bluuebunny/crossref_metadata_2025 huggingface dataset:
Long‐term survival of centrally projecting axons in the optic nerve of the frog following destruction of the retina
Authors: Matsumoto Dan E. , Scalia Frank
Published: May 2005

A significant number of unmyelinated axons and their synaptic endings in the frog, Rana pipiens, were found to retain a normal morphology long after separation from their cell bodies. At the end of various survival periods following unilateral removal of the retina, horseradish peroxidase (HRP) was administered to the optic nerve stump by a fiber‐filling method. In frogs maintained at 20°C, unmyelinated optic nerve axons conducted HRP from the site of application in the orbit to layers A, C, and E of the contralateral optic tectum, even though their retinas had been removed up to 69 days earlier. Such fiberfilling was absent beyond 19 days in other frogs surviving at 35°C. No labeled fibers were continuous with any intracerebral neurons. The HRP was always localized intraaxonally, and the marked axons and terminals were ultrastructurally normal. Counts of surviving axons from electron micrographs of the optic nerves showed that, at 20°C, more than half of the normal complement of unmyelinated axons disappeared in the first 10 days. All the myelinated axons degenerated during the first 6 weeks survival. However, approximately 55,000 normal‐appearing unmyelinated axons (12% of the unmyelinated fiber population) persisted in the optic nerve at 10 weeks following removal of the retina. The survival rate was lower at 35°C.

In other frogs, one eye was injected with 3H‐leucine to initiate axonal transport into the retinal ganglion cell axons. That eye was removed 48 hours later. Autoradiographic analysis of brain sections of frogs surviving an additional 31 to 61 days at 20°C showed strong labeling of the optic tract and layers A, C, and E of the contralateral optic tectum. The absence of displaced ganglion cells that might exist within the optic nerve was verified by other observations.

It is hypothesized that the potential shown by frog optic axons for long‐term survival in the absence of the cell‐body expresses a general property of vertebrate (and invertebrate) axons, rather than a special property of the frog optic nerve.
The structure, distribution, and quantitative relationships of the glia in the abdominal ganglia of the horse leech, Haemopis sanguisuga
Authors: Kai‐Kai M. A. , Pentreath V. W.
Published: May 2005

The glial cells in abdominal ganglia of the horse leech Haemopis sanguisuga were studied by electron microscopy and analysed quantitatively to evaluate the suitability of this easily obtainable carnivorous species for physiological studies.

Each abdominal ganglion contains eight giant glial cells, 12,000–14,000 small glial cells, and approximately 300 neurons. The giant glial cells constitute 44.6% and the small glial cells 6.4% of the ganglion's volume. The giant glial cells contain glycogen and bundles of filaments that are chiefly located in their periphery, close to the neurons into which they send processes. The small glial cells are frequently surrounded by the giant glial cells but also occur around neuronal perikarya and axon tracts, as well as against the basal lamina and connective tissue layers. The small glial cells contain lysosomes and sometimes form a trophospongium with the neurons. A system of extracellular channels, which is continuous with the basal lamina, indents the giant glial cells and extends around parts of the neurons. The extracellular channels contain a matrix that appears very similar to the basal lamina and to the cytoplasm in the processes of the small glial cells. Some of the extracellular channels contain collagen fibrils. Hemidesmosomes join the matrix‐filled extracellular channels to both the neurons and the giant glial cells. Ionic lanthanum has free access to the neurons and glial cells via the extracellular spaces and matrix‐filled channels. Areas of synaptic intermingling rarely contain glial cell processes.
Afferent connections to the amygdaloid complex of the rat with some observations in the cat. III. Afferents from the lower brain stem
Authors: Ottersen Ole P.
Published: May 2005

The projections from the medulla oblongata, pons, and mesencephalon to each nucleus of the amygdaloid complex of the rat were investigated by the use of retrograde transport of horseradish peroxidase (HRP). The enzyme was injected stereotactically by microiontophoresis using four different approaches.

The findings indicate that the majority of the ascending fibers terminate in the central and medial amygdalar nuclei. Injections in the central nucleus label neurons at the dorsal aspect of substantia nigra, pars compacta, and in the adjacent ventral tegmental area and peripeduncular nucleus. At more caudal levels, reactive neurons are found in the periaqueductal gray substance, various raphe nuclei, the locus coeruleus, the parabrachial nucleus, the nucleus of the solitary tract, and the mesencephalic and bulbar reticular formation. Injections in the medial nucleus lead to labeling of neurons in the peripeduncular nucleus, the dorsal raphe and superior central nuclei, the parabrachial nucleus, and in the dorsomedial extreme of the dorsal nucleus of the lateral lemniscus.

The parabrachial nucleus is the most important lower brain stem source of amygdalopetal fibers. This nucleus projects to the ipsilateral as well as the contralateral amygdala in a topographical manner.

