bluuebunny/crossref_metadata_2025 huggingface dataset:
Immunohistochemical localization of leucine‐enkephalin in the spinal cord of the cat: Enkephalin‐containing marginal neurons and pain modulation
Authors: Glazer E. J. , Basbaum A. I.
Published: January 2005

This study examined the spinal cord distribution of the endogenous opioid peptide leucine‐enkephalin in the cat using immunohistochemical techniques. The distribution of nerve processes was studied in untreated cats; colchicine was administered to study the distribution and morphology of spinal enkephalin‐containing perikarya.

Enkephalin immunoreactive processes were greatest in laminae I and II (marginal layer and substantia gelatinosa) of the superficial dorsal horn. In many sections, the outer substantia gelatinosa (SG), lamina IIa, was discernibly less immunoreactive than I or IIb. Laminae III and IV were relatively devoid of staining. Laminae V and VII had moderate enkephalin‐immunoreactivity, lamina VI somewhat less. Enkephalin immunoreactivity in lamina X, around the central canal, was very dense. Enkephalin‐containing beaded varicosities coursed throughout the ventral horn.

Although previous studies in the rat emphasized the enkephalin‐somata of the SG, we found that in the cat the majority of superficial dorsal horn enkephalinsomata are in the marginal layer. These enkephalin‐containing marginal cells were morphologically similar to a population of marginal neurons which project to the brainstem and/or the thalamus. Some light staining small SG neurons were also identified; many were located at the lamina I‐II border. Considerably more cells were found ventral to the SG, in lamina III, and at the IV‐V border. These latter cells had dendrites coursing dorsally, toward the SG. Numerous immunoreactive cells were found in lamina VII, in a band across the intermediate gray. These cells fused medially with cells of lamina X. Enkephalin cells were also found in the sacral autonomic nucleus and encircling the central cervical nucleus, Clarke's column, and Stilling's nucleus. Although surrounded by labeled cells, the latter regions were devoid of enkephalin‐immunoreactive processes.

Many of these spinal enkephalin neurons are morphologically similar to and distributed in regions known to contain projection neurons. Thus it is suggested that many spinal enkephalin neurons, generally thought to be local circuit neurons, project rostrally, to other spinal levels and perhaps to brainstem and/or thalamus.
Further evidence for an early critical period in the development of the cat's dorsal lateral geniculate nucleus
Authors: Sherman S. Murray , Wilson James R.
Published: January 2005

The concept of an early postnatal critical period of development for the lateral geniculate nucleus was assessed by determining in adult cats whether previously established properties of geniculate neurons could be altered by varying the cats' visual experience. The analysis was limited to lamina A1 and the binocular segment of lamina A, and the properties studied were the percentage of physiologically recorded Y‐cells and cell soma size. Eleven experimental cats in four groups were studied, and three cats reared normally plus three cats reared with continuous monocular lid suture served as controls. Two cats raised first with monocular suture followed by a prolonged period in adulthood with both eyes open had cell size distributions and Y‐cell proportions that were indistinguishable from cats raised with continuous monocular suture. Four cats raised first with one eye sutured underwent a reverse suture procedure in adulthood (i.e., the originally sutured eye opened and the other closed) and were maintained in this fashion for a prolonged period. These cats also had geniculate cell size distributions and Y‐cell proportions that were indistinguishable from cats raised with continuous monocular suture. Two cats were raised first with binocular suture followed by a prolonged period in adulthood with one eye opened. Their geniculate cell size distributions and Y‐cell proportions showed no effect of the adult monocular deprivation and were indistinguishable from previously published data concerning cats raised with continuous binocular suture. Finally, three normally raised cats underwent a prolonged period of monocular suture in adulthood. Their geniculate cell size distributions and Y‐cell proportions showed no effects of the adult monocular deprivation. From these data, we conclude that an early critical period of development occurs for geniculate cell sizes and Y‐cell proportions. Adult visual environments, whether normal or abnormal, had no detectable effect on geniculate neurons for these previously developed properties, whether normal or abnormal.
Medial rectus subgroups of the oculomotor nucleus and their abducens internuclear input in the monkey
Authors: Büttner‐Ennever J. A. , Akert K.
Published: January 2005

Physiological experiments show that the abducens internuclear pathway is involved in the activation of only the medial rectus (MR) eye muscle. Previous anatomical experiments have shown that this pathway terminates in multiple foci within the oculomotor nucleus (OMN) of the monkey, and not only over the classical motoneuron subgroup. In this study the location of MR motoneurons in the monkey OMN is reinvestigated, and compared with the detailed pattern of terminations of the abducens internuclear pathway. The motoneurons were labelled by injections of retrograde tracer substances, HRP and [125I] wheat germ agglutinin (WGA), into extraocular muscles. Labelled MR motoneurons were found in three main divisions, called subgroup A, B, and C. Subgroup A corresponds mainly to the classical ventral MR subgroup. Subgroup B lies dorsal and caudal in OMN, occupying an area classically reserved for inferior rectus (IR). However, the representation of IR is shown to be further rostral in the dorsal OMN. Subgroup C is on the dorsomedial border of OMN. Its cells are significantly smaller than those of group A and B. In addition C could be labelled independently of the other subgroups by small injections into the outer (orbital) layer of MR muscle. This indicates a functional difference between the subgroups. It is suggested that subgroup C may be important for the tonic component of MR activity, possibly convergence. The location of abducens internuclear terminals, labelled by the injection of tritiated amino acids into the abudens nucleus, corresponds exactly to the position of MR motoneurons. These experiments provide a new picture of the internal OMN organization, and support the physiological findings that the abducens internuclear pathway activates only MR motoneurons.
Golgi‐impregnated amacrine cells and GABAergic retinal neurons: A comparison of dendritic, immunocytochemical, and histochemical stratification in the inner plexiform layer of rat retina
Authors: Famiglietti Edward V. , Vaughn James E.
Published: January 2005

This paper concerns the banding pattern produced in the inner plexiform layer of rat retina by glutamic acid decarboxylase (GAD) immunocytochemistry. It presents a comparison of this pattern with the dendritic stratification of neurons that are reasonable candidates for GABAergic amacrine cells in Golgi preparations, and also with the banding patterns produced by other histochemical techniques. First, the spacing of five dense GAD‐positive bands and four intervening less dense bands in central retina is quantitatively described. Second, examples of a particular, morphologically homogenous group of Golgi‐impregnated amacrine cells are examined in the details of their structure, espeically with regard to their dendritic stratification. Computer reconstructions of the dendritic trees of some of these narrow‐field, multistratified amacrines are compared with the GAD‐positive banding pattern. This group of amacrines is judged to represent many of the GABAergic neurons in rat retina, accounting for the form and distribution of GAD‐positive synaptic terminals by their dendritic morphology and stratification. Third, a general schema for the laminar subdivision (stratification) of the inner plexiform layer in rat retina is derived from a comparison of the results of several histochemical procedures. Finally, similarities and differences in the distribution of GAD‐positive amacrine cell dendrites are noted among mammals and the functional implications of their broad distribution are discussed. A conspicuous difference is cited between mammals and certain nonmammalian vertebrates in which GAD‐positive dendrites are restricted to sublamina b (ON‐center cells) of the inner plexiform layer.
Afferent synaptic connections between hair cells and the somata of intramacular neurons in the gravity receptor system of the statocyst of octopus vulgaris
Authors: Colmers William F.
Published: January 2005

In the sensory epithelium (macula) of the gravity receptor system of the statocyst of Octopus vulgaris, there are two types of afferent neurons, distinguished according to their position in the epithelium. The somata of one type lie accumulated in a ring peripheral to the hair cell layer of the epithelium; these are disignated as perimacular neurons. The somata of the other type lie among the hair cells, below the level of their nuclei; these are designated as intramacular neurons. Axons of afferent neurons which touch the hair cells are postsynaptic to some of the hair cells touched. As the somata of the intramacular neurons also touch the hair cells, they were investigated by serial electron microscopic reconstruction to determine if afferent synaptic contacts between hair cells and these somata occur.

An average of about 600 intramacular neurons was counted in two maculae. Afferent synapses were seen to occur between hair cells and the somata of 76% of the intramacular neurons investigated. The postsynaptic processes of the intramacular neurons' somata were of two morphological types; one with a finger‐like and one with a flat postsynaptic process (average of one synapse of each type per soma). The soma of an intramacular neuron can be postsynaptic to more than one hair cell simultaneously (average of 1–2 hair cells per soma). In addition to being presynaptic to only one neuron's soma, a hair cell could be simultaneously presynaptic to the axons of one or more afferent neurons. The morphological findings are discussed as to their possible physiological consequences.
Expansion of the ipsilateral visual corticotectal projection in hamsters subjected to partial lesions of the visual cortex during infancy: Anatomical experiments
Authors: Rhoades Robert W.
Published: January 2005

Electrophysiological methods were employed to determine whether or not partial visual cortical lesions in neonatal (7–11‐day) hamsters produced large scotomas in the cortical visual representation. In cases where such scotomas were present electrophoretic deposits of radioactive amino acids in the visually responsive “cortical remnant” of the damaged hemisphere resulted in labeling throughout the lower portion of the stratum griseum superficiale and the stratum opticum of the ipsilateral superior colliculus. No differential labeling of the part of the colliculus which was topographically matched with the remaining visual representation in the cortical remnant was observed. In normal hamsters relatively localized, visual cortical deposits of radioactive amino acids resulted in superficial layer labeling only in portions of the colliculus which corresponded to the locus of the cortical deposit.

