Journal of The Royal Society Interface最新文献

A number of techniques have been developed to measure the three-dimensional trajectories of protists, which require special experimental set-ups, such as a pair of orthogonal cameras. On the other hand, machine learning techniques have been used to estimate the vertical position of spherical particles from the defocus pattern, but they require the acquisition of a labelled dataset with finely spaced vertical positions. Here, we describe a simple way to make a dataset of Paramecium images labelled with vertical position from a single 5 min movie, based on a tilted slide set-up. We used this dataset to train a simple convolutional network to estimate the vertical position of Paramecium from conventional bright field images. As an application, we show that this technique has sufficient accuracy to study the surface following behaviour of Paramecium (thigmotaxis).

Seed dispersal through wind was historically considered a random process; however, plants can influence their dispersal through non-random seed detachment or abscission. Dandelion seeds facing the wind tend to abscise before those facing downwind, yet the mechanism that supports this has remained unclear. We measured the force needed for abscission in different directions and performed imaging of the detachment process. This revealed an asymmetry in the seed attachment morphology, which results in massive differences in the abscission force needed relative to the direction. We developed a mechanistic model to explain this directional bias and identified morphological factors that determine the properties of seed abscission. This discovery highlights plant adaptations that shape the seed dispersal profile to enhance reproductive success and can be used to improve population dynamic models of wind-dispersed plants.

Myopia, or near-sightedness, is rapidly growing in prevalence, with significant long-term implications for ocular health. There is thus great impetus to better understand molecular signalling pathways leading to myopia. We and others have reported that all-trans retinoic acid (atRA) is involved in myopigenic signalling, yet the understanding of how atRA is transported and exerts a myopigenic influence is poor. Here we measured the concentrations of atRA in the serum in wild-type C57BL/6 mice under control conditions and after atRA feeding, previously shown to induce myopia. We also developed a mathematical model that describes fluid fluxes and the advective-diffusive transport of atRA in choroid and sclera, including atRA synthesis in the choriocapillaris, atRA degradation by scleral cells, and binding of atRA to the carrier protein serum albumin. This model, developed for both mice and humans, showed that atRA produced in the choriocapillaris was able to permeate well into the sclera in both mice and humans at biologically relevant concentrations, and that atRA feeding greatly increased tissue levels of atRA across both the choroid and sclera. We were also able to identify which parameters most influence atRA concentration in ocular tissues, guiding future experimental work. Our findings support atRA's role in myopigenic signalling.

Severe fever with thrombocytopaenia syndrome virus (SFTSV) was identified by the World Health Organization as a priority pathogen due to its high case-fatality rate in humans and rapid spread. It is maintained in nature through three transmission pathways: systemic, non-systemic and transovarial. Understanding the relative contributions of these transmission pathways is crucial for developing evidence-informed public health interventions to reduce its spillover risks to humans. Using next-generation matrices, sensitivity analyses, elasticity analyses and random forest models, we estimated the basic reproduction number R₀, relative contribution of each pathway, and identified the most sensitive model parameters across 27 scenarios. Results showed that [Formula: see text] ranged from 0.72 to 2.08 across scenarios, increasing with higher tick abundance and longer viraemia. Transovarial transmission dominated in 26 scenarios, while the importance of the other two varied, with non-systemic transmission more important under high tick abundance, short viraemia or aggregated tick distribution. [Formula: see text] dropped below 1 in all scenarios when transovarial transmission was excluded. These findings emphasize the need for interventions targeting transovarial transmission, such as reducing female adult tick survival and limiting large vertebrate host movement, and underscore the importance of laboratory studies measuring sensitive parameters including transovarial transmission efficiency, tick survival probabilities and the duration of viraemia and potential for non-systemic transmission for key animal host species with high seroprevalence rates.

Nano-engineered particles are a promising tool for medical diagnostics, biomedical imaging and targeted drug delivery. Fundamental to the assessment of particle performance are in vitro particle-cell interaction experiments. These experiments can be summarized with key parameters that facilitate objective comparisons across various cell and particle pairs, such as the particle-cell association rate. Previous studies often focus on point estimates of such parameters and neglect heterogeneity in routine measurements. In this study, we develop an ordinary differential equation-based mechanistic mathematical model that incorporates and exploits the heterogeneity in routine measurements. Connecting this model to data using approximate Bayesian computation parameter inference and prediction tools, we reveal the significant role of heterogeneity in parameters that characterize particle-cell interactions. We then generate predictions for key quantities, such as the time evolution of the number of particles per cell. Finally, by systematically exploring how the choice of experimental time points influences estimates of key quantities, we identify optimal experimental time points that maximize the information that is gained from particle-cell interaction experiments.

