bluuebunny/crossref_metadata_2025 huggingface dataset:
Afferent influences on brainstem auditory nuclei of the chicken: Regulation of transcriptional activity followiqg cochlea removal
Authors: Garden Gwenn A. , Redeker‐DeWulf Valerie , Rubel Edwin W
Published: January 2005

Neuronal survival in the cochlear nucleus of young animals is regulated by afferent activity. Removal or blockade of nerve VIII input results in the death of 20–40% of neurons in the cochlear nucleus, nucleus magnocellularis (NM), of the 10–14 days posthatch chick. Neuronal death in NM is preceded by complete failure of protein synthesis and degradation of ribosomes. In addition, there is a biphasic change in the immunoreactivity of ribosomes for a monoclonal antiribosomal RNA antibody, Y10B. Initially, the entire population of afferentdeprived NM neurons loses Y10B immunoreactivity, but, after 6 or 12 hours of afferent deprivation, lack of Y10B immunoreactivity specifically marks dying NM neurons. Whether RNA synthesis is also altered in afferent‐deprived NM neurons has not previously been studied. To determine whether RNA synthesis in NM neurons is regulated by loss of afferent activity, we injected chicks with 3H‐uridine following unilateral cochlea removal and measured the incorporation of RNA precursor with tissue autoradiography. As early as 1 hour after cochlea removal, there was a significant decrease in 3H‐uridine incorporation by afferent‐deprived NM neurons. After longer periods of afferent deprivation (6 or 12 hours), the majority of dying NM neurons (marked by loss of Y10B immunoreactivity) fail to incorporate RNA precursor. Six or 12 hours following cochlea removal, the subpopulation of surviving NM neurons incorporates 3H‐uridine at increased levels over those observed 1 or 3 hours after cochlea removal. These findings suggest that nuclear function is regulated by afferent synaptic activity and that failure of RNA synthesis occurs early in the cell death process. © 1995 Wiley‐Liss, Inc.
Caudal medullary pathways to lumbosacral motoneuronal cell groups in the cat: Evidence for direct projections possibly representing the final common pathway for lordosis
Authors: Vanderhorst Veronique G. J. M. , Holstege Gert
Published: January 2005

The nucleus retroambiguus (NRA) projects to distinct brainstem and cervical and thoracic cord motoneuronal cell groups. The present paper describes NRA projections to distinct motoneuronal cell groups in the lumbar enlargement. Lumbosacral injections of wheat germ agglutinin‐horseradish peroxidase (WGA‐HRP) were made to localize and quantify the retrogradely labeled neurons in the caudal medullary lateral tegmentum. These injections were combined with spinal hemisections to distinguish between neurons having ipsi‐ or contralaterally descending axons. The NRA‐lumbosacral fibers descend almost exclusively contralaterally, but neurons in areas surrounding the NRA project mainly ipsilaterally.

In an anterograde tracing study, injections of WGA‐HRP or tritiated leucine were made in the region of the NRA to determine the NRA targets in the lumbosacral cord. Hemisections in C2 made it possible to distinguish between NRA projections and projections from neurons in the adjoining lateral tegmentum. The results show delicate NRA projections to distinct lumbosacral motoneuronal cell groups innervating specific hindlimb muscles (iliopsoas, adductors, and hamstrings) as well as axial muscles (medial longissimus and proximal tail muscles). The projection is bilateral, with a contralateral predominance. Ipsilaterally terminating fibers are derived from NRA neurons whose axons cross the midline at the level of the obex, descend through the contralateral spinal white matter, and recross at the level of termination. A conceptual description is presented in which the periaqueductal gray‐NRA‐lumbosacral projections form the final common pathway for lordosis in the cat. © 1995 Wiley‐Liss, Inc.
Intratelencephalic projections of the visual wulst in pigeons (Columba livia)
Authors: Shimizu Toru , Cox Kevin , Karten Harvey J.
Published: January 2005

The visual wulst is the telencephalic target of the thalamofugal visual pathway of birds, and thus the avian equivalent of the striate cortex of mammals. The anterograde tracer Phaseolus vulgaris leucoagglutinin was used to follow the intratelencephalic connections of the major constituents of the visual wulst in pigeons. In particular, efferent pathways from the granular layer (Intercalated nucleus of the hyperstriatum accessorium, IHA), supragranular layer (hyperstriatum accessorium, HA), and infragranular layers (hyperstriatum intercalatus superior and/or hyperstriatum dorsale, HIS/HD) were investigated. These efferent projections were confirmed by injections of the retrograde tracer cholera toxin subunit B into their terminal fields.

When a deposit of the anterograde tracer was centered in IHA, which receives the visual thalamic input, efferent fibers were seen to extend mainly dorsomedially to HA. When a deposit of the anterograde tracer was centered in HA, efferent fibers were seen to extend mainly in three directions: (1) medially to the tractus septomesencephalicus, which sends projections to extratelencephalic visual nuclei; (2) ventrolaterally to the lateral portion of the neostriatum frontale, where there were also labeled cells after the retrograde tracer was injected in HA; and (3) ventromedially to the paleosfriatal complex, which is the avian equivalent of the mammalian basal ganglia. Furthermore, relatively minor terminal fields were seen in (4) the neostriatum caudale, (5) neostriaturn intermedium, (6) archistriatum intermedium, and (7) hyperstriatum laterale. Finally, HIS/HD have projections predominantly to HA and the dorsocaudal telencephaion (area corticoidea dorsolateralis and area parahippocampalis), as well as relatively minor projections to the areas which also receive projections from HA. No anterogradely labeled fibers were seen in the tractus septomesencephalicus following the tracer injections in HIS/HD.

These results indicate that the visual information from the granular layer is distributed via the supragranular layer HA to multiple areas within the telencephalon, such as the neostriatum frontale and paleostriatal complex. In addition, HA is the source of an extratelencephalic projection via the tractus septomesencephalicus. Thus, the avian supragranular layer HA contains neurons which are the source of both intratelencephalic and extratelencephalic projections, whereas neurons of the mammalian cortex are segregated into two distinct layers, supragranular and infragranular layers, based on the targets of their projections. The findings are further discussed and compared to the mammalian striate cortex. © 1995 Wiley‐Liss, Inc.
Cells of the perireticular nucleus project to the developing neocortex of the rat
Authors: Adams Niels C. , Baker Gary E.
Published: January 2005

The perireticular nucleus is a recently described thin sheet of small cells among the fibres of the internal capsule, lying lateral to the thalamic reticular nucleus and medial to the globus pallidus (Clemence and Mitrofanis [1992]. J. Comp. Neurol. 322:167–180). During development, the perireticular nucleus is relatively large, lying in the path of the growing corticofugal and thalamocortical axons and filling the area of the internal capsule lateral to the thalamic reticular nucleus. After these axons have formed their connections, the perireticular nucleus rapidly decreases in size, leaving only a few cells in the adult (Mitrofanis [1992] J. Comp. Neurol. 320:161–181).

In this study, we aiwed to investigate the connections between the developing cortex and thalamus by making injections of tracer into the cortical plate. Injections of Horse Radish Peroxidase (HRP), Wheat Germ Agglutinin bound to HRP (WGA‐HRP) and l'dioctadecyl 3, 3, 3′, 3 tetramethycarbocyanine perchlorate (DiI) were made in vivo between embryonic day (E)18 and adult and DiI was placed in the fixed brains of rats aged between E16 and postnatal day (P)1.

Between E17 and P10, the retrograde perikaryal labelling resulting from these injections revealed a transient projection from the perireticular nucleus to the ipsilateral cortical plate. No cells were labelled in the thalamic reticular nucleus.

This suggests that the perireticular nucleus must be regarded as a group of cells distinct from the thalamic reticular nucleus and having a separate role in development. Comparisons between the perireticular cells and the cells of the cortical subplate suggest that both may be playing comparable roles in early development, possibly guiding fibres towards their end stations or serving to rearrange the complex mapped projections linking thalamus and cortex. © 1995 Wiley‐Liss, Inc.
Macrophages and glia participate in the removal of apoptotic neurons from the Drosophila embryonic nervous system
Authors: Sonnenfeld Margaret J. , Jacobs J. Roger
Published: January 2005

Cell death in the Drosophila embryonic central nervous system (CNS) proceeds by apoptosis, which is revealed ultrastructurally by nuclear condensation, shrinkage of cytoplasmic volume, and preservation of intracellular organelles. Apoptotic cells do not accumulate in the CNS but are continuously removed and engulfed by phagocytic haemocytes. To determine whether embryonic glia can function as phagocytes, we studied serial electron microscopic sections of the Drosophila CNS. Apoptotic cells in the nervous system are engulfed by a variety of glia including midline glia interface (or longitudinal tract) glia, and nerve root glia. However, the majority of apoptotic cells in the CNS are engulfed by subperineurial glia in a fashion similar to the microglia of the vertebrate CNS. A close proximity between macrophages and subperineurial glia suggests that glia may transfer apoptotic profiles to the macrophages. Embryos affected by the maternal‐effect mutation Bicaudal‐D have no macrophages. In the absence of macrophages, most apoptotic cells are retained at the outer surfaces of the CNS, and subperineurial glia contain an abundance of apoptotic cells. Some apoptotic cells are expelled from the CNS, which suggests that the removal of apoptotic cells can occur in the absence of macrophages. The number of subperineurial glia is unaffected by changes in the rate of neuronal apoptosis. © 1995 Wiley‐Liss, Inc.
Cell body response to injury in motoneurons and primary sensory neurons of a mutant mouse, ola (Wld), in which wallerian degeneration is delayed
Authors: Bisby M. A. , Tetzlaff W. , Brown M. C.
Published: January 2005

We examined the response to axon injury in the facial motoneurons and dorsal root ganglion (DRG) neurons of C57BL/Ola (Wld) mice, compared with the responses of C57BL/6J mice. The peripheral nerves of Ola mutants undergo remarkably slowed and muted Wallerian degeneration after injury. The increase in GAP‐43 mRNA levels in facial motoneurons and DRG neurons was similar in both strains of mice, as was the initial decrease in medium‐weight neurofilament (NFM) mRNA in facial motoneurons, and the increase in JUN immunoreactivity in both types of neurons. However, the subsequent recovery to normal low levels of JUN and GAP‐43 mRNA expression and high levels of NFM mRNA was delayed in Ola motoneurons. We ascribe this delay to the slow regeneration and target reinnervation of facial axons in the Ola mice.

