bluuebunny/crossref_metadata_2025 huggingface dataset:
The long‐term fate of neurons in allografts of ganglia in AG‐B‐compatible normal and immunologically tolerant rats
Authors: Zalewski Andrew A. , Silvers Willys K.
Published: January 2005

Neurons in Ag‐B‐incompatible allografts of ganglia are acutely rejected while those in Ag‐B‐compatible grafts are able to survive the immune reaction directed against them. The present study was undertaken to determine the long‐term fate of neurons in allografts of ganglia in Ag‐B‐compatible rats. Isogenic strains of Ag‐B‐compatible adult Lewis (LE) and Fischer (FR) rats were used. The sensory nodose ganglia were reciprocally exchanged between normal LE and FR and between LE and FR animals rendered immunologically tolerant of each other's histocompatibity antigens. The findings were similar in both rat strains and revealed that although neurons and glial cells (i.e., satellite and Schwann cells) could survive for prolonged periods they were nevertheless eventually rejected by normal (nonimmunosuppressed) recipients. On the other hand, neurons and glial cells survived indefinitely in allografts in tolerant rats. Moreover, these neurons were functional because they regenerated nerve fibers into cotransplanted isografts of tongue and exerted the neurotrophic influence of inducing taste bud regeneration. The results demonstrate that, unlike kidney and heart, neurons in ganglia allografts cannot survive indefinitely without immunosuppression in Ag‐B‐compatible animals. Nevertheless, the permanent survival and function of neurons in Ag‐B‐compatible grafts can be achieved, as it is in Ag‐B‐incompatible ganglia grafts, by rendering the recipient immunologically tolerant.
A histofluorescence study of events accompanying accumulation and migration of norepinephrine within locally cooled nerves
Authors: Brimijoin Stephen
Published: January 2005

Glyoxylic acid was used to induce fluorescence in sections of rabbit sciatic nerve. In fresh nerves treated with this agent there were scattered finely beaded axons with a weak blue‐green fluorescence. During local cooling, blue—green fluorescence accumulated steadily at the proximal boundary of the cooled region but never at its distal boundary. This accumulation gave rise to dilated axons that often swelled into brilliantly fluorescent balloon‐like structures up to 10 μm in diameter. Axonal fluorescence was probably specific for norepinephrine, being enhanced by inhibition of the metabolism and diminished by inhibition of the synthesis or storage of this neurotransmitter. After local cooling of nerves for 1.5 hr, specific fluorescence was confined within 0.8 mm of the cooled region. Rewarming led to rapid removal of fluorescence from the cooled region and to disappearance of most of the balloon‐like swellings. Simultaneously, rewarming caused brightly fluorescent fibers that were neither dilated nor swollen to appear in distal regions of nerve. As this wave of fluorescence migrated distally with increasing duration of rewarming, it was spread over increasingly broad regions of nerve, which suggests that axonal transport of norepinephrine may involve some kind of dispersive process.
Effects of methylazoxymethanol given at different stages of postnatal life on development of the rat brain. Comparison with those of thyroid deficiency
Authors: Rabié Alain , Selme‐Matrat Maryse , Clavel Marie‐Claude , Clos Jean , Legrand Jacques
Published: January 2005

Newborn rats were treated at different stages of their development with low doses of methylazoxymethanol acetate. The postnatal increase of the DNA content of the cerebrum did not differ from that of controls. In the cerebellum, the DNA content was transitorily reduced, but later, the external granular layer became thicker and DNA deposition increased in comparison with controls; finally, the cerebellar DNA returned to a normal value. Morphological abnormalities of the cerebellum, abnormal orientation of migrating cells, scattering of Purkinje cell bodies within the internal granule cells and specially striking abnormalities of the morphology and orientation of Purkinje cell dendrites were noted in rats treated with MAM from birth to day 3. The effects on the Purkinje cell morphogenesis persisted but were much less marked when MAM was given from 4 to 7 or from 8 to 11 days. Neonatal thyroid deficiency, as MAM‐treatment between days 0 and 3, leads to an abnormal position of Purkinje cell bodies within the cerebellar cortex; it also leads to morphological abnormalities of their dendritic arborization which closely resemble those observed after MAM‐treatment during the second postnatal week. It also alters the cell formation in the cerebellum. Thyroid deficiency probably exerts its effect on cell formation earlier than previous biochemical studies have shown. On another hand, the morphological abnormalities of Purkinje cell arborizations in the thyroid‐deficient animals may be partly due to the perturbations of cell formation which persist later in the cerebellum.
Rapid axonal transport in vitro. Effects of derivatives of cyclic AMP and other agents acting on the cyclic AMP system
Authors: Edström Anders
Published: January 2005

