bluuebunny/crossref_metadata_2025 huggingface dataset:
Gap junctions between non‐pyramidal cell dendrites in the rat hippocampus (CA1 and CA3 regions): A combined Golgi‐electron microscopy study
Authors: Kosaka Toshio , Hama Kiyoshi
Published: January 2005

Non‐pyramidal cells in the rat hippocampus were examined with a combined Golgi‐electron microscopic method.

The somata of non‐pyramidal cells were ovoid, about 15 × 30 μm, and several smooth and/or varicose dendrites extended from them. With electron microscopy, Golgi‐impregnated gold‐toned non‐pyramidal cells showed distinctive fine structural features. The somata displayed large nuclei and an extensive perikaryal cytoplasm. The nuclei showed extensive cytoplasmic invaginations, little heterochromatin, conspicuous nucleoli, and intranuclear rods composed of filamentous bundles. The perikaryal cytoplasm was rich in cell organelles such as well‐developed cisternae of rough endoplasmic reticulum and Golgi apparatus, and numerous clusters of free ribosomes and mitochondria. Many synaptic boutons, most of which formed asymmetrical synapses, impinged upon the somata and dendrites. Gap junctions were seen on varicose dendrites of Golgi‐impregnated non‐pyramidal cells. These gap junctions were patch‐like, about 0.1–0.6 μm in diameter, and situated in the stratum radiatum or stratum oriens of the CA1 and CA3 regions 70–230 μm from the soma. They displayed a characteristic cytoplasmic semidense material undercoating the junctional membranes. The gap junctions were usually formed between impregnated and unimpregnated varicose dendrites. Thirteen of a total of 22 gap junctions involving the impregnated dendrites were situated singly, whereas the remaining nine were on four impregnated dendrites in clusters of two or three side by side. In the latter cases, two pairs of junctions were formed between pairs of dendrites running parallel to each other, and each of the other two pairs was formed among three dendrites, appearing to make a dendritic network bridged by gap junctions. One gap junction was seen between two impregnated dendrites originating from two identified Golgi‐impregnated non‐pyramidal cells. These observations revealed unequivocally that non‐pyramidal cells in the hippocampus form gap junctions with one another on their dendrites.
A combined electron microscopic HRP and immunocytochemical study of the limbic projections to rat hypothalamic nuclei containing vasopressin and oxytocin neurons
Authors: Oldfield B. J. , Hou‐Yu A. , Silverman A.‐J.
Published: January 2005

Light microscopic studies in our laboratory have indicated that the lateral septum, amygdala, and ventral subiculum project in a perinuclear fashion to the paraventricular (PVN), supraoptic (SON), and suprachiasmatic (SCN) nuclei (Oldfield et al., '82; Silverman and Oldfield, '84). In the present paper a combined anterograde HRP and immunocytochemical procedure has been used to determine the connectivity between these limbic efferents and peptide‐containing processes emanating from the above mentioned hypothalamic nuclei. Synaptic associations were found to exist between efferents from (1) the septum and both vasopressin (VP) and oxytocin (OX)‐positive dendrites derived from cells in the PVN and SON, (2) the septum and VP dendrites dorsal to the SCN, (3) the ventral subiculum and both VP and OX dendrites arising from the PVN and SON, and (iv) the amygdala and VP dendrites from the PVN. These observations help clarify an apparent discrepancy between electrophysiological data, in which limbic efferents have been shown to influence the activity of VP and OX neurons in the PVN ami SON, and anatomical evidence which indicates only a perinuclear innervation from these sites not encroaching on the hypothalamic nuclei themselves. In each case the synaptic connections are made on dendrites external to the nucleus: those lateral and ventrolateral to the PVN, dorsal to the SON, and dorsal or dorsolateral to the SCN.
Distribution of GABA‐T‐intensive neurons in the rat hindbrain
Authors: Nagai T. , Maeda T. , Imai H. , McGeer P. L. , McGeer E. G.
Published: January 2005

The pharmacohistochemical method previously used to identify the distribution in rat brain of γ‐aminobutyric acid transaminase (GABA‐T)‐intensive neurons has been applied to the rat pons and medulla. The method involves systemic administration of the irreversible GABA‐T inhibitor Gabaculine and the detection, 12 to 15 hours after the injection of the newly synthesized GABA‐T by histochemical means, GABA‐T‐intensive neurons were found to be rich in the following hindbrain structures: inferior colliculus, nuclei of the raphe system, nuclei parabrachialis dorsails and ventralis, nucleus cuneiformis, nucleus vestibularis medialis, nucleus tractus spinalis nervi trigemini, nucleus vagus, nucleus cochlearis, nucleus reticularis lateralis, nucleus ambiguus, nucleus cuneatus lateralis, inferior olive, and reticular formation of the pons and medulla. Neurons of the deep cerebellar nuclei and the rostral portion of the lateral vestibular nucleus were negative for GABA‐T but were surrounded by granular staining indicative of impinging GABA‐T‐rich nerve endings. These results provide further support for the hypothesis that GABA neurons are far more GABA‐T‐intensive than other neurons in the central nervous system.
Retinal pigment epithelial correlates of avian retinal degeneration: Electron microscopic analysis
Authors: Fite Katherine V. , Bengston Lynn , Doran Peter
Published: January 2005

