bluuebunny/crossref_metadata_2025 huggingface dataset:
Neuronal types in the deep dorsal cochlear nucleus of the cat: I. Giant neurons
Authors: Kane Eileen S. , Puglisi Susan G. , Gordon Beverly S.
Published: January 2005

Large or “giant” neurons (average somatic diameter > 22μm) of the dorsal cochlear nucleus (DCN) have been carefully described in this light (LM) and electron (EM) microscopic study of normal Nissl‐stained and Golgi‐impregnated cat brain stems. These neurons can be roughly classed by somatic shape (width:length ratio = r) as elongate (r < 0.65), ovoid (0.65 < r < 0.75), or spherical (0.75 ≤ r ≤ 1.0) in Nissl‐stained sections. However, orientation and location of somata, size, number, and distribution of basal dendrites and other cytological features seen in Nissl material provided five, easily recognized classes of large neurons: elongate bipolar, elongate multipolar, globular, radiate, and oriented multipolar giant cells. Further cytological details of the dendritic tree and axonal morphology of these neurons, observed in rapid Golgi impregnations of cat and kitten brain stems, extended these descriptive categories of giant neurons. These same deep DCN giant cells were identified in thick plastic sections and in subsequent thin sections. Thin sections showed further neuronal distinctions by relative density of somatic and dendritic synaptic inputs. All giant cells have dense synaptic inputs to basal and primary dendrites but only elongate multipolar and radiate giant cell somata have nearly continuous synaptic coverage of somata. Many axodendritic terminals and some axosomatic endings resemble cochlear endings as identified on fusiform cells of the DCN. Nauta preparations after ipsilateral cochlear ablations have confirmed (1) cochlear input to all giant cell types and (2) different patterns of input to each type. Hence, each giant cell type must process incoming auditory signals, but each cell must receive slightly different primary information. Since some giant cells of each type had observable axons heading into the dorsal acoustic stria, they must all carry encoded primary information to higher auditory centers.
Organization of substance P fibers within the hippocampal formation demonstrated with a biotin‐avidin immunoperoxidase technique
Authors: Vincent S. R. , Kimura H. , McGeer E. G.
Published: January 2005

The distribution of substance P‐containing fibers within the hippocampal formation of the cat was examined using an immunohistochemical approach. A new, indirect immunoperoxidase method based on the high affinity binding of vitamin H (biotin) by avidin was developed to demonstrate substance P‐like immunoreactive fibers. The neocortex contained only occasional single substance P fibers. In contrast, the archicortical structures contained a well organized substance P innervation. The entorhinal area of the parahippocampal gyrus contained a delicate network of varicose axons which appeared to ascend form the subcortical white matter to terminate predominantly in layer II. The subiculum contained a network of positive varicosities throughout the neuropil of both the pyramidal and the molecular layers. These substance P terminals appeared to arise, at least in part, from fibers entering laterally across the angular bundle. Within the ventral hippocampus the substance P innervation was predominantly in the pyramidal cell layer, and was heaviest in field CA3 and weakest in CA1. Some fibers were also observed in strata oriens, lucidum, and radiatum. Occasional varicose fibers could be seen entering the hippocampus from the fimbria. Within the dentate gyrus the substance P fibers were most concentrated in the supragranular layer and among the more superficial of the granule cells. A moderately dense plexus of fibers also occurred in the neuropil of the hilus among the polymorphic cells. In addition, a distinct, narrow band of varicosities was found at the outer edge of the inner molecular layer, while the outer molecular layer did not contain any positive elements.

It is concluded that the hippocampal formation receives a distinct, well organized substance P innervation. Substance P fibers appear to enter the hippocampus both laterally across the angular bundle and ventrally through the fimbria. From this detailed examination of the distribution of the substance P fibers within the hippocampus in relation to the other known inputs to this area it is suggested that many of the substance P fibers arise in or, more probably, pass through the septal area to innervate the hippocampus.
Light‐microscopic immunocytochemical localization of tyrosine hydroxylase in prenatal rat brain. I. Early ontogeny
Authors: Specht Linda A. , Pickel Virginia M. , Joh Tong H. , Reis Donald J.
Published: January 2005

The immunocytochemical localization of tyrosine hydroxylase is examined during ontogeny in the fetal rat brain in order to determine the age of first detection and subsequent cellular localization of the enzyme and the developmental characteristics of the immature catecholaminergic neurons. Fetal atlases of the tyrosine hydroxylase‐labeled neurons are presented at embryonic day (E) 12.5, 13.5, and 14.5.

Tyrosine hydroxylase is first detected immunocytochemically at E 12.5. At this stage, the labeled neurons have completed final mitosis, but are still migrating and are cytologically immature. Tyrosine hydroxylase can also be detected in axons and axonal growth cones at this stage of development. The age of first immunocytochemical detection of the enzyme precedes the demonstration of catecholamine fluorescence by 1 to 2 days in certain nuclear groups.

