摘要:

AbstractAs shown by autoradiographic techniques, the pattern of retinogeniculate projections in the pigmented rabbit is generally similar to that described in preious studies. Each retina projects bilaterally to the α segment of the dorsal lateral geniculate nucleus (LGd) and to the external segment of the ventral lateral geniculate nucleus (LGv). The β segment of the LGd and internal layer of the LGv receive contralateral inputs only.The α segment of the LGd contains an irregularly shaped region which receives overlapping bilateral projections. Within this region the ipsilateral input is continuous and predominant. This pattern of ipsilateral projection can account for both the laminar arrangement perpendicular to the lines of projection and the “hidden lamination” which have been described previously for the rabbit LGd.A separate bilateral projection is identified for a group of cells lying between the LGd and LGv rostrally. Caudally this intergeniculate leaflet extends medial and ventral to the LGv and appears to merge with the zona i

ISSN:0092-7317    

DOI:10.1002/cne.901750102

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractTwo types of horizontal cells are seen in Golgi‐impregnated retinas of the pigeon. Type I horizontal cells are compact, “brush‐shaped,” and have an axon ending as an irregular spinous arborization. The majority of the dendrites terminate in the distal part of the outer plexiform layer (OPL) as clusters which contact cones, but some terminate as single expansions in the proximal part of the OPL. The axon terminal spines are found only in the distal part of the OPL and contact both rods and cones. Pigeon Type I horizontal cells are Caja's “brush‐shaped” cells, and their axon terminals resemble Caja's “stellate” cells. Type II horizontal cells have irregular, wavy, multi‐branched dendrites, appear horizontally flattened, and lack axons. The dendrites terminate in the proximal part of the OPL as isolated spines and contact only cones. The Type II horizontal cells of the pigeon have not been previously described

ISSN:0092-7317    

DOI:10.1002/cne.901750103

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractDistribution of cell body volumes of motoneurons innervating the soleus (slow‐twitch or tonic) and medial gastrocnemius (fast‐twitch or phasic) muscles was examined in adult cats and a series of kittens ranging from one to 140 days in age. To identify the soleus (Sol) and the medial gastrocnemius (MG) motoneurons, each group of motoneurons was labeled differentially by utilizing retrograde axonal transport of horseradish peroxidase injected into the muscles.It was verified statistically that in the adult cat, the mean cell body volume of the Sol motoneurons was smaller than that of the MG motoneurons. Difference of the mean cell body volume between the Sol and MG motoneurons was found to be significant around the tenth postnatal day. The mean cell body volumes of both Sol and MG motoneurons increased mainly during the third to the seventh week after birth. After this period, increase of the cell body volume was relatively slight and in the fifth month after birth, some of the motoneurons still appeared to be growing. Our findings also suggested that the MG motoneurons may exhibit the adult pattern of distribution of cell body volume in an earlier postnatal stage than do the Sol motoneurons, and that differentiation of motoneurons into the gamma and alpha types may occur earlier than differentiation into the tonic and phasic ty

ISSN:0092-7317    

DOI:10.1002/cne.901750104

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractThe efferent connections of the paramedian pontine reticular formation have been studied in the cat in autoradiographic experiments designed to analyze direct and indirect preoculomotor pathways. Injections of tritium‐labelled amino acids were placed (1) near the border between the oral and caudal subdivisions of the nucleus pontis centralis, (2) in more rostral and dorsal parts of the pontine tegmentum, (3) at the pontomesencephalic border, and (4) at the pontomedullary border.Tegmental injections of the first group were unique in labelling a direct ipsilateral pathway to the abducens nucleus and nucleus prepositus hypoglossi. More rostral injections failed to produce discrete labelling of the nuclei of the extraocular muscles but labelled nearby tegmentum and central gray substance. Caudal deposits, involving the pontomedullary reticular formation at its junction with the abducens, perihypoglossal and vestibular nuclei, labelled a decussating fiber system reaching the contralateral abducens nucleus, nucleus prepositus hypoglossi and parts of the vestibular complex. In a single additional case, an injection placed in the oculomotor complex produced heavy labelling of the abducens nuclei.All tegmental injections labelled discrete reticulo‐reticular and other variably complex longitudinal pathways. Most injections of (a) the pontomedullary and (b) the pontomesencephalic zones elicited labelling of the pretectum including the nucleus of the optic tract. An incidental finding in the latter group was dense labelling of the pars compacta of the substantia nigra, subthalamic nucleus, and (1 case) entopeduncular nucleus; in one case of each of these groups, labelled fibers were traced to the external pallidum.These observations suggest that, with respect to its efferent oculomotor affiliations, the paramedian pontine tegmentum may be divided into compartments whose supranuclear connections are distinct but for the most part heavily weighted toward influencing the abducens nucleus and periabducens region. Considered within the framework of behavioral and physiological studies of the so‐called pontine gaze center, and studies of pontine afferents, the findings are interpreted as suggesting a functional differentiation of these tegmental zones with respect to their influence on eye‐head coord

ISSN:0092-7317    

DOI:10.1002/cne.901750105

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractThe early embryonic development of axodendritic and axosomatic synapses upon motor neurons has been investigated in mouse spinal cord. This investigation had two main objectives: (a) to determine the earliest embryonic day on which recognizable synaptic contacts occur upon motor neurons, and (b) to compare the development of synaptic contacts upon the dendrites and somata of motor neurons during the early synaptogenic period. The broad goal of this investigation was to determine whether the location of early‐forming synapses upon motor neurons is consistent with the possibility that axosomatic synapses might be involved in the primary induction of motor neuronal dendrogenesis.Embryonic day 11 (E11) was the earliest developmental time at which synaptic contacts were observed in developing mouse spinal cord. All of these synaptic contacts appeared to be located upon motor neuronal dendrites within the lateral and ventral marginal zones. The number of synaptic contacts observed on E11 was too small to be detected by thequantitative sampling procedureused in this investigation, but the procedure was sufficiently sensitive to detect synaptic contacts on embryonic day 12. Both axodendritic and axosomatic synapses were found upon E12 motor neurons, but there were about four times as many synaptic contacts per unit length of dendritic membrane as there were per equivalent length of somal membrane. Furthermore, dendritic membranes continued to exhibit a higher density of synaptic contacts on all of the remaining embryonic days (i.e., 13–16) examined in this investigation. These quantitative data and the E11 observations indicate that axosomatic synaptic contacts are not a necessary prelude to the formation of motor neuronal dendrites. Therefore, it is suggested that axosomatic synapses do not play an obligatory role in the primary induction of motor neuronal dendrogenesis.The experimental findings of other investigators, however, have provided reasons to suspect that early‐forming axosomatic synapses may somehow facilitate dendritic development once it has been induced. This possibility is discussed in terms of our observation that early‐forming axosomatic synapses rather commonly occur at sites which may represent somal growth regions. This relationship leads us to suggest that early axosomatic synapses may facilitate dendritic development by signalling the motor somata that the formation of a synaptogenic axonal field is underway. Furthermore, we speculate that the positioning of early axosomatic contacts might be providing directive cues as to the location of the developing synaptogenic field. Thus adirective facilitationof dendritic growth is suggested as a function of early axosomatic synapses rather than one involved with theprimary inductionof dendro

ISSN:0092-7317    

DOI:10.1002/cne.901750106

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractThe efferent projections of the fornix system have been studied in the squirrel monkey using modified silver staining techniques to delineate degenerating fibers and terminal boutons after inducing careful lesions of the subcallosal fornix and dorsal fornix.Subcallosal fornix projections, after supplying the medial and lateral septal nuclei, are traced via precommissural fibers to terminal degeneration in the nucleus of the diagonal band of Broca, nucleus accumbens, gyrus rectus, olfactory tubercle, medial and lateral preoptic areas, and medial hypothalamus. Degenerating precommissural subcallosal fornix fibers course with the medial forebrain bundle throughout the extent of the lateral hypothalamus, extending caudally to the medial mammillary nucleus with specific hypothalamic offsets to the tuberal region and nucleus intercalatus (“lateral cortico‐hypothalamic tract”). Subcallosal postcommissural fornix fibers are traced to terminal degeneration in the bed nucleus of the stria terminalis and medial preoptic and anterior hypothalamic structures (“medial cortico‐hypothalamic tract”); fornix column fibers disperse throughout the perifornical nucleus; these fibers more caudally supply nucleus intercalatus and medial mamillary nucleus. In the thalamus postcommissural fibers supply the nucleus reuniens, the paraventricular, anterior ventral, and lateral dorsal nuclei. In the mammillary nucleus a laminated radiation is described with some fibers extending caudally to the prerubral field.A “midline subcallosal stria,” derived from the subcallosal fornices, distributes fibers to the subfornical organ, the dorsal part of the medial septum, the precommissural fornix and especially the medial cortico‐hypothalamic tract.The dorsal fornix projection is predominantly pericallosal to the gyrus rectus and parolfactory area, with only a minor callosal‐penetrating contribution to pre‐ and postcommissural fibers.The composite projections of the hippocampal formation fornix system appear more extensive than those of the amygdala to basal forebrain, preoptic, a

ISSN:0092-7317    

DOI:10.1002/cne.901750107

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.901750101

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY