bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of synaptic transmission at autonomic synapses in vitro revealed by cytochrome oxidase histochemistry
Authors: Mawe G. M. , Gardette R. , D'Agostaro L. , Role L. W. 
Published: January 2005

AbstractWe have studied the development of synaptic transmission by innervating sympathetic neurons in vitro and monitoring synaptic activity with both physiological recording and cytochrome oxidase histochemistry. The onset of synaptic transmission was reflected in increased cytochrome oxidase reaction product within individual neurons. Within 24 hours of co‐culture, relatively low frequency suprathreshold potentials wer recorded in approximately 20% of the innervated neurons. At this stage the cytochrome oxidase activity of innervated neurons, as assessed by optical density of the histochemical reaction product, was increased twofold compared with uninnervated neurons. Over the next 2–4 days of innervation, changes in the pattern and extent of synaptic activity and superthreshold events were accompanied by a net fourfold increase in cytochrome oxidase activity levels compared with noninnervated neurons. The increase in density of cytochrome oxidase reaction product observed after innervation was reversed completely by blockade of synaptic transmission. Differences in the efficacy of synaptic input provided to the sympathetic neurons by appropriate versus inappropriate presynaptic sources was determined by co‐culturing sympathetic neurons with explants that contained either preganglionic neurons or somatic motor neurons. Although sympathetic neurons innervated by motor neuron explants had increased levels of cytochrome oxidase activity compared with noninnervated controls, the density of cytochrome oxidase reaction product was even greater in sympathetic neurons innervated by preganglionic explants. We conclude that both the onset of innervation of sympathetic neurons as well as the subsequent maturation of synaptic function is directly reflected in graded increases in cytochrome oxidase reaction product.
Elevated potassium shortens action potential duration by altering outward currents in chick dorsal root ganglia neurons
Authors: Yang Jay , Zorumski Charles F. 
Published: January 2005

AbstractDissociated embryonic chick dorsal root ganglion (DRG) neurons maintained in culture exhibit a mixed Na+/ Ca2+ action potential. The characteristic “shoulder” on the repolarizing phase is due to the relatively prolonged inward Ca2+ current. DRG neurons grown in an elevated K+ medium (25 versus. 5 mM) lack the plateau phase of the action potential. Voltage‐clamp analysis showed that this plastic change in action potential duration is not due to the loss of the inward Ca2+ current but is partly due to the appearance of a Ca2+ dependent, 4‐aminopyridine‐(4‐AP)‐sensitive transient outward current. Faster activation of the purely voltage‐dependent delayed rectifier outward current also contributes to the rapid repolarization observed in neurons cultured in elevated K+ medium.
Distribution and characterization of pedal peptide immunoreactivity in Aplysia
Authors: Pearson Wade L. , Lloyd Philip E. 
Published: January 2005

AbstractPedal peptide (Pep) is a very abundant neuropeptide in Aplysia. A radioimmunoassay (RIA) was developed to quantify Pep‐like immunoreactivity (IR‐Pep) in tissue extracts. IR‐Pep was present in very high concentrations in the central nervous system (CNS) and two peripheral tissues: the large hermaphroditic duct (LHD) and the foot. RIA of fractions from high‐pressure liquid chromatography (HPLC) indicated that Pep itself was the predominant immunoreactive species in each of these tissues. Lower concentrations of Pep were found in a number of other peripheral tissues. Incorporation of labelled amino acid indicated that Pep was synthesized in the LHD, whereas Pep in the foot was synthesized primarily in central neurons and transported to the foot. IR‐Pep was further localized by immunocytology. All peripheral IR‐Pep appeared to be associated with neuronal fibers, most commonly varicose axons. Immunoreactive innervation of the LHD and foot was particularly dense but positive staining was also observed in other tissues including tegument, gill, gut, and heart. IR‐Pep innervation in all tissues including the LHD appeared to be localized predominantly in muscular portions of the tissue. Spontaneous contractions of isolated LHD were accelerated by the application of Pep. Pep appears to act as a transmitter or neuromodulator at a number of different sites in Aplysia.
Hormonally mediated changes in simple reflex circuits during metamorphosis in Manduca
Authors: Levine Richard B. , Weeks Janis C. 
Published: January 2005

AbstractDuring insect metamorphosis, the nervous system must be reorganized to allow the production of unique behaviors during each life stage. In the hawkmoth, Manduca sexta, it has been possible to follow this postembryonic phase of neuronal development at the level of identified neurons. Of particular interest in the present context are sensory neurons, motoneurons, and interneurons which persist through metamorphosis, but participate in different types of behavior at different stages of life. Many of these neurons undergo striking changes in their dendritic arborizations and axonal projection patterns, which can be correlated with changes in their synaptic interactions with other neurons. Manipulations of the ecdysteroid and juvenile hormone titers, both in vivo and in vitro, implicate these hormones in the regulation of metamorphic changes within the nervous system. Taking advantage of this endocrine control, it has been possible to create heterochronic mosaic animals that allow the relationship between specific cellular changes and behavioral alterations to be tested directly.
Retrofitting larval neuromuscular circuits in the metamorphosing frog
Authors: Alley Keith E. 
Published: January 2005

AbstractMaturation of vertebrate neuromuscular systems typically occurs in a continuous, orderly progression. After an initial period of developmental adjustment by means of cell death and axonal pruning, relatively stable relationships, with only subtle modifications, are maintained between motoneurons and their appropriate targets throughout life. However, among a restricted group of vertebrates (amphibians and especially the anuran amphibians) the sequential maturation of neuromuscular systems is altered by an abrupt reordering of the basic body plan that encompasses cellular changes in all tissues from skeleton to nervous system. Many anuran amphibians possess neuromuscular circuits that are remarkable by virtue of their complete reorganization during the brief span of metamorphosis. During this period motor systems initially designed for the behavioral patterns of aquatic tadpoles are adjusted to meet the drastically different motor activities of postmetamorphic terrestrial life. This adjustment involves the deletion of neural elements mediating larval specific activities, the accelerated maturation of neural circuits eliciting adult‐specific activities and the retrofitting of larval neuromuscular components to serve postmetamorphic behaviors. This review focuses on the cellular events associated with the neuromuscular adaptation in the jaw complex during metamorphosis of the leopard frog, Rana pipiens. As part of the metamorphic reorganization of the jaw apparatus there is a complete turnover of the myofiber complement of the adductor mandibulae musculature. Trigeminal motoneurons initially deployed to the larval myofibers are redirected to new muscle fibers. Simultaneously the cellular geometry and synaptic input to these motoneurons is revamped. These changes suggest that trigeminal neuromuscular circuitry established during embryogenesis is updated during metamorphosis and reused to provide the basis for adult jaw motor activity that is far different than its larval counterpart.
Postmetamorphic development of neuromuscular junctions and muscle fibers in the frog cutaneous pectoris
Authors: Herrera Albert A. , Banner Lisa R. , Werle Michael J. , Regnier Michael , Stevens Naomi Nagaya 
Published: January 2005

AbstractSynaptic size, synaptic remodelling, polyneuronal innervation, and synaptic efficacy of neuromuscular junctions were studied as a function of growth in cutaneous pectoris muscles of postmetamorphic Rana pipiens. Recently metamorphosed frogs grew rapidly, and this growth was accompanied by hypertrophy of muscle fibers, myogenesis, and increases in the size and complexity of neuromuscular junctions. There were pronounced gradients in pre‐ and postsynaptic size across the width of the muscle, with neuromuscular junctions and muscle fibers near the medial edge being smaller than in more lateral regions. The incidence of polyneuronal innervation, measured physiologically and histologically, was also higher near the medial edge. Growth‐associated declines in all measures of polyneuronal innervation indicated that synapse elimination occurs throughout life. Electrophysiology also demonstrated regional differences in synaptic efficacy and showed that doubly innervated junctions have lower synaptic efficacy than singly innervated junctions. Repeated, in vivo observations revealed extensive growth and remodelling of motor nerve terminals and confirmed that synapse elimination is a slow process. It was concluded that some processes normally associated with embryonic development persist long into adulthood in frog muscles.
Induction of K‐channel expression in a neuroblastoma cell line
Authors: Smith‐Maxwell Catherine J. , Eatock Ruth Anne , Begenisich Ted 
Published: January 2005

