Isolation and characterisation of polymorphic microsatellite loci in the vulnerable spectacled flying fox, Pteropus conspicillatus

The spectacled flying fox, Pteropus conspicillatus, is listed as vulnerable in Australia and is under threat from numerous impacts. Primers to amplify eight co-dominant microsatellite loci were designed for Pteropus conspicillatus, based on an enriched genomic library. Four loci were monomorphic in this species while the remaining four loci were highly polymorphic with 16–23 alleles. Two of the four monomorphic loci were found to be polymorphic in Pteropus alecto, a closely related congener. All but one of the six polymorphic loci were in Hardy Weinberg equilibrium. Additionally, six microsatellite loci isolated for Pteropus rodricensis were tested against individuals of P. conspicillatus with all loci amplifying reliably. These loci will be used to investigate population genetic structure in the vulnerable spectacled flying fox.     

Total Dental Occlusal Area as a Feeding Constraint Feature in Extant Walruses (Odobenus rosmarus), and Implications for the Evolution of Molluscivory in Odobenidae

Journal of Mammalian Evolution - Mammalian dental formulae often are highly conserved, at least at a generic level. In walruses (Odobenus rosmarus), the constraints of dentition in light of...     

Zic1 mRNA is transiently upregulated in subcutaneous fat of acutely cold-exposed mice

In the mammalian adipose organ cold exposure not only activates typical brown adipose tissue, but also induces browning, that is the formation of thermogenic multilocular adipocytes in white, or predominantly white, adipose depots such as subcutaneous fat. Unlike typical brown adipocytes, newly formed thermogenic adipocytes have been reported not to express the gene zinc finger of the cerebellum 1 (Zic1). Here, a time course approach enabled us to document a significant increase in Zic1 messenger RNA in inguinal subcutaneous fat from acutely (24 hr) cold-exposed mice, which was paralleled by an increase in multilocular and paucilocular uncoupling protein 1-positive adipocytes and in parenchymal noradrenergic innervation. This transient, depot-specific molecular signature was associated not to Zic1 promoter demethylation, but to chromatin remodeling through an H3K9me3 histone modification. These findings challenge the notion that Zic1 is exclusively expressed by typical brown adipocytes and suggest its involvement in brown adipocyte precursor differentiation and/or white-to-brown adipocyte transdifferentiation.     

Generation and characterization of neuregulin-2-deficient mice

The neuregulins (NRGs) are a family of four structurally related growth factors that are expressed in the developing and adult brain. NRG-1 is essential for normal heart formation and has been implicated in the development and maintenance of both neurons and glia. NRG-2 was identified on the basis of its homology to NRG-1 and, like NRG-1, is expressed predominantly by neurons in the central nervous system. We have generated mice with the active domain of NRG-2 deleted in an effort to characterize the biological function of NRG-2 in vivo. In contrast to the NRG-1 knockout animals, NRG-2 knockouts have no apparent heart defects and survive embryogenesis. Mutant mice display early growth retardation and reduced reproductive capacity. No obvious histological differences were observed in the major sites of NRG-2 expression. Our results indicate that in vivo NRG-2 activity differs substantially from that of NRG-1 and that it is not essential for normal development in utero.     

Pollinarium morphology and floral rewards in Brazilian Maxillariinae (Orchidaceae)

BACKGROUND AND AIMS: There is strong support for the monophyly of the orchid subtribe Maxillariinae s.l., yet generic boundaries within it are unsatisfactory and need re-evaluation. In an effort to assemble sets of morphological characters to distinguish major clades within this subtribe, the pollinarium morphology and floral rewards of representative Brazilian species of this subtribe were studied. METHODS: The study was based on fresh material from 60 species and seven genera obtained from cultivated specimens. Variation of pollinarium structure and floral rewards was assessed using a stereomicroscope and by SEM analysis. KEY RESULTS: Four morphological types of pollinaria are described. Type 1 appears to be the most widespread and is characterized by a well-developed tegula. Type 2 lacks a stipe and the pollinia are attached directly to the viscidium. Type 3 also lacks a stipe, and the viscidium is rigid and dark. In Type 4, the stipe consists of the whole median rostelar portion and, so far, is known only from Maxillaria uncata. Nectar, trichomes, wax-like and resin-like secretions are described as flower rewards for different groups of species within the genus Maxillaria. Data on the biomechanics and pollination biology are also discussed and illustrated. In Maxillariinae flowers with arcuate viscidia, the pollinaria are deposited on the scuttellum of their Hymenopteran pollinators. In contrast, some flowers with rounded to rectangular, pad-like viscidia fix their pollinaria on the face of their pollinators. CONCLUSIONS: Pollinarium morphology and floral features related to pollination in Brazilian Maxillariinae are more diverse than previously suggested. It is hoped that the data presented herein, together with other data sources such as vegetative traits and molecular tools, will be helpful in redefining and diagnosing clades within the subtribe Maxillariinae.     

Comparison of different probe-level analysis techniques for oligonucleotide microarrays

Three different software packages for the probe-level analysis of high-density oligonucleotide microarray data were compared using an experiment-derived data set that was validated using real-time PCR. The efficiency with which these three programs could identify true positives in this data set was assessed. In addition, estimates of false-positive and false-negative rates were determined. The performance of the programs using very small data sets was also compared, and recommendations for use are suggested.     

Increased attention to spatial context increases both place field stability and spatial memory

The hippocampal formation is critical for the acquisition and consolidation of memories. When recorded in freely moving animals, hippocampal pyramidal neurons fire in a location-specific manner: they are "place" cells, comprising a hippocampal representation of the animal's environment. To explore the relationship between place cells and spatial memory, we recorded from mice in several behavioral contexts. We found that long-term stability of place cell firing fields correlates with the degree of attentional demands and that successful spatial task performance was associated with stable place fields. Furthermore, conditions that maximize place field stability greatly increase orientation to novel cues. This suggests that storage and retrieval of place cells is modulated by a top-down cognitive process resembling attention and that place cells are neural correlates of spatial memory. We propose a model whereby attention provides the requisite neuromodulatation to switch short-term homosynaptic plasticity to long-term heterosynaptic plasticity, and we implicate dopamine in this process.     

Gating the bacterial mechanosensitive channels: MscS a new paradigm?

Mechanosensitive channels play major roles in protecting bacteria from hypo-osmotic shock. In the millisecond timescale they must achieve the transition from tightly closed oligomers to large, relatively non-discriminating pores. The crystal structure for MscL, combined with genetic and biochemical analysis, provided the initial insights for the mechanism by which this structural transition might be made. Discovery of the gene for a second class of mechanosensitive channel, MscS, and its subsequent crystallisation, has provided a new paradigm for mechanosensation, enabling a deeper understanding of the mechanisms of sensing membrane tension.