bluuebunny/crossref_metadata_2025 huggingface dataset:
A golgi‐electron microscopic study of goldfish optic tectum. II. Quantitative aspects of synaptic organization
Authors: Meek J.
Published: January 2005

The size, density, and number of the synaptic contacts of three types of interneurons (types I, III, and XIV of Meek and Schellart, 1978) and three types of efferent neurons (types VI, XII, and XIII) of the goldfish optic tectum were quantified by means of a quantitative stereological study of Golgi‐EM serial sections. Furthermore, an estimation was made of the percentage of optic terminals on these six cell types and of the ratio between terminals with pleomorphic and terminals with round vesicles.

The mean density of contacts per receptive component (i.e. the cell body and the different parts of the dendritic tree) varies from 0 to 100 per 100/μm2 surface, corresponding to 0‐8% receptive surface. Each cell type has a characteristic average density as well as a characteristic density distribution along the distinct components. This suggests that the receptive components of the tectal cell types investigated have a predetermined density and that a morphological classification of tectal cells has functional relevance.

The mean length of the contact zones in the ultrathin sections varies from 213 to 332 nm for identified postsynaptic elements and from 188 to 293 nm for identified presynaptic elements. The size of the contacts on the distinct receptive components appears to be primarily related to the tectal lamination pattern. Distinct types of axons, however, have characteristic mean sizes of contacts. This might suggest that the size of the contacts, contrary to their density, is primarily determined by the presynaptic elements.

The mean number of synaptic contacts calculated per cell type is as follows: type XIV, 200; type III, 450; type VI, 1,400; type I, 2,100; type XII, 4,200; and type XIII1, 5,400. Multiplication of these numbers with the number of cells per tectal half shows that the population of type XIV cells has by far the most synaptic contacts, since their low number of synaptic contacts is clearly overruled by their high frequency of occurrence.

Optic terminals, identified by their characteristic mitochondria and large round vesicles, appear to contribute to about 10–20% of the contacts on identified postsynaptic elements in layer 5. The ratio between presynaptic elements with pleomorphic vesicles and those with round vesicles shows a slight tendency to increase when the distance to the origin of the axon decreases.

It is concluded that a combination of the Golgi‐EM technique with quantitative stereological methods appears well suited to the study of the synaptic organization of brain centers, and that combination of quantitative Golgi‐EM with neuronal tracing methods (degeneration, HRP, autoradiography) offers good prospects for detailed investigations of neuronal connectivity.
The middle temporal visual area in the macaque: Myeloarchitecture, connections, functional properties and topographic organization
Authors: Van Essen D. C. , Maunsell J. H. R. , Bixby J. L.
Published: January 2005

The location, topographic organization, and function of the middle temporal visual area (MT) in the macaque monkey was studied using anatomical and physiological techniques. MT is a small, elliptically shaped area on the posterior bank of the superior temporal sulcus which can be identified by its direct inputs from striate cortex and by its distinctive pattern of heavy myelination. Its average surface area is 33 mm2, which is less than 3% of the size of striate cortex. It contains a complete, topographically organized representation of the contralateral visual hemifield. There are substantial irregularities in the detailed pattern of topographic organization, however, and the representation is significantly more complex than that found for MT in other primates. Much of MT is devoted to the representation of central visual fields, with the emphasis on central vision being similar to that found in striate cortex.

Electrophysiological recordings have confirmed previous reports of a high incidence of direction selective cells in MT. The transition in functional properties, from cells lacking direction selectivity outside MT to direction selective cells within, occurs over a distance of 0.1–0.2 mm or less along the lateral border of MT. Such a transition does not occur along the medial border, however, as the cortex medial to MT contains many cells with strong direction selectivity. Nevertheless, this region differs from MT in its myeloarchitecture, its lack of inputs from striate cortex, and the large size of its receptive fields. These results demonstrate the existence of three distinct visual areas on the posterior bank of the superior temporal sulcus which can be distinguished on the basis of both physiological and anatomical criteria.
Freeze‐fracture study of the crayfish stretch receptor
Authors: Tao‐Cheng Jung‐Hwa , Hirosawa Kazushige , Nakajima Yasuko , Peng H. Benjamin
Published: January 2005

The crayfish slow‐adapting stretch receptor was fixed under relaxed or stretched conditions (twice the relaxed length) and then processed for freeze‐fracture study. The sensory neuron membrane had evenly distributed intramembrane particles mostly on its P face. The density of these particles was higher in the cell body than in the dendritic tips, which are the terminal portions of the dendrites. The dendritic tips were cylindrical under the relaxed condition and showed deformations with stretch stimuli. When they were fixed under the stretched condition with 1.6% glutaraldehyde in 0.12 M phosphate buffer (the total osmolarity of this fixative is isosmotic with the physiological solution), the dendritic tips showed regional swelling and shrinkage. The intramembrane particle density of the swollen parts decreased and there were particle‐free patches of membrane, whereas the particle density of the shrunken parts increased. On the other hand, when the receptor was fixed with 1.6% glutaraldehyde in 0.2 M phosphate buffer (the total osmolarity is hyperosmotic but buffer osmolarity is isosmotic), the diameter of the dendritic tips became smaller, and their membrane particle densities were almost the same as that under the relaxed condition. The sheath cells covering the sensory neuron were characterized by their sheet‐like profiles, gap junctions, and crater‐like protrusions. The receptor muscle membrane had longitudinal foldings, occasional invaginations, peripheral couplings, stringshaped particle aggregates, and band‐shaped particle aggregates.
Comparative scanning electron microscopic investigations of the sensory epithelia in the teleost sacculus and lagena
Authors: Popper Arthur N.
Published: January 2005

