bluuebunny/crossref_metadata_2025 huggingface dataset:
Time of neuron origin in the anterior olfactory nucleus and nucleus of the lateral olfactory tract of the mouse: An autoradiographic study
Authors: Creps Elaine S.
Published: January 2005

Time of neuron origin in the anterior olfactory nucleus (AO) and nucleus of the lateral olfactory tract (NTOL) was determined autoradiographically in adult mice which received tritiated thymidine once during development. Each subdivision of AO has an individualized period and pattern of neuron origin. All subdivisions contain neurons which arise on E11; but the medial, dorsal, and external subdivisions complete their complement by E18 whereas posterior and lateral neurons continue to arise through P1. No gradients along the caudorostral axis were discerned. Neurons of NTOL arise early (E10‐14), typical of large neurons and similar to those of the surrounding anterior amygdaloid area.
Efferent cortico‐cortical fiber connections of area 18 in the squirrel monkey (Saimiri)
Authors: Tigges J. , Spatz W. B. , Tigges M.
Published: January 2005

Association fibers, degenerating as a result of laminar heat lesions in area 18 of Saimiri, were traced to their respective cortical terminal sites. A strong intrinsic fiber system connected the supragranular cell layers with the underlying layer V of area 18. In addition, the supragranular layers of area 18 projected ipsilaterally to area 17, the territory of area 19 and area MT in the posterior bank of the superior temporal sulcus. Sparse fibers were traced to the cortex in the intraparietal sulcus and to area 8. The projection upon area 17 was strictly topographical; the termination of these fibers was restricted to layer I of area 17. The projection upon area 18 also showed signs of a topographical organization, though less distinct. The evidence for the existence of Brodmann's classic area 19 or its possible replacement as suggested by Allman and coworkers is discussed.

Callosal fibers terminated in a topographically organized manner in a strip of cortex posterior in area 18, i.e., the OBg of von Bonin, and in a strip of cortex probably in anterior area 18. A sparse projection connected area 18 with the contralateral area MT.
The cochlear nuclei of lizards
Authors: Miller Malcolm R.
Published: January 2005

The cochlear nuclei of 14 lizard species (eight families) were studied in normal animals and in a small series of animals with lesions of the posterior division of the eight nerve. The development of the cochlear nuclei is directly related to the length and complexity of the papilla basilaris. The best development of basilar papillae and cochlear nuclei is found in teiid and gekkonid lizards, and an intermediate grade of development in scincid, lacertid, and anguid lizards. A lesser degree of development occurs in the igunids, and practically no cochlear nuclei differentiation is observed in chameleo.

Two well defined cochlear nuclei are found in most lizard families: nucleus angularis (NA) and nucleus magnocellularis medialis (NMM). NA is located in the cephalic third of the acoustic tubercle and contains variably sized darkly staining cells. NMM is the most caudally located nuclear group and is characterized by regularly round to ovoid cells. The development of NMM is more closely related to papilla basilaris length and complexity than is NA.

Two less well defined cochlear nuclei are also thought to be present. In the region between NA and NMM is a sparsely cell‐populated area, nucleus magno‐cellularis lateralis (NMM), which consists of a variety of small, darkly staining cells and large, pale staining cells which are usually laterally located in the nucleus. Like NMM, NML is better developed in lizards with more complex papillae basilares. Nucleus laminaris may be represented by a few fusiform cells in the ventral portion of the NML region.
Horizontal cell axons and axon terminals in goldfish retina
Authors: Stell William K.
Published: January 2005

Retinas of ordinary and black moor varieties of goldfish (Carassius auratus) were prepared by the Golgi method, mounted flat or sectioned vertically, and studied in the light microscope. Three types of horizontal cells whose dendrites contact only cones, and one type whose dendrites contact only rods, were observed. The cone horizontal cells (Cajal's “external horizontal cells”) all have slender axons which descend gradually to the inner nuclear layer and terminate there in long, fusiform expansions (Cajal's “internal horizontal cells”). The thin and thick portions of the axons, as well as the perikarya of the horizontal cells, bear small numbers of straight, horizontally‐directed, knobby filamentous appendages which may be sites of synaptic contact. The cone horizontal cell axons in goldfish, unlike those in higher vertebrates, do not terminate in contact with synaptic endings of photoreceptor cells, but in proximity to cells and processes deep in the inner nuclear layer. Axons have not yet been demonstrated on rod horizontal cells in goldfish.
Scanning and transmission electron microscope studies of interkinetic nuclear migration in the cerebral vesicles of the rat
Authors: Seymour R. M. , Berry M.
Published: January 2005

A scanning electron microscope (SEM) was used to examine the morphology and surface texture of neuroepithelial cells during interkinetic nuclear migration in the cerebral visicles of the rat at 12, 13 and 14 days of gestation. Serial sections of embryonic material of the same age were also prepared for the transmission electron microscope (TEM). Particular attention was paid to the SEM and TEM appearance of mitotic neuroepithelial cells which occur exclusively along the ventrivcular border of the neural epithelium. Three distinctly‐shaped classes of mitotic cells were recognised in sacnning micrographs. (1) Pyriform cell. This type of mitotic cells was characterised by the presence of very long, fin procsses rediating from the tip and shoulders of a short external (basal) process. These fine processes were temed “intramitoticfilopodia” Microvilli were found on the surface of most pyriform cells. (2) Conical cells. Thee lacked an external process but there were large numbers of intramototic filopodia at the basal pole of the cell body, and the perkikaryal surface was rich in microvilli. (3)Globular cells. It was possible to subdivide this class of cell into large and small types. An external process and microvilli were absent in globuar cells of both sizes, but usually a few short intramitotic filopodia were absent in globlar cells of both sizes, but usually a few short intramitotic filopodia were present at the bnasal pole. The perikaryal surfced of the globular population were reised in coarse liums and bubble‐like protrusions.