At later stages of development (E 13.5 and E 14.5), the major groups of perikarya and processes labeled for tyrosine hydroxylase have a distribution similar to that previously described by catecholamine fluorescence. At E 14.5, the perikarya undergo considerable changes in their cytology and exhibit the first dendrites immunocytochemically labeled for the enzyme. The first terminal fields are also detected in the rudimentary caudate‐putamen at this stage.
The distribution of neurons projecting from the retina and visual cortex to the thalamus and tectum opticum of the barn owl, Tyto alba, and the burrowing owl, Speotyto cunicularia
Authors: Bravo Hermes , Pettigrew John D.
Published: January 2005

Using the HRP retrograde transport technique in two different genera of owls (Speotyto and Tyto), we have studied the distribution of neurons projecting to the optic tectum and the visual thalamus. Small injections of HRP were made into these structures from the pial surface after they had been visualized directly by dissection of the overlying bone.

In contrast to the findings in mammals, retinal ganglion cells were labeled only in the eye contralateral to the injection site, whether this was in the thalamus or tectum, and the labeled ganglion cells were found on both nasal and temporal sides of the vertical retinal meridian through the fovea. After thalamic injection, labeling was prominent in temporal retina representing the binocular field, temporal to the optic nerve head. Retinothalamic ganglion cells formed roughly concentric lines of isodensity centered on the fovea (Speotyto) or area centralis (Tyto); labeling form thalamic injections involved both large and medium‐sized neurons, but did not involve the smallest nor a conspicuous class of very large neurons. Tectal injections led to prominent labeling along the horizontal streak region, with horizontally elongated isodensity contours in both Tyto and Speotyto; retinotectal ganglion cells were heterogeneous and included a group of very large neurons and another group of small neurons, neither of which was labeled from the thalamus.

In the visual Wulst, labeled neurons were confined to the supragranular layers after both tectal and thalamic injections. Corticotectal neurons were found in both ipsilateral and contralateral visual Wulst. They were characterized by large cell bodies and prominent dendrites. Corticotectal neurons were distributed throughout the mediolateal extent of the ipsilateral Wulst and therefore involved both the monocular and binocular representations of the visual field. Corticothalamic neurons, found only in the ipsilateral Wulst, were characterized by smaller cell bodies and fine dendrites. They were confined to the monocular crescent on the extreme medial edge of the Wulst.
The distribution of ganglion cells in the retina of the north american opossum (Didelphis virginiana)
Authors: Rapaport David H. , Wilson Paul D. , Rowe Michael H.
Published: January 2005

The distribution of ganglion cells in the retina of the opossum was determined from whole‐mounted retinae stained with cresyl violet. Isodensity lines were approximately circular with a peak density of 2,000 to 2,700 cells/mm2 in superior temporal retina (area centralis). The total number of retinal ganglion cells was estimated to be 72,000 to 135,000 (mean 101,026) in retinae ranging from 125 to 187 mm2 in total area. Three groups of ganglion cells were distinguished on the basis of soma size and retinal topography. Large cells (24 to 32 μm diameter) were fairly evenly distributed across the retina. Medium cells (12 to 23 μm diameter) were more numerous in the superior temporal quadrant than in other regions of the retina. Small cells (7 to 11 μm diameter) were prominent in all retinal regions, but particularly in nasal and inferior retina. An analysis of topographical differences in soma size distribution suggests that the medium size cells can be further subdivided into small‐medium and large‐medium groups.
Ultrastructure of the crayfish stretch receptor in relation to its function
Authors: Tao‐Cheng Jung‐Hwa , Hirosawa Kazushige , Nakajima Yasuko
Published: January 2005

The crayfish slow‐adapting abdominal stretch receptor was fixed under the relaxed or stretched condition. During this procedure action potentials of the sensory neuron were recorded by a suction electrode. The receptor organ consists of a receptor muscle and a sensory neuron with its dendrites embedded in the connective tissue zone in the receptor muscle. From the cell body of the neuron, several “primary dendrites” arise, branch successively into “dendritic branches”, and finally terminate as “dendritic tips”, which are cylindrical processes of fairly uniform diameter. In contrast to the primary dendrites and the dendritic branches, the dendritic tips have neither mitochondria nor sheaths and are embedded in the connective tissue zone or apposed to the receptor muscle with a gap of about 15 nm. Microtubules and smooth ER are seen in all parts of the dendrites. When the receptor is stretched and then fixed with 1.6% glutaraldehyde in 0.12 M phosphate buffer (total osmolarity of this solution is isosmotic with the physiological solution), dendritic tips became more parallel to the long axis of the receptor muscle and showed marked deformation consisting of alternate regions of swelling and shrinkage, resulting in a bead‐like appearance. When fixed with 1.6% glutaraldehyde in 0.2 M phosphate buffer (total osmolarity of this solution is hyperosmotic), the dendritic tips showed less tendency toward such deformation. These results suggest that the dendritic tip membrane is susceptible to stretch and might be the region where the generator potential is produced.
Development of the pyramidal tract in the hamster. I. A light microscopic study
Authors: Reh Thomas , Kalil Katherine
Published: January 2005

The development of the pyramidal tract and other projections from the sensorimotor cortex was studied in the postnatal hamster with both (3H) proline and horseradish peroxidase (HRP) as anterograde tracers. In the 1‐day‐old animal labeled axons extend as far as the pons. Other corticofugal fibers have penetrated into the corpus striatum and the thalamus. By 2 days postnatally, the pyramidal tract has grown to midmedullary levels and there is substantial retrograde (HRP) and anterograde labeling in the thalamus. The pyramidal decussation is formed at 3 days of age and by 4 days the pyramidal tract has descended in the dorsal funiculus as far as midcervical spinal cord. Corticofugal fibers invade the pontine nuclei at 4 days and both the dorsal column nuclei and the superior colliculus at 6 days of age. At 6 days the pyramidal tract can be traced to midthoracic levels of the spinal cord, by 8 days the tract reaches lumbar levels, and by 14 days it has completed its caudal growth to the coccygeal spinal cord. Fibers first penetrate the gray matter of a given spinal cord level approximately 2 days after the tract has grown past that level in the dorsal funiculus. Pyramidal fibers continue their lateral growth into the dorsal horn at all levels of the cord throughout the third postnatal week such that by 21 days of age the pyramidal tract appears similar to that of the adult.

The projections from sensorimotor cortex to the pontine nuclei, the superior colliculus, and the dorsal column nuclei appear to have a pattern similar to that of the adult soon after the fibers grow into these structures. There is a consistent delay of 2 to 3 days between the arrival of the pyramidal tract axons in the white matter adjacent to target structures and their innervation of a given terminal field. The pyramidal tract grows more quickly through the dorsal funiculus of the spinal cord than it does along the ventral surface of the medulla. Extensive elongation of pyramidal tract axons is achieved long before the growth and differentiation of the sensorimotor cortical neurons from which they originate. Finally, the pyramidal tract appears to grow as a compact bundle and not by the addition of temporally staggered groups of fibers. The relatively protracted period of innervation of the spinal cord by the pyramidal tract coupled with the immaturity of the cortical neurons at birth may be factors contributing to the significant regrowth of pyramidal tract axons severed early in development.
Identified neurons in an insect embryo: The pattern of neurons innervating the metathoracic leg of the locust
Authors: Whitington Paul M. , Seifert Eveline
Published: January 2005

The population of motorneurons which send axons to the metathoracic leg of the locust embryo has been stained by a cobalt backfilling technique. Embryogenesis lasts 11 days and an adultlike distribution of motorneuron cell bodies is seen as early as day 6: Several identified adult motorneurons can be recognized in the embryo. The total number of filled cells, the overall distribution of stained cell bodies, and the relative positions of identified neuron cell bodies do not change between 6 days and hatching. No motorneurons are stained which are clearly not leg motorneurons, and an adult pattern ofaxon branching at the level of peripheral nerve roots is already present at day 6. These observations provide information about the timing of motorneuron production and motor axon growth into the embryonic limb. The development of central dendritic arborizations can also be followed. The results are discussed with respect to mechanisms for neuron determination and differentiation.
Projections from the superior colliculus and the neocortex to the pulvinar nucleus in Galago
Authors: Raczkowski Denis , Diamond I. T.
Published: January 2005

We have studied the projections from the superior colliculus and the neocortex to the pulvinar nucleus in Galago senegalensis. by using the retrograde transport of horseradish peroxidase (HRP). Injections of various parts of the pulvinar complex, both the inferior and superior divisions, both the tectorecipient zone and the nontectorecipient zone as defined by Glendenning et. al. ('75), produce labeled cells in the lower tier of stratum griseum superficiale. The distribution of labeled cells in the superior colliculus varies with the locus of the injection, indicating a retinotopic projection system from the entire superior colliculus to all sectors of the pulvinar complex.

These experiments also provide an opportunity to study the distribution and laminar origin ofneurons giving rise to cortical descending projections. The entire visual cortex projects onto the pulvinar complex. The cells of origin can be divided into two populations–one located in layer V and the other in layer VI. In seven of the nine cases reported, the layer V population is restricted entirely or mainly to the striate area. In the two exceptional cases, the layer V population is located in the adjacent extrastriate cortex, areas 18 and 19. The difference in the layer of origin of the cortical descending fibers reflects a difference in the layer of termination of the reciprocal ascending projection.

These findings identify the entire visual field as primary visual cortex. The importance of this conclusion is underscored by the fact that the visual field comprises as much as one‐half of the whole neocortex.
(3H)‐Dihydrotestosterone in catecholamine neurons of rat brain stem: Combined localization by autoradiography and formaldehyde‐induced fluorescence
Authors: Heritage Aileen S. , Stumpf Walter E. , Sar Madhabananda , Grant Lester D.
Published: January 2005

A combined formaldehyde‐induced fluorescence (FIF)‐autoradiography procedure was used to determine how and where the androgen, dihydrotestosterone (DHT), is associated with catecholamine systems in the rat brain. With this dual localization method, (3H)‐DHT target sites can be visualized in relation to catecholamine perikarya and terminals. In the hindbrain, catecholamine neurons adjacent to the fourth ventricle (group A4), the nucleus (n.) olivaris superior (group A5), the n. parabrachialis medialis (group A7), and in the locus coeruleus (group A6) and subcoeruleal regions, as well as in the substantia grisea centralis, concentrate (3H)‐DHT in their nuclei. (3H)‐DHT target neurons appear to be innervated by numerous catecholamine terminals in the following hindbrain regions: n. motorius dorsalis nervi vagi, n. tractus solitarii, n. commissuralis, n. raphe pallidus, n. olivaris inferior, the ventrolateral portion of the substantia grisea centralis, n. cuneiformis, and the ventrolateral reticular formation in the caudal mesencephalon. In the forebrain, (3H)‐DHT concentrates in nuclei of catecholamine neurons located in the n. arcuatus and n. periventricularis (group A12). In addition, (3H)‐DHT target neurons appear to be innervated by numerous catecholamine terminals in the following forebrain regions: n. periventricularis rotundocellularis, n. paraventricularis, n. dorsomedialis, n. periventricularis, area retrochiasmatica, n. interstititalis striae terminalis (ventral portion), and n. amygdaloideus centralis.

