bluuebunny/crossref_metadata_2025_split huggingface dataset:
Catecholamine neurons in Aplysia: Improved light‐microscopic resolution and ultrastructural study using paraformaldehyde and glutaraldehyde (FaGlu) cytochemistry
Authors: Goldstein Ronald S. , Schwartz James H. 
Published: January 2005

AbstractWe have modified the formaldehyde‐glutaraldehyde (FaGlu) histofluorescence method of Furness, Costa, and Blessing (1977a) and Furness, Costa, and Wilson (1977b) to examine wholemounts and sections of both juvenile and adult ganglia as well as peripheral tissues of Aplysia californica. FaGlu fluorescence is the result of a reaction between formaldehyde and tissue catecholamines to produce water‐insoluble (fixed) fluorophores. In serially sectioned cerebral ganglia, 70–80 positive neurons were observed (many in clusters of 10–20 cells), many more than were found using the glyoxylic acid technique. Catecholamine‐containing varicosities were densely packed in localized portions of the neuropil of all central ganglia. Exclusive localization in the neuropil of presumed dopamine release sites is similar to that previously found for the neuropeptide SCP but differs form the widespread ramification of varicose neurites containing 5‐HT, FMRFamide, and ELH. The FaGlu technique also enabled us to study the ultrastructure of catecholamine‐containing neurons. In contrast to the larger vesicles found in serotonergic and histaminergic neurons, these dopaminergic neurons contain 70 nm dense‐cored vesicles.
Long‐term cultures of neurons from adult frog brain express GABA and glutamate‐activated channels
Authors: Wetzel D. M. , Lee V. M‐Y. , Erulkar S. D. 
Published: January 2005

AbstractCells from adult Xenopus laevis brainstem and spinal cord were dissociated with mild enzymatic treatment and grown in long‐term cell culture. These cells had specific attachment/substrate and medium/serum requirements. Cells with bipolar and multipolar morphology were positively identified as neurons using immunohistochemistry with monoclonal antibodies to rat and bovine neurofilament proteins which we show here cross‐react with similar amphibian proteins. Patch clamp recordings demonstrated that these neurons have populations of ionic channels which are activated by L‐glutamate or γ‐aminobutyric acid (GABA).Abbreviations: ABC, avidin‐biotin‐complex; dHnO, distilled water; GABA, γ‐aminohutyric acid; L‐15, Leibovitz's 15 medium; NCM, zero calcium zero magnesium Ringers' solution; NF, neurofilament; NFRS, normal frog Ringers' solution; PAP, peroxidase antiperoxidase.
The characteristics of these channels were similar to those previously described for GABA‐ and glutamate‐activated channels in embryonic mammalian neurons isolated in culture. Cell cultures of neurons isolated from adult Xenopus laevis brain may be a useful and simple preparation with which to examine the modulation of neuronal properties by various agents over longer time intervals then has been previously possible.
Neuronal plasticity in the adult invertebrate nervous system
Authors: Bulloch A. G. M. , Ridgway R. L. 
Published: January 2005

AbstractThis essay provides a brief overview of neuronal plasticity in adult invertebrate nervous systems. Our discussion focuses on the factors which influence sprouting by adult neurons, i.e., (1) the nature of the neuron itself, (2) axon integrity, (3) the presence of targets, (4) diffusible factors, and (5) ageing. Evidence that the neurites of some adult neurons exhibit a dynamic equilibrium of expansion and retraction is presented, a topic which prompted us to speculate on the significance of such plasticity in altered behavioral states. We conclude with some suggestions as to specific questions that need to be addressed by future studies in this challenging area.
Structural plasticity at identified synapses during long‐term memory in Aplysia
Authors: Bailey Craig H. , Chen Mary 
Published: January 2005

