Activation Of AMP-Activated Protein Kinase As An Early Indicator For Stress In The Lobster, Homarus Americanus

Variations in water temperature, salinity, pH, and oxygen concentration are stressors that marine invertebrates face on a daily basis. Each of these physiological stressors creates a large cellular demand for energy. In mammals, energy metabolism is regulated by the enzyme AMP-activated protein kinase (AMPK), which is highly conserved during evolution. This project was designed to test the hypothesis that AMPK is present and activated by temperature, hypoxia, and anoxia stress in the lobster, Homarus americanus. Animals were exposed to a rapid and progressive increase in temperature (6ºC per hour) beginning at 14 ºC. We measured lactate concentrations and AMPK activity and heat shock protein 70 (HSP70) levels in 2ºC increments (14-32ºC) in heart, muscle, and liver tissue. Lactate concentration remained at low control levels between 14 and 28ºC and increased significantly (ANOVA, p Secondly, lobsters were exposed for a 24 hour time period to the sub-lethal temperature of 28°C. The prolonged exposure to heat led to a significant increase in AMPK liver activity up to 2.1±0.1 fold between 0 and 24 hours. AMPK did not significantly increase in the heart or muscle tissues. HSP70 levels remained constant in heart, liver, and muscle tissues. Lastly, to characterize the role of AMPK during hypoxia lobsters were exposed for 24 hours to a low oxygen concentration of 4 kPa. The same measurements as described above were performed at 0, 4 and 24 hours. We found up to a 6-fold increase in AMPK activity and a nearly 40 fold increase in AMPK mRNA expression of heart tissue after 24 h of hypoxia. In the liver nearly a 1000 fold increase was found in AMPK mRNA expression. HSP70 mRNA and protein expression remained unchanged. The data show that in lobsters AMPK activation is an early indicator of stress when cellular energy levels are depleted, as indicated by the concurrence of AMPK activation and lactate accumulation. The traditionally used marker, HSP70, was a less reliable indicator for stress. Future comparison with other crustacean species will indicate whether AMPK activation during stress is a more potent mechanism than HSP70 for assessing stress levels in other populations of invertebrates

Higher Derivative Fermionic Field Equation in the First Order Formalism

The generalized Dirac equation of the third order, describing particles with spin 1/2 and three mass states, is analyzed. We obtain the first order generalized Dirac equation in the 24-dimensional matrix form. The mass and spin projection operators are found which extract solutions of the wave equation corresponding to pure spin states of particles. The density of the electromagnetic current is obtained, and minimal and non-minimal (anomalous) electromagnetic interactions of fermions are considered by introducing three phenomenological parameters. The Hamiltonian form of the first order equation has been obtained.Comment: 16 pages, title changed, new section, appendixes, and references adde

Asymptotic theory for range-based estimation of integrated variance of a continuous semi-martingale

We provide a set of probabilistic laws for range-based estimation of integrated variance of a continuous semi-martingale. To accomplish this, we exploit the properties of the price range as a volatility proxy and suggest a new method for non-parametric measurement of return variation. Assuming the entire sample path realization of the log-price process is available - and given weak technical conditions - we prove that the high-low statistic converges in probability to the integrated variance. Moreover, with slightly stronger condi- tions, in particular a zero drift-term, we ¯nd an asymptotic distribution theory. To relax the mean-zero constraint, we modify the estimator using an adjusted range. A weak law of large numbers and central limit theorem is then derived under more general assump- tions about drift. In practice, inference about integrated variance is drawn from discretely sampled data. Here, we split the sampling period into sub-intervals containing the same number of price recordings and estimate the true range. In this setting, we also prove consistency and asymptotic normality. Finally, we analyze our framework in the presence of microstructure noise. JEL Classification: C10; C22; C80

Enhancing Thermal Tolerance By Eliminating The Pejus Range: A Comparative Study With Three Decapod Crustaceans

Marine invertebrates in the intertidal and subtidal zones are often exposed to highly variable environmental conditions, especially rapid changes in temperature. The ability to survive at different temperatures has previously been described using an extended version of Shelford’s law of tolerance, with optimum, pejus (Latin: ‘turning worse’), and pessimum ranges, and the respective thresholds, critical (Tc) and pejus (Tp) temperatures, that mark the transition from one range into the next. The width of the pejus range, in which the scope for activity gradually declines, varies among species. We tested the hypothesis that the width of the pejus range is correlated to the temperature stability of the species’ respective habitats. We used locomotor activity, heart rate, lactate accumulation, heat shock protein 70 (HSP70) levels, and the activation of AMP-activated protein kinase (AMPK) to identify Tc and Tp in 3 decapod crustaceans: green crab Carcinus maenas, rock crab Cancer irroratus, and lobster Homarus americanus. We found species specific patterns of temperature-induced changes in all parameters, especially in HSP70 protein and AMPK activity. The width of the pejus range (between Tp and Tc) was 8 to 12°C for rock crabs and 12 to 16°C for lobsters. Most importantly, green crab, the most temperature-tolerant of our 3 species and which lives in a highly variable habitat, switched directly from optimum to pessimum range, meaning that the pejus range was eliminated completely. Additionally, even lethal temperatures did not activate AMPK in green crabs, pointing to a different cellular tolerance strategy than in rock crabs and lobsters. This modified tolerance pattern might represent a broader strategy to enhance physiological tolerance in a highly variable habitat