bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bidirectional axonal transport of free glycine in identified neurons R3–R14 of Aplysia
Authors: Price Christopher H. , McAdoo David J. , Farr William , Okuda Roy 
Published: January 2005

AbstractThe axonal transport of 3H‐amino acids was studied in the axons of identified neurons R3–R14 in the parietovisceral ganglion (PVG) of the mollusc Aplysia. The PVG was incubated (3–24 hr) in media containing physiological concentrations of single 3H‐amino acids while the isolated nerve was superfused with plain or chemically altered media. The nerve was then sliced into sequential segments for biochemical analyses or fixed for autoradiography. 3H‐glycine was transported at 70 mm/day in 6X greater quantities than other amino acids which were transported at <40 mm/day. In the 3H‐glycine experiments, >80% of the label transported into the nerve remained as free glycine, comigrating with glycine in thin‐layer chromatographs. In autoradiographs of sections 4 mm from the ganglion‐nerve barrier, >50% of the silver grains were over R3–R14 axons which occupy <10% of the nerve cross‐sectional area. EM autoradiographs confirmed that grains were within R3–R14 and not in surrounding glia. The selective transport of glycine was inhibited by Hg2+, by vinblastine and Nocodazole, and by low Ca2+ media. Autoradiographs of vinblastine‐treated nerves showed a drastic reduction in label over R3–R14 and other axons. Label was also transported retrogradely; this transport rate was similar to the orthograde rate, but 5–10 times less label moved retrogradely. Autoradiographs showed that the retrograde label was localized to R3–R14 axons. This report clearly demonstrates the rapid, selective, and bidirectional transport of a free amino acid and provides further evidence that glycine may be used as a neurochemical messenger by neurons R3–R14.
Investigation of burst generation by the electrically coupled cyberchron network in the snail Helisoma using a single‐electrode voltage clamp
Authors: Merickel Michael , Gray Richard 
Published: January 2005

AbstractThis paper describes the results of investigating burst generation by the cyberchron network in the snail Helisoma. The cyberchron network is composed of approximately 20 electrically coupled neurons and controls the feeding behavior of the snail. The electrical coupling between network members has made it particularly difficult to distinguish between the importance and involvement of single‐cell and network properties in burst generation by this system. The present investigations utilized the new single‐electrode voltage clamp to examine the membrane properties and network interactions of the cyberchron neurons: (1) A slow outward current is activated by moderately large depolarizing commands (−40 to 0 mV) and does not undergo inactivation decay (i.e., decline in magnitude) during a command potential step maintained for 10 sec or more. The lack of inactivation of the outward current in cyberchron neurons appears to be due to the dominating role of a Ca‐dependent K current. (2) There are two functionally distinct classes of cyberchrons—current generator cyberchrons and follower cyberchrons. (3) Primary current generator cyberchrons have membrane properties similar to endogenous bursting neurons (e.g., persistent inward Ca current and negative resistance region in I–V plot) and appear to provide the main driving and timing current for the rest of the network. (4) The vast majority of cyberchrons are secondary current generator cyberchrons with membrane properties which exhibit inward‐going rectification and appear to burst as a result of regenerative excitation with one another and the primary current generator cyberchrons. (5) The second class of cyberchrons are driven by the electrical synaptic input from the current generator cyberchrons, do not exhibit inward‐going rectification, and are called follower cyberchrons. (6) Burst termination is due to activation of a slow outward tail current in most cyberchrons during the burst (probably Ca‐activated K current) which causes a hyperpolarization in individual cyberchrons, terminating the burst. (7) Decay of the outward tail current causes the cyberchrons to depolarize, which activates the persistent inward Ca current in the primary current generator cyberchrons, starting the burst cycle anew.
Muscarinic cholinergic binding sites in an orthopteran central nervous system
Authors: Meyer Mark R. , Edwards John S. 
Published: January 2005

AbstractHomogenates of cricket (Acheta domesticus) central nervous system (CNS) specifically bind the potent muscarinic ligand [3H]‐QNB. Binding assay and pharmacologic data indicate that the cricket CNS contains a high density of muscarinic cholinergic binding sites. These sites appear to be a unique class of invertebrate cholinergic receptor with properties distinct from those of previously described nicotinic receptors.
The peripheral and central nervous organization of the locust coxo–trochanteral joint
Authors: Bräunig Peter 
Published: January 2005

