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Reactive oxygen species (ROS) have been proven to be important activators for various cellular activities, including cell differentiation. Several reports showed the necessity of ROS during cell differentiation of the megakaryocytic (MK) lineage. In this study, we employed near ultraviolet (near-UV) irradiation to generate endogenous oxidative stress in an MK differentiation process of K562 cells with phorbol 12-myristate 13-acetate (PMA) induction. A significant increase in the intracellular ROS level was detected on day 1 after near-UV irradiation. In the initial stage of differentiation, a shifted fraction of G1 and G2 phase cells was obtained using near-UV irradiation, giving an increased percentage of G2 phase cells (up from 31.1 to 68.7%). The near-UV irradiation-induced upregulation of the p21 gene, which is a cell cycle inhibitor, suggested that the G2 phase cells were prevented from undergoing cell division. It was found that the percentage of high ploidy (8N and 16N) cells was enhanced significantly at the later stage of the K562 cell culture with near-UV irradiation. Moreover, time-lapse analysis showed that near-UV irradiation encouraged the expression of CD41, a specific surface marker of megakaryocytes. This is the first report that the elevated oxidative stress through the near-UV irradiation promoted the MK differentiation of PMA-induced K562 cells.
The oligodendrocyte progenitors (OPCs) are the abundant population of NG2-positive cells in the young and adult CNS. They are capable of myelinogenesis, but they are also among the first cells to react to CNS injuries. Over the last decade, these glia commited progenitors have been however the subject of intensive research in context of their assumed neural stem cell properties. In our studies we have addressed the question of the impact of the local tissue microenvironment on the OPC commitment and differentiation. Their susceptibility to external stimuli and assumed intrinsic neurogenic potential have been investigated in co-culture models with organotypic slices derived from two distinct CNS regions (hippocampus and spinal cord). The hippocampal slice culture exposed to oxygen glucose deprivation (OGD) was used to evaluate the cell differentiation in microenvironment conditioned by traumatized tissue. The results have shown that the local instructive clues not only trigger the neuronal commitment of oligodendrocyte progenitors, but also govern the oligodendroglial maturation. While the trophic factors secreted by hippocampal slices efficiently promoted neurogenesis, the observed effect was significantly abolished in co-cultures with the OGD-subjected tissue. The less pronounced susceptibility to adopting neuronal phenotype and the considerable slowdown of oligodendroglial differentiation was observed in the co-cultures with the spinal cord slices. Our findings indicate that OPCs actually meet some of the neural stem cell criteria. The obtained results also suggest that the specificity of the instructive clue cocktail might module the fate choice of mobilized endogenous or transplanted cells, which is important while planning neurorepair strategies. Supported by grant 0345/B/P01/2010/38.
Tumor Necrosis Factor-alpha (TNFα) is a pleiotrophic cytokine, affects either normal or tumor cells, and influences cellular differentiation. TNFα role in female reproduction has been proven to be mediated through an influence on prostaglandin (PGs) synthesis and output. To evaluate the possible role of TNFα in an auto-/paracrine regulation in the cat uterus, mRNA expression coding for TNFα and its receptors (TNFR1 and TNFR2), and TNFα protein content at different stages of the estrous cycle were investigated. Additionally, TNFα involvement in PG secretion at different stages of the estrous cycle was investigated by in vitro tissue culture. Gene expressions coding for TNFα and TNFR1 were the highest at diestrus (P < 0.05). TNFα protein expression was the lowest at interestrus (P < 0.05). Nevertheless, TNFR2 was not affected by the estrous stage. TNFα at a dose of 1 ng/ml significantly increased PGF₂α secretion at estrus (P < 0.01) and PGE₂ secretion at diestrus (P < 0.001) after 12h incubation. Overall findings indicate that TNFα locally produced in the cat’s uterus, stimulates PG secretion in an estrous cycle-related manner.
In this study we have investigated the impact of differentiation of neuronal cells on their sensitivity to microbial toxins. We used the human neural crest-derived tumor cell line Paju, which can be induced to differentiation in vitro by treatment with phorbol 12-myristate 13-acetate. Addition of the highly toxic potassium ionophores cereulide (4.5 and 9.0 ng/ml) or valinomycin (20 ng/ml), to cultures of undifferenti­ated Paju cells caused collapse of the mitochondrial membrane potential — measured with the fluorescent probe 5,5',6,6'-tetrachloro-1,1',3,3'-tetrabenzimidazole carbo- cyanine iodide (JC-1) followed by detachment of the cells and their apoptotic death. After induced differentiation of the Paju cells, their mitochondria retained the mem­brane potential upon exposure to the toxins and the cells displayed increased resis­tance to apoptosis as compared with undifferentiated cells. This effect may be caused by an elevated expression of the anti-apoptotic protein Bcl-2 and of the neuroprotective factor, stanniocalcin, in differentiated cells.
4-Hydroxy-2,3-nonenal (HNE) is a biologically active aldehydic end product of oxidative decomposition of w-3 and w-6 polyunsaturated fatty acids of membrane phospholipids, a process referred to as lipid peroxidation. HNE has been detected in several experimental and clinical conditions in which oxidative stress has been reported to occur and several authors have suggested that HNE and related 4-hydroxy-2,3-alkenals (HAKs) of different chain length may act not only as toxic and mutagenic mediators of oxidative stress-related injury but also as biological signals in normal and pathological conditions. In this paper we will review the literature supporting the concept that HNE and HAKs may act as signal molecules able to modulate biological events such as chemotaxis, signal transduction, gene expression, cell proliferation and cell differentiation.
Cell proliferation and differentiation is a complex process involving many cellular mechanisms. One of the best-studied phenomena in cell differentiation is erythrocyte development during hematopoiesis in vertebrates. In recent years, a new class of small, endogenous, non-coding RNAs called microRNAs (miRNAs) emerged as important regulators of gene expression at the post-transcriptional level. Thousands of miRNAs have been identified in various organisms, including protozoa, fungi, bacteria and viruses, proving that the regulatory miRNA pathway is conserved in evolution. There are many examples of miRNA-mediated regulation of gene expression in the processes of cell proliferation, differentiation and apoptosis, and in cancer genesis. Many of the collected data clearly show the dependence of the proteome of a cell on the qualitative and quantitative composition of endogenous miRNAs. Numerous specific miRNAs are present in the hematopoietic erythroid line. This review attempts to summarize the state of knowledge on the role of miRNAs in the regulation of different stages of erythropoiesis. Original experimental data and results obtained with bioinformatics tools were combined to elucidate the currently known regulatory network of miRNAs that guide the process of differentiation of red blood cells.
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