A computer program for estimating size distribution of spherical organelles from electron micrographs

Size distributions of intracellular organelles in an ultra-thin section are usually distorted when the section thickness is not negligible. A computer program is developed here to estimate true size distributions of spherical organelles from transmission electron micrographs of ultra-thin sections. The method is applied to determine size distributions of chromaffin granules isolated from bovine adrenal medullary cells as a basis for further physiological measurements

Immunocytochemical Analysis of α-Tubulin Distribution Before and After Rapid Axopodial Contraction in the Centrohelid Raphidocystis contractilis

The centrohelid Raphidocystis contractilis is a heliozoan that has many radiating axopodia, each containing a bundle of microtubules. Although the rapid contraction of the axopodia at nearly a video rate (30 frames/s) is induced by mechanical stimuli, the mechanism underlying this phenomenon in R. contractilis has not yet been elucidated. In the present study, we described for the first time an adequate immunocytochemical fixation procedure for R. contractilis and the cellular distribution of α-tubulin before and after rapid axopodial contraction. We developed a flow-through chamber equipped with a micro-syringe pump that allowed the test solution to be injected at a flow rate below the threshold required to induce rapid axopodial contraction. Next, we used this injection method for evaluating the effects of different combinations of two fixatives (paraformaldehyde or glutaraldehyde) and two buffers (phosphate buffer or PHEM) on the morphological structure of the axopodia. A low concentration of glutaraldehyde in PHEM was identified as an adequate fixative for immunocytochemistry. The distribution of α-tubulin before and after rapid axopodial contraction was examined using immunocytochemistry and confocal laser scanning fluorescence microscopy. Positive signals were initially detected along the extended axopodia from the tips to the bases and were distributed in a non-uniform manner within the axopodia. Conversely, after the induction of a rapid axopodial contraction, these positive signals accumulated in the peripheral region of the cell. These results indicated that axopodial microtubules disassemble into fragments and/ or tubulin subunits during rapid axopodial contraction. Therefore, we hypothesize that the mechanism of extremely rapid axopodial contraction accompanied by cytoskeletal microtubule degradation in R. contractilis involves microtubule-severing at multiple sites

Cytoskeletal elements in an acoelomorph worm, Praesagittifera naikaiensis

Acoel flatworms can move in a variety of ways such as muscular and ciliary movements via cytoskeletal elements and their neural regulations. However, those locomotive mechanisms have not yet been fully elucidated. In this study, we examined the distribution of cytoskeletal elements including filamentous actin (F-actin) and tubulin, and the neuroanatomical organization in an acoelomorph worm, Praesagittifera naikaiensis (P. naikaiensis). Video microscopy revealed the elongation/contraction and the bending/rotation processes, and the ciliary gliding movement of P. naikaiensis. Histochemical and morphological analysis demonstrated that F-actin networks of inner longitudinal and outer circular muscle fibers were positioned along the entire surface of the body, and that the average distance between the circular muscle fibers in the contracted organism was decreased in the anterior region compared with that in the elongated organism. Electron microscopy showed dense bodies on the muscle cells of P. naikaiensis, which indicates that those muscle cells have the appearance of vertebrate smooth muscle cells. Immunohistochemical analysis revealed that -tubulin-positive signals on the ciliary microtubules had close contact with the F-actin network, and that neurite bundles labelled with anti dSap47 antibody as a neuronal marker run along the anterior-posterior body axis. These results indicate that the well-organized cytoskeletal elements and their neural control systems are preserved in P. naikaiensis, and that their mechanisms involved in those regulation systems are similar to those vertebrate systems. Further studies are needed to clarify the physiological mechanisms underlying the muscular and ciliary movements in P. naikaiensis

