摘要:

AbstractAn analysis of the cells and their processes within the island of Calleja complexes (ICC) was made in light and electron microscopic preparations to determine synaptic relationships within this part of the basal forebrain. The light microscopic preparations showed that the ICC contained two cell types, granule cells and large cells. In electron microscopic preparations, the somata of granule cells were grouped together and were directly apposed to other somata of granule cells. Specialized junctions (4–6 nm wide) that occurred at sites of somal apposition suggested ephaptic coupling of granule cells. The granule cell somata had nuclei that contained clumps of heterochromatin adjacent to smooth nuclear envelopes. The perikaryal cytoplasm of these cells consisted of a relatively thin rim containing few organelles. Spinous dendrites of small diameter were occasionally found in continuity with these cells. Axon terminals rarely formed synapses with the somata of granule cells, but were more frequently found to synapse on their dendrites and dendritic spines. These features for granule cells are similar to those for medium‐sized spiny neurons in the neostriatum.The somata of the large cells were found either within the core or along the dorsal margin of the ICC. The large cells had infolded nuclei and an abundant perikaryal cytoplasm that contained many organelles. Large diameter dendrites that tapered down to smaller diameters emanated in many directions from these somata. Axon terminals covered nearly the entire surface of these somata and dendrites where they commonly formed symmetric synaptic junctions. These characteristics of large cells indicate a resemblance to the large cells in the globus pallidus and ventral pallidum. Therefore, the ICC have ultrastructural features found in both the neostriatum and globus palli

ISSN:0092-7317    

DOI:10.1002/cne.902050302

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

年代:1982

数据来源: WILEY

摘要:

AbstractAn electrophysiological study on single afferent nerve fibers in the ophthalmic nerve of the goose revealed two kinds of temperature‐sensitive mechanoreceptors in the beak, which are innervated by large‐diameter myelinated axons. Some Herbst corpuscles, which display rapidly adapting responses to mechanical stimulation, discharge tonically to cooling the receptive field. A static response maximum occurs at temperatures between 15 and 25°C. The vibration sensitivity of Herbst corpuscles decreases with temperature. Many slowly adapting Ruffini endings also respond with sustained discharges to cooling but behave like rapidly adapting mechanoreceptors on warming the receptive field. The temperature at which the maximal static response occurs in different slowly adapting units varies between 10 and 30°C.The fine structure of Herbst corpuscles and Ruffini endings was investigated electron microscopically in order to elucidate possible morphological substrates for the specific functional properties of the two receptor types. Both Herbst corpuscles and Ruffini endings are characterized by a distinct but different combination of nervous and nonnervous (auxiliary) tissue elements and by the occurrence of special structural units at the sensory nerve endings. Such “transducer sites” presumably correspond to those areas of the receptor membrane where the mechanoelectric transduction process takes place. The most prominent constituent of a transducer site is a spurlike axon process, which in the Herbst corpuscle projects between the lamellae of the inner core, and in the Ruffini endings comes into contact with collagenous microfibrils, either directly or indirectly through the mediation of Schwann cell processes.Two morphological variants of Ruffini endings were recognized and were found to occur at different locations in the dermis underlying the horny covering of the bill tip. One type is distinguished by the presence of a specialized terminal cell making contact with the initial branches of the arborizing receptor axon. The other type of Ruffini ending lacks the terminal cell.The structure‐function relations in Herbst corpuscles and Ruffini endings are discussed on the basis of the electrophysiological and ultrastructural observations. It is argued that the different response characteristics of both receptor types to mechanical stimuli result from the specific kind and arrangements of the auxiliary receptor structures and from the mechanical properties of the latter. On this basis the thermosensitivity of Herbst corpuscles and Ruffini endings can be explained as a consequence of the differential effects which temperature changes have on one hand on the auxillary receptor structures and on the other hand on the mechanically elicited receptor potential. It is concluded that the temperature sensitivity of some types of mechanoreceptors may be a secondary result of that differentiation of the auxiliary receptor structures which makes the discriminative function of the different types of mechanoreceptors possible and, therefore, does not necessarily conflict with the principle of modality specificity in sensor

ISSN:0092-7317    

DOI:10.1002/cne.902050303

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

年代:1982

数据来源: WILEY

摘要:

