bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crossed corticothalamic and thalamocortical connections of macaque prefrontal cortex
Authors: Preuss Todd M. , Goldman‐Rakic Patricia S. 
Published: January 2005

AbstractWe have conducted a systematic comparison of the ipsilateral (uncrossed) and contralateral (crossed) thalamic connections of prefrontal cortex in macaque monkeys, using cortical implants of horseradish peroxidase pellets and tetramethyl benzidine histochemistry to demonstrate anterograde and retrograde thalamic labeling. Contrary to the prevailing belief that thalamocortical projections are entirely uncrossed, our findings indicate that a modest crossed projection to prefrontal cortex arises from the mesial thalamus, principally the anteromedial and midline nuclei. Also, while confirming that corticothalamic projections are bilateral, we found that the pattern of crossed projections differs from that of uncrossed projections. Projections to mesial thalamic nuclei, specifically to the anteromedial nucleus, the midline nuclei, and the magnocellular part of the mediodorsal nucleus are bilateral, the contralateral projection being nearly as dense as the ipsilateral projection. Projections to the parvicellular part of the mediodorsal and ventral anterior nuclei are also bilateral, but the contralateral projection is much weaker than the ipsilateral projection. Prefrontal projections to the reticular nucleus, medial pulvinar, suprageniculate nucleus, and limitans nucleus appear to be exclusively ipsilateral.These results indicate that prefrontal cortex has prominent bilateral and reciprocal connections with the nuclei of the mesial thalamic region. As this region of the diencephalon has been implicated by anatomical and behavioral studies in memory functions, our findings suggest that prefrontal cortex, through its connections with this region, may be involved in the bilateral integration of mnemonic systems.
Neurotensin in projection neurons of the striatum and nucleus accumbens, with reference to coexistence with enkephalin and GABA: An immunohistochemical study in the cat
Authors: Sugimoto Tetsuo , Mizuno Noboru 
Published: January 2005

AbstractNeurotensin‐like immunoreactivity (NT‐LI) was demonstrated in projection neurons of the striatum and nucleus accumbens in the cat by combining immunohistochemistry and the fluorescent retrograde neuronal labeling method. In colchicine‐treated cats, many neurons with NT‐LI were found in the caudate nucleus, nucleus accumbens, and putamen. Most of these neurons were medium‐sized neurons with spiny dendrites. NT‐LI of neuronal elements in the caudate nucleus and nucleus accumbens formed dense aggregates with irregular figures, which appeared to correspond to the striosomes of Graybiel et al. (Proc. Natl. Acad. Sci. USA 75: 5723–5726, '78; Exp. Brain Res. 34: 189–195, '79; Neuroscience 6: 377–397, '81). Fibers with NT‐LI were distributed massively to the globus pallidus and ventral midbrain regions, but not to the entopeduncular nucleus. In the ventral midbrain regions, many fine varicose fibers with NT‐LI were distributed to the pars compacta and pars lateralis of the substantia nigra, ventral tegmental area, and retrorubral area. In the pars reticulata of the substantia nigra, however, fibers with NT‐LI were rather sparse.Examination of consecutive sections immunostained for NT, enkephalin (Enk), GABA, and substance P (SP) revealed that 50% of neurons with NT‐LI in the caudate nucleus and nucleus accumbens exhibited Enk‐LI, 15% showed GABA‐LI, and 5% manifested both Enk‐LI and GABA‐LI; no NT‐positive neurons in the striatum and nucleus accumbens showed SP‐LI. No morphological differences were found between NT‐positive neurons with Enk‐LI and/or GABA‐LI and those without Enk‐LI and GABA‐LI.Most neurons with NT‐LI in the striatum and nucleus accumbens were retrogradely labeled with True Blue injected into the globus pallidus, pars compacta and pars lateralis of the substantia nigra, and ventral tegmental area. After hemitransection severing neuronal connections between the ventral midbrain regions and the forebrain structures, fibers with NT‐LI and those with Enk‐LI in the ventral midbrain regions were markedly reduced in number.On the basis of the present results, combined with those reported previously, it was assumed that most of the NT‐containing neurons in the striatum and nucleus accumbens sent projection fibers massively to the globus pallidus, pars compacta and pars lateralis of the substantia nigra, and retrorubral area, and sparsely to the pars reticulata of the substantia nigra; NT‐containing striatal neurons with Enk‐LI sent projection fibers mainly to the globus pallidus, pars compacta and pars lateralis of the substantia nigra.
Development of the precerebellar nuclei in the rat: I. The precerebellar neuroepithelium of the rhombencephalon
Authors: Altman Joseph , Bayer Shirley A. 
Published: January 2005