These results show that absence of rapid Wallerian degeneration does not affect the initial cell body response to axonal injury. They also provide further evidence that restoration of normal levels of expression of GAP‐43 and NFM mRNAs is dependent on target reinnervation and/or trophic factors provided by the distal nerve, Impaired regeneration in the Ola mouse does not seem to be a consequence of a defective cell body response to injury, and our results illustrate the general principle that, even if there is a vigorous cell body response to injury, normal axonal regeneration requires the additional provision of a favorable environment for growth. © 1995 Wiley‐Liss, Inc.
Differential regenerative response of purkinje cell and inferior olivary axons confronted with embryonic grafts: Environmental cues versus intrinsic neuronal determinants
Authors: Rossi Ferdinando , Jankovski Aleksandar , Sotelo Constantino
Published: January 2005

Regeneration of severed central axons is supposed to depend on two factors: a permissive local environment and the particular intrinsic properties of axotomized neurones. To assess the role of each of these factors in axonal regeneration, the capability of two particular axon populations of the adult mouse cerebellum to grow into target‐specific (cerebellum) and target‐unspecific (neocortex) embryonic grafts was determined. Purkinje cell and inferior olivary axons were transected by passing a microscalpel through the axial white matter of the cerebellar folia, particularly, those of the anterior lobe. Immediately after the injury, solid transplants were placed in the lesion cavity. Purkinje cell axons were labelled by using anticalbindin immunocytochemistry, and olivocerebellar fibres were visualized by biotinylated dextran amine anterograde axonal tracing.

Following axotomy, Purkinje cell axons appeared as thickened processes ending with large terminal clubs. Their morphology and number did not change up to the longest survival time considered (2 months), thereby confirming previous demonstrations that Purkinje cells survive axon injury (I. Dusart and C. Sotelo, 1994, J. Comp. Neurol. 347:211–232). Inferior olivary axons were thinner and bore smaller terminal bulbs. When embryonic cerebellar grafts, containing cortical and deep nuclear, precursors, were placed close to the injured axons, olivocerebellar fibres vigorously regenerated into the transplants and ended in new climbing fibies along the dendrites of grafted Purkinje cells. By contrast, host Purkinje cell axons never showed any outgrowth towards the graft. Similarly, these axons failed to regenerate into grafts containing solely the rostromedial portion of the cerebellar anlage, mostly consisting of deep nuclear neurones, their main targets. Comparable results were obtained by transplanting embryonic neocortical tissue: inferior olivary axons also regenerated into the grafts, although with distinct terminal arbours without the climbing fibre phenotype, whereas Purkinje cell axons always failed to grow.

These results provide the first direct demonstration that severed inferior olivary axons are able to regenerate. In addition, they show that the growth‐permissive/‐promoting conditions created by embryonic nervous tissue are not sufficient to induce the regeneration of every axonal type and allow us to hypothesise that successful regenamtion depends on the mterplay between environmental cues and intrinsic properties of the axotornized neurones. © 1995 Wiley‐Liss, Inc.
Reorganization of central terminals of myelinated primary afferents in the rat dorsal horn following peripheral axotomy
Authors: Woolf C. J. , Shortland P. , Reynolds M. , Ridings J. , Doubell T. , Coggeshall R. E.
Published: January 2005

We have investigated the time course and extent to which peripheral nerve lesions cause a morphological reorganization of the central terminals of choleragenoid‐horseradish peroxidase (B‐HRP)‐labelled primary afferent fibers in the mammalian dorsal horn. Choleragenoid horseradish peroxidase is retrogradely transported by myelinated (A) sensory axons to laminae I, III, IV and V of the normal dorsal horn of the spinal cord, leaving lamina II unlabelled. We previously showed that peripheral axotomy results in the sprouting of numerous B‐HRP labelled large myelinated sensory axons into lamina II. We show here that this spread of B‐HRP‐labelled axons into lamina II is detectable at 1 week, maximal by 2 weeks and persists for over 6 months postlesion. By 9 months, however, B‐HRP fibers no longer appear in lamina II. The sprouting into lamina II occurs whether regeneration is allowed (crush) or prevented (section with ligation), and does not reverse at times when peripheral fibers reinnervate the periphery. We also show that 15 times more synaptic terminals in lamina II are labelled by B‐HRP 2 weeks after axotomy than in the normal. We interpret this as indicating that the sprouting fibers are making synaptic contacts with postsynaptic targets. This implies that A‐fiber terminal reorganization is a prominent and long‐lasting but not permanent feature of peripheral axotomy. We also provide evidence that this sprouting is the consequence of a combination of an atrophic loss of central synaptic terminals and the conditioning of the sensory neurons by peripheral axotomy. The sprouting of large sensory fibers into the spinal territory where postsynaptic targets usually receive only small afferent fiber input may bear on the intractable touch‐evoked pain that can follow nerve injury. © 1995 Wiley‐Liss, Inc.
Dendritic morphology of CA1 pyramidal neurones from the rat hippocampus: II. Spine distributions
Authors: Bannister N. J. , Larkman A. U.
Published: January 2005

The numbers and distributions of dendritic spines were estimated for six adult and three juvenile biocytin‐injected neurones from the CA1 region of the hippocampus of the albino rat. For each cell, a sample of long dendritic segments that lay favourably in the plane of focus was drawn at high magnification and the visible spines counted. Correction was made for spines obscured by dendritic shafts. Within individual cells, dendrites of similar type and diameter had similar spine densities. For adults, long basal segments averaged 2.4 spines/μm and obliques averaged 3.2 spines/μm. In juveniles, basals averaged 2.3 spines/μm and obliques, 2.5 spines/μm. Apical tuft segments were less spiny, averaging 1.4 spines/μm in adult cells and 1.8 spines/μm in juveniles. There was a positive correlation between spine density and dendrite diameter.

