bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure of the piriform cortex of the opossum. II. Fine structure of cell bodies and neuropil
Authors: Haberly Lewis B. , Feig Sherry L. 
Published: January 2005

AbstractThe fine structure of cell bodies and neuropil in the piriform cortex of the opossum has been examined. A close similarity in ultrastructure of many features has been demonstrated between this pylogenetically old cortex in a primitive mammal and the neocortex of higher mammals.Cell bodies of pyramidal cells are very similar to those in the neocortex: The nucleus is pale with a smooth surface, the cytoplasm has a modest number of organelles, and the soma receives a small number of exclusively symmetrical synapses. Semilunar cells, which have apical but no basal den‐drites, are very similar to pyramidal cells in ultrastructure of their cell bodies.Two populations of neurons with nonpyramidal ultrastructural features have been distinguished: (1) cells in layer III that closely resemble the well‐known large multipolar cells in neocortex by virtue of a large number of symmetrical and asymmetrical somatic synapses and long cisterns of rough endoplasmic reticulum (ER); and (2) large cells in layer I with very few somatic synapses, a large number of mitochondria, and short cisterns of rough ER that may correspond to cells with somatic appendages described with the Golgi method.Large numbers of profiles are found in all layers that contain round vesicles and make asymmetrical synapses onto dendritic spines, and occasionally, dendritic shafts. Theseprofileshavedistinctly different morphological features in layer Ia, in which olfactory bulb afferents are concentrated, and in layers Ib, II, and III, which contain terminals of association and commis‐sural fibers. A smaller number of profiles containing pleomorphic vesicles make symmetrical contacts onto initial segments, dendritic shafts, cell bodies, and occasionally, dendritic spines.Most dendritic spines in all layers are small to medium in size (0.3–1.2 μm) and presumably originate from pyramidal cells. In layer Ia, however, large, flattened spines are also present which appear to originate from semi‐lunar cells. In layer III, and to a lesser extent other layers, large irregular spines are present that may be branched appendages on dendrites of complex appendage cells (Haberly, 1983).
Postmetamorphic changes in the lumbar lateral motor column in relation to muscle growth in the toad, Bufo americanus
Authors: Sperry David G. , Grobstein Paul 
Published: January 2005

AbstractMotoneuron number and size (nuclear cross‐sectional area) were measured from serially sectioned spinal cords of Bufo americanus to investigate the relation between changes in the lumbar lateral motor column (L‐LMC) and postmetamorphic increases in hindlimb muscle fiber number. Previous studies of neuron number in a variety of anuran species reported a correlation between number and body size, suggesting the possible addition of neurons during growth. Our results show a poor correlation between motoneu‐ron number and body size with at most a 25% increase in neuron number occurring over the body size range where previous work had shown a hind‐limb muscle fiber increase often to 20‐fold. Thus, most new muscle fibers must be incorporated into motor units that exist at metamorphosis. Moto‐neurons, but not ependymal cells, showed a significant size increase with increasing body size; this is perhaps related to an increased motor unit size that results from axonal sprouting. The range of variation of L‐LMC cell numbers in newly metamorphosed toads was nearly equal to that of all other toads examined. This suggests that the weak correlations between motoneu‐ron number and size observed in this and previous studies may be due to differential survival of individuals with larger neuron populations rather than to postmetamorphic addition of motoneurons. Our findings also show a strong bilateral correlation of motoneuron numbers, a finding suggesting that factors other than peripheral size may be important in regulating motoneuron number.
Cortical connections between rat cingulate cortex and visual, motor, and postsubicular cortices
Authors: Vogt Brent A. , Miller Michael W. 
Published: January 2005

