Revealing the structure of stereociliary actin by X-ray nanoimaging

Hair cell stereocilia are crucial for hearing and the sense of balance. They include an array of accurately packed, parallel actin filaments and act as levers, which transform mechanical deformation into neuronal signals. The length of vestibular stereocilia reaches several micrometers, whereas, for individual microfilaments, the diameter and therefore the characteristic length scale in the lateral direction is on the order of a few nanometers. These orders of magnitude render X-rays an ideal tool for investigating actin packing, and numerous studies on reconstituted in vitro systems have revealed important information. Here we report on the characterization of intact stereocilia using two nanoscale X-ray techniques. We use X-ray ptychography to image stereocilia with quantitative phase contrast and high dose efficiency, showing stereocilia with diameters and lengths in the expected range. We further employ X-ray nanodiffraction using a nanofocused X-ray beam on the same order of magnitude as the width of a stereocilium. Despite the small probe volume we can clearly visualize the stereocilia bundles. From the individual diffraction patterns we determine the local orientation of the actin structures and can clearly correlate them with the corresponding visible-light fluorescence images. Furthermore, azimuthal integration of individual diffraction patterns reveals distinct intensity curves, showing modulations of the signal, which reflect the relevant length scales and pronounced order in the biological system. The applied techniques are not limited to the studies on stereocilia but have the potential of being applied to many biological and soft-matter systems, in particular if a pronounced degree of order is present.

Dynamics of counterion-induced attraction between vimentin filaments followed in microfluidic drops

Intermediate filaments (IFs) are fiber-forming proteins and part of the cytoskeleton of eukaryotes. In vitro the network formation of purified IF systems is mediated, for example, by the interaction with multivalent ions. The understanding of these interaction mechanisms increases the knowledge of the cytoskeleton on a fundamental level. Here, we employ time-lapse fluorescence microscopy to directly image the evolution of network formation of vimentin IFs upon addition of divalent ions. We are thus able to follow the process starting a few seconds after the first encounter of free filaments and ions up to several minutes when the networks are in equilibrium. The local protein density in the compacted networks can reach a factor of 45 higher than the original solution concentration. The competition between mono- and divalent ion condensation onto the protein explains our observations and reveals the polyelectrolyte nature of vimentin as a reason for the protein attraction in the presence of small cations. The method for time-lapse studies in microfluidic drops presented here can be generalized to other dynamic systems.

Experimental Investigation of PC-Films Using Optical Measurements

The alignment of polymer chains is a well known microstructural evolution effect due to straining of polymers. This has a drastic influence on the macroscopic properties of the initially isotropic material. In this work, cold forming is performed at room temperature on a tensile testing machine. Polycarbonate films are examined in two loading phases. In the first phase, the specimen is loaded to induce anisotropy, and in the second, it is re-loaded, while the material direction is varied. The investigations are supported by an optical measurement system to gain knowledge about the inhomogeneous material behavior in the initial loading phase and about the anisotropic homogeneous behavior during the re-loading phase. Two dimensional strain contours are obtained from the test data. Additionally, we propose a method for approximation of the macroscopic true stress and compare the results with a common approach based on volume consistency. In the future, the test data will set a basis for parameter identification of constitutive equations taking into account a combination of inhomogenous and homogenous material behavior, exhibiting strain induced anisotropy.

Vimentin networks at tunable ion-concentration in microfluidic drops

The structure and function of biological systems, for example, cells and proteins, depend strongly on their chemical environment. To investigate such dependence, we design a polydimethylsiloxane-based microfluidic device to encapsulate biological systems in picoliter-sized drops. The content of each individual drop is tuned in a defined manner. As a key feature of our method, the individual chemical composition is determined and related to the drop content. In our case, the drop content is imaged using microscopy methods, while the drops are immobilized to allow for long-time studies. As an application of our device, we study the influence of divalent ions on vimentin intermediate filament networks in a quantitative way by tuning the magnesium concentration from drop to drop. This way we are able to directly image the effect of magnesium on the fluorescently tagged protein in a few hundreds of drops. Our study shows that with increasing magnesium concentration in the drops, the compaction of the networks becomes more pronounced. The degree of compaction is characterized by different morphologies; freely fluctuating networks are observed at comparatively low magnesium concentrations of 5-10 mM, while with increasing magnesium concentration reaching 16 mM they develop into fully aggregated networks. Our approach demonstrates how a systematic study of interactions in biological systems can benefit from the exceptional controllability of microfluidic methods.

