bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of iontophoresis of noradrenaline and stimulation of the periaqueductal gray on single‐unit activity in the rat superficial dorsal horn
Authors: Millar Julian , Williams Graham V.
Published: January 2005

Recordings were made with a new form of low‐noise carbon fibre microelectrode from 75 units in the superficial laminae of the lumbar dorsal horn of the anaesthetized rat. The response of each unit to adequate stimulation of its peripheral receptive field, to noradrenaline (NA) applied iontophoretically, and to electrical stimulation of the periaqueductal gray (PAG) was investigated. Only units that could be excited by iontophoresis of glutamate (10–100 nA) were analyzed. Recording sites in the spinal cord and stimulation sites in the brainstem were identified histologically at the end of each experiment.

Forty‐six units with low‐threshold receptive fields and small spike amplitudes were found, mainly located in laminae II and III. Both stimulation of the PAG and NA iontophoresis excited the majority (32/46) of these units. The rest were unaffected. Eight high‐threshold (HT) units were located in the region of lamina I. Twenty‐one wide‐dynamic‐range (WDR) units were found mainly in deeper laminae. Both WDR and HT units were inhibited by NA and PAG stimulation. This inhibition affected both glutamate‐evoked activity and responses to nociceptive stimuli.

We suggest that the small LT units are inhibitory interneurones of the substantia gelatinosa (SG), which act on the WDR and HT units to produce nociceptive‐specific inhibition. The inhibition can be modality‐specific without necessarily being presynaptic because of the laminar arrangement of the dorsal horn. The PAG could thus exert its known antinociceptive effects at least partly via descending noradrenergic axons that excite these SG cells.
Cellular localization of substance P‐ and neurokinin A‐encoding preprotachykinin mRna in the female rat brain
Authors: Harlan Richard E. , Garcia Meredith M. , Krause James E.
Published: January 2005

To determine the locations of neurons in the rat brain expressing substance P and neurokinin A mRNA, we performed in situ hybridization with a radiolabeled cRNA probe that was complementary to α‐, β‐, and γ‐preprotachykinin mRNA. Several types of controls indicated specificity of the labeling. Brain regions containing many labeled neurons include the anterior olfactory nucleus, layer II of the olfactory tubercle, the islands of Calleja, the nucleus accumbens, the caudate‐putamen, portions of the amygdala and hypothalamus, the medial habenular nucleus, nuclei of the pontine tegmentum, several raphe nuclei, several portions of the reticular formation, and the nucleus of the solitary tract. Less frequent labeled neurons were also found in many other regions of the brain. These results extend many previous immunocytochemical studies of the locations of neurons containing immunoreactive substance P, neurokinin A, and neuropeptide K.
Computer‐assisted three‐dimensional reconstructions of [14C]‐2‐deoxy‐D‐glucose metabolism in cat lumbosacral spinal cord following cutaneous stimulation of the hindfoot
Authors: Crockett D. P. , Smith W. K. , Proshansky E. , Kauer J. S. , Stewart W. B. , Woodward D. J. , Schlusselberg D. S. , Egger M. D.
Published: January 2005

We report on computer‐assisted three‐dimensional reconstruction of spinal cord activity associated with stimulation of the plantar cushion (PC) as revealed by [14C]‐2‐deoxy‐D‐glucose (2‐DG) serial autoradiographs. Moderate PC stimulation in cats elicits a reflex phasic plantar flexion of the toes.

Four cats were chornically spinalized at about T6 under barbiturate anesthesia. Four to 11 days later, the cats were injected (i.v.) with 2‐DG (100 μCi/kg) and the PC was electrically stimulated with needle electrodes at 2–5 times threshold for eliciting a reflex. Following stimulation, the spinal cord was processed for autoradiography. Subsequently, autoradiographs, representing approximately 8–18 mm from spinal segments L6–;S1, were digitized for computer analysis and 3‐D reconstruction.

Several strategies of analysis were employed: (1) Three‐dimensional volume images were color‐coded to represent different levels of functional activity. (2) On the reconstructed volumes, “virtual” sections were made in the horizontal, sagittal, and transverse planes to view regions of 2‐DG activity. (3) In addition, we were able to sample different regions within the grey and white matter semi‐quantitatively (i.e., pixel intensity) from section to section to reveal differences between ipsi‐ and contralateral activity, as well as possible variation between sections.

These analyses revealed 2‐DG activity associated with moderate PC stimulation, not only in the ipsilateral dorsal horn as we had previously demonstrated, but also in both the ipsilateral and contralateral ventral horns, as well as in the intermediate grey matter. The use of novel computer analysis techniques—combined with an unanesthetized preparation—enabled us to demonstrate that the increased metabolic activity in the lumbosacral spinal cord associated with PC stimulation was much more extensive than had heretofore been observed.
Organization of cholinergic synapses in the cat's dorsal lateral geniculate and perigeniculate nuclei
Authors: Raczkowski Denis , Fitzpatrick David
Published: January 2005