Most of the lower brain stem structures found to project to the amygdala in the rat are identified as sources of amygdalopetal fibers in the cat as well.
Somatotopic organization of the thoracic spinal nerve in the dorsal horn demonstrated with transganglionic degeneration
Authors: Grant G. , Ygge J.
Published: May 2005

Transganglionic degeneration in primary sensory neurons (TGD) has been studied with the Fink‐Heimer and cupric silver methods in the adult rat after transection of thoracic spinal nerve branches. Degeneration was found in the ipsilateral dorsal horn after 13 to 53 days postoperative survival. It was observed in laminae III and IV, inconsistently in lamina I, but not in lamina II (substantia gelatinosa). After transection of the dorsal ramus of the spinal nerve degeneration was seen in the lateral third of the laminae. Transection of the intercostal nerve (ventral ramus) at about the costal angle gave rise to degeneration in the medial two‐thirds and transection more distally, at about the mid‐clavicular line, in the most medial part of the dorsal horn. The results are in accordance with previous anatomical and physiological studies of the somatotopical organization of the dorsal horn. They clearly show the usefulness of TGD as a tool for analysis of central projections of primary sensory neurons.
Asymmetries and symmetries in the number of thoracic dorsal root ganglion cells
Authors: Ygge J. , Aldskogius H. , Grant G.
Published: May 2005

The right/left ratio for the number of neurons in individual pairs as well as series of pairs of normal rat and guinea pig thoracic dorsal root ganglia have been investigated. After perfusion of the animals with aldehyde fixatives, the 13 pairs of thoracic ganglia were embedded in resin, serially sectioned, and stained with azur methylene blue. Counts of neuronal nucleoli (with correction for possible split nucleoli) were used as an indicator of the number of neurons in each ganglion. In individual pairs the right/left difference varied between 0 and 47% in the rat and 0 and 26% in the guinea pig. There appeared to be no particular level with a preference for large right/left differences. However, when the total number of neurons from the 13 ganglia on one side were compared with the corresponding figure from the other side, the right/left differences were reduced to less than 3% in the rat and less than 2% in the guinea pig. These results show that the organization of the thoracic spinal nerve unit is markedly asymmetrical at the segmental level, but strictly symmetrical in terms of the total number of dorsal root ganglion cells. The marked asymmetry in individual ganglion pairs necessitates caution when evaluating the effect of unilateral experimental manipulations on the number of neurons in thoracic spinal ganglia.
Age‐ and position‐dependent effects of monaural acoustic deprivation in nucleus magnocellularis of the chicken
Authors: Conlee John W. , Parks Thomas N.
Published: May 2005

The effect of a moderately severe monaural conductive hearing loss on the development of neuronal size in the avian nucleus magnocellularis (NM) was investigated. NM is considered to be the homologue of the mammalian anteroventral cochlear nucleus and receives large calyceal synaptic endings from the cochlear nerve. Silicone plastic earplugs which produce a 40 dB broadband conductive hearing loss were placed in one external auditory canal of chick embryos on the 18th day of incubation. After hatching, all animals were housed in communal brooders and sacrificed at 4, 10, 25, and 60 days of age. Nissl‐stained sections from paraffin‐ and plastic‐embedded brains were used to sample neuronal cross‐sectional areas in NM on the deprived and nondeprived sides of the brain. These samples were obtained separately in each brain from three posterior‐to‐anterior percentage quartiles within NM. Statistical analyses of these data showed that the severity of deprivation‐induced cell size changes in NM varied as a function of both age and position. In the 4‐ and 10‐day groups, no significant deprived‐versus‐nondeprived differences in neuronal size were seen in any area of the nucleus. At 25 days after hatching, only the third posterior‐to‐anterior quartile (i.e., 50–74%) showed a significant difference; this difference was also significantly greater than those in the second and fourth quartiles at this age. By 60 days, all three sampled areas in NM showed highly significant differences (averaging 12%) in mean neuronal cross‐sectional area. Cell size values from the deprived and nondeprived sides of 60‐day‐old experimental animals were also compared with values from 60‐day‐old control subjects. Whereas the deprived NM cells were significantly smaller than controls, there was no evidence for a reliable hypertrophy in the nondeprived cells. Thus, the principal effect of the acoustic deprivation produced was to retard continued growth of the deprived neurons after 4 days of age.
Cells of origin of pathways descending to the spinal cord in two chondrichthyans, the shark Scyliorhinus canicula and the ray Raja clavata
Authors: Smeets Wilhelmus J. A. J. , Timerick Steve J. B.
Published: May 2005

