Horizontal transfer between loose compartments stabilizes replication of fragmented ribozymes

The emergence of replicases that can replicate themselves is a central issue in the origin of life. Recent experiments suggest that such replicases can be realized if an RNA polymerase ribozyme is divided into fragments short enough to be replicable by the ribozyme and if these fragments self-assemble into a functional ribozyme. However, the continued self-replication of such replicases requires that the production of every essential fragment be balanced and sustained. Here, we use mathematical modeling to investigate whether and under what conditions fragmented replicases achieve continued self-replication. We first show that under a simple batch condition, the replicases fail to display continued self-replication owing to positive feedback inherent in these replicases. This positive feedback inevitably biases replication toward a subset of fragments, so that the replicases eventually fail to sustain the production of all essential fragments. We then show that this inherent instability can be resolved by small rates of random content exchange between loose compartments (i.e., horizontal transfer). In this case, the balanced production of all fragments is achieved through negative frequency-dependent selection operating in the population dynamics of compartments. This selection mechanism arises from an interaction mediated by horizontal transfer between intracellular and intercellular symmetry breaking. The horizontal transfer also ensures the presence of all essential fragments in each compartment, sustaining self-replication. Taken together, our results underline compartmentalization and horizontal transfer in the origin of the first self-replicating replicases.Comment: 14 pages, 4 figures, and supplemental materia

A scaling law of multilevel evolution: how the balance between within- and among-collective evolution is determined

Numerous living systems are hierarchically organised, whereby replicating components are grouped into reproducing collectives -- e.g., organelles are grouped into cells, and cells are grouped into multicellular organisms. In such systems, evolution can operate at two levels: evolution among collectives, which tends to promote selfless cooperation among components within collectives (called altruism), and evolution within collectives, which tends to promote cheating among components within collectives. The balance between within- and among-collective evolution thus exerts profound impacts on the fitness of these systems. Here, we investigate how this balance depends on the size of a collective (denoted by $N$) and the mutation rate of components ($m$) through mathematical analyses and computer simulations of multiple population genetics models. We first confirm a previous result that increasing $N$ or $m$ accelerates within-collective evolution relative to among-collective evolution, thus promoting the evolution of cheating. Moreover, we show that when within- and among-collective evolution exactly balance each other out, the following scaling relation generally holds: $Nm^{\alpha}$ is a constant, where scaling exponent $\alpha$ depends on multiple parameters, such as the strength of selection and whether altruism is a binary or quantitative trait. This relation indicates that although $N$ and $m$ have quantitatively distinct impacts on the balance between within- and among-collective evolution, their impacts become identical if $m$ is scaled with a proper exponent. Our results thus provide a novel insight into conditions under which cheating or altruism evolves in hierarchically-organised replicating systems.Comment: Accepted in Genetics after a minor revision. Revised based on referee reports. Added results on a binary-trait model. Conclusions do not chang

Development of a multipurpose hand controller for JEMRMS

A prototype multipurpose hand controller for the JEMRMS (Japanese Experiment Module Remote Manipulator System) was developed. The hand controller (H/C) is an orthogonal type, with 6 degrees of freedom (DOF) and small size. The orthogonal type H/C is very simple for coordinate transformations and can easily control any type of manipulators. In fact, the JEMRMS is planned to have two manipulators controlled by a common H/C at this stage. The H/C was able to be used as a rate control joystick and a force reflection master arm, using an experimental 6 DOF manipulator. Good maneuverability was confirmed in the verification test. The orthogonal type H/C is suitable for use as a common H/C for the two manipulators of the JEMRMS

Metallosupramolecular Structures Derived from a Series of Diphosphine-bridged Digold (I) Metalloligands with Terminal D-Penicillamine

This is the accepted version of the following article: N. Yoshinari and T. Konno, "Metallosupramolecular Structures Derived from a Series of Diphosphine-bridged Digold(I) Metalloligands with Terminal d-Penicillamine," Chem. Rec., 16(3), 1647–1663, John Wiley & Sons, 2016, which has　been published in final form at http://dx.doi.org/10.1002/tcr.201600026. This article may be used for non-commercial purposes in accordance with the Wiley Self-Archiving Policy

A histochemical study on hydrolytic and oxidative enzymes in human sarcomas

Histochemical evaluations of human sarcomas such as reticulum cell sarcoma, fibrosarcoma, lymphosarcoma and neurofibrosarcoma, were carried out with five hydrolytic enzymes and eight oxidative enzymes. The activities of acid phosphatase and beta-glucuronidase were slightly positive in the neoplastic cells observed. Beta-esterase activity was also positive but varied according to the kind of sarcomas. Alkaline phosphatase activity was faint or negative in sarcoma cells, though positive in capillary walls. Leucine aminopeptidase activity was negative giving not any appreciable coloration of the cell as far as the method employed is concerned. Among the activities of dehydrogenases, the most intense activity was observed in lactic dehydrogenase. The activities of succinic and beta-hydroxybutyric dehydrogenases were slight. The activities of alpha-glycerophosphate, glutamic and betahydroxybutyric dehydrogenases were faint or slight. The activities of NADPlinked dehydrogenases, glucose-6-phosphate and isocitric dehydrogenase were all faint or slight in these sarcoma cells.</p

cyclo-Tetrakis(μ_2-D-penicillaminato-κ^4N,S:O,S)tetrapalladium(II) 9.75-hydrate

This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited