Development of upper respiratory tract motor nuclei in the rat (Rattus norvegicus).
Item
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Title
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Development of upper respiratory tract motor nuclei in the rat (Rattus norvegicus).
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Identifier
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AAI9405527
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identifier
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9405527
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Creator
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Friedland, David Richard.
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Contributor
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Advisers: Jeffrey T. Laitman | Avrim R. Eden
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Date
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1993
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Language
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English
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Publisher
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City University of New York.
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Subject
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Biology, Neuroscience | Biology, Anatomy | Health Sciences, Human Development
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Abstract
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The mammalian upper respiratory tract serves as the common modality for functions of respiration, deglutition and vocalization. The role of the URT in establishing these functions is largely defined by muscles of the tongue, pharynx and larynx. As such, the neuromuscular system subserving URT control must be capable of coordinating activity between these muscle groups and of eliciting actions specific to individual URT behaviors. Little is known, however, regarding the development of URT neuromuscular control, in particular, of the brainstem motor nuclei innervating URT muscles.;This study investigated the development of URT motor nuclei innervating muscles of the tongue, pharynx and larynx. Specifically, the course of motoneuron cell death in the nucleus ambiguous (NA) and the hypoglossal nucleus (XII) was charted in pre- and postnatal rats. Motoneuron cell death (MCD) is a normal developmental process by which an initial overproduction of motoneurons is reduced to adult levels in response to epigenetic signals from target muscles and afferent neurons. The development of NA and XII was further studied by experiments charting migration of URT motoneurons and the establishment of GABAergic innervation in both nuclei.;Results indicated MCD in both URT motor nuclei occurring entirely prenatally. MCD in the hypoglossal nucleus (XII) appeared to initiate approximately one day before that in the nucleus ambiguous (NA). Further, cell death in XII consisted of a loss of 40-45% of motoneurons versus 55-60% in NA. Migration and interneuron studies supported the methodologies used to assess MCD. In addition, these studies indicated that NA motoneurons arise from two regions of the basal plate and that GABAergic innervation was established in NA and XII during the period of MCD.;This investigation indicates the presence of critical periods in the development of URT motor nuclei during late gestation in the rat. As such, a template has been established upon which to predicate the development of normal and pathological URT neuromuscular control in humans. Discussions have been included with regard to URT incoordination pathologies such as the Sudden Infant Death Syndrome, and the role of MCD in the evolution of the human URT and the origins of articulate speech.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
