Acute myelogenous leukemia (AML) is the most common adult leukemia, characterized by the clonal expansion of immature myeloblasts initiating from rare leukemic stem (LS) cells. To understand the functional properties of human LS cells, we developed a primary human AML xenotransplantation model using newborn nonobese diabetic/severe combined immunodeficient/interleukin (NOD/SCID/IL)2r gamma(null) mice carrying a complete null mutation of the cytokine gamma c upon the SCID background. Using this model, we demonstrated that LS cells exclusively recapitulate AML and retain self-renewal capacity in vivo. They home to and engraft within the osteoblast-rich area of the bone marrow, where AML cells are protected from chemotherapy-induced apoptosis. Quiescence of human LS cells may be a mechanism underlying resistance to cell cycle-dependent cytotoxic therapy. Global transcriptional profiling identified LS cell-specific transcripts that are stable through serial transplantation. These results indicate the potential utility of this AML xenograft model in the development of novel therapeutic strategies targeted at LS cells.

A poly(3-hexylthiophene) containing an interacting amino chain end enhances the performance of P3HT/CdSe solar cells by increasing the dispersion of CdSe nanocrystals and improving the morphology of the nanocomposite without introducing insulating surfactants.

Cellular redox is controlled by the thioredoxin (Trx) and glutathione (GSH) systems that scavenge harmful intracellular reactive oxygen species (ROS). Oxidative stress also evokes many intracellular events including apoptosis. There are two major pathways through which apoptosis is induced; one involves death receptors and is exemplified by Fas-mediated caspase-8 activation, and another is the stress- or mitochondria-mediated caspase-9 activation pathway. Both pathways converge on caspase-3 activation, resulting in nuclear degradation and cellular morphological change. Oxidative stress induces cytochrome c release from mitochondria and activation of caspases, p53, and kinases, including apoptosis signal-regulating kinase 1 (ASK1), c-Jun N-terminal kinase, and p38 mitogen-activated protein kinase. Trx inhibits apoptosis signaling not only by scavenging intracellular ROS in cooperation with the GSH system, but also by inhibiting the activity of ASK1 and p38. Mitochondria-specific thioredoxin (Trx-2) and Trx peroxidases (peroxiredoxins) are suggested to regulate cytochrome c release from mitochondria, which is a critical early step in the apoptotis-signaling pathway. dATP/ATP and reducing factors including Trx determine the manifestation of cell death, apoptosis or necrosis, by regulating the activation process and the activity of redox-sensitive caspases. As mitochondria are the most redox-active organelle and indispensable for cells to initiate or inhibit the apoptosis process, the regulation of mitochondrial function is the central focus in the research field of apoptosis and redox.

The bulk synthesis of the [2 + 2] dimer of fullerene C 60 was achieved by the solid-state mechanochemical reaction of C 60 with KCN by the use of a high-speed vibration milling (HSVM) technique. This reaction took place also by the use of potassium salts such as K 2 CO 3 and CH 3 -CO 2 K, metals such as Li, Na, K, Mg, Al, and Zn, and organic bases such as 4-(dimethylamino)-and 4-aminopyridine. Under optimum conditions, the reaction afforded only the dimer C 120 and unchanged C 60 in a ratio of about 3:7 (by weight) regardless of the reagent used. The dimer C 120 was fully characterized by IR, UV-vis, 13 C NMR, and TOF MS spectroscopies, cyclic voltammetry, and differential scanning calorimetry. Comparison of the IR and 13 C NMR spectral data of C 120 with those reported for all-carbon C 60 polymers implied that the [2 + 2] dimer C 120 represents the essential subunit of these polymers. The dimer C 120 underwent facile dissociation into two C 60 molecules by heat, HSVM treatment, exposure to room light, or electrochemical reduction. The dimer C 120 encapsulating 3 He in one of the C 60 cages was synthesized and was used to confirm the scrambling of a C 60 cage between the monomer and the dimer during the HSVM reaction. A possible mechanism for the selective formation of the dimer C 120 is proposed.

Thioredoxin‐2 (Trx‐2) is a mitochondria‐specific member of the thioredoxin superfamily. Mitochondria have a crucial role in the signal transduction for apoptosis. To investigate the biological significance of Trx‐2, we cloned chicken TRX‐2 cDNA and generated clones of the conditional Trx‐2‐deficient cells using chicken B‐cell line, DT40. Here we show that TRX‐2 is an essential gene and that Trx‐2‐deficient cells undergo apoptosis upon repression of the TRX‐2 transgene, showing an accumulation of intracellular reactive oxygen species (ROS). Cytochrome c is released from mitochondria, while caspase‐9 and caspase‐3, but not caspase‐8, are activated upon inhibition of the TRX‐2 transgene. In addition, Trx‐2 and cytochrome c are co‐immunoprecipitated in an in vitro assay. These results suggest that mitochondrial Trx‐2 is essential for cell viability, playing a crucial role in the scavenging ROS in mitochondria and regulating the mitochondrial apoptosis signaling pathway.

