Experimental Studies on the Epidemiology of the Host-Parasite System Hydra and Hydramoeba hydroxena (entz). I. The Effect of the Parasite on the Individual Host

1962 ◽  
Vol 35 (2) ◽  
pp. 166-178 ◽  
Author(s):  
Alan E. Stiven
2019 ◽  
Author(s):  
Abdou Moutalab Fofana ◽  
Amy Hurford

AbstractMany parasites induce decreased host movement, known as lethargy, which can impact disease spread and the evolution of virulence. Mathematical models have investigated virulence evolution when parasites cause host death, but disease-induced decreased host movement has received relatively less attention. Here, we consider a model where, due to the within-host parasite replication rate, an infected host can become lethargic and shift from a moving to a resting state, where it can die. We find that when the lethargy and disease-induced mortality costs to the parasites are not high, then evolutionary bistability can arise, and either moderate or high virulence can evolve depending on the initial virulence and the magnitude of mutation. These results suggest, firstly, the transient coexistence of strains with different virulence, which may explain the coexistence of low- and high-pathogenic strains of avian influenza and human immunodeficiency viruses, and secondly, that medical interventions to treat the symptoms of lethargy or prevent disease-induced host deaths can result in a large jump in virulence and the rapid evolution of high virulence. In complement to existing results that show bistability when hosts are heterogeneous at the population-level, we show that evolutionary bistability may arise due to transmission heterogeneity at the individual host-level.


2021 ◽  
Vol 17 (1) ◽  
Author(s):  
Natalia Szeligowska ◽  
Paulina Cholewińska ◽  
Katarzyna Czyż ◽  
Konrad Wojnarowski ◽  
Marzena Janczak

Abstract Background The microbiome of the digestive tract of ruminants contains microbial ecosystem that is affected by both environmental and genetic factors. The subject of this study concerns the influence of selected genetic factors, such as species of animals and “host” individual differences on the digestive tract microbiome composition. The results show the core microbiological composition (Firmicutes and Bacteroidetes) of ruminants digestive tract (based on feces) depending on breed and “host”. The Bacteroidetes and Firmicutes phyla are the most abundant in ruminants digestive tract. The aim of the study was to determine the differences prevalence level of Bacteroidetes and Firmicutes phyla in feces of Charolaise cattle and Polish Olkuska Sheep with respect to intra- and inter-species variability. Results The research group in the experiment consisted of animals at the age of 3 months kept in the same environmental conditions – rams of Polish Olkuska Sheep (n = 10) and Charolaise bulls (n = 10). Feces were collected individually from each animal (animals without disease symptoms were selected), living on the same environmental conditions. The analysis of the results in terms of species showed differences in the Firmicutes phylum level and Lactobacillaceae family between rams and bulls. Subsequently, the analysis performed for the “host effect” showed differentiation in the levels of the Bacteroidetes and Firmicutes phyla between individuals in a group and also between the groups. Conclusion The obtained results suggest that, apart from the diet and the environment, the species and the individual host are equally important factors influencing the microbiological composition of the digestive system of ruminants.


1984 ◽  
Vol 4 (2) ◽  
pp. 241-249 ◽  
Author(s):  
Albert Gjedde ◽  
Ove Christensen

Tracer studies on facilitated diffusion across the blood–brain barrier lead to the calculation of Michaelis-Menten constants that describe the rate of transport. However, the barrier consists of two endothelial cell membranes, and the relevance of single Michaelis-Menten constants in relation to the two cell membranes is unknown. We have formulated a model of two endothelial cell membranes and show that the measured Michaelis-Menten constants are simple functions of the properties of the individual membranes when transport across the endothelium is rapid ( P1 > 10−6 cm s−1). We also show that the Michaelis-Menten constants determined in tracer experiments describe facilitated diffusion in the steady state only if the two membranes have similar transport properties. As an application of this observation, we have examined three experimental studies that measure glucose transport in the steady state and show that the Michaelis-Menten constants for glucose transport calculated from the tracer experiments are equal to the constants calculated from the steady-state experiments. We conclude that the luminal and abluminal membranes of brain capillary endothelial cells have equal glucose transport properties.


2020 ◽  
Author(s):  
Umer Chaudhry ◽  
Qasim Ali ◽  
Lynn Zheng ◽  
Imran Rashid ◽  
Muhammad Zubair Shabbir ◽  
...  

AbstractThe present study was designed to improve understanding of Theileria annulata in sympatric water buffalo and cattle in the Punjab province of Pakistan. The prevalence of tropical theileriosis is high, buparvaquone resistance is widespread, and vaccine protection is poor in the field. Better understanding is, therefore, needed of the factors that influence the genetics of T. annulata populations both within its hosts and in its overall populations. Here we utilise a panel of six satellites and a mitochondrial cytochrome b marker to explore the multiplicity of T. annulata infection and patterns of emergence and spread of different parasite genotypes. Parasite materials were collected from infected animals in defined regions, where water buffalo and cattle are kept together. Our results show that T. annulata is genetically more diverse in cattle- than in water buffalo-derived populations (the mean numbers of unique satellite alleles were 13.3 and 1.8 and numbers of unique cytochrome b locus alleles were 65 and 27 in cattle- and water buffalo-derived populations, respectively). The data show a high level of genetic diversity among the individual host-derived populations (the overall heterozygosity (He) indices were 0.912 and 0.931 in cattle, and 0.874 and 0.861 in buffalo, based on satellite and cytochrome b loci, respectively). When considered in the context of high parasite transmission rates and frequent animal movements between different regions, the predominance of multiple T. annulata genotypes, with multiple introductions of infection in the hosts from which the parasite populations were derived, may have practical implications for the spread of parasite genetic adaptations; such as those conferring vaccine cross-protection against different strains affecting cattle and buffalo, or resistance to antiprotozoal drugs.


