Judging the 'passability' of dynamic gaps in a virtual rugby environment.

Affordances have recently been proposed as a guiding principle in perception-action research in sport (Fajen, Riley, & Turvey, 2009). In the present study, perception of the 'passability' affordance of a gap between two approaching defenders in rugby is explored. A simplified rugby gap closure scenario was created using immersive, interactive virtual reality technology where 14 novice participants (attacker) judged the passability of the gap between two virtual defenders via a perceptual judgment (button press) task. The scenario was modeled according to tau theory (Lee, 1976) and a psychophysical function was fitted to the response data. Results revealed that a tau-based informational quantity could account for 82% of the variance in the data. Findings suggest that the passability affordance in this case, is defined by this variable and participants were able to use it in order to inform prospective judgments as to passability. These findings contribute to our understanding of affordances and how they may be defined in this particular sporting scenario; however, some limitations regarding methodology, such as decoupling perception and action are also acknowledged.

Thrombospondin 2 functions as an endogenous regulator of angiogenesis and inflammation in rheumatoid arthritis.

Thrombospondin 2 (TSP2), a matricellular protein with a primary role in modulating cell-matrix interactions, has been implicated in tissue repair and foreign body responses. Here we show that TSP2 has regulatory function in the chronic inflammatory lesions of rheumatoid arthritis. Tissue TSP2, produced by synovial fibroblasts, endothelial cells, and macrophages correlated not only with the intensity of angiogenesis but also with the architecture of lymphoid infiltrates. Synovial tissues with diffuse inflammatory infiltrates had high levels of TSP2, whereas synovial tissues with ectopic germinal center reactions and T cell-B cell aggregates produced low levels. Cell-based gene therapy with TSP2 was used to examine the in vivo effects of the matrix protein on neoangiogenesis and lymphoid organization. Human synovium-severe combined immunodeficiency (SCID) mouse chimeras were treated with TSP2-transfected fibroblasts deposited into the peritoneum. Overexpression of TSP2 led to the accumulation of TSP2 protein in the inflamed synovium and resulted in a prompt inhibition of lesional vascularization. Beside its anti-angiogenic activity, TSP2 also suppressed the production of the proinflammatory mediators, interferon-gamma and tumor necrosis factor-alpha, and induced the depletion of tissue-residing T cells. We propose that TSP2 is an endogenous regulator of angiogenesis and autoimmune inflammation in the synovium and represents a protective mechanism preventing ectopic lympho-organogenesis and persistent inflammation in this tissue site.