bluuebunny/crossref_metadata_2025_split huggingface dataset:
Morphology of axosomatic endings in an avian cochlear nucleus: Nucleus magnocellularis of the chicken
Authors: Parks Thomas N. 
Published: May 2005

AbstractThe axonal endings formed on the somata of neurons in the brainstem auditory nucleus magnocellularis (NM) were measured and classified in thin‐sectioned material from adult chickens. Degeneration of primary endings after destruction of the basilar papilla and labeling of cochlear nerve fibers by injection of horseradish peroxidase (HRP) into the inner ear were used to determine which ending types arise from the cochlear ganglion. About 60% of the perikaryal surface is apposed by primary type terminals. These primary endbulbs are characterized by round clear synaptic vesicles distributed at an average density of 63 vesicles/μm2 and a number of small, punctate, highly asymmetrical synaptic contacts. The primary type is the only class of endings which disappears after destruction of the basilar papilla and which is consistently labeled after HRP injections into the ear. These endings probably account for the “fast” EPSP seen in NM during stimulation of the cochlear nerve. NM neurons receive two types of nonprimary ending. About 13% of the perikaryal surface is apposed by a morphologically homogeneous class of small “symmetrical” endings; these are characterized by a flattened rhomboidal shape, numerous mitochondria, frequent coated vesicles, and small round or ovoid synaptic vesicles at an average density of 165 vesicles/μm2. Most of the length of the apposition between ending and cell body is occupied by a synaptic complex with thin symmetrical presynaptic and postsynaptic densities. These endings were frequently found on short somatic processes. The second nonprimary axosomatic ending type in NM is most easily identified in experimental material; these endings occupy about 5% of the cell surface area and have a distinctly rounded profile in cross section. These endings typically exhibit clear round synaptic vesicles at a density of 111 vesicles/μm2 arrayed before synaptic contacts which occupy a substantially larger fraction of the total appostion length than in the endbulbs. Many of these synaptic contacts show well‐defined presynaptic grids and have postsynaptic densities intermediate in width between the endbulbs and the symmetrical endings. This second type of nonprimary ending may be responsible for the long‐latency excitatory postsynaptic potentials seen in intracellular recordings from NM during electrical stimulation of the cochlear nerve. The morphology and distribution of the three ending types does not differ significantly along the posterior‐to‐anterior axis of NM.
The organization of centrifugal projections from the anterior olfactory nucleus, ventral hippocampal rudiment, and piriform cortex to the main olfactory bulb in the hamster: An autoradiographic study
Authors: Davis Barry J. , Macrides Foteos 
Published: May 2005

AbstractThe centrifugal projections from the various subdivisions of the anterior olfactory nucleus (AON) can be categorized into four groups based on the organization of terminal fields in the main olfactory bulb (MOB). Pars lateralis and dorsalis have bilaterally asymmetric laminar projections to the MOB. The ipsilateral projections terminate primarily in the superficial half of the granule cell layer and in the deep third of the glomerular layer, whereas the contralateral projections terminate primarily in the superficial half of the granule cell layer and do not extend into the glomerular layer. Pars ventralis and posterior have bilaterally symmetric laminar projections with heavy terminations both in the superficial half of the granule cell layer and in the deep third of the glomerular layer. Pars medialis sends predominantly ipsilateral projections to the deep half of the granule cell layer. Pars externa has predominantly contralateral projections with a very narrow terminal field immediately deep to the internal plexiform layer. The projections to the MOB from the ventral hippocampal rudiment (HR) and the piriform cortex (PC) are exclusively ipsilateral. The projections from the ventral HR terminate primarily in the deep half of the granule cell layer. The projections from the PC also terminate predominantly in the granule cell layer, but there is a progressive shifting of terminal fields from the superficial half of this layer toward deeper regions for centrifugal axons arising from progressively more caudal levels of the PC. The laminar termination patterns of cortical afferents to the ipsilateral MOB thus are correlated with the mediolateral axis of the olfactory peduncle and the rostrocaudal axis of the piriform cortex.The centrifugal axons from these various sources enter directly into the granule cell layer of the caudal MOB or pass through the internal plexiform layer of the accessory olfactory bulb to reach the middle and anterior part of the MOB. We have termed these two routes the final common bulbar pathway. The centrifugal axons from the laterally situated sources join the anterior and bulbar limbs of the anterior commissure before entering the final common bulbar pathway. In contrast, the centrifugal axons from pars medialis and the ventral HR travel diffusely in the cellular layer of the ipsilateral olfactory peduncle. A small component of the centrifugal projections from the PC travels in association with the lateral olfactory tract.
Maturation of rat visual cortex. II. A combined Golgi‐electron microscope study of pyramidal neurons
Authors: Miller Michael , Peters Alan 
Published: May 2005