The delayed amelanotic (DAM) strain of domestic chicken is characterized by an early, developmental onset of choroidal inflammation and destruction of both feather and choroidal melanocytes. Secondarily, retinal pigment epithelial (RPE) cells in the peripapillary region develop abnormalities, and a series of progressive histopathological changes ensues which includes reduction and ultimate loss of RPE‐melanin granules and RPE‐cell atrophy. The earliest sign of RPE‐cell abnormality is a dramatic alteration in the distribution of intracellular melanin granules. Apical processes also show a lessening of contact with photoreceptor outer segments, leading in more advanced stages to their retraction and development of retinal detachments. Other progressive alterations in RPE cells include disorganization and loss of basal infoldings; size reductions and density increases in both mitochondria and myeloid bodies from early to advanced stages; appearance of large macrophages in the subretinal space; loss of intercellular junctional complexes; and progressive reduction in the density of melanin granules. These abnormalities appear to spread in a cell‐by‐cell, radial pattern, until widespread areas of the retina become severely pathologic and atrophic. The DAM chorioretinal disorder appears to show many of the histopathologic features which characterize experimentally induced uveitis and other ocular diseases which may result from hypersensitivity to, or autoimmune reaction against, pigments of the uveal tract.
Variability in the terminations of GABAergic chandelier cell axons on initial segments of pyramidal cell axons in the monkey sensory‐motor cortex
Authors: Defelipe J. , Hendry S. H. C. , Jones E. G. , Schmechel D.
Published: January 2005

Chandelier cell axons were studied in the sensory‐motor cortex of adult monkeys. The axonal fields of Golgi‐impregnated chandelier cells in layer II in motor cortex are flattened sagittally. The vertical terminal portions of the axons varied both in length and in the numbers converging to form terminations of‐greater or lesser complexity. Golgi‐impregnated plexuses were embedded in plastic and resectioned serially at 2.5–3.0 μm. A single axonal field could have as many as 400 terminal rows. All lie 3–13 μm beneath pyramidal cell somata. These terminations are not randomly distributed but, instead, form clusters. Further resectioning the plastic sections for electron microscopy revealed that all the terminations are on the initial axon segments of pyramidal cells and all form symmetric synaptic contacts.

In immunocytochemical material stained for glutamic acid decarboxylase (GAD), the enzyme involved in the synthesis of GABA, GAD‐positive boutons were found to form symmetric synaptic contacts with a variety of postsynaptic elements including the axon hillocks and axon initial segments of pyramidal cells. Serial reconstructions from electron micrographs revealed GAD‐positive terminals synapsing with the axon initial segment of pyramidal cells joined by cytoplasmic bridges and forming vertically oriented rows identical to those of chandelier cell terminals identified positively in the resectioned Golgi material. The GAD‐positive terminals forming initial segment synapses were never continuous with GAD‐positive terminals forming axon hillock synapses. The latter probably arise from basket cell axons. Initial segments of pyramidal cell axons in layers II and III were contacted by more GAD‐positive terminals than the initial segments of pyramidal cell axons in layer V. The largest pyramidal cells in layer III received the most synapses. Many larger pyramidal cells, identified as callosally projecting cells by the retrograde transport of horseradish peroxidase (HRP), were shown in serial electron micrographs to possess large numbers of initial segment synapses, comparable to those seen in the immunocytochemical material.

Serial reconstructions of pyramidal cell axons from axon hillock to the first myelin internode in resectioned Golgi, immunocytochemical and HRP material showed that the number of synapses varied from 2 to 52 for layers II and III and from 2 to 26 for layer V. The number of synapses on the axon hillocks varied from zero to 12. The variability in these terminations may be an important factor in the shaping of the functional properties of the pyramidal cells.
Ultrastructure and synaptic contacts of enkephalinergic amacrine cells in the retina of turtle (Pseudemys scripta)
Authors: Eldred William D. , Karten Harvey J.
Published: January 2005

Bistratified amacrine cells of the turtle retina containing enkephalin‐like immunoreactivity were examined with the electron microscope with the aid of peroxidase immunocytochemical techniques. Our goal was to determine the nature and the location of the synaptic contacts of these cells and the intracellular localization of the immunoreactivity. There was a diffuse reaction product throughout the cytoplasm which coated the surfaces of all the organelles and a dense reaction product which filled the core of some large cytoplasmic vesicles (130 nm in dia.). These labeled amacrine cells received conventional synaptic contacts from other unlabeled amacrine cells and ribbon synaptic contacts from unlabeled bipolar cells, in both the proximal and distal inner plexiform layer. These enkephalin‐positive amacrine cells made conventional synaptic contacts containing unlabeled synaptic vesicles (60 nm in dia.), with ganglion cells in the proximal inner plexiform layer and with bipolar cells in the distal inner plexiform layer. These results suggest that enkephalin‐like material coexists with another neurotransmitter within these neurons and that these amacrine cells are able to integrate information from both amacrine cells and bipolar cells and provide synaptic input to bipolar cells, ganglion cells, and possibly other amacrine cells.
Studies of innervation patterns in grafted chick wings
Authors: Neset Monica , Muniak Charles , Edwards Charles
Published: January 2005

