摘要:

AbstractA study has been made of the growth of cervical nerves C3‐C6to the ral diaphragm. At 11 days of embryonic age these cervical nerves first project out of the spinal cord toward the cardinal veins and later form the left and right phrenic nerve trunks. During the next 2 days, the phrenic nerves grow caudally in close association with the cardinal veins toward the diaphragm. At the growing tips of these nerve trunks the growth cones of axons were observed every 1–2 μm. The last axon did not project more than 2 μm ahead of any neighbouring axons. At 14 days the phrenic nerves reach the level of the developing diaphragm and converge into pools of premuscle cells. Previous studies have suggested that the phrenic nerve enters the premuscle masses of the diaphragm at an early developmental stage when the premuscle masses; are at approximately the segmenlal levels C3‐C6This study shows that the phrenic nerves must grow to more caudal levels in order to reach the premuscle cells of the diaphragm. Furthermore, the leading axons of the phrenic nerve trunk do not project in a pioneering fashion, far in advance of the trailin

ISSN:0092-7317    

DOI:10.1002/cne.902180402

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractThe neuronal connections in the central gustatory system of the crucian carp were examined by means of degeneration and HRP methods. Cell morphology in the primary gustatory lobes was studied in Golgi‐impregnated material.Medium‐sized neurons of the facial lobe emit axons which project to the secondary gustatory nucleus. The nucleus intermedius facialis of Herrick ('05) projects bilaterally. Large neurons send axons through the spinal trigeminal tract to terminate in the spinal trigeminal nucleus and in the medial funicular nucleus. In the vagal lobs, second‐order neurons for the ascending projections are located in the superficial part of the sensory zone. These neurons project exclusively to the ipsilateral secondary gustatory nucleus. Neurons located in the deeper part of the sensory zone send axons to the motor zone and to the brainstem reticular formation to form short reflex arcs. The glossopharyngeal lobe has similar neuronal connections to the vagal sensory zone.Both facial and vagal lobes receive afferent projections from the following central structures: nucleus posterioris thalami, nucleus diffusus lobi inferioris, optic tectum, motor nucleus of the trigeminal nerve, medullary reticular formation, and the gray matter of the upper spinal cord. The facial lobe has an additional afferent from the mesencephalic reticular formation. The major sources to the medullary gustatory lobes are the nucleus posterioris thalami and nucleus diffusus lobi inferioris.Each type of neuron classified by morphology and location in the facial, glossopharyngeal, and vagal Jobes was correlated with its particular destination. Topographic projections were demonstrated in the secondary and tertiary gustatory ce

ISSN:0092-7317    

DOI:10.1002/cne.902180403

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractDrastic alterations in oral behavior characterize metamorphosis of anu ran amphibians. Changes cascade through all components of the jaw appa ratus from bone to muscle to nerve. In this investigation, tritiated thymi dine autoradiography was used to determine the production schedule of the trigeminal motoneurons in the leopard frog,Rana pipiens.The time of origir of these neurons and their subsequent fate are of special interest given the breakdown of the larval jaw muscles and the de novo generation of adul muscle fibers during metamorphosis. Specifically, we wanted toalearr whether trigeminal motoneurons are added, deleted, or reused during meta morphic climax.The entire complement of trigeminal motoneurons was produced over 4‐day span commencing at embryonic stage 13 and terminating at stage 20 Newly formed neurons are added to the primordial trigeminal nucleus in ar orderly pattern. Firstborn neurons settle in the ventrorostral region of the nucleus; cells with progressively later birth dates were added in a postero dorsal direction. No additional trigeminal motoneurons are generated dur ing larval maturation or at metamorphosis, thus indicating that the same population of neurons is present throughout the lifespan of the animal. From these observations we suggest that, during metamorphosis, the trigemina motoneurons that supply the larval muscles switch their allegiance to the newly formed adult jaw muscles. This change of peripheral targets can be viewed as a respecification of the trigeminal motoneuron

