Effects of Osmotic Stress on the Electrical Activities of the Giant Axon of a Marine Osmoconformer, Sabella Penicillus

1978 ◽  
Vol 75 (1) ◽  
pp. 237-251
Author(s):  
A. D. CARLSON ◽  
Y. PICHON ◽  
J. E. TREHERNE
Keyword(s):  
Giant Axon ◽  
Ionic Concentration ◽  
Rapid Decline ◽  
Osmotic Concentration ◽  
Bathing Medium ◽  
Axonal Membrane ◽  
Abrupt Changes ◽  
Slow Potassium ◽  
Electrical Activities

Reprint requests should be addressed to Dr Treherne. The giant axons of the polychaete, Sabella penicillus, can withstand, in vitro, abrupt changes in osmotic and ionic concentration of the bathing medium in the range measured in the blood of this osmoconformer (543–1236 m-osmol) at different external salinities. Isosmotic dilution of the external ions (i.e. when osmotic concentration was maintained by sucrose) induced a modest hyperpolarization of the axonal membrane and a rapid decline in the overshoot of the action potential. In contrast, abrupt hyposmotic dilution resulted in a relatively slow and complex decline in overshoot in the absence of axonal hyperpolarization. A slow potassium depolarization and rate of decrease in overshoot in sodium-free conditions suggests that there is a reduced intercellular access to the axon surfaces following exposure to hyposmotic media. It is suggested that this restricted access could provide short-term protection from fluctuations in blood osmotic concentration.

Axonal Adaptations to Osmotic and Ionic Stress in an Invertebrate Osmoconformer (Mercierella Enigmatica Fauvel): II. Effects of Ionic Dilution on the Resting and Action Potentials

1978 ◽  
Vol 76 (1) ◽  
pp. 205-219
Author(s):  
J. A. BENSON ◽  
J. E. TREHERNE
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Prolonged Exposure ◽  
Giant Axon ◽  
Sodium Concentration ◽  
Ionic Concentration ◽  
Osmotic Concentration ◽  
Bathing Medium ◽  
Axon Membrane ◽  
Wide Range

The giant axon of this extreme euryhaline osmoconformer possess an unusual ability to produce action potentials of large amplitude over a wide range of ionic dilution when constant osmotic concentration is maintained by the addition of mannitol to the bathing medium. Ionic dilution under these circumstances causes a decline in the overshoot of the action potential (resulting largely from reduction in [Na+]0) and an appreciable axonal hyperpolarization (primarily as a result of decrease in [K+]0). This hyperpolarization tends to compensate for the reduction in the extent of the overshoot and so maintains the amplitude of the sodium-mediated action potentials during isosmotic dilution of the bathing medium. The axonal hyperpolarization also appears to reduce sodium inactivation so as to maintain a rapid rate of rise of the action potential despite drastic reduction in the ionic concentration of the bathing medium. Prolonged exposure to reduced ionic concentrations appears to induce a ouabain sensitive reduction in intracellular sodium concentration which increases the sodium gradient across the axon membrane during isosmotic dilution of the external medium.

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.

Neurofilaments and Paired Helical Filaments

1985 ◽  
Vol 43 ◽  
pp. 740-743
Author(s):  
J. Metuzals
Keyword(s):  
Animal Model ◽  
Posttranslational Modifications ◽  
Posttranslational Modification ◽  
Giant Axon ◽  
Paired Helical Filaments ◽  
Squid Giant Axon ◽  
In Vitro Experiments ◽  
Thin Sections ◽  
Structural Relationships

It has been demonstrated that the neurofibrillary tangles in biopsies of Alzheimer patients, composed of typical paired helical filaments (PHF), consist also of typical neurofilaments (NF) and 15nm wide filaments. Close structural relationships, and even continuity between NF and PHF, have been observed. In this paper, such relationships are investigated from the standpoint that the PHF are formed through posttranslational modifications of NF. To investigate the validity of the posttranslational modification hypothesis of PHF formation, we have identified in thin sections from frontal lobe biopsies of Alzheimer patients all existing conformations of NF and PHF and ordered these conformations in a hypothetical sequence. However, only experiments with animal model preparations will prove or disprove the validity of the interpretations of static structural observations made on patients. For this purpose, the results of in vitro experiments with the squid giant axon preparations are compared with those obtained from human patients. This approach is essential in discovering etiological factors of Alzheimer's disease and its early diagnosis.

