Lack of osmoregulation in Aplysia brasiliana: correlation with response of neuron R15 to osphradial stimulation

1991 ◽  
Vol 260 (4) ◽  
pp. R777-R784 ◽  
Author(s):  
E. Scemes ◽  
L. C. Salomao ◽  
J. C. McNamara ◽  
A. C. Cassola
Keyword(s):  
Electrical Activity ◽  
Salinity Tolerance ◽  
Body Fluid ◽  
Regulatory Mechanism ◽  
Relative Weight ◽  
Transient Increase ◽  
Quiescent Period ◽  
Bursting Neuron ◽  
Osmoregulatory Mechanism ◽  
Chloride Concentrations

The exposure of Aplysia brasiliana to dilute seawater (90 and 80%) caused an increase of the relative weight, which returned to the original values after a few hours. Both osmotic and chloride concentrations of the hemolymph decreased on exposure to 80 and 90% dilute seawater, and after 3-h exposure there were no differences between the hemolymph and external media osmotic and chloride concentrations. In contrast to the clear regulatory capabilities reported for A. californica, A. brasiliana cannot maintain the osmolality of its body fluid in dilute media. In A. californica, osphradial receptors and neuron R15 are apparently involved in this regulatory mechanism. Perfusion of osphradium of A. brasiliana with dilute seawater (95-80%) did not affect electrical activity of the bursting neuron R15; perfusion with 70 and 60% seawater caused a transient increase in the duration of the quiescent period. In contrast to the model established for A. californica, in A. brasiliana no relationship was found between exposure of the osphradium to dilute media and electrical activity in neuron R15, which is in accordance with the lack of an osmoregulatory mechanism in this species. Such differences may reflect inherent differences in salinity tolerance between the two species.

Bistability and its regulation by serotonin in the endogenously bursting neuron R15 in Aplysia

1996 ◽  
Vol 75 (2) ◽  
pp. 957-962 ◽  
Author(s):  
H. A. Lechner ◽  
D. A. Baxter ◽  
J. W. Clark ◽  
J. H. Byrne
Keyword(s):  
Electrical Activity ◽  
Dynamic Properties ◽  
Computational Studies ◽  
Nonlinear Dynamical ◽  
Bursting Neuron ◽  
Current Pulses ◽  
Low Concentrations ◽  
Dynamical Properties ◽  
Mode Transitions ◽  
Model Support

1. Previous computational studies of models of neuron R15 in Aplysia have indicated that several distinct modes of electrical activity may coexist at a given set of parameters, that this multistability can be modulated by transmitters such as serotonin (5-HT) and that brief perturbations of the membrane potential can induce persistent changes in the mode of electrical activity. To test these predictions, the responses of R15 neurons to injections of brief (1.5 s) current pulses were recorded intracellularly in the absence and presence of 5-HT. 2. In the absence of 5-HT, brief perturbations induced abrupt transitions in the electrical activity from bursting to beating. Such transitions were observed in approximately 20% of the cases. The duration of beating activity varied from several seconds to tens of minutes. In the presence of low concentrations (1 microM) of 5-HT, both the probability of mode transitions and the duration of induced beating activity increased significantly. 3. These results indicate that at least two stable modes of electrical activity can coexist in R15 neurons and that this bistability can be regulated by 5-HT. In general, these conclusions agree with the results from analyses of mathematical models of R15. Although the function of these dynamic properties in R15 is speculative, our results, interpreted on the background of the model, support the notion that nonlinear dynamical properties of individual neurons can endow them with richer forms of information processing than has generally been appreciated.

Salinity tolerance and osmoregulation of Taeniomembers microstomus (Gunther, 1861) (Pisces: Mugiliformes: Atherinidae) from Australian salt lakes

1969 ◽  
Vol 20 (2) ◽  
pp. 157 ◽  
Author(s):  
LC Lui
Keyword(s):  
Salinity Tolerance ◽  
Body Fluid ◽  
Freezing Point ◽  
Probit Analysis ◽  
Salt Lakes ◽  
Salinity Range ◽  
Freezing Point Depression

Salinity tolerance and osmoregulation of a population of Taeniomembras microstomus were studied. Results indicated that this atherinid fish is extremely euryhaline. Probit analysis revealed that the upper and lower L.D.50 values for salinity were 108‰ and 3.3‰, respectively. Salinity tolerance was apparently independent of acclimation, Taeniomembras microstomus has remarkable hypo-osmoregulatory abilities. The freezing point depression of body fluid varied from 0.558� to 2.729� when fish were exposed to a salinity range of 5-120‰.

INFLUENCE OF A HIGHLY PURIFIED THYMUS EXTRACT UPON THE ADRENALS OF GUINEA-PIGS

1955 ◽  
Vol 13 (1) ◽  
pp. 7-10 ◽  
Author(s):  
J. COMSA ◽  
H. LEROUX
Keyword(s):  
Vitamin C ◽  
Adrenal Cortex ◽  
Guinea Pigs ◽  
Relative Weight ◽  
Cholesterol Content ◽  
Transient Increase ◽  
Daily Injection ◽  
Thymus Extract

SUMMARY 1. An attempt has been made to demonstrate the influence of the thymus upon the adrenal in guinea-pigs by daily injection of unphysiological amounts of a highly purified thymus extract. 2. Such injections caused a marked but transient increase in both the vitamin C and cholesterol content of the adrenal. 3. Morphologically, there was a decrease in the weight of the adrenal cortex relative to that of the whole gland, while the relative weight of the medulla increased correspondingly. This change was not transient, but persisted up to 110 days of treatment. 4. It is concluded that the effect of injecting thymus extract is opposite to that of injecting ACTH and gives rise to a resting condition of the adrenal cortex.

scholarly journals Electricial Activity in a Slug Ganglion in Relation to the Concentration of Locke Solution

1956 ◽  
Vol 33 (2) ◽  
pp. 282-294
Author(s):  
G. M. HUGHES
Keyword(s):  
Electrical Activity ◽  
Body Fluid ◽  
Silver Chloride ◽  
Rhythmic Activity ◽  
Solution Concentration ◽  
Characteristic Size ◽  
Bathing Solution ◽  
Locke Solution ◽  
Silver Silver ◽  
Silver Silver Chloride

1. A method is described by which the electrical activity of single units in the isolated pedal ganglia of the slug Agriolimax reticulatus can be studied quantitatively for many hours. When tungsten microelectrodes were used the results were more simple and less variable than those obtained using external silver-silver chloride electrodes. 2. The activity studied consisted of potentials of characteristic size and shape. Their frequency was usually about 30/min. No correlation was observed between these and any rhythmic activity of the animal. 3. The blood of the slug shows considerable variation in its water-content, ranging from a concentration equivalent to that of a 1.4 Locke solution in dehydrated animals to one equivalent to 0-45 Locke in hydrated animals. Animals taken straight from a garden in the evening had a body fluid equivalent to 0.7 Locke. 4. The ‘spontaneous’ activity of the isolated pedal ganglia was greatly affected by a change in the concentration of the bathing solution. Concentration of the medium decreased the activity and dilution increased the activity. This effect appears to be due to the change in osmotic pressure rather than a change in the concentration of individual ions. The possible significance of these changes in the life of the animal is discussed.

Measurement of spontaneous neuronal membrane activity by time lapse confocal microscopy

1995 ◽  
Vol 53 ◽  
pp. 972-973
Author(s):  
R H. Selinfreund ◽  
A. H. Cornell-Bell
Keyword(s):  
Membrane Potential ◽  
Confocal Microscopy ◽  
Patch Clamp ◽  
Electrical Activity ◽  
Time Lapse ◽  
Neuronal Firing ◽  
Neuronal Membrane ◽  
Pituitary Cells ◽  
Patch Clamp Recording ◽  
Spontaneous Electrical Activity

