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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 145 (1974), S. 261-267 
    ISSN: 1432-0568
    Keywords: Dorsal lateral geniculate nucleus ; Morphology (ultrastructure) ; Mouse ; Synaptic vesicles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Neuronal perikarya, dendrites, extraglomerular neuropil, and synaptic glomeruli were examined by electron microscopy in the dorsal lateral geniculate nucleus (LGd) of the mouse. Particular attention was paid to boutons containing “flattened” synaptic vesicles. In line with recent studies of rat LGd (Lieberman and Webster, 1972; Lieberman, 1973), but in contrast to the findings of Rafols and Valverde (1973) on the mouse LGd, two distinct classes of ‘flat’-vesicle-containing boutons could be distinguished. P-boutons—were traced to and probably originate entirely from the presynaptic dendrites of the intrinsic neurons. They are concentrated within the glomeruli and are postsynaptic as well as presynaptic, being the intermediate elements in numerous intraglomerular serial synapses. F-boutons—are interpreted as axon terminals and are exclusively presynaptic. Some were traced from myelinated fibres. Synaptic vesicles are more concentrated in F-boutons than in P-boutons, appear flatter, and lie in a darker matrix. F-boutons synapse extensively in the extraglomerular neuropil, but are outnumbered by P-boutons in the glomeruli. The synaptic relationships established within the glomeruli are summarized.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 151 (1977), S. 35-51 
    ISSN: 1432-0568
    Keywords: CNS ; Development ; Thalamus ; vLGN
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The morphology and distribution of neurons in the ventral lateral geniculate nucleus (vLGN) of adult rats, and the postnatal growth and differentiation of these neurons were studied in Golgi-Cox preparations. In the adult, two main cell classes were recognized: class A cells and class B cells. The former are assumed to be projection neurons. The latter closely resemble the class B cells of the dorsal lateral geniculate nucleus and are interpreted as presynaptic dendrite-bearing interneurons. Class A cells predominated and three subtypes were tentatively identified: small-medium size multipolar neurons, with short, branched spiny dendrites (most numerous in dorsolateral vLGN); medium-large fusiorm cells with one or two stem dendrites at each pole (most numerous in medial vLGN); large multipolar neurons with long, sparsely branched dendrites (most numerous in ventral vLGN). Class A and B cells were distinguishable at birth and showed parallel cell body size increases up to postnatal day 24. The dendrites of both classes of cell also reached the adult stage of differentiation at about day 24 but the differentiation of class B cell dendrites lags slightly behind that of class A cell dendrites.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0568
    Keywords: Retino-geniculate projection ; Development ; Enucleation ; Horseradish peroxidase ; Albino rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The postnatal development of ipsilateral retinofugal projections to the lateral geniculate body in normal albino rats, and in rats unilaterally enucleated at birth has been examined. At postnatal ages ranging from 1 day to 6 months, horseradish peroxidase was injected into one eye of normal rats and into the remaining eye of neonatally enucleated animals. After approximately 20 hours, the animals were perfused, the brains sectioned and reaction product visualised using tetramethylbenzidine. Ipsilateral retinal projections to the lateral geniculate body in normal animals were extensive on postnatal day 1 and became reduced over the next few days, the adult pattern being established between days 9 and 12. In the enucleated group, the terminal fields of the ipsilateral projections to the lateral geniculate body from the remaining eye remained larger and displayed a greater density of terminal labelling than in age-matched controls. In addition, the ipsilateral terminal field in the dorsal lateral geniculate nucleus occupied a more lateral position than in control animals. These findings support previous suggestions that the abnormally large ipsilateral retino-fugal projections observed in adult rats following removal of one eye, at or close to, birth, result from a failure of the ipsilateral projection to become restricted and that terminal or preterminal sprouting of retinal axons may also make a small contribution to the formation of the exuberant ipsilateral projection.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 155 (1979), S. 1-14 
    ISSN: 1432-0568
    Keywords: Visual cortex ; Non-pyramidal neurons ; Development ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We have studied the maturation of non-pyramidal cells in layers II–VI of the visual cortex of albino rats from birth to maturity, using Golgi-Cox and rapid Golgi preparations. At birth, non-pyramidall cells are sparse, immature and concentrated in the deep part of the cortical plate: their number increases towards the end of the first week but they remain sparse and immature in the upper part of the cortical plate. During the second postnatal week, the number, size and extent of dendritic and axonal branching of these cells undergo considerable increases and the cells become conspicuous in layer IV and apparent in the supragranular layers: this “growth spurt’ occurs just after (and may be related to) the arrival and establishment in the cortex during the second half of the first postnatal week, of extrinsic afferents. During the third postnatal week, most of the cells complete their maturation. At the end of this week, the number of spinous cells is greater and the spine density of some cells is higher than in the adult, falling to adult values during the fourth postnatal week. It is noteworthy that the non-pyramidal cells appear to reach maturity at about the same time in all the layers studied, and at the same time as the pyramidal cells with which they are associated. These observations are not in accord with the prevalent view that non-pyramidal cells complete their differentiation much later than pyramidal cells.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 157 (1979), S. 311-328 
