxins.

Heptafluorobutyrate (HFB) derivatives have not previously been used for GC of Alternaria mycotoxins. Capillary (0.5 micron film) GC-mass spectrometry (MS) showed that full and partial derivatives of alternariol (AOH), alternariol monomethyl ether (AME) and altenuene (ALT); a structurally uncharacterized derivative of altertoxin I (ALTX-I); and a tris-HFB derivative of tenuazonic acid (TA) were formed with heptafluorobutyric anhydride and a basic catalyst. Full and partial trimethylsilyl (TMS) ethers of these mycotoxins were formed with Tri-Sil TBT. Apple juice extracts caused increased response in GC-MS of AOH bis-HFB and bis-TMS derivatives. Natural occurrence of AOH in apple juice has been demonstrated.

Alternaria↗
PubMed1997

Evaluation of enzyme-linked immunosorbent assay for analysis of beer for fumonisins.

A recently developed sensitive indirect competitive enzyme-linked immunosorbent assay (ELISA) was applied to the determination of fumonisins in beer. Intra-assay and inter-assay recoveries averaged 98.7-102.8% at added fumonisin B1 (FB1) levels of 0.5-50 ng/ml beer, and coefficients of variation were 2.8-4.4 and 4.7-8.6%, respectively. Cross-reactivity of fumonisin B2 (FB2) compared with FB1 averaged 67% in beer. Two experiments were carried out to compare ELISA with liquid chromatography (LC) for determination of fumonisins in beer. In the first experiment, 19 samples (five previously known positive, nine other samples and five spiked samples) were passed through commercial immunoaffinity columns (ICs) and analysed by LC before conducting blind ELISA determinations on the extracts and beers directly. The known positive beers and extracts were used as blind duplicates. The second comparative experiment screened 46 beer samples by ELISA and then 22 positive and three of the negative samples were analysed by LC; the highest level found was 64.3 ng total fumonisins/ml measured by LC (24.7 ng/ml by ELISA). Regression analyses showed good correlation between ELISA and LC in the first experiment but low level interferences (equivalent to up to 5.35 ng fumonisin/ml) were observed by ELISA in the IC extracts. Five of nine beers negative by LC showed < 1 ng/ml ELISA responses on direct beer analysis. The second comparative experiment indicated underestimation by ELISA. However, there were two samples which tested positive by ELISA (0.2 ng/ml) but were found negative by LC (results close to the detection limits of both methods, which were 0.1 or 0.2 ng/ml by ELISA and 0.1-0.15 ng each fumonisin/ml by LC). There were no false negatives. It is concluded that ELISA has considerable value in rapid screening of beer directly for fumonisins.

Beer↗
PubMed1997

In vitro preclinical evaluation studies with the echinocandin antifungal MK-0991 (L-743,872).

The echinocandin MK-0991, formerly L-743,872, is a water-soluble lipopeptide that has been demonstrated in preclinical studies to have potent activity against Candida spp., Aspergillus fumigatus, and Pneumocystis carinii. An extensive in vitro biological evaluation of MK-0991 was performed to better define the potential activities of this novel compound. Susceptibility testing with MK-0991 against approximately 200 clinical isolates of Candida, Cryptococcus neoformans, and Aspergillus isolates was conducted to determine MICs and minimum fungicidal concentrations MF(s). The MFC at which 90% of isolates are inhibited for 40 C. albicans clinical isolates was 0.5 microg/ml. Susceptibility testing with panels of antifungal agent-resistant species of Candida and C. neoformans isolates indicated that the MK-0991 MFCs for these isolates are comparable to those obtained for susceptible isolates. Growth kinetic studies of MK-0991 against Candida albicans and Candida tropicalis isolates showed that the compound exhibited fungicidal activity (i.e., a 99% reduction in viability) within 3 to 7 h at concentrations ranging from 0.06 to 1 microg/ml (0.25 to 4 times the MIC). Drug combination studies with MK-0991 plus amphotericin B found that this combination was not antagonistic against C. albicans, C. neoformans, or A. fumigatus in vitro. Studies with 0 to 50% pooled human or mouse serum established that fungal susceptibility to MK-0991 was not significantly influenced by the presence of human or mouse serum. Results from resistance induction studies suggested that the susceptibility of C. albicans was not altered by repeated exposure (40 passages) to MK-0991. Erythrocyte hemolysis studies with MK-0991 with washed and unwashed human or mouse erythrocytes indicated minimal hemolytic potential with this compound. These favorable results of preclinical studies support further studies with MK-0991 with humans.

