bluuebunny/crossref_metadata_2025_split huggingface dataset:
Golgi and EM studies of the formation of dendritic and axonal arbors: The interneurons of the substantia gelatinosa of rolando in newborn kittens
Authors: Falls William , Gobel Stephen 
Published: January 2005

AbstractGolgi studies in newborn kittens show that the two most prevalent interneurons in Rexed's lamina II of the dorsal horn of the medulla, the stalked cell and islet cell (Gobel, 1975a,b, 1978b) form their dendritic arbors in a similar fashion. At birth, both cell types are present in forms ranging from immature, in which numerous short dendrites radiate from the cell body in all directions, to relatively mature in which their dendritic arbors have elongated in specific directions and the adult branching pattern is already evident. During postnatal maturation, many dendrites are lost while only a few go on to lengthen. The unmyelinated axons of both cells are first recognized in forms in which lengthening dendrites have taken on their preferred direction of orientation.The two parts of Rexed's lamina II, i.e., layers IIa and IIb have already reached their adult mediolateral width at birth and the neuropil has nearly achieved its adult compactness. Space in the compact neuropil for elongating neuronal and astrocytic processes becomes available through the disintegration of many existing dendrites and by an overall fourfold increase in the rostrocaudal length of the dorsal horn of the medulla during postnatal maturation. At birth, the lengthening of the plasma membranes of elongating neuronal and astrocytic processes proceeds as vesicles (addition vesicles) found in aggregates throughout dendrites, unmyelinated axons and astrocytic processes fuse with and become incorporated into the existing plasma membranes.In addition, many dendrites in layers IIa and IIb are beading up and disintegrating. Within the beads, neurotubules are lost and addition vesicles fuse with each other to form small cavities. These cavities continue to enlarge, hollowing out the beads. The cavities ultimately open to the intercellular space as their membranes fuse with the plasma membrane of the beads. Finally, the beads disintegrate and their plasma membranes fragment. The thread‐like segments between adjacent disintegrating beads shrivel until they ultimately disappear. Disintegration of beaded dendrites results in very little debris and does not provoke a phagocytic glial reaction. The disintegration of a dendritic branch takes place in spite of synaptic input from non‐primary axons and is thought to occur from a failure to establish synaptic connections with primary axonal endings.
Rod photoreceptors and scotopic vision in ground squirrels
Authors: Jacobs Gerald H. , Tootell R. B. H. , Fisher Steven K. , Anderson Don H. 
Published: January 2005

AbstractGround squirrel retinas contain a relatively small complement of rods (5–10% of all photoreceptors) which are thought to provide the basis for a weak scotopic visual capacity. In a previous investigation of the California ground squirrel (Spermophilus beecheyi) involving the recording of a retinal gross potential, the electroretinogram (ERG), electrophysiological evidence for a viable scotopic signal could be obtained from some, but not all of the ground squirrels examined. To further pursue the possibility that there is a structural/functional discrepancy in the relationship between rod photoreceptors and scotopic vision in the ground squirrel, several experiments involving electrophysiological, behavioral, and anatomical observations have been conducted. We found that although about one‐third of the ERGs recorded from a large sample of California ground squirrels lack those characteristics which would indicate the presence of a viable scotopic signal, the retinas of all the squirrels appear to contain the same small population of rod photoreceptors. Additional experiments on the golden‐mantled ground squirrel (Spermophilus lateralis), including behavioral as well as ERG measurements and anatomical observations, lead to this same conclusion.
Rod and cone inputs to bipolar cells in goldfish retina
Authors: Ishida A. T. , Stell W. K. , Lightfoot D. O. 
Published: January 2005

AbstractFive morphological types of bipolar cells which make synaptic contact with rods and cones are distinguished in the retina of adult goldfish (Carassius auratus) by characteristics readily observable in the light microscope. Cells were designated type a or type b according to whether their axons terminate in the distal part (sublamina a) or proximal part (sublamina b) of the inner plexiform layer, respectively. Analysis of serial semi‐thin sections of Golgiimpregnated cells demonstrates that each subtype of bipolar contacts rods and a characteristic set of chromatic subtypes of cones: types al and bl cells contact rods and red‐sensitive cones, while types a2, b2, and b3 contact rods and red and green‐sensitive cones. Comparison with published descriptions of cells stained with Procion Yellow after intracellular recordings had been made suggests that type a cells should be off‐center types and type b on‐center. Furthermore, it is suggested that the receptive fields of cell types al and bl should be non‐color‐coded, and those of a2, b2, and b3 color‐coded.
Somatotopographic organization in the second somatosensory area of M. fascicularis
Authors: Robinson C. J. , Burton H. 
Published: January 2005

AbstractThe second somatosensory area (SII) of awake, untrained cynomolgus monkeys was surveyed with recordings from nearly 1,000 single neurons. A detailed somatotopographic organization could be demonstrated in SII because the majority of these neurons had contralateral, moderate to well‐defined receptive fields of < 10cm2, and because neighboring neurons possessed receptive fields that were only slightly displaced from one another. Different body regions were represented in successive anterior to posterior strips that were oriented across the parietal operculum with an anterolateral to posteromedial slant. Neurons with trigeminal receptive fields were found in the anterior portion of SII; these neurons were the only ones in SII with predominantly bilateral receptive fields (r.f.'s). Neurons with digit or hand r.f.'s form the largest component of the map, and were located posterior to those with face r.f.s. Most of these neurons had only contralateral activation. The hand and digit region was followed in turn by the arm, the upper and lower trunk, and the hindlimb regions. Although the overall SII orientation was along an anterior‐posterior gradient, recordings at individual coronal planes often demonstrated isolated sequences of receptive fields that exhibited a medial‐lateral progression. The principle example of this latter gradient was seen in the forelimb region where digits one through five were represented in an overlapping sequence across the parietal operculum. Except for portions of the digit representation, neighboring sequences of neurons in SII do not form a precise topologic map of the body that is comparable to the somatotopic maps observed in areas 3b and 1. The present findings contrast with previous physiological studies of SII in the primate. These discrepancies are discussed in relation to methodological differences and in terms of distinctions used to define the boundaries of SII.
Autoradiographic tracing of developing subcortical projections of the occipital region in fetal rabbits
Authors: Distel H. , Holländer H. 
Published: January 2005

AbstractThirty rabbit embryos and two neonates (E18‐P1) received micropipette injections of 3H‐Leucine into the occipital region of one hemisphere and were killed after 0.5–5 hours. Incorporated tracer was demonstrated by autoradiography of serial sections of the brains. The first axons were seen in the intermediate zone of the developing cerebral cortex, on day E20, and by day E22 they reached the internal capsule. The entire cortico‐peduncular bundle and a short branch of the superficial (thalamic) bundle were labeled on day E24. On day E25, additional branches directed to claustrum, thalamus (deep bundle), and cerebellum were distinguished. By day E28 the first indications of terminal field development were observed. One day before birth (E30), the neonate pattern of subcortical pathways was fully established and silver grain condensations were present over most of the subcortical target areas.Subcortically, the axons followed preferentially preexisting fiber tracts. There was a period of at least 2–3 days between the arrival of the supplying bundles at the target sites and the onset of terminal field formation: The axon bundles grew first towards more distal targets, and even beyond, before terminal fields developed proximally. Transient axon bundles reaching the cerebellar paraflocculus and traveling along the pyramidal tract and the external and extreme capsules failed to form terminal fields and disappeared around birth. The data suggest that growth of long axonal tracts and the development of terminal fields are separate phenomena possibly regulated by different mechanisms.
Fluorescence and electron microscopical observations on the amine‐accumulating neurons of the cebus monkey retina
Authors: Dowling John E. , Ehinger Berndt , Florén Ingrid 
Published: January 2005

