bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitative studies of retinal ganglion cells in a turtle, Pseudemys scripta elegans. I. Number and distribution of ganglion cells
Authors: Peterson Ellengene H. , Ulinski P. S.
Published: January 2005

Multiple pathways for the transmission of visual information from retina to brain have been described in reptiles, but little is known about their functional organization. These parallel channels begin at the retina, and we have therefore begun to study the functional organization of retinal ganglion cells in the turtle, Pseudemys scripta elegans. This paper describes the numbers and distribution of cells in the ganglion cell layer.

To develop criteria for the identification of ganglion cells, we labelled them retrogradely by applying horseradish peroxidase (HRP) to the optic nerve. Ganglion cells were found to vary substantially in size and cytology. In low density areas of the retina, ganglion cells typically have cytoplasm with well developed Nissl substance, a distinct, pale nucleus, and a large nucleolus. In high density areas of retina, ganglion cells are small, densely staining, and gliaform. The average minimum proportion of ganglion cells in the ganglion cell layer is 75–80% of total profiles. No more than five or six percent of profiles in the ganglion cell layer are neurons which do not send an axon into the optic nerve (displaced amacrine cells or intraretinal association cells).

The ganglion cell layer of P. s. elegans can be divided into a number of regions on the basis of cell density. Isodensity maps constructed from Nisslstained, wholemounted retinas indicate that there is an elongated region of high ganglion cell density, the visual streak, which extends from nasal to temporal retina and is oriented such that its long axis follows the horizontal axis of the eye. The streak is aligned with the externally visible iris line. Seen in cross‐section, the ganglion cell layer in the streak is three to four cells thick; in nonstreak retina, ganglion cells form only a monolayer of somas. Ganglion cell density drops off more rapidly above the streak than below it. The temporal arm of the streak is both shorter and broader than the nasal arm. There is a peak in ganglion cell density at the midpoint of the streak, in the approximate center of the retina. Here, ganglion cell densities exceed 20,000 cells mm−2. The total number of ganglion cells in the retina is 350,000–390,000.
Layer I of striate cortex of Tupaia glis and Galago senegalensis: Projections from thalamus and claustrum revealed by retrograde transport of horseradish peroxidase
Authors: Carey Russell G. , Fitzpatrick David , Diamond Irving T.
Published: January 2005

We have examined the origin of the subcortical projections to the superficial layers of the striate cortex in Tupaia glis and Galago senegalensis by using the retrograde transport of HRP. Crystals of HRP were laid directly on the moist pial surface of the cortex which had been gently pricked with a small glass pipette. The diffusion of HRP was limited to layers I and II by restricting the length of time that the HRP was in contact with the surface. Following the application of HRP to the striate cortex, labeled cells were found in restricted regions of the lateral geniculate body of both species. Layers 4 and 5 of galago and layer 3 of tree shrew contained dense clusters of labeled cells. Labeled neurons were also found in the zones between the layers of the lateral geniculate body in species and these cells were always in register with the labeled cells within the layers. In galago, curved columns of labeled cells were observed in the inferior and superior subdivisions of the pulvinar nucleus. These columns were arranged in the shape of two arcs, joined at the fiber bundle which separates the two subdivisions. The position of the bands in the pulvinar nucleus varied with the locus of the application in the striate cortex. While no labeled cells were seen in the body of the pulvinar nucleus of tree shrew, small labeled neurons were found in the external medullary lamina forming the capsule of the pulvinar nucleus. These cells were continuous with a larger population of labeled cells in the lateral intermediate nucleus. In both species, labeled cells were also found in the intralaminar nuclei (particularly the paracentral nucleus) and in the dorsal‐caudal portion of the claustrum. In the claustrum, few unlabeled neurons were present within the zone containing labeled cells. In conclusion, layer I of striate cortex appears to be the site of convergence of several projection systems originating from principal and intralaminar thalamic nuclei as well as the claustrum. The significance of this overlap is discussed in terms of the total cortical extent of each system.
The connections of the septal region in the rat
Authors: Swanson L. W. , Cowan W. M.
Published: January 2005

The efferent, afferent and intrinsic connections of the septal region have been analyzed in the rat with the autoradiographic method. The lateral septal nucleus, which can be divided into dorsal, intermediate and ventral parts, receives its major input from the hippocampal formation and projects to the medial septal‐diagonal band complex. The ventral part of the nucleus also sends fibers through the medial forebrain bundle to the medial preoptic and anterior hypothalamic areas, to the lateral hypothalamic area and the dorsomedial nucleus, to the mammillary body (including the supramammillary region), and to the ventral tegmental area. The medial septal nucleus/diagonal band complex projects back to the hippocampal formation by way of the dorsal fornix, fimbria, and possibly the cingulum. Both nuclei also project through the medial forebrain bundle to the medial and lateral preoptic areas, to the lateral hypothalamic area, and to the mammillary complex. The medial septal nucleus also sends fibers to the midbrain (the ventral tegmental area and raphe nuclei) and to the parataenial nucleus of the thalamus, while the nucleus of the diagonal band has an additional projection to the anterior limbic area. Ascending inputs to the medial septal nucleus/diagonal band complex arise in several hypothalamic nuclei and in the brainstem aminergic cell groups. The posterior septal nuclei (the septofimbrail and triangular nuclei) receive their major input from the hippocampal formation, and project in a topographically ordered manner upon the habenular nuclei and the interpeduncular nuclear complex.

