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Biomedical subjects

C Burnett

Publications and source records attributed to C Burnett.

At least 37 records · Page 2Linked to original sources
PubMed1991

An experimental model for the surgical correction of tracheomalacia.

Tracheomalacia may result from large intrathoracic goiters. Due to the chronic compression, particularly within the confines of the thoracic inlet, the tracheal wall weakens, with disintegration of some of the cartilaginous rings. Tracheomalacia can cause acute airway distress, particularly during the post-operative period, and may occasionally result in death. The other major cause of tracheomalacia is related to either prolonged endotracheal intubation or over-inflation of the tracheostomy cuff. While various techniques such as internal stenting, external support devices, tracheostomy, and tracheal resection have been used based on individual circumstances, no one method appears to be perfect. To further study this difficult problem, an experimental model of tracheomalacia was created in eight dogs. Six to seven rings of the tracheal cartilages were dissected submucosally. More than half of the circumference of the tracheal rings was resected. The tracheal walls were reconstructed with polytetrafluoroethylene (PTFE) grafts. The grafts strengthened the tracheal wall without causing luminal constriction. Tracheostomy was not performed on any of the dogs. All dogs tolerated the procedure well and were extubated at the conclusion of the experiment. The dogs were followed for 4 to 6 months and then sacrificed so that the tracheal wall could be examined histologically. There was considerable fibrosis leading to stiff neotrachea. The results of this experimental technique for prosthetic reconstruction to counteract problems simulating tracheomalacia are very encouraging.

Animals↗
PubMed1989

Goiters and airway problems.

Even though thyroid enlargement occurs commonly, the incidence of goiter has decreased in the United States due to the routine use of iodized salt. We continue to see a large number of patients with neglected goiters that cause airway compression. The progressive nature of this disease occasionally results in severe tracheal compression and acute airway distress. We treated 120 patients with airway compression secondary to goiters during a 7-year period. Thirty patients presented initially with acute airway distress requiring either intubation or semiemergent surgery. The decision to operate was based primarily on clinical evaluation and airway films. Ninety patients had substernal goiters. Only one patient required sternal splitting. If one lobe was enlarged causing tracheal deviation, lobectomy was performed; if both lobes were enlarged, subtotal thyroidectomy was performed. Two patients required tracheostomy. There were no operative deaths, and morbidity was limited to minor wound problems. It is important to consider early surgical decompression whenever tracheal compression is caused by goiters, especially if the patients are symptomatic or there is mediastinal extension.

Adult↗
PubMed1987

A case-control study of bladder cancer using city directories as a source of occupational data.

Commercial city directories, currently produced in 1,250 United States cities, potentially provide yearly information on occupation and employer for all city residents over age 18 years. To investigate the usefulness of these occupational data, the authors have conducted a case-control study of male bladder cancer mortality in Hamilton County, Ohio (which includes Cincinnati). A total of 731 bladder cancer cases who died during 1960-1982 were matched on age, sex, race, date-of-death, and residence at death to two controls per case. Risks of bladder cancer death were calculated by occupation, industry, and specific employer, using both city directories (multiple statements) and death certificates (single statement). Four companies showed a significant excess bladder cancer risk when using city directories. Only one would have been identified using death certificates, which ask for usual lifetime type of industry rather than a specific company name. Using city directories, significant positive associations were found between bladder cancer and occupation as an engineer, tailor, carpenter, furnace operator, blending machine operator, chemist, pressing machine operator, house cleaner, or salesman. For industry, the authors found significant positive associations for the textile, chemical, grain mill, foundry, petroleum, building service, entertainment, and advertising industries. A significant increase in risk for those with 20 or more years of employment was seen for those employed as truck drivers and furnace operators, or those employed in the railroad industry. A check of the validity of city directory data indicated that 77 per cent of the listings agreed with Social Security earnings reports for employer in any given year. One limitation of Hamilton County city directory data was the fairly large number of yearly listings without any occupational data (15 per cent for occupation, 36 per cent for employer). While city directory data do provide work history over time, unlike death certificates, such data are available only for years of residence in the city in question.

Death Certificates↗
PubMed1986

The titration of clostridial toxoids and antisera in cell culture.

The practicability of cell culture titration methods for antigens and antitoxins derived from Clostridium perfringens, Cl. septicum and Cl. novyi was investigated. Toxin neutralization could not be demonstrated with Cl. perfringens filtrates but assays for antitoxin based on the use of cultures of Vero cells were practicable for Cl. novyi and Cl. septicum. In the case of the latter, the precision and reproducibility of the test was sufficient for quality control purposes.

Animals↗
PubMed1985

Improving the use of epidemiologic data in health risk assessment.

Epidemiologic data with quantitative exposure measures is infrequently available for specific environmental agents. This lack of exposure measures creates confusion in interpreting epidemiologic data and therefore has impeded its efficient use in health risk analysis. This paper discusses screening and evaluating epidemiologic studies for use in assessing health risk. It also describes the larger role of epidemiology in reducing uncertainties in risk analysis. The approach recognizes that the various designs used to increase statistical power and to control for covariables have different functions in contemporary risk assessment as practiced by regulatory agencies. Each of these study designs is categorized for its role in risk analysis as useful for hazard identification or for dose-response assessment. Studies presenting geographic correlations are construed to be not directly useful in health risk assessment. The numerical level of the exposure data is a deciding factor in using valid epidemiologic studies. However, data measured on an ordinal scale can be used in qualitative assessments and can demonstrate the strength of the relationship. The application of this procedure is illustrated using epidemiologic studies on the carcinogenicity of chemicals contaminated with dioxins.

