bluuebunny/crossref_metadata_2025 huggingface dataset:
The astrocyte as a locus of carbonic anhydrase in the brains of normal and dysmyelinating mutant mice
Authors: Cammer Wendy , Tasey Francine A.
Published: January 2005

There is some controversy in the literature whether carbonic anhydrase occurs in astrocytes, as well as in oligodendrocytes and myelin, in the mammalian brain. In the present study this issue was addressed by double immunostaining for carbonic anhydrase and two astrocytic “markers” in the brains of normal mice and two dysmyelinating mutants, jimpy and shiverer. In the brains of young mice, carbonic anhydrase and glutamine synthetase were colocalized in astrocytes in the cortical gray matter. In gray matter of the adult mouse brain, it was possible to immunostain both carbonic anhydrase and glial fibrillary acidic protein (GFAP) in the same cells. However, in contrast to the findings in gray matter, in and near subcortical white matter carbonic anhydrase could be detected only in oligodendrocytes and myelinated fibers. In the brains of jimpy mice, virtually all the carbonic‐anhydrase‐positive cells were also GFAP positive, even in regions normally occupied by white matter. In the brains of young and adult shiverer mice, carbonic anhydrase was localized in astrocytes in the gray matter, but in and near the tracts normally occupied by white matter carbonic anhydrase could be detected only in oligodendrocytes and their abundant process. The findings confirmed the oligodendrocyte‐myelin unit to be the primary locus of carbonic anhydrase in the normal mouse brain and showed the astrocytes in gray matter normally to be a secondary locus of carbonic anhydrase. The immunostaining in the jimpy mouse brain suggested further that reactive astrocytes, in particular, might be rich in carbonic anhydrase.
Cholinergic neurons in the brain of a teleost fish (Porichthys notatus) located with a monoclonal antibody to choline acetyltransferase
Authors: Brantley Richard K. , Bass Andrew H.
Published: January 2005

A monoclonal antibody (Ab8) to choline acetyltransferase (ChAT) was used to locate structures showing ChAT‐like immunoreactivity (ChAT‐IR) in the brain of a teleost fish, the midshipman (Porichthys notatus). ChAT is the synthetic enzyme for acetylcholine found in neurons using that neurotransmitter; thus ChAT‐IR may be interpreted as indicating putative cholinergic activity. Robust staining is seen in all cranial nerve motor nuclei. In addition, the brainstem of Porichthys is distinguished by two other expansive ChAT‐IR zones: a sonic motor nucleus, which innervates swimbladder “drum” muscles, and an octavolateralis efferent nucleus, which innervates acoustic, vestibular, and lateral line end organs. Scattered labeled cells are found in several cranial sensory nuclei–the vagal lobe, and the main and descending trigeminal nuclei. ChAT‐IR cells form restricted subpopulations in other noncranial nerve nuclei, including the granule cell layer of the cerebellum; superior, medial, and inferior divisions of the reticular formation; the stratum periventriculare of the midbrain's optic tectum; and the nucleus isthmi in the midbrain tegmentum. In the telencephalon, a dense population of ChAT‐IR cells is found in the ventral nucleus of area ventralis; terminals and fine fibers are found in the dorsal, medial, and central nuclei of area dorsalis. Together, the data represent the first complete report of ChAT‐IR cell bodies in the brain of any nonmammal with the monoclonal antibody Ab8, which has already been extensively used on a variety of vertebrate brains. The results are thus discussed from a comparative viewpoint, considering reports of ChAT‐IR in different taxa.
Onset and development of intersegmental projections in the chick embryo spinal cord
Authors: Oppenheim Ronald W. , Shneiderman Amiram , Shimizu Iwao , Yaginuma Hiroyuki
Published: January 2005

The ontogeny of intersegmental (propriospinal) projections was studied in the chick embryo spinal cord between embryonic day 2.5 and day 6. Our goals were (1) to determine the earliest projections of intersegmental interneurons between specific spinal regions and to establish the cell types involved; and (2) to follow the ontogeny of these projections during the early formative stages of spinal cord development. Studies were carried out in vitro by using an isolated spinal cord/brainstem preparation. Horseradish peroxidase injections were made either uni‐ or bilaterally at various levels of the spinal cord along the rostrocaudal axis of the embryo. HRP histochemistry was done on Vibratome sections with diaminobenzidine as the chromogen.

Following unilateral injections at day 2.5, labelled commissural interneurons were found contralaterally and were confined to the injected segment. Subsequently, labelled cells were found progressively further away from the injected segment. By day 4.5 reciprocal projections extended between lumbar and brachial regions. Interneurons with intersegmental axonal projections were often undifferentiated, consisting of primitive unipolar or bipolar cells with little, if any, dendritic development. In some cases migrating interneurons could be retrogradely labelled from two or three segments away from the location of their translocating cell body. Anterograde Golgi‐like labelling of early undifferentiated cells revealed growing axons, axonal terminals, and growth cones. Five or six reasonably distinct classes of intersegmental interneurons were identified based on their location, axonal projections, and morphology of dendritic arbors. These appeared to be segmentally and bilaterally arranged along the rostrocaudal axis of the spinal cord. The axons of some of these types of interneurons exhibited preferences in their longitudinal projections within the ventral and ventrolateral marginal zone at the very onset of pathway formation. From the present observations it can be concluded that intersegmental connectivity precedes the development of ascending and descending supraspinal, as well as primary afferent connections in the chick embryo spinal cord.
Neuronal surface changes in the dorsal vagal motor nucleus of the guinea pig in response to axotomy
Authors: Engel Andreas K. , Kreutzberg Georg W.
Published: January 2005

Ultrastructural changes occurring in the dorsal motor nucleus of the vagus of the guinea pig after nerve transection were investigated. Two neuronal populations could be distinguished. Large neurons corresponding to the vagal motoneurons showed chromatolysis. They were found to develop complex changes in cell surface, which appeared either as a folding up and formation of flaplike processes or as invagination of adjacent neuronal or glial elements. Large processes often covered part of the plasmalemma and formed stacks of several neuronal lamellae. Smaller processes were mostly seen to extend into the neuropil, where they intermingled and adopted a budlike shape. These changes occurred in the cell somata within the first week after axotomy. The dendrites were affected after a short delay. The changes persisted for several months in most of the neurons, including the ones that showed signs of recovery from chromatolysis. The newly formed cellular extensions had a growth‐cone‐like internal structure, containing numerous smooth‐surfaced vesicles or cisternae, a feltwork of filamentous material, dense‐cored vesicles, and occasionally free polyribosomes. These surface changes did not occur in the second neuronal cell type of this nucleus, which had a smaller perikaryon characterized by a scanty cytoplasm. These cells did not show a retrograde degeneration and thus are probably interneurons. Acetylcholinesterase was used as a cytochemical marker of neuronal membranes. Surprisingly, the vagal motoneurons did not show a loss of enzymatic activity after nerve transection. Rather, a redistribution seemed to occur with intensified staining of the plasmalemma. The newly formed processes were consistently found to be acetylcholinesterase positive. It is suggested that the morphological changes observed correspond to an asyetunobserved growth process in the adult central nervous system, which involves perikarya and dendrites of regenerating guinea pig vagal motoneurons.
Development of the rat thalamus: III. Time and site of origin and settling pattern of neurons of the reticular nucleus
Authors: Altman Joseph , Bayer Shirley A.
Published: January 2005

Short‐survival, sequential, and long‐survival thymidine radiograms of rat embryos, fetuses, and young pups were analyzed in order to examine the time of origin, settling pattern, migratory route, and site of origin of neurons of the reticular nuclear complex of the thalamus. On the basis of its chronoarchitectonics, the reticular nucleus was divided into a central, medial, and lateral subnucleus. The central subnucleus is the earliest produced component of the entire thalamus with over 50% of its neurons being generated on day E13 and another 40% on day E14. Peak production of neurons of the lateral and medial subnuclei is on day E14. There is a lateral (earlier) to medial (later) neurogenetic gradient between these two components of the reticular complex: only about 12% of the lateral subnucleus neurons, but close to 30% of the medial subnucleus neurons, are generated on day E15. Because the lateral and medial subnuclei display the typical outside‐in gradient found in the thalamus, they are considered to constitute a single cytogenetic sector; the early generated central subnucleus, which violates this order, is considered to constitute a separate cytogenetic sector.

Observations are presented that neurons of the central reticular subnucleus originate in a unique neuroepithelial region, the reticular protuberance. The migration of heavily labeled cells was traced from this region in rats labeled with 3H‐thymidine on day E13 and killed on the subsequent days. The neurons of the lateral and medial reticular subnuclei originate in the reticular lobule of the thalamic neuroepithelium. The migration of heavily labeled, spindle‐shaped cells was traced from this region in rats labeled with 3H‐thymidine on days E14 and E15 and killed at daily intervals thereafter. The neurogenetic gradient of the reticula thalamic complex seen in postnatal rats is established before birth.
Neuronal cell proliferation and ocular enlargement in black moor goldfish
Authors: Raymond Pamela A. , Hitchcock Peter F. , Palopoli Michae F.
Published: January 2005

The mechanisms that control cell proliferation in the developing nervous system are not well understood. In larval and adult goldfish addition of new retinal neurons continues as the eye grows, but the factors that modulate the rate of cell proliferation are unknown. The eyes of Black Moors grow excessively during postembryonic life, probably as a direct result of abnormally elevated intraocular pressure. Ocular growth must be partly autonomous in Black Moors because in some individuals the two eyes are very different in size. To determine whether cell proliferation and neuronal cell number in the retina were correlated with size of the eye, we counted dividing neuronal progenitor cells (rod precursors) and mature retinal neurons (ganglion cells) in the retinas of ocularly asymmetric fish. Rod Precursors, which are scattered across the retina in the outer nuclear layer, were labeled with 3H‐thymidine and counted on histological sections processed for autoradiography. Ganglion cells were counted in retinal whole mounts. We found that the total population of dividing rod precursors and the total number of ganglion cells were systematically greater in the large eye compared to the small eye of individual fish. We conclude that control of the rate of neuronal proliferation in the teleost retina is intrinsic to the eye and is probably regulated by the same factors that control ocular growth.
Anatomic organization of basoventral and mediodorsal visual recipient prefrontal regions in the rhesus monkey
Authors: Barbas H.
Published: January 2005

