Distribution Analysis of Axonal Conduction Delay in In vitro Reconstructed Sensory Fiber

2021 ◽  
Vol 141 (12) ◽  
pp. 1331-1339
Author(s):  
Koji Sakai ◽  
Kenta Shimba ◽  
Kiyoshi Kotani ◽  
Yasuhiko Jimbo
Keyword(s):  
Conduction Delay ◽  
Distribution Analysis ◽  
Axonal Conduction ◽  
Sensory Fiber

Effects of octanol on canine subendocardial Purkinje-to-ventricular transmission

1985 ◽  
Vol 249 (6) ◽  
pp. H1228-H1231 ◽  
Author(s):  
R. W. Joyner ◽  
E. D. Overholt
Keyword(s):  
Action Potential ◽  
Conduction Velocity ◽  
Current Flow ◽  
Conduction Delay ◽  
Papillary Muscles ◽  
Maximal Rate ◽  
Gap Junctional ◽  
Junctional Resistance ◽  
P Cells

The effects of 0.2 mM octanol on action potential propagation were investigated using in vitro preparations of canine papillary muscles. In these preparations an action potential initiated in the superficial Purkinje (P) layer propagates across specific Purkinje-ventricular junction (PVJ) sites into the underlying ventricular (V) layer. The conduction delay at PVJ sites increased from 4.85 +/- 1.55 to 8.85 +/- 3.34 (mean +/- SD) ms (n = 10, P less than 0.005), an 82% increase. However, propagation within the V syncytium was much less affected, with a decrease of conduction velocity by only 10% and a decrease in the maximal rate of rise of the action potential of 23%. The results indicate that octanol, which has previously been shown to increase gap junctional resistance, has a preferential effect on PVJ sites, as predicted by the hypothesis that there is a restricted pathway for intracellular current flow from P cells to V cells at these sites.

Measuring gluconeogenesis with [2-13C]glycerol and mass isotopomer distribution analysis of glucose

1995 ◽  
Vol 269 (3) ◽  
pp. E516-E523 ◽  
Author(s):  
O. Peroni ◽  
V. Large ◽  
M. Beylot
Keyword(s):  
Glucose Production ◽  
Distribution Analysis ◽  
Isotopomer Distribution ◽  
Mass Isotopomer Distribution Analysis ◽  
Total Glucose ◽  
Glucose Output ◽  
Total Glycerol ◽  
Mass Isotopomer

We tested the validity of the use of [2-13C]glycerol and of the mass isotopomer distribution analysis of glucose for measuring gluconeogenesis in vitro and in vivo. When isolated rat livers (starved for 48 h) were infused with labeled glycerol without or with lactate+pyruvate, gluconeogenesis accounted for > 90% of glucose production. When glucose was added to the infusate so that glucose produced by the liver represented only 80 or 45% of total glucose output, this dilution could be calculated from the mass isotopomer distribution of glucose. When postabsorptive and starved rats were infused with [2-13C]glycerol, gluconeogenesis accounted for 54 +/- 2 and 89 +/- 1%, respectively, of glucose production. However, accurate measures could be obtained, particularly in postabsorptive rats, only with high tracer infusion rates (representing > or = 50% of endogenous glycerol production rate). In both groups of rats, these infusion rates resulted in an increase in total glycerol turnover rate and gluconeogenesis from glycerol. In addition, hepatic concentration of glycerol 3-phosphate was increased. In conclusion, [2-13C]glycerol infusion and mass isotopomer distribution analysis of glucose appear to be useful methods for studies of gluconeogenesis in vitro and in vivo; however, accurate measurements in vivo can be obtained only at the expense of some perturbation of the metabolic pathway studied.

scholarly journals Impact of Yttrium-90 Microsphere Density, Flow Dynamics, and Administration Technique on Spatial Distribution: Analysis Using an In Vitro Model

2017 ◽  
Vol 28 (2) ◽  
pp. 260-268.e2 ◽  
Author(s):  
Marcus Caine ◽  
Michael S. McCafferty ◽  
Scott McGhee ◽  
Pedro Garcia ◽  
Wayne M. Mullett ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
In Vitro Model ◽  
Flow Dynamics ◽  
Distribution Analysis ◽  
Density Flow ◽  
Vitro Model ◽  
Yttrium 90

scholarly journals THE EFFECT OF DEPRIVATION OF GLUCOSE ON THE ULTRASTRUCTURE AND FUNCTION OF THE SUPERIOR CERVICAL GANGLION OF THE RAT IN VITRO

1966 ◽  
Vol 29 (2) ◽  
pp. 267-285 ◽  
Author(s):  
P. Nicolescu ◽  
M. Dolivo ◽  
C. Rouiller ◽  
C. Foroglou-Kerameus
Keyword(s):  
Synaptic Transmission ◽  
Ganglion Cells ◽  
Glucose Deprivation ◽  
Axonal Conduction ◽  
Electrophysiological Measurements ◽  
Cervical Ganglion ◽  
Cervical Sympathetic ◽  
Ultrastructure And Function ◽  
And Function