The disclosure of a morphologic association between (3H)‐DHT target sites and certain brain catecholamine systems suggests a close functional interdependence between androgens and catecholamines.
Development of axosomatic synapses of the Xenopus spinal cord with special reference to subsurface cisterns and C‐type synapses
Authors: Watanabe Hiroshi
Published: January 2005

The relationships of highly flattened subsurface cisterns (SCCs) were investigated electron microscopically in the spinal cord at various devel‐ opmental stages of tadpoles and adult toads, Xenopus laeuis.

In medial ventral motor cells (MVCs) of the adult, more than 90% of 156 SSCs examined were situated postsynaptically. Similarly, more than 909% of 540 SSCs in lateral motor column cells (LMCs) were postsynaptic. By contrast, in early developmental stages, the SSCs were initially formed by regional flattening of cisterns of rough‐surfaced endoplasmic reticulum just beneath the cell surfaces opposite to glial processes. Then, the glial processes were displaced by nerve endings with an elongated bouton, and thus the C‐type synapses were formed. The ratio of post‐ synaptic SSCs to the total SSCs reached the adult level at around Stage 60. This finding suggests that the SSCs in the MVCs and LMCs draw a certain type of nerve ending to form C‐type synapses. Such a mechanism is totally lacking in the dorsal and lateral small nerve cells, since the SSCs in these cells were always situated under the surface opposite to glial processes throughout the developmental stages and in the adult.

In mature C‐type synapses, an aggregate of synaptic vesicles and a structural specialization of presynaptic membrane occurred only at the region where the postsynaptic membrane was associated with the SSC. The postsynaptic membrane itself of the C‐type synapse showed no marked structural specialization at any stage of development or in the adult.

The postsynaptic SSC in the mature C‐type synapse seems to be involved in some way in the reception of synaptic transmission.
Connections of the amygdala of the rat. IV: Corticoamygdaloid and intraamygdaloid connections as studied with axonal transport of horseradish peroxidase
Authors: Ottersen Ole P.
Published: January 2005

The corticoamygdaloid and intraamygdaloid projections of the rat were studied by the use of retrograde transport of horseradish peroxidase (HRP). Observations based on anterograde transport of the enzyme were exploited to determine the course of the intrinsic connections. The HRP was injected stereotactically by means of iontophoresis. Most of the amygdaloid nuclei were selectively injected, and all but a few were reached by more than one approach.

The vast majority of corticoamygdaloid fibers was found to originate in cortical areas defined as allocortical (Stephan, 1975). From the medial frontal cortex the central amygdaloid nucleus (AC) receives a hitherto undescribed projection originating in the tenia tecta; and both the AC and the lateral amygdaloid nucleus (AL) receive fibers from the prelimbic and infralimbic areas. The anterior cingulate area entertains a weak connection with the basolateral amygdaloid nucleus (BL). As to the insular cortex, the posterior agranular insular area projects to all amygdaloid subdivisions; the BL, AC, and the anterior cortical nucleus (COa) receive, in addition, fibers from the ventral agranular area. The prepyriform cortex connects with the entire amygdala except the medial nucleus (Am)

The amygdala receives afferents from a transitional area between the amygdala and the entorhinal area. The entorhinal area proper is related to the amygdala via projections from the ventral part of the lateral entorhinal area to the AL and from the dorsal part of the lateral entorhinal area to the BL. The former nucleus also receives fibers from the perirhinal region. Additional amygdalopetal connections from the hippocampal region include a previously undescribed projection from the temporal two‐thirds of CA1 to the AL and BL and to the posterior cortical nucleus (COp) with the adjacent periamygdaloid cortex (PAC). The subiculum projects to the AL, and more modestly to other amygdaloid nuclei

There is an extensive network of intraamygdaloid connections, the Am and AC being the only nuclei not giving rise to intrinsic fibers.
Physiological and morphological identification of two types of on‐center bipolar cells in the carp retina
Authors: Saito Takehiko , Kujiraoka Toru
Published: January 2005

