S-N dissociation energies of S-nitrosothiols: on the origins of nitrosothiol decomposition rates.
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Biological Transport, Active↗
Biomedical subjects
S C Powell
Publications and source records attributed to S C Powell.
Different characteristics distinguish early versus late arising adaptive mutations in Escherichia coli FC40.
The Escherichia coli strain FC40 has frequently been employed to investigate the mechanism of adaptive mutations. The strain cannot utilize lactose due to a +1 frameshift mutation that reduces beta-galactosidase to about 1% of normal levels. Cells undergo a high rate of mutation from Lac- to Lac+ when cells are grown with lactose as the sole energy source. Almost all Lac+ colonies arising 3-6 days after plating result from a base pair deletion in runs of iterated base pairs within a 130-bp target region. In this study we characterized Lac+ colonies arising 3-10 days after plating. Temperature gradient gel electrophoresis (TGGE) was used to detect mutations in the target region as a function of the day a colony appears. TGGE results confirmed the occurrence of mutations within the target region in 36 of 37 FC40 Lac+ colonies arising on days 3-7. However, mutations in this region were not detected in 23 of 37 Lac+ colonies arising from days 8-10. Sequencing data verified the TGGE results. Half of the Lac+ mutants arising on days 8-10 with no base pair change in the target region were unstable and exhibited a Lac- phenotype after successive growth cycles in rich medium. The results suggest that amplification of the lac operon region is a common factor in late arising colonies, and that different characteristics distinguish early and late arising Lac+ colonies.
Adaptation, Biological↗
An evaluation of the collection and analysis of epidemiological data for support of food safety control systems.
Food-borne disease data collected by three U. K. environmental health departments were used in this study. The data were analyzed using a database designed to rank disease agents, food ingredients, and processing factors which contribute to cases of food-borne disease. The results established changes in patterns of food-borne disease over time, pattern differences between U. K. localities and differences between areas of the United Kingdom and the United States. This type of analysis of epidemiological data provides scientific underpinning for hazard analysis critical control point systems for food safety control. The work highlights the need for a consistent procedure for collection of food-borne disease data and for a national database to facilitate analysis.
Data Collection↗
A comparative study of food retail premises by means of visual inspection and microbiological quality of food.
The relationship between visual inspection ratings given to ten food retail premises and the microbiological quality of food samples was examined. Viable counts of bacteria and of Staphylococcus aureus were determined for cooked meat samples from each of the premises. There was no correlation between potential risk of foodborne infection, as assessed by total inspection rating, and bacteriological counts in food (P < 0.05). Neither was there a consistent relationship between scores given to any component of the total rating and the bacteriological quality of food. The effectiveness of the current UK inspection scheme in assessing risk of foodborne infection is questioned. Inclusion of appropriately weighted criteria such as food temperature abuse is suggested to improve the scheme.
Animals↗
Percutaneous transluminal angioplasty for subclavian artery stenosis.
Treatment of brachiocephalic arterial lesions by percutaneous transluminal angioplasty (PTA) has only recently been performed with sufficient frequency to allow full assessment of its value. In this series, we report our results with PTA of 36 symptomatic subclavian stenoses in 33 patients seen from February 1981 through February 1992. Initial success rate was 94 per cent. There were no deaths and no CNS complications. Five minor complications occurred. Review of published surgical series suggests a similar early success rate but a significantly higher morbidity. These excellent early results of PTA and long-term results from other studies confirm that PTA of subclavian artery stenoses is a safe, highly effective procedure and should be considered the treatment of choice for symptomatic subclavian artery stenoses.
Adult↗
Specific cytogenetic abnormalities in two new human colorectal adenoma-derived epithelial cell lines.
Two new epithelial cell lines from sporadic human colorectal adenomas designated S/AN and S/RG are reported. S/AN was from a villous adenoma and S/RG from a tubular adenoma. Both cell lines have extended growth capacities in vitro reaching passages 18 and 15, respectively, so far and show no signs of senescence. S/AN and S/RG have retained in vitro the ability to form mucin-producing goblet-like cells. Every cell of S/AN has a deletion on the short arm of chromosome 1 and one normal copy of chromosome 1. S/AN is also monosomic for chromosome 18. The majority of cells of S/RG only have one normal copy of chromosomes 6, 7, 14, 17, 18, and 22. S/RG also has several marker chromosomes. Although aneuploid S/AN and S/RG are nontumorigenic in athymic nude mice, these cytogenetic abnormalities are insufficient for the fully tumorigenic phenotype. The common abnormality for S/AN and S/RG is monosomy for chromosome 18, indicating that this is a central and important step in colorectal carcinogenesis. Our cytogenetic analysis of the adenoma cell lines suggests at least two possible routes by which premalignant colonic cells can develop and progress to malignancy. S/RG, unlike most other adenoma cell lines, is clonogenic. Aneuploidy, clonogenicity, and extended in vitro growth capacity may therefore be useful in vitro markers for adenoma cell lines with a relatively high malignant potential.
Adenoma↗
In vitro culture of human foetal colonic epithelial cells and their transformation with origin minus SV40 DNA.
