bluuebunny/crossref_metadata_2025 huggingface dataset:
The motor complex and primary projections of the trigeminal nerve in the monitor lizard, varanus exanthematicus
Authors: Barbas‐Henry Heleen A. , Lohman Anthony H. M.
Published: January 2005

The sensory projections and the motor complex of the trigeminal nerve of the reptile Varanus exanthematicus were studied with the methods of anterograde degeneration and anterograde and retrograde axonal transport. The primary afferent fibers diverge in the brainstem into a short ascending and a long descending tract. The former distributes its fibers to the principal sensory trigeminal nucleus, where nerves V1, V2, and V3 are represented along a lateromedial axis. The fibers of the descending tract enter the nucleus of this tract and the reticular formation. Both in the tract and its nucleus, nerves V1, V2 and V3 occupy succesively more dorsal position. A small contingent of nerve V1 fibers course to the accessory abducens nucleus. The descending tract extends caudally into the first and second cervical segments of the spinal cord. The trigeminal motor complex consists of dorsal, ventral, and dorsomedial nuclei. The m. adductor mandibulae externus (the main jaw closer) is represented in the dorsal nucleus, predominantly in its rostral part. The muscles innervated by nerve V3 are represented in the ventral nucleus, mainly in its caudal part. All three divisions of the trigeminal nerve contain peripheral branches of the mesencephalic trigeminal system. Collaterals of the central branches of this system were traced to the ventral motor and the principal sensory trigeminal nuclei.
Development of segmental differences in the pressure mechanosensory neurons of the leech haementeria ghilianii
Authors: Loer Curtis M. , Schley Carol , Zipser Birgit , Kristan William B.
Published: January 2005

Using a monoclonal antibody specific for the pressure mechanosensory neurons (P cells) of the leech Haementeria ghilianii, we have examined the segmental differences between P cells in the adult nerve cord, as well as the development of these differences during embryogenesis. The standard segmental ganglion contains two pairs of P cells of about the same size and staining intensity. The sex ganglia appear to be missing the P cells that normally innervate ventral skin, and ganglia 20 and 21 have much smaller ventral P cells than most segments. The pattern of P cells in the head and tail ganglia also differs slightly from that of the standard ganglia. During embryogenesis, when the neurons are first stained by the antibody, there are two pairs of P cells of equal size in each segmental ganglion. Obvious segmental differences arise subsequently, modifying an initially identical set of cells.
Vascular atrophy in the retinal degenerative rd mouse
Authors: Blanks Janet C. , Johnson Lincoln V.
Published: January 2005

We have observed that the lectin Ricinus communis agglutinin I (RCA), which binds to terminal galaotose moieties, serves as a marker for vasculature in the mouse retina. The binding of fluorescein‐isothiocyanate‐conjugated RCA was used to study the development of retinal vasculature in normal mice and in rd (retinal degeneration) mutant mice, which exhibit a massive loss of photoreceptor cells during the first month of life. In the normal mouse, retinal capillaries develop in an ordered manner and are concentrated in three major zones between the inner limiting membrane and the outer plexiform layer. In the rd mouse, the vessels appear to form normally but begin to degenerate by the end of the second postnatal week. By the end of the fourth postnatal week there is approximately a 35% reduction in the total number of vascular profiles in the rd retina compared to normal littermate controls. This reduction in vascularity is temporally associated with the photoreceptor degeneration.
Identification of a subtype of cone photoreceptor, likely to be blue sensitive, in the human retina
Authors: Ahnelt Peter K. , Kolb Helga , Pflug Renate
Published: January 2005

A minor population of cone photoreceptors (called B‐cones) can be distinguished from the major population (called R‐cones) on morphological criteria as seen by light microscopy in foveal and peripheral human retina. The B‐cones are characterized by (1) a longer inner segment projecting into subretinal space, (2) a larger‐diameter inner segment, (3) an increased staining intensity of the inner segment, and (4) a different distribution relative to the R‐cones in the cone mosaic. B‐cones occur even in the foveolar center (3–5%) and rise to a maximum (15%) in the foveolar slope. They can also be identified in peripheral retina where they form 7–10% of the total cone population. The B‐cone population follows the distribution profile postulated for the blue‐sensitive system from histochemical studies on monkeys and from psychophysical studies on humans. The B‐cones also share many of the same morphological features of the putative blue cones of the ground squirrel and monkey retinas. For these reasons we suggest that our B‐cone group is the blue cone population of the human retina.
Correcting errors in estimating neuron area caused by the position of the nucleolus
Authors: Born Donald E. , Carman Charles S. , Rubel Edwin W
Published: January 2005

The technique of measuring soma cross‐sectional area at the plane of the nucleolus leads to systematic errors that depend on how far the nucleolus is displaced from the center of the soma. A set of correction factors was produced based on calculations from a geometric model of the measurement process. Applying the correction factors to measurements of second‐order auditory neurons led to substantial changes in the estimated soma area.
The morphology, number, and distribution of a large population of confirmed displaced amacrine cells in the adult cat retina
Authors: Wong R. O. L. , Hughes A.
Published: January 2005

The presence of a large population of some 730,000 displaced amacrines is confirmed in the ganglion cell layer of the cat retina. These cells correspond to the microneurons of Hughes and Wieniawa‐Narkiewicz (Nature 284:468–470,'80) and the bar‐cells of Hughes (J. Comp. Neurol. 197:303–339, '81): a population of profiles of which the majority had previously been presumed to be glia (Stone:J. Comp. Neurol 12:337–352, '65;J. Comp. Neurol 180:753–772, '78; Hughes:J. Comp. Neurol 163:107–128, '75).

