Three-dimensional mapping reveals scale-dependent dynamics in biogenic reef habitat structure

Habitat structure influences a broad range of ecological interactions and ecosystem functions across biomes. To understand and effectively manage dynamic ecosystems, we need detailed information about habitat properties and how they vary across spatial and temporal scales. Measuring and monitoring variation in three-dimensional (3D) habitat structure has traditionally been challenging, despite recognition of its importance to ecological processes. Modern 3D mapping technologies present opportunities to characterize spatial and temporal variation in habitat structure at a range of ecologically relevant scales. Biogenic reefs are structurally complex and dynamic habitats, in which structure has a pivotal influence on ecosystem biodiversity, function and resilience. For the first time, we characterized spatial and temporal dynamics in the 3D structure of intertidal Sabellaria alveolata biogenic reef across scales. We used drone-derived structure-from-motion photogrammetry and terrestrial laser scanning to characterize reef structural variation at mm-to-cm resolutions at a habitat scale (~35 000 m2) over 1 year, and at a plot scale (2500 m2) over 5 years (2014–2019, 6-month intervals). We found that most of the variation in reef emergence above the substrate, accretion rate and erosion rate was explained by a combination of systematic trends with shore height and positive spatial autocorrelation up to the scale of colonies (1.5 m) or small patches (up to 4 m). We identified previously undocumented temporal patterns in intertidal S. alveolata reef accretion and erosion, specifically groups of rapidly accreting, short-lived colonies and slow-accreting, long-lived colonies. We showed that these highly dynamic colony-scale structural changes compensate for each other, resulting in seemingly stable reef habitat structure over larger spatial and temporal scales. These patterns could only be detected with the use of modern 3D mapping technologies, demonstrating their potential to enhance our understanding of ecosystem dynamics across scales

Spin density wave induced disordering of the vortex lattice in superconducting La2−x_{2-x}Srx_xCuO4_4

We use small angle neutron scattering to study the superconducting vortex lattice in La$_{2-x}$Sr$_x$CuO$_4$ as a function of doping and magnetic field. We show that near optimally doping the vortex lattice coordination and the superconducting coherence length $\xi$ are controlled by a van-Hove singularity crossing the Fermi level near the Brillouin zone boundary. The vortex lattice properties change dramatically as a spin-density-wave instability is approached upon underdoping. The Bragg glass paradigm provides a good description of this regime and suggests that SDW order acts as a novel source of disorder on the vortex lattice.Comment: Accepted in Phys. Rev.

A for-loop is all you need. For solving the inverse problem in the case of personalized tumor growth modeling

Solving the inverse problem is the key step in evaluating the capacity of a physical model to describe real phenomena. In medical image computing, it aligns with the classical theme of image-based model personalization. Traditionally, a solution to the problem is obtained by performing either sampling or variational inference based methods. Both approaches aim to identify a set of free physical model parameters that results in a simulation best matching an empirical observation. When applied to brain tumor modeling, one of the instances of image-based model personalization in medical image computing, the overarching drawback of the methods is the time complexity of finding such a set. In a clinical setting with limited time between imaging and diagnosis or even intervention, this time complexity may prove critical. As the history of quantitative science is the history of compression (Schmidhuber and Fridman, 2018), we align in this paper with the historical tendency and propose a method compressing complex traditional strategies for solving an inverse problem into a simple database query task. We evaluated different ways of performing the database query task assessing the trade-off between accuracy and execution time. On the exemplary task of brain tumor growth modeling, we prove that the proposed method achieves one order speed-up compared to existing approaches for solving the inverse problem. The resulting compute time offers critical means for relying on more complex and, hence, realistic models, for integrating image preprocessing and inverse modeling even deeper, or for implementing the current model into a clinical workflow. The code is available at https://github.com/IvanEz/for-loop-tumor

Global distribution and bioclimatic characterization of alpine biomes

Although there is a general consensus on the distribution and ecological features of terrestrial biomes, the allocation of alpine ecosystems in the global biogeographic system is still unclear. Here, we delineate a global map of alpine areas above the treeline by modelling regional treeline elevation at 30 m resolution, using global forest cover data and quantile regression. We then used global datasets to 1) assess the climatic characteristics of alpine ecosystems using principal component analysis, 2) define bioclimatic groups by an optimized cluster analysis and 3) evaluate patterns of primary productivity based on the normalized difference vegetation index. As defined here, alpine biomes cover 3.56 Mkm(2) or 2.64% of land outside Antarctica. Despite temperature differences across latitude, these ecosystems converge below a sharp threshold of 5.9 degrees C and towards the colder end of the global climatic space. Below that temperature threshold, alpine ecosystems are influenced by a latitudinal gradient of mean annual temperature and they are climatically differentiated by seasonality and continentality. This gradient delineates a climatic envelope of global alpine biomes around temperate, boreal and tundra biomes as defined in Whittaker's scheme. Although alpine biomes are similarly dominated by poorly vegetated areas, world ecoregions show strong differences in the productivity of their alpine belt irrespectively of major climate zones. These results suggest that vegetation structure and function of alpine ecosystems are driven by regional and local contingencies in addition to macroclimatic factors

