bluuebunny/crossref_metadata_2025 huggingface dataset:
Dopaminergic neurons in the human retina
Authors: Frederick Jeanne M. , Rayborn Mary E. , Laties Alan M. , Lam Dominic M. K. , Hollyfield Joe G.
Published: January 2005

The utilization of dopamine in the adult human retina was examined by using high‐affinity uptake, localization, synthesis, and release as neurotransmitter‐specific physiological probes. Autoradiographic and histochemical studies have shown that dopamine‐accumulating and dopamine‐containing cells of the human retina belong to a population of neurons whose somata are located in the proximal regions of the inner nuclear layer. Some of these are amacrine cells which are pre‐and postsynaptic to other amacrine cells exclusively in the inner plexiform layer. However, evidence is presented which indicates the existence of interplexiform dopaminergic neurons which send processes to both plexiform layers of the retina. These neurons contain a high concentration of dopamine, take up 3H‐dopamine by a high‐affinity mechanism, and release endogenous or accumulated dopamine by a Ca2+‐dependent mechanism upon depolarization with high extracellular K+. An endogenous level of about 20 pmoles dopamine per mg protein was measured in freshly isolated retina using high‐pressure liquid chromatography with electrochemical detection. These results demonstrate that mechanisms for dopaminergic neurotransmission are present in the human retina.
Organization and development of brain stem auditory nuclei in the chick: Ontogeny of postsynaptic responses
Authors: Jackson Hunter , Hackett John T. , Rubel Edwin W.
Published: January 2005

The onset of responsiveness to eighth nerve stimulation was examined in n. magnocellularis and n. laminaris, (second‐ and third‐order neurons) of the chick brainstem auditory system. Extracellular microelectrode mapping techniques were used to examine postsynaptic responses in in vitro brainstem preparations. Two specific questions were addressed. First, what is the earliest time at which postsynaptic action potentials can be evoked in n. magnocellularis and n. laminaris by eighth nerve stimulation? Second, does responsiveness to eighth nerve stimulation develop along a spatial gradient in n. magnocellularis and, if so, how does this gradient compare with other developmental events observed in the chick auditory system?

Postsynaptic responses in n. magnocellularis were first recorded at 11 days of incubation. Nucleus laminaris responses to direct stimulation of n. magnocellularis were also first recorded at 11 days, although n. laminaris responses to eighth nerve stimulation were not seen until 12 days of incubation.

A gradient of response development within n. magnocellularis was indicated by mapping of responsive sites on days 11–13. At 11 days, responses to eighth nerve stimulation were restricted to the most anteromedial portion of n. magnocellularis. Between 11 and 13 days, cells in increasingly more posterolateral portions of n. magnocellularis became responsive. This is anteromedial‐to‐posterolateral gradient in n. magnocellularis is correlated with the basal‐to‐apical gradient of morphogenesis observed in the basilar papilla and morphogenetic gradients previously observed in n. magnocellularis and n. laminaris.
Projections of the dorsal lateral geniculate and lateral posterior nuclei to visual cortex in the rabbit
Authors: Towns Lex C. , Burton S. L. , Kimberly C. J. , Fetterman M. R.
Published: January 2005

The origin and terminations of thalamic inputs to the striate cortex and the occipital cortex of the rabbit were studied using both anterograde autoradiographic techniques and retrograde transport of horseradish peroxidase (HRP). After injections of [3H]‐leucine into the dorsal lateral geniculate nucleus (DLGN) the transport of radiolabeled material was demonstrated in separate loci in both the striate and the occipital cortex. In both these cortical areas, the principal site of geniculocortical termination was in lamina IV with some diminished input spreading into laminae II‐III and a light termination in layer I overlying the lamina IV termination. Layer VI of striate cortex received a substantial projection from DLGN while infragranular laminae of occipital cortex received a similar although lighter and more diffuse projection. The lateral posterior nucleus (LPN) was similarly demonstrated to project to both striate and occipital cortices, the projection terminating principally in lamina IV of occipital cortex, lamina V of striate cortex, and layer I over a large, continuous area of the posterior pole of the cortex. Moreover, a projection from LPN to the retrosplenial cortex medial to the striate area was consistently seen.

The autoradiographic demonstration of a projection from DLGN and LPN to both striate cortex and occipital cortex was corroborated by the retrograde studies. Following the injection of HRP into either the striate or occipital cortex, columns of retrogradely filled somata were identified in both the DLGN and LPN. The location of the column of labeled neurons within each nucleus varied predictably with the location of the injection in either the striate or the occipital cortex.
The morphology of corticofugal axons to the dorsal lateral geniculate nucleus in the cat
Authors: Robson J. A.
Published: January 2005

The structural features of corticogeniculate axons were studied in adult cats after labeling them with horseradish peroxidase (HRP). Injections of HRP into the optic radiations near the dorsal lateral geniculate nucleus result in Golgi‐like filling of both geniculate relay neurons and corticogeniculate axons. In the present material at least two main types of axons could be defined. The most common type is called the type I axon because it so closely resembles the type I axons described by Guillery (1966, 1967) in Golgi preparations. These fine axons have smooth surfaces and consistent fiber diameter. Most terminal swellings are at the ends of short collateral branches and these swellings form asymmetric synaptic contacts onto small and medium‐sized dendrites. Type I axons typically innervate more than one lamina as well as interlaminar zones and they clearly arise from the cerebral cortex. The second type of axon is called the beaded axon because of its numerous swellings, en passant. These swellings frequently are larger than those on type I axons and they differ from previously described corticogeniculate axon terminals in their ultrastructural features. That is, their synaptic contacts appear symmetrical and they form axosomatic contacts. Because of these differences, the possibility that beaded axons are of subcortical origin, particularly from the perigeniculate nucleus, is discussed.

