bluuebunny/crossref_metadata_2025 huggingface dataset:
A reticular pattern of intrinsic connections in primate area V2 (area 18)
Authors: Rockland Kathleen S.
Published: January 2005

A system of periodic intrinsic connections is demonstrated in area V2 (area 18) of squirrel and macaque monkeys by large injections of tritiated amino acids, horseradish peroxidase (HRP), and fluorescent latex beads. These connections originate from pyramidal neurons concentrated in layers 3 and 5. Terminations occur in all cortical layers, largely coextensive with labeled neurons but more restricted in layer 4. This multilaminar distribution contrasts with the mainly supragranular localization of periodic intrinsic connections in V1 (area 17), and may imply a close interaction, in V2, of periodic intrinsic connections with pulvinocortical, as well as with corticocortical terminations (concentrated, respectively, in layers 3 and 5, and in lower 3 and 4). As in V1, the tangential configuration of these connections in V2 is reticular or latticelike, and is detectable for 2.5–3.0 mm from an injection site of HRP, 3H amino acids, or latex beads. Cross‐sectional widths of labeled regions vary from 250 to 800 μm in squirrel monkey and from 400 to 1,000 μm in macaque, depending on which portion of the lattice is measured. When periodic intrinsic connections are compared with stripes labeled histochemically by cytochrome oxidase (CO), no clear relationship is obvious between the two systems. This result contrasts with the orderly tangential alignment reported between CO‐reactive zones in V2 and certain extrinsic connections; namely, pulvinocortical terminations (Livingstone and Hubel, '82) and clusters of neurons projecting to area V4 (DeYoe and Van Essen, '84). Other extrinsic connections, however, such as backgoing connections from V2 to V1, do not seem to have a periodic distribution. Thus, although some discontinuous cortical connections relate to each other in a precise mosaic fashion, intrinsic and some extrinsic connections may observe different modes of organization.
Functional organization of the cochlear nucleus of rufous horseshoe bats (Rhinolophus rouxi): Frequencies and internal connections are arranged in slabs
Authors: Feng Albert S. , Vater Marianne
Published: January 2005

The functional organization of the cochlear nucleus (CN) was studied with physiological recording and anatomical tracing techniques. Recordings were made from single CN neurons to examine their temporal firing patterns to tone burst stimuli and their frequency tuning characteristics. Recording loci of individual neurons were carefully monitored in order to understand how the functional properties of a cell relate to its location within the CN. We found that tonal frequencies were systematically represented in each of the three CN divisions (anteroventral, AVCN; posteroventral, PVCN; dorsal, DCN). Eight temporal response patterns were observed in CN neurons when stimulated at units' best excitatory frequencies (BF). With a few exceptions, neurons in each CN division could generate all eight firing patterns with different distributions for the three divisions. A focal injection of horseradish peroxidase (HRP), at the end of the physiological study, to a group of neurons possessing a similar BF in one CN division resulted in anterograde labeling of nerve terminals in the other two divisions at precisely the areas where the same frequency band was processed in these divisions. Labeled terminals in each division were closely congregated in the form of a thin slab. The slab orientation was division specific whereas its location was frequency specific, which could be predicted on the basis of physiological data. HRP injections into the DCN also resulted in retrograde labeling of somata in the AVCN and PVCN. On the other hand, only DCN neurons were retrogradely labeled when HRP was injected into the AVCN or the PVCN. These data showed how the three CN divisions are internally connected. Furthermore, retrogradely labeled cells occupied the same slabs where we found anterogradely labeled nerve terminals. Additionally, in a group of bats, HRP was injected into various functionally (i.e., BF) identified regions of the central nucleus of the inferior coliculus (IC) to clarify the type and location of CN projecting neurons. Retrogradely labeled cells in individual CN divisions likewise were arranged in slabs whose locations in the CN nuclei depended on the BFs of neurons at the injection site in the IC. These results show that slabs represent units of functional organization (i.e., tonal frequency, local connection and central projection) in the CN.
Reexamination of photoreceptor‐bipolar connectivity patterns in carp retina: HRP‐EM and golgi‐EM studies
Authors: Saito Takehiko , Kujiraoka Toru , Yonaha Tomohide , Chino Yuzo
Published: January 2005

On‐ and off‐center bipolar cells were identified in the carp retina by means of intracellular recording, intracellular injection of HRP, and Golgi silver‐chromate impregnation. Light and electron microscopy revealed that these functionally different bipolar cells make synaptic contacts with both rods and cones, and that both on‐ and off‐center cells can be further divided into two subtypes (I and II) according to the relationship between the position of their dendritic processes and the synaptic ribbons in the photoreceptor terminal. The type I on‐center bipolar cell is characterized by a large cell body, a thick primary dendrite, and a big swelling of the axon terminal in the innermost part of the inner plexiform layer (IPL). Dendritic processes of this cell type make predominantly ribbon contacts with rods and nonribbon contacts with cones. The type II on‐center cell, having a large dendritic tree in the outer plexiform layer and a large ramification of the axon terminal extending over the inner part of the IPL makes mostly nonribbon contacts with rods and cones. Many of these type II cell processes, however, terminate very close to cone synaptic ribbons. The type I off‐center cell shows two varieties in the axon terminal structure; a large terminal swelling or a large flat ramification of the terminal in the outermost part of the IPL. These cells make predominantly ribbon contacts with rods and cones. Usually, but not always, the process of a type I off‐center cell runs parallel to the synaptic ridge apex of cones. The type II off‐center cell, showing a large ramification of the axon terminal extending over the outer half of the IPL, makes mainly nonribbon contacts with rods and cones. The results from the HRP‐EM study generally agree with those from the Golgi‐EM study. A few discrepancies between the results obtained with these two techniques are noted and their implication is discussed.
Torpedo electromotor system development: Neuronal cell death and electric organ development in the fourth branchial arch
Authors: Fox Geoffrey Q. , Richardson Guy P. , Kirk C.
Published: January 2005