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Cell Transformation, Viral↗
A study of ras gene mutations in colonic adenomas from familial polyposis coli patients.
Using an in vitro amplification step (polymerase chain reaction) followed by oligonucleotide dot blot analysis, DNA samples from 29 familial polyposis coli patients (75 polyp-derived and 26 'normal' colon samples with no epithelial atypia) were screened for the presence of K-, N-, and H-ras mutations. Only 5 polyps contained ras mutations (7%)--all in K-ras codon 12. In each case 'normal' colon DNA was available and found to be negative in this assay. We also report the detection of K-ras codon 12 mutations in a stably non-tumorigenic immortal adenoma-derived cell line, PC/AA, and in a tumorigenic colorectal carcinoma cell line, PC/JW. Both epithelial cell lines were derived from different FPC patients. An activated K-ras gene was also found in cell line S/AN, isolated from a sporadic villous adenoma. These results provide further evidence that there are common molecular events involved in sporadic and hereditary colorectal carcinogenesis and that K-ras mutations can precede the development of malignancy. To our knowledge PC/AA is the first reported example of a human cell line bearing a mutant ras gene that is not tumorigenic and shows that the presence of an activated ras gene even in an immortal human cell line is insufficient for malignancy.
Adenoma↗
Myoglobin determination by high-performance liquid chromatography.
Urine and serum myoglobin have been separated on an anion-exchange column, packed by the slurry technique. Urine or serum was injected directly into the column and eluted isocratically with Tris buffer. Freshly prepared myoglobin from human muscle gives two peaks in the chromatogram. Upon storage, one peak slowly decreases while the other increases in size and has the same capacity factor as horse myoglobin. In myoglobinuria, the latter peak is usually detected in urine, while in serum both peaks are detected. For routine assays, horse myoglobin is used as a standard. The minimum detectable level is 2 mg/l. Urine myoglobin from patients with myoglobinuria ranged from 20 to 3000 mg/l, while normal subjects had undetectable levels. Patients with myoglobinuria also had detectable levels of myoglobin in their serum. Urine myoglobin was found to be unstable; it should be analyzed immediately. Although the present method is not sensitive enough to detect myoglobin in the urine of normal subjects, it is clinically useful for confirming and determining myoglobin in patients with myoglobinuria. It has the advantage of speed and simplicity. Using more sensitive detectors would enhance the usefulness of this method.
Animals↗
Assay of urinary N-acetyl-beta-glucosaminidase in a centrifugal analyzer.
We describe a kinetic, fluorometric assay for urinary N-acetyl-beta-glucosaminidase (EC 3.2.1.30) by measurement of the release of 4-methylumbelliferone (7-hydroxy-4-methylcoumarin). The method is simple, involving only a single reagent, and is applicable to the assay of other enzymes that hydrolyze similar fluorescent-labeled substrates. The enzyme distribution in human tissues and fluids is described. The enzyme is present in high concentrations in human kidney, liver, and lung. Its concentration in urine is shown to be a sensitive indicator of early renal damage, which precedes changes in serum creatinine and urinary protein. Assay of the enzyme is quite useful in monitoring renal damage due to myoglobinuria.
Acetylglucosaminidase↗
Occurrence of copper in sickling erythrocytes.
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Anemia, Sickle Cell↗
The use of epidemiological data in the control of foodborne viruses.
The Codex Committee on Food Hygiene has recommended the adoption of Hazard Analysis and Critical Control Point (HACCP) as the basis for food safety control. To provide an objective basis for the construction of HACCP systems, epidemiological data are required. The data should be accurate, up-to-date, and identify emerging pathogens, such as viruses. The number of laboratory reports of small, round-structured viruses in England and Wales has increased from 400 cases in 1990 to 2387 in 1996. Although a food vehicle is not essential for the spread of viral particles, food my be the primary unidentified vehicle. The Advisory Committee on the Microbiological Safety of Foods recommends the use of the Kaplan Criteria, which can give strong circumstantial evidence that an outbreak is attributable to small, round-structured viruses. The application of these criteria would give a more accurate reflection of the involvement of viruses in the incidence of foodborne disease. This review considers the use of epidemiological data to support HACCP and risk-assessment systems. It discusses the implications of focusing on traditional pathogens, for example Salmonella spp., as opposed to emerging pathogens, for the design of control systems. Recommendations are made for improving the system of data collection.
Disease Outbreaks↗
The use of epidemiological data to direct resources in food safety control.
In the United States, food-borne disease results in financial losses estimated at $2.9 to $6.7 billion annually as a result of illness that is due to six specific food-borne pathogens. A model is proposed that analyzes epidemiological data and highlights areas in food safety control that have the greatest impact on food-borne disease. The model identifies Critical Control Points for use by the food industry, prioritizes criteria for inspection of food processes by regulatory authorities, and provides a focus for food hygiene training programs and campaigns. The model also provides a cost-benefit analysis that can be used to direct resources that are used in food safety control in a cost-effective manner.
Cost-Benefit Analysis↗