THE BIO-ELECTRIC POTENTIALS OF PLANTS AND THEIR FUNCTIONAL SIGNIFICANCE: I. AN ELECTROKINETIC THEORY OF TRANSPORT

1957 ◽  
Vol 35 (4) ◽  
pp. 573-582 ◽  
Author(s):  
D. S. Fensom
Keyword(s):  
Metabolic Activity ◽  
Functional Significance ◽  
Membrane Diffusion ◽  
Streaming Potentials ◽  
Electro Osmosis ◽  
Electric Potentials ◽  
Electrical Theory ◽  
The Way

The background of bio-potentials in relation to transport is briefly reviewed and the chief difficulties lying in the way of an electrical theory of transport are pointed out. A re-examination of electro-osmosis and streaming potentials in xylem and phloem vessels suggests that the bio-electrical forces are sufficiently large in magnitude to cause transport and that they certainly operate in a direction to assist it. The productions of the potentials through metabolic activity and membrane diffusion is discussed.

ELECTRO-OSMOSIS, WITH SOME APPLICATIONS TO PLANT PHYSIOLOGY

1963 ◽  
Vol 41 (6) ◽  
pp. 953-966 ◽  
Author(s):  
J. Dainty ◽  
P. C. Croghan ◽  
D. S. Fensom
Keyword(s):  
Plant Physiology ◽  
Cell Walls ◽  
Membrane Conductance ◽  
Irreversible Thermodynamics ◽  
Osmotic Pump ◽  
Biological Cell ◽  
Applied Potential ◽  
Electrokinetic Phenomena ◽  
Streaming Potentials ◽  
Electro Osmosis

General expressions for electrokinetic phenomena of relevance in biology are derived using the methods of irreversible thermodynamics and Onsager coefficients, not only for a Helmholtz-Smoluchowski model but also for a factional model and the model of Schmid. These last two models would seem to be more appropriate for biological cell membranes.Some applications of these expressions to plant physiology include the following: the pressure contribution of electro-osmosis to the turgor of Nitella or Chara cells is found to be negligible; the power used by an electro-osmotic pump can never be less than that used by a pressure mechanism; electro-osmosis may account for the present discrepancies between calculations of membrane conductance using tracer ions fluxes and those using applied potential differences; the streaming potentials developed by pressures across biological membranes would be too small to detect, but in large pores such as xylem or phloem vessels or in cell walls small pressures would result in easily measured potentials.

Self-potential signals from pumping tests in laboratory experiments

Geophysics ◽  
2014 ◽  
Vol 79 (6) ◽  
pp. EN125-EN133 ◽  
Author(s):  
Suzan S. Vasconcelos ◽  
Carlos A. Mendonça ◽  
Nilton Silva
Keyword(s):  
Homogeneous Medium ◽  
Water Circulation ◽  
Source Imaging ◽  
Pumping Tests ◽  
Medium Theory ◽  
Streaming Potentials ◽  
Resistivity Model ◽  
Electric Potentials ◽  
Self Potential ◽  
Field Criterion

Streaming potentials can be generated when geologic porous media are subjected to pumping tests. For a homogeneous medium, theory predicts that input and output points for water circulation generate field responses in the form of electric potentials that are equivalent to those produced by current sources that are externally driven by a power source. We evaluated tank experiments showing that this assumption is valid for common geophysical scenarios and can be used to determine charge density for porous geologic media, a key parameter in interpreting electrokinetic and interfacial properties in hydrogeophysics. We also determined that when water circulation encompasses a heterogeneity, the equivalence with single current poles is lost, and this can be used as a field criterion to detect inhomogeneities near a well. Our experimental results were analyzed with finite-element modeling of water and charge flow, showing that an interfacial distribution of currents must be expected as the cause of distortions in self-potential fields. We developed a procedure that used the background resistivity model to better image the distribution of currents onto media interfaces, pointing out advances still needed and challenges still remaining to improve source imaging.

THE BIOELECTRIC POTENTIALS OF PLANTS AND THEIR FUNCTIONAL SIGNIFICANCE: IV. CHANGES IN THE RATE OF WATER ABSORPTION IN EXCISED STEMS OF ACER SACCHARUM INDUCED BY APPLIED ELECTROMOTIVE FORCES: THE "FLUSHING EFFECT"

1962 ◽  
Vol 40 (3) ◽  
pp. 405-413 ◽  
Author(s):  
D. S. Fensom
Keyword(s):  
Electrical Stimulation ◽  
Functional Significance ◽  
Acer Saccharum ◽  
The Other ◽  
Streaming Potentials ◽  
Artificial Flow ◽  
Flow Through ◽  
Temporary Disturbance ◽  
Bioelectric Potentials ◽  
Stimulation Of

