bluuebunny/crossref_metadata_2025_split huggingface dataset:
Connectivity changes in an isolated molluscan ganglion during in vivo culture
Authors: Bulloch A. G. M. , Kater S. B. , Murphy A. D. 
Published: January 2005

AbstractThe stability of neuronal connections in the isolated buccal ganglia of Helisoma trivolvis was examined during in vivo culture for periods up to one month. After 4–8 days the characteristic IPSP input to protractor motoneurons (PMNs) was either abolished or reduced in efficacy. This is apparently due to reduced efficacy of chemical synapses, since the input resistance and resting potential of the motoneurons is unchanged and a fraction of spike‐evoked IPSPs from premotor neurons (cyberchrons) onto PMNs was absent. PMNs lacking IPSP input nevertheless exhibit vigorous cyclical bursts of action potentials driven by electrical EPSPs. The IPSP of PMNs showed partial or full restoration after 14–32 days of culture despite the lack of reinnervation of normal targets. Existing electrical synapses were apparently more stable during culture, but electrical connections between cyberchrons and PMNs were strengthened. Probably because of the reinforcement of these electrical synapses, regenerative cycles of activity in both cyberchrons and PMNs may often be initiated by brief stimulation of a single PMN in cultured ganglia. This is in marked contrast to normal ganglia in which PMNs possess a limited ability to generate such activity. It is concluded that isolation of the buccal ganglia results in a predictable, functional alteration of its neuronal circuitry. Such a perturbation of connectivity indicates that a significant degree of plasticity can be exhibited by adult molluscan neurons.
Stimulation is necessary for the development of tolerance to a neuronal effect of ethanol
Authors: Traynor Alexis E. , Schlapfer Werner T. , Barondes Samuel J. 
Published: January 2005

AbstractEthanol accelerates the decay of post‐tetanic potentiation at an identified synapse in Aplysia. We have previously shown that with repeated exposures the ethanol effect diminishes, a development termed “tolerance.” Here we present evidence that the establishment of tolerance depends on adequate stimulation of the presynaptic terminal in the presence of ethanol. Elevated magnesium in the perfusion medium prevents tolerance, whereas elevated calcium in the perfusion medium reduces the amount of stimulation required for tolerance to develop.
γ‐Aminobutyric acid receptors in brain postsynaptic densities
Authors: Matus Andrew , Pehling Gundula , Wilkinson Diane 
Published: January 2005

AbstractRat brain synaptic plasma membranes contain two receptorlike binding sites for the inhibitory transmitter γ‐aminobutyric acid. Postsynaptic junctional structures (postsynaptic densities) isolated from these membranes contain only the higher affinity site enriched more than sixfold compared to the membranes. The results provide the first direct evidence for the association of transmitter receptors with postsynaptic junctional sites in the brain.
Neurite growth promoting factors of embryonic chick—ontogeny, regional distribution, and characteristics
Authors: Riopelle R. J. , Cameron D. A. 
Published: January 2005

AbstractA single neuronal cell biological assay for NGF has been used to quantitate factors in soluble extract of chick embryo that promote neurite outgrowth. The neurite growth promoting activity is detected as early as day 1.5 of embryonic life. Specific activity increases to maximum over the first four days and then decreases from day 5 to 6 during a growth spurt of the embryo. The tissue distribution of neurite growth promoting activity at eight embryonic days shows higher specific activity in peripheral structures that are richly innervated. Extract from all embryonic stages and from all tissues studied induces neurite outgrowth that is inhibited only partially by antibody to mouse NGF. Furthermore, the kinetics of neurite outgrowth and the neuronal populations responsive to extract differ from that of NGF. These observations indicate heterogeneity of the neurite growth promoting factors in soluble extracts of embryonic chick and demonstrate the presence of these factors before the responsive neurons leave the cell cycle and begin their differentiation processes.
Cerebral [K+]e increase as an index of the differential susceptibility of brain structures to terminal anoxia and electroconvulsive shock
Authors: Bureš J. , Burešová O. 
Published: January 2005

