scholarly journals A Mathematical Study of the Influence of Hypoxia and Acidity on the Evolutionary Dynamics of Cancer

2021 ◽  
Vol 83 (7) ◽  
Author(s):  
Giada Fiandaca ◽  
Marcello Delitala ◽  
Tommaso Lorenzi
Keyword(s):  
Cancer Cells ◽  
Evolutionary Dynamics ◽  
Environmental Gradients ◽  
Abiotic Factors ◽  
Spatial Dynamics ◽  
Real Data ◽  
Tumour Cells ◽  
Environmental Stressors ◽  
Theoretical Understanding ◽  
Spatio Temporal

AbstractHypoxia and acidity act as environmental stressors promoting selection for cancer cells with a more aggressive phenotype. As a result, a deeper theoretical understanding of the spatio-temporal processes that drive the adaptation of tumour cells to hypoxic and acidic microenvironments may open up new avenues of research in oncology and cancer treatment. We present a mathematical model to study the influence of hypoxia and acidity on the evolutionary dynamics of cancer cells in vascularised tumours. The model is formulated as a system of partial integro-differential equations that describe the phenotypic evolution of cancer cells in response to dynamic variations in the spatial distribution of three abiotic factors that are key players in tumour metabolism: oxygen, glucose and lactate. The results of numerical simulations of a calibrated version of the model based on real data recapitulate the eco-evolutionary spatial dynamics of tumour cells and their adaptation to hypoxic and acidic microenvironments. Moreover, such results demonstrate how nonlinear interactions between tumour cells and abiotic factors can lead to the formation of environmental gradients which select for cells with phenotypic characteristics that vary with distance from intra-tumour blood vessels, thus promoting the emergence of intra-tumour phenotypic heterogeneity. Finally, our theoretical findings reconcile the conclusions of earlier studies by showing that the order in which resistance to hypoxia and resistance to acidity arise in tumours depend on the ways in which oxygen and lactate act as environmental stressors in the evolutionary dynamics of cancer cells.

scholarly journals Spatio-temporal distribution patterns of Chironomidae communities in the wadis of Northern Tunisia

2022 ◽  
Vol 82 ◽  
Author(s):  
S. Boulaaba ◽  
S. Zrelli ◽  
A. Hedfi ◽  
M. Ben Ali ◽  
M. Boumaiza ◽  
...  
Keyword(s):  
Linear Models ◽  
Environmental Gradients ◽  
Abiotic Factors ◽  
Temporal Distribution ◽  
Thermal Conditions ◽  
Sodium Concentration ◽  
Dominant Group ◽  
Water Conductivity ◽  
Northern Tunisia ◽  
Spatio Temporal

Abstract In Northern Tunisia, seasonal streams, called wadi, are characterized by extreme hydrological and thermal conditions. These freshwater systems have very particular features as a result of their strong irregularity of flow due to limited precipitation runoff regime, leading to strong seasonal hydrologic fluctuations. The current study focused on the spatio-temporal distribution of chironomids in 28 sampling sites spread across the Northern Tunisia. By emplying PERMANOVA, the results indicated a significant spatio-temporal variation along various environmental gradients. The main abiotic factors responsible for noted differences in the spatial distribution of chironomids in wadi were the conductivity and temperature, closely followed by altitude, pH, salinity, talweg slope and dissolved oxygen, identified as such by employing distance-based linear models’ procedure. The Distance-based redundancy analysis ordination showed two main groups: the first clustered the Bizerte sites, which were characterized by high water conductivity, sodium concentration and salinity. The second main group comprised sites from the Tell zone and was characterized by low temperatures, neutral pH, low conductivity and nutrients content. The subfamily TANYPODIINAE (e.g., Prochladius sp., Prochladius choerus (Meigen, 1804) and Macropelopia sp.) was the dominant group at Tell zone, whereas species such as Diamesa starmachi (Kownacki et Kownacha, 1970) and Potthastia gaedii (Meigen, 1838) were found only in Tell Wadis. In contrast, chironomid species such as Diamesa starmachi (Kownacki et Kownacha, 1970), Potthastia gaedii (Meigen, 1838), Procladius choreus (Meigen, 1804) were specific for Tell Mountain. Cap Bon wadis region was dominated by genus Cladotanytarsus sp. The results of this survey liked the taxonomic composition of chironomid assemblages to the variation of hydromorphological and physic-chemical gradients across the northern Tunisia wadis.