Values from this sample were used to assign spine densities to the other segments, and so the total number of spines was estimated for each cell. Adult cells averaged 30,500 ± 3,900 (S. D.) spines and juveniles, 23,800 ± 7,100 spines. Adult cells had roughly 50% of their spines in stratum radiatum, 40% in s. oriens, and 10% in s. lacunosum‐moleculare. Juvenile cells had a rather higher proportion (20%) in s. lacunosum‐moleculare. In general, some 50% of all spines were located within a path length of 200 μm from the soma. These total numbers of spines were much higher than earlier values from Golgi‐impregnated cells but align well with estimates of the numbers of axonal boutons supplied to CA1 by CA3 pyramidal cells. © 1995 Wiley‐Liss, Inc.
A population of wide‐field bipolar cells in the rabbit's retina
Authors: Jeon Chang‐Jin , Masland Richard H.
Published: January 2005

We have stained an unusual population of retinal bipolar cells. When the low molecular weight tracer biocytin was injected into the vitreous body of rabbits, it subsequently accumulated in the somata and processes of a population of wide‐field bipolar cells. The cells have 2–4 primary dendrites. Their dendritic arbors span a field 50 to 200 μm in diameter. The axonal arbors are sparse and often highly asymmetric. The longest dimension of the axonal arbor ranges from 100 to 300 μm. The cells are moderately evenly spaced. They make up less than 1% of the total population of bipolar cells in the rabbit retina.

With the whole population stained, regularities in the spatial arrangement of nearby cells can be recognized. Their dendrites often run to a common point, where they have the appearance of making contact with each other. A similar arrangement is seen for the cells' axonal arbors, so that the whole population is spatially linked in both the outer retina and the inner. The exact nature of the points of conjunction cannot be learned from light microscopy. One possibility is that the processes run together because they contact a common target. If so, the target structures (one in the outer retina and one in the inner) must be sparse. An alternative is that the points of conjunction represent synapses or gap junctions among wide‐field bipolars of this type. © 1995 Wiley‐Liss, Inc.
Ultrastructure and synaptology of the nucleus ambiguus in the rat: The compact formation
Authors: Hopkins David A.
Published: January 2005

The fine structure of the esophagomotor compact formation of the nucleus ambiguus was studied. Esophageal motoneurons are atypical in that they have extensive direct somato somatic and somato‐dendritic appositions without intervening glial processes. A unique feature is the presence of finger‐ and leaf‐like somatic protrusions which partially wrap longitudinally oriented dendrites and occasionally, small groups of dendrites and axons. The neuropil contains many longitudinally oriented, small‐diameter dendrites of relatively uniform size (1.1 ± 0.4 S. D. μm in diameter). Motoneuronal somatic profiles have 0–5 synapses per profile which represents a synaptic density of 10.6 synapses per soma. Axodendritic synapses measure 0.5 × 0.7 μm in the transverse plane and are up to 3.0 μm long in the sagittal plane. Many axon terminals contact both a soma and dendrite in close apposition. Most axon terminals (>90%) contain round vesicles and form asymmetric junctions with somata and dendrites. Axon terminal degeneration after electrolytic lesions and labelling after injections of wheat germ agglutinin‐horseradish peroxidase in the nucleus of the tractus solitarius show that afferent connections to the compact formation form axodendritic synapses.

The ultrastructure and synaptology of esophageal motoneurons is characterized by the close apposition of somata and dendrites (somatic‐dendritic bundling), and the longitudinal orientation of dendrites (dendritic bundling), axons and axon terminals in the neuropil. These features may be important morphological substrates for synchronization and coordination of esophageal motoneuronal activity and esophageal peristalsis. © 1995 Wiley‐Liss, Inc.
Vasopressin and galanin mRNAs coexist in the nucleus of the horizontal diagonal band: A novel site of vasopressin gene expression
Authors: Planas Barbara , Kolb Pamella E. , Raskind Murray A. , Miller Margaret A.
Published: January 2005

Vasopressin (VP) neurons have been identified in several brain regions where VP has been hypothesized to act as a neurotransmitter or neuromodulator. In many sites, VP is colocalized with the neuropeptide galanin (GAL). Here, using single in situ hybridization histochemistry, we have identified a novel group of neurons within the nucleus of the horizontal diagonal band of Broca (HDB) that express the VP gene and have assessed the distribution of these cells in adult male and female rats (90 days old, n = 7/group). VP mRNA‐expressing neurons were scattered throughout the rostrocaudal extent of the HDB, and the number of VP neurons detected unilaterally ranged from 1 to 17 cells per 20 μm section. Using double in situ hybridization histochemistry on alternate sections, we have assessed the number of cells expressing VP and/or GAL mRNAin the diagonal band and have determined the extent of their colocalization. Approximately 50% of all VP‐expressing neurons in the HDB coexpressed GAL mRNA, and 33% of GAL‐expressing neurons in this region coexpressed VP mRNA. No sex differences were detected in the number of neurons expressing either VP or GAL mRNA or in the incidence of coexpression of VP and GAL mRNAs in this region. VP neurons in the HDB exhibited a low level of expression, and cellular VP mRNA content did not differ between male and female rats. However, sex differences were present in the bed nucleus of the stria terminalis (BNST) of these same rats. Consistent with our previous findings, both the number of VP‐expressing neurons (P ≤ 0.0004) and the cellular VP mRNA content (P ≤ 0.02) in the BNST were greater in male than in female rats. These results suggest that VP gene expression is differentially regulated by gonadal hormones in the HDB compared to the BNST. Because GAL was previously reported to colocalize with acetyicholine (ACh) and gonadotropin‐releasing hormone (GnRH) in the diagonal band of Broca, our findings suggest that VP may also colocalize with these transmitters in this brain region. Our observations may provide an anatomical basis for the postulated actions of VP in functions involving ACh or GnRH pathways. © 1995 Wiley‐Liss, Inc.
Effects of neonatal enucleation on the organization of callosal linkages in striate cortex of the rat
Authors: Olavarria Jaime F. , Li Chi‐pei
Published: January 2005

