bluuebunny/crossref_metadata_2025 huggingface dataset:
Intrinsic connections within and between cochlear nucleus subdivisions in cat
Authors: Snyder Russell L. , Leake Patricia A.
Published: January 2005

The cat cochlear nuclear complex (CNC) is divided into three major subdivisions: the anteroventral, the posteroventral, and the dorsal cochlear nuclei (AVCN, PVCN, and DCN, respectively). Each of these subdivisions receives a topographic projection from the cochlea and each consists of a number of different cell types. The interconnections between these subdivisions and the cell types which give rise to them were studied by means of small injections of horseradish peroxidase (HRP) made at physiologically identified locations. DCN injections resulted in few labeled cells in the DCN, suggesting that its internal connections are very limited. In contrast, these same DCN injections resulted in numerous labeled cells in the PVCN and AVCN. Labeled PVCN cells, consisting of multipolar, octopus, and small spindle‐shaped cells, were located in spatially restricted laminae stretching the entire rostrocaudal length of the nucleus, while labeled AVCN cells consisting of multipolar, globular, small spindle‐shaped and small spherical cells were broadly distributed over the posterior half of the nucleus. Similar injections placed in the PVCN resulted in numerous labeled cells in all three subdivisions. The PVCN and AVCN cells labeled after PVCN injections were widely distributed across the isofrequency representations in both nuclei, while the labeled DCN cells were restricted to locations over the injection sites. Injections placed in the posterior half of the AVCN resulted in only very few labeled cells in the DCN. No cells were labeled following injections in the rostral AVCN.
Plasticity in the developing chick visual system: Topography and maintenance of experimentally induced ipsilateral projections
Authors: Thanos Solon , Düutting Dieter
Published: January 2005

The present work examines the topography of the contra‐ and ipsilateral centrifugal projections from the isthmooptic nuclei (IONs) to the remaining retina in monocular chick embryos. After removal of the left eyecup at embryonic day (E)1.5, the IONs were investigated at various embryonic stages by the retrograde transport of fluorescent dyes and horseradish perioxidase (HRP) injected into the remaining eye. The projection of the ipsilateral ION was consistently found at E13 and frequently disappeared by E18 to E19. Selective regional labeling of the remaining retina in monocular embryos with DiI (1,1′‐dioctadecyl‐3,3,3′,3′‐tetramethyl‐indocarbocyanine perchlorate) revealed that the retinotopic order of the enhanced projection from the ipsilateral ION corresponded precisely to the normal one from the contralateral ION.

The formation of the projection from the retina to the ipsilateral tectum was also investigated at E18 to E19 by means of intravitreally injected HRP or rhodamine‐B‐isothiocyanate (RITC) in monocular embryos after early eyecup removal. In cases with persistent ION, the eye enucleations resulted in ipsilateral retinotectal projections consisting of varying numbers of retinofugal fibers.

The data are consistent with the view that there is a certain degree of plasticity in the embryonic development of the chick visual system. If an ION projection to the ipsilateral retina is strongly developed, it is retinotopically organized and probably influences the maintenance of the ipsilateral retinotectal projection. The stabilization of the otherwise transiently formed ipsilateral retinotectal projection may be influenced by the tectal neurons which receive retinal input and are efferently connected with persisting ION neurons.
New high‐resolution 2‐deoxyglucose method featuring double labeling and automated data collection
Authors: McCasland James S. , Woolsey Thomas A.
Published: January 2005

A new approach to high‐resolution 2‐deoxy‐D‐glucose (2DG) emulsion‐autoradiography which combines improved retention of 2DG labeling, staining with immunohistochemical and other specific markers, and automated data collection and analysis of local silver grain and stain densities is described. The Durham et al. (J. Neurosci. 1:519–526, '81) procedure for fixation of 2DG with periodate‐lysine‐paraformaldehyde (PLP, McLean and Nakane: J. Histochem. Cytochem. 22:1077–1083, '74) was adapted to increase retained label roughly tenfold. Phenobarbital anesthesia is induced 45 minutes after 2DG injection. Barbiturate anesthesia increases brain glycogen (Nelson et al.: J. Neurochem. 15:1271–1279, '68) and presumably increases the incorporation of intracellular 2DG from 2DG‐6P into brain glycogen and other molecules (Nelson et al.: J. Neurochem. 43:949–956, '84; Pentreath et al.: Neuroscience 7:759–767, '82). Iodoacetate is added to cold fixative to prevent glycogen breakdown (Cammermeyer and Fenton: Histochemistry 76:339–356, '82).

This high‐resolution 2DG protocol is directly compatible with many other neuroanatomical techniques. We demonstrate 2DG emulsion autoradiography combined with cytochrome oxidase (CO) histochemistry, markers for axonal pathway tracing, plastic embedding for semithin sections, and immunohistochemical staining for glutamate decarboxylase (GAD). The method should be compatible with antibodies for other antigens and with other neuroanatomical stains.

