Somatic cell nuclear transfer and transcription-factor-based reprogramming revert adult cells to an embryonic state, and yield pluripotent stem cells that can generate all tissues. Through different ...mechanisms and kinetics, these two reprogramming methods reset genomic methylation, an epigenetic modification of DNA that influences gene expression, leading us to hypothesize that the resulting pluripotent stem cells might have different properties. Here we observe that low-passage induced pluripotent stem cells (iPSCs) derived by factor-based reprogramming of adult murine tissues harbour residual DNA methylation signatures characteristic of their somatic tissue of origin, which favours their differentiation along lineages related to the donor cell, while restricting alternative cell fates. Such an 'epigenetic memory' of the donor tissue could be reset by differentiation and serial reprogramming, or by treatment of iPSCs with chromatin-modifying drugs. In contrast, the differentiation and methylation of nuclear-transfer-derived pluripotent stem cells were more similar to classical embryonic stem cells than were iPSCs. Our data indicate that nuclear transfer is more effective at establishing the ground state of pluripotency than factor-based reprogramming, which can leave an epigenetic memory of the tissue of origin that may influence efforts at directed differentiation for applications in disease modelling or treatment.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Many types of adult tissues, especially for high turnover tissues such as the blood and intestinal system, stand on a hierarchical tissue-specific stem cell system. Tissue-specific stem cells ...concurrently have self-renewal capacity and potential to give rise to all types of mature cells in their tissue. The differentiation process of the tissue-specific stem cell is successive restriction of these capacities. The first progeny of tissue-specific stem cells are multipotent progenitors (MPPs) that lose long-term self-renewal capacity yet have full lineage potential. MPPs in turn give rise to oligopotent progenitors, which then commit into lineage-restricted progenitors. This hierarchical system enables a lifelong supply of matured functional cells that generally have a short life span and a relatively high turnover rate. In this chapter, we review our findings and other key experiments that have led to the establishment of the current cellular stem and progenitor hierarchy in the blood-forming systems of mice and humans for both normal and leukemic hematopoiesis. We also review select signaling pathways intrinsic to normal hematopoietic and leukemic stem cell populations as well our recent findings elucidating the possible origin of the leukemia stem cell.
Epigenetic modifications must underlie lineage-specific differentiation as terminally differentiated cells express tissue-specific genes, but their DNA sequence is unchanged. Haematopoiesis provides ...a well-defined model to study epigenetic modifications during cell-fate decisions, as multipotent progenitors (MPPs) differentiate into progressively restricted myeloid or lymphoid progenitors. Although DNA methylation is critical for myeloid versus lymphoid differentiation, as demonstrated by the myeloerythroid bias in Dnmt1 hypomorphs, a comprehensive DNA methylation map of haematopoietic progenitors, or of any multipotent/oligopotent lineage, does not exist. Here we examined 4.6 million CpG sites throughout the genome for MPPs, common lymphoid progenitors (CLPs), common myeloid progenitors (CMPs), granulocyte/macrophage progenitors (GMPs), and thymocyte progenitors (DN1, DN2, DN3). Marked epigenetic plasticity accompanied both lymphoid and myeloid restriction. Myeloid commitment involved less global DNA methylation than lymphoid commitment, supported functionally by myeloid skewing of progenitors following treatment with a DNA methyltransferase inhibitor. Differential DNA methylation correlated with gene expression more strongly at CpG island shores than CpG islands. Many examples of genes and pathways not previously known to be involved in choice between lymphoid/myeloid differentiation have been identified, such as Arl4c and Jdp2. Several transcription factors, including Meis1, were methylated and silenced during differentiation, indicating a role in maintaining an undifferentiated state. Additionally, epigenetic modification of modifiers of the epigenome seems to be important in haematopoietic differentiation. Our results directly demonstrate that modulation of DNA methylation occurs during lineage-specific differentiation and defines a comprehensive map of the methylation and transcriptional changes that accompany myeloid versus lymphoid fate decisions.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The vast development of golf courses implemented in arid and semiarid regions, and the intense aquifer pumping rate of the water needed to irrigate these grass lands, provokes saline problems, mainly ...in the coastal areas, due to sea water intrusion. The reuse of treated wastewater to irrigate golf courses is considered as an alternative to the use of potable and ground water. The objective of this work was to study the response of Bermuda grass (
Cynodon dactylon
, L. Pers) to several irrigation rates I with reused treated municipal wastewater in two locations in southern Portugal. Three different irrigation regimes based on different values of electrical conductivity (EC
w
), namely EC
w
= 0.3 dS m
−1
(potable water; control treatment), EC
w
= 1.6 dS m
−1
, and EC
w
= 2.4 dS m
−1
, using the sprinkler point source as experimental design, were established. Grass yield (aboveground biomass) was recorded monthly, and linear regressions between yield and net irrigation rates I were obtained. The results showed a clear and pronounced influence of the nutrient concentration in wastewater on the response of the turfgrass irrigated under several water regimes and saline conditions. Higher irrigation rates (I > 6 mm d
−1
) triggered higher yields, but this increase was slightly lower under higher salinity conditions (EC
w
= 2.4 dS m
−1
). We conclude that wastewater can be used to irrigate turfgrass as an alternative to potable water due to the presence of significant quantities of some essential nutrients, like K. However, the EC of wastewater can be a limiting factor.