The superior cervical sympathetic ganglion of the rat kept in vitro in a bicarbonate-buffered Krebs' solution retains its capacity for synaptic transmission and axonal conduction during more than 36 hr. After glucose withdrawal, synaptic transmission is lost in 2½ hr and this loss is irreversible; on the other hand, axonal conduction can still be measured on the postganglionic nerve for more than 24 hr after glucose deprivation. Electrophysiological measurements as well as electron microscope studies revealed specific changes at the level of the presynaptic terminal processes, while the ganglion cells and the satellite cells remained relatively unaltered. The presynaptic lesion due to lack of glucose can be prevented by keeping the preparation in vitro at 6°C. This strongly suggests that this lesion results from a major disturbance of the metabolism of the presynaptic fibers.

scholarly journals Acceleration of conduction velocity linked to clustering of nodal components precedes myelination

2015 ◽  
Vol 112 (3) ◽  
pp. E321-E328 ◽  
Author(s):  
Sean A. Freeman ◽  
Anne Desmazières ◽  
Jean Simonnet ◽  
Marie Gatta ◽  
Friederike Pfeiffer ◽  
...  
Keyword(s):  
Hippocampal Neurons ◽  
Pyramidal Neurons ◽  
Axonal Conduction ◽  
Electrophysiological Recordings ◽  
Single Axon ◽  
Physiological Relevance ◽  
Saltatory Conduction ◽  
Insight Into

High-density accumulation of voltage-gated sodium (Nav) channels at nodes of Ranvier ensures rapid saltatory conduction along myelinated axons. To gain insight into mechanisms of node assembly in the CNS, we focused on early steps of nodal protein clustering. We show in hippocampal cultures that prenodes (i.e., clusters of Nav channels colocalizing with the scaffold protein ankyrinG and nodal cell adhesion molecules) are detected before myelin deposition along axons. These clusters can be induced on purified neurons by addition of oligodendroglial-secreted factor(s), whereas ankyrinG silencing prevents their formation. The Nav isoforms Nav1.1, Nav1.2, and Nav1.6 are detected at prenodes, with Nav1.6 progressively replacing Nav1.2 over time in hippocampal neurons cultured with oligodendrocytes and astrocytes. However, the oligodendrocyte-secreted factor(s) can induce the clustering of Nav1.1 and Nav1.2 but not of Nav1.6 on purified neurons. We observed that prenodes are restricted to GABAergic neurons, whereas clustering of nodal proteins only occurs concomitantly with myelin ensheathment on pyramidal neurons, implying separate mechanisms of assembly among different neuronal subpopulations. To address the functional significance of these early clusters, we used single-axon electrophysiological recordings in vitro and showed that prenode formation is sufficient to accelerate the speed of axonal conduction before myelination. Finally, we provide evidence that prenodal clusters are also detected in vivo before myelination, further strengthening their physiological relevance.

scholarly journals The Impact of Nylon-3 Copolymer Composition on the Efficiency of siRNA Delivery to Glioblastoma Cells

Nanomaterials ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 986 ◽  
Author(s):  
Natascha Hartl ◽  
Friederike Adams ◽  
Gabriella Costabile ◽  
Lorenz Isert ◽  
Markus Döblinger ◽  
...  
Keyword(s):  
Particle Size ◽  
Electrostatic Interactions ◽  
Laser Doppler Anemometry ◽  
Sirna Delivery ◽  
Copolymer Composition ◽  
Distribution Analysis ◽  
Glioblastoma Cells ◽  
Promising Therapeutic Approach ◽  
The Impact

Glioblastoma multiforme is a devastating disease that has attracted enormous attention due to poor prognosis and high recurrence. Small interfering RNA (siRNA) in principle offers a promising therapeutic approach by the downregulation of disease-related genes via RNA interference. For efficient siRNA delivery to target sites, cationic polymers are often used in preclinical studies for the protection of siRNA and complex formation based on electrostatic interactions. In an effort to develop biocompatible and efficient nanocarriers with a translational outlook for optimal gene silencing at reduced toxicity, we synthesized two sets of nylon-3 copolymers with variable cationic content (DM or NM monomer) and hydrophobic subunits (CP monomer) and evaluated their suitability for in vitro siRNA delivery into glioblastoma cells. DM0.4/CP0.6 and NM0.4/CP0.6 polymers with similar subunit ratios were synthesized to compare the effect of different cationic subunits. Additionally, we utilized NM0.2/CP0.8 polymers to evaluate the impact of the different hydrophobic content in the polymer chain. The siRNA condensation ability and polymer–siRNA complex stability was evaluated by unmodified and modified SYBR gold assays, respectively. Further physicochemical characteristics, e.g., particle size and surface charge, were evaluated by dynamic light scattering and laser Doppler anemometry, whereas a relatively new method for polyplex size distribution analysis—tunable resistive pulse sensing—was additionally developed and compared to DLS measurements. Transfection efficiencies, the route of cell internalization, and protein knockdown abilities in glioblastoma cells were investigated by flow cytometry. Furthermore, cellular tolerability was evaluated by MTT and LDH assays. All the polymers efficiently condensed siRNA at N/P ratios of three, whereas polymers with NM cationic subunits demonstrated smaller particle size and lower polyplex stability. Furthermore, NM0.2/CP0.8 polyplexes with the highest hydrophobic content displayed significantly higher cellular internalization in comparison to more cationic formulations and successful knockdown capabilities. Detailed investigations of the cellular uptake route demonstrated that these polyplexes mainly follow clathrin-mediated endocytotic uptake mechanisms, implying high interaction capacity with cellular membranes. Taken together with conducive toxicity profiles, highly hydrophobic nylon-3 polymers provide an appropriate siRNA delivery agent for the potential treatment of glioblastoma.

Bidirectional flow of action potentials in axons drives activity dynamics in neuronal cultures

2021 ◽  
Author(s):  
José Mateus ◽  
Cátia Lopes ◽  
Miguel Aroso ◽  
Ana Costa ◽  
Ana Geros ◽  
...  
Keyword(s):  
Network Activity ◽  
Neuronal Cultures ◽  
Axonal Conduction ◽  
Technological Advances ◽  
Transduction Mechanisms ◽  
Or Gene ◽  
Bidirectional Propagation ◽  
Bidirectional Flow ◽  
Activity Dynamics

Abstract Objective: Recent technological advances are revealing the complex physiology of the axon and challenging long-standing assumptions. Namely, while most action potential (AP) initiation occurs at the axon initial segment in central nervous system neurons, initiation in distal parts of the axon has been reported to occur in both physiological and pathological conditions. The functional role of these ectopic APs, if exists, is still not clear, nor its impact on network activity dynamics. Approach: Using an electrophysiology platform specifically designed for assessing axonal conduction we show here for the first time regular and effective bidirectional axonal conduction in hippocampal and dorsal root ganglia cultures. We investigate and characterize this bidirectional propagation both in physiological conditions and after distal axotomy. Main results: A significant fraction of APs are not coming from the canonical synapse-dendrite-soma signal flow, but instead from signals originating at the distal axon. Importantly, antidromic APs may carry information and can have a functional impact on the neuron, as they consistently depolarize the soma. Thus, plasticity or gene transduction mechanisms triggered by soma depolarization can also be affected by these antidromic APs. Conduction velocity is asymmetrical, with antidromic conduction being slower than orthodromic. Significance: Altogether these findings have important implications for the study of neuronal function in vitro, reshaping our understanding on how information flows in neuronal cultures.

scholarly journals Rat gastric mucin is synthesized and secreted exclusively as filamentous oligomers

1991 ◽  
Vol 279 (1) ◽  
pp. 251-256 ◽  
Author(s):  
J Dekker ◽  
A van der Ende ◽  
P H Aelmans ◽  
G J Strous
Keyword(s):  
Gel Filtration ◽  
Length Distribution ◽  
Gastric Mucin ◽  
Distribution Analysis ◽  
Electron Microscopic ◽  
Disulphide Bonds ◽  
Attachment Sites ◽  
Heterogenous Population ◽  
End To End

Oligomeric gastric mucin was isolated from the fundic part of the rat stomach. Previously we have shown by biochemical analysis that this oligomeric mucin consists of disulphide-linked homo-oligomers, which contain no other covalently attached proteins [Dekker, Aelmans & Strous (1991) Biochem. J. 277, 423-427]. Electron-microscopic images of the oligomeric mucin revealed a heterogenous population of long filamentous molecules of 300-3000 nm length. After reduction and carboxymethylation the monomeric mucins displayed a length distribution with a single peak at about 279 nm. Length-distribution analysis of oligomeric molecules with length up to 1000 nm revealed three subpopulations with one, two or three times the length of the monomeric mucin. The oligomers displayed small globular domains of about 15 nm, which were equally spaced along the molecule's length. As the distance between these globular domains was similar to the monomer length, these domains most likely indicate attachment sites of the monomers. These results show that the mucin monomers attached end-to-end in the oligomer. Biosynthesis of the mucin oligomers was studied by labelling of stomach explants in vitro with [35S]methionine, [3H]galactose or [35S]sulphate and subsequent immunoprecipitation of the mucin with a specific antiserum. Analysis by electrophoresis and gel filtration revealed that the oligomerization takes place by formation of disulphide bonds between the 300 kDa mucin precursors. The mucin was exclusively synthesized and secreted as fully glycosylated oligomers, as neither precursor proteins nor monomeric mucin were detected in the culture medium. A model for the biosynthesis of rat gastric mucin is proposed in which the filamentous mucin monomers are linked end-to-end by disulphide bonds.

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