When type I axons and geniculate relay neurons are filled in the same region of the nucleus it is possible to identify probable sites of synaptic contactby using the light microscope. Such analyses indicate thatcorticogenic‐ulate axons synapse directly onto relay cells, primarily on peripheral dendritic branches. Further, it appears that single axons contact many geniculate neurons and that single neurons are contacted by many axons.
Extrinsic and intrinsic fiber connections of the telencephalon in a teleost, Sebastiscus marmoratus
Authors: Murakami Takeshi , Morita Yasuhiro , Ito Hironobu
Published: January 2005

Extrinsic and intrinsic fiber connections of the telencephalic subdivisions of Nieuwenhuys (1962) in a teleost, Sebastiscus marmoratus, were studied by means of horseradish peroxidase (HRP) and Fink‐Heimer methods

The olfactory bulb projects bilaterally to area dorsalis pars posterior, area ventralis pars ventralis, pars lateralis, pars posterior, pars intermedia, and the nucleus posterior tuberis of Peter et al. (1975) and receives fibers from ipsilateral area dorsalis pars centralis, pars posterior, area ventralis pars dorsalis, and pars supracommissuralis. Area dorsalis pars posterior sends numerous fibers to the ipsilateral ventral region of area dorsalis pars medialis, from which fibers of the medial forebrain bundle arise and terminate in the inferior lobe and nucleus posterior tuberis

Area dorsalis pars lateralis, pars dorsalis, and the dorsal region of pars medialis are the main targets of extratelencephalic ascending afferents. Area dorsalis pars lateralis receives fibers from the ipsilateral nucleus pre‐thalamicus of Meacler (1934), where tectal projections terminate massively. Area dorsalis pars dorsalis and the dorsal region of pars medialis receive afferents from the ipsilateral nucleus prcglomerulosus of Schnitzlein (1962), nucleus posterior tuberis, area preoptica pars medialis of Crosby and Showers (1969), and nucleus entopeduncularis of Sheldon (1912). Raphe nuclei and locus ceruleus project bilaterally to area dorsalis pars centralis, pars dorsalis, pars lateralis, and the dorsal region of pars medialis. Area dorsalis pars centralis, pars dorsalis, and the dorsal region of pars medialis are important sources of extrateiencephalic efferents. These subdivisions give rise to the lateral forebrain bundle and project to the ipsilateral nucleus prethalamicus, nucleus pregiomerulosus, inferior lobe, nucleus paracommissuralis of Ito et al. (1982), optic tectum, torus semicircularis, and the bilateral mesencephalic tegmentum

Within the telencephalon, most of the ventral subdivisions project to ipsilateral area dorsalis pars centralis, pars dorsalis, pars lateralis, and the dorsal region of pars medialis. Area dorsalis pars centralis has reciprocal connections with ipsilateral area dorsalis pars lateralis, pars dorsalis, pars posterior, and the dorsal region of pars medialis. A dorsal part of the anterior commissure is composed of axons of the ventral region of area dorsalis pars medialis destined to the contralateral ventral region of area dorsalis pars medialis. A ventral part of the anterior commissure contains axons of area dorsalis pars centralis destined to contralateral area dorsalis pars lateralis.
Comparative cytoarchitectonic study of gudden's tegmental nuclei in some mammals
Authors: Hayakawa Tetsu , Zyo Katuya
Published: January 2005

The structure and location of the dorsal and ventral tegmental nuclei of Gudden were studied in brains of 12 species of mammals. The ventral teg‐mental nucleus of Gudden is composed of oval or polygonal, medium‐sized, well‐stained cells, and includes the pars principalis situated ventral to the fasciculus longitudinalis medialis, and the pars suprafascicularis in the cen‐tral gray matter dorsal to the fasciculus longitudinalis medialis (in the golden hamster, mouse, vole, and house shrew).

The dorsal tegmental nucleus of Gudden is situated within the central gray matter. This nucleus includes the pars ventralis, composed of oval or triangular cells, medium‐sized but smaller than those of the ventral tegmen‐tal nucleus of Gudden, and the pars dorsalis, composed of round, small, and lightly stained cells, and often encapsulated by fibers of the fasciculus longi‐tudinalis dorsalis.

