bluuebunny/crossref_metadata_2025_split huggingface dataset:
The organization of immature callosal connections
Authors: Innocenti Giorgio M. , Clarke Stephanie 
Published: January 2005

AbstractIn newborn kittens, the anterograde transport of horseradish peroxidase, alone or bound to wheat‐germ agglutinin, indicates that callosal axons have entered selectively the restricted portions of the neocortical gray matter (e.g., the area 17/18 border) which receive callosal afferents in adults. The callosal axons do also reach regions where they lack in the adult, but there they seem not to penetrate far into the gray matter.Neonatal injections of retrograde fluorescent tracers restricted to the gray matter in areas 17, 18, and posteromedial lateral suprasylvian area (PMLS) label neurons in the contralateral hemisphere only when the tracers were directed into regions known to receive callosal axons. In particular, injections near the 17/18 border label neurons in the contralateral hemisphere at the homologous site and at restricted, retinotopically corresponding locations in other visual areas: a pattern similar to the adult one.In contrast, an injection reaching the white matter of areas 17 or 18 labels a wider, continuous territory extending mediolaterally over most visual areas from 17 to posterolateral lateral suprasylvian area (PLLS) and including regions which later become acallosal; in addition, labeled neurons are found in the limbic cortex medial to area 17 and in the auditory cortex lateral to PLLS, none of which is known to project to either 17 or 18 in the adult. In flattened reconstructions of the cortex, the shape of the territory labeled by each of these injections is characteristically, although somewhat irregularly, crescent shaped; its rostrocaudal position varies with that of the injection. An injection extending into the white matter of more lateral visual areas (19, 21a, PMLS) labels callosal neurons over a similar territory, which extensively overlaps that labeled by the 17/18 border injections and likewise includes regions which are acallosal in the adult.In spite of the overlapping distribution of labeling obtained from separate injection sites, as in adults, each cytoarchitectonically (or retinotopically) defined area seems to receive from a different set of neurons, although a few neurons send bifurcating axons to more than one area.In conclusion, injections restricted to the cortical gray matter reveal a topographic organization of juvenile callosal connections similar to that of the adult. In contrast, injections extending into the white matter and adequate to reach the transitory callosal axons which appear to be confined there reveal what appears to be an earlier organization. These two organizations probably reflect different morphogenetic factors.
Cortical connections of area 17 in tree shrews
Authors: Sesma M. A. , Casagrande V. A. , Kaas J. H. 
Published: January 2005

AbstractIn order to better understand the organization of extrastriate cortex in tree shrews, injections in area 17 of wheat germ agglutinin or tritiated proline were used to reveal an intrinsic pattern of connections, ipsilateral connections with area 18 and two other subdivisions of cortex, and callosal connections with areas 17 and 18 of the opposite cerebral hemisphere. Areal patterns of connections were best seen in sections cut parallel to the surface of flattened cortex. Within area 17, periodic foci of labeled terminations and cells extended from and surrounded injection sites as described by Rockland et al. ('82). Single injections produced multiple foci of labeled terminations and cells in area 18. The foci tended to fuse into short bands that sometimes crossed the width of area 18. Double injections produced more foci, and multiple injections tended to produce more continuous regions of label. An overall retinotopic pattern was evident with rostral area 17 connected to rostral area 18 and caudal area 17 connected to caudal area 18. Terminations extended through layers II–VI, with some increase in density in layer IV. Cells in area 18 projecting back to area 17 were in layers III and V. The injections also allowed identification of previously undefined subdivisions of visual cortex in temporal cortex immediately adjoining area 18. Dense reciprocal connections were observed in a 13 mm2 oval of cortex on the lateral border of the middle section of area 18 that we define as the temporal dorsal area, TD. Connections indicate a crude topographic organization with lower field represented rostrally and upper field caudally. Inputs were most dense in the middle cortical layers, and labeled cells were supragranular, and less frequently, infragranular. A 10‐mm2 oval of cortex near the posterior edge of the hemisphere, the temporal posterior area (TP), contained labeled cells after area 17 injections, but terminal labeling was only obvious in the dorsal part. Single injections sometimes produced quite separate dorsal and ventral zones of label in TP, suggesting a small separate dorsal division. A crude retinotopic order appears to exist within ventral TP, with the lower field most ventral. Labeled cells were largely supragranular. A fourth zone of ipsilateral connections was in posterior limbic cortex bordering area 17 on the ventromedial surface of the cerebral hemisphere. The callosal connections were reciprocal and included regions 1 mm wide on either side of the area 17 and area 18 border. Callosal connections were roughly homotopic. Callosal terminations included superficial layers, and projecting cells were both supragranular and infragranular. We conclude that extrastriate cortex in tree shrews contains at least three subdivisions, one of which (TD) may be the homologue of the middle temporal visual area of primates.
The development of synapses and “spoon” synaptic terminal space in the tangential vestibular nucleus: A quantitative electron microscope study
Authors: Peusner Kenna D. 
Published: January 2005

