The importance of microclimate variation in determining size,growth and survival of avian offspring: experimental evidence from a cavity nesting passerine

Organisms are expected to balance energy allocation in such a way that fitness is maximized. While much research has focussed on allocation strategies of reproducing parents, in particular birds, relatively little attention has been paid to how nestlings allocate energy while in the nest. Nestling birds are faced with a trade-off between devoting energy to growth or to thermoregulation, and in altricial species it is likely that the thermal environment of the nest site influences the nature of this trade-off. Here, we experimentally investigate how altering the microclimate of nests affects the growth, size and survival, as well as cell-mediated immune (CMI) response, of nestling tree swallows (Tachycineta bicolor) in a temperate environment. We place air-activated heating pads in nests of swallows when young were between 4 days and 16 days of age, and compared performance of offspring to control nests. Our manipulation raised temperatures of heated nests by approximately 5°C compared to control nests. Offspring in heated nests had enhanced survival while in the nest, and we also found that they were heavier and had longer ninth primary feathers at 16 days of age. In addition, heating nest boxes resulted in significantly faster growth of primaries, and there was a trend for growth rates of mass to also be higher in heated nests. There were no significant differences between heated and control nests in growth rate or size of tarsus at age 16 days, and we speculate that this lack of response to elevated nest temperatures may be due to growth of skeletal structures being limited by other factors such as calcium availability. We also found no difference between heated and control nests in CMI response. Nonetheless, our results show overall that increasing temperatures of nests has significant benefits that enhance the fitness of offspring. As provisioning rates to offspring did not differ between heated and control nests, we suspect that the beneficial effects of heating were not the consequence of changes in parental behaviour. Our results provide insight into factors, other than food supply, that have important consequences in determining reproductive success of birds breeding in temperate environments.     

Simple Reaching Is Not So Simple: Association Between Hand Use and Grip Preferences in Captive Chimpanzees

We assessed the relationship between grip preference and hand use in chimpanzees in 2 experiments. In experiment 1, we evaluated consistency in hand use and grip preference across 4 food types. The chimpanzees showed population-level right-handedness and there are significant positive associations for both hand and grip use across food types. In experiment 2, we assessed validity of hand use in relation to grip preference in 2 colonies of chimpanzees via the same methodology. Differences in hand preferences between colonies were associated with variation in the observed grip preferences. There was no evidence of rearing effects on handedness in either colony. We discuss the overall results in the context of the evolution of handedness in relation to increasing motor demands as manifest in variation on grasping behavior.     

Activated bovine cytoplasts prepared by demecolcine-induced enucleation support development of nuclear transfer embryos in vitro

Demecolcine-induced enucleation (IE) of mouse oocytes has been shown to improve development to term of cloned mice. In this study, we characterized the kinetics and morphological progression of bovine oocytes subjected to IE, and evaluated their ability to support embryo development to the blastocyst stage after nuclear transfer (NT). In vitro matured bovine oocytes were parthenogenetically activated and subsequently exposed to demecolcine at various times post-activation. Onset and duration of demecolcine treatment significantly altered activation and IE frequencies, which varied from 7.1% to 100% and 33.3% to 91.7%, respectively, at 5 hr post-activation. A significant decrease in IE frequencies was observed at 17 hr post-activation (3.4%-46.1%), possibly due to reincorporation of chromosomes into the oocyte after incomplete second polar body (PB) extrusion. Oocytes were reconstructed by NT before (treatment 1) or after (treatment 2) activation and demecolcine treatment, and cultured in vitro. Cleavage (48.1%-54.2%) and blastocyst rates (15.7%-19%) were equivalent for the two treatments, as well as the total cell number in NT blastocysts. Furthermore, most of the blastocysts were completely diploid (treatment 2) or heteroploid but with a majority of diploid nuclei (treatment 1). Our results demonstrate that the IE method can be successfully used to produce enucleated bovine cytoplasts that are competent to support development to the blastocyst stage after NT. This technically simple approach may provide a more efficient method to enhance the success rate of NT procedures. Further studies are needed to improve the in vitro development efficiency and to expand our understanding of the mechanism(s) involved in demecolcine-induced enucleation.     

Gp78, a membrane-anchored ubiquitin ligase, associates with Insig-1 and couples sterol-regulated ubiquitination to degradation of HMG CoA reductase

Sterol-regulated ubiquitination is an obligatory step in ER-associated degradation (ERAD) of HMG CoA reductase, a rate-limiting enzyme in cholesterol synthesis. Accelerated degradation of reductase, one of several strategies animal cells use to limit production of cholesterol, requires sterol-induced binding of the enzyme to ER membrane proteins called Insigs. Once formed, the reductase-Insig complex is recognized by a putative membrane-associated ubiquitin ligase (E3) that mediates the reductase ubiquitination reaction. Here, we show that gp78, a membrane bound E3, binds to Insig-1 and is required for sterol-regulated ubiquitination of reductase. In addition, gp78 couples regulated ubiquitination to degradation of reductase by binding to VCP, an ATPase that plays a key role in recognition and degradation of ERAD substrates. The current results identify gp78 as the E3 that initiates sterol-accelerated degradation of reductase, and Insig-1 as a bridge between gp78/VCP and the reductase substrate.     