scholarly journals A stochastic metapopulation state-space approach to modeling and estimating COVID-19 spread

2021 ◽  
Vol 18 (6) ◽  
pp. 7685-7710
Author(s):  
Yukun Tan ◽  
◽  
Durward Cator III ◽  
Martial Ndeffo-Mbah ◽  
Ulisses Braga-Neto ◽  
...  
Keyword(s):  
State Space ◽  
State Space Model ◽  
Synthetic Data ◽  
Public Health Intervention ◽  
Disease Outbreaks ◽  
Real Data ◽  
Epidemiological Data ◽  
Transmission Parameters ◽  
Intervention Measures ◽  
Spatio Temporal

<abstract><p>Mathematical models are widely recognized as an important tool for analyzing and understanding the dynamics of infectious disease outbreaks, predict their future trends, and evaluate public health intervention measures for disease control and elimination. We propose a novel stochastic metapopulation state-space model for COVID-19 transmission, which is based on a discrete-time spatio-temporal susceptible, exposed, infected, recovered, and deceased (SEIRD) model. The proposed framework allows the hidden SEIRD states and unknown transmission parameters to be estimated from noisy, incomplete time series of reported epidemiological data, by application of unscented Kalman filtering (UKF), maximum-likelihood adaptive filtering, and metaheuristic optimization. Experiments using both synthetic data and real data from the Fall 2020 COVID-19 wave in the state of Texas demonstrate the effectiveness of the proposed model.</p></abstract>

scholarly journals Chimpanzee (Pan troglodytes verus) density and environmental gradients at their biogeographical range edge

2020 ◽  
Author(s):  
Erin G. Wessling ◽  
Paula Dieguez ◽  
Manuel Llana ◽  
Liliana Pacheco ◽  
Jill D. Pruetz ◽  
...  
Keyword(s):  
Pan Troglodytes ◽  
Habitat Heterogeneity ◽  
Environmental Gradients ◽  
Abiotic Factors ◽  
Habitat Characteristics ◽  
Pan Troglodytes Verus ◽  
Range Limit ◽  
Range Edge ◽  
Food Species ◽  
Underlying Mechanisms

ABSTRACTIdentifying ecological gradients at the range edge of a species is an essential step in revealing the underlying mechanisms and constraints that limit the species’ geographic range. We aimed to describe the patterns of variation in chimpanzee (Pan troglodytes verus) density and habitat characteristics perpendicular to the northern edge of their range and to investigate potential environmental mechanisms underlying chimpanzee distribution in a savanna-mosaic habitat. We estimated chimpanzee densities at six sites forming a 126 km latitudinal gradient at the biogeographical range edge of the western chimpanzee in the savanna-mosaic habitats of southeastern Senegal. To accompany these data, we used systematically placed vegetation plots to characterize the habitats at each site for habitat heterogeneity, tree density and size, floral assemblages, among other variables. We found that both biotic and abiotic factors are potential determinants of the chimpanzee range limit in this ecoregion. Specifically, chimpanzee-occupied landscapes at the limit had smaller available floral assemblages, less habitat heterogeneity, and contained fewer closed canopy habitats in which chimpanzees could seek refuge from high temperatures than landscapes farther from the range limit. This pattern was accompanied by a decline in chimpanzee density with increasing proximity to the range limit. Our results provide several indications of the potential limits of food species diversity, thermal refuge, and water availability to the chimpanzee niche and the implications of these limits for chimpanzee biogeography, especially in the face of climate change predictions, as well as to species distributional modeling more generally.

scholarly journals Spatio-temporal ecological and evolutionary dynamics in natural butterfly populations

2017 ◽  
Vol 40 ◽  
pp. 31-36
Author(s):  
Zachariah Gompert ◽  
Lauren Lucas
Keyword(s):  
Evolutionary Dynamics ◽  
Natural Populations ◽  
Distance Sampling ◽  
Spatial And Temporal Variation ◽  
Insect Community ◽  
Long Term Study ◽  
Greater Yellowstone Area ◽  
Genome Wide ◽  
Spatio Temporal

Long term studies of wild populations indicate that natural selection can cause rapid and dramatic changes in traits, with spatial and temporal variation in the strength of selection a critical driver of genetic variation in natural populations. In 2012, we began a long term study of genome-wide molecular evolution in populations of the butterfly Lycaeides ideas in the Greater Yellowstone Area (GYA). We aimed to quantify the role of environment-dependent selection on evolution in these populations. Building on previous work, in 2017 we collected new samples, incorporated distance sampling, and surveyed the insect community at each site. We also defined the habitat boundary at anew, eleventh site. Our preliminary analyses suggest that both genetic drift and selection are important drivers in this system.   Featured photo from Figure 1 in report.

