摘要:

AbstractThe efferent connections of the suprachiasmatic nucleus of the hypothalamus have been studied in the rat by the injection of3H‐proline into the nucleus and the surrounding regions of the rostral hypothalamus, and by the injection of the enzyme marker, horseradish peroxidase, into the region of the ventromedial hypothalamic nucleus. After an injection of3H‐proline confined to the ventral portion of the suprachiasmatic nucleus, transported label can be followed, in the autoradiographs, dorsally and caudally in the periventricular area as far as the caudal end of the ventromedial nucleus, into the triangular area between this nucleus and the arcuate nucleus, and along the ventral aspect of the tuberal region, just lateral to the ventromedial nucleus. A small number of silver grains are also seen over the internal lamina of the median eminence. No label can be followed rostrally or immediately lateral to the nucleus. Comparable injections into adjoining regions of the hypothalamus (especially the anterior hypothalamic area, the medial preoptic area, and the retrochiasmatic region) show transported label over the same regions, but with a somewhat different pattern of grain distribution; in addition, the anterior hypothalamic area shows an extensive projection through the medial forebrain bundle to the mammillary and supramammillary nuclei, the midbrain tegmentum, and certain of the midline thalamic nuclei. Although it is difficult in our autoradiographs to distinguish between the course of the efferent fibers from the suprachiasmatic nucleus and the zones in which they terminate, our evidence favors a termination among the cells of the periventricular area, and upon dendrites of the cells in the ventromedial, dorsomedial and arcuate nuclei, which extend beyond the limits of the nuclei into the periventricular area and to the area beneath the ventromedial nucl

ISSN:0092-7317    

DOI:10.1002/cne.901600102

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

年代:1975

数据来源: WILEY

摘要:

AbstractArchistriatal involvement in visually conditioned heart rate change (established by pairing light and foot‐shock) was studied in 198 pigeons by evaluating conditioning performance following lesions of different archistriatal subdivisions or interruption of their subtelencephalic projections. Lesions of the anterior‐intermedium archistriatum or interruption of its descending projection (tractus occipitomesencephalicus) had no effect on conditioned response development. In contrast, destruction of the posterior‐mediale region or interruption of its descending projection (tractus occipitomesencephalicus, pars hypothalami) produced profound conditioning deficits. The findings are entirely consistent with a recent anatomical analysis (Zeier and Karten, 1971) suggesting that only the posterior‐mediale archistriatum constitutes the avian amygdalar homologue. It is concluded that the integrity of the posterior‐mediale region and its projection to the hypothalamus via the tractus occipitomesencephalicus, pars hypothalami are essential for establishing visually conditioned heart rate change in a defensive conditioning paradigm, and these findings are discussed in the context of structures previously implicated in mediating this conditioned autonomic

ISSN:0092-7317    

DOI:10.1002/cne.901600103

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe present experiments represent an attempt to further clarify the role of the brain in embryonic motility and behavior. By making high chronic cervical transections (“gaps”) at early prefuntional stages of incubation (i.e., 40–50 hours) and studying the subsequent emergence of motility in the chick it has been possible to determine that supraspinal input is not functional until about the tenth day of incubation. Acute cervical transections done at either 4–5 or 8–9 days lead to the same conclusion.At ten days and thereafter chronic cervical transection results in a modification of the temporal pattern (rhythm) of motility without affecting the frequency of activity. Qualitatively the movements of spinal embryos are indistinguishable from controls up to 16–17 days. At that time there are detectable differences in the character of spontaneous movements, in reflex responsivity and in hatching behavior; spinal embroyos are not able to initiate the coordinated Type III movements necessary for escape from the shell.Injection of strychinine into chronic cervical and control embryos at 10 days and at 16–17 days indicates that certain aspects of the typical strychnine response are lost following removal of brain input to the spinal cord.Finally, chronic thoracic gaps result in a clear modification of cyclic motility at 7‐days of incubation, whereas chronic cervical gaps have no effect at this age. These data suggest that propriospinal integration is present at least several days prior to the onset of supraspinal input in the ch

ISSN:0092-7317    

DOI:10.1002/cne.901600104

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe part of turtle general cortex that receives afferent fibers from the dorsal lateral geniculate nucleus and that shows evoked potentials to light stimuli has been studied with the electron microscope. This cortex consists of an outer molecular layer, a perikaryal layer, and a subcellular layer lying on a row of ependymal cell bodies. Neurons in the perikaryal lamina are characterized by long spine‐bearing apical dendrites ascending through the outer molecular layer and short finer basal dendrites in the subcellular zone. Scattered neurons without apical dendrites occur in both the molecular and subcellular zones. Two types of dendritic spines can be distinguished. Some are large, have a complex irregular shape, contain a variety of membranous sacs and mitochondria, and occasionally, a single bundle of microtubules embedded in an electron‐dense background opacity. These large spines are the most common postsynaptic element in the outer third of the molecular layer, where they are located on the distal tips of the apical dendrites. Other spines are small, with a simple spherical distal enlargement that contains only electron‐dense fuzz. They are the most common post‐synaptic element in the lower two‐thirds of the molecular layer where they arise from the proximal portion of apical dendrites. Most synaptic contacts are found on the dendritic spines and are of the “round‐asymmetrical” type. Not infrequently “flat‐symmetrical” synapses are seen coupled to “round‐asymmetrical” contacts on individual large spines. The few contacts present on spine‐bearing dendritic shafts are of both types. Axo‐somatic contacts are mainly of the “flat‐symmetrical” variety. Thus the synaptic patterns on the principal cells of turtle visual cortex are remarkably similar to those found on pyramidal cells of mammalian neocortex. In addition, however, axon terminals, dendrites and glial (ependymal) processes were often seen to give rise to membranous pouches containing large vacuoles and invaginating into dendritic shafts or spines. Rarely, axon terminals were seen to form contacts, identical in appearance to synaptic contacts, on cell bodies in the ependymal lining. More frequently, unusual types of membrane differentiations were present at the site of apposition of the membranes of axon terminals and ependymal processes. They are interpreted

ISSN:0092-7317    

DOI:10.1002/cne.901600105

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe morphology and distribution of axon terminals on central column and marginal neurons of the cat medial superior olivary nucleus (MSO) were analyzed by electron microscopy. Individual neurons or groups of cells oriented such that substantial lengths of their dendrites were within a 5–7 μthick section were selected for detailed study. Thin sections were cut from remounted thick sections. Boutons with spherical vesicles arise directly from myelinated axons; more than one synaptic region of an axon, each separated by a myelinated segment, may contact a given dendrite. Boutons with flattened and occasionally dense core vesicles arise from both myelinated and unmyelinated portions of axons; these axons may also have more than one synaptic region. Both dinds of synaptic profiles are found on the somata and dendrits of all MSO neurons.To determine which nerve endings are from the cochlear nucleus (CN) lesions were made to produce othograde degeneration. Following unilateral CN lesion degenerating spherical vesicle terminals were observed on the lateral dendrites and somata of ipsilateral central column cells and the medial dendrites and somata of contralateral neurons. Degenerating terminals were rarely seen on the opposite dendrite (three of 48 cells). In six of seven instances where medial and lateral dendrites of two cells overlapped degeneration was limited to the one oriented toward the lesion. Marginal cells examined received virtually all spherical vesicle terminals from only one CN. Terminals with flattened vesicles persisted on the somata and dendrites of all neurons studied including cells from cats with bilateral lesio

ISSN:0092-7317    

DOI:10.1002/cne.901600106

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

年代:1975

数据来源: WILEY

摘要:

AbstractA scanning electron microscope (SEM) was used to examine the morphology and surface texture of neuroepithelial cells during interkinetic nuclear migration in the cerebral visicles of the rat at 12, 13 and 14 days of gestation. Serial sections of embryonic material of the same age were also prepared for the transmission electron microscope (TEM). Particular attention was paid to the SEM and TEM appearance of mitotic neuroepithelial cells which occur exclusively along the ventrivcular border of the neural epithelium. Three distinctly‐shaped classes of mitotic cells were recognised in sacnning micrographs. (1)Pyriform cell. This type of mitotic cells was characterised by the presence of very long, fin procsses rediating from the tip and shoulders of a short external (basal) process. These fine processes were temed “intramitoticfilopodia” Microvilli were found on the surface of most pyriform cells. (2)Conical cells. Thee lacked an external process but there were large numbers of intramototic filopodia at the basal pole of the cell body, and the perkikaryal surface was rich in microvilli. (3)Globular cells. It was possible to subdivide this class of cell into large and small types. An external process and microvilli were absent in globuar cells of both sizes, but usually a few short intramitotic filopodia were absent in globlar cells of both sizes, but usually a few short intramitotic filopodia were present at the bnasal pole. The perikaryal surfced of the globular population were reised in coarse liums and bubble‐like protrusions.By pooling TEM and SEM information we were able to deduce that pyriform cells probably possess a prphase or prometaphase chromosome morphology, While conical cells exhibit a chromosome morphologyu somewhere between prometphase and early anaphase. Lrge globular mitotic cells were found to be between metaphase and late anaphase and small glbular cells were indentified as early telophase cells.On the basis of these findings we have proposed that as a bipolar neuroepithelial cell rounds up for motosis it passes first through a pyriform state during which the external process is retracted or broken down, and then through a conical stage when the cell consolidates its position on the verntricular surface. Finally, the cell enters a large gobular stage before dividing into two small filopodia play in this procss of roun

ISSN:0092-7317    

DOI:10.1002/cne.901600107

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

年代:1975

数据来源: WILEY

摘要:

AbstractThis is a detailed report of a previously described projection from the presubiculum to the entorhinal are (Shipley,1974). The terminal degeneration in the entorhinal area is specifically confined to the outer three layers of this cortex. The projection is topographically organized and confined to dorsal and medial parts of the entorhinal area. A similarly organized projection courses via the dorsal psalterium (dorsal hippocambal commissure) to the contralateral entorhinal area. Thus each presubiculum has an orgainzed terminal pathway to the entorhinal cortices of both hemisphers.

ISSN:0092-7317    

DOI:10.1002/cne.901600108

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

年代:1975

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.901600101

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

年代:1975

数据来源: WILEY