bluuebunny/crossref_metadata_2025 huggingface dataset:
Further evidence of extrinsic forces in bending of the neural plate
Authors: Smith Jodi L. , Schoenwolf Gary C.
Published: January 2005

Bending of the neural plate has long been considered to be driven by principally intrinsic forces generated by wedging of neurepithelial cells. Our previous studies have shown that during neural fold elevation, significant neurepithelial cell wedging occurs only within the median hinge point (MHP), the midline region of neural plate anchored to the notochord. We have also shown that neural fold elevation can still occur when MHP cells are prevented from becoming wedge‐shaped but fails to occur when the neural plate is separated from lateral nonneurepithelial tissues, even though MHP cells still become wedge‐shaped and the midline neural plate still furrows. Together, these results suggest that neural fold elevation, rather than being driven by neurepithelial cell wedging, is driven, at least in part, by extrinsic forces generated by lateral nonneurepithelial tissues. However, it could be argued that in the absence of localized neurepithelial cell wedging, compensatory and atypical cell wedging occurred uniformly throughout the neural plate, providing forces adequate for neural fold elevation. Likewise, it could be argued that in the process of separating the neural plate from lateral nonneurepithelial tissues, the neural plate was damaged to the extent that the neural folds were unable to elevate. To investigate the validity of these arguments, we removed the following tissues microsurgically prior to neural fold elevation: MHP cells, varying amounts of lateral neurepithelial cells (L cells), and the tissues directly underlying these two populations of neurepithelial cells. We found that the neural folds still formed and underwent elevation, convergence, and fusion, resulting in an essentially normal neural tube, even though MHP cells, the underlying notochord, and some L cells were absent for long craniocaudal distances. These results demonstrate that microsurgery alone does not damage the neural plate sufficiently to prevent neural fold elevation, convergence, and fusion. Moreover, the fact that each of the two persisting remnants of lateral neurepithelium generally remained straight and consistently changed their orientation from horizontal to vertical rather than curling suggests very strongly that bending of the neural plate in these embryos is not the result of compensatory and atypical cell wedging. Finally, the results provide further direct evidence of extrinsic forces in bending because the two remnants of lateral neurepithelium, which were oriented horizontally at the time of tissue extirpation, could not have become oriented vertically in the absence of such forces.
Development and migration of avian sympathetic preganglionic neurons
Authors: Prasad Anita , Hollyday Margaret
Published: January 2005

Modern neuronanatomical techniques were used to investigate the development of the avian sympathetic preganglionic cell column in the spinal cord of the chick embryo. [3H]thymidine autoradiography indicated that the majority of these preganglionic, or “Terni column” neurons are generated between stages 18 and 24 (days 2–4). This coincides with the genesis of the somatic motoneurons in the thoracic levels of the cord, and therefore differences in the time of origin cannot explain the divergent fates of these two neuronal populations. Data obtained from short‐survival autoradiographic experiments indicated that many early born cells remain close to the ventral region of the ventricular epithelium until day 5 of incubation. Ventral root injections used to label retrogradely neurons projecting an axon into the ventral root (Terni cells and somatic motoneurons) have labeled neurons next to the ventricular epithelium at the same early stages. Thus, it seems likely that some Terni cells, if not all, maintain medial positions and do not migrate laterally to join a common motor column before initiating a dorsal migration. Analysis of a closely staged series of embryos, whose Terni column neurons were retrogradely labeled with wheat germ agglutinin‐horseradish peroxidase (WGA‐HRP), revealed that between days 5 and 8 of incubation, Terni column neurons migrated dorsally to attain their adult position adjacent to the central canal. These changes in position were reflected in the changing morphology of the Terni column neurons, visualized by the Golgi‐like HRP labeling. The positions of the migrating Terni cells differed from those of commissural cells, indicating that these fibers are not the substrate for the dorsal migration. The dorsal migration of Terni column cells was not disrupted by the surgical removal of the sympathetic ganglia, the synaptic targets of these neurons, nor by disruption of spinal afferents. Taken together, these results suggest that the migratory behavior of Terni cells is distinctive when compared to that of somatic motoneurons, and that local and/or intrinsic cues within the spinal cord guide the dorsal migration of Terni column cells.
Morphology and frequency of axon terminals on the somata, proximal dendrites, and distal dendrites of dorsal neck motoneurons in the cat
Authors: Rose P. K. , Neuber‐Hess M.
Published: January 2005

The purpose of the present study was to compare the frequency of different classes of axon terminals on selected regions of the somatodendritic surface of dorsal neck motoneurons. Single motoneurons supplying neck extensor muscles were antidromically identified and intracellularly stained with horseradish peroxidase. By using light microscopic reconstructions as a guide, axon terminals on the somata, proximal dendrites (within 250 μm of the soma), and distal dendrites (more than 540 μm from the soma) were examined at the electron microscopic level.

