bluuebunny/crossref_metadata_2025_split huggingface dataset:
Topographical features of the substratum for growth of pioneering neurons in the manduca wing disc
Authors: Nardi James B. , Vernon Rebecca A. 
Published: January 2005

AbstractThe sensory neurons of the Manduca wing form a planar network nestled between the wing's upper and lower monolayers. The pioneering axons of this network grow in a distal‐to‐proximal direction over the basal surface of the upper epithelial monolayer. The basal surface of this monolayer has been examined ultrastructurally during the period of axonal outgrowth. The cellular terrain traversed by axons shows a graded distribution of epithelial processes, with the number of processes increasing in a proximal direction. Growth cones of axons, therefore, encounter increasing surface areas for contact with their substratum as they move toward the base of the wing. Because a basal lamina is laid down over these epithelial processes after axons have pioneered the neural pathways of the wing, axonal guidance cues apparently lie on surfaces of these basal processes. At branch points of the neural pathway examined in this study, axons avoid pathways in which the basal surfaces of cells in the upper wing monolayer interdigitate with basal surfaces of underlying tracheal cells. This interaction between wing epithelial cells and tracheal epithelial cells could act as a physical barrier to axonal outgrowth.
Neuroanatomical specificity in the co‐localization of aromatase and estrogen receptors
Authors: Balthazart Jacques , Foidart Agnes , Surlemont Chantal , Harada Nobuhiro 
Published: January 2005

AbstractThe relative distributions of aromatase and of estrogen receptors were studied in the brain of the Japanese quail by a double‐label immunocytochemical technique. Aromatase immunoreactive cells (ARO‐ir) were found in the medial preoptic nucleus, in the septal region, and in a large cell cluster extending from the dorso‐lateral aspect of the ventromedial nucleus of the hypothalamus to the tuber at the level of the nucleus inferioris hypothalami. Immunoreactive estrogen receptors (ER) were also found in each of these brain areas but their distribution was much broader and included larger parts of the preoptic, spetal, and tuberal regions. In the ventromedial and tuberal hypothalamus, the majority of the ARO‐ir cells (over 75%) also contained immunoreactive ER. By contrast, very few of the ARO‐ir cells were double‐labeled in the preoptic area and in the septum. More than 80% of the aromatase‐containing cells contained no ER in these regions. This suggests that the estrogens, which are formed centrally by aromatization of testosterone, might not exert their biological effects through binding with the classical nuclear ER. The fact that significant amounts of aromatase activity are found in synaptosomes purified by differential centrifugation and that aromatase immunoreactivity is observed at the electron microscope level in synaptic boutons suggests that aromatase might produce estrogens that act at the synaptic level as neurohomones or neuromodulators.
Ionic currents of the nodal membrane underlying the fastest saltory conduction in myelinated giant nerve fibers of the shrimp Penaeus japonicus
Authors: Terakawa Susumu , Hsu Ke 
Published: January 2005

AbstractThe myelinated giant nerve fiber of the shrimp, Penaeus japonicus, is known to have the fastest velocity of saltatory impulse conduction among all nerve fibers so far studied, owing to its long distances between nodal regions and large diameter. For a better understanding of the basis of this fast conduction, a medial giant fiber of the ventral nerve cord of the shrimp was isolated, and ionic currents of its presynaptic membrane (a functional node) were examined using the sucrose‐gap voltage‐clamp method. Inward currents induced by depolarizing voltage pulses had a maximum value of 0.5 μA and a reversal potential of 120 mV. These currents were completely suppressed by tetrodotoxin and greatly prolonged by scorpion toxin, suggesting that they are the Na current.Both activation and inactivation kinetics of the Na current were unusually rapid in comparison with those of vertebrate nodes. According to a rough estimation of the excitable area, the density of Na current reached 500 mA/cm2. In many cases, the late outward currents were induced only by depolarizing pulses larger than 50 mV in amplitude. The slope conductance measured from late currents were mostly smaller than that measured from the Na current, suggesting a low density of K channels in the synaptic membrane. These characteristics are in good harmony with the fact that the presynaptic membrane plays a role as functional node in the fastest impulse conduction of this nerve fiber.
Synergistic interactions between transforming growth factor beta and fibroblast growth factor regulate Schwann cell mitosis
Authors: Schubert David 
Published: January 2005

