Analyses of HH and GHK equations with another perspective: Can ion adsorption also govern trans-membrane potential?

Two mathematically distinct physiological concepts, the Goldman-Hodgkin-Katz eq. (GHK eq.) and the Hodgkin-Huxley model (HH model) were successfully associated with each other in a prior work. The previous work was performed on the following premises (i) The membrane potential is generated by ion adsorption, as opposed to the classical ion transport mechanisms, (ii) The living cell is a thermodynamically real system rather than an ideal system, and (iii) The conductance employed in the HH model is replaced by the ion activity coefficient, which is weighted with the role of conductance. Consequently, the GHK eq. was mathematically associated with the HH model through the intermediary of Boltzmann ion distribution and mass action law. To verify if our theoretical formularization could afford a physiologically, physically and chemically viable model, we performed computational analysis using the formulae (quantitative correlations between various variables) we derived in the previous work. The computational results obtained through associating the GHK eq. with the HH model validated our model and its predictions. This outcome suggests that the current prevailing physiological concepts could be expanded further, to incorporate the newly proposed mechanisms. That is, GHK eq. and HH model could be interpreted via another set of founding principles that incorporate the ubiquitous phenomena of ion-adsorption.

Reversibility of excitation waves in brain and heart and the energy of interfacial water. Can reversibility be explained by it?

In this manuscript, we interpret the implications of a discovery we made in 1993 for the understanding of the spread of excitation waves in axon, central gray matter (isolated retina) and heart. We propose that the initial burst of energy dissipation in these waves measured as potentials drops, ionic activities marked changes or optical properties being mostly the effect of dissociated water becoming liquid water and be reversible due to the further on dissociation during the refractory period. We also propose experiments in order to falsify or agree with this conjecture.

GHK eq. and HH eq. for a real system is mathematically associable to each other but their physiological interpretation needs a reconsideration.

Despite the long and broad acceptance of the Goldman - Hodgkin - Katz equation (GHK eq.) and the Hodgkin - Huxley equation (HH eq.) as strong tools for the quantitative analysis of the membrane potential behavior, for a long time they have been utilized as separate concepts. That is the GHK eq. and the HH eq. have not been associated with each other mathematically. In this paper, an attempt to associate these equations to each other mathematically was demonstrated and was successful by viewing the system in question as a thermodynamically real system rather than an ideal system. For achieving that, two fundamental physical chemistry concepts, the mass action law, and the Boltzmann distribution were employed. Hence, this paper's achievement is completely within the framework of common thermodynamics. Through this work, the origin of the membrane potential generation attributed to the ion adsorption-desorption process and governed by the mass action law and the Boltzmann distribution is expressed to be plausible, whereas the existing membrane potential generation mechanism states that membrane potential is generated by transmembrane ion transport. As at this moment, this work does not intend to deny the transmembrane ion transport as a membrane potential generation mechanism but urges the readers to reconsider its validity, since this work suggests that the ion adsorption-desorption mechanism is as plausible as the transmembrane ion transport mechanism as a cause of membrane potential generation.

Increasing influenza and pneumococcal vaccine uptake in the elderly: study protocol for the multi-methods prospective intervention study Vaccination60.

BACKGROUND: Influenza and pneumococcal vaccination can prevent disease and potentially life-threatening complications like sepsis. Elderly people have an increased risk of severe disease and therefore constitute a major target group for vaccination. To increase vaccination coverage, targeted interventions are needed that take theory-based specific determinants of vaccination behaviour into account. Moreover, message and campaign design should consider specific age-related characteristics (e.g., information processing, media use). The aim of this study is (i) to identify the specific informational and interventional needs of this risk group, (ii) to design and implement a targeted intervention aiming to decrease vaccine hesitancy, increase vaccine uptake and decrease the health and economic burden due to the respective diseases, and (iii) to measure the effect of this evidence-informed intervention on various levels. METHODS: Prospective, multi-methods intervention study targeting individuals aged ≥60 years in a model region in Germany (federal state of Thuringia, 500,000 inhabitants ≥60 years old). The development of the intervention follows theory-based and evidence-informed principles: Data from a cross-sectional representative study provide insights into specific determinants of the target group's vaccination behaviour. Additionally, media use is analysed to identify adequate communication channels for specific subgroups. In pilot studies, the intervention materials are adapted to the specific cognitive requirements of the target group. For development and implementation of the intervention, an interdisciplinary and trans-sectoral approach is used, including psychology, communication science, design, medical science, epidemiology and various public health players. The intervention will be implemented in autumn and winter 2017/18 and 2018/19 and adjusted in between. Evaluation of the intervention includes: awareness, use and recall of intervention materials, effects on changes in determinants of vaccination behaviour, self-reported vaccine uptake, and vaccination coverage in the intervention area (primary outcomes), as well as disease incidences (secondary outcomes) and the economic burden of influenza, pneumonia, invasive pneumococcal disease and sepsis for the healthcare system (tertiary outcomes). DISCUSSION: The data will add to the body of evidence on the effectiveness of evidence-informed vaccination campaign development as well as on the clinical and economic effects of pneumococcal and influenza vaccination. The effect of the intervention will teach valuable lessons about the principles of campaign development and evaluation, and can motivate a subsequent nationwide intervention. TRIAL REGISTRATION: DRKS00012653 . Registered 24.11.2017. Retrospectively registered.