Axon terminals were divided into several classes based on the shape, density, and distribution of their synaptic vesicles. The proportion of axon terminals belonging to each axon terminal class was similar on the somata and proximal dendrites. However, there were major shifts in the relative frequency of most classes of axon terminals on the distal dendrites. The most common classes of axon terminals on the somata and proximal dendrites contained clumps of either spherical or pleomorphic vesicles. These types of axon terminals accounted for more than 60% of the axon terminals on these regions. In contrast, only 11% of the axon terminals found on distal dendrites belonged to these types of axon terminals. The most commonly encountered axon terminal on distal dendrites contained a dense collection of uniformly distributed spherical vesicles. These types of axon terminals accounted for 40% of all terminals on the distal dendrites, but only 5–7% of the axon terminals on the somata and proximal dendrites. Total synaptic density on each of the three regions examined was similar. However, the percentage of membrane in contract with axon terminals was approximately four times smaller on distal dendrites than somata or proximal dendrites. Axon terminals (regardless of type) were usually larger on somata and proximal dendrites than distal dendrites.

These results indicate that there are major differences in the types and arrangement of axon terminals on the proximal and distal regions of dorsal neck motoneurons and suggest that afferents from different sources may preferentially contact proximal or distal regions of the dendritic trees of these cells.
Estrogen influences on oxytocin mRNA expression in preoptic and anterior hypothalamic regions studied by in situ hybridization
Authors: Chung Sookja K. , McCabe Joseph T. , Pfaff Donald W.
Published: January 2005

Possible estrogen influences on oxytocin mRNA expression were studied in preoptic and anterior hypothalamic regions as might be important for behavioral as well as neuroendocrine controls. In situ hybridization for oxytocin mRNA determination was supported by immunocytochemical identification and was compared with vasopressin mRNA in situ hybridization. With these techniques, oxytocin‐expressing neurons were identified in medial preoptic, anterior commissural, periventricular, paraventricular, supraoptic, and perifornical nuclei as well as the bed nucleus of the stria terminalis and intersupraopticoparaventricular (internuclear) islands. Distribution and number of oxytocin mRNA‐containing neurons and oxytocin mRNA levels were compared between ovariectomized control rats given cholesterol implants and ovariectomized rats given short‐term (2 days) or long‐term (2 months) estradiol treatment (10% estradiol, subcutaneous silastic implants). Effectiveness of long‐term estrogen treatment was confirmed behaviorally. While there was a trend in several cell groups for a larger number of oxytocin‐mRNA‐containing neurons to be observed following 2 days of estrogen treatment, this was not statistically significant. Moreover, additional oxytocin‐mRNA containing cell groups were not seen after short or long estradiol treatment. With computer‐aided analysis, mean pixels per oxytocin‐mRNA expressing neuron (reflecting oxytocin mRNA content) were compared between groups: In the supraoptic nucleus and the anterior commissural nucleus, these were increased both by 2 days and 2 months of estradiol treatment. These differences may be important in modulating female reproductive behavior. Present findings also suggest that estradiol can affect the oxytocinergic system via an indirect route since the cell groups influenced here by estradiol do not contain estrogen receptors. Oxytocinergic neurons may serve as a good system to compare direct transcriptional with indirect effects of hormones.
Brain sites projecting to the spinal nucleus of the bulbocavernosus
Authors: Monaghan Edward P. , Breedlove S. Marc
Published: January 2005

Motoneurons of the spinal, nucleus of the bulbocavernosus (SNB) occupy a distinct dorsomedial position in the ventral horn of lumbar segments 5 and 6 and innervate sexually dimorphic striated muscles of the rat perineum, including the bulbocavernosus and levator ani. To begin the study of brain influences upon SNB function, we used retrograde tracers to identify brain regions that project to the area of SNB motoneurons. Our findings provide strong evidence that lateral vestibular and several reticular nuclei innervate the SNB. Additional possible afferents include the superior and medial vestibular nuclei raphe nucleus, red nucleus, interstitial nucleus of the medial longitudinal fasciculus, and paraventricular nucleus.
Immunohistochemical differentiation of electrophysiologically defined neuronal populations in the region of the rat hypothalamic paraventricular nucleus
Authors: Hoffman N. W. , Tasker J. G. , Dudek F. E.
Published: January 2005

Intracellular recording and labeling were combined with neurophysin immunohistochemistry to study neurons in the paraventricular nucleus region of the rat hypothalamus. Neuronal membrane properties were examined in hypothalamic slices, and cells were labeled by injecting biocytin or Lucifer yellow. Slices were then embedded, sectioned, and immunohistochemically processed for neurophysin. Immunoreactivity patterns, and in some cases counterstaining, enabled determinations of the cytoarchitectonic positions of recorded cells to be made. Recorded cells were divided into three types according to their electrophysiological characteristics. The first type lacked low‐threshold Ca2+ spikes and displayed linear current‐voltage relations, a short time constant, and evidence for an A current. These were relatively large cells that were typically immunoreactive for neurophysin and were situated near other neurophysin‐positive neurons. The second type had relatively small low‐threshold potentials that did not generate bursts of Na+ spikes. These cells had heterogeneous current‐voltage relations and intermediate time constants. They did not label for neurophysin, and most were located in the parvicellular subregion of the paraventricular nucleus. The third type had large low‐threshold Ca2+ spikes that generated bursts of Na+ spikes, and these cells had nonlinear current‐voltage relations and long time constants. These neurons were dorsal or dorsolateral to the paraventricular nucleus and were not immunoreactive for neurophysin. These results indicate that paraventricular magnocellular neurons lack low‐threshold potentials, whereas paraventricular parvicellular neurons display low‐threshold potentials that generate one or two action potentials. Neurons that fire spike bursts from low‐threshold potentials are adjacent to the paraventricular nucleus, confirming earlier reports.
Nerve growth factor receptor immunoreactivity in the rat septohippocampal pathway: A Light and electron microscope investigation
Authors: Kawaja Michael D. , Gage Fred H.
Published: January 2005

