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Cyclic adenosine 3′,5′monophosphate (cAMP) regulated element binding protein (CREB) is a transcription factor involved in many different signaling processes including memory storage and retrieval. The mouse hippocampal neuronal cell line HT22 is widely used as a model system for neuronal cell death and cellular signal pathway investigations. For the present work a variant of HT22 with a stably expressed CRE-luciferase (CRE-luc) reporter (HT22CRE) is introduced, characterized and used to investigate cAMP-dependent and independent CRE-dependent signal processes. Trehalose (Mykose or 1-α-Glucopyranosyl-1-α-glucopyranosid) is a naturally occurring disaccharide consisting of two α,α′,1,1-glycosidic connected glucose molecules in a wide range of organisms but usually not found in mammals. Trehalose has been shown to activate autophagy, a process which regulates the degradation and recycling of proteins and organelles. The exact processes how trehalose application works on mammalian neuronal cells is not yet understood. The present work shows that trehalose application dose-dependently elevates CRE-luc activity in HT22 cells and acts synergistically with cAMP-elevating agents. In this pathway cAMP-dependent protein kinase (PKA) appears to be the most important factor and the stress kinase p38 and protein tyrosine kinases (PTKs) act as modulators.
We study the relevance of signaling and marketing as explanations for the discount control mechanisms that a closed-end fund may choose to adopt in its prospectus. These policies are designed to narrow the potential gap between share price and net asset value, measured by the fund’s discount. The two most common discount control mechanisms are explicit discretion to repurchase shares based on the magnitude of the fund discount and mandatory continuation votes that provide shareholders the opportunity to liquidate the fund. We find very limited evidence that a discount control mechanism serves as costly signal of information. Funds with mandatory voting are not more likely to delist than the rest of the CEFs in general or whenever the fund discount is large. Similarly, funds that explicitly discuss share repurchases as a potential response do not subsequently buy back shares more often when discounts do increase. Instead, the existence of these policies is more consistent with marketing explanations because the policies are associated with an increased probability of issuing more equity in subsequent periods.