bluuebunny/crossref_metadata_2025_split huggingface dataset:
Acetylcholine activates cerebral interneurons and feeding motor program in Limax maximus
Authors: King Michael S. , Delaney Kerry , Gelperin Alan 
Published: January 2005

AbstractThe cellular and network effects of acetylcholine (ACh) on the control system for feeding in Limax maximus were measured by intracellular recordings from feeding command‐like interneurons and whole nerve recordings from buccal ganglion motor nerve roots that normally innervate the ingestive feeding muscles. The buccal ganglion motor nerve root discharge pattern that causes rhythmic feeding movements, termed the feeding motor program (FMP), was elicited either by attractive taste solutions applied to the lip chemoreceptors or by ACh applied to the cerebral ganglia. The ability of exogeneous ACh applied to the cerebral ganglia to trigger FMP was blocked by the cholinergic antagonists curare and atropine. If the strength of the lip‐applied taste stimulus was in the range of 1–2 times threshold, cerebral application of the cholinergic antagonists blocked or greatly decreased the ability of lip‐applied taste solutions to trigger FMP (5 of 8 trials). The cerebral feeding interneurons, some of which activate FMP when stimulated intracellularly, are excited by small pulses of ACh applied directly to the cell body from an ACh‐filled micropipette. A pulse of ACh that activates several of the feeding interneurons simultaneously triggers FMP. The data suggest that under certain stimulus conditions an obligatory set of cholinergic synapses onto the feedininterneurons must be activated for taste inputs to trigger ingestion. The determination of ACh's action within the feeding control system is necessary for understanding how enhanced cholinergic transmission leads to prolonged associative memory retention (Sahley, et al., 1986).
Multiple transmitter neurons in Tritonia. II. Control of gut motility
Authors: Lloyd Philip E. , Willows A. O. Dennis 
Published: January 2005

AbstractTwo large multiple transmitter neurons are located in each buccal ganglion of Tritonia. One of these neurons (B11) contains large quantities of two neuropeptides and acetylcholine (ACh), whereas the other neuron (B12) appears to contain the same two peptides but no ACh. One of the peptides present in these neurons has recently been sequenced and is termed small cardioactive peptide B (SCPB). Both neurons regulate the motility of the gut. Stimulation of B11 produces a posteriorly directed peristalsis after a short latency. This gut movement may normally accompany swallowing. B11 stimulation also produces an increase in the rate of endogenous contractile activity that is similar to that produced by superfusion of the gut with low concentrations (10−8 M) of SCPB. Stimulation of B12 produces a vigorous longitudinal contraction of the gut, initiated in the posterior part of the gut and not peristaltic in nature. This movement appears incompatible with swallowing behavior and may be involved in regurgitation.
The molluscan neuropeptide, SCPB, increases the responsiveness of the feeding motor program of Limax maximus
Authors: Prior David J. , Watson Winsor H. 
Published: January 2005

AbstractSmall cardioactive peptide B (SCPB) has an excitatory effect on both buccal neurons and musculature in numerous molluscan species. The present study reports the effects of SCPB on the activity of specified buccal neurons and the expression of the feeding motor program of the terrestrial slug, Limax maximums. Superfusion of an isolated CNS preparation with 10−6 M SCPB results in a 3–4‐fold increase in the burst frequency of the fast salivary burster neuron (FSB), while having no effect on the activity of another endogenous burster, the bilateral salivary neuron (BSN). The response of the FSB to SCPB iS dose dependent, with a threshold concentration of 2 × 10−8M. The response of the FSB to SCPB showed no indication of desensitization, even after long‐term exposure (20 min).The feeding motor program (FMP) in Limax is a discrete pattern of cyclical motor activity that can be initiated by lip nerve stimulation. In the presence of SCPB a previously subthreshold stimulus can initiate the full FMP. The pattern of the FMP, once initiated, appears unaffected by SCPB. Thus it is the responsiveness of the initiation process that is enhanced by SCPB. Histochemical studies revealed a number of buccal neuron somata and fibers that stain for SCPB‐like immunoreactive material (SLIM).
Acetylcholine receptor clustering and triton solubility: Neural effect
Authors: Podleski Thomas R. , Salpeter Miriam M. 
Published: January 2005