The pattern of innervation of 12 day embryonic chick wings was studied by morphological and electrophysiological techniques. Several types of chick wing grafts were performed to investigate the rules governing nerve pattern formation: whether the motor neurons actively seek out and connect with specific muscles or are passively guided and whether cell death plays any role in pattern formation. In each type of graft the outgrowing neurons were confronted with extra targets distal to the elbow. Two grafts replicated lower arm parts in series (proximodistal graft) or in parallel (forearm and hand replicated, in the same pattern of asymmetry in a split limb graft); a third produced a mirror image limb. The flexor carpi ulnaris muscle (F.C.U.) was studied in these limbs.

The innervation of the most distal f.c.u. muscle in proximodistal grafted limbs varied with the extent of host f.c.u. muscle present. The f.c.u. muscles in the split limb graft were always innervated. In both limb grafts the f.c.u. muscles were innervated by the appropriate neurons, as determined by retrograde HRP technique and electrophysiological recordings. This strongly suggests that the motor neurons are able to seek out and connect with their appropriate muscle. Results of the mirror image limb graft suggest that other factors may be involved.

In addition, motor neuron cell counts were performed. From this one can infer that the normally occurring pattern of cell death was not affected by the grafts. Cell death is therefore excluded as a major factor in nerve pattern formation.
Anatomical evidence for medial pulvinar connections with the posterior cingulate cortex, the retrosplenial area, and the posterior parahippocampal gyrus in monkeys
Authors: Baleydier C. , Mauguiere F.
Published: January 2005

Reciprocal connections between the medial pulvinar and the limbic neocortex in monkeys were demonstrated by means of tritiated amino acid injections in the medial pulvinar and the cingulate cortex, and HRP injections in the medial pulvinar. It appears that the medial nucleus of the pulvinar sends projection fibres to the posterior cingulate gyrus (area 23), the retrosplenial area, and the posterior parahippocampal gyrus (areas TH and TF). The labeled terminals were concentrated in two bands, one in the deeper part of layer III and in layer IV, and the other in layer I. These projections were observed to be reciprocal, and the cortical afferent fibers to the medial pulvinar were found to originate from the deep layers of the cortex.

The medial nucleus of the pulvinar was already known to be connected with the prefrontal cortex and with the inferior parietal lobule. Since this nucleus is now demonstrated to be connected with the posterior limbic neocortex, it is envisaged as being the thalamic counterpart of a cortical triad (prefrontal, parietal, and limbic) involved in modulating directed attention.
Regeneration of lumbar dorsal root axons into the spinal cord of adult frogs (rana pipiens), an HRP study
Authors: Liuzzi Francis J. , Lasek Raymond J.
Published: January 2005

Lumbar dorsal roots of adult frogs were crushed or cut and reanastomosed. Following survival times of up to 75 days, the regenerating dorsal roots were recut and anterogradely injury‐filled with horseradish peroxidase. This revealed that in the adult frog, regenerating axons re‐enter the spinal cord. Comparison of the distribution of these axons with that of normal, dorsal root axons showed that there is a partial restoration of the segmental distribution in the gray matter. However, the long ascending sensory tract of the dorsal funiculus was not restored, The dorsal funiculus was markedly gliotic and had relatively few labelled, regenerated axons. The labelled axons that were seen in the dorsal funiculus either extended longitudinally for a distance just beneath the pia, apparently in association with the glia limitans, or traversed the region to enter the dorsal gray matter. Most of the large and small diameter axons that entered the gray matter did so by passing through the region of the dorsolateral fasciculus. Within the gray matter, small diameter, regenerated axons arborized in the region of the dorsal terminal field, a region that has been shown in the normal frog to receive cutaneous afferents only. Many large diameter axons, presumably muscle afferents, arborized in the ventral terminal field, a region shown in the normal frog to receive muscle afferents exclusively. However, many of these large diameter axons had arborizations that extended to both terminal fields, thus suggesting that some abberant connections are made during dorsal root regeneration in the adult frog.
Rat medulla oblongata. I. Cytoarchitectonic considerations
Authors: Kalia Madhu , Fuxe Kjell
Published: January 2005

The goal of thin study was to define the detailed cytoarchitecture of the medulla oblongata of the rat in order to accurately localize immunocytochemically distinct populations of neurons in this region. The cytoarchitectonic features of this region of the rat brain stem were examined in 40 μm thick serial sections of celloidin embedded brains blocked in the Horsley‐Clarke stereotaxic plane. These sections were stained with cresyl violet and examined at a number of different magnifications with a variety of different intensities of staining to demonstrate particular features of the cells in this region. High magnification photomicrographs of this material revealed characteristic features of the various populations of cells.

The results illustrate that the cytoarchitecture of the medulla oblongata of the rat changes remarkably within very short distances in the rostrocaudal direction. These changes indicate the need to study the anatomy and immunocytochemistry of this region in detailed serial sections. The ventral reticular formation of the rat medulla is cytoarchitectonically complex. Nuclear groups such as the lateral reticular nucleus (LRt) contain a number of cytoarchitectonically distinct subnuclei, as does the dorsally located nucleus of the tractus solitarious (nTS) (Kalia and Sullivan, '82). These nuclei occupy a considerable length of the medulla and terminate abruptly at the pontomedullary boundary. A number of other cytoarchitectonic features of the medulla were examined and the detailed characteristics were defined.
Development of the human retina: Patterns of cell distribution and redistribution in the ganglion cell layer
Authors: Provis Jan M. , Van Driel Diana , Billson Frank A. , Russell Peter
Published: January 2005

Neurogenesis in the ventricular layer and the development of cell topography in the ganglion cell layer have been studied in whole‐mounts of human fetal retinae. At the end of the embryonic period mitotic figures were seen over the entire outer surface of the retina. By about 14 weeks gestation mitosis had ceased in central retina and differentiation of photoreceptor nuclei was evident within a well‐defined area which constituted about 2% of total retina area. This area was approximately centered on the site of the putative fovea, identified by the exclusive development of cone nuclei at that location. The area of retina in which mitosis had ceased increased as gestation progressed. By mid‐gestation mitosis in the ventricular layer occupied about 77% of the outer surface of the retina and by about 30 weeks gestation mitosis in the ventricular layer had ceased. Cell density distributions in the ganglion cell layer were nonuniform at all stages studied (14–40 weeks). Densities were highest at about 17 weeks gestation, and by mid‐gestation the adult pattern of cell topography was present with maps showing elevated cell densities in posterior retina and along the horizontal meridian. Cell densities generally declined throughout the remainder of the gestation period, except in the posterior retina, where densities in the perifoveal ganglion cell layer remained high during the second half of gestation. There is a rapid decline in cell density in the foveal ganglion cell layer toward the end of gestation, and it is suggested that the persistence of high densities in the perifoveal region may be related to migration of cells away from the developing fovea. The total population of cells in the ganglion cell layer was highest (2.2–2.5 million cells) between about weeks 18 and 30 of gestation. After this the cell population declined rapidly to 1.5–1.7 million cells. It is suggested that naturally occurring neuronal death is largely responsible for this decline.
The ultrastructural localization of enkephalin and substance P immunoreactivities in the nucleus tractus solitarii of the cat
Authors: Maley Bruce E.
Published: January 2005

In the medial and commissural subdivisions of the nucleus tractus solitarii enkephalin and substance P immunoreactivities were localized within synaptic terminals, unmyelinated axons, and neuronal cell bodies. Both enkephalin and substance P immunoreactivities were contained within synaptic terminals which had a mixture of small clear vesicles and dense core vesicles. The presence of dense core vesicles within both the enkephalin‐and substance P‐immunoreactive terminals was a consistent feature, although they were not associated with the actual synaptic junction. While enkephalin‐ and substance P‐immunoreactive terminals shared a similar morphology, their respective distributions along the dendritic tree were quite distinct. Enkephalin‐immunoreactive terminals contacted mainly the cell body and proximal portions of the dendritic tree. In contrast, substance P‐immunoreactive terminals synapsed predominantly with spines and shafts of small to medium‐sized dendrites. Few substance P‐immunoreactive terminals contacted proximal dendrites and they were never presynaptic to the neuronal cell body. This apparent segregation of synaptic terminals on neurons suggests that enkephalin synapses have a more pronounced effect than substance P terminals.
Cortical projections of the dorsolateral visual area in owl monkeys: The prestriate relay to inferior temporal cortex
Authors: Weller R. E. , Kaas J. H.
Published: January 2005

The dorsolateral visual area (DL) is one of a number of visual areas that have been defined by electrophysiological mapping procedures and cortical architecture in the extrastriate cortex of owl monkeys. The projections of DL were determined by the intra‐axonal transport of 3H‐proline, 3H‐aceytl‐wheat germ agglutinin, and horseradish peroxidase after cortical injections. The major ipsilateral projection of DL defined a new subdivision of the visual cortex in owl monkeys, the caudal inferior temporal cortex. Single injections in DL sometimes produced label in two separate regions in the caudal inferior temporal cortex, suggesting that functional subdivisions exist in this projection zone. Other targets of DL included the region of the frontal eye fields, the dorsomedial visual area, the dorsointermediate visual area (DI), a region of the cortex rostral to DI which we call the temporoparietal cortex, and possibly the ventral (V) and posterior parietal areas. A major feedback projection of DL was to V‐II. Projections from DL to V‐II and the dorsomedial visual area were roughly retinotopic. Projections from DL to the contralateral cerebral hemisphere were to DL and the inferior temporal cortex. Overall, the results support the concept that a major relay of visual information proceeds from V‐I to V‐II to DL and then to the inferior temporal cortex. In addition, similarities in connection patterns of DL in owl monkeys and V4 in macaque monkeys suggest that DL and much or all of V4 are homologous.
Direct cortical projections to the parabrachial nucleus in the cat
Authors: Yasui Yukihiko , Itoh Kazuo , Takada Masahiko , Mitani Akira , Kaneko Takeshi , Mizuno Noboru
Published: January 2005

Direct projections from the cerebral cortex to the parabrachial nucleus in the cat were examined by the horseradish peroxidase (HRP)method. When HRP was injected into the parabrachial nucleus, retrogradely labeled neuronal cell bodies were seen, bilaterally with an ipsilateral predominance, mainly in the orbital gyrus, the lateral bank of the presylvian sulcus, and a restricted region in the infralimbic cortex on the medial surface of the frontal lobe (stereotaxic coordinates; Fr: 22, L: 1, H: ‐1); all labeled neurons were in deep pyramidal cell layer.

