bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of fungiform papillae, taste buds, and their innervation in the hamster
Authors: Whitehead Mark C. , Kachele Diane L. 
Published: January 2005

AbstractFungiform taste buds in mature hamsters are less subject to neurotrophic influences than those of other species. This study evaluates taste‐bud neurotrophism during development in hamsters by examining the relation between growing nerves and differentiating fungiform papillae. Chorda tympani (CT) or lingual (trigeminal) nerve (LN) fibers were labelled with Lucifer Yellow as they grew into (CT fibers) or around (LN fibers) developing taste buds. Developing fungiform papillae and taste pores were counted with the aid of a topical tongue stain.The tongue forms on embryonic days (E) 10.5–11 and contains deeply placed CT and LN fibers but no papillae. By E12, the tongue epithelium develops scattered elevations. These “eminences” selectively become innervated by LN fibers that grow to the epithelium earlier and in larger numbers than CT fibers. Definitive fungiform papillae form rapidly during E13–14 and become heavily innervated by LN fibers. Intraepithelial CT fibers, rare at E13, invariably innervate fungiform papillae containing nascent taste buds at E14. During E14–15 (birth = E15–16), most papillae contain taste buds with pores, extensive perigemmal LN innervation, and extensive intragemmal CT innervation. At birth, numbers of fungiform papillae and taste pores are adultlike.The results show that fungiform eminences begin forming in the absence of innervation. The subsequent differentiation of definitive fungiform papillae and their innervation by LN fibers occur synchronously, prior to the differentiation of taste buds and their CT innervation. The hamster is precocious (e.g., compared to rat) in terms of LN development and the structural maturity of the anterior tongue at birth. © Wiley‐Liss, Inc.
Blockade of NMDA receptors increases cell death and birth in the developing rat dentate gyrus
Authors: Gould Elizabeth , Cameron Heather A. , McEwen Bruce S. 
Published: January 2005

AbstractExcitatory input regulates cell birth and survival in many systems. The granule cell population of the rat dentate gyrus is formed primarily during the postnatal period. Excitatory afferents enter the dentate gyrus and begin to form synapses with granule cells during the first postnatal week, the time of maximal cell birth and death. In order to determine whether excitatory input plays a role in the regulation of cell birth and survival in the developing granule cell layers and their germinal regions, the subependymal layer and hilus, we treated rat pups with the N‐methyl D‐aspartate (NMDA) receptor antagonists MK‐801, CGP 37849, or CGP 43487 during the first postnatal week and examined the numbers of 3H‐thymidine‐labeled cells, pyknotic cells, and healthy cells in these regions. In order to determine the cell type that was affected, sections from brains of MK‐801‐treated rats were processed for 3H‐thymidine autoradiography combined with immunohistochemistry for the marker of radial glia, vimentin, and the marker of mature astrocytes, glial fibrillary acidic protein (GFAP).Within the dentate gyrus, NMDA receptor blockade resulted in the following changes: (1) the density of 3H‐thymidine‐labeled cells was increased, (2) the density of pyknotic cells was increased, (3) the density of 3H‐thymidine‐labeled pyknotic cells was increased, and (4) the density of healthy cells was decreased. The infrapyramidal blade/hilus showed changes throughout its extent, whereas the suprapyramidal blade showed changes only at the rostral level. No change in the numbers of 3H‐thymidine‐labeled vimentin‐immunoreactive or GFAP‐immunoreactive cells was observed in the dentate gyrus with MK‐801 treatment, indicating that glia are not primarily affected by NMDA receptor blockade.Blockade of NMDA receptors resulted in gross morphologic changes in the dentate gyrus; in most cases, the infrapyramidal blade was indistinguishable from the hilus. Moreover, in several brains of animals treated with CGP 37849 or CGP 43487 on postnatal day (P)5, an abnormal aggregation of cells was observed ventral to the normal location of the infrapyramidal blade. This cellular cluster contained many pyknotic and 3H‐thymidine‐labeled cells and may represent cells that normally comprise the infrapyramidal blade. Dramatic changes to the subependymal layer were also seen following NMDA receptor blockade. The cross‐sectional area of this region was significantly increased with MK‐801, CGP 37849, or CGP 43487 treatment and contained a high density of 3H‐thymidine‐labeled cells and 3H‐thymidine‐labeled pyknotic cells.These results indicate that NMDA receptor activation is critical for the normal development of the rat dentate gyrus. The finding that blockade of NMDA receptors resulted in increased levels of cell death and birth supports the hypothesis that NMDA receptor activation is a natural signal for the inhibition of these processes in the developing dentate gyrus. © Wiley‐Liss, Inc.
Distribution of primary afferent fibers projecting from hindlimb cutaneous nerves to the medulla oblongata in the cat and rat
Authors: Ueyama Teizo , Houtani Takeshi , Ikeda Michiko , Sato Kazuo , Sugimoto Tetsuo , Mizuno Noboru 
Published: January 2005

