bluuebunny/crossref_metadata_2025 huggingface dataset:
A note on the organization of the amphibian olfactory bulb
Authors: Scalia Frank , Gallousis Gregory , Roca Suri
Published: January 2005

After horseradish peroxidase (HRP) injections were made in limited sectors of the main olfactory bulb in the adult frog Rana pipiens, the cellular morphology of mitral cells and granule cells impregnated with HRP were examined in uninjected regions of the bulb. Mitral cells were observed to possess glomerular dendrites and prominent secondary dendrites, both of which have smooth shafts. The glomerular dendrites may be multiple, are often branched, and may arise from secondary dendrites, as well as from the cell body. The axon may also arise from a secondary dendrite. Granule cells have simple or branched peripheral dendrites, and these are spiny, where they intermingle with the mitral cell secondary dendrites. The prominence of the secondary dendrites of frog mitral cells contrasts sharply with their reported insignificance in urodeles, as studied in earlier literature.

The layers of the main olfactory bulb are not as fully concentric in the frog, as they are in mammals. The implantation cone and glomerular layer occupy a small part of the surface area of the olfactory bulb on its anteroventral aspect, while the perimeters of the subjacent layers extend farther posteriorly and dorsally in successive steps. The granule cell core extends well beyond the perimeter of the mitral cell layer in a posterior direction. Long secondary dendrites of mitral cells also extend posteriorly beyond the perimeter of the mitral cell‐external plexiform layer and interlace with granule cell peripheral dendrites in a plexiform layer external to the posterior region of the granule cell core. This layer, the superficial plexiform layer, forms an apron around the posterior segment of the olfactory bulb and contributes to the interbulbar adhesion. It appears likely that it is an extension to the microcircuitry typically confined within the external plexiform layer in mammalian species.
Distribution, laminar location, and morphology of tectal neurons projecting to the isthmo‐optic nucleus and the nucleus isthmi, pars parvocellularis in the pigeon (Columba livia) and chick (Gallus domesticus): A retrograde labelling study
Authors: Woodson Walter , Reiner Anton , Anderson Keith , Karten Harvey J.
Published: January 2005

Retrograde transport of Phaseolus vulgaris leucoagglutinin (PHA‐L), fluorogold, fast blue, rhodamine labelled microspheres, and horseradish peroxidase (HRP) was employed to study the distribution, laminar location within the optic tectum, and morphology of tectal cells projecting upon the isthmo‐optic nucleus (ION) and the nucleus isthmi, pars parvocellularis (Ipc), in the pigeon and chick.

Following injections into the ION, all retrograde markers labelled tecto‐ION neurons and their dendrites in the ipsilateral tectum. The cells were located within a relatively narrow band at the border between layers 9 and 10 of the stratum griseum et fibrosum superficial (SGFS). Retrogradely labelled neuronal somata were different in both dendritic branching and shape; however, tecto‐ION neurons generally possessed non‐spiny radially oriented and multi‐branched dendrites. The apical processes extended into the retino‐recipient layers (2–7) of the SGFS and basal dendrites extended into layers 12–14 of the SGFS. Positive neuronal somata were observed throughout the rostro‐caudal extent of the optic tectum. The average distance between adjacent tecto‐ION neurons varied from one region to another. Specifically, retro‐gradely labelled cells were more numerous in the caudal, lateral, and ventral tectum, and less numerous at rostro‐dorsal levels. Approximately 12,000 tecto‐ION neurons were labelled within the ipsilateral optic tectum following either PHA‐L or fluorescent dye injections.

While the regional distribution of tecto‐Ipc neurons was not examined, the morphology indicated that the cells had a single radially oriented dendritic process. Therefore, the apical dendrites are more restricted than those of tecto‐ION cells. Moreover, the dendrites were spiny and arborized within layers 3, 5, and 9 of the ipsilateral optic tectum. The axon of tecto‐Ipc cells arise from the apical process as a shepherd's crook and descend into the deep layers of the optic tectum.

These results indicate that (1) tecto‐ION and tecto‐Ipc neurons are possibly monosynaptically activated by retinal input, (2) tecto‐ION neurons are heterogeneous in morphology, and (3) there is a differential distribution of the tecto‐ION neurons throughout the rostro‐caudal extent of the optic tectum, suggesting a greater representation of the caudo‐ventral portion of the optic tectum within the ION.

The discussion primarily concerns the organization of the retino‐tecto‐ION‐retinal circuit in light of the distribution and morphology of tecto‐ION neurons within the optic tectum.
Alz‐50 immunoreactive neuropil differentiates hippocampal complex subfields in Alzheimer's disease
Authors: Brady Daniel R. , Mufson Elliott J.
Published: January 2005

