bluuebunny/crossref_metadata_2025_split huggingface dataset:
Morphology of afferent synapses in the mauthner cell of larval Xenopus laevis
Authors: Cioni Carla , De Palma Francesca , Stefanelli Alberto 
Published: January 2005

AbstractThe fine structure of the afferent synapses on the Mauthner cell of larval Xenopus laevis has been studied as a first step toward comparing the fine structure of the afferent synaptic apparatus before and after metamorphosis. There are various types of afferent endings on this cell, some of which are confined to specific cellular regions, while others are distributed over most of the large surface of the neuron. Four different main types of endings have been observed: club endings, round‐vesicle end bulbs, flattened‐vesicle end bulbs and spiral fibers endings. While the myelinated club endings and the spiral fibers endings are located at the distal end of the lateral dendrite and in the axon cap, respectively, the end bulbs are widely distributed over the whole cell. A further type of ending has been observed, although rarely, on the Mauthner cell soma and dendrites: end bulbs characterized by an unusually dense presynaptic substance. Results obtained in the present research suggest that, as in fish, different endings on the anuran Mauthner neuron correspond to different synaptic inputs. The possible origin of some of these inputs is discussed.
Recovery from cortical blindness mediated by destruction of nontectotectal fibers in the commissure of the superior colliculus in the cat
Authors: Wallace Steven F. , Rosenquist Alan C. , Sprague James M. 
Published: January 2005

AbstractTransection of the commissure of the superior colliculus restores visual orientation behavior to a cat previously rendered hemianopic by a unilateral visual cortical lesion (the Sprague effect). Using two methods, we asked whether this recovery resulted from the severing of the tectotectal component of the commissure or whether the destruction of some other connection was responsible. First, we transected either the rostral or the caudal one‐half of the tectal commissure in hemianopic cats. If destruction of tectotectal fibers is responsible for the Sprague effect, then only rostral transections should produce the recovery since nearly all tectotectal connections lie in the rostral one‐half of the commissure. However, rostral cuts failed to produce a recovery, whereas caudal commisurotomies did. Second, ibotenic acid was used to destroy the cells in the superior colliculus contralateral to the cortical lesion. This lesion eliminated the contralateral tectotectal pathway from the contralateral colliculus but left other fibers (originating elsewhere but coursing through the commissure) largely intact. These ibotenic acid lesions failed to produce the recovery; but when the caudal portion of the tectal commissure was subsequently transected in the same animals, the recovery was observed. The results of both experiments support the conclusion that the transection of a nontectotectal component of the commissure of the superior colliculus is responsible for the recovery of visual orientation behavior in a cortically blind cat.
Development of GABA immunoreactivity in brainstem auditory nuclei of the chick: Ontogeny of gradients in terminal staining
Authors: Code Rebecca A. , Burd Gail D. , Rubel Edwin W 
Published: January 2005

AbstractThe development of gamma‐aminobutyric acid‐immunoreactivity (GABA‐I) in nucleus magnocellularis (NM) and nucleus laminaris (NL) of the chick was studied by using an antiserum to GABA. In posthatch chicks, GABA‐I is localized to small, round punctate structures in the neuropil and surrounding nerve cell bodies. Electron microscopic immunocytochemistry demonstrates that these puncta make synaptic contact with neuronal cell bodies in NM; thus, they are believed to be axon terminals. GABAergic terminals are distributed in a gradient of increasing density from the rostromedial to the caudolateral regions of NM.The distribution of GABA‐I was studied during embryonic development. At embryonic days (E) 9‐11, there is little GABA‐I staining in either NM or NL. Around E12‐14, a few fibers are immunopositive but no gradient is seen. More GABA‐I structures are present at E14‐15. They are reminiscent of axons with varicosities along their length, preterminal axonal thickenings and fiber plexuses. At E15, terminals become apparent circumscribing neuronal somata and are also discernible in the neuropil of both nuclei. In E16‐17 embryos, terminals are the predominantly labeled GABA‐I structures and they are uniformly distributed throughout NM. The density of GABAergic terminals increases in caudolateral regions of NM such that by E17‐19, there is a gradient of increasing density of GABA‐I terminals from the rostromedial to caudolateral regions of NM. The steepness of this gradient increases during development and is the greatest in posthatch (P) chicks.Cell bodies labeled with the GABA antiserum are located around the borders of both NM and NL and in the neuropil between these two nuclei. Occasionally, GABA‐I neurons can be found within these auditory brainstem nuclei in both embryonic and posthatch chicks. Nucleus angularis (NA) contains some GABAergic cells.The appearance of GABA‐I terminals around E15 is correlated in time with the formation of end‐bulbs of Held on NM neurons. Thus, the ontogeny of presumed inhibitory inputs to chick auditory brainstem nuclei temporally correlates with, and could modulate the development of, excitatory auditory afferent structure and function.
Organization of astrocytes in the visual pathways of the goldfish: An immunohistochemical study
Authors: Levine R. L. 
Published: January 2005

