Conduction in demyelinated axons—A simplified model

This paper is concerned with conduction of the nervous impulse in a myelinated axon and the effect of demyelination on conduction characteristics. A model of nerve conduction called the “gunpowder fuse” model is presented which accurately predicts conduction velocities in both myelinated and unmyelinated nerves. The effect on conduction velocity in this model by reducing myelin thickness is examined by utilizing basic data and building and equivalent circuit. The result is a curve relating reduced conduction velocity to reduced myelin thickness. A similar analysis and resultant curve is derived from a saltatory conduction model. Supported in part by National Multiple Sclerosis Society Research Grant No. 516 and Air Force Grant AFOSR 669-67.     

Physiological bases of oligotrophy of microorganisms and the concept of microbial community

Three groups of physiological processes in microorganisms are considered the physiological basis of oligotrophy: the greater substrate affinity of the oligotrophs' transport systems, efficient or “economical” metabolism, and existence of a “master reaction” or “rate-determining steps” controlling the rate of metabolism. Heterotrophic microorganisms are divided into three unequal groups according to “reaction norma.” Two groups representing the extremes are small groups with the “narrow” reaction norma, regarding the concentrations and structure of the assimilated organic compounds and variability limits of the physiological characteristics mentioned above. The third, intermediate group includes the majority of microorganisms with the “wide” reaction norma.     

Study of changes in diacylglycerol content on nerve excitation

Rhythmic excitation of a rabbit myelin nerve increased diacylglycerol (DAG) content from 1.53 to 2.17 microg/mg lipids. Inhibition of phosphoinositide-specific phospholipase C decreased DAG content. This suggests involvement of this enzyme in processes accompanying rhythmic excitation. The increase in membrane potential of the nerve fiber (K+-depolarization) was accompanied by increase in DAG and phosphatidylinositol monophosphate and decrease in phosphatidylinositol triphosphate and phosphatidylinositol diphosphate content. Treatment of the nerve with DAG or a protein kinase C activator increased (45)Ca influx by 40%, whereas treatment with an inhibitor of this enzyme, polymyxin, inhibited this parameter by 34%. The role of phosphoinositides and protein kinase C in the regulation of Ca2+ transport during rhythmic excitation of the myelin nerve is discussed.     

Reflex responses of the spinal cord under conditions of the spinal “superreflexia” evoked by pharmacological agents increasing its excitability

We studied monosynaptic reflex discharges (MRD) recorded from the ventral roots (VR) of rats subjected to systemic administration with thyroliberin, thyroxin, or 4-aminopyridine (4-AP). Under such conditions, in some of the experiments the MRD amplitude reached values sufficient to excite non-active VR fibers. In these cases, immediately after the MRD peak had been reached, abnormally increased responses (AIR) developed, whose amplitude was 2–2.5 times higher than the amplitude of highly facilitated MRD. Proofs are presented that AIR reflect excitation of “neighboring” VR fibers, which were not involved in the reflex response, and MRD plays the role of a “stimulus” exciting these fibers. Therefore, we demonstrate the possibility of transmission of excitation from “active” to “silent” fibers within a nerve trunk under conditions of the development of “superreflexia”. This state can be considered a model of excitation spreading via a non-synaptic pathway under conditions of hyperexcitability of the CNS structures, in seizure states in particular. neirofiziologiya/Neurophysiology, Vol. 32, No. 2, pp. 120–127, March–April, 2000.     

Role of acetylcholine in regulation of interaction between axon and Schwann cell during rhythmic excitation of nerve fibers

Axon excitation increases the number of acetylcholine receptors (ACR) of the Schwann cell (SC) depending on the frequency of rhythmic excitation (RE) and on intercellular concentrations of K+, Ca2+, and acetylcholine. During RE, activity of axonal acetylcholine esterase is decreased, thus providing for high intercellular acetylcholine concentration. Increased intercellular concentration of acetylcholine activates phosphoinositide-specific phospholipase C (PIPLC) of the myelin nerve fiber. During RE, K+ depolarization and acetylcholine exocytosis can activate Ca2+ entry via Ca2+ channels, thus inducing SC ACR phosphorylation mediated by PIPLC stimulation.     

