bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quantitative synaptology of feline motoneurones to external anal sphincter muscle
Authors: Pullen A. H. 
Published: January 2005

AbstractMotoneurones innervating the cat external anal sphincter muscle were labelled retrogradely following intramuscular injections with horseradish peroxidase (HRP). Labelled motoneurones were examined by correlative light and electron microscopy (LM and EM) with special regard to a qualitative and morphometric analysis of the axon terminals resident on the neuronal membrane.By LM, labelled motoneurones were (1) ipsilateral to the injections; (2) all in S1‐S2; (3) found only in the superior dorsomedial region of Onuf's nucleus; and (4) exhibited a broad spectrum of diameters (25–72 μm, mean 47.4 ± 11.3 μm).By EM, axon terminals on the neuronal membrane when classified according to size, vesicle shape, and synaptic complex ultrastructure conformed to the S‐, F‐, T‐, M‐, and C‐type terminals previously described for cat lumbosacral motoneurones. C‐terminals confirmed these sphincteric motoneurones to be skeletomotor. Pooled data from midnuclear sections through 15 random labelled motoneurones (20–64‐μm diameter) revealed that S‐ and F‐type terminals predominated, with numerically few M and C types. Notwithstanding their low frequency (0.3/100 μm membrane) C‐terminals contributed 1% of the mean areal coverage by terminals, which implies a potentially larger synaptic influence relative to other terminal types. Linear relationships occurred between terminal frequency (or cover) and motoneurone diameter. While motoneurones >40μm in diameter exhibited all five terminal types, labelled motoneurones ≤30 μ generally possessed only S‐, F‐, and occasional T‐type terminals, and in this respect resembled gamma motoneurones.
Spatial organization of the retinal projection to the avian lentiform nucleus of the mesencephalon
Authors: Bodnarenko Stefan R. , Rojas Ximena , McKenna Olivia C. 
Published: January 2005

AbstractUtilizing the horseradish peroxidase retrograde tracing technique and the 2‐deoxy‐D‐glucose metabolic mapping technique, we have demonstrated in chickens the distribution of retinal ganglion cells that project to the lentiform nucleus of the mesencephalon (LM) and the retinotopic organization of the projection in the LM. Retinal ganglion cells labeled after a nearly complete injection into the LM were found in the four quadrants, distributed in a wide horizontal belt lying along both sides of the retinal equator and stretching from the temporal to the nasal retina. The HRP‐labeled cells, which appeared round or oval, ranged from 25 to 840 μm2 in size with most in the smaller size range. Results of partial HRP injections into the LM and metabolic mapping patterns in the LM produced by stimulation of half the retina with horizontal visual motion suggest that there is an orderly mapping of the retina onto the LM. The inferior temporal quadrant projects to the rostrodorsal LM; the inferior nasal quadrant projects to the caudodorsal LM. The superior temporal quadrant projects to the middle and ventral LM, extending from the rostral to the caudal pole, whereas the superior nasal quadrant projects to a small zone in the caudal LM. The mapping of the retinal quadrants in the LM is remarkably similar to that reported in the optic tectum of birds. We suggest that a common embryological anlage with the optic tectum and the arrangement of retinal axons in the optic tract are important factors in establishing the retinotopic organization of the LM.
Abnormal pigmentation and unusual morphogenesis of the optic stalk may be correlated with retinal axon misguidance in embryonic siamese cats
Authors: Webster M. J. , Shatz C. J. , Kliot M. , Silver J. 
Published: January 2005

AbstractStudies of albino rodents have shown that an absence of pigment in the developing optic stalk may alter the position of the first retinal fibers that grow toward the brain, thereby disrupting the gross topographic relationship of fibers in the nerve (Silver and Sapiro: J. Comp. Neurol. 202:521–538, ′81). The abnormalities associated with albinism are more extensive in the Siamese cat than in previously studied species. Therefore, any abnormalities in differentiation of the stalk and axon guidance may be more readily detected. To investigate the guidance and/or misguidance of optic axons, light and electron microscope analyses were made of serial sections through the optic stalk in normally pigmented and Siamese fetal cats.On E20, before axons enter the optic stalk, the only clear morphological distinction between Siamese and normal cats is the distribution of pigment in the stalk. Pigment is found in the dorsal stalk cells of the normal cat for 200 μm from the optic disc. Although the retinal pigment epithelium of the Siamese cat embryo contains pigment, pigment could not be detected in the Siamese optic stalk. By E23 axons invade the ventral optic stalk in both strains. Concurrent with the early stages of axonal exit from the retina, there is complete separation of the stalk's dorsal and ventral tiers. As the cleavage occurs, basal lamina invaginates into the zone of separation following along the plane of the old lumen. The ventral stalk fills with axons while the dorsal tier is shed gradually. In contrast, in the Siamese cat, dorsal stalk cells are not sloughed off properly and instead are incorporated ectopically into the nerve. Basal lamina invagination is irregular. Axons do not fill the Siamese stalk symmetrically but enter the region of ectopic cells, which in turn disrupts gross fiber position. Usually, in the mutant, axons originating from the retina temporal to the optic fissure are those that invade the dorsal tier of ectopic cells. The altered position of optic axons in the mutant stalk may provide an explanation for the chiasmatic misrouting of optic axons in this species.
Visceral cortex: Integration of the mucosal senses with limbic information in the rat agranular insular cortex
Authors: Krushel Leslie A. , van Der Kooy Derek 
Published: January 2005

AbstractThe organization of the subcortical and cortical connections of the rat agranular insular cortex was examined. Retrogradely transported dyes were used to map the agranular insular cortex efferents to brainstem visceral nuclei (the nucleus of the solitary tract and the parabrachial nucleus), to gustatory‐visceral and limbic thalamic nuclei (medial ventrobasal and mediodorsal thalamus, respectively), and to association cortex (medial prefrontal and contralateral agranular insular cortex). The results revealed that a specific area within the ipsilateral agranular insular cortex projected to all of the subcortical and cortical areas listed above. This area of overlap in the agranular insular cortex stretched from the level of the genu of the corpus callosum rostrally to the crossing of the anterior commissure caudally.Anterograde projections from the medial ventrobasal and mediodorsal thalamus and from the olfactory bulb to the agranular insular cortex were mapped with wheat germ agglutinin conjugated to horseradish peroxidase. The terminal cortical projections from these areas were generally separate, except in an area where they overlap immediately medial to the rhinal fissure in the agranular insular cortex. This overlap area matched the area in the agranular insular cortex where there was an overlap of cortical efferent cells projecting to the brainstem, thalamus, and association cortex, as revealed in the retrograde tracing studies. We refer to this region of convergence in the agranular insular cortex as the visceral cortex, and suggest its involvement in the efficient integration of specific visceral sensory stimuli with correlated limbic or motivational consequences. The visceral cortex may help regulate the organism's visceral response to stress.
Mammalian motoneuron development: Effect of peripheral deprivation on motoneuron numbers in a marsupial
Authors: Comans P. E. , McLennan I. S. , Mark R. F. , Hendry I. A. 
Published: January 2005

AbstractIn nonmammalian vertebrates, the survival of developing motoneurons is dependent on their contacting appropriate target cells. It is generally accepted that developing mammalian motoneurons have a similar dependency on their target, but as yet there is little experimental evidence to support this contention. This is mainly because of the difficulty of experimenting on eutherian embryos. We have, therefore, been studying neuronal development in the tammar (an Australian marsupial) as its nervous system is immature at birth. Radical or partial removal of hindlimb buds from newborn tammars resulted in an increased motoneuron cell death. The motoneurons which survived in the operated tammars did so by innervating muscle remnants. In the instances where a group of muscles was totally removed, the corresponding motonuclei appeared to be totally lost. This study supports the hypothesis that mammalian motoneurons must contact their appropriate muscle in order to survive through the period of natural neuronal cell death.
Immunocytochemical localization of peptides and other neurochemicals in the rat laterodorsal tegmental nucleus and adjacent area
Authors: Sutin Ellen L. , Jacobowitz David M. 
Published: January 2005