In the preceding article, we showed that cholinergic fibers originating from the brainstem reticular formation provide a dense innervation of the lateral geniculate nucleus. In this report we describe the ultrastructure of these fibers and their relations with other elements in the neuropil of the lateral geniculate nucleus. Cholinergic fibers were labeled with an antibody to choline acetyltransferase (ChAT), the synthesizing enzyme for acetylcholine (ACh). In the A‐laminae of the lateral geniculate nucleus, ChAT + profiles are small and contain tightly packed, mostly round vesicles. Some end in encapsulated synaptic zones where they form asymmetrical synaptic contacts with processes of both projection cells and interneurons. Others form synapses upon the shafts of dendrites. Of the four classical types of vesicle‐containing profiles identified by Guillery (Z. Zellforsch: Mikrosk. 96: 1–38, '69; Vision Res. [Suppl.] 3: 211–227, '71), ChAT + profiles most closely resemble RSD profiles (Round vesicles, Small profile, Dark mitochondria). However, as a population, ChAT + profiles can be distinguished from the unlabeled population of RSD profiles because they are larger in size, contain more mitochondria, and make synapses with smaller postsynaptic membrane specializations. Each of these differences is statistically significant and together they indicate that ChAT + profiles are a distinct morphological type of synaptic profile. ChAT + profiles in the perigeniculate nucleus resemble those found in the lateral geniculate nucleus; they also make synapses with obvious postsynaptic thickenings.
Ontogeny of catecholaminergic and cholinergic cell distributions in the cat's retina
Authors: Mitrofanis John , Maslim Juliani , Stone Jonathan
Published: January 2005

The development of catecholaminergic and cholinergic neurones in the cat's retina has been examined with antibodies against their respective ratelimiting enzymes, tyrosine hydroxylase (TH) and choline acetyl transferase (ChAT). ChAT‐immunoreactive (IR) cells were first detected at E (embryonic day) 56 with somata in the ganglion cell layer (GCL) or in the inner cytoblast layer (CBL). At P (postnatal day) 1, two faint bands of ChAT‐IR fibres were evident in an inner and outer strata of the inner plexiform layer (IPL) and by P26, the bands were similar to those in the adult. TH immunoreactivity was first detected at E59 in either darkly labelled somata in the inner CBL with processes extending toward the IPL or in lightly labelled somata also located in CBL but with no processes. At P1, most TH‐IR cells had prominently labelled dendrites and, by P8, most of the features of the adult cells were evident.

Soma size gradients among TH‐IR cells were first detected at P8, with cells in temporal retina being larger than those in nasal retina or at the area centralis. The smaller sizes of cells at the area centralis emerged after P26. The smaller sizes of ChAT‐IR somata at the area centralis, by contrast, emerged between P8 and P26.

The number of both TH‐IR and ChAT‐IR cells declined from the time they first appeared till adulthood. The decline was smaller among ChAT‐IR cells (24%) than among TH‐IR cells (68%). In distribution, the differential expansion of the retina appeared to be largely responsible for generating the final adult distribution of ChAT‐IR cells. However, during late postnatal development (P26 to adulthood), the density of ChAT‐IR cells in the periphery declined more than that of the ganglion cells, suggesting that some ChAT‐IR cells may die in the periphery during this time. Prior to P26, the changes in the distribution of TH‐IR cells were inconsistent with the pattern of retinal expansion. It is suggested that during this period, regional cell loss and cell addition may account for the changes in distribution of TH‐IR cells. Later in development (P26 to adulthood), the changes in the density of TH‐IR cells closely conformed to the differential expansion of the retina.
Monoclonal antibody markers for amphibian oligodendrocytes and neurons
Authors: Steen P. , Kalghatgi L. , Constantine‐Paton M.
Published: January 2005

Few immunocytochemical probes have been developed for cold‐blooded vertebrates, thus hampering analyses of cellular processes in these species. Those developed from mammalian and avian tissue often fail either to react or to show similar specificities in poikilotherms. Therefore, we have begun raising monoclonal antibodies (mabs) in mice against frog and tadpole brain tissue. The following analyses of two of these mabs suggest that these antibodies represent specific probes for frog axons and oligodendrocytes.

Mab Olig recognizes all the myelinated axon tracts of the mature frog brain and spinal cord, as well as the tracts of the developing tadpole CNS once they have become myelinated. Axons cut in cross section show characteristic o‐shaped staining around individual axons when processed with this antibody. Particularly easy to visualize in the tadpole are immunoreactive cell bodies and processes, seen in continuity with the myelin sheath. Occasionally, in this developing tissue, cells with highly branched processes characteristic of immature oligodendrocytes are observed. No other cells or processes within the brain or spinal cord react with this antibody.

Mab Linc stains numerous filaments in all axonal projections. Occasionally, a thin rim of filamentous staining is observed in cell somata, but many regions rich in neuronal somata or dendrites are unreactive to this antibody. This in vivo staining pattern suggests that the Linc antigen is differentially distributed within neurons and exhibits a high concentration in axons.

Linc immunoreactivity is robust in the processes of a subpopulation of dissociated tectal cells in culture. These Linc‐positive cells are characterized as neurons on morphological criteria. Also, intense Linc immunoreactivity is present in the bundles of retinal axons that extend from retinal explants. Olig immunoreactivity, however, has not been detected in tectal cultures or retinal explants.

