bluuebunny/crossref_metadata_2025_split huggingface dataset:
Apolipophorin III is dramatically up‐regulated during the programmed death of insect skeletal muscle and neurons
Authors: Sun Danhui , Ziegler Rolf , Milligan Carolanne E. , Fahrbach Susan , Schwartz Lawrence M. 
Published: January 2005

AbstractThe intersegmental muscles (ISMs) of the tobacco hawkmoth Manduca sexta, participate in the emergence behavior of the adult moth and then die during the subsequent 30 hours. In addition, several populations of interneurons and uniquely identified motor neurons also die after adult emergence. The trigger for all of these deaths is a decline in the circulating titer of the insect molting hormone 20‐hydroxyecdysone. The ability of the muscles and neurons to die requires de novo gene expression. A differential hybridization screen of a “condemned” ISM cDNA library permitted the isolation of clones encoding four new up‐regulated mRNAs. On sequencing, one of these recombinants was found to encode apolipophorin III (apoLp‐III), a component of lipophorin, the major hemolymph lipoprotein of insects, previously shown to be synthesized in fat body. Although apoLp‐III mRNA and protein were expressed at all stages of ISM development, levels of both molecules were dramatically elevated with the commitment of the cells to die. When ISM cell death was delayed by injection of 20‐hydroxyecdysone, expression of apoLp‐III at both the RNA and protein levels was markedly reduced at the normal time of cell death. Immunocytochemistry demonstrated that apoLp‐III protein was abundantly expressed in the cytoplasm of dying muscles, interneurons, and identified motor neurons at the time of cell death. Apolipoproteins I and II, required components of lipophorin, were not expressed at detectable levels in the muscles or neurons. Furthermore, Western blots of native gels suggest that apoLp‐III was not associated with any other proteins. These data suggest that apoLp‐III has activities independent of lipid transport that may play a role in programmed cell death. ApoLp‐III joins apolipoproteins E and J (clusterin, sulfated glycoprotein‐2) as a group of proteins that function in both lipid transfer and cell death. © 1995 John Wiley & Sons, Inc.
Differential induction of the ZENK gene in the avian forebrain and song control circuit after metrazole‐induced depolarization
Authors: Mello Claudio V. , Clayton David F. 
Published: January 2005

AbstractZENK is an immediate early gene (IEG) that encodes a transcription factor protein, and its induction has been proposed as a necessary step in the cellular process underlying long‐term memory formation. We have previously shown that ZENK is induced in adult songbird brain by the sound of birdsong, but, interestingly, induction did not occur in several areas known to respond to song stimuli. Conceivably, the ZENK gene may be repressed in these areas in adult birds. As a further test of this hypothesis, we administered metrazole, a strong GABAergic antagonist that leads to widespread excitation in the brain. Following metrazole, ZENK mRNA increases more than 10‐fold throughout most of the telencephalon in both canaries and zebra finches, and primarily in neurons. In contrast, ZENK induction is much lower or absent in the archistriatum, the primary telencephalic sensory‐recipient areas (including auditory field L), and the three telencephalic androgen receptor‐containing song nuclei (high vocal center, lateral magnocellular nucleus of the anterior neostriatum, and the robust nucleus of the archistriatum). We did not observe any differences in ZENK induction patterns in juvenile versus adult zebra finches, or fall versus spring male canaries. Together with our previous studies of induction by song, these results suggest that in specific parts of the forebrain, including most of the song control system, IEG expression is subject to different constraints than in the rest of the forebrain. Understanding the molecular basis for this differential gene regulation may prove invaluable in understanding the organization of the song control circuit and the avian telencephalon. © 1995 John Wiley & Sons, Inc.
Synapse elimination, the size principle, and Hebbian synapses
Authors: Stollberg Jes 
Published: January 2005

