摘要:

AbstractThe retrograde, horseradish peroxidase technique has been used to demonstrate the cells of origin of corticofugal fiber systems arising in the rat somatic sensory cortex and projecting to the striatum, diencephalon, brainstem, and spinal cord. Correlative experiments conducted with the anterograde, autoradiographic method have been used to confirm the terminal distribution of many of these fiber systems. Corticofugal pathways directed to subcortical structures arise in the first and second somatic sensory areas exclusively from pyramidal cells of the infragranular layers, V and VI. Fibers which descend to the midbrain, pons, medulla and spinal cord arise exclusively from the largest pyramidal cells, the somata of which are found in the deep part of layer V (layer VB). There is some evidence for a sublaminar organization of the different classes of efferent cells within this layer. Fibers projecting to the diencephalon arise from somata situated throughout layer VI and to a lesser extent in layer V. Corticostriatal fibers arise only from cells with somata in layer V, but the somata are more superficially situated than those of the other classes of corticofugal neurons. The laminar distribution of the somata of corticofugal neurons differs considerably from that of commissural and ipsilateral corticocortical neurons.

ISSN:0092-7317    

DOI:10.1002/cne.901750202

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractThe normal synaptic organization of the rat external cuneate nucleus (ECN) has been investigated. The characteristic feature of the ECN neuropil is complex synaptic arrangements termed synaptic glomeruli. These involve both axo‐dendritic and axo‐axonic synapses and usually are isolated from the surrounding neuropil by lamellar glial sheaths. Glial isolation of synaptic glomeruli is conspicuous near capillaries. Central glomerular bouton profiles vary in size (2–9 μm diam) and configuration. They form asymmetrical synapses onto dendritic shafts and spines and occasionally receive symmetrical synapses fromen passantbouton profiles.Other forms of axo‐dendritic synapses not associated with synaptic glomeruli are observed. The type frequently observed is formed by one or more boutons (0.5–4.0 μm diam) synapsing onto a dendrite or dendritic spine. “Isolated” axo‐dendritic synapses are surrounded by glial lamellae. Elongated “giant” boutons make multiple synaptic contacts along a dendritic shaft.Serial axo‐axonic synapses are found mainly in caudal regions of the nucleus. Axo‐somatic synapses are formed by small boutons (0.3–2.0 μm diam) contacting medium (16–24 μ) and small (9–14 μm) neurons. The least frequently observed bouton type in the rat ECN contains numerous granular vesicles, 80‐100 nm in diameter. These boutons may contact dendri

ISSN:0092-7317    

DOI:10.1002/cne.901750203

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractUnilateral, intradural dorsal rhizotomies (C3‐C8) were performed on adult rats to study the patterns of synaptic organization of ascending dorsal root fibers in the external cuneate nucleus (ECN). Animals were permitted to survive for periods of time ranging from 3hours to 12 days. Sham‐operated animals presented a morphology indistinguishable from that of normal, unoperated animals. In rhizotomized animals, degeneration was observed ipsilaterally at all survival periods. After postoperative survivals of 3 to 14 hours some terminal boutons displayed clumbing and diminution in numbers of synaptic vesicles and, in addition, degenerating myelinated axons were observed at this time. There was considerable degeneration in the neuropil between 24 and 48 hours postoperative. Two forms of degeneration occurred in axons and terminal boutons with comparable frequency: electron lucent degeneration and electron opaque degeneration. Reactive phagocytic glial cells contained degenerated masses, lipoid droplets, lysosome‐like structures and myelin fragments. After postoperative survivals of four to six days, lucent and opaque degenerating terminals were less numerous. Neurofilamentous degeneration was observed only occasionally. Unaltered synaptic membrane specializations were present and were usually abutted by glia. At 12 days postoperative, synaptic glomeruli and serial synapses were not seen. Invaginating dendritic spines were rarely seen. Bouton populations that remained unaltered were: small (0.3‐3.0 μm) boutons that contact dendritic shafts and somata, nodal synaptic boutons and boutons containing granular vesicles (8

ISSN:0092-7317    

DOI:10.1002/cne.901750204

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractThe growth of corticospinal axons into the spinal cord has been demonstrated using the autoradiographic and the Fink‐Heimer silver degeneration methods. In addition, the development of several types of placing reactions has been studied. After unilateral injections of radioactive proline or unilateral injections of radioactive proline or unilateral ablations of the somatosesory‐motor cortex, corticospinal axons were found to extend into the contralateral dorsal funiculus of the lower cervical cord at one day postnatally, into mid‐thoracic segments at three days, into upper lumbar cord by five days and into coccygeal segments by nine days. Corticospinal axons are first present in the contralateral spinal gray of lower cervical cord at day 5 and in the contralateral spinal gray of lower lumbar and sacral cord by day 9. Little change in the topographical distribution or in the density of the projection is found at all levels of the spinal gray after the fourteenth postnatal day. Comparable results were found with both experimental techniques.Forelimb placing is first seen between 4 to 7 days and hind limb placing between 9 to 13 days. The last placing response to appear in both the forelimbs and the hindlimbs is placing in response to tactile and light proprioceptive stimuli. After the initial onset of the placing reactions, there is a gradual increase in the frequency and speed of the responses until 14 to 17 days postnatally, at which time the reactions appear to be mature.While a causative relationship between the growth of corticospinal axons into the spinal cord and the development of placing has not been established, a close temporal relationship has been found between first: the appearance of fore‐ or hindlimb placing responses and the appearance of corticospinal axons within the spinal gray at the appropriate levels of the cord and second: between the completion of the primary growth of corticospinal axons at the light microscopic level and the maturation of the placing re

ISSN:0092-7317    

DOI:10.1002/cne.901750205

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractMossy fiber rosettes in the granular layer of the cerebellar cortex were studied after sections of the lateral funculus of the spinal cord of the chicken and silver impregnation with the Fink‐Heimer ('67) method I. After a survival time of two or three days two types of degenerated rosettes were found. The first type is characterized by digitiform protrusions, the second type of rosette is spherical. Both types are covered by small argyrophilic particles which disappear when the degeneration proceeds. With longer survival times the rosettes become swollen and finally desintergrate and loss their argyrophilia. After a survival time of 30 days only debris of rosettes can be found.These observations were used to determine the cerebellar cortical projection of mossy fibers originating from segments of the spinal cord isolated in “successive degeneration” experiments consisting of a chronic cordotomy followed by an acute cordotomy rostral to the firs

ISSN:0092-7317    

DOI:10.1002/cne.901750206

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractThis study identifies climbing fibers in the cerebellar cortex following brain stem lesions. Antegrade nerve fiber degeneration was studied after electrolytic destruction of rhombencephalic structures in 24 domestic fowl. Direct damage to the cerebellum was precluded by a retropharyngeal surgical approach. Only lesions that include the inferior olivary nucleus were compatible with Fink‐Heimer staining of degenerating nerve fibers in the Purkinje cell and molecular layers. Degenerating axons were identified as climbing fibers from their trajectory in association with Purkinje cell soma and dendrites. Terminal nerve endings were observed only in the basal one‐third to one‐half of the molecular layer. The presence of climbing fibers in only the contralateral molecular layer was observed in autoradiographic preparations subsequent to unilateral injection of tritiated leucine into the inferior olivary nucleus of three hens. The morphology of the labeled and impregnated degenerating nerve fibers closely coincides with information provided by previous investigators using Golgi stained histological preparations and electron micro

ISSN:0092-7317    

DOI:10.1002/cne.901750207

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.901750201

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY