bluuebunny/crossref_metadata_2025 huggingface dataset:
Reduced branching and length of dendrites detected in cervical spinal cord motoneurons of wobbler mouse, a model for inherited motoneuron disease
Authors: Ma Weiya , Vacca‐Galloway L. L.
Published: January 2005

The Wobbler mouse (wr) has been proposed as a model for human inherited motoneuron disease (infantile spinal muscular atrophy). The primary defect is thought to be in the motoneurons. Therefore we undertook a survey of the qualitative and quantitative changes occurring in the cervical spinal motoneurons of Wobbler mice during a late stage of the motoneuron disease compared with age‐ and sex‐matched normal phenotype (NFR/wr) littermates. The Rapid Golgi Method was applied. In control and Wobbler mice, four types of neurons were identified according to their dendritic patterns: multipolar, tripolar, bipolar, and unipolar cells. Unipolar cells were observed more often in the Wobbler specimens than the controls and may represent a final stage in the degeneration of other cell types with greater numbers of primary dendrites. Medium (300–999 μm2) and large (> 1,000 μm2) impregnated neurons (presumably alpha‐motoneurons) showed strong indications of cell degeneration, including statistically significant reductions in the measurements for dendritic length, distribution, and branching, as well as the number of spines. In contrast, the small (< 300 μm2) neurons showed only mild signs of degeneration, including slight reductions in dendritic length, but no significant differences appeared in the distribution and branching of dendrites, or in the number of spines. Instead, a small increase could be detected in the number of primary and secondary dendritic branches emanating from the small neurons, as well as in the number of dendritic spines. These findings suggest that sprouting may occur to a slight extent. Although previous studies document that swelling with subsequent vacuolation of motoneurons is the predominant feature characterizing the Wobbler disease, the mean soma area (μm2) calculated for the impregnated neurons of the Wobbler specimens showed no significant difference from the controls. It is hypothesized that the advanced signs of the Wobbler motoneuron disease are primarily reflected in the degeneration of the dendrites and spines on the medium and large alpha‐motoneurons. The small neurons (presumably a mixed population of gamma‐motoneurons, interneurons, and Renshaw cells) possess dendrites and spines that seem to be less affected, and instead show signs of sprouting.
Motor neurons supplying hindwing muscles of a grasshopper: Topography and distribution into anatomical groups
Authors: Siegler Melody V. S. , Phong Mario P. , Pousman Cynthia A.
Published: January 2005

The motor neurons supplying the dorsoventral wing muscles in the metathorax of the grasshopper Schistocerca americana were stained by backfilling muscle‐nerves with cobaltous chloride, which was then precipitated and intensified as silver sulfide. Stained motor neurons were examined in wholemounts and in sectioned ganglia. Two unifunctional muscles are innervated by a single motor neuron each, whereas four bifunctional muscles, involved in leg and wing movements, are innervated by two or three motor neurons each. Each of the motor neurons is in one of four identified anatomical groups. All members of a group have primary neurites that enter the ganglion core as part of an anatomically denned bundle and have cell bodies that lie near each other in the ganglion cortex (Siegler and Pousman, J Comp Neurol: 297:298, 1990). The morphology of the neuropilar branches of the motor neurons is correlated with the pairwise topographic arrangement of the target muscles rather than the muscles' functions. Thus, motor neurons that innervate antagonistic pairs of muscles may be more similar in morphology than motor neurons that innervate synergistic muscles. We find no evidence that particular main branches of the different motor neurons are uniquely associated with a particular motor function. Significant differences in the nature and distribution of synaptic inputs to motor neurons of different function would necessarily be expected as a basis for known differences in synaptic connectivity, but may not be apparent at the level of resolution available from light microscope examination.
Ultrastructural changes in the nucleolus of facial motor neurons following axotomy during an early critical period in development
Authors: Clark Pamela , Jones Kathryn J. , La Velle Arthur
Published: January 2005

In this study, the effects of axotomy on the ultrastructure of the nucleolus and associated organelles were examined in fetal, newborn, and early postnatal facial motoneurons of the hamster. Golden hamsters used for this study were the 14‐day fetus, newborn (0 days; < 6 hr) and 2, 4, 7, and 9 days postnatal ages, with 3 animals per group. For prenatal surgeries, pregnant hamsters were anesthetized and the facial nerves severed in the fetuses via electrocautery through the uterine wall and amniotic membrane. For postnatal surgeries, the animals were anesthetized and the right facial nerve exposed and severed at its exit from the stylomastoid foramen. At the appropriate postoperative times, the animals were reanesthetized and perfused‐fixed. The facial nuclear groups were dissected and processed for routine electron microscopy. Microbody and coiled body frequencies were determined from the number of neurons containing these structures per number of neurons sampled per animal in each experimental or control group and subjected to statistical analysis. Nucleolar reactive changes that occurred during this developmental sequence fell into two major categories. The first category displayed by most injured cells consisted of an initial compacting of fibrillar material and reduction in vacuolar space. The second category appeared to represent a progression from this first stage of nucleolar reactivity into degenerative changes involving a striking segregation of nucleolar components into five distinct regions. The incidence of microbodies increased as a result of axotomy, whereas the presence of coiled bodies decreased at the later postoperative stages in the older animals. With increasing age and nucleolar maturation, the nucleolar reactive pattern became less pronounced and severe, and neuronal survival predominated. It appears, therefore, that the two categories of nucleolar changes following axotomy during early development correlate with changes observed in nucleoli under conditions of rRNA downregulation. It is hypothesized from these results that a key step in the ability of neurons to survive axotomy and successfully regenerate at these early developmental stages occurs at some point in ribosomal RNA transcription and/or processing. Complementary information at the molecular level concerning changes in nucleolar synthetic activity and ribosome production will be necessary to test this hypothesis.
Intraorbital transection of the rabbit optic nerve: Consequences for ganglion cells and neuroglia in the retina
Authors: Scherer Jürgen , Schnitzer Jutta
Published: January 2005

