bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regional specialization in retinal ganglion cell projection to optic tectum of Dipsosaurus dorsalis (lguanidae)
Authors: Peterson Ellengene H. 
Published: January 2005

AbstractRegional variation in the composition of the ganglion cell layer is a characteristic feature of vertebrate retinas. This suggests that corresponding patterns of regional variation might be expected in CNS structures which receive a direct, topographic projection from the retina. To investigate this possibility, I studied the retinotectal projection in an iguanid lizard (Dipsosaurus dorsalis), which shows a marked degree of regional variation in its retinal ganglion cell layer. Results of these experiments indicate that in D. dorsalis the optic tectum is differentiated horizontally into five regions which can be distinguished on the basis of cytoarchitecture and the patterning of retinal afferents, as visualized with silver degeneration and autoradiographic tracing techniques. These five areas are named according to their location: (1) Ventral Rim, (2) Lateral Wall, (3) Dorsolateral Area, (4) Dorsal Wall and (5) Medial Rim.Following enucleation, the Medial and Ventral Rim are characterized by fascicles of coarse degenerated fibers in layers 13, 12, and 9, by a relative absence of fine particulate debris in reduced silver material, and by the absence of silver grains in autoradiographs following intraocular injections of tritiated proline. They differ in the density of large calibre fibers and in the temporal course of degeneration. In the Lateral Wall the cellular layers are best differentiated, and nine retino‐recipient layers can be distinguished below the stratum opticum. Degeneration is particularly heavy over the plexiform layers 9, 11, and 13. There is a superficial to deep gradient of degeneration density and of silver grains within layers 13 and 11. In the lower half of layer 11, argyrophilic debris and silver grains are aligned in vertical columns. The Dorsolateral Area is a circular region which covers the dorsolateral convexity of the tectum just caudal to mid tectal levels. It is characterized by a relatively low density of degenerated fibers in layers 13, 12, and especially in layer 9. Finally, the Dorsal Wall is similar to the Lateral Wall in the laminar distribution of degeneration and silver grains, except that there is an additional band of fine debris over layers 12 and 13 which is not visible in the Lateral Wall. Rostrally, the Dorsal Wall is greatly expanded (the Dorsal Expansion) and in this region a well developed plate of neurons lies immediately subjacent to the stratum opticum. This is the only tectal area which shows substantial degeneration at short survival times.These data suggest that in D. dorsalis there is horizontal variation in the morphology and patterning of retinal ganglion cell axons to the superficial tectal layers. Since Dipsosaurus retina exhibits a substantial degree of regional variation in the ganglion cell layer, and since the retina projects topographically onto the tectum, it is suggested that regional variation in the optic tectum may reflect regional variation in the ganglion cell layer of the retina.
An analysis of the sympathetic preganglionic neurons projecting from the upper thoracic spinal roots of the cat
Authors: Oldfield B. J. , McLachlan Elspeth M. 
Published: January 2005

AbstractThe distribution of sympathetic preganglionic neurons that project via the right stellate ganglion has been studied quantitatively in adult cats. Retrograde transport of horseradish peroxidase (HRP) injected into the ganglion or applied to transected axons of the cervical sympathetic trunk (CST) resulted in labelling of neurons in the ipsilateral spinal cord over T1–T9 and T1–T7, respectively. Their distribution and morphology in the subnuclei of the intermediate zone were determined. Neurons within the principal part of the intermediolateral column (ILp) comprised the majority of labelled cells at all levels, irrespective of the site of HRP application, while more medially located neurons projected differentially. A combination of the application procedures labelled what appeared to be a sum of the individual projections, and few ILp cells remained unlabelled in the most rostral segments. From reconstructions of different segmental levels, most of the cells in the ILp were found to lie in a column ∼200 μm in diameter composed of a series of cell aggregations of 20–150 neurons at intervals of ∼300 μm. Less frequently, mediolaterally aligned cells extended toward the central canal, near which small cell clusters were also detected. After selective HRP application to individual rami of T1–T3, labelled cells were restricted to one segment's length, so that neurons located more caudally must project extraspinally to the stellate ganglion. Consideration of the maximum cell numbers labelled by each procedure suggests that preganglionic collaterals (probably unmyelinated) diverging from the pathway to the preferred target of their parent neuron were not labelled by this technique.
An electron microscopic analysis of the dorsal root in the frog
Authors: Wilhelm Gary B. , Coggeshall Richard E. 
Published: January 2005