In a similar fashion, small lesions at physiologically defined loci in the cortical remnant produced degeneration throughout most of the superficial tectal laminae, but a more restricted “focus” of denser degeneration was also visible in these cases. The position of this focus in the colliculus for a given cortical lesion varied with the nature of the visual map in the cortical remnant. In several additional neonatally brain‐damaged hamsters large lesions of the visual cortex in the intact hemisphere were combined with radioactive amino acid deposits in the cortical remnant to determine whether or not axons from the crossed corticocollicular pathway previously demonstrated in such hamsters were intermingled with fibers from the ipsilateral corticotectal projection. In alternate sections processed for autoradiography or by the Fink‐Heimer ('67) method autoradiographic label and degeneration argyrophilia were both observed in the medial part of the colliculus ipsilateral to the neonatal cortical lesion.
Expansion of the ipsilateral visual corticotectal projection in hamsters subjected to partial lesions of the visual cortex during infancy: Electrophysiological experiments
Authors: Rhoades Robert W.
Published: January 2005

Single unit recording from cells in the superior colliculus ipsilateral to the damaged hemisphere in hamsters subjected to unilateral removal of a part of the posterior neocortex during infancy was combined with electrical stimulation of the cortical remnant and the visual cortex in the undamaged hemisphere. Cells activated by stimulation of the cortical remnant were recorded in all portions of the colliculus. No differences in percentages of driven cells or threshold current intensities were noted between electrode penetrations in which collicular neurons having receptive fields within the remaining visual cortical representation were recorded and tracks where units with receptive fields outside this region were isolated. In the medial part of the tectum ipsilateral to the damaged hemisphere cells driven by stimulation of either cortex were encountered. It was also demonstrated that stimulation of the ipsilateral cortical remnant and/or the contralateral cortex was capable of suppressing discharges normally elicited by optic chiasm or visual stimulation in a manner qualitatively similar to that observed for collicular cells in normal hamsters. The response properties of cells functionally influenced by the ipsilateral and/or contralateral corticles were not different from those of neurons which received no demonstrable cortical input. The receptive field characteristics of the sample of neurons recorded were, on the whole, quite similar to those of collicular neurons in hamsters subjected to lesions of the visual cortex as adults.
An electron microscopic study of the afferent connections of the lateral reticular nucleus of the cat
Authors: Hrycyshyn A. W. , Flumerfelt B. A.
Published: January 2005

The mode and pattern of termination of the afferents to the lateral reticular nucleus (LRN) of the cat were examined at the cellular level through the ultrastructural localization of induced degeneration. Examination of the LRN following hemicordotomy at the fifth and sixth cervical levels revealed that most of the degenerating terminals were in contact with intermediate and distal dendrites, and that most of these degenerating terminals were small and contained round vesicles. Fewer degenerating terminals were observed on the somata and proximal dendrites after spinal hemisection, and most of these terminals were large and contained round vesicles. Following lesions of the pericruciate cortex, small degenerating terminals were occasionally observed making contact onto intermediate and distal dendrites. Degenerating rubral terminals were observed synapsing on somata, somatic and dendritic spines, proximal dendrites and most commonly on intermediate and distal dendrites following lesioning of the red nucleus. The degenerating axosomatic rubro‐LRN terminals belonged to the large, round‐vesicle terminal population, while those degenerating terminals contacting intermediate and distal dendrites belonged to the small, round‐vesicle population. Small, degenerating terminals were occasionally seen following lesions of the fastigial nucleus, and they made synaptic contact mainly onto intermediate and distal dendrites and dendritic spines.

The present ultrastructural observations taken together with the convergence pattern of LRN afferents and the available electrophysiological data on inputs to the LRN suggest an extensive integration of converging impulses from two or more afferent sources to the rostral LRN neurons. The results of this study therefore support the view that the rostral LRN functions as a comparator of command signals from the motor cortex and red nucleus and feedback signals from the spinal cord and cerebellum during ongoing movement.
A diffuse, invaginating cone bipolar cell in primate retina
Authors: Mariani Andrew P.
Published: January 2005

A bipolar cell type forming invaginating contacts with many cones was found by light and electron microscopy of Golgi preparations of the rhesus monkey retina. This diffuse, invaginating cone bipolar cell resembles, superficially, rod (“mop”) bipolars, and so may correspond to Polyak's “brush” bipolar. However, it differs from rod bipolars in that its dendrites are finer and they end in a single stratum containing cone pedicles in the outer plexiform layer (OPL). In the inner plexiform layer (IPL) its axon terminal is located sclerad (S4) to those of rod bipolars (S5), is thinner, and also more branched, and wider in span than rod bipolar axon terminals. Resectioning of Golgi‐impregnated diffuse, invaginating cone bipolars to study their connections in the OPL shows that their dendrites invaginate as many as seven cone pedicles, and terminate as central elements at the ribbon synaptic complex. Thus, the primate retina has multiple (diffuse) and single (midget) cone‐contacting bipolar cell pathways in both invaginating as well as flat varieties.
Afferents to the midbrain auditory center in the bullfrog, Rana catesbeiana
Authors: Wilczynski Walter
Published: January 2005

