bluuebunny/crossref_metadata_2025_split huggingface dataset:
The medial geniculate body of the tree shrew, Tupaia glis I. Cytoarchitecture and midbrain connections
Authors: Oliver Douglas L. , Hall William C. 
Published: January 2005

AbstractIn this study of the medial geniculate body in the tree shrew eight subdivisions are identified on the basis of differences recognized in Nissl‐stained material. Experiments using the methods of anterograde and retrograde axonal transport and anterograde degeneration show that each subdivision has a unique pattern of connections with the midbrain.The ventral division of the medial geniculate body contains at least two subdivisions, the ventral nucleus and the caudomarginal nucleus. The ventral nucleus is characterized by densely‐packed cells and receives topographically organized projections from the central nucleus of the inferior colliculus. The caudomarginal nucleus, on the other hand, receives its major midbrain projections from the medial nucleus in the inferior colliculus.In the dorsal division four subdivisions are distinguished. The suprageniculate nucleus contains large, loosely‐packed cells and receives projections from the deep layers of the superior colliculus and from the midbrain tegmentum. The dorsal nucleus receives projections from the midbrain tegmentum. The deep dorsal and anterodorsal nuclei have neurons which resemble those in the dorsal nucleus. Both receive projections from the roof nucleus of the inferior colliculus but the deep dorsal nucleus receives an additional projection from the parabrachial tegmentum.The medial division has a rostral and a caudal subdivision. The ascending projections to the rostral nucleus are from the lateral zone in the inferior colliculus and from the spinal cord. The caudal nucleus contains cells with large somas and receives projections from most of the midbrain areas which project to the other subdivisions of the medial geniculate body.
The medial geniculate body of the tree shrew, Tupaia glis II. Connections with the neocortex
Authors: Oliver Douglas L. , Hall William C. 
Published: January 2005

AbstractIn this study the temporal cortex of the tree shrew was subdivided on the basis of cytoarchitectonic criteria, and the connections of each subdivision with the thalamus and midbrain were analyzed with retrograde and anterograde techniques.The results indicate that, with one exception, each subdivision of the medial geniculate body projects to a separate cortical area. The primary auditory cortex receives projections from the ventral nucleus. Surrounding the primary cortex are at least five additional cytoarchitectonically distinct areas which receive projections from the remaining medial geniculate subdivisions. The evidence suggests that there is very little overlap in the projections from each of these geniculate subdivisions. An exception is the projection of the caudal nucleus of the medial division. This subdivision apparently projects to most, if not all, of the cortical target of the medial geniculate body. Although the cortical projections of the caudal nucleus overlap those of the other medial geniculate subdivisions, the laminar distribution of its terminationsin cortex is different. The caudal nucleus projects primarily to layer VI whereas the other subdivisions of the medial geniculate body project primarily to layer IV and the adjacent part of layer III.Anterograde techniques were also used to study the projections from the cortex back to the thalamus and to the midbrain. The projections to the thalamus precisely reciprocate the thalamocortical connections. The projections to the midbrain are to the same areas which the preceding study (Oliver and Hall, '78) showed give rise to ascending projections to the medial geniculate body. An exception is the central nucleus of the inferior colliculus which apparently does not receive a projection from the temporal cortex.
Isogenic grasshoppers: Genetic variability in the morphology of identified neurons
Authors: Goodman Corey S. 
Published: January 2005

AbstractAlthough identified neurons are defined as constant and unique from animal to animal within the same species, we might expect to find phenotypic variablity in the number, morphology, and physiology of identified neurons if we examined them in enough sexually reproduced animals of the same species. Morphological variability and axonal abnormalities were previously encountered in a study of the large ocellar interneurons in 50 grasshoppers.Both the somata and arborizations in the brain of the ocellar interneurons from one or more ocelli can be stained easily and repeatedly with cobalt, so that one can routinely examine the morephology of large numbers of cells in large numbers of animals.In the present study, the large ocellar interneurons were examined in three types of animals: (i) animals from two different breeding poplulations and their offspring, (ii) the offspring within clutches from single mated pairs of known phenotypes, and (iii) isogenic animals from the parthenogenetic clones of single unmated females. The soma location, axonal pathway, location of arborizations, and fine branching patterns of 14 of the large ocellar interneurons were examined in 430 grasshoppers.The large ocellar interneurons were examined in 11 clones raised in nearly constant and identical conditions. In most of the clones, the morphology of interneurons L5L and L5R was normal; all of the 82 animals examined from clones 4, 7, 9, 10, 12, 13, 16, and 17 were normal. Clones 8 and 2 had high percentages of animals with axonal abnormalities of interneuron L5: 16 out of 24 animals (66%) in clone 8 and 37 out of 42 animals (88%) in clone 2. All of the ocellar interneurons except for L5 were normal in all of these animals.Thus, the abnormal development of at least one identified interneuron, L5, can occur with a high degree of genetic control and a high degree of specificity. The axonal abnormality of interneuron L5 was not the same in each of the 37 animals from clone, 2, although common mistakes and patterns were detected.
The identification of relay neurons in the dorsal lateral geniculate nucleus of monkeys using horseradish peroxidase
Authors: Norden J. J. , Kaas J. H. 
Published: January 2005

AbstractIntraaxonal retrograde transport of the protein horseradish peroxidase (HRP) was used to identify relay neurons in the dorsal lateral geniculate nucleus (LGN) of owl (Aotus trivirgatus) and rhesus (Macaca mulatta) monkeys. In both species, from 94.1–98.6% of the neurons within columns extending through both parvocellular and magnocellular layers were labeled following injection of HRP into striate cortex. Labeled neurons were also identified in the thin ventral‐most S(0) Layers. Although most of the cells within the thin interlaminar regions in the LGN of both species were labeled following injections of HRP, many unlabeled neurons were identified within the large cell‐rich interlaminar region (IL) between the internal parvocellular and internal magnocellular layers in the LGN of the owl monkey, suggesting that IL may be a specialized containing a large number of intrinsic neurons. Finally, measurement of the cell diameters of neurons within the densely labeled areas in relay layers revealed that labeled and unlabeled neurons could not be distinguished on the basis of cell body size alone and that some of the smallest cells of the LGN project to striate cortex. These findings indicate that nearly all of the neurons of the main relay layers of the LGN in these two primates are relay cells and that the organization of the LGN in primates may differ significantly from that of other mammals with respect to the percentage of interneurons.
Proliferative and degenerative events in the early development of chick dorsal root ganglia. I. Normal development
Authors: McMillan Carr Virginia , Simpson Sidney B. 
Published: January 2005

AbstractDevelopment of the chick dorsal root ganglia was examined in 4.5‐ to 9.5‐day embryos. Tritiated thymidine (3H ‐ TdR) and autoradiography was used to analyze proliferative activity and the Feulgen procedure to analyze degenerative activity in ganglia 12–17. Proliferative activity was found to be elevated through 4.5 days of incubation when as many as 14% of the ganglionic cells become labelled following a one‐hour exposure to 3H‐ TdR. By 6.5 to 7.5 days proliferative activity decreased to 2–4% in the lateroventral (LV) regions and to approximately 1% in the mediodorsal (MD) regions of the ganglia. However there appears to be increased proliferative activity by the end of the experimental period at 9.5 days. Birthdate studies demonstrate that large‐scale neuronal production occurs between 4.5 and 6.5 days in LV regions and between 4.5 and 7.5 days in the MD regions. After those times ganglionic proliferative activity must be largely nonneuronal in nature. This nonneuronal proliferation is greater in LV than in MD regions and in brachial than in nonbrachial ganglia.Degenerative activity was found to be absent from the ganglia until after 4.5 days of incubation. It then increases rapidly, and by 5.5 days 5% of the LV cells in nonbrachial ganglia are degenerating. Degenerative activity then declines but is still present at 9.5 days. In contrast to results of an earlier study (Hamburger and Levi‐Montalcini, '49), degenerative activity was also found in the LV region of brachial ganglia and the MD regions of brachial and nonbrachial ganglia. The pattern of LV degenerative activity in brachial ganglia is similar to that in nonbrachial activity increases throughout the experimental period, and by 9.5 days as many as 4% of the MD cells are degenerating.
A preganglionic autonomic nucleus in the dorsal gray commissure of the lumbar spinal cord of the rat
Authors: Hancock Michael B. , Peveto Cynthia A. 
Published: January 2005

