Die Physik der Superhelden : James Kakalios zeigt, wie man mit Comics Physik lernt

Rezension zu: James Kakalios : Physik der Superhelden ; Aus dem Amerikanischen von Doris Gerstner und Christoph Hahn, Verlag Rogner & Bernhard bei Zweitausendeins, Berlin 2006, ISBN: 3807710183, 471 Seiten, 29,90 Euro

Bio – Matrices Interaction: from Microstructured Hydrogel Volumes and Hydrogel Surfaces

In vivo cellular behavior is highly relevant to understand for various diseases and future tissue engineering but challenging to study using traditional in vitro cell growth methods: Many cellular mechanism functions differently when cells are grown in three-dimensional (3D) conditions similar to in vivo conditions as in traditional 2D culture techniques. As it is known for some time that 2D cell cultures and their mechanical properties influence the cellular behavior, this is also true for the 3D environment. Especially for the stability of the nucleus, the subcellular compartment responsible for storing the main part of our DNA, the 3D environment, and the mechanical and structural properties of it are highly valuable. Considering an implant inside the body’s soft tissue, the mechanical and structural properties will mediate the cell-matrix interaction. Recent advances in biomaterial research have enabled both cell growth in 3D and increased control of the cell-matrix interaction on an artificial substrate, e.g., as with structured PDMS channels. Despite these advances, there remain challenges in this field. An essential challenge until now is the creation of 3D structured samples that display the properties of the extracellular matrix in a controllable manner. These properties are hydration for the diffusive exchange of nutrition, controllable variability of the mechanical properties, and highly controllable biofunctionalization in 3D. In this thesis, novel means of growing cells in 3D environments with defined mechanical properties, creating new bio-crosslinker and investigating substance release from hydrated matrices showing the power of biomaterial-cell interactions for life sciences and biomedical research are presented In the first part of this work, the 3D cell-matrix interactions are discussed using fibrosarcoma cells grown in 3D-microstructured hydrogel matrices with a range of controlled mechanical properties. With the tuning of the matrix stiffness, cell behavior was affected, creating a preference for specific positions within the structured environment. Interestingly, the mechanical properties of the matrix were also found to impact the nucleus, affecting the stability of the nuclear envelope, and the intracellular position of the nucleus during cell migration. The second part of this thesis focuses on two different approaches for cell-matrix interactions in two dimensions (2D). In the first approach, the focus is on the compliance of miniaturized biosensors to primary endothelial cells. In the second approach, a chemically engineered bio-crosslinker is presented for enhanced biofunctionalization and cell adhesion. For studying the new bio-crosslinker (BCL) effectiveness, cells were grown on pHEMA, a protein-inert hydrogel. Once inserted inside the pHEMA precursor mixture, the pHEMA hydrogels included free reactive groups and can be biofunctionalized with fibronectin instantly to support cell adhesion. In the final part of this thesis, I present a study of hydrogel matrices, which release different drugs. I demonstrate the influence of the drug solution on hydrogel swelling and its release for an anti-seizure drug. The possibility of matrix degradation within the incubation time is also investigated. Initial studies have shown that the substances were released over several days, attesting to the high suitability for indirect drug administration. In the second approach, an anti-inflammatory drug release from swollen hydrogel matrices is investigated. The aim here was to create an anti-inflammatory soft substratum for future tissue cuts. The results of the investigations presented in this work have also highlighted three essential features of biomaterials: matrix structural size, matrix topography or architecture, and dimensionality. Each element played a key role in the studies presented in this work, clearly demonstrating the importance of each when designing, and working with biomaterials

The synthesis of ammonia from hydrogen and atomic nitrogen on the Rh(110) surface