AbstractThe dorsal column nuclear complex, one of the most important relays for tactile perception, has well been known to be somatotopically organized. Topographical arrangements of terminal sites of individual cutaneous nerves within the dorsal column nuclei, however, have not been examined systematically, although many studies have been done upon primary afferents to the medulla oblongata, including the dorsal column nuclear complex. Thus, in the present study, distribution of primary afferent fibers projecting from the hindlimb cutaneous nerves to the medulla oblongata was examined in the cat and rat by means of the transganglionic transport method with horseradish peroxidase. Cutaneous primary afferent fibers projecting from the hindlimb to the medulla oblongata were distributed mainly in the ipsilateral gracile nucleus. Terminal labeling in the gracile nucleus was seen at all rostrocaudal levels of the nucleus, occasionally including the nuclear part straddling the midline (the median or accessory nucleus). The labeled axon terminals in the gracile nucleus were more densely distributed in the middle and caudal parts of the nucleus than in the rostral part. Although the fields of termination of the hindlimb cutaneous nerves overlapped in the gracile nucleus, the foci of the terminal labeling of the nerves innervating the distal parts of the hindlimb were located more medially or dorsomedially than those of the nerves innervating the proximal parts. Terminal labeling was further found in a small zone immediately medial to the rostromedial border of the external cuneate nucleus. This hitherto undescribed zone (U zone) contained a small cluster of medium‐sized neurons in the cat. Although no particular cell cluster was found in the U zone of the rat, convergence of the primary afferent fibers of the cutaneous nerve from the hindlimb appeared to occur as in the U zone of the cat.
Neurons of the medial cortex outer plexiform layer of the lizard Podarcis hispanica: Golgi and immunocytochemical studies
Authors: de la Iglesia J. A. Luis , Martinez‐Guijarro F. J. , Lopez‐Garcia C. 
Published: January 2005

AbstractThe study of Golgi‐impregnated lizard brains has revealed a scarce but heterogeneous neuronal population in the outer plexiform layer of the medial cortex. Some of the neuronal types detected here resemble the neurons of the dentate molecular layer of the mammalian hippocampus.According to their morphology, five intrinsic neuronal types have been clearly identified: short axon aspinous bipolar neuron (type 1, or sarmentous neuron), short axon aspinous juxtasomatic neuron (type 2, or coral neuron), short axon sparsely spinous multipolar neuron (type 3, or stellate neuron), short axon sparsely spinous juxtasomatic multipolar neuron (type 4, or deep stellate neuron, and sparsely spinous juxtasomatic horizontal neuron (type 5, or couchant neuron).Most neuronal types were identified as γ‐aminobutyric acid (GABA) and parvalbumin immunoreactive, and are thus probably involved in medial cortex inhibition. Moreover, a small fraction of them displayed ß‐endorphin immunoreactivity.The distribution of these neuronal types is not uniform in the laminae of the outer plexiform layer. Type 1 (sarmentous) and type 3 (stellate) neurons overlap the axonal field projection coming from the dorsal cortex and the thalamus, whereas types 4 (deep stellate) and 5 (couchant) neurons overlap ipsi‐ and contralateral dorsomedial projection fields as well as raphe serotoninergic and opioid immunoreactive axonal plexi. Thus, these neuronal types may be involved in the control of specific inputs to the medial cortex by presumably feed‐forward inhibition; nevertheless, feed‐back inhibition may also occur regarding type 4 (deep stellate) neurons that extend deep dendrites to the zinc‐rich bouton field.
Morphology of two classes of target‐specific bullfrog sympathetic preganglionic neurons
Authors: Peruzzi Daniel , Forehand Cynthia J. 
Published: January 2005

