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Journal of Mathematical Biology Apr 2024Cell-cell adhesion plays a vital role in the development and maintenance of multicellular organisms. One of its functions is regulation of cell migration, such as...
Cell-cell adhesion plays a vital role in the development and maintenance of multicellular organisms. One of its functions is regulation of cell migration, such as occurs, e.g. during embryogenesis or in cancer. In this work, we develop a versatile multiscale approach to modelling a moving self-adhesive cell population that combines a careful microscopic description of a deterministic adhesion-driven motion component with an efficient mesoscopic representation of a stochastic velocity-jump process. This approach gives rise to mesoscopic models in the form of kinetic transport equations featuring multiple non-localities. Subsequent parabolic and hyperbolic scalings produce general classes of equations with non-local adhesion and myopic diffusion, a special case being the classical macroscopic model proposed in Armstrong et al. (J Theoret Biol 243(1): 98-113, 2006). Our simulations show how the combination of the two motion effects can unfold. Cell-cell adhesion relies on the subcellular cell adhesion molecule binding. Our approach lends itself conveniently to capturing this microscopic effect. On the macroscale, this results in an additional non-linear integral equation of a novel type that is coupled to the cell density equation.
Topics: Cell Adhesion; Cell Movement; Diffusion; Embryonic Development; Kinetics
PubMed: 38568280
DOI: 10.1007/s00285-024-02079-8 -
Heliyon Jan 2024The use cases of blockchain as an innovative technology have increasingly captured the attention of tourism enterprises. To date, the literature tends to discuss...
The use cases of blockchain as an innovative technology have increasingly captured the attention of tourism enterprises. To date, the literature tends to discuss blockchain's advantages rather than how early enterprise adopters and innovators experience and perceive the technology. As such, the extent of technology diffusion is not well understood. This study critically explores the factors influencing blockchain diffusion in tourism and how blockchain innovation is diffused in tourism. We conducted semistructured interviews with founders and senior executives of tourism enterprises in the United States and Europe who are early adopters and innovators of blockchain in tourism. From the thematic analysis, our empirical findings indicate that blockchain has much to offer despite the nascent link between blockchain's business value to an enterprise's strategic plans and the limited success of use cases in tourism. We summarize the findings in a conceptual framework and offer propositions based on the antecedents (motivators and drivers and challenges and barriers) of blockchain diffusion of innovation for enterprises to achieve competitive advantage. The propositions provide a research agenda to guide the strategic implementation of blockchain.
PubMed: 38304774
DOI: 10.1016/j.heliyon.2024.e24675 -
Nature Communications Feb 2024Drosophila male germline stem cells (GSCs) reside at the tip of the testis and surround a cluster of niche cells. Decapentaplegic (Dpp) is one of the well-established...
Drosophila male germline stem cells (GSCs) reside at the tip of the testis and surround a cluster of niche cells. Decapentaplegic (Dpp) is one of the well-established ligands and has a major role in maintaining stem cells located in close proximity. However, the existence and the role of the diffusible fraction of Dpp outside of the niche have been unclear. Here, using genetically-encoded nanobodies called Morphotraps, we physically block Dpp diffusion without interfering with niche-stem cell signaling and find that a diffusible fraction of Dpp is required to ensure differentiation of GSC daughter cells, opposite of its role in maintenance of GSC in the niche. Our work provides an example in which a soluble niche ligand induces opposed cellular responses in stem cells versus in differentiating descendants to ensure spatial control of the niche. This may be a common mechanism to regulate tissue homeostasis.
Topics: Animals; Male; Drosophila Proteins; Ligands; Cell Differentiation; Drosophila; Signal Transduction; Stem Cell Niche; Germ Cells; Drosophila melanogaster
PubMed: 38326318
DOI: 10.1038/s41467-024-45408-7 -
Nanoscale Advances Sep 2023Here, the magnetohydrodynamic bioconvective flow of a non-Newtonian nanomaterial over a stretched sheet is scrutinized. The characteristics of convective conditions are...
Here, the magnetohydrodynamic bioconvective flow of a non-Newtonian nanomaterial over a stretched sheet is scrutinized. The characteristics of convective conditions are analyzed. Irreversibility analysis in the presence of gyrotactic micro-organisms is discussed. Energy expression is assisted with thermal radiation, heat generation and ohmic heating. Buongiorno's model is employed to discuss the characteristics of the nanoliquid through thermophoresis and random diffusions. Nonlinear expressions of the given model are transformed through adequate transformations. The obtained expressions have been computed by the Newton built in-shooting technique. Results of influential variables for velocity, concentration, microorganism field, temperature and entropy rate are graphically studied. Clearly, velocity reduction is witnessed for the bioconvection Rayleigh number and magnetic variable. A higher heat generation variable leads to augmentation of temperature. An increase in the magnetic variable results in entropy and temperature enhancement. A higher Peclet number results in microorganism field reduction. Temperature distribution rises for radiation and the thermal Biot number. A higher solutal Biot number intensifies the concentration. The entropy rate for radiation and diffusion variables is enhanced.
PubMed: 37705799
DOI: 10.1039/d3na00338h -
Scientific Reports Sep 2023Children cooled for HIE and who did not develop cerebral palsy (CP) still underperform at early school age in motor and cognitive domains and have altered...
Children cooled for HIE and who did not develop cerebral palsy (CP) still underperform at early school age in motor and cognitive domains and have altered supra-tentorial brain volumes and white matter connectivity. We obtained T1-weighted and diffusion-weighted MRI, motor (MABC-2) and cognitive (WISC-IV) scores from children aged 6-8 years who were cooled for HIE secondary to perinatal asphyxia without CP (cases), and controls matched for age, sex, and socioeconomic status. In 35 case children, we measured cerebellar growth from infancy (age 4-15 days after birth) to childhood. In childhood, cerebellar volumes were measured in 26 cases and 23 controls. Diffusion properties (mean diffusivity, MD and fractional anisotropy, FA) were calculated in 24 cases and 19 controls, in 9 cerebellar regions. Cases with FSIQ ≤ 85 had reduced growth of cerebellar width compared to those with FSIQ > 85 (p = 0.0005). Regional cerebellar volumes were smaller in cases compared to controls (p < 0.05); these differences were not significant when normalised to total brain volume. There were no case-control differences in MD or FA. Interposed nucleus volume was more strongly associated with IQ in cases than in controls (p = 0.0196). Other associations with developmental outcome did not differ between cases and controls.
Topics: Infant, Newborn; Female; Pregnancy; Child; Humans; Cerebral Palsy; Brain Diseases; Infant, Newborn, Diseases; Brain; Cerebellum
PubMed: 37684324
DOI: 10.1038/s41598-023-41838-3 -
Biological Psychiatry. Cognitive... Aug 2023Integrating multiple neuroimaging modalities to identify clusters of individuals and then associating these clusters with psychopathology is a promising approach for...
BACKGROUND
Integrating multiple neuroimaging modalities to identify clusters of individuals and then associating these clusters with psychopathology is a promising approach for understanding neurobiological mechanisms that underlie psychopathology and the extent to which these features are associated with clinical symptoms.
METHODS
We leveraged neuroimaging data from T1-weighted, diffusion-weighted, and resting-state functional magnetic resonance images from the Adolescent Brain Cognitive Development (ABCD) Study (N = 8035) and used similarity network fusion and spectral clustering to identify subgroups of participants. We examined neuroimaging measures as a function of clustering profiles using 1, 2, or 3 imaging modalities (i.e., data combinations), calculated the stability of the clustering assignment in each respective data combination, and compared the consistency of clusters across different data combinations. We then compared the extent to which clusters were associated with overall psychopathology at the baseline assessment and at 2 yearly follow-up visits.
RESULTS
Each data combination resulted in optimal clusters ranging from 2 to 4 subgroups for each data combination. Clusters were stable across subsampling of the ABCD Study cohort. Widespread structural measures (surface area, fractional anisotropy, and mean diffusivity) were important features contributing to clustering across different data combinations. Five of the seven data combinations were associated with overall psychopathology, both at baseline and over time (d = 0.08-0.41). Generally, lower global cortical volume and surface area, widespread reduced fractional anisotropy, and increased radial diffusivity were associated with increased overall psychopathology.
CONCLUSIONS
Profiles constructed from neuroimaging data combinations are associated with concurrent and future psychopathology trajectories.
Topics: Humans; Adolescent; Brain; Diffusion Tensor Imaging; Magnetic Resonance Imaging; Neuroimaging; Mental Disorders
PubMed: 37121399
DOI: 10.1016/j.bpsc.2023.04.007 -
Theoretical Population Biology Feb 2024Consider the diffusion process defined by the forward equation u(t,x)=12{xu(t,x)}-α{xu(t,x)} for t,x≥0 and -∞<α<∞, with an initial condition u(0,x)=δ(x-x). This...
Consider the diffusion process defined by the forward equation u(t,x)=12{xu(t,x)}-α{xu(t,x)} for t,x≥0 and -∞<α<∞, with an initial condition u(0,x)=δ(x-x). This equation was introduced and solved by Feller to model the growth of a population of independently reproducing individuals. We explore important coalescent processes related to Feller's solution. For any α and x>0 we calculate the distribution of the random variable A(s;t), defined as the finite number of ancestors at a time s in the past of a sample of size n taken from the infinite population of a Feller diffusion at a time t since its initiation. In a subcritical diffusion we find the distribution of population and sample coalescent trees from time t back, conditional on non-extinction as t→∞. In a supercritical diffusion we construct a coalescent tree which has a single founder and derive the distribution of coalescent times.
