bluuebunny/crossref_metadata_2025 huggingface dataset:
Localization of 5‐HT2A receptor mRNA by in situ hybridization in the olfactory bulb of the postnatal rat
Authors: McLean John H. , Darby‐King Andrea , Paterno Gary D.
Published: January 2005

The olfactory bulb receives a dense serotonergic input and appears to require serotonergic input in early olfactory associational learning. However, it is not known which cell types receive the serotonergic input or whether the cells express markers for the input throughout life. These issues need resolution in order for the mechanisms of serotonergic interactions to be better understood. The mRNA for the 5‐HT2A receptor was localized in the olfactory bulb of postnatal day 1, 2, 14 and 9‐month‐old Sprague‐Dawley rats as well as in the bulb of adult (6 months) and aged (22‐30 month) Fisher 344 rats by in situ hybridization using an 35S‐labelled 5‐HT2A specific oligonucleotide probe mixture. In all animals, hybridization was observed in mitral cells which are the major output cells of the main olfactory bulb. Tufted cells, located in the external plexiform layer and juxtaglomerular region, were readily observed in adult and aged animals and were also observed, albeit not as readily, in neonate pups. Quantitative analysis of the silver grain density over cells confirmed qualitative observations and showed that mitral and tufted cells were labelled in the neonate as well as in adult and aged animals. Labelled cells were also numerous in the external division of the anterior olfactory nucleus in all animals. 5‐HT2A receptor mRNA could not be detected either qualitatively or quantitatively by in situ hybridization in the accessory olfactory bulb, nor could it be observed in the olfactory epithelium. The results suggest that the output cells of the main olfactory bulb receive serotonergic input via 5‐HT2A receptors and that the serotonergic input onto these cells could influence olfactory functioning at all postnatal ages. © 1995 Wiley‐Liss, Inc.
Substance P, bombesin, and leucine‐enkephalin immunoreactivities are restored in the frog tectum after optic nerve regeneration
Authors: Humphrey M. F. , Renshaw G. M. C. , Kitchener P. D. , Beazley L. D.
Published: January 2005

Extensive regeneration of the optic nerve takes place in adult Amphibia. In this study, we have determined whether one aspect of retinotectal organisation, namely immunoreactive laminae in the retinorecipient layers of the optic tectum, is restored after optic nerve regeneration. To do so, the distributions of substance‐P, bombesin, and leucine‐enkephalin immunoreactivities were examined in the optic tectum of the frog Litoria (Hyla) moorei. Results of a normal series were compared with those at intervals up to 84 days and at 196 days after either unilateral deafferentation or optic nerve crush.

In the normal series, distinct neuropeptide immunoreactive laminae were located within the retinorecipient tectal layers. There were two major laminae with substance‐P, two with bombesin, and one with leucine‐enkephalin immunoreactivities. Additional faint laminae of both substance‐P and bombesin immunoreactivity were present in the tectal region that receives input from the visual streak. In addition, labelling of cell bodies and dendrites was seen elsewhere in the tectum.

All except one immunoreactive lamina changed after deafferentation. The deeper of those with substance‐P immunoreactivity, along with both bombesin laminae, were eventually lost the lamina with leucine‐enkephalin immunoreactivity was halved in intensity. We assume that these laminae are wholely or, in the case of the leucine‐enkephalin lamina, partially associated with primary optic input. By contrast, the more superficial lamina with substance‐P immunoreactivity remained unchanged and is presumably not directly related to visual input.

During nerve regeneration, the intensity of all laminae associated with optic input initially fell as in the deafferentation series but, in the long term, recovered to approximately 80% of normal intensities. We conclude that ganglion cells associated with each of the immunoreactivities tested had successfully regenerated. The reduced intensity of immunoreactivities after regeneration is due presumably in part to the cell loss from the ganglion cell population.

Furthermore, we discuss the findings of similar studies for Rana pipiens (Kuljis and Karten [1983] J. Comp. Neurol. 217:239–251 and [1985] 240:1–15) in light of the present findings. We argue that some of the previous observations can be reinterpreted to indicate that regeneration was not limited to ganglion cells associated with substance‐P immunoreactivity as first thought. © 1995 Wiley‐Liss, Inc.
Differential distribution of six calcium‐binding proteins in the rat olfactory epithelium during postnatal development and adulthood
Authors: Bastianelli Enrico , Polans Arthur S. , Hidaka Hiroyoshi , Pochet Roland
Published: January 2005

Odorant stimulation of receptor cells results in a calcium influx that activates the transduction pathway. Ca2+ acceptors, such as calmodulin, may mediate between the change in intracellular calcium and the conductance mechanism underlying the initial electrical event. Ca2+ acceptors also may participate in subsequent processing of olfactory information. The identification and characterization of these molecules, therefore, should provide important information about the complex signal transduction pathway involving calcium in olfaction as well as other sensory systems.

