bluuebunny/crossref_metadata_2025_split huggingface dataset:
Establishment of vagal sensorimotor circuits during fetal development in rats
Authors: Rinaman Linda , Levitt Pat 
Published: January 2005

AbstractThe differentiation of vagal motor neurons and their emerging central relationship with vagal sensory afferents was examined in fetal rats. To identify peripherally projecting sensory and motor neurons, 1,1′‐dioctadecyl 3,3,3′,3′‐tetramethylindocarbocyanine perchloarate (DiI) was inserted into the proximal gut or cervical vagus nerve in fixed preparations. At embryonic day (E) 12, labeled vagal sensory neurons are present in the nodose ganglia and a few sensory axons project into the dorsolateral medulla. Central sensory processes become increasingly prevalent between E13 and E14 but remain restricted to the solitary tract. Vagal motor neurons are first labeled at E13, clustered within a region corresponding to the nucleus ambiguus (NA). Additional motor neurons appear to be migrating toward the NA from the germinal zone of the fourth ventricle. Motor neurons in the dorsal motor nucleus of the vagus (DMV) first project to the gut at E14 and have processes that remain in physical contact with the ventricular zone through E16. Sensory axons emerge from the solitary tract at E15 and project medially through the region of the nucleus of the solitary tract (NST) to end in the ventricular zone. A possible substrate for direct vagovagal, sensorimotor interaction appears at E16, when vagal sensory fibers arborize within the DMV and DMV dendrites extend into the NST. By E18, the vagal nuclei appear remarkably mature. These data suggest specific and discrete targeting of vagal sensory afferents and motor neuron dendrites in fetal rats and define an orderly sequence of developmental events that precedes the establishment of vagal sensorimotor circuits. © 1993 John Wiley & Sons, Inc.
Bromodeoxyuridine labeling reveals a class of satellite‐Like cells within the electric organ
Authors: Patterson John M. , Zakon Harold H. 
Published: January 2005

AbstractWhen the electric organ (EO) of weakly electric fish is amputated, a blastema forms from which new EO and muscle cells arise. However, the progenitor cells that contribute to the blastema are unknown. We studied regeneration of the electric organ in Sternopygus to answer this question. The EO of this species is composed of electrocyte cells surrounded by peripheral bundles of muscle fibers. Fish were injected with 5′‐bromodeoxyuridine (BrdU) 24 h after amputating the terminal portion of the EO. At this time, a population of small cells were labeled in the extracellular matrix between electrocytes and muscle fibers. These cells did not label in control fish injected with saline or in nonamputated BrdU‐injected fish. For the first 6 days postamputation, increasing numbers of BrdU‐labeled cells appeared at the wound margin. A blastema formed 6 days after amputation and contained numerous BrdU‐labeled cells. At 10 days postamputation, clusters of BrdU‐positive cells were seen throughout the wound margin and proximal blastema. At 14 days, BrdU‐labeled nuclei were present within developing electrocytes. Labeling alternate sections with MF20 antimyosin and AE1 anticytokeratin antibodies confirmed that BrdU‐positive multinucleate cells coexpress myosin and cytokeratin epitopes, diagnostic of newly regenerated electrocytes. Electron micrographs reveal that the small cells surrounding muscles and electrocytes are similar; they contain an elongate nucleus, are largely devoid of cytoplasm, and possess few organelles. This morphology and evidence of myogenic potential suggests that these cells are satellite cells. © 1993 John Wiley & Sons, Inc.
Neuronal development in the Drosophila retina
Authors: Venkatesh Tadmiri 
Published: January 2005

AbstractNervous systems of higher organisms are comprised of a variety of cell types which are interconnected in a precise manner. The molecular mechanisms that lead to the specification of neuronal cell types are not well understood. The compound eye of the fruit fly Drosophila is an attractive experimental system to understand these mechanism. The compound eye is a reiterated neural pattern with several hundred unit structures and is amenable to both classical and molecular genetic methods. During the development of the compound eye cell–cell interactions and positional information play a critical role in the determination of cell fate. Recent genetic and molecular studies have provided important clues regarding the nature of the molecules involved in cellular signalling and neuronal differentiation. © 1993 John Wiley & Sons, Inc.
Natural fluctuation and gonadal hormone regulation of astrocyte immunoreactivity in dentate gyrus
Authors: Luquin Sonia , Naftolin Frederick , Garcia‐Segura Luis Miguel 
Published: January 2005