Extracellular matrix and its role in conveying glial/neural interactions in health and disease.

We review the concepts and findings that may be related to the occurrence of non-linear glial/neural dynamics involving interactions between polyelectrolytes of the extracellular matrix and the basement membranes that cover the endfeet of glia at CNS interfaces. Distortions of perception and blocking of learning expressed in functional syndromes are interpreted as macroscopic electrochemical patterns that emerge in grey matter through glial/neural interactions.

Membrane-modifying properties of crotamine, a small peptide-toxin from Crotalus durissus terifficus venom.

BACKGROUND: Crotamine is a small, highly basic myotoxin from the venom of the South American rattlesnake Crotalus durissus terifficus. It is structurally well defined and exhibits some similarities with the ß-defensins of vertebrates. An amazing variety of functions and targets that range from analgesia and tumor-related activity to cell penetration have been associated with crotamine. Similar to defensins, it had been argued that crotamine has antimicrobial activity, and this supposition was recently proven.Moreover, it has been argued that the antimicrobial activity of crotamine is due to the membrane permeabilizing properties of the peptide. However, until now, the detailed mechanism of this postulated membrane permeabilization was still unclear. METHODS: In this paper, we used gradient SDS-gels, mass spectroscopy (MALDI-TOF), and monolayer and planar lipid bilayer experiments to investigate the membrane modifying properties of crotamine. RESULTS: We showed that crotamine itself forms stable monolayers because of its amphipathic structure, is easily incorporated into lipid monolayers and forms well-defined pores with low cationic selectivity in planar lipid bilayers; these properties might account for the antimicrobial activity of crotamine. The pores are probably oligomericaggregates of crotamine molecules, as suggested by the tendency of crotamine to form oligomers in aqueous solution and the fact that the structure of crotamine does not allow pore formation by monomers. CONCLUSIONS: The membrane modifying and antimicrobial properties of crotamine are probably due to homo oligomeric pore formation in membranes. GENERAL SIGNIFICANCE: The results should be highly interesting to researchers in the fields of biophysics, pharmacology,toxicology and antibiotics.

Odorant-evoked electrical responses in Grueneberg ganglion neurons rely on cGMP-associated signaling proteins.

The Grueneberg ganglion (GG) in the anterior nasal region of mice is considered as an olfactory compartment since its neurons were recently observed to be activated by chemical stimuli, in particular by the odorant 2,3-dimethylpyrazine (2,3-DMP). However, it is unclear whether the GG indeed serves an olfactory function since these findings are solely based on the expression of the activity-dependent gene c-Fos. Consequently, it is yet uncertain whether chemical compounds, such as given odorants, elicit electrical responses in GG neurons which are required to convey the chemosensory information to the brain. Therefore, in the present study, electrical recording experiments on tissue sections through the anterior nasal region of mice were conducted which revealed that 2,3-DMP induces electrical signals in the GG. These responses were restricted to sites harboring GG neurons, indicating that 2,3-DMP elicits an electrical signal only in these but not in other cells of the anterior nasal region. 2,3-DMP-sensitive GG neurons express signaling proteins associated with the second messenger substance cyclic guanosine monophosphate (cGMP); most notably the cyclic nucleotide-gated ion channel CNGA3 and the transmembrane guanylyl cyclase GC-G. Using mice deficient for CNGA3 or GC-G demonstrated that the 2,3-DMP-evoked electrical signals in the GG of these knockout mice were substantially lower than in the GG of wildtype conspecifics, indicating that cGMP signaling plays a crucial role for odorant-induced electrical responses in the GG.

The kinetics of non-synaptically triggered acute excitotoxic responses in the central nervous system observed using intrinsic optical signals.

