Emergence and stability of endoplasmic reticulum network streaming in plant cells.

The endoplasmic reticulum (ER) network is highly complex and highly dynamic in its geometry, and undergoes extensive remodeling and bulk flow. It is known that the ER dynamics are driven by actin-myosin dependent processes. ER motion through the cytoplasm will cause forces on the cytoplasm that will induce flow.

Brain-wide dendrites in a near-optimal performance of dynamic range and information transmission.

Dendrites receive and process signals from other neurons. The range of signal intensities that can be robustly distinguished by dendrites is quantified by the dynamic range. We investigate the dynamic range and information transmission efficiency of dendrites in relation to dendritic morphology.

Synchronization stability of power-grid-tied converters.

Synchronization stability is one of central problems in power systems, and it is becoming much more complicated with the high penetration of renewable energy and power electronics devices. In this paper, we review recent work by several nonlinear models for renewable-dominated power systems in terms of multiple timescales, in particular, grid-tied converters within the DC voltage timescale. For the simplest model, a second-order differential equations called the generalized swing equation by considering only the phase-locked loop (PLL) is obtained, which shows a similar form with the well-known swing equation for a synchronous generator in the traditional power systems.

Bursting hierarchy in an adaptive exponential integrate-and-fire network synchronization.

Neuronal network synchronization has received wide interest. In the present manuscript, we study the influence of initial membrane potentials together with network topology on bursting synchronization, in particular the sequential order of stabilized bursting among neurons. We find a hierarchical phenomenon on their bursting order.

Asynchronous changes of normal lung lobes during respiration based on quantitative computed tomography (CT).

Background: This study aimed to explore the coordinated and independent actions of lung lobes during respiration using quantitative computed tomography (CT) in order to increase our understanding of pulmonary anatomy.

Methods: Cases for whom test results showed normal pulmonary function tests (PFTs) results, and normal paired inspiratory-expiratory chest CT findings, as assessed by 2 radiologists, were retrospectively included in this study. From the chest CT results, we measured quantitative indices of lung volume (LV) and mean lung density (MLD) for the total lung (TL), left lung (LL), right lung (RL), and 5 lobes in inspiratory and expiratory phases.

Modelling the motion of organelles in an elongated cell via the coordination of heterogeneous drift-diffusion and long-range transport.

 Cellular distribution of organelles in living cells is achieved via a variety of transport mechanisms, including directed motion, mediated by molecular motors along microtubules (MTs), and diffusion which is predominantly heterogeneous in space. In this paper, we introduce a model for particle transport in elongated cells that couples poleward drift, long-range bidirectional transport and diffusion with spatial heterogeneity in a three-dimensional space. Using stochastic simulations and analysis of a related population model, we find parameter regions where the three-dimensional model can be reduced to a coupled one-dimensional model or even a one-dimensional scalar model.

Domino-like transient dynamics at seizure onset in epilepsy.

The International League Against Epilepsy (ILAE) groups seizures into "focal", "generalized" and "unknown" based on whether the seizure onset is confined to a brain region in one hemisphere, arises in several brain region simultaneously, or is not known, respectively. This separation fails to account for the rich diversity of clinically and experimentally observed spatiotemporal patterns of seizure onset and even less so for the properties of the brain networks generating them. We consider three different patterns of domino-like seizure onset in Idiopathic Generalized Epilepsy (IGE) and present a novel approach to classification of seizures.

Miro2 tethers the ER to mitochondria to promote mitochondrial fusion in tobacco leaf epidermal cells.

Mitochondria are highly pleomorphic, undergoing rounds of fission and fusion. Mitochondria are essential for energy conversion, with fusion favouring higher energy demand. Unlike fission, the molecular components involved in mitochondrial fusion in plants are unknown.

Modelling brain-wide neuronal morphology via rooted Cayley trees.

Neuronal morphology is an essential element for brain activity and function. We take advantage of current availability of brain-wide neuron digital reconstructions of the Pyramidal cells from a mouse brain, and analyze several emergent features of brain-wide neuronal morphology. We observe that axonal trees are self-affine while dendritic trees are self-similar.