AbstractThe number and the surface density of cells immunoreactive for the specific astrocytic marker glial fibrillary acidic protein (GFAP), were evaluated in both the hilus of the dentate gyrus and the granular layer of the vermis of the cerebellar cortex of adult female rats during the different phases of the estrous cycle, after ovariectomy and after the pharmacological administration of estradiol and/or progesterone to overiectomized rats. Although no significant differences were detected in the number of immunoreactive cells among the different experimental groups studied, their surface density showed significant changes in the hilus of the dentate gyrus. The surface density of immunoreactive cells was increased in the afternoon of proestrus and on the morning of estrus compared to the morning of proestrus, diestrus, and metestrus, was decreased after ovariectomy, and showed a dose‐dependent increase in ovariectomized rats injected with 17β estradiol (1, 10, or 300 μg/rat), alone or in combination with progesterone (500 μg/rat). In contrast, it was not affected by the administration of 17β estradiol (300 μg/rat). The surface density of immunoreactive cells was significantly increased over control values by 5 h after the injection of 17β estradiol (300 μg/rat) and as early as 1 h after the administration of progesterone. The separate injection of either 17β estradiol or progesterone had smaller effects on the surface density of immunoreactive cells than did the administration of both hormones together. The surface density of GFAP‐immunoreactive cells reached maximal values by 24 h after the administration of 17β estradiol and/or progesterone and returned to control levels by 48 h after the combined injection of progesterone and 17β estradiol, while in the rats that were injected with only one of the two hormones, the surface density of immunoreactive cells remained over control values for at least 9 days. No such hormonal effects on GFAP‐immunoreactive cells were observed in the cerebellar cortex. © 1993 John Wiley & Sons, Inc.
Synaptic repression at crayfish neuromuscular junctions. I. Generation after partial target area removal
Authors: Prosser Pamela , Rhee John , Vélez Samuel J. 
Published: January 2005

AbstractSynaptic repression, the inability of synaptic junctions to generate normal‐sized postsynaptic potentials under normal physiological conditions, is reported here for crayfish neuromuscular synapses. The synapses in the superficial flexor muscle system of the crayfish change their efficiency in generating a postsynaptic response as a result of a specific alteration in their immediate environment. When the superficial flexor nerve is cut halfway into the target muscle field and the lateral muscle fibers are removed, the intact medial synapses do not generate normal‐sized junction potentials (JP) at the 17° –19°C temperature of the Ringers solution. JPs cannot be recorded in 83% of the muscle fibers at 2 weeks after the operation and of the few JPs that can be detected, 80% are smaller than 1 mV in size. By 8 weeks after the operation, JPs were detected in 55% of the muscle fibers, and now only 46% of these are smaller than 1 mV. When the lateral muscle fibers are left in place during the original operation, providing a target area for the cut nerve to grow into, JPs were then detected in 60%–80% of all medial fibers at all time periods after the operation; their size profile, with 10%–25% of the muscle fibers having JP's less than 1 mV, was similar to control values. These results suggest that the efficiency of these synaptic contacts become affected as a result of partial axotomy and removal of the target area of the cut branches of the axons. © 1993 John Wiley & Sons, Inc.
Glutamate receptor‐mediated currents and toxicity in embryonal carcinoma cells
Authors: Turetsky D. M. , Huettner J. E. , Gottlieb D. I. , Goldberg M. P. , Choi D. W. 
Published: January 2005