BACKGROUND AND PURPOSE: Excitotoxic central nervous system (CNS) response is believed to be important in the pathophysiology of irreversible sequelae of anoxia and brain trauma. Furthermore, the sodium pump has been associated with functional CNS syndromes such as migraine and epilepsy. Thus, a detailed description of the kinetics of excitotoxic responses elicited by glutamatergic pathway activation and sodium pump blockade can be useful in pre-clinical research. This should be aimed at minimizing the brain damage due to anoxia or trauma or the prophylaxis of functional syndromes. EXPERIMENTAL APPROACH: The kinetics of the intrinsic optical signals of excitotoxic responses were examined in detail following N-methyl-D-aspartic acid or ouabain extrinsic pulses in in vitro retinas and compared to optical profiles of retinal spreading depression waves in intact retinae in chicken eye-cups. Additional experiments recorded field potentials simultaneously with the intrinsic optical signals. The protective effects of extracellular magnesium and glutathione were also examined. RESULTS: The initial phase (10 min) of the excitotoxic responses were very similar, however the final outcome was different: usually, irreversible damage was restricted to patches of tissue following N-methyl-D-aspartic acid pulses. By contrast, extrinsic ouabain experiments resulted in whole tissue death even with concentrations as low as 10 nM, except in three experiments in which glutathione at physiological concentrations was added to the perfusion 60 min before the pulse. CONCLUSION: the glial sodium pump must be a receptor of endogenous cardiac glycosides and its blockade can trigger excitotoxicity with a non-synaptic mechanism. The demonstration of glutathione protective effect suggests the importance of the transducer role of this membrane ATPase in the CNS.

The synergetic modulation of the excitability of central gray matter by a neuropeptide: two protocols using excitation waves in chick retina.

The isolated chick retina provides an in vitro tissue model, in which two protocols were developed to verify the efficacy of a peptide in the excitability control of the central gray matter. In the first, extra-cellular potassium homeostasis is challenged at long intervals and in the second, a wave is trapped in a ring of tissue causing the system to be under self-sustained challenge. Within the neuropil, the extra-cellular potassium transient observed in the first protocol was affected from the initial rising phase to the final concentration at the end of the five-minute pulse. There was no change in the concomitants of excitation waves elicited by the extra-cellular rise of potassium. However, there was an increase on the elicited waves latency and/or a rise in the threshold potassium concentration for these waves to appear. In the second protocol, the wave concomitants and the propagation velocity were affected by the peptide. The results suggest a synergetic action of the peptide on glial and synaptic membranes: by accelerating the glial Na/KATPase and changing the kinetics of the glial potassium channels, with glia tending to accumulate KCl. At the same time, there is an increase in potassium currents through nerve terminals.

The synergetic modulation of the excitability of central gray matter by a neuropeptide: two protocols using excitation waves in chick retina

The isolated chick retina provides an in vitro tissue model, in which two protocols were developed to verify the efficacy of a peptide in the excitability control of the central gray matter. In the first, extra-cellular potassium homeostasis is challenged at long intervals and in the second, a wave is trapped in a ring of tissue causing the system to be under self-sustained challenge. Within the neuropil, the extra-cellular potassium transient observed in the first protocol was affected from the initial rising phase to the final concentration at the end of the five-minute pulse. There was no change in the concomitants of excitation waves elicited by the extra-cellular rise of potassium. However, there was an increase on the elicited waves latency and/or a rise in the threshold potassium concentration for these waves to appear. In the second protocol, the wave concomitants and the propagation velocity were affected by the peptide. The results suggest a synergetic action of the peptide on glial and synaptic membranes: by accelerating the glial Na/KATPase and changing the kinetics of the glial potassium channels, with glia tending to accumulate KCl. At the same time, there is an increase in potassium currents through nerve terminals.

Retinas de pinto isoladas proporcionam um modelo de tecidos in vitro, para o qual dois protocolos foram desenvolvidos para verificar a eficácia de um peptídeo no controle da excitabilidade da matéria cinzenta central. No primeiro, a homeostase do potássio extra-celular é desafiada por intervalos longos (1 hora) e no segundo, uma onda é capturada em um anel de tecido, de tal maneira que o sistema permaneça em estado de desafio auto-sustentado. Dentro da neuropil, o transiente de potássio extra-celular observado no primeiro protocolo foi afetado da fase de início de aumento à concentração final, ao final do pulso de cinco minutos. Não há mudanças nos parâmetros concomitantes das ondas de excitação geradas pelo aumento do potássio extra-celular. Entretanto, houve um aumento da latência das ondas geradas e/ou um aumento no nível de concentração de potássio necessário para gerar a onda. No segundo protocolo, os parâmetros concomitantes da onda e sua velocidade de propagação foram afetados pelo peptídeo. Os resultados sugerem uma ação sinergética do peptídeo nas membranas gliais e sinápticas: acelerando o Na/KATPase glial e mudando a cinética dos canais de potássio gliais, com a glia tendendo a acumular KCl. Nesse período, não há aumento nas correntes de potássio nas terminações nervosas.

