bluuebunny/crossref_metadata_2025_split huggingface dataset:
Primate supplementary eye field: I. Comparative aspects of mesencephalic and pontine connections
Authors: Shook B. L. , Schlag‐Rey M. , Schlag J. 
Published: January 2005

AbstractWGA‐HRP was used to examine projections to the brainstem from the supplementary eye field (SEF). The SEF was defined electrophysiologically in awake, behaving monkeys and connections were compared to those of the arcuate frontal eye field (FEF), area 6DC, and primary motor cortex. The SEF was found to have either direct or indirect connections with almost every known pre‐ and paraoculomotor structure of the brainstem. The SEF was found to project bilaterally to layers I and IV of a tangentially widespread region of the superior colliculus. Terminal label was evident in the pretectal olivary nucleus, nucleus of the optic tract, nucleus raphe interpositus (omnipause region), nucleus prepositus hypoglossi, the perioculomotor cap of the central gray, dorsal central gray, nucleus reticularis tegmenti pontis, nucleus reticularis pontis oralis, and to multiple nuclei of the basis pontis (most densely to the dorsomedial nucleus). Bilateral projections were found in the parvicellular red nucleus. Reciprocal connections were present in the nucleus limitans, the mesencephalic reticular formation, locus coeruleus, and the serotonergic nuclei of the raphe complex (dorsalis and central superior). Overall patterns of connectivity were similar to those of the FEF and markedly different from those of the contiguous dorsocaudal area 6 or primary motor cortex. It was concluded that observed patterns of SEF‐brainstem connectivity further justifies viewing this region as a distinct eye field that is likely to serve preparatory and trigger functions in the generation of saccadic eye movements.
Morphological types of projection neurons in layer 5 of cat visual cortex
Authors: Hübener Mark , Schwarz Cornelius , Bolz Jürgen 
Published: January 2005

AbstractPyramidal cells in layer 5 of the visual cortex have multiple cortical and subcortical projection sites. Previous studies found that many cells possess bifurcating axons and innervate more than one cortical or subcortical target, but cells projecting to both cortical and subcortical targets were not observed. The present study examines the morphology of cells in cat visual cortex projecting to the superior colliculus, the main subcortical target of layer 5, and cells in layer 5 projecting to cortical areas 18 and 19. The neurons that give rise to these different projections were retrogradely labelled and intracellularly stained in living brain slices.Our results show that cells within each projection group have several morphological features in common. All corticotectal cells have a long apical dendrite forming a large terminal tuft in layer 1. Their cell bodies are medium sized to large, and their basal dendrites form a dense and symmetrical dendritic field. Corticocortical cells in layer 5 have a very different morphology: their apical dendrites are short and they never reach higher than layers 2/3. Their cells bodies are small to medium sized and they have fewer basal dendrites than corticotectal cells. Thus there are two morphologically distinct projection systems in layer 5, one projecting to cortical and the other one to subcortical targets, suggesting that these two systems transmit different information from the visual cortex.Among the corticotectal cells with the largest cell bodies we found some cells whose basal and apical dendrites were almost devoid of spines. Spiny and spinefree corticotectal cells also have different intrinsic axon collaterals and therefore play different roles in the cortical circuitry. While many spiny corticotectal cells have axon collaterals that project to layer 6, spinefree corticotectal cells have fewer axon collaterals and these do not arborize in layer 6. We suggest that the two morphological types of corticotectal cells might be related to functional differences known to exist among these cells. We discuss how the presence or absence of spines affects the integration of the synaptic input and how this might be related to the cells' functional properties.
Morphological changes of the myenteric plexus neurons in the bullfrog (Rana catesbeiana) duodenum during metamorphosis
Authors: Torihashi Shigeko 
Published: January 2005

AbstractMyenteric plexus neurons of the duodenum in the bullfrog Rana catesbeiana were examined during metamorphosis by the Gros‐Bielschowsky silver impregnation method and electron microscopy.Larval type neurons with slender and curved cell soma were recognized in the duodenum of the premetamorphic tadpole. They degenerate and decrease in number during early metamorphic climax through shrinkage of the cell soma and autolysis of the cytoplasm. These larval type neurons reduce to debris and then disappear. Two new cell types (adult type neurons) subsequently appear. These new neurons develop and increase in number during late climax and after metamorphosis. Those that appear first are large type A neurons each with a prominent axon and they stain darkly with silver. They enlarge during late stages. Subsequently small type B neurons appear which stain weakly with silver. They increase the number of their dendrites, change their shape, but enlarge only slightly during late development.In summary, therefore, it is concluded that during metamorphosis, the larval myenteric plexus neurons in the bullfrog duodenum are replaced by two new populations of adult neurons.
Terminal arbors of individual, physiologically identified geniculocortical axons in the tree shrew's striate cortex
Authors: Raczkowski Denis , Fitzpatrick David 
Published: January 2005

AbstractWe studied the terminal patterns of single, physiologically identified geniculocortical axons in the striate cortex of the tree shrew by using intracellular recording and labeling methods. Axons were classified by their response to the onset (ON‐center) or offset (OFF‐center) of a light stimulus presented to the ipsilateral or contralateral eye. Then, we attempted to penetrate each axon for labeling with horseradish peroxidase. We recovered 23 axons and studied 16 of these in detail. Light microscopic reconstructions of these axons revealed several distinct terminal patterns within cortical layer IV. ON‐center axons had terminal arbors that ended mainly in the upper part of layer IV (IVa), while OFF‐center axons ended in the lower part of layer IV (IVb). Within layers IVa and IVb, axons driven by the ipsilateral eye and those driven by the contralateral eye had overlapping distributions. However, their terminal arbors differed in size, in shape, and in the number of boutons. Compared with contralateral eye arbors, ipsilateral eye axons were on average three times larger in lateral extent (925 μm vs. 325 μm), spread over four times the surface area (0.13 mm2 vs. 0.03 mm2), and supported one and one‐half times as many terminal boutons (1,647 vs. 1,086). The ipsilateral eye axons had more boutons at the edges of layer IV (i.e., the upper part of layer IVa and the lower part of layer IVb), while those from the contralateral eye axons were more evenly distributed. These results show that each functional class of geniculocortical fiber has a different laminar and areal arrangement of boutons and we consider the significance of these differences for visual cortical function.
Plasticity of GABA‐ and glutamate‐containing terminals in the mouse thalamic ventrobasal complex deprived of vibrissal afferents: An immunogold‐electron microscopic study
Authors: Hámori J. , Takács J. , Verley R. , Petrusz P. , Farkas‐Bargeton E. 
Published: January 2005

AbstractGABA and glutamate immunogold staining demonstrated that nerve cells of the thalamic ventrobasal complex (VB) of mice were positive exclusively for glutamate. None of the neuronal perikarya reacted the GABA antibody. By using alternate thin sections of the normal VB, it was also shown that large “specific” somatosensory and small corticothalamic terminals, both of which contained spherical synaptic vesicles, exhibited only glutamate‐like immunoreactivity. A third axonal type, containing flat‐ovoid synaptic vesicles, stained only for GABA.Seventy‐five days after coagulation of the vibrissal follicles in newborn mice, a characteristic multiplication of GABA positive axon terminals was observed. In addition, it was demonstrated that, similarly to modified cortical endings (Hámori et al., J. Comp. Neurol. 254:166–183, '86), many GABA positive terminals appeared as specific afferent endings, replacing the missing “specific” vibrissal afferents. This finding shows a remarkable plasticity of inhibitory GABA axons during developmental synaptogenesis and provides further evidence that the size, location, and the type of attachment of presynaptic terminals are dependent on their postsynaptic target.
Ultrastructural and morphometric analysis of nuclear and nuclear changes during the early growth period in hamster facial neurons
Authors: Clark Pamela , Jones Kathryn J. , LaVelle Arthur 
Published: January 2005

