bluuebunny/crossref_metadata_2025_split huggingface dataset:
Floccular efferents in the rhesus macaque as revealed by autoradiography and horseradish peroxidase
Authors: Langer T. , Fuchs A. F. , Chubb M. C. , Scudder C. A. , Lisberger S. G. 
Published: January 2005

AbstractTo fulfill its putative role in short‐ and long‐term modification of the vestibulo‐ocular reflex, the flocculus of the cerebellum must send efferents to brainstem nuclei involved in the control of eye movements. In order to reveal the sites of these interactions, we determined the projections of the flocculus by autoradiography and orthograde transport of horseradish peroxidase in five rhesus macaques.Anterogradely labeled axons collected at the base of the injected folia and coursed caudally and medially between the middle cerebellar peduncle and the flocculus. They swept medially over the caudal surface of the middle cerebellar peduncle, over the dorsal surface of the cochlear nuclei, and then caudally along the lateral surface of the inferior cerebellar peduncle to pass over its dorsal surface in the cerebellopontine angle and terminate exclusively in the ipsilateral vestibular nuclei.Three contingents of axons could be differentiated. The axons of one group flowed caudally and medially into the y‐group, which clearly received the densest floccular projection. Other, notably thicker, axons of this group continued rostrally and medially to terminate chiefly in the large‐cell core of the superior vestibular nucleus. A second large contingent of thin axons streamed caudal and ventral to the y‐group to form a compact tract adjacent to the lateral angle of the fourth ventricle and dorsal to the medial vestibular nucleus. Fibers from this tract (the angular bundle of Löwy) supplied a sizable projection to the rostral part of the medial vestibular nucleus and modest projection to the ventrolateral vestibular nucleus. A final group of fibers extended caudally and medially from the y‐group in a plexus ventral to the dentate and interposed nuclei to terminate in the basal interstitial nucleus of the cerebellum (Langer, '85), a broadly distributed cerebellar nucleus on the roof of the fourth ventricle.The flocculus can affect vestibulo‐ocular behavior only through these efferents to the vestibular nuclei and the basal interstitial nucleus of the cerebellum.
Basal interstitial nucleus of the cerebellum: Cerebellar nucleus related to the flocculus
Authors: Langer Thomas P. 
Published: January 2005

AbstractWe have shown that the monkey flocculus is not connected with any of the major, well‐demarcated cerebellar nuclei. There is, however, a broadly distributed interstitial population of neurons in the white matter ventral to the cerebellar nuclei and extending into the peduncle of the flocculus; this population, previously undescribed in the monkey, has reciprocal connections with the flocculus (Langer et al., '85a,b). Several lines of evidence indicate that this collection of neurons, called the basal interstitial nucleus of the cerebellum (BIN/Cb), can justifiably be considered a nucleus.(1) Injection of horseradish peroxidase (HRP) into the flocculus always labels a group of neurons that lie immediately ventral to the well‐demarcated cerebellar nuclei and extend posteromedially into the lateral margin of the nodulus and rostrolaterally around the caudal surface of the y‐group, infiltrating the peduncle of the flocculus.(2) In Nissl‐stained material there is a readily seen collection of neurons that are clearly distinct from the overlying cerebellar nuclei, with precisely the same distribution. These neurons have a characteristic morphology: they are intermediate‐sized, chromatophilic, multipolar, and fusiform, and have rapidly tapering proximal dendrites. The cell nucleus is generally placed eccentrically in the cell body, against the plasma membrane or in one pole of the cell. The Nissl substance is usually finely granular in the center of the cell body and forms dense clumps adjacent to the cell membrane.(3) Anterograde label from injections of HRP or tritiated amino acids into the flocculus extends over the same group of neurons.In one brain with an HRP injection involving a part of the BIN/Cb there was a patchy, clustered distribution of labeled Purkinje cells extending throughout the flocculus and into the adjacent lateral parts of the simple lobule. The clusters were confined to the medial half of many of the floccular folia.
Compartmentalization of the cat lateral gastrocnemius motor nucleus
Authors: Weeks O. I. , English A. W. 
Published: January 2005

