bluuebunny/crossref_metadata_2025_split huggingface dataset:
The ultrastructure of the cat olfactory bulb
Authors: Willey T. Joe 
Published: May 2005

AbstractThe fine structure of the olfactory bulb was investigated in the cat. Five types of bulbar neurons were identified on the basis of size, location, cytoplasmic organelles and synaptic complexes with the neuron perikaryon. The smallest diameter neurons were predominatly located in the glomerular and granule cell layers. Ultrastructural characteristics for these two neuron populations, viz., periglomerular and internal granule cells, were identical. Tufted cells, smaller in diameter than mitral cells, were located in the external plexiform and glomerular layers and possessed all the morphological characteristics of the mitral cells. Mitral cells were the largest bulbar neurons and were located in a single lamina. Stellate (short‐axon) neurons were found in the glomerular, external plexiform and granule cell layers.Reciprocal synapses were observed in all laminae of the bulb except the primary olfactory nerve and deeper granule cell layers. Such synapses were found in the glomeruli, on tufted and mitral cells, in the neuropil of the external plexiform layer, and on the axon hillock and initial segments of the mitral cells. The morphology in the cat olfactory bulb corroborated bulbar ultrastructure described for other mammals.
Fluorescence histochemistry of monoamine‐containing cell bodies in the brain stem of the squirrel monkey (Saimiri sciureus). IV. An atlas
Authors: Di Carlo Vincenzo , Hubbard Jack E. , Pate Patricia 
Published: May 2005

AbstractThe topography of the various groups of catecholamine‐ and serotonin‐containing cell bodies in the squirrel monkey (Saimiri sciureus), as described in the preceding three papers of this series, is presented in an atlas of Nissl and myelin stained frontal sections. The major findings of this study are reviewed and discussed. These include: (1) evidence of fundamental similarities in the topographic distribution of the cell groups between the primate and the rat and of significant differences between the primate and the cat; (2) identification as the catecholaminergic cells of the locus caeruleus of a cellular group incorrectly identified in the literature as nucleus tracti mesencephalici nervi trigemini; (3) consolidation of several catecholamine‐containing cell groups as belonging respectively to the locus caeruleus (C4, C6, C7) and the substantia nigra (C8 and C9); (4) predominant distribution of the serotoninergic cell groups in the midline raphe region (with lateral extensions in some cases) and location within well defined nuclei, such as the nucleus raphe obscurus, nucleus raphe pallidus, nucleus raphe magnus, nucleus raphe pontis, nucleus raphe dorsalis and nucleus centralis superior.
The motor nucleus of the facial nerve in the opossum (Didelphis marsupialis virginiana). Its organization and connections
Authors: Dom Richard , Falls William , Martin George F. 
Published: May 2005

AbstractThe organization of the facial nucleus was studied in the opossum by localizing neurons which stin poorly for acetylcholinesterase activity following transection of identified facial rami. The caudal auricular representation is limited to the ventromedial extreme of the nucleus, whereas the neurons contributing to the cervical ramus are situated dorsally and medially. The zygomatic representation extends throughout the intermediate portion of the nucleus, apparently overlapping with that of the palpebral and rostral auricular muscles which is limited to the ventral extreme of the intermediate zone. The buccolabial area is particularly large in the opossum and encompasses most of the lateral facial enlargement.Midbrain‐facial projections were identified from the superior colliculus, the midbrain tegmentum (particularly caudal ventromedial areas) and the red nucleus. The location of terminal degeneration in the facial nucleus following lesions within each of these areas was plotted and interpreted in light of facial organization. Of particular note is the fact that the fibers of rubral origin distribute preferentially to the zygomatic and, to some extent, buccolabial areas, whereas the ventromedial tegmental system distributes most strongly to the areas of caudal auricular, cervical, palpebral and rostral auricualar representation. The medial and intermediate regions of the facial nucleus receive a denser midbrain projection than does the lateral (buccolabial) area. In contrast, evidence was obtained for an extensive facial projection from the parvocellular reticular formation and the caudal spinal trigeminal nucleus which strongly favors the buccolabial enlargement. The possibility exists that the medial pontine and medullary reticular formation as well as portions of the dorsal column nuclei also have a facial projection. Spino‐facial fibers arise rostral to the cervical enlargement and show a predilection for the medial facial enlargement (cervical and caudal auricular areas). Although some systems distribute preferentially to specific areas of the facial nucleus, overlap is present suggesting considerable integration.
Astrocyte‐specific protein and neuroglial differentiation. An immunofluorescence study with antibodies to the glial fibrillary acidic protein
Authors: Bignami A. , Dahl D. 
Published: May 2005

AbstractThe topographical features of the neuroglial network in the mature rat CNS and the differentiation of fibrous neuroglia in the neocortex and hippocampus have been studied by immunofluorescence using antibodies to the glial fibrillary acidic (GFA) protein. In the mature brain and spinal cord the distribution and appearance of neuroglia as observed with immunofluorescence were similar to those described by Weigert ('95) using his method for astrocytic fibers. In the developing rat immunofluorescence started to appear on the surface of the neocortex in the first week after birth. In 9‐day‐old rats a continuous external glial membrane had formed by immunofluorescence. Immunofluorescence of the perivascular glial membrane appeared later. Blood vessels completely surrounded by a fluorescent membrane were not observed in the middle cortical layers before the eighteenth day of life. An unexpected finding in the hippocampus was the sudden appearance in the 8‐day‐old rat of a radial system of immunofluorescent fibers crossing the granular layer and extending in the molecular layer. The radial fibers were still present in the adult rat. However, they became widely spaced and thus less prominent than in the immature animal. In fetal rats immunofluorescent fibers first appeared in the medial wall of the lateral ventricles on the eighteenth post‐conceptionaly day. The radial system of glial fibers extending from the ventricles to the surface of the brain and characteristic of this stage of development was not stained by immunofluorescence.
Fine structure of dendritic and axonal growth cones in embryonic chick spinal cord
Authors: Skoff Robert P. , Hamburger Viktor 
Published: May 2005

AbstractOur preliminary electron microscopic observations of embryonic chick spinal cord indicate that the majority of synapses in the cervical cord at the fourth and sixth days of incubation are found in the marginal layer rather than the mantle layer. These findings raise two basic questions about the type of connections in the marginal zone during the first week of development: are all these early synapses axondendritic, and are synaptic junctions present on axonal and dendritic growth cones? Since criteria for distinguishing between axonal and dendritic growth cones are scarce or nonexistent, serial section electron microscopy was employed to definitively identify the two types of terminals.Two types of dendritic growth cones are present in the marginal layer during the first week of development. The first type is distinguished by a dendritic stalk which expands into a club‐shaped or bulb‐like terminal. A characteristic feature of this type of dendritic ending is the presence of numerous vesicles which vary in diameter from about 1000 Å to 2500 Å. Its cytoplasm has a floccular appearance and is frequently electron lucent. In contrast, the second type of dendritic terminal is electron dense, has a consistently homogeneous appearance, and usually lacks the large vesicles of the first type. The shape of the second type is a finger‐like process (filopodium) roughly of the same diameter as the main dendritic trunk. Evidence is presented that some dendritic growth cones observed in this study represent growing, motile processes rather than quiescent enlargements. Synapses on dendritic growth cones are quite numerous and, in addition, the first synapses on dendrites appear to form on growth cones. The hypothesis is put forward that synapses on dendritic growth cones. The hypothesis is put forward that synapses on dendritic growth cones are incorporated onto the dendritic trunk as the terminal continues to grow.Axonal growth cones may be distinguished from dendritic growth cones on the basis of their overall morphology and their cytoplasmic components. An axonal growth cone is, in general, a larger and more irregular structure than the dendritic terminal. This irregularity is due to the large number of processes radiating away from the terminal enlargement or varicosity. While dendritic terminals almost always have finger‐like projections, processes of axonal growth cones are more often sheet‐like extensions of cytoplasm (folipodia). Another important difference between axonal and dendritic growth cones is that ribosomes in axonal varicosities are infrequently encountered and rarely aggregated into polysomes as in dendritic terminals. Axonal growth cones are occasionally observed to be presynaptic to a dendrite during the first week of development.
Ascending connections of a midbrain auditory area in a crocodile, Caiman crocodilus
Authors: Pritz Michael B. 
Published: May 2005

AbstractThe torus semicircularis is a tonotopically organized auditory region in the midbrain of the crocodile, Caiman crocodilus (Manley, '71). Two distinct regions of the torus can be distinguished in Caiman: an external nucleus, which is continuous with the deep layers of the optic tectum, and a central nucleus. Ascending connections of the central nucleus were studied with the light microscope by means of the Fink‐Heimer procedure after unilateral, anodal stereotaxic lesions. Efferent axons leave the central nucleus in the lateral lemniscus to enter the tecto‐reuniens tract where they course as far rostrally as nucleus Z. At this level, this bundle bifurcates. The majority of these fibers turn medially and then pass through and probably synapse on interposed neurons of nucleus Z, prior to their termination in nucleus reuniens. The remaining axons continue ventrally past nucleus Z to enter the ventral supraoptic decussation where they travel anteriorly to a level just posterior to the optic chiasm. Here the fascicles cross the midline and swing caudally, still in the ventral supraoptic decussation, until they reach nucleus Z of the contralateral side. At this level, these fibers enter the tecto‐reuniens tract and turn medially, to pass through and perhaps end on the intercalated neurons of nucleus Z, prior to their termination in nucleus reuniens. The neuronal architecture of nucleus Z and that of the nucleus reuniens complex are described. The latter, a midline nuclear group, consists of two subdivisions: a pars centralis and a pars diffusa. Each of these subdivisions is segregated into two neuronal aggregates at the midline. Efferents of the central nucleus terminate massively in the pars centralis and, to a considerably lesser extent, in the pars diffusa of nucleus reuniens.The results of this study are compared with similar ones in pigeons and mammals. Parallels in the fiber connections of midbrain auditory and visual areas and the segregation of these modalities in the mesencephalon and diencephalon are discussed.
Fluorescence histochemistry of monoamine‐containing cell bodies in the brain stem of the squirrel monkey (Saimiri sciureus). III. Serotonin‐containing groups
Authors: Hubbard Jack E. , Carlo Vincenzo Di 
Published: May 2005

AbstractThe distribution and cytological characteristics of the serotonin‐containing cell bodies in the brain stem of the squirrel monkey (Saimiri sciureus) are described using the fluorescence histochemical technique of Falck and Hillarp for the demonstration of monoamines. Eight groups of serotonin‐containing neurons were found, located predominantly in the midline raphe region of the brain stem within defined nuclei, such as the nucleus raphe obscurus, nucleus raphe pallidus, nucleus raphe magnus, nucleus raphe pontis, nucleus raphe dorsalis and nucleus centralis superior. Portions of some of the groups also extend laterally in the brain stem, particularly at the levels of the upper pons and midbrain. The appearance and distribution of the serotonin‐containing groups of cell bodies in the squirrel monkey were found to be somewhat similar to that described for the rat, but differed in at least one major respect from that reported for the cat.
The optic tectum of a perciform teleost I. General configuration and cytoarchitecture
Authors: Vanegas Horacio , Laufer Miguel , Amat José 
Published: May 2005

