bluuebunny/crossref_metadata_2025_split huggingface dataset:
Coding in tuberous and ampullary organs of a gymnotid electric fish
Authors: Suga Nonuo 
Published: January 2005

AbstractThe coding mechanisms of the tuberous and ampullary organs of Gymnotus carapo were studied. The tuberous fibers had no or irregular spontaneous discharges and showed phasic on and/or off responses to 50 msec electric pulses, while the ampullary fibers had regular spontaneous discharges and showed tonic responses to the pulses. The threshold measured with the electric pulses was 1.5 mV/cm on the average for the tuberous fibers and 0.26 mV/cm for the ampullary fibers. For the tuberous fibers, a 0.5–1.0 msec electric pulse was sufficiently long to evoke the maximum response when the intensity of the pulse was 3–10 times higher than the threshold of a given fiber. However, responses of the ampullary fibers were more dependent on duration.To repetitive stimuli of 0.5 msec electric pulses, the tuberous fibers discharged several impulses per stimulus; while the ampullary fibers responded by changingpontaneous discharges from an unlocked to a locked state only in a certain range of intensity and repetition rate of stimulus pulses. The number of impulses per stimulus in the locked state was not modified by change in stimulus intensity. More than half the tuberous fibers and all amullary fibers were mechanically excitable. However, these organs are not considered to act as mechanoreceptors in natural conditions, but to act as electroreceptors.
The fine structure of the caudate nucleus of the cat
Authors: Adinolfi Anthony M. , Pappas George D. 
Published: January 2005

AbstractThe fine structure of the caudate nucleus was studied by electron microscopy. Examination of various regions revealed (1) the majority of neurons are small (10–15 μ ) and can be distinguished from larger neurons by the absence of Nissl bodies, (2) synapses occur most often on dendritic spines, and (3) myelinated fibers in the neuropil have a mean diameter of about 630 mμ and occur singly or in small bundles. These observations suggest a functional organization involving predominantly axodendritic synapses. In addition, small diameter, slow‐conducting efferent fibers might explain, in part, the long latency of responses in thalamic, lenticular and entopeduncular elements following caudate stimulation. This is discussed in conjunction with recent physiological findings.
The septum in the human brain
Authors: Andy Orlando J. , Stephan Heinz 
Published: January 2005

AbstractThe septum of the human brain was studied in relation to its location, composition and development. It was possible to divide it into two parts: septum pellucidum, composed of fiber tracts and glia, and septum verum (true septum) which in addition to fiber tracts and glia, contain neurons arranged in a nuclear pattern. The septum verum in the human corresponds to the septum as described in lower forms. The human septum has been thought to have regressed and be nearly functionless in contrast to lower forms. However, the nucleus septalis triangularis is the only septal nucleus which regressed in development when compared to that in the brains of insectivores and primates. The rest of the septal nuclei progressively increased in size during primate development. Finally, it should be emphasized that the septum verum of the human has attained its highest degree of development in primate phylogeny.
The main sensory trigeminal nucleus in the pigeon: A single‐unit analysis
Authors: Zeigler H. Philip , Witkovsky Paul 
Published: January 2005

AbstractA single‐unit analysis of the main sensory trigeminal nucleus of the pigeon was carried out. A total of 130 units from 20 birds were isolated and their modality, adaptive properties and receptive field characteristics were defined.Seventy‐two percent of the cells were activated by mechanical stimulation ranging from very light touch to pressure. Receptive field areas were generally less than five mm2 in extent. Six units had receptive fields in the region of the orbit, but the receptive fields of most units were confined to the ipsilateral dorsal or ventral beak. Both inner and outer beak surfaces were represented, but no units responsive to tongue stimulation were encountered. Somatotopic organization was evident only in the dorso‐ventral plane where there was a clear sequence of representation from mandibular to maxillary to opthalmic areas. Of the units responsive to mechanical stimulation, 60% were slowly‐adapting, 40% were fast‐adapting.A number of cells (28%) were driven by opening or closing the mouth. Most of these signalled the displacement by a change in their steady discharge rate; a few cells responded to beak displacement with a transient burst.These results clarify the nature of the feeding deficits produced by lesions of the main sensory trigeminal nucleus and suggest an involvement of the nucleus in the sensory control of mandibulation during feeding in the pigeon.
Light and electron microscopical obervations of the ventral horn and ventral root in long term cultures of the spinal cord of the fetal mouse
Authors: Guillery R. W. , Sobkowicz Hanna M. , Scott G. L. 
Published: January 2005

AbstractSegments of spinal cord from 14 to 16 day old fetal mice, grown in vitro for three weeks or longer, show some of the cytoarchitectonic subdivisions of adults cord and several characterstic fiber bundles. In the ventral horns the largest cells have thick axons which leave the explants in well defined ventral roots. These axons run a long course through the outgrowth zone and branch repeatedly there. They have no branches that ramify in the explants nor do they return to the explants. Smaller cells in the ventral horns from a distinct class of cells. Their axons ramify entirely within the explants, mainly within the homo‐ or contralateral ventral horn. Axons of dorsal horn cells also ramify within the ventral horns. Some of their branches pass into a fiber band that surrounds the explant while others enter the outgrowth zone. These last generally return to the explant and form terminal ramifications there.The development of fiber bundles and the appearance of cell groups can be followed in unstained explants, and it appears that each of the characteristic axon patterns develops in vitro.Dendrites of ventral horn cells enter the outgrowth zone and in the ventral roots they are closely related to many passing axons. At some distance from the original explant these processes from a tissue that resembles the central nervous system. New synaptic junctions are formed and the neuronal elements lie embedded amongst glial cells and their processes. The glial cells also from a more or less continuous epithelium separating the feeding solution from the neuronal elements.
Limb immobilization and the diameters and number of nerve fibers
Authors: Tomanek Robert J. 
Published: January 2005

AbstractThe right hind limbs of young and adult male albino rats (aged 35 and 101 days) were immobilized with plaster of paris casts for a period of 11 weeks. The medial gastrocnemius nerve was then excised, and fixed under slight temsion in 0.5% osmium tetroxide. Transverse sections of the nerve were projected onto drawing paper and the diameters of all myelinated fibers were measured.While the results demonstrated a disuse atrophy of the gastrocnemius muscle, the mean nerve fiber diameters of the immoblized groups did not differ from those of the controls. However, immoblization in adult animals was associated with a reduction in the frequency of fibers < 7 μ. On the basis of these data, it is suggested that muscle atrophy may proceed without concomitant alterations in nerve fiber diameter.The number of myelinated fibers in nerves from animals immobilized during postnatal growth is significantly liwer than those of the controls. This finding indicates that limb immobilization retards myelination.
The origins, course and distribution of the dorsal and intermediate acoustic striae in the rhesus monkey
Authors: Strominger Norman L. 
Published: January 2005

AbstractAttempts were made to produce discrete stereotactic lesions in the dorsal cochlear nucleus (Dc) in a series of rhesus monkeys. Anterograde degeneration was studied using Nauta and Fink‐Heimer techniques. Following lesions confined to the caudal pole of Dc, a few degenerated fibers projected to the contralateral lateral superior olivary nucleus via the dorsal acoustic stria. Degeneration was distributed to the contralateral ventral and to a lesser extent dorsal nuclei of the lateral lemniscus. The contralateral central nucleus of the inferior colliculus was a major site of termination of second order auditory fibers; a small number of degenerated fibers ascended to this nucleus ipsilaterally, and a few crossed in its commissure. A few degenerated fibers also were present in the contralateral magnocellular division of the medial geniculate body.When Dc was damaged at levels which overlie the posteroventral cochlear nucleus (Pv), or after lesions involving both subdivisions, degeneration was seen in the intermediate as well as in the dorsal acoustic stria. Fibers arising in Pv coursed through Dc and were interrupted by lesions in the latter. In addition to degeneration described above, fibers projected to the ipsilateral lateral superior olivary nucleus, contralateral medial trapezoid nucleus, and bilaterally to dorsal retroolivary and to preolivary cell groups. No degeneration was seen in the trapezoid body. Lesions involving the posteroventral and anteroventral (Av) cochlear nuclei produced degeneration in the intermediate acoustic stria and in the trapezoid body, but not in the dorsal stria. Degeneration in the intermediate acoustic stria was similar to that present after lesions affecting Dc and Pv. Thus, since Av does not project crossed fibers to this structure, these findings indicate that Pv sends some fibers to the contralateral as well as ipsilateral lateral superior olivary nucleus.
Organization of neurons in the visual cortex, area 17, of the monkey (Macaca mulatta)
Authors: Lund Jennifer S. 
Published: January 2005

