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Many theories propose that sleep serves a purpose in synaptic plasticity. We tested the hypothesis, therefore, that manipulation of sleep would affect the expression of molecules known to be involved in synaptic plasticity. mRNA expression of four molecules [brain-derived neurotrophic factor (BDNF), activity-regulated cytoskeleton-associated protein (Arc), matrix metalloproteinase-9 (MMP-9), and tissue plasminogen activator (tPA)] was determined after 8 h of sleep deprivation and after 6 h of a mild increase in ambient temperature, a condition that enhances sleep in rats. After sleep deprivation, BDNF, Arc, and tPA mRNAs in the cerebral cortex increased while MMP-9 mRNA levels decreased. Conversely, after enhanced ambient temperature, BDNF, Arc, and tPA mRNAs decreased while MMP-9 mRNA increased. In the hippocampus, sleep deprivation did not significantly affect BDNF and tPA expression, although Arc mRNA increased and MMP-9 mRNA decreased. Brain temperature enhancement decreased Arc mRNA levels in the hippocampus but did not affect BDNF, MMP-9, or tPA in this area. Results are consistent with the notion that sleep plays a role in synaptic plasticity.

A study was conducted with a pilot-scale sterilization system based on 27-MHz radio frequency (RF) energy to investigate the effectiveness in shortening process time and in improving quality for foods sealed in 6-pound military-ration polymeric trays. Chemical marker M-1 was used to evaluate heating uniformity in 20% whey protein gels as a model food, and macaroni and cheese was processed to assess the influence of RF process on product quality. With the RF system, a lethality (F 0 = 10 min) was achieved in both model food and macaroni and cheese within 30 min with relative uniform heating, compared to a 90 min conventional retort process that delivered a similar lethality.

Thermal resistance of Clostridium sporogenes (PA 3679) was determined at 115.6°C, 118.3°C, and 121.1°C (240°F, 245°F, and 250°F, respectively) in phosphate buffer (pH 7.0) and mashed potatoes (pH 6.3) using aluminum thermal-death-time (TDT) tubes developed at Washington State Univ. D-values were 1.8, 1.1, and 0.62 min in phosphate buffer and 2.2, 1.1, and 0.61 min in mashed potatoes at 115.6°C, 118.3°C, and 121.1°C, respectively. Z-values were 12°C and 10°C in phosphate buffer and mashed potatoes, respectively. The thermal inactivation kinetic results were then used to validate a novel thermal process based on 27.12 MHz radio frequency (RF) energy. Trays of mashed potatoes inoculated with PA 3679 were subjected to 3 processing levels: target process (F 0~4 .3), under-target process (F 0~2 .4), and over-target process (F 0~7 . 3). The microbial challenge test data showed that microbial destruction from the RF process agreed with the calculated sterilization values. This study suggests that thermal processes based on RF energy can produce safe and shelf-stable packaged foods.

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