ROLE OF GILL CALCIUM-ATPASES IN BLOOD CALCIUM REGULATION IN THE KILLIFISH, (FUNDULUS HETEROCLITUS) (CA-REGULATING HORMONES).
Item
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Title
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ROLE OF GILL CALCIUM-ATPASES IN BLOOD CALCIUM REGULATION IN THE KILLIFISH, (FUNDULUS HETEROCLITUS) (CA-REGULATING HORMONES).
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Identifier
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AAI8629726
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identifier
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8629726
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Creator
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PAUL, MARY JANE FRANCES.
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Contributor
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Carolyn Burdick
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Date
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1986
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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, Animal Physiology
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Abstract
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Killifish, a euryhaline fish has the ability to maintain a constant blood calcium level in both seawater and freshwater environments. These fish face a constant calcium challenge which is closely related to the external media. Seawater-adapted fish are hypo-osmotic to the environment and have the problem of Ca('2+) overload. Freshwater-adapted fish are hyperosmotic to the environment and have the problem of Ca('2+) loss.;Preliminary studies showed the presence of two Ca-ATPases in the gill epithelium microsomal fraction from killifish; Ca('2+)+Mg('2+)-ATPase and Ca('2+)+Na('+)-ATPase.;Characterization of the two Ca-ATPases revealed: (1) A Ca('2+)+Mg('2+)-ATPase which has a high affinity for Ca('2+), requires Mg('2+) for activity and may be controlled by calmodulin; and (2) A Ca('2+)+Na('+)-ATPase which has a low affinity for Ca('2+), requires Na('+) for activity, does not require Mg('2+) and is probably not controlled by calmodulin.;Environmental calcium specifically controls the activities of the killifish branchial epithelium Ca-ATPases. The experiments provided evidence that the activity of Ca('2+)+Mg('2+)-ATPase was significantly higher in killifish adapted to freshwater and calcium-deficient seawater--both low calcium environments. On the other hand, Ca('2+)+Na('+)-ATPase activity was significantly higher in killifish adapted to seawater and calcium-enriched freshwater--both high calcium environments. These finding suggest that one gill epithelium Ca-ATPase is pumping calcium from the environment into fish adapted to a low calcium environment while the other gill epithelium Ca-ATPase is pumping calcium out of fish adapted to a high calcium environment.;The interrelationship between changes in plasma Ca('2+) and Ca('2+)+Mg('2+)-ATPase and Ca('2+)+Na('+)-ATPase activities was investigated, two types of mechanisms are involved when killifish are transferred to a new environment. One is a fast adaptation mechanism which appears to occur within a few days of transfer not involving changes in Ca-ATPase activity and the other is a slow adaptation mechanism which appears to occur within two weeks following transfer and does not involve changes in enzyme activity.;It appears that the branchial epithelium Ca-ATPases are under the influence of the Ca('2+) regulating hormones (pituitary gland and corpuscles of Stannius). Results suggest that Ca('2+)+Na('+)-ATPase activity is decreased by prolactin while Ca('2+)+Mg('2+)-ATPase activity is not affected by prolactin but may be stimulated by another hypercalcemic factor(s) in the pituitary gland. (Abstract shortened with permission of author.).
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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.
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Program
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Biology
