Artificial Rearing System for Praesagittifera naikaiensis (Acoela, Acoelomorpha) <Article>

Praesagittifera naikaiensis is an acoelomorph worm native to the seashore of the Seto Inland Sea. P. naikaiensis harbors a species of prasinophytes, Tetraselmis sp., as a symbiont. The symbiotic algae are acquired horizontally from the environment during the larval stage. In this study, we established a method for the rearing of adult P. naikaiensis as a first step toward using the animal in the study of development, evolution, and the symbiotic mechanism. We kept the animals in aquaria with closed seawater circulations. The bottom of the aquarium was half covered with sand collected from the seashore of the Seto Inland Sea. An LED light was suspended over the aquarium to aid photosynthesis. The system was maintained at a salinity of 32–33 ppt and a temperature of 14°C, on a 14-h light (35–80 μmol quanta m−2s−1)/10-h dark photoperiod. We succeeded in constantly producing sexually mature animals, independent of season. The system developed here will serve as a foundation for future studies on acoel evolution and development.本研究は科学研究費補助金(26924012)の助成を受けたものである

ポイントクラスターホウ オ モチイタ ヒザ カンセツ ウンドウ ノ セイド ケンテイ

The Point Cluster Technique （PCT） was developed in recent years for application in three-dimensional human motion analysis. Since the advance of this technique is to minimize the target marker position error that caused by skin deformation, PCT has been applied for knee joint movement analysis. In spite of the above-mentioned advantages the accuracy of PCT has not been verified clearly. In this study, to evaluate the accuracy of PCT we made inspecting tool that was composed by two body segments and one joint. Reflective markers were attached on the surface of two bodies and the maker positions were measured with 3-dimensional motion analysis system （VICON MX）, The joint angle and joint center position were calculated using the measured maker data by the PCT. At the same time the reference joint angle was measured using laser beam device. The differences of joint angles between calculated with PCT and reference data were within 0.6 degrees. The influence of knee marker placement error per unit length （mm） was 0.18 degrees （MAX） for angle, and .0.7 mm （MAX） for knee joint position. The influence of z-direction marker placement error was relatively small. To double the number of marker （30 point） achieved 1.6 times higher accuracy of knee joint position than that of 15-point marker. Increasing the number of marker could reduce the influence of marker placement error

A draft nuclear-genome assembly of the acoel flatworm Praesagittifera naikaiensis

Background:Acoels are primitive bilaterians with very simple soft bodies, in which many organs, including the gut, are not developed. They provide platforms for studying molecular and developmental mechanisms involved in the formation of the basic bilaterian body plan, whole-body regeneration, and symbiosis with photosynthetic microalgae. Because genomic information is essential for future research on acoel biology, we sequenced and assembled the nuclear genome of an acoel, Praesagittifera naikaiensis.Findings:To avoid sequence contamination derived from symbiotic microalgae, DNA was extracted from embryos that were free of algae. More than 290x sequencing coverage was achieved using a combination of Illumina (paired-end and mate-pair libraries) and PacBio sequencing. RNA sequencing and Iso-Seq data from embryos, larvae, and adults were also obtained. First, a preliminary ∼17–kilobase pair (kb) mitochondrial genome was assembled, which was deleted from the nuclear sequence assembly. As a result, a draft nuclear genome assembly was ∼656 Mb in length, with a scaffold N50 of 117 kb and a contig N50 of 57 kb. Although ∼70% of the assembled sequences were likely composed of repetitive sequences that include DNA transposons and retrotransposons, the draft genome was estimated to contain 22,143 protein-coding genes, ∼99% of which were substantiated by corresponding transcripts. We could not find horizontally transferred microalgal genes in the acoel genome. Benchmarking Universal Single-Copy Orthologs analyses indicated that 77% of the conserved single-copy genes were complete. Pfam domain analyses provided a basic set of gene families for transcription factors and signaling molecules.Conclusions:Our present sequencing and assembly of the P. naikaiensis nuclear genome are comparable to those of other metazoan genomes, providing basic information for future studies of genic and genomic attributes of this animal group. Such studies may shed light on the origins and evolution of simple bilaterians