Improved staining following Triton X‐100 treatment of tissue sections suggests that neither of the mabs recognizes lipid antigens and that both are probably localized within the cell cytoplasm. Only the Linc mab reacts on Western blots of denatured brain protein. Linc consistently recognizes two Triton X‐100‐insoluble proteins with apparent molecular weights of 56 and 58 kD.

The epitopes recognized by the Olig and Linc mabs have been surveyed in terms of their resistance to optic nerve crush and their consequent value in studies requiring such procedures. Possible homologies to known cell‐type‐specific molecules are discussed.
Structure‐Function relationships in rat brainstem subnucleus interpolaris: VII. Primary afferent central terminal arbors in adults subjected to infraorbital nerve section at birth
Authors: Renehan William E. , Rhoades Robert W. , Jacquin Mark F.
Published: January 2005

Prior studies in this series have clarified the normal organization of subnucleus interpolaris and the response of higher‐order neurons to neonatal deafferentation. The present report describes the response of individual rat trigeminal primary afferents to transection of the infraorbital (IO) nerve on the day of birth. Physiologically characterized afferents in adult animals were labeled by intraaxonal injection of horseradish peroxidase (HRP). Qualitative and quantitative examination of the interpolaris collaterals of 62 recovered neurons revealed: (1) an increase in the transverse area of vibrissa afferent terminal arbors, (2) a decrease in the number of boutons per collateral of vibrissa afferents, (3) a decrease in the bouton density of both vibrissa and guard hair primary afferents, (4) a decrease in the circularity of guard hair afferent arbors, (5) an increase in the number of collaterals given off by nociceptive fibers, and (6) abnormal primary afferent topography. The data support the hypothesis that vibrissa afferents respond to neonatal axotomy by central arbor expansion, but not by sprouting. Arbor expansion provides a morphological substrate for the abnormal histochemical staining patterns seen in animals subjected to IO damage in the early postnatal period.
Quantitative analysis of cone photoreceptor–horizontal cell connectivity patterns in the retina of a cyprinid fish: Electron microscopy of functionally identified and HRP‐labelled horizontal cells
Authors: Downing J. E. G. , Djamgoz M. B. A.
Published: January 2005

Horizontal cells generating photopic luminosity and biphasic/chromaticity‐type S‐potentials were identified and intracellularly labelled with horseradish peroxidase in the retina of the roach. The synaptic connectivity patterns of the horizontal cell dendrites within pedicles of different spectral types of cone were then quantitatively studied by electron microscopy. Luminositytype responses were generated by H1‐like horizontal cells contacting similar numbers of red‐ and green‐sensitive cones and very few blue‐sensitive cones. Most dendritic contacts were lateral to synaptic ribbons. Central contacts with ribbons were made almost exclusively within red‐sensitive cone pedicles. Biphasic/chromaticity‐type S‐potentials were generated by H2‐like horizontal cells. The dendrites of the latter contacted green‐ and blue‐sensitive cones, both at central and lateral sites at synaptic ribbons. An attempt was made to correlate cone ribbon connectivity patterns and spectral characteristics of the horizontal cells according to several hypotheses, some proposed in earlier studies.
Cholinergic innervation of the rat cerebellum: Qualitative and quantitative analyses of elements immunoreactive to a monoclonal antibody against choline acetyltransferase
Authors: Ojima Hisayuki , Kawajiri Shin‐Ichi , Yamasaki Terukiyo
Published: January 2005

Cholinergic innervation of the rat cerebellum was investigated immunohistochemically by using a monoclonal antibody against choline acetyltransferase. Immunoreactive structures included: (1) a subpopulation of mossy fibers and glomerular rosettes; (2) thin varicose fibers, which wre closely associated with the Purkinje cell layer and also found in the molecular layer; and (3) relatively dense networks of varicose fibers distributing in the cerebellar nuclei. Quantitative analysis indicated that a great many immunoreactive rosettes were localized in lobules IXc and X, although their density in lobule X was approximately four times that in the lobule IXc. A considerable number of immunoreactive structures were also present in all other lobules. In the hemispheres they were confined to a zone immediately beneath the Purkinje cell layer, whereas in the vermis they were scattered throughout the granular layer. Most of the immunoreactive fibers found in the molecular layer coursed toward the pial surface and were distributed within the inner half of the molecular layer. In the cerebellar nuclei, portions of the medial nucleus and magnocellular portion of the lateral nucleus had moderately dense networks of immunoreactive fibers, whereas loose networks of fibers were observed in the posterior interposed nucleus. Other parts of the cerebellar nuclei contained a smaller number of varicose fibers.
Fiber counts at multiple sites along the rat ventral root after neonatal peripheral neurectomy or dorsal rhizotomy
Authors: Nam Sang Chae , Kim Kwang Jin , Leem Joong Woo , Chung Kyungsoon , Chung Jin Mo
Published: January 2005

We hypothesized that the afferent fibers in the ventral root of the rat are the third branches of dorsal root ganglion cells; these afferent processes in the ventral root are of varying length and end bluntly along the length of the root. In the case of an injury at either the central or the peripheral processes of the dorsal root ganglion cells in the neonatal stage, these fibers sprout at the blunt endings along the length of the ventral root. We cut either the sciatic nerve or the dorsal root on one side in neonatal rats. After the rats were fully grown, the number of both myelinated and unmyelinated fibers was counted in electron photomicrographs at multiple sites along the length of the ventral root. We observed a greatly increased number of unmyelinated fibers in the ventral root after the sciatic nerve had been cut at the neonatal stage. The magnitude of increase was more at the distal than at the proximal portion of the ventral root, suggesting that added fibers originated from the distal side. Neonatal dorsal rhizotomy, however, did not produce the same result. These results are consistent with our hypothesis that peripheral nerve injury at the neonatal stage triggers sprouting of the third branches of the dorsal root ganglion cells which end bluntly along the length of the ventral root in the normal animal.
Motor innervation of respiratory muscles and an opercular display muscle in siamese fighting fish Betta splendens
Authors: Gorlick Dennis L.
Published: January 2005

Horseradish peroxidase was used to identify motor neurons projecting to the adductor mandibulae, levator hyomandibulae, levator operculi, adductor operculi, and dilator operculi muscles in Siamese fighting fish, Betta splendens. These muscles participate in the production of respiratory and feeding movements in teleost fishes. The dilator operculi is also the effector muscle for gill‐cover erection behavior that is part of Betta's aggressive display. The motor innervation of these muscles in Betta was compared to that previously described for carp.

Motor neurons of the adductor mandibulae, levator hyomandibulae, and dilator operculi are located in the trigeminal motor nucleus, and motor neurons of the adductor operculi and levator operculi are located in the facial motor nucleus in Betta and in carp. The trigeminal motor nucleus in both species is divided into rostral and caudal subnuclei. However, there are substantial differences in the organization of the subnuclei, and in the distribution of motor neurons within them. In Betta, the rostral trigeminal subnucleus consists of a single part but the caudal subnucleus is divided into two parts. Motor neurons for the dilator operculi and levator hyomandibulae muscles are located in the lateral part of the caudal subnucleus; the medial part of the caudal subnucleus contains only dilator operculi motor neurons. The single caudal subnucleus in carp is located laterally, and contains motor neurons of both the dilator operculi and levator hyomandibulae muscles.

Differences in the organization of the trigeminal motor nucleus may relate to the use of the dilator operculi muscle for aggressive display behavior by perciform fishes such as Betta but not by cypriniform fishes such as carp. Five species of perciform fishes that perform gill‐cover erection behavior had a Betta‐like pattern of organization of the caudal trigeminal nucleus and a similar distribution of dilator operculi motor neurons. Goldfish, which like carp are cypriniform fish and do not display, had a carp‐like trigeminal organization and dilator operculi motor neuron distribution.
Screening of aromatase‐containing neurons in rat forebrain: An immunohistochemical study with antibody against human placental antigen x‐P2 (hPAX‐P2)
Authors: Shinoda Koh , Yagi Hideo , Fujita Hisao , Osawa Yoshio , Shiotani Yahe
Published: January 2005

Aromatase‐containing neurons were immunohistochemically examined in rat brains by using a polyclonal antibody against human placental antigen. The antibody recognizes cytochrome P‐450 portion of aromatase, an enzyme converting androgen to estrogen. A large group of strongly immunoreactive cells was identified in the ventral pallidum, which extends caudally from the area surrounding the islands of Calleja. Other strongly or moderately stained cell groups were observed in the cerebral cortex, the amygdaloid area, the nucleus of the diagonal band, and the area anterior to the posterior commissure. Only a few stained cells were present in the medial preoptic region.

These findings cast doubt upon the previous assumption, based on biochemical analysis of tissue samples, that the center of the aromatizing system is in the medial preoptic region. They indicate instead that most aromatase‐containing neurons of rats lie within the ventral pallidum ventromedially adjacent to the preoptic area.
Immunocytological localization of the highly polysialylated form of the neural cell adhesion molecule during development of the murine cerebellar cortex
Authors: Hekmat Anusch , Bitter‐Suermann Dieter , Schachner Melitta
Published: January 2005

The expression of the highly polysialylated form of the neural cell adhesion molecule (N‐CAM)—the so‐called embryonic N‐CAM (E‐N‐CAM)‐was investigated in the developing and adult mouse cerebellar cortex by immunohistology and immunocytology at the light and electron microscopic levels. E‐N‐CAM was never (from embryonic day 14 to postnatal day 15) detectable in the germinal zone of neuroblasts destined to form or forming the external granular layer and was only observed once small cerebellar interneurons had become postmitotic before the beginning of granule cell migration. Granule cells expressed E‐N‐CAM on cell bodies, axons, and leading and trailing processes also during migration but ceased to reveal detectable levels of E‐N‐CAM at the end of migration after having reached their final position in the internal granular layer. Other cerebellar cell types, such as Purkinje cells, Bergmann glia, astrocytes, oligodendrocytes, and most prominently, stellate and basket cells, also expressed E‐N‐CAM, but became E‐N‐CAM‐negative during the third and fourth postnatal weeks, coinciding with overt cessation of cerebellar histogenesis. Thus, except for neuroblasts, E‐N‐CAM appeared characteristic of growing and moving cellular structures, in agreement with the notion that the highly polysialylated form of N‐CAM is less adhesive than the adult form.
Ultrastructure of the crossed isthmotectal projection in xenopus frogs
Authors: Udin Susan B. , Fisher Mark D. , Norden Jeanette J.
Published: January 2005

The nucleus isthmi NI of frogs is a relay for input from the eye to the ipsilateral tectum; each NI receives retinotopic input from one tectum and sends retinotopic output to both tecta. The crossed isthmotectal projection in Xenopus displays tremendous plasticity during development. Physiological and anatomical studies have suggested that the location at which a developing isthmotectal axon will terminate is determined by the correlation of its visually evoked activity with the activity of nearby retinotectal terminals.