The effects of agents known to affect the cyclic AMP (cAMP) system in nervous tissue have been studied on the rapid axonal transport in vitro of [3H]leucine‐labeled proteins in the frog sciatic nerve. The transport was inhibited by 3 different cAMP analogues; dibutyryl cAMP (1 mM), zeatin (0.5 mM), and zeatin riboside (0.5 mM), whereas another N6‐substituted adenine derivative, N6‐, isopentyl‐adenine (DMA) (0.5 mM), and also dibutyryl cyclic GMP (1 mM), lacked effects. Two inhibitors of cAMP phosphodiesterases, papaverine and RO 207222, increased the level of cAMP in the nerve and arrested the transport. Papaverine was very potent and caused a reversible transport block at 0.05 mM. Adenosine (3 mM) increased the cAMP content about 16 times, much more than any of the other drugs tested, but only inhibited the transport by about 50%. Veratridine, a depolarizing agent, irreversibly blocked the transport at a low concentration (0.01 mM), which did not change the cAMP level.

Transport inhibitory effects by another depolarizing substance, ouabain, and tricyclic psychotropic agent, chlorpromazine, have been described earlier. Ouabain (0.1 mM), in contrast to chlorpromazine (0.1 mM), caused a small increase in the cAMP content.

The present results do not suggest the existence of a close relationship between rapid axonal transport and the cAMP system. Transport inhibitory effects due to disturbed energy metabolism will be discussed.
Effects of denervation on the permeability of acetylcholine‐activated channels to organic cations
Authors: Guy H. Robert , Dekin Michael S. , Morello Robert
Published: January 2005

Experiments were performed on chronically denervated frog sartorius muscles to determine the permeability of the acetylcholine‐activated channels to organic cations. The membrane voltage response to bath‐applied acetylcholine was measured with the moving electrode when the muscles were bathed in normal Ringer and in Ringer in which all of the Na+ had been replaced with an organic cation. The magnitude of the maximum voltage response was used to estimate the permeability of the channel to the organic cation. These results were compared with those which have been reported for innervated frog sartorius muscles (Maeno, Edwards, and Anraku, 1977). It is concluded that the permeability to a wide range of organic cations is virtually identical for the extrajunctional channels which develop following denervation and the channels which are localized at the junctional region of innervated muscles.
Physiological properties of the penis retractor muscle of Aplysia
Authors: Blankenship J. E. , Rock M. K. , Hill J.
Published: January 2005

The properties of the penis retractor muscle of Aplysia have been studied using intracellular, sucrose gap and tension recording. The fibers are of the invertebrate smooth muscle type and exhibit slow contractions which occur spontaneously or in response to stretch in isolated preparations. Individual muscle fibers are innervated by excitatory and inhibitory axons. A variety of sizes of excitatory and inhibitory junctional potentials can be recorded from them. The innervation is probably diffuse and functionally polyneuronal. The fibers are electrically coupled, permeable to potassium and chloride at rest, and exhibit no overshooting active responses. The muscle shows graded responses of depolarization and contraction proportional to strength of nerve stimulation. Facilitation and depression of junctional potentials are seen with various frequencies of nerve stimulation. Post‐tetanic potentiation occurs with nerve stimulation at frequencies from 2 to 50 Hz and is suppressed in the presence of increased extracellular calcium concentrations.
Penis‐retractor muscle of Aplysia: Excitatory motor neurons
Authors: Rock M. K. , Blankenship J. E. , Lebeda F. J.
Published: January 2005

Cobalt axonal iontophoresis and intracellular recordings were used to identify a cluster of several motor neurons innervating the penis‐retractor muscle of Aplysia. Intracellularly recorded motor neuron action potentials elicited direct, one‐for‐one, constant latency excitatory junctional potentials (ejps) in individual muscle fibers. The axons of motor neurons could be recorded extracellularly in the penis‐retractor nerve and stimulation of the nerve backfired the motor neurons. Perfusion of the ganglion, the muscle, or both with solutions of either increased Mg++/decreased Ca++ or increased Ca++ sea water indicated that the presumed motor neuron impaled was not a sensory cell and that interneurons were not intercalated in the pathway. Innervation of muscle fibers was found to be functionally polyneuronal and diffuse. The ejps were found to undergo marked facilitation with repetitive motor‐neuron stimulation. The motor neurons were isolated in a distinct cluster in the right pedal ganglion. Their electrical activity was characterized by spontaneous irregular action potentials and a moderate input of postsynaptic potentials.
Fast‐axon synapses of a crab leg muscle
Authors: Atwood H. L. , Jahromi S. S.
Published: January 2005