The topographic distribution of Alz‐50 containing profiles was determined within the hippocampal formation and anterior parahippocampal gyrus by using a monoclonal antibody directed against the A68 protein in normal and Alzheimer's diseased (AD) brains. Although there was a paucity of immunoreactive neuropil in the normal hippocampal complex, there were a few Alz‐50 positive neurons that occupied the hippocampal subfield, CA2. In most AD cases, Alz‐50 immunoreactive neuropil was prominent in the outer two‐thirds of the molecular layer of the dentate gyrus, although a few cases exhibited staining in the inner third of the molecular layer. CA2 was characterized by an increased density of neuropil staining within stratum pyramidale. The neuropil in subfield CA1 was stained densely with Alz‐50 in strata oriens, pyramidale, and at the border between strata lacunosum‐moleculare and radiatum. Alz‐50 immunostained neurites occupied primarily the lateral two‐thirds of the subiculum proper, whereas only sparse staining was seen in the adjacent presubiculum. Alz‐50 neuropil and neuronal staining displayed three distinct laminar patterns along the mediolateral extent of the entorhinal cortex, whereas the perirhinal cortex exhibited a bilaminar pattern of immunoreactivity involving heavy staining in layers 1–3 as compared to layer 5. In general, the density of Alz‐50 neurite staining in the neuropil appeared inversely proportional to the distribution of Alz‐50 immunoreactivity within dendritic and somal compartments. Interestingly, the patterns of Alz‐50 staining observed in the hippocampal complex in AD coincides with patterns of well‐characterized afferent fiber pathways to these regions, thus further supporting the suggestion that hippocampal subfield specific pathology effectively disconnects medial temporal structures from adjacent neocortex in AD.
Galanin‐like immunoreactivity in the brain of teleosts: Distribution and relation to substance P, vasotocin, and isotocin in the atlantic salmon (Salmo salar)
Authors: Holmqvist Bo I. , Ekström Peter
Published: January 2005

The presence of galanin‐like substances and their relation to substance P‐, vasotocin‐, and isotocin‐immunoreactive neurons and fibers in the brain of teleosts was investigated with immunohistochemical methods. Two specific antisera against synthetic porcine galanin (GAL) revealed cell bodies and fibers in the brain of four different teleost species (Salmo salar, Carassius carassius, Gasterosteus aculeatus, and Anguilla anguilla). In all four species the main location of galanin immunoreactivity was in the hypothalamo‐pituitary region. A detailed study of the distribution of galanin immunoreactivity in S. salar showed that galanin immunoreactive (GALir) perikarya were present in the nucleus preopticus periventricularis, an area that may be compared to the supraoptic nucleus in mammals, and in the nucleus lateralis tuberis, a nucleus involved in pituitary control in fishes that may be compared with the arcuate nucleus in mammals, GALir perikarya were found also in the nucleus recessus lateralis and in the nucleus recessus posterior. Numerous GALir fibers were present in the telencephalon and diencephalon, whereas only small numbers of fibers were found in the brainstem. In contrast to the situation in mammals, no GALir perikarya were observed in the brainstem areas corresponding to the noradrenergic locus coeruleus and serotonergic raphe nuclei in S. salar. We did not find any coexistence of GALir substances with arginine vasotocin or isotocin in neurosecretory neurons, as has been shown for galanin with the mammalian counterparts vasopressin and oxytocin. Also, the galanin‐like substance(s) and their structurally closest related peptide family, the tachykinins, belong to separate neuronal systems in teleosts. The presence of GALir neurons in brain areas known to be involved in pituitary control, and a massive GALir innervation of the pituitary, strongly indicate a role for galanin‐like substances in pituitary control also in teleosts. Furthermore, the presence of extrahypothalamic GALir fibers suggests involvement of galanin‐like substances in other brain functions in teleosts. In conclusion, there are general similarities between teleosts and mammals concerning the distribution of galanin‐like substances. However, there seem to be substantial differences in their distribution relative to functionally related peptides within the hypothalamo‐pituitary system. Whereas galanin appears to be colocalized and released together with vasopressin and oxytocin in mammals, in teleosts the homologous substances are contained within different sets of neurons that innervate the same target, the pituitary.
Projections from the periaqueductal gray to the rostromedial pericoerulear region and nucleus locus coeruleus: Anatomic and physiologic studies
Authors: Ennis Matthew , Behbehani Michael , Shipley Michael T. , van Bockstaele Elisabeth J. , Aston‐Jones Gary
Published: January 2005

Previous studies showed that the nucleus locus coeruleus (LC) receives two major afferent inputs from (1) nucleus paragigantocellularis and (2) nucleus prepositus hypoglossi, both in the rostral medulla. Recent reports suggested that the midbrain periaqueductal gray (PAG) projects to the rostromedial pericoerulear area and LC. Since the PAG is a major site for control of central antinociception, and since descending nonadrenergic fibers have been implicated in pain modulation, we have investigated in detail the functional anatomy of projections from PAG to the dorsolateral pontine tegmentum. A combined anatomical and electrophysiological approach was used to assess the organization and synaptic influence of PAG on neurons in the rostromedial pericoerulear region and in LC proper.

Injections of the tracer wheatgerm agglutinin conjugated to horseradish peroxidase encompassing LC proper and the rostromedial pericoerulear area retrogradely labeled neurons in PAG located lateral and ventrolateral to the cerebral aqueduct; injections restricted to LC proper did not consistently label PAG neurons. Deposits of the anterograde axonal tracer Phaseolus vulgaris leucoagglutinin into this same region of PAG labeled axons that robustly innervated the zone rostral and medial to LC. Only sparse fibers were observed in LC proper. Consistent with these results, focal electrical stimulation of LC antidromically activated only a few PAG neurons (6 of 100); all of these driven cells were located lateral and ventrolateral to the cerebral aqueduct.