Scanning electron microscopic studies were conducted on the sensory epithelia of the auditory portions of the ears in teleost species representing wide taxonomic diversity. A number of the features of the ears investigated resem‐ bled features found in other teleost species, although some major exceptions to earlier patterns were found, particularly in the saccular sensory epithelium. The saccular maculae of all but one species contained basically similar ciliary bundles on the sensory hair cells while there was some significant variation on the lagenar maculae. Hair cell orientation patterns on the sacculus contained four orientation groups in all of the species, other than the mormyrid, Gnathonemus, which only had two groups. Lagenar maculae had two orientation groups, and the orientation patterns were similar to one another. The most divergent form of lagenar macula was found in Gnathonemus. These data, combined with data from earlier investigations, provide a broad overview of the surface features of the ear in teleost fishes. Most significantly, it now appears that there are at least five different saccular hair cell orientation patterns among teleost fishes, and all of these patterns are found spread through many major teleost taxa. While there is some similarity in ear structures among some groups of closely related species, such as the Elopomorpha and the Gadiformes, it is becoming more apparent that there is extensive convergence in a number of features of the teleost ear that most likely reflect similar selective pressures during the evolution of the ear. The nature of these selective pressures, however, are not well understood.
Physiological demonstration of multiple representation in the forelimb region of the cat motor cortex
Authors: Pappas C. L. , Strick P. L.
Published: January 2005

Earlier studies in primates have demonstrated a double representation of the distal forelimb in area 4. In this study intracortical stimulation was used to map the representation of the forelimb in area 4 of the cat. Maps of individual animals revealed two spatially separate representations for the distal forelimb in area 4. Two “digit zones.” regions in which threshold stimulation evoked contractions limited to digit musculature, were seen in all animals. Although the absolute location of the two digit zones varied among animals, the zones were always separated by a field in which more proximal musculature was represented. In some experiments EMG activity was monitored from selected forelimb muscles in order to determine the muscles represented in the two zones. Activity of the same digit muscle could be evoked by stimulation in each digit zone. This analysis demonstrated that some digit muscles were represented in both the digit zones. Thus, this study demonstrates that multiple representation of the distal forelimb in area 4 is not an isolated species‐specific phenomenon, but is likely to be a generalized pattern of motor cortex organization.
Direct projection from the dorsal lateral geniculate nucleus to the prestriate cortex in macaque monkeys
Authors: Yukie Masao , Iwai Eiichi
Published: January 2005

The enzyme horseradish peroxidase (HRP) was separately injected into striate, prestriate, inferotemporal, and parietal cortices in 19 macaque monkeys, and the lateral geniculate nucleus (LGN) was examined for retrograde transport. Labeled LGN cells were identified only in the animals with HRP injections into the striate and prestriate cortex. Following injections into either of these regions, labeled cells were found in both parvocellular and magnocellular regions of the ipsilateral LGN only, in keeping with the topographic relation of HRP injection sites in the cortex to labeled areas in the LGN. It was also found that (1) labeled LGN cells were less numerous in both laminar and interlaminar zones following HRP injection into the prestriate cortex, whereas following HRP injection into the striate cortex labeled cells were found almost exclusively in the laminae, and localized to a wedge‐shaped region; (2) following HRP injection into the prestriate cortex, the mean sizes of the labeled parvocellular and magnocellular cells, estimated in projected diameter, were almost the same, these means being significantly larger than the mean size of labeled parvocellular cells and much smaller than that of labeled magnocellular cells following HRP injection into the striate cortex; (3) the shapes of the labeled LGN cells following HRP injection into the prestriate cortex were ovoid, fusiform, or triangular (or multipolar), whereas those following HRP injection into the striate cortex were uniformly ovoid or round. The above findings following HRP injections into the prestriate cortex in normal monkeys were confirmed by HRP injections into the prestriate cortex of monkeys whose striate cortex had been removed several months prior to the injection; labeled cells were found in the confines of areas of retrograde degeneration in the LGN and their labeling pattern was the same as that in intact animals. It was concluded that in macaque monkeys, just as in the cat, a geniculoprestriate projection system exists; it was suggested that there are two parallel systems of visual information processing from the LGN to the prestriate cortex, a direct one and an indirect one through the striate cortex.
Physiological and anatomical evidence for a discontinuous representation of the trunk in S‐I of tree shrews
Authors: Sur Mriganka , Weller Rosalyn E. , Kaas Jon H.
Published: January 2005