To collect the data directly from microscope slides, a computer‐controlled microscope was integrated with image‐processing software to eliminate the need for manual counting and scoring of autoradiograms. Regions of interest are scanned automatically at high resolution to map regional labeling and/or stain density. There is excellent correspondence between computer‐enhanced two‐dimensional maps of the data and the original autoradiograms. Automated counts for five specimens were compared to counts of labeled cells by trained observer. The correlation between the two sets of measurements is high (r =. 93).

Automated data collection has been generalized to measure regional stain densities on the autoradiographed sections for direct comparison with silver grain density. The method is extremely flexible, especially since new image‐processing strategies can be developed in software to extract the desired information from materials labeled by other methods (e.g., HRP).

The combination of experimental and data collection strategies generates two‐ or three‐dimensional “maps” of 2DG labeling, histochemical stain, etc., over a brain area of interest and allows direct comparison of these different maps. To our knowledge this is the first report of quantitative reconstructions of 2DG labeling patterns on the basis of large and systematically scanned data samples from emulsion autoradiograms.
Morphology of fungiform papillae in canine lingual epithelium: Location of intercellular junctions in the epithelium
Authors: Holland V. F. , Zampighi G. A. , Simon S. A.
Published: January 2005

The localization and structure of intercellular junctions and barriers in the extragemmal epithelium of canine fungiform papillae were determined by using both morphological and electrophysiological methods. Gap junctions were located in all epithelial strata with the exception of the stratum corneum, suggesting that the epithelium functions as a syncytium. The extracellular space of the stratum corneum was composed of a discontinuous, three‐dimensional network of tight junctions, modified desmosomes, and lamellar bodies. A zonula occludens, which stops the penetration of lanthanum, is present in the uppermost layer of the stratum granulosum. In freeze‐fracture replicas, tight junctions appear as extended networks of ridges of variable thickness on the PF fracture face and complementary grooves on the EF fracture face. The relatively high resistance pathway resulting from the layers of corneocytes and networks of tight junctions and lamellar bodies in the stratum corneum is bypassed by the low‐resistance pathway provided by the taste pore.
Immunohistochemical distribution of serotonin in spinal autonomic nuclei: I. Fiber patterns in the adult rat
Authors: Newton Bruce W. , Hamill Robert W.
Published: January 2005

The differential distribution of serotonin (5HT) fibers in spinal laminae VII and X is described for the adult rat. The results indicate that descending 5HT fibers preferentially innervate those regions of lamina VII that contain sympathetic and parasympathetic neurons. In lamina X, especially the dorsal commissural nucleus, large numbers of 5HT fibers are observed throughout the spinal cord. Moreover, sympathetic nuclei are more richly innervated with 5HT than the spinal parasympathetic nuclei. Spinal cord hemisections reveal that spinal autonomic nuclei are differentially innervated: ipsilateral serotoninergic projections to the intermediolateral cell column are preferentially interrupted. In addition, a large crossed 5HT projection exists throughout the length of the spinal cord that decussates five to six spinal segments rostral to its termination. Both crossed and uncrossed 5HT fibers span many spinal segments and have large numbers of collaterals. Spinal cord transections show that the vast majority of spinal 5HT descends from the brainstem but that some 5HT fibers are of intrinsic origin.
Immunohistochemical distribution of serotonin in spinal autonomic nuclei: II. Early and late postnatal ontogeny in the rat
Authors: Newton Bruce W. , Burkhart Amy B. , Hamill Robert W.
Published: January 2005

These studies reveal that the postnatal ontogeny of serotonin (5HT) in the sympathetic nuclei of the rat spinal cord is protracted; the adult complement of 5HT‐immunoreactive fibers is not achieved until at least 60 days of age. As descending serotonin fibers innervate and demarcate the distribution of preganglionic sympathetic nuclei, rostral‐caudal and temporal gradients exist. Additionally, a heterogeneous segmental 5HT ontogenetic pattern is observed in sympathetic nuclei. Most serotonin fibers in laminae VII and X are unorganized at birth except for some sympathetic nuclei in high thoracic regions where the 5HT sympathetic pattern is being initiated. By postnatal day 6 the framework of the 5HT pattern is established in all sympathetic nuclei, and by postnatal day 16 a pattern is formed, which develops into the compact adult state by postnatal day 60. The protracted period of sympathetic 5HT development corresponds with the length of time it takes for the autonomic nervous system to mature. In addition, 5HT intraspinal cell bodies are observed at all time points examined, except for the day of birth, and are found in the same regions as adult 5HT neurons, i.e., dorsal or lateral to the central canal in laminae VII and X and in all spinal segments except cervical levels. Many of the 5HT neurons are pericanalicular and bipolar in appearance. Multipolar 5HT neurons are first observed on postnatal day 45.
Golgi study of the mouse striatum: Age‐related dendritic changes in different neuronal populations
Authors: Rafols José A. , Cheng Heng Wei , McNeill Thomas H.
Published: January 2005

The Van der Loos modification of the Golgi‐Cox method and morphometric analyses were used to study the neuronal types in the striatum of adult (3, 6, and 10 months) and aged (20, 25, and 30 months) C57BL/6N mice. In adult mice six types of striatal neurons were distinguished primarily on the basis of the morphology of their cell body and dendrites. Each of these types was compared with morphologically similar neurons from previous Golgi classifications in other species and discussed within the framework of recent immunocytochemical work.