The fourth branchial arch of Torpedo marmorata has been examined at the light and electron microscopic level during development. Of interest was the determination of the extent of electric organ tissue reported to be present in this arch and its possible relationship to electromotoneuron cell death in the electric lobes. The main electric organ of the torpedo is derived from the hyoid and first three branchial arches and is innervated by four major electromotor nerves. Extensive electromotoneuron cell death occurs in the electric lobes and most notably in the posterior poles. This feature could be due to a tendency for these neurons to innervate the fourth branchial arch where little or no electric tissue is formed. Our findings support this conclusion but are not entirely consistent with the idea that a population mismatch has occurred. This is because cell death precedes the genesis of the target cells. The presence of innervated differentiated electric tissue in this arch is also reported, leading to the conclusion that Torpedo marmorata possesses an accessory electric organ.
Distribution of certain peptide‐containing nerve fibres and endocrine cells in the gastrointestinal mucosa in five mammalian species
Authors: Keast J. R. , Furness J. B. , Costa M.
Published: January 2005

The distribution of mucosal nerve fibres containing vasoactive intestinal peptide (VIP), substance P, somatostatin, neuropeptide Y (NPY), and enkephalinlike immunoreactivity was mapped by conventional immunohistochemical techniques throughout the mucosa of the esophagus, stomach, small and large intestines, and gall bladder. In addition, the distributions of endocrine cells immunoreactive for three peptides localized by these antisera (namely somatostatin, pancreatic polypeptide, and substance P) were recorded. Tissues from guinea pigs, rats, dogs, marmosets, and humans were studied. It was hoped that this information would enable possible target tissues and functional roles for the peptides to be identified.

In the mucosa, peptide nerve fibres were found throughout the lamina propria, including some which were close to the epithelium and others associated with small blood vessels. Although there was a general similarity of peptide nerve distribution between regions and species, many small variations were observed. VIP and substance P fibres were the most prevalent nerve type; NPY fibres were also usually quite common. The distribution of somatostatin fibres was extremely variable between regions and species, and enkephalin fibres were usually rare. Endocrine cells of open (flask‐or pyramid‐shaped) and closed (rounded) types were seen; basal cytoplasmic processes (of variable length) were seen on many cells immunoreactive for somatostatin or pancreatic polypeptide. Epithelial cells immunoreactive for substance P were seen in the dog, marmoset, and human. The distributions and shapes of endocrine cells varied widely between areas and species.

These studies provide a basis for the correlation of nerve distribution with pharmacological and physiological studies.
The distribution of somatostatin‐like immunoreactivity in the monkey hippocampal formation
Authors: Bakst I. , Morrison J. H. , Amaral D. G.
Published: January 2005

The distribution of somatostatin‐Like immunoreactivity was studied in the hippocampal formation of the Old World (Macaca fascicularis) and New World (Saimiri sciureus) monkeys. Series of coronal sections were processed by the unlabeled second antiserum method using primary antisera which recognize somatostatin‐28 (S309) or somatostatin‐281–12 (S320). Neuronal cell bodies were more readily stained with antiserum S309 and were observed throughout the hippocampal formation. The most prominent accumulations of stained neurons occur in the hilar region of the dentate gyrus, in strata oriens and pyramidale of regio inferior of the hippocampus, and in the deep layers of the entorhinal cortex. Both antisera demonstrated extensive fiber systems which varied in density regionally in the hippocampal formation. Stained fibers were most prominent in the outer two‐thirds of the molecular layer of the dentate gyrus, in stratum lacunosum‐moleculare of the hippocampus, in layer I of the presubiculum and in layers I, III, and V of the entorhinal cortex.
Replacement of damaged cortical projections by homotypic transplants of entorhinal cortex
Authors: Gibbs Robert B. , Harris Eric W. , Cotman Carl W.
Published: January 2005

The extent to which transplants of embryonic cortical tissue can be used to replace damaged cortical projections has been examined. Embryonic entorhinal cortex was implanted into the entorhinal region of young adult rats that had previously received a lesion through the angular bundle. Projections between transplant and host were examined by using WGA‐HRP and the fluorescent dye Fast Blue. Implants selectively innervated areas of the host hippocampus and amygdala which normally receive entorhinal afferents. Implants were innervated by cells in the host diagonal band and, in one case, by cells in the contralateral entorhinal and/or presubicular cortex. In most cases, host fibers were differentially distributed within transplants, possibly reflecting an ability of host fibers to recognize and selectively innervate their appropriate targets even though the cellular organization of the implant is different from that present during normal development. These data suggest that homotypic implants of embryonic entorhinal cortex can, in some ways, replace severed cortical projections and may eventually be able to reconstituve normal cortical circuitry.
Central projections of cat retinal ganglion cells
Authors: Leventhal A. G. , Rodieck R. W. , Drehkr B.
Published: January 2005