AbstractCultured Schwann cells divide in response to a limited repertoire of mitogens. In addition to cyclic AMP analogs and reagents that raise intracellular cyclic AMP, the only purified mitogens for Schwann cells are transforming growth factor beta (TGFβ), acidic (a) and basic (b) fibroblast growth factor (FGF), and the BB and AB dimers of platelet‐derived growth factor (PDGF). Although individually each one of these growth factors is only weakly mitogenic, it is shown here that when TGFβ and bFGF are added to Schwann cell cultures together, they interact to produce a mitogenic response that is much greater than that produced by either growth factor alone. Both the absolute concentration of each protein and the molar ratio of TGFβ to bFGF determines the magnitude of the Schwann cell response.
Local regeneration in the retina of the goldfish
Authors: Hitchcock Peter F. , Myhr Karen J. Lindsey , Easter Stephen S. , Mangione‐Smith Rita , Jones Daphne Dwyer 
Published: January 2005

AbstractWe have studied regeneration of the retina in the goldfish as a model of regenerative neurogenesis in the central nervous system. Using a transsclearal surgical approach, we excised small patches of retina that were replaced over several weeks by regeneration. Lesioned retinas from three groups of animals were studied to characterize, respectively, the qualitative changes of the retina and surrounding tissues during regeneration, the concomitant cellular proliferation, and the quantitative relationship between regenerated and intact retina. The qualitative and quantitative analyses were done on retinas prepared using standard methods for light microscopy. The planimetric density of regenerated and intact retinal neurons was computed in a group of animals in which the normal planimetric density ranged from high to low. Cell proliferation was investigated by making intraocular injections of 5‐bromo‐2′‐deoxyuridine (BUdr) at various survival times to label proliferating cells and processing retinal sections for BUdr immunocytochemistry. The qualitative analysis showed that the surgery created a gap in the existing retina that was replaced with new retina over the subsequent weeks. The BUdr‐labeling experiments demonstrated that the excised retina was replaced by regeneration of new neurons. Neuroepithiallike cells clustered on the wound margin and migrated centripetally, appositionally adding new retina to the old. The quantitative analysis showed that the planimetric density of the regenerated neurons approximated that of the intact ones.
Immunocytochemical detection of the growth‐associated protein B‐50 by newly characterized monoclonal antibodies in human brain and muscle
Authors: Mercken Marc , Lübke Ursula , Vandermeeren Marc , Gheuens Jan , Oestreicher A. Beate 
Published: January 2005

AbstractThe growth‐associated protein B‐50 also termed GAP‐43, F1, pp46, P‐57 and neuromodulin is a nervous tissuespecific protein kinase C (PKC) substrate that is considered to play a major role in neurite formation, regeneration, and neuroplasticity. We describe the isolation of seven mouse monoclonal antibodies (Mabs) directed against B‐50. The Mabs are produced against the bovine B‐50, selected by ELISA for cross‐reactivity with its human counterpart, and evaluated on Western blots in comparison with the well‐characterized affinity‐purified rabbit polyclonal antibodies to rat‐B‐50. The Western blots show that the Mabs NM1, NM4, and NM6 recognize specifically the B‐50 of bovine, human, and rat brain extract and the purified PKC phosphorylated and unphosphorylated rat B‐50 isoforms. The Mabs NM2 and NM3 cross‐react with bovine B‐50 immunoreactive c‐kinase substrate (BICKS), a protein sharing a 17 amino acid sequence homology with B‐50. Two Mabs are useful for the detection of B‐50 immunoreactivity in formalin‐fixed human and rat brain tissues. In human specimen of the hippocampus, a characteristic neuropil distribution of B‐50 is detected by the Mabs. In human muscle, Mabs reveal B‐50 in nerve bundles and in axons at motor end plates. Thus, these Mabs are useful in investigating the function and localization of the B‐50 protein.
Demonstration of motoneuron‐12 sparing in cultured Manduca sexta ventral nerve cords
Authors: Choi Mikyung Kim , Fahrbach S. E. 
Published: January 2005