The present study describes the distribution of six calcium‐binding proteins in the rat main olfactory epithelium during postnatal development to determine when different Ca2+ acceptors can be detected and whether they segregate into different layers or p6 rtions of the epithelium. Calmodulin, calretinin, calbindin‐D28k, neurocalcin, and recoverin were detected immunohistochemically in olfactory receptors but not in basal cells. S‐100 immunoreactivity was restricted to glial cells primarily around the cribriform plate. During postnatal development (from P1 to P20), calmodulin, calretinin, calbindin‐D28k, and neurocalcin formed a gradient of immunoreactivity descending from the central to the lateral areas in the nasal cavity, whereas recoverin was expressed only in sporadic, mature receptors in the proximal region of the mucosa. At P20, the immunoreactivity pattern for each calcium‐binding protein was identical to the adult profile, indicating that the olfactory epithelium had reached maturity by this stage. Olfactory nerve fiber bundles displayed a differential staining pattern from P 1 until adulthood for calbindin‐D28k and calretinin (internal portions of bundles). Differential calmodulin immunoreactivity of olfactory nerves (large external portions of bundles) appeared at P10. The immunoreactivity of the nerve fiber bundles may reflect a further degree of organization relevant to odor discrimination. © 1995 Wiley‐Liss, Inc.
Dopaminergic and GABAergic cerebrospinal fluid‐contacting neurons along the central canal of the spinal cord of the eel and trout
Authors: Roberts B. L. , Maslam Suharti , Scholten G. , Smit W.
Published: January 2005

In anamniote vertebrates the central region of the spinal cord has been implicated in its regeneration. This is a complex region and so as a first step in understanding its possible regenerative role we have examined the organization of the cells that contact the lumen of the spinal cord in two teleost fishes, eel and trout, using immunohistochemical procedures and light and electron microscopy.

Cell bodies immunoreacting positively with antibodies for tyrosine hydroxylase and for dopamine were located at the ventral rim of the central canal, whereas cell bodies reacting for an antibody for gamma‐aminobutyric acid were more laterally located. None of the canal‐contacting cells were positively immunoreactive for choline acetyltransferase. All immunopositive cells have a similar morphology: the amphora‐shaped perikaryon is bipolar and has a single process that extends to the lumen of the canal, and another that branches and forms extensive lateral and ventral plexuses. Electron microscopic investigations of the ventral dopaminergic cells showed that the apical processes bear one or more cilia, which protrude into the canal lumen and which originate from within a superficial rosette of nonciliated processes. The ventral process was occasionally seen to form synapses; the cell body was also the target of synapses. © 1995 Wiley‐Liss, Inc.
Development of A‐type (axonless) horizontal cells in the rabbit retina
Authors: Scheibe Ronald , Schnitzer Jutta , Röhrenbeck Jürgen , Wohlrab Frank , Reichenbach Andreas
Published: January 2005

The development of A‐type horizontal cells (HC) was studied in the rabbit retina between embryonic day (E)24 and adulthood [the day of birth was called postnatal day (P)1 and corresponds to E31–32]. The cells were visualized by several methods 1) by immunolabeling with antibodies to neurofilament 70000 (NF‐70kD), 2) by immunolabeling with antibodies to a calcium binding protein (CaBP‐28kD), 3) by two different methods of silver impregnation, and (4) by histochemical demonstration of NADH‐diaphorase activity. Most methods labeled A‐type HC only in the dorsal retina; thus, our study is restricted to HC of this region. HC densities were determined at each developmental stage. The cells were drawn at scale, and size, quotient of symmetry, and topographical orientation of dendritic trees were studied by image analysis. The growth of HC dendritic fields was correlated with data on the postnatal local retinal expansion, which is known to be driven by the intraocular pressure (after cessation of retinal cell proliferation at P9). This expansion was evaluated in an earlier paper (Reichenbach et al. [1993] Vis. Neurosci. 10:479–498) by using local subpopulations of Müller cells as “markers” of distinct topographic regions of the retinae. After E24, when the final number of HC is established, we can discriminate three distinct developmental stages of A‐type HC. During the first stage, between E24 and E27, the young cells are often vertically oriented and may extend their first short dendrites within (the primordia of) both plexiform layers. The irregular HC mosaic at E24 shows a significant difference to all other stages. The second stage begins after birth when the dendritic trees of the cells are already restricted to the outer plexiform layer. Between P3 and P9, their dendritic trees enlarge more than the surrounding retinal tissue expands, and the coverage factor almost doubles from 2.5 to 4.4. The third stage occurs after P9 when the growth rate of dendritic tree areas corresponds to that of the local retinal tissue expansion caused by “passive stretching” of the postmitotic tissue, and the coverage factor remains constant. This is compatible with the view that mature synaptic connections of A‐type HC are mostly established after the first week of life and are then maintained. © 1995 Wiley‐Liss, Inc.
Neurotransmitter modulation of Fos‐ and Jun‐like proteins in the turtle retina
Authors: Yaqub Asma , Guimaraes Marilia , Eldred William D.
Published: January 2005

The expression of the Fos and Jun families of nuclear phosphoproteins can be induced by a variety of extracellular stimuli and is known to participate in the transcriptional regulation of target genes. To examine the role of these transcription factors in retinal function, we used polyclonal antisera to localize these protein families in the turtle retina. Fos‐like immunoreactivity was in many somata in the inner nuclear and ganglion cell layers. In contrast, Jun‐like immunoreactivity was in a smaller number of amacrine cells and many somata in the ganglion cell layer. The monostratified dendritic arbors of one prominent amacrine cell type with Jun‐like immunoreactivity were also labeled. There were no dramatic differences in the levels of Fos‐like immunoreactivity or Jun‐like immunoreactivity between light‐ or dark‐adapted retinas.

