bluuebunny/crossref_metadata_2025_split huggingface dataset:
Active zone organization and vesicle content scale with bouton size at a vertebrate central synapse
Authors: Yeow M. B. L. , Peterson E. H. 
Published: January 2005

AbstractA common observation in studies of neuronal structure is that axons differ in the size of their synaptic boutons. The significance of this size variation is unclear, in part because we do not know how the size of synaptic boutons is related to their internal organization. The present study has addressed this issue by using three‐dimensional reconstruction of serial thin sections to examine the ultrastructure of synaptic boutons that vary in size. Our observations are based on complete or near‐complete reconstructions of 53 synaptic boutons contacting large neurons in the ventromedial gray matter of the upper cervical spinal cord (probable neck motor neurons).We characterized bouton size in terms of volume and total area of membrane apposed to the motor neuron surface (apposition area). Boutons vary in apposition area by a factor of 40, and there is a significant positive correlation between our two measures of bouton size. In addition, bouton size is systematically related to four ultrastructural variables: 1) total active zone area, 2) number of active zones, 3) individual active zone area, and 4) number of synaptic vesicles. The correlations between these variables and both of our measures of bouton size are positive and significant. These data suggest that bouton size may be an index of ultrastructural features that are thought to influence transmitter storage and release.
Androgenic regulation of dendritic trees of motoneurons in the spinal nucleus of the bulbocavernosus: Reconstruction after intracellular iontophoresis of horseradish peroxidase
Authors: Sasaki Mitsuyoshi , Arnold Arthur P. 
Published: January 2005

AbstractAndrogen‐sensitive motoneurons in the spinal nucleus of the bulbocavernosus (SNB) in adult male rats were labeled after intracellular iontophoresis of horseradish peroxidase, after which they were fully reconstructed in three dimensions in order to measure their dendritic trees. Three groups of rats were compared: intact adult male rats and male rats castrated as adults and given Silastic tube implants containing either testosterone or nothing. In the high‐androgen groups (intact males and testosterone‐treated castrates), soma size and the diameter of the first‐order dendrites were larger than in blank‐treated castrates. Moreover, the terminal dendrites in all groups possessed growth cones, implying that the dendrites of these motoneurons are capable of growth in adulthood. However, there were no statistically significant group differences in the length, membrane surface area, or volume of the dendritic trees, or in the orientation or branching symmetry of dendrites. In general, there were positive correlations between the size of the motoneuronal soma and various measures of the size of the dendritic tree and between the diameter of individual stem (first‐order) dendritic branches and the size of remainder of that dendrite. These data suggest that there may be a modest effect of androgen on the size of the dendritic trees of SNB motoneurons in adulthood, although the effect is much smaller than has previously been reported.
Accurate prediction of Purkinje cell number from cerebellar weight can be achieved with the fractionator
Authors: Mayhew Terry M. 
Published: January 2005

AbstractPurkinje cell nucleoli are used as counting units in order to obtain unbiased (fractionator)estimates of the number, N, of Purkinje neurons in adult mammalian cerebella of known weight, W. Regression analysis is then employed to establish the nature of the relationship between logN and logW. The linear regression equation defines an allometric relation that is employed to predict number in cerebella of known weight from other mammals. Predicted numbers are tested against empirical estimates.For 19 cerebella ranging in weight from 0.2 g (rat) to 113 g (human), the allometric relation between Purkinje cell number and organ weight was determined. By using this relation, the mean complement in three rabbit cerebella (average weight, 0.87 g) is predicted to be 0.63 million. This figure is confirmed by fractionator estimates made on the same three brains. The cat cerebellum should contain about 1.5–2.0 million Purkinje cells. An estimate of 1.2–1.3 million cells is to be found in the literature.Including rabbit cerebella in a refined equation yields the following relation:

With this refined equation, further predictions are made about the numbers likely to be found in the cerebella of the dog, goat, pig, ox, and horse. The numbers predicted for these animals must await experimental verification, but they are entirely consistent with previous suggestions that neuronal packing densities decrease with increasing brain size.
Projections to the basis pontis from the superior temporal sulcus and superior temporal region in the rhesus monkey
Authors: Schmahmann Jeremy D. , Pandya Deepak N. 
Published: January 2005

AbstractThe present investigation was designed to determine the origins in the temporal lobe, and terminations in the pons, of the temporopontine pathway. Injections of tritiated amino acids were placed in multimodal regions in the upper bank of the superior temporal sulcus (STS), and in unimodal visual, somatosensory, and auditory areas in different sectors of the lower bank of the STS, the superior temporal gyrus (STG), and the supratemporal plane (STP). The distribution of terminal label in the nuclei of the basis pontis was studied using the autoradiographic technique.Following injections of isotope into the multimodal areas (TPO and PGa) in the upper bank of the STS, intense aggregations of label were observed in the extreme dorsolateral, dorsolateral, and lateral nuclei of the pons, and modest amounts of label were seen in the peripeduncular nucleus. The caudalmost area TPO projected in addition to the ventral and intrapeduncular pontine nuclei. The second auditory area, AII, and the adjacent auditory association areas of the STG and STP contributed modest projections to the dorsolateral, lateral, and peripeduncular nuclei, but generally spared the extreme dorsolateral nucleus. The lower bank of the STS, which subserves central vision, the somatosensory associated region at the fundus of the rostral STS, and the primary auditory area did not project to the pons.The higher order, multimodal STS contribution to the corticopontocerebellar circuit may provide a partial anatomical substrate for the hypothesis that the cerebellum contributes to the modulation of nonmotor functions.
Central projections of cervical primary afferent fibers in the guinea pig: An HRP and WGA/HRP tracer study
Authors: Prihoda Manfred , Hiller Maria‐Sophie , Mayr Robert 
Published: January 2005

AbstractThe central course and the projections of the first and the second cervical dorsal root ganglia and of suboccipital muscle primary afferent fibers in the guinea pig were studied by means of anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA/HRP) or aqueous solution of horseradish peroxidase (HRP).Injections of WGA/HRP into the second cervical dorsal root ganglion produced labeling in the dorsal and ventral horns. Within the spinal cord, the largest amount of HRP reaction product was found within the lateral third of the substantia gelatinosa and within the central cervical nucleus. The main area of termination in the medulla was the external cuneate nucleus. However, HRP reaction product was also found within the medial and inferior vestibular nuclei, cell group x, the perihypoglossal nuclei, the nucleus of the solitary tract, and the nucleus of the spinal trigeminal tract. Descending fibers could be detected as caudal as spinal segment T5.Injections of WGA/HRP into the first cervical dorsal root ganglion produced heavy terminal label within the central cervical nucleus but not within the substantia gelatinosa. Again, the external cuneate nucleus was the main area of termination within the medulla. Label could not be observed within the vestibular nuclear complex or within the spinal trigeminal nucleus.Injections of aqueous HRP into the suboccipital muscles produced heavy transganglionic label within the central cervical nucleus, whereas the substantia gelatinosa totally lacked terminal label. Ascending proprioceptive fibers reached the external cuneate nucleus and group x. Scanty projections could be detected within the vestibular nuclei as well as within the perihypoglossal nuclei except for the nucleus prepositus hypoglossi. Label was absent, in the spinal trigeminal nucleus.
Synaptogenesis in the primary visual cortex of the tree shrew (Tupaia belangeri)
Authors: Ungersböck Alfred , Kretz Robert , Rager Günter 
Published: January 2005