Lewis and Olavarria ([1995] J. Comp. Neurol. 361:119–137) showed that the mediolateral organization of callosal linkages differs markedly between medial and lateral regions of striate cortex in the rat. Thus, callosal fibers originating from medial regions of striate cortex interconnect loci that are mirror‐symmetric with respect to the midsagittal plane. In contrast, fibers from lateral regions of striate cortex show a reversed pattern of connections: tracer injections into the 17/18a border produce retrograde cell labeling in regions medial to the contralateral 17/18a border, whereas injections placed somewhat medial to the 17/18a border label cells located at the contralateral 17/18a border.

Based on the interpretation that callosal fibers from lateral striate cortex connect retinotopically corresponding loci (Lewis and Olavarria [1995] J. Comp. Neurol. 361:119–137) we propose here that the development of the reversed pattern of connections in lateral portions of striate cortex is guided by activity‐dependert cues originating from spontaneously active ganglion cells in temporal retina. In the present study we have attempted to falsify this hypothesis by investigating the effects of neonatal bilateral enucleation on the organization of callosal linkages in striate cortex of the rat.

Once enucleated rats reached adulthood, we studied the mediolateral organization of callosal connections by placing small injections of different fluorescent tracers into different loci within medial and lateral striate cortex. The analysis of the distribution of retrogradely labeledcallosal cells indicated that connections from lateral portions of striate cortex were no longer organized in a reversed fashion, rather, they resembled the mirror image pattern normally found in the medial callosal region, i. e., injections at the 17/18a border produced labeled cells at the opposite 17/18a border, whereas injections into slightly more medial regions produced labeled cells in the opposite, mirror‐symmetric location. In addition, we found that enucleation does not alter the organization of callosal linkages in medial portions of striate cortex.

Thus, by showing that enucleation significantly changes the pattern of connections from lateral portions of striate cortex, the present study does not falsify, but rather strengthens the hypothesis that interhemispheric correlated activity driven from the temporal retinal crescent guides the normal development of reversed callosal linkages in lateral portions of rat striate cortex. Furthermore, the present study shows that, in the absence of the eyes, the pattern of callosal linkages in lateral portions of striate cortex resembles the mirror image pattern normally found only in medial striate cortex. © 1995 Wiley‐Liss, Inc.
Distribution of non‐NMDA glutamate receptor mRNAs in the developing rat cochlea
Authors: Luo Lin , Brumm Duane , Ryan Allen F.
Published: January 2005

In situ hybridization was used to document the distribution of mRNA encoding six subunit isoforms of non‐N‐methyl D‐aspartic acid (NMDA) glutamate receptors (GluR1, GluR2, GluR3, GluR4, GluR5 and GluR6) in the inner ears of embryonic, postnatal and adult rats. GluR2 and GluR3 expression in the spiral ganglion appeared well before birth, and reached adult levels several days before the onset of function in the cochlea. In the spiral limbus, expression of GluR2 and GluR3 mRNA reached very high levels at around the time of birth, then declined after a few days. Low levels of GluR1, GluR4 and GluR6 expression were detected in various tissues of the cochlea during development. In the adult cochlea, GluR expression was limited to GluR2 and GluR3 mRNAs in the spiral ganglion neurons and GluR2 mRNA in fibrocytes of the spiral limbus, a non‐neural tissue. The ontogenetic expression of additional GluR subunit genes and their appearance in different cochlear tissues could reflect different roles for these genes during development, or less precise regulation of gene expression within the GluR family. In particular, the very high levels of GluR gene expression in the spiral limbus during the perinatal period support a non‐neural function, perhaps as cell surface receptors during tissue differentiation. © 1995 Wiley‐Liss, Inc.
Glutamatergic and GABAergic input to rat spinothalamic tract cells in the superficial dorsal horn
Authors: Lekan Helena A. , Carlton Susan M.
Published: January 2005

The distribution of synaptic terminals onto spinothalamic tract cells (types I and II) of the superficial dorsal horn was determined with special reference to the amino acid transmitters glutamate and γ‐aminobutyric acid. Fifteen spinothalamic cells retrogradely labeled from the thalamus with the neuroanatomical tracer wheatgerm agglutinin conjugated to horseradish peroxidase were sectioned for electron microscopy. Serial sections from several levels through each cell were immunostained for glutamate and γ‐aminobutyric acid using a postembedding immunogold technique. Perimeter measurements of spinothalamic cell somata and dendrites and the lengths of apposition for all terminal profiles in contact with the spinothalamic cells were obtained from electron micrographs using a digitizing tablet. These data were used to determine the density of terminals on the soma and dendrites. In addition, the terminal population on these cells was categorized by transmitter content (glutamate, γ‐aminobutyric acid, or unlabeled). The results demonstrate that terminal density increased on dendrites relative to their distance from the soma. Glutamatergic and GABAergic input composed 37% and 20% of the terminal population, respectively, and these percentages remained uniform for the soma and dendrites. There were no significant differences among the 15 cells analyzed for this study. The results, therefore, suggest that both type I and type II STT cells of the superficial DH have similar synaptic organizations. © 1995 Wiley‐Liss, Inc.
“Satellite cells” and nerve terminals in the crayfish opener muscle visualized with fluorescent dyes
Authors: Harrington C. C. , Atwood H. L.
Published: January 2005