Neuromuscular 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

A 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

Denervated 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

After 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

Two‐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

Cytochalasin‐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

The 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

Electrical 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

The 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

Unilateral 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

Chick 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

The 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

The 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

In 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

Simultaneous 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

The 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

Axoplasmic 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

Colchicine 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

Inhibitory 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

3H‐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.
Neurosecretory cells in the central nervous system of the giant garden slug, limax maximumus
Authors: van Minnen J. , Sokolove P. G.
Published: January 2005

The neurosecretory system of the giant garden slug Limax maximus was studied using the alcian blue/alcian yellow (AB/AY) staining technique for neurosecretion. Stainable cells could be identified in the paired cerebral, pleural, parietal, and buccal ganglia, and in the visceral ganglion. The cells occur as single cells or in groups of up to 100, with diameters ranging between 10 and 70 μm. Axon tracts could only be traced for a small number of cells; neurohemal areas were not conclusively identified. The morphological similarities of the neurosecretory system of L. maximus is compared with that of other investigated stylommatophoran slugs.
Effect of chronic ethanol exposure on the electric membrane properties of DRG neurons in cell culture
Authors: Scott Brian S. , Edwards Beverley A. V.
Published: January 2005

Neural cell cultures of adult mouse dorsal root ganglia were utilized to investigate the effects of chronic ethanol exposure on neuronal electric membrane properties (EMP). After 12 days of exposure to various ethanol concentrations, the EMP of the neurons were determined in ethanol‐free medium. Significant changes in a number of EMP were observed. Of particular physiological significance were decreased specific membrane resistance, increased specific membrane capacitance, relatively little change in membrane time constant, and increased electrical excitability. Various features of the action potential were also affected, e.g., reduced overshoot, afterhyperpolarization, and rate of rise. In preliminary experiments, EMP were determined at varying periods after the cultures had been withdrawn from ethanol medium and maintained in ethanol‐free medium. These results indicated that the altered EMP persisted as long as one (Cm) to two (Rm) weeks after ethanol withdrawal. A possible mechanism for these ethanol‐induced changes in EMP was suggested, utilizing the membrane expansion theory of anesthesia. Because of few previous reports demonstrating significant electrophysiological effects of ethanol at pharmacological concentrations, the neural cell culture system provides a useful new experimental model for studying the action of chronic ethanol exposure on neuronal EMP and the physical basis of the tolerance and withdrawal phenomena found in alcoholism and addiction in general. After being maintained for 12 days in culture media containing various concentrations of ethanol, non‐neuronal cell survival was observed to have decreased in an approximately linear manner with increasing ethanol levels. By contrast, neuron survival was not affected until ethanol concentrations greater than 0.34 g % were used. This decreased cell survival due to chronic exposure to physiological levels of ethanol has not been reported previously. Neural cell cultures may therefore be useful for investigating the cellular pathology of chronic alcoholism and fetal alcohol syndrome.
Pacemaking mechanism of the afterdischarge of the ovulation hormone‐producing caudo‐dorsal cells in the gastropod mollusc Lymnaea stagnalis
Authors: Kits K. S. , Bos N. P. A.
Published: January 2005

The ovulation hormone‐producing caudo‐dorsal cells (CDC) of Lymnaea stagnalis have three states of excitability (active, inhibited, and resting), which are related to the egg‐laying cycle. Active state CDC produce a firing pattern of prolonged spiking activity (1 spike/2 s), which in the animal occurs shortly before egg laying. In preparations it is evoked as an afterdischarge upon repetitive stimulation of CDC. The afterdischarge is not synaptically driven, but rests on a pacemaking mechanism. CDC are silent in the inhibited and resting states, which follow egg laying. In these states the membrane potential is mainly dependent on [K+]0. In the active state the ratio of the K+, Na+, and Ca2+ permeabilities has changed considerably, probably resulting from an increased permeability to Na+ and Ca2+. The firing rate in the afterdischarge is dependent on the membrane potential, which is confirmed experimentally by varying [K+]0.[Na+]0 and [Ca2+]0 directly influence the firing rate. Firing stops in Na+‐free saline, but is enhanced by Ca2+‐free or high‐Mg2+ saline. TTX does not affect firing. Relatively high concentrations of Co2+ and La3+ (2 × 10−3M) strongly inhibit CDC. Regular firing can be changed into bursting by various means, such as high K+ or addition of 1 mM Ba2+. Bursting normally occurs at the beginning of the afterdischarge. Postburst hyperpolarizations are reduced in Ca2+‐free saline and by low Co2+ (10−4‐5 10−4M). Active CDC are driven by a pacemaking mechanism constituted by a voltage‐dependent Na+/Ca2+ channel and a Ca2+‐dependent K+ channel, thus resembling that of bursting pacemakers. The pacemaking mechanism is inactive in the resting and inhibited state.
Patterns of slow transport in sensory nerves
Authors: Stromska D. P. , Ochs S.
Published: January 2005

