摘要:

AbstractBecause the globus pallidus gives rise to the principal efferent system of the corpus striatum and is traversed by several fibers systems, attempts were made to study the projections of its cells by autoradiographic technics. Tritiated amino acids (L‐leucine, L‐proline and L‐lysine) were injected into: (1) the medial pallidal segment (MPS), (2) the MPS and the substantia innominata (SI), (3) portions of the MPS and the lateral pallidal segment (LPS) and (4) parts of the putamen.Cells labeled by injections of the MPS transported isotope to thalamic nuclei (ventral anterior, VApc, ventral lateral, VLo and VLm, and the centromedian, CM), the pedunculopontine nucleus (PPN), and the lateral habenular nucleus (Hbl). Labeled cells of the MPS and SI transported isotope to: (1) thalamic nuclei (VLo, VLm and CM), (2) PPN, (3) Hbl, (4) lateral and posterior regions of the hypothalamus, and (5) extensive dorsal regions of the substantia nigra (SN). Comparisons of label transported from uptake of isotope by cells of the MPS, and cells of both pallidal segments, suggest that the LPS projects fibers only to the subthalamic nucleus (STN). Not all regions of the STN appear to receive fibers from the LPS. Selectively labeled neurons of the putamen transport isotope to broad regions of both pallidal segments and to the pars reticulata of the SN.This study suggests that cells of the MPS project profusely and topographically to: (1) the rostral ventral tier thalamic nuclei (VApc, VLo and VLm), (2) lateral portions of CM, and (3) the PPN. Fibers of the lenticular fasciculus appear to terminate preferentially in VLo. Cells in sublenticular portions of SI, and those extending into the medullary laminae of the pallidum, appear to project to: (1) HBl via the stria medullaris, (2) the pars compacta of SN, (3) lateral and posterior regions of the hypothalamus, and (4) the so‐called nucleus of the ansa lenticularis. Some fibers from cells of SI appear to join the dorsal stria terminalis, but none enter the inferior thalamic peduncle and none project to any part of the dorsomedial nucleus of the t

ISSN:0092-7317    

DOI:10.1002/cne.901690302

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

年代:1976

数据来源: WILEY

摘要:

AbstractElectron microscopy and3H‐thymidine autoradiographic techniques were used to study the fine structure of proliferating cells in developing rat optic nerve. Before the closure of the optic canal almost all of the cells incorporating radioactive thymidine are ventricular cells, but after closure (16 days of gestation) the vast majority are differentiating astroblasts or oligodendroblasts. Labeled astroblasts show a range in their degree of differentiation; some cells lack 90 Å cytoplasmic filaments while others have glial filaments and abundant cytoplasmic organelles. In contrast to astroblasts, all of the labeled oligodendroblasts are in the early stages of differentiation. The proliferation of oligodendroblasts starts at five days postnatal, approximately a day or two before the onset of myelination. During myelinogenesis a few of the labeled oligodendroblasts show presumptive connections to myelin sheaths. Microglial cells do not appear to play a major role in gliogenesis since they form less than 2% of all the labeled cells.The results of this study indicate that astroblasts and oligodendroblasts, rather than undifferentiated glioblasts, are the major source of macroglia. The finding that proliferating glia are in the process of differentiation agrees with recent studies which show that differentiated cells can divi

ISSN:0092-7317    

DOI:10.1002/cne.901690303

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe time of origin for astrocytes and oligodendrocytes in rat optic nerve was studied by3H‐thymidine autoradiographic techniques similar to those used in dating the time of origin for neurons. This study shows that astrocytes are formed throughout late embryonic and all of postnatal development, while oligodendrocytes are generated only during the postnatal period.A few astroglia undergo their final cell division as early as 15.5 days of gestation, but most astrocytes are not generated until the first week of postnatal development. Although the final cell division for more than half of the astrocytes takes place before the end of the first postnatal week, fully mature, fibrous astrocytes are not observed in electron micrographs until after 14 days of age. This time lag implies that the differentiation of these early generated cells takes place gradually over a 2‐to 3‐week interval.Oligodendroglia begin their final division a day or two before the onset of myelination (6–7 days postnatal), but the vast majority are produced during the period of myelinogenesis. After almost all of the axons have been myelinated, oligodendrocytes are still being generated in small numbers. These late forming cells are generally less differentiated in appearance than those formed earlier; this suggests that the degree of differentiation of oligodendrocytes may be dependent upon the number of axons available for myelination. As with astrocytes, oligodendrocytes show a lag of about two weeks from the time of final cell division until they transform into morphologically differentiated cells.In transverse sections of the optic nerve heavily labeled neuroglia are randomly distributed, indicating there are no temporal‐radial gradients for the individual cell types. This observation taken together with the other information obtained from the present and the previous study (Skoff et al., '76) strongly suggest that the factors controlling gliogenesis are different from those governing neuro

ISSN:0092-7317    

DOI:10.1002/cne.901690304

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe physiological and morphological recovery of cricket (Acheta domesticus) abdominal giant interneurons following varying periods of deafferentation and subsequent regeneration was examined. The principal afferent input to two identified interneurons was removed by surgically ablating an abdominal sensory appendage, the cercus. Deafferentation restricts the growth of the dendrites of the medial giant interneuron. Reinnervation by the peripheral sensory field leads to recovery of the dendrite length which is dependent on the time allowed for recovery. The response properties of the reinnervated neurons never completely recovers irregardless of how short the period of deafferentation. Reinnervated neurons respond more weakly to standard tones than do control neurons. This is due in part to faciliation of an inhibitory synaptic input which is activated by the control cercus. The results suggest that the balance between the excitatory and the inhibitory synaptic inputs to these interneurons is irrevocably altered by brief periods of deafferentation early in life.

ISSN:0092-7317    

DOI:10.1002/cne.901690305

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe pathway from the entorhinal cortical region to the hippocampal formation has previously been shown to be comprised of two sub‐systems, one of which projects predominantly to the ipsilateral fascia dentata and regio inferior of the hippocampus proper, and a second which projects bilaterally to regio superior. The goal of the present investigation was to determine if these two pathways might originate from different cell populations within the entorhinal area. The cells of origin of these entorhinal pathways were identified by retrograde labeling with horseradish peroxidase (HRP).Injections which labeled the entorhinal terminal fields in both the fascia dentata and regio superior resulted in the retrograde labeling of two populations of cells in the entorhinal area. Ipsilateral to the injection, HRP reaction product was found in the cells of layer II (predominantly stellate cells) and the cells of layer III (predominantly pyramidal cells). Contralateral to the injections, however, the reaction product was found almost exclusively in the cells of layer III.With selective injections of the entorhinal terminal field in regio superior, only the cells of layer III were labeled, but these were labeled bilaterally. Selective injection of the entorhinal terminal field in the fascia dentata, however, resulted in the labeling of cells of layer II, but not of layer III, and these cells of layer II were labeled almost exclusively ipsilaterally. A very small number of labeled cells in layer II were, however, found contralateral to the injection as well.No labeled cells were found either in the presubiculum or parasubiculum following injections of the hippocampal formation. These cell populations were found capable of retrograde transport of HRP, however, since cells in both presubiculum and parasubiculum were labeled following HRP injections into the contralateral entorhinal area.These results suggest that the projections to the fascia dentata originate from the cells of layer II, while the projections to regio superior originate from the cells of layer III of the entorhinal region proper. The very slight crossed projection from the entorhinal area to the contralateral area dentata probably originates from the small population of cells in layer II which are labeled following HRP injections in the contralateral area dentat

ISSN:0092-7317    

DOI:10.1002/cne.901690306

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe areal and laminar distribution of the cortical efferents of the medial, lateral and inferior pulvinar nuclei (PM, PL and PI respectively) were determined in rhesus monkey using autoradiography and Horseradish Peroxidase (HRP). The autoradiographic data indicated that: areas 8a, 45 and 46 on the convexity and 11 and 12 on the orbital surface of the frontal lobe received projections from PM; areas 20, 21 and 22 in temporal lobe received projections from PM primarily with caudal‐medial parts of PM projecting to more rostral‐dorsal parts of temporal lobe and rostral‐lateral parts of PM projecting to more caudal‐ventral parts of temporal lobe but PL also sends some efferents to caudal temporal lobe; areas 5 and 7 in parietal lobe and 18 and 19 in occipital lobe received projections primarily from the region in pulvinar comprising PL and PI with the more ventral parts of this region projecting to the ventral‐lateral parts of occipital lobe and the more dorsal parts of this region projecting to the more dorsal‐lateral and medial parts of parieto‐occipital cortex and with PM contributing slightly to these projections rostrally.The autoradiographic information on the pulvinar projections to frontal lobe and temporal pole was supplemented by data derived from cortical HRP injections. These indicated that although only PM of the pulvinar subnuclei projected to these regions, three other caudal thalamic structures, i.e., medial dorsal nucleus, nucleus limitans and suprageniculate nucleus also projected to these regions raising some questions about the identity of the densocellular part of the medial dorsal nucleus which has also been considered to be part of pulvinar.The laminar distribution of pulvinar cortical efferents was uniformly similar regardless of the pulvinar recipient area examined. Elevated numbers of silver grains were observed over all cortical layers, but the silver grains were densest over the deep parts of layer III.The thalamic reticular nucleus was the only diencephalic structure observed to receive projections from pulvinar and it did so from PM, PL and PI.The pulvinar's efferents are to homotypical rather than heterotypical cortex and its connections are most extensive with cortex rather than with subcortic

ISSN:0092-7317    

DOI:10.1002/cne.901690307

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

年代:1976

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.901690301

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

年代:1976

数据来源: WILEY