Heterogeneity of cell membrane structure studied by single molecule tracking

Heterogeneity in cell membrane structure, typified by microdomains with different biophysical and biochemical properties, is thought to impact on a variety of cell functions. Integral membrane proteins act as nanometre-sized probes of the lipid environment and their thermally-driven movements can be used to report local variations in membrane properties. In the current study, we have used total internal reflection fluorescence microscopy (TIRFM) combined with super-resolution tracking of multiple individual molecules, in order to create high-resolution maps of local membrane viscosity. We used a quadrat sampling method and show how statistical tests for membrane heterogeneity can be conducted by analysing the paths of many molecules that pass through the same unit area of membrane. We describe experiments performed on cultured primary cells, stable cell lines and ex vivo tissue slices using a variety of membrane proteins, under different imaging conditions. In some cell types, we find no evidence for heterogeneity in mobility across the plasma membrane, but in others we find statistically significant differences with some regions of membrane showing significantly higher viscosity than others

Improved prediction equations for estimating height in adults from ethnically diverse backgrounds

Background & aims When body height cannot be measured, it can be predicted from ulna length (UL). However, commonly used published prediction equations may not provide useful estimates in adults from all ethnicities. This study aimed to evaluate the relationship between UL and height in adults from diverse ethnic groups and to consider whether this can be used to provide useful prediction equations for height in practice. Methods Standing height and UL were measured in 542 adults at seven UK locations. Ethnicity was self-defined using UK Census 2011 categories. Data were modelled to give two groups of height prediction equations based on UL, sex and ethnicity and these were tested against an independent dataset (n = 180). Results UL and height were significantly associated overall and in all groups except one with few participants (P = 0.059). The new equations yielded predicted height (H p) that was closer to measured height in the Asian and Black subgroups of the independent population than the Malnutrition Universal Screening Tool (MUST) equations. For Asian men, (H p (cm) = 3.26 UL (cm) + 83.58), mean difference from measured (95% confidence intervals) was −0.6 (−2.4, +1.2); Asian women, (H p = 3.26 UL + 77.62), mean difference +0.5 (−1.4, 2.4) cm. For Black men, H p = 3.14 UL + 85.80, −0.4 (−2.4, 1.7); Black women, H p = 3.14 UL + 79.55, −0.8 (−2.8, 1.2). These differences were not statistically significant while predictions from MUST equations were significantly different from measured height. Conclusions The new prediction equations provide an alternative for estimating height in adults from Asian and Black groups and give mean predicted values that are closer to measured height than MUST equations

The Effect of Flax Oil Cake on the Structural and Rheological - Properties of Pasta

This article discusses the qualitative indicators of pasta products obtained by partially replacing high-quality wheat powder with flaxseed cake. This is due to the fact that flaxseed cake has a high energy value, is rich in essential protein, macro-, microelements and vitamins, fats remaining in flaxseed cake after fat extraction have all useful properties, contain alpha-linolenic (omega-3) fatty acid, as well as other unsaturated fatty acids. After the procedure of "pressing" of raw materials, organoleptic and Physico-chemical parameters were considered, the indicator of shape preservation after the "cooking" process was determined. Quality indicators of GOST 31743-2017 "Pasta. General technical conditions", GOST 31964-2012 "Pasta. Acceptance rules and methods for determining quality", GOST 10974-95 "Flax cake. Technical conditions" are defined in accordance with regulatory and technical documents. The enrichment of pasta with flax cake improves the biological, nutritional properties of the product and allows you to replace high-quality wheat flour with economic raw materials. The results of the study obtained by quality indicators meet the established requirements. The moisture content of pasta when replacing premium wheat powder by 3.8%, 7.7% and 15.5% with flax cake is 28% (after the procedure of "pressing raw materials"). The use of flax cake as a raw material reduces the cooking time of pasta, ensures that the mold after cooking will meet the requirements and will not stick together

