scholarly journals A Rectifying Electrotonic Synapse in the Central Nervous System of a Vertebrate

1969 ◽  
Vol 53 (2) ◽  
pp. 211-237 ◽  
Author(s):  
A. A. Auerbach ◽  
M. V. L. Bennett
Keyword(s):  
Giant Fiber ◽  
Transfer Resistance ◽  
Data Rectification ◽  
Pectoral Fins ◽  
Adductor Muscles ◽  
Escape Reflex ◽  
The Central Nervous System ◽  
Coupling Resistance ◽  
Resistance Data ◽  
Good Agreement

The adductor muscles of the pectoral fins of the hatchetfish Gasteropelecus are innervated by bilateral pools of about 40 motoneurons which lie primarily in the first spinal segment. A pair of giant fibers on each side of the medulla send processes ventroposteriorly to the motoneuron pools. Electrophysiological evidence indicates that giant fibers are presynaptic to ipsilateral motoneurons, but not to contralateral ones. Transmission across the giant fiber, motoneuron synapse is electrically mediated as is indicated by direct measurement of electrotonic spread in either direction across the synapse, and by the extremely short latency of the giant fiber postsynaptic potentials (PSP's) in the motoneuron. The coupling resistance across the synapse was calculated from measurements of input and transfer resistance. The coupling resistance rectifies in such a way as to facilitate spread of depolarization from giant fiber to motoneuron, and to oppose transmission in the opposite direction. As a consequence of rectification, the giant fiber PSP in a motoneuron is augmented by hyperpolarization of the motoneuron. The coupling resistance calculated on the basis of this effect is in good agreement with calculations from input and transfer resistance data. Rectification at the electrotonic synapses may permit the motoneurons to act in small swimming movements as well as to fire synchronously in an extremely fast escape reflex mediated by Mauthner and giant fibers.

scholarly journals Chemically Mediated Transmission at a Giant Fiber Synapse in the Central Nervous System of a Vertebrate

1969 ◽  
Vol 53 (2) ◽  
pp. 183-210 ◽  
Author(s):  
A. A. Auerbach ◽  
M. V. L. Bennett
Keyword(s):  
Postsynaptic Membrane ◽  
High Frequency Stimulation ◽  
Giant Fiber ◽  
Pectoral Fin ◽  
Quantum Size ◽  
Adductor Muscles ◽  
Single Spike ◽  
The Central Nervous System ◽  
Frequency Stimulation ◽  
Presynaptic Spike

The hatchetfish, Gasteropelecus, possesses large pectoral fin adductor muscles whose simultaneous contraction enables the fish to dart upwards at the approach of a predator. These muscles can be excited by either Mauthner fiber. In the medulla, each Mauthner fiber forms axo-axonic synapses on four "giant fibers," two on each side of the midline. Each pair of giant fibers innervates ipsilateral motoneurons controlling the pectoral fin adductor muscles. Mauthner fibers and giant fibers can be penetrated simultaneously by microelectrodes close to the synapses between them. Electrophysiological evidence indicates that transmission from Mauthner to giant fiber is chemically mediated. Under some conditions miniature postsynaptic potentials (PSP's) are observed, suggesting quantal release of transmitter. However, relatively high frequency stimulation reduces PSP amplitude below that of the miniature potentials, but causes no complete failures of PSP's. Thus quantum size is reduced or postsynaptic membrane is desensitized. Ramp currents in Mauthner fibers that rise too slowly to initiate spikes can evoke responses in giant fibers that appear to be asynchronous PSP's. Probably both spikes and ramp currents act on the same secretory mechanism. A single Mauthner fiber spike is followed by prolonged depression of transmission; also PSP amplitude is little affected by current pulses that markedly alter presynaptic spike height. These findings suggest that even a small spike releases most of an immediately available store of transmitter. If so, the probability of release by a single spike is high for any quantum of transmitter within this store.

scholarly journals Distinct aging-vulnerable trajectories of motor circuit functions in oxidation- and temperature-stressed Drosophila