Nerve terminals and associated cells on the muscle's surface were visualized in the crayfish opener muscle with several fluorescent dyes in conjunction with confocal microscopy and conventional fluorescence microscopy. The nerve terminals of the excitatory and inhibitory axons were best seen with 4‐diethylaminostyryl‐N‐methylpyridinium iodide (4‐Di‐2‐Asp). This dye is selectively accumulated in mitochondria, which are numerous both in the axons and in synapse‐bearing terminal varicosities. Muscle nuclei were also clearly visualized, because they excluded 4‐Di‐2‐Asp but were stained by acridine orange (AO). A positive attraction between muscle nuclei and nerve terminals was evident by visual inspection and was confirmed by spatial statistics. Additional flat cells on the muscle's surface appeared as bright rings with elongated processes that were often close to or overlapped nearby nerve terminals. The structure of these cells was established by electron microscopy after labeling them with fluorescent polystyrene beads, which could be found over structures on the muscle surface in sections of embedded specimens. The flat surface cells were distinct from peripheral glial cells closely associated with axons and nerve terminals. Nevertheless, spatial statistics showed that the surface cells were grouped near nerve terminals. They occupied a small fraction of the muscle cell's surface. Their functional role has not been determined in crustacean muscles. © 1995 Wiley‐Liss, Inc.
Immunocytochemical identification of cone bipolar cells in the rat retina
Authors: Euler Thomas , Wässle Heinz
Published: January 2005

We studied the morphology of bipolar cells in fixed vertical tissue sections of the rat retina by injecting the cells with Lucifer Yellow and neurobiotin. In addition to the rod bipolar cell, nine different putative cone bipolar cell types were distinguished according to the position of their somata in the inner nuclear layer and the branching pattern and stratification level of their axon terminals in the inner plexiform layer. Some of these bipolar cell populations were labeled immunocytochemically in vertical and horizontal sections using antibodies against the calcium‐binding protein recoverin, the glutamate transporter GLT‐1, the alpha isoform of the protein kinase C, and the Purkinje cell marker L7. These immunocytochemically labeled cell types were characterized in terms of cell density and distribution.

We found that rod bipolar cells and GLT‐1‐positive cone bipolar cells occur at higher densities in a small region located in the upper central retina. This area probably corresponds to the central area, which is the region of highest ganglion cell density. A second peak of rod bipolar cell density in the lower temporal periphery matches the retinal area of binocular overlap. The population densities of the immunocytochemically characterized bipolar cells indicate that at least 50% of all bipolar cells are cone bipolar cells. The variety and total number of cone bipolar cells is surprising because the retina of the rat contains 99% rods. Our findings suggest that cone bipolar cells may play a more important role in the visual system of the rat than previously thought. © 1995 Wiley‐Liss, Inc.
Nitric oxide synthase in tiger salamander retina
Authors: Kurenni Dmitri E. , Thurlow Genevieve A. , Turner Ray W. , Moroz Leonid L. , Sharkey Keith A. , Barnes Steven
Published: January 2005

Previous studies have indicated that nitric oxide, a labile freely diffusible biological messenger synthesized by nitric oxide synthase, may modulate light transduction and signal transmission in the retina. In the present work, the large size of retinal cells in tiger salamander (Ambystoma tigrinum) allowed the utilization of nicotinamide adenine dinucleotide phosphate (NADPH)‐diaphorase histochemistry and nitric oxide synthase immunocytochemistry to delineate the cell‐specific intracellular localization of nitric oxide synthase. NADPH‐diaphorase activity was highly concentrated in the outer retina, in rod and cone inner segment ellipsoids, and between and adjacent to the photoreceptor cell bodies in the outer nuclear layer. Examination of enzymatically isolated retinal cells indicated that outer nuclear layer NADPHdiaphorase activity was localized to the distal processes of the retinal glial (Müller) cells and to putative bipolar cell Landolt clubs. Less intense NADPH‐diaphorase activity was seen in the photoreceptor inner segment myoid region, in a small number of inner nuclear layer cells, in cap‐like configurations at the distal poles of cells in the ganglion cell layer and surrounding ganglion cell layer somata, and in punctate form within both plexiform layers, the pigment epithelium, and the optic nerve. Nitric oxide synthase–like immunoreactivity was similarly localized, but was also concentrated along a thin sublamina centered within the inner plexiform layer. The potential for nitric oxide generation at multiple retinal sites suggests that this molecule may play a number of roles in the processing of visual information in the retina. © 1995 Wiley‐Liss, Inc.
Centrifugal projections upon the retina: An anterograde tracing study in the pigeon (Columba livia)
Authors: Woodson Walter , Shimizu Toru , Wild J. Martin , Schimke Jan , Cox Kevin , Karten Harvey J.
Published: January 2005

Previous work has shown that the avian retina receives two types of centrifugal fibers from the brain. These types can be distinguished based on the size and the morphology of their terminal endings and have been termed convergent and divergent. The centrifugal fibers arise from the isthmooptic nucleus (ION) and the surrounding ectopic cell region (ECR). We used injections of anterograde tracers either to the ION/ECR or to the ECR only to determine the morphology, depth of termination, and regional distribution of the centrifugal fibers arising from each.