With similar methods the age‐related changes occurring on the dendrites of three of the six striatal types were also analyzed. In the mediumsized neuron with spine‐laden dendrites, various dendritic tree shapes and sizes were distinguished in all age groups studied. Qualitative observations as well as measurements of total dendritic length per cell suggested that the dendrites in this type may both grow and regress throughout the life span, although signs of dendritic atrophy and regression were observed only in the aged groups. In the other two types of neuron, one a medium aspiny cell with thin varicose dendrites and the other a large spiny neuron with many dendrites, measurements of total dendritic lengths revealed sustained growth of the tree well into advanced age, followed by moderate regression in the oldest groups. The present findings also indicate that the dendrites of each type of striatal neuron follow unique temporal patterns of growth and regression during the life span of the mouse.
Early postnatal development of the monkey globus pallidus: A Golgi and electron microscopic study
Authors: Cano Josefina , Pasik Pedro , Pasik Tauba
Published: January 2005

The globus pallidus of 20 monkeys ranging in age from newborn to 4 months was examined in Golgi‐impregnated material and ultrastructurally. There was no discernible difference between the lateral and medial segments of the structure. At the light microscope level, all neuronal types described in the adult are found at birth. The most common, the large fusifom cell, shows initial signs of immaturity such as blunt protrusions and dendritic dilations at bifurcation points, as well as growth cones, filopodia, and filiform processes. These features become more rare with age, and by 4 months, the neurons appear fully mature save for the terminal dendritic arborizations which are still underdeveloped. From the earliest ages examined, the large globular cells and the interneurons are more mature than the previous type. The afferent radial fibers of striatal origin are observed from birth, but they are grouped in bundles only after 8 weeks. The density of their climbing branches increases over time, reaching a mature appearance by 16 weeks. Afferents entering from the ventral surface do not yet show clusters of varicosities at 2 weeks. At the latter age, plexuses of fine beaded fibers are already seen covering large extensions of the nucleus.

The fine structure correlates well with the Golgi material. The basic features of the neuropil are present at birth, albeit with immature characteristics such as the incomplete covering of the dendrites with axonal boutons and the low level of myelination of the radial fibers. Growth cones and profiles with signs of degeneration are observed during the first month. In the early ages examined, most dendrites show large varicosities and protrusions, some of which are spinelike and can be postsynaptic to multiple terminals. The other dendritic type, with only an occasional axodendritic synapse, is also seen from birth and increases in size as a function of time. The type I axonal boutons, of probable striatal origin, are quite immature at birth, and their characteristic interdigitations are seen only after the first week. The type II, III, IV, and V boutons appear mature at all ages examined but crest synapses formed by the type III terminals are observed in the later stages of the study. Finally, postsynaptic vesicle‐containing profiles are present at 4 weeks, but triadic synaptic arrangements are formed only by 16 weeks.

Results indicate the occurrence of progressive changes in neuronal and neuropil morphology of both segments of the primate globus pallidus in the first 4 postnatal months and suggest that this structure matures earlier than the neostriatum, probably as a reflection of its diencephalic origin.
Connections of the olfactory bulb and nucleus olfactorius anterior in the hedgehog (Erinaceus europaeus): Fluorescent tracers and HRP study
Authors: De Carlos Juan A. , López‐Mascaraque Laura , Valverde Facundo
Published: January 2005

The projections of the main olfactory bulbs (MOBs) and the dorsal part of the anterior olfactory nucleus (NOA) in the hedgehog (Erinaceus europaeus) have been studied by fluorescent tracers and the horseradish peroxidase method (HRP), respectively, to reveal the pattern of labeling from these structures.

After different dye injections in both MOBs, labeled cells were present in the following structures: tenia tecta, vertical limb of the diagonal band of Broca, and medial septal nucleus in the ipsilateral injection site; and the NOA, piriform cortex, nucleus of the lateral olfactory tract, horizontal limb of the diagonal band of Broca, posterolateral cortical amygdaloid nucleus, anterior amygdaloid area, and dorsal raphe nucleus in both hemispheres. Structures showing double‐labeled cells were the NOA, horizontal limb of the diagonal band of Broca, nucleus of the lateral olfactory tract, anterior amygdaloid area, and posterolateral cortical amygdaloid nucleus.

After HRP injections in the dorsal part of the NOA, labeled cells were distributed in the NOA, nucleus of the lateral olfactory tract, posterolateral cortical amygdaloid nucleus, piriform cortex, horizontal and vertical limbs of the diagonal band of Broca, mitral cell layer of the MOB, tenia tecta, anterior amygdaloid area, and the contralateral NOA. We suggest that the contralateral projection nuclei to the MOB of the hedgehog, unusual in other mammals, and the large number of cells with axonal collaterals projecting to both hemispheres, may be a strategy in these animals to bilaterally integrate brain functions at the expense of its reduced corpus callosum.
Immunohistochemical localization of seven different peptides in the human spinal cord
Authors: Chung K. , Carlton S. M. , Westlund K. N. , Briner R. P.
Published: January 2005

