The mammalian central nervous synaptic cleft contains a high density of periodically organized complexes.

Cryo-electron microscopy of vitreous section makes it possible to observe cells and tissues at high resolution in a close-to-native state. The specimen remains hydrated; chemical fixation and staining are fully avoided. There is minimal molecular aggregation and the density observed in the image corresponds to the density in the object. Accordingly, organotypic hippocampal rat slices were vitrified under high pressure and controlled cryoprotection conditions, cryosectioned at a final thickness of approximately 70 nm and observed below -170 degrees C in a transmission electron microscope. The general aspect of the tissue compares with previous electron microscopy observations. The detailed analysis of the synapse reveals that the density of material in the synaptic cleft is high, even higher than in the cytoplasm, and that it is organized in 8.2-nm periodic transcleft complexes. Previously undescribed structures of presynaptic and postsynaptic elements are also described.

Histone-specific RNA 3' processing in nuclear extracts from mammalian cells.

The mature 3' ends of histone mRNAs are formed by endonucleolytic cleavage of longer precursor transcripts. This process occurs in the nucleus and can be regarded as the equivalent of the polyadenylation reaction involved in 3′-end-generation of all other mRNAs. A sea urchin H3 gene that failed to be properly processed in the Xenopus oocyte system proved particularly useful, because it allowed the identification of a processing component from sea urchins by a complementation assay. Nuclear extracts prepared from cells under various growth conditions have helped to reveal proliferation-dependent changes in the efficiency of histone RNA 3′ processing. RNA substrates for in vitro processing are best prepared by runoff transcription of specific DNA templates with bacterial or phage RNA polymerases. For this purpose, a restriction fragment containing the 3′-terminal region of a histone gene and including the conserved palindrome and spacer motifs is cloned into a polylinker sequence downstream of a strong promoter.

The CODE MGEX orbit and clock solution

The Center for Orbit Determination in Europe (CODE) is contributing as a global Analysis center to the International GNSS Service (IGS) since many years. The processing of GPS and GLONASS data is well established in CODE’s ultra-rapid, rapid, and final product lines. With the introduction of new signals for the established and new GNSS, new challenges and opportunities are arising for the GNSS data management and processing. The IGS started the Multi-GNSS-EXperiment (MGEX) in 2012 in order to gain first experience with the new data formats and to develop new strategies for making optimal use of these additional measurements. CODE has started to contribute to IGS MGEX with a consistent, rigorously combined triple-system orbit solution (GPS, GLONASS, and Galileo). SLR residuals for the computed Galileo satellite orbits are of the order of 10 cm. Furthermore CODE established a GPS and Galileo clock solution. A quality assessment shows that these experimental orbit and clock products allow even a Galileo-only precise point positioning (PPP) with accuracies on the decimeter- (static PPP) to meter-level (kinematic PPP) for selected stations.