Amphotericin B↗
PubMed1997

Evaluation of experimental therapeutics in a new mouse model of Helicobacter felis utilizing 16S rRNA polymerase chain reaction for detection.

BACKGROUND: A new mouse model of Helicobacter felis infection, which mimics the human infection observed with H. pylori, has recently been developed utilizing polymerase chain reaction (PCR) based on the 16S rRNA gene sequence for detection of infection. METHODS: We tested several therapeutic regimens in this model, including some currently utilized in the clinic and some shown ineffective in the clinic. RESULTS: The therapeutic results obtained by PCR with this model are consistent with results observed in the published human H. pylori clinical trials and also with results obtained in another H. felis mouse model utilizing culture and histology. CONCLUSIONS: These results support further use of this new model in screening for new therapeutic regimens for the management of Helicobacter disease.

Animals↗
PubMed1996

Determination of the Fusarium mycotoxin beauvericin at micrograms/kg levels in corn by high-performance liquid chromatography with diode-array detection.

A method is described for the detection of the Fusarium mycotoxin beauvericin (BEA) in corn and corn meal. Spectral data obtained with a diode-array detector showed that the most sensitive wavelength for the detection of BEA is 192 nm. The detection limit for BEA was 50 micrograms/kg, which is an increase in sensitivity by a factor of at least twenty compared to previously published analytical methods for this mycotoxin.

Anti-Bacterial Agents↗
PubMed1996

Determination of alternariol and alternariol methyl ether in apple juice using solid-phase extraction and high performance liquid chromatography.

The present work describes a new method for determination of alternariol (AOH) and alternariol methyl ether (AME) in apple juice using solid-phase extraction (SPE) columns for extraction and cleanup of samples for high-performance liquid chromatography (HPLC). Chromatograms of spiked samples show that both toxins can be easily detected without interferences, and good recoveries for AOH (82.8 +/- 7.4%) and AME (91.9 +/- 6.1%) with detection limits as low as 1.6 and 0.7 micrograms/l, respectively, were obtained.

Beverages↗
PubMed1996

Biological fate of fumonisin B1 in food-producing animals.

The presence of mycotoxins in grains and feedstuffs causes not only animal health problems, but also a valid concern about the transmission of potentially toxic residues into animal-derived products intended for human consumption. In a series of studies at Agriculture and Agri-Food Canada, we investigated the biological fate of fumonisin B1 (FB1) in several food-producing animals (grower pigs, laying hens, dairy cattle), as well as monitored various parameters for evidence of toxicity in these species. In several experiments involving either single-dose protocols (iv, po) or longer-term feeding trials, the pharmacokinetic profiles of FB1 (purity > 95%) in these species were determined, including tissue accumulation and transmission of residues. Toxicological (and economical) implications such as performance (feed consumption, growth), productivity, and carcass quality were also measured when appropriate.

Absorption↗
PubMed1996

Approaches to the risk assessment of fumonisins in corn-based foods in Canada.

The presence of fumonisins and associated mycotoxins from Fusarium moniliforme in corn-based foods has recently become a concern in North America and elsewhere. Monitoring of various corn based foods and food commodities for fumonisins is ongoing in both the USA and Canada, and the results can be used for preliminary exposure assessments. The role of Fusarium moniliforme and the fumonisins in some diseases of livestock has been established. Considerable information is available on the mechanism of action of the fumonisins. With the availability of increased quantities of pure fumonisins, several subchronic toxicity studies, designed to establish dose response characteristics in rodents have now been completed. However, since concerns about the chronic toxicity of the fumonisins have not yet been adequately addressed, a tolerable daily intake cannot be established at this time. With the information at hand it is, nevertheless, possible to arrive at an interim risk assessment, which can be used to make interim risk management decisions. A total of 361 samples, covering 4 years of a Canadian survey, have been analyzed to date. Of these, 64 contained > or = 0.1 micrograms/g fumonisin B1, and 10 contained > or = 1 microgram/g. The 'all persons' estimate for the intake of fumonisins from these foods was < 0.089 micrograms/kg bw for 5-11 year-old children, and lower for other age groups. Based on an assessment of the available information on the toxicity of fumonisins, it can be concluded that these estimated intakes are unlikely to pose a health risk.

