Macromere cell fates during sea urchin development

This paper examines the cell lineage relationships and cell fates in embryos of the sea urchin Strongylocentrotus purpuratus leading to the various cell types derived from the definitive vegetal plate territory or the veg_2 tier of cells. These cell types are gut, pigment cells, basal cells and coelomic pouches. They are cell types that constitute embryonic structures through cellular migration or rearrangement unlike the relatively non-motile ectoderm cell types. For this analysis, we use previous knowledge of lineage to assign macromeres to one of four types: VOM, the oral macromere; VAM, the aboral macromere, right and left VLM, the lateral macromeres. Each of the four macromeres contributes progeny to all of the cell types that descend from the definitive vegetal plate. Thus in the gut each macromere contributes to the esophagus, stomach and intestine, and the stripe of labeled cells descendant from a macromere reflects the re-arrangement of cells that occurs during archenteron elongation. Pigment cell contributions exhibit no consistent pattern among the four macromeres, and are haphazardly distributed throughout the ectoderm. Gut and pigment cell contributions are thus radially symmetrical. In contrast, the VOM blastomere contributes to both of the coelomic pouches while the other three macromeres contribute to only one or the other pouch. The total of the macromere contribution amounts to 60% of the cells constituting the coelomic pouches

The oral-aboral axis of a sea urchin embryo is specified by first cleavage

Several lines of evidence suggest that the oral-aboral axis in Strongylocentrotus purpuratus embryos is specified at or before the 8-cell stage. Were the oral-aboral axis specified independently of the first cleavage plane, then a random association of this plane with the blastomeres of the four embryo quadrants in the oral-aboral plane (viz. oral, aboral, right and left) would be expected. Lineage tracer dye injection into one blastomere at the 2-cell stage and observation of the resultant labeling patterns demonstrates instead a strongly nonrandom association. In at least ninety percent of cases, the progeny of the aboral blastomeres are associated with those of the left lateral blastomeres and the progeny of the oral blastomeres with the right lateral ones, respectively. Thus, ninety percent of the time the oral pole of the future oral-aboral axis lies 45 degrees clockwise from the first cleavage plane as viewed from the animal pole. The nonrandom association of blastomeres after labeling of the 2-cell stage implies that there is a mechanistic relation between axis specification and the positioning of the first cleavage plane

Atlantic water variability on the SE Greenland continental shelf and its relationship to SST and bathymetry

Author Posting. © American Geophysical Union, 2013. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 118 (2013): 847–855, doi:10.1029/2012JC008354.Interaction of warm, Atlantic-origin water (AW) and colder, polar origin water (PW) advecting southward in the East Greenland Current (EGC) influences the heat content of water entering Greenland's outlet glacial fjords. Here we use depth and temperature data derived from deep-diving seals to map out water mass variability across the continental shelf and to augment existing bathymetric products. We compare depths derived from the seal dives with the IBCAO Version 3 bathymetric database over the shelf and find differences up to 300 m near several large submarine canyons. In the vertical temperature structure, we find two dominant modes: a cold mode, with the typical AW/PW layering observed in the EGC, and a warm mode, where AW is present throughout the water column. The prevalence of these modes varies seasonally and spatially across the continental shelf, implying distinct AW pathways. In addition, we find that satellite sea surface temperatures (SST) correlate significantly with temperatures in the upper 50 m (R = 0.54), but this correlation decreases with depth (R = 0.22 at 200 m), and becomes insignificant below 250 m. Thus, care must be taken in using SST as a proxy for heat content, as AW mainly resides in these deeper layers.Funding for this work came from National Science Foundation OPP grant 0909373 and OCE grant 1130008, plus the WHOI Arctic Research Initiative. The Greenland Institute of Natural Resources and the Department of Fisheries and Oceans, Canada, supported the seal tagging logistics.2013-08-2

Seasonal variability of the warm Atlantic Water layer in the vicinity of the Greenland shelf break

The warmest water reaching the east and west coast of Greenland is found between 200?m and 600?m. Whilst important for melting Greenland's outlet glaciers, limited winter observations of this layer prohibit determination of its seasonality. To address this, temperature data from Argo profiling floats, a range of sources within the World Ocean Database and unprecedented coverage from marine-mammal borne sensors have been analysed for the period 2002-2011. A significant seasonal range in temperature (~1-2?°C) is found in the warm layer, in contrast to most of the surrounding ocean. The phase of the seasonal cycle exhibits considerable spatial variability, with the warmest water found near the eastern and southwestern shelf-break towards the end of the calendar year. High-resolution ocean model trajectory analysis suggest the timing of the arrival of the year's warmest water is a function of advection time from the subduction site in the Irminger Basin

Trying to make sense of the chaos: Clinical psychologists' experiences and perceptions of clients with borderline personality disorder'

Background Evidence of negative perceptions of clients with borderline personality disorder (BPD) in mental health professionals has been well documented. However, few researchers have focused upon perspectives of clinical psychologists on this client group. The aim of the present research was to explore clinical psychologists' experiences and perceptions of clients with BPD. Method Sixteen female clinical psychologists (including trainees and qualified staff) participated in focus groups, 12 of whom had direct clinical experience with this client group. All four groups' audio recordings were transcribed verbatim and analysed using interpretative phenomenological analysis (Smith, 1996). Results The following eight superordinate themes emerged from the analysis: negative perceptions of the client, undesirable feelings in the psychologist, positive perceptions of the client, desirable feelings in the psychologist, awareness of negativity, trying to make sense of the chaos, working in contrast to the system and improving our role. Discussion Implications include concerns regarding negativity, yet also the suggestion of hope and optimism in working with this client group. Copyright (C) 2012 John Wiley &amp; Sons, Ltd.</p

Phenotypic robustness can increase phenotypic variability after non-genetic perturbations in gene regulatory circuits

Non-genetic perturbations, such as environmental change or developmental noise, can induce novel phenotypes. If an induced phenotype confers a fitness advantage, selection may promote its genetic stabilization. Non-genetic perturbations can thus initiate evolutionary innovation. Genetic variation that is not usually phenotypically visible may play an important role in this process. Populations under stabilizing selection on a phenotype that is robust to mutations can accumulate such variation. After non-genetic perturbations, this variation can become a source of new phenotypes. We here study the relationship between a phenotype's robustness to mutations and a population's potential to generate novel phenotypic variation. To this end, we use a well-studied model of transcriptional regulation circuits. Such circuits are important in many evolutionary innovations. We find that phenotypic robustness promotes phenotypic variability in response to non-genetic perturbations, but not in response to mutation. Our work suggests that non-genetic perturbations may initiate innovation more frequently in mutationally robust gene expression traits.Comment: 11 pages, 5 figure

Optimal experience and personal growth. Flow and the consolidation of place identity

This study examined the relationship between flow experience and place identity, based on eudaimonistic identity theory (EIT) which prioritizes self-defining activities as important for an individual's identification of his/her goals, values, beliefs, and interests corresponding to one's own identity development or enhancement. This study focuses on place identity, the identity's features relating to a person's relation with her/his place. The study is also based on flow theory, according to which some salient features of an activity experience are important for happiness and well-being. Questionnaire surveys on Italian and Greek residents focused on their perceived flow and place identity in relation to their own specific local place experiences. The overall findings revealed that flow experience occurring in one's own preferred place is widely reported as resulting from a range of self-defining activities, irrespective of gender or age, and it is positively and significantly associated with one's own place identity. Such findings provide the first quantitative evidence about the link between flow experienced during meaningfully located self-defining activities and identity experienced at the place level, similarly to the corresponding personal and social levels that had been previously already empirically tested. Results are also discussed in terms of their implications for EIT's understanding and enrichment, especially by its generalization from the traditional, personal identity level up to that of place identity. More generally, this study has implications for maintaining or enhancing one's own place identity, and therefore people place relations, by means of facilitating a person's flow experience within psychologically meaningful place

Event‐scale dynamics of a parabolic dune and its relevance for mesoscale evolution

Parabolic dunes are wide-spread aeolian landforms found in a variety of environments. Despite modelling advances and good understanding of how they evolve, there is limited empirical data on their dynamics at short time-scales of hours, and on how these dynamics relate to their medium-term evolution. This study presents the most comprehensive dataset to date on aeolian processes (airflow and sediment transport) inside a parabolic dune at an event-scale. This is coupled with information on elevation changes inside the landform to understand its morphological response to a single wind event. Results are contextualized against the medium-term (years) allowing us to investigate one of the most persistent conundrums in geomorphology, that of the significance of short-term findings for landform evolution. Our field data suggested three key findings: 1) sediment transport rates inside parabolic dunes correlate well with wind speeds rather than turbulence; 2) up to several tonnes of sand can move through these landforms in a few hours; 3) short-term elevation changes inside parabolic dunes can be complex and different from long-term net spatial patterns, including simultaneous erosion and accumulation along the same wall. Modeled airflow patterns along the basin were similar to those measured in situ for a range of common wind directions, demonstrating the potential for strong transport during multiple events. Meso-scale analyses suggested that the measured event was representative of the type of events potentially driving significant geomorphic changes over years, with supply-limiting conditions playing an important role in resultant flux amounts