bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of fetal retina, tectum, and cortex transplanted to the superior colliculus of adult rats
Authors: McLoon Steven C. , Lund Raymond D.
Published: January 2005

Earlier studies showed that embryonic retina, cortex, or tectum transplanted adjacent to the superior colliculus of newborn host rats differentiated many of the histological features appropriate for the donor region and developed interconnections with the host nervous system. In the study presented here, the same regions were transplanted to the brain of adult host rats and the development of these transplants was compared to those into newborn hosts. Retina, rostral tectum, or occipital cortex was dissected from donor rat embryos on gestational day 14 or 15. A portion of cortex was aspirated in 2‐;menth‐old host rats to expose the right superior colliculus, and one of the donor tissues was placed adjacent to the colliculus in each host. Two to 4 months after transplantation, transplant histology and neuronal interconnections between the transplant and host nervous system were studied by using Nissl and neurofibrillar stains and 3H‐proline and HRP tract tracing techniques.

Four main points can be drawn from these results. First, 80% of the transplants survived in adult hosts –a percentage comparable to that found in newborn hosts. Second, each of the types of tissues transplanted differentiated histological characteristics appropriate for its site of origin, although the degree of differentiation was always much less than in transplants to newborns. Third, the transplants developed only relatively local projections into the host cortex and superior colliculus. This contrasts with the extensive projections found from the transplants into the brain of newborn hosts. Fourth, no definitive projections from the host retina or brain were identified to any of the transplants into adults, whereas both cortical and tectal transplants into newborns received projections from the host.
Ontogeny of cholecystokinin‐8‐containing neuron system of the rat: An immunohistochemical analysis. I. Forebrain and upper brainstem
Authors: Cho Hee Jung , Shiotani Yahe , Shiosaka Sadao , Inagaki Shinobu , Kubota Yoshiyuki , Kiyama Hiroshi , Umegaki Kanji , Tateishi Kayoko , Hashimura Etsuo , Hamaoka Toshiyuki , Tohyama Masaya
Published: January 2005

Ontogeny of the cholecystokinin‐8 (CCK) neuron system in the fore‐brain and upper brainstem of the rat was investigated by means of indirect immunofluorescence. CCK ceils and fibers first appeared in the developing ventral tegmental area and in the primordium of the medial forebrain bundle, respectively, at gestational day 15 (12–14‐mm embryos). From that time, CCK cells appeared in various areas of the forebrain and upper brain‐stem until birth and reached the maximum content at postnatal day 10. After postnatal day 10, although CCK cells tended to decrease slightly in number, colchicine treatment in the adult rats brought out numerous CCK cells in the same areas. In contrast, although CCK fibers developed only slightly during the fetal period, marked development was seen after birth, particularly between postnatal days 5 and 10. After that time, as the rats grew, CCK fibers continued to increase in number and formed a meshwork of varying density in various areas of the forebrain and upper brainstem.
The specificity of central nervous projections of locust mechanoreceptors
Authors: Bräunig P. , Pflüger H.‐J. , Hustert R.
Published: January 2005

The central projections of hairplates and groups of campaniform sensilla of various parts of the locust head, neck, and thorax are compared. Receptors with approximately the same peripheral location (e.g., dorsal head, wing, or proximal leg) tend to exhibit similar central projection patterns. Specificity of the projections due to different morphological types of sensory neurones may influence shape and extent of segmental ramifications; this is observed with receptors of the proximal leg joints in particular.
The relationship between retinal axon ingrowth, terminal morphology, and terminal patterning in the optic tectum of the frog
Authors: Constantine‐Paton Martha , Pitts Eleanor C. , Reh Thomas A.
Published: January 2005

The mode of entry of retinal ganglion cell (RGC) axons and the detailed morphology of their arbors has been studied in the tectal lobes of the frog Ranapipiens. These tecta were subjected intact to HRP histochemistry and subsequently flal‐mounted for examination under a compound microscope. Subsets of RGC axons were labelled by inserting small pellets of solidified HRP into the optic chiasm region or into the tectal neuropil itself. Annular or semiannular patterns of retinal ganglion cell arbors were always observed after placement of HRP in the chiasm region. HRP pellets in the tectal neuropil labelled segments of annuli in caudal tectal regions. These tectal patterns corresponded to a similar annular distribution of HRP‐filled RGC bodies in the topographically appropriate regions of the contralateral retina.

The morphologies and trajectories of RGC axons were found to vary systematically depending on the age of the animal and the region of the tectal lobe examined. In rostral tectum the tangential spread of large‐caliber RGC axon arbors appears to decrease with increasing animal age and in large adult frogs there is a general tendency for arbors in caudal tectum to be larger than arbors in rostral tectum. In addition, axons contributing to terminal annuli in the central region of young and old frog tecta travel in a strict rostrocaudal direction over the anterior regions of the lobe. A predominantly rostrocaudal trajectory is also established by axons terminating in lateral and medial regions of the tecta of young postmetamorphic frogs. In the lateral and medial regions of mature optic tecta, however, axons arborizing in peripheral terminal annuli turn rather abruptly off the medial and lateral optic tracts and establish radially oriented trajectories. The annular patterning of terminal arbors and the age‐ and position‐dependent differences in arbor morphology are discussed in the context of a developmental sequence where arbors from newly arrived RGC axons distribute themselves along the tectal borders.

The question of whether such a high degree of fiber and terminal ordering actually dictates synaptic patterning in the tectal lobe has also been addressed in this study by using the stereotyped striped pattern found in the dually innervated tectal lobes of three‐eyed frogs (Constantine‐Paton and Law, 78;Law and Constantine‐Paton, '81). The presentresults indicate that eye‐specific segregation in the terminal zone is independent of bundling of axons in the optic tract. Stripes are also shown to be independent of the path taken by axons en route to the tectum and of the way in which axons enter the tectal plate. These observations and our earlier conclusions (Reh et al., '83) concerning order in the Rana optic nerve are discussed in terms of recent models of retino tectal development which postulate a role for passive “extra‐tectal” factors in the formation of this visual map.
The inferior colliculopontine neurons of the cat in relation to other collicular descending neurons
Authors: Hashikawa Tsutomu
Published: January 2005

Cells of origin of the pontine afferents from the inferior colliculus (IC) of cats have been identified by means of retrograde axonal transport of horseradish peroxidase (HRP). Following injections of HRP in the pontine nuclei, many labeled neurons were found ipsilaterally in the caudal parts of the external and pericentral nuclei, while a few cells were found in the central nucleus. Additional neurons occurred in the nuclei of the middle and rostral parts. This organization contrasts with that of other collicular descending systems. Thus, neurons projecting to the superior olivary complex and cochlear nuclei were found predominantly in the central nucleus bilaterally. In the external nucleus labeled cells tended to be distributed in the middle to rostral regions, but they were few in number in the caudal part.

Since the locations of IC‐pontine neurons are found to be different from those of other IC descending neurons, it may be assumed that the IC‐pon‐ tine system does not share common functional properties with the other collicular descending neurons. Functional aspects of the IC‐pontine neurons are discussed, with a comment on a pathway for the transmission of auditory impulses to the midvermal area of the cerebellum.
Central distribution of afferent and efferent components of the pudendal nerve in cat
Authors: Ueyama Teizo , Mizuno Noboru , Nomura Sakashi , Konishi Akira , Itoh Kazuo , Arakawa Hisao
Published: January 2005

Central distribution of afferent and efferent components of the pudendal nerve was examined in the cat by the HRP method after applying HRP to the central cut end of the pudendal nerve.

Retrogradely labeled neuronal cell bodies were located primarily in the feline homologue of the Onuf's X nucleus, constituting a slender longitudinal cell column in the ventral horn of the S1 and S2 cord segments. The Onuf's nucleus was present constantly from middle S1 to high S2 cord segments, and occasionally extended rostrally to high S1 or low L7, and caudally to middle S2, low S2, or high S3 cord segments. No sex differences were observed in the distribution pattern, number, and soma size of labeled neurons in the Onuf's nucleus.

Transganglionically labeled dorsal root fibers were found to terminate ipsilaterally in the lamina I of the dorsal horn at levels of lower lumbar, sacral, and higher coccygeal cord segments and the gracile nucleus, and bilaterally with an ipsilateral predominance in the dorsal commissural gray and laminae III, IV, V, and VI of the dorsal horn at levels of lower lumbar, sacral, and higher coccygeal cord segments. Some labeled dorsal root fibers appeared to end ipsilaterally in the regions where the sacral parasympathetic preganglionic neurons have been shown to be located.
Electrical and morphological properties of off‐center bipolar cells in the carp retina
Authors: Saito Takehiko , Kujiraoka Toru , Toyoda Jun‐Ichi
Published: January 2005

Electrical membrane properties of carp off‐center bipolar cells were studied by injecting a ramp of current (changing at a rate of about 0.3 nA/s) through one barrel of a double‐barreled electrode and recording the voltage drop through the other barrel. The light‐elicited response reversed the polarity at a positive membrane potential. The current‐voltage curve showed inward and outward rectifications which modified the amplitude of the light‐elicited response. The degree of membrane rectifications varied considerably among the cells sampled.

Off‐center bipolar cells were stained by iontophoretic injections of Lucifer‐yellow dye after studying their electrical properties. There was a significant correlation between the difference in cell morphology and the degree of membrane rectification. The cells, which were characterized by small cell bodies lying close to the proximal part of the inner nuclear layer and by thin primary dendrites, tended to show rectifying membrane properties, compared to those characterized by large cell bodies lying close to the distal part of the inner nuclear layer and by thick primary dendrites. A site showing rectifying membrane properties and the origins of a large variability in membrane rectifications are discussed in detail.
The neuronal architecture of the inferior colliculus in the cat: Defining the functional anatomy of the auditory midbrain
Authors: Morest D. Kent , Oliver Douglas L.
Published: January 2005

This study defines anatomical subdivisions in Golgi‐impregnated material from the inferior colliculus of the cat. The findings demonstrate that the inferior colliculus consists of a mosaic of morphologically distinct parts of neuropil. Each part is also characterized by a unique set of neuronal types.