Nerve growth factor receptor immunoreactivity in the septohippocampal pathway of adult Fischer 344 rats was assessed at the light and electron microscope level. The medial septum possesses immunoreactive somata, dendrites, axons, and terminals. Immunostained somata are either bipolar or multipolar in appearance. Dendritic processes of immunoreactive septal neurons are categorized into two groups: proximal dendrites with smooth plasma membranes and distal dendrites with numerous swellings. Immunoreactive axons within the septum are long and slender and do not possess varicosities. At the electron microscope level, immunoreactivity is confined predominantly to the plasma membrane of cell bodies and dendrites of septal neurons, as well as to the plasma membrane of axons and terminals. Both immunoreactive and nonimmunoreactive terminals that contain clear, spherical vesicles are observed contacting immunoreactive dendrites and somata. Although accumulations of vesicles are evident within these terminals at sites of contact, distinct synaptic specializations are difficult to distinguish due to the localization of reaction product on the apposing plasma membranes. Axons possessing immunoreactivity are also observed in the fimbria‐fornix pathway, a major source of afferent inputs to the hippocampus. Immunoreactive axons and terminals are topographically organized in the hippocampal dentate gyrus. The density of immunostained axons and terminals is highest immediately adjacent to the granular layer. In comparison, a moderate density of immunoreactive axons is found in the outer molecular layer and a weak density in the inner molecular, granular, and polymorphic layers. Immunoreactivity is found on the plasma membrane of small unmyelinated axons and terminals aggregated into clusters throughout the dentate gyrus. Definitive examples of axosomatic and axodendritic synapses possessing immunoreactivity presynaptically are not observed. Immunoreactive profiles within the medial septum and hippocampus also circumfuse a small number of intracerebral vessels. Ultrastructural examination reveals that immunoreactivity is present within a narrowed extension of the subarachnoid space and appears to be closely associated with the plasma membrane of leptomeningeal cell processes. The present study provides direct evidence for the cellular distribution of nerve growth factor receptor immunoreactivity in the medial septum and dentate gyrus in the adult rat and offers new insight into the ultrastructural localization of nerve growth factor receptor among septal cholinergic neurons and their efferent projections to the hippocampus.
Distribution of 3H‐GABA uptake sites in the nematode Ascaris
Authors: Guastella John , Stretton Antony O. W.
Published: January 2005

The distribution of uptake sites for the inhibitory neurotransmitter γ‐aminobutyric acid (GABA) in the nematode Ascaris suum was examined by autoradiography of 3H‐GABA uptake. Single neural processes in both the ventral and dorsal nerve cords were labeled with 3H‐GABA. Serial section analysis identified the cells of origin of these processes as the RMEV‐like and RMED‐like neurons. These cells belong to a set of four neurons in the nerve ring, all of which are labeled by 3H‐GABA. 3H‐GABA labeling of at least two other sets of cephalic neurons was seen. One of these pairs consists of medium‐sized lateral ganglia neurons, located at the level of the amphid commissure bundle. A second pair is located in the lateral ganglia at the level of the deirid commissure bundle. The position and size of these lateral ganglia cells suggest that they are the GABA‐immunoreactive lateral ganglia cells frequently seen in whole‐mount immunocytochemical preparations (Guastella et al., J Comp Neurol 307:584–597, 1991).

Four neuronal cell bodies located in the retrovesicular ganglion were also labeled with 3H‐GABA. These cells, which are probably cholinergic excitatory motor neurons, do not contain detectable GABA‐like immunoreactivity. Heavy labeling of muscle cells was also observed. The ventral and dorsal nerve cord inhibitory motor neurons, which are known to contain GABA‐like immunoreactivity, were not labeled above background with 3H‐GABA.

Together with the experiments reported previously (Guastella et al., J Comp Neurol 307:584–597, 1991), these results define three classes of GABA‐associated neurons in Ascaris: 1) neurons that contain endogenous GABA and possess a GABA uptake system; 2) neurons that contain endogenous GABA, but that either lack a GABA uptake system or possess a GABA uptake system of low activity; 3) neurons that possess a GABA uptake system, but that lack endogenous GABA.
Immunocytochemical localization of octopamine in the central nervous system of Limulus polyphemus: A light and electron microscopic study
Authors: Lee Helen M. , Wyse Gordon A.
Published: January 2005

