bluuebunny/crossref_metadata_2025_split huggingface dataset:
Time of neuron origin in the diencephalon of the mouse. An autoradiographic study
Authors: Angevine Jay B. 
Published: December 2004

AbstractTime of origin of neurons of thalamus ventralis, thalamus dorsalis, and epithalamus was determined autoradiographically at three transverse levels in adults which received thymidine‐H3 once during gestation. A ventrodorsal gradient in the entire region demonstrates a wave of neuron origin in the forebrain, probably rostrocaudal originally but revectored by rearrangement of neuromeres I–III. A caudorostral gradient in dorsal thalamus similarly may represent redirection of an earlier ventrodorsal one. A lateromedial gradient in dorsal thalamus and epithalamus (opposite that in cortex) may reflect lateral displacement of neuroblasts (or their nuclei) by younger elements. Large neurons generally arise before small ones, as seen in epithalamus; the two habenular nuclei illustrate programmed origin of large and small neurons and glia consecutively, with progressively restricted potentiality by the primitive ependyma. Phylogenetically, slight differences in duration of proliferation might radically alter the numbers of small neurons. Although dorsal thalamic nuclei “appear” in external germinal and mantle layers, their neuroblasts originate in primitive ependyma; time of origin accords with subsequent recognition of nuclei and appearance of thalamocortical connections. Massive proliferation (from the 10th to 15th days of gestation) and the gradients overshadow nuclear differences and demonstrate a developmental unity in the dorsal thalamus. The findings further validate Herrick's diencephalic zones and suggest some orderly mechanism, probably at the molecular level, underlying generation of the neurons in this complex brain region.
Thalamo‐cortical projections in the tree shrew (Tupaia glis)
Authors: Diamond I. T. , Snyder M. , Killackey H. , Jane J. , Hall W. C. 
Published: December 2004

AbstractCortical lesions were placed in 18 hemispheres, and thalamic degeneration was studied after a survival period of at least six weeks. Very small lesions within the striate area produced complete degeneration of neurons in a column through the lateral geniculate, from medial to lateral borders and comprising all of the laminae. Lesions of various loci within the striate area reveal a precise topographic projection, with the rostral lateral geniculate sending fibers to the caudal extremity of the striate area and the caudal lateral geniculate projecting to the rostral extremity of the striate; further, the dorso‐ventral dimension in the lateral geniculate projects to the medio‐lateral dimension in the striate area. Finally, the evidence from striate area lesions suggests that the lateral geniculate projections are confined to the striate area as defined by cytoarchitecture, which in turn corresponds precisely with visual area I as defined by electrophysiological recording. This conclusion is supported by the failure to find retrograde degeneration after lesions of the belt of cortex adjacent to the striate area. The temporal area which occupies an extensive section from V II to the rhinal fissure and the auditory cortex and which has been shown to be a visual receiving area, is the target of essential projections from the pulvinar. The pulvinar also sends sustaining collaterals within the temporal area and probably outside as well, especially to V II. However, the very crude topographic organization apparent in the pulvinar projections does not seem to be sufficiently refined to account for the organization of V II. A suggestion was made in closing that V II may be the result of convergent evolution in different mammalian lines of descent.
Functional variation in dermatomes in the macaque monkey following dorsal root lesions
Authors: Kirk Edwin J. , Denny‐Brown D. 
Published: December 2004