The majority of neurons in the rostromedial pericoerulear area were robustly activated by single pulse stimulation of PAG. In contrast, single pulse electrical stimulation of lateral PAG produced weak to moderate synaptic activation of some LC neurons; stimulation of ventrolateral PAG produced predominant inhibition of LC discharge, perhaps through recurrent collaterals subsequent to antidromic activation of neighboring LC cells.

Taken together, these results indicate that PAG strongly innervates the region rostral and medial to LC, including Barrington's nucleus, but only weakly innervates LC proper. Although recent studies indicate that the dendrites of LC neurons ramify heavily and selectively in the rostromedial pericoerulear region, the results of the present physiological studies suggest that PAG preferentially targets rostromedial pericoerulear neurons rather than LC dendrites.
Visual topography of area TEO in the macaque
Authors: Boussaoud Driss , Desimone Robert , Ungerleider Leslie G.
Published: January 2005

Previous studies have mapped the visuotopic organization of visual areas from V1 through V4 in the occipital cortex and of area TE in the temporal cortex, but the cortex in between, at the occipito‐temporal junction, has remained relatively unexplored. To determine the visuotopic organization of this region, receptive fields were mapped at 1,200 visually responsive sites on 370 penetrations in the ventral occipital and temporal cortex of five macaques. We identified a new visual area, roughly corresponding to cytoarchitectonic area TEO, located between the ventral portion of V4 and area TE. Receptive fields in TEO are intermediate in size between those in V4 and TE and have a coarse visuotopic organization. Collectively, receptive fields in TEO appear to cover nearly the entire contralateral visual field. The foveal and parafoveal representation of TEO is located laterally on the convexity of the inferior temporal gyrus, and the peripheral field is represented medially on the ventral surface of the hemisphere, within and medial to the occipitotemporal sulcus. Beyond the medial border of TEO, within cyteoarchitectonic area TF, is another visually responsive region, which we have termed VTF; this region may also have some crude visual topography. Bands of constant eccentricity in TEO appear to be continuous with those in V2, V3v, and V4. The upper field representation in TEO is located adjacent to that in ventral V4, with a representation of the horizontal meridian forming the boundary between the two areas. The lower field representation in TEO is located just anterior to the upper field but is smaller. In contrast to the orderly representation of eccentricity in TEO, we found little consistent representation of polar angle, other than the separation of upper and lower fields. The results of injecting anatomical tracers in two animals suggest that TEO is an important link in the pathway that relays visual information from VI to the inferior temporal cortex. TEO is thus likely to play an important role in pattern perception.
Volumetric and histological changes in the cochlear nuclei of visually deprived rats: A possible morphological basis for intermodal sensory compensation
Authors: Dyson Susan E. , Warton Svetlana S. , Cockman Brett
Published: January 2005

The cochlear nucleus of 90 day‐old rats was studied to determine whether bilateral visual deafferentation at birth induced compensatory structural changes in the auditory system.

Computer‐assisted reconstructions of the cochlear nucleus ware used to demonstrate the three‐dimensional organization of the nucleus and for calculating volumes of the subdivisions. In enucleated rats the volume of the granular region of the nucleus (GCD) increased 22.6% relative to controls, and the volume of the anterior ventral nucleus (AVCN) also increased by 10.0%. The posterior ventral nucleus (PVCN) and dorsal nucleus (DCN) were not affected.

Since the volume change in GCD was substantial, this region was subjected to further analysis, Two types of granular cells were identified in the GCD of both control and enucleated rats with Kluver‐Barrera staining. Type 1 cells contained an ovoid dark nucleus with clumpy chromatin and possessed only a very thin rim of cytoplasm. Type 2 cells were larger with pale spheroidal nuclei and with a more prominent cytoplasmic rim. There was an obvious stratification of these two cell types in the superficial layers over the lateral aspect of the AVCN in both groups. In contrast to this, the subpeduncular corner was not distinctively laminated and contained predominantly Type 2 cells. In enucleated animals the nuclear size of Type 1 cells increased by 3.8% while the size of Type 2 nuclei was not affected.

Granule cell numbers increased by 28% in the visually deafferented rats. The GCD seems to be more highly developed in species which are dependent on non‐visual modalities for spatial location. The regional hypertrophy of the GCD and AVCN seen in the present study may indicate that intermodal sensory compensation is taking place in the auditory system of visually deafferented rats.
Morphological organization of rat hippocampal slice cultures
Authors: Caeser Manfred , Aertsen Ad
Published: January 2005

Using various histological methods, we investigated the cellular and morphological organization of rat hippocampal slice cultures. Many of the typical features of the hippocampus were retained in vitro over a long period of time. The principal cell types of the hippocampus and dentate gyrus, the pyramidal cells and granule cells, were well preserved and matured in vitro. Nonpyramidal cells and γ‐aminobutyric‐acid (GABA) cells were also present in slice cultures and exhibited a strikingly similar dendritic appearance at the light microscopic level. Moreover, GABA‐immunoreactive cell bodies and presynaptic terminals could be identified at the electron microscopic level; they expressed typical symmetric synaptic contacts with cell bodies and dendrites. The course of the intrinsic hippocampal fiber pathways—the mossy fibers, Schaffer collaterals, and alveus–was generally retained in vitro. Additional aberrant fiber projections could be identified. Finally, three types of nonneuronal cells could be distinguished on the basis of immunocytochemical methods.
An electron microscopic, immunogold analysis of glutamate and glutamine in terminals of rat spinocerebellar fibers
Authors: Ji Zhongqi , Aas Jan‐Erik , Laake Jon , Walberg Fred , Ottersen Ole Petter
Published: January 2005