AbstractThe emergence of the adult Manduca sexta moth is accompained by the death of half of the neurons present in the pupal abdominal nervous system (Truman, 1983). This developmental neuronal death is highly selective, so that the same neurons die at the same time relative to emergence in every moth. In the case of the MN‐12 motoneurons, this cell death is regulated both by hemolymph concentrations of a steroid hormone, 20‐hydroxyecdysone, and by actions exerted by adjacent ganglia (Truman and Schwartz, 1984; Fahrbach and Truman, 1987). This latter effect, which has been previously described in isolated abdomens and in moths with transected ventral nerve cords, has now been reproduced under controlled culture conditions in which the selectivity and extent of postemergence neuronal death is comparable to that seen in vivo. With respect to the MN‐12 neurons found in the most anterior unfused abdominal ganglion, A3, the pterothoracic ganglion appears to be the source of a factor that permits these neurons to die according to their usual developmental schedule. © 1992 John Wiley & Sons, Inc.
Modifications of motoneuron development following transplantation of thoracic spinal cord to the lumbar region in the chick embryo: Evidence for target‐derived signals that regulate differentiation
Authors: Yin Qin‐Wei , Oppenheim Ronald W. 
Published: January 2005

AbstractIn order to examine the role of target cells in the development of spinal motoneurons, the neural tube from thoracic segments was transplanted to the lumbar region on embryonic day (E) 2, and allowed to innervate hindlimb muscles in the chick embryo. When examined at later stages of development, the proportion of white and gray matter in the thoracic transplant was altered to resemble normal lumbar cord. Many thoracic motoneurons were able to survive up to posthatching stages following transplantation. The branching and arborization of dendrites of thoracic motoneurons innervating hindlimb muscles, as well as motoneuron (soma) size, were also increased to an extent approximating that seen in normal lumbar motoneurons. In support of previous studies using a similar transplant model, we have also found that the peripheral (intramuscular) branching pattern of thoracic motoneuron axons innervating hindlimb muscles was similar to that of normal lumbar motoneurons. Axon size and the degree of myelination of transplanted thoracic motoneuron axons were also increased so that these parameters more closely resembled axons of normal lumbar than normal thoracic spinal motoneurons. Virtually all of the changes in motoneuron properties noted above were observed irrespective of whether or not the transplanted spinal cord had developed in anatomical continuity with the host rostral cord. Accordingly, it is unlikely that the changes in the development of transplanted thoracic motoneurons reported here are induced either entirely, or in part, by signals derived from the host central nervous system. Rather, these changes appear to be mediated by interactions between the transplanted motoneurons and the hindlimb. We favor the notion that retrograde trophic signals derived from the hindlimb act to modulate the development of innervating motoneurons. Whether this signal involves a diffusible trophic agent released from target cells, or acts by some other mechanism is presently unknown. © 1992 John Wiley & Sons, Inc.
Modulation of sprouting in organ culture after axotomy of an identified molluscan neuron
Authors: Berdan R. C. , Easaw J. C. 
Published: January 2005

AbstractWe examined a variety of factors that might modulate the initiation of neurite outgrowth in an attempt to identify means by which its initiation might be accelerated. We examined this initiatio from an identified molluscan neuron, Helisoma trivolvis buccal neuron B5 after axotomy, and determined whether the site of injury, temperature, ion channel blockers, pH, the second messenger cAMP, and protein synthesis affect the initiation of neurite outgrowth. Neurite outgrowth was assayed from axotomized neurons by filling the neurons intracellularly with Lucifer Yellow and examining the percentage of axons that extended (sprouted) new process after 9 or 24 h in organ culture. About one‐third (31%) of axotomized neurons sprouted from the site of injury after 9 h (n = 22), and 88% (n = 20) sprouted after 24 h in saline at 22°–24°C when the injury was located 800 μm from the soma. Elevating the temperature to 32°C or moving the lesion site to 400 or 1500 μm from the soma did not significantly alter the incidence of sprouting. Blocking sodium channels with tetrodotoxin [TTX (2 × 10−5 M)] did not significantly reduce the incidence of sprouting, whereas the sodium channel agonist, veratridine (10−5 M) did. The calcium channel blocker lanthanum (10−6–10−4 M), stimulated neurite outgrowth; however, the organic calcium channel blocker verapamil (10−3–10−5 M), and the calcium ionophore A23187 (10−5 M), had no effect on sprouting. Exposure of neurons to the potassium channel blocker tetraethylammonium [TEA (20 mM)], elevation of intracellular pH with NH4Cl (5 mM), or treatment with the adenylate cyclase activator forskolin (10−5 M) reduced the incidence of sprouting, whereas dideoxy‐forskolin (10−5 M) had no effect. Inhibition of protein synthesis with anisomycin (2 × 10−4 to 2 × 10−6 M) did not significantly suppress sprouting 24 h after axotomy. Both d and l isomers of glutamate (300 μM) stimulated sprouting. The present results suggest that the initiation of sprouting is regulated locally at or near the site of injury, and that blocking specific ion channels may either inhibit or enhance the initiation of neurite outgrowth.
Nonitegrin laminin receptors in the nervous system: Evidence for lack of a relationship to P40
Authors: Yang Guang , Douville Philippe , Gee Stephen , Carbonetto Salvatore 
Published: January 2005