Two types of on‐center bipolar cells, rod‐ and cone‐dominant bipolars have been identified in the dark‐adapted retina of the carp by means of intracellular recordings and Lucifer‐yellow dye injection. They differ physiologically and morphologically in the following respects: (1) responses of rod‐dominant cells to bright lights are characterized by a tansient depolarization followed by a smaller sustained depolarization, while those of cone‐dominant cells are approximately rectangular; (2) the cone‐dominant cells are about 1.5 log units less sensitive to light than the rod‐dominant cells; (3) the latency of the response is shorter in the cone‐dominant cells than in the rod‐dominant cells; (4) the mean diameters of the cone‐dominant cell receptive field (0.7 mm) and dendritic field (90 μm) are larger than those of the rod‐dominant cell receptive field (0.5 mm) and dendritic field (56 μm); (5) the mean diameter of the cone‐dominant cell soma (8 μm) is smaller than that of the rod‐dominant cell soma (13 μm); and (6) the terminations of the cone‐dominant cell axons form a ramification (67 μm mean diameter) in contrast to a big terminal swelling of the rod‐dominant cell axons (37 μm mean diameter). At least two ionic mechanisms are responsible for generating the depolarizing response of on‐center bipolar cells, one having a reversal at a positive potential and the other at a negative potential. Responses with a negative reversal potential only are obtained from some of cone‐dominant cells and responses with a positive reversal potential only are obtained from some other cone‐dominant cells and the rod‐dominant cells. There are a large number of bipolar cells that respond by both ionic mechanisms, although the ratio between them varied considerably in different cells.
Transplantation of reaggregates of embryonic neural retinae to neonatal rat brain: Differentiation and formation of connections
Authors: McLoon Linda Kirschen , Lund Raymond D. , McLoon Steven C.
Published: January 2005

Embryonic day 14 neural retinae were dissociated into single cells and reaggregated prior to transplantation over the superior colliculi of newborn rats. One month after transplantation, the brains of the host rats were examined for transplant differentiation and the formation of projections from the transplant to the host brain.

All reaggregated retinal transplants differentiated in the host brain, showing normal lamination and cellular morphology. Electron microscopic examination demonstrated normal synaptology within the transplanted retinal neuropil. Horseradish peroxidase injections into the host superior colliculus retrogradely filled cells within the transplant. These cells were found in the lamina corresponding to the ganglion cell layer and displayed a morphology characteristic of normal ganglion cells. Lesions of the transplants confirmed the projection of the reaggregated retinal transplants to superior colliculus. Degeneration was also traced into a number of other nuclei that are normally retinorecipient. The presence of degenerating synaptic terminals resembling those seen after eye removal in control rats was confirmed by electron microscopic examination.

It appears that despite disruption of initial cell‐cell associations early in retinal development and prior to transplantation, the reaggregated transplants retain the ability to differentiate and form appropriate connections with the host brain.
Ontogeny of the leucine‐enkephalin neuron system of the rat: Immunohistochemical analysis. I. Lower brainstem
Authors: Senba Emiko , Shiosaka Sadao , Hara Yoshinobu , Inagaki Shinobu , Kawai Yuriko , Takatsuki Kenichi , Sakanaka Masahiro , Iida Hisashi , Takagi Hiroshi , Minagawa Hideo , Tohyama Masaya
Published: January 2005

Ontogeny of the leucine‐enkephalin (L‐Enk) neuron system in the lower brainstem of the rat was investigated by means of indirect immunofluorescence.

L‐Enk‐containing cells first appear in the primordium of the medullary reticular formation just medial to the n. tractus spinalis nervi trigemini at the level of the rostral half of the inferior olivary nucleus, in the n. cuneiformis, and in the mesencephalic reticular formation of the fetus at gestational day 16 (14–15‐mm embryos). From that time onward, L‐Enk‐containing cells appear in various areas of the lower brainstem one after another until birth. After birth, although L‐Enk‐containing cells decrease slightly in number as the rats grow, L‐Enk‐containing fibers continue to increase in number.
The morphology and connections of the posterior hypothalamus in the cynomolgus monkey (Macaca fascicularis). I. Cytoarchitectonic organization
Authors: Veazey R. B. , Amaral D. G. , Cowan W. M.
Published: January 2005

The cytoarchitectonic organization of the posterior hypothalamus of the cynomolgus monkey (Macaca fascicularis) was analyzed in Nissl, Golgi, acetylcholinesterase, and reduced silver preparations. The region consists of a number of cell masses that differ considerably in their discreteness and in the homogeneity of their neuronal populations. The nuclei identified include: the medial mamillary nucleus (in which at least three distinct subdivisions can be recognized—a pars medialis, a pars lateralis, and a pars basalis); the small‐celled nucleus intercalatus; the large‐celled lateral mamillary nucleus; a single premamillary nucleus; the tuberomamillary nucleus; the posterior hypothalamic nucleus; the caudal extension of the lateral hypothalamic area; the supramamillary area; and the paramamillary nucleus (which appears to correspond to the nucleus of the nucleus of the ansa lenticularis of other workers). As a basis for the subsequent experimental study of the efferent connections of the posterior hypothalamus, the location of each of these cell masses is described and illustrated in a series of low‐power photomicrographs, as are the form and distribution of the resident neuronal populations of the various components of themamillary complex as seen in Golgi preparations.
The serotonin neurons in nucleus raphe dorsalis of adult rat: A light and electron microscope radioautographic study
Authors: Descarries Laurent , Watkins Kenneth C. , Garcia Sylvia , Beaudet Alain
Published: January 2005