By pooling TEM and SEM information we were able to deduce that pyriform cells probably possess a prphase or prometaphase chromosome morphology, While conical cells exhibit a chromosome morphologyu somewhere between prometphase and early anaphase. Lrge globular mitotic cells were found to be between metaphase and late anaphase and small glbular cells were indentified as early telophase cells.

On the basis of these findings we have proposed that as a bipolar neuroepithelial cell rounds up for motosis it passes first through a pyriform state during which the external process is retracted or broken down, and then through a conical stage when the cell consolidates its position on the verntricular surface. Finally, the cell enters a large gobular stage before dividing into two small filopodia play in this procss of rounding up.
The development of synapses in the visual system of the cat
Authors: Cragg B. G.
Published: January 2005

Synapses have been counted by electron microscopy and neurones by light microscopy through the depth of the visual cortex in a series of cats from 37 days gestation to adulthood. A few definite synapses are present as early as three weeks before birth, but there is then a latent period of four weeks before synapses increase rapidly in number 8–37 days after birth. The synapses occur just above and just below the cell plate at first, but in the adult cat they become evenly distributed in the depth of the cortex. The gradual separation of neurones by neuropil during development precedes a parallel increase in the density of synapses by about one week. The average number of synapses associated with one neurone rises to a peak of about 13,000 at seven weeks after birth. The densities of synapses and of neurones subsequently fall to slightly lower values in adult cats as the glial cells continue to develop.

The timing of synaptic development in the visual cortex has been compared quantitatively with that in the L. G. N. and qualitatively with synaptogenesis in the retina. Synapses develop in the L. G. N. and cortex in a parallel fashion, and the L. G. N. precedes the cortex by a short interval of about two days. In the cell plate of the retina a few receptor synapses are present nine days before birth. Inner plexiform synapses are also present at this time, but ribbon‐containing synapses do not appear until birth. Very few receptors possess outer segments with discs at birth, but five days later disc‐bearing outer segments have developed.

Thus synaptic development starts before afferent impulses can enter the visual system, but the main increase in synapses in the L. G. N. and cortex takes place four weeks after the start of synapse formation while the visual system is being used.
Quantitative relationships between nerve and satellite cells in spinal ganglia: An electron microscopical study. II. Reptiles
Authors: Pannese Ennio , Ventura Raoul , Bianchi Rossella
Published: January 2005

In the spinal ganglia of two species of reptiles (gecko and lizard) the volume of the perikaryal satellite cell sheath was found directly proportional both to the volume and surface area of the related neuronal body. This result agrees with that obtained in a previous research on two species of mammals (cat and rabbit). A quantitative balance between neuronal bodies and their associated glial tissue therefore exists also in the spinal ganglia of zoological species phylogenetically quite distant from mammals.

The quantitative relationship between glial and nerve tissue was found to be lower in the gecko and lizard than in the cat and rabbit. This difference could have a phylogenetic significance, and/or it could be explained by the lower metabolic rate in the nervous system of the poikilotherms in respect to mammals.
Human brain in tissue culture. II. Studies of long‐term cultures
Authors: Wroblewska Zofia , Devlin Mary , Gilden Donald H. , Santoli Daniela , Friedman Harvey , Koprowski Hilary
Published: January 2005

This paper describes the techniques used to maintain and reconstitute from storage adult human brain cells in culture. Growth characteristics, cell morphology, lifespan, and karyotypic analysis of cell lines derived from patients with multiple sclerosis (MS), non‐MS neurologic diseases, and normal brains are compared.
Human brain in tissue culture. IV. Morphological characteristics
Authors: Rorke Lucy Balian , Gilden Donald H. , Wroblewska Zofia , Santoli Daniela
Published: January 2005

The morphology of cells from normal and diseased brains and PML‐SV40 transformed brain cells grown on glass cover slips in culture is described. Seven types of cells are identifiable, four of which are probably of mesenchymal origin whereas the remaining three are neuroglial. A classification on the basis of the morphologic features is presented.
Axonal numbers and sizes in the connectives and peripheral nerves of the leech
Authors: Wilkinson Joyce M. , Coggeshall Richard E.
Published: January 2005

