Mitochondrion to endoplasmic reticulum apposition length in zebrafish embryo spinal progenitors is unchanged in response to perturbations associated with Alzheimer’s disease

Published: June 21, 2017Mutations in the human genes PRESENILIN1 (PSEN1), PRESENILIN2 (PSEN2) and AMYLOID BETA A4 PRECURSOR PROTEIN (APP) have been identified in familial Alzheimer's disease (AD). The length of mitochondrion-endoplasmic reticulum (M-ER) appositions is increased in Psen1-/-/Psen2-/- double knockout murine embryonic fibroblasts and in fibroblasts from AD-affected individuals. Development of an easily accessible, genetically manipulable, in vivo system for studying M-ER appositions would be valuable so we attempted to manipulate M-ER apposition length in zebrafish (Danio rerio) embryos. We injected fertilized zebrafish eggs with antisense morpholino oligonucleotides (MOs) that inhibit expression of zebrafish familial AD gene orthologues psen1 and psen2. Furthermore, we treated zebrafish embryos with DAPT (a highly specific γ-secretase inhibitor) or with sodium azide (to mimic partially hypoxic conditions). We then analyzed M-ER apposition in an identified, presumably proliferative neural cell type using electron microscopy. Our analysis showed no significant differences in M-ER apposition lengths at 48 hours post fertilization (hpf) between psen1 & psen2 MO co-injected embryos, embryos treated with DAPT, or sodium azide, and control embryos. Instead, the distribution of M-ER apposition lengths into different length classes was close to identical. However, this indicates that it is feasible to reproducibly measure M-ER size distributions in zebrafish embryos. While our observations differ from those of murine and human studies, this may be due to differences in cellular differentiation and metabolic state, cell age, or species-specific responses. In particular, by focusing on a presumably proliferative embryonic cell type, we may have selected a cell heavily already reliant on anaerobic glycolysis and less responsive to factors affecting M-ER apposition. Future examination of more differentiated, more secretory cell types may reveal measurable responses of M-ER apposition to environmental and genetic manipulation.Morgan Newman, Lena Halter, Anne Lim, Michael Lardell

A simple computer program for calculating stress and strain rate in 2D viscous inclusion-matrix systems

Computer-based numerical solutions of geomechanical problems are important to understand the processes forming rock structures as well as to quantify the associated pressure, stresses and strain rates. However, the development of such computer programs and the underlying mathematical methods are commonly not taught in a standard structural geology curriculum. Here, we present a simple computer program to calculate the stress, pressure, velocity and strain rate fields for two-dimensional (2D) viscous inclusion-matrix systems under pure shear and simple shear. The main aim of our contribution is to explain this computer program in a simple and transparent way, so that it can be used for introductory courses on geomechanical numerical modelling in structural geology. We present the governing equations of 2D viscous deformation and program the equations in the same order and style, so that the equations are still recognizable in the computer program. The computer program can treat stiff and weak inclusions of any shape and considers both linear and power-law viscous flow laws. We present numerical calculations for various inclusion-matrix scenarios. The program is written with the software MATLAB, is provided as supplementary material, and can also be run with the freely available software GNU Octave

A simple method for the determination of refractive indices of (rough) transparent solids

Simple methods for the determination of refractive indices of transparent polymers and inorganic and organic solids of irregular geometry or with scratched or corrugated surfaces are rare. A classical procedure is based on the invisibility of a body immersed in a liquid with the same refractive index as that of the body. In order to avoid the laborious procedure connected with the search for a liquid with matching refractive index and to find an approach which is independent of the observation by eye, we describe here a modified immersion method which allows the ready determination of the refractive index of solids. The present method is based on the interpolation of the maximum transmission (nTmax) of a solid immersed in liquids with different, typically non-matching, refractive indices. Illustrations with quartz glass, crown glass and poly(vinylidene fluoride) (PVDF) films showed that nTmax can be determined with a reproducibility of ± 0.003. By comparison with refractive indices determined by ellipsometry, it was concluded that the refractive index of a solid can be determined with the modified immersion method within an accuracy better than ± 0.01 when systematic errors resulting from the fit method are also taken into consideratio

Bodin and Althusius on the nature of sovereignty

Shows how Bodin's theory of absolute sovereignty and Althusius' doctrine of popular sovereignty both lead to the notion of constitutional law which is binding on the sovereign

Interpreting the seasonal cycles of atmospheric oxygen and carbon dioxide concentrations at American Samoa Observatory

We present seven years of atmospheric O2/N2 ratio and CO2 concentration data measured from flask samples collected at American Samoa. These data are unusual, exhibiting higher short-term variability, and seasonal cycles not in phase with other sampling stations. The unique nature of atmospheric data from Samoa has been noted previously from measurements of CO2, methyl chloroform, and ozone. With our O2 data, we observe greater magnitude in the short-term variability, but, in contrast, no clear seasonal pattern to this variability. This we attribute to significant regional sources and sinks existing for O2 in both hemispheres, and a dependence on both the latitudinal and altitudinal origins of air masses. We also hypothesize that some samples exhibit a component of "older" air, demonstrating recirculation of air within the tropics. Our findings could be used to help constrain atmospheric transport models which are not well characterized in tropical regions

On the generalized Davenport constant and the Noether number

Known results on the generalized Davenport constant related to zero-sum sequences over a finite abelian group are extended to the generalized Noether number related to the rings of polynomial invariants of an arbitrary finite group. An improved general upper bound is given on the degrees of polynomial invariants of a non-cyclic finite group which cut out the zero vector.Comment: 14 page

Boosting the Frontier: Australian Settler Colonialism in the Pacific 1860s–1900s

Australia, itself a union of settler colonies, also gave birth to speculative land and settlement schemes for colonists to migrate to the nearby Pacific Islands and become sugar or copra planters, throughout the period from the 1860s to the early 1900s. The number that migrated to these proposed settler colonies was small, notwithstanding the boosting, promotional rhetoric that accompanied the schemes. Two of these schemes, in the late 1860s and the early 1900s, bookend the era of sub-empire propaganda and imperial jousting that saw hundreds of Australian settlers sail to Fiji and Vanuatu. Both were ‘company’ schemes, speculative ventures, born out of the nineteenth-century capitalist fervour characteristic of Melbourne and Sydney. A comparison of the two ventures and the boosting literature that supported them reveals the ambiguous promises that were made to settlers and the local challenges that were overlooked in the popular Australian imagination of the region

Intergroup Dialogue in a High School Classroom

In this paper, we share our work using Intergroup Dialogue (IGD) for increasing group understanding, building relationships across difference, and enhancing understanding of social inequities. IGD is an emerging area of research in K–12 settings and with adolescents. Taking this into consideration, we used this well-developed critical pedagogy in higher education–related settings to design a qualitative case study that explored its use in a high school classroom. We worked with ninth- and tenth-grade students in their sociology class to examine how IGD affected their understanding of gender and society. We found evidence that IGD enhances empathy across different lived experiences, backgrounds, and perspectives. Furthermore, findings show IGD’s impact on improving intergroup understanding and relationships