The Notch signaling pathway plays a crucial role in specifying cellular fates by interaction between cellular neighbors; however, the molecular mechanism underlying smooth muscle cell (SMC) differentiation by Notch signaling has not been well characterized. Here we demonstrate that Jagged1-Notch signaling promotes SMC differentiation from mesenchymal cells. Overexpression of the Notch intracellular domain, an activated form of Notch, up-regulates the expression of multiple SMC marker genes including SMCmyosin heavy chain (Sm-mhc) in mesenchymal 10T1/2 cells, but not in non-mesenchymal cells. Physiological Notch stimulation by its ligand Jagged1, but not Dll4, directly induces Sm-mhc expression in 10T1/2 cells without de novo protein synthesis, indicative of a ligand-selective effect. Jagged1-induced expression of SM-MHC was blocked by ␥-secretase inhibitor, N-(N-(3,5-difluorophenyl)-Lalanyl)-S-phenylglycine t-butyl ester, which impedes Notch signaling. Using Rbp-j-deficient cells and site-specific mutagenesis of the SM-MHC gene, we show that such an induction is independent of the myocardin-serum response factor-CArG complex, but absolutely dependent on RBP-J, a major mediator of Notch signaling, and its cognate binding sequence. Of importance, Notch signaling and myocardin synergistically activate SM-MHC gene expression. Taken together, these data suggest that the Jagged1-Notch pathway constitutes an instructive signal for SMC differentiation through an RBP-J-dependent mechanism and augments gene expression mediated by the myocardin-SRF-CArG complex. Given that Notch pathway components are expressed in vascular SMC during normal development and disease, Notch signaling is likely to play a pivotal role in such situations to modulate the vascular smooth muscle cell phenotype. Vascular smooth muscle cells (VSMC)2 maintain considerable phenotypic plasticity throughout life and this plasticity is essential for vascular development and the pathogenesis of vascular disease such as atherosclerosis and restenosis following angioplasty (1). Differentiated VSMC exhibit a contractile phenotype that is characterized by a low rate of proliferation, low synthetic activity, and expression of a unique repertoire of proteins such as smooth muscle ␣-actin (SM ␣-actin), SM22␣, h-caldesmon (h-CaD), smoothelin-B, and smooth muscle-myosin heavy chain (SM-MHC). Once VSMC are exposed to injurious stimuli, they dedifferentiate into a so-called synthetic phenotype that exhibits a high rate of proliferation, high synthetic activity, and down-regulated expression of SMC marker genes accompanied by the induction of some marker genes for immature SMC.Among the many transcription factors involved in SMC differentiation, the myocardin-SRF complex is a key regulator as its expression is essential for SMC differentiation (2-5). Promoter/enhancer regions of most SMC marker genes such as SM-MHC and SM22␣ include several SRF binding elements, referred to as CArG or SRE. SRF recruits a potent coactivator, myocardin, resulting in the induction of SMC...

Hypertrophy allows the heart to adapt to workload but culminates in later pump failure; how it is achieved remains uncertain. Previously, we showed that hypertrophy is accompanied by activation of cyclin T/Cdk9, which phosphorylates the C-terminal domain of the large subunit of RNA polymerase II, stimulating transcription elongation and pre-mRNA processing; Cdk9 activity was required for hypertrophy in culture, whereas heart-specific activation of Cdk9 by cyclin T1 provoked hypertrophy in mice. Here, we report that aMHC-cyclin T1 mice appear normal at baseline yet suffer fulminant apoptotic cardiomyopathy when challenged by mechanical stress or signaling by the G-protein Gq. At pathophysiological levels, Cdk9 activity suppresses many genes for mitochondrial proteins including master regulators of mitochondrial function (peroxisome proliferator-activated receptor gamma coactivator 1 (PGC-1), nuclear respiratory factor-1). In culture, cyclin T1/Cdk9 suppresses PGC-1, decreases mitochondrial membrane potential, and sensitizes cardiomyocytes to apoptosis, effects rescued by exogenous PGC-1. Cyclin T1/Cdk9 inhibits PGC-1 promoter activity and preinitiation complex assembly. Thus, chronic activation of Cdk9 causes not only cardiomyocyte enlargement but also defective mitochondrial function, via diminished PGC-1 transcription, and a resulting susceptibility to apoptotic cardiomyopathy.

This study examined the surface staining mechanism of a photopolymerized composite by coffee, oolong tea, and red wine.Dental composite was subjected to an experimental 24-hour staining cycle: 17-hour immersion in artificial saliva solution containing 0.3％ mucin followed by 7-hour immersion in coffee, tea, or wine. After one, two, and four weeks, digital images of the composite surface were analyzed in grayscale mode with an imaging analyzer. Specimens polished but not immersed were used as a baseline measurement for color change. Additionally, the effects of mechanical brushing and chlorhexidine on drink-induced staining were examined.Wine caused the most severe staining, followed by tea and coffee. After four weeks of immersion, brushing reduced surface staining by wine. On the contrary, chlorhexidine increased the staining effect of tea and coffee（p＜0.05）when compared to the control specimens. In conclusion, we showed that common drinks stained the dental composite, but each by a specific mechanism that depended on external conditions such as the presence of chlorhexidine.