AbstractTissue removed from 3, 6, 9, 12, 15, and 21‐day‐old rats has been prepared for correlative light and electron microscopy to examine the maturation of cell bodies, dendrites, and axons of pyramidal neurons in layer V of rat visual cortex. As the size of the cell body increases steadily during the first 3 postnatal weeks there is an equivalent growth in nuclear volume. By day 15, there are infoldings in the nuclear envelope which may be induced by eye opening on day 14. Nucleoli increase in size until day 9, after which they appear to condense. Within the perikarya, the most conspicuous change is the amount and organization of the rough endoplasmic reticulum. Symmetric axosomatic synapses are evident by day 6. The ultrastructure of dendrites does not change substantially with age. Dendrites form synapses with symmetric densities as early as day 3 and asymmetric ones by day 9. It seems that dendritic spines begin as low, broad protrusions having symmetric junctions with smaller diameter axonal processes. With time they become taller stumps, before acquiring their mature lollipop shape and participating in asymmetric synapses with axonal varicosities. Other dendritic appendages, filopodia, and growth cones are transient structures, being conspicuous only between days 3 and 12. “Terminal” growth cones are essential for extension of dendritic processes, whereas “en passant” growth cones and filopodia seem important for dendritic branching. Boutons of mature pyramidal cell axons form asymmetric synapses with dendritic shafts and spines, but the developing synapses formed by these axons have more symmetric junctions. The maturation of pyramidal cell features progresses in concert with such extrinsic determinants as afferent input and is probably influenced by the competency of synaptic connections.
Bilateral serotonergic projections to the dorsal hippocampus of the rat: Simultaneous localization of 3H‐5HT and HRP after retrograde transport
Authors: Azmitia Efrain C. 
Published: May 2005

AbstractHorseradish peroxidase (HRP, Sigma VI, 30–70 nl of a 10–15% solution in saline) or 3H‐5HT (30 Ci/mmole, 2.5 × 10−3 M containing 3.3 × 10−3 M norepinephrine in saline, 50–100 nl) was injected unilaterally into the dorsal hippocampus in separate groups of rats.HRP‐labeled cells were seen in the hippocampus, medial septal nucleus, nucleus of the diagonal band, supramammilary nucleus, median raphe nucleus, interfascicular portion of the dorsal raphe nucleus, and the locus coeruleus. In contrast, 3H‐5HT‐labeled cells were largely restricted to the raphe nuclei. In this nucleus an equal number of ipsilateral and bilateral cells were found. Occasionally, these labeled cells stretched across the midline (bridge pattern).In another series, the 3H‐5HT and HRP were injected into the same hippocampus either as a mixture or sequentially. This resulted in double labeling of the median and dorsal raphe neurons. A final group of rats received injections of 3H‐5HT and HRP into opposing hippocampi. Double‐labeled cells accounted for 10% of the neurons labeled. In addition, closely paired neurons composed of an HRP‐and 3H‐5HT‐containing cell were found. In summary, the serotonergic fibers may play a key role in harmonizing the electrical activity of the hippocampi by use of bilateral projections, paired neurons with differential projections, and bridging neurons stretching across the midline but with unilateral projections.
Myelination kinetics of spiral ganglion cells in kitten
Authors: Romand R. , Romand M.‐R. 
Published: May 2005

AbstractA study of the regions of myelination of spiral ganglion cell bodies at birth in the kitten revealed that the first signs of myelination occurred before birth. A quantitative analysis of myelinated versus unmyelinated cells, and the distribution of myelin lamellae of the ganglion cell sheath reflect the kinetics of the later stages of cochlear maturation. The onset of the final maturation process begins in the basal region of the first turn, which is 20% of the length of the spiral lamina measured from the basal extremity of the cochlea. This maturation proceeds in an orderly manner from the lower half of the first turn to the apex, but also develops to a smaller degree toward the hook region. Results are compared with previous findings.
Further observations on the cerebellar projections from the pontine nuclei and the nucleus reticularis tegmenti pontis in the rhesus monkey
Authors: Brodal Per 
Published: May 2005