AbstractQuantitative electron microscopy was used to examine the ability of aged (2‐year‐old) and young adult (90‐day‐old) rats to replace those synapses lost (85–90%) in the outer two‐thirds of the molecular layer of the dentate gyrus after a complete unilateral lesion of the entorhinal cortex. In aged rats the synaptic density is significantly lower than that of young adults at 10 days postlesion. Synaptic replacement begins between 2 and 4 days postlesion in young adults, whereas there is a delay until after 10 days postlesion in aged rats. Once synapse replacement begins in aged rats, the rate of synapse reappearance is about equal that of young adults. Thus the initial 10 days postlesion appears critical to growth of responding afferents and reformation of synaptic contacts.Analysis of synapses in terms of noncomplex and complex synaptic types shows that the noncomplex type accounts for the significant synaptic density difference between the two age groups. Replacement of complex synapses is nearly indistinguishable between age groups and is complete by 60 days postlesion. In contrast the initial replacement rate of noncomplex synapses in aged rats is much slower than young adults, though the control synaptic density is achieved by the end of the

ISSN:0092-7317    

DOI:10.1002/cne.902050304

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

年代:1982

数据来源: WILEY

摘要:

AbstractPreviously we reported that a delayed onset in the reinnervation of the outer two‐thirds of the dentate molecular layer occurred in aged rats after an entorhinal lesion. Several factors associated with formation of new synaptic contacts and removal of degenerative debris may affect the reinnervation process. In this study the appearance and removal of degeneration was analyzed and evaluated with respect to the delayed reinnervation process in aged rats. After a complete lesion of the entorhinal cortex, 85–90% of the input to the outer two‐thirds of the ipsilateral molecular layer is lost. Electron‐dense and electron‐lucent degeneration are present throughout the outer two‐thirds of the denervated molecular layer. In both aged and young adult rats, the electron‐lucent degeneration disappears by 10 days postlesion. The predominant electron dense degeneration, however, is removed at a different rate by young adult and aged rats. Young adults demonstrate a biphasic degeneration removal process, with almost half of this degeneration rapidly lost by 10 days postlesion, and nearly all by 60 days post‐lesion. Aged animals in contrast, have lost only 16% of the dense degeneration at 10 days postlesion, with about 30% of the degeneration remaining at 60 days postlesion. The impaired removal of the degeneration from the denervated zone appears to be reciprocally related to the reinnervation response in both age groups and may be related to the normal astrocyte hypertrophy and elevated corticosteroid leve

ISSN:0092-7317    

DOI:10.1002/cne.902050305

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

年代:1982

数据来源: WILEY

摘要:

AbstractA method that allows the concurrent localization of an antigen and a retrogradely transported fluorescent dye (true blue) was used to identify, immunohistochemically, cells in the paraventricular nucleus of the hypothalamus (PVH) that project to autonomic centers in the brainstem or in the spinal cord of the adult albino rat. After placing injections of true blue in the dorsal vagal complex or in upper thoracic segments of the spinal cord, series of evenly spaced sections through the PVH were stained with antisera directed against oxytocin, vasopressin, somatostatin, methionine‐enkephalin, or leucine‐encephalin. The results indicate that both oxytocin‐ and vasopressin‐stained cells in the PVH project to the spinal cord and (or) to the dorsal vagal complex, although about three times as many oxytocinstained cells were doubly labeled after injections centered in either terminal field. The oxytocin‐ and vasopressin‐stained cells that give rise to these long descending projections were found primarily in caudal parts of theparvo cellulardivision of the PVH, where immunoreactive cells were shown to be significantly smaller than oxytocin‐ and vasopressin‐stained cells in parts of the nucleus that project to the posterior pituitary. Small populations of cells in the PVH that cross‐react with antisera against somatostatin, leucine‐enkephalin, or methionine‐enkephalin were also shown to project directly to the region of the dorsal vagal complex and to the spinal cord, and to have a unique distribution within the PVH. Collectively, the total number of doubly labeled cells that were identified in these experiments accounts for only about one‐fourth of the total number of PVH neurons with long descending projections, thus suggesting that additional neuroactive substances are containe

ISSN:0092-7317    

DOI:10.1002/cne.902050306

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe hypoglossal nucleus has been described as the sole ipsilateral source of somatic motor innervation of the lingual and geniohyoideus muscles (Streeter, 1940; Barnard, 1940; Crosby et al., 1962; Watkins, 1978; Jenkins, 1978). In this study microliter amounts of 30% solution of horseradish peroxidase (HRP) were injected into intact but surgically isolated canine genioglossus, hyoglossus, styloglossus, geniohyoideus, and intrinsic lingual muscles. All injections were confined to the left half of the tongue, and the right half served as control. The HRP injections resulted in ipsilateral labeling of hypoglossal neurons with the exception of the injections into the genioglossus muscle, which labeled this nucleus bilaterally. Surprisingly, a few neurons associated with the ventromedial aspect of the caudal pole of the ipsilateral facial motor nucleus also labeled after injections of lingual muscles. The somatotopic representation of the geniohyoideus and lingual muscles within the hypoglossal nucleus suggested that those muscles known to originate from the same or related primodia labeled in the same or closely related hypoglossal subnuclei. The presence of labeled neurons associated with facial motor nucleus supported the hypothesis (Langman, 1975) of a possible dual origin of lingual muscles.

ISSN:0092-7317    

DOI:10.1002/cne.902050307

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe genusGalagoprovides an unique opportunity to study the relation between layers of the lateral geniculate body and classes of retinal ganglion cells. In the present experiments HRP was restricted to individual layers of the lateral geniculate body with the following results: After injections of the magnocellular layers, layers 1 and 2, labeled retinal ganglion cells ranged in size from 8 to 20 μm. After injections of the parvocellular layers, layers 3 and 6, labeled retinal ganglion cells ranged in size from 6 to 12 μm. After injections involving layers 4 and 5, which layers contain only very small, pale cells, labeled retinal ganglion cells ranged in size from 5 to 14 μm. Thus, the very largest ganglion cells were labeled only after injections of magnocellular layers 1 and 2, while small and medium retinal ganglion cells were labeled after HRP injections in every layer of the lateral geniculate body. Because the magnocellular layers actually contain a mixture of large, medium, and small‐sized cells, we suggest that retinal ganglion cells of different size‐classes project to geniculate relay cells of the corresponding size

ISSN:0092-7317    

DOI:10.1002/cne.902050308

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

年代:1982

数据来源: WILEY

摘要:

AbstractFiber connections of the corpus glomerulosum (CG) in a teleost,Navodon modestus, were studied by means of horseradish peroxidase (HRP) and a pars rotunda (GR). Both the GR and the GA have the same cell components and glomeruli. The GR is composed of four layers arranged concentrically around a central fiber net in the following order (Ito and Kishida, 1975): a glomerular layer, a fibrous layer, a small‐cell layer, and a peripheral fibrous capsule including large cells. The GA consists of a central glomerular layer and a peripheral small‐cell which contains some large cells. Following HRP injections into the GR, HRP‐positive cells were found bilaterally in the nucleus corticalis and ipsilaterally in the nucleus intermedius of Brickner (1929). Lesions of the nucleus coryicalis produced degenerating terminals bilaterally in glomeruli in the CG. The course of the fiber connections was coincident with that of the commissura horizontalis. Lesions of the nucleus intermedius resulted in degenerating terminala in the fibrous layer of the GR and the small‐cell layer of the GA. Following the destruction of the GR degenerating terminals occurres in the ipsilateral lobus inferior. Both small and large cells in the ipsilateral CG were labeled after HRP injections into the lobus i

ISSN:0092-7317    

DOI:10.1002/cne.902050309

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

年代:1982

数据来源: WILEY

摘要:

AbstractCytoarchitecture and fiber connections of the nucleus isthmi in a teleost (Navodon modestus) were studied by means of Nissl, Bodian, toluidine blue, Golgi, and Fink‐Heimer methods. Synaptic terminals were classified by the ultrastructural characteristics, and their origins were determined by electron microscopic degeneration experiments.The nucleus isthmi is composed of an outer cellular area or shell and an inner noncellular area or core. The shell covers anterior, dorsal, and ventral aspects of the core. The cell bodies in the shell are oval (15 × 20 μm) with an anteroposterior long axis, and have many somatic spines. Spines are also seen on the initial segment of the axon. Primary dendrites extend postermedially and branch out in the core. The core contains thin and thick myelinated fibers, which originate in the optic tectun and in the nucleus pretectalis, respectively.At least two types of axons terminal were distinguished in the nucleus isthmi: S type, containing spherical vesciles, and F type, containing flattened vesicles. S terminals are derived from thin myelinated fibers and are only seen in the core where they form asymmetric synapses with dendrites. Frequently a portion of the S terminal membrane near the usual synaptic cleft is in close apposition with the membrane of an adjacent small dendrite or spine. F terminals, which derived from thick myelinated fibers, make symmetric synaptic contacts with both cell bodies in the shell and dendrites in the core. S terminals degenerate after ipsilateral ablation of the optic tectum, whereas F terminals degenerate after destruction of the nucleus pretecta

ISSN:0092-7317    

DOI:10.1002/cne.902050310

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.902050301

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

年代:1982

数据来源: WILEY