AbstractThe micromorphology of the locust coxo–trochanteral joint was examined in cobalt‐stained material. Peripheral nervous system, musculature, and internal proprioceptors—two strand receptors and a muscle receptor organ—of the metathoracic coxa are compared with those of the pro‐ and mesothoracic legs. The number and position of trochanter levator and depressor motoneurons as well as the central projections of coxal sense organs are described. Evidence for a femoro–tibial strand receptor was obtained by tracing the path of a particular nerve branch.
A comparative study by serial electron microscopy of neuromuscular junctions in the dimorphic claws of the snapping shrimp, Alpheus heterochelis
Authors: Phillips Christine E. , Wilson John A. , Mellon Deforest 
Published: January 2005

AbstractWe compared the neuromuscular junctions on the main closer muscle in the first pair of chelipeds in the snapping shrimp Alpheus heterochelis by serial section electron microscopy. We sought an ultrastructural basis for the different behavioral and physiological functions of these dimorphic claws and for the role of the nervous system in claw transformation. We were unable to detect any statistically significant morphological differences between the junctions. Further, we found the muscle fiber populations and filament arrangements, as well as the electrical properties of the fibers, to be more homogeneous and similar to each other in A. heterochelis than those reported for another species, A. armillatus. We consider our results in light of recent data on the anatomy and electrical properties of the motor neurons within the CNS and conclude that the neural trigger for claw transformation involves factors not revealed by conventional electron microscopy.
Calcium‐activated potassium conductance noise in snail neurons
Authors: Westerfield Monte , Lux H. D. 
Published: January 2005

AbstractCurrent fluctuations were measured in small, 3–6‐μm‐diameter patches of soma membrane in bursting neurons of the snail, Helix pomatia. The fluctuations dramatically increased in magnitude with depolarization of the membrane potential under voltage clamp conditions. Two components of conductance noise were identified in the power spectra calculated from the membrane currents. One component had a corner frequency which increased with depolarization. This component was blocked by intracellular injection of TEA and was relatively insensitive to extracellular calcium levels (as long as the total number of effective divalent cations remained constant). It was identified as fluctuations of the voltage‐dependent component of delayed outward current. The second component of conductance noise had a corner frequency which decreased with depolarization. It was relatively unaffected by TEA injection and was reversibly blocked by substitution of extracellular calcium with magnesium, cobalt, or nickel. This second component of noise was identified as fluctuations of the calcium‐dependent potassium current. The results suggest that the two components of delayed outward current are conducted through physically distinct channels.
Rapid axoplasmic transport of free leucine
Authors: Schmid Georg , Wagner Lothar , Weiss Dieter G. 
Published: January 2005

AbstractAxoplasmic transport of free 3H‐leucine has been studied in vivo in the pike olfactory nerve following application of labeled leucine to the olfactory mucosa. A considerable amount of free 3H‐leucine is transported at constant velocity along the axon in the form of a distinct peak. The maximum transport velocity for free 3H‐leucine is the same as for rapidly transported 3H‐protein (130 and 135 mm/day, respectively, at 19°C). Microtubule inhibitors block or significantly reduce the amount of free 3H‐leucine transported, but do not influence the transport velocity. Disruption of the oxygen supply abolishes free 3H‐leucine transport, so that this phenomenon cannot be explained by diffusion. The amount of free leucine in the rapidly moving peak decreases with time and distance along the axon and is not detectable after 5 h or more. The transported 3H‐leucine is not derived from the circulation or from proteolysis of rapidly transported proteins. This study may help to resolve the controversy over the axoplasmic transport of free amino acids since it shows that free 3H‐leucine is transported rapidly but does not travel by rapid axoplasmic transport to the end of axons longer than about 30 mm.
Electrophoretic analysis of axonally transported proteins in rabbit vagus nerve
Authors: McLean W. G. , McKay A. L. , Sjøstrand J. 
Published: January 2005