Catalytic synthesis of ammonia from hydrogen and atomic nitrogen was demonstrated on polycrystalline platinum and single crystal face Rh(110) catalysts. The atomic nitrogen was prepared by a microwave discharge in a nitrogen-hydrogen gas mixture and quantified by gas phase titration with nitric oxide. The afterglow from the microwave discharge was characterized spectroscopically; no NH, NH2, or NH3 species were found, and excited nitrogen species other than atomic nitrogen had sufficiently short half lives that a delay system permitted their complete decay before the afterglow reached the catalyst. Atomic nitrogen was therefore the only excited nitrogen species reaching the catalyst. No ammonia was formed in the absence of a catalyst. The rate of ammonia synthesis over Rh(110) was measured as a function of the partial pressures of N2, H2, and N over pressure ranges 100 \u3c PN2 \u3c 570 Pa, 110 PH2 \u3c 1000 Pa, 13 \u3c P N \u3c 160 Pa, 330 \u3c P Total \u3c 1200 Pa. The Reynolds number was on the order of 10[superscript]-3. Most measurements were made at 500°C, the turnover number for ammonia synthesis on Rh(110) varying from 0.0079 to 0.073 molecules site[superscript]-1 sec[superscript]-1. A study of the dependence of synthesis rate on Rh(110) on temperature at fixed reactant partial pressures covered the range 400° to 750°C;Over the partial pressure ranges covered at 500°C on Rh(110) the ammonia synthesis rate could be represented within experimental error by a model assuming it to be proportional to the nitrogen adatom coverage [theta] N only. The latter was interpreted through a steady state model in which the atomic nitrogen adsorption rate, proportional to P N and to (1 - [theta] N, was exactly balanced by rates loss of nitrogen adatoms due to ammonia synthesis (proportional to [theta] N) and to recombination and desorption as N2 (proportional to [theta]N[superscript]2). Variations in PN2 and PH2 only affected the synthesis rate insofar as they affected P N. At fixed microwave discharge power, however, P N varied considerably with PH2 and PN2, being approximately proportional to PH2 at fixed PN2 and for fixed PH2, going through a maximum as PN2 increased. Qualitative interpretations of this behavior are presented. For fixed partial pressures, the ammonia synthesis rate decreases as the temperature increases, i.e., the apparent activation energy is negative. Several possible interpretations of this behavior are presented. ftn[superscript]1DOE Report IS-T-1363. This work was performed under Contract W-7405-Eng-82 with the Department of Energy

Prelimbic Cortical Synaptic and Structural Plasticity Following Cocaine Self-administration and Abstinence in Rats: Role of Glutamatergic Pathway Specificity

The primary goal of this dissertation is to further examine the role of the prelimbic (PrL) subdivision of the rodent medial prefrontal cortex in relapse to cocaine seeking following abstinence, and to extend our understanding of pathway-specific adaptations in the PrL cortex projection to the nucleus accumbens (NAc) core that drives relapse. Previous findings indicate that the PrL cortex shows a biphasic response to abstinence from cocaine exposure. Specifically, early withdrawal (two hours after the final self-administration session) results in dephosphorylation of glutamate NMDA receptors and glutamate signaling regulators including extracellular signal-regulated kinase and the downstream transcription factor cAMP response-element binding protein (CREB). One week of abstinence enhances p-CREB and AMPA receptor subunit GluA1 phosphorylation in the PrL cortex, and Synapsin I in the NAc core. Interventions that act to normalize glutamate transmission in the PrL cortex during early withdrawal provide an enduring suppression of drug-seeking by normalizing activity in the PrL-NAc core pathway. Using a combination of biochemical and behavioral pharmacology techniques, we have found that the cocaine-induced activation of STriatal-Enriched protein tyrosine Phosphatase in the PrL cortex during early withdrawal plays a role in subsequent cocaine seeking by dephosphorylating extra-cellular signal-regulated kinase. We also show that chemogenetic-mediated activation of the PrL cortex, or PrL-NAc core neurons, immediately after self-administration transiently reduces drug seeking which is not sustained. Finally, using an array of immunohistochemistry, pathway-specific viral vectors, and high-resolution confocal microscopy techniques, we provide evidence that PrL-NAc core neurons show reduced immunoreactivity of the activity markers Fos and p-CREB, reduced dendritic spine head diameter, and reduced GluA1/2 expression in subsets of dendritic spines during early withdrawal. The opposite effect was found after one week of abstinence. At this timepoint, PrL-NAc core neurons showed heightened nuclear p-CREB, spine head diameter, and GluA1/2 expression in dendritic spines. These findings suggest that the PrL cortex, and specifically PrL-NAc core neurons, undergoes an abstinence duration-dependent transformation in glutamate transmission which may be regulated by the activation of STEP during early withdrawal