AbstractThe connections of rat cingulate cortex with visual, motor, and postsubicular cortices were investigated with retrograde and anterograde tracing techniques. In addition, connections between visual and the postsubicular (area 48) and parasubicular (area 49) cortices were evaluated with the same techniques. The following conclusions were drawnArea 29 connections: Afferents to area 29 originate mainly from cingulate areas 24 and 25, visual cortex (primarily area 18b), motor cortex area 8, area 11 of frontal cortex, areas 48 and 49, and the subiculum. Efferent connections of area 29 within cingulate cortex and to visual areas differ for each cytoarchitectural subdivision of area 29. Thus, area 29c has limited projections both within cingulate cortex and to areas 48 and 49, while area 29d projects to these areas as well as to area 8, area 18b, and medial area 17. These visual cortex afferents originate mainly from layer V neurons of areas 29b and 29d, while areas 29a and 29c have virtually no projections to visual cortexArea 24 connections: Afferents to area 24 originate primarily from cingulate areas 25 and 29 and visual area 18b and medial area 17. Efferent projections of area 24a are distributed within cingulate cortex, while area 24b has more extensive projections to posterior cingulate and visual cortices. Area 24b is the cingulate subdivision which is both the primary recipient of visual cortex afferents as well as the source of most of the projections of anterior cingulate cortex to visual areasVisual cortex has reciprocal connections with parts of the postsubicular and parasubicular cortices. Neurons of the internal pyramidal cell layer of both areas 48 and 49 project to areas 17 and 18b, while layers I and III of these parahippocampal areas receive projections from areas 17 and 18bIn conclusion, areas 29d and 24b have particularly extensive interconnections with visual cortex, while area 29d also maintains projections to area 8 of motor cortex. This connection scheme supports the view that cingulate cortex may have a role in feature extraction from the sensory environment, as well as in sensorimotor integration. Finally, the postsubiculum may be classified as alimbic association cortex in which extensive visual and cingulate efferents converge.
Intrinsic laminar lattice connections in primate visual cortex
Authors: Rockland Kathleen S. , Lund Jennifer S. 
Published: January 2005

AbstractIntracortical injections of horseradish peroxidase (HRP) reveal a system of periodically organized intrinsic connections in primate striate cortex. In layers 2 and 3 these connections form a reticular or latticelike pattern, extending for about 1.5–2.0 mm around an injection. This connectional lattice is composed of HRP‐labeled walls (350–450 μm apart in Saimiri and about 500–600 μm in macaque) surrounding unlabeled central lacunae. Within the lattice walls there are regularly arranged punctate loci of particularly dense HRP label, appearing as isolated patches as the lattice wall labeling thins further from the injection site. A periodic organization has also been demonstrated for the intrinsic connections in layer 4B, which are apparently in register with the supragranular periodicities, although separated from these by a thin unlabeled region. The 4B lattice is particularly prominent in squirrel monkey, extending for 2–3 mm from an injection. In both layers, these intrinsic connections are demonstrated by orthogradely and retrogradely transported HRP and seem to reflect a system of neurons with long horizontal axon collaterals, presumably with arborizations at regularly spaced intervals. The intrinsic connectional lattice in layers 2 and 3 resembles the repetitive array of cytochrome oxidase activity in these layers; but despite similarities of dimension and pattern, the two systems do not appear identical. In primate, as previously described in tree shrews (Rockland et al., 1982), the HRP‐labeled anatomical connections resemble the pattern of 2‐deoxy‐glucose accumulation resulting from stimulation with oriented lines, although the functional importance of these connections remains obscure.
The nucleus isthmi as an intertectal relay for the ipsilateral oculotectal projection in the frog, Rana pipiens
Authors: Grobstein Paul , Comer Christopher 
Published: January 2005