AbstractGolgi techniques have been employed to study the cytoarchitecture of the optic tectum in the perciform teleost Eugerres plumieri. The stratum marginale (SM) contains abundant fine axons which contact the spiny dendritic tree of large pyramidal neurons of the stratum fibrosum et griseum superficiale (SFGS). Such arborizations arise from a robust, naked apical dendritic shaft. The pyramidal neurons also have a basal dendritic shaft and an axon, both of which ramify in overlapping horizontal fields within the stratum griseum centrale (SGC). The SGC contains fusiform neurons with apical and basal dendritic shafts which ramify horizontally at the SFGS and just above the stratum album centrale (SAC), respectively; an axon “a crosse” originates from the apical shaft. Also in the SGC is the soma of the small pyriform neuron; from it originates a slender dendritic stem which branches out at the SM. Other neurons of SGC and SAC are the small and the large multipolar neurons, and the large pyriform neuron. The large pyriform neurons send a thick dendritic stem which gives horizontal branches mainly at the SFGS, and from which an axon “a crosse” originates. The stratum periventriculare contains small pyriform neurons whose slender dendritic stem ramifies at the stratum opticum as well as at other strata. No axon was seen to originate from these neurons.
The optic tectum of a perciform teleost III. Electron microscopy of degenerating retino‐tectal afferents
Authors: Laufer Miguel , Vanegas Horacio 
Published: May 2005

AbstractAxonal and terminal degeneration has been studied with the electron microscope in the optic tectum of the teleost Eugerres plumieri, at 7, 15 and 35 days after eye enucleation. The distribution of degenerating elements corresponds to that found in light microscopical studies; it is confined to myelinated axons and terminals in stratum opticum, stratum fibrosum et griseum superficiale, and stratum album centrale. No degeneration was seen in other strata. Early axonal degeneration includes increase in filaments, sometimes accompanied by axoplasmic densification, as well as formation of vacuoles and membrane bound bodies. Myelin appears normal in a large proportion of axons at seven days after eye enucleation. Degenerating terminals may show increased number of filaments as well as densification, but neither reaction is marked; they show characteristic vacuoles and membrane bound bodies. Increase in vesicle size was observed only in few degenerating terminals. At 15 days after enucleation, there is myelin breakdown, bizarre axoplasmic inclusions, and glial and perivascular cell ingestion of debris. At 35 days, no terminals are found, and various stages of axonal degeneration are present.
Cytological evidence for catecholamine‐containing sensory cells bordering the ventricle of the toad hypothalamus
Authors: McKenna Olivia C. , Rosenbluth Jack 
Published: May 2005

AbstractA laminar group of catecholamine‐containing cells bordering the infundibular recess of the toad hypothalamus has been studied by both fluorescence histochemical and electron microscopic methods. The perikarya of these cells form up to ten layers beneath the ependymal lining and send stout apical processes between the ependymal cells into the ventricle where they terminate as bulbous expansions. These cells fluoresce yellow‐green when studied by the method of Falck and Hillarp, indicating the presence of catecholamines. The fluorescence intensity is consistently greater in the bulbous ventricular endings than in the cell bodies and is greater in males than in females except when ovulation is induced. Electron microscopy shows that the ventricular bulb, apical process and cell body contain three distinctive cytoplasmic components: a population of dense cored vesicles (700 to 1500 Å in diameter), large aggregates of clear vesicles (440 to 600 Å in diameter) and mitochondria filled with crystalline inclusions. The nucleus is prominently lobulated. A slender process also extends from the base of the cell into the underlying neuropil; this basal process, however, contains only microtubules, a few vesicles of both types and a few mitochondria. The basal, lateral and apical surfaces of the cells form many synapses with neighboring processes. By and large these junctions are somatodendritic and are characterized by accumulations of either clear or a mixture of clear and dense cored vesiles against the perikaryal membrane. Axosomatic synapses in contrast occur only infrequently. The cytological characteristics of the cells suggest that their primary function may be to detect compounds in the cerebrospinal fluid and relay this information to neighboring neurons via the somatodendritic synapses.
Synaptic interactions of reticulospinal neurons and nerve cells in the spinal cord of the sea lamprey
Authors: Rovainen Carl M. 
Published: May 2005