Microelectrode mapping methods revealed that the representation of the body surface in the first somatosensory area of cortex, S‐I, of the tree shrew is unique in that only the ventral trunk was found in the usual location of the trunk representation in cortex of the dorsolateral surface of the cerebral hemisphere. Instead, the dorsal trunk was found as an extension of the representation of the posterior leg in cortex on the medial wall. The separation of the representation of the trunk occurs along a line that is counter to the orientation of the dorsal root dermatomes, so that S‐I of the tree shrew clearly cannot be characterized as a serial representation of dermatomes. Anatomical studies of connections support the conclusion that the representation of the trunk is split in S‐I. Both the representation of the dorsal trunk on the medial wall of the cerebral hemisphere and S‐I of the dorsolateral surface were found to project to S‐II when horseradish peroxidase was injected into S‐II.
Morphology of radial glia, ependymal cells, and periventricular neurons in the optic tectum of goldfish (Carassius auratus)
Authors: Stevenson James A. , Yoon Myong G.
Published: January 2005

There are three populations of cells in the deep layers of the optic tectum in a normal adult goldfish: the periventricular neurons, the ependymal cells, and the radial glia. The characteristic morphological features which distinguish the three cell populations are examined at light and electron microscopic levels in the present work.

A radial glial cell has a deeply invaginated nucleus located in a subependymal layer. Its cytoplasm contains mitochondria with 35‐nm dark granules and 20‐nm microtubules but no intermediate filaments. Its prominent radial process extends through the superficial tectal layers. In contrast, the processes of an ependymal cell ramify and interweave within the ependymal region. The cytoplasm of an ependymal cell contains prominent bundles of intermediate filaments but no microtubules. Its soma lies at or near the ventricular surface. A periventricular neuron has a round nucleus and a smooth dendrite which extends toward the superficial tectal layers. Its cytoplasm contains microtubules and agranular mitochondria. Axosomatic and axodendritic synapses are found on periventricular neurons.

The morphological characteristics of these cell types are considered in relation to previous descriptions of teleost tectal cytology and with regard to the atypical natures of the cytoskeletal elements of the ependymal and radial glial cells.
The effect of neonatal 6‐hydroxydopamine treatment on synaptogenesis in the visual cortex of the rat
Authors: Blue Mary E. , Parnavelas John G.
Published: January 2005

It has been proposed repeatedly that the noradrenergic (NE) system may exert an influence on cortical development. We have tested this proposition by examining synaptogenesis in the visual cortex of rats whose NE afferents were selectively lesioned by injections of the neurotoxin 6‐hy‐droxydopamine (6‐OHDA). Control littermates were injected with equal volumes of vehicle. Montages of electron micrographs covering approximately 50 μm‐wide strips of cortex were assembed from both groups of animals at 2,4,6,8,14, and 90 days of age. Symapses counts revealed a significantly higher density of synapses in the cortex of 6‐OHDA‐treated rats during the first week of postnatal life. The difference between the experimental and control rats was less apparent during the second postnatal week, and at day 90 the densities of synapses were similar for the two groups of animals. The enhanced density, which was the result of the increased number of Gray's type I synapses, was confined to the subplate region at day 2 but became more widespread in the cortex at subsequent stages of development. From these observations it would appear that the NE system exerts an inhibitory influence on synapse formation in the visual cortex in early postnatal life.
The island of Calleja complex of rat basal forebrain. I. Light and electron microscopic observations
Authors: Ribak Charles E. , Fallon James H.
Published: January 2005

An analysis of the cells and their processes within the island of Calleja complexes (ICC) was made in light and electron microscopic preparations to determine synaptic relationships within this part of the basal forebrain. The light microscopic preparations showed that the ICC contained two cell types, granule cells and large cells. In electron microscopic preparations, the somata of granule cells were grouped together and were directly apposed to other somata of granule cells. Specialized junctions (4–6 nm wide) that occurred at sites of somal apposition suggested ephaptic coupling of granule cells. The granule cell somata had nuclei that contained clumps of heterochromatin adjacent to smooth nuclear envelopes. The perikaryal cytoplasm of these cells consisted of a relatively thin rim containing few organelles. Spinous dendrites of small diameter were occasionally found in continuity with these cells. Axon terminals rarely formed synapses with the somata of granule cells, but were more frequently found to synapse on their dendrites and dendritic spines. These features for granule cells are similar to those for medium‐sized spiny neurons in the neostriatum.

The somata of the large cells were found either within the core or along the dorsal margin of the ICC. The large cells had infolded nuclei and an abundant perikaryal cytoplasm that contained many organelles. Large diameter dendrites that tapered down to smaller diameters emanated in many directions from these somata. Axon terminals covered nearly the entire surface of these somata and dendrites where they commonly formed symmetric synaptic junctions. These characteristics of large cells indicate a resemblance to the large cells in the globus pallidus and ventral pallidum. Therefore, the ICC have ultrastructural features found in both the neostriatum and globus pallidus.
Guidance of neuritic growth in the transverse plane of embryonic mouse spinal cord
Authors: Holley John A. , Nornes Howard O. , Morita Michio
Published: January 2005

The development of cytoarchitecture in the lumbar spinal cord of mouse embryo between embryonic day 13 (E13) and E15 was studied by scanning and transmission electron microscopy. A pattern of two perpendicularly oriented sets of cellular elements was found in the intermediate zone at both E13 and E14. One set consisted of radially oriented processes that often originated from cell bodies in the ventricular zone. The second set consisted of cell bodies and processes that were oriented predominantly parallel to the neural tube margin and in the transverse plane. This set was termed circumferential elements and included most of the immature neurons. At E13, the circumferentially oriented cells were arranged into rostrocaudally compressed sheets or layers that were partially segregated one from another by flattened bundles of radially oriented processes. This pattern of orthogonally arranged circumferential and radial elements remained evident through E14 when the profuse growth of cellular processes began to obscure the identity of individual cells seen on the scanned surface. The exposed intermediate zone surface at E14 and E15 often had relatively flat transverse areas separated by ledges of broken tissues, indicating that most neurites grow in the transverse plane. These observations indicate that the sequential patterned development of an organized morphological substratum is an important factor in orienting neurite growth.
Topographic organization of the brainstem afferents to the mediodorsal thalamic nucleus
Authors: Velayos José Luis , Reinoso‐Suarez Fernando
Published: January 2005

The afferent projections from the brainstem to the mediodorsal thalamic nucleus (MD) were studied in the cat, by means of retrograde transport of horseradish peroxidase. A topographical arrangement of these projections is described. The medial part of MD is the area of the nucleus which receives fewer afferents from the brainstem. After injections in this part, labeled neurons were observed mainly in the interpeduncular nucleus, the ventral tegmental area and the substantia nigra. After injections of HRP in the intermediate part of the MD, labeled cells were seen mainly in the interpeduncular nucleus, substantia nigra, dorsal and centralis superior raphe nuclei, dorsal tegmental nucleus, and coeruleus complex. Less conspicuous was the number of labeled cells in the central gray and the dorsolateral portion of the tegmentum of the mesencephalon and pons. After injections in the lateral part of MD, labeled neurons were observed mainly in the deep layers of the superior colliculus, central gray, the oral paramedian pontine reticular tegmentum, and the interpeduncular nucleus. Labeled cells were also observed in the substantia nigra, locus coeruleus, dorsal tegmental nucleus, cuneiform area, and the mesencephalic reticular formation. These findings show the MD as a thalamic link of three different groups of brainstem structures projecting to different cortical areas with different functional significance.
Connections of the octopus optic lobe: An HRP study
Authors: Saidel William M.
Published: January 2005

The major visual centers of the octopus central nervous system are the paired optic lobes. Bidirectional transport of horseradish peroxidase (HRP) was used to determine connections of the optic lobe. Cells afferent to the optic lobe were identified by retrograde HRP transport in the following lobes of the central ganglia: anterior basal, median basal, dorsal basal, interbasal, subvertical, precommissural, brachial, and magnocellular. Labeled cells were also observed within the contralateral optic lobe, various optic tract lobes bilaterally, and in photoreceptors of the ipsilateral retina. Additionally, individual fibers, in part originating from cells in the posterior subvertical lobe, were labeled within the central neuropil core of various vertical lobules. Differences in results between superficial and deep optic lobe medulla injections indicate that some afferent projections from central sources may terminate on cell populations at specific depths within the lobe.

Efferent optic lobe fibers into the superior frontal and lateral basal lobes were labeled by anterograde transport. Other possible optic lobe efferent projections terminated in supraesophageal lobes and the magnocellular lobe.

The many inputs to the optic lobe from higher motor and associative centers in the central ganglia emphasize that the medulla region of the optic lobe is an exceptionally complex integrative area.
Alterations of the crossed parabigeminotectal projection induced by neonatal eye removal in rats
Authors: Stevenson James A. , Lund Raymond D.
Published: January 2005

Projections of the parabigeminal nucleus to the contralateral superior colliculus and dorsal lateral geniculate nucleus were examined in normal adult pigmented rats and in adult rats from which one or both eyes had been removed at birth. In normal rats the crossed parabigeminotectal projection is restricted to the superficial layers in anterior and medial areas of colliculus, regions innervated also by the lower temporal portion of the ipsilateral retina. In unilaterally enucleated animals the crossed parabigeminotectal projection to the “denervated” colliculus is expanded, as is the retinal projection from the ipsilateral eye. In addition, there is acrossed parabigeminal projection to the “denervated” dorsal lateral geniculate nucleus in these rats. In bilaterally enucleated animals the parabigeminotectal projection is expanded, but not as greatly as in unilateral enucleation cases; there is a crossed parabigeminothalamic projectionin these animals as well.

The corresponding termination patterns of the contralateral parabigeminal nucleus and the ipsilateral retina in the normal superior colliculus mayindicate a functional and/or developmental interdependence between the projections from these two regions. The existence of an expanded parabigeminotectal projection in bilaterally enucleated rats shows that a sustained ipsilateral retinotectal projection is not necessary for the establishment of a crossed parabigeminotectal projection, but points to the possibility that ipsilateral retinal input may constrain the parabigeminal projection to terminate within certain boundaries. The even greater expansion of the projection from the parabigeminal nucleus to the colliculus which receives an expanded projection from the ipsilateral retina of unilaterally enucleated rats suggests that the functional organization of the ipsilateral retinotectal projection may be capable of restricting the size of the terminal field of the crossed parabigeminotectal projection.
Innervation of avian latissimus dorsi muscles and axonal outgrowth pattern in the posterior latissimus dorsi motor nerve during embryonic development
Authors: Bourgeois Jean‐Pierre , Toutant Madeleine
Published: January 2005

The distribution of the innervation to the anterior latissimus dorsi (ALD) and posterior latissimus dorsi (PLD) muscles of the chicken are described on the day of hatching and 6 weeks later using electron microscopy. In the ALD muscle, there are 5,000 muscle fibres and 374,400 endplates supplied by about 169 skeletomotor axons; in the PLD muscle, there are 12,000 focally innervated muscle fibers supplied by about 20 skeletomotor axons. On the cell surface of the muscle fibers the mean total subsynaptic area contacted by each motor axon is comparable in the ALD and PLD muscles. The growth pattern of the axons in the PLD motor nerve was described from the ninth day in ovo up to 6 weeks after hatching. The axons arrive in the PLD muscle in two successive waves: first, the large somatic axons which are already present before the ninth day in ovo and second, the small autonomic axons which continue to accumulate until hatching. The total number of somatic axons decreases from the ninth day until the hatching day when it reaches its definitive value. This decrease takes place during a period when the numbers of myofibers and of endplates dramatically increase, and it coincides with the axonal segregation by the Schwann cells. The myelination of the axons starts on the 15th day in ovo and is essentially complete upon hatching.

Despite the decreasing number of somatic axons in the PLD nerve, the decrease in number of nerve endings per PLD endplate and the increasing number of PLD endplates per PLD muscle, it was found that between the 16th day in ovo and 6 weeks after hatching the mean number of axonal branches per PLD motor axon does not decrease.
Enkephalin‐mediated basal ganglia influences over the optic tectum: Immunohistochemistry of the tectum and the lateral spiriform nucleus in pigeon
Authors: Reiner Anton , Karten Harvey J. , Brecha Nicholas C.
Published: January 2005

By using immunohistochemical techniques with antisera directed against either leucine‐enkephalin or methionine‐enkephalin (generously supplied by K. ‐J. Chang), four distinct bands of fibers with enkephalinlike immunoreactivity were demonstrated in the pigeon tectum: (1) a thin band of thick fibers and tightly clustered bulbous swellings in layer 3, (2) a broader band of fibers with less tightly clustered bulbous swellings in layer 5, (3) a broad band of numerous obliquely and radially oriented fibers that spanned layers 8–13, and (4) a band of sinuous fibers in layer 15. In addition, numerous enkephalinergic cell bodies with radially ascending processes were seen in layers 8–10. Since the neurons of the avian lateral spiriform nucleus (SpL) of the pretectum are known to contain enkephalin (Davis et al., 1980; De Lanerolle et al., 1981) and project to the tectum (Brecha et al., 1976; Reiner et al., 1982), unilateral electrolytic lesions were made of SpL. In birds with unilateral lesions of SpL, layers 8–13 of the ipsilateral tectum were nearly devoid of enkephalinergic fibers, but no alterations were seen in layers 3, 5, and 15. Since no other neurons in the vicinity of SpL are enkephalinergic and project to the tectum, the loss of enkephalin‐immunoreactive fibers in the ipsilateral tectal layers 8–13 is attributable to the destruction of SpL. Although the source of the enkephalinergic fibers in tectal layers 3, 5, and 15 is unclear, part of the enkephalin pattern in layers 3 and 5 may derive from the ascending processes of the enkephalinergic neurons of layer 8–10. The present results indicate that SpL has an enkephalinergic projection to layers 8–13 of the ipsilateral tectum. The avian SpL receives its major input from the ascending processes of the enkephalinergic neurons of layers 8–10. nuclei that themselves receive major basal ganglia inputs (Reiner et al., 1982), and projects to the tectal layers 8–13 (Reiner et al., 1982), the layers of origin of the major tectal efferent projections (Reiner and Karten, 1982). The enkephalinergic fibers in layers 8–13 may, thus, have some influence upon the motor output functions of the avian tectum.
Spinocerebellar projections to lobules III to V of the anterior lobe in the cat, as studied by retrograde transport of horseradish peroxidase
Authors: Matsushita Matsuo , Hosoya Yasuhiko
Published: January 2005

Spinocerebellar tract (SCT) neurons projecting to lobules III to V of the cerebellar anterior lobe were identified by the retrograde horseradish peroxidase technique.