We examined the effects of excitatory amino acids and γ‐aminobutyric acid (GABA) on the expression of these proteins in vitro. In some experiments, cobalt was used to block synaptic transmission. The excitatory amino acids increased both Fos‐ and Jun‐like immunoreactivity, while GABA generally showed no such stimulatory effect. In cobalt‐treated retinas, the same cell types had Jun‐like immunoreactivity as seen in the controls, but overall levels of immunoreactivity were increased. In cobalt‐treated dark‐adapted retinas, some excitatory amino acids increased cytoplasmic Fos‐like immunoreactivity in the somata and processes of large cells in the ganglion cell layer. Our results suggest that Fos‐ and Jun‐related proteins may play an important role in the postsynaptic responses to amino acid transmitters in a wide variety of amacrine and ganglion cells. © 1995 Wiley‐Liss, Inc.
Morphology of physiologically identified retinal X and Y axons in the cat's thalamus and midbrain as revealed by intraaxonal injection of biocytin
Authors: Tamamaki Nobuaki , Uhlrich Daniel J. , Sherman S. Murray
Published: January 2005

Prior morphological studies of individual retinal X and Y axon arbors based on intraaxonal labeling with horseradish peroxidase have been limited by restricted diffusion or transport of the label. We used biocytin instead as the intraaxonal label, and this completely delineated each of our six X and 14 Y axons, including both thalamic and midbrain arbors. Arbors in the lateral geniculate nucleus appeared generally as has been well documented previously. Interestingly, all of the labeled axons projected a branch beyond thalamus to the midbrain. Each X axon formed a terminal arbor in the pretectum, but none continued to the superior colliculus. In contrast, 11 of 14 Y axons innervated both the pretectum and the superior colliculus, one innervated only the pretectum, and two innervated only the superior colliculus. Two of the Y axons were quite unusual in that their receptive fields were located well into the hemifield ipsilateral with respect to the hemisphere into which they were injected. These axons exhibited remarkable arbors in the lateral geniculate nucleus, diffusely innervating the C‐laminae and medial interlaminar nucleus, but, unlike all other X and Y arbors, they did not innervate the A‐laminae at all. In addition to these qualitative observations, we analyzed a number of quantitative features of these axons in terms of numbers and distributions of terminal boutons. We found that Y arbors contained more boutons than did X arbors in both thalamus and midbrain. Also, for axons with receptive fields in the contralateral hemifield (all X and all but two Y axons), 90–95% of their boutons terminated in the lateral geniculate nucleus; the other two Y axons had more of their arbors located in midbrain. © 1995 Wiley‐Liss, Inc.
Electron microscopy of cell islands in layer II of the primate entorhinal cortex
Authors: Goldenberg Todd M. , Bakay Roy A. E. , Ribak Charles E.
Published: January 2005

An electron microscopic analysis of cell islands in layer II of the entorhinal cortex from rhesus monkeys was made to determine the ultrastructural features of these unique neuronal clusters. The rostral, intermediate, and caudal divisions of the entorhinal cortex were selected for electron microscopic examination. In the rostral division, neurons were grouped together in prominent clusters, often with 10 or more contiguous somata. Somatic and dendrosomatic appositions were frequent, without intervening cellular processes or specialized junctions. Somata were relatively small, typically 10–15 μm in diameter, with oval or circular nuclei that were euchromatic and contained nucleoli. Small nuclear infoldings were commonly seen. A thin shell of perikaryal cytoplasm contained numerous organelles. Axosomatic synapses were infrequent, with a mean of only 1. 0 synapse per neuron per thin section. The neuropil contained numerous synapses, and myelinated axons were seen infrequently. In the intermediate division, somatic appositions were rarely observed. Somata were relatively large, typically 15–20 μm in diameter, and displayed a moderate amount of cytoplasm. Axosomatic synapses were relatively common, with a mean of 3. 3 synapses per neuron per thin section. In the caudal division, neurons were typically grouped in clusters of two to three contiguous somata. Neurons were about 15 μm in diameter and displayed a moderate amount of cytoplasm. Axosomatic synapses were of moderate frequency, with a mean of 2. 5 synapses per neuron per thin section. The neuropil in the caudal division displayed a relatively high frequency of myelinated axons.

