bluuebunny/crossref_metadata_2025 huggingface dataset:
Early stages in the formation of the cerebellum in the frog
Authors: Uray Nándor J.
Published: January 2005

The formation of the cerebellum was studied during the first 6 months of the tadpole stage of the bullfrog by using standard histological methods and reconstructions from serial horizontal sections.

Three major developmental phases were noted in the formation of the cerebellum. (1) During the first 5 weeks of development, the neuroepithelium proliferated and the dorsal metencephalic plates increased in size. (2) Starting in the sixth week, a patch of neuroepithelium began to differentiate and gave rise to a small population of Purkinje cells. In subsequent weeks, the area of differentiation continued to spread and a Purkinje cell layer became established along the dorsal margin of the cerebellar plate. (3) In the 12th week, the ventrolateral part of the cerebellar plate began to increase in size and generate two populations of small cells. The lateralmost part of the neuroepithelium in this area generated a group of cells that formed an external granular layer that was one cell deep. Cells of this external granular layer migrated inward into the primitive molecular layer, and by the 26th week only a remnant of an external granular layer remained in the cerebellum. The more medially situated part of the neuroepithelium gave rise to another population of small cells that formed a column, which appeared to be continuous with the Purkinje cells, but differed from them in size. It should be noted that full maturation of the cerebellum occurs during metamorphosis, which in this species remains some 2 years away.
Morphology of identified interneurons in the CA1 regions of guinea pig hippocampus
Authors: Schwartzkroin Philip A. , Kunkel Dennis D.
Published: January 2005

Identified interneurons in the CA1 region of guinea pig hippocampus were examined using light and electron microscopic (EM) techniques. The HRP was intracellularly injected into cells, recorded in the in vitro slice preparation, which met physiological criteria for interneurons. These neurons were characterized at the light and electron microscopic level, and used as standards for identifying interneurons which had not been HRP‐labeled. Pyramidal basket cell somata were found in stratum oriens and stratum pyramidale; they were easily identifiable by their convoluted nucleus, dense endoplasmic reticulum, and numerous organelles. Aspinous dendrites reached into strata radiatum and lacunosum/moleculare, as well as ramifying within stratum oriens, where they received profuse synaptic input (primarily asymmetric synapses). Many of the asymmetric synapses degenerated following commissural lesions, suggesting that much of the input to interneurons was from extrinsic afferents. Dendrites were characterized by their spindled appearance, especially at distal sites. They showed postsynaptic degenerative changes following commissural lesions. Interneuron axons were extremely fine, with regular enlargements or “beads” which made apparent synaptic contacts primarily on pyramidal cell somata. The axon of a single, HRP‐injected interneuron made many apparent contacts on large numbers of pyramidal cells; axons arborized over distances of several hundred micra within stratum pyramidale.

This study provides direct evidence that neurons, with an identified inhibitory interneuron function in hippocampus, can mediate feed‐forward as well as feed‐back (recurrent) inhibition. Interneuron output showed extreme divergence, with influence over large distances. The high density of intracellular organelles in these cells suggested high metabolic activity and demand, perhaps making these interneurons exceptionally vulnerable to trauma‐induced damage.
Neuronal death and synapse elimination in the olivocerebellar system. II. Cell counts in the inferior olive of adult X‐irradiated rats and weaver and reeler mutant mice
Authors: Shojaeian Hadi , Delhaye‐Bouchaud Nicole , Mariani Jean
Published: January 2005

Cell death in the developing rat inferior olive precedes the regression of the polyneuronal innervation of Purkinje cells by olivary axons (i.e., climbing fibers), suggesting that the involution of the redundant olivocerebellar contacts is caused by a withdrawal of supernumerary axonal collaterals rather than by degeneration of the parent cell. However, a subsequent apparent increase of the olivary population occurs, which could eventually mask a residual presynaptic cell death taking place at the same time. Therefore, cell counts were performed in the inferior olive of adult rodents in which the multiple innervation of Purkinje cells by olivary axons is maintained, with the idea that if cell death plays a role in the regression of supernumerary climbing fibers, the number of olivary cells should be higher in these animals than in their controls. The results show that the size of the cell population in the inferior olive of weaver and reeler mutant mice and rats degranulated by early postnatal x‐irradiation does not differ significantly from that of their controls. Similarly, the distribution of the cells in the four main olivary subnuclei is not modified in weaver mice and x‐irradiated rats. The present data further support the assumption that the regression of the polyneuronal innervation of Purkinje cells occurs independently of cell death in the presynaptic population.
6‐OHDA‐Induced ectopia of external granule cells in the subarachnoid space covering the cerebellum. III. Morphology and synaptic organization of ectopic cerebellar neurons: A scanning and transmission electron microscopic study
Authors: Sievers Jobst , Mangold Ulrich , Berry Martin
Published: January 2005

