Hormonal regulation of programmed cell death in the labial gland of the tobacco hornworm, Manduca sexta.
Item
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Title
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Hormonal regulation of programmed cell death in the labial gland of the tobacco hornworm, Manduca sexta.
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Identifier
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AAI9732921
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identifier
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9732921
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Creator
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Halaby, Reginald.
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Contributor
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Adviser: Zahra Zakeri
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Date
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1997
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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, Cell | Biology, Molecular | Biology, Animal Physiology
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Abstract
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The labial glands of the tobacco hornworm, Manduca sexta, is a good model system for studying programmed cell death (PCD). The lysosomal death of the glands, which occurs during the larval to pupal metamorphosis, is predictable, precise, controllable, and nearly synchronous. Cytoplasmic alterations, such as activation of lysosomes, are among the earliest detectable morphological features in dying glands, while nuclear changes are late. We used the following parameters to monitor cell death; morphology by light and electron microscopy; lysosomal enzyme activity; DNA fragmentation; macromolecular synthesis; and energetics. Studies on metabolic parameters of the gland cells during involution revealed that the late modifications In the levels of energy resources and signaling molecules were not likely to trigger PCD. Since the bimodal secretion of 20-hydroxyecdysone (20-HE) coincides with morphologic alterations in dying gland cells and the fact that 20-HE had been used by others to induce cell other tissues, we investigated the hormone's role in labial gland PCD. We developed an in vitro system to more precisely define the mechanisms that regulate gland cell death. Our in vitro experiments demonstrated that glands can be maintained in culture, but 20-HE alone did not cause gland cells to die. Since the internal environment of the animal may be important for 20-HE's regulation of gland PCD, we performed a series of in vivo experiments with glands from intact and ligated animals. 20-HE in vivo induced impaired mitochondrial respiration, movement and activation of lysosomes, and DNA fragmentation in glands. A single exposure of glands to 20-HE, rather than sustained exposure, was sufficient to induce cell death. Cells from treated glands displayed more shrinkage compared to controls.
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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.
