摘要:

AbstractThe location of the motor nuclei and the projection of the primary afferent fibers of the facial nerve of the reptileVaranus exanthematicuswere studied by means of the HRP method and the anterograde degeneration technique. The motor nuclei are located ventrolaterally in the rhombencephalon and are constituted by a medial cell group consisting of large, polygonal cells and a lateral cell group consisting of medium‐sized, spindleshaped, and multipolar cells. From HRP applications to the various branches of the facial nerve it could be concluded that the medial cell group represents the branchiomotor nucleus and the lateral cell group the superior salivatory nucleus. The efferent axons from the motor nuclei course dorsomedially toward the fourth ventricle, where they form a genu, and exit from the brainstem in the ventral fiber bundle of the facial nerve.The primary afferent fibers enter the brainstem in the dorsal bundle ofthe facial nerve. This bundle courses medially, enters the solitary tract, and diverges into rostrally and caudally running fibers. Part of the caudally directed fibers leave the solitary tract and course laterally toward the descending trigeminal tract. Some fibers enter the nucleus of this tract. There was no noticeable terminal degeneration in the solitary tract or in the descending trigeminal tract or its nucleu

ISSN:0092-7317    

DOI:10.1002/cne.902070202

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe cytoarchitectonic organization of the posterior hypothalamus of the cynomolgus monkey(Macaca fascicularis)was analyzed in Nissl, Golgi, acetylcholinesterase, and reduced silver preparations. The region consists of a number of cell masses that differ considerably in their discreteness and in the homogeneity of their neuronal populations. The nuclei identified include: themedial mamillary nucleus(in which at least three distinct subdivisions can be recognized—apars medialis, apars lateralis, and apars basalis); the small‐cellednucleus intercalatus; the large‐celledlateral mamillary nucleus; a singlepremamillary nucleus; thetuberomamillary nucleus; theposterior hypothalamic nucleus; the caudal extension of thelateral hypothalamic area; thesupramamillary area; and theparamamillary nucleus(which appears to correspond to the nucleus of the nucleus of theansa lenticularisof other workers). As a basis for the subsequent experimental study of the efferent connections of the posterior hypothalamus, the location of each of these cell masses is described and illustrated in a series of low‐power photomicrographs, as are the form and distribution of the resident neuronal populations of the various components of themamillary complex as seen in Golgi prepa

ISSN:0092-7317    

DOI:10.1002/cne.902070203

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe efferent connections of the posterior hypothalamus have been analyzed autoradiographically in a series of eight cynomolgus monkey(Macaca fascicularis)brains with injections of3H‐amino acids in different regions of the mamillary complex and the surrounding areas.The medial mamillary nucleus was found to project through the mamillothalamic tract to the ipsilateral anteroventral, anteromedial, and interanteromedial nuclei, and by way of the mamillotegmental tract principally to the deep tegmental nucleus (of Gudden). It also appears to contribute fibers to the medial forebrain bundle, some of which reach as far rostrally as the medial septal nucleus. The lateral mamillary nucleus projects through the mamillothalamic tract bilaterally upon the anterodorsal nuclei of the thalamus, and through the mamillotegmental system to the dorsal tegmental nucleus; it also appears to contribute fibers to the medial forebrain bundle. The supramamillary area has extensive ascending and descending connections that are distributed with the medial forebrain bundle to the hypothalamus and rostral midbrain; in addition, it gives rise to an unusually well‐defined projection to field CA2 of the hippocampus and to a narrow zone overlying the outer part of the granule cell layer and the adjoining part of the molecular layer of the dentate gyrus. We have not been able to distinguish the connections of the posterior hypothalamic nucleus from those of the caudal part of the lateral hypothalamic area: they both appear to contribute substantially to the ascending components of the medial forebrain bundle, and through its descending projection to the tegmental fields of the midbrain, the nucleus centralis superior of the raphe complex, the locus coeruleus, and the central gray as far caudally as the facial nerve. Their further projections to the spinal cord were not examined.Viewed broadly, and in the light of previous work, our observations confirm, once again, the constancy of the connections of the hypothalamus in the mammalian brain, and the pivotal position that the posterior hypothalamus occupies in the elaborate system of connections that links the limbic areas of the forebrain with the complex of structures that Nauta has aptly designated the “midbrain limbic re

ISSN:0092-7317    

DOI:10.1002/cne.902070204

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe subcortical afferent connections of the amygdaloid complex of the cat were studied by means of retrograde tracing of horseradish peroxidase and the fluorescent substances bisbenzimid and nuclear yellow. The results of the present study indicate that structures in the basal forebrain, hypothalamus, brainstem, and thalamus project in a topographical manner to the various amygdaloid nuclei.Within the basal forebrain “ventral pallidal” structures project to the lateral and basolateral amygdaloid nuclei. The nucleus of the horizontal limb of the diagonal band and the medial part of the bed nucleus of the stria terminalis project predominantly to the medial and the medial central amygdaloid nuclei. Fibers from the substantia innominata distribute to nearly the entire expanse of the amygdaloid complex.The medial preoptic area and medial hypothalamic nuclei, including the paraventricular, ventromedial, arcuate, premammillary, and supramammillary nuclei, project most heavily to a region of the amygdala which includes the medial and the medial central nuclei. The caudal part of the lateral hypothalamic area sends strong projections to the medial central amygdaloid nucleus and more weakly projects to the basolateral nucleus.Brainstem neurons located in the cell groups A8 and A10, the dorsal raphe nucleus, the locus coeruleus, and the parabrachial nucleus project mainly to the medial central amygdaloid nucleus. Fibers originating in the medial part of the parabrachial nucleus in addition have a dense termination in the anteror amygdaloid area.Of the various midline nuclei of the thalamus which project to the amygdaloid complex, the paraventricular and ventral reuniens nuclei distribute fibers to the medial central and basolateral nuclei. The parataenial and the interventral nuclei project only to the medial central amygdaloid nucleus. Fibers from the interanteromedial nucleus exclusively reach the basolateral nucleus of the amygdala. Caudally in the ventral thalamus the subparafascicular and peripeduncular nuclei have been found to project to the medial, central, lateral, and cortical nuclei. In the posterior thalamus the medial part of the medial geniculate nucleus and the nucleus mediolateralis‐suprageniculate complex give rise to fibers which reach the lateral central amygdaloid nu

ISSN:0092-7317    

DOI:10.1002/cne.902070205

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

年代:1982

数据来源: WILEY

摘要:

AbstractReports in the literature have established that reconnection of central neural tracts occurs following commissurotomy and cerebral ganglion excision in the primitive pulmonate snailMelampus bidentatusand have suggested the possibility that long‐term regeneration might result in the appearance of new neurons in the ganglion bud. We have used electron microscopy to examine the ganglion buds that form by reconnection of cerebral nerves, commissure, and connectives following cerebral ganglion excision in adultMelampus.The buds were examined from 2.5 to 12 months postoperatively. By 2.5 months, ganglion buds consist of a mixture of axon tracts that travel through the bud region and some dendritic processes; a few synaptic contacts can be identified at this stage, scattered throughout the bud. By 5–6 months, some of the most advanced ganglia have undifferentiated cells that are distinct from glia. By 7 months, differentiated neurons with clear, small dense‐core or neurosecretory vesicles are present, although these cells are not all concentrated in a rind on the ganglion surface. Another cell type, the pigment‐sheath cell, is present by this stage. By 11–12 months, the most advanced regenerating ganglia have neurons which form a cell rind on the ganglion surface. The gross appearance of a regenerated ganglion at this stage is similar to that of the intact contralateral cerebral ganglion, although the regenerated ganglion is smaller. One 12‐month ganglion was found to possess fairly normal intraganglionic morphology, with lobes and cell types that were recognizable. Hence, nerve cell regeneration can occur in the absence of body part regeneration in adult members of one species of pulm

ISSN:0092-7317    

DOI:10.1002/cne.902070206

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

年代:1982

数据来源: WILEY

摘要:

AbstractElectromotoneuron proliferation and cell death have been quantitativelystudied in the electric lobe ofTorpedo marmoratafrom an embryonic body‐length stage of 26‐mm to adult animals. These neurons project to the electric organ and form synapses with electrocytes which possess a remarkably large postsynaptic target surface. For this reason cell death would not be predicted to occur if synaptic competition were to be hypothesized as thecause. Isolated observations at the ultrastructural level suggested, however, that cell death was indeed taking place and therefore it seemed appropriate to examine this question in detail.Our findings show first that neuron production appears to be a continuous process throughout the period studied, generating totals of over 70,000 electromotoneurons per lobe by adulthood. Second, two waves of cell death were identified, one occurring early in embryogenesis (stage 30 mm), well before the onset of synaptogenesis, and a second coincident with the onset ofsynaptogenesis (stages 55‐74 mm). It is difficult to reconcile this latter wave with the hypothesis of synaptic competition as the postsynaptic surface at this time of development is largely devoid of synaptic contacts. We conclude that in the electromotor system ofTorpedo, synaptic competition is probably not the mechanism of cell

ISSN:0092-7317    

DOI:10.1002/cne.902070207

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

年代:1982

数据来源: WILEY

摘要:

AbstractProjections of the parabigeminal nucleus to the contralateral superior colliculus and dorsal lateral geniculate nucleus were examined in normal adult pigmented rats and in adult rats from which one or both eyes had been removed at birth. In normal rats the crossed parabigeminotectal projection is restricted to the superficial layers in anterior and medial areas of colliculus, regions innervated also by the lower temporal portion of the ipsilateral retina. In unilaterally enucleated animals the crossed parabigeminotectal projection to the “denervated” colliculus is expanded, as is the retinal projection from the ipsilateral eye. In addition, there is acrossed parabigeminal projection to the “denervated” dorsal lateral geniculate nucleus in these rats. In bilaterally enucleated animals the parabigeminotectal projection is expanded, but not as greatly as in unilateral enucleation cases; there is a crossed parabigeminothalamic projectionin these animals as well.The corresponding termination patterns of the contralateral parabigeminal nucleus and the ipsilateral retina in the normal superior colliculus mayindicate a functional and/or developmental interdependence between the projections from these two regions. The existence of an expanded parabigeminotectal projection in bilaterally enucleated rats shows that a sustained ipsilateral retinotectal projection is not necessary for the establishment of a crossed parabigeminotectal projection, but points to the possibility that ipsilateral retinal input may constrain the parabigeminal projection to terminate within certain boundaries. The even greater expansion of the projection from the parabigeminal nucleus to the colliculus which receives an expanded projection from the ipsilateral retina of unilaterally enucleated rats suggests that the functional organization of the ipsilateral retinotectal projection may be capable of restricting the size of the terminal field of the crossed parabigeminotectal pro

ISSN:0092-7317    

DOI:10.1002/cne.902070208

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.902070201

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

年代:1982

数据来源: WILEY