bluuebunny/crossref_metadata_2025 huggingface dataset:
Heterogeneity of layer II neurons in human entorhinal cortex
Authors: Beall Melissa J. , Lewis David A.
Published: January 2005

Abnormalities in the layer II neurons of human entorhinal cortex have been implicated in the pathophysiology of Alzheimer's disease and schizophrenia. The reported abnormalities are not homogeneously distributed throughout the entorhinal cortex, suggesting that layer II of entorhinal cortex may contain different subpopulations of neurons, each with a different susceptibility to pathological mechanisms. In order to investigate the possible heterogeneity of neurons in layer II of human entorhinal cortex, we first identified distinct subdivisions of human entorhinal cortex by adapting the cytoarchitectonic criteria for subdivisions of monkey entorhinal cortex described by Amaral et al. (J Comp Neurol 264:326, 1987). The morphology and regional distribution of distinct subpopulations of human layer II neurons were determined through the use of immunohistochemical techniques. Multipolar, stellate, and modified pyramidal neurons in the characteristic cell clusters or islands of layer II were immunoreactive for nonphosphorylated neurofilament proteins. The intensity of immunoreactivity for the nonphosphorylated neurofilament proteins gradually increased along the rostrocaudal axis of entorhinal cortex and was primarily due to a similar gradient in the density of labeled neurons per island. The calcium‐binding protein calbindin D‐28K was found in both pyramidal and nonpyramidal neurons in layers II and superficial III. The distribution of calbindin‐immunoreactive neurons also depended upon the region of entorhinal cortex. In rostral entorhinal cortex, labeled neurons were scattered throughout the superficial layers, whereas in caudal entorhinal cortex, distinctive patches of small calbindin‐immunoreactive neurons were found among the layer II islands. Another calcium‐binding protein, parvalbumin, was present in nonpyramidal neurons in layers II and III that were distinct from those containing calbindin. The regional distribution of parvalbumin‐positive neurons was very similar to that of the neurofilament immunoreactive neurons; in rostral entorhinal cortex very few parvalbumin‐labeled neurons were present but their frequency gradually increased in the caudal direction. In addition, punctate parvalbumin immunoreactivity was frequently encountered in the location of the nonphosphorylated neurofilament protein‐positive layer II islands. These findings demonstrate that layer II of human entorhinal cortex contains distinct subpopulations of neurons, that the relative density of each subpopulation differs across cytoarchitectonic regions, and that the patterns of distribution of these subpopulations are in some cases similar and in other cases complementary. This heterogeneity in the organization of layer II of human entorhinal cortex has important implications for the study of some neuropsychiatric disorders. © 1992 Wiley‐Liss, Inc.
Two classes of vesicles are present and change in relative proportion during post‐embryonic development of rectifying electrical synapses in the crayfish
Authors: Leitch B. , Heitler W. J. , Pitman R. M. , Cobb J. L. S.
Published: January 2005

The size and shape of vesicles at junctional appositions of the rectifying electrical synapses between the medial giant fibre and motor giant neurone of the crayfish were measured during the first 2 months after hatching. Summed data over this period reveal a bimodal distribution in vesicle diameter.

From the day of hatching until about 7 days of age, small vesicles (circa 25 nm diameter) predominate. From day 7 onwards, larger vesicles (circa 55 nm diameter) occur in increasing numbers, until at day 56 they constitute about 85% of the population at any one junctional apposition. At intermediate ages (day 7–28) individual junctional appositions may show the same bimodal distribution in size as does the age group as a whole, indicating that large and small vesicles occur together at the same junction. The larger vesicles are mainly circular, while the small vesicles are pleomorphic, with shapes ranging from almost circular down to a shape factor of about 0.6. © 1992 Wiley‐Liss, Inc.
Connections from the lateral vestibular nucleus to the upper cervical spinal cord of the cat: A study with the anterograde tracer PHA‐L
Authors: Rose P. K. , Wainwright K. , Neuber‐Hess M.
Published: January 2005

The projections of neurons in the lateral vestibular nucleus (LVN) to the upper cervical spinal cord of the cat were investigated by means of the anterograde tracer Phaseolus vulgaris leucoagglutinin (PHA‐L). At the junction of C1 and C2, axons were distributed bilaterally in the ventromedial funiculi, and ipsilaterally in the ventrolateral and lateral funiculi. The majority of boutons were found ipsilateral to the injection sites and most of these boutons were found at the base of the ventral horn and throughout the medial two‐thirds of lamina VIII. A more modest termination zone was found along the ventral border of lamina VII and a small number of boutons were scattered in the dorsal horn. Contralateral termination zones were similar to the ipsilateral projections.

There were significant changes in the distribution of vestibulospinal axons and density of boutons at the junction of C3 and C4. At this level, most vestibulospinal axons travelled ipsilaterally and were found along the medial border of the ventromedial funiculus and the ventral margin of the ventrolateral funiculus. The overall distribution of boutons near the border of C3 and C4 was similar to the pattern seen at the junction of C1 and C2. However, bouton density fell by a factor of three. Large zones of the grey matter were devoid of boutons in individual experiments.

These results demonstrate that the projections of neurons in the LVN to the upper cervical spinal cord are densest in the regions containing motoneurons supplying suboccipital muscles. This result suggests that monosynaptic connections to those motoneurons may be an important part of the neural circuitry responsible for vestibulocollic reflexes. However, the large number of boutons found in regions dorsal to motoneuron nuclei in all upper cervical segments indicates that the primary path from vestibulospinal axons to neck motoneurons may be indirect and involve relays via spinal interneurons. © 1992 Wiley‐Liss, Inc.
Sex differences in densities of dopaminergic fibers and GABAergic neurons in the prenatal rat striatum
Authors: Ovtscharoff W. , Eusterschulte B. , Zienecker R. , Reisert I. , Pilgrim C.
Published: January 2005

On the basis of observations on dopaminergic neurons developing in gender‐specific cultures of embryonic rat mesencephalon, we have hypothesized that as yet unknown sexual dimorphisms might be found in projection areas of dopaminergic neurons. Therefore we searched for possible sex differences in the striatum during the period when massive ingrowth of mesencephalic afferents occurs and the striatal gamma‐aminobutyric acid (GABA)ergic neurons differentiate.

Male and female rats of embryonic days (E) 16, 18, 20, and 21 were fixed by perfusion through the heart. Vibratome sections were cut from the striatal anlage and sequentially immuno stained for GABA by the immunogold‐silver technique and tyrosine hydroxylase (TH) by the avidin‐biotin‐peroxidase method. Ultrathin sections were scanned for numbers of GABA‐ and TH‐immunoreactive (IR) elements.

Densities of TH‐IR axons as well as of GABA‐IR cell body profiles progressed with time. Contacts between TH‐IR axons and GABA‐IR and immunonegative cells were observed as early as E‐16, increasing in numbers toward later stages. Throughout prenatal development, female striata displayed higher densities of both TH‐TR axon and GABA‐TR cell body profiles than male ones.

This is the first report of a distinct anatomical sex difference regarding two major components of a key center of motor control. Prenatal sexual differentiation of the striatum may lead to a sexually dimorphic extrapyramidal circuitry, the existence of which, in the adult, is suggested by experimental and clinical data. © 1992 Wiley‐Liss, Inc.
Expression of cholecystokinin and somatostatin genes in the human thalamus
Authors: Burgunder J.‐M. , Young W. S.
Published: January 2005

The cholecystokinin (CCK) gene is expressed in thalamocortical and thalamostriatal neurons of the rat. In the cat, this peptide is found in some intralaminar and midline nuclei, whereas somatostatin (SRIF) is expressed in the reticular nucleus of the cat but not in rat. Since the putative neurotransmitters used by thalamic neurons are still incompletely known, especially in humans, we investigated the expression of the CCK and SRIF genes in the human thalamus by using hybridization histochemistry.

CCK mRNA was found in many neurons, located in several nuclei of the dorsal thalamus. They were especially numerous and widespread in the nuclei associated with the internal thalamic lamina. They formed a continuum in the basal medial thalamus, from the central‐medial nucleus, through the centre median/parafascicular complex to the limitans and suprageniculate nuclei. In addition, neurons with CCK mRNA were found medially and laterally to the mediodorsal nucleus, in the midline and intralaminar nuclei. Only rare neurons with CCK mRNA were found in other nuclei (e.g., in the ventral group of nuclei). SRIF mRNA was found in many neurons of the reticular nucleus, but not in the dorsal thalamus.

Neurochemical features of the human thalamus, for the genes studied here, resemble those found in the cat. SRIF may play a role in modulating dorsal thalamic impulses, which may be conveyed through CCK innervation to the striatum and, partly, to the cortex.
Immunohistochemical localization of ryanodine binding proteins in the central nervous system of gymnotiform fish
Authors: Zupanc Günther K. H. , Airey Judith A. , Maler Leonard , Sutko John L. , Ellisman Mark H.
Published: January 2005

The ryanodine receptor, an integral membrane protein of the sarcoplasmic reticulum in muscle, embodies a high conductance channel permeable to calcium ions. Recent studies have identified ryanodine‐binding proteins in avian and mammalian central nervous systems. These neuronal ryanodine receptors appear to function as Ca2− channels which may gate the release of Ca2+ from caffeine‐sensitive intracellular pools in neurons.

In the present investigation, we employed monoclonal antibodies against ryanodine‐binding proteins of avian muscle cells to the brain of weakly electric gymnotiform fish. Immunoprecipitation and Western blot analysis revealed two isoforms in the fish brain, with molecular weights comparable to those of avian and fish muscle ryanodine‐binding proteins. By employing immunohistochemical techniques, we mapped these proteins in fish brain.

Ryanodine receptor‐like immunoreactivity was found in nerve cell bodies as well as dendrites and axonal processes. The ryanodine‐binding protein is distributed throughout the neuraxis in specific cell types of the gymnotiform brain. In the telencephalon, immunoreactive cells were found in the glomerular layer of the olfactory bulb, in the supracommissural subdivision of the ventral telencephalon, and in the intermediate rostral subdivision of the ventral telencephalon. In the diencephalon, immunoreactive cells or fibers were observed in the nucleus prethalamicus and the habenula, within the nucleus at the base of the optic tract and the adjacent dorsal tegmental nucleus, the pretectal nuclei A and B, and the nucleus electrosensorius. In addition, immunopositive cells were seen in several nuclei of the hypothalamus, with the inferior and lateral subdivision of the nucleus recessus lateralis displaying the highest concentration of neurons. In the mesencephalon, the optic tectum contained the greatest number of immunopositive cells. In the rhombencephalon, labelling was seen in the nucleus of the lateral valvula, central gray, lateral tegmental nucleus, in boundary cells of the nucleus praeminentialis, efferent octavolateral nucleus, an area adjacent to the medial edge of the lateral reticular nucleus, nucleus medialis, and electrosensory lateral line lobe. As in avian brain, cerebellar Purkinje cells were positive for ryanodine‐binding protein, although only subsets of Purkinje cells were labelled. © 1992 Wiley‐Liss, Inc.
Transient expression of GABA immunoreactivity in the developing rat spinal cord
Authors: Ma Wu , Behar Toby , Barker Jeffery L.
Published: January 2005

The development of GABAergic neurons in the spinal cord of the rat has been investigated by immunocytochemical staining of frozen sections with anti‐γ‐aminobutyric acid (GABA) antiserum. In the cervical cord, GABA‐immunoreactive fibers first appeared at embryonic day (E) 13 in the presumptive white matter within the ventral commissure, ventral funiculus, and dorsal root entrance zone, and in the ventral roots. There were no GABA‐immunoreactive cell bodies detected at this age. By E14, motoneurons, the earliest generated spinal cells, were the first cell population to become GABA‐immunoreactive at the cell body level. Thereafter, GABA‐immunoreactive neurons increased progressively in number and extended from ventral to dorsal regions. GABA‐immunoreactive relay neurons within lamina I of the dorsal horn were initially detected at E17. Interneurons in the substantia gelatinosa, the latest generated cells in the spinal cord, were also the last to express the GABA immunoreactivity at E18. Immunoreactive neurons peaked in intensity and extent at E18 and 19. GABA immunoreactivity was only detectable in neurons within the intermediate and marginal zones 1–3 days after they withdrew from the cell cycle. This contrasts to glutamate decarboxylase immunoreactivity, which is detected in precursor cells in the ventricular zone prior to, or during, withdrawal from the cell cycle. Toward the end of gestation, GABA immunoreactivity declined in intensity and extent. This regression began in the ventral horn of the cervical region and ended in the dorsal horn of the lumbosacral region. During the first week after birth, immunoreactivity in motoneurons and in many other neurons within the ventral horn, intermediate gray, and deeper layers of the dorsal horn disappeared, and only in those neurons predominantly within the superficial layers of the dorsal horn did it persist into adulthood. Thus, the expression and regression of GABA immunoreactivity in the spinal cord followed ventral‐to‐dorsal, rostral‐to‐caudal, and medial‐to‐lateral gradients. These observations indicate that the majority of embryonic spinal neurons pass through a stage of transient expression of GABA immunoreactivity. The functional significance of this transient expression is unknown, but it coincides with the period of intense neurite growth of motoneurons, sensory neurons, and interneurons, and of neuromuscular junction formation, suggesting that the transient presence of GABA may play an important role in the differentiation of sensorimotor neuronal circuits. © 1992 Wiley‐Liss, Inc.
Cytoarchitecture and visual field representation in area 17 of the tammar wallaby (macropus eugenii)
Authors: Vidyasagar T. R. , Wye‐Dvorak J. , Henry G. H. , Mark R. F.
Published: January 2005

Tritiated proline was injected into one eye in the tammar wallaby and transported label was studied in the cortex after transneuronal passage through the lateral geniculate nucleus. The autoradiographic label and cytoarchitecture were used to anatomically demarcate the borders of area 17. Electrophysiological recordings from single units were done to obtain a retinotopic map of area 17. Single units in area 17 were found to have orientation sensitivity comparable‐to those seen in placental mammals such as cat and monkey. They could also be classified as simple, complex, and hypercomplex cells. Changes in the cortical areal magnification factor with eccentricity were found to match the drop off in retinal ganglion cell density only along the vertical meridian representation. Along the horizontal meridian, the cortical magnification falls off significantly with eccentricity, whereas the ganglion cell density shows only a mild reduction. Thus central vision, especially the binocular segment, is heavily represented at the cost of the periphery. © 1992 Wiley‐Liss, Inc.
Pattern of substance P‐ and cholecystokinin‐like immunoreactivity during regeneration of the neural complex in the ascidian Ciona intestinalis
Authors: Bollner Tomas , Beesley Philip W. , Thorndyke Michael C.
Published: January 2005

The neural ganglion of ascidians exhibits a novel and rapid pattern of regeneration whereby within approximately 28–35 days of total ablation an entirely new neural complex is formed. In normal adults, neuronal cell bodies expressing substance P‐ (SP‐Li), neurokinin A‐(NKA‐Li), CCK/gastrin‐ (CCK‐Li), and insulin‐like immunoreactivity exhibit a clearly defined pattern of localization in the cortical rind of the ganglion with characteristic long processes arising from the perikarya running throughout the neuropile. CCK‐Li cell bodies are particularly concentrated close to the points of exit of the main nerve trunks. We have used antisera raised against these peptides to monitor the process of regeneration up to postoperative (pa) day 35. Only SP and CGK antisera produced positive staining in the regenerating tissue. Immunoreactive cell bodies first appear following 14 days pa. At this time CCK‐Li neurons are more abundant than SP‐Li neurons and in contrast to the pattern found in the normal adult ganglion, immunoreactive cell bodies are located both peripherally and centrally in the core of the ganglion and processes were rarely seen. Later stages exhibited an increasing number of SP‐Li neurons and at 35 days pa SP‐Li cell bodies clearly predominate. CCK‐Li neurons typically become clustered close to the points of emergence of the anterior nerve roots. The early expression of CCK‐Li and SP‐Li molecules during regeneration is considered in terms of their potential role in development and cell proliferation in the newly forming ganglion. © 1992 Wiley‐Liss, Inc.
Distribution of nerve growth factor‐like immunoreactive neurons in the adult rat brain following colchicine treatment
Authors: Conner J. M. , Varon S.
Published: January 2005