ISSN:0092-7317    

DOI:10.1002/cne.902180404

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractDevelopment of the trigeminal motor system was analyzed inRana pipienslarvae and adults. The aim of this investigation was to determine the postmetamorphic fate of the primary motoneurons that innervate the larval jaw muscles. Specifically, we wanted to ascertain whether these neurons were deleted in conjunction with their muscular targets during metamorphosis or reused to innervate the adult jaw muscles. Cell counts and horseradish peroxidase tracer were used to distinguish between these two possibilities.The number of trigeminal motoneurons was relatively constant in premetamorphic and prometamorphic larvae. A small reduction in the cellular complement of the motor nucleus occurred during metamorphic climax, but the majority (≈︁ 90%) of the primary motoneurons were retained from the larval to the adult nervous system. The cell loss may represent motoneurons that innervated specific larval muscles that have no adult successors and thus the entire myoneural unit degenerates. Retrograde tracers indicated that all trigeminal motoneurcns extended axons into the jaw muscles of both premetamorphic larvae and adult frogs. These observations provide further support for the recycling of the trigeminal motoneur

ISSN:0092-7317    

DOI:10.1002/cne.902180405

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractThe cellular composition of the antennal neuropile of the crayfish is described. As a context for this work the distribution of neuronal cell bodies throughout the supraoesophageal ganglion (brain) is also described. The neuronal cell bodies in the brain are concentrated in 19 distinct clusters Three paired clusters are located on the dorsal side of the brain, four paired and one midline cluster bend around the brain laterally and frontally respectively. Fewer than ten somata lie outside of these clusters. The antennal neuropile is composed of primary afferent terminals, efferents, and projecting and local interneurons. The structures of individual neurons of all four types were determined by filling them with Lucifer yellow, and an overview of the neuropile structure was obtained with cobalt backfills of selected nerves The antennal afferents are concentrated in four main tracts that run medially in the outer layer of the antennal neuropile. Up to 11 orthogonal side branches occur at equal distances (25–35 μm) along the main branches and penetrate the neuropile. The efferents contribute very thin dendrites to the antennal neuropile. The majority of the neuronal mass of the antennal lobe consists of projecting and local interneurons. The branching pattern of the interneurons within the antennal neuropile also shows an orthogonal arrangement of main branches and higher‐order branches. Thus the antennal neuropile displays a strong geometrical regularity: Main processes of all four types of neurons run in bundles the length of the long axis of the neuropile (lateral to medial inside the brain) giving rise to orthogonal side branches at regular intervals. This branching pattern leads to a striped appearance of the antennal

ISSN:0092-7317    

DOI:10.1002/cne.902180406

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractThe luteinizing hormone‐releasing hormone (LHRH) systems of rat olfactory bulbs and nasal areas were studied in neonatal and adult rats. Animals were perfused with Zamboni's fixative and olfactory bulbs with nasal olfactory areas intact were removed, postfixed, and decalcified. LHRH was immunohistochemically demonstrated in unembedded frozen or vibratome sections.Luteinizinghormone‐releasinghormoneimmunoreactive elements were found along the course of the nervus terminalis (NT) and within both the main and accessory olfactory bulbs (MOB and AOB, respectively). Both LHRH neurons and fibers were present in the AOB, but only fibers were detected in the MOB. The fibers of the AOB were not confined to any particular lamina while fibers in the MOB were found mainly in the external plexi‐form layer. LHRH fibers were found in the mucosa of the olfactory epithelium of the vomeronasal organ in both neonatal and adult rats.The NT probably serves as a source of LHRH fibers for both the AOB and the MOB and for fibers observed in the olfactory epithelium of the vomeronasal organ. Other likely sources of LHRH fibers in the olfactory bulb are disc