Lamins as cancer biomarkers

2010 ◽  
Vol 38 (1) ◽  
pp. 297-300 ◽  
Author(s):  
Clare R. Foster ◽  
Stefan A. Przyborski ◽  
Robert G. Wilson ◽  
Christopher J. Hutchison
Keyword(s):  
Cancer Cells ◽  
Patient Survival ◽  
Cancer Biomarkers ◽  
Tumour Cells ◽  
Diagnostic Biomarkers ◽  
Cancer Subtypes ◽  
Multifunctional Proteins ◽  
Poor Patient ◽  
Poor Patient Survival

Lamins are multifunctional proteins that are often aberrantly expressed or localized in tumours. Here, we endeavour to assess their uses as cancer biomarkers: to diagnose tumours, analyse cancer characteristics and predict patient survival. It appears that the nature of lamin function in cancer is very complex. Lamin expression can be variable between and even within cancer subtypes, which limits their uses as diagnostic biomarkers. Expression of A-type lamins is a marker of differentiated tumour cells and has been shown to be a marker of good or poor patient survival depending on tumour subtype. Further research into the functions of lamins in cancer cells and the mechanisms that determine its patterns of expression may provide more potential uses of lamins as cancer biomarkers.

MATHEMATICAL MODELLING OF CANCER CELL INVASION OF TISSUE: THE ROLE OF THE UROKINASE PLASMINOGEN ACTIVATION SYSTEM

2005 ◽  
Vol 15 (11) ◽  
pp. 1685-1734 ◽  
Author(s):  
M. A. J. CHAPLAIN ◽  
G. LOLAS
Keyword(s):  
Cancer Cells ◽  
Cancer Cell ◽  
Cell Invasion ◽  
The Body ◽  
Plasminogen Activation ◽  
Cancer Cell Invasion ◽  
Plasminogen Activation System ◽  
Activation System ◽  
Spatio Temporal

The growth of solid tumours proceeds through two distinct phases: the avascular and the vascular phase. It is during the latter stage that the insidious process of cancer invasion of peritumoral tissue can and does take place. Vascular tumours grow rapidly allowing the cancer cells to establish a new colony in distant organs, a process that is known as metastasis. The progression from a single, primary tumour to multiple tumours in distant sites throughout the body is known as the metastatic cascade. This is a multistep process that first involves the over-expression by the cancer cells of proteolytic enzyme activity, such as the urokinase-type plasminogen activator (uPA) and matrix metalloproteinases (MMPs). uPA itself initiates the activation of an enzymatic cascade that primarily involves the activation of plasminogen and subsequently its matrix degrading protein plasmin. Degradation of the matrix then enables the cancer cells to migrate through the tissue and subsequently to spread to secondary sites in the body. In this paper we consider a mathematical model of cancer cell invasion of tissue (extracellular matrix) which focuses on the role of the plasminogen activation system. The model consists of a system of reaction-diffusion-taxis partial differential equations describing the interactions between cancer cells, urokinase plasminogen activator (uPA), uPA inhibitors, plasmin and the host tissue. The focus of the modelling is on the spatio-temporal dynamics of the uPA system and how this influences the migratory properties of the cancer cells through random motility, chemotaxis and haptotaxis. The results obtained from numerical computations carried out on the model equations produce rich, dynamic heterogeneous spatio-temporal solutions and demonstrate the ability of rather simple models to produce complicated dynamics, all of which are associated with tumour heterogeneity and cancer cell progression and invasion.