AbstractWhole‐cell currents were examined in mouse neuroblastoma cells of the N2AB‐1 line. In standard culture medium, N2AB‐1 cells exhibited large voltage‐dependent Na currents but no discernible K currents. Treatment of N2AB‐1 cells with either dimethylsulfoxide (DMSO) in low‐serum medium or with retinoic acid (RA) caused the expression of delayed rectifier K currents. Currents from two types of K channel with single channel slope conductances of 15.0 pS and 6.4 pS were observed in outside‐out patches from cells of both treatment groups. Thus, while N2AB‐1 cells did not exhibit K currents under standard culture conditions, they did possess the gene (s) encoding K channels. The treatments caused other changes that were not directly linked to K‐channel expression. RA treatment caused neurite extension in most, but not all, N2AB‐1 cells; however, all RA‐treated cells, including those without neurites, expressed K currents. RA treatment did not suppress cell division or cause hypertrophy. In contrast, treatment with DMSO/low serum suppressed cell division and caused cellular hypertrophy, but did not cause long neurites to form. Thus, the regulation of K channels was not coupled in a simple fashion to properties that have been associated with a differentiated neuronal phenotype: neurite elaboration, changes in cell size, and inhibition of cell division. These results suggest that N2AB‐1 cells may be a good model system for investigating the processes regulating K‐channel expression.
Dual muscarinic and nicotinic action on a motor program in Drosophila
Authors: Gorczyca Michael G. , Budnik Vivian , White Kalpana , Wu C. F. 
Published: January 2005

AbstractThe effect of cholinergic agonists and antagonists on the central pattern generator of the pharyngeal muscles has been studied in third instar larvae of Drosophila. The pharyngeal muscles are a group of rhythmically active fibers involved in feeding. Bath application of the cholinergic agonists carbachol, musarine, pilocarpine, and acetylcholine (ACh) to a semiintact preparation including the pharyngeal muscles and the central nervous system (CNS), initiated long‐lasting endogenous‐like bursting activity in the muscles. The muscarinic antagonists, atropine and scopolamine, blocked these responses as well as endogenous activity. Perfusion with nicotine elicited a short, tonic response that was marginally blocked by mecamylamine but not by curare, α‐bungarotoxin, hexamethonium, or the muscarinic antagonists. This is the first time that a response to cholinergic drugs has been examined in Drosophila. The pharyngeal muscle preparation may prove to be a valuable system for studying mutations of cholinergic metabolism, receptors, and second messengers.
Laminin‐like immunoreactivity in the snail Helisoma: Involvement of a ∼300 kD extracellular matrix protein in promoting outgrowth from identified neurons
Authors: Miller John D. , Hadley Robert D. 
Published: January 2005