The bed nucleus of the stria terminalis receives its major input from the amygdala (Krettek and Price, '78); but other afferents arise from the ventral subiculum, the ventromedial nucleus, and the brainstem aminergic cell groups. The principal output of the bed nucleus is through the medial forebrain bundle to the substantia innominata, the nucleus accumbens, most parts of the hypothalamus and the preoptic area, the central tegmental fields of the midbrain, the ventral tegmental area, the dorsal and median nuclei of the raphe, and the locus coeruleus. The bed nucleus also projects to the anterior nuclei of the thalamus, the parataenial and paraventricular nuclei, and the medial habenular nucleus, and through the stria terminalis to the medial and central nuclei of the amygdala, and to the amygdalo‐hippocampal transition area.
The raphe nuclei of the rabbit brain stem
Authors: Felten David L. , Cummings John P.
Published: January 2005

The raphe nuclei of the rabbit brain stem were found in the midline and adjacent reticular formation of the medulla, pons, and mesencephalon. Nuclei raphe obscurus, pallidus, and magnus were located in the medulla. Nucleus raphe pontis and the caudal portion of nuclei raphe dorsalis and centralis superior were present in the pons. The rostral portion of nuclei raphe dorsalis and centralis superior, and nuclei linearis caudalis and intermedius were present in the msencephalon. Wings of neurons extended from the midline clusters of raphe neurons into the adjacent reticular formation. These wings of neurons contained serotonergic perikarya which were cytoarchitecturally indistinguishable from the midline neurons. A detailed localization of these nuclei is presented in atlas form. These raphe nuclei contained hetrogeneous populations of neurons which varied in the size, shape and density of the cell bodies. In addition, the dendritic branching, specific orientation of dendrites, and appearance of spines were distinct for each of the raphe nuclei. Individual raphe nuclei often contained several subpopulations of neurons characterized by unique spatial configuration and orientation. The main morphological similarities of the raphe nuclei are location in or adjacent to the midline, the presence of serotonergic cell bodies in all raphe nuclei except the linear nuclei, and heterogeneous cell populations.
The longitudinal zonal pattern in the paramedian lobule of the cat's cerebellum: An analysis based on a correlation of recent HRP data with results of studies with other methods
Authors: Walberg F. , Brodal A.
Published: January 2005

In a preceding study of the distribution of retrogradely labeled cells in the inferior olive of the cat after microinjections of horseradish peroxidase (HRP) in the contralateral paramedian lobule (Brodal and Walberg, 1977b), three longitudinal zones were distinguished. The zones were assumed to correspond to Voogd's zones C1, C2 and D, receiving their afferents from parts of the dorsal accessory olive, of the medial accessory olive and of the dorsal lamella of the principal olive, respectively. Labeled cells were not found in the ventral lamella of the principal olive, however, although there is no doubt that also this projects to the paramedian lobule.

In the present study, iontophoretic ejections, covering the extreme lateral part of the paramedian lobule, gave rise to labeling of cells in the ventral lamella. It is concluded that the zone D in the paramedian lobule can be subdivided into two, a lateral, D2 and a medial, D1, receiving fibers from the ventral and dorsal lamella, respectively. Neither zone extends throughout the entire length of the paramedian lobule. Both are lacking most rostrally and most caudally.

This and other findings prompted a renewed analysis of the entire pattern of zonal representation in the paramedian lobule, based on correlations of our observations with the HRP method with data obtained with other methods. The results of this analysis are briefly described and summarized in a diagram (fig. 3B). It is particularly remarkable that zone B is present in some folia medially. A somatotopical arrangement appears to be present within all zones. A full account and documentation will be presented separately (Brodal and Kawamura, 1980).
The inferior pulvinar complex in owl monkeys: Architectonic subdivisions and patterns of input from the superior colliculus and subdivisions of visual cortex
Authors: Lin C.‐S. , Kaas J. H.
Published: January 2005

Patterns of connections with other visual structures and architectonic characteristics were used to subdivide the inferior pulvinar complex of owl monkeys into three distinct nuclei termed the central inferior pulvinar, IPc, the medial inferior pulvinar, IPm, and the posterior inferior pulvinar, IPp. IPc occupies about 70%; IPm about 20%, and IPp about 10% of the inferior pulvinar complex. Encapsulating fiber bands distinguish the boundaries of the three nuceli. IPm is also identified by a much greater packing density of neurons than IPc and IPp. Both IPp and IPc receive input from the superior colliculus, but the terminations in IPp are denser. Visual cortical Areas 17, 18, MT, DM, M and PP (Allman and Kaas, '76) project to IPc and IPm in patterns that indicate that central vision is represented dorsorostrally and peripheral vision ventrocaudally in both nuclei. Terminations in IPm from Area MT are particularly dense. None of these visual areas projects to IPp. Rather, input to IPp appears to originate in cortex rostral to Area MT in the temporal lobe.
Projections of the cerebellar and dorsal column nuclei upon the inferior olive in the rhesus monkey: An autoradiographic study
Authors: Kalil Katherine
Published: January 2005

Projections from the cerebellar and dorsal column nuclei to the inferior olive of the rhesus monkey were traced with anterograde autoradiographic methods.

