Electrophysiology and Co-ordinated Behavioural Responses in the Colonial Bryozoan Membranipora Membranacea (L.)

1975 ◽  
Vol 62 (2) ◽  
pp. 389-404
Author(s):  
J. P. THORPE ◽  
G. A. B. SHELTON ◽  
M. S. LAVERACK
Keyword(s):  
Nervous System ◽  
Conduction Velocity ◽  
Giant Axon ◽  
Nerve Plexus ◽  
Retractor Muscle ◽  
Contraction Rate ◽  
Membranipora Membranacea ◽  
Behavioural Responses ◽  
Electra Pilosa

1. There is a colonial retraction response in the Bryozoans Membranipora membranacea and Electra pilosa. 2. The conduction velocity of the response is about 100 cm sec−1. 3. The colonial response will circumnavigate the end of a cut, but will not cross it. 4. The lophophore retraction time is 60–80 msec. 5. The lophophore retractor muscle with a peak contraction rate of 20 + muscle lengths per second is probably one of the fastest contracting muscles known. 6. The colonial responses to successive stimuli under certain circumstances are similar to those of some corals. 7. Nervous pulses can be recorded travelling across the colony at the same velocity as the colonial response. 8. Increases and decreases in the number and frequency of T1 pulses correspond with increases and decreases in the area and duration of the colonial response and are produced in response to the same stimuli. 9. Other pulses can be recorded which correspond to the retraction of the lophophore retractor muscle. 10. The lophophore retractor muscle is apparently under the control of a giant axon from the zooidal ganglion. 11. The colonial nervous system has many of the properties expected of a nerve plexus.

Neurofilaments and pathologies of the Peripheral Nervous System

2014 ◽  
Author(s):  
◽  
Jeffrey Dale
Keyword(s):  
Nervous System ◽  
Peripheral Nervous System ◽  
Conduction Velocity ◽  
Radial Growth ◽  
Stride Length ◽  
Wild Type ◽  
Axon Diameter ◽  
Internodal Length ◽  
Axonal Diameter ◽  
Myelin Thickness

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] The efficiency of signal propagation in the peripheral nervous system (PNS) is maximized by myelination and axon diameter. Myelination induces axonal expansion through radial growth. Radial growth is dependent on neurofilaments (NFs) that can be made up of the neurofilament light (NF-L) subunit in association with either the neurofilament medium (NF-M) or neurofilament heavy (NF-H) subunit. Myelin thickness and length (internodal) are established proportional to axon diameter for optimal conduction velocity. Myelin thickness is regulated by total neuregulin I type III (Nrg1 type III) levels present on the axon whereas the mechanisms that control the establishment of internodal length are less understood. My work expands on previous data demonstrating that myelin thickness does not respond to alterations in axonal diameter. In contrast to the previous study, my work describes myelin thickness in the context of decreased axonal diameters. NF subunit mutants that result in varying degrees of altered axonal diameter were used as a tool to study the response of myelin thickness to larger reductions in axonal diameter. At two and six months, g-ratios corresponded to the degree of axonal diameter change. At two months, the size of axons arranged into the following order: wild type > NF-H[superscript [[delta]]Tail] > NF-M[superscript [[delta]]Tail]>NF-(M/H) [superscript [[delta]]Tail]. Correspondingly, g-ratios arranged into the same order indicating the larger the decrease in axon diameter, the greater the proportional increase in myelin thickness. At six months, axon diameters grouped into "wild type" sizes and "NFM?Tail" sizes. Similarly, g-ratios grouped into "wild type" ratios and "NF-M?Tail" ratios indicating that myelin thickness did not respond to increased radial growth. At six months NF-M?Tail mice demonstrated decreased internodal length suggesting that internodal length responded to alterations in axon diameter. My work provides the first evidence of the consequence of altered myelin thickness in isolation. Mice with hypomyelination, alone, demonstrated reduced swing speed and stride length in all limbs. Mutations in proteins specific to myelin result CMT1 that display uniform slowing of conduction velocity. In contrast, CMT2E arises from mutations to axonal proteins resulting in non-uniform slowing of conduction velocity. We generated a mouse model of CMT2E by expressing a hNF-L[superscript E397K] transgene. hNF-L[superscript E397K] expression causes inherent defects to the neurofilament network. As a result, our CMT2E model demonstrates altered myelin thickness in motor and sensory nerves and unilateral gait alterations that include decreased stride length, increased foot drags, and altered coordination of coupled limbs. The correlation between defects observed in our hypomyelination model and our CMT2E model suggest that altered myelin thickness may play a role in CMT2E phenotype. NF accumulations first appear at the NMJs of the diaphragm in SMA?7 mice. Motor axon loss and decreased axonal diameter is observed in the cervical spinal cord which is responsible for innervating the diaphragm. Taken together, these data suggest that inherent NF defects may be present in SMA?7 mice. My work provides a comprehensive analysis of the NF network in a cell, sciatic nerve, where analyses wouldn't be confounded by axonal loss. My analyses demonstrated that total NF levels, trafficking, and deposition were unaffected in SMA?7 mice suggesting that the NF network was uncompromised. Therefore, NF accumulations at the NMJ are most likely due to local alterations to NF dynamics. Furthermore, my work demonstrates that alterations to the transport of retrograde motors and anterograde transport of vital synaptic vesicle proteins coincide with the appearance of NF accumulations.