Each part of the inferior colliculus can be defined as tectal or tegmental on the basis of the fundamental pattern of dendritic branching. The main subdivisions of the auditory tectum are the central nucleus, the cortex, and the paracentral nuclei. The central nucleus is distinguished by its laminated neuropil composed of neurons with disc‐shaped dendritic fields oriented in parallel arrays with the lemniscal axons. In contrast, the cortex is identified by its broad layers of loosely woven neuropil, which are orthogonal to those in the central nucleus and lack neurons with disc‐shaped dendritic fields. The paracentral nuclei, so called because of their scattered arrangement around the central nucleus, are the commissural, dorsomedial, rostral pole, lateral, and ventrolateral nuclei. The main subdivisions of the auditory tegmentum are the pericollicular areas, the nucleus of the brachium of the inferior colliculus, and the sagulum. The pericollicular areas are intercollicular or subcollicular and separate the tectal division from the superior colliculus, central gray, and remaining portions of the tegmentum. The afferent projections to each tectal and tegmental subdivision, as observed in silver‐degeneration experiments, distinguish the parcellations based on the Golgi findings. Subdivisions containing tectal cell types receive afferents predominantly from the auditory pathways, in contrast to subdivisions with tegmental cell types, which receive inputs from a wide variety of sources. This suggests a correlation between neuronal types and the nature of their inputs.

This analysis of the subdivisions of the inferior colliculus differs from previous studies, especially those relying on Nissl stains. It is likely that subdivisions distinguished by the pattern of the neuropil differ functionally, since the structural components identified in the Golgi‐impregnated material are essential parts of the synaptic organization of the auditory midbrain. Future physiological studies should benefit from approaches in which the cell types serve as the focus for the analysis.
Histological and ultrastructural studies on the origin of caudal neural crest cells in mouse embryos
Authors: Schoenwolf Gary C. , Nichols David H.
Published: January 2005

The origin of neural crest cells was studied histologically and ultrastructurally in caudal regions of mouse embryos at 8.5–11 days of gestation (day of vaginal plug = day 0). The neural tube of caudal regions develops in two different phases, called primary and secondary neurulation. The primary (more cranial) portion of the neural tube originates from the ectodermal neural plate, whereas the secondary (most caudal) portion originates from the tail bud. We asked in this study: Do neural crest cells of caudal regions originate exclusively from the developing primary portion of the neural tube and, Subsequently, migrate into areas undergoing secondary neurulation; or do some of these cells originate from the tail bud, with the secondary portion of the neural tube, forming in situ in caudal areas? Most embryos were preserved with fixative containing cetylpyridinium chloride (CPC) to facilitate the identification of neural crest cells, which stain darkly after exposure to CPC during fixation. Our results suggest that there are two sources of neural crest cells in caudal regions: the neuroectoderm of the neural folds flanking the closing posterior neuropore, and the tail bud. Neural crest cells derived from the neuroectoderm are designated as the primary neural crest, because they form in conjunction with the primary portion of the neural tube during primary neurulation, whereas neural crest cells derived from the tail bud are designated as the secondary neural crest, because they form in conjunction with the secondary portion of the neural tube during secondary neurulation.
Experimental immunohistochemical studies on the substance P neuron system in the lateral habenular nucleus of the rat: Distribution and origins
Authors: Shinoda Koh , Inagaki Shinobu , Shiosaka Sadao , Kohno Jōji , Tohyama Masaya
Published: January 2005

We examined the distribution and afferent projections of substance P‐like immunoreactive (SPI) fibers in the lateral habenular nucleus of the rats by using the indirect immunofluorescence method.

On the basis of the distribution, a dense plexus of SPI fibers in the lateral habenular nucleus (LHb) could be divided into two parts: medial (mLHb) and lateral (lLHb).

The present study demonstrates that SPI fibers in the lLHb originate from SPI cells in the rostral entopeduncular nucleus (rEP) and the adjacent area, while those in the mLHb originate from SPI cells in the medial habenular nucleus. Moreover, we showed that the axons from SPI cells in the rEP reached the lLHB via the “pallidohabenular tract.”
The course of axons of retinal ganglion cells within the optic nerve and tract of the chick (Gallus gallus)
Authors: Ehrlich David , Mark Richard
Published: January 2005

Small laser lesions placed in the posthatch chicken retina resulted in axotomy and then death of all ganglion cells located in a sector peripheral to the primary damage. With the use of silver techniques, the patterns of degenerating retinal fibers in the optic nerve, chiasm, and optic tract were examined.

In the proximal part of the optic nerve, radial retinal lesions resulted in a sheet of degenerating axons along the rostrocaudal extent of the nerve. The position of degenerating axons was related to the site of their entry in the optic nerve head with an overlapping distribution of degenerating fibers entering the optic nerve head from equivalent points from the temporal and nasal sides. In the optic chiasm, the distribution of fibers was similar to that seen in the proximal part of the optic nerve. In the optic tract there was a similar mixing of fibers from opposite sides of the retina. The ventral, nasal and temporal retinal fibers lay in the superficial part of the tract whereas the fibers from the nasal and temporal dorsal retina ran in the deeper, medial aspect of the tract. The central‐to‐peripheral axes of the retina were mapped along the rostrocaudal axis of the tract. As the tract approached the tectum degenerating fibers from single retinal lesions did not always remain together. In the case of a lesion in the ventral nasal retina, degenerating fibers split into two bundles located at opposite ends of the tract only to reunite at their terminal regional at the caudal pole of the tectum.