AbstractThis developmental study focuses on the quantitation of synapses and synaptic terminal space belonging to one identifiable population of synaptic endings, the spoon endings. Spoon endings contact only one cell type, the principal cells of the chick tangential nucleus. The tangential nucleus is an interstitial nucleus of the vestibular nerve, comprising part of the avian lateral vestibular complex. In addition to the spoon endings formed by the vestibular fibers, the principal cell bodies receive synaptic contacts from small endings of vestibular and non‐vestibular inputs.The spoon ending's synaptic space on the target cell diminishes significantly at or around the time of hatching. This diminution is expressed in quantitative terms. The spoon ending covers 34.8% of the somatic linear surface in the embryo, 10.9% in the hatchling, and 9.8% in the 3 year old. Although the spoon ending's vesicular synapses become rare after hatching, the spoon‐ending interface exhibits a significant increase in gap‐junction density during development. Neither the spoon endings nor their target cells exhibit a constancy in synaptic junction covering during development, although the spoon endings show a constant covering of attachment plaques. In the light of the present findings, the role of very large endings in the formation of synaptic connections and the control of developmental changes in junctional complexes is discussed.
Morphology of lumbar motoneurons innervating hindlimb muscles in the turtle Pseudemys scripta elegans: An intracellular horseradish peroxidase study
Authors: Ruigrok T. J. H. , Crowe A. , Donkelaar H. J. Ten 
Published: January 2005

AbstractMotoneurons in the turtle lumbar spinal cord, electrophysiologically identified as innervating a muscle belonging to a functional group, were injected with horseradish peroxidase by electrophoresis. A total of 45 motoneurons were reconstructed from transverse sections. Eleven motoneurons were identified as innervating knee extensor muscles, eight as innervating hip retractor and knee flexor muscles, 14 as supplying ankle and/or toe extensors, and 12 as innervating ankle and/or toe flexor muscles.The cell bodies were elongated and spindle‐shaped in the transverse plane. The mean equivalent soma diameter was calculated to be 33.4 μm. The mean axon conduction velocity was 15.7 m/second. Significant, though rather weak, positive correlations were found between soma diameter, axon diameter, and axon conduction velocity. The axons of the reconstructed motoneurons did not reveal a recurrent axon collateral. However, a few unidentified motoneurons did possess such collaterals.The dendritic trees were restricted to the ipsilateral side of the cord, but reached out in lateral, ventral, and ventromedial directions to the subpial surface. Easily recognizable and characteristic dendrites were found both in the dorsal dendritic tree and in the dorsomedial dendritic tree. Correlations were calculated between the soma diameter and (1) the number of first‐order dendrites, (2) the mean diameter of the first‐order dendrites, and (3) the combined diameter of the first‐order dendrites. In each case no correlations or only weak correlations were found. Fair correlations were observed between the diameter of a first‐order dendrite and the number of terminal dendritic branches (r = .61) and the combined dendritic length (r = .78). However, correlations between the combined diameter of all first‐order dendrites per neuron and the total number of terminal dendritic branches and the total combined dendritic length of a neuron were extremely weak.The overall appearance of turtle spinal motoneurons is comparable to that observed in other “lower” vertebrates such as frog and lizard. However, similarities are also observed between certain morphometric parameters in turtle and cat lumbar motoneurons.
Optic axons ignore foreign denervated sites in goldfish tectum even after removal of some of their normal termination sites
Authors: Marotte J. R. 
Published: January 2005