AbstractWhile primary neuronal cell cultures have been used to investigate excitotoxicity, development of cell lines exhibiting glutamate receptor‐mediated death is desirable. P19 mouse embryonal carcinoma cells, exposed to retinoic acid and plated onto a layer of cultured mouse cortical glial cells, differentiated into neuron‐like elements immunoreactive for neurofilaments and neuron‐specific enolase. Whole‐cell recordings revealed inward currents in response to extracellular application of either NMDA or kainate. The NMDA‐induced currents exhibited a voltage‐dependent blockade by magnesium, required glycine for maximal activation, and were blocked by the NMDA antagonist dizocilpine. Kainate‐induced currents were blocked by the AMPA/kainate receptor antagonist CNQX. Exposure to 500 μM NMDA for 24 h destroyed most P19 cells (EC50 approximately 70 μM); death was prevented by dizocilpine or D‐APV. Exposure to 500 μM kainate also resulted in widespread death reduced by CNQX. Thus differentiated P19 cells exhibited both excitatory amino acid responses and vulnerability to excitotoxicity, characteristic of CNS neurons. These cells may provide a genetically open system useful for studying glutamate receptor‐mediated phenomena at a molecular level. © 1993 John Wiley & Sons, Inc.
Effects of the steroid hormone 20‐hydroxyecdysone and prior sensory input on the survival and growth of moth central olfactory neurons in vitro
Authors: Oland Lynne A. , Hayashi Jon H. 
Published: January 2005

AbstractNeurons in the developing (antennal) olfactory lobe of the moth Manduca sexta undergo a period of extensive process outgrowth and branching that coincides temporally with both a rising titer of the steroid hormone 20‐hydroxyecdysone and the ingrowth of sensory axons from receptors in the antenna. To evaluate the contribution of these two influences to the morphological development of antennal‐lobe neurons, we placed the neurons in cell culture. Antennal‐lobe neurons were dissociated from normal and chronically unafferented lobes at different stages of development and were exposed to different doses of hormone. Six neuronal cell types with distinctive and stable morphologies appeared in cultures from all stages of pupal development. Morphological changes in these neuronal types were examined quantitatively by comparison of the total length and number of branches. We found that 20‐hydroxyecdysone had little direct effect on the morphological development of antennal‐lobe neurons, but brief exposure to sensory axons in vivo prior to dissociation significantly enhanced subsequent outgrowth in culture. © 1993 John Wiley & Sons, Inc.
Transplantation of neurons reveals processing areas and rules for synaptic connectivity in the cricket nervous system
Authors: Killian K. A. , Merritt D. J. , Murphey R. K. 
Published: January 2005

AbstractIn order to assess the nature of spatial cues in determining the characteristic projection sites of sensory neurons in the CNS, we have transplanted sensory neurons of the cricket Acheta domesticus to ectopic locations. Thoracic campaniform sensilla (CS) function as proprioceptors and project to an intermediate layer of neuropil in thoracic ganglia while cercal CS transduce tactile information and project into a ventral layer in the terminal abdominal ganglion (TAG). When transplanted to ectopic locations, these afferents retain their modality‐specific projection in the host ganglion and terminate in the layer of neuropil homologous to that of their ganglion of origin. Thus, thoracic CS neurons project to intermediate neuropil when transplanted to the abdomen and cercal CS neurons project to a ventral layer of neuropil when transplanted to the thorax. We conclude that CS can be separated into two classes based on their characteristic axonal projections within each segmental ganglion. We also found that the sensory neurons innervating tactile hairs project to ventral neuropil in any ganglion they encounter after transplantation. Ectopic sensory neurons can form functional synaptic connections with identified interneurons located within the host ganglia. The new contacts formed by these ectopic sensory neurons can be with normal targets, which arborize within the same layer of neuropil in each segmental ganglion, or with novel targets, which lack dendrites in the normal ganglion and are thus normally unavailable for synaptogenesis. These observations suggest that a limited set of molecular markers are utilized for cell–cell recognition in each segmentally homologous ganglion. Regenerating sensory neurons can recognize novel postsynaptic neurons if they have dendrites in the appropriate layer of neuropil. We suggest that spatial constraints produced by the segmentation and the modality‐specific layering of the nervous system have a pivotal role in determining synaptic specificity. © 1993 John Wiley & Sons, Inc.
Hoxhomeobox genes and regionalisation of the nervous system
Authors: Krumlauf Robb , Marshall Heather , Studer Michéle , Nonchev Stefan , Sham Mai Har , Lumsden Andrew 
Published: January 2005