The present report describes the ultrastructure, surface morphology, and synaptic connectivity of ectopically placed cerebellar neurons after treatment of newborn rats with 100 μg 6‐hydroxydopamine (6‐OHDA), administered intracisternally. In addition to granule cells which form the majority of ectopic neurons, neurons exhibiting the ultrastructure of basket/stellate cells are found in the subarachnoid space over the cerebellum. The ectopic neurons present an almost complete spectrum of homologous efferent and afferent connections. Parallel fiber synapses are found on thorns of spiny branchlets of Purkinje cell dendrites which also have grown out into the subarachnoid space, and on the somata and dendrites of basket/stellate cells. Many ectopic parallel fibers are seen to pass into the molecular layer of the underlying cerebellar cortex through defects in the pial surface, presumably connecting with intracortical postsynaptic partners. Synapses between ectopic Purkinje cell dendrites and basket/stellate cell axons are also observed; however, the source of these axons remains uncertain. Granule cell dendrites are engaged in glomeruli with mossy fibers. Moreover, ectopic granule cell colonies are densely innervated by noradrenergic fibers. Our results show that the technique of generating ectopia of external granule cells provides an additional model for investigating influences of epigenetic factors on the development of nerve cells.
Aging in the rat medial nucleus of the trapezoid Body. II. Electron microscopy
Authors: Casey Michael A. , Feldman Martin L.
Published: January 2005

The medial nucleus of the trapezoid body (MTB), the largest cell group of the rat superior olivary complex, was studied ultrastructurally in five groups of rats ranging in age from 2 to 33 months. Relatively little aging pigment (lipofuscin) accumulates intraneuronally, even in rats aged 33 months. The heaviest accumulation of age pigment is in glial and perivascular cells of the MTB. In rats aged 24–33 months, there is evidence of axonal and dendritic degeneration in the MTB neuropil. Aged rats also show evidence of degeneration of nerve endings. This includes the loss of calycine axosomatic terminals synapsing with MTB principal cells. All of the ultrastructural changes observed in the MTB gradually increase in frequency with advancing age.
Ultrastructural study of cholecystokinin‐immunoreactive cells and processes in area CA1 of the rat hippocampus
Authors: Harris Kristen M. , Marshall Patricia E. , Landis Dennis M. D.
Published: January 2005

We used light and electron microscopic immunocytochemical methods to examine the structure of neuronal perikarya and processes containing cholecystokinin‐like immunoreactivity (CCK‐IR) in area CA1 of the rat hippocampus. The morphology of stained perikarya, their positions within all laminae, and the orientation of their dendrites indicate that CCK‐IR is located in interneurons. These cells were seen in the electron microscope to have deeply folded nuclei and to receive both symmetric and asymmetric synaptic junctions on their cell somata and dendritic shafts. Their dendrites are essentially spine‐free, but form bulges at the site of some asymmetric synaptic junctions. Axonal varicosities containing CCK‐IR make symmetric synaptic junctions with cell somata and dendritic shafts of both pyramidal and non‐pyramidal neurons. In addition, CCK‐IR varicosities form symmetric junctions with unstained non‐pyramidal neurons and with CCK‐IR cells, suggesting either recurrent innervation of one cell on itself or interaction between interneurons. The presence of CCK‐IR varicosities and synaptic junctions on pyramidal cells is in agreement with physiological data which indicate that CCK has a direct postsynaptic action. The observation of CCK‐IR varicosities forming synaptic junctions on non‐pyramidal cells suggests that CCK might also modify the response of interneurons.
The vasopressinergic innervation of the brain in normal and castrated rats
Authors: DeVries G. J. , Buijs R. M. , van Leeuwen F. W. , Caffé A. R. , Swaab D. F.
Published: January 2005

A detailed description is given of the distribution of vasopressin‐immunoreactive structures in the brain of intact adult male rats. By application of a modified immunocytochemical procedure, vasopressin‐ immunoreactive fibers were detected in many new areas.

In adult male rats which were castrated 15 weeks before death, vasopressin‐immunoreactive cell bodies had disappeared from the bed nucleus of the stria terminalis and the medial amygdaloid nucleus. No obvious changes were found in vasopressin‐immunoreactive cell bodies in other areas. Furthermore, a very strong reduction was seen in the density of vasopressin‐immunoreactive fibers in the olfactory tubercle, nucleus of the diagonal band and its immediate surroundings, ventral pallidum, basal nucleus of Meynert, lateral septum, septofimbrial nucleus, ventral hippocampal formation, amygdaloid area, pre‐ and supramammillary nucleus, supramam‐millary decussation, (inter)dorsomedial, parafascicular, and ventral aspect of paraventricular thalamic nuclei, zona incerta, lateral habenular nucleus, ventral tegmental area, substantia nigra, periventricular gray, dorsal and median raphe nucleus, and locus coeruleus. No changes were observed in other areas containing vasopressin‐immunoreactive fibers. These changes following gonadectomy were not observed in castrated rats which had been treated with testosterone.

The results suggest that vasopressin projections from the bed nucleus of the stria terminalis and possibly from the medial amygdaloid nucleus require the presence of gonadal hormones for their normal appearance. This is in contrast to pathways arising from the hypothalamic vasopressin‐producing nuclei, which fail to show obvious changes following castration.
Synaptic connections between the hindwing stretch receptor and flight motor neurones in the locust revealed by double cobalt labelling for electron microscopy
Authors: Peters Brian H. , Altman Jennifer S. , Tyrer N. Mark
Published: January 2005

Synaptic interactions between sensory and motor neurones in the locust flight system have been investigated by using intracellular labelling with cobalt and nickel for electron microscopy. Simultaneous axonal filling of two neurones with different concentrations of metal ions produces differential labelling, so that contacts between them in the central nervous system can be recognized. We have investigated the connectivity of the hindwing stretch receptor neurone (SR) with a direct hindwing depressor motor neurone (MN 127) known from physiological experiments to receive monosynaptic input from the SR, and an indirect hindwing depressor motor neurone (MN 112/1), for which no monosynaptic connection with the SR has been reported.