AbstractThe time course of the [K+]e increase elicited by terminal anoxia or by electroconvulsive shock (ECS) was compared in various parts of the rat brain. The [K+]e was measured with ion‐selective microelectrodes stereotaxically introduced into the target area. Respiration arrest induced in anesthetized rats a slow [K+]e increase to about 6–10 mM followed by an abrupt rise to 30–50 mM (doubling time 5–14 sec) in the neocortex, hippocampus, amygdala, caudate nucleus, and thalamus. In the reticular formation, zona incerta, and lateral hypothalamus the second phase of [K+]e increase was much slower (doubling time 30–50 sec) and lacked the autoregenerative character. Trans‐pinnate ECS (50 Hz, 0.5 sec, 80 mA), administered to rats immobilized with gallamine triethiodide, elicited a generalized [K+]e increase of the spreading depression type in neocortex and hippocampus (40 mM) as well as in the caudate nucleus and thalamus (20–30 mM), followed by slow [K+]e decrease (half‐time 40–60 sec). Much lower ECS‐induced [K+]e increase (to 5–6 mM) was observed in the reticular formation, zona incerta, lateral hypothalamus and, surprisingly, in the amygdala. It is concluded that the autoregenerative [K+]e release of spreading depression type develops in structures with high density of membranes reacting to partial depolarization by increased sodium permeability.
Deutocerebrum of the cockroach Blaberus craniifer burm. Quantitative study and automated identification of the glomeruli
Authors: Rospars Jean Pierre , Chambille Irène 
Published: January 2005

AbstractThe glomerular organization of the hemideutocerebrum is analyzed quantitatively, using only spatial position, in four individuals (eight hDTCs) after a visual identification of glomeruli on graphic reconstructions. In order to assess directly the invariance of the neuropil in an insect brain the following is done: (1) The position of each glomerulus is compared to the position A′ it should occupy if the hDTCs were identical. It is shown that in 80 and 71% of the cases, respectively, intra‐ and interindividual comparisons in the studied glomerulus is the nearest to A′. (2) The actual position is equally compared to the theoretical location A″ each glomerulus should occupy if its absolute position could be changed but not its relative position with respect to its neighbors. The calculation of A″ is based on process (3). In 86 and 80% of the cases, respectively, it is found that the actual position is that which is nearest to A″. (3) An automated identification process, based on absolute and relative locations, but completely independent of visual identification, is described. It allows the identification of 77 and 74% of glomeruli, respectively. These matchings are in 96 and 90% of the cases identical to the visual matchings. The location predictability of most glomeruli is discussed to show the existence, nature, and limits of the hemideutocerebral invariance.
Soma spike of neuroendocrine bag cells of aplysia californica
Authors: Acosta‐Urquidi Juan , Dudek F. Edward 
Published: January 2005

AbstractSoma action potentials of the neuroendocrine bag cells of Aplysia californica were studied with intracellular recording and current injection. Spikes in artificial sea water (ASW) were either graded with increasing depolarizing current pulses, or had a well‐defined threshold. The latter spikes typically had faster rise times with larger overshoots and hyperpolarizing afterpotentials. Repetitive stimulation led to spike potentiation (SP), manifested as an increase in overshoot amplitude and duration of successive spikes in a train. SP was usually detectable at 0.5 Hz, and maximal between 0.8 and 4 Hz. Concomitant accommodation occurred rapidly at ≥5 Hz. The increase in spike duration during SP resulted from a progressive enhancement of an inflection on the repolarizing phase. The inflection was dependent on membrane potential; small depolarizations (5–10 m V) enhanced it; hyperpolarization (<35 m V) reduced it. Solutions with O—Na+ (Tris‐substituted) or O—Ca2+ (1 μM EGTA) revealed mixed Na+/Ca2+ spikes with variable degrees of Na+ versus Ca2+ dominance. Cd2+, Co2+, and Mn2+ reversibly abolished the inflection on the repolarizing phase, indicating that it is Ca2+ mediated; the spike was reduced irreversibly at higher concentrations. SP was generally reduced only if the spike was severely attenuated. It is proposed that SP results primarily from a voltage‐ and time‐dependent potassium inactivation which then unmasks a calcium current. SP may play a role in augmenting the release of egg‐laying hormone.
Multiple‐rate components of axonally transported proteins in the hypothalamo‐neurohypophysial system of the rat
Authors: Fink David J. , Russell James T. , Gainer Harold , Brownstein Michael J. , Baumgold Jesse 
Published: January 2005

