Identification of genes differentially expressed in rat brain during postnatal development

During neuronal development CNS neurons extend axons over long distances. This high growth potential is lost during postnatal development resulting in very poor axonal outgrowth and regeneration in the adult CNS. This pronounced decline of axon growth potential and regenerative capability might be related to alterations in the expression level of growth-associated genes during postnatal development. The aim of the present study was the identification of candidate molecules that might be associated with axon growth, i.e. which are strongly expressed during axonal outgrowth and are downregulated as neuronal maturation proceeds. As the time periods of developmental axonal outgrowth and decrease in growth potential are well studied in rat cerebellum and entorhinal cortex, these two brain regions were chosen as model systems for analysis of gene expression patterns during axonal extension and after completion of pathway formation. In a first approach the study focused on the identification of transcription factors, because they are known to be involved in the regulation of cellular identity and differentiation and hence might also determine the intrinsic growth state of a neuron. In order to identify transcription factors from rat cerebellum and entorhinal cortex at the time of maximal axonal outgrowth, PCR with degenerate oligonucleotides, specific for the conserved DNA-binding domains of distinct transcription factor classes, was performed with cDNA from cerebellum at E18 and entorhinal cortex at P0, respectively. A limited number of PCR products could be isolated from the above brain regions by the use of primers for the POU and zinc finger family of transcription factors. Because of the small number of candidate molecules and considerable difficulties in constructing cDNA probes for further analysis this approach was not further pursued. A second approach aimed at the comparison of the transcriptional activity of young differentiating CNS neurons, which extend axons, with that of more mature neurons, which have lost growth competence. The method of suppression subtractive hybridisation (SSH) was performed in two distinct CNS tissues, rat cerebellum and entorhinal cortex, at two developmental stages (E18 and P35 for cerebellum and P0 an P10 for entorhinal cortex, respectively) in order to enrich for genes, which are downregulated during postnatal development. Several differentially expressed genes were identified, and the temporal and spatial expression pattern of some of these genes was further examined in rat brain by Northern- and in situ-hybridisation analysis at different developmental stages. One of the identified genes, rMMS2, was not known in the rat before and was characterised in this study for the first time. In addition, CRHSP-24, whose expression pattern had not previously been examined in the developing brain, was identified as a differentially expressed gene. Further analysis showed that rMMS2 and CRHSP-24 were strongly expressed in many brain regions during late embryonic and early postnatal development. Expression of both genes was significantly downregulated during the first postnatal weeks and was only weak or absent in the adult brain. As this regulated distribution correlates well with the time period of establishment of axonal connections in the developing brain, these molecules might play a role in neuronal differentiation processes. However, their function in neuronal development is not yet clear and remains to be elucidated. Because only a fraction of the enriched genes has been analysed by now the pool of subtracted genes might serve as a valuable source for the identification of further candidate genes, which might be associated with neuronal differentiation and axonal outgrowth

Editorial Lehrpraxis im Transfer

Es freut mich Ihnen die dreizehnte reguläre Ausgabe des Praxisjournals vorlegen zu können. Schwerpunkt dieser Ausgabe sind die Beiträge der 2016 abgeschlossenen Lehr-Lern-Projekte der 5. Kohorte im Verbundprojekt Lehrpraxis im Transfer

Photon-Upconverting Materials: Advances and Prospects for Various Emerging Applications

Rare-earth-doped upconversion materials, featuring exceptional photophysical properties including long lifetime, sharp emission lines, large anti-Stokes shift, low autofluorescence of the background, and low toxicity, are promising for many applications. These materials have been investigated extensively since the 1960s and employed in many optical devices. However, due to rapid development of synthesis strategies for nanomaterials, upconversion materials have been rehighlighted on the basis of nanotechnology. Herein, we discuss the recent advances in upconversion materials. We start by considering energy transfer processes involved in the basic study of upconversion emission phenomena, as well as synthesis strategies of these materials. Progress in different energy transfer processes, which play an important role in determining luminescence efficiency, is then discussed. Newer applications of these materials have been vastly reviewed