AbstractPrevious experiments have shown that optic axons ignore foreign denervated territory in the goldfish tectum and preferentially reinnervate their normal layers of termination. In the present experiments ultrastructural morphometry was used to test whether this was still the case if optic axons were deprived of some of their normal termination sites. The stratum fibrosum marginale (SFM) of the tectum was partially denervated to provide foreign synaptic sites and the caudal half of the tectum was ablated at the same time. This removed approximately half the normal sites of optic termination. In the majority of cases optic axons grew into the SFM but there was no evidence of any significant formation of synapses by them in the SFM. Instead they synapsed in their normal layers. Myelinated optic axons in the SFM were present in significantly higher numbers in fish operated on in spring than in fish operated on in autumn after similar survival times. Although removal of some of the normal sites of termination promoted growth of optic axons into foreign denervated territory, the axons did not synapse there. Instead they passed through the foreign region and reinnervated their normal layers even though this meant reorganizing the optic projection within the reduced tectal space.
Bilateral cerebral metabolic alterations following lesion of the ventromedial thalamic nucleus: Mapping by the 14C‐deoxyglucose method in conscious rats
Authors: Girault Jean‐Antoine , Savaki Helen E. , Desban Marcel , Glowinski Jacques , Besson Marie‐Jo 
Published: January 2005

AbstractThe functional role of the ventromedial thalamic nucleus (VM) was investigated by means of the quantitative autoradiographic 14C‐deoxyglucose method. Local cerebral glucose utilization (LCGU) was measured bilaterally in 53 discrete brain areas of conscious rats 1 week and 1 month following electrolytic lesion of the VM. There was no difference observed in the LCGU values between the two groups of lesioned animals. In the VM‐lesioned rats glucose consumption was decreased in several ipsilateral (prefrontal, frontal, cingulate, sensorimotor, visual) and in some contralateral (cingulate, sensorimotor, visual) cortical areas. Furthermore, LCGU values were depressed bilaterally in the striatum, hippocampus, dentate gyrus, substantia nigra compacta, superficial layers of the superior colliculus, oculomotor complex, and cerebellar dentate nuclei. Glucose utilization was diminished also in the deep layers of the superior colliculus and in the fastigial nucleus ipsilateral to the lesion. Within the thalamus, glucose metabolism was decreased in several nuclei either bilaterally (reticular, intralaminar, paralamellar mediodorsal) or ipsilaterally (lateroposterior, ventrobasal, ventrolateral, ventroanterior, and medioventral) to the lesion. A significant correlation between the percentage of injured VM and the regional metabolic depression was demonstrated in the areas displaying the most pronounced decrease in LCGU. These results support a widespread influence of the VM on brain function extending beyond the limits of purely motor systems and reveal the consequences of a unilateral lesion of the thalamus on metabolic activity in several contralateral structures.
Gap junctions between non‐pyramidal cell dendrites in the rat hippocampus (CA1 and CA3 regions): A combined Golgi‐electron microscopy study
Authors: Kosaka Toshio , Hama Kiyoshi 
Published: January 2005