AbstractSynapse elimination at the vertebrate neuromuscular junction reduces a polyinnervated population of muscle fibers to a monoinnervated state. The function of this developmental phenomenon (if any) is unproven. A theoretical analysis of Hebbian (correlation) rules connecting presynaptic and postsynaptic activity and synaptic strength at the neuromuscular junction is presented. The following points are demonstrated: (1) Correlational competition leads to the reduction of polyinnervation to a stable monoinnervated state; (2) the competition gives rise to the size principle over a wide range of the plausible parameter space; (3) over a significant subrange, the competition selectively eliminates topographically incorrect synapses; and (4) in cases in which topographic projection errors overwhelm the system, both error correction and the development of the size principle are disrupted. Correlational competition may explain contradictory experimental results concerning the effects of stimulating or silencing subpopulations of motor neurons. It may also explain an otherwise puzzling instance of a breakdown in the size principle seen in humans undergoing neural regeneration. Taken together, these findings suggest a novel hypothesis for the function of synapse elimination at the neuromuscular junction: the establishment of the size principle. © 1995 John Wiley & Sons, Inc.
Posttetanic potentiation and presynaptically induced long‐term potentiation at the mossy fiber synapse in rat hippocampus
Authors: Langdon Ronald B. , Johnson Jon W. , Barrionuevo German 
Published: January 2005

AbstractA form of long‐term potentiation (LTP) is induced at the mossy fiber (MF) synapse in the hippocampus by highfrequency presynaptic stimulation (HFS). It is generally accepted that induction of this form of LTP (MF LTP) does not depend on postsynaptic Ca2+ current gated by N‐methyl‐D‐aspartate receptors, but it has remained controversial whether induction depends on postsynaptic depolarization and voltage‐gated entry of Ca2+. There are also contradictory data on the time course of both LTP and post‐tetanic potentiation (PTP), a shorter duration form of potentiation observed at MF synapses immediately following HFS. It has been proposed that some of these differences in results may have arisen because of difficulties in isolating monosynaptic responses to MF input. In the present study, whole cell recording was used to observe excitatory postsynaptic currents (EPSCs) elicited in CA3 pyramidal cells by input from MFs. Postsynaptic cells were dialyzed with 1,2‐bis(o‐aminophenoxy)‐ethane‐N,N,N′,N′‐tetraacetic acid (BAPTA) and F− to inhibit postsynaptic mechanisms that required Ca2+, cells were under voltage clamp during HFS, and conditions were selected to minimize the likelihood of polysynaptic contamination. Under these conditions, HFS nevertheless induced robust LTP (mean magnitude, 62%). The possibility that EPSCs were contaminated by polysynaptic components was investigated by exposing the slices to a suppressing medium (one that partially blocked neurotransmission). EPSC waveforms did not change shape during suppression, indicating that contamination was absent. The LTP observed always was accompanied by prominent PTP that lasted through the first 5 to 15 min following HFS (mean decay time constant, 3.2 min). Induction of this LTP was not cooperative; there was no relationship between the size of responses and the magnitude of the LTP induced. LTP magnitude also was unrelated to the extent to which postsynaptic cells depolarized during HFS. These results show that high rates of presynaptic MF activity elicit robust LTP whether or not there is accompanying postsynaptic depolarization or increase in the concentration of postsynaptic Ca2+. High‐frequency MF activity also results in a PTP that is unusually large and long. © 1995 John Wiley & Sons, Inc.
Differential delay of reinnervating axons alters specificity in the rat serratus anterior muscle
Authors: Grow Wade A. , Kendall‐Wassmuth Eydie , Ulibarri Catherine , Laskowski Michael B. 
Published: January 2005

AbstractPrevious studies have shown remarkable rostrocaudal selectivity by regenerating motoneurons to the rat serratus anterior (SA) muscle after freezing, crushing, or sectioning the long thoracic (LT) nerve. The LT nerve contains motoneurons from both the sixth and seventh cervical spinal nerves (C6 and C7), with C6 motoneurons as the major source of innervation throughout the muscle, and with C7 motoneurons innervating a larger percentage of muscle fibers caudally than rostrally. To determine if synaptic competition can play a role in neuromuscular topography, both the LT nerve and the branch carrying C6 (rostral) motoneurons to the LT nerve were crushed in newborn rats. This approach provides a temporal advantage to regenerating C7 (caudal) motoneurons. After an initial period during which C7 motoneurons reinnervated a larger proportion of muscle fibers than normal in all SA muscle sectors, C6 motoneurons regained their original proportion of rostral muscle fibers. Caudally, however, C7 motoneurons maintained an expanded territory. With this two‐site crush method, the number of C6 motoneurons that reinnervate the SA muscle was significantly decreased from normal, whereas the number of C7 motoneurons remained the same. It is concluded that when C7 motoneurons are given a temporal advantage, synaptic specificity can be altered transiently in rostral muscle sectors and permanently in caudal sectors, and this is correlated with a disproportionate loss of C6 motoneurons. Moreover, this may be an important model for studies of synaptic competition, where terminals destined to be eliminated can be identified beforehand. © 1995 John Wiley & Sons, Inc.
Seasonal variation in hippocampal volume in a food‐storing bird, the black‐capped chickadee
Authors: Smulders T. V. , Sasson A. D. , DeVoogd T. J. 
Published: January 2005

