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At least 19 recordsLinked to original sources
PubMed1975

Electrophysiology of the peripheral nerve net in the polyclad flatworm Freemania litoricola.

1. A diffuse-conducting system close to the dorsal epithelium of the polyclad flatworm Freemania litoricola is described. Tactile stimuli elicit small action potentials which can be conducted around lesions through the body wall. The potentials can occur in bursts or barrages. 2. This conducting system appears to be insensitive to Mg2+ ions. 3. Conduction velocities (0-26--71 m/sec) vary over the animal. Conduction spread in the anterior half of the animal appears to be greater than that in the posterior portion. 4. Response decrement to repeated stimulation can be recorded in the peripheral system but it is not clear if this is due to habituation or fatigue. 5. Conduction from the peripheral net to the brain occurs. Some central units appear to pick up information only, or mainly, through the anterior nerves, while other units can respond to information conducted through the network to nerves of the contralateral side. 6. Different possibilities to account for this system are discussed, and it is suggested that the animals either possess a unique Mg2+ insensitive synaptic nerve-net or else the network is electrically coupled.

Action Potentials↗
PubMed1992

Characterization of a RFamide-positive subset of ganglionic cells in the hydrozoan planular nerve net.

The complexity of the hydrozoan planular nervous system was examined. Using a whole-mount technique with indirect immunofluorescence, the spatial pattern of ganglionic cells showing RFamide-like immunoreactivity was visualized. RFamide antiserum bound a subset of ganglionic cells in the anterior and upper middle regions of the planula and a few ganglionic cells in the upper tail region. Labeled cells consisted of bipolar and multipolar neurons. Stained processes from these cells formed a three-dimensional nerve net that followed the contour of the mesoglea; such fibers were striking in terms of their large numbers, long lengths, and organization into distinct bundles. Labeled fibers were seen to contact other ganglionic cells, sensory cells, epithelio-muscle cells, the mesoglea, and the outside free surface. All stained cell bodies and fibers were found in the ectoderm. Using the same technique the reappearance of RFamide-positive ganglionic cells in epithelial tissue of chimeric grafts of planulae was observed. Interstitial cells capable of forming RFamide-positive ganglionic cells underwent extensive anterior-posterior migrations in the grafts, moved into the epithelial tissue, and differentiated into RFamide-positive ganglionic cells. Stained repopulated ganglionic cells always formed in the same position in the epithelial tissue as was observed in control planulae suggesting that the expression of RFamide-like substances may be position dependent in the planula.

Animals↗
PubMed1975

Colonial conduction systems in the Anthozoa: Octocorallia.

1. The octocorals Alcyonium digitatum, Pennatula phosphorea and Virgularia mirabilis each have a through-conducting nerve net. The nerve net demonstrated electrophysiologically may well be the same as that previously shown by the use of histological techniques. 2. It exhibits both facilitation and defacilitation in the rate of conduction of pulses. 3. The distance of spread of nerve net activity is not limited by the number of stimuli applied. 4. The nerve net controls fast muscle contractions; the frequency of pulses is important in determining which muscles contract and in which sequence. 5. The nerve net is 'spontaneously' active. 6. A previously undescirbed slow system has been identified in Pennatula. It has many of the properties of slow systems in sea anemones and may well be ectodermal. It is suggested that multiple conduction systems are of common occurrence in the Anthozoa.

Animals↗
PubMed1992

Nerve ring of the hypostome in hydra. I. Its structure, development, and maintenance.

The anatomy and developmental dynamics of the nerve ring in the hypostome of Hydra oligactis were examined immunocytochemically with an antiserum against a neuropeptide and with neuron-specific monoclonal antibodies. The nerve ring is unique in the mesh-like nerve net of hydra. It is a distinct neuronal complex consisting of a thick nerve bundle running circumferentially at the border between the hypostome and tentacle zone. Immunostaining showed that the nerve ring was heterogeneous and contained at least four different subsets of neurons. During head regeneration and budding, the nerve ring appeared only after the nerve net of ganglion and sensory cells had formed. Every epithelial cell is continuously displaced with neurons toward either head or foot in an adult hydra. However, the ectoderm in the immediate vicinity of, and including, the nerve ring constitutes a stationary zone that is not displaced. Tissue immediately above this zone is displaced toward the tip of the hypostome, while tissue below is displaced along the tentacles. Correspondingly, the production of new neurons in the ring as measured by their differentiation kinetics is much slower than in surrounding areas. Thus, the nerve ring is static and stable in contrast to the dynamic features of the nerve net of hydra.