AbstractA study of neuron morphology in Golgi Rapid and Kopsch preparations of area 17 of the monkey has shown three basic cell groups— pyramidal neurons, stellate neurons with spinous dendrites and stellate neurons with spine‐free or sparsely spined dendrites. These three neuron groups show different distributions in depth from pia to white matter and differ in their relationship to zones of concentrated termination of geniculo‐cortical axons. The neuron type most closely related to the laminae receiving a heavy geniculo‐cortical projection is the spinous stellate cell. This cell type is restricted to lamina IV. Included in this zone is the broadest band of geniculo‐cortical axon projection (lamina IVC), the horizontal fiber band (lamina IVB) comprising the major portion of the stria of Gennari (receiving little or no thalamic projection) and the narrow band of thalamo‐cortical fiber termination which occurs superficial to the stria of Gennari (lamina IVA). Pyramidal neuron cell bodies are almost totally excluded from lamina IVC and the apical dendrites of lower pyramidal neurons bear many fewer spines in lamina IVC than in laminae V and VI. The basal dendrites of upper pyramidal cells spread superficial and deep to lamina IVA rather than within it. Spine‐free stellate neurons occur at all cortical levels and sparselyspined varieties have not been impregnated in lamina IV, but occur in the other laminae.Three groups of presumed thalamo‐cortical axons have been identified, two of which resemble each other in morphology (having long collaterals which appear to terminate by means of spine‐like projections of the axonal surface) but not in distribution. One group of these axons bearing spine‐like projections distributes in laminae IVC (principally in the deeper half, IVCβ) and IVA; the other is restricted in distribution to the upper half of lamina IVC (IVCα). The third group of thalamo‐cortical axons distributes to lamina I and appears to lack the spine‐like projections shown by the other two axon groups.
Transneuronal changes in the gracile nucleus
Authors: Loewy Arthur D. 
Published: January 2005

AbstractThe gracile nucleus was studied in the monkey and man with light microscopic methods after lesions to the posterior columns. The medullas from six autopsy cases were studied; four of these were from patients who had survived spinal cord transections for periods of 2, 22, 41 days, and 22 years. The deafferented gracile neurons did not show changes in Nissl substance, in neurofibrillar patterns, or in nuclear structure that could be directly related to posterior column denervation. Neuron counts of the gracile nucleus were made in one case of a T9 spinal transection of 22 years standing and yielded figures not significantly different from those established by systematic counts in other human autopsy material in which CNS lesions were not present.In the monkey, the neuronal population of the gracile nucleus did not change as a result of posterior column transection. In cases of six months standing, the denervated neurons showed a 25% decrease in mean cell body area and about a 20% decrease in mean nuclear area. About 1% of the neurons on the operated side appeared darker in reduced silver preparations than any of the gracile neurons from the unoperated side.
The connections between bipolar cells and photoreceptors in the retina of the domestic cat
Authors: Boycott B. B. , Kolb H. 
Published: January 2005

