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Cycle Effects (cycle + effects)

Distribution by Scientific Domains
Polymers and Materials Science28%
Medical Sciences28%

Kinds of Cycle Effects

  • cell cycle effects
    		•

    Selected Abstracts

    Cytotoxicity and Cell Cycle Effects of Bare and Poly(vinyl alcohol)-Coated Iron Oxide Nanoparticles in Mouse Fibroblasts

    ADVANCED ENGINEERING MATERIALS, Issue 12 2009
    Morteza Mahmoudi
    Super-paramagnetic iron oxide nanoparticles (SPIONs) are recognized as powerful biocompatible materials for use in various biomedical applications, such as drug delivery, magnetic-resonance imaging, cell/protein separation, hyperthermia and transfection. This study investigates the impact of high concentrations of SPIONs on cytotoxicity and cell-cycle effects. The interactions of surface-saturated (via interactions with cell medium) bare SPIONs and those coated with poly(vinyl alcohol) (PVA) with adhesive mouse fibroblast cells (L929) are investigated using an MTT assay. The two SPION formulations are synthesized using a co-precipitation method. The bare and coated magnetic nanoparticles with passivated surfaces both result in changes in cell morphology, possibly due to clustering through their magnetostatic effect. At concentrations ranging up to 80,×,10,3,M, cells exposed to the PVA-coated nanoparticles demonstrate high cell viability without necrosis and apoptosis. In contrast, significant apoptosis is observed in cells exposed to bare SPIONs at a concentration of 80,×,10,3,M. Nanoparticle exposure (20,80,×,10,3,M) leads to variations in both apoptosis and cell cycle, possibly due to irreversible DNA damage and repair of oxidative DNA lesions, respectively. Additionally, the formation of vacuoles within the cells and granular cells indicates autophagy cell death rather than either apoptosis or necrosis. [source]

    Cell cycle effects resulting from inhibition of hepatocyte growth factor and its receptor c-Met in regenerating rat livers by RNA interference,

    HEPATOLOGY, Issue 6 2007
    Shirish Paranjpe
    Hepatocyte growth factor (HGF) and its receptor c-Met are involved in liver regeneration. The role of HGF and c-Met in liver regeneration in rat following two-thirds partial hepatectomy (PHx) was investigated using RNA interference to silence HGF and c-Met in separate experiments. A mixture of 2 c-Met-specific short hairpin RNA (ShRNA) sequences, ShM1 and ShM2, and 3 HGF-specific ShRNA, ShH1, ShH3, and ShH4, were complexed with linear polyethylenimine. Rats were injected with the ShRNA/PEI complex 24 hours before and at the time of PHx. A mismatch and a scrambled ShRNA served as negative controls. ShRNA treatment resulted in suppression of c-Met and HGF mRNA and protein compared with that in controls. The regenerative response was assessed by PCNA, mitotic index, and BrdU labeling. Treatment with the ShHGF mixture resulted in moderate suppression of hepatocyte proliferation. Immunohistochemical analysis revealed severe suppression of incorporation of BrdU and complete absence of mitosis in rats treated with ShMet 24 hours after PHx compared with that in controls. Gene array analyses indicated abnormal expression patterns in many cell-cycle- and apoptosis-related genes. The active form of caspase 3 was seen to increase in ShMet-treated rats. The TUNEL assay indicated a slight increase in apoptosis in ShMet-treated rats compared with that in controls. Conclusion: The data indicated that in vivo silencing of c-Met and HGF mRNA by RNA interference in normal rats results in suppression of mRNA and protein, which had a measurable effect on proliferation kinetics associated with liver regeneration. (HEPATOLOGY 2007.) [source]

    Simulation of microalgae growth in limiting light conditions: Flow effect

    AICHE JOURNAL, Issue 5 2002
    J. Pruvost
    Effect of hydrodynamical conditions on a microalgae culture growth was investigated in a photobioreactor with annular light chambers, with the focus on the relation between the cell displacement and the amount of light received by microorganisms, by comparing two different flow conditions in light chambers: an axial flow generating a poor radial mixing and a 3-D swirling motion. To determine microorganism trajectories, a Lagrangian approach was retained, allowing light received to be considered from a single microalga point of view. The light distribution was calculated using Beer,Lambert law, and a biological modeling of the culture growth was proposed, with consideration of light/dark cycle effects induced by cell displacement in the depth of the culture. Finally, batch cultures of Porphyridium purpureum were simulated for both hydrodynamical conditions in light chambers. The advantage of applying a three-dimensional motion to generate cell renewal in front of the light source, allowing microorganisms to use light more efficiently, is clearly shown. [source]