AbstractPrevious studies by Prives et al. (1980, 1982a and b) have shown that acetylcholine receptors (AchRs) are extracted from muscle cells in vitro by Triton X‐100 at different rates, and that clustered receptors extract most slowly. The present study was aimed at comparing the relative extractability of receptors in clusters with those in intercluster regions and the role of neural factors in regulating this extractability. Using primary rat muscle cells in vitro we confirmed that receptor extraction with Triton X‐100 does not fit a single exponential but has more than one rate, and that in control cells clustered receptors extract more slowly than do receptors in intercluster regions. The major new observation in this study was that neural extract lowered the overall Triton extraction rate of intercluster receptors to that of clustered receptors. Additional new observations include the findings that (1) both clustered and intercluster receptors show multiphasic extraction rates; (2) stabilization of AchRs against Triton extraction increases with time in the surface membrane; (3) the effect of neural extract on Triton extractability of AChR is dependent on factors that control RNA synthesis, cytoskeletal elements, and collagen; (4) fixation and/or buffer washes accelerate receptor extraction only incells that are treated with Triton, but not in control cells; (5) in control cells (not exposed to neural factors) Triton X‐100 causes new clusters to form. From experiments using Con A we suggest that the Tritoninduced new clusters may not be formed by a redistribution of receptorsbut are, most likely, due to the presence of groups of intercluster receptors with extraction rates lower than thoseof surrounding receptors.
Regeneration of goldfish retina: Rod precursors are a likely source of regenerated cells
Authors: Raymond Pamela A. , Reifler Michael J. , Rivlin Patricia K. 
Published: January 2005

AbstractThis study describes regeneration of the neural retina in juvenile goldfish. The retina was destroyed with an intraocular injection of ouabain, a technique introduced by Wolburg and colleagues (Maier and Wolburg, 1979; Kurz‐Isler and Wolburg, 1982). We confirmed their observation that the level of damage produced by the toxin was graded, in that neurons in the inner retinal layers were preferentially destroyed, and only in the more severely affected retinas were cells in the outer nuclear layer (i.e., photoreceptor cells) damaged. Evidence of retinal regeneration could be seen beginning about 2 weeks after the injection of ouabain. In contrast to previous studies (Maier and Wolburg, 1979), we found that regeneration took place only in those retinas in which photoreceptors had been destroyed. In cases in which the outer nuclear layer was spared, no regeneration of inner layers occurred, even after 6 months. Thymidine autoradiography was used to document the regeneration of new retinal neurons and to show that rod precursors, like other dividing cells, were not destroyed by the oubain, but in contrast showed an increased mitotic activity. Regeneration did not proceed uniformly, but was initiated at neurogenic foci scattered across the retina. These foci consisted of clusters of dividing neuroepithelial‐like cells. The evidence is consistent with the proposal that these cells were derived from rod precursors. These results imply that rod precursors are capable of a wider range of developmental fates than they normally express.
Dissociation of the inhibition of fast axonal transport by chlorimipramine from an effect on axonal microtubules
Authors: Lavoie P.‐A. , Filion P. R. , Pharand M. 
Published: January 2005

AbstractThe effect of in vitro exposure of bullfrog spinal nerves to 0.2 mM chlorimipramine on the density of axonal microtubules was studied in an attempt to clarify the mechanism by which chlorimipramine inhibits fast axonal transport. A 17‐ h exposure to chlorimipramine reduced the density of microtubules in unmyelinated axons by only 18%; this microtubular loss does not reach the upper limit of the range of microtubule reduction associated with inhibition of fast axonal transport. A 23‐ h exposure to chlorimipramine, which had decreased microtubular density in unmyelinated axons by 40% in a previous study, did not decrease microtubular density in myelinated axons in the present study. These results rule out microtubular destruction as the mechanism responsible for inhibition of fast orthograde axonal transport by chorimipramine, and greatly reduce the likelihood that microtubular destruction plays a significant role in the inhibition of fast retrograde transport by chlorimipramine.
Neural and glial phenotypic expression by neural crest cells in culture: Effects of control and presumptive aganglionic bowel from ls/ls mice
Authors: Coulter H. David , Gershon Michael D. , Rothman Taube P. 
Published: January 2005