The isthmus between the dorsal and ventral tegmental nuclei of Gudden is distinct. In the cat, dog, rat, gerbil, and rabbit, the isthmus stands at the dorsal edge of the fasciculus longitudinalis medialis; in the golden hamster, mouse, vole, and house shrew, within the central gray matter; and in the guinea pig, at the ventral edge of the fasciculus longitudinalis medialis. In the green monkey and man, we could not find a ventral tegmental nucleus of Gudden, and in the house shrew and man, the pars ventralis and pars dor‐salis of the dorsal tegmental nucleus of Gudden could not be separated.
The laminar distribution of intracortical fibers originating in the olfactory cortex of the rat
Authors: Luskin Marla B. , Price Josephl.
Published: January 2005

In this study, the autoradiographic method for tracing axonal connections was used to identify the laminar distribution of intracortical fibers originating in the olfactory cortical areas of the rat. Most of the projections can be divided into two major fiber systems with different laminar patterns of termination. The first of these, termed the layer Ib fiber system, arises in the anterior olfactory nucleus, the anterior and posterior piriform cortex, and the lateral entorhinal cortex, and terminates predominantly in layer Ib and, in many cases, layer III of the entire olfactory cortex. The second system, termed the layer II‐deep Ib fiber system, originates in three relatively small olfactory cortical areas‐the dorsal peduncular cortex, the ventral tenia tecta, and the periamygdaloid cortex and terminates in and around the cells of layer II in most parts of the olfactory cortex. There is significant overlap in the laminar distribution of the two systems, although the distinction between them is readily apparent.

Within the layer Ib fiber system there are relatively slight but consistent differences in the lamination of fibers from different areas. The fibers from the anterior olfactory nucleus are concentrated in the deep part of layer Ib while those from the anterior piriform cortex are concentrated in the superficial part of this layer. The fibers from the posterior piriform cortex tend to be densest in the middle of layer Ib. These differences are maintained in all areas of termination of each set of fibers, both ipsilaterally and contra‐laterally.

In addition, intracortical fibers from the anterior cortical nucleus of the amygdala are distributed throughout layer I, including layer la and Ib. Fibers from the nucleus of the lateral olfactory tract terminate bilaterally around the cells of the islands of Callej a and the medial edge of the anterior piriform cortex.
Fine structure of nigral and pallidal afferents in the thalamus: An em autoradiography study in the cat
Authors: Kultas‐ilinsky K. , Ilinsky I. , Warton S. , Smith K. R.
Published: January 2005

Ultrastructural characteristics and distribution of nigral and pallidal axon terminals on thalamic neurons were studied after injections of tritiated leucine into substantia nigra and entopeduncular nucleus respectively.

Adult cats received 0.1–0.2‐μl injections of 2, 3, 4, 5, 3H‐leucine in a concentration 60 μCi/μl and were allowed to survive for 4–5 days. The brain tissue was processed for electron (EM) and light microscopic (LM) autoradiography. EM samples were obtained from the ventral medial and ventral anterior thalamic nuclei. Ultrastructural features of labelled nigral and pallidal boutons were analyzed both qualitatively and quantitatively.

Ultrastructural characteristics of nigral and pallidal boutons appeared similar. Their length along postsynaptic membrane ranged from 0.8 to 10 μm, with average length of apposition around 2 μm. Both types of bouton contained small clear vesicles of extremely variable shape and formed symmetrical type contacts. Mean diameter of synaptic vesicles profiles (n = 500) was 32.5 nm and 33.3 nm in nigral and pallidal terminal respectively, and mean vesicle profile areas were 846 nm2 in nigral terminals and 878m2 in pallidal. Both parameters showed normal distribution in percentage distribution histograms. The mean ratios of longest and shortest diameters was 1.6 for synaptic vesicles in both types of boutons.

Thus, no significant differences in morphological parameters of nigral and pallidal axon terminals were discovered except that pallidal afferents often formed “en passant”‐type synapses while nigral did not. However, this feature alone is not sufficient for distinction between the two types of termi‐nals in unlabelled tissue.

Analysis of distribution of synaptic sites showed that only pallidal bou‐tons formed axosomatic synapses on thalamocortical projection neurons (TCPN), which comprised 21% of total number of pallidal terminals studied. On primary dendritic trunks of TCPN the proportion of nigral boutons was larger (28.8%) as compared to pallidal (19%). The percentage of both types of bouton contacting secondary TCPN dendrites was similar (36% pallidal, 30.6% nigral), while the proportion of nigral terminals on tertiary TCPN den‐drites was larger (23.6% versus 13%). Both afferents revealed a tendency to synapse preferentially at the branching points of TCPN dendrites with sev‐eral boutons often found along the perimeter of the branching site. Small but equal proportions (8%) of both types of axon terminal were found to synapse on vesicle‐containing dendrites of local circuit neurons. Nigral boutons were also found in complex synaptic arrangements in glomeruli.

It is concluded that the organizations of pallidal and nigral afferent in‐puts in the thalamus are rather similar. Both occupy strategic positions which would allow them to exert strong influence on the firing pattern of TCPN.
Differentiation of fly visual interneurons after laser ablation of their central targets early in development
Authors: Näaassel Dick R. , Geiger Gad , Seyan Harjit S.
Published: January 2005

To test the differentiation of visual interneurons that had their targets removed before axogenesis, we ablated neuronal precursors in brains of first instar fly larvae by using a laser microsurgery unit. We describe ablations that resulted in the elimination of the third neuropil region (the lobula complex) of the optic lobes. Neural differentiation in the more peripheral second and first neuropil regions (the medulla and the lamina) was thus studied in the absence of the lobula complex.

