bluuebunny/crossref_metadata_2025 huggingface dataset:
Visual intensity and pattern discrimination after lesions of the thalamofugal visual pathway in pigeons
Authors: Hodos William , Karten Harvey J. , Bonbright James C.
Published: January 2005

Twenty‐seven pigeons were trained to discriminate between stimuli that differed in intensity or pattern. In 16 cases, bilateral, electrolytic, stereotaxic lesions were made in the nucleus opticus principalis thalami (OPT), which is the main thalamic terminus of the optic tract. In some cases, the lesions also interrupted the efferent fibers of nucleus rotundus thalami, which receives major input from the optic tectum. In an additional 11 cases, bilateral telencephalic lesions were made by aspiration. These lesions were in the accessory hyperstriatum, which contains the nucleus intercalatus, hyperstriati accessorii (IHA), which is the telencephalic target of OPT. Extensive destruction of either IHA or OPT produced little or no impairment of discrimination performance. However, those cases in which both OPT and nucleus rotundus were involved showed serious performance losses.
Experimental reorganization of the cerebellar cortex. II. Effects of elimination of most microneurons with prolonged x‐irradiation started at four days
Authors: Altman Joseph , Anderson William J.
Published: January 2005

The heads of Long‐Evans rats were irradiated from the fourth day after birth with a schedule of repeated doses of low‐level x‐ray which essentially prevented the formation of basket, stellate and granule cells in all except the earliest‐forming lobules (nodulus and uvula). The morphogenic and synaptogenic effects of this treatment were examined with light and electron microscopy in 30 day old animals, with particular attention paid to the pyramis. Although when irradiation was started the Purkinje cells formed a monolayer and had upward oriented apical poles, they became scattered later and had randomly oriented dendrites. This secondary disorientation was attributed to insufficient space available in the arrested cerebellum for the rapidly expanding Purkinje cells. Although basket cell terminals were scarce, basket cell‐like terminals were formed on the somata of Purkinje cells, apparently by recurrent axon collaterals of these cells. The most common synapses with the thorns of Purkinje dendrites were formed by climbing fibers but other elements, including glial processes, were also in contact with postsynaptic loci on the thorns. Many mossy fiber terminals reached the surface. Where parallel fibers were present they were often thicker than in unirradiated animals and contained neurofilaments. No pathological changes were seen in these cerebella, with the possible exception of excessive lobulation of the nuclei of many Purkinje cells.
The organization of the seventh lumbar spinal ganglion of the cat
Authors: Burton Harold , McFarlane John J.
Published: January 2005

The organization of the seventh lumbar dorsal root ganglion (DRG) of the cat has been investigated both anatomically and electrophysiologically. In the first two series of experiments an attempt was made to relate the topographic location of identified groups of cells in the ganglion with the rostro‐caudal position of their central processes in the filaments of the dorsal root. 3H‐proline was injected into various sectors of the ganglion and the distribution of the axonically transported proteins, in individual dorsal rootlets, was determined by means of liquid scintillation spectroscopy and the location of the injections was determined by autoradiography of the sectioned ganglia. The projection pattern was also determined by antidromically activating DRG cells in various parts of the ganglion by sequentially stimulating each of six dorsal root filaments. The results of both groups of experiments indicate that cells located in the medial (caudal) parts of the ganglion project into the most caudal rootlets of the dorsal root; cells in the most lateral (rostral) parts of the ganglion project into the most rostral rootlets, while cells in the intermediate parts of the ganglion project into the middle rootlets. In a third series of experiments, a shifting pattern of overlapping receptive fields was demonstrated for a series of recordings that traversed the ganglion from medial to lateral. This pattern was shown to be nearly equivalent to the organization of receptive fields previously demonstrated by Kuhn ('53) for a rostral to caudal sequence of dorsal rootlets, i.e., foot and leg preaxial fields predominated in the lateral sectors, while postaxial fields were found in the medial sectors of the ganglion.
Fluorescence and electron microscopic studies of the early development of the substantia nigra and area ventralis tegmenti in the fetal rabbit
Authors: Tennyson Virginia M. , Mytilineou Catherine , Barrett Robert E.
Published: January 2005

The anlage of the substantia nigra compacta and the area ventralis tegmenti appears as a fluorescent zone in the midventral proliferation in the caudal mesencephalon of the rabbit at day 14 of gestation. Fluorescence is present in cell bodies and their processes in the mantle layer of the basal plate just ventral to the ependymal zone. By day 16 of gestation, the number of fluorescent cells and processes has increased, and they form an inverted “V” shaped zone in the midline mantle layer. A fluorescent fiber tract, the presumptive mesolimbic and nigroneostriatal pathway, extends from the fluorescent zone through the lateral hypothalamus as far as the caudal portion of the telencephalon. Electron microscopic studies of the inverted “V” shaped anlage show that most of the cells are spindle‐shaped bipolar neuroblasts, but some globular neuroblasts are present as well. The large 800 to 1000 Å dense core vesicle is found in the perikarya of the neuroblasts and also in processes in the neuropil. Axonal growth cones are common, but synaptic profiles are rare.