AbstractThe projections from the pontine nuclei and the nucleus reticularis tegmenti pontis (N.r.t.) onto the flocculus, uvula, and the paramedian lobule were studied with retrograde transport of horseradish peroxidase in the rhesus monkey. The main findings are as follows:There is a conspicuous tendency for labeled cells to occur in numerous discrete clusters in the pontine nuclei after injections of these parts of the cerebellum.There appears to be very limited overlap between pontine cell groups projecting to the flocculus, the uvula, and the paramedian lobule, respectively.The flocculus appears to receive a substantial projection from the pontine nuclei. The projection is almost totally crossed (3% ipsilateral), and arises mainly laterally in the rostral half of the pons, but in addition from a minor group dorsomedially. The flocculus receives a bilateral projection (slight contralateral preponderance) from medial and dorsomedial parts of the NRT. The number of labeled cells in the NRT was 13% of the number in the pontine nuclei.The uvula is amply supplied from the pontine nuclei. The projection takes origin throughout the rostrocaudal extent of the pons, from one medial and one dorsolateral region. Labeled cells are found in greatest number dorsolaterally in the rostral half of the pons. In the caudal N.r.t., one medial and one lateral cell group were labeled after injection of the uvula. The number of labeled cells in the N.r.t. was only 4% of the number in the pontine nuclei.Findings with regard to the paramedian lobule confirm and extend earlier observations in the monkey (Brodal, '79, '80).The present results are discussed in relation to HRP studies of the pontocerebellar projection in lower animals. Several possible species differences are noted—for example, with regard to projections to the flocculus. There is some evidence that the pontocerebellar projection is more precisely organized in the monkey than in lower animals.
Localization and morphology of cat extraocular muscle afferent neurones identified by retrograde transport of horseradish peroxidase
Authors: Porter John D. , Spencer Robert F. 
Published: May 2005

AbstractAfferent neurones that provide proprioceptive innervation of extraocular muscles of the cat have been identified by means of retrograde axonal transport of horseradish peroxidase (HRP). Discrete injections of HRP into the medial rectus, lateral rectus, or retractor bulbi muscles labeled pseudounipolar neurones that were localized exclusively to the ipsilateral semilunar ganglion. The distribution of labeled neurones within the ganglion was consistent with its somatotopic organization with the majority found within the ophthalmic subdivision. Cell counts indicating approximately 90 labeled neurones per horizontal rectus muscle correlated well with earlier quantitative observations regarding the percentage of afferent fibers in oculomotor nerves and the number of proprioceptive terminals in the extraocular muscles. Neither the trigeminal mesencephalic nucleus nor the contralateral semilunar ganglion contained labeled neurones following injections of HRP into extraocular muscles.Consistent with other studies of spinal and cranial ganglia the contingent of pseudounipolar neurones present in the cat semilunar ganglion included both light and dark cell types. Light and electron microscope analysis of HRP‐labeled neurones in combination with acetylcholinesterase (AChE) histochemistry revealed that only one of the two neuronal types, the light cell, subserves extraocular muscle proprioception. Our data support the hypothesis that ganglion neurone type and, more specifically, soma diameter, are important determinants of functional status.
Ontogeny of somatostatin‐containing neuron system of the rat: Immunohistochemical analysis. II. Forebrain and diencephalon
Authors: Shiosaka Sadao , Takatsuki Kenichi , Sakanaka Masahiro , Inagaki Shinobu , Takagi Hiroshi , Senba Emiko , Kawai Yuriko , Iida Hisashi , Minagawa Hideo , Hara Yoshinobu , Matsuzaki Takashi , Tohyama Masaya 
Published: May 2005

