bluuebunny/crossref_metadata_2025 huggingface dataset:
Neurotrophin‐3 affects proliferation and differentiation of distinct neural crest cells and is present in the early neural tube of avian embryos
Authors: Pinco Ofrit , Carmeli Chana , Rosenthal Arnon , Kalcheim Chaya
Published: January 2005

Neurotrophin‐3 is mitogenic for cultured quail neural crest cells (Kalcheim et al., 1992, Proc. Natl. Acad. Sci. USA 89:1661–1665). We now report that neurotrophin‐3 also influences the survival and/or differentiation of a subset of postmitotic neural crest precursors into neurons, provided these progenitors are grown on a cellular substrate. When cultured for 1 day on monolayers of NT‐3‐producing, chinese hamster ovary cells, 59% of the neural crest clusters growing on the transfected line revealed the presence of intense neuronal outgrowht, compared to 25% of that in controls. Moreover, dissociated neural crest cells grown for 20 h on top of mesodermal cells in the presence of various concentrations of purified recombinant neurotrophin‐3 displayed a dose‐dependent increase in neuronal number. Localization experiments using specific polyclonal antibodies, revealed that neurotrophin‐3 is confined to neuroepithelial cells of quail neural tubes in situ on E2 and E3, and to E2 neural tubes grown in culture for 24 h. At this stage, neural crest cells and somites were negative. At later stages, staining was likewise apparent in peripheral nerves and dorsal root ganglia. We, therefore, propose that NT‐3, a factor that is expressed in the early avian central nervous system, has multiple effects both on the proliferation and differentiation of distinct neural crest cells, which depend on the state of committment of the responsive progenitors. © 1993 John Wiley & Sons, Inc.
Cell recognition during synaptogenesis is revealed after temperature‐shock‐induced perturbations in the developing fly's optic lamina
Authors: Fröuhlich A. , Meinertzhagen I. A.
Published: January 2005

Houseflies (Musca domestica) were exposed to pulses of heat (1 h) or cold (several hours) during early pupal life, and the effects were investigated on the development of the first optic neuropile, or lamina, of the visual system. The treatments were designed to perturb the cellular or ganization of the cartridges, the unit synaptic structures of the lamina, so as to provide novel synaptic opportunities amongst the normally fixed composition of these modules, thereby testing the preferences of their component cells during synaptogenesis. Various abnormalities were identified, but these were not always consistent between flies: retinal abnormalities included the loss and fusion of rhabdomeres, especially of the central cells of the ommatidium, whereas in the lamina low frequencies of abnormal cartridges were found. These included seven that were studied with serial sections, which instead of the normal pair of L1 and L2 monopolar interneurons had supernumerary cells of this type. The normal pairing of L1 and L2 at postsynaptic sites of receptor terminal tetrad synapses was preserved in these cases, the cells eschewing pairings of homologous L1/L1 or L2/L2 partners. This meant that more than one L1 could pair with a single L2 and vice versa, even at the same terminal, and appeared to do so opportunistically on the basis of proximity, with cells closer to each other pairing more frequently. Thus the cells behave during synaptogenesis as if they recognize other cells only as cell types (receptor, L1 or L2) and not as individual cells. © 1993 John Wiley & Sons, Inc.
Developmental temperature selectively regulates a voltage‐activated potassium current in Drosophila
Authors: Chopra Maninder , Singh Satpal
Published: January 2005

Ionic currents are regulated by many conditions including disease states, ageing, learning and memory, and chronic drug treatment. Here we describe a novel phenomenon of regulation of ionic currents by developmental temperature. Raising Drosophila larvae at 28°C instead of 18°C increased one of the two voltage‐activated K+‐ currents, the delayed sustained IK, in their muscles by up to 3.5‐fold, with little effect on the early transient current, IA. Consistent with this increase in IK, the amplitude and the duration of the action potentials were reduced. The major increase in IK occurred between a rather abrupt interval from 25° to 28°C. The activation curve of the increased current was shifted towards hyperpolarizing potentials. There was no change in activation kinetics. This phenomenon has mechanistic implications for activity‐dependent neuronal plasticity, expression of ion channels in cultured cells and heterologus systems, phototransduction, and behavior. The specificity of the regulation suggests a discrete mechanism geared to affect excitability such that it can respond to altered external stimuli such as temperature. 1994 John Wiley & Sons, Inc.
Hu neuronal proteins are expressed in proliferating neurogenic cells
Authors: Marusich Michael F. , Furneaux Henry M. , Henion Paul D. , Weston James A.
Published: January 2005

We have utilized immunochemical techniques to investigate the developmental expression of the Hu proteins, a neuron‐specific family of RNA binding proteins in vertebrates. Previous work suggests that these proteins may play an important role in neuronal development and maintenance. For the present study, we developed a monoclonal antibody (MAb 16A11) that binds specifically to an epitope present in gene products of all known Hu genes, including HuD, HuC, and Hel‐N1. Using brief pulses (1–2 h) of the DNA precursor analog bromodeoxyruridine (BrdU) in conjunction with MAb 16A11, we observed Hu+/BrU+ cells in nascent sensory and sympathetic ganglia in vivo, and in populations of cultured neural crest cells. In addition, a few Hu+ cells were ambiguously BrdU+ in the neural tube. We conclude that Hu+ cells first appear in avian neurogenic populations immediately before neuronal birthdays in the peripheral nervous system, and at the time of withdrawal from the mitotic cycle in the central nervous system. Consistent with these conclusions, we have also observed neural crest‐derived cells that are both Hu+ and in metaphase of the cell cycle. We suggest that Hu proteins function early in neurogenic differentiation. 1994 John Wiley & Sons, Inc.
Colocalization of tyrosine hydroxylase and Fos in the male Syrian hamster brain following different states of arousal
Authors: Asmus Stephen E. , Newman Sarah Winans
Published: January 2005

In an investigation of the role that central tyrosine hydroxylase‐(TH) containing neurons play in copulation in the male Syrian hamster, The induction of Fos protein was used as an index of neuronal activation. With a double immunoperoxidase technique, the activation of TH neurons was compared in hamsters from three experimental groups: (1) mated in a new cage; (2) handled controls placed in a new cage, and (3) unhandled controls. Although mating selectively induces Fos production in the medial amygdaloid nucleus (Me), more than half of the TH neurons in Me (a region outside of the classical catecholamine systems) expressed Fos equally in all of the experimental groups. In the paraventricular hypothalamic nucleus (PVN), TH neurons were activated equivalently in mated and handled control animals compared to unhandled controls. TH neurons in the neucleus of the solitary tract (NST) were also activated in handled control animals, and mating further enhanced the level of Fos immunostaining in these neurons above both groups of nonmated animals. Although not quantified, co‐localization of Fos and TH was also observed in all experimental groups in the olfactory bulbs and the interfascicular nucleus, and in the horizontal limb of the diagonal band of Broca and the cerebral cortex, regions which contain TH neurons but are not part of the classically described TH cell groups. Few, if any, TH neurons in other catecholaminergic brain regions, such as the substantia nigra and locus coeruleus, produced Fos in any of the experimental groups. These results suggest that TH neurons in the PVN and NST may be activated during different states of arousal, and that nonclassical TH neurons in the amygdala produce high levels of Fos even in unstimulated animals. 1994 John Wiley & Sons, Inc.
Neurite outgrowth from cultured CNS neurons is promoted by inhibitors of protein and RNA synthesis
Authors: Louis Jean‐Claude , Burnham Patricia , Varon Silvio
Published: January 2005

We examined the effects of changes caused by the blocking of protein and RNA synthesis on neurite outgrowth from neurons of the central nervous system (CNS) in primary culture. Exposure to cycloheximide and actinomycin‐D led to dramatic increases in the length of neurites in cultures of neurons from various rat or chick CNS regions. Inhibitor‐induced neurite outgrowth was observed (1) from dopaminergic neurons in mixed cultures of the rat substantia nigra or (2) in pure cultures of rat and chick neurons grown on a polyornithine/laminin substratum. These results suggest that neurite outgrowth from CNS neurons is kept restricted, at least in culture, by the continuous production of a labile neurite‐inhibiting protein intrinsic to the neurons, which rapidly decays following inhibition of protein or RNA synthesis. 1994 John Wiley & Sons, Inc.
Divergent axon collaterals originate in the estrogen receptive ventromedial nucleus of hypothalamus in the rat
Authors: Akesson Thomas R. , Ulibarri Catherine , Truitt Sharon
Published: January 2005

The ventromedial nucleus of the hypothalamus (VMH) plays a crucial role in the mediation of lordosis by integrating predominantly inhibitory limbic signals with cyclic variation of ovarian steroids and sending a stimulatory output to the midbrain, especially the periaqueductal gray (PAG). Tract‐tracing studies have established projections of the VMH and Golgi studies have shown these neurons to frequently give rise to axon collaterals, but the anatomical pattern of shared projections has not been explored. We have used a combination of retrograde tracers to map VMH projections to the medial division of the medial preoptic nucleus (MPNm), posterodorsal division of the medial nucleus of the amygdala (MeApd), and the PAG. Neurons with dual projections were mainly confined to the VMHvl and represented 31%–37% of each projection subset. Neurons simultaneously projecting to the MPNm, MeApd, and PAG represented 7%–9% of each projection subset. By combining tract‐tracing with steroid autoradiography, we found that approximately one‐quarter of each projection subset in the VMHvl concentrated 3H‐estradiol. Thus, some of the VMHvl neurons that communicate a facilitatory signal to the PAG may also act to stimulate lordosis through a feedback suppression of the net inhibition formed by efferent signals from the forebrain. The even distribution of estrogen binding among projection subsets suggests a lack of compartmentalization of estrogen‐regulated processes that are relevant to lordosis. 1994 John Wiley & Sons, Inc.
Glutamate receptor binding in juvenile and adult Rana pipiens CNS
Authors: Cline Hollis T. , McDonald J. W. , Constantine‐Paton Martha
Published: January 2005

Autoradiographic methods were used to map NMDA and quisqualate‐sensitive glutamate binding sites in the brain of mature and juvenile Rana pipiens frogs. NMDA and quisqualate‐sensitive sites were consistently co‐localized in the CNS. The highest glutamate binding occurred in the telencephalon, hypothalamus, and cerebellum. Glutamate binding sites were also specifical neuropil of the optic tectum, consistent with glutamate being the retinal ganglion cell neurotransmitter. The distribution of glutamate binding sites in the brain of juvenile postmate morphic frogs was similar to that in adults. In general, Quis binding increased about twofold in adults compared to juveniles, whereas NMDA binding did not show a comparable developmental increase. To test whether glutamate binding sites are located on retinal axon terminals or on tectal cell dendrites in the optic tectum, juvenile postmetamorphic frogs were enucleated unilaterally, and receptor binding was performed following 1, 3, 7, and 14 days survival. The denervated tectal neuropil showed a delayed decrease in NMDA‐and quiequalate‐sensitive binding, consistent with the receptors being located on postsynaptic tectal cell dendrites. © 1994 John Wiley & Sons, Inc.
Expression of trkC receptor mRNA during development of the avian nervous system
Authors: Kahane Nitza , Kalcheim Chaya
Published: January 2005

Neurotrophin‐3 (NT‐3) has mitogenic and neurogenic activities on distinct central and peripheral nervous system (CNS and PNS) progenitors in avian embryos. It was therefore important to characterize in detail the expression pattern of TrkC, a high‐affinity receptor for NT‐3, during nervous system ontogeny. We report that trkC‐encoding transcripts are expressed in the CNS primordium in several spatiotemporal distinct waves. trkC mRNA becomes evident in the dividing neuroepithelium where it is expressed homogeneously. A subsequent enhancement of the signal in dorsal areas of the neural tube occurs concomitant with the migration of neural crest cells from the CNS. Expression of trkC mRNA is then reduced in the germinal epithelium while progressively appearing on postmitotic neurons at the periphery of the neural tube. At a time preceeding the onset of normal motoneuron death, trkC signal is transiently undetectable in the ventral third of the neural tube. Diffuse expression in the spinal cord is resumed on embryonic day (E) 7. Subsets of premigratory and migrating neural crest progenitors also express the trkC receptor. Intense trkC signal is then evident throughout the newly organizing dorsal root ganglia (DRG), and becomes later restricted to defined postmitotic neuronal populations. Cranial ganglia also express the trkC gene from early stages of gangliogenesis. Furthermore, whereas the primary sympathetic ganglia show trkC mRNA, in the secondary ganglia a barely detectable signal could be observed. The dynamic up‐and down‐regulations of trkC reported here to occur both in the CNS and PNS primordia correspond to diverse, though only partially known, developmental processes. Taken together, these results support the notion that the NT‐3–TrkC complex mediates diverse functions during neural development. © 1994 John Wiley & Sons, Inc.
Sequencing and promoter analysis of the genomic region between the rat neuronal nicotinic acetylcholine receptor β4 and α3 genes
Authors: Boyd R. Thomas
Published: January 2005

Nicotinic acetylcholine receptors (nAChRs) found on neurons are composed of ligand binding (α) and structural (β) subunits. Different combinations of α and β subunits produce nAChR subtypes with different pharmacological and ion‐conducting proeprties. Transcriptional regulation may be an important determinant of receptor subtype in a neuronal population and thus influence transmission through a ganglion or group of neurons in the CNS by controlling the nAChR subtype (s) present. In order to understand the transcriptional regulation of neuronal nAChRs by cell contact and electrical activity, it will be first necessary to identify DNA elements that control the expression of memebrs of this family and to identify factors required for the expression of these genes. In this report we have begun to examine the 5′‐ flanking region of one member of the nAChR family of genes, α3. We have sequenced the region between the β4 and α3 genes and have identified two promoter regions in the β4‐α3 intergenic region. One region is close to the β4 gene downstream of exon 6 and has strong promoter activity in both orientations; the other is close to the start of the α3 gene coding region. A region with putative silencer acitivity is also found near the upstream promoter. This bidirectional promoter region could be involved in the control of α3 and β4 gene expression. 1994 John Wiley & Sons, Inc.
Sexual differentiation in the CNS of the moth, Manduca sexta. I. Sex and segment‐specificity in production, differentiation, and survival of the imaginal midline neurons
Authors: Thorn Robert S. , Truman James W.
Published: January 2005

We analyzed the development of several sets of postembryonic sex‐specific motoneurons in Manduca sexta which belong to a group of homologous lineage of neurons called the imaginal midline neurons (IMNs). Adult female oviduct motoneurons and male sperm duct motoneurons are IMNs that show similar anatomical features and differentiate during metamorphosis, despite appearing in different segments: A7 for oviduct neurons, A9 for sperm duct neurons. These cells are born at the same time and, initially, similar sets are found in A7 and A9 ganglia of larvae of both sexes. The dimorphic adult pattern is generated by sex‐specific production and cell death. A7 IMNs differentiate in both sexes through early pupal stages, whereupon they disappear in the male and become the oviduct motoneurons in the female. A9 IMNs are overproduced in the male, and subsequent cell death reduces male cell number and eliminates the small complement of female cells; the surviving male cells develop into the sperm duct motoneurons. Similar IMN arrays are generated in nongenital ganglia, but show non‐sex‐specific fates. This suggests that both the sex of these cells and their segment of residence play major roles in their subsequent differentiation. 1994 John Wiley & Sons, Inc.
Neural organization of the ventilatory activity in the frog, Rana catesbeiana. I
Authors: Kogo Naoki , Perry Steven F. , Remmers John E.
Published: January 2005

In order to elucidate the neural basis for lung ventilation in the frog, we have investigated the efferent neural activity to oropharyngeal muscles in the decerebrate, paralyzed, unanesthetized bullfrog, Rana catesbeiana. Efferent motor output was recorded from the mandibular branch of the trigeminal (Vmd), the laryngeal branch of the vagus (Xl), and the main and sternohyoid branches of the hypoglossal nerve (Hm and Hsh, respectively). Two types of rhythmic bursting outputs were observed: (1) a high‐frequency, low‐amplitude, reciprocal oscillation between Vmd, a buccal levator nerve, and Hsh, a buccal depressor nerve; and (2) a low‐frequency, high amplitude, synchronous bursting of Vmd, Hm, Hsh, and Xl. The first type is inferred to represent fictive oropharyngeal ventilation. The second type of burst was divided into four intervals: (a)augmenting acitivity of Hsh; (b) activation of Xl with continued activation of Hsh; (c) activation of Vmd and Hm (a buccal levator nerve), continued activation of Xl, and termination of Hsh activity; and (d) waning activity in Vmd and Hm associated with a prominent second wave in Xl. This coordinated activity is inferred to represent fictive pulmonary ventilation because the neurograms in these four intervals correspond closely EMGs and neurograms recorded in the intact frog during the four phases of pulmonary ventilation, namely, buccal depression, pulmonary expiration, pulmonary inspiration, and glottal closure. Hypercapnia, vagotomy, and cutaneus pinching enhanced the high‐amplitude, low‐frequency rhythm, but not the low‐amplitude, high‐frequency oscillation. Lung inflation generally inhibited the former and not the latter, but in some cases lung inflation stimulated pulmonary ventilation. We conclude that oropharyngeal and pulmonary ventilation of the frog are produced by one or, possibly, two intrinsically active generators. 1994 John Wiley & Sons, Inc.
The TRH neuronal phenotype forms embryonic cell clusters that go on to establish a regionalized cell fate in forebrain
Authors: Hayes William Pär
Published: January 2005

How neurons diversify in developing brain to produce discrete cell fates in their appropriate regions remains a fundamental question. Embryonic Xenopus was previously used to identify juxtaposed embryonic cells that first express proopiomelanocortin mRNA in forebrain and pituitary, supporting the idea that this neuropeptide phenotype is induced locally. (Hayes and Loh, 1990, Development 110:747–757). To begin to examine how a more widespread population of forebrain cells is set up, the present focus is on the thyrotropin‐releasing hormone (TRH) phenotype. Serial section in situ hybridization histochemistry produced the unexpected finding that the adult‐like TRH system spanning forebrain and comprising over six different telencephalic and diencephalic nuclei, is preceded by an embryonic TRH cell population that is initially localized and then highly regionalized in the area from which the adult pattern develops. Thus, the first TRH cells, detected in vivo after 35 h (stage 29/30), were confined to discrete anterior or posterior bilateral clusters in embryonic forebrain or hindbrain. Thereafter, the TRH cell clusters in diencephelon, but not hindbrain, expanded to form rows, extending anteriorly into telencephalon and bifurcating posteriorly around the infundibulum. By 80 h (stage 42), after extensive brain morphogenesis, these forebrain rows showed regional differences in levels of TRH and mRNA corresponding to the specific brain nuclei that have been shown to contain TRH cells in adult. These findings show that subsets of phenotype‐specific forebrain cell first form a regionalized neuronal cell fate before distinct brain nuclei form. This is turn points to the testable hypothesis in Xenopus that certain neuronal cell fates in forebrain may be dictated by cell lineage or local induction. 1994 John Wiley & Sons, Inc.
Neuronal differentiation of PC12 cells as a result of prevention of cell death by bcl‐2
Authors: Sato Noboru , Hotta Kazuhiko , Waguri Satoshi , Nitatori Tohru , Tohyama Koujiro , Tsujimoto Yoshihide , Uchiyama Yasuo
Published: January 2005

Rat pheochromocytoma PC12 cells die when cultured in serum‐free medium. Neurotrophic factors can rescue PC12 cells from cell death, and induce neuronal differentiation. To further investigation the relationship among cell death, survival, and differentiation, the bcl‐2 cDNA, which is known to prevent apoptosis in various types of cells, was transfected into PC12 cells. Six monoclonal bcl‐2‐transfected cell lines were isolated and confirmed to express mRNA and protein product of bcl‐2. The wild‐type and bcl‐2‐transfected PC12 cells were kept to adhere to collagen‐coated dishes at the inintiation of serum‐free experiments to avoid cellular damage due to detachment of the cells by triturtion. Even under the conditions, the control PC12 cells mostly died within 24 h, when cultured in serum‐free medium whereas those expressing Bcl‐2 survived even for 7 days in serum‐free medium. Moreover, outgrowth of long processes in thebcl‐2‐transfected cells was only observed under the condition to keep the cells attached to the dishes in serum‐free medium without any additive neurotrophic or growth factors. Neurofilament medium protein, which is a neuron‐specific cytoskeletal component, was also expressed in the differentited cells, suggesting that the long processes in bcl‐2‐transfected PC12 cells are neurites. However, neuronal differentiation of PC12 cells expressing Bcl‐2 was not observed when cultured in serum‐containing medium. Accordingly, survival of PC12 cells expressing Bcl‐2 under the condition which cells usually die may be accompanied with neuronal differentiation. 1994 John Wiley & Sons, Inc.
Neutrophic influence of denervated sciatic nerve of on adult dorsal root ganglion neurons
Authors: Kuffler Damien P. , Megwinoff Olga
Published: January 2005

Isolated adult frog dorsal root ganglion neurons survive in vitro in a defined medium for more than 4 weeks and extend processes. When co‐cultured with a 1‐mm piece of peripheral nerve the average tottal process lenght per neuron was 10 times longer than that of control neurons by 8 days, and the processes had a significantly different morphology from that of control neurons. This influence on process length increased with increasing time of nerve denervation length increased with increasing time of nerve denervation prior to co‐culturing. These results suggest the release of a neurotrophic factor/s from the cells of the peripheral nerve. The neurotropic influence was completely blocked by antibodies against mouse nerve growth factor (NGF). Although NGF increased the average process length by twofold over control neurons, its influence never reached that of the nerve‐released factor, and the NGF‐induced processes had a distinctly different morphology. The frog nerve‐released factor promoted process outgrowth from E11 chick sympathetic ganglia, although the process number, length, and their fasciculation differed greatly from those induced by NGF. These results suggest that the nerve‐released factor/s are immunologically and functionally related to NGF but have not estabished whether a single factor or an aggregate of several secreted molecules are responsible. This article presents a new preparation in which the varied influences of different neurotrophic factors can be studied in great detail on large populations of isolated adult vertebrte neurons and sets the stage for the characterization and isolation of the frog peripheral nerve neurotrophic factor, as well as examining the influence of this facor on neuronal morphology and its ability to direct process outgrowth. 1994 John Wiley & Sons, Inc.
Expression of the ligand‐binding nicotinic acetylcholine receptor subunit Dα2 in the Drosophila central nervous system
Authors: Jonas Petra E. , Phannavong Bounpheng , Schuster Renate , Schröder Christiane , Gundelfinger Eckart D.
Published: January 2005

The Dα2 gene encodes a ligand‐binding subunit of nicotinic acetylcholine receptors (nAChRs) from Drosophila melanogaster. We have studied the distribution of Dα2 transcripts and protein by in situ hybridization and immunohistochemistry, respectively, as well as the regulation of Dα2 gene expression in vivo using Dα2 promoter fragments fused to the Escherichia coli lacZ gene. transcripts and protein from the Dα2 gene were detected exclusively in the central nervous system. Both in late embryos and adults Dα2‐like immunoreactivity is widely but not uniformly distributed in the synaptic neuropil, suggesting that the Dα2protein is a subunit of a synaptic nicotinic receptor. Its. distribution resembles that of ALS and ARD protein, two other nAChR subunits of the fly. Five different Dα2‐lacZ fusion gene constructs were introduced into theDrosophila genome by P‐element–mediated gene transfer to identity functional elements of the Dα2 promoter. All constructs produce a basic lacZ expression pattern that is compatible with the distribution of Dα2 transcripts and protein. A 880 bp upstream fragment harbors the cis elements for the expression of a weak but specific basic Dα2 pattern. The next 350 bp further upstream significantly enhance β‐galactosidase expression without influencing the pattern of expression. Between 1.7 and 7.3 kb upstream of the transcription start site one or more elements that are required for Dα2 expression in optic lobe tangential cells are located. 1994 John Wiley & Sons, Inc.
Outgrowth morphology and intracellular calcium of crustacean neurons displaying distinct morphologies in primary culture
Authors: Graf Robert A. , Cooke Ian M.
Published: January 2005

Peptidesecreting neurons from crustacean X‐organ regenerating in defined culture possess different ionic current profiles correlated with two distinct morphological types, veiling and branching; voltage‐dependent Ca2+ current is prominent in neurons consistently extending large veils, but is small in neurons that repetitively branch. Intracellular free calcium ([Ca2+]i) have been implicated in regulation of neurite outgrowth underlying the establishment of distinct morphologies. Here, basal [Ca2+]i was measured by fura‐2 fluorescence ratio imaging from these morphologically distinct neurons and compared. Both morphological tapes can extend out processes over a [Ca2+]i range (approximately 50 to 300 nM) that is much greater than that reported for neurons of other phyla. Application of high k+ saline led to increases in [Ca2+]i in soma, neurite, and lamellipodium of veiling neurons. Increase were great for veiling than branching neurons. These observations were consistent with the previous voltage clamp data for calcium currents. Media altered to perturb [Ca2+]i were used to assess the role of [Ca2+]i in veiling or branching outgrowth programs. Outgrowth of veiling cells was arrested addition of 100 μMCD2+, a calcium channel blocker. Outgrowth resumed following brief exposures to Cd2+. Branching neurons were unaffected by Cd2+. Cd2+ at lower levels (10 μM) had no effect on outgrowth of either neuronal type, whereas at higher levels (1 mM), outgrowth of both types was arrested. Reduction of extracellular sodium to 0.001 of normal concentration stopped veiling outgrowth, but branching outgrowth continued, although it was less robust. Addition of tetrodotoxin (1 μM) did not alter outgrowth of either neuronal type relative to controls. Thus, peptidergic neurons of differing intrinsic morphologies maintain similar basal [Ca2+]i levels under identical culture conditions, yet show differing sensitivities to manipulations influencing [Ca2+]i with respect to regenerative outgrowth, but not its form. 1994 John Wiley & Sons, Inc.
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

The 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

ZENK 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

Synapse 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

A 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

Previous 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

Black‐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

This 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

Although 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

Specific 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

The 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

Differences 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.