    ISSN: 1432-0568
    Keywords: Visual cortex ; Development ; Pyramidal neurons ; Non-pyramidal neurons ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The postnatal development of neuronal perikarya in layers II–VI of the visual cortex of perfusion-fixed albino rats, 12 h to 180 days old, has been studied by electron microscopy. Particular attention was paid to cells in photographic montages of 75μm wide strips extending through the full depth of the occipital cortex, cut from 100 μm vibratome sections of the brain. At birth, and during the first few postnatal days, most of the neurons present in the cortex are small, tightly packed ‘indifferent’ cells with scanty cytoplasm containing mitochondria and chiefly free ribosomes; a few presumptive pyramidal cells with a developing apical dendrite and more voluminous cytoplasm can be recognized in deep cortex. Non-pyramidal cells can be identified on postnatal day 6, when although scarce and with immature cytoplasmic features, they already display a more electron opaque chromatin pattern than developing pyramidal cells and receive axo-somatic contacts of Gray's type I. During the second postnatal week there are conspicuous increases in the maturity of the cells, which acquire a rich complement of cytoplasmic organelles: in general cells situated in the deep cortical plate are larger and better differentiated than those in the superficial plate, and non-pyramidal cells are less well differentiated than the associated pyramidal cells. By the end of the second week, differences in cytoplasmic maturity between superficial and deep, and between pyramidal and non-pyramidal cells are less evident. Maturation proceeds during the third postnatal week; both types of cells acquire an adult complement of axo-somatic synapses and their mature nuclear and cytoplasmic features, and by day 24 are indistinguishable from their adult counterparts. In keeping with previous Golgi studies of this same cortex, the non-pyramidal cells did not acquire mature ultrastructural features significantly later than the pyramidal cells. A possible correlate of particularly active synaptogenesis and plasticity in the population of nonpyramidal, cells during the third postnatal week (immediately after eyeopening), was that at this time these cells contained very prominent accumulations of granular reticulum, ribosomes and Golgi apparatus, and appeared hypertrophic.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 171 (1985), S. 223-234 
    ISSN: 1432-0568
    Keywords: Lateral geniculate nucleus ; Retinal axons ; Horseradish peroxidase ; Hamster ; Synaptic organization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The synaptic organization of the α sector of the dorsal lateral geniculate nucleus has been examined by electron microscopy in normal adult hamsters and in adult hamsters subjected to unilateral eye enucleation or intravitreal injection of horseradish peroxidase. Two types of neuropil are apparent. Islands of complex neuropil partially enclosed by astrocyte processes (synaptic glomeruli) are surrounded by a sea of simpler non-glomerular neuropil. The latter is dominated by small axon terminals with spherical synaptic vesicles and Gray type 1 axodendritic contacts (SR-boutons) and also contains axon terminals with flattened synaptic vesicles (F-boutons). The glomerular neuropil contains (i) exclusively postsynaptic dendrites and dendritic protrusions of presumptive projection cells; (ii) pre- and postsynaptic pleomorphic-vesiclecontaining P-boutons (interpreted as appendages of the dendrites of interneurons); (iii) large axon terminals containing spherical synaptic vesicles and large pale mitochondria (R-boutons) which were experimentally identified as retinal terminals and which are presynaptic to both projection cell dendrites and P-boutons at Gray type 1 contacts; (iv) F-boutons (minority component). F-boutons and P-boutons are presynaptic to both projection cell dendrites and P-boutons and P-boutons are the intermediate elements of various serial synapses including triplet (triadic) synapses. Medium-large terminals with spherical synatpic vesicles and dark mitochondria (RLD-boutons) which were commonly invaginated by dendritic spines of projection cells in small glomerulus-like formations were also identified. The origin of RLD-boutons is unknown but SR-boutons probably derive chiefly from ipsilateral visual cortex and possibly also from superior colliculus, and non-glomerular F-boutons probably originate in the ipsilateral thalamic reticular nucleus. No differences in synaptic organization were found between the part of the nucleus which receives uncrossed retinal input and the part which receives crossed input, nor were differences seen in the size, fine structure or relationships between the terminals of identified crossed and uncrossed retinal axons.