AbstractIt is generally accepted that each dorsal root ganglion cell gives rise to a single central axon that enters the spinal cord via the dorsal root. This concept arose, in large part, from the reports that the numbers of dorsal root ganglion cells and dorsal root axons in mammals are equal. By contrast, in the frog a considerable excess of ganglion cells over axons was reported. None of these reports can be accepted, however, because the unmyelinated dorsal root axons could not be counted accurately with the light microscope. In the present study the counts in the frog are repeated, except that the axons are counted in the electron microscope, which has the necessary resolution for unmyelinated axons, and surgical controls are done to make certain that there are no extraneous axons in the root. When this is done, we show a considerable excess of axons to ganglion cells for all spinal segments in the frog, and there are no extraneous axons in the root. These data are interpreted as indicating that dorsal root axons branch either in the ganglion or in the root itself. Thus the concept that each frog dorsal root ganglion cell sends a single central process to the spinal cord needs to be modified.One of our control procedures was to make certain that no fibers survive in the proximal stump of a dorsal rhizotomy. This shows that there are no dorsal root efferents in frog dorsal roots, an important consideration in the interpretation of certain physiological phenomena that result from dorsal root stimulation.Finally, the study shows that there is a total of 43,000 dorsal root ganglion cells and 72,000 dorsal root axons in the bullfrog. These figures are considerably lower than similar figures from mammals and make an interesting comparison with some useful invertebrate preparations.
The aberrant retino‐retinal projection during optic nerve regeneration in the frog. III. Effects of crushing both nerves
Authors: Bohn Ronald C. , Stelzner Dennis J. 
Published: January 2005

AbstractPrevious reports from this laboratory have shown that a substantial number of optic axons are misrouted after optic nerve regeneration in the adult frog, Rana pipiens. Regenerating axons from a crushed optic nerve are distributed throughout the opposite nerve. In this study, we report the effect of crushing both optic nerves (double crush) on the pattern and degree of axonal misrouting. In 28 frogs both optic nerves were crushed at the same time (simultaneous double crush) and animals survived for varying periods before the right eye was injected with 3H‐proline and the brain processed for autoradiography 24 hours later. In every frog with postoperative survivals longer than 2 weeks, labeled axons from the right eye were found in the left optic nerve. However, when compared to the amount of label seen in frogs in which only the right optic nerve was crushed (single crush) there was substantially less label within the left nerve of frogs after crushing both nerves. Label was also found only at the edge of the left nerve in material from double crush frogs, unlike that found after single crush. In four of six frogs where the left nerve was crushed 1 week after the right nerve (delayed double crush), the proximal end of the left nerve was completely filled with label, but more distally, label was found only along the edge of this nerve. Although fewer optic axons were labeled in the opposite optic nerve of double crush frogs, label did extend to the optic disc of that eye. However, label was not apparent in the ganglion cell fiber layer of the opposite eye. Instead, it was confined to the edge of the optic disc in a space apparently associated with papilledema resulting from crushing the optic nerve of that eye. In six frogs the retina of the left eye was removed at the same time the right optic nerve was crushed. Labeled axons of the right eye filled the left optic nerve to the retina‐less shell of the left eye. Thus, these data show that the amount and distribution of axonal misrouting into the opposite optic nerve during optic nerve regeneration is affected by intact or regenerating optic axons from the other eye.
Topographic and morphometric effects of bilateral embryonic eye removal on the optic tectum and nucleus isthmus of the leopard frog
Authors: Constantine‐Paton Martha , Ferrari‐Eastman Patricia 
Published: January 2005

