background: premature chromosome condensation (pcc) is a method for interphase chromosome analysis in biodosimetry. this study was performed to verify the usefulness of pcc induced by calyculin a in human peripheral blood lymphocytes (pbl) for biological dosimetry and possible construction of dose-response curve. materials and methods: peripheral blood was obtained from a healthy donor and expo...

The phosphatase inhibitors okadaic acid and calyculin A were found to elicit or to modify several neutrophil responses, suggesting that dephosphorylation plays a regulatory role. The concentrations of okadaic acid (> or = 1 mumol/L) that were effective on neutrophil functions (shape changes and marginal stimulation of pinocytosis) were shown to stimulate the incorporation of 32PO4 into many neu...

Calyculin A, isolated from a marine sponge, has a novel spiro ketal skeleton. Structurally unrelated to okadaic acid, calyculin A bound to the okadaic acid receptors in particulate and soluble fractions of mouse skin. The biochemical and tumor-promoting activities of calyculin A were studied with those of okadaic acid. Calyculin A inhibited the activity of protein phosphatases, which serve as t...

Human lymphocytes were cultured in vitro and treated with calyculin A. The aim of this work was to estimate the influence of calyculin A on chromosome morphology and banding patterns. It was also interesting whether calyculin A treatment is useful in cytogenetic analysis of human karyotype. We proved that calyculin A induces chromosome condensation in lymphocytes and raises the mitotic index si...

Effects of calyculin A, a potent inhibitor of protein phosphatases 1 and 2A, on X-ray cell killing and chromatin structure were studied using cultured mammalian cells (BHK21). Calyculin A at concentrations of 2.5-20 nM enhanced X-ray cell killing when exponentially growing BHK21 cells were treated with calyculin A for 30 min after X-irradiation. A 30-min treatment with this drug induced chromat...

Actin and myosin inhibitors often blocked anaphase movements in insect spermatocytes in previous experiments. Here we treat cells with an enhancer of myosin, Calyculin A, which inhibits myosin-light-chain phosphatase from dephosphorylating myosin; myosin thus is hyperactivated. Calyculin A causes anaphase crane-fly spermatocyte chromosomes to accelerate poleward; after they reach the poles they...

We have analyzed the spontaneous symmetry breaking and initiation of actin-based motility in keratocytes (fish epithelial cells). In stationary keratocytes, the actin network flow was inwards and radially symmetric. Immediately before motility initiation, the actin network flow increased at the prospective cell rear and reoriented in the perinuclear region, aligning with the prospective axis of...

Calyculin A was used to examine the importance of phosphatases in the modulation of cardiac contractile magnitude in the absence of any neural or humoral stimulation. Protein phosphatase (PP)1 and PP2A activity, twitch contractions, intracellular Ca(2+) concentration ([Ca(2+)](i)) transients, action potentials, membrane currents, and myofilament Ca(2+) sensitivity were measured in isolated mous...

Na+/H+ exchanger 3 (NHE3) is phosphorylated and regulated by multiple kinases, including PKA, SGK1, and CK2; however, the role of phosphatases in the dephosphorylation and regulation of NHE3 remains unknown. The purpose of this study was to determine whether serine/threonine phosphatases alter NHE3 activity and phosphorylation and, if so, at which sites. To this end, we first examined the effec...

Cyclin D1 is a key regulator of the cell cycle that is over expressed in more than half of breast cancer patients. The levels of cyclin D1 are controlled primarily through post-translational mechanisms and phosphorylation of cyclin D1 at T286 induces its proteasomal degradation. To date, no studies have explored the involvement of phosphatases in this process. Here we treated human breast cance...