We have found no direct synapses between the SR and MN 112/1, although some of their branches lie close together in the neuropile. We have, however, found some evidence for polysynaptic connections between them.

There are many synapses of conventional dyadic morphology from both the lateral and mediolateral branches of the SR to MN 127; the medial branch was not examined. Those from the lateral branch contact the motor neurone on branches close to the neuropilar segment, while those from the mediolateral branch contact long, thin distal twigs. We estimate that there are about 600 anatomical synapses between these two neurones. Our results suggest that a large number of widely distributed anatomical synapses constitute the physiological synaptic connection between the SR and MN 127. The dyadic arrangement of these synapses provides an anatomical correlate for the physiologically established divergence of SR outputs onto interneurones and motor neurones.
A combined golgi and autoradiographic study of (3H)glycine‐accumulating amacrine cells in the cat retina
Authors: Pourcho Roberta G. , Goebel Dennis J.
Published: January 2005

Golgi techniques were combined with electron microscopic autoradiography to identify four subpopulations of amacrine cell in the cat retina which accumulate (3H)glycine. These subpopulations include types A3, A4, A7(AII), and A8 amacrine cells. All are narrow‐field cells with dendritic spreads of less than 100 μm. Quantification of silver grains showed that each subpopulation exhibits a consistent affinity for (3H)glycine. Type A8 cells were found to have the greatest affinity with normalized grain densities of 0.88–1.0 grains/μm2 on a scale in which 1.0 represents the most heavily labeled cell. Type A4 cells were moderately labeled with grain densities ranging from 0.40 to 0.68 grains/μm2. A7(AII) and A3 amacrines were lightly labeled with grain densities of 0.33–0.35 grains/μm2 and 0.28–0.30 grains/μm2, respectively.
Development of the subretinal space in the preterm human eye: Ultrastructural and immunocytochemical studies
Authors: Johnson A. Tim , Kretzer Frank L. , Hittner Helen M. , Glazebrook Pat A. , Bridges C. D. B. , Lam Dominic M. K.
Published: January 2005

To investigate the development of the subretinal space in the human infant, eyes were obtained from 12 live‐born, anomaly‐free, preterm infants from 20 to 32 weeks gestation and from one 3‐month postterm infant. The retinas were studied by light microscopy, electron microscopy, and immunocytochemistry. The immunocytochemical studies utilized rabbit antiserum against purified bovine interstitial retinol binding protein (IRBP). A subretinal space containing IRBP was present in the central retina at 20 weeks and extended further into the periphery (expressed as a percentage of the distance from the optic disc to the ora serrata in the temporal hemisphere) as the retina developed. At 28 weeks, IRBP was absent only from the most peripheral 25% of the retina and reached the temporal ora serrata at 32 weeks. At 3 months postterm, IRBP immunofluorescence outlined fully developed photoreceptors, which were present from the optic disc to the ora serrata. The appearance of IRBP in the subretinal space correlated with the development of the first photoreceptor outer segment discs.
Multiaxonal horizontal cells in the retina of the tree shrew, Tupaia glis
Authors: Mariani Andrew P.
Published: January 2005

The retinas of most vertebrates contain two or more morphologically distinct types of horizontal cell, and usually one of these types lacks an axon. Among mammals, in which two types are observed, primates are exceptional in that both types of horizontal cell have axons. It then seemed of interest to study the horizontal cells of tree shrews (Tupaia glis), insectivores thought to be closely related to primates. Golgi impregnations of whole, flat‐preparations revealed two types of horizontal cell. Uniaxonal cells have a compact dendritic organization with clusters of terminals, and a single thin axon with short collaterals and a few terminals, located along its length. Multiaxonal cells have a relatively large dendritic tree, and arising from the tips of about four to eight dendrites of an individual cell are thin axonlike processes which terminate as profusely branched telodendritic arborizations. This identification of the multiaxonal horizontal cells in Tupaia retina is the first time any vertebrate horizontal cell has been found to possess more than a single axon. A comparison of horizonal cells in tree shrew, monkey, cat, and squirrel retinas shows a remarkable morphological diversity within this class of mammalian retinal neuron.
Anterograde axonal transport and intercellular transfer of WGA‐HRP in trigeminal‐innervated sensory receptors of rat incisive papilla
Authors: Chan Kwan Y. , Byers Margaret R.
Published: January 2005

