bluuebunny/crossref_metadata_2025_split huggingface dataset:
Learning, using natural reinforcements, in insect preparations that permit cellular neuronal analysis
Authors: Hoyle Graham 
Published: January 2005

AbstractA general paradigm is described that permits testing the ability of an arthropod to learn (by operant conditioning) to alter the position of a single leg segment in order to relate to behaviorally appropriate reinforcement. The paradigm was designed so that intracellular recording from identified neurons involved would be possible during the training of a locust or grasshopper, for which extensive neuron maps are available. As a prelude to such studies, electromyograms were made from the antagonistic muscles that move the conditioned limb, which in the present experiments was the tibia of the metathoracic leg. Negative (aversive) reinforcement was provided by a loud sound/vibration and positive (reward) reinforcement by food in the form of sugar‐water or fresh‐growing grass. In the aversive reinforcement experiments the sound, which reflexly caused flexion, was on continually except when the tibia of one hind leg was voluntarily placed in an electronically set position “window” displaced, in extension, away from the preferred position. In feeding experiments, food was brought automatically to the mouth by a motor‐driven arm when the tibia was held within a position window set away from the preferred position in either extension or flexion. Whole or headless insects learned to turn off the sound permanently, except for sporadic brief interruptions, by tonic shifting of tibial position. Insects learned to bring food to the mouth by modifying the plateau phase of a position displacement lasting for a few minutes, that was found to occur from time to time also in controls. In aversive learning, minimum times to turn off the sound were 22 sec for the easiest position and 4 min for the most difficult. The longest time in the easiest position was 1 min 40 sec and in the most difficult 39 min; excluding measurement for individuals that did not learn. In reward learning, the minimum time in the easiest position was just under 1 min, and 12 min in the most difficult position. The longest times were about 8 hr regardless of difficulty.
Primary cultures of dispersed hypothalamic cells from fetal rats: Morphology, electrical activity, and peptide content
Authors: Vaccaro Dennis E. , Leeman Susan E. , Messer Anne , Dichter Marc A. 
Published: January 2005

AbstractCultures prepared from dispersed fetal hypothalamic tissue have cells which can be identified as neurons by their morphology and electrical activity. The elongation of neuritic processes in these cultures is increased by treatment with 1‐β‐D‐arabinofuranosylcytosine (ara‐C). Hypothalamic cultures have measurable quantities of immunoreactive substance P and neurotensin, and the neurons can accumulate (3H)GABA.
GABA inactivation at the crayfish neuromuscular junction
Authors: Horwitz I. S. , Orkand R. K. 
Published: January 2005

AbstractChanges in the effective membrane resistance of the abductor muscle of the dactylopodite of the crayfish were used to indicate changes in the GABA concentration in the synaptic cleft. Following bath application of GABA (10−5 to 5 × 10−5M), the muscle membrane resistance decreased and then increased slowly over the next few minutes. Renewing the solution or stirring the bath restored the GABA effect. Higher GABA concentrations produced a large stable decrease in membrane resistance. An active uptake system for GABA in the junctional region is suggested by the observation that the slow increase in membrane resistance following GABA application was decreased by cooling to 2°C or by the addition of known GABA uptake blockers such as L‐DABA, β‐guanidinopropionic acid, or nipecotic acid. The transport inhibitors, PCMBS and chlorpromazine, produced irreversible decreases in muscle membrane resistance, which precluded examining their effects on GABA inactivation. The decrease in GABA effect was not dependent on the external sodium concentration or on the degree of receptor activation. Nipecotic acid, which blocked GABA inactivation, did not affect the decay of the neurally evoked inhibitory junctional potential.
Effects of p‐chloroamphetamine, a serotonin‐depleting drug, on the median eminence and pituitary pars intermedia
Authors: Saland L. C. , Dail W. G. , Reyes E. 
Published: January 2005

