Processing two-dimensional X-ray diffraction and small-angle scattering data in DAWN 2

The Powder Calibration and Processing packages implemented in DAWN 2 provide an automated diffraction-geometry calibration and data processing environment for two-dimensional diffraction experiments. The customizable processing chains permit the execution of data processing steps to convert raw two-dimensional data into meaningful data and diffractograms. The provenance of the processed data is maintained, which guarantees reproducibility and transparency of the data treatment.

A software package for the calibration and processing of powder X-ray diffraction and small-angle X-ray scattering data is presented. It provides a multitude of data processing and visualization tools as well as a command-line scripting interface for on-the-fly processing and the incorporation of complex data treatment tasks. Customizable processing chains permit the execution of many data processing steps to convert a single image or a batch of raw two-dimensional data into meaningful data and one-dimensional diffractograms. The processed data files contain the full data provenance of each process applied to the data. The calibration routines can run automatically even for high energies and also for large detector tilt angles. Some of the functionalities are highlighted by specific use cases.

Activity-Dependent Exocytosis of Lysosomes Regulates the Structural Plasticity of Dendritic Spines

Lysosomes have traditionally been viewed as degradative organelles, although a growing body of evidence suggests that they can function as Ca²⁺ stores. Here we examined the function of these stores in hippocampal pyramidal neurons. We found that back-propagating action potentials (bpAPs) could elicit Ca²⁺ release from lysosomes in the dendrites. This Ca²⁺ release triggered the fusion of lysosomes with the plasma membrane, resulting in the release of Cathepsin B. Cathepsin B increased the activity of matrix metalloproteinase 9 (MMP-9), an enzyme involved in extracellular matrix (ECM) remodelling and synaptic plasticity. Inhibition of either lysosomal Ca²⁺ signaling or Cathepsin B release prevented the maintenance of dendritic spine growth induced by Hebbian activity. This impairment could be rescued by exogenous application of active MMP-9. Our findings suggest that activity-dependent exocytosis of Cathepsin B from lysosomes regulates the long-term structural plasticity of dendritic spines by triggering MMP-9 activation and ECM remodelling.

•

Back-propagating action potentials induce Ca²⁺ release from lysosomes in neurons

•

Lysosomal Ca²⁺ release triggers exocytosis of the lysosomal protease Cathepsin B

•

Cathepsin B maintains activity-dependent dendritic spine growth by activating MMP-9

Complete elliptical ring geometry provides energy and instrument calibration for synchrotron-based two-dimensional X-ray diffraction

A complete calibration method to characterize a static planar two-dimensional detector for use in X-ray diffraction at an arbitrary wavelength is described. This method is based upon geometry describing the point of intersection between a cone's axis and its elliptical conic section. This point of intersection is neither the ellipse centre nor one of the ellipse focal points, but some other point which lies in between. The presented solution is closed form, algebraic and non-iterative in its application, and gives values for the X-ray beam energy, the sample-to-detector distance, the location of the beam centre on the detector surface and the detector tilt relative to the incident beam. Previous techniques have tended to require prior knowledge of either the X-ray beam energy or the sample-to-detector distance, whilst other techniques have been iterative. The new calibration procedure is performed by collecting diffraction data, in the form of diffraction rings from a powder standard, at known displacements of the detector along the beam path.

Presynaptic NMDARs in the hippocampus facilitate transmitter release at theta frequency

A rise in [Ca(2+)](i) provides the trigger for neurotransmitter release at neuronal boutons. We have used confocal microscopy and Ca(2+) sensitive dyes to directly measure the action potential-evoked [Ca(2+)](i) in the boutons of Schaffer collaterals. This reveals that the trial-by-trial amplitude of the evoked Ca(2+) transient is bimodally distributed. We demonstrate that "large" Ca(2+) transients occur when presynaptic NMDA receptors are activated following transmitter release. Presynaptic NMDA receptor activation proves critical in producing facilitation of transmission at theta frequencies. Because large Ca(2+) transients "report" transmitter release, their frequency on a trial-by-trial basis can be used to estimate the probability of release, p(r). We use this novel estimator to show that p(r) increases following the induction of long-term potentiation.