Experiments on excised stems of maple (Acer saccharum Marsh) in the winter and growing states have shown that artificial flow through open channels can alter the existing biopotential and thus produce local streaming potentials. On the other hand, artificially applied voltages could produce two effects: a small and temporary disturbance in flow which appeared to be electroosmotic in nature and direction: a sudden large surge of flow into the stem after prolonged electrical stimulation of up to 45,000 mv. The latter effect was called "flushing" and only occurred in young green stems which had previously been well exposed to sunlight. Artificial guttation was found to be associated with flushing.

scholarly journals Butyrate Producers as Potential Next-Generation Probiotics: Safety Assessment of the Administration of Butyricicoccus pullicaecorum to Healthy Volunteers

mSystems ◽  
2018 ◽  
Vol 3 (6) ◽  
Author(s):  
Leen Boesmans ◽  
Mireia Valles-Colomer ◽  
Jun Wang ◽  
Venessa Eeckhaut ◽  
Gwen Falony ◽  
...  
Keyword(s):  
Animal Models ◽  
Adverse Events ◽  
Gut Microbiota ◽  
Healthy Volunteers ◽  
Metabolic Activity ◽  
Microbiota Composition ◽  
Next Generation ◽  
Content Type ◽  
The Way

ABSTRACT Advances in gut microbiota research have triggered interest in developing colon butyrate producers as niche-specific next-generation probiotics, targeted at increasing colon butyrate production and countering disease-associated microbiota alterations. Crucial steps in the development of next-generation probiotics are the design of formulations with a reasonable shelf life as well as the safety demonstration of an intervention in healthy volunteers. One such potential next-generation butyrate-producing probiotic is Butyricicoccus pullicaecorum 25-3T, with demonstrated safety in in vitro as well as animal models. Here, we examined the strain’s safety, tolerability, and impact on microbiota composition and metabolic activity in healthy volunteers in a randomized, double-blind, placebo-controlled crossover study in 30 healthy volunteers. The study design consisted of two 4-week intervention periods (108 CFU B. pullicaecorum [treatment] or maltodextrin [placebo] per day) with a 3-week washout in between. We assessed adverse events, blood parameters (primary endpoints), and fecal microbiota composition and metabolite profiles (secondary endpoints). The number of reported adverse events during the B. pullicaecorum treatment was similar to that of placebo intervention, as were observed changes in blood chemistry parameters, bowel habits, and fecal calprotectin concentrations. Administration of the strain did not induce any disruptive effect in microbiota composition or metabolic activity. In this first human intervention trial with a butyrate-producing Clostridium cluster IV isolate, we demonstrated B. pullicaecorum 25-3T administration to be both safe and well tolerated by healthy participants. This safety study paves the way for the further development of the strain as a next-generation probiotic. IMPORTANCE This study is the first to determine the safety and tolerance in humans of a butyrate-producing Clostridium cluster IV next-generation probiotic. Advances in gut microbiota research have triggered interest in developing colon butyrate producers as next-generation probiotics. Butyricicoccus pullicaecorum 25-3T is one such potential probiotic, with demonstrated safety in vitro as well as in animal models. Here, we produced an encapsulated B. pullicaecorum formulation that largely preserved its viability over an 8-month storage period at 4°C. Administration of this formulation to healthy volunteers allowed us to establish the intervention as safe and well tolerated. The probiotic intervention did not cause disruptive alterations in the composition or metabolic activity of health-associated microbiota. The results presented pave the way for the exploration of the impact of the strain on microbiota alterations in a clinical setting.

scholarly journals Single-molecule detection: Unravelling surface receptor diffusion in live neurons

2005 ◽  
Vol 27 (5) ◽  
pp. 5-8 ◽  
Author(s):  
Laurent Groc ◽  
Daniel Choquet ◽  
Brahim Lounis ◽  
Laurent Cognet
Keyword(s):  
Single Molecule ◽  
Cellular Imaging ◽  
Single Molecule Detection ◽  
Live Cells ◽  
Membrane Diffusion ◽  
Surface Receptor ◽  
Cellular Compartments ◽  
Sub Wavelength ◽  
The Way

Over the last decade, single-molecule detection (SMD) gave biologists a tool to turn their dream, to follow a single molecule in live cells, into reality. SMD provides the advantages of identifying subpopulations and of localizing molecules with sub-wavelength precision. The use of nanometre-sized ligand–fluorophore complexes has even made it possible to track targets within confined cellular compartments. In this review, we first describe the main benefits of SMD in cellular imaging. We then show how SMD was used to unravel the membrane diffusion of glutamatergic receptors and how it sheds light on the way neurons can regulate membrane distribution of receptors.

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