Interplay of Plasmodium falciparum and thrombin in brain endothelial barrier disruption.

Recent concepts suggest that both Plasmodium falciparum factors and coagulation contribute to endothelial activation and dysfunction in pediatric cerebral malaria (CM) pathology. However, there is still limited understanding of how these complex inflammatory stimuli are integrated by brain endothelial cells. In this study, we examined how mature-stage P. falciparum infected erythrocytes (IE) interact with tumor necrosis factor α (TNFα) and thrombin in the activation and permeability of primary human brain microvascular endothelial cell (HBMEC) monolayers. Whereas trophozoite-stage P. falciparum-IE have limited effect on the viability of HBMEC or the secretion of pro-inflammatory cytokines or chemokines, except at super physiological parasite-host cell ratios, schizont-stage P. falciparum-IE induced low levels of cell death. Additionally, schizont-stage parasites were more barrier disruptive than trophozoite-stage P. falciparum-IE and prolonged thrombin-induced barrier disruption in both resting and TNFα-activated HBMEC monolayers. These results provide evidence that parasite products and thrombin may interact to increase brain endothelial permeability.

Estimated Distributions of Usual Physical Activity during Recess.

PURPOSE: This study aimed to estimate distributions of usual physical activity during recess in schools in low-income areas using measurement error models and to compare model-adjusted distributions to unadjusted distributions based on a single day of measurement. METHODS: A randomized study of the Playworks program was conducted in 29 schools from six U.S. cities. A sample of 365 fourth- and fifth-grade students in 26 of the study schools wore accelerometers during their recess periods on two school days. Estimates for the percentage of time spent in moderate to vigorous physical activity (MVPA) during recess were constructed from the accelerometer data for each school day. Using measurement error models, distributions for the usual amount of time spent in MVPA during recess were estimated for intervention and control groups of males and females. Unadjusted distributions for these same groups were also constructed using data from a single school day. RESULTS: There is considerable intraindividual variability in the students' physical activity, which accounts for 67%-83% of the overall variability, depending on the study group. Unadjusted single-day distributions are much wider and have more weight in the tails than model-adjusted distributions owing to this large intraindividual variability in the data. CONCLUSIONS: Using measurement error models to analyze physical activity data collected from recess periods will allow for more accurate and reliable inferences on students' physical activity.

The impact of Playworks on students' physical activity during recess: findings from a randomized controlled trial.

OBJECTIVE: To evaluate the impact of Playworks on students' physical activity during recess. METHOD: Twenty-seven elementary schools from six U.S. cities were grouped into blocks and randomly assigned to implement Playworks (treatment) or not (control) during an entire school year (either 2010-2011 or 2011-2012). Study data were collected at the end of the school year only. Fourth- and 5th-grade students (n=2278) reported on their physical activity during recess, and a subset (n=1537) wore accelerometers during recess. Teachers (n=111) also reported on their students' physical activity during recess. RESULTS: A significantly higher percentage of teachers in treatment schools reported that their students engaged in an intense physical activity during recess (p=0.01). Marginally significant differences between treatment and control groups were found for the mean number of accelerometer intensity counts recorded per minute during recess (p=0.10) and the mean percentage of time spent in vigorous physical activity during recess (p=0.07). No significant differences were found for student reports about their physical activity during recess (p=0.92). CONCLUSION: Teachers in Playworks schools reported that students were more active during recess, but accelerometer and student survey measures showed either no impacts or marginally significant impacts.