AbstractPrevious definitions of dermatomes, in various species, have revealed a characteristic pattern of serial overlapping root areas. Most investigators have used either the method of “remaining sensibility” or recordings of dorsal nerve root potentials, and have sectioned the dorsal nerve roots within the spinal canal, proximal to the dorsal root ganglia.We have used the method of “remaining sensibility” in experiments in macaque monkeys. Section of the neighboring dorsal roots proximal to their ganglia produced dermatomes which resembled closely those isolated by Sherrington. However, we found consistently that when the neighboring spinal nerves were sectioned distal to their dorsal root ganglia, the isolated root areas on the trunk were approximately twice as large as before and now also showed persistent hyperesthesia. Re‐sectioning of the dorsal roots of these nerves within the dura reduced the isolated root areas to their “classical” size, but usually only after a delay of three or four days. The injection of subconvulsive doses of strychnine sulfate solution produced an enormous expansion of an isolated dermatome, irrespective of whether the neighboring roots had been sectioned intradurally or beyond their ganglia; no change in area was observed after the injection of morphine sulfate solution. Conversely, the size of a dermatome which had been isolated by intradural section of three dorsal roots above and below was reduced by subsequent section of three additional roots above and below.We have concluded that the observed size of an isolated dermatome is a variable quantity and can be taken as an index of the efficiency of sensory transmission within the same and neighboring segments of the spinal cord.
The salivatory nuclei in the brainstem of the monkey (Macaca mulatta)
Authors: Bijlani Veena , Keswani N. H. 
Published: December 2004

AbstractBy inducing retrograde degeneration the salivatory nuclei were localized in the brainstem of the Macaca mulatta. It was observed that the neurons sending efferent fibres to the three salivary glands lie in two discrete groups, the lateral and medial salivatory nuclei situated under the floor of the fourth ventricle at the level of the pontomedullary junction. The lateral nucleus was in close relation to the medial and lateral vestibular nuclei, was about 0.3 mm long and consisted of mediumsized neurons. The medial nucleus was situated close to the median raphe, was about 0.5 mm long and consisted of smaller‐sized neurons. The caudal parts of the nuclei showed evidence of sending fibres to the ipsilateral glands, the cranial parts to the contralateral glands, and that the intermediate zones sent fibres bilaterally.
A quantitative study of the purkinje cells in the cerebellum of the albino rat
Authors: Armstrong David M. , Schild Renée F. 
Published: December 2004

AbstractHistological techniques have been used to study the layer of Purkinje cells in the cerebellum of the albino rat. A method has been devised for “unfolding” the layer into two dimensions. The shape after unfolding strikingly resembled the shape of the unfolded human cerebellar cortex. The total area of the Purkinje cell layer after histological processing was estimated at between 270 and 280 mm 2 in four rats, and at 240 mm 2 in a fifth. Approximately 25% of the layer lies rostral to the primary fissure. In each of three rats the mean density of cells in the Purkinje cell layer was approximately 1,200 cells/mm2. There were considerable local variations in cell density. In these theree rats the total number of Purkinje cells present in the cerebellar cortex was estimated to be 3.2 × 105, 3.2 × 105 and 3.6 × 105 cells. The limitations of the methods used have been discussed.
Projection fibers from the main sensory trigeminal nucleus and the supratrigeminal region
Authors: Mizuno Noboru 
Published: December 2004

AbstractFiber projections from the main sensory trigeminal nucleus and the supratrigeminal region (reticular formation dorsal and rostrodorsal to the motor trigeminal nucleus) in the cat and monkey have been studied by the Nauta, Fink‐Heimer and Marchi methods.Following experimental lesions in the main sensory trigeminal nucleus and its vicinity, the crossed ventral and the uncrossed dorsal trigeminal tracts were traced rostrally to the posteromedial ventral nucleus of the thalamus. The uncrossed dorsal trigeminal tract ascended through Forel's tegmental fascicle (tractus fasciculorum tegmenti Foreli). However, Forel's tegmental fascicle was composed mainly of the ascending reticular fibers terminating in the intralaminar nuclei of the thalamus and in the subthalamus. Commissural components distributing chidfly to the motor trigeminal nucleus of the opposite side appeared to arise from the supratrigeminal region as well as from the main sensory trigeminal nucleus. A fiber bundle, arising from the reticular zones surrounding the motor trigeminal nucleus, descended through the lateral reticular formation immediately ventromedial to the spinal trigeminal nucleus down to lower levels of the medulla oblongata.The functional significance of the supratrigeminal region as an interneuron system intercalated between the trigeminal sensory and the cranial motor systems is discussed.
Anatomy of cultured mouse cerebellum. I. Golgi and electron microscopic demonstrations of granule cells, their afferent and efferent synapses
Authors: Wolf Merrill K. , Dubois‐Dalcq Monique 
Published: December 2004

