bluuebunny/crossref_metadata_2025_split huggingface dataset:
Adrenal steroids regulate postnatal development of the rat dentate gyrus: II. Effects of glucocorticoids and mineralocorticoids on cell birth
Authors: Gould Elizabeth , Woolley Catherine S. , Cameron Heather A. , Daniels Deborah C. , McEwen Bruce S. 
Published: January 2005

AbstractUnlike the majority of mammalian brain regions, the rat dentate gyrus undergoes maximal cell birth and cell death during the same developmental time period. Granule cell birth and death peak at the end of the first postnatal week. We have found that manipulations of glucocorticoid levels during the stress hyporesponsive period profoundly influence the density of pyknotic cells in the dentate gyrus while apparently not affecting the density of healthy cells. This raises the possibility that glucocorticoids are regulating processes in addition to cell death, i.e., cell birth. In order to determine whether increases in circulating glucocorticoids or mineralocorticoids affect the birth of cells in the developing dentate gyrus, 3H‐thymidine autoradiography was performed on brains of rat pups treated with either corticosterone or aldosterone during the first postnatal week. Quantitative analysis of 3H‐thymidine‐labelled cells revealed significant decreases in the density of labelled cells in the granule cell layers with both corticosterone and aldosterone treatment. In these same brains, significant decreases in the density of pyknotic cells were also observed in the granule cell layers. However, no changes in the numbers of 3H‐thymidine‐labelled pyknotic cells were observed with any treatment. Increases in circulating corticosterone or aldosterone resulted in significant increases in the density of both 3H‐thymidine‐labelled and pyknotic cells in the hilus. These results suggest that dentate gyrus cell birth and cell death are related and that these processes are regulated by adrenal steroids.
Relationships between neuronal birthdates and cytoarchitecture in the rat inferior olivary complex
Authors: Bourrat Franck , Sotelo Constantino 
Published: January 2005

AbstractThe correlation between birthdates of neurons and their ultimate location within the inferior olivary nucleus (ION) was investigated in the rat by the 5‐bromodeoxyuridine (BrdU) method. We performed injections every 4 hours throughout the ION generation period, and were thus able to demonstrate that (1) neurons are distributed in the adult ION following characteristic gradients that define subdivisions identical to those established by hodological studies; and (2) ION neurons born at the same time tend to be arrayed in small clusters in the adult structure. Implications of these findings for the mechanisms of olivary neuron migration, selective aggregation, and elaboration of projectional topography are discussed. This study provides direct evidence that one of the factors governing the elaboration of the cytoarchitecture of a neuronal nucleus is the temporal sequence of generation of its neurons.
Ultrastructure and synaptic organization of axon terminals from brainstem structures to the mediodorsal thalamic nucleus of the rat
Authors: Kuroda Masaru , Price Joseph L. 
Published: January 2005

AbstractThe ultrastructural characteristics and synaptic organization of afferent terminals from the brainstem to the mediodorsal thalamic nucleus (MD) of the rat have been studied with the electron microscope, by means of anterograde transport of wheat germ agglutinin‐horseradish peroxidase (WGA‐HRP).Labeled fibers were seen predominantly in the lateral portion of MD after the injections of WGA‐HRP into the substantia nigra pars reticulata (SNr), the superior colliculus (SC), and the dorsal tegmental region (DT). The boutons arising from the SC were relatively small (< 1.5 μm in diameter), formed asymmetric synaptic contacts with small dendrites and dendritic spines, and contained round synaptic vesicles. The axon terminals from the DT were mostly large boutons (2–4.5 μm) with asymmetric synaptic specializations and round vesicles. These boutons and their postsynaptic targets formed synaptic glomeruli that were entirely or partially ensheathed by glial lamellae. The ultrastructural features are almost identical to those of boutons in the medial and central segments of MD that were previously shown to originate from the basal amygdaloid nucleus and the piriform cortex. The boutons from the SNr had a wide range in size, but the majority were medium‐sized to large (1.5–4 μm). The nigral boutons established symmetric synaptic contacts with dendritic shafts and occasionally with somata, and contained pleomorphic vesicles. However, like the DT terminals, they participated in glomerular formations. The nigral terminals closely resemble previously described terminals in the medial part of MD from the ventral pallidum, except that the nigral terminals formed en passant and axosomatic synapses as well as axodendritic synapses.A combined immunohistochemistry and WGA‐HRP tracing study revealed that the nigral inputs were immunoreactive for glutamic acid decarboxylase and the axon terminals from the DT were immunoreactive for choline acetyltransferase. In a separate study, the colliculothalamic fibers have been shown to take up and transport the transmitter specific tracer [3H]‐D‐aspartate, and are therefore putatively glutamatergic and/or aspartatergic. Taken together: with this, the present results suggest that the collicular afferents are excitatory and glutamatergic and/or aspartatergic, that the inputs from the DT are also excitatory and cholinergic, while the nigral inputs are inhibitory and GABAergic.
Receptor‐mediated retrograde transport in CNS neurons after intraventricular administration of NGF and growth factors
Authors: Ferguson Ian A. , Schweitzer John B. , Bartlett Perry F. , Johnson Eugene M. 
Published: January 2005

AbstractRadiolabel tracer techniques were used to follow the distribution of nerve growth factor (NGF) and other neuromodulatory factors after intraventricular injection. Autoradiography showed that shortly after intraventricular injection of radio‐iodinated NGF (125I‐NGF), substantial amounts of radioactivity had penetrated the ventricular wall surfaces; this binding was transient and nonspecific. The 125I‐NGF was progressively cleared from the central nervous system (CNS), presumably via the flow of cerebrospinal fluid (CSF) into the blood. A relatively small proportion of the injected 125I‐NGF was taken up by NGF receptor‐positive neurons in the CNS. Retrograde accumulation of radiolabel was observed within the basal forebrain cholinergic neurons at 5 hours after intraventricular injection. Labeling intensity was maximal at 18 hours and much reduced by 30 hours. This labeling was blocked by co‐injection of an excess of unlabeled NGF. Specific and saturable retrograde labeling was also observed within other NGF receptor‐bearing neurons, including the prepositus hypoglossal nucleus and the raphe obscurus nucleus. When epidermal growth factor (EGF), transforming growth factor‐β1 (TGF‐β1), platelet‐derived growth factor‐AA (PDGF‐AA), PDGF‐BB, leukemia inhibitory factor (LIF), insulin‐like growth factor‐I (IGF‐I), or IGF‐II was radiolabeled and injected intraventricularly, specific labeling of neurons was observed for 125I‐IGF‐II and 125I‐LIF within separate subpopulations of the dorsal and medial raphe. No retrograde accumulation within neurons was observed for EGF, TGF‐β1, PDGF‐AA, PDGF‐BB, or IGF‐I. This study describes an in vivo method for identifying putative neuromodulatory factors and their responsive neurons.
Cholinergic neurons in the rat septal complex: Ultrastructural characterization and synaptic relations with catecholaminergic terminals
Authors: Milner Teresa A. 
Published: January 2005