We conclude that ordering is present throughout the primary optic pathways. The ordering is not faithfully retinotopic and may not contain sufficient cues to produce the retinotopic map on the tectum by fiber‐to‐fiber interactions alone.
Regional (14C) 2‐deoxyglucose uptake during forelimb movements evoked by rat motor cortex stimulation: Pons, cerebellum, medulla, spinal cord, muscle
Authors: Sharp Frank R. , Ryan Allen F.
Published: January 2005

Electrical stimulation of the right forelimb motor (MI) sensory (SI) cortex in normal, adult rats produced repetitive left forelimb movements. Regions of increased (14C) 2‐deoxyglucose (2DG) uptake were mapped autoradiographically during these movements. MI stimulation activated the ipsilateral reticular tegmental pontine nucleus (RTF) and the middle (rostral‐caudal) third of the pontine nuclei including pyramidal (P), medial (POM), ventral (POV), and lateral (POL) pontine nuclei. The ipsilateral inferior olivary complex was activated including dorsal accessory olive (DAO), principal olive (PO), and medial accessory olive (MAO).

The contralateral lateral reticular (LR) nucleus and nucleus cuneatus (CU) were activated. Lateral vermal, paravermal, and hemispheric portions of the contralateral cerebellum were also activated. Parts of vermian lobules IV, V, VI, VII, and VIII, and lobulus simplex, crus I, crus II, paramedian lobule, and copula pyramidis were activated. Granule cell layers were activated much more than molecular layers. Discrete microzones of high granule cell 2DG uptake alternated with zones of low uptake in left paramedian lobule and copula pyramidis and may correlate with the fractured cerebellar somatotopy described physiologically by Welker and his associates. Portions of the left lateral and interpositus nuclei were metabolically activated.

Medial portions of laminae I‐VI were activated in the dorsal horn of cervical spinal cord. The 2DG uptake was either unchanged or decreased in the ventral horn. Thoracic and lumbar spinal cord were not activated. Monsynaptic MI and SI connections to P, POM, POV, POL, RTF, DAO, PO, MAO, LR, CU, and spinal cord could account for activation of those structures. However, there are no direct MI or SI connections to the deep cerebellar nuclei, the cerebellar hemisphere, or the muscles. Activation of these structures must be due to activation of polysynaptic pathways, sensory feedback from the moving forelimb, or both. The present experiments cannot distinguish these possibilities.

Comparison of the regions activated during forelimb MI stimulation (FLMIS) to those activated during vibrissae MI stimulation (VMIS) suggests that the pontine nuclei, cerebellar hemisphere, and possibly the deep cerebellar nuclei are somatotopically organized. RTP, LR, CU, and spinal cord were activated during FLMIS but were not activated during VMIS. The failure to activate the ventral horn of cervical spinal cord may be due to known inhibition of alpha‐motor neurons during motor cortex stimulation.
Development of the transient ipsilateral retinotectal projection in the chick embryo: A numerical flourescence‐microscopic analysis
Authors: Thanos Solon , Bonhoeffer Friedrich
Published: January 2005

The ipsilateral retinotectal projection in the developing chick was examined by using rhodamine‐B‐isothiocyanate (RITC)as an anterograde and retrograde vital marker for the retinal ganglion cells and their axons. Staining of the entire retina following intravitreal RITC injection between incubation days 3 and 16 revealed a small number of anterogradely labeled fibers in the optic tract and the anterior half of the optic tectum ipsilateral to the injection site. The total number of ipsilaterally projecting fibers was estimated to be about 2,000 on developmental day 9. The ipsilateral projection totally disappeared after day 15. The arrangement of fibers within the ipsilateral projection was examined by local anterograde RITC staining of localized retinal regions between days 9 and 10. The projection was retinotopically organized along the dorsoventral axis such that fibers of dorsal retinal origin projected on the ventral tectal half, whereas fibers of ventral retinal orgin projected on the dorsal tectal half.

The localization of ipsilaterally projecting ganglion cell bodies was examined by retrograde RITC staining during days 9 and 15. Ganglion cells of all four quadrants of the central retina contributed to the production of the ipsilateral projection. The ipsilaterally growing retinotectal fibers did not represent collaterals of contralaterally projecting retinotectal axons.

We assume that the tendency of early growing retinotectal axons to grow straight, as well as the ability of axonal growth cones to “sample” the environment, lead to a crossing of axons to the contralateral side. Ipsilateral projections would therefore represent “pathfinding errors.” Explanations for the elimination of the ipsilateral retinotectal projection are discussed.
Asymmetric and symmetric synaptic junctions in the dorsal lateral geniculate nucleus of cat and monkey
Authors: Rapisardi Salvatore C. , Lipsenthal Lee
Published: January 2005

We have investigated the applicability of traditional classifications of synaptic junctions in the dorsal lateral geniculate nucleus (DLGN) of the cat and monkey. Our principal sample is restricted to synapses made by the retinal terminal (round vesicles) in DLGN and to synapses made by flattened vesicle processes that were postsynaptic to the retinal terminal. We inspected consecutive thin sections through 250 synaptic junctions that showed clear synaptic clefts in every section. The thickness of the membrane and postsynaptic density (PSD) was measured on each section and an average thickness was computed for each synaptic junction. In both species the frequency distribution for these measurements forms an uninterrupted progression from the absence of a continuous PSD through the presence of a heavy density with most synaptic contacts falling in the midrange. Twenty‐two of the round vesicle profiles and 40 of the flat vesicle profiles we studied had very modest densities (13–16 nm) and exhibited an continuous PSD on some sections, but only small puffs of a complete lack of density on others. We concluded that this group which constituted 25% of the synaptic contacts we studied could not be classified as asymmetric of symmetric.