The dynamic behavior of phycobilisome movement during light state transitions in cyanobacterium <Emphasis Type="Italic">Synechocystis</Emphasis> PCC6803

Light state transition is a physiological function of oxygenic organisms to balance the excitation of photosystem II (PSII) and photosystem I (PSI), hence a prerequisite of oxygen-evolving photosynthesis. For cyanobacteria, phycobilisome (PBS) movement during light state transition has long been expected, but never observed. Here the dynamic behavior of PBS movement during state transition in cyanobacterium Synechocystis PCC6803 is experimentally detected via time-dependent fluorescence fluctuation. Under continuous excitation of PBSs in the intact cells, time-dependent fluorescence fluctuations resemble “damped oscillation” mode, which indicates dynamic searching of a PBS in an “overcorrection” manner for the “balance” position where PSII and PSI are excited equally. Based on the parallel model, it is suggested that the “damped oscillation” fluorescence fluctuation is originated from a collective movement of all the PBSs to find the “balance” position. Based on the continuous fluorescence fluctuation during light state transition and also variety of solar spectra, it may be deduced that light state transition of oxygen-evolution organisms is a natural behavior that occurs daily rather than an artificial phenomenon at extreme light conditions in laboratory.     

A biophysical approach to the investigation of physiological processes

It was shown that understanding the mechanism of rhythmic excitation in cells and tissues requires the combination of physiological and biophysical approaches. Systemic studies of changes in the physicochemical characteristics of the object were carried out by a protocol that takes into account the mode of rhythmic excitation and the functional sate of the object being studied. The validity of the approach was proved in studies of rhythmic excitation in somatic nonmyelinic and myelinic nerves, and in model systems. The approach can be used in studies of many physiological processes.     

Theodore H. Bullock: pioneer of integrative and comparative neurobiology

Theodore H. Bullock (1905–2005) was a pioneer of integrative and comparative neurobiology and one of the founders of neuroethology. His work—distinguished by the tremendous number of different research themes and animal taxa studied—provided the basis for a comprehensive analysis of brain evolution. Among his major achievements are: one of the first physiological analyses of rhythmic central pattern generators; the first simultaneous recording from both the presynaptic and postsynaptic region of a chemical synapse; the demonstration of intercellular communication through graded potentials; and the discovery of two novel sensory organs formed by infrared receptors in pit vipers and electroreceptors in electric fish. He was also one of the first who applied computational tools to the analysis of complex neural signals and to perform a comparative analysis of cognitive events. His two-volume treatise “Structure and function in the nervous system of invertebrates” (with G. Adrian Horridge) remains the most comprehensive, authoritative review of this topic ever written. In addition to his research merits, his legacy is particularly based on his cosmopolitan way of thinking and acting, his large, worldwide school of students, and his committed advocacy for comparative and systems-oriented neurobiology.     

Remark on some correspondences between the characteristics of the nerve impulse and those of ferroelectric polarization

Ferroelectric polarization currents have characteristics which may be of use in the study of the nerve impulse either directly or indirectly through the suggestion of parallel experiments in the two domains. For example, the “all or none” aspect of the excitation of the nerve impulse can be considered to correspond in some sense to the coercive force required for the reversal of a ferroelectric polarization. The refractory period then corresponds to the lack of a relaxation process in ferroelectric polarization; for a second application of voltage in a given direction does not produce a ferroelectric current; it is necessary that the polarization be reversed by a reversal of voltage. The “heat block” in nerve conduction may correspond to a ferroelectric Curie point at about 40°C. Velocities of propagation of ferroelectric polarization are of the order of magnitude of the velocities of sound and therefore in a range suitable for the interpretation of the observed velocities of nerve impulses. These and other parallels between ferroelectric behavior and the characteristics of the nerve impulse suggest that there may be a useful degree of similarity between the molecular processes responsible for the nerve impulse and those responsible for ferroelectric polarization. *** DIRECT SUPPORT *** A01E2080 00002     

Mechanism of activation of Na, K-ATPase in nerve fibres during rhythmic excitation

The mechanism of activation of Na, K-ATPase in nerve fibres during rhythmic excitation was studied. 3H-ouabain binding to the nerve was found to be dependent on the frequency of rhythmic excitation. During rhythmic excitation 3H-ouabain binding was increased in all nerves tested. The maximum of 3H-ouabain binding in squid and crab nerves was observed at 10 impulses/s, and in frog nerve at 100 impulses/s. The level of bound glycoside decreased during high-frequency excitation. Rhythmic excitation did not change Na, K-ATPase affinity to ouabain, but it appeared to increase the concentration of ouabain sensitive sites in the nerve membrane. The enhancement of 3H-ouabain binding to nerve during rhythmic excitation is interpreted as arising from transformation of "inactive" forms of the enzyme to "active" ones.     