The sources of ipsilateral cortical afferent projections to basoventral and mediodorsal prefrontal cortices that receive some visual input were studied with retrograde tracers (horseradish peroxidase or fluorescent dyes) in eight rhesus monkeys. The basoventral regions injected with tracers included basal (orbital) areas 11 and 12, lateral area 12, and ventral area 46. The mediodorsal regions included portions of medial area 32 and the caudal part of dorsal area 8. These sites represent areas within basoventral and mediodorsal prefrontal cortices that show a gradual increase in architectonic differentiation in a direction from the least differentiated orbital and medial limbic cortices toward the most differentiated cortices in the arcuate concavity. The results showed that the visual input to basoventral and mediodorsal prefrontal cortices originated largely in topographically distinct visual areas. Thus, basoventral sites received most of their visual cortical projections from the inferior temporal cortex. The rostral inferior temporal region was the predominant source of visual projections to orbital prefrontal sites, whereas lateral area 12 and ventral area 46 also received projections which were found more caudally. In contrast, mediodorsal prefrontal sites received most of their visual projections from dorsolateral and dorsomedial visual areas. The cells of origin were located in rostromedial visual cortices after injection of retrograde tracers in area 32 and in more caudal medial and dorsolateral visual areas after injection in caudal area 8. The latter also received substantial projections from visuomotor regions in the caudal portion of the lateral bank of the intraparietal sulcus. These results suggest that the basoventral prefrontal cortices are connected with ventral visual areas implicated in pattern recognition and discrimination, whereas the mediodorsal cortices are connected with medial and dorsolateral occipital and parietal areas associated with visuospatial functions. In addition, the prefrontal areas studied received projections from auditory and/or somatosensory cortices, from areas associated with more than one modality, and from limbic regions. Orbital area 12 seemed to be a major target of projections from somatosensory cortices and the rostral portion of medial area 32 received substantial projections from auditory cortices. The least architectonically differentiated areas (orbital area 11 and medial area 32) had more widespread corticocortical connections, including strong links with limbic cortices. In contrast, areas which showed the highest degree of architectonic differentiation within the basoventral (area 46) and the mediodorsal (area 8) prefrontal cortices had restricted corticocortical connections.
Retinal ganglion cell topography in teleosts: A comparison between nissl‐stained material and retrograde labelling from the optic nerve
Authors: Collin Shaun P. , Pettigrew John D.
Published: January 2005

The retinal topography of cells within the ganglion cell layer of three teleost species is examined in Nissl‐stained material in which all neuronal elements containing Nissl substance in the cytoplasm are counted. A topographic comparison is made with retrogradely labelled ganglion cells to differentiate the proportion of nonganglion cells not possessing an axon joining the optic nerve. In the three species studied 92%, 80%, and 66% were found to be the maximum proportion of true ganglion cells in the area centralis, horizontal streak, and periphery, respectively. The proportion of nonganglion cells in the total population of cells counted was 24%. The major contribution to this discrepancy is from peripheral nonspecialized regions of the retina. There is little difference in both topography and peak densities of retinal ganglion cells between the two techniques. The soma areas of both populations are analysed, with the homogeneous nonganglion cell population possessing cells between 5 and 15 μm2 and the heterogeneous ganglion cell soma between 5 and 68 μm2, increasing in size with eccentricity.
Evidence for direct projections from the nucleus of the solitary tract onto medullary adrenaline cells
Authors: Hancock M. B.
Published: January 2005

The anatomic relationships between projections from the intermediate portion of the nucleus of the solitary tract (NTS) and phenylethanolamine N‐methyl transferaselike‐immunoreactive (PNMT‐LI) cells in the medulla oblongata were analyzed in Sprague‐Dawley rats by using two‐color immunoperoxidase staining combined with the anterograde transport of Phaseolus vulgaris leucoagglutinin (PHA‐L). PHA‐L was iontophoretically deposited in the intermediate region of the NTS and the subjacent dorsal motor nucleus of the vagus (DMX) at the level of the middle of the area postrema. Blackstained PHA‐L‐immunoreactive (PHA‐LI) fibers and terminals were present throughout the length of the ipsilateral NTS, where many were seen in close apposition to amber‐stained PNMT‐LI cells belonging to the C2 cell group. Less profuse PHA‐LI projections were present in the contralateral NTS, especially at the level of the PHA‐L deposit. Bundles of smooth fibers emerged from the lateral edge of the DMX and could be followed to the ventrolateral surface of the medulla; these were likely vagal efferent fibers. PHA‐LI terminal arborizations were prominent in the region of the nucleus ambiguus (NA) and amongst PNMT‐LI cells in the lateral C1 cell group ventral to NA. Multiple sites of contiguity between PHA‐LI varicose fibers or boutons and PNMT‐LI cells in C1 were observed frequently and probably represent sites of functional connection.

