bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fast‐axon synapses of a crab leg muscle
Authors: Atwood H. L. , Jahromi S. S. 
Published: January 2005

AbstractNeuromuscular synapses of the “fast” excitatory axon supplying the main extensor muscle in the leg of the shore crab Pachygrapsus crassipes were studied with electrophysiological and electron‐microscopic techniques. Electrical recording showed that many muscle fibers of the central region of the extensor muscle responded only to stimulation of the fast axon, and electron microscopy revealed many unitary subterminal axon branches. Maintained stimulation, even at a low frequency, resulted in depression of the excitatory junctional potentials (EJPs) set up by the fast axon but EJPs of different muscle fibers depressed at different rates, indicating some physiological heterogeneity among the fast‐axon synapses. Focal recording at individual synaptic sites on the surfaces of the muscle fibers showed quantal contents ranging from 1.4 to 5.5 at different synapses; these values are relatively high in comparison with similar determinations made in the crayfish opener muscle. Synapse‐bearing nerve terminals were generally relatively small in diameter and filiform, with many individual synaptic contact areas of uniform size averaging 0.6 μm2. All of the individual synapses had a presynaptic “dense body” at which synaptic vesicles clustered. If these structures represent release points for transmitter quanta, the initial high quantal content would have an ultrastructural basis. The mitochondial content of the nerve terminals, the synaptic vesicle population, and the specialized subsynaptic sarcoplasm were all much reduced in comparison with tonic axon synaptic regions in this and other crustaceans. The latter features may be correlated with the relatively infrequent use of this axon by the animal, and with rapid fatigue.
New technique for measuring dynamic axonal transport and its application to temperature effects
Authors: Takenaka Toshifumi , Horie Hidenori , Sugita Tohru 
Published: January 2005

AbstractA new technique was devised for the dynamic detection of the axoplasmic transport of β‐radioactively labeled materials in which a semiconductor radiation detector was used as the β‐ray counter. The detector element is a silicon p‐n junction diode and has a diameter of 2.0 mm. With this detector, the β‐radioactive distribution of axoplasmic transport could be measured in an axon maintained physiologically without cutting nerves. This method makes possible determination of the transport rate using one bundle of peripheral nerves. The rate in the bullfrog was 6.4 mm per hour at 24.0 °C. Temperature effects on the bullfrog axoplasmic transport were also observed at different temperatures, ranging from 5.0 to 24.0 °C. At these temperatures the rate increased as an exponential function of temperature from 1.1 to 6.4 mm per hour. Within this temperature range, the Q10 is 2.5 and an Arrhenius plot of the natural logarithm of velocity versus the reciprocal of absolute temperature yielded an apparent activation energy of 14.8 Kcal. This technique offers great advantages in permitting direct study of the axoplasmic flow of the axon in a physiological condition.
Increased cyclic GMP in the end‐plate region of denervated frog muscle
Authors: Allen D. O. , Gardner R. M. , Yount R. A. , Ochs S. 
Published: January 2005

AbstractDenervated frog sartorius muscles showed an approximately 2–3 fold increase of cyclic GMP in their end‐plate rich regions which did not appear up to 5 weeks after denervation in the normally end‐plate‐free pelvic region. No increase in cyclic AMP was seen in these preparations. The results suggest that the increase of cyclic GMP is related to processes specific to the region in which end plates are normally present.
Routing of transported materials in the dorsal root and nerve fiber branches of the dorsal root ganglion
Authors: Ochs S. , Erdman J. , Jersild R. A. , McAdoo V. 
Published: January 2005

AbstractAfter injection of the L7 dorsal root ganglion with 3H‐leucine, fast axoplasmic transport carries some 3–5 × more labeled materials down the sensory fibers branches entering the sciatic nerve as compared to the dorsal root fiber branches of the neurons. Freeze‐substitution preparations taken from the two sides of the lumbar seventh dorsal root ganglia of cats and monkeys showed little difference in the histograms of nerve fiber diameters of the sensory nerve fiber branch of these neurons as compared to the dorsal root fiber branches. A similar density of microtubules and of neurofilaments in the dorsal root and sensory nerve fiber branches over a wide range of fiber diameters was found in electron micrograph preparations. In the absence of an anatomical difference in the fibers to account for the asymmetrical outflow, a functional explanation based on the transport filament model was advanced.
Qualitative analysis of proteins rapidly transported in ventral horn motoneurons and bidirectionally from dorsal root ganglia
Authors: Stone George C. , Wilson David L. 
Published: January 2005