AbstractThe reticulospinal system is the major descending pathway from the brain to the spinal cord in the sea lamprey, Petromyzon marinus. In order to determine the synaptic connections of this system and to gain a better understanding of its functions, individual cell bodies and axons of identified reticulospinal neurons were stimulated intracellularly while recording from spinal interneurons and motoneurons.
Stimulation of reticulospinal axons of the bulbar and vagal groups produced unitary composite EPSP's in lateral cells. Both components of these EPSP's followed repetitive presynaptic action potentials one‐to‐one at constant short latencies. The first component was due to electrical coupling between the cell and axon. The second component was due to chemical transmission because it was eliminated after extracellular Ca was replaced with Mg and because it changed in amplitude during repeated stimulation. Evidence is presented that the second component, as well as the first, is monosynaptic.
Both fast and slow motoneurons to myotomal muscle received a predominantly electrical synapse from the Müller axon I1. They also exhibited composite EPSP's after stimulation of M1, M3, some bulbar cells, and the Mauthner cell. Stimulation of ventral roots produced depolarizations in Müller axons which excited motoneurons. Polysynaptic EPSP's were observed in a fin motoneuron after stimulation of the contralateral axon M3 or I1.
Some edge cells exhibited a composite EPSP after stimulation of the bursting axon I2.
Morphologically mixed synapses with both chemical and electrical junctions were observed between Müller axons and unidentified dendrites.
The cells of origin of the bursting axons were the pair I2. Stimulation of these axons in situ produced either no movements or weak fin movements. No synaptic potentials were observed in motoneurons in the cord or in bulbar cells in the brain after stimulation of I2.
Intracellular stimulation of giant interneurons produced EPSP's in one pair of bulbar cells.
The conclusions drawn from this and the preceding study are as follows: (a) Connections of identified neurons in the lamprey are specific but do not always occur. (b) The majority of synapses from large axons to identified cells utilize dual electrical and chemical transmission. (c) Most unitary EPSP's are subthreshold. Thus, other sources of excitation, especially from smaller unidentified neurons, are required for activity.
Uptake of tracer proteins in the developing cerebellum, particularly by the growth cones and blood vessels
Authors: del Cerro Manuel 
Published: May 2005

AbstractTracer proteins ferritin (M. W. 500,000 daltons) and horseradish peroxidase (M. W. 40,000 daltons) were injected into the cerebella of suckling rats to study the uptake of macromolecules by growth cones and other structures in the developing nervous tissue. The animals were killed between 30 minutes and 6 hours after injection, and areas adjacent to, but excluding the injection site were studied by electron microscopy with optical microscopical controls.At all time intervals both proteins were present in the extra‐ and intracellular compartments, although there was a clear time‐related increase of the concentration in the latter. Both tracers flowed through the intercellular gaps, permeated synaptic clefts, and concentrated in large amounts within the basal laminae of the pia mater and blood vessels. Upon crossing the laminae the markers were incorporated by pial and endothelial cells. The latter showed pinocytotic vesicles taking the marker at the abluminal surface and similarly labeled vesicles underneath the luminal surface or actually opening into the vascular lumina. Vessels of cerebella fixed by immersion showed similar uptake pattern and free tracer was found in the capillary lumina. These data indicate that a vesicle‐mediated transendothelial passage of proteins, from the parenchyma to the blood takes place under these experimental conditions.The somata of neurons and glial cells showed a high degree of incorproation, the protein being taken by pinocytosis and stored in lysosomes. The vesicles populating growth cones (“growth vesicles”) regularly contained marker although in variable proportions. At any given time most of the vesicles in the glial cones were labeled, while only some were labeled in the axonal and dendritic cones. Since pinocytotic activity was low in growth cones, labeling of the “growth vesicles” could be tentatively explained by postulating that they become passively labeled when they open into and coalesce with the membrane of the cone (as in Bray's, '73, model). If that were the case differential labeling between neural and glial cones could be an indication of a differential rate of membrane increment and therefore a differential rate of growth. Alternative possiblities are considered.