Rabbit retinae were stained with antibodies to glial fibrillary acidic protein (GFAP) at various times up to 5 months after complete unilateral intraorbital optic nerve transection, which is known to induce degeneration of ganglion cell axons and perikarya in the retina. A transient immunoreactivity for GFAP was observed in Müller glial cells that normally lack this marker. Müller‐cell GFAP immunoreactivity became detectable 4 days after the lesion, but Müller cells were no longer labeled 3 months later. GFAP‐labeled astrocytes located in the nerve fiber layer showed no change in immunoreactivity at any stage after transection.

Application of horseradish peroxidase to the left and right superior colliculus of a rabbit whose optic nerve had been transected unilaterally 2 years before confirmed the completeness of the transection. Yet electron microscopy showed the presence of some healthy‐looking ganglion cell axons in the lesioned retina, although these cells were deprived of their target.

Labeling retinal wholemounts with neurofilament antibodies confirmed the presence of some ganglion cell axons and perikarya in the retina more than 2 years after transection. The course of these axons suggested that they were remnants of axons. Using antibodies to galactocerebroside (GC) we found that, as in the normal rabbit, these persisting ganglion cell axons were myelinated in the medullary rays. Although many ganglion cell axons had disappeared after 2 years, the number of neuroglial cells (including astrocytes and oligodendrocytes) present in the medullary ray region was not altered. The cell bodies of some oligodendrocytes were covered with a myelin sheath, an aberrant feature not seen normally.
Cross‐species septohippocampal transplants: Ultrastructure of Thy‐1.2‐labeled donor fibers into the dentate gyrus
Authors: Wells Joseph , Vietje Brad P. , McKeon Robert J.
Published: January 2005

A naturally occurring species‐specific membrane marker was used to identify unambiguously transplanted septal cells and their fibers which have grown into host tissue. Cell suspensions of the septum/basal forebrain region of C57B1/6 mouse embryos were transplanted into the dentate gyrus of Sprague‐Dawley rats that had received a fornix lesion. The membranes of the mouse contained Thy‐1.2, while the membranes of the rat contained Thy‐1.1. An antibody to Thy‐1.2 clearly identified the donor tissue and did not react with the Thy‐1.1 of the host's membranes. The ultrastructure of the immunoreactively labeled tissue confirmed previous biochemical findings on the distribution of Thy‐1 and showed Thy‐1.2 immunoreactivity on axons and dendrites, microtubules, some mitochondrial membranes, and the surface membranes of cell bodies. Within the transplant, a few glial profiles showed immunoreactive fibrils, but most glial profiles within the transplant and all glial profiles outside the transplant were not immunoreactive. Astrocyte fibers enclosed the outgrowing labeled fibers to form fascicles, but did not penetrate the fascicle. There was no other distinctive association of astrocytic profiles with immunoreactive fibers. Dendrites grew for long distances into the host's molecular layer. Many immunoreactive dendritic profiles formed synapses with unlabeled terminal profiles from the host. The host synapses on the long dendrites of the transplanted neurons may form an important source of input for the initiation of physiological activity in the new circuits established by the transplant. A few labeled (donor) synaptic terminals were observed in the molecular layer, but Thy‐1.2‐labeled dendritic profiles were much more prominent than labeled axonal profiles.
Localization of aspartate‐like immunoreactivity in the retina of the turtle (Pseudemys scripta)
Authors: Yaqub Asma , Eldred William D.
Published: January 2005

Aspartate has been reported to be a putative excitatory neurotransmitter in the retina, but little detailed information is available concerning its anatomical distribution. We used an antiserum directed against an aspartate‐albumin conjugate to analyze the anatomy, dendritic stratification, and regional distribution of cell types with aspartate‐like immunoreactivity in the turtle retina. The results showed dramatic differences in immunoreactivity in the peripheral versus the central retina. Strong aspartate‐like immunoreactivity was shown in the peripheral retina, with many well‐labeled processes in the inner plexiform layer. Many bipolar, horizontal, amacrine, and ganglion cells, some photoreceptors, and some unidentified cells were strongly immunoreactive in the peripheral retina. In contrast, although the central retina showed well‐labeled horizontal cells, there was only light labeling in the inner plexiform layer with weakly immunoreactive amacrine and ganglion cells and no labeled bipolar cells. There were several strongly immunoreactive efferent nerve fibers which left the optic nerve head and arborized extensively in the retina. At the electron microscopic level, electron‐dense reaction product was associated with synaptic vesicles at bipolar and amacrine cell synapses in the inner plexiform layer. These results suggest that aspartate may be involved in many diverse synaptic interactions in both the outer plexiform layer and the inner plexiform layer of the turtle retina.
Lysosomal activity in developing cat alpha‐motor axons under normal conditions and during retrograde axonal transport of horseradish peroxidase
Authors: Gatzinsky Kliment P. , Berthold Claes‐Henric , Fabricius Christian
Published: January 2005