AbstractRana pipiens were raised through metamorphosis after extirpation of both eye primordia at Shumway embryonic stage 17 (Shumway '40). The visual connections between the isthmic nuclei and the optic tectum were examined in these animals using horseradish peroxidase (HRP) histochemistry. Isthmo‐tectal projections are normally aligned with the primary retinotectal map. We asked whether these connections would develop normal topographic organization in the absence of normal retinal input.HRP was formed into a solid pellet (≃ 200–500 μm diameter) and inserted into one tectal lobe on the tip of a fine metal probe. The procedure produced relatively restricted retrograde label in somas and dendrites in both isthmi nuclei. In the nucleus isthmus ipsilateral to the tectal lobe receiving the HRP pellet, processes of tecto‐isthmi neurons were labeled by anterograde transport.The topography of the isthmo‐tectal and tecto‐isthmic projections were identical in the developmentally enucleated animals and in normal frogs, even though eye removal severely reduced the volume of the optic tecta and the isthmi nuclei. Thus our analyses indicate that retinal contacts do not play an active role in the development of the positional or polarity cues that are involved in “mapping” projections between central visual nuclei. These results are discussed in the context of peripheral specification of central connections and in terms of models that have recently been proposed to explain the development of the retinotectal system.
Spinal projections from the medullary reticular formation of the North American opossum: Evidence for connectional heterogeneity
Authors: Martin G. F. , Cabana T. , Humbertson A. O. , Laxson L. C. , Panneton W. M. 
Published: January 2005

AbstractRetrograde and orthograde transport techniques show that the nucleus reticularis gigantocellularis pars ventralis and the nucleus reticularis gigantocellularis project the entire length of the spinal cord. Double‐labelling methods show that some of the neurons in each area innervate both cervical and lumbar levels. There is evidence, however, that neurons in the lateral part of the nucleus reticularis gigantocellularis pars ventralis and the dorsal extreme of the nucleus reticularis gigantocellularis project mainly to cervical and thoracic levels. The autoradiographic method shows that the above nuclei supply direct innervation to somatic and autonomic motor columns as well as to laminae V–VIII and X. The nucleus reticularis gigantocellularis pars ventralis provides additional projections to lamina I and the outer part of lamina II.Several areas of the medullary reticular formation project mainly, and in some cases exclusively, to cervical and thoracic levels. These areas include the nucleus reticularis parvocellularis, the nucleus reticularis lateralis, the nucleus retrofacialis, the nucleus ambiguus, the nucleus lateralis reticularis, caudal parts of the nuclei reticularis medullae oblongatee dorsalis and ventralis, and the nucleus supraspinalis. Autoradiographic experiments reveal that neurons in the ventrolateral medulla, particularly rostrally (the nucleus reticularis lateralis and neurons related to the nucleus lateralis reticularis), innervate sympathetic nuclei.Our results indicate that spinal projections from bulbar areas of the reticular formation are more complicated than previously supposed. Axons from separate areas project to different spinal levels and in some cases to different nuclear targets. These data are in conformity with the evolving concept of reticular heterogeneity.
The monoamine‐containing neurons in avian brain: I. A study of the brain stem of the chicken (Gallus domesticus) by means of fluorescence and acetylcholinesterase histochemistry
Authors: Dubé Lorraine , Parent Andre 
Published: January 2005

