Some Methods for Strengthening the Common χ 2 Tests

Cochran, William G.

doi:10.2307/3001616

Cited by 3,433 publications

(1,662 citation statements)

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“…MN staining was performed as described. Statistical significant differences between control and irradiated cells were assessed with the w 2 -test (Cohen, 1960) and significance of dose-dependency with the CochranArmitage test (Cochran, 1954;Armitage, 1955).…”

Section: Micronuclei Assaymentioning

confidence: 99%

UVA radiation causes DNA strand breaks, chromosomal aberrations and tumorigenic transformation in HaCaT skin keratinocytes

et al. 2008

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The role of UVA-radiation-the major fraction in sunlight-in human skin carcinogenesis is still elusive. We here report that different UVA exposure regime (4 Â 5 J/cm 2 per week or 1 Â 20 J/cm 2 per week) caused tumorigenic conversion (tumors in nude mice) of the HaCaT skin keratinocytes. While tumorigenicity was not associated with general telomere shortening, we found new chromosomal changes characteristic for each recultivated tumor. Since this suggested a nontelomere-dependent relationship between UVA irradiation and chromosomal aberrations, we investigated for alternate mechanisms of UVA-dependent genomic instability. Using the alkaline and neutral comet assay as well as c-H2AX foci formation on irradiated HaCaT cells (20-60 J/cm 2 ), we show a dosedependent and long lasting induction of DNA single and double (ds) strand breaks. Extending this to normal human skin keratinocytes, we demonstrate a comparable damage response and, additionally, a significant induction and maintenance of micronuclei (MN) with more acentric fragments (indicative of ds breaks) than entire chromosomes particularly 5 days post irradiation. Thus, physiologically relevant UVA doses cause long-lasting DNA strand breaks, a prerequisite for chromosomal aberration that most likely contribute to tumorigenic conversion of the HaCaT cells. Since normal keratinocytes responded similarly, UVA may likewise contribute to the complex karyotype characteristic for human skin carcinomas.

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Section: Micronuclei Assaymentioning

confidence: 99%

UVA radiation causes DNA strand breaks, chromosomal aberrations and tumorigenic transformation in HaCaT skin keratinocytes

et al. 2008

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“…The dose-response relationship was evaluated using the Cochran-Armitage trend test (24,25). P-values of less than 0.05 were considered to be statistically significant.…”

Section: Statistical Proceduresmentioning

confidence: 99%

Geonotoxicity study of illegal drug MDMA and its nitroso derivative N-MDMA by micronucleus and chromosomal aberration tests using Chinese hamsger lung fibroblast cell line

Yoshioka

Shimizu

Toyama

et al. 2007

Environ Health Prev Med

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Objectives: An increase in incidence of the illegal use of tablets containing 3,4-methylenedioxymethamphetamine hydrochloride (MDMA) has recently become a widespread social problem. MDMA ingested orally reacts with nitrite in the stomach and is synthesized into N-nitroso-3,4-methylenedioxymethamphetamine (N-MDMA). The aim of this study is to investigate the genotoxic effects of MDMA and N-MDMA on the basis of the results of an in vitro micronucleus (MN) test and an in vitro chromosomal aberration (CA) test using a Chinese hamster lung fibroblast cell line (CHL/IU).Methods: Tablets containing MDMA obtained from the Regional Bureau of the Ministry of Health, Labor and Welfare were purified, and N-MDMA was synthesized from MDMA in our laboratory. To evaluate the effects of MDMA and N-MDMA, the MN test established by our laboratory and the CA test in accordance with the guidelines for toxicity studies of drugs recommended by the Ministry of Health, Labor and Welfare were performed.Results: In the MN test, no increased frequency of MNs was not found for MDMA. On the other hand, an apparently increased frequency of MNs was observed for N-MDMA. In the CA test, no CA was found for MDMA, but CA was observed for N-MDMA apparently.Conclusion: N-MDMA genotoxicity was observed in the MN and CA tests. However, no MDMA genotoxicity was observed.

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“…Under the null hypothesis of no association and assume HWE in each stratum, using simple algebra we can obtain

{\overset{λ}{true}}_{l} = {\overset{true^}{V a r}}_{H_{0}} ({\overset{Δ}{true}}_{l}) = (m + 1) {(1 - {\overset{p}{true}}_{l})}^{2} {\overset{p}{true}}_{l}^{2} / (r_{l} m)

where

{\overset{p}{true}}_{l} = [2 (r_{2 l} + s_{2 l}) + (r_{1 l} + s_{1 l})] / [2 (m + 1) r_{l}]

. Thus, using the same motivation as the Cochran-Mantel-Haenszel (CMH) statistic [1,25,26] we can construct the stratified model reduction test (SMRT):…”

Section: Methodsmentioning

confidence: 99%

Robust tests for matched case-control genetic association studies

Zang

Fung

2010

BMC Genet

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BackgroundThe Cochran-Armitage trend test (CATT) is powerful in detecting association between a susceptible marker and a disease. This test, however, may suffer from a substantial loss of power when the underlying genetic model is unknown and incorrectly specified. Thus, it is useful to derive tests obtaining the plausible power against all common genetic models. For this purpose, the genetic model selection (GMS) and genetic model exclusion (GME) methods were proposed recently. Simulation results showed that GMS and GME can obtain the plausible power against three common genetic models while the overall type I error is well controlled.ResultsAlthough GMS and GME are powerful statistically, they could be seriously affected by known confounding factors such as gender, age and race. Therefore, in this paper, via comparing the difference of Hardy-Weinberg disequilibrium coefficients between the cases and the controls within each sub-population, we propose the stratified genetic model selection (SGMS) and exclusion (SGME) methods which could eliminate the effect of confounding factors by adopting a matching framework. Our goal in this paper is to investigate the robustness of the proposed statistics and compare them with other commonly used efficiency robust tests such as MAX3 and χ2 with 2 degrees of freedom (df) test in matched case-control association designs through simulation studies.ConclusionSimulation results showed that if the mean genetic effect of the heterozygous genotype is between those of the two homozygous genotypes, then the proposed tests and MAX3 are preferred. Otherwise, χ2 with 2 df test may be used. To illustrate the robust procedures, the proposed tests are applied to a real matched pair case-control etiologic study of sarcoidosis.

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Some Methods for Strengthening the Common χ 2 Tests

Cited by 3,433 publications

References 16 publications

UVA radiation causes DNA strand breaks, chromosomal aberrations and tumorigenic transformation in HaCaT skin keratinocytes

UVA radiation causes DNA strand breaks, chromosomal aberrations and tumorigenic transformation in HaCaT skin keratinocytes

Geonotoxicity study of illegal drug MDMA and its nitroso derivative N-MDMA by micronucleus and chromosomal aberration tests using Chinese hamsger lung fibroblast cell line

Robust tests for matched case-control genetic association studies

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