Our analysis of three regions of the entorhinal cortex revealed significant differences in the frequency of somatic appositions and axosomatic synapses, and in certain ultrastructural features of the somata and neuropil. These results showed that cell islands in layer II of the entorhinal cortex display regional morphologic differences. The paucity of symmetric axosomatic synapses in the rostral division may correlate with this region's vulnerability in certain diseases.
Oligodendrocytes in female carriers of the jimpy gene make more myelin than normal oligodendrocytes
Authors: Skoff Robert P. , Said Ghandour M.
Published: January 2005

The female carrier of the jimpy (jp) gene is a model system to study the plasticity of neuroglial cells and the mechanisms they use to compensate for a temporary deficit in myelin. Myelin in the female carriers is reduced 30‐40% during the first postnatal month but is normal in adults. We hypothesized that the number of oligodendrocytes (OLs) in the female carriers is increased, based upon previous data showing OL proliferation is increased but the number of dying OLs is only slightly elevated in development. To test this hypothesis, antibodies to carbonic anhydrase (CA)II, an OL‐specific marker, were used to quantify the number of OLs in the spinal cords of 1‐month‐old and adult female carriers. Contrary to expectations, the number of OLs is significantly reduced in the dorsal funiculus and grey matter by 21% in adult female carriers compared to controls. A reduction of lesser magnitude is present in the 1‐month‐old animals. Electron microscopic montages prepared from normal and carrier dorsal funiculus we used to count total numbers of glia. Ultrastructural quantification shows a similar reduction in the number of OLs and confirms the validity of the CAII immunostaining as a means to quantify OLs.

These data show that there are 21% fewer OLs in the central nervous system (CNS) of adult female carriers but normal amounts of myelin. Presumably, some OLs in the carrier CNS are maintaining more myelin than their counterparts in normal CNS would. These findings demonstrate that (1) a reduction in number of OLs does not necessarily involve a reduction in the amount of myelin, and (2) OLs have considerable flexibility in the amount of myelin they can make.
Ultrastructural examination of the targets of serotoninn immunoreactive descending interneurons in the guinea pig small intestine
Authors: Young H. M. , Furness J. B.
Published: January 2005

Serotonin neurons are descending interneurons in the myenteric plexus of the guinea pig small intestine. Preembedding single‐ and double‐label immunocytochemistries at the ultrastructural level were used to identify the targets of these serotonin interneurons.

Serial ultrathin sections were taken through a myenteric ganglion that had been processed for serotonin immunocytochemistry. The ganglion contained the cell bodies of 69 neurons, including 2 serotonin neurons and 6 neurons with the ultrastructural features of Dogiel type II cells. For each cell body in the ganglion, the number of serotonin inputs (synapses and close contacts) was determined. About 50% of the cell bodies did not receive any serotonin inputs. The most abundant serotonin terminals were related to two targets: other serotonin descending interneurons and a population of neurons with Dogiel type I morphology, but whose neurochemistry and function is unknown. The serotonin inputs to the serotonin cell bodies were located predominantly on the lamellar dendrites. Each of the Dogiel type II neurons received 3 or fewer serotonin inputs, and none of the serotonin inputs to Dogiel type II neurons formed a synapse. Overall, about 40% of the serotonin inputs formed synapses. The serotonin inputs to neurons that received many serotonin inputs were more likely to show synaptic specializations than serotonin inputs to neurons that received few serotonin inputs.

Inhibitory motor neurons contain nitric oxide synthase (NOS). At the light microscope level, serotonin nerve fibers do not form dense pericellular baskets around NOS cell bodies. To determine whether there are serotonin input to NOS neurons, serial ultrathin sections were taken through a myenteric ganglion that had been processed for preembedding double‐label immunocytochemistry, in which the NOS neurons were labeled with peroxidase‐diaminobenzidine and the serotonin neurons with silver‐intensified 1 nm gold. Only 1 out of 9 NOS cells examined in serial section received more than 5 serotonin inputs. The results suggest that, in the guinea pig small intestine, the serotonin descending interneurons are not an essential element of the descending inhibitory reflex. © 1995 Wiley‐Liss, Inc.
Thalamocortical synapses between axons from the mediodorsal thalamic nucleus and pyramidal cells in the prelimbic cortex of the rat
Authors: Kuroda Masaru , Murakami Kunio , Kishi Kiyoshi , Price Joseph L.
Published: January 2005

A combined anterograde axonal degeneration and Golgi electron microscopic (Golgi‐EM) study was undertaken to identify thalamocortical synaptic connections between axon terminals from the mediodorsal thalamic nucleus (MD) and pyramidal cells in layers III and V of the agranular prelimbic cortex in the rat. The morphological characteristics of thalamocortical synapses from MD were also examined by labeling axon terminals with anterograde transport of wheat germ agglutinin‐horseradish peroxidase (WGA‐HRP).

WGA‐HRP labeled axon terminals from MD to the prelimbic cortex were small in size (0.5–1 μm in diameter), contained round synaptic vesicles, and formed axospinous synapses with asymmetrical membrane thickenings. With Golgi‐EM methods, gold‐toned apical dendrites in layer III were analyzed by reconstruction of serial ultrathin sections. Following lesions in the thalamus, degenerating thalamocortical axon terminals formed asymmetrical contacts exclusively on dendritic spines of the identified apical dendrites. More thalamocortical synapses were found on apical dendrites of layer V pyramidal cells than on apical dendrites of layer III pyramidal cells. In addition to thalamocortical synapses, a very few unlabeled symmetrical synapses were found on apical dendrites and somata of pyramidal cells, but they were not quantified and their sources are unknown. © Wiley‐Liss, Inc.
Expression of neurofilament proteins during development of the nervous system in the squid Loligo pealei
Authors: Grant Philip , Tseng Daniel , Gould Robert M. , Gainer Harold , Pant Harish C.
Published: January 2005