We have determined the distribution and localization of the monoamine octopamrne in the prosomal central nervous system of the horseshoe crab, Limulus polyphemus, by light and electron microscopic immunocytochemistry. Sixteen discrete clustery of octopamine‐like immunoreactive neurons are situated bilaterally in the tritocerebrum and circumesophageal ring of fused thoracic ganglia. Two pairs of anterior clusters are located laterally in the cheliceral and first pedal ganglia; the remaining six pairs of clusters are located ventromedially in the second through fifth pedal ganglia, chilarial ganglia, and opercular ganglia. The immunoreactive somata range from about 40 to 100 μm in diameter and occur in clusters of 12–24 cells. There is extensive distribution of octopamine‐immunoreactive nerve fibers in Limulus; dense fiber tracts course anteroposteriorly through the central nervous system, and most neuropil regions are innervated by immunoreactive processes and terminals. This wide distribution of octopamine‐like immunoreactivity provides an anatomical basis for the several effects of octopamine in Limulus. We determined the subcellular localization of octopamine by postembedding immunoelectron microscopy. The immunogold‐labelled terminals are morphologically unique; they contain large, distinctively shaped dense‐core granules, typically cylindrical with a prominent indentation in one end. These large granules are 100–150 nm in diameter and range from 150–400 nm in length. The dense labelling of these unusual granules with immunogold particles indicates that octopamine is sequestered in or associated with the granules.
Arrestin mRNA expression, biosynthesis, and localization in degenerating photoreceptors of mutant rds mice retinas
Authors: Nir Izhak , Agarwal Neeraj
Published: January 2005

The retinal photoreceptors of the mutant rds mouse are unable to form normal outer segments. Eventually the abnormal cells die in the months following birth. The genetic defect in the rds mouse was recently localized to the peripherin gene that encodes a protein in the outer segment disc margin. Although this mutation may explain the morphogenetic defect, i.e., the failure to form outer segments, the reason for subsequent cell death is not clear. Previously, we demonstrated that the capability to synthesize opsin, an outer segment integral membrane protein, is not compromised by the morphogenetic defect although the opsin steady‐state content is considerably reduced, since it is not incorporated into an organized outer segment. We have now studied arrestin, a cytoplasmic protein that is part of the phototransduction cascade and appears to shuttle between the inner and outer segment during the light/dark cycle. Since rds mice lack outer segments, it was of interest to determine the effects of the photoreceptor abnormality on arrestin gene expression. Arrestin mRNA levels and protein synthetic rates were high in young rds retinas. When corrected for cell loss, the steady‐state arrestin content per cell in the rds retina was comparable to normal. However, in the absence of an outer segment, the total amount of arrestin is concentrated in the remaining inner segment. Consequently, a relatively high level of arrestin is present in the rds inner segment throughout the light/dark cycle. We suggest that the morphogenetic defect indirectly precipitates secondary effects such as the persistent presence of high levels of arrestin or other soluble proteins in the abnormal photoreceptor inner segment, nucleus, and synaptic terminal. This condition, if toxic to the cells, may compromise photoreceptor viability in the rds retina.
Dopaminergic innervation of substance P‐containing striatal neurons by fetal nigral grafts: An ultrastructural double‐labeling immunocytochemical study
Authors: Mendez I. , Elisevich K. , Flumerfelt B.
Published: January 2005

Evidence for survival and growth of fetal substantia nigra grafts in host striatum and partial reversal of behavioural and biochemical deficits in the host animal is well documented. Afferent synaptic connections arising from the graft and contacting host structures have also been reported; however, the properties of the neurons receiving this input is less clear. The purpose of this study was to determine if substance P‐containing neostriatal neurons receive a dopaminergic input from nigral grafts. Fetal substantia nigra cell suspensions were stereotaxically implanted in the deafferented neostriatum of Wistar rats 2 weeks after a unilateral 6‐hydroxydopamine (6‐OHDA) lesion in the ipsilateral substantia nigra or medial forebrain bundle. The ultrastructural features of the graft‐host synaptic interactions were analysed by employing an electron microscope immunocytochemical double‐labeling technique. Tyrosine hydroxylase (TH) and substance P‐immunoreactive structures were simultaneously demonstrated by means of the peroxidase‐antiperoxidase method using two different chromogens with distinct reaction products easily differentiated at the light and electron microscope levels. TH‐immunoreactive sites were first demonstrated using 3,3′‐diaminobenzidine tetrahydrochloride (DAB); then substance P immunoreactivity was localized using benzidine dihydrochloride (BDHC). TH‐immunoreactive terminals of axons originating from the graft made synaptic contacts with substance P‐positive cell bodies and dendrites from the host. These results indicate that at least partial restoration of the normal nigrostriatal circuitry can be achieved following nigral grafts. The demonstration of specific synaptic input on host substance P neurons provides an anatomical basis for direct functional modulation of the deafferented host neostriatum by the nigral graft.
Prior optic nerve transection reduces capsaicin‐induced degeneration in rat subcortical visual structures
Authors: Ritter Sue , Dinh Thu T.
Published: January 2005