AbstractPolyclonal antibodies directed against laminin (LM), and against the A and B chains of reduced LM were used to identify antigenically related proteins in the extracellular matrix (ECM) of the snail Helisoma trivolvis Immunofluorescence of snail central ganglionic rings using either the anti‐LM or anti‐B chain antibodies labeled the ECM within ganglionic sheaths as well as basal laminae surrounding the ganglia. Both the anti‐LM and anti‐B chain antibodies recognized a prominent, ∼300‐kD protein on immunoblots of a snail central ganglion preparation enriched in ECM components. The anti‐A chain antibody failed to label any structures in sections of snail ganglia or to recognize any proteins on immunoblots of ganglionic ECM. A polyclonal antibody was raised against the ∼300‐kD snail protein. Immunofluorescence of snail ganglia with the anti‐∼300‐kD antibody gave a distribution of labeled structures comparable to that obtained with the anti‐LM antibody. Immunofluorescent labeling of sections of snail muscle and salivary gland with the anti‐∼300‐kD antibody revealed a distribution of reactive protein characteristic of an ECM component. Probing immunoblots of ganglionic ECM with the anti‐ ∼300‐kD antibody revealed the recognition of the same ∼ 300‐kD protein as identified by the anti‐LM antibodies. Media conditioned by Helisoma central ganglionic rings (CM) contains an unidentified neurite outgrowth promoting factor (NOPF). Immunoblots of CM probed with the anti‐B chain and anti‐ ∼300‐kD antibodies reveal the recognition of a soluble ∼300‐kD protein similar to the ∼300‐kD protein identified in snail ECM. The ganglionic ECM preparation containing the ∼300‐kD protein supported outgrowth from cultured snail buccal neurons B5, and addition of anti‐ ∼300‐kD Fab fragments to CM abolished its outgrowth promoting activity. These results suggest that the ∼300‐kD ECM protein may be the NOPF in CM and /or functions in promoting neurite outgrowth.
Development of palecortical projections through the anterior commissure of hamsters adopts progressive, not regressive, strategies
Authors: Lent Roberto , Guimarães Ricardo Z. P. 
Published: January 2005

AbstractThe perinatal development of anterior commissure projections was studied in hamsters by use of carbocyanine crystals implanted either into the commissure or into the ventrolateral prosencephalon. The earliest fascicles of growing commissural fibers had reached the midline on day 14 of gestation (E14). On E15, these fibers had entered the opposite hemisphere and reached the borders of their target regions. No waiting period was observed, since on E16 axons were already collateralizing into most targets. On P1, labelled cells were seen in all regions projecting through the anterior commissure in adults, namely, the anterior olfactory nucleus, olfactory tubercle, piriform cortex, nucleus of the lateral olfactory tract, bed nucleus of the stria terminalis, insular, perirhinal, entorhinal, and temporal cortices, as well as the amygdaloid complex. No evidence of topographical exuberance was detected. Counts of labelled neurons showed that the number of commissural cells increased gradually after birth. It is concluded that the development of paleocortical connections through the anterior commissure employs progressive strategies, lacking the regressive phenomena that are characteristic of the neocortical projections through the corpus callosum.
A comparison of calcium homeostasis in isolated and attached growth cones of the snail Helisoma
Authors: Rehder Vincent , Jensen John R. , Dou Ping , Kater S. B. 
Published: January 2005

AbstractThis study examines the capability of growth cones from identified neurons of the snail Helisoma trivolvis to perform calcium homeostasis. Calcium influx into the cytoplasm was eliminated or increased experimentally to alter [Ca]i, and the compensatory response of the growth cone was measured with the fluorescent calcium indicator Fura‐2. Growth cones compensated for both increases and decreases in calcium influx by restoring [Ca]i towards basal levels under both types of challenges. The intrinsic ability of growth cones to control [Ca]i was examined in physically isolated growth cones. Isolated growth cones demonstrated essentially identical calcium homeostatic properties to their intact counterparts, indicating that mechanisms governing calcium homeostasis exist intrinsically in the growth cone. Such independence may add significantly to the growth cone's potential to locally interpret and respond to stimuli encountered en route to its appropriate target.
Evidence for homologous peptidergic neurons in the buccal ganglia of diverse nudibranch mollusks
Authors: Watson Winsor H. , Willows A. O. Dennis 
Published: January 2005

AbstractThe buccal ganglia of seven nudibranches (Aeolidia papillosa, Armina californica, Dirona albolineata, D. picta, Hermissenda crassicornis, Melibe leonina, and Tritonia diomedea) were examined to explore possible homologies between large cells that reacted with antibodies directed against small cardioactive peptide B (SCPB). The buccal ganglion of each species possessed a pair of large, dorsal–lateral, whitish neurons that contained an SCPB‐like peptide. We refer to these neurons as the SLB (SCPB‐immunoreactive Large Buccal) cells. In all species examined, the SLB cells project out the gastroesophageal nerves and appear to innervate the esophagus.In each species, an apparent rhythmic feeding motor program (FMP) was observed by intracellular recording from both SLB neurons and other neurons in isolated preparations of the buccal ganglia. SLB cells often fire at a high frequency, and usually burst in a specific phase relation to the FMP activity. Stimulation of SLB cells enhances expression of the feeding motor program, either by potentiating existing activity or eliciting the FMP in quiescent preparations. Finally, perfusion of isolated buccal ganglia with SCPB excites the SLB cells and activates FMPs. Thus, both the immunohistochemical and electrophysiological data suggest that the SLB cells within three suborders of the opistobranchia (Dendronotacea, Arminacea, and Aeolidacea) are homologous. A comparison of our data with previously published studies indicates that SLB cell homologs may exist in other gastropods as well.
Structure of the caudal neural tube in an ascidian larva: Vestiges of its possible evolutionary origin from a ciliated band
Authors: Crowther Robert J. , Whittaker J. R. 
Published: January 2005

AbstractUltrastructural analysis and differential immunocytochemical staining with two antitubulin monoclonal antibodies were used to reexamine the organization and development of the neural tube in the larva of an ascidian, Ciona intestinalis, in appraisal of a theory that the dorsal tubular nervous system of the chordates evolved from two halves of a ciliated band in an auricularia‐like larva of the kind found in echinoderms and hemichordates. One of the antibodies stained cilia in the nervous system and elsewhere; the other reacted primarily with neuronal axons. The caudal neural tube consists of four rows of large ciliated ependymal‐glial cells enclosing an axial neural canal into which their single cilia extend. Two ventrolateral nerve tracts, containing axons, arise in the posterior brain region and extend along the length of the caudal tube, partially surrounded by the ependymal cells. The nonnervous, ciliated, ependymal neural tube of the ascidian larva with its two associated nerve tracts survives as a primitive early condition that could result from a ciliated band transformation. Tissues in the distal‐most part of the ascidian larval tail have cell lineage origins that indicate an evolutionary history different from those in the proximal majority of the tail. The ependymal cells in this presumed later addition to the tail are not ciliated, although all of the others in the caudal ependymal tube appear to be.
Progestin receptors in substance P‐immunoreactive neurons in the hypothalamus of male guinea pigs after behaviorally effective estradiol pulse treatment
Authors: Olster Deborah H. , Blaustein Jeffrey D. 
Published: January 2005

AbstractPulsatile administration of estradiol effectively primes orchidectomized (ORCH) male guinea pigs to display progesterone‐facilitated lordosis. In contrast, a single injection of estradiol benzoate (EB) is not behaviorally effective. In ovariectomized female guinea pigs, estradiol pulses induce progestin receptors selectively in substance P neurons in the ventrolateral hypothalamus (VLH), a site at which estradiol primes females to respond behaviorally to progesterone. To test the hypothesis that behaviorally effective estradiol pulses induce progestin receptors selectively in substance P neurons in the VLH in males, ORCH animals received a single injection of EB 40 h before, or two pulses of estradiol‐17β, 39 and 11 h before perfusion. Colchicine was administered intracerebroventricularly prior to perfusion. The only difference found between the two estradiol treatment groups was a higher number of progestin receptorimmunoreactive (PR‐IR) cells in the rostral VLH of estradiol pulse‐treated males. There were no significant differences in the number of PR‐IR cells in the mid‐ or caudal VLH, nor in the number of substance P‐immunoreactive (SP‐IR) neurons in the VLH/ventromedial hypothalamus (VMH) of animals receiving the two estradiol treatments. Furthermore, the percentage of PR‐IR cells in the VLH also immunoreactive for SP did not differ between the estradiol pulse‐ (22%–25%) and the EB‐injected animals (22%–32%). These data do not support the hypothesis that administration of behaviorally effective estradiol pulses, as compared to behaviorally ineffective EB injections, induce progestin receptors selectively in substance P neurons in the VLH of male guinea pigs.