bluuebunny/crossref_metadata_2025 huggingface dataset:
Cytochemical identification of cholinergic amacrine cells in cat retina
Authors: Pourcho Roberta G. , Osman Kamal
Published: January 2005

Golgi studies of cat retina have revealed the presence of matching subpopulations of starburst‐like amacrine and displaced amacrine cells that are morphologically similar to the cholinergic cells of rabbit retina. The displaced amacrines appear identical with the A14 cells described by Kolb et al. (Kolb, Nelson, and Mariani: Vision Res. 21:1081‐1114, 1981). In order to determine whether these cells may be cholinergic, we carried out autoradiography to localize newly synthesized (3H)acetylcholine and immunocytochemistry to demonstrate the distribution of choline acetyltransferase. Autoradiographs showed labeling in somas of both amacrine and displaced amacrine cells. Choline acetyltransferase was found in amacrine cells that ramify in sublamina a of the inner plexiform layer and in displaced amacrine cells ramifying in sublamina b. The pattern of cholinergic neurons in the cat is similar to that in other vertebrates and suggests that acetylcholine may play an important and consistent role in retinal function.
Distribution of altered hippocampal neurons and axons immunoreactive with antisera against neuropeptide Y in Alzheimer's‐type dementia
Authors: Chan‐Palay V. , Lang W. , Haesler U. , Köhler C. , Yasargil G.
Published: January 2005

This paper provides detailed information on the distribution of neuropeptide tyrosine (neuropeptide Y; NPY) immunoreactive neurons and fibers in the hippocampal region of eight neuropathologically confirmed cases of Alzheimer's‐type dementia (ATD) at postmortem. These neuronal networks are detected by a polyclonal antibody raised against the unconjugated peptide and controls were obtained by using liquid phase absorption immunocytochemistry. The description covers the subfields area dentata, CA3 and CA1, the subicular complex, and the entorhinal area. The hippocampal regions in which the NPY‐i neuron networks are most severely affected are the hilus, CA1, the parasubiculum, and the entorhinal cortex. Less obvious reductions occurred in CA3, subiculum, and the presubiculum. Parallel semiquantitative estimates were made of the numbers of neuritic plaques and neurofibrillary tangles in the other hippocampus of the brains in every ATD case. The areas of heaviest pathological changes by these indices are CA1 and the entorhinal cortex. The subicular complex CA3 and the area dentata are less affected. These findings show that the areas with the most severe loss of NPY‐i neurons and axons, CA1 and the entorhinal cortex, are the same as those areas most severely affected by the other indices of ATD. Thus NPY‐i networks are involved in the ATD disease process. However, other NPY‐i networks survive, in some subfields better than in others. The cumulative evidence suggests a population of hippocampal peptide neurons that are remarkably resistant in terminal neurological disease. These neurons have the capability to participate in the maintenance of minimal functioning circuits in target areas of the disease and as such hold significant links for our understanding of synaptic plasticity in disease.
Ultrastructural features of the ventromedial region of the laminar nucleus in the red‐eared turtle (Chrysemys scripta elegans)
Authors: Drakontides Anna B. , Browner Robert H.
Published: January 2005

The nuclei of the torus semicircularis, in particular the laminar nucleus, have been functionally implicated in sound localization, vocalization, and mating behavior. In the red‐eared turtle the ventromedial region of the laminar nucleus (containing two discrete dense cellular areas and the surrounding neuropil) was examined electron microscopically in the present study.

Neuronal cell bodies in the two cellular areas were different in size, shape, cytoplasmic constitutents, and their relationship to each other. Cell bodies in the layer beneath the ependymal surface were almost always surrounded by lamellae while cell bodies in the layer above the central nucleus were in close apposition. We are speculating that cell bodies in the superficial layer may be neuroendocrine in nature. This speculation is based on the presence of lipidlike droplets within cell bodies, and previous findings indicating steroid binding and synthesis in this region in reptilian brains. Cell bodies located above the central nucleus were characteristic in that they contained lamellar bodies and extensive well‐developed Golgi regions. Closely apposed groups of these cell bodies were frequently surrounded by or in close apposition to large axonal profiles. These profiles were filled with clear core vesicles, numerous mitochondria, and clusters of small dense core particles. Synaptic contacts between large axonal profiles and cell bodies were not observed. The neuropil surrounding cell bodies of the inner layer of this region of the laminar nucleus contained glomeruli composed of a central axon surrounded, and in synaptic contact, with dendrites. Throughout the area of the laminar nucleus studied, synapses appeared to be primarily of the asymmetrical type.
Neuromuscular relationships in a muscle having segregated motor endplate zones. I. Anatomical and physiological considerations
Authors: Wines Melvin M. , Hall‐Craggs E. C. B.
Published: January 2005

The cranial portion of the rat anterior gracilis muscle is innervated by the obturator nerve at two discrete motor endplate zones of which the distal s supplied by well‐defined branches of the nerve. Prior to the use of this muscle in a study of motoneuron sprouting, further morphological and physiological studies have shown that its fibers vary in length but a number traverse the whole muscle or are long enough to extend through both endplate zones. The distribution of muscle fiber types is typical of a rat fasttwitch muscle, and each fiber is innervated at a single endplate. Myography showed that the spinal cord segments, which may contribute to the muscle's innervation, are L2, 3, and 4, of which L3 is constant and predominant, and that denervation of the distal endplate zone leads to a 50% reduction of the maximum isometric tension developed by the muscle.

Antidromic stimulation of nerves supplying the distal endplate zone produced contraction of the proximal part of the muscle and, following similar antidromic stimulation, intracellular recordings made at proximal zone endplates showed the presence of endplate potentials. It was concluded from these data that endplates at both the proximal and distal zones can form part of the same motor unit.
Trigeminotectal and other trigeminofugal projections in neonatal kittens: An anatomical demonstration with horseradish peroxidase and tritiated leucine
Authors: McHaffie John G. , Ogasawara Kosuke , Stein Barry E.
Published: January 2005

The trigeminal projection to the superior colliculus in neonatal kittens was studied by using both anterograde and retrograde neuroanatomical tracing techniques. Trigeminothalamic observations also were made. In the first series of experiments, horseradish peroxidase was injected into the superior colliculus in kittens on the day of parturition and in adult cats. Retrogradely labeled cells were found throughout the contralateral sensory trigeminal complex: the greatest numbers of cells were concentrated in pars oralis, with fewer in the principal nucleus, and fewer still in pars interpolaris and pars caudialis. Thus, the distribution pattern of trigeminotectal cells in neonates is similar to that in adult animals.

In the second series of experiments, we injected tritiated leucine into the rostral portion of the spinal trigeminal nucleus in neonatal kittens and adult cats and compared the laminar and spatial distribution of anterogradely transported label in the superior colliculus and thalamus. Terminal label was observed in both structures in animals as young as 1‐2 days postpartum. The label in the superior colliculus was overwhelmingly contralateral and formed a tier of discontinuous patches in the stratum griseum intermediale and, in a more diffuse manner, in the stratum griseum profundum. Most of the patches were located in the rostral 80% of the superior colliculus and were 60‐280 μm in width. Although the size of the patches was smaller in the neonates, their distribution was similar to that in adult cats. Thus, with the exception of the difference in patch size, the terminal pattern of trigeminotectal projections is essentially adultlike at birth. The dense pattern of contralateral terminal label in the arcuate division of the ventrobasal complex also was similar to that of the adult cat, as was the trigeminal projection to the supraoculomotor gray.

These data indicate that the development of the spatial organization of a major ascending somatosensory pathway to the superior colliculus (and to the thalamus) is largely a prenatal event. It is likely that the further maturationn of these systems during postnatal life is limited to fine changes in axonal terminals and synaptic formation within prenatally determined terminal territories. The in utero maturation of these trigeminofugal projections is necessary to enable the newborn kitten to utilize the perioral tactile cues necessary for early orientation and suckling behaviors.
The organization of the motoneurons innervating the axial musculature of vertebrates. I. Goldfish (Carassius auratus) and mudpuppies (Necturus maculosus)
Authors: Fetcho Joseph R.
Published: January 2005

The motoneurons innervating different regions of the myomeres in goldfish and mudpuppies were examined by applying HRP to the musculature or to branches of spinal nerves. In goldfish, the populations of motoneurons innervating epaxial or hypaxial muscle occupied similar positions in the motor column and had similar size distributions. There was no relationship between the size or location of a motoneuron in the motor column and the dorsoventral location of the muscle it innervated in the myomeres. Instead, different populations of motoneurons innervated the functionally different red and white musculature. The red muscle was innervated only by small motoneurons that occupied the ventral portion of the motor column. Their small axons passed lateral to the Mauthner axon in the cord, and most of them traveled in a separate branch of each spinal nerve that ran in the horizontal septum to the red muscle. The white muscle was innervated by a population of motoneurons that did not innervate red. They were large and they occupied a characteristic position in the extreme dorsal part of the motor column. Their large axons traveled medial to the Mauthner axon in the cord and entered branches of spinal nerves running deep in the epaxial or hypaxial muscle. The white muscle was probably also innervated by some smaller motoneurons similar to those innervating red; however, these may have been motoneurons whose axons ran through white muscle to reach other muscle. The large motoneurons innervating only white muscle are similar to the primary motoneurons identified in developmental studies in teleosts (Myers: Soc. Neurosci. Abstr. 9:848, '83); the smaller ones, innervating both red and white, are like secondary motoneurons. Therefore, in goldfish, motoneurons having different morphology and developmental history also innervate different regions in the myomeres.

The motor column in mudpuppies was, in general respects, similar to the column in goldfish. There were large primary motoneurons and small secondary ones. Though there were slight differences in the locations of motoneurons filled from nerves entering epaxial and hypaxial muscle, their distributions in the cord overlapped substantially.

