Assessment of the developmental totipotency of neural cells in the cerebral cortex of mouse embryo by nuclear transfer

When neural cells were collected from the entire cerebral cortex of developing mouse fetuses (15.5–17.5 days postcoitum) and their nuclei were transferred into enucleated oocytes, 5.5% of the reconstructed oocytes developed into normal offspring. This success rate was the highest among all previous mouse cloning experiments that used somatic cells. Forty-four percent of live embryos at 10.5 days postcoitum were morphologically normal when premature and early-postmitotic neural cells from the ventricular side of the cortex were used. In contrast, the majority (95%) of embryos were morphologically abnormal (including structural abnormalities in the neural tube) when postmitotic-differentiated neurons from the pial side of the cortex were used for cloning. Whereas 4.3% of embryos cloned with ventricular-side cells developed into healthy offspring, only 0.5% of those cloned with differentiated neurons in the pial side did so. These facts seem to suggest that the nuclei of neural cells in advanced stages of differentiation had lost their developmental totipotency. The underlying mechanism for this developmental limitation could be somatic DNA rearrangements in differentiating neural cells

Plasma Confinement Studies in LHD

"The initial experiments of the Large Helical Device (LHD) have extended confinement studies on currentless plasmas to a large scale (R=3.9 m, a = 0.6 m). Heating by NBI of 3 MW has produced plasmas with a fusion triple product of 8 x 10^18 keVm^-3s at a magnetic field of 1.5T. An electron temperature of 1.5 keV and an ion temperature of l.1 keV have been achieved simultaneously at the line-averaged electron density of 1.5 x 10^19 m^-3. The maximum stored energy has reached 0.22 MJ with neither unexpected confinement deterioration nor visible MHD instabilities, which corresponds to =0.7%. Energy confinement times, reaching 0.17 s at the maximum, have shown a manner similar to the present scaling law derived from the existing medium sized helical devices, but improve on it by 50%. A distinguishing feature of a favorable dependence of energy confinement time on density remains in the present power density (~40kW/m^3) and the electron density (3x 10^19m^-3) regimes unlike L-mode in tokamaks. Temperatures of both electrons and ions as high as 200 eV have been observed at the outermost flux surface, which indicates a qualitative jump in performance from the helical devices to date. Spontaneously generated toroidal currents agree with the physical picture of neoclassical bootstrap currents. Change of magnetic configuration due to finite-beta eff\u27ect has been well described by the 3-D MHD equilibrium analysis. An escape of particles from the core region leading to a hollow density profile has been observed in hydrogen plasmas, which is mitigated through core fueling with a pellet injection or in helium discharges.

An Overview of the Large Helical Device Project

"AN OVERVIEW OF THE LARGE HELICAL DEVICE PROJECT. The Large Helical Device (LHD) has successfully started running plasma confinement experiments after a long construction period of eight years. During the construction and machine commissioning phases, a variety of milestones have been attained in fusion engineering, which successflly led to the first operation, and the first plasma was ignited on March 31, 1998. Two experimental campaigns are planned in 1998. In the first campaign, the magnetic flux mapping clearly demonstrated a nested structure of magnetic surfaces. The first plasma experiments were conducted with second harmonic 84-GHz and 82.6-GHz ECH at a heating power input of 0.35 MW. The magnetic field was set at 1.5 T in the first year so as to accumulate operational experience of the superconducting coils. In the second campaign, auxiliary heating with NBI at 3 MW has been carried out. The averaged electron densities up to 6x 10^19 m^-3 , central temperatures ranging 1.4 to 1.5 keV and stored energies up to 220 kJ have been attained despite the fact that impurity level is not yet minimized. The obtained scaling of energy confinement time has been found to be consistent with the ISS95 scaling law with some enhancement.