Adult skeletal muscle stem cell migration is mediated by a blebbing/amoeboid mechanism

Adult skeletal muscle possesses a resident stem cell population called satellite cells which are responsible for tissue repair following damage. Satellite cell migration is crucial in promoting rapid tissue regeneration but is a poorly understood process. Furthermore, the mechanisms facilitating satellite cell movement have yet to be elucidated. Here the process of satellite cell migration has been investigated revealing that they undergo two distinct phases of movement; firstly under the basal lamina and then rapidly increasing their velocity when on the myofibre surface. Most significantly we show that satellite cells move using a highly dynamic blebbing based mechanism and not via lamellopodia mediated propulsion. We show that nitric oxide and non-canonical Wnt signalling pathways are necessary for regulating the formation of blebs and the migration of satellite cells. In summary, we propose that the formation of blebs and their necessity for satellite cell migration has significant implications in the future development of therapeutic regimes aimed at promoting skeletal muscle regeneration.

The effect of triacylglycerol fatty acid positional distribution on postprandial plasma metabolite and hormone responses in normal adult men

The present study has examined the possibility that the positional distribution of fatty acids on dietary triacyglycerol (TAG) influences the postprandial response to a liquid meal in adult subjects. Postprandial TAG, non-esterified fatty acids (NEFA), ketones, glucose, insulin and gastric inhibitory polypeptide (GIP) responses were monitored in sixteen normal adult male subjects over 6 h following consumption of test meals containing dietary TAG in which palmitic acid was predominantly on the sn-1 (Control) or sn-2 positions (Betapol). Plasma total TAG, chylomicron-rich TAG and chylomicron-poor TAG concentrations were identical in response to the two test meals. The peak increase (mean (SD)) in chylomicron TAG was 0.85 (0.46) mmol/l after the Control meal and 0.85 (0.42) mmol/l after the Betapol meal. Plasma glucose, insulin, GIP, NEFA and ketone concentrations were also very similar following the two meals. It is concluded that dietary TAG containing saturated fatty acids on the sn-2 position appear in plasma at a similar level and over a similar timescale to TAG in which saturated fatty acids are predominantly located on sn-1 or sn-3 positions. The results reported in the present study demonstrate that the positional distribution of fatty acids on dietary TAG is not an important determinant of postprandial lipaemia in adult male subjects, but do not exclude the possibility that different responses may occur when these dietary TAG are given long term.

An analysis of verbal responses to music in a group of adult non-specialists

In a workshop setting, two pieces of recorded music were presented to a group of adult non-specialists; a key feature was to set up structured discussion within which the respondents considered each piece of music as a whole and not in its constituent parts. There were two areas of interest, namely to explore whether the respondents were likely to identify the musical features or to make extra-musical associations and, to establish the extent to which there would be commonality and difference in their approach to formulating the verbal responses. An inductive approach was used in the analysis of data to reveal some of the working theories underpinning the intuitive musicianship of the adult non-specialist listener. Findings have shown that, when unprompted by forced choice responses, the listeners generated responses that could be said to be information-poor in terms of musical features but rich in terms of the level of personal investment they made in formulating their responses. This is evidenced in a number of connections they made between the discursive and the non-discursive, including those which are relational and mediated by their experiences. Implications for music education are considered.

Language dominance and lexical diversity: how bilinguals and L2 learners differ in their knowledge and use of French lexical and functional items

This chapter compares lexical diversity of French words used by Dutch-French bilinguals, English-French bilinguals and Flemish L2 learners of French.

Canonical Wnt signalling induces satellite-cell proliferation during adult skeletal muscle regeneration

Satellite cells represent the stem cell population of adult skeletal muscle. The molecular mechanisms that control the proliferation of satellite cells are not well understood. In this study, we show that in response to injury, myofibres activate Wnt ligand transcription and activate a reporter cell line that is sensitive to the canonical Wnt-signalling pathway. Activated satellite cells on isolated cultured myofibres show robust expression of activated-β-catenin (Act-β-Cat), a key downstream transcriptional coactivator of canonical Wnt signalling. We provide evidence that the Wnt family of secreted glycoproteins act on satellite cells in a ligand-specific manner. Overexpression of Wnt1, Wnt3a or Wnt5a protein causes a dramatic increase in satellite-cell proliferation. By contrast, exposure of satellite cells to Wnt4 or Wnt6 diminishes this process. Moreover, we show that the prolonged satellite-cell quiescence induced by inhibitory Wnt is reversible and exposing inhibited satellite cells to stimulatory Wnt signalling restores their proliferation rate. Stimulatory Wnt proteins induce premature satellite cell BrdU incorporation as well as nuclear translocation of Act-β-Cat. Finally, we provide evidence that the Act-β-Cat translocation observed in single fibres during in vitro culture also occurs in cases of acute and chronic skeletal muscle regeneration in rodents and humans. We propose that Wnt proteins may be key factors that regulate the rate of satellite-cell proliferation on adult muscle fibres during the wound-healing response.