The motor columns in these two anamniotes differ substantially from the motor columns in those amniotes that have been studied. In amniotes, the motoneurons innervating epaxial and hypaxial muscles are spatially segregated in the cord (Smith and Hollyday: J. Comp. Neurol 220:16‐28, '83; Fetcho: J. Comp. Neurol 249:551‐563, '86). The absence of a comparable segregation in goldfish and mudpuppies implies that the medial motor column has undergone a major reorganization during the evolution of vertebrates.
Ultrastructural organization of choline acetyltransferase‐immunoreactive fibres innervating the neocortex from embryonic ventral forebrain grafts
Authors: Clarke Deborah J. , Dunnett Stephen B.
Published: January 2005

Suspension grafts of foetal tissue rich in cholinergic neurones were transplanted into the frontoparietal cortex of rats that had previously undergone deafferentation of the extrinsic cholinergic innervation of the cortex by injection of ibotenic acid into the nucleus basalis magnocellularis. The cortical tissue containing the graft was processed for electron microscopic immunocytochemistry by using a monoclonal antibody to choline acetyltransferase (ChAT) in order to examine the contacts established between cholinergic fibres from the graft and the host neocortex. The density, distribution, and targets of this graft‐host innervation were compared with those seen in the intact and deafferented cortex. ChAT‐positive fibres in both grafted and control animals formed extensive synaptic connections with various cortical neural elements–those of graft origin being of similar morphology to those in the intact cortex. However, the distribution of postsynaptic cortical targets of the graft‐derived ChAT‐immunoreactive boutons was abnormal, such that a greater percentage of such terminals formed synaptic contacts with neuronal perikarya, especially layer V pyramidal neurones, than was seen in control brains. It is possible that the formation of new synaptic contacts between the embryonic graft and host frontoparietal cortex may, in part, be necessary for the restoration of functional activity that has been previously reported in these grafted animals.
The organization of hypothalamocerebellar cortical fibers in the squirrel monkey (Saimiri sciureus)
Authors: Haines D. E. , Dietrichs E. , Culberson J. L. , Sowa T. E.
Published: January 2005

The organization and distribution of hypothalamocerebellar cortical fibers in squirrel monkey were investigated by using horseradish peroxidase (HRP, WGA‐HRP) and 3H‐leucine as anterograde tracers. Following hypothalamic injections, anterogradely labeled fibers coursed bilaterally through the periventricular gray (ipsilateral preponderance) and into the cerebellar white matter. Sparse numbers of labeled fibers appeared to descend into the reticular formation and enter the cerebellum via the brachium pontis.

The pattern of cerebellar cortical labeling does not conform to that of mossy or climbing fibers. Labeled axons enter and branch within the granular layer, proceed around Purkinje cell somata, and enter the molecular layer. Within the latter some labeled fibers branch outwardly in a fanlike manner whereas others ascend before branching. Many fibers within the molecular layer ultimately assume an orientation that is similar to that of parallel fibers. The distribution patterns of hypothalamocerebellar cortical axons resemble those reported for monoaminergic fibers in the cerebellar cortex. Afferent fibers to the cerebellar cortex (including hypothalamocerebellar) that do not terminate as mossy or climbing fibers may collectively constitute a third general category of cerebellar afferent axons. On the basis of their distribution within all cortical layers these fibers are designated as multilayered fibers.

The morphology of multilayered fibers stands in contrast to the presumptive mossy fiber labeling seen in lobules IX and X following large injections. Such labeling may represent a subpopulation of hypothalamocerebellar fibers or result from enzyme deposition in areas bordering the hypothalamus that project to cerebellar structures.
Effects of unilateral and bilateral cochlea removal on 2‐deoxyglucose patterns in the chick auditory system
Authors: Heil Peter , Scheich Henning
Published: January 2005

The 2‐deoxyglucose (2DG) method was used to map functional activity in the auditory system of chicks that had been subjected to unilateral or bilateral cochlea removal. Following survival times of 1 day to 4 weeks, chicks were exposed to continuous white noise in the 2DG experiments. In monaural subjects nucleus angularis and nucleus magnocellularis showed faint 2DG uptake on the side contralateral to the intact ear. In the binaural nucleus laminaris, the asymmetrical and almost mirror‐imaged labeling pattern (Lippe, Stewart, and Rubel: Brain Res. 196:43–58, '80) was produced. The superior olive (OS) was strongly labeled on the ipsilateral side, whereas the contralateral OS showed only a slight 2DG uptake at its medial border. The lateral lemniscus and nucleus lemnisci lateralis, pars ventralis (LLv) showed stronger activation on the contralateral side. Both Nissl stains and 2DG patterns provide evidence that nucleus ventralis lemnisci lateralis (VLV) can be subdivided into an anterior (VLVa) and a posterior (VLVp) part. Whereas VLVp is labeled only contralaterally, VLVa is labeled on both sides with similar intensity. Nucleus mesencephalicus lateralis, pars dorsalis (MLD) is strongly labeled throughout contralaterally. The ipsilateral MLD shows a defined ventral portion of high 2DG uptake. Intensity of labeling here is symmetrical to the corresponding area of the contralateral MLD. These symmetrical patterns were related to the tonotopic organization of MLD, which was mapped in intact animals by using tone stimuli. Assuming that symmetrical 2DG uptake in monaural animals indicates excitatory input from both ears (EE‐cells), it appears that these EE‐cells occupy a sector of each isofrequency plane in MLD. Nucleus ovoidalis (Ov) generally was stronger labeled on the contralateral side. The columnar organization of field L as seen in monaural chicks has already been described (Scheich, Exp. Brain Res. 51:199–205, '83). In bilaterally deafened chicks, MLD, Ov, and layer L2 of field L showed strong but spatially restricted 2DG accumulation in contrast to absence of labeling in peripheral nuclei.