AbstractReconstruction of serial sections through the nucleus isthmi in the frog Rana pipiens shows that the cortex of the nucleus consists of a sheet of cells which is folded back on itself to form two more or less parallel faces. Cyto‐architectural features allow three regions to be distinguished: a 7“rim region,” which previous work had suggested may be involved in the physiological pathway from one eye to the ipsilateral tectal lobe, and two additional regions which are here termed the anterior and posterior “nonrim cortex,” re‐spectively. The cytoarchitectural features which distinguish the rim region from the other two regions are largely absent in the tadpole.Analysis of retrograde transport of horseradish peroxidase (HRP) following widespread injections into one tectal lobe indicates that the anterior nonrim cortex projects ipsilaterally while the rim cortex and posterior nonrim cortex both project contralaterally. The differing projections of the three regions are paralleled by the pattern of retrograde degeneration observed after unilateral tectal lesions.We have studied the topographic organization of the connections between the nucleus isthmi and the two tectal lobes by making small injections of HRP at tectal loci with known visual field input. Patterns of retrograde cellular labelling show that the anterior nonrim cortex projects topographically to the entirety of the tectal lobe on the same side of the brain. The rim region projects topographically to the binocularly activated part of the opposite tectal lobe; the posterior nonrim cortex projects to the monocularly activated part. There is a discontinuity in the mapping from the nucleus to the opposite tectal lobe which corresponds to the border between binocular and monocular tectum. Patterns of anterograde labelling indicate that the afferent projection from the ipsilateral tectal lobe is topographic and organized so that afferents from a given tectal locus contact cells in the rostral part of the nucleus which project back to that locus. Afferents from tectal re‐gions representing binocular visual field in addition continue across the nucleus to terminate within the rim region. The organization of the afferent and efferent projections of this region is such as to link tectal loci which relate to the same direction in visual space.Our findings provide new evidence that the nucleus isthmi is involved in the pathway from one eye to the ipsilateral tectal lobe. They also show how the nucleus is organized to distribute information from a given locus in one tectal lobe to cells which project to the visually corresponding but in general anatomically different pairs of loci in the two tectal lobes. Finally, our findings confirm the existence of a projection from the nucleus isthmi to the opposite monocular tectum and suggest that this may be part of an intertectal circuit linking anatomically corresponding rather than visually corresponding pairs of tectal loci.
Neuronal organization in fly optic lobes altered by laser ablations early in development or by mutations of the eye
Authors: Nässel Dick R. , Geiger Gad 
Published: January 2005

AbstractThe role of afferent and efferent connections in the differentiation of optic lobe interneurons was investigated by using laser ablations of neuronal precursors in the brain of Musca domestica and analysis of two eye mutants of the same species.The first mutant, split eye, had no connections between the retina and the optic lobes. In this case the optic lobes were drastically reduced in volume and the neural organization within the neuropil regions was altered. The other mutant, spindle, had reduced retinae that innervated reduced optic lobes with a normal‐appearing orderly arrangement of neurons. In addition disordered neuropil, composed of identified visual interneurons, was found that had no afferent innervation.Three main types of alterations resulting from laser ablations were analyzed. These ablations removed entire neuropil regions or parts of these: (1) removal of the first optic neuropil region (the lamina) resulting in receptor axons projecting directly to the second neuropil (the medulla) and sprouting of medulla neurons toward the receptor layer; (2) removal of one part of the third optic neuropil (the lobula plate) and severe alteration of the other part (the lobula) resulting in sprouting of lobula neurons into the medulla neuro‐pil; and (3) removal of the entire optic lobe resulting in reduction of the volume of the lateral midbrain and photoreceptor axons forming a tangle beneath the retina.Our findings confirm that afferent retinal input is essential for normal differentiation and maintenance of many optic lobe interneurons. Furthermore, it was seen that a normal columnar organization of the neuropils and the dendritic patterns of visual interneurons are dependent on afferent inputs. A common response to removal of inputs was a reorganization of axo‐nal and dendritic projections.
Ultrastructure of neurons in the nucleus basalis of meynert in squirrel monkey
Authors: Walker Lary C. , Tigges Margarete , Tigges Johannes 
Published: January 2005

AbstractThe nucleus basalis of Meynert in the squirrel monkey exhibits numerous labeled neurons following the retrograde transport of horseradish perox‐idase from occipital cortical injection sites. The typically large, often clustered, labeled cells are seen most frequently in association with the fibrous bordering structures of the substantia innominata and in the internal and external laminae of the globus pallidus. Ultrastructurally the copious cytoplasm of nucleus basalis neurons abounds with organelles. Large, vacuo‐lated lipofuscin granules proliferate as a function of age and are not evident in younger monkeys. Approximately 4% of the somal surface is occupied by symmetrical synapses with either flat or pleomorphic vesicles. The remainder is covered mostly by neuroglial processes. Somatic spines bearing synapses are occasionally observed. In the neuropil surrounding nucleus ba‐salis somata, the synapses onto dendrites and spines are mostly asymmetrical with large, round vesicles. Labeled nucleus basalis cells in the substantia innominata immediately lateral to the optic tract are larger and rounder than cells in the internal and external pallidal laminae. However, no remarkable ultrastructural differences were observed between nucleus basalis so‐mata in the substantia innominata and external pallidal lamina, or between horseradish peroxidase‐labeled and unlabeled large cells.
Late appearance and deprivation‐sensitive growth of permanent dendrites in the avian cochlear nucleus (Nuc. magnocellularis)
Authors: Conlee John W. , Parks Thomas N. 
Published: January 2005

