摘要:

AbstractSubstance‐P (SP), somatostatin (SOM), enkephalin (ENK), and serotonin (5‐HT) immunoreactive elements were studied in the spinal cord of the opossum at each 10‐mm snout‐rump (S‐R) length interval between 18 (newborn) and 127 mm (75 days after birth). The opossum is born 12 days after conception and undergoes a protracted postnatal development in an external pouch which makes it a good model for such a study. SP‐like immunoreactivity was detected in the newborn opossum; it was found within fibers located mainly in the dorsolateral marginal zone. SP‐like immunoreactive fibers soon become fairly abundant within presumptive laminae I, II, and X and were scattered within other areas of the spinal gray matter including the intermediolateral cell column. By 30 days after birth (57 mm S‐R length), the adult distribution was established. SOM‐like immunoreactivity was not detected within the spinal cord at birth. However, by postnatal day 5 (24 mm S‐R length) it was present in fibers which were numerous within the marginal zone and present within presumptive laminae I–III as well as in more ventral areas of the gray matter. By approximately postnatal day 30, evidence for SOM immunoreactivity was found within all areas of the spinal gray matter expected from studies of the adult opossum. ENK‐like immunoreactivity was present at birth within fibers of the dorsolateral marginal zone. By postnatal day 30 ENK immunoreactive fibers were found within most of the areas containing them in the adult animal, except for laminae I and II. ENK‐like immunoreactivity was not observed in laminae I and II until approximately postnatal day 50 (84 mm S‐R length). Fibers showing 5‐HT‐like immunoreactivity were remarkably abundant within the cervical marginal zone at birth but sparse at lumbosacral levels. They were found within laminae IV–Xby postnatal day 15 (35 mm S‐R length) and within the intermediolateral cell column by at least day 30. The adult distribution was not present until approximately 50 days after birth when 5‐HT‐like immunoreactivity was found within fibers of laminae I and II. Demonstration of SOM‐, ENK‐, and 5‐HT‐like immunoreactivities in neuronal somata of the spinal cord was age dependent.Our results suggest that axons containing SP, SOM, ENK, and 5‐HT are present within the opossum's spinal cord very early in development and that they grow in

ISSN:0092-7317    

DOI:10.1002/cne.902130302

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractA cytoarchitectonic analysis was performed on the diencephalic nuclei of the bullfrog,Rana catesbeiana.The epithalamus contains two widely recognized habenular nuclei. The thalamus has three subdivisions: dorsal and ventral thalamus, and posterior tuberculum. The dorsal thalamus may be further parcelled into anterior, middle, and posterior zones. Connectional data from other studies support this zonation. The anterior zone projects to the telencephalic pallium. The middle zone nuclei receive a strong input from the midbrain roof and project to the telencephalic striatal complex. The posterior zone nuclei do not appear to project to the telencephalon; they may eventually be placed in the pretectum, a transitional area between the diencephalon and mesencephalon. Two of the ventral thalamic populations have been frequently placed in the dorsal thalamus and called the nucleus rotundus and the lateral geniculate nucleus. These terms imply homology with sauropsid dorsal thalamic nuclei, but our analysis and current connectional information do not support such homologies. We have given these populations more neutral names. The hypothalamus is divisible into a preoptic and infundibular hypothalamus, and the preoptic area can be further separated into anterior and posterior preoptic areas. The posterior area contains the magnocellular preoptic nucleus and a dorsal arm of this nucleus, often placed in the ventral thalamus, was recognized. We have tentatively placed the posterior entopeduncular nucleus in the hypothalamus.

ISSN:0092-7317    

DOI:10.1002/cne.902130303

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractThe hair cell orientation patterns and the number of innervating nerve cells was determined for the ear of the holostean fishAmia calva.Scanning electron microscopy was used to analyze the sensory cells of the three otolith organs: the saccule, the lagena, and the utricle. The utricular hair cell orientation pattern is similar to that found in most vertebrates, while the lagenar hair cell pattern is similar to that in ostariophysine fishes. The saccule has both horizontally and vertically oriented hair cells, although in the living animal many of the horizontally oriented cells are really oriented lateromedially. The transition region between cells oriented horizontally and vertically suggests that the horizontal cells are ontogenetically derived from vertically oriented cells. The lagenar macula has the largest sensory region, with over 216,000 cells in its main sensory part. The utricular macula contains over 56,400 cells in the main sensory region, and the saccular macula over 8,600 cells. The otic nerve divides into anterior and posterior rami, and ganglion cell counts totaled 2,021 in the anterior ramus and 1,619 in the posterior ramus. There are three populations of ganglion cells in each ramus, on the basis of differences in cell diameter. By a rough estimate, the ratio of sensory to ganglion cells is at least 90:1. By comparing SEM data fromAmia, other nonteleosts, and various teleost species, we suggest that the ontogenetic derivations of the horizontal cells in the teleosts and nonteleosts are substantially different and apparently unrelated to each other and that the most primitive ray‐finned fishes had only vertically oriented sensory cells while the horizontally oriented cells subsequently evolved at least twice, once inAmiaand other nonteleosts, and once in the ancestors of the teleost