Using immunohistochemical techniques, we have previously localized nerve growth factor (NGF)‐like immunoreactivity in the normal adult rat centralnervous system (CNS) exclusively in the hippocampal mossy fiber region andwithin basal forebrain cholinergic neurons—a cell population believed to be primary NGF consumers within the CNS. In the present investigation, we have attempted to identify potential producers of NGF by pretreating animals with colchicine. Such a treatment would be expected to block microtubule‐assisted neuritic transport mechanisms, thus preventing the accumulation of antigens normally obtained by retrograde transport and forcingthe accumulation of cell products normally exported anterogradely. Forty‐eight hours after colchicine administration within their innervation territories, basal forebrain cholinergic neurons showed a marked loss of NGF‐like immunoreactivity. Conversely, following colchicine treatment, many new populations of NGF‐like immunoreactive cells were detected, several of which have been previously observed with in situ hybridization techniques for NGF mRNA. Many NGF‐like immunoreactive populations, however, were not previously recognized by in situ hybridization methods, including cells of the striatum, reticular thalamic nucleus, paraventricular hypothalamic nucleus, supraoptic nucleus, lateral and medial septum, substantia innominata, and nucleus basalis. Furthermore, evidence is provided that colchicine‐blocked, NGF‐like immunoreactive neurons within the basal forebrain are not cholinergic, thus reinforcing the hypothesis that trophic support for these NGF‐dependent neurons may be derived from distant and local sources. The distinctive distribution of NGF‐like immunoreactive cells observed in this study strongly correlates with the reported distribution of NGF mRNA in CNS neurons, thus suggesting that our antibodies are uniquely recognizing NGF and not other related neurotrophins. © 1992 Wiley‐Liss, Inc.
Growth and regression of thalamic efferents in the song‐control system of male zebra finches
Authors: Johnson Frank , Bottjer Sarah W.
Published: January 2005

A serial forebrain pathway in the songbird brain plays a critical role in vocal learning; Area X of the parolfactory lobe (X) projects to the medial portion of the dorsolateral nucleus of the anterior thalamus (DLM), which in turn projects to the lateral magnocellular nucleus of the anterior neostriatum (IMAN). Lesions of this pathway in juvenile birds disrupt vocal development, whereas identical lesions in adult birds do not influence the production of already learned song. During the course of vocal learning, IMAN undergoes a phase of massive neuronal loss, whereas the neuronal population of X more than doubles. In the present study, the development of neuron number in DLM was analyzed and found not to change during the course of vocal learning. Anterograde DiI labeling of DLM efferent fibers was then used to analyze the morphological development of this projection in relation to both the loss of neurons from IMAN and the loss of the ability of X‐DLM‐IMAN lesions to influence vocal production. We found that DLM axons arrive within IMAN by 15 days of age, prior to both the loss of neurons from IMAN and the onset of vocal production. The volume of anterograde DiI label over IMAN did not change between 15 and 20 days of age, but this volume more than doubled between 20 and 35 days of age. During this phase of exuberant growth, anterograde label matched the dorsal border of IMAN but extended beyond all other borders of IMAN into a surrounding “shell” of parvicellular neurons. By adulthood, the volume of both IMAN and anterograde DiI label declined substantially, but anterograde label continued to fill a parvicellular region of neostriatum surrounding all but the dorsal border of IMAN. Because DLM neuron number is stable during vocal development, these changes must reflect the growth and regression of some aspect(s) of DLM axonal morphology. Rearrangement of DLM axonal arborization may therefore be an important factor in the functional development of the X‐DLM‐IMAN pathway. © 1982 Wiley‐Liss, Inc. © 1992 Wiley‐Liss, Inc.
Entorhinal cortex of the human, monkey, and rat: Metabolic map as revealed by cytochrome oxidase
Authors: Hevner Robert F. , Wong‐Riley Margaret T.
Published: January 2005

The entorhinal cortex (EC) is a medial temporal lobe area involved in memory consolidation. Results from previous studies suggest that the upper layers of the EC may be organized into anatomical‐neurochemical modules associated with pathways through the neuron clusters in layers II and III. To study metabolic patterns in the EC and to look for correlates of the proposed modules, we examined the distribution of cytochrome oxidase (CO) in the human, monkey, and rat EC. CO is a mitochondrial enzyme that has been used to study modules in other cortical areas.

In all three species, the neuron clusters in layers II‐III were darkly CO‐reactive, whereas most of the neuropil between clusters was lightly or moderately CO‐reactive. However, some neuropil regions directly adjacent to the neuron clusters were also darkly CO‐reactive, especially in the human; these neuropil areas included portions of layers I and II. In tangential sections through layers I‐II, the areas of dark staining formed a consistent pattern, comprised of partially interconnected islands and stripes associated with the neuron clusters. In the EC from one human hemisphere, ∼200–250 CO‐reactive layer II islands were present. EC layers other than I‐III also showed characteristic CO staining intensities, but no evidence of modularity.

Our results indicate that CO staining labels distinct compartments related to the neuron clusters in the upper EC layers. We propose that these compartments may represent modules for cortical processing, analogous to the CO‐labeled modules in some other areas of cortex. © 1982 Wiley‐Liss, Inc. © 1992 Wiley‐Liss, Inc.
Development of GABA‐immunoreactivity in the neocortex of the mouse
Authors: Del Rio Jose A. , Soriano Eduardo , Ferrer Isidro
Published: January 2005

The prenatal and postanatal development of GABAergic elements in the neocortex of the mouse was analyzed by GABA‐immunocytochemistry. Radial distribution of cells and laminar numerical densities were calculated at each developmental stage to substantiate qualitative observations. The first immunoreactive neurons were observed in the cortical anlage at embryonic day 12‐embryonic day 13 (E12–E13) in the primitive plexiform layer. At following prenatal stages (E14–E19), most GABA‐positive neurons were present in the marginal zone, subplate, and subventricular zone. GABA‐immunoreactivity in the cortical plate appeared early (E14), although the complete maturation of its derivatives was achieved postnatally. At prenatal stages we noted a well‐developed system of immunopositive fibers in the subplate. As indicated by the direction of growth cones, most of these fibers had an extracortical origin and invaded the cortex laterally through the internal capsule and striatum. In rostral and middle telencephalic levels, fibers originating in the septal region contributed to the cingulate bundle. Presumably corticofugal fibers and callosal axons were also noticed. At postnatal stages the maturation of GABA‐immunoreactivity appeared to be a complex, long‐lasting process, in which the adult pattern was produced at the same time as the appearance of certain regressive phenomena. Thus, between postnatal day 0 and postnatal day 8 (P0–P8), GABA‐positive populations disappeared from the subventricular zone, marginal zone and to a lesser extent from the subplate. At the same ages we noticed the presence of morphologically abnormal, GABA‐immunoreactive neurons in the subventricular zone and subplate which are interpreted as correlates of neuronal degeneration. Most GABA‐positive subplate fibers also disappeared whereas GABA‐immunoreactive axons were seen in the cingulate bundle until the adult stage. In the derivatives of the cortical plate, the maturation of GABA‐immunoreactive elements progressed according to the “inside‐out” gradient of cortical development, with the important exception of layer IV, which was the last layer to exhibit an adult‐like appearance. Within each layer deriving from the cortical plate (layers VIa to II–III), GABA‐immunoreactivity showed a protracted maturation in which the first GABA‐positive cells were detected a few days after cell birth but substantial numbers of neurons began to express GABA considerably later. The later phase occurred concurrently with the maturation of GABA‐positive axonal plexuses. These results suggest that different GABA‐positive populations show different developmental regulation of GABA expression during cortical ontogenesis. © 1992 Wiley‐Liss, Inc.
Central projections of auditory nerve fibers of differing spontaneous rate, II: Posteroventral and dorsal cochlear nuclei
Authors: Liberman M. Charles
Published: January 2005

Response properties of auditory nerve fibers (ANFs), including threshold sensitivity, vary systematically with spontaneous discharge rate (SR) (Liberman, M.C.: J. Acoust. Soc Amer. 63:442–455, 1978). Thus, an understanding of the mechanisms underlying signal transformation in the cochlear nucleus (CN) must include a description of any SR‐based difference in ANF projections. This study is the second of a pair describing the CN projections of intracellularly labeled ANFs of known SR, the first of which summarized projection to the anteroventral CN (Liberman, M.C.: J. Comp. Neurol. 313:240–258, (1991). For each swelling from each labeled fiber, the position (within CN subdivisions), the size, and the type of cell contacted (if determinable) was noted: roughly one in four labeled swellings appeared in intimate contact with the soma or proximal dendrites of a CN cell. In all such cases, cell size and swelling size were measured. As reported for auteroventral cochlear nucleus, the ANF innervation of the small‐cell regions of posteroventral CN (PVCN) was almost exclusively by low‐and medium‐SR fibers. Other significant SR‐based trends in ANF projections included (1) a tendency for high‐SR fibers to contact larger cells in PVCN, (2) a meager projection of low‐ and medium‐SR fibers to octopus cells, and 3) a tendency in the dorsal CN (DCN) for low‐SR terminals to end closer to the fusiform cell layer than high‐SR terminals. There were no significant SR‐based difference in ANF swelling sizes in any subdivision. A consideration of the average cell sizes, ANF swelling sizes and estimated numbers of ANFs of different CF and SR converging on each CN cell help explain some of the differences in response transformation associated with different cell types in the CN. © 1993 Wiley‐Liss, Inc.
Immunohistochemical identification of trigeminal ganglion neurons that innervate the mouse cornea: Relevance to intercellular spread of herpes simplex virus
Authors: LaVail Jennifer H. , Johnson Welkin E. , Spencer Lawrence C.
Published: January 2005

Inoculation of the scarified cornea with herpes simplex virus (type 1) leads to herpetic infection of trigeminal ganglion cells. A recent study of the susceptibility of ganglion cells revealed that there may be at least four populations of trigeminal ganglion cells that are infectable by herpes. Two classes were identified by their neuropeptide content: Substance P or calcitonin gene‐related peptide. One class was identified by its affinity for a monoclonal antibody, SSEA‐3. The fourth class was recognized by its common affinity for both the monoclonal antibody LD2 and for the lectin Bandeiraea simplicifolia isolectin. However, there has been no direct evidence of which types are infected directly as a result of retrograde transport from the corneal site and which may be infected by cell‐to‐cell spread. The aim of this study was to determine which classes of neurons, which are known to become infected with HSV after ocular inoculation, supply corneal innervation.

We have identified four classes of trigeminal ganglion neurons that supply axons to the central cornea of the mouse, on the basis of their ability to transport Fluoro‐Gold retrograde from axons in the central corneal epithelium and stroma. About 40% of the neurons that innervate the cornea contain Substance P or calcitonin gene‐related peptide; about 60% of the neurons that innervate the cornea react with the monoclonal antibody SSEA‐3. About 36% of all neurons in the whole ophthalmic division react with the LD2 or Bandeiraea simplicifolia isolectin, and Fluoro‐Gold labels only 2% of them. Thus, the population of LD2/Bandeiraea Simplicifolia Isolectin neurons that innervates the cornea represents less than 1% of the total neurons in the ophthalmic division, although it constitutes about 20% of the infected cells in that division at three days after viral inoculation. We conclude that most of the LD2/Bandeiraea simplicifolia isolectin‐positive ganglion cells that are infected with herpes at 3 days are infected as a result of HSV spread from nearby cells in the ganglion or proximal trigeminal root. Neurons labeled with antibodies to Substance P, calcitonin gene‐related peptide, or α‐SSEA‐3 that are primarily infected may be sources of the cell‐to‐cell spread of virus. © 1993 Wiley‐Liss, Inc.
Development of the dorsal root ganglion in a teleost, Oreochromis mossambicus (Peters)
Authors: Laudel Timothy P. , Lim Tit‐Meng
Published: January 2005

The precursor crest cells of the spinal dorsal root ganglia (DRG) in the tilapia, Oreochromis mossambicus, were analysed by HNK‐1 antibody staining, scanning electron microscopy, and DiI labeling techniques. The ontogeny of the DRG was followed in the embryos and young fry of the fish. Neural crest cells which contribute to the formation of the DRG were observed to commence their migration in the trunk region after 40 hours postfertilization. They do not penetrate the somites but travel through the space between the neural tube and the somite. Crest cells destined to become the DRG accumulate at the midsomitic region where the ventral root exits. At 50 to 80 hours postfertilization, they differentiate and become bipolar sensory cells. The DRG continues to grow and develop right through hatching at 115 hours. During the early larval stages, crest cells accumulate around the ventral root and the DRG eventually fuses with the motor root, giving rise to a situation in which the DRG contains not only the sensory cells but also motor fibres. The mixed nature of the DRG was confirmed by HRP retrograde labeling. We believe that this is the first report in describing the formation of the DRG in a teleost. © 1993 Wiley‐Liss, Inc.
Effect of wound healing and tissue transplantation on the navigation of axons in organ‐cultured embryonic chick eyes
Authors: Halfter Willi
Published: January 2005

Wound closure and repair of embryonic neuroepithelium were studied in organ‐cultured embryonic retinae. Eyes from 3 to 4‐day‐old embryos were cultured after removing pieces of retinal tissue. During the subsequent 24 hours of incubation, the 150 to 200 μm wide holes in the retina closed completely. Histological studies showed that the wound closure was not accomplished by cell migration or cell proliferation, but by an approximation of the wound edges mediated by extracellular matrix fibrils of the vitreous body. The wound contraction facilitated the integration of transplants into the retinal neuroepithelium with a perfect alignment of the implants with the host at the vitreal surface. Within 24 hours, a continuous inner limiting membrane between transplant and host retina was established. The effect of wound healing and tissue transplantation on the navigation of optic axons in the retina was investigated. The wound contraction in the retina caused the optic axons near the lesion site to grow to the wound center, where the axons traversed the retina and formed a neuroma at the ventricular side, resembling the organization of axons at the optic disc. In the transplantation paradigm, axons from the host retina migrated into the transplant and vice versa. However, due to the wound contraction around the transplant, most axons grew into the interface between the transplant and host tissue. 1993 Wiley‐Liss, Inc.
Fine structure of calcitonin gene‐related peptide immunoreactive synaptic contacts in the thalamus of the rat
Authors: Williamson Andrew M. , Ralston Henry J.
Published: January 2005

Recent studies have shown a prominent calcitonin gene‐related peptide immunoreactive (CGRP‐ir) pathway extending from the external medial and external lateral para‐brachial nuclei to the area surrounding and including the gustatory nuclei in the thalamus, and the cortex and amygdala. The function of the CGRP‐ir pathway is not completely understood, but may be involved with the processing of both nociceptive and gustatory information in the thalamus.