The cerebellar nuclei give rise to a massive projection which reaches the contralateral inferior olivary complex by way of the descending limb of the superior cerebellar peduncle. Dentato‐olivary fibers project exclusively upon the principal olivary nucleus (PO) and observe a strict topography. The dorsal, lateral, and ventral dentate project respectively to the dorsal, lateral, and ventral lamellae of the PO. Within the lamellae, the dentato‐olivary fibers are related point for point in the medio‐lateral axis. By contrast, the rostro‐caudal topography is reversed so that the rostral pole of the dentate projects to the caudal PO and the caudal dentate to the rostral PO. These connections are predominantly crossed but a small ipsilateral component recrosses the midline at the olivary commissure and mirrors the topography on the opposite side. The anterior interpositus projects only to the medial half of the DAO and the posterior interpositus projects only to the rostral two thirds of the MAO. The ipsilateral component is minor in comparison with the contralateral projection, but appears to be more substantial than the ïpsilateral projection to the PO arising from the dentate nucleus. The fastigial nucleus does not project upon the olivary complex.

The dorsal column nuclei project topographically upon the contralateral accessory nuclei with the gracile nucleus sending fibers primarily to the lateal half of the DAO and the cuneate nucleus projecting to rostral cell groups of the MAO.

The present results when compared with other olivary connections described by previous studies in a veriety of species suggest that regions of the MAO and DAO receiving sensory information from the periphery may lie outside the influence of cerebellar feedback loops.
Commissural projections of the cortical hand motor area in monkeys
Authors: Jenny A. B.
Published: January 2005

The topographical organization of the contralateral cortical projections of the motor hand area was studied with autoradiographic methods in 11 macaque monkeys.

Two general observations were noted in the material studied. (1) The commissural cortico‐cortical connections of the motor hand area were directed to the contralateral precentral gyrus. The projections were preferentially directed to both homotopic and non‐homotopic areas. (2) Focally labeled areas of motor cortex (diameter 900 μm) gave rise to individual terminal columns of label (diameter 600–900 μm). Larger areas of labeled motor cortex, (3,000 μm in diameter) gave rise to contralateral terminal bands of label. These bands (600–1,000 μm in width) were oriented in an antero‐posterior direction and appeared to be formed by a sequence of adjacent labeled columns.
Development of the diencephalon in the rat. V. Thymidine‐radiographic observations on internuclear and intranuclear gradients in the thalmus
Authors: Altman Joseph , Bayer Shirley A.
Published: January 2005

Groups of pregnant rats were injected with two successive daily doses of 3H‐thymidine from gestational days 13 and 14 (E13 + 14) until the day before birth (E21 + 22). Internuclear and intranuclear cytogenetic gradients were examined in radiograms of the thalamus sectioned in the coronal, sagittal and horizontal planes. There was a precise and segregated lateral‐to medial gradient between and within the habenular nuclei. In the ventral thalamus the reticular nucleus had a lateral‐to‐medial gradient, the subthalamic nucleus a laterodorsal‐to‐medioventral gradient. There was a caudal‐to‐rostral gradient between the medial geniculate and dorsal lateral geniculate nuclei, and between the pars posterior and pars anterior of the lateral nucleus. A clear intranuclear gradient could not be detected in the sensory relay nuclei with the exception of the medial geniculate nucleus. A lateral‐to‐medial internuclear gradient was seen between the relay nuclei and the intralaminar nuclei, and between the latter and some of the midline nuclei.

On the basis of a consideration of the time of origin and time span of production of neurons of various thalamic nuclei, and taking into account some of the recognizable internuclear and intranuclear gradients, the thalamus was divided into five principal cytogenetic components: the epithalamus, the ventral thalamus, the dorsal thalamus, the medial thalamus, and the posterior thalamus. The epithalamic nuclei form over a protracted period resembling the nuclei of the hypothalamus. The nuclei of the ventral thalamus are generated early and over a relatively long period. The dorsal thalamus consists of the relay nuclei and the intralaminar nuclei; they form rapidly and ahead of the medial thalamus. The medial thalamus was subdivided into the earlier‐forming antero‐medial nuclei and the latest‐forming midline nuclei. The posterior thalamus was not examined in detail.
The cells of origin of the primate spinothalamic tract
Authors: Willis W. D. , Kenshalo D. R. , Leonard R. B.
Published: January 2005

