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  • 1
    Electronic Resource
    Electronic Resource
    REGIONALIZATION OF THE PROSENCEPHALIC NEURAL PLATE (1998)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Neuroscience 21 (1998), S. 445-477 
    Details
    ISSN: 0147-006X
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Medicine
    Notes: Abstract Recent embryological studies are beginning to establish that the underlying organization of the forebrain may be reduced to relatively simple elements that are common to all vertebrates. We begin this chapter by reviewing studies that describe the similarities in prospective fate and molecular organization of the developing neural plate in fish, frogs, chickens, and mice. The chapter next addresses mechanisms that regulate regional specification in the anterior central nervous system. There is now evidence that the axial mesendoderm anterior to the notochord (the prechordal plate) has a central role in induction of the floor and basal plate primordia (hypothalamus) of the forebrain. Patterning of the anterolateral neural plate (telencephalon) may be regulated by FGF8 produced in the anterior neural ridge. Thus, the synthesis of information from fate mapping and experimental embryological and genetic studies is illuminating the mechanisms that generate the different components of the forebrain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.neuro.21.1.445
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  • 2
    Electronic Resource
    Electronic Resource
    Mesencephalic and diencephalic afferent connections to the thalamic nucleus rotundus in the lizard, Psammodromus algirus (2002)
    Oxford, UK : Blackwell Science, Ltd
    European journal of neuroscience 16 (2002), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The present work is an analysis of the afferent projections to the thalamic nucleus rotundus in a lizard, both at the light- and electron-microscopic level, using biotinylated dextran amine (BDA) as a neuroanatomical tracer. This study has confirmed previously reported afferent projections to nucleus rotundus in reptiles and has also identified a number of new cellular aggregates projecting to this dorsal thalamic nucleus. After BDA injections into nucleus rotundus, retrogradely labelled neurons were observed consistently within the following neuronal groups in the midbrain and the diencephalon: (i) the stratum griseum centrale of the optic tectum; (ii) the nucleus subpretectalis in the pretectum; (iii) the nucleus ansa lenticularis posterior, the posterior nucleus of the ventral supraoptic commissure, and the posteroventral nucleus, in the dorsal thalamus and (iv) the lateral suprachiasmatic nucleus and part of the reticular complex in the ventral thalamus. Tectal axons entering nucleus rotundus were fine and varicose and formed exclusively asymmetric synaptic contacts, mainly on small dendritic profiles. Rotundal neurons had symmetric synapses made by large boutons probably of nontectal origin. After comparing our results with those in other reptiles, birds and mammals, we propose that the sauropsidian nucleus rotundus forms part of a visual tectofugal pathway that conveys mesencephalic visual information to the striatum and dorsal ventricular ridge, and is similar to the mammalian colliculo-posterior/intralaminar–striatoamygdaloid pathway, the function of which may be to participate in visually guided behaviour.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9568.2002.02091.x
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  • 3
    Electronic Resource
    Electronic Resource
    Morphological Fate of Rhombomeres in Quail/Chick Chimeras: A Segmental Analysis of Hindbrain Nuclei (1995)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 7 (1995), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Quail rhombomeres two to six (r2-r6) were individually grafted homotopically into the hindbrain of chick embryos at 2 days of incubation. Nine to 10 days after the operation the chimeric embryos were fixed and processed for parallel cytoarchitectural and immunocytochemical study (with an anti-quail antibody) in order to map the anatomical fate of the grafted tissue. Emphasis was placed on conventionally identified and distinct neuronal populations composing the sensory and motor longitudinal columns. Grafted rhombomeres consistently developed as complete transverse slices of the chimeric hindbrain. Interrhombomeric cell migration was either sparse or restricted to specific nuclei. The cranial nerve motor nuclei showed rhombomeric origins consistent with the patterns described in early embryos. Unexpectedly, alar r2 was found to form the auricular part of the cerebellum. As regards the cochlear nuclei, we found that nucleus angularis derives from r3 to r6, nucleus laminaris from r5 to r6, nucleus magnocellularis from r6 to r7 and nucleus olivaris superior from r5. The nuclei of the lateral lemniscus originated between r1 and r3. We also delimited the respective rhombomeric subdivisions of the sensory vestibular and trigeminal columns, both of which extend from r1 caudalwards throughout the hindbrain. There were consistently some interrhombomeric neuronal migrations inside the vestibular column, some motor nuclei and the reticular formation, involving only one rhombomere length. The pontine nuclei, which extended from r1 to r7, showed neuronal migrations that crossed several rhombomeres. On the whole, these results represent the first anatomical analysis of the mature avian hindbrain in terms of rhombomere-derived domains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.1995.tb00693.x