The purpose of this study was to characterize the nature of the CGRP‐ir synaptic contacts in the gustatory nucleus. Electron microscopic examination of CGRP‐ir synaptic contacts revealed two classes of CGRP‐ir terminals. One class, which was large, formed asymmetric synaptic contacts on dendritic appendages, had many small, round synaptic vesicles, and heavy patches of reaction product which obscured any underlying organelles. Since similar terminals in unstained tissue contained large numbers of dense‐cored vesicles, it was concluded that CGRP‐ir was contained predominantly in dense‐cored vesicles.

A second class of CGRP‐ir terminals was smaller and made either asymmetric or symmetric synaptic contacts. Both symmetric and asymmetric small terminals contained small, round synaptic vesicles and fewer patches of dense reaction product. Several of the CGRP‐ir terminals making symmetric contacts also contained pleomorphic vesicles. There were very few contacts on cell bodies. There were no contacts on other CGRP‐ir elements, somal or dendritic, or on axon terminals. None of the CGRP‐ir terminal elements were postsynaptic to unlabeled terminals. Axons containing CGRP‐ir were primarily unmyelinated, but a few myelinated axons were also seen. © 1993 Wiley‐Liss, Inc.
Localisation of mRNA encoding the protein precursor of galanin in the monkey hypothalamus and basal forebrain
Authors: Evans Helen F. , Huntley George W. , Morrison John H. , Shine John
Published: January 2005

The hypothalamic and basal forebrain sites of synthesis of preprogalanin mRNA were identified in three adult monkeys (Macaca fascicularis) by in situ hybridisation performed with a radiolabelled cRNA probe transcribed from human preprogalanin cDNA. With stringent hybridisation conditions, the cRNA probe was hybridised to free‐floating sections containing structures contiguous with the rostral hypothalamus through to the caudal limit of the hypothalamus as defined by the mammillary bodies. Specific hybridisation of the preprogalanin cRNA probe occurred throughout the hypothalamus but was particularly intense in the arcuate, paraventricular (parvicellular and magnocellular portions), and dorsomedial nuclei. Moderate hybridisation was found in the periventricular nucleus and scattered hybridisation in the medial preoptic nucleus. The medial preoptic area and the anterior and lateral hypothalmic areas showed moderate to intense hybridisation in scattered cells. A few cells in the tuberal portion and dorsal cap of the anterior portion of the supraoptic nucleus were labelled. Isolated cells were also labelled in the zona incerta. There was little labelling in the dorsal hypothalamic area but moderate labelling in the posterior hypothalamic area. Structures contiguous with the rostral hypothalamus including the diagonal band of Broca, bed nucleus of stria terminalis, substantia innominata, and basal nucleus of Meynert showed intense hybridisation. These data indicate a widespread distribution of preprogalanin mRNA in the monkey hypothalamus. A comparison with the previously reported distribution of preprogalanin mRNA in the rat, as well as with the distribution of galanin‐like immunoreactivity in the rat and human, suggests some important species differences. Of particular interest were differences in the supraoptic, suprachiasmatic, and dorsomedial nuclei. The intense hybridisation throughout the paraventricular nucleus and in the rostral arcuate nucleus suggests that galanin may play a role in the regulation of both posterior and anterior pituitary function. © 1993 Wiley‐Liss, Inc.
Local circuit neurons of developing and mature macaque prefrontal cortex: Golgi and immunocytochemical characteristics
Authors: Lund Jennifer S. , Lewis David A.
Published: January 2005

A study has been made of the nonpyramidal, local circuit neurons in developing and mature macaque monkey prefrontal cortex with Golgi and immunocytochemical techniques. The area chosen for study is located between the cingulate gyrus and the ventral bank of the principal sulcus, and contains areas 9 and 46 as described by Walker (J. Comp. Neurol. 73:59–86, '40). In Golgi studies, the unique axonal features of impregnated neurons made possible the identification of thirteen separate classes of local circuit neurons. Five of these cell types, in their general characteristics, resembled classes identified in human prefrontal cortex, as well as in other cortical areas of macaque monkeys and other species. Measurements of the scale of axon arbors and dendritic fields of the Golgi‐stained local circuit neurons also suggested particular spatial relationships of certain classes to the scale of intrinsic lattice connections made by the axons of pyramidal neurons in the same region. Similarities in morphology between cells described in human prefrontal cortex and neuron varieties described in this study indicate that this region of monkey prefrontal cortex may serve as a useful model for neuron populations in human prefrontal cortex.

Sufficient morphological detail was present in immunocytochemical studies to suggest one or more identifying biochemical characteristics for seven of the thirteen classes of local circuit neurons. The calcium binding proteins, parvalbumin, calbindin D‐28K, and calretinin, were found in chandelier and wide arbor neurons, neurogliaform cells, and double bouquet neurons, respectively. In addition, cholecystokinin immunoreactivity was present in medium arbor neurons and in narrow arbor cells connecting layers 2 and 4. Somatostatin 281–12 immunoreactivity was detected in beaded axon neurons in layers 5 and 6. This biochemical characterization of local circuit neurons, although incomplete, confirms the separate identity of at least some of the varieties distinguished by Golgi morphology, and allows a start to be made on studies examining changes in their functional state. The general inhibitory nature of these interneurons suggests that they are likely to play a crucial role in determining patterns of neural activation in the prefrontal cortex. © 1993 Wiley‐Liss, Inc.
A motor neuron‐specific epitope and the low‐affinity nerve growth factor receptor display reciprocal patterns of during development, axotomy, and regeneration
Authors: Chiu Arlene Y. , Chen Edmond W. , Loera Sofia
Published: January 2005

Somatic motor neurons begin to express the transmitter synthesizing enzyme, choline acetyltransferase (ChAT) and the low‐affinity nerve growth factor receptor (NGFR) during embryonic development. However, as motor neurons mature in postnatal life, they lose immunoreactivity for NGFR and acquire a motor neuron‐specific epitope that is recognized by the monoclonal antibody, MO‐1. The present study was undertaken to examine the effect of nerve injury in adult rats on these three developmentally regulated markers in two populations of somatic motor neurons.

