Ornithine decarboxylase and ornithine decarboxylase‐inhibiting activity in rat thymocytes

Abstract

Isolation of thymocytes from rat thymus resulted in the disappearance of the high activity of ornithine decarboxylase (ODC) that characterizes the thymus of young rats, together with the appearance of an antizyme-like ODC inhibiting activity, which showed a chromatographic profile that resembled that of dexamethasone-treated rat thymus. Omission of serum or addition of dexamethasone or spermidine did not affect appreciably the extent of the antizyme-like activity. On the other hand, a variety of hormonal effectors, i.e. insulin, glucagon, adrenalin and T3, as well as the phorbol ester, PMA or the mitogen, concanavalin A (Con A) induced ODC activity in cultured thymocytes together with the disappearance of the antizyme-like activity. A paradoxical, transient induction of ODC was caused by the transcriptional inhibitor, actinomycin D. Complexed ODC was detected in rat thymus, but not in thymocytes, either quiescent or stimulated by mitogens. These results indicate that thymic lymphocytes can express either ODC activity or its inhibitor depending on the hormonal and proliferative status of the cells.

Epithelial-mesenchymal interactions and lung branching morphogenesis. Role of polyamines and transforming growth factor ß1

“…The pellets were extracted with 100 µl of 50 mM TRIS-HCl, at pH 7.5, 0.1 mM EDTA, 5 mM dithiothreitol, 0.05 mM pyridoxal-5'-phosphate and 0.5% Triton X-100 (lysis buffer). Lung lysates were centrifuged at 7,000 g for 15 min at 4°C, and the resulting supernatants were used immediately for ODC assay (Stefanelli et al, 1992) and the determination of proteins by Bradford's method (1976). ODC activity was carried out in a 50 µl total volume, 40 µl of which were of lung extract origin.…”

Depletion of Polyamines and Increase of Transforming Growth Factor‐β1, c‐myc, Collagen‐Type I, Matrix Metalloproteinase‐1, and Metalloproteinase‐2 mRNA in Primary Human Gingival Fibroblasts

“…The cell lysates were centrifuged at 7,000× g for 15 minutes at 4°C, and the resulting supernatants were used immediately for ODC assay and the determination of protein by the Bradford method. 26 ODC activity was measured according to the method of Stefanelli et al 27 Briefly, enzyme assays were carried out in a total volume of 50 µl, 40 of which were of cell extract origin. The assay mixture (final concentration) contained 50 mM TrisHCl, at pH 7.5, 0.1 mM EDTA, 5 mM dithiothreitol, 0.05 mM pyridoxal 5′-phosphate, 0.5% Triton X-100, 0.4 mM L-ornithine, and 0.1 µCi of 14 C-ornithine (sp.…”

Ornithine decarboxylase, polyamines and CD11b expression in HL-60 cells during differentiation induced by retinoic acid

“…The cell lysates were centrifuged at 7000 × g per 15 min at 4 °C, and the resulting supernatants were used immediately for ODC assay and the determination of protein by the Bradford method [14]. ODC activity was measured as described previously [15]. Briefly, enzyme assays were carried out in a total volume of 50 µl, 40 of which were of cell extract origin.…”