bluuebunny/crossref_metadata_2025_split huggingface dataset:
Expansion of the ipsilateral retinal projection in the frog brain during optic nerve regeneration: Sequence of reinnervation and retinotopic organization
Authors: Stelzner Dennis J. , Bohn Ronald C. , Strauss Judith A. 
Published: May 2005

AbstractThe sequential reinnervation and distribution of optics axons in diencephalic and mesencephalic targets was studied after crushing the optic nerve in 37 adult Rana pipiens. Following intravitreal injection of 3H‐proline at various times after nerve crush the distribution of regenerating optic axons was traced using autoradiographic methods. The maximal distribution of regenerating axons was reached between 6 and 8 weeks after optic nerve crush. On the contralateral side of the brain, the distribution of fibers was similar to the normal projection. Ipsilaterally, silver grain density was greater than normal in the optic tract and projections were expanded to all optic targets on this side of the brain. These abnormal projections were sustained for a least 6 months after nerve crush.The sequence of reinnervation of targets on both sides of the brain differed from normal development. Unlike development, regenerating optic axons were found in the ipsilateral optic tract prior to the time they were found on the contralateral side of the brain. Also unlike development, regenerating axons did not begin to reinnervate targets in the anterior thalamus until several weeks after reinnervation of the posterior thalamus and tectum had begun. The expanded distribution of regenerating axons within optic targets on the ipsilateral side of the brain became evident at the time optic axons first invaded each area.Most optic axons appeared to regenerate from the point of nerve crush. The retinal stump of the crushed nerve was filled with labeled axons in all six frogs given intravitreal 3H‐proline injections between 1 and 7 days after nerve crush. In addition, using a modified Fink‐Heimer method, few degenerating axons were found in the retinal stump of four frogs sacrificed between 2 and 8 days after optic nerve crush.In ten frogs studied between 3 and 6 months after nerve crush, horseradish peroxidase (HRP) was placed on different portions of the tectum ipsilateral to the crush. In each case HRP was retrogradely transported to ganglion cells in both retinae. The cells labeled in the ipsilateral retina corresponded in position to the same region of the contralateral retina although many fewer cells were labeled ipsilaterally. Cutting the optic tract on the side opposite the HRP placement did not affect the results. No ganglion cells were labeled in the ipsilateral retina of two frogs not receiving optic nerve crush.These results show that axons from all parts of the retina regenerate to the ipsilateral side of the brain during optic nerve regeneration and the distribution of these misrouted axons, at least to the tectum, overlaps the intact distribution from the other eye. Differences between development and regeneration in the patterns of growth of optic axons may be related to this anomaly.
Projections from the pontine nuclei proper and reticular tegmental nucleus onto the cerebellar cortex in the cat. An autoradiographic study
Authors: Kawamura Koki , Hashikawa Tsutomu 
Published: May 2005

AbstractAfter injections of 0.5 μI of tritiated leucine and/or proline into various parts of the pontine nuclei proper or the pontine tegmental reticular nucleus (N.r.t.) of 34 cats, labeled terminals of pontocerebellar fibers were found in the cerebellar cortex.Fibers from the pontine nuclei and N.r.t. terminate as mossy fibers in the granular layer of the cerebellum, and no evidence is obtained of labeled fibers in the molecular layer. The pontocerebellar projection is, in general, bilateral with a contralateral preponderance, and a complex organization has been shown to exist in the cat.Clear evidence of divergence of this projection from a small pontine area has been demonstrated. Thus, the dorsolateral nucleus has a heavy projection to lobule VII, besides modest projections to lobules VI, VIII, and IX, crus I and II, paraflocculus, and paramedian lobule. On the other hand, a particular cerebellar region receives afferent fibers from several pontine regions, confirming previous HRP studies. For example, lobule VII receives heavy projections from parts of the dorsolateral, peduncular, and paramedian nuclei, less heavy projections from the lateral part of the lateral nucleus, and some from other parts of the pontine nuclei. This is a convergent feature of the pontocerebellar projections.In addition, small adjoining areas within a pontine subdivision have different patterns of cerebellar projections, showing preferential sites of terminations. This suggests some degree of localization within the pontine nuclei. The cerebellar projection from the N.r.t. shows an essentially similar organization as the projection from the pontine nuclei proper, an apparent difference being only that the former is more extensive in the fields of termination than the latter.Some evidence for a parasagittal termination of pontocerebellar projections to the paramedian lobule has been found in this study. However, this is not as clear‐cut as such patterns in the cerebellar projections from the spinal cord, cuneate nucleus, and lateral reticular nucleus shown recently in rat and cat.
The phrenic nucleus of the albino rat: A correlative HRP and Golgi study
Authors: Goshgarian Harry G. , Rafols José A. 
Published: May 2005