What structures could mediate such communication? We have examined quantitatively the ultrastructural characteristics of crossed isthmotectal axons and synapses in order to determine whether retinotectal axons communicate directly with isthmotectal axons via axo‐axonic synapses or whether the communication is indirect, e.g., via common postsynaptic dendrites. Our results support the conclusion that isthmotectal axons interact with retinotec tal axons indirectly and that tectal cell dendrites are the critical site of interaction.
Compartmental and topographical specificity of reinnervation of the glutaeus muscle in the adult toad (bufo marinus)
Authors: Brown David R. , Everett Alan W.
Published: January 2005

The extent to which the compartmental and topographical innervation patterns were re‐established in the mature glutaeus muscle after nerve cut was determined by HRP retrograde labelling procedures and single motor unit glycogen depletion experiments. Glutaeus muscle axons normally cluster together along the length of the sciatic nerve and enter the triceps femoris nerve along with axons to the cruralis and tensor fasciae latae muscles. Glutaeus axons did not specifically reinnervate the glutaeus muscle after cutting the triceps femoris nerve. Axons within the glutaeus muscle nerve are grouped according to the primary nerve branch, and therefore muscle compartment, for which they are destined. When the glutaeus nerve was cut, regenerating axons lost their compartmental organization within the glutaeus nerve and nonspecifically reinnervated both glutaeus muscle compartments. In marked contrast, the topographical projection of spinal motoneurones to the ventral and dorsal halves of the glutaeus muscle was largely re‐established after glutaeus nerve cut; that is, rostral motoneurones mostly reinnervated ventral muscle fibres, whereas caudal motoneurones reinnervated dorsally located muscle fibres. The relatively confined caudal projection was closely related to the sharp fibre type divisions within the glutaeus muscle. The results suggest that factor(s) present during development that determine the correct innervation of a muscle and its compartments no longer operate in the adult, although cues that direct motor terminals to their appropriate muscle region do, and these are most likely related to the topographical distribution of fibre types.
Distribution of histaminergic neurons in the brain of the lamprey lampetra fluviatilis as revealed by histamine‐immunohistochemistry
Authors: Brodin Lennart , Hökfelt Tomas , Grillner Sten , Panula Pertti
Published: January 2005

An antiserum against conjugated histamine was used to study the distribution of histaminergic neurons in the CNS of the lamprey Lampetra fluviatilis. Numerous histamine‐immunoreactive cell bodies were detected in the dorsal and ventral hypothalamic nuclei and in the adjacent postinfundibular commissural ncleus. Histamine‐immunoreactive fibers of high density were present in the ventral hypothalamus, and fibers could also be traced dorsally from the hypothalamus to the corpus striatum and septal nucleus where they appeared to terminate in dense plexuses. Another, smaller group of histamine‐immunoreactive perikarya was observed in the border area between mesencephalon and rhombencephalon, near the caudal pole of the mesencephalic reticular nucleus. Sparsely distributed histamine‐immunoreactive fibers were present in the ventral mesencephalon. The distribution of histaminergic neurons in cyclostomes, which diverged very early from the main vertebrate line, shows similarities with the corresponding systems in the CNS of amphibians and mammals, which suggests that histaminergic neuronal systems are phylogenetically old and have been conserved during evolution.
Regeneration and soma size changes following axotomy of the trochlear nerve
Authors: Murphy E. Hazel , Brown Joyce , Iannuzzelli Pasquale G. , Baker Robert
Published: January 2005

The effects of CNS and PNS axotomy of the IVth nerve on cell death, soma size, axon size, and axon number were investigated. In adult cats, the IVth nerve was axotomised by using four surgical paradigms: (1) peripheral IVth nerve crush, (2) peripheral IVth nerve cut, (3) peripheral IVth nerve resection, and (4) a CNS IVth nerve cut in the velum. The extent of cell death resulting from each surgical paradigm was determined. Following axotomy distal to the decussation of the IVth nerves, cell death was least after nerve crush, intermediate after nerve cut, and maximal after resection of 5–7 mm of the nerve. Following axotomy at the decussation—a CNS lesion—most cells died but some successful regeneration was observed.

Soma size measurements following a short‐term survival (3 days to 4 weeks) before the regenerating axons reached their target muscle revealed that somas of axotomised cells underwent hypotrophy within 1 week of axotomy and then gradually increased in size. They re‐attained normal size by 4 weeks postoperative when regenerating axons first reach their target. Following a long‐term survival (>2 months), somas were significantly hypertrophied, and the degree of hypertrophy was inversely related to the extent of cell survival up to a limit of 40% soma size increase.

