bluuebunny/crossref_metadata_2025_split huggingface dataset:
Distributions of choline acetyltransferase and acetylcholinesterase activities in the retinal layers of the red‐tailed hawk and road runner
Authors: White Leonard E. , Ross C. David , Godfrey Donald A. 
Published: January 2005

AbstractThe activities of choline acetyltransferase and acetylcholinesterase were assayed in submicrogram samples from layers of red‐tailed hawk and road runner retina. Both enzyme activities were concentrated in and near the inner plexiform layer. Within the inner plexiform layers of both species, activities of each enzyme were concentrated in two bands, one in each half of this layer. Little choline acetyltransferase activity was found superficial to the middle third of the inner nuclear layer. The distributions of acetylcholinesterase activities corresponded well to those of choline acetyltransferase, except in the outer plexiform layer and the outer margin of the inner nuclear layer of the hawk. These distributions of enzyme activities indicate that populations of amacrine cells in the retinae of these species are cholinergic. In addition to these same cells and presumably cholinoceptive amacrine and ganglion cells, acetylcholinesterase activity in the hawk was associated with a population of horizontal cells that may be unrelated to synaptic cholinergic neurotransmission. Choline acetyltransferase activities associated with amacrine somata and processes were about four times greater in the hawk than in the road runner suggesting important differences in the density and function of cholinergic elements between species. Possible synaptic relationships in the inner plexiform layer consistent with the interspecies differences in enzyme activities are considered.
Fine structure of synapses and retinal innervation of substance P and adenosin deaminase containing neurons in the superior colliculus of the rat
Authors: Miguel‐Hidalgo J. Javier , Senba Emiko , Takatsuji Koichi , Tohyama Masaya 
Published: January 2005

AbstractThe fine structure of substance P (SP) and adenosine deaminase (ADA) immunoreactive structures in synaptic contacts localized to the superficial layers of the superior colliculus of the rat was investigated by means of immunoelectron microscopy. We also examined the possibility of retinal innervation of SP‐ and ADA‐ containing neurons by immunohistochemistry after degeneration of retinal terminals caused by enucleation.SP‐like immunoreactive presynaptic terminals of the stratum griseum superficial (SGS) formed both asymmetric and symmetric synaptic contacts, Presynaptic dendrite like structures were also observed. SP immunoreactive postsynaptic elements made contacts with terminals showing diverse features. ADA‐like immunoreactive structures were seen only as postsynaptic elements to different kinds of nonimmunoreactive terminals and were mostly localized in the ventral third of the SGS and the dorsalmost stratum opticum (SO).After enucleation, degenerating retinal terminals were found to form synaptic contacts with SP and ADA immunoreactive structures. The highest number of such degenerating terminals on ADA immunoreactive structures was observed 2 days after retinal denervation, very few being seen after 5 days. These degenerating terminals were restricted to the ventral SGS and dorsal SO. SP immunoreactive structures postsynaptic to degenerating retinal terminals were most numerous 5 days after enucleation and mainly localized in the dorsal SGS. Occasionally, SP immunoreactive dendrite like processes forming synapses with degenerating retinal terminals were simultaneously presynaptic to other nonimmunoreactive profiles, defining, therefore, serial synapses. The present results suggest that SP‐I and ADA‐I collicular neurons may be part of distinct channels carrying visual information to the lateral posterior and lateral geniculate nuclei of the thalamus, respectively.
Dendritic and axonal morphology of HRP‐injected neurons in the inferior colliculus of the cat
Authors: Oliver Douglas L. , Kuwada Shigeyuki , Yin Tom C. T. , Haberly Lewis B. , Henkel Craig K. 
Published: January 2005

