Carbon fixation by phytoplankton near the surface and the sinking of this particulate material to deeper waters are key components of the biological carbon pump. The efficiency of the biological pump ...is influenced by the size and taxonomic composition of the phytoplankton community. Large, heavily ballasted taxa such as diatoms sink quickly and thus efficiently remove fixed carbon from the upper ocean. Smaller, nonballasted species such as picoplanktonic cyanobacteria are usually thought to contribute little to export production. Research in the past decade, however, has shed new light on the potential importance of small phytoplankton to carbon export, especially in oligotrophic oceans, where small cells dominate primary productivity. Here, I examine the mechanisms and pathways through which small-phytoplankton carbon is exported from the surface ocean and the role of small phytoplankton in food webs of a variety of ocean ecosystems.
A wealth of evidence has revealed that deficits in social cognitive skills (including facial affect recognition (FAR), social cue perception, Theory of Mind (ToM), and attributional style) are ...evident in schizophrenia and are linked to a variety of domains of functional outcome. In light of these associations, a growing number of studies have attempted to ameliorate these deficits as a means of improving outcome in the disorder through the use of structured behavioral training. This study used quantitative methods of meta-analysis to assess the efficacy of behavioral training programs designed to improve social cognitive function. A total of 19 studies consisting of 692 clients were aggregated from relevant databases. Outcome measures were organized according to whether they were social cognitive tests proximal to the intervention or whether they represented measures of treatment generalization (symptoms, observer-rated community, and institutional function). With respect to social cognitive measures, weighted effect-size analysis revealed that there were moderate-large effects of social cognitive training procedures on FAR (identification, d = 0.71 and discrimination, d = 1.01) and small-moderate effects of training on ToM (d = 0.46), while effects on social cue perception and attributional style were not significant. For measures of generalization, weighted effect-size analysis revealed that there were moderate-large effect on total symptoms (d = 0.68) and observer-rated community and institutional function (d = 0.78). Effects of social cognitive training programs on positive and negative symptoms of schizophrenia were nonsignificant. Moderating variables and implications for future research and treatment development are discussed.
The epithelial-mesenchymal transition (EMT) has been associated with the acquisition of motility, invasiveness, and self-renewal traits. During both normal development and tumor pathogenesis, this ...change in cell phenotype is induced by contextual signals that epithelial cells receive from their microenvironment. The signals that are responsible for inducing an EMT and maintaining the resulting cellular state have been unclear. We describe three signaling pathways, involving transforming growth factor (TGF)-β and canonical and noncanonical Wnt signaling, that collaborate to induce activation of the EMT program and thereafter function in an autocrine fashion to maintain the resulting mesenchymal state. Downregulation of endogenously synthesized inhibitors of autocrine signals in epithelial cells enables the induction of the EMT program. Conversely, disruption of autocrine signaling by added inhibitors of these pathways inhibits migration and self-renewal in primary mammary epithelial cells and reduces tumorigenicity and metastasis by their transformed derivatives.
Display omitted
► Induction of EMT in mammary epithelial cells depends on collaborating pathways ► Pathways that induce EMT also maintain the resultant cellular state ► Autocrine signaling maintains the mesenchymal and stem-cell traits induced by EMT ► Similar signals maintain both normal and neoplastic mammary stem cells
This book offers the first comprehensive account and re-appraisal of the formative phase of what is often termed the 'Grotian tradition' in international relations theory: the view that sovereign ...states are not free to act at will, but are akin to members of a society, bound by its norms. It examines the period from the later fifteenth to the mid-seventeenth centuries, focusing on four thinkers: Erasmus, Vitoria, Gentili and Grotius himself, and is structured by the author's concept of international society. Erasmus' views on international relations have been entirely neglected, but underlying his work is a consistent image of international society. The theologian Francisco de Vitoria concerns himself with its normative principles, the lawyer Alberico Gentili - unexpectedly, the central figure in the narrative - with its extensive practical applications. Grotius, however, does not re-affirm the concept, but wavers at crucial points. This book suggests that the Grotian tradition is a misnomer.
The HIF transcription factor promotes adaptation to hypoxia and stimulates the growth of certain cancers, including triple-negative breast cancer (TNBC). The HIFα subunit is usually ...prolyl-hydroxylated by EglN family members under normoxic conditions, causing its rapid degradation. We confirmed that TNBC cells secrete glutamate, which we found is both necessary and sufficient for the paracrine induction of HIF1α in such cells under normoxic conditions. Glutamate inhibits the xCT glutamate-cystine antiporter, leading to intracellular cysteine depletion. EglN1, the main HIFα prolyl-hydroxylase, undergoes oxidative self-inactivation in the absence of cysteine both in biochemical assays and in cells, resulting in HIF1α accumulation. Therefore, EglN1 senses both oxygen and cysteine.
Display omitted
•HIF1 promotes triple-negative breast carcinogenesis•Triple-negative breast cancers secrete large amounts of glutamate•Extracellular glutamate inhibits cystine uptake by the xCT antiporter•Intracellular cysteine depletion directly inhibits the HIF prolyl-hydroxylases
Increased glutamate secretion by triple-negative breast cancer cells affects cellular cysteine levels and drives activation of HIF through disabling EglN1 under normoxic conditions. Thus, EglN1, which is known to sense oxygen, also senses cysteine.