Abstractp‐Chloroamphetamine (PCA), an agent known to cause depletion of levels of brain serotonin in rodents, was administered to rats in three sequential injections (10 mg/kg) to study effects on the hypothalamic median eminence and pituitary gland. One week following the initial sequence of injections of PCA, light and electron micrographs revealed degenerate fibers in the outer zone of the median eminence. Lower drug doses or single 10‐mg/kg doses did not lead to morphologic changes. Neuronal processes located in the pituitary intermediate lobe appeared normal, although there was a significant increase in the numbers of secretory granules contained within intermediate lobe cells of drug‐treated rats, as compared to controls. Fluorometric analysis of levels of catecholamine and indoleamine showed a decrease in serotonin in median eminence and pons‐medulla, but no change in that of the pituitary. Levels of dopamine and norepinephrine remained unchanged after PCA treatment. The data suggest that fibers affected in the median eminence contain serotonin. Processes in the intermediate lobe may be resistant to the serotonin‐lowering effects of PCA observed in brain tissue. In addition, PCA may directly affect granule release from pituitary cells, or may alternatively act on hypothalamic regions which affect the release of intermediate lobe cell hormones.
Excitatory neuromuscular transmission in crayfish: Calcium dependence is unaffected by picrotoxin
Authors: Staggs D. R. , Pofcher E. , L'Heureux Ramona , Ortiz C. L. , Orkand R. K. 
Published: January 2005

AbstractPicrotoxin, 1 × 10−5M to 1.6 × 10−3M, had little or no effect on the amplitude of intracellularly recorded excitatory junctional potentials (EJPs) at extracellular calcium concentrations [Ca2+]0 ranging from 0.5 to 15 mM. The slope of the log EJP vs. log[Ca2+]0 relationship was approximately 1 with or without picrotoxin. The reduction of EJP amplitude resulting from the addition of 5 × 10−5M GABA was largely reversed by 10−5M picrotoxin.
Identification and localization of catecholamines in the nervous system of Limulus polyphemus
Authors: O'Connor Edward F. , Watson Winsor H. , Wyse Gordon A. 
Published: January 2005

AbstractThe concentrations of various catecholamines in the nervous system of the horseshoe crab Limulus polyphemus have been determined by high‐performance liquid chromatography with electrochemical detection. Dopamine, norepinephrine, epinephrine, and their precursor L‐Dopa were present in appreciable quantities in discrete regions of the central nervous system and cardiac ganglion. The catecholamines were localized more precisely by use of the glyoxylic‐acid‐histofluorescence technique of de la Torre and Surgeon (1976). Catecholamine fluorescence appeared in protocerebral and tritocerebral neuropile, including regions of the central body and optic medulla. Posterior to these brain areas, tracts extended through the circumesophageal ganglionic ring and laterally out each of the pedal ganglia. Small clusters of large fluorescent somata were present in the protocerebrum. No fluorescence was observed in the corpora pedunculata.
Gangliosides associated with microsomal subfractions of brain: Comparison with synaptic plasma membranes
Authors: Skrivanek J. A. , Ledeen R. W. , Margolis R. U. , Margolis R. K. 
Published: January 2005

AbstractTo study ganglioside distribution within subcellular components and test the hypothesis that they are localized at the nerve ending, microsomes and synaptic plasma membranes were isolated from young adult rat brains and compared with respect to ganglioside composition. These were shown to be heterogeneous preparations by fractionation on a discontinuous sucrose gradient into subfractions which had differing ganglioside concentrations. The highest ganglioside concentrations occurred in membranes banding at the 0.8M/1.0M and 1.0M/1.3M interfaces for both microsomes and synaptic plasma membranes. These subfractions had closely similar ganglioside concentrations and pattern distributions. In addition, the kinetics of ganglioside labeling following administration of [3H]‐glucosamine were similar for the two preparations. The fact that microsomal subfractions representing heterogeneous mixtures of brain cell membranes showed close similarity to synaptosomal plasma membranes argues against localization of gangliosides at the nerve ending. These results, together with other lines of evidence, support the concept that gangliosides are distributed over large portions of the neuron (and perhaps other brain cells). Data concerning the labeling of gangliosides in different microsomal subfractions indicated a movement of label over time from the more dense to the less dense membranes, as was also noted for the glycoproteins in the same subfractions. Specific radioactivity of the gangliosides increased relative to that of the glycoproteins with time.
The ionic dependence of black widow spider venom action at the stretch receptor neuron and neuromuscular junction of crustaceans
Authors: Fritz L. C. , Mauro A. 
Published: January 2005