AbstractTheHoxfamily of homeobox‐containing genes are intimately associated with the processes of axial patterning in vertebrate embryos. This family of transcription factors is widely conserved in evolution and by analogy with theirDrosophilacounterparts, theHOM‐Chomeotic genes, may play a role in establishing regional identity in a number of embryonic systems, including the CNS. The patterns of expression of these genes are linked with the generation of rhombomeres and neural crest in the developing hindbrain, and suggest that they provide a molecular system for generating a combinatorial patterning mechanism. Analysis of mouseHoxmutants generated by homologous recombination have clearly demonstrated that the genes have important roles in normal regionalisation of the hindbrain and branchial arches, and this has lead to interest in how their early patterns are established in the nervous system. TheHoxgenes and their relation to hindbrain segmentation therefore provide a means of examining the cascade of events which regulates pattern formation in early neural development. © 1993 John Wiley & Sons, Inc.
Antennapedia‐Class homeobox genes define diverse neuronal sets in the embryonic CNS of the leech
Authors: Aisemberg Gabriel O. , Wysocka‐Diller Joanna , Wong Victoria Y. , Macagno Eduardo R. 
Published: January 2005

AbstractStudies of the Antennapedia‐class homeobox genes suggest that specific combinations of these transcription factors play a role in defining neuronal identities. We examined the expression of these genes in the leech Hirudo medicinalis, an organism well‐suited for neurobiological research at the level of identified neurons. Leeches contain at least as many Antennapedia‐class and related genes as insects do, despite the apparently lower complexity of the leech body plan. The CNS expression patterns of two Antennapedia‐class leech homeobox genes (Lox genes) were examined in detail. Lox1 is expressed during early gangliogenesis in only one pair of transient neurons present in every segment (the Bipolar cells) and, at later stages of embryonic development, in 15–20 pairs of central neurons repeated in most segments. The monoclonal antibody Laz1‐1 identified two pairs of Lox1‐expressing neurons as the Bipolar cells and the L1 neurons. The Bipolar cells extended processes in the primordia of the longitudinal connective nerves and later degenerated. The L1 neurons were detected late in gangliogenesis and became stable neurons. Lox2 is expressed in an iterated set of neurons in the posterior two‐thirds of the CNS. On the basis of cell body position and relative size, two pairs of Lox2‐expressing cells were identified as the RPE‐like neurons and the CV motor neurons. Other Lox genes are also expressed in segmentally repeated subpopulations of neurons. These neuronal subpopulations appear to be different from one another but partially overlapping. Different combinations of Lox genes that may be expressed in individual cells could in theory generate enough variability to specify all central neurons in a leech ganglion. © 1993 John Wiley & Sons, Inc.
Developmental analysis reveals labial and subradular ganglia and the primary framework of the nervous system in nudibranch gastropods
Authors: Page Louise R. 
Published: January 2005