After injecting HRP conjugated to wheat germ agglutinin (WGA‐HRP) into the cortical regions where retrogradely labeled neurons were found after injecting HRP into the parabrachial nucleus, anterogradely labeled cortical fibers were traced to the parabrachial nucleus. Corticoparabrachial fibers originating from the orbital gyrus and the lateral bank of the presylvian sulcus ran ipsilaterally through the internal capsule and the cerebral peduncle down to the lower brainstem, whereas those from the infralimbic cortex coursed down ipsilaterally through the medial forebrain bundle. These cortical fibers to the parabrachial nucleus were distributed bilaterally with an ipsilateral predominance. Cortical fiber terminals in the parabrachial nucleus were topographically arranged: Corticoparabrachial fibers from the lateral bank of the presylvian sulcus ended most massively in the dorsal part of the lateral parabrachial nucleus. Corticoparabrachial fibers from the orbital gyrus ended most heavily in the medial parabrachial nucleus and less heavily in the lateral parabrachial nucleus. Corticoparabrachial fibers from the infralimbic cortex ended mostly in the parabrachial regions surrounding the brachium conjunctivum.
The neuronal composition of area 17 of rat visual cortex. II. The nonpyramidal cells
Authors: Peters Alan , Kara Daniel A.
Published: January 2005

In the preceding article the characteristics of the various types of pyramidal cells present in area 17 of rat visual cortex were described (Peters and Kara, '85). In the present article the nonpyramidal cell population of this cortex is considered. It is known from Golgi preparations that in layers II–VIa there are bipolar cells, smooth or sparsely spinous multipolar and bitufted cells with either unmyelinated local plexus or myelinated axons, and chandelier cells. Each of these cell types has been previously examined in Golgi‐electron microscopic preparations. The question now being asked is whether the information about the characteristics of these different types of nonpyramidal cells derived from the Golgi‐electron microscopic studies can be used to identify the cell bodies of nonpyramidal cells in tissue prepared for conventional electron microscopy. If this can be done then the neuronal composition of area 17 can be determined.

It has been found that the cell bodies of bipolar cells can be readily identified because they are elongate and have nuclei with a vertical infolding and few axosomatic synapses, which are of both the symmetric and asymmetric varieties. Evidence is presented to show that there are two types of bipolar cells, small ones and large ones, the large ones being distinguished by their well‐developed endoplasmic reticulum in which the cisternae are arranged parallel to the cell surface. Bipolar cells account for 6% of the neuronal profiles in layer II/III, 3% in layer IV, 5% in layer V, and 2% in layer VIa.

The cell bodies of other types of nonpyramidal cells in layers II–VIa cannot be distinguished from each other in thin sections, because recognition of the different cell types depends upon the characteristics and distribution of their dendrites and axons. However, it is evident that in this group of neurons there are some with small cell bodies and others with large cell bodies, and in both size groups there are varieties of neurons which can be recognized from the characteristics of their perikaryal cytoplasm. All of these neurons have both symmetric and asymmetric axosomatic synapses. The greatest number of these nonpyramidal cells which are not bipolar in form is found within layer II/III, where they account for 7% of all neuronal profiles. These neurons comprise 4% of all neuronal profiles in layer IV, 6% in layer V, and 2% in layer VIa.

Layers I and VIb contain only nonpyramidal cells, but these are different from the ones in layers II–VIa.

Overall, bipolar cells account for 4% of the neuronal profiles encountered in layers II–VIa, and the other nonpyramidal cells account for 6% of the neuronal population. Consequently, in these layers 90% of the neurons are pyramidal cells. These results are considered in relation to analyses of the neuronal population of rat area 17 carried out by previous authors, and in the context of information about the disposition and frequency of nonpyramidal cells derived from the use of antibodies to potential neurotransmitters.
Degeneration of thalamic neurons in “Purkinje cell degeneration” mutant mice. I. Distribution of neuron loss
Authors: O'Gorman Stephen , Sidman Richard L.
Published: January 2005

The Purkinje cell degeneration (pcd)mutation of the mouse is an autosomal recessive allele which previous studies have shown to be the cause of rapid degeneration of nearly all cerebellar Purkinje cells between 18 and 30 postnatal days of age (P18–P30), and slowly developing, progressive losses of retinal photoreceptor cells and mitral cells of the olfactory bulb. Through examination of serial frozen sections alternately stained for Nissl substance and for degenerating neuronal processes, we have found that discrete populations of thalamic neurons degenerate rapidly between P50 and P60. Severely affected nuclei, in which a majority of neurons degenerate, include the central division of the mediodorsal nucleus, the ventral medial geniculate, posterior, posterior ventromedial, and submedial nuclei, and those portions of the ventrolateral and posteromedial nuclei which immediately surround the medial division of the ventrobasal complex. More subtle cell losses occur during the same time period in restricted portions of the lateral ventrobasal, dorsal lateral geniculate, and lateral posterior nuclei, but even at P180 these nuclei are not markedly atrophic.