The present study is an electron microscopic analysis of the numbers and sizes of axons in the connectives and nerves of the medicianal leech. In either the right or left connectives for ganglis 14–18, there are approximately 2860 (± 294 S.D) axons. Ninety‐seven percent of these axons are less than one micron in diameter. The median connective, Faivre's nerve, contains 97 (± 3 S.D.) axons, and 94% of these fibers are smaller than one micron. In the peripheral nerve roots for ganglia 14–18, there are approximately 2351 (± 311 S.D.) axons. Ninety‐eight percent of the axons in the nerves are less than one micron in diameter. Thus, there are approximately 20,000 axons associated with each of the segmental ganglia 14–18 in the leech, and the vast majority of these fibers are less than one micron in diameter.
The projection of the retina upon the optic tectum of the pigeon
Authors: Hunt S. P. , Webster K. E.
Published: January 2005

The projection of the retina onto the optic tectum of the pigeon has been investigated using silver impregnation methods for degenerating axons and terminals, autoradiographic tracing, and the Golgi methods. Degenerating optic afferents distribute to sublaminae a–d and f of the stratum griseum et fibrosum superficiale over the whole tectum, but two major fields are observed. One occupies the caudal and ventral tectum (in which region laminar cytoarchitecture is marked), and the other rostral and dorsal tectum (where demarcation of cell laminae is relatively poor). Degeneration in the latter field is coarse and clearly distributes in a distinctly laminated fashion within the stratum griseum et fibrosum superficiale. In contrast, degeneration in the caudo‐ventral region is fine, and laminated distribution less clear. The evolution of the degeneration pattern over survival periods from 3 to 56 days suggests that these laminar distributions reflect the existence of several different types of optic terminal ramification present in all parts of the tectum. A selective laminar distribution of such optic afferent types correlates well with our own and other Golgi studies. The results of the autoradiography experiments are broadly compatible with these findings.
Radiation‐induced interference with postnatal hippocampal cytogenesis in rats and its long‐term effects on the acquisition of neurons and glia
Authors: Bayer Shirley A. , Altman Joseph
Published: January 2005

The long term consequences of graduated interference with the acquisition of hippocampal neurons and glia during early infancy were examined with quantitative histology and 3H‐thymidine autoradiography. The head region containing the hippocampus was irradiated from day two on with either two (2X), four (4X), six (6X) or eight (8X) doses of 150–200r X‐rays. The animals were killed at 30, 60, 90 and 120 days of age.

The morphology of the hippocampus was normal in all irradiated groups with the characteristic interlocking folds of the pyramidal and granular layers. While the number of pyramidal cells of Ammon's horn was unaffected, the number of granule cells of the dentate gyrus was progressively and permanently reduced from control levels by the different dosage schedules (2X, 59% reduction; 4X, 77%; 6X, 83%; 8X, 84%). Incidental observations in control animals indicated a 20% increase in granule cells between 30 and 120 days of age in agreement with earlier observations of granule cell labelling after 3H‐thymidine injections in adult rats.

The time of origin of the approximately 15–16% of the granule cells surviving irradiation in the 8X group was determined by injecting either pregnant females (gestation days 19–20) or pups (days 0 and 1) with two successive doses of 3H‐thymidine; the animals were irradiated from day two on with eight X‐ray doses. The granule cells surviving in the postnatally injected group were all unlabelled and comparable in number to the unlabelled cells in control animals that were given five successive postnatal injections of 3H‐thymidine. This established that the radioresistant complement of granule cells is formed prenatally. In the prenatally injected group, over half the surviving cells were labelled; it was assumed that those not labelled were formed before gestation day 19.

In contrast to the permanent reduction in the number of granule cells, there was some reestablishment of the number of cells in the dentate molecular layer and the Ammonic stratum oriens; in the fimbria, recovery in cell number was complete by 60 days. In a supplementary autoradiographic experiment, cell proliferation in the granular layer and in the fimbria was determined at 60 days of age after a single postnatal injection of 3H‐thymidine on either day 15 or day 20 in the control, 2X, 4X and 6X groups. The number of labelled cells in the irradiated groups was always well below control levels in the granular layer, but it was either above or at the same level as controls in the fimbria. Tentative interpretations were offered for the differential long‐term effects of variable X‐ray schedules on the neuronal and glial populations of the hippocampus.
A quantitative analysis of the cat retinal ganglion cell topography
Authors: Hughes A.
Published: January 2005

A retinal ganglion cell distribution map has been prepared for the cresyl violet stained cat retina. It differs from previously published maps in revealing the visual streak to be more substantial and in showing a higher peak density of 9–10,000 ganglion cells/mm2 at the presumed visual pole. The map was used to obtain a minimum estimate of the retinal ganglion cell population as 217,000 cells, more than double the total previously reported. The problem of classifying the cells of the ganglion cell layer is discussed in detail and examples of criterion cells illustrated. The paper also includes an account of retinal mensuration (dimensions, area, etc.) and a discussion of the visual streak orientation.
Retinogeniculate projections in albino and ocularly hypopigmented rats
Authors: Creel Donnell , Giolli Roland A.
Published: January 2005

