bluuebunny/crossref_metadata_2025_split huggingface dataset:
Immunocytochemistry of gamma‐aminobutyric acid, glutamate, serotonin, and histamine in Necturus taste buds
Authors: Jain S. , Roper S. D. 
Published: January 2005

AbstractLittle information is currently available about which neurotransmitters are involved in signal processing in the peripheral sensory organs of taste, taste buds. Synaptic contacts between taste cells and sensory axons have long been known to exist, but what substances are active at these synapses is not known. Our objective in this study was to test for the presence of the neurotransmitter candidates, GABA, glutamate, serotonin, and histamine in taste buds of Necturus maculosus. Light microscopic irnmunocytochemical techniques were used to investigate the location of these substances in taste buds and surrounding epithelium. GABA and glutamate were detected in nerve fibers that innervate the taste buds, and, to a substantially lesser extent, in fine, varicose axons that penetrated the surrounding nontaste epithelium. Serotonin immunostaining was strong in basal cells in frog taste discs but was only faintly detected in Necturus taste buds. Histamine was not detected at all in taste buds. We conclude that amino acid neurotransmission may be involved in taste mechanisms and that monoamines may also play a role in chemosensory transduction in the taste bud. On the basis of our inability to detect histamine with immunocytochemical techniques, we conclude that this substance is unlikely to be a major neurotransmitter in Necturus taste buds.
Morphology and distribution of catecholaminergic amacrine cells in the cone‐dominated tree shrew retina
Authors: Müller Brigitte , Peichl Leo 
Published: January 2005

AbstractThe tree shrew (Tupaia belangeri) has a cone‐dominated retina with a rod proportion of only 5%. This is in contrast to the usual mammalian pattern of rod‐dominated retinae. Rod bipolar cells are present at relatively low densities in the tree shrew retina, suggesting that a reduced, but normal, rod pathway might be preserved. The present study investigated another common constituent of the rod pathway, the dopaminergic amacrine cells, and analysed their morphology and distribution by light and electron microscopy.Catecholaminergic (presumed dopaminergic) amacrine cells were labelled with an antibody against tyrosine hydroxylase (TH). Intense TH‐immunoreactivity was found in perikarya and dendrites of a uniform amacrine, cell population. TH‐immunoreactive amacrine cell density varies across the retina from 10 cells/mm2 in the periphery to 40 cells/mm2 in more central regions (mean cell density about 25 cells/mm2). The relatively large cell bodies are located exclusively in the innermost part of the inner nuclear layer. The dendrites form a dense plexus at the border between the inner plexiform layer and the inner nuclear layer. The finer dendritic processes contain many varicosities and form characteristic dendritic “rings” like those seen in other mammals. TH‐immunoreactive processes also run between cell bodies in the vitread inner nuclear layer; a few extend into the sclerad inner nuclear layer and occasionally reach the outer plexiform layer (possible interplexiform cells). A few TH‐immunoreactive processes are seen in the middle of the inner plexiform layer. Electron microscopy of TH‐immunoreactive processes revealed conventional synapses onto somata and processes of unlabelled amacrine cells.
Myelinated fiber regeneration after crush injury is retarded in sciatic nerves of aging mice
Authors: Tanaka Kaoru , deF. Webster Henry 
Published: January 2005

AbstractTo compare nerve regeneration in young adult and aging mice, the right sciatic nerves of 6‐ and 24‐month‐old mice were crushed at the sciatic notch. Two weeks later, both groups of mice were perfused with an aldehyde solution, and, after additional fixation, the sciatic nerves were processed so that the transverse sections of each, nerve subsequently studied by light and electron microscopy included the entire posterior tibial fascicle 5 mm distal to the crush site. The same level was sectioned in unoperated contralateral nerves; these nerves served as controls. Electron micrographs and the Bioquant Image Analysis System IV were used to measure areas of posterior tibial fascicles and count the number of myelinated axons, the number of unmyelinated axons, and their frequency in Schwann cell units. In aging mice, the total number of regenerating myelinated axons was significantly reduced, but totals of regenerating unmyelinated axons in aging and young adults did not differ significantly. In aging mice, the frequency of Schwann cells that contained a single unmyelinated axon was greater, suggesting that before myelination began, Schwann cell ensheathment of axons also was slowed. After axotomy by a crush injury, the area of the posterior tibial fascicle was less than that in young adults and the distal disintegration of myelin sheath remnants also appeared to be retarded. The results indicate that responses of neurons, axons, and Schwann cells could be important in slowing the regeneration of myelinated fibers found in sciatic nerves from aging mice.
Calcitonin gene‐related peptide (CGRP) immunoreactive projections from the thalamus to the striatum and amygdala in the rat
Authors: Yasui Yukihiko , Saper Clifford B. , Cechetto David F. 
Published: January 2005

