scholarly journals An axon initial segment is required for temporal precision in action potential encoding by neuronal populations

2018 ◽  
Vol 4 (11) ◽  
pp. eaau8621 ◽  
Author(s):  
Elinor Lazarov ◽  
Melanie Dannemeyer ◽  
Barbara Feulner ◽  
Jörg Enderlein ◽  
Michael J. Gutnick ◽  
...  
Keyword(s):  
Initial Segment ◽  
Axon Initial Segment ◽  
High Concentration ◽  
Information Encoding ◽  
Temporal Precision ◽  
Network Function ◽  
Evolutionary Innovation ◽  
Voltage Dependent ◽  
Vitro Model

Central neurons initiate action potentials (APs) in the axon initial segment (AIS), a compartment characterized by a high concentration of voltage-dependent ion channels and specialized cytoskeletal anchoring proteins arranged in a regular nanoscale pattern. Although the AIS was a key evolutionary innovation in neurons, the functional benefits it confers are not clear. Using a mutation of the AIS cytoskeletal protein βIV-spectrin, we here establish an in vitro model of neurons with a perturbed AIS architecture that retains nanoscale order but loses the ability to maintain a high NaV density. Combining experiments and simulations, we show that a high NaV density in the AIS is not required for axonal AP initiation; it is, however, crucial for a high bandwidth of information encoding and AP timing precision. Our results provide the first experimental demonstration of axonal AP initiation without high axonal channel density and suggest that increasing the bandwidth of the neuronal code and, hence, the computational efficiency of network function, was a major benefit of the evolution of the AIS.

scholarly journals Oxidative Stress Induces Disruption of the Axon Initial Segment

ASN NEURO ◽  
2017 ◽  
Vol 9 (6) ◽  
pp. 175909141774542 ◽  
Author(s):  
Kareem C. Clark ◽  
Brooke A. Sword ◽  
Jeffrey L. Dupree
Keyword(s):  
Oxidative Stress ◽  
Central Nervous System ◽  
Nervous System ◽  
Cortical Neurons ◽  
Initial Segment ◽  
Reactive Oxygen ◽  
Axon Initial Segment ◽  
Voltage Dependent ◽  
Reversible Loss

The axon initial segment (AIS), the domain responsible for action potential initiation and maintenance of neuronal polarity, is targeted for disruption in a variety of central nervous system pathological insults. Previous work in our laboratory implicates oxidative stress as a potential mediator of structural AIS alterations in two separate mouse models of central nervous system inflammation, as these effects were attenuated following reactive oxygen species scavenging and NADPH oxidase-2 ablation. While these studies suggest a role for oxidative stress in modulation of the AIS, the direct effects of reactive oxygen and nitrogen species (ROS/RNS) on the stability of this domain remain unclear. Here, we demonstrate that oxidative stress, as induced through treatment with 3-morpholinosydnonimine (SIN-1), a spontaneous ROS/RNS generator, drives a reversible loss of AIS protein clustering in primary cortical neurons in vitro. Pharmacological inhibition of both voltage-dependent and intracellular calcium (Ca2+) channels suggests that this mechanism of AIS disruption involves Ca2+ entry specifically through L-type voltage-dependent Ca2+ channels and its release from IP3-gated intracellular stores. Furthermore, ROS/RNS-induced AIS disruption is dependent upon activation of calpain, a Ca2+-activated protease previously shown to drive AIS modulation. Overall, we demonstrate for the first time that oxidative stress, as induced through exogenously applied ROS/RNS, is capable of driving structural alterations in the AIS complex.

