scholarly journals Modelling Functional Shifts in Two-Species Hypercycles

Mathematics ◽  
2021 ◽  
Vol 9 (15) ◽  
pp. 1809
Author(s):  
Bernat Bassols ◽  
Ernest Fontich ◽  
Daniel Oro ◽  
David Alonso ◽  
Josep Sardanyés

Research on hypercycles focuses on cooperative interactions among replicating species, including the emergence of catalytic parasites and catalytic shortcircuits. Further interactions may be expected to arise in cooperative systems. For instance, molecular replicators are subject to mutational processes and ecological species to behavioural shifts due to environmental and ecological changes. Such changes could involve switches from cooperative to antagonistic interactions, in what we call a functional shift. In this article, we investigate a model for a two-member hypercycle model, considering that one species performs a functional shift. First, we introduce the model dynamics without functional shifts to illustrate the dynamics only considering obligate and facultative cooperation. Then, two more cases maintaining cross-catalysis are considered: (i) a model describing the dynamics of ribozymes where a fraction of the population of one replicator degrades the other molecular species while the other fraction still receives catalytic aid; and (ii) a system in which a given fraction of the population predates on the cooperating species while the rest of the population still receives aid. We have characterised the key bifurcation parameters determining extinction, survival, and coexistence of species. We show that predation, regardless of the fraction that benefits from it, does not significantly change dynamics with respect to the degradative case (i), thus conserving dynamics and bifurcations. Their biological significance is interpreted, and their potential implications for the dynamics of early replicators and ecological species are outlined.

2015 ◽  
Vol 19 (7) ◽  
pp. 364-365 ◽  
Author(s):  
Alan G. Sanfey ◽  
Claudia Civai ◽  
Peter Vavra

2019 ◽  
Author(s):  
Huifang Guo ◽  
Na Wang ◽  
Hongtao Niu ◽  
Dongxiao Zhao ◽  
Zhichun Zhang

Abstract Background Co-infection of endosymbionts in the same host is ubiquitous, and the interactions of the most common symbiont Wolbachia with other symbionts, including Spiroplasma et al., in invertebrate organisms have received increasing attention. However, the interactions between Wolbachia and Arsenophonus, another widely distributed symbiont in nature, are poorly understood. We tested the co-infection of Wolbachia and Arsenophonus in different populations of Nilaparvata lugens and investigated whether co-infection affected the population size of the symbionts in their host. Results A significant difference was observed in the co-infection incidence of Wolbachia and Arsenophonus among 5 populations of N. lugens from China, with nearly half of the individuals in the Zhenjiang population harbouring the two symbionts simultaneously, and the rate of occurrence was significantly higher than that of the other 4 populations. The Arsenophonus density in the superinfection line was significantly higher only in the Maanshan population compared with that of the single-infection line. Differences in the density of Wolbachia and Arsenophonus were found in all the tested double-infection lines, and the dominant symbiont species varied with the population only in the Nanjing population, with Arsenophonus the overall dominant symbiont. Conclusions Wolbachia and Arsenophonus could coexist in N. lugens, and the co-infection incidence varied with the geographic populations. Antagonistic interactions were not observed between Arsenophonus and Wolbachia, and the latter was the dominant symbiont in most populations.


1979 ◽  
Vol 65 (6) ◽  
pp. 677-686 ◽  
Author(s):  
Maria Cristina Cella ◽  
Gabriella Fibbi ◽  
Cristina Cantini ◽  
Zita Del Panta ◽  
Simonetta Vannucchi ◽  
...  

Intercellular glycosaminoglycans (GAGs) from various tissues were analyzed by cellulose acetate electrophoresis and enzymatic treatment with specific mucopolysaccharidases. Each tissue exhibits a particular composition of sulfated and unsulfated molecular species. Invariably, malignant human neoplasias and their metastases show striking variations in the electrophoretic pattern typical of the corresponding normal tissue. An absolute or relative increase in surface ChS A/C and HA seems to be a consistent feature of neoplastic transformation. On the other hand, the GAGs composition of benign noninfiltrative tumors does not vary greatly with respect to the original normal tissue.


1937 ◽  
Vol 65 (3) ◽  
pp. 393-414 ◽  
Author(s):  
Michael Heidelberger ◽  
Kai O. Pedersen

1. Highly purified rabbit Type III pneumococcus anticarbohydrate proved to be homogeneous in the ultracentrifuge and its sedimentation constant, 7.0·10–13, did not differ from that of the principal component of normal rabbit globulin or of immune rabbit globulin containing up to 50 per cent of anti-egg albumin. The molecular weight of antibody in the rabbit is therefore probably very close to that of the principal normal globulin component, namely, 150,000. 2. Highly purified horse Type I pneumococcus anticarbohydrate, on the other hand, was only homogeneous in the ultracentrifuge when prepared from sera stored without preservative. Its sedimentation constant, 18.4·10–13, coincided with that of the principal globulin component in most of the Felton solutions and purified antibody solutions studied. The molecular weight of pneumococcus anticarbohydrate in the horse is probably three to four times that of the principal normal globulin component. 3. The significance of the differences between pneumococcus anticarbohydrate formed in the rabbit and in the horse is discussed. 4. Results are given of ultracentrifuge studies on the molecular species in solutions of egg albumin-anti-egg albumin specific precipitates dissolved in excess egg albumin. The implications of the results are discussed.