AbstractThe dendritic and axonal morphology of neurons in the inferior colliculus of the cat was investigated after intracellular injection of HRP, in vivo. All injected axons gave off local collaterals, and most showed a widespread distribution and lacked a specific orientation. In contrast, the dendrites of injected neurons were distinguished by their degree of orientation and the direction of the longest axis of orientation. Dendrites showed a high, moderate, or low degree of orientation. Most highly oriented cells had their longest axis in the rostrocaudal direction with fewer in the mediolateral direction. In the central nucleus, only the rostrocaudally oriented cells correspond to the disc‐shaped cells identified in Golgi preparations. Unlike most cells in our sample, the two cells that were disc‐shaped had axons that were parallel to the orientation of the dendritic tree. In the dorsal cortex, rostrocaudally oriented cells also were found, but they had unoriented axons. In both the central nucleus and dorsal cortex, cells with a mediolateral axis of orientation or no specific orientation correspond to stellate cells and had axons with widespread local collaterals.These results suggest that an extensive network of local axon collaterals may contribute to neural processing within the inferior colliculus. In the central nucleus, local axons may establish connections within or across the fibrodendritic laminae. In the dorsal cortex, the local and afferent axons may form a complex reticular network. Finally, some injected cells had axons terminating locally and also entering the brachium of the inferior colliculus. This suggests that cells in the inferior colliculus may function as both interneurons and projection neurons.
Posteroventral cochlear nucleus projections to olivocochlear neurons
Authors: Thompson Ann M. , Thompson Glenn C. 
Published: January 2005

AbstractThe presence of ascending auditory inputs from the posteroventral cochlear nucleus (PVCN) to olivocochlear neurons was examined in guinea pig by using the combination Phaseolus vulgaris‐leucoagglutinin (PHA‐L) anterograde and horseradish peroxidase (HRP) retrograde tract‐tracing technique. By labeling the somata of olivocochlear neurons after injection of HRP into the cochlea and simultaneously labeling terminal endings of PVCN efferent neurons after injection of PHA‐L into PVCN, we observed neuronal connections between these two elements within all regions of the superior olivary Complex known to contain olivocochlear neurons. These regions include the superior paraolivary nucleus, medial nucleus of the trapezoid body, lateral superior olive, and periolivary regions. All possible projection patterns regarding side of input and output of both large (four combinations) and small (two combinations) olivocochlear neurons were observed. However, the most frequently observed pattern was the PVCN projection to a contralaterally located and contralaterally projecting, large olivocochlear neuron. Thus the most prevalent pattern demonstrated a feedback pathway that crossed the brainstem twice. Additional patterns demonstrated pathways that fed back to the same cochlea as well as pathways that fed forward to the opposite cochlea.
Autonomic responses and efferent pathways from the insular cortex in the rat
Authors: Yasui Yukihiko , Breder Christopher D. , Safer Clifford B. , Cechetto David F. 
Published: January 2005

AbstractThe anatomical distribution of autonomic, particularly cardiovascular, responses originating in the insular cortex was examined by using systematic electrical microstimulation. The localization of these responses to cell bodies in the insular cortex was demonstrated by using microinjection of the excitatory amino acid, D, L‐homocysteic acid. The efferents from the cardiovascular responsive sites were traced by iontophoretic injection of the anterograde axonal tracer Phaseoleus vulgaris leucoagglutinin (PHA‐L).Two distinct patterns of cardiovascular response were elicited from the insular cortex: an increase in arterial pressure accompanied by tachycardia or a decrease in arterial pressure with bradycardia. The pressor responses were obtained by stimulation of the rostral half of the posterior insular cortex while depressor sites were located in the caudal part of the posterior insular area. Both types of site were primarily located in the dysgranular and agranular insular cortex. Gastric motility, changes originated from a separate but adjacent region immediately rostral to the cardiovascular responsive sites in the anterior insular cortex.Tracing of efferents with PHA‐L indicated a number of differences in connectivity between the pressor and depressor sites. Pressor sites had substantially more intense connections with other limbic regions including the infralimbic cortex, the amygdala, the bed nucleus of the stria terminalis and the medial dorsal and intralaminar nuclei of the thalamus. Alternatively, the depressor region of the insular cortex more heavily innervated sensory areas of the brain including layer I of the primary somatosensory cortex, a peripheral region of the sensory relay nuclei of the thalamus and the caudal spinal trigeminal nucleus. In addition, there were topographical differences in the projection to the lateral hypothalamic area, the primary site of autonomic outflow for these responses from the insular cortex. These differences in connectivity may provide the anatomic substrate for the specific cardiovascular responses and behaviors integrated in the insular cortex.
Factors determining the morphology and distribution of astrocytes in the cat retina: A ‘contact‐spacing’ model of astrocyte interaction
Authors: Chan‐Ling Tailoi , Stone Jonathan 
Published: January 2005

