The effect of vibratory disturbance on sexual behaviour of the southern green stink bug Nezara viridula (Heteroptera, Pentatomidae)

The effect of vibratory disturbance on sexual behaviour and substrate-borne sound communication of the southern green stink bug, Nezara viridula L. was studied. Disturbance signals do not change the time N. viridula males need to locate the source of vibratory signals, but decrease the number of males responding with the calling and courtship song to calling females. Female N. viridula proceed calling during stimulation with disturbance signals but some of them change the song rhythm by skipping one or more signal intervals or emitting the repelling signals. The number of females which change the dominant frequency of the calling song decreases proportionally with increasing differences between the dominant frequency of the disturbance signals and the emitted female calling song. Variation of the song dominant frequency probably serves females to avoid interference by increasing the signal to noise ratio. Signal duration and repetition rate do not change significantly when the female is stimulated with the disturbance signals. This indicates that frequency shift by calling females is the main strategy for reducing interference by competitive signalers in N. viridula vibrational communication.     

Protein identification pipeline for the homology-driven proteomics

Homology-driven proteomics is a major tool to characterize proteomes of organisms with unsequenced genomes. This paper addresses practical aspects of automated homology-driven protein identifications by LC-MS/MS on a hybrid LTQ Orbitrap mass spectrometer. All essential software elements supporting the presented pipeline are either hosted at the publicly accessible web server, or are available for free download.     

Fibrinogen binding sites P336 and Y338 of clumping factor A are crucial for Staphylococcus aureus virulence

We have earlier shown that clumping factor A (ClfA), a fibrinogen binding surface protein of Staphylococcus aureus, is an important virulence factor in septic arthritis. When two amino acids in the ClfA molecule, P(336) and Y(338), were changed to serine and alanine, respectively, the fibrinogen binding property was lost. ClfAP(336)Y(338) mutants have been constructed in two virulent S. aureus strains Newman and LS-1. The aim of this study was to analyze if these two amino acids which are vital for the fibrinogen binding of ClfA are of importance for the ability of S. aureus to generate disease. Septic arthritis or sepsis were induced in mice by intravenous inoculation of bacteria. The clfAP(336)Y(338) mutant induced significantly less arthritis than the wild type strain, both with respect to severity and frequency. The mutant infected mice developed also a much milder systemic inflammation, measured as lower mortality, weight loss, bacterial growth in kidneys and lower IL-6 levels. The data were verified with a second mutant where clfAP(336) and Y(338) were changed to alanine and serine respectively. When sepsis was induced by a larger bacterial inoculum, the clfAP(336)Y(338) mutants induced significantly less septic death. Importantly, immunization with the recombinant A domain of ClfAP(336)SY(338)A mutant but not with recombinant ClfA, protected against septic death. Our data strongly suggest that the fibrinogen binding activity of ClfA is crucial for the ability of S. aureus to provoke disease manifestations, and that the vaccine potential of recombinant ClfA is improved by removing its ability to bind fibrinogen.     

The role of bryozoans in fossil reefs—an example from the Middle Devonian of the Western Sahara

Stenolaemate bryozoans with their stable calcitic skeletons play a significant role in reef building. In the Middle Devonian Sabkhat Lafayrina reef complex (Western Sahara), bryozoans are abundant and diverse. Although they do not form part of the principal framework of reefs, bryozoans are involved significantly in reef growth, especially in the initial stage. In this way, bryozoans are important with respect to initiating reef growth. They contribute greatly to sediment stabilization, making it possible for principal reef builders to grow on hardened and stabilized substrates, and also play sediment-baffling and sediment-filling roles. The aim of this study is to document the diversity of bryozoans in a Middle Devonian reef complex and to estimate their potential for initiation and contribution to reef structures.     

Thermal acoustic radiation from multilamellar vesicles in lipid phase transition

A new acoustical method for the investigation of lipid phase transition is introduced based on the measurement of the thermal acoustic radiation (TAR) inherent in lipids. The TAR of multilamellar vesicles from dipalmitoylphosphatidylcholine (DPPC) and dimyristoylphosphatidylcholine (DMPC) was measured in the megahertz range and the variations in the radiation intensity during the lipid phase transition were recorded. Two types of variations are possible: if the temperature of the vesicles decreases (in the process of transition from the liquid crystalline state to the gel state) then the TAR intensity increases, and if the temperature increases (in the reverse transition) then the TAR intensity decreases. These effects are connected with an increase in the ultrasonic absorption in the vesicles under lipid phase transition. Basing on the results of the TAR investigation, a new theoretical estimate has been developed of the variation in the absorption coefficient during the lipid phase transition. In this estimate, the variation is equated to the ratio of the phase transition entropy to the gas constant.     