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  • 7
    ISSN: 1432-0568
    Keywords: Anterior thalamus ; Laterodorsal tegmental nucleus ; Pedunculopontine nucleus ; Cholinergic neurons Double-labelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Retrograde transport of horseradish peroxidase (HRP) was combined with choline acetyltransferase (ChAT) immunohistochemistry to study cholinergic projections to the anterior thalamic nuclei in the rat. Small iontophoretic injections of HRP placed into different subdivisions of the anterior thalamic nuclear complex resulted in distinct patterns of retrograde labelling in two major cholinergic cell groups of the mesopontine tegmentum, the laterodorsal tegmental nucleus (LDTg), in which a majority of the labelled cells was located, and the pedunculopontine tegmental nucleus (PPT). After injections into the posterior subdivision of the anteroventral thalamic nucleus (AVp), double-labelled neurons were present predominantly in the ipsilateral LDTg while a smaller number was found in the PPT. In the ipsilateral LDTg, 60–70% of ChAT-positive neurons were HRP-labelled, and 90–95% of the HRP-labelled neurons were ChAT-positive. In the contralateral LDTg, 30–40% of ChAT-positive neurons were HRP-labelled. After injections in the medial subdivision of the anteroventral thalamic nucleus (AVm), the pattern of labelling in LDTg was similar to that detected after injections in the AVp. The number of double-labelled neurons in the LDTg and PPT was much lower after injections into AVm than after injections into AVp. When injections were confined to the anterodorsal thalamic nucleus (AD), no HRP-labelled cells were present in the LDTg or PPT. These results show that the LDTg and PPT are the sources of the cholinergic input to the rat anterior thalamus. The major projection from LDTg and PPT is to the AVp, whereas there is a lighter cholinergic projection to the AVm. The AD does not receive a projection from cholinergic cells in the mesopontine tegmentum.
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  • 8
    ISSN: 1432-1106
    Keywords: Key words Amino acid immunocytochemistry ; Axon collateralization ; Thalamus ; Fluorescent tracers ; Limbic system ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Small, stereotaxically guided injections of true blue (TB) were made into the retrosplenial granular cortex (RSg) and of diamidino yellow (DY) into the dorsal portion of the rostral pole of the thalamic reticular nucleus (TRN) in 16 adult rats to determine whether axons projecting from the anterior thalamic nuclear complex (ATN) to the TRN are branches of axons also projecting to the RSg. Following injections of the fluorescent dyes, serial coronal sections of the brain revealed single retrogradely labelled, and large numbers of double retrogradely labelled neuronal cell bodies in the ipsilateral anteroventral and anterodorsal nuclei and smaller numbers in the anteromedial nucleus of the ATN complex. In a se- cond series of six adult rats with similar double injections of TB and DY, two sections in three were immunoreacted, one with antiserum against glutamate and one with antiserum against aspartate, using indirect immunofluorescence with rhodamine to detect reactive cells. The great majority of both single and double retrogradely labelled cell bodies were also immunoreactive for aspartate or glutamate. In addition, a moderate to small number of non-immunolabelled neurons projecting to the TRN and/or to the RSg were also found in all three nuclei of the ATN complex. These results are compatible with the possibility that large numbers of neurons in the ATN send axonal branches to both the RSg and the TRN, and that many such neurons use glutamate and/or aspartate as transmitters. The findings also suggest that the projections from the ATN might be heterogeneous with respect to transmitter phenotype.