Capsaicin is a neurotoxin capable of causing degeneration in specific sites throughout the neuraxis, including the suprachiasmatic nucleus (SCh), the ventrolateral geniculate nucleus (VLG), the intergeniculate leaflet (IGL), and the olivary and medial pretectal nuclei (OPT and MPT). In this experiment, we tested the hypothesis that capsaicin‐induced terminal degeneration in the SCh, VLG, IGL, OPT, and MPT results from destruction of retinal ganglion cells and their axonal projections to these sites. In the first experiment, silver stains were used to examine degeneration in the retina induced by systemic capsaicin treatment. Capsaicin caused degeneration of ganglion cells, bipolar cells, and nerve terminals in the retina, which could be observed between 2 and 24 hours after treatment. In the second experiment, 15‐day‐old rat pups were enucleated unilaterally. Five days or 2, 5, or 10 months later, they were injected systemically with capsaicin and killed 6 hours (pups) or 18 hours (adults) later for analysis with a cupric silver stain. In rats of all ages, prior monocular enucleation reduced or eliminated capsaicin‐induced degeneration in the contralateral SCh, VLG, IGL, OPT, and MPT. In the third experiment, rat pups were treated systemically with capsaicin or vehicle solution at 12 days of age and given unilateral intravitreal injections of cholera toxin conjugated to horseradish peroxidase (CT‐HRP) 3 days prior to sacrifice at 20 days of age. Transport of CT‐HRP to the SCh, VLG, IGL, MPT, and OPT was attenuated but not abolished by capsaicin pretreatment. Results suggest that capsaicin causes degeneration in the SCh, VLG, IGL, MPT, and OPT by selective destruction of a subpopulation of retinal ganglion cells with axonal projections to these sites.
GABA and enkephalin in the lateral septum of the guinea pig: Light and electron microscopic evidence for interrelations
Authors: Beauvillain J. C. , Mitchell V. , Tramu G. , Mazzuca M.
Published: January 2005

Tract tracing techniques combined with immunohistochemistry in rats and guinea pigs have demonstrated the existence of a hypothalamo‐lateral septum enkephalinergic pathway. Numerous enkephalinergic nerve endings encompass cell bodies located in the lateral septum. The present immunocytochemical study, at light and electron microscopic levels, was undertaken in the guinea pig brain to determine whether the contacted perikarya contain γ‐aminobutyric acid (GABA).

The antisera against GABA revealed the presence of immunoreactive cell bodies throughout the lateral septum. At the light microscopic level, most GABA neurons appeared round while others were oval with one or two emerging dendrites. Ultrastructurally, cell bodies displayed a moderate number of organelles and a pale nucleus with frequent indentations of the nuclear envelope.

The precise relationship between GABA neurons and enkephalinergic terminals was examined by means of a double‐immunostaining method showing that 60% of cell bodies receiving synaptic inputs from enkephalinergic afferents contained GABA.

These results show that the hypothalamo‐septal enkephalinergic pathway prominently innervates GABA‐containing neurons and also provide anatomical basis suggesting a disinhibitory role for this enkephalinergic tract.
Patterns of sensory intermodality relationships in the cerebral cortex of the rat
Authors: Paperna Tamar , Malach Rafael
Published: January 2005

Patterns of connections underlying cross‐modality integration were studied by injecting distinguishable, retrograde tracers (Fluoro‐Gold and diamidino yellow) in pairwise manner into different sensory representations (visual, somatosensory, and auditory) in the cerebral cortex of the rat.

In agreement with previous single tracer studies, our results indicate that the central core of sensory areas receives projections mainly from a set of association areas located in a ringlike fashion along the margin of the cortical mantle. The visual cortex received projections from areas 48/49, area 29d, posterior agranular medial cortex (AGm), area 11, area 13, and area 35. All these areas were also connected to the auditory cortex with the exception of areas 29d and AGm. However, lateral to area 29d and posterior AGm, a band of neurons projecting to the auditory cortex was present. Somatosensory cortex was connected mainly with the more anterior aspect of the hemisphere, which included primary motor area, area 11, and area 13.

The patterns of intermodality relationships revealed in the present study were of two main categories. In the anterior, and lateral areas, an intermingling of cells projecting to different sensory modalities was observed. In contrast, in areas located along the medial aspect of the hemisphere, cells connected to different sensory modality representations tended to be segregated from each other. Postsubicular cortex (areas 48/49) contained both intermingled and segregated groups of cells. The incidence of clearly identified double‐labeled cells concurrently projecting to two different sensory representations was extremely rare. These patterns may form a substrate for different levels of cross‐modal sensory integration in the rat cortex.
Cortical areas in the medial frontal lobe of the cat delineated by quantitative analysis of thalamic afferents
Authors: Musil S. Y. , Olson C. R.
Published: January 2005

The aim of these experiments was to establish the number and location of connectionally distinct areas in the medial frontal lobe of the cat. Thirty deposits of distinguishable retrograde tracers were placed at restricted sites spanning the medial frontal lobe in 16 cats. Following each deposit, the number of retrogradely labeled neurons in each of 17 thalamic nuclei was determined. Variations of the thalamic labeling pattern dependent on the location of the cortical tracer deposit were then analyzed by a quantitative procedure.

The results indicate that the medial frontal lobe contains three fundamental divisions: the anterior cingulate area, medial area 6, and the medial prefrontal district. The anterior cingulate area derives its strongest thalamic input from the anteromedial nucleus. Medial area 6 is the target of afferents originating in a dorsolateral sector of the mediodorsal nucleus and in the ventroanterior nucleus. Medial prefrontal cortex is heavily innervated by pathways originating in the core of the mediodorsal nucleus and in the principal ventromedial nucleus. Within each major district, thalamic connectional patterns exhibit graded regional variation, with the result that, whereas the connections of the district are not uniform, it is difficult to define further discrete subdivisions.