AbstractTwo‐dimensional electrophoresis has allowed a higher‐resolution comparison of rapid transport in ventral horn motoneurons and bidirectionally in dorsal root sensory neurons. Dorsal root ganglia 8 and 9, or hemisected spinal cords, from frog were selectively exposed in vitro to 35S‐methionine. Transported, labelled proteins that accumulated in 3 mm segments proximal to ligatures on dorsal roots and spinal nerves or sciatic nerves were subjected to two‐dimensional gel electrophoresis. Comparisons were made of fluorographic patterns from dried gels. Sixty‐five species of proteins were found to be rapidly transported in both bifurcations of dorsal root sensory neurons. No abundant species of protein was rapidly transported in dorsal roots that was not also found in spinal nerves. A comparison of proteins rapidly transported in the sciatic nerve from ventral horn motoneurons with those from dorsal root sensory neurons yielded 50 common species of polypeptides. At most four minor species were possibly transported only in ventral horn motoneurons. An overall comparison indicates that at least 45 species of proteins, including all of the more abundantly transported ones, were consistently common to both dorsal root bifurcations and to ventral horn motoneurons. This appears to be the case despite the very different functions carried out by motoneurons and sensory neurons.
Muscle fibrillation caused by Cytochalasin‐B applied to the motor nerve
Authors: Ramirez Beatriz U. 
Published: January 2005

AbstractCytochalasin‐B, a drug known to interfere with axoplasmic transport, evoked fibrillary potentials in the geniohyoid muscle when applied to its motor nerve. Despite this denervation‐like effect, neuromuscular transmission remained normal. Some contractile characteristics of the muscle were studied. It was found that contraction time, isometric twitch tension, and half‐relaxation time were not altered by the drug treatment. The present findings show that neurogenic molecular factors conveyed by axoplasmic transport to the nerve terminal are involved in the regualtion of some muscle membrane characteristics but do not modify the muscle contractile features.
Developmental plasticity of central noradrenaline neurons after neonatal damage—changes in transmitter functions
Authors: Jonsson G. , Wiesel F.‐A. , Hallman H. 
Published: January 2005

AbstractThe effects of neonatal 6‐hydroxydopamine (6‐OH‐DA) treatment (systemic administration) on norasrenaline (NA) metabolism, trun over, and receptor charasteristics have been investigated in rat brain in the adult atage. This treatment is known to preferentially affect the locus coeruleus (LC) NA system leading to a marked NA denervation in the cerebral cortex and a hyperinnervation of NA nerve terminals in the pons and medulla oblongata without influencing the LC perikarya. The main NA metabolite, 3‐methoxy‐4‐hydroxyphenylglycol (MOPEG) was reduced by about 70% in the cerebral cortex after 6‐OH‐DA‐treatment at birth while the endogenous NA was almost completely depleted (‐92%). The MOPEG levels were not significantly changed in the pons medulla after 6‐OH‐DA treatment in contrast to the 60% increase of the endogenous NA concentration. The relative reduction of NA in the cerebral cortex of 6‐OH‐Da treated rats increased in the cerebral cortex is increased after 6‐OH‐DA, while decreased in the pons‐medulla, possibly related to changes in the activation of presynaptic α‐adrenoreceptors in both regions. NA‐induced formation of cAMP in vitro was found to be markedly increased in the cerebral cortex after 6‐OH‐DA, whereas no consistent change was observed in the pons medulla. Measurements of α‐ and β‐receptor binding in vitro using radioligand techniques showed an increase of binding sites (20%–50%) for both receptors in the neocortex after 6‐OH‐DA, whereas no changes were observed in the pons medulla. The 6‐OH‐Da induced changes in NA turnover, cAMP generating systems, and receptor density may all represent compensatory processes following the altered development of the NA neurons induced by 6‐OH‐DA.
Primitive nervous systems: Electrical activity in ventral nerve cords of the flatworm, Notoplana acticola
Authors: Koopowitz Harld , Bernardo Kerry , Keenan Larry 
Published: January 2005

