Generation of Leptin Receptor Bone Marrow Chimeras: Recovery From Irradiation,Immune Cellularity,Cytokine Expression,and Metabolic Parameters

Leptin regulates appetite and metabolism but also immunity and inflammation. Although functional leptin receptors (LepR) are expressed on hematopoietic cells, the role of these receptors in regulating immune function in vivo remains controversial. To clarify this issue, we performed bone marrow (BM) transplantation between obese db/db mice, lacking LepR, and wild‐type (WT) mice. Results indicate that expression of LepR on BM‐derived cells directly, though partially, regulates spleen and thymus cellularity, although the environment of db mice contributes to maintaining reduced cellularity of these organs. Selective expression of LepR on BM‐derived cells also modulates leptin and adiponectin levels, with induction of a more favorable adipokine environment in the WT→db/db group. However, LepR signaling in BM‐derived cells is not involved in regulation of body weight (BW) and composition, glycemia, hepatosteatosis or adipose tissue inflammation, although it modulates expression of interleukin (IL)‐1β in the brain. Finally, data indicate that db mice have an increased susceptibility to irradiation compared to WT mice in terms of BW loss and recovery of leukocyte counts in peripheral blood. Therefore, interpretation of results obtained using BM chimeras between WT and db mice should take into account the difference in radiation sensitivity between the two types of animals.     

A comparison of the autecology of two seed-taking ant genera, <Emphasis Type="Italic">Rhytidoponera</Emphasis> and <Emphasis Type="Italic">Melophorus</Emphasis>

Members of the genus Rhytidoponera and, to a lesser extent, certain Melophorus spp. are keystone mutualists for the dispersal of seeds in the southwest of Western Australia, with important ramifications for the ecology and speciation of plants in this biodiversity hotspot. For this reason, it is important to understand the autecology of the relevant ant species and the way in which they interact with plant seeds. This paper addresses key aspects of the ecology of three such ant species, Rhytidoponera violacea (Forel), R. inornata Crawley and Melophorus turneri perthensis Wheeler. Data are presented on their geographic distribution, seasonality of foraging, diurnal activity, response to fire, nest site preference, nest structure, colony size, feeding habits, foraging response to seed availability, and seedling emergence from nests. The role of all three species as seed dispersers is confirmed, and all three species have ecologies that are well-suited for dispersal and survival of native plant seeds. Preservation of this interaction is important for the conservation of plants, and it is fortuitous that all three species are able to survive disturbance and return to rehabilitated areas. However, the smaller R. inornata, and to a lesser extent, the larger R. violacea, are vulnerable to invasive ant [Pheidole megacephala (Fabricius)] incursions. M. turneri perthensis is able to coexist with the invasive ant unless this is at high densities, probably as a result of its ability to forage during high temperatures when the invasive species is inactive.     

Study of permeation and blocker binding in TMEM16A calcium-activated chloride channels

We studied the effects of mutations of positively charged amino acid residues in the pore of X. tropicalis TMEM16A calcium-activated chloride channels: K613E, K628E, K630E; R646E and R761E. The activation and deactivation kinetics were not affected, and only K613E showed a lower current density. K628E and R761E affect anion selectivity without affecting Na⁺ permeation, whereas K613E, R646E and the double mutant K613E + R646E affect anion selectivity and permeability to Na⁺. Furthermore, altered blockade by the chloride channel blockers anthracene-9-carboxylic acid (A-9-C), 4, 4''-Diisothiocyano-2,2''-stilbenedisulfonic acid (DIDS) and T16inh-A01 was observed. These results suggest the existence of 2 binding sites for anions within the pore at electrical distances of 0.3 and 0.5. These sites are also relevant for anion permeation and blockade.