AbstractAn invaginating bipolar cell that has dendritic terminals forming the central elements of the cone triads is described for the retina of the cat. This type of bipolar contacts a minimum of four or five and a maximum of nine or ten cones. There is no evidence for a bipolar cell which contacts only one cone, i.e., a midget bipolar cell as in simians. There are flat bipolar cells that make superficial contacts with the bases of the cone pedicles and are postsynaptic to between 8 and 14 cones. One cone can be in contact with both an invaginating and a flat bipolar cell. There is evidence suggestive of two kinds of flat bipolars. A comparison is made between the bipolar connections in simians and the cat. The comparison is summarized in figures 29 and 30.
Growth, differentiation and ribonucleic acid content of the fetal rat spinal ganglion cells in culture
Authors: Sobkowicz Hanna M. , Hartmann Henrik A. , Monzain Rachel , Desnoyers Patricia 
Published: January 2005

AbstractObservations were made on 324 cultures of spinal ganglia which were excised from fetal rats between the tenth and eighteenth day of gestation. The cultures were maintained up to 81 days in vitro. As a control sixteen Sprague‐Dawley rats from two litters were sacrificed at different ages. RNA content of the cell bodies in both normal and cultured spinal ganglia was determined by the Edström method. The volume of the cell bodies was determined by the optical reconstruction method of Micklewright. Spinal ganglion cells in culture develop at a much slower pace than in situ, but show the normal sequential order of cytodifferentiation. A few days after explantation, the cells increase rapidly in size and a large fibrillogenous zone becomes apparent around the centrosome. All of the neurofibrillar network of the cell and the axon seem to derive from this zone. At this stage the Nissl material is found mainly at the periphery of the cell body since the fibrillogenous zone is essentially free from Nissl granules. The initial development of the zone in culture is accompanied by no or a very small increase in the cellular RNA content present at the time of explantation though the cell volume increases greatly. In later stages, the fibrillogenous zone disappears slowly as a separate entity while the Nissl bodies invade the entire soma of the cell. When this is accomplished the neurofibrillar network becomes complex, the Nissl bodies form distinct patterns, the growing fibers start to myelinate. The cells increase only slowly in size. After four to ten weeks in culture the typical spinal ganglion cell is a monopolar neuron which is morphologically advanced to various degrees. However, some less common morphological forms can be seen occasionally in culture as is also the case in normal material.Our cytochemical determinations suggest that a growth‐curve relationship exists in normal material between the RNA content of the cell and the age of the animal up to about eighth to eleventh day after birth. The largest increase in RNA content in normal material occurs in the second week after birth when nearly adult values are reached. In culture, a similar relationship exists between the age of the culture and the RNA content of the cells though the data points are scattered considerably. In sharp contrast to the normal material, however, the slope of the growth‐curve is very much less steep and no plateau is apparent up to 81 days in vitro. Since the initial increase in cell volume in culture is due to a formation of the fibrillogenous zone and is not accompanied by a proportional increase in RNA it seems likely that the increase in RNA content of the cell during normal development is primarily due to the formation and differentiation of Nissl material.
Electron microscopy of non‐neuronal cellular changes accompanying neural degeneration in thalamic nuclei of the rabbit. I. Reactive hematogenous and perivascular elements within the basal lamina
Authors: Matthews Murray A. , Kruger Lawrence 
Published: January 2005

AbstractElectron microscopic examination of several thalamic nuclei undergoing neural degeneration following ablation of their cortical projection fields revealed reactive changes in vessels unrelated to direct mechanical trauma. A series of 30 rabbits were studied at post‐operative survivals of one to 238 days. Many neurons display signs of retrograde atrophy within the first week accompanied by a distinct increase in the number of perivascular cells within the basal lamina surrounding venules and large capillaries. This reaction was optimally observed between 5 and 98 days post‐operatively and was limited to the circumscribed zones of degeneration. In early stages, some vessels displayed margination of hematogenous elements, predominantly agranular leukocytes, of which some examples were seen in phases suggestive of diapedesis. Cells within the perivascular space exhibited diverse morphology. In addition to the indigenous “pericyte” population, there were numerous agranular leukocytes, and a few plasma cells and eosinophils. Within the second to third week postoperatively, some perivascular elements become enlarged and display electron‐lucent lipid vacuoles and PTA‐positive dense bodies of complex morphology, many of which are clearly lysosomal in nature. This cellular reaction persists for three to four months, after which time the cytoplasm displays evidence of cholesterol crystals and lysosomal transformations suggestive of terminal or residual bodies. Morphological criteria for identifying the possible origin of vacuolated, lysosomeladen perivascular cells are presented for a consideration of their possible derivation from pericytes and/or hematogenous elements. Of the several hypotheses considered to account for these findings, it appears likely that lipid and protein end‐products of neural degeneration provide the stimulus for perivascular aggregation and subsequent transformation.
Cytoarchitectural subdivisions of the periaqueductal gray matter in the cat
Authors: Hamilton Betty L. 
Published: January 2005

AbstractThe neuronal population of the PAG consists of relatively small cells, ranging from approximately 8 μ to 30 μ in diameter. These neurons are of three different types and are classified as I, II, and III for the sake of convenience. Each class aggregates in certain areas of the central gray to form subdivisions distinguishable by differing neuronal distributions as well as by cellular characteristics. Class I neurons are small, spindle shaped cells that stain darkly with cresyl violet. They aggregate loosely around the cerebral aqueduct, thus forming the comparatively acellular inner ring of the PAG, the nucleus medialis. The class II cells are also small and darkly staining, but they are fusiform to spherical in shape. These cells cluster more closely and are surrounded by many glial cells. They congregate in the area dorsal to the cerebral aqueduct to form the nucleus dorsalis. The largest cells of the PAG, the class III neurons are spherical or tringular in shape and stain lightly due to their sparse Nissl substance. Frequently glial cells abut the perikaryon of these neurons. They aggregate very closely to form the dense cellular outer portion of the PAG. This mantle of cells is called the nucleus lateralis.
Architectonic studies of the diencephalon of Iguana iguana (Linnaeus)
Authors: Butler Ann B. , Northcutt R. Glenn 
Published: January 2005

AbstractThe normal anatomy of the nuclei and major fiber tracts of the diencephalon and pretectum of the lizard, Iguana iguana, are described and compared to descriptions of the diencephalon of other reptiles. Clarification of variations in the nomenclature has been attempted, based on comparison of normal and experimental material. Experimental studies of afferent and efferent projections of the diencephalon of various reptiles are reviewed and discussed. The earlier literature on thalamic homologies between reptiles and other vertebrates is re‐examined, and a new interpretation offered based on these new results.
A comparative study of spinocerebellar systems in three classes of poikilothermic vertebrates
Authors: Hayle T. H. 
Published: January 2005

AbstractSpinocerebellar systems have been investigated in three classes of poikilothermic vertebrates. Lesions were made in the spinal cord of a number of dogfish, rudd and frogs which were selected as representatives of their classes. After a postoperative survival period the resulting fibre degeneration was demonstrated by means of a suitable silver impregnation technique. The findings have provided experimental confirmation of a spinocerebellar pathway in each species examined. In the dogfish these fibres form part of a mixed spinal lemniscus, which ascends through the brainstem, and leave it to enter the corpus cerebelli, through its peduncles. In the rudd two separate systems were found, one of which corresponds to that seen in the dogfish. The other forms a separate compact fasciculus which lies more dorsally in the brainstem throughout its course. This one can be followed into the cerebellum through the peduncle. Within the corpus cerebelli it was not possible to distinguish between the two systems. In the frog also two separate systems were seen. These retained their individual identity from the spinal cord to their entrance into the cerebellar peduncle beyond which they appeared to merge. These findings have been compared with the results of other authors, and an attempt has been made to show how and why such systems have evolved.