PIKfyve-dependent regulation of the Cl− channel ClC-2

The widely expressed chloride channel ClC-2 is stimulated by the serum and glucocorticoid inducible kinase SGK1. The SGK1-dependent regulation of several carriers involves the mammalian phosphatidylinositol-3-phosphate-5-kinase PIKfyve (PIP5K3). The present experiments explored whether SGK1-dependent regulation of ClC-2 similarly involves PIKfyve. The conductance of Xenopus oocytes is increased more than eightfold by ClC-2 expression. In ClC-2-expressing oocytes, but not in water-injected oocytes, the current was further enhanced by coexpression of either, PIKfyve or constitutively active ^S422DSGK1. Coexpression of the inactive SGK1 mutant ^K127NSGK1 did not significantly alter the current in ClC-2-expressing oocytes and abrogated the stimulation of the current by PIKfyve-coexpression. The stimulating effect of PIKfyve was abolished by replacement of the serine with alanine in the SGK1 consensus sequence (^S318APIKfyve). Coexpression of ^S318APIKfyve significantly blunted the stimulating effect of ^S422DSGK1 on ClC-2-activity. In conclusion, PIKfyve is a potent stimulator of ClC-2-activity and contributes to SGK1-dependent regulation of ClC-2.     

Biological activity and structural aspects of PGLa interaction with membrane mimetic systems

Peptidyl-glycine-leucine-carboxyamide (PGLa), isolated from granular skin glands of Xenopus laevis, is practically devoid of secondary structure in aqueous solution and in the presence of zwitterionic phospholipids, when added exogenously, but adopts an α-helix in the presence of anionic lipids. The peptide was shown to exhibit antifungal activity and to have antimicrobial activity towards both Gram-negative and Gram-positive bacteria. As a broad variety of peptides is found in the secretions of amphibian skin combinatorial treatment of PGLa and magainin 2 was studied showing enhanced activity by a heterodimer formation. Thus production of mutually recognizing peptides seems to be an effective way in nature to increase selective membrane activity. Biophysical studies on membrane mimics demonstrated that PGLa can discriminate between different lipid species, preferentially interacting with negatively charged lipids, which are major components of bacterial but not mammalian cell membranes. This emphasizes the role of electrostatic interactions as a major determinant to trigger the affinity of antimicrobial peptides towards bacterial membranes. PGLa induced the formation of a quasi-interdigitated phase in phosphatidylglycerol bilayers below their chain melting transition, which is due to the creation of voids below the peptide being aligned parallel to the membrane surface. In the fluid phase of phosphatidylglycerol the peptide inserts perpendicularly into the bilayer above a threshold concentration, which results in a hydrophobic mismatch of the peptide length and bilayer core for lipids ≤ C16. This mismatch is compensated by stretching of the acyl chains and in turn thickening of the bilayer demonstrating that membrane thinning cannot be taken generally as the hallmark of pore formation by antimicrobial peptides. Furthermore, PGLa was shown to affect membrane curvature strain of phosphatidylethanolamine, another main lipid component of bacterial membranes, where a cubic phase coexists with the fluid bilayer phase. Investigations on living Escherichia coli showed distinct changes in cell envelope morphology, when treated with the peptide. In a first stage loss of surface stiffness and consequently of topographic features was observed, followed in a second stage by permeabilization of the outer membrane and rupture of the inner (cytoplasmic) membrane supposedly by the mechanism(s) derived from model studies.     

Stair climbing results in more challenging patellofemoral contact mechanics and kinematics than walking at early knee flexion under physiological-like quadriceps loading

The mechanical environment during stair climbing has been associated with patellofemoral pain, but the contribution of loading to this condition is not clearly understood. It was hypothesized that the loading conditions during stair climbing induce higher patellofemoral pressures, a more lateral force distribution on the trochlea and a more lateral shift and tilt of the patella compared to walking at early knee flexion. Optical markers for kinematic measurements were attached to eight cadaveric knees, which were loaded with muscle forces at instances of walking and stair climbing cycles at 12° and 30° knee flexion. Contact mechanics were determined using a pressure sensitive film. At 12° knee flexion, stair climbing loads resulted in higher peak pressure (p=0.012) than walking, more lateral force distribution (p=0.012) and more lateral tilt (p=0.012), whilst mean pressure (p=0.069) and contact area (p=0.123) were not significantly different. At 30° knee flexion, although stair climbing compared to walking loads resulted in significantly higher patellofemoral mean (p=0.012) and peak pressures (p=0.012), contact area (p=0.025), as well as tilt (p=0.017), the medial–lateral force distribution (p=0.674) was not significantly different. No significant differences were observed in patellar shift between walking and stair climbing at either 12° (p=0.093) or 30° (p=0.575) knee flexion. Stair climbing thus leads to more challenging patellofemoral contact mechanics and kinematics than level walking at early knee flexion. The increase in patellofemoral pressure, lateral force distribution and lateral tilt during stair climbing provides a possible biomechanical explanation for the patellofemoral pain frequently experienced during this activity.     