We found that the ECR gives rise only to the divergent type of the centrifugal fiber, whereas the ION gives rise mainly to the convergent type but may also send some fibers of the divergent type. Most of the fibers project contralaterally, although a few from the ECR project ipsilaterally. The terminals of either type are not uniformly distributed throughout the retina; instead, they are found mainly in the inferior, midtemporal, to nasal portion of the retina and appear to avoid the fovea and most of the red field. By comparison, the ION receives a major projection from portions of the tectum that receive input from the fovea and the red field in a type of neural loop. The neural loop does not project to the same point (homotopic), but projects from the red field to the inferior retina (heterotopic), as was recently proposed by Holden (1990; Vis. Neurosci. 4:493–497).

The distribution of centrifugal axons corresponds to displaced ganglion cells that selectively innervate the nuclei of the accessory optic system (AOS), including the nucleus of the basal optic root (dorsal, ventral, and lateral) and the nucleus lentiformis mesencephali, pars magnocellularis. We suggest that the centrifugal axons act by increasing the gain on the AOS, thereby enhancing retinal stabilization of gaze with improved accuracy of pecking of small objects. © 1995 Wiley‐Liss Inc.
Postnatal development of periodontal ruffini endings in rat incisors: An immunoelectron microscopic study using protein gene product 9.5 (PGP 9.5) antibody
Authors: Nakakura‐Ohshima Kuniko , Maeda Takeyasu , Ohshima Hayato , Noda Tadashi , Takano Yoshiro
Published: January 2005

Postnatal development of Ruffini endings was ultrastructuraally investigated in the upper incisors of the rat from 1 day to 60 days after birth by means of protein gene product 9. 5 (PGP 9. 5) immunocytochemistry. The immunostaining with PGP 9. 5 antibody clearly demonstrated chronological alterations of the distribution and ultrastructure of the Ruffini endings during postnatal development. At 1 day after birth, the PGP 9. 5 positive nerve terminals contained a few mitochondria and vesicles immunonegative for PGP 9. 5. Dendritic terminals appeared at 4 days after birth, with a small number of expanded or bulbous portions. These expanded portions possessed morphological features similar to those of the growth cone: several mitochondria and various kinds of vesicles. Typical Ruffini endings with dendritic ramification and expanded portions appeared 7–11 days after birth. At this stage, parts of the axon terminals extended through the slits of Schwann cell covering and formed finger‐like projections called axonal spines. These Ruffini endings increased dramatically in number after 24–26 days and were identical in density and morphology to those seen in adult rats. After the commencement of the occlusion between the incisors, the number of large mitochondria increased, in contrast to the decrease of the vesicles in the axon terminals. Moreover, the axonal spines increased both in number and in length. Thus, the periodontal nerve endings showed stage‐specific morphological features intimately related in timing to tooth eruption and occlusion. Functional stimuli possibly contribute to the final differentiation and maturation of the periodontal Ruffini endings. © 1995 Wiley‐Liss Inc.
An immunochemical, ultrastructural, and developmental characterization of the horizontal basal cells of rat olfactory epithelium
Authors: Holbrook Eric H. , Szumowski Karen E. Mieleszko , Schwob James E.
Published: January 2005

The olfactory epithelium, which retains a capacity for neurogenesis throughout life, contains two categories of basal cells, dark/horizontal and light/globose, neither of which is fully characterized with respect to their function during the processes of neurogenesis and epithelial reconstitution after injury. The aim of this study was to define the potential biological role(s) of dark/horizontal basal cells (D/HBCs) in the epithelium by performing immunochemical, electron microscopic, and developmental analyses of this cell population. The D/HBCs express several specific immunochemical characteristics, which include the rat homologues of human cytokeratins 5 and 14, which were identified on the basis of staining with subunit‐ specific monoclonal antibodies and two‐dimensional immunoblot analysis of the immunoreactive proteins. Indeed, the D/HBCs are the only cells in the olfactory mucosa that express these specific cytokeratins. The D/HBCs also express an α‐galactose or α‐N galactosamine moiety to which the Iß4 isolectin from Bandeiraea simplicifolia binds. Moreover, the D/HBCs are heavily labeled by two different antibodies against the EGF receptor and by a monoclonal antibody that binds to phosphotyrosine. These characteristics are also common to the basal cells of respiratory epithelium. The electron microscopic analysis of the basal region of the olfactory epithelium and the light microscopic immunofluorescence observations demonstrate that the D/HBCs provide a bridge between the basal processes of some sustentacular cells and the basal lamina. The most striking ultrastructural feature of the D/HBCa is their enfolding of virtually all bundles of olfactory axons within tunnels formed where D/HBCs arch over the basal lamina. The intimacy of the arrangement between D/HBCs and olfactory axons suggests that signals may pass from axons to D/HBCs or vice‐versa. With respect to the development of D/HBCs, cells that express cytokeratins 5 and 14 and the EGF receptor first appear near the boundary with respiratory epithelium late in development, but do not extend throughout the olfactory epithelium until the middle of the first postnatal week. Taken together, the present findings and previously published data suggest that D/HBCs help to maintain the structural integrity of the olfactory epithelium, participate in its recovery from injury, and may also function to signal the status of the neuronal population of the epithelium. © 1995 Wiley‐Liss, Inc.
Cytoskeleton gradients in three dimensions during neurulation in the rabbit
Authors: Viebahn Christoph , Lane E. Birgitte , Ramaekers Frans C. S.
Published: January 2005

