The Journal of neuroscience : the official journal of the Society for Neuroscience
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An anatomically discrete system of interconnected brain nuclei controls production of learned song patterns in adult male zebra finches (Poephila guttata). The corresponding nuclei in females, who do not sing, are greatly reduced in volume. Cells in some telencephalic song-control nuclei accumulate androgens, and male nuclei contain a much higher proportion of hormone-concentrating cells than do female nuclei. ⋯ The volumes of HVc and RA were smaller in females than in males at all ages studied. Between 12 and 25 days the volumes of female HVc and RA increased less than brain regions not involved with song control. Female HVc and RA decreased slightly in volume between 25 and 53 days.(ABSTRACT TRUNCATED AT 250 WORDS)
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Photoreceptors of the Limulus lateral eye shed their light-sensitive membranes (rhabdoms) in a burst early each morning when the animal is maintained in natural lighting. This shedding burst produces a cloud of multivesicular bodies which coalesce and migrate away from the rhabdom. Within 24 hr, these gradually collapse to combination bodies and ultimately to lamellar bodies. ⋯ Within 15 min of light onset the area of photosensitive membrane decreases by about 70%, and within an hour the rhabdom returns to essentially its preburst size. At other times in the diurnal light cycle, the size of the rhabdom undergoes significant variations which are not abolished by blocking the efferent input. Apparently the daily burst of shedding overlays a second cycle of membrane metabolism that is not controlled by efferent optic nerve activity.
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Axotomy of the peripheral axon of dorsal root ganglion (DRG) cells is known to result in chromatolysis and changes in protein synthesis in DRG cells. We investigated whether a stimulus produced by peripheral branch axotomy would affect the regenerative properties of both the central and peripheral axon of the DRG cell equally. To examine this question, a conditioning crush lesion was made distally on the sciatic nerve 2 weeks prior to a testing lesion of either the dorsal root or peripheral branch axon near the DRG. ⋯ A population of more slowly growing axons in the dorsal root also does not exhibit accelerated outgrowth in response to a peripheral conditioning lesion. The results of these experiments indicate that changes in the DRG neuron's metabolism induced by prior axotomy of its peripheral axon do not affect the regenerative properties of both axons equally. This raises the possibility that accelerated axonal outgrowth in only one axonal branch results from a differentially regulated supply of proteins to the two axons by the DRG cell body.
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The existence of bombesin/gastrin-releasing peptide-like immunoreactivity (BN-GRP-LI) in rat sensory ganglia and spinal cord was confirmed using immunocytochemistry, gel filtration chromatography, and high performance liquid chromatography combined with radioimmunoassay. Immunohistochemical studies showed that in the spinal sensory ganglia of the rat about 5% of the neurons exhibited BN-GRP-LI, whereas about 20% of the neurons exhibited substance P-like immunoreactivity (SP-LI). The two immunoreactivities were found in different cells, but both were located in small ganglion cells. ⋯ In extracts prepared from spinal ganglia, two molecular weight forms of BN-GRP-LI were found using gel filtration chromatography. The high molecular weight form coeluted with porcine GRP and the low molecular weight form was smaller than bombesin. The low molecular weight BN-GRP-LI extracted from spinal cord was more hydrophilic than bombesin or ranatensin.
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Motor patterns of songs of swamp and song sparrows, Melospiza georgiana and M. melodia, deafened early in life display a significant degree of species-specific structure. Normal songs of the two species differ in the degree to which they are segmented. Swamp sparrow song consists of a single segment, and song sparrow songs are multisegmental. ⋯ Species-specific trends were also evident in song durations and frequency characteristics. Abnormalities were found, however, in the morphology of the notes and syllables from which songs of early deafened sparrows are constructed. These results require emendation of the auditory template hypothesis of song learning in birds.