Potential influence of tubicolous worms on the bottom roughness length z0 in the south-western Baltic Sea

The influence of three different species of tubicolous worms (Pygospio elegans, Polydora ciliata and Lagis koreni) on the hydrodynamic bottom roughness length (z₀) was analysed in this study. Flume experiments and geospatial methods were combined to determine the potential interactions between worm tubes and the near-bed flow regime and the resulting effects on sediment transport in the south-western Baltic Sea. The three selected species are common in the area of interest (3539 km²). Their species-specific population densities were taken from existing macrozoobenthos datasets and transferred into a Geographic Information System (GIS). In analogy to the sediment roughness length, the hydrodynamic roughness lengths generated by the tubicolous worms were calculated and corresponding sediment transport values, derived from flume experiments with artificial tube lawns, were geospatially analysed using GIS. In order to show the direct influence of worm tubes on the surrounding sediment surface flume experiments were conducted at two given current velocities of 20 cm s^− 1 for sediment displacement effects and 5 cm s^− 1 for deposition effects. The roughness length was shown to increase by a factor of 2 to 30 in the presence of biogenic structures such as the worm tubes. The near-bed hydrodynamic conditions are significantly influenced at low roughness densities through independent or isolated flow conditions at 0.7 to 1.9% and at high roughness densities between 4.2 and 7.5%, resulting in unaffected sediment surfaces through “skimming flow”, as well. The GIS analysis revealed that this effect occurs over 4% (137 km²) of the area of investigation, whereas sediment displacement at roughness densities between 0.7 and 1.9% due to increased turbulence is the predominant effect over 33% (present on 1172 km²) of the area of investigation. These findings reveal the important influence of species-generated microtopography on sediment transport processes.     

Influence of the mode of macrofauna-mediated bioturbation on the vertical distribution of living benthic foraminifera: First insight from axial tomodensitometry

We investigated the influence of bioturbation by macrofauna on the vertical distribution of living (stained) benthic foraminifera in marine intertidal sediments. We investigated the links between macrofaunal bioturbation and foraminiferal distribution, by sampling from stations situated on a gradient of perturbation by oyster-farming, which has a major effect on benthic faunal assemblages. Sediment cores were collected on the French Atlantic coast, from three intertidal stations: an oyster farm, an area without oysters but affected by oyster biodeposits, and a control station. Axial tomodensitometry (CT-scan) was used for three-dimensional visualization and two-dimensional analysis of the cores. Biogenic structure volumes were quantified and compared between cores. We collected the macrofauna, living foraminifera, shells and gravel from the cores after scanning, to validate image analysis. We did not investigate differences in the biogenic structure volume between cores. However, biogenic structure volume is not necessarily proportional to the extent of bioturbation in a core, given that many biodiffusive activities cannot be detected on CT-scans. Biodiffusors and larger gallery-diffusors were abundant in macrofaunal assemblage at the control station. By contrast, macrofaunal assemblages consisted principally of downward-conveyors at the two stations affected by oyster farming. At the control station, the vertical distribution of biogenic structures mainly built by the biodiffusor Scorbicularia plana and the large gallery-diffusor Hediste diversicolor was significantly correlated with the vertical profiles of living foraminifera in the sediment, whereas vertical distributions of foraminifera and downward-conveyors were not correlated at the station affected by oyster farming. This relationship was probably responsible for the collection of foraminifera in deep sediment layers (> 6 cm below the sediment surface) at the control station. As previously suggested for other species, oxygen diffusion may occur via the burrows built by S. plana and H. diversicolor, potentially increasing oxygen penetration and providing a favorable microhabitat for foraminifera in terms of oxygen levels. By contrast, the absence of living foraminifera below 6 cm at the stations affected by oyster farming was probably associated with a lack of biodiffusor and large gallery-diffusor bioturbation. Our findings suggest that the effect of macrofaunal bioturbation on the vertical distribution of foraminiferal assemblages in sediments depends on the effects of the macrofauna on bioirrigation and sediment oxidation, as deduced by Eh values, rather than on the biogenic structure volume produced by macrofauna. The loss of bioturbator functional diversity due to oyster farming may thus indirectly affect infaunal communities by suppressing favorable microhabitats produced by bioturbation.     