50-nm Gate Schottky Source/Drain p-MOSFETs With a SiGe Channel

Abstract-We propose new SiGe channel p-MOSFETs with germano-silicide Schottky source/drains (S/Ds). The Schottky barrier-height (SBH) for SiGe is expected to be low enough to improve the injection of carriers into the SiGe channel and, as a result, current drivability is also expected to improve. In this letter, we demonstrate the proposed Schottky S/D p-MOSFETs down to a 50-nm gate-length. The drain current and transconductance are 339 A m and 285 S m at GS = DS = 1 5 V, respectively. By increasing the Ge content in the SiGe channel from 30% to 35%, the drive current and transconductance can be improved up to 23% and 18%, respectively. This is partly due to the lower barrier-height for strained Si 0 65 Ge 0 35 channel than those for strained Si 0 7 Ge 0 3 channel device and partly due to the lower effective mass of the holes

Effects of Active Conductance Distribution over Dendrites on the Synaptic Integration in an Identified Nonspiking Interneuron

The synaptic integration in individual central neuron is critically affected by how active conductances are distributed over dendrites. It has been well known that the dendrites of central neurons are richly endowed with voltage- and ligand-regulated ion conductances. Nonspiking interneurons (NSIs), almost exclusively characteristic to arthropod central nervous systems, do not generate action potentials and hence lack voltage-regulated sodium channels, yet having a variety of voltage-regulated potassium conductances on their dendritic membrane including the one similar to the delayed-rectifier type potassium conductance. It remains unknown, however, how the active conductances are distributed over dendrites and how the synaptic integration is affected by those conductances in NSIs and other invertebrate neurons where the cell body is not included in the signal pathway from input synapses to output sites. In the present study, we quantitatively investigated the functional significance of active conductance distribution pattern in the spatio-temporal spread of synaptic potentials over dendrites of an identified NSI in the crayfish central nervous system by computer simulation. We systematically changed the distribution pattern of active conductances in the neuron's multicompartment model and examined how the synaptic potential waveform was affected by each distribution pattern. It was revealed that specific patterns of nonuniform distribution of potassium conductances were consistent, while other patterns were not, with the waveform of compound synaptic potentials recorded physiologically in the major input-output pathway of the cell, suggesting that the possibility of nonuniform distribution of potassium conductances over the dendrite cannot be excluded as well as the possibility of uniform distribution. Local synaptic circuits involving input and output synapses on the same branch or on the same side were found to be potentially affected under the condition of nonuniform distribution while operation of the major input-output pathway from the soma side to the one on the opposite side remained the same under both conditions of uniform and nonuniform distribution of potassium conductances over the NSI dendrite

Genome evolution in the allotetraploid frog Xenopus laevis

To explore the origins and consequences of tetraploidy in the African clawed frog, we sequenced the Xenopus laevis genome and compared it to the related diploid X. tropicalis genome. We characterize the allotetraploid origin of X. laevis by partitioning its genome into two homoeologous subgenomes, marked by distinct families of ???fossil??? transposable elements. On the basis of the activity of these elements and the age of hundreds of unitary pseudogenes, we estimate that the two diploid progenitor species diverged around 34 million years ago (Ma) and combined to form an allotetraploid around 17-18 Ma. More than 56% of all genes were retained in two homoeologous copies. Protein function, gene expression, and the amount of conserved flanking sequence all correlate with retention rates. The subgenomes have evolved asymmetrically, with one chromosome set more often preserving the ancestral state and the other experiencing more gene loss, deletion, rearrangement, and reduced gene expression.ope

Changes in Cerebral Hemodynamics during Complex Motor Learning by Character Entry into Touch-Screen Terminals

