A Sensitive New Method for Clinically Monitoring Cytarabine Concentrations at the DNA level in Leukemic Cells

Cytarabine (ara-C), a major antileukemic agent, is phosphorylated in the cell to cytarabine triphosphate (ara-CTP), which then is partly incorporated into DNA. The drug incorporation into DNA poisons the extending primer against further incorporation of deoxyribonucleotides including dCTP, ultimately inhibiting DNA synthesis. While intracellular ara-CTP concentration has been found to predict clinical outcome, cytotoxicity in vitro is determined primarily by the extent of drug incorporation into DNA. However, clinically appropriate quantitation methods for ara-C at the DNA level have not been available. We developed a sensitive new method for monitoring ara-C incorporated into DNA in vivo. After DNA from leukemic cells was fractionated using the Schmidt-Thannhauser-Schneider method, it was degraded to constituent nucleosides to release ara-C, which was isolated from the nucleosides using HPLC and then measured by radioimmunoassay. Recovery for DNA fractionation, ara-C release by degradation, and ara-C isolation were 92.0 ± 6.4%, 90.7 ± 9.4%, and 98.5 ± 1.4%, respectively. The method was found to determine ara-C incorporation into DNA of ara-C-treated HL60 cells in vitro with minimal interassay variation. The values determined were compatible with those determined by scintillation counting in parallel experiments using tritiated ara-C. Our method could be used to monitor DNA-incorporated ara-C concentrations during ara-C therapy, together with plasma ara-C and intracellular ara-CTP concentrations. ara-C incorporation into DNA appeared to be associated with intracellular retention of ara-CTP or persistence of plasma ara-C. Thus, the present method is sensitive, accurate, precise, and may permit therapeutic drug monitoring at the DNA level for better individualization of antileukemic regimens

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早大学位記番号:新6373早稲田大

Alkylator-Induced DNA Excision Repair in Human Leukemia CCRF-CEM Cells In Vitro, Measured Using the Single-Cell Gel Electrophoresis (Comet) Assay

The capacity to repair DNA damage is an important factor that affects the therapeutic outcome in cancer treatment. To clarify the cellular repair response, we investigated the kinetics of DNA excision repair initiated by 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) in human leukemia CCRF-CEM cells at an exponential growth phase in vitro. Using the alkaline single-cell gel electrophoresis (comet) assay, we quantitated the repair kinetics as the amount of DNA single-strand breaks that were generated from the incision and were diminished by the rejoining in the repair process. CEM cells could initiate DNA excision repair in response to BCNU by starting an incision reaction. However, the incision capacity came to a plateau at a concentration of 80 to 1003M or after an incubation time of 90 to 120 minutes. When the cells were pulsed with 403M BCNU, the maximal incision occurred at the end of the incubation period, and the repair process was completed within 4 hours.When cells were treated with 1003M BCNU, the incised DNA was not rejoined at 4 hours, suggesting that the repair was not completed. Higher concentrations might surpass the cellular capacity for repair and would be associated with increased cell death. Evaluation of the repair process may provide a clue for therapeutic strategies to improve clinical efficacy if accelerated DNA repair is responsible for the drug resistance

Spin-orbit torque generation in bilayers composed of CoFeB and epitaxial SrIrO3_{3} grown on an orthorhombic DyScO3_{3} substrate

We report on the highly efficient spin-orbit torque (SOT) generation in epitaxial SrIrO$_{3}$(SIO), which is grown on an orthorhombic DyScO$_{3}$(110) substrate. By conducting harmonic Hall measurement in Co$_{20}$Fe$_{60}$B$_{20}$ (CoFeB)/SIO bilayers, we characterize two kinds of the SOTs, i.e., dampinglike (DL) and fieldlike ones to find that the former is much larger than the latter. By comparison with the Pt control sample with the same CoFeB thickness, the observed DL SOT efficiency $\xi$$_{DL}$ of SIO ($\sim$0.32) is three times higher than that of Pt ($\sim$0.093). The $\xi$$_{DL}$ is nearly constant as a function of the CoFeB thickness, suggesting that the SIO plays a crucial role in the large SOT generation. These results on the CoFeB/SIO bilayers highlight that the epitaxial SIO is promising for low-current and reliable spin-orbit torque-controlled devices.Comment: arXiv admin note: text overlap with arXiv:2305.1788