The occurrence of acid phosphatase (AcPase)‐positive bodies, i.e., lysosomes, in lumbosacral alpha‐motor axons of kittens, 0–16 weeks of age, was analyzed by light and electron cytochemical methods under normal conditions and after intramuscular injection of horseradish peroxidase (HRP). Axonal lysosomes wore rare early postnatally. In 3‐week‐old animals, a few AcPase‐positive bodies appeared in the axoplasm at some nodes of Ranvier in the peripheral nervous system (PNS) and internodally in the intrafunicular motor axon parts within the central nervous system (CNS). From 6 weeks postnatally, a nodal concentration of AcPase‐positive bodies was also noted in the CNS. The number of AcPase‐positive bodies continued to increase gradually in the course of neuronal maturation. In 16‐week‐old animals, axonal AcPase activity was still at considerably lower levels than at adult stages. At all ages, acid hydrolase‐containing organelles were most commonly found at ventral root nodes. After injection of HRP in the medial gastrocnemius muscle, accumulations of AcPase‐positive bodies were seen in the axoplasm at some PNS nodes of the HRP‐injected sides of kittens aged 8, 12, and 16 weeks. Incubation for demonstration of both HRP and AcPase activity showed that some organelles at HRP‐transporting nodes contained both types of reaction product. The nodal AcPase activity in the intrafunicular, CNS parts of alpha‐motor axons of the HRP‐exposed sides did not differ from that of the contralateral, uninjected sides.

In view of our previous observations in alpha‐motor neurons of adult cats in which a lysosome‐mediated degradation of axonally transported materials may take place at PNS nodes of Ranvier, the present study illuminates possible differences in the ability to interfere with axonal transport between developing and mature neurons. The infrequent presence of lysosomes in developing alpha‐motor axons and the implied disability of their nodal regions to interfere with axonally transported constituents in a way similar to that seen in adult animals may be of significance in that trophic and chemical signals can pass unhindered between the periphery and perikaryon. However, this could also have negative consequences for the vulnerable immature neuron in that various materials retrieved at the axon terminals outside the CNS are permitted a more‐or‐less free access to the perikaryon.
N‐acetylaspartylglutamate immunoreactivity in neurons of the monkey's visual pathway
Authors: Tieman Suzannah Bliss , Neale Joseph H. , Tieman David G.
Published: January 2005

The acidic dipeptide N‐acetylaspartylglutamate (NAAG) was identified immunohistochemically within neurons of the visual pathways of two adult macaque monkeys which had undergone midsagittal sectioning of the optic chiasm 6 or 9 years earlier. In both temporal and nasal retinae, amacrine cells, including some displaced amacrine cells, expressed NAAG immunoreactivity. In temporal but not nasal retina, retinal ganglion cells were stained, as were their dendrites in‐the inner plexiform layer, and their axons in the optic nerve fiber layer. In nasal retina, the ganglion cells had degenerated because they were axotomized by the optic chiasm section. In the target regions of the retinal ganglion cells, the superior colliculus and the lateral geniculate nucleus (LGN), both neuropil and cell bodies were stained. In LGN, staining was confined to layers 2, 3, and 5, that is, to the layers innervated by the intact ipsilateral pathway. Immunoreactivity was also seen in the cells of layers 2, 3A, 4B, 5, and 6 of area 17 and layers 3 and 5 of area 18. The neuropil was stained in all layers of area 17, but more heavily in layers 1, 2, 4B, the bottom of 4Cβ, 5B, and 6B. Within 4C the staining was patchy; in tangential sections there were alternating bands of light and dark label which matched the ocular dominance bands demonstrated by cytochrome oxidase histochemistry in adjacent sections. This banding pattern is consistent with the presence of NAAG in geniculocortical terminals of the intact ipsilateral pathway and the absence of such terminals for the contralateral pathway, which had undergone transneuronal degeneration due to the optic chiasm sectioning. Overall, our results for monkey are very similar to those in cat and suggest that NAAG or a structurally related molecule may have a prominent role in the communication of visual signals at retinal, thalamic, and cortical levels.
Diverse thalamic projections to the prefrontal cortex in the rhesus monkey
Authors: Barbas H. , Henion T. H. Haswell , Dermon C. R.
Published: January 2005

We studied the sources of thalamic projections to prefrontal areas of nine rhesus monkeys with the aid of retrograde tracers (horseradish peroxidase or fluorescent dyes). Our goal was to determine the proportion of labeled neurons contributing to this projection system by the mediodorsal (MD) nucleus compared to those distributed in other thalamic nuclei, and to investigate the relationship of thalamic projections to specific architectonic areas of the prefrontal cortex. We selected areas for study within both the basoventral (areas 11, 12, and ventral 46) and the mediodorsal (areas 32, 14, 46, and 8) prefrontal sectors. This choice was based on our previous studies, which indicate differences in cortical projections to these two distinct architectonic sectors (Barbas, '88; Barbas and Pandya, '89). In addition, for each sector we included areas with different architectonic profiles, which is also relevant to the connectional patterns of the prefrontal cortices.