AbstractLaminins are extracellular matrix proteins that mediate their effects on cells through integrin and nonitegrin receptors. Two receptors of 67 and 110 kD that bind laminin with a high affinity (Kd ∼ nM) have been reported in neural cells. Here, we discuss these and other nonintegrin laminin receptors that have been implicated in neural function. In addition, we report studies characterizing a 43 kD protein, (P40), immunologically related to the 67 kD laminin receptor, which may be involved in retinal development.In our studies, polyclonal antisera (anti‐P‐20‐A) to a synthetic peptide derived from the sequence of a cDNA for a putative high‐affinity laminin receptor (67 kD) detected a protein of 43 kD in immunoblots of adult rat retinas. Immunohistochemistry with this antiserum showed that the retinal immunoreactivity was predominantly localized in the ganglion cell layer of both adult chicken and rat retinas where it appeared to be intracellular. Retinal ganglion cells were shown to be immunoreactive by retrogradely labeling them from the superior colliculus with a lipophillic dye and subsequently with anti‐P‐20‐A antisera. Consistent with the preferential localization of the P‐20‐A immunoreactivity in ganglion cells, there was a substantial decrease in the amounts of P40 on Western blots following optic nerve section and resulting retinal ganglion cell death. Screening of a rat (PC12 cell) cDNA library with the anti‐P‐20‐A antiserum further confirmed the specificity of the antiserum for the rat homologue of P40. Rat P40 is 97% identical to the mouse and 87% identical to human P40 at the nucleic acid level and 98% at the protein level. Restriction mapping of the rather abundant positive clones in the library that cross‐hybridized with a human cDNA probe for P40 indicated that the full‐length cDNA of 1.2 kb was the major and perhaps the only cDNA in the library. In Northern blots of adult rat retina, these clones hybridized to a single 1.2‐kb transcript. Electroblots of retinal homogenates probed with radioiodinated laminin demon strated binding to a broad band at 110 kD, but none at 43 kD. Taken together these findings suggest that P40 may not be a laminin receptor and are in keeping with the hydrophillic composition of the protein, its intracellular localization, as well as other features predicted by its nucleic acid sequence. P40 copurifies with the protein synthesis initiation factor eIF‐4A, a finding consistent with recent data from other laboratories (G. Brawerman, personal communication), implicating P40 in the regulation of protein synthesis perhaps related to topographic specification of retinal ganglion cells. © 1992 John Wiley & Sons, Inc.
Degeneration of photoreceptors in rhodopsin mutants of Drosophila
Authors: Leonard Debra S. , Bowman Valorie D. , Ready Donald F. , Pak William L. 
Published: January 2005

AbstractFive different, well‐characterized mutants of the R1–6 rhodopsin gene (ninaE), which corresponds to the rod opsin gene of vertebrates, have been examined morphologically as a function of age (up to 9 weeks) to determine whether or not the photoreceptors degenerate and to assess the pattern of degeneration. Structural deterioration of R1–6 photoreceptors with age has been found in all five mutants. The structural pattern of degeneration is similar in the five mutants, but the time course of degeneration is allele dependent and varies greatly among the five, with the strongest alleles causing the fastest degeneration. The degeneration appears to be independent of either the illumination cycle to which the animals are exposed or the presence of screening pigments in the eye. Although the degeneration first appears in R1–6 photoreceptors, eventually R7/8 photoreceptors, which correspond to cones of vertebrates, are also affected. In many of these mutants, striking proliferations of membrane processes have been observed in the subrhabdomeric region of R1–6 photoreceptors. It is hypothesized that (1) this accumulation of membranes may be caused by the failure of newly synthesized membranes that are inserted into the base of microvilli to be assembled into R1–6 rhabdomeres and (2) this failure may be caused by the extremely low concentration of normal R1–6 rhodopsin in the nina E mutants. © 1992 John Wiley & Sons, Inc.
Sex‐dependent loss of projection neurons involved in avian song learning
Authors: Nordeen E. J. , Grace A. , Burek M. J. , Nordeen K. W. 
Published: January 2005