No common denominator among target cell populations has been established. The pcd allele affects a diverse assortment of specific relay nuclei; degeneration has not been recognized in thalamic nuclei characterized primarily or exclusively by subcortical projections or by cortical projections directed relatively selectively to superficial or deep cortical laminae. The neuronal degenerations in the thalamus are not precipitated by prior or concurrent degeneration of cortical targets or afferent sources, though striking transneuronal changes, including cell death, do develop following thalamic neuronal degeneration in this mutant. No previously described murine mutant phenotype includes the rapid degeneration of highly restricted neuronal populations beginning at these relatively advanced ages.
A Golgi study of the human neostriatum: Neurons and afferent fibers
Authors: Graveland Gerda A. , Williams Roger S. , Difiglia Marian
Published: January 2005

The neostriatum of 20 adult humans was examined in Golgi‐Kopsch and rapid Golgi preparations. At least five types of neurons and four types of afferent fibers are described. Neurons of medium size with spine‐rich dendrites (spiny type I) are the most frequent type. These cells exhibit a greater morphological diversity than those previously studied in the monkey. Also, quantitative data show that, compared to the monkey, spiny type I neurons in man have a greater somal size and dendritic field radius. Although the types of spines are similar, the mean density and radial distribution of spines along dendrites differ in the two species. Morphologic features of the axon, which is usually long with extensive collateral branches, suggest that more than one process from the axon may be efferent. Medium to large neurons with sparsely spined dendrites (spiny‐type II) differ from type I neurons in having a poorer branching and greater radial spread of their dendrites and a lower density of spines. They also differ from spiny type I neurons in their distribution and relative proportion of various spine types. The axon of the spiny type II neuron is long and has collaterals which are poorly arborized in comparison to those of spiny type I cells. Aspiny neurons are of medium (aspiny type I) and large (aspiny type II) size. They have varicose, curved dendrites and a short axon which arborizes mostly within the dendritic field. A group of smaller neurons with more variable dendritic morphology is also seen. Observations suggest that in the human brain the proportion of medium‐sized aspiny neurons and small neurons may be greater than in other species.
Serotoninlike immunoreactivity in the cestode Hymenolepis diminuta
Authors: Webb Rodney A. , Mizukawa K.
Published: January 2005

Serotoninlike immunoreactivity in the cestode Hymenolepis diminuta was studied at the light microscope level by using an antibody specific to serotonin. The rostellum, the cerebral ganglia and commissure, and the strobila contained numerous process‐free, unipolar and multipolar serotoninlike immunoreactive cells. The suckers contained a plexus of branching immunoreactive fibers. In the strobila the multipolar cell bodies were situated laterodorsal and lateroventral to the longitudinal nerve cords, from which neurites were directed to the contralateral and ipsilateral nerve cord to form up to three transverse commissures per proglottid. Secondary varicose branches passed anteriorly, posteriorly, and obliquely along the proglottids at the level of the deep longitudinal muscles. Other varicose multibranching neurites passed centrifugally from the primary and secondary neurites, forming vertebratelike en passant or terminal varicosities on the deep longitudinal muscles with bulbous or spinose terminals at the level of the superficial longitudinal muscles, or in the cortical parenchyma, Serotoninlike immunoreactivity was seen on the external seminal vesicle, the sphincter and cirrus sac, and the proximal portion of the vagina. Varicose terminals were concentrated at the sphincter. The close association of serotoninlike immunoreactive terminals and varicosities with the longitudinal muscles gives credence to the concept that serotoinin functions as a neuromuscular transmitter or modulator in the platyhelminths.
Floccular efferents in the rhesus macaque as revealed by autoradiography and horseradish peroxidase
Authors: Langer T. , Fuchs A. F. , Chubb M. C. , Scudder C. A. , Lisberger S. G.
Published: January 2005

To fulfill its putative role in short‐ and long‐term modification of the vestibulo‐ocular reflex, the flocculus of the cerebellum must send efferents to brainstem nuclei involved in the control of eye movements. In order to reveal the sites of these interactions, we determined the projections of the flocculus by autoradiography and orthograde transport of horseradish peroxidase in five rhesus macaques.

Anterogradely labeled axons collected at the base of the injected folia and coursed caudally and medially between the middle cerebellar peduncle and the flocculus. They swept medially over the caudal surface of the middle cerebellar peduncle, over the dorsal surface of the cochlear nuclei, and then caudally along the lateral surface of the inferior cerebellar peduncle to pass over its dorsal surface in the cerebellopontine angle and terminate exclusively in the ipsilateral vestibular nuclei.