AbstractBlack‐capped chickadees (Parus atricapillus) in upstate New York show a peak in food‐hoarding intensity in October. We caught chickadees at six different times of the year and measured the volume of several brain structures. We found that the hippocampal formation, which is involved in spatial memory for cached food items, has a larger volume, relative to the rest of the brain, in October than at any other time of the year. We conclude that there is an association between the intensity of food hoarding and the volume of the hippocampal formation and suggest that the enhanced anatomy might be caused by the increased use of spatial memory. © 1995 John Wiley & Sons, Inc.
Voltage‐gated currents and firing properties of embryonic Drosophila neurons grown in a chemically defined medium
Authors: O'Dowd D. K. 
Published: January 2005

AbstractThis study reports the composition of a chemically defined medium (DDM1) that supports the survival and differentiation of neurons in dissociated cell cultures prepared from midgastrula stage Drosophila embryos. Cells with neuronal morphology that stain with a neural‐specific marker are clearly differentiated by 1 day in vitro and can be maintained in culture for up to 2 weeks. Although the whole cell capacitance measurements from neurons grown in DDM1 were 5‐ to 10‐fold larger than those of neurons grown in a conventional serum‐supplemented medium, the potassium current densities were similar in the two growth conditions. A small but significant increase in the sodium current density was observed in the neurons grown in DDM1 compared with those in serum‐supplemented medium. The majority of neurons grown in DDM1 fired either single or trains of action potentials in response to injection of depolarizing current. Contributing to the observed heterogeneity in the firing properties between individual neurons grown in DDM1 was heterogeneity in the levels of expression and gating properties of voltage‐dependent sodium, calcium, and pottassium currents. The ability of embryonic Drosophila neurons to differentiate in a chemically defined medium and the fact that they are amenable to both voltage‐clamp and current‐clamp analysis makes this system well suited to studies aimed at understanding the mechanisms regulating expression of ion channels involved in electrical excitability. © 1995 John Wiley & Sons, Inc.
Developmental regulation of plasticity along neurite shafts
Authors: Williams Cheri V. , Davenport Roger W. , Dou Ping , Kater S. B. 
Published: January 2005

AbstractAlthough it is becoming increasingly clear that structural dynamics on neurite shafts play important roles in establishing neuronal architecture, the underlying mechanisms are unknown. The present study investigates local induction of filopodia along the shafts of neurites, a process that, by analogy to the growth cone, can represent the first stage in the generation of a new neuronal process. We show that filopodia can be induced reliably along the neurite shaft in response to a localized electric field stimulus that evokes large local intracellular calcium increases. Neither induction of filopodia nor a local rise in intracellular calcium occurred in calcium free medium. Although calcium induction of neurite filopodia is highly reliable, forming in response to more than 90% of attempts, it is developmental state‐dependent, since neurite filopodia could not be induced in neurons previously defined as “stable state.” We have found two distinct changes in stable state neurons that can decrease the ability to induce new neurites. The first is a reduced calcium response: Field stimulation produced large local rises (280 nM) in stable state neurons. Second, stable state neurons change so that even when the stimulus intensity was increased to elicit a calcium response that would have been sufficient to induce filopodia in growing neurites, neurite filopodia were still not induced. Thus, intracellular calcium plays a key role in structural changes along the shafts of neurites. Furthermore, developmental changes in both calcium homeostatic components, and in calcium responsiveness (i.e., the sensitivity of cellular components that modulate neurite morphology) underlie shifts from plasticity to stability of neuronal architecture in this system. © 1995 John Wiley & Sons, Inc.
Androgen regulation of neuromuscular junction structure and function in a sexually dimorphic muscle of the frog Xenopus laevis
Authors: Brennan C. , Henderson L. P. 
Published: January 2005

AbstractSpecific forelimb muscles in anurans are sexually dimorphic and underlie the androgen‐dependent clasping response of males during amplexus. Previous studies have reported that androgen treatment slows the contractile properties of these sexually dimorphic forelimb muscles. In amphibians, the expression of functionally distinct acetycholine (ACh) receptors, the levels of acetylcholinesterase (AChE), the extent of multiple innervation, and the structure of individual end plates vary with the contractile properties of the muscle fibers. In higher vertebrates, androgens have been reported to alter the expression of ACh receptors, AChE, and the neuromodulator, calcitonin gene‐related peptide (CGRP). To determine whether the known androgen‐dependent changes in contraction of androgen‐sensitive forelimb muscles are accompanied by concomitant changes in synaptic structure or function, we have compared functional neuromuscular transmission, the pattern of innervation, and CGRP immunoreactivity in nerve or muscle preparation from castrated (C) and castrated and testosterone‐treated (CT) adult male Xenopus laevis. CGRP expression in androgen receptor (AR)‐immunopositive neurons was increased in CT animals. However, no significant differences were found in ACh‐mediated single channel or macroscopic currents, the extent of multiple end plates, or end plate morphology for forelimb fibers isolated from C and CT Xenopus. In contrast, analysis of forelimb fibers from gonadally intact adult females and juvenile animals of both sexes revealed that macroscopic synaptic currents were significantly shorter in these animals than in either C or CT adult males. Our data suggest that forelimb fibers in sexually dimorphic muscles of Xenopus do show significant differences in synaptic transmission; however, neither end‐plate organization nor functional neuromuscular transmission are subject to activational effects of androgens in adult male frogs. © 1995 John Wiley & Sons, Inc.
Retinal pigmented epithelium does not transdifferentiate in adult goldfish
Authors: Knight Jennifer K. , Raymond Pamela A. 
Published: January 2005

AbstractThe neural retina of adult goldfish can regenerate from an intrinsic source of proliferative neuronal progenitor cells, but it is not known whether the retina can regenerate by transdifferentiation of the retinal pigmented epithelium (RPE), a phenomenon demonstrated in adult newts. In this study, we asked whether following surgical removal of the neural retina in adult goldfish the RPE was capable of autonomously transdifferentiating and generating new neural retina. The retina was prelabeled by injecting the fluorescent dye Fluoro‐Gold (FG) into the eye prior to surgical removal; this procedure ensured that residual retina was labeled with FG and could therefore be distinguished from unlabeled, regenerated retina. To examine the time course of retinal regeneration, and to identify regenerated retinal neurons, the thymidine analogue bromodeoxyuridine was injected intraocularly, and retinas were examined up to 2 months later. We found that the RPE did not transdifferentiate; instead, retinas regenerated only when pieces of residual neural retina were left intact. Under these circumstances, newly regenerated cells derived from proliferating cells intrinsic to the residual neural retina. When retinas were completely removed, as was evident from a lack of FG labeling, there was no retinal regeneration. © 1995 John Wiley & Sons, Inc.
Comparison of mauthner cell size in sexually developed and undeveloped male red‐bellied newts
Authors: Matsumoto Akira , Arai Yasumasa , Kouki Tomu , Kikuyama Sakae 
Published: January 2005

AbstractDifferences in Mauthner (M) cell size were examined in sexually developed and undeveloped male red‐bellied newts, Cynops pyrrhogaster. The mean areas of nuclei and cell bodies of M cells and mean maximum and minimum diameters of the cell bodies in the sexually developed males were significantly larger than those in the sexually undeveloped ones. In the hypophysectomized male newts, all these parameters were not significantly different from those in the sexually undeveloped ones. These values were significantly increased by treatment with both bovine prolactin and human chorionic gonadotropin every other day for 3 weeks after hypophysectomy, and these measures were comparable to those in the sexually developed males. These findings suggest that differences in M cell size between sexually developed and undeveloped male newts are due to alteration in hormonal milieu. © 1995 John Wiley & Sons, Inc.
Interaction of a vasopressin antagonist with vasopressin receptors in the septum of the rat brain
Authors: Dorsa Daniel M. , Brot Michelle D. , Shewey Linda M. , Meyers Kathleen M. , Szot Patricia , Miller Margaret A. 
Published: January 2005

AbstractThe ability of d(CH2)5‐Tyr(Me)‐arginine‐8‐vasopressin, an antagonist of peripheral pressoric (V1‐type) vasopressin receptors, to label vasopressin binding sites in the septum of the rat brain was evaluated. Using crude membrane preparations from the septum, 3H‐arginine‐8‐vasopressin (AVP) specifically labels a single class of binding sites with a Kd of 2.9nM and maximum binding site concentration of 19.8 fmole/mg protein. 3H‐Antag also labels a single class of membrane sites but with higher affinity (Kd=0.47nM) and lower capacity (10.1 fmole/mg protein) than 3H‐AVP. The rank order of potency of various competitor peptides for 3H‐AVP and 3H‐Antag binding was similar. Oxytocin was 100–1,000 fold less potent than AVP in competing for binding with both ligands. 3H‐AVP and 3H‐Antag showed similar labeling patterns when incubated with septal tissue slices. Unlabeled Antag also effectively antagonized vasopressin‐stimulated phosphatidylinositol hydrolysis in septal tissue slices.
Localization of substance P binding sites in submucous plexus of guinea pig ileum, using whole‐mount autoradiography
Authors: Burcher Elizabeth , Bornstein Joel C. 
Published: January 2005

AbstractWhole mounts of guinea pig ileum submucosa were incubated with radiolabeled tachykinins, and binding sites were visualized using autoradiography. Very dense specific binding for [125I]‐Bolton‐Hunter substance P (BHSP) was observed over ganglia of the submucous plexus, with weaker binding over internodal strands. Dense specific binding was also seen over occasional strands of circular muscle, with weak binding over clumps of mucosa. Although very weak binding was seen over some large blood vessels, no binding was associated with smaller blood vessels. Localization of binding was absent in whole‐mounts coincubated with 1 nM substance P, used to define nonspecific binding. Localization of BHSP‐specific binding was also abolished in whole‐mounts coincubated with 1 nM substance P, but not with 1 nM neurokinin B, suggesting that binding was probably to an NK‐1 tachykinin receptor. In whole‐mounts incubated in [125I]‐iodohistidyl neurokinin A (INKA) or [125I]‐Bolton‐Hunter neurokinin B (BHNKB), no specific binding over ganglia was observed. These binding sites for BHSP are probably identical with the neuronal substance P receptors mediating mucosal ion transport.
SKF 38393 alters the rate‐dependent D2‐mediated inhibition of nigrostriatal but not mesoaccumbens dopamine neurons
Authors: Kelland Mark D. , Freeman Arthur S. , Chiodo Louis A. 
Published: January 2005

AbstractPrevious electrophysiological studies have failed to identify significant effects of the D1 dopamine (DA) agonist SKF 38393, either alone or in combination with the D2 agonist quinpirole (LY 171555), on the spontaneous firing rate of midbrain DA neurons. We have utilized extracellular single‐unit recording techniques to examine whether SKF 38393 can alter D2‐mediated inhibition of DA cell activity. Quinpirole induced inhibition of the spontaneous activity of midbrain DA neurons was observed to be positively correlated with the basal firing rate of the neuron being examined (i.e., faster cells required higher doses to achieve 50% and maximal inhibition). Pretreatment with SKF 38393 (1.0 mg/kg, i.v.; 4 minutes) eliminated the rate dependency of quinpirole induced inhibition of nigrostriatal but not mesoaccumbens DA neurons. This effect of SKF 38393 was blocked both by the D1 antagonist SCH 23390 and by hemitransections of the forebrain. In summary, SKF 38393 appears to exert Dl‐specific, feedback pathway‐dependent effects on the profile of responsiveness of nigrostriatal DA neurons to D2‐mediated inhibition of cell firing rate.