The ultrastructure and identification of WGA‐HRP‐labeled sensory receptors in the rat incisive papilla (the most anterior part of hard palate) were studied using semiserial thin sections. Various sensory receptors were organized according to three locations: dome region (ventral), chemosensory corpuscle region (medial to orifice of incisive canal), and lateral labium (apposing the incisive canal). In the dome region, the sensory receptors were localized in three sensory zones that were associated with surface ridges (one medial and two lateral). In each of these zones, intraepithelial receptor axons and Merkel receptors occurred in the epithelium, while simple unencapsulated corpuscles, glomerular‐Meissner corpuscles, and incisive (encapsulated) corpuscles occurred in the lamina propria. In the chemosensory corpuscle region, chemosensory corpuscles and intraepithelial receptor axons were located in the epithelium, and incisive corpuscles were present in the lamina propria. In the lateral labium, only intraepithelial receptor axons were prominent. In all these sensory receptors, the preterminal axons and axon terminals were labeled with the tracer protein. In addition, some nonneuronal cells closely associated with the axon terminals were selectively labeled, e.g., terminal Schwann cells, lamellar Schwann cells, Merkel cells, corpuscular basal cells, and chemosensory cells. Other adjacent cells were not labeled, e.g., unspecialized epithelial cells, capsular cells, corpuscular sustentacular cells, and fibroblasts. In both labeled axons and cells, WGA‐HRP was incorporated into vesicles, tubules, and vacuolar organelles. The specific intercellular transfer of tracer protein may indicate trophic interactions between axon terminals and support cells in sensory receptors. The specific organization of multiple sensory receptors in the rat incisive papilla may provide a useful alternative system for studying somatosensory physiology.
The pretectal nucleus Lentiformis mesencephali of Rana pipiens
Authors: Montgomery Neil M. , Fite Katherine V. , Grigonis Antony M.
Published: January 2005

The pretectal nucleus lentiformis mesencephali (nLM) of Rana pipiens was investigated with autoradiographic, horseradish peroxidase (HRP), and Golgi techniques. Retinal afferents to nLM originate primarily from the central retina. The primary projection is contralateral with a small ipsilateral component. Following optic nerve transection and HRP impregnation, contralateral retinal afferents show a restricted, dense core of HRP label in the superficial portion of the nucleus with sparser HRP label in the surround. Ipsilateral retinal afferents arborize throughout nLM, except in the dense‐core region. Additional afferents to nLM originate from the ipsilateral tectum, the nucleus rotundus, the mesencephalic pretectal gray, the contralateral nLM, and the nucleus of the basal optic root. Afferents from the accessory optic system arborize only in the dense‐core region, following HRP injections into the nucleus of the basal optic root, while afferents from the mesencephalic pretectal gray arborize in all parts of nLM except the dense core. Afferents from the tectum and anterior thalamus appear to arborize throughout the nucleus without discernible pattern.

The lamination of afferent terminals in nLM was correlated with Nissl‐stained cytoarchitectural material in which the majority of large neurons cluster around the dense core of nLM. Three types of neurons occur in nLM: large neurons (25‐μm dia.), fusiform neurons (12.5‐μm dia.), and stellate neurons (10‐μm dia.). Additionally, two cell groups outside nLM which send dendrites into the nucleus were observed: cells of the posterior lateral nucleus and cells of the posterior thalamic pretectal gray. Both large and fusiform neurone project to the deep layers of the optic tectum as well as to the ventral rhombencephalon superficial to the abducens nucleus. While a small number of fusiform neurons project to the nucleus of the basal optic root, the stellate neurons appear to be intrinsic to nLM.

The anuran nLM strongly resembles the nucleus of the optic tract in mammals in terms of the site of origin of its retinal afferents, lamination of afferent terminations, its central connections, and its demonstrated involvement in horizontal optokinetic nystagmus.
An investigation of cholinergic circuitry in cat striate cortex using acetylcholinesterase histochemistry
Authors: Bear Mark F. , Carnes Kenneth M. , Ebner Ford F.
Published: January 2005

The organization of cholinergic inputs to cat striate cortex (area 17) was studied by using a histochemical stain for acetylcholinesterase (AChE). Axons were labelled in all layers of the striate cortex, with distinct plexuses occurring in layer I, lower layer III, layer IVc, and layer VI. In addition to the stained axons, a population of layer V pyramidal cells was intensely AChE‐positive.

Surgical undercutting eliminated virtually all of the AChE‐positive axons in the striate cortex, thus indicating that this innervation arises entirely from an extrinsic source in the cat. To identify this source, cell groups projecting to area 17 were retrogradely labelled with horseradish peroxidase. Cell groups labelled with horseradish peroxidase that were also intensely AChE‐positive were considered as possible candidates for providing the cholinergic input to the striate cortex. These included the basal forebrain, several intralaminar nuclei, and the lateral geniculate nucleus. Kainate lesions were then made in each of these structures to assess their individual contributions to the cortical AChE pattern. Cortical AChE was depleted only after lesions of the basal forebrain, suggesting that this is the sole source of AChE‐positive axons in area 17. Because the cortically projecting cells in this region have been shown to contain choline acetyltransferase in a number of species, we postulate that the AChE‐positive fibers we describe in the cat striate cortex are in fact cholinergic.
Localization of serotonin immunoreactivity in the opossum cerebellum
Authors: Bishop Georgia A. , Ho Raymond H. , King James S.
Published: January 2005

We have used the indirect antibody peroxidase‐antiperoxidase technique to analyze (1) the course of serotonin (5‐hydroxytryptamine; 5HT) fibers to the deep cerebellar nuclei; (2) the distribution of serotonin within the nuclei; (3) the continued course of 5HT fibers to the cerebellar cortex; and (4) the lobular and laminar distribution of this indoleamine in the cerebellar cortex. Only rarely are fibers found in either the restiform body or the brachium pontis. However, a distinct bundle of serotoninergic axons is present in the medial aspect of the brachium conjunctivum. Axons arise from this bundle and course dorsally into the neuropil of the deep cerebellar nuclei. The densest immunostaining is present in posterior and ventral regions of all four cerebellar nuclei. Within the nuclei large (24% of total) and small (76% of total) varicosities are present. The average distance between varicosities on individual axons is 3.85 μm (S.D. = 1.2). The innervation of the cerebellar cortex is derived primarily from fibers that course through the deep nuclei. At levels caudal to the deep nuclei a single midsagittal band courses into lobules VIII and IX.