AbstractThe retina provides a valuable opportunity to examine the interaction of astrocytes with neurones and vasculature, in adult tissue and in vivo. We have studied astrocytes in cat retina to delineate the interactions that determine their morphology and distribution. Their morphology varied with their interaction with surrounding cells, from a classic stellate shape to an elongated bipolar form associated with axon bundles. Evidence is presented that the distribution of astrocytes across the retina is determined by their morphology and by a previously unrecognised interaction between astrocytes, which we term ‘contact‐spacing’ in which astrocytes maintain contact with their neighbours through their processes, but keep their somas apart. Evidence is also presented that astrocytes are not influenced in their distribution by surrounding neurones, and the influence of developmental mechanisms is identified. These observations are summarised in a contact‐spacing model of astrocyte distribution, and four predictions of the model are tested. The concentration of astrocytes along axon bundles dispersed when the axons degenerate but not when vessels were prevented from forming. Further, when both axons and vessels were eliminated, the concentrations of astrocytes dispersed and they became stellate in form. Finally, in the retina of the rat, in which astrocytes show no affinity for axons, the distribution of astrocytes is essentially uniform. We suggest that the contact‐spacing interaction among astrocytes provides the anatomical basis of a functional glial network extending across the retina and throughout the central nervous system.
Region‐specific expression of the mRNAs encoding β subunits (β1, β2, and β3) of GABAA receptor in the rat brain
Authors: Zhang Jian‐Hua , Sato Makoto , Tohyama Masaya 
Published: January 2005

AbstractThe expression of mRNAs encoding different β subunits (β1, β2 and β3) of the gamma‐aminobutyric acidA (GABAA) receptor in the rat brain was investigated by in situ hybridization histochemistry. Transcripts of each subunit showed region‐specific localization. Some areas contained all three β subunit mRNAs, while other areas showed marked differences in the location and level of expression of each subunit mRNA. The regions with strong to very strong labeling by the β3 probe were as follows: the olfactory bulb, the cortex, the caudate‐putamen, the accumbens nucleus, the hypothalamus, the amygdala, the hippocampal formation, and some areas of the brainstem and spinal cord. Weak to moderate labeling was detected in the thalamus, superior and inferior colliculus, and many areas of the brainstem. The regions with strong to very strong labeling by the β 2 probe were as follows: the olfactory bulb, the ventral pallidum, the globus pallidus, the nucleus of the diagonal band, the preoptic magnocellular nucleus, the thalamus, the subthalamic nucleus, the substantia nigra, and the cerebellum. Weak to moderate labeling was detected in the regions that showed strong expression of β3 subunit mRNA. Expression of β1 subunit mRNA was only weak to moderate compared to that of the β2 and β3 subunit mRNAs. The regions with moderate labeling by the β1 probe were the following: the cortex, the claustrum, the bed nucleus of the stria terminale, some nuclei of thalamus and amygdala, the hypothalamus, the hippocampal formation, the subiculum, the cerebellum, and several areas of the brainstem and spinal cord. Thus, our findings showed that the β subunit mRNAs of the GABAA receptor were differentially expressed in the rat brain, perhaps indicating the existence of different subtypes of the GABAA receptor in different brain regions.
Influence of grafting a smaller target muscle on the magnitude of naturally occurring trochlear motor neuron death during development
Authors: Sohal G. S. , Stoney S. D. , Campbell L. R. , Arumugam T. , Kumaresan K. , Hirano S. 
Published: January 2005

AbstractAbout half of the motor neurons produced by some neural centers die during the course of normal development. It is thought that the size of the target muscle determines the number of surviving motor neurons. Previously, we tested the role of target size in limiting the number of survivors by forcing neurons to innervate a larger target (Sohal et al., '86). Results did not support the size‐matching hypothesis because quail trochlear motor neurons innervating duck superior oblique muscle were not rescued. We have now performed the opposite experiment, i.e., forcing neurons to innervate a smaller target. By substituting the embryonic forebrain region of the duck with the same region of the quail before cell death begins, chimera embryos were produced that had a smaller quail superior oblique muscle successfully innervated by the trochlear motor neurons of the duck. The number of surviving trochlear motor neurons in chimeras was significantly higher than in the normal quail but less than in the normal duck. The smaller target resulted in some additional loss of neurons, suggesting that the target size may regulate neuron survival to a limited extent. Failure to achieve neuron loss corresponding to the reduction in target size suggests that there must be other factors that regulate neuron numbers during development.
Crossed and uncrossed projections to cat sacrocaudal spinal cord: II. Axons from muscle spindle primary endings
Authors: Ritz Louis A. , Bailey Steven M. , Carter Richard L. , Sparkes Mary L. , Masson Robert L. , Rhoton Eric L. 
Published: January 2005

AbstractThe terminal fields of primary afferent fibers from tail muscle spindle primary endings were mapped within cat sacrocaudal spinal cord (S3‐Ca7), using intra‐axonal recording and horseradish peroxidase staining techniques. We sought to determine the ipsilateral and contralateral projection patterns and to relate these to the fibers' muscles of origin.Fifty‐three group Ia fibers were successfully stained. Segmental collaterals originated from either the ascending or descending branch within the dorsal columns. Collaterals coursed rostromedially within the dorsal columns and traversed the medial aspect of the dorsal horn. Ipsilateral terminations were similar for all fibers. Within the ventral horn, boutons were consistently observed in the medial or central portions of lamina VII. In lamina VIII, a variable number of boutons was seen on fine branches emerging from larger fibers coursing ventrally. Clusters of terminals were plentiful in the regions of motoneurons, i.e., lamina IX and the nucleus commissuralis. Terminals were found in the adjacent white matter.In addition to ipsilateral terminations, some group Ia fibers (20 of 53) had collateral branches that crossed ventrally to the central canal, terminating within the midline ventral gray commissure and/or the contralateral ventral horn. Crossed projections always originated in medial (dorsal or ventral), but not lateral, muscles of the tail.These data suggest that ipsilateral projections of group Ia fibers make connections on sacrocaudal motoneurons, on neurons mediating segmental reflex functions and on neurons conveying ascending information. It is speculated that crossed and uncrossed connections between group Ia fibers from medial muscles and bilateral dendritic trees of motoneurons subserve synchronized co‐contraction of synergistic muscles located on the two sides of the body, such as with dorsal or ventral flexion of the tail. Group Ia projections from lateral muscles, that are entirely ipsilateral, would be involved with lateral movements of the tail.
Immunocytochemical localization and development of multiple kinds of neuropeptides and neuroendocrine proteins in the chick ultimobranchial gland
Authors: Kameda Yoko 
Published: January 2005

