scholarly journals Myelin sheath and cyanobacterial thylakoids as concentric multilamellar structures with similar bioenergetic properties

Open Biology ◽  
2021 ◽  
Vol 11 (12) ◽  
Author(s):  
Alessandro Maria Morelli ◽  
Mariachiara Chiantore ◽  
Silvia Ravera ◽  
Felix Scholkmann ◽  
Isabella Panfoli
Keyword(s):  
Nervous System ◽  
Atp Synthase ◽  
Myelin Sheath ◽  
Convergent Evolution ◽  
Molecular Structures ◽  
Morphological Similarity ◽  
Photosystems I And Ii ◽  
Evolution Of Life ◽  
Life On Earth ◽  
Trophic Role

There is a surprisingly high morphological similarity between multilamellar concentric thylakoids in cyanobacteria and the myelin sheath that wraps the nerve axons. Thylakoids are multilamellar structures, which express photosystems I and II, cytochromes and ATP synthase necessary for the light-dependent reaction of photosynthesis. Myelin is a multilamellar structure that surrounds many axons in the nervous system and has long been believed to act simply as an insulator. However, it has been shown that myelin has a trophic role, conveying nutrients to the axons and producing ATP through oxidative phosphorylation. Therefore, it is tempting to presume that both membranous structures, although distant in the evolution tree, share not only a morphological but also a functional similarity, acting in feeding ATP synthesized by the ATP synthase to the centre of the multilamellar structure. Therefore, both molecular structures may represent a convergent evolution of life on Earth to fulfill fundamentally similar functions.

The Quickening of Chemistry

2017 ◽  
Author(s):  
John L. Culliney ◽  
David Jones
Keyword(s):  
Living Cells ◽  
Molecular Structures ◽  
Complex Molecules ◽  
Competition And Cooperation ◽  
Creation Science ◽  
Dna And Rna ◽  
Evolution Of Life ◽  
Biochemical Research ◽  
Life On Earth ◽  
The Universe

For billions of years, competition and cooperation (or attractive forces) oscillated in influence in the evolution of the universe. Consistently, the latter prevailed with a slight edge in that affinitive entities in the universe were free to associate, bond, assemble, facilitate, and cooperate, rise above the leveling action of competition, and generate emergence on progressively higher levels: chemical, biological, and social. This chapter returns to cooperation and examines its constructive power in what might be termed ascendant chemistry—the self-organization of molecules and catalysis that led through pathways of burgeoning complexity to the threshold of biology and the evolution of life on earth. Against the illogic of “creation science,” modern biochemical research illuminates how life arose as an assemblage of complex molecules with strong cooperative tendencies within and among themselves. Carbon’s capacity to build with itself and other elements tremendously variable molecular structures with interlocking functions—most notably of the four basic complex chemicals of life: proteins, carbohydrates, lipids, and nucleic acids (DNA and RNA)—ultimately led to the evolution of living cells.

scholarly journals Is free-energy minimisation the mark of the cognitive?

2021 ◽  
Vol 36 (2) ◽  
Author(s):  
Julian Kiverstein ◽  
Matt Sims
Keyword(s):  
Nervous System ◽  
Free Energy ◽  
Problem Solving ◽  
Living Systems ◽  
Energy Principle ◽  
Free Energy Principle ◽  
Energy Minimisation ◽  
Long Run ◽  
Evolution Of Life ◽  
Mark Of The Cognitive