AbstractPhysiological and pharmacological studies have suggested that catecholamines modulate cholinergic neurons in the medial septal and diagonal band nuclei (i.e., the septal complex). Thus, the ultrastructural morphology of neurons containing choline acetyltransferase (ChAT), the biosynthetic enzyme for acetylcholine, and their relation to catecholaminergic terminals exhibiting immunoreactivity for the catecholamine synthesizing enzyme tyrosine hydroxylase (TH) were examined in the rat septal complex. Dual immunoautoradiographic and peroxidase anti‐peroxidase labeling methods were used to simultaneously localize antibodies raised in rabbits against TH and from rat‐mouse hybridomas against ChAT in single sections. At least two types of perikarya with ChAT‐immunoreactivity (ChAT‐I) were observed. The first type were large (20–30 μm), elongated or round, and contained a small indented nucleus with an abundant cytoplasm and an occasional lamellar body. The second type was also either ovoid or round but was medium‐sized (15–20 μm) and contained a larger indented nucleus and a smaller amount of cytoplasm than the first type. Both types of perikarya as well as dendrites with ChAT‐I were surrounded by astrocytic processes apposed to most of their plasmalemmal surfaces. The distribution and types of terminal associations (i.e., asymmetric synapses, symmetric synapses and appositions which lacked a membrane specialization in the plane of section analyzed) with, ChAT‐labeled perikarya and dendrites were quantitatively evaluated. The majority (68% of 197) of the presynaptic terminals were unlabeled; the remaining terminals were immunoreactive for TH (25%) or ChAT (7%). All three types of terminals contacted primarily the shafts of small dendrites and more rarely ChAT‐labeled perikarya and large dendrites.ChAT‐labeled terminals: (1) formed associations with unlabeled perikarya and dendrites (31% of 176); (2) formed associations with perikarya and dendrites with ChAT‐I (7%); (3) contacted the same unlabeled perikarya and dendrite as a TH‐containing terminal (21%); (4) were in apposition to TH‐labeled terminals (25%); or (5) were either in apposition to unlabeled or ChAT‐labeled terminals or lacked associations with any processes. The majority of associations formed by the terminals with ChAT‐I were on the shafts of small dendrites. Moreover, most of the associations formed were either symmetric synapses or appositions not separated by astrocytes in the plane of section analyzed.These findings provide cellular substrates in the septal complex (1) for sparse synaptic input relative to astrocytic investment of cholinergic neurons and (2) for direct synaptic modulation of cholinergic and non‐cholinergic neurons by catecholamines and/or acetylcholine. These findings have direct relevance to catecholaminergic‐cholinergic interactions and to the neuropathological basis for Alzheimer's disease.
Development of the olfactory bulb in the clawed frog,Xenopus laevis: A morphological and quantitative analysis
Authors: Byrd Christine A. , Burd Gail D. 
Published: January 2005

AbstractThe relationship between olfactory axons and the cells of the olfactory bulb during normal development was analyzed to determine whether olfactory afferent axons could play a role in the induction of olfactory bulb formation. The morphology of the olfactory bulb in Xenopus larvae from stages 26 to 58 and in adult frogs was analyzed with light and electron microscopy. Axons were first observed beneath the basal lamina of the neural tube at stages 30 and 32; at stage 32, neurons in this area of the neural tube began to differentiate. Synapses of olfactory axons onto young neuronal processes were observed as early as stages 36 and 38. By stage 44, all of the layers of the olfactory bulb were present. The basic structure of the mature form of the olfactory bulb was apparent as early as stage 48/49 and remained constant throughout late larval life and even into adulthood, with only the size increasing.To determine the numerical relationship between olfactory axons from both main and vomeronasal epithelia and mitral/tufted cells in the main and accessory olfactory bulbs, a quantitative study was also performed in which the number of olfactory axons and the number of mitral/tufted cells were estimated for larval stages (stages 50 to 58) and adults. The number of axons increased with stage, with a 16‐fold increase between stage 58 and adulthood. The number of mitral/tufted cells increased with stage, with only a 2.3‐fold increase between stage 58 and adults. There is a correlation between axon number and mitral/tufted cell number during larval development that is consistent with the hypothesis that olfactory axons influence olfactory bulb development. The convergence ratio of olfactory axons onto mitral/tufted cells was 5:1 in larvae and increased to 34:1 in adults; this increase probably results in increased olfactory sensitivity in adult frogs.
Major differences in CNS sulfonylurea receptor distribution between the rat (newborn, adult) and turtle
Authors: Xia Ying , Haddad Gabriel G. 
Published: January 2005