A semiquantitative, electron microscopic immunocytochemical procedure based on the use of colloidal gold particles as markers was employed to analyze the subcellular distribution of glutamate and glutamine, a major glutamate precursor, in a subpopulation of spinocerebellar mossy fiber terminals. These terminals were identified by anterograde transport of a horseradish peroxidase‐wheat germ agglutinin conjugate, injected in the thoracic spinal cord. Gold particles signalling glutamate‐like immunoreactivity were enriched over clusters of synaptic vesicles relative to organelle‐free cytoplasmic matrix, and there was a strong positive correlation between gold particle and synaptic vesicle densities (correlation coefficient 0.94). Gold particles indicating glutamine‐ike immunoreactivity showed a much weaker correlation with vesicle density (correlation coefficient 0.36) and were about equally concentrated over cytoplasmic matrix as over clusters of synaptic vesicles.

Compared with the mossy fibers, the putative GABAergic Golgi cell terminals exhibited a lower level of glutamate‐like immunoreactivity, which was very weakly correlated with the vesicle density (correlation coefficient 0.27). The level of glutamine‐like immunoreactivity in the Golgi cell terminals was similar to that in mossy fibers, but much lower than that in glial cells.

The anterogradely labelled mossy fiber terminals were not enriched in immunoreactivities for aspartate or GABA.

These results suggest that the level and subcellular distribution of glutamate in presumed glutamatergic terminals differs from that in terminals in which glutamate only serves metabolic or precursor roles, and that these differences can be exploited in immunocytochemical studies aimed at identifying glutamate‐using neurons. In contrast, glutamine immunocytochemistry does not seem to be generally useful in this regard.
The optic tectum of the dogfish Scyliorhinus canicula L.: A Golgi study
Authors: Manso M. Jesús , Anadon Ramón
Published: January 2005

The optic tectum of the dogfish Scyliorhinus canicula L. was studied by using the methods of Nissl, reduced silver nitrate, Golgi‐aldehyde, and Golgi‐Cox. Six layers and eight types of neurons were recognized. These cell types are not restricted to one layer; in fact some are found in all six tectal layers. The types of cells found are A) monopolar, B) triangular, C) radial bipolar, D) horizontal fusiform, E) large tectal, F) small tectal, G) pyriform, and H) stellate cells. In at least six of the cell types a series of dendritic specializations can be observed, such as spines in the form of “drumsticks” and thin varicose appendages, similar to those reported previously in the optic tecta of amphibians and teleosts. The optic tectum of the dogfish shows a degree of complexity comparable to that of amphibians and teleosts.
Active zone organization and vesicle content scale with bouton size at a vertebrate central synapse
Authors: Yeow M. B. L. , Peterson E. H.
Published: January 2005

A common observation in studies of neuronal structure is that axons differ in the size of their synaptic boutons. The significance of this size variation is unclear, in part because we do not know how the size of synaptic boutons is related to their internal organization. The present study has addressed this issue by using three‐dimensional reconstruction of serial thin sections to examine the ultrastructure of synaptic boutons that vary in size. Our observations are based on complete or near‐complete reconstructions of 53 synaptic boutons contacting large neurons in the ventromedial gray matter of the upper cervical spinal cord (probable neck motor neurons).

We characterized bouton size in terms of volume and total area of membrane apposed to the motor neuron surface (apposition area). Boutons vary in apposition area by a factor of 40, and there is a significant positive correlation between our two measures of bouton size. In addition, bouton size is systematically related to four ultrastructural variables: 1) total active zone area, 2) number of active zones, 3) individual active zone area, and 4) number of synaptic vesicles. The correlations between these variables and both of our measures of bouton size are positive and significant. These data suggest that bouton size may be an index of ultrastructural features that are thought to influence transmitter storage and release.
Androgenic regulation of dendritic trees of motoneurons in the spinal nucleus of the bulbocavernosus: Reconstruction after intracellular iontophoresis of horseradish peroxidase
Authors: Sasaki Mitsuyoshi , Arnold Arthur P.
Published: January 2005

Androgen‐sensitive motoneurons in the spinal nucleus of the bulbocavernosus (SNB) in adult male rats were labeled after intracellular iontophoresis of horseradish peroxidase, after which they were fully reconstructed in three dimensions in order to measure their dendritic trees. Three groups of rats were compared: intact adult male rats and male rats castrated as adults and given Silastic tube implants containing either testosterone or nothing. In the high‐androgen groups (intact males and testosterone‐treated castrates), soma size and the diameter of the first‐order dendrites were larger than in blank‐treated castrates. Moreover, the terminal dendrites in all groups possessed growth cones, implying that the dendrites of these motoneurons are capable of growth in adulthood. However, there were no statistically significant group differences in the length, membrane surface area, or volume of the dendritic trees, or in the orientation or branching symmetry of dendrites. In general, there were positive correlations between the size of the motoneuronal soma and various measures of the size of the dendritic tree and between the diameter of individual stem (first‐order) dendritic branches and the size of remainder of that dendrite. These data suggest that there may be a modest effect of androgen on the size of the dendritic trees of SNB motoneurons in adulthood, although the effect is much smaller than has previously been reported.
Accurate prediction of Purkinje cell number from cerebellar weight can be achieved with the fractionator
Authors: Mayhew Terry M.
Published: January 2005

Purkinje cell nucleoli are used as counting units in order to obtain unbiased (fractionator)estimates of the number, N, of Purkinje neurons in adult mammalian cerebella of known weight, W. Regression analysis is then employed to establish the nature of the relationship between logN and logW. The linear regression equation defines an allometric relation that is employed to predict number in cerebella of known weight from other mammals. Predicted numbers are tested against empirical estimates.