1985 ◽  
Vol 119 (1) ◽  
pp. 103-114
Author(s):  
H.-O. NALBACH ◽  
P. THIER ◽  
D. VARJÚ

1. The movements of both distal eye stalks in the horizontal plane, elicited by optokinetic stimuli, have been recorded simultaneously. 2. A panorama was split into two separate halves and was either oscillated around the animal in a sinusoidal fashion or displaced in a stepwise manner. Both eyes could be stimulated independently. 3. The stimuli on both sides differed either (a) in the illumination, or (b) in the total amount of light impinging upon the eyes or (c) in the relative phase of the sinusoidal stimuli to either eye. 4. As the illumination decreases the optokinetic response weakens. 5. If one eye has no or only weak optokinetic input, it will be driven by the other eye. The response mediated by the contralateral optokinetic stimulus diminishes if the amount of light impinging upon the driven eye is increased. 6. There is a logarithmic relationship between the response of the driving eye and that of the driven eye. 7. The possible biological significance of these relationships is seen in the enhanced coupling at low light intensities. 8. The variable strength of coupling and possible roles of movable eyes are discussed.


2020 ◽  
Vol 3 (3) ◽  
pp. 276-296 ◽  
Author(s):  
Dun-Xian Tan ◽  
Rüdiger Hardeland

Increased evidence implies that melatonin may be a promising molecule for combating COVID-19 due to its potent antioxidative, anti-inflammatory and immunoregulatory capacities. A frequently asked question concerns the suitable dosage of melatonin for deadly virus infections including COVID-19 patients. The golden standards for a suitable dosage of medicine are safety and effectiveness. By reviewing the pharmacokinetics as well as animal studies and clinical trials of melatonin in the deadly viral infections and sepsis, we estimate that a dose of 8 mg/kg/day of melatonin is suitable for COVID-19 patients, especially for the severe cases. To maintain an elevated melatonin serum level lasting longer and smoother, this daily dose can be divided into 5 sub-doses with the initial dose of doubling over the other sub-doses. The recommended dose is in the ranges used to treat septic patients clinically and is devoid of any adverse effect; thus, it is safe. This dose is calculated from an effective dose which significantly reduces the mortality of virus-infected mice and is, therefore, assumed to be effective for COVID-19 severe patients. In our opinion, a dose or a medicine which can only improve the symptoms of mild or moderately severe patients of COVID-19 lack biological significance since virus infection is a self-limited disease and most of the patients with mild or moderate symptoms will recover by themselves whether treated or not. A meaningful treatment is to target the severe patients and significantly reduce the resulting mortality. The suggested melatonin dose is, thus, mainly recommended for the severe COVID-19 patients. The possibility of using suppositories for the delivery of highly dosed melatonin is also addressed, since long-term experience with this treatment is available for another disease. 


1969 ◽  
Vol 173 (1032) ◽  
pp. 407-410 ◽  

I shall first try to illustrate the close integration of the fibrinolytic system with other proteolytic processes in blood, by recalling some of the efforts to segregate it from the intrinsic plasma kinin forming system. Attempts at clear chemical distinction between plasmin and the specific kininogenases were complicated by two factors: (1) the activities associated with plasmin resided possibly in more than one molecular species (Markus & Ambrus 1960); (2) plasma kininogenases were distinguished from plasmin only by minor quantitative or by negative criteria. The kininogenases act only on natural or synthetic substrates which are attacked by plasmin as well. The active centre of plasma kininogenase differs from that of plasmin mainly by the substrates which it does not attack. Its constitution is probably very similar to the centres of plasmin, thrombin, trypsin and chymotrypsin. Clearer differences appeared when the activation of the pre-active enzymes in human plasma was considered (Eisen 1963). Figure 1 shows that streptokinase levels activating all plasminogen in human plasma induced much smaller kinin formation than did glass powder. Yet, when clotted, the first plasma lysed in a few seconds, and the other in more than 24 hours. Similarly, the small kinin formation resulting from the complete activation by streptokinase, was greatly enhanced when activation by glass or kaolin was superimposed in the same plasma sample.


1981 ◽  
Vol 97 (2) ◽  
pp. 166-175 ◽  
Author(s):  
F. Strollo ◽  
J. Harlin ◽  
H. Hernandez-Montes ◽  
D. M. Robertson ◽  
A. A. Zaidi ◽  
...  