In the cerebellar cortex, serotoninergic axons and varicosities are present in all lobules; however, the fiber density is not uniform. The densest distribution is present in vermal lobule VIII and the dorsal folia of lobule IX. Within the granule cell layer of lobules VIII and IX, immunoreactive elements form a midsagittal band, and to a lesser degree, two parasagittal bands. Beaded serotoninergic fibers course through the deep and middle portion of the granule cell layer and give rise to a plexus at the border between the Purkinje cell and granule cell layers. Within this plexus axons extend long distances in the transverse and sagittal planes. Long beaded axons oriented in the transverse plane of the folia are also present in the deep molecular layer. A few radial serotoninergic fibers ascend to the pial surface and give rise to very short tangential branches. In all three cortical layers, both large (19% of total) and small (81% of total) varicosities are present. The average distance between varicosities on individual fibers is 5.3 μm (S.D. = 2.2).

In summary, these data have shown that (1) serotoninergic fibers enter the cerebellum via the brachium conjunctivum and form a dense plexus within the deep cerebellar nuclei; (2) there is a differential distribution of serotonin within these nuclei; (3) serotoninergic fibers pass through the deep nuclei and are topographically organized in their course to specific regions of the cerebellar cortex; (4) there is a differential distribution of serotonin to the various cortical lobules; (5) the densest distribution of serotonin within the cortex is to the Purkinje‐cell‐granule‐cell border; little immunoreactiveity is present in the molecular layer; and (6) this distribution is species specifie.
Morphology and laminar organization of electrophysiologically identified neurons in the primary auditory cortex in the cat
Authors: Mitani Akira , Shimokouchi Minoru , Itoh Kazuo , Nomura Sakashi , Kudo Motoi , Mizuno Noboru
Published: January 2005

The morphology of electrophysiologically identified neurons was examined in the primary auditory cortex (AI) of the cat. After stimulation of the medial geniculate nucleus (MG), second auditory cortex, posterior ectosylvian gyrus, contralateral AI, or corpus callosum, intracellular potentials were recorded from AI neurons, which were then injected intracellularly with horseradish peroxidase and recovered.

Layer IV neurons, which receive MG fibers monosynaptically, are spiny and nonspiny stellate cells, small and medium‐sized nonspiny tufted cells, and fusiform cells. They send their axons to layer III of the AI. Corticocortical AI neurons are medium‐sized pyramidal cells in layer III. They receive axons from layer IV neurons of the AI and send their axons to layers I, II, IV, and V of the AI. Horizontal cells in layer I receive slow‐conducting MG fibers monosynaptically, and send their axons to layer II of the AI. Stellate cells and small pyramidal cells in layer II receive afferent inputs polysynaptically from the MG. Layer II pyramidal cells receive afferent inputs from the MG via AI neurons in layers I and III, and send their axons to layers V and VI. The axons of layer II stellate cells were distributed within layer II. Pyramidal cells which send their axons to the MG are located in layers V and VI, distributing their axon collaterals to layers III–VI of the AI.
Trigeminal mesencephalic neurons innervating functionally identified muscle spindles and involved in the monosynaptic stretch reflex of the lateral pterygoid muscle of the guinea pig
Authors: Nozaki Shuichi , Iriki Atsushi , Nakamura Yoshio
Published: January 2005

Location of the neurons in the trigeminal mesencephalic nucleus innervating stretch receptors of the lateral pterygoid muscle and the mode of their synaptic connection on the lateral pterygoid motoneurons of the guinea pig were studied physiologically as well as morphologically, in comparison with the trigeminal mesencephalic neurons innervating muscle spindles in the superficial masseter muscle, with the following results: (1) stimulation of the caudal half of the trigeminal mesencephalic nucleus evoked monosynaptic excitatory postsynaptic potentials in the ipsilateral lateral pterygoid motoneurons. (2) Stimulation of the lateral pterygoid nerve directly evoked spike potentials in the neurons located in the caudal half of the ipsilateral trigeminal mesencephalic nucleus, which responded with increased firing to stretch, and with silent period to twitch, of the ipsilateral lateral pterygoid muscle. (3) Averaging of intracellular potentials of the lateral pterygoid motoneurons with extracellular spike potentials of these trigeminal mesencephalic neurons revealed excitatory postsynaptic potentials after a monosynaptic latency, but no inhibitory postsynaptic potentials. (4) Injection of horseradish peroxidase into the lateral pterygoid muscle labeled 15–20 cells in the caudal half of the ipsilateral trigeminal mesencephalic nucleus, while 174–228 cells retrogradely labeled by horseradish peroxidase were found throughout the whole rostrocaudal extent of the ipsilateral trigeminal mesencephalic nucleus following injection of horseradish peroxidase into the masseter muscle. It was concluded that neurons in the caudal half of the trigeminal mesencephalic nucleus send their peripheral processes to stretch receptors, presumably muscle spindles, in the ipsilateral lateral pterygoid muscle and that their central processes have excitatory synapses on ipsilateral lateral pterygoid motoneurons, thus comprising the afferent limb of a monosynaptic stretch reflex arc of the lateral pterygoid muscle of the guinea pig.
Topography of the retinal projection to the superficial pretectal parvicellular nucleus of goldfish: A cobaltous‐lysine study
Authors: Springer Alan D. , Mednick Adam S.
Published: January 2005