The retinogeniculate fiber projections were studied by degeneration methods in several strains of rats with pigmentation in their eyes and pelts ranging from the intensely pigmented self phenotype to the albino. The ipsilateral retinogeniculate input in the self, Irish, and hooded rats, and rats with “bicolor fundus” is located medially within the dorsal lateral geniculate nucleus (LGd) and is seen as a single lamina of moderately dense degeneration. The contralateral retinogeniculate input in these ocularly pigmented rats is a dense network of degeneration covering all of the LGd except for the region receiving the ipsilateral input which is an area of sparse degeneration forming a “pocket.” There is a general paucity of ipsilateral fibers in albino rats. The ipsilateral projections in albino, light‐eyed cream‐pelted rats, and the rats with heterochromia irides is seen as several fragmented laminae. The contralateral input to the LGd is evenly distributed, is dense throughout and lacks any discernible “pocket” of sparse degeneration. Only the presence of melanin pigment of optic cup origin appears to correlate positively with the development of normal retinogeniculate projections. Variability was found between animals regardless of the degree of pigmentation shown by the animal. There would appear to be enough genetic modifying factors inducing variation of these fiber projections that the appearance of a particular pattern of input to the LGd should be considered as having only a statistical probability of occurrence.
Dendroaxonic synapses in the substantia gelatinosa glomeruli of the spinal trigeminal nucleus of the cat
Authors: Gobel Stephen
Published: January 2005

The glomeruli in the substantia gelatinosa layer of the spinal trigeminal nucleus of the cat contain three kinds of dendritic processes. One of these, the type 2 dendrite, contains large synaptic vesicles in its spine heads and in its shaft. The type 2 dendrite receives axodendritic synapses from primary trigeminal afferent (C) axons and an occasional axodendritic synapse from small axonal (P) endings with small synaptic vesicles. The type 2 dendrites in turn form dendroaxonic synapses on the C endings. The dendroaxonic synapse and the axodendritic synapse of the C ending typically occur in reciprocal pairs. The axodendritic synapse usually lies in the depths of scalloped depressions in the surface of the C ending while the dendroaxonic synapse is found on the rim of the depression. Type 1 spines, i.e., dendritic spines receiving axodendritic synapses from the primary ending and lacking synaptic vesicles, also receive dendrodendritic synapses from type 2 dendrites.

The types 2 dendrite with its large, rounded synaptic vesicles is considered to be excitatory at its dendroaxonic and dendrodendritic synapses. The type 2 dendrites course from glomerulus to glomerulus receiving their excitatory input through the axodendritic synapses of C axons. A type 2 dendrite, in response to C axon excitation would activate type 1 spines directly through their dendrodendritic synapses (C→2→1) and indirectly by increasing transmitter release at the axodendritic synapses of the C axonal endings through their dendroaxonic synapses (2→C→1). The type 2 dendrites could serve two functions. First, they may prolong transmitter release from the axodendritic synapses of C axonal endings beyond the time of arrival of incoming action potentials because of the reciprocal pairing of dendroaxonic and axodendritic synapses (C⇋2). Second, they may extend the spatial range of the excitatory output of active primary afferent axons to type 1 spines of glomeruli whose primary afferent axons may be inactive (C→2→1).
The retina and retinal projection on the lamina ganglionaris of the crayfish Pacifastacus leniusculus (Dana)
Authors: Nassel D. R.
Published: January 2005

The retinular cell morphology and ommatidia arrangement in the crayfish retina are studied, Each ommatidium contains eight receptor cells (R1–R8). Seven of the them (R1–R7) contribute to a large spindle‐shaped rhabdom with orthogonal layers of microvilli.

Distal to the rhabdom of R1–R7, the 8th receptor cell forms a separate rhabdom with horizontal microvilli. The cell is four‐lobed, is devoid of screening pigments, and forms a thin axon projecting past the first optic neuropile (lamina ganglionaris) and has a terminal in the second (medulla externa), indicating a separate function of the receptor.

The axons from the eight receptors of one ommatidium project to different synaptic compartments (cartridges) in the lamina. A pattern is described where eight axons from three adjacent ommatidia join in one cartridge; and conversely, the axons from one ommatidium split and join to three cartridges.

The seven axons from R1–R7 terminate in two levels of the lamina plexiform layer (epl 1 and epl 2), four in the distal and three in the proximal part. Among the monopolar ganglion cells, two types are found with lateral branches restricted to either of the two receptor terminal layers (M3 in epl 1 and M4 in epl 2) and axons terminating in the second optic neuropile. A correlation between the two orthogonal channels for e‐vector discrimination and the two levels of terminals within the lamina is suggested.

The retina is divided into a dorsal and a ventral part with a mirror symmetry axis horizontally in the eye.
Reconstruction of neurons of dorsal horn proper using golgi‐stained serial sections
Authors: Mannen Hajime , Sugiura Yasuo
Published: January 2005

Three neurons located in the dorsal horn (Lamina III) have been reconstructed using Golgi‐stained serial sections. These cells including dendritic and axonal branchings appear to remain within the dorsal horn and to belong to small‐sized local interneurons of the dorsal horn proper.

