Episodic, transient systemic acidosis delays evolution of the malignant phenotype: Possible mechanism for cancer prevention by increased physical activity

Background\ud \ud The transition from premalignant to invasive tumour growth is a prolonged multistep process governed by phenotypic adaptation to changing microenvironmental selection pressures. Cancer prevention strategies are required to interrupt or delay somatic evolution of the malignant invasive phenotype. Empirical studies have consistently demonstrated that increased physical activity is highly effective in reducing the risk of breast cancer but the mechanism is unknown.\ud \ud Results\ud \ud Here we propose the hypothesis that exercise-induced transient systemic acidosis will alter the in situ tumour microenvironment and delay tumour adaptation to regional hypoxia and acidosis in the later stages of carcinogenesis. We test this hypothesis using a hybrid cellular automaton approach. This model has been previously applied to somatic evolution on epithelial surfaces and demonstrated three phases of somatic evolution, with cancer cells escaping in turn from the constraints of limited space, nutrient supply and waste removal. In this paper we extend the model to test our hypothesis that transient systemic acidosis is sufficient to arrest, or at least delay, transition from in situ to invasive cancer.\ud \ud Conclusions\ud \ud Model simulations demonstrate that repeated episodes of transient systemic acidosis will interrupt critical evolutionary steps in the later stages of carcinogenesis resulting in substantial delay in the evolution to the invasive phenotype. Our results suggest transient systemic acidosis may mediate the observed reduction in cancer risk associated with increased physical activity

Benchmarking the Minimum Electron Beam (eBeam) Dose Required to Achieve Sterility of Space Foods

The safety, nutrition, acceptability, and shelf life of space foods are of paramount importance to NASA, especially on long-duration missions. Since food and mealtimes play a key role in reducing stress and boredom of prolonged missions, the acceptability of food in terms of appearance, flavor, texture and aroma can have significant psychological ramifications on astronaut performance. The FDA, which oversees space foods, currently requires a minimum dose of 44 kGy for irradiated space foods. The underlying hypothesis is that commercial sterility of space foods could be achieved at significantly lower doses. Lowering the minimum dose can positively impact the visual appearance, sensory attributes, nutrient content, and overall acceptability of space foods. The focus of this project was to use beef fajitas (an example NASA space food) and employ eBeam processing to benchmark the minimum eBeam dose required for sterility. A 15 kGy dose was able to achieve an approximately 10 log reduction in STEC bacteria, and 5 log reduction in Clostridium sporogenes spores. Furthermore, accelerated shelf life testing (ASLT) to determine sensory and quality characteristics under various conditions was conducted. Using GC/MS-olfactory analysis, numerous volatiles were shown to be dependent on the dose applied to the product. Furthermore, concentrations of off –flavor aroma compounds such as dimethyl sulfide were decreased at the reduced 15 kGy dose. The long-term goal of this project is to collect empirical data to enable NASA to petition the FDA to lower the minimum dose from 44 kGy to significantly lower doses