Three contingents of axons could be differentiated. The axons of one group flowed caudally and medially into the y‐group, which clearly received the densest floccular projection. Other, notably thicker, axons of this group continued rostrally and medially to terminate chiefly in the large‐cell core of the superior vestibular nucleus. A second large contingent of thin axons streamed caudal and ventral to the y‐group to form a compact tract adjacent to the lateral angle of the fourth ventricle and dorsal to the medial vestibular nucleus. Fibers from this tract (the angular bundle of Löwy) supplied a sizable projection to the rostral part of the medial vestibular nucleus and modest projection to the ventrolateral vestibular nucleus. A final group of fibers extended caudally and medially from the y‐group in a plexus ventral to the dentate and interposed nuclei to terminate in the basal interstitial nucleus of the cerebellum (Langer, '85), a broadly distributed cerebellar nucleus on the roof of the fourth ventricle.

The flocculus can affect vestibulo‐ocular behavior only through these efferents to the vestibular nuclei and the basal interstitial nucleus of the cerebellum.
Basal interstitial nucleus of the cerebellum: Cerebellar nucleus related to the flocculus
Authors: Langer Thomas P.
Published: January 2005

We have shown that the monkey flocculus is not connected with any of the major, well‐demarcated cerebellar nuclei. There is, however, a broadly distributed interstitial population of neurons in the white matter ventral to the cerebellar nuclei and extending into the peduncle of the flocculus; this population, previously undescribed in the monkey, has reciprocal connections with the flocculus (Langer et al., '85a,b). Several lines of evidence indicate that this collection of neurons, called the basal interstitial nucleus of the cerebellum (BIN/Cb), can justifiably be considered a nucleus.

(1) Injection of horseradish peroxidase (HRP) into the flocculus always labels a group of neurons that lie immediately ventral to the well‐demarcated cerebellar nuclei and extend posteromedially into the lateral margin of the nodulus and rostrolaterally around the caudal surface of the y‐group, infiltrating the peduncle of the flocculus.

(2) In Nissl‐stained material there is a readily seen collection of neurons that are clearly distinct from the overlying cerebellar nuclei, with precisely the same distribution. These neurons have a characteristic morphology: they are intermediate‐sized, chromatophilic, multipolar, and fusiform, and have rapidly tapering proximal dendrites. The cell nucleus is generally placed eccentrically in the cell body, against the plasma membrane or in one pole of the cell. The Nissl substance is usually finely granular in the center of the cell body and forms dense clumps adjacent to the cell membrane.

(3) Anterograde label from injections of HRP or tritiated amino acids into the flocculus extends over the same group of neurons.

In one brain with an HRP injection involving a part of the BIN/Cb there was a patchy, clustered distribution of labeled Purkinje cells extending throughout the flocculus and into the adjacent lateral parts of the simple lobule. The clusters were confined to the medial half of many of the floccular folia.
Compartmentalization of the cat lateral gastrocnemius motor nucleus
Authors: Weeks O. I. , English A. W.
Published: January 2005

The spatial and size distributions of motoneurons which supply the cat lateral gastrocnemius (LG) neuromuscular compartments were examined to determine their anatomical organization. Individual primary muscle nerve branches (PMNB) to LG were isolated by microdissection, cut, and soaked in horseradish peroxidase (HRP). As a control in each case, the entire contralateral lateral gastrocnemius‐soleus (LG‐S) nerve was similarly cut and soaked. Retrogradely labeled motoneurons were identified, their positions plotted, and their sizes measured on both sides of the cord. Results show that extensive overlap exists in the spatial distribution of motoneurons innervating different PMNBs. Labeled cells supplying each PMNB also vary considerably in their sizes. However, both a highly significant topography‐like organization and a preferential size distribution are found between different groups of motoneurons. Neurons which supply proximal compartments occupy more rostral portions of the LG motor nucleus and are among the largest in the pool. Very few small motoneurons innervate proximal compartments. Neurons supplying more distal compartments are distributed in more caudal parts of the pool and contain both large and small cells in relatively equal numbers. If the large cells are alpha and the small cells gamma motoneurons, then proximal compartments are relatively poor in gamma innervation and presumably muscle spindles, and distal compartments are rich in fusimotor innervation.
Neonatal 6‐hydroxydopamine destroys spinal cord noradrenergic axons from the locus coeruleus, but not those from lateral tegmental cell groups
Authors: McBride Russell L. , Ozment Richard V. , Sutin Jerome
Published: January 2005

Subcutaneous injection of 6‐hydroxydopamine (6‐OHDA) in neonatal rats results in sprouting of collateral axons in locus coeruleus (LC) and lateral tegmental noradrenergic neurons. It has been suggested that this sprouting represents maintenance of neuronal membrane area following “pruning” of axon terminals of long projections to cortex and cord. The chemical or surgical lesions of long axons used to produce “pruning” could also result in the loss of some parent cell bodies. We tested the hypothesis that long axon damage, rather than cell loss, is sufficient to produce collateral sprouting of proximal axons in noradrenergic neurons. With neonatal injections of 6‐OHDA at doses which do not produce a loss of LC neurons, there is an 85% decrease in retrograde LC labeling following horseradish peroxidase or true blue injections into the spinal cord but no significant change in the numbers of retrogradely labeled neurons in other noradrenergic cell groups which also sprout collaterals. There is no change in the number of labeled LC neurons following cerebellar injections.

In experiments using the fluorescent dyes diamidino yellow and true blue, the number and distribution of LC neurons labeled from spinal cord and cerebellum injections are similar to those in the horseradish peroxidase experiments. Doubly labeled neurons are found in the caudal two‐thirds of LC in control rats, but as expected, rarely observed in 6‐OHDA‐treated animals.

This study demonstrates that (1) cell loss in the LC is not necessary for sprouting following neurotoxin treatment, and (2) the increased number of norepinephrine (NE) terminals in the pons is not due exclusively to a “pruning effect,” since NE cells outside the LC, which are known to contribute to the hyperinnervation, retain their long projections to the spinal cord.
Timing and positioning of occlusion of the spinal neurocele in the chick embryo
Authors: Desmond Mary E. , Schoenwolf Gary C.
Published: January 2005

The timing and positioning of occlusion of the spinal neurocele were studied in living and serially sectioned chick embryos at stages 8–14. Occlusion occurs in three phases: preocclusion, incipient occlusion, and definitive occlusion. Preocclusion occurs at stage 8. At this time, the neural groove of the spinal cord has not yet closed to form a neural tube. Incipient occlusion begins as early as stage 9 and lasts until stage 11. The neural groove of the cranial spinal cord closes during these stages and incipient occlusion occurs concomitantly with this closure. Seventy‐eight percent of the embryos exhibit incipient occlusion. Incipient occlusion extends along the mid‐somitic region of the neuroaxis, occupying about one‐half the length of the spinal cord. Injection of the brains of living embryos with dyes often reopens incipient occluded areas. Definitive occlusion occurs at stages 11–14 and is present in 89% of the embryos. Definitive occlusion is restricted to mid‐somitic regions, as was incipient occlusion, but it extends approximately two‐thirds the length of the spinal cord. Injection of the brains of living embryos with dyes rarely reopens definitive occluded areas, even when injection pressures are maximal. Six morphological types of definitive occlusion can be identified on the basis of the relative proportions and locations of total and partial occlusion. Closure of the cranial neuropore and roof plate of the hindbrian occurs near the end of the incipient occlusion phase, whereas closure of the caudal neuropore occurs well after definitive occlusion is initiated. Physiological occlusion is due to both anatomical occlusion and back pressure, which prevent the flow of liquids into a blind, narrow tube. Further studies are required to document the reopening phases of the spinal neurocele, as well as the forces involved in causing and maintaining occlusion and reopening.
Topographical projections of the cerebral cortex to the subthalamic nucleus
Authors: Afsharpour Salman
Published: January 2005

Corticosubthalamic projections in the rat were investigated using the autoradiographic anterograde axonal tracing technique. After unilateral injections of tritiated amino acids in the cerebral cortex, projections to the ipsilateral subthalamic nucleus (STH) could be found arising only from the frontal agranular cortex and the zone of MI‐SI overlap. Injections into granular areas of the cortex (e.g., somatosensory and visual areas) did not result in labeling in STH. Following injections in the frontal agranular cortex, labeling was present in the ipsilateral but not the contralateral STH. In general, injections that involved the lateral agranular field of frontal cortex, as defined by Donoghue and Wise (1982), resulted in a greater amount of labeling in STH than injections within the medial agranular area or the zone of MI‐SI overlap. The projection from the frontal agranular areas to STH is topographically organized. The rostral part of the lateral agranular cortex projects to the lateral portion of the rostral two‐thirds of STH, and the caudal part of this field projects to the ventral aspect of the middle third of STH. Injections in the rostral part of the medial agranular cortex resulted in labeling throughout the ventral two‐thirds of the medial half of STH. The caudal part of the medial agranular cortex projects to the dorsolateral part of the caudal two‐thirds of STH.

The present results reveal projections from only the frontal agranular cortex and the zone of MI‐SI overlap to STH in the rat. The cortico‐STH projection is ipsilateral and terminates in a topographical manner in all parts of STH.
Mechanoreceptive neurons in an insect brain
Authors: Bräunig P.
Published: January 2005

Staining deutocerebral nerves in locusts with cobalt chloride revealed a connective tisssue strand innervated by the first side branch of the nervus scapalis medialis. The strand spans the joint between the basal segment of the antenna (scapus) and the head capsule (tentorium), parallel to the levator scapi muscle. It is shortest with the antenna completely elevated and becomes stretched during depression.

The four to five neurons innervating the strand near its distal insertion are activated by mechanical stimuli such as direct elongation of the strand or depression of the antenna. As revealed by centripetal staining these neurons have their central arborizations in the posterior deutocerebrum, but their perikarya are located in the protocerebrum, close to the pars intercerebralis and the central body.

These morphological and physiological characteristics identify the structure as a mechanoreceptive sense organ of the strand receptor class.