The central projections of different groups of cat retinal ganglion cells were studied following small iontophoretic injections of horseradish peroxidase (HRP) into physiologically characterized sites. Analysis was restricted to labeled cells in the upper periphery of the nasal retina, contralateral to the injection site. Injections were made to the A lamina and C lamina of the dorsal lateral geniculate nucleus (LGNd‐A,C), the geniculate wing (LGNd‐W), the ventral lateral geniculate nucleus (LGNv), the pretectum (PT), and the superior colliculus (SC).

The dendritic fields of alpha, beta, and epsilon cells were well labeled by the procedures we employed. A group, termed “g1,” had somal sizes within the range of the smaller beta and epsilon cells, but dendritic morphologies distinct from either class. The g1 group may consist of a number of types, but our material provided no basis for further distinguishing them. Many cells were observed that had smaller somas; all had thin axons, and few had dendritic fields that labeled to any significant extent. We were not able to further distinguish these cells, and refer to this group, which may include a number of types, as “g2” cells.

From the peripheral nasal retina, alpha cells project to LGNd‐A, LGNd‐C, PT, and SC. Beta cells project to LGNd‐A, LGNd‐C, and PT. Epsilon and g1 cells project to the LGNd‐C, LGNd‐W, LGNv, PT, and SC.

We determined the total spatial density of cells in the region of the retina analyzed, using a Nissl‐stained preparation. We then estimated the relative fraction of cells in each of the above groupings by injecting HRP throughout a cross section of the optic tract. Multiplying this relative fraction by the total spatial density gave an estimate of the spatial density of each of these groupings. From the spatial density of cells labeled from the injection site; we were able to estimate the fraction of cells of each retinal grouping that project to each of the zones investigated.

By these calculations, almost all alpha cells from the upper nasal retina project to LGNd‐A and LGNd‐C; most project to SC, and about a third to PT. Beta cells, by contrast, project almost exclusively to LGNd‐A, with about 10% going to LGNd‐C, and about 1% to the PT. The great majority of epsilon cells, if not all, project to LGNd‐W, and up to half of this population also project to the other zones noted above. The remaining groups show little indication of branching, and separate to project, in varying proportions, to the terminal zones noted above.
Effects of continuous light on the retina of a fish, notemigonus crysoleucas
Authors: Penn John S.
Published: January 2005

Notemigonus crysoleucas organisms were exposed to light at 1,250 and 850 lux in regimes of 12L:12D and 24L:0D. Each layer of cells in the retina was evaluated employing light microscopy and measurements for quantitative analysis were recorded from the retinas of over 150 fish. These values were compared for dorsal and ventral portions of the retina, for the two intensities, and for the two regimes. Fish maintained under the 24L:0D light regime exhibited significant light damage to the retina, characterized by reduction of outer segments of photoreceptors, reduction in the density of nuclear layers, and disintegration of ganglion cells. The dorsal portion of the retina experienced significantly greater deterioration than the ventral portion. Fish which had been subjected to 96 hours of continuous light displayed no ability to repair damage after 96 hours under 12L:12D.
Light microscopic observations on cat Renshaw cells after intracellular staining with horseradish peroxidase. I. The axonal systems
Authors: Lagerbäck Per‐Åke , Kellerth Jan‐Olof
Published: January 2005

Five intracellularly HRP‐stained Renshaw cells were subjected to light microscopic analysis of the trajectories, branching patterns, and projections of the axonal systems.

The cell bodies were located ventrally in lamina VII. In three neurons the axon originated from the cell body and in the remaining two cells from a dendrite. After a 600–870‐μm distance the axons entered the ventral funiculus, where all of them continued rostrally. Two axons also gave off a caudal branch in the funiculus. The diameters of the main axons varied between 2.1 and 10.0 μm.

The main axons gave off one to four first‐order collaterals before entering the ventral funiculus and up to three collaterals could be seen to originate from the same node of Ranvier. In the ventral funiculus up to five first‐order collaterals could be traced from the same main axon. The axon collateral trees were often very extensive and daughter branches up to the 22nd order were observed. The distance between two successive branching points varied between 4 and 410 μm. A large number of boutonlike swellings were found along (59%) or at the ends of the collateral branches. At the most, 1,278 swellings originated from a single axon collateral tree. Most of the swellings were located in lamina IX, but they also appeared ventrally and dorsolaterally in lamina VII.
Light microscopic observations on cat Renshaw cells after intracellular staining with horseradish peroxidase. II. The cell bodies and dendrites
Authors: Lagerbäck Per‐Åke , Kellerth Jan‐Olof
Published: January 2005

The cell bodies and dendritic trees of five lumbosacral Renshaw cells of adult cats were studied in the light microscope (LM) after intracellular injection with horseradish peroxidase (HRP).

