S. J. Chae

Optogenetic control of endogenous Ca 2+ channels in vivo

Calcium (Ca2+) signals that are precisely modulated in space and time mediate a myriad of cellular processes, including contraction, excitation, growth, differentiation and apoptosis. However, study of Ca2+ responses has been hampered by technological limitations of existing Ca2+-modulating tools. Here we present OptoSTIM1, an optogenetic tool for manipulating intracellular Ca2+ levels through activation of Ca2+-selective endogenous Ca2+ release−activated Ca2+ (CRAC) channels. Using OptoSTIM1, which combines a plant photoreceptor and the CRAC channel regulator STIM1 (ref. 4), we quantitatively and qualitatively controlled intracellular Ca2+ levels in various biological systems, including zebrafish embryos and human embryonic stem cells. We demonstrate that activating OptoSTIM1 in the CA1 hippocampal region of mice selectively reinforced contextual memory formation. The broad utility of OptoSTIM1 will expand our mechanistic understanding of numerous Ca2+-associated processes and facilitate screening for drug candidates that antagonize Ca2+ signals.

Thalamic T-Type Ca2+ Channels Mediate Frontal Lobe Dysfunctions Caused by a Hypoxia-Like Damage in the Prefrontal Cortex

Hypoxic damage to the prefrontal cortex (PFC) has been implicated in the frontal lobe dysfunction found in various neuropsychiatric disorders. The underlying subcortical mechanisms, however, have not been well explored. In this study, we induced a PFC-specific hypoxia-like damage by cobalt-wire implantation to demonstrate that the role of the mediodorsal thalamus (MD) is critical for the development of frontal lobe dysfunction, including frontal lobe-specific seizures and abnormal hyperactivity. Before the onset of these abnormalities, the cross talk between the MD and PFC nuclei at theta frequencies was enhanced. During the theta frequency interactions, burst spikes, known to depend on T-type Ca2+ channels, were increased in MD neurons. In vivo knockout or knockdown of the T-type Ca2+ channel gene (CaV3.1) in the MD substantially reduced the theta frequency MD–PFC cross talk, frontal lobe-specific seizures, and locomotor hyperactivity in this model. These results suggest a two-step model of prefrontal dysfunction in which the response to a hypoxic lesion in the PFC results in abnormal thalamocortical feedback driven by thalamic T-type Ca2+ channels, which, in turn, leads to the onset of neurological and behavioral abnormalities. This study provides valuable insights into preventing the development of neuropsychiatric disorders arising from irreversible PFC damage.

High-spin isomer and level structure of 145Sm

Abstract High-spin states of 145 Sm were studied by using the reactions 20 Ne( 136 Xe,α7n), 16 O( 136 Xe,7n), 139 La( 10 B,4n) and 138 Ba( 13 C,6n). The level scheme was extended up to the state at 14.6 MeV. The excitation energy and the spin-parity of the 0.96 μs high-spin isomer were determined to be 8.8 MeV and ( 49 2 + ), respectively. Experimental results were discussed comparing with the deformed independent particle model calculation. High-spin isomers observed in N = 83 isotones were interpreted to be caused by the sudden shape change from near spherical to oblate. The Z = 64 shell gap energy was found to decrease from 2.4 to 2.0 MeV as the proton number decreases from Z = 64 to 61.

Left brain cortical activity modulates stress effects on social behavior.

When subjected to stress, some individuals develop maladaptive symptoms whereas others retain normal behavior. The medial prefrontal cortex (mPFC) is known to control these adaptive responses to stress. Here, we show that mPFC neurons in the left hemisphere control stress effects on social behavior. Mice made socially avoidant by the stress of chronic social defeats showed depressed neural activity in the left mPFC. Photoactivation of these neurons reversed social avoidance and restored social activity. Despite social defeats, resilient mice with normal sociability showed normal firing rates in the left mPFC; however, photoinhibition of these neurons induced social avoidance. The same photomodulation administered to the right mPFC caused no significant effects. These results explain how stressed individuals develop maladaptive behaviors through left cortical depression, as reported in mood and anxiety disorders.