Animals↗
PubMed1979

Atrial acetylcholinesterase activity in various heart diseases of man.

Distribution and activity of the acetylcholinesterase enzyme in the human atrial myocardium was studied histochemically in a clinical series of patients subjected to cardiac surgery for (1) uncomplicated atrial septal defect (ASD), (2) ischaemic heart disease (IHD), (3) mitral and/or aortic valvular disease (VHD) necessitating replacement with a prosthetic valve, without major symptoms or signs of myocardial incompensation, or (4) clinically overt congestive heart failure (CHF) due to VHD prior to cardiac surgery. In all specimens, a rich distribution of acetylcholinesterase-positive single axons and small fascicles, constituting a three-dimensional nerve net, was observed within the myocardial tissue. This nerve net was obviously mainly parenchymatous, i.e. unrelated to the blood vessels. Small groups of acetylcholinesterase-positive small nerve cells were observed in some specimens, with loosely woven fascicles of axons emerging from one pole of the ganglia. No differences in the distribution of the acetylcholinesterase activity or in the pattern of the inbuilt intrinsic nervous apparatus were observed in the various groups of patients. All specimens were completely devoid of non-specific cholinesterase activity. It was concluded that (I) the human atrial myocardium is richly supplied with cholinergic intrinsic (post-ganglionic vagal) axons and (II) the acetylcholinesterase activity is not a major determinant of the parasympathetic abnormalities associated with cardiac diseases, especially with myocardial pump failure.

Acetylcholinesterase↗
PubMed1992

The presence and distribution of Antho-RFamide-like material in scyphomedusae.

The nervous systems of the scyphomedusae Chrysaora hysoscella, Cyanea capillata and Cyanea lamarckii (Phylum Cnidaria) were stained using an anti-serum against the anthozoan neuropeptide Antho-RFamide. Staining was widespread in all three species. In Chrysaora, the antiserum revealed nerve nets in the subumbrella and exumbrella ectoderm, in both faces of the oral lobes, and in the endoderm lining the subumbrella and exumbrella surfaces of the gastric cavity. The most prominent staining occurred in a dense plexus of neurons in the ectoderm at the base of the tentacles. This nerve net sent projections into the subumbrella ectoderm. For the most part, staining in the two species of Cyanea was similar to that in Chrysaora, with a few exceptions. These include the presence, in Cyanea, of an obvious tentacular nerve tract and nerve nets associated with clusters of cnidocytes in the tentacles. Radioimmunoassays of extracts from Chrysaora and Cyanea lamarkii revealed that both species contain large amounts of Antho-RFamide-like material (up to 55 nmol/animal). The results indicate that Antho-RFamide-like neuropeptides are widespread in scyphomedusae.

Animals↗
PubMed1976

Delayed initiation of SS1 pulses in the sea anemone Calliactis parasitica: evidence for a fourth conducting system.

1. Single electrical shocks to the column sometimes elicit a series of 1-6 pulses in the SS1 (ectodermal slow system) but the first pulse does not appear until 5-28 s after stimulation. These pulses occur in addition to the early SS1 pulse which follows every shock and which has a conduction delay of less than 1 s. 2. The threshold of the delayed SS1 response is different from the thresholds of the three known conducting systems (through-conducting nerve net, SS1, and SS2). 3. In the case of stimulation of the column, the delayed SS1 pulses do not arise at the point of stimulation but probably originate in the tentacles or upper column. The pulse origin can shift during a single burst. 4. The pathway from the point of stimulation to the site of origin of delayed SS1 pulses is endodermal. We propose that this pathway represents a fourth conducting system (Delayed Initiation System--DIS). The DIS must connect, across the mesogloea, with the ectodermal SS1. The long pulse delay and repetitive firing may derive from pacemaker activity in the DIS. The DIS pacemakers closely resemble the pacemakers connected to the through-conducting nerve net. The DIS may be neuronal. 5. Delayed SS1 pulse bursts from unattached anemones showed an earlier onset, and more pulses/burst, than those from attached anemones. 6. Delayed SS1 pulses can also be evoked by electrical, and in some cases mechanical, stimulation of the pedal disc, tentacles, and pharynx, but there are regional differences in the number of pulses evoked, in their delay, and in their site of origin.

Action Potentials↗
PubMed1977

Ultrastructure of nerve plexus in flatworms. III. The infra-epithelial nervous system.