AbstractThe distribution of monoamine (MA)‐containing nerve cell bodies in the brain stem of the chicken (Gallus domesticus) was studied by means of paraformaldehyde and glyoxylic acid fluorescent histochemical methods. The MA neurons were further characterized morphologically and histochemically in material prepared for the demonstration of acetylcholinesterase (AChE).In the rostral midbrain of the chicken, two large collections of catecholamine (CA)‐containing cells are found: one located in the ventromedial and the other in the dorsolateral (pedunculopontine nucleus) portions of the tegmentum. On the basis of their topographic location, CA content, and fiber connections, these ventromedial and dorsolateral cell groups can be tentatively associated with the CA‐containing neuronal populations of the mammalian ventral tegmental area and pars compacta of the substantia nigra, respectively. In the caudal midbrain of the chicken, numerous CA‐containing cells are intermingled with serotonin (5HT)‐containing perikarya beneath as well as within the decussation of the superior cerebellar peduncles. At isthmus levels, abundant, closely‐packed CA‐containing cells are encountered along the lateral border of the central gray. These neurons, which display a very high AChE activity, appear to be equivalent to those of the mammalian locus coeruleus. A multitude of medium‐sized 5HT‐containing neuronal somata occurs within the raphe region of the isthmus. Some of these somata closely surround the medial longitudinal fasciculus. This 5HT‐containing cell group also massively invades the lateral tegmentum, where it be comes closely intermingled with the CA‐containing neurons of the locus coeruleus and subcoeruleus. All of these 5 HT‐containing neurons display a moderate to high AChE activity. In the medulla the number of MA‐containing neurons is much smaller than in the upper brain stem. Nevertheless, 5HT‐containing cells are present within the raphe region, particularly in the upper two‐thirds of the medulla, and CA‐containing perikarya can be found along the lateral border of the medulla and within the confines of the nucleus solitarius.The findings of the present study reveal that the MA‐containing neuronal systems in the avain brain stem are organized according to a pattern that is much more complex than the one disclosed in reptiles or in other nonmammalian vertebrates. This complexity arises in large part from the fact that the 5HT‐containing systems undergo a prominent lateralization in birds, which leads to a close intermingling of 5HT‐containing and CA‐containing neuronal elements at various levels of the neuraxis.
Neurogenesis in the brain stem of the rabbit: An autoradiographic study
Authors: Oblinger Monica M. , Das Gopal D. 
Published: January 2005

AbstractWith the aid of (H3)‐thymidine autoradiography, neurogenesis was documented in the nuclear groups of the medualla oblongata, pons, and midbrain, as well as in the brain stem reticular formation of the rabbit. Following single injections of (H3)‐thymidine, counts were taken of intensely labeled neurons within the nuclei of the functional columns related to the cranial nerves, nuclei of several other functional classifications, and nuclei that did not fit into a functional category. In the brain stem as a whole, neurogenesis was found to occur between days 10.0 and 18.5 of gestation; however, the majority of nuclei studied contained intensely labeled neurons only between days 12.0 and 15.0. Only in the pontine nucleus and the tectum were intensely labeled cells observed as late as day 18.5. Directional gradients of histogenesis were often observed within, as well as between, various nuclei. Within the nuclear columns related to the cranial nerves, a clear mediolateral spread of neurogenesis was observable such that nuclei of the motor columns reached a peak in neurogenesis before those in the sensory columns. Likewise, a mediolateral proliferation pattern was seen in the brain stem reticular formation. Other individual directional gradients were discernible; however, in the brain stem as a whole, distinct overall gradients were not observable. In many individual nuclei, gradients in neuron size were observed such that large neurons preferentially arose prior to smaller neurons. Information pertaining to gradients in neurogenesis, as well as to relationships among functionally related nuclei, are disscussed.
Connections of the corticomedial amygdala in the golden hamster. I. Efferents of the “vomeronasal amygdala”
Authors: Kevetter Golda A. , Winans Sarah S. 
Published: January 2005

AbstractThe medial (M) and posteromedial cortical (C3) amygdaloid nuclei and the nucleus of the accessory olfactory tract (NAOT) are disignated the “vomeronasal amygdala” because they are the only components of the amygdala to receive a direct projection from the accessory olfactory bulb (AOB). The efferents of M and C3 were traced after injections of 3H‐proline into the amygdala in male golden hamsters. Frozen sections of the brains were processed for autoradiography.The efferents of the “vomeronasal amygdala” are largely to areas which are primary and secondary terminal areas along the vomeronasal pathway, although the efferents from C3 and M terminate in different layers in these areas than do the projections from the vomeronasal nerve or the AOB. Specifically, C3 projects ipsilaterally to the internal granule cell layer of the AOB, the cellular layer of NAOT, and layer lb of M. Additional fibers from C3 terminate in a retrocommissural component of the bed nucleus of the stria terminalis (BNST) bilaterally, and in the cellular layers of the contralateral C3. The medial nucleus projects to the cellular layer of the ipsilateral NAOT, layer lb of C3, and bilaterally to the medial component of BNST.Projections from M to non‐vomeronasal areas terminate in the medial preoptic area‐anterior hypothalamic junction, ventromedial nucleus of the hypothalamus, ventral premammillary nucleus and possibly in the ventral subiculum.These results demonstrate reciprocal connections between primary and secondary vomeronasal areas and between the secondary areas themselves. They suggest that M, but not C3, projects to areas outside this vomeronasal network. The medial amygdaloid nucleus is therefore an important link between the vomeronasal organ and areas of the brain not receiving direct vomeronasal input.
Histogenesis of the cochlear nucleus of the mouse
Authors: Martin Michael R. , Rickets Christine 
Published: January 2005

