Theory in Biosciences最新文献

The origin of life was a cosmic event happened on primitive Earth. A critical problem to better understand the origins of life in Earth is the search for chemical scenarios on which the basic building blocks of biological molecules could be produced. Classic works in pre-biotic chemistry frequently considered early Earth as an homogeneous atmosphere constituted by chemical elements such as methane (CH₄), ammonia (NH₃), water (H₂O), hydrogen (H₂) and hydrogen sulfide (H₂S). Under that scenario, Stanley Miller was capable to produce amino acids and solved the question about the abiotic origin of proteins. Conversely, the origin of nucleic acids has tricked scientists for decades once nucleotides are complex, though necessary molecules to allow the existence of life. Here we review possible chemical scenarios that allowed not only the formation of nucleotides but also other significant biomolecules. We aim to provide a theoretical solution for the origin of biomolecules at specific sites named "Prebiotic Chemical Refugia." Prebiotic chemical refugium should therefore be understood as a geographic site in prebiotic Earth on which certain chemical elements were accumulated in higher proportion than expected, facilitating the production of basic building blocks for biomolecules. This higher proportion should not be understood as static, but dynamic; once the physicochemical conditions of our planet changed periodically. These different concentration of elements, together with geochemical and astronomical changes along days, synodic months and years provided somewhat periodic changes in temperature, pressure, electromagnetic fields, and conditions of humidity, among other features. Recent and classic works suggesting most likely prebiotic refugia on which the main building blocks for biological molecules might be accumulated are reviewed and discussed.

In this paper, a new mathematical model that describes the dynamics of the within-host COVID-19 epidemic is formulated. We show the stochastic dynamics of Target-Latent-Infected-Virus free within the human body with discrete delay and noise. Positivity and uniqueness of the solutions are established. Our study shows the extinction and persistence of the disease inside the human body through the stability analysis of the disease-free equilibrium [Formula: see text] and the endemic equilibrium [Formula: see text], respectively. Moreover, we show the impact of delay tactics and noise on the extinction of the disease. The most interesting result is even if the deterministic system is inevitably pandemic at a specific point, extinction will become possible in the stochastic version of our model.

We study seasonal mutualistic interactions between two species. The model takes into account the climate-mediated shifts that can change the phenologies of mutualistic species. We show conditions on the parameters of the model that guarantee global stability. Numerical simulations are performed for different scenarios associated with seasonal changes. They show that if periodic time-dependence is used to approximate an almost periodic one, then not only the densities of the mutualistic populations but also the overlapping intervals describing the interval of co-occurrence can be either underestimated or overestimated. Therefore, using an almost periodic model can be more adequate to design conservation strategies for asynchronous phenology.

How did Chinese scientific intellectuals react to the dispute over evolutionary mechanisms during the period of the "eclipse of Darwinism"? This is my focal question. To answer it, I survey the attitudes of three groups of people toward the debate in the early decades of the twentieth century: Chinese paleontologists and their general embrace of the anti-Darwinian position, a group of non-specialists (or semi-specialists) and their assertion of a "revival of Lamarckism," and the American-trained Chinese biologists and their typical agnostic stance toward the antagonism between Darwinism and the mutation theory. Different concerns or motivations underlay these three different stances. There were also interesting attempts by biologists like Chen Zhen to exploit some recreational breeding traditions like goldfish breeding peculiar to China to participate in the dispute more directly.

The thermodynamic principles for system biology are reviewed and formulated, and then basic patterns of flower pigmentation are interpreted. Main thoughts: (1) any biological trait (color or function of a cell) is logically related to a thermodynamic system (or physiological system, signaling network of the cell), (2) the striped, speckled and circle are three basic patterns of flower pigmentation, the development of flowers is an irreversible process, (3) the patterns of flower pigmentation are formed in flower development, (4) the flower cells can change its color in a period of development and this process is controlled thermodynamically, (5) there is giant space of physiology within an organism and within its numerous thermal states can appear under different conditions. In this theory, the dominant inheritance means that a gene contributes great to the thermodynamic stability of a trait related system; different genes can be interacted or integrated thermodynamically according to their contribution to the stability of its related system. By combination of Turing theory and our views, complex patterns of pigmentation could be explained theoretically.