In addition to a submuscular and subepithelial nerve plexus an infra-epithelial nerve-net also occurs in Notoplana acticola. It contains naked nerve cells which lie between the bases of epithelial cells. Individual neurites occur separately or in small tracts. Synapses contain clear spherical vesicles and are polarized. Post-synaptic neurites tend to be flat and ribbon-like. Rhabdite and mucus secreting cells in the epithelium have synapses associated with them. Neurites ending on the rhabdites appear to originate in the subepithelial plexus. The "sensory-free nerve endings" of earlier workers are reinterpreted as being motor terminals on epithelial secretory cells.

Animals↗
PubMed1991

Nervous system of Clonorchis sinensis as revealed by acetylcholinesterase activity.

The gross neuroanatomy of Clonorchis sinensis has been revealed by the localization of acetylcholinesterase, well known to be associated with the nervous system. The central nervous system is composed of two cerebral ganglia situated postero-dorsally to the pharynx and connected by a transverse commissure. These ganglia give off four pairs of nerves anteriorly and three pairs posteriorly. The anterior nerves contribute to the pharynx and to the formation of the circum-oral ring located in the oral sucker. The posterior nerves, of which the postero-ventral nerve cords are the most prominent, contribute to the innervation of the acetabulum, the gut, the reproductive organs and the excretory bladder. All the posterior nerve cords are connected by a number of transverse connections throughout their course forming a complicated nerve net. At least two types of nerve cells, bipolar and multipolar ones, were observed.

Acetylcholinesterase↗
PubMed1978

[Spatial filtration in the nerve networks].

A simplified neuronal model leads to studies of multiunit nerve nets. Properties of spatial integration and differentiation are exhibited according to the structure of the interconnections. A spatial periodicity of nervous signal appears in nets with backward lateral inhibitions. It is a fundamental property of this structure.

Models, Neurological↗
PubMed1976

Fluorescence histochemical and electron-microscopical observations on the innervation of the atrial myocardium of the adult human heart.

The existence of both adrenergic and cholinergic innervation of the atrial myocardium of the adult human heart was demonstrated by means of fluorescence induced by formaldehyde or glyoxylic acid and by electron microscopy. The adrenergic fluorescing axons (1) followed the course of blood vessels as typical perivascular nerve plexuses, and (2) formed a three-dimensional fairly dense nerve net obviously not related to the blood vessels. The varicosities frequently came into close apposition on myocardial cells. Several types of nerve terminals were differentiated at electron microscopy: (1) an "adrenergic" type containing small (diameter 450-700 A) dense-cored vesicles and usually (in various proportions) small "empty" and/or large (900-1500 A) dense-cored vesicles, (2) a "cholinergic" type containing small (ca. 500 A) "empty" vesicles and occasionally also some large (mean diameter ca. 1200 A) dense-cored vesicles, (3) a "pale" type containing only a few or no vesicles, (4) a "disintegrated" type containing degenerated mitochondria, autophagic vacuoles, and occasional normal-looking mitochondria, (5) nerve terminals containing a large number of mitochondria in addition to varying vesicle populations, and (6) a (possibly baroreceptive type of) nerve terminal containing myelinlike lamellated structures. The "disintegrated" and the "pale" types of nerve terminals possibly represent different stages of axonal degeneration, or may correspond to diminution in the transmitter substance concentration under certain pathophysiologic conditions, respectively. Nerve terminals crowded with mitochondria may be sensory and involved in mechano-or chemoreceptive functions. In preliminary experiments convincing evidence was obtained that the glyoxylic acid-induced fluorescence histochemical method will be suitable for comparative studies on (human) clinical specimens, e.g., for analyzing the degree of the functional activity of the intrinsic adrenergic innervation of the myocardium under various pathophysiologic conditions. The modification which appeared most appropriate for such studies is described in detail, and is proposed for use as a standard method in other similar or related studies on human clinical series. The essential criteria for analyzing the specimens at fluorescence microscopy are suggested as well.

Adult↗
PubMed1977

Sympathetic innervation of the human leg arteries.

Sympathetic innervation of the human main leg arteries was morphologically investigated by the Formaldehyde-induced fluorescence method of Falck and the silver-impregnation method of Bodian. The following points were established: 1. There is a compact fine-meshed nerve-net directly on the surface of the media. 2. In the dorsal pedal, the anterior tibial, the peroneal, the posterior tibial, and the femoral artery, fine unmyelinated nerve fibers which run on the surface of the media penetrate constantly into the extreme outer layer of the media together with elastic and collagenous elements of the adventitia. 3. There is no difference in the innervation mode of the media of various leg arteries. 4. It seems that there is no correlation between the innervation of the arterial wall and the morbidity difference in the chronic arterial occlusive diseases of leg arteries.