The 2DG patterns in monaural chicks are likely to reflect excitatory input within the auditory system. In addition they reveal new insights into the functional organization of some of its nuclei. In particular, they support the notion that MLD contains maps of several interaural integration mechanisms similar to field L. Labeling in the auditory system of bilaterally deafened chicks may result from descending projections or from other than auditory inputs.
Mystacial vibrissae representation within the trigeminal sensory nuclei of the cat
Authors: Nomura Sakashi , Itoh Kazuo , Sugimoto Tetsuo , Yasui Yukihiko , Kamiya Hiroto , Mizuno Noboru
Published: January 2005

Somatotopic arrangements of axon terminals of primary afferent fibers innervating follicles of the mystacial vibrissae were examined in the cat by the transganglionic horseradish peroxidase (HRP) method. Forty to 60 hours after injecting HRP into a single or a group of vibrissal follicles, transported HRP was visualized by the tetramethylbenzidine technique. HRP‐labeled axon terminals were distributed in the ventral subnucleus of the principal sensory trigeminal nucleus (ventral Vp), in the oral and interpolar spinal trigeminal nuclei (Vo and Vi), and in the caudal spinal trigeminal nucleus (Vc) (layer I, deep part of layer II, layers III–V) with its spinal extension into the dorsal horn of the first cervical cord segment (rostral C1). In cross sections through the caudal parts of the ventral Vp, Vi, and layer IV of the Vc and rostral C1, a single mystacial vibrissa was represented in a one‐to‐one fashion by a patch of dense terminal arbors of primary afferent fibers. The more dorsally a horizontal row of the mystacial vibrissae was located, the more ventrally was it represented in the ventral Vp, the more ventrolaterally in the Vi, and the more ventrally in layer IV of the Vc and the rostral C1. In addition, the more anteriorly a vibrissa was located in a horizontal row of the mystacial vibrissae, the more medially was it represented in the ventral Vp, the more ventromedially in the Vi, and the more laterally in layer IV of the Vc and rostral C1; the most posteriorly located vibrissae in the horizontal rows of the mystacial vibrissae were represented along the lateral border of the ventral Vp and Vi, and most medially in layer IV of the Vc and rostral C1. Thus, the representation pattern in the ventral Vp was rotated clockwise at about 45° angle in the Vi, and projected as a mirror image in layer IV of the Vc and rostral C1. It was also indicated that the anterior‐posterior arrangement of the mystacial vibrissae was represented in a rostral‐caudal organization within layer IV of the Vc and rostral C1. It was also indicated that the anterior‐posterior arrangement of the mystacial vibrissae was represented in a rostral‐caudal organization within layer IV of the Vc and rostral C1.

Patchy patterns probably replicating the distribution of the vibrissae on the face of the cat were also revealed by the cytochrome oxidase histochemical staining in cross sections through the caudal parts of the ventral Vp, Vi, and layer IV of the Vc and rostral C1.
The influence of testosterone on the sex‐dependent structural asymmetry of the medial habenular nucleus in the chicken
Authors: Gurusinghe Chandan J. , Zappia Joseph V. , Ehrlich David
Published: January 2005

The volume of the left and right medial habenular nuclei of male and female chicks was analysed for evidence of structural asymmetry. The influence of exogenous testosterone on habenular asymmetry was also examined. Male and female chickens were injected intramuscularly with either testosterone enanthate or an oil vehicle on day 2 (15 animals per group) and were perfused at days 5, 12, and 19 respectively. Paraffin sections (8 μm) containing the medial habenular nucleus were stained with cresyl violet and both left and right medial habenular nuclei were measured by planimetry. In control chicks, males had structural asymmetry at day 12, whereas females did not show any structural asymmetry. Testosterone did not appear to influence asymmetry in the male chick but induced structural asymmetry at all three ages in the female to favour the right hemisphere. This study demonstrates a role for testosterone in influencing structural asymmetry of a nucleus in the vertebrate brain.
Corticospinal neurons with branching axons to the dorsal column nuclei in the monkey
Authors: Bentivoglio M. , Rustioni A.
Published: January 2005

Previous work in cats has shown that cells of origin of the corticospinal tract give rise to collateral branches to the dorsal column nuclei (DCN). The present experiments were performed in monkeys (Macaca fascicularis) in which 2% fast blue and 2% diamidino yellow were delivered to infiltrate the dorsolateral funiculus at levels between C2 and C6 and the cuneate nucleus on the same side. Retrograde labelling in the cortex allows simultaneous visualizaion of three classes of neurons: corticospinal tract (CST) neurons, corticocuneate tract (CCT) neurons, and double‐labelled neurons. The morphological features and distribution of CST and CCT neurons are similar to those previously reported from investigations based mainly upon the retrograde transport of horseradish peroxidase (HRP). CST neurons occur in layer V in the pre‐ and postcentral gyri, except for the lateral part (face representation), in the supplementary motor and sensory cortex, and in SII. CCT neurons are present in layer V largely in the postcentral gyrus and in SII. Double‐labelled neurons are present wherever CST and CCT neurons are found. Reconstruction and quantitative data from the pericentral corted show that up to 60% of CCT neurons are double‐labelled and are found predominantly in areas 1 and 2, and that their perikarya are in the size range of the larger CCT neurons.

