Isolation and partial characterization of dinoflagellate chromatin

Chromatin was prepared by two different methods from isolated nuclei of Gyrodinium cohnii (Cryptothecodinium cohnii) and Peridinium trochoideum. These isolation procedures are different from those generally used to prepare eukaryote chromatin, because the latter do not work for dinoflagellate chromatin. The chemical composition of this chromatin is similar for both methods of preparation and both organisms. Dinoflagellate chromatin contains DNA, RNA, acid-soluble and acid-insoluble protein as does chromatin from higher plants and animals, but the amount of acid-soluble protein relative to DNA (0.02-0.08) is much lower than that of typical eukaryotes (about 1). Evidence is presented to show that proteolytic degradation is unlikely to account for the low acid-soluble protein content in dinoflagellate chromatin. Exclusion chromatography of the chromatin on large-pore gels (Bio Gel A-15m or Sephadex G-200) indicates that the bulk of the protein present in the chromatin preparations migrates with the DNA. G. cohnii and P. trochoideum chromatin show an ultraviolet absorption spectrum, which is intermediate between DNA and typical eukaryote chromatin, and this is not significantly changed by gel exclusion chromatography. Preliminary results suggest that the dinoflagellate DNA-associated proteins do not stabilize the DNA against melting. Chromatin prepared from log-phase cells has more protein and RNA than chromatin from stationary-phase cells. The chemical composition of dinoflagellate chromatin is compared with that of prokaryotes and eukaryotes.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22352/1/0000798.pd

Induction of leaf senescence in Arabidopsis thaliana by long days through a light-dosage effect

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74662/1/j.1399-3054.1996.tb00463.x.pd

The Mode of Action of Maleic Hydrazide: Inhibition of Growth

Maleic hydrazide (MH) inhibits corn root elongation through an effect on cell division apparently without inhibiting cell enlargement. The decrease in the rate of elongation was apparent only after a considerable lag, over 14 hours, even with a concentration as high as 5 mM. MH (1 mM) did not inhibit His growth of roots from corn seeds given very large doses of Γ-irradiation or excised corn root segments including the elongation Zone or the cell enlargement induced by IAA in corn coleoptile sections. Many compounds including purines, pyrimidines, nucleosides. cysteine, pyridoxal, pyruvate. kinetin and CoCl 2 , many of which had previously been reported to alleviate MH inhibition in other tissues, were tested for their ability to prevent the inhibition of corn root elongation by MH, but none were effective. These data do not support the theory that MH acts by inhibiting the synthesis of or competing with some simple metabolite or hormone. Whatever its mechanism of action the failure of MH to inhibit cell enlargement in most systems indicates that it is fairly selective.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74891/1/j.1399-3054.1969.tb07375.x.pd

Changes in the mineral composition of soybean xylem sap during monocarpic senescence and alterations by depodding

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74392/1/j.1399-3054.1987.tb04332.x.pd