摘要:

AbstractThe organization of part of the primary somatosensory cortex was examined in anesthetized raccoons at 2, 8, or 16 weeks after the normal peripheral input to this region of cortex had been removed by amputation of the fifth digit. Electrophysiological recordings were made in and around the cortical area representing the fifth digit. Eight intact animals were used to verify that this specific area could be accurately localized on the basis of the sulci and to determine the normal response characteristics of this area. The results from nine animals with the fifth digit removed provided evidence for a gradual reorganization of the cortical area which had been functionally denervated. At 2 weeks postamputation the field was almost totally unresponsive to sensory input. At 8 weeks many sites were responsive to high intensity stimulation of rather extensive regions of the hand. At 16 weeks the cells fired more readily to peripheral stimulation than at 8 weeks and tended to have smaller, more restricted receptive fields. The location of receptive fields in this latter group suggested that the fifth digit area was taken over primarily by input from the fourth digit. The time course of this reorganization is suggestive of extensive anatomical changes either within the cortex itself or at subcortical levels.

ISSN:0092-7317    

DOI:10.1002/cne.902050402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractThe morphology of the interstitial nucleus of Cajal (INC) in the rat was studied with the light and electron microscope. The INC was mapped throughout its rostrocaudal extent from cresyl violet‐stained frozen sections cut transversely through the midbrain in the stereotaxic plane. Caudally, the INC consisted of a small number of scattered cells lying ventrolateral to the periaqueductal grey. In three of four cases studied, the caudal tip of the nucleus was located between 40 and 120 μm rostral to the rostral tip of the somatic cell columns of the oculomotor nucleus. Proceeding rostrally, the INC increased in size, reaching its maximal development just caudal to its most rostral extent. The INC was limited rostrally by the fibers of the fasciculus retroflexus. The mean rostrocaudal length of the INC was 1.12 mm.On the basis of light microscopic observations of cresyl violet‐stained paraffin sections, two groups of neurons could be distinguished in the INC. One group consisted of large, oval to multipolar cells with mean dimensions of 33 × 23 μm. The second group, which included by far the greatest number of cells, consisted of small to medium neurons, round, triangular, polygonal or fusiform in shape, with mean dimensions of 19 × 14 μm.Injection of horseradish peroxidase into lesions in the cervical spinal cord resulted in retrograde labeling of neurons of all sizes and shapes throughout the length of the INC. Labeled neurons were also found in the red nucleus, the mesencephalic reticular formation, and the nucleus of the posterior commissure.All the morphological varieties of neurons described with the light microscope could be identified in the electron microscope. Large neurons, and some cells of the small to medium group, contained well developed Nissl bodies, together with numerous cytoplasmic organelles. Many neurons in the small to medium group, however, did not contain conspicuous Nissl bodies, and had a poorly developed rough endoplasmic reticulum.Axon terminals containing either round or pleomorphic vesicles were seen in the INC. Axosomatic synapses were formed by both types of terminals. Such synapses were usually symmetrical, regardless of the shape of the vesicles within the terminal. In a number of neurons, the percentage of the surface of the neuronal somata in direct apposition to axon terminals was measured. The results of such measurements suggest that a greater percentage (more than 50%) of the surface of larger neurons is apposed by axon terminals than is the case with smaller neurons, which, on the average, were invested by axon terminals over 15% of their total surface in any given single plane of section. Axon terminals investing the surfaces of proximal dendrites were morphologically similar to those in apposition to neurona

ISSN:0092-7317    

DOI:10.1002/cne.902050403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractOntogeny of the leucine‐enkephalin (L‐Enk) neuron system in the lower brainstem of the rat was investigated by means of indirect immunofluorescence.L‐Enk‐containing cells first appear in the primordium of the medullary reticular formation just medial to the n. tractus spinalis nervi trigemini at the level of the rostral half of the inferior olivary nucleus, in the n. cuneiformis, and in the mesencephalic reticular formation of the fetus at gestational day 16 (14–15‐mm embryos). From that time onward, L‐Enk‐containing cells appear in various areas of the lower brainstem one after another until birth. After birth, although L‐Enk‐containing cells decrease slightly in number as the rats grow, L‐Enk‐containing fibers continu