AbstractThe spatial and size distributions of motoneurons which supply the cat lateral gastrocnemius (LG) neuromuscular compartments were examined to determine their anatomical organization. Individual primary muscle nerve branches (PMNB) to LG were isolated by microdissection, cut, and soaked in horseradish peroxidase (HRP). As a control in each case, the entire contralateral lateral gastrocnemius‐soleus (LG‐S) nerve was similarly cut and soaked. Retrogradely labeled motoneurons were identified, their positions plotted, and their sizes measured on both sides of the cord. Results show that extensive overlap exists in the spatial distribution of motoneurons innervating different PMNBs. Labeled cells supplying each PMNB also vary considerably in their sizes. However, both a highly significant topography‐like organization and a preferential size distribution are found between different groups of motoneurons. Neurons which supply proximal compartments occupy more rostral portions of the LG motor nucleus and are among the largest in the pool. Very few small motoneurons innervate proximal compartments. Neurons supplying more distal compartments are distributed in more caudal parts of the pool and contain both large and small cells in relatively equal numbers. If the large cells are alpha and the small cells gamma motoneurons, then proximal compartments are relatively poor in gamma innervation and presumably muscle spindles, and distal compartments are rich in fusimotor innervation.
Neonatal 6‐hydroxydopamine destroys spinal cord noradrenergic axons from the locus coeruleus, but not those from lateral tegmental cell groups
Authors: McBride Russell L. , Ozment Richard V. , Sutin Jerome 
Published: January 2005

AbstractSubcutaneous injection of 6‐hydroxydopamine (6‐OHDA) in neonatal rats results in sprouting of collateral axons in locus coeruleus (LC) and lateral tegmental noradrenergic neurons. It has been suggested that this sprouting represents maintenance of neuronal membrane area following “pruning” of axon terminals of long projections to cortex and cord. The chemical or surgical lesions of long axons used to produce “pruning” could also result in the loss of some parent cell bodies. We tested the hypothesis that long axon damage, rather than cell loss, is sufficient to produce collateral sprouting of proximal axons in noradrenergic neurons. With neonatal injections of 6‐OHDA at doses which do not produce a loss of LC neurons, there is an 85% decrease in retrograde LC labeling following horseradish peroxidase or true blue injections into the spinal cord but no significant change in the numbers of retrogradely labeled neurons in other noradrenergic cell groups which also sprout collaterals. There is no change in the number of labeled LC neurons following cerebellar injections.In experiments using the fluorescent dyes diamidino yellow and true blue, the number and distribution of LC neurons labeled from spinal cord and cerebellum injections are similar to those in the horseradish peroxidase experiments. Doubly labeled neurons are found in the caudal two‐thirds of LC in control rats, but as expected, rarely observed in 6‐OHDA‐treated animals.This study demonstrates that (1) cell loss in the LC is not necessary for sprouting following neurotoxin treatment, and (2) the increased number of norepinephrine (NE) terminals in the pons is not due exclusively to a “pruning effect,” since NE cells outside the LC, which are known to contribute to the hyperinnervation, retain their long projections to the spinal cord.
Timing and positioning of occlusion of the spinal neurocele in the chick embryo
Authors: Desmond Mary E. , Schoenwolf Gary C. 
Published: January 2005

AbstractThe timing and positioning of occlusion of the spinal neurocele were studied in living and serially sectioned chick embryos at stages 8–14. Occlusion occurs in three phases: preocclusion, incipient occlusion, and definitive occlusion. Preocclusion occurs at stage 8. At this time, the neural groove of the spinal cord has not yet closed to form a neural tube. Incipient occlusion begins as early as stage 9 and lasts until stage 11. The neural groove of the cranial spinal cord closes during these stages and incipient occlusion occurs concomitantly with this closure. Seventy‐eight percent of the embryos exhibit incipient occlusion. Incipient occlusion extends along the mid‐somitic region of the neuroaxis, occupying about one‐half the length of the spinal cord. Injection of the brains of living embryos with dyes often reopens incipient occluded areas. Definitive occlusion occurs at stages 11–14 and is present in 89% of the embryos. Definitive occlusion is restricted to mid‐somitic regions, as was incipient occlusion, but it extends approximately two‐thirds the length of the spinal cord. Injection of the brains of living embryos with dyes rarely reopens definitive occluded areas, even when injection pressures are maximal. Six morphological types of definitive occlusion can be identified on the basis of the relative proportions and locations of total and partial occlusion. Closure of the cranial neuropore and roof plate of the hindbrian occurs near the end of the incipient occlusion phase, whereas closure of the caudal neuropore occurs well after definitive occlusion is initiated. Physiological occlusion is due to both anatomical occlusion and back pressure, which prevent the flow of liquids into a blind, narrow tube. Further studies are required to document the reopening phases of the spinal neurocele, as well as the forces involved in causing and maintaining occlusion and reopening.
Topographical projections of the cerebral cortex to the subthalamic nucleus
Authors: Afsharpour Salman 
Published: January 2005

AbstractCorticosubthalamic projections in the rat were investigated using the autoradiographic anterograde axonal tracing technique. After unilateral injections of tritiated amino acids in the cerebral cortex, projections to the ipsilateral subthalamic nucleus (STH) could be found arising only from the frontal agranular cortex and the zone of MI‐SI overlap. Injections into granular areas of the cortex (e.g., somatosensory and visual areas) did not result in labeling in STH. Following injections in the frontal agranular cortex, labeling was present in the ipsilateral but not the contralateral STH. In general, injections that involved the lateral agranular field of frontal cortex, as defined by Donoghue and Wise (1982), resulted in a greater amount of labeling in STH than injections within the medial agranular area or the zone of MI‐SI overlap. The projection from the frontal agranular areas to STH is topographically organized. The rostral part of the lateral agranular cortex projects to the lateral portion of the rostral two‐thirds of STH, and the caudal part of this field projects to the ventral aspect of the middle third of STH. Injections in the rostral part of the medial agranular cortex resulted in labeling throughout the ventral two‐thirds of the medial half of STH. The caudal part of the medial agranular cortex projects to the dorsolateral part of the caudal two‐thirds of STH.The present results reveal projections from only the frontal agranular cortex and the zone of MI‐SI overlap to STH in the rat. The cortico‐STH projection is ipsilateral and terminates in a topographical manner in all parts of STH.
Mechanoreceptive neurons in an insect brain
Authors: Bräunig P. 
Published: January 2005

AbstractStaining deutocerebral nerves in locusts with cobalt chloride revealed a connective tisssue strand innervated by the first side branch of the nervus scapalis medialis. The strand spans the joint between the basal segment of the antenna (scapus) and the head capsule (tentorium), parallel to the levator scapi muscle. It is shortest with the antenna completely elevated and becomes stretched during depression.The four to five neurons innervating the strand near its distal insertion are activated by mechanical stimuli such as direct elongation of the strand or depression of the antenna. As revealed by centripetal staining these neurons have their central arborizations in the posterior deutocerebrum, but their perikarya are located in the protocerebrum, close to the pars intercerebralis and the central body.These morphological and physiological characteristics identify the structure as a mechanoreceptive sense organ of the strand receptor class.
Retinal ganglion cell death during optic nerve regeneration in the frog hyla moorei
Authors: Humphrey M. F. , Beazley L. D. 
Published: January 2005

AbstractIn the frog Hyla moorei we have estimated there to be between approximately 450,000 and 750,000 cells in the retinal ganglion cell layer. Optic axon counts and retrograde transport of horseradish peroxidase (HRP) indicated that 72–76% of these were ganglion cells. Cells of this type were distributed as a temporally situated area centralis within a horizontal visual streak.Cell and optic axon counts showed that there was an approximately 40% loss of ganglion cells during optic nerve regeneration. Ganglion cells appeared chromatolysed by 6–8 days after an extracranial nerve crush but there was no indication of cell death until 15 days. By this stage anterograde transport of HRP indicated that axons had reached the chiasma. Death was first seen in the area centralis, extended along the streak, and finally was observed in the periphery by 65 days; cell counts demonstrated that at this time the wave of death was almost complete. We have previously shown by electrophysiological visual mapping (Humphrey and Beazley, 1982) and confirmed in this study that visuotectal projections were retinotopically organized during regeneration. Multiunit receptive fields were initially large but progressively refined starting in nasal field (temporal retina) to restore a normal projection. The similar sequences whereby the visuotectal projection became refined and death took place in the retinal ganglion cell layer suggested that death may be related to a process of organization within the regenerating projection.In normal animals primary visual pathways revealed by anterograde transport of HRP were essentially similar to those of Rana pipiens and R. esculenta. Regenerating axons generally remained within optic pathways. Exceptions were a retinoretinal projection which was not completely withdrawn even after 1,028 days and a direct projection to the ipsilateral tectum via an inappropriate part of the optic tract.
Freeze‐fracture study of filipin binding in photoreceptor outer segments and pigment epithelium of dystrophic and normal retinas
Authors: Caldwell Ruth B. , McLaughlin Barbara J. 
Published: January 2005