Counts and measurements of axons revealed that mean axon diameter of regenerated axons was much smaller than normal 3 months after axotomy, increased during the third to sixth postoperative months, but then showed no subsequent increase and remained below normal. In animals with cell death varying from 10% to 70%, the number of axons in the nerve was maintained constant at approximately 1,000. These data indicate that there is a mechanism for the production and maintenance of the appropriate number of regenerative axonal branches following axotomy. In animals in which cell death exceeded 70%, the number of axons was controlled by a maximum ratio of 3 to 4 axon branches per surviving cell.

The results suggest that axon number is strongly influenced by the target muscle and that hypertrophy of regenerated cells is related to the number of axonal sprouts each cell has to produce and support in order to re‐establish the preoperative number of axons in the regenerated trochlear nerve.
Innervation of the serotonin‐immunoreactive cells distributed in the wall of the common carotid artery and its branches in the chicken
Authors: Kameda Yoko
Published: January 2005

In the chicken, serotonin‐immunoreactive cells were widely distributed not only in the carotid body but also in the wall of the common carotid artery and around each artery arising from the common carotid artery. Almost all of the serotonin cells in the wall of the common carotid artery were intensely immunoreactive to the neuropeptide Y, met‐ and leu‐enkephalin antisera, whereas in the carotid body only a few cells were immunoreactive to these antisera. Innervation of the serotonin cells in and around arteries of chickens was investigated by immunohistochemistry and electron microscopy, in comparison with that of the carotid body. The serotonin cell groups in and around arteries, as well as the carotid body, received numerous peptidergic nerve fibers. Calcitonin gene‐related peptide (CGRP)‐and substance P‐immunoreactive varicose nerve fibers were densely distributed, and somatostatin‐immunoreactive fibers were moderately distributed in the serotonin cell groups. Galanin‐and vasoactive intestinal peptide (VIP)‐immunoreactive fibers were sparsely distributed in the cell groups. By electron microscopy, the serotonin cells in and around arteries were characterized by the presence of numerous dense‐cored vesicles, 70–220 nm in diameter. The granule‐containing cells were in close association with numerous axons. Naked axons regarded axon terminals were frequently apposed on the granular cells. The axon terminals were usually long and often partly invested the granular cells. Numerous synaptic junctions were detected along the contact between the granular cells and axon terminals. Most of the synaptic junctions showed afferent morphology; the secretory granules were accumulated near and attached to the asymmetrical membrane thickenings. Thus, the serotonin cells in and around arteries, like the carotid body, constitute chemoreceptive tissue.
Telodendrial contact of HRP‐filled photoreceptors in the turtle retina: Pathways of photoreceptor coupling
Authors: Ohtsuka Teruya , Kawamata Kunihiko
Published: January 2005

Synaptic contacts of photoreceptors in the turtle retina were studied by intracellular injection of horseradish peroxidase (HRP) and electron microscopy. Both cone and rod photoreceptors radiated basal processes (telodendria) from their terminal endings. These telodendria ran laterally in the outer plexifrom layer. The telodendria of cones gave rise to many fine branches that penetrated synaptic cavities of several neighboring cones. Tips of these branches terminated near the walls of synaptic cavities. Some of the telodendrial contact formed two types of basal junction: symmetrical and punctate. The distribution of cones that made telodendrial contacts with the HRP‐filled cone were quantitatively investigated. Green‐sensitive cones (n = 3) made telodendrial contacts with neighboring red‐and blue‐sensitive cones, blue‐sensitive cones (n = 4) with red‐ and green‐sensitive cones, and red‐sensitive cones (n = 9) with red‐ and green‐sensitive cones. In contrast to these cone connections, rod telodendria did not penetrate neighboring photoreceptors. Direct synaptic contacts were not found between rods and cones. Our results clarify the variety of cone couplings in turtle retina: the three chromatic classes of cones are selectively coupled by the basal junctions at the ends of telodendrial processes.
Identification of pedicles of putative blue‐sensitive cones in the human retina
Authors: Ahnelt Peter , Keri Christian , Kolb Helga
Published: January 2005

Cone photoreceptor pedicles from midperipheral regions of the human retina (6 mm from the foveal center) have been studied by light and electron microscopy. Three areas of cone pedicle mosaic were serially thin‐sectioned, in the tangential plane, from the inner border of the outer plexiform layer to the emergence of the cone axons from the cone pedicles. Semithin sections were then collected from the cone axon level through the cone cell bodies to the cone inner segment level. Two hundred twenty‐one cone pedicles were followed by this means to their respective inner segments. Eight percent of the cone pedicles were from cones with inner segment characteristics of the blue cones. All 221 cone pedicles were reconstructed by tracing images from electron micrographs. The cone pedicle locations, surface areas, telodendrial projections, and synaptic ribbons could then be measured by morphometry and analyzed by statistical methods. Some selected cone pedicles were reconstructed by computer graphics methods.

The cone pedicles identified as belonging to the blue cone type could be distinguished from the surrounding longer wavelength types on the following morphological criteria: 1) they were smaller (50% the area of the surrounding pedicles), 2) they contained shorter synaptic ribbons, 3) they exhibited essentially no telodendrial contact to neighboring cone pedicles, 4) they were positioned slightly more vitread in the outer plexiform layer than neighboring pedicles, and 5) their irregular occurrence in the cone mosaic coincided with the distribution criteria established in our previous paper (Ahnelt et al: J. Comp. Neurol. 255:18‐34, 87) for putative blue sensitive cones in midperipheral human retina.
Implantation of cultured sensory neurons and schwann cells into lesioned neonatal rat spinal cord. I. Methods for preparing implants from dissociated cells
Authors: Kuhlengel Keith R. , Bunge Mary Bartlett , Bunge Richard P.
Published: January 2005

Our goal was to devise methods of implanting defined populations of the cellular constituents of peripheral nerve into regions of spinal cord injury. This objective derived from the knowledge that the cellular environment of peripheral nerve is known to be supportive of axon regeneration from both central and peripheral neurons. Two of the constituents of the peripheral nerve environment known to influence axonal growth are the Schwann cell and extracellular matrix (particularly basal lamina), both of which can be obtained in culture. We describe here large‐scale methods of establishing purified populations of rat sensory neurons to which purified populations of Schwann cells were added. These essentially monolayer preparations were then scrolled and cut into lengths of proper shape and size to provide implants for sites of spinal cord injury in newborn rats. We also describe methods enabling the addition of leptomeningeal components to the implants; this addition contributes a proliferating population of vascular endothelial cells (identified by immunostaining) to the otherwise vasculature‐free neuron/Schwann cell implant. Light and electron microscopic observations were made to characterize the implants. When the implant was ready for use, it contained Schwann cells that were differentiated, i. e., had begun to ensheathe axons and form basal lamina. The use of a medium containing human plasma to foster endothelial cell growth led to increased neurite fasciculation and Schwann cell migratory activity in the outgrowth, particularly when the neurons and Schwann cells were cultured on leptomeninges. The second paper in this series reports the deportment of these implants and their influence on corticospinal tract growth after placement into regions of dorsal column injury in neonatal rats (Kuhlengel et al., J. Comp. Neurol 293:74‐91, 1990).
Origin of spinal cord axons in the lizard regenerated tail: Supernormal projections from local spinal neurons
Authors: Duffy Mark T. , Simpson Sidney B. , Liebich Diana R. , Davis Brian M.
Published: January 2005

During tail regeneration most lizards also regenerate the tail spinal cord. The regenerated spinal cord primarily contains neuroepithelium (i.e., the ependymal tube which forms the central canal) and descending axons. The present experiments identify the source of the axons in the regenerated spinal cord. Application of HRP to normal tail spinal cord resulted in labeled cells in the nucleus paraventricularis, the interstitial nucleus of the fasciculus longitudinalis medialis, the nucleus ruber, the medullary reticular formation (including raphe nuclei), as well as in vestibular nuclei. HRP applied to the regenerated spinal cord labeled only 4% of the cells seen in normal animals, and these were confined to rhombencephalic nuclei. The lack of labeling of more rostral nuclei was not due to the death of descending neurons. Application of HRP immediately rostral to the regenerated spinal cord resulted in the labeling of a normal, and in some cases, greater than normal, number of neurons.

To quantify the origin of axons in the regenerated spinal cord, electron microscopic montages of the regenerated spinal cord were made and the number of axons counted, before and after various spinal lesions. Only lesions within one spinal segment of the regenerated spinal cord had a significant effect on the number of axons in the regenerated tail spinal cord. This indicated that most of the regenerated axons were of local spinal origin. A significant increase in the number of labeled local spinal neurons was revealed following application of HRP to a regenerated tail spinal cord. These results suggest that while various portions of the lizard central nervous system can grow axons into the regenerating tail spinal cord, the great majority of axons in the regenerate are of local origin and that some of these arise from neurons that do not normally possess descending projections. Finally, to test whether new neurons were participating in the regeneration process, 3H‐thymidine was injected during the regrowth of the tail. No labeled spinal cord cells were conclusively identified as neurons. Thus, the regenerating lizard tail spinal cord exhibits robust axonal sprouting from neurons near the site of a spinal transection in a manner reminiscent of sprouting in the mammalian CNS. This sprouting can develop into descending spinal projections that extend for significant distances into the regenerated tail spinal cord and provides a unique model for exploring the requirements for successful axon growth in an adult vertebrate CNS.
Development of olivocerebellar fibers in the clawed toad, Xenopus laevis: A light and electron microscopical HRP study
Authors: Van Der Linden J. A. M. , Ten Donkelaar H. J. , De Boer‐van Huizen R.
Published: January 2005

An anterograde tracer study was undertaken to provide a light‐ and electron microscopical description of climbing fiber development in the clawed toad, Xenopus laevis, ranging from premetamorphic stages to the adult state. The inferior olive was unilaterally labeled with horseradish peroxidase and the contralateral climbing fiber morphology investigated. At early stages of development, only undifferentiated fibers were observed in the rostral alar plate. At later stage, these fibers form large varicosities, which contact presumed cerebellar Purkinje cells. Finger‐like protrusions arising from the Purkinje cell somata penetrate the climbing fiber varicosities and form synaptic specializations at these contact sites. In older tadpoles, a large variety of climbing fiber morphologies was found displaying a mediolateral gradient. At dorsolateral cerebellar areas long and straight climbing fibers follow the Purkinje cell primary dendrites. However, in ventromedial areas pericellular baskets or nests were found on presumed Purkinje cell somata. These pericellular nests were found throughout development but were not observed in adult animals. Both pericellular nests and real climbing fibers make synaptic contacts on spiny protrusions of the Purkinje cell's somatic or dendritic surface. In several cases, labeled as well as unlabeled climbing fiber profiles were observed on the same Purkinje cell, indicating multiple, convergent innervation. Also, divergent Purkinje cell innervation was found. In conclusion, this study shows that anuran climbing fiber development encompasses stages and processes similar to those observed in mammals. The only principal difference with climbing fiber development in mammals is the low degree of synchrony observed in anurans.
Ultrastructure of the mammillotegmental projections to the ventral tegmental nucleus of gudden in the rat
Authors: Hayakawa Tetsu , Zyo Katuya
Published: January 2005