As a group the round vesicle synaptic junctions exhibited a heavier PSD than the flat vesicle contacts. The difference between the mean thickness the mean thickness in both species was statistically significant. However, we hesitate to describe the round vesicle contacts as symmetric because such a large proportion of the former made synaptic contacts with a PSD thickness within the range of the latter.
The morphology of dorsal column postsynaptic spinomedullary neurons in the cat
Authors: Bennett Gary J. , Nishikawa Nozomu , Lu Guo‐Wei , Hoffert Marvin Jay , Dubner Ronald
Published: January 2005

Dorsal column postsynaptic (DCPS) spinomedullary neurons from the cat's lumbosacral enlargement were identified by antidromic stimulation of the cervical dorsal columns and stained intracellularly with horseradish peroxidase. The cell bodies were located in laminae III‐IV. Their dendritic arbors were elongated rostrocaudally but narrow mediolaterally. On the average, the arbors were ×5 longer than they were wide. Most of the neurons had nearly all of their dendrites in laminae III‐IV and some of the neurons had, in addition, a considerable amount of dendritic surface area in lamina V. Only one neuron had more than a very small amount of dendritic surface area dorsal to lamina III. Seven of the neurons had unmyelinated axon collaterals that arborized extensively and issued varicosity‐bearing terminal branches in laminae III‐V, both within and beneath their dendritic territories. All of the neurons were excited by myelinated, low‐threshold mechanoreceptors. Since the rostrocaudally elongated and mediolaterally narrow dendritic arbors of DCPS neurons are in register with the laminae III‐IV terminal distributions of myelinated, low‐threshold mechanoreceptors, it is probable that this excitation arises from a monosynaptic and topographically discrete innervation. About one‐half of the DCPS neurons were also excited by noxious stimuli. It is probable that this excitation is accomplished by a polysynaptic distributions are largely or completely separate.
The lateral suprasylvian corticotectal projection in cats
Authors: Segal Richard L. , Beckstead Robert M.
Published: January 2005

The projection from the lateral suprasylvian visual areas to the superior colliculus was investigated in cats using both anterograde and retrograde tracing techniques. The retrograde transport of horseradish peroxidase (HRP) or wheat germ agglutinin‐HRP (WGA‐HRP) from their site of deposit in the superior colliculus indicates that all divisions of the lateral suprasylvian visual areas project to both the superficial and deep layers of the superior colliculus. However, following tracer deposits in the superior colliculus that are confined to the layers below the stratum opticum (deep layers), more neurons are labeled along the lateral bank than along the medial bank of the middle suprasylvian sulcus. Conversely, tracer deposits in the superior colliculus dorsal to and including the stratum opticum label more cells in the medial than the lateral bank. These retrograde experiments also confirm that the visual cortex along the lateral gyrus (areas 17 and 18) projects to the superficial, but apparently not to the deep layers. The visual area in the cortex surrounding the caudal two‐thirds of the anterior ectosylvian sulcus projects to the deep, but not to the superficial layers.

The laminar and areal patterns of anterograde axon labeling in the superior colliculus were examined after single deposits of 3H‐amino acids (autoradiography), HRP, or WGA‐HRP in the lateral suprasylvian cortical regions, or combined isotope and WGA‐HRP deposits. Axon labeling in the superior colliculus is generally densest in the stratum opticum and extends either dorsally into the superficial layers or ventrally into the intermediate gray layer. Specifically, the anterior divisions of the lateral suprasylvian cortex project primarily to the lateral portion of the superior colliculus, with the projection from the medial bank biased toward the superficial layers and axons from the lateral bank aimed mainly at the intermediate gray layer with some axons even reaching the deepest gray layer of the superior colliculus. Both the posteromedial and posterolateral divisions of the lateral suprasylvian cortex project to more extensive portions of the mediolateral and rostrocaudal dimensions of the superior colliculus than the anterior divisions. However, the posterolateral division projects more heavily to the intermediate gray layer than the posteromedial division; from the latter, axons distribute more superficially in the superior colliculus. Finally, the cortex surrounding the posterior suprasylvian sulcus projects primarily to the medial part of the superficial layers of the superior colliculus.