AbstractNon‐pyramidal cells in the rat hippocampus were examined with a combined Golgi‐electron microscopic method.The somata of non‐pyramidal cells were ovoid, about 15 × 30 μm, and several smooth and/or varicose dendrites extended from them. With electron microscopy, Golgi‐impregnated gold‐toned non‐pyramidal cells showed distinctive fine structural features. The somata displayed large nuclei and an extensive perikaryal cytoplasm. The nuclei showed extensive cytoplasmic invaginations, little heterochromatin, conspicuous nucleoli, and intranuclear rods composed of filamentous bundles. The perikaryal cytoplasm was rich in cell organelles such as well‐developed cisternae of rough endoplasmic reticulum and Golgi apparatus, and numerous clusters of free ribosomes and mitochondria. Many synaptic boutons, most of which formed asymmetrical synapses, impinged upon the somata and dendrites. Gap junctions were seen on varicose dendrites of Golgi‐impregnated non‐pyramidal cells. These gap junctions were patch‐like, about 0.1–0.6 μm in diameter, and situated in the stratum radiatum or stratum oriens of the CA1 and CA3 regions 70–230 μm from the soma. They displayed a characteristic cytoplasmic semidense material undercoating the junctional membranes. The gap junctions were usually formed between impregnated and unimpregnated varicose dendrites. Thirteen of a total of 22 gap junctions involving the impregnated dendrites were situated singly, whereas the remaining nine were on four impregnated dendrites in clusters of two or three side by side. In the latter cases, two pairs of junctions were formed between pairs of dendrites running parallel to each other, and each of the other two pairs was formed among three dendrites, appearing to make a dendritic network bridged by gap junctions. One gap junction was seen between two impregnated dendrites originating from two identified Golgi‐impregnated non‐pyramidal cells. These observations revealed unequivocally that non‐pyramidal cells in the hippocampus form gap junctions with one another on their dendrites.
A combined electron microscopic HRP and immunocytochemical study of the limbic projections to rat hypothalamic nuclei containing vasopressin and oxytocin neurons
Authors: Oldfield B. J. , Hou‐Yu A. , Silverman A.‐J. 
Published: January 2005

AbstractLight microscopic studies in our laboratory have indicated that the lateral septum, amygdala, and ventral subiculum project in a perinuclear fashion to the paraventricular (PVN), supraoptic (SON), and suprachiasmatic (SCN) nuclei (Oldfield et al., '82; Silverman and Oldfield, '84). In the present paper a combined anterograde HRP and immunocytochemical procedure has been used to determine the connectivity between these limbic efferents and peptide‐containing processes emanating from the above mentioned hypothalamic nuclei. Synaptic associations were found to exist between efferents from (1) the septum and both vasopressin (VP) and oxytocin (OX)‐positive dendrites derived from cells in the PVN and SON, (2) the septum and VP dendrites dorsal to the SCN, (3) the ventral subiculum and both VP and OX dendrites arising from the PVN and SON, and (iv) the amygdala and VP dendrites from the PVN. These observations help clarify an apparent discrepancy between electrophysiological data, in which limbic efferents have been shown to influence the activity of VP and OX neurons in the PVN ami SON, and anatomical evidence which indicates only a perinuclear innervation from these sites not encroaching on the hypothalamic nuclei themselves. In each case the synaptic connections are made on dendrites external to the nucleus: those lateral and ventrolateral to the PVN, dorsal to the SON, and dorsal or dorsolateral to the SCN.
Distribution of GABA‐T‐intensive neurons in the rat hindbrain
Authors: Nagai T. , Maeda T. , Imai H. , McGeer P. L. , McGeer E. G. 
Published: January 2005

AbstractThe pharmacohistochemical method previously used to identify the distribution in rat brain of γ‐aminobutyric acid transaminase (GABA‐T)‐intensive neurons has been applied to the rat pons and medulla. The method involves systemic administration of the irreversible GABA‐T inhibitor Gabaculine and the detection, 12 to 15 hours after the injection of the newly synthesized GABA‐T by histochemical means, GABA‐T‐intensive neurons were found to be rich in the following hindbrain structures: inferior colliculus, nuclei of the raphe system, nuclei parabrachialis dorsails and ventralis, nucleus cuneiformis, nucleus vestibularis medialis, nucleus tractus spinalis nervi trigemini, nucleus vagus, nucleus cochlearis, nucleus reticularis lateralis, nucleus ambiguus, nucleus cuneatus lateralis, inferior olive, and reticular formation of the pons and medulla. Neurons of the deep cerebellar nuclei and the rostral portion of the lateral vestibular nucleus were negative for GABA‐T but were surrounded by granular staining indicative of impinging GABA‐T‐rich nerve endings. These results provide further support for the hypothesis that GABA neurons are far more GABA‐T‐intensive than other neurons in the central nervous system.
Retinal pigment epithelial correlates of avian retinal degeneration: Electron microscopic analysis
Authors: Fite Katherine V. , Bengston Lynn , Doran Peter 
Published: January 2005