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  • 4
    Electronic Resource
    Electronic Resource
    A Golgi-Study of oculomotor neuroblasts migrating across the midline in chick embryos (1978)
    Springer
    Anatomy and embryology 152 (1978), S. 205-215 
    Details
    ISSN: 1432-0568
    Keywords: Oculomotor ; Neuroblast ; Migration ; Neurotropism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The Golgi-Stensaas impregnation technique was employed at appropriate stages of development to study the morphology of the oculomotor neuroblasts as these migrate across the midline. Data reported in previous publications were confirmed, such as the timing of the migration (occurring between the 4th and the 9th days of inoculation), the fact that the migrating cells carry their axons across the midline as trailing processes, and the absence of prexisting fibrillar structures able to provide contact guidance for this migration. The most striking new fact discovered is that the leading processes of the oculomotor neuroblasts are often branched, and that all these branches are uniformly oriented towards the midline. This seems to indicate the existence of a non-random growth process. It is argued in the discussion that this can be explained through the presence of an orienting neurotropic influence. This one could have its source in certain non-oculomotor neuroblasts which were detected within the midline ventricular zone. On morphological grounds, this group of cells may be tentatively identified as the avian counterpart of the midventral mesencephalic proliferation described in several mammals. This proliferative zone is known to contain dopamine at early stages of development. A hypothetic causal mechanism of the oculomotor migration is therefore advanced, wherein dopamine, diffusing out of the non-oculomotor midline neuroblasts, induces at short range oriented outgrowth of oculomotor leading processes across the midline.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00315925
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  • 5
    Electronic Resource
    Electronic Resource
    A Golgi study on the early sequence of differentiation of ganglion cells in the chick embryo retina (1981)
    Springer
    Anatomy and embryology 161 (1981), S. 305-317 
    Details
    ISSN: 1432-0568
    Keywords: Neurogenesis ; Neuroblast ; Retina ; Ganglion cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary An examination of retinal structure in chick embryos, impregnated with the Golgi-Stensaas method between 2 and 6 days of incubation, discloses, on the one hand, a uniform typology of the proliferating ventricular cells, the pre- and postmitotic forms of which were tentatively identified; on the other hand, postmitotic neuroblasts are evidenced in the stages of differentiation previous to the growth of their neurites. In the earliest embryos (up to 51/2 days of incubation), all cells that detach from the ventricular lining to differentiate as neurons do so while the ventricular cell precursor has an interphasic configuration. This means that, although they free themselves from the scleral attachment site, they keep for a while a vitreal attachment. The vitreally-attached endfeet subsequently transform into axonal growth cones, sprouting filopodia and lamellipodia. While the axons grow towards the optic nerve head, cell bodies and remaining scleral processes are progressively retracted inwards, leading to the appearance of typical ganglion cells. After 51/2 days of incubation, a great number of postmitotic neuroblasts detach while still in the G1 phase of the ventricular cell cycle. Those of them that show the longest leading processes become also ganglion cells, after their leading tip has acquired a growth cone configuaration and has bent into the optic fiber layer. These results on early mechanisms of ganglion cell genesis are discussed in relation to data in the literature, and a simple hypothesis is offered which explains the biphasic pattern in which presumptive ganglion cells detach from the ventricular lining of the chick retina.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00301828
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  • 6
    Electronic Resource
    Electronic Resource
    Autoradiographic and Golgi study on the early development of n. isthmi principalis and adjacent grisea in the chick embryo: a tridimensional viewpoint (1987)
    Springer
    Anatomy and embryology 176 (1987), S. 19-34 
    Details
    ISSN: 1432-0568
    Keywords: Neurogenesis ; Isthmic nuclei ; Isthmic migration ; Neuromeres ; Neuroblasts ; Generation patterns