The serotoninergic nerve cell body population of nucleus raphe dorsalis (RD) was identified by radioautography following cerebroventricular instillation of tritiated serotonin ([3H]5‐HT) in adult rats pretreated with a monoamine oxidase inhibitor. Series of histological sections taken throughout the midbrain and upper pons exhibited a similar distribution and number of labeled nerve cell bodies in RD after prolonged administration ofeither 10−5 or 10−4 M [3H]5‐HT or 10−4 M [3H]5‐HT and 10−3 M nonradioactive noradrenaline. This allowed systematic mapping and quantification of serotoninergic nerve cell bodies at various levels of the RD. Their extrapolated total number averaged 11,500. Twice as many unreactive (nonserotoninergic) neurons were present within the same region. In electron microscope radioautographs, the labeled cells were usually larger (17.9 μm mean diameter) than their unlabeled congeners (13.1 μm), but stereological sampling of their perikarial organelle content failed to reveal any difference in cytoplasmic composition. Few [3H]5‐HT‐labeled axonal varicosities were observed in RD and none were found in close apposition or in synaptic junction with labeled nerve cell bodies, dendrites, or unreactive perikarya. A detailed statistical analysis of silver grain distribution in both labeled and “unlabeled” nerve cell bodies indicated that in the former, but not in the latter, dense bodies had a relatively high affinity for [3H]5‐HT. Mitochondria and the cytoplasmic membrane were the only other organelles to show higher labeling indices in labeled than in unlabeled cells. Other sites of[3H]5‐HT localization could be ascribed to artefactitious cross‐linkage of the tracer by the fixative, since they had the same relative affinity in the two cell populations. These results provide new insights into the morphology and cytofunctional properties of the 5‐HT neurons of rat RD.
Mature Purkinje cells in cerebellar tissue cultures: An ultrastructural study
Authors: Blank Nathan K. , Seil Fredrick J.
Published: January 2005

Mature Purkinje cells in mouse cerebellar tissue cultures were morphologically analyzed by electron microscopy. Explants maintained for 19 to 31 days in vitro contained Purkinje cells that were similar in most respects to those described in vivo except for incomplete arborization of the dendritic trees. Typical features included (1) absence of Purkinje cell perisomatic spines; (2) a paucity of naked Purkinje cell dendritic spines; (3) a 1:1 relationship of Purkinje cell dendritic spines to parallel fiber terminals; and (4) almost complete astroglial investment of Purkinje cell somata and dendrites. Minimal extracellular space was present in the neuropil of the explants and unusual synapses involving Purkinje cells were absent. Atypical features described by some investigators may be a function of retarded development in suboptimal culture conditions and do not represent the limit of tissue culture methodology.
Tracing of two‐neuron pathways in the olfactory system by the aid of transneuronal degeneration: Projections to the amygdaloid body and hippocampal formation
Authors: Carlsen Jørn , de Olmos Jose , Heimer Lennart
Published: January 2005

Following an olfactory bulb lesion in guinea pig (2 to 3 days), neuronal degeneration occurs in several olfactory‐bulb‐related areas, primarily in the piriform cortex. The degenerating neurons, which are argyrophilic, are also found in the posterolateral cortical amygdaloid nucleus and the ventrolateral entorhinal cortex. It is suggested that the neurons degenerate because of a transneuronal effect due to a sudden loss of afferent input from the the olfactory bulb, although a retrograde effect acting in concert with transneuronal factors cannot be excluded.

Terminal degeneration can be identified in several areas outside the olfactory bulb projection area, and is interpreted as degeneration in the axons of the degenerating cortical neurons. Such terminal degeneration, which is best seen 3 to 4 days postoperatively, has been identified in part of the basolateral amygdaloid complex, in the basomedial amygdaloid nucleus, and in the temporal parts of the fascia dentata of the hippocampal formation. Terminal degeneration has also been observed in the deep layers of the anterior olfactory nucleus, the olfactory tubercle, the nucleus of the lateral olfactory tract, and the anterior amygdaloid area. All these projections, apparently, represent the second link in two‐neuron pathways, where mitral or tufted cells in the olfactory bulb make up the first neuron. This interpretation was confirmed in control experiments in which areas of argyrophilic neurons coincided with the location of retrogradely labeled neurons following injection of flurorescent substances into several of the abovementioned areas of terminal degeneration.
Effect of morphine on 3H‐Thymidine incorporation in the subependyma of the rat: An autoradiographic study
Authors: Miller Clara R. Dodge , O'steen W. Keith , Deadwyler Sam A.
Published: January 2005

Following morphine treatment, an autoradiographic study investigated the uptake of 3H‐thymidine by the subependymal cells in the rat brain. 3H‐thymidine was administered subcutaneously to adult, male Sprague‐Daw‐ley rats 30 minutes after saline or morphine (10 mg/kg) injection. The animals were sacrified 1 hour after 3H‐thymidine administration. In some experiments the opioid antagonist, naloxone, was given alone 45 minutes before 3H‐thymidine or 15 minutes before morphine treatment. Three areas of the subependyma were evaluated in terms of the percentage labeled cells and number of grains per nucleus, and a dorsal‐to‐ventral gradiant was described. Morphine treatment significantly increased the number of 3H‐thymidine labeled subependymal cells and number of grains/nucleus within labeled cells. Examination of the distribution of grains/nucleus showed that morphine‐treated animals had significantly more cells labeled with 30 or more grains than did saline‐injected controls. Prior administration of naloxone blocked the increased 3H‐thymidine uptake in morphine‐treated animals but had no significant influence on cell proliferation when administered alone. The data are discussed in terms of morphine's possible dual influence on mechanisms which enhance cell transition from G to S phase and/or which accelerate DNA synthesis once these cells have entered the S phase of cell replication.
Indirect visual cortical input to the deep layers of the hamster's superior colliculus via the basal ganglia
Authors: Rhoades Robert W. , Kuo David C. , Polcer Jeffrey D. , Fish Stephen E. , Voneida Theodore J.
Published: January 2005

Anterograde and retrograde tracing techniques were employed to delineate the organization of a visual cortical input to the deep layers of the hamster's superior colliculus which may be mediated by links in the striatum and substantia nigra.

Autoradiographic experiments showed that areas 17, 18a, and the cortex medial to area 17 (areas 18b and 29) all projected to the dorsocaudal part of the ipsilateral striatum. This projection was organized so that the rostrocaudal axis of the visual cortex was represented along the anteroposterior axis of the striatum. Large posterior neocortical injections which included all of these areas also revealed a weak, crossed corticostriatal pathway. Such injections also demonstrated clear discontinuities in the terminal distribution of the visual corticostriatal projection, similar to those which have been noted after injections of tracers into the motor and premotor cortices.

Retrograde tracing experiments showed that the cells of origin of the visual cortical projections to the striatum were medium‐sized pyramidal neurons located primarily in the upper portion of lamina V.

Anterograde transport of [3H]‐leucine and HRP showed that the portion of the striatum heavily innervated by the visual cortex projected to the part of substantia nigra, pars reticulata immediately adjacent to the cerebral peduncle. Injections in the rostral striatum labeled more medial portions of this nucleus. The cells of origin of the striatonigral pathway measured between 13 and 20 μm in diameter and they were located primarily in the dorsal and lateral parts of the striatum.

Anterograde tracing after substantia nigra, pars reticulata injections revealed a projection to both superior colliculi. The uncrossed pathway terminated primarily as a series of patches throughout the mediolateral and rostrocaudal extents of the lower stratum griseum intermediale and stratum album intermedium. Labeling was also visible in the lateral portion of the stratum griseum profundum. The crossed nigrotectal pathway terminated primarily in the rostrolateral stratum griseum profundum. The cells of origin of the nigrocollicular pathway were fusiform or multipolar cells and were located primarily adjacent to the cerebral peduncle throughout the rostral half of the substantia nigra, pars reticulata.
A physiological and morphological study of the horizontal cell types of the rabbit retina
Authors: Bloomfield Stewart A. , Miller Robert F.
Published: January 2005

A perfused, isolated retina‐eyecup preparation of the rabbit was utilized to correlate the physiology and morphology of horizontal cells. Neurons were physiologically characterized by intracellular recording techniques and subsequently stained with intracellular iontophoretically injected horseradish peroxidase for morphological identification. Three types of rabbit horizontal cell recordings have been differentiated, based on variations in response waveform, amplitude‐intensity properties, and area summation characteristics. These three types have been unequivocally associated with the axonless A‐type horizontal cells and the somatic and axon terminal endings (each displaying its own distinct physiology) of B‐type horizontal cells first described in studies using Golgi‐impregnation techniques (Fisher and Boycott, 1974). In addition, the sizes of A‐type horizontal cells were found to be directly related to their retinal eccentricities from the optic disk. However, a unique subclass of A‐type cells has been discovered (elongated or Ae type) which displayed the largest dendritic field of any cells studied here, yet had the smallest eccentricities—within 1.4 mm of the optic disk. Moreover, elongated A‐type cells exhibited long asymmetrical dendritic fields which were oriented parallel with the visual streak. The unique asymmetry and orientation of these cells suggests that they may have orientation‐biased receptive field properties. Physiological evidence for an orientation‐biased horizontal cell is presented in support of this notion.
Anatomy of the isolated area dentata grown in the rat anterior eye chamber
Authors: Goldowitz Dan , Seiger Åke , Olson Lars
Published: January 2005

We used the intraocular transplantation technique to test the developmental potential of isolated, fetal area dentata, and to help define the determinants of such critical aspects of brain development as cell arrangements, dendritic arborization, axon growth, synaptogenesis, and connectional specificity. Fetal hippocampal formations were removed from embryos of 19 to 20 days of embryonic age. A region, termed area dentata, was dissected from the hippocampal formation. This region included the anlage of the dentate gyrus, the hilus, and the medial regio inferior. Areae dentatae were transplanted into the anterior eye chamber of isogenic, adult rats. The growth and vascularization of area dentata transplants were monitored over the first 2 months in oculo. From 2 to 7 months after transplantation host animals were killed and the area dentata transplants were examined with a variety of histological techniques. The cytoarchitectonics of a great majority of the transplants were highly reminiscent of area dentata in situ. A typical morphogenetic outcome included tightly packed, continuous, C‐shaped sheets of granule cells with mossy fibers which made contact with the proximal dendrites of a segregated group of dispersed hilar cells and a loosely packed layer of pyramidal cells. The axons of pyramidal and hilar cells, in turn, provided the major innervation of the granule cell dendrites. The granule cell dendritic spine density was nearly normal, and synapses were common in the granule cell neuropil. Very little innervation of the transplant was found to originate from the axons of the ciliary or trigeminal ganglia which innervate the host iris and enter the transplant. Sympathetic fibers from the host iris innervate the transplant in a reproducible and organotypic fashion although the degree of innervation is less than the in situ noradrenergic innervation of area dentata. Few Timm‐positive fibers of the transplant were found to leave the transplant and enter the host iris. Area dentata transplants had several features which were different from their in situ counterparts. These differences included less expansive granule cell dendrites, extensive presence of fibrous astrocytes, pyramidal cells with reduced kainic acid sensitivity, hypervascularized neuropil, and transformation of peripheral adrenergic fiber morphology to one of central characteristics.

Thus, pieces of isolated area dentata display a great self‐developing capacity, in terms of cellular and afferent organization, both of which follow “rules” present in situ. A powerful capacity for intrinsic and appropriate innervation of area dentata is apparent in the face of a total lack of normal extrinsic afferents and an availability of extrinsic but inappropriate sources of innervation. This initial description of isolated area dentata organization in oculo is meant to lay the groundwork for experimental investigations into the regulatory mechanisms governing morphogenesis and afferent organization.
Cytoarchitecture of the central amygdaloid nucleus of the rat
Authors: McDonald Alexander J.
Published: January 2005

Since recent studies indicate that distinct neuropeptides and projections are associated with discrete portions of the central amygdaloid nucleus (CN), a detailed investigation of the cytoarchitecture of CN should contribute to an understanding of its organization. Qualitative and quantitative analyses of the rat CN using Nissl, Klüver‐Barrera, and Golgi techniques suggests that it consists of four subdivisions. The medial subdivision (CM), which is closely associated with the stria terminalis, is narrow caudally but enlarges near the rostral pole of CN. Most neurons in CM have long dendrites that branch sparingly and have a moderate number of dendritic spines. A smaller number of CM neurons have thick dendrites with virtually no spines. Lateral to CM is the lateral subdivision (CL) which appears round in coronal sections. Neurons of CL have a very dense covering of dendritic spines and resemble medium‐size spiny neurons of the striatum. Area X of Hall contains spiny neurons similar to those of CL and spine‐sparse neurons that resemble medium‐size spine‐sparse cells of the striatum. Since area X encapsulates the lateral aspect of CL, it is termed the lateral capsular subdivision (CLC) of CN. The lateral capsular subdivision enlarges rostrally and is divided into dorsal and ventral portions by a laminar extension of the putamen. Near the rostral pole of CN a small region of tightly packed, intensely stained neurons is interposed between CL and CM. Golgi preparations reveal that this intermediate subdivision (CI) of CN contains neurons similar to those of CM. The lateral subdivision, CLC, and CM correspond, in part, to subdivisions recognized in previous Nissl studies. The intermediate subdivision has not been recognized as a distinct subdivision in previous investigations. This is the first Golgi study to recognize differences in neuronal morphology in particular subdivisions of the rat CN. The correlation of Nissl and Golgi preparations has permitted a more accurate determination of the boundaries and total extent of each subdivision than the use of Nissl techniques alone.
Neuronal addition and retinal expansion during growth of the crucian carp eye
Authors: Kock Jan‐Henrik
Published: January 2005

Using standard paraffin technique the addition of new cells in crucian carp retinas was examined. Between eye diameters 4.4 and 10.0 mm the number of ganglion cells increases from 103,000 to 205,000, INL cells from 1.5 to 3 million, cones from 250,000 to 900,000, and rods from 2 to 9 million. Concomitantly retinal area increases fivefold and the cell densities decrease by 37% for the cones, 57% for th e INL cells, and 58% for the ganglion cells, while the rod density remains stable.

In relation to the rods the cell ratios at different retinal loci undergo marked changes during growth. The contributions to retinal growth by addition of new neurons and by expansion of the retina have been determined for the different retinal layers. The layer of rods grows exclusively by addition of new rod mosaic. In the cone layer 81% of growth is due to addition of new cone mosaic. In the inner nuclear layer (INL) 56% of growth is due to addition of new cells and in the ganglion cell layer 52% is due to cell addition. In each case retinal expansion accounts for the remainder of increase in retinal area.

On morphological grounds six cone types can be found in the crucian carp retina. Their ratios are constant during retinal growth and at different retinal loci.
A quantitative study of the reinnervation of the goldfish optic tectum following optic nerve crush
Authors: Murray Marion , Edwards Michael A.
Published: January 2005

Stereological and quantitative morphometric methods were used to study changes in the stratum fibrosum et griseum superficialis (SFGS), the major retinal target, in optic tectum of goldfish, during regeneration of the optic nerve. Orthograde transport of HRP by optic axons was used to characterize the retinal projection in SFGS. Profiles of HRP‐labeled optic terminals contained round vesicles, contacted small dendrites, and were distributed uniformly throughout the area of SFGS sampled; labeling density estimates indicate that at least 37% of the total terminal population in SFGS is retinal in origin. Partial denervation of the tectum by optic nerve crush is accompanied by a loss of 40% of the total terminal population in SFGS and by a marked decrease of SFGS thickness. Entry of massive numbers of regenerating optic axons into SFGS begins about 3 weeks postoperatively, about the time that some visual function recovers and produces a marked increase in SFGS thickness which persists for several months postoperatively. The area occupied by regenerating axons and the number of terminals in the tectum only approach preoperative levels 3 months postoperatively. The recovery of normal synaptic number is therefore delayed several months beyond the time of entry of regenerative axonal sprouts. The results indicate that return of synaptic number to normal is temporally associated with the reduction of the excess number of regenerating optic axons and that both these processes are prolonged.