Vancomycin Adsorption During in vitro Model of Hemoperfusion with HA380 Cartridge

Nephron ◽  
2021 ◽  
pp. 1-7
Author(s):  
Ilaria Godi ◽  
Anna Lorenzin ◽  
Silvia De Rosa ◽  
Gianlorenzo Golino ◽  
Maira Knust ◽  
...  
Keyword(s):  
Complete Removal ◽  
Potential Interaction ◽  
Blood Purification ◽  
Therapeutic Monitoring ◽  
High Concentration ◽  
Langmuir Isotherm Model ◽  
Vitro Model ◽  
Kinetics Of ◽  
Balanced Solution

<b><i>Introduction:</i></b> A critical point for using blood purification during sepsis may be the potential interaction with antimicrobial therapy, the mainstay of sepsis treatment. The aim of our study was to investigate the vancomycin removal during hemoperfusion (HP) using HA380 cartridge. <b><i>Methods:</i></b> This is an experimental study, in which 500 mL of solution was circulated in a closed-circuit (blood flow of 250 mL/min) simulating HP ran using HA380. Vancomycin was added to reach a through concentration or a very high concentration to evaluate the removal ratio (RR) during 120 min of HP. Comparison between blood-crystalloid solution and balanced solution was performed by using Kruskal-Wallis test. The kinetics of vancomycin removal and the adsorption isotherm were evaluated. <b><i>Results:</i></b> We found a complete removal of vancomycin at baseline through concentration of 23.0 ± 7.4 mg/L. Using extremely high concentration (baseline 777.0 ± 62.2 mg/L), RR was 90.1 ± 0.6% at 5 min and 99.2 ± 0.6% at 120 min. No difference in terms of RR was found between blood-crystalloid mixture and balanced solution. The kinetics of the vancomycin reduction followed an exponential decay. Repeated boluses (total amount of 2,000 mg) resulted in cumulative adsorption of 1,919.4 mg with RR of 96.6 ± 1.4%, regardless of the amount injected (100 vs. 500 mg). Vancomycin adsorption onto HA380 followed the Langmuir isotherm model. <b><i>Conclusions:</i></b> A considerable amount of vancomycin was rapidly removed during in vitro HP with HA380. Clinical studies are needed to determine whether this may lead to underdosing. Drug therapeutic monitoring is highly recommended when using HA380 for blood purification in patients receiving vancomycin.

Role of calcium and calmodulin in release of kallikrein and tonin from rat submandibular gland

1986 ◽  
Vol 250 (3) ◽  
pp. C480-C485 ◽  
Author(s):  
S. R. Maitra ◽  
O. A. Carretero ◽  
S. W. Smith ◽  
S. F. Rabito
Keyword(s):  
Submandibular Gland ◽  
Incubation Medium ◽  
High Concentration ◽  
Calcium Blockers ◽  
Control Value ◽  
Voltage Dependent ◽  
Voltage Dependent Calcium Channels ◽  
Intracellular Mediators

We investigated the role of calcium and calmodulin as intracellular mediators of kallikrein and tonin release induced by norepinephrine (NE). We studied the secretion rate of kallikrein and tonin from submandibular gland of rat in response to NE in the presence or absence of calcium, two calcium blockers, and four different calmodulin antagonists. Submandibular gland slices were incubated in vitro, and glandular kallikrein and tonin secreted into the incubation medium were determined by direct radioimmunoassays and expressed as nanograms per minute per milligram tissue. NE (10(-5) and 10(-4) M) increased the kallikrein secretion from the control value of 8.2 +/- 2.6 to 134.9 +/- 41.4 (P less than 0.05) and to 191.2 +/- 62.7 (P less than 0.05), and the release of tonin from a basal rate of 3.5 +/- 0.6 to 51.5 +/- 9.1 (P less than 0.05) and to 64.4 +/- 13.7 (P less than 0.05). The deletion of calcium and addition of EGTA into the incubation medium significantly attenuated the secretion of kallikrein and tonin induced by NE. Nifedipine, at concentrations which inhibit voltage-dependent calcium channels, did not affect the release of kallikrein and tonin, and only a high concentration (10(-4) M) reduced the release. TMB-8, a blocker of intracellular calcium, had no effect either. Phenothiazines, triflupromazine (10(-6) M) and trifluoperazine (10(-4) M), decreased significantly the kallikrein release elicited by 10(-5) M NE.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals The Swallowing Characteristics of Thickeners, Jellies and Yoghurt Observed Using an In Vitro Model