Condensed tannins extracted from Quebracho affect the fermentation profile, nutritional quality and in vitro gas production of pornunça (Manihot spp.) silages

2021 ◽  
pp. 1-10
Author(s):  
D. T. Q. Carvalho ◽  
A. R. F. Lucena ◽  
T. V. C. Nascimento ◽  
L. M. L. Moura ◽  
P. D. R. Marcelino ◽  
...  
Keyword(s):  
Nutritional Quality ◽  
Dry Matter ◽  
Condensed Tannin ◽  
Gas Production ◽  
Rapid Decline ◽  
Randomized Design ◽  
In Vitro Gas Production ◽  
Acid Detergent Fibre ◽  
Fermentation Profile

Abstract The objective was to evaluate the fermentation profile, in vitro gas production and nutritional quality of pornunça (Manihot spp.) silages containing levels of condensed tannin (CT; 0, 4, 8 and 12% on dry matter (DM) basis), at five opening times (0, 3, 7, 14, 28 and 56 days). A completely randomized design in a 4 × 5 factorial arrangement was adopted, with four replications, totalling 80 experimental silos. The pH and NH3-N analyses were performed at all opening times of the silos. The other analyses were performed only with silages opened at 56 days of storage. There was an interaction effect between CT levels and silo opening times for pH and NH3-N. Tannin levels in pornunça silages after 56 days ensiling increased the pH and DM and reduced crude protein (CP) and neutral detergent fibre (NDF). There was a quadratic effect for NH3-N, acetic acid, butyric acid, gas losses, dry matter recovery (DMR), hemicellulose and acid detergent fibre. Inclusion of 4 and 8% CT in pornunça silage promotes a rapid decline in pH, being within the acceptable limit for adequate fermentation at 3 days of ensiling. Silages with 4% CT establish the pH at 28 days of opening the silos, with reduced NH3-N. Silages with 4% CT present higher concentrations of acetic and butyric acids and greater DMR. Inclusion of CT in pornunça silage after 56 days ensiling increases DM and reduces CP and NDF, directly affecting the in vitro degradability and reducing gas production.

Administration of a live attenuated Salmonella vaccine using an inactivated oil-emulsion vaccine as a vehicle for commercial chicken flocks

2018 ◽  
Vol 58 (7) ◽  
pp. 1316
Author(s):  
P. J. Groves ◽  
T. Harris ◽  
S. M. Sharpe
Keyword(s):  
Serum Antibody ◽  
In Vivo Studies ◽  
Rapid Decline ◽  
Inactivated Vaccine ◽  
Serological Response ◽  
Oil Emulsion ◽  
Commercial Chicken ◽  
Viral Vaccine

Since the finding that inoculating an aroA- deletion live Salmonella Typhimurium vaccine parenterally provides improved and longer-lasting protection against Salmonella colonisation of the laying-hen intestine, this administration route has been adopted by the industry. To make this method practicable and economical, mixing the live bacterial vaccine with an inactivated viral vaccine has become popular. In vitro and in vivo studies were performed designed to assess the effect on the survival of the live salmonellae and the ability to stimulate serum antibody when mixed into oil-emulsion vaccines, compared with more traditional diluents. A rapid decline in viable salmonellae was observed when mixing with an inactivated Riemerella/Pasteurella bacterin. Mixing with an inactivated viral vaccine produced a less severe and more gradual decline in viable salmonellae over time; however, there was a surprising resuscitation of the bacteria 60 min after mixing. Serum antibody 14 days after inoculation of vaccine diluted in a universal diluent rose significantly, compared with sham vaccinated birds. Birds receiving the vaccine diluted in an inactivated vaccine at the time of preparation did not show a significant serological response; however, when given 60 min post-preparation, serum antibody was significantly increased. There appeared to be a correlation of the magnitude of serum antibody produced with the number of viable salmonellae inoculated. The use of the live vaccine incorporated into an inactivated vaccine may give variable results and needs assessment before adoption.

scholarly journals A MICROCALORIMETRIC STUDY OF TURTLE CORTICAL SLICES: INSIGHTS INTO BRAIN METABOLIC DEPRESSION

1994 ◽  
Vol 191 (1) ◽  
pp. 141-153 ◽  
Author(s):  
C Doll ◽  
P Hochachka ◽  
S Hand
Keyword(s):  
Cortical Neurons ◽  
Heat Dissipation ◽  
Energy Charge ◽  
Utilization Rate ◽  
Rapid Decline ◽  
Metabolic Depression ◽  
Slice Preparation ◽  
Cortical Slices

In previous papers, we have examined turtle cortical neurons in vitro for mechanisms of anoxic metabolic depression ('channel arrest' and changes in electrical parameters). Negative results prompted the current study with the aim of examining more closely the energy profile and metabolism of turtle cortical slices. Calorimetry is used to measure heat dissipation during normoxia and nitrogen perfusion (120 min) and the results are converted into an ATP utilization rate. These indicate that the control rate of ATP utilization (1.72 µmol ATP g-1 min-1) agrees closely with in vivo whole-brain metabolic measurements. Both nitrogen perfusion and pharmacologically induced anoxic (cyanide+N2) groups depressed heat dissipation considerably compared with the control value (nitrogen 37 %; pharmacological anoxia 49 %). The resulting ATP utilization estimates indicate metabolic depressions of 30 % (nitrogen) and 42 % (pharmacological anoxia). The slice preparation did not exhibit a change in any measured adenylate parameter for up to 120 min of anoxia or pharmacological anoxia. Significant changes did occur in [ADP], ATP/ADP ratio and energy charge after 240 min of exposure to anoxic conditions. These results support the idea that the turtle cortical slice preparation has a profound resistance to anoxia, with both nitrogen perfusion and pharmacological anoxia causing a rapid decline in heat dissipation and metabolism.

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.

The Sensitivity of the Pedal Ganglion of the Slug to Osmotic Pressure Changes

1956 ◽  
Vol 33 (3) ◽  
pp. 493-501
Author(s):  
G. A. KERKUT ◽  
B. J. R. TAYLOR
Keyword(s):  
Osmotic Pressure ◽  
Ionic Concentration ◽  
The Body ◽  
Bathing Solution ◽  
Pedal Ganglion ◽  
Bathing Medium ◽  
Rates Of Change ◽  
Fluid Concentration ◽  
Locke Solution ◽  
Pressure Changes

1. The effects of different dilutions of Locke solution on the electrical activity of the isolated pedal ganglion of the slug can be reproduced by adding different concentrations of glucose of mannitol to a given concentration of Locke. 2. This indicates that certain cells in the pedal ganglion are sensitive to the osmotic pressure of the solution and not its ionic concentration. 3. The preparation is sensitive to slow changes in the concentration of the bathing medium. The cells increased their activity when the bathing solution was slowly changed from 0.7 Locke to 0.6 Locke, the change taking 43 min. This corresponds approximately to a change of 1% of the body fluid concentration over 4 min. Such rates of change are found in the normal intact animal. 4. The sensitivity of the preparation compares well with that of the mammalian osmoreceptors.

Neuromuscular transmission in the jellyfish Aglantha digitale

1985 ◽  
Vol 116 (1) ◽  
pp. 1-25 ◽  
Author(s):  
P. A. Kerfoot ◽  
G. O. Mackie ◽  
R. W. Meech ◽  
A. Roberts ◽  
C. L. Singla
Keyword(s):  
Dimensional Space ◽  
Thin Sheet ◽  
Current Source ◽  
Giant Axon ◽  
The Body ◽  
Two Dimensional ◽  
Bathing Medium ◽  
Giant Axons ◽  
Motor Neurones ◽  
Stimulation Of

In the jellyfish Aglantha digitale escape swimming is mediated by the nearly synchronous activity of eight giant motor axons which make direct synaptic contact with contractile myoepithelial cells on the under-surface of the body wall. The delay in transmission at these synapses was 0.7 +/− 0.1 ms (+/− S.D.;N = 6) at 12 degrees C as measured from intracellular records. Transmission depended on the presence of Ca2+ in the bathing medium. It was not blocked by increasing the level of Mg2+ to 127 mmol l-1. The myoepithelium is a thin sheet of electrically coupled cells and injection of current at one point was found to depolarize the surrounding cells. The potential change declined with distance from the current source as expected for two-dimensional current spread. The two-dimensional space constant (lambda) was 770 micron for current flow in the circular direction and 177 micron for radial flow. The internal resistance of the epithelium (178–201 omega cm) and the membrane time constant (5–10 ms) were direction independent. No propagated epithelial action potentials were observed. Spontaneous miniature synaptic potentials of similar amplitude and rise-time were recorded intracellularly at distances of up to 1 mm from the motor giant axon. Ultrastructural evidence confirms that neuro-myoepithelial synapses also occur away from the giant axons. It is likely that synaptic sites are widespread in the myoepithelium, probably associated with the lateral motor neurones as well as the giant axons. Local stimulation of lateral motor neurones generally produced contraction in distinct fields. We suppose that stimulation of a single motor giant axon excites a whole population of lateral motor neurones and hence a broad area of the myoepithelium.

Fluid secretion in the nephron: Relation to renal failure

1976 ◽  
Vol 56 (1) ◽  
pp. 248-258 ◽  
Author(s):  
J. J. Grantham
Keyword(s):  
Fluid Transport ◽  
Fluid Secretion ◽  
Cystic Kidney Disease ◽  
Rabbit Kidney ◽  
Cystic Kidney ◽  
Obstructive Nephropathy ◽  
Bathing Medium ◽  
Pars Recta ◽  
Uremic Syndrome

It had been generally accepted that glomerular filtration and tubular reabsorption were the basic modes of fluid transport in mammalian nephrons. Recently, evidence was obtained to indicate that net fluid secretion may occur in mammalian nephrons as well. In the pars recta portion of proximal tubules of rabbit kidney net fluid secretion was observed in vitro in response to PAH and other aryl acids in the peritubular bathing medium. Net fluid secretion appeared to be coupled to the transcellular transport of aryl acid from bath to lumen. Serum from uremic subjects stimulated net fluid secretion in the pars recta in a manner similar to PAH. The accumulation of high levels of endogenous aryl acids may contribute to the general organ dysfunction that is a part of the uremic syndrome of advanced renal insufficiency. Futhermore, there is evidence to suggest that the fluid-secretion phenomenon in association with aryl acids may significantly affect renal excretion and morphology in slow-flow states, in patients with cystic kidney disease, and in obstructive nephropathy.

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