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Summary The responses to synthetic d,l abscisin have been studied in a variety of tests. When fed in aqueous solution continuously to leaves of seedlings growing under long day conditions, d,l abscisin caused the cessation of extension growth and the formation of typical resting-buds in Betula pubescens, Acer pseudoplatanus and Ribes nigrum. Abscisin also inhibited the growth of non-dormant buds of potato when applied to the whole tubers, but was much less effective when applied to isolated tuber plugs.Abscisin accelerates the senescence of leaf discs of a wide variety of species, but is less effective when sprayed on to attached leaves, except at relatively high concentrations (50–100 ppm).Abscisin inhibited flower induction in the long day species, Lolium temulentum and Spinacia oleracea, when applied to the leaves during a period of exposure to 15-long-day cycles. Abscisin promoted flowering in the short-day plants Pharbitis nil, Ribes nigrum and strawberry when applied under long day conditions, but it did not induce flowering in certain other typical short day plants. Tuberization in Solanum andigena and two cultivars of S. tuberosum was promoted by abscisin when applied to the leaves of plants growing under long-day conditions. 相似文献
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Polymethionyl ((Met)5·3-H8PT), polyvalyl ((Val)4·4-H8PT) and polyglycyl ((Gly)3·2-H8PT) derivatives of the heme octapeptide of equine heart cytochrome c were prepared with the aid of the N-carboxyl anhydrides of their respective amino acids. Only for the (Met)5·3-H8PT did the γ-peak in the absorption spectrum of the reduced form shift from 412.5 nm, the value for the unsubstituted octapeptide, to 414 nm, the value close to the γ-peak of intact ferrocytochrome c. The γ-peak of the oxidized form of the octapeptide did not shift significantly from 397 nm. Amino acids attached to the N-terminal cysteine of the octapeptide, with methionine excepted, have little or no effect on the spectrum, and apparently cannot serve as either an intramolecular or intermolecular ligand for the iron. This result is in marked contrast to those previously obtained with the substituted cytochrome c heme undecapeptide (ref. 8) where all three derivatives had altered spectra. For the octapeptide, the ratio, absorbance of the γ-peak of the oxidized form to absorbance of the γ-peak of the reduced form, did not change appreciably for any of the derivatives, although when the reaction products from excess methionine anhydride were present (before centrifugation and dialysis) the ratio was lower and approached the ratio for cytochrome c. 相似文献
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Gilda G. Hillman Norbert Roessler Richard S. Fulbright J. Edson Pontes Gabriel P. Haas 《Cancer immunology, immunotherapy : CII》1993,36(6):351-356
To assess the cytotoxic activity of immune cells, we have developed a51Cr-retention assay in which the radioactivity retained by51Cr-labeled target cells, following coincubation with cytotoxic cells, is monitored using the automated Matrix 96 beta counter. The Matrix 96 is designed for simultaneously counting 96 samples isolated from a 96-well microplate. It uses 96 uniform and independent detectors operating on the principle of avalanche gas ionization in the Geiger-Muller mode. Samples must be dry because the detectors are of the open-window type. Therefore, samples from the 96 wells of the microplate are simultaneously harvested onto a filter using the MicroMate 196, a 96-well cell harvester, dried and quantified in the Matrix 96. Usually the51Cr isotope is measured by the detection of gamma radiation in gamma counters. The Matrix 96, however, monitors Auger electrons, which are also emitted by51Cr. We have shown that the retention assay can be used to monitor the cytotoxic activity of activated lymphocytes including lymphokine-activated killer cells and tumor-infiltrating lymphocytes against various tumor cell lines. This assay is most suitable for experiments in which low E/T ratios are sufficient to detect highly cytotoxic cells, such as clone screening in cloning assays or in limiting-dilution analysis assays. These assays involve processing and reading large numbers of microplates. In this case, the retention assay monitored in the Matrix 96 will improve the work flow and decrease the amount of radioactive waste.This work was supported by the American Cancer Society grant IN-162-C 相似文献