A sample of such nonganglion cells was identified by Nissl criteria in an area of retina subsequently subjected to serial sectioning and electron microscopy. Such cells form synapses with other processes in the inner plexiform layer. Members of each morphological subclass were found to bear synapses. In some instances, synapses occurred both onto and from the soma and processes of a cell, which is strong evidence for their being displaced amacrines, or preferably, “amacrines of the ganglion cell layer.”

In confirmation of their amacrine nature, it was established that the microneurons and bar‐cells survive optic nerve section for up to 2.5 years. Ganglion cells underwent retrograde degeneration and completely disappeared in a much shorter time. Injection of kainic acid, a neurotoxin, into an eye whose optic nerve had been cut over 2 years previously resulted in the pyknosis of all morphologically classified microneurons and bar‐cells without influence on conventional glial cells. These results further support the conclusion that microneurons and bar‐cells are neurons and that they collectively form the displaced amacrine population of the cat ganglion cell layer.

The topographic distribution of the displaced amacrines resembles that of the ganglion cells in form; their density peaks at 4,500–5,000 cells mm−2in the area centralis and falls to less than 1,000 mm−2in peripheral retina. A ganglion cell distribution map based on the latest morphological criteria derived from this study confirms that there are 170,000 ganglion cells in the cat retina. Displaced amacrines form some 80% of thetotalneuron population of the cat ganglion cell layer.

The large population magnitude of these confirmed displaced amacrines implies their nonectopic origin and now provides a fresh insight into the ontogeny of the cat retinal ganglion cell layer.
Mapping of neuropeptide Y‐like immunoreactivity in the feline hypothalamus and hypophysis
Authors: Leger Lucienne , Charnay Yves , Danger Jean‐Michel , Vaudry Hubert , Pelletier Georges , Dubois Paul‐Marie , Jouvet Michel
Published: January 2005

The distribution of neuropeptide Y (NPY) in the cat hypothalamus and hypophysis was studied with the indirect immunofluorescence technique of Coons and co‐workers (Coons, Leduc, and Connolly: J. Exp. Med. 102:49–60, 1955), which provided a detailed map of NPY‐like immunoreactive neurons. The immunolabelling was detected in cell bodies, fibers, and terminallike structures widely distributed throughout the whole hypothalamus. A large population of medium‐sized NPY‐like immunoreactive cell bodies was localized in the area of arcuate nucleus. The number of immunoreactive cell bodies visualized was dramatically increased after intracerebroventricular injections of colchicine. Numerous immunolabelled cell bodies were also visible in the median eminence and scattered in the lateral hypothalamic area. Dense plexuses of NPY‐immunoreactive fibers were observed in the arcuate nucleus, internal layer of median eminence, periventricular zone, and paraventricular nucleus. Other regions of hypothalamus displaying numerous NPY‐like immunoreactive fibers included dorsal and ventrolateral hypothalamic areas. In contrast, certain hypothalamic areas were almost devoid of NPY‐like immunoreactive fibers—namely, the mamillary bodies and suprachiasmatic nucleus. Finally, in neurohypophysis, bright immunofluorescent fibers were observed along the pituitary stalk and penetrating the neural lobe.

These results suggest the widespread distribution of the NPY‐containing neuronal systems in the cat hypothalamus and hypophysis.
Comparison of met‐enkephalin‐, dynorphin A‐, and neurotensin‐immunoreactive neurons in the cat and rat spinal cords: I. Lumbar cord
Authors: Miller Kenneth E. , Seybold Virginia S.
Published: January 2005

