摘要:

AbstractA study has been made of the efferent connections of the trigeminal sibnucleus caudalis in 12 shep. Lesions were placed in this nucleus either surgically or by means of an electrical cautery device. Resulting degeneration was determined by staining serially prepared frozen sections according to the silver techniques of Nauta and Fink‐Heimer. Ipsilateral connections are desribed with the fifth, seventh eleventh and twelfth cranial nerve motor nuclei, and ascending ipsilateral connections with all of the more rostral portions of the trigeminal nuclear complex. Evidence of widespread bilateral trigemino‐reticular connections is reported. By contrast, only a small number of fibers from the subnucleus caudalis were found to ascend in the mdial lemniscus; few of these lemniscal fibers appear to ascend beyond mesencephalic lev

ISSN:0092-7317    

DOI:10.1002/cne.901410302

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

年代:1971

数据来源: WILEY

摘要:

AbstractThe cytology of the postmitotic migratory granule cell and its relationship to Bergmann glial processes was examined with Golgi staining and electron microscopy in the three cardinal planes in the developing cerebellar cortex of Macacus rhesus at various late fetal and early postnatal ages. After final mitosis the granule cell body transforms from a nearly round shape in the superficial zone of the external granular layer to a horizontal bipolar form with elongated processes oriented longitudinally to the folium, at the outer border of the molecular layer. Another descending process develops, and the cell soma becomes a pyramid flattened in the plane longitudinal to the folium. The nucleus moves into the descending process and the cell soma assumes a vertically oriented spindle shape while migrating among previously formed parallel fibers deeper in the molecular layer, and finally attains a round shape again when it lies deep to the Purkinje cell layer. During these transformations, the cell cytoplasm becomes more voluminous and contains a prominent Golgi apparatus, numerous free ribosomes, mitochondria, multivesicular and dense bodies, and fascicles of microtubules Longitudinally oriented microtubules concentrated in the vertical leading process disappear by the time the cell soma enters the granular layer. The slender trailing process loss most of its cytoplasmic organelles, acquires microtubules and together with the horizontal processes forms the characteristic T‐shaped axon. The axon forms synapses with Purkinje and stellate cell dendrites at a time when other granule cells are still migrating among them.During the entire course of their migration across the molecular layer, granule cells are directly apposed to vertically oriented Bergmann fibers belonging to the Golgi epithelial cells. The sequence of developmental stages indicates that Golgi epithelial cells are a type of protoplasmic astrocyte. The Bergmann fibers were present at all stages examined, and their constant apposition to granule cells suggests a role in the lartter's migration. Numerous electronluscent beady enlargements are seen along the fiber except at sites were the surface is in contact with migrating cells; probably these enlargements change position as the granule cells pass along the Bergmann fiber. Lamellate expansions also project from the main shaft of the glial fiber and envelop the synaptic sites on spines of Purkinje cell dendrites. These expansions seem more durable, and the young neuron appears to avoid collision with them by sprialling around the glial shaft during its descent to the granular layer. The neuron‐glia relationship apparently provides the necessary conditions for the migration of the young granule cell. Especially at late developmental stages when the molecular layer is more than 250 μ wide and is densely packed with highly oriented cell processes that have already established synaptic connect

ISSN:0092-7317    

DOI:10.1002/cne.901410303

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

年代:1971

数据来源: WILEY

摘要:

AbstractThe fields of origin of the amygdalofugal pathways in the albino rat were studied by using the Fink‐Heimer technique to stain degenerating fibers and terminals in brains of animals sacrificed four and seven days after small unilateral lesions of the amygdale. A surprisingly restricted field of origin was found for the supracommissural stria terminalis — the component projecting to the ventromedial nucleus of the hypothalamus Only a lesion in the most posterior part of the cortical nucleus produced degeneration in this pathway. The postcommissural stria terminalis which apparently distributes to the bed nucleus of the stria terminalis and preoptic area originates in a more widespread area including parts of both the basolateral and corticomedial complexes. Although intense terminal degeneration could be seen within the amygdala following all lesions, long fibers projecting into the anterior amygdaloid area, lateral preoptic area and lateral hypothalamus were found only after lesions in which fibers of passage from periamygdaloid cortex could have been interrupted. Convincing evidence, therefore, of a long axon ventral amygdalofugal pathway of the rat was not found in this st

