Community reorganization revealed by exploring shifts in the diet of an apex predator,the Golden Eagle Aquila chrysaetos,with stable isotopes and prey remains

Golden Eagles Aquila chrysaetos colonized the northern California Channel Islands, an archipelago located off the coast of southern California, USA, in the early 1990s, owing in part to the presence of Feral Pigs Sus scrofa. Eagles preyed on piglets and on the endemic Island Fox Urocyon littoralis, driving three endemic subspecies of the Island Fox (U. l. santacruzae, U. l. santarosae and U. l. littoralis) toward extirpation. Using stable isotopes (δ¹³C and δ¹⁵N) measured from feathers and blood of Golden Eagles and from meat and bone of their prey, along with the proportion of prey consumed estimated from nest excavations as informative priors, we show that shifts in Eagle isotopic signatures tracked community reorganization: when pigs and foxes were abundant, Eagles consumed them in higher proportions than other prey; when foxes became scarce owing to Eagle predation, Eagle diet shifted toward pigs, but also diversified to include Common Ravens Corvus corax and seabirds (Larus spp. and Phalacrocorax spp.); and finally, after pigs were eradicated and 35 Golden Eagles had been captured and removed from Santa Cruz Island, a lone remaining pair of Eagles reversed their diet to include more foxes. Our findings reveal that shifts in stable isotope signatures from tissues of an apex predator can be used as a general proxy to monitor changes in the prey community; however, if sample sizes are small, informative priors are both essential and overwhelmingly influential, and changes in abundance of preferred prey may mask or fail to reveal changes in less preferred prey. Given that apex predators are at the top of trophic hierarchies, that they are often important drivers of community structure and that they sample prey continuously from their community, isotopic signatures of their tissues may be useful for monitoring community change.     

JNK2 translocates to the mitochondria and mediates cytochrome c release in PC12 cells in response to 6-hydroxydopamine

6-Hydroxydopamine (6-OHDA) causes death of dopaminergic neurons by mitochondrial dysfunction with JNKs as central mediators. Here we provide novel insights into specific actions of JNK isoforms in 6-OHDA-induced death of PC12 cells. Twenty five mum 6-OHDA enhanced total JNK activity in the cytoplasm, nucleus, and at the mitochondria. Inhibition of JNKs by 2 mum SP600125 or transfection with dominant-negative JNK2 (dnJNK2) rescued more than 60% of the otherwise dying PC12 cells after 24 h, whereas transfection with dnJNK1 had no protective effects. In contrast to constitutively present JNK1, JNK2 amounts increased in the nucleus and at the mitochondria after 6-OHDA stimulation. JNK inhibition by SP600125 or transfection of dnJNK2 reduced the pool of active JNKs in the nucleus, the release of cytochrome c, as well as the cleavage of caspase-3 and its substrate poly(ADP-ribose) polymerase-1. Transfection with dnJNK1, however, had no effects on the translocation of JNKs to the mitochondria or the release of cytochrome c. Our data provide novel functional insights into the pathological role of individual JNK isoforms, the signalosome at the mitochondria, and the mode of JNK-induced release of cytochrome c.     

The yeast kinome displays scale free topology with functional hub clusters

Background  

The availability of interaction databases provides an opportunity for researchers to utilize immense amounts of data exclusively in silico. Recently there has been an emphasis on studying the global properties of biological interactions using network analysis. While this type of analysis offers a wide variety of global insights it has surprisingly not been used to examine more localized interactions based on mechanism. In as such we have particular interest in the role of key topological components in signal transduction cascades as they are vital regulators of healthy and diseased cell states.     

Selection of polarized growth sites in yeast

The budding yeast Saccharomyces cerevisiae responds to intracellular and extracellular cues to direct cell growth. Genetic analysis has revealed many components that participate in this process and has provided insight into the mechanisms by which these proteins function. Several of these components, such as the septins, pheromone receptors and GTPase proteins, have homologues in multicellular eukaryotes, suggesting that many aspects of polarized cell growth may be conserved throughout evolution. This review discusses our current understanding of the molecular mechanisms of growth-site selection during the different stages of the yeast life cycle.     

Growth and cell wall composition of glucose-limited bean cells (Phaseolus vulgaris L.)

Glucose-limited bean cells (Phaseolus vulgaris L.) were grown in a modified bacterial fermentor at a constant pH of 4.8. The cultures were kept in steady state at different specific growth rates varying from 0.00216 h^–1 to 0.0106 h^–1. Culture conditions are described that are needed to start a continuous culture. First, it was essential to use log-phase cells as starting material. Second, it was important to increase the dilution rate gradually, otherwise cells in the culture aggregated. Cells grown at the highest dilution rate employed contained twice as much protein per gram dry weight as cells grown at the lowest dilution rate. The composition of the cell walls also varied with the dilution rate in contrast to their relatively constant composition when grown in batch culture.     

Zur Frage des spezifischen Gewichtes von Äpfeln als Eigenschaftsmerkmal

Ohne ZusammenfassungMit 8 Abbildungen     

Structure activity relationship of orally active enkephalin analogues as analgesics.

Substitution of glycine in position 2 of the naturally occurring methionine-enkephalin by D-alanine, methylation of tyrosine and phenylalanine i in position 1 and 4 respectively and conversion of the methionine in position 5 to the corresponding alcohol sulfoxide lead to potent orally active enkephalin analogues with marked analgesic properties.     

Effects of prostaglandins, calcium, and bradykinin on guanylate cyclase in different organs.

The effects of prostaglandins and bradykinin on the activity of guanylate cyclase in plasma membranes from rat uterus and duodenum have been found strongly dependent on calcium content.