AbstractThe second‐order auditory neurons in the avian nucleus magnocellularis (NM) do not begin to grow permanent dendrites until about embryonic day 17 (E17), a few days before hatching. Since the auditory periphery and brain‐stem auditory nuclei are functional by E14 at the latest, the late appearance and growth of permanent dendrites in NM provides an unusual opportunity to examine the role of sensory experience in the very early stages of dendritic growth. We studied the development of NM dendrites in normal chickens and in animals with sustained monaural acoustic deprivation. In Golgi‐Hortega preparations at E17 and posthatching days 4 (P4), 10 (P10), and 60 (P60), the proportion of stained NM neurons with a dendritic process (“dendritic neurons”) and the length of these dendrites were measured. In normal animals the mean proportion of dendritic neurons rose from about 14% at E17 to 40% at P4 and thereafter. The mean length of NM dendrites in normal animals, however, grew significantly until P10, rising from about 14 μm at E17 to 48 μm by P4, and about 100 μm at P10 and P60. A 40‐dB monaural conductive hearing loss maintained with plastic earplugs from E18 on produced substantial retardation of dendritic growth after P4; at P10 the difference in length between deprived and nondeprived dendrites was 32% and at P60 was 38%. The proportion of dendritic neurons in the deprived NM and the mean diameter of the deprived dendrites were not affected by deprivation. Deprived dendrites in experimental animals were also significantly shorter than those in normal control animals. The length of nondeprived dendrites in experimental animals did not differ from that of controls, arguing against any compensatory hypertrophy. The functions of NM dendrites in the central processing of auditory information are as yet unknown. The facts that these dendrites (1) undergo their most rapid growth during the period of the animal's first exposure to airborne sound and (2) are markedly stunted by a nondeafferenting moderately severe acoustic deprivation suggest that acoustic experience has a strong facilitative function in the posthatching development of the cochlear nucleus. These results also suggest that afferent synaptic stimulation can affect the subsequent elongation, but not the initial outgrowth, of dendrites.
Striatal neurons containing both somatostatin‐ and avian pancreatic polypeptide (APP)‐like immunoreactivities and NADPH‐diaphorase activity: A light and electron microscopic study
Authors: Vincent Steven R. , Johansson Olle 
Published: January 2005

AbstractStriatal neurons containing both somatostatin‐ and avian pancreatic polypeptide (APP)‐like immunoreactivities have been shown to be selectively stained by the histochemical method for nicotinamide adenine dinucleotide phosphate (NADPH)‐diaphorase activity. In the present study, we have utilized this histochemical technique to examine the morphology of these Striatal neurons at the light and electron microscopic levels. Our results indicate that the Striatal somatostatin/APP/NADPH‐diaphorase neurons occur throughout the striatum and have long, aspiny dendrites, oval, invaginated nuclei with prominent nucleoli, and receive few axosomatic contacts. These cells appear to correspond to a population of medium‐sized aspiny interneurons reported previously in Golgi and electron microscopic studies of the striatum.
Subdivisions of the inferior colliculus in the barn owl (Tyto alba)
Authors: Knudsen Eric I. 
Published: January 2005

AbstractThe inferior colliculus in the barn owl contains three subdivisions: the central (ICC), external (1CX), and superficial (ICS) nuclei. The nuclei are distinguished on the basis of their cyto‐ and myeloarchitecture, connectivity, and physiological properties. The ICC may be further divided into dorsal (ICCd) and ventral (ICCv) parts. Auditory fibers ascending in the lateral lemniscus enter the ICCd and ICCv, but not the ICX or ICS. The ICX receives its auditory input from the ICC. The ICC and ICX in owls are similar in position, anatomy, connectivity, and physiology to the ICC and ICX in mammals, suggesting that these structures are homologous. Units in the ICC are organized to potopically, whereas units in the ICX are organized according to the locationns of their spatial receptive fields. This implies that a transformation from tonotopic to a spatiotopic organization takes place in the ICX of the owl.
The perihypoglossal nuclei in the macaque monkey and thechimpanzee
Authors: Brodal A. 
Published: January 2005