ISSN:0092-7317    

DOI:10.1002/cne.902130304

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractThe effects of anterograde transneuronal atrophy were studied in two visual nuclei of the chick—the ectomamillary nucleus (EMN), which shows marked degenerative changes following enucleation, and the ventral lateral geniculate nucleus (GLv), which shows less severe changes following enucleation. The chicks were enucleated on the day of hatching and killed between 2 and 81 days later.Reconstructions of the EMN and GLv revealed that enucleation retarded the growth of these two nuclei. The volume of the control EMN and GLv, ipsilateral to the removed eye, continued to increase after eye removal. The experimental EMN did not increase in volume during this time while the experimental GLv increased in volume but at a slower rate than the control GLv. The volume of the experimental GLv remained smaller than the control volume.In order to determine whether the volumetric changes were due to arrest of cellular growth or to atrophy of the neurons, a morphometric study was carried out in the two nuclei. Measurements of the cross‐sectional area of EMN neurons revealed a 20% decrease in soma area in the experimental EMN in comparison with those in the control EMN. Since neurons in the control EMN did not increase in area after hatching, it was concluded that the changes were due to atrophy rather than arrest of neuron growth. Furthermore, there was a 35% neuron loss in the EMN. The GLv, which is composed of two laminae, consistently showed a greater decrease in soma cross‐sectional area and neuron loss in its neuropil lamina (comparable to the transneuronal effects in the EMN) than in its lamina interna. Thus, in both nuclei, eye removal led to neuron loss and a decrease in soma cross‐sectional area when compared with the contralateral (control)

ISSN:0092-7317    

DOI:10.1002/cne.902130305

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractNeurons in the ectomamillary nucleus (EMN) undergo both atrophy and cell death following eye removal at hatching. It is not known whether all EMN neurons are affected uniformly by transneuronal atrophy or whether cell loss is an artifact due to misidentification of atrophied neurons as glia.In a preliminary morphological study, four types of neurons were found in the EMN by using the rapid Golgi method: A large multipolar neuron (type I); two medium‐sized spindle‐shaped neurons, one possessing many dendritic branches (type II) and the other possessing few dendritic branches (type III); and a small round neuron (type IV). Horseradish peroxidase (HRP) was then injected into two of the EMN projection fields in enucleated chicks in order to label retrogradely as many EMN neurons as possible. Types, I, II, and III neurons were identified both in the control and experimental EMN. The three types of backfilled neurons showed different degrees of transneuronal atrophy ranging from 12 to 47%. The type IV neuron, which could not be backfilled, was inferred to atrophy by 33%. Substantial differences in transneuronal atrophy, therefore, exist among the different types of neurons within the same nucleus.Since no glialike neurons could be retrogradely labeled it was concluded that there is a true neuron loss in the EMN following eye removal rather than mistaken identification of neurons as g

ISSN:0092-7317    

DOI:10.1002/cne.902130306

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractThe medullary projections of the anterior lateral line nerve, dorsal branch (Alln.d), the posterior lateral line nerve, dorsal branch (PLLn.d), associated cutaneous nerves, and the VIIIth nerve inXenopus laevishave been delineated by axonal infusion of cobalt chloride and silver intensification. The peripheral innervation of the posterior lateral line sense organs has also been traced. From wholemount and sectioned preparations, we describe three central projections, extending the length of the ipsilateral medulla but occupying distinct zones: lateral line afferents dorsomedially, stato‐acoustic dorsolaterally, and cutaneous ventrolaterally.Arborizations of ALLn.d and PLLn.d afferents are morphologically similar, intermingling throughout the lateral line lobe. Each divides into ascending and descending limbs bearing collaterals, which terminate in the lateral line neuropile and nucleus. Evidence is presented for directional and positional mapping in the branching of individual PLLn.d afferents and for topography in the ALLn.d projection. Second‐order neurones have been identified by transneuronal staining and their axons traced into the contralateral torus semicircularis. The morphology of efferent neurones is also described.Rostral branches of PLLn.d also contain cutaneous afferents which run through the medulla into the spinal cord, similar to the nerve V (cutaneous) projection. In nerve VIII preparations, the projection to the compact cochlear nucleus and the massive vestibular projection are identified. Cutaneous and vestibular but not lateral line afferents extend into the cerebellum.The separation of VIIIth nerve and lateral line afferents inXenopusmedulla is considered as evidence against the validity of the acousticolateralis concept. Information processing in the lateral line lobe is discussed in relation to connectivity patterns between first‐ and second‐order n