AbstractThese experiments took advantage of the unique ability to define target‐specific sympa‐thetic preganglionic neurons in the bullfrog spinal cord in order to examine the morphologies of different classes of preganglionic neurons. Sympathetic preganglionic neurons were identified by retrograde transport of fast blue from the sympathetic chain. Subsequently, fast blue‐labelled sympathetic preganglionic neurons in fixed spinal cord slices were filled with lucifer yellow and processed for visualization with lucifer yellow antiserum, biotinylated secondary antiserum, and avidin peroxidase. Target specificity of sympathetic preganglionic neurons was determined by anatomical position; sympathetic preganglionic neurons that control the vasculature (C‐type sympathetic preganglionic neurons) lie in a position caudal to those that control nonvascular targets [B‐type sympathetic preganglionic neurons; Horn and Stofer (1988) J. Comp. Neurol. 268:71].These two classes of sympathetic preganglionic neurons have qualitatively similar morphologies. However, they exhibit significant quantitative differences in total dendritic length and the rostrocaudal extent of dendrites. These differences are likely to be associated with differences in the number of synapses received by these two classes of sympathetic preganglionic neurons. Moreover, the segmental control of sympathetic preganglionic neurons by descending brainstem projections is likely to be finer for those involved in vascular control than for those that influence other targets.
Development and organization of the ocular motor nuclei in the larval sea lamprey, Petromyzon marinus L.: An HRP study
Authors: Pombal Manuel A. , Rodicio M. Celina , Anadon Ramón 
Published: January 2005

AbstractRetrograde transport of horseradish peroxidase (HRP) after its application into the orbit was used to investigate the development of the different ocular motor nuclei in larvae of the sea lamprey (Petromyzon marinus) and to identify their regions of origin. In the smallest larvae studied (10–19 mm in length), the oculomotor and abducens neurons were ipsilateral to the site of HRP application, whilst trochlear neurons were contralateral. These motoneurons did not have dendritic processes. In larvae more than 19 mm in length, both ipsilateral and contralateral components were found in the oculomotor and trochlear nuclei; dendrites were present, and their length and branching increased with larval age. An adult‐like pattern of topographic organization and dendritic arborization was reached in larvae of about 45–60 mm in length. In oculomotor neurons, medial dendrites appear first, then dorsolateral dendrites, and finally ventral dendries. Similarly, in trochlear neurons ventral and ventrolateral dendrites develop first, foll owed by dorsal dendrites that course either to the caudal optic tectum or to the terminal fields of the octaval and lateral line nerves in the cerebellar plate. Dorsal and ventral dendrites of the abducens neurons arise at the same time, but dorsal dendrites attain an adult‐like morphology earlier. A few motoneurons showed ventricular attachments in larvae longer than 40 mm. The significance of these processes and their possible usefulness as a marker for the regions of origin of the ocular motor nuclei are discussed. Finally, the results presented here indicate that differentiation of the ocular motor nuclei in larval lampreys precedes and is independent of the maturation of the eye at transformation.
A comparison of synapses onto the somata of intrinsically bursting and regular spiking neurons in layer V of rat SmI cortex
Authors: White Edward L. , Amitai Yael , Gutnick Michael J. 
Published: January 2005

AbstractRegular spiking (RS) and intrinsically bursting (IB) neurons show distinct differences in their inhibitory responses. Under various conditions, the synaptic responses of RS cells display marked inhibitory postsynaptic potentials (IPSPs), whereas the responses of most IB cells do not (Silva et al: Soc Neurosci Abstr 14:883, 1988; Chagnac‐Amitai and Connors: J Neurophysiol 61:747, 62:1149, 1989; Connors and Gutnick: TINS 13:99, 1990). This investigation is designed to determine if differences in the inhibitory responses of RS versus IB cells are reflected in differences in the concentration of inhibitory synapses into their somata. RS and IB neurons in rat somatosensory cortex were identified by using intracellular recording and labeling, examined with the light microscope, and then serial thin‐sectioned prior to examination with the electron microscope. Axonal terminals presynaptic to their somata and proximal dendrites were identified and classified according to criteria described by Peters and coworkers (Peters et al: J Neurocytol 19:584, 1990; Peters and Harriman: J Neurocytol 19:154, 1990; 21:679, 1992). The locations of these boutons were displayed on the surfaces of 3‐D reconstructions of the somata and proximal dendrites. The reconstructions were produced directly from the serial thin sections by using a novel, electron microscopic, image‐processing computer resource. Our analysis showed no significant difference in the types and concentration of boutons presynaptic to the cell bodies and proximal dendrites of intrinsically bursting versus regular spiking neurons. We conclude that the differences observed in the inhibitory responses of intrinsically bursting versus regular spiking neurons cannot be explained by differences in the concentrations of synapses onto their somata. © 1994 Wiley‐Liss, Inc.
5‐HT innervation of reticulospinal neurons and other brainstem structures in lamprey
Authors: Di Prisco Gonzalo Viana , Dubuc Réjean , Grillner Sten 
Published: January 2005