The cells of origin of pathways descending to the spinal cord in the shark Scyliorhinus canicula and in the ray Raja clavata have been demonstrated by using the horseradish peroxidase (HRP) technique. Following HRP injections in the spinal cord of Scyliorhinus (fourth to sixth segment) and of Raja (15th to 20th segment) labeled neurons could be identified in the rhombencephalon, the mesencephalon, and in the diencephalon. Cells of origin of diencephalic nuclei, which project to the spinal cord, were observed in the nucleus periventricularis hypothalami and in the thalamus ventralis pars medialis which can in this respect be considered hypothalamic. Descending pathways from mesencephalic structures originate from the interstitial nucleus of the fasciculus longitudinalis medialis, the tectum mesencephali, the nucleus intercollicularis, the tectotegmental junction zone, and from diffusely arranged tegmental neurons. A contralateral rubrospinal pathway could be recognized in Raja, but not in Scyliorhinus. Rhombencephalic cells of origin of pathways descending to the spinal cord were found in all parts of the reticular formation, i.e., the nucleus raphes inferior, the nucleus reticularis inferior, medius, superior, and isthmi, in two vestibular nuclei, and in three nuclei, which have been tentatively indicated as nucleus B, F, and G. Furthermore cells of origin of descending pathways have been found in the nucleus tractus descendens nervi trigemini, in the nucleus funiculi lateralis, and in the nucleus tractus solitarii. The descending pathways of the two species studied have been compared with those of other vertebrates. It is concluded that the basic pattern in the organization of descending pathways to the spinal cord, as proposed by ten Donkelaar ('76) for terrestrial vertebrates, also holds for cartilaginous fishes.
A quantitative light microscopic study of the dendrites of cat spinal α‐motoneurons after intracellular staining with horseradish peroxidase
Authors: Ulfhake B. , Kellerth J.‐O.
Published: May 2005

The cell bodies and dendrites of cat spinal α‐motoneurons were studied after intracellular staining with horseradish peroxidase.

The mean diameter of the soma was positively correlated to both the mean diameter and the combined diameter of the first‐order dendrites, but not to the number of first‐order dendrites. On the average, 11.2 dendrites originated from the soma.

The dendritic trees were more extensive than has been described previously. The mean value for the combined length of a whole dendrite was 4.7 mm, while the mean values for the total surface area and volume of a dendrite were 33.0 × 103 m̈m2 and 27.2 × 103 m̈m3, respectively. The diameter of the first‐order dendrite was positively correlated to the combined length of the entire dendrite, the number of dendritic branching points, and the number of dendritic end branches. The diameter of the first‐order dendrite was also directly proportional to the volume and the surface area of the entire dendrite. About 75% of the dendritic surface area and 55% of the dendritic volume was located more than 300 m̈m away from the soma. The dendrites constituted about 97% of the surface area and about 75% of the volume of the entire motoneuron (excluding the axon).

The dendritic tapering was moderate. On the average, the distal decrease in dendritic diameters caused a reduction in the combined dendritic parameter (Σ3/2) by 1.5% and 15% at 500 m̈m and 800 m̈m distance, respectively, from the soma.
A quantitative light microscopic study of the dendrites of cat spinal γ‐motoneurons after intracellular staining with horseradish peroxidase
Authors: Ulfhake B. , Cullheim S.
Published: May 2005

By the use of intracellular staining with horseradish peroxidase (HRP), the dendric systems of spinal γ‐motoneurons of the adult cat were studied with a light microscope.

The dendrites extended in various directions up to 1.5 mm from the cell body. The dendric branching was sparse and even unbranched dendrites were occasionally seen. The number and combined diameter of the first‐order dendrites increased in parallel with the mean cell body diamter.

The number of dendric end branches, the combined dendritic length, the membrane surface area, and the volume of the entire dendrite correlated positively with the diameter of the parent first‐order dendrite.

In comparison with the α‐motoneurons (Ulfhake and Kellerth, '81) the γ‐motoneurons had smaller values for mean cell body diameter and mean diameter of the first‐order dendrites and they also had a smaller number of first‐order dendrites. The dendrites of the γ‐motoneurons were also found to have fewer branching points and larger values for combined dendritic length. The relation between the diameter of the first‐order dendrite and the surface area of the entire dendrite was almost identical for the two types of motoneurons.
Ontogeny of somatostatin‐containing neuron system of the rat: Immunohistochemical observations. I. Lower brainstem
Authors: Shiosaka Sadao , Takatsuki Kenichi , Sakanaka Masahiro , Inagaki Shinobu , Takagi Hiroshi , Senba Emiko , Kawai Yuriko , Tohyama Masaya
Published: May 2005

The ontogeny of the somatostatin (SRIF) neuron system in the lower brainstem of the rat was analyzed using the indirect immunofluorescence technique of Coons.

SRIF‐positive structures first appeared in the primordium of the ventral nucleus of the lemniscus lateralis of the rat fetus corresponding to gestational day 15 (12–14‐mm embryos). On and after gestational day 15, these structures appeared in progressively more diverse areas of the lower brainstem and continued to show an increase in number and intensity up till birth. The maximum SRIF‐positive structures were histochemically identified in the lower brainstem at the perinatal stage. However, after birth, the numbers of SRIF‐positive structures in the lower brainstem began to decrease as the rat grew and none or only a few SRIF‐positive structures were detected in the adult rats. This ontogenetical study of the SRIF neuron system in the lower brainstem of the rat strongly suggests that SRIF might play an important role in the development of the lower brainstem other than in its neurotransmitter or neuromodulator function.
The dorsal lateral geniculate nucleus of the normal ferret and its postnatal development
Authors: Linden D. Card , Guillery R. W. , Cucchiaro Josephine
Published: May 2005

The anterograde transport of 3H proline and of horseradish peroxidase has been used to study the retinogeniculate pathway in normal adult ferrets and in young ferrets during postnatal development. The lateral geniculate nucleus in adults shows a characteristic “carnivore” pattern, with layers A, A1, C, C1, C2, and C3, and a medial interlaminar nucleus recognizable either cytoarchitectonically or on the basis of the retinogeniculate innervation. In addition, there is a well‐defined, rather large perigeniculate nucleus.