AbstractElectrical activity evoked in the major cords of the ventral submuscular nerve plexus were measured. Recordings and stimulation utilized suction electrodes attached directly to exposed nerve cords. Four categories have been recorded: (a) short latency spikes which have relatively high thresholds and appear to be single units; (b) short duration fast compound spikes that are made up of a large units; (c) long duration compound potentials that are made up from a large number of smaller units, and (d) small amplitude potentials with long latencies and a characteristic shape. These can be conducted diffesely through the nerve plexus. The first two categories of spikes are called “fast” potentials because of their characteristic rise and fall times and the last categories are known as “diffuse” potentials. The spikelike fast potentials were only recorded from the main trunks (nerves VI), while diffuse potentials could also be recorded from side branches of these nerves. The diffuse potential appears to be concluded throughout the plexus but preferential conducting pathways occur lesions. Both diffuse and fast potentials show facilitation of response to repeated stimulation. Facilitation can be demonstrated in the presence of high Mg2+ concentrations. Conductance of the diffuse potential also occurs in the presence of high ambient Mg2+. In Ca2+ free medium containing 1‐mM EGTA one can also observe facilitatory events. The possibility of Mg2+‐insensitive synapses is discussed.
Ganglioside patterns and cholera toxin‐peroxidase labeling of aggregating cells from the chick optic tectum
Authors: Engel Edgar L. , Wood John G. , Byrd Frances I. 
Published: January 2005

AbstractThe ganglioside compositions of the chick optic tectum and aggregating tectal cell cultures were examined. Both showed similar trends in changes in ganglioside patterns during development. GD and GD1b were the predominant gangliosides early in development, while GD1a and several other multisialogan gliosides increased in relative amounts with increasing age in vivo and in vitro. Four gangliosides were present early in development which have not previously been reported. These gangliosides are not present at later developmental times suggesting a possible role for them during the critical early stages of nervous tissue differentiation. Some differences were noted when comparing in vivo versus in vitro ganglioside patterns; these differences may possibly be due to the lack of normal retinotectal connections in the cultures. Cytochemical studies on the localization of the presumed cholera toxin‐peroxidase binding site GM1 showed conjugate binding correlates with increasing levels of GM1 in the cultures. In older cultures, the conjugate was uniformly localized on all cells and processes in the aggregates. The conjugate also bound to synaptic membranes and intensely stained the synaptic cleft. This latter observation suggests an enrichment of GM1 in the synaptic cleft region.
Lobster claw motorneurons respond to contralateral sensory stimuli
Authors: Govind C. K. , Meiss D. E. , Lang F. 
Published: January 2005

AbstractUnilateral sensory stimuli in an isolated lobster claw‐ganglion preparation elicits soma and axon spikes in homologous motorneurons in the ipsilateral as well as the contralateral hemiganglion. This cross excitation of the motorneurons provides a basis for bilateral reflexes in the claw and is likely mediated through interneuron(s).
Two‐dimensional analysis of autophosphorylated chick brain synaptic subfractions
Authors: Breithaupt Thomas B. , Babitch Joseph A. , Hodges Donald H. 
Published: January 2005

AbstractChick brain synaptosomes were autophosphorylated upon incubation with [32PO4] and glucose, exposed to depolarizing ionic conditions, subsequently lysed, and respective synaptic subfractions were isolated. Analysis of these subfractions by two‐dimensional electrophoresis revealed complex and unique phosphopeptide patterns. The phosphorylation levels of several soluble and membrane polypeptides appeared to change upon exposure to the depolarizing conditions.
States of excitability in ovulation hormone producing neuroendocrine cells of Lymnaea stagnalis (gastropoda) and their relation to the egg‐laying cycle
Authors: Kits K. S. 
Published: January 2005

AbstractThe electrotonically coupled network of about 100 neuroendocrine caudodorsal cells (CDC) of the freshwater snail Lymnaea stagnalis exhibits three states of excitability with distinct electrophysiological characteristics. Transitions between these states occur spontaneously or can be induced experimentally. The CDC produce an ovulation hormone, and the excitability states are clearly related to the egg‐laying cycle of the snail. Two hours before egg laying, the cells enter an active state, which lasts one hour. This phase is characterized by a spontaneous firing pattern, which in preparations can be evoked as an afterdischarge, and during which the hormone is thought to be released. After this, the cells enter an inhibited state in which no other activity than directly stimulus‐dependent ortho‐ and antidromic action potentials can be evoked. This phase lasts till about four hours after egg laying. The subsequent resting state is characterized by facilitation of the responses upon repetitive stimulation of the cells, leading to depolarization of the network and additional action potentials. In this phase, an afterdischarge can be evoked, which brings the cells into the active stage again.
Spontaneous and evoked postsynaptic potentials in an embryonic neuromuscular system of the lobster, Homarus americanus
Authors: Cole James J. , Lang Fred 
Published: January 2005