SCT neurons projecting to lobule III with crossed ascending axons were located mainly in the central cervical nucleus (CCN), the medial part of lamina VII of L6 to the caudal segments, and the dorsal horn (lamina V) and ventral horn (lamina VIII) of the sacral‐caudal segments. Spinal border cells with crossed ascending axons also projected to lobule III. SCT neurons projecting to this lobule with uncrossed ascending axons were located in the medial part of lamina VI of the cervical segments and the middle part of lamina VII of C6 to T1, lamina V of the lower cervical, thoracic and the lumbar segments, Clarke's column including marginal neurons, and the medial part of lamina VI of L5 and L6. These neuronal groups also projected to lobule IV, except for those present caudal to L6 (in the medial part of lamina VII, and laminae V and VIII of the sacral‐caudal segments). A far smaller number of similar neurons projected to lobule V.

Injections of HRP restricted to the vermal region labeled mainly neurons in the CCN and Clarke's column while restricted injections to the intermediate‐lateral regions labeled ipsilaterally spinal border cells, lamina V neurons, and Clarke column neurons, especially of the lumbar segments as well as marginal neurons of this column.
The corticopontine system in the rat. I. Mapping of corticopontine neurons
Authors: Wiesendanger R. , Wiesendanger M.
Published: January 2005

The expanse of cerebral cortex containing corticopontine neurons was explored in rats. The retrograde tracer horseradish peroxidase (HRP) was iontophoresed into subdivisions of the pontine nuclei (PN). The densest projection was seen to originate from somatosensory and motor areas. Visual areas also provide a major contingent of corticopontine neurons, whereas auditory areas appear to have only a minor projection. Consistent labeling of cells was also seen in the granular cingulate cortex, especially in the junction region of anterior and posterior cingulate cortex. This and a sparse projection from dorsal and posterior “insular” cortex (rhinal sulcus) have not been described in detail in previous studies.
Neuropeptide immunoreactivity in Limulus. I. Substance p‐like immunoreactivity in the lateral eye and protocerebrum
Authors: Chamberlain Steven C. , Engbretson Gustav A.
Published: January 2005

Substance P‐like immunoreactivity was examined in the Limulus lateral eye and protocerebrum by the unlabeled antibody peroxidase‐antiperoxidase method. Small‐diameter immunoreactive fibers innervate the corneal epidermis of the lateral eye and appear to be part of a generalized epidermal innervation. No immunoreactive neurons or fibers were found in the ventral, median, or lateral optic nerves nor in the lamina or chiasma. The optic medulla contains neurons with immunoreactive perinuclear caps in the ganglion cell layer and fibers of undetermined origin in the posterolateral regions of the neuropil. The central body contains many immunoreactive fibers in its neuropil, some or all of which arise from neurons adjacent to its anteromedial tips. Immunoreactive neurons within the curve of the central body give rise to processes which join the central neuropil of the protocerebrum. The immunoreactive innervation of the corpora pedunculata includes processes which terminate among Kenyon cell somata, and processes in the peduncular neuropil, all of which arise from a bilateral cluster of neurons along the midline. Attempts to investigate the source of the immunoreactive fibers using cobalt impregnation of the severed circumesophageal connective have revealed two additional innervations of the corpora pedunculata, one from raphe neurons along the midline and one from lateral portions of the midline ganglion adjacent to but separate from that portion containing the immunoreactive neurons. The results demonstrate that immunocytochemical methods are another powerful tool for the study of neuronal pathways in invertebrates.
A study of the extrinsic innervation of the guinea pig pylorus with the horseradish peroxidase tracing technique
Authors: Elfvin L.‐G. , Lindh B.
Published: January 2005

The extrinsic innervation of the guinea pig pylorus was studied by the use of the horseradish peroxidase (HRP) tracing technique. Forty‐eight hours after injection of HRP into the pyloric sphincter labeled neurons of varying sizes were found throughout the rostrocaudal extent of the dorsal motor nuclei of the vagus. No HRP positive cells were seen in the medial solitary nuclei or the ambiguus nuclei. Many HRP‐positive cells were observed in the celiac‐superior mesenteric ganglion complex. Occasional cells in the superior cervical and stellate ganglia were also labeled. When the vagal ganglia were analyzed many enzyme‐containing cells were found in the nodose ganglia and some cells in the jugular ganglia. Furthermore, about 15–20% of the labeled afferent neurons were located in dorsal root ganglia on both sides, with the majority of cells at the T5–T10 levels. The results are discussed in relation to recent transmitter histochemical findings as well as to possible functional roles of the neurons.
Morphology of the substantia nigra pars reticulata projection neurons intracellularly labeled with HRP
Authors: Grofova I. , Deniau J. M. , Kitai S. T.
Published: January 2005

The technique of intracellular recording and staining of the same neuron with horseradish peroxidase (HRP) was used to study the soma‐dendritic and axonal morphology of nigrothalamic and nigrotectal cells in the rats.

