摘要:

AbstractDegenerating cells may be observed with light microscopy in the hamster retinal ganglion cell layer during early postnatal development. On the first postnatal day, degenerating cell profiles were found at a rate of 2.7 per 1,000 live cells. This rate increased to a peak of 14.7 degenerating cells per 1,000 live on postnatal day 5 and then slowed to 4.2 per 1,000 live by postnatal day 10. These rates of cell death correspond to a 49% reduction in cell number in the ganglion cell layer. Examination of the spatial pattern of cell death revealed that although on visual inspection degenerating cells appear to occur in clumps, statistical analyses demonstrated a random distribution within retinal areas. Across the retina, cell death rates were higher in peripheral retina than in central retina. The timing and pattern observed correspond well with that of cell degeneration observed in the superficial layers of the superior colliculus, the major target of the retinal projection.

ISSN:0092-7317    

DOI:10.1002/cne.902040402

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

年代:1982

数据来源: WILEY

摘要:

AbstractDegenerating cells may be observed with light microscopy in the hamster superior colliculus during early postnatal development. In the superficial gray layer and stratum opticum, 1.8 degenerating cells for each 1,000 live cells could be seen on the first postnatal day. This rate increased to 5.6 degenerating cells per 1,000 live cells by postnatal day 5, and declined to 2.6 per 1,000 live cells by postnatal day 8. The rate of cell degeneration was consistently elevated at the medial, lateral, and caudal margins of the superficial gray layer relative to the center. In the intermediate and deep gray layers, the rate of cell death was consistently higher, starting at three degenerating cells per 1,000 on the first postnatal day, increasing to 15 per 1,000 on postnatal day 5, and declining to 4.7 per 1,000 by postnatal day 8. In contrast to the superficial gray layer, the number of degenerating cells in the central versus peripheral segments of the intermediate and deep gray layers was quite similar.Although the rate of observable degeneration is low, the likely rapid clearance of degenerating cell debris indicates a substantial loss of cells from the midbrain tectum in early development. The time course of observable degeneration, the amount, and the distribution of degenerating cells are quite similar in the tectum, and its major innervating structure, the retina.

ISSN:0092-7317    

DOI:10.1002/cne.902040403

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

年代:1982

数据来源: WILEY

摘要:

AbstractAfferent pathways to the optic tectum in the longnose gar were determined by unilateral tectal injections of HRP. Retrogradely labeled cells were observed in the ipsilateral caudal portion of the rostral entopeduncular nucleus and bilaterally in the rostral half of the lateral zone of area dorsalis of the telencephalon. The following diencephalic cell groups were also labeled following tectal injections: the ipsilateral anterior, ventrolateral, and ventromedial thalamic nuclei, the periventricular pretectal nucleus, and the central pretectal nucleus (bilaterally); the ventromedial thalamic and central pretectal nuclei revealed the largest number of labeled cells. At midbrain levels, retrogradely labeled cells were seen in the ipsilateral torus longitudinalis, nucleus isthmi, and accessory optic nucleus; cells were labeled bilaterally in the torus semicircularis and a rostral tegmental nucleus. Only a few cells were labeled in the contralateral optic tectum, suggesting that few of the fibers of the intertectal commissure are actually commissural to the tectum. At hindbrain levels, retrogradely labeled cells were seen bilaterally in the locus coeruleus, the superior, medial, and inferior reticular formations, the eurydendroid cells of the cerebellum, and the nucleus of the descending trigeminal tract; the contralateral dorsal funicular nucleus also exhibited labeling. Clearly, the tectum in gars receives a substantial number of nonvisual afferents from all major brain areas, most of which have been reported in other vertebrates. The functional significance of these afferent sources and their probable homologues in other vertebrate groups are discussed.