The squid nervous system includes various brain ganglia, optic lobes (the visual center), and the stellate ganglia, the system of giant motor fibers responsible for rapid jet‐propelled escape behavior. The large caliber of giant fibers is due, in part, to the accumulation of squid‐specific neurofilaments (NFs) made up of a heavily phosphorylated NF 220 protein together with NF 70 and NF 60 subunits. Using antibodies prepared against known peptide sequences in these proteins, together with a mammalian‐derived antibody that specifically recognizes phosphorylated squid NF 220, we studied the localization of NFs in adult tissues and during neural development. Immunoblot and immunohistochemical analyses showed that NFs were present in adult neural tissues, primarily in selected fibers, with giant axons showing the most robust expression. After the first neurons differentiated at stage 22, immunoblots showed NF 60– and NF 70–immunoreactive proteins at all stages. The NF 220 subunit, however, was not detected in immunoblots at any developmental stage. Phosphorylated NF 220 immunoreactivity, although absent in immunoblots, was first seen in selected fibers of the stellate ganglia at stage 25, increasing thereafter in all giant fibers until hatching (stage 30). The stellate ganglion is the first neural tissue to acquire a mature neurofilament complement (i. e., phosphorylated NF 220), shortly before the onset of jet‐propelled escape behavior. The temporal pattern of expression of the NFs during development resembled that seen in vertebrates; i. e., the smaller NFs appeared before the larger subunit in most neural tissues. In the squid, the expression pattern seems to depend upon the post‐transcriptional regulation of a single gene rather than upon transcriptional regulation of three independent genes as in vertebrates. © 1995 Wiley‐Liss, Inc.
Circuit reorganization in granuloprival cerebellar cultures in the absence of neuronal activity
Authors: Seil Fredrick J. , Drake‐Baumann Rosemarie
Published: January 2005

Neonatal mouse cerebellar cultures exposed to cytosine arabinoside for the first 5 days in vitro to destroy granule cells and compromise glia undergo a circuit reorganization featured by profuse sprouting of Purkinje cell recurrent axon collaterals, which hyperinnervate the somata of other Purkinje cells and project to Purkir& cell dendritic spines. Such granuloprival cultures were exposed continuously from explanation to tetrodotoxin and elevated levels of magnesium to block neuronal activity. A similar circuit reorganization occurred, except that there was a reduction in the number of axospinous synapses and Purkinje cell axosomatic synapses, which in this case were all inhibitory. Functionally, after recovery from the blockade, granuloprival cultures developed sustained cortical hyperactivity, which was consistent with the reduction of inhibitory synapses. While the absence of neuronal activity did not prevent reorganizational changes following granule cell loss, the full development of the inhibitory circuitry was not attained. These results further support the concept that spontaneous neuronal activity is necessary for the complete development of inhibitory synapses. © 1995 Wiley‐Liss, Inc.
Morphology and kainate‐receptor immunoreactivity of identified neurons within the entorhinal cortex projecting to superior temporal sulcus in the cynomolgus monkey
Authors: Good Paul F. , Morrison John H.
Published: January 2005

Projections of the entorhinal cortex to the hippocampus are well known from the classical studies of Cajal (Ramon y Cajal, 1904) and Lorente de Nö (1933). Projections from the entorhinal cortex to neocortical areas are less well understood. Such connectivity is likely to underlie the consolidation of long‐term declarative memory in neocortical sites. In the present study, a projection arising in layer V of the entorhinal cortex and terminating in a polymodal association area of the superior temporal gyrus has been identified with the use of retrograde tracing. The dendritic arbors of neurons giving rise to this projection were further investigated by cell filling and confocal microscopy with computer reconstruction. This analysis demonstrated that the dendritic arbor of identified projection neurons was largely confined to layer V, with the exception of a solitary, simple apical dendrite occasionally ascending to superficial laminae but often confined to the lamina dissecans (layer IV). Finally, immunoreactivity for glutamate‐receptor subunit proteins GluR 5/6/7 of the dendritic arbor of identified entorhinal projection neurons was examined. The solitary apical dendrite of identified entorhinal projection neurons was prominently immunolabeled for GluR 5/6/7, as was the dendritic arbor of basilar dendrites of these neurons. The restriction of the large bulk of the dendritic arbor of identified entorhinal projection neurons to layer V implies that these neurons are likely to be heavily influenced by hippocampal output arriving in the deep layers of the entorhinal cortex. Immunoreactivity for GluR 5/6/7 throughout the dendritic arbor of such neurons indicates that this class of glutamate receptor is in a position to play a prominent role in mediating excitatory neurotransmission within hippocampal‐entorhinal circuits. © 1995 Wiley‐Liss, Inc.
Requirement of RNA synthesis for pathfinding by growing axons
Authors: Von Bernhardi R. , Bastiani M. J.
Published: January 2005

The effects of actinomycin D were studied in cultured grasshopper embryos at different stages of development by following the outgrowth patterns of identified neurones known as aCC, pCC, and Q1. When administered at stages occurring before 31% of embryonic development, actinomycin D (0.05‐0.10 μM for 24‐48 hours) prevented axon extension, whereas it did not affect the development of the nervous system in embryos older than 34% of development. At 31‐‐34% of development, actinomycin D perturbed pathfinding of aCC without blocking axon extension. Thus, only 22% of the aCCs (n=271) in embryos treated with actinomycin D extended an axon along the intersegmental nerve as in control embryos. In the remaining embryos, aCC failed to turn into the intersegmental nerve root; its growth cone remained in the longitudinal connective, above or below the turning point. Neurones of the group caudal to the intersegmental nerve root could extend along either the anterior or posterior commissure of the next posterior segment.