AbstractThe laterodorsal tegmental nucleus (ntdl) contains a cluster of cells located just medial to the locus coeruleus in the pontine brainstem. The ntdl has been shown to project both rostrally to the forebrain and diencephalon and caudally to the spinal cord. In an effort to characterize this region neurochemically, the present study was conducted to identify a variety of neurochemicals localized within perikarya and fibers of the ntdl and surrounding nuclei. Rats were perfused with formalin, and brain sections were processed for fluorescence immunocytochemistry and acetylcholinesterase (AChE). Of the neurochemicals screened, atrial natriuretic factor (ANF), choline acetyltransferase (ChAT), cholecystokinin (CCK), calcitonin gene‐related peptide (CGRP), dynorphin B (Dyn B), galanin, somatostatin, substance P, neurotensin (NT), neuropeptide Y (NPY), vasopressin, vasoactive intestinal polypeptide (VIP), serotonin (5HT), glutamic acid decarboxylase (GAD), and tyrosine hydroxylase (TH) were studied. AChE and ChAT staining revealed that the ntdl contains mostly cholinergic neurons. In addition, brightly reactive substance P and galanin and paler staining CRF, ANF, CGRP, NT, VIP, and Dyn B cell bodies were found within the ntdl. Varicose fibers in this nucleus also contained these peptides in addition to CCK, GAD, TH, 5HT, and NPY. The dorsal tegmental nucleus, dorsal raphe nucleus, locus coeruleus, and the parabrachial region contained a dense and varied assortment of peptides with distinct positions and patterns. This multiplicity of neurochemicals within this area suggests a possible influence on a variety of functions modulated by the ntdl and other closely associated tegmental nuclei.
Circadian regulation of retinomotor movements: II. The role of gaba in the regulation of cone position
Authors: Pierce Mary E. , Besharse Joseph C. 
Published: January 2005

AbstractCone photoreceptor movements in lower vertebrates are regulated by the interaction of the light‐dark cycle and an endogenous circadian clock. We have suggested that melatonin and dopamine interact to regulate dark‐ and light‐adaptive movements, respectively, and that melatonin affects cones indirectly by inhibiting dopamine release. In fact, any factor modulating dopaminergic neurons in the retina may have effects on either cone elongation or contraction. We have utilized an in vitro eyecup preparation from the African clawed frog, Xenopus laevis, to evaluate a possible role of the neurotransmitter GABA, which is thought to tonically suppress dopamine release. GABA agonists mimic the effects of darkness and induce cone elongation; the effects of GABA agonists are blocked by dopamine. Muscimol‐induced cone elongation occurs at low light intensity but is inhibited by bright light in eyecups prepared from cyclic‐light‐maintained animals. Although neither melatonin nor muscimol stimulates cone elongation in bright light, simultaneous application of both drugs induces elongation. The GABA antagonist picrotoxin induces cone contraction which is blocked by the dopamine receptor antagonist spiroperidol, which suggests that GABA may affect cone movement in Xenopus by regulating dopamine neurons. Consistent with this, picrotoxin‐induced cone contraction is Ca+2 dependent and is blocked by high Mg+2 or the Ca+2 antagonist nifedipine. Pharmacological analysis suggests that the effects of GABA may result from its action at more than one receptor subtype. Our results support the hypothesis that dopamine is part of the light signal for cone contraction and that its suppression is part of the signal for cone elongation.
Neuropeptide Y‐immunoreactive amacrine cells in the retina of the turtle Pseudemys scripta elegans
Authors: Isayama Tomoki , Eldred William D. 
Published: January 2005