AbstractA mark of the cognitive should allow us to specify theoretical principles for demarcating cognitive from non-cognitive causes of behaviour in organisms. Specific criteria are required to settle the question of when in the evolution of life cognition first emerged. An answer to this question should however avoid two pitfalls. It should avoid overintellectualising the minds of other organisms, ascribing to them cognitive capacities for which they have no need given the lives they lead within the niches they inhabit. But equally it should do justice to the remarkable flexibility and adaptiveness that can be observed in the behaviour of microorganisms that do not have a nervous system. We should resist seeking non-cognitive explanations of behaviour simply because an organism fails to exhibit human-like feats of thinking, reasoning and problem-solving. We will show how Karl Friston’s Free-Energy Principle (FEP) can serve as the basis for a mark of the cognitive that avoids the twin pitfalls of overintellectualising or underestimating the cognitive achievements of evolutionarily primitive organisms. The FEP purports to describe principles of organisation that any organism must instantiate if it is to remain well-adapted to its environment. Living systems from plants and microorganisms all the way up to humans act in ways that tend in the long run to minimise free energy. If the FEP provides a mark of the cognitive, as we will argue it does, it mandates that cognition should indeed be ascribed to plants, microorganisms and other organisms that lack a nervous system.

Mineral photoelectrons and their implications for the origin and early evolution of life on Earth

2014 ◽  
Vol 57 (5) ◽  
pp. 897-902 ◽  
Author(s):  
AnHuai Lu ◽  
Xin Wang ◽  
Yan Li ◽  
HongRui Ding ◽  
ChangQiu Wang ◽  
...  
Keyword(s):  
Early Evolution ◽  
Evolution Of Life ◽  
Life On Earth

scholarly journals New Evo-SETI results about civilizations and molecular clock

2016 ◽  
Vol 16 (1) ◽  
pp. 40-59 ◽  
Author(s):  
Claudio Maccone
Keyword(s):  
Probability Density ◽  
Molecular Clock ◽  
Modern Human ◽  
Peak Time ◽  
List Type ◽  
Type Number ◽  
Death Time ◽  
Evolution Of Life ◽  
History Of ◽  
Life On Earth

AbstractIn two recent papers (Maccone 2013, 2014) as well as in the book (Maccone 2012), this author described the Evolution of life on Earth over the last 3.5 billion years as a lognormal stochastic process in the increasing number of living Species. In (Maccone 2012, 2013), the process used was ‘Geometric Brownian Motion’ (GBM), largely used in Financial Mathematics (Black-Sholes models). The GBM mean value, also called ‘the trend’, always is an exponential in time and this fact corresponds to the so-called ‘Malthusian growth’ typical of population genetics. In (Maccone 2014), the author made an important generalization of his theory by extending it to lognormal stochastic processes having an arbitrary trend mL(t), rather than just a simple exponential trend as the GBM have.The author named ‘Evo-SETI’ (Evolution and SETI) his theory inasmuch as it may be used not only to describe the full evolution of life on Earth from RNA to modern human societies, but also the possible evolution of life on exoplanets, thus leading to SETI, the current Search for ExtraTerrestrial Intelligence. In the Evo-SETI Theory, the life of a living being (let it be a cell or an animal or a human or a Civilization of humans or even an ET Civilization) is represented by a b-lognormal, i.e. a lognormal probability density function starting at a precise instant b (‘birth’) then increasing up to a peak-time p, then decreasing to a senility-time s (the descending inflexion point) and then continuing as a straight line down to the death-time d (‘finite b-lognormal’).(1)Having so said, the present paper describes the further mathematical advances made by this author in 2014–2015, and is divided in two halves: Part One, devoted to new mathematical results about the History of Civilizations as b-lognormals, and(2)Part Two, about the applications of the Evo-SETI Theory to the Molecular Clock, well known to evolutionary geneticists since 50 years: the idea is that our EvoEntropy grows linearly in time just as the molecular clock. (a)Summarizing the new results contained in this paper: In Part One, we start from the History Formulae already given in (Maccone 2012, 2013) and improve them by showing that it is possible to determine the b-lognormal not only by assigning its birth, senility and death, but rather by assigning birth, peak and death (BPD Theorem: no assigned senility). This is precisely what usually happens in History, when the life of a VIP is summarized by giving birth time, death time, and the date of the peak of activity in between them, from which the senility may then be calculated (approximately only, not exactly). One might even conceive a b-scalene (triangle) probability density just centred on these three points (b, p, d) and we derive the relevant equations. As for the uniform distribution between birth and death only, that is clearly the minimal description of someone's life, we compare it with both the b-lognormal and the b-scalene by comparing the Shannon Entropy of each, which is the measure of how much information each of them conveys. Finally we prove that the Central Limit Theorem (CLT) of Statistics becomes a new ‘E-Pluribus-Unum’ Theorem of the Evo-SETI Theory, giving formulae by which it is possible to find the b-lognormal of the History of a Civilization C if the lives of its Citizens Ci are known, even if only in the form of birth and death for the vast majority of the Citizens.(b)In Part Two, we firstly prove the crucial Peak-Locus Theorem for any given trend mL(t) and not just for the GBM exponential. Then we show that the resulting Evo-Entropy grows exactly linearly in time if the trend is the exponential GMB trend.(c)In addition, three Appendixes (online) with all the relevant mathematical proofs are attached to this paper. They are written in the Maxima language, and Maxima is a symbolic manipulator that may be downloaded for free from the web.In conclusion, this paper further increases the huge mathematical spectrum of applications of the Evo-SETI Theory to prepare Humans for the first Contact with an Extra-Terrestrial Civilization.