AbstractIn order to determine if reticulospinal neurons involved in the control of locomotion and responsive to exogenously applied 5‐hydroxtryptamine (5‐HT) are innervated by fibers that contain serotonin, the serotoninergic innervation of reticulospinal neurons, identified by retrograde labeling with fluorescein‐conjugated dextran‐amine (FDA), was investigated by immunohistochemistry in the lamprey brainstem. A widespread distribution of 5‐HT immunoreactive (5‐HT‐ir) fibers was seen within the basal plate of the brainstem, an area containing reticulospinal somata and dendritic arborizations. Numerous 5‐HT varicose fibers were found in close relation to large reticulospinal cell bodies, particularly in the middle and anterior rhombencephalic reticular nuclei (MRRN and ARRN). Some of these reticulospinal somata were surrounded by a very dense pericellular 5‐HT innervation. 5‐HT‐ir fibers were also seen in other brain structures that are known to influence reticulospinal neurons such as the rhombencephalic alar plate containing sensory relay interneurons, cranial nerves (III–X), cerebellum, and tectum. These findings suggest that, as in the spinal cord, motor behavior controlled by reticulospinal neurons may be subject to a serotoninergic modulation. © 1994 Wiley‐Liss, Inc.
Neuropeptides myomodulin, small cardioactive peptide, and buccalin in the central nervous system of Lymnaea stagnalis: Purification, immunoreactivity, and artifacts
Authors: Santama Niovi , Wheeler Colin H. , Burke Julian F. , Benjamin Paul R. 
Published: January 2005

AbstractThe neuropeptides myomodulin, small cardioactive peptide (SCP), and buccalin are widely distributed in the phylum Mollusca and have important physiological functions. Here, we describe the detailed distribution of each class of peptide in the central nervous system (CNS) of the snail Lymnaea stagnalis by the use of immunocytochemical techniques combined with dye‐marking of electrophysiologically identified neurons. We report the isolation and structural characterization of a Lymnaea myomodulin, PMSMLRLamide, identical to myomodulin A of Aplysia californica. Myomodulin immunoreactivity was localized in all 11 ganglia, in their connectives, and in peripheral nerves. In many cases, myomodulin immunoreactivity appeared localized in neuronal clusters expressing FMRFamide‐like peptides, but also in a large number of additional neurons. Double‐labelling experiments demonstrated myomodulin immunoreactivity in the visceral white interneuron, involved in regulation of cardiorespiration. SCP‐like immunoreactivity also appeared in all ganglia, and double‐labelling experiments revealed that in many locations it was specifically associated with clusters expressing distinct exons of the FMRFamide gene that are differentially expressed in the CNS. Characterization of the two types of SCP‐antisera used in this study, however, suggested that they cross‐reacted with both FMRFamide and N‐terminally extended FMRFamide‐like peptides. Selective preadsorption with these cross‐reacting peptides resulted in elimination of the widespread staining and retention of bona fide SCP immunoreactivity in the buccal and pedal ganglia only. Buccalin immunoreactivity was limited to the buccal and pedal ganglia. It did not coincide with the distribution of either myomodulin or SCP. Most immunoreactive clusters were found in the pedal ganglia. © 1994 Wiley‐Liss, Inc.
Interaction between enkephalin and γ‐aminobutyric acid in the chicken retina: A double‐label immunoelectron microscopic analysis
Authors: Watt Carl B. , Glazebrook Patricia A. 
Published: January 2005