This study compared the distribution of methionine enkephalin‐, dynorphin A 1–8‐, and neurotensin‐immunoreactive (IR) perikarya in laminae I and IV–VII of selected segments of lumbar spinal cord of cat(L5) and rat(4). Immunoreactive neurons for each peptide were found throughout the dorsal horn and dorsal lamina VII but were quantified only within laminae I and IV–VII. In lamina I, both large (>20 μm) and small (<20 μm) IR neurons were identified. Large IR neurons for each peptide in both species resembled Waldeyer neurons studied by Golgi stain and were outnumbered by small IR neurons. Comparison among the laminae of the distribution of metenkephalin IR neurons showed a similar pattern in the two species with the majority of IR neurons (>65%) in laminae V and VI. Differences in laminar distribution occurred between species for the other peptides. Dynorphin IR neurons were greatest in number in lamina V in rat but greatest in number in laminae I and V in cat. Neurotensin IR neurons occurred predominately in cat lamina I but were nearly equal in density in rat laminae I and VI. The topographic distribution of each peptide in laminae V and VI was similar between the two species with IR neurons occuring laterally in lamina V and more medially in lamina VI. Comparisons between species of the numbers of IR neurons/segment indicated distinct relationships for each peptide. The number of met‐enkephalin IR neurons in laminae of cat L5 was generally two times greater than the number of IR neurons in the same laminae of rat L4, except in laminae I and IV, where the numbers were nearly equal. In contrast, the number of dynorphin IR neurons in cat laminae was generally one‐half the number in rat, except in lamina I, where the number in cat was two times greater than rat. A high degree of variability occurred in laminar comparisons of neurotensin IR neurons. Neurotensin IR neurons in lamina I of cat outnumbered those of rat 2:1, but in laminae IV–VII, the ratio of cat to rat IR neurons varied from 1:1 to 1:20. The metenkephalin, dynorphin, and neurotensin IR neurons quantified in this study may be interneurons or may serve as projection neurons to brainstem and/or thalamic nuclei. The observed differences in distribution may be relevant to differences in spinal cord physiology in the two species.
Quantitative analysis of cervical musculature in rats: Histochemical composition and motor pool organization. I. Muscles of the spinal accessory complex
Authors: Brichta A. M. , Callister R. J. , Peterson E. H.
Published: January 2005

In this paper we characterize the architecture and segmental innervation, histochemical composition, muscle spindle populations, and motor pool organization of rat spinal accessory (SA) muscles: sternomastoid (SM), cleidomastoid (CM), cleidotrapezius (CT), and acromiotrapezius (AT). We also consider (1) whether individual rat neck muscles are supplied by more than one population of motor neurons as they are in turtles and cats and (2) whether in SA muscles motor neuron size scales with target muscle fiber type.

SM, CM, and CT are ventral, parallel strap muscles. Each can be divided into grossly visible white and red compartments. AT is a dorsolateral sheetlike muscle that shows no gross compartmentalization. All four muscles are dominated by fast‐twitch glycolytic (FG) and fast oxidative glycolytic (FOG) fibers, and FG fibers are significantly more numerous than the FOG type in three out of four muscles. Thus SA muscles in rats appear to be specialized for rapid, phasic head movements. Topographical analyses revealed that there is a striking compartmentalization of fiber types in the ventral muscles that corresponds to the red and white segments seen grossly. Spindles are found only in regions containing slow‐twitch oxidative (SO) fibers. Cross‐muscle comparisons indicate that there are significant differences between SA muscles in their fiber type composition.

The motor pools of SA muscles form a single column from lower medulla to C5. Rostral cells lie dorsomedially in the ventral horn and, at the C1/C2 junction, the column shifts ventrolaterally. Within this column, each motor pool occupies a characteristic rostrocaudal position in the order SM:CM:CT:AT. Thus SM and (in part) CM motor neurons lie more medially than cells supplying the trapezius complex, suggesting that they may be under different patterns of synaptic drive. We saw no evidence that rat SA muscles are supplied by more than one population of motor neurons. Direct comparisons between the soma sizes of motor neurons that supply muscles or parts of muscles with significantly different histochemical compositions indicate that these size differences are in the direction predicted from their histochemical profiles, thus suggesting that in these muscles motor neuron soma size may scale with muscle fiber type.
Quantitative analysis of cervical musculature in rats: Histochemical composition and motor pool organization. II. Deep dorsal muscles
Authors: Callister R. J. , Brichta A. M. , Peterson E. H.
Published: January 2005

In this paper we characterize the architecture, histochemistry, spindle composition, and motor pool organization of rat dorsal neck muscles: splenius (SP), biventer cervicis (BC) and complexus (COM). We also consider (1) whether individual rat neck muscles are innervated by more than one population of motor neurons as they are in turtles and cats and (2) whether in these muscles motor neuron size scales with muscle fiber type.

Dorsal neck muscles are divided by tendinous inscriptions into quasiserially arranged compartments. Each compartment is supplied by a separate peripheral nerve branch from C1–C5 dorsal rami; thus each dorsal neck muscle is innervated from multiple segments. Our histochemical data indicate that slow‐twitch oxidative (SO) fibers are always the least numerous group, and fast fibers are split almost equally between fast oxidative glycolytic (FOG) and fast glycolytic (FG) types. There are significant cross‐muscle differences in the relative frequency of each fiber type. Topographic analyses reveal a mosaic pattern of fiber types with no clear compartmentalization, and muscle spindle distribution is essentially homogeneous.