The retinal projection to the superficial pretectal parvicellular nucleus (SPp) of goldfish was examined by filling select groups of optic axons with cobaltous‐lysine. The tracer was applied intraocularly to peripheral retinal slits in some fish. In other fish, it was applied to optic axons from an intact hemiretina after one‐half of the retina was ablated and the corresponding optic axons had degenerated. The results indicated that SPp is a folded structure, having a dorsal surface innervated by axons from temporal retinal ganglion cells and a ventral surface innervated by axons from nasal retinal ganglion cells. Peripheral retina innervates the anterodorsal and anteroventral edges of SPp, while central retina innervates the posterior genu. Dorsal retina innervates lateral SPp and ventral retina innervates medial SPp. Thus, although SPp is a folded nucleus, the topography of the retino‐SPp projection is similar to the topography of the retinotectal projection. That is, the relative position of optic axons within SPp mirrors the retinal location of the ganglion cells that project to SPp. Retino‐SPp axons occupy the center of the main optic tract before it divides into the two optic brachia. These axons are topographically arranged, with temporal retino‐SPp axons being flanked on both sides by nasal retino‐SPp axons. Retino‐SPp axons arborize within SPp and then continue to enter the superficial tectal retinorecipient lamina. Thus, these axons innervate both SPp and the optic tectum. These findings are discussed with respect to chemospecific and morphogenetic views of visual system topography.
Substance P‐like immunoreactivity is present in the central nervous system of Limulus polyphemus
Authors: Mancillas Jorge R. , Selverston Allen I.
Published: January 2005

The distribution of substance P‐like immunoreactivity (substance P‐li) in the central nervous system of Limulus polyphemus was studied by using indirect immunocytochemical techniques. Six bilaterally symmetrical pairs of cell clusters in the circumesophageal connectives and the subesophageal mass contain substance P‐li. Two of those pairs are the source of a system of efferent fibers that is involved in the expression of circadian rhythms of photosensitivity by the lateral eye. Substance P‐li‐containing cells were also observed scattered along the length of the circumesophageal connectives, which contain abundant stained fibers and some terminals. Substance P‐li fibers leave through the ventral and dorsal nerves of the posterior circumesophageal ring. The neuropil of the subesophageal mass contains an abundance of stained terminals. Immunoreactive fibers can be seen throughout the length of the two longitudinal connectives of the ventral cord, in discrete fiber tracts in the lateral edges of the interganglionic connectives, and in the dorsal and ventral nerves of abdominal ganglia 1–4. Each of these ganglia contains three pairs of 3ubstance P‐immunoreactive cell body clusters: an anterolateral, a medial longitudinal, and a medial posterior cluster. Substance P‐li fibers entering through the ventral (posterior) nerves form very distinctive fascicles in each side of the ganglia, giving off fibers throughout their length. The neuropil is filled with immunoreactive terminals distributed homogeneously.

The anterolateral clusters of the abdominal ganglia may be involved in cardioregulation The six pairs of clusters in the posterior circumesophageal ring, and perhaps some of those in the abdominal ganglia, are believed to constitute a neurosecretory system, projecting to multiple targets throughout the organism. This system is postulated to modulate various sensory inputs and motor activity, and could be driven by a circadian clock, as well as by other systems responsible for integrated organismic responses.
The afferent and sympathetic components of the lumbar spinal outflow to the colon and pelvic organs in the cat. II. The lumbar splanchnic nerves
Authors: Baron R. , Jäunig W. , McLachlan Elspeth M.
Published: January 2005

The cell bodies of the lumbar sensory and sympathetic pre‐ and postganglionic neurons that project to the inferior mesenteric ganglion in the lumbar splanchnic nerves of the cat have been labeled retrogradely with horseradish peroxidase applied to the central end of their cut axons near the inferior mesenteric ganglion. The numbers, segmental distribution, location, and size of these labeled somata have been determined quantitatively. After all the lumbar splanchnic nerves on one side of an animal were labeled, most labeled cell bodies were situated ipsilaterally in dorsal root ganglia, ganglia of the lumbar sympathetic trunk, and spinal cord segments L2–L5, with the maximum numbers in L3 and L4. A few labeled somata lay contra‐laterally or rostral to L2. After labeling of only one lumbar splanchnic nerve, the majority of cell bodies were found in the labeled segment, but a few were also present up to three segments rostral or caudal. These variations could always be attributed to extraspinal connections usually via the lumbar sympathetic trunk. Cross‐sectional areas of labeled afferent somata were small relative to those of the entire population of dorsal root ganglion cells. Preganglionic cell bodies were labeled in the intermediate gray matter extending from its lateral border ventrolaterally across to the central canal. Two regions of high density were observed: one laterally just medial to the edge of the white matter and the other lateral to the central canal. The dorsolateral group lay somewhat medial and caudal to the usual limits of the intermediolateral column. Labeled preganglionic neurons were on the average larger than the unlabeled cells in the inferior mesenteric ganglion, with the group lying medially being larger than those that were laterally positioned. From the data, it is estimated that about 4,600 afferent axons, about 4,600 preganglionic axons, and about 2,800 postganglionic axons travel in the lumbar splanchnic nerves to the inferior mesenteric ganglion of the cat.
Plasticity of acid phosphatase (FRAP) afferent terminal fields and of dorsal horn cell growth in the neonatal rat
Authors: Fitzgerald Maria , Vrbová Gerta
Published: January 2005