AbstractShort‐survival thymidine radiograms from rat embryos aged 13–19 days were analyzed to delineate the precerebellar neuroepithelium of the rhombencephalon. The original definition of the term “rhombencephalon” was modified to refer only to the unique dorsal portion (surface plate) of the medulla and pons where the neural groove fails to fuse and, instead, the medullary velum covers the rhomboid lumen of the fourth ventricle. Initially, the neuroepithelial tissue of the rhombencephalon consists of a pair of rostral and caudal bridgeheads: the former the primary neuroepithelium of the cerebellum and the latter the primary neuroepithelium of the octavo‐precerebellar system. The spatial relationship between the cerebellar and precerebellar neuroepithelia soon changes as a result of ongoing morphogenetic events, such that the cerebellar primordium assumes a dorsal position and the precerebellar primordium a ventral position, and the distance between the two decreases. Concurrently the tela choroidea invaginates into the fourth ventricle and a secondary precerebellar neuroepithelium develops. The rostral portion of the secondary precerebellar neuroepithelium grows forward along the choroid plexus and forms the medial recess of the anterior fourth ventricle, while its caudal portion grows in the opposite direction beneath the medullary velum and forms the rostral wall of the posterior fourth ventricle. Evidence will be presented in the succeeding papers that the primary precerebellar neuroepithelium first generates the neurons of the inferior olive that migrate by a circumferential intramural (parenchymal) route to their destination. Next, the neurons of the lateral reticular and external cuneate nuclei are generated. These migrate by a posterior extramural (superficial) route and settle contralaterally. Subsequently, the primary precerebellar neuroepithelium produces the neurons of the nucleus reticularis tegmenti pontis and these form the anterior extramural migratory stream and settle ipsilaterally. Finally, the secondary precerebellar neuroepithelium produces the latest generated neurons of the basal pontine gray that follow the anterior extramural stream and settle ipsilaterally.
Development of the precerebellar nuclei in the rat: IV. The anterior precerebellar extramural migratory stream and the nucleus reticularis tegmenti pontis and the basal pontine gray
Authors: Altman Joseph , Bayer Shirley A. 
Published: January 2005