On reinforcement and interference between stimuli

It is shown that the current “two-factor” theory of nerve excitation can account for sustained inhibition or enhancement by a sequence of stimulus pulses, and for the decrease in the reinforcement period with each successive pulse of the train.     

Energy efficiency of electron plasma emitters

Electron emission influence from gas-discharge plasma on plasma emitter energy parameters is considered. It is shown, that electron emission from plasma is accompanied by energy contribution redistribution in the gas-discharge from plasma emitter supplies sources—the gas-discharge power supply and the accelerating voltage power supply. Some modes of electron emission as a result can be realized: “a probe measurements mode,” “a transitive mode,” and “a full switching mode.”     

“Ignition” phenomena in random nets

The spread of excitation in a “random net” is investigated. It is shown that if the thresholds of individual neurons in the net are equal to unity, a positive steady state of excitation will be reached equal to γ, which previously had been computed as the weak connectivity of the net. If, however, the individual thresholds are greater than unity, either no positive steady state exists, or two such states depending on the magnitude of the axone density. In the latter case the smaller of the two steady states is unstable and hence resembles an “ignition point” of the net. If the initial stimulation (assumed instantaneous) exceeds the “ignition point,” the excitation of the net eventually assumes the greater steady state. Possible connections between this model and the phenomenon of the “preset” response are discussed.     

Source-sink landscape theory and its ecological significance

Exploring the relationships between landscape pattern and ecological processes is the key topic of landscape ecology, for which, a large number of indices as well as landscape pattern analysis model were developed. However, one problem faced by landscape ecologists is that it is hard to link the landscape indices with a specific ecological process. Linking landscape pattern and ecological processes has become a challenge for landscape ecologists. “Source” and “sink” are common concepts used in air pollution research, by which the movement direction and pattern of different pollutants in air can be clearly identified. In fact, for any ecological process, the research can be considered as a balance between the source and the sink in space. Thus, the concepts of “source” and “sink” could be implemented to the research of landscape pattern and ecological processes. In this paper, a theory of sourcesink landscape was proposed, which include: (1) In the research of landscape pattern and ecological process, all landscape types can be divided into two groups, “source” landscape and “sink” landscape. “Source” landscape contributes positively to the ecological process, while “sink” landscape is unhelpful to the ecological process. (2) Both landscapes are recognized with regard to the specific ecological process. “Source” landscape in a target ecological process may change into a “sink” landscape as in another ecological process. Therefore, the ecological process should be determined before “source” or “sink” landscape were defined. (3) The key point to distinguish “source” landscape from “sink” landscape is to quantify the effect of landscape on ecological process. The positive effect is made by “source” landscape, and the negative effect by “sink” landscape. (4) For the same ecological process, the contribution of “source” landscapes may vary, and it is the same to the “sink” landscapes. It is required to determine the weight of each landscape type on ecological processes. (5) The sourcesink principle can be applied to non-point source pollution control, biologic diversity protection, urban heat island effect mitigation, etc. However, the landscape evaluation models need to be calibrated respectively, because different ecological processes correspond with different source-sink landscapes and evaluation models for the different study areas. This theory is helpful to further study landscape pattern and ecological process, and offers a basis for new landscape index design. __________ Translated from Acta Ecologica Sinica, 2006, 26(5): 1444–1449 [译自: 生态学报]     

Self-reproduction and serial message transfer: Two related problems

For a certain class of physical machines, termed “structure-determined,” the problem of self-reproduction can be reduced to the problem of serial message reproduction. Serial message reproduction however presupposes a sort of “open system” constraint. This leads to the principle of pseudo, or exogenously standardized, respectively, self-reproduction. It seems to be consistent with both chemical and biological self-reproduction. It thus may reflect a general principle of biological design. The proposed principle is a physico chemical analog to Robert Rosen's abstract relational self-reproduction constraint.     

Terahertz vibrational properties of water nanoclusters relevant to biology

Water nanoclusters are shown from first-principles calculations to possess unique terahertz-frequency vibrational modes in the 1–6 THz range, corresponding to O–O–O “bending,” “squashing,” and “twisting” “surface” distortions of the clusters. The cluster molecular-orbital LUMOs are huge Rydberg-like “S,” “P,” “D,” and “F” orbitals that accept an extra electron via optical excitation, ionization, or electron donation from interacting biomolecules. Dynamic Jahn–Teller coupling of these “hydrated-electron” orbitals to the THz vibrations promotes such water clusters as vibronically active “structured water” essential to biomolecular function such as protein folding. In biological microtubules, confined water-cluster THz vibrations may induce their “quantum coherence” communicated by Jahn–Teller phonons via coupling of the THz electromagnetic field to the water clusters’ large electric dipole moments.     