The nigrothalamic and nigrotectal cells were spread throughout the dorsoventral extent of the pars reticulata (SNR) and exhibited the same soma‐dendritic and axonal features. Both populations consisted of medium‐sized and large cells with extensive dendritic fields overlapping in all three directions. Their axons collateralized within the substantia nigra (SN) and in the mesencephalic tegmentum. The intrinsic collaterals were thin and branched partly within the dendritic field of a parent cell partly in remote regions of the SNR, and even in the pars compacta (SNC). The extrinsic branches involved thin arborizations in the rostroventral mesencephalic reticular substance and thicker descending and ascending collaterals.

This material was supplemented by physiologically nonidentified HRP stained medium‐sized and large neurons located in the SNR. The two kinds displayed the same extent and orientation of their dendrites but the branching patterns differed slightly. Proximal dendrites of all cells were coarse and smooth; thinner distal dendrites had varicosities and spinelike appendages. Some dendrites, especially those near the crus cerebri, terminated in dendritic thickets bearing many pleomorphic appendages.

The orientation of dendritic fields varied with dorsoventral position of cells within the SNR. The most ventral region of the SNR contained neurons with dendrites oriented parallel to the crus cerebri and thus remained confined to the deepest stratum. The dendrites of cells in the central region of SNR were oriented mainly anteroposteriorly and ventrally, the ventral dendrites terminating in the ventralmost layer. Cells in the dorsolateral part of the SNR were characterized by the large dorsoventral extent of their dendrites which penetrated the entire thickness of SN. This variation in the arrangement of dendritic fields indicates that the SN is organized in three dorsoventral layers.
Myelination of S1 dorsal root axons in the cat
Authors: Berthold C.‐H. , Carlstedt T.
Published: January 2005

Samples of S1 dorsal root nerve fibers from cats of different pre‐ and postnatal ages were examined electron microscopically with regard to axon caliber and number of myelin lamellae. Each root was examined at four different cross‐sectional levels. Two levels were situated close to the spinal cord entrance on each side of the peripheral (PNS) and central nervous system (CNS) border. The third and fourth levels were located more distally. The first compact myelin lamella was observed in the CNS part of the root in a 47‐day‐old fetus. In the 53‐day‐old fetus the degree of myelination was the same in the CNS as distal in the PNS part of the root. Surprisingly, all axons appeared unmyelinated close to the PNS‐CNS border and remained so for a further 10‐day period. After this time lag, this part of the root became myelinated and showed a rapid increase in myelin sheath thickness. Calculations of axonal growth, mesaxonal length, and myelin volume indicated a maturation process that progressed discontinuously. Myelination did not proceed in a strict somatofugal direction, but was a regionally differentiated process. The maximal myelin production, expressed as the increase in myelin volume per Schwann cell, was found during the second to fourth postnatal months, i. e., very late in development.
LHRH immunopositive cells and their projections to the median eminence and organum vasculosum of the lamina terminalis
Authors: King J. C. , Tobet S. A. , Snavely F. L. , Arimura A. A.
Published: January 2005

The purpose of this study was to determine the distribution of luteinizing hormone‐releasing hormone (LHRH) cells and pathways projecting to the median eminence and organum vasculosum of the lamina terminalis in the hypothalamus of the rat. Immunopositive LHRH was detected by the PAP method of immunocytochemistry on vibratome sections without embedding. Female rats were ovariectomized and treated with estradiol benzoate or implanted with estradiol capsules prior to sacrifice in order to minimize variations in LH and ultimately to maximize hypothalamic LHRH content. Immunoreactive LHRH perikarya are diffusely aggregated across several nuclear groups: nucleus of the vertical limb of the diagonal band of Broca, medial septal nucleus, medians preoptic nucleus, rostral and medial preoptic areas, anterior hypothalamic area, and lateral and basal hypothalamic areas. The aggregate of LHRH cells when projected upon a horizontal plane resembles the form of a V bisected by the third ventricle. The apex of the V is directed rostrally toward the midline nuclear groups whereas the ends of the V incline ventrally toward the base of the brain and the median eminence. The majority of LHRH cells are in the rostral portion of the V in preoptic and anterior hypothalamic areas. Few cells are present in the basal hypothalamus. The processes of LHRH cells form two diffuse fiber systems which are separated by the midline hypothalamic nuclei over most of their course and converge in the basal hypothalamus close to the median eminence. The more lateral fiber system forms part of the medial forebrain bundle, while the periventricular system is associated with the wall of the third ventricle. The dispersion of LHRH cells over many nuclear groups may allow for the integration of afferents from divergent regions of the neuraxis to mediate both tonic and phasic gonadotropin secretion in the rat.
A quantitative study of regenerative sprouting by optic axons in goldfish
Authors: Murray Marion
Published: January 2005

Regenerative sprouting by optic axons of goldfish was examined distal to the site of a crush lesion. Normally, optic nerves of large goldfish contain approximately 2 × 105 myelinated axons. The number of axonal processes in the nerve distal to the lesion increases fourfold during the first 3 months postoperatively and then returns toward preoperative numbers after 3 months. The excess number of axonal processes therefore persists several months beyond the return of visual function. The magnitude and time course of regenerative sprouting by goldfish optic axons is similar to that reported for mammalian and nonmammalian peripheral axons.
The pattern of distribution of the local axonal collaterals of Purkinje cells in the intermediate cortex of the anterior lobe and paramedian lobule of the cat cerebellum
Authors: Bishop Georgia A.
Published: January 2005

Purkinje cells in the intermediate cortex of the anterior lobe and paramedian lobule of the cat cerebellum were intracellularly injected with horseradish peroxidase. Light microcopic analysis of the distribution paterns of the local collaterals arising from the axons of Purkinje cells in these two cortical areas was carried out. These data suggest that the distribution of the axon collaterals is different in these two areas of the cerebellar cortex. Collaterals arising from the axons of Purkinje cells in the anterior lobe form a highly branched, densely beaded plexus which is restricted to the immediate area of the cell of origin. The axonal ramification is located primarily along the Purkinje cell layer, although a few branches extend into the deep to middle molecular layer. In contrast, collaterals derived from Purkinje cells in the paramedian lobule branch infrequently, and give rise to only a few beaded chains. They extend for great distances, up to 1 mm from the cell of origin. In some cases, collateral branches of paramedian lobule Purkinje cells course into the subcortical white matter to the opposite side of their folium of origin or extend to adjacent folia. These data suggest that the distribution pattern of recurrent collaterals within the cerebellar cortex may not be uniform. In addition, differences in distribution may be correlated with differences in the afferent and efferent organization of the two areas in the cerebellar cortex.
Neural correlates of flight loss in a mexican grasshopper, Barytettix psolus. I. Motor and sensory cells
Authors: Arbas Edmund A.
Published: January 2005

The nervous systems of locusts (Schistocerca gregaria) and flightless grasshoppers (Barytettix psolus) are compared to evaluate modifications to neurons which are associated with flight loss.

Locusts are well known for their powerful flight capability. Barytettix never fly. They lack hindwings, have immobile vestiges of forewings, and are devoid of skeletal specializations for wing movement. Their pterothoracic musculature is similar to that of locusts, except for the absence of those muscles that, in locusts, have the primary function of moving the wings.

Individually identified leg motorneurons, the extensors of the tibia, were compared between locusts and Barytettix and were found to have very similar morphologies.

Nerve roots which correspond to those suppyling wing muscles of locusts were stained by cobalt backfilling in Barytettix to test for presence of counterparts to wing muscle motorneurons.

Cobalt backfills of metathoracic nerve 1 reveal the presence in Barytettix of neurons corresponding to locust dorsal longitudinal motorneurons‐neurons which persist in adult Barytettix in the complete absence of pe‐ripheral targets. These cells occupy characteristic positions within the CNS but their soma sizes are greatly reduced by comparison to their locust counterparts.

Locust metathoracic ganglia bear large flight motorneurons on their ventral anterolateral margin. Viewed in toluidine blue‐stained wholemounts, Barytettix ganglia show considerably smaller neuron somata in the corresponding region. In locusts, comparisons of the fast extensor tibiae (FETi) motorneuron soma profile areas with those of the largest anterior cell showed no significant difference between the two, while in Barytettix, the largest anterior cell is 51% smaller than the FETi.

A counterpart to the locust wing hinge stretch receptor (SR) was revealed by backfilling metathoracic nerve 1 in Barytettix. Despite its lack of function as a wing movement detector, the central projection of Barytettix SR differs from its locust counterpart only in reduced spread of specific central branches.
Distribution of substance P‐like immunoreactivity in the brain of the newt (Triturus cristatus)
Authors: Taban C. H. , Cathieni M.
Published: January 2005

The distribution of immunoreactive substance P (sP)‐containing structures in the newt brain and spinal cord was explored with an indirect im‐munofluorescence method. Five sP‐positive elements were detected: perikarya, dots, fibers, pericellular appositions, and pipe‐shaped structures. Perikarya were seen at the levels of the spinal ganglia, spinal cord, raphe nucleus, interpeduncular nucleus, mesencephalon, preoptic area, infundibulum, dorsocaudal part of the ventral hypothalamus, habenula, and corpus striatum. Pericellular terminals were observed in periventricular areas, known to be rich in catecholaminergic cells; pipe‐shaped structures were ob‐served from the corpus striatum to diencephalon, and in mesencephalon. The olfactory nerve and nuclei were devoid of sP‐positive elements. Six sP‐immunofluorescent pathways were detected. One of them is composed of axons with huge varicosities and extends from the lateral spinal cord area to the mesencephalon. This pathway has not been described as yet in other animals and could be peculiar to the newt.