An examination of the pattern of outflow of radioactivity in sciatic nerves was made at times from 1 to 82 days in the rat and up to 132 days in the cat after injecting the L5 and L7 dorsal root ganglia, respectively, with 3H‐leucine. Slow waves moving at a rate of 1–2 mm/day were looked for on the basis of their reported presence in the motor fibers of the rat. A consistent pattern of slow waves was not seen in the cat or rat sensory fibers of the sciatic nerves nor was evidence of a slow wave found in the cat dorsal columns. Irregularities in the pattern of outflow which at times appeared as “waves” did so in an irregular fashion, a pattern inconsistent with a steady progression of slow waves in the fibers. The decrease of radioactivity appearing first near the ganglia helps create the impression of a wave along with irregular decreases in the overall levels of radioactivity with time. The results were explained on the basis of the unitary hypothesis. The labeled components are considered to be moved down the fiber by the fast transport mechanism, those components dropping off locally in the fibers early on, constituting the slow wave. As those components turn over locally in the various organelles of fiber and are further redistributed, they may at times give rise to what appears as waves.
Axoplasmic transport of microtubule‐associated proteins in the rat sciatic nerve
Authors: Takenaka Toshifumi , Inomata Kimie
Published: January 2005

32P‐ATP was injected into the L5 dorsal root ganglion and axoplasmic transport of the phosphorylated MA proteins 2, microtubule‐associated proteins 2, was observed. After the injection of 32P‐ATP, the nerve was dissected out at prescribed time intervals and sliced into 5‐mm pieces. Each segment was electrophoresed on an SDS‐polyacrylamide slab gel and subjected to autoradiography. A protein of 310,000 dalton was transported at a velocity of 6.6‐10.6 mm/day in the axon with the electrophoretic mobility identical to that of MA proteins 2, one of the key components associated with the microtubules.
Physiological basis of feeding behavior in Tritonia diomedea. III. Role of depolarizing afterpotentials
Authors: Bulloch Andrew G. M. , Willows A. O. Dennis
Published: January 2005

The nature and role of the depolarizing afterpotentials (DAPs) of buccal motoneurons of Tritonia diomedea were examined. Neuron B5 exhibits a DAP whose ionic dependence and modifiability by TEA and 4‐AP suggest a similarity to the DAP previously described in pleural pacemaker neurons. Reduction of the DAP severely reduces the ability of these neurons to generate bursts of action potentials. Certain other motoneurons (B1 and B6) are reexcited by a slow DAP (SDAP) which appears to be of synaptic origin. It is concluded that DAPs, which are dependent upon motoneuron activity, contribute to the synthesis of motor output by the buccal ganglion.
The molluscan cardioactive neuropeptide FMRFamide: Subcellular localization in bivalve ganglia
Authors: Nagle Gregg T.
Published: January 2005

Ganglia of the marine mollusk Macrocallista nimbosa were pooled, homogenized, and subjected to differential centrifugation. The neuropeptide Phe‐Met‐Arg‐Phe‐NH2 (FMRFamide) was concentrated in the microsomal pellet. When the medium‐speed supernatant was centrifuged in a discontinuous sucrose gradient, three separate peaks of activity were detected and identified as acetylcholine, 5‐hydroxytryptamine, and FMRFamide. The relative concentration of FMRFamide in each fraction was determined by bioassay and by radioimmunoassay (RIA). Both determinations revealed a peak of peptide in the middle of the sucrose gradient. Electron micrographs of each of the gradient interfaces were analyzed. The interface containing the peak of biological FMRFamide activity was enriched two‐ to fivefold in neurosecretory granules with a mean diameter of 104 nm and various electron densities. Morphologically similar vesicles were also seen in intact ganglia. These findings support the notion that FMRFamide is a neurosecretory product. But the physiological function of the peptide in bivalve ganglia remains unknown.
Serotonin has both excitatory and inhibitory modulatory effects on feeding muscles in Aplysia
Authors: Ram Jeffrey L. , Shukla Umesh A. , Ajimal Gurjit S.
Published: January 2005