ISSN:0092-7317    

DOI:10.1002/cne.901410304

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

年代:1971

数据来源: WILEY

摘要:

AbstractThe afferent olfactory connections of the lateral hypothalamus of the rat were studied by producing lesions of olfactory cortex and staining for degeneration by the method of Fink and Heimer ('67) and by electropysiological recording of responses to olfactory bulb shock and odor stimulation. Direct connections from olfactory areas were found only in a ventrolateral part of the medial forebrain bundle. In the posterior hypothalamus the olfactory fibers turned dorsally and terminated in a more medial area. The region from which strong olfactory responses could be recorded coincided with the path of degenerating axons. Lesions of the olfactory tuercle of hamsters and mice produced a similar restricted pattern of degeneration.

ISSN:0092-7317    

DOI:10.1002/cne.901410305

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

年代:1971

数据来源: WILEY

摘要:

AbstractStellate cells have rounded or oval cell bodies which contain nuclei bounded by a ruffled, and frequently indented, nuclear envelope. Te cytoplasm of these neurons is usually darker than that of pyramidal neurons because it contains a greater concetration of ribosomes. Where the perikaryal cytoplasm is thick, the granular endoplasmic reticulum is often arranged in parallel arrays. On the surface of the perikarya are three types of synapses: (1) ones with a wide cleft and a prominent postsynaptic density, (2) ones with a wide and straight synaptic cleft that lack a prominent postsynaptic density, and (3) ones with a narrow synaptic cleft and short synaptic complexes. The dendrites of stellate cells lack spines and frequently bear many synapses. On the thinner dendritic branches the type of synapse with a side cleft and a prominent postsynaptic density is most common. The cytoplasm of the dendrites is characterized by closely arranged microtubules.

ISSN:0092-7317    

DOI:10.1002/cne.901410306

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

年代:1971

数据来源: WILEY

摘要:

AbstractDNA synthesis and interlayer migrations of cells in the optic tectum of larvalRana pipienswere investigated, using several series of larvae which had been subjected to unilateral enucleation at stage 25, the last embryonic stage. It has been found that DNA synthesis occurs in all cellular layers of the tectum with least activity in peripheral layers. The location of the most active DNA synthesis during the larval period is the same as the location of cell division in the larval tectum, namely, in the layers bordering the ventricle of the optic lobeUnilateral enucleation of stage 25 embryos results in a decrease in DNA synthesis in all cellular layers of the optic tectum contralateral to the operation when compared to the corresponding layers in the ipsilateral tectum. The differences in rate of incorporation of3H‐thymidine between the control and affected lobes become greater during development. Fewer cells are found in each layer of the affected larval tectum than in the corresponding layer of the control tectum. The decrease is greatest in more peripheral layers, whose cells are more intimately associated with the visual circuit than are cells of the deeper layers. Peripheral to layers 1 and 2, the percentages of labeled cells found in each layer are very similar on the two sides, suggesting common factors which control migration. Differences in cell number, therefore, reflect differential cell production rather than differential cell migrations.The distribution of label resulting from3H‐thymidine incorporation at stage III indicates that the distribution of mitotic activity is not uniform in the cephalocaudal axis of the tectum. Greater cell proliferation occurs in the posterior portion of the tectum than in the anterior region throughout larval development.The peripheral control of mitotic divisions in the frog optic tectum remains unknown. The data in the present study, however, support the hypothesis that influences from afferent fibers of the optic tract modify the rates or timing of DNA synthesis in the optic tectum. The data support the notion that the deepest tectal cells respond earliest to the stimulus and these may be ependymal cells which have processes extending to the outer surface of the tec

ISSN:0092-7317    

DOI:10.1002/cne.901410307

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

年代:1971

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.901410301

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

年代:1971

数据来源: WILEY