It is necessary to study the normal chemical contents in the human spinal cord in order to understand neurochemical changes that might occur under pathological conditions. In the present study, the comparative distribution of seven peptides was examined immunohistochemically in four levels (cervical, C; thoracic, T; lumbar, L; sacral, S) of the human spinal cord by means of the peroxidase‐antiperoxidase technique. The peptides examined included bombesin (BOM), substance P (SP), cholecystokinin (CCK), somatostatin (SOM), methionine‐enkephalin (M‐ENK), vasoactive intestinal polypeptide (VIP), and thyrotropin releasing hormone (TRH). Among the seven peptides examined, four (BOM, CCK, SOM, and TRH) have never been described in the human spinal cord and the present work clearly demonstrates their existence in specific patterns. The terminals that were immunostained for BOM and CCK were localized in high concentration in the superficial dorsal horn (laminae I‐II), in moderate amounts in the lateral part of laminae V and VII, and lesser amounts in the intermediate gray (lamina VII) and the dorsal part of the central gray (lamina X). Whereas BOM showed a similar distribution pattern at all spinal levels, CCK was mainly found in thoracic and lumbar levels. The SOM terminals were localized in the superficial dorsal horn (the highest density in lamina II but very few in lamina I), the intermediolateral cell column, intermediate gray, and central gray. This peptide was more widely distributed in the sacral cord with its terminal field extending into the ventral horn. The TRH terminals were mainly located in the ventral horn. Frequently, TRH terminals were seen adjacent to large ventral horn neurons. Furthermore, many neurons in the ventral and intermediate gray and Clarke's column demonstrated TRH immunoreactivity. The other three peptides (SP, M‐ENK, and VIP) have been previously demonstrated in the human spinal cord and the present study confirmed their general spinal distribution with minor differences.
Amacrine and ganglion cells with corticotropin‐releasing‐factor‐like immunoreactivity in the turtle retina
Authors: Williamson Douglas E. , Eldred William D.
Published: January 2005

This study, which uses immunocytochemical methods at the light microscopical level, examines the cell types in the turtle retina that contain corticotropin‐releasing factor (CRF)‐like immunoreactivity. Two anatomically distinct amacrine cell types are labeled when antiserum directed against ovine CRF is used to label the turtle retina. These cell types each have a different dendritic arborization pattern and regional distribution. Type A cells are found only in the visual streak and have elongated dendritic arborizations that run parallel to the visual streak. These cells arborize primarily in stratum 1 and near the border of strata 2 and 3, with some processes extending into stratum 5. Type B amacrine cells are found only ventral to the visual streak and arborize primarily in a wide band in strata 4 and 5 with sparse dendritic arborizations in stratum 1. No labeled amacrine cells of any type were found dorsal to the visual streak. The asymmetric dendritic arborizations of the type A amacrine cells and the different regional distributions of the A and B cell types suggest that these two amacrine cell types perform distinct physiological functions.

In addition to these labeled amacrine cells, there are also some immunoreactive cell bodies in the ganglion cell layer. Rhodamine crystals were applied to the optic tectum to retrogradely label the ganglion cell bodies. Double label studies indicate that some of the rhodamine‐labeled ganglion cells also contain CRF‐like immunoreactivity. The localization of CRF‐like immunoreactivity in two distinct amacrine cell types and in ganglion cells suggests that it may play multiple roles in visual processing in the turtle retina.
Regeneration of muscle axons in the frog is directed by diffusible factors from denervated muscle and nerve tubes
Authors: Kuffler Damien P.
Published: January 2005

In the frog, peripheral muscle axons regenerate after a lesion to reinnervate the original synaptic sites on muscle fibers. Previous experiments in the frog have shown that satellite cells of the nerve tube direct the outgrowth of regenerating muscle axons over distances of many millimeters. In the present experiments, denervated muscle was used as a target for regenerating muscle axons. Muscle and satellite cells of the nerve tube also were placed in filters to determine if their influence on axonal outgrowth was exerted by diffusible factors. Filters were used with a pore size of 0.22 μm. With this pore size, target cells were isolated from physical contact with the surrounding cells; yet an exchange of fluids–and therefore of molecules released by the target cells–could occur across the filter.

In the presence of denervated muscle or satellite cells of the nerve tube in filters, regenerating axons turn and grow toward the target cells. This influence on the direction of axonal outgrowth was produced over distances of 6 mm by muscles and 4 mm by cells of the nerve tubes. This directed outgrowth is in marked contrast to the random pattern of outgrowth in the absence of the targets.