AbstractSequential thymidine radiograms from rats injected on days E16, E17, E18, and E19 and killed 2 hours after injection and at daily intervals up to day E22 were used to establish the site of origin, migratory route, and settling patterns of neurons of the nucleus reticularis tegmenti pontis and basal pontine gray. The nucleus reticularis tegmenti pontis neurons, which are produced predominantly on days E15 and E16, derive from the primary precerebellar neuroepithelium. These cells, unlike those of the lateral reticular and external cuneate nuclei, take an anteroventral subpial route, forming the anterior precerebellar extramural migratory stream. This migratory stream reaches the anterior pole of the pons by day E18. In rats injected on day E16 and killed on day E18 some of the cells that reach the pons are unlabeled, indicating that they represent the early component of neurons generated on day E15. The cells labeled on day E16 begin to settle in the pons on day E19, 3 days after their production. These cells, migrating in an orderly temporal sequence, form a posterodorsal‐to‐anteroventral gradient in the nucleus reticularis tegmenti pontis.Unlike the neurons of all the other precerebellar nuclei, the basal pontine gray neurons derive from the secondary precerebellar neuroepithelium. The secondary precerebellar neuroepithelium forms on day E16 as an outgrowth of the primary precerebellar neuroepithelium, and it remains mitotically active through day E19, spanning the entire period of basal pontine gray neurogenesis. The secondary precerebellar neuroepithelium is surrounded by a horizontal layer of postmitotic cells, representing the headwaters of the anterior precerebellar extramural migratory stream. In rats injected on day E18 and killed on day E19 the cells are labeled in the proximal half of the stream around the medulla but those closer to the pons are unlabeled, indicating an orderly sequence of migration. In rats injected on day E18 and killed on day E20 the labeled cells reach the pole of the pons. In the basal pontine gray the sequentially generated neurons settle in a precise order. The neurons generated on day E16 form a small core posteriorly and the neurons generated on days E17, E18, and E19 form regular concentric rings around the core in an inside‐out sequence.
The projection of the nucleus reticularis tegmenti pontis and adjacent regions of the pontine nuclei to the central cerebellar nuclei in the cat
Authors: Gerrits N. M. , Voogd J. 
Published: January 2005

AbstractThe projection of the nucleus reticularis tegmenti pontis (NRTP) and the pontine nuclei (NP) to the central cerebellar nuclei (CCN) was investigated by means of anterograde transport of tritiated leucine. Although termination was found in all the CCN, it was most pronounced in the lateral nucleus and the lateral aspect of the posterior interposed nucleus. The extreme lateral aspect of the anterior interposed nucleus and the caudal part of the fastigial nucleus received a projection of modest intensity. Termination in the infracerebellar nucleus and group Y is likely to be present but could not be confirmed with certainty from the light microscopical material. The contribution from the NP was small and originated from the dorsolateral and dorsal paramedian subdivisions of the NP. Within the NRTP the total area giving rise to projections to the CCN was extensive, and the origin of the projections to the individual CCN overlapped considerably.The projection of the NRTP to the ventrocaudal part of the lateral nucleus was found in conjunction with a projection to the ventrolateral part of the posterior interposed nucleus. Both projections seemed to branch off the fiber bundle terminating in the ventral paraflocculus. Similar correlations could be established in the projection of the NRTP to the dorsal paraflocculus and crus II of the ansiform lobule with other parts of the lateral and posterior interposed nuclei.It was concluded that the transverse, lobular organization of mossy fibers, which differs fundamentally from the longitudinal, modular organization of climbing fibers, is maintained in the collateral projection to the CCN. The results are further discussed in relation to the corticonuclear projection and the engagement of the NRTP and different parts of the CCN in pontocerebellar circuits.
Structural alteration and possible growth of afferents after kainate lesion in the adult rat thalamus
Authors: Peschanski Marc , Besson Jean‐Marie 
Published: January 2005

