External Ca2+ regulates polycystin-2 (TRPP2) cation currents in LLC-PK1 renal epithelial cells

Polycystin-2 (PC2, TRPP2) is a nonselective cation channel whose dysfunction is associated with the onset of autosomal dominant polycystic kidney disease (ADPKD). PC2 contributes to Ca²⁺ transport and cell signaling in renal epithelia and other tissues. Little is known however, as to the external Ca²⁺ regulation of PC2 channel function. In this study, we explored the effect of external Ca²⁺ on endogenous PC2 in wild type LLC-PK1 renal epithelial cells. We obtained whole cell currents at different external Ca²⁺ concentrations, and observed that the basal whole cell conductance in normal Ca²⁺(1.2 mM), decreased by 30.2% in zero (nominal) Ca²⁺ and conversely, increased by 38% in high external Ca²⁺(6.2 mM). The high Ca²⁺-increased whole cell currents were completely inhibited by either PC2 gene silencing, or intracellular dialysis with active, but not denatured by boiling, PC2 antibody. Exposure of cells to high Ca²⁺ was also associated with relocation of PC2 to the plasma membrane. To explore whether a Ca²⁺ sensing receptor (CaSR) was implicated in the external Ca²⁺ modulation of PC2 currents, we tested the effect of the CaSR agonists, spermine and the calcimimetic R-568, which largely mimicked the effect of high Ca²⁺ under Ca²⁺-free conditions. The CaSR agonist gentamicin also increased the PC2 currents in the presence of normal Ca²⁺. The presence of CaSR was confirmed by immunocytochemistry, which partially colocalized with the intracellular PC2 protein, in an external Ca²⁺-dependent manner. The data support a novel Ca²⁺ sensing mechanism for PC2 expression and functional regulation in renal epithelial cells.     

Prey preferences and recent changes in diet of a breeding population of the Northern Goshawk Accipiter gentilis in Southwestern Europe

Capsule: Northern Goshawk Accipiter gentilis diet has changed significantly since the 1980s, probably due to changes in populations of preferred prey species.

Aims and methods: To assess changes to the breeding season diet of the Northern Goshawk in southwest Europe over three decades. We examined prey remains at and around nests and assessed avian prey availability using point count and line transect surveys.

Results: During 2008–11, Goshawks mainly ate birds, with Feral Pigeons Columba livia f. domestica being the most important prey species. Goshawks preferred prey of 100?400?g and forest prey species to non-forest species. Goshawk diet has changed significantly over recent decades: 22% of current prey items belong to species that were not part of the diet in the 1980s. We suggest that these dietary changes reflect changes in the abundance of prey species of the preferred size caused by changes in land use leading to an increase in forest cover, new prey species colonization and changes in the abundance and management of domestic prey.

Conclusion: This study emphasizes that major transformations occurring in agroforestry systems are affecting the main preferred prey of important forest predators, which may have consequences for conservation of both the predators and their prey.     

A comparison of methods for selecting non-target species for risk assessment of the biological control agent <Emphasis Type="Italic">Cotesia urabae</Emphasis>

A computer-based tool called PRONTI (priority ranking of non-target invertebrates) has been developed to aid the selection of non-target species (NTS) for pre-release testing with entomophagous biological control agents. To test whether PRONTI can improve NTS selection, we used it to produce a prioritised list of NTS for the agent Cotesia urabae Austin & Allen (Hymenoptera: Braconidae), and compared it with the original list that was produced before this species was released in New Zealand in 2011. While the two lists were similar, with five NTS occurring in the top nine of both lists, the remaining four NTS in the top nine of each list were different, primarily because the selection criteria used by the two methods were weighted differently (e.g., PRONTI put more weight on the likelihood of a NTS being exposed to the agent). Post-release testing has demonstrated that C. urabae is able to oviposit in two NTS that were ranked highly on both lists, suggesting both methods are useful for species selection. The main advantages of PRONTI were considered to be its ability to rank hundreds of NTS simultaneously, and to provide a body of information that can be used to both understand each NTS’ ranking and to justify more objectively the selection of NTS for pre-release testing.     

Comparison of the relative efficacy of an insect baiting method and selective media for diversity studies of Metarhizium species in the soil

Metarhizium are a commonly occurring group of entomopathogenic fungi normally found in soil. The most common methods to assess the diversity of Metarhizium species in soil are (i) the use of selective media and (ii) insect baiting using Galleria mellonella larvae. We compared the recovery efficiency from soil of four common species of Metarhizium (Metarhizium anisopliae, Metarhizium pingshaense, Metarhizium brunneum and Metarhizium robertsii) using these two methods. Firstly, we compared the number of colony forming units (CFU) produced in vitro when grown on two selective media, one containing chloramphenicol, thiabendazole and cycloheximidethe (CTC) and one based on the fungicide dodine (n-dodecylguanidine acetate) (DOD). Secondly, we artificially inoculated natural/non-sterile soil with the four fungal species at a rate of 2×10² and 2×10³ conidia g^?1of soil, baited with G. mellonella, and processed for evaluation using the selective media. The in vitro results showed that the greatest number of CFUs were recorded for M. brunneum. In contrast, when inoculated into soil, more G. mellonella larvae became infected by M. anisopliae. Finally, when using selective media, most CFUs recovered were for M. robertsii. The importance of our results in selecting a method to study the natural occurrence of Metarhizium in soil are discussed.