We discuss these results in relation to previously proposed schemes for parcellation of the cat's medial frontal lobe and conclude that the infralimbic and prelimbic areas (areas 25 and 32) of previous systems are best understood not as discrete areas but as ventral and intermediate sectors of a continuous medial prefrontal domain.
Nerve growth factor receptor immunoreactivity in the new world monkey (Cebus apella) and human cerebellum
Authors: Mufson Elliott J. , Higgins Gerald A. , Kordower Jeffrey H.
Published: January 2005

The present study used the NGFR‐5 monoclonal antibody raised against human nerve growth factor receptor (NGFR) to determine the extent of NGFR immunoreactivity within the embryonic and young adult Cebus apella cerebellum as well as the human cerebellum. Immunohistochemically processed tissue revealed NGFR expressing Purkinje cell somata, axons, and dendrites, the latter being observed within the molecular layer of both adult species. Within all regions of the cerebellum we observed both darkly and lightly immunostained Purkinje cells. The proximal axons of these cells, which were visualized for short distances within the granular cell layer, appeared to contain bulbous aggregates of reaction product. In sagittal sections, the full extent of the Purkinje cell dendritic tree was observed in the more lightly stained portions of the cerebellum. In situ hybridization experiments revealed NGFR mRNA within Purkinje cells in a pattern similar to that seen with immunohistochemistry. The distribution of NGFR immunoreactivity within the cerebellum exhibits a general topographic organization with the heaviest and most consistent staining occurring within the archi‐ and neocerebellum and weaker staining within the paleocerebellum. In fetal Cebus monkey cerebellum obtained at gestational day 50 and 70, NGFR immunoreactivity was observed as a band composed of developing Purkinje cell neurites. These profiles were seen in the paleo‐ and neocerebellum, but not the archicerebellum. The present investigation is the first demonstration of NGFR immunoreactive profiles in the adult monkey and human cerebellum. These findings suggest that nerve growth factor may influence locomotor and vestibular behaviors that are mediated by cerebellar circuitry. The precise mode of action for the NGF/NGFR system within the cerebellum remains to be determined.
Comparative aspects of the basal ganglia‐tectal pathways in reptiles
Authors: Medina Loreta , Smeets Wilhelmus J. A. J.
Published: January 2005

To determine how the basal ganglia in reptiles may influence visuomotor behavior, the connections from the basal ganglia to the tectum of the midbrain were studied in several species of reptiles. Immunohistochemical studies by means of antibodies against Leu‐enkephalin (LENK) as well as experimental hodological studies with anterograde (PHA‐L) and retrograde (HRP, Fluorogold, Cholera toxin) tracers were carried out. The results indicate that within the class of Reptilia, two different patterns occur: one in which information from the basal ganglia is relayed to the tectum via the substantia nigra as well as via a pretectal, enkephalinergic cell group, and another one in which only the ventral route, via the substantia nigra, is present. The former pattern is found in turtles, crocodiles, and the lacertid lizards Podarcis and Gallotia, and the latter pattern in the gekkonid lizards Gekko and Eublepharis, in Varanus, and in the snakes Python and Thamnophis. The presence or absence of the pretectal relay center is reflected in the laminar distribution of LENK immunoreactivity in the tectum.

The apparent lack of a pretectal relay in nocturnal gekkonids and in snakes underlines the hypothesis (Reiner et al., '84: T.I.N.S. 7:320–325) that a de‐emphasis of visual‐basal ganglia mechanisms has occurred during the evolution of ancestral reptiles to modern mammals.
Central projections of primary sensory neurons innervating different parts of the vibrissae follicles and intervibrissal skin on the mystacial pad of the rat
Authors: Arvidsson J. , Rice F. L.
Published: January 2005

The cell bodies and central projections of neurons innervating the vibrissae follicles and adjacent skin in the rat were investigated by retrograde and transganglionic transport of HRP. The cell bodies of neurons innervating the vibrissa follicle via the deep vibrissa nerve (DVN) were the largest, followed by those innervating the follicle via the superficial vibrissa nerve (SVN). The smallest cell bodies were those innervating the intervibrissal skin. The DVN neurons terminated centrally as an almost uninterrupted column through the trigeminal sensory nuclear complex. The DVN projections to nucleus caudalis and C1 dorsal horn were entirely restricted to laminae III, IV, and V. Besides the projections to lamina V, the DVN projections were strictly localized somatotopically at all levels replicating the peripheral organization of the vibrissae. The SVNs projected sparsely to midlevels of the main sensory nucleus but not to nuclei oralis and interpolaris. The main SVN projections appeared in laminae I‐III of nucleus caudalis. In addition, a small projection to lamina V was observed. The projections to laminae II and III were organized mediolaterally in a similar way as the DVN projections; those to laminae I and V were less restricted. The intervibrissal skin neurons projected sparsely to the caudal main sensory nucleus and to the border between nuclei oralis and interpolaris. The projections to nucleus caudalis were restricted to laminae I‐III and V and were organized in a similar way as the SVN projections.
Segment‐specific modifications of a neuropeptide phenotype in embryonic neurons of the moth, Manduca sexta
Authors: Wall John B. , Taghert Paul H.
Published: January 2005