Horseradish peroxidase (HRP) histochemistry was used to visualize cells afferent to the bullfrog torus semicircularis. These afferent cells are located in several sensory and nonsensory nuclei. The sensory structures which project to the torus are mainly auditory nuclei, with the major input coming from the ipsilateral superior olive. A very small contralateral projection is also present. In addition, afferents arise from the contralateral, and to a lesser extent ipsilateral, dorsal acoustic nucleus and nucleus caudalis, both primary eighth nerve nuclei. A vestibular input is also apparent in that HRP‐positive cells were seen in the magnocellular vestibular nucleus and among elongated bipolar cells at the ventral border of the eighth nerve nuclei. In addition, the torus receives somatosensory input from the contralateral perisolitary band. Afferents from spinal cord cells proved difficult to visualize. Nonsensory areas throughout the brain innervate the torus as well. In the medulla, HRP‐positive cells were present bilaterally in both medial and lateral reticular areas. The tegmentum contributes a major input from the superficial isthmal reticular nucleus and a minor input from the tegmental fields. Commissural toral projections are also present. Descending forebrain input arises from the pretectal gray bilaterally, the ventral half of the ipsilateral lateral pretectal nucleus, and, possibly, from the ipsilateral posterior thalamic nucleus. HRP‐positive cells were also occasionally seen in the posterior tuberculum, ventral hypothalamus, and caudal suprachiasmatic preoptic area. Finally, a telencephalic projection from the ipsilateral anterior entopeduncular nucleus is present.
Postnatal histogenetic death of rat forelimb motoneurons
Authors: Rootman D. S. , Tatton W. G. , Hay M.
Published: January 2005

Previous workers have reported a five fold decrease in motoneuron numbers occurring from birth to adulthood in the rat. It has also been reported that forelimb muscles receive connections from motoneurons in both ventral horns prior to day 14 of life in the rat and that the contralateral cells subsequently degenerate completely by day 21. In the present study, postnatal changes in motoneuron number and distribution within the ventral horn were studied in the rat using the technique of retrograde horseradish peroxidase (HRP) transport following intramuscular infusion of HRP into biceps brachii (BB). Peripheral nerves other than those to BB were sectioned and ligated to control for HRP diffusion. The spatial organization of BB motoneurons was compared in animals 9‐14 days old and adult animals using computer 3‐D reconstruction. This allowed observations of the BB motoneurons from a variety of perspectives in relationship to a number of spinal cord landmarks and avoided the necessity for transverse and horizontal sectioning of the cords in alternate animals. A decrease of 50‐75% in the number of HRP filled motoneurons number was found from birth to adulthood (adults 98‐150, neonates 172‐243). The spatial arrangement of the BB motoneurons with regard to the root entry zones and other landmarks such as the dorsolateral convexity of the ventral horn, remains constant from birth to adulthood. No evidence was found to support the existence of inappropriate connections from motoneurons in either the ipsi or contralateral ventral horns of neonate rats. It is suggested that the comparatively small decrease in motoneurons postnatally could be a continuation of the histogenetic processes of cell death begun in utero and is related to the postnatal development of the central and peripheral connections of motoneurons.
Olivocerebellar projections to the pyramis and copula pyramidis in the rat: Differential projections to parasagittal zones
Authors: Eisenman Leonard M.
Published: January 2005

The organization of the olivocerebellar projection to the pyramis and copula pyramidis in the rat has been studied with the use of microinjections of horseradish peroxidase (HRP). These injections were made in different mediolateral positions along the width of this lobule. The objective was to determine the subnuclear origin of parasagittal zones of olivary innervation. The results indicate that six zones of varying width can be distinguished, each of which receives a different olivary projection. Injections in the pyramis in succedingly more lateral positions resulted in retrograde labeling of the lateral part of the caudal medial accessory olive (MAO), nucleus ß of the MAO, and a slightly more rostral part of the lateral MAO. Injections in the copula pyramidis result in retrograde labeling of the lateral part of the dorsal accessory olive (DAO), the intermediate part of the MAO, and the caudal tip of the principal olive. In very few of the experiments was there labeling of more than one subnuclear locus within the inferior olivary complex. These results suggest that parasagittal zones within the pyramis and copula pyramidis of the rat cerebellum receive highly ordered and differential projections from the inferior olivary complex.
Fine structure of the superficial layers of the viper optic tectum. A golgi and electron‐microscopic study
Authors: Repérant J. , Peyrichoux J. , Rio J. P.
Published: January 2005

The superficial layers of the viper optic tectum, which receive fibers from the retina, were studied using both light and electron microscopes. The optic fibers layer, or stratum opticum, is composed of 200 to 250 tight fascicles containing thin fibers, nearly all of which are myelinated. In the main optic terminal layers, the stratum griseum et fibrosum superficiale, the greatest part of the cellular population is composed of small vertically oriented neurons and horizontal nerve cells, many of which are probably local circuit neurons.