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Neurogenesis, cell migration and early histogenesis of the isthmic nuclear complex in chick embryos were investigated in autoradiographic and Golgi material. The aim of the experimental observations was to detect whether the apparent origin of different grisea of this complex at separate matrix territories (neuromeres) was accompanied by peculiar generation patterns, consistent with predictions of neuromeric theory. Differential birthday patterns were indeed obtained for a) n. semilunaris — born in the rh1a rhombomere, b) n. isthmi principalis pars parvocellularis, nn. lemnisci lateralis dorsalis and ventralis, and n. isthmi ventralis — born in the isthmic rhombomere, and c) n. isthmi principalis pars magnocellularis — born at the m1 mesomere. Only the nuclear group at (b) shows a clear-cut gradient of generation. The morphological analysis aimed to describe isthmic neuroblast cell form before, during and immediately after migration into the mesencephalic optic lobe. Golgi data indicate that isthmic neuroblasts emerge as free cells from the matrix and aggregate into a dense superficial mantle layer. Between stages HH26 and 30, the whole mass of cells translocates tangentially in a rostrolateroventral direction, invading the m2 mesomere. The individual migrating neuroblasts have a leading axonal process which rapidly grows into the tectum in advance of the cell body, which follows at a slower pace. As the migration runs to an end the neuroblasts start to differentiate, sprouting dendritic processes. A joint origin in the isthmic mantle primordium is proposed for the nuclear group at (b) (above), whereas n. isthmi principalis pars magnocellularis is formed separatedly from the rest, and shows no tangential migratory behaviour of its neuroblasts. The complex histogenetic and morphogenetic processes at the isthmo-mesencephalic boundary may be explained on the basis of these new data, but this requires a tridimensional viewpoint that is exposed in the Discussion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00309748
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  • 7
    Electronic Resource
    Electronic Resource
    Do oculomotor neuroblasts migrate across the midline in the fetal rat brain? (1977)
    Springer
    Anatomy and embryology 150 (1977), S. 187-206 
    Details
    ISSN: 1432-0568
    Keywords: Migration ; Neuroblast ; Oculomotor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Toluidine blue-stained semithin sections and Cajal-Castro preparations are used to study in rat fetuses whether oculomotor neuroblasts migrate across the midline at a certain period of development. In confirmation of previous studies, a group of oculomotor neuroblasts was detected which first grow cytoplasmic processes into the mesencephalic midline, and afterwards translocate their somata towards the midline, between the 12th and the 15th days of gestation. At this moment a midline mass of neuroblasts characterizes the meeting at this landmark of both left and right migrating neuroblastic groups. No crossing oculomotor axons yet are demonstrable with reduced silver techniques. In further stages of development the neuroblasts continue their migration until they arrive at the contralateral nucleus at the 16th and 17th day of gestation. At the midline the mass of neuroblasts disappears gradually and crossed oculomotor axons become visible. The electron microscope was then used to study ultrastructurally the migrating motoneurons. It was discovered that no preexisting structure guides their movement by contact. Their leading processes show no filopodial activity, and contain abundant microtubules and thick bundles of neurofilaments in eccentric position. The neuroblasts carry their axon across the midline as a trailing process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00316650
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  • 8
    Electronic Resource
    Electronic Resource
    Two modes of free migration of amacrine cell neuroblasts in the chick retina (1987)
    Springer
    Anatomy and embryology 175 (1987), S. 281-287 
    Details
    ISSN: 1432-0568
    Keywords: Amacrine neuroblasts ; Migration ; Retina
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The migration of amacrine neuroblasts toward the prospective amacrine cell layer in the chick embryo retina has been studied, in Golgi-stained sections, between days 5 and 9 of embryogenesis. Two distinct populations of presumptive amacrine neuroblasts have been identified on the basis of their shape and migratory behavior. One population (smooth amacrine neuroblasts) display smooth, monopolar or bipolar contours, moving freely across the retina without major changes in the original postmitotic shape, and give processes only after reaching the primitive inner plexiform layer. The second population (multipodial amacrine neuroblasts) includes multipolar neuroblasts with abundant filiform and/or lamelliform processes sprouting in various directions; these highly plastic cells begin modifying their shapes at the time of release from the ventricular lining and continue to do so as they move toward their definitive location. Thus, the well-known heterogeneity of adult amacrine cells seems to be preluded by differences in neuroblastic migratory patterns, suggesting the existence of at least two different subsets of amacrine cell precursors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00309842