AbstractOur previous results have shown that KATP channels play an important role in K+ efflux and extracellular K+ accumulation in the rat brain, and this role was quantitatively more important in the adult than in the newborn brain. The purpose of this study was to localize by autoradiographic techniques the binding sites of glibenclamide, a potent sulfonylurea ligand that targets KATP channels, in the adult and newborn fat central nervous system (CNS). Since the adult turtle is resistant to anoxia, we also compared the rat to the turtle brain sulfonylurea receptor distribution. In all three animal groups (newborn rat, adult rat, adult turtle), specific glibenclamide binding was saturable. Scatchard plots were curvilinear in the rat, thus suggesting that glibenclamide binds to two types of sites, i.e., high and low affinity sites. Scatchard analysis on turtle brain tissue showed evidence of one binding site only, We also found that the distribution of glibenclamide binding sites was heterogeneous in the adult rat CNS with a higher density in rostral than in caudal regions. The highest binding densities were seen in the cortex, hippocampus, cerebellum, substantia nigra, and a few thalamic nuclei; intermediate densities were observed in the basal ganglia, septum, thalamus, and the hypoglossal nucleus. There was a low density in most areas of the hypothalamus, midbrain, brainstem, and spinal cord. Compared with the adult rat, the newborn had a very homogeneous distribution of binding sites and densities were very low throughout the CNS; the level of binding density was even lower and in some regions undetectable in the adult turtle. Our results indicate that (1) there are high and low affinity sulfonylurea receptors in the rat CNS, (2) there is a striking heterogeneity in the distribution and density of sulfonylurea receptors in the adult rat CNS and this is in sharp contrast to the homogeneous distribution and low density in both newborn rat and adult turtle; (3) sulfonylurea receptors increase in number postnatally in the rat since binding density increases and the Kd in the newborn rat is similar to that in the adult rat. We speculate that KATP channels and sulfonylurea receptors are poorly developed in the turtle and develop mostly after birth in the rat, reaching highest density in adulthood.
Ramifications of the axons of AH‐neurons injected with the intracellular marker biocytin in the myenteric plexus of the guinea pig small intestine
Authors: Bornstein J. C. , Hendriks R. , Furness J. B. , Trussell D. C. 
Published: January 2005

AbstractThe projections and terminal ramifications of electrophysiologically characterized myenteric neurons of the guinea pig small intestine were studied after intracellular injection of the marker substance biocytin. Myenteric neurons were impaled with microelectrodes containing 4% biocytin in 2 M KCl (pH 7.4) and characterized electrophysiologically as either AH‐neurons or S‐neurons. AH‐neurons were neurons in which action potentials were followed by prolonged after‐hyperpolarizations (lasting >4 seconds). S‐neurons were neurons in which such hyperpolarizations were not seen. Electrical stimulation of internodal strands evoked prominent fast excitatory synaptic potentials in S‐neurons, but not in AH‐neurons. Biocytin was injected electrophoretically into the impaled AH‐neurons by passage of hyperpolarizing current (0.6–0.8 nA for 5–15 minutes) through the recording electrode. The preparation was then fixed in Zamboni's fixative, dehydrated, and exposed to avidin coupled to horseradish peroxidase which allowed the injected biocytin to be visualised via a diaminobenzidine reaction. In many cases, the injected biocytin appeared to fill all the processes of injected AH‐neurons that ramified within the myenteric plexus. The filled processes included axons running up to 4 mm within the plexus and profuse varicose terminals ramifying within both the ganglion containing the injected cell body and nearby ganglia. Most (90%) cell bodies of the injected AH‐neurons had the morphology of Dogiel type II neurons; large, mostly smooth cell bodies with few short processes and several long processes. The other 10% of the AH‐neurons had similar cell bodies and long processes but also had prominent short filamentous processes. This population was termed dendritic AH‐neurons. The projections and terminals of 28 AH/Dogiel type II neurons and 7 dendritic AH‐neurons were analysed in detail. Both types of neurons project circumferentially to provide terminals to nearby ganglia, but the AH/Dogiel type II neurons also provide terminals to their own ganglia while the dendritic AH‐neurons typically do not. Although many of the injected AH‐neurons had projections orally or anally along the intestine no evidence for a preferential direction of projection was obtained. Analysis of the areas and distributions of the terminal fields of the AH/Dogiel type II neurons suggests that each may contact several other myenteric neurons and that each myenteric neuron may receive input from about ten AH/Dogiel type II neurons.
Receptive field properties of somatosensory neurons in the cat superior colliculus
Authors: Clemo H. Ruth , Stein Barry E. 
Published: January 2005