Animals↗
PubMed1996

Determination of hydrolysed fumonisin B1 in alkali-processed corn foods.

Treatment of fumonisin B1 (FB1)-contaminated corn with calcium hydroxide solution is known to cause large losses of FB1 and formation of the aminopentol AP1 by hydrolysis. Methodology was developed for determination of AP1 in foods manufactured from calcium hydroxide-processed corn. The ground food (tortilla chips, nacho chips, taco shells, or air-dried corn tortillas) was extracted with methanol-water (8:2) or methanol-acetonitrile-water (25:25:50), which also extracted FB1 and fumonisin B2 (FB2). Clean-up for fumonisin determination was carried out on a 1 ml strong anion exchange (SAX) solid phase extraction (SPE) column. The water wash from this column, containing AP1, was cleaned up on a 1 ml C-18 SPE column. AP1 and, separately, FB1 and FB2 were determined as their o-phthaldialdehyde-mercaptoethanol (OPA/MCE) and, in some cases, 4-fluoro-7-nitrobenzofurazan (NBD-F) derivatives by gradient reverse phase liquid chromatography with fluorescence detection. Recoveries of AP1, FB1 and FB2 from spiked samples were generally satisfactory, but FB1 and FB2 recoveries were low with some samples. Better recovery of FB1 with the methanol-acetonitrile-water (25:25:50) extraction solvent compared with methanol-water (8:2) was observed for naturally-contaminated samples. Detection limits were about 10 ng AP1 per g and 20 ng FB1 and FB2 per g with OPA/MCE derivatization, but there were interferences for FB2. Analysis of 31 samples of alkali-processed corn foods (including three known already to contain FB1) showed measurable levels of AP1 in nine samples, all < 100 ng/g and lower than the corresponding FB1 concentrations.

Carcinogens, Environmental↗
PubMed1996

PCR detection of colonization by Helicobacter pylori in conventional, euthymic mice based on the 16S ribosomal gene sequence.

Many animal models of Helicobacter infection have been described, including infection in rhesus monkeys, ferrets, gnotobiotic piglets, and mice. These animal models utilize a combination of detection methods, including culture, urease testing, and histopathology, all of which may be unreliable, insensitive, or labor-intensive. Development of new animal models of Helicobacter pylori requires new methods of detection with increased sensitivity and specificity. We have developed sensitive and specific PCR primers based on the 16S ribosomal gene sequence of H. pylori. The primers detected single-copy 16S DNA representing 0.2 cell of pure H. pylori (2 cells in the presence of mouse stomach mucosal DNA) and did not cross-react with closely related bacteria. We were able to detect colonization by H. pylori in conventional, euthymic, outbred mice up to 4 weeks postinoculation with a high percentage of isolates tested. One isolate of H. pylori was detected by PCR in 100% of the mice at 6 months and 60% of the mice 1 year after inoculation. Approximately 10(3) to 10(4) H. pylori cells per stomach were detected by utilizing this PCR methodology semiquantitatively. These primers and PCR methodology have facilitated detection of H. pylori colonization in conventional, euthymic mice, colonization which may not have been detectable by other methods.

Animals↗
PubMed1996

A sensitive and specific PCR method to detect Helicobacter felis in a conventional mouse model.