AbstractWe have studied sterol distribution in the retinal pigment epithelial (RPE) microvillous and outer segment disc membranes of rats with inherited retinal degeneration (RCS; RCS‐p/+) and of normal genetic controls (RCS‐rdy+, RCS‐rdy+‐p/+) by using the polyene antibiotic filipin, which binds specifically to 3‐B‐hydroxy‐sterols, and freeze‐fracture techniques. Retinas were perfusion‐fixed, incubated with filipin in the same fixative, and prepared routinely for freeze‐fracture electron microscopy. In the normal retina, the distribution of filipin binding sites on both RPE microvillous and outer segment disc membranes changes during development. Prior to outer segment elongation and the onset of phagocytosis (10 days postnatal), filipin sterol complexes are homogeneously distributed in both microvillous and outer segment membranes. With the onset of phagocytosis (2 weeks postnatal and later) filipin binding in both tissues forms a proximal‐to‐distal gradient, and binding sites decrease as distance from the cell body increases. In the normal RPE microvillous membranes, binding sites are numerous proximally and sparse on the distal tips. In the normal outer segment disc membranes, binding sites are often present on the basal discs, but are sparse on the intact apical discs prior to shedding. As the discs are cast off and engulfed by the RPE, however, filipin binding increases on both disc and phagosome membranes. In the dystrophic retina, the distribution of filipin binding sites differs from the normal. First, in the microvillous membranes, the proximal‐to‐distal gradient in filipin binding is rarely present at 2 weeks postnatal and becomes prominent only after the buildup of membranous debris has begun (3–6 weeks postnatal). Second, as the photoreceptors degenerate and the membrane debris disappears (4 months postnatal), filipin binding on the microvillous membranes becomes relatively sparse and homogeneous. Third, filipin binding on the intact disc membranes does not change with outer segment elongation, and numerous filipin binding sites are present on both apical and basal outer segment disc membranes. Fourth, large aggregates of filipin binding sites occupy the vast expanses of particlefree areas of debris membranes which accumulate between the photoreceptors and the RPE. These changes in the amount and distribution of filipin binding sites in the dystrophic retina add to the evidence that the disease process involves outer segment as well as RPE membranes and suggest that alterations in cholesterol distribution could contribute to the phagocytic defect.
Brainstem origins and projections of the cervical and abdominal vagus in the golden hamster: A horseradish peroxidase study
Authors: Miceli Mario O. , Malsbury Charles W. 
Published: January 2005

AbstractVagal afferent projections, and preganglionic parasympathetic neurones contributing to the vagus nerve in golden hamsters were traced following application of horseradish peroxidase (HRP) to the proximal end of the cervical or abdominal nerve stump. Efferents in the cervical vagus were traced to their perikarya of origin in the dorsal motor nucleus (DMN) of the vagus, the commissural gray of the cervical spinal cord, the nucleus ambiguus, the nucleus of the accessory spinal nerve (NASN), and in the ventral horn dorsolateral to the NASN. Perikarya in the NASN and the region dorsolateral to it did not contribute efferent fibres to the abdominal vagus. In the remaining cell groups, fewer labelled perikarya were labelled in the abdominal cases than in the cervical cases. Extraperikaryal labelling (presumptive terminals) in the cervical cases was seen primarily in the nucleus of the solitary tract. A modest distribution of extraperikaryal grains was also noted along the inner rim of the area postrema and the ventral border of the DMN. Anterograde labelling was sparser and had a more restricted distribution in the abdominal cases. A detailed description of brainstem pathways of vagal efferent and afferent fibres is provided, as is a comparison of the present observations with those in similar studies of other species.
Morphology of central terminations of intra‐axonally stained, large, myelinated primary afferent fibers from facial skin in the rat
Authors: Hayashi Haruhide 
Published: January 2005