AbstractThe organization of calcitonin gene‐related peptide‐like immunoreactive (CGRPir) innervation of the amygdala and caudate‐putamen in the rat was examined by using immunohistochemistry for CGRP combined with retrograde transport of the fluorescent dye fluoro‐gold, as well as anterograde transport of Phaseoleus vulgaris leucoagglutinin (PHA‐L).The lateral part of the central nucleus of the amygdala and the amygdalostriatal transition zone was densely innervated by CGRPir terminals at all anterior‐posterior levels. More caudally, the lateral part of the caudate‐putamen also had large numbers of CGRPir terminals. Injections of fluoro‐gold into the amygdala and amygdalostriatal transition area followed by immunohistochemistry for CGRP revealed double‐labeled neurons in the subparafascicular, lateral subparafascicular, and posterior intralaminar nuclei of the thalamus and peripeduncular nucleus. Injections into the caudate‐putamen demonstrated double‐labeled neurons in the more lateral parts of this same nuclear complex.PHA‐L injections into the posterior thalamic nuclei from which the CGRPir projections arise confirmed the medial‐to‐lateral organization of the projections to the amygdala and striatum. The subparafascicular nucleus and the rostral portion of the lateral subparafascicular nucleus primarily projected to the medial amygdala and the amygdalostriatal transition area, while the more lateral cell groups, including the caudal part of the lateral parafascicular, posterior intralaminar, and peripeduncular nuclei projected to the lateral amygdala and the caudate‐putamen. These CGRPir projections may be involved in mediating conditioned autonomic and behavioral responses to acoustic stimuli or somatosensory stimuli.
Reidentification of larval interneurons in the pupal stage of the tobacco hornworm, Manduca sexta
Authors: Sandstrom David J. , Weeks Janis C. 
Published: January 2005

AbstractThe abdominal prolegs are the primary locomotory appendages of Manduca sexta larvae. After the prolegs are lost at pupation, some of the proleg motoneurons die while the survivors are respecified to carry out different functions in the adult moth. As a first step toward investigating the process of functional respecification at the synaptic level, we searched for larval interneurons that affected the activity of proleg motoneurons, and followed these interneurons into the pupal stage. Interneurons were judged to be individually identifiable based on their effects on proleg motoneuron activity and their anatomical features. Seven larval interneurons were identified and placed in five physiological classes based on their effects on proleg motoneurons: ipsilateral excitors, contralateral exciters, ipsilateral inhibitors, contralateral inhibitors, and bilateral inhibitor‐excitors. Four of the larval interneurons produced apparently monosynaptic postsynaptic potentials in proleg motoneuron. Of the five larval interneurons that were reidentified in the early pupal stage, two showed minor but consistent structural modifications from the larval stage. Interneurons that produced unitary postsynaptic potentials in larval motoneurons continued to do so in pupal motoneurons. These studies demonstrate that individually identified interneurons can be followed through the larval‐pupal transformation, during the initial stages of motoneuron respecification.
Histochemical demonstration of zinc in the hippocampal region of the domestic pig: III. The dentate area
Authors: Holm Ida E. , Geneser Finn A. 
Published: January 2005