Cellular electrophysiological properties are normally monitored by standard patch clamp techniques . The combination of membrane potential dyes with time-lapse laser confocal microscopy provides a more direct, least destructive rapid method for monitoring changes in neuronal electrical activity. Using membrane potential dyes we found that spontaneous action potential firing can be detected using time-lapse confocal microscopy. Initially, patch clamp recording techniques were used to verify spontaneous electrical activity in GH4\C1 pituitary cells. It was found that serum depleted cells had reduced spontaneous electrical activity. Brief exposure to the serum derived growth factor, IGF-1, reconstituted electrical activity. We have examined the possibility of developing a rapid fluorescent assay to measure neuronal activity using membrane potential dyes. This neuronal regeneration assay has been adapted to run on a confocal microscope. Quantitative fluorescence is then used to measure a compounds ability to regenerate neuronal firing.The membrane potential dye di-8-ANEPPS was selected for these experiments. Di-8- ANEPPS is internalized slowly, has a high signal to noise ratio (40:1), has a linear fluorescent response to change in voltage.

Fate of sperm membrane in fertilized ova

1993 ◽  
Vol 51 ◽  
pp. 40-41
Author(s):  
Frank J. Longo
Keyword(s):  
Electron Microscopy ◽  
Electrical Activity ◽  
Sea Urchins ◽  
Morphological Changes ◽  
Integrated System ◽  
Electrophysiological Recording ◽  
Experimental Conditions ◽  
The Status ◽  
Sperm Membrane ◽  
Temporal And Spatial

Measurement of the egg's electrical activity, the fertilization potential or the activation current (in voltage clamped eggs), provides a means of detecting the earliest perceivable response of the egg to the fertilizing sperm. By using the electrical physiological record as a “real time” indicator of the instant of electrical continuity between the gametes, eggs can be inseminated with sperm at lower, more physiological densities, thereby assuring that only one sperm interacts with the egg. Integrating techniques of intracellular electrophysiological recording, video-imaging, and electron microscopy, we are able to identify the fertilizing sperm precisely and correlate the status of gamete organelles with the first indication (fertilization potential/activation current) of the egg's response to the attached sperm. Hence, this integrated system provides improved temporal and spatial resolution of morphological changes at the site of gamete interaction, under a variety of experimental conditions. Using these integrated techniques, we have investigated when sperm-egg plasma membrane fusion occurs in sea urchins with respect to the onset of the egg's change in electrical activity.

Ineffective Thrombopoiesis

1990 ◽  
Vol 48 (3) ◽  
pp. 266-267
Author(s):  
JM Radley ◽  
SL Ellis
Keyword(s):  
Microscopic Examination ◽  
Phosphate Buffer ◽  
Primary Myelofibrosis ◽  
Transient Increase ◽  
Major Difficulty ◽  
Adult Mice ◽  
Dense Cytoplasm

In effective thrombopoies is has been inferred to occur in several disease sates from considerations of megakaryocyte mass and platelet kinetics. Microscopic examination has demonstrated increased numbers of megakaryocytes, with a typical forms particularly pronounced, in primary myelofibrosis. It has not been documented if megakaryocyte ever fail to reach maturity in non-pathological situations. A major difficulty of establishing this is that the number of megakaryocytes normally present in the marrow is extremely low. A large transient increase in megakaryocytopoiesis can how ever be induced in mice by an injection of 5-fluorouracil. We have utilised this treatment and report here evidence for in effective thrombopoies is in healthy mice.Adult mice were perfused (2% glutaraldehyde in 0.08M phosphate buffer, pH 7.4) 8 days following an injection of 5-fluorouracil (150mg/kg). Femurs were subsequently decalcified in 10% neutral E.D.T.A. and embedded in Spurrs resin. Transverse sections of marrow revealed many megakaryocytes at various stages of maturity. Occasional megakaryocytes (less than 1%) were found to be under going degeneration prior to achieving full maturation and releasing cytoplasm as platelets. These cells were characterized by a peripheral rim of dense cytoplasm which enveloped a mass of organelles and vacuoles (Fig. 1). Numerous microtubules were foundaround and with in the organelle-rich zone (Fig 2).

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