Morphogenetic movements leading to the formation of the neural tube and cellular differentiation leading to neuronal and glial cell lineages are both part of early development of the vertebrate nervous system. In order to analyze the degree of overlap between these processes, cellular differentiation during the shaping of the neural plate is investigated immunohistochemically by using monoclonal intermediate filament protein antibodies and the 7.5–8.0‐day‐old rabbit embryo as a model. Western blotting is used to confirm the specificity of the antibodies, which include a new monoclonal vimentin antibody suitable for double‐labeling in combination with monoclonal cytokeratin (and fibronectin) antibodies. Starting in the early somite embryo and concomitant with neural plate folding, a gradual loss of cytokeratin 8 (and 18) expression in the neuroepithelium is mirrored by a gain in virnentin expression with partial coexpression of both proteins. At the prospective rhombencephalic and spinocaudal levels, vimentin expression, in particular, changes (i. e., increases) along gradients in three dimensions: along the longitudinal axis of each neuroepithelial cell from bssal to apical, in the transverse plane of the embryo from dorsolateral to veritromedial and along the craniocaudal axis from prospective rhombencephalic toward spinocaudal levels of the neural plate. At the prospective mes‐ and prosencephalic levels, the expression change also proceeds from basal to apical within each neuroepithelial cell, but along the other axes described here, the progress in expression change is more complex. Although the functional meaning of these highly ordered expression changes is at present unclear, the gradients suggest a novel pattern of neuroepithelial differentiation which may be functionally related to the process of interkinetic nuclear migration (Sauer [1935] J. Comp. Neurol. 62:377–402) and which partially coincides with the morphogenetic movements involved in the shaping of the neural plate. © 1995 Wiley‐Liss, Inc.
Dependence of developing group Ia afferents on neurotrophin‐3
Authors: Kucera Jan , Fan Guoping , Jaenisch Rudolf , Linnarsson Sten , Ernfors Patrik
Published: January 2005

At birth, group Ia proprioceptive afferents and muscle spindles, whose formation is Ia afferent‐dependent, are absent in mice carrying a deletion in the gene for neurotrophin‐3 (NT‐3 –/–). Whether Ia afferents contact myotubes, resulting in the formation of spindles which subsequently degenerate, or whether Ia afferents and spindles never form was examined in NT‐3 –/– mice at embryonic days (E) 10.5–18.5 by light and electron microscopy. Three sets of data indicate that Ia neurons do not develop and spindles do not form in NT‐3‐deflcient mice. First, peripheral projections of Ia afferents did not innervate hindlimbs of NT‐3 –/– mice, as reflected by a deficiency of nerve fibers in limb peripheral nerves and an absence of afferent nerve‐muscle contacts and spindles in the soleus muscle at E13.5–E18.5. Second, central projections of Ia afferents did not innervate the spinal cord in the absence of NT‐3, as shown by an atrophy of the dorsal spinal roots and absence of afferent projections from limb musculature to spinal motor neurons at E13.5 or E15.5. Lastly, the lumbar dorsal root ganglia (DRGs) at E10.5–E 14.5, the stages of development that precede or coincide with the innervation of the spinal cord and hindlimbs by Ia afferents, were 20–64% smaller in mutant than in wild‐type mice, presumably because the cell bodies of Ia neurons were absent in embryos lacking NT‐3.

The failure of Ia neurons to differentiate and/or survive and Ia afferent projections to form in early fetal mice lacking NT‐3 suggests that NT‐3 may regulate neuronal numbers by mechanisms operating prior to neurite outgrowth to target innervation fields. Thus, developing Ia neurons may be dependent on NT‐3 intrinsic to the DRGs before they reach a stage of potential dependence on NT‐3 retrogradely derived from skeletal muscles or spinal motor neurons. © 1995 Wiley‐Liss, Inc.
Anatomy of the antennal motoneurons in the brain of the honeybee (Apis mellifera)
Authors: Kloppenburg Peter
Published: January 2005

This paper describes the morphology and location of the cerebral motoneurons that control the movement of the antennae in the honeybee. The position of each antenna is controlled by two muscle systems; the basal segment (scape) is moved by four muscles within the head capsule, and two muscles within the scape control the distal segments (flagellum) of the antenna. The motor system of the scape is controlled by nine motoneurons, and that of the flagellum by six motoneurons. All of these motoneurons share the dorsal lobe as a common projection area where their dendritic fields overlap extensively. These motoneurons do not have contralateral projections. The cell bodies of the antennal motoneurons are located in the soma layer lateral to the dorsal lobe. The somata for each muscle system are arranged in three clusters; two clusters are located in a region of the cortex dorsal to the dorsal lobe and one cluster is located in the cortex ventral to the dorsal lobe. In the cortex dorsal to the dorsal lobe, one cluster of each muscle system shares the same region. Altogether five groups of cell bodies can be distinguished. Double labeling of the motoneurons and presumptive mechanosensory primary antennal afferents with fluorescent dyes has shown that there is an extensive overlap of axonal projection of antennal mechanosensory afferents with dendritic fields of antennal motoneurons. © 1995 Wiley‐Liss, Inc.