AbstractThe ontogeny of the somatostatin (SRIF) neuron system in the forebrain and diencephalon of the rat was investigated by means of the indirect immunofluorescence method.SRIF‐positive cells first appear in the primordium of the hypothalamus surrounding the fasciculus mammillothalamicus of the fetus at gestational day 14 (10–12‐mm embryo). At gestational days 16–17 (14–17‐mm embryo), SRIF‐positive cells appear in the developing piriform cortex and entopeduncular nucleus. The fetus at gestational days 18–19 (17–26‐mm embryos) showed a remarkable increase in the number of SRIF‐positive cells and numerous groups of such cells are detectable in various forebrain and diencephalic areas such as the hypothalamic periventricular zone, zona incerta, area lateral to the commissura posterior (ACP), area between the optic tract and capsula interna, pars retrolenticularis (AOR), n. caudatus putamen, hippocampus, somatic sensory cortex, and n. accumbens, etc. At gestational day 20, SRIF‐positive cells newly appear in the septum, olfactory bulb, diagonal band of Broca, claustrum, lateral preoptic area, and lateral habenular nucleus. The majority of SRIF‐positive structures found in the forebrain and diencephalon increase in number during the perinatal stage (between gestational day 21 and postnatal day 2) and more or less maintain their immunoreactivity even in adult rats. However, SRIF‐positive cells located in the AOR, ACP, and lateral septal area, etc., begin to decrease in number during the perinatal stage and no or only a few SRIF‐containing cells are identified in these areas of infant and adult rats.
The thalamic connectivity of the primary motor cortex (MI) in the raccoon
Authors: Sakai Sharleen T. 
Published: May 2005

AbstractThe purpose of this study was to determine the pattern of thalamic projections of the primary motor cortex (MI) in the raccoon, a carnivore species noted for neural specialization of sensorimotor function.Following electrophysiological identification of circumscribed regions of MI, injections of horseradish peroxidase (HRP) or HRP combined with tritiated amino acids were made in 15 animals. Labeled thalamic cells were found predominantly in the ventral lateral nucleus (VL). For a given cortical injection site within MI, labeled neurons in VL formed a crescent‐shaped band which extended in a dorsoventral direction when viewed in coronal sections. These bands were topographically organized. Following an injection of the MI hindlimb area in the medial part of the posterior cruciate gyrus, both retrogradely labeled neurons and anterograde label formed a thin band at the lateral edge of VL while an injection of the MI face area in the lateral part of the anterior cruciate gyrus resulted in both anterograde and retrograde label in medial VL and the principal division of the ventromedial nucleus (VMp). An injection of the MI forepaw area localized to the rostral and central part of the posterior cruciate gyrus resulted in a band of labeled neurons occupying the dorsal extent of VL and continuing into the ventrolateral aspect of the ventral anterior nucleus (VA). In contrast, an injection of the MI forepaw area which was localized to the caudal extent of the posterior cruciate gyrus resulted in a wide and diffuse band of labeled neurons and anterograde label in the ventral portion of VL. All injections of MI produced cell labeling in the paracentral nucleus (PC) and the central lateral nucleus (CL) of the intralaminar group.These results demonstrate that VL is the primary thalamic dependency of MI in the raccoon. Labeled cells were not observed in the ventrobasal complex. The MI pattern of thalamic connectivity observed in the present study suggests that while differences exist in the regional specialization of sensorimotor structures among species, there appears to be little variation in the overall organization of thalamocortical relations.
Membrane specializations in the outer plexiform layer of the turtle retina
Authors: Schaeffer Susan F. , Raviola Elio , Heuser John E. 
Published: May 2005