AbstractWe have used the gill‐ and siphon‐withdrawal reflex of Aplysia californica to determine the morphological basis of the prolonged changes in synaptic effectiveness that underlie long‐term habituation and sensitization. We have found that clear structural changes accompany behavioral modification and have demonstrated that these can be detected at the level of identified sensory neuron synapses, a critical site of plasticity for the short‐term forms of both types of learning. These alterations occur at two different levels of synaptic organization and include (1) changes in focal regions of synaptic membrane specialization—the number, size and vesicle complement of sensory neuron active zones are larger in sensitized animals and smaller in habituated animals compared with controls—and (2) a parallel but more dramatic and global trend involving modulation of the total number of presynaptic varicosities per sensory neuron. Quantitative analysis of the time course over which these structural alterations occur during sensitization has further demonstrated that changes in the number of varicosities and active zones persist in parallel with the behavioral retention of the memory. This increase in the number of sensory neuron synapses during long‐term sensitization in Aplysia is similar to changes in the number of synapses in the mammalian brain following various forms of environmental manipulations and learning (Greenough, 1984). Therefore learning may involve a form of neuronal growth across a braod segment of the animal kingdom, thereby suggesting a role for structural synaptic plasticity during long‐term behavioral modifications.
Rapid introduction of long‐lasting synaptic changes at crustacean neuromuscular junctions
Authors: Atwood H. L. , Dixon D. , Wojtowicz J. M. 
Published: January 2005

AbstractIn this review we present recent evidence implicating second‐messenger systems in two forms of long‐lasting synaptic change seen at crustacean neuromuscular junctions. Crustacean motor axons are endowed with numerous terminals, each possessing many individual synapses. Some synapses appear to be quiescent or impotent, but can be recruited in response to imposed functional demands. Supernormal impulse activity leads to long‐term facilitation (LTF) which persists for many hours. During the persistent phase, additional synapses are physiologically effective, and morphological changes in synapses are seen at the ultrastructural level. Pulsatile application of serotonin, a neuromodulator, also enhances synaptic transmission, but this enhancement declines more rapidly than LTF. Elevation of intraterminal Ca2+ is neither necessary nor sufficient for long‐lasting enhancement of transmission, but activation of A‐kinase is necessary. LTF is set in motion by an unknown depolarization‐dependent mechanism leading to A‐kinase activation, whereas serotonin facilitation depends for its initiation on the phosphatidylinositol system. The initial phase of serotonin facilitation may be accounted for by production of inositol triphosphate, whereas the secondary long‐lasting phase appears to require participation of both C kinase and A kinase. Neither LTF nor serotonin facilitation requires an intact neuron; both are presynaptic phenomena expressed by the nerve terminals. Brief comparison is made with long‐lasting synaptic changes in other systems.
Effect of putative neuromodulators on rhythmic buccal motor output in Lymnaea stagnalis
Authors: Kyriakides M. A. , McCrohan C. R. 
Published: January 2005

AbstractThe effects of a variety of neuromodulator substances on rhythmic motor output and activity in neurons in the feeding circuitry of Lymnaea stagnalis were examined. Each neuromodulator produced a unique combination of effects at different levels in the network: i.e., pattern‐generating interneurons (N1, N2, and N3), an identified higher‐order interneuron (cerebral giant cell, CGC), and buccal motoneurons. 5‐Hydroxytryptamine, acetylcholine, and FMRFamide all inhibited rhythmic motor activity. However, this was achieved in different ways. Dopamine changed the nature of rhythmic activity from one in which N2 interneuronal activity was predominant (“N2 rhythm”) to a feeding rhythm. Dopamine was the only substance capable of activating the feeding rhythm. Activity in the CGC was increased by 5‐hydroxytryptamine, dopamine, and acetylcholine and reduced by FMRFamide. Differential responses in buccal motoneurons were also observed. The results are discussed in relation to previous work on other species and also in terms of the selection of different patterns of motor output by neuromodulators.
ATP and calmodulin dependent actomyosin aggregates induced by cytochalasin D in goldfish retinal ganglion cell axons in vitro
Authors: Edmonds Brain T. , Koeing Edward 
Published: January 2005

AbstractGrowing retinal ganglion cell (RGC) axons of the goldfish have mobile varicosities, which play a role in rapid bulk redistribution of axoplasm (Koenig, Kinsman, Repasky, and Sultz, 1985; Edmonds and Koeing, 1987). Varicosities contain a tubulo‐vesicular SER embedded in an actin‐containing cytomatrix (Koenig et al., 1985). Cytochalasin D (CD) induces the formation of focal cytoskeletal aggregates throughout preterminal axons and especially in varicosities. The aggregates are visible when labelled with fluoroscein isothiocyanate (FITC)‐conjugated phalloidin. Double‐labelling experiments show that Texas red‐myosin or rhodamine isothiocyanate (RITC)‐calmodulin immunofluorescence co‐localizes with FITC‐phalloidin‐labelled aggregates. Formation of aggregates is blocked by calmidazolium, a calmodulin antagonist. Axon models permeabilized with digitonin retain the capacity to form focal aggregates in response to CD, when ATP or adenosine‐5′‐O(3‐thiotriphosphate) (ATP‐γS) is present in the permeabilization buffer, but not when 5′‐adenylylimidodiphosphate (AMP‐PNP) is present. The latter result indicates that formation of focal aggregates depends on ATP. The findings suggest that the formation of focal aggregates in immature axons is a manifestation of actomyosin interactions after free actin‐filament ends are generated by CD treatment.
A kinematic analysis of hindlimb motility in 9‐ and 10‐day‐old chick embryos
Authors: Watson Sandra J. , Bekoff Anne 
Published: January 2005

AbstractAlthough chick embryonic leg movements appear jerky and disorganized, the underlying motor patterns are coordinated. This apparent conflict in results was investigated using kinematic analyses to provide detailed quantitative descriptions of leg movements during spontaneous motility in 9‐ and 10‐day‐old chick embryos. In many respects, hip, knee, and ankle movements were highly variable. There was variation in movement durations and in the number of leg joints that participated in a given movement. Motion could begin with either flexion or extension. Furthermore, the limb could return to its rest position between movements or move continuously to produce sequences of variable lengths. Patterns of interlimb coordination included alternating, synchronous and independent movements of the legs. We propose that these variable features account for the uncoordinated appearance of embryonic leg movements. In addition to variable features, however, some consistent characteristics were identified. For example, when more than one joint was active, activity typically began and ended synchronously. Furthermore, all active joints generally extended or flexed together and movements were symmetrical. These data are consistent with previous EMG results. Therefore, despite the variability in some parameters that results in the perception that embryonic leg movements are random and uncoordinated, our kinematic analyses show that an organized pattern of interjoint coordination is a prominent feature. This basic pattern shows some similarities to, but is less complex than, kinematic patterns found during a variety of posthatching behaviors.
The vocal motor neurons of Xenopus laevis: Development of sex differences in axon number
Authors: Kelley Darcy B. , Dennison Jane 
Published: January 2005

AbstractSex differences in the number of muscle fibers in the larynx of clawed frogs (Xenopus laevis) develop after metamorphosis. In order to examine possible contributions of neural innervation to this process, we prepared sections of the laryngeal nerve from tadpole stage 56, when the sexes can first be distinguished, through adulthood, and counted axons on electron micrographs. The adult number of axons is achieved by a sexually differentiated pattern of axonal addition and loss. Axon numbers are high at tadpole stage 56 and equal for males and females; thereafter, males have more axons. Sex differences are most pronounced at tadpole stage 62 because between stages 59 and 62 the number of laryngeal axons in males increases by an average of 119 per nerve. Ultra‐structural evidence is congruent with the hypothesis that new axons are added to the laryngeal nerve between tadpole stages 56 and 62. The loss of axons from the laryngeal nerve is greater for females than for males. Between tadpole stages 56 and adulthood, overall axon number decreases by 47% in males and by 64% in females. Signs of axonal degeneration are present in both sexes before metamorphosis but are rare at juvenile or adult stages. The numbers of axons in juvenile frogs do not differ from those in adults and continue to be greater in males than in females. In contrast to the amount of axon addition and loss, the timing of axon loss and the percentage of myelinated axons is the same for males and females throughout development. Thus sex differences in the innervation of laryngeal muscle originate before metamorphosis and could contribute to the marked sex differences in muscle fiber addition that occur thereafter.
Phentolamine selectively affects the fast sodium component of sensory adaptation in an insect mechanoreceptor
Authors: Ramirez J.‐M. , French A. S. 
Published: January 2005

AbstractPhentolamine and related compounds have several different actions on nervous tissues in vertebrates and invertebrates, including a local anesthetic effect. However, recent work suggests that phentolamine can interfere with sensory transduction in insect mechanoreceptors at significantly lower concetrations than are required for conduction block. We tested the actions of phentolamine on sensory transduction and encoding in an insect mechanoreceptor, the cockroach tactile spine neuron and found that 500 μM phentolamine increased the action potential threshold by 50%. The passive membrane properties of the neuron were not affected, but one component of dynamic threshold change was strongly and selectively reduced. This component has previously been attributed to slowly inactivating sodium channels in the action potential initiating region, suggesting that these channels are the most phentolamine‐sensitive sites.
Differential effects of denervation on acetylcholinesterase activity in parasympathetic and sympathetic ganglia of the frog,Rana pipiens
Authors: Streichert Laura C. , Sargent Peter B. 
Published: January 2005

AbstractThe transsynaptic regulation of acetylcholinesterase (AChE) was studied by recording the changes in enzymatic activity following denervation in two types of autonomic ganglia in the frog,Rana pipiens. Opposite effects on AChE were found in the parasympathetic cardiac ganglion and in the sympathetic lumbar ganglion; denervation produced a significant increase in AChE activity in cardiac ganglia but a significant decrease in lumbar ganglia. The relative effects of denervation on intracellular and total AChE were examined by selectively inhibiting extracellular AChE with echothiophate, a poorly lipid‐soluble cholinesterase inhibitor. Denervation resulted in a significant increase in intracellular AChE in cholinergic cardiac ganglia but had no effect on intracellular AChE activity in adrenergic lumbar ganglia. Histochemical studies revealed little change in extracellular AChE staining upon denervation in the cardiac ganglion, whereas in the lumbar ganglia there was a loss of AChE‐specific reaction product. These results raise the possibility that the transsynaptic control of AChE activity by innervation in the frog is influenced by the transmitter synthetic properties of the postsynaptic ganglion cells.
Neuronal adaptation accompanying metamorphosis in the flatfish
Authors: Graf Werner , Baker Robert 
Published: January 2005

AbstractFlatfish provide a natural paradigm to investigate adaptive changes in the central nervous system of vertebrates. During their metamorphosis, the animals undergo a 90° tilt to one side or the other to become the bottom‐adapted adult flatfish. The eye on the down side is pushed over to the up side. Thus, vestibular and oculomotor coordinate systems rotate 90° relative to each other. As a result, during swimming movements different types of compensatory eye movements are produced before and after metamorphosis by the same vestibular stimulation. Intracellular staining of central neurons with horseradish peroxidase revealed that in postmetamorphic flatfish second‐order horizontal canal neurons contact vertical eye muscle motoneuron pools on both sides of the brain via pathways that are absent in all other vertebrates studied. These unique connections provide the necessary and sufficient connectivity to adapt the flatfish's eye movement system to the animals' postmetamorphic existence. Although the adult fish has a bilaterally asymmetric appearance, the central nervous connectivity reestablishes symmetry in the vestibulooculomotor system.
Parallel motor pathways from thoracic interneurons of the ventral giant interneurons system of the cockroach, Periplaneta americana
Authors: Ritzmann Roy E. , Pollack Alan J. 
Published: January 2005

AbstractThe data described here complete the principal components of the cockroach wind‐mediated escape circuit form cercal afferents to leg motor neurons. It was previously known that the cercal afferents excite ventral giant interneurons which then conduct information on wind stimuli to thoracic ganglia. The ventral giant interneurons connect to a large population of interneurons in the thoracic ganglia which, in turn, are capable of exciting motor neurons that control leg movements. Thoracic interneurons that receive constant short latency inputs from ventral giant interneurons have been referred to as type A thoracic interneurons (TIAs). In this paper, we demonstrate that the motor response of TIAs occurs in adjacent ganglia as well as in the ganglion of origin for the TIA. We then describe the pathway from TIAs to motor neurons in both ganglia. Our observations reveal complex interactions between thoracic interneurons and leg motor neurons. Two parallel pathways exist. TIAs excite leg motor neurons directly and via local interneurons. Latency and amplitude of post‐synaptic potentials (PSPs) in motor neurons and local interneurons either in the ganglion of origin or in adjacent ganglia are all similar. However, the sign of the responses recorded in local interneurons (LI) and motor neurons varies according to the TIA subpopulation based on the location of their cell bodies. One group, the dorsal posterior group, (DPGs) has dorsal cell bodies, whereas the other group, the ventral median cells, (VMC) has ventral cell bodies. All DPG interneurons either excited postsynaptic cells or failed to show any connection at all. In contrast, all VMC interneurons either inhibited postsynaptic cells or failed to show any connection. It appears that the TIAs utilize directional wind information from the ventral giant interneurons to make a decision on the optimal direction of escape. The output connections, which project not only to cells within the ganglion of origin but also to adjacent ganglia and perhaps beyond, could allow this decision to be made throughout the thoracic ganglia as a single unit. However, nothing in these connections indicates a mechanism for making appropriate coordinated leg movements. Because each pair of legs plays a unique role in the turn, this coordination should be controlled by circuits didicated to each leg. We suggest that this is accomplished by local interneurons between TIAs and leg motor neurons.
Lateralization of syringeal function during song production in the canary
Authors: Hartley Rebecca S. , Suthers Roderick A. 
Published: January 2005

AbstractThe canary (Serinus canaria) vocal organ, the syrinx, has two separate sound sources, one in the cranial end of each bronchus. Previous investigations of whether song syllables are produced unilaterally or bilaterally have provided two contradictory results, as one researcher suggested that almost all syllables are produced by the left side of the syrinx alone, whereas another researcher suggested that both sides contribute similarly to all syllables. Our experiments, which involved unilateral bronchus plugging followed later by denervation of the ipsilateral syringeal muscles, attempted to resolve this disagreement. The males with right bronchus plugs, singing on the left side of the syrinx alone, produced nearly normal songs, whereas the birds with left bronchus plugs, singing on the right side, sang quite poorly. Interpretation of these data is difficult because it is not clear how syringeal function would be affected if the airflow rate through the intact side is increased above normal, nor is it known if the bird can compensate for bronchus occlusion. Nonetheless, we suggest that in male canaries most syllables are normally sung by the left side alone, with some syllables being produced by the right side alone and some being sung by both sides together. Right nerve section had little effect on the right‐bronchus‐plugged males' ability to sing, but the repertoires of the left‐plugged males were altered after left nerve section, indicating the possibility that signals carried by the left nerve exert an influence on the contralateral side.
Ependymin as a substrate for outgrowth of axons from cultured explants of goldfish retina
Authors: Schmidt John T. , Schmidt Rupert , Lin Weichun , Jian Xiaoying , Stuermer Claudia A. O. 
Published: January 2005

AbstractEpendymin, a prominent protein of the brain's extracellular fluid (ECF) was‐previously implicated in the consolidation of memory and in the activity‐driven sharpening of the retinotectal projection. Because both these phenomena probably involve the growth and elaboration of appropriate synapses, we have tested whether ependymin can serve as a substrate for the growth of axons from goldfish retinal ganglion cells in a culture assay. Ependymin (Ep), laminin (LAM), polylysine (PL), and Concanavalin A (Con A) were plated on glass coverslips either uniformly or in striped patterns. Ep alone, either soluble or partly polymerized (by dropping calcium concentration and pH), was a good substrate for axonal outgrowth, as good or better than PL and Con A, but not as good as LAM. Neurites grew faster on LAM (71 μm/h) than on Ep (32 μm/h) or on PL (22 μm/h). Fasciculation was low on LAM, intermediate on Ep, and highest on PL. In exclusive side‐by‐side stripe assays, axons preferred LAM over Ep, but gave weak or no preference for Ep over Con A or PL. With stripes of LAM + Ep alongside pure LAM, the axons preferred the mixture of LAM + Ep. When antibodies to Ep were plated in stripes over continuous Ep substrate, the axons avoided the antibody‐blocked stripes and grew on the Ep stripes. Antibodies to Ep did not, however, block growth on laminin substrates, nor did antibodies to LAM block growth on Ep. Dot blots and western blots showed very little cross recognition between the antibodies. Ependymin is a good substrate for neurite outgrowth, which is normally present in ECF, and adhesion to Ep is independent of LAM and possibly additive to it.