On the ‘Visceral Nervous System’ of Ciona

1995 ◽  
Vol 75 (1) ◽  
pp. 141-151 ◽  
Author(s):  
G.O. Mackie
Keyword(s):  
Nervous System ◽  
Ciona Intestinalis ◽  
Gonadotropin Releasing Hormone ◽  
Nerve Plexus ◽  
Full Extent ◽  
Releasing Hormone ◽  
Blood Sinus ◽  
The Brain

Ciona intestinalis has a well developed nerve plexus associated with the dorsal strand, as first described by Marco Fedele. The dorsal strand plexus is immunoreactive with antisera against gonadotropin-releasing hormone. Immunoreactivity is seen in the cell bodies, which lie peripherally, and in processes which run throughout the dorsal blood sinus, enter the branchial sac and penetrate the brain via the visceral nerve. The plexus provides a rich innervation of the gonoducts, and processes have been seen in the gonads. The pericardium is not innervated by processes from the plexus and the rectum is poorly innervated, but the full extent of the plexus in the viscera remains uncertain. While this study confirms many of Fedele's observations, it does not support the view that the dorsal strand plexus is equivalent to the vertebrate visceral nervous system.

Conduction velocity and gating current in the squid giant axon

1975 ◽  
Vol 189 (1094) ◽  
pp. 81-86 ◽  
Keyword(s):  
Sodium Channel ◽  
Conduction Velocity ◽  
Charged Particles ◽  
Giant Axon ◽  
Squid Giant Axon ◽  
Gating Current ◽  
Giant Axons ◽  
Sodium Conductance ◽  
Conduction Velocities

As predicted by Hodgkin (1975), calculation of conduction velocities in squid giant axons shows that if each sodium channel is gated by charged particles moving in the membrane field there will be a maximum in the relation between sodium conductance and conduction velocity.

The Identity of Some Cyphonautes Larvae (Polyzoa)

1964 ◽  
Vol 44 (3) ◽  
pp. 645-654 ◽  
Author(s):  
J. S. Ryland
Keyword(s):  
Brackish Water ◽  
Membranipora Membranacea ◽  
Electra Pilosa ◽  
European Seas

SUMMARYFive cyphonautes are described in Nordisches Plankton (Lohmann, 1911). Cyphonautes schneideri and C. borealis are larvae of Membranipora membranacea and represent extremes of variation in the shape of the shell. Cyphonautes balticus, like C. compressus which was very inadequately described, is the larva of Electra pilosa. The cyphonautes of these two species are the only ones likely to be encountered in the plankton of normally saline European seas. Cyphonautes barroisi is the larva of the brackish-water Electra crustulenta.Cyphonautes balticus Thorson (1946), not Lohmann, is the larva of M. membranacea.Larval synonymies for M. membranacea and E. pilosa are given.The use of the Cyphonautes names is undesirable, and those of the polyzoan adults should be employed.

scholarly journals The Heat Shock Protein 26 Gene is Required for Ethanol Tolerance in Drosophila

2011 ◽  
Vol 5 ◽  
pp. JEN.S6280 ◽  
Author(s):  
Awoyemi A. Awofala ◽  
Susan Jones ◽  
Jane A. Davies
Keyword(s):  
Nervous System ◽  
Heat Shock ◽  
Heat Shock Protein ◽  
Ethanol Tolerance ◽  
Stress Proteins ◽  
Ethanol Exposure ◽  
P Element ◽  
Behavioural Responses ◽  
Percentage Difference