AbstractIn zebra finches, only males sing, and the neural regions controlling song exhibit prominent, hormone‐induced sex diffences in neuron number. In order to understand how sexual differentiation regulates neuron number within one song nucleus, the lateral magnocellular nucleus of the anterior neostriatum (IMAN), we studied the development of sex differences among IMAN neurons that project to the robust nucleus of the archistriatum (RA). The IMAN is implicated in song learning, and previous ontogenetic studies have indicated that males lose over 50% of their IMAN neurons during the juvenile song learning period. Based on developmental changes in both the extent of androgen accumulation within the IMAN and its appearance in Nissl‐stained tissue, it had been hypothesized that IMAN neuron loss was even greater in young females, resulting in sex differences in neuron number. However, this hypothesis has not been tested directly because the Nissl‐stained boundaries of the IMAN sometimes are ambiguous in young animals, and are not evident at all in adult females. To circumvent these problems, we employed the retrograde tracer fast blue to study the development of IMAN neurons defined on the basis of their projections to the RA. We find that the number of these IMAN‐RA projection neurons is much greater in adult males than in females, and that this sex difference develops during the juvenile period of sexual differentiation and song learning because a significant number of these neurons are lost in females but not in males. With respect to sexual differentiation, we conclude that masculinization (which is stimulated by the hormone estradiol) promotes the retention of IMAN‐RA projection neurons. In addition, our results indicate that any loss of IMAN neurons that may occur in young males does not include cells projecting to the RA. © 1992 John Wiley & Sons, Inc.
Transient expression of somatostatin peptide is a widespread feature of developing sensory and sympathetic neurons in the embryonic rat
Authors: Katz David M. , He Huajun , White Melissa 
Published: January 2005

AbstractPrevious studies from this and other laboratories demonstrated that many embryonic sensory ganglion cells in the rat transiently express the catecholamine synthesizing enzyme tyrosine hydroxylase (TH), a trait not expressed by most mature sensory neurons. We, therefore, sought to determine whether transient expression was uniquely associated with catecholaminergic traits, or, alternatively, whether embryonic ganglion cells transiently expressed peptidergic properties as well. Of the four peptides examined {somatostatin [somatotropin release inhibiting factor] (SRIF), galanin (Gal), calcitonin gene‐related peptide (CGRP), and substance P (SP)}, only SRIF was found to be transiently expressed during early stages of sensory gangliogenesis. Surprisingly, SRIF immunoreactivity was observed in virtually all cranial and spinal sensory ganglion cells on embryonic day (E) 12.5. In addition to perikaryal labeling, intense SRIF immunoreactivity was also observed in the central and peripheral processes of E12.5 sensory neurons, suggesting the peptide may be released from nerve endings. The time course of SRIF appearance in cranial ganglion cells paralleled that previously described for TH, and double labeling studies revealed extensive co‐localization of these two phenotypes. By E16.5, however, the number of neurons expressing SRIF had diminished markedly, indicating that SRIF is only transiently expressed by most sensory neurons during early stages of ganglion development. An unexpected finding was that transient expression of SRIF is also a prominent feature of sympathetic ganglion cells; however, the temporal pattern of staining in the sympathetic and sensory ganglia differed substantially. Whereas virtually no SRIF staining was observed in E12.5 sympathetics, the vast majority of cells in the E16.5 superior cervical ganglion (SCG) were labeled. This contrasted sharply with the adult SCG, in which only low levels of SRIF expression were found. These findings demonstrate that SRIF peptide is transiently expressed at high levels in peripheral sensory and sympathetic neurons during embryogenesis. The time course and widespread distribution of SRIF expression indicates that the peptide may play a role in early stages of ganglion cell growth and development. Moreover, these data, in conjunction with previous studies demonstrating SRIF immunoreactivity in developing central neurons, suggest that transient expression of this peptide is a common property of diverse neuronal cell types. © 1992 John Wiley & Sons, Inc.