bluuebunny/crossref_metadata_2025_split huggingface dataset:
Neurosecretory cells in the central nervous system of the giant garden slug, limax maximumus
Authors: van Minnen J. , Sokolove P. G. 
Published: January 2005

AbstractThe 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

AbstractNeural 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 In preliminary experiments, EMP were determined at varying periods after the cultures had been withdrawn from ethanol medium and maintained in ethanol‐free medium.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

AbstractThe 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

AbstractAn 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

Abstract32P‐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

AbstractThe 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

AbstractGanglia 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

AbstractSerotonin (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

AbstractThe 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

AbstractThe 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

AbstractHabituation 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

AbstractThe 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.
Conduction velocity and spike duration during afterdischarge in neuroendocrine bag cells of Aplysia
Authors: Dudek F. Edward , Kossatz Anne 
Published: January 2005

AbstractChanges in conduction velocity and spike duration during electrically triggered afterdischarges were determined with extracellular recordings from bag‐cell neurites of Aplysia. Spikes with high conduction velocity and short duration occurred at the onset of the afterdischarge during the period of high‐frequency firing and regular interspike intervals. Later in the afterdischarge, spike frequency and conduction velocity decreased, while spike duration increased. During the short bursts within the later part of the afterdischarge, conduction velocity was highest for the first spike and decreased for successive spikes in the burst. That conduction velocity and spike frequency were both maximal during the first minute of the afterdischarge and lower during the later periods of the spike train supports the hypothesis that changes in the excitability of the bag‐cell neurites occur during this firing pattern. Furthermore, the slower conduction velocity and longer duration of spikes from the bag‐cell neurites late in the afterdischarge, and late in the individual bursts within the afterdischarge, suggest the hypothesis of enhanced hormone release per action potential during these periods.
Seasonal modulation of synthesis of the neurosecretory egg‐laying hormone of Aplysia
Authors: Berry Robert W. 
Published: January 2005

AbstractBiosynthesis of the peptide egg‐laying hormone by the bag cells of Aplysia was monitored throughout the year to determine whether the synthesis of neurosecretory proteins is modulated in accordance with secretory demand. The rate of synthesis of precursors to the hormone was found to vary seasonally, being approximately twofold higher during the late summer egg‐laying season than during midwinter. Since there was no change in the distribution of radioactivity among members of the proteolytic processing sequence leading to the hormone, these data imply a seasonal modulation of the production of the secretory product. The synthetic rate showed no correlation with animal maturity or recent egg‐laying history. However, there was a significant interaction between the seasonal effect and elevation of hormone synthesis induced by exposure to elevated external potassium, suggesting that these two modulatory factors exert their effects at a common point in the mechanism of hormone biosynthesis.
Variability and frequent failure of lucifer yellow to pass between two electrically coupled neurons in Lymnaea stagnalis
Authors: Audesirk Gerald , Audesirk Teresa , Bowsher Peggy 
Published: January 2005

AbstractThe electrically coupled giant neurosecretory neurons VD1 and RPD2 of Lymnaea stagnalis were found to have coupling coefficients ranging from ca. 0.1–0.6. When the fluorescent dye Lucifer Yellow was injected intracellularly into one of the neurons, in most preparations no dye was observed to pass through into the coupled cell body or the process leading to it. There was no apparent correlation between the amount of dye coupling and the length of time allowed for diffusion of the dye in the cells. In eight preparations, the electrical coupling coefficient was measured before dye was injected. There was no correlation between dye coupling and the electrical coupling coefficient.
Prolonged alteration in composition of fast transported protein in axons prevented from regenerating after injury
Authors: Bisby M. A. 
Published: January 2005

AbstractA previous study revealed a characteristic alteration in the ratio of labeling of two fast axonally transported polypeptides identified as S1 (22,000 daltons) and S2 (18,000 daltons) and their ratio (S2/S1) in rat motoneuron axons following axonal injury and subsequent regeneration. In this study the S2/S1 ratio was determined for axons which were resected and ligated proximally and which did not regenerate to reinnervate muscle. While the initial increase in the S2/S1 ratio following section was the same as that following a crush, the S2/S1 ratio did not return towards normal values after 42 days, but remained elevated for at least 98 days after injury. It is concluded that the return of S2/S1 ratio to normal values, like some other manifestations of the cell body reaction, is delayed if the injured axons do not regenerate.
Position‐sensitive detector studies of the axonal transport of a pulse of radioisotope
Authors: O'Brien D. W. , Snyder R. E. 
Published: January 2005

AbstractAxonal transport of a pulse of 35S‐methionine‐labelled material was studied in vitro in amphibian sciatic nerve using position sensitive detectors. Following formation of a pulse of activity using the cold block technique, the nerve was ligated proximal and distal to the pulse and its movement monitored at room temperature (22.5–23.5°C) for up to 16 h. Material transported in the anterograde direction did so with an average maximum velocity of 147 mm/d. The pulse was found to disperse at an average rate of 0.23 mm/mm travel; however, dispersion was found to vary from preparation to preparation more than would be predicted from experimental error alone. Label was observed to reverse direction at the distal ligature in only 2 of 13 preparations. Reversal of label began within approximately 0.4 h of first arrival, and the most rapidly retrogradely transported material moved at a velocity of 80% that of the most repidly anterogradely transported material.
Unchanged rate of axonal regeneration by cyclophosphamide in rat sciatic nerve
Authors: Komiya Yoshiaki 
Published: January 2005

AbstractThe rates of axonal regeneration and initial delay in motor and sensory axons of cyclophosphamide‐treated and control rat sciatic nerves after cold injury were determined by using fast axoplasmic transport. The rates in motor and sensory nerves were not significantly different between the two groups. The difference of initial delay in motor nerve was not significant, but in sensory nerve the drug‐treated group showed a longer initial delay than the control. These results suggest that the enhancement of motor function recovery by cyclophosphamide is not due directly to an increased rate of axonal regeneration, nor to a decreased initial delay.
Calcium‐dependent proteolysis in neural tissue is activated at physiologic intracellular Ca2+ levels and inhibited by some anticonvulsants
Authors: Nosek Thomas M. , Crosland Marcia B. 
Published: January 2005

AbstractThe level of calcium‐activated neutral protease (CANP) activity in the brain and nerve cord of the crayfish Procambarus clarkii was assayed by measuring the degradation of casein yellow by tissue homogenates. When care was taken to maintain the ionic strength of all incubation media at 0.15M and to buffer the Ca2+activity of the media with 5mM EGTA, CANP was found to be very sensitive to Ca2+; maximal activity was achieved at 1 × 10−3M Ca2+, with 50% of this maximum present at the physiologic intracellular Ca2+activity of 1 × 10−7M. We found that the anticonvulsant agent phenytoin was without effect on CANP activity while pentobarbital and a relatively new anticonvulsant agent, valproic acid (an eight‐carbon branched fatty acid), significantly inhibited CANP activity in a dose‐dependent manner. The inhibitory effect of valproic acid was shared by a straight‐chain eight‐carbon fatty acid, caprylic acid. These findings demonstrate that inhibition of CANP activity is not limited to agents with a specific molecular structure. They also suggest that CANP plays a role in the normal turnover of proteins that control various cellular functions.