AbstractThe organization of the Cebus monkey retina was analysed after the intraocular injection of 5,6‐dihydroxytryptamine. This amine was taken up not only by the previously known dopaminergic neurons, but also by a set of indoleamine‐accumulating neurons, whose processes are confined to the inner plexiform layer.The synaptic contacts of the dopaminergic neurons were analysed in the electron microscope after the processes of the indoleamine‐accumulating neurons were destroyed by the intrvitreal injection of the neurotoxic indoleamine, 5,7‐dihydroxytryptamine. The subsequent injection of 5,6‐dihydroxytryptamine induces certain changes in the dopaminergic neurons which accumulate the substance: electron‐dense cores appear in the synaptic vesicles, and increased electron‐density of mitochondrial and cellular membranes is often observed.The dopaminergic neurons were found to be presynaptic to amacrine cell perikarya and processes in the inner plexiform layer. In the outer plexiform layer they were presynaptic to both bipolar and horizontal cells, but they did not contact photoreceptors. The dopaminergic neurons received synapses only in the inner plexiform layer, from amacrine cell processes. It is inferred that in Cebus most dopaminergic neurons belong to a special class of retinal neuron, the interplexiform cells, which appear to transmit information centrifugally within the retina, from the inner to the outer plexiform layers. There are considerable similarities between the synaptology of the dopaminergic interplexiform neurons in the Cebus monkey and the goldfish retina, and the function of interplexiform neurons may therefore be similar in these two species.
Neurons in cat lateral geniculate nucleus that concentrate exogenous [3H]‐γ‐aminobutyric acid (GABA)
Authors: Sterling Peter , Davis Thomas L. 
Published: January 2005

AbstractAbout one‐quarter of the neurons in the A‐laminae of the cat lateral geniculate selectively accumulate exogenous [3H]‐γ‐aminobutyric acid (GABA), its analog, [3H]‐2,4‐diaminobutyric acid (DABA), and the GABA agonist, [3H] muscimol. These neurons are small (12–18 μm diameter) and lack a laminar body, which suggests that they correspond to the class III cell identified in Golgi material. GABA and DABA are also accumulated by F‐terminals which are post‐synaptic to retinal terminals and presynaptic to relay cell dendrites. It is suggested that GABA may be the transmitter for these small neurons which appear to mediate by means of local circuits a feed‐forward inhibition onto the relay cells.
Identification of early neurons in the brainstem and spinal cord: I. An autoradiographic study in the chick
Authors: McConnell Jo Ann , Sechrist John W. 
Published: January 2005

AbstractEarly stages in chick neurogenesis were investigated with tritiated thymidine (3H‐Tdr) autoradiography to determine the location and identity of the first neurons produced for the central nervous system. These cells have been shown to arise prior to neural tube closure (Sechrist, '75). Chicks were treated at selected intervals between 20 and 72 hours of incubation with 3H‐Tdr in a modified pulse‐labeling technique, and terminated on the 18th day of embryonic development (E18), when neuronal types could be determined. Some of the earliest neurons start their final DNA synthesis before 20 hours of incubation (head process, Hamburger‐Hamilton stage 5). These are primarily medium‐sized cells of the reticular formation in the medulla and at the diencephalic‐mesencephalic junction, but also in the intermediate zone of the spinal cord. Motor neurons of the brainstem and spinal cord begin to appear next, after 26–28 hours incubation; the first sensory neurons arise after 32 hours. Other workers (Ramon y Cajal, '60; Tello, '23; Windle and Austin, '36) found that neurons of the reticular formation were the first to differentiate neurofibrils, during the latter part of E2, indicating that fibrillogenesis in these cells begins about 24 hours after the initial cessation of DNA replication.
Neuromorphometric features and dimensional analysis of the vestibular end organ in the little brown bat (Myotis lucifugus)
Authors: Ramprashad Fred , Landolt Jack P. , Money Kenneth E. , Laufer Jerry 
Published: January 2005