Comparison of these results with those obtained previously in cats by using HRP and tritiated, enzymatically inactive HRP (3H‐apo‐HRP, Rustioniand Hayes: Exp. Brain Res. 43:237–245, 1981) suggests that CST neurons with branching axons to the DCN are considerably more numerous in monkeys than in cats. To determine whether this difference is caused by the different tracers used in the two species. 2% fast blue and 2% diamidino yellow were delivered in cats to infiltrate the dorsolateral funiculus at C2‐C3 and the nucleus on the same side. The results in these cats are remarkably similar to those obtained in the previous study, which used HRP and 3H‐apo‐HRP: double‐labelled neurons occur predominantly in area 3a and constitute 14–16% of the CCT neurons in the pericruciate area.

The results bear upon mechanisms of descending control and tuning of performances that characterize the dorsal column‐medial lemniscal system, e.g., discrimination of discrete spatiotemporal cues. The species differences may be related to the higher degree of tactile resolution and synchronous control of sensory inflow at the DCN and spinal cord in monkeys relative to cats.
Quantification of thalamocortical synapses with spiny stellate neurons in layer IV of mouse somatosensory cortex
Authors: Benshalom Gadi , White Edward L.
Published: January 2005

The distribution of thalamocortical (TC) and other synapses involving spiny stellate neurons in layer IV of the barrel region of mouse primary somatosensory cortex (SmI) was examined in seven male CD/1 mice. TC axon terminals were labeled by lesion‐induced degeneration, which has been shown to label reliably all TC synapses in mouse barrel cortex. Spiny stellate neurons, labeled by Golgi impregnation and gold toning, were identified with the light microscope prior to thin sectioning and electron microscopy. Analysis of eight dendritic segments from seven spiny stellate neurons showed that most of their synapses are with their dendritic spines, rather than with their shafts. Axospinous synapses are primarily of the asymmetrical type, whereas axodendritic synapses are mainly of the symmetrical type. Dendrites of spiny stellate neurons consistently form thalamocortical synapses, most of which involve spine heads rather than spine stalks or dendritic shafts. From 10.4% to 22.9% of all asymmetrical synapses with dendrites of spiny stellate neurons involve TC axon terminals. In general, this is a higher range than the ranges that characterize the TC synaptic connectivity of dendrites belonging to other types of neurons, implying that spiny stellate neurons are perhaps more strongly influenced by TC synaptic Input than other types of cortical neurons examined previously. Spines involved in TC synapses were distributed irregularly along each of the stellate cell dendrites; about half of the interspinous intervals between these spines were about 5 μm or less. Modulations of the efficacy of TC synaptic input to dendrites of layer IV spiny stellate neurons are discussed in the light of recently reported computer simulated analyses of axospinous synaptic connections.
Neurotensin binding sites in the forebrain and midbrain of the pigeon
Authors: Brauth Steven E. , Kitt Cheryl A. , Reiner Anton , Quirion Remi
Published: January 2005

An autoradiographic method was used to assess the distribution of binding sites for [3H] neurotensin (NT) in the forebrain and midbrain of the pigeon. Within the telencephalon the highest levels of NT binding sites were observed within the hyperstriatum ventrale (HV). Moderate to high levels of NT binding were observed within the archistriatum, neostriatum intermedium, and hyperstriatum accessorium. These telecephalic regions and HV are thought to be comparable to portions of mammalian neocortex. Lower levels of binding sites were observed within the striatal complex including the laterally situated paleostriatum augmentatum and medially situated lobus parolfactorius. The lowest levels of NT binding sites in the telencephalon were observed within the paleostriatum primitivum (PP, considered comparable to mammalian globus pallidus), ectostriatum (comparable to layer IV of mammalian extrastriate visual cortex), field “L” (comparable to layer IV of mammalian auditory cortex), hippocampus, septum, and preoptic area. Despite considerable regional variation, the overall level of NT binding throughout the pigeon telencephalon appears to be significantly higher than that reported for mammals, particularly within pallial areas.

Within the brainstem, moderate levels of NT binding sites were observed in the lateral habenular nuclei, the ventral tegmental area of Tsai, nucleus tegmentipedunculopontinus, pars compacta (comparable to the mammalian substantia nigra, pars compacta), locus coeruleus, and the nucleus subcoeruleus dorsalis. The latter four cell groups contain numerous catecholaminergic neurons. Corresponding catecholaminergic cell groups in mammalian forms also contain high levels of NT receptors. As in mammals, lower levels of NT binding were observed in most diencephalic nuclei. Somewhat higher levels of NT binding were observed within the pretectal nuclei spiriformis lateralis and spiriformis medialis. Moderate levels of NT binding sites were observed within the retinal terminal layers of the tectum (i.e., layers 1–7).

Immunohistochemical experiments (Reiner and Carraway; Brain Res. 341:365–371, '85; Reiner: ARVO Abstracts: p. 185,'86) lccalizing NT and a related hexapeptide, LANT6, have shown that LANT6 is present in retinal ganglion cells, in cells of the paleostraitum, and in the striatoitegmental and striatopretectal fiber pathways of the pigeon. Thus some features of the NT binding observed here in pigeon brain including the existence of substantial NT binding sites in the brainstem catecholamine nuclei, pretectum (nucleus spiriformis lateralis), and optic tectum may reflect the existence, at least in part, of functional receptors for LANT6. The possibility that the tritiated NT ligand used in this study may bind to the same receptors as LANT6 is discussed in detail.
Motoneurons of the tail of young xenopus tadpoles
Authors: Nordlander Ruth H.
Published: January 2005

The purpose of this study was to identify, characterize, and follow the morphogenesis of motoneurons innervating tail myotomes of Xenopus during early and middle larval stages (33–48). Application of horseradish peroxidase to a single myotome results in a column of labeled motor cells extending over four spinal segments. By midlarval stages two morphologically distinct cell types were recognizable in this column‐primary and secondary motoneurons. Primary motoneurons occupied the more rostral and secondary motoneurons the more caudal portions of the column with some overlap of the two populations. Primary neurons developed earlier, were larger, and displayed thicker axons and proximal dendrites. Secondary neurons, in contrast, were smaller, more variable in configuration and dendritic distribution, and displayed thinner axons and dendrites. Development of the labeled motor column during the period observed involved the addition of more labeled neurons, principally secondary cells, and the enlargement of individual cell somata with the progressive elaboration of more and longer dendrites into the developing lateral fasciculus.
Morphology of neurons in the dorsal lateral geniculate complex in turtles of the genera Pseudemys and Chrysemys
Authors: Todd Rainey W. , Ulinski Philip S.
Published: January 2005

The morphology of neurons in the dorsal lateral geniculate complex of pond turtles has been studied by extracellular filling with horseradish peroxidase.

The dorsal lateral geniculate complex is a rostrocaudally elongate structure that includes the nucleus ovalis and dorsal lateral geniculate nucleus of Papez. It is divided into three cytoarchitecturally distinct subnuclei: (1) the subnucleus ovalis, (2) the dorsal subnucleus, and (3) the ventral subnucleus. Each subnucleus consists of a neuropile immediately internal to the optic tract and a cell plate of densely packed somata forming the medial face of the complex. The cell plate contains medial (or parvicellular) and lateral (or magnocellular) sublaminae that are separated by a cell‐poor zone in subnucleus ovalis and the ventral subnucleus. The density and size of somata vary between subnuclei.

Geniculate neurons fall into two distinct groups. Cell plate neurons have somata in the cell plate and vary substantially in morphology. Those in the medial sublamina have fusiform somata and dendrites that extend either mediolaterally (subnucleus ovalis) or run rostrocaudally in the cell plate (dorsal and ventral subnuclei). Those in the lateral sublamina have some dendrites that extend medially within the cell plate and others that extend into the neuropile. The latter dendrites branch and bear arbors of fingerlike, varicose branchlets in the outer half of the neuropile. By contrast, neuropile cells have fusiform somata and dendrites extending concentrically with the optic tract in the neuropile. Both groups of geniculate neurons can be retrogradely labeled by horseradish peroxidase injections in the lateral forebrain bundle.

These results lead to the recognition of two principles of geniculate organization in turtles. The first is that the geniculate complex is divided into three subnuclei that vary in size and density of their neurons. The second is that the complex has a form of laminar organization different than that seen in the geniculate complex of mammals.
Changes in the postsynaptic density with long‐term potentiation in the dentate gyrus
Authors: Desmond Nancy L. , Levy William B.
Published: January 2005

The present study documents alterations in the size of the postsynaptic density (PSD) of synapses formed by entorhinal afferents with granule cell dendritic spines with long‐term potentiation (LTP). These changes appear early and persist for at least 60 minutes after LTP‐inducing conditioning stimulation.

Each animal received test and conditioning stimulation typical of LTP paradigms. Electron microscopic preparation of the dentate gyri from each animal followed conventional procedures. PSD trace lengths of identified asymmetric synaptic profiles were measured. The total PSD length for four categories of synaptic profiles was determined for each third of the molecular layer. PSD surface area per unit volume of tissue (Sv) was then computed from these data. Statical analysis of the Sv data used multivariate analysis of variance. PSD surface area per synapse was also estimated.

Total PSD surface area per unit volume does not change significantly throughout the entire molecular layer with LTP‐inducing conditioning stimulation. However, in the activated portion of the molecular layer, total PSD surface area per unit volume tends to increase with conditioning stimulation.