It was found that the medulla neuropil differentiated with normal columnar and layered organization. The neuropil, however, folded along its central surface. The only connection between the medulla and more central neuropil (the midbrain) was via a bundle of axons (the Cuccati bundle) present also in the normal optic lobes. Some types of neurons that normally connect the medulla and the lobula complex could be identified. These appeared to end in a disorganized neuropil mass in the center of the folded medulla.

The differentiation of the lamina neuropil also appeared normal in flies with the lobula complex eliminated and the medulla folded. Also, in optic lobes where the medulla was severely disorganized and/or reduced due to laser ablations, the lamina neuropil appeared more or less normal.

The results suggest that lamina and medulla nerve cells can differentiate and develop normal neuropil patterns in absence of their appropriate targets.
The cerebeillopontine system in the rat. II. Electron microscopic studies
Authors: Watt Carl B. , Mihailoff Gregory A.
Published: January 2005

Cerebellopontine axonal boutons in the neuropil of the basilar pontine nuclei (BPN) were marked for ultrastructural identification by producing unilateral electrolytic lesions of the superior cerebellar peduncle (SCP) as it exited from the cerebellum and before its decussation in the caudal midbrain. Three varieties of degenerating boutons were distinguished on the basis of size, type of degeneration, and postsynaptic locus. A relatively large variety of bouton (2.5–6.0 μm) that exhibited filamentous degeneration throughout the range of survival times employed (1–14 days) was the most frequently observed type of degenerating Cerebellopontine bouton. Such boutons formed synaptic contacts with several small, dendritic, spinelike profiles as well as the shafts of intermediate or proximal dendrites. A second, far less numerous and somewhat smaller type of bouton (1.5–4.5 μm) was distinguished by the fact that it exhibited advanced dark degenerative changes after a 2‐day survival period, formed multiple spine contacts (but not shafts), and was no longer apparent in the neuropil after a postlesion survival time of 6 days. The third variety of degenerating bouton was small (0.8–2.0 μm), exhibited dark degeneration with a 2–6‐day survival period, contacted primarily shafts of small‐diameter dendrites, and was observed more frequently than the larger dark boutons but less often than the large filamentous boutons. All three types of degenerating boutons contained round, clear, synaptic vesicles and formed only asymmetric synaptic active sites. It is suggested that the three types of degenerating axon terminals arise from at least three varieties of neurons in the deep cerebellar nuclei. Further it is suggested that such boutons originate from cerebellar efferent axons which distribute in collateral fashion to the thalamus, red nucleus, and/or the inferior olive.
Motor neuron columns in the lumbar spinal cord of the rat
Authors: Nicolopoulos‐Stournaras Stavroula , Iles John F.
Published: January 2005

The location in the rat spinal cord of motor neurons innervating 23 muscles or muscle groups of the hind limb has been determined by using retrograde transport of horseradish peroxidase. The motor neurons supplying a single muscle form a discrete longitudinal column in the lateral ventral horn. The columns extend through up to three adjacent spinal segments and their longitudinal location varies by as much as one segment in different animals. The relative positions of the columns supplying different muscles and their transverse location in the spinal cord are very consistent between individuals and a stereotaxic map has been constructed. This is briefly compared with descriptions from other species. Counts of the numbers of motor axons in seven different muscle nerves have been made with the aid of acetylcholin‐esterase histochemistry to identify the motor component. The numbers of motor neuron somata labelled with horseradish peroxidase are on average 70% of the axon counts.
Retrograde and anterograde‐transneuronal degeneration in the parabigeminal nucleus following tectal lesions in developing rats
Authors: Linden Rafael , Perry V. Hugh
Published: January 2005

Degenerative effects in the parabigeminal nucleus were studied in adult rats that had received lesions of the superior colliculus at different postnatal ages. Unilateral lesions lead to complete degeneration of the dorsal and ventral divisions of the parabigeminal nucleus, which connect reciprocally with the damaged tecturn, and produce effects on the middle division which receives afferents from the ipsilateral and projects to the contralateral tectum. On the side contralateral to the lesion there was a reduction in the cross‐sectional area of the division as a consequence of retrograde degeneration, except in rats operated on at birth or when adults; ipsilateral to the lesion there was a reduction in the cross‐sectional area of the division as a result of anterograde‐transneuronal degeneration, except in animals operated on when adults. The reduction in cross‐sectional area is partly due to a decrease in the number of neurones in the middle division. The maximal effects in both cases occurred in animals operated on at 10 days after birth, and the sensitivity to retrograde degeneration follows a U‐shaped curve. Bilateral tectal lesions performed at birth or 5 days after birth produce virtually complete degeneration of the whole parabigeminal nuclei. Anterograde radio‐autographic tracing showed that all parabigeminal divisions receive topographically organized projections from the ipsilateral superior colliculus. Ipsilateral projections from the dorsal and ventral divisions and crossed projections from the middle division were identified in the tectum of newborn rats with fluorescent retrograde tracers. Possible explanations for the cases in which tectal lesions failed to produce an effect on the architecture of the middle division include increased resistance to axonal damage and regulative processes over natural neuronal death. The results also indicate that the two forms of degeneration are additive with regard to the whole population of developing parabigeminal neurones.
The organization of the fibers in the optic nerve of normal and tectum‐less Rana pipiens
Authors: Reh Thomas A. , Pitts Eleanor , Constantine‐Paton Martha
Published: January 2005

We have examined the detailed order of retinal ganglion cell (RGC) axons in the optic nerve and tract of the frog, Ranapipiens. By using horseradish peroxidase (HRP) injections into small regions of theretina, the tectum, and at various points along the visual pathway, it hasbeen possible to follow labelled fibers throughout their course in the nerve and tract.