Motor neurons supplying rat dorsal neck muscles are restricted to the ventral third of the ipsilateral ventral horn from lower medulla to C4. The SP motor pool is located dorsally in the ventral horn, and BC and COM motor pools form overlapping columns in the tip. There is little evidence that these muscles are supplied by more than one population of motor neurons, as reported in turtles and cats. To help assess these differing results, in two cats we infiltrated the C2 nerve to BC and COM; our results were similar to those previously reported in cats including the presence of contralateral motor neurons. Thus disparate results between rat and cat experiments may represent species differences in neck muscle innervation. In five experiments we made direct comparisons between the sizes of motor neurons that supply muscles with significantly different histochemical compositions. In each case there was a difference in mean soma size in the direction predicted by the muscles' histochemical profiles, thus suggesting that in these muscles motor neuron size may scale with muscle fiber type.
Axon trajectories and pattern of terminal arborization during the prenatal development of the cat's retinogeniculate pathway
Authors: Sretavan David W. , Shatz Carla J.
Published: January 2005

In this study we have examined the trajectories taken by populations of ganglion cell axons and the spatial gradients of terminal arbor maturity within the lateral geniculate nucleus (LGN) during the prenatal development of the cat's visual system. To do so, an in vitro method of labeling optic tract axons from fetal brains between embryonic day 37 (E37) and postnatal day 2 (P2) with horseradish peroxidose (HRP) was used.

At the earliest ages studied (E37–E53), optic axons leave the optic tract to run across the LGN toward their sites of termination in straight trajectories parallel to each other. At later ages (E57–P2), however, axons with abrupt changes in their course across the nucleus can be clearly identified. When the detailed terminal arbor morphology of the set of retinogeniculate axons filled with HRP at a given age was examined, two different spatial gradients of maturation could be detected. The terminal arbors of axons within LGN layer A are always more mature than those ending in layer A1, an observation consistent with previous findings that axons from the contralateral eye arrive within the LGN several days before those from the ipsilateral eye. Moreover, the terminal arbors of axons projecting to the medial portions of each layer are always more mature than their more lateral counterparts. These gradients are likely to be a direct reflection of the central‐first, peripheral‐last gradient associated with the neurogenesis of the retinal ganglion cells themselves.

In the oldest animals studied (E58–P2), a remarkable periodic pattern of terminal arbor labeling was seen following a localized HRP injection into the optic tract. Within the labeled portions of the LGN, densely filled axon terminal arbors are separated by unlabeled gaps of similar width. This pattern of labeling could reflect local topographic disorder within the optic tract or could arise if axons of different classes of retinal ganglion cells run in separate portions of the optic tract.

Taken together, all of these observations suggest that there may be a fair degree of topographic order in the retinogeniculate projection within the cat's LGN early on in development. However, when topographic errors are present, some can be corrected by minor readjustments in axonal trajectories.
Inability of neural crest cells to colonize the presumptive aganglionic bowel of ls/ls mutant mice: Requirement for a permissive microenvironment
Authors: Jacobs‐Cohen R. J. , Payette R. F. , Gershon M. D. , Rothman T. P.
Published: January 2005

The enteric system is formed by cells that migrate to the bowel from the neural crest. In order to gain insight into intraenteric factors that influence this migration, the colonization of the bowel of the ls/ls mouse was investigated. The terminal 2 mm of ls/ls intestine fails to become colonized by crest cells and thus remains aganglionic. The entire bowel of control mice and ls/ls mice was explanted before the appearance in situ of recognizable neurons and grown in organotypic tissue culture. Neurons, detected by the histochemical demonstration of acetylcholinesterase activity, developed throughout the length of the control gut, but, even in vitro, were excluded from the terminal segment of the ls/ls intestine. Co‐culture experiments were done, in which primary and secondary sources of crest cells were combined with recipient segments of bowel, to test the ability of the recipient tissue to become colonized by neural precursors. The primary source was murine crest cells migrating away from an explant of the neuraxis. Secondary sources included avian and murine foregut (control and ls/ls) containing migratory crest cells as well as the quail ganglion of Remak. Recipient segments of bowel included control avian and murine hindgut, explanted before the tissue had become colonized by crest cells in situ, as well as the presumptive aganglionic bowel of ls/ls mice. Both primary and secondary sources of crest cells proved to be able to contribute neurons to the control segments of recipient hindgut. Species differences were no barrier to the colonization of the bowel in vitro. Moreover, the ls/ls foregut was as good a source of neural precursors for a normal recipient bowel, as was control avian or murine foregut. In contrast, none of the sources of crest cells that were utilized contributed neurons to the presumptive aganglionic gut of ls/ls mice. Both cells and processes of enteric neurons developing in vitro (detected by demonstrating neurofilament immunoreactivity) tended to be excluded from the presumptive aganglionic tissue. On the other hand, neurites, but not cell bodies, of dorsal root ganglia co‐cultured with presumptive aganglionic ls/ls bowel did enter the abnormal zone. These data are consistent with the hypothesis that nonneuronal elements of the wall of the presumptive aganglionic region of the ls/ls gut are abnormal and prevent the colonization of this segment of the gut with viable neural precursors from the neural crest. This defect in the ls/ls intestine is restricted to intrinsic elements and does not prevent it from becoming innervated by ingrowing extrinsic nerve fibers, such as those from dorsal root ganglia. Since ls/ls crest cells can colonize the proximal ls/ls bowel as well as explants of hindgut from control mice or birds, the ls/ls crest cells themselves are probably not abnormal.
Distribution of opiate receptor subtypes and enkephalin and dynorphin immunoreactivity in the hippocampus of squirrel, guinea pig, rat, and hamster
Authors: McLean Stafford , Rothman Richard B. , Jacobson Arthur E. , Rice Kenner C. , Herkenham Miles
Published: January 2005