In the middle third of the molecular layer, total PSD surface area per unit volume associated with the concave spine profiles increases significantly while there is a statistically significant decrease in total PSD Sv associated with the nonconcave spine profiles. The PSD surface area per synapse also increases markedly. Since it seems that there is an interconversion of spine synapses from nonconcave to concave with LTP (Desmond and Levy: J. Comp. Neurol. In press, ′86a), these data suggest that potentiated synapses have larger responses because, in part, they have larger neurotransmitter receptive regions.
Synaptic connections of cholecystokinin‐immunoreactive neurons and terminals in the rat fascia dentata: A combined light and electron microscopic study
Authors: Leranth Csaba , Frotscher Michael
Published: January 2005

We report here on the fine structure and synaptic connections of neurons and axon terminals in the rat fascia dentata displaying immunoreactivity to antibodies against cholecystokinin octapeptide (CCK). In the fascia dentata and hilar region, CCK‐immunoreactivity was confined to nonpyramidal neurons that were similar in appearance to basket cells known to use gamma‐aminobutyric acid (GABA) as neurotransmitter. These neurons exhibited dense accumulations of endoplasmic reticulum and infolded nuclei, and established asymmetric and symmetric synaptic contacts with presynaptic terminals. Among those terminals that formed assymetric synaptic contacts, giant mossy fiber boutons arising from granule cell axons were identified.

Cholecystokinin‐immunoreactive terminals established symmetric synaptic contacts on the cell bodies and dendrites of granule cells. Similar contacts were formed on nonimmunoreactive hilar neurons. Some of these hilar cells were identified as commissural neurons by retrograde filling with horseradish peroxidase (HRP) following injection of the tracer into the contralateral fascia dentata. Synaptic contacts were rarely observed between immunolabeled pre‐ and postsynaptic elements.

The results are discussed with regard to inhibitory processes in the fascia dentata since other studies have shown that CCK is coexistent with GABA in hippocampal nonpyramidal neurons.
Localization of motoneurons innervating the extraocular muscles in salamandra salamandra L. (amphibia, urodela)
Authors: Naujoks‐Manteuffel Christiane , Manteuffel Gerhard , Himstedt Werner
Published: January 2005

The central innervation patterns of the extraocular muscles were investigated in the European fire salamander Salamandra salamandra L. by means of the horseradish peroxidase method. The ipsilateral portion of the nucleus nervi oculomotorii, which is located in the rostral ventral tegmentum mesencephali, supplies the musculi recti inferior and medialis and the musculus obliquus inferior without a clear somatotopic representation of the motoneurons. The musclus rectus superior is innervated mainly by a contralateral portion of this nucleus. A definite nucleus Edinger‐Westphal could not be recognized. The nucleus nervi trochlearis, which rostrally joins the nucleus nervi oculomotorii with a gap of only about 40 m̈m between the nuclei, is situated completely contralateral to the musculus obliquus superior supplied by it. The nucleus nervi abducentis, innervating the musculus rectus lateralis, and the nucleus accessorius nervi abducentis, supplying the musculus retractor bulbi, are found in the ipsilateral medulla oblongata and exhibit a large rostrocaudal extension from the eight cranial nerve to the first root of the vagus nerve. Dendrites of the nucleus nervi oculumotorii and of the nucleus accessorius nervi abducentis extend into neuropil areas receiving primary sensory afferents.
Thalamic projections to retrosplenial cortex in the rat
Authors: Sripanidkulchai Kittisak , Wyss J. Michael
Published: January 2005

The topographic relationships between anterior thalamic neurons and their terminal projection fields in the retrosplenial cortex of the rat were characterized by experiments with the fluorescent dye retrograde labeling technique. The results demonstrate that the anterodorsal (DAD) and anteroventral (AV) nuclei project heavily to retrosplenial granular cortex (Rg) and to a lesser extent to retrospenial agranular cortex (Rag). In contrast, the anteromedial (AM) and lateral dorsal (LD) nuclei project heavily to Rag and more lightly to Rg. Irrespective of terminal field in Rg or Rag, the neuronal cell bodies in AD and AV are organized topographically so that the neurons in the caudal part of each nucleus project to rostral retrosplenial cortex and the neurons in the rostral portion of each nucleus project to the caudal retrosplenial cortex. Further, the ventromedial AD and AV neurons project to rostral retrosplenial cortex, whereas dorsolateral neurons in both nuclei project to caudal retrosplenial cortex. LD neurons display a different topographic organization. The neurons in the medioventral part of LD project primarily to the rostral retrosplenial cortex, and the neurons in lateral LD project to the caudal retrosplenial cortex. This latter projection to the caudal retrosplenial cortex is also contributed to by neurons residing in the mediodorsal part of caudal LD. The neurons in AM that project to the retrosplenial cortex display less segregation than the AV, AD, or LD neurons. In all experiments, a number of neurons in the dorsal ventro‐anterolateral nucleus were labeled by retrosplenial injections. The largest number of cells in this nucleus were labeled after Rag injections, and these were topographically organized such that the neurons projecting to the rostral Rag were located immediately deep to the internal medullary lamina, and the neurons projecting to the caudal Rag were more ventrally located. Very few thalamic neurons have axon collaterals to different areas of the retrosplenial cortex as shown by double labeling experiments. Together, these results demonstrate a highly organized thalamic projection to the retrosplenial cortex.
A quantitative electron microscopic study of the intracellular localization of wheat germ agglutinin in retinal neurons
Authors: Harker Rhodes C. , Stieber Anna , Gonatas Nicholas K.
Published: January 2005

Previous work has established that, following endocytosis, wheat germ agglutinin, like a number of other plasma membrane bound ligands, is transported to the Golgi apparatus‐complex. Previous studies that provided qualitative information about the intracellular distribution of internalized wheat germ agglutinin used techniques that precluded any quantitative conclusions about the relative magnitude of the labeling of endosomes, lysosomes, and the Golgi apparatus‐complex. Using quantitative ultrastructural autoradiography, this study compares the time course and relative magnitude of labeling of various intracellular compartments to the labeling in the Golgi area.

Fifteen minutes after intraocular injection, wheat germ agglutinin is confined to the inner surface of the retina and the immediate subsurface neuropil with little labeling of the retinal ganglion cell perikarya. Thirty minutes after injection, the plasma membrane (6.97 ± 1.17), endosomes (10.27 ± 3.98), smooth vesicles and tubules (1.94 ± 1.66), and lysosomes (2.42 ± 1.21) of the retinal ganglion cells are labeled, while the Golgi apparatus‐complex is not labeled (0.29 ± 0.25). (Figures in parentheses are the calculated relative radioactive source density ± the standard deviation.)

The relative labeling density of the plasma membrane and endosomes decreases somewhat during the next 90 minutes (plasma membrane, 4.76 ± 0.67; endosomes, 7.23 ± 2.02), while the labeling density of smooth vesicles and tubules and of lysosomes rises (smooth vesicles and tubules, 5.56 ± 0.94; lysosomes, 7.76 ± 1.56). The Golgi apparatus‐complex, which is unlabeled at 30 minutes, is weakly labeled at 2 hours (1.26 ± 0.28).

The fact that the lysosomes are already labeled at 30 minutes while the Golgi apparatus‐complex is unlabeled at that time indicates that the transport of wheat germ agglutinin to the Golgi apparatus‐complex is a relatively late phenomenon, and suggests that the bulk of the wheat germ agglutinin destined for lysosomes does not pass through the Golgi apparatus‐complex.
Distribution of vestibular afferents that innervate the sacculus and posterior canal in the gerbil
Authors: Kevetter Golda Anne , Perachio Adrian A.
Published: January 2005

The central distribution of afferents that innervate the macula of the saccule and the crista of the posterior canal was assessed in the gerbil following the direct injection of horseradish peroxidase (HRP) separately into the sensory neuroepithelia of each peripheral receptor organ. Ganglion cells innervating the posterior canal were located in the caudal part of the inferior ganglion, while those cells innervating the saccule were located in the rostral part of the inferior ganglion, scattered in the superior ganglion, and concentrated at the junction (isthmus) between the two. The paths of the central axons of these two groups of ganglion cells through the vestibular root and their division into ascending or descending pathways were similar. However, the distributions of their terminals were different. The posterior canal projected to medial parts of the vestibular nuclear complex. Terminals were found in the medial and superior vestibular nuclei. The posterior canal also projected to the uvula of the cerebellum. The saccule projected to more lateral‐lying brainstem areas. Terminal fields were located in the lateral and descending vestibular nuclei and cell group y. Saccule projections outside the vestibular complex were observed to the lateral cuneate nucleus, the N. gigantocellularis, and the cerebellar cortex. Of the eight areas receiving primary afferent projections from these two organs, only within the medial and descending vestibular nuclei and the cerebellar cortex were overlapping projections observed.
Embryogenesis of arborization pattern and topography of individual axons in N. Laminaris of the chicken brain stem
Authors: Young Steven R. , Rubel Edwin W.
Published: January 2005

This study examined the development of individual axon terminal fields in n. laminaris (NL) of the chicken brainstem. In their mature form axons from the nucleus magnocellularis (NM), second‐order auditory neurons in the chicken brainstem, project bilaterally onto the NL. Axons from the ipsilateral and contralateral NM neurons from spatially segregated, elongated arbors in the dorsal and ventral neuropil of NL, respectively. The long axes of these arbors correspond to physiologically defined isofrequency bands To assess the development of this stereotyped arborization pattern, 6–17 day embryonic chicken brain stems were maintained in vitro while injecting horseradish peroxidase into small groups of axons. Three dimensional reconstructions were made from serial sections and projected onto a cartesian plane for quantitative analyses.

At embryonic day 6 (E6), the ventral axons already course beneath the recently migrated NL neurons. The arrival of the dorsal NM axon branches is delayed and their paths are indirect. They first loop dorsally into the the ventricular layer, where they seem to make specific connections with migrating NL neurons and use these as guides to their appropriate positions in the NL.

During the period from E9 to E17 the dorsal and ventral terminal fields become similar, each adopting properties of the other's initial pattern. The dorsal terminal fields extend to from bands similar to the early ventral terminal fields, while the ventral terminal fields narrow and appear to shift position in order to achieve the tonotopic specificity characteristic of the early dorsal terminal fields.

The results show that a complex, mature pattern of neuronal connections can be formed during development by the combination and reorganization of two simple patterns–each shaped, in turn, by its respective axonal trajectory.