Spinothalamic tract cells in the lumbar, sacral and caudal segments of the primate spinal cord were labelled by the retrograde transport of horseradish peroxidase (HRP) injected into the thalamus. The laminar distribution of stained spinothalamic cells in the lumbosacral enlargement differed according to whether the HRP was injected into the lateral or the medial thalamus. Lateral injections labelled cells in most laminae, but the largest numbers of cells were in laminae I and V. The highest concentrations of cells labelled from the medial thalamus were in laminae VI‐VIII. Ninety percent or more of the stained spinothalamic cells in the lumbosacral enlargement were contralateral to the injection site. In the conus medullaris stained spinothalamic cells were most numerous in laminae I, V and VI following lateral thalamic injections of HRP. Many of the cells of the conus were in Stilling's nucleus. Twenty‐three percent of the cells in the conus were ipsilateral to the injection site in the lateral thalamus. Only a few cells in the conus were labelled by medial thalamic injections. The total number of spinothalamic cells from L5 caudally was estimated to be at least 1,200‐2,500. An injection of HRP into the midbrain resulted in a laminar distribution of labelled cells much like that produced by a lateral thalamic injection. The types of spinothalamic tract cells and the sizes of their somata were determined for different laminae. The cells types resemble those already described from Golgi and other studies of the spinal cord gray matter. The spinothalamic tract cells in lamina I included Waldeyer cells and numerous small fusiform, pyriform or triangular cells. Those in lamina II included limitrophe and central cells. Spinothalamic cells in lamina III were central cells. Most of the labelled cells in laminae IV‐X were polygonal, although there were also flattened cells in these layers. The smallest spinothalamic cells were in laminae I‐III, while the largest were in laminae V and VII‐IX. Spinothalamic cells in the conus medullaris included cells like those in the lumbosacral enlargement, but also a special cell type in Stilling's nucleus. Some cells in the conus had dendrites that crossed the midline. Spinothalamic axons could sometimes be traced to the ventral white commissure within one or a few sections. In longitudinal sections, most labelled axons were in the ventral part of the lateral funiculus on the side of the injection, although a few were in the ventral funiculus or on the contralateral side. The axons were widely dispersed, and a few were located adjacent to the pia‐glial membrane.
The emergence, localization and maturation of neurotransmitter systems during development of the retina in Xenopus laevis. I. γ‐aminobutyric acid
Authors: Hollyfiels Joe G. , Rayborn Mary E. , Sarthy P. Vijay , Lam Dominic M. K.
Published: January 2005

The high‐affinity uptake, biosynthesis and release of GABA have been studied in the retina of Xenopus laevis. In the mature retina, [3H]‐GABA is accumulated predominantly by horizontal cells. A second population of cells located in the inner nuclear layer (possibly a type of amacrine cell) also showed a specific GABA uptake. In addition, this retina contains significant activities of L‐glutamic acid decarboxylase and also releases [3H]‐GABA in response to increasing K+ concentrations in the medium. We have followed the appearance and maturation of these GABA‐ergic properties during embryonic development of this retina. Our results indicate that these properties emerge in a precise temporal pattern during retinal differentiation: the specific neuronal uptake of GABA synthesis which is followed by K+‐stimulated GABA release.
A second type of horizontal cell in the monkey retina
Authors: Kole Helga , Mariani Andrew , Gallego Antonio
Published: January 2005

A second type of horizontal cell with a distinctly different appearance from the previously known horizontal cell has been seen in Golgi‐impregnated monkey retinas. The new HII cell has a different dendritic branching pattern from the commonly described HI cell type, and it has a short convoluted axon with collaterals bearing small clusters of terminals. Comparisons of the two cell types at different retinal eccentricities show that HII cells have larger dendritic trees than HI cells in the foveal region but smaller dendritic trees than HIs in peripheral retina. Dendritic terminals of the new HII cell, like the HI cell, contact cone pedicles as lateral elements of the ribbon synapses. The isolated terminals or clusters of terminals borne by the short axon of the HII cell also contact cone pedicles as lateral elements rather than contacting rod spherules as lateral elements like HI terminal arborizations. Thus, the monkey like other vertebrates has at least two horizontal cell types which differ in morphology and synaptic connections.
A mechanism for the guidance and topographic patterning of retinal ganglion cell axons
Authors: Silver Jerry , Sidman Richard L.
Published: January 2005

Three dimensional reconstruction, with the use of serial, 1‐μm sections, has revealed a system of oriented intercellular spaces within the undifferentiated optic cup. These large openings appear in the marginal zone of the primitive retina and optic stalk prior to the formation of the first retinal ganglion cell axons. The spaces at the region of the optic disc form sets of long, interconnecting tunnels oriented in the direction of the stalk. The spaces at the back and rim of the cup form blind, radially arranged pockets. The extracellular tunnels of the optic disc region strictly maintain their positions in relation to the optic fissure and, thus, discrete portions of the retina become connected by continuous openings with equivalent regions in the stalk. The path taken by the earliest outgrowing optic fibers is identical to the one previously established by the intercellular tunnels. We propose that the tunnel and pocket layout may provide directional and topographic information to the first forming optic axons.
The paleostriatal system of Caiman crocodilus
Authors: Brauth Steven E. , Kitt Cheryl A.
Published: January 2005