AbstractIn the present study, double‐label immunoelectron microscopy was used to examine the synaptic relationships between amacrine cell populations in the chicken retina that contain either enkephalin or γ‐aminobutyric acid (GABA) or both enkephalin and GABA. The objectives of the present study were twofold. First, the ultrastructural features and synaptic organization of enkephalin and enkephalin/GABA amacrine cells were compared. Second, the synaptic interactions between these populations and the population of GABA amacrine cells were examined.A total of 475 synaptic arrangements were observed to involve enkephalin or enkephalin/GABA amacrine cell processes. The synaptic relationships of enkephalin and enkephalin/GABA amacrine cells were quite similar. Each population was pre‐ and postsynaptic to amacrine cells, postsynaptic to bipolar cells, and presynaptic to processes possibly originating from ganglion cells. A substantial percentage of each population's pre‐ and postsynaptic relationships were with the processes of GABAergic amacrine cells. Moreover, when enkephalin and enkephalin/ GABA amacrine cell processes were postsynaptic to bipolar cells, their dyadic partner was observed frequently to be a GABA amacrine cell process.The present study suggests a diversity in the population of chicken enkephalin amacrine cells with respect to their expression of the classical inhibitory transmitter GABA. Moreover, a functional relationship between enkephalinergic and GABAergic pathways is indicated by studies showing that both enkephalin and enkephalin/GABA amacrine cells exhibit substantial synaptic interaction with GABA amacrine cells. © 1994 Wiley‐Liss, Inc.
Temporal onset of synapsin I gene expression coincides with neuronal differentiation during the development of the nervous system
Authors: Melloni Richard H. , Degennaro Louis J. 
Published: January 2005

AbstractSynapsin I is the best characterized member of a family of nerve terminal‐specific phosphoproteins implicated in the regulation of neurotransmitter release. During development, the expression of synapsin I correlates temporally and topographically with synapse formation, and recent physiological studies (Lu et al. [1992] Neuron 8:521–529.) have suggested that synapsin I may participate in the functional maturation of synapses. To better understand the temporal relationship between synapsin I gene expression and particular cellular events during neuronal development, we have used in situ hybridization histochemistry to localize synapsin I mRNA throughout the rat central and peripheral nervous systems during embryonic and postnatal development. From the earliest embryonic time points assayed (E12), the expression of the synapsin I gene was detectable in both the central and peripheral nervous systems. While, in general, levels of synapsin I mRNAs were high in utero, synapsin I cDNA probes revealed specific patterns of hybridization in different regions of the embryonic nervous system. To determine precisely the temporal onset of expression of the synapsin I gene during neuronal development, we examined in detail the appearance of synapsin I mRNA during the well characterized postnatal development of granule cells of the rat cerebellum and hippocampus. In both regions, the onset of synapsin I gene expression correlated with the period of stem cell commitment to terminal differentiation. Finally, our data demonstrate that, in a second phase, synapsin I gene expression increases to a maximum for a given neuronal population during a particular phase of differentiation, i.e., synaptogenesis. © 1994 Wiley‐Liss, Inc.
Afferents to the nucleus reticularis parvicellularis of the cat medulla oblongata: A tract‐tracing study with cholera toxin B subunit
Authors: Fort Patrice , Luppi Pierre‐Hervé , Jouvet Michel 
Published: January 2005

AbstractThe aim of this study was to examine anatomical evidence in cats of whether the nucleus reticularis parvicellularis (Pc) is part of the circuit responsible for the inhibition of brainstem motoneurons during paradoxical sleep. For this purpose, we made iontophoretic injections of the retrograde and anterograde tracer cholera toxin B subunit (CTb) in the Pc.After CTb injections in the Pc, a large number of retrogradely labeled neurons were seen in the central nucleus of the amygdala, the lateral part of the bed nucleus of the stria terminalis, the posterior hypothalamic areas, the mesencephalic reticular formation, the nucleus locus subcoeruleus, the nucleus pontis caudalis, other portions of the Pc, the nucleus reticularis dorsalis, the trigeminal sensory complex, and the nucleus of the solitary tract. We further found that the Pc receives (1) serotoninergic afferents from the raphe dorsalis, magnus, and obscurus nuclei; (2) noradrenergic inputs from the dorsolateral pontine tegmentum; (3) cholinergic afferents from the lateral medullary reticular formation; (4) substance P‐like afferents from the central nucleus of the amygdala, bed nucleus of the stria terminalis, periaqueductal gray, and nucleus of the solitary tract; and (5) methionine‐enkephalin‐like projections from the periaqueductal gray, the nucleus of the solitary tract, the lateral pontine and medullary reticular formation, and the spinal trigeminal nucleus. We further found that the Pc do not receive afferents from brainstem structures responsible for muscle atonia, such as the ventromedial medulla and the dorsomedial pontine tegmentum, and therefore may not be part of the circuit inhibiting the brainstem motoneurons during paradoxical sleep. © 1994 Wiley‐Liss, Inc.