AbstractIn this study, progressive developmental changes in the nucleus and associated organelles, including the nucleolus, coiled bodies, nuclear envelope, and nucleoplasm, of hamster facial motor neurons were characterized by two parallel analyses: ultrastructural and morphometric. Golden hamsters (Mesocricetus auratus) used for this series were the 14‐day fetus, newborn (<6 hr), and 1, 2, 3, 4, 5, 7, 9, 11, and 13 days postnatal ages, with 3 animals per group. Following anesthesia and perfusion fixation, facial nuclear groups were dissected and processed for electron microscopy. Electron micrographs and camera lucida tracings of nuclear profiles were collected and analyzed. The ultrastructural analysis revealed progressive changes in the nucleolus from a compact, segregated type to a reticulated form characteristic of actively protein‐secreting cells. Nucleolar microbodies and fibrillar centers were seen at all ages; the latter structures appeared to decrease in size and increase with age in the series. The nucleolus‐associated chromatin became less condensed, suggesting an increase in the incorporation of rDNA into the nucleolus proper. Coiled bodies, both free and attached to nucleoli, were found in varying frequencies. The nucleoplasm of neurons at the earliest stages contained large numbers of heterochromatin clumps, which decreased concomitantly with an increase in interchromatin granules and fibrils during the later stages. Nuclear envelope imaginations, polarized along one side of the nucleus, increased throughout the developmental period examined. These changes occurred in concert with a 61% increase in nuclear size and a 47% increase in the length of nuclear envelope. The sequence of nuclear changes observed during this early period of normal facial neuronal growth completes the study of a series of distinctly defined cytomorphic events in this cell type, the lability of which can be experimentally tested for their functional roles in neuronal development.
Auditory brainstem of the ferret: Early cessation of developmental sensitivity of neurons in the cochlear nucleus to removal of the cochlea
Authors: Moore David R. 
Published: January 2005

AbstractThe role of primary afferent innervation in the maintenance of neurons in the mammalian auditory system was assessed by performing unilateral removals of the cochlea in neonatal and mature ferrets of known birth dates. Removals were performed under steroid anesthesia and resulted in the complete destruction of the organ of Corti and the loss of at least 80% of type I spiral ganglion neurons. Four main age groups [postnatal days (P)5, P24, P90, and P180] were used. Additional animals received no surgery, partial removals, or complete removals at older ages. Three months after the cochlear removal the animals were reanesthetized and perfused. The brainstem and the temporal bones were wax‐embedded, frontally sectioned, and Nissl‐stained. Sections of the right and left cochlear nuclei were compared quantitatively. Removal of the cochlea at P5 resulted in the loss of more than 50% of large (nongranular) neurons throughout the ipsilateral cochlear nucleus. Lesions at older ages did not produce any neuron loss. The size of the remaining neurons was reduced by 10–15% in all age groups. Partial lesions at P5 produced a graded response in the cochlear nucleus that was related to the extent of the lesion. The developmental sensitive period for the effects of cochlear removal on the ferret cochlear nucleus is therefore over before the age (P28–P30) at which the animal begins to hear. The present result differs markedly from the chicken, in which the sensitive period for removal of the cochlea persists for at least 2 months after the onset of hearing.
Crossing fiber arrays in the rat hippocampus as demonstrated by three‐dimensional reconstruction
Authors: Tamamaki Nobuaki , Nojyo Yoshiaki 
Published: January 2005

AbstractThe hippocampus is a neural substrate playing a key role in short‐term memory. In order to achieve a better understand‐ding of how the hippocampus functions in “learning and memory,” we conducted an intracellular horseradish peroxidase (HRP) study of the CA3 pyramidal neurons and the granule cells of the fascia dentata. The axon of the CA3 pyramidal neurons has two components, the longitudinal association system and the Schaffer collateral system. The latter component is organized in a lamellar fashion and follows the alvear fiber stream. An electron microscopic analysis of myelinated fibers suggested that most myelinated fibers in the hippocampus are organized parallel to the alvear fibers. The mossy fibers of the granule cells, however, do not follow the alvear fiber stream. We propose a new model of the organization of the intrinsic excitatory circuitry of the rat hippocampus in which the distinct lamellar organization of the pyramidal and granule cells creates a crossing neural network.
Effects of testosterone on a selected neuronal population within the preoptic sexually dimorphic nucleus of the Japanese quail
Authors: Panzica Giancarlo , Viglietti‐Panzica Carla , Sanchez Fernando , Sante Philippe , Balthazart Jacques 
Published: January 2005

AbstractThe effects of testosterone on the volume and cytoarchitecture of the sexually dimorphic nucleus of the preoptic area (POM) were investigated in male and female Japanese quail. It was confirmed that castration decreases the POM volume in males and that, in gonadectomized birds of both sexes, testosterone increases this volume to values similar to those observed in intact sexually mature males. This suggests that the sex difference in POM volume results from a differential activation by T so that this brain morphological characteristic is not truly differentiated in the organizational sense. This conclusion was extended here by demonstrating that males exposed to a photoperiod simulating long days and that are known to have high plasma levels of testosterone have a larger POM than short‐day males that have inactive testes. Detailed morphometric studies of POM neurons revealed a structural heterogeneity within the nucleus. A population of large neurons (cross‐sectional area larger than 70–80 μm2) was well represented in the dorsolateral but was almost absent in the medial part of POM. This lateral population of neurons was sensitive to variations of testosterone levels in males but not in females. The cross‐sectional area, diameter, and perimeter of the dorsolateral neurons were significantly increased in males exposed to high testosterone levels (intact birds exposed to long days or castrated birds treated with the steroid). These changes were not observed in the medial part of the nucleus. Interestingly, the size of the dorsolateral neurons was not affected by testosterone treatments in females. These results suggest that the swelling of neurons in the lateral POM of males might be responsible for the increase in total volume of the nucleus, which is observed in physiological situations associated with a high testosteronemia. In addition, the sensitivity to testosterone of the dorsolateral neurons in the POM appears to be sexually differentiated. This differential response to testosterone might represent a truly dimorphic feature in the organizational sense and additional studies manipulating the early steroid environment should be performed to test this possibility.
Development of the olfactory nerve in the African clawed frog, Xenopus laevis: I. Normal development
Authors: Burd Gail D. 
Published: January 2005

AbstractQuantitative and morphological data were obtained on developing olfactory axons in the African clawed frog, Xenopus laevis, during late premetamorphosis (stages 48–54), prometamorphosis (stages 55–57), and halfway through metamorphic climax (stages 58–62). Larval axons throughout these stages of development did not change with respect to morphology or diameter and were similar in all respects to olfactory axons described in other vertebrate species. The number of axons in the olfactory nerve increased throughout development, more rapidly after stage 54. Based on comparisons of the number of axons in proximal and distal regions of the nerve, there also appeared to be more axons growing into the olfactory nerve at early metamorphic climax than during premetamorphosis. Through the onset of metamorphic climax, the number of olfactory axons was correlated with other measures of body growth. In the later stages of climax, however, the number of olfactory axons continued to rise, whereas body weight, length, and width, as well as olfactory nerve length, decreased. Not all animals developed at the same rate, but for all quantitative measurements in this study, stage was a better predictor of any given parameter than age of the animal. Rearing conditions affected the rate of development but did not have a significant effect on most of the features analyzed quantitatively. Although most of the new olfactory axons in these larval animals probably represent addition of fibers resulting from development, the ensheathing glial cells at all stages showed evidence of phagocytic activity, suggesting that there might be turnover of olfactory receptor cells during larval development. The results presented here provide a baseline for future reports on various factors that may influence normal development in this system.
Ultrastructure of the ganglion cells of the terminal nerve in the dwarf gourami (Colisa lalia)
Authors: Oka Yoshitaka , Ichikawa Masumi 
Published: January 2005