Although many detection methods have been used to determine Helicobacter colonization in small animal models, the sensitivity and specificity of these detection methods are limited. To improve the Helicobacter felis conventional mouse model for accurate evaluation of therapeutic regimens, we developed a PCR for detection of, and a competitive PCR for quantitation of, H. felis in viral antibody-free (VAF) mice. The PCR was based on the H. felis 16S rRNA gene. An internal control DNA was used for competitive quantitation of the PCR. VAF conventional Swiss-Webster mice were infected with an H. felis culture by oral gavage. At various times after H. felis challenge and therapy, stomach mucosa was collected and evaluated by PCR. PCR detected approximately 50 to 100 H. felis cells per mouse stomach and showed no cross-reaction with other bacteria commonly found in mouse stomachs. Colonization of H. felis in the mouse stomach was confirmed by culture isolation from germfree mice and histological examination of VAF mice. Response to therapy in this H. felis model correlated well with results seen in human clinical trials with H. pylori. A model utilizing PCR detection which may be useful for discovering new antibiotics and/or vaccines against Helicobacter ulcer disease has been developed.

Animals↗
PubMed1995

Screening surgeons for HIV infection. A cost-effectiveness analysis.

UNLABELLED: OBJECTIVE. To determine the cost-effectiveness of a policy to screen surgeons for human immunodeficiency virus (HIV) infection to prevent transmission of HIV to patients having invasive procedures. DESIGN: Cost-effectiveness analysis. RESULTS: A one-time national screening program would identify approximately 137 surgeons with HIV infection (range, 28 to 423 surgeons) and would prevent approximately 4.3 infections (range, 1.9 to 21.3 infections) in patients treated by infected surgeons and 0.9 infections (range, 0 to 12.9 infections) in sexual partners of infected surgeons at a direct cost of $8.1 million and an induced cost of approximately $44 million. It would result in expenditures of $458,000 per year of life saved (range, $147,000 to $687,000 per year of life saved), whereas an annual screening program would result in expenditures of approximately $1.1 million per year of life saved (range, $338,000 to $1,886,000 per year of life saved). If the prevalence of HIV infection in surgeons is estimated to be three times our base-case estimate (an increase from 0.1% to 0.3%), annual screening would result in expenditures of approximately $741,000 per year of life saved. If the probability of seroconversion after a patient is exposed to a contaminated instrument is increased to 5.0% from our base-case estimate of 0.29%, an annual screening program would still cost more than $228,000 per year of life saved. CONCLUSION: Screening surgeons for HIV to prevent transmission of HIV to patients having invasive procedures requires expenditures per year of life saved that are considerably in excess of those of most accepted health interventions. Surveillance studies of patients treated by surgeons infected with HIV should be continued to confirm that transmission of HIV to patients having invasive procedures is rare.

Cost-Benefit Analysis↗
PubMed1994

Cervical necrotizing fasciitis and tonsillitis.

We present a case of cervical necrotizing fasciitis following quinsy in a previously fit and healthy man. This is a potentially fatal condition with few specific clinical signs that requires early diagnosis and surgical debridement. Other features of the disease are discussed.

Anti-Bacterial Agents↗
PubMed1994

Determination of fumonisins in milk.

Fumonisin B1 (FB1) and fumonisin B2 (FB2) were determined in milk by liquid chromatography (LC) following immunoaffinity column cleanup. Recoveries from milk spiked with 5-50 ng each fumonisin/ml averaged 79-109%. The aminopentol hydrolysis product of FB1 (AP1) was determined by LC after cleanup on a C18 solid phase phase extraction column; mean recoveries were 69-83% at spiking levels of 50-100 ng AP1/ml milk. Detection limits were of the order 3-7 ng/ml for FB1 and FB2, and 20-25 ng/ml for AP1. A stability study showed no losses of FB1 and FB2 in milk under conditions of freezing, refrigeration and boiling. A transmission study using four cows dosed with pure FB1 either orally (1.0 and 5.0 mg FB1/kg b.w.) or by i.v. injection (0.05 and 0.20 mg FB1/kg b.w.) showed no detectable residues of FB1 or AP1 in the milk, with or without hydrolytic treatment with beta-glucuronidase/sulfatase to liberate any conjugates.

Administration, Oral↗