The present findings set the stage for tissue culture experiments in which the phenomena observed in vivo can be analyzed in terms of mechanisms. The present finding that denervated muscle attracts regenerating axons means that sufficient material may be available for the characterization and isolation of the relevant molecules.
Differential colocalization of neuropeptide Y‐ and methionine‐enkephalin‐Arg6‐Gly7‐Leu8‐ like immunoreactivity in catecholaminergic neurons in the rat brain stem
Authors: Murakami Sadatsugu , Okamura Hitoshi , Pelletier Georges , Ibata Yasuhiko
Published: January 2005

The present study, using a combination of catecholamine (CA) histofluorescence and peptide immunocytochemistry in the same tissue sections, investigated the coexistence of neuropeptide Y (NPY) and methionine‐enkephalin‐Arg6‐Gly7‐Leu8 (MEAGL)‐like immunoreactivity (LI) in catecholaminergic neurons of colchicine‐treated rat brain stems. Of the total number of catecholaminergic neurons in the A1/C1, A2/C2, A3, A4, and A6 regions approximately 83, 28, 98, 76, and 36%, respectively, contained both NPY‐LI and CA. Of the total number of catecholaminergic neurons in A1/C1, A2/C2, A3, and A5 regions, approximately 47, 4, 8, and 17%, respectively, contained both MEAGL‐LI and CA. Moreover, about 24% of the catecholaminergic neurons in the A1/C1 region contained both NPY‐ and MEAGL‐LI. Neither the noradrenergic neurons (A7) in the pons nor any of the dopaminergic neurons in the midbrain (A8, A9, A10) contained NPY‐ or MEAGL‐LI. Neurons containing both NPY‐ and MEAGL‐like immunoreactive peptides without CA were not found in the rat brain stem.

These findings indicate that catecholaminergic neurons in the brain stem of the rat can be subdivided into distinct subgroups on the basis of the coexistence of specific peptides.
Structure‐function relationships in rat brainstem subnucleus interpolaris: V. Functional consequences of neonatal infraorbital nerve section
Authors: Jacquin Mark F.
Published: January 2005

In a prior study (Jacquin et al., '86c), the response properties and projections of neonatally axotomized trigeminal (V) primary afferents were studied in the adult rat. Here, single‐unit recording, electrical stimulation, and receptive field (RF) mapping techniques were also used to assess the functional consequences of neonatal infraorbital nerve section upon postsynaptic cells in V brainstem subnucleus interpolaris (SpVi). Of 904 cells studied, 385 were from normal adults and 519 were from neonatally deafferented adults. Infraorbital nerve section at birth resulted in: (1) a substantial reduction in those areas of SpVi containing cells with infraorbital RFs, and only a slight increase in areas solely responsive to noninfraorbital surfaces, (2) an absence of orderly topography within cells expressing regenerate primary afferent inputs, (3) a slight increase in mean discharge latency to V ganglion or thalamic shocks, (4) an increased relative percentage of cells orthodromically activated by diencephalic or cerebellar shocks, (5) a decreased relative percentage of mystacial vibrissa‐sensitive local circuit neurons, with a corresponding increase in local circuit nociceptors and unresponsive cells, (6) an increased relative percentage of mystacial nociceptors, vibrissae, guard hair, and/or skin sensitive cells projecting to thalamus and/or cerebellum, (7) an increased percentage of local circuit neurons with RFs including more than one vibrissa, whereas projection neurons did not differ from normal in the number of vibrissae composing their RFs, and (8) an increased relative percentage of cells expressing interdivisional and intermodality convergence, split RFs, spontaneous activity, directional, high velocity, and neuroma sensitivity.

Thus neonatal nerve section produces changes in topography, inputs, projection status, and responses of surviving postsynaptic neurons. Although many of these centrally observed alterations can be attributed to altered peripheral projections in axotomized V primary afferents, others must reflect central reorganization. The central mechanisms responsible for the synthesis of deafferentation‐induced RFs remain to be elucidated.
HRP study of cerebellar corticonuclear‐nucleocortical topography of the dorsal culminate lobule—lobule v—in a prosimian primate (Galago): with comments on nucleocortical cell types
Authors: Haines D. E.
Published: January 2005

The distribution of retrogradely labeled cerebellar nucleocortical (NC) cells and anterogradely labeled corticonuclear (CN) fibers was investigated in a prosimian primate (Galago) by means of horseradish peroxidase as a tracer. Iontophoretic and pressure injections were made in the cortex of lobule V and the resultant patterns of label were determined in the cerebellar nuclei. Following iontophoretic injections in vermal (zone A), intermediate (zones C1, C3), and lateral (zone D) cortices, retrogradely labeled cells were present in medial (NM), anterior interposed (NIA), and lateral (NL) cerebellar nuclei, respectively. Larger injections that involved A‐C2 zones resulted in NC label in NM, medial NIA, and throughout the posterior interposed (NIP) nucleus. Retrogradely labeled NC cells were usually found in areas of their respective nuclei that also contained anterogradely filled CN axons. In addition, retrogradely labeled cells were seen contralateral to some injections. Contralateral NC cells were found mainly in the NM and NIP and seemed to be labeled in response to injections that involved zones A, C2, and possibly x on the opposite side. No contralateral CN labeling was seen. It appears that the NC projections of lobule V follows a basic zonal (sagittal) orientation and that most are reciprocal to CN fibers arising from the same cortical area.

There is evidence of zonal heterogeneity in the ipsilateral NC projection. Iontophoretic injections placed in adjacent zones resulted in markedly different numbers of retrogradely labeled NC cells in their respective nuclei. Also, after pressure injections that involved two or more adjoining zones, the number of labeled NC cells was large in one nucleus but minimal in an adjacent nucleus. These data suggest that different cerebellar cortical zones have quantitatively different NC input; this may relate to specific functional demands placed on each nucleus and its corresponding cortical zone.

On the basis of their known connections, it is hypothesized that there are at least three and possibly four categories of NC cells. Ipsilateral reciprocal NC cells are found in, or on the periphery of, CN terminal fields formed by axons originating from the same cortical area to which the NC cells project. Ipsilateral nonreciprocal NC cells are located outside the CN terminal field and may even be found in an adjacent nucleus; these are fewer in number than the reciprocal population. Contralateral NC cells are found in the opposite cerebellar nuclei and appear to be topographically related to the ipsilateral contingent as well as to the injection site. It is probable that different types of NC cells have individualized functional characteristics.
Functional subdivisions in the auditory cortex of the guinea pig
Authors: Redies H. , Sieben U. , Creutzfeldt O. D.
Published: January 2005

The auditory fields in the cortex of the guinea pig were investigated with microelectrode mapping techniques. Pure tones of varying frequencies and amplitudes were used as acoustic stimuli. Mainly, multiunit activity was recorded.

A large tonotopic area is found in the anterior half of the auditory cortex. This area is named the anterior field (field A). Frequency tuning curves of multiunits in field A are generally narrow. Responses to tone stimuli are strong, and latencies are short. Low best frequencies are represented rostrally, high best frequencies caudally. The tonotopy is continuous and quite regular. Field A is narrow dorsally and becomes gradually broader ventrally. Correspondingly, the isofrequency lines slightly diverge from dorsal to ventral.

Caudal to the first field, there is a second, smaller tonotopic area. It lies in the dorsal half of the posterior auditory cortex and is therefore named the dorsocaudal field (field DC). The frequency specificity of the cell clusters in this area is as strong as in field A, but the tonotopy is discontinuous: In the dorsal half of field DC, high best frequencies (16‐32 kHz) are represented rostrally; the low frequencies (0.5‐2.8 kHz) are represented immediately caudal to the high frequencies, while the intermediate frequencies are missing. Ventrally in field DC, the frequency representation is more complete. Except for this discontinuous map, we did not notice any differences between fields A and DC. A third tonotopic field was found rostral to field A. This field extends over a surface of less than 1 mm2 and was named the small field (field S). It contains a complete representation of the frequency range; high best frequencies are located rostrally, low frequencies caudally. The response latencies are slightly longer in field S than in fields A or DC, and the tuning curves are broader.

A broad strip of nontonotopic cortex (auditory belt) surrounds fields A and DC caudally. We subdivided this area into the dorsocaudal and the ventrocaudal belt region. In both areas, tuning curves are often broad, and response latencies are longer than in the tonotopic cortex. In the dorsocaudal belt, most multiunits react with a phasic on‐response to pure tones; in the ventrocaudal belt, tonic responses occur more frequently. Another nontonotopic region is located in the anterior auditory cortex, rostral to the tonotopic fields, and was therefore named the rostral belt. Tuning curves in this area are broad, latencies are short, and reponse thresholds are often high.

In the discussion, the guinea pig is compared with other mammalian species. Species‐specific features in the organization of the tonotopic cortex of the guinea pig are revealed.
Cranial motor neurons contain either galanin‐ or calcitonin gene‐related peptidelike immunoreactivity
Authors: Moore Robert Y.
Published: January 2005

The demonstration of coexistence of a peptide or peptides in neurons that produce a small molecule neurotransmitter has become increasingly frequent. The calcitonin gene‐related peptide (CGRP) is known to be colocalized in the cholinergic neurons of both cranial and spinal motor nuclei. The present study demonstrates that all somatic motor cranial nerve nuclei contain CGRP‐and galaninlike immunoreactivity. The perikaryal content of both peptides is increased by colchicine pretreatment and by transecting axons arising from the perikarya, and both peptides are found in nerve fibers innervating striated musculature. CGRP‐ and galaninlike immunoreactivity appear to be present in different populations of neurons. In contrast to CGRP, galaninlike immunoreactivity was not detected in spinal motor neurons. These observations suggest that galanin and CGRP participate in the process of synaptic transmission at the neuromuscular junction of cranial motor neurons.
Effects of very early monocular and binocular enucleation on primary visual centers in the tammar wallaby (Macropus eugenii)
Authors: Marotte L. R. , Flett D. L. , Mark R. F.
Published: January 2005

The role of retinal afferents and their binocular interactions in the development of mammalian primary visual centers has been studied in the marsupial wallaby. Monocular and binocular enucleation was performed prior to any retinal innervation of the visual centers. After monocular enucleation retinal projections were traced by horseradish peroxidase histochemistry and compared with those in normal animals and those during development. The topography of retinal projections to the superior colliculus and the dorsal lateral geniculate nucleus after monocular enucleation was determined by making retinal lesions and tracing the remaining projections with horseradish peroxidase. The position and nature of the filling defects in terminal label were compared with controls with similarly placed lesions.

The superior colliculus and dorsal lateral geniculate nucleus ipsilateral to the remaining eye were shrunken. Projections to the ipsilateral superior colliculus, ipsilateral accessory optic nuclei, and ipsilateral suprachiasmatic nucleus, although enlarged, never approached the density contralaterally, as was also the case during normal development. The expanded projection in the ipsilateral superior colliculus came primarily from temporal and ventral retina. In the dorsal lateral geniculate nucleus, terminal bands and cellular laminae, although not identical to normal, did develop. During normal development overlap of afferents from the two eyes occurs in the binocular region. The decrease in volume of the nucleus ipsilateral to the remaining eye after monocular enucleation suggests that the monocular region disappears in the absence of appropriate input and the binocular region survives. Contralaterally there was no decrease in volume, compatible with this idea. The topography of retinal projections supports this interpretation. It was normal contralaterally while ipsilaterally it was appropriate for the normal binocular region. There was an expansion of the projection along the lines of projection in what would normally be binocular regions of the nucleus, where retinal afferents failed to segregate in the absence of binocular competition.

After binocular enucleation the α and β segments of the dorsal lateral geniculate nucleus were still recognizable but cell‐sparse zones were absent, as was the characteristic orientation of primary dendrites of geniculocortical cells.

There are rigid developmental constraints operating on the innervation of territory by retinal afferents from the two eyes, and many features of the mature pattern arise without binocular interactions during development.
Structure and histogenesis of the principal sensory nucleus of the trigeminal nerve: Effects of prenatal exposure to ethanol
Authors: Miller Michael W. , Muller Susan J.
Published: January 2005

Clinical and experimental evidence shows that prenatal exposure to ethanol causes craniofacial malformations, microcephaly, and abnormal development of the central nervous system. This study describes the effects of ethanol on the development of the principal sensory nucleus of the trigeminal nerve (PSN). The offspring of two groups of rats were examined. Pregnant females in one group were fed a liquid diet containing 6.7% (v/v) ethanol (Et) and rats in the other group were fed an isocaloric liquid control diet (Ct). Each pregnant rat was administered [3H]thymidine on one day during the period from gestational day (G) 10 to G22. After pups grew to 30 days of age, they were killed and their brains were processed by an autoradiographic procedure.

Qualitatively, the PSN of Ct‐ and Et‐treated rats appeared similar; they were composed chiefly of small neurons and a few scattered large neurons. On the other hand, quantitative analyses revealed significant differences between both groups. Although the volume of the PSN of Et‐treated rats was not significantly different (‐3.2%) than that for Ct‐treated rats, the PSN of Et‐treated rats had significantly (P <0.01) fewer (30.0%) neurons than did the PSN of Ct‐treated rats. The number of the small neurons, but not of the large neurons, was affected most by the ethanol exposure. Prenatal exposure to ethanol also altered the generation of PSN neurons. Most neurons in the PSN of Ct‐treated rats were born between G12 and G15, the small neurons being generated before the large neurons. In Et‐treated rats, too, small neurons were born before the large neurons; however, the time frame of neuronogenesis was delayed as it occurred between G13 and G16.

Thus, prenatal exposure to ethanol produces profound developmental abnormalities that lead to permanent alterations in the structure of the mature central nervous system.
Topography of cones and rods in the tree shrew retina
Authors: Müller Brigitte , Peichl Leo
Published: January 2005

The topographical distribution of cones and rods in the tree shrew retina was analysed quantitatively in whole‐mounted retinae and horizontal semithin sections stained with cresyl violet or toluidine blue. The outer nuclear layer consists of a single layer of photoreceptor nuclei with the rod nuclei slightly displaced towards the outer plexiform layer. This facilitated quantification of the photoreceptor populations. The density of cones ranges from 12,000/mm2 in the peripheral retina to a maximum of 36,000/mm2 in the inferior retina. Unlike ganglion cell density, the density of cones does not peak in the temporal retina. Rod density, between 500/mm2 and 3,500/mm2, also peaks in the inferior retina, but not in the same region as cone density. Rods constitute from 1 to 14% of the photoreceptor population, depending on retinal location, and have a local minimum at the central area. Amongst the cones a regularly arrayed subpopulation of presumed blue‐sensitive cones is distinguished by its special staining properties. These cones constitute between 4 and 10% of the cone population depending on retinal location. A second, irregularly spaced, subpopulation of possibly pathological cones is also described.
Integrity of the blood‐brain barrier in retinal xenografts is correlated with the immunological status of the host
Authors: Young Michael J. , Rao Kanchan , Lund Raymond D.
Published: January 2005

The purpose of this study was to determine the immunological correlates of blood‐brain barrier breakdown in retinal xenografts in rats by utilizing skin grafting to initiate a timed immune response to the transplanted neural tissue. Embryonic day 13–14 CD‐1 mouse retinae were grafted into the brainstem parenchyma of neonatal Sprague‐Dawley rats. In one group of animals a 100 mm2 CD‐1 skin graft was placed on the flank 21 days after the initial neural transplant in order to provoke an immune response to the neural graft. Control animals received no skin graft. Animals were injected with horseradish peroxidase (HRP) in the femoral vein 2–8 days after skin grafting. Brains were processed for Nissl, HRP‐tetramethylbenzidine, and anti‐M‐6, ‐lymphocyte, ‐macrophage, and ‐astrocyte antibodies. Experimental and control animals injected 2–4 days after skin grafting showed no leakage of reaction product in the grafted tissue. A small percentage (one of eight) of 5‐day animals showed isolated, patchy leakage, but no evidence of rejection of the neural graft. At 6 days all of the grafts showed evidence of leakage, and 71% of these grafts showed infiltration of lymphocytes. By 7–8 days extensive leakage of HRP and widespread infiltration of lymphocytes and macrophages were clearly evident.

The present study demonstrates that blood‐brain barrier breakdown is correlated closely with the sequence of immunological rejection of the graft. While these results confirm that a barrier exists in healthy neural transplants, they suggest that immunological factors should be considered in cases in which grafts are not protected by an intact barrier.
Structure of a tonically transmitting synapse between identified interneurone in the locust brain
Authors: Simmons Peter J. , Littlewood P. M. Henk
Published: January 2005

The ultrastructure and distribution of synapses between large second‐order and third‐order neurones of a locust ocellus are described. Pairs of neurones, shown by physiological tests to be connected by a tonically transmitting, excitatory connection, have been injected with hexamminecobaltic ions, which allows their profiles to be recognised with electron microscopy. The synapses are made in the lateral ocellar tract, between the axons of some of the second‐order neurones and a network of fine processes from the third‐order neurone. A physiological connection is composed of several thousand discrete anatomical synapses. Each anatomical synapse is composed of a presynaptic density associated with a cloud of round, electron‐lucent vesicles overlying an intercellular cleft. Parallel with the presynaptic density is a row of omegashaped invaginations of the presynaptic plasmalemma. The synapses are diadic and are close to synapses from small, unidentified neuronal profiles onto the third‐order neurone.
Calbindin‐immunoreactive sensory neurons of dorsal root ganglion project to skeletal muscle in the chick
Authors: Philippe E. , Droz B.
Published: January 2005

In the chicken dorsal root ganglia, two neuronal subpopulations referred to as A1 and B1 share in common an immunoreactivity to antisera raised to calbindin D‐28k but are distinguished by their cytological and ultrastructural characteristics. To determine the peripheral targets innervated by calbindin‐immunoreactive neurons in lumbosacral dorsal root ganglia, cryostat sections of various hindlimb tissues were treated with anticalbindin antisera. Calbindin‐immunostained axons were clearly detected in skeletal muscle. Large myelinated nerve fibres and afferent axon terminals in neuromuscular spindles were calbindin‐immunoreactive; thin unmyelinated nerve fibres were also immunostained in nerve bundles of the perimysium. Since motoneurons and neurons of the autonomic nervous system were devoid of calbindin immunostaining, it was suggested that the immunoreactive axons found in skeletal muscle originate from sensory neurons expressing a calbindin immunoreaction in the dorsal root ganglia. This hypothesis was corroborated after introduction of wheat germ agglutinin coupled with horseradish peroxidase or colloidal gold particles into the sartorius muscle. The retrogradely transported tracer was collected only in ganglion cell bodies which displayed the ultrastructural characteristics of A1 and B1 sensory neurons. On the basis of calbindin immunoreaction and of tracer retrograde transport, it is concluded that ganglion cells of subclasses A1 and B1 contribute to the sensory innervation of skeletal muscle in the chicken.
Ultrastructural analysis of somatostatin‐immunoreactive neurons and synapses in the temporal and occipital cortex of the macaque monkey
Authors: De Lima Ana D. , Morrison John H.
Published: January 2005

Somatostatin‐containing neurons and terminals have been analyzed in monkey temporal and occipital cortex by using light and electron microscopic immunohistochemistry. An antibody against Somatostatin‐28(1–12), that was shown previously preferentially to label fibers (Morrison et al.: Brain Research 262:344–351, 1983), was utilized. As expected, few cell bodies were labeled. At the electron microscopic level, labeled cells presented a characteristic asymmetric position of the nucleus and very few symmetric or asymmetric synapses on the somatic surface. In all areas examined, somatostatin fibers formed a dense plexus in the most superficial layers (I‐upper III). The density of labeled fibers in intermediate (deep III–IV) and deep layers (V–VI) varied considerably among areas. The synaptic relationships of the immunoreactive fibers were analyzed and postsynaptic targets quantified in V1, V2, and the superior and inferior temporal gyrus (STG and ITG, respectively). The synapses formed by somatostatin‐labeled boutons were of the symmetric type (type II) and the primary postsynaptic targets were dendritic shafts. No regional differences were found in the distribution of the postsynaptic targets in layers I‐upper III. The pattern of synapses in the deep layers was examined in STG. The frequency and distribution of postsynaptic targets was similar to the superficial layers of STG and the other temporal and occipital regions. In intermediate layers of the temporal cortex areas there was an increase in the proportion of synapses on dendritic spines. In a correlated light and electron microscopic analysis we examined synapses made by radial fibers in these regions and found that although the main targets are distal dendritic shafts, almost 40% of synapses were on dendritic spines. We suggest that the radial fibers may originate from a specialized interneuron, previously described as the double bouquet cell, and that this particular subset of somatostatin‐containing double bouquet cells is likely to exhibit a very high degree of regional heterogeneity with a preference for association cortices with extensive cortico‐cortical convergence.