Peripheral nerve section results in depletion of fluoride‐resistant acid phosphatase (FRAP) from the nerve terminals in the dorsal horn of the spinal cord (Schoenen et al., '68) and this has been used in the past to map the termination field of individual nerves (Rustioni et al., '71; Devor and Claman, '80). In the present study we show that a similar central depletion occurs following sciatic nerve section or crush in neonatal rats. Unlike adults, however, the area of depletion is rapidly filled by sprouting of FRAP‐containing afferent terminals from nearby intact peripheral nerves. The sprouting is extensive but never completely fills the depleted area. After nerve crush there is some recovery of FRAP from the sciatic nerve terminals themselves as well as from nearby nerve terminals. The source of recovered FRAP is demonstrated by resectioning or recrushing the nerves. The sprouting occurred when the sciatic was injured on day 1 but failed to take place when the injury was applied on or after day 10.

Sciatic nerve section on day 1 also produces marked growth retardation of the ipsilateral dorsal horn gray matter that becomes more apparent as the rat matures. Nerve crush produces a less marked shrinkage that is slower in onset. If the nerve is crushed repeatedly, however, so that regeneration is prevented, the shrinkage is analogous to that following nerve section. No shrinkage occurs if the nerve is cut or crushed on day 10.

The results show that separation of the spinal cord from its peripheral input at a critical stage in development results in disruption of the somatotopic organization of the C fibre afferent input to the dorsal horn and in slowing of growth of the dorsal horn gray matter.
Organization of motor pools supplying the cervical musculature in a cryptodyran turtle, Pseudemys scripta elegans. II. Medial motor nucleus and muscles supplied by two motor nuclei
Authors: Yeow M. B. L. , Peterson E. H.
Published: January 2005

In this paper we describe the medial motor nucleus of Pseudemys cervical spinal cord and the motor pools of three neck muscles that exhibit an unusual pattern of innervation. Cells of the medial motor nucleus form a longitudinal column at the dorsomedial gray/white border of the ventral horn from C1 through C8. In Nissl‐stained transverse sections they appear fusiform with prominent medially projecting dendrites; in HRP material these dendrites are seen to cross into the contralateral ventral funiculus. Medial nuclear cells vary in size (12–31 μm in diameter) and are often relatively large (>21 μm in diameter). They are significantly larger and more numerous in caudal than in rostral cervical segments.

Medial nuclear cells supply three of the cervical muscles examined in this study: mm. retrahens capitis collique (RCCQ), testocervicis, and longus colli. These three muscles differ from other cervical muscles in Pseudemys and from vertebrate limb muscles in that they are supplied in parallel by two populations of motor neurons: the medial and ventral motor nuclei (cf. Yeow and Peterson, '86). Ventral nuclear cells supplying these three muscles are organized into a musculotopic pattern with m. testocervicis motor neurons most medial and m. RCCQ motor neurons lateral; in contrast, the location of medial nuclear motor neurons is invariant with respect to muscle position. HRP‐positive medial nuclear cells are sometimes smaller (m. testocervicis) but more often are as large or larger (mm. RCCQ and longus colli) than ventral nuclear cells supplying the same muscles, thus suggesting that they supply extrafusal muscle fibers, perhaps different muscle unit types in the three muscles. Based on the morphology of medial nuclear cells and the probable actions of the muscles they innervate, we hypothesize that the medial motor nucleus may represent a discrete functional system for producing bilaterally synchronous muscle activation, and that this system is accessed by a subset of muscles in the cervical complex.
Hypothalamic and ventral thalamic projections to the superior colliculus in the cat
Authors: Rieck Richard W. , Huerta Michael F. , Harting John K. , Weber Joseph T.
Published: January 2005

The present report describes the organization of collicular afferents that arise within either the hypothalamus or the ventral thalamus. Following the placement of large injections of WGA‐HRP into the superior colliculus of the cat, retrogradely labeled neurons are located within the reticular nucleus of the thalamus, the zona incerta, the fields of Forel, and throughout the hypothalamus. Although the dorsal hypothalamic area contains the largest number of labeled hypothalamic neurons, labeled cells are also found within the periventricular, paraventricular, dorsomedial, ventromedial, posterior, lateral, and anterior hypothalamic nuclei. A strikingly similar pattern of distribution of labeled neurons is also observed following placement of small injections of WGA‐HRP that are restricted within the stratum griseum intermedium (SGI). In contrast, hypothalamic and ventral thalamic labeling is not seen after placement of injections within the stratum griseum superficiale. Following the placement of injections of tritiated anterograde tracers within the dorsal hypothalamic area, transported label is organized in two bands of clusters over the SGI. When injections of tritiated tracers are placed within the zona incerta, terminal label is also located over the SGI; however, the distribution of silver grains does not appear as clusters or distinct puffs. On the basis of the comparison of the cellular types that give rise to these projections and the differences in terminal distribution, we suggest that the hypothalamic and ventral thalamic projections to the superior colliculus are totally separate and unrelated pathways. The functional implications of the hypothalamotectal pathway are also discussed.
Immunocytochemical localization of luteinizing hormone‐releasing hormone (LHRH) pathways in the sheep brain during anestrus and the mid‐luteal phase of the estrous cycle
Authors: Lehman Michael N. , Robinson Jane E. , Karsch Fred J. , Silverman Ann‐Judith
Published: January 2005