Dysphagia ◽  
2019 ◽  
Vol 35 (4) ◽  
pp. 685-695 ◽  
Author(s):  
Simmi Patel ◽  
William J. McAuley ◽  
Michael T. Cook ◽  
Yi Sun ◽  
Shaheen Hamdy ◽  
...  
Keyword(s):  
Transit Time ◽  
Mechanical Model ◽  
Xanthan Gum ◽  
In Vitro Model ◽  
High Concentration ◽  
High Concentrations ◽  
Vitro Model ◽  
Thickening Agents

Abstract Drinks and foods may be thickened to improve swallowing safety for dysphagia patients, but the resultant consistencies are not always palatable. Characterising alternative appetising foods is an important task. The study aims to characterise the in vitro swallowing behaviour of specifically formulated thickened dysphagia fluids containing xanthan gum and/or starch with standard jellies and yoghurt using a validated mechanical model, the “Cambridge Throat”. Observing from the side, the model throat can follow an experimental oral transit time (in vitro-OTT) and a bolus length (BL) at the juncture of the pharynx and larynx, to assess the velocity and cohesion of bolus flow. Our results showed that higher thickener concentration produced longer in vitro-OTT and shorter BL. At high concentration (spoon-thick), fluids thickened with starch-based thickener showed significantly longer in vitro-OTT than when xanthan gum-based thickener was used (84.5 s ± 34.5 s and 5.5 s ± 1.6 s, respectively, p < 0.05). In contrast, at low concentration (nectar-like), fluids containing xanthan gum-based thickener demonstrated shorter BL than those of starch-based thickener (6.4 mm ± 0.5 mm and 8.2 mm ± 0.8 mm, respectively, p < 0.05). The jellies and yoghurt had comparable in vitro-OTT and BL to thickeners at high concentrations (honey-like and spoon-thick), indicating similar swallowing characteristics. The in vitro results showed correlation with published in vivo data though the limitations of applying the in vitro swallowing test for dysphagia studies were noted. These findings contribute useful information for designing new thickening agents and selecting alternative and palatable safe-to-swallow foods.

Release of galanin from isolated perfused porcine adrenal glands: role of splanchnic nerves

1991 ◽  
Vol 261 (1) ◽  
pp. E31-E40 ◽  
Author(s):  
J. J. Holst ◽  
M. Ehrhart-Bornstein ◽  
T. Messell ◽  
S. S. Poulsen ◽  
H. Harling
Keyword(s):  
Nerve Stimulation ◽  
Adrenal Glands ◽  
Splanchnic Nerve ◽  
High Concentration ◽  
Vitro Model ◽  
Arterial Plasma ◽  
Regulatory Functions ◽  
Splanchnic Nerve Stimulation

We found a high concentration of galanin in extracts of porcine adrenal glands (114 pmol/g). By immunohistochemistry, galanin was localized to groups of medullary cells previously shown to produce norepinephrine. To study mechanisms for the release of galanin, we developed the following in vitro model: isolated perfused porcine adrenals with intact splanchnic nerve supply. When the nerves were electrically stimulated, epinephrine and norepinephrine secretion increased 276- and 291-fold, respectively, and galanin release increased up to 1,300-fold. Acetylcholine at 10(-6) M stimulated galanin release, and hexamethonium almost abolished the response to nerve stimulation. Galanin infusions had no effect on epinephrine and norepinephrine secretion in concentrations of 10(-8) and 10(-7) M, but increased both cortisol and aldosterone secretion (P less than 0.05). Splanchnic nerve stimulation in anesthetized pigs increased the concentration of galanin in the caval vein but not in arterial plasma. It is concluded that galanin, coreleased with catecholamines from the adrenal glands, may have endocrine functions but that galanin may also have local regulatory functions in the adrenals.

Immunolocalisation of collagenase in rabbit periosteal tissue explants and extraction of the enzyme. The effect of the cytokines IL-1 alpha and EGF

1994 ◽  
Vol 107 (4) ◽  
pp. 1047-1053 ◽  
Author(s):  
E. van der Zee ◽  
V. Everts ◽  
K. Hoeben ◽  
W. Beertsen
Keyword(s):  
Extracellular Matrix ◽  
In Vitro Model ◽  
Interleukin 1 ◽  
Immunohistochemical Analysis ◽  
Model System ◽  
High Concentration ◽  
Active Collagenase ◽  
Epidermal Growth ◽  
Vitro Model