The results showed that MD included a clear majority (over 80%) of all thalamic neurons directed to some prefrontal cortices (areas 11, 46, and 8); it contributed just over half to some others (areas 12 and 32), and less than a third to area 14. Clusters of neurons directed to basoventral and mediodorsal prefrontal areas were largely segregated within MD: the former were found ventrally, the latter dorsally. However, the most striking findings establish a relationship between thalamic origin and laminar definition of the prefrontal target areas. Most thalamic neurons directed to lateral prefrontal cortices, which are characterized by a high degree of laminar definition (areas 46 and 8), originated in the parvicellular and multiform subdivisions of MD, and only a few were found in other nuclei. In contrast, orbital and medial cortices, which have a low degree of laminar differentiation, were targeted by the magnocellular subdivision of MD and by numerous other limbic thalamic nuclei, including the midline and the anterior. Thus topographic specificity in the origin of thalamic projections increased as the laminar definition of the target area increased. Moreover, the rostrocaudal distribution of labeled neurons in MD and the medial pulvinar also differed depending on the degree of the laminar definition of the prefrontal target areas. The rostral parts of MD and the medial pulvinar projected to the eulaminate lateral prefrontal cortices, whereas their caudal parts projected to orbital and medial limbic cortices. Selective destruction of caudal MD is known to disrupt mnemonic processes in both humans and monkeys, suggesting that this thalamic‐limbic prefrontal loop may constitute an important pathway for memory.
Reorganization of organotypic cultures of mouse cerebellum exposed to cytosine arabinoside: A timed ultrastructural study
Authors: Seil Fredrick J. , Herndon Robert M. , Tiekotter Kenneth L. , Blank Nathan K.
Published: January 2005

This study was designed to examine the sequential changes in the developing granuloprival cerebellar culture. In this model of anomalous cerebellar development, organotypic cultures derived from newborn Swiss‐Webster mice were exposed to the DNA synthesis inhibitor, cytosine arabinoside, at explantation and were fixed for electron microscopic examination on successive days in vitro. Similar developmental stages were compared in control explants. Granule cell destruction began early, and was widespread by 2 days in vitro, when oligodendrocyte destruction also began in treated cultures. A few granule cells survived, but no recognizable oligodendrocytes remained by 7 days in vitro, at a time when myelin was initially evident in control explants. Purkinje cell recurrent axon collateral sprouting began at 3 days in vitro in cultures exposed to cytosine arabinoside, and the sprouted terminals initially synapsed with Purkinje cell somata, somatic spines and dendritic shafts. Synapses with Purkinje cell dendritic spines developed later, at approximately the same time as parallel fiber‐Purkinje cell dendritic spine synapses formed in control cultures. Astrocytic ensheathment of control Purkinje cells was well underway by 6 days in vitro and Purkinje cell somata were relatively rounded and almost completely ensheathed by 9 days in vitro. Glial ensheathment did not occur in cytosine arabinoside treated cultures, and Purkinje cell somata were scalloped at 7 days in vitro by excess impinging recurrent axon collateral terminals, and never developed the smooth contours characteristic of control Purkinje cells. Purkinje cell somatic spines persisted in treated explants, and reduction of excess extracellular space was delayed until 12 days in vitro, when most‐of the developmental changes had been completed. The earlier development of synapses by excess recurrent axon collateral terminals with Purkinje cell somata, somatic spines and dendritic shafts, followed by the later development of heterotypical synapses with dendritic spines, in parallel with synapse formation by normal presynaptic elements, suggests that the sequence of development of synapses is a function of the maturational state of the postsynaptic components.
Morphological taxonomy of the neurons of the primate striatum
Authors: Yelnik Jérôme , Francis Chantal , Percheron Gérard , Tandéa Dominique
Published: January 2005

A quantitative taxonomy of primate striatal neurons was elaborated on the basis of the morphology of Golgi‐impregnated neurons. Dendritic arborizations were reconstructed from serial sections and digitized in three dimensions by means of a video computer system. Topological, metrical, and geometrical parameters were measured for each neuron. Groups of neurons were isolated by using uni‐ and multidimensional statistical tests. A neuronal species was defined as a group of neurons characterized, quantitatively by a series of nonredundant parameters, differing statistically from other groups, and appearing as a separate cluster in principal component analysis. Four neuronal species were isolated: (1) the spiny neuronal species (96% of striatal neurons) characterized by spine‐free proximal dendrites (up to 31 μm) and spine‐laden distal dendrites, which are more numerous, shorter, and less spiny in the human than in the monkey, (2) the leptodendritic neuronal species (2%) characterized by a small number of long, thick, smooth, and sparsely ramified dendrites, (3) the spidery neuronal species (1%) characterized by very thick dendritic stems and a large number of varicose recurrent distal processes, and (4) the microneuronal species (1%) characterized by numerous short, thin, and beaded axonlike processes. All striatal neurons give off a local axonal arborization.