PubMed: 38092137
DOI: 10.1016/j.tpb.2023.12.001 -
The Journal of Physical Chemistry. B Aug 2023Immunoglobulin G (IgG) is the most common type of antibody found in blood and extracellular fluids and plays an essential role in our immune response. However, studies...
Immunoglobulin G (IgG) is the most common type of antibody found in blood and extracellular fluids and plays an essential role in our immune response. However, studies of the dynamics and reaction kinetics of IgG-antigen binding under physiological crowding conditions are scarce. Herein, we develop a coarse-grained model of IgG consisting of only six beads that we find minimal for a coarse representation of IgG's shape and a decent reproduction of its flexibility and diffusion properties measured experimentally. Using this model in Brownian dynamics simulations, we find that macromolecular crowding affects only slightly the IgG's flexibility, as described by the distribution of angles between the IgG's arms and stem. Our simulations indicate that, contrary to expectations, crowders slow down the translational diffusion of an IgG less strongly than they do for a smaller Ficoll 70, which we relate to the IgG's conformational size changes induced by crowding. We also find that crowders affect the binding kinetics by decreasing the rate of the first binding step and enhancing the second binding step.
Topics: Immunoglobulin G; Diffusion; Ficoll; Kinetics
PubMed: 37591305
DOI: 10.1021/acs.jpcb.3c02383 -
Biophysical Journal Nov 2023To characterize the mechanisms governing the diffusion of particles in biological scenarios, it is essential to accurately determine their diffusive properties. To do...
To characterize the mechanisms governing the diffusion of particles in biological scenarios, it is essential to accurately determine their diffusive properties. To do so, we propose a machine-learning method to characterize diffusion processes with time-dependent properties at the experimental time resolution. Our approach operates at the single-trajectory level predicting the properties of interest, such as the diffusion coefficient or the anomalous diffusion exponent, at every time step of the trajectory. In this way, changes in the diffusive properties occurring along the trajectory emerge naturally in the prediction and thus allow the characterization without any prior knowledge or assumption about the system. We first benchmark the method on synthetic trajectories simulated under several conditions. We show that our approach can successfully characterize both abrupt and continuous changes in the diffusion coefficient or the anomalous diffusion exponent. Finally, we leverage the method to analyze experiments of single-molecule diffusion of two membrane proteins in living cells: the pathogen-recognition receptor DC-SIGN and the integrin α5β1. The analysis allows us to characterize physical parameters and diffusive states with unprecedented accuracy, shedding new light on the underlying mechanisms.
Topics: Deep Learning; Diffusion
PubMed: 37853693
DOI: 10.1016/j.bpj.2023.10.015 -
The Journal of Neuroscience : the... Aug 2023Amyloid β protein (Aβ) and tau, the two main proteins implicated in causing Alzheimer's disease (AD), are posited to trigger synaptic dysfunction long before...
Amyloid β protein (Aβ) and tau, the two main proteins implicated in causing Alzheimer's disease (AD), are posited to trigger synaptic dysfunction long before significant synaptic loss occurs in vulnerable circuits. Whereas soluble Aβ aggregates from AD brain are well recognized potent synaptotoxins, less is known about the synaptotoxicity of soluble tau from AD or other tauopathy patient brains. Minimally manipulated patient-derived aqueous brain extracts contain the more diffusible native forms of these proteins. Here, we explore how intracerebral injection of Aβ and tau present in such aqueous extracts of patient brain contribute to disruption of synaptic plasticity in the CA1 area of the male rat hippocampus. Aqueous extracts of certain AD brains acutely inhibited long-term potentiation (LTP) of synaptic transmission in a manner that required both Aβ and tau. Tau-containing aqueous extracts of a brain from a patient with Pick's disease (PiD) also impaired LTP, and diffusible tau from either AD or PiD brain lowered the threshold for AD brain Aβ to inhibit LTP. Remarkably, the disruption of LTP persisted for at least 2 weeks after a single injection. These findings support a critical role for diffusible tau in causing rapid onset, persistent synaptic plasticity deficits, and promoting Aβ-mediated synaptic dysfunction. The microtubule-associated protein tau forms relatively insoluble fibrillar deposits in the brains of people with neurodegenerative diseases including Alzheimer's and Pick's diseases. More soluble aggregates of disease-associated tau may diffuse between cells and could cause damage to synapses in vulnerable circuits. We prepared aqueous extracts of diseased cerebral cortex and tested their ability to interfere with synaptic function in the brains of live rats. Tau in these extracts rapidly and persistently disrupted synaptic plasticity and facilitated impairments caused by amyloid β protein, the other major pathologic protein in Alzheimer's disease. These findings show that certain diffusible forms of tau can mediate synaptic dysfunction and may be a target for therapy.
Topics: Male; Rats; Animals; Amyloid beta-Peptides; Long-Term Potentiation; Alzheimer Disease; tau Proteins; Neuronal Plasticity; Synapses; Hippocampus; Brain
PubMed: 37491315
DOI: 10.1523/JNEUROSCI.0082-23.2023