Structure and function of tegmentum vasculosum in avian cochlea

In spite of the importance of endocochlear DC potential (EP) and the K+-rich endolymph for the avian cochlea, the structure and function of the tegmentum vasculosum (TV) has not yet been fully elucidated, compared with those of the stria vascularis in the mammalian cochlea. In this study, we examined structural analysis of the epithelial cells, gene expressions of Na+-K+-ATPase (Atp1A1) and Kir4.1 (Kcnj10), and protein localizations of Na+-K+-ATPase and Kir4.1, in the TV. Tight junctional structures were observed between epithelial dark cells and light cells in the TV. Both Atp1a1 and Kcnj10 genes were detected in the TV. In addition, immunopositive signals for both Na+-K+-ATPase and Kir4.1 were recognized in the TV. These results indicate that Na+-K+-ATPase and Kir4.1 play roles in maintaining the EP and high K+ concentration of the endolymph. Further studies are needed to clarify the physiological functions of the TV. This is the first report which demonstrates that gene and protein expression data contribute to the avian inner ear homeostasis

The New Type of Lectures on the Development of Science Teaching Plans and Materials Tried in the Department ofEducation

岡山大学教育学部の理科教育講座に所属する3年生を対象に,理科教材･授業案開発を指向した新しい講義を始めたのでその報告を行う｡本講義では,近隣の小,中学校や公民館,科学館等の協力も得て実践の場を確保し,開発した教材や授業案を実践することで生きた教材開発の訓練を行なうことを目指している｡教科内容学担当教員と教科教育学担当教員の協働を模索すると同時に,大学教員の教科内容の専門知識や技量を教材や授業案に有効に活用できる講義を意識した。This is a report of the new type of lectures on the development of teaching plans and teaching materials attempted in the science class for 3rd grade students in the Department of Education Okayama Universlty. The students practiced the development of teaching plans and teaching materials, and they conducted their activities not only at university but also at the neighboring schools, the public hall, the science museum etc. We expected the development of further collaboration in the academic staffs in the science education course, and the science abilities will be helpful for the development of teaching plans and teaching materials

Engineered Heart Tissue: A Novel Tool to Study the Ischemic Changes of the Heart In Vitro

Background: Understanding the basic mechanisms and prevention of any disease pattern lies mainly on development of a successful experimental model. Recently, engineered heart tissue (EHT) has been demonstrated to be a useful tool in experimental transplantation. Here, we demonstrate a novel function for the spontaneously contracting EHT as an experimental model in studying the acute ischemia-induced changes in vitro. Methodology/Principal Findings: EHT was constructed by mixing cardiomyocytes isolated from the neonatal rats and cultured in a ring-shaped scaffold for five days. This was followed by mechanical stretching of the EHT for another one week under incubation. Fully developed EHT was subjected to hypoxia with 1 % O2 for 6 hours after treating them with cell protective agents such as cyclosporine A (CsA) and acetylcholine (ACh). During culture, EHT started to show spontaneous contractions that became more synchronous following mechanical stretching. This was confirmed by the increased expression of gap junctional protein connexin 43 and improved action potential recordings using an optical mapping system after mechanical stretching. When subjected to hypoxia, EHT demonstrated conduction defects, dephosphorylation of connexin-43, and down-regulation of cell survival proteins identical to the adult heart. These effects were inhibited by treating the EHT with cell protective agents. Conclusions/Significance: Under hypoxic conditions, the EHT responds similarly to the adult myocardium, thus making EHT a promising material for the study of cardiac functions in vitro

The Lectures on the Development of Teaching Plans and Teaching Materials Tried in the Science Education Class in Master's Course, Okayama University

岡山大学大学院教育学研究科の理科教育専攻の講義として、教材開発・授業案開発をテーマとした新しい講義を試みたのでその報告を行う。本講義は、理科教育講座に所属する大学院生、理科教育講座の大学教員、附属学校の理科関係の教諭が三者協働で進めることが特徴である。課題設定、教材開発を含めた実践準備および実践を院生チームを組み遂行させ、さらに経験や専門性の異なる人材と論議を重ねて活動を進めることを通じ、将来、協働で学校現場の課題提案・解決を行うことのできる能力を養うことを目標とした。This is a report of the new type of lectures on the development of teaching plans and teaching materials attempted in the science class in the Master's Course, Okayama University. The lectures were conducted in collaboration of the graduate students and the academic staffs in the science education course, and the science teachers of the attached school of Okayama University. The graduate students were grouped into two teams of five or six people, assigned to decide on themes, prepare and practice the development of teaching plans and teaching materials. They conducted their activities discussing problems with people of different experience and specialty, thus developing the ability to jointly propose and solve problems at schools in future