AbstractThe topography of the perihypoglossal nuclei (nucleus intercalatus, nucleus prepositus, and nucleus of Roller) of the macaque and the chimpanzee was studied in serial Nissl‐stained sections through the brainstem. Maps of the nuclei in the two species are presented.Although in both species the perihypoglossal nuclei are organized according to the general mammalian pattern, they show some particular features, reflecting in part, an increasing phylogenetic differentiation. In the chimpanzee the nucleus prepositus is relatively larger, the nucleus of Roller is more of a separate unit, and its cellular composition is more uniform than is the case in the macaque. A cellular connection between the two nuclei is present in the macaque (even more conspicuous in the cat, apparently absent in man), but is barely discernible in the chimpanzee. A conspicuous difference between the chimpanzee and the macaque concerns the nucleus supra‐genualis nervi facialis, forming a rostral continuation of the prepositus. In the chimpanzee it is a loosely structured region of small cells (as in the cat and in man). In the macaque, however, it appears as a rather well‐delimited column of chiefly medium‐sized cells.Some comparative anatomical and functional aspects are discussed. Many contingents of afferents to ‐ and efferents from – the nucleus preposi tus have their preferential sites of termination or origin in the nucleus, although with considerable overlapping. This indicates the presence of topical patterns in the prepositus. In general the caudal parts appear to be more related to the cooperation with the cerebellum than the rostral part, whereas the latter appears to be more particularly linked with the oculomotor apparatus.
Death of motorneurons during the postnatal loss of polyneuronal innervation of rat muscles
Authors: Bennett M. R. , McGrath P. A. , Davey D. F. , Hutchinson I. 
Published: January 2005

AbstractA study was made of the decline in the number of motor neurons and axons of the brachial spinal cord of the rat during postnatal development. The injection of horseradish perodidase (HRP) into the biceps muscle showed that it was innervated by motor neurons located in the dordolateral position of the lateral mototr coluimn in segments C5 and C6; HRP injections into the triceps muscle showed that it was innervated by mototr neurons located in the ventrolateral posotion of the lateral motor coumn in segments C7 and C8. There was no change in the position of these motor neurons pools between birth and maturity, However, these was a decline in the number of neurons in each pool during the postnatal period; over 35% of the neurons presents at birth had disappeared by maturity. This loose of neurons was uniform throughout the restrocaudal extent of each pool. It was accompanied by a similar percentage loss in the number of axons in a ventral root at the brachial level (C8). Electrophjysiological measurements showed that the disappearance of motor neurons was accompanied by a loss in the polyneuronal innervation of synaptic sites in the biceps muscle. The possibility that a decrease in the number of neurons contributes to the loss of polyneorunal innervation is discussed.
Neuronal subpopulations in cat retina which accumulate the GABA agonist, (3H)muscimol: A combined Golgi and autoradiographic study
Authors: Pourcho Roberta G. , Goebel Dennis J. 
Published: January 2005

AbstractGolgi impregnation techniques were combined with, electron microscopic autoradiography of (3H)muscimol in order to provide morphological identification of labeled neurons in the cat retina. This γ‐aminobutyric acid (GABA) agonist has been shown to label the same neurons which accumulate (3H)GABA. Selected cells were photographed and drawn by the aid of a camera lucida drawing tube prior to being thin sectioned for autoradiography.The (3H)muscimol‐accumulating neurons which were identified include an interplexiform cell, five classes of conventional amacrine cell, and another cell with its soma located in the ganglion cell layer which is either a ganglion cell or a displaced amacrine. The conventional amacrine cells were compared with the recent morphological classification of Kolb et al. (Vision Res. 21: 1081‐1114, '81) and identified as A2, A10, A13, A17, and A19 amacrine cells. These cells exhibit a widespread distribution providing input to all five strata of the inner plexiform layer.