For 19 cerebella ranging in weight from 0.2 g (rat) to 113 g (human), the allometric relation between Purkinje cell number and organ weight was determined. By using this relation, the mean complement in three rabbit cerebella (average weight, 0.87 g) is predicted to be 0.63 million. This figure is confirmed by fractionator estimates made on the same three brains. The cat cerebellum should contain about 1.5–2.0 million Purkinje cells. An estimate of 1.2–1.3 million cells is to be found in the literature.

Including rabbit cerebella in a refined equation yields the following relation:

With this refined equation, further predictions are made about the numbers likely to be found in the cerebella of the dog, goat, pig, ox, and horse. The numbers predicted for these animals must await experimental verification, but they are entirely consistent with previous suggestions that neuronal packing densities decrease with increasing brain size.
Projections to the basis pontis from the superior temporal sulcus and superior temporal region in the rhesus monkey
Authors: Schmahmann Jeremy D. , Pandya Deepak N.
Published: January 2005

The present investigation was designed to determine the origins in the temporal lobe, and terminations in the pons, of the temporopontine pathway. Injections of tritiated amino acids were placed in multimodal regions in the upper bank of the superior temporal sulcus (STS), and in unimodal visual, somatosensory, and auditory areas in different sectors of the lower bank of the STS, the superior temporal gyrus (STG), and the supratemporal plane (STP). The distribution of terminal label in the nuclei of the basis pontis was studied using the autoradiographic technique.

Following injections of isotope into the multimodal areas (TPO and PGa) in the upper bank of the STS, intense aggregations of label were observed in the extreme dorsolateral, dorsolateral, and lateral nuclei of the pons, and modest amounts of label were seen in the peripeduncular nucleus. The caudalmost area TPO projected in addition to the ventral and intrapeduncular pontine nuclei. The second auditory area, AII, and the adjacent auditory association areas of the STG and STP contributed modest projections to the dorsolateral, lateral, and peripeduncular nuclei, but generally spared the extreme dorsolateral nucleus. The lower bank of the STS, which subserves central vision, the somatosensory associated region at the fundus of the rostral STS, and the primary auditory area did not project to the pons.

The higher order, multimodal STS contribution to the corticopontocerebellar circuit may provide a partial anatomical substrate for the hypothesis that the cerebellum contributes to the modulation of nonmotor functions.
Central projections of cervical primary afferent fibers in the guinea pig: An HRP and WGA/HRP tracer study
Authors: Prihoda Manfred , Hiller Maria‐Sophie , Mayr Robert
Published: January 2005

The central course and the projections of the first and the second cervical dorsal root ganglia and of suboccipital muscle primary afferent fibers in the guinea pig were studied by means of anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA/HRP) or aqueous solution of horseradish peroxidase (HRP).

Injections of WGA/HRP into the second cervical dorsal root ganglion produced labeling in the dorsal and ventral horns. Within the spinal cord, the largest amount of HRP reaction product was found within the lateral third of the substantia gelatinosa and within the central cervical nucleus. The main area of termination in the medulla was the external cuneate nucleus. However, HRP reaction product was also found within the medial and inferior vestibular nuclei, cell group x, the perihypoglossal nuclei, the nucleus of the solitary tract, and the nucleus of the spinal trigeminal tract. Descending fibers could be detected as caudal as spinal segment T5.

Injections of WGA/HRP into the first cervical dorsal root ganglion produced heavy terminal label within the central cervical nucleus but not within the substantia gelatinosa. Again, the external cuneate nucleus was the main area of termination within the medulla. Label could not be observed within the vestibular nuclear complex or within the spinal trigeminal nucleus.

Injections of aqueous HRP into the suboccipital muscles produced heavy transganglionic label within the central cervical nucleus, whereas the substantia gelatinosa totally lacked terminal label. Ascending proprioceptive fibers reached the external cuneate nucleus and group x. Scanty projections could be detected within the vestibular nuclei as well as within the perihypoglossal nuclei except for the nucleus prepositus hypoglossi. Label was absent, in the spinal trigeminal nucleus.
Synaptogenesis in the primary visual cortex of the tree shrew (Tupaia belangeri)
Authors: Ungersböck Alfred , Kretz Robert , Rager Günter
Published: January 2005

The primary visual cortex of the tree shrew is characterized by the lack of ocular dominance columns. The two eyes are represented in sublayers of laminae 3 and 4. In an earlier study using the transneuronal transport we observed that the geniculate afferents from the two eyes do not initially overlap and then segregate into their appropriate sublaminae. The final distribution pattern can already be observed during the early postnatal period. Since segregation and elimination of afferent terminal branches do not seem to take place, we wanted to investigate whether or not an overproduction of synapses can be observed as in several other animals. We examined layers 3B, 3C, 4A, and 4B, which receive afferents from the retina via the lateral geniculate nucleus, from P5 to maturity by using the electron microscope. The brain tissue was excised in the region where the central vision is represented in adult animals. Then we determined the density of synapses per 100 μm2 neuropil for each of the four sublayers at the ages P5, P15, P19, P23, P31, and P42 and in the adult animal (AD). In determining the neuropil we measured the size of two additional compartments, i.e., the compartments consisting of perikarya and of blood vessels. At a higher resolution we determined the fraction of Gray type I and type II synapses in each sublamina and in each developmental stage.