The luteinizing hormone‐releasing hormone (LHRH) system of the sheep brain was examined by light microscopic immunocytochemistry with thick, unembedded sections. We compared the distribution and morphology of LHRH cells and their fibers in intact and ovariectomized anestrous ewes, and in breeding season ewes during the mid‐luteal phase of their estrous cycle. In all animals, a majority of LHRH neurons were found in the medial preoptic area adjacent to the organum vasculosum of the lamina terminalis. These cells formed a continuum rostrally with immunoreactive neurons in the diagonal band of Broca and medial septum and caudally with cells in the ventrolateral anterior hypothalamus and lateral hypothalamus. Relatively few cells (1–2%) were seen in the arcuate nucleus or its vicinity. Preoptic LHRH neurons project to the tubero‐infundibular sulcus of the median eminence by at least two routes: a major ventrolateral projection above the optic tract in the anterior and lateral hypothalamus, and a less prominent periventricular pathway along the third ventricle. LHRH fibers were also observed in a number of extrahypothalamic regions, including the medial amygdala and the accessory olfactory bulb.

Immunoreactive LHRH neurons in the sheep exhibited a complex light microscopic morphology unlike that seen in LHRH cells of any other species to date. LHRH cells with extensive, branching processes were frequently found in clusters with close somatic appositions between neighboring cells. Multiple thin protuberances emanated from the soma of many immunoreactive neurons. Immunoreactive fibers with beaded varicosities often were intimately associated with both cell bodies and their dendritic processes. Morphometric analyses revealed that preoptic LHRH neurons in three of four mid‐luteal phase ewes had a shorter total dendritic length than those neurons in either intact or ovariectomized anestrous ewes, but this difference between breeding season and anestrous ewes was not statistically significant. Evidence for possible seasonal and/or steroid‐induced alterations in the morphology of LHRH neurons must be documented by further studies, including immunocytochemical observations at an ultrastructural level.
Laminar distribution and patchiness of cytochrome oxidase in mouse superior colliculus
Authors: Wiener Sidney I.
Published: January 2005

The cytochrome oxidase (CO), acetylcholinesterase (AChE), myelin, and Nissl stains were studied and compared to develop an anatomical system identifying the laminar architecture of the mouse superior colliculus. The CO and myelin stains are shown to define collicular laminae more distinctly than does the Nissl stain. The layer of large rostrocaudally coursing fiber bundles that has formerly been referred to in the rodent literature as stratum album intermediale (SAI; layer V) is renamed as a sublayer of the stratum griseum intermediale (SGI; layer IV) to conform with the nomenclature for the cat superior colliculus of Kaneseki and Sprague ('74, J. Comp. Neurol. 158:319–338).

Patches of CO activity in layer IV (SGI) are shown that contain intensely stained, large, multipolar cell bodies. The CO patches do not correspond to those previously reported for AChE. The CO, myelin, and AChE stains all Indicate the presence of a large lateral extension termed the flank of layer IV (SGI). In contrast to the classical lamination pattern of the superior colliculus, the flank has no overlying layer II (stratum griseum superficiale, SGS) or layer III (stratum opticum, SO).
Delayed development of song control nuclei in the zebra finch is related to behavioral development
Authors: Herrmann Kathrin , Bischof Hans‐Joachim
Published: January 2005

The postnatal development of two visual areas (nucleus rotundus and ectostriatum) and two song control areas (hyperstriatum ventrale pars caudale, HVc, and nucleus robustus archistriatalis, RA) of the zebra finch brain was followed from birth to adulthood. The following parameters were investigated: (1) neuron size, (2) volume of the brain nuclei, and (3) myelination of axons. The nucleus rotundus, the diencephalic station of the tectofugal pathway, exhibits the fastest development: rotundal neurons reach their maximum size at 20 days of age; the volume of this structure reaches adult size at the same time. The process of myelination begins between day 5 and day 10 and is completed at 40 days of age. A similar temporal sequence of development is seen in the ectostriatum, except myelination starts some days later. Thus the development of these visual areas is completed at 40 days. In, contrast, the development of the song control nuclei is delayed. Neurons in RA and HVc grow steadily up to 40 days of age, attaining a size larger than that observed in adults. Whereas the volume of HVc increases until day 40 and remains stable thereafter, RA volume increases until day 70 and evidences a decrease thereafter. It is not until postnatal day 20 (RA) and day 40 (HVc) that the myelination process starts in the song control areas. Adult myelin density is achieved by 70 days in RA and by 100 days in HVc. It can be demonstrated that the development of the visual system parallels the development of visual performance of the birds. Delayed growth of song control nuclei coincides with development of song.