bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synaptic organization in the dorsal cochlear nucleus of the cat: A light and electron microscopic study
Authors: Kane Eileen Cohen 
Published: January 2005

AbstractThis report describes some observations of the synaptic organization of one region of the cat dorsal cochlear nucleus (DCN). The large “fusiform cell” and its innervation from the cochlea are emphasized. The morphology of the mature fusiform cell and its postnatal development are described in rapid Golgi impregnations of perfusion‐fixed littermate cats. The mature features are correlated with profiles of fusiform cell bodies, apical dendrites, and basal dendritic trunks in electron micrographs from adult cat brains. Small neurons and granule cells are also identified in electron micrographs. In Golgi impregnations, axons of small cells and granule cells may terminate upon fusiform cells. Six classes of axons can be distinguished in rapid Golgi impregnations of the DCN. Two classes are of cochlear origin. One axonal class arises from small cells. The sources of the remaining axonal classes have not been identified in this study. Primary afferents can terminate as large, mossy endings in the DCN neuropil. They can also participate in axonal nests along with axons and dendrites of small cells. In electron micrographs, four synaptic endings can be distinguished. Primary cochlear fibers end in large terminals with asymmetrical synaptic complexes and round, clear vesicles. Primary axons can end in glomeruli, resembling those of the cerebellum, or in synaptic nests which are conglomerates of neuronal processes including other types of endings. The origins of the other synaptic types are not yet known. According to this study, primary afferent input could influence fusiform cells directly or indirectly, via small cells and granule cells.
Fine structure of the synaptic endings on the Mauthner cell of the goldfish
Authors: Nakajima Yasuko 
Published: January 2005

AbstractThis study has investigated the fine structure of the Mauthner cell of the goldfish. The animals were divided into three groups of three fish and each group was perfused with one of the following fixatives: osmium tetroxide, glutaraldehyde, or formaldehyde. Large myelinated club endings and smallvesicle boutons (SVBs) are found on the distal part of the lateral dendrite. The club endings have the structure of the mixed synapse and contain large, round synaptic vesicles. The SVBs, appearing as small boutons, show structural features of the chemical synapse, and contain small synaptic vesicles, which are round when fixed with osmium tetroxide, but become elongated when fixed with aldehyde fixatives. Small myelinated club endings, SVBs, and large‐vesicle boutons (LVBs) are observed on the proximal part of the lateral dendrite, on the ventral dendrite, and on the cell body (excluding the axon hillock region). The LVBs, mostly appearing as large boutons, show the structure of either the mixed or the chemical synapse. They contain large, round vesicles. On the axon hillock and initial axon segment, there exist unmyelinated club endings containing medium‐size elongated vesicles and spiral fiber endings containing round medium‐size vesicles. An attempt was made to correlate these different types of endings within physiological functions.
Genetically‐associated variations in the destribution of dentate granule cell synapses upon the pyramidal cell dendrites in mouse hippocampus
Authors: Barber Robert P. , Vaughn James E. , Wimer Richard E. , Wimer Cynthia C. 
Published: January 2005

AbstractThe Ammonic system of inbred mouse strains was examined with light and electron microscopic methods in order to determine whether genetically‐associated variations occur in the distribution of dentate granule cell synapses (mossy fiber boutons) upon the dendrites of hippocampal pyramidal neurons in Regio Inferior. The results of this investigation showed that both qualitative and quantitative variations of the mossy fiber system occur among the strains examined. The most striking variation was seen in strain BALB/cJ. These mice are unique in that their mossy fibers do not form an appreciable infrapyramidal synaptic field, but form an extensive intrapyramidal synaptic field instead. In marked contrast, SM/J mice exhibit an extensive development of infrapyramidal mossy fiber boutons while their intrapyramidal mossy fiber synaptic field, when present at all, is limited to a very small portion of Regio Inferior adjacent to the hilus of Area Dentata.Since the mouse strains used in this study do not exhibit neurological defects (i.e., they are not neurological mutants identified through the presence of gross behavioral or external anatomical abnormalities), the described variations may be thought of as representing genotype‐dependent differences in the connectivity of the Ammonic system which might occur within a “normal,” heterogeneous population of mice, Genetic, developmental and functional implications of the observed variations in the distribution of mossy fiber boutons upon Regio inferior pyramids are discussed.
Degeneration argyrophilia as an index of neural maturation: Studies on the optic tract of the golden hamster
Authors: Leonard Christiana M. 
Published: January 2005

AbstractThe maturation of the retinofugal Systems of the golden hamster has been traced by using the Fink‐Heimer silver technique to stain the degenerating axons and terminal arorizations aferr enucleation at different ages from birth to adulthool. From birth to 12 days of age intense degeneration argyrophilia can only be seen at short (15–36 hours) survival times in the optic tract and its terminal areas. By 72 hours after enucleation virtually all traces of axon degeneration have vanished. Starting at about 14 days of age (time of eye opening) sparse evidence of residual degeneration argyrophilia can be found in strtum opticum and stratum griseum superficiale of the superior colliculus at 72 and even at 240 hours survival. The intensity of the long‐lasting degeneration argyrophilia rapidly increases durin the next two weeks although shortlatency degeneration argyrophiloia does not start decreasing in intensity until 24 days of age.Since Lund and Lund (1972) have found that typicl optic tract synapses are first identifiable in the superior colliculus of the rat at the time of eye opening (12 to 14 days), it is possibnle that the onset of long‐lasting degeneration argyrophilia signals an important structural or functional change in the neuron. Since degeneration methods can be used to trace the maturation of fiber tracts of known origin and trajectory, they may provide a relatively convenient means of identifying periods in which particular fiber Systems are underoing rapid developmental changes.
Morphological and cytochemical studies of synapses formed in culture between isolated rat superior cervical ganglion neurons
Authors: Rees Rosemary , Bunge Richard P. 
Published: January 2005

AbstractNeurons from the superior cervical ganglia (SCG) of perinatal rats were mechanically dissociated and established in culture by a method modified from that of Bray ('70). The neurons attached to the collagen substrate with some degree of reaggregation, and their rapidly growing processes soon formed an interconnecting network. Light and electron microscope examination showed that the morphology of the cultured cells resembled that of the SCG principal cell; neither satellite cells nor the small intensely fluorescent interneurons were observed. After six to seven days in culture, synapses were seen on both the principal cell somata and on their processes. After aldehyde fixation, the synapses contained clear, pleiomorphic vesicles; after KMnO4 fixation a variable number of the vesicles contained dense cores.After reserpine treatment and KMnO4 fixation the synaptic vesicles of the cultured networks contained few dense cores. Similarly treated cultured networks showed an increase in the number of synaptic vesicles with dense cores if incubated with dihydroxyphenylalanine prior to fixation, but a suppression of this increase in the presence of a specific inhibitor of dopamine B‐hydroxylase, FLA 63.The morphology of synapses in the cultured networks was compared to that of endings in the intact rat SCG and iris in vivo, both before and after treatment with norepinephrine and 5‐hydroxydopamine. The vesicles in the synaptic endings in cultures were found to resemble those of the adrenergic endings of the rat iris, and to be similar to those seen within neuronal processes in the rat SCG. Our findings indicate that adrenergic synapses are formed between isolated SCG principal neurons in culture, and thus support recent evidence that such synapses occur in the intact rat SCG. The absence of other tissues which could receive innervation, and of ensheathing satellite cells, may provide a possible explanation for their frequency in the culture situation.
Motor and sensory flight neurones in a locust demonstrated using cobalt chloride
Authors: Tyrer N. M. , Altman J. S. 
Published: January 2005

AbstractThe central projections of motor and sensory neurons involved in the control of the wing beat in locusts have been analysed using cobalt chloride introduced axonally. From sections fo cobalt material, components of particular neuropile regions can be identified. The cobalt method offers an important advance in the analysis of insect neuropile.The flight motor neurones in the mesothoracic ganglion are all basically similar in shape, with no clear distinction between elevator and depressor neurones. All have a highly branched dendritic tree which ramifies extensively through the dorsal neuropile. A neurone innervating a particular muscle can be recognised in different individuals by characteristic features but the pattern of dendritic branching is variable. Neurones involved in both flight and walking have some branches in a deeper layer of neuropile than those concerned only with flight, where the branches lie superficially.Sensory projections from the flight sense organs are complex but compact and their positions in the neuropile are very predictable. They have large interganglionic components. The stretch receptors and wing sense organ projections lie mainly in the dorsal neuropile, whereas the other thoracic sensory receptors project ventrally, with branches to the dorsal neuropile at a few specific points. Associations between certain branches of sensory and motor neurones are demonstrated and their implications for the organisation of the flight reflexes discussed. It is suggested that parts of the motor neurone dendritic tree may be functionally equivalent to interneurones.
Morphology of extraganglionic fluorescent neurons in the myenteric plexus of the small intestine of the rat
Authors: Oosaki Takeo , Sugai Naonori 
Published: January 2005

AbstractFluorescent histochemical observations on the small intestine of the rat demonstrated that single fluorescent cells, separate from the principal ganglia, were present in the myenteric plexus. These extraganglionic cells gave rise to single processes which entered the ganglia and the interganglionic strands. They were of a very small size and were generally unipolar or pseudounipolar. A few fluorescent cells were also observed scattered along the interganglionic strands. Interruption of extrinsic nerve pathways to the small intestine caused a disappearance of meshworks of fluorescent fibers in the myenteric plexus, but in some areas the fluorescent cell alone was seen to remain. A photograph taken from the denervated myenteric plexus revealed that the cell possessed a quite long process.
Branched chorda tympani neurons and interactions among taste receptors
Authors: Miller Inglis J. 
Published: January 2005

AbstractThe preterminal branching pattern of nerve fibers from the chorda tympani nerve was examined in the tongues of rats using a normal silver stain. The lingual branch of the trigeminal nerve was sectioned unilaterally proximal to where it is joined by the chorda tympani and these fibers were allowed to degenerate from eight to ten days prior to sacrifice of the animals. Termination of the chorda tympani fibers in the anterior tongue was found to be limited to the taste bud region of the fungiform papillae. The control side of the tongue showed ubiquitous fiber terminations in the basal layers of the common epithelium of the filiform papillae as well as in the lateral walls of the fungiform papillae. These fibers were assumed to be of trigeminal origin. Seventy‐nine percent of the fungiform papillae on the experimental side of the tongue received fibers from a branched nerve bundle. Branch points within the nerve bundles were located deep within the tongue 300–500 μ below the taste bud in 43% of the papillae, at the base of 36% of the fungiform papillae about 125 μ below the taste bud, and within the papilla.These data corroborate electrophysiological observations that single chorda tympani fibers receive input from more than one taste bud. Lateral inhibition observed among adjacent taste buds has been postulated to result from interaction of fiber inputs at branch points in the afferent fiber. From a theoretical consideration of the morphology of chorda tympani nerve fibers it is concluded that modification of the neural response may be feasible at branch points.
Olfactory bulb connections with basal rhinencephalon in the ferret: An evoked potential and neuroanatomical study
Authors: Dennis Barbara J. , Kerr David I. B. 
Published: January 2005

AbstractThe lateral olfactory tract (LOT) of the ferret has been shown to project to most of the pyriform lobe, as in the cat. Only a small medio‐posterior region of the pyriform cortex (the angular cortex), which has a distinctly different appearance in Nissl stained sections, proves to be devoid of olfactory connections. Despite the fact that sub‐areas can be recognized within olfactory cortex, there is an underlying constancy in design throughout. Latency measurements indicate that fine collateral branches of the LOT reach the posterior olfactory cortex, whereas mainly larger diameter (faster conducting) fibres comprise the contribution to anterior olfactory cortex. Thus in the present context it is sufficient to recognise just an anterior and posterior subdivision of olfactory cortex, contingent on the above criterion and correlated with cytoarchitectural features, chiefly variations in cortical layers II and III of the regions concerned.Pyriform cortex directly in receipt of LOT fibres, and associated deeper cortical zones, generated potentials in the olfactory bulbs which can only be attributed to centrifugal input, thus further substantiating an olfactory role for this cortex. In addition, non‐cortical regions in receipt of LOT fibres, namely the anterior olfactory nucleus, olfactory tubercle, cortical amygdaloid nucleus and nucleus of the lateral olfactory tract, also contribute centrifugal input to the bulbs. All these regions are thereby capable of providing a rather direct feedback on olfactory bulb activity. The exact pathways concerned have yet to be determined.
An autoradiographic study of the time of origin and the pattern of granule cell migration in the dentate gyrus of the rat
Authors: Schlessinger Alice R. , Cowan W. M. , Gottlieb D. I. 
Published: January 2005

AbstractThe dentate gyrus of the rat contains about 600,000 granule cells. These small neurons are generated over a prolonged period from the 14th day of gestation until sime time after the second postnatal week. The majority of the cells pass through their last phase of DNA synthesis in the postnatal period, and during the peak period of cell generation, between the fifth and seventh days after birth, up to 50,000 granule cells are formed each day. Contrary to earlier reports, most of the cells pass through their last mitotic division either within the stratum granulosum itself, or within the hilar region of the developing gyrus. The precursor population of cells in the hilar region must therefore constitute a pool of true neuroblasts. The origin of this pool of cells has not been definitely established but it seems probable that its cells are derived from the neuroepithelium lining the lateral ventricle adjacent to the region from which the hippocampal pyramidal cells are generated. Examination of the final location of granule cells labeled at different stages reveals three distinct morphogenetic gradients in the gyrus. The cells in the dorsal blade tend to be formed earlier than those in the ventral blade; cells in the more caudal (or temporal) portions of the gyrus are generated earlier than those in more rostral (or septal) regions; and in all regions the more superficial neurons in the stratum granulosum are formed earlier than the deeper granule cells. The bearing of some of these findings on the development and organization of the connections of the dentate gyrus is discussed.
Anatomical evidence for cone and rod‐like receptors in the gray squirrel, ground squirrel, and prairie dog retinas
Authors: West Roger W. , Dowling John E. 
Published: January 2005

AbstractIn the gray squirrel (Sciurus carolinensis), the prairie dog (Cynomys ludovicianus), and the Mexican and 13‐line ground squirrels (Citellus mexicanus and C. tridecemlineatus) there exist two distinct classes of photoreceptors that have cone‐like and rod‐like anatomical features respectively. These two receptor classes were previously known to exist in the gray squirrel, but only the cone‐like (C) receptor had been observed in the other species. We have now found small numbers of rod‐like (R) receptors in the other species. as well. R‐receptors comprise about 40% of the receptors in the gray squirrel, 10% of the receptors in the prairie dog, and 4–5% of the receptors in the two species of ground squirrel.This paper describes certain light and electron microscopic features of these two receptor classes including their synaptic connections with second‐order cells and with each other. We find that the C‐receptor has a morphology and synaptic organization characteristic of other mammalian cones. However. the R‐receptor differs from other mammalian rods in certain morphological respects, and its synaptic organization has both cone and rod characteristics as well as some unusual features.
Nerve fiber hypertrophy in posterior tibial nerves of mice in response to voluntary running activity during aging
Authors: Samorajski T. , Rolsten Carolyn 
Published: January 2005

AbstractThree‐month‐old male C57BL/10 mice were exercised by voluntary running activity in vertically revolving wheels for two hours each day until 24 months of age. Activity scores were recorded each day and the animals were regularly weighed and inspected for abnormalities. Control animals were similarly treated except that the acitvity wheels were immobilized.At the end of the exercise period, survival was 84% for the exercise group and 64% for the controls. Light microscopic examination of the posterior tibial nerve of the surviving animals showed a significant fiber hypertrophy in response to the exercise. The number of myelinated fibers in nerves from exercised animals did not differ from those of the controls.On the basis of these data, it is suggested that prolonged exercise does not prevent the loss of peripheral nerve fibers associated with age but rather, may exert an effect on the nervous system by modifying the surviving cells.
The pattern of ocular dominance columns in macaque visual cortex revealed by a reduced silver stain
Authors: LeVay Simon , Hubel David H. , Wiesel Torsten N. 
Published: January 2005

AbstractA pattern of alternative dark and pale bands was observed in the straite cortex of the macaque monkey. The bands, which ran parallel to the surface, were seen in tangential sections stained with a reduced silver method for normal fibers and were most clear in layer 4C α, immediately deep to the line of Gennari. The dark bands were about 300 μ wide and showed blind endings and bifurcations. The light bands were about 50 μ wide and did not branch or terminate within area 17.Because the dark bands were similar in width to the bands of terminal degeneration which have been shown to result from single‐layer lesions of the lateral geniculate body, it seemed possible that they corresponded to ocular dominance columns. To test this idea, the boundaries of ocular dominance columns were marked in a physiological experiment: tangential electrode penetrations were made in an anesthetized monkey and, as the electrode was advanced horizontally in the fourth layer, the eye preference of single units and of the background activity was monitored. Small electrolytic lesions were placed at the points where a change in eye preference occurred. The brain was subsequently fixed, sectioned tangentially and stained with the silver method. All the lesions — a total of 12 — fell directly on the pale bands. Moreover, the electrode had not passed over any pale bands without a lesion being placed. It was concluded that the dark bands do correspond to single ocular dominance columns and the pale bands to the boundaries between columns.The banding appearance is due to a greater density of tangential fibers within columns than at the borders of columns. These tangential fibers are in part the preterminal arborizations of geniculocortical axons, since some of them have been shown to degenerate after geniculate lesion.The ocular dominance columns were mapped for most of the striate cortex, using serial tengential sections stained with the silver method. The overall pattern was similar in several monkeys, though the details of the branching arrangements vaired from animal to animal. The columns met the 17–18 border at rigtht angles. On the outer surface of the hemisphere the columns converged from the 17–18 border, turned medially with repeated fusions of columns, and streamed over the lip of the calcarine fissure. In the roof of the fissure they met a second system of columns oriented parasagittally. In terms of the visual field, the columns ran roughly horizontally for the central 10° of the field, and circumferentially beyond that. The columns were not mapped in the stem of the fissure, the area corresponding to the far periphery of the field.The constancy of column width across the cortex probably allows a functional matching between ocular‐dominance and orientation columns.
The topographical and laminar organization of the presubiculum's projection to the ipsi‐ and contralateral entorhinal cortex in the guinea pig
Authors: Shipley Michael T. 
Published: January 2005

AbstractThis is a detailed report of a previously described projection from the presubiculum to the entorhinal are (Shipley,1974). The terminal degeneration in the entorhinal area is specifically confined to the outer three layers of this cortex. The projection is topographically organized and confined to dorsal and medial parts of the entorhinal area. A similarly organized projection courses via the dorsal psalterium (dorsal hippocambal commissure) to the contralateral entorhinal area. Thus each presubiculum has an orgainzed terminal pathway to the entorhinal cortices of both hemisphers.