Dynamics of intermediate filament assembly followed in micro-flow by small angle X-ray scattering

The assembly of intermediate filaments (IFs) is a complex process that can be recapitulated through a series of distinct steps in vitro. The combination of microfluidics and small angle X-ray scattering (SAXS) provides a powerful tool to investigate the kinetics of this process on the relevant timescales. Microfluidic mixers based on the principle of hydrodynamic focusing allow for precise control of the mixing of proteins and smaller reagents like ions. Here, we present a multi-layer device that prevents proteins from adsorbing to the channel walls by engulfing the protein jet with a fluid layer of buffer. To ensure compatibility with SAXS, the device is fabricated from UV-curable adhesive (NOA 81). To demonstrate the successful prevention of contact between the protein jet and the channel walls we measure the distribution of a fluorescent dye in the device by confocal microscopy at various flow speeds and compare the results to finite element method (FEM) simulations. The prevention of contact enables the investigation of the assembly of IFs in flow by gradually increasing the salt concentration in the protein jet. The diffusion of salt into the jet can be determined by FEM simulations. SAXS data are collected at different positions in the jet, corresponding to different salt concentrations, and they reveal distinct differences between the earliest assembly states. We find that the mean square radius of gyration perpendicular to the filament axis increases from 13 nm(2) to 58 nm(2) upon assembly. Thereby we provide dynamic structural data of a complex assembly process that was amenable up to now only by microscopic techniques.

Betriebswirtschaftliche Auswirkungen der thorakalen Epiduralanästhesie bei urologischen Operationen

INTRODUCTION

Using the surgical procedure OPS 5-604.0 (radical retropubic prostatectomy) as an example, our study identifies revenue-relevant patient characteristics and describes the impact of the perioperative application of thoracic epidural analgesia (TEA).

METHODS

Factors affecting duration of stay were determined in 460 patients undergoing OPS 5-604.0 in the year 2001 and 2002 using multifactorial regression analysis. Preoperative parameters served as factors for matched-pair analysis of the effects of TEA.

RESULTS

Characteristics significantly affecting length of postoperative hospital stay were ASA status, age, preoperative haemoglobin concentration, postoperative tachycardia, number of transfused packed red cells, wound infection and surgical revision. Based on identical matching criteria 27 pairs (with/without TEA) could be formed. While the induction time in the TEA group was 8+/-18 min longer (p=0.04), emergence was briefer by 3+/-9 min (p=0.045). Neither anaesthesia presence time nor anaesthesia costs or total costs of surgery differed significantly between the pairs. However, duration of epidural postoperative pain therapy was longer with TEA but in contrast, the postoperative length of hospital stay after TEA was reduced. Assuming a continuous demand for OPS 5-604.0 procedures, TEA enables 32 more procedures to be carried out per year with an increased yield on turnover of 2.7%.

CONCLUSION

At first sight combined anaesthesia procedures require more human resources and material, however, as a result of shortened hospital stay and optimized pain therapy patient satisfaction increases and a substantial potential for increased revenue is gained.

Inhibition of phosphoinositide-specific phospholipase C results in the induction of pathogenesis-related genes in soybean

The inositol 1,4,5-trisphosphate (IP3) content is decreased in soybean cells following infection with Pseudomonas syringae pv. glycinea (Psg). In this investigation, a differential display approach was applied to isolate soybean genes that are transcriptionally up-regulated by the inhibition of phosphoinositide-specific phospholipase C (PI-PLC) activity and to study if the transcription of those genes is altered following Psg infection. Four genes, transcriptionally activated following treatment with the PI-PLC-specific inhibitor U-73122, were cloned. Three of the four genes were induced following infection with Psg. The transcripts of a hydrolase homologue (GmHy) were induced in the incompatible but not compatible soybean-Psg interaction. The transcripts of a putative ascorbate oxidase gene (GmAO) were induced in both compatible and incompatible interactions. GmHy and GmAO may represent new classes of pathogenesis-related genes. In addition to these two novel genes, homologues of PR-10 and polygalacturonase inhibitor protein (GmPR10 and GmPGIP, respectively) were identified. These two genes have previously been reported as pathogenesis-related. Transcripts of GmPR-10, but not GmPGIP, were induced in both compatible and incompatible soybean-Psg interactions. Induction of these genes, except for GmPGIP, following inhibition of PI-PLC by either the U-73122 treatment or bacterial infection suggests that PI-PLC may negatively regulate the expression of defence genes.

Subcellular targeting of nine calcium-dependent protein kinase isoforms from Arabidopsis

Calcium-dependent protein kinases (CDPKs) are specific to plants and some protists. Their activation by calcium makes them important switches for the transduction of intracellular calcium signals. Here, we identify the subcellular targeting potentials for nine CDPK isoforms from Arabidopsis, as determined by expression of green fluorescent protein (GFP) fusions in transgenic plants. Subcellular locations were determined by fluorescence microscopy in cells near the root tip. Isoforms AtCPK3-GFP and AtCPK4-GFP showed a nuclear and cytosolic distribution similar to that of free GFP. Membrane fractionation experiments confirmed that these isoforms were primarily soluble. A membrane association was observed for AtCPKs 1, 7, 8, 9, 16, 21, and 28, based on imaging and membrane fractionation experiments. This correlates with the presence of potential N-terminal acylation sites, consistent with acylation as an important factor in membrane association. All but one of the membrane-associated isoforms targeted exclusively to the plasma membrane. The exception was AtCPK1-GFP, which targeted to peroxisomes, as determined by covisualization with a peroxisome marker. Peroxisome targeting of AtCPK1-GFP was disrupted by a deletion of two potential N-terminal acylation sites. The observation of a peroxisome-located CDPK suggests a mechanism for calcium regulation of peroxisomal functions involved in oxidative stress and lipid metabolism.

The matrix metalloproteinase gene GmMMP2 is activated in response to pathogenic infections in soybean

Matrix metalloproteinases (MMPs) play an important role in host defense responses against pathogens in mammals where their activities lead to the production of antimicrobial peptides. We have identified a novel soybean (Glycine max) metalloproteinase gene, GmMMP2, that is transcriptionally up-regulated in infected tissues. The deduced amino acid sequence indicates that this gene belongs to the MMP family. It is a preproprotein containing an N-terminal signal peptide, a cysteine switch, a zinc-binding catalytic motif, and a C-terminal transmembrane domain. The GmMMP2 expressed in and purified from Escherichia coli exhibited an in vitro enzymatic activity in digesting myelin basic protein. All plant metalloproteinases reported so far have no known functions. However, they have been suggested to be involved in extracellular cell matrix degradation during development or senescence. Our investigations demonstrate that the GmMMP2 transcript levels were rapidly increased in compatible and incompatible interactions of soybean tissues with the oomycete pathogen Phytophthora sojae or the bacterial pathogen Pseudomonas syringae pv. glycinea. In agreement with the GmMMP2 activation, a metalloproteinase activity was gradually increased in suspension-cultured cells following the bacterial infection. GmMMP2 was also activated in response to wounding and dehydration. However, GmMMP2 activation did not correlate with the oxidative burst leading to the hypersensitive response cell death or the tissue senescence progress that involves programmed cell death. Our investigations suggest that GmMMP2 may be involved in a novel defense response of soybean against pathogenic infections.

The matrix metalloproteinase gene GmMMP2 is activated in response to pathogenic infections in soybean

Matrix metalloproteinases (MMPs) play an important role in host defense responses against pathogens in mammals where their activities lead to the production of antimicrobial peptides. We have identified a novel soybean (Glycine max) metalloproteinase gene, GmMMP2, that is transcriptionally up-regulated in infected tissues. The deduced amino acid sequence indicates that this gene belongs to the MMP family. It is a preproprotein containing an N-terminal signal peptide, a cysteine switch, a zinc-binding catalytic motif, and a C-terminal transmembrane domain. The GmMMP2 expressed in and purified from Escherichia coli exhibited an in vitro enzymatic activity in digesting myelin basic protein. All plant metalloproteinases reported so far have no known functions. However, they have been suggested to be involved in extracellular cell matrix degradation during development or senescence. Our investigations demonstrate that the GmMMP2 transcript levels were rapidly increased in compatible and incompatible interactions of soybean tissues with the oomycete pathogen Phytophthora sojae or the bacterial pathogen Pseudomonas syringae pv. glycinea. In agreement with the GmMMP2 activation, a metalloproteinase activity was gradually increased in suspension-cultured cells following the bacterial infection. GmMMP2 was also activated in response to wounding and dehydration. However, GmMMP2 activation did not correlate with the oxidative burst leading to the hypersensitive response cell death or the tissue senescence progress that involves programmed cell death. Our investigations suggest that GmMMP2 may be involved in a novel defense response of soybean against pathogenic infections.