The organization and projections of the presumed homologue of the mammalian corpus striatum, the ventrolateral area (VLA) of the telencephalon, were investigated in the reptile Caiman crocodilus. The caiman VLA was divided into two major cell fields on the basis of cytoarchitectonic criteria: a rostromedial small celled field (VLA s.c.) and a large celled field occupying the dorsal, lateral and ventrocaudal portions of the VLA (VLA l.c.). Histochemical results indicate that the VLA s.c. contains high levels of both cholinesterase and catecholamine (CA) activity. An intense lacy plexus of CA‐containing axons and terminals was found in the VLA s.c. Far less CA activity was found within the VLA l.c. CA activity within the VLA appears to be derived primarily from axons of cells located within a large field of the midbrain tegmentum which is called in this report nucleus tegmenti pedunculo pontinus (TP). In the caiman the VLA also receives projections from the CA‐positive cells of the locus ceruleus and from serotonin containing cells of the midline raphe system.

Anatomical experiments indicate that the VLA L.C. receives projections from neurons in the VLA S.C. and projects upon these subtelencephalic cell groups: the anterior and posterior entopeduncular nuclei (ENa and ENp), the ventral lateral and ventral medial thalamic areas (Avl and Avm), the dorsal nucleus of the posterior commissure (nDCP), and TP. The VLA s.c. projects upon TP. ENa neurons project upon cells in the VLA l.c. Cells of Avl and Avm receive both paleostriatal and cerebellar projections; Avl neurons project upon portions of the rostral telencephalon external to the VLA. NDCP neurons project upon the optic tectum.

The organization and projections of the VLA in Caiman crocodilus are compared to the organization and projections of the paleostriatal complex of the pigeon (Karten and Dubbeldam, '73; Brauth, Ferguson and Kitt, '78) and to the mammalian basal ganglia. The following paleostriatal characteristics appear to be common features in these species and may represent retained characteristics derived from the common ancestor: (1) an ascending catecholaminergic system derived from neurons in the midbrain tegmentum; (2) projections from the basal striatum upon the catecholamine containing neurons of the midbrain tegmentum; (3) an intrinsic cholinergic system; (4) projections upon thalamic cell groups which are also in receipt of cerebellar projections and which project upon telencephalic regions external to the paleostriatum; (5) reciprocal connections between the paleostriatum and the ventral or subthalamus; and (6) projections upon cell groups which project to the optic tectum. The results are discussed in terms of the overall role of the basal ganglia in the neural control of behavior.
Fine structure of noradrenaline nerve terminals in the dorsomedial portion of the nucleus tractus solitarii as demonstrated by a modified potassium permanganate method
Authors: Takahashi Yasuyuki , Tohyama Masaya , Satoh Keiji , Sakumoto Tetsuro , Kashiba Akira , Shimizu Nobuo
Published: January 2005

Fine structure of the noradrenaline (NA) nerve terminals in the dorsomedial portion of the nucleus tractus solitarii (NTS) was investigated by glyoxylic acid—potassium permanganate fixation method. The NA nerve terminals in this area contained a large number of small cored vesicles (SCV) (about 400‐600 Å in diameter) together with a few large cored vesicles (LCV) (about 1000 Å in diameter).

The most frequent feature of NA nerve terminals observed in this area was axo‐dendritic contact. An axo‐axonic contact between NA and non‐NA terminals was also occasionally identified, while no axo‐somatic contact was found in this area as far as examined. At the contact zone between NA terminals and other neuronal elements, the following profiles suggestive of synapse‐like contact were identified: (1) somewhat dense material between contact membranes (intersynaptic filaments); (2) a slight accumulation of dense material adjacent to postcontact membranes; (3) disarrangement of contact membranes and enlargement of the space between these membranes; (4) aggregation of SCV and LCV to contact membranes.

Finally it should be emphasized that NA nerve terminals often made a neuronal cluster or rosette with other neuronal elements, suggestive of a complicated role of NA on NTS function.
Receptive field properties of simple and complex striate neurons in Siamese cats
Authors: Chino Yuzo M. , Shansky Michael S. , Pizzi William J.
Published: January 2005

Responses of striate cortical cells in Midwestern Siamese cats to moving slits and stationary flashed spots were recorded and compared to similar data in common cat controls obtained under identical experimental conditions. Over 90% of the neurons sampled had receptive fields within 10° of the area centralis.

The proportion of binocularly excited cells in Siamese striate cortex was less than that found in the control cats, but more than has previously been reported, and was inversely related to the extent of convergent misalignment exhibited by each animal. Those striate neurons which could be driven by either eye had normal binocular receptive fields and demonstrated normal binocular interaction effects except facilitation.