Fifty years ago, the enigmatic Brazilian myxomycete-species Didymium aquatile was described and analyzed with respect to the structure of the plasmodium and its spores. In this study, we compare this rare plasmodial slime mold with another, temporarily aquatic taxon from Europe, Didymium nigripes. Phenotypic plasticity of D. nigripes was investigated under various environmental conditions. Large changes in the morphology of the plasmodia were observed. For species identification, characteristics of the fruiting bodies are key features. However, Didymium aquatile was only characterized by its "abnormal" plasmodia, but no molecular data were available. Here, we analyzed DNA-sequences of 22 species of the genera Didymium and Diderma with a focus on this South American taxon via molecular genetics. A comparison of 18S-rDNA-sequences from D. aquatile and 21 other Didymium (and Diderma)-species indicates that D. aquatile is a reproductively isolated morpho-species. Phenotypic plasticity of D. nigripes is documented with respect to plasmodium morphology and the formation of fruiting bodies, as an example of an adaptation of a terrestrial species to aquatic environments.

What role does nationality-or the image of a nation-play in how one thinks and receives scientific ideas? This paper investigates the commonly held ideas about "German science" and "French science" in early nineteenth-century France. During the politically turbulent time, the seemingly independent scientific community found itself in a difficult position: first, between the cosmopolitan ideals of scientific community and the invasive political reality, and second, between the popularized image of national differences and the actual comparisons of international scientific ideas. The tension between multiple sets of fictions and realities underscores the fragility of the concept of nationality as a scientific measure. A case study comparing morphological ideas, receptions in France, and the actual scientific texts of J. W. von Goethe and A. P. de Candolle further illustrates this fragility. Goethe and Candolle make an ideal comparative case because they were received in very different lights despite their similar concept of the plant type. Our sentence-classification and visualization methods are applied to their scientific texts, to compare the actual compositions and forms of the texts that purportedly represented German and French sciences. This paper concludes that there was a gap between what French readers assumed they read and what they really read, when it came to foreign scientific texts. The differences between Goethe's and Candolle's texts transcended the perceived national differences between German Romanticism and French Classicism.

Breast cancer stem cells (BCSCs) with the ability to self-renew and differentiate have been identified in primary breast cancer tissues and cell lines. The BCSCs are often resistant to traditional radiation and/or chemotherapies. Previous studies have also shown that successful therapy must eradicate cancer stem cells. The purpose of this paper is to develop a mathematical model with self-feedback mechanism to illustrate the issues regarding the difficulties of absolutely eliminating a breast cancer. In addition, we introduce the mechanism of the epithelial-mesenchymal transition (EMT) to investigate the influence of EMT on the effects of breast cancer growth and treatment. Results indicate that the EMT mechanism facilitates the growth of breast cancer and makes breast cancer more difficult to be cured. Therefore, targeting the signals involved in EMT can halt tumor progression in breast cancer. Finally, we apply the experimental data to carry out numerical simulations and validate our theoretical conclusions.

The search for life elsewhere in the universe represents not only a potential expansion of our knowledge regarding life, but also a clarification of the first principles applicable to terrestrial life, which thus restrict the very search for extra-terrestrial life. Although there are no exact figures for how many species have existed throughout Earth's total history, we can still make inferences about how the distribution of this life has proceeded through a bell curve. This graph shows the totality of life, from its origin to its end. The system enclosing life contains a number of first principles designated the walls of minimal complexity and adaptive possibility, the fence of adaptation, and right-skewed extension. In this discussion of life, a framework will be formulated that, based on the dynamic relationship between mesophiles and extremophiles, will be imposed on exoworlds in order to utilize the graph's predictive power to analyze how extra-terrestrial life could unfold. In this framework the evolutionary variation does not depend on the specific biochemistry involved. Once life is 'up and running,' the various biochemical systems that can constitute terrestrial and extra-terrestrial life will have secondary significance. The extremophilic tail represents a range expansion in which all habitat possibilities are tested and occupied. This tail moves to the right not because of the biochemistry constitutions of organisms, but because it can do nothing else. Thus, it can be predicted that graphs of terrestrial and extra-terrestrial life will be similar overall. A number of other predictions can be made; for example, for worlds in which the atmospheric disequilibrium is approaching equilibrium, it is predicted that life may still be present because the extremophilic range expansion is stretched increasingly farther to the right. Because life necessarily arises at a left wall of minimal complexity, it is predicted that any origin of cellular life will have a close structural resemblance to that of the first terrestrial life. Thus, in principle, life may have originated more than once on Earth, and still exist. It is also predicted that there may be an entire subset of life existing among other domains that we do not see because, in an abstract sense, we are inside the graph. If we view the graph in its entirety, this subset appears very much like a vast supra-domain of life.