AbstractProteins synthesized in the nodose ganglia of rabbits were radiolabeled with 35S‐methionine and the proteins present in the vagus nerve, at various times later, were analyzed by SDS (sodium dodecyl sulfate)–polyacrylamide gel electrophoresis. Three major groups of proteins were transported as waves of radioactivity within the nerve at rates of 15–17 mm/h, 12–15 mm/day, and 25–30 mm/day. The front of the fastest wave was composed of two proteins only, of apparent molecular weights 21,000 and 24,000. These were followed after a delay by a number of proteins of higher molecular weight, traveling at the same fast rate. The 25‐mm/day wave contained several proteins including a major one of molecular weight 43,000 while the 12‐mm/day wave was composed entirely of two proteins of molecular weights 54,000 and 56,000. These groups of slowly transported proteins are therefore similar to those transported much more slowly in other mammalian nerves, with the exception that no proteins with molecular weight similar to the neurofilament proteins could be detected. We have confirmed the dependence of slow transport for both groups of proteins on contact between cell body and axon and suggest that it may be a general phenomenon in all mammalian nerves.
Dopamine in a molluscan nervous system: Synthesis and fluorescence histochemistry
Authors: Trimble Dorothea L. , Barker David L. , Bullard Brad J. 
Published: January 2005

AbstractThe nervous system of the pond snail, Helisoma trivolvis, was investigated for its ability to synthesize and accumulate 3H‐catecholamines from 3H‐tyrosine. 3H‐Dopamine, but not 3H‐norepinephrine, was synthesized by several ganglia. The highest accumulations were found in the cerebral, pedal, and buccal ganglia. The Falck‐Hillarp and glyoxylic acid fluorescence histochemical techniques were applied to the buccal ganglia to visualize dopamine‐containing cells. Fluorescing cells were found on both dorsal and ventral sides of the ganglion. Peripheral nerves of the buccal ganglia also displayed catecholamine fluorescence and accumulated 3H‐dopamine. However, no 3H‐dopamine synthesis occurred in the cerebral‐buccal connectives, which connect the buccal ganglia with the rest of the central nervous system. Therefore, we conclude that there is a dopaminergic system intrinsic to the buccal ganglia and their peripheral targets.
One‐trial reward learning in the snail Lymnea stagnalis
Authors: Alexander James , Audesirk Teresa E. , Audesirk Gerald J. 
Published: January 2005

AbstractWe present evidence that the pond snail Lymnaea stagnalis is capable of aquisition and extensive retention of an appetitively reinforced feeding response after only a single training trial. Food‐deprived snails presented with a single pairing of a phagostimulant (a mixture of sucrose and casein digest) and a novel, non‐food chemostimulus (amyl acetate) subsequently made feeding responses to the amyl acetate and retained the association for at least 19 days. This demonstration of one‐trial, non‐aversive classical conditioning enhances the utility of Lymnaea stagnalis as a model system for the detailed analysis of neural mechanisms underlying plasticity.
Extracellular calcium dependence of contracture and modulation by serotonin in buccal muscle E1 of Aplysia
Authors: Ram Jeffrey L. , Shukla Umesh A. , Parti Rajesh , Goines Roy L. 
Published: January 2005

AbstractSerotonin [5‐hydroxytryptamine (5‐HT)] enhances acetyl choline (ACh)‐elicited contractures of Aplysia buccal muscles E1 and I5. The possible role of external calcium in regulating the magnitude of ACh contracture in the presence and absence of 5‐HT was investigated. Superfusion of E1 with zero calcium medium caused ACh contractures to fail within one to two minutes. Recovery of ACh contracture upon restoring normal medium occurred within two to four minutes. In the absence of 5‐HT, ACh contracture decreased proportionally to external [Ca++] in the concentration range of 0–10 mM; however, the amount of enhancement of of ACh contracture following 5‐HT treatment did not decrease with external [Ca++] as long as [Ca++] was above a threshold concentration that varied from preparation to preparation. For most preparations, the enhancement of ACh contracture by 5‐HT was dependent on the presence of external calcium during 5‐HT treatment. Calcium influx into muscles E1 and I5 increased approximately two and a half fold in the presence of 10−6 M 5‐HT. A model in which 5‐HT brings about calcium “loading” of an ACh releasable intracellular storage site is discussed.
Inhibition of the retrograde axonal transport of acetylcholinesterase by the anti‐calmodulin agents amitriptyline and desipramine
Authors: Tiberi M. , Lavoie P.‐A. 
Published: January 2005