At birth the lateral geniculate nucleus is unlaminated and essentially all parts are reached by afferents from both eyes. The crossed component is by far the larger. It extends from the optic tract medially well into the perigeniculate field, in contrast to the uncrossed component which barely reaches the perigeniculate field. During the first 3 postnatal days the uncrossed fibers restrict their arbors to a small posterior and medial region, the precursor of the binocular segment of the nucleus. The crossed fibers gradually retreat from the region within which the uncrossed fibers have concentrated. Between the fourth and eighth postnatal days the field occupied by the ipsilateral component expands again to form a major focus that will define lamina A1 and a minor focus that will define C1. At this stage the crossed and the uncrossed fibers overlap at the borders of lamina A1 and the whole region of lamina C1 is also occupied by arbors of the crossed component. The perigeniculate field becomes clearly distinguishable from the lateral geniculate nucleus and the medial interlaminar nucleus is becoming clearly recognizable between days 3 and 8.

Between days 8 and 15 the cytoarchitectonic borders between layers A and A1 become clearly defined, but the retinogeniculate axons from each eye still extend across this border. These axons retreat into their appropriate lamina after the 15th postnatal day and the nucleus reaches its essentially adult structure by about the fourth postnatal week. Segregation of retinofugal axons in the C layers occurs after segregation in the A layers, but many of the cells within the C layers show signs of cytological maturity earlier than those of the A layers. The nucleus undergoes a series of migrations and changes of shape as the ipsilateral and contralateral components become segregated. Whereas in the newborn the nucleus is roughly comma‐shaped and on the lateral aspect of the dorsal thalamus, in the adult it is “L”‐shaped and mainly on the posterior aspect of the dorsal thalamus.
3H‐thymidine long survival autoradiography as a method for dating the time of neuronal origin in the chick embryo: The locus coeruleus and cerebellar Purkinje cells
Authors: Yurkewicz Lorraine , Lauder Jean M. , Marchi Mario , Giacobini Ezio
Published: May 2005

Contrary to previous assumptions, we have found that a single dose of 3H‐thymidine (25 μCi), injected into the yolk sac of White Leghorn chick eggs on 2 days of incubation (d.i.) only remains available for DNA‐synthesizing (proliferating) cells for 48 hours following the time of injection. This finding now makes it possible to date the time of neuronal origin in the avian embryo using a single injection of isotope and a long survival time (30 days posthatch) as in mammalian studies where 3H‐thymidine is only available as a short “pulse.” Using this method, we have determined that neurons in the chick locus coeruleus (LC) cease proliferation on 2–6 d.i. with a peak of neuronal genesis on 3–5 d.i. In addition, neuronal genesis is not homogeneous throughout the LC cell population, but occurs in a predominantly caudorostral gradient. Conversely, the cerebellar Purkinje cells cease division on 3–8 d.i. with a peak of heavy labeling on 4–6 d.i., 1 day later than that observed in the LC.
Multiple classes of photoreceptors and neurons in the frontal organ of Rana pipiens
Authors: Eldred William D. , Nolte John
Published: May 2005

An attempt has been made to characterize the photoreceptors and neurons of the frontal organ of Rana pipiens and the synaptic contacts of these cells, in order to provide morphological correlates for previous physiological findings. Neurons, glial cells, and photoreceptors with two different appearances can be seen in normal anatomical preparations. The photoreceptors make ribbon synaptic contacts onto both neurons and other photoreceptors. Retrograde transport of either cobalt or horseradish peroxidase through the frontal nerve results in labeling of neurons which are often located near the exit point of the frontal nerve from the frontal organ. Some of the dendritic processes of these neurons ramify among the neurons themselves, while others ramify among the photoreceptors. In addition, the frontal organ contains two photoreceptor types which synaptically contact both neurons and other photoreceptors. In some frontal organs labeled with cobalt (but never in peroxidase‐labeled preparations) certain photoreceptors were also labeled. The labeled photoreceptors were probably the result of transcellular cobalt movement from labeled neurons, and not the result of some photoreceptors having axons in the frontal nerve. These results are discussed in conjunction with physiological evidence that chromatic interactions occur within single photoreceptors, each of which contains a single visual pigment with two physiologically active states.
Organization and development of brain stem auditory nuclei of the chicken: Dendritic development in N. Laminaris
Authors: Smith Zaid D. J.
Published: May 2005

Nucleus laminaris (NL) is a third‐order auditory nucleus in the avian brain stem which receives spatially segregated binaural inputs from the second‐order nuclei magnocellularis. The examination of the development of dendritic structure in NL revealed a number of events:

In the initial period of dendritic growth (E 8–9) there is no gradient of dendritic morphology or apparent size.

