Bromodeoxyuridine enhancement of 1-beta-D-arabinofuranosylcytosine metabolic activation and toxicity in HL-60 leukemic cells.

We tested whether bromodeoxyuridine (BrdUrd), an analogue of thymidine (dThd), enhances 1-beta-D-arabinofuranosylcytosine (ara-C) metabolic activation, as does dThd. HL-60 cells were exposed to 10, 100, or 1000 nM ara-C for 3 h. Simultaneous exposure of log phase HL-60 cells to BrdUrd (1-1000 microM) and ara-C for 3 h resulted in enhancement of ara-C incorporation into DNA, with a doubling of incorporation in response to 10 nM ara-C occurring at concentrations of BrdUrd greater than 100 microM. Preexposure of cells to BrdUrd for 16 h followed by addition of ara-C for 3 h resulted in even greater ara-C incorporation into DNA. This increase was most marked at the lower concentrations of ara-C (10 and 100 nM), where approximately 3-fold enhancement of ara-C incorporation was observed in response to BrdUrd concentrations greater than 100 microM. Intracellular pools of 1-beta-D-arabinofuranosyl-CTP increased significantly (up to 3-fold) following 16-h exposure to BrdUrd (30, 100, or 300 microM) at all concentrations of ara-C tested. The ara-C phosphorylating activity of cell-free extracts obtained following 16-h exposure of cells to BrdUrd increased 1.5- to 2.3-fold over control. Intracellular dCTP pools fell to approximately 50% of control after exposure to 750 microM BrdUrd or dThd. Exposure to BrdUrd for 16 h caused a concentration-dependent increase in cells with S-phase DNA content, as assessed by flow cytometry, with a doubling of cells in S phase (to 60%) observed in response to 500 microM BrdUrd. HL-60 cells exposed to identical conditions of BrdUrd for 3 h showed no significant alteration in cell cycle phase distribution. Thus, although BrdUrd does increase cells in S phase, the increased ara-C incorporation caused by BrdUrd cannot be explained solely on a cytokinetic basis since enhancement of incorporation was observed after a 3-h exposure of cells to BrdUrd and ara-C. The combination of ara-C (100 nM) and BrdUrd (100-1000 microM) exhibited cytotoxic synergism, as measured by the fluorescein diacetate/propidium iodide method. These data demonstrate a clear potential for BrdUrd modulation of ara-C metabolism in human leukemia. Additionally, the interaction of BrdUrd and ara-C should be considered in the interpretation of studies of the effects of ara-C on DNA synthesis as measured by flow cytometric quantification of incorporated BrdUrd.

Therapeutic Effects of Herbal Chemicals in Traditional Chinese Medicine on Alzheimer's Disease.

Alzheimer's disease (AD) is the most common type of dementia that leads to increasing death and mental disability among humans. Current therapy of AD mainly relies on the use of acetylcholinesterase inhibitors (AChEIs) or antagonists of N-methyl-D-aspartate receptors (NMDARs), which only relieve the symptoms of the disease but not halt its progression. Nevertheless, Traditional Chinese medicines (TCM) are highly prized as many bioactive components isolated from TCM are beneficial for treating AD. In this review, we summarize the latest information on TCM and the bioactive components according to their mechanistic role in alleviating AD. They act as modulators of α- and ß-secretases, and inhibitors of betaamyloid (Aß) aggregation. Some of them suppress Aß-induced neuronal cytotoxicity and inflammation. Hence, this work has demonstrated the feasibility of applying TCM in AD therapy and the possibility of screening of constituents in TCM in the near future.

[Prostaglandin E (PGE) and gastric carcinoma].

Since 1984, an experimental and clinical study on the relation between PGE and gastric carcinoma has been performed by determining PGE content in the bioptic gastric mucosa and plasma. It is found the PGE content in the gastric mucosa and plasma is increased in all patients with gastric cancer, especially with signet ring cell carcinoma. It is higher in the regional lymph node metastasis than in the early cancer, extensive metastases and normal subjects. The PGE content in the plasma is reduced obviously 7-10 days after operation but is increased markedly in recurrent patients. There is no significant difference in extensive metastases, relapse free and normal subjects. The PGE content in the plasma is significantly higher in gastric carcinoma than in chronic atrophic gastritis, but no difference is present between chronic atrophic gastritis and normal subjects.

Stimulatory effects of hepatocyte growth factor on hemopoiesis of SCF/c-kit system-deficient mice.

In this study, we report that W/W mutant mice, which have severe macrocytic anemia caused by a deficit of extracellular domain in c-kit molecules and therefore die perinatally, have hemopoietic stem cells (HSCs) and mature hematolymphoid cells in the bone marrow (BM), thymus, and spleen, although there are significant decreases in cell counts. Moreover, the mitogen-induced proliferative response, mixed lymphocyte reaction, and anti-SRBC plaque formation of spleen cells in W/W mice are similar to those in age-matched +/? littermates and normal mice, suggesting that the SCF/c-kit system is necessary for cell proliferation but not essential for HSCs to differentiate. We next examine the stimulatory effects of hepatocyte growth factor (HGF) on hemopoiesis in W/W mice. HGF has a stimulatory effect on the colony formation (CFU-C) of W/W BM cells when cultured using either a methylcellulose assay (containing cytokines) or a long-term culture (LTC) assay. A similar stimulatory effect of HGF is observed in the other W or SI locus-mutant mice (W/Wv and SI/SId mice), which show less severe anemia than W/W. The numbers of nonadherent cells and cobblestone colonies significantly increase in the LTCs using their BM cells. In addition, in vivo administration of HGF shows a transient increase in the CFU-C counts in BM cells and peripheral blood cells. RBC, WBC, and platelet counts also increased. These results suggest that the SCF/c-kit system is not essential to hemopoiesis but that a compensatory system such as the HGF/c-met system functions in the SCF/c-kit system-deficient mice.