In contrast to the observations made with aCC, only 1.2% of pCC (n=166) and 0.0% of Q1 (n=45) in embryos treated with actinomycin D showed axon growth along aberrant pathways. The position of the growth cones of most pCCs and all Q1s observed were in various points along their normal pathway. Both pCC and Q1, as a population, showed an extension rate significantly lower than that of their control counterparts.

The effect of actinomycin D on aCC pathway choice was probably mediated by inhibition of RNA synthesis, because incorporation of uridine into RNA was reduced by 40%. The labelling of several monoclonal antibodies (1C10, 3B11, 7F7) that recognise surface glycoproteins (lachesin, fasciclin I, and REGA‐1) involved in nervous system development of grasshopper embryos was suppressed. Our results suggest that the navigation of some axons along different pathways requires the synthesis of new mRNA. © 1995 Wiley‐Liss, Inc.
Differential distribution of exogenous BDNF, NGF, and NT‐3 in the brain corresponds to the relative abundance and distribution of high‐affinity and low‐affinity neurotrophin receptors
Authors: Anderson Keith D. , Alderson Ralph F. , Altar C. Anthony , DiStefano Peter S. , Corcoran Thomas L. , Lindsay Ronald M. , Wiegand Stanley J.
Published: January 2005

To evaluate effective means for delivering exogenous neurotrophins to neuron populations in the brain, we compared the distribution and transport of brain‐derived neurotrophic factor (BDNF), nerve growth factor (NGF), and neurotrophin‐3 (NT‐3) following intracerebral delivery. Rats received an injection of radioiodinated or unlabeled neurotrophin into the lateral ventricle and were killed humanely after 1.5–24 hours. Other rats received continuous infusion of unlabeled neurotrophin into the lateral ventricle, the striatum, or the hippocampus for 3–14 days. The neurotrophins were detected by autoradiography or immunohistochemistry. There were striking differences between BDNF, NGF, and NT‐3 in their penetration through brain tissue. These differences occurred regardless of the site or method of delivery, but were most pronounced following a bolus intracerebroventricular (ICV) injection. After ICV injection, NGF was widely distributed in tissues around the ventricles and at the surface of the brain, whereas the penetration of BDNF into brain tissue was distinctly less than that of NGF, and the penetration of NT‐3 was intermediate. An ICV injection of NGF produced prominent but transient labeling of cells that contain the low‐affinity NGF receptor, whereas an injection of BDNF prominently labeled the ventricular ependyma. During ICV infusion (12 g/day), the distribution of BDNF was no greater than that observed after a 12‐g bolus injection. A sixfold increase in the amount of BDNF infused (72 g/day) produced a more widespread distribution in the brain and doubled the depth of penetration into periventricular tissues near the cannula. Corresponding to their differences in penetration, NGF was retrogradely transported by basal forebrain cholinergic neurons after ICV or intrastriatal delivery, whereas NT‐3 was transported by a few basal forebrain neurons after ICV delivery, and BDNF was rarely detected in neurons after ICV delivery. Delivery of BDNF directly to the striatum or the hippocampus labeled numerous neurons in nuclei afferent to these structures. In situ hybridization studies confirmed that the high‐affinity BDNF receptor (TrkB) was much more widely expressed in neurons than was the high‐affinity NGF receptor (TrkA). Moreover, mRNA for truncated forms of TrkB was expressed at high levels in the ependyma, the choroid epithelium, and the gray matter. It is likely that binding of BDNF to TrkB, which appears to be more abundant and ubiquitous than TrkA, restricts the diffusion of BDNF relative to that of NGF. © 1995 Wiley‐Liss, Inc.
An ultrastructural double‐label immunohistochemical study of the enkephalinergic input to dopaminergic neurons of the substantia nigra in pigeons
Authors: Medina Loreta , Keith D. Anderson , Ellen J. Karle , Keiner Anton
Published: January 2005

