According to the basic concepts of precision and the principles of analysis of variance (ANOVA), precision types for experiments and variety comparison in regional crop trials (RCT) were studied and developed; expecte...According to the basic concepts of precision and the principles of analysis of variance (ANOVA), precision types for experiments and variety comparison in regional crop trials (RCT) were studied and developed; expected variety comparison precision (EVCP) and realized variety comparison precision (RVCP) and the corresponding statistical indexes of them were proposed. It was explained that experimental precision (EP) and variety comparison precision (VCP) are two kinds of precision of RCT; EP includes error precision and variety mean precision, which can be measured respectively by the coefficient of variation of single observation's error (CVe) and the coefficient of variation of variety mean's error (CVy); VCP includes EVCP and RVCP, which can be measured respectively by the detectable least relative difference (DLRD) and the relative least significant distance (RLSD); EP is an important factor of VCP but not identical to it; RVCP is the realization of EVCP. Besides error, experimental design and GE interaction and ANOVA model affect VCP. Several application examples for these precision indexes were presented, and the precision of regional cotton trials in the Yellow River Valley and the Changjiang Valley were investigated through the historical data of RCTs from 1980 to 1999.展开更多
Chemoprevention is one of the cancer prevention approaches wherein natural/synthetic agent(s) are prescribed with the aim to delay or disrupt multiple pathways and processes involved at multiple steps, i.e., initiatio...Chemoprevention is one of the cancer prevention approaches wherein natural/synthetic agent(s) are prescribed with the aim to delay or disrupt multiple pathways and processes involved at multiple steps, i.e., initiation, promotion, and progression of cancer. Amongst environmental chemopreventive compounds, diet/beverage-derived components are under evaluation, because of their long history of exposure to humans, high tolerability, low toxicity, and reported biological activities. This compilation briefly covers and compares the available evidence on chemopreventive efficacy and probable mechanism of chemoprevention by selected dietary phytochemicals(capsaicin, curcumin, diallyl sulphide, genistein, green/black tea polyphenols, indoles, lycopene, phenethyl isocyanate, resveratrol, retinoids and tocopherols) in experimental systems and clinical trials. All the dietary phytochemicals covered in this review have demonstrated chemopreventive efficacy against spontaneous or carcinogen-induced experimental tumors and/or associated biomarkers and processes in rodents at several organ sites. The observed anti-initiating, anti-promoting and anti-progression activity of dietary phytochemicals in carcinogen-induced experimental models involve phytochemical-mediated redox changes, modulation of enzymes and signaling kinases resulting to effects on multiple genes and cell signaling pathways. Results from clinical trials using these compounds have not shown them to be chemopreventive. This may be due to our:(1) inability to reproduce the exposure conditions, i.e., levels, complexity, other host and lifestyle factors; and(2) lack of understanding about the mechanisms of action and agent-mediated toxicity in several organs and physiological processes in the host. Current research efforts in addressing the issues of exposure conditions, bioavailability, toxicity and the mode of action of dietary phytochemicals may help address the reason for observed mismatch that may ultimately lead to identification of new chemopreventive agents for protection against broad spectrum of exposures.展开更多
文摘According to the basic concepts of precision and the principles of analysis of variance (ANOVA), precision types for experiments and variety comparison in regional crop trials (RCT) were studied and developed; expected variety comparison precision (EVCP) and realized variety comparison precision (RVCP) and the corresponding statistical indexes of them were proposed. It was explained that experimental precision (EP) and variety comparison precision (VCP) are two kinds of precision of RCT; EP includes error precision and variety mean precision, which can be measured respectively by the coefficient of variation of single observation's error (CVe) and the coefficient of variation of variety mean's error (CVy); VCP includes EVCP and RVCP, which can be measured respectively by the detectable least relative difference (DLRD) and the relative least significant distance (RLSD); EP is an important factor of VCP but not identical to it; RVCP is the realization of EVCP. Besides error, experimental design and GE interaction and ANOVA model affect VCP. Several application examples for these precision indexes were presented, and the precision of regional cotton trials in the Yellow River Valley and the Changjiang Valley were investigated through the historical data of RCTs from 1980 to 1999.
文摘Chemoprevention is one of the cancer prevention approaches wherein natural/synthetic agent(s) are prescribed with the aim to delay or disrupt multiple pathways and processes involved at multiple steps, i.e., initiation, promotion, and progression of cancer. Amongst environmental chemopreventive compounds, diet/beverage-derived components are under evaluation, because of their long history of exposure to humans, high tolerability, low toxicity, and reported biological activities. This compilation briefly covers and compares the available evidence on chemopreventive efficacy and probable mechanism of chemoprevention by selected dietary phytochemicals(capsaicin, curcumin, diallyl sulphide, genistein, green/black tea polyphenols, indoles, lycopene, phenethyl isocyanate, resveratrol, retinoids and tocopherols) in experimental systems and clinical trials. All the dietary phytochemicals covered in this review have demonstrated chemopreventive efficacy against spontaneous or carcinogen-induced experimental tumors and/or associated biomarkers and processes in rodents at several organ sites. The observed anti-initiating, anti-promoting and anti-progression activity of dietary phytochemicals in carcinogen-induced experimental models involve phytochemical-mediated redox changes, modulation of enzymes and signaling kinases resulting to effects on multiple genes and cell signaling pathways. Results from clinical trials using these compounds have not shown them to be chemopreventive. This may be due to our:(1) inability to reproduce the exposure conditions, i.e., levels, complexity, other host and lifestyle factors; and(2) lack of understanding about the mechanisms of action and agent-mediated toxicity in several organs and physiological processes in the host. Current research efforts in addressing the issues of exposure conditions, bioavailability, toxicity and the mode of action of dietary phytochemicals may help address the reason for observed mismatch that may ultimately lead to identification of new chemopreventive agents for protection against broad spectrum of exposures.