The measurements have been made with various criteria: the medio‐lateral, dorso‐ventral and rostro‐caudal extents of the dendritic tree as well as the axonal branchings, total dendritic and axonal length, number of axonal endings and distance from the starting point of the axon at the dendrite to the point where the dendrite joins the soma (S‐A distance).
The cat optic nerve: Fibre total count and diameter spectrum
Authors: Hughes A. , Wässle H.
Published: January 2005

An electron microscopic examination of two cat optic nerves indicates a mean total count of 193,000 fibres ranging from 0.5μ to 13.5μin diameter. This count, although nearly double any previously reported, supports recent minimum estimates of the retinal ganglion cell population of the cat eye. A radial gradient of packing density exists across the nerve close to the globe; a high density “core” with a unimodal fibre diameter spectrum may be identified as the area centralis outflow and a peripheral low density region with a trimodal diameter spectrum contains the projection of the peripheral retina. Division of the peripheral fibre spectrum suggests the percentages of α,βandγ ganglion cells in the peripheral retina to be 5%, 42% and 53% respectively.
The structural maturation of the stato‐acoustic nerve in the cat
Authors: Romand Raymond , Sans Alain , Romand Marie Rose , Marty Robert
Published: January 2005

The maturation of the stato‐acoustic nerve in the cat was studied by light and electron microscopy from the fetal stage to the adult. Measurement of the outer diameter of the fibers and the study of the myelination process revealed that myelination begins earlier for the vestibular nerve than for the cochlear nerve: by the fifty‐third day of gestation 64% of the vestibular fibers have already passed the promyelin stage whereas for the cochlear nerve this promyelin stage begins for the majority of fibers on the fifty‐seventh gestation day. Afterward, maturation proceeds more rapidly for the cochlear nerve. In the case of both nerves, maturation is still incomplete at two months of age.

Concerning the relationship between the thickness of the myelin sheath and the axoplasmic diameter, there is already a good correlation by the fifty‐seventh day of gestation in the vestibular nerve, whereas it appears several days after birth in the cochlear nerve.
Complementary laminar terminations of afferents to area 17 originating in area 18 and in the lateral geniculate nucleus in squirrel monkey
Authors: Tigges Johannes , Tigges Margarete , Perachio Adrian A.
Published: January 2005

The projections from area 18 and the lateral geniculate nucleus onto area 17 of the squirrel monkey (Saimiri) were investigated with retrograde (horseradish peroxidase) and anterograde (tritiated proline) labelling techniques, and the (Fink‐Heimer) silver impregnation method for degenerating axons and their terminals.

The association fibers from area 18 terminated in all layers of area 17 except in layer IV and in the lower aspect of layer IIIc. The greatest number of terminals were in layers I, V and VI. The bulk of geniculocortical fibers terminated in layer IV and the lower aspect of layer IIIc; a minority of the geniculocortical fibers terminated in layer VI and the lower aspect of layer IIIb. Thus, the majority of fibers from the two sources investigated terminate in a complementary laminar fashion in area 17.

The portion of area 17 on the lateral surface of the hemisphere, where the central visual field is represented, received a less dense projection from the geniculate nucleus than the striate cortex in the calcarine fissure, where the peripheral visual field is represented. Ocular dominance columns were not apparent in the striate cortex. No evidence was found that the lateral geniculate nucleus projects to area 18.

The results of combined injections of horseradish peroxidase and tritiated proline in area 17 indicated a point‐to‐point reciprocity between area 17 and the ipsilateral lateral geniculate nucleus.
Observations on labeling of neuronal cell bodies, axons, and terminals after injection of horseradish peroxidase into rat brain
Authors: Hedreen John C. , McGrath Susan
Published: January 2005

We observed with light microscopy the evolution of neuronal labeling phenomena in rats with two hours to eight days survival following injection of horseradish peroxidase (HRP) into the neostriatum. We compared the results of neostriatal injection with those injection of the overlying neocortex. The following conclusions were reached.

The zone of diffuse background HRP around the injection site began to shrink after 18 hours. The extent of the early zone of diffusion was marked from 18 hours to two days by a universal granular labeling of neurons. This granular cell labeling appears to be the result of earlier diffuse cell labeling rather than retrograde axonal transport.

Retrograde labeling of cells takes place from terminals and from damaged axons. Anterograde labeling of what appear to be terminals and fine preterminal axons takes place only from cells in the injection area, and not from either intact or damaged axons of passage. Usually the axons engaged in such retrograde or anterograde transport are not visibly labeled. Labeling of cells and terminals is generally optimal at 12 to 24 hours, but corticostriatal cells in layer V of the neocortex are seen best at 24 to 36 hours. The area from which retrograde labeling of cells takes place is larger than that from which anterograde labeling of terminals occurs.

Massive intra‐axonal movement of HRP away from the injection site occurs within a few hours in axons of passage as well as those originating there. This axonal labeling fades in most axons by 24 hours, but certain axons remain darkly labeled. The latter are probably damaged, since labeled axons which appear to be degenerating are later (3–5 days) seen in the same place, and Fink‐Heimer staining of adjacent sections also shows degenerating axons in these regions. The early massive labeling of axons can lead to short‐lived labeling of complete axonal arborizations within the range of this intra‐axonal movement of HRP. But it seems to have no relation to the longer‐lived labeling of distant cells and terminals, which presumably results from active axonal transport. This suggests that HRP entering axons of passage is not captured by the axonal transport mechanisms.
An autoradiographic study of the descending connections of the mammillary nuclei of the rat
Authors: Cruce Judith A. F.
Published: January 2005

The descending connections of the mammillary nuclei of the rat were studied using the autoradiographic technique to trace anterograde axonal connections. Injections of tritiated leucine or tritiated proline were stereotaxically aimed at either the medial or lateral mammillary nucleus. Label in the medial and lateral mammillary nuclei was rated as either high or low. With a rating of high in both medial and lateral mammillary nuclei (11 animals) three major projection sites were seen: the dorsal tegmental nucleus (DTN), the ventral tegmental nucleus (VTN) and a pontine region which included both the pontine grey and the tegmental reticular nucleus. In the nine animals in which the medial mammillary nucleus was rated high but the lateral mammillary nucleus was rated low, no label was present in DTN, although the other two regions were labeled. The one animal in which the lateral mammillary nucleus was high but the medial was low, had label in all three major projection sites; since fibers destined for the DTN pass through the VTN, it could not be determined whether or not lateral mammillary efferents were in synaptic contact with the VTN. Labeled fibers were present throughout a wide dorsal‐ventral extent of the mesencephalon; these fibers are components of the mammillotegmental system and not part of the mammillary peduncle.
Early development of amacrine cells in the mouse retina: An electron microscopic, serial section analysis
Authors: Hinds James W. , Hinds Patricia L.
Published: January 2005

The development of retinal amacrine cells in mice at the fifteenth day of gestation (E‐15) has been analyzed by reconstructing large numbers of cells from serial thin sections. This information has been supplemented by reconstructing cells from E13 and E17 retinas as well as autoradiographic studies of time of origin of cells arising in the period before E15. The presence of bipolar amacrine cells in the outer ventricular layer, first suggested by Cajal, has been confirmed by reconstructing cells from the E17 retina when a clearly defined inner plexiform layer (IPL) is first found. The less mature bipolar amacrine cells present at E17 resemble similar cells found in the E15 retina; they are distinguished from the pre‐axonic, migratory stage of ganglion cells by their flattened rather than cylindrical processes, the darker cytoplasm of these processes, and the position of their centrioles closer to the nucleus. Examination of large numbers of reconstructed cells throughout the thickness of the E15 retina has revealed no forms directly transitional from ventricualr cells to bipolar amacrine cells; insted, bipolar amacrine cells appear to be derived by retrograde (sclerally directed) migration of cells in the ganglion cell layer that resemble normal ganglion cells but lack axons. The origin of these anaxonic cells of the ganglion cell layer is not certain but several findings, including evidence of degenerating axons in the optic nerve, sugest that they are derived by loss of the primitive axons of ganglion cells. Thus amacrine cells may be formed by a relatively late differentiating event that occurs after migration of cells to the ganglion cell layer. Such a developmental origin would offer a plausible explanation for the displaced amacrine cells in the ganglion cell layer and IPL described in the adult, as well as perhaps the close similarity of the dendritic trees of certain subtypes of normal, nondisplaced, ganglion and amacrine cells.
A cytologic study of grandry corpuscle development in chicken toe skin
Authors: Idé Chizuka , Munger Bryce L.
Published: January 2005

The developmental sequence of Grandry corpuscles was traced in the toe skin of embryonic, young and adult chickens by light and electron microscopy. The developing Grandry cells as well as Schwann cells can first be identified at stage 38(˜ 12 days of incubation) due to the cytoplasmic content of scattered secretory granules of ˜ 100 nm in diameter. Such developing Grandry cells are always associated with nerve fibers. During late stages (stages 40–42, 14–16 days of incubation) several immature Grandry cells formed cell clusters in the dermis. Such cell clusters were always in contact with growing nerve tips or Schwann cells. Immature Grandry cells were separated from one another and dispersed in the connective tissue compartment at stages 44–45 (near hatching). By the time of hatching the developing Grandry cells began to have the morphological characteristics of adult cells. They were relatively large in cell diameter (˜ 10 μm) containing numerous secretory granules and bundles of filamentous material. These cells had finger‐like cytoplasmic processes. The Grandry cells at this time had an intimate relationship with nerve fibers and satellite cells. The fact that Grandry cells were always associated with nerve fibers throughout deveopment would support the hypothesis that Grandry cells are derived from neural elements, perhaps neural crest. Satellite cells of Grandry corpuscles are apparently derived from Schwann cells. Grandry cells and corpuscles are adult in form by two to three months of age.
An autoradiographic study of midbrain‐diencephalic projections to the inferior olivary nucleus in the opossum (Didelphis virginiana)
Authors: Linauts M. , Martin G. F.
Published: January 2005

Techniques of intra‐axonal transport were utilized to elucidate the organization of diencephalic and midbrain projections to the inferior olivary nucleus of the Virginia opossum. Retrograde transport of horseradish peroxidase injected into olive suggests that terminals within it arise from the subparafascicular nucleus of the caudal thalamus, the nucleus of Darkschewitsch, the fields of Forel, the interstitial nucleus of Cajal, the periaqueductal grey, the caudla pretectal nucleus, the tegmentum dorsomedial to the red nucleus, the red nucleus (minimal), the nucleus linearis, as well as the dorsolateral midbrain tegmentum and tectum (Henkel et al., '75).

