Possible role of immune surveillance at the initial phase of metastasis produced by B16BL6 melanoma cells

AbstractThe relationship among the real-time trafficking of lung metastatic B16BL6 cells, metastatic potential, and the injected number of the cells was examined, since the smaller the number of tumor cells injected, the more clearly the immune defense may be observed. When 1×106 or 1×105 B16BL6 cells were injected into mice via the tail vein, both numbers of cells accumulated in the lung at a similar rate: there was an approximately 10-fold difference in the number of accumulated cells between the two doses. Elimination from the lung was not dependent on the cell number but on the proportion of accumulated cells. However, the injection of 1×104 cells resulted in lung accumulation less than one-tenth of that obtained with 1×105 cell injection. Metastasis was observed when 1×105 or 1×106 B16BL6 cells were injected, but not after injection of 1×104 cells. To clarify the roles of the immune defense system at the initial phase of metastasis, we challenged macrophage-depleted mice with 1×104 tumor cells. Treatment of mice with 2-chloroadenosine prior to the tumor cell challenge cancelled the suppression of not only metastasis but also the lung accumulation. Furthermore, the administration of 2-chloroadenosine following the tumor cell challenge had little effect on the metastatic potential. These results suggest that the immune surveillance whose action was obvious at the low dose of challenged tumor cells functions strongly at the initial phase but not at the advanced stages of the metastatic process, and that macrophages play an important role in the suppression of metastasis

A non-compensatory choice modeling analysis of Japanese consumers’ preferences for beef: A choice experiment approach

The purpose of this paper is to examine, using choice experiments, the Japanese consumers’ valuation of domestic Wagyu beef, domestic dairy beef, Australian beef, and US beef when considering their bovine spongiform encephalopathy (BSE) test status. Some Japanese consumers give high priority to food safety while purchasing beef; this is expected to cause a non-compensatory valuation of food safety. As compared to the results derived from a compensatory utility model, a random parameters logit (RPL) with a non-compensatory utility model provides estimation results that are fitter for the respondents’ decision-making rules and also provides more valid willingness to pay (WTP) for each type of beef. The results suggest that the RPL with the non-compensatory utility model is more suitable for measuring the valuation of food safety with regard to beef by the food safety conscious Japanese consumers. Moreover, the WTP for each BSE-tested type of beef reveals that the Japanese consumers seem to regard the BSE test to be very important for ensuring the food safety of beef

食品安全性に配慮して生産された牛肉の消費者評価

The purpose of this paper was to verify the stability of consumers\u27 evaluations of food safety by conducting the identical choice experiments questionnaire survey at the same site two different times. The two surveys, measuring the consumers\u27 evaluations of beef derived from cattle fed in accordance with improved food safety measures were　conducted in January 2003 (n = 83) and March 2004 (n = 369) in Kiyota ward of Sapporo city in Hokkaido, Japan. A comparison of the results of the two surveys suggests that social issues related to the choice experiment questions can significantly influence the consumers\u27 inferred values for food safety on the basis of the questions