The effect of interleukin-1 alpha (IL-1 alpha) and murine epidermal growth factor (EGF) on incorporation of endogenously produced collagenase in the extracellular matrix of soft connective tissue was studied in an in vitro model system using periosteal explants obtained from rabbit calvariae. Immunohistochemical analysis indicated the highest level of collagenase in explants cultured for 72 hours with IL-1 alpha in combination with EGF. Most enzyme appeared to be associated with the extracellular matrix, but labeling was also found in numerous fibroblast-like cells. Explants cultured in the presence of IL-1 alpha alone contained less enzyme and in periostea treated without cytokines, or with EGF alone, only a faint label, if any, was seen. Freshly isolated, non-cultured periostea contained no detectable enzyme. Extraction of collagenase from periostea revealed that: (1) non-cultured periosteum did not contain detectable levels of enzyme. (2) The amount of total activatable enzyme synergistically increased (10-fold) under the influence of IL-1 alpha and EGF, whereas IL-1 alpha alone showed a 4-fold enhancement compared to control or EGF-incubated explants. (3) The latent fraction of the enzyme was synergistically increased (up to 100-fold or more) in periostea cultured in the presence of IL-1 alpha + EGF (21.17 mU/explant versus 0.05 mU/explant in controls). (4) Active collagenase, on the other hand, appeared to be present in a relatively high concentration in explants cultured without cytokines (2.45 mU/explant versus 0.36 mU/explant in IL-1 alpha + EGF-treated explants).(ABSTRACT TRUNCATED AT 250 WORDS)

Encoding the Timing of Inhibitory Inputs

2005 ◽  
Vol 93 (5) ◽  
pp. 2887-2897 ◽  
Author(s):  
Patrick O. Kanold ◽  
Paul B. Manis
Keyword(s):  
Spike Timing ◽  
Dorsal Cochlear Nucleus ◽  
Heterogeneous Distribution ◽  
Information Encoding ◽  
Neuronal Populations ◽  
Voltage Change ◽  
Voltage Dependent ◽  
Inhibitory Potential ◽  
Neuronal Systems

Many neuronal systems represent information by the timing of individual spikes, and it is generally assumed that spike timing predominantly encodes excitatory inputs. We show here that the timing of inhibition can also be explicitly encoded in spike times using time-dependent and voltage-dependent properties of a rapidly inactivating potassium channel ( IKIF). In vitro recordings in rat dorsal cochlear nucleus show that the effects of inhibition on spike timing can long outlast the duration of the inhibitory potential and that this depends only on the membrane voltage change during the inhibitory postsynaptic potential. Modeling results show that small neuronal populations with a heterogeneous distribution of IKIF voltage dependence can robustly encode intervals of >100 ms between inhibition and excitation. Thus neuronal systems can detect and represent the precise timing of inhibition, suggesting the importance of inhibition in information encoding.

scholarly journals Background Synaptic Conductance and Precision of EPSP-Spike Coupling at Pyramidal Cells

2005 ◽  
Vol 93 (6) ◽  
pp. 3248-3256 ◽  
Author(s):  
Veronika Zsiros ◽  
Shaul Hestrin
Keyword(s):  
Time Course ◽  
Pyramidal Cells ◽  
Spike Timing ◽  
Synaptic Activity ◽  
Synaptic Conductance ◽  
Temporal Precision ◽  
Voltage Dependent ◽  
Cortical Slices

The temporal precision of converting excitatory postsynaptic potentials (EPSPs) into spikes at pyramidal cells is critical for the coding of information in the cortex. Several in vitro studies have shown that voltage-dependent conductances in pyramidal cells can prolong the EPSP time course resulting in an imprecise EPSP-spike coupling. We have used dynamic-clamp techniques to mimic the in vivo background synaptic conductance in cortical slices and investigated how the ongoing synaptic activity may affect the EPSP time course near threshold and the EPSP spike coupling. We report here that background synaptic conductance dramatically diminished the depolarization related prolongation of the EPSPs in pyramidal cells and improved the precision of spike timing. Furthermore, we found that background synaptic conductance can affect the interaction among action potentials in a spike train. Thus the level of ongoing synaptic activity in the cortex may regulate the capacity of pyramidal cells to process temporal information.