Tritiated leucine injections were made into each of the above‐mentioned cell groups so that the olivary terminals of their axons could be demonstrated autoradiographically. In general, the projection systems show three basic patterns of organization. Ventormedial areas of the midbrain, including the ventral periaqueductal grey, the interstitial nucleus of Cajal, part of the red nucleus and the tegmentum dorso‐medial to it, provide a substantial and topographically organized projection to the principal nucleus of the olive, as well as minor inputs to the accessory neclei. Secondly, neurons within the subparafascicular nucleus, the nucleus of Darkschewitsch and the fields of Forel project most heavily to parts of the medial accessory nucleus, although they also provide input to the other major subdivisions of the olive. Third, axons from the dorsolateral tegmentum and tectum completely avoid the principal nucleus, while supplying small regions of the accessory nuclei.
The vestibular nuclei in the domstic hen (Gallus domesticus). III. Ascending projections to the mesencephalic eye motor nuclei
Authors: Wold Jan Egil
Published: January 2005

Following injections of horseradish peroxidase in the oculomotor and the trochlear nuclei in the hen, the occurrence of labeled cells was plotted in the vestibular nuclei. The majority of labeled cells was localized in the superior, the medial, and the tangential nucleus. Within the superior nucleus the cells were found mainly caudally, extending medially and ventrally in central areas. In the medial nucleus labeled cells were localized exclusively in its rostral half, mainly in ventrolanteral regions. Most, if not all, cells in the nucleus tangentialis project rostrally. In addition, rostrally projecting vestibular cells were found in the cell group A and the rosrolateral part of the descending nucleus. The projection to the oculomotor nuclear complex is from the superior nucleus and the cell group A bilateral but chiefly ipsilateral, from the medial nucleus bilateral, from, the tangential nucleus and the rostral pole of the descending nucleus chiefly contralateral. Massive labeling was found in the abducens nucleus, somewhat less in the reticular formation, mainly in lateral regions of the medial part at the level of the abducens and facial nuclei. Labeled cells were, in addition, found in the deep layers of the optic tectum, and scattered cells in the nucleus raphe. The findings are discussed in the light of what is known of the organization of the vestibular nuclei in the hen and the rostral projection of the vestibular nuclei in mammals.
Radioautographic investigation of gliogenesis in the corpus callosum of young Rats I. Sequential changes in oligodendrocytes
Authors: Imamoto Kikuko , Paterson Jean A. , Leblond C. P.
Published: January 2005

The corpus callosum of young rats was examined to clarify the behavior of the three subtypes of oligodendrocytes (the large organelle‐rich “light oligodendrocytes,” the smaller and more densely stained cells referred to as “medium oligodendrocytes,” and the even smaller and denser “dark oligodendrocytes”). It was hoped to find out whether cells of the three subtypes undergo division and how they are related to one another. 3H‐thymidine was given intraperitoneally as single or three shortly spaced injections to a first group of 19‐ to 20‐day old rats weighing about 40 g, and to a second group of 25‐day old rats weighing about 80 g. The animals were sacrificed at various time intervals from 2 hours to 35 days after 3H‐thymidine administration. Pieces of corpus callosum were taken near the superior lateral angle of the lateral ventricles; and semithin sections were radioautographed and stained with toluidine blue.

Two hours after 3H‐thymidine injection, label is virtually absent from light, medium and dark oligodendrocytes, from microglia, and probably from astrocytes, but is present in about 10% of the immature glial cells, which include the poorly differentiated glioblasts and the partially differentiated oligodendroblasts and astroblasts. Hence, the cells undergoing DNA synthesis and mitosis in the corpus callosum are these three types of immature cells.

During the week that follows the administration of 3H‐thymidine, label appears in oligodendrocytes and astrocytes, which presumably have arisen from the initially labeled immature cells. The oligodendrocytes acquire label in a sequential manner: the light cells show label first and their labeling index reaches a peak at the seven‐day interval; the medium oligodendrocytes become labeled next with a labeling peak toward the 14‐ and 21‐day intervals and, finally, the dark oligodendrocytes with a peak around the 28‐day interval. Analysis by the method of Zilversmit et al. (1942‐1943) provides precise details on the sequence: immature cells presumed to be oligodendroblasts give rise to light oligodendrocytes which, after four to seven days, transform into medium oligodendrocytes which, after another 11 to 18 days, transform into dark oligodendrocytes. The dark cells may persist indefinitely or turn over at a very slow rate.

It is concluded that oligodendrocytes arise from the last division of oligodendroblasts and develop in three main periods; a light stage lasting less than a week, a medium stage lasting about two week, and a very long lasting dark stage.
Catecholamine innervation of the basal forebrain II. Amygdala, suprarhinal cortex and entorhinal cortex
Authors: Fallon James H. , Koziell David A. , Moore Robert Y.
Published: January 2005

The catecholamine (CA) innervation of the posterior basal forebrain, the amygdala, suprarhinal cortex and entorhinal cortex, was studied in the rat using biochemical assay and fluorescence histochemistry. The assay studies demonstrate a moderate norepinephrine (NE) content in the amygdala and entorhinal cortex with a lower value for the suprarhinal cortex. Following destruction of the locus coeruleus, the decrease in NE content of these basal forebrain structures indicates that their principal NE innervation is from locus coeruleus. An additional small NE input arises from the medullary NE neuron groups. Ablation of dopamine (DA) cell groups (substantia nigra‐ventral tegmental area, SN‐VTA) indicates that the DA input to the amygdala arises from the lateral VTA and medial half of the SN.