Stress plays an important role in drug- and addiction-related behaviours. However, the mechanisms underlying these behavioural responses are still poorly understood. In the light of recent reports that show consistent regulation of many genes encoding stress proteins including heat shock proteins following ethanol exposure in Drosophila, it was hypothesised that transition to alcohol dependence may involve the dysregulation of the circuits that mediate behavioural responses to stressors. Thus, behavioural genetic methodologies were used to investigate the role of the Drosophila hsp26 gene, a small heat shock protein coding gene which is induced in response to various stresses, in the development of rapid tolerance to ethanol sedation. Rapid tolerance was quantified as the percentage difference in the mean sedation times between the second and first ethanol exposure. Two independently isolated P-element mutations near the hsp26 gene eliminated the capacity for tolerance. In addition, RNAi-mediated functional knockdown of hsp26 expression in the glial cells and the whole nervous system also caused a defect in tolerance development. The rapid tolerance phenotype of the hsp26 mutants was rescued by the expression of the wild-type hsp26 gene in the nervous system. None of these manipulations of the hsp26 gene caused changes in the rate of ethanol absorption. Hsp26 genes are evolutionary conserved, thus the role of hsp26 in ethanol tolerance may present a new direction for research into alcohol dependency.

A Bioassay Model for Testing the Incapacitating Effects of Exposure To Combustion Product Atmospheres Using Cynomolgus Monkeys

1984 ◽  
Vol 2 (1) ◽  
pp. 20-36 ◽  
Author(s):  
David A. Purser
Keyword(s):  
Central Nervous System ◽  
Carbon Monoxide ◽  
Nervous System ◽  
Cardiac Function ◽  
Conduction Velocity ◽  
Hydrogen Cyanide ◽  
Nerve Conduction ◽  
Nerve Conduction Velocity ◽  
Central Nervous System Depression ◽  
Physiological Tests

A bioassay model has been developed to test the time course and degree of in capacitation produced by exposures to thermal decomposition products from polymeric materials. A battery of physiological tests was used during separate exposures to atmospheres of carbon monoxide, hydrogen cyanide, hypoxia, hypercapnia and heated air. Each atmosphere was designed to simulate one aspect of the conditions commonly encountered in fires. Measurements were made of the animals' respiration, cardiac function and respiratory blood gases. Neurological function was monitored by measurements of the elec troencephalogram, auditory cortical evoked potentials and peripheral nerve con duction velocity. Hypoxia (10% oxygen) caused muscle weakness, a decrease in nerve conduction velocity, abnormal cardiac function accompanied by a fall in blood pressure and central nervous system depression. At 1000 ppm carbon monoxide, venous carboxyhaemoglobin levels reached 30%. There was a reduc tion of nerve conduction velocity and in some cases severe central nervous system depression. At 60 ppm hydrogen cyanide had a slight depressive effect on the central nervous system, while at 80-150 ppm severe central nervous system depression and incapacitation occurred. The main result of 5% carbon dioxide exposure was a three-fold increase in respiratory minute volume. It is concluded that the model is capable of detecting early physiological signs of in capacitation induced by fire conditions. It is suggested that exposures to a com bination of hydrogen cyanide and carbon monoxide with accompanying changes in cerebral blood flow during attempts to escape from fires may be a cause of col lapse and subsequent death.

V - The development of Haliotis Tuberculata , with special reference to organogenesis during torsion

1937 ◽  
Vol 228 (552) ◽  
pp. 219-268 ◽  
Keyword(s):  
Nervous System ◽  
Special Reference ◽  
Larval Development ◽  
Retractor Muscle ◽  
Larval Life ◽  
Free Living ◽  
Larval Stages ◽  
Haliotis Tuberculata ◽  
New Interpretation ◽  
Selection Of