Medullary PNMT‐LI cells project to the intermediolateral cell columns of the spinal cord and to the hypothalamus and have been implicated in cardiovascular regulation. Based on the observations in this study, it is concluded that certain medullary PNMT‐LI cells in the C1 and C2 cell groups receive direct input from the intermediate NTS and thus play a role in baroreceptor‐mediated changes in cardiovascular activity.
Projections from the medial cortex in the brain of lizards: Correlation of anterograde and retrograde transport of horseradish peroxidase with timm staining
Authors: Olucha F. , Martinez‐Garcia F. , Poch L. , Schwerdtfeger W. K. , Lopez‐Garcia C.
Published: January 2005

Efferent projections of the medial cortex of the lizards Podarcis hispanica and Gallotia stehlinii were studied by examining the transport of horseradish peroxidase; results were correlated with those from Timm‐stained sections. Two efferent systems were found. The first reaches the distal part of the outer plexiform layer in the medial, dorsomedial, and dorsal cortices, i.e., zones that are negative to Timm staining, and possibly originates from horizontal fusiform neurons. The second reaches the Timm‐positive zones in the cortex and septum and is topographically arranged: the vertical portion of the intermediate and caudal medial cortex and the entire rostral medial cortex project to the inner two‐thirds of the outer plexiform layer of the dorsomedial cortex and of the medial subfield of the dorsal cortex; to the paraventricular zone of the inner plexiform layer of the medial cortex; and bilaterally to the dorsal part of the dorsal precommissural septum. The dorsal part of the intermediate and caudal medial cortex and the ventralmost folded part of its caudal edge project rostrally to the juxtasomatic zone of the outer plexiform layer and the entire inner plexiform layer of the intermediate and lateral subfields of the dorsal cortex and to the ventral part of the dorsal septum. In its intense Timm reaction and its ultrastructural properties, as reported in earlier studies, the Timm‐positive fiber system of the lizard brain shows a close resemblance to the mossy fiber system of the mammalian hippocampus.
Organization of calcitonin gene‐related peptide‐immunoreactive terminals in the primate dorsal horn
Authors: Carlton S. M. , McNeill D. L. , Chung K. , Coggeshall R. E.
Published: January 2005

The present paper is concerned with the arrangement of axons and synaptic terminals immunostained for calcitonin gene‐related peptide (CGRP), a primary afferent marker, in the primate (Macaca fascicularis) dorsal horn. The CGRP axons and terminals are uniformly distributed in laminae I and II outer (o) but they are concentrated laterally and distributed intermittently in the reticulated region of lamina V. A prominent bundle of labeled axons is seen in the sacral cord dorsal to the central canal. Emphasis is given to the relation of CGRP‐immunoreactive terminals to other terminals, both labeled and unlabeled, in laminae I and IIo. In this regard, adjacent CGRP‐immunoreactive terminals are often united by puncta adhaerentia. Of particular interest is the observation that CGRP‐immunoreactive terminals can be found presynaptic to other terminals which sometimes resemble central primary afferent endings. In addition CGRP‐immunoreactive terminals end on other CGRP terminals. Both findings suggest that primary afferent terminals interact synaptically with other primary afferent terminals.
Morphogenesis of the brain in the harbour porpoise
Authors: Buhl Eberhard H. , Oelschläger Helmut A.
Published: January 2005

Morphogenesis of the brain in a cetacean species has been investigated by means of reconstructions from serial sections of successive prenatal stages of the harbour porpoise (Phocoena phocoena). Four specimens ranging from 10 to 46 mm crown‐rump length (CRL) were selected and three‐dimensional reconstructions of the developing brains were obtained with the plate model method. External and internal characteristics, established as criteria for staging embryonic development of primates and rodents, revealed that a common ontogenetic plan regarding the chronological sequence of morphogenetic events exists in mammalian orders as different as primates and odontocetes. Comparison of the 10‐mm and 11.5‐mm CRL harbour porpoise brains with those in other mammalian embryos of a similar ontogenetic stage (stages 16 and 17) showed a high degree of correspondence in morphological features. This ontogenetic age group therefore might still be considered as a generalized mammalian one. However, during succeeding morphogenesis of the Phocoena brain, qualititative and quantitative divergences from other mammalian groups became manifest, such as those found in the 24‐mm CRL specimen (corresponding to mammalian stages 20, 21). Early foetuses of the harbour porpoise (46 and 65 mm CRL) already exhibited a variety of typical odontocete brain features, such as absence of olfactory bulb, thick cochlear nerve, and strong progression of brainstem structures. Morphogenesis of the harbour porpoise brain is discussed from a comparative perspective, incorporating the literature on the development of mammalian brains. Part of this study has been published in abstract form (Buhl and Oelschläger: Acta Anat. (Basel) 120:15–16 (Abstract), '84.
Dorsal raphe serotoninergic branching neurons projecting both to the lateral geniculate body and superior colliculus: A combined retrograde tracing–immunohistochemical study in the rat
Authors: Villar Marcelo J. , Vitale Maria L. , Hökfelt Tomas , Verhofstad Albert A. J.
Published: January 2005

Injections of HRP into the superior colliculus labelled cells in the lateral cell groups of the dorsal raphe nucleus. The cytoarchitectural features and location of these cells showed remarkable similarities with those known to project to the lateral geniculate body, and, therefore, the possible existence of branching neurons in the dorsal raphe nucleus projecting to these two visual structures was tested. Injections into the lateral geniculate body and the superior colliculus of several fluorescent tracers—namely, Fast Blue, Fluoro‐Gold, propidium iodide, rhodamine‐B‐isothiocyanate, and Diamidino Yellow, used in different combinations, showed single‐ and double‐labelled neurons in the lateral wings of the dorsal raphe nucleus. In order to verify the chemical nature of these cells, the tissue was processed for immunofluorescence with serotonin antibodies. The results obtained showed several triple‐labelled cells exhibiting two fluorescent tracers as well as 5‐hydroxytryptamine‐like immunoreactivity. Some immunonegative tracer‐positive cells were also observed, suggesting their nonserotoninergic nature. Finally, electrolytic lesions of the lateral wings of the dorsal raphe nucleus caused a gradual disappearance of serotonin‐immunoreactive fibers in these visual areas following different survival times. This correlated well with a decrease in the serotonin content studied by high‐pressure liquid chromatography.