AbstractThe distribution in the spinal cord of the rat of preganglionic neurons sending fibers into the hypogastric nerve was determined with the retrograde transport of horseradish peroxidase (HRP). Labeled cells were present in the intermediate gray matter of spinal segments L1‐L2. The majority (81%) of HRP‐filled cells formed a continuous column along the midline in the dorsal gray commissure. This cell column was termed the dorsal commissural nucleus (DCN). The remainder of HRP‐labeled cells were present bilaterally in the middle and lateral regions of the intermediate gray; the majority of the latter cells were located along the lateral border of the intermediate gray.The present finding of a midline preganglionic autonomic cell column in the spinal cord of a mammal is contrary to previous reports, in which sympathetic preganglionic neurons have been localized primarily in the lateral intermediate gray. The DCN may be species‐specific and related to the system of short adrenergic neurons present in the pelvis.
A Golgi study of the early postnatal development of the visual cortex of the hooded rat
Authors: Juraska Janice M. , Fifková Eva 
Published: January 2005

AbstractAlthough neuroanatomical plasticity has been demonstrated in the rat visual cortex, no systematic data on the dendritic development of the area are available. In the present study, the visual cortex of hooded rats at 1, 3, 5, 7, 10 and 15 postnatal days of age (P1‐P15) was impregnated with the rapid Golgi method. The cortex was divided into the superficial layers, II‐IV, and the middle layer V. At P1, pyramidal neurons had apical shafts and the beginning of the apical terminal arch. Analysis of both basilar and oblique dendritic number showed that pyramidal neurons of the middle layer developed more quickly than those in the superficial layers. The number of lower order basilar dendritic branches reached asymptote over the examined time period, whereas the higher order branches were still increasing in number but at a decelerating rate by P15. Dendrites at all ages exhibited varicosities which were especially prominent on the thin dendritic branches of the earlier ages. Some thin, filamentous processes, termed protospines, were found on dendrites and cell bodies at P1 to P5. They seemed to decrease by P7, when a few mature spines appeared. Spines increased in number on days P10 and P15. A comparison of the data from this study with quantified Golgi studies in adult rats indicates that by P10 and P15 the number of basilar branches is in the range seen in the adult.
Projections of a telencephalic auditory nucleus– field L–in the canary
Authors: Kelley Darcy B. , Nottebohm Fernando 
Published: January 2005

AbstractAnterograde projections of a telencephalic auditory area – field L of the neostriatum – were traced in canaries, Serinus canarius. Field L was defined as the neostriatal projection of nucleus ovoidalis of the thalamus. Using amino acid autoradiography, two efferent projections of field L and adjacent neostriatum were observed: (1) a projection to the medial and ventral borders of nucleus hyperstriatum ventrale, pars caudale (HVc) and (2) a smaller projection to medial paleostriatum augmentatu (PA). When autoradiographic injection sites included neostriatum postero‐ventral to field L, a projection to archistriatum outlining the anterior and ventral borders of the nucleus robustus archistriatalis (RA) resulted. Injection sites that included neostriatum antero‐lateral to “L” gave rise to projections to the interior of HVc proper. Above background numbers of silver grains were consistently observed over caudal dorso‐lateral portions of nucleus ovoidalis. Following lesion of field L and adjacent neostriatum, argyrophilic degeneration was traced to medial PA and to a shelf of neostriatum underlying HVc. All observed anterograde projections were ipsilateral.Two of the nuclei outlined by neostriatal projections in this study, HVc and RA, have important roles in the motor control of canary song (Nottebohm et al., '76). The development of song is dependent on auditory information. Auditory‐vocal neural connections described here may be involved in song learning.
Synaptic fine structure and the termination of corticospinal fibers in the lateral basal region of the cat spinal cord
Authors: Hanaway Joseph , Smith Jeanne M. 
Published: January 2005