The size and shape of cell bodies were analyzed quantitatively in Golgi material and in materials treated for Nissl‐staining, immunohistochemical demonstration of parvalbumin and histochemical demonstration of acetylcholinesterase. Only three types were distinguishable: small, round cell bodies corresponding to either spiny neurons or microneurons, medium‐size elongated cell bodies, which were parvalbumin‐immunoreactive and corresponded to leptodendritic neurons, and large round cell bodies, which were acetylcholinesterase‐positive and corresponded to spidery neurons. Thorough analysis of previously elaborated classifications revealed that spidery neurons do not exist in rats and cats and that large cholinergic neurons in these species correspond to leptodendritic neurons. From this, it can be assumed that the dendritic domain of striatal cholinergic neurons is considerably smaller in primates than in other species.

Computer simulations based on both the frequency of each neuronal species and their three‐dimensional dendritic morphology revealed that the striatum consists of two intertwined dendritic lattices: a fine‐grain lattice (300–600 μm) formed by the dendritic arborizations of spiny, spidery, and microneurons, and a large‐grain lattice (1,200 μm) formed by the dendritic arborizations of leptodendritic neurons. This suggests that cortical information can be processed in the striatum through two different systems: a fine‐grain system that would conserve the precision of the cortical input, and a large‐grain system that would blur it.
Segmental differentiation in the leech central nervous system: Proposed segmental homologs of the heart accessory neurons
Authors: Stewart R. R. , Gao W.‐Q. , Macagno E. R.
Published: January 2005

As part of an on‐going study of segmental differentiation in the central nervous system (CNS) of the leech Hirudo medicinalis, a search was made for putative segmental homologs of the heart accessory (HA) neurons, which exist exclusively as a bilateral pair in the ganglia of the fifth and sixth body segments. As it is not yet feasible to obtain adequate cell lineage information in H. medicinalis potential homologs of the HA neurons were determined using morphological, immunohistochemical, and electrophysiological criteria. Among cells in other body ganglia with somata in the same locations as HA neurons, a pair was found having extensive morphological and physiological similarities to HA neurons. These we have called HA‐like (HAL) neurons.

Adult HA and HAL neurons have closely related patterns of primary branching, in terms of shape, intraganglionic pathways taken, and extraganglionic projections. The number, location, and relative thickness of branches are also similar among these cells. In embryos 10 to 11 days old, HA and HAL neurons have virtually identical branching patterns, with primary and secondary branches of nearly uniform caliber. Differences in branch thickness develop gradually; by embryonic day 20, they resemble those found in adult neurons. Two features found to differ between HA and HAL neurons were the cell body diameter (larger for the HA cells) and the expression of antigens recognized by the monoclonal antibody Laz1‐1 (absent at a detectable level in the HA neurons). At a physiological level, the HA and HAL neurons showed action potentials of similar size and shape, as well as inhibitory synaptic inputs from a common source, the heart interneurons (HN).

The observations presented here suggest that there is a common developmental origin for the HA and HAL neurons, and hence that their fates are positionally determined by as yet unknown factors.
Adrenal steroids regulate postnatal development of the rat dentate gyrus: I. Effects of glucocorticoids on cell death
Authors: Gould Elizabeth , Woolley Catherine S. , McEwen Bruce S.
Published: January 2005

The rat dentate gyrus undergoes a period of naturally occurring cell death during the first postnatal week. In the adult rat, removal of circulating adrenal steroids by adrenalectomy is followed by massive death in the granule cell layer, thus raising the possibility that developmental cell death results from low levels of these hormones. Interestingly, the first two postnatal weeks of life in the rat, termed the stress hyporesponsive period, are characterized by very low levels of adrenal steroids. In order to determine whether low levels of adrenal steroids enable developmental cell death to occur in the dentate gyrus, we examined the density of pyknotic and healthy cells in the dentate gyrus of rat pups which received one of the following treatments: (1) injections of the endogenous rat glucocorticoid corticosterone during the first postnatal week, or (2) adrenalectomy at the time when glucocorticoid levels normally rise. Quantitative analysis of the density of pyknotic cells in the granule cell layers revealed significant decreases with corticosterone treatment by the end of the first postnatal week. In these same brains, treatment with corticosterone resulted in a substantial increase in the density of pyknotic cells in the hilus. Adrenalectomy resulted in a significant increase in the density of pyknotic cells in the granule cell layer as well as in the hilus. Despite the dramatic alterations in the density of pyknotic cells with both increases and decreases in glucocorticoid levels, the density of healthy cells remained the same. These observations suggest that glucocorticoids regulate several processes, possibly including neurogenesis and migration, in addition to cell death.
Differential regulation of the low‐affinity nerve growth factor receptor during postnatal development of the rat brain
Authors: Koh Sookyong , Higgins Gerald A.
Published: January 2005