ISSN:0092-7317    

DOI:10.1002/cne.902130307

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractThe migration and early development of trigeminal (V) motoneurons were studied in chick embryos in which two different populations of primary trigeminal sensory neurons had been removed prior to the birthdate of the V motoneurons. Ablation of mesencephalic neural crest cells, which eliminates monosynaptic sensory input, did not affect the migration, early development, or later differentiation of the V motoneurons. However, when the anlagen of the V ganglion were removed, the V motor root did not exit from the brainstem and the V motor nucleus did not develop. Although the neurons of the V ganglion do not innervate adult V motoneurons, these populations are related developmentally. In those embryos in which the V ganglion did not develop, medial column cells, which are midline, postmitotic, premigratory V motoneurons, and a few medial, elongated cells (possibly migratory) were present until days 5–6, but these cells did not complete their lateral migration to form the lateral nucleus of V. In cases where the ganglion anlagen were not completely removed, the number of postmigratory V motoneurons was positively correlated to the size of the ganglion remnant. There also was a correlation between the axial position of the postmigratory V motoneurons and the ganglion remnants. If a caudal remnant developed, only caudal V motoneurons, whose axons reached the ganglion, migrated; if a rostral remnant developed, only rostral V motoneurons, with axons reaching this remnant, migrated. Additionally, if the central axons of the ganglion remnant entered the metencephalon in either dorsal or ventral ectopic positions, the V motor nucleus was located in a corresponding aberrant position. Thus, some characteristic of the V ganglion cells appears to guide the motor axons and somas to their final brainstem positio

ISSN:0092-7317    

DOI:10.1002/cne.902130308

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractIn the chick embryo the trigeminal (V) sensory ganglion cells send axons into the metencephalon a few hours before the V motoneurons migrate from the midline to form a lateral nucleus adjacent to the ingrowing sensory axons. This relationship suggests that the ganglion axons may influence the initiation and direction of V motoneuron migration. In the present experiment the development of the ganglion axons was retarded by removing the neural crest anlage of the V ganglion. Subsequently, V ganglion cells which were derived from the ectodermal placode anlage sent axons into the metencephalon up to 2 days later than normal. The lateral migration of the V motoneurons was similarly delayed, commencing only after the central axons from the placodal ganglia penetrated the metencephalon. This study demonstrates that the presence of V ganglion perikarya alone is not sufficient to guide the appropriate migration of V motoneurons. This migration occurs only after the axons from the V sensory ganglion cells have penetrated the brainstem.

ISSN:0092-7317    

DOI:10.1002/cne.902130309

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractThe previous study in this series demonstrated that the ingrowth of the central axons of the trigeminal (V) ganglion is prerequisite to V motor axon outgrowth and somatic translocation. In the present experiment we determined whether further interactions with V ganglion cell bodies were required by V motoneurons after the V ganglion innervates the brainstem. Soon after the ganglion axons had penetrated the brainstem they were severed, and a barner, either permeable or impermeable, was placed between the ganglion cell bodies and the metencephalon. V motor axons grew along aberrant pathways to circumvent the impermeable barriers, many rerouting to reach the V ganglion. Only those V motor nerves which contacted the V ganglion distal to the barrier reached their target musculature in the mandible. The pattern of migration of V motoneurons was normal regardless of the V motor nerve trajectory, but the cell bodies of those axons which did not reach a muscle were not fully differentiated.When permeable barriers (Millipore filters) were implanted, the nerves followed two types of trajectories. If the pore size of the filter was small (0.45 and 0.025 μm), the V motor nerves grew identically to those observed in embryos in which impermeable barriers had been implanted. If the pore size of the filter was large (8.0 and 0.08 μm), the V motor nerve grew along its normal path directly to the barrier. Small axonal bundles from these nerves frequently grew into the filter toward the distal V ganglion.These results indicate that V motor axons preferentially grow to the V ganglion perikarya after exiting from the brainstem. Contact with the V ganglion always results in V motor nerve growth to the mandible while growth of the V motor axons to aberrant target sites only occurs when the axons fail to contact the V ganglion cells distal to the barrie

ISSN:0092-7317    

DOI:10.1002/cne.902130310

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902130301

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY