Severe Hypoxia Up-regulates Gluconeogenesis in Daphnia

Hypoxia is a significant low oxygen state that has complex and diverse impacts on organisms. In aerobes, various adaptive responses to hypoxia are observed that vary depending on the level of oxygen depletion and previous adaptation, hence the continued attention to hypoxia as an important abiotic stressor. Adaptive responses to hypoxia are primarily governed by the hypoxia-inducible factors (HIFs), which activate downstream genetic pathways responsible for oxygen transport and metabolic plasticity. In aquatic habitats, oxygen availability can vary greatly over time and space. Therefore, aquatic organisms’ adaptation to hypoxia is likely pervasive, especially in genotypes originating from waterbodies prone to hypoxia. Here we report the transcriptional response to severe hypoxia in the freshwater crustacean Daphnia magna. We observe improved survival in media containing elevated calcium ion (Ca2+) concentrations. Additionally, we observe changes in lactate and pyruvate concentrations within tissues. To elucidate the transcriptome basis of these effects, we examine transcripts with known gene ontologies indicating roles in Ca2+ homeostasis and signaling, and in pyruvate metabolism, including gluconeogenesis (GNG). We observe the up-regulation of numerous transcripts encoding GNG pathway enzymes, including the rate-limiting enzyme phosphoenolpyruvate carboxykinase (PEPCK-C) and fructose-1,6-bisphosphatase (FBP). In contrast, no transcripts involved in Ca2+ homeostasis or signaling showed any significant differential expression. Some GNG transcripts are more up-regulated in clones from permanent waterbodies not prone to hypoxia, inconsistent with the hypothesis about its protective effects. One exception is the FBP transcript, which has been identified to be up-regulated in some hypoxia-tolerant aquatic organisms

Severe Hypoxia Alters Metabolism in Daphnia by Inducing Gluconeogenesis

Hypoxia has become a subject of interest among the many environmental stressors as its role in biology is complex and diverse. Hypoxia is a significant low oxygen condition that causes many pathologies and adaptive responses in organisms. It can lead to a moderate or dangerous loss of respiration and can be an indication of tumorigenesis as many tumors lack adequate blood supply. Organisms possess adaptive responses to hypoxia that include hypoxia-inducible factors (HIFs) that activate several downstream pathways that are responsible for altering metabolism and maintaining homeostasis. Within aquatic organisms, hypoxia is an important ecological constraint as oxygen availability within bodies of water can vary greatly over time and space. Therefore, adaptation to hypoxia is likely pervasive, especially in genotypes originating from bodies of water that are prone to hypoxia. Here we report the transcriptional response to acute hypoxia in the clonal freshwater crustacean Daphnia magna. Daphnia were subjected to 1mg/O2 for 12 hours. Then, RNA was extracted, reverse transcribed, and sequenced using Oxford Nanopore MinION. We find that severe hypoxia significantly up-regulates key enzymes in the gluconeogenesis pathway. Additionally, we report genotype-by-environment interactions showing that Daphnia clones from habitats that are hypoxia prone survive better in hypoxia

Application of the group-theoretical method to physical problems

The concept of the theory of continuous groups of transformations has attracted the attention of applied mathematicians and engineers to solve many physical problems in the engineering sciences. Three applications are presented in this paper. The first one is the problem of time-dependent vertical temperature distribution in a stagnant lake. Two cases have been considered for the forms of the water parameters, namely water density and thermal conductivity. The second application is the unsteady free-convective boundary-layer flow on a non-isothermal vertical flat plate. The third application is the study of the dispersion of gaseous pollutants in the presence of a temperature inversion. The results are found in closed form and the effect of parameters are discussed

Bidder Earnings Management, Cynical Targets and Acquisition Premia

Mergers and acquisitions are the result of negotiations between bidder and target managers and shareholders where both sides have incentives to manipulate the value of shares and assets. While a naive target investor may perceive higher share value for a bidder who engages in income increasing earnings management, an informed target would recognize that the impact of such management is transient. In this paper, we find that non-cash acquirers that adopt income-increasing pre-merger earnings management pay higher acquisition premia in completing their M&A deals. However, there is no significant relationship between earnings management and acquisition premia in cash bids, and evidence suggests that there is no significant incremental impact of bidder earnings management on premia for stock transactions versus cash transactions. Our results support the cynical investor hypothesis, which posits that target management and its financial advisors are suspicious of bidders with low earnings quality and are able to detect and thwart bidder earnings management schemes designed to obtain a lower acquisition price in stock transactions. The results are counter to the naive investor hypothesis