Witch hazel (Hamamelis virginiana) fractions and the importance of gallate moieties--electron transfer capacities in their antitumoral properties.

Witch hazel ( Hamamelis virginia ) extracts are used in traditional medicine. They are particularly rich in gallate esters included in proanthocyanidins, hydrolyzable tannins (galloylated sugars), and methyl gallate. This study examines the response of human colon cancer cells to treatment with fractions obtained from a witch hazel polyphenolic extract. The results are compared with those obtained previously with homologous fractions from grape (less galloylated) and pine (nongalloylated). Witch hazel fractions were the most efficient in inhibiting cell proliferation in HT29 and HCT116 human colon cancer cell lines, which clearly shows that the more galloylated the fractions, the more effective they were at inhibiting proliferation of colon cancer cells. Witch hazel fractions were, in addition, more potent in arresting the cell cycle at the S phase and inducing apoptosis; they also induced a significant percentage of necrosis. Interestingly, the apoptosis and cell cycle arrest effects induced were proportional to their galloylation. Moreover, witch hazel fractions with a high degree of galloylation were also the most effective as scavengers of both hydroxyl and superoxide radicals and in protecting against DNA damage triggered by the hydroxyl radical system. These findings provide a better understanding of the structure-bioactivity relationships of polyphenolics, which should be of assistance in choosing an appropriate source and preparing a rational design for formulations of plant polyphenols in nutritional supplements

Signaling in Context: Elite Influence and the Dynamics of Public Support for Clinton's Health Security Act

A growing body of research shows the influence of political elites on the public's policy preferences. Yet we know little about the dynamics of elite influence or the cognitive mechanisms through which elite signals are interpreted in "real time"-that is, as public deliberation over a policy initiative actually evolves. In this paper, we present preliminary results from a longer-term project that explores elite influences on the dynamics of public support on policy proposals. Conceptually, we hypothesize how elite influences on mass opinion may change during the course of a policy debate. We pay especial attention to partisanship as a central contextual mediator of elite signals. Empirically, we exploit the unusual circumstances involving the health care reform debate in 1993-94, where debate was salient, elite signals were clear, and opinion polling was abundant. Methodologically, we propose a novel means of examining elite influences in real time. Using pooled data from 53 opinion polls fielded betwe en August 1993 and August 1994, we find substantial evidence that elite signaling shaped public views on President Clinton's Health Security Act. This elite influence is often distinctly partisan in effect. But its influence varies in form, being sometimes informative, sometimes symbolic. And the duration of signaling effects too appears to vary depending on the nature of the signal and the predisposing characteristics of the respondent. We conclude with some thoughts on future directions for research in this area.