Receptive field dimensions (length, width, area) were significantly larger in Siamese than in common cats. For the simple cells, strabismic Siamese cats had larger receptive fields than orthophoric Siamese cats. Average spontaneous activity in Siamese cats was significantly higher than in the controls. However, similar encounter rates of simple, complex, and hypercomplex units were observed in both Siamese and common cats, and peak responses were not different. Velocity preference in complex Siamese units was shifted to slower velocities compared to common cat complex cells. A loss of direction selectivity was also revealed in the Siamese simple and complex neurons. Finally, sharpness of orientation tuning was dramatically reduced in Siamese complex cells, and this reduction was directly related to the extent of convergent squint exhibited by each animal. The results are discussed in terms of developmental anomalies and neurophysiological retinal abnormalities in Siamese cats.
The retinal projection to the superior colliculus in the cat: A quantitative study with HRP
Authors: Wässle H. , Illing R.‐B.
Published: January 2005

The projections of cat retinal ganglion cells to the superior colliculus (SC) were examined using the method of retrograde axonal transport of horseradish peroxidase (HRP). Several injections of HRP were made in a single SC after the visual projection to the injection sites had been established physiologically. The HRP injections resulted in a homogeneous distribution of labelled ganglion cells in whole mount preparations of the retinae of both eyes. In the eye contralateral to the injected colliculus, ganglion cells with a crossed projection were labelled in both nasal and temporal retina; in the ipsilateral eye, ganglion cells with uncrossed projection were labelled only in the temporal retina. Analysis of the counterstained retinal whole mounts indicated that at least 50% of all ganglion cells in the nasal retina and 26% in the temporal retina have a crossed projection to SC, and that 24% of all ganglion cells of the temporal retina have an uncrossed projection to the SC.

The morphological classes of retinal ganglion cells have different patterns of crossed/uncrossed decussation and they participate in varying proportions in the retino‐tectal projection. Almost all Alpha cells in the retina send axon collaterals to the SC. Probably only about 10% of the Beta cells project to the SC and at least 80% of all Gamma cells send axons to the SC.
Differntial discrimination of appropriate pathways by regenerating identified neurons in Helisoma
Authors: Murphy A. D. , Kater S. B.
Published: January 2005

Pathway selection by two different identified neurons (neuron 4 and neuron 5) in the pond snail Helisoma was studied by intracellular injection of the fluorescent dye, Lucifer Yellow CH. The axonal projections of these neurons in normal animals are remarkably constant. Axons of neuron 4 and 5 share a common nerve, the esophageal trunk (ET), which bifurcates to form the gastric nerve (GN) and the salivary nerve (SN). Neuron 5's axon traverses the GN and “avoids” the SN; neuron 4's axon traverses the SN and “avoids” the GN. On rare occasions when neuron 4 enters the GN it may make right angle turns, leave the gastric nerve cylinder, and extend directly to its target, the salivary glands. Anomalously located neuron 4 somata also may extend axons to their correct targets via unusual routes. Following ET crush both neurons 4 and 5 regenerate. Sprouts from neuron 5 encountering the bifurcation of the ET basically recapitulate the normal neuron 5 axonal projection. In contrast, neuron 4 sprouts indiscriminately into “correct” and “incorrect” branches of the ET. These experiments indicate that pathway selection by growing neurites can be differentially and specfically regulated for different neurons of the same nerve trunk. The fidelity of different regenerating neurons for selecting nerves which normally contain their axons differs. Though the mechanism of pathway selection cannot yet be identified, the regenerate axonal projections cannot be accounted for by direct guidance of sprouts by the surviving distal axon segments, as has been reported for some identified neurons in the leech.
Subnuclear organization of the ophidian trigeminal motor nucleus.I. Localization of neurons and synaptic bouton distribution
Authors: Moody Sally A. , Meszler Richard M.
Published: January 2005

Among the Reptilia the morphology of the trigeminal (V) motor nucleus is a rather good indicator of the sophistication of jaw kinetics. As it becomes more complex, the nucleus shifts ventrolaterally and becomes divisible into subnuclear groups. The cottonmouth moccasin, a pit viper with very finely developed jaw musculature and kinetics, has a very large V motor nucleus. It is divisible into three subnuclei: the ventral and intermediate, containing predominantly large neurons (40–60 μm), and the dorsal subnucleus, containing only small neurons (20 μm).

Ultrastructural study has indicated that these subnuclei can also be characterized according to the types of boutons synapsing on the cells. The soma of neurons in the ventral and intermediate subnuclei have up to 50% of their profile covered with clusters of boutons. The neurons of the dorsal subnucleus usually have only one cluster of two to three boutons per profile. Both cell types have more boutons containing spherical vesicles in axo‐dendritic synapses than those containing flattened vesicles, and approximately equal numbers of these boutons in axosomatic contacts. However, the small cells have proportionately more boutons containing spherical vesicles synapsing on them.

Boutons similar to those described in mammalian spinal cord were identified in the snake V motor nucleus. Small terminals containing spherical (S) or flattened (F) vesicles and terminals associated with postsynaptic cisternae (C) or with dense bodies (T) are commonly found in the ventral and intermediate subnuclei. C‐ and T‐boutons are rare in the dorsal subnucleus. Large terminals with multiple active sites and postsynaptic dense bodies (M) and their associated, small, preterminal boutons (P) were not observed in the snake V motor nucleus. Boutons containing only large granular vesicles (G) were also not observed.

