RESUMO
At the research and development stage, decision-makers may wish to classify several competing designs with respect to a control (or standard) one. The classification problem may become very difficult when the products are highly reliable, since only a few (or even no) failures may be observed under normal use condition. The accelerated life test model resolves this difficulty by shortening the time of life testing and quickly provides life data of products. For highly-reliable products with a Weibull log-linear model, we propose a classification rule based on a locally optimal criterion. A suitable sampling plan based on this rule is also developed. The performance of this rule is compared with a pairwise comparison classification rule. It is shown that the sample sizes needed for the new rule are considerably lower than those needed for the pairwise comparison rule.
Assuntos
Tábuas de Vida , Algoritmos , Classificação , Desenho de Equipamento , Modelos Lineares , ProbabilidadeRESUMO
Treatment of the cultured human breast-cancer cells BC-M1 with dexamethasone induced a placental-type alkaline phosphatase (ALP). Both the ALP activity and the mRNA level in the cells were increased. The induction of ALP activity by dexamethasone was time- and dose-dependent. The accumulation of ALP mRNA was inhibited by both actinomycin D and cycloheximide, indicating that its induction is a complex event and may involve other regulatory proteins. Retinoic acid showed opposing effects with dexamethasone on the expression of alkaline phosphatase. Retinoic acid (RA) and phorbol 12-myristate 13-acetate also substantially reduced the dexamethasone-induced expression of ALP. Studies on thermostability and sensitivity to various amino acid inhibitors indicated that the BC-M1 ALP is most similar to the placental form. Northern hybridization analysis also revealed that ALP mRNA transcripts in BC-M1 and term placenta are similar in size and are distinct from that of the placental-like mRNA transcript in choriocarcinoma cells. Analysis of the degradation of BC-M1 ALP mRNA showed a similar half-life of 27 h in the untreated and in dexamethasone- or RA-treated cells. These findings demonstrated that the induction of ALP in BC-M1 cells by dexamethasone is mainly due to the increase in the transcription of the ALP gene.
Assuntos
Fosfatase Alcalina/biossíntese , Regulação Enzimológica da Expressão Gênica , Regulação Neoplásica da Expressão Gênica , Northern Blotting , Neoplasias da Mama , Linhagem Celular , Dexametasona/farmacologia , Relação Dose-Resposta a Droga , Feminino , Regulação Enzimológica da Expressão Gênica/efeitos dos fármacos , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Humanos , Cinética , Placenta/enzimologia , Gravidez , Inibidores da Síntese de Proteínas/farmacologia , RNA Mensageiro/biossíntese , Acetato de Tetradecanoilforbol/farmacologia , Tretinoína/farmacologia , Células Tumorais CultivadasRESUMO
The effect of riboflavin deficiency and simultaneously, nitrosodimethylamine given by gastric intubation on the glutathione content of rat liver is reported. On different days of the experiments, glutathione content in the riboflavin deficient rat liver decreased to 55-61% of the controls. When nitrosodimethylamine was given by gastric intubation, glutathione content decreased markedly to 39-43% of the controls. The hepatic glutathione content of riboflavin deficient rats recovered to the level of the controls by supplying riboflavin. The alteration of rat hepatic glutathione content during riboflavin deficiency may imply as one of the promoting effects of riboflavin deficiency on the carcinogenesis of nitrosamines.