AbstractThe effects of black widow spider venom (BWSV) on the crayfish stretch receptor and the lobster neuromuscular junction were examined. In crayfish stretch receptor neurons, BWSV caused a slight hyperpolarization followed by a large depolarization. The venom‐induced depolarization of the strech receptor was caused by an increase in membrane conductance to Na+ and Ca2+. Black widow spider venom also caused an increase in the frequency of miniature inhibitory postsynaptic potentials recorded in the strech receptor. The ability of BWSV to increase the frequency of miniature excitatory postsynaptic potentials (MEPSPs) at the lobster neuromuscular junction was dependent on the divalent cation composition of the bathing medium. Ringer solutions containing Ca2+ supported the greatest venom‐induced increase in MEPSP frequency, Mg2+ and Mn2+ supported a moderate increase in MEPSP frequency, while Co2+ and Zn2+ blocked this venom effect entirely. Black widow spider venom did not block axonal conduction in lobster walking leg axons or in the axon of the crayfish stretch receptor. The results suggest that in crustaceans, BWSV interacts specifically with membrane of the soma‐dendritic region of the stretch receptor and with nerve terminal membrane, causing an increase in Na+ and Ca2+ conductance.
UV–visible antagonism in extraocular photosensitive neurons of the anthomedusa, spirocodon saltatrix (tilesius)
Authors: Ohtsu Kohzoh 
Published: January 2005

AbstractAttempts were made to identify extraocular photosensitive cells in the subtentacular region (the area between the ocelli and the nerve ring) and around the inner‐nerve ring of the anthomedusan Spirocodon saltatrix. Irradiation with ultraviolet light (UV) led to inhibition of spontaneous impulses and after UV‐off, an afterinhibition which lasted for a few minutes. This afterinhibition was rapidly overcome by exposure to visible light (VIS). UV–VIS antagonism of this type was identified in six different impulse systems monitored in extracellular recordings. Intracellular recordings from two of the six cell types showed that UV irradiation causes hyperpolarization which inhibits spontaneous activity. The other cell types showed no membrane potential changes during UV irradiation even though the cells' spontaneous outputs were inhibited. It was concluded that the photosensitivity lies in three kinds of nerves which are distributed widely through the subtentacular region and the nerve ring.
Enhancement of inward current by serotonin in neurons of Aplysia
Authors: Pellmar Terry C. 
Published: January 2005

AbstractIn RB cells of Aplysia, serotonin, in the presence of TEA, 4AP and Ba, elicits a voltage‐dependent inward current. In Ba‐TEA‐4AP seawater, RB cells showed a negative slope region (NSR) in their current‐voltage (I‐V) relationship when measured at the end of 2‐s commands from a holding potential of −60 mV. Addition of serotonin to the bathing solution enhanced the NSR. When holding potential was lowered to −10 mV, the NSR as well as the effects of serotonin were greatly reduced. Addition of 20 mM cobalt to the bathing solution blocked both the NSR and the inward current produced by serotonin. Changes in potassium concentration produced no consistent shift in voltage sensitivity nor change in amplitude of the current elicited by serotonin. Intracellular injection of cesium sufficient to broaden action potentials did not block the enhancement of NSR by serotonin. These results support the conclusion that in RB cells, serotonin produces a voltage‐dependent current carried by calcium ions.
Scanning and freeze‐fracture study of larval nerves and neuromuscular junctions in Manduca sexta
Authors: Schaner Pamela J. , Rheuben Mary B. 
Published: January 2005

AbstractThe nerves and nerve terminals to tonic larval muscle fibers in third and fifth instar caterpillars were studied to compare them with those formed by the same motor neurons on phasic flight muscles in adult moths.Scanning micrographs showed a primary nerve branch running the length of each fiber, with secondary nerve branches extending from it at intervals. There was a great deal of variability in both the length of the branches and the distance from the nerve at which the neuromuscular junctions were formed. The rapid increase in muscle fiber size during larval development may be responsible for this variability. The nerves and junctions were often found to be obscure by overlying fibroblasts and tracheoblasts or entering the deep muscle clefts. Those examined were similar in appearance to the adult junctions formed by the same neurons, although some may have formed single branches instead of y‐shapes.The membrane specializations of the synapse seen in freeze‐fractured specimens were similar to those of the adult junction. However, the overall shape of the nerve terminal within the junction differed. The larval nerve terminals appeared varicose instead of having a uniform diameter. The spacing of the nerve plaques varied, in contrast with the relatively straight alignment and even spacing of plaques found in adult junctions. Such differences could result from an interaction between the motor neuron and the two different types of muscle fiber that it innervates, an intrinsic change in the motor neurons themselves that occurs with metamorphosis, or a plastic functional response that occurs as a result of the different types of motor patterns that are used in the two stages.
Unresponsive, a behavioral mutant in Xenopus laevis: Electrophysiological studies of the neuromuscular system
Authors: Dudek F. Edward , Ide Charles F. , Tompkins Robert 
Published: January 2005

AbstractNormal Xenopus laevis embryos begin movements at 1 day after fertilization. Embryos homozygous for the unresponsive mutation fail to move until 4 days after fertilization (just prior to feeding), after which they recover slowly. Electrophysiological studies were undertaken to determine the focus of this mutation. Formamide treatment of normal embryos was used to produce a phenocopy of the unresponsive condition, permitting direct comparisons between mutant and normal embryos. Intracellular recordings from muscle cells were obtained in formamide‐treated and untreated preparations with both normal and unresponsive animals. Local electrical stimulation evoked either isolated endplate potentials and action potentials or after‐discharges of these events in all preparations. A decrease in illumination also caused a burst of endplate potentials and action potentials. Therefore, the electrophysiology of the neuromuscular junction in unresponsive appears qualitatively normal; the effect of the mutation on the motor system is probably distal to the neuromuscular junction, either at or subsequent to excitation‐contraction coupling.
Estrogen accumulation in zebra finch song control nuclei: Implications for sexual differentiation and adult activation of song behavior
Authors: Nordeen K. W. , Nordeen E. J. , Arnold A. P. 
Published: January 2005

AbstractIn zebra finches the gonadal steroid estradiol (E2) directs the sexual differentiation of neural regions controlling song and synergizes with androgens to stimulate song in adulthood. To identify regions where E2 may act to exert these effects, steroid autoradiographic techniques were used to assess cellular accumulation of 3[H]‐E2 or its metabolites within various nuclei of the zebra finch brain. In Experiment 1 we examined brains from juvenile females, still within the critical period for E2's effect on sexual differentiation. In Experiment 2 the pattern and extent of labeling in adult male brains was determined following injection of 3[H]‐E2, 3[H]‐testosterone, or 3[H]‐dihydrotestosterone. The results suggest that, both during development and in adulthood, most song‐control nuclei contain few E2‐accumulating cells. In contrast, many cells densely labeled by 3[H]‐E2 or its metabolites are present in the hypothalamus and in close proximity to one song‐control region, the hyperstriatum ventralis pars caudalis (HVc). The distribution of these latter cells overlaps with cells that project to another song‐related nucleus, Area X. Thus, in Experiment 3 fluourescent retrograde tracing and steroid autoradiographic techniques were combined to determine if E2‐accumulating cells project to Area X in adult males. Although a few retrogradely labeled cells were lightly labeled by 3[H]‐E2 or its metabolites, for the most part these appear to be two distinct populations of cells. The sparse accumulation of E2 in the zebra finch song system contrasts with that described in other song birds and has important implications as to the mechanism of E2 action on the developing and mature song system.
Activity sharpens the regenerating retinotectal projection in goldfish: Sensitive period for strobe illumination and lack of effect on synaptogenesis and on ganglion cell receptive field properties
Authors: Eisele Leslie E. , Schmidt John T. 
Published: January 2005

AbstractThe regenerating optic nerve of goldfish first reestablishes a rough retinotopic map on the contralateral tectum and then sharpens it. Disruption of visual activity, either by blocking activity with intraocular tetrodotoxin (TTX; Schmidt and Edwards, 1983) or by synchronizing activity with strobe illumination (Schmidt and Eisele, 1985), disrupts the sharpening process: the map is correctly oriented but the multiunit receptive fields at each point average 25–40° in diameter. In order to test whether strobe and TTX interfere with the same mechanism, we have tested whether their sensitive periods are the same, and whether strobe, like TTX treatment, does not affect either ganglion cell receptive field properties or synaptogenesis. In parallel studies, we exposed fish to 2 weeks of either strobe illumination or intraocular TTX beginning at various times after crush and determined via electrophysiological recordings that the periods of sensitivity were nearly identical. There was no effect of either treatment during the first 2 weeks (before the fibers arrive at the tectum), maximal disruption of sharpening between 14 and 50 days (the period of rapid synaptogenesis), decreasing disruption between 50 and 125 days, and no effect beyond that point or in the normal projection. In addition, long strobe exposures of up to 142 days produced no greater disruptions than shorter 2–3‐week exposures, indicating no cumulative effect. The reestablishment of synaptic transmission in tectum, assayed by recording field potentials elicited by optic nerve shock, was not affected by stroboscopic illumination. Finally, individual ganglion cells, recorded intraretinally following long‐term strobe exposure, had receptive fields that were normal both in size and in their characteristic responses to light‐on, to light‐off, or to both on and off. These findings support the hypothesis that strobe‐like TTX prevents retinotopic refinement by preventing the correction of errors initially made by the ingrowing optic axons (Schmidt et al., 1988).
The role of the sexual organs in the generation of postembryonic neurons in the leech Hirudo medicinalis
Authors: Baptista Carlos A. , Macagno Eduardo R. 
Published: January 2005

AbstractIn adult Hirudo medicinalis, the segmental ganglia (SG) of the fifth and sixth body segments contain a few hundred more cells than the other segmental ganglia of the body (Macagno, 1980). These ganglia innervate the sex organs and are known as the sex SG. As shown here, these cells are stained by neuron‐specific antibodies. Cell counts at several developmental stages reveal that the extra cells are added exclusively to the sex SG, and that this addition occurs gradually and almost entirely postembryonically (embryogenesis ends at 30 days of development). Hence, we refer to them as PE cells. Until 16 days of development, deleting the male genitalia or disconnecting them from the sex ganglia results in a complete absence of the PE cells. From 16 days onward, the generation of the PE cells is independent of the male genitalia. No PE cells appear in non‐sex SG that innervate male genitalia transplanted to ectopic locations at 10 days or later, indicating that as early as about 10 days of development sex SG are different from other SG in their ability to acquire PE cells. These data suggest that the PE cells are generated within the sex SG, in a process that is triggered by an interaction with the male genitalia and mediated through the innervation of the organs by these ganglia.
Regenerative specificity of motor axons when reinnervation is partially suppressed
Authors: Farel Paul B. , Wray Sibyl E. 
Published: January 2005

AbstractWe asked whether regenerating hindlimb motor axons would innervate inappropriate hindlimb regions if competition from appropriate innervation were prevented. The three ventral roots that innervate the hindlimb in the bullfrog (Rana catesbeiana) tadpole were transected, and the two more rostral roots were ligated to prevent regeneration. The most caudal root, which primarily supplies more distal limb musculature in unoperated tadpoles, was left free to regnerate. The specificity of regeneration was assessed by retrogradely labeling spinal motoneurons with HRP placed in the ventral thigh, a region that receives most of its innervation from the ligated roots. Despite the lack of competition from appropriate innervation, the regenerating root did not provide substantial innervation to proximal limb musculature. The same result was obtained in tadpoles operated upon at stages when regeneration of motor axons is specific and in tadpoles at stages when regenerating motor axons do not reinnervate their appropriate targets (Farel and Bemelmans, 1986), although the mechanisms in each case are likely different.