Identification of potential mechanisms of toxicity after di-(2-ethylhexyl)-phthalate (DEHP) adult exposure in the liver using a systems biology approach

Phthalates are industrial additives widely used as plasticizers. In addition to deleterious effects on male genital development, population studies have documented correlations between phthalates exposure and impacts on reproductive tract development and on the metabolic syndrome in male adults. In this work we investigated potential mechanisms underlying the impact of DEHP on adult mouse liver in vivo. A parallel analysis of hepatic transcript and metabolic profiles from adult mice exposed to varying DEHP doses was performed. Hepatic genes modulated by DEHP are predominantly PPARalpha targets. However, the induction of prototypic cytochrome P450 genes strongly supports the activation of additional NR pathways, including Constitutive Androstane Receptor (CAR). Integration of transcriptomic and metabonomic profiles revealed a correlation between the impacts of DEHP on genes and metabolites related to heme synthesis and to the Rev-erbalpha pathway that senses endogenous heme level. We further confirmed the combined impact of DEHP on the hepatic expression of Alas1, a critical enzyme in heme synthesis and on the expression of Rev-erbalpha target genes involved in the cellular clock and in energy metabolism. This work shows that DEHP interferes with hepatic CAR and Rev-erbalpha pathways which are both involved in the control of metabolism. The identification of these new hepatic pathways targeted by DEHP could contribute to metabolic and endocrine disruption associated with phthalate exposure. Gene expression profiles performed on microdissected testis territories displayed a differential responsiveness to DEHP. Altogether, this suggests that impacts of DEHP on adult organs, including testis, could be documented and deserve further investigations.

Selective listening in L2 learners of French

This paper considers the issue raised by Brown (2008) regarding whether nouns are ‘privileged’ in memory over verbs during listening tasks, and whether attention to nouns, at least in the early stages of L2 learning, is a desirable strategy to be taught to learners, as Brown suggests it might be. The question of verb/noun recognition was explored in the present study using data from 30 lower-intermediate learners of French in England. Learners completed a listening task on two occasions, six months apart, producing recall protocols for short oral passages in French. We also explored learners’ attentional strategy use by asking them to report on this in writing immediately after the recall task. An analysis of verbs and nouns recognised indicated that verb recognition was lower than that of nouns, and that progress in verb recognition over six months was negligible. A qualitative analysis of learners’ strategy use indicated that learners with a more balanced verb/noun recognition profile took a broader focus, tending to focus their attention consciously at phrase/sentence level rather than at word level. These findings are discussed in terms of the development of listening skills over time, and the implications of this for L2 listening pedagogy.

Learners’ perceptions of being identified as very able: insights from Modern Foreign Languages and Physical Education

While learners’ attitudes to Modern Foreign Languages (MFL) and to Physical Education (PE) in the UK have been widely investigated in previous research, an under-explored area is learners’ feelings about being highly able in these subjects. The present study explored this issue, among 78 learners (aged 12-13) from two schools in England, a Specialist Language College, and a Specialist Sports College. Learners completed a questionnaire exploring their feelings about the prospect of being identified as gifted/talented in these subjects, and their perceptions of the characteristics of highly able learners in MFL and PE. Questionnaires were chosen as the data collection method to encourage more open responses from these young learners than might have been elicited in an interview. While learners were enthusiastic about the idea of being highly able in both subjects, this enthusiasm was more muted for MFL. School specialism was related to learners’ enthusiasm only in the Sports College. Learners expressed fairly stereotypical views of the characteristics of the highly able in MFL and PE. The relevance of these findings for motivation and curriculum design within both subjects is discussed.

Processing of regular and irregular past tense morphology in highly proficient second language learners of English: a self-paced reading study

Dual-system models suggest that English past tense morphology involves two processing routes: rule application for regular verbs and memory retrieval for irregular verbs (Pinker, 1999). In second language (L2) processing research, Ullman (2001a) suggested that both verb types are retrieved from memory, but more recently Clahsen and Felser (2006) and Ullman (2004) argued that past tense rule application can be automatised with experience by L2 learners. To address this controversy, we tested highly proficient Greek-English learners with naturalistic or classroom L2 exposure compared to native English speakers in a self-paced reading task involving past tense forms embedded in plausible sentences. Our results suggest that, irrespective to the type of exposure, proficient L2 learners of extended L2 exposure apply rule-based processing.