AbstractThe embryonic motor innervation to the deep extensor abdominal muscles was studied in lobster eggs in which reflex twitches and tail flips could be evoked by mechanical stimulation in early embryos. Recordings from impaled fibers during early and later stages of embryonic development revealed spontaneous depolarizing and hyperpolarizing potentials, suggesting the presence of excitatory and inhibitory axons. Stimulation of the extensor motor innervation produced a variety of EPSPs and IPSPs. The depolarizing responses included small and large EPSPs and nonovershooting spikes. Although moderate facilitation of the EPSP was sometimes observed, defacilatation was observed in the majority of fibers of all stages. Spiking could not be evoked by motor axon stimulation in embryos of early stages. These findings indicate that from the outset the deep abdominal extensor neuromuscular system of the lobster is phasic in its response to nerve stimulation and is functional as part of the tail flip reflex at least six months before hatching.
Neuronal repair and avoidance behavior in the flatworm, Notoplana acticola
Authors: Faisst J. , Keenan C. L. , Koopowitz H. 
Published: January 2005

AbstractIn Notoplana avoidance behavior is lost after bisection of the brain or removal of one of its lobes. Behavioral recovery usually occurs within 3–10 days. Recovery of individuals may be gradual or abrupt. Grouped data shows gradual linear repair of turning behavior. Most animals with all connectives between the two lobes of the brain severed recovered preoperative responses, while those with one lobe of the brain removed averaged about 60% of the preoperative level of response. Some individuals in both groups recovered completely. Histological evidence of neuronal repair was found in all animals. Where the lobes of the brain were separated, connectives between them appeared to re‐form. In worms with one lobe of the brain removed, the nerves disconnected by the excision joined the remaining lobe. Action potentials are conducted across repaired tissue in both split‐brain and half‐brain worms in both seawater and Mg2+‐rich solutions. CNS repair appears to involve functional synaptic contacts. Notoplana does not replace ganglionic tissue but does compensate adequately for CNS damage.
Flight pattern induced by temperature in a single‐gene mutant of Drosophila melanogaster
Authors: Koenig J. H. , Ikeda K. 
Published: January 2005

AbstractSimultaneous intracellular recordings were made from the six dorsal longitudinal flight muscle (DLM) fibers in the temperature‐sensitive mutant of Drosophila melanogaster, shibirets 1 (shi). The DLM firing pattern induced by temperature in shi was compared with the DLM pattern of a wild‐type fly in stationary flight. The firing pattern, induced at temperatures between about 26 and 27°C, was very similar to that of the wild‐type pattern. At higher temperatures, the pattern became abnormal, characterzed by many synchronous firings among the fibers and occasional bursting.
Neurotrophic control of 16S acetylcholinesterase from mammalian skeletal muscle in organ culture
Authors: Fernandez Hugo L. , Patterson Michael R. , Duell Myron J. 
Published: January 2005

AbstractThe effects of rat obturator nerve extracts on total and 16S acetylcholinesterase (AChE) activity were studied in endplate regions of denervated anterior gracilis muscles maintained in organ culture for 48 hr. The decrease of total AChE activity in cultured muscles was similar to that observed in denervated muscles in vivo. This decrease in activity was partly prevented by addition of either 100 or 200 μl nerve extract (2.7 mg/ml protein) to the nutrient medium. Nerve extract treatment also decreased the release of AChE activity from the muscle into the bathing medium. Conversely, rat serum (20 μl; 90 mg/ml protein) had no effect on total AChE activity in muscle endplates, nor on release of the enzyme by the muscle. The 16S form of AChE was confined to motor endplate muscle regions and its activity was drastically decreased by denervation in both organ culture and in vivo preparations in a comparable manner. Nerve‐extract supplemented cultures contained a significantly (p ≪ 0.001) larger amount of endplate 16S AChE activity (140–145%) than the corresponding controls (100‐). Our results suggest that some nerve soluble substance, other than serum contaminants or 16S AChE itself, affects the maintenance of 16S AChE at the neuromuscular junction.
External detection of axoplasmic transport using 32P‐ATP as precursor
Authors: Takenaka Toshifumi , Ochs Sidney 
Published: January 2005