2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Tao Yin ◽  
Peihong Ma ◽  
Zilei Tian ◽  
Kunnan Xie ◽  
Zhaoxuan He ◽  
...  

The effects of acupuncture facilitating neural plasticity for treating diseases have been identified by clinical and experimental studies. In the last two decades, the application of neuroimaging techniques in acupuncture research provided visualized evidence for acupuncture promoting neuroplasticity. Recently, the integration of machine learning (ML) and neuroimaging techniques becomes a focus in neuroscience and brings a new and promising approach to understand the facilitation of acupuncture on neuroplasticity at the individual level. This review is aimed at providing an overview of this rapidly growing field by introducing the commonly used ML algorithms in neuroimaging studies briefly and analyzing the characteristics of the acupuncture studies based on ML and neuroimaging, so as to provide references for future research.


Author(s):  
Andrew Kerner

The term ownership society is commonly used to describe a suite of policies promoted during the second George W. Bush administration that sought, among other things, to increase popular ownership of housing and financial assets. The ownership society was always in large part an attempt at social engineering. That attempt rests on two premises: first, that asset ownership pushes individuals’ politics to the right; and second, that governments can engineer a more right-leaning populace by promoting asset ownership. While the term was novel, the ideas were not. Bush’s ownership society bore more than a striking resemblance to Thatcher’s “enterprise society,” for example, and similar ideas percolated in some quarters of Latin American neoliberalism of the 1980s and 1990s. But foreign referents are in this case not necessary; the ownership society was in large part an expansion of a preexisting American tradition of promoting private ownership explicitly for its capacity to transform the owner’s politics. Despite its consistent appeal to right-of-center governments, political science has not come to any tidy conclusions about whether the ownership society exists or, if it does exist, how it works and how it interacts with financial and housing markets. Turmoil in those markets over the past 10 years, and the accompanying political fallout, underline the need to consolidate what we know about the ownership society and to set a course for theoretical and empirical development. Two themes in the literature are particularly noteworthy as it moves forward. First, there is a substantial contrast between “static” and “dynamic” theories of ownership society politics. Static theories argue that the fact of asset ownership per se affects the owner’s politics; dynamic theories look more toward movements in asset markets, arguing that asset ownership’s political effects vary according to the financial consequences of that ownership on the individual. While the latter appears to better fit the empirical evidence, the relevant scope conditions—when should we expect a dynamic theory to obtain, and where should we expect a static theory to obtain—remain unclear. Second, the empirical study of the ownership society is made difficult by the fact that asset ownership is virtually never randomly assigned, and the political antecedents of asset ownership are difficult to convincingly control for using observational data. In lieu of a perfect research design, better communication between observational and experimental studies can help move the literature forward.


2018 ◽  
Vol 23 (1) ◽  
Author(s):  
Isabel Araya-Muñoz ◽  
Matilde Fonseca-Argüello ◽  
Jilma Majano-Benavides ◽  
María Eugenia Ugalde-Villalobos

This article presents the results of the exploratory pre-experimental evaluation process of design and didactic development of three subjects using the semi-distance learning model or blended learning, through a pilot application plan in bachelor’s degrees of the Faculty of Social Sciences at the Universidad Nacional de Costa Rica. First, the blended learning model was applied. Later, scientific information was collected through a survey of students, a panel discussion with teachers, and an analysis of the contents of the study programs. The results show that the interaction between students and teachers increases through their favorite activities such as forums and tasks, which strengthen the individual and collaborative work and the reflective analysis, aspects that favor building learnings. Various lines of research arise from this study; they are necessary to go in depth, specifically, in quasi-experimental studies. Some of these lines are the following: to show the assumptions of the blended learning and educational factors that favor the development of meaningful learning for the student; to determine what the cognitive processes, carried out in mixed learning environments, are; and to test the positive relationship between the student’s academic performance and the semi-distance didactics.


2017 ◽  
Vol 62 (4) ◽  
pp. 2081-2087 ◽  
Author(s):  
T. Pała ◽  
I. Dzioba

Abstract The paper presents the results of two butt welded joints by conventional method. The welding process was performed using a variety of linear welding energy. The studies included experimental and computational part. In experimental studies determined the distribution of hardness and mechanical properties of the individual analyzed sections of welded joints. The data obtained were intended to determine the extent of zones in the welded joints that have certain strength characteristics. Also conducted uniaxial tensile tests of welded joints with the registration of displacement fields on the surface of specimens by means of Aramis video-system what the final result are images of strain fields map on the surface of welded joints. The resulting strain values were compared with the results of numerical computations FEM.


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