Several surprising features in the order of fibers in the visual pathway were discovered in our investigation. The fascicular pattern of RGC axons in che retina is similar to that described in other vertebrates; however, immediately central to their entry into the optic nerve head, approximately half of the fibers from the nasal or temporal retina cross over to the opposite side of the nerve. Although the axons from the dorsal and ventral regions of the retina generally remain in the dorsal and ventral regions of the nerve, some fiber crossing occurs in those axons as well. The result of this seemingly complex rearrangement is that the optic nerve of Rana pipiens contains mirror symmetric representations of the retinal surface on either side of the dorsal ventral midline of the nerve. The fibers in each of these representation are arranged as semicircles representing the full circumference of the retina. This precise fiber order is preserved in the nerve until immediately periphearal to the optic chiasm, at which point age‐related axon from both side of the nerve bundle together. Consequently, when a small pellet of HRP is placed in the chiasmic region of the nerve, an annualus of retinal ganglion cells and a corresponding annulus of RGC terminals in the tectum are la belled. As the age‐related bundles of fibers emerge from the chiasm they split to form a medial bundle and a lateral bundle, which grow in the medial and lateral branches of the optic tract, respectively. Although the course followed by RGC axons in the visual pathv/ay is complex, we propose a model in which the organization of fibers in the nerve and tract can arise from a few rules of axon guidance.

To determine whether the optic tecta, the primary retinal targets, play a role in the development and organization of the optic nerve and tract, we removed the tectal primordia in Rana embryos and examined the order in the nerve when the animals had reached larval stages. We found that the order in the nerve and tract was well preserved in tectumless frogs. Therefore, we propose that guidance factors independent of the target direct axon growth in the frog visual system.
Fast and slow motoneurons with unique forms and activity patterns in lobster claws
Authors: Hill R. H. , Govind C. K.
Published: January 2005

The form of the fast closer excitor (FCE) and the slow closer excitor (SCE) motoneurons to the closer muscle in the claw of the lobster Homarus americanus was determined by injecting cobalt chloride or Lucifer Yellow into their respective somata. Both neurons are monopolar with the single neurite rising vertically to the dorsal surface of the ganglion, then travelling along this surface to where it gives offits dendrites before entering the second nerve root as an axon. The FCE and SCE motoneurons, however, differ in their dendritic form in several respects. First, the FCE completely lacks an anterior dendritic field, which is well elaborated in the SCE. Second, the FCE has fewer large primary dendrites in its posterior field than the SCE. Third, the posterior dendritic field of the FCE is not as extensive as that of the SCE. Fourch, the axon of the FCE originates from one of the posterior primary dendrites while that of the SCE is an axial extension of its neurite. Thus the SCE has a more elaborate dendritic field than the FCE, which may account for its greater excitability. For instance, recordings from intact lobsters show that the SCE has a lower firing threshold and is active for longer periods of time and at higher frequencies than the FCE.
Antennal neuropile in the brain of the crayfish: Morphology of neurons
Authors: Tautz Jürgen , Muller‐Tautz Rosemarie
Published: January 2005

The cellular composition of the antennal neuropile of the crayfish is described. As a context for this work the distribution of neuronal cell bodies throughout the supraoesophageal ganglion (brain) is also described. The neuronal cell bodies in the brain are concentrated in 19 distinct clusters Three paired clusters are located on the dorsal side of the brain, four paired and one midline cluster bend around the brain laterally and frontally respectively. Fewer than ten somata lie outside of these clusters. The antennal neuropile is composed of primary afferent terminals, efferents, and projecting and local interneurons. The structures of individual neurons of all four types were determined by filling them with Lucifer yellow, and an overview of the neuropile structure was obtained with cobalt backfills of selected nerves The antennal afferents are concentrated in four main tracts that run medially in the outer layer of the antennal neuropile. Up to 11 orthogonal side branches occur at equal distances (25–35 μm) along the main branches and penetrate the neuropile. The efferents contribute very thin dendrites to the antennal neuropile. The majority of the neuronal mass of the antennal lobe consists of projecting and local interneurons. The branching pattern of the interneurons within the antennal neuropile also shows an orthogonal arrangement of main branches and higher‐order branches. Thus the antennal neuropile displays a strong geometrical regularity: Main processes of all four types of neurons run in bundles the length of the long axis of the neuropile (lateral to medial inside the brain) giving rise to orthogonal side branches at regular intervals. This branching pattern leads to a striped appearance of the antennal lobe.
Spatial‐Temporal progress of peripheral nerve regeneration within a silicone chamber: Parameters for a bioassay
Authors: Williams Lawrence R. , Longo Frank M. , Powell Henry C. , Lundborg Göran , Varon Silvio
Published: January 2005

The spatial‐temporal progress of peripheral nerve regeneration across a 10‐mmgap within a silicone chamber was examined with the light and electron microscope at 2‐mm intervals. A coaxial, fibrin matrix was observed at 1 week with a proximal‐distal narrowing that extended beyond the midpoint of the chamber. At 2 weeks, Schwann cells, fibroblasts, and endothelial cells had migrated into the matrix from both nerve stumps. There was a delay of 7–14 days after nerve transection and chamber implantation before regenerating axons appeared in the chamber. At 2 weeks, nonmyelinated axons were seen only in the proximal 1–5 mm of the chamber in association with Schwann cells. Axons reached the distal stump by 3 weeks and a proximal‐distal gradient of myelination was observed. These observations define the parameters of a morphologic assay for regeneration in this chamber model which can be used to investigate cellular and molecular mechanisms underlying the success of peripheral nerve regeneration.
The embryonic development of the inferior olivary complex in normal and reeler (rlORL) mutant mice
Authors: Goffinet A. M.
Published: January 2005

The development of the inferior olivary complex has been studied comparatively in normal and reeler mutant mice, from embryonic day 14 to birth. In both genotypes, cells migrate tangentially, from the lateral recess of the fourth ventricle, until they reach the ventral rhombencephalon where they enter the olive radially. Some cells also enter the olive laterally, from its external side. In both genotypes, olivary neurons differentiate following the same morphological sequence, both in terms of dendritic deployment and of axonal growth. Olivofugal axons cross the midline as early as E14. Synapses are rare in the inferior olivary complex during the prenatal period. Radial glial cells and the first stages of astrocytogenesis appear similar in both genotypes.

The process of olivary maturation begins at E15. In normal embryos, this occurs concurrently with a subdivision of the olivary complex, clearly defined at birth: the principal olive (PO) is “U” shaped and located between the medial accessory olive (MAO) and the dorsal accessory olive (DAO). In reeler mutants, there are abnormalities in the configuration of the inferior olivary complex. Even the earliest lobulated contours are anomalous. The ultimate configuration, though containing the principal elements of the normal complex, is blunted, compact, and very much less “calligraphic” in its undulation than in the normal animal. The reeler dysplasia is mild at E15 and becomes increasingly evident at later developmental stages.

These observations show that the reeler gene primarily affects the position of neuronal cells relative to other cellular elements and to fiber strata, while leaving relatively intact the phenomena of cell migration and differentiation. Afferent fibers from spinal and midbrain origin are probably involved in the division of the olivary complex into its components (Martin et al., '80). In addition, the development of the cerebellar cortex could influence the morphogenesis of the olivary nuclei. However, the architectonic malformation of the reeler inferior olive can hardly be exclusively attributed to perturbations of its hodological relationships. It is proposed that the abnormal development of the inferior olive in reeler mutants is largely dependent on a local, intrinsic action of the mutant gene on the olivary primordium.
The growth of neurites from explants of brachial spinal cord exposed to different components of wing bud mesenchyme
Authors: Nurcombe V. , Bennett M. R.
Published: January 2005

The extension of peripheral axons from the brachial spinal cord into the embryonic chick wing bud suggests that the target premuscle cell masses may act as the source of an adhesion gradient which establishes selective nerve pathways. Wing premuscle cell masses were explanted from different stage embryos and tested against age‐matched brachial spinal cord for their ability to promote directional neurite outgrowth. It was found that target premuscle which does not contain myotubes could still elicit directional outgrowth in vitro. In contrast, skin and precartilage were unable to promote neuritic outgrowth significantly. Serum‐free conditioned media were prepared from stages 20‐38 premuscle and tested against age‐matched spinal cord explants. There was an increase in the effects of conditioned media on neuritic outgrowth up to stage 35; conditioned media from older‐stage pre‐ muscles had less effect than that of stage 35 premuscles. These results were shown to be dependent on the maturation of the premuscles and not on that of the spinal cord. When the premuscle conditioned media were preincubated over polylysine substrata, the ability to induce neuritic outgrowth was abolished from media derived from premuscle at stage 27 and older. Conditioned media derived from premuscle at stage 27 or older contain a polylysine‐binding neurite‐promoting factor which is present in greater amounts in more differentiated muscle. The time of first detection of neurite‐ promoting factors in stage 27 premuscle conditioned media correlates with the in vivo stages at which muscle‐specific nerves branch from the main nerve trunks.
Characterization and quantification of peptidergic amacrine cells in the turtle retina: Enkephalin, neurotensin, and glucagon
Authors: Eldred William D. , Karten Harvey J.
Published: January 2005

Immunocytochemical methods were used for selective labeling and characterization of amacrine cells of the turtle (Pseudemys scripta elegans) retina which contained neuropeptide‐like immunoreactivity (leu‐enkephalin, glucagon, and neurotensin). Processes of amacrine cells arborized in specific strata of the inner plexiform layer (IPL). Different strata were defined in relation to the boundaries of the IPL. Zero represented the strata nearest the inner nuclear layer and 100 represented the strata nearest the ganglion cells.

Antisera directed against leu‐enkephalin labeled approximately 7,300 amacrine cells in a single turtle retina which were concentrated in the region of the visual streak and decreased in density toward the periphery. In retinal regions outside the visual streak the labeled neurons were similar in size and shape with dendritic arbors which lacked a particular orientation. In contrast, in the visual streak, there were particular neurons which were labeled with enkephalin antiserum which had elongated dendritic arbors that ran parallel to the streak. Both types of amacrine cells with enkephalinergic immunoreactivity sent their dendrites into the 0–20 region and the 65–100 region of the IPL.