AbstractThe possible involvement of calmodulin in mediating the calcium requirement for retrograde axonal transport of acetylcholinesterase was studied in vitro in bullfrog spinal nerves, with the use of the calmodulin inhibitors amitriptyline and desipramine. When nerves were preincubated with 0.2 mM amitriptyline or desipramine for 5 h, and were then ligated and incubated for an additional 17–18 h in drug‐containing medium, the accumulation of acetylcholinesterase distal to the ligature was significantly reduced as compared to contralateral control nerves maintained in drug‐free medium. The identical degree of transport inhibition observed for both drugs is consistent with their similar anti‐calmodulin activity.
Restoration of sensory and motor function in earthworm escape reflex pathways following ventral nerve cord transplantation
Authors: Vining E. P. , Drewes C. D. 
Published: January 2005

AbstractTwelve segments of earthworm ventral nerve cord (VNC) were excised from either segments 10–22 (i.e., within the MGF sensory field) or segments 75–87 (i.e., within the LGF sensory field) in donor worms and heterotopically, or homotopically, transplanted into recipient animals. Morphological evidence indicated that by four days after transplantation, peripheral connections were formed between the transplanted VNC and the body wall of the recipient, many of these connections involving novel pathways projecting ventrally from the transplant. Restoration of giant fiber touch sensitivity in the transplant occurred from 4–14 days after transplantation. Regardless of the site of transplantation, the restored sensitivity (i.e., MGF versus LGF sensory field) always reflected the origin of the donor VNC. Restoration of MGF‐mediated motor activity in the transplant occurred approximately 17–22 days after transplantation. In the case of heterotopic transplants (i.e., anterior VNC into posterior segments), the restored MGF‐mediated muscle potentials were facilitating, indicating at least some tendency for persistance of this feature after transplantation. Behavioral observations suggested that reconnections involving other reflex pathways (e.g., those controlling setal movements and peristaltic locomotion) were made within the transplant region and that properties of the restored reflexes reflected those of the donor VNC. The rapid restoration of sensory and motor connections, despite heterotopic placement, indicates a significant capacity for peripheral regeneration by the transplanted VNC. On the other hand, the maintenance of various properties of reflex function, despite heterotopic transplantation, suggests a limited capacity for rearrangement of established central connections in the transplanted VNC.
Sustained sensitivity modifications induced by brief length perturbations in the crayfish slowly adapting stretch receptor
Authors: Da Rocha A. F. , Buño W. 
Published: January 2005

AbstractThese experiments in the slowly adapting stretch receptor of crayfish test the effects of brief length perturbations (i.e., pulses) when presented in isolation at different constant elongations or superimposed on trapezoidal stretches of different amplitudes. Within “in vivo” lengths, during static responses, perturbations reduced firing rates to below control values and, in extreme cases, could silence the receptor. This effect, or “down‐step,” was sustained, occurred above a threshold pulse amplitude and background stretch, and increased with both stimulus characteristics, but was not present during dynamic responses. Beyond “in vivo” lengths, and in a few cases within those limits but close to the extremes, the receptor was silent but perturbations could restore activity. Lengthening pulses were more effective than shortening ones in generating after‐effects. Perturbations change, during indefinitively long periods, the receptor's length or static sensitivity acting as a negative feedback which tends to maintain the discharge rate within fixed values. Perturbations disclose marked nonlinerities, which suggest that the classical view of a proportional control in the reflex loop in which the receptor participates may not operate in natural conditions.
What is the correct value for Na, K‐ATPase activity in homogenates of cerebral cortex?
Authors: Křivánek J. 
Published: January 2005