Dioxins↗
PubMed1982

The effect of dimethylsulfoxide on the mutagenicity of the hair dye p-phenylenediamine.

Published data on the mutagenicity of the oxidative hair dye intermediate p-phenylenediamine in the Ames test are conflicting. The work reported here resolves the discrepancies, showing that the activity of p-phenylenediamine in the Ames Salmonella/microsome test is markedly influenced by the use of dimethylsulfoxide as solvent, and by the age of the solution prior to plating. Thus, aqueous solutions of p-phenylenediamine are non-mutagenic; fresh solutions in DMSO are equally non-mutagenic, but become highly active on standing at room temperature for 4 hr. These results suggest the need for caution in the choice of solvents and tight controls in the execution of the test.

Dimethyl Sulfoxide↗
PubMed1980

Evaluation of the toxicity and carcinogenicity of hair dyes.

The chronic toxicological and carcinogenic potential following skin painting in mice was evaluated for nine oxidative and three nonoxidative hair dyes. Groups of male and female Swiss mice were treated one time weekly for at least 20 mo with one dose level of each dye. The oxidative dyes were mixed 1:1 with 6% hydrogen peroxide before treatment and the three semipermanent formulations were applied without dilution. Control groups were shaved only and received no applications. Body weights and survival rates did not differ between appropriate male and female treatment and control groups. Absolute and relative liver and kidney weights were equivalent for treatment and control groups. After 7 and 9 mo of treatment, 10 males and 10 females randomly selected from each group were necropsied and tissues taken for histopathologic evaluation. Animals found dead or sacrificed in moribund condition or at termination of the study were necropsied and evaluated histopathologically. Comparison of incidence of tumors and of nontumor pathology among the various treatment and control groups revealed no biologically significant differences. Toxicological and carcinogenic effects were not induced by the hair dye formulations.

Animals↗
PubMed1979

Reproductive tract peroxidases as endproducts of estrogen-specific gene expression.

Estrogen is an essential requirement for the postpubertal trophic development and maintenance of the differentiated state of the oviduct, uterus, cervix, vagina and mammary glands of mammals. Estrogen, apparently functioning through its specific cytoplasmic receptor protein via a multistep interaction pathway induces gene expression of specific biochemical events leading to growth and differentiation of target tissues (Jensen et al., Proc Natl Acad Sci, 59:632, 1968; Gorski et al., Recent Prog Horm Res 24:45, 1968). One biochemical expression of the estrogen gene is the synthesis of specific mRNA transcripts for certain specific marker proteins, including ovalbumin, lysozyme and ovomucoid in the chick oviduct (O'Malley and McGuire, Proc Natl Acad Sci 60:1527, 1968; Palmiter and Schimke, J Biol Chem 248:1502, 1973), tubulin in the mammalian oviduct (Brenner and Anderson, Handbook of Physiology 7(2):123, 1973; Brenner et al., Endocrinology 95:1094, 1974) and peroxidase (EC 1,11.1.7) in the rodent uterus (Brockelmann and Fawcett, Biol Reprod 1:59, 1969; Churg and Anderson, J Cell Biol 62:449, 1974; Anderson et al., J Cell Biol 64:668, 1975).

Animals↗
PubMed1977

Dominant lethal mutagenicity study on hair dyes.

A dominant lethal mutagenicity study was performed in rats with the following chemicals that may be used to dye hair: 2-nitro-p-phenylenediamine, 4-nitro-o-phenylenediamine, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, p-toluenediamine, 2,4-diaminoanisole, 2,5-diaminoanisole, 2-amino-4-nitrophenol, 2-amino-5-nitrophenol, and 4-amino-2-nitrophenol. The compounds were administered intraperitoneally three times weekly for 8 weeks to groups of 20 sexually mature Charles River CD male rats at a dose of 20 mg/kg. This amount of dye is an enormous exaggeration of the human exposure from brief montly topical application of a hair color product containing 2 g (40 mg/kg) or less total dye. There was no evidence of an increase in postimplantation fetal loss which could indicate a dominant lethal effect. Included are data on the acute toxicity of the dyes by various routes of administration in different vehicles.

Animals↗
PubMed1976

Teratology and percutaneous toxicity studies on hair dyes.

Twelve hair dye formulations were tested for systemic toxicity by topical application twice weekly for 13 wk to groups of 12 New Zealand white rabbits and for teratologic effects following applications to groups of 20 pregnant Charles River CD rats on days 1, 4, 7, 10, 13, 16, and 19 of gestation. The three semipermanent formulations were applied as is, and the nine oxidation dyes were mixed 1:1 with 6% hydrogen peroxide just prior to application, as in normal use. The formulations induced a broad spectrum of dyes and dye intermediates used or considered useful in oxidative and semipermanent hair color products. In the teratology study no biologically significant soft tissue or skeletal changes were noted. Similarly, the mean numbers of corpora lutea, implantation sites, live fetuses, and resorptions per pregnancy, as well as numbers of litters with resporptions, were not significantly affected by the dye treatment. In the percutaneous toxicity study there was no evidence of compound-induced systemic effects. Microscopic examination of 25 tissues from each animal gave no indication of histomorphologic evidence of toxicity. No dye discoloration of urine was seen at any time during the test or at necropsy. Some of the dye groups showed epidermal hyperplasia, which was probably a reflection of slight irritation due to the frequency of application of the oxidation formulations.

Abnormalities, Drug-Induced↗