精胺和亚精胺影响水稻种子萌发与温度的关系(简报)

在25℃下以0．01～1．0mmol·L-1精胺和0．01～0．1mmol·L-1亚精胺预处理水稻种子48h，可以提高16℃下萌发指数和活力指数，但对28℃下的种子萌发无影响。种子萌发时胚芽中α-淀粉酶活性和胚芽、胚根的呼吸速率的变化规律基本上与活力指数相似。     

Cytochemical localization of calcium in renal sac nephrocytes of Helix aspersa

In renal sac nephrocytes of Helix aspersa, intracellular calcium has been localized using the oxalate-pyroantimonate (OPA) and phosphate-pyroantimonate (PPA) methods. Pyroantimonate precipitates are preferentially localized in the excretory spherule and in vesicles located in the basal and lateral regions of the nephrocyte. Such vesicles appear to release their content into the excretory vacuole. Calcium may interact with diverse types of molecules present in the excretory vacuole, thus favouring stabilization and packaging of the excretory spherule.     

Three-dimensional structure of the regular surface glycoprotein layer of Halobacterium volcanii from the Dead Sea

A three-dimensional reconstruction from electron micrographs of negatively stained cell envelopes of Halobacterium volcanii has revealed the structure of the surface glycoprotein to a resolution of 2 nm. The glycoprotein is arranged on a p6 lattice with a lattice constant of 16.8 nm. It forms 4.5 nm high, dome-shaped, morphological complexes with a narrow pore at the apex opening into a `funnel' towards the cell membrane. The polarity of the structure was derived from freeze-etching experiments and `edge' views. Six radial protrusions emanate from each morphological complex and join around the 3-fold axis to provide lateral connectivity. Using the primary structure of the surface glycoprotein of the closely related species Halobacterium halobium (Lechner and Sumper, 1987) and the cell envelope profile from a previous X-ray analysis of the same species (Blaurock et al., 1976) we have integrated our reconstruction into a model of halobacterial cell envelope.