AbstractAfferents to the thalamic ventrobasal complex (VB) originating from the spinal cord, the dorsal column nuclei, and the somatosensory cortex were anterogradely labeled by WGA‐HRP 30 days after an injection of kainic acid (KA), which produced a complete unilateral neuronal loss in the VB, the opposite side being used as a control.At the light microscopic level, there was no obvious rerouting of spinal afferents away from the lesioned areas towards unlesioned parts of VB. There was an apparent decrease in the number of lemniscal afferents to the lesioned side, which may indicate a progressive retrograde degeneration. At higher magnification, all three afferent systems studied demonstrated morphological changes, predominantly manifested by terminal swellings that reached up to 25 μm in diameter. Control experiments suggested that these morphological alterations were related neither to a direct action of the excitotoxin nor to the absence of a different afferent system but to the loss of neuronal postsynaptic targets.At the electron microscopic level, the normal ultrastructural features of VB were not observed after a KA lesion. No neuronal somata, dendrites, or normal presynaptic elements were observed. Neural elements, some of which were labeled from the somatosensory cortex or the dorsal column nuclei, were essentially of two types: varicosities and unmyelinated axonal profiles. Varicosities could be separated into two broad classes: (1) The majority were large structures derived from large, sometimes myelinated, axons and containing a wealth of organelles. Since they were not completely surrounded by glial elements, we have denoted them unensheathed varicosities. Among the organelles, the most obvious features were vesicles and tubules of smooth endoplasmic reticulum, microtubules, mitochondria, and various lysosome‐like inclusions. These unensheathed varicosities gave rise to large, mound‐like protrusions containing large vacuoles and thin long protrusions either filled with neurofilaments or resembling unmyelinated axonal profiles. (2) Others were completely surrounded by a glial sheet and were therefore called ensheathed varicosities. These ensheathed varicosities presented several characteristics typical of degenerating profiles, including neurofilamentous proliferation and morphological alterations of the mitochondria. Unmyelinated axonal profiles occupied a substantial territory in the lesioned area. They were most often grouped in bundles sometimes wrapped by glial processes.The proliferation of unmyelinated fibers and the appearance of axonal varicosities are compared to the regeneration phenomena described in the literature after a lesion in the central nervous system. The hypothesis that the varicosities are growth‐cone‐like structures in the adult CNS is discussed.
Distribution of laminin and fibronectin along peripheral trigeminal axon pathways in the developing chick
Authors: Riggott Marcia J. , Moody Sally A. 
Published: January 2005

AbstractThe trigeminal region of the chick was studied with indirect immunofluorescence in order to determine whether extracellular matrix components might be distributed in such a way as to guide trigeminal axons to their peripheral targets in the mandibular arch. Tissue sections from stages 13–15 and 21/22 were immunolabeled indirectly with affinity‐purified antibodies raised against fibronectin and laminin, two extracellular matrix glycoproteins that support axon growth in vitro. Fibronectin was distributed ubiquitously throughout the head mesenchyme prior to and during initial axon growth from the brainstem (stages 13–15). Shortly after trigeminal axons reached their target tissues (stage 21/22), fibronectin immunolabeling was distributed throughout the head mesenchyme, but was present only at low levels in the trigeminal ganglion and motor nerve. Laminin immunolabeling was distributed in the lateral head mesenchyme at stage 13 as small specks and patches. At stage 14, when the motor axons first exit from the brainstem, short, linear arrays of laminin immunostaining were present from the basement membrane of the neural tube to the core of the mandibular arch, and many were parallel to the direction of axon growth. By stage 21/22 the trigeminal ganglion and motor root showed intense antilaminin immunofluorescence as did the central core of the mandibular arch. These studies suggest that the distribution of fibronectin within the head mesenchyme cannot give directional information to the growing trigeminal axons because of its homogeneous distribution. However, the initial distribution of laminin during the earliest stages of axon outgrowth may provide an extracellular matrix pathway that permits trigeminal axons to reach their targets.
Study of the selectivity of the impregnation of neurons by the Golgi method
Authors: Shimono Masatake , Tsuji Nobuyuki 
Published: January 2005

AbstractThe selectivity of the impregnation of neurons by the Golgi method was examined by comparing Nissl‐stained specimens with Golgi‐stained specimens in terms of the somatic orientation, cross‐sectional area, and long and short axes of the soma in the ventromedial hypothalamic nucleus (VMH) and lateral hypothalamic area (LHA) of 5‐week‐old rats. With regard to somatic orientation, we made comparisons directly between the Nissl distribution pattern and the Golgi pattern. The two distribution patterns did not differ significantly in either VMH or LHA (Smirnov test, P > 0.05). For somatic cross‐sectional area and diameter (long and short), a mean value of every 10% of the total frequency was estimated for each histogram; the histogram was segmented into 10 percentile frequency domains, and a mean value for each domain was estimated. A linear regression was calculated between Golgi mean values and Nissl's at the same place. By use of the linear regression, all of the observed values on Nissl sections for somatic cross‐sectional area and diameter were transformed into their corresponding Golgi values. The frequency distribution of these transformed Nissl values was compared with that of the actually observed Golgi values. There was a high degree of similarity between the two distribution patterns in all regions examined for long and short diameters as well as cross‐sectional area of the soma (Smirnov test, P > 0.05). These findings suggest that the sampling of VMH and LHA neurons in the Golgi method used in the present study is similar to the corresponding sampling in Nissl preparation. The result thus provides evidence that the Golgi method impregnates neurons nonselectively, at least hypothalamic neurons. We have also demonstrated, through direct comparisons between Nissl and Golgi specimens, that somatic orientation serves as a useful parameter in the evaluation of the selectivity/nonselectivity of the Golgi method.
Synaptic circuits involving an individual retinogeniculate axon in the cat
Authors: Hamos James E. , Van Horn Susan C. , Raczkowski Denis , Sherman S. Murray 
Published: January 2005