Electron microscopic immunohistochemical double‐label studies were carried out in pigeons to characterize the ultrastructural organization and postsynaptic targets of enkephalinergic (ENK+) striatonigral projection. ENK+ terminals in the substantia nigra were labeled with antileucineenkephalin antiserum by using peroxidase‐antiperoxidase methods, and dopaminergic neurons were labeled with anti‐tyrosine hydroxylase antiserum by using silver‐intensified immunogold methods. ENK+ terminals on dopaminergic neurons were equal in abundance to ENK+ terminals on nondopaminergic neurons, although the former were typically somewhat smaller than the latter (mean size: 0.50 vs. 0.75 pm, respectively). ENK+ terminals were evenly distributed on the cell bodies and dendrites of dopaminergic neurons, and they were evenly distributed on dendrites but rare on perikarya of nondopaminergic neurons. Transection of the basal telencephalic output revealed that 75% of the nigral ENK+ terminals were of basal telencephalic origin. These telencephalic ENK+ terminals included over 80% of those smaller than 0.80 pm on dopaminergic neurons and smaller than 1.0 pm on nondopaminergic neurons, and none greater than this in size. Both telencephalic and the nontelencephalic ENK+ nigral terminals made predominantly symmetric synapses on nigral neurons. Although the basal telencephalic ENK+ terminals uniformly targeted dendrites and perikarya, nontelencephalic ENK+ terminals seemed to avoid perikarya. The results indicate that ENK+ striatonigral neurons in birds may directly influence both dopaminergic and nondopaminergic neurons of the substantia nigra. Based on similar data for substance Pcontaining striatonigral terminals, the roles of enkephalin and substance P in influencing nigral dopaminergic neurons may differ slightly, as they appear to target preferentially different portions of dopaminergic neurons. The overall results in pigeons are similar to those for ENK+ terminals in the ventral tegmental area in rats, suggesting that the synaptic organization of the ENK+ input to the tegmental dopaminergic cell fields is similar in mammals and birds. © 1995 Wiley‐Liss, Inc.
Ultrastructural and immunocytochemical observations on the superior olivary complex of the mustached bat
Authors: Vater Marianne
Published: January 2005

This study investigates the functional organization of the superior olivary complex of the mustached bat with classical transmission electron microscopy and postembedding immunocytochemistry for gamma‐aminobutyric acid (GABA) and glycine antisera in semithin serial sections. The ultrastructure and distribution of terminal types in the lateral superior olive (LSO) and the medial nucleus of the trapezoid body (MNTB) closely resemble that of other mammals; the organization within the medial superior olive (MSO) differs significantly. The differences concern the relative proportion of putatively inhibitory boutons, which appear as symmetrical synapses with flattened vesicles on MSO somata. In the bat, inhibitory boutons comprised 75–100% of perisomatic boutons, a value identical to that observed in the LSO. These terminals most likely arise from the MNTB. In other species, putatively inhibitory terminals form a much smaller proportion of perisomatic boutons in MSO. This difference suggests that in the bat MSO excitatory input to cell somata is considerably reduced and outweighed by inhibitory input. This suggestion is corroborated by immunocytochemical data. Glycine‐immunoreactive puncta encrust somata of LSO and MSO cells to a similar degree and in rather homogeneous patterns throughout these nuclei. Putatively GABAergic terminals are located inainly on distal dendrites of MSO and LSO cells. Regional variations in the density of GABA‐immunoreactive puncta in LSO suggest that different tonotopic zones are under differential modulatory influence. Both the LSO and MSO of the mustached bat contain significant amounts of putatively inhibitory projection cells. Coexistence of both antigens was commonly observed in subsets of cells. Quantitative analyses of labeling patterns and comparisons with other mammals suggest that the mix of neurotransmitters in projection cells of LSO and MSO is phylogenetically flexible, and thus the details of the functions of ascending pathways are species specific. In contrast to other mammals, the bat MSO forms parallel output pathways with excitatory and inhibitory components. Data are discussed in relation to specialized physiological response features. © 1995 Wiley‐Liss, Inc.
Variation and evolution of mammalian corticospinal somata with special reference to primates
Authors: Nudo R. J. , Sutherland D. P. , Masterton R. B.
Published: January 2005

The morphology of the somata originating the corticospinal tract was examined in 24 species of mammals to identify commonalities and major sources of variation among the different species. Horseradish peroxidase was applied to a hemisection of the spinal cord at the C1–C2 junction. After tetramethylbenzidine processing, the labeled somata throughout the cerebral cortex were plotted and counted. Then, 23 morphological characteristics of the corticospinal somata were examined, including their number, size, and density across the cortical surface.

The results show that morphological characteristics of corticospinal somata are closely related to an animal's body, brain, and cerebral cortex size. That is, mammals with large neocortical surfaces tend to have larger as well as more corticospinal somata; mammals with large bodies tend to have corticospinal somata that are less densely distributed. Moreover, the probable increase in the ratio of local noncorticospinal somata to corticospinal somata implies that the evolution of the corticospinal tract was accomplished by an increase in “support” or “server” cells as well as an increase in the size of the tract itself.

The results also show that several characteristics are reliably related to an animal's taxonomic classification and hence its ancestry. Comparisons among three mammalian lineages indicate that some characteristics may have changed uniquely in the anthropoid primate lineage, and thus, presumably, in the human lineage. The results suggest that if morphological characteristics of the corticospinal tract important in the evolution of the specialized motor abilities in anthropoid primates are sought, then examination of the role of changes in soma diameter, rostral (motor)/caudal (sensory) ratios of density, concentration, surface density, and volume density may be more instructive than examination of the total number of corticospinal neurons alone. © 1995 Wiley‐Liss, Inc.
Organization of the olfactory system in the adult zebrafish: Histological, immunohistochemical, and quantitative analysis
Authors: Byrd Christine A. , Brunjes Peter C.
Published: January 2005

The zebrafish, Danio rerio, is becoming an important model system for developmental studies. We have used a variety of histological techniques to characterize the adult structure of the olfactory system in this teleost to form a base for future developmental work. The olfactory epithelium in this fish contains ciliated and microvillar sensory neurons, microvillar supporting cells, secretory goblet cells, and basal cells, and the adjacent nonsensory epithelium contains ciliated supporting cells. The olfactory bulb is a diffusely organized structure with four laminae: olfactory nerve, glomerular, mixed mitral cell/plexiform, and granule cell layers. These structures and the synapses observed in the olfactory bulb are typical of what is found in other vertebrates. We also examined the distribution of several neurotransmitter markers (tyrosine hydroxylase, neuropeptide Y, dopamine‐β‐hydroxylase, and serotonin) in the olfactory bulb. Antibodies to neuropeptide Y, dopamine‐β‐hydroxylase, and serotonin labeled fibers in the olfactory bulb and cell bodies in caudal regions of the brain in distributions comparable to other species. Tyrosine hydroxylase immunoreactivity was observed in a set of intrinsic bulb neurons with extensive processes in the glomerular layer. In addition, the structural proteins glial fibrillary acidic protein and vimentin have distributions similar to those in the olfactory bulbs of other animals. Thus, the adult olfactory structures are analogous to the structures in other vertebrate animals in morphology and chemical neuroanatomy. This similarity, along with its numerous advantages for developmental studies, makes the zebrafish a good model for studies of olfaction and forebrain maturation. © 1995 Wiley‐Liss, Inc.
Acutely isolated and cultured cells from the electrosensory lateral line lobe of a gymnotiform teleost
Authors: Turner Ray W. , Borg Laurie L.
Published: January 2005

The present study established the morphological and immunocytochemical criteria necessary to identify neuronal and nonneuronal cells after dissociating select regions of the medullary electrosensory lateral line lobe of adult weakly electric fish (Apteronotus Zeptorhynchus). Cells dissociated from the pyramidal cell body layers of the centromedial and lateral segments exhibited similar characteristics in the acutely dissociated preparation and up to 14 days in culture. Basilar and nonbasilar pyramidal cells were tentatively identified according to a bipolar or monopolar process extension, and polymorphic cells by the extension of three or more processes and positive immunoreactivity for gamma‐aminobutyric acid. Nonneuronal cells were identified by the pattern of process arborization and positive immunolabel for gamma‐aminobutyric acid or glial fibrillary acidic protein. Neuronal cells increased in total number over the first 4 days and could appear for the first time on any day in culture. Individual pyramidal cells could maintain their morphology from the time of dissociation and over several days in culture. Pyramidal cell processes were phenotypically similar to apical and basal dendrites found in situ but were reduced in size and in the degree of process branching. These results indicate that dissociated adult apteronotid neurons can maintain a morphology sufficiently similar to that found in situ as to allow tentative identification, opening up a wide range of possibilities for studying the electrophysiological and regenerative properties of electrosensory neurons. © 1995 Wiley‐Liss, Inc.
Arcuate nucleus neurons that project to the hypothalamic paraventricular nucleus: Neuropeptidergic identity and consequences of adrenalectomy on mRNA levels in the rat
Authors: Baker Ross A. , Herkenham Miles
Published: January 2005

The possible role that the hypothalamic arcuate nucleus might play in mediating the increase in paraventricular nucleus corticotropin‐releasing hormone mRNA levels following adrenalectomy was investigated in two series of experiments. In the first series, in situ hybridization histochemistry was used to quantify levels of eight arcuate nucleus neuropeptide and neurotransmitter mRNAs in neurons that potentially relay adrenal steroid feedback to the paraventricular nucleus. In the second series of experiments, arcuate neuropeptidergic projections to the hypothalamic paraventricular nucleus were characterized using retrograde tracing in combination with in situ hybridization histochemistry. Despite an increase in paraventricular nucleus corticotropin‐releasing hormone (60%) and pituitary proopiomelanocortin mRNA levels (sixfold), arcuate mRNA levels for proopiomelanocortin, neuropeptide Y, somatostatin, galanin, dynorphin, tyrosine hydroxylase, glutamate decarboxylase, and the glucocorticoid receptor were unchanged 14 days following adrenalectomy. Neuropeptidergic characterization of arcuatoparaventricular projections was achieved by injection of the retrograde tracer fluorogold into the paraventricular nucleus; retrogradely labeled neurons were characterized with polyclonal antisera against fluorogold in combination with oligonucleotide probes directed against neuropeptide Y, proopiomelanocortin, or somatostatin. Out of these three arcuate neuropeptides, neuropeptide Y mRNA was contained in 18% of the fluorogold‐positive neurons in the arcuate, proopiornelanocortin mRNA was contained in 8%, and somatostatin mRNA was contained in 6%. Overall, the results from both experiments suggest that the arcuatoparaventricular neuropeptide Y, proopiomelanocortin, and somatostatin projections are not sensitive to a chronic (14 day) lack of adrenal steroids. These projections as well as the other arcuate neurotransmitter and neuropeptide systems appear not to contribute to the persistent elevations in paraventricular nucleus corticotropin‐releasing hormone mRNA levels or pituitary proopiomelanocortin mRNA levels found in 14 day adremlectomized rats. © 1995 Wiley‐Liss, Inc.

This article is a US Government work and, as in the public domain in the United States of America.