Central nervous tissue: an excitable medium. a study using the retinal spreading depression as a tool.

According to its physicochemical properties, neuronal tissue, including the central nervous system (CNS) and thus the human brain, is an excitable medium, which consequently exhibits, among other things, self-organization, pattern formation and propagating waves. Furthermore, such systems can be controlled by weak external forces. The spreading depression (SD), a propagating wave of excitation-depression, is such an event, which is additionally linked to a variety of medically important situations, classical migraine being just one example. Especially in retinal tissue, a true part of the CNS, the SD can be observed very easily with the naked eye and by video imaging techniques due to its big intrinsic optical signal. We have investigated the retinal SD and its control by external physical parameters such as gravity and temperature. Beyond this, especially due to its medical relevance, the control of CNS excitability by pharmacological tools is of specific interest, and we have studied this question in detail using the retinal SD as an experimental tool to collect information about the control of CNS tissue excitability.

Intrinsic optical signal of retinal spreading depression: second phase depends on energy metabolism and nitric oxide.

Spreading depression (SD) is a wave-like phenomenon that spreads through the gray matter of central nervous tissue. The aim of this work is to investigate how cellular energy supply and nitric oxide (NO) influence the recovery period after SD wave propagation. We have examined the SD wave in chicken retina by registration of the intrinsic optical signal (IOS). The changes of the IOS were observed via a microscope, transferred to a photomultiplier and amplified. The IOS of the SD wave consists of two phases. The first phase of IOS coexists with cellular swelling induced by ion distribution; the second phase is thought to reflect metabolic changes and reflects the refractory (recovery) period. To analyze the IOS, the amplitude, the duration and the front and the back maximal slopes of the both phases were analyzed. To reduce the cellular level of ATP the blocker of glucose transport-dexamethasone (glucocorticoid hormone) and the blocker of the respiratory chain-potassium cyanide were used. Sodium nitroprusside and trinitroglycerine were chosen as NO-donors. Our results show that during and after SD wave propagation (i) increased NO concentration changes the first and the second phases of IOS (duration of both phases is NO independent), (ii) reduced glucose uptake leads to an increased second phase duration and (iii) block of the respiratory chain prolongs the first phase. According to the results here presented, we propose that glycogen synthesis is one of the mechanisms reflected by the second phase of the IOS.

Propagation velocity and triggering threshold of retinal spreading depression are not correlated.

Spreading depression (SD) is a pronounced but transient disturbance of cellular homeostasis in the neuropil of the central nervous system which spreads in a wave-like manner across the tissue. At the wavefront the cells depolarize and a distinct ion redistribution between intra- and extracellular space is observed. In the aftermath of SD the recovering tissue is refractory: during an early absolute refractory period no further SD can be triggered, during the subsequent relative refractory period SD waves spread at lower velocity than usual. In this paper we shall examine the influence of temperature on SD triggering and on SD propagation in the chicken retina (retinal spreading depression, rSD) and we shall examine rSD triggering and rSD propagation in the refractory period. It will be shown that cooling decreases the threshold of rSD triggering, i.e. it becomes easier to trigger rSD when the temperature is reduced. At the same time cooling slows rSD propagation. In contrast, during the relative refractory period triggering rSD is more difficult than usual while rSD propagation is also slowed. These results demonstrate that the propagation velocity of rSD is not correlated with the triggering threshold. In particular, the propagation velocity of rSD must not be used to predict the influence of experimental conditions on the triggering threshold.

Correlation between the durations of refractory period and intrinsic optical signal of retinal spreading depression during temperature variations.

Spreading depression (SD) is a neurophysiological phenomenon which occurs in the grey substance of the central nervous system. SD is characterised by a wave-like spread of depressed neuronal activity, by large ion shifts between intra- and extracellular space, by cellular depolarization, and by altered optical properties of the tissue giving rise to an intrinsic optical signal (IOS). In the shadow of SD further waves are difficult to trigger and such waves spread at lower velocity than usual. In this paper we examine the temperature dependence of the duration of this recovery (refractory) period and the temperature dependence of the duration of the IOS in the chicken retina. It is shown that these SD accompanying events are strongly dependent on temperature and that they are likely to depend on the metabolic rate in the tissue. The observed correlation of the duration of the IOS with the duration of the refractory period suggests that the IOS is a good indicator for the duration of the tissue recovery. Such a correlation would be of great value to the experimentalist who must know about the duration of the refractory period: while the latter is laborious to determine, recording the IOS is convenient.