AbstractThe distribution of zinc was described in the dentate area, a part of the hippocampal region, of the domestic pig. A modification of Timm's sulphide silver procedure, the Neo‐Timm method, was used for the histochemical demonstration of zinc. The staining of the dentate area exhibited a well‐defined stratified pattern, the predominant part of the staining being restricted to the neuropil, although weakly stained nerve cell bodies were observed in the hilus fasciae dentatae.In the molecular layer, three distinct sublaminae were seen at most septotemporal levels. The outer and inner sublaminae displayed medium staining intensity, whereas the intermediate sublamina appeared extremely pale. The granular cell layer was well stained in its superficial two thirds, because of dense masses of staining occupying the interstices between the unstained granular cells. In the hilus fasciae dentatae, extreme differences in staining intensity were seen between the layers, ranging from very intense staining of the outer hilar cell layer to generally weak staining of the inner plexiform layer.The distribution of zinc in the pig was compared with that in the guinea pig and rat, described previously. The staining pattern of the molecular layer showed striking species differences, whereas the granular cell layer appeared very near identical. The stratified staining pattern seen in the hilus of the pig is very similar to the distribution observed in the guinea pig, but differs from the essentially homogeneous staining of the rat hilus. However, the differences in hilar staining pattern between the pig and guinea pig on the one hand and the rat on the other essentially display variation in the cytoarchitectural organization of the hilus, rather than expressing a true species difference.
Musculotopic organization of the hypoglossal nucleus in the grass frog, Rana pipiens
Authors: Sokoloff Alan J. 
Published: January 2005

AbstractRecent neural tracer studies in several mammalian species have demonstrated a similar musculotopic organization of the hypoglossal motoneurons which innervate individual tongue muscles. The distribution of this musculotopic organization in nonmammalian tetrapods, however, has not received detailed investigation. As part of an ongoing study on the comparative organization of the vertebrate hypoglossal nucleus, the musculotopic organization of the hypoglossal nucleus of Rana pipiens was studied by injection of lectin‐conjugated horseradish peroxidase into four distinct tongue muscles and the geniohyoid muscle. Injections into the hyoglossus muscle label neurons in dorsal regions of the hypoglossal nucleus in middle and rostral nucleus levels. Injections into the genioglossus basalis muscle label neurons in ventral and lateral regions of the hypoglossal nucleus in caudal nucleus levels. Injections into the genioglossus medialis muscle label neurons in dorsal regions in caudal levels, throughout the nucleus in middle levels, and in ventral regions in more rostral levels. Injections into the geniohyoid muscle label neurons in the ventral tip of the hypoglossal nucleus and in the ventromedial corner of the medullary gray matter in middle and rostral nucleus levels. These results demonstrate that the organization of the hypoglossal nucleus in Rana pipiens is more complex than previous tracer studies indicated. Similarities in the musculotopic organization of the amphibian and mammalian hypoglossal nuclei suggest an evolutionary conservatism of the motor system controlling tongue movement.
A golgi study of dendritic development in the dorsal lateral geniculate nucleus of normal ferrets
Authors: Sutton J. Keith , Brunso‐Bechtold Judy K. 
Published: January 2005

AbstractThe development of neurons in the dorsal lateral geniculate nucleus (dLGN) of pigmented ferrets was studied by using the Golgi‐Hortega technique. In adult ferrets, four dLGN cell classes were defined on the basis of somatic and dendritic morphology. Classes 1 and 2 were divided into stellate and oriented subtypes. Class 1 and 4 cells are characterized by filiform appendages, class 2 cells by club‐like appendages, and class 3 cells by stalked appendages. At birth, dLGN neurons have simple dendritic arbors. During the first postnatal week, dendritic length and proximal branching density increase markedly. By postnatal day 21 (P21), dendritic morphology begins to take on mature characteristics and by the time of eye opening (P30‐P35), most neurons can be classified. Also by that time, dLGN cells are covered with abundant filiform appendages. Developmental changes in appendage density were quantified for class 1 stellate cells. These data reveal that appendage density reaches a peak at P56, decreases sharply until P90, and then gradually declines to mature levels by P180. Elaboration and elimination of transient appendages occurs centrifugally; at maturity appendage density remains greater distally.
Cytogenesis in the monkey retina
Authors: la Vail Matthew M. , Rapaport David H. , Rakic Pasko 
Published: January 2005