Modeling the Geometry and Dynamics of the Endoplasmic Reticulum Network.

The endoplasmic reticulum (ER) is an intricate network that pervades the entire cortex of plant cells and its geometric shape undergoes drastic changes. This paper proposes a mathematical model to reconstruct geometric network dynamics by combining the node movements within the network and topological changes engendered by these nodes. The network topology in the model is determined by a modified optimization procedure from the work (Lemarchand, et al.

Modeling Endoplasmic Reticulum Network Maintenance in a Plant Cell.

The endoplasmic reticulum (ER) in plant cells forms a highly dynamic network of complex geometry. ER network morphology and dynamics are influenced by a number of biophysical processes, including filament/tubule tension, viscous forces, Brownian diffusion, and interactions with many other organelles and cytoskeletal elements. Previous studies have indicated that ER networks can be thought of as constrained minimal-length networks acted on by a variety of forces that perturb and/or remodel the network.

Spatial organization of organelles in fungi: Insights from mathematical modelling.

Mathematical modelling in cellular systems aims to describe biological processes in a quantitative manner. Most accurate modelling is based on robust experimental data. Here we review recent progress in the theoretical description of motor behaviour, early endosome motility, ribosome distribution and peroxisome transport in the fungal model system Ustilago maydis and illustrate the power of modelling in our quest to understand molecular details and cellular roles of membrane trafficking in filamentous fungi.

Active diffusion and microtubule-based transport oppose myosin forces to position organelles in cells.

Even distribution of peroxisomes (POs) and lipid droplets (LDs) is critical to their role in lipid and reactive oxygen species homeostasis. How even distribution is achieved remains elusive, but diffusive motion and directed motility may play a role. Here we show that in the fungus Ustilago maydis ∼95% of POs and LDs undergo diffusive motions.

Plant ER geometry and dynamics: biophysical and cytoskeletal control during growth and biotic response.

The endoplasmic reticulum (ER) is an intricate and dynamic network of membrane tubules and cisternae. In plant cells, the ER 'web' pervades the cortex and endoplasm and is continuous with adjacent cells as it passes through plasmodesmata. It is therefore the largest membranous organelle in plant cells.

Structure and dynamics of ER: minimal networks and biophysical constraints.

The endoplasmic reticulum (ER) in live cells is a highly mobile network whose structure dynamically changes on a number of timescales. The role of such drastic changes in any system is unclear, although there are correlations with ER function. A better understanding of the fundamental biophysical constraints on the system will allow biologists to determine the effects of molecular factors on ER dynamics.

Motor-mediated bidirectional transport along an antipolar microtubule bundle: a mathematical model.

Long-distance bidirectional transport of organelles depends on the coordinated motion of various motor proteins on the cytoskeleton. Recent quantitative live cell imaging in the elongated hyphal cells of Ustilago maydis has demonstrated that long-range motility of motors and their endosomal cargo occurs on unipolar microtubules (MTs) near the extremities of the cell. These MTs are bundled into antipolar bundles within the central part of the cell.

Controlled and stochastic retention concentrates dynein at microtubule ends to keep endosomes on track.

Bidirectional transport of early endosomes (EEs) involves microtubules (MTs) and associated motors. In fungi, the dynein/dynactin motor complex concentrates in a comet-like accumulation at MT plus-ends to receive kinesin-3-delivered EEs for retrograde transport. Here, we analyse the loading of endosomes onto dynein by combining live imaging of photoactivated endosomes and fluorescent dynein with mathematical modelling.

Queueing induced by bidirectional motor motion near the end of a microtubule.

Recent live observations of motors in long-range microtubule (MT) dependent transport in the fungus Ustilago maydis have reported bidirectional motion of dynein and an accumulation of the motors at the polymerization-active (the plus-end) of the microtubule. Quantitative data derived from in vivo observation of dynein has enabled us to develop an accurate, quantitatively-valid asymmetric simple exclusion process (ASEP) model that describes the coordinated motion of anterograde and retrograde motors sharing a single oriented microtubule. We give approximate expressions for the size and distribution of the accumulation, and discuss queueing properties for motors entering this accumulation.