Response of American sycamore seedlings to maleic hydrazide and sodium chloride

American sycamore (Platanus occidentals L.) seedlings grown in a hydroponics system were treated with a growth regulator, maleic hydrazide (MH) or sodium chloride, or a combination of the two. Application of maleic hydrazide or sodium chloride retarded plant growth, but combined application did not show significant interaction effects. Treatment with both sodium chloride and MH reduced the dry weight of plant tissue to a greater extent than sodium chloride application alone. Elemental analyses of various plant parts revealed that MH was generally without effect on the level of either sodium or chloride ions. In old stem tissue, however, treatment with MH had no effect in the absence of sodium chloride but was associated with lower chloride content in its presence.     

A critical review of the effectiveness of rodent pharmaceutical carcinogenesis testing in predicting for human risk

The pharmaceutical industry and regulatory agency toxicology testing paradigms in the United States currently appear successful, in part because of the continuously increasing life expectancy and the declining age-adjusted cancer rates in the United States. Although drugs likely have a minimal impact on the population statistics for cancer rates, pharmaceutical pathologists and toxicologists must focus on the individual risk for pharmaceutical carcinogenesis. As our understanding of carcinogenesis increases exponentially, and after hundreds if not thousands of rodent cancer tests, significant improvement in the precision of human pharmaceutical carcinogenesis hazard identification should now be possible and would enable a reduction in the substantial false-negative and false positive-rates reported herein. The appropriate use of acute, subchronic, chronic, and special toxicology tests to identify the major associated cancer risk factors, specifically, hormonal modulation, immunosuppression, genetic toxicity, and chronic toxicity, can be recognized through this review of pharmaceutical carcinogens. Significant opportunities exist for improving the effectiveness and efficiency of the current cancer risk assessment paradigm.