ISSN:0092-7317    

DOI:10.1002/cne.902050404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractThe development of cytoarchitecture in the lumbar spinal cord of mouse embryo between embryonic day 13 (E13) and E15 was studied by scanning and transmission electron microscopy. A pattern of two perpendicularly oriented sets of cellular elements was found in the intermediate zone at both E13 and E14. One set consisted of radially oriented processes that often originated from cell bodies in the ventricular zone. The second set consisted of cell bodies and processes that were oriented predominantly parallel to the neural tube margin and in the transverse plane. This set was termed circumferential elements and included most of the immature neurons. At E13, the circumferentially oriented cells were arranged into rostrocaudally compressed sheets or layers that were partially segregated one from another by flattened bundles of radially oriented processes. This pattern of orthogonally arranged circumferential and radial elements remained evident through E14 when the profuse growth of cellular processes began to obscure the identity of individual cells seen on the scanned surface. The exposed intermediate zone surface at E14 and E15 often had relatively flat transverse areas separated by ledges of broken tissues, indicating that most neurites grow in the transverse plane. These observations indicate that the sequential patterned development of an organized morphological substratum is an important factor in orienting neurite growth.

ISSN:0092-7317    

DOI:10.1002/cne.902050405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractThe early development of the circumferential axonal pathway in the brachial and lumbar spinal cord of mouse and chick embryos was studied by scanning and transmission electron microscopy. The cellular processes which comprise this pathway grow in the transverse plane and along the lateral margin of the marginal zone (i.e., circumferentially oriented), as typified by the early embryonic commissural axons. The first formative event observed was in the ventrolateral margin of the primitive spinal cord ventricular zone. Cellular processes were found near the external limiting membrane that appeared to grow a variable distance either dorsally or ventrally. Later in development, presumptive motor column neurons migrated into the ventrolateral region, distal to these early circumferentially oriented processes. Concurrently, other circumferentially oriented perikarya and processes appeared along the dorsolateral margin. Due to their aligned sites of origin and parallel growth, the circumferential processes formed a more or less continuous line or pathway, which in about 10% of the scanned specimens could be followed along the entire lateral margin of the embryonic spinal cord. Several specimens later in development had two sets of aligned circumferential processes in the ventral region. Large numbers of circumferential axons were then found to follow the preformed pathway by fasciculation, after the primitive motor column had become established. Since the earliest circumferential processes appeared to differentiate into axons and were found nearly 24 hours prior to growth of most circumferential axons, their role in guidance aspioneering axonswas suggested.

ISSN:0092-7317    

DOI:10.1002/cne.902050406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractMotor neurones in the thoracic ganglia of the locust were impaled with microelectrodes and identified according to the muscle they innervated and their other physiological properties. They were then labeled by intracellular injection of horseradish peroxidase and processed for electron microscopy. The nature and distribution of synapses on each motor neurone was examined and, by the use of reconstructions from serial sections, their spatial relationships revealed. The metathoracic fast extensor tibiae and mesothoracic tergosternal flight motor neurones have both output and input synapses on their neuropilar branches. These synapses are involved in serial, reciprocal, and recurrent relationships showing that the structural equivalent of a physiological synapse may be complex. The metathoracic slow extensor tibiae and anterior fast flexor tibiae motor neurones apparently have only input synapses within the neuropile.

ISSN:0092-7317    

DOI:10.1002/cne.902050407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractThe cytoarchitecture of the caudate nucleus was examined in Nisslstained sections from rhesus monkeys, in some of which the corticostriatal terminals had also been labeled by anterograde transport of tritiated amino acids injected into prefrontal cortex. The cytoarchitectonic analysis revealed the existence of two cellular compartments that could be distinguished on the basis of cell size, density, orientation, and tinctorial properties: (1) cellislandsconsisting of approximately 1,500 to 15,000 densely packed neurons that form aggregates of variable shapes and sizes embedded in (2) amatrixcompartment of slightly larger and more loosely packed neurons that comprise the remaining and greater part of the caudate nucleus. In coronal sections, cellular islands appear mostly as round or elliptically shaped areas, 300–600 μm in diameter, but can assume more elongated and complex forms particularly in the sagittal and horizontal planes. They are encircled by fibers arranged in a thin, cell‐sparse capsule that sets them apart from the matrix compartment. Analysis of cellular organization and corticostriatal connections in counterstained autoradiograms indicates that the prefrontal cortex projects only to the matrix zone and not to the territory occupied by island cells. Therefore, according to present observations the neostriatum in primates should be viewed as a cytoarchitectonically heterogeneous structure composed of at least two distinct cellular compartments with specific connectivity. These compartments may be related to the histochemical and functional diversity of the neostri

ISSN:0092-7317    

DOI:10.1002/cne.902050408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902050401

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY