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Abstract: The effect of ATP on mitochondrial membrane depolarization in rat submandibular glands was investigated. Exposure of the cell suspension to high concentrations of ATP induced a sustained depolarization of mitochondrial membrane. This effect was blocked in the presence of magnesium and reproduced by low concentrations of 2′,3′-O-(4-benzoylbenzoyl)adenosine 5′-triphosphate (BzATP), suggesting the implication of the P2X7 purinergic receptor. This point was confirmed by comparison of the response to ATP by wild-type and P2X7 knock-out (P2X7R−/−) mice. Mitochondria took up calcium after ATP stimulation but the depolarization of the mitochondrial membrane by ATP was not affected by the removal of calcium from the extracellular medium. It was nearly fully suppressed in the absence of sodium and partially blocked by the mitochondrial Na/Ca exchanger inhibitor 7-chloro-5-(2-chlorophenyl)-1,5-dihydro-4,1-benzothiazepin-2(3H)-one (CGP-37157). Both ATP and monensin increased the uptake of extracellular sodium (as shown by the depolarization of the plasma membrane) but the sodium ionophore did not affect the mitochondrial membrane potential. It is concluded that the activation of P2X7 receptors depolarizes the mitochondrial membrane. The uptake of extracellular sodium is necessary but not sufficient to induce this response. [Copyright &y& Elsevier]

In the present study we have used FISH to analyze the incidence of trisomy 8 in acute leukemias following either a primary myeloproliferative disorder (MPD) or a myelodysplastic syndrome (MDS) and correlated it with both the immunophenotype and the cell-cycle distribution of the leukemic blast cells. Six of the 21 (28%) acute leukemias studied displayed trisomy 8 by FISH. The number of trisomic cells in these cases ranged from 20 to 84%, with a mean of 46 +/- 24%. Trisomy 8 was associated with a homogeneous population of leukemic cells, phenotypically characterized by CD34+/HLADR+/CD13+/CD33+/CD11b-/ CD15-/CD14-. No significant differences were observed on the proliferative rate of cases with trisomy 8, as compared with blast cells from the remaining patients. Overall, our findings suggest that in acute leukemias secondary to MPD or MDS, trisomy 8 is associated with a blockade of myeloid maturation at an early step of the differentiation process. [ABSTRACT FROM AUTHOR]

AIM: To evaluate the validity of the colony forming unit-granulocyte macrophage (CFU-GM) assay for predicting relapse in patients with acute myeloid leukaemia (AML). METHODS: The study population comprised 32 patients with AML in remission, followed for a median of 18 months. A mean of four studies was carried out per patient. Three patterns of in vitro growth based on the number of CFU-GM in normal bone marrow were defined: 1 = normal (normal number of CFU-GM and a cluster:colony ratio < 2); 2 = hypoplastic (low number of CFU-GM and a cluster:colony ratio < 2); 3 = anomalous (low or normal number of CFU-GM and a cluster:colony ratio > 2). RESULTS: Eleven patients relapsed, all of whom had previously displayed an abnormal CFU-GM pattern: anomalous in nine and hypoplastic in two. The remaining 25 patients were in complete remission at the time of writing, 16 of whom had a normal growth pattern. The other nine had anomalous (eight patients) or hypoplastic (one patient) growth. The latter may be false positive results. The in vitro growth pattern was not constant during follow up analysis. All 15 patients in whom the growth pattern switched from abnormal to normal remain in complete remission. By contrast, of the five cases in whom the pattern changed from normal to abnormal, three have relapsed and the other two had other indicators of relapse. The growth pattern remained unchanged in the remaining 16 patients. CONCLUSION: The present data show that the sequential investigation of the CFU-GM growth pattern may be of value in predicting relapse in patients with AML. [ABSTRACT FROM PUBLISHER]

Abstract: Background: Agonists of P2X7 receptors increase the production of reactive oxygen species (ROS) in immunocytes. In this work we tested this response and its effect on mitochondrial inner membrane potential (Δψm) in exocrine glands. Methods: The production of ROS by rat submandibular glands was investigated by measuring the oxidation of dichlorodihydrofluorescein (DCFH), a fluorescent probe. The Δψm was estimated with tetramethylrhodamine. Results: Activation of P2X7 receptors by ATP or Bz-ATP increased the production of ROS. This response was not modified by inhibitors of phospholipase A2 or of various kinases. The effect of ATP was calcium-dependent and was blocked by diphenyliodonium, an inhibitor of flavoproteins. It was not affected by rotenone, an inhibitor of the complex I of the mitochondrial electron transfer chain. Scavengers of ROS had no effect on the dissipation of Δψm by ATP. Conclusions: We conclude that, in rat submandibular glands, P2X7 receptors stimulate in a calcium-dependent manner an oxidase generating ROS, suggesting the involvement of the dual oxidase Duox2. The production of ROS does not contribute to the depolarization of mitochondria by purinergic agonists. General significance: Purinergic receptors could be regulators of the bactericidal properties of saliva by promoting both the secretion of peroxidase from acinar cells and by activating Duox2. [ABSTRACT FROM AUTHOR]