The cell bodies were all located in the ventral part of lamina VII. The dendrites extended up to 0.7 mm from the cell body into the neighbouring parts of laminae VIII and IX as well as into more dorsal parts of lamina VII. The dendritic branching was sparse and about half the dendrites were unbranched. The mean diameter of the cell body was positively correlated to both the combined and mean diameters of the first‐order dendrites. Between four and eight dendrites originated from the cell bodies.

The number of dendritic endbranches, the combined dendritic length, the mean dendritic length from the cell body to the termination of the end branches, the distance from the cell body to the termination of the most remote end‐branch, the dendritic surface area, and the dendritic volume all correlated positively with the diameter of the parent first‐order dendrite. The dendritic tapering was somewhat more pronounced in the Renshaw cells than previously observed in α‐ and γ‐motoneurons. The present data are discussed in relation to previous morphological observations on Renshaw cells and α‐ and γ‐motoneurons.
Colocalization of GAD‐like immunoreactivity and 3H‐GABA uptake in amacrine cells of rabbit retina
Authors: Mosinger Judith L. , Yazulla Stephen
Published: January 2005

Rabbit retinae were double labeled to determine the degree of colocalization of glutamic‐acid‐decarboxylase‐like immunoreactivity (GAD‐like IR) and 3H‐GABA uptake using light (LM) and electron microscopic (EM) auto‐radiography. Both GAD‐like IR and 3H‐GABA uptake were found in amacrine cell bodies in the inner nuclear layer (INL) as well as in cell bodies in the ganglion cell layer (GCL), and throughout the inner plexiform layer. GAD‐like IR was found in 32% of the amacrine cells in the INL, 86% of which also showed 3H‐GABA uptake; 3H‐GABA uptake was observed in 38% of the amacrine cells. However, only 72% of these cells showed GAD‐like IR. Labeled cells in the GCL were only 10–15% as common as similarly labeled cells in the INL. As in the INI., all GAD‐positive cells in the GCL were double labeled, but only 53% of the cells taking up 3H‐GABA were double labeled. We suggest that labeled cells in the GCL were ganglion cells rather than displaced amacrine cells. Cells, in both the INL and GCL, that showed 3H‐GABA uptake but no GAD‐like IR had a higher average grain density than double‐labeled cells, indicating that uptake by these cells was specific. The relevance to GABAergic function of 3H‐GABA uptake without an indication of GAD‐like IR is yet to be determined. Statistical analysis at the EM level showed that one‐third of the GAD‐positive synaptic terminals of amacrine cells were double labeled after a 4‐month exposure. Longer exposures at the EM level should reveal a higher percentage of GAD‐positive terminals because at the LM level, one‐half of the double‐labeled cell bodies were “lightly” labeled with grains. The high degree of colocalization of GAD‐like IR and 3H‐GABA uptake suggests that both markers may be useful for labeling GABAergic neurons in the rabbit retina.
Specific responsiveness of chick trigeminal motor nucleus explants to target‐conditioned media
Authors: Heaton Marieta B. , Wayne Denise B.
Published: January 2005

Explants of the neural tube from stage 11 chick embryos containing the metencephalic trigeminal (V) motor nucleus were cultured in standard control medium, in medium conditioned by appropriate target musculature (the mandibular process of the first visceral arch that gives rise to jaw musculature innervated by motor V) or in medium conditioned by inappropriate target musculature (rostral limb bud tissue). The appropriate and inappropriate muscle tissues were of the same developmental stage (stage 22) and were in similar states of differentiation. At this point in vivo, both are just beginning to be innervated. The neuritic outgrowth from the explants was quantified after 6 days in vitro. While explants from all three groups appeared healthy and exhibited some neuritic outgrowth, the density and complexity of this growth was significantly greater in the group cultured with the appropriate (jaw) muscle‐conditioned medium. Growth in this group significantly surpassed that of both the control and the inappropriate (limb) muscle‐conditioned medium group. The inappropriate muscle‐conditioned medium group did not differ from the control group.

These results demonstrate a specific responsiveness of the trigeminal motor nucleus population to its appropriate target tissue. Since relatively small amounts of the muscle‐conditioned medium were used with each explant, it is suggested that there is a high degree of sensitivity of this population to factors present in their target at the time innervation would normally be occurring. It is hypothesized that such selective responsiveness may play a role in guiding or sustaining growth during normal neurogenesis.
Projections of thalamic gustatory and lingual areas in the monkey, Macaca fascicularis
Authors: Pritchard T. C. , Hamilton R. B. , Morse J. R. , Norgren R.
Published: January 2005

The efferent projections of the parvicellular division of the ventroposteromedial nucleus of the thalamus (VMPpc; thalamic taste area) were traced to cortex in Macaca fascicularis by using tritiated amino acid autoradiography. Labeled fascicles could be traced from VPMpc to two discrete regions of cortex. The primary efferent projection was located on ipsilateral insular‐opercular cortex adjacent to the superior limiting sulcus and extended as far rostrally as the posterior lateral orbitofrontal cortex. An additional projection was located within primary somatosensory (SI) cortex subjacent to the anterior subcentral sulcus. Following autoradiographic injections in VPM, the trigeminal somatosensory relay, a dense terminal plexus was labeled on SI cortex of both pre‐ and postcentral gyri, but not within insular‐opercular cortex. The autoradiographic data were verified by injecting each cortical projection area with horseradish peroxidase (HRP) and observing the pattern of retrogradely labeled somata within the thalamus. Injections in the precentral gyrus near the anterior subcentral sulcus retrogradely labeled neurons within VPMpc, whereas injections further caudally near the floor of the central sulcus labeled, neurons within VPM. Injections of HRP within opercular, insular, or posterior lateral orbitofrontal cortex retrogradely labeled neurons within VPMpc.
Distribution and morphology of tegmental neurons receiving nigral inhibitory inputs in the cat: An intracellular HRP study
Authors: Noda T. , Oka H.
Published: January 2005