Spin current generation from an epitaxial tungsten dioxide WO2_{2}

We report on efficient spin current generation at room temperature in rutile type WO$_{2}$ grown on Al$_{2}$O$_{3}$(0001) substrate. The optimal WO$_{2}$ film has (010)-oriented monoclinically distorted rutile structure with metallic conductivity due to 5$\it{d}$$^2$ electrons, as characterized by x-ray diffraction, electronic transport, and x-ray photoelectron spectroscopy. By conducting harmonic Hall measurement in Ni$_{81}$Fe$_{19}$/WO$_{2}$ bilayer, we estimate two symmetries of the spin-orbit torque (SOT), i.e., dampinglike (DL) and fieldlike ones to find that the former is larger than the latter. By comparison with the Ni$_{81}$Fe$_{19}$/W control sample, the observed DL SOT efficiency $\xi$$_{DL}$ of WO$_{2}$ (+0.174) is about two thirds of that of W (-0.281) in magnitude, with a striking difference in their signs. The magnitude of the $\xi$$_{DL}$ of WO$_{2}$ exhibits comparable value to those of widely reported Pt and Ta, and Ir oxide IrO$_{2}$. The positive sign of the $\xi$$_{DL}$ of WO$_{2}$ can be explained by the preceding theoretical study based on the 4$\it{d}$ oxides. These results highlight that the epitaxial WO$_{2}$ offers a great opportunity of rutile oxides with spintronic functionalities, leading to future spin-orbit torque-controlled devices.Comment: 14 pages, 4 figure

Effect of interface quality on spin Hall magnetoresistance in Pt/MgFe2_{2}O4_{4} bilayers

We report on spin Hall magnetoresistance (SMR) in bilayers composed of Pt and magnetic insulator MgFe$_{2}$O$_{4}$ (MFO) with spinel structure. The Pt thickness dependence of the SMR reveals that annealing of the MFO surface before depositing the Pt layer is crucial for a large SMR with better interface quality. We also found that oxygen pressure during the MFO growth hardly affects the SMR while it influences on magnetic property of the MFO film. Our findings provide important clues to further understanding the spin transport at interfaces containing magnetic insulators, facilitating development of low power consumption devices.Comment: 4 figures, 1 tabl

Relation Between Severity of Magnesium Deficiency and Frequency of Anginal Attacks in Men With Variant Angina

AbstractObjectives. We evaluated whether the severity of magnesium deficiency was correlated with the frequency of attacks of variant angina.Background. Magnesium deficiency may be associated with the development of variant angina. However, the relation between the activity of variant angina and magnesium deficiency remains to be elucidated.Methods. We assessed the body magnesium status of 18 men with variant angina: Group 1 (≥4 attacks/week, n = 7) and Group 2 (<4 attacks/week, n = 11). Concentrations of magnesium were determined in serum, urine, mononuclear cells and erythrocytes, and the 24-h magnesium retention rate was determined.Results. Group 1 showed a higher 24-h magnesium retention rate (mean ± SEM 63.5 ± 7.6% vs. 24.9 ± 2.7%, p < 0.01) and a lower intracellular concentration of magnesium in mononuclear cells and erythrocytes than did Group 2 (respectively, 156.3 ± 13.5 vs. 212.1 ± 6.9 fg/cell, p < 0.01; and 3.5 ± 0.5 vs. 5.2 ± 0.4 fg/cell, p < 0.05), demonstrating the presence of magnesium deficiency in Group 1. The 24-h magnesium retention rate and intracellular concentrations of magnesium in mononuclear cells and erythrocytes correlated well with the frequency of anginal attacks (r = 0.78, p < 0.01; r = −0.78, p < 0.01; r = −0.62, p < 0.01, respectively) for all patients.Conclusions. Data suggest that the magnesium status of men with variant angina is closely related to disease activity

Effect of interface quality on spin Hall magnetoresistance in Pt/MgFe2O4 bilayers

Sugino M., Ueda K., Kida T., et al. Effect of interface quality on spin Hall magnetoresistance in Pt/MgFe2O4 bilayers. Applied Physics Express 17, 013003 (2024); https://doi.org/10.35848/1882-0786/ad0ba4.We report on spin Hall magnetoresistance (SMR) in bilayers composed of Pt and magnetic insulator MgFe2O4 (MFO) with spinel structure. The Pt thickness dependence of the SMR reveals that annealing of the MFO surface before depositing the Pt layer is crucial for a large SMR with better interface quality. We also found that oxygen pressure during the MFO growth hardly affects the SMR, while it influences the magnetic property of the MFO film. Our findings provide important clues to further understanding the spin transport at interfaces containing magnetic insulators, facilitating development of low power consumption devices

Esophageal erosion as a possible bacterial entry site in an acute lymphoblastic leukemia patient with sepsis

A 69-year-old man with relapsed acute lymphoid leukemia was treated with adriamycin, vincristine, and prednisolone. During this chemotherapy, the patient developed sepsis and meningitis. Although many kinds of antimicrobial drugs, including imipenem, meropenem, amphotericin-B, and γ-globulin were administered, the patient died of respiratory failure. A positive result for Enterococcus faecalis was obtained in both blood and cerebrospinal fluid culture. Autopsy revealed multiple small erosions in the lower esophagus. Histopathological examination showed multiple nuclear inclusion bodies of herpes simplex virus in the squamous epithelial cells at the edge of the erosions. Moreover, proliferation of micrococci was observed at the base of the erosions and in the lumina of the submucosal small vessels. These findings suggested that E faecalis entered the blood circulation from this lesion. In many patients with febrile neutropenia, the pathogenesis of infection remains unclear. Our case seems significant for clarifying the focus and pathogenesis of febrile neutropenia