We suggest that the ventral and intermediate subnuclei consist of α‐ and possibly β‐motoneurons and the dorsal subnucleus contains γ‐motoneurons. This anatomical segregation of function may be important to the physiology of ophidian mastication, which is quite different from that of mammals. However, there do exist several morphological similarities to mammals, suggesting that the snake brainstem may be a good model for comparative structure–function correlations.
Somatosensory thalamus of a prosimian primate (Galago senegalensis). I. Configuration of nuclei and termination of spinothalamic fibers
Authors: Pearson J. C. , Haines D. E.
Published: January 2005

The configuration of somatosensory relay nuclei and termination of spinothalamic fibers were studied in the dorsal thalamus of a prosimian primate (Galago senegalensis) using Nissl, Klüver and Barrera ('53), Weil ('45), and Fink and Heimer ('67) methods. The ventral posterolateral nucleus (VPL) is divided into medial and lateral parts (VPLm and VPLl, respectively) by a sheet‐like lamina of fibers. Spinothalamic input to Galago VPL is somatopically arranged; input from the forelimb terminates in VPLm and that from hindlimb in VPLl. In addition, preterminal debris in caudal VPL is dense and organized into “parcellated bursts” (terminology of Mehler, '69). Consequently, the nature of the spinothalamic debris in VPL of Galago is similar to that reported for higher primates (Mehler et al., '60). Located dorsomedial to the rostral extension of VPL is a zone of large, deeply staining cells designated as the ventral intermediate nucleus (Vim). Following hemisection at either cervical or lumbar spinal cord levels, preterminal debris, independent of that coursing into VPL, enters the Vim. This substantiates the presence of an intermediate nucleus (i.e., Vim) between VPL and the more rostral ventral lateral nucleus.

In the medial thalamic region, axonal degeneration is located in the central lateral nucleus (CL) and in the densocellular and the multiform portions of the dorsomedial nucleus. Only fibers of passage are identified in the centre median, the paracentral and the subparacentral nuclei. The posterior nuclear group (PO) in Galago is divided into medial and lateral parts designated as POm and POl, respectively. In addition, PO contains three distinct nuclei: 1) the magnocellular (MC) portion of the medial geniculate nucleus; 2) the nucleus limitans (Lim); and 3) the suprageniculate nucleus (SG). Following spinal cord hemisection, preterminal debris is located throughout the POm and around cells of the MC. Lim and SG contain no discernible degeneration. Preterminals are also found in a group of cells designated as the caudal part of the central lateral nucleus (CLC).
An experimental study of the ventral striatum of the golden hamster. I. Neuronal connections of the nucleus accumbens
Authors: Newman Richard , Winans Sarah Schilling
Published: January 2005

As part of an experimental study of the ventral striatum, the horseradish peroxidase (HRP) method was used to examine the afferent and efferent neuronal connections of the nucleus accumbens. Following iontophoretic applications or hydraulic injections of HRP in nucleus accumbens, cells labeled by retrograde transport of HRP were observed in the ipsilateral telencephalon in the posterior agranular insular, perirhinal, entorhinal, and primary olfactory cortices, in the subiculum and hippocampal field CA1, and in the anterior and posterior divisions of the basolateral amygdaloid nucleus. In the diencephalon, labeled neurons were present ipsilaterally in the central medial, paracentral and parafascicular intralaminar nuclei, and in the midline nuclei parataenialis, paraventricularis, and reuniens. Retrograde labeling was observed in the ipsilateral brainstem in cells of the ventral tegmental area and dorsal raphe. Many of these projections to nucleus accumbens were found to be topographically organized.

Anterograde transport of HRP from nucleus accumbens demonstrated ipsilateral terminal fields in the ventral pallidum and substantia nigra, pars reticulata.

The afferent projections to nucleus accumbens from the posterior insular and perirhinal neocortices, intralaminar thalamus, and the dopamine‐containing ventral tegmental area are analogous to the connections of the caudatoputamen, as are the efferents from nucleus accumbens to the substantia nigra and ventral globus pallidus. These connections substantiate the classification of nucleus accumbens as a striatal structure and provide support for the recently proposed concept of the ventral striatum. Furthermore, the demonstration that a number of limbic system structures, including the amygdala, hippocampal formation, entorhinal cortex, and olfactory cortex are important sources of afferents to the nucleus accumbens, suggests that the ventral striatum may serve to integrate limbic information into the striatal system.
Postnatal development of dopaminergic cells in the rat retina
Authors: Kato S. , Nakamura T. , Negishi K.
Published: January 2005