AbstractWe have used antisera directed against glial cytoskeletal proteins to examine the distribution and organization of astrocytes in the visual pathways of the goldfish. We describe two different types of cells, which may be distinguished by their unique cytoskeletal proteins. Antibodies raised against a 48 Kd optic nerve protein react with stellate astrocytes in the optic nerve but virtually no glial cells in the brain (although blood vessels and the meninges in the brain were stained). The optic nerve astrocytes form a dense meshwork of processes through which the optic fibers pass. The intraorbital and intracranial segments of the nerve are divided into fascicles, each bounded by a glia limitans, which extend across the optic chiasm. Astroglial cells in the brain bind antibodies raised against a 50 Kd brain cytoskeletal protein. These antibodies show a very limited cross‐reactivity with optic nerve cells. Brain astrocytes have filiform profiles and most appear to be deployed as radial glia. The glial fabric of the brain, as revealed by these antibodies, is far more loosely woven than that of the optic nerve. There is a sharp boundary between the two types of glial cells, immediately behind the optic chiasm. Glial processes in the optic tracts arise from cells in the preoptic area, whereas those in the optic tectum arise from cells that reside locally. In the optic tract, a glia limitans was often difficult to discern, whereas in the tectum one was always evident and composed of endfeet at the pial extremities of radial glial processes.These findings are discussed both in the context of previous observations by other workers as well as with regard to their possible functional implications.
Time course of expression of neuropeptide Y, calcitonin gene‐related peptide, and NADPH diaphorase activity in neurons of the developing murine bowel and the appearance of 5‐hydroxytryptamine in mucosal enterochromaffin cells
Authors: Branchek Theresa A. , Gershon Michael D. 
Published: January 2005

AbstractSerotoninergic and cholinergic neurons are known to appear earlier in the ontogeny (day E12) of the murine gut than those containing substance P or vasoactive intestinal peptide (day E14). It has also been demonstrated that proliferating neural precursors coexist with mature neurons in developing enteric ganglia. These observations have led to the hypotheses that peptidergic neurons develop later than those that utilize small molecule neurotransmitters and that the activity of early developing neurons may affect the phenotypic expression of coexisting neuroblasts. As a partial test of these hypotheses we studied the phenotypic expression of neurons recognized by antisera to neuropeptide Y (NPY) and calcitonin gene‐related peptide (CGRP), and of those visualized by the histochemical demonstration of reduced nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase activity. NADPH diaphorase activity, which is coexpressed with NPY immunoreactivity in all submucosal and many myenteric neurons, was first found on day E11 in clusters of cells in the dorsal mesogastrium. These cells also expressed neurofilament reactivity and thus were developing along a neuronal lineage. Enteric neurons that expressed NADPH diaphorase activity were visualized in the stomach one day later, on day E12. At this time, NADPH diaphorase‐containing cells could no longer be demonstrated in the dorsal mesogastrium. NPY immunoreactivity first appeared in the wall of the bowel on day E12, when it was seen in cells in the presumptive stomach. By day E13, the entire length of the bowel contained NPY‐immunoreactive neurons. Cells that displayed NADPH diaphorase activity were found at this time at both ends of the alimentary tract, but did not appear in the ileum until day E18. In contrast, CGRP immunoreactivity could not be detected anywhere in the gut until day E17, but by day E18 all regions of the bowel contained CGRP‐immunoreactive neurons. Endogenous 5‐HT was first detected at day E16 in mucosal epithelial cells in all segments of the gut except the stomach, where it appeared at day E18. The NPY/NADPH diaphorase set of neurons thus develop before the acquisition of a detectable level of endogenous 5‐HT or enteric neural 5‐HT receptors (which arise in the foregut at day E14). These observations demonstrate that enteric neurons that express small molecule.
Development of the nerve fiber layer in the olfactory bulb of mouse embryos
Authors: Doucette R. 
Published: January 2005

AbstractThe purpose of this study was to provide an ultrastructural description of the development of the olfactory nerve fiber layer (ONL) in the olfactory bulbs of mouse embryos. The developmental age of each embryo was determined by means of the Theiler staging system. During stages 17 and 18, the olfactory axons grew through the mesenchyme toward the cerebral vesicle; they were accompanied by a group of electron‐dense cells which were referred to as peripheral glial progenitor cells (GPCs) because they ensheathed the adjacent axons. In Theiler stage 19–21 embryos, the axons and the peripheral GPCs grew dorsocaudally along the external surface of the bulb primordium forming a presumptive ONL immediately superficial to its glia limitans. Through small breaks in this glia limitans, the axons, but not the peripheral GPCs, penetrated into the marginal zone of the bulb primordium. Even though by the first half of stage 21 there were only short stretches of glia limitans separating the presumptive ONL from the marginal zone, there was no intermingling of the perikarya between the two layers. A definitive ONL could be identified by the second half of Theiler stage 21, by which time the glia limitans of the bulb primordium had totally disappeared. However, up to Theiler stage 24 of development the only cells to be found in this definitive ONL were the peripheral GPCs. Although in Theiler stage 25 and 26 embryos there was an additional population of less‐electron‐dense GPCs within the definitive ONL, these cells were likely derived from the previous group of peripheral GPCs rather than from cells newly emigrated from the deeper layers of the developing bulb. This developmental data necessitated a reevaluation of the cell lineages of the two glial cell types that reside within the ONL of the adult olfactory bulb.
Dendritic maturation of displaced putative cholinergic amacrine cells in the rabbit retina
Authors: Wong R. O. L. , Collin S. P. 
Published: January 2005

AbstractThe dendritic trees of Cb, cholinergic, amacrine cells in the ganglion cell layer of the developing rabbit retina are revealed by intracellular injection with Lucifer yellow to have the adult dendritic branching pattern at birth. It is demonstrated that these cells maintain a constant number of dendritic branches throughout postnatal development and that their dendritic trees increase in size by the growth and subsequent elongation of all branches. Proximal and distal dendrites increase in length by almost the same proportions between birth and adulthood.Although the adult pattern of dendritic branching of Cb amacrine cells is established by birth, dendrities in the young possess numerous short appendages (1–5 μm in length) resembling the “dendritic spines” of immature cat retinal ganglion cells. Some of these structures remain on the dendrites of adult cells but the majority are lost at the end of the third postnatal week. As dendritic spines disappear, the dendrites of Cb amacrine cells, especially the distal portion of the tree, acquire numerous varicosities. At each stage after P10, the gain in the number of varicosities greatly exceeds the loss in spines; this is not consistent with the hypothesis that all varicosities are retracted dendritic spines. The rapid increase in the number of varicosities on distal dendrites of Cb amacrine cells during the first 3 postnatal weeks coincides with the maturation of amacrine cell physiological responses.There is no distinct centroperipheral gradient in the postnatal dendritic maturation (acquisition of varicosities, loss of spines, attainment of the adult number of branches) of Cb amacrine cells from the visual streak to the peripheral retina. However, the area of their dendritic tree increases relatively more in the retinal periphery compared to that in the visual streak.
Development of synapses between chick retinal neurons in dispersed culture
Authors: Gleason Evanna , Wilson Martin 
Published: January 2005

AbstractMorphological criteria allow several kinds of synapse to be recognized in the vertebrate retina. It is, however, not presently known if, or how, these morphological differences reflect physiological distinctions. Since a proper investigation of synaptic physiology in the intact retina is compromised by technical difficulties, we have examined dispersed cultures to discover if they are likely to provide a more tractable physiological preparation. The chief question addressed here concerns the extent to which normal synaptic development takes place in the impoverished conditions of dispersed cell culture.Cultures were established from embryonic day 8 chick retina and fixed for microscopy on embryonic equivalent (E.E.) days 12, 14, 16, and 18. Neuronal processes appeared shortly after plating and continued to increase in number and extent through E.E. 16. Cone cells were recognizable by virtue of their distinctive oil droplets. Two classes of cone could be distinguished on the basis of the density of their cytoplasmic staining. Presynaptic ribbons could be observed in cone cells on E.E. 12, but characteristic dyad and triad postsynaptic organization was seldom present at this stage nor was it often observed at subsequent times. An increase in the number of ribbon synapses in culture was seen on E.E. 18. These synapses may represent those of bipolar cells. Conventional synapses were found at all times examined but the number of these increased greatly between E.E. 14 and 16. Of these conventional synapses, we found some whose anatomy was characteristic of synapses made by amacrine cells as well as some whose anatomy was characteristic of synapses made by bipolar cells.
Effects of prenatal exposure to ethanol on neocortical development: II. Cell proliferation in the ventricular and subventricular zones of the rat
Authors: Miller Michael W. 
Published: January 2005

AbstractPrenatal exposure to ethanol alters the generation of neocortical neurons; ethanol reduces the numbers of neurons generated between gestational day (G) 12 and G19 but paradoxically increases neuronogenesis after G19. The present study used [3H]thymidine autoradiography to examine the effects of ethanol on the proliferation of cells in the two cortical germinal zones, the ventricular and subventricular zones. Pregnant rats were fed one of three diets: a liquid ethanol‐containing (6.7% v/v) diet (Et), a nutritionally matched isocaloric liquid diet (Ct), or chow and water (Ch). Fetuses were administered with [3H]thymidine on G13, G17, or G20 and killed 45–60 minutes later. Autoradiographs were prepared to identify radiolabeled and mitotic cells. Additional brains from 13–23‐day‐old fetuses were processed for cytoarchitectonic analyses.The size of the lateral ventricles in the fetuses was not significantly affected by the prenatal exposure. Both the ventricular and subventricular zones were evident throughout the period from G13 to G23. In all three groups, the ventricular zone was thickest from G13 to G17, but from G15 on, the ventricular zone of Et‐treated fetuses was significantly thinner than those of either controls. On G13, G17, and G20, the labeling index (the ratio of radiolabeled cells to the total population) was significantly less in Et‐treated fetuses. The mitotic index was similar in Et‐, Ch‐, and Ct‐treated fetuses. The subventricular zone of all fetuses was most prominent during later fetal ages and it was thicker in Et‐treated fetuses than in controls. Moreover, the labeling and mitotic indices for the subventricular zone of Et‐treated rats were significantly greater than for controls.Thus, ethanol had different effects on the two neocortical germinal zones: the proliferation of ventricular cells was inhibited, whereas the proliferation of subventricular cells was stimulated. These data suggest that ethanol‐induced changes in neuronogenesis result from alterations in proliferative activity.
Spinocerebellar projections from spinal border cells in the cat as studied by anterograde transport of wheat germ agglutinin‐horseradish peroxidase
Authors: Matsushita Matsuo , Yaginuma Hiroyuki 
Published: January 2005

AbstractThe cerebellar projections of spinal border cells, which give rise to crossed ascending axons, were studied in the lower lumbar segments by the anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA‐HRP) in the cat. Prior to the injections, the spinal cord was lesioned rostral and ipsilateral to the WGA‐HRP injections to eliminate labeling of the ipsilaterally ascending axons.Following injections of WGA‐HRP into the L4‐L6 segments, labeled terminals were seen in sublobules Ib‐Vf of the anterior lobe, sublobules VIf‐VIe, lobule VIII, the paramedian lobule, and crus II. More than 90% of the total number of labeled terminals were in the anterior lobe; the projections were predominantly ipsilateral to their cells of origin (about 90% or more labeled terminals of the total number in each of sublobules IIb‐Va). Many labeled terminals were seen ipsilaterally in sublobules IIb (11.1–17.5% of the total number), IIIa (11.7–12.9%), IIIb (16.1–17.6%), IVa (8.8–10.8%), IVb (6.2–10.5%), and Va (9.7–10.3%). In the posterior lobe, labeled terminals were numerous only in sublobule C of the ipsilateral paramedian lobule (2.7–4.9%).The projection fields in the horizontal plane of the lobules were reconstructed from a series of cross‐sections through each lobule. In the anteriorlobe, labeled terminals were distributed in four major areas. In sublobules IIa–IVa, area 1 was located between 1.0 and 2.0 mm lateral to the midline in zones B–C1 of Voogd; area 2, between 2.0 and 3.0 mm lateral to the midline in zones C1–C2; area 3, between 3.0 and 4.0 mm in zones C2–C3; and area 4, lateral to 4.0 mm from the midline in zone C3. These areas extended apicobasally in the apical to middle parts of the lobules. On the rostral side of sublobule C1 of the ipsilateral paramedian lobule, the projection areas extended in the entire apicobasal and the mediolateral axis of the sublobule, except in the most lateral part. The present results suggest that the SBCs project to specific areas in the cerebellar lobules.
Ultrastructural analysis of enkephalinergic terminals in parasympathetic ganglia innervating the urinary bladder of the cat
Authors: Kawatani M. , Shioda S. , Nakai Y. , Takeshige C. , de Groat W. C. 
Published: January 2005

AbstractLeucine enkephalin immunoreactivity was identified in axons and varicosities in parasympathetic ganglia located in the pelvic plexus and on the surface of the urinary bladder of the cat. Electron microscopic immunohistochemical studies revealed that varicosities containing leucine enkephalin exhibited large dense core vesicles and small, clear, spherical vesicles, which were similar to those found in cholinergic terminals. Leucine enkephalin immunoreactivity was primarily associated with large dense core vesicles. The varicosities formed axodendritic and axosomatic synapses with principal ganglion cells. Axoaxonic synapses were not detected. Some axosomatic enkephalinergic synapses were detected embedded within or invaginating the principal ganglion cells. Varicosities containing flattened and/or small dense core vesicles did not exhibit enkephalin immunoreactivity.Bladder ganglion cells identified by retrograde HRP tracing from the urinary bladder exhibited similar leucine enkephalinergic synapses. These observations, coupled with previous reports that leucine enkephalin is present in sacral preganglionc neurons and released by preganglionic nerve stimulation, suggest that leucine enkephalin and acetylcholine are cotransmitters stored and released from the same nerve terminals in bladder parasympahtitic ganglia.
Distribution of substance P‐like, leucine‐enkephalin‐like, and bombesine‐like immunoreactivity and acetylcholinesterase activity in the visual system of salamanders
Authors: Schmidt Andrea , Roth Gerhard , Ernst Monika 
Published: January 2005

AbstractIn the urodele species Salamandra salamandra and Batrachoseps attenuatus, the distribution of the neuropeptides substance P (SP), leucine‐enkephalin (LENK), and bombesine (BOMB) was investigated by means of immunohistochemistry in brain areas containing retinofugal projection sites (tectum mesencephali, praetectum, thalamus) as well as in brain regions postsynaptic to the tectum. The activity of acetylcholinesterase (AChE) was studied histochemically.Despite its simplified, two‐layered morphology, the salamander tectum shows a high degree of neurochemical differentiation, characterized by a laminar organization of neuropeptide‐like immunoreactivity and AChE‐activity comparable to that found in the anuran tectum, which has a multi‐layered morphology. SP‐like immunoreactivity constituted four tectal laminae, two of them occurring in the stratum opticum. LENK‐like immunoreactivity formed three laminae, one in the stratum opticum. BOMB‐like immunoreactivity formed one lamina within the stratum opticum and one in the tectal efferent layers. Layers 1 and 2 of the stratum opticum revealed high AChE‐activity, whereas low activity was found in deep fiber layers containing tectal efferents. The outer cellular layer also revealed AChE‐activity. After enucleation of one eye, the contralateral tectum lacked neuropeptide‐like immunoreactivity and AChE‐activity in the layers containing retinofugal projection sites. No reduction of immunoreactivity was found in nuclei postsynaptic to the tectum.Our experiments suggest that the secondary simplification that has taken place in salamanders with respect to tectal morphology did not affect the neurochemical differentiation of the tectum.