Starting about E 9–10, there is a spatiotemporal gradient of proliferation of numerous fine dendritic processes, from rostromedial to caudolateral, corresponding with the morphological lamination of NL, and possibly with the onset of cell death. This is followed by a spatiotemporal gradient of the elimination of the overproliferated processes, from rostromedial to caudolateral, possibly coinciding with the cessation of cell death. A result of the spatiotemporal gradients of dendritic process proliferation and elimination is a spatial gradient in the morphology (extension, branching) of the remaining “mature” dendrites.

At E 15 there is only a slight spatial gradient of total dendritic size across NL; this gradient is larger at E 19, and by P 25 there is a 13‐fold change in dendritic size from rostromedial to caudolateral. Regression analyses suggest the size gradient begins to form when NL activity becomes driven by cochlear activity, at about E 14. The progressive formation of the size gradient is largely the result of two factors: the growth of dendritic trees, and the loss of primary dendrites.

The growth rate of the dendritic trees of NL cells was found to be very highly correlated with the intensities of the sound frequencies to which the cells respond.

From E 15 to P 25 there is a 50% loss of the “mature” primary dendrites of NL neurons.

The separate dorsal and ventral dendritic size gradients seen at E 15 realign to coincide at E 19, and the moderate correlation of dorsal and ventral dendritic sizes seen at E 15 and E 19 is significantly increased at P 25, indicating a developmental process of sharpening in the relationship of the dorsal and ventral dendritic organizations in the nucleus.

The data suggest that a key element in the regulation of dendritic size and structure in n. laminaris may be the activity of the afferents to the cells.
Retinal projections in the goldfish: A study using cobaltous‐lysine
Authors: Springer Alan D. , Gaffney James S.
Published: May 2005

Cobaltous lysine applied to the distal stump of a severed opticnerve was used to study the retinal projections of normal adult goldfish. Both the termination areas of optic axons and the pathways they traveled were established. Contrary to previous descriptions of the goldfish visual system, the optic nerves do not decussate completely at the optic chiasm. Fascicles that entered the ipsilateral optic tract innervated targets in the ipsilateral thalamus and optic tectum. Other optic fibers crossed the posterior commissure from the contralateral side of the brain and also innervated the ipsilateral tectum and thalamus. In addition, optic fibers bilaterally innervated a hypothalamic target in close proximity to the infundibulum that may correspond to the nucleus tuberis lateralis. The contralateral preoptic region contained two discrete areas of innervation, each served by separate fascicles. The ipsilateral preoptic region was similarly innervated, but more sparsely. Fibers that entered the contralateral ventral thalamus originated from three fascicles and terminated in three distinct targets. In contrast, three targets in the contralateral dorsal thalamus were served by one fascicle, and fibers passed from one nucleus to the other two. Innervation of the ipsilateral thalamus was similar to that seen contralaterally. Each main optic tract divided into three tracts, two of which entered the optic tectum, while the other innervated several pretectal areas. Other fibers innervated an accessory optic nucleus located near nucleus glomerulosus. The contralateral tectum contained numerous radially oriented optic fascicles. These fascicles represented optic fibers that left thalamic and pretectal targets to enter the optic tectum from beneath the stratum periventriculare. Optic fibers were also observed in the transverse commissure, tractus rotundus, horizontal commissure, tractus rotundus, horizontal commissure, tectobulbar tract, and fasciculus retroflexus. Therefore, it appears that many of the anomalous projections seen after tectal ablation or after optic nerve crush are not in fact aberrant. Such projections probably reflect the presence of unusually large numbers of optic fibers in tracts that normally contain optic axons, as well as increased innervation of areas that normally receive sparse retinal projections. Filled tectal cells that could represent cells projecting to the retina were not observed in either tectal lobe. The ipsilateral retinal projections could not be attributed to cobaltouslysine being transneuronally transported in readily detectable amounts.
Aging in the rat olfactory system: Correlation of changes in the olfactory epithelium and olfactory bulb
Authors: Hinds James W. , McNelly Nancy A.
Published: May 2005

Two regions closely linked synaptically (olfactory epithelium and olfactory bulb) have been compared in an agegraded series of rats. Previous findings of growth and atrophy of constituent elements in Sprague‐Dawley Wisconsin (SD) rats have now been confirmed in Charles River (Crl) rats. In the olfactory bulbs of Charles River (Crl) rats, the volume of layers, the number of olfactory axodendritic synapses in the glomeruli, the total volume of glomerular dendrites, and the size of mitral cell bodies all approximately double between 3 and 24–27 months, and then all decrease by 36 months. Unlike SD rats, however, no loss in the number of mitral cells occurs in Crl rats, and the increase in volume of the olfactory bulbs from 3 to 24 months is approximately double that of SD rats. In the olfactory epithelium the total number of septal olfactory receptors more than doubles between 3 and 18–24 months and then declines markedly, as does the volume of olfactory axons in olfactory bulb glomeruli. Comparison of the regression lines for changes in number of septal receptors with that of the size of mitral cell bodies discloses that the decline in number of receptors begins several months earlier than the decline in mitral cell size. This suggests that the atrophic changes in the olfactory bulb may in part be secondary to changes in the receptors of the olfactory epithelium. Numbers of synapses in the glomeruli appear to decline less markedly with age than the number of receptors, and a significant increase in number of synapses per receptor occurs in the oldest group studied (33 months), suggesting a compensatory increase in the relative number of synapses per receptor in the surviving receptors.
Structural patterns in the corpora pedunculata of orthoptera: A reduced silver analysis
Authors: Weiss Mitchell J.
Published: May 2005