We studied the temporal and spatial localization of the low‐affinity nerve growth factor receptor (LNGF‐R) during the early postnatal period in rat brain in order to understand better the relationship between nerve growth factor (NGF)‐like responsiveness and the development of specific central neuronal populations. Four different developmental patterns of LNGF‐R mRNA hybridization were found in this study. First, some neurons contain high levels of LNGF‐R mRNA from postnatal time points into adulthood, as exemplified by neurons of the cholinergic basal forebrain and mesencephalic trigeminal nucleus. Second, several cell groups exhibit robust hybridization during the early postnatal period but contain much reduced levels of LNGF‐R mRNA in the adult brain. These include striatal neurons, Purkinje cells of the cerebellum, and several medullary nuclei. A third group of cells produces the LNGF‐R transiently during development, including cranial nerve nuclei of the brainstem, the periolivary nuclei complex, the reticular formation, and the deep cerebellar nuclei. Finally, cell populations which may exist only transiently during central nervous system (CNS) development, such as subplate neurons of the cerebral cortex, appear to express the LNGF‐R during only a brief period. These results show that the LNGF‐R gene is differentially regulated in a cell type‐specific manner during development, and suggests that diverse neuronal populations require only transient growth factor sensitivity, while others exhibit NGF‐like responsitivity into maturity.
Distribution of hippocampal CA1 and subicular efferents in the prefrontal cortex of the rat studied by means of anterograde transport of Phaseolus vulgaris‐leucoagglutinin
Authors: Jay Thérèse M. , Witter Menno P.
Published: January 2005

Projections of the hippocampal formation to the prefrontal cortex were visualized in the rat by means of the anterograde tracer Phaseolus vulgaris‐leucoagglutinin. These projections distribute only to the prelimbic and the medial orbital cortices and arise exclusively from restricted portions of field CA1 of the Ammon's horn and the subiculum. The most dorsal portion of CA1 does not contribute fibers to this projection. In the subiculum, its origin is restricted to the proximal half, i.e., the portion that directly borders field CA1. Fibers from field CA1 and the subiculum have comparable distribution patterns in the prelimbic and medial orbital cortices. The density and distribution in the prefrontal cortex of the projections from the proximal portion of the subiculum depends on the location of the injections along the dorsoventral axis of the hippocampal formation: the intermediate portion of the subiculum projects more densely and diffusely than its dorsal and ventral portions.

In the prelimbic cortex, labeled fibers are present in all layers, showing marked morphological differences in deep versus superficial layers. In layers V and VI, most of the fibers are vertically oriented, while in layers II and III they are short and oriented towards the pial surface. Although no clear differences in terminal distribution were observed along the rostrocaudal extent of the prelimbic cortex, its dorsal and ventral portions show different innervation patterns. In the ventral portion of the prelimbic cortex, varicose fibers and terminal arborizations were present in all cortical layers, deep (V and VI) as well as superficial (II and III). In its dorsal part, the innervation was less dense and mostly present in the deep layers (V and VI). The fiber and terminal distribution in the medial orbital cortex was diffuse in all layers with a slight preference for layers deep to layer II.
Preferential regeneration of spinal axons through the scar in hemisected lamprey spinal cord
Authors: Lurie Diana I. , Selzer Michael E.
Published: January 2005

Axons of lamprey spinal cord can regenerate across a complete spinal transection. Thus, unlike the scar of injured mammalian spinal cords, the scar in the lamprey is not an absolute impediment to regeneration. However, it is still not known whether the scar is a relative impediment or whether it provides a favorable environment for regeneration compared to the spinal cord parenchyma. In order to answer this question, the cords of 12 large arval sea lampreys (4–5 years old) were hemisected at the level of the third gill and the animals allowed to recover for 10 weeks. The large reticulospinal neurons (Müller and Mauthner cells) or their giant axons were injected intracellularly with HRP and their regenerating neurites visualized in central nervous system (CNS) wholemounts. Forty‐five of seventy‐one regenerating neurites (64%) grew beyond the level of the hemisection. Of these, 36 (82%) regenerated through the scar and remained on the same side of the cord as their parent axons, while only 8 (18%) crossed the midline and grew around the scar. Thus, regenerating neurites of giant reticulospinal axons tended to grow through the hemisection scar rather than around it. Once they passed the level of injury, they continued to elongate in their appropriate paths.

It is possible that this tendency for axons to regenerate through the scar reflects the greater amount of empty spaces on the hemisected side. In order to rule this out, 13 animals received contralateral simultaneous hemisections at the level of the 3rd and 7th gills. This procedure created large numbers of degenerating axons and potential empty spaces both rostral and caudal to the scars within both hemicords; 92 of 158 neurites (58%) regenerated beyond the level of their respective hemisections. All of these grew through the scar and none crossed to the contralateral side. Distal to either hemisection, neurites remained on their correct side regardless of whether the contralateral cord contained normal CNS parenchyma or axonal debris and empty spaces produced by Wallerian degeneration. Moreover, in hemisected and double hemisected animals, as well as in completely transected control animals, neurites regenerating in their correct direction grew further than those that were misrouted.