ISSN:0092-7317    

DOI:10.1002/cne.902180407

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractImplants of embryonic CNS tissue, dissected from the developing brainstem, cerebellum, and hippocampus of rat fetuses, were analyzed after 2–14 months survival in an intracephalic transplantation cavity in adult host rats. The mature anatomical organization of the implants was studied in specimens taken from early (embryonic day, (E) 12–14) and late (E17–20) gestational stages and compared with the results previously obtained in explant cultures and in experiments with transplants to the anterior eye chamber and to the brains of neonatal rats.The resulting volume of the implanted tissue is dependent on the gestational age of the donor fetus. For all regions analyzed the early gestational tissue develops to become larger than the late gestational tissue. Moreover, tissue dissected from different regions of the neuraxis at a specific developmental time point exhibits differing amounts of proliferation within the intracephalic cavity of the host. Though all early gestation transplants demonstrate continued cell genesis as indicated by their subsequent increase in size, late gestation brainstem specimens fail to show an increase in tissue volume and the late gestation cerebellar implants actually exhibit a reduction in final size. Early gestation hippocampal transplants demonstrate the greatest increase in tissue volume (over 3,800%) and completely fill the intracephalic cavity with no apparent encroachment upon the host CNS tissue. However, hydrocephalus was present in one host animal which contained a transplant contaminated by connective tissue that obstructed the lateral ventricle.Each implanted CNS region demonstrates cytoarchitectural features characteristic for the specific region in vivo. The results demonstrate that (1) neuroepithelial cells in the implants taken from various regions of the neuraxis can continue cell genesis after transplantation to an adult CNS environment; cells are capable of normal migration within the implant; and they continue to differentiate to produce neurons with many of their normal in vivo morphologic characteristics; (2) neurons generated before the embryonic tissue is taken for transplantation can, at least to some degree, survive and retain their cytoarchitectural features in the new environment; (3) many characteristics of the intrinsic organization and three‐dimensional architecture of each CNS region can develop even in an ectopic intracephalic site in the adult host. These observations indicate that the in cerebro implantation technique can provide an extremely valuable experimental preparation in which to analyze various aspects of development which may influence the organization of specific CNS regions, including parameters that regulate the morphology of individual neurons. The developmental questions that can be explored with this technique should complement those which can be addressed with in vitro explant or reaggregation procedures and with the intraocular grafting technique. In particular, the intracephalic implantation technique should prove valuable for obtaining new insights into cellular events that determine the complex three‐dimensional organization of the mammalian CNS during de

ISSN:0092-7317    

DOI:10.1002/cne.902180408

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractThe spatial‐temporal progress of peripheral nerve regeneration across a 10‐mmgap within a silicone chamber was examined with the light and electron microscope at 2‐mm intervals. A coaxial, fibrin matrix was observed at 1 week with a proximal‐distal narrowing that extended beyond the midpoint of the chamber. At 2 weeks, Schwann cells, fibroblasts, and endothelial cells had migrated into the matrix from both nerve stumps. There was a delay of 7–14 days after nerve transection and chamber implantation before regenerating axons appeared in the chamber. At 2 weeks, nonmyelinated axons were seen only in the proximal 1–5 mm of the chamber in association with Schwann cells. Axons reached the distal stump by 3 weeks and a proximal‐distal gradient of myelination was observed. These observations define the parameters of a morphologic assay for regeneration in this chamber model which can be used to investigate cellular and molecular mechanisms underlying the success of peripheral nerve

ISSN:0092-7317    

DOI:10.1002/cne.902180409

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractThe retina of the cichlid fish,Astronotus ocellatus, contains an unusual class of amacrine cell, the interstitial amacrine cell, which has its soma and processes restricted to a sublamina of the proximal inner plexiform layer. The interstitial amacrine cell is unique in making synapses which contain a presynaptic dense bar specialization. The interstitial amacrine cell makes reciprocal synapses with bipolar cell terminals and is presynaptic to other amacrine cells and to ganglion cell dendrites. Processes of interstitial amacrine cells are connected to each other by large gap junctions.

ISSN:0092-7317    

DOI:10.1002/cne.902180410

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902180411

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY