bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fibronectin‐like immunoreactivity in Helisoma buccal ganglia: Evidence that an endogenous fibronectin‐like molecule promotes neurite outgrowth
Authors: Mattson Mark P. , Kater Stanley B. 
Published: January 2005

AbstractWe examined the distribution of fibronectin‐like (FNL) immunoreactivity associated with intact buccal ganglia, cell‐cultured buccal ganglia neurons and nonneuronal cells, and brain‐conditioned medium from the snail Helisoma. In addition, the possible roles of fibronectin in the regulation of neurite outgrowth were studied. Immunofluorescent staining for FNL antigens revealed intense staining in patches and fibrous arrays over the connective tissue sheaths of buccal ganglia and nerve trunks. Within the ganglia, heavy staining was seen surrounding neurons and in track‐like arrangements. In cell cultures, specific staining was associated with nonneuronal cell surfaces and to a lesser degree with the surface of identified neurons. In addition, a noncellular, substrate‐bound component of brain‐conditioned medium displayed FNL immunoreactivity. Since cultured Helisoma neurons require a substrate‐associated, brain‐derived conditioning factor (CF) in order to elaborate neurites with motile growth cones, we tested whether the FNL immunoreactive substance might act as a neuritotropic agent. Fibronectin antiserum suppressed, in a dose‐dependent manner, the CF‐induced sprouting of identified neurons in isolated cell culture. When added at increasing concentrations to neurons already growing in response to CF, fibronectin antiserum exerted a biphasic effect on neurite elongation; outgrowth was accelerated at low, but inhibited at high, antiserum concentrations. In contrast, growth cone structures associated with motility (filopodia and lamellipodia) were progressively reduced by increasing levels of antiserum. A short peptide derived from fibronectin's cell‐binding domain (Arg‐Gly‐Asp‐Ser) also greatly reduced neurite outgrowth. The combined results of this study indicate an abundance of FNL immunoreactive molecules within the CNS of Helisoma, their probable production by nonneuronal cells, and their function as a substrate‐associated component of CF which promotes growth cone filopodial and lamellipodial activity.
Song‐related brain regions in the red‐winged blackbird are affected by sex and season but not repertoire size
Authors: Kirn John R. , Clower Robert P. , Kroodsma Donald E. , Devoogd Timothy J. 
Published: January 2005

AbstractPrevious work in songbirds has delimited a neural system responsible for song production and control. Earlier studies have suggested that functional capacity in the song system may be related to the mass of the system in an animal's brain, and that adult plasticity in this neural system may be related to adult capacity for behavioral modification. We now test these hypotheses in adult red‐winged blackbirds (Agelaius phoeniceus), a species in which song is produced primarily by males, new song types are added to the male's repertoire in adulthood, and there are substantial differences among males in song complexity. We find that the song system in males is much larger than in females. Song system nuclei become smaller in both sexes as the animals experience shorter days. We do not find any association between repertoire size and size of any of the song system structures examined. Thus, although sex differences in song may be related to differences between sexes in the mass of song system structures, individual differences in song do not appear to be directly related to mass within males. Seasonal change in song system structures in male redwings is consistent with there being a relation between adult plasticity in anatomy and in behavior; the large seasonal change in these structures in females suggests large seasonal changes in the function of these nuclei.
Fly photoreceptor synapses: Their development, evolution, and plasticity
Authors: Meinertzhagen I. A. 
Published: January 2005

AbstractRecent studies are reviewed on the synapses of photoreceptor terminals in the first optic neuropile of the flies, Musca and Drosophila. Afferent synaptic contacts are of uniform dimensions; they have a postsynaptic tetrad with a membrane organization of P‐face particles, resembling other inhibitory synapses. A distributed population of such contact sites forms progressively during synaptogenesis by the selective, sequential accretion of identified postsynaptic elements at the receptor terminal. The comparative anatomy of this synapse indicates that elements have also been added during its phylogeny from an ancestral dyad. All cells are homologs of those in other species of Diptera. The number of synaptic sites is regulated by both pre‐ and postsynaptic cells, in proportion to their cell surfaces; an independent size increase in the receptor terminals (procured in the Drosophila mutant gigas) produces an increase in their synaptic population. The number of sites declines with age, however, accompanied by an increase in size of those synaptic sites remaining; this occurs for both afferent and feedback photoreceptor synapses. Lastly, the number of sites changes with visual experience; the frequency of feedback synapses is larger following dark rearing during early adult life than following visual experience.
Characterization of protein‐linked glycoconjugates produced by identified neurons of Aplysia californica
Authors: Gabel Christopher A. , Den Halina , Ambron Richard T. 
Published: January 2005

AbstractThe biosynthetic capabilities of individual neurons of the abdominal ganglion of the marine mollusc Aplysia californica have been analyzed after intrasomatic injection of 3H‐monosaccharides. Glycopeptides prepared from the metabolically labeled cells were fractionated using serial lectin affinity and gel filtration chromatography. The fractionation procedure yielded eight populations of glycopeptides, and comparison of two different neurons (R2 and R14) showed that the quantity of the individual species produced is cell‐dependent. Structural analysis indicated that the glycoconjugates produced by the Aplysia neuron constitute both O‐ and N‐linked structures as well as an unusual class of oligosaccharide whose linkage to protein is unknown. The O‐linked units are small and consist only of N‐acetylglucosamine or N‐acetylgalactosamine attached to protein. High‐mannose‐type asparagine‐linked units are produced by the neurons, and some of these appear to be processed to biantennary complex‐type units that bind to lentil lectin‐agarose. Overall, although the Aplysia neurons produce oligosaccharides of a nature similar to that produced by higher eucaryotes, the N‐ and O‐linked structures produced by the neurons do not achieve the complexity of the comparable structures produced by mammalian cells. The results provide a basis for further studies aimed at understanding the role of glycoconjugates in the development of the nervous system.
Factors released by ciliary neurons and spinal cord explants induce acetylcholine receptor mRNA expression in cultured muscle cells
Authors: Bursztajn S. , Berman S. A. , Gilbert W. 
Published: January 2005

AbstractThe nuclei of cultured noninnervated muscles cells are heterogeneous with respect to production of mRNA for the nicotinic actycholine receptor (AChR). Some nuclei actively express AChR mRNA while others have a low level of activity or are inactive. To determine if innervation, or a factor released by neurons, influences nuclear expression of AChR mRNA, we examined mRNA at a single cell level via in situ hybridization and autoradiography with an α‐subunit AChR genomic probe. Four days after plating, we co‐cultured chicken primary muscle cells with spinal cord explants, ciliary neurons, or dorsal root ganglia (DRG) cells. In situ hybridization of the spinal‐cord and muscle‐cell co‐cultures with the AChR α‐subunit genomic probe revealed a high density of silver grains on muscle cells, which were within two explant diameters of the spinal cord explant, and a graded decrease in silver grain density as the distance from the explant increased, as well as the appearance of a strikingly nonhomogenous distribution of active and inactive muscle cell nuclei. When ciliary neurons were uniformly distributed over the muscle cells, a high level of AChR mRNA was induced, but no gradients appeared. Neither an increased mRNA level nor a gradient was observed when DRG cells were co‐cultured with muscle cells. When ciliary neurons are cultured within Costar permeable inserts, which prevent any contact between the neurons and the underlying muscle cells, AChR messenger RNA is still induced, showing that diffusible factors are responsible. Our results indicate that molecules released by cholinergic neurons regulate the expression of AChR mRNA in the myotubes and raise the possibility that AChR expression depends on both neuronal signals and on intracellular information from the muscle cell.
Induction of differentiation of rat retinal, germinal, neuroepithelial cells by dbcAMP
Authors: Taylor M. , Reh T. A. 
Published: January 2005

AbstractLittle is known about the factors that regulate the production of neurons during the development of the vertebrae central nervous system (CNS); however, evidence from several neuronal cell lines suggests that an increase in intracellular cAMP might trigger the process of differentiation. To determine if a similar process is involved in differentiation during normal CNS neurogenesis, we raised the intracellular level of cAMP in primary cultures of mitotically active, germinal neuroepithelial cells from fetal and postnatal rat retina. This treatment induced differentiation of the CNS precursors, causing the cells to cease DNA synthesis and increase their expression of proteins normally found in differentiated retinal cells. These results indicate that germinal neuroepithelial cell differentiation can be controlled through the cAMP second messenger system, and that the regulation of this system may in part determine the numbers and ratios of the various classes of neurons during the normal development of the CNS.
Sexual dimorphisms in the vocal control system of a teleost fish: Morphology of physiologically identified neurons
Authors: Bass Andrew H. , Baker Robert 
Published: January 2005

AbstractIn one species of vocalizing (sonic) fish, the midshipman (Porichthys notatus), there are two classes of sexually mature males—Types I and II—distinguished by a number of traits including body size, gonad size, and reproductive tactic. The larger Type‐I males (unlike Type‐II males and females) build nests, guard eggs, and generate several types of vocalizations. Sound production by Type‐I males is paralleled by a proportionate increase of 600% in their sonic muscle mass. The motor volley from ventral occipital roots innervating the sonic muscles establishes their contraction rate and, in turn, the fundamental frequency of emitted sounds. Electrical stimulation of the midbrain in every male and female elicited a rhythmic sonic discharge as recorded in the occipital roots; however, the fundamental frequency was slightly, but significantly, higher (20%) in Type‐I males. Intracellular recording from identified motoneurons and presumed presynaptic “pacemaker” neurons showed their synaptic and action potentials had the same frequency as that of the nerve volley in every male and female. Reconstructions of physiologically identified motoneurons and pacemaker neurons following intracellular horseradish‐peroxidase (HRP) filling showed their somata and dendrites to be 100–300% larger in Type‐I males. These data unambiguously show that the size of a target muscle is correlated with the size of both the respective motoneurons and their presynaptic afferent neurons. As discussed, this implies that the dramatic increase in neuron size in the sonic motor system of Type‐I males is causally dependent upon expansion of the sonic muscle. It is further likely that the more modest sex difference in the rhythmic central discharge is established by the intrinsic membrane properties of sonic neurons. These results also corroborate, at a number of behavioral, morphological, and neurophysiological levels, that the sonic motor system of “sneak spawning” Type‐II males is similar to that of females. Thus, unlike the vocalizing Type‐I males, sexual differentiation of the reproductive system in Type‐II males is not linked to concomitant changes in the neurophysiological and morphological features of the sonic motor circuit.
Neuromuscular development following tetrodotoxin‐induced inactivity in mouse embryos
Authors: Houenou Lucien J. , Pinçon‐Raymond Martine , Garcia Luis , Harris A. John , Rieger François 
Published: January 2005

AbstractDevelopmental aspects of the neuromuscular system in mouse embryos chronically paralyzed in utero with tetrodotoxin (TTX) between embryonic days 14 and 18 were studied using biochemical and histological methods. The number of lumbar spinal motoneurons (MNs) was higher in inactive embryos than in controls suggesting a decreased motoneuron cell death. In association with the increase in MN number, choline acetyltransferase activity was significantly increased in both spinal cord and peripheral synaptic sites. Paralyzed muscles exhibited a decreased number of mature myofibers and the nuclei were centrally located. Creatine kinase activity was greatly decreased and total acetylcholine receptor and receptor cluster numbers per myofiber were significantly increased in paralyzed muscles. A similar pattern of changes occurs in the neuromuscular system of the mutant mouse muscular dysgenesis (mdg). However, in contrast to the mdg mutant, tetrodotoxin‐treated muscles were similar to controls in their innervation pattern, in the ultrastructural aspects of the excitation–contraction coupling system (i.e., dyads and triads) and in the extent of dihydropyridine binding. Thus, neuromuscular inactivity is not sufficient to impair the pattern of muscle innervation or the appearance of either the triadic junctions or dihydropyridine receptors. These results indicate that alterations of dihydropyridine binding sites and triads in muscular dysgenesis cannot be accounted for by inactivity but rather must reflect a more primary defect involving the structural gene(s) regulating the development of one or more aspects of muscle differentiation.
Short‐term action of insulin on Aplysia neurons: Generation of a possible novel modulator of ion channels
Authors: Shapiro Eli , Brown Steven D. , Saltiel Alan R. , Schwartz James H. 
Published: January 2005

AbstractIn mollusks as in other animals, peptides can act as hormones, growth factors, and neurotransmitters. The presence of insulin in vertebrate brain as well as its actions on nerve cells led us to examine the electrophysiological effects of the mammalian hormone on Aplysia neurons. Application of insulin extracellularly causes hyperpolarization of L14 and L10, identified neurons of the abdominal ganglion. This hyperpolarization is associated with a decreased membrane conductance that reverses at −35 mV. We also injected inositol phosphate glycan (IPG) into the identified neurons. This complex sugar, which was purified from rat liver and which is a putative second messenger for insulin in nonneural vertebrate cells (Saltiel and Cuatrecasas, 1986; Saltiel, Osterman, and Darnell, 1988), causes hyperpolarization with decreased membrane conductance in L14 and L10 similar to the effects of insulin. Furthermore, exposure of isolated ganglia to insulin results in the generation of IPG with a compensating decrease in its glycosyl‐phosphatidylinositol precursor. We suggest that, in addition to its other roles, insulin may function as a neuropeptide transmitter using IPG as a second messenger.
Development of estradiol‐induced progestin receptor immunoreactivity in the hypothalamus of female guinea pigs
Authors: Olster Deborah H. , Blaustein Jeffrey D. 
Published: January 2005

AbstractThe inability of young female guinea pigs to display progesterone‐facilitated lordosis has been attributed, in part, to a deficiency in the concentration of hypothalamic estradiol‐induced progestin receptors, as measured by in vitro binding assays. An immunocytochemical technique was used to ascertain where, within the mediobasal hypothalamus, estradiol‐induced progestin receptor levels are lower in immature than in adult females. Adult (>7 weeks) and juvenile (3 weeks) ovariectomized females received 10 μg estradiol benzoate, a dose that primes adult, but not immature females to respond behaviorally to progesterone. Progestin receptor‐immunoreactive (PR‐IR) cells were counted in the arcuate nucleus (ARC) and ventrolateral hypothalamus (VLH), the two regions containing the densest populations of estradiol‐induced progestin receptors in the mediobasal hypothalamus. There was no age difference in the number of PR‐IR cells in the rostral or caudal VLH, but immunostaining was darker in the rostral VLH of juveniles as compared to adults. We found similar numbers of PR‐IR cells in the rostral and mid‐ARC, but 35% fewer immunostained cells in the caudal ARC of immature, as compared to adult females. Furthermore, staining intensity was weaker in the mid‐ and caudal ARC of the juvenile females. These data suggest that the ARC, not the VLH, is a site of fewer estradiol‐induced progestin receptors in immature females.
Neuron loss and addition in developing zebra finch song nuclei are independent of auditory experience during song learning
Authors: Burek Michael J. , Nordeen Kathy W. , Nordeen Ernest J. 
Published: January 2005

AbstractIn zebra finches early auditory experience is critical for normal song development. Young males first listen to and memorize a suitable song model and then use auditory feedback from their own vocalizations to mimic that model. During these two phases of vocal learning, songrelated brain regions exhibit large, hormone‐induced changes in volume and neuron number. Overlap between these neural changes and auditory‐based vocal learning suggests that processing and acquiring auditory input may influence cellular processes that determine neuron number in the song system. We addressed this hypothesis by measuring neuron density, nuclear volume, and neuron number within the song system of normal male zebra finches and males deafened prior to song learning (10 days of age). Measures were obtained at 25, 50, 65, and 120 days of age, and included four song nuclei: the hyperstriatum ventralis pars caudalis or higher vocal center (HVc), Area X, the robust nucleus of the archistriatum (RA), and the lateral magnocellular nucleus of the anterior neostriatum (lMAN). In both HVc and Area X, nuclear volume and neuron number increased markedly with age in both normal and deafened birds. The volume of RA also increased with age and was not affected by early deafening. In lMAN, deafening also did not affect the overall age‐related loss of neurons, although at 25 days neuron number was slightly less in deafened than in normal birds. We conclude that while the addition and loss of neurons in the developing song system may provide plasticity essential for song learning, these changes do not reflect learning. Thus, in the zebra finch song system neither the growth of song nuclei nor the developmental regulation of neuron number depend on auditory learning during song development.
Distinctions in growth cone morphology and motility between monopolar and multipolar neurons in Drosophila CNS cultures
Authors: Kim Yun‐Taik , Wu Chun‐Fang 
Published: January 2005

AbstractGrowth cones play a central role in determining neurite extension, pathfinding and branching, and in establishing synaptic connections. This paper describes an initial characterization of growth cone morphology and behavior in dissociated larval central nervous system (CNS) cultures of Drosophila. Contrast‐enhanced video images of growth cones in monopolar and multipolar neurons were characterized by employing morphometric parameters such as the number and length of filopodia, and the area and roundness of the lamellipodia. Behavior of growth cones was analyzed by a motility index and boundary flow plots originally devised for measuring motility in other cellular systems. We found that separate CNS regions yielded cultures of different major cell types with distinct neuritic patterns that could be correlated with the morphology and motility of the associated growth cones. Monopolar neurons were the major cell type in brain cultures, whereas multipolar neurons were predominant in ventral ganglion cultures. Moreover, the growth cones of monopolar neurons, which are likely to be associated with the axonal processes, differed from those of multipolar neurons, which might be related to dendritic terminals. Growth cones in monopolar neurons had larger lamellipodia of less erratic shape accompanied by fewer and shorter filopodia, and, when active, displayed much higher motility and less directionality in motion. Alternatively, these morphological and behavioral distinctions between monopolar and multipolar neurons may result from intrinsic differences in membrane adhesion and intracellular transport properties.
Transneuronal induction of muscle atrophy in grasshoppers
Authors: Arbas Edmund A. , Weidner Mark H. 
Published: January 2005

AbstractAutotomy is a process in grasshoppers whereby one or both hindlimbs can be shed to escape a predator or can be abandoned if damaged. It occurs between the trochanter and the femur (second and third leg segments) and once lost, the legs never regenerate. Autotomy severs branches of the leg nerve (N5) but damages no muscles since none span the autotomy plane. We find, however, that undamaged muscles intrinsic to the thorax of grass‐hoppers, Barytettix psolus, atrophy to <15% of their normal mass after autotomy of a hindlimb. These muscles operate the coxa and trochanter (first and second leg segments) and are innervated by branches of nerves 3 and 4; nerve branches that are not damaged by autotomy. Atrophy is localized to the side and body segment where autotomy occurs. Atrophy is evident 7–10 days after loss of a limb, is complete by about 30 days, and follows a similar time course whether induced in young adult, or sexually mature grasshoppers. During autotomy, leg nerve 5 is severed distal to the trochanter, the thoracic muscles lose their normal static and dynamic load, and these muscles are subsequently no longer used to support the weight of the insect during posture and locomotion. Experimental loading and unloading of the affected muscles, and cutting of nerves indicated that it is the severing of leg nerve 5 during autotomy that transneuronally induces muscle atrophy.