Unilateral transection, ligation, or crushing of the sciatic nerve resulted in a loss of MO‐1 binding and a concomitant rise in immunoreactivity for NGFR within axotomized motor neurons in lumbar levels of the spinal cord. These changes, detectable within 5 days following nerve injury, are reversed with reinnervation, but persist if reinnervation is prevented by chronic axotomy. Thus, regulation of the expression of NGFR and the MO‐1 epitope appears to be critically dependent upon interactions between motor neurons and target muscles. These observations are also consistent with the idea that during regeneration, neurons may revert to a developmentally immature state; in motor neurons, this state is characterized by the presence of NGFRs and the absence of the MO‐1 epitope.

Transection of the hypoglossal nerve, a purely motor nerve, resulted in a similar loss of MO‐1 binding and a selective rise in NGFR immunoreactivity in neurons within the ipsilateral hypoglossal motor nucleus. In addition immunoreactivity for ChAT was also lost in axotomized hypoglossal motor neurons. In contrast, injury to the sciatic nerve, which bears both sensory and motor axons, did not result in any detectable change in ChAT immunoreactivity in spinal motor neurons. © 1993 Wiley‐Liss, Inc.
Multimorphic growth cones in the embryonic medicinal leech: Relationship between shape changes and outgrowth transitions
Authors: Kopp Diane M. , Jellies John
Published: January 2005

Comparative studies of growth cone morphology may provide insight into the mechanisms underlying motility and navigation in vivo. Here we analyzed the morphology of a unique set of growth cones in the embryonic medicinal leech, Hirudo medicinalis. The comb or C‐cell is a transient cell found as a bilateral pair in each midbody segment. Early in development, from embryonic day (E)7 to E11, each C‐cell adds and orients about 70 parallel growth cones that remain relatively nonmotile until E12 when rapid process outgrowth is initiated. Individual C‐cells from E10 to E14 were injected with Lucifer yellow and growth cones were traced with a camera lucida. Growth cone morphology was quantified from the drawings. Lamellar regions increased in area with age and change in extension rate. Young, relatively nonmotile growth cones had numerous short filopodia in many orientations, while at highly motile stages filopodial number decreased, length increased, and orientation became more restricted in the direction of outgrowth. Thus, while filopodia were distributed symmetrically, such that the average filopodial angle was predictive of the direction of outgrowth at all stages, younger (relatively nonmotile) growth cones project more filopodia in many directions than do older more motile growth cones. These results suggest that: (1) alterations in morphology may reflect developmentally regulated changes in extension and the local environment, (2) these growth cones maintain a large area for environmental sampling as they increase extension rate, even as filopodia become more restricted in orientation, and (3) C‐cell growth cones might progressively alter their affinity for local cellular cues as they initiate rapid and directed outgrowth. The C‐cell of embryonic leech may provide a relatively simple system in which to test these ideas experimentally. © 1993 Wiley‐Liss, Inc.
The projections of intracellularly labeled auditory nerve fibers to the dorsal cochlear nucleus of cats
Authors: Ryugo David K. , May Sarah K.
Published: January 2005

The cochlear nucleus receives incoming auditory nerve discharges, preserves or transforms the signals, and distributes outgoing activity to higher centers. The organization of auditory nerve input to the cochlear nucleus will heavily influence the mechanisms by which acoustic information is processed. In order to study structure‐function relationships between auditory nerve and cochlear nucleus, the axonal arborizations of type I spiral ganglion cells were labeled with intracellular injections of horseradish peroxidase after first being electrophysiologically characterized by recording with a micropipette inserted into the axon. For each auditory nerve fiber, spontaneous discharge rate (SR) and a frequency tuning curve were determined. The tuning curve yielded the characteristic frequency (CF, that frequency to which the fiber is most sensitive) and CF threshold in dB SPL. Individual axonal arborizations including all terminal swellings were reconstructed through serial sections with the aid of a light microscope and drawing tube. On average, 13.4 ± 8.1% of the terminal swellings were found in the dorsal cochlear nucleus (DCN) and the remaining terminal swellings were located in the ventral cochlear nucleus. In the DCN, the terminal fields of auditory nerve fibers were restricted to layer III, contributed to cytoarchitectonic striations, and exhibited a systematic relationship between fiber CF and position along the strial (or long) axis of the nucleus. Computer‐aided rotations revealed that the terminal fields were anisotropic, being flattened within the trans‐strial axis. The maximal width of the terminal fields along the strial axis ranged from 31–321 μm and was inversely related to fiber CF and SR. Variation in the number of terminals or depth of the terminal field within layer III was not related to SR grouping or CF of the fiber. © 1993 Wiley‐Liss, Inc.