Antisense-mediated depletion of potato leaf omega3 fatty acid desaturase lowers linolenic acid content and reduces gene activation in response to wounding

Fatty acid omega3 desaturases act on membrane lipids to catalyse the formation of trienoic fatty acids, the most abundant in plant tissues being alpha-linolenic acid. This fatty acid is a precursor of jasmonic acid, a plant growth regulator involved in the control of wound-induced gene activation in plants and in the induction of tuberization in potato. We isolated a potato omega3 desaturase cDNA, possibly encoding a plastidial isoform, and used it to investigate its expression pattern throughout plant development and in response to wounding. Plastidial omega3 desaturase gene transcripts accumulate rapidly upon wounding, preceding the jasmonate-dependent induction of the wound-responsive proteinase inhibitor II gene. We generated transgenic potato plants constitutively expressing an antisense RNA to this plastidial omega3 desaturase. Selected transgenic lines in which the cognate omega3 desaturase mRNA is largely depleted show a marked reduction, of up to 60%, in trienoic acids in leaves and tubers. In these lines, a corresponding reduction in jasmonate content and proteinase inhibitor II expression is observed upon wounding. Our results indicate that a reduction in omega3 desaturase mRNA levels compromises the wound-induced activation of proteinase inhibitor II, suggesting that wound-induced synthesis of linolenic acid is required for jasmonic acid production. The antisense-mediated depletion of fatty acid omega3 desaturases is a viable alternative for reducing trienoic fatty acid content in plant species in which a mutant screening approach is not applicable.

Abscisic acid and jasmonic acid activate wound-inducible genes in potato through separate, organ-specific signal transduction pathways

Mechanical damage to leaf tissue causes an increase in abscisic acid (ABA) which in turn activates the biosynthesis of jasmonic acid (JA). The resulting higher endogenous JA levels subsequently activate the expression of wound-inducible genes. This study shows that JA induces the expression of different sets of genes in roots and leaves of potato plants. When roots of intact plants were treated with JA, high levels of proteinase inhibitor II (pin2), cathepsin D inhibitor, leucine aminopeptidase and threonine deaminase mRNAs accumulated in the systemic leaves. However, in the treated roots, very low, if any, expression of these genes could be detected. In contrast, a novel, root-specific pin2 homologue accumulated in the JA-treated root tissue which could not be detected in leaves, either systemic or those directly treated with JA. Application of okadaic acid and staurosporine revealed that a protein phosphorylation step is involved in the regulation of this differential response. In leaves, a protein phosphatase is required for the JA-induced expression of pin2 and the other genes analysed. This phosphatase activity is not necessary for the JA-induced expression of a pin2 homologue in roots, suggesting the existence of different transduction pathways for the JA signal in these organs. The requirement of a protein phosphatase activity for JA-mediated gene induction has enabled identification of a JA-independent pathway for ABA induction of pin2 and the other wound-inducible genes. This alternative pathway involves a protein kinase, and appears to be selective for wound-inducible genes. Our data suggest the presence of a complex, organ-specific transduction network for regulating the effects of the plant hormones ABA and JA on gene expression upon wounding.

Serum levels of sCD23 and sCD25 in children with asthma and in healthy controls

To investigate whether markers of lymphocyte activation are useful markers of disease activity in childhood asthma, we studied serum levels of soluble CD25 (receptor for IL-2) and soluble CD23 (low-affinity receptor for IgE) in 178 children (aged 2-18 years) suffering from mild to moderate asthma (mean asthma severity score: 2, range: 1-4), and in 175 healthy age-matched controls. Levels of sCD23 and sCD25 were inversely related to age. sCD23 was lower in patients with asthma (means per age group: 4.93-2.29 micrograms/l; controls: 6.92-4.11 micrograms/l, P < 0.05), while sCD25 tended to be higher (1601-597 kU/ml, controls: 1350-661 kU/ml, P = NS). sCD25 correlated significantly with asthma severity score (r = 0.41; P < 0.01) and MEF25 (maximum expiratory flow at 25% of vital capacity, r = -0.43; P < 0.05) in children < 10 years, while sCD23 correlated with asthma severity (r = 0.28; P < 0.05) in children > 10 years. On follow-up, levels of sCD25 normalized with clinical improvement. In children with nonatopic asthma, levels of sCD25 were significantly higher than in atopic patients. Our observations provide further evidence of the role of T-cell activation in asthma. Monitoring of lymphocyte activation markers, particularly levels of sCD25, may be useful in the follow-up of asthmatic children.