By day 18 of gestation, some of the fluorescent cell bodies have migrated lateral to midline and as far rostral as the central portion of the midbrain. Fluorescent axons of the presumptive nigroneostriatal pathway have reached the putamen and have formed minute varicose terminals. These axons, therefore, have reached their terminal nucleus before their cell bodies have finished migrating to their final positions. Electron microscopic study of the anlage located lateral to midline shows that the cells are multipolar and exhibit extensive new growth of dendrites. Immature synaptic profiles and a few mature junctions are occasionally found in the neuropil.

By day 20 of gestation, a distinct substantia nigra compacta and reticulata can be recognized lateral to the area ventralis tegmenti. The neurons of the substantia nigra have relatively abundant perikaryal cytoplasm and the cells are frequently adjacent to one another. The perikarya of the area ventralis are some what smaller and they are spaced more widely apart. Large dense core vesicles are present in some perikarya of both regions. Synaptic terminals are more common, but still not numerous. The meso‐limbic and nigroneostriatal pathway are well established at this stage.
The effects of monocular lid suture upon the development of the visual cortex in squirrels (Sciureus carolinensis)
Authors: Guillery R. W. , Kaas J. H.
Published: January 2005

Three infant squirrels had the lids of one eye sutured prior to eye opening. The animals were killed when they were adults and the cells in the visual cortex were studied after Nissl staining.

On the side contralateral to the suture, the cortical nerve cells were more closely packed than on the side of the suture. This asymmetry was clearly evident in cortical layers II–VI, and it was as marked in the regions of cortex receiving from the monocular crescent of the visual field as it was in the binocular segments. Thus, these cortical changes cannot be dependent upon the geniculate cell changes, since the latter occur in the binocular but not the monocular segments of the nucleus.
Ontogeny of monoamine neurons in the locus coeruleus, raphe nuclei and substantia nigra of the rat. I. Cell differentiation
Authors: Lauder Jean M. , Bloom Floyd E.
Published: January 2005

The onset of cell differentiation in the locus coeruleus, dorsal and medial raphe nuclei, and substantia nigra (zona compacta) was studied using the technique of long‐survival H3‐thymidine autoradiography to date neurogenesis. Pregnant female rats were injected with isotope on day 10, 11, 12, 13, 14, 15, 16 or 17 of gestation. Litters were born on day 22 and allowed to survive for 30 days. Brains were prepared for the fluorescence histochemical demonstration of monoamines or fixed by formalin perfusion. Autoradiography was carried out on sections adjacent to those in which monoamine‐nuclear groups were identified by the fluorescence method and also on sections from perfused brains, which were used to facilitate cell counting. The norepinephrine cells of the locus coeruleus began to differentiate (presence of heavily labelled cells) on days 10–13 of gestation, with a peak of heavy labelling on day 12, whereas the 5‐HT cells of the raphe nuclei and the dopamine cells of the substantia nigra began differentiating on days 11–15. In the dorsal raphe nucleus, the peak of heavy labelling occurred on day 14, whereas in the medial nucleus this took place on days 13–14. The substantia nigra, on the other hand, peaked on day 13.

Cell differentiation was also studied in the cerebellar Purkinje cells and hippocampal macroneurons (pyramidal and polymorph cells) of areas CA3 and CA4, to which the locus coeruleus has been reported to project. Differentiation of these cells commenced on days 14–15 (Purkinje cells) and 13–18 (hippocampal cells), with both cell types peaking on day 15, a full three days after the peak of heavy labelling in the locus coeruleus.

Evidence is discussed for the possible neurotrophic role of monoamine neurons in the neurogenesis of monoaminergic receptive cells.
An autoradiographic study of retinogeniculate pathways in the cat and the fox
Authors: Hickey T. L. , Gullery R. W.
Published: January 2005

The distribution of retinal afferents to the dorsal lateral geniculate nucleus of the cat and the fox has been studied using ocular injections of 3(H)‐leucine and autoradiographic techniques. Whereas fiber degeneration methods have shown only five distinct layers in the lateral geniculate nucleus, autoradiographs show six well defined layers in both species. Laminae A and C receive afferents from the contralateral eye, while laminae A1 and C1 receive from the ipsilateral eye. A retinal input to the region lying between lamina C1 and the optic tract could not be demonstrated by fiber degeneration methods, but this region can now be divided into two distinct layers. The antero‐dorsal of these two layers (lamina C2) receives afferents from the contralateral eye, while the postero‐ventral layer, nearest the optic tract, appears to receive no direct afferents from either eye.