The size of the neuropil increases from 57% at P5 to 81% in AD whereas the compartment of perikarya decreases from 42% to 15% and the compartment of blood vessels increases from 1.3% to 3.9%. The synaptic density starts with very low values (3.5/100 μm2) at P5. Then it increases rapidly and attains a maximal rate of increase during the period of eyelid opening. After this period the increase is slowed down and approaches the adult value (12.5/100 μm2) slowly. An overproduction of synapses could not be observed. The percentage of type I and type II synapses also changes during this period. The fraction of type I synapses amounts to 73% at P5 and increases to 92% in AD. The increase intensity of type I synapses is continuous and does not show any sign of overproduction. The density of type II synapses rapidly reaches its final value and then remains constant. Possibly there is a slight overproduction during the period of eyelid opening. The fact that an overproduction of synapses could not be observed may be related to the specific pattern of ingrowth of geniculate afferents which seem to go to their appropriate laminae without any detectable sign of segregation.
Blood‐nerve barrier in the frog during wallerian degeneration: Are axons necessary for maintenance of barrier function?
Authors: Latker Carole H. , Wadhwani Kishena C. , Balbo Andrea , Rapoport Stanley I.
Published: January 2005

Blood‐nerve barrier tissues (endoneurial blood vessels and perineurium) of the frog's sciatic nerve were studied during chronic Wallerian degeneration to determine whether barrier function depends on the presence of intact axons. Sciatic nerves of adult frogs were transected in the abdominal cavity; the ends were tied to prevent regeneration and the distal nerve stumps were examined. Vascular permeabilities to horseradish peroxidase and to [14C]sucrose increased to day 14, returned toward normal levels by 6 weeks, and continued at near normal levels to 9 months. Perineurial permeabilities to the tracers increased by day 10 and remained elevated at 9 months. Proliferation of perineurial, endothelial, and mast cells occurred between 3 days and 6 weeks, resulting in an increased vascular space (measured with [3H]dextran) and number of vascular profiles. The perineurium increased in thickness and the mast cells increased in number. This study indicates that during Wallerian degeneration of the frog's sciatic nerve there is (1) a transitory increase in vascular permeability distal to the lesion, that is related to changes within the endoneurium; (2) an irreversible increase in permeability of the perineurium, which begins later than that seen in the endoneurial blood vessels; and (3) proliferation of non‐neuronal components in the absence of regenerating neuronal elements. The results indicate that maintenance of vascular integrity does not require the presence of axons in the frog's peripheral nerve, whereas perineurial integrity and barrier function are affected irreversibly by Wallerian degeneration.
Topographic organization of cortical input to striate cortex in the Cebus monkey: A fluorescent tracer study
Authors: Sousa Aglai P. B. , Piñon Maria Carmen G. P. , Gattass Ricardo , Rosa Marcello G. P.
Published: January 2005

Cortical afferents to area V1 were studied in seven Cebus monkeys by means of retrograde fluorescent tracers. Injections were placed in V1, under electrophysiological guidance, in the regions of representation of both the upper and lower visual quadrants, at eccentricities that ranged from 0.5 to 64 degrees.

In all cases retrogradely filled neurons were found in retinotopically corresponding portions of areas V2 and MT, as denned electrophysiologically (Rosa et al: J. Comp. Neurol. 275:326, 1988; Fiorani et al: J Comp Neurol 287:98, 1989). The results also revealed two other visual zones located anterior to V2 here named third and fourth visual areas. A topographical organization of the connections was observed in these areas, with upper quadrant located ventrally and lower quadrant located dorsally. A clear central‐peripheral gradient, from the lateral to the medial cortical surface, was also observed in these areas.

Lower field injections revealed crude topographic organization in area DZ and a diffuse projecting zone in the annectent gyrus. Peripheral injections in V1 revealed a clear upper and lower field segregation in areas PO and prostriata as well as a complex topography in MST. In addition, another region of labeling revealed the presence of an area, the temporal ventral posterior region, with an organized topographic representation of the upper field, with a central to peripheral gradient, from the lateral to the medial cortical surface.

