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Cook, Jeremy E.; Becker, David L.; Kapila, Rakesh
doi: 10.1002/cne.903180402pmid: 1578007
Goldfish retinal ganglion cells were filled with horseradish peroxidase and studied in flatmounts. Two regular mosaics of large neurons with many of the properties of mammalian alpha ganglion cells were found, differing from each other in spacing, size, and dendritic stratification. The existence of biplexiform ganglion cells with additional dendrites in the outer plexiform layer was also confirmed.
doi: 10.1002/cne.903180403pmid: 1578008
The organ of Corti of the echolocating horseshoe bat (Rhinolophus rouxi) was investigated with scanning electron microscopy in order to provide a comparison with non‐echolocating mammals.
Vater, Marianne; Lenoir, Marc; Pujol, Remy
doi: 10.1002/cne.903180404pmid: 1578009
The fine structure of the organ of Corti was investigated in the echolocating horseshoe bat (Rhinolophus rouxi) by transmission electron microscopy. Particular emphasis was placed on the receptor cells and their supporting cells.
Bagnoli, Paola; Fontanesi, Gigliola; Alesci, Roberto; Erichsen, Jonathan T.
doi: 10.1002/cne.903180405pmid: 1374443
The distribution of three neuroactive substances, neuropeptide Y, substance P, and choline acetyltransferase, was studied by immunocytochemical methods in central visual regions of adult, developing, and ablated pigeon brains. In normal adult brains, neuropeptide Y‐positive cells and processes were present in the nucleus pretectalis, the nucleus of the basal optic root, the nucleus of the marginal optic tract, and the visual Wulst. Substance P‐positive cells and processes were found in the optic tectum and in the visual Wulst. Stained fibers and terminal‐like processes, but no cells, were also observed in several visual thalamic nuclei. Choline acetyltransferase‐positive cells and processes were located in the optic tectum, visual Wulst, the nucleus isthmo opticus, nucleus isthmi and certain visual thalamic nuclei. Cholinergic fibers and processes, but no cells, were present in the nucleus principalis precommissuralis, the supraoptic decussation, and the nucleus lentiformis mesencephali, pars magnocellularis. In the course of development, the distribution of immunoreactivity for all three substances was found to vary. These changes often involved either progressive increases or decreases in the density of labeled cells, neuropil and/or terminal‐like profiles. Experiments with retina ablated pigeons clearly demonstrated that changes in the normal pattern of immunoreactivity distribution only occurred if the retina was removed immediately after hatching, i.e., before retinofugal connections have been established. The adult pattern of immunoreactivity for all three substances appears to be reached at about the same time that the anatomical and functional maturation of the pigeon visual system is completed. The present results suggest that this temporal correlation reflects the important role that retinal afferents play in the development of these putative peptidergic and cholinergic systems.
Rubel, Edwin W.; MacDonald, Glen H.
doi: 10.1002/cne.903180406pmid: 1374444
Removal of the cochlea or pharmacological blockade of eighth nerve activity in young postnatal chickens results in rapid transneuronal cell death and atrophy in neurons of n. magnocellularis. The present experiments were designed to examine the influence of afferent input on astrocyte structure in n. magnocellularis. Young chickens were subjected to unilateral cochlea removal. At times ranging from 5 minuses to 72 hours later, the brainstems were histologically processed with a polyclonal antibody against glial fibrillary acidic protein (GFAP). A second group of chick brainstems was impregnated by a Golgi method 6 hours after unilateral cochlea removal and impregnated three‐dimensional reconstructions were made of glial cells in n. magnocellularis (NM).
Lyckman, A. W.; Heidelbaugh, S. M.; Bittner, G. D.
doi: 10.1002/cne.903180407pmid: 1578010
This study analyzes the detailed morphometric pattern at various postoperative times of neuritic outgrowths from the proximal and distal stumps of two uniquely identifiable axons. Morphological patterns of neuritic outgrowths from stumps of severed axons were compared for medial and lateral giant axons in the central nervous system of the earthworm Lumbricus terrestris. Outgrowths from proximal and distal stumps were labeled by injection of fluorescent dye into axonal stumps and assessed according to morphometric parameters. Outgrowths from axonal stumps of severed giant axons were statistically indistinguishable for most morphometric measures of neuritic quantity, shape, direction, and location. There were two exceptions to this general rule: 1) proximal stumps of medial giant axons produced significantly more neurites than distal stumps of medial giant axons, and 2) proximal stumps of lateral giant axons produced significantly longer neurites than proximal stumps of medial giant axons. No measure of neuritic outgrowth showed a significant change from the second through seventh postoperative week, suggesting that most outgrowth occurred in the first two postoperative weeks and that neuritic morphology remained stable through the seventh postoperative week. Neurites grew across the lesion site in relatively straight trajectories parallel to the longitudinal axis of the ventral nerve cord and often grew alongside the appropriate axonal stump across the lesion site. The length of neurites growing in close apposition to appropriate axonal stumps or giant axons was much greater than expected, had outgrowth been randomly directed. These data provide a basis for future investigations of the mechanisms that regulate neuritic outgrowth.
Brännström, Thomas; Havton, Leif; Kellerth, Jan‐Olof
doi: 10.1002/cne.903180408pmid: 1578011
This study was performed to analyse quantitatively the changes in dimensions and dendritic branching patterns of adult cat spinal α‐motoneurons following permanent axotomy, i.e., in a situation in which the transected motoraxons are prevented from reinnervating their peripheral target muscle. After transection and ligation of the medial gastrocnemius nerve of adult cats, homonymous α‐motoneurons were intracellularly labelled with horseradish peroxidase and subjected to quantitative light microscopic analyses. The cell bodies and proximal dendrites were studied at 3, 6, and 12 weeks after the axotomy. An initial increase in cell body size at 3 weeks was followed by a gradual return towards normal values. The mean diameter of the stem dendrites was decreased at all time periods studied, and the combined diameter of the stem dendrites was reduced at 12 weeks after the axotomy. Entire dendritic trees were reconstructed at 12 weeks postoperatively, and the regression equations describing the correlations between dendritic stem diameter, on one hand, and the size of the entire dendrite, on the other, were used to calculate the total dendritic length, volume, and membrane area of whole axotomized motoneurons. The dendritic branching patterns were also analysed. In comparison with normal medial gastrocnemius α‐motoneurons, the dendritic membrane area and volume of the axotomized cells had decreased by 36% and 29%, respectively, at 12 weeks after the axotomy. This reduction in dendritic size was due to a loss of preterminal and terminal dendritic segments. Abnormal dendritic elongations were observed in 2 of 16 completely reconstructed dendrites.
Brännström, Thomas; Havton, Leif; Kellerth, Jan‐Olof
doi: 10.1002/cne.903180409pmid: 1578012
In a preceding paper [Brännström, et al. (1992) J. Comp. Neurol. 318:439–451] a marked reduction in dendritic size was observed in cat spinal motoneurons following permanent axotomy. The aim of the present study was to analyse the possible restorative effects of peripheral reinnervation on the size and dendritic branching patterns of cat spinal motoneurons which had been deprived of neuromuscular contact for an extended period of time.
Diamond, Mathew E.; Armstrong‐James, Michael; Ebner, Ford F.
doi: 10.1002/cne.903180410pmid: 1578013
The rodent barrel field cortex integrates somatosensory information from two separate thalamic nuclei, the ventral posterior medial nucleus (VPM) and the rostral sector of the posterior complex (POm). This paper compares the sensory responses of POm and VPM cells in urethane‐anesthetized rats as a first step in determining how cortex integrates multiple sensory pathways.
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