Since the rapid component of the axoplasmic transport labels axon terminals to a greater extent than fibers of passage, the autoradiographic method demonstrates, more successfully than fiber degeneration methods, that there is no significant binocular overlap between the retinal projections to alternate geniculate layers.
Topographic atlas of catecholamine and acetylcholinesterase‐containing neurons in the rat brain. I. Forebrain (telencephalon, diencephalon)
Authors: Jacobowitz David M. , Palkovits Miklos
Published: January 2005

Transverse sections of the rat forebrain have been studied by the histofluorescence and acetylcholinesterase histochemical methods. A detailed stereotaxic atlas of the catecholaminergic and acetylcholinesterase‐containing neural structures.
Locomotor behavior of decerebellated arboreal mammals — Monkey and raccoon
Authors: Wirth Fremont P. , O'Leary James L.
Published: January 2005

Total and partial cerebellectomies were carried out on 36 arboboreal animals, 15 racoons and 21 rhesus monkeys. The animals were evaluated pre‐ and post‐operatively for ability to swim, walk‐run, leap, and climb. Tone, reflexes, strength and other aspects of behavior were also studied. Both species exhibited rapid recovery from the procedure and were self‐sufficient shortly after surgery. Adult racoons and monkeys rapidly regained their ability to climb, and six months after surgery were able to do so normally except for mild residual ataxia when hurried. Ability to walk or run was regained at a much slower rate and was incomplete at six months, although at one year monkeys were not greatly incapacitated in walking. These differences indicated greater impairment of physiological extensor muscle groups than of flexors following cerebellectomy. The vestibular aspect of cerebellar deficit appeared to be related to recovery to a lesser extent. Swimming was very little altered by cerebellectomy.

Muscular strength was recoverable in the monkey following cerebellar ablation. Power and force were measured before and after cerebellectomy. The latter was evaluated by food reinforcement to occasion pulling a weighted lever by selected trained monkeys. Recovery of power, which involved return of rapid, effective movements was slower, but could also occur completely. Careful histological examination conducted on all deceased animals indicated that the anticipated removals were accomplished without significant brain stem injury. Hydrocephalus was observed to develop in a significant number of animals following cerebellectomy. This factor has not been excluded in many previous reports, and may have contributed to failure to achieve effective compensation.
The optic system of the teleost Cichlasoma biocellatum
Authors: Anders Juanita J. , Hibbard Emerson
Published: January 2005

The retinal projections of the fresh water teleost. Cichlasoma biocellatum, were examined using a modification of the Nauta‐Gygax method following unilateral enucleations and removal of retinal quadrants. After the unilateral enucleations, degeneration was found in the fasciculus medialis nervioptici, fasciculus geniculatus tractus optici, fasciculus dorsomedialis tractus optici, and the accessory optic tract. The pretectal nucleus, nucleus corticalis, and accessory optic nucleus contained debris of terminal degeneration. The majority of the optic fibers terminated in five layers in the optic tectum. The quadrant removals showed that fibers from the retinal quadrants formed layers in the ribbon shaped optic nerve running the width of the nerve. The dorsal to ventral arrangement of the fibers was: dorsal nasal quadrant; dorsal temporal quadrant; ventral nasal quadrant; and the ventral temporal quadrant. The fibers from only the posterior half of the retina supplied the fasciculus geniculatus tractus optici and the corpus geniculatum laterale. Fibers from the anterior half of the retina supplied the accessory optic tract and nucleus. All other tracts and nuclei examined received fibers from all the retinal quadrants. The projection of the retinal quadrants to the tectal quadrants was specific and always formed five layers of degeneration.
Origin of specific synaptic types in the motoneuron neuropil of the monkey
Authors: Bodian David
Published: January 2005

An attempt has been made to establish, so far as possible, the specific types of synaptic bulbs on motoneurons which arise from extrinsic (descending and dorsal root) and intrinsic sources (interneurons). This has involved the laborious analysis of thousands of electron micrographs of material from normal motoneuron neuropil, and motoneuron neuropil of animals with lesions of spinal tracts, spinal roots, and motor cortex.

Our studies have established that the large synaptic bulbs on dendrites, which are the only type in the spinal cord to possess pre‐synaptic synapses (serial synapses), are derived from monosynaptic dorsal root fibers (R bulbs). The presynaptic component of the serial synapse appeared to degenerate at levels below spinal cord transections (P bulbs). By means of transections of spinal cord we have found that descending fibers in the spinal cord terminate as one of at least two distinct classes of synaptic bulbs, one with spheroid synaptic vesicles (S) and one with flattened vesicles (F). There is evidence from several sources that the first type may often be excitatory in function and the second type inhibitory. Only synaptic bulbs with spheroid vesicles show definite signs of degeneration after lesions of the opposite motor cortex. The large (L) synaptic bulbs on motoneuron somata, associated with subsynaptic cisterns, are clearly not derived from the descending systems, or from posterior root fibers.
The central projections of the trigeminal, facial and anterior lateral line nerves in the carp (Cyprinus carpioL.)
Authors: Luiten P. G. M.
Published: January 2005

The central projections of the trigeminal, facial and anterior lateral line nerves were studied in the carp (Cyprinus carpio) by the Nauta and Fink‐Heimer silver techniques following rhizotomy.

