Reggie-1/flotillin-2 promotes secretion of the long-range signalling forms of Wingless and Hedgehog in Drosophila

The lipid-modified morphogens Wnt and Hedgehog diffuse poorly in isolation yet can spread over long distances in vivo, predicting existence of two distinct forms of these morphogens. The first is poorly mobile and activates short-range target genes. The second is specifically packed for efficient spreading to induce long-range targets. Subcellular mechanisms involved in the discriminative secretion of these two forms remain elusive. Wnt and Hedgehog can associate with membrane microdomains, but the function of this association was unknown. Here we show that a major protein component of membrane microdomains, reggie-1/flotillin-2, plays important roles in secretion and spreading of Wnt and Hedgehog in Drosophila. Reggie-1 loss-of-function results in reduced spreading of the morphogens, while its overexpression stimulates secretion of Wnt and Hedgehog and expands their diffusion. The resulting changes in the morphogen gradients differently affect the short- and long-range targets. In its action reggie-1 appears specific for Wnt and Hedgehog. These data suggest that reggie-1 is an important component of the Wnt and Hedgehog secretion pathway dedicated to formation of the mobile pool of these morphogens.     

Mps1 checks up on chromosome attachment

The protein kinase Mps1, a crucial regulator of the spindle-assembly checkpoint, now turns out to be essential for correcting errors in chromosome attachment (Jelluma et al., 2008). Mps1 exerts this effect by regulating the activity of the Aurora B kinase through phosphorylation of its partner protein Borealin.     

Composition of the Phyllospheric Microbial Populations on Vegetable Plants with Different Glucosinolate and Carotenoid Compositions

The plant phyllosphere is intensely colonized by a complex and highly diverse microbial population and shows pronounced plant-species-specific differences. The mechanisms and influencing factors determining whether and in which density microorganisms colonize plant phyllosphere tissues are not yet fully understood. One of the key influencing factors is thought to be phytochemical concentration and composition. Therefore, correlations between various concentrations of individual glucosinolates and carotenoids in four different plant species-Brassica juncea, Brassica campestris, Cichorium endivia, and Spinacea oleracea-and the phyllospheric bacterial population size associated with the aerial parts of the same plants were analyzed. The concentration of various individual glucosinolates and carotenoids were measured using high-performance liquid chromatography. The phyllospheric bacterial population size including both nonculturable and culturable organisms was assessed using quantitative real-time polymerase chain reaction, and the physiological profile of the culturable microbial community was analyzed using the Biolog system. Results show significant differences between plant species in both concentration and composition of secondary metabolites, bacterial population size, and microbial community composition in three consecutively performed experiments. An interesting and underlying trend was that bacterial density was positively correlated to concentrations of beta-carotene in the plant phyllosphere of the four plant species examined. Likewise, the alkenyl glucosinolates, 2-propenyl, 3-butenyl, and 4-pentenyl, concentrations were positively correlated to the bacterial population density, whereas the aromatic glucosinolate 2-phenylethyl showed a negative correlation to the phyllospheric bacterial population size. Thus, we report for the first time the relationship between individual glucosinolate and carotenoid concentrations and the phyllospheric bacterial population size of nonculturable and culturable organisms and the phyllospheric microbial physiological profiles.     

A quantitative comparison of different methods to detect cardiorespiratory coordination during night-time sleep

Background

The univariate approaches used to analyze heart rate variability have recently been extended by several bivariate approaches with respect to cardiorespiratory coordination. Some approaches are explicitly based on mathematical models which investigate the synchronization between weakly coupled complex systems. Others use an heuristic approach, i.e. characteristic features of both time series, to develop appropriate bivariate methods.

Objective

In this study six different methods used to analyze cardiorespiratory coordination have been quantitatively compared with respect to their performance (no. of sequences with cardiorespiratory coordination, no. of heart beats coordinated with respiration). Five of these approaches have been suggested in the recent literature whereas one method originates from older studies.

Results

The methods were applied to the simultaneous recordings of an electrocardiogram and a respiratory trace of 20 healthy subjects during night-time sleep from 0:00 to 6:00. The best temporal resolution and the highest number of coordinated heart beats were obtained with the analysis of 'Phase Recurrences'. Apart from the oldest method, all methods showed similar qualitative results although the quantities varied between the different approaches. In contrast, the oldest method detected considerably fewer coordinated heart beats since it only used part of the maximum amount of information available in each recording.