We have studied differences in the development of segmentally homologous neurons to identify factors that may regulate a neuropeptide phenotype. Bilaterally paired homologs of the peripheral neuron L1 were identified in the thoracic and abdominal segments in embryos of the moth Manduca: each bipolar neuron arises at a stereotyped location and, at 40% of embryogenesis, projects its major process within the transverse nerve of its own segment. Shortly after the initiation of axonogenesis (∼41%), L1 homologs in all but the prothoracic segment (T1) were labelled specifically by an antiserum to the molluscan neuropeptide Phe‐Met‐Arg‐Phe‐NH2 (authentic‐ FMRFamide). Levels of peptide‐immunoreactivity (IR) were comparable in all such segmental homologs up to the ∼60% stage of embryogenesis, whereupon two distinct levels of peptide IR were displayed: homologs in the three most rostral segments (T2, T3, and A1; [abdominal segment 1]) showed high levels and were called Type I L1 neurons; homologs in the more caudal segments (A2‐A8) typically showed low levels of IR and were called Type II L1 neurons. This segment‐specific difference represented mature differentiated states and was retained in postembryonic stages. Intracellular dye fills of embryonic L1 neurons revealed that the morphogenesis of the Type I and II L1 neuron homologs was similar until ∼48% of embryogenesis; thereafter it differed in two salient ways: (1) the cell bodies of Type II L1 neurons migrated ∼150 m̈m laterally from their point of origin, and (2) the distal processes of the Type II L1 neurons contacted the heart, whereas those of Type I L1 neurons did not. Ultrastructural studies of both mature and developing L1 homologs showed that the FMRFamide‐like antigen(s) localized specifically to secretory granules. Further, whereas the secretory granules in segmental homologs appeared similar initially (i.e., at ∼50% of development), following the establishment of segment‐specific differences, secretory granules found in mature Type I and II L1 neurons were cell type‐specific.
Single dopaminergic nigrostriatal neurons form two chemically distinct synaptic types: Possible transmitter segregation within neurons
Authors: Hattori T. , Takada M. , Moriizumi T. , Van Der Kooy D.
Published: January 2005

These experiments were designed to examine a paradox present in the literature with regard to the fine structure of nigrostriatal dopamine terminals within the rat striatum. Previous studies have shown that anterograde transport of tritiated labeled proteins from the substantia nigra to the striatum over short survival times primarily labels asymmetric synapses (and that these asymmetric synapses are preferentially vulnerable to selective dopaminergic neurotoxins such as 6‐hydroxydopamine). In contrast, fine structural immunohistochemical studies with antibodies to tyrosine hydroxylase and dopamine have consistently labeled primarily symmetric synapses en passant within the striatum. We have now confirmed that these two seemingly contradictory types of labeled synapses (radio‐ and immuno‐labeled) can both be present, but most often separate from one another, in single ultrathin sections. However, we also found that radiolabeled unmyelinated axons were usually double‐labeled by tyrosine hydroxylase immunohistochemistry. Employing longer survival times (10 days after the nigral isotope injections) in order to enhance the ratio of “enpassant” to terminal labeling produced a large increase in the occurrence of radiolabeled striatal axonal varicosities with the result that many symmetric synapses en passant were double‐labeled with both the autoradiographic and the immunohistochemical markers. Given that more than 95% of the nigrostriatal projection arises from dopamine fluorescent neurons, it would appear that both the asymmetric and symmetric terminals belong to the same type of neuron. Thus, we suggest that single dopaminergic neurons in the substantia nigra make two types of synaptic contact with striatal cells: (1) symmetric synapses en passant, which can be stained with tyrosine hydroxylase and dopamine and which contact dendritic spine necks, and (2) asymmetric terminal boutons of unknown chemical nature which end on dendritic spine heads. We conclude that both the asymmetric terminal and symmetric en passant synapses take origin from a single nigrostriatal dopaminergic neuronal population and that dopaminergic transmitter markers occur only in one of these synaptic types in the rat striatum.
Distribution of somatostatin receptors in the cat and monkey visual cortex demonstrated by in vitro receptor autoradiography
Authors: Rosier A. M. , Leroux P. , Vaudry H. , Orban G. A. , Vandesande F.
Published: January 2005

Somatostatin (SRIF, S14) receptors in the cat and monkey visual cortex were visualized by means of in vitro autoradiography with an iodinated agonist of SRIF, [125I‐Tyr0, DTrp8]S14. The kinetics, performed on tissue sections, revealed an apparently single, saturable site (KD = 3.92 ± 0.31 10−10 M for the cat, and 3.82 ± 0.28 10−10 M for the monkey visual cortex) with pharmacological specificity for S14 and [DTrp]‐substituted S14. Autoradiography, performed on frontal sections of the cat and monkey visual cortex, revealed a heterogeneous regional and laminar distribution of SRIF receptor.