AbstractThe phrenic nucleus of the adult albino rat was studied by utilizing the O‐dianisidine method for the retrograde transport of horseradish peroxidase in conjunction with the zinc chromate modification of the Golgi technique. Application of HRP to the transected phrenic nerve in the neck labeled a column of phrenic motor neurons from C3 to C5 in the ipsilateral spinal cord. However, when HRP was applied to the phrenic nerve intrathoracically, labeled neurons were found from C3 to C6. The long axis of the column of phrenic neurons was oriented tangentially from rostral to caudal poles. There was a gradual shift of the column from posterior to anterior and from lateral to medial positions in the ventral horn. The peroxidase material was also used to localize impregnated phrenic motor neurons in the Golgi sections and to provide quantitative data on phrenic motor neurons. In Golgi‐impregnated material two types of phrenic neurons were distinguished on the basis of dendritic morphology and orientation. These neurons were designated (1) larger neurons with smooth, radially oriented dendrites, and (2) smaller neurons with varicose, tangentially oriented dendrites. Both types of neurons had a small number of spines and bulbous appendages issuing from the dendritic trunks and branches. The dendritic fields of adjacent phrenic neurons overlapped extensively with one another and with dendrites of more distally placed ventral horn motor neurons. In peroxidase‐labeled sagittal sections the dendrites of phrenic neurons were primarily oriented in the rostrocaudal plane. The mean total number of peroxidase‐labeled neurons in the phrenic nucleus was 415.75 ± 18.36 cells. In sagittal sections the mean long axis diameter of phrenic cell bodies was 34.5 μm. In frontal sections the mean long axis diameter of phrenic cell bodies was 22.5 μm. Thus, from direct measurement, the phrenic neurons were 34% longer in the sagittal plane than in the frontal plane. In the present study each phrenic nucleus contributed fibers only to the ipsilateral phrenic nerve, and no evidence for peripheral crossing of fibers was found.
Embryonic and postembryonic morphogenesis of a grasshopper interneuron
Authors: Bentley David , Toroian‐Raymond Alma 
Published: May 2005

AbstractThe object of this study was to describe the embryonic and postembryonic morphogenesis of a grasshopper interneuron in order to determine how, and when, this cell comes to assume its mature form. DCMD is an intensively investigated interneuron whose morphology, input and output physiology, and role in behavior are relatively well‐known in the adult. We examined the morphology of DCMD in the brain at each stage of its development with silver‐intesified cobalt‐fills. It arises at 40 ± 4% of embryogenesis and is probably one of the early progeny from its stem cell. In the ensuing 40% of development, its brain arborization grows quite directly into its mature form. Branches appear first and are always longest and densest in the brain region where the adult arborization is found. Thus, the adult form arises by initially directed growth and not by secondary selection of branches from a diffuse or overgrown arborization. Restricted secondary branch loss of lateral filopodia and probably of a few early branches does occur.Embryonic and postembryonic development of the cell are distinctly different. Embryogenesis is the period of morphological differentiation as indicated by the growth and shaping of the brain and also thoracic (axonal) arborizations, the appearance of cytological specializations, and the logarithmic growth of the neurite and soma. The brain arborization has its mature form, although not size, by the completion of embryogenesis. Postembryonic development is a period of substantial, but primarily allometric, growth. The soma and neurite grow linearly (with time), and the arborization grows in proportion to brain size.
Ruffed cell: A new type of neuron with a distinctive initial unmyelinated portion of the axon in the olfactory bulb of the goldfish (Carassius auratus). III. Three‐dimensional structure of the ruffed cell dendrite
Authors: Kosaka Toshio , Hama Kiyoshi 
Published: May 2005

AbstractThe three‐dimensional structure of the ruffed cell dendrite in the olfactory bulb of the goldfish (Carassius auratus) was studied by means of light and high‐voltage electron microscopy of Golgi‐impregnated material, combined Golgi‐electron microscopy, and electron microscopy of serial thin sections.Ruffed cell dendrites ramify in the glomerular area with tufted branching patterns. They give rise to many appendages of various shapes and sizes: sheetlike processes, fingerlike projections, or small tuftlike appendages. These appendages, singly or together, appear to entwine or cover other neuronal processes. In thin sections ruffed cell dendritic appendages frequently look like glial processes; that is, they appear to conform in shape to the contours of surrounding neuronal elements, such as mitral and granule cell dendrites.Ruffed cell dendrites display intimate relationships with mitral cell dendrites. The former appear to coil around and cover the latter. Notwithstanding the intimate relationship between ruffed cell dendrites and mitral cell dendrites, there seem to be no synaptic connection between them. Ruffed cell dendrites bear a rather small number of presynaptic and postsynaptic sites, most of which are with granule cell dendrites. Ruffed cell dendrites seem to receive no synapses from olfactory nerve terminals.
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

AbstractA 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

AbstractThe 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

AbstractThe 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

AbstractTransganglionic 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

AbstractThe 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

AbstractThe 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

AbstractThe 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.