Soil dumping techniques and afforestation drive ground-dwelling beetle assemblages in a 25-year-old open-cast mining reclamation area

The open-cast lignite mine “Hambach” (NW-Germany) and the accompanying land reclamation replace a large ancient forest. Reclamation of an 1000 ha large overburden dump started 25 years ago and is still in progress. Reclamation methods comprise combinations of different topsoil dumping techniques and reclamation measures such as seeding or afforestation. In accordance with the spatial heterogeneity hypothesis, we hypothesize that beetle assemblages from sites where the topsoil was left structured are more diverse than those from sites with levelled topsoil, and that richly structured mid-successional sites harbour more heterogeneous assemblages than afforested sites. We tested the influence of environmental variables on assemblage characteristics of pitfall-trapped beetles from 17 sites on the overburden dump. The results are based on 35,588 individuals from 339 species. Species assemblages differed significantly between almost all sites. Habitat age did not affect assemblage characteristics, while species richness was significantly influenced by surface structure. Sites that were not levelled and that additionally included pits that slope down for several meters exhibited the highest species richness. Abundance of beetles increased in parallel to the canopy cover, whereas assemblage heterogeneity (MVDISP) decreased. Successional and grassland sites usually exhibited higher diversity (Fisher's α) than afforested sites, but diversity was not significantly predicted by a single environmental factor. Instead, diversity increased along with increasing MVDISP-values. Afforestations speed up the successional process and some euryecious forest species are already well established, but stenecious forest specialists have not yet been found.     

Identification and subcellular localization of molecular complexes of Gq/11α protein in HEK293 cells

Heterotrimeric G-proteins localized in the plasma membrane convey the signals from G-protein-coupled receptors (GPCRs) to different effectors. At least some types of G-protein α subunits have been shown to be partly released from plasma membranes and to move into the cytosol after receptor activation by the agonists. However, the mechanism underlying subcellular redistribution of trimeric G-proteins is not well understood and no definitive conclusions have been reached regarding the translocation of Gα subunits between membranes and cytosol. Here we used subcellular fractionation and clear-native polyacrylamide gel electrophoresis to identify molecular complexes of G(q/11)α protein and to determine their localization in isolated fractions and stability in na?ve and thyrotropin-releasing hormone (TRH)-treated HEK293 cells expressing high levels of TRH receptor and G(11)α protein. We identified two high-molecular-weight complexes of 300 and 140 kDa in size comprising the G(q/11) protein, which were found to be membrane-bound. Both of these complexes dissociated after prolonged treatment with TRH. Still other G(q/11)α protein complexes of lower molecular weight were determined in the cytosol. These 70 kDa protein complexes were barely detectable under control conditions but their levels markedly increased after prolonged (4-16 h) hormone treatment. These results support the notion that a portion of G(q/11)α can undergo translocation from the membrane fraction into soluble fraction after a long-term activation of TRH receptor. At the same time, these findings indicate that the redistribution of G(q/11)α is brought about by the dissociation of high-molecular-weight complexes and concomitant formation of low-molecular-weight complexes containing the G(q/11)α protein.     

Altered myocardial Gs protein and adenylyl cyclase signaling in rats exposed to chronic hypoxia and normoxic recovery.

The present work has analyzed the consequences of chronic intermittent high-altitude hypoxia for functioning of the G protein-mediated adenylyl cyclase (AC) signaling system in the right (RV) and left ventricular (LV) myocardium in rats. Adaptation to hypoxia did not appreciably affect the number of beta-adrenoceptors and the content of predominantly membrane-bound alpha-subunit (G(s)alpha) of the stimulatory G protein, but it raised the amount of cytosolic G(s)alpha in RV. The levels of myocardial inhibitory Galpha protein were not altered. Activity of AC stimulated by GTP, fluoride, forskolin, or isoprotertenol was reduced by approximately 50% in RV from chronically hypoxic rats, and a weaker depression was also found in LV. In addition, hypoxia significantly diminished a functional activity of membrane-bound G(s)alpha in both RV and LV. The RV baseline contractile function was markedly increased in chronically hypoxic animals, and its sensitivity to beta-adrenergic stimulation was decreased. Animals recovering from hypoxia for 5 wk still exhibited markedly elevated levels of cytosolic G(s)alpha and significantly lower activity of AC in RV than did age-matched controls, but contractile responsiveness to beta-agonists was normal.     

Increased transmission potential of Leishmania major/Leishmania infantum hybrids

Development of Leishmania infantum/Leishmania major hybrids was studied in two sand fly species. In Phlebotomus papatasi, which supported development of L. major but not L. infantum, the hybrids produced heavy late-stage infections with high numbers of metacyclic promastigotes. In the permissive vector Lutzomyia longipalpis, all Leishmania strains included in this study developed well. Hybrids were found to express L. major lipophosphoglycan, apparently enabling them to survive in P. papatasi midgut. The genetic exchange of the hybrids thus appeared to have enhanced their transmission potential and fitness. A potentially serious consequence is the future spread of the hybrids using this peridomestic and antropophilic vector.     

The SH3 domain of Src can downregulate its kinase activity in the absence of the SH2 domain-pY527 interaction

The contact between the SH2 domain and the C-terminal tail of c-Src inhibits its kinase activity via a complex network of interactions, including the SH3 domain. We examined the role of the SH3 domain in v-Src, where the C-terminal tail is mutated and unbound. We used the v-Src variants Prague C (PRC) and Schmidt-Ruppin A (SRA), which are of low and high kinase activities, respectively, to measure phosphorylation in vitro by immunoprecipitated kinases produced in Saccharomyces cerevisiae. Swapping the regulatory domains between SRA and PRC revealed that N117D, I96T, and V124L mutations in the n-src- and RT-loops of the SH3 domain of PRC are responsible for the low kinase activity of PRC. Moreover, introducing D117N, R95W, T96I, and L124V into activated c-Src(Y527F) caused a 2.5-fold increase in its activity. The mutations in the CD linker KP249,250DG and L255A, which were shown to activate c-Src, had no effect on the activity of the "SH2-activated" Src kinases. Together our data suggest that in the "SH2-activated" forms of Src, the SH3 domain continues to influence the kinase activity via the direct contacts of the n-src- and RT-loops with the kinase N-terminal lobe.     

Autophagic activity in the midgut gland of the overwintering harvestmen Gyas annulatus (Phalangiidae,Opiliones)

Juvenile harvestmen Gyas annulatus overwinter in dormancy in hypogean habitats for 4–5 months. The ultrastructure of the autophagic structures in their midgut epithelium cells was studied by light microscopy, transmission electron microscopy (TEM) and immunofluorescence microscopy (IFM) during this non-feeding period. Before overwintering (November), autophagic structures were scarce. In the middle (January) and at the end of overwintering (March), phagophores, autophagosomes and autolysosomes were present in the cytoplasm of both the secretory and the digestive midgut epithelium cells, gradually increasing their abundance during overwintering. In addition, vacuolization of the cytoplasm intensified. Both processes are induced by starvation. Autophagic structures and cytoplasm vacuolization enable the reuse of the cell's own components required for the maintenance of vital processes during dormancy. While TEM is a much more convenient method for recognition of the autophagic structure types and their ultrastructure, IFM enables exact counting of these structures.