AbstractIn general, knowledge of the internal organization of receptive fields has played an important role in shaping current understanding of sensory physiology. Such knowledge is particularly important for understanding the function of the superior colliculus, since this structure is at once implicated in spatial localization and has relatively large receptive fields. While this issue has been addressed in the visual and auditory modalities represented in the superior colliculus, there are no previous studies of its somatosensory receptive field organization. Here, the properties of somatosendory receptive fields in the cat superior colliculus were studied quantitatively to determine whether they contain internal non‐homogeneities that might aid in the determination of stimulus detail. Of special interest was the possibility that these comparatively large receptive fields would contain areas of differential excitability that could aid in spatial resolution, that within‐field spatial summation and/or inhibition would be exhibited, and that the borders of the excitatory receptive field would be flanked by inhibitory regions. The data demonstrate that while inhibition beyond the receptive field borders is a rarity, these somatosensory receptive fields nearly always contain a well‐defined area of maximal sensitivity within which the size of the stimulus is a critical feature in determining the magnitude of the response. These best areas are systematically distributed across receptive fields as a function of their location in the structure, and indicate that the resolution of stimulus location and size may be greater than expected on the basis of receptive field size alone.
Organization of the superior olivary complex in the guinea pig. I. Cytoarchitecture, cytochrome oxidase histochemistry, and dendritic morphology
Authors: Schofield Brett R. , Cant Nell B. 
Published: January 2005

AbstractThe superior olivary complex is a prominent component of the auditory system. It consists of the lateral and medial superior olivary nuclei and a large number of smaller cell groups known as the periolivary nuclei, which are sources of both ascending and descending projections. The goal of this study was to establish criteria for identifying the periolivary nuclei in the guinea pig. Use of Nissl stains, the Golgi impregnation technique, and cytochrome oxidase histochemistry allowed us to distinguish eleven periolivary nuclei on the basis of differences in the types of cells they contain, in the distribution of cell types, and in the cytochrome oxidase staining characteristics of both the cells and the neuropil. The nuclei, named according to their position with respect to the lateral and medial superior olivary nuclei, can. be divided into four groups: (1) a lateral group comprising the lateral nucleus of the trapezoid body and the anterolateral and posteroventral periolivary nuclei, (2) a dorsal group comprising the dorsal and dorsolateral periolivary nuclei, (3) a ventral group comprising the ventral nucleus of the trapezoid body and the anteroventral, ventromedial and rostral periolivary nuclei, and (4) a medial group comprising the medial nucleus of the trapezoid body and the superior paraolivary nucleus. Cytological distinctions among the periolivary nuclei are consistent with other evidence that they serve different functions and highlight the need for detailed study of their connections, immunocytochemistry and physiological response properties.
Morphometric analysis of phrenic motoneurons in the cat during postnatal development
Authors: Cameron William E. , He F. , Kalipatnapu P. , Jodkowski J. S. , Guthrie R. D. 
Published: January 2005

AbstractThe dendritic geometry of 20 phrenic motoneurons from four postnatal ages (2 weeks, 1 and 2 months, and adult) was examined by using intracellular injection of horseradish peroxidase. The number of primary dendrites (∼ 11∼12) remained constant throughout postnatal development. In general, postnatal growth of the dendrites resulted from an increase in the branching and in the length and diameter of segments at all orders of the dendritic tree. There was one exception. Between 2 weeks and 1 month, the maximum extent of the dendrites increased in parallel with the growth of the spinal cord; however, there was no increase in either combined dendritic length or total membrane surface area. In addition, there was a significant decrease in the number of dendritic terminals per cell (59.8 ± 9.3 vs. 46.4 ± 7.4 for 2 weeks and 1 month, respectively).The distance from the soma, where the peak number of dendritic terminals per cell occurred, ranged from 700–900 μm at 2 weeks and 2 months to 1,300–1,700 μm in the adult. The diameter of dendrites as a function of distance from the soma along the dendritic path increased with age. The process of maturation tended to increase the distance from the soma over which the surface area and dendritic trunk parameter (∑d1.5/D1.5) remained constant. The three‐dimensional distribution of dendrites was analyzed by dividing space into six equal volumes or hexants. This analysis revealed that the postnatal growth in surface area in the rostral and caudal hexants was proportionately larger than that in either the medial, lateral, dorsal, or ventral hexants. Strong linear correlations were found between the diameter of the primary dendrite and the combined length, surface area, volume, and number of terminals of the dendrite at all ages studied.