AbstractActivity of Na, K‐ATPase in homogenates of fresh cerebral cortex of rats was compared with that of cortex frozen under different conditions. Activity yields after rapid in situ freezing of the exposed cerebral cortex were twice, higher (26.1 U) than in homogenates of the fresh cortex (13.3 U). Fresh brain kept on ice for 60 and 300 s and subsequently frozen in liquid nitrogen yielded activities comparable to those of the tissue frozen in situ (24.1 U and 24.9 U for 60 s and 300 s periods, respectively). Inhibition of Na, K‐ATPase by 10−7 M vanadate was significantly stronger (38%) in homogenates of the fresh brain then in those of the cortex frozen in situ (28%). High Na, K‐ATPase activity (47.6 U) in suspensions of synaptosomal membranes (SM) prepared from fresh cortical homogenates was only slightly inhibited by 10−7 M vanadate (12%). Various treatments of homogenates or SM suspensions, like increase of piston rotation speed, repeated freezing and thawing procedure or vigorous shaking did not significantly affect the enzyme activity. Mg‐ATPase activity and its sensitivity to vanadate was also modified by tissue treatment but the effect was much less pronounced.
Cellular analyses of hormone influence on motoneuronal development and function
Authors: Breedlove S. Marc 
Published: January 2005

AbstractThe striated bulbocavernosus (BC) muscles of the rodent perineum are innervated by motoneurons in the spinal nucleus of the bulbocavernosus (SNB). In adulthood, the BC muscles are present in males only. However, newborn female rats have BC muscles, and SNB cells have made both anatomical and functional contact with them. Nevertheless, both motoneurons and muscles will degenerate unless androgens are administered perinatally. Such androgen treatment appears to be acting primarily on the BC muscles themselves, since the muscles are spared by androgen even after the loss of supraspinal neural afferents or even the entire lumbosacral spinal cord. Furthermore, androgen can spare SNB motoneurons that are themselves androgen insensitive. Perinatal steroid treatments can also alter the final spinal location of SNB cells as determined by retrograde tracing studies. Androgen continues to modify the morphology of the SNB system in adulthood, altering the size of both motoneurons and targets, which may be important for the reproductive function of BC muscles. Finally, the sexually dimorphic character of motoneuronal groups innervating perineal muscles seems to be common in mammals, since the homologue of the SNB, Onuf's nucleus, has more cells in males than in females in both dogs and humans.
The effects of trifluoperazine on fast and slow axonal transport in the rabbit vagus nerve
Authors: Ekström Per , Kanje Martin , McLean W. Graham 
Published: January 2005

AbstractThe effects of trifluoperazine (TFP) on fast and slow axonal transport (AXT) of labeled proteins were examined in the rabbit vagus nerve. Cuffs soaked in a 10 mM, but not 0.1 mM or 1 mM, concentration of TFP applied locally around the vagus nerve in vivo blocked both fast and slow AXT, as measured by the accumulation of 3H‐labeled proteins. In vitro, fast AXT was affected by 0.1 mM TFP. The TFP cuff treatment caused a reduction in the number of axonal microtubules (MT) whereas cuffs soaked in saline had no effect. The levels of ATP, ADP, and AMP were not significantly lowered by the TFP treatment. The results suggest that both fast and slow AXT are sensitive to TFP treatment, and that the axonal MT‐system may be the main target of the drug.
Multiple transmitter neurons in Tritonia. I. Biochemical studies
Authors: Lloyd Philip E. , Masinovsky Boris P. , Willows A. O. Dennis 
Published: January 2005

AbstractThe buccal ganglia of the marine mollusc Tritonia control a variety of movements associated with feeding, including gut motility. The buccal ganglia and gut contain a class of peptides termed small cardioactive peptides (SCPs). Cobalt backfilling of the nerve which innervates the gut stains several buccal neurons including two pairs of reidentifiable cells, B11 and B12. Both appear white under epiillumination, a characteristic of peptidergic neurons in gastropods. Enzymatic and biochemical analyses of extracts from microdissected B11 cell bodies demonstrate that this neuron contains two species of SCPs. Labeling in organ culture followed by dissection and extraction of cell bodies indicates that these peptides were synthesized in B11. One of these peptides appears to be identical to SCPB, one of two SCPs that have been sequenced. The other SCP present in these neurons is novel. Less extensive analyses of extracts of B12 somata suggest that it also contains the same SCPs. In addition to the peptides, B11 also contains large quantities of acetylcholine (ACh) as determined by a radioenzymatic assay of cell body extracts. B12 does not contain measureable ACh. The concentration of the two peptides and ACh in the B11 cytoplasm is approximately 1 mM. Neuron B11 appears to be an appropriate model system for studying the biochemical and physiological properties of multiple transmitter neurons.