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M S Linhart

Publications and source records attributed to M S Linhart.

6 recordsLinked to original sources
PubMed1981

Evaluating statistical analyses and reproducibility of microbial mutagenicity assays.

The NCI/NTP has completed the first phase of a 4-laboratory study on the reproducibility of testing chemicals for mutagenicity in the Salmonella/microsome assay. This paper is a report of the statistical analysis of some of that data. This analysis involved (1) identifying and removing spurious data; (2) determining the adequacy of the remaining data in making a decision on the mutagenicity of the test chemical; (3) performing the statistical tests; and (4) interpreting the results. Using this procedure, 7 approaches were used to determine the mutagenicity of a test. These approaches were the (1) 2-fold rule, (20 modified 2-fold rule, (3) one-way analysis of variance (homogeneity test), (4) test for linear trend, (5) combination of 3 and 4, (6) 97.5th percentile threshold rule and (7) confidence interval threshold rule. The conclusions drawn by each rule were compared to the microbiologists' interpretation, and the results of these comparisons were presented. In addition, the strengths and weakness of each rule were discussed. The reproducibility of the assay in this study was examined, and a discussion of the significance of these results was presented.

Histidine↗
PubMed1980

In vitro information system for collection and analysis of experimental data.

The In Vitro information System (IVIS) provides for the collection, maintenance, analysis and reporting of mutagenesis data for the In Vitro Carcinogenesis Program of the Carcinogenesis Testing Program in the National Cancer Institute. Initial development or IVIS focused on the microbial mutagenicity assays conducted in a collaborative study in four laboratories. Information is collected about contract management, chemicals, microorganisms strain checks, preparation of activation enzymes, test results, and confirmation of mutation. IVIS provides for editing and maintenance of the information on computers at the National Institutes of Health. Analysis and reporting features were designed to assist both laboratory investigators and NCI staff in evaluating the mutagenic activity of test compounds. The analysis has focused on two principal goals: using the computer to examine the results of each test to determine if the test was adequate for a further statistical analysis; and secondly, if the plate counts are adequate, developing statistics that indicate whether there is a positive or negative trend. Reports have been developed for tabular displays of test results, frequency distributions, dose response graphs and statistical computations.

Bacteria↗
PubMed1979

Neoplastic and nonneoplastic lesions in aging (C57BL/6N x C3H/HeN)F1 (B6C3F1) mice.

Neoplastic and nonneoplastic lesions in untreated (C57BL/6N x C3H/HeN)F1 (B6C3F1) mice used as controls in carcinogenesis tests were tabulated and evaluated. The most common neoplasms in 2,543 male mice were hepatocellular adenomas and carcinomas. In 2,522 female mice, common tumors were lymphomas, leukemias, pulmonary adenomas and carcinomas, hepatocellular adenomas and carcinomas, and pituitary adenomas. The risk of developing most neoplasms increased with the age of the mouse. Hepatocellular carcinomas metastasized in 12% of the animals with these tumors. Other than lymphomas and leukemias, few other tumors metastasized. Nonneoplastic lesions included cystic hyperplasia of the uterus, nephritis, ovarian and uterine cysts, inflammatory lesions of the lung, mineralization in the brain, and focal hyperplasias in several tissues. The focal hyperplasias in lung and pituitary, adrenal, and thyroid glands were suggestive of the early stages of neoplasia. Comparative aspects of lesions in aging mice and their interpretation in carcinogenesis tests are discussed.

Age Factors↗