Because lamprey spinal axons grow preferentially through a scar rather than around it, the scar may play a positive role in supporting axonal regeneration.
Functional projections from striate cortex and superior temporal sulcus to the nucleus of the optic tract (NOT) and dorsal terminal nucleus of the accessory optic tract (DTN) of macaque monkeys
Authors: Hoffmann K.‐P. , Distler C. , Erickson R.
Published: January 2005

The nucleus of the optic tract (NOT) and the dorsal terminal nucleus of the accessory optic tract (DTN) have been recognized to be relevant structures for optokinetic and vestibuloocular reflexes. NOT‐DTN neurons relay visual information to the vestibular nuclei via the nucleus prepositus hypoglossi and to the flocculus via the dorsal cap of the inferior olive. It has been previously shown that in carnivores the NOT‐DTN receives information from primary visual cortical areas in addition to the direct retinal input. In this study we demonstrate the presence and some functional characteristics such as latency and evicacy of considerable cortical projections to the NOT‐DTN in macaque monkeys.

In anaesthetized and paralyzed monkeys NOT‐DTN neurons were identified physiologically and tested for cortical input by electrical stimulation in various cortical areas. Successful sites of stimulation to activate NOT‐DTN neurons orthodromically lie in the primary visual cortex (V1) and in the motion‐processing areas in the superior temporal sulcus (STS). In contrast, electrical stimulation in area V4 and in parietal areas in most cases did not yield orthodromic responses. Overall latencies of action potentials elicited by stimulation in V1 were 0.5 ms longer than those elicited from STS. These short latency differences between V1 and STS stimulation suggest a direct projection from both V1 and STS to the NOT‐DTN.

The physiological results were supported by the results of anatomical experiments by using horseradish peroxidase as anterograde tracer. Both injections into V1 and into the lower bank of STS resulted in anterogradely labelled fibers and terminals around the recording sites of direction‐specific NOT‐DTN neurons.

This paper is a first step in clarifying the significance of corticofugal projections from individual areas involved in the analysis of visual motion for the optokinetic reflex.
A title oscillation: Journal of Comparative Neurology and Psychology, 1904–1910
Authors: Wight Randall D.
Published: January 2005

From 1904 through 1910, the Journal of Comparative Neurology became the Journal of Comparative Neurology and Psychology. This articles attempts a reconstruction of the events behind this title oscillation from archival sources.
Administration or deprivation of nerve growth factor during development permanently alters neuronal geometry
Authors: Ruit Kenneth G. , Snider William D.
Published: January 2005

We investigated whether the administration or deprivation of a neuronal growth factor during development can permanently alter the dendritic architecture of sensitive neurons. Nerve growth factor (NGF) or NGF antiserum treatment in the first 2–3 postnatal weeks markedly affected the survival, size, and dendritic arborization of mouse sympathetic ganglion cells acutely. Six months after the completion of treatment, the number of surviving neurons, cell body size, and higher order dendritic branching had changed considerably from their values at 3 weeks, suggesting that these parameters remain malleable throughout postnatal life. However, the number of primary dendrites, a fundamental determinant of organization within sympathetic ganglia, was permanently altered by the neonatal treatment protocol.

The idea emerging from this study is that NGF influences the elaboration of primary dendrites by sympathetic ganglion cells only during a critical developmental period. In maturity, NGF acts as a “maintenance” factor necessary for normal neuronal function and survival, but neurons lose the capacity to respond with wholesale rearrangements of dendritic architecture.
Brain macrophages and microglia respond differently to lesions of the developing and adult visual system
Authors: Milligan Carolanne E. , Levitt Pat , Cunningham Timothy J.
Published: January 2005

Traumatic injury in the brain usually results in rapid degeneration of neuronal elements and a response by peripherally derived macrophages (brain macrophages, BMOs) and resident microglia. One intriguing result of lesions performed in the developing brain as compared to lesions of the mature brain is the faster resolution of the cellular debris and the absence of significant scarring. The purpose of this study was to examine the response of BMOs to induced cell death distant to the lesion site and to investigate possible differences in the responding phagocytic populations (BMOs versus microglia) following lesions in neonates and adults. Ablation of the visual cortex at birth results in very rapid retrograde degeneration and removal of neurons of the dorsal lateral geniculate nucleus (dLGN) within a few days. Lesions to the visual cortex of adult rats also induce neurons within the dLGN to die, but these cells do so over a much more protracted time course. Utilizing differences in morphology and immunocytochemical staining with the monoclonal antibodies EDI and OX‐42 to distinguish between BMOs and microglia, we found that in the developing CNS, BMOs are signalled rapidly and specifically to the location of induced cell death. Microglia are not involved in this response. As might be expected, the temporal response in the adult is much more protracted. In contrast to the developing brain, microglia and not macrophages are the predominant responding cell class after the adult lesion. The data suggest that these are distinct populations of phagocytic cells that respond to brain damage during development and in the adult, which may be critical in modulating the resolution and growth response after injury.
Postnatal development of cholinergic markers in the rat olfactory bulb: A histochemical and immunocytochemical study
Authors: Le Jeune Hélène , Jourdan François
Published: January 2005