Investigation of the development of Haliotis tuberculata , Linnaeus, was undertaken as a natural sequel to an examination of the bionomics and anatomy of Haliotis (Crofts 1929, p. 159). It is an attempt to elucidate the organogenesis during the changing larval habits, in the hope of adding to the scanty ontogenetical evidence available towards solving the problems of gastropod evolution. Excellent accounts of the embryonic phase, including patiently worked out details of the cleavage and of gastrulation, have been published for Crepidula (Conklin 1897), Patella (Patten 1886; Wilson 1904; and Smith 1935), Trochus (Robert 1902), Physa (Wierzejski 1905), Dentalium (Wilson 1904). The only comprehensive accounts of gastropod larval development already published are of Paludina (Erlanger 1891; Tonniges 1896; Drummond 1902; Andersen 1924) and of Patella (Patten 1886; Smith I935). The accounts of Paludina elucidate the details of development of the coelom and its derivatives. The viviparous habit and consequent loss of free larval life in Paludina , however, make it a very unsuitable example of gastropod development. Evolutionary stages are more likely to be traced from the development of less specialized gastropods, an adequate selection of whose free-living larval stages can be obtained. The larval development of Patel, Acmaea, Trochus and Haliotis has been described, in varying completeness for the different genera. Patten’s work on Patella coerulea (1886) gives a description only of the beginning of organogenesis. After a lapse of fifty years a more detailed account of the development of P. vulgata has been given by Smith (1935). This work gives a new interpretation of the development of the mesoderm, of the muscles and of the nervous system. The dorsal retractor muscle of the larva, which Patten indicated for P. coerula , is shown in P. vulgata to be placed asymmetrically and torsion takes place “ under the action” of this muscle.

scholarly journals Microstructure of the nerve plexus of the muscular membrane of the gut of domestic ducks (Anas platyrhynchos domesticus) of different ages

2021 ◽  
Vol 12 (1) ◽  
pp. 3-8
Author(s):  
М. М. Kushch ◽  
D. S. Makhotyna ◽  
I. A. Fesenko ◽  
M. M. Savenko ◽  
A. Y. Ulianytska
Keyword(s):  
Nervous System ◽  
Enteric Nervous System ◽  
Anas Platyrhynchos ◽  
Postnatal Period ◽  
The State ◽  
Nerve Plexus ◽  
Domestic Ducks ◽  
Different Ages ◽  
Density Of Neurons ◽  
Myenteric Ganglia

As evidenced by the publications of recent years, contrary to the existing dogma about the immutability of the state of the enteric nervous system during the postnatal period of ontogenesis, the population of intestinal neurons is a dynamic formation, decreasing with age and changing due to the action of environmental factors. The current article presents the results of study of the microscopic structure of the nerve plexus of the muscular membrane of the enteric nervous system of domestic ducks (Anas platyrhynchos domesticus) of the black white–breasted breed, of nine age groups of 1–365 days of age. The topography, number, area of nerve nodes, as well as the density of neurons in them were determined on transverse sections of the duodenum, jejunum, ileum, caecum and rectum. For the purpose of a generalized assessment of the morphofunctional state of the nerve plexuses, two parameters were determined: the average age indicator of the gut and intestines. The average age indicator of a certain structure of each intestine was determined as the arithmetical average of its nine age indicators. The average age indicator of a certain gut structure was determined as the arithmetic average of the average age indicator of the structure of all five intestines. It has been established that the nerve plexus of the muscular membrane (myenteric, plexus Auerbachi) of the gut of domestic ducks, in contrast to mammals, is not located between the layers of the muscular membrane, but in its outer layer. On a transverse section of the gut wall, the myenteric ganglia and cords that connect have a predominantly elliptical shape. Despite a significant increase with age in the diameter and thickness of the gut wall, the total number of myenteric ganglia changed little, increasing or decreasing with varying degrees of reliability relative to the previous age. In the gut of ducks, during the first year of the postnatal period of ontogenesis, the smallest number of myenteric ganglia was found in the cecum, and the largest – in the ileum. The general pattern of the dynamics of the size of the myenteric ganglia of the gut of ducks was an increase in their area with age. Moreover, this indicator reached the greatest value at different ages of ducks: at 30 days of age in the ileum and cecum, at 180 days of age – in the rectum and at 365 days of age – in the duodenum. The smallest area of the myenteric ganglia was found in the jejunum, and the largest – in the duodenum and ileum. The smallest number of neurons in the ganglion was found in the cecum, and the largest – in the rectum, the lowest density of neurons in the ganglion was found in the cecum, and the largest – in the jejunum. The general quantitative pattern of neurons in the ganglion was the decrease in their density with age. Changes in the morphometric parameters of the ganglia of the nerve plexus of the muscular membrane of the ducks’ gut indicate the plasticity of the enteric nervous system, its ability to dynamically respond to the action of factors of the internal and external environment. It is promising to study the state of the submucous nerve plexus, as well as the cellular composition of the population of neurons of the enteric nervous system of domestic and wild poultry.

scholarly journals The effects of myomodulin and structurally related neuropeptides on skeletal neuromuscular transmission in the locust.