ISSN:0092-7317    

DOI:10.1002/cne.902040404

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe locations of lumbosacral spinocerebellar neurons were examined by two anatomical methods in kittens. In one group of animals chromatolytic changes were provoked by cerebellar lesions. In another group horseradish peroxidase (HRP) was injected into the cerebellum. Projection laterality was investigated by making unilateral spinal lesions prior to the cerebellar HRP injections. Diaminobenzidine (DAB) or tetramethylbenzidine (TMB) was used as substrate for HRP. The morphological characteristics of HRP‐labeled neurons in the TMB‐processed material were examined.Neurons marked by the two methods were located within the same regions. A greater number of cells were marked with the HRP method, however, than with the retrograde chromatolysis method. Spinocerebellar neurons were found in laminae IV–IX with large differences with regard to specific locations depending on segmental level. Numerous marked neurons were found in the following areas: laminae IV–VI in L3–L7, the column of Clarke in L3–L4, the medial part of lamina VII in L6–L7, the lateral part of lamina VII in L3–L4, the dorsolateral nucleus of lamina IX in L3–L6, the ventrolateral nucleus of lamina IX in L4–L5, and the ventromedial nucleus of lamina IX in S3 (and Ca1). Dorsally located neurons were in general more likely to project ipsilaterally than ventrally located neurons. Marked structural differences were frequently observed between spinocerebellar neurons in different locations.These results provide additional information on the anatomical complexity of the spinocerebellar pathways from the lumbosacral region in the cat. Together with results from some other recent anatomical studies on spinocerebellar tracts, they also form a basis for further anatomical and physiological investigations which could contribute to a better understanding of the organization of the spi

ISSN:0092-7317    

DOI:10.1002/cne.902040405

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

年代:1982

数据来源: WILEY

摘要:

AbstractAnatomical staining methods including Nissl, Weil, Golgi, and horseradish peroxidase stain have been used to elucidate the cyto‐ and myeloarchitectural organization of the periaqueductal gray in monkey, cat, and rat. From these various staining methods it appears that the periaqueductal gray is composed of a tightly packed group of cells, which show a slight increase in soma size, dendritic diameter, and degree of myelinization from central to peripheral borders. This central gray region contains a wide variety of cell types including multipolar, fusiform, stellate, and pyramidal neurons. Clearly delineated subnuclei, distinguished on the basis of soma size, dendritic arborizations, pigmentation, or evidence of cytological individuality could not be discerned in this study. Together with the immunohistochemical and connectivity studies the present data suggest that the neuronal organization of the PAG could be described as a mosaic of clusters of functional related neurons rather than as three distinct subnuclei, each with its own unique cytoarchitecture and connectivit

ISSN:0092-7317    

DOI:10.1002/cne.902040406

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

年代:1982

数据来源: WILEY

摘要:

AbstractWe describe the relation between growth and branching of an identified dendrite and the formation of synapses on its surface during a 3 1/2‐day period early in development. We studied the lateral dendrite and the adjacent lateral perikaryon of the Mauthner cell (M‐cell) during embryonic stages 39–43 in the axolotlAmbystoma mexicanum. Reconstructions from light micrographs of serial sections through the cell revealed that during this interval the dendrite elongates rapidly, and large numbers of ventrally directed branches are formed. Samples of the same material by electron microscopy showed that large numbers of synaptic contacts appear during the same interval. We quantitatively estimated changes in local synapse densities (the number of contacts/100 μm2of M‐cell surface) and local surface areas of the M‐cell and found that synapses were most densely clustered, and accumulated most rapidly, on regions of the cell that were rapidly expanding. These data are in accord with previous evidence from work in this and in other systems that synaptic contacts induce local growth of dendrites. Furthermore, the data are consistent with a proposal that outgrowth of new dendritic branches is induced or stabilized by synapses in a concentration‐depen

ISSN:0092-7317    

DOI:10.1002/cne.902040407

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

年代:1982

数据来源: WILEY

摘要:

AbstractMethionine‐enkephalin, substance P, and somatostatin immunoreactivities are associated with different classes of neurons in the main olfactory bulb of the hamster. In the glomerular layer, methionine‐enkephalin immunoreactivity is observed in the somata and dendrites of periglomerular cells whereas substance P immunoreactivity is present in the somata and dendrites of external tufted cells. Substance P immunoreactivity may also be present in the superficial short axon cells. In the deeper layers, methionine‐enkephalin immunoreactivity is observed in a mixed population of neurons which appear to be primarily granule cells, whereas somatostatin immunoreactivity is present only in deep short axon cells. Methionine‐enkephalin‐, substance P‐, and somatostatin‐positive fibers of central origin are also observed in the main o

ISSN:0092-7317    

DOI:10.1002/cne.902040408

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe locations of brainstem motor nuclei supplying efferents to organs of the vocal tract of the budgerigar(Melopsittacus undulatus)were determined as a first step in describing brain pathways for vocal control in this species. We identified four major nerves supplying the muscles of the syrinx, larynx, and tongue, and separately treated each of these with horseradish peroxidase. Nerves supplying efferents to the larynx and tongue arise from ipsilateral cells in the nucleus ambiguus and hypoglossal nucleus, respectively. Each right and left half of the syrinx is supplied by both right and left halves of the hypoglossal nucleus, via axons crossing in the common anastomosis of the tracheosyringeal nerves. This bilateral innervation of the syrinx will allow testing for central asymmetries of dominance for vocal control in the absence of any underlying anatomical laterality in the periphery.

