scholarly journals Phospholipid turnover in Torpedo marmorata electric organ during discharge in vivo

1976 ◽  
Vol 158 (3) ◽  
pp. 557-565 ◽  
Author(s):  
J E Bleasdale ◽  
J N Hawthorne ◽  
L Widlund ◽  
E Heilbronn
Keyword(s):  
Electrical Stimulation ◽  
Density Gradient ◽  
Synaptic Vesicles ◽  
Electric Organ ◽  
The Other ◽  
Torpedo Marmorata ◽  
Phospholipid Turnover ◽  
Unstimulated Control ◽  
The Brain

One electric organ of anaesthetized Torpedo marmorata was stimulated through electrodes placed on the electric lobe of the brain. Nerves to the other electric organ were cut to provide an unstimulated control. Glucose 6-[32P]phosphate was injected into each organ 16h before electrical stimulation. After stimulation for 10 min at 5 Hz, the organs were removed homogenized and centrifuged on a density gradient for the preparation of subcellular fractions. Stimulation increased the incorporation of 32P into phosphatidate, phosphatidylinositol and phosphatidylcholine. The increased phosphatidate labelling, but not that of the other two lipids, was seen in fractions rich in synaptic vesicles. Stimulation had no effect on ATP labelling. The phosphatidate content of most fractions fell slightly after stimulation, but amounts of other phospholipids were not affected.

scholarly journals Submicroscopic Changes of the Nerve Endings in the Adrenal Medulla after Stimulation of the Splanchnic Nerve

1957 ◽  
Vol 3 (4) ◽  
pp. 611-614 ◽  
Author(s):  
Eduardo De Robertis ◽  
Alberto Vaz Ferreira
Keyword(s):  
Electrical Stimulation ◽  
Electron Microscope ◽  
Adrenal Medulla ◽  
Synaptic Vesicles ◽  
Splanchnic Nerve ◽  
The Other ◽  
Nerve Endings ◽  
The Mean ◽  
Increased Activity ◽  
Stimulation Of

The nerve endings of the adrenal medulla of the rabbit were studied under the electron microscope in the normal condition and after prolonged electrical stimulation of the splanchnic nerve. With a stimulus of 100 pulses per second for 10 minutes, there is an increase in the number of synaptic vesicles in the nerve ending. The mean number is of 82.6 vesicles per square micron in the normal and of 132.7 per square micron in the stimulated glands. With a stimulus of 400 pulses per second for 10 minutes, there is a considerable depletion of synaptic vesicles and other changes occur in the nerve endings. The mean number of vesicles is of 29.2 per square micron. These results are interpreted as indicative of an increased activity of the ending in one case, and as a diminished activity and fatigue of the synaptic junction in the other.

Alternative splicing of the mouse profilin II gene generates functionally different profilin isoforms

2000 ◽  
Vol 113 (21) ◽  
pp. 3795-3803 ◽  
Author(s):  
A. Di Nardo ◽  
R. Gareus ◽  
D. Kwiatkowski ◽  
W. Witke
Keyword(s):  
Alternative Splicing ◽  
Cell Motility ◽  
Hela Cells ◽  
The Other ◽  
Actin Dynamics ◽  
High Affinity ◽  
Other Hand ◽  
The Brain

Profilins are a conserved family of proteins participating in actin dynamics and cell motility. In the mouse, two profilin genes are known. Profilin I is expressed universally at high levels, while profilin II is expressed mainly in the brain. Here we describe the occurrence of two mouse profilin II isoforms, A and B, which are derived by alternative splicing. They are identical through residue 107 of the protein, but then have distinct C-terminal sequences. Profilin IIA binds to poly-L-proline and actin with high affinity similar to profilin I. Profilin IIB on the other hand does not bind to actin and the affinity for poly-L-proline is greatly diminished. However, tubulin was found to bind to GST-profilin IIB, and in vivo GFP-profilin IIB was recruited to spindles and asters during mitosis in HeLa cells. Our results indicate unexpected diversity in the functions of the profilin family of proteins, and suggest that in mouse profilin IIA is intimately involved in actin dynamics, while profilin IIB associates with other cytoskeletal components.

scholarly journals The heterogeneity of bound acetylcholine and synaptic vesicles

1972 ◽  
Vol 129 (5) ◽  
pp. 1049-1061 ◽  
Author(s):  
R. M. Marchbanks ◽  
M. Israël
Keyword(s):  
Surface Layer ◽  
Synaptic Vesicles ◽  
Osmotic Shock ◽  
Gel Filtration ◽  
Specific Radioactivity ◽  
Electric Organ ◽  
Reciprocal Relationship ◽  
The Other ◽  
Theoretical Treatment ◽  
Torpedo Electric Organ

Synaptic vesicles containing radioactive acetylcholine have been isolated from slices of Torpedo electric organ incubated with radioactive choline. The recently synthesized radioactive acetylcholine is preferentially removed from the vesicles by iso-osmotic gel filtration. There is therefore a small compartment of loosely bound recently synthesized acetylcholine within the monodisperse vesicle fraction. The specific radioactivity of this compartment correlates most closely with the ‘free’ acetylcholine of electric organ that is lost when the tissue is homogenized. Membrane-associated vesicles did not contain any particular enrichment of this compartment. On standing at 6°C the loosely bound compartment stabilizes so that it survives iso-osmotic filtration. A study of this phenomenon revealed that it was proportional to the extent of the loss of tightly bound acetylcholine from the vesicles. Incubation with Ca2+, at pH5.5, or partial hypo-osmotic shock, caused losses of tightly bound acetylcholine and proportional increases in the stabilization of loosely bound acetylcholine of vesicles. Incubation at 20°C caused less loss of tightly bound, and less stabilization of loosely bound, acetylcholine. A theoretical treatment of these exchanges also shows that the random factors promoting loss of tightly bound acetylcholine are statistically correlated with those which cause stabilization of loosely bound acetylcholine. The reciprocal relationship between the exchanges is inconsistent with there being two distinct populations of vesicles, one containing recently synthesized, loosely bound acetylcholine and the other containing tightly bound acetylcholine. It is proposed that all the vesicles contain a core of tightly bound acetylcholine and a surface layer of loosely bound acetylcholine. The origin of the extravesicular acetylcholine and also of the acetylcholine released on stimulation is discussed in the light of these results.

scholarly journals Effect of Topical Adenosine Deaminase Treatment on the Functional Hyperemic and Hypoxic Responses of Cerebrocortical Microcirculation

1984 ◽  
Vol 4 (3) ◽  
pp. 447-457 ◽  
Author(s):  
Eörs Dóra ◽  
Ákos Koller ◽  
Arisztid G. B. Kovách
Keyword(s):  
Electrical Stimulation ◽  
Adenosine Deaminase ◽  
Brain Cortex ◽  
Brain Activation ◽  
Epileptic Seizures ◽  
Direct Electrical Stimulation ◽  
Cyanide Poisoning ◽  
Vascular Volume ◽  
The Brain

The purpose of this study was to investigate the possible importance of adenosine in cerebrocortical vasodilatation accompanying brain activation (epileptic seizures and direct electrical stimulation) and hypoxia (arterial hypoxia and cyanide poisoning of the brain cortex). In chloralose-anesthetized cats a circumscribed area of the brain cortex was treated with adenosine deaminase (Type III; Sigma), which potently deaminates adenosine to the nonvasoactive inosine. Cerebrocortical vascular volume and fluorescence of reduced nicotinamide adenine dinucleotide were measured in vivo by surface fluororeflectometry. The responses of small pial and intracortical vessels to brain activation and hypoxia were studied in brain cortices superfused with artificial (mock) CSF and 5 U/ml adenosine deaminase. It was found that superficially applied adenosine deaminase readily diffuses onto the brain cortex. Prolonged pretreatment of the brain cortices with 0.025 U/ml adenosine deaminase eliminated almost completely the vasodilative effect of 10−7 mol/ml adenosine. The inhibitory effect of the enzyme on adenosine-induced cortical vasodilatation was specific, because 5 U/ml adenosine deaminase did not attenuate the vasodilative potency of 10−8 mol/ml 2-chloroadenosine. Adenosine deaminase (5 U/ml) pretreatment of the brain cortices did not diminish the cerebrocortical vascular volume, which increased with arterial hypoxia, topical cyanide poisoning, and direct electrical stimulation. However, it slightly decreased the vasodilative effect of epileptic seizures. On the basis of these results, it seems very unlikely that adenosine is a critical factor in the control of cerebrovascular tone during arterial hypoxia and brain activation.