We conclude that regions along the lateral bank of the middle suprasylvian sulcus have quantitatively the greatest direct access to the deep layers, and may, therefore, have a profound influence on the sensorimotor functions attributed to the cells in the deep layers of the superior colliculus.
Serotonin‐immunoreactive neurons in the brain of the honeybee
Authors: Schürmann F. W. , Klemm N.
Published: January 2005

The distribution of serotonin‐immunoreactive neurons in the brain of the worker honey bee Apis mellifera was studied by means of immunocytochemical staining by using a well‐characterized antibody to serotonin (5‐HT). About 75 immunoreactive perikarya are grouped into clusters in the optic lobe and in the median and dorsal protocerebrum. Immunoreactive fibers were resolved in all areas of the brain. The optic lobe shows restricted layers of 5‐HT‐immunoreactive fibers in the lamina and medulla organized perpendicular to the retinotopic elements. Immunoreactive fibers in the lobula represent invasions of protocerebral giant wide‐field neurons. The nonglomerular neuropil of the brain exhibits a meshwork of immunoreactive fibres invading glomerular neuropil of the mushroom bodies, central body complex, and antennal lobes. Mushroom body stalks and lobes contain immunoreactive fibers arranged perpendicular to the Kenyon cell fibers and matching subcompartments of these corpora pedunculata areas. The calyces are devoid of immunofluorescence. Serotonin‐positive fibres in the central body complex are arranged in its subcompartments. No 5‐HT immunoreactivity was found in the pons. Antennal glomeruli contain immunoreactive fibers restricted around the margin of the glomeruli. The selective mapping of 5‐HT‐immunoreactive neurons complements studies on the distribution of monoamine‐containing neurons in the bee brain. Serotonin‐ and catecholamine‐containing neurons often occur together in the same brain areas and subcompartments. The immunohistochemical approach in chemoneuroanatomy gives new evidence for a more complicated architecture of the brain than could be deduced from the classical neuroanatomical studies.
An EM‐autoradiographic analysis of the projection from cortical areas 17, 18, and 19 to the superior colliculus in the cat
Authors: Behan Mary
Published: January 2005

The electron microscopic autoradiographic method was used to identify terminals of axons from cortical areas 17, 18, and 19 in the superficial layers of the superior colliculus. The results show that terminals of area 17 neurons contain round vesicles and made asymmetrical synaptic contacts predominantly onto one or more dendrites or dendritic appendages. Some profiles postsynaptic to labeled terminals contain vesicles and presumably are involved in serial synaptic arrangements.

Terminals of area 18 and 19 neurons in the superficial collicular layers appear to comprise two populations, one similar in most respects to area 17 terminals, containing round vesicles and making asymmetrical contacts. The other contains pleomorphic vesicles and makes symmetrical contacts upon dendrites and dendritic appendages. These terminals rarely contact more than one postsynaptic profile, and rarely do the postsynaptic profiles contain vesicles. The two populations of area 18 and 19 terminals containing round and pleomorphic vesicles, respectively, are present in the ratio of approximately 3:1, although this ratio varies throughout the sublaminae of the superficial collicular layers.

The presence of two distinct types of cortical terminals in the colliculus suggests that cortical modulation of collicular processing is more complex than was previously conceived.
Projections from the superior olivary complex to the cochlear nucleus in the tree shrew
Authors: Covey E. , Jones D. R. , Casseday J. H.
Published: January 2005

The origins and targets of projections from the superior olivary complex to the cochlear nuclei were studied in the tree shrew by placing small injections of horseradish peroxidase (HRP) in the cochlear nucleus and small injections of 3H‐leucine in the superior olivary complex. The results show that the descending pathways originate in periolivary cell groups surrounding the medial and lateral superior olives and that the periolivary nuclei differ from one another in their patterns of projections to the cochlear nucleus. For example, cell groups may project either ipsilaterally or bilaterally. Cells in the lateral nucleus of the trapezoid body project only to the ipsilateral cochlear nucleus. Other periolivary cell groups project bilaterally, although some of these may project more heavily to one side than the other. Some pathways have widespread targets in the cochlear nucleus whereas others have relatively specific targets. Diffuse projections to all divisions of the cochlear nucleus arise from the lateral nucleus of the trapezoid body ipsilaterally and from the medial perioliviary nucleus bilaterally. The targets of other descending pathways are more restricted. The anterolateral, dorsal, and dorsolateral periolivary nuclei project mainly to the anteroventral cochlear nucleus; the ventral nucleus of the trapezoid body and the posterior periolivary nucleus project mainly to the dorsal and posteroventral cochlear nuclei. All of these specific projections are bilateral. These results suggest that projections from the periolivary cell groups to the cochlear nucleus consist of multiple components with different degrees of specificity.
Retinal terminals in the goldfish optic tectum: Identification and characterization
Authors: Airhart Mark J. , Kriebel Richard M.
Published: January 2005

Retinal terminal profiles in the goldfish optic tectum were identified electron microscopically after (1) labeling with horseradish peroxidase and (2) in the early stages of degeneration in short‐term eye enucleates. All labeled terminals shared certain common morphological characteristics which were identical to those of a population of terminals in normal tecta. Terminals of this type disappeared 30 days after enucleation of the contralateral eye.

Retinal terminal presynaptic profiles were characterized by (1) round and oval synaptic vesicles; (2) mitochondria with irregular, randomly oriented cristae, large intracristal spaces, dilated membrane spaces, and primarily light matrices; (3) a wide range in profile area, 0.06–6.82 μm2; (4) large numbers of synaptic vesicles per profile area 168± 33 synaptic vesicles per μm2; (5) asymmetric synapses; and (6) multiple synaptic contacts (1.46 ± 0.73 per terminal profile). The postsynaptic elements included both dendritic and, less commonly, pleomorphic vesicle‐containing profiles. The majority of postsynaptic dendritic profiles were small (0.01–0.40 μm2). Serial synaptic contacts were occasionally seen.