AbstractIn our previous light microscopic studies (Oka et al., Brain Res. 367:341–345, '86; Oka and Ichikawa, J. Comp. Neurol. 300:511–522, '90), we reported that there are at least two types of terminal nerve (TN) cells based on cell size and immunoreactivity: type I cells had large cell bodies, while type II cells had smaller cell bodies. Type I TN cells were immunoreactive to gonadotropin‐releasing hormone (GnRH) and may be the major source of GnRH‐immunoreactive fibers that are widely distributed throughout the brain. Type if TN cells, on the other Hand, were not immunoreactive to GnRH. In the present paper, we examined the cytology and synaptology of these two types of TN cells with electron microscopy. Type I TN cell bodies were found to have morphological characteristics similar to those of other peptide‐synthesizing neurons and are likely to be actively synthesizing GnRH. The frequent occurrence of coated vesicles close to the plasma membrane of the cell body was suggestive of membrane retrieval following exocytosis of the vesicular contents from the cell surface. Neighboring TN cells were either in direct juxtaposition with one another or made specialized “glomeruloid” cell‐to‐cell contacts; these specializations may be relevant for nonsynaptic intercellular communications among the TN cells. Within these glomeruloid complexes, the somatic processes of TN cells received inputs from two types of synaptic terminals: one containing only spherical synaptic vesicles and another containing a small number of dense‐cored vesicles in addition to the spherical synaptic vesicles. Axosomatic synapses were rare on type I TN cell bodies. In contrast, type II TN cell bodies had morphological characteristics similar to those of neurons in other brain regions. These receive axosomatic inputs from synaptic terminals containing only spherical synaptic vesicles and those with a small number of dense‐cored vesicles in addition to the spherical synaptic vesicles. Thus, each type of TN cell has unique fine structural characteristics which may correlate to their different functional roles.
Sprouting of peripherally regenerating primary sensory neurones in the adult central nervous system
Authors: McMahon Stephen B. , Kett‐White Rupert 
Published: January 2005

AbstractWe have studied the ability of primary afferent neurones to proliferate within the grey matter of the dorsal horn following the degeneration of other, nearby, afferent fibres. The peripheral branches of primary afferents have the capacity to regenerate successfully over long distances, and we have examined the possibility that when they are so doing, the neurones' status changes to facilitate greatly the sprouting of afferent fibres within the dorsal horn.“Spared root” preparations (rhizotomies of L3, L4, L6, S1, and the caudal half of L5, sparing the rostral half of the L5 dorsal root) were made in adult rats. In some animals (acute preparations) the distribution of the central terminals of the spared root was assessed by labelling the sciatic nerve with WGA‐HRP at the time of the rhizotomies. In other animals (chronic preparations, symmetrical bilateral spared roots were made and the sciatic nerve on one side was concomitantly crushed to trigger regrowth of the peripheral branches of these axons. Eight to 10 weeks later the sciatic nerves on both sides were labelled with HRP‐WGA.In the acute preparations the reaction product was found in a limited rostrocaudal and mediolateral region of the dorsal horn. In lamina II (the lamina of densest labelling the labelled terminals occupied an average of 1.17 ± 0.21 mm2. In chronic preparations, the area of labelled terminals on the side of the uncrushed sciatic nerve was 1.34 ± 0.28 mm2 (not significantly different from acute animals). However, the labelled area on the side of the crushed sciatic nerve was significantly greater, averaging 2.17 ± 0.14 mm2. Hence, primary afferent nerve fibres show greatly enhanced sprouting within the grey matter of the dorsal horn of the spinal cord when two conditions are fulfilled; 1) vacant synaptic sites are created by the degeneration of other primary afferent fibres; and 2) the peripheral branches of the axons are actively regenerating.