2020 ◽  
Author(s):  
Atulya Srisudarshan Ram Iyengar ◽  
Hongyu Ruan ◽  
Chun-Fang Wu
Keyword(s):  
Superoxide Dismutase ◽  
High Temperature ◽  
Superoxide Dismutase 1 ◽  
Giant Fiber ◽  
Motor Processing ◽  
Aging Studies ◽  
Sensory Motor ◽  
Age Dependent ◽  
Escape Reflex ◽  
The Common

AbstractWe examined several sensory-motor processing circuits in Drosophila across the lifespan and uncovered distinctive age-resilient and age-vulnerable trajectories in their established functional properties. We observed relatively little deterioration toward the end of lifespan in the giant-fiber (GF) and downstream circuit elements responsible for the jump-and-flight escape reflex. In contrast, we found substantial age-dependent modifications in the performance of GF inputs and other circuits driving flight motoneuron activities. Importantly, in high temperature (HT)-reared flies (29 °C), the characteristic age-dependent progression of these properties was largely maintained, albeit over a compressed time scale, lending support for the common practice of expediting Drosophila aging studies by HT rearing. We discovered shortened lifespans in Cu2+/Zn2+Superoxide Dismutase 1 (Sod) mutant flies were accompanied by alterations distinct from HT-reared flies, highlighting differential effects of oxidative vs temperature stressors. This work also establishes several age-vulnerable parameters that may serve as quantitative neurophysiological landmarks for aging in Drosophila.

Analysis of the zebrafishsmoothenedmutant reveals conserved and divergent functions of hedgehog activity

Development ◽  
2001 ◽  
Vol 128 (12) ◽  
pp. 2385-2396 ◽  
Author(s):  
Wenbiao Chen ◽  
Shawn Burgess ◽  
Nancy Hopkins
Keyword(s):  
Dopaminergic Neurons ◽  
Hedgehog Signaling ◽  
Floor Plate ◽  
Hedgehog Signaling Pathway ◽  
Pectoral Fins ◽  
Midbrain Dopaminergic Neurons ◽  
The Central Nervous System ◽  
Similarities And Differences ◽  
Kinase A

Despite extensive studies, there are still many unanswered questions regarding the mechanism of hedgehog signaling and the phylogenic conservation of hedgehog function in vertebrates. For example, whether hedgehog signaling in vertebrates requires smoothened is unclear, and the role of hedgehog activity in zebrafish is controversial. We show that inactivation of smoothened by retroviral insertions in zebrafish results in defects that are characteristic of hedgehog deficiencies, including abnormalities in body size, the central nervous system, adaxial mesoderm, cartilage and pectoral fins. We demonstrate that, as in Drosophila, vertebrate smoothened is essential for hedgehog signaling, and functions upstream of protein kinase A. Further analysis of neural tube defects revealed the absence of lateral floor plate and secondary motoneurons, but the presence of medial floor plate and primary motoneurons in smoothened mutant embryos. Blocking maternal hedgehog signaling by cyclopamine eliminates primary motoneurons, but not medial floor plate. Interestingly, even after inhibition of maternal hedgehog activity, the midbrain dopaminergic neurons still form, and looping of the heart does not randomize in the mutants. We also found decreased proliferation and increased apoptosis in the mutants. Taken together, these data demonstrate the conserved role of vertebrate smoothened in the hedgehog signaling pathway, and reveal similarities and differences of hedgehog function between teleosts and amniotes.

scholarly journals Computational simulation and modelling of uranium extraction using tributylphosphate through membrane extractor

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Rahmad Syah ◽  
Dadan Ramadan ◽  
Marischa Elveny ◽  
Yan Cao ◽  
Afrasyab Khan ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Concentration Distribution ◽  
Uranium Concentration ◽  
Computational Simulation ◽  
Hollow Fibre ◽  
The Finite Element Method ◽  
Extractant Concentration ◽  
Transfer Resistance ◽  
Uranium Extraction ◽  
Good Agreement

AbstractNon-disperse solvent extraction is an effective technique for the extraction of metal ions from aqueous solution. In this study, uranium extraction using n-dodecane solvent containing tributylphosphate extractant in a membrane contactor was investigated. A 2D mathematical model was developed for the fluid flow and mass transfer in the hollow fibre membrane extractor. The equations of the created model were solved using the finite element method. The uranium concentration distribution in the extractor at different extractant concentrations as well as feed acidity was studied. The results showed that there is reasonable good agreement between experimental uranium extraction and modelling outputs at different extractant concentrations. Increasing extractant concentration from 5 to 30% led to the enhancement of uranium extraction from 2.60 to 34.13%. Also, there was an increase in the uranium extraction with increasing feed acidity in the range of 1–3 M. Furthermore, based on the radial uranium concentration distribution, it was found that the main mass transfer resistance in the system was microporous membrane section. Finally, it was obtained that the uranium extraction efficiency could be improved significantly by increasing porosity-to-tortuosity ratio. It was concluded that the membrane specification plays the most important role as the dominant mass transfer resistant was in the membrane subdomain.

Distribution and Elimination of [2-14C]Amino-3, 8-Dimethylimidazo [4, 5-f] quinoxaline in Mice. Analysis by Whole Animal Autoradiography

1991 ◽  
Vol 10 (5) ◽  
pp. 337-345 ◽  
Author(s):  
N.J. Gooderham ◽  
A. Soames ◽  
J.C. Rice ◽  
A.R. Boobis ◽  
D.S. Davies
Keyword(s):  
Central Nervous System ◽  
Time Course ◽  
Liver Enzymes ◽  
Early Time ◽  
Body Tissue ◽  
Significant Extent ◽  
Time Points ◽  
The Central Nervous System ◽  
Extrahepatic Tissues ◽  
Good Agreement

1 2-Amino-3,8-dimethylimidazo[4,5- f]quinoxaline (MeIQx) is a potent bacterial pro-mutagen and carcinogen, formed when beef is cooked. In mammals, MeIQx is metabolized and activated by liver enzymes, but induces tumours in both hepatic and extrahepatic tissues. 2 Intravenous administration of [14C]MeIQx and whole animal autoradiography has been employed to examine the diposition of MeIQx. Within 10 min, radiolabel was distributed throughout body tissue. Liver levels of radioactivity rapidly rose and remained elevated in comparison to other tissues, throughout the period of study (4 d). 3 At early time points radioactivity accumulated in the stomach, kidney and salivary glands then later in the intestine. Radioactivity was rapidly eliminated from the majority of tissues although did persist in liver and intestines throughout the duration of the study, probably due to covalently bound material. No radioactivity could be detected in the central nervous system, thus neither MeIQx nor its metabolites cross the blood—brain barrier to any significant extent. 4 The rapid elimination of radioactivity from the tissues is in good agreement with the time course of excretion of MeIQx. Irrespective of the route of administration (i.v., i.p., p.o.), a substantial proportion of the labelled material is excreted within 24 h and is present in both urine and faeces in similar quantities. 5 Thus MeIQx is extensively bioavailable, is distributed throughout body tissue and, although the majority is quickly cleared, some remains bound to liver and intestine.

scholarly journals Evaluation of the force applied by the adductor muscles in a healthy student population performing an adduction task

2021 ◽  
Vol 31 (Supplement_2) ◽  
Author(s):  
Maria Cruz ◽  
Deolinda Rasteiro ◽  
Filipe Carvalho ◽  
Jorge Lains ◽  
Luis Roseiro
Keyword(s):  
Motor Neurons ◽  
Skeletal Muscles ◽  
Sedentary Lifestyle ◽  
Lower Limb Injuries ◽  
Performance Time ◽  
Student Community ◽  
Adductor Muscles ◽  
Limb Injuries ◽  
Resting Metabolism ◽  
The Central Nervous System