Adolescent↗
PubMed1979

Pattern separability in a random neural net with inhibitory connections.

Some interesting properties on pattern separation have been shown through researches by neural models of cerebellar cortex. It seems to us that those results are a part of the properties of pattern separation. A two layer random nerve net with inhibitory connections is given as a model of the cerebellar cortex. The model is composed of threshold elements there. A more general theory of pattern separation than those studied earlier is given, and the pattern separability of the model is considered. It is revealed that the standard deviation of threshold values of threshold elements has a great effect on the pattern separability and the control of the firing rate. The present study is also intended to investigate the pattern separability in such a case that the firing rate of input patterns are not equal, and a pattern includes the other pattern. It is assumed there that the standard deviation is small. Some properties of the degree of pattern separation are cleaned up.

Cerebellum↗
PubMed1991

Innervation of the rat thymus gland.

Current views from different laboratories on the innervation of the thymus gland are reviewed with particular reference to the rat. Noradrenergic nerve profiles of the sympathetic nervous system have been demonstrated in the subcapsular cortex, at the corticomedullary junction and in the cortex itself, and extremely sparsely in the medulla. By following beta-adrenergic receptor development in postnatal rats, it has been shown that there is a marked increase in density and morphological organization of the receptor in the medulla with the maturation of thymocyte function (monitored by measuring the proliferation response to concanavalin A) and a sexual dimorphism during the ontogeny of the receptor. Chemical sympathectomy of adult rats with 6-hydroxydopamine (6-OHDA) or guanethidine resulted in a loss of thymus weight, decreased cellularity, and increased apoptosis but a rise in the numbers of proliferating cells in the cortex. By contrast, proliferation of peripheral T cells was reduced after the use of 6-OHDA. Chemical sympathectomy also demonstrated that there were at least three nerve nets in the gland: noradrenergic neural profiles that were destroyed with both 6-OHDA and guanethidine, vasoactive intestinal polypeptide (VIP)-positive profiles that persisted, and AChE- and CGRP-positive profiles and cells that also persisted but had a different distribution to VIP-positive fibers. Some functional correlates of thymic innervation are discussed although the subject now needs to be further researched.

Acetylcholine↗
PubMed1977

Studies of auricular catecholamines by fluorescence histochemistry in various heart diseases of man.

A comparative histochemical and clinical study concerning the state of the intrinsic adrenergic innervation of the human atrial myocardium was carried out, using the glyoxylic acid-induced fluorescence histochemical method. Specimens from the right auricular appendage were obtained during open-heart surgery from patients suffering from 1. ischaemic heart disease (IHD), 2. atrial septal defect of the secundum type (ASD), and 3. left-sided univalvular or multivalvular heart disease (VHD) with or without congestive heart failure (CHF) experienced prior to surgery. In the IHD group the densities of both the perivascular and the "free" myocardial adrenergic nerve net were greater than in the ASD group and especially in the VHD/CHF group. Secondly, the intensity of fluorescence of the adrenergic structures was generally higher in the IHD group than that in the VDH/CHF group. Further, the average size of the varicosities, the number of varicosities per given length of axon, and the proportional share of the large varicosities were greater in the IHD group than in the ASD and VHD/CHF groups. The difference between the IHD and ASD groups was not great but was obvious in any case. In some patients with VHD/CHF fluorescing axons were observed only occasionally, and the tiny varicosities exhibited a hardly discernible fluorescence. Thus the amount of noradrenaline (NA) in the adrenergic fibres in the IHD group seems to be higher than in the ASD and especially VHD/CHF groups. The level of NA in the IHD group is assumed to constitute a contributory factor in both intracellular metabolic changes and the systemic changes typical of myocardial ischaemia and infarction. In one patient with IHD and in six patients with VHD/CHF with significantly higher heart volume (mean+/-SD) compared with the rest of the patients (P less than 0.001), huge local axonal accumulations of NA in the form of "droplet fibres" were found. These enlarged, bulging adrenergic axons are assumed to be a consequence of mechanical trauma with stretching or disruption of the axons due to myodegenerative processes. It is further assumed that these "droplet fibres" are relatively common in those patients with diseased myocardium. They may constitute an extra contributory factor to the tendency to arrhythmiility of non-atuomatic tissue.

Adult↗