AbstractThe internal organization of the plasma membrane at specialized contacts in the outer plexiform layer of the turtle, Pseudemys scripta elegans, was analyzed with the aid of the freeze‐fracturing technique. In the invaginating synapse of cone pedicles the plasma membrane of the photoreceptor ending contains an aggregate of P‐face particles, images of synaptic vesicle exocytosis, and rows of forming coated vesicles which are arranged in sequence from apex to base of the synaptic ridge. Thus, freeze‐fracturing provides positive evidence that the synaptic ridge represents the active zone at the surface of the photoreceptor endings. Horizontal cell processes of dyads and triads have an aggregate of P‐face particles opposite the apex of the ridge, but lack images of vesicle exocytosis. Deep‐etching and rotaryshadowing demonstrate that an array of minute protrusions decorates the true outer surface of the horizontal cell membrane at the site of the intramembrane particle aggregate. The membrane of the invaginating bipolar dendrite is unspecialized. At basal junctions, the cone pedicle membrane has a sparse complement of P‐face particles, but images of vesicle exocytosis are absent. The adjoining bipolar membrane is characterized by a prominent aggregate of E‐face particles, often arranged in an orthogonal lattice. The freeze‐fracture profile therefore suggests the existence of (1) a sign‐conserving cone‐to‐horizontal cell synapse; (2) a sign‐inverting synapse between cones and invaginating bipolar dendrites; and (3) a sign‐conserving synapse between cones and bipolar dendrites at basal junctions. No freezefracture evidence was found for a horizontal‐to‐cone or horizontal‐to‐bipolar cell synapse within the synaptic invaginations.
Organization of the hand area in the primary somatic sensory cortex (SmI) of the prosimian primate, Nycticebus coucang
Authors: Carlson Mary , Fitzpatrick Kathleen A. 
Published: May 2005

AbstractThe topography of low‐threshold (LT) cutaneous input from the hand to SmI cortex of the prosimian primate Nycticebus coucang was mapped in detail by means of threshold receptive field techniques. The area of cortex responding to LT stimulation of the hand can be divided into three distinct subdivisions on the basis of physiological as well as cytoarchitectonic criteria. The rostral subdivision in the hand area (G1) responds to stimulation of the glabrous surface of the digits and hand. Within this field cells located rostrally have receptive fields located on the glabrous digit tips, while caudally located cells respond to stimulation of the proximal glabrous palm. Receptive fields in G1 are small in size and have low thresholds. G1 is coextensive with an area of cortex having the cytoarchitectonic features of koniocortex. The caudal region of the LT hand area consists of two subdivisions. Laterally, cells in this caudal region (H) respond to stimulation of the dorsal hairy digits and hand. Receptive fields on the dorsal hairy digits are found rostrally in this subdivision, while receptive fields on the dorsal hand and wrist are encountered caudally. Thus, the hand is projected serially across G1 and H. Within H, thresholds are similar to those in G1, but receptive fields are much larger in H than in G1. A second glabrous hand area (G2), is found in the medial part of the caudal region of the LT hand area. In G2 receptive fields on the glabrous ulnar digits are encountered rostrally, while more caudally cells respond to stimulation of the radial digits. Few glabrous palm fields were found in G2. Receptive field sizes and thresholds in G2 are quite similar to those in G1. Subdivisions H and G2 have the cytoarchitectonic characteristics of parakoniocortex. Although H and G2 are not distinguishable from one another, they can be easily separated from the more rostral koniocortex which contains the first glabrous hand area (G1). Thus, the SmI hand area of Nycticebus is unique among those of the other prosimian, Galago, thus far mapped in that two separate somatotopic projection patterns of the glabrous hand are present within the LT area. In this respect, Nycticebus more closely resembles simian species in which multiple LT hand areas are present in SmI in all forms which have been mapped. This is not to suggest that G2 in Nycticebus is either homologous to, or a precursor of, those multiple cutaneous areas reported for Old and New World simian species. Rather we suggest that the second glabrous projection in Nycticebus, and that of simian species, may have been achieved by the displacement of the dorsal hand projection occupying the architectonically distinct caudal SmI field in earlier prosimian species.
Cell death in the mammalian visual system during normal development: I. Retinal ganglion cells
Authors: Sengelaub D. R. , Finlay B. L. 
Published: May 2005

AbstractDegenerating cells may be observed with light microscopy in the hamster retinal ganglion cell layer during early postnatal development. On the first postnatal day, degenerating cell profiles were found at a rate of 2.7 per 1,000 live cells. This rate increased to a peak of 14.7 degenerating cells per 1,000 live on postnatal day 5 and then slowed to 4.2 per 1,000 live by postnatal day 10. These rates of cell death correspond to a 49% reduction in cell number in the ganglion cell layer. Examination of the spatial pattern of cell death revealed that although on visual inspection degenerating cells appear to occur in clumps, statistical analyses demonstrated a random distribution within retinal areas. Across the retina, cell death rates were higher in peripheral retina than in central retina. The timing and pattern observed correspond well with that of cell degeneration observed in the superficial layers of the superior colliculus, the major target of the retinal projection.