Degenerating trigeminal fibers were found projecting on the nucleus of the descending trigeminal root and on the medial funicular nucleus. The former can be subdivided in five portions lying dorsal to the various cranial motor nuclei. The afferent facial fibers could be traced into the facial, glossopharyngeal and vagal lobes, while the anterior lateral line nerve projects on rostral, medial and caudal parts of the medial nucleus and on the eminetia granularis. The anterior lateral line nerve can be divided into a dorsal and a ventral root, each following the same course. The role trigeminal and facial nerves play in proprioception of respiratory muscles is discussed.
Autoradiographic investigations of glial proliferation in the brain of adult mice. II. Cycle time and mode of proliferation of neuroglia and endothelial cells
Authors: Korr Hubert , Schultze Brigitte , Maurer Werner
Published: January 2005

The cycle time of the proliferating glial cells outside the subependymal layer of the lateral ventricle as well as that of endothelial cells was studied autoradiographically in the brains of adult and untreated mice. To determine the mean cycle time two independent methods were used. A mean cycle time of about 20 hours was obtained for glial and endothelial cells from the decrease of the mean grain number/nucleus as a function of time after tritiated thymidine (3H‐TdR) injection.

Another group of experiments utilized the “method of labeled S phases.” With this method the passage of labeled cells through successive S phases is observed. Passing through S phase following 3H‐TdR injection the 3H‐labeled cells are double labeled by an additional 14C‐TdR injection. This method again resulted in a cycle time of 20 hours for glial and endothelial cells. From the present work and a former study (Korr et al., 11973) the following cell cycle parameters were derived: Cycle time 20 hours; S phase 9.4 hours; G2 less than three hours; (G2 + M) five hours; G1 five hours. The growth fraction of glial cells related to all glial cells is only 0.004.

Furthermore, the present experiments show that in the case of glial cells 17% of the daughter cells after mitosis become pyknotic and are eliminated from the glial cell population. Apart from this cell loss, after mitosis about onefourth of the daughter cells do not enter the next S phase. These cells leave the growth fraction and are replaced by a corresponding number of non‐proliferating glial cells. There is a relatively extensive permanent exchange of cells between the growth fraction and non‐growth fraction of glial cell.
Crossed pathways from the entorhinal area to the fascia dentata. I. Normal in rabbits
Authors: Hjorth‐Simonsen A. , Zimmer J.
Published: January 2005

The entorhinal area projects to the Ammon's horn and the fascia dentata by way of the medial and lateral perforant paths that originate in the medial and lateral part of that area, respectively. The two tracts terminate at different laminar levels in the molecular layers of the ipsilateral hippocampal regio inferior and fascia dentata.

Using the Fink‐Heimer technique, each of the perforant paths in the normal rabbit is now shown to innervate the antero‐dorsal extremes of the Ammon's horn and fascia dentata in both hemispheres. The crossed and uncrossed components of each path innervate homotopic zones on each side. This bilateral innervation contrasts with the situation in the rat where only very weak crossed components exist. Degeneration particles in the fascia dentata contralateral to a lesion of the perforant paths diminish in number along the course of the fibers as they proceed away from the midline, but are traceable for several millimeters. Crossed fibers are shown to pass from one hemisphere into the other directly through the fused molecular layers of the fasciae dentatae.

The bilateral innervation in the rabbit indicates that even though the axons of the perforant paths are highly specific with respect to the class of neuron and the dendritic segments upon which they form synapses, they apparently do not possess a mechanism by which they can distinguish between the receptive fields in the two hemispheres. It is concluded that during ontogeny the perforant path fibers from both sides most likely compete for available synaptic sites in the rostral part of their terminal fields and that their relative amounts in the two hemispheres is governed by spatial and temporal factors.
Scanning electron microscopy of epiplexus macrophages (Kolmer cells) in the dog
Authors: Allen Delmas J.
Published: January 2005

Young dogs (6–14 weeks) were perfused with buffered aldehydes by standard techniques. The inferior medullary velum and tela choroidea were removed intact from the fourth ventricle, post‐osmicated, dehydrated, critical point dried, coated with palladium‐gold and examined in a Cambridge Stereoscan S4 scanning electron microscope. Selected samples after thorough scanning were routinely prepared for transmission electron microscopy (TEM).

This study depicts numerous epiplexus (Kolmer cell) macrophages that exhibit extreme polymorphism. Because of the pleomorphic nature of these cells and their processes, classification based on external morphology is not practical. TEM shows their internal structure to be that of a macrophage. Bleb‐like structures and bulbous projections appear to emerge from certain ependymal cell surfaces which seem to be completely or partially devoid of cilia.
Human brain in tissue culture. I. Acquisition, initial processing, and establishment of brain cell cultures
Authors: Gilden Donald H. , Devlin Mary , Wroblewska Zofia , Friedman Harvey , Rorke Lucy Balian , Santoli Daniela , Koprowski Hilary
Published: January 2005

This paper details the in vitro techniques used to establish cells in culture from the brains of 40 patients, most of whom had chronic neurologic disease. The clinical and pathologic features of these patients are given. The success in establishing cell lines was dependent upon the origin of tissue (biopsy vs. autopsy), the site of removal from the brain, and various environmental and technical manipulations in vitro.
Human brain in tissue culture. III. PML‐SV40‐induced transformation of brain cells and establishment of permanent lines
Authors: Santoli Daniela , Wroblewska Zofia , Gilden Donald H. , Girardi Anthony , Koprowski Hilary
Published: January 2005

