We diverge from existing studies and open up new avenues of research by revealing the extent to which 38 Degrees rests on a hybrid mix of digital and professional media-centric repertoires. This hybrid campaign approach is designed not only to influence journalists but also serves to legitimate the movement to its own supporters by providing visible signs of a campaign's authenticity and its supporters' efficacy. This a source of power but also a source of vulnerability. Delicately balanced relations of interdependence between horizontalist digital media activism and professional media work can quickly dissolve and be replaced by simpler relations of dependence on professional media. We show that when professional media attention fades, interdependence turns to dependence, and a 38 Degrees campaign is more likely to falter. 3Explaining how and why this happens is one of our goals. To summarize our findings, it is not because 38 Degrees is adapting to 'mass media' logic and becoming just another elite-focused insider interest group whose primary goal is to get its stories in the press. Nor is it because professional media trivialize and marginalize 38 Degrees by personalizing its campaigns or framing it as a deviant 'protest' group. These are well-established explanations for movement 'failure' in earlier social movement research (see for example Gamson and Wolfsfeld, 1993;Gitlin, 1980;Rucht, 2004) but we find little evidence for these factors in the case of 38 Degrees campaigns.38 Degrees' leadership certainly try to gain professional media coverage to convey campaign momentum to their dispersed membership base, but how this works is complex and differs from how it worked in earlier social movements (Gamson and Wolfsfeld, 1993;Gitlin, 1980;Rucht, 2004). Professional media coverage is a mirror used by the 38 Degrees core team to show its members that a campaign is still emergent and moving toward a successful outcome. It is seen as a credible means of reflecting the iterative successes of members' actions, thereby potentially expanding the scope and scale of future action. But as we show, 38 Degrees leaders and members both capitalize on the nature of today's media. Collectively, members produce large-scale, publicly visible informational traces of their own actions online: responses to issue-priority email polls, online petition signatures, social media comments, 'likes,' 'shares,' and retweets. These are mobilized in the leadership's interactions with professional media. The professional media coverage that follows is then used by the leadership to reinforce momentum and build individual members' efficacy, further increasing the likelihood that members will go on to participate in yet further online actions. Subsequent professional media coverage will again further increase the likelihood of member action, and so it goes on, in a virtuous circle. However, when this circle is broken, it becomes difficult to sustain a campaign's momentum. Despite this fragility and interdependence, we conclude our 4 analysis with...

This article examines how the UK political organization Momentum uses social media within its campaigning. Drawing on a mixed-method research design, combining interviews with activists in Portsmouth and discourse analysis of content posted on Facebook and Twitter, this article tests whether the leadership provides meaningful influence for members. At the national level, there is little evidence of Momentum fulfilling its "people-powered" vision. Instead, supporters are instructed to undertake tasks at the direction of the leadership. However, this is not a straightforward case of controlled interactivity. The local group in Portsmouth is semiautonomous, providing member-driven advocacy that is coordinated through a Facebook Group. By using social media to underpin different organizational norms and campaigning tactics at different spatial levels, Momentum represents a "movement faction".

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This current study analyzed macrophage/biomaterial interactions as modulators of endothelial cell proliferation. Rabbit peritoneal macrophages were harvested and seeded (1 x 10(6) cells/ml) into culture flasks with Dulbecco's modified Eagle medium and 10% platelet-poor, plasma-derived equine serum. Macrophages were identified by morphologic characteristics, nonspecific esterase, and Fc (immunoglobulin G) receptors on the cell membranes. Culture conditions were (1) no prosthetic material, (2) Dacron, or (3) Polyglactin 910 (PG910) (Ethicon, Inc., Somerville, N.J.). Both prosthetic materials were finely shredded into the media. After 5 weeks in culture, PG910 inclusions were seen within macrophage cytoplasm. No intracytoplasmic Dacron was observed. Conditioned media from all three groups were collected weekly from week 5 to week 10, centrifuged, filtered, and added in serial dilutions to cultured quiescent murine capillary lung endothelial cells. Quiescence was achieved by serum deprivation and verified by [3H]thymidine incorporation. Sixteen hours after addition of conditioned media, [3H]thymidine was measured in and expressed as percent increase above quiescent levels. Mitogenic activity in the PG910 group progressively increased from weeks 6 to 10. At week 10, the PG910 group (1:10 dilution) yielded a 620% increase in DNA synthesis. The Dacron group never varied from the control group (no prosthetic). The mean increases in [3H]thymidine incorporations over weeks 7 to 10 were PG910, 540% +/- 65%; Dacron, 323% +/- 65%, and control, 343% +/- 26% (PG910 vs Dacron, p less than or equal to 0.004). These studies suggest macrophage activation by bioresorbable prostheses, yielding growth factor release with subsequent enhanced endothelial cell proliferation.