Pistachio is a major nut crop worldwide; however, there is a lack of standardized non-destructive methods to effectively evaluate maturity and kernel filling for improved management and harvest timing. This study presents an image-based approach to determine pistachio nut maturation and blank kernel incidence by analysing the surface colour patterns of individual nuts at three time points during late development. We identified eight major hull colours to represent the full colour spectrum and applied principal component analysis to divide each nut into seven spatial sections. Within each section, we constructed eight colour-based feature variables (covariates) and associated them with a binary response variable indicating kernel presence or absence. We explored the specific response-covariate relationships at each developmental time point using a data-driven method called categorical exploratory data analysis, which identified key first-order and second-order feature-categories that link hull colour patterns with kernel status. These relationships were visualized using block-structured heatmaps, revealing consistent distinctions between filled and blank nuts. Based on these findings, we developed an algorithm with two main functions: (i) identifying a nut's growth stage from its image for optimal harvest timing and (ii) estimating blank nut incidence for quality assessment and economic decision-making.

In temperate regions, respiratory viruses such as SARS-CoV-2 are better transmitted in winter than in summer. Understanding how the weather is associated with SARS-CoV-2 transmissibility can enhance projections of COVID-19 incidence and improve estimation of the effectiveness of control measures. During the pandemic, transmissibility was tracked by the reproduction number R_t. This study aims to determine whether information about the daily temperature, absolute humidity and solar radiation improves predictions of R_t in The Netherlands from 2020 to 2022, and to quantify the relationship between R_t and daily weather data. We conducted a regression analysis, accounting for immunity from vaccination and previous infection, higher transmissibility of new variants and changes in contact behaviour due to control measures. Results show a linear association between logR_t and daily solar radiation and temperature, indicating a ratio of R_t in winter versus summer of 1.7 (95% CI, 1.4; 2.1). The possibility that this association arises from unrelated seasonal patterns was dismissed, as weather data from earlier years provided poorer fits with only small effect sizes. This suggests a causal relationship between solar radiation and temperature with SARS-CoV-2 transmissibility, enhancing confidence in using this relationship for short-term predictions and other epidemiological analyses.

The umbilical cord plays a critical role in delivering nutrients and oxygen from the placenta to the fetus through the umbilical vein, while the two umbilical arteries carry deoxygenated blood with waste products back to the placenta. Although solute exchange in the placenta has been extensively studied, exchange within the cord tissue has not been investigated. Here, we explore the hypothesis that the coiled structure of the umbilical cord could strengthen diffusive coupling between the arteries and the vein, resulting in a functional shunt. We calculate the diffusion of solutes, such as oxygen, and heat in the umbilical cord to quantify how this shunt is affected by vascular configuration within the cord. We demonstrate that the shunt is enhanced by coiling and vessel proximity. Furthermore, our model predicts that typical vascular configurations of the human cord tend to minimize shunting, which could otherwise disrupt thermal regulation of the fetus. We also show that the exchange, amplified by coiling, can provide additional oxygen supply to the cord tissue surrounding the umbilical vessels.

Toxin-antitoxin systems (TASs) are ubiquitous in the chromosomes of free-living bacteria, yet their primary biological function remains poorly understood. Bacteria reproduce exponentially via 2ⁿ growth kinetics and thus must respond to changing nutrient availability to reproduce rapidly during short periods of feast and survive during long periods of famine. Type II TASs represent stable enzyme-unstable inhibitor systems that are regulated by reversible competitive inhibition, which allows them to efficiently produce pleiotropic effects on prokaryotic cells in a continuous (analogue) manner due to varying concentrations of free toxin throughout the life cycle. A nutrient-responsive cybernetic system (NRCS) model is proposed where intracellular nutrient concentration feeds back to control the emergent properties of growth, death and growth/death arrest, which results in a novel fitness strategy termed K Sensing and Control. When nutrients become limiting, alternative general stress response sigma factors Ϭ^S and Ϭ^B regulate the expression of hundreds of genes that may control the transformation of vegetative bacteria into coccoid, stress-tolerant 'motherspores'. An integrated NRCS model is presented that shows how TASs and sigma factors may work in concert to efficiently regulate population dynamics, cellular physiology and cellular differentiation throughout the life cycle, which optimizes the biological fitness of free-living bacteria.

Worms extend burrows through muddy sediments by fracture, and the mechanics of crack propagation through heterogeneous sediments affects both navigation by burrowers and the release of particulate material, which is mixed through bioturbation. Crack propagation follows the path of least resistance or the lowest fracture toughness. Previous work showed that applying asymmetrical stress to burrow walls to simulate steering had minimal effect on crack propagation direction, suggesting that crack branching or the fusing of microcracks near the crack tip with the main burrow allows for burrowers to navigate by choosing between two directions. Here we use the lattice element method for modelling of fracture in heterogeneous materials to examine how fracture toughness, variability in fracture toughness and worm behaviours affect crack branching and microcracking. Experimental observations of worms burrowing in custom-built ant farm tanks support the modelling results that burrowing activities create microcracks both within the vicinity of the crack tip and in the surrounding sediment. In addition, hydraulic fracture driven by burrow irrigation reduces microcracking outside of the fracture process zone, potentially increasing the efficiency of burrowing. These results highlight the potential feedback between burrowing activities and sediment heterogeneity that characterize ecosystem engineering of sediment habitats by infaunal burrowers.