Internal Seminar: Shintake Unit and Maruyama Unit

Quantum Wave Microscopy Unit (Tsumoru Shintake)

Speaker : Tsumoru Shintake

Title : Technical Challenge for Low Energy Electron Microscope

Abstract : Today, the electron microscope has dramatically advanced in its resolution, exceeding Angstrom atomic resolutions by means of the aberration correction technology, such as, CS or CC effects. However, on the bio-sample imaging, in practice the available resolution is far below than the instrument resolution, because it is limited by the sample damage. Cooling the sample, like ice-embeded cryo-microscopy, damages of sample due to high energy electron impact can be tolerated, but still far from researchers wish, thus people need to rely on "averaging" on many sample assuming certain symmetry on the structure. For non symmetric structure, this technique does not work. We are challenging this difficulty by means of extremely low energy electron beam and diffraction microscopy technique.

Information Processing Biology Unit (Takashi Murayama)

Speaker : Takashi Murayama

Title : Behavioral changes in C. elegans chemotaxis to alkaline pH

Abstract : Monitoring of environmental and tissue pH is crucial for the survival of animals. The nematode C. elegans is an excellent model organism for the analysis of neural circuits that regulate animal behaviors. The animal is attracted to mildly alkaline pH, and avoids strongly alkaline pH. Our genetic dissection and Ca2+ imaging demonstrated that ASEL and ASH are the major sensory neurons responsible for attraction to mildly alkaline pH and repulsion from strongly alkaline pH, respectively. In ASEL, a transmembrane guanylyl cyclase, GCY-14, is activated by environmental alkalinization, and in turn, a cGMP-gated channel serves for Ca2+ influx into the sensory neuron. In ASH, TRPV channels are found to be required for the neural activation upon stimulation with strongly alkaline pH. To understand the animal’s behavioral changes at molecular and cellular levels, we have analyzed behaviors of mutants defective in ASEL and/or ASH under various alkaline pH, and have found that activities of ASEL and ASH compete each other for the behavioral change. While mildly alkaline pH preferentially activates ASEL, strongly alkaline pH activates both ASEL and ASH, and ASH activity overrides the activity of ASEL. Neural circuits responsible for this behavioral change will also be discussed.