The present study has defined the developmental time course and the distribution patterns of neuronal fibers and cell bodies displaying acetylcholinesterase (AChE) activity or choline acetyltransferase (ChAT) immunoreactivity in the rat olfactory bulb. The results indicate that the deployment of centrifugal AChE‐containing fibers is essentially postnatal. The subset of atypical glomeruli, including the modified glomerular complex, is innervated as early as the first postnatal day while the normal ones are not reached by this type of afferent before postnatal day 6. The comparison of AChE labelling with ChAT immunoreactivity strongly supports the assumption that AChE‐containing fibers represent mainly, if not exclusively, the cholinergic bulbopetal innervation emanating from the basal forebrain. A quantitative study has confirmed that the density of labelled fibers increases gradually in the postnatal period and spreads heterogeneously among the bulbar layers. The selective precocious innervation of atypical glomeruli is in favor of their involvement in the early processing of olfactory information in the olfactory bulb. Acetylcholinesterase is also expressed within a subset of ChAT‐negative interneurons of the developing olfactory bulb. The number of neurons expressing AChE increases from birth to postnatal day 15 and then decreases to reach the adult value on about postnatal day 30. This neuronal population could constitute a cholinoceptive subset mediating the effects of cholinergic afferents on the bulbar neuronal network.
Appearance and distribution of the 275 kD hair‐cell antigen during development of the avian inner ear
Authors: Bartolami S. , Goodyear R. , Richardson G.
Published: January 2005

The 275 kD hair‐cell antigen (HCA) is a protein that was originally identified using immunological techniques in the inner ears of early hatchling and adult chickens. The HCA is specifically associated with the apical surface of sensory hair cells; in the vestibular system the antigen is distributed over the entire stereocilia bundle, but in the auditory system it only extends a short distance up the shafts of the stereocilia. The objectives of this study were to ascertain when the HCA is first expressed during inner ear development, to compare the temporal and spatial patterns of HCA expression with those of neurite ingrowth, and to determine how the distribution of the antigen observed in the auditory system arises during development. Serial sections of otocysts from embryonic day (ED) 4 to ED7.5 (stages 24 to 32) were stained with a monoclonal antibody to the HCA and polyclonal antibodies to the neuron–glial cell adhesion molecule in order to analyse patterns of HCA expression and neurite ingrowth. Nerve fibres are first observed in the anterior pole of the otocyst at ED4.5 (stage 24), and in the evaginating basilar papilla by EDS (stage 26). The HCA first appears within the vestibular system in the anterior pole of the otocyst at EDS (stage 26), and within the auditory system in the distal end of the basilar papilla at ED6.5 (stage 29). Serial section analysis indicates that expression of the HCA is always limited to areas of the epithelium where nerve fibres are found, although the delay between the onset of innervation and the onset of HCA expression varies from one region of the otocyst to another. The growth of stereocilia bundles in the auditory system was studied from ED10 to 2 days after hatching in sections from the medial to distal regions of the basilar papilla double labelled with rhodamine phalloidin and monoclonal anti‐HCA, At ED12 the stereocilia bundles are 1.7 μm high and the staining observed with both phalloidin and the antibody extend to the same maximum height above the apical surface of the hair cell. The maximum height that anti‐HCA staining extends up the stereocilia bundle remains almost constant between ED12 and postnatal day 2, but between ED15 and ED18 the stereocilia bundle grows rapidly in height, with a membrane domain lacking the HCA forming at the distal ends of the stereocilia. The restricted distribution of the HCA observed on the apical surface of mature auditory hair cells in the basilar papilla is therefore generated during the final growth phase of the stereocilia bundle by the accumulation of HCA‐free membrane at the distal ends of the stereocilia.
Altered expression of pp60c‐src induced by peripheral nerve injury
Authors: Ignelzi Michael A. , Padilla Stephanie S. , Warder Daryl E. , Maness Patricia F.
Published: January 2005

The normal src protein (pp60c‐src) is localized principally in the nerve growth cone of developing neurons and declines to low levels with synaptic maturation. To determine whether pp60c‐src is reexpressed in regenerating axons, its expression was studied by immunoblotting and immunocytochemical analyses in adult chicken sciatic nerve following nerve crush injury. pp60c‐src expression was found to increase during nerve repair with a temporal and spatial pattern consistent with a localization in regenerating axons. At the crush site, pp60c‐src increased to maximal levels 7 days postinjury, increasing fivefold relative to 0 day nerve. In the nerve segment distal to the injury, the maximal increase in pp60c‐src was sevenfold and occurred between 11 and 21 days postinjury. Immunoperoxidase staining revealed pp60c‐src in regenerating axons and certain nonneuronal cells at the site of nerve repair. pp60c‐src was induced in both motor and sensory neurons, as shown by increased pp60c‐src immunoreactivity in their cell bodies located in the spinal cord and dorsal root ganglion. Phosphotyrosine‐modified proteins that were potential targets of pp60c‐src increased following nerve crush, and were localized to outgrowing neurites as well as to nonneuronal cells. These results suggest that pp60c‐src is a common component of cellular mechanisms regulating growth cone migration in both regenerating and developing axons.