摘要:

AbstractSynaptogenesis was studied in the monoamine (MA) cell groups locus coeruleus (LC), dorsal and medial raphe nuclei (RN) and substantia nigra, zona compacta (SN) between day 18 of gestation and postnatal day 60 using ethanolic phosphotungstic acid (E‐PTA) to visualize synaptic profiles. Nuclear area, and cellular packing density (inversely proportional to area of neuropil) were also determined.As determined using the E‐PTA method, synaptogenesis begins in the neuropil of the SN first, on or before 18 days of gestation, and in the LC and RN at 19 days. Synaptogenesis on MA cell perikarya is first observed in the SN, on or before 18 days, and in the LC and RN at 20 days. The onset of somatic synaptogenesis coincides with the beginning of nuclear growth and development of the neuropil (decrease in cellular packing density) in all MA cell areas, raising the possibility of common factors in the initiation of these processes.Nonsynaptic contacts precede the appearance of synaptic profiles both in the neuropil and on the somata of the MA cells of the LC, RN and SN, and may represent precursors of mature synapses or desmosome‐like contacts. Somatosomatic nonsynaptic contacts occur only prenatally between adjacent MA neurons in the LC, RN and SN.Although some synaptogenesis occurs prenatally in these MA cell groups (indicating that these parts of the MA circuitry may be functional before birth), most of this synaptogenesis occurs postnatally and continues into adulthood. Since such synaptogenesis does not begin until 2–4 days prior to birth, whereas these neurons and their processes exhibit MA fluorescence as early as 12–14 days of gestation, they apparently are capable of synthesizing transmitter and proliferating terminals before they themselves are i

ISSN:0092-7317    

DOI:10.1002/cne.901630302

出版商:The Wistar Institute of Anatomy and Biology    

年代:1975

数据来源: WILEY

摘要:

AbstractThe possibility that the arrival of retinal ganglion cell axons in their efferent target field could influence the subsequent progress of cytomorphogenesis in the ganglion cells was tested by destroying all or portions of the primordial optic tectum at four or five days of incubation. The lesions were made essentially prior to the outgrowth of axons from the eye. Complete bilateral or unilateral destruction of the primordial tectal field did not detectably alter the morphogenesis of the inner retina or of the ganglion cells until 11 days of incubation. After this time, extensive loss of ganglion cells occurred within the retinas contralateral to the projection field that were destroyed. The cytology of this degeneration is described as seen with the light and electron microscope. After smaller lesions involving the anterior or posterior half‐tectum on one side, however, variable results occurred both in tectal development and in the retinal locus of ganglion cell degeneration observed in flat mount preparations. Many partial or punctate lesions, in fact, resulted in no detectable loss of cells from the ganglion cell layer. These results are discussed in regard to specification and possible regulatory capabilities of the tectum. Cell death in normal retinas, not previously reported in the chick, is also considered in relation to the experimental result

ISSN:0092-7317    

DOI:10.1002/cne.901630303

出版商:The Wistar Institute of Anatomy and Biology    

年代:1975

数据来源: WILEY

摘要:

AbstractEfferent projections of neurons in the cat nucleus gracilis to the ventrobasal complex (VB) of the thalamus and the dorsal accessory portion of the inferior olive (IOd) were studied using tracing techniques that exploit neuronal orthograde and retrograde intra‐axonal transport processes. These projections were studied in order to determine if the heterogeneity of the morphology, physiology and afferent input of the nucleus gracilis is paralleled by a similar heterogeneity in its efferent projections.In an orthograde study,3H‐leucine and/or3H‐proline were injected into the nucleus gracilis of different subjects in an attempt to label different proportions of large (>18 μ) and small cells. This procedure permitted study of the efferent targets of the two cell types. The amount of labeling in VB was a constant ratio of the number of large cells in the nucleus gracilis that had incorporated the isotope. This relationship was not observed for the small cells. The amount of labeling in IOd was dependent neither on the number of large nor the number of small cells that had incorporated the isotope.In a retrograde study following extensive injections of horseradish peroxidase (HRP) into the thalamus, only large cells (>18 μ) in the dorsal column nuclei were filled with HRP reaction product. These cells were located predominantly in clusters in the middle zone of the nucleus gracilis as well as rostrally. After injections including (but not confined to) the inferior olive, small cells located in the rostral and middle zones were filled with reaction product. A few large cells located ventrally in the middle zone of the nucleus gracilis and rostrally were also filled. Some of these ventrally located large cells may project in a collateral fashion both to the thalamus and to the inferior olive.The results of both the orthograde and retrograde studies are consistent with other evidence on the heterogeneity of the nucleus gracilis. These data strongly support the conclusion that the population of cells in the nucleus gracilis that projects to the thalamus overlaps with but is not identical to the population of cells that projects to the inferio

ISSN:0092-7317    

DOI:10.1002/cne.901630304

出版商:The Wistar Institute of Anatomy and Biology    

年代:1975

数据来源: WILEY

摘要:

AbstractThe plasticity of cervical primary afferents has been investigated in young adult cats in which the trigeminal root, together with most of the ganglion, had been excised via a new approach to these structures during the first week after birth.Once degeneration debris had disappeared, bilateral ganglionectomies of the upper three cervical dorsal roots were done in five animals and the IXthand Xthroots transected on the side of the chronic trigeminal denervation in one instance; the degeneration pattern on the chronically denervated side was compared to that on the normal side.There was mild evidence of increased degeneration of the cervical afferents in the C1 segment and in the medulla (subnucleus interpolaris of V) on the chronically denervated side. The proliferation was more apparent in the kitten operated at three days of age and was only vestigial in animals operated at six or seven days; it had no appreciable tendency to extend into the large contiguous pool of denervated trigeminal neurons. There was no evidence of sprouting of the IXthand Xthnerve afferents.These observations indicate that primary afferents of the upper cervical roots and of the glossopharyngeal and vagus nerves have little neuroplastic potential even at early stages.The literature on neuroplasticity is controversial and a brief review of this together with suggestions regarding the reasons for some of these conflicts is presented. Some structural and functional effects of chronic trigeminal denervation are briefly described.

ISSN:0092-7317    

DOI:10.1002/cne.901630305

出版商:The Wistar Institute of Anatomy and Biology    

年代:1975

数据来源: WILEY

摘要:

AbstractThe efferent connections of the main and accessory olfactory bulbs in the female albino rabbit have been studied using the autoradiographic method for tracing axonal pathways. Following unilateral injections of3H‐leucine into the main olfactory bulb, radioactively labeled material transported intraaxonally by axoplasmic flow in an anterograde direction from soma to axon terminal is present ipsilaterally in the superficial half of the plexiform layer (IA) of: the entire circumference of the olfactory peduncle, the tenia tecta, the full mediolateral extent of the olfactory tubercle, the entire length of the prepyriform cortex, a transition area between the prepyriform cortex and the horizontal limb of the nucleus of the diagonal band, the nucleus of the lateral olfactory tract, the anterior cortical and posterolateral cortical amygdaloid nuclei (periamygdaloid areas 1, rostral half of 2, 5 of Rose, '31), and the ventrolateral entorhinal cortex (entorhinal areas 1, 2, 4, 5, 7 of Rose, '31). No subcortical or contralateral projection of main bulb efferents was found.After a unilateral injection of3H‐leucine into the accessory olfactory bulb, transported material could be followed caudally along the dorsal surface of the ipsilateral lateral olfactory tract. This heavily labeled projection is distinct from the unlabeled lateral olfactory tract and has been termed the accessory olfactory tract. Beginning at the level of the caudal third of the olfactory tubercle and extending caudally to the nucleus of the lateral olfactory tract is a group of small neurons intimately associated with the accessory olfactory tract. This cell group is referred to as the bed nucleus of the accessory olfactory tract. Projection sites of the accessory bulb include the bed nucleus of the accessory olfactory tract and layer IA of the medial nucleus and the posteromedial cortical nucleus of the amygdala (periamygdaloid areas 3, 4, PAM, caudal half of 2, 6 of Rose, '31). An additional accessory bulb efferent projection was found to enter the stria terminalis at the level of the medial amygdaloid nucleus and could be traced to a posterior segment of the bed nucleus of the stria terminalis.The autoradiographic findings indicate that the accessory olfactory bulb connects with portions of the amygdala that do not receive afferent input from the main olfactory bulb and provide evidence for the existence of two distinct and separate olfactory syst

ISSN:0092-7317    

DOI:10.1002/cne.901630306

出版商:The Wistar Institute of Anatomy and Biology    

年代:1975

数据来源: WILEY

摘要:

AbstractTo date, anatomical studies of ascending principal sensory trigeminal nuclear (PrV) axons in the monkey have been restricted to few incomplete investigations utilizing the Marchi method. In the present study total or partial unilateral stereotaxic lesions of PrV were made in cebus and rhesus monkeys and analyzed with the aid of a variety of Nauta silver impregnation techniques applied to frozen sections.Analysis of the fiber degeneration emanating from PrV lesions indicates that PrV fibers from an ascending system composed of two distinct components. Most PrV axons project ventromedially from PrV through the ventral pontine tegmentum and gradually decussate across the midline in the mesencephalic tegmentum up to the level of the caudal pole of nucleus interpeduncularis. These decussated fibers form the trigeminal lemniscus, which courses dorsomedial to the medial lemniscus during its ascent into the diencephalon. A few whorls of preterminal fiber degeneration separating from the trigeminal lemniscus first appear in the magnocellular area of the thalamus medial to the medial geniculate body. The lemniscal PrV axons terminate densely throughout most, but not all, of the magnocellular part of nucleus ventralis posteromedialis (VPM) contralateral to the side of their origin. Some collateral‐like fibers from the trigeminal lemniscus also were observed ending in the ventral segment of the zona incerta. Other axons, arising chiefly from the dorsal one‐third of PrV, form a smaller ipsilateral trigeminothalamic projection. These fibers all remain on the side of their origin and terminate consistently in a discrete dorsomedial paralaminar portion of VPM that does not receive lemniscal PrV connections.A commissural fiber system at the pontine level connects parvicellular reticular cells with their counterparts and the motor trigeminal nucleus of the opposite side. These interconnections appear to provide an anatomical link for the integration of bilateral trigeminal sensory information and motor funct

ISSN:0092-7317    

DOI:10.1002/cne.901630307

出版商:The Wistar Institute of Anatomy and Biology    

年代:1975

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.901630301

出版商:The Wistar Institute of Anatomy and Biology    

年代:1975

数据来源: WILEY