Mitochondrial Networking Protects β-Cells From Nutrient-Induced Apoptosis

OBJECTIVE: Previous studies have reported that β-cell mitochondria exist as discrete organelles that exhibit heterogeneous bioenergetic capacity. To date, networking activity, and its role in mediating β-cell mitochondrial morphology and function, remains unclear. In this article, we investigate β-cell mitochondrial fusion and fission in detail and report alterations in response to various combinations of nutrients. RESEARCH DESIGN AND METHODS: Using matrix-targeted photoactivatable green fluorescent protein, mitochondria were tagged and tracked in β-cells within intact islets, as isolated cells and as cell lines, revealing frequent fusion and fission events. Manipulations of key mitochondrial dynamics proteins OPA1, DRP1, and Fis1 were tested for their role in β-cell mitochondrial morphology. The combined effects of free fatty acid and glucose on β-cell survival, function, and mitochondrial morphology were explored with relation to alterations in fusion and fission capacity. RESULTS: β-Cell mitochondria are constantly involved in fusion and fission activity that underlies the overall morphology of the organelle. We find that networking activity among mitochondria is capable of distributing a localized green fluorescent protein signal throughout an isolated β-cell, a β-cell within an islet, and an INS1 cell. Under noxious conditions, we find that β-cell mitochondria become fragmented and lose their ability to undergo fusion. Interestingly, manipulations that shift the dynamic balance to favor fusion are able to prevent mitochondrial fragmentation, maintain mitochondrial dynamics, and prevent apoptosis. CONCLUSIONS: These data suggest that alterations in mitochondrial fusion and fission play a critical role in nutrient-induced β-cell apoptosis and may be involved in the pathophysiology of type 2 diabetes.National Institutes of Health (R01HL071629-03, R01DK074778, 5T32DK007201

Mitochondrial Reactive Oxygen Species Are Obligatory Signals for Glucose-Induced Insulin Secretion

OBJECTIVE—Insulin secretion involves complex events in which the mitochondria play a pivotal role in the generation of signals that couple glucose detection to insulin secretion. Studies on the mitochondrial generation of reactive oxygen species (ROS) generally focus on chronic nutrient exposure. Here, we investigate whether transient mitochondrial ROS production linked to glucose-induced increased respiration might act as a signal for monitoring insulin secretion

Diabetes causes marked inhibition of mitochondrial metabolism in pancreatic β-cells

Diabetes is a global health problem caused primarily by the inability of pancreatic β-cells to secrete adequate levels of insulin. The molecular mechanisms underlying the progressive failure of β-cells to respond to glucose in type-2 diabetes remain unresolved. Using a combination of transcriptomics and proteomics, we find significant dysregulation of major metabolic pathways in islets of diabetic βV59M mice, a non-obese, eulipidaemic diabetes model. Multiple genes/proteins involved in glycolysis/gluconeogenesis are upregulated, whereas those involved in oxidative phosphorylation are downregulated. In isolated islets, glucose-induced increases in NADH and ATP are impaired and both oxidative and glycolytic glucose metabolism are reduced. INS-1 β-cells cultured chronically at high glucose show similar changes in protein expression and reduced glucose-stimulated oxygen consumption: targeted metabolomics reveals impaired metabolism. These data indicate hyperglycaemia induces metabolic changes in β-cells that markedly reduce mitochondrial metabolism and ATP synthesis. We propose this underlies the progressive failure of β-cells in diabetes.Peer reviewe

Proinflammatory Cytokines Activate the Intrinsic Apoptotic Pathway in β-Cells

OBJECTIVE:Proinflammatory cytokines are cytotoxic to beta-cells and have been implicated in the pathogenesis of type 1 diabetes and islet graft failure. The importance of the intrinsic mitochondrial apoptotic pathway in cytokine-induced beta-cell death is unclear. Here, cytokine activation of the intrinsic apoptotic pathway and the role of the two proapoptotic Bcl-2 proteins, Bad and Bax, were examined in beta-cells.RESEARCH DESIGN AND METHODS:Human and rat islets and INS-1 cells were exposed to a combination of proinflammatory cytokines (interleukin-1beta, interferon-gamma, and/or tumor necrosis factor-alpha). Activation of Bad was determined by Ser136 dephosphorylation, mitochondrial stress by changes in mitochondrial metabolic activity and cytochrome c release, downstream apoptotic signaling by activation of caspase-9 and -3, and DNA fragmentation. The inhibitors FK506 and V5 were used to investigate the role of Bad and Bax activation, respectively. [...

Modern cities modelled as “super-cells” rather than multicellular organisms: Implications for industry, goods and services

The structure and “metabolism” (movement and conversion of goods and energy) of urban areas has caused cities to be identified as “super-organisms”, placed between ecosystems and the biosphere, in the hierarchy of living systems. Yet most such analogies are weak, and render the super-organism model ineffective for sustainable development of cities. Via a cluster analysis of 15 shared traits of the hierarchical living system, we found that industrialized cities are more similar to eukaryotic cells than to multicellular organisms; enclosed systems, such as factories and greenhouses, paralleling organelles in eukaryotic cells. We further developed a “super-cell” industrialized city model: a “eukarcity” with citynucleus (urban area) as a regulating centre, and organaras (enclosed systems, which provide the majority of goods and services) as the functional components, and cityplasm (natural ecosystems and farmlands) as the matrix. This model may improve the vitality and sustainability of cities through planning and management