Despite being a hallmark of hematopoietic stem cells (HSCs), HSC self-renewal has never been quantitatively assessed. Establishment of a clonal and quantitative assay for HSC function permitted ...demonstration that adult mouse HSCs are significantly heterogeneous in degree of multilineage repopulation and that higher repopulating potential reflects higher self-renewal activity. An HSC with high repopulating potential could regenerate approximately 1000 HSCs, whereas the repopulating activity of regenerated HSCs on average was significantly reduced, indicating extensive but limited self-renewal capacity in HSCs. Comparisons of wild-type mice with mutant mice deficient in the signal adaptor molecule Lnk showed that not only HSC numbers but also the self-renewal capacity of some HSCs are markedly increased when Lnk function is lost. Lnk appears to control HSC numbers by negatively regulating HSC self-renewal signaling.
The general behavior of Newtonian, shear-thinning, shear-thickening, thixotropic, negative thixotropic, and viscoelastic fluids is characterized and briefly discussed in terms of existing theoretical ...models. Whenever possible, examples of these types of fluids taken from everyday life are given for better understanding. This theoretical introduction is the basis for same, simple, and inexpensive laboratory work employing no special glassware and generally done by pairs of students. The work involves the synthesis of two well-known viscoelastic materials displaying unique properties: poly(vinyl alcohol) (PVA) and white glue, a poly(vinyl acetate)-based emulsion. The students are asked to perform a series of representative mechanical tests on both gels and to describe their observations in full detail. In particular, they are expected to recognize and identify the origin of the intriguing behaviors found (elasticity, spinability, self-siphoning effect, die-swell effect, Weissenberg effect). The tests include the preparation of fibers by extrusion, introducing concepts such as water solubility, hydrogen bonding, and glass transition temperature. The long list of questions, which ideally should be answered at the end of the laboratory work, allows the students to apply the new concepts acquired.
Background. To identify risk factors for preexisting carotid and aortic disease in coronary artery bypass grafting (CABG), preoperative parameters were analyzed.
Methods. Three-hundred eight ...consecutive patients undergoing elective isolated CABG were investigated through preoperative duplex scanning of the carotid artery, computed tomography of the chest, and intraoperative ultrasonography of the ascending aorta.
Results. Prevalence of carotid stenosis and ascending aortic atherosclerosis was 14.3% (44 of 308) and 30.2% (93 of 308), respectively. Multivariate analysis indicated that significant independent risk factors for carotid stenosis were atherosclerosis of the ascending aorta (
p = 0.028, odds ratio OR = 2.16), peripheral vascular disease (
p = 0.008, OR = 4.08), and history of stroke (
p = 0.0004, OR = 3.73). Significant independent risk factors for ascending aortic atherosclerosis were peripheral vascular disease (
p = 0.029, OR = 3.05), age older than 60 years (
p = 0.009, OR = 2.94), and carotid stenosis (
p = 0.018, OR = 2.27). Modifications on the operative procedure for aortic atherosclerosis were carried out in 49 patients. Overall hospital mortality and morbidity for stroke were 0.97% and 0.65%, respectively.
Conclusions. Prevalence of carotid and aortic disease was not low among candidates for CABG. Carotid and aortic screening may help to modify the operative strategy to reduce morbidity of stroke.
This is a case report of an IVC filter penetration identified during lymph-node dissection for endometrial carcinoma. Although the spread strut put the adjacent abdominal aorta in danger of ...penetration, surgical removal of the filter could not be performed because there was still an increased risk of pulmonary embolism. Instead of IVC interruption, we used a wrapping technique as a prophylaxis against major bleeding complication due to IVC filter dislocation and recurrent pulmonary embolism.
The patient was a 72-year-old male with three-vessel coronary artery disease, chronic dissecting aneurysm of the ascending aorta with moderate aortic regurgitation, and abdominal aortic aneurysm 7 cm ...in diameter. Because staged procedure seemed to exacerbate the risk due to the remaining lesion, simultaneous procedures (double coronary artery bypass, aortic root remodeling, tube replacement of the ascending aorta and Y-graft replacement of the abdominal aneurysm) were performed. The patient recovered completely without any serious complication.
We herein report a case of third coronary artery bypass grafting (CABG) using a bilateral radial artery T graft. There were patent grafts on the anterior aspect of the heart other than the occluded ...left internal thoracic artery to the left anterior descending (LAD) artery. A T shaped bilateral radial artery conduit was anastomosed from the left subclavian artery to the LAD and first diagonal branch through a left thoracotomy approach. Postoperative angiography demonstrated excellent flow of radial artery conduits. Left thoracotomy with the use of a bilateral radial artery T graft is a useful substitute for anterior re-sternotomy entry in redo CABG.
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