Three groups of cortical areas were distinguished according to the laminar distribution of neurons labeled from V1. In the first group, which is characterized by dense infra‐ and supragranular labeling, only V2 was included. The second group consists of areas V3, MT, and PO. These areas show dense labeling in the infragranular layers and occasionally sparse labeling in the supragranular layers. Finally, V4 and the other projecting areas, which are characterized by exclusive labeling of the infragranular layers were included in the third group.
Patterning in the regeneration of electroreceptors in the fin of Kryptopterus
Authors: Bever Michele Miller , Borgens Richard B.
Published: January 2005

The influence of the target tissue on afferent nerve regeneration was studied in the adult glass catfish, Kryptopterus. In this fish, electroreceptors in the anal fin are distributed in a characteristic pattern in the proximal part of the fin and are absent in the distal portion of the fin. We tested whether axons were more likely to induce electroreceptors in certain regions of fin epidermis than in others. We rotated fin transplants so that the location of the degenerating electroreceptors was altered with respect to the regenerating axons in the host tissue dorsal to the fin. The effects of these rotations were observed in the living animal with differential interference contrast optics over a period of 10 weeks. When transplants were reversed rostrocaudally, new electroreceptors formed in the caudal half of the interradial zone, where degenerating electroreceptors were at the time of transplantation. When transplants were rotated so that the dorsoventral and rostrocaudal axes were reversed, some new receptors formed in the old target site regions that were located in the caudal interradial zones (in the distal half of the graft with respect to the host). Regenerating axons reached these regions of the transplant by taking unusual routes around the electroreceptor‐free regions of fin. Very few electroreceptors formed in the distal/caudal or proximal/caudal interradial quadrants of grafts where the original orientation of the tissue was maintained. We suggest that old target sites have a neurotropic influence on the regenerating afferent axons and discuss the possibility that the distal fin epidermis is not as permissive to electroreceptor formation as proximal fin epidermis.
Cell counts and maps in the larval central nervous system of the ascidian ciona intestinalis (L.)
Authors: Nicol Dianne , Meinertzhagen I. A.
Published: January 2005

Although the ascidian tadpole larva harbors a prospectively valuable prototype of the chordate nervous system, with extensively characterized neural plate cell lineages, the simple cellular composition of the resultant central nervous system (CNS) is not documented in detail. The average total number of cells in the larval CNS of Ciona intestinalis is 335 (range ±4, n = 3), 65 or 66 of which reside in the nerve cord of the tail. The estimates were made by tracing and counting the number of nuclei in serial semithin (1 m̈m) sections cut longitudinally through three larvae, fixed no later than 2 hours after hatching. Within a single fourth larva, L4, 266 cells constituted the CNS in the trunk region of the larva, 45 of which occurred within the visceral ganglion, 215 in the sensory vesicle, and 6 in the neck between the two. Each cell was assigned to one of thirteen categories. Most (182, roughly 68%) are classified as ependymal, a specialized non‐neural cell peculiar to embryonic and larval chordates, from their position lining the cavities of the neural tube's elaborations or from clear similarities in the cytological appearance to those that do. Five cells are accessory cells of the sensory structures: three lens cells and a pigment‐cup cell in the ocellus, and a single pigment cell in the otolith. Of the remaining 79 cells, 36 are sensory, 17 receptors in the ocellus and 19 presumed hydrostatic pressure receptors; these lie on the right and left, sides of the sensory vesicle, respectively. Eighteen of the visceral ganglion cells have been tentatively classified as neurons, as have the remaining 25 cells which form two clusters in the posterior region of the sensory vesicle.
Neuropeptide Y (NPY)‐immunoreactive neurons in the primate fascia dentata; occasional coexistence with calcium‐binding proteins: A light and electron microscopic study
Authors: Nitsch Robrt , Leranth Csaba
Published: January 2005

Neuropeptide Y (NPY)‐containing neurons are known to be highly vulnerable following sustained electrical stimulation in rats and in humans suffering from temporal lobe epilepsy. This has been related to a strong excitatory input. In contrast, there is evidence that neurons containing calcium‐binding proteins exhibit a high resistance under experimental seizure and hypoxia conditions. The aim of this study was to determine the coexistence of NPY and calcium‐binding proteins in inhibitory neurons of the primate fascia dentata and their synaptic connections. Vibratome sections of hippocampi of African green monkeys (Cercopithecus aethiops) were immunostained with antibodies against NPY, PARV, and CB. A quantitative coexistence study was performed for NPY and PARV on consecutive semithin sections. In contrast to the rodent hippocampus, NPY‐immunoreactive neurons were found exclusively in the hilus of fascia dentata with horizontally oriented dendrites which did not extend into the granular and molecular layer. Conversely, PARV‐immunoreactive neurons were also present in the granular and inner molecular layer and extended their dendrites far out in the molecular layer and the hilus. Axon terminals immunoreactive for NPY were mostly concentrated in the middle and outer molecular layer and the hilar region and were rare in the granular layer. PARV‐immunoreactive boutons were basically restricted to the granular layer where they formed typical baskets. The antibody against calbindin stained almost exclusively granule cells. Coexistence of NPY‐ and PARV‐immunoreactivity was found only in hilar neurons and was rare (9 out of 152 cells analyzed). These results suggest that most NPY‐immunoreactive neurons do not contain calcium‐binding proteins. NPY‐containing neurons exhibited ultrastructural characteristics as described for inhibitory neurons. Their dendrites were only sparsely contacted by mostly asymmetric synaptic terminals, including a very small number of mossy fiber axon terminals. In turn, numerous NPY‐immunoreactive axon terminals formed symmetric synapses with spines and dendritic shafts of unlabeled neurons in the middle and outer molecular layer, whereas no contact with granule cell bodies was evident. Thus, we conclude that the vulnerability of NPY‐containing inhibitory neurons may be due more to the lack of calcium‐binding proteins than to a strong excitatory innervation. As their axons may contribute to the inhibitory control of the major excitatory input from the entorhinal cortex, their loss following overstimulation may play a role in perpetuating hippocampal seizure activity.
Organization of the zebra finch song control system: Functional organization of outputs from nucleus robustus archistriatalis
Authors: Vicario David S.
Published: January 2005