AbstractThe development of granule cells and their connections was reinvestigated in organotypic cultures of cerebellum. Modified Golgi‐Cox preparations showed numerous maturing granule cells, some with fully mature claw‐shaped dendritic endings, within presumptive cortex. Large cortical neurons often had dendrites richly encrusted with synaptic spines. Sometimes bundles of thin parallel processes were oriented orthogonally to the spiny dendrites. Semithin sections and electron micrographs showed granule cell somas distributed in closely packed clusters, with directly apposed cell membranes. Several types of glio‐glial membrane apposition were observed, including extensive desmosome‐like junctions. The neuropil contained closely packed bundles of thin parallel processes and numerous synaptic complexes, often within the parallel bundles. The postsynaptic elements, when identifiable, often proved to be dendritic spines; axodendritic and axosomatic synapses were less common than axospinous. A few synaptic complexes resembled glomeruli, with linked granule cell dendrites surrounding a presynaptic element. The concurrence of several lines of evidence proves the identity of granule cells in presumptive cortex, but the existence of basket and Golgi Type II neurons and the source of presynaptic element in the glomerulus cannot be demonstrated. The criteria and importance of rigorous cell identification in cultures are discussed.
The inner plexiform layer of the vertebrate retina: A quantitative and comparative electron microscopic analysis
Authors: Dubin M. W. 
Published: December 2004

AbstractThe inner plexiform layer of human, monkey, cat, rat, rabbit, ground squirrel, frog and pigeon retinas was studied by electron microscopy. All showed the same qualitative synaptic arrangements: bipolar cells made dyad ribbon synapses onto amacrine and ganglion cells; amacrine cells made conventional synaptic contacts onto bipolar, ganglion cells; amacrine cells montage of electron micrographs through the full thickness of the inner plexiform layer were made for each species and were scored for synaptic contacts. Both absolute and relative quantitative differences were found between species. The ratio of amacrine cell (conventional) synapses to bipolar cell (ribbon) synapses, the absolute number of amacrine cell synapses and the number of inter‐amacrine cell synapses were all found to be higher in those animals which are known to have relatively complex retinal ganglion cell receptive field properties. It is suggested that the amacrine cell is involved in mediating complex visual transformations in certain vertebrate retinas.
Distribution of thymidine‐H3 in the overgrown brain of the chick embryo
Authors: Wilson Doris Burda 
Published: December 2004

AbstractThe pattern of incororation of thymidine‐H3 was studied in chick embryos in which overgrowth was experimentally induced in the optic tectum. Radioautograhs were prepared for experimental and control embryos ranging in age from three to five days' incubation at post‐label periods of one hours, and eight hours. Under conditions of overgrowth, S‐phase cells are situated not only in the periphery of the wall of the tectum, but are also found scattered among mitotic cells along the ventricular border. Labeled intraventricular cells are commonly seen in the defective brains. The onset of neuroblast differentiation, as indicated by a loss in ability of certain cells to incorporate thymidine‐H3, appears to be the same in the tectum of experimental and normal embryos and takes place toward the end of the fourth day of incubation. As development continues, the pattern of labeling becomes increasingly distorted in the severely affected potions of the overgrown tectum, and neuroepithelial cells become interspersed among differentiated neuroblasts.
Projections of the subnucleus caudalis of the trigeminal nucleus in the sheep
Authors: Roberts P. A. , Matzke H. A. 
Published: December 2004

AbstractA study has been made of the efferent connections of the trigeminal sibnucleus caudalis in 12 shep. Lesions were placed in this nucleus either surgically or by means of an electrical cautery device. Resulting degeneration was determined by staining serially prepared frozen sections according to the silver techniques of Nauta and Fink‐Heimer. Ipsilateral connections are desribed with the fifth, seventh eleventh and twelfth cranial nerve motor nuclei, and ascending ipsilateral connections with all of the more rostral portions of the trigeminal nuclear complex. Evidence of widespread bilateral trigemino‐reticular connections is reported. By contrast, only a small number of fibers from the subnucleus caudalis were found to ascend in the mdial lemniscus; few of these lemniscal fibers appear to ascend beyond mesencephalic levels.
Neuron‐glia relationship during granule cell migration in developing cerebellar cortex. A Golgi and electonmicroscopic study in Macacus rhesus
Authors: Rakic Pasko 
Published: December 2004