AbstractIn order to describe the circuitry of a single retinal X‐cell axon in the lateral geniculate nucleus, we physiologically characterized such an axon in the optic tract and injected it intra‐axonally with horseradish peroxidase. Subsequently, we recovered the axon and employed electron microscopic techniques to examine the distribution of synapses from 18% of its labeled terminals by reconstructing the unlabeled postsynaptic neurons through a series of 1,200 consecutive thin sections. We found remarkable selectivity for the axon's output, since only four of the 43 available neurons in a limited portion of the terminal arbor receive synapses from labeled terminals. Moreover, the distribution of these synapses on the four neurons, which we term cells 1 through 4, varies with respect to synapses from other classes of terminals that contact the same cells, including synapses from unlabeled retinal terminals. For cells 1 and 3, the labeled terminals provide 49% and 33%, respectively, of their retinal synapses, and these are located on both dendritic shafts and appendages. Synapses from the injected axon to these cells are thus integrated with those from other retinal axons. For cell 2, the labeled terminals provide 100% of its retinal synapses, but these synapses converge on clusters of dendritic appendages where they are integrated with convergent inhibitory inputs. Finally, for cell 4, the labeled terminals provide less than 2% of its retinal inputs, and these are distally located; we suggest that these synapses are remnants of physiologically inappropriate miswiring that occurs during development. The findings from this study support a concept of selectivity in neuronal circuitry in the mammalian central nervous system and also reveal some of the diverse integrative properties of neurons in the lateral geniculate nucleus.
Growth of axons into developing muscles of the chick forelimb is preceded by cells that stain with Schwann cell antibodies
Authors: Noakes Peter G. , Bennett Max R. 
Published: January 2005

AbstractA study has been made of the development of limb and muscle nerves in relation to the first appearance of Schwann cells in the flexor digitorum profundus (fdp) and flexor carpi ulnaris (fcu) muscles of the avian forelimb. Schwann cells were identified by immunofluorescent techniques with antibodies to the glycoprotein HNK‐1. Myotubes and nerves were identified by using antibodies to myosin and to neurofilament, respectively. At stage 24/25 The brachialis longus inferior (Bli n) and superior (Bls n) nerve trunks within proximal regions of the forelimb were surrounded by Schwann cells. These cells extended in a column for a distance of approximately 100 μm beyond the growing ends of nerves. At stage 26 both interosseus nerve (in n) and the medial‐ulnar nerve (m‐u n) had formed from the Bli n; each of these branches was surrounded by Schwann cells, which again extended approximately 100 μm beyond the growing ends of the nerves. By stage 26/27 the fdp and fcu muscles were clearly delineated by groups of myotubes. No nerves were detected within these groups; however, Schwann cells were observed between the myotubes. At stage 27 axons had left the in n and m‐u n and grown into the fdp and fcu muscles, respectively. These axons were surrounded by Schwann cells.The present observations show that Schwann cells are located ahead of the main limb and muscle nerves as they grow into the fdp and fcu muscles of the limb. It is possible that these Schwann cells play a role in guiding nerves to their correct muscles in the developing chick forelimb.