The neuropil of the stratum griseum et fibrosum superficiale is made up of small nerve elements, including three types of profiles containing synaptic vesicles: (1) boutons with pleiomorphic synaptic vesicles (P), representing over 47% of the total population of profiles containing synaptic vesicles and comprising three subgroups (P1, P2, and P3); (2) boutons with spheroidal synaptic vesicles (S), forming more than 29% of the total population of profiles containing synaptic vesicles and comprising two categories, S1 and S2 (S2, the more numerous, represents the optic boutons, which make up 22% of the total population of profiles containing synaptic vesicles); and (3) dendrites with pleiomorphic vesicles, accounting for approximately 23% of the total population of profiles containing synaptic vesicles. A study of synaptic patterns revealed a large number of serial synapses and a lesser number of triplets or triadic synapses. The presynaptic components are boutons containing spheroidal (S1, S2) or pleiomorphic (P1, P2, P3) synaptic vesicles. The intermediate profile was always a dendrite with synaptic vesicles which frequently belonged to the small neurons of the stratum griseum et fibrosum superficiale. Comparison of the present results with other recent data shows that the synaptic circuitry in the optic tectum of Vipera aspis closely resembles the pattern observed in the optic tectum of other vertebrates, ranging from fish to mammals. However, quantitative differences exist, especially with regard to the proportion of dendrites containing synaptic vesicles. Their number seems to be higher in sauropsidians than in mammals, particularly in primates.
Conduction velocity groups in the optic nerve of the north american opossum (Didelphis virginiana): Retinal origins and central projections
Authors: Rowe Michael H. , Wilson Paul D. , Rapaport David H.
Published: January 2005

The axonal conduction velocity groups in the optic nerve of the North American opossum were analyzed electrophysiologically and related to soma size groups of ganglion cells in terms of their retinal origin and laterality of projection. On the basis of analysis of field potentials and single unit responses recorded at the optic disc, three velocity groups were identified (d1, d2, and d3) and estimated to have average conduction velocities of 12, 8, and 5 meters/second. From recordings of the field potential around the perimeter of the optic disc, it was found that the d1 group was equally represented at all points around the disc, whereas the d2 group was largest in amplitude in superior temporal regions. Electrical stimulation of the optic tracts indicated that axons in the d1 group project either ipsilaterally or contralaterally, whereas the d2 group projects predominantly ipsilaterally, and the d3 group projects predominantly contralaterally.

In order to relate these physiological data directly to soma size groups, horseradish peroxidase (HRP) was injected into one optic tract, and subsequently the retinae were processed for peroxidase reaction product in the ganglion cells. Labeled cells were seen in contralateral nasal, contralateral temporal, and ipsilateral temporal retina. Cells in all size classes were labeled in contralateral nasal retina. In contralateral temporal retina, labeled cells were either 10–17 μm diameter (small and medium) or 23–27 μm diameter (large), whereas in ipsilateral temporal retina, most labeled cells (94%) were 15–30 μm diameter (medium and large). The correspondence between these conduction velocity groups and the soma size groups described in the preceding paper (Rapaport et al., '81) is discussed.
On the structural and phyletic origin of the aminergic nerves of the hypophysis of frog tadpoles (Rana temporaria) with special reference to pars distalis
Authors: Aronsson Stig , Enemar Anders
Published: January 2005

With the aid of lesion experiments and the Falck‐Hillarp fluorescence technique, it is shown that the aminergic nerves of the hypophysis, including pars distalis, originate in the caudal hypothalamus and reach the gland via a fibre tract in the floor of tuber cinereum. However, some contribution to the eminentia cmediana from the preoptic area could not be excluded.

A vasomotor function of the pars distalis nerves is unlikely.

Based on a comparative survey the hypothesis is put forward, that the pars distalis nerves, which disappear during the metamorphic climax, are remnants of an aminergic innervation existing together with a hypophyseal portal system as a functional link between brain and pituitary in the fish‐like ancestor of amphibians. Aspects are given on the problem of why a direct pars distalis innervation has neither been retained nor evolved during evolution of tetrapods.
The effects of refeeding after varying periods of neonatal undernutrition on the morphology of Purkinje cells in the cerebellum of the rat
Authors: McConnell P. , Berry M.
Published: January 2005

Undernutrition of the rat for the first 30 days of postnatal life is known to permanently alter Purkinje cell (PC) dendritic morphology. The effects of earlier nutritional rehabilitation have not previously been determined.

Neonatal rat pups were undernourished by limiting their access to the lactating dam. After 10, 15, or 20 days of food restriction, animals were either killed for histological comparison with normally fed controls, or provided with ad libitum food until 80 dpp, and then killed.

Network analysis of Golgi Cox impregnated PCs from the undernourished animals revealed alterations in dendritic length, segment frequency, and branching pattern, which first became apparent at 15 dpp, accompanied by a reduction in the number of granule cells (GCs) per PC. If undernourished animals were refed from 10 or 15 days, however, the total lengths and segment frequencies of their PC trees were indistinguishable from those of controls at 80 dpp, although the 15‐day group showed persistent topological alterations. The GC:PC ratios of these refed groups were also found to be similar to those of the controls. In animals refed after 20 days of undernutrition, network size remained reduced, as did the GC:PC ratio.

The different degrees of recovery of PC dendritic field parameters recorded in the refed animals could be related either to enhanced GC replication afforded by refeeding, or to the existence of intrinsic mechanisms which limit the growth capacity of the PC dendrites.
Some observation on the catecholaminergic innervation of the intermediate zone of the thoracolumbar spinal cord of the cat
Authors: McLachlan Elspeth M. , Oldfield B. J.
Published: January 2005

The anatomical arrangement of catecholaminergic nerve terminals in the intermediate zone of the thoracolumbar spinal cord was examined with the fluorescence microscope in serial sections of spinal cord from adult cats perfused with a formaldehyde‐glutaraldehyde mixture. Specific fluorescence in this material was assumed to represent noradrenaline. The distribution of fluorescent varicose nerve terminals was compared with that of neuron cell bodies in the same sections after Nissl counterstaining, and with the known topographic distribution of sympathetic preganglionic neurons. Dense accumulations of noradrenergic fibers were found in the intermediate zone in all segments between the caudal part of C8 and the rostral part of L4. These were not only associated with preganglionic neurons in the intermediolateral columns (ILN), but below T5 also extended in bands (1–3 per mm of spinal cord) toward, and in some segments across, the midline. Noradrenergic terminals were associated with cell bodies in most parts of the ILN from T1 to T8 and in L2–3. Between T9 and L2, the innervation of the ILN was patchy, and the majority of the noradrenergic fibers projected to regions medial to the ILN. These corresponded to sites at which preganglionic neurons and also possible interneurons of the intermediomedial nucleus occur. Although preganglionic neurons and clusters of noradrenergic terminals are located in similar regions across the intermediate zone, their densities and patterns of distribution differ. This observation applies to comparisons both between anatomical subnuclei and between segments in a characteristic way along the length of the thoracolumbar cord.
Laminar origin of cortical neurons which project upon the caudate nucleus: A horseradish peroxidase investigation in the cat
Authors: Royce G. James
Published: January 2005

The horseradish peroxidase method was used to study the cortical projections upon the caudate nucleus in the cat. The cells of origin of the corticostriatal projection arise from both the supragranular (II and III) and infragranular (V and VI) cortical layers, in contrast to all other known corticofugal pathways to subcortical structures, which appear to arise only from the infragranular layers. This finding has been verified in the present study by several novel surgical procedures, which include direct injections into the caudate nucleus, after the overlying tissues have been removed.

The present study also shows that there is a truly widespread distribution of the cells contributing to the corticostriatal projection. Some portion of every neocortical gyrus contains labeled cells, though their relative numbers vary greatly. Also, simple topographical relationships are maintained, but there is much overlap. In addition, present findings show that the corticostriatal projection is strikingly bilateral and originates from regions which are homotopic to the ipsilateral projection.
Connections of the small bipolar cells with the photoreceptors in the turtle. An electron microscope study of Golgi‐impregnated, gold‐toned retinas
Authors: Dacheux Ramon F.
Published: January 2005

The connections between photoreceptors and the small bipolar cells with a Landolt club in the turtle retina (Pseudemys scripta elegans) were analyzed with the electron microscope after Golgi impregnation and gold toning. The dendritic tree of several bipolars was partially or completely reconstructed from continuous series of thin sections. All bipolar cells studied established both basal and invaginating junctions with cone pedicles; in invaginating junctions, their dendrites invariably ended as the central process of triads. Dendrites of this bipolar cell type make invaginating synapses, basal junctions, or a mixture of both. In turn, each pedicle found within the dendritic field of the bipolar cell contacts it with a mixture of invaginating and basal junctions; furthermore, each pedicle synapses with more than one dendrite from the same bipolar cell. All small bipolar cells examined also synapse with rod pedicles; the geometry of the connections and the types of synapses are the same for both rods and cones. The fact that small turtle bipolars can form both basal and invaginating contacts with a single cone indicates that the polarity of the postsynaptic response can not be predicted on the basis of the structure of the photoreceptor‐to‐bipolar cell synapse.
The afferent connections of the tectum mesencephali in two chondrichthyans, the shark Scyliorhinus canicula and the ray Raja clavata
Authors: Smeets Wilhelmus J. A. J.
Published: January 2005

The afferent connection of the tectum mesencephali were studied in the spotted dogfish Scyliorhinus canicula and the thornback ray Raja clavata by means of the horseradish peroxidase (HRP) technique. Following unilateral injections in the tectum, labeled neurons could be identified in all main divisions of the brain and in the cervical spinal cord. Telencephalic neurons which project to the tectum mesencephali were observed in the caudal part of the pallium. Diencephalic projections to the tectum originate from the thalamus dorsalis pars medialis, the thalamus ventralis pars lateralis, the nucleus medius infundibuli, and the pretectal area. In Scyliorhinus labeled neurons could also be found in the corpus geniculatum laterale. Mesencephalic cells of origin of tectal afferent pathways were identified in the stratum cellulare externum of the contralateral tectum, in the nucleus tegmentalis lateralis, in the ventrolateral tegmentum, and in the nucleus ruber. Rhombencephalic cells projecting to the tectum could be identified in the nucleus cerebelli (only in Scyliorhinus), the nucleus vestibularis superior, the reticular formation, the nucleus funiculi lateralis, the nucleus tractus descendens nervi trigemini, and the nucleus dorsalis and intermedius areae octavolateralis. In addition a number of small‐and medium‐sized cells of the reticular formation were found labeled. Diffusely scattered labeled cells could be observed in the dorsal part of the cervical spinal cord. It is concluded that the tectal afferent connections in the chondrichthyans studied in general resemble those of other vertebrates, but that some striking differences exist. In particular, tectal afferents originating from the nucleus medius infundibuli, the nucleus cerebelli, and the nucleus dorsalis and intermedius areae octavolateralis have not been reported in other vertebrates.
Retinal degeneration during clinical scrapie encephalopathy in hamsters
Authors: Buyukmihci Ned , Goehring‐Harmon Faye , Marsh Richard F.
Published: January 2005

Weanling hamsters were inoculated intracerebrally with brain suspensions from normal or scrapie‐infected hamsters. A third group of uninoculated animals was fed cuprizone. Histologic and electron microscopic examination of the neural retinas and retinal pigment epithelium was done. At 50 days postinoculation, when scrapie‐infected animals began to show clinical signs of encephalopathy, there was a variable degree of photoreceptor degeneration. By the time animals were moribund, at 74 days postinoculation, photoreceptor degeneration was severe, as demonstrated by loss of most outer and inner segments and cell bodies. The outer plexiform, inner nuclear, and inner plexiform layers were reduced in thickness. Some retinal pigment epithelial cells contained lipoidal inclusions. The neural retinas and retinal pigment epithelium of noninfected and cuprizone‐treated animals were normal. We have previously shown that the scrapie agent accumulates in the retina; that together with our present work, we conclude that the scrapie agent is the cause of photoreceptor degeneration in experimentally inoculated hamsters.
Peripheral control of midbrain mitotic activity in the frog
Authors: Kollros Jerry J.
Published: January 2005

Eyes were removed unilaterally from stage 19–25 embryos and stage I larvae of Rana pipiens. Control and operated animals were fixed 2–27 days later, at stages I through V +. Midbrains were removed and sectioned, and complete counts of all mitoses in both tecta were made, to permit comparisons between tecta receiving optic nerve fibers and those lacking them. Differences between the two sides were insignificant in control animals and in those fixed at stages I and II. In the 39 stage III animals differences approached significance (P < 0.06), whereas for stages IV and V, with 20 animals in each group, significance was seen (P < 0.01). Rostral parts of the tectum, richly supplied by optic nerve fibers, showed much greater percentage differences in mitotic activity than did the caudal parts of the tectum, poorly supplied or lacking such fiber input. Overall, areas of ventricular surface in the affected tecta at stages IV and V were reduced very nearly to the same degree as was cell division. The role of the optic nerve fibers in maintaining division rates is made evident, particularly by the reduction of numbers of prospective ependymal cells. That the influence is seen so very early implies that production of prospective neurons, not just glia, has been affected.
A light and electron microscopic study of the interstitial nucleus of cajal in rat
Authors: Rutherford J. G. , Gwyn D. G.
Published: January 2005

The morphology of the interstitial nucleus of Cajal (INC) in the rat was studied with the light and electron microscope. The INC was mapped throughout its rostrocaudal extent from cresyl violet‐stained frozen sections cut transversely through the midbrain in the stereotaxic plane. Caudally, the INC consisted of a small number of scattered cells lying ventrolateral to the periaqueductal grey. In three of four cases studied, the caudal tip of the nucleus was located between 40 and 120 μm rostral to the rostral tip of the somatic cell columns of the oculomotor nucleus. Proceeding rostrally, the INC increased in size, reaching its maximal development just caudal to its most rostral extent. The INC was limited rostrally by the fibers of the fasciculus retroflexus. The mean rostrocaudal length of the INC was 1.12 mm.

On the basis of light microscopic observations of cresyl violet‐stained paraffin sections, two groups of neurons could be distinguished in the INC. One group consisted of large, oval to multipolar cells with mean dimensions of 33 × 23 μm. The second group, which included by far the greatest number of cells, consisted of small to medium neurons, round, triangular, polygonal or fusiform in shape, with mean dimensions of 19 × 14 μm.

Injection of horseradish peroxidase into lesions in the cervical spinal cord resulted in retrograde labeling of neurons of all sizes and shapes throughout the length of the INC. Labeled neurons were also found in the red nucleus, the mesencephalic reticular formation, and the nucleus of the posterior commissure.

All the morphological varieties of neurons described with the light microscope could be identified in the electron microscope. Large neurons, and some cells of the small to medium group, contained well developed Nissl bodies, together with numerous cytoplasmic organelles. Many neurons in the small to medium group, however, did not contain conspicuous Nissl bodies, and had a poorly developed rough endoplasmic reticulum.

Axon terminals containing either round or pleomorphic vesicles were seen in the INC. Axosomatic synapses were formed by both types of terminals. Such synapses were usually symmetrical, regardless of the shape of the vesicles within the terminal. In a number of neurons, the percentage of the surface of the neuronal somata in direct apposition to axon terminals was measured. The results of such measurements suggest that a greater percentage (more than 50%) of the surface of larger neurons is apposed by axon terminals than is the case with smaller neurons, which, on the average, were invested by axon terminals over 15% of their total surface in any given single plane of section. Axon terminals investing the surfaces of proximal dendrites were morphologically similar to those in apposition to neuronal somata.
Immunohistochemical evidence of indolamine neurons in monkey spinal cord
Authors: Lamotte Carole C. , Johns Donald R. , de Lanerolle Nihal C.
Published: January 2005

In this study, we have identified over 150 cells in the adult macaque spinal cord that are immunoreactive when stained with an antibody to 5‐HT by means of the PAP method. The staining was blocked by preabsorption of the primary antibody by the 5‐HT‐BSA conjugate (used to generate the antibody) and by 5‐HT, while BSA, dopamine, norepinephrine, 5‐methoxytryptamine and tryptamine preabsorption did not block staining. In addition, the Falck‐Hillarp histofluorescence technique was applied to the lumbosacral cord from one of the three monkeys studied; results confirm the presence of cells with yellow fluorescence and rapid fading to brown characteristic for serotoninergic cells.

The neuronal identity of these immunoreactive cells is based on light and electron microscopic morphology and the presence of synaptic terminals in contact with labeled somata and dendrites. Most of these neurons were small (10–25 μm) and located ventral to the central canal in lamina X. Some processes of the cells extended into the intermediate gray and the ventromedial area of the ventral horn; other processes wrapped around large blood vessels in lamina X or around the wall of the central canal. Cells were most frequent in the cervical cord (approximately 6–7/mm length of cord) and less frequent in thoracic (1.5/mm), lumbar (3/mm), and sacral (2/mm) cord. A few cells were also found in the marginal and gelatinosa regions of the dorsal horn of the sacral cord.

Examination of sections from the medulla‐spinal cord junction (obex level) indicates that the spinal cells may be an extension of cell groups located near the raphe obscurus in the gray region around the IVth ventricle. The indolamine spinal cells may act as interneurons in spinal circuits, control spinal blood flow through vessel innervation, or play a role in CSF composition through central canal innervation.
Chandelier cells in rat visual cortex
Authors: Peters Alan , Proskauer Charmian C. , Ribak Charles E.
Published: January 2005

Golgi‐impregnated chandelier cells in rat visual cortex have been examined by both light and electron microscopy. All of the chandelier cells impregnated have their cell bodies within layer II/III and although they occur throughout area 17, there are increased numbers at the area 17/18a border and to a lesser extent at the area 17/18 border. Most of the chandelier cells are bitufted neurons, with groups of dendrites extending from the upper and lower poles of an elongate cell body, but some cells have a more multipolar configuration. The perikaryal cytoplasm is rich in rough endoplasmic reticulum and both the cell body and the sparsely spinous dendrites receive axon terminals forming symmetric and asymmetric synapses. The axons of these neurons arise from either the lower pole of the cell body or the base of one of the dendrites in the lower tuft, and the axons form laterally spread plexuses which terminate in vertical strings of boutons. The boutons in each string synapse with axon initial segments of layer II/III pyramidal cells, the uppermost bouton in each string being 7 to 14 μm distant from the pyramidal cell body. Some layer II/III pyramidal cells seem to receive boutons from more than one chandelier cell, others from a single chandelier cell, and still others appear to receive no chandelier cell terminals. The axon terminals of the chandelier cells are irregular in shape, contain pleomorphic synaptic vesicles, and form symmetric synapses. Evidence is presented to show that axon terminals exhibiting the same morphological features and site of synaptic termination as those of the chandelier cells contain glutamic acid decarboxylase (GAD), the enzyme which synthesizes GABA. Hence the chandelier cells are probably GABAergic, inhibitory neurons. Other GAD‐positive axon terminals synapse with the cell bodies, axon hillocks, and proximal portions of the axon initial segments of the layer II/III pyramidal cells, and these terminals are probably derived from the smooth and sparsely spinous stellate cells.
Quantitative electron microscopic analysis of the optic nerve of the turtle, Pseudemys
Authors: Geri George A. , Kimsey Randall A. , Dvorak Charles A.
Published: January 2005

It is estimated by means of electron microscopy that the optic nerve of the turtle Pseudemys scripta elegans contains 394,900 fibers of which approximately 80% are myelinated. The total fiber count agrees well withcounts obtained from electron microscopic studies on other turtle species. There are, however, differences among these species in the percentage of myelinated fibers in the optic nerve. The axon diameter distribution of the myelinated fibers (excluding myelin) has a mode at 0.87 μm while that of the unmyelinated fibers has a mode at 0.42 μm. Both distributions are unimodal and are of a similar form in all areas of the nerve sampled. The total fiber count reported here agrees well with previous reports of ganglion cell counts in Pseudemys and the characteristics of the fiber distributions are comparable to those reported for nonreptilian vertebrates.