By means of a histofluorescence technique (FGS method), a postnatal ontogeny of dopaminergic neurons (DA‐cells) in the retina was studied in rats which had been born and reared under diurnal lighting (LD), reversed lighting (DL), constant lighting (LL), or continuous dark conditions (DD). The time of first appearance of DA‐cells was not altered by any of the above conditions; weakly fluorescent cell bodies were visible at about the 10th postnatal day. After the eyes were open the DA fluorescence of the cell body was gradually increased in intensity in all LD, DL, and LL rats, but not for DD rats. At the 16–17th day the processes of the cell first became visible, extending laterally to the inner plexiform layer. The somata and their processes appeared to be well developed at the postnatal 4–6th week, and they resembled those of the adult rat. On the other hand, the DA‐cells in the DD rats showed a weak fluorescence in both the somata and their processes. When the DD rats were transferred and reared under LD conditions for 1–3 days, the DA fluorescence was increased. These results strongly suggest that the initiation of retinal DA synthesis is independent of environmental lighting condition, but an adequate light stimulus is required for continued normal development of DA‐cells. Unlike in the rat, fluorescent cells in the guinea pig and chick retinas were observed to be fairly mature at birth or hatching. The developmental pattern of DA‐cells in the three species examined coincides with the maturation of visual function.
Development of the dorsal lateral geniculate nucleus in normal and visually deprived siamese cats
Authors: Robertson T. W. , Hickey T. L. , Guillery R. W.
Published: January 2005

Neuronal cell bodies in the lateral geniculate nucleus of normal and of monocularly‐deprived Siamese cats have been measured. Seventeen normally reared Siamese cats, ranging in age between 20 and 120 days, were used to determine rates of normal geniculate cell growth. A second group of five adult Siamese cats reared from birth with the lids of one eye closed were used to study the effects of monocular visual deprivation upon geniculate cell size. For each of the normal and visually deprived Siamese cats, the cross‐sectional areas of 600 lateral geniculate cells were measured from camera lucida drawings of Nissl preparations.

During normal development the geniculate cells rapidly increase in size during the first postnatal month of life and reach their adult size sometime between days 28 and 56. While this course of geniculate cell growth is similar to that seen in normally pigmented cats, the pattern of change seen after monocular deprivation is quite different in Siamese cats from that found in normally pigmented cats. In Siamese cats the regions of the nucleus receiving a contralateral projection from the deprived eye appear to be shielded from the effects of binocular competition. Cells throughout lamina A and in the abnormal, contralaterally innervated segment of lamina A1 show only about a 10% reduction in cell size. There are no noticeable differences between the parts of lamina A in the binocular and monocular segments of the nucleus. Cells in the ipsilaterally innervated segment of lamina A1, in contrast, show deprivation‐induced changes that average 27.1%.

Two mechanisms are proposed to explain why some geniculate cells in Siamese cats appear to be shielded from binocular competition: one depends on possible interactions between geniculo‐cortical cells lying in adjacent parts of the same geniculate lamina, and the other depends on an anatomical segregation of the cell type (“Y‐cells”) most heavily affected by the binocular competition. Each proposed mechanism is related to earlier observations on monocularly deprived, normally pigmented cats.
Pattern of development of ascending and descending fibers in embryonic spinal cord of chick: I. Role of position information
Authors: Nornes Howard O. , Hart Henry , Carry Michael
Published: January 2005

Previous studies on the rigid time and position pattern of embryonic spinal cord development are extended to include the pattern of growth of axonal processes. This study was designed to analyze the position of axons in the marginal zone as they course (fasciculate) in the ascending and descending direction from a single spinal segment. Injections of 3H‐proline were made into L1 or T6 of chick embryos of stages 21–29 (3.5–6 days of incubation). The location of radioactive label in the marginal zone was analyzed autoradiographically to show the location of labeled axons originating from the injected segment. In the early stages of development (stage 21), the labeled descending axons were located in the most ventromedial aspect of the marginal zone. The labled ascending axons were located more laterally and to the perimeter of this zone. In stages 27–29, the labeled axons near the site of injection were located in the inner two‐thirds of the marginal zone, and in the progressively more rostral levels the label shifted laterally and to the perimeter in a laminar pattern. It was concluded that the labeled ascending axons from an individual spinal segment layer upon the axons which originate from the more rostral segments. How this rigid time and position pattern of axonal growth can impart a topographic order into fiber tracts of the spinal cord was discussed.
Gradients between nasal and temporal areas of the cat retina in the properties of retinal ganglion cells
Authors: Stone Jonathan , Leventhal Audie , Watson Charles R. R. , Keens Jeremy , Clarke Rosemary
Published: January 2005

Evidence is presented of gradients between nasal and temporal areas of the cat's retina in the properties of their ganglion cell populations. Mean ganglion cell size is greater in temporal retina than in nasal retina, partly because the α‐ and β‐cells of temporal retina are distinctly bigger than their counterparts in nasal retina, and partly because more medium‐sized cells, and fewer small cells, are to be found in temporal retina. This high proportion of medium‐sized ganglion cells may reflect a high proportion of β‐cells or of the medium sized γ‐cells described by Stone and Clarke ('80). Several of these differences can be related to prior morphological, electrophysiological, and behavioural observations in the cat, and similar differnces have been reported in several other mammalian species. Evidence is presented that, in the cat, at least some of these differences are less marked near the vertical meridian of the retina than more temporally or nasally. The present results may therefore, be evidence of a nasal‐temporal gradient in retinal structure and function common to many mammals, and distinct from previously recognised gradients in ganglion cell properties related to the area centralis and visual streak specialisations.