Cells from explants and monolayer subcultures of adult human brain obtained from biopsies or autopsies of ten multiple sclerosis (MS) cases, one case each of Jakob‐Creutzfeld (JC) and amyotrophic lateral sclerosis (ALS) and three cases with no central nervous system (CNS) involvement were transformed with PML‐SV40 virus. Transformation was effected to establish permanent lines of these particular adult brain cells so that sufficient quantities would be available for other research projects. The procedure previously used to transform human fibroblasts (Koprowski et al., '62) was successfully applied to human brain cells. The success of transformation was dependent on the growth condition of the cultures at the time of infection. Events occurring after viral infection and during the pre‐transformation and the post‐transformation phases are described.
The ascending projections of the dorsolateral funiculus of the spinal cord in the primate
Authors: Nijensohn Daniel E. , Kerr Frederick W. L.
Published: January 2005

The ascending projections of the dorsolateral funiculus of the spinal cord to the brain stem have been determined in five macaque monkeys. Connections to the lateral cervical nucleus and to the reticular nucleus of the cord in the C1 and C2 segments are present. In the medulla the most prominent connections are to the nuclei “Z” and “x” of Brodal and Pompeiano, to the rostral portion of n. gracilis and to the n. proprius of the restiform body. Minor projections reach the rostral part of the medial and lateral cuneate nuclei, the reticular nucleus, the n. centralis dorsalis and the periependymal gray. There were no projections to planes rostral to the medulla.

In view of the connections established it is concluded that ascending systems in the DLF to the brain stem of primates are concerned with transmission of mechanoreceptor input to the cerebellum and thalamus and that nociceptive relay appears very unlikely.
Patterning of neuronal locus specificities in retinal ganglion cells after partial extirpation of the embryonic eye
Authors: Hunt R. K. , Berman Nancy
Published: January 2005

A variety of transplantation procedures were used to analyze the determinants of locus specificity pattern in eye fragments prepared at stage 31/32. When right eye fragments were rotated through 0–360° in situ, or grafted to a stage 31/32 or stage 27/28 host, or grown in vitro 48 hours prior to reimplantation, the orientation of the retinotectal map always matched the anatomical orientation of the rounded‐up fragment, while the internal organization of the map was characteristic for the original fragment type: normal or double‐nasal in NF eye grafts, normal or double‐temporal in TF eye grafts, normal or double‐ventral in VF eye grafts. Fragments from stage 31/32 left eyes showed similar behavior, but mapped from the right orbit with one axis inverted as occurs after contralateral transplantation of whole left eyes. When one rounded‐up fragment and one normal eye (or one rounded‐up nasal fragment and one rounded‐up temporal fragment) were placed side‐by‐side in the same orbit and allowed to “superinnervate” the same tectum, both retinae mapped across the entire tectum with no unshared tectal regions. Finally, in fragments prepared from previously‐rotated (at stage 25/26) eyes, the organization and orientation of the map conformed to the new retinal axes, often in direct conflict with the anatomical polarity of the eye. The results are considered in terms of (1) the histogenesis of the retina in eye fragments; (2) the stability of the program for patterning of locus specificities, which is set down when the optic cup undergoes axial specification at stages 28–31; (3) the factors controlling selective modification of this program and their localization in eye fragments; and (4) the extent to which the range of locus specificities, deployed across the ganglion cell population of rounded‐up fragments, approximates that found in the normal unoperated eye.
The nerve ring of the nematode Caenorhabditis elegans: Sensory input and motor output
Authors: Ware Randle W. , Clark David , Crossland Kathryn , Russell Richard L.
Published: January 2005

The general organization and structure of the nerve ring, the main mass of central nervous system neuropil, in the small soil nematode Caenorhabditis elegans is described. The nerve ring receives sensory input from the anterior tip of the animal by means of six nerve bundles, all nerve fibers of which have centrally located cell bodies. The anterior sensory structures are classically divided into two types, papillary and amphidial, and are assumed responsible for mechano‐ and chemoreception, respectively. Papillary fibers enter directly into the nerve ring, whereas amphidial fibers enter the ventral ganglion, a posterior extension of the nerve ring, in a circuitous manner which is not discussed in detail. Of those papillary fibers which project into the nerve ring neuropil, 22 end in easily characterized sensory structures whereas 14 terminate distally near sensory organs but have no function which can be deduced on the basis of comparative morphology. After entering the ring the fibers maintain their identity and do not anastamose with one another. Cell bodies of each papillary sensory neuron have been mapped around the nerve ring. The cephalic musculature is shown to consist of 32 muscle cells which form four longitudinal submedial groups of eight muscles each. Innervation of this musculature occurs wholly within the CNS by means of processes of the muscle cells which are sent centrally. The anterior 16 cephalic muscle cells are innervated by the ring only, in well delimited regions termed muscle plates. The posterior 16 are dually innervated by means of processes sent both to the nerve ring plates and to their nearest medial longtitudinal nerve cord. The nerve ring neuropil is characterized as having fibers containing one of four morphologically distinct vesicle types. Gap junction contacts are observed within the main neuropil involving one of these fiber types and within the muscle plate regions among muscle processes, which do not contain vesicles. An evolutionarily primitive sensory‐motor synapse within the nerve ring is described from an identified sensory neuron onto an identified cephalic muscle cell process. Comparisons are made with the nervous system of Ascaris lumbricoides, the only other nematode to be extensively studied, to illustrate the conservativeness of the nemic nervous system.
Transneuronal changes of synaptic endings and nuclear chromatin in the trapezoid body following cochlear ablations in cats
Authors: Jean‐Baptiste Michel , Morest D. Kent
Published: January 2005

