Autolysis and release of daughter spheroids in the green alga Volvox carteri.
Item
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Title
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Autolysis and release of daughter spheroids in the green alga Volvox carteri.
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Identifier
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AAI9000056
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identifier
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9000056
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Creator
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Pannaman, Laura Joyce.
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Contributor
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Adviser: Roy McGowan
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Date
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1989
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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, General
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Abstract
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The release of daughter spheroids in the green alga Volvox carteri is an enzymatic process resulting in dissolution of the glycoprotein sheath. Various aspects of release in Volvox carteri f. nagariensis were studied.;Light microscopic examination of spheroids at various stages of release demonstrates numerous exit holes in the sheath. This verifies reports that each daughter exits the parent through its own exit hole, rather than through one hole as has been reported for other Volvox species.;The crude Volvox autolysin was isolated from synchronously grown cultures and its effect on different age classes of formaldehyde-killed spheroids measured. Results show that only mature spheroids, containing daughters at least 150u in diameter, are susceptible to autolytic digestion.;The trypsin-like nature of the Volvox autolysin was confirmed. Mature Volvox spheroids were incubated with inhibitors of proteolytic enzymes and the effect on release observed. In all cases, soybean trypsin inhibitor, benzamidine and leupeptin, all inhibitors of trypsin, inhibit release of daughters from the mature parent. Pepstatin, an inhibitor of acid endopeptidases, and chymostatin, a chymotrypsin inhibitor, were without effect.;The effect of purified autolysin on the synthetic trypsin substrate benzoyl arginine ethyl ester (BAEE) was measured spectrophotometrically. The autolysin cleaves BAEE, verifying it as a trypsin-like protease.;A time course study of the effect of soybean trypsin inhibitor on release shows the autolysin is likely synthesized 2-4 hours prior to onset of release without manifesting its activity.;The sheath (glyco)proteins from post-inversion and pre-release Volvox were purified and their banding patterns on polyacrylamide gels compared. The susceptibility of these two age classes of (glyco)proteins to digestion by proteolytic enzymes was also studied. Pre-release sheath contains three high molecular weight bands never found in post-inversion sheath. Post-inversion sheath contains many more low molecular weight bands and is less susceptible to digestion by trypsin and autolysin. Both are equally susceptible to the digestion by pronase and {dollar}\alpha{dollar}-chymotrypsin. The presence of eight post-inversion bands susceptible to neither trypsin nor Volvox autolysin may indicate that these are "backbone" polypeptides responsible for resistance of post-inversion sheath to enzymatic digestion.
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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.
