Behaviour and dispersal in adult Taeniopteryx nebulosa (Linnaeus, 1758) and Perlodes microcephalus (Pictet, 1833) (Plecoptera) in Denmark

Adult Taeniopteryx nebulosa (Linnaeus, 1758 Linnaeus, C. (1758), Systema Naturae (10th ed.), Tom 1, Holmiae. [Google Scholar]) and Perlodes microcephalus (Pictet, 1833 Pictet, J., (1833), ‘Memoire sur la Metamorphoses des Perles’, Annales des Sciences Naturelles, XXVII, 44–55. [Google Scholar]) emerge late winter to early spring in Danish streams. Based on 13 years of study, we have provided new data and discussed little-known aspects of biology of these two species. Taeniopteryx nebulosa male deposits a spermatophore on the female gonopore. Both species are poor fliers and seek high posts for take-off, where they thermoregulate by basking in a pre-flight sun posture for heating flight muscles. Oviposition flight is erratic and short. The females skim back to land. Taeniopteryx nebulosa eggs drift a long distance as single eggs before adhering to vegetation. Perlodes microcephalus eggs drift a short distance as intact eggpackets before they fasten and disintegrate on the bottom. Perlodes microcephalus females select oviposition sites on or close to upstream a riffle. This is critical in ensuring that eggs fasten on stable gravel and stone bottoms. The fast recolonisation of P. microcephalus in Danish streams following restoration measures indicates efficient dispersal ability despite poor flight performance. Adults of both species adhere to clothes, feather and fur. Taeniopteryx nebulosa tarsomeres have many hooked setae, P. microcephalus tarsomeres have some hooked setae and a dense cover of microtrichia. They may disperse by hitchhiking on birds and mammals.     

Urokinase links plasminogen activation and cell adhesion by cleavage of the RGD motif in vitronectin

Components of the plasminogen activation system including urokinase (uPA), its inhibitor (PAI‐1) and its cell surface receptor (uPAR) have been implicated in a wide variety of biological processes related to tissue homoeostasis. Firstly, the binding of uPA to uPAR favours extracellular proteolysis by enhancing cell surface plasminogen activation. Secondly, it promotes cell adhesion and signalling through binding of the provisional matrix protein vitronectin. We now report that uPA and plasmin induces a potent negative feedback on cell adhesion through specific cleavage of the RGD motif in vitronectin. Cleavage of vitronectin by uPA displays a remarkable receptor dependence and requires concomitant binding of both uPA and vitronectin to uPAR. Moreover, we show that PAI‐1 counteracts the negative feedback and behaves as a proteolysis‐triggered stabilizer of uPAR‐mediated cell adhesion to vitronectin. These findings identify a novel and highly specific function for the plasminogen activation system in the regulation of cell adhesion to vitronectin. The cleavage of vitronectin by uPA and plasmin results in the release of N‐terminal vitronectin fragments that can be detected in vivo, underscoring the potential physiological relevance of the process.     

Deciphering structure-activity relationships in a series of Tat/TAR inhibitors

A series of pentameric “Polyamide Amino Acids” (PAAs) compounds derived from the same trimeric precursor have been synthesized and investigated as HIV TAR RNA ligands, in the absence and in the presence of a Tat fragment. All PAAs bind TAR with similar sub-micromolar affinities but their ability to compete efficiently with the Tat fragment strongly differs, IC₅₀ ranging from 35 nM to >2 μM. While NMR and CD studies reveal that all PAA interact with TAR at the same site and induce globally the same RNA conformational change upon binding, a comparative thermodynamic study of PAA/TAR equilibria highlights distinct TAR binding modes for Tat competitor and non-competitor PAAs. This led us to suggest two distinct interaction modes that have been further validated by molecular modeling studies. While the binding of Tat competitor PAAs induces a contraction at the TAR bulge region, the binding of non-competitor ones widens it. This could account for the distinct PAA ability to compete with Tat fragment. Our work illustrates how comparative thermodynamic studies of a series of RNA ligands of same chemical family are of value for understanding their binding modes and for rationalizing structure-activity relationships.     

EDTA/gelatin zymography method to identify C1s versus activated MMP‐9 in plasma and immune complexes of patients with systemic lupus erythematosus

Gelatin zymography analysis is a sensitive method and commonly used to characterize and quantify the presence of the gelatinases (MMP‐2 and MMP‐9) in biological samples. In human plasma samples from healthy controls and systemic lupus erythematosus (SLE) patients, we observed a gelatinolytic molecule at 80 kDa, suggestive for activated human MMP‐9. However, by developing and using the EDTA/gelatin zymography method and after purification of the 80 kDa entity, we proved that this molecule was the C1s subunit of the complement system. The zymolytic capacity of C1s was validated and found to be enhanced, in the absence of calcium and in the presence of EDTA. Our findings indicate that for correct identification of gelatinolytic proteins in complex biological samples the use of EDTA/gelatin zymography for enzyme development is advised. In addition, by quantification of EDTA/gelatin zymography analysis and ELISA, we observed that the levels of C1s were higher in plasma and immune complexes of SLE patients than of healthy individuals. Therefore, our data imply that C1s may become a marker for the diagnosis of SLE.     

Mechanisms Preserving Insulin Action during High Dietary Fat Intake

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Seed germination and dormancy traits of forbs and shrubs important for restoration of North American dryland ecosystems

• In degraded dryland systems, native plant community re‐establishment following disturbance is almost exclusively carried out using seeds, but these efforts commonly fail. Much of this failure can be attributed to the limited understanding of seed dormancy and germination traits.
• We undertook a systematic classification of seed dormancy of 26 species of annual and perennial forbs and shrubs that represent key, dominant genera used in restoration of the Great Basin ecosystem in the western United States. We examined germination across a wide thermal profile to depict species‐specific characteristics and assessed the potential of gibberellic acid (GA₃) and karrikinolide (KAR₁) to expand the thermal germination envelope of fresh seeds.
• Of the tested species, 81% produce seeds that are dormant at maturity. The largest proportion (62%) exhibited physiological (PD), followed by physical (PY, 8%), combinational (PY + PD, 8%) and morphophysiological (MPD, 4%) dormancy classes. The effects of chemical stimulants were temperature‐ and species‐mediated. In general, mean germination across the thermal profile was improved by GA₃ and KAR₁ for 11 and five species, respectively. We detected a strong germination response to temperature in freshly collected seeds of 20 species. Temperatures below 10 °C limited the germination of all except Agoseris heterophylla, suggesting that in their dormant state, the majority of these species are thermally restricted.
• Our findings demonstrate the utility of dormancy classification as a foundation for understanding the critical regenerative traits in these ecologically important species and highlight its importance in restoration planning.

     

The MlotiK1 channel transports ions along the canonical conduction pore

Although the cyclic nucleotide-modulated potassium channel from Mesorhizobium loti, MlotiK1, is easily studied using a 86Rb+ flux assay, its comparatively low activity raises serious concerns about the integrity of the purified protein. We investigated the pathway of uptake using a multi-pronged approach. First, we probed the conduction pathway using quaternary ammonium compounds known to block conduction in eukaryotic K+ channels. Second, we examined the effect of chemical modification of putative pore-lining residues. Our results are consistent with ions traversing MlotiK1 along a conduction pathway like that of the eukaryotic channels, but at a much slower rate.