Investigation of amino acid containing [FeFe] hydrogenase models concerning pendant base effects

The present investigations deal with the modeling of the peptide surrounding of [FeFe] hydrogenase using amine containing disulphides to simulate possible influences of the amino acid lysine (K237) on the electrochemical and electrocatalytic properties of biomimetic compounds based on [Fe2S2] moieties. Fe₃(CO)₁₂ was reacted with Boc-4-amino-1,2-dithiolane, Boc-Adt-OMe (Adt = 4-amino-1,2-dithiolane-4-carboxylic acid, Boc = tert-butoxycarbonyl) and Boc-Adp tert-butyl ester (Adp = (S)-2-amino-3-(1,2-dithiolan-4-yl)propionic acid) to elongate the FeN distance in comparison to the well known [Fe₂{(SCH₂)₂NR}(CO)₆] model complexes. Efforts to deprotect the complexes containing Boc-4-amino-1,2-dithiolane with trifluoroacetic acid result in the formation of [Fe₃(μ³-O)(μ-O₂C₂F₃)₆(OC₄H₈)₂(H₂O)]. The novel [2Fe2S] complexes are characterized using spectroscopic, electrochemical techniques and X-ray diffraction studies.     

Pollen grains adhere to the moist mouthparts in the flower visiting beetle Cetonia aurata (Scarabaeidae, Coleoptera)

Flower visiting beetles possess numerous structural adaptations of their mouthparts to adhere and ingest pollen grains. Using a Cryo-SEM approach the examination of the mouthparts in rapidly frozen Cetonia aurata (Scarabaeidae) indicates a previously unknown technique of pollen uptake in Coleoptera. Cryo-SEM micrographs of the mouthparts reveal a fluid covering the bristles on the buccal surface. In this way the bristles of the galeae form a wet brush which represents the primary organ of pollen uptake. The fluid improves adhesion of pollen to bristles lacking any specialized adhering surface or highly sculptured cuticle as present in other pollen feeding Coleoptera. The well developed mola region of the otherwise non-biting mandibles of C. aurata indicates that these beetles open pollen grains mechanically before ingestion. Examination of gut content demonstrated that crushed and intact pollen occur in all regions. The Cryo-SEM method represents a new approach to study functional morphology including the interaction of microstructures and fluids on cuticular surfaces of insects. Handling editor: Gimme Walter     

Unstable Prefrontal Response to Emotional Conflict and Activation of Lower Limbic Structures and Brainstem in Remitted Panic Disorder

Background

The neural mechanisms of panic disorder (PD) are only incompletely understood. Higher sensitivity of patients to unspecific fear cues and similarities to conditioned fear suggest involvement of lower limbic and brainstem structures. We investigated if emotion perception is altered in remitted PD as a trait feature.

Methodology/Principal Findings

We used blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) to study neural and behavioural responses of 18 remitted PD patients and 18 healthy subjects to the emotional conflict paradigm that is based on the presentation of emotionally congruent and incongruent face/word pairs. We observed that patients showed stronger behavioural interference and lower adaptation to interference conflict. Overall performance in patients was slower but not less accurate. In the context of preceding congruence, stronger dorsal anterior cingulate cortex (dACC) activation during conflict detection was found in patients. In the context of preceding incongruence, controls expanded dACC activity and succeeded in reducing behavioural interference. In contrast, patients demonstrated a dropout of dACC and dorsomedial prefrontal cortex (dmPFC) recruitment but activation of the lower limbic areas (including right amygdala) and brainstem.

Conclusions/Significance

This study provides evidence that stimulus order in the presentation of emotional stimuli has a markedly larger influence on the brain''s response in remitted PD than in controls, leading to abnormal responses of the dACC/dmPFC and lower limbic structures (including the amygdala) and brainstem. Processing of non-panic related emotional stimuli is disturbed in PD patients despite clinical remission.     

Henipavirus RNA in African Bats

Background

Henipaviruses (Hendra and Nipah virus) are highly pathogenic members of the family Paramyxoviridae. Fruit-eating bats of the Pteropus genus have been suggested as their natural reservoir. Human Henipavirus infections have been reported in a region extending from Australia via Malaysia into Bangladesh, compatible with the geographic range of Pteropus. These bats do not occur in continental Africa, but a whole range of other fruit bats is encountered. One of the most abundant is Eidolon helvum, the African Straw-coloured fruit bat.

Methodology/Principal Findings

Feces from E. helvum roosting in an urban setting in Kumasi/Ghana were tested for Henipavirus RNA. Sequences of three novel viruses in phylogenetic relationship to known Henipaviruses were detected. Virus RNA concentrations in feces were low.

Conclusions/Significance

The finding of novel putative Henipaviruses outside Australia and Asia contributes a significant extension of the region of potential endemicity of one of the most pathogenic virus genera known in humans.