Abstract Background The adduction and abduction movement (closing and open the legs) are important tasks in daily activities. The evaluation and monitor of the force exerted by the adductor muscles can be used as a rehabilitation progress indicator, particularly in people with injuries in the central nervous system or motor neurons. The development of biomechanical devices to quantify and identify patterns in this type of force with healthy people can be a contribution in this domain. This work, approved by the Ethical Committee of IPC, aims to evaluate the force applied by the adductor muscles from a healthy group of students, performing the closing legs task. Methods The study was carried out at Applied Biomechanics Laboratory of IPC, with a group of 32 healthy volunteers from the student community (19-26 yo), half men - half women, without lower limb injuries, 59,38% with a prevalence of sedentary lifestyle. Volunteers, sitting in a comfortable position, press a biomechanical device placed between the legs. The time-force was registered for four discrete open-leg positions. Results The maximum mean forces were 199N in women and 257N in men, both in the shorter range of the open-leg position. The peak of force decreases with open leg distance for both genders and was achieved between 34%–54% of the performance time ([3, 28] seconds). Moderate correlations were identified between forces applied and skeletal muscles and resting metabolism. Conclusion The time-force applied was identified and registered with a developed biomechanical device. Obtained values are reliable and can be a support for future investigations.

scholarly journals Mathematical Model of VOCs Emission in Three-layer Building Materials

2021 ◽  
Vol 257 ◽  
pp. 03047
Author(s):  
Zhehua Du ◽  
Xin Lin
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Mathematical Model ◽  
Building Materials ◽  
Present Model ◽  
Transfer Resistance ◽  
Model Predictions ◽  
Layer Resistance ◽  
Boundary Layer Resistance ◽  
Good Agreement

A simple mathematical model is proposed to account for emissions of Volatile Organic Compounds (VOCs) from three-layer building materials. The model considers both the diffusion within three layer building materials and the mass transfer resistance through the air boundary layer. A general solution method based on Laplace transform is presented. Compared to other models capable of accounting for emissions of VOCs from multi layer building materials, the present model is fully analytical instead of being numerical. The present model was validated by the experimental data from the specially designed test. The results indicated that there was a good agreement between the model predictions and the experimental data. It can also be seen from calculation that model ignoring the boundary layer resistance cannot fully reflect the real situation.

Mutations resulting in transient and localized degeneration in the developing zebrafish brain

1997 ◽  
Vol 75 (5) ◽  
pp. 579-600 ◽  
Author(s):  
Michael Rodriguez ◽  
Wolfgang Driever
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Large Scale ◽  
Late Onset ◽  
Pharyngeal Arches ◽  
Pectoral Fins ◽  
Group 4 ◽  
Entry Points ◽  
The Central Nervous System ◽  
Group 2

In a large-scale mutagenesis screen in the zebrafish, Danio rerio, we have identified a heterogeneous group of 30 recessive, embryonic lethal mutations characterized by degeneration in the developing central nervous system that is either transient or initially localized to one area of the brain. Transient degeneration is defined as abnormal cell death occurring during a restricted period of development. Following degeneration, the affected structures do not appear to regenerate. In each case degeneration is identified after somitogenesis is complete and is not associated with visually identified patterning defects. These 30 mutations, forming 21 complementation groups, have been classified into four phenotypic groups: group 1, transient degeneration (13 mutations); group 2, spreading degeneration, early onset, in which degeneration is initially confined to the optic tectum but subsequently spreads to other areas of the central nervous system (7 mutations); group 3, late-onset degeneration, initially identified after 4 days (6 mutations); and group 4, degeneration with abnormal pigmentation (4 mutations). Although apoptotic cells are seen in the retina and tectum of all mutants, the distribution, temporal progression, and severity of degeneration vary between mutations. Several mutations also show pleiotropic effects, with degeneration involving extraneural structures including the pharyngeal arches and pectoral fins. We discuss some of the pathways important for cell survival in the nervous system and suggest that these mutations will provide entry points for identifying genes that affect the survival of restricted neural populations.

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