University of Tokyo

About: University of Tokyo is a education organization based out in Tokyo, Japan. It is known for research contribution in the topics: Population & Gene. The organization has 134564 authors who have published 337567 publications receiving 10178620 citations. The organization is also known as: Todai & Universitas Tociensis.

Concise review: isolation and characterization of cells from human term placenta: outcome of the first international Workshop on Placenta Derived Stem Cells.

Abstract: Placental tissue draws great interest as a source of cells for regenerative medicine because of the phenotypic plasticity of many of the cell types isolated from this tissue. Furthermore, placenta, which is involved in maintaining fetal tolerance, contains cells that display immunomodulatory properties. These two features could prove useful for future cell therapy-based clinical applications. Placental tissue is readily available and easily procured without invasive procedures, and its use does not elicit ethical debate. Numerous reports describing stem cells from different parts of the placenta, using nearly as numerous isolation and characterization procedures, have been published. Considering the complexity of the placenta, an urgent need exists to define, as clearly as possible, the region of origin and methods of isolation of cells derived from this tissue. On March 23-24, 2007, the first international Workshop on Placenta Derived Stem Cells was held in Brescia, Italy. Most of the research published in this area focuses on mesenchymal stromal cells isolated from various parts of the placenta or epithelial cells isolated from amniotic membrane. The aim of this review is to summarize and provide the state of the art of research in this field, addressing aspects such as cell isolation protocols and characteristics of these cells, as well as providing preliminary indications of the possibilities for use of these cells in future clinical applications.

Insect olfactory receptors are heteromeric ligand-gated ion channels

Abstract: In many organisms, from worms to humans, olfactory cues are detected by large families of seven transmembrane-spanning receptors, which have until now been classified as G protein-coupled receptors. Insects, however, have evolved a surprisingly simple and efficient sense of smell in which the odorant receptors require a second component — the ion-channel-forming chaperone protein Or83b — for correct function. In the first of two related papers, Sato et al. show that these heteromeric receptors form ligand-gated cation channels that are not dependent on G protein-coupled second messengers, and speculate that other seven transmembrane-spanning proteins may show similar ion channel activity. Wicher et al. show that, in addition to direct channel activation, ligand binding to odorant receptors causes G protein-coupled channel activation. This work has implications for the search for insect odorant receptor inhibitors for possible use in controlling host seeking behaviour of disease carrying insects such as the mosquito. Olfactory cues are detected by large families of seven transmembrane-spanning receptors, which have until now been classified as G-protein-coupled receptors. In insects, these odorant receptors require a second protein (Or83b) for correct function. These heteromeric receptors form ligand-gated cation channels that are not dependent on G protein-coupled second messengers and it is speculated that seven other transmembrane-spanning proteins may show similar ion channel activity. In insects, each olfactory sensory neuron expresses between one and three ligand-binding members of the olfactory receptor (OR) gene family, along with the highly conserved and broadly expressed Or83b co-receptor1,2,3,4,5,6,7,8,9. The functional insect OR consists of a heteromeric complex of unknown stoichiometry but comprising at least one variable odorant-binding subunit and one constant Or83b family subunit10,11,12,13,14,15,16. Insect ORs lack homology to G-protein-coupled chemosensory receptors in vertebrates17 and possess a distinct seven-transmembrane topology with the amino terminus located intracellularly10,18. Here we provide evidence that heteromeric insect ORs comprise a new class of ligand-activated non-selective cation channels. Heterologous cells expressing silkmoth, fruitfly or mosquito heteromeric OR complexes showed extracellular Ca2+influx and cation-non-selective ion conductance on stimulation with odorant. Odour-evoked OR currents are independent of known G-protein-coupled second messenger pathways. The fast response kinetics and OR-subunit-dependent K+ ion selectivity of the insect OR complex support the hypothesis that the complex between OR and Or83b itself confers channel activity. Direct evidence for odorant-gated channels was obtained by outside-out patch-clamp recording of Xenopus oocyte and HEK293T cell membranes expressing insect OR complexes. The ligand-gated ion channel formed by an insect OR complex seems to be the basis for a unique strategy that insects have acquired to respond to the olfactory environment.

Elevated blood pressure and craniofacial abnormalities in mice deficient in endothelin-1.

Abstract: The endothelin-1 (ET-1) gene was disrupted in mouse embryonic stem cells by homologous recombination to generate mice deficient in ET-1. These ET-1-/- homozygous mice die of respiratory failure at birth and have morphological abnormalities of the pharyngeal-arch-derived craniofacial tissues and organs. ET-1+/- heterozygous mice, which produce lower levels of ET-1 than wild-type mice, develop elevated blood pressure. These results suggest that ET-1 is essential for normal mouse development and may also play a physiological role in cardiovascular homeostasis.

Roles of continuous neurogenesis in the structural and functional integrity of the adult forebrain

Abstract: Neurogenesis occurs continuously in the forebrain of adult mammals, but the functional importance of adult neurogenesis is still unclear. Here, using a genetic labeling method in adult mice, we found that continuous neurogenesis results in the replacement of the majority of granule neurons in the olfactory bulb and a substantial addition of granule neurons to the hippocampal dentate gyrus. Genetic ablation of newly formed neurons in adult mice led to a gradual decrease in the number of granule cells in the olfactory bulb, inhibition of increases in the granule cell number in the dentate gyrus and impairment of behaviors in contextual and spatial memory, which are known to depend on hippocampus. These results suggest that continuous neurogenesis is required for the maintenance and reorganization of the whole interneuron system in the olfactory bulb, the modulation and refinement of the existing neuronal circuits in the dentate gyrus and the normal behaviors involved in hippocampal-dependent memory.