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  • 9
    Electronic Resource
    Electronic Resource
    Postembryonic neural proliferation in the zebrafish forebrain and its relationship to prosomeric domains (1999)
    Springer
    Anatomy and embryology 199 (1999), S. 329-348 
    Details
    ISSN: 1432-0568
    Keywords: Key words Diencephalon ; Forebrain ; Proliferating cell nuclear antigen ; Prosomeres ; Zebrafish brain development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Large gaps of knowledge exist regarding postembryonic brain morphogenesis of the zebrafish Danio rerio (Cyprinidae, Teleostei). The zebrafish represents – together with the frog (Xenopus), chick and mouse – one of four major models for the genetic study of early brain development. Here, we used normal silver-stained Bodian material and immunohistochemical material stained with a monoclonal antibody against the proliferating cell nuclear antigen (PCNA, cyclin) to study the morphogenetic appearance and location of proliferation zones of the zebrafish brain between day 1 and day 10, focussing on the forebrain at day 5 postfertilization. Our results directly demonstrate that the dorsal telencephalic proliferation zone (i.e. the pallium) extends – consistent with the process of eversion – some distance laterally on top of the telencephalon. The subpallial telencephalic proliferation consists of dorsal and ventral zones. The preoptic region also includes dorsal and ventral proliferation zones. In the diencephalon proper, separate proliferation zones are present in the habenula, and in the periventricular cell masses of the dorsal thalamus, the ventral thalamus, and the pretectum. More ventrocaudally, the latter three massive proliferation zones appear to be replaced each by thinner, but distinct proliferation zones. Two of them represent ventrocaudal continuations of the dorsal and ventral thalamus and lie in the region referred to as the posterior tubercular area in adult teleostean neuroanatomy. The third lies in the region of the nucleus of the medial longitudinal fascicle. In addition, several hypothalamic proliferation zones are present. The data for the diencephalon are largely in agreement with the neuromeric model of brain organization of Puelles and Rubenstein (1993), which is mostly based on amniote data. Generally, the understanding of the prosomeric origin of teleostean prosencephalic cell masses may be regarded as pivotal for their comparative interpretation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004290050232
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  • 10
    Electronic Resource
    Electronic Resource
    Cytoarchitectonic subdivisions in the subtectal midbrain of the lizard Gallotia galloti (2000)
    Springer
    Journal of neurocytology 29 (2000), S. 569-593 
    Details
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Contemporary study of molecular patterning in the vertebrate midbrain is handicapped by the lack of a complete topological map of the diverse neuronal complexes differentiated in this domain. The relatively less deformed reptilian midbrain was chosen for resolving this fundamental issue in a way that can be extrapolated to other tetrapods. The organization of midbrain centers was mapped topologically in terms of longitudinal columns and cellular strata on transverse, Nissl-stained sections in the lizard Gallotia galloti. Four columns extend along the whole length of the midbrain. In dorsoventral order: 1) the dorsal band contains the optic tectum, surrounded by three ventricularly prominent subdivisions, named griseum tectale, intermediate area and torus semicircularis, in rostrocaudal order; 2) a subjacent region is named here the lateral band, which forms the ventral margin of the alar plate and also shows three rostrocaudal divisions; 3) the basal band forms the basal plate or tegmentum proper; it appears subdivided into medial and lateral parts: the medial part contains the oculomotor and accessory efferent neurons and the medial basal part of the reticular formation, which includes the red nucleus rostrally; the lateral part contains the lateral basal reticular formation, and includes the substantia nigra caudally; 4) the median band contains the ventral tegmental area, representing the mesencephalic floor plate. The alar regions (dorsal and lateral) show an overall cellular stratification into periventricular, central and superficial strata, with characteristic cytoarchitecture for each part. The lateral band contains two well developed superficial nuclei, one of which is commonly misidentified as an isthmic formation. The basal longitudinal subdivisions are simpler and basically consist of periventricular and central strata.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011067918585
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