AbstractHorseradish peroxidase was intra‐axonally injected into functionally identified primary afferent fibers within the rat spinal trigeminal tract in order to study the morphology of their central terminations. They were physiologically determined to be large, myelinated, cutaneous primary afferents by means of electrical and mechanical stimulation of their receptive fields. Ninety‐three axons that innervated vibrissa follicles, guard hair follicles, and slowly adapting receptors were stained for distances of 4–12 mm at the levels of the main sensory nucleus, spinal trigeminal nucleus, and rostral cervical spinal cord. The collaterals of single axons from these receptors formed terminal arbors in the outer part of the spinal trigeminal nucleus rostral to and near the level of the obex (rostral type collaterals). In the rostral part of the subnucleus caudalis (Vc) they were confined to lamina V (caudalis type collaterals) and in the caudal part of Vc and in cervical segments they were confined to lamina III/IV (spinal‐dorsal‐horn‐type collaterals). There were no transitional forms between the rostral and caudalis types, but there was a transitional form between the caudalis and spinal dorsal horn types. This transitional form was distributed in laminae III/IV and V. The terminal arbors of the rostral type of collaterals formed an interrupted, rostrocaudally oriented column like those seen in the lumbar dorsal horn, but the column shifted down to lamina V near the obex, and more caudally, gradually shifted upward to lamina III. Major morphological differences were not observed among the three different functional types of collaterals with respect to the rostrocaudal distribution of collaterals, and the shape and location of collaterals. The differential laminar distribution of collateral arbors of single axons along the rostrocaudal axis distinguishes the spinal trigeminal nucleus from the spinal dorsal horn where functional types of mechanoreceptive afferents form continuous or interrupted sagittal columns of terminal arbors that do not shift dorsoventrally within segments.
Development of the spinocerebellar system in the postnatal rat
Authors: Nunes M. L. Arséanio , Sotelo C. 
Published: January 2005

AbstractThe distribution of Spinocerebellar projections from birth to adulthood in rats was analyzed by anterograde and retrograde tracing methods. A correlation between mossy fiber synaptogenesis and the establishment of Spinocerebellar topography was also investigated with electron microscopy.Experiments with retrograde transport techniques indicate that the spinal axons reach the cerebellum in two successive groups: the first one, appearing prenatally, contains axons from neurons in the central cervical nucleus, Clarke's column, the sacral nucleus of Stilling, as well as from border cells. The second group, which reaches the cerebellum by P3, arises from new neurons of the same nuclear regions and from scattered cells of the spinal gray matter. The distribution and the morphological appearance of the spinal cells change between P1 and P3 and give the adult pattern by P7.The establishment of Spinocerebellar projections occurs in four successive stages. In a first stage, spinal axons reach the cerebellum and occupy the prospective white matter of the anterior vermal lobe and of the pyramis. Later, during a “waiting” stage between P1 and P3, the spinal fibers become denser in the central white matter of both their anterior and posterior target zones but do not penetrate the gray matter. From P3 to P5 the protocolumnar stage takes place, and spinal axons invade the granular layer of the anterior lobe, where they begin to be organized in nascent sagittal columns. At the end of this stage, identifiable synaptic contacts between mossy terminals and granule cell dendrites are first observed in the anterior lobe by electon microscopy. In the pyramis, invasion of the granular layer begins only at P5. Between P5 and P7 the low intercolumnar dispersion of spinal fibers disappears and the projection roaches its fourth and final stage, characterized by a columnar organization corresponding to the adult pattern of the spinocerebellar projection.These results indicate that (1) the adult pattern of spinocerebellar projections is attained by P7. (2) The asynchronous invasion of the gray matter in the anterior and posterior lobes may be related to the chronology of mossy fiber maturation in these regions. (3) There is a temporal correlation between the columnar organization of the spinal axons and the appearance of the earliest‐maturing mossy rosettes. However, a clear relationship between synaptogenesis and topographic organization could not be demonstrated.