Constructing a Stochastic Model of Bumblebee Flights from Experimental Data

PMCID: PMC3592844This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Intrinsic and extrinsic factors influencing large African herbivore movements

This document is the Accepted Manuscript version of the following article: Jan A. Venter, Herbert H. T. Prins, Alla Mashanova, Willem F. de Boer, and Rob Slotow, 'Intrinsic and extrinsic factors influencing large African herbivore movements', Ecological Informatics, Vol. 30: 257-262, November 2015, doi: https://doi.org/10.1016/j.ecoinf.2015.05.006. This manuscript version is made available under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License (http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited, and is not altered, transformed, or built upon in any way.Understanding environmental as well as anthropogenic factors that influence large herbivore ecological patterns and processes should underpin their conservation and management. We assessed the influence of intrinsic, extrinsic environmental and extrinsic anthropogenic factors on movement behaviour of eight African large herbivore species. A cumulative odds ordinal logistic regression was used to determine the effect of season, feeding niche, number of vegetation types, home range size, and fences on the number of exponential distributions observed. When animals faced the trade-off between forage quality and quantity during the dry season, they moved further between forage areas and water sources in order to get to better forage, which added to the number of movement scales observed. Elephants had a lower number of movement scales, compared to all the other feeding types, which could be attributed to them being able to switch between browse and graze. The number of movement scales increased in more heterogeneous areas. Animals with larger home ranges, which are also larger species, and animals more restricted by fences, had fewer movement scales. In order for managers to effectively manage protected areas and associated biodiversity they need take cognisance of the different scales animals operate under, and the different factors that may be important for different species.Peer reviewe

How Landscape Heterogeneity Frames Optimal Diffusivity in Searching Processes

Theoretical and empirical investigations of search strategies typically have failed to distinguish the distinct roles played by density versus patchiness of resources. It is well known that motility and diffusivity of organisms often increase in environments with low density of resources, but thus far there has been little progress in understanding the specific role of landscape heterogeneity and disorder on random, non-oriented motility. Here we address the general question of how the landscape heterogeneity affects the efficiency of encounter interactions under global constant density of scarce resources. We unveil the key mechanism coupling the landscape structure with optimal search diffusivity. In particular, our main result leads to an empirically testable prediction: enhanced diffusivity (including superdiffusive searches), with shift in the diffusion exponent, favors the success of target encounters in heterogeneous landscapes

Density-dependent dispersal may explain the mid-season crash in some aphid populations

Copyright 2008 Elsevier B.V., All rights reserved.Aphid population dynamics during the season show a characteristic pattern with rapid increase in numbers at the beginning followed by a sudden drop in the middle of the season. This pattern is usually associated with predation and/or change in food quality during the summer. By developing a mechanistic model of aphid population dynamics we show that this pattern can arise from density-dependent dispersal behaviour of aphids. The dynamics produced by the model were similar to those observed in real populations of the alder aphid (Pterocallis alni). The two mechanisms required for these oscillations to arise were the perception of density through the number of contacts with other individuals and the inter-generational transfer of information (the maternal effect). Both mechanisms are examples of delayed density-dependence and, therefore, this study adds to the evidence that delayed density-dependence might cause complex population dynamics. To reproduce the seasonal dynamics of the alder aphid with the model, the maternal effect was essential, indicating that this could be an important factor in alder aphid dynamics. According to our model, external regulations (e.g., predation and/or change in food quality) were not required to explain the highly oscillatory population dynamics of aphids during a season.Peer reviewe

Comment on: “Lévy walks evolve through interaction between movement and environmental complexity”

de Jager et al. (Reports, 24 June 2011, p. 1551) concluded that mussels Lévy walk. We confronted a larger model set with these data and found that mussels do not Lévy walk: Their movement is best described by a composite Brownian walk. This shows how model selection based on an impoverished set of candidate models can lead to incorrect inferences.Peer reviewe