The distribution of enkephalin and dynorphin immunoreactivity in the hippocampus of four rodent species (gray squirrel, guinea pig, rat, and hamster) is compared with the pattern of opiate receptor subtypes (mu, delta, and kappa). The distribution of opioid peptides is fairly consistent in the anterior hippocampus of these four species. Intense immunoreactivity for dynorphin and enkephalin is found in the hilus of the dentate gyrus and in the mossy fiber system. Occasional immunoreactive processes are seen in the dentate molecular layer and scattered throughout the CA1 and CA3 fields. In the rat and hamster, an additional plexus of enkephalinergic fibers straddles both sides of the hippocampal fissure. Cells immunoreactive for both opioid peptides are located in and just superficial to the dentate granule cell layer.

Opiate receptors are variably distributed in these rodent species. In the squirrel, guinea pig, and hamster, mu and kappa binding is dense in the stratum lucidum of CA3 and the molecular layer of the dentate gyrus. In the rat, dense mu and kappa binding is localized within and adjacent to the pyramidal and granule cell layers. Delta receptor patterns show additional species differences. In the rat, the delta distribution is similar to the mu and kappa patterns. In the other species, the delta binding pattern is generally the inverse of the mu/kappa pattern: most areas of the hippocampus are enriched in delta sites, whereas the stratum lucidum and the pyramidal cell layer are receptor‐sparse. Thus, the stratum lucidum–site of dense terminations of mossy fibers containing opioid peptides–is characterized by selectively sparse delta receptors in four species and by selectively dense kappa receptors in three species. The three receptor subtypes, taken either individually or together and compared to the peptides, are more variably and more widely distributed throughout the hippocampus and fail to show a correspondence with opioid‐peptide‐containing terminals. The mismatches suggest that receptor locations and densities are organized without relation to the sites of relevant transmitter release.
The ventral striatopallidothalamic projection: I. The striatopallidal link originating in the striatal parts of the olfactory tubercle
Authors: Heimer L. , Zaborszky L. , Zahm D. S. , Alheid G. F.
Published: January 2005

The projections from the striatal part of the olfactory tubercle were examined in rats, both with the aid of experimental silver impregnation methods following superficial laminar heat lesions of the tubercle and by the use of anterograde transport of Phaseolus vulgaris‐leucoagglutinin (PHA‐L) following injections of the lectin in the dense cell layer of the tubercle. Retrograde transport of fluorescent substances following injections of the tracer in the multiform layer of the tubercle were used to corroborate the results obtained by the anterograde transport and degeneration methods. The main and apparently only significant termination from the striatal cells in the olfactory tubercle is located immediately deep to the dense cell layer in areas that could be identified as part of the ventral pallidum on the basis of either the Nissl method or glutamate decarboxylase immunocytochemistry. Whereas a mediolateral topography is generally maintained by the ventral striatopallidal pathway originating in the dense cell layer, there is a considerable spread of the projection in the rostrocaudal direction. The dense projection field of the olfactory tubercle component of the ventral striatopallidal pathway permeates the ventrolateral part of the ventral pallidum, thereby complementing the termination of the accumbens projection to the more mediodorsal parts of the ventral pallidum.
Morphology of striatal neurons containing VIP‐like immunoreactivity
Authors: Theriault Elizabeth , Landis Dennis M. D.
Published: January 2005

We have used light and electron microscopic immunocytochemical techniques to study the distribution and morphology of neurons that contain vasoactive intestinal polypeptide‐like immunoreactivity (VIP‐Ir) in the adult rat striatum. VIP‐Ir cells were sparsely distributed throughout all rostrocaudal levels of the striatum. Cell bodies were of medium size (12–17 m̈m) and gave rise to three to five primary dendrites, which branched close to the soma and became varicose. These dendrites appeared aspiny at the light microscope level and could be traced up to 250 m̈m in length. Dendrites frequently traversed axonal bundles in the striatum, a pattern not exhibited by neurons containing somatostatin‐like or substance P‐like immunoreactivity. In several instances, very fine varicose processes arborized extensively within 40 m̈m of the VIP‐Ir soma; these may represent axons. In thin‐sectioned preparations, examined under the electron microscope, the nucleus of VIP‐Ir neurons was eccentrically located and showed several deep invaginations. Immunoreactive dendrites of VIP‐Ir cells appeared virtually spine‐free. Synapses with asymmetric or symmetric junctional specializations were present on the dendritic surface. Several VIP‐Ir varicosities were found to terminate on the VIP‐Ir cell body, forming synaptic junctions with symmetric specializations; these synapses may derive from recurrent collaterals. VIP‐Ir cells thus resemble other aspiny striatal neurons considered likely to be local circuit neurons.
Antigenic map of the rat cerebellar cortex: The distribution of parasagittal bands as revealed by monoclonal anti‐purkinje cell antibody mabQ113
Authors: Hawkes Richard , Leclerc Nicole
Published: January 2005