Serotonin (10−8M) produced opposite long‐lasting (up to 10 min) effects on acetylcholine‐elicited contractions of different buccal mass muscles of Aplysia. Contractions of the dorsal extrinsic muscle and accessory radula closer muscle were enhanced by serotonin; whereas contractions of the ventral extrinsic muscles were inhibited by serotonin. The effect of higher concentrations of serotonin on dorsal and ventral extrinsic muscles was in the same direction as at 10−8M but was greater in both magnitude and duration. The phase of feeding‐protraction or retraction—during which a muscle is active—is not correlated with the direction of modulation produced by serotonin.
Influence of innervation on the levels of noradrenaline and serotonin in the circumvallate papilla of the rat
Authors: Cano J. , Lobera B. , Rodriguez‐Echandia E. L. , Machado A.
Published: January 2005

The levels and the distribution of monoamines within the rat circumvallate papilla have been studied. Noradrenaline was found in the connective tissue underlying the taste buds, whereas serotonin was located in the basal area of the gustatory epithelium but not inside the taste buds. Following denervation, noradrenaline levels decreased and serotonin levels increased. These results suggest that both neurotransmitters may have some mutual interaction in modulating transmission at the papilla.
Uptake of [NMe3H]‐choline by synaptosomes from the central nervous system of Locusta migratoria
Authors: Breer Heinz
Published: January 2005

The accumulation of 3H‐choline by isolated synaptosomes from the central nervous system of locust was studied at concentrations varying from 0.05 to 40μM. Kinetic analysis of the saturable process revealed a high‐affinity and a low‐affinity system. The high‐affinity uptake was competitively inhibited by hemicholinium‐3 and was absolutely dependent on external sodium. Elevated potassium concentrations inhibited choline uptake. The choline uptake by insect synaptosomes was found to be remarkably resistant to a variety of metabolic inhibitors. The reduced choline uptake under depolarizing conditions (high potassium concentration or veratridine) in the absence of calcium implies that electrochemical gradients are important for high‐affinity choline uptake. Depolarization of preloaded synaptosomes under appropriate conditions resulted in a significant release of newly accumulated choline radioactivity.
Neurophysiological mechanisms underlying habituation of the tentacle retraction reflex in the land slug Ariolimax
Authors: Chan Christopher Y. , Moffett Stacia
Published: January 2005

Habituation of the tentacle retraction reflex was studied at the following response levels: (1) Muscle tension elicited in the tentacle retractor muscle by repeated stimulation of a cerebral nerve (at 60‐sec intervals) declined in parallel with evoked activity of the largest unit in the tentacle retractor nerve. (2) The largest unit in the tentacle retractor nerve (L4) showed spontaneous recovery and dishabituation. The rate of response decrement was inversely related to the strength of stimulus, and an optimal interstimulus interval ca. 60 s was found. Retention of habituation for 24 h was exhibited. (3) The major retractor motoneurons (L2, L3, L4) all showed habituation, dishabituation, and spontaneous recovery. The decline of L4 activity was parallelled by a decline in muscle response. (4) Compound EPSPs elicited in the retractor motoneurons by stimulation of sensory pathways showed habituation and dishabituation. (5) Unitary EPSPs elicited by stimulation of cerebral nerves and connectives with minimal stimulus strengths also showed habituation and were unaffected by spontaneously occurring EPSPs. Dishabituation by another pathway was also shown. (6) Depolarization of L4 by a constant current produced spike trains of constant firing rate and evoked a constant level of muscle tension in repeated trials, suggesting the absence of habituation in a peripheral nerve net or at the neuromuscular junction.
Characterization of the synaptic actions of an interneuron in the central nervous system of Tritonia
Authors: Snow Robert W.
Published: January 2005

The motor program that drives the swimming behavior of the marine mollusk Tritonia diomedea is generated by three interneuronal populations in the cerebral ganglia. One of these populations, the pair of C2 neurons, is shown to also exert powerful synaptic actions upon most cells in the contralateral pedal ganglion. Intracellular staining with Co2+ showed that the C2 neurons projected to the contralateral pedal ganglion as a single unbranched axon, and nearly all contralateral pedal neurons received monosynaptic input from C2. Orthodromic stimulation of most peripheral nerves caused monosynaptic excitation of C2 by afferent sensory cells and, in some cases, monosynaptic inhibition from an unidentified source. C2 neurons produced four types of postsynaptic potential (PSP) on pedal neurons: (1) a fast, Cl−‐mediated inhibition (FIPSP); (2) a fast, Na+‐mediated excitation (FEPSP); (3) a slow, K+‐mediated inhibition (SIPSP); and (4) a slow, conductance‐decrease excitation (SEPSP). All four could be recorded simultaneously in some pedal neurons. The C2 neurons appear to be high‐order, multiaction neurons involved in both the generation of a complex motor program and the coordination of ancillary neuronal activity.