Analysis of Xenorhabdus nematophila metabolic mutants yields insight into stages of Steinernema carpocapsae nematode intestinal colonization

Xenorhabdus nematophila colonizes the intestinal tract of infective-juvenile (IJ) stage Steinernema carpocapsae nematodes. During colonization, X. nematophila multiplies within the lumen of a discrete region of the IJ intestine termed the vesicle. To begin to understand bacterial nutritional requirements during multiplication in the IJ vesicle, we analysed the colonization behaviour of several X. nematophila metabolic mutants, including amino acid and vitamin auxotrophs. X. nematophila mutants defective for para-aminobenzoate, pyridoxine or l-threonine biosynthesis exhibit substantially decreased colonization of IJs (0.1-50% of wild-type colonization). Analysis of gfp-labelled variants revealed that those mutant cells that can colonize the IJ vesicle differ noticeably from wild-type X. nematophila. One aberrant colonization phenotype exhibited by the metabolic mutants tested, but not wild-type X. nematophila, is a spherical shape indicative of apparently non-viable X. nematophila cells within the vesicle. Because these spherical cells appear to have initiated colonization but failed to proliferate, we term this type of colonization 'abortive'. In a portion of IJs grown on para-aminobenzoate auxotrophs, X. nematophila does not exhibit abortive colonization but rather reduced growth and filamentous cell morphology. Several mutants with defects in other amino acid, vitamin and nutrient metabolism pathways colonize IJs to wild-type levels suggesting that the IJ vesicle is replete with respect to a number of nutrients.     

The lipid A palmitoyltransferase PagP: molecular mechanisms and role in bacterial pathogenesis

Palmitoylated lipid A can both protect pathogenic bacteria from host immune defences and attenuate the activation of those same defences through the TLR4 signal transduction pathway. A palmitate chain from a phospholipid is incorporated into lipid A by an outer membrane enzyme PagP, which is an 8-stranded antiparallel beta-barrel preceded by an amino-terminal amphipathic alpha-helix. The PagP barrel axis is tilted by 25 degrees with respect to the membrane normal. An interior hydrophobic pocket in the outer leaflet-exposed half of the molecule functions as a hydrocarbon ruler that allows the enzyme to distinguish palmitate from other acyl chains found in phospholipids. Internalization of a phospholipid palmitoyl group within the barrel appears to occur by lateral diffusion from the outer leaflet through non-hydrogen-bonded regions between beta-strands. The MsbA-dependent trafficking of lipids from the inner membrane to the outer membrane outer leaflet is necessary for lipid A palmitoylation in vivo. The mechanisms by which bacteria regulate pagP gene expression strikingly reflect the corresponding pathogenic lifestyle of the bacterium. Variations on PagP structure and function can be illustrated with the known homologues from Gram-negative bacteria, which include pathogens of humans and other mammals in addition to pathogens of insects and plants. The PagP enzyme is potentially a target for the development of anti-infective agents, a probe of outer membrane lipid asymmetry, and a tool for the synthesis of lipid A-based vaccine adjuvants and endotoxin antagonists.     

A role for topoisomerase III in a recombination pathway alternative to RuvABC

The physiological role of topoisomerase III is unclear for any organism. We show here that the removal of topoisomerase III in temperature sensitive topoisomerase IV mutants in Escherichia coli results in inviability at the permissive temperature. The removal of topoisomerase III has no effect on the accumulation of catenated intermediates of DNA replication, even when topoisomerase IV activity is removed. Either recQ or recA null mutations, but not helD null or lexA3, partially rescued the synthetic lethality of the double topoisomerase III/IV mutant, indicating a role for topoisomerase III in recombination. We find a bias against deleting the gene encoding topoisomerase III in ruvC53 or DeltaruvABC backgrounds compared with the isogenic wild-type strains. The topoisomerase III RuvC double mutants that can be constructed are five- to 10-fold more sensitive to UV irradiation and mitomycin C treatment and are twofold less efficient in transduction efficiency than ruvC53 mutants. The overexpression of ruvABC allows the construction of the topoisomerase III/IV double mutant. These data are consistent with a role for topoisomerase III in disentangling recombination intermediates as an alternative to RuvABC to maintain the stability of the genome.     

Structure-based design of protein tyrosine phosphatase-1B inhibitors

Using structure-based design, a new class of inhibitors of protein tyrosine phosphatase-1B (PTP1B) has been identified, which incorporate the 1,2,5-thiadiazolidin-3-one-1,1-dioxide template.     

Synthesis of alkyne derivatives of a novel triazolopyrazine as A(2A) adenosine receptor antagonists

A novel [1,2,4]triazolo[1,5-a]pyrazine core was synthesized and coupled with terminal acetylenes. The structure-activity relationship of the alkynes from this novel template was studied for their in vitro and in vivo adenosine A(2A) receptor antagonism. Selected compounds from this series were shown to have potent in vitro and in vivo activities against adenosine A(2A) receptor. Compound 12, in particular, was found to be orally active at 3mg/kg in both a mouse catalepsy model and a 6-hydroxydopamine-lesioned rat model.     

Design, synthesis, and evaluation of proline based melanocortin receptor ligands

A series of proline based melanocortin ligands has been developed on the basis of initial piperazine leads by using a more conformationally rigid scaffold. A number of these novel ligands showed significant binding affinity for MC3 and MC4 receptors.