Both anatomical and physiological mapping methods have revealed that the mammalian cerebellar cortex consists of a family of parasagittal bands of cells, each band with its own pattern of afferent and efferent axons. Monoclonal antibody mabQ113 recognizes an unknown polypeptide antigen that is confined to a subset of rat cerebellar Purkinje cells. Immunoreactive cells are arranged into parasagittal bands extending throughout the vermis and hemispheres. Expression of the Q113 epitope by individual Purkinje cells may not be all‐or‐nothing, since the bands tend to be more strongly stained in the vermis than the hemispheres. The band display is symmetrical about the midline and reproducible from individual to individual. Wholemount immunocytochemistry and serial reconstruction reveal a median band of mabQ113+ Purkinje cells adjacent to the midline (P1 + ) and six other positive bands disposed symmetrically at either side (P2+ to P7 + ). Bands are distinct throughout most of the cortex but tend to fuse ventrally and caudally. There are two sources of interindividual differences. Firstly, most animals express supernumerary “satellite” bands in the vermis. Satellite bands are usually only one cell wide, are not bilaterally symmetrical, and differ in position and number from individual to individual. Secondly, the precise position of an individual band can differ, perhaps according to the variable cortical lobulation, for example, the position of P4+ in lobules VIII/IX and P6+ in lobule VII. While a scheme of parasagittal bands is a good description of the vermian organization, the distribution of mabQ113+ and mabQ113‐ Purkinje cells in the hemispheres may be better described as a checkerboard of antigenic patches.
Terminations of individual optic tract fibers in the lateral geniculate nuclei of Galago crassicaudatus and Tupaia belangeri
Authors: Conley Michael , Penny G. Richard , Diamond Irving T.
Published: January 2005

The morphology and laminar distribution of individual optic fibers projecting to the lateral geniculate nucleus (GL) of Galago and Tupaia were studied following iontophoretic injections of horseradish peroxidase (HRP) into the optic tract. In Galago the GL is composed of three functionally matched pairs of layers, each characterized by cells of a given size, one large, one medium‐sized, and one small. The results show that there is a close correspondence between the size of the afferent fibers and the size of the neurons in the target layer: large axons project to the magnocellular layers, medium‐sized axons project to the parvicellular layers, and small fibers project to the intercalated layers. In Tupaia the GL is composed of two functionally matched pairs and two unmatched layers. Optic fibers that project to the medial matched pair (1 and 2) are only slightly larger than those that project to the lateral matched pair (4 and 5), but both are larger than those that project to the unmatched layers (3 and 6).

In both species terminal arbors and the distribution of terminal boutons within layers corresponded closely with the organization of dendritic processes of cells in the target layer. This correspondence was particularly evident in the parvicellular layers in Galago and in layer 6 in Tupaia: parvicellular terminal arbors, like the dendrites of parvicellular cells, are organized in narrow columns oriented along lines of projection, whereas layer 6 terminal arbors, like the dendrites of layer 6 cells, are oriented in elongated strips perpendicular to lines of projection. In both species there was evidence for sublaminar terminations in some layers. These were restricted to the parvicellular layers in Galago and layers 4 and 5 in Tupaia.

With the exception of a small number of fine fibers in the intercalated layers in Galago, optic fibers in both species terminated in one and only one layer in a set. The significance of this result depends on the relation between ganglion cell classes and what is being segregated in different GL layers. Lateral geniculate lamination varies even in closely related species and has evolved independently in such distantly related lines as carnivores and primates. It is not surprising, therefore, that what is being segregated varies from species to species.
Serotonin storage and uptake by identified neurons in the leech Haementeria ghilianii
Authors: Glover Joel C.
Published: January 2005

Characterization of serotonin‐containing neurons in the glossiphoniid leech Haementeria ghilianii was undertaken to provide a reference for developmental studies of their differentiation and for comparative studies of their distribution and function. Five types of serotonin‐containing neurons were identified with an antiserum against serotonin and by radioenzymatic assay of individual isolated somata. They contain high concentrations of serotonin (in some cases exceeding saturation in aqueous solution) and their serotonin content increases with growth of the animal. Each type is capable of taking serotonin up from the extracellular fluid, as demonstrated autoradiographically. They exhibit segment‐specific, and on comparison with hirudinid leeches, species‐specific, differences in distribution, morphology, and the expression of serotonin metabolism.
Architecture and frontal cortical connections of the premotor cortex (area 6) in the rhesus monkey
Authors: Barbas H. , Pandya D. N.
Published: January 2005

