Size and sex matter: reproductive biology and determinants of offspring survival in Gazella marica

For prey, many behavioural traits are constrained by the risk of predation. Therefore, shifts between warning and cryptic coloration have been suggested to result in parallel changes in several behaviours. In the present study, we tested whether changes in chromatic contrast among eight populations of the strawberry poison‐dart frog, Dendrobates pumilio, co‐vary with behaviour, as expected if selection is imposed by predators relying on visual detection of prey. These eight populations are geographically isolated on different island in the Bocas del Toro region of Panama and have recently diverged morphologically and genetically. We found that aggression and explorative behaviour were strongly correlated and also that males tended to be more aggressive and explorative if they belonged to populations with conspicuously coloured individuals. We discuss how evolutionary switches between predator avoidance strategies and associated behavioural divergence between populations may affect reproductive isolation. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ●● , ●●–●●.     

Cellulase–lignin interactions—The role of carbohydrate-binding module and pH in non-productive binding

Non-productive cellulase adsorption onto lignin is a major inhibitory mechanism preventing enzymatic hydrolysis of lignocellulosic feedstocks. Therefore, understanding of enzyme–lignin interactions is essential for the development of enzyme mixtures and processes for lignocellulose hydrolysis. We have studied cellulase–lignin interactions using model enzymes, Melanocarpus albomyces Cel45A endoglucanase (MaCel45A) and its fusions with native and mutated carbohydrate-binding modules (CBMs) from Trichoderma reesei Cel7A. Binding of MaCel45A to lignin was dependent on pH in the presence and absence of the CBM; at high pH, less enzyme bound to isolated lignins. Potentiometric titration of the lignin preparations showed that negatively charged groups were present in the lignin samples and that negative charge in the samples was increased with increasing pH. The results suggest that electrostatic interactions contributed to non-productive enzyme adsorption: Reduced enzyme binding at high pH was presumably due to repulsive electrostatic interactions between the enzymes and lignin. The CBM increased binding of MaCel45A to the isolated lignins only at high pH. Hydrophobic interactions are probably involved in CBM binding to lignin, because the same aromatic amino acids that are essential in CBM–cellulose interaction were also shown to contribute to lignin-binding.     

High production of cold-tolerant chitinases on shrimp wastes in bench-top bioreactor by the Antarctic fungus Lecanicillium muscarium CCFEE 5003: Bioprocess optimization and characterization of two main enzymes

The Antarctic fungus Lecanicillium muscarium CCFEE-5003 was preliminary cultivated in shaken flasks to check its chitinase production on rough shrimp and crab wastes. Production on shrimp shells was much higher than that on crab shells (104.6 ± 9.3 and 48.6 ± 3.1 U/L, respectively). For possible industrial applications, bioprocess optimization was studied on shrimp shells in bioreactor using RSM to state best conditions of pH and substrate concentration. Optimization improved the production by 137% (243.6 ± 17.3). Two chitinolytic enzymes (CHI1 and CHI2) were purified and characterized. CHI1 (MW ca. 61 kDa) showed optima at pH 5.5 and 45 °C while CHI2 (MW ca. 25 kDa) optima were at pH 4.5 and 40 °C. Both enzymes maintained high activity levels at 5 °C and were inhibited by Fe⁺⁺, Hg⁺⁺ and Cu⁺⁺. CHI2 was strongly allosamidin-sensitive. Both proteins were N-acetyl-hexosaminidases (E.C. 3.2.1.52) but showed different roles in chitin hydrolysis: CHI1 could be defined as “chitobiase” while CHI2 revealed a main “eso-chitinase” activity.     

‘We all eat the same bread’: the roots and limits of cosmopolitan bridging ties developed by Romanians in London

This paper investigates the social ties forged by Romanians in London with migrants of different origins in work and non-work contexts to offer a more nuanced view of ‘bridging’ social ties and related discussions of ‘everyday’ cosmopolitanism. Contrary to the overemphasis on ethnic ties seen as a form of bonding in migration research, the paper shows how Romanians bridge informally with many other migrants based on shared ‘non-native’ status. Alongside non-ethnically marked commonalities, ethnicity emerges as an important ingredient of cosmopolitan socialization, yet without necessarily signalling coexisting ethnic identities, as commonly assumed. Romanians' experiences further show that despite providing significant social and cultural capital, bridging ties with migrants, rather than natives, rarely accrue effective resources for social mobility. The findings suggest the need to disaggregate and qualify current understandings of ‘bridging’ social ties usually depicted in positive terms and uniformly as cross-ethnic relationships, or only linked with the ‘mainstream’ population.     

“New Canadians are new conservatives”: race,incorporation and achieving electoral success in multicultural Canada

Despite declarations of race's irrelevance, the Conservative Party of Canada's (CPC) stance on race-related policies under former Prime Minister Stephen Harper's leadership was key to every electoral campaign it fought. Moreover, it is not despite but because of their race that racialized political elites have been incorporated into the CPC and its antecedents. Indeed, beginning in the 1990s, the inclusion of Asian Members of Parliament (MP) became for the Reform Party of Canada, a weapon in the struggle for electoral success; that is, part of an era of Conservative racial realignment. By tracing the role of Asian Conservative MP in the rise of the Reform Party since its 1987 inception and the electoral success of the CPC (2006–2015), this article explores how racialized political elites become crucial to the legitimization of the racial state when it is through a discourse of inclusion that exclusion is crafted.     

Preparedness as a counter-memory. School desegregation,social chances and life chances

ABSTRACT

How should we understand the conundrum of love for the segregated school – a system built to keep you in your place? In Gone Home. Race and Roots through Appalachia, Karida L. Brown looks at African American teacher’s work in segregated schools and shows how desegregation could be felt in both gains and losses in the black community. Those teachers prepared their students for a world of integration without freedom. This essay proposes a counter-memory of segregation, a relational agency of teachers past that remains to this day. Former students’ commemoration of teachers, principals, and schools dating from the time of institutionalized racial exclusion works as a symbolic reminder in a still-racist world, representing not only the need to be prepared, but also to stay prepared.     

Rodent Diversity and Land Use in Montebello,Chiapas, Mexico

We analyzed the abundance and diversity of Heteromyid and Murid rodents in the Lagos de Montebello National Park and adjacent areas, Chiapas, Mexico. We sampled three habitat types with different degrees of disturbance: pine-oak-liquidambar forest, ecotone and crop farming lands. Habitat types were defined considering characteristics such as heterogeneity, structural complexity and arboreal cover. We obtained ancillary habitat data considered important for small mammal requirements. Data on rodent communities were obtained by capture-mark-recapture between February and October 1996. We made 410 captures in 3820 trap-nights effort. Ten species were recorded, including one endemic with restricted distribution in Chiapas. Mouse diversity in the forest was significantly higher than within the farm lands. A Kendall correlation analysis showed positive relationship between rodent community species richness and habitat heterogeneity. Diversity of rodents was associated with the habitat complexity and structural elements, and negatively correlated with farming intensity. We found a high beta diversity and low similarity of the rodent communities in the three different habitats. Community composition strongly changed from the forest through the ecotone into the farm lands, with five species gained and seven species lost. The highest species richness was found in the ecotone; however, it showed a strong dominance of a single species that can convert into a plague of crops, and relatively low abundance of the other species. The pine-oak-liquidambar forest had the highest diversity indices, sheltering a particular rodent community within the study area, it therefore probably has the most important role in the conservation of the local biodiversity.     

Sphingosine-1-phosphate Phosphatase 1 Regulates Keratinocyte Differentiation and Epidermal Homeostasis

Sphingosine 1-phosphate (S1P) is a bioactive lipid whose levels are tightly regulated by its synthesis and degradation. Intracellularly, S1P is dephosphorylated by the actions of two S1P-specific phosphatases, sphingosine-1-phosphate phosphatases 1 and 2. To identify the physiological functions of S1P phosphatase 1, we have studied mice with its gene, Sgpp1, deleted. Sgpp1^−/− mice appeared normal at birth, but during the 1st week of life they exhibited stunted growth and suffered desquamation, with most dying before weaning. Both Sgpp1^−/− pups and surviving adults exhibited multiple epidermal abnormalities. Interestingly, the epidermal permeability barrier developed normally during embryogenesis in Sgpp1^−/− mice. Keratinocytes isolated from the skin of Sgpp1^−/− pups had increased intracellular S1P levels and displayed a gene expression profile that indicated overexpression of genes associated with keratinocyte differentiation. The results reveal S1P metabolism as a regulator of keratinocyte differentiation and epidermal homeostasis.     

Interaction of p190RhoGAP with C-terminal Domain of p120-catenin Modulates Endothelial Cytoskeleton and Permeability

p120-catenin is a multidomain intracellular protein, which mediates a number of cellular functions, including stabilization of cell-cell transmembrane cadherin complexes as well as regulation of actin dynamics associated with barrier function, lamellipodia formation, and cell migration via modulation of the activities of small GTPAses. One mechanism involves p120 catenin interaction with Rho GTPase activating protein (p190RhoGAP), leading to p190RhoGAP recruitment to cell periphery and local inhibition of Rho activity. In this study, we have identified a stretch of 23 amino acids within the C-terminal domain of p120 catenin as the minimal sequence responsible for the recruitment of p190RhoGAP (herein referred to as CRAD; catenin-RhoGAP association domain). Expression of the p120-catenin truncated mutant lacking the CRAD in endothelial cells attenuated effects of barrier protective oxidized phospholipid, OxPAPC. This effect was accompanied by inhibition of membrane translocation of p190RhoGAP, increased Rho signaling, as well as suppressed activation of Rac1 and its cytoskeletal effectors PAK1 (p21-activated kinase 1) and cortactin. Expression of p120 catenin-truncated mutant lacking CRAD also delayed the recovery process after thrombin-induced endothelial barrier disruption. Concomitantly, RhoA activation and downstream signaling were sustained for a longer period of time, whereas Rac signaling was inhibited. These data demonstrate a critical role for p120-catenin (amino acids 820–843) domain in the p120-catenin·p190RhoGAP signaling complex assembly, membrane targeting, and stimulation of p190RhoGAP activity toward inhibition of the Rho pathway and reciprocal up-regulation of Rac signaling critical for endothelial barrier regulation.     

Mesenchyme-specific Knockout of ESET Histone Methyltransferase Causes Ectopic Hypertrophy and Terminal Differentiation of Articular Chondrocytes

The exact molecular mechanisms governing articular chondrocytes remain unknown in skeletal biology. In this study, we have found that ESET (an ERG-associated protein with a SET domain, also called SETDB1) histone methyltransferase is expressed in articular cartilage. To test whether ESET regulates articular chondrocytes, we carried out mesenchyme-specific deletion of the ESET gene in mice. ESET knock-out did not affect generation of articular chondrocytes during embryonic development. Two weeks after birth, there was minimal qualitative difference at the knee joints between wild-type and ESET knock-out animals. At 1 month, ectopic hypertrophy, proliferation, and apoptosis of articular chondrocytes were seen in the articular cartilage of ESET-null animals. At 3 months, additional signs of terminal differentiation such as increased alkaline phosphatase activity and an elevated level of matrix metalloproteinase (MMP)-13 were found in ESET-null cartilage. Staining for type II collagen and proteoglycan revealed that cartilage degeneration became progressively worse from 2 weeks to 12 months at the knee joints of ESET knock-out mutants. Analysis of over 14 pairs of age- and sex-matched wild-type and knock-out mice indicated that the articular chondrocyte phenotype in ESET-null mutants is 100% penetrant. Our results demonstrate that expression of ESET plays an essential role in the maintenance of articular cartilage by preventing articular chondrocytes from terminal differentiation and may have implications in joint diseases such as osteoarthritis.