Giant cells: multiple cells unite to survive

Multinucleated Giant Cells (MGCs) are specialized cells that develop from the fusion of multiple cells, and their presence is commonly observed in human cells during various infections. However, MGC formation is not restricted to infections alone but can also occur through different mechanisms, such as endoreplication and abortive cell cycle. These processes lead to the formation of polyploid cells, eventually resulting in the formation of MGCs. In Entamoeba, a protozoan parasite that causes amoebic dysentery and liver abscesses in humans, the formation of MGCs is a unique phenomenon and not been reported in any other protozoa. This organism is exposed to various hostile environmental conditions, including changes in temperature, pH, and nutrient availability, which can lead to stress and damage to its cells. The formation of MGCs in Entamoeba is thought to be a survival strategy to cope with these adverse conditions. This organism forms MGCs through cell aggregation and fusion in response to osmotic and heat stress. The MGCs in Entamoeba are thought to have increased resistance to various stresses and can survive longer than normal cells under adverse conditions. This increased survival could be due to the presence of multiple nuclei, which could provide redundancy in case of DNA damage or mutations. Additionally, MGCs may play a role in the virulence of Entamoeba as they are found in the inflammatory foci of amoebic liver abscesses and other infections caused by Entamoeba. The presence of MGCs in these infections suggests that they may contribute to the pathogenesis of the disease. Overall, this article offers valuable insights into the intriguing phenomenon of MGC formation in Entamoeba. By unraveling the mechanisms behind this process and examining its implications, researchers can gain a deeper understanding of the complex biology of Entamoeba and potentially identify new targets for therapeutic interventions. The study of MGCs in Entamoeba serves as a gateway to exploring the broader field of cell fusion in various organisms, providing a foundation for future investigations into related cellular processes and their significance in health and disease

Spatiotemporal pattern formation in a prey–predator model with generalist predator

Generalist predators exploit multiple food sources and it is economical for them to reduce predation pressure on a particular prey species when their density level becomes comparatively less. As a result, a prey-predator system tends to become more stable in the presence of a generalist predator. In this article, we investigate the roles of both the diffusion and nonlocal prey consumption in shaping the population distributions for interacting generalist predator and its focal prey species. In this regard, we first derive the conditions associated with Turing instability through linear analysis. Then, we perform a weakly nonlinear analysis and derive a cubic Stuart-Landau equation governing amplitude of the resulting patterns near Turing bifurcation boundary. Further, we present a wide variety of numerical simulations to corroborate our analytical findings as well as to illustrate some other complex spatiotemporal dynamics. Interestingly, our study reveals the existence of traveling wave solutions connecting two spatially homogeneous coexistence steady states in Turing domain under the influence of temporal bistability phenomenon. Also, our investigation shows that nonlocal prey consumption acts as a stabilizing force for the system dynamics

Dynamics of a Diffusive Two-Prey-One-Predator Model with Nonlocal Intra-Specific Competition for Both the Prey Species

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Pattern Formation in a Three-Species Cyclic Competition Model

International audienceIn nature, different species compete among themselves for common resources and favorable habitat. Therefore, it becomes really important to determine the key factors in maintaining the biodiversity. Also, some competing species follow cyclic competition in real world where the competitive dominance is characterized by a cyclic ordering. In this paper, we study the formation of a wide variety of spatiotemporal patterns including stationary, periodic, quasi-periodic and chaotic population distributions for a diffusive Lotka-Volterra type three-species cyclic competition model with two different types of cyclic ordering. For both types of cyclic ordering, the temporal dynamics of the corresponding non-spatial system show the extinction of two species through global bifurcations such as homoclinic and heteroclinic bifurcations. For the spatial system, we show that the existence of Turing patterns is possible for a particular cyclic ordering, while it is not the case for the other cyclic ordering through both the analytical and numerical methods. Further, we illustrate an interesting scenario of short-range invasion as opposed to the usual invasion phenomenon over the entire habitat. Also, our study reveals that both the stationary and dynamic population distributions can coexist in different parts of a habitat. Finally, we extend the spatial system by incorporating nonlocal intra-specific competition terms for all the three competing species. Our study shows that the introduction of nonlocality in intra-specific competitions stabilizes the system dynamics by transforming a dynamic population distribution to stationary. Surprisingly, this nonlocality-induced stationary pattern formation leads to the extinction of one species and hence, gives rise to the loss of biodiversity for intermediate ranges of nonlocality. However, the biodiversity can be restored for sufficiently large extent of nonlocality

Electronic spectrum of GeTe : An <i>ab initio</i> based configuration interaction study

163-172Low-lying electronic states of GeTe within 40 000 cm-1 of energy have been studied by using ab initio based configuration interaction calculations which include relativistic effective core potentials (RECP) of Ge and Te atoms. We have computed potential energy curves of 18Λ-S states which correlate with the Ge(3Pg)+ Te(3Pg) dissociation limit. In addition, curves of two highly excited 31Σ+ and 31 II states are also computed. There are 12 bound states of the Λ-S symmetry below 40 000 cm-1. Spectroscopic constants of these Λ-S states are reported and compared with the available experimental data. The ground state of GeTe is designated as X1Σ+ which is dominated by at least two equally important configurations. The calculated rc and ωc values of X1Σ+ are 2.395 Å and 298 cm-1, respectively. The ground-state dissociation energy of GeTe is 3.67 eV as compared with the experimental value of 4.1 ± 0.4 eV. The calculated transition energy of the A1II-X1Σ+  transition is found to be 26 860 cm-1 which is somewhat smaller than the experimental value of 27 751 cm-1. The 21Σ+ state is tentatively assigned as the E state which is observed in the E←X absorption. Potential energy curves of all 50 Ω states arising from the spin-orbit interactions amung 18 Λ-S states are also computed. We have reported 17 Ω states which are bound below 30 000 cm-1 of energy. The 3II2-3II0+ splitting is estimated to be about 2200 cm-1. The compositions of the spinorbit CI wavefunctions of all bound Ω states at rc are calculated. Transition probabilities of several dipole-allowed transitions are calculated from CI energies and wavefunctions. The A1II-X1Σ+  transition is found to be strong. In presence of the spin-orbit coupling, A1II1-X1Σ+0+   and 3II0+-X1Σ+0+  transitions are most probable. Radiative lifetimes of the upper states A1II1 and 3II0+ at the lowest vibrational level are estimated

On the structural sensitivity of some diffusion–reaction models of population dynamics

In mathematical ecology, it is often assumed that properties of a mathematical model are robust to specific parameterization of functional responses, in particular preserving the bifurcation structure of the system, as long as different functions are qualitatively similar. This intuitive assumption has been challenged recently (Fussmann & Blasius, 2005). Having considered the prey–predator system as a paradigm of nonlinear population dynamics, it has been shown that in fact both the bifurcation structure and the structure of the phase space can be rather different even when the component functions are apparently close to each other. However, these observations have so far been largely limited to nonspatial systems described by ODEs. In this paper, our main interest is to investigate whether such structural sensitivity occurs in spatially explicit models of population dynamics, in particular those that are described by PDEs. We consider a prey–predator model described by a system of two nonlinear reaction–diffusion–advection equations where the predation term is parameterized by three different yet numerically close functions. Using some analytical tools along with numerical simulations, we show that the properties of spatiotemporal dynamics are rather different between the three cases, so that patterns observed for one parameterization may not occur for the other two ones.</p