AbstractAntiserum directed against neuropeptide Y selectively labeled certain amacrine cells in the turtle retina. The cell types, sizes, dendritic stratification, regional distribution, and degrees of immunolabeling were examined. The results indicated that three morphologically distinct cell types were labeled: types A, B, and C. Computer rotation of digitized data from camera lucida drawings was used to study dendritic stratification. The type A somata were large (11.5 μm in diameter), well‐stained, and located in the third tier of the inner nuclear layer. Type A somata gave rise to well‐stained processes which arborized within the inner plexiform layer in strata 1 and 3 and at the border between strata 4 and 5. Processes in stratum 1 were sparse and delicate with small boutons. Processes in stratum 3 were numerous and often coarse, with many large and small boutons. At the border between strata 4 and 5 the processes were frequently numerous but slender, with many small boutons. Occasional immunolabeled processes were found in the ganglion cell layer. The somata of the type B cells were smaller (9.0 μm in diameter) and gave rise to single labeled processes which descended into the inner plexiform layer and divided quickly into two secondary processes. These secondary processes gave rise to lightly labeled dendritic fields which arborized primarily in strata 2 and 4. The type C cells were usually observed at the periphery of the retina and had large somata (12.0 μm in diameter) with simple, but very elongated, dendritic arborizations in strata 1, 4, and 5. Observations also showed that type A and B cells were often found in close proximity to each other and suggested that dendrites of these cells made contact with each other. The labeled neurons were distributed relatively evenly throughout the retina except for the visual streak where they were sparse. This study indicates that neuropeptide Y–like immunoreactivity is found in more than one anatomically distinct class of amacrine cells in the turtle retina.
Somatostatin‐containing neuron systems in the rat hypothalamus: Retrograde tracing and immunohistochemical studies
Authors: Kawano Hitoshi , Daikoku Shigeo 
Published: January 2005

AbstractBy employing a combination of the immunohistochemistry for somatostatin (SRIF) and retrograde tracing with biotinylated wheat germ agglutinin (b‐WGA) injected into the posterior pituitary (group 1) or into the median eminence (group 2), functional topography of hypothalamic SRIF neurons was determined in the rat hypothalamus. In group 1, large numbers of WGA‐labeled neurons appeared in the rostral periventricular region and in the magnocellular division of the paraventricular and supraoptic nuclei; none of them were SRIF immunoreactive. In group 2, WGA‐labeled neurons were numerous in the rostral periventricular region, the parvicellular division of the paraventricular nucleus, and the arcuate nucleus; most of the WGA‐labeled neurons in the rostral periventricular region and some in the paraventricular nucleus were SRIF immunoreactive, but none in the arcuate nucleus showed immunoreactivity for SRIF. It is concluded that, in the rat hypothalamus, the locations of neurons containing hypophysiotrophic SRIF are confined within the rostral periventricular region and the parvicellular paraventricular nucleus. Our results do not support previous suggestions that SRIF immunoreactive axons innervate the posterior lobe of the pituitary.
Multiple pathways from the superior colliculus to the extrageniculate visual thalamus of the cat
Authors: Abramson Bruce P. , Chalupa Leo M. 
Published: January 2005

AbstractThe projections from the cat's superior colliculus to the extrageniculate visual thalamus were examined by the anterograde and retrograde transport of WGA‐HRP. An acetylthiocholinesterase (ATChE) stain was employed to facilitate the differentiation of regions within the posterior thalamus. On the basis of the distribution of terminal label as well as the laminar origin of projection neurons, four pathways were delineated. Cells in the stratum griseum superficiale (primarily sublaminae II and III) innervate two regions within the nucleus lateralis posterior (LP): the medial zone, which stains darkly for ATChE, and a restricted portion of the lateral zone, adjacent to the pulvinar. Both of these pathways were found to be topographically organized. By using the fluorescent retrograde tracers, fast blue and rhodamine labeled microspheres, it was determined that the inputs to the medial and lateral zones of LP originate primarily from separate cell populations since very few neurons were found to be double‐labeled. A third pathway originates principally from cells in the stratum opticum and terminates in an area just below the cholinesterase‐rich region of the LP, designated as the ventral division of the LP. The fourth projection is primarily from the stratum griseum intermedium to the suprageniculate complex. Each of these four pathways arises from a population of neurons with heterogeneous morphological characteristics, and for the most part, each pathway comprises morphologically similar cells. These results suggest that visual information from the superior colliculus is conveyed to the extrageniculate thalamus via multiple pathways that may subserve diverse functions.
Opioid peptide gene expression in rat trigeminal nucleus caudalis neurons: Normal distribution and effects of trigeminal deafferentation
Authors: Nishimori Toshikazu , Moskowitz Michael A. , Uhl George R. 
Published: January 2005

