Background-Mast cells (MCs), which are a major source of cytokines and growth factors, have been implicated in various fibrotic disorders. To clarify the contribution of MCs to fibrogenesis, lung tissue from patients with the acute respiratory distress syndrome (ARDS) was examined during exudative through to fibroproliferative stages. Methods-Lung tissue was obtained from 17 patients with ARDS who had pathological features of the early exudative stage (n = 6) or the later reparative stages (n = 11), from four patients with idiopathic pulmonary fibrosis, and from three patients with normal lung tissue. Immunohistochemical localisation of tryptase (found in all human MCs), chymase (found in a subset of human MCs), -smooth muscle actin (identifies myofibroblasts), and procollagen type I was performed. Results-Normal lung tissue exhibited myofibroblast and procollagen type I immunolocalisation scores each of <5 and MC scores of 1. Increased scores were defined as myofibroblast and procollagen type I scores of >10 and MC scores of >2. Eighty percent of lung tissue samples from the early exudative stage of ARDS exhibited increased numbers of myofibroblasts, 50% had increased numbers of procollagen type I producing cells, while only 17% had increased numbers of MCs compared with control samples. All samples from the later reparative stages of ARDS had increased numbers of myofibroblasts and procollagen type I producing cells. Increased numbers of MCs were seen in 55% of samples from the reparative stages. There was no significant shift in MC phenotype in the ARDS samples. Conclusions-Increased numbers of myofibroblasts and procollagen type I producing cells were frequently found early in the course of ARDS. MC hyperplasia was unusual during this stage, but was often a feature of the later reparative stages. MCs do not appear to initiate fibroproliferation in ARDS. (Thorax 1998;53:823-829)

Action research has been shown to be effective in a variety of ways for teachers in the classroom setting. While the focus of the action research project has primarily been at the graduate level or tailored to the needs of working professionals, we propose that it is possible to do much more for the student teacher as he or she completes the program requirements through the student teaching experience. Through the incorporation of training in methods of data collection and analysis, student teachers will stand to gain a much greater degree of insight into areas of their professional pedagogical disposition through active reflection. This will develop a reflective habit of mind that is crucial for teachers to be effective in their classrooms and adaptive to the changing needs of their students, and allow for a greater degree of professional self-efficacy and satisfaction on the part of the teachers themselves.

No abstract