AbstractAxoplasmic transport was studied by employing a new external detection method, comparing it to the scintillation method. 32P‐ATP was used as the precursor, and the pattern obtained was one typical of slow transport. The patterns recorded from nerves with the external detector system were seen to be closely similar to those found in the same nerves with the usual scintillation method, the external detector systems having the advantage of allowing studies to be made of changes in the pattern of transport in the same nerve over a period of days.
Colchicine reversibly inhibits electrical activity in arthropod mechanoreceptors
Authors: Schafer Rollie , Reagan Paul D. 
Published: January 2005

AbstractColchicine and some other microtubule‐active agents inhibit the electrical responses of cockroach tibial spine mechanoreceptors. Lumicolchicine, a colchicine analog which does not bind to microtubule protein, does not inhibit mechanoreceptive responses. Colchicine inhibition of peripheral mechanoreceptive responses is fully reversible and dose dependent, but colchicine has no effect on conduction in leg nerve axons. Colchicine inhibition is therefore an effect on the sensory dendrites or soma. The inhibition produced by colchicine could be produced by several effects. Colchicine may inhibit because it (1) disrupts the numerous intracellular microtubules which are a part of this sensory receptor's dendrite, (2) blocks axoplasmic transport of essential materials to the sensory dendrite, or (3) binds to tubulin or other proteins in the dendritic membrane.
Release of 3H‐gamma‐aminobutyric acid (GABA) by inhibitory neurons of the crayfish
Authors: Craelius William , Fricke Russell A. 
Published: January 2005

AbstractInhibitory neurons innervating the muscle receptor organ (MRO) of crayfish were used to study the uptake and release of tritiated GABA. MROs that have been directly exposed to 3H GABA for 60–75 min release radioactivity during low‐frequency electrical stimulation. When ganglia containing the inhibitory cell bodies are exposed to 3H GABA, the isotope travels along a pathway unique to the inhibitory axon, at rates that range between 160 and 240 mm per day. Electrical stimulation of inhibitory axons whose cell bodies have been exposed to 3H GABA for 4–5 hr produces release of isotope from isolated MROs. Low calcium, high magnesium exposure prevents the stimulus‐dependent release of radioactivity. Thin layer chromatographic analyses indicate that GABA comprises at least a major fraction of the radioactivity collected from stimulated preparations. A number of unidentified radioactive compounds are usually present with GABA, and it is suggested that most of these are catabolites of GABA.
Action of detergents and pre‐ and postsynaptic localization of 3H‐naloxone binding in synaptosomal membranes. A structural approach
Authors: Criado Manuel , Aguilar José S. , de Robertis E. 
Published: January 2005

Abstract3H‐naloxone specific binding was carried out on synaptosomal membranes isolated from basal ganglia of the cat brain. A high‐ and a low‐affinity site with Kd1 = 3.7 nM and Kd2 = 35 nM having Bmax 1 = 79 pmole/g protein and Bmax 2 = 224 pmole/g protein were found. The Hill number for the high‐ and low‐affinity sites were, respectively, 1.01 and 0.86. Digitonin and Triton X‐100 had an inhibitory effect on the binding at concentrations between 10−5 and 10−1% (w/v). Deoxycholate and Nonidet P‐40 also inhibited the binding of 3H‐nal‐oxone, but at 10−4% produced a 50% enhancement. After the binding to membranes, the 3H‐naloxone receptor complex is stable to the action of Triton X‐100 and dissociates slowly. In membranes bound with 10 nM 3H‐naloxone and then submitted to 0.1‐0.2% Triton X‐100, in which only the presynaptic membrane disintegrates, the specific radioactivity is decreased. With a more drastic treatment that disintegrates the postsynaptic membrane, the 3H‐naloxone binding to synaptosomal membranes is almost completely abolished. These results suggest that opiate receptors may be localized both pre‐ and postsynaptically in central synapses.