AbstractThe lateral basal region (LBR) of the spinal cord gray matter (Rexed's laminae IV‐VII) by physiologic and anatomic criteria is the major terminal zone for the corticospinal (CS) tract in the cat. The neurons in this area are medium‐sized with abundant spines on their dendrites. Axon terminals on the dendrites and somata of these neurons form synapses easily classified as asymmetric with spheroid vesicles and symmetric with flattened vesicles. There are rare exceptions to this. In a systematic count of terminals, 82% have spheroid and 18% flattened vesicles. The majority of all terminals are on dendrites (84.9%) and a minority on somata (14.1%). Less than 1% are axoaxonic.Degeneration of the corticospinal tract was produced by transecting one hemisphere of our experimental cats. Its termination in the lower cervical cord was studied for 17 hours to 7 days after surgery. Vesicle depletion and clumping and dense polymembranous inclusions were the most common forms of degeneration. Filamentous proliferation in the terminals was also prominent; dark degeneration, however, was infrequent. The percent of degenerating CS terminals in the LBR was the following: 17 hours – 2.2%, 36 hours – 4.19%, 2 days – 10.3%, 3 days – 8.4%, 4 days – 6.9%, 7 days – 10.25%; 84.8% of degenerating CS terminals were axodendritic and 15.2% axosomatic.
The time of origin of the mesencephalic trigeminal neurons in Xenopus
Authors: Lewis Simon , Straznicky Charles 
Published: January 2005

AbstractTime of orgin of the mesencephalic trigeminal cells (MTC) in Xenopus has been studied with 3H‐thymidine autoradiography. The first MTC's were formed at stage 20, and they continued to arise up to stage 58. The mitotic rate of MTC's was found to be ten per cent at any time from stages 20–50, with a slow decrease thereafter. MTC's in the tectum were distributed in a spatiotemporal manner. Cells generated earliest were located in the rostral pole of the tectum and were followed in caudomedial sequence by cells formed later. The generation times of MTC and the neurons of the sensory trigeminal ganglion (TGC) were strikingly dissimilar, indicating that they probably do not represent a common cell lineage, that is, the former may not arise from the mesencephalic neural crest. It is proposed that the majority of MTC's generated from stage 30 onward, derive through proliferative activity of precursor cells in the di‐mesencephalic junction and in the tectal neuroepithelium.
Afferent influences on the development of the brain stem auditory nuclei of the chicken: Otocyst ablation
Authors: Parks Thomas N. 
Published: January 2005

AbstractThe effects of embryonic deafferentation on the morphological development of the avian cochlear nuclei, n. angularis (NA) and n. magnocellularis (NM), were investigated. The right otocyst was surgically removed from chick embryos at 55 to 60 hours of incubation and the subsequent development of total volume, neuron number, and neuron cross‐sectional area were studied with quantitative methods in animals sacrificed at 2‐day intervals between embryonic days 9 and 19 and at 28 days posthatching. The development of NA and NM is severely affected by otocyst ablation. Between embryonic days 9 and 19, a large group of NA neurons in the medioventral portion of the nucleus on the perated side moves to an ectopic ventromedial position, while the remainder of this nucleus stays in its normal dorsolateral position. Beginning about day 13 of incubation, the normal increase in the volume of NA and the size of its neurons becomes progressively retarded and 40% of its neurons are lost. The growth of NM is also retarded after day 11 of incubation and the growth of mean neuron size is retarded after day 15. There is a 30% loss of neurons in NM which begins after embronic day 11.The results indecate the primary cochlear fibers make a critical contribution to the growth and maintenance of their target neurons. The absence of this facilitative influence following otocyst ablation becomes apparent just at the time synapses would normally be formed between the promary auditory afferents and the brain stem auditory neurons. The abnormal movement of neurons in nucleus angularis to an ectopic position after otocyst ablation suggests that primary auditory afferents may serve to stabilize the position of their target cells within the developing brain.
Histofluorescence and ultrastructural evidence for catecholamine‐containing sensory neurons bordering the interventricular foramen of the toad brain
Authors: McKenna Olivia C. , Gorski Victoria A. 
Published: January 2005