AbstractIn Nissl‐stained preparations of the cochlear nucleus there are nine recognizable cell types. These cells are born during three periods of histogenesis prenatally. On gestation days 10.0, 10.5, and 11.0 the pyramidal, giant, and dark‐staining cells are born. The spherical, globular, multipolar, and horizontal cells are formed on gestation days 12.0, 12.5, and 13.0 and small cells follow on gestation day 14.5. The onset of granule cell formation is gestation day 14.5 and continues to birth on gestation day 19. At birth, and for at least the first 2 postnatal weeks, glial cells are born. There are no regional gradients in cell birth dates, cells from all birth dates being intermixed. Cell birth proceeds in an orderly sequence that is related only to cell size. Although there were no apparent spatiotemporal patterns, some clustering of labeled cells was evident. These observations do not support the hypothesis that Golgi Type I cells precede Golgi Type II cells in their order of birth since both large and small neurons project beyond the nucleus. There is, nonetheless, a sequential pattern in the onset of cell birth for the auditory system, with cochlear nucleus neurons preceding cochlear neurons.
Cerebellothalamic projections in the rat: An autoradiographic and degeneration study
Authors: Haroian Alan J. , Massopust Leo C. , Young Paul A. 
Published: January 2005

AbstractThe purpose of this study was to determine the topographical organization of cerebellothalamic projections in the rat. Following stereotaxic injections of 3H‐leucine or electrolytic lesions in the cerebellar nuclei, efferent fibers were observed to emerge from the cerebellum through two discrete routes. Fibers from the fastigial nucleus decussated within the cerebellum, formed the crossed ascending limb of the uncinate fasciculus, ascended in the dorsal part of the midbrain tegmentum, and entered the thalamus. Cerebellothalamic fibers from the interpositus and dentate nuclei coursed in the ipsilateral brachium conjuctivum, decussated in the caudal midbrain, and ascended to the thalamus via the crossed ascending limb of the brachium conjunctivum.Cerebellar terminations were observed in the intralaminar, lateral, and ventral tier thalamic nuclei as well as in the medial dorsal nucleus. Projections to the intralaminar nuclei were more pronounced from the dentate and posterior interpositus than from the anterior interpositus and fastigial nuclei. The lateral thalamic nuclei received a projection from the dentate and posterior interpositus nuclei while the fastigial nucleus projected to the medial dorsal nucleus. Within the rostral ventral tier nuclei fastigiothalamic terminations were localized in the medial parts of the ventral medial and ventral lateral nuclei, whereas dentatothalamic projections were concentrated in the lateral parts of the ventral medial nucleus and the medial half of the ventral lateral nucleus. Terminations from the posterior interpositus nucleus were observed ventrally and laterally within the caudal two‐thirds of the ventral medial nucleus and throughout the ventral lateral nucleus, where they were densest in the lateral part of its lateral wing and within the central part of its cap. The anterior interpositus nucleus also projected to the central and lateral parts of the ventral lateral nucleus, but these terminations were considerably less dense than those from the posterior interpositus. A few fibers from the interpositus nuclei terminated in the medial part of the rostral pole of the ventral posterior nucleus.A prominent recrossing of cerebellothalamic fibers from the fastigial, posterior interpositus, and dentate nuclei occurred through the central medial nucleus of the internal medullary lamina. These terminated within the ipsilateral ventral lateral and intralaminar nuclei.These results show that each of the cerebellar nuclei project to the thalamus and that their terminations are topographically organized in the rostral ventral tier nuclei. The clustering of autoradiographic silver grains or terminal degeneration observed in the thalamic nuclei suggests a medial‐to‐lateral organization of this cerebellothalamic system.