This study examines the termination pattern of axons from the medial mammillary nucleus within the ventral tegmental nucleus of Gudden (TV) in rats by using anterograde transport of horseradish peroxidase conjugated with wheat germ agglutinin (WGA‐HRP) and visualized with tetramethylbenzidine. The neuropil of TV contains three classes of axodendritic terminals, that is, terminals containing round, flat, and pleomorphic synaptic vesicles. These types make up 55.6%, 26.1%, and 18.3%, respectively, of all normal axodendritic terminals. Injection of WGA‐HRP into the medial mammillary nucleus permits ultrastructural recognition of anterogradely labeled terminals within the TV. More than 80% of the labeled terminals contain round synaptic vesicles and form asymmetric synaptic contacts, whereas about 16% contain flat synaptic vesicles with symmetric synaptic contacts. There are a few labeled terminals with pleomorphic vesicles and only a few axosomatic terminals. Almost all labeled terminals are small, having diameters of less than 1.5 μm. Compared with the distributions of normal and labeled terminals with round vesicles, there is an increase of the percentage of labeled terminals with round vesicles on the intermediate dendrites (1‐2 μm diameter) and a decrease on the distal dendrites (less than 1 μm diameter). Anterogradely labeled axon terminals often contact retrogradely labeled dendrites.

These results suggest that the medial mammillary neurons send mainly excitatory as well as a few inhibitory inputs to the dendrites of TV and have direct reciprocal contacts with the TV neurons.
Development of retinotopy in projections from the eye to the dorsal lateral geniculate nucleus and superior colliculus of the wallaby (Macropus eugenii)
Authors: Marotte L. R.
Published: January 2005

The development of retinotopy in projections from the eye to the dorsal lateral geniculate (dLGN) and superior colliculus (SC) has been studied in the marsupial wallaby. Discrete retinal lesions were made and the remaining retinal projections were traced with horseradish peroxidase in animals at stages ranging from just after optic innervation of the dLGN and SC to the time when the projections are mature.

Topographically organised projections could be recognized a few weeks after axons first reached the dLGN and SC with a topographically discrete projection from nasoventral retina recognized later than from dorsal, dorsotemporal, temporal, and temporoventral retina. Over time there was an increase in precision of the retinotopy as judged by an increase in sharpness of the borders of filling defects in the projection labelled with horseradish peroxidase. Refinement of the projection from temporal retina preceded that from nasal retina in both the dLGN and SC and in the former occurred concomitantly with the segregation of eye‐specific terminal bands. Refinement was complete 16 weeks after birth, prior to eye opening at around 20 weeks after birth. Inequalities in retinal representations in both nuclei were present from the time retinotopy could first be detected. This was before the inequalities in retinal ganglion cell distribution, which underly these representations in the adult, were obvious.

Retinotopy and inequalities in retinal representation characteristic of the adult are present from a very early stage in the protracted development of visual projections in the wallaby. Refinement may involve death of inappropriately projecting cells, pruning of inappropriately projecting axon arborizations or could be achieved by growth of the retinorecipient neuropil. Temporonasal differences in the time course of refinement may reflect gradients of maturation in the retina.
Delineation of a brain nucleus: Comparisons of cytochemical, hodological, and cytoarchitectural views of the song control nucleus HVC of the adult canary
Authors: Gahr Manfred
Published: January 2005

The present investigation used stable area‐specific, neuronal properties instead of Nissl stain to delineate the boundaries of the nucleus hyperstriatalis caudal c (HVc) in the telencephalon of the adult male canary. Immunocytochemical procedures combined with retrograde tracing labeled a large population of perennial long‐projecting neurons that contain estrogen receptors in the canary HVc. The HVc area defined by the distribution of these neurons was congruent with the HVc area defined in Nissl‐stained sections during the breeding period. The HVc area defined in Nissl‐stained preparations showed an extensive seasonal change in size, confirming previous results Nottebohm: Science, 214:1368–1370, '81. In contrast, the HVc area defined by the distribution of the estrogen receptor containing long‐projection neurons showed little or no seasonal change in size. Because these neurons are permanent, the HVc seems to be of rather constant size year round. The internal morphology of the HVc, however, undergoes seasonal alterations, which are reflected in changes in size of the HVc area distinguishable in Nissl‐stained sections. The combination of cytoarchitectural criteria of Nissl‐stained preparations with area‐specific cytochemical and hodological markers to delineate the boundaries of a brain nucleus might give new insights in the partitioning and neural plasticity of brain areas.