We examined the mechanisms by which two different types of photonic radiation, short wavelength UV (UV-C) and gamma radiation, activate transcription factor NF-kappaB. Exposure of mammalian cells to either form of radiation resulted in induction with similar kinetics of NF-kappaB DNA binding activity, nuclear translocation of its p65(RelA) subunit, and degradation of the major NF-kappaB inhibitor IkappaBalpha. In both cases, induction of NF-kappaB activity was attenuated by proteasome inhibitors and a mutation in ubiquitin-activating enzyme, suggesting that both UV-C and gamma radiation induce degradation of IkappaBs by means of the ubiquitin/proteasome pathway. However, although the induction of IkappaBalpha degradation by gamma rays was dependent on its phosphorylation at Ser-32 and Ser-36, UV-C-induced IkappaBalpha degradation was not dependent on phosphorylation of these residues. Even the "super repressor" IkappaBalpha mutant, which contains alanines at positions 32 and 36, was still susceptible to UV-C-induced degradation. Correspondingly, we found that gamma radiation led to activation of IKK, the protein kinase that phosphorylates IkappaBalpha at Ser-32 and Ser-36, whereas UV-C radiation did not. Furthermore, expression of a catalytically inactive IKKbeta mutant prevented NF-kappaB activation by gamma radiation, but not by UV-C. These results indicate that gamma radiation and UV-C activate NF-kappaB through two distinct mechanisms.
Self-efficacy, the degree of confidence an individual has for performing a given behavior, is a central concept in social learning theory. Self-efficacy is a strong correlate of current exercise and a consistent predictor of future exercise behavior. This study was designed to explore the correlates of exercise self-efficacy in order to determine whether early experiences with exercise and sports fosters exercise self-efficacy in adulthood. This study explored historical and contemporaneous correlates of exercise self-efficacy using a path analytic approach and a randomly selected sample of adults. Historical experiences with exercise and sports were classified as more or less organized and as proximal or distal in time. The activities studied included those reported during elementary (ages 6–14), high school (15–18), and the period after high school. The historical activities, scaled using factor analysis, were found to have no significant direct association with self-efficacy and only marginal indirect associations with self-efficacy mediated by contemporaneous social learning variables. Contemporaneous variables drawn from social learning theory were found to have the largest direct and indirect associations with self-efficacy specifically related to vigorous exercise. Directions for experimental analysis and health promotion policy implications are discussed.
The present study evaluated a measure of perceived physical environments that may influence physical activity. Forty-three self-report items were used to assess environmental variables at homes, in neighborhoods, or on frequently traveled routes. The presence of facilitators of (e.g., equipment, programs, attractive surroundings) and barriers to (e.g., high crime) physical activity was assessed. In 110 college students, test-retest reliabilities were .89 for the home equipment scale, .68 for the neighborhood scale, and .80 for the convenient facilities scale. Home equipment and convenient facilities scales were correlated with self-reported physical activity. In multiple regression analyses, the only significant association, after adjusting for neighborhood socioeconomic status, was home equipment with strength exercise. Further research is needed to identify other environmental characteristics that may influence physical activity.
The purpose of the study is to evaluate the performance of theoretically-derived mediators of health behavior change. Participants were university seniors (184 females; 154 males) randomly assigned to an intervention course designed to promote physical activity or to a control course. Five physical activity outcomes and nine psychosocial mediating variables were assessed at baseline and the end of the 16-week course. For women, the intervention had significant effects on five of the mediators, including self-efficacy for making time, self-efficacy for resisting relapse, social support from friends, and experiential and behavioral processes of change. Among men, the intervention improved use of behavioral processes of change but also had the unintended effect of increasing perceived barriers to activity. For women, significant contributors to regressions explaining physical activity change were social support from friends (for total activity) and change in self-efficacy for resisting relapse (for vigorous exercise). For men, significant explanatory variables included change in enjoyment (for total activity), change in self-efficacy for resisting relapse (for strength exercise), and change in benefits (for moderate intensity activity). For both sexes, there were significant findings in the unexpected direction. Across the five physical activity outcomes, hypothesized mediators were inconsistent and weak contributors to the models. Investigating mediators of behavior change has the potential to stimulate improvements in theories and interventions.
Background. Physical inactivity has been linked with chronic disease and obesity in most western populations. However, prevalence of inactivity, health beliefs, and knowledge of the risks of inactivity have rarely been assessed across a wide range of developed and developing countries. Methods. A cross-sectional survey was carried out with 19,298 university students from 23 countries varying in culture and level of economic development. Data concerning leisure-time physical activity, health beliefs, and health knowledge were collected. Results. The prevalence of inactivity in leisure time varied with cultural and economic developmental factors, averaging 23% (North-Western Europe and the United States), 30% (Central and Eastern Europe), 39% (Mediterranean), 42% (Pacific Asian), and 44% (developing countries). The likelihood of leisure-time physical activity was positively associated with the strength of beliefs in the health benefits of activity and with national economic development (per capita gross domestic product). Knowledge about activity and health was disappointing, with only 40–60% being aware that physical activity was relevant to risk of heart disease. Conclusions. Leisure-time physical activity is below recommended levels in a substantial proportion of students, and is related to cultural factors and stage of national economic development. The relationship between health beliefs and behavior is robust across cultures, but health knowledge remains deficient.