AbstractThe enteric nervous system is formed by cells that migrate to the bowel from the neural crest. Previous experiments have established that avian crest cells in vitro will colonize explants of murine bowel and there give rise to neurons. It has been proposed that phenotypic expression by the crest‐ derived precursors of enteric neurons and glia is critically influenced by the microenvironment these cells encounter within the gut. To test this hypothesis, quail crest cells were cocultured with explants of control or presumptive aganglionic bowel from the ls/ls mutant mouse, and the effects of the enteric tissue on five phenotypic markers of crest cell development were followed. Aganglionosis develops in the terminal region of the colon of the ls/ls mouse because viable crest‐ derived neural and glial precursors fail to colonize this tissue. Expression of the phenotypic markers in the cocultures was compared with that in cultures of crest alone, crest plus neural tube, and gut grown alone. The markers examined were melanogenesis and immunostaining with antisera to 5‐ hydroxytryptamine (5‐ HT) and tyrosine hydroxylase (TH) and the monoclonal antibodies, NC‐ 1 and GlN1. Explants of control, but not presumptive aganglionic ls/ls gut were found to increase the incidence of the expression of 5‐ HT and NC‐ 1 immunoreactivities; moreover, especially near the gut, the assumption of a neuronal morphology by 5‐ HT‐, NC‐1‐, and GlN1‐ immunoreactive cells was also increased. Coincidence of expression of 5‐ HT with NC‐ 1 and GlN1 immunoreactivities was observed. The effect of the bowel was selective in that the expression of TH immunoreactivity, which is not a marker of mature enteric neurons, was reduced rather than enhanced. The effect of enteric explants on crest cell development was specific in that it was not mimicked by explants of metanephros, which inhibited expression of 5‐ HT immunoreactivity and the acquisition of a neuritic form by NC‐ 1‐ immunoreactive cells. It is concluded that theenteric microenvironment affects the phenotypic expression of subsets of crest cells and that this action of the bowel.Is manifested in vitro. The inability of presumptive aganglionic gut from ls/ls mice to influence neural phenotypic expression may be due to the failure of this tissue to produce putative factor(s) required for theeffector to the inability of the crest‐ derived precursor cells to migrate into the abnormal enteric tissue.
Wind‐activated thoracic interneurons of the cockroach: I. Responses to controlled wind stimulation
Authors: Westin Joanne , Ritzmann Roy E. , Goddard Donald J. 
Published: January 2005

AbstractThe cockroach escape response begins with a turn away from a wind puff such as that generated by an approaching predator. The presence and direction of that wind is detected by hairs on the animal's cerci, and this information is conducted to the thoracic ganglia via two populations of giant interneurons. In the thoracic ganglia, the giant interneurons excite a number of interneurons, at least some of which in turn excite motor neurons that control leg movement. In this paper we examine response properties of various thoracic neurons to wind stimuli originating from different directions.Three sets of thoracic neurons were distinguished on the basis of latency. Type A interneurons had short latencies to wind stimuli (1.3–2.25 ms). Type B interneurons had longer latencies (4–6 ms), and motor neurons had the longest latencies (5.6–17.0 ms). Individual type A interneurons either responded equally to wind from all directions or were biased in their response. Directionality was related to the presence of ventral branches near one or both sides of the midline of the ganglion. Cells with ventral median (VM) branches on either side tended to be omnidirectional or front‐rear biased, whereas cells with VM branches on only one side were biased to that side. Although several type B interneurons had strong wind responses and were directionally sensitive, they did not have VM branches. We hypothesize that the presence of VM branches in type A interneurons permits connection with ventral giant interneurons, and this connection accounts for their short latency and directional properties. This hypothesis will be tested in the companion paper.
Development and senescence of control of ciliary locomotion in a gastropod veliger
Authors: Arkett Stuart A. 
Published: January 2005

AbstractThe rhythmical ciliary arrest behavior characteristic of the veliger larvae of the prosobranch Calliostoma ligatum develops in a predictable sequence of events. Spontaneous, small‐amplitude (1–3 mV) postsynaptic potentials (PSPs) are first recorded intracellularly from prototrochal ciliated cells at about 45 h after fertilization. Prototrochal ciliated cells, which are precusors of the locomotory, preoral ciliated cells of mature veligers, are electrically coupled to each other. Cilia beat continuously and erratically at this stage. PSP amplitude and duration gradually increase with age, and at about 56 h, preoral ciliated cells become electrically excitable. A single regenerative action potential first occurs at this time and causes a velum‐wide, ciliary arrest. Between 56 and 72 h, the duration of the depolarizing phase of the preoral ciliated cell action potential decreases, the amplitude increases, and the hyperpolarizing undershoot develops. Preoral ciliated cell action potentials appear to be Ca2+‐dependent throughout development. Shortening of the action potential duration and development of the hyperpolarizing undershoot may be due to activation of later developing K+ channels. As veligers become competent to metamorphose, the preoral velar cells and their connections with the body deteriorate.
The effect of cyclic AMP on neuritic outgrowth in explant cultures of developing chick olfactory epithelium
Authors: Johnson Randall R. , Farbman Albert I. , Gonzales Federico 
Published: January 2005

AbstractThe effect of cyclic AMP (cAMP) analogs and phosphodiesterase (PDE) inhibitors on neurite outgrowth was studied in explant cultures of olfactory neurons. Nasal pits from 5‐ or 6‐day‐old chick embryos were minced, explanted into culture dishes, and grown in a serum‐free medium. One of the cyclic AMP analogs, dibutyryl cyclic AMP (dbcAMP) or 8‐bromo‐cyclic AMP (8‐Br‐cAMP), or one of the PDE inhibitors, theophylline or isobutylmethylxanthine (IBMX), was added to the culture medium. The explants were examined for neurite outgrowth after 2 days in vitro. Db‐cAMP Increased the number of explants expressing neurites by 25–35% over control cultures, whereas 8‐Br‐cAMP had essentially no effect at the same concentrations. Addition of dibutyryl cyclic GMP (dbcGMP) gave no increase in neurite out growth, thus indicating that the effect of enhancing neuritic growth is specific to cAMP and not cyclic nucleotides in general. The resulting increase in neurite outgrowth is due to the cyclic nucleotide component of dbcAMP, since both IBMX and theophylline, which elevate intracellular cAMP, also increased neurite outgrowth significantly. When forskolin was added to the culture medium, there was a trend to increased neurite outgrowth; this was significantly enhanced when a subthreshold concentration of theophylline was added in addition to the forskolin.
Inhibitor of protein synthesis blocks longterm behavioral sensitization in the isolated gill‐withdrawal reflex of Aplysia
Authors: Castellucci V. F. , Blumenfeld H. , Goelet P. , Kandel E. R. 
Published: January 2005

AbstractTo study the effect of protein synthesis inhibition on long‐term sensitization of the gill‐ and siphon‐withdrawal reflex of Aplysia, we have developed an isolated reflex preparation in which we could expose the inhibitor to only that part of the central nervous system involved in mediating the reflex and not to the other parts of the animal's central nervous system, thus minimizing the possible systemic side effects. We have found that long‐term sensitization can be obtained in the isolated gill reflex, and that this long‐term process, but not the short‐term process, is blocked selectively by anisomycin, a reversible inhibitor of protein synthesis. Moreover, to obtain this blockade of long‐term sensitization, this drug need only be applied during the training procedure.
ω‐Aga‐I: A presynaptic calcium channel antagonist from venom of the funnel web spider, Agelenopsis aperta
Authors: Bindokas Vytautas P. , Adams Michael E. 
Published: January 2005

AbstractSpider venoms are proving to be important sources of specific ion channel toxins. Venom of Agelenopsis aperta, a funnel web spider, contains a class of polypeptide toxins which blocks neuromuscular synapses at nanomolar concentrations. Detailed physiological analyses of block caused by one of these toxins, ω‐Aga‐I show that it suppresses transmitter release at insect and frog neuromuscular junctions and blocks calcium spikes in insect neuronal cell bodies. ω‐Aga‐I may define a binding site on neuronal calcium channels which is common to both vertebrates and invertebrates.
Androgens modulate endplate size and ACh receptor density at synapses in rat levator ani muscle
Authors: Bleisch William V. , Harrelson Allan 
Published: January 2005