Fluorescent and dispersion experiments on biological membranes under micro-gravity.

Almost all biological processes, especially those involved in signal reception and signal transduction, depend on the physical and physiological properties of biological membranes. It has been shown, that neuronal tissue and the speed of the action potential (AP) which is the basic neuronal unit of all nervous activity, is sensitive to changes in gravity as well as to other weak external forces. We strongly suppose the membrane to be the most important factor in gravitational responses although it is very difficult to observe the effects of gravity changes on these fragile thermodynamic systems. Therefore we developed two different experiments to measure the structural changes and the lateral membrane tension of spheroid cells under microgravity.

Gravity sensing in the central nervous system.

For human based space research it is of high importance to understand the influence of gravity on the properties of the central nervous system (CNS). Until now it is not much known about how neuronal tissue can sense gravity. The aim of this study was to find out weather and how the CNS, as a complex system, can percept and react to changes in gravity. Neuronal tissue and especially the CNS fulfils all the requirements for excitable media. Consequently, self-organisation, pattern formation and propagating excitation waves as typical events of excitable media have been observed in such tissue. The spreading depression (SD), an excitation depression wave is the most obvious and best described of these phenomena in the CNS. In our experiments we showed that the properties of the SD and therefore the CNS in its properties as an excitable medium reacts very sensitive to changes in gravity.

Patch-clamp experiments under micro-gravity.

For human based space research it is of high importance to understand the influence of gravity on the properties of single ion channels in biological membranes, as these are involved in about all biological processes. The patch clamp technique is the best established method to investigate electrophysiological properties of single ion channels in detail. Consequently, a patch clamp set-up was designed for the drop tower in Bremen, Germany. Using this set-up among others, successfully leech neurons have been patched under micro-gravity, delivering data about ion channel behaviour, which were compared to results from bilayer experiments in the drop tower and to results from lab controls under 1 g and under higher gravity.

Wave onset in central gray matter - its intrinsic optical signal and phase transitions in extracellular polymers

The brain is an excitable media in which excitation waves propagate at several scales of time and space. ''One-dimensional'' action potentials (millisecond scale) along the axon membrane, and spreading depression waves (seconds to minutes) at the three dimensions of the gray matter neuropil (complex of interacting membranes) are examples of excitation waves. In the retina, excitation waves have a prominent intrinsic optical signal (IOS). This optical signal is created by light scatter and has different components at the red and blue end of the spectrum. We could observe the wave onset in the retina, and measure the optical changes at the critical transition from quiescence to propagating wave. The results demonstrated the presence of fluctuations preceding propagation and suggested a phase transition. We have interpreted these results based on an extrapolation from Tasaki's experiments with action potentials and volume phase transitions of polymers. Thus, the scatter of red light appeared to be a volume phase transition in the extracellular matrix that was caused by the interactions between the cellular membrane cell coat and the extracellular sugar and protein complexes. If this hypothesis were correct, then forcing extracellular current flow should create a similar signal in another tissue, provided that this tissue was also transparent to light and with a similarly narrow extracellular space. This control tissue exists and it is the crystalline lens. We performed the experiments and confirmed the optical changes. Phase transitions in the extracellular polymers could be an important part of the long-range correlations found during wave propagation in central nervous tissue

Descriçäo compartimentalizada das dinâmicas iônicas intra e extracelulares de tecidos neuronais / Compartment description of intracellular and extracellular ionic dynamics of neuronal tissues

Em geral, a modelagem realística de sistemas neuronais considera os circuitos elétricos análogos aos mecanismos de geração de correntes elétricas, potenciais e campos elétricos, não considerando os de difusão e eletrodifusão. Entretanto, na simulação de fenômenos que envolvem grandes fluxos iônicos, tais como o fenômeno da Depressão Alastrante de Leão, onde esses mecanismos são comprovadamente essenciais, faz-se necessária a descrição das dinâmicas iônicas envolvidas. Com esse objetivo, este trabalho apresenta o desenvolvimento de uma representação compartimentalizada para as dinâmicas intra e extracelulares em tecidos neuronais, a qual pode ser verificada como representativa de um modelo analítico, de onde leis básicas, tais como a lei de Fick e a equação de Nerst, podem ser deduzidas.