Docosahexaenoic Acid Reduces Palmitic Acid-Induced Endoplasmic Reticulum Stress in Pancreatic Β Cells

Endoplasmic reticulum (ER) stress leads to peripheral insulin resistance and the progression of pancreatic beta cell failure in type 2 diabetes. Although ER stress plays an important role in the pathogenesis of diabetes, it is indispensable for cellular activity. Therefore, when assessing the pathological significance of ER stress, it is important to monitor and quantify ER stress levels. Here, we have established a novel system to monitor ER stress levels quickly and sensitively, and using this method, we have clarified the effect of differences in glucose concentration and various fatty acids on the ER of pancreatic β cells. First, we developed a cell system that secretes Gaussia luciferase in culture medium depending on the activation of the GRP78 promoter. This system could sensitively monitor ER stress levels that could not be detected with real-time RT-PCR and immunoblotting. This system revealed that hyperglycemia does not induce unfolded protein response (UPR) in a short period of time in MIN6 cells, a mouse pancreatic β cell line. Physiological concentrations of palmitic acid, a saturated fatty acid, induced ER stress quickly, while physiological concentrations of oleic acid, an unsaturated fatty acid, did not. Docosahexaenoic acid, an n-3 unsaturated fatty acid, inhibited palmitic acid-induced ER stress. In this study, we have established a system that can sensitively detect ER stress levels of living cells in a short period of time. This system can be used to monitor the state of the ER in living cells and lead to the investigation of the significance of physiological or pathological ER stress levels.

DYNAMIC PORTFOLIO SELECTION WITH UNCERTAINTY

How to make a prompt decision for uncertainty investment is always a key problem in financial market. In this paper, we present a new dynamic portfolio selection strategy in stock market. The investor is assumed to seek an investment strategy that will maximize his/her final wealth and minimize the total risk. An analytically optimal strategy in closed form is obtained by solving a dynamic programming problem. Some applications are also presented to illustrate this model.

Assembly of a rod-shaped virus. Disk aggregate of cucumber green mottle mosaic virus protein and its function

Although it is established that in the assembly of tobacco mosaic virus (TMV) in vitro, a 20 S disk aggregate of protein is essential for the initiation of the reaction, there is no agreement as to whether subsequent rod elongation proceeds by the addition of protein subunits or disks. Cucumber green mottle mosaic virus (CGMMV) is a rod-shaped virus closely related to TMV. It was observed directly by electron microscopy that CGMMV-protein also formed a single- or double-layer disk aggregate under conditions where reconstitution with the protein and TMV-RNA proceeds efficiently. Whichever forms, a single or double layer, a disk aggregate is required for the initiation of reconstitution, but cannot participate in rod elongation. These results obtained with CGMMV support our model proposed for the mechanism of assembly of TMV and rod-shaped viruses; i.e., the assembly occurs in two steps; disk aggregates of protein are essential only for initiation, and rod eleongation proceeds by subsequent addition of subunits.