AbstractNeuromorphometric parameters of the vestibular system were determined from serial sections of temporal bones from four little brown bats. Well‐developed eminentiae cruciatae project from the cristae ampullares of the anterior and posterior membranous ampullae. A total of 4,500 bipolar ganglion cells were enumerated within the vestibular ganglion. The widths of the cell somas varied from 2.5 to 20μm, with 70% of them having widths between 5.0 and 12.5 μm. Two maxima were observed in a curve of ganglion cell density as a function of the length of the ganglion. The first maximum indicated a density of 4,800 cells per mm2 at a length 0.20 mm from the apex of the ganglion (in the pars dorsalis); the second, a density of 4,750 cells per mm2 at 0.38 mm (in the pars ventralis). The morphometric parameters studied were the radii of curvature of the semicircular ducts, the cross‐sectional diameters of the semicircular canals and ducts, the dimensions of the cristae ampullares and their membranous ampullae, and dimensions pertaining to the statoconial organs. Surface areas (measured from graphic projections) were determined as 0.098 mm2 and 0.016 mm2 and hair cell count 500 and 1,300 cells for the saccular and utricular maculae, respectively. The radii of curvature of the three semicircular ducts, R, were dissimilar, with the anterior duct having the largest radius (R = 0.91 mm) and the posterior duct the smallest one (R = 0.91 mm) and the posterior duct the smallest one (R = 0.69 mm). The average crosssectional diameters of the anterior, lateral, and posterior ducts were measured as 0.11 mm, 0.14 mm, and 0.13 mm, respectively. Some of the morphological parameters were used to ascertain information regarding the dynamics of semicircular–canal function. In particular, the coefficients θ and Π in the torsion pendulum model (Steinhausen, '31; Egmond et al., '49), and the time constants ζL ⋍ Π/Δ and ζS ⋍ θ/Π of the torsion pendulum model were estimated for the little brown bat from these parameters. Where appropriate, comparisons were made to time constants obtained for other species.
Freeze‐fracture study of the postsynaptic membrane of the cerebellar mossy fiber synapse in the frog
Authors: Korte Gary E. , Rosenbluth Jack 
Published: January 2005

AbstractWe have examined the postsynaptic membrane of the synaptic junctions of frog cerebellar mossy fibers by electron microscopy of freeze‐fracture replicas and thin sections. The intramembranous particles (imps) in the E fracture face of the postsynaptic membrane are approximately 10 nm in size and form conspicuous aggregates which we classified as macular, annular, or anastomotic in form, according to the occurrence and placement of imp‐free ‘windows’ within the aggregate. The size and shape of the aggregates appear related in that the area of macular aggregates is consistently smaller than the area of annular or anastomotic aggregates. Measurements of aggregate area range from 0.06 to 0.75 μm2. The variable size and shape of the imp aggregate in the postsynaptic membrane sets it apart from other excitatory synapses in the central nervous system, where macular aggregates are usually described. Examination of serial thin sections suggests that the shape of the postsynaptic density is equivalent to that of the imp aggregate observed in the postsynaptic membrane by freeze‐fracture. This supports the notion that the region of postsynaptic membrane associate with the postsynaptic density in thin sections correponds to the particle‐rich regions of E face membrane observed in freeze‐fracture replicas.
Descending projections from the spinal and mesencephalic nuclei of the trigeminal nerve to the spinal cord in the cat. A study with the horseradish peroxidase technique
Authors: Matsushita Matsuo , Okado Nobuo , Hosoya Yasuhiko , Ikeda Michiko 
Published: January 2005

AbstractDescending projections from the spinal (Vsp) and the mesencephalic nuclei (Vme) of the trigeminal nerve to the spinal cord were studied by means of the retrograde horseradish peroxidase technique in the cat.The number of labeled neurons was largest in the case of high cervical injections and decreased as the injections were placed caudally. Small laminae III and IV neurons of the nucleus caudalis (Vc) were labeled ipsilaterally following injections placed as caudally as the middle cervical segments (C4‐C5). Lamina I (marginal) neurons of the Vc were labeled ipsilaterally after injections at the middle thoracic level (T6) but those of C1 were labeled after lumbar injections (L3). Lamina V neurons of C1 and the medullary counterparts were labeled bilaterally after injections placed caudally to thoracic segments. A few small neurons were labeled in the ipsilateral nucleus interpolaris (Vi) after injections placed as caudally as the middle cervical segments (C6). Among the subdivisions of the Vsp, the labeled neurons were most numerous in the nucleus oralis (Vo). They were medium‐sized and large, and appeared bilaterally, with an ipsilateral predominance at the level of the superior olive. The great majority projected to the cervical segments but a few also projected to the lower cervical to the thoracic segments (C8‐T9). Neurons of the Vme projected ipsilaterally to the upper cervical segments (C1‐C3). No projections were found from the principal sensory nucleus.The present study suggests that the trigeminospinal projections of the Vsp and the Vme are composed of various cells of origin and thereby subserve not only the trigeminospinal reflex but other unknown functions.
HRP study of the organization of auditory afferents ascending to central nucleus of inferior colliculus in cat
Authors: Brunso‐Bechtold J. K. , Thompson G. C. , Masterton R. B. 
Published: January 2005

AbstractThe ascending auditory projections to central nucleus of inferior colliculus its ventrolateral and dorsomedial subdivisions (ICVI, and ICDM) have been studied in cat using both pressure and electrophoretic injections of horseradish peroxidase (HRP). The results indicate that the predominant ascending projections to inferior colliculus orginate in (1) contralateral cochlear nucleus, (2) contralateral and ipsilateral lateral superior olive, (3) ipsilateral medial superior olive, (4) ipsilateral ventral nucleus of the lateral lemniscus, (5) ipsilateral and contralateral dorsal nucleus of the lateral lemniscus, and (6) contralateral inferior colliculus. In addition, ipsilateral cochlear nucleus, ipsilateral and contralateral intermediate nucleus of the lateral lemniscus, ipsilateral, and to a lesser extent contralateral, periolivary nuclei project to inferior colliculus. Of these nuclei, the lateral superior olive projects exclusively to ICVL and ipsilateral cochlear nucleus and contralateral inferior colliculus project mostly, if not exclusively, to ICDM. Many of these projections demonstrate a cochleotopic organization and frequently a nucleotopic organization as well. A cochleotopic organization of the projections is apparent for cochlear nucleus and superior olivary complex. A nucleotopic organization suggests that the heaviest terminations of contralateral inferior colliculus are medial and dorsal in inferior colliculus, of medial superior olive are dorsal and lateral, of superior olivary complex are rostral, of cochlear nucleus are caudal, and of ventral nucleus of the lateral leminiscus are caudal.
Freeze‐fracture study of photoreceptor outer segments and pigment epithelium in dystrophic and normal retinas
Authors: McLaughlin Barbara J. , Boykins Lou G. 
Published: January 2005

AbstractThe intramembrane organization of outer segment (OS) membranes and pigment epithlial (PE) microvilli has been studied in rats (10–17 postnatal days) with inherited retinal degeneration (RCS) and in normal retinas from genetically controlled rats (RCS‐rdy +). The OS plasma membranes of both dystrophic and normal retinas are characterized by large particles surrounding circular, particle‐free zones on the P‐faces (cytoplasmic leaflets) and a sparse distribution of particles on the E‐faces (external leaflets). No regional differences in particle distribution are observed in either basal or distal plasma membrane regions. Outer segment disc membranes are characterized by large, densely packed P‐face particles and ridged E‐faces with very few particles. Small, particle‐free patches of membrane are present in the basal disc P‐faces of both normal and dystrophic retinas, which Andrews and Cohen (1979) have described as characteristic of newly added disc membrane. In dystrophic retinas, larger, particle‐free domains are observed in the distal disc membranes (P‐faces) and accumulating membranous debris. In older retinas, which have accumulated more debris, the particle‐free domains occupy vast areas of the membrane faces and it is not possible to identify these membranes as belonging to either discs or plasma membranes. No comparable areas of particle‐free membrane are observed in the distal discs and OS plasma membranes of normal retinas. Pigment epithelial microvillus membranes are characterized by an intermixture of large and medium‐sized particles surrounding irregular particleq‐free areas, but no differences between normal and dystrophic PE membranes are observed. The changes in particle distribution observed in the dystrophic retinas suggests that the intramembrane molecular composition of older disc membranes has become altered or rearranged as the OS membranes accumulate as debris.