Abstract. A single bolus of 100 μg of gonadoliberin (LRH) was administered intravenously to 8 post-menopausal and 9 normally menstruating women and blood was withdrawn before and 30, 60, 120 and 240 min after LRH stimulation. The plasma samples obtained at different time intervals from women showing a sufficiently high response to LRH (menopausal: 8, menstruating: 3) were combined and 2 ml samples of each pool were fractionated in triplicate by electrofocusing on sucrose density gradient. In addition, two plasma pools, obtained 30 min following LRH stimulation, one from 4 normally menstruating women (exhibiting a relatively low LH-response) and the other from 2 normally menstruating women aged 40, were analyzed in the same way in duplicate electrofocusing experiments. The hLH activity was determined in each electrofocusing fraction by an in vitro bioassay method following elution and purification by gel filtration. The LH activity was distributed as four major peaks at pI values of 7.10 ± 0.05, 7.58 ± 0.06, 8.10 ± 0.04 and 8.54 ± 0.05 and a broad area of activity comprising a number of peaks in the pH range of 8.69–9.50. The analysis of the data revealed marked differences in the relative distribution of the various molecular species present in the blood of menopausal women and of normally menstruating women. A molecular species exhibiting a pI value of 7.10 was invariably present (10 – 15% of the total) in all samples of post-menopausal plasma (PMP) but was consistently absent from all samples of midcycle plasma (MCP). The amount of relatively 'less alkaline' material (eluted from pH range 7.37–8.32) was significantly higher (P < 0.001) in the PMP samples compared to MCP samples. On the other hand, in the MCP samples the amount of relatively 'more alkaline' material eluted from the pH range 8.33–9.50 was significantly (P < 0.001) higher (about 60% of the total recovered activity) compared to the PMP samples (about 30% of the total). Following LRH stimulation significant temporal changes were observed in the relative contribution of various molecular species to the hLH profile. A gradual increase, up to 60 min, in the material eluted in the pH range 6.87–7.36 in the post-menopausal plasma samples was accompanied by a gradual decrease in the material eluted in the pH range 7.84–8.32. Two hours after LRH stimulation a significant drop was found in the material collected from pH range 8.33–8.68, with a concomitant rise in the material eluted in the pH range 8.69–9.50. This last mentioned shift was also observed in the plasma of normally menstruating women. It is concluded that major differences exist in the composition of biologically active hLH species present in the peripheral blood of post-menopausal and normally menstruating women. Moreover, significant temporal changes occur in the composition of circulating hLH species following stimulation by LRH both in post-menopausal and in normally menstruating women.


2009 ◽  
Vol 2009 ◽  
pp. 1-13 ◽  
Author(s):  
Sabata Martino ◽  
Ilaria di Girolamo ◽  
Antonio Orlacchio ◽  
Alessandro Datti ◽  
Aldo Orlacchio

MicroRNAs (miRNAs) have rapidly emerged as biologically important mediators of posttranscriptional and epigenetic regulation in both plants and animals. miRNAs function through a variety of mechanisms including mRNA degradation and translational repression; additionally, miRNAs may guide gene expression by serving as transcription factors. miRNAs are highly expressed in human brain. Tissue and cell type-specific enrichments of certain miRNAs within the nervous system argue for a biological significance during neurodevelopmental stages. On the other hand, a large number of studies have reported links between alterations of miRNA homeostasis and pathologic conditions such as cancer, heart diseases, and neurodegeneration. Thus, profiles of distinct or aberrant miRNA signatures have most recently surged as one of the most fascinating interests in current biology. Here, the most recent insights into the involvement of miRNAs in the biology of the nervous system and the occurrence of neuropathological disorders are reviewed and discussed.


2018 ◽  
Author(s):  
Shota Shibasaki

AbstractMutualistic interspecific interactions, including Müllerian mimicry and division of labor, are common in nature. In contrast to antagonistic interactions, where faster evolution is favored, mutualism can favor slower evolution under some conditions. This is called the Red King effect. After Bergstrom and Lachmann (2003) proposed Red King effect, it has been investigated in two species models. However, biological examples suggest that the mutualisms can include three or more species. Here, I modeled the evolutionary dynamics of mutualism in communities where there exist two or more species, and all species mutually interact with one another. Regardless of the number of species in the community, it is possible to derive conditions for the stable equilibria. Although there exist nonlinear relationship between the evolutionary rates and the evolutionary fate of each species in the multi-species communities, the model suggests that it is possible to predict whether the faster evolution is favored or disfavored for the relatively fast species; on the other hand, it is difficult to predict the evolutionary fate of relatively slow species because the evolutionary dynamics of the slow species is affected by the evolutionary fate of the fast species.


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