This study demonstrates long‐lasting structural changes in highly specific synaptic endings, the calyces of Held, and in the principal cells, contacted by calyces, in the medial trapezoid nucleus following acoustic deafferentation of adult cats. The normal structure of the principal cell and its afferent axosomatic endings, including the calyx and other, smaller endings, was defined in rapid Golgi impregnations and electron micrographs. Each calyciferous axon, arising from the contralateral cochlear nucleus, forms a calyx, about 35 μm in diameter, around only one principal cell body; each principal cell receives only one calyx. In electron micrographs a calycine profile typically contains a central core of neurofilaments, surrounded by mitochondria; spherical vesicles gather at multiple, asymmetric synaptic complexes. Fifteen and 30 days after unilateral labyrinthectomy the contralateral calyces showed neurofilamentous hyperplasia; mitochondria and the now enlarged synaptic vesicles decreased in number. After 30 days the contralateral principal neurons showed increased condensation of nuclear chromatin. All of these changes diminished after 56 days and were gone by seven months, when the principal cell body had shrunk by 30%. The calyx, which exhibits strongly excitatory synaptic transmission spontaneously and during acoustic stimulation, could mediate significant trophic effects. Such effects are no doubt reflected in the extensive transneuronal changes after interruption of cochlear input. These changes must involve pre‐ and post‐synaptic alterations of protein metabolism, control of which may be linked to synaptic transmission.
Some aspects of the organization of the thalamic reticular complex
Authors: Jones E. G.
Published: January 2005

Anatomical methods which depend upon the anterograde axonal transport of isotopically labeled neuronal proteins or the retrograde axonal transport of the enzyme. Horseradis peroxidase, have been used to elucidate the relationships between the reticular complex and the dorsal thalamus and cerebral cortex. Injections of tritiated amino acide in the dorsal thalamus or cerebrasl cortex in rate, cats and monkey, show that as the bundles of thalamo‐cortical and cortico‐thalamic fibers joining a paarticular dorsal thalamic nucleus to its associated area of the cerebral cortex traverse the reticular complex, they each give rise tp dense zone of terminals occupying a sector of reticular complex which is relatively constant for that dorsal thalamic nucleus and cortical area. However, because of the wide extent of the dendritic fields of the reticular cells and the degree of overlap between the sectors of the complex subtended by adjacent dorsal thalamic nuclei and adjacent cortical areas, it is likely that the reticular complex samples thalamo‐cortical and cortico‐thalamic activity in a somewhat unspecific manner. Fibers passing to the reticular complex from the intralaminar nuclei of the thalamus appear to be associated with the projection from the intralaminar nuclei of the thalamus appear to be associatied with the projection from the intralaminar nuclei to the striatu.

Injections of tritiated amino acids in the reticular complex itself and injections of horseradish peroxidase in various other parts of the brain show that the only efferent pathway from thr reticular complex terminates in the nuclei of the dorsal thalamus. The reticdular complex does not appear to send fibers to other components of the ventral thalamus nor to the cerebral cortex.
Observation on the lateral olfactory tract of the rat
Authors: Price J. L. , Sprich W. W.
Published: January 2005

The number and size of the axons in the lateral olfactory tract of the rat have been measured at several rostro‐caudal levels, from material prepared for electron microscopy. Immediately caudal to the olfactory peduncle, an average of 42,000 ± 3,000 axons were counted in the tract, while near the caudal limit of the tract an averge of 32,000 ± 2,800 axons were counted. The average internal cross‐sectional area of axons measured at two levels of the tract was 1.6 ± 1.3 μm2 and 1.1 ± 0.9 μ2, corresponding to averge internal diameters 1.4 ± 1.3 μm and 1.2 ± 1.1 μ, respectively. The axons in the lateral part of the tract were found to be significantly larger than those in the medial part of the tract; for one level the average cross‐sectional area of axons in the lateral part of the tract was 1.6 ± 1.0 μm2 (equivalent diameter 1.4 ± 1.1 μm) while only 0.7 ± 0.6 μm2 (equivalent diameter 0.9 ± 0.9 μm) in the medial part of the tract. The thickness of the myelin sheath of the axons is generally related to axon diameter, increasing from 0.1–0.2 μm for axons 0.4 to 0.8 μm in diameter to 0.3–0.4 μm for axons greater than 2.0 μm in diameter. The ratio of the inside diameter to the outside diameter of the fiber (ratio “g”) is between 0.7 and 0.8 for most axons in the lateral olfactory tract.

The axons which leave the tract laterally and medially are substantially smaller than the axons within the tract (average cross‐sectional area 0.55 ± 0.35 μm2 on the lateral side) and probably are collaterals of the axons within the tract. Unmyelinated nerve processes, probably axons, were also found in the tract.

Qualitative observations from light and electron microscopical material agree well with the quantitative data, and further suggest that mixing of axons from different parts of the olfactory bulb occurs in the rostral part of the tract. This is supported by experiments with injections of 3H‐amimo acids into localized portions of the olfactory bulb. These indicate that there is some degree of point‐to‐point organization in the most rostral part of the tract, but that this is lost in the caudal part of the olfactory peduncle.
Neuroplasticity in the rearrangement of olfactory tract fibers after neonatal transection in hamsters
Authors: Devor Marshall
Published: January 2005

Olfactory bulb efferent axons run caudally in the lateral olfactory tract (LOT) to end in a broad cortical field in the ventral forebrain. Principles governing the plastic rearrangement of this fiber population after early lesions were probed by cutting the tract in hamster pups and studying the distribution of surviving olfactory bulb projections in adulthood using silver and autoradiographic techniques. The spatial pattern of rearrangement proved to depend on the extent of the cut and also the age at which it was made. For example, after complete LOT section at seven days of age no bulb efferents appeared distal to the cut but the proximal projection increased in laminar thickness and spread laterally and medially beyond its normal cytoarchitectonic boundaries. This spread was less pronounced in animals with earlier or later lesions. After transection of only part of the LOT fibers at seven days of age the proximal input was similarly increased. Just distal to the transection, uncut fibers sprouted collaterals to fill the terminal sites vacated as a result of the lesion. In these cases, however, the farthest distal parts of the projection field lost their normal innervation. In a tentative interpretation of these data it is proposed that developing LOT fibers tend to conserve their total amount of axonal arbor. That is, when distal branches are pruned off surgically, the axon compensates by producing extra proximal branches. When an overabundance of proximal collaterals are produced in axons that have not been surgically pruned, the growth of more distal axonal branches is stunted in compensation.
Synapses in the interpeduncular nucleus: Electron microscopy of normal and habenula lesioned rats
Authors: Lenn Nicholas J.
Published: January 2005

Four types of synapses have been identified in the rat interpeduncular nucleus. The S synapses were formed by the main horizontal plexus of habenulointerpeduncular axons. They contained spherical synaptic vesicles and formed asymmetrical en passant contacts with dendritic processes. The crest synapses had all of these features in common with the S synapses, but occurred in pairs with the two contact zones coextensive and largely parallel on opposite sides of markedly attenuated dendritic processes. Synaptic glomeruli found in this nucleus consisted of several crest synapses engulfed by sheet‐like dendritic processes. Identical crest synapses also occurred on dendritic crests. In a limited number of cases, both S and crest synapses arose in common from single axons. Following destruction of the habenular nuclei unilaterally or bilaterally, as expected from the above observations, both S and crest synapses underwent dense degeneration. In some cases with bilateral lesions and in all cases with unilateral lesions, only one of the two axonal endings forming a crest synapse degenerated while the other remained unaffected.

Axons containing flat vesicles forming symmetrical axodendritic synapses, axosomatic synapses, and subjunctional bodies associated with S or crest synapses were all minor features of this nucleus. Aspects of the unusual synaptology of this nucleus are discussed in terms of morphology, physiology and transmitter chemistry.
Auditory pathways to the cortex in Tupaia glis
Authors: Casseday J. H. , Diamond I. T. , Harting J. K.
Published: January 2005

The auditory system of the tree shrew, Tupaia glis, was investigated by identifying axonal degeneration after lesions of the lateral lemniscus, the inferior colliculus, the medial geniculate nucleus and the auditory cortex. The results show that the lateral lemniscus projects to the central nucleus of the inferior colliculus which in turn projects principally to the ventral division of the medial geniculate nucleus but to a lesser extent to the magnocellular division of the medial geniculate nucleus. The final step in the pathway to the cortex is achieved by a projection from the ventral division to the fourth layer of auditory koniocortex. There appear to be several auditory pathways parallel to this primary path. The lateral lemniscus projects to the dorsal division of the medial geniculate nucleus; the deeper layers of the superior colliculus project to the posterior nucleus; and both the dorsal division and the posterior nucleus project to the belt caudal to auditory koniocortex. The caudal division of the medial geniculate nucleus may constitute a relay in still another path from the pericentral division of the inferior colliculus. Finally, the magnocellular division also appears to be distinct insofar as its cortical projections are confined chiefly to the deeper layers. A comparison between the tree shrew and the cat reveals a similar organization in the two species. In the cat the starting point for understanding the organization of the several auditory pathways is the distinction between a core cortical zone which corresponds to koniocortex and to AI and a peripheral belt. The core receives essential projections from the ventral division; the belt receives sustaining projections from the cell groups which surround the ventral division. It is reasonable to hypothesize that this difference between the core and the belt is characteristic of all mammals.
On the striate area of the human isocortex. A golgi‐ and pigmentarchitectonic study
Authors: Braak Heiko
Published: January 2005

The distribution pattern of the pigment in various layers of the primary visual cortex of man is described by means of a method for the stereomicroscopical demonstration of neurolipofuscins in sections up to 1,000 μm thick.

This paper presents the striate area as being composed of 12 cellular layers, which can be clearly delineated by a successive examination of both the Nissl and the pigment preparations.

Layers I, II, and III resemble more or less the corresponding laminae of other isocortical fields. The pyramids within the deep portion of layer III are unusually small and additionally are intermingled with thorny stellate cells which are a characteristic component of layer IV. Accordingly, this band of cells is called IIIc–IVa. The subjacent layers IVb and IVcα are poorly pigmented. In Nissl‐preparations layer IVb, which contains only a few cells, is followed by a broad band of cells tightly packed together, which includes layers IVcα, IVcβ, IVd, and Va. These layers cannot be reliably delineated in Nissl‐preparations but appear in pigment preparations as distinct and sharply limited laminae. Particularly, layer IVcß, which is built up by minute thorny stellate cells, is marked by coarse and intensely stained lipofuscin granules, whereas IVd is mainly populated by minute pyramids which are almost devoid of pigment deposits. A remarkably narrowed layer Va, the pyramids of which store a medium number of lipofuscin grains, completes this series (IVcα, IVcβ, IVd, Va). The cell‐sparse layer Vb is almost devoid of pigment granules. Layer Via has specialized pyramidal cells containing finely grained pigment. The relatively broad layer VIb shows loosely arranged cells poorly endowed with lipofuscin granules.
Topographic organization of the projections from the entorhinal area to the hippocampal formation of the rat
Authors: Steward Oswald
Published: January 2005

The present study re‐examines, with autoradiographic methods, the pattern of termination of fibers originating from various medio‐lateral divisions of the entorhinal cortex on dentate granule cells and on hippocampa pyramidal cells of the rat. Entorhinal fibers were found to distribute in a proximodistal gradient along the dendrites of dentate granule cells, with afferents from the medial entorhinal area terminating in the innermost portion of the entorhinal synaptic field, afferents from the lateral entorhinal area terminating in the most superficial portions of the entorhinal synaptic field, and intermediate medio‐lateral locations in the entorhinal area terminating in intermediate loca tions in the entorhinal synaptic zone. A similar graded pattern of termination of medial and lateral entorhinal fibers was apparent in the very slight crossed projection of the entorhinal area to the contralateral dentate gyrus. In addition, a comparable gradient in the pattern of termination of entorhinal fibers was evident in the entorhinal projection field in the distal dendritic regions of the pyramidal cells of regio inferior of the hippocampus proper.

Entorhinal projections to regio superior were, however, organized in quite a different fashion. In this zone, there was no evidence of a proximo‐distal gradient in the patterns of termination of medial and lateral entorhinal areas along the dendrites of regio superior pyramidal cells. Rather, the medio‐lateral organization was in a longitudinal dimension, with medial entorhinal afferents terminating in the portions of regio superior near the CA1‐CA2 transition, and lateral entorhinal afferents terminating furthest from the CA1‐CA2 transition, immediately adjacent to the CA1‐subicular transition, and in the molecular layer of the subiculum proper. A comparable longitudinal organization of entorhinal projections to regio superior was also evident in the zones of termination of the crossed temporo‐ammonic tract, contralateral to the injection. These results demonstrate a heretofore unrecognized complexity in the patterns of projection of the entorhinal area to the hippocampal formation, and illustrate that the entorhinal cortex cannot be divided into only two discrete divisions on the basis of the pattern of projection.
Involvement of the avian hypothalamus in defensively conditioned heart rate change
Authors: Cohen David H. , Macdonald Robert L.
Published: January 2005

Hypothalamic involvement in visually conditioned heart rate change (established by pairing light and foot‐shock) was studied in 128 pigeons by evaluating conditioning performance following lesions of various hypothalamic areas. Extensive destruction of the posterior hypothalamus severely impaired development of conditioned heart rate change. Anterior hypothalamic lesions also produced serious deficits, though not as severe as following posterior hypothalamic damage. Partial posterior hypothalamic, unilateral and tuberal lesions produced only minor to moderate deficits. The critical locus for profound impairment of conditioned response development appeared to be the medial hypothalamus, and it is suggested that more specifically it is the terminal field of the archistriatal projection upon the medial hypothalamus. It is concluded that the medial hypothalamus is essential for the development of defensively conditioned heart rate change, and based on previous findings it is suggested that the critical descending pathway for expression of this conditioned response involves the archistriatal projection upon the medial hypothalamus and subsequently a polysynaptic pathway through the ventral brainstem.