Long-term Adaptations of Sabella Giant Axons to Hyposmotic Stress

1978 ◽  
Vol 75 (1) ◽  
pp. 253-263
Author(s):  
J. E. TREHERNE ◽  
Y. PICHON
Keyword(s):  
Sea Water ◽  
Potassium Concentration ◽  
Resting Potential ◽  
Sodium Permeability ◽  
Bathing Medium ◽  
Appreciable Change ◽  
Axon Membrane ◽  
Giant Axons

Reprint requests should be addressed to Dr Treherne. Sabella is a euryhaline osmoconformer which is killed by direct transfer to 50% sea water, but can adapt to this salinity with progressive dilution of the sea water. The giant axons were adapted to progressive dilution of the bathing medium (both in vivo and in vitro) and were able to function at hyposmotic dilutions (down to 50%) sufficient to induce conduction block in unadapted axons. Hyposmotic adaptation of the giant axon involves a decrease in intracellular potassium concentration which tends to maintain a relatively constant resting potential during adaptation despite the reduction in external potassium concentration. There is no appreciable change in the intracellular sodium concentration, but the relative sodium permeability of the active membrane increases during hyposmotic adaptation. This increase partially compensates for the reduction in sodium gradient across the axon membrane, during dilution of the bathing media, by increasing the overshoot of the action potentials recorded in hyposmotically adapted axons.

A Critical Study of the Evidence for Peripheral Inhibitory Axons in Insects

1968 ◽  
Vol 49 (1) ◽  
pp. 201-222
Author(s):  
P. N. R. USHERWOOD
Keyword(s):  
Potassium Concentration ◽  
Chloride Concentration ◽  
Chloride Ions ◽  
Resting Potential ◽  
Equilibrium Potential ◽  
Critical Study ◽  
Muscle Fibres ◽  
High Concentration ◽  
Bathing Medium

1. The metathoracic anterior coxal adductor (a.c.a.) muscle of the locust and the grasshopper is innervated by a peripheral inhibitory axon similar to the inhibitory axon which innervates the metathoracic extensor tibiae muscles of these insects. No evidence was found to justify calling this axon an inhibitory-conditioning axon. 2. Hyperpolarizing inhibitory postsynaptic potentials (IPSPs) are normally recorded from a.c.a. muscle fibres during stimulation of this axon, and if the bathing medium contains a high concentration of potassium ions the tonic fibres of the a.c.a. muscle relax slightly during inhibitory stimulation. 3. The IPSPs are chloride potentials and can be converted to depolarizing responses by changing either the external or internal chloride concentration of the a.c.a. muscle fibres. Depolarizing IPSPs are frequently accompanied by small contractions of a.c.a. muscle fibres innervated by the inhibitory axon. 4. The a.c.a. muscle fibres are permeable to potassium and chloride ions but influx of potassium chloride is much faster than efflux. Therefore when a.c.a. muscle fibres are loaded with chloride by exposing them to high-K saline (20-100 m-equiv. potassium/l.) and are then returned to normal (10 m-equiv. potassium/l.) saline the internal chloride concentration remains elevated for some time and during this period the equilibrium potential for the inhibitory response is less negative than the resting potential and the IPSPs are depolarizing. 5. Depolarizing IPSPs are usually recorded from a.c.a. muscle fibres of locusts and grasshoppers when these fibres are transferred from their normal bathing medium, haemolymph, to 10 K saline. Probably the main reason for this reversal of the IPSPs is the entry of KCl into the muscle fibres during dissection of the nerve-muscle preparations. Large quantities of KCl would be released into the environment surrounding these preparations from muscle fibres cut and removed during dissection. 6.Depolarizing IPSPs were more frequently recorded from muscle fibres of grassfed locusts than from fibres of starved locusts. The potassium concentration of haemolymph of grass fed locusts is higher than that of locust saline (10 m-equiv./l.). 7. The potassium concentration of locust haemolymph presumably fluctuates in vivo but these fluctuations are too slow to affect the sign of the IPSP. The IPSPs are therefore always hyperpolarizing in vivo. 8. The effect of changes in the potassium concentration of the bathing medium on the magnitude and polarity of the IPSP could account for the diverse responses recorded previously from a.c.a. muscle fibres of locusts and grasshoppers.

scholarly journals Resting and Action Potentials of the Squid Giant Axon in Vivo

1960 ◽  
Vol 43 (5) ◽  
pp. 961-970 ◽  
Author(s):  
John W. Moore ◽  
Kenneth S. Cole
Keyword(s):  
Sea Water ◽  
Giant Axon ◽  
Blood Oxygenation ◽  
Resting Potential ◽  
Liquid Junction ◽  
Axon Membrane ◽  
Nernst Potential ◽  
Initial Action ◽  
Calculated Liquid

Blood oxygenation and circulation were maintained in Loligo pealii for several hours by a strong flow of sea water over both gills on the open, flat mantle. Potentials were measured with a 3 M KCl-filled glass microelectrode penetrating the giant axon membrane. An hour or more after the mantle was opened, the potentials were similar to those observed in excised axons and in preparations without circulation; spike height 100 mv.; undershoot 12 mv., decaying at 6 v./sec.; resting potential 63 mv. However, the earliest (20 minute) resting potentials were up to 70 mv. and 73 mv. Occasional initial action potential measurements (40 to 50 minute) showed a decay of the undershoot that was less than one-tenth the rate observed later. This suggests that in even better preparations there would be no decay, thereby increasing the resting potential and spike height by 12 mv. With the calculated liquid junction potential of 4 mv. the absolute resting potential in the "normal" axon in vivo is estimated to be about 77 mv., which is close to the Nernst potential for the potassium ratio between squid blood and axoplasm. The differences between such a normal axon and the usual isolated axon can be accounted for by a negligible leakage conductance in the normal axon.

scholarly journals The Effectiveness of Candidate Probiotic Bacteria to Control Vibriosis Disease

2017 ◽  
Vol 5 (2) ◽  
pp. 1
Author(s):  
Mulyati Mulyati ◽  
Suryati Suryati ◽  
Irfani Baga
Keyword(s):  
Survival Rate ◽  
Sea Water ◽  
Challenge Test ◽  
Probiotic Bacteria ◽  
Pathogenicity Test ◽  
Inhibitory Ability ◽  
Significant Difference ◽  
Portunid Crab

The study aims to isolate, characterize, and examine probiotic bacteria's inhibitory ability against Vibrio harveyi bacteria, both in-vitro and in vivo. Methods used in the study consist of 1) An Isolation of Candidate Probiotic Bacteria, 2) An Antagonistic Test of Candidate Probiotic Bacteria in vitro, 3) An Identification of Bacteria, 4) A Pathogenicity Test of Candidate Probiotic Bacteria, 5) An Antagonistic Test of Candidate Probiotic Bacteria against V. harveyi in vivo. According to the isolation of candidate probiotic bacteria, there are 18 isolated candidate probiotic. After being tested for its inhibitory ability in vitro, there are 8 isolates with zone of inhibition as follows: isolate MM 7 from intestine (22 mm), isolate MM 6 from intestine (12 mm), isolate MM 10 from sea water (10 mm), isolate MM 5 from intestine (9 mm), isolate MM 4 from intestine (8 mm), isolate MM 3 from intestine (7 mm), isolate MM 2.2 from intestine (7 mm), isolate MM 2.1 from intestine (7 mm). Eight genera of the candidate probiotic bacteria is derived from Portunid crab, they are Staphylococcus, Streptococcus, bacillus, vibrio, Alcaligenes, Lactobacillus, micrococcus. Before proceeding the V. harveyi bacterial challenge test in vivo, three potential isolates consisting of MM6, MM7 and MM10 as the probiotic bacteria are pathogenicity-tested against V. harveyi. The survival rate of Portunid crab on pathogenicity test using MM6, MM7 and MM10 generates 91.11-100%, while the control generates 100% survival rate. Variance analysis result through post-hoc Tukey's Honest Significant Difference (HSD) test at 95% confidence interval indicates that isolate MM7 and MM10 are significantly able to increase hatchling Portunid crab's survival rate.

Studies on the mechanism of fluid secretion by isolated salivary glands of Calliphora

1976 ◽  
Vol 64 (2) ◽  
pp. 311-322
Author(s):  
M. J. Berridge ◽  
B. D. Lindley ◽  
W. T. Prince
Keyword(s):  
Salivary Glands ◽  
Apical Membrane ◽  
Potassium Concentration ◽  
Basal Membrane ◽  
Fluid Secretion ◽  
Sodium Permeability ◽  
Bathing Medium ◽  
Major Cation ◽  
Diuretic Agent ◽  
External Potassium

1. Potassium is the major cation in the secretion of the salivary glands of Calliphora and is necessary for full secretory rates. 2. Other ions (rubidium and sodium) can support secretion in the absence of potassium. 39. During stimulation with 5-HT a Nernst plot of the basal membrane potential has a slope of 53 mV for a tenfold change in external potassium concentration and the slope at rest deviates from this over the range I-20 mM external potassium. 4. Hyperpolarization of the basal membrane by 5-HT is abolished if the chloride in the bathing medium is replaced by isethionate. 5. The diuretic agent amiloride inhibits fluid secretion by a mechanism which may include a reduction in calcium entry in addition to its recognized effect on sodium permeability. 6. A model is proposed in which fluid secretion is driven by the active transport of potassium across the apical membrane with chloride following passively.

Metabolic importance of Na+/K+-ATPase activity during sea urchin development.

1997 ◽  
Vol 200 (22) ◽  
pp. 2881-2892 ◽  
Author(s):  
P Leong ◽  
D Manahan
Keyword(s):  
Enzyme Activity ◽  
Atpase Activity ◽  
Sea Urchin ◽  
Sodium Pump ◽  
Sea Water ◽  
Strongylocentrotus Purpuratus ◽  
Lytechinus Pictus ◽  
Stimulation Of

Early stages of animal development have high mass-specific rates of metabolism. The biochemical processes that establish metabolic rate and how these processes change during development are not understood. In this study, changes in Na+/K+-ATPase activity (the sodium pump) and rate of oxygen consumption were measured during embryonic and early larval development for two species of sea urchin, Strongylocentrotus purpuratus and Lytechinus pictus. Total (in vitro) Na+/K+-ATPase activity increased during development and could potentially account for up to 77 % of larval oxygen consumption in Strongylocentrotus purpuratus (pluteus stage) and 80 % in Lytechinus pictus (prism stage). The critical issue was addressed of what percentage of total enzyme activity is physiologically active in living embryos and larvae and thus what percentage of metabolism is established by the activity of the sodium pump during development. Early developmental stages of sea urchins are ideal for understanding the in vivo metabolic importance of Na+/K+-ATPase because of their small size and high permeability to radioactive tracers (86Rb+) added to sea water. A comparison of total and in vivo Na+/K+-ATPase activities revealed that approximately half of the total activity was utilized in vivo. The remainder represented a functionally active reserve that was subject to regulation, as verified by stimulation of in vivo Na+/K+-ATPase activity in the presence of the ionophore monensin. In the presence of monensin, in vivo Na+/K+-ATPase activities in embryos of S. purpuratus increased to 94 % of the maximum enzyme activity measured in vitro. Stimulation of in vivo Na+/K+-ATPase activity was also observed in the presence of dissolved alanine, presumably due to the requirement to remove the additional intracellular Na+ that was cotransported with alanine from sea water. The metabolic cost of maintaining the ionic balance was found to be high, with this process alone accounting for 40 % of the metabolic rate of sea urchin larvae (based on the measured fraction of total Na+/K+-ATPase that is physiologically active in larvae of S. purpuratus). Ontogenetic changes in pump activity and environmentally induced regulation of reserve Na+/K+-ATPase activity are important factors that determine a major proportion of the metabolic costs of sea urchin development.

Mechanisms of neocortical epileptogenesis in vitro

1982 ◽  
Vol 48 (6) ◽  
pp. 1321-1335 ◽  
Author(s):  
M. J. Gutnick ◽  
B. W. Connors ◽  
D. A. Prince
Keyword(s):  
Reversal Potential ◽  
Excitatory Input ◽  
Short Latency ◽  
Resting Potential ◽  
Excitatory Postsynaptic Potential ◽  
Cellular Mechanisms ◽  
Voltage Dependent ◽  
Intact Cortex

1. The cellular mechanisms underlying interictal epileptogenesis have been examined in an in vitro slice preparation of guinea pig neocortex. Penicillin or bicuculline was applied to the tissue, and intracellular recordings were obtained from neurons and glia. 2. Following convulsant application, stimulation could elicit a short-latency excitatory postsynaptic potential (EPSP) and a large, longer latency depolarization shift (DS) in single neurons. DSs in neurons of the slice were very similar to those evoked in neurons of neocortex in vivo in that they displayed an all-or-none character, large shifts in latency during repetitive stimuli, long afterpotentials, and a prolonged refractory period. In contrast to epileptogenesis produced by penicillin in intact cortex, neither spontaneous DSs nor ictal episodes were observed in neocortical slices. 3. In simultaneous recordings from pairs of neurons within the same cortical column, DS generation and latency shifts were invariably synchronous. DS generation in neurons was also coincident with large, paroxysmal increases of extracellular [K+], as indicated by simultaneous recordings from glia. 4. When polarizing currents were applied to neurons injected with the local anesthetic QX-314, the DS amplitude varied monotonically and had an extrapolated reversal potential near 0 mV. In neurons injected with the K+-current blocker Cs+, large displacements of membrane potential were possible, and both the short-latency EPSP and the peak of the DS diminished completely at about 0 mV. At potentials positive to this, the short-latency EPSP was reversed, and the DS was replaced by a paroxysmal hyperpolarization whose rise time and peak latency were prolonged compared to the DS evoked at resting potential. The paroxysmal hyperpolarization probably represents the prolonged activation of the impaled neuron by EPSPs. 5. Voltage-dependent components, including slow spikes, appeared to contribute to generation of the DS at resting potential in Cs+-filled cells, and these components were blocked during large depolarizations. 6. The results suggest that DS generation in single neocortical neurons occurs during synchronous synaptic activation of a large group of cells. DS onset in a given neuron is determined by the timing of a variable-latency excitatory input that differs from the short-latency EPSP. The DS slow envelope appears to be generated by long-duration excitatory synaptic currents and may be modulated by intrinsic voltage-dependent membrane conductances. 7. We present a hypothesis for the initiation of the DS, based on the anatomical and physiological organization of the intrinsic neocortical circuits.

scholarly journals The Ionic Basis of the Resting Potential in a Cross-Striated Muscle of the Aquatic Snail Lymnaea Stagnalis

1984 ◽  
Vol 108 (1) ◽  
pp. 305-314
Author(s):  
B. L. BREZDEN ◽  
D. R. GARDNER
Keyword(s):  
Membrane Potential ◽  
Lymnaea Stagnalis ◽  
Striated Muscle ◽  
Potassium Concentration ◽  
Muscle Cells ◽  
Resting Potential ◽  
Extracellular Potassium ◽  
Heart Ventricle ◽  
Sodium Permeability ◽  
Ionic Basis

The mean resting potential in the heart ventricle muscle cells of the freshwater snail Lymnaea stagnalis was found to be −61.2±3.5 (˙˙) mV (ranging from −56mV to −68mV). The average intracellular potassium concentration was estimated to be 51.5±14.6(˙˙) m (ranging from 27.8 m to 77.3 m). The membrane of the heart ventricle muscle cells appears to be permeable to both potassium and chloride, as changes in the extracellular concentration of either of these ions resulted in a change in the membrane potential. A ten-fold change in the extracellular potassium concentration was associated with a 50.4±3.8(˙˙) mV slope when the potassium concentration was above about 6 m. Deviations from the straight-line relation predicted for a potassium electrode could be accounted for by introducing a term for sodium permeability. The ionic basis of the membrane potential in these cells can be described by a modified form of the Goldman-Hodgkin- Katz equation.

Axonal Adaptations to Osmotic and Ionic Stress in an Invertebrate Osmoconformer (Mercierella Enigmatica Fauvel): III. Adaptations to Hyposmotic Dilution

1978 ◽  
Vol 76 (1) ◽  
pp. 221-235
Author(s):  
J. A. BENSON ◽  
J. E. TREHERNE
Keyword(s):  
Axonal Swelling ◽  
Osmotic Concentration ◽  
Bathing Medium ◽  
Axon Membrane ◽  
Ionic Stress ◽  
Sodium Inactivation ◽  
Sodium Extrusion ◽  
Potassium Gradient ◽  
Sodium And Potassium

The giant axons of this extreme osmoconformer were adapted, in vitro, to progressive hyposmotic dilution of the bathing medium (from 1024 m-Osmol to concentrations as low as 76.8 m-Osmol). Hyposmotic adaptation is associated with reductions in the intracellular concentrations of both sodium and potassium ions. These reductions do not appear to result from appreciable axonal swelling. The different electrical responses to isosmotic and hyposmotic dilution suggest that reduction in [Na+]1 results from ouabain-dependent sodium extrusion, in response to ionic dilution, and that reduction in [K+]1 is induced by a combination of ionic and osmotic dilution. The reduced level of intracellular potassium achieved during hyposmotic adaptation represents a balance between the necessity to contribute to osmotic equilibration and to maintain a potassium gradient across the axon membrane sufficient to produce appreciable axonal hyperpolarization during dilution of the bathing medium. This hyperpolarization tends to maintain the amplitude of the action potential, by compensating for reduction in overshoot (with decline in ENa), and by reducing sodium inactivation. This, together with the reduction in [Na+]1, enables overshooting action potentials of relatively large amplitude and rapid rise time to be maintained during more than tenfold dilution of the ionic and osmotic concentration of the bathing medium.

scholarly journals Anti-Inflammatory Properties of Mineral-Balanced Deep Sea Water in In-Vitro and In-Vivo Models of Inflamed Intestinal Epithelium

2020 ◽  
Vol 10 (15) ◽  
pp. 5183
Author(s):  
Jain Nam ◽  
Kyeong Jin Kim ◽  
Geonhee Park ◽  
Byeong Goo Kim ◽  
Gwi-Hwa Jeong ◽  
...  
Keyword(s):  
Deep Sea ◽  
Sea Water ◽  
Cell Model ◽  
Mineral Waters ◽  
In Vivo Models ◽  
Deep Sea Water ◽  
High Calcium ◽  
A Cell

This study aimed to determine the effect of deep-sea water (DSW)-derived mineral waters on intestinal health, using a cell model and a dextran sulfate sodium (DSS)-induced enteritis mouse model. DSW was desalted and minerals were added to generate mineral waters that were classified as trace mineral (TM), high magnesium (HM), high magnesium low salt (HMLS), and high magnesium high calcium (HMHC), using a tabletop electrodialysis device. Caco-2 cells cocultured with Raw264.7 cells were either pre-treated or not with the four water groups, and inflammation was induced by treatment with lipopolysaccharide (LPS). Compared to LPS-treated Caco-2 cells, HMLS-cotreated cells maintained high transepithelial electrical resistance, similar to control cells. FITC-dextran permeability was lower in HMLS-treated than in other cells. In vivo, in comparison to DSS-treated mice, colon shortening was inhibited, and disease activity and colon injury were suppressed in HMLS-cotreated mice. RNA-seq of colonic tissues revealed that inflammatory gene expression was similar among the control and HMLS mice, and DSS-induced expression of inflammation-related genes such as TNF-α and NOS2 and inflammatory chemokine genes was suppressed. Our findings suggest that DSW-derived mineral water intake can help reduce colitis symptoms, and the effects may be partially regulated by magnesium and other minerals.

Possible Effects of Depolarizing GABAA Conductance on the Neuronal Input–Output Relationship: A Modeling Study

2005 ◽  
Vol 93 (6) ◽  
pp. 3504-3523 ◽  
Author(s):  
Kenji Morita ◽  
Kunichika Tsumoto ◽  
Kazuyuki Aihara
Keyword(s):  
Firing Rate ◽  
Cortical Neurons ◽  
Reversal Potential ◽  
Pyramidal Cells ◽  
Resting Potential ◽  
Input Output ◽  
Wide Range ◽  
The Relationship

Recent in vitro experiments revealed that the GABAA reversal potential is about 10 mV higher than the resting potential in mature mammalian neocortical pyramidal cells; thus GABAergic inputs could have facilitatory, rather than inhibitory, effects on action potential generation under certain conditions. However, how the relationship between excitatory input conductances and the output firing rate is modulated by such depolarizing GABAergic inputs under in vivo circumstances has not yet been understood. We examine herewith the input–output relationship in a simple conductance-based model of cortical neurons with the depolarized GABAA reversal potential, and show that a tonic depolarizing GABAergic conductance up to a certain amount does not change the relationship between a tonic glutamatergic driving conductance and the output firing rate, whereas a higher GABAergic conductance prevents spike generation. When the tonic glutamatergic and GABAergic conductances are replaced by in vivo–like highly fluctuating inputs, on the other hand, the effect of depolarizing GABAergic inputs on the input–output relationship critically depends on the degree of coincidence between glutamatergic input events and GABAergic ones. Although a wide range of depolarizing GABAergic inputs hardly changes the firing rate of a neuron driven by noncoincident glutamatergic inputs, a certain range of these inputs considerably decreases the firing rate if a large number of driving glutamatergic inputs are coincident with them. These results raise the possibility that the depolarized GABAA reversal potential is not a paradoxical mystery, but is instead a sophisticated device for discriminative firing rate modulation.

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