AbstractThe cytology of the postmitotic migratory granule cell and its relationship to Bergmann glial processes was examined with Golgi staining and electron microscopy in the three cardinal planes in the developing cerebellar cortex of Macacus rhesus at various late fetal and early postnatal ages. After final mitosis the granule cell body transforms from a nearly round shape in the superficial zone of the external granular layer to a horizontal bipolar form with elongated processes oriented longitudinally to the folium, at the outer border of the molecular layer. Another descending process develops, and the cell soma becomes a pyramid flattened in the plane longitudinal to the folium. The nucleus moves into the descending process and the cell soma assumes a vertically oriented spindle shape while migrating among previously formed parallel fibers deeper in the molecular layer, and finally attains a round shape again when it lies deep to the Purkinje cell layer. During these transformations, the cell cytoplasm becomes more voluminous and contains a prominent Golgi apparatus, numerous free ribosomes, mitochondria, multivesicular and dense bodies, and fascicles of microtubules Longitudinally oriented microtubules concentrated in the vertical leading process disappear by the time the cell soma enters the granular layer. The slender trailing process loss most of its cytoplasmic organelles, acquires microtubules and together with the horizontal processes forms the characteristic T‐shaped axon. The axon forms synapses with Purkinje and stellate cell dendrites at a time when other granule cells are still migrating among them.During the entire course of their migration across the molecular layer, granule cells are directly apposed to vertically oriented Bergmann fibers belonging to the Golgi epithelial cells. The sequence of developmental stages indicates that Golgi epithelial cells are a type of protoplasmic astrocyte. The Bergmann fibers were present at all stages examined, and their constant apposition to granule cells suggests a role in the lartter's migration. Numerous electronluscent beady enlargements are seen along the fiber except at sites were the surface is in contact with migrating cells; probably these enlargements change position as the granule cells pass along the Bergmann fiber. Lamellate expansions also project from the main shaft of the glial fiber and envelop the synaptic sites on spines of Purkinje cell dendrites. These expansions seem more durable, and the young neuron appears to avoid collision with them by sprialling around the glial shaft during its descent to the granular layer. The neuron‐glia relationship apparently provides the necessary conditions for the migration of the young granule cell. Especially at late developmental stages when the molecular layer is more than 250 μ wide and is densely packed with highly oriented cell processes that have already established synaptic connections.
Synapses made by myelinated fibers running to teleost and elasmobranch retinas
Authors: Witkovsky Paul 
Published: December 2004

AbstractMyelinated fibers are described in teleost (carp, goldfish) and elasmobranch (dogfish) retinas which make synapses onto amacrine cell bodies and bipolar cell terminals. The fibers run in parallel with bundles of optic nerve fibers radiating from the optic disk until at some point they traverse the inner plexiform layer, turning again horizontally to course under the layer of amacrine cell bodies for 0.5–0.75 mm. En route each fiber makes several en passant synapses characterized by a cessation of the myelin sheath, a local increase in axonal diameter, an accumulation of agranular vesicles 300–400 Å in diameter and increased densification of pre‐ and post‐synaptic membranes. These fibers are not post‐synaptic to any retinal element. The evidence that the myelinated fibers described form an efferent system is based on their resemblance in many particulars to the centrifugal fiber system innervating the pigeon retina. Degeneration experiments, however, could not distinguish conclusively between a true efferent system, originating in some central nucleus, and a recurrent collateral system branching from afferent optic nerve axons.
Changes in the numbers of neurons and glial cells in the lateral geniculate nucleus of the monkey during retrograde cell degeneration
Authors: Mihailović Ljubodrag T. , Čupić Dragoslava , Dekleva Nikola 
Published: December 2004