The calyx region and pedunculus of the corpora pedunculata (“mushroom bodies”) were studied comparatively in reduced silver preparations of the brain from 16 species of Orthoptera representing four families (Acrididae, Gryllidae, Tettigoniidae, and Gryllacrididae). In the acridid grasshopper Melanoplus femurrubrum (de Geer), on which emphasis was placed, the concave primary calyx is bilayered and exhibits a special central zone. Globuli cell axons occur within both layers. The bulbous accessory calyx is unlayered and sends anterior extensions beneath the primary calyx. The main input tracts into primary and accessory calyx, respectively, are the tractus olfactorio‐globularis and tritocerebral tract. The pedunculus consists of one barrel with three major fiber columns, of which two originate in the primary calyx and one in the accessory calyx. Its fibers display a coaxial arrangement, superimposed on the tripartite organization. Structural conditions in other acridids are similar.

In the other families the calyx region similarly includes a bilayered primary calyx and unlayered accessory calyx. The latter, variable in form, is closely associated with the base of the primary calyx in tettigoniids and gryllacridids. The calyces receive the same major tracts as in acridids. The pedunculus is coaxially organized.

These features are theorized to have originated as follows. In the progenitors of Orthoptera the corpora pedunculata included two mutually equivalent, bilayered calyces and a “double‐barreled” pedunculus. The orthopteran primary calyx arose through coalescence of these calyces. Concomitantly, the two peduncular barrels fused into one. The accessory calyx originated at the base of the primary calyx, from the class of globuli cell axons of the latter's external layer. Probably this occurred in response to increased functional importance of tritocerebral input.
Monoamine cell distribution in the cat brain stem. A fluorescence histochemical study with quantification of indolaminergic and locus coeruleus cell groups
Authors: Wiklund Leif , Léager Lucienne , Persson Mats
Published: May 2005

The distribution of monoaminergic cell bodies in the brainstem of the cat has been examined with Falck‐Hillarp fluorescence histochemical technique. Quantitative determinations indicate that the cat brainstem contains about 60,300 indolaminergic (IA) cells. The majority of these (about 46,700, or 77.5%) are located within raphe nuclei. The largest number is contained within nucleus raphe dorsalis (RD), accounting for around 24,300 IA cells, while raphe pallidus (RP) holds about 8,000, raphe centralis superior (RCS) 7,400, raphe magnus (RM) 2,400, raphe obscurus (RO) 2,300, linearis intermedius (LI) 2,100, and the raphe pontis (RPo) only some 280 IA cells. The IA cells represent, however, only part of the neuronal population of raphe nuclei, which, in addition, hold varying numbers of other medium‐sized and small‐sized neurons. Thus, quantifications in Nissl‐stained material indicate that the IA cells make up about 70% of the medium‐sized cells in RD, 50% in RP, 35% in RCS and RO, 25% in LI, 15% in RM, and only 10% in RPo. The substantial numbers of small‐sized perikarya observed in all raphe nuclei may represent interneurons.

Significant numbers of IA cells were consistently located outside the raphe nuclei at all brainstem levels. In all, these amounted to approximately 13,600, or 22.5% of the total number of IA cells. Thus, IA cells occurred in the myelinated bundles, and sometimes in reticular formation, bordering the raphe nuclei; in the ventral brainstem forming a lateral extension from the ventral raphe (RP, RM, RPo, RCS, and LI) to the position of the rubrospinal bundle; in the periventricular gray and subjacent tegmentum of dorsal pons and caudal mesencephalon; in the locus coeruleus (LC) complex; around the motor trigeminal nucleus; caudal to the red nucleus; and in the interpeduncular and interfascicular nuclei. The wide distribution of IA cells leads to a considerable mixing with catecholaminergic (CA) cell groups.

Our observations on CA cell distribution are essentially in accordance with previous reports. Quantifications indicate that the LC complex contains about 9,150 CA cells, unilaterally. A previously unnoticed group of scattered CA cells was found in relation to the vestibular nuclei and extending dorsally toward the deep cerebellar nuclei.
Plasticity in the chick ventral lateral geniculate nucleus
Authors: Crossland W. J.
Published: May 2005