Antisera directed against glucagon labeled approximately 2,500 amacrine cells in a single turtle retina. These cells were concentrated in areas near the visual streak. Amacrine cells labeled with glucagon antiserum had dendritic arbors which were asymmetrically skewed toward one end of the cell and ramified in the 0–20 strata with sparse projections at the 40 and 80 strata of the IPL.

Antisera directed against neurotensin labeled 12,800 amacrine cells in a single turtle retina These cells were concentrated in the region of the visual streak. Two distinct amacrine cell types were labeled selectively. One type had a large, vertically oriented cell body (10 × 14 μm) which gave rise to a single 2‐μm‐thick process that branched and ramified within the 45–70 strata. The other amacrine cell type with neurotensin‐like immunoreactivity had a smaller cell body (8 μm) that sent numerous thin dendrites into the same 45–70 strata.

The present results indicated that various neuropeptides were present in amacrine cells of the turtle retina and that a specific neuropeptide could be found in more than one anatomical type of amacrine cell. Each anatomical type of amacrine cell had a unique dendritic arborization which ramified within particular strata within the IPL.
A stereotaxic atlas of the brain of the cynomolgus monkey (Macaca fascicularis)
Authors: Szabo J. , Cowan W. M.
Published: January 2005

Outline drawings of representative frontal sections of the Macaca fascicularis brain are presented in stereotaxic coordinates. The levels extend from the rostral tip of the neostriatum to the posterior end of the deep cerebellar nuclei. The illustrations are based on photographs of unstained frozen sections of three formalin‐fixed brains in which stainless steel needles were inserted to mark the horizontal zero and several anteroposterior positions. The sections were not stained in order to prevent shrinkage. Stereotaxic measurements were taken in situ of the highest points on the cortical surface, the position of the central and lunate sulcus, and of certain landmarks at the base of the cranium in a large number of monkeys. These data along with brain dimensions and the weight of animals are displayed in tables to indicate individual variations and to aid investigators in determining the best stereotaxic coordinates for a given structure. It is recommended that the cortical point of entry for an electrode or needle be routinely noted and be compared to the parameters in the atlas to compensate for deviations in the horizontal plane.
The large fourth abdominal intersegmental interneuron: A new type of wind‐sensitive ventral cord interneuron in locusts
Authors: Pflüger Hans‐Joachim
Published: January 2005

A large interneuron in Locusta migratoria is described that extends from the fourth abdominal ganglion to the brain. The morphology was revealed by injection of cobaltous ions or Lucifer yellow into the cell. As its cell body lies within the fourth abdominal ganglion it is named A4I1, the first identified intersegmental interneuron of the fourth abdominal ganglion. This neuron receives input from highly flexible, wind‐sensitive hairs on the prosternum, the pronotum, and the head (field 1). Sensory connections with A4I1 are made within the prothoracic ganglion. Stimulation of the receptive field initiates spikes in A4I1 which travel anteriorly and posteriorly from the prothoracic ganglion. Intracellular recording from the axon and the soma shows that the cell membrane becomes inactive within the fourth abdominal ganglion. Spikes could be generated within the fourth abdominal ganglion by current injection into the soma. Occasionally excitatory postsynaptic potentials were observed in a soma recording, but up to now there is no evidence for a second spike initiation site.

By intracellular current injection into the soma of the left and right A4I1 cell it is shown that the two cells are not electrically coupled.
Occurrence of neurotensinlike immunoreactivity in subpopulations of hypothalamic, mesencephalic, and medullary catecholamine neurons
Authors: Hökfelt Tomas , Everitt Barry J. , Theodorsson‐Norheim Elvar , Goldstein Menek
Published: January 2005

By using indirect immunofluorescence histochemistry combined with the elution‐restaining technique, the presence of a neurotensinlike peptide in some catecholamine neurons in the rat brain has been demonstrated. At the level of the medulla oblongata neurotensinlike immunoreactivity was observed in most of the small‐sized catecholamine (adrenaline) cell bodies in the dorsolateral part of the nucleus of the solitary tract and in some catecholamine (noradrenaline) cells in the medial part. Neurotensin‐positive fibers were found throughout the solitary tract nucleus with increasing concentrations in the rostral direction. Very few neurotensin fibers were seen in the vagal dorsal motor nucleus, which contained a dense network of adrenaline fibers. In the ventral mesencephalon, neurotensinlike immunoreactivity was seen mainly in dopamine cell bodies in the ventral tegmental area, including midline structures, with only single examples of coexistence in the substantia nigra. The dopamine cell bodies of both the A9 and A10 cell groups were surrounded by dense to medium‐dense networks of neurotensin fibers. In the hypothalamus numerous dopamine neurons in the arcuate nucleus exhibited neurotensinlike immunoreactivity. Neurotensin‐positive nerve terminals, partially overlapping catecholamine (mainly dopamine) fibers, were seen in the external layer of the median eminence. The present results demonstrate coexistence of neurotensinlike immunoreactivity and catecholamines in populations of neurons in some of the central catecholamine cell groups and provide a morphological basis for interactions between the peptide and amines.
Neuronal organization of the lateral and basolateral amygdaloid nuclei in the rat
Authors: McDonald Alexander J.
Published: January 2005