Osteopetrosis, femoral fracture, and chronic osteomyelitis caused by Staphylococcus aureus small colony variants (SCV) treated by girdlestone resection--6-year follow-up

Chronic osteomyelitis caused by Staphylococcus aureus small colony variants in combination with osteopetrosis is a unique combination of disorders that confronted us with major challenges. The therapeutic approach included four serial debridements and antimicrobial therapy. The aggressive treatment led to an instability of the brittle and hard osteopetrotic bone, and after 11 weeks, a fracture of the femoral neck occurred. A salvage procedure of the femur was performed, and the cultures obtained during this intervention remained negative. At a 6-year follow-up, the girdlestone situation still showed an acceptable functional outcome without any recurrence of osteomyelitis.

Deterministic dynamics in the minority game

The minority game (MG) behaves as a stochastically disturbed deterministic system due to the coin toss invoked to resolve tied strategies. Averaging over this stochasticity yields a description of the MG's deterministic dynamics via mapping equations for the strategy score and global information. The strategy-score map contains both restoring-force and bias terms, whose magnitudes depend on the game's quenched disorder. Approximate analytical expressions are obtained and the effect of "market impact" is discussed. The global-information map represents a trajectory on a de Bruijn graph. For small quenched disorder, a Eulerian trail represents a stable attractor. It is shown analytically how antipersistence arises. The response to perturbations and different initial conditions is also discussed.

MHCII, Tlr4 and Nramp1 genes control host pulmonary resistance against the opportunistic bacterium Pasteurella pneumotropica

MHCII, Tlr4, and Nramp1 genes are each independently important in pulmonary immunity. To determine the effect of these genes on host resistance, mice carrying various combinations of functional alleles for these three genes were experimentally challenged with the opportunistic bacterium, Pasteurella pneumotropica. MHCII-/-, Tlr4d/d, and Nramp1s/s mice were significantly more susceptible to experimental infections by P. pneumotropica after intranasal challenge compared to mice carrying functional alleles at only one of those genes. P. pneumotropica were cultured from the lungs of challenged mice, and the severity of the pneumonia strongly correlated with the number of isolated bacteria. Mice with the genotype MHCII-/- Tlr4n/n genotype were less susceptible to pneumonia than MHCII+/+, Tlr4d/d mice. It is interesting that the Nramp1 gene contribution to host resistance was apparent only in the absence of functional MHCII or Tlr4 genes. These data suggest that MHCII, Tlr4, and Nramp1 genes are important to pulmonary bacterial resistance.

Interaction of mannose-binding lectin with primary isolates of human immunodeficiency virus type 1

Mannose-binding lectin (MBL) is present in human serum and plays an important role in innate immunity by binding to carbohydrate on micro-organisms. Whereas the gp120/gp41 of human immunodeficiency virus type 1 (HIV-1) contains numerous N-linked glycosylation sites and many of these sites contain high-mannose glycans which could interact with MBL, the interaction between MBL and primary isolates (PI) of HIV-1 has not been studied. To determine if PI of HIV bind to MBL, a virus capture assay was developed in which virus was incubated in MBL-coated microtitre wells followed by detection of bound virus with an ELISA for p24 antigen. The X4 HIV-1(MN) T cell line-adapted strain and PI of HIV (R5 and X4) bound to MBL. Binding of virus to MBL was via the carbohydrate-recognition domain of MBL since binding did not occur in the absence of Ca(2+) and was blocked by preincubation of MBL-coated wells with soluble mannan. The interaction of virus with MBL-coated wells was also inhibited by preincubation of virus with soluble MBL, indicating that both immobilized and soluble forms of MBL bound to HIV. Although host cell glycoproteins are incorporated into the membrane of HIV, binding of virus to immobilized MBL required expression of gp120/gp41 on virus particles, suggesting the presence of either an unusually high carbohydrate density and/or a unique carbohydrate structure on gp120/gp41 that is the target of MBL. This study shows that PI of HIV bind to MBL and suggests that MBL can selectively interact with HIV in vivo via carbohydrate structures on gp120/gp41.

The biosynthesis of elastin by an aortic medial cell culture

A long term culture of aortic medial cells, derived from newborn pig aorta, has been established. The ability of these cells to synthesize soluble elastin has been demonstrated by isolation and characterization of the radioactively labeled protein, using soluble elastin of copper-deficient pig aorta as the carrier. The synthesis of corsslinked elastin was shown by the isolation and identification of the lysine-derived crosslinks after incubating the cultures with [14C]-labeled lysine. The precursor relationship of soluble to insoluble elastin was demonstrated by incubating the [3H]-labeled soluble elastin from copper-deficient pig aorta with the culture and isolating labeled crosslinks from the insoluble elastin residue.