Three Dimensional Periodic U(1)U(1) Gauge Theory and Strings

It will be argued that among the known systems in three dimensions that have string like excitations periodic U(1) pure gauge theories are the most likely candidates to lead to a string representation of their universal properties. Some recent work with F. David will also be reviewed.Comment: 5

Development and characterization of high-frequency sources for supersonic beams of fluorine radicals

We present and compare two high-pressure, high-frequency electric-discharge sources for the generation of supersonic beams of fluorine radicals. The sources are based on dielectric-barrier-discharge (DBD) and plate-discharge units attached to a pulsed solenoid valve. The corrosion-resistant discharge sources were operated with fluorine gas seeded in helium up to backing pressures as high as 30 bar. We employed a (3+1) resonance-enhanced multiphoton ionization combined with velocity-map imaging for the optimization, characterization and comparison of the fluorine beams. Additionally, universal femtosecond-laser-ionization detection was used for the characterization of the discharge sources at experimental repetition rates up to 200 Hz. Our results show that the plate discharge is more efficient in F$_{2}$ dissociation than the DBD by a factor of 8-9, whereas the DBD produces internally colder fluorine radicals.Comment: 6 pages, 7 figure

Electrical conduction of ion tracks in tetrahedral amorphous carbon: temperature, field and doping dependence and comparison with matrix data

This paper gives an extended overview of the electrical properties of ion tracks in hydrogen-free tetrahedral amorphous carbon (ta-C) with a sp(3) bond fraction of about 80%. The films were grown by mass selected ion beam deposition of 100 eV C-12(+) ions. The ion tracks are generated by irradiation of ta-C films with uranium ions of 1 GeV kinetic energy. Along the ion path a conversion from diamondlike (sp(3)) carbon to graphite-like (sp(2)) carbon takes place. Topography and current measurements of individual ion tracks were performed by atomic force microscopy at ambient temperature. The temperature dependence of the electric conductivity was studied between 15 and 390 K by means of 0.28 mm(2) large contact pads averaging over about 10 7 tracks. For each sample and at each temperature the conductivity as a function of the applied electrical field (non-ohmic behaviour) was measured separately and the data were extrapolated to field zero. In this way, the zero-field conductivity was determined independent from the field dependence. In spite of large differences in the absolute values, the temperature dependence of the zero-field conductivities is found to be very similar in shape for all samples. The conductivities follow a T-1/4 law up to temperatures slightly below room temperature. At higher temperatures a transport mechanism based on over-barrier hopping dominates with an activation energy of about 220 meV for tracks and 260 meV for the ta-C matrix. The field dependence measurements show that the deviation of the I-V characteristics from ohmic behaviour decreases with increasing zero-field conductivity. We also tested Cu-doped ta-C samples and found that they conduct significantly better than pure ta-C. However, the doping also increases the zero-field conductivity resulting in a weaker contrast between the track and matrix. The data are interpreted within the so-called 'barrier model' where the electrons are assumed to move fairly freely in well-conducting sp(2) regions but encounter barriers in track sections consisting of more sp(3)-like bonds

Hyperfine resolved optical spectroscopy of the A²Π ←X²Σ⁺ transition in MgF

We report on hyperfine-resolved laser spectroscopy of the A2Π ←X2Σ+ transition of MgF, relevant for laser cooling. We recorded 25 rotational transitions with an absolute accuracy of better than 20 MHz, assigned 56 hyperfine lines and determined precise rotational, fine and hyperfine structure parameters for the A2Π state. The radiative lifetime of the A2Π state was determined to be 7.2(3) ns, in good agreement with \textit{ab initio} calculations. The transition isotope shift between bosonic isotopologues of the molecule is recorded and compared to predicted values within the Born-Oppenheimer approximation. We measured the Stark effect of selected rotational lines of the A2Π ←X2Σ+ transition by applying electric fields of up to 10.6 kV cm-1 and determined the permanent electric dipole moments of 24MgF in its ground X2Σ+ and first excited A2Π states to be μX=2.88(20) D and μA=3.20(22) D, respectively. Based on these measurements, we caution for potential losses from the optical cycling transition, due to electric field induced parity mixing in the excited state. In order to scatter 104 photons, the electric field must be controlled to below 1 V cm-1