    Orientation and strain cycle effects on the impact performance of polyethylene

    POLYMER ENGINEERING & SCIENCE, Issue 4 2005
    Alexis Paizis
    The effects of orientation by plastic strain on the impact fracture resistance of a pipe-grade polyethylene have been investigated. Isotropic samples of bulk polymer were subjected, by plane-strain compression, to uniform Hencky strains of up to ±40%. In some samples this strain was reversed to restore the original dimensions. Impact bend specimens were prepared from samples oriented either normal to or within the fracture plane. Plane-strain fracture resistance and transition temperature were measured at 1 m/s by using the ISO 17281 method, and plane stress fracture resistance was measured by using the Reversed Charpy test. Orientation within the fracture plane by plastic compression across it compromises the relatively high plane-stress toughness of this material and increases the brittle-tough transition temperature, while the opposite is true of plastic extension. Reversion from a state of adverse orientation, by completing a strain cycle, only partially restores the fracture resistance of the isotropic polymer. POLYM. ENG. SCI., 45:596,605, 2005. © 2005 Society of Plastics Engineers [source]

    Innovation, Technological Conditions and New Firm Survival,

    THE ECONOMIC RECORD, Issue 267 2008
    PAUL H. JENSEN
    High neonatal mortality is one of the most salient ,facts' about firm performance in the industrial organisation literature. We model firm survival and examine the relative influence of firm, industry and macroeconomic factors on survival for new vis-à-vis incumbent firms in Australia. In particular, we focus on how the intensity of innovation in each industry relates to firm survival. Our results imply that while new firms thrive in risky and innovative industries, they are also more susceptible to business cycle effects such as changes in the rate of growth of industry profits and the availability of equity finance. [source]

    Effect of ultraviolet (UV) A, UVB or ionizing radiation on the cell cycle of human melanoma cells

    BRITISH JOURNAL OF DERMATOLOGY, Issue 5 2007
    M. Placzek
    Summary Background, One important component of the cellular response to irradiation is the activation of cell cycle checkpoints. It is known that both ultraviolet (UV) radiation and ionizing radiation (IR) can activate checkpoints at transitions from G1 to S phase, from G2 phase to mitosis and during DNA replication. Objectives, To evaluate the effects of irradiation with different wavelengths on cell cycle alterations. Methods, p53-deficient IPC-298 melanoma cells were irradiated with 10 J cm,2 UVA, 40 mJ cm,2 UVB, or with 7·5 Gy IR. Cell cycle effects were then determined by DNA/5-bromodeoxyuridine dual-parameter flow cytometry. Results, IPC-298 cells irradiated in G1 with UVA were not arrested at the G1/S transition, but at the G2/M transition. Despite p53 deficiency, the cells showed a G1 arrest after UVB exposure. Furthermore, IR did not affect G1 or S phase, but induced G2 phase arrest. Hence, the effects of UVA, but not of UVB, on the cell cycle in p53-deficient melanoma cells are comparable with those of IR. Conclusions, UVA and IR induce radical-mediated strand breaks and DNA lesions, and UVB essentially induces thymine dimers that lead to excision repair-related strand breaks. Different cell cycle effects may be a consequence of different types of DNA damage. The results showed that UVB-irradiated p53-deficient cells are arrested in G1. Irradiation with the solar radiation component UVB can therefore result in a beneficial retardation of tumour promotion in human skin carrying p53-mutated cell clones. [source]

    Effects of the PKC inhibitor PD 406976 on cell cycle progression, proliferation, PKC isozymes and apoptosis in glioma and SVG-transformed glial cells

    CELL PROLIFERATION, Issue 2 2005
    C. Russell
    However, reports differ on which PKC isozymes are responsible for glioma proliferation. As a means to further elucidate this, the objectives of our research were to determine how inhibition of PKC-,, PKC-, and PKCµ with PD 406976 regulates the cell cycle, cell proliferation and PKC during glioma growth and development. To establish the cell cycle effects of PD 406976 on brain cells (SVG, U-138MG and U-373MG glioma cells), specimens were treated with either dimethylsulfoxide (DMSO; control) or PD 406976 (2 µm). Results from flow cytometry demonstrated that PD 406976 delayed the entry DNA synthesis phase in SVG cells and delayed the number of cells entering and exiting the DNA synthesis phase in both U-138MG and U-373MG cells, indicating that PD 406976 may inhibit G1/S and S phase progression. Assessment of cell viability demonstrated a cytostatic effect of PD 406976 on SVG, U-138MG and U-373MG glioma cell proliferation. The PD 406976-induced decreased proliferation was sustained at 48,96 h. A PKC activity assay was quantified and demonstrated that exposure of SVG and U-373MG glioma cells to PD 406976 suppressed PKC activity. Western blotting demonstrated reduced PKC-,1, PKC-, and PKC-, protein content in cells treated with PD 406976. We determined that the growth inhibitory effect of PD 406976 was not as a result of apoptosis. [source]