Tissue engineering with muscle-derived stem cells

Tissue engineering and cell therapy approaches aim to take advantage of the repopulating ability and plasticity of multipotent stem cells to regenerate lost or diseased tissue. Researchers continue to investigate stem cells in mature tissues and demonstrate the potential ability of organ-specific cells to differentiate into multiple lineages. One stem cell that displays such promise is the muscle-derived stem cell (MDSC). Data supporting the existence of MDSCs have emerged as part of investigations to improve myoblast cell transplantation for the treatment of muscular dystrophies. As these efforts continue, the potential for MDSC-based therapy for other musculoskeletal injuries, as well as for cardiac and smooth muscle injuries, is currently being explored.     

Integration of signalling pathways in the establishment of the legume-rhizobia symbiosis

The establishment of the legume-rhizobia symbiosis requires recognition of the bacterial microsymbiont at the root epidermis followed by initiation of plant infection and nodule organogenesis programmes. These phenomena are initiated by rhizobial lipochitooligosaccharidic symbiotic signals (the Nod factors). Studies of Nod factor activities, coupled with the recent cloning of genes required for their initiation, are leading to an understanding of the first steps in the signalling pathways. Moreover studies, especially on ethylene, auxin and cytokinin, have shown that phytohormones are involved in controlling or mediating symbiotic responses. The challenge for the future will be to establish how Nod factor signalling integrates with phytohormone activities in the control of infection and nodulation in the establishment of this agronomically and ecologically important symbiosis.     

Temporal genetic patterns of diversity and structure evidence chaotic genetic patchiness in a spiny lobster

Population structure of many marine organisms is spatially patchy and varies within and between years, a phenomenon defined as chaotic genetic patchiness. This results from the combination of planktonic larval dispersal and environmental stochasticity. Additionally, in species with bi‐partite life, postsettlement selection can magnify these genetic differences. The high fecundity (up to 500,000 eggs annually) and protracted larval duration (12–24 months) and dispersal of the southern rock lobster, Jasus edwardsii, make it a good test species for chaotic genetic patchiness and selection during early benthic life. Here, we used double digest restriction site‐associated DNA sequencing (ddRADseq) to investigate chaotic genetic patchiness and postsettlement selection in this species. We assessed differences in genetic structure and diversity of recently settled pueruli across four settlement years and between two sites in southeast Australia separated by approximately 1,000 km. Postsettlement selection was investigated by identifying loci under putative positive selection between recently settled pueruli and postpueruli and quantifying differences in the magnitude and strength of the selection at each year and site. Genetic differences within and among sites through time in neutral SNP markers indicated chaotic genetic patchiness. Recently settled puerulus at the southernmost site exhibited lower genetic diversity during years of low puerulus catches, further supporting this hypothesis. Finally, analyses of outlier SNPs detected fluctuations in the magnitude and strength of the markers putatively under positive selection over space and time. One locus under putative positive selection was consistent at both locations during the same years, suggesting the existence of weak postsettlement selection.     

Analysis of the gut-specific microbiome from field-captured tsetse flies,and its potential relevance to host trypanosome vector competence

Background

The tsetse fly (Glossina sp.) midgut is colonized by maternally transmitted and environmentally acquired bacteria. Additionally, the midgut serves as a niche in which pathogenic African trypanosomes reside within infected flies. Tsetse’s bacterial microbiota impacts many aspects of the fly’s physiology. However, little is known about the structure of tsetse’s midgut-associated bacterial communities as they relate to geographically distinct fly habitats in east Africa and their contributions to parasite infection outcomes. We utilized culture dependent and independent methods to characterize the taxonomic structure and density of bacterial communities that reside within the midgut of tsetse flies collected at geographically distinct locations in Kenya and Uganda.

Results

Using culture dependent methods, we isolated 34 strains of bacteria from four different tsetse species (G. pallidipes, G. brevipalpis, G. fuscipes and G. fuscipleuris) captured at three distinct locations in Kenya. To increase the depth of this study, we deep sequenced midguts from individual uninfected and trypanosome infected G. pallidipes captured at two distinct locations in Kenya and one in Uganda. We found that tsetse’s obligate endosymbiont, Wigglesworthia, was the most abundant bacterium present in the midgut of G. pallidipes, and the density of this bacterium remained largely consistent regardless of whether or not its tsetse host was infected with trypanosomes. These fly populations also housed the commensal symbiont Sodalis, which was found at significantly higher densities in trypanosome infected compared to uninfected flies. Finally, midguts of field-captured G. pallidipes were colonized with distinct, low density communities of environmentally acquired microbes that differed in taxonomic structure depending on parasite infection status and the geographic location from which the flies were collected.

Conclusions

The results of this study will enhance our understanding of the tripartite relationship between tsetse, its microbiota and trypanosome vector competence. This information may be useful for developing novel disease control strategies or enhancing the efficacy of those already in use.

     

Ability to alter song in two grassland songbirds exposed to simulated anthropogenic noise is not related to pre-existing variability

Organisms encounter noise naturally in the environment. However, increasing prevalence of human-caused noise seems to be resulting in behavioural changes in many animals that can affect survival and reproduction. Not all species react the same way to noise; some adjust their vocal signals while others do not. We hypothesized that species with more variability in their vocal signals would be better able to adjust their signals to be audible over anthropogenic noise. We tested this within a large-scale manipulative experiment by recording songs of two grassland songbirds, Baird’s sparrow (Ammodramus bairdii) and Savannah sparrow (Passerculus sandwichensis), both of which are found in areas increasingly affected by energy extraction noise. We compared these species because Savannah sparrows have more variability in their songs geographically and temporally compared to Baird’s sparrows. We recorded both species’ songs before, during and after high-fidelity playbacks of oil well drilling noise. Surprisingly, both species changed parts of their songs in the presence of noise (Baird’s sparrow usually decreasing frequency and Savannah sparrow increasing frequency) and these changes were not related to seasonal, song, or syllable variability. We suggest instead that acoustically heterogeneous environments may favour the evolution of species that are capable of adjusting their songs in response to variable ambient noise.     

The Deviant ATP-binding Site of the Multidrug Efflux Pump Pdr5 Plays an Active Role in the Transport Cycle

Pdr5 is the founding member of a large subfamily of evolutionarily distinct, clinically important fungal ABC transporters containing a characteristic, deviant ATP-binding site with altered Walker A, Walker B, Signature (C-loop), and Q-loop residues. In contrast to these motifs, the D-loops of the two ATP-binding sites have similar sequences, including a completely conserved aspartate residue. Alanine substitution mutants in the deviant Walker A and Signature motifs retain significant, albeit reduced, ATPase activity and drug resistance. The D-loop residue mutants D340A and D1042A showed a striking reduction in plasma membrane transporter levels. The D1042N mutation localized properly had nearly WT ATPase activity but was defective in transport and was profoundly hypersensitive to Pdr5 substrates. Therefore, there was a strong uncoupling of ATPase activity and drug efflux. Taken together, the properties of the mutants suggest an additional, critical intradomain signaling role for deviant ATP-binding sites.     

Not just class: towards an understanding of the whiteness of middle-class schooling choice

There is increased attention to questions of class in studies of education, particularly among those who adopt a Bourdieuian perspective. This paper explores the burgeoning literature on school choice and class (in particular middle ‘classness’) to argue that there are serious analytical and sociological costs to a singular focus on class without due attention to race. Examining interview material, it will show instances where the racialized nature of schooling choice has been ignored or overlooked. It argues that viewing the literature through the lens of race and class is imperative for an understanding of the complexities of class and white middle classness in particular.     

Long-Lasting Insecticidal Nets Are Synergistic with Mass Drug Administration for Interruption of Lymphatic Filariasis Transmission in Nigeria

In central Nigeria Anopheles mosquitoes transmit malaria and lymphatic filariasis (LF). The strategy used for interrupting LF transmission in this area is annual mass drug administration (MDA) with albendazole and ivermectin, but after 8 years of MDA, entomological evaluations in sentinel villages showed continued low-grade mosquito infection rates of 0.32%. After long-lasting insecticidal net (LLIN) distribution by the national malaria program in late 2010, however, we were no longer able to detect infected vectors over a 24-month period. This is evidence that LLINs are synergistic with MDA in interrupting LF transmission.