AbstractThe delayed amelanotic (DAM) strain of domestic chicken is characterized by an early, developmental onset of choroidal inflammation and destruction of both feather and choroidal melanocytes. Secondarily, retinal pigment epithelial (RPE) cells in the peripapillary region develop abnormalities, and a series of progressive histopathological changes ensues which includes reduction and ultimate loss of RPE‐melanin granules and RPE‐cell atrophy. The earliest sign of RPE‐cell abnormality is a dramatic alteration in the distribution of intracellular melanin granules. Apical processes also show a lessening of contact with photoreceptor outer segments, leading in more advanced stages to their retraction and development of retinal detachments. Other progressive alterations in RPE cells include disorganization and loss of basal infoldings; size reductions and density increases in both mitochondria and myeloid bodies from early to advanced stages; appearance of large macrophages in the subretinal space; loss of intercellular junctional complexes; and progressive reduction in the density of melanin granules. These abnormalities appear to spread in a cell‐by‐cell, radial pattern, until widespread areas of the retina become severely pathologic and atrophic. The DAM chorioretinal disorder appears to show many of the histopathologic features which characterize experimentally induced uveitis and other ocular diseases which may result from hypersensitivity to, or autoimmune reaction against, pigments of the uveal tract.
Variability in the terminations of GABAergic chandelier cell axons on initial segments of pyramidal cell axons in the monkey sensory‐motor cortex
Authors: Defelipe J. , Hendry S. H. C. , Jones E. G. , Schmechel D. 
Published: January 2005

AbstractChandelier cell axons were studied in the sensory‐motor cortex of adult monkeys. The axonal fields of Golgi‐impregnated chandelier cells in layer II in motor cortex are flattened sagittally. The vertical terminal portions of the axons varied both in length and in the numbers converging to form terminations of‐greater or lesser complexity. Golgi‐impregnated plexuses were embedded in plastic and resectioned serially at 2.5–3.0 μm. A single axonal field could have as many as 400 terminal rows. All lie 3–13 μm beneath pyramidal cell somata. These terminations are not randomly distributed but, instead, form clusters. Further resectioning the plastic sections for electron microscopy revealed that all the terminations are on the initial axon segments of pyramidal cells and all form symmetric synaptic contacts.In immunocytochemical material stained for glutamic acid decarboxylase (GAD), the enzyme involved in the synthesis of GABA, GAD‐positive boutons were found to form symmetric synaptic contacts with a variety of postsynaptic elements including the axon hillocks and axon initial segments of pyramidal cells. Serial reconstructions from electron micrographs revealed GAD‐positive terminals synapsing with the axon initial segment of pyramidal cells joined by cytoplasmic bridges and forming vertically oriented rows identical to those of chandelier cell terminals identified positively in the resectioned Golgi material. The GAD‐positive terminals forming initial segment synapses were never continuous with GAD‐positive terminals forming axon hillock synapses. The latter probably arise from basket cell axons. Initial segments of pyramidal cell axons in layers II and III were contacted by more GAD‐positive terminals than the initial segments of pyramidal cell axons in layer V. The largest pyramidal cells in layer III received the most synapses. Many larger pyramidal cells, identified as callosally projecting cells by the retrograde transport of horseradish peroxidase (HRP), were shown in serial electron micrographs to possess large numbers of initial segment synapses, comparable to those seen in the immunocytochemical material.Serial reconstructions of pyramidal cell axons from axon hillock to the first myelin internode in resectioned Golgi, immunocytochemical and HRP material showed that the number of synapses varied from 2 to 52 for layers II and III and from 2 to 26 for layer V. The number of synapses on the axon hillocks varied from zero to 12. The variability in these terminations may be an important factor in the shaping of the functional properties of the pyramidal cells.