Coulomb excitation of 174Hf K-isomer. γ-ray spectroscopy with high-spin isomer beam

Abstract A new experimental technique utilizing a high-spin isomer beam (HSIB) has been developed. The HSIB of 174Hf was produced by the 9Be(170Er, 5n)174Hf reaction in inverse kinematics. By using the HSIB, the Coulomb excitation of the Kπ = 8− isomer in 174Hf was measured. The γ-rays from the 9− level, which is the first excited state built on the isomer, were observed as well as the cascade γ-rays of the ground-state rotational band. From the measured γ-ray yield, a value of 2 ± 1 e2b2 was extracted for the B(E2: 8− → 9−). This is the first experiment of γ-ray spectroscopy by means of the HSIB-induced secondary reactions.

Energy measurement of 50 MeV proton beam with a NaI(Tl) scintillator

Abstract Energy measurement of 50 MeV proton beam produced on the AVF MC-50 Cyclotron was conducted using a detector telescope with a NaI(Tl) scintillator as an E counter. Protons of various energies, elastically and inelastically scattered from the 12 C target nucleus were measured at four different angles of 35°, 40°, 50° and 55°. We applied the chi-square method to determine the beam energy, which showed a well defined minimum chi-square corresponding to a beam energy of 49.6 ± 2.3 MeV at the 68% confidence level. Also the light output response of NaI(Tl) to proton energies between 31 and 44 MeV is linear within 0.5 MeV and is in good accord with the recent result of Romero et al. [Nucl. Instr. and Meth. A 301 (1991) 241].

Rotational bands in115Sb

High-spin states of115Sb were studied by inbeamγ-ray spectroscopy using the89Y (29Si, 2pn) fusionevaporation reaction at a beam energy of 108 MeV. The experiments includedγ-γ coincidence and directional correlation of oriented nuclei (DCO) ratio measurements using six BGO Compton suppressed Ge detectors. An intruderΔJ=2 rotational band has been identified for the first time and it is interpreted as the h11/2 proton coupled to a two particle-two hole (2p − 2h) deformed state of the114Sn core. A ΔJ=1 rotational band based on the 2p − 1h, π{g72/2⊗g92/−1}, configuration has been extended to the 29/2+ state at an excitation energy of 5241 keV.

High-spin states of odd-odd156Ho

High spin states in the nucleus156Ho have been studied via the fusion-evaporation reaction140Ce(19F,3nγ)156Ho at the beam energy of 82 MeV.γ-γ coincidences, Eγ, Iγ and excitation functions have been measured. With two rotationally-aligned bands identified as π[h11/2]ν [i13/2], we found two new bands with a signature splitting, whose structure is believed to arise from either ν[h9/2] or ν[f7/2] coupled to π[h11/2]. Our placement of γ rays belonging to these new bands suggests that the previously known level scheme should be corrected. We also found many new low-energy γ rays in the low excitation energy. As compared to154Ho, the present nucleus with two more neutrons becomes more collective, and shows well-observed rotationally-aligned bands with a clear signature splitting.

High-spin states of145Sm

High-spin states of145Sm were studied by using the20Ne(136Xe, α7n),139La (10B, 4n) and138Ba(13C,6n) reactions. The decay scheme of a high-spin isomer of145Sm was established. The excitation energy and the spin-parity of the isomer were determined to be 8.8 MeV and (49/2+), respectively. The level scheme was extended up to the (65/2) state at 14.6 MeV. The experimental results were discussed comparing with the deformed independent particle model (DIPM) calculation.

High-spin isomers and high-spin isomer beams

Yrast traps were found in N=83 isotones, 144Pm and 145Sm, by using inverse kinematic reactions, 14N(136Xe, 6n)144Pm and 16O(136Xe, 7n)145Sm. Their probable spin-parities are (27+) and (492+), respectively. Excitation energies of these isomers are 7.5 and 8.7 MeV Reaction products were transported by a gas filled recoil ion separation system and collected at 6 m down stream of the primary target position . The possible utilization of these high-spin isomers as secondary beams are discussed.