These results support a role of the serotoninergic dorsal raphe projection to the lateral geniculate body and to the superior colliculus in the processing of visual information, and they suggest that serotonin may have a coordinating influence on primary visual centers.
Motor nuclei of peroneal muscles in the cat spinal cord
Authors: Horcholle‐Bossavit G. , Jami L. , Thiesson D. , Zytnicki D.
Published: January 2005

The cat peroneal muscles have been used in numerous investigations dealing with the physiological properties of motor units, muscle spindles, and Golgi tendon organs. This report presents a study of the organization of peroneal motor pools in the cat spinal cord by means of retrograde axonal transport of horseradish peroxidase from individual muscles to the corresponding motoneurons. The motor nuclei of peroneus longus (PL), peroneus brevis (PB), and peroneus tertius (PT) muscles formed thin columns in the lateral part of the ventral horn in spinal segments L6–S1. In the transverse plane, the PT and PL nuclei occupied, respectively, dorsolateral and ventromedial positions, with PB nucleus in an intermediate position overlapping with the other two nuclei. Measurements of cell body diameters allowed identification of α and γ subgroups in peroneal motoneuron populations. The average numbers of motoneurons were about 96 α and 60 γ in PL, 75 α and 54 γ in PB, and 34 α and 23 γ in PT. Comparison with data from electrophysiological studies indicated that whole populations of motoneurons were labeled in each motor nucleus. The proportions of γ motoneurons were the same, and cell bodies of γ motoneurons had similar sizes in the three peroneal populations. In contrast, α motoneurons were significantly smaller in PB than in the two other pools, in keeping with the fact that PB contains a proportion of slow motor units larger than the two other muscles. In large samples of homonymous motoneurons, the numbers of first‐order dendrites correlated linearly with motoneuron sizes.
Postnatal development of cat hind limb motoneurons. II: In vivo morphology of dendritic growth cones and the maturation of dendrite morphology
Authors: Ulfhake Brun , Cullheim Staffan
Published: January 2005

The maturation of dendrite morphology was studied by light and electron microscopy in cat spinal α‐motoneurons intracellularly labeled with horseradish peroxidase. Alpha‐motoneurons supplying the triceps surae (TS) and the intrinsic foot sole (SP) muscles were investigated in kittens from birth to 44–46 days of postnatal (d.p.n.) age.

At birth, a large number of dendritic branches displayed growth cones, filopodia, and fusiform processes. The growth cones were of lamellipodial and filopodial types, but intermediate forms also occurred. The growth cones shared several morphological features with the neuritic growth cones studied in vitro. It was suggested that the occurrence of different types of growth cones—even in the same dendrite—may reflect their transformation from one type to the other and the level of growth activity could be inferred from the number and form of the growth cones.

About 50–70% of the terminal branches in the dendrites of newborn kittens possessed growth cones, filopodia, and/or fusiform processes. The corresponding figure for preterminal branches was 20–30%, with a clear decrease in incidence when approaching the soma. During the period under study, most of these growth‐associated processes disappeared from the dendrites so that at 44–46 d.p.n. of age only about 10% of the terminal and >1% of the preterminal branches had growth‐associated processes. Analysis of the three‐dimensional distribution of dendritic branches with such processes disclosed that they were relatively more frequent in the medial, rostral, and caudal dendritic territories. It was concluded that the pattern of distribution and disappearence of growth cones, filopodia, and fusiform processes coincided with postnatal longitudinal dendritic growth and the development of the adult dendritic territories described in a preceding paper (Ulfhake et al., '88). Dendritic growth, with respect to length and caliber, also occurred in the absence of growth cones and filopodia. It is suggested that the important role of these processes may be to act as a steering device in establishing the adult distribution and synaptology of the dendrites.

Comparison of TS and SP α‐motoneuron dendrite morphology at birth and at 22–24 d.p.n. age showed that the SP neurons lagged in the maturation process.

Light and electron microscopic observations indicated that postnatally direct contacts might exist between dendrites and fine blood vessels in the neuropil without any interposing glial sheath. The number of such suspected contacts diminished during the period under study, indicating that the glial ensheathment of the blood vessel takes place, in part, postnatally.
Collateralization of the amygdaloid projections of the rat prelimbic and infralimbic cortices
Authors: Cassell M. D. , Chittick C. A. , Siegel M. A. , Wright D. J.
Published: January 2005