In cat areas 17, 18, and 19, SRIF receptors occur mainly in the supragranular layers, although small interareal and intra‐areal differences are observed. The infragranular layers (V–VI) in area 19 contain a significantly higher proportion of SRIF receptors compared to both areas 17 and 18. In the antero‐ (AMLS) and posteromedial lateral suprasylvian area (PMLS), layers V and VI contain the highest proportion of SRIF receptors. This latter pattern is also observed in the area prostriata medially adjoining area 17 in the splenial sulcu.

In the monkey visual cortex, areas 17 and 18 exhibit similar distribution patterns, SRIF receptors being primarily concentrated in layers V and V.

Neither in the cat nor the monkey visual cortex could we observe significant differences in SRIF receptor distribution between different retinotopic subdivisions within one are.
Human olfactory epithelium in normal aging, alzheimer's disease, and other neurodegenerative disorders
Authors: Trojanowski John Q. , Newman Paul D. , Hill William D. , Lee Virginia M.‐Y.
Published: January 2005

By use of immunohistochemistry, we characterized the molecular phenotype of human olfactory epithelial (OE) cells and assessed the nature of the dystrophic olfactory neurites described initially in Alzheimer's disease (AD). Keratin 8 was present in all classes of OE cells. Sustentacular cells lacked other cell type specific polypeptides and were distinguished from neurons and basal cells because the latter two classes of OE cells expressed neural cell adhesion molecules (N‐CAMs) and microtubule associated proteins (MAPs), i.e., MAP5. Basal cells expressed nerve growth factor receptors (NGFRs), which distinguished them from olfactory neurons. Unlike their perikarya, olfactory axons expressed vimentin and GAP‐43, but not peripherin or neurofilament (NF) proteins. Olfactory nerves were distinguished from other axons because the latter were positive for all three NF subunits and peripherin, in addition to vimentin and GAP‐43.

Dystrophic neurites in the OE were GAP‐43 positive, but they also expressed proteins that were not detected in normal olfactory nerves (i.e., synaptophysin, MAP2, tau, peripherin, NF proteins). Further, rare NF positive olfactory neurons gave rise to NF positive dystrophic neurites. These neurites were present in all 11 AD cases, 11 of 14 subjects with other neurodegenerative diseases, and 6 of 8 neurologically normal adult controls, but no dystrophic neurites were seen in 9 fetal and neonatal case.

We conclude that the molecular phenotype of different human OE cells is distinct and that dystrophic olfactory neurites occur very frequently in neurologically normal adults. The relevance of these neurites to aging or specific disease processes remains speculativ.
Cytoarchitecture and intrafrontal connections of the frontal cortex of the brain of the hamadryas baboon (Papio hamadryas)
Authors: Watanabe‐Sawaguchi Kyoko , Kubota Kisou , Arikuni Tomio
Published: January 2005

A study was made of the cytoarchitecture of the lateral and medial frontal cortex in the hamadryas baboon (Papio hamadryas). The frontal corticocortical connections of areas 46, 8, 6, and 4 were investigated by injection of wheat‐germ agglutinine conjugated to horseradish peroxiase (WGA‐HRP) into different regions of areas 46, 8, and 6. The lateral region of the frontal lobe of the baboon consists of broad areas of motor (area 4), premotor (area 6), and the dorsolateral prefrontal cortex, each of which is further divided into subdivisions with distinct cytoarchitectural features: areas 4a, 4b, 4c; 6aα, 6aβ, 6aγ, 6bα, and 6β; 8A and 8B; 45; 46 and 46ps; 9; 10; and 12. Although the frontal cortex of the baboon brain exhibits the same basic cytoarchitectural features as the frontal corticies of the cercopithecus (campbelli?) (Vogt and Vogt, '19) or the macaque (Walker, '40; Barbas and Pandya, '87, '89), the baboon frontal cortex is very different from that of the macaque and cercopithecus in terms of cytoarchitecture: (1) the baboon frontal cortex has an additional area, termed here “6aγ”, within area 6, which has cytoarchitectural characteristics that are intermediate between those of areas 6 and 8; (2) the aggregation of giant pyramidal cells (> 50 μm. in diameter) is found only in area 4a in the baboon, whereas such aggregates are found in areas 4a and 4b and, occasionally, in area 4c in the macaque; and (3) area 46 of the prefrontal cortex of the baboon can be subdivided into the cortex that surrounds the principal sulcus (area 46) and the upper and lower banks of the principal sulcus (area 46ps).

Retrogradely WGA‐HRP labeled cells and anterogradely WGA‐HRP labeled terminals coexisted in the frontal cortex in a columnar fashion, indicative of a reciprocity among the connections. The frontal cortico‐cortical connections of areas 46, 8, 6, and 4 in the hamadryas baboon were organized as follows: (1) areas 46, 8, and 6 were connected to one another, (2) area 4 was connected only to area 6, and (3) these connections showed a gross ventrodorsal topography: the ventral regions of each of areas 46, 8, and 6 were connected more strongly to the ventral than the dorsal regions of the other areas; the dorsal regions of each of areas 46, 8, and 6 were connected more strongly to the dorsal than the ventral regions of the other areas. Moreover, the ventral region of area 6 was more strongly connected to the ventral than to the dorsal region of area 4, whereas the dorsal region of area 6 was more strongly connected to the dorsal than to the ventral region of area 4.