The premotor cortex (area 6) has several architectonic sectors that can be delineated on the basis of cytoarchitectonic and myeloarchitectonic features. Area 6 may be broadly subdivided into a dorsal and a ventral sector at the spur of the arcuate sulcus. Dorsal 6 lacks a granular layer IV, but ventral 6 has an emergent layer IV that separates laminae III and V. Dorsal 6 has a higher myelin content than ventral 6. Dorsal area 6 is further subdivided into a caudal and a rostral sector on the basis of the presence of large pyramidal cells in the caudal but not in the rostral sector. The rostral sector of area 6 can be subdivided into a medial region distinguished from a more laterally situated area by the presence of more compact and darkly stained cells in layers III and V. Ventral area 6 can be subdivided into an upper and lower division. The upper part has more prominent pyramidal cells in layers III and V, and a better developed outer Baillarger band and vertical plexus than the lower division. The efferent and afferent connections of area 6 were studied with anterograde and retrograde tracers. The frontal connections of dorsal area 6 are restricted to neighboring dorsal frontal regions. Only the caudal sector of dorsal area 6 is connected with the motor cortex. In contrast, ventral area 6 is not only connected with the prefrontal cortex, but also directly with the motor cortex, the parainsular gustatory area, and with somatosensory areas in the frontal operculum. The widespread connections of ventral area 6 may be related to the specialization of the head, neck, and face structures that are represented ventrally within the premotor cortex.
Nerve growth factor (NGF) receptor expression in chicken cranial development
Authors: Raivich Gennadij , Zimmermann Astrid , Sutter Arne
Published: January 2005

In order to map the expression of receptors for nerve growth factor (NGF) during brain and cranial ganglia development, iodinated NGF (125IβNGF) was used as a probe in an autoradiographical analysis performed between embryonic day 3 (E3) and posthatching day 3 (P3) of chicken development. Heavy autoradiographic labelling was observed at the classical NGF target sites, the proximal cranial sensory ganglia and the sympathetic superior cervical ganglion, throughout development and after hatching. In contrast, only weak Labelling could be detected during a restricted time span in the vestibulocochlear (E4–E8) and the distal cranial sensory ganglia (E4–E10), the neurons of which originate from the otic and epibranchial placodes. Specific 125b̃3NGF binding was also observed in various brain regions during early brain development. NGF receptor expression there followed a characteristic pattern. The neuroepithelial layer displayed very low levels of specific 125Ib̃NGF binding, while strong 125Ib̃NGF labelling was found in the mantle layer. Brainstem somatomotor nuclei, visceromotor columns, brain‐stem alar plate, cerebellar anlage, tectum, and basal forebrain (epithalamus, striatum) were found to be transiently labelled by 125Ib̃NGF in early development (E4–E12). Non‐nervous tissues such as parts of the otic vesicle epithelium and skeletal muscle anlagen of the head were also labelled. These results, showing specific binding of 125Ib̃NGF to cranial cells of different origin (neural tube, neural crest, placode, and possibly mesoderm) strengthen the concept that NGF may have diverse functions in growth and differentiation of various tissues and cell types.
Plasticity of dendrodendritic microcircuits following mitral cell loss in the olfactory bulb of the murine mutant purkinje cell degeneration
Authors: Greek Charles A. , Halász Norbert
Published: January 2005

Mitral cells of the olfactory bulb typically form reciprocal dendrodendritic synapses with anaxonic interneurons, granule cells, within a sublamina of the external plexiform layer. As a result of mitral cell loss in the murine mutant Purkinjie cell degeneration (PCD), subpopulations of these granule cells are denervated. The present report examines the capacity of these denervated interneurons to form new dendrodendritic microcircuits with a second population of olfactory bulb neurons, tufted cells.

Quantitative ultrastructural assessments were made of the morphology and distribution of dendrodendritic circuits in the olfactory bulbs of normal heterozygous litter mates and affected homozygous recessive PCD mice following mitral cell loss. There were no apparent morphological characteristics that distinguished the reciprocal synaptic connections formed by mitral cells from those formed by tufted cells. However, the segregation of mitral cell dendrodendritic circuits in the deep sublamina of the external plexiform layer (EPL) and tufted cell circuits in the superficial sublamina provided the basis for a comparative analysis of synaptic organization following mitral cell loss. Following mitral cell loss there was a significant reduction in the area occupied by characteristic mitral cell dendrites within the deep sublamina of the EPL. A slight but nonsignificant increase in the area occupied by granule cell spines was also observed. The number of synaptic appositions involving granule cells decreased slightly, the number involving tufted cells increased significantly in the mutant mice. This indicates that many granule cell spines survive denervation and establish new reciprocal dendrodendritic synapses at available sites on tufted cells. In both the control and mutant mice the ratios of symmetrical: asymmetrical dendrodendritic synapses closely approached 1. This demonstrates that not only do the denervated spines receive new afferent input from tufted cell dendrites, but they also establish the reciprocal efferent projection. These data are discussed in terms of the sublaminar organization of dendrodendritic microcircuits in the olfactory bulb and their capacity of plasticity and reorganization following pertubation.
Development of the spinal nerves in the lamprey: I. Rohon‐beard cells and interneurons
Authors: Nakao Taisuke , Ishizawa Akimitsu
Published: January 2005

Two types of large neurons are described in the caudal one‐third of the spinal cord of larval lampreys (26‐day, 13‐mm), Lampetra japonica.