Organisms With Nervous Systems

2019 ◽  
pp. 23-34
Author(s):  
Dale Purves
Keyword(s):  
Nervous System ◽  
Operating Principle ◽  
The Other ◽  
Neural Systems ◽  
Animal Kingdom ◽  
Nervous Systems ◽  
Life On Earth

Definitions of the term “animals” in dictionaries and textbooks are surprisingly vague. The characteristics usually mentioned are eukaryotic, multicellular, heterotrophic, sexually reproducing, and capable of rapid and independent movement. But some or all of these properties are characteristic of many organisms in the other kingdoms of life on Earth. In fact, the major distinguishing feature of animals in most cases is the presence of a nervous system. But if nervous systems are indeed one of the main attributes that distinguish organisms in the animal kingdom, what exactly are nervous systems and what advantages do they bring? Without at least some provisional answers, seeking the operating principle of neural systems would be futile.

scholarly journals Individual neuronal subtypes control initial myelin sheath growth and stabilization

2020 ◽  
Vol 15 (1) ◽  
Author(s):  
Heather N. Nelson ◽  
Anthony J. Treichel ◽  
Erin N. Eggum ◽  
Madeline R. Martell ◽  
Amanda J. Kaiser ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Central Nervous System ◽  
Nervous System ◽  
Myelin Sheath ◽  
Time Lapse ◽  
Marked Individual ◽  
Larval Zebrafish ◽  
Sheath Formation ◽  
Time Lapse Imaging

Abstract Background In the developing central nervous system, pre-myelinating oligodendrocytes sample candidate nerve axons by extending and retracting process extensions. Some contacts stabilize, leading to the initiation of axon wrapping, nascent myelin sheath formation, concentric wrapping and sheath elongation, and sheath stabilization or pruning by oligodendrocytes. Although axonal signals influence the overall process of myelination, the precise oligodendrocyte behaviors that require signaling from axons are not completely understood. In this study, we investigated whether oligodendrocyte behaviors during the early events of myelination are mediated by an oligodendrocyte-intrinsic myelination program or are over-ridden by axonal factors. Methods To address this, we utilized in vivo time-lapse imaging in embryonic and larval zebrafish spinal cord during the initial hours and days of axon wrapping and myelination. Transgenic reporter lines marked individual axon subtypes or oligodendrocyte membranes. Results In the larval zebrafish spinal cord, individual axon subtypes supported distinct nascent sheath growth rates and stabilization frequencies. Oligodendrocytes ensheathed individual axon subtypes at different rates during a two-day period after initial axon wrapping. When descending reticulospinal axons were ablated, local spinal axons supported a constant ensheathment rate despite the increased ratio of oligodendrocytes to target axons. Conclusion We conclude that properties of individual axon subtypes instruct oligodendrocyte behaviors during initial stages of myelination by differentially controlling nascent sheath growth and stabilization.

Sign in / Sign up

Export Citation Format

Share Document