The neuronal organization of the lateral (L) and basolateral (BL) amygdaloid nuclei was studied in the rat by using Golgi techniques. All nuclear subdivisions, which were identified in Nissl and acetylcholinesterase preparations, contain spiny class I neurons and spine‐sparse class II neurons. Three of four neurogliaform class III neurons observed were located in the anterior division of BL (BLa). The exact arrangement of class I and class II neurons varies in different portions of L and BL. At the periphery of these nuclei, where L and BL border fiber bundles, major dendrites tend to be oriented parallel to nuclear borders. Many smaller dendritic branches, however, may extend into the adjacent fiber bundles. At most borders between nuclear subdivisions dendritic overlap is minimized by the fact that major dendrites tend to run parallel to subdivisional boundaries. One exception is the junction of BLa with the posterior division of BL (BLp), where unrestricted dendritic overlap of both class I and class II neurons occurs. Within most nuclear subdivisions dendrites of class I and class II neurons ramify freely and exhibit little order. In caudal portions of BLp, however, almost all class I neurons are pyramidal cells with vertically oriented apical dendrites. Dendrites of class II neurons in this region tend to be oriented horizontally, perpendicular to apical dendrites of class I cells. Class II neurons were not evenly distributed in Golgi preparations but were concentrated at the BLa‐BLp border, near the boundary between the dorsolateral and ventromedial subdivisions of L and in the dorsal portion of BLp. The latter cells blend with similar spine‐sparse neurons contained within the external capsule. Analysis of Nissl preparations reveals that small neurons, which correspond to small class II and class III cells, are sometimes observed in a clustered arrangement.
Projections from the periaqueductal gray matter to the B3 cellular area (nucleus raphe magnus and nucleus reticularis paragigantocellularis) as revealed by the retrograde transport of horseradish peroxidase in the rat
Authors: Fardin V. , Oliveras J. L. , Besson J. M.
Published: January 2005

Afferent projections from the periaqueductal gray matter (PAG) to the B3 region (nucleus raphe magnus, NRM; and nucleus reticularis paragigantocellularis, NPG) were examined by means of the horseradish peroxidase (HRP) method revealed by using the tetramethylbenzidine (TMB) procedure. Following iontophoretic injection of HRP into the B3 cellular area, numerous labeled neurons were found between the third oculomotor complex and the rostral part of the tegmental nucleus dorsalis of Gudden. The most densely labeled regions were the lateral parts of the dorsal raphe nucleus (wings of the DRN) and Hamilton's nucleus dorsalis of the PAG. Very few neurons were found within the medial part of the DRN. In contrast, results with control injections performed outside the B3 area gave a different distribution of labeled neurons.

The functional significance of these connections, particularly those emanating from the wings of the DRN which represent new information, is briefly discussed with regard to mechanisms operative in the control of pain.

Although the major PAG‐B3 direct projections could underlie a role for the B3 area in PAG‐induced analgesia, the comparison of our anatomical and behavioral results points out some problems. Indeed, there is no strict correlation between the location of stimulation sites which induce analgesia in the freely moving rats and the distribution within the PAG of B3 projections. These observations lead us to question the role of direct PAG‐B3 connections in the antinociception induced by PAG stimulation and alternative hypotheses are proposed.
The central projections of tooth pulp afferent neurons in the rat as determined by the transganglionic transport of horseradish peroxidase
Authors: Marfurt Carl F. , Turner Dennis F.
Published: January 2005

Transganglionic transport of horseradish peroxidase (HRP) or horseradish peroxidase‐wheat germ agglutinin conjugate (HRP‐WGA) was used to map in detail the central projections of trigeminal primary afferent neurons that innervate the dental pulp organ of the rat. In each of ten animals, 0.5–2.0 μl of enzyme solution was injected into the pulp chamber of the first maxillary molar tooth. Postmortem examination of the decalcified teeth in all cases showed that the HRP/HRP‐WGA remained confined to the pulp chamber and pulp roots, with no spread of enzyme into periapical tissues.

HRP‐labeled tooth pulp afferent fibers projected to all four rostrocaudal subdivisions of the ipsilateral trigeminal brainstem nuclear complex (TBNC) and to the upper cervical spinal cord. The labeled terminal fields formed a column that stretched relatively uninterrupted from just caudal to the rostromedial tip of the trigeminal principal sensory nucleus to at least the C2 segment of the spinal cord. The density of the afferent projection varied markedly from one rostrocaudal level of the TBNC to the next but was heaviest in an area encompassing the caudal one‐half of the principal sensory nucleus and the rostral two‐thirds of pars oralis. Fibers projected only lightly to pars caudalis, where they terminated preferentially in laminae I, IIa, and the junctional zone between laminae IV and V. HRP‐labeled terminals in C1 and C2 were located almost exclusively in laminae I. In the dorsoventral axis, the terminal fields in the TBNC were located in a surprisingly dorsal part of the complex, well within what has been shown by others to be largely an area of termination for mandibular division fibers. Most fibers ended in medial parts of the TBNC, with the exception of two modestly labeled terminal fields located in the lateral aspects of rostral pars oralis and rostral pars caudalis. No labeled fibers terminated in the contralateral TBNC or contralateral cervical spinal cord.