The combination of vesicular and mitochondrial morphology (1 and 2 above) was necessary and sufficient to establish the retinal origin of a terminal, but use of such criteria would underestimate the number of retinotectal terminals by omitting those which did not have a mitochondrion in the plane of section. The number of such terminals was calculated from independent measurements, and the total number of retinal terminal profiles per area of neuropil was estimated.
Genesis of resting microglia in the gray matter of mouse hippocampus
Authors: Kitamura Tadahisa , Miyake Toshihiko , Fujita Setsuya
Published: January 2005

The genesis of resting microglia in the gray matter of mouse hippocampus was studied by 3H‐thymidine autoradiography in combination with electron microscopy. Newborn mice were injected with 3H‐thymidine singly or repeatedly at different postnatal stages, and killed shortly after the injection or after various intervals. Tissue specimens of the hippocampus at CA1 and CA2 were processed for light and electron microscopic autoradiography. The results showed that at least 91% of glial cells in the stratum radiatum of the hippocampus are produced after birth. About three‐fourths of astroglia in this area are produced before the sixth postnatal day, and a larger part of resting microglia are formed after the ninth postnatal day. Morphological transition can be traced from either proliferating cells in the stratum radiatum at late postnatal days to resting microglia or from those in early postnatal days to astroglia. A continuous morphological transition was observed between the proliferating cells at the late postnatal days (microglial production period) and those at the early postnatal days (astroglial production period). The latter retain some fine structural characteristics similar to small glioblasts in the subependymal layer. These findings strongly suggest that resting microglia, as well as astroglia, are derived from glioblasts, and are of neurectodermal origin.
The motor nuclei and primary projections of the IXth, Xth, XIth, and XIIth cranial nerves in the monitor lizard, Varanus exanthematicus
Authors: Barbas‐Henry Heleen A. , Lohman Anthony H. M.
Published: January 2005

The motor nuclei and sensory connections of the IXth, Xth, XIth, and XIIth cranial nerves of the reptile Varanus exanthematicus were studied with the methods of anterograde degeneration and anterograde and retrograde axonal transport. The motor nuclei of nerve IX are located ventrally in the rhombencephalon and are constituted medially by the large‐celled glossopharyngeal part of the nucleus ambiguus and laterally by the small‐celled nucleus salivatorius inferior. The motor nuclei of nerve X consist of the dorsomedially located dorsal motor nucleus of the vagus and the laterally located vagal part of the nucleus ambiguus. The rostral portion of the latter cell group contains smaller cells than its caudal portion and is rostrally continuous with the nucleus salivatorius inferior of nerve IX. The efferent axons of nerves IX and X arising from the ventrolateral medulla first course dorsomedially, form genua beneath the IVth ventricle, and then exit the brainstem. All primary afferent fibers of nerve IX and the majority of those of nerve X enter the solitary tract. Terminations of vagal fibers were observed in the postvagal portion of the nucleus of the solitary tract, the dorsal motor nucleus of the vagus, and the nucleus of the commissura infima. A small contingent of vagal fibers courses caudally just dorsolateral to the descending trigeminal tract. A separate spinal component of nerve XI could not be found. The bulbar component of this nerve forms part of nerve X and takes its main origin from a detached caudal element of the nucleus ambiguus. The motor nuclear complex of nerve XII consists of a large dorsal nucleus and a small ventral nucleus that extend from the medulla oblongata into the first segment of the cervical spinal cord.
The subnuclear distribution of substance P, cholecystokinin, vasoactive intestinal peptide, somatostatin, leu‐enkephalin, dopamine‐β‐hydroxylase, and serotonin in the rat interpeduncular nucleus
Authors: Hamill Geoffrey S. , Olschowka John A. , Lenn Nicholas J. , Jacobowitz David M.
Published: January 2005

The distribution of immunofluorescent somata and processes within the interpeduncular nucleus (IPN) containing substance P (SP), cholecystokinin (CCK), vasoactive intestinal peptide (VIP), somatostatin (SST), leu‐enkephalin (L‐ENK), dopamine β hydroxylase (DBH), and serotonin (5HT) was examined in male rats treated with colchicine 48 hours prior to perfusion. Serial sections were examined for immunofluorescence and variations in the density of fluorescence rated 1+ (sparse) to 4+ (dense).

The rostral subnucleus contained SP, SST, and L‐ENK‐positive somata and processes. Substance P and VIP processes were present throughout the rostral subnucleus but were concentrated in two ovoid areas located dorsally in the caudal region of this subnucleus. Cholecystokinin and L‐ENK processes surrounded these ovoid areas. The entire width of the central subnucleus was crossed by SP and L‐ENK processes oriented horizontally in narrow bands. Substance P processes were also aligned into vertical columns adjacent to the lateral margins of the central subnucleus. Leu‐enkephalin and 5HT processes were distributed throughout this subnucleus, while VIP processes were present only caudally. Dopamine β hydroxylase processes were evenly distributed but were restricted from the vertical columns laterally.

The intermediate subnuclei contained a sparse density of SP and 5HT processes that were present in proximity to the major blood vessels penetrating this subnucleus. Only DBH processes were evenly distributed.

The lateral subnuclei contained a dense concentration of SP processes. The medial edges of this subnucleus were distinguished by VIP, CCK, L‐ENK, and 5HT processes.

The dorsal subnucleus contained 5HT, L‐ENK, and SST‐positive somata and processes. Substance P, VIP, CCK., and DBH processes were also present. Dorsal‐lateral subnuclei contained SP, SST, L‐ENK, and DBH processes. Interstitial subnuclei contained SP, CCK, L‐ENK, 5HT, and DBH processes.

This study demonstrates that perikarya and processes containing peptides and monoamines are distributed within subnuclei of IPN in a topographic and heterogeneous pattern. New features of IPN organization are revealed.
The distribution and synaptic organization of serotoninergic elements in the inferior olivary complex of the opossum
Authors: King James S. , Ho Raymond H. , Burry Richard W.
Published: January 2005

Immunohistochemistry and high‐resolution autoradiography were used to analyze the distribution and synaptic organization of serotonin (5HT) ‐containing elements in the inferior olivary complex of the opossum. Immunoreactive beaded varicosities are present throughout the olivary complex. The densest 5HT immunostaining is present in subnucleus b of the caudal medial accessory nucleus. The rostral principal olive is sparsely populated with immunoreactive elements.

Fine beaded fibers arborize throughout the neuropil of all the olivary nuclei except in subnucleus b of the caudal medial accessory nucleus where they also circumscribe neuronal cell bodies. In addition, a distinct population of large beaded fibers are occasionally encountered in the neuropil of the medial accessory nucleus. Ultrastructurally, labeled profiles that correspond in size to the smaller beads (< 1 μm) contain tubulovesicular elements, large dense‐cored vesicles, and clear vesicles. In contrast, larger profiles (> 2 μm) are characterized by numerous clear synaptic vesicles. Synaptic junctions were encountered in only 2% of the labeled elements. The majority of the labeled profiles were in juxtaposition to small‐diameter dendrites (< 2 μm) except in the caudal medial accessory nucleus, where they also were found in apposition to olivary cell bodies.

Our results, when compared with other accounts, indicate that rather than major differences in the nuclear distribution of serotonin between species, there are differences in the density of serotoninergic elements in specific nuclei of the mammalian inferior olive. Based on the size of the labeled profiles and the distinct vesicle populations, our data suggest there are at least two populations of 5HT varicosities that are in juxtaposition to olivary neurons. Further, boutons containing 5HT primarily interact with the distal dendrites of olivary neurons except in the caudal medial accessory nucleus where cell bodies are in apposition to 5HT varicosities.
Distribution of tyrosine‐hydroxylase‐immunoreactive neurons in the hypothalamus of rats
Authors: Chan‐Palay Victoria , Záborszky László , Köhler Christer , Goldstein Menek , Palay Sanford L.
Published: January 2005

The distribution and morphology of cells containing tyrosine hydroxylase (TH) immunoreactivity in the hypothalamus of rats were studied by using a modified immunoperoxidase technique. The TH cell system is more complexly organized than was previously thought. On the basis of their clustering patterns, hypothalamic TH neurons could be subdivided into two groups: dorsal and ventral. The ventral group consists of a prominent aggregate of cells located in the caudal part of the arcuate nucleus. From here, cells extend around the caudal part of the ventromedial and dorsomedial nuclei and the base of the diencephalon. Tyrosine hydroxylase‐positive cells are present throughout the arcuate nucleus, except in its ventromedial part. Anteriorly, immunoreactive cells appear in the suprachiasmatic and supraoptic nuclei, in the retrochiasmatic area, and in the ventral part of the anterior hypothalamic nucleus. The dorsal group has its main concentration of cells in the medial part of the zona incerta, from which two clusters of cells, one medial and one lateral, extend rostralward. The medial group comprises cells in the medial part of the dorsomedial, paraventricular, and anterior hypothalamic nuclei. These cells adjoin the periventricular cells. The lateral group of cells emanating from the zona incerta occupies the lateral part of the dorsomedial and anterior hypothalamic nuclei and the dorsal hypothalamic area. The dorsal and ventral TH cell groups are in continuity medially in the periventricular layer, and laterally through the cells that surround the ventromedial nucleus.

Although the cells vary widely in size, shape, and dendritic arborization pattern, there are two main cell types. Small (21 × 11 μm), round to fusiform cells, with two or three dendrites arborizing simply, were frequently seen in the arcuate, suprachiasmatic, periventricular, supramammillary nuclei and at the borders of the ventromedial nucleus. The other cell type is larger (40 × 15 μm) and multipolar, with three to five frequently branching dendrites. The dendritic field is large and the cells are intensely TH‐immunoreactive. Although the larger cells occur occasionally in every hypothalamic nucleus, their principal locations are in the dorsal parts of the dorsomedial, posterior hypothalamic nuclei and the dorsal and lateral parts of the zona incerta, and in the areas dorsal and medial to the mammillothalamic tract at caudal hypothalamic levels. In this paper we give a detailed description of TH‐immunoreactive fibers and terminals in the hypothalamus and a comparison with previous studies of catecholamine cells in the hypothalamus.