AbstractThe transport of labeled proteins from the hypothalamus to the neurohypophysis following 35 S‐methionine injection into the rat supraoptic nucleus was studied using a unique approach adapted for the study of short‐axon systems. Multiple‐rate components comparable to those found in other neuronal systems were demonstrated. Neurosecretory vesicle‐containing proteins (e.g., neurophysins) were transported at fast rates (≥ 120 mm/day), whereas the cytoskeletal protein, actin, moved principally in the slow component of transport. Two‐dimensional gel electrophoresis was used to analyze the diverse patterns of labeled proteins found in the various rate components of axonal transport in this system.
Some effects of proctolin on the cardiac ganglion of the maine lobster, Homarus americanus (Milne Edwards)
Authors: Miller Mark W. , Sullivan Robert E. 
Published: January 2005

AbstractThe neuropeptide proctolin has excitatory effects on the isolated lobster cardiac ganglion. Selective application to the anterior cell body region produces a dose‐dependent (10−8–10−5M) prolonged depolarization of large anterior cells as well as marked increases in burst frequency and/or duration. In ganglia which have been silenced with tetrodotoxin, proctolin application to anterior cells elicits long‐lasting depolarizing responses which are accompained by a 10–30% increase of the apparent membrane input resistance. Higher proctolin concentrations produce high‐frequency trains of driver potentials. It is proposed that a proctolinlike peptide may serve a neurohumoral role in the lobster cardiac ganglion and that the anterior motor neurons exhibit endogenous rhythmicity in its presence.
Amine modulation of the neurogenic Limulus heart
Authors: Augustine George J. , Fetterer Raymond , Watson Winsor H. 
Published: January 2005

Abstract(1) The biogenic amines octopamine (OCT), dopamine (DA), epinephrine (E), and norepinephrine (NE) cause dose‐dependent increases in both the rate and amplitude of contractions of the isolated Limulus heart‐cardiac ganglion. Their relative ability to produce this excitation is OCT > DA ∼ E > NE. (2) The excitatory effects of all these amines are antagonized by the α‐adrenergic blocker phentolamine and the dopaminergic antagonist haloperidol. The β‐adrenergic antagonist dichloroisoproterenol slightly reduces amine excitation, but is also a partial agonist. The β‐adrenergic antagonist propanolol, the α‐blocker phenoxybenzamine, and the serotonin antagonist metergoline are ineffective. (3) In addition to their excitatory effects, DA and, to a lesser extent, NE initially reduce contraction rate and amplitude. (4) The transient inhibition is eliminated selectively by metergoline and is unaffected by the other antagonists. (5) The amines all increase the frequency of cardiac ganglion electrical bursting activity, whether ganglia are isolated or attached to cardiac muscle. Dopamine and NE also transiently inhibit the cardiac ganglion. (6) The amines do not alter myocardial resting tension, contractility, or membrane potential. (7) These amines appear to exert their modulatory effects on Limulus heart by altering the properties of the neurons which comprise its cardiac ganglion.
Formation of novel central and peripheral connections between molluscan central neurons in organ cultured ganglia
Authors: Hadley Robert D. , Wong Richard G. , Kater Stanley B. , Barker David L. , Bulloch Andrew G. M. 
Published: January 2005

AbstractAn in vitro organ culture system for buccal ganglia of the adult snail, Helisoma, is described. The system supports: (1) maintenance of characterstic electrophysiological parameters of identified neurons over seven days of culture; (2) choline metabolism including uptake and synthesis over the same duration; (3) sprouting and growth of neurons in response to axotomy; (4) the formation of novel central electrotonic connections between identified neurons as a result of sprouting and growth. These observations on neuronal growth and the formation of connections are similar to those made with in vivo culture. The use of in vitro culture allows precise manipulations not previously possible. When buccal ganglia are cultured in vitro with the cut distal ends of peripheral nerve trunks held closely apposed, axons of neurons 5R and 5L in the nerve trunks are capable of forming electrotonic connections similar to central connections. The capability of these neurons to form electrotonic connections via their peripheral axons implies that special structures (i. e., central neurites) are not required for the formation of connections; and neither are special environments (i. e., the central neurites) required for these connections.
Differential effects of amino acids on the period of the circadian rhythm from the Aplysia eye
Authors: Eskin Arnold 
Published: January 2005

AbstractThe effect of continuous treatments of single L‐amino acids (0.1mM) on the free running rhythm from the isolated Aplysia eye was examined. A variation in the change in free running period produced by different amino acids was observed. Two well‐known precursors of neurotransmitter (tyrosine, tryptophan) had the largest effects. These amino acids lengthened the period ca. 1.7 h. Another group of amino acids (alanine, threonine, proline) lengthened the period by about 1 h. Smaller effects were produced by aspartic acid and leucine and no effects were caused by lysine, glycine, valine, and serine. Phenylalanine may shorten the period a small amount. Glucose (5mM) lengthens the period a small amount (0.4 h), decreases the effect of tyrosine somewhat, and has no effect on the lengthening of the period produced by tryptophan. Three amino acids not involved in protein synthesis (ornithine, β‐alanine, citrulline) had at most small effects on the free running period. Also, D‐tryptophan lengthened the period by 0.6 h but the effect of D‐tryptophan was considerably smaller than the effect of L‐tryptophan. A few of the amino acids had small short‐term effects on spike rate and longer‐term effects on the amplitudes of the rhythms but these effects did not correlate with the effects of the amino acids on the free running period. Though continuous treatments of certain amino acids lengthened the periods, shorter treatments (tryptophan, 6 h) did not phase‐shift the rhythm. Since eyes maintained in a commonly used culture medium have longer periods than eyes in a simple seawater medium, the amino acids of the culture medium must be responsible, at least in part, for the lengthening effect of the culture medium. The mechanism of action of the amino acids is unknown. The magnitude of the effects did not correlate with physical‐chemical properties of the amino acids nor with whether the amino acids were “essential” or “nonessential.” The effects of the amino acids may be mediated by their effects on neurotransmitter and/or protein synthesis.
Ventriculo–cisternal perfusion of twelve amino acids in the rabbit
Authors: Davson H. , Hollingsworth J. G. , Carey M. B. , Fenstermacher J. D. 
Published: January 2005

AbstractThe clearances of twelve amino acids from the ventricles during ventriculocisternal perfusion in the rabbit have been measured; uptake by the brain was also measured and this permitted the separate computation of loss to brain and loss to blood during the perfusion. Clearance under carrier‐free conditions was greater than when a concentration of 5mM unlabeled amino acid was present in the perfusion fluid. Brain uptake was also usually reduced by the presence of unlabeled amino acid due presumably to suppression of accumulation by brain cells. Reduction of transport across the blood‐brain barrier would tend to increase brain uptake, and there was some evidence for a balance between the two opposing tendencies. Inhibition of clearance of a given labeled amino acid could be brought about by unlabeled amino acids of different molecular species. In general, the amino acids fell into three categories: neutral, acidic, and basic, and there was some overlap between them; of the neutral amino acids the A‐ and L‐classification of Christensen was valid, although once again there was some overlap. If, during ventriculo‐cisternal perfusion of a labeled amino acid, the activity of this labeled amino acid in the blood was raised well above that in the inflowing perfusion fluid, the labeled amino acid continued to be cleared from the perfusion fluid, suggesting uphill transport. On this basis it was suggested that the normally low concentrations of amino acids in the cerebrospinal fluid (CSF), by comparison with those in plasma, were due to an active transport from the CSF to the blood. Substrate‐facilitated transport, whereby the penetration of labeled amino acid into the perfusion fluid from blood could be accelerated by adding unlabeled amino acid to the perfusion fluid, or vice versa, was demonstrated.
Cobalt mapping of the nervous system: How to avoid artifacts
Authors: Hackney C. M. , Altman J. S. 
Published: January 2005