Fluorescence histochemical studies using the glyoxylic acid‐Vibratome technique demonstrate the presence of four distinct types of CA neuron terminal plexus in the posterior basal forebrain. These include two different DA fiber types arising in SN‐VTA, small NE fibers with small varicosities arising in locus coeruleus and NE fibers with larger varicosities arising in other brainstem NE cell groups. The large NE fibers appear to enter the amygdala via the ansa peduncularis‐ventral amygdaloid bundle to innervate the central and basolateral nucleus and the anterior amygdaloid area. The locus coeruleus NE fibers appear to enter the posterior basal forebrain via both the stria terminalis and ansa peduncularis‐ventral amygdaloid bundle system to form a moderately dense innervation of the central and basolateral nuclei of the amygdala and a less dense innervation of the other areas. The DA neuron axons are concentrated in the central and basal nuclei and intercalated cell groups. Other areas receive a more diffuse DA input, with the exception of the moderately dense innervation of the suprarhinal cortex and DA “islands” in the ventral‐anterior entorhinal cortex. The DA input to the posterior basal forebrain is complex and heterogeneous and the axonal morphology differs greatly among the terminal fields within the amygdala and adjacent cortical areas.
Somatotopic organization of mechanosensory projections to SII cerebral neocortex in the raccoon (Procyon lotor)
Authors: Herron Paul
Published: January 2005

The pattern of projections of peripheral receptors to the neocortex in the second somesthetic receiving area (SII) was mapped in raccoons. The purpose was to determine if the projection area of peripheral receptors to the forepaw area in the SII region is disproportionally enlarged as it is in SI.

Tungsten microelectrode recording procedures were used to map thoroughly the inferior wall of the suprasylvian sulcus for regions responsive to mechanical stimulation of peripheral receptors.

The results show that:

The forepaw area in SII shows an enlargement commensurate with that found in the SI. This suggests that those factors that are selective for tactile acuity of the raccoon forepaw were operating in the evolution of SII as they were in SI.

The somatotopic organization of mechanoreceptive projections to SII is reversed mediolaterally compared to previous descriptions of this arrangement in other mammals: projections form axial structures lie medially and those from apical structures lie laterally along the inferior bank of the suprasylvian sulcus in the raccoon.
Organizational features of the cat and monkey cerebellar nucleocortical projection
Authors: Tolbert Daniel L. , Bantli Heinrich , Bloedel James R.
Published: January 2005

The organization of the cerebellar nucleocortical projection in the cat and the monkey has been studied using orthograde and retrograde neuroanatomical tracing techniques. Injections of tritiated leucine in the cat cerebellar nuclei orthogradely labeled neucleocortical fibers throughout their course to the cerebellar cortex. Their branch points in the corpus medullare, in the folial white matter, and in the granular layer were evident from the dense, continuous distribution of silver grains overlying these labeled axons. The results from the cat showed that the cerebellar nucleocortical projection is organized principally into three rostrocaudally oriented longitudinal cortical zones. Fastigial nucleocortical fibers were directed principally to the medial 1.5–2.5 mm of the ipsilateral vermis, with a lighter projection to the lateral vermis ipsilaterally and to the medial area of the vermis contralaterally. The interposed nuclei projected mainly to the paravermis‐medial hemispheric zone of the cerebellar cortex. Nucleocortical fibers from the posterior interposed nucleus projected principally to the paramedian lobule, to the medial hemispheric area of Crus I and the lobus simplex, and to the flocculus and paraflocculus. Nucleocortical projections from the anterior interposed nucleus coursed to the anterior lobe paravermis and to the ventral folia of the paramedian lobule. A lighter projection from the interposed nuclei was found to the lateral edge of the vermis and into intermediate areas of the hemisphere. Dentatocortical fibers were directed into the lateral folia of Crus I and Crus II of the lateral hemispheric zone, with a lighter projection to intermediate areas of the hemisphere of the posterior lobe and along the lateral edge of the anterior lobe hemisphere. Along the periphery of each cortical zone, the nucleocortical projection from adjacent deep nuclei overlapped slightly. The retrograde transport of horseradish peroxidase (HRP) from injection sites in the lateral hemisphere, in the medial hemisphere — paravermis, and in the vermis labeled neurons localized mainly within the dentate, interposed, and fastigial nuclei, respectively. Retrograde labeling experiments carried out in monkeys indicated that the organization of the neucleocortical projection in this species is different than that of the cat. In the primate, the nucleocortical projection to the lateral hemisphere, to the medial hemisphere — paravermis, and to the vermis appeared to arise principally from the dentate nucleus. There was a secondary input to the paravermis and vermis arising from the interposed and fastigial nuclei, respectively. This evidence suggests that the cerebellar nucleocortical system undergoes a significant phylogenetic change in its organization between the cat and primate. These organizational differences are discussed in light of possible functional implicatons.