The organization of projections from nucleus robustus archistriatalis (RA) was mapped by a combination of anatomical tracer techniques. After injections of retrograde tracers in the syringeal part of the hypoglossal motor nucleus (nXIIts), labelled cells were seen in ipsilateral RA, in agreement with previous work. However, a shallow band in the dorsal and dorsocaudal part of RA did not contain labelled cells. Cells in this “cap” area were labelled following tracer injections in the dorsomedial nucleus of midbrain ICo (DM), the other known target of RA projections. The topography of outputs to nXIIts was further examined by making small injections of retrograde tracer into physiologically identified control zones for individual syringeal muscles in nXIIts. The distribution of labelled cells in RA revealed bands of cells that cross RA in approximately horizontal layers and project to different parts of nXIIts. This topography was confirmed with the anterograde tracer PHA‐L. Thus RA contains two functional subdivisions, one related to midbrain centers for vocalization and the other directly controlling syringeal motorneurons. The latter area can be further divided into zones that preferentially engage particular syringeal muscles.
Retinal ganglion cell terminals in the hamster superior colliculus: An ultrastructural study
Authors: Carter D. A. , Aguayo A. J. , Bray G. M.
Published: January 2005

The distribution, cross‐sectional area, and presynaptic and postsynaptic characteristics of retinal ganglion cell axon terminals in the superior colliculus of normal adult female Syrian hamsters were investigated by quantitative ultrastructural techniques. After an intravitreal injection of horseradish peroxidase, most labelled axon terminals were found in the stratum griseum superficiale and stratum opticum of the contralateral superior colliculus. However, a small proportion (approximately 2%) of retinal ganglion cell axon terminals were located in deeper layers of the superior colliculus between the stratum opticum and the periaqueductal grey matter. Terminals were smaller in the upper two‐thirds of the stratum griseum superficiale than in the lower one‐third of this layer, the stratum opticum, and the stratum griseum intermedium. Presynaptic characteristics such as the length and number of contacts and the postsynaptic neuronal domains (somata, dendritic spines, or shafts) contacted by retinal ganglion cell axons in the superior colliculus were similar in all layers.
Neuronal differentiation and maturation in the mouse trigeminal sensory system, in vivo and in vitro
Authors: Stainier Didier Y. R. , Gilbert Walter
Published: January 2005

We have isolated and characterized four monoclonal antibodies (mAbs B33, E1.9, B30, and B10) that recognize mouse trigeminal sensory neurons at specific times during development. These antibodies permit the study of neuronal differentiation, axon outgrowth, and neuronal maturation in the trigeminal sensory system. With B33, we can follow migrating neural crest and placode cells into the anlagen of the trigeminal ganglion. E1.9 immunoreactivity marks neuronal differentiation and appears in the central nervous system at embryonic day 8.5 (E8.5) and in the peripheral nervous system at E9. E1.9 and B30 show the axonal outgrowth of trigeminal sensory neurons and reveal the pioneering of the peripheral tracts by an early population of ganglionic neurons. At this stage, in the central nervous system, mesencephalic trigeminal neurons are also E1.9 and B30 positive as they migrate to their final location in the rostral metencephalon. B30 and B10 allow us to follow the maturation of these neurons. Also, in about 1% of the embryos, we identified mispositioned or misrouted trigeminal neurons. Furthermore, these biochemical markers facilitate the study of neuronal development in vitro. We find that, based on morphological and biochemical criteria, the maturation of trigeminal neurons in culture is target independent.
Embryonic development and survival of brachial motoneurons projecting to muscleless chick wings
Authors: Phelan Kevin A. , Hollyday Margaret
Published: January 2005

The role of muscle cells in the survival of embryonic motoneurons projecting to the developing wing was directly examined. Embryos lacking muscle in one of their wings were produced by surgically removing the embryonic precursors of muscle cells, the somites. The resulting limb lacked only muscle cells, with the derivatives of the other limb contributor, the lateral plate mesoderm, left intact. Counts of apparently healthy lateral motor column (LMC) motoneurons supplying normal wings between stages 28 and 36 showed little decline in motoneuron number until stage 34; approximately 24% of the motoneurons died between stages 34 and 36. In contrast, the number of LMC motoneurons supplying muscleless wings declined progressively from stages 28 to 36. This decline resulted in the loss of about 77% of the motoneurons present at stage 28. In addition, the LMCs supplying muscleless wings had fewer motoneurons at all stages examined than similarly staged controls; this difference ranged from 27% in the youngest cases to 75% in the older embryos. Motoneurons were lost equivalently from all rostrocaudal levels of the brachial LMC. From these studies we conclude that motoneuron survival depends on the presence of muscle cells in the developing wing. In the absence of muscle cells, motoneuron death was increased compared to normal embryos at stages prior to the onset of naturally occurring cell death.