AbstractPrevious ultrastructural observations on late stage larvae of dorid nudibranchs (Gastropoda, Opisthobranchia) revealed two pairs of ganglia within the base of the foot that do not have obvious counterparts in existing descriptions of other gastropod larvae [Chia and Koss (1989). Cell Tiss. Res. 256:17–26.] One of these ganglionic pairs has been implicated in the initiation of settlement preceding metamorphosis [Arkett et al. (1989). Biol. Bull. 176:155–160.] By examining neurogenesis in sequential larval stages, I have found that the pattern of connectives and commissures associated with these enigmatic ganglia is comparable to patterns found in less consolidated adult nervous systems of chitons, monoplacophorans, and archaeogastropods. These comparative date suggest that the two pairs of ganglia in dorid nudibranch larvae are homologues of labial and subradular ganglia. The labial ganglia become incorporated into the cerebral ganglia at metamorphosis. In an attempt to integrate anatomical and developmental observations with behavioral andneurophysiological results, I suggest that receptor cells of the larval labial ganglia may become postmetamorphic primary mechanoreceptors of the oral tube, which have central cell bodies within the “cerebral” ganglia and which help coordinate feeding. Results of this study also address a larger evolutionary issue by questioning the traditional model of an ancestral molluscan nervous system that consists of four longitudinal nerve cords that arise from separate sites along a circumesophageal nerve ring. This pattern results from secondary connections in nudibranchs and possibly other molluscs. The primary condition of a single axon bundle emerging from each cerebral ganglion is more similar to the developing nervous system in polychaete annelids than what has been recognized previously. © 1993 John Wiley & Sons, Inc.
Aspects of early postnatal development of cortical neurons that proceed independently of normally present extrinsic influences
Authors: Annis Casey M. , Robertson Richard T. , O'Dowd Diane K. 
Published: January 2005

AbstractTo examine the contribution of local versus extrinsic influences on postnatal development of cortical neurons, we compared the maturation of deep (infragranular) layer neurons in isolated slices of neocortex grown in organotypic culture to a similar population of neurons developingin vivo. All slice cultures were prepared from sensorimotor cortices of newborn mice (P0) and neurons in these cultures were examined at daily intervals during the first 9 daysin vitro(DIV). The maturational state of neurons developingin vivoover this same time period was assessed in acute slices prepared from animals of equivalent postnatal age, P1–P9. Electrophysiological recordings were obtained from neurons in both cultured and acute slices, using Lucifer yellow filled whole‐cell recording electrodes, enabling subsequent morphometric analysis of the labeled cells. We report significant changes in both cellular morphology and electrical membrane properties of these deep layer cortical neurons during the frist week in culture. Morphological maturation over this time period was characterized by a two‐ to three‐fold increase in cell body size and total process length, and an increase in dendritic complexity. In this same population of cells a three‐fold decrease in input resistance and changes in the action potential waveform, including a two‐fold decrease in the AP duration, also occur. The degree of morphological and electrophysiological differentiation of individual neurons was highly correlated across developmental ages, suggesting that the maturational state of a cell is reflected in both cellular morphology and intrinsic membrane properties. A remarkably similar pattern of neuronal maturation was observed in neurons in layers V, VI/SP examined in acute slices prepared from animals between P1–P9. Because our culture system preserves many aspects of the local cortical environment while eliminating normal extrinsic influences (including thalamic, brainstem, and callosal connections), our findings argue that this early phase of neuronal differentiation, including the rate and extent of dendritic growth and development of AP waveform, results from instructive and/or permissive local influences, and appears to proceed independently of the many normally present extrinsic factors. © 1993 John Wiley & Sons, Inc.
Different forms of 130 kD connective tissue protein are specific for boundaries in the nervous system and basement membrane of muscle cells in leech
Authors: Thorey Irmgard , Zipser Birgit 
Published: January 2005

AbstractThe nervous system and muscle tissue of the leech express two different organ‐specific forms of connective tissue protein. The nervous system‐specific form appears in regional boundaries separating cell bodies, axonal tracts and areas of the neuropile during late embryogenesis. In contrast, the muscle‐specific form appears earlier during development in the basement membrane of muscle cells. In extraction experiments both forms behave like extracellular matrix proteins and because of their molecular weight, are considered members of a group of cell type‐specific 130 kD proteins (leech gp130s). How ever, the two forms differ in their posttranslational modification. As determined by Con A and lentil lectin affinity chromatography, only the nervous system‐specific, but not the muscle‐specific form, has fucosylated and high mannose N‐linked carbohydrates. These differences in the developmental onset and glycosylation suggest that nervous system‐specific and muscle‐specific connective tissue proteins are regulated differently and participate in different molecular interactions. © 1993 John Wiley & Sons, Inc.