eyeless/Pax6 controls the production of glial cells in the visual center of Drosophila melanogaster

AbstractPax6 is known as a neurogenic factor in the development of the central nervous system and regulates proliferation of neuronal progenitor cells and promotes neuronal differentiation. In addition to neurogenesis, Pax6 is also involved in the specification and maturation of glial cells. Here, we show that Eyeless (Ey), Drosophila homolog of Pax6, regulates the production of glial cells in the brain. In the developing fly visual center, the production of neurons and glial cells are controlled by the temporal transcription factors that are sequentially expressed in neuroblasts (NBs). Among them, NBs of the last temporal window produce astrocyte-like glial cells. Ey is strongly expressed in the middle aged NBs, whose temporal window is earlier compared with glia producing older NBs. Weak Ey expression is also detected in the glia producing NBs. Our results suggest that Ey expression in the middle aged NBs indirectly control gliogenesis from the oldest NBs by regulating other temporal transcription factors. Additionally, weak Ey expression in the NBs of last temporal window may directly control gliogenesis. Ey is also expressed in neurons produced from the NBs of Ey-positive temporal window. Interestingly, neuron-specific overexpression of Ey causes significant increase in glial cells suggesting that neuronal expression of Ey may also contribute to gliogenesis. Thus, Pax6-dependent regulation of astrocyte-like glial development is conserved throughout the animal kingdom

Measurement of Tritium Partial Pressure by BIXS (I) : Total Pressure Dependence of Hydrogen Isotopes

The correlation between the intensity of X-rays induced by β-rays of tritium and the total pressure of hydrogen isotope mixtures was examined in a pressure range from 10-1 to 105 Pa by using three different tritium gases, i.e., pure T2, D2-1%T2 and H2-1%T2 mixtures. It was found that linear pressure dependence was obtained up to a few kPa for all of the measured gases by taking dead time of the X-ray detector into account. Above this pressure, however, downward deviation from the linear relation appeared. It was revealed that the effect of self-absorption of β-rays on the pressure dependence was not negligibly small, because the ratios of the counting rates corrected by dead time to total pressure, i.e., specific counting rates, could not be reproduced by a simple exponential function using the absorption coefficients of hydrogen isotopes as variables. The results suggested that an additional factor such as contribution of an X-ray formation on the surfaces of a measuring cell must be taken into consideration in changing in the specific counting rates