AbstractThe primary visual cortex of the tree shrew is characterized by the lack of ocular dominance columns. The two eyes are represented in sublayers of laminae 3 and 4. In an earlier study using the transneuronal transport we observed that the geniculate afferents from the two eyes do not initially overlap and then segregate into their appropriate sublaminae. The final distribution pattern can already be observed during the early postnatal period. Since segregation and elimination of afferent terminal branches do not seem to take place, we wanted to investigate whether or not an overproduction of synapses can be observed as in several other animals. We examined layers 3B, 3C, 4A, and 4B, which receive afferents from the retina via the lateral geniculate nucleus, from P5 to maturity by using the electron microscope. The brain tissue was excised in the region where the central vision is represented in adult animals. Then we determined the density of synapses per 100 μm2 neuropil for each of the four sublayers at the ages P5, P15, P19, P23, P31, and P42 and in the adult animal (AD). In determining the neuropil we measured the size of two additional compartments, i.e., the compartments consisting of perikarya and of blood vessels. At a higher resolution we determined the fraction of Gray type I and type II synapses in each sublamina and in each developmental stage.The size of the neuropil increases from 57% at P5 to 81% in AD whereas the compartment of perikarya decreases from 42% to 15% and the compartment of blood vessels increases from 1.3% to 3.9%. The synaptic density starts with very low values (3.5/100 μm2) at P5. Then it increases rapidly and attains a maximal rate of increase during the period of eyelid opening. After this period the increase is slowed down and approaches the adult value (12.5/100 μm2) slowly. An overproduction of synapses could not be observed. The percentage of type I and type II synapses also changes during this period. The fraction of type I synapses amounts to 73% at P5 and increases to 92% in AD. The increase intensity of type I synapses is continuous and does not show any sign of overproduction. The density of type II synapses rapidly reaches its final value and then remains constant. Possibly there is a slight overproduction during the period of eyelid opening. The fact that an overproduction of synapses could not be observed may be related to the specific pattern of ingrowth of geniculate afferents which seem to go to their appropriate laminae without any detectable sign of segregation.
Blood‐nerve barrier in the frog during wallerian degeneration: Are axons necessary for maintenance of barrier function?
Authors: Latker Carole H. , Wadhwani Kishena C. , Balbo Andrea , Rapoport Stanley I. 
Published: January 2005

AbstractBlood‐nerve barrier tissues (endoneurial blood vessels and perineurium) of the frog's sciatic nerve were studied during chronic Wallerian degeneration to determine whether barrier function depends on the presence of intact axons. Sciatic nerves of adult frogs were transected in the abdominal cavity; the ends were tied to prevent regeneration and the distal nerve stumps were examined. Vascular permeabilities to horseradish peroxidase and to [14C]sucrose increased to day 14, returned toward normal levels by 6 weeks, and continued at near normal levels to 9 months. Perineurial permeabilities to the tracers increased by day 10 and remained elevated at 9 months. Proliferation of perineurial, endothelial, and mast cells occurred between 3 days and 6 weeks, resulting in an increased vascular space (measured with [3H]dextran) and number of vascular profiles. The perineurium increased in thickness and the mast cells increased in number. This study indicates that during Wallerian degeneration of the frog's sciatic nerve there is (1) a transitory increase in vascular permeability distal to the lesion, that is related to changes within the endoneurium; (2) an irreversible increase in permeability of the perineurium, which begins later than that seen in the endoneurial blood vessels; and (3) proliferation of non‐neuronal components in the absence of regenerating neuronal elements. The results indicate that maintenance of vascular integrity does not require the presence of axons in the frog's peripheral nerve, whereas perineurial integrity and barrier function are affected irreversibly by Wallerian degeneration.
Topographic organization of cortical input to striate cortex in the Cebus monkey: A fluorescent tracer study
Authors: Sousa Aglai P. B. , Piñon Maria Carmen G. P. , Gattass Ricardo , Rosa Marcello G. P. 
Published: January 2005

AbstractCortical afferents to area V1 were studied in seven Cebus monkeys by means of retrograde fluorescent tracers. Injections were placed in V1, under electrophysiological guidance, in the regions of representation of both the upper and lower visual quadrants, at eccentricities that ranged from 0.5 to 64 degrees.In all cases retrogradely filled neurons were found in retinotopically corresponding portions of areas V2 and MT, as denned electrophysiologically (Rosa et al: J. Comp. Neurol. 275:326, 1988; Fiorani et al: J Comp Neurol 287:98, 1989). The results also revealed two other visual zones located anterior to V2 here named third and fourth visual areas. A topographical organization of the connections was observed in these areas, with upper quadrant located ventrally and lower quadrant located dorsally. A clear central‐peripheral gradient, from the lateral to the medial cortical surface, was also observed in these areas.Lower field injections revealed crude topographic organization in area DZ and a diffuse projecting zone in the annectent gyrus. Peripheral injections in V1 revealed a clear upper and lower field segregation in areas PO and prostriata as well as a complex topography in MST. In addition, another region of labeling revealed the presence of an area, the temporal ventral posterior region, with an organized topographic representation of the upper field, with a central to peripheral gradient, from the lateral to the medial cortical surface.Three groups of cortical areas were distinguished according to the laminar distribution of neurons labeled from V1. In the first group, which is characterized by dense infra‐ and supragranular labeling, only V2 was included. The second group consists of areas V3, MT, and PO. These areas show dense labeling in the infragranular layers and occasionally sparse labeling in the supragranular layers. Finally, V4 and the other projecting areas, which are characterized by exclusive labeling of the infragranular layers were included in the third group.
Patterning in the regeneration of electroreceptors in the fin of Kryptopterus
Authors: Bever Michele Miller , Borgens Richard B. 
Published: January 2005

AbstractThe influence of the target tissue on afferent nerve regeneration was studied in the adult glass catfish, Kryptopterus. In this fish, electroreceptors in the anal fin are distributed in a characteristic pattern in the proximal part of the fin and are absent in the distal portion of the fin. We tested whether axons were more likely to induce electroreceptors in certain regions of fin epidermis than in others. We rotated fin transplants so that the location of the degenerating electroreceptors was altered with respect to the regenerating axons in the host tissue dorsal to the fin. The effects of these rotations were observed in the living animal with differential interference contrast optics over a period of 10 weeks. When transplants were reversed rostrocaudally, new electroreceptors formed in the caudal half of the interradial zone, where degenerating electroreceptors were at the time of transplantation. When transplants were rotated so that the dorsoventral and rostrocaudal axes were reversed, some new receptors formed in the old target site regions that were located in the caudal interradial zones (in the distal half of the graft with respect to the host). Regenerating axons reached these regions of the transplant by taking unusual routes around the electroreceptor‐free regions of fin. Very few electroreceptors formed in the distal/caudal or proximal/caudal interradial quadrants of grafts where the original orientation of the tissue was maintained. We suggest that old target sites have a neurotropic influence on the regenerating afferent axons and discuss the possibility that the distal fin epidermis is not as permissive to electroreceptor formation as proximal fin epidermis.
Cell counts and maps in the larval central nervous system of the ascidian ciona intestinalis (L.)
Authors: Nicol Dianne , Meinertzhagen I. A. 
Published: January 2005

AbstractAlthough the ascidian tadpole larva harbors a prospectively valuable prototype of the chordate nervous system, with extensively characterized neural plate cell lineages, the simple cellular composition of the resultant central nervous system (CNS) is not documented in detail. The average total number of cells in the larval CNS of Ciona intestinalis is 335 (range ±4, n = 3), 65 or 66 of which reside in the nerve cord of the tail. The estimates were made by tracing and counting the number of nuclei in serial semithin (1 m̈m) sections cut longitudinally through three larvae, fixed no later than 2 hours after hatching. Within a single fourth larva, L4, 266 cells constituted the CNS in the trunk region of the larva, 45 of which occurred within the visceral ganglion, 215 in the sensory vesicle, and 6 in the neck between the two. Each cell was assigned to one of thirteen categories. Most (182, roughly 68%) are classified as ependymal, a specialized non‐neural cell peculiar to embryonic and larval chordates, from their position lining the cavities of the neural tube's elaborations or from clear similarities in the cytological appearance to those that do. Five cells are accessory cells of the sensory structures: three lens cells and a pigment‐cup cell in the ocellus, and a single pigment cell in the otolith. Of the remaining 79 cells, 36 are sensory, 17 receptors in the ocellus and 19 presumed hydrostatic pressure receptors; these lie on the right and left, sides of the sensory vesicle, respectively. Eighteen of the visceral ganglion cells have been tentatively classified as neurons, as have the remaining 25 cells which form two clusters in the posterior region of the sensory vesicle.
Neuropeptide Y (NPY)‐immunoreactive neurons in the primate fascia dentata; occasional coexistence with calcium‐binding proteins: A light and electron microscopic study
Authors: Nitsch Robrt , Leranth Csaba 
Published: January 2005

AbstractNeuropeptide Y (NPY)‐containing neurons are known to be highly vulnerable following sustained electrical stimulation in rats and in humans suffering from temporal lobe epilepsy. This has been related to a strong excitatory input. In contrast, there is evidence that neurons containing calcium‐binding proteins exhibit a high resistance under experimental seizure and hypoxia conditions. The aim of this study was to determine the coexistence of NPY and calcium‐binding proteins in inhibitory neurons of the primate fascia dentata and their synaptic connections. Vibratome sections of hippocampi of African green monkeys (Cercopithecus aethiops) were immunostained with antibodies against NPY, PARV, and CB. A quantitative coexistence study was performed for NPY and PARV on consecutive semithin sections. In contrast to the rodent hippocampus, NPY‐immunoreactive neurons were found exclusively in the hilus of fascia dentata with horizontally oriented dendrites which did not extend into the granular and molecular layer. Conversely, PARV‐immunoreactive neurons were also present in the granular and inner molecular layer and extended their dendrites far out in the molecular layer and the hilus. Axon terminals immunoreactive for NPY were mostly concentrated in the middle and outer molecular layer and the hilar region and were rare in the granular layer. PARV‐immunoreactive boutons were basically restricted to the granular layer where they formed typical baskets. The antibody against calbindin stained almost exclusively granule cells. Coexistence of NPY‐ and PARV‐immunoreactivity was found only in hilar neurons and was rare (9 out of 152 cells analyzed). These results suggest that most NPY‐immunoreactive neurons do not contain calcium‐binding proteins. NPY‐containing neurons exhibited ultrastructural characteristics as described for inhibitory neurons. Their dendrites were only sparsely contacted by mostly asymmetric synaptic terminals, including a very small number of mossy fiber axon terminals. In turn, numerous NPY‐immunoreactive axon terminals formed symmetric synapses with spines and dendritic shafts of unlabeled neurons in the middle and outer molecular layer, whereas no contact with granule cell bodies was evident. Thus, we conclude that the vulnerability of NPY‐containing inhibitory neurons may be due more to the lack of calcium‐binding proteins than to a strong excitatory innervation. As their axons may contribute to the inhibitory control of the major excitatory input from the entorhinal cortex, their loss following overstimulation may play a role in perpetuating hippocampal seizure activity.
Organization of the zebra finch song control system: Functional organization of outputs from nucleus robustus archistriatalis
Authors: Vicario David S. 
Published: January 2005

AbstractThe organization of projections from nucleus robustus archistriatalis (RA) was mapped by a combination of anatomical tracer techniques. After injections of retrograde tracers in the syringeal part of the hypoglossal motor nucleus (nXIIts), labelled cells were seen in ipsilateral RA, in agreement with previous work. However, a shallow band in the dorsal and dorsocaudal part of RA did not contain labelled cells. Cells in this “cap” area were labelled following tracer injections in the dorsomedial nucleus of midbrain ICo (DM), the other known target of RA projections. The topography of outputs to nXIIts was further examined by making small injections of retrograde tracer into physiologically identified control zones for individual syringeal muscles in nXIIts. The distribution of labelled cells in RA revealed bands of cells that cross RA in approximately horizontal layers and project to different parts of nXIIts. This topography was confirmed with the anterograde tracer PHA‐L. Thus RA contains two functional subdivisions, one related to midbrain centers for vocalization and the other directly controlling syringeal motorneurons. The latter area can be further divided into zones that preferentially engage particular syringeal muscles.