AbstractTime of cell origin in the retina of the rhesus monkey (Macaca mulatto) was studied by plotting the number of heavily radiolabeled nuclei in autoradiograms prepared from 2‐ to 6‐month‐old animals, each of which was exposed to a pulse of 3H‐thymidine (3H‐TdR) on a single embryonic (E) or postnatal (P) day. Cell birth in the monkey retina begins just after E27, and approximately 96% of cells are generated by E120. The remaining cells are produced during the last (∼ 45) prenatal days and into the first several weeks after birth. Cell genesis begins near the fovea, and proceeds towards the periphery. Cell division largely ceases in the foveal and perifoveal regions by E56.Despite extensive overlap, a class‐specific sequence of cell birth was observed. Ganglion and horizontal cells, which are born first, have largely congruent periods of cell genesis with the peak between E38 and E43, and termination around E70. The first labeled cones were apparent by E33, and their highest density was achieved between E43 and E56, tapering to low values at E70, although some cones are generated in the far periphery as late as E110. Amacrine cells are next in the cell birth sequence and begin genesis at E43, reach a peak production between E56 and E85, and cease by E110. Bipolar cell birth begins at the same time as amacrines, but appears to be separate from them temporally since their production reaches a peak between E56 and E102, and persists beyond the day of birth. Müller cells and rod photoreceptors, which begin to be generated at E45, achieve a peak, and decrease in density at the same time as bipolar cells, but continue genesis at low density on the day of birth. Thus, bipolar, Müller, and rod cells have a similar time of origin. The maximal temporal separation of cell birth is between cones and amacrine cells so that cell generation exhibits two relatively distinct phases: the first phase gives rise to ganglion, horizontal, and cone cells, and the second phase to amacrine, bipolar, rod, and Müller cells. In addition, cells of the first phase are generated faster than the second phase cells, and there are differences in the topography of spread of labeled cells between the two phases.Each cell class displays a central‐to‐peripheral gradient in genesis, although the spatiotemporal characteristics of the gradients differ between the classes. Heavily labeled ganglion cells, horizontal cells, and cone photoreceptors (phase 1) are found near the retinal margin much sooner than amacrine, bipolar, Müller, and rod photoreceptor cells (phase 2). As a consequence, genesis of phase 1 cells generally occurs over a more extensive retinal area, extending to the retinal margin, while phase 2 cell genesis ceases centrally by the time cell birth begins near the margin. The site of initial cessation of cell division is more variable than it is for the beginning of cytogenesis, although for all cell classes it is roughly centered on the fovea.
Glutamate‐like immunoreactivity in retinal terminals in the nucleus of the optic tract in rabbits
Authors: Cardozo Bob Nunes , Buijs Ruud , van der Want Johannes 
Published: January 2005

AbstractThe ultrastructural organization of retinal terminals within the nucleus of the optic tract of rabbits was investigated with a combination of anterograde tracing and immunocytochemistry. The anterogradely transported WGA‐HRP injected in the vitreous of the eye was visualized with the sensitive gold‐substituted silver peroxidase (GSSP) method. Glutamate and GABA immunoreactivity were identified with postembedding colloidal gold particles.Retinal ganglion cell terminals (R‐terminals) in the nucleus of the optic tract formed asymmetric synapses and contained spherical vesicles and electron lucent mitochondria. R‐terminals were observed in large clusters in the neuropil and in synaptic contact with large initial dendrites and somata. Within the clusters of neuropil the R‐terminals formed two types of glomeruluslike arrangements: (1) an R‐terminal centrally located and surrounded by small dendritic and axonal profiles and (2) several R‐terminals surrounding a single dendrite or a group of dendritic profiles, presumably of interneuronal origin. All R‐terminals identified with WGA‐HRP as well as those exhibiting similar ultrastructural characteristics showed high levels of glutamate immunoreactivity, but no GABA immunoreactivity. The presence of glutamate and the absence of GABA in R‐terminals suggest that glutamate is involved in neurotransmission in the pathway from retina to the nucleus of the optic tract of rabbits.
An electron microscopic description of glutamate‐like immunoreactive axon terminals in the rat principal sensory and spinal trigeminal nuclei
Authors: Clements Jane R. , Beitz Alvin J. 
Published: January 2005