Frequency clustering in spontaneous otoacoustic emissions from a lizard's ear

Spontaneous otoacoustic emissions (SOAEs) are indicators of an active process in the inner ear that enhances the sensitivity and frequency selectivity of hearing. They are particularly regular and robust in certain lizards, so these animals are good model organisms for studying how SOAEs are generated. We show that the published properties of SOAEs in the bobtail lizard are wholly consistent with a mathematical model in which active oscillators, with exponentially varying characteristic frequencies, are coupled together in a chain by visco-elastic elements. Physically, each oscillator corresponds to a small group of hair cells, covered by a tectorial sallet, so our theoretical analysis directly links SOAEs to the micromechanics of active hair bundles.     

Myosin V passing over Arp2/3 junctions: branching ratio calculated from the elastic lever arm model

Myosin V is a two-headed processive motor protein that walks in a hand-over-hand fashion along actin filaments. When it encounters a filament branch, formed by the Arp2/3 complex, it can either stay on the straight mother filament, or switch to the daughter filament. We study both probabilities using the elastic lever arm model for myosin V. We calculate the shapes and bending energies of all relevant configurations in which the trail head is bound to the actin filament before Arp2/3 and the lead head is bound either to the mother or to the daughter filament. Based on the assumption that the probability for a head to bind to a certain actin subunit is proportional to the Boltzmann factor obtained from the elastic energy, we calculate the mother/daughter filament branching ratio. Our model predicts a value of 27% for the daughter and 73% for the mother filament. This result is in good agreement with recent experimental data.     

Crossability relationships between Korean firs Abies koreana , A. nephrolepis and A. holophylla and some other representatives of the genus Abies

Artificial crossing experiments involving 3 Abies species native to Korean peninsula and 5 other representatives of Abies revealed a high hybridological affinity between Abies koreana and A. nephrolepis. Both these species are reproductively isolated from A. holophylla. All the three Korean species were found to exhibit incompatible relationships with the North American species A. concolor. The species A. holophylla and A. koreana differ also in their abilities to intercross with the Mediterranean firs. The former has been successfully crossed with A. nordmanniana, A. alba and A. cilicica exhibiting 19.1–55.3% crossability, whereas the latter produced filled seeds only with A. nordmanniana reaching 46.4% crossability. A considerable differentiation is postulated to exist between the pair of species A. koreana and A. nephrolepis on the one side and A. holophylla on the other side.     

The Lysis System of the <Emphasis Type="Italic">Streptomyces aureofaciens</Emphasis> Phage μ1/6

Previously, two genes, designated as lyt and hol, were identified in the lysis module of phage μ1/6. They were cloned and expressed in Escherichia coli. An additional candidate holin gene, hol2, was found downstream from the hol gene based on one predicted transmembrane domain and a highly charged C-terminal sequence of the encoded protein. Expression of hol or hol2 in E. coli was shown to cause cell death. The concomitant expression of λ endolysin (R) and μ1/6 holin resulted in cell lysis. Similarly, the coexpression of the endolysin and holin of phage μ1/6 led to lysis, apparently due to the ability of μ1/6 endolysin to hydrolyze the peptidoglycan layer of this bacterium. In contrast, the simultaneous expression of μ1/6 hol2 and the endolysin gene (λR or μ1/6 lyt) did not cause detectable lysis of the host cells. Demonstration of the holin function in streptomycetes was achieved by providing for the release of μ1/6 endolysin to the periplasm and subsequent cleavage of the peptidoglycan, which strongly suggested that the holin produces lesions in the streptomycete membrane.     

Arginine vasopressin in fever: a still unsolved puzzle

(1) Administration of arginine vasopressin (AVP) in the ventral septal area (VSA) or intracerebroventricularly (i.c.v.) is thought to attenuate lipopolysaccharide (LPS) or prostaglandin (PG) E₂ fevers in rabbits and rats by acting on the V₁ receptor. (2) We found that the fever response of rabbits to intravenous LPS (200 ng/kg) or intra-VSA PGE₂ (500 ng) was not attenuated but enhanced by intra-VSA AVP (5 μg); a pharmacological analysis showed that this fever-enhancing effect was mediated by the V₂ receptor. (3) The febrile response of rats to intraperitoneal (50 μg/kg) or i.c.v. (100 ng) LPS was unaffected by i.c.v. AVP (2.5–100 ng). (4) The role of AVP in fever should be re-examined.