1994 ◽  
Vol 190 (1) ◽  
pp. 253-264 ◽  
Author(s):  
P D Evans
Keyword(s):  
Nervous System ◽  
Relaxation Rate ◽  
Neuromuscular Transmission ◽  
Contraction Rate ◽  
Low Frequencies ◽  
Consistent Effect ◽  
Frequency Of Stimulation ◽  
Stimulation Of

1. The modulatory actions of myomodulin A on tension generated in the extensortibiae muscle of the locust hindleg by stimulation of the slow excitatory motoneurone (SETi) depend upon the frequency of stimulation. Myomodulin A has no consistent effect on the tension induced by the fast extensor motoneurone (FETi) or upon the myogenic rhythm present in the extensor. The effects of a range of structurally related neuropeptides have also been assessed. 2. At low frequencies of SETi stimulation (1 Hz and below), the predominant modulatory effects are increases in the amplitude, contraction rate and relaxation rate of twitch tension. At higher frequencies, where twitches summate but tetanus is incomplete (up to 20 Hz), these effects are superimposed upon an increase of maintained tension. 3. The modulatory actions of myomodulin-like peptides show some similarities to and some differences from the modulatory actions of octopamine, proctolin and FMRFamide-like neuropeptides in this preparation, but are likely to be mediated via a distinct set of receptors. 4. The results of the present study, taken together with the localization of myomodulin-like immunoreactivity in specific sets of neurones in the locust nervous system, suggest the presence of a novel modulatory system in insects that uses myomodulin-like neuropeptides. It also indicates that myomodulins, which were first identified in molluscs, may represent another interphyletic family of neuropeptides.

scholarly journals Endurance training increases ventricular refractoriness and wavelength of the cardiac impulse without participation of parasympathetic postganglionic neurons. A study in isolated rabbit heart

2021 ◽  
Vol 42 (Supplement_1) ◽  
Author(s):  
A Rodrigo-Garcia ◽  
L Such-Miquel ◽  
G Parra ◽  
C J Calvo ◽  
O J Arias-Mutis ◽  
...  
Keyword(s):  
Nervous System ◽  
Endurance Training ◽  
Conduction Velocity ◽  
Physical Training ◽  
Cycle Length ◽  
Sham Group ◽  
Parasympathetic Nervous System ◽  
Nervous System Activity ◽  
Before And After ◽  
Parasympathetic Nervous System Activity

Abstract Background Endurance physical training plays a protective role in against ventricular fibrillation (VF), but the exact underlying mechanisms are not completely understood. It is well-known that modifications in myocardial ventricular properties such as refractoriness, conduction velocity and wavelength are key in the initiation and maintenance of VF; furthermore, vagus nerve stimulation has prophylactic effects on malignant arrhythmias and VF. On the other hand, parasympathetic nervous system activity is increased in trained individuals, which in turn affects different ventricular electrophysiological properties. We hypothesized that physical training increases conduction velocity and wavelength, and that these changes are mediated by myocardial cholinergic neurons. Methods To test this hypothesis, ten rabbits were submitted to a six-week endurance training protocol and twenty controls were not trained (divided in control group, n=10 and sham group n=10). After training, rabbits were euthanized and their hearts excised, isolated and perfused in a Langendorff system. A pacing electrode and a plaque with 240 recoding electrodes acquiring at 1 KHz were positioned on the left ventricle (LV). Extraestimulus test using four different pacing cycle lengths (90% basal cycle length, 250, 200 and 150 ms) was performed before and after atropine (1μM, control and trained groups) or vehicle (tyrode, sham group) infusion. We studied 1) LV effective refractory period (ERP), 2) LV functional refractory period (FRP), 3) LV conduction velocity (CV), and 4) LV wavelength, determined as LV FRP x CV. Factorial ANOVA (mixed model) was used for statistical analysis (p<0.05). Results Before parasympathetic blockade, LV FRP increased in trained animals (Figure, B) whereas no difference was found in LV CV between trained and control animals at any pacing cycle length (Figure, A). In consequence, LV wavelength increased in trained animals (Figure, C). There were no changes in LV ERP, FRP, CV and wavelength when comparisons were made within groups before and after atropine infusion. In sham animals, vehicle infusion or time-course of the experiment did not modify LV FRP, ERP, CV and wavelength. Conclusion Physical training increases LV wavelength, which can be one electrophysiological mechanism by which endurance training could protect against VF. Since modifications of ventricular refractoriness and wavelength do not seem dependent of intrinsic parasympathetic nervous system activity, other intrinsic mechanisms could be implied and warrant further research. FUNDunding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Instituto de Salud Carlos III, Generalitat Valenciana

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