AbstractThe spinal and principal sensory trigeminal nuclei relay noxious and nonnoxious stimuli from the orofacial region to the thalamus. Physiological studies have implicated glutamate as an important neurotransmitter in this region. Despite its importance as a potential transmitter, few studies have examined the anatomical distribution of glutamate within these nuclei. We therefore chose to use a monoclonal antibody raised against glutamate conjugated to a carrier protein to identify and describe glutamate‐like immunoreactive processes at the electron microscopic level.Glutamate‐like immunoreactive axon terminals were identified throughout the spinal trigeminal and principal sensory trigeminal nucleus. In. subnucleus caudalis glutamate‐like immunoreactive terminals occurred frequently in all laminae and were morphologically heterogeneous. In lamina I, glutamate‐like immunoreactive terminals were primarily ovoid, contained spherical synaptic vesicles, and participated in synaptic complexes with both dendritic and axonal profiles. In laminae II and III many glutamate‐like immunoreactive axon terminals were identified as the central element in synaptic glomeruli. Within discrete patches of lamina II, large numbers of glutamate‐like immunoreactive terminals contained dense core vesicles.The majority of glutamate‐like immunoreactive terminals in subnucleus interpolaris, subnucleus oralis, and principal sensory trigeminal nucleus were similar in morphology and synaptic interaction to the glutamate‐like immunoreactive terminals found in subnucleus caudalis, Glutamate‐like immunoreactive terminals that were the central presynaptic element in glomerular complexes were seen in all subnuclei. In sections from subnucleus interpolaris and subnucleus oralis central glutamate‐like immunoreactive terminations within glomerular complexes had much smoother profiles, and in subnucleus interpolaris participated primarily in axodendritic synaptic junctions. In the principal sensory trigeminal nucleus central glutamate‐like immunoreactive terminations were highly scalloped and participated in numerous axoaxonic synaptic junctions.The above observations are consistent with the hypothesis that glutamate‐like immunoreactivity is present in some primary afferent terminations and functions as an important excitatory transmitter involved in the relay of sensory information to the spinal trigeminal and principal sensory trigeminal nucleus.
Rat tooth pulp projections to spinal trigeminal subnucleus caudalis are glutamate‐like immunoreactive
Authors: Clements J. R. , Magnusson K. R. , Hautman J. , Beitz A. J. 
Published: January 2005

AbstractIt has been shown that glutamate‐like immunoreactive axon terminals are present within the spinal trigeminal nucleus, including subnucleus caudalis. The morphology of many of these terminations is consistent with their identification as primary afferents. To establish whether primary afferent projections to subnucleus caudalis are glutamate‐like immunoreactive, we injected an anterograde tract tracer into rat incisor tooth pulp, histochemically visualized this tracer within subnucleus caudalis, and then used an immunocytochemical technique to label glutamate‐like immunoreactive profiles within these same sections.The anterograde tract tracer used, the B subunit of cholera toxin conjugated to horseradish peroxidase (B‐HRP), is transported transganglionically and can be used to localize tooth pulp projection fibers in the spinal trigeminal nucleus. A majority of B‐HRP projection fibers from rat lower incisors terminated ipsilaterally in axon terminals in the dorsal region of subnucleus caudalis. Labeled axon terminals were both scallop‐shaped and smooth in profile. Small numbers of fibers containing B‐HRP extended into laminae I‐III caudally and were present in both the border zone between laminae IV and V and the most lateral region of lamina V rostrally. Approximately 75% of the B‐HRP‐labeled projection fibers were glutamate‐like immunoreactive, providing evidence that the excitatory amino acid glutamate functions as a neurotransmitter in a subpopulation of these fibers. Terminals reactive for both B‐HRP and glutamate‐like immunoreactivity contained small, spherical round vesicles, formed asymmetric synapses, and participated in axoaxonic and axodendritic synaptic junctions. These results support the hypothesis that glutamate may be a transmitter of A delta and C fibers involved in relaying nociceptive information from the tooth pulp.