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  • 9
    ISSN: 1432-1106
    Keywords: Key words Anterodorsal thalamic nucleus ; Anteroventral thalamic nucleus ; Retrograde labelling ; Postembedding immunoelectron microscopy ; Inhibitory synapses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We have carried out a semi-quantitative ultrastructural study to determine the characteristics and distribution of γ-aminobutyric acid (GABA)-containing constituents of the anterodorsal (AD) and anteroventral (AV) thalamic nuclei in adult rats. We used a polyclonal antibody to GABA and a postembedding immunogold detection method in animals in which the cortical projection neurons of these nuclei had been labelled by retrograde transport of cholera toxin/horseradish peroxidase (HRP) injected into the retrosplenial granular cortex. Two types of GABA-immunopositive structures were identified, with gold particle densities 4–40 times higher than the highest densities over blood-vessel lumens and areas of empty resin: (1) an apparently homogeneous population of axon terminals with Gray type-2 (symmetric) synaptic contacts corresponding to F-axon terminals; and (2) small–medium sized myelinated axons scattered individually or in small groups within the neuropil which may be their parent axons. These axons and terminals may originate from the ipsilateral thalamic reticular nucleus; others may arise from the basal forebrain or brainstem. The GABA-immunopositive terminals comprised approximately 16% of all axon terminal profiles in AD and 12% in AV, a significant difference. However, because the immunoreactive axon terminals in AD were significantly larger than those in AV (1.09±0.47 µm2 vs 0.90±0.43 µm2) and would therefore be encountered more frequently, it is not possible to conclude that the GABAergic innervation of AD is heavier than that of AV. The GABA-positive terminals established synaptic contacts with cell bodies and dendrites of all sizes (some of which were HRP-labelled) with the following frequency distribution (AD/AV, no significant difference): somata 5%/7%; large dendrites (≥1.5 µm) 14%/9%; medium dendrites (1.00–1.49 µm) 35%/45% and small dendrites (〈1 µm) 46%/40%. Despite evidence from previous studies, we found no evidence in this study for the presence of GABAergic interneurons or for GABA-containing projection neurons in AD or AV.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-1106
    Keywords: Superior colliculus ; Horseradish peroxidase ; Connections ; Albinism ; Thalamus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Subcortical connections of the superior colliculus were investigated in albino and pigmented rats using retrograde and anterograde tracing with horseradish peroxidase (HRP), following unilateral injection of HRP into the superior colliculus. Afferents project bilaterally from the parabigeminal nuclei, the nucleus of the optic tract, the posterior pretectal region, the dorsal part of the lateral posterior-pulvinar complex and the ventral nucleus of the lateral lemniscus; and ipsilaterally from the substantia nigra pars reticulata, the pars lateralis of the ventral lateral geniculate nucleus, the intergeniculate leaflet, the zona incerta, the olivary pretectal nucleus, the nucleus of the posterior commissure, the lateral thalamus, Forel's field H2, and the ventromedial hypothalamus. Collicular efferents terminate ipsilaterally in the anterior, posterior and olivary pretectal nuclei, the nuclei of the optic tract and posterior commissure, the ventrolateral part of the dorsal lateral geniculate nucleus, the pars lateralis of the ventral lateral geniculate nucleus, the intergeniculate leaflet, and the zona incerta; and bilaterally in the parabigeminal nuclei and lateral posterior-pulvinar complex (chiefly its dorsal part). The general topographical patterns of some of the afferent and efferent projections were also determined: the caudal and rostral parts of the parabigeminal nucleus project to the caudal and rostral regions, respectively, of the superior colliculus; caudal superior colliculus projects to the most lateral, and lateral superior colliculus to the most caudal part of the terminal field in the dorsal lateral geniculate nucleus; caudolateral superior colliculus projects to the caudal ventrolateral part of the ventral lateral geniculate nucleus, while rostromedial parts of the colliculus project more rostrally and dorsomedially. Following comparable injections in pigmented and albino animals, fewer retrogradely labelled cells were found in subcortical structures in the albino than in the pigmented rats. The difference was most marked in nuclei contralateral to the injected colliculus. Thus, the effects of albinism on the nervous system may be more widespread than previously thought.
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