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  • 1
    Electronic Resource
    Electronic Resource
    GABAergic boutons establish synaptic contacts with the soma and dendrites of cuneothalamic relay neurons in the rat cuneate nucleus (1994)
    Springer
    Experimental brain research 98 (1994), S. 13-20 
    Details
    ISSN: 1432-1106
    Keywords: Cuneate nucleus ; Cuneothalamic relay neuron ; Immunogold electron microscopy ; GABA-immunoreactive bouton ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This study investigates the synaptic relation between γ-aminobutyric acid-immunoreactive (GABA-IR) and cuneothalamic relay neurons (CTNs) in the rat cuneate nucleus. Retrograde transport of wheat germ agglutinin conjugated with horseradish peroxidase complex (WGA-HRP) was used to label CTNs while anti-GABA immunogold serum was used for the detection of GABA-IR boutons associated with CTNs. With these procedures, immunogold-labelled GABA-IR boutons were found to form axosomatic, axodendritic and axospinous synapses with the WGA-HRP-labelled but immunonegative CTNs. Quantitative estimation showed that the mean ratios of GABA-IR to GABA-immunonegative boutons making synaptic contacts with somata, proximal dendrites, and distal dendrites were 47.9%, 49.1% and 34.7%, respectively. Statistical analysis showed that the incidence of GABA-IR boutons on the somata and proximal dendrites of CTNs was significantly higher than on the distal dendrites. Our results indicate that GABA is the primary inhibitory neurotransmitter in the cuneate nucleus, thereby emphasizing the importance of postsynaptic inhibition on cuneothalamic relay neurons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229104
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  • 2
    Electronic Resource
    Electronic Resource
    An ultrastructural study of cuneocerebellar neurons and primary afferent terminals in the external cuneate nucleus of gerbils as revealed by retrograde and transganglionic transport of horseradish peroxidase (1995)
    Springer
    Journal of neurocytology 24 (1995), S. 465-477 
    Details
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The present study examined the synaptic organization of cuneocerebellar neurons and their relationships with the primary afferents in the gerbil external cuneate nucleus following multiple injections of horseradish peroxidase over a widespread area in the cerebellum in conjunction with a simultaneous injection of horseradish peroxidase into the cervical or brachial nerve plexus. The external cuneate nucleus is topographically organized: the rostral portion receiving the primary afferents from the cervical plexus and the caudal portion primary afferents from the brachial plexus. This study attempted to correlate the synaptology with the topography and different cytoarchitecture in these two specific regions in the external cuneate nucleus. Ultrastructurally, the profiles of horseradish peroxidase-labelled cuneocerebellar neurons could be divided into three types, namely, small, medium and large on the basis of their cross-sectional areas. Axon terminals which formed axosomatic synapses could be classified into: round (Rs type; 22.2%), pleomorphic (Ps type; 55.6%) and flattened (Fs type; 22.2%) vesicle boutons. The horseradish peroxidase-labelled dendritic elements of the cuneocerebellar neurons were postsynaptic to a greater number of axon terminals which were also classified into Rd (77.5%), Pd (18.8%) and Fd (3.7%) type boutons. Some of the Rd boutons making direct synaptic contacts with the cuneocerebellar neurons originated from primary afferents since they were simultaneously labelled by transganglionic transport of horseradish peroxidase. In the rostral external cuneate nucleus, synapses on cuneocerebellar neurons were more frequent on their primary dendrites as compared with those on the primary dendrites of the caudal cuneocerebellar neurons. The latter, on the other hand, showed more synapses on their distal dendrites. This may have functional implications with regard to the afferent inputs to cuneocerebellar neurons in the rostral and caudal external cuneate nucleus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01181607
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  • 3
    Electronic Resource
    Electronic Resource
    Ultrastructural identification of cholinergic neurons in the external cuneate nucleus of the gerbil: acetylcholinesterase histochemistry and choline acetyltransferase immunocytochemistry (1995)
    Springer
    Journal of neurocytology 24 (1995), S. 838-852 
    Details
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Using acetylcholinesterase histochemical and choline acetyltransferase immunocytochemical localization methods, this study has provided conclusive evidence for the existence of cholinergic neurons in the external cuneate nucleus of gerbils. By light microscopy, both acetylcholinesterase and choline acetyltransferase labelling was confined to the rostral portion of the external cuneate nucleus. Ultrastructurally, acetylcholinesterase reaction products were found in the nuclear envelope, cisternae of rough endoplasmic reticulum and Golgi saccules of some somata and large dendrites as well as in the membranes of small dendrites, myelinated axons and axon terminals. These neuronal elements were also stained for choline acetyltransferase; immunoreactivity was associated with nuclear pores, nuclear envelope, perikaryal membrane and all the membranous structures within the cytoplasm. Of the total choline acetyltransferase-labelled neuronal profiles analysed, 79% were myelinated axons, 15% dendrites, 4% somata and 2% axon terminals. The immunostained