AbstractPreproenkephalin (preproenkephalin A) and preprodynorphin (preproenkephalin B) are the opioid peptide genes expressed in neurons of the nucleus caudalis of the trigeminal nuclear complex. We have used recently developed techniques for quantitative in situ hybridization to identify the neurons in laminae I and II of the nucleus caudalis that display the mRNA products of each of these genes. The specificity of these hybridization patterns is supported by several biochemical features, and by qualitative and quantitative parallels with previous immunohistochemical results. In animals killed 4 days after unilateral lesions of the trigeminal ganglion, neuronal expression of both preproenkephalin and preprodynorphin is altered in the nucleus caudalis. Decreases in preproenkephalin mRNA are due to a decline in the number of neurons that appear to express this gene. Conversely, preprodynorphin mRNA increases by adding a significant population of expressing neurons. These deafferentation‐induced changes in gene expression may provide clues to the role of primary afferent information in modulating the functions of nucleus caudalis neurons containing opioid peptides.
GABA‐immunoreactive neurons and terminals in the lateral cervical nucleus of the cat
Authors: Broman Jonas , Westman Jan 
Published: January 2005

AbstractPrevious findings have indicated the presence of local circuit neurons in the lateral cervical nucleus (LCN). An immunohistochemical study with γ‐aminobutyric acid (GABA) antiserum was therefore performed both to investigate whether GABA‐immunoreactive neurons are present in the LCN, and if so, to compare their characteristics with those previously assigned to probable internuncial neurons in the nucleus. The fine structure and synaptology of GABA‐positive boutons in the LCN were also studied.Transversely cut sections from the upper cervical spinal cord of three cats were processed for GABA immunohistochemistry with the free‐floating PAP technique. On light microscopic examination immunoreactive neurons were observed within the ventromedial half of the LCN. Their total number was estimated to be 42.5 ± 11.7 in the entire LCN on one side of the cervical spinal cord, but this may have been an underestimation, as the penetration by the antisera was limited. The labeled neurons were small and had a relatively large nucleus and a low bouton covering ratio. In their number, localization, and ultrastructural appearance the GABA‐positive neurons closely resembled the population of neurons previously suggested to be local circuit neurons.Immunoreactive bouton‐sized puncta were scattered throughout the LCN. Ultrastructural examination showed labeled terminals with a mean sectional area of 0.85 μm2 and a relatively high density of synaptic vesicles. The vast majority of GABA‐positive terminals were in contact with dendrites and only a minority had synaptic contact with cell bodies. No axoaxonal synapses were observed. The GABA‐positive boutons probably derive at least partly from the observed GABA‐positive neurons, but there is also a possibility of extrinsic GABAergic input.
Morphology and synaptic connections of HRP‐filled, axon‐bearing horizontal cells in the Xenopus retina
Authors: Witkovsky Paul , Stone Susan , MaCdonald E. Douglas 
Published: January 2005

AbstractAxon‐bearing horizontal cells of the Xenopus retina were studied by intracellular injection of HRP following physiological characterization. The profile of the cell viewed in whole mount consisted of a round or oval perikaryon about 50 μm in diameter and an axon about 1 mm long which lacked a prominent terminal expansion. The axonal diameter was 0.5‐1.0 μm in its proximal third but 2‐4 μm in its distal portion. Along its course the axon emitted 25‐40 branchlets each 0.2 μm in diameter, up to 10 μm long and terminating in a cluster of two to six synaptic knobs. Electron microscopic examination revealed that both perikaryal dendrites and axon branchlets ended in both rod and cone synaptic bases; cone contacts outnumbered rod contacts by two‐ to threefold. We were unable to document synapses of presumed interplexiform cells onto identified horizontal cells. Horizontal cell axons are joined in their distal portions by numerous, small (0.2 μm long) gap junctions. Other gap junctions were noted between horizontal cell processes within the synaptic endings of photoreceptors. An hypothesis is advanced whereby the cluster of axon branchlet synaptic knobs permits dynamic interaction of rod and cone synaptic inputs to the horizontal cell.