AbstractThe ultimobranchial gland is an endocrine organ consisting of C cell groups. In chickens, the glands are richly supplied by nerve fibers immunoreactive for neurofilaments. It was found by immunocytochemical staining that C cells of chick ultimobranchial glands showed immunoreactivities for multiple kinds of neuropeptides and neuroendocrine proteins in addition to calcitonin, i.e., calcitonin gene‐related peptide (CGRP), somatostatin, neurotensin, chromogranin A, and tyrosine hydroxylase. Furthermore, enkephalin‐immunoreactive cells that showed long cytoplasmic processes and large cell bodies, being distinct from the C cell feature, were detected. The densities of these cells per unit area of ultimobranchial gland were assessed using computer‐assisted image analysis system; calcitonin cells were 42.9 ± 10.0%; CGRP cells 26.9 ± 5.6%; neurotensin cells 8.6 ± 6.9%; somatostatin cells 3.1 ± 1.4%, chromogranin A cells 11.8 ± 1.8%; tyrosine hydroxylase cells 10.0 ± 5.2%; enkephalin cells 2.9 ± 1.3%. Dense distributions of peptidergic nerve fibers were also detected in chick ultimobranchial glands. Numerous varicose fibers immunoreactive for substance P were distributed in the close vicinity to C cell clusters and blood vessels. Enkephalin‐immunoreactive fibers were also prominent around C cell clusters. Galanin‐, vasoactive intestinal peptide (VIP)‐, and tyrosine hydroxylase‐immunoreactive fibers were distributed around blood vessels only. Subsequently, the ontogeny of these neuropeptides, neuroendocrine proteins, and peptidergic innervations was examined in chickens at various developmental stages. In 10‐day‐old embryos, weak to moderately intense immunoreactivity for calcitonin was already present in almost all C cells. Immunoreactivities for somatostatin, CGRP, and tyrosine hydroxylase began to appear at this age. At 12 days of incubation, substance P‐immunoreactive fibers were first detected in the parenchyma of ultimobranchial glands. Considerable numbers of enkephalin‐immunoreactive fibers and cells were also observed. At 14 days of incubation, the largest populations of somatostatin‐ and enkephalin‐immunoreactive cells were attained; the densities of somatostatin‐ and enkephalin‐immunoreactive cells per unit area were 21.2 ± 3.2% and 12.9 ± 3.1%, respectively. Substance P‐immunoreactive fibers became numerous throughout the gland at this age. Thereafter, calcitonin‐, CGRP‐, tyrosine hydroxylase‐immunoreactive cells progressively increased in number with embryonic age, whereas somatostatin‐ and enkephalin‐immunoreactive cells started to decrease. Chromogranin A‐ and neurotensin‐immurioreactive cells began to appear at 16 days and 18 days of incubation, respectively. Galanin‐, VIP‐, and tyrosine hydroxylase‐immunoreactive fibers were inconspicuous during embryonic life.
Topographical organization in the origin of serotoninergic projections to different regions of the cat cerebellar cortex
Authors: Kerr Christopher W. H. , Bishop Georgia A. 
Published: January 2005

AbstractThe distribution of serotonin immunoreactivity in the cat cerebellum was studied by using the indirect antibody peroxidase‐antiperoxidase (PAP) technique. Furthermore, the origin of these chemically defined afferents was determined by combining the retrograde transport of horseradish peroxidase (HRP) with the PAP technique. In the cerebellar cortex, serotonin immunoreactivity is present in a plexus of beaded fibers that is confined almost exclusively to the granule and Purkinje cell layers; a few fibers are present in the molecular layer. Serotoninergic axons and varicosities have a dense and uniform distribution throughout all lobules of the cerebellum with the exception of lobule X where the fiber density is sparse. Serotonin cell bodies were not found within the cerebellar cortex. However, following pretreatment with pargyline and L‐tryptophan, serotonin positive cell bodies were found in all deep cerebellar nuclei as well as the raphe and reticular nuclei in the brainstem.The present study demonstrates that the serotoninergic projection to the cat's cerebellum has some degree of topographical organization. Serotoninergic fibers in the anterior vermis (lobules I–V) were shown to arise from neurons located within the paramedian reticular nucleus, the lateral reticular nucleus, and the lateral tegmental field. Injections of HRP into either the posterior vermis (lobule VI–IX) or the paramedian lobule, labeled serotoninergic neurons exclusively in the lateral reticular nucleus. Lobus simplex, crus I and crus II (the hemisphere) receive a serotoninergic input from cells located in the lateral tegmental field, the peri‐olivary reticular formation and the paramedian reticular nucleus. In no cases were neurons in the raphe double‐labeled, although there were cells positive for HRP or serotonin alone.The data indicate that there is a topographical organization in the serotoninergic projection from the caudal brainstem to specific regions of the cat's cerebellar cortex. In addition to climbing and mossy fibers, this projection represents a third major source of cerebellar afferents based on its dense and widespread distribution as well as its morphological and chemical characteristics.