AbstractThe time‐course of disintegration of neurons, and the concomitant reactions of various types of glial cells, in the dorsal nucleus of the lateral geniculate body (LG) were studied in 12 Rhesus monkeys sacrificed in groups of two at time intervals of 1, 3, 6, 12, 25 and 50 weeks following unilateral removal of the occipital lobe. The change in the mean number of neurons, astrocytes, oligodendrocytes and microglia, found per unit of volume, in Nissl preparations, of the degenerated LG, was expressed as a percentage of the mean number of the corresponding cells estimated in the normal LG on the same slide. The number of degenerating neurons decreased progressively. While 12 weeks following surgery a few isolated nerve cell nuclei could still be seen in the LG, by the end of the twenty‐fifth postoperative week the nucleus was practically devoid of neurons. The reaction of the astrocytes indicated a biphasic process—proliferation with subsequent reversal to an almost normal level. The oligodendrocytes and microglia multiplied at a somewhat slower rate, but remained far above the control values over a period of 50 postoperative weeks.
Projection of dorsal column nuclei and spinal cord to brainstem and thalamus in the tree shrew, Tupaia glis
Authors: Schroeder Dolores M. , Jane John A. 
Published: December 2004

AbstractThe aim of this study was to compare the projections of the dorsal column nuclei and spinal pathways to the brainstem and thalamus in Tupaia glis. Animals with unilateral lesions in the dorsal column nuclei or with lateral hemisections were perfused after 5 to 14 days survival time and sections were treated with Nauta or Fink/Heimer silver impregnation methods. The findings indicate that efferent fibers of dorsal column nuclei terminate not only in the thalamus but also in the dorsal accessory nucleus of the inferior olive and bilaterally in the external nucleus of the inferior colliculus. Some fibers terminate in periaqueductal gray and a few in pontine nuclei. In the diencephalon, efferents of the dorsal column nuclei were found to terminate in the posterior group (PO), ventroposterior nucleus (VP) and zona incerta. Spinal efferents were traced to the medial and dorsal accessory nuclei of the inferior olive, medullary and mesencephalic reticular formation, facial and vestibular nuclei, cuneiform nucleus, locus caeruleus, parabrachial nuclei and periaqueductal gray, and also to the external nucleus of the inferior colliculus. Evidence was found of more limited additional spinal projections to PO intralaminar nuclei and VP. The results of this study indicate that the dorsal column system, generally considered to be a phylogenetically new direct pathway to the thalamus, contains other components comparable to some of the spinal efferent connections with the brainstem. Moreover, even in this intermediate form, whose exact taxonomic position is unsettled, the dorsal column‐medial lemniscus system to the thalamus appears to be of greater volume than the anterolateral spinothalamic connection.
Histogenesis of the cerebellar climbing fiber in the rat
Authors: O'Leary James L. , Inukai Joseph , Smith Jeanne M. 
Published: December 2004

AbstractEarly climbing fiber metamorphosis has been studied in 250 Golgi preparations of 5–12 day postnatal rat cerebellum, and in less numerous 12–18 day ones. EM controls were provided for the early phase covering maturation of Purkinje cytoplasm, status of axonal neuropil, and synapses between the evanescent nid structure and Purkinje soma membrane.Ramon y Cajal (1890, '11), Athias (1897) and others have contributed extensively to climbing fiber histogenesis. Our results are confirmatory but support more varied developmental detail including that of axonal collateralization within the granular layer, all of which may not persist to maturity. Distinguishing characteristics of climbing fibers are recognized early in histogenesis, including varicosities, redundancies in course, and a manner of branching called cross‐over. The curvaceous path a climbing fiber pursues across the granular layer can be corrected at the ganglionic level by a horizontal segment having length equivalent to the offset. These and other redundancies may straighten out with areal expansion of cortical surface as compared to the restricted white matter base.While supporting multiple innervation of nids by local collateralizations proceeding from stem axons in white matter, the study does not preclude a one to one relationship between adult climbing fiber and Purkinje cell as basic design. Unknown factors are the relative amounts of local collateralization proceeding from several versus a single axon stem, and the extent to which branches are issued from a single fiber to different folia.