ISSN:0092-7317    

DOI:10.1002/cne.902040409

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

年代:1982

数据来源: WILEY

摘要:

AbstractVasotocin (VT)‐ and neurophysin (NP)‐synthesizing neurons were demonstrated by immunocytochemistry in the diencephalon of the pigeon,Columba livia.Three diencephalic regions contain VT‐NP cells: (1) periventricular preoptic area and hypothalamus, including nucleus periventricularis magnocellularis (PVM); (2) lateral preoptic area and hypothalamus; and (3) dorsal diencephalon. The immunoreactive cells in each of these three regions were divided into groups based on cytology and topography. No differences were found in the location of VT and NP cell groups.The periventricular region contains three continuous cell groups (P1–P3) extending from the posteroventral preoptic area to the anterodorsal hypothalamus and PVM. The lateral region has two cell groups composed of medium‐ to large‐sized cells associated with the quintofrontal tract (L1) or with the optic tract (L2), while a third group (L3) lies between these two cell groups. Two accessory cell groups reside in the dorsolateral hypothalamus; L4 contains scattered cells of varied size, whereas L5 has small‐ to medium‐sized cells clumped together. The dorsal diencephalic cell groups are found in the following locations: (1) lateral and dorsal to the lateral forebrain bundle (DD1); (2) in the area ventral to the dorsomedial anterior thalamic nucleus and dorsolateral to PVM (DD2); and (3) at the dorsolateral border of nucleus rotundus (DD3).To avoid potentially inaccurate mammalian homologies, the cell group nomenclature denotes topographic position. Nevertheless, the presence of VT‐NP cells in PVM and projections to the brainstem and spinal cord suggest a homology between PVM and some of the parvocellular subnuclei of the mammalian parave

ISSN:0092-7317    

DOI:10.1002/cne.902040410

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

年代:1982

数据来源: WILEY

摘要:

AbstractInteractions between enteric noradrenergic and serotonergic neurites in the myenteric plexus were examined. The influence of exogenous norepinephrine (NE) and endogenously released NE on the release of3H‐serotonin (3H‐5‐HT) from electrically stimulated, everted segments of guinea pig small intestine were analyzed. In addition, methods were employed to permit the ultrastructural identification of enteric serotonergic and noradrenergic neurites. These included electron microscopic radioautographic localization of3H‐5‐HT in gut from animals treated with 6‐hydroxydopamine (6‐HD; 100 mg/kg) and examination of NaMnO4‐fixed tissue from animals given desmethylimipramine and the indolic neurotoxin, 5, 7‐dihydroxytryptamine (5,7‐DHT). Exogenous NE antagonized the stimulated release of3H‐5‐HT; this action was mediated through alpha adrenoceptors. Evidence was obtained, however, that endogenous NE liberated from sympathetic postganglionic nerve terminals had a different action on the stimulated release of3H‐5‐HT from that of exogenous NE. Endogenous NE appeared to facilitate3H‐5‐HT release through an action on beta adrenoceptors. Terminals identified as probably serotonergic by radioautographic labeling with3H‐5‐HT or by loading with 5,7‐DHT were most often found to end on neuronal somata or proximal dendrites. Synaptic specializations were found by radioautography in these locations. Terminals, dendrites, and cell bodies that took up 5,7‐DHT could be identified in NaMnO4‐fixed material that also permitted the simultaneous recognition of noradrenergic varicosities. Apparent noradrenergic‐serotonergic axoaxonic contacts were found by means of this double‐labeling technique. Together with the results of the experiments on the release of3H‐5‐HT, these anatomical observations suggest that noradrenergic axons form facilitatory axo

ISSN:0092-7317    

DOI:10.1002/cne.902040411

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

年代:1982

数据来源: WILEY