Previous studies indicate that the distribution of corticoamygdaloid neurons in the rat prelimbic (PL) and infralimbic (IL) cortices overlaps with the distribution of neurons projecting to the contralateral medial prefrontal cortex (MPC), insular cortex, mediodorsal thalamus, and dorsal medulla. In view of the poorly differentiated cytoarchitecture of PL and IL, and their designation as cortical regions transitional between the allocortex and isocortex, the present study sought to determine whether several cortical and subcortical projections from these areas arise as collaterals of corticoamygdaloid neurons. Injections of the fluorescent dyes Fast Blue (FB) or bisbenzimide (BB) were made into the amygdaloid complex and the following areas: agranular and granular insular cortices; mediodorsal thalamic nucleus (MD); nucleus tractus solitarii/dorsal medulla (NTS); contralateral amygdaloid complex; and ipsilateral and contralateral MPC. Neurons projecting to the ipsilateral amygdaloid complex were located mainly in layers II and V with fewer cells in layer III. Concomitant injections into the insular cortex, MD, and NTS labeled populations of neurons arranged in laminae that partially overlapped with, but were essentially separate from, corticoamygdaloid neurons. Projections to the insular cortex arose from layers II and V; those to MD arose from layers V and VI. Corticobulbar projections from IL originated from neurons arranged in a thin lamina in the deep part of layer V. Very few neurons projecting to both the amygdaloid complex and any of these areas were observed. Bilateral injections of FB and BB into the amygdaloid complex producted very few double‐labeled cells in PL and IL. Further, in layer V, ipsilaterally projecting corticoamygdaloid neurons tended to be located more deeply than contralaterally projecting neurons. Combined injections of BB and FB into the amygdaloid complex and the contralateral (but not ipsilateral) MPC resulted in significant numbers of double‐labeled neurons in layers II, III, and V of PL and IL. Control injections of fluorescent dyes into the cerebrospinal fluid labeled few neurons in the superficial layers of PL and IL and a combined injection into the amygdaloid complex (FB) and subarachnoid space (BB) resulted in a very small number of double‐labeled cells in layer II only. The results suggest that a significant proportion of neurons in PL and IL projecting to the amygdaloid complex issue collaterals innervating the contralateral MPC. Evidence is discussed that suggests that the interhemispheric collaterals of MPC corticoamygdaloid neurons may serve to correlate the amygdaloid outputs of the MPC bilaterally.
Catecholamine innervation of the human cerebral cortex as revealed by comparative immunohistochemistry of tyrosine hydroxylase and dopamine‐beta‐hydroxylase
Authors: Gaspar Patricia , Berger Brigitte , Febvret Aude , Vigny Annette , Henry Jean Pierre
Published: January 2005

The organization of the cortical monoamine systems, dopamine (DA), and noradrenaline (NA), which have been studied extensively in the rat and more recently in the monkey, had not yet been investigated directly in the human brain. We report here the first systematic account of the regional and laminar distributions of the catecholamine fibers in the human cerebral cortex, using immunohistochemistry of the catecholamine biosynthetic enzymes, tyrosine hydroxylase (TH), and dopamine‐β‐hydroxylase (DBH) in 13 cytoarchitectonic areas (4, 6, 9, 3b, 5, 40, 17, 18, 23, 24, 29, insula, and hippocampus) sampled postmortem.

The noradrenergic (NA) innervation, mapped with DBH‐immunoreactivity (DBH‐IR), displayed a characteristic density gradient in the neocortex (highest in the primary sensorimotor areas, decreasing rostrally and caudally) that contrasted with the more uniform density in the limbic cortices (24, 23, 29, insula, hippocampus). NA axons were present in all cortical layers and were least numerous in layer I. The DBH‐IR fibers were only partly TH‐immunostained (10–50%, on double‐labeled sections), suggesting a heterogeneity of the cortical NA axons.

The putative dopaminergic (DA) fibers were identified by comparing alternate or double‐immunolabeled (DBH‐TH) sections, as the TH‐IR fibers which contain no DBH‐IR. A DA‐like innervation was present in all cortical areas, with major regional differences in density and laminar distribution, which closely paralleled cytoarchitectural buildups: (1) the DA‐like innervation was densest in the agranular areas, primary and secondary motor areas, anterior cingulate, and insula; it distributed throughout layers I–VI; (2) density was lower in the granular cortices, areas 9 (prefrontal cortex), 23, 3b, 5, 40, and 18, displaying a bilaminar pattern in layers I and V–VI. In all areas, DA‐like fibers were most abundant in the molecular layer, with a predominant distribution in its deepest part. Convoluted and coily fibers represented a unique morphologic aspect of the CA innervation in the human cortex.

These findings are in agreement with findings in nonhuman primates and demonstrate major evolutionary changes in the organization of the cortical aminergic input as compared with rodents. The most striking features are the expansion of the DA innervation to the whole cortex and the peak of highest density in the motor areas. The regional differentiation of NA innervation is also accentuated. Slight differences were found in the laminar distributions of the amines in humans and primates. These data seem quite promising and open new research fields in neurologic and psychiatric diseases.
Ventral mesencephalic neurons containing both cholecystokinin‐ and tyrosine hydroxylase‐like immunoreactivities project to forebrain regions
Authors: Seroogy Kim B. , Dangaran Karol , Lim Steven , Haycock John W. , Fallon James H.
Published: January 2005

The coexistence of cholecystokinin‐ and tyrosine hydroxylase‐like immunoreactivities within neurons of the rat ventral mesencephalon was analyzed by using an indirect immunofluorescence technique for the simultaneous demonstration of two antigens in the same tissue section. A high degree of colocalization was observed in the substantia nigra pars compacta, in which 80–90% of all labeled neurons at rostral and up to 70% at intermediate levels contained both cholecystokinin and tyrosine hydroxylase. At caudal levels, the incidence of colocalization declined to approximately 30–50%. All of the immunoreactive perikarya in the substantia nigra pars lateralis were labeled with both substances. Other areas of the ventral midbrain that exhibited a moderate proportion of neurons immunoreactive for both cholecystokinin and tyrosine hydroxylase included the ventral tegmental area, interfascicular nucleus, and rostral and caudal linear nuclei. In addition, coexistence was occasionally observed within neurons of the central and ventral periaqueductal gray matter, supramammillary region, peripeduncular region, retrorubral field, and, extremely rarely, within the substantia nigra pars reticulata. Cell bodies containing tyrosine hydroxylase‐like immunoreactivity (indicative of dopamine) usually outnumbered those containing the peptide except in the supramammillary region and in the ventral periaqueductal gray matter, where the cholecystokinin perikarya were present in higher numbers.

The double‐labeling colocalization technique was combined with fluorescence retrograde tracing to determine some of the forebrain projections of these neurons. Ventral midbrain neurons containing both cholecystokinin and tyrosine hydroxylase were found to project to the caudate‐putamen, nucleus accumbens, prefrontal cortex, and amygdala. These projections originated from neurons located predominantly in the substantia nigra pars compacta and the ventral tegmental area. Thus, cholecystokinin occurs within the well‐known dopaminergic nigrostriatal pathway in the rat. Overall, these results demonstrate that a significant proportion of the dopamine neurons giving rise to the ascending mesotelencephalic projections also contain the peptide cholecystokinin.
Organization and synaptic interconnections of GABAergic and cholinergic elements in the rat amygdaloid nuclei: Single‐ and double‐ immunolabeling studies
Authors: Nitecka Liliana , Frotscher Michael
Published: January 2005

The aim of this study was to describe the localization of cholinergic and GABAergic neurons and terminals in the amygdaloid nuclei of the rat. Double immunolabeling was performed to study cholinergic‐GABAergic synaptic interconnections.

Cholinergic elements were labeled by using a monoclonal antibody to choline acetyltransferase (ChAT), the acetylcholine synthesizing enzyme. Antibodies against glutamate decarboxylase (GAD), the GABA‐ synthesizing enzyme, were employed to identify GABAergic perikarya and terminals. The tissue sites of the antibody bindings were detected by using either Sternberger's peroxidase‐antiperoxidase (PAP) method or a biotinylated secondary antibody and avidinated ferritin. These two contrasting immunolabels allowed us to study GABAergic‐cholinergic interconnections at the electron microscopic level.

Our study revealed a characteristic distribution of GABAergic and cholinergic elements in the various amygdaloid nuclei: 1) Large, ChATimmunopositive cells with heavily labeled dendrites were observed in the anterior amygdaloid area and in the lateral and medial zones of the central nucleus. These cells seem to constitute the intraamygdaloid extension of the magnocellular basal nucleus. Their dendrites invaded other amygdaloid nuclei, in particular the intercalated nuclei, the lateral olfactory tract nucleus, and the central zone of the central nucleus. These ChAT‐immunoreactive dendrites formed synaptic contacts with GAD‐positive terminals. GABAergic terminals probably thus exert an inhibitory amygdaloid influence onto cholinergic neurons of the magnocellular basal nucleus. 2) Two amygdaloid nuclei‐the basal dorsal nucleus and the lateral olfactory tract nucleus‐contained a dense network of ChAT‐immunoreactive fibers and terminals, but they also contained numerous GAD‐positive perikarya. Double‐immunolabeling experiments revealed cholinergic terminals forming synaptic contacts on GAD‐immunopositive cell bodies, dendritic shafts, and spines. 3) The central and medial nucleus seem to be the main target of GABAergic fibers to the amygdala. Both nuclei contained a dense plexus of GAD‐immunoreactive terminals that may arise, at least in part, from the GABAergic neurons in the basal dorsal nucleus. Inhibition of the centromedial “excitatory” region through intraamygdaloid GABAergic connections may reduce excitatory amygdaloid influence onto hypothalamus and brainstem.
Development of central projections of lumbosacral sensory neurons in the chick
Authors: Davis Brian M. , Frank Eric , Johnson Frances A. , Scott Sheryl A.
Published: January 2005

The development of central projections of sensory neurons in lumbosacral dorsal root ganglia (DRGs) was examined by using horseradish peroxidase labeling techniques in chick embryos from stage 23 (E4) to stage 39 (E13). Our results show that primary afferents reach the spinal cord by stage 23. Afferent axons extend in the primordium of the dorsal funiculus for several segments rostral and caudal to their segment of entry for over 24 hours before invading the gray matter at stage 28 (E6). Sensory fibers grow into the vicinity of motoneuron dendrites by stage 32 (E7.5), about the time that reflexes and apparent monosynaptic EPSPs can first be elicited. Dense projections into the dorsal laminae of the spinal cord, presumably representing cutaneous afferents, appear somewhat later, at about stage 39 (E13), when the segmental projection pattern begins to resemble the mature pattern.
Structure of the nucleus olfactorius anterior of the hedgehog (Erinaceus europaeus)
Authors: Valverde Facundo , López‐Mascaraque Laura , De Carlos Juan A.
Published: January 2005

The cytoarchitecture, topography, and cellular structure of the nucleus olfactorius anterior (NOA) in the hedgehog have been studied in Nissl‐stained and Golgi preparations. The NOA is an important receptive allocortical formation for olfactory fibers and the major source of association fibers relating the main olfactory bulb with the rest of the olfactory brain. It was divided into a bulbar part; four subdivisions named lateral, dorsal, medial, and ventral; an external part; and a posterior part. Except for the external and posterior subdivisions, the NOA is relatively homogeneous and, in spite of the apparent lack of sublamination in Niss‐stained material, four clearly defined cellular laminae were distinguished by the Golgi method. These layers were found to be strikingly similar to those in the piriform cortex. Layer I contains the terminal ramifications of apical dendrites of pyramidal cells and the collaterals of the lateral olfactory tract. The superficial part of layer II contains extraverted pyramidal cells with two or three apical dendrites ramifying in layer I. Most pyramidal cells in the deep part of layer II and layer III are typical pyramidal cells with axons entering the commissura anterior. Some pyramidal cell axons bifurcate into two branches running in opposite directions in the commissura anterior. The interstitial zone below layer III contains deep pyramidal cells and polymorphic cells with ascending branches. Cells with intrinsic axons were classified into four main categories according to the distribution of their axonal ramifications: (1) cells with very restricted axons, (2) cells with axons oriented tangentially in the superficial part of layer II, (3) cells with ascending axons located in the deep part, and (4) chandelierlike cells. Finally, some functional considerations are discussed.
Visual projections to the pontine nuclei in the rabbit: Orthograde and retrograde tracing studies with WGA‐HRP
Authors: Wells Graham R. , Hardiman Mervyn J. , Yeo Christopher H.
Published: January 2005

Visual projections to the pontine nuclei in the rabbit were examined by means of both orthograde and retrograde tracing of WGA‐HRP. The tectopontine projection was examined following microinjections of WGA‐HRP in the right superior colliculus. The projection to the pontine nuclei is strictly ipsilateral and terminates at middle and caudal levels of the pons. The projection is absent in rostral pontine nuclei. The strongest projection is to the dorsal border of the dorsolateral pontine nuclei and is the only projection seen when the primary injection site is confined to superficial laminae. When the primary injection site also includes intermediate and deep laminae, patches of labelled terminals are also seen within dorsolateral, lateral, peduncular, paramedian, and ventral pontine nuclei as well as in the contralateral nucleus reticularis tegmenti pontis.

The striate corticopontine projection was also examined with orthograde tracing of WGA‐HRP. The striate corticopontine projection is ipsilateral. Most labelled terminals were seen in dorsolateral and lateral pontine nuclei throughout the rostral half of pons with some additional terminal labelling in paramedian and peduncular nuclei. Labelled terminals were also seen in ventral pontine nuclei throughout the middle and caudal levels of the pons.

In a retrograde tracing study, visual projections to the pontine nuclei were examined following microinjections of WGA‐HRP into the pontine nuclei. Labelled cells were seen ipsilaterally in superficial and deep laminae of the superior colliculus and in layer V of striate and surrounding occipital cortex. The pontine nuclei also receive ipsilateral projections from the ventral lateral geniculate, the nucleus of the optic tract, anterior and posterior pretectal nuclei, and the dorsal and medial terminal nuclei of the accessory optic system. These pathways are potential sources of visual input to the cerebellum.
Ganglion cell arrangement and axonal trajectories in the anterior lateral line nerve of the weakly electric fish Apteronotus leptorhynchus (Gymnotiformes)
Authors: Lannoo Michael J. , Maler Leonard , Tinner Barbro
Published: January 2005

To determine the organizational principles underlying the peripheral electrosensory nervous system of weakly electric gymnotiform teleosts we labelled each of the four anterior lateral line nerve branches with HRP. We determined the position of labelled cell bodies within the ganglion and followed anterogradely filled fibers to their termination sites in one of the four somatotopic maps in the electroreceptive lateral line lobe (ELL). Within the ganglion, cell bodies exhibit a loose somatotopy based on nerve branch position: trunk electroreceptors have their cell bodies located in the caudal ganglion; cell bodies to the head receptors are rostral. Cell bodies to the head exhibit a rough dorsoventral polarity, supraorbital cells tend to be located dorsally, infraorbital cells centrally, and mandibular cells ventrally. Despite this general somatotopy there is substantial overlap (up to 30%) of cell bodies among regions. There appears to be no rostrocaudal topography within nerve branch regions. Iontophoretic WGA‐HRP injected into the medial segment of the ELL retrogradely labelled cell bodies that innervate ampullary organs. These cell bodies were dispersed throughout the ganglion, indicating that cell bodies do not cluster by receptor type. Peripherally directed axons from the ganglion appear to undergo an active reorganization in order to form the nerve branches. Within nerve branches, axons to a particular area of skin do not cluster together.

Centrally from the ganglion, axons retain the position of their cell body until they reach the ELL border. Once in the ELL, fibers become sorted in the deep fiber layer according to receptor type and the map they terminate in. This reorganization involves rearrangement of fascicles and axons within fascicles. In toto, proceeding from peripheral to central, the electrosensory periphery loses at least a portion of its receptor topography in the distal nerve and ganglion and then acquires both a functional and somatotopic organization after reaching the ELL; conceptually it is torn down and rebuilt again. From an ontogenetic perspective, axonal growth occurs from the ganglion outward; the fact that ganglion cell bodies are not highly organized while the receptors they innervate and their central processes are suggests that active axonal guidance mechanisms are involved.