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The signal transducers and activators of transcription - STAT5A and STAT5B - are responsible for the control of proliferation, differentiation and apoptosis, via their effect on gene expression. They are activated by the binding of many cytokines, growth factors and hormones to their receptors on the cell surface. Many of these cytokines regulate hematopoietic cell development; therefore, STAT5 proteins are suggested to play an important role in hematopoiesis. There are numerous contradictory reports available in the literature on the role of STAT5 in normal hematopoietic cell development; hence, the question of the real function of STAT5 proteins clearly requires further studies. The aim of our study was to evaluate the role of STAT5 in normal hematopoiesis using oligodeoxynucleotide (ODN) strategy against STAT5 mRNA. We employed the RT-PCR method to study STAT5 mRNA expression in cells after their incubation with ODNs. We analyzed the effect of blocking STAT5 proteins on the viability and clonogenecity of the CFU-GM (Colony Forming Unit of Granulocyte-Macrophages) and the BFU-E (Burst Forming Unit of Erythrocytes) obtained from human cord blood (CB). The clonogenic growth of the cells was assessed in methylcellulose cultures according to the type of oligodeoxynucleotides. We also attempted to estimate the level of apoptosis induced in cord blood mononuclear and CD34+ cells by employing different assays: i) Annexin V staining using flow cytometry (FACSCalibur); ii) terminal deoxynucleotidyltransferase dUTP nick end labeling (TUNEL); iii) analysis of Bax and Bcl-XL gene expression by RT-PCR. Perturbation of STAT5 expression with antisense oligodeoxynucleotides had no impact on the viability, clonogenecity and apoptosis of CB hematopoietic cells. Our results showed that STAT5 proteins do not play a significant role in the regulation of proliferation of normal hematopoietic cells derived from cord blood.
Similarly to the production of red blood cells, the production and development of leukocytes takes place in the bone marrow in the process of hematopoiesis. The key stages in the development of leukocytic cell lines are: neutrophilic, eosinophilic and basophilic granulopoiesis, monocytopoiesis, lymphopoiesis and megakaryopoiesis. Leukocytes produced at various developmental stages are characterized by differently shaped nuclei, the presence or absence of nucleoli, and variations in cytoplasm staining. The experiment was carried out on 10 clinically healthy HF cows. Bone marrow aspirate smears stained by the MGG method were analyzed. The study found significant differences in the number, size, and staining intensity of individual myeloid cell lines.
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.
Leptin is an adipocyte-derived hormone regulating energy homeostasis and body weight. Leptin also plays a role in hematopoesis, cell cycle regulation, and in oncogenesis. The leptin receptor is a single transmembrane protein belonging to the superfamily of cytokine receptors, structurally related to the hemopoietin receptor family. The aim of the study was to evaluate bone marrow and peripheral blood leptin level and frequency of distribution of leptin receptor gene polymorphism Gln223Arg in children with acute leukemia. The examined group included 92 children with acute leukemia (83 ALL and 9 AML) and 39 non-leukemic control children. Leptin level was measured by ELISA method at the day of leukemia diagnosis. Genomic DNA was isolated with the use of a column method and the genotyping of DNA sequence variation was carried out by the restriction enzyme analysis of PCR – amplified DNA. The samples were then electrophoresed on 2.5% agarose gel. Leptin level in leukemic children was lower than in healthy children. Bone marrow leptin level was significantly lower than that in the blood in leukemic children with ALL-T and AML. An analysis of frequency distribution of the Gln233Arg polymorphism in the leptin receptor gene in leukemic children showed lack of differences between the patients and controls. There was no difference in the genotype frequencies between the leukemic AML and ALL groups either. The results indicate a possible relation between the leptin level and leukemia development in children. The effectory effect of the hormone seems not related to Gln223Arg polymorphism of its receptor.
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