Rohon‐Beard cells (RB cells) are large neurons (8–14 m̈m in diameter) consistently positioned superficially in the dorsolateral part of the medullary wall and separated from the extramedullary space only by a basal lamina and a thin glia limitans and from the central canal lumen by the ependyma. The RB cell contains an extensive Golgi apparatus and granular endoplasmic reticulum. Its two processes arise from the basal part of the perikaryon and join the dorsolateral tract (DLT) to extend rostrally and caudally within the DLT, which is formed exclusively by contribution of RB cell processes at least in the caudal one‐third of the tail spinal cord. RB cells receive no synaptic nerve endings on their surfaces. The early developing RB cell exhibits an apical process that reaches the luminal surface of the central canal.

Interneurons (15–19 m̈m in diameter) lie in the lateral region of the cord between the DLT and ependyma and receive from the DLT many synaptic nerve endings that contain aggregates of small, clear vesicles. They contribute axonal processes to the ventrolateral tract (VLT). Some developing interneurons have an apical process that contains abundant free ribosomes and granular ER.

A presumptive model of how these cell classes are interconnected within the cord is presented.
The morphology of a population of thoracic intersegmental interneurones in the locust
Authors: Laurent Gilles
Published: January 2005

A population of intersegmental interneurones with axons extending from the meso‐ to the metathoracic ganglion of the locust is described. They receive specific mechanosensory inputs from one mesothoracic leg. Their cell bodies are in group at the posterior of the mesothoracic ganglion, lying over the lateral base of each connective, and their primary neurites emerge in one of four bundles. Their mesothoracic branches are ipsilateral to the cell bodies and the leg from which they receive inputs. Each interneurone has two to six mesothoracic secondary neurites that divide and form a dense field of arborizations in specific regions of the neuropil so that each individual interneurone has a characteristic shape that is an elaboration of a basic and common plan.

An interneurone excited by tibial campaniform sensilla and tarsal hair afferents branches in the intermediate neuropil and the ventral association center where the afferents from these receptors also project. An interneurone excited by proprioceptive inputs from the tarsus arborizes in the dorsal and intermediate neuropils, lateral to the ventral intermediate and ventral median tracts, in the same area as the proprioceptors afferents. An interneurone inhibited by proprioceptive inputs from the tibia (and wing) arborizes only in the dorsal neuropil, where there are no afferent projections.

Some interneurones have one to three axonal branches with sparse and varicose side branches in the mesothoracic ganglion, which resemble the metathoracic axonal branches.

The metathoracic axonal branches are mostly restricted to the dorsal neuropil and the dorsal part of the intermediate neuropil where local non‐spiking interneurones and motor neurones controlling movements of the hind leg also project.

The overlap between the branches of the sensory afferents and the intersegmental interneurones in the mesothoracic ganglion and between those of the nonspiking local interneurones or motor neurones and intersegmental interneurones in the metathoracic ganglion suggest that these interneurones are responsible for transferring information about the action of one leg to an adjacent leg.
Transmitter localization and vesicle turnover at a serotoninergic synapse between identified leech neurons in culture
Authors: Kuffler Damien P. , Nicholls John , Drapeau Pierre
Published: January 2005

An electron microscopic study has been made of chemical synapses that develop between identified nerve cells isolated from the CNS of the leech and maintained in culture. Structures resembling synapses were observed in pairs of Retzius cells and P sensory cells at which chemical transmission had been demonstrated by recording with microelectrodes. Vesicle recycling was shown by following the uptake of extracellular markers after stimulation.

The membrane separation between the presynaptic Retzius cell (which is known to liberate serotonin) and the postsynaptic P cell was wider in synaptic than in extrasynaptic regions. The Retzius cell contained clusters of clear vesicles apposed to thickenings of the presynaptic membrane. These clear vesicle clusters were capped by a layer of dense core vesicles that did not contact the presynaptic membrane thickenings. Subsynaptic cisternae were found in the postsynaptic cell opposite the presynaptic membrane thickenings. Occasional slight postsynaptic membrane thickenings were seen. Extracellular material was observed within the synaptic cleft.

Similar synaptic structures developed between pairs of Retzius cells in culture; even a single Retzius cell was able to form autapses upon itself.

Structures resembling transmitter release sites were found in Retzius cells at a distance from any postsynaptic membranes. These are presumed to be locations for the diffuse release of transmitter.

Presynaptic structures resembling release sites were never observed in P cells apposed to Retzius cells.

Antibody to serotonin (5‐HT) labelled with colloidal gold showed serotonin to be localized in the dense core vesicles in Retzius cells.

Stimulation of pairs of Retzius and P cells by raised concentrations of K+ resulted in uptake of extracellular markers. Only Retzius cells became labelled. Ferritin was found in cisternae, in dense core vesicles, and in clear vesicles. HRP was found in cisternae and in clear vesicles. Colloidal gold was taken up by coated vesicles and was occasionally found in both clear and dense core vesicles. The uptake of extracellular markers following stimulation was blocked by high Mg ++.

These results show that structures develop between pairs of cells at which chemical transmission develops and that transmitter release leads to turnover of dense core and clear vesicles.