scholarly journals Corrosion Study of Implanted Tin Electrodes Using Excessive Electrical Stimulation in Minipigs

Metals ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 389 ◽  
Author(s):  
Suzan Meijs ◽  
Kristian Rechendorff ◽  
Søren Sørensen ◽  
Nico Rijkhoff
Keyword(s):  
Electrical Stimulation ◽  
Tissue Damage ◽  
Charge Injection ◽  
The Other ◽  
Electrochemical Tests ◽  
Implanted Electrodes ◽  
Electrode Degradation ◽  
Lower Charge

(1) Background: Titanium nitride (TiN) electrodes have been used for implantable stimulation and sensing electrodes for decades. Nevertheless, there still is a discrepancy between the in vitro and in vivo determined safe charge injection limits. This study investigated the consequences of pulsing implanted electrodes beyond the in vivo safe charge injection limits. (2) Methods: The electrodes were implanted for a month and then pulsed at 20 mA and 50 mA and 200 Hz and 400 Hz. Afterwards, the electrodes were investigated using electrochemical and analytical methods to evaluate whether electrode degradation had occurred. (3) Results: Electrochemical tests showed that electrodes that pulsed at 20 mA and 200 Hz (lowest electrical dose) had a significantly lower charge injection capacity and higher impedance than the other used and unused electrodes. (4) Conclusions: The electrodes pulsed at the lowest electrical dose, for which no tissue damage was found, appeared to have degraded. Electrodes pulsed at higher electrical doses for which tissue damage did occur, on the other hand, show no significant degradation in electrochemical tests compared to unused implanted and not implanted electrodes. It is thus clear that the tissue surrounding the electrode has an influence on the charge injection properties of the electrodes and vice versa.

scholarly journals Gel-electrophoretic identification of hen brain neurotoxic esterase, labelled with tritiated di-isopropyl phosphorofluoridate

1981 ◽  
Vol 199 (2) ◽  
pp. 323-333 ◽  
Author(s):  
D G Williams ◽  
M K Johnson
Keyword(s):  
Active Site ◽  
Gel Electrophoresis ◽  
Polyacrylamide Gel Electrophoresis ◽  
The Other ◽  
Particulate Fraction ◽  
Molecular Weights ◽  
The Brain ◽  
Neurotoxic Esterase

The particulate fraction from hen brain was labelled with [3H]di-isopropyl phosphorofluoridate (DiPF) and separated by polyacrylamide-gel electrophoresis. Four radioactive protein bands (1--4) of molecular weights 155000, 92000, 60000, and 30000 were resolved. Most of the labelling of bands 2, 3 and 4 was inhibited by preincubation with Paraoxon. The residue in band 4 was sensitive to pH 5.2. Successive treatments with Paraoxon and pH 5.2 resulted in the abolition of bands 3 and 4. Bands 1 and 2 contained one and two polypeptides respectively, whose labelling was sensitive to Mipafox, but one, in band 2, was sensitive to higher concentrations of Paraoxon. The concentrations of the other two polypeptides were 6.7 and 1.95 pmol of DiPF bound/g of brain in bands 1 and 2 respectively. Both were as sensitive to Mipafox as neurotoxic esterase and were also sensitive to phenyl benzylcarbamate. 4-Nitrophenyl di-n-pentylphosphinate given in vivo inhibited neurotoxic esterase and the labelling of the band-1 polypeptide by 82% and 84% respectively, but inhibited the labelling of the band 2 polypeptide by 51%. The phosphinate in vitro produced 98% inhibition of the labelling of the band-1 polypeptide, with only 26% inhibition of the band-2 polypeptide, under conditions sufficient to inhibit neurotoxic esterase totally. Both neurotoxic esterase and the band-1 polypeptide were found in the forebrain at 1.74-fold their concentration in the rest of the brain, whereas the band-2 polypeptide was uniformly distributed. The evidence indicates that the Mipafox-sensitive polypeptide in band 1 is the [3H]DiPF-labelled active-site subunit of neurotoxic esterase. The catalytic-centre activity of the enzyme for phenyl valerate hydrolysis was found to be 2.6 x 10(5) min-1.

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