AbstractInfusion of cobalt ions into cut axons is an established method for tracing neuron projections in the central nervous system. Artifacts, where unintended neurons are stained, however, have been reported, leading to difficulties in interpretation. Experiments in the locust Schistocera gregaria Forskål show that such artifacts can be induced through damage to axons caused by cutting peripheral nerves and by using high cobalt chloride concentrations (0.4M and above). Mixtures of cobalt and nickel chlorides and nickel chloride alone were introduced into different branches of the same nerve and developed with rubeanic acid to give precipitates of different colors in the two sets of axons. Preparations were examined with the light microscope, where mixing of ions would appear as intermediate colors, and by x‐ray probe microanalysis. No evidence for leakage of metal ions from the filled axons or for ion uptake by other axons could be detected, provided that low concentrations of cobalt and nickel chlorides were used and nerve cutting was reduced to a minimum by making preparations in vivo. If extreme conditions are avoided when making the preparation, the risk of producing artifacts is minimized, thus enabling the cobalt method to be used with greater confidence for describing neuronal projections.
Neuronal elements in snail tentacles as revealed by horseradish peroxidase backfilling
Authors: Chase Ronald , Kamil Rifa'at 
Published: January 2005

AbstractThe snail tentacle ganglion is a prominent structure that innervates an epithelial pad sensitive to wind and odors. Its neural composition, and that of the sensory pad, was studied in the terrestrial snail Achatina fulica by applying horseradish peroxidase to the distal end of the cut tentactle nerve. Five types of neurons were labelled by the procedure: receptors, located in the subepithelial region; three kinds of interneurons, located in the ganglion and its digitlike extensions; and a bipolar neuron, located in the dermo‐muscular wall of the tentacle. In contrast to earlier descriptions based on silver stains, the present results demonstrate the presence of neurons of large size (soma diameters up to 46 μm). Also, contrary to earlier interpretations, the results indicate that all five identified cell types send axons directly to the CNS.
Modulation of the Aplysia gill withdrawal reflex by dopamine
Authors: Ruben Peter , Lukowiak Ken 
Published: January 2005

AbstractThe ability of dopamine to modulate gill contractions was tested in Aplysia. When dopamine was perfused through the gill vasculature, gill contractions caused by siphon stimulation (gill withdrawal reflex) and by depolarization of the gill motor neuron L7 were increased in amplitude, as compared with those evoked during seawater perfusion. Habituation of gill movements, brought about by repetitive stimulation of the siphon or of L7, was prevented by dopamine. Despite the absence of reflex habituation, the number of action potentials in central gill motor neurons, evoked by siphon stimulation, showed normal decrement. Dopamine's effects were blocked when the ctenidial nerve was cut or when L7 hyperpolarized. These data suggest that dopamine acts peripherally to increase the efficacy of L7's synpatic transmission onto gill muscle or elements of the gill neural plexus.
Aminergic neurons in the anterior nervous system of the rat acanthocephalan moniliformis dubius
Authors: Eva Budziakowski M. , Mettrick D. F. , Webb Rodney A. 
Published: January 2005

AbstractThe cerebral ganglion and nerve tracts of Moniliformis dubius show intense, specific, green fluorescence that is also associated with the lateral and apical sensory bulbs. Radioenzymatic assays showed that high levels of dopamine were present but only small amounts of the catecholamines norepinephrine and epinephrine were identified. Incubations of the proboscis sac in dilute solutions of dopamine increased fluorescence while incubations in reserpine resulted in loss of fluorescence. Nonfluorogenic amine octopamine was also detected radioenzymatically. Neutral red vitally stained a number of cells in the cerebral ganglion and the nerve tracts extending from the ganglion. Electron microscopy showed that many neurons contained electron‐dense vesicles. The close association of the fluorescing, amine‐containing nerve tracts with the sensory bulbs suggests that they may play a functional role in sensory reception and transmission in M. dubius. This is the first report on the presence of biogenic amines in the Acanthocephala.
Retinal illumination produces synaptic inhibition of a neurosecretory organ in the crayfish, pacifastacus leniusculus (Dana)
Authors: Kirk Mark D. , Prugh John I. , Glantz Raymon M. 
Published: January 2005

AbstractWe have identified a cluster of neurosecretory cells in the crayfish eyestalk that possess dendrites in the second optic neuropil (Medulla) and project axons to the first optic neuropil (Lamina). Illumination of the ipsilateral retina produces a synaptic inhibition of these cells that is mimicked by iontophoresis of gamma‐aminobutyric acid within the medullary neuropil. The neurosecretory nature of the cells, the efferent projection of their axons, and the strong inhibition of their spiking activity upon retinal illumination suggest that they may be involved in the feedback control of dark adaptation and/or circadian changes in visual sensitivity.