Spatio-Temporal Data Mining for Air Pollution Problems

2011 ◽  
pp. 1815-1822 ◽  
Author(s):  
Seoung Bum Kim ◽  
Chivalai Temiyasathit ◽  
Sun-Kyoung Park ◽  
Victoria C.P. Chen
Keyword(s):  
Data Mining ◽  
Air Pollution ◽  
Real Data ◽  
Ambient Air ◽  
Ambient Air Pollution ◽  
Temporal Data Mining ◽  
Area Of Interest ◽  
Mining Methods ◽  
Spatio Temporal ◽  
Temporal And Spatial Characteristics

Vast amounts of data are being generated to extract implicit patterns of ambient air pollution. Because air pollution data are generally collected in a wide area of interest over a relatively long period, such analyses should take into account both temporal and spatial characteristics. Furthermore, combinations of observations from multiple monitoring stations, each with a large number of serially correlated values, lead to a situation that poses a great challenge to analytical and computational capabilities. Data mining methods are efficient for analyzing such large and complicated data. Despite the great potential of applying data mining methods to such complicated air pollution data, the appropriate methods remain premature and insufficient. The major aim of this chapter is to present some data mining methods, along with the real data, as a tool for analyzing the complex behavior of ambient air pollutants.

scholarly journals Large-Scale Image Analysis for Investigating Spatio-Temporal Changes in Nuclear DNA Damage Caused by Nitrogen Atmospheric Pressure Plasma Jets

2020 ◽  
Vol 21 (11) ◽  
pp. 4127
Author(s):  
Xu Han ◽  
James Kapaldo ◽  
Yueying Liu ◽  
M. Sharon Stack ◽  
Elahe Alizadeh ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Image Analysis ◽  
Cancer Cells ◽  
Atmospheric Pressure ◽  
Large Scale ◽  
Nuclear Dna ◽  
Atmospheric Pressure Plasma ◽  
Plasma Jet ◽  
Spatio Temporal

The effective clinical application of atmospheric pressure plasma jet (APPJ) treatments requires a well-founded methodology that can describe the interactions between the plasma jet and a treated sample and the temporal and spatial changes that result from the treatment. In this study, we developed a large-scale image analysis method to identify the cell-cycle stage and quantify damage to nuclear DNA in single cells. The method was then tested and used to examine spatio-temporal distributions of nuclear DNA damage in two cell lines from the same anatomic location, namely the oral cavity, after treatment with a nitrogen APPJ. One cell line was malignant, and the other, nonmalignant. The results showed that DNA damage in cancer cells was maximized at the plasma jet treatment region, where the APPJ directly contacted the sample, and declined radially outward. As incubation continued, DNA damage in cancer cells decreased slightly over the first 4 h before rapidly decreasing by approximately 60% at 8 h post-treatment. In nonmalignant cells, no damage was observed within 1 h after treatment, but damage was detected 2 h after treatment. Notably, the damage was 5-fold less than that detected in irradiated cancer cells. Moreover, examining damage with respect to the cell cycle showed that S phase cells were more susceptible to DNA damage than either G1 or G2 phase cells. The proposed methodology for large-scale image analysis is not limited to APPJ post-treatment applications and can be utilized to evaluate biological samples affected by any type of radiation, and, more so, the cell-cycle classification can be used on any cell type with any nuclear DNA staining.

scholarly journals Testing biodiversity theory using species richness of reef-building corals across a depth gradient

2019 ◽  
Vol 15 (10) ◽  
pp. 20190493 ◽  
Author(s):  
T. Edward Roberts ◽  
Sally A. Keith ◽  
Carsten Rahbek ◽  
Tom C. L. Bridge ◽  
M. Julian Caley ◽  
...  
Keyword(s):  
Species Richness ◽  
Large Scale ◽  
Coral Species ◽  
Environmental Gradients ◽  
Abiotic Factors ◽  
Empirical Support ◽  
Null Model ◽  
Local Scale ◽  
Small Scale ◽  
Energy Availability

Natural environmental gradients encompass systematic variation in abiotic factors that can be exploited to test competing explanations of biodiversity patterns. The species–energy (SE) hypothesis attempts to explain species richness gradients as a function of energy availability. However, limited empirical support for SE is often attributed to idiosyncratic, local-scale processes distorting the underlying SE relationship. Meanwhile, studies are also often confounded by factors such as sampling biases, dispersal boundaries and unclear definitions of energy availability. Here, we used spatially structured observations of 8460 colonies of photo-symbiotic reef-building corals and a null-model to test whether energy can explain observed coral species richness over depth. Species richness was left-skewed, hump-shaped and unrelated to energy availability. While local-scale processes were evident, their influence on species richness was insufficient to reconcile observations with model predictions. Therefore, energy availability, either in isolation or in combination with local deterministic processes, was unable to explain coral species richness across depth. Our results demonstrate that local-scale processes do not necessarily explain deviations in species richness from theoretical models, and that the use of idiosyncratic small-scale factors to explain large-scale ecological patterns requires the utmost caution.

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