The Properties of Water in the Pressure–Temperature Landscape

Water represents the major component of most food systems. During thermal or high-pressure processing, physical and chemical properties of water are changed. The p–T diagram represents an obvious presentation of isoproperty lines and their pressure and temperature dependencies. In this work, 15 different properties of pure water are shown as isoproperty lines in the pressure–temperature landscape. By using functional relationships from the “International Association for the Properties of Water and Steam” and databases from the “National Institute of Standards and Technology,” highest accuracy is guaranteed. Applying the generated graphs, a compact overview is given and a wide range of thermal and high-pressure processes can easily be compared. The different pressure and temperature dependencies of all properties showed the complexity of medium conditions during thermal and high-pressure processing. An extended understanding of pressure–temperature dependencies will improve process concepts as well as industrial applications at high temperature and high isostatic pressure.     

Hierarchical Categorical Perception in Sensing and Cognitive Processes

This article considers categorical perception (CP) as a crucial process involved in all sort of communication throughout the biological hierarchy, i.e. in all of biosemiosis. Until now, there has been consideration of CP exclusively within the functional cycle of perception–cognition–action and it has not been considered the possibility to extend this kind of phenomena to the mere physiological level. To generalise the notion of CP in this sense, I have proposed to distinguish between categorical perception (CP) and categorical sensing (CS) in order to extend the CP framework to all communication processes in living systems, including intracellular, intercellular, metabolic, physiological, cognitive and ecological levels. The main idea is to provide an account that considers the heterarchical embeddedness of many instances of CP and CS. This will take me to relate the hierarchical nature of categorical sensing and perception with the equally hierarchical issues of the “binding problem”, “triadic causality”, the “emergent interpretant” and the increasing semiotic freedom observed in biological and cognitive systems.

Interactive Bodies: The Semiosis of Architectural Forms

In this paper architectural forms are presented as symbolic forms issued from the complex semiosis that characterises human cognition (Ferreira (2007, 2010)). Being semiotic objects, these symbolic forms are, consequently, context- dependent_they emerge and have meaning, i.e., they are assigned a functional and/or aesthetic value, in particular physical, social and cultural frameworks. As it happens with all semiotic objects, architectural forms, whatever their nature, are not static but highly interactive. In fact, they act as agents of specific semiotic processes, engaged in a permanent dialectic relationship with the environment they are embedded in. From this dialectics important physical, social, cultural and economic changes frequently arise, redefining this way the original framework for decades to come. As Pallasmaa (2009) points out: “Architecture is existentially rooted, and it expresses fundamental existential experiences, the complex condensation of how it feels to be human being in this world. Architecture grounds and frames existence and creates specific horizons of perception, understanding and identity.” Architecture happens in the context of particular landscapes both natural and man-made, individuating spaces, assigning them an identity, turning the frequently undifferentiated physical environment into “locus”, “place”, “site”, “ort”, definitely contributing to the definition of the mental map that individual minds are able to share collectively. The fundamental role played by architectural forms in the definition of “place” and identity and in the shaping or reshaping of a physical, social and cultural environment is analysed in this paper through a case study that observes the consequences of this dynamics in the development of the social and cultural tissue of a particular city.     

Multiform wave organization of neurophysiological processes-universal “language” of human brain in realization of informational-controlling functions

The paper summarizes literature data and results of many-year Laboratory studies disclosing principles of the multiform spatial-time organization of differing by rates of neurophysiologic brain processes as the universal “language” of its informational-controlling functions. There are considered current concepts of electrogenesis and physiological significance of ratios of gradual changes of biopotentials and impulse activity of neurons considered in studies of cerebral mechanisms of regulation of normal and pathological states, and organization of human psychic activity. Put forward and argumented are concepts of the probability principle of hierarchical organization of differing by rates of neurophysiologic processes brain zones, structures, and areas in formation of the brain systems participating in provision of the higher psychic functions and states. It is proposed to discuss the concept of the brain as the “swimming,” many-contour, neurodynamic informational-controlling suprasystem with universal, hierarchically organized neurodynamic structures—”functional organs” by A.A. Ukhtomskii (1978), of which formation provides large informational brain capacity and a wide specter of adaptive possibilities of the human organism.