Intracellular recordings and morphological identification of neurons by means of intracellular HRP staining were performed in the midbrain‐pontine tegmentum of the cat. Electrical stimulation of the substantia nigra, pars reticulata, induced short‐latency inhibitory postsynaptic potentials in tegmental neurons, as previously reported. These tegmental neurons were distributed not only in the pedunculopontine tegmental nucleus (PPTN) (26 cells), but also in the cuneiform nucleus (CNF) (13 cells), the central gray substance (CG) (four cells), the parabrachial nucleus (three cells), and the tegmentum between the inferior colliculus and the CG (two cells). The morphological characteristics of the HRP‐stained tegmental neurons were analyzed by camera lucida drawings of 16 well‐stained cells, i.e., ten PPTN neurons, three CNF neurons, two neurons in the tegmentum between the IC/CG, and one CG neuron. All of these neurons seem to be classified as “isodendritic” neurons. Regardless of the soma size (15–120 μm in diameter), most of the tegmental neurons showed wide dendritic fields of 1‐2 mm, mediolaterally, and 0.5–1. mm, dorsoventrally.

These results indicate that the nigrotegmental projections exert an inhibitory influence on the neurons located in a wide variety of nuclei of the midbrain‐pontine dorsal tegmentum.
The early embryogenesis of papillary (sweat duct) ridges in primate glabrous skin: The dermatotopic map of cutaneous mechanoreceptors and dermatoglyphics
Authors: Dell David A. , Munger Bryce L.
Published: January 2005

The present study documents the early innervation of the epidermis prior to the onset of differentiation of the papillary (sweat duct) ridge in glabrous digital skin of rhesus monkey embryos measuring 45, 50 and 55 mm (crown‐rump) length. We observed small papillary ridges, spaced at a distance of approximately 40 μm, projecting into the dermis in the center of the distal glabrous digital pad of digits 2–5 in the 55‐mm embryo. The other digital pads lacked any sign of ridge formation. A two‐dimensional, approximately hexagonal grid of afferent nerves was present in the superficial dermis of all digital and palmar pads. At regular intervals of approximately 40 μm, afferent nerves ascended from the superficial dermal nerve plexus and innervated the overlying epidermis. By electrom microscopy, axonal growth cones were identified contacting Merkel cells that projected several microns down into the superficial dermis in the digital pad of digit 3. Thus, the earliest wave of differentiated dorsal root ganglion neuroblasts innervates Merkel cells. Schwann cells partially encircled these growing axon tips and could be identified by the presence of rough endoplasmic reticulum and free ribosomes. The youngest embryo studied had no sign of ridge formation; however, axons ascended from the superficial dermal nerve net at 30–40‐μm intervals to innervate the epidermis. We conclude that afferent nerve fibers provide a two‐dimensional grid that could modulate the spacing and arrangement of the papillary or sweat duct ridges of successive digits. Such an interaction is possible between digits based on the overlapping dermatotopic maps of each rete ridge. An abnormal fingerprint could thus reflect abnormal dorsal root ganglion neuroblasts expressed through mesenchyme and epidermis.
Optic tectum, of the eastern garter snake, thamnophis sirtalis. I. Efferent pathways
Authors: Dacey Dennis M. , Ulinski Philip S.
Published: January 2005

Extracellular, iontophoretic injections of horseradish peroxidase were used to anterogradely fill axons efferent from the optic tectum in garter snakes. The tectal efferent pathways consist of six axon types with distinct projections and terminal morphologies. Tectogeniculate axons pass into the diencephalon via the optic tract, bearing collaterals that form spatially restricted, rodlike arbors in the pretectum, the ventral lateral geniculate nucleus, and the ventrolateral nucleus. Tectoisthmi axons exit the tectum as a thin‐caliber component of the ventral tectobulbar tract. They form spatially restricted, spherical arbors within nucleus isthmi. Tectoisthmobulbar axons also give rise to small, spherical arbors within nucleus isthmi, but the parent axons continue caudally into the pontine and medullary reticular formation issuing many short collateral branches. Tectorotundal axons reach the diencephalon via the tectothalamic tract and give rise to fine terminal collaterals in the nucleus of the tectothalamic tract ipsilaterally and in nucleus rotundus bilaterally. Single axons form sheetlike terminal fields that span the rostrocaudal extent of nucleus rotundus. Ipsilateral tectobulbar axons descend into the midbrain tegmentum where they issue several thick collaterals that terminate widely throughout the nucleus lateralis profundus mesencephali. The parent axon continues caudally giving off several widely spreading collaterals within the pontine and medullary reticular formation. Crossed tectobulbar axons enter the dorsal tectobulbar tract and cross the midline to form the predorsal bundle. Single axons give rise to terminal collaterals in the nucleus lateralis profundus mesencephali bilaterally, the contralateral pontine and medullary reticular formation, and the intermediate gray of the cervical spinal cord.
Monoclonal antibodies to the cockroach nervous system
Authors: Denburg Jeffrey L. , Caldwell Robert T. , Marner Joyce A. M.
Published: January 2005

In the cockroach nervous system individual motor neurons may be identified with respect to their position. in the thoracic ganglia and to the muscles they innervate. When their axons are cut they have the ability to regrow such that when regeneration is completed they have specifically reinnervated their normal target muscles. This suggests the existence of a specific intercellular recognition process between motor neurons and muscles, and that neurons innervating different muscles are biochemically distinct from one another. The goal of this study was to use hybridoma techniques to obtain monoclonal antibodies that bind to some motor neurons and not others.

Mice were injected with whole nerve cord and hybridoma supernatants were screened immunohistochemically on sections of ganglion and leg muscle. The monoclonal antibodies were categorized according to four types of specificity: tissue, regional, cell‐type, and neuron‐subset specificities. Antibodies expressing neuron‐subset specificity were obtained very rarely. The probability of their occurrence could be increased by treating the mice with immunosuppressant drugs after initial administration of immunogen or by fixing the immunogen with paraformaldehyde in a manner similar to that of the tissue sections used in the screening process.

Two of the neuron‐subset specific monoclonal antibodies (MAbs) are of particular interest with respect to the goals of this study. They bind to axon terminals in the muscles of some neurons and not others. They do not bind to neuronal cell bodies in the ganglion, which makes identification of the neurons difficult. However, from the known innervation pattern of the coxal depressor muscles it appears that one of these MAbs selectively binds to axon terminals from either the inhibitory motor neurons or the dorsal unpaired median cells. Other antibodies of interest bind selectively to the synapse‐rich neuropile in the ganglia or to peripheral parts of the nervous system like the nerve roots.
Optic tectum of the eastern garter snake, Thamnophis sirtalis. III. Morphology of intrinsic neurons
Authors: Dacey Dennis M. , Ulinski Philip S.
Published: January 2005

Extracellular iontophoretic injections of horseradish peroxidase and Golgi preparations were used to study the distribution and morphology of intrinsic neurons of the garter snake optic tectum. Four morphologically distinct classes of neurons were identified. The type A neuron is found throughout the retinorecipient tectal layers. It has a large, fusiform soma and infrequently branching dendrites than radiate in the horizontal plane and are studded with varicose appendages. An axon arises from the soma or proximal dendrite and gives rise to, widely spreading branches that overlap the cell's dendritic field. The type B neuron has a small, spherical soma in sublayer b of the stratum fibrosum et griseum superficiale. Thick, varicose dendrites ascend from the soma and form a bushy arbor in the overlying sublayer a. A thin axon descends vertically from the soma and arborizes in vertical alignment with the cell's dendritic field in sublayer c of the stratum fibrosum et griseum superficiale and the upper third of the stratum griseum centrale. The type C neuron is a bipolar cell with a small, vertically fusiform soma situated at the upper border of the stratum griseum centrale. Thin, sparsely branching dendrites extend vertically into the superficial and central gray layers. An axon arises from the soma and courses ventrally into the stratum griseum centrale where it gives rise to a plexus of widely spreading branches that extend medially from the cell's dendritic field. The type D neuron is a small, stellate cell with a spherical soma and fine, appendage‐laden dendrites that are restricted to the stratum griseum centrale. The axon of the type D cell courses in the central gray, where it gives rise to widely spreading branches that extend laterally from the cell's dendritic field.
Afferent and efferent connections of cerebellar lobe C3 of the mormyrid fish Gnathonemus petersi: An HRP study
Authors: Meek J. , Nieuwenhuys R. , Elsevier D.
Published: January 2005

The present paper is devoted to the extrinsic connections of lobe C3 of the highly differentiated corpus cerebelli of the electric fish Gnathonemus petersi. For this purpose, HRP injections or gels were placed in distinct parts of lobe C3 or its peduncle, in the pretectal region, and in the eye. Moreover, the presence of serotonin and tyrosine‐hydroxylase was studied with immunohistochemical methods.

The afferent connections of the rostral and caudal part of lobe C3 appear to differ considerably. Although both parts receive comparable projections from two pretectal nuclei (termed nucleus geniculatus and dorsal anterior pretectal nucleus) and the inferior olive, they receive projections from different parts of the nucleus lateralis valvulae, a large cell mass in the midbrain tegmentum, composed of small, tightly packed neurons. The caudal part of lobe C3 receives a projection from the most rostromedial cap of cells of this nucleus, whereas the rostral cap of lobe C3 receives efferents from the neighboring, more caudolateral, zone of cells of the nucleus lateralis valvulae. The caudal part of lobe C3, but not its rostral part, receives an additional projection from a nucleus in the isthmus region, termed nucleus Q. This nucleus sends a collateral projection to the torus longitudinalis.

The efferents of both parts of lobe C3 project to slightly different parts of the midbrain tegmentum and the nucleus reticularis superior, and originate at least partly from eurydendroid cells. None of the nuclei and fiber tracts labeled could be shown to contain serotonin or catecholamines.

The connections of lobe C3, as revealed by the present study, are compared with those of other parts of the mormyrid cerebellum and with those of the corpus cerebelli of other teleosts, with emphasis on the homology and functional significance of pretectocerebellar connections, the topical order in the cerebellar projections of the nucleus lateralis valvulae, and the relations between the cerebellum and torus longitudinalis. Comparison of the cerebellar connections in different teleostean species suggests that the strong development and the considerable differentiation of the cerebellum of mormyrids are related to at least two types of changes in the extrinsic connections, i.e.: (1) a redistribution or parcelling of connections and (2) the development of connections specific for mormyrids.
Organisation of lateral line and auditory areas in the midbrain of Xenopus laevis
Authors: Lowe D. A.
Published: January 2005

Lateral line areas in the midbrain of Xenopus laevis were identified by recording evoked potentials and neural activity elicited by stimulating anterior and posterior lateral line nerves. Spike activity was found in the lateral half of the optic tectum, ventrolateral tectum, and torus semicircularis. Contra‐ and ipsilateral lateral line pathways to these regions were identified. Spike discharge was associated with an evoked potential (EP) consisting of a large negative‐positive wave sometimes preceded by a small positive‐negative deflection. EP depth profiles varied according to electrode position within the lateral line midbrain projection field. In the middle of the field a dramatic increase in EP growth occurred as the electrode passed through the torus semicircularis, with peak amplitudes being achieved 900–1,100 μm from the surface within nucleus principalis and monocellularis. Tracks at the lateral edge of the field showed a steady growth of EP, with peak amplitudes around 600 μm as the electrode passed through ventrolateral tectum. Auditory responses to tone pips were found in the nucleus laminaris and principalis in caudomedial regions of the torus semicircularis, in areas lying medial to the main centers of lateral line evoked activity; this is a similar organisation to that found in teleost fish. The results indicate the torus semicircularis and deep layers of the lateral tectum to be involved in lateral line processing Some topographic separation of the representation of anterior and posterior lateral line systems is indicated. The possible involvement of these areas in lateral line stimulus localisation is discussed.
Ultrastructure of spinal efferents to the lateral reticular nucleus: An EM study using anterograde transport of WGA‐HRP complex
Authors: Westman J. , Danckwardt‐Lillieström N. , Dietrichs E. , Svensson B. A. , Walberg F.
Published: January 2005

Anterograde transport of lectin‐conjugated horseradish peroxidase and subsequent incubation with tetramethylbenzidine were employed to label the spinal terminals within the feline lateral reticular nucleus (NRL) for ultrastructural identification. Quantitative studies demonstrated that compared to the unlabelled terminals the spinal boutons were more than twice as large and contained fewer synaptic vesicles. Most of the synaptic contacts of the labelled terminals were located on dendritic shafts but contacts on dendritic spines as well as perikarya were also present. In four cases (all with cervical injections), the postsynaptic cells could be studied in the transversal sections of the medulla in the nuclear plane. The neurons were large and elongated with longest and shortest diameters of about 60 × 30 μm, belonging to the largest category of cells within the NRL. The observations were discussed and related to the findings made in other studies of the NRL.
Fine structure of the optic fiber termination layer in the tectum of the teleost Rutilus: A stereological and morphometric study
Authors: Peyrichoux J. , Pierre J. , Repérant J. , Rio J. P.
Published: January 2005

The stratum fibrosum et griseum superficial. (SFGS) of the Rutilus optic tectum, which receives a massive fiber from the projection from the contralateral retina, was studied by electron microscopy The qualitative and quantitative analysis of the laterodorsal (LD) portion of the stratum involved both a stereological examination of the different elements and a morphometric study of the various profiles containing synaptic vesicles (PCSVs). The relative volume of each element in the LD SFGS was as follows: myelinated and unmyelinated axons, 6.6%; PCSVs, 38%; dendrites without vesicles, spines, and cell bodies, 41.7%; glia, 10.5%. With the fixation employed, 35% of PCSVs showed spheroidal synaptic vesicles. These profiles could be subdivided into three types: (1) S1 (23.5%) represented optic terminals, since they degenerated after retinal ablation or were labeled after intraocular injection of HEP or [3H] proline. Three subgroups of S1 were identified: Slm‐profiles containing clear mitochondria;Sli‐isolated profiles that were contiguous with S1m and lacked mitochondria;Sli‐isolated profiles without mitochondria. (2)S2(9.3%) were characterised mainly by their dark mitochondria.(3)S3 (2.2%) corresponded to small nonvisual terminals that were isolated and lacked mitochondria. The PCSVs with pleiomorphic synaptic vesicles (65%) were subdivided into three groups: P1 (38%), P2 (19%), and P3 (8%). P1 and P2 were axonal in nature; P2 could be distinguished from P1 by a greater density of synaptic vesicles. P3 was of dendritic origin. Analysis of synaptic patterns revealed a small number of serial synapses. The presynaptic elements were optic boutons, whereas the intermediate profiles were dendrites with synaptic vesicles (P3). Results are compared with ultrastructural data obtained in the superficial tectal layers of other teleosts and other vertebrate groups.
Central projections of the ethmoidal nerve of the cat as determined by the horseradish peroxidase tracer technique
Authors: Lucier Gregory E. , Egizii Rita
Published: January 2005

The ethmoidal nerve innervates the nasal mucosa and constitutes the afferent limb of several upper airway protective reflexes. Protective reflexes, such as sneezing, coughing, and apnea, are those reflexes that either expel foreign substances from the respiratory tract or stop them from gaining access to the lungs. The afferents for nasal receptors are thought to be a part of the trigeminal system rather than olfactory in nature. The objective of this study was to localize the cell bodies of these ethmoidal afferents and to trace the central projections of these neurons. Horseradish peroxidase was applied to the ethmoidal nerve in 11 adult cats. Following a survival period of 48‐72 hours, the animals were killed and the tissue was processed according to the tetramethylbenzidine method. Reaction product was localized in cell bodies within the trigeminal ganglion, concentrated caudal to the entrance of the ophthalmic trunk of the trigeminal nerve. Transganglionic projections to the spinal trigeminal nucleus were localized primarily in the subnucleus interpolaris and in layers I and II of the subnucleus caudalis. There was also reaction product in cell bodies within the mesencephalic trigeminal nucleus. These results are in keeping with projections of other ophthalmic division receptor afferents, such as the cornea and the supraorbital nerve.
Neurotensin in the rat parabrachial region: Ultrastructural localization and extrinsic sources of immunoreactivity
Authors: Milner T. A. , Pickel Virginia M.
Published: January 2005

We sought to determine (1) the ultrastructural localization and (2) the extrinsic sources of neurotensin‐like immunoreactivity (NTLI) in the parabrachial region (PBR). The brains from untreated adult male rats and from others that received intraventricular injections of colchicine (100 μg/7.5 μl saline) 24 hours prior to death were fixed by perfusion with acrolein or glutaraldehyde and paraformaldehyde. Coronal sections were immunocytochemically labeled with a polyclonal rabbit antiserum to neurotensin and the PAP method. Western dot‐blots and immunocytochemical labeling with adsorbed antiserum revealed significant cross‐reaction only against NT, NT8‐13, and glutamine (Gln)4‐NT.

In the ultrastructural study, the most numerous labeled profiles were axons and axon terminals in both colchicine‐treated and control animals. The terminals containing NTLI were characterized by a mixed population of small, clear and large, dense core vesicles; asymmetric junctions principally with unlabeled dendrites; and a few synaptic specializations with unlabeled axon terminals. Compared to axon terminals, relatively few perikarya or dendrites had detectable levels of NTLI in either untreated or colchicine‐treated animals. The labeled perikarya measured 8‐10 μm in longest cross‐sectional diameter, contained NTLI throughout a narrow rim of cytoplasm, and received a few somatic synapses from unlabeled terminals. From the relative density of axon terminals and sparsity of perikarya and dendrites, we conclude that the NTLI in the PBR is principally derived from extrinsic neurons. However, the intrinsic neurons with NTLI may also contribute to the immunoreactivity in the axon terminals of the PBR.

We sought to determine the precise location of the extrinsic neurons that contribute to the NTLI in axon terminals in the PBR. Following unilateral injections of wheat germ agglutinin‐conjugated horseradish peroxidase (WGA‐HRP), dual labeling was most evident in a large population of neurons located in the dorsal, medial and commissural nuclei of the solitary tracts, ipsilateral to the side of the injection. However, a few perikarya containing both the retrogradely transported WGA‐HRP and immunocytochemical labels for NT were also detected in the caudal ventrolateral reticular formation, the locus coeruleus, and the paraventricular and lateral hypothalamic nuclei. We conclude that (1) NT or a closely related peptide is present in intrinsic neurons and multiple afferent pathways to the PBR; and (2) the axon terminals with NTLI have synaptic interactions with dendrites of intrinsic neurons and with axon terminals that may have either extrinsic or intrinsic origins.
Neuronal changes in the forebrain of mice following penetration by regenerating olfactory axons
Authors: Graziadei P. P. C. , Graziadei G. A. Monti
Published: January 2005

Following total, unilateral bulbectomy in neonatal mice, the olfactory sensory axons regrow from a reconstituted population of sensory neurons, cross the lamina cribrosa, and invade the spared forebrain that has leaned forward toward the anteroventral wall of the cranial cavity. The sensory axons invade several regions of the spared forebrain, at times penetrating deeply into the brain parenchyma. These axons terminate in characteristic globose structures resembling the glomeruli of the olfactory bulb. However, they can be distinguished from the latter by the absence of periglomerular cells. These ectopic glomerular structures are formed by the commingling of the olfactory axon terminals and the dendrites of brain neurons that lie in their proximity. Previously we have established that synaptic contacts occur between the sensory axon terminals and the dendrites of the brain neurons. Our present study describes large neurons, resembling mitral cells, that expand their dendrites into the intracerebral glomeruli. These neurons are recognized by virtue of their relatively large diameter, their selective stainability with silver methods, and the unorthodox arrangement of their dendrites in comparison with the neurons of the region. Their appearance is contingent upon the presence of ectopic glomeruli. The possibility is discussed that the large argyrophilic neurons may be derived from developing neuronal elements of the brain.