Diet of six deep-sea grenadiers (Macrouridae)

Feeding habits of six deep-sea demersal trawl-caught macrourids on Chatham Rise, New Zealand, were examined from stomach contents during the austral summer. Three species were predominantly benthic foragers: smallbanded rattail Coelorinchus parvifasciatus on small epifaunal crustaceans, twosaddle rattail Coelorinchus biclinozonalis on epifaunal decapods and humpback rattail Coryphaenoides dossenus on benthic fishes and epifaunal decapods. Three species were predominantly benthopelagic foragers: banded rattail Coelorinchus fasciatus on hyperiid and gammarid amphipods and calanoid copepods, blackspot rattail Lucigadus nigromaculatus on small epifaunal crustaceans and suprabenthic mysids and Mahia rattail Coelorinchus matamua on epifaunal decapods and calanoid copepods. The most important predictors of diet variability were identified using distance-based linear models and included areal predictors in C. parvifasciatus, L. nigromaculatus and C. dossenus, fish size in C. dossenus, C. biclinozonalis and C. matamua, sample year in C. biclinozonalis and C. fasciatus and depth in C. matamua. Results are compared with previously published data for four other macrourid species from the same study area. The 10 grenadier species comprise benthic, benthopelagic and mesopelagic foraging guilds. This study brings the number of grenadier species for which diet on Chatham Rise has been described in detail to 12.     

Engineering of a target site-specific recombinase by a combined evolution- and structure-guided approach

Site-specific recombinases (SSRs) can perform DNA rearrangements, including deletions, inversions and translocations when their naive target sequences are placed strategically into the genome of an organism. Hence, in order to employ SSRs in heterologous hosts, their target sites have to be introduced into the genome of an organism before the enzyme can be practically employed. Engineered SSRs hold great promise for biotechnology and advanced biomedical applications, as they promise to extend the usefulness of SSRs to allow efficient and specific recombination of pre-existing, natural genomic sequences. However, the generation of enzymes with desired properties remains challenging. Here, we use substrate-linked directed evolution in combination with molecular modeling to rationally engineer an efficient and specific recombinase (sTre) that readily and specifically recombines a sequence present in the HIV-1 genome. We elucidate the role of key residues implicated in the molecular recognition mechanism and we present a rationale for sTre’s enhanced specificity. Combining evolutionary and rational approaches should help in accelerating the generation of enzymes with desired properties for use in biotechnology and biomedicine.     

Agonist binding to the GluK5 subunit is sufficient for functional surface expression of heteromeric GluK2/GluK5 kainate receptors

Trafficking of ionotropic glutamate receptors to the plasma membrane commonly requires occupation of the agonist binding sites. This quality control check does not typically involve receptor activation, as binding by competitive antagonists or to non-functional channels may also permit surface expression. The tetrameric kainate receptors can be assembled from five different subunits (GluK1–GluK5). While the “low-affinity” GluK1-3 subunits are able to produce functional homomeric receptors, the “high-affinity” GluK4 and GluK5 subunits require co-assembly with GluK1, 2, or 3 for surface expression. These two different types of subunits have distinct functional roles in the receptor. Therefore, we examined the relative importance of occupancy of the agonist site of the GluK2 or GluK5 subunit for surface expression of heteromeric receptors. We created subunits with a mutation within the S2 ligand-binding domain which decreased agonist affinity. Mutations at this site reduced functional surface expression of homomeric GluK2 receptors, but surface expression of these receptors could be increased with either a competitive antagonist or co-assembly with wild-type GluK5. In contrast, mutations in the GluK5 subunit reduced the production of functional heteromeric receptors at the membrane, and could not be rescued with either an antagonist or wild-type GluK2. These findings indicate that ligand binding to only the GluK5 subunit is both necessary and sufficient to allow trafficking of recombinant GluK2/K5 heteromers to the cell membrane, but that occupancy of the GluK2 site alone is not. Our results suggest a distinct role for the GluK5 subunit in regulating surface expression of heteromeric kainate receptors.     

Induced Formation and Maturation of Acetylcholine Receptor Clusters in a Defined 3D Bio-Artificial Muscle

Dysfunction of the neuromuscular junction is involved in a wide range of muscular diseases. The development of neuromuscular junction through which skeletal muscle is innervated requires the functional modulation of acetylcholine receptor (AchR) clustering on myofibers. However, studies on AchR clustering in vitro are mostly done on monolayer muscle cell culture, which lacks a three-dimensional (3D) structure, a prominent limitation of the two-dimensional (2D) system. To enable a better understanding on the structure–function correlation underlying skeletal muscle innervation, a muscle system with a well-defined geometry mimicking the in vivo muscular setting is needed. Here, we report a 3D bio-artificial muscle (BAM) bioengineered from green fluorescent protein-transduced C3H murine myoblasts as a novel in vitro tissue-based model for muscle innervation studies. Our cell biological and molecular analysis showed that this BAM is structurally similar to in vivo muscle tissue and can reach the perinatal differentiation stage, higher than does 2D culture. Effective clustering and morphological maturation of AchRs on BAMs induced by agrin and laminin indicate the functional activity and plasticity of this BAM system toward innervation. Taken together, our results show that the BAM provides a favorable 3D environment that at least partially recapitulates real physiological skeletal muscle with regard to innervation. With a convenience of fabrication and manipulation, this 3D in vitro system offers a novel model for studying mechanisms underlying skeletal muscle innervation and testing therapeutic strategies for relevant nervous and muscular diseases.     

Therapy Dogs Improve Student Affect but Not Memory

ABSTRACT

While students are increasingly struggling with anxiety and depression, the effects of therapy dogs on student stress has only recently been explored. This study was conducted to investigate whether therapy dogs can improve student affect and to determine if these benefits extend to cognition in the form of enhanced ability to remember information. Forty-four college students were randomly assigned to interact with a therapy dog or not during both learning (session 1) and testing (session 2) in a paired-associates procedure. Arousal, stress, and mood were measured at the beginning and end of each session. As predicted, therapy dogs increased happiness and decreased stress and arousal. However, there was no difference in recognition memory for the paired associates between the therapy dog and control conditions. Mood was a significant predictor of memory, such that decreased happiness in session 2 predicted better recognition performance. These findings indicate that the benefits of therapy dogs are primarily affective and not cognitive.     

Spectacles of South Asia at the American circus, 1890–1940

This article examines how racial and gendered images of South Asia were played out in performance at the American circus around 1900. These representations reinforced the Anglo‐American construct of a racial hierarchy in which South Asians were depicted to be static, and unable to keep pace with the Anglo‐American “race”. American circus spectacles featuring Indian subjects glorified British imperialism and helped to popularize the common colonialist stereotype that a minority of English officials were needed to rule millions of Indians. The American circus, as the most popular form of American public entertainment in an era before movies and television, helped to form a constellation of racial and sexual stereotypes concerning South Asia which continue to this day.