On the glutamine and γ-aminobutyric acid contents of various regions of the cat brain

Résumé Les auteurs ont déterminé par la méthode de la chromatographie à deux dimensions, la teneur en glutamine et en acide -aminobutyrique des différentes parties du cerveau du chat. La concentration la plus élevée de l'acide -aminobutyrique a été trouvé dans l'hypothalamus, tandis que celle de la glutamine a été constatée dans le noyau caudé. Les concentrations les plus basses de ces deux protéines apparaissent dans la substance blanche du cerveau.     

"数字地球"时代的我国西部可持续发展

“数字地球”作为新世纪信息时代的新目标和制高点,必将在西部大开发战略的实施过程中起到至关重要的作用。从“数字地球”的基本概念出发,应用“数字地球”的理论和技术,阐述了“数字地球”技术对西部大开发的战略意义和应用方向,为我国西部地区的可持续发展提供了新的思路和技术方法。     

Hox cluster disintegration with persistent anteroposterior order of expression in Oikopleura dioica

Tunicate embryos and larvae have small cell numbers and simple anatomical features in comparison with other chordates, including vertebrates. Although they branch near the base of chordate phylogenetic trees, their degree of divergence from the common chordate ancestor remains difficult to evaluate. Here we show that the tunicate Oikopleura dioica has a complement of nine Hox genes in which all central genes are lacking but a full vertebrate-like set of posterior genes is present. In contrast to all bilaterians studied so far, Hox genes are not clustered in the Oikopleura genome. Their expression occurs mostly in the tail, with some tissue preference, and a strong partition of expression domains in the nerve cord, in the notochord and in the muscle. In each tissue of the tail, the anteroposterior order of Hox gene expression evokes spatial collinearity, with several alterations. We propose a relationship between the Hox cluster breakdown, the separation of Hox expression domains, and a transition to a determinative mode of development.     

The PSI-H subunit of photosystem I is essential for state transitions in plant photosynthesis

Photosynthesis in plants involves two photosystems responsible for converting light energy into redox processes. The photosystems, PSI and PSII, operate largely in series, and therefore their excitation must be balanced in order to optimize photosynthetic performance. When plants are exposed to illumination favouring either PSII or PSI they can redistribute excitation towards the light-limited photosystem. Long-term changes in illumination lead to changes in photosystem stoichiometry. In contrast, state transition is a dynamic mechanism that enables plants to respond rapidly to changes in illumination. When PSII is favoured (state 2), the redox conditions in the thylakoids change and result in activation of a protein kinase. The kinase phosphorylates the main light-harvesting complex (LHCII) and the mobile antenna complex is detached from PSII. It has not been clear if attachment of LHCII to PSI in state 2 is important in state transitions. Here we show that in the absence of a specific PSI subunit, PSI-H, LHCII cannot transfer energy to PSI, and state transitions are impaired.