Introduction Studies of cerebral hemodynamics during motor learning have mostly focused on neurorehabilitation interventions and their effectiveness. However, only a few imaging studies of motor learning and the underlying complex cognitive processes have been performed. Methods We measured cerebral hemodynamics using near-infrared spectroscopy (NIRS) in relation to acquisition patterns of motor skills in healthy subjects using character entry into a touchscreen terminal. Twenty healthy, right-handed subjects who had no previous experience with character entry using a touch-screen terminal participated in this study. They were asked to enter the characters of a randomly formed Japanese syllabary into the touchscreen terminal. All subjects performed the task with their right thumb for 15 s alternating with 25 s of rest for 30 repetitions. Performance was calculated by subtracting the number of incorrect answers from the number of correct answers, and gains in motor skills were evaluated according to the changes in performance across cycles. Behavioral and oxygenated hemoglobin concentration changes across task cycles were analyzed using Spearman\u27s rank correlations. Results Performance correlated positively with task cycle, thus confirming motor learning. Hemodynamic activation over the left sensorimotor cortex (SMC) showed a positive correlation with task cycle, whereas activations over the right prefrontal cortex (PFC) and supplementary motor area (SMA) showed negative correlations. Conclusions We suggest that increases in finger momentum with motor learning are reflected in the activity of the left SMC. We further speculate that the right PFC and SMA were activated during the early phases of motor learning, and that this activity was attenuated with learning progress

A systematic search and classification of T2 family miniature inverted-repeat transposable elements (MITEs) in Xenopus tropicalis suggests the existence of recently active MITE subfamilies

To reveal the genome-wide aspects of Xenopus T2 family miniature inverted-repeat transposable elements (MITEs), we performed a systematic search and classification of MITEs by a newly developed procedure. A terminal sequence motif (T2-motif: TTAAAGGRR) was retrieved from the Xenopus tropicalis genome database. We then selected 51- to 1,000-bp MITE candidates framed by an inverted pair of 2 T2-motifs. The 34,398 candidates were classified into possible clusters by a novel terminal sequence (TS)-clustering method on the basis of differences in their short terminal sequences. Finally, 19,242 MITEs were classified into 16 major MITE subfamilies (TS subfamilies), 10 of which showed apparent homologies to known T2 MITE subfamilies, and the rest were novel TS subfamilies. Intra-and inter-subfamily similarities or differences were investigated by analyses of diversity in GC content, total length, and sequence alignments. Furthermore, genome-wide conservation of the inverted pair structure of subfamily-specific TS stretches and their target site sequence (TTAA) were analyzed. The results suggested that some TS subfamilies might include active or at least recently active MITEs for transposition and/or amplification, but some others might have lost such activities a long time ago. The present methodology was efficient in identifying and classifying MITEs, thereby providing information on the evolutionary dynamics of MITEs

Artifi cial rearing and oviposition of Waminoa sp. (Acoela, Acoelomorpha) : Toward the development of a model system to study animal-algal symbiosis. <Articles>

Waminoa sp. is an acoelomorph worm that infests corals and harbors two species of dinofl agellates, Amphidinium sp. and Symbiodinium sp.. These symbiotic algae are inherited vertically from parent to offspring during oogenesis. In this study, we established a method for artificial breeding of Waminoa sp., as the first step toward using Waminoa sp. in the study of the mechanism underlying animal–algal symbiosis and the evolution of this symbiosis. We developed a system in which an aquarium circulated approximately 80 L of artifi cial seawater between an upper aquarium and a lower sump, each of which was 45 cm × 30 cm × 35 cm in size and contained 40 L of seawater. Water flowed into the upper aquarium from the sump alternately through a pipe outlet. The upper aquarium contained the hard coral Symphyllia valenciennesii, live rocks, and a layer of fine sand. A 150-W metal halide lamp was suspended over the aquarium to aid photosynthesis. The system was maintained at a salinity of 32–33 ppt and a temperature of 23°C, on a 14-h light (17–50 μmol quanta m-2s-1) : 10-h dark photoperiod. We succeeded in producing almost every stage of the life cycle of Waminoa sp., including the zygote, embryo, larva, juvenile, and adult stages, independent of seasons. In addition, we developed an artificial oviposition procedure that involved isolation from coral in the mature stage. The system developed in this study will serve as a foundation for future studies on acoel–algal symbiosis