Enhancing breadth of knowledge within multidisciplinary doctoral research: reflections from the Cambridge Generic Nutrition Training course for non-nutritionist postgraduates and professionals

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Effect of pH and ionic strength on μ- and m-calpain inhibition by calpastatin

The objectives of this study were to determine the extent to which pH and ionic strength influence μ- and m-calpain activity and the inhibition of calpains by calpastatin. Calpastatin, μ-calpain, and m-calpain were purified from at-death porcine semimembranosus. μ-Calpain or m-calpain (0.45 U) were incubated with the calpain substrate Suc-Leu-Leu-Val-Tyr-7-amino-4-methyl coumarin in the presence of calpastatin (0, 0.15, or 0.30 U of calpain inhibitory activity) under the following pH and ionic strength conditions: pH 7.5 and 165 mM NaCl or 295 mM NaCl; pH 6.5 and 165 mM NaCl or 295 mM NaCl; and pH 6.0 and 165 mM NaCl or 295 mM NaCl. The reactions were initiated with addition of 100 μM (μ-calpain) or 1 mM CaCl2 (m-calpain), and calpain activity was recorded at 30 and 60 min. μ-Calpain had the greatest (P \u3c 0.01) activity at pH 6.5 at each ionic strength. Higher ionic strength decreased μ-calpain activity (P\u3c 0.01) at all pH conditions. Inhibition percent of μ-calpain by calpastatin was not affected by pH; however, it was influenced by ionic strength. Inhibition of μ-calpain by calpastatin was higher (P \u3c 0.01) at 295 mM NaCl than at 165 mM NaCl when 0.3 units of calpastatin were included in the assay. Activity of m-calpain was greater (P \u3c 0.01) at pH 7.5 than at pH 6.5. m-Calpain activity was not detected at pH 6.0. Inhibition of m-calpain was greater (P \u3c 0.01) when 0.15 and 0.3 U calpastatin were added at pH 6.5 than 7.5 at 165 mM NaCl, whereas percentage inhibition of m-calpain was greater (P \u3c 0.01) at 295 mM than 165 mM NaCl at pH 7.5 and 6.5. These observations provide new evidence that defines further the influence of pH decline and increased ionic strength on μ-calpain, m-calpain, and calpastatin activity, thereby helping to more accurately define a role for these enzymes in the process of postmortem tenderization

Oxidative environments decrease tenderization of beef steaks through inactivation of μ-calpain

This study was designed to test the hypothesis that oxidative conditions in postmortem (PM) tissue decrease calpain activity and proteolysis, subsequently minimizing the extent of tenderization. To achieve different levels of oxidation, the diets of beef cattle were supplemented with vitamin E for the last 126 d on feed, and beef steaks were irradiated early PM. Ten steers were fed a finishing diet with the inclusion of vitamin E at 1,000 IU per steer daily (VITE). Another 10 beef steers were fed the same finishing diet without added vitamin E (CON). At 22 to 24 h PM, strip loins from each carcass were cut into 2.54-cm-thick steaks and individually vacuum packaged. Within 26 h PM, steaks were irradiated at 0 or 6.4 kGy and then aged at 4°C for 0, 1, 3, 7, and 14 d postirradiation. Steaks from each time point were used to determine Warner-Bratzler shear force (WBSF) and calpain activity, and for western blotting of sarcoplasmic proteins and myofibrillar proteins. Calpastatin activity was determined at 0, 3, and 14 d postirradiation. At 1, 3, 7, and 14 d postirradiation, WBSF values of irradiated steaks were higher (P \u3c 0.03) than for nonirradiated steaks. Western blots of troponin-T and desmin showed decreased proteolysis in irradiated samples compared with nonirradiated samples. At 2 d PM, troponin-T degradation products were more evident (P \u3c 0.03) in nonirradiated steaks supplemented with VITE than nonirradiated steaks from the CON diet. Similarly, VITE treatment resulted in steaks with lower (P \u3c 0.05) calpastatin activity at 1 d PM than in steaks from steers fed the CON diet. Irradiation diminished the rate of calpastatin inactivation. Irradiated samples, regardless of diet, had no detectable levels of intact titin or nebulin. Irradiation decreased μ-calpain activity and autolysis, whereas m-calpain activity was not affected by diet or irradiation. Inactivation of μ-calpain by oxidation during early times PM decreased the amount of myofibrillar proteolysis, thereby decreasing the extent of tenderization of beef steaks

Implementation and Simulation Results using Autonomous Aerobraking Development Software

An Autonomous Aerobraking software system is currently under development with support from the NASA Engineering and Safety Center (NESC) that would move typically ground-based operations functions to onboard an aerobraking spacecraft, reducing mission risk and mission cost. The suite of software that will enable autonomous aerobraking is the Autonomous Aerobraking Development Software (AADS) and consists of an ephemeris model, onboard atmosphere estimator, temperature and loads prediction, and a maneuver calculation. The software calculates the maneuver time, magnitude and direction commands to maintain the spacecraft periapsis parameters within design structural load and/or thermal constraints. The AADS is currently tested in simulations at Mars, with plans to also evaluate feasibility and performance at Venus and Titan

Effect of oxidation, pH, and ionic strength on calpastatin inhibition of μ- and m-calpain

The objective of this study was to evaluate the effect of oxidation on μ- and m-calpain activity at varying pH and ionic strength conditions in the presence of calpastatin. In 2 separate experiments, purified porcine skeletal muscle μ- or m-calpain (0.45 units of caseinolytic activity) was incubated in the presence of calpastatin (0, 0.15, or 0.30 units) at pH 7.5, 6.5, or 6.0 with either 165 or 295 mM NaCl. The reactions were initiated with the addition of CaCl2 (100 μM for μ-calpain; 1 mM for m-calpain). In Experiment 1, μ- or m-calpain was incubated with the calpain substrate Suc-Leu-Leu-Val-Tyr-AMC (170 μM). Either 0 or 16 μ μM H2O2 was added to each assay. Activity was measured at 60 min. In Experiment 2, calpain was incubated with highly purified porcine myofibrils (4 mg/mL) under conditions described. Either 0 or 100 μM H2O2 was added immediately prior to the addition of calpain. Degradation of desmin was determined on samples collected at 2, 15, 60, and 120 min. Results from Experiment 1 indicated that oxidation decreased (P \u3c 0.01) activity of μ-calpain. μ-Calpain had the greatest (P \u3c 0.01) activity at pH 6.5, and m-calpain had the greatest (P \u3c 0.01) activity at pH 7.5 at 60 min. m-Calpain activity was not detected at pH 6.0. μ- and m-calpain activity were lower (P \u3c 0.01) at 295 mM NaCl than at 165 mM NaCl at all pH conditions. Oxidation lowered (P \u3c 0.01) calpastatin inhibition of μ-and m-calpain at all pH and ionic strength combinations. In Experiment 2, oxidation decreased proteolytic activity of μ-calpain against desmin at pH 6.0 (P \u3c 0.05 at 15, 60, and 120 min) and decreased m-calpain at all pH conditions. However, desmin degradation by μ-calpain was not as efficiently inhibited by calpastatin at pH 7.5 and as at pH 6.5 (P = 0.03 at 60 min) when oxidizing conditions were created. This is consistent with the results from Experiment 1, which indicated that oxidation decreased the ability of calpastatin to inhibit μ-calpain. These studies provide evidence that oxidation influences calpain activity and inhibition of calpains by calpastatin differently under varying environmental conditions. The results suggest that, at the higher pH conditions used, calpastatin may limit the possibility of oxidation-induced inactivation of μ-calpain

Post2 End-to-End Descent and Landing Simulation for ALHAT Design Analysis Cycle 2

The ALHAT project is an agency-level program involving NASA centers, academia, and industry, with a primary goal to develop a safe, autonomous, precision-landing system for robotic and crew-piloted lunar and planetary descent vehicles. POST2 is used as the 6DOF descent and landing trajectory simulation for determining integrated system performance of ALHAT landing-system models and lunar environment models. This paper presents updates in the development of the ALHAT POST2 simulation, as well as preliminary system performance analysis for ALDAC-2 used for the testing and assessment of ALHAT system models. The ALDAC-2 POST2 Monte Carlo simulation results have been generated and focus on HRN model performance with the fully integrated system, as well performance improvements of AGNC and TSAR model since the previous design analysis cycl

Switching model with two habitats and a predator involving group defence

Switching model with one predator and two prey species is considered. The prey species have the ability of group defence. Therefore, the predator will be attracted towards that habitat where prey are less in number. The stability analysis is carried out for two equilibrium values. The theoretical results are compared with the numerical results for a set of values. The Hopf bifuracation analysis is done to support the stability results