AbstractThe dorsal bulbocavernosus or “levator ani” muscle of the rat is highly responsive to androgens. Both the muscle and the motoneurons which innervate it contain high concentrations of androgen receptors. The neuromuscular synapses in this muscle are also affected by changing androgen levels. In particular, the total number of ACh receptors (AChRs) in the muscle is lower in males that have been castrated, and it increases after treatment with the androgens, testosterone and 5 α‐dihydrotestosterone. An examination of individual endplates using histochemistry and quantitative autoradiography suggested that the reduction in AChR number following castration is caused by reductions in both the size of endplates and in the density of AChRs at each synapse.
Cell death of motoneurons in the chick embryo spinal cord. X. Synapse formation on motoneurons following the reduction of cell death by neuromuscular blockade
Authors: Okada A. , Furber S. , Okado N. , Homma S. , Oppenheim R. W. 
Published: January 2005

AbstractChronic treatment of chick embryos with neuromuscular blocking agents, such as curare, rescues motoneurons from naturally occurring cell death. In the present study, embryos treated with curare from E6 to E9 had 35% more motoneurons than controls on E10 and 42% more than controls on E16. Previous studies have shown that several aspects of motoneuron differentiation occur normally in curare‐treated embryos. We report here that dendrite growth and arborization is also unaltered on E10 and E16 following curare treatment. A quantitative analysis of afferent synapses on motoneurons shows that the packing density of both axosomatic and axodendritic synapses is also normal on E10 in curare‐treated embryos, despite the greater number of motoneurons present. This indicates that the interneurons that provide presynaptic input to motoneurons are able to compensate for the increased number of synaptic sites made available by curare treatment. However, by E16 the packing density of synapses is reduced by about half. Because motoneurons and their dendrites continue to grow between E10 and E16, the further increase in synaptic sites made available in curare‐treated embryos apparently exceeds the compensatory capacity of presynaptic interneurons on E16. One can conclude from these results that the increased survival of motoneurons in curare‐treated embryos in not owing to an increase in afferent synapses. Motoneurons in these embryos continue to survive in the face of either no change (E10) or a reduction (E16) in the number of axodendritic and axosomatic synapses. Therefore, increased motoneuron survival in this situation is very likely regulated primarily by motoneuron–target interactions.
The use of hormonally induced mosaics to study alterations in the synaptic connections made by persistent sensory neurons during insect metamorphosis
Authors: Levine Richard B. , Waldrop Brian , Tamarkin Dawn 
Published: January 2005

AbstractDuring the initial phase of metamorphosis in the hawkmoth, Manduca sexta, persistent mechanosensory neurons expand their terminal arborizations within the CNS and evoke a reflex response in the pupa which is different than in the larva. In an effort to determine the contribution of sensory neuron modifications to the difference in reflex responses, manipulations of juvenile hormone and 20‐hydroxyecdysone were used to generate mosaic animals in which the sensory neurons were advanced or delayed developmentally with respect to the rest of the animal, including circuit components within the CNS. In the larval stage electrical stimulation of the sensory axons evokes a slow depolarization and a prolonged burst of action potentials in the ipsilateral intersegmental muscle motor neurons. By contrast, in pupal preparations the same motor neurons respond to an identical stimulus with a larger, more rapid depolarization which leads to a relatively brief, high‐frequency burst of action potentials. Motor responses on the contralateral side of the body are also altered during pupal development. In mosaic animals where larval‐like sensory neurons interact with a pupal CNS, a larval reflex response is generated. In the converse situation, pupal‐like sensory neurons interacting with a larval or prepupal CNS evoke a motor response that is typical of larvae or prepupae. We conclude, therefore, that pupal development of the sensory neurons is necessary, but not sufficient, for the production of the pupal reflex.
Synaptic plasticity at the crayfish opener neuromuscular preparation
Authors: Bittner George D. 
Published: January 2005

AbstractThe crayfish opener neuromuscular preparation exhibits most of the plasticities yet described for any synpase, including facilitation, long‐term potentiation, presynaptic inhibition, and modulation. Since the presynaptic terminals and postsynaptic muscle fibers can both be intracellularly penetrated, one can now more easily examine the cellular/molecular bases for these plasticities. Data from such studies suggest that facilitation may be influenced by something other than residual free calcium and that presynaptic inhibition is produced by a conductance increase to chloride in the terminals of the excitor axon. Several drugs (ethanol, pentobarbital) have significant effects on these synaptic plasticities over concentration ranges which produce obvious behavioral effects in crayfish and mammals. Hence, this preparation should be a useful model system to determine cellular/molecular bases for various synaptic plasticities and the effects of drugs on these plasticities.