The chick ventral lateral geniculate nucleus (GLv) receives topographically corresponding projections from the retina and optic tectum. Tectal lesions produced on the day of hatching removed the tectogeniculate input to the GLv region corresponding to the tectal lesion and also severed some retinotectal axons. Following a survival period of 3 to 10 weeks, a patch of augmented retinogeniculate projection was noted in the GLv segment that corresponds topographically to the damaged area of the tectum. Changing the site of the tectal lesion led to changes in the locus of heavy retinal projection to the GLv predictable from topographic maps. Nuclei which received retinal but not tectal projections did not appear to have regions of augmented retinal termination nor did nuclei which received tectal but not retinal innervation. It is unlikely that the increased retinogeniculate termination is due to rerouting of growing retinotectal axons since the chick retinofugal pathway is well established by the time of hatching. Furthermore, there was no evidence of a projection from the ipsilateral eye to the affected GLv. On the basis of these light microscopic studies, it would appear that retinogeniculate terminals have sprouted in the GLv and that competition for terminal space, conservation of terminal space, proximity, and perhaps other factors are necessary for the augmented projection to occur.
The hippocampal mossy fiber system of the rat studied with retrograde tracing techniques. Correlation between topographic organization and neurogenetic gradients
Authors: Gaarskjaer Frank B.
Published: May 2005

The topographical organization of the hippocampal mossy fiber system, which connects the dentate granule cells with the pyramidal cells of the regio inferior, has been examined in rats with retrograde tracing methods. Following the application of the fluorescent dye True Blue to different parts of the mossy fiber layer in the hippocampal regio inferior, retrogradely labeled granule cells were observed in the dentate fascia. The distribution of the labeled cells within the dentate granule cell layer indicates that all mossy fibers have an almost parallel, slightly descending course in regio inferior near the dentate hilus. In the ventricular part of regio inferior, particularly toward the transition to the regio superior, the mossy fibers are sorted out according to the position of their parent cell bodies within the granular layer. Near the transition to regio superior the fibers from lateral granule cells extend both septally and temporally over a longer distance than the fibers from more medial cells. Similarly, the fibers coming from the superficial cells extend both septally and temporally over a longer distance than those from the deep cells. The mossy fibers arising from a specific septotemporal level of the dentate fascia innervate a segment of the regio inferior that extends approximately 180 μm above to approximately 1,600 μm below the level of origin. Similar results were obtained following injections of Nuclear Yellow and horseradish peroxidase.

Since previous studies have demonstrated that the granule cells are formed along gradients from lateral to medial and from superficial to deep, there appears to be a correlation between the formation, and hence the position, of the granule cells and the topography of their projection into the regio inferior.
Experimental studies on cerebellar foliation. I. A qualitative morphological analysis of cerebellar fissuration defects after neonatal treatment with 6‐OHDA in the rat
Authors: Sievers J. , Mangold U. , Berry M. , Allen C. , Schlossberger H. G.
Published: May 2005

The present report describes the natural history of defective cerebellar fissuration in the rat after neonatal treatment with 6‐hydroxydopamine (6‐OHDA). Within 24 hours after an intracisternal (IC) injection of 100 μg 6‐OHDA cerebellar pial fibroblasts degenerated almost completely and were phagocytosed by macrophages within 2–5 days postinjection (dpi) leaving the cerebellar surface denuded of pia. Bergmann glia end feet at first exhibited morphological signs of gliosis and later formed new sprouts that penetrated the basal lamina and grew into the subarachnoid space covering regenerating pial fibroblasts and also invading ectopic colonies of external granular layer (EGL) cells. Breaches in the basal lamina appeared after the pial fibroblasts had been destroyed and were confined to areas where Bergmann glia end feet were absent and where EGL cells were opposed to the basal lamina. EGL cells escaped through these fractures into the subarachnoid space in the fissures, where they proliferated to form large colonies of granule and stellate cells. In those fissures in which EGL ectopia featured, opposing folia fused and fissures were lost. These findings suggest that pial fibroblasts and the basal lamina have an important role in maintaining lobular partition during development of the cerebellum, in establishing cerebellar fissures, and in consolidating Bergmann glia‐EGL cell relationships as a prerequisite for orderly migration of EGL cells.
Experimental studies on cerebellar foliation. II. A morphometric analysis of cerebellar fissuration defects and growth retardation after neonatal treatment with 6‐OHDA in the rat
Authors: Allen C. , Sievers J. , Berry M. , Jenner S.
Published: May 2005

Quantitative analyses were undertaken of the gross morphological changes in cerebellar foliation and fissuration patterns in the rat induced by neonatal treatment with 6‐hydroxydopamine (6‐OHDA). After an intracisternal (IC) injection of 100 μg 6‐OHDA, cerebella were much smaller than those of controls and progressively developed abnormal fissures with age, characterized by a loss of pial coverings and fusion of adjacent external granular layers (EGL). Such deformities were most severe anteriorly with relative sparing of posterior fissures. It was also found that the growth rate of individual folia was reduced differentially with a clear linear relationship between the magnitude of the reduction of folial growth rates and the extent to which adjacent fissures were spared. This relationship implied that the basal lamina fractured when the rate of expansion of folia outstripped the rate of deposition of the lamina.

The adverse effects of 6‐OHDA on pial fibroblasts were reduced by concomitant IC injection of 10 μg bovine serum albumin (BSA) which allowed fissures to develop normally although most other cerebellar growth defects were unaltered. These findings thus demonstrated the importance of the pia mater for the establishment of fissures.