AbstractA population of catecholamine‐containing cells that borders the interventricular foramen of the toad brain has been studied by both fluorescence histochemical and electron microscopic methods. The perikaryon of these cells, which lies immediately subjacent to the ependyma, sends a fluorescent apical process between the ependymal cells to border on the ventricular surface and a basal process displaying fluorescent varicosities into the underlying neuropil. A few cells possess a broad lateral extension which runs parallel to the ventricular surface. Histochemical and pharmacological specificity tests indicate that the cells contain catecholamines, including epinephrine. The most distinctive ultrastructural feature of the subependymal cells' cytoplasm is large numbers of dense cored vesicles that vary in diameter from 500 A to 2,400 A; these are found in the perikarya, apical and basal processes, and lateral extensions. In addition, bundles of filaments ($100 A in diameter) are seen lying adjacent to the nucleus, and numerous axosomatic synapses are found along the surface of the cell bodies. The luminal surface of the apical processes is covered by microvilli and extends a short distance into the ventricular lumen. The basal processes are narrow in diameter, measuring 0.5‐1.1 $m, and contain some filaments, microtubules and dense cored vesicles, but no clusters of ribosomes and no granular endoplasmic reticulum. The characteristics of these subependymal cells, i.e., apical processes which contact the cerebrospinal fluid and basal processes which resemble axons, suggest that the cells may be sensory neurons, and as such, they may respond to the changing composition or pressure of the cerebrospinal fluid and relay this information via their axons to other neurons. The results of this study contribute further evidence that the cerebrospinal fluid provides a means of chemical communication within the brain.
Synaptic Contacts of the Horizontal Cells in the Retina of the Marine Teleost, Callionymus Iyra L.
Authors: van Haesendonck E. , Missotten L. 
Published: January 2005

AbstractThe horizontal cell system in the retina of the fish Callionymus Iyra L. was investigated light microscopically and electron microscopically. One type of rod horizontal cells, which are only found in the mixed ventral part, exclusively contacts spherules with lateral endknobs in the triads. Three types of cone horizontal cells occur. The first type, c‐H1, contacts pedicles of pale and dark double cones and single cones. The processes always have a lateral position in the triads. This type has a constant contact pattern with the photoreceptor cells. The second type, c‐H2, selectively contacts pedicles of pale double cones and the endbuds occupy a central position in the triads. In the single cone pedicles in the dendritic field of the c‐H2 horizontal cell, the endbuds never seem to reach the triads. The third type, c‐H3, only sends processes to pedicles of single cones where the endbuds occupy a central position in the triads. The synaptic connections of the horizontal cells of Callionymus differ from those observed in Nannacara anomala and Carassius auratus. The difference from the results obtained from Carassius is such that the information transfer model proposed for Carassius cannot apply to Callionymus.
The organization of feline entopeduncular nucleus projections: Anatomical studies
Authors: Larsen Kenneth D. , McBride Russell L. 
Published: January 2005

AbstractThe organization of entopeduncular nucleus (EPN) projections was studied in cats using autoradiographic and horseradish peroxidase (HRP) techniques. In autoradiographic studies, EPN axons were found to terminate in a J‐shaped region in the dorsal and medial part of the ventral anterior nucleus (VA) and the rostral portion of the adjacent ventral lateral nucleus (VL). EPN axons also terminated in the rostral portion of the centrum medianum (CM), the ventrolateral portion of the lateral habenular nucleus (LHB), and the pedunculopontine nucleus (PP). The VA included the largest terminal field although the LHB had the greatest density of terminals. Regardless of the region of EPN into which amino acids were injected, the terminal fields were the same: there was no localization within the EPN of the cells projecting to one region. HRP‐containing cells were distributed throughout the EPN following injections into the VA, LHB, or PP, although many more cells were labeled following injections into either VA or LHB than PP. EPN cells containing HRP following injections into either VA or LHB were not morphologically different from those not containing HRP in the same respective animals. Following HRP injections into stria medullaris, only cells in the rostral part of the EPN were labeled, providing evidence that rostrally and caudally located EPN neurons have different paths to LHB. Although there may be a rostrocaudal organization of pathways to LHB, individual regions of the nucleus project to the same areas.