Effect of wind on the chemical uptake kinetics of a passive air sampler.

Passive air samplers (PASs) operate in different types of environment under various wind conditions, which may affect sampling rates and thus introduce uncertainty to PAS-derived air concentrations. To quantify the effect of wind speed and angle on the uptake in cylindrical PASs using XAD-resin as the sampling medium, we measured the uptake kinetics of polychlorinated biphenyls (PCBs) in XAD and of water in silica-gel, both under quasi wind-still condition and with lab-generated wind blowing toward the PASs at various speeds and angles. Passive sampling rates (PSRs) of PCBs under laboratory generated windy conditions were approximately 3-4 times higher than under wind-still indoor conditions. The rate of water uptake by silica-gel increased with wind speed, following a logarithmic function so that PSRs are more strongly influenced at lower wind speed. PSRs of both PCBs and water varied little with wind angle, which is consistent with computational fluid dynamic simulations showing that different angles of wind incidence cause only minor variations of air velocities within the cylindrical sampler housing. Because modifications of the design of the cylindrical PAS were not successful in eliminating the wind speed dependence of PSRs at low wind levels, indoor and outdoor deployments require different sets of PSRs. The effect of wind speed and angle on the PSRs of the cylindrical PAS are much smaller than what has been reported for the double-bowl polyurethane foam PAS. PSRs of the cylindrical XAD-PAS therefore tend to vary much less between sampling sites exposed to different wind conditions.

Hyperinsulinemia in rats causes impairment of spatial memory and learning with defects in hippocampal synaptic plasticity by involvement of postsynaptic mechanisms.

In addition to its peripheral metabolic functions, insulin acts as a central neuromodulator and affects synaptic plasticity of the hippocampal neurons. In this study, hyperinsulinemic obese zucker rats (OZR) with autosomal recessive mutation of the fa-gene were tested in water maze for learning and memory. The animals were then decapitated and hippocampal slices were prepared for electrophysiological examination. In the water maze test, the OZR performed less efficient than their counter lean control rats (LCR). The OZR showed prolonged latency and increased distance swam to reach a hidden platform. In the electrophysiological experiments, the hippocampal slices were examined for paired-pulse facilitation (PPF), long-term potentiation (LTP), and depression expression. The results showed that while the PPF (thus mainly the presynaptic mechanisms) was not affected, the LTP expression (169.9 ± 16.6 vs. 310.7 ± 2.4 %) and the synaptic plasticity range (69.2 vs. 211.2 %) were both reduced in the OZR animals compared to the LCR. It is concluded that hyperinsulinemia in the OZR resulted in defects in hippocampal synaptic plasticity associated with deterioration in spatial learning and memory functions.