Abstract
The observed massive end of the galaxy stellar mass function is steeper than its predicted dark matter halo counterpart in the standard Λ cold dark matter paradigm. In this paper, we ...investigate the impact of active galactic nuclei (AGN) feedback on star formation in massive galaxies. We isolate the impact of AGN by comparing two simulations from the HORIZON suite, which are identical except that one also includes supermassive black holes (SMBHs) and related feedback models. This allows us to cross-identify individual galaxies between simulations and quantify the effect of AGN feedback on their properties, including stellar mass and gas outflows. We find that massive galaxies (M
* ≥ 1011 M⊙) are quenched by AGN feedback to the extent that their stellar masses decrease by up to 80 per cent at z = 0. SMBHs affect their host halo through a combination of outflows that reduce their baryonic mass, particularly for galaxies in the mass range 109 M⊙ ≤ M
* ≤ 1011 M⊙, and a disruption of central gas inflows, which limits in situ star formation. As a result, net gas inflows on to massive galaxies, M
* ≥ 1011 M⊙, drop by up to 70 per cent. We measure a redshift evolution in the stellar mass ratio of twin galaxies with and without AGN feedback, with galaxies of a given stellar mass showing stronger signs of quenching earlier on. This evolution is driven by a progressive flattening of the M
SMBH–M
* relation with redshift, particularly for galaxies with M
* ≤ 1010 M⊙. M
SMBH/M
* ratios decrease over time, as falling average gas densities in galaxies curb SMBH growth.
Despite their crucial role in health and disease, our knowledge of immune cells within human tissues remains limited. We surveyed the immune compartment of 16 tissues from 12 adult donors by ...single-cell RNA sequencing and VDJ sequencing generating a dataset of ~360,000 cells. To systematically resolve immune cell heterogeneity across tissues, we developed CellTypist, a machine learning tool for rapid and precise cell type annotation. Using this approach, combined with detailed curation, we determined the tissue distribution of finely phenotyped immune cell types, revealing hitherto unappreciated tissue-specific features and clonal architecture of T and B cells. Our multitissue approach lays the foundation for identifying highly resolved immune cell types by leveraging a common reference dataset, tissue-integrated expression analysis, and antigen receptor sequencing.
•Research into local adaptation at fine spatial scales has received little attention.•We develop new quantitative definitions for microgeographic adaptation and the spatial scale of ...adaptation.•Mechanisms promoting microgeographic adaptation include strong natural selection and reductions in gene flow.•Microgeographic adaptation can fundamentally alter understanding of ecological and evolutionary dynamics.•New frontiers are needed in spatial evolutionary research, particularly the lower spatial bounds of local adaptation.
Local adaptation has been a major focus of evolutionary ecologists working across diverse systems for decades. However, little of this research has explored variation at microgeographic scales because it has often been assumed that high rates of gene flow will prevent adaptive divergence at fine spatial scales. Here, we establish a quantitative definition of microgeographic adaptation based on Wright's dispersal neighborhood that standardizes dispersal abilities, enabling this measure to be compared across species. We use this definition to evaluate growing evidence of evolutionary divergence at fine spatial scales. We identify the main mechanisms known to facilitate this adaptation and highlight illustrative examples of microgeographic evolution in nature. Collectively, this evidence requires that we revisit our understanding of the spatial scale of adaptation and consider how microgeographic adaptation and its driving mechanisms can fundamentally alter ecological and evolutionary dynamics in nature.
Display omitted
•Dynamic soaring of albatrosses and UAVs was simulated with a two-layer dynamic model.•Observed upwind dynamic soaring of albatrosses was successfully modeled.•Upwind dynamic soaring ...of a robotic albatross UAV was simulated with the same model.•A UAV can soar upwind faster than an albatross due to superior strength.•A possible fast UAV survey mode uses parallel diagonal tracks relative to wind.
Albatrosses have been observed to soar in an upwind direction using what is called here an upwind mode of dynamic soaring. The upwind mode was modeled using the dynamics of a two-layer Rayleigh cycle in which the lower layer has zero velocity and the upper layer has a uniform wind speed of W. The upwind mode consists of a climb across the wind-shear layer headed upwind, a 90° turn and descent across the wind-shear layer perpendicular to the wind, followed by a 90° turn into the wind. The increase of airspeed gained from crossing the wind-shear layer headed upwind was balanced by the decrease of airspeed caused by drag. Results show that a wandering albatross can soar over the ocean in an upwind direction at a mean speed of 8.4m/s in a 3.6m/s wind, which is the minimum wind speed necessary for sustained dynamic soaring. A main result is that albatrosses can soar upwind much faster than the wind speed. Furthermore, albatrosses were found to be able to increase upwind speeds in winds greater than 3.6m/s, reaching an upwind speed of 12.1m/s in a wind speed of 7m/s (for example).
The upwind dynamic soaring mode of a possible robotic albatross UAV (Unmanned Aerial Vehicle) was modeled using a Rayleigh cycle and characteristics of a high-performance glider. Maximum possible airspeeds are equal to approximately 9.5 times the wind speed of the upper layer. In a wind of 10m/s, the maximum possible upwind (56m/s) and across-wind (61m/s) components of UAV velocity over the ocean result in a diagonal upwind velocity of 83m/s. In sufficient wind, a UAV could, in principle, use fast diagonal speeds to rapidly survey large areas of the ocean surface and the marine boundary layer. In practice, the maximum speeds of a UAV soaring over the ocean could be significantly less than these predictions. Some limitations to achieving fast travel velocities over the ocean are discussed and suggestions are made for further studies to test the concept of a robotic albatross.
PDF