axon terminals consisted of two types containing either round (Rd type; 62.5%) or pleomorphic (Pd type; 37.5%) vesicles. Both were associated directly with choline acetyltransferase-positive dendrites. In contrast to the paucity of choline acetyltransferase-labelled axon terminals, numerous choline acetyltransferase-positive myelinated axons were present. It may thus be hypothesized that most, if not all, of the external cuneate nucleus cholinergic neurons are projection cells; such cells may give rise to axonal collaterals which synapse onto their own dendrites for possible feedback control. Choline acetyltransferase-positive dendrites were contacted by numerous unlabelled presynaptic boutons, 60% of which contained round or spherical synaptic vesicles (Rd boutons) and 40% flattened vesicles (Fd boutons), suggesting that these neurons are under strong inhibitory control. The preferential concentration of cholinergic components in the rostral external cuneate nucleus may be significant in the light of the highly organized somatotopy in the external cuneate nucleus and its extensive efferent projections to medullary autonomic-related nuclei. Our results suggest that the cholinergic neurons may be involved in somatoautonomic integration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01179983
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  • 4
    Electronic Resource
    Electronic Resource
    Down-regulation of membrane glycoprotein in amoeboid microglia transforming into ramified microglia in postnatal rat brain (1994)
    Springer
    Journal of neurocytology 23 (1994), S. 258-269 
    Details
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The present study describes the ultrastructural localization and labelling pattern of lectin in different microglial cell phenotypes in the postnatal rat brain using the isolectin, GSA I-B4. The nascent round and amoeboid microglial cells (round cells and cells displaying short processes) were labelled at their cytoplasmic membrane and the membrane of the subplasmalemmal vacuoles. In the course of their transformation into ramified forms with age, dense lectin labelling was observed successively at different sites in the differentiating cells. The most striking feature was the staining of the Golgi saccules on the trans face, the trans tubular network and associated vesicles and vacuoles in the ‘intermediate’ ramified microglia (ramified cells bearing thick and long processes and those with thin and long processes). The vacuoles with accumulated reaction products were closely associated with many microtubules extending into the cytoplasmic processes. At the surface, the lectin-labelled vacuoles and vesicles appeared to fuse with the membrane and their contents communicated with the exterior. In the advanced or most differentiated ramified microglial cells (cells bearing attenuated processes), the lectin staining at all the above mentioned sites became diminished. In conclusion, in the transformation of the round microglia into their ramified derivatives, the glycoconjugates at the cytoplasmic membrane are progressively reduced. It is postulated from this study that the down-regulation of the glycoconjugates of the microglial plasma membrane is due primarily to their internalization during endocytosis. This process would trigger ade novo galactosyl protein synthesis and/or modification at the trans Golgi saccules and trans tubular network probably in an attempt to degrade the internalized membrane glycoproteins or to replenish the consumption of the membrane glycoconjugates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01275530
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  • 5
    Electronic Resource
    Electronic Resource
    Degenerative changes of neurons in the superior cervical ganglion following an injection of Ricinus communis agglutinin-60 into the vagus nerve in hamsters (1990)
    Springer
    Journal of neurocytology 19 (1990), S. 1-9 
    Details
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The present study describes neuronal changes in the superior cervical ganglion of hamsters following injection of Ricinus communis agglutinin-60 (RCA-60) into the ipsilateral vagus nerve in the cervical region. There were no noticeable structural changes in the ganglion 1 day after injection. Between 3 and 15 days after injection, a small number of neurons located in the caudal part of the ganglion underwent degenerative changes including disappearance of rough endoplasmic reticulum and cytoplasmic vacuolation. The structural alterations were most acute 7 days after the injection when some neurons showed signs of total vacuolation and lysis. A second phase of neuronal change occurred after longer survival periods extending from 60 to 120 days after injection. The most striking feature of such neurons was darkening of their dendrites associated with abnormally high density cytoplasm that contained mitochondria with disrupted cristae. As distinct from the early phase in which cell necrosis was observed, there was no evidence of cell death of neurons bearing darkened dendrites. Since examples of exfoliation of the affected dendrites and their phagocytosis by satellite cells were extremely rare, it is postulated that these structural alterations are probably reversible but over an extended period. The significance of the two phases of degenerative change is discussed in connection with the acute and possible chronic effects of the toxic lectin. The present study also confirms the presence of postganglionic sympathetic axons in the cervical vagus nerve.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01188435
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