Effects of prostaglandins and endoperoxide analogs on canine saphenous vein

1977 ◽  
Vol 233 (3) ◽  
pp. H361-H368
Author(s):  
M. R. Goldberg ◽  
V. S. Hebert ◽  
P. J. Kadowitz
Keyword(s):  
Saphenous Vein ◽  
High Concentration ◽  
Venous Tone ◽  
Canine Saphenous Vein ◽  
Saphenous Veins ◽  
Venous Function ◽  
Vitro Model ◽  
Induced Changes

Contractile effects of prostaglandins (PGs) have not been widely studied in the canine saphenous vein, as in vitro model for venous function. We studied responses to two PG endoperoxide analogs (PGEA) and to monoenoic and bisenoic PGs of the A, B, E, and F series in helical strips of canine saphenous veins. Isometric changes in force were measured. All agents elicited marked contractions. PGEA were several orders of magnitude more potent than either primary PGs or other venoconstrictors, including norepinephrine. E- and A-types PG had unusual concentration and contraction at high concentration. B-types PG evoked a biphasic contractile response. Bisenoic PGs tended to be more potent than monoenoic PGs of the same type. These results show that canine saphenous veins are highly responsive to PGs and PGEA. These data suggest that these substances could influence venous tone in vivo. However, PG-induced changes in venous tone would depend on which PG or intermediate was present, on PG concentration, and on the prior state of venous tone.

scholarly journals HGG-03. THE GLYCOSPHINGOLIPIDS METABOLISM IS A NOVEL TARGET IN H3K27M-MUTANT DIFFUSE MIDLINE GLIOMA

2021 ◽  
Vol 23 (Supplement_1) ◽  
pp. i17-i17
Author(s):  
Claudia Paret ◽  
Roger Sandhoff ◽  
Khalifa El Malki ◽  
Katrin B M Frauenknecht ◽  
Arthur Wingerter ◽  
...  
Keyword(s):  
Primary Cells ◽  
Lysosomal Storage ◽  
High Concentration ◽  
Paediatric Patients ◽  
Tumour Entity ◽  
Vitro Model ◽  
Novel Target ◽  
Layer Chromatography ◽  
Diffuse Midline Glioma

Abstract H3K27M-mutant diffuse midline glioma (H3K27M-mutant DMG) is a rare malignant brain tumour entity in children and adults with a median overall survival of around 12 months. Genomic and proteomic analysis may help to identify new target structures, however not all relevant targets are covered by these analyses. Glycosphingolipids and particularly gangliosides play a major role in brain development and have been involved in the pathology of brain tumours. The conversion of ceramide to glucosylceramide via glucosylceramide synthase (GCS) is one of the first steps in the synthesis of glycosphingolipids. Therefore, targeting GCS will inhibit their synthesis. Here we analysed the glycosphingolipids composition and tested GCS inhibitors in an in vitro model of H3K27M-mutant DMG. Methods: H3K27M-mutant DMG primary cells were established from needle biopsies of two paediatric patients and characterised by immunohistochemistry. Glycosphingolipids were analysed by thin layer chromatography, liquid chromatography-coupled tandem mass spectrometry and flow cytometry. The effect of the GCS inhibitor eliglustat on the cell proliferation was examined. Results. The primary cells maintained the features of the tumour of origin, including the H3K27M mutation. Neutral glycosphingolipids with 1 to 4 monosaccharides and the ganglioside GD2 were expressed at high concentration. Eliglustat completely abrogated the proliferation of the H3K27M-mutant DMG primary cells. Conclusions. The glycosphingolipids oncometabolism represents a novel target in H3K27M-mutant DMG. The GCS inhibitors eliglusat and miglustat are already used to treat paediatric patients with the lysosomal storage disorders Niemann Pick’s and Gaucher′s disease and miglustat can cross the blood-brain barrier. Thus, our finding may accelerate the access of H3K27M-mutant DMG patients to novel innovative clinical studies based on the inhibition of the glycosphingolipids metabolism.

Sign in / Sign up

Export Citation Format

Share Document