Conclusions

The method of 'Phase Recurrences' should be the method of choice for the detection of cardiorespiratory coordination since it offers the best temporal resolution and the highest number of coordinated sequences and heart beats. Excluding the oldest method, the results of the heuristic approaches may also be interpreted in terms of the mathematical models.

     

Sulindac derivatives inhibit cell growth and induce apoptosis in primary cells from malignant peripheral nerve sheath tumors of NF1-patients

Background  

Malignant peripheral nerve sheath tumors (MPNSTs) are neoplasms leading to death in most cases. Patients with Neurofibromatosis type 1 have an increased risk of developing this malignancy. The metabolites of the inactive prodrug Sulindac, Sulindac Sulfide and Sulindac Sulfone (Exisulind) are new chemopreventive agents that show promising results in the treatment of different cancer types. In this study we examined the antineoplastic effect of these compounds on primary cells derived from two MPNSTs of Neurofibromatosis type 1 patients.     

The poplar K+ channel KPT1 is associated with K+ uptake during stomatal opening and bud development

To gain insights into the performance of poplar guard cells, we have measured stomatal conductance and aperture, guard cell K+ content and K+-channel activity of the guard cell plasma membrane in intact poplar leaves. In contrast to Arabidopsis, broad bean and tobacco grown under same conditions, poplar stomata operated just in the dynamic range - any change in conductance altered the rate of photosynthesis. In response to light, CO2 and abscisic acid (ABA), the stomatal opening velocity was two to five times faster than that measured for Arabidopsis thaliana, Nicotiana tabacum and Vicia faba. When stomata opened, the K+ content of guard cells increased almost twofold, indicating that the very fast stomatal opening in this species is mediated via potassium uptake. Following impalement of single guard cells embedded in their natural environment of intact leaves with triple-barrelled microelectrodes, time-dependent inward and outward-rectifying K+-channel-mediated currents of large amplitude were recorded. To analyse the molecular nature of genes encoding guard cell K+-uptake channels, we cloned K+-transporter Populustremula (KPT)1 and functionally expressed this potassium channel in a K+-uptake-deficient Escherichia coli mutant. In addition to guard cells, this K+-transporter gene was expressed in buds, where the KPT1 gene activity strongly correlated with bud break. Thus, KPT1 represents one of only few poplar genes associated with bud flush.     

Solution phase parallel synthesis and evaluation of MAPK inhibitory activities of close structural analogues of a Ras pathway modulator

A solution phase parallel synthesis approach was undertaken to rapidly explore the structure-activity relationship of an inhibitor of the Ras/Raf protein interaction identified from a small molecule compound library. Evaluation of the MAPK pathway signaling inhibitory activity of the synthesized analogues as well as their antiproliferative activity and ability to inhibit soft agar growth were performed.     

Cognitive neuroscience: acting on numbers

The parietal cortex is a central part of the brain's system for representing numbers and magnitudes. Activity in the parietal cortex might reflect number representation or actions made in response to the numbers.     

Bioelectrical impedance assay to monitor changes in cell shape during apoptosis

Apoptosis is a strictly regulated and genetically encoded cell 'suicide' that may be triggered by cytokines, depletion of growth factors or certain chemicals. It is morphologically characterized by severe alterations in cell shape like cell shrinkage and disintegration of cell-cell contacts. We applied a non-invasive electrochemical technique referred to as electric cell-substrate impedance sensing (ECIS) in order to monitor the apoptosis-induced changes in cell shape in an integral and quantitative fashion with a time resolution in the order of minutes. In ECIS the cells are grown directly on the surface of small gold-film electrodes (d = 2 mm). From readings of the electrical impedance of the cell-covered electrode, performed with non-invasive, low amplitude sensing voltages, it is possible to deduce alterations in cell-cell and cell-substrate contacts. To improve the sensitivity of this impedance assay we used endothelial cells derived from cerebral micro-vessels as cellular model systems since these are well known to express electrically tight intercellular junctions. Apoptosis was induced by cycloheximide (CHX) and verified by biochemical and cytological assays. The time course of cell shape changes was followed with unprecedented time resolution by impedance readings at 1 kHz and correlated with biochemical parameters. From impedance readings along a broad frequency range of 1-10(6) Hz we could assign the observed impedance changes to alterations on the subcellular level. We observed that disassembly of barrier-forming tight junctions precedes changes in cell-substrate contacts and correlates strongly with the time course of protease activation.