Folia were diminutive after 6‐OHDA treatment but otherwise surprisingly normal even in areas where pia‐lined fissures were absent. This finding suggests that although foliation and fissuration may be complementary morphogenic entities, the former is the primary event resulting from buckling forces generated by proliferation of EGL cells during ontogeny. Basal lamina investment is dependent on glia limitans/pia mater interaction, which normally keeps pace with folial expansion.
The intercollicular pathway in the golden hamster: An anatomical study
Authors: Fish Stephen E. , Goodman Dianne K. , Kuo David C. , Polcer Jeffrey D. , Rhoades Robert W.
Published: May 2005

The intercollicular pathway of the hamster was studied by means of a combination of horseradish peroxidase (HRP), autoradiographic, and double‐labeling (nuclear yellow‐HRP) techniques. Small deposits of HRP marked significant numbers of cells in the contralateral colliculus only when the injection site included the laminae ventral to the stratum opticum. Anterior deposits labeled many more neurons than injections into the caudal part of the tectum. Of the cells labeled by our injections, 18.2% were located in the superficial collicular laminae (stratum griseum superficiale and stratum opticum), and the remainder (81.8%) were in the deep layers. A wide variety of morphological cell types contributed axons to the intercollicular projection, and in a given animal the loci of the labeled neurons were generally symmetrical with the injection site.

Small deposits of [3H]‐leucine resulted in contralateral labeling only when the injection included the deep collicular laminae. The transported label was most dense in the stratum griseum intermediale and stratum griseum profundum, and its location was generally homotopic with the injection site.

Experiments in which collicular HRP deposits were combined with large cervical spinal or pontine reticular injections of Nuclear Yellow indicated that intertectal neurons did not, in most cases, contribute axon branches to the spinal or pontine reticular projections of the colliculus.

Receptive field data obtained at the time of the HRP and/or [3H]‐leucine deposits demonstrated that the collicular representations of the ipsilateral and at least 45° of the contralateral hemifields were encompassed by intercollicular connections. This was also true for the somatosensory representation of the entire head and a portion of the neck.
Locust local nonspiking interneurons which tonically drive antagonistic motor neurons: Physiology, morphology, and ultrastructure
Authors: Wilson John A. , Phillips Christine E.
Published: May 2005

Local nonspiking interneurons have been implicated in the control of behavior. We have characterized the physiology of two local nonspiking interneurons in the locust and subsequently examined the neurons in the light and electron microscopes. Physiologically the two interneurons have opposite effects upon antagonistic motor neurons and are tonically releasing transmitter at their “resting potentials.” This combination of tonic release and reciprocal driving of antagonistic motor neurons by single interneurons provides a hitherto undescribed means of controlling posture. One interneuron (DCVII, 4) excites flexor tibiae and inhibits the slow extensor tibiae motor neurons when depolarized. The other interneuron (DCVII, 5) inhibits the flexor tibiae and excites the slow extensor tibiae motor neurons when depolarized. In both cases, when the interneurons are hyperpolarized, they have the opposite effects upon the same motor neurons. Intracellular staining of these neurons confirms that they are local interneurons. Furthermore, an examination of sectioned material shows that the neurons are unique and can be identified as such in a population of locust neurons. Ultrastructurally, we find synapses only on the smaller (less than 2 μm) branches. These neurons may form the presynaptic element in either of two configurations, these being the discrete density (one presynaptic, one postsynaptic) and the dense bar (one presynaptic, two postsynaptic) type of configurations. The functional implications of these findings for neurons controlling posture are discussed.
Retinal W‐cell projections to the medial interlaminar nucleus in the cat: Implications for ganglion cell classification
Authors: Rowe Michael H. , Dreher Bogdan
Published: May 2005

The perikaryal sizes and retinal distribution of ganglion cells labeled after small iontophoretic injections of horseradish peroxidase (HRP) into the medial interlaminar nucleus (MIN) were studied. Injections were also made into the LGNv and the C‐laminae of the dorsal lateral geniculate nucleus (LGNd) for comparison. The results are consistent with suggestions that the MIN contains three approximately vertically oriented laminae which, from medial to lateral, receive their retinal input from, respectively, contralateral nasal, ipsilateral temporal, and contralateral temporal retina.

Each MIN lamina receives afferents from two distinct groups of retinal ganglion cells: (1) cells with large somas (over 25 μm), coarse primary dendrites, large dendritic trees (500–900 μm in diameter), and coarse axons; (2) cells with medium‐sized somas (14–20 μm), medium‐caliber primary dendrites, large dendritic trees (350–700 μm), and fine axons. The large cells are clearly Y‐cells or alpha cells, and they provide approximately 50% of the retinal input to all layers of the MIN. The medium‐sized cells, which provide the remaining 50% of the retinal input to the MIN, are, we argue, W‐cells, since they do not differ in soma size, dendritic morphology, axon caliber, or receptive field properties from medium‐sized W‐cells which project to other thalamic or midbrain structures. These